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Sample records for cross-linked polyethylene shelf-aged

  1. In vivo oxidation in remelted highly cross-linked retrievals.

    Science.gov (United States)

    Currier, B H; Van Citters, D W; Currier, J H; Collier, J P

    2010-10-20

    Elimination of free radicals to prevent oxidation has played a major role in the development and product differentiation of the latest generation of highly cross-linked ultra-high molecular weight polyethylene bearing materials. In the current study, we (1) examined oxidation in a series of retrieved remelted highly cross-linked ultra-high molecular weight polyethylene bearings from a number of device manufacturers and (2) compared the retrieval results with findings for shelf-stored control specimens. The hypothesis was that radiation-cross-linked remelted ultra-high molecular weight polyethylene would maintain oxidative stability in vivo comparable with the stability during shelf storage and in published laboratory aging tests. Fifty remelted highly cross-linked ultra-high molecular weight polyethylene acetabular liners and nineteen remelted highly cross-linked ultra-high molecular weight polyethylene tibial inserts were received after retrieval from twenty-one surgeons from across the U.S. Thirty-two of the retrievals had been in vivo for two years or more. Each was measured for oxidation with use of Fourier transform infrared spectroscopy. A control series of remelted highly cross-linked ultra-high molecular weight polyethylene acetabular liners from three manufacturers was analyzed with electron paramagnetic resonance spectroscopy to measure free radical content and with Fourier transform infrared spectroscopy to measure oxidation initially and after eight to nine years of shelf storage in air. The never-implanted, shelf-aged controls had no measurable free-radical content initially or after eight to nine years of shelf storage. The never-implanted controls showed no increase in oxidation during shelf storage. Oxidation measurements showed measurable oxidation in 22% of the retrieved remelted highly cross-linked liners and inserts after an average of two years in vivo. Because never-implanted remelted highly cross-linked ultra-high molecular weight

  2. Cross-linked compared with historical polyethylene in THA: an 8-year clinical study.

    Science.gov (United States)

    Geerdink, Carel H; Grimm, Bernd; Vencken, Wendy; Heyligers, Ide C; Tonino, Alphons J

    2009-04-01

    Wear particle-induced osteolysis is a major cause of aseptic loosening in THA. Increasing wear resistance of polyethylene (PE) occurs by increasing the cross-link density and early reports document low wear rates with such implants. To confirm longer-term reductions in wear we compared cross-linked polyethylene (irradiation in nitrogen, annealing) with historical polyethylene (irradiation in air) in a prospective, randomized clinical study involving 48 patients who underwent THAs with a minimum followup of 7 years (mean, 8 years; range, 7-9 years). The insert material was the only variable. The Harris hip score, radiographic signs of osteolysis, and polyethylene wear were recorded annually. Twenty-three historical and 17 moderately cross-linked polyethylene inserts were analyzed (five patients died, three were lost to followup). At 8 years, the wear rate was lower for cross-linked polyethylene (0.088 +/- 0.03 mm/year) than for the historical polyethylene (0.142 +/- 0.07 mm/year). This reduction (38%) did not diminish with time (33% at 5 years). Acetabular cyst formation was less frequent (39% versus 12%), affected fewer DeLee and Charnley zones (17% versus 4%), and was less severe for the cross-linked polyethylene. The only revision was for an aseptically loose cup in the historical polyethylene group. Moderately cross-linked polyethylene maintained its wear advantage with time and produced less osteolysis, showing no signs of aging at mid-term followup. Level I, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

  3. Heating tubes of cross-linked polyethylene

    International Nuclear Information System (INIS)

    Knoeppler, H.; Hoffmann, M.

    1981-01-01

    Oxygen permeability of plastic tubes for floor heating systems was measured as a function of the reduced oxygen content of water in plastic tubes at a flow rate of 0.5 m/s and a temperature of 30 0 C and as a function of oxygen uptake of low-oxygen water in floor heating tubes. Pipes of VEP, periodically cross-linked polyethylene (Engels process), polypropylene copolymeride, and polybutene were compared. The permeability of periodically cross-linked polyethylene is twice as high as that of VEP. Measurements, results, and consequences for floor heating systems are discussed. (KH) [de

  4. Development of new cross-linked polyethylene for atomic energy

    International Nuclear Information System (INIS)

    Fujimura, Shun-ichi; Ohya, Shingo; Kubo, Masaji; Tsutsumi, Yukihiro; Seguchi, Tadao.

    1988-01-01

    Cross-linked polyethylene is the material which is used most as the insulating material for electric wires and cables, but for the cables for nuclear power stations and the wiring materials within machinery and equipment, the cross-linked polyethylene which is hard to burn by mixing burning-retarding agent is frequently used as the disaster-preventing countermeasures. As the burning-retarding agent for cross-linked polyethylene, bromine system agent that gives high burning retardation, chlorine system agent that can prevent melting and dripping at the time of burning and so on have been used so as to meet the objective. However by the addition of burning-retarding agents, the electrical and mechanical characteristics of cross-linked polyethylene lower, therefore consideration must be given to the use. In this paper, the results of the examination on the application of condensed acenaphthylene bromide as a new burning-retarding agent to cross-linked polyethylene are reported. White lead was effective for catching HBr. It was confirmed that more than 30 parts of this agent ensured burning retardation. By mixing this agent, the tensile strength increased, but the elongation lowered. It was found that the good radiation resistance was obtained by adding this agent. (K.I.)

  5. Vitamin E diffused highly cross-linked polyethylene in total hip arthroplasty at five years

    DEFF Research Database (Denmark)

    Nebergall, Audrey K; Greene, M. E.; Laursen, M B

    2017-01-01

    Aims: The objective of this five-year prospective, blinded, randomised controlled trial (RCT) was to compare femoral head penetration into a Vitamin E diffused highly cross-linked polyethylene (HXLPE) liner with penetration into a medium cross-linked polyethylene control liner using......, ArComXL. This is the longest-term RCT comparing the wear performance and clinical outcome of Vitamin E diffused HXLPE with a previous generation of medium cross-linked polyethylene....... radiostereometric analysis. Patients and Methods: Patients scheduled for total hip arthroplasty (THA) were randomised to receive either the study E1 (32 patients) or the control ArComXL polyethylene (35 patients). The median age (range) of the overall cohort was 66 years (40 to 76). Results: The five-year median...

  6. Development of extremely low wear cross-link polyethylene for 30 years

    International Nuclear Information System (INIS)

    Oonishi, Hironobu; Fujita, Hiroshi; Kim, Seok-Cheol; Ito, Shigeru; Masuda, Shingo; Clarke, I.C.

    2003-01-01

    In this report we present our long-term developmental and clinical results with both highly cross-linked and extensively cross-linked polyethylene materials. Beginning in 1970s, we performed wear screening studies on ultra high molecular weight polyethylene (UHMWPE) (GUR412) sterilized by gamma-irradiation in air (range 0 to 10,000 kGy). From these scientific studies the 1,000 kGy dose (100 Mrad) appeared optimal, and so we began clinical use in 1971, and that continued into 1978. The radiographic wear-rates in patients with 1,000 kGy sockets, assessed by radiography, appeared 6-fold reduced compared to our standard UHMWPE sockets. Note also that we had not used any post-sterilization heat treatment for these pioneering extensively cross-linked polyethylene sockets. With clinical use now over 30 years, it was also clear that there was no adverse oxidation created by any free radicals present in our extensively cross-linked polyethylene sockets. With these encouraging clinical results, we further studied laboratory wear results with the modern UHMWPE resins, using the irradiation doses 1,000, 5,000, 10,000 and 15,000 kGy and with both saline and serum lubricants in hip simulators. These more recent studies demonstrated that the wear in extensively cross-linked polyethylene sockets was undetectable, less even than the measurement errors in the simulator techniques. It was unfortunate that the physical properties of such extensively cross-linked polyethylene sockets did not meet the current International Organization for Standardization (ISO) and American Society for Testing and Materials (ASTM) standards. Thus, despite the excellent wear performance of these materials, we decided to investigate also the properties of the 60 kGy irradiated UHMWPE. The polyethylene sheet (GUR1050) was first irradiated with 35 kGy under N2 and then heat treated to remove free radicals. The socket liners were then machined to shape and resterilized with 25 kGy under N2 gas. The

  7. Manufacture of polyethylene foam by electron beam cross-linking

    International Nuclear Information System (INIS)

    Tamai, Isamu

    1976-01-01

    The manufacturing process of polyethylene foam, comparison between electron beam cross-linking process and chemical cross-linking process, the electron beam irradiation technique for continuous sheets, the characteristics and uses of polyethylene foam are reviewed. The pore diameter can be controlled by selecting the dose rate, because there is strong relationship between the pore diameter and the dose rate. As the dose if higher, the foam becomes finer. The electron accelerators having large capacity show the lowest cost as the radiation source, and are applicable industrially. If the production capacity exceeds about 200 tons per month, the costs of electron beam irradiation process may be more advantageous than that of chemical process according to the circumstances. It is difficult to obtain the uniform distribution of absorption dose in the direction of thickness. General characteristics of cross-linked polyethylene foam are listed. The special feature of electron beam process is that the degree of cross-linking can be controlled arbitrarily before foaming. The products obtained by the electron beam cross-linking process have finer foams and smoother surfaces than those obtained by the chemical process, because the separation of the decomposition of foaming agents from that of cross-linking agents in the chemical cross-linking is difficult. (Iwakiri, K.)

  8. An Investigation on Rheology of Peroxide Cross-linking of Low Density Polyethylene

    DEFF Research Database (Denmark)

    Ghasemi, Ismaeil; Rasmussen, Henrik K.; Szabo, Peter

    2005-01-01

    One of the most important post-reactor modifications of polyethylene is cross-linking. It improves some properties of polyethylene such as environmental stress cracking resistance, chemical and abrasion resistance, and service temperature. In this study, the effect of peroxide cross-linking on th......One of the most important post-reactor modifications of polyethylene is cross-linking. It improves some properties of polyethylene such as environmental stress cracking resistance, chemical and abrasion resistance, and service temperature. In this study, the effect of peroxide cross......-linking on the rheological behaviour of low density polyethylene was investigated by using a combination of creep test and differential scanning calorimeter (DSC) in isotherm condition. The used peroxide was di-cumyl peroxide and its concentration was 2 wt%. The experiments were carried out at 150,160, and 170 degrees C...

  9. Physical and mechanical properties of gamma radiation cross-linked polyethylene

    International Nuclear Information System (INIS)

    Gonzalez, Maria E.; Romero, G.; Smolko, Eduardo E.

    1999-01-01

    Granulated LDPE 2003 polyethylene was extruded and irradiated under nitrogen with 150, 200 and 300 kGy gamma rays doses to produce cross-linking. The study of the physical and mechanical properties shows that the product has a high degree of molecular cross-linking, can be heated up to 200 C for 2 hours without deformation and that the mechanical properties improve. Preliminary aging tests indicate that after heating at 60 C for 4 weeks no physical or mechanical deterioration can be observed. (author)

  10. Cross-linked polyethylene does not reduce wear in total knee arthroplasty.

    Science.gov (United States)

    Lasurt-Bachs, S; Torner, P; Maculé, F; Prats, E; Menéndez-García, F; Ríos-Guillermo, J; Torrents, A

    To compare two different types of inserts: Ultra-high molecular weight polyethylene (UHMWPE) and cross-linked polyethylene with a quantitative and qualitative study of polyethylene wear particles in synovial fluid 3 years after total knee arthroplasty. A prospective, randomized, controlled cohort study with blinded evaluation was carried out on 25 patients undergoing staged bilateral total knee replacement, 6 months apart. Knee arthrocentesis was performed on 12 patients 3 years after surgery, and the polyethylene particles were analyzed. No significant differences were found in the number of particles generated by the two different types of inserts at 3 years from total knee arthroplasty (3,000×: x¯ cross-linked=849.7; x¯ UHMWPE=796.9; P=.63; 20,000×: x¯ cross-linked=66.3; x¯ UHMWPE=73.1; P=.76). Likewise, no differences in the probability of finding elongated (χ 2 =0.19; P=.66) or rounded (χ 2 =1.44; P=.23) particles in both types of inserts were observed. However, the probability of finding fibrillar particles is 3.08 times greater in UHMWPE. Cross-linked polyethylene does not significantly reduce the generation of polyethylene particles in patients with total knee arthroplasty, 3 years after the surgical procedure. Copyright © 2018 SECOT. Publicado por Elsevier España, S.L.U. All rights reserved.

  11. Aging Mechanisms and Nondestructive Aging Indicator of Filled Cross-linked Polyethylene (XLPE) Exposed to Simultaneous Thermal and Gamma Radiation

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Shuaishuai; Fifield, Leonard S.; Bowler, Nicola

    2018-04-11

    Aging mechanisms and a nondestructive aging indicator of filled cross-linked polyethylene (XLPE) cable insulation material used in nuclear power plants (NPPs) are studied. Using various material characterization techniques, likely candidates and functions for the main additives in a commercial filled-XLPE insulation material have been identified. These include decabromodiphenyl ether and Sb2O3 as flame retardants, ZnS as white pigment and polymerized 1,2-dihydro-2,2,4-trimethylquinoline as antioxidant. Gas chromatography-mass spectrometry, differential scanning calorimetry, oxidation induction time and measurements of dielectric loss tangent are utilized to monitor property changes as a function of thermal and radiation exposure of the cable material. Small-molecular-weight hydrocarbons are evolve with gamma radiation aging at 90 °C. The level of antioxidant decreases with aging by volatilization and chemical reaction with free radicals. Thermal aging at 90 °C for 25 days or less causes no observable change to the cross-linked polymer structure. Gamma radiation causes damage to crystalline polymer regions and introduces defects. Dielectric loss tangent is shown to be an effective and reliable nondestructive indicator of the aging severity of the filled-XLPE insulation material.

  12. Characterization of the degree of cross-linking in radiation cross-linked low and high density polyethylenes

    International Nuclear Information System (INIS)

    Posselt, K.; Haedrich, W.

    1986-01-01

    In practice the cross-linking of irradiated polyethylene is mostly characterized by solubility and thermomechanical data. The irradiation of samples of a LDPE and a HDPE yields very different gel-dose curves. But for a quantitative comparison the complicated connection between the gel values and the corresponding densities of cross-links, especially the dependence on the initial molecular size distribution, has to take into consideration. The analysis of the solubility data according to the statistical theory of cross-linking developed by Inokuti and Saito shows that at equal doses in both investigated PE types in spite of the different gel values nearly the same densities of cross-links are present. That result is confirmed by the densities of cross-links determined from stress-strain measurements at 423 K. (author)

  13. The effect of gamma irradiation and shelf aging in air on the oxidation of ultra-high molecular weight polyethylene

    International Nuclear Information System (INIS)

    Al-Ma'adeed, M.A.; Al-Qaradawi, I.Y.; Madi, N.; Al-Thani, N.J.

    2006-01-01

    This study has investigated the effect of shelf aging, for up to one year in air, on the properties of gamma-irradiated ultra-high molecular weight polyethylene (UHMWPE). A variety of techniques were used to characterize the properties of treated samples. Differential scanning calorimetery (DSC) was used to characterize the morphology. The extent of cross-linking in a polymer network was detected by swelling measurements. The durometer hardness test was used to measure the relative hardness of this material, and changes in density were also measured. Results from all these measurements were combined to explain the changes in the microstructure of the aged, irradiated UHMWPE. This study shows that crystallinity is increased with radiation dose and with aging due to chain scission, which leads to a reduction in the molecular weight of the material. This allows the chains to rearrange to form crystalline regions. Positron annihilation lifetime spectroscopy confirms these conclusions. Fractional free volumes have been deduced from lifetime parameters, which correlate with the data obtained by the other techniques

  14. Wear of PEEK-OPTIMA® and PEEK-OPTIMA®-Wear Performance articulating against highly cross-linked polyethylene.

    Science.gov (United States)

    East, Rebecca H; Briscoe, Adam; Unsworth, Anthony

    2015-03-01

    The idea of all polymer artificial joints, particularly for the knee and finger, has been raised several times in the past 20 years. This is partly because of weight but also to reduce stress shielding in the bone when stiffer materials such as metals or ceramics are used. With this in mind, pin-on-plate studies of various polyetheretherketone preparations against highly cross-linked polyethylene were conducted to investigate the possibility of using such a combination in the design of a new generation of artificial joints. PEEK-OPTIMA(®) (no fibre) against highly cross-linked polyethylene gave very low wear factors of 0.0384 × 10(-6) mm(3)/N m for the polyetheretherketone pins and -0.025 × 10(-6) mm(3)/N m for the highly cross-linked polyethylene plates. The carbon-fibre-reinforced polyetheretherketone (PEEK-OPTIMA(®)-Wear Performance) also produced very low wear rates in the polyetheretherketone pins but produced very high wear in the highly cross-linked polyethylene, as might have been predicted since the carbon fibres are quite abrasive. When the fibres were predominantly tangential to the sliding plane, the mean wear factor was 0.052 × 10(-6) mm(3)/N m for the pins and 49.3 × 10(-6) mm(3)/N m for the highly cross-linked polyethylene plates; a half of that when the fibres ran axially in the pins (0.138 × 10(-6) mm(3)/N m for the pins and 97.5 × 10(-6) mm/ N m for the cross-linked polyethylene plates). PEEK-OPTIMA(®) against highly cross-linked polyethylene merits further investigation. © IMechE 2015.

  15. Flammability of radiation cross-linked low density polyethylene as an insulating material for wire and cable

    International Nuclear Information System (INIS)

    Basfar, A.A.

    2002-01-01

    Various formulations of low-density polyethylene blended with ethylene vinyl acetate were prepared to improve the flame retardancy for wire and cable applications. The prepared formulations were cross-linked by γ-rays to 50, 100, 150 and 200 kGy in the presence of trimethylolpropane triacrylate (TMPTA). The effect of thermal aging on mechanical properties of these formulations were investigated. In addition, the influence of various combinations of aluminum trihydroxide and zinc borate as flame retardant fillers on the flammability was explored. Limiting oxygen index (LOI) and average extent of burning were used to characterize the flammability of investigated formulations. An improved flame retardancy of low density polyethylene was achieved by various combinations of flame ratardant fillers and cross-linking by gamma radiation

  16. Relationship between product demand, tibial polyethylene insert shelf age, and total knee arthroplasty survival: retrospective review of total knees of one design.

    Science.gov (United States)

    Urban, Joshua A; Collier, Matthew B; Engh, C Anderson; Engh, Gerard A

    2006-04-01

    Shelf aging of gamma-irradiated-in-air polyethylene tibial components has been associated with increased articular surface wear and an elevated risk for revision. Nine hundred fifty cruciate-retaining inserts of one design were implanted between 1987 and 1996 (shelf age, 1.0 +/- 1.2 years). Less frequently used inserts (smallest/largest sizes, thicker thicknesses, supplemental articular constraint) had longer shelf ages (means ranged from 1.2 to 2.6 years). Survival analysis showed that shelf age (P product demand and can be of aid when diagnosing the painful knee.

  17. Model experiments on the sensitization of polyethylene cross-linking of oligobutadienes

    International Nuclear Information System (INIS)

    Brede, O.; Beckert, D.; Hoesselbarth, B.; Specht, W.; Tannert, F.; Wunsch, K.

    1988-01-01

    In presence of ≥ 1 % of 1,2-oligobutadiene the efficiency of the radiation-induced cross-linking of polyethylene was found to be increased in comparison to the pure matrix. Model experiments with solutions of the sensitizer in long chain n-alkanes showed that after addition of alkyl radicals onto the oligobutadiene (reaction with the vinyl groups) the sensitizer forms an own network which is grafted by the alkyl groups. In comparison to this grafting reaction proceeding with G of about 5 the vinyl consumption happened with about the threefold of it indicating a short (intra- and intermolecular) vinyl reaction chain. Pulse radiolysis measurements in solutions of the 1,2-oligobutadiene in n-hexadecane and in molten PE blends resulted in the observation of radical transients of the cross-linking reaction. (author)

  18. Wear of cross-linked polyethylene against itself: a material suitable for surface replacement of the finger joint.

    Science.gov (United States)

    Sibly, T F; Unsworth, A

    1991-05-01

    Cross-linking of polyethylene (XLPE) has dramatically improved its properties in industrial applications, and it may also have some application in the field of human joint replacement. Additionally it has the advantage of permitting a lower molecular weight base material to be used, so that components may be injection moulded rather than machined. This study therefore investigates the wear resistance of medical grade cross-linked polyethylene (XLPE), cross-linked by a silane-grafting process, with a molecular weight between cross links of 5430 g mol(-1). This first report investigates the wear resistance of XLPE against itself, because for certain joints, such as the metacarpo-phalangeal joint, the material may have a high enough wear resistance to allow both bearing surfaces to be made from it. Tests were carried out both on a reciprocating pin and plate machine with pins loaded at 10 and 40 N and also on a new finger joint simulator, which simulates the loads applied to and the movements of, the metacarpo-phalangeal joint. An average wear rate of 1.8 x 10(-6) mm3 N-1 m-1 was found (range 0.9-2.75 x 10(-6) mm3 N-1 m-1). This is about six times greater than the wear rate of non-cross-linked ultra high molecular weight polyethylene (UHMWPE) against stainless steel, but for applications with low loading, such as the metacarpo-phalangeal joint, this material is shown to have adequate wear resistance. The coefficient of friction was 0.1, which is similar to that of UHMWPE on stainless steel.

  19. Comparative Results From a National Joint Registry Hip Data Set of a New Cross-Linked Annealed Polyethylene vs Both Conventional Polyethylene and Ceramic Bearings.

    Science.gov (United States)

    Epinette, Jean-Alain; Jolles-Haeberli, Brigitte M

    2016-07-01

    Major concerns in hip arthroplasty concern the fate of bearing surfaces. Highly cross-linked polyethylene materials (HXLPE) currently demonstrate successful in vitro results with new technical procedures of cross-linking the polyethylene material, whereas processing the polyethylene below its melting temperature to produce so-called "annealed HXLPE" would allow retention of important mechanical properties. Data released by the National Joint Registry of England and Wales addressing in 45,877 hips the same Trident uncemented cup, allowed us to compare the performance of a consecutive cohort of patients implanted with the newest generation of annealed HXLPE acetabular bearings (X3: 21,470) vs 2 consecutive nonselected cohorts, one with conventional polyethylene (N2vac: 8225) and one with ceramic-on-ceramic (CoC) hip bearings (AL: 16,182). The main end point in survivorship has been first defined as revision for any cause, then for any cause which could be related to a failure of the bearing couple. At 6-year follow-up, all Trident cups demonstrated encouraging global survival cumulative rates all between 95% and 99%. A first study demonstrated better survivorship with X3-HXLPE liners vs conventional ultrahigh molecular weight polyethylene. On the second parallel study, the cumulative survival rates were better for X3 liners as compared to CoC bearings. Moreover, when ranking the yearly cumulative percent revision rates, again the best results were obtained with X3 liners with small alumina heads (cumulative percent revision rate at 0.298). Within the frame of this Trident study, the use of this X3 highly cross-linked annealed polyethylene could be considered as a reliable alternate solution to CoC bearings. Copyright © 2016 Elsevier Inc. All rights reserved.

  20. Early experience with dual mobility acetabular systems featuring highly cross-linked polyethylene liners for primary hip arthroplasty in patients under fifty five years of age: an international multi-centre preliminary study.

    Science.gov (United States)

    Epinette, Jean-Alain; Harwin, Steven F; Rowan, Fiachra E; Tracol, Philippe; Mont, Michael A; Chughtai, Morad; Westrich, Geoffrey H

    2017-03-01

    To evaluate early performance of contemporary dual mobility acetabular systems with second generation annealed highly cross-linked polyethylene for primary hip arthroplasty of patients under 55 years of age. A prospective observational five years study across five centers in Europe and the USA of 321 patients with a mean age of 48.1 years was performed. Patients were assessed for causes of revision, hip instability, intra-prosthetic dissociation, Harris hip score and radiological signs of osteolysis. There were no dislocations and no intra-prosthetic dissociations. Kaplan Meier analysis demonstrated 97.51% survivorship for all cause revision and 99.68% survivorship for acetabular component revision at five years. Mean Harris hip score was 93.6. Two acetabular shells were revised for neck-rim implant impingement without dislocation and ten femoral stems were revised for causes unrelated to dual mobility implants. Contemporary highly cross-linked polyethylene dual mobility systems demonstrate excellent early clinical, radiological, and survivorship results in a cohort of patients that demand high performance from their implants. It is envisaged that DM and second generation annealed HXLPE may reduce THA instability and wear, the two most common causes of THA revision in hip arthroplasty.

  1. Characterization of radiation-cross-linked, high-density polyethylene for thermal energy storage

    International Nuclear Information System (INIS)

    Whitaker, R.B.; Craven, S.M.; Etter, D.E.; Jendrek, E.F.; Nease, A.B.

    1983-01-01

    Electron beam cross-linked high-density polyethylene (HDPE) pellets (DuPont Alathon, 0.93 MI) have been characterized for potential utility in thermal energy storage applications, before and after up to 500 melt-freeze cycles in ethylene glycol. Up to 95% of the HDPE's initial DSC differential scanning calorimetry Δ H/sub f/ value (44.7 cal/g) (at 1.25 0 C/min cooling rates) was retained up to 9.0 Mrad radiation dosage. Form-stability after 500 melt-freeze cycles was very good at this dosage level. X-ray diffraction measurements showed little difference between irradiated HDPE's and the unirradiated control, indicating that cross-linking occurred primarily in the amorphous regions. FTIR spectroscopy showed the pellets to be uniformly reacted. The ratios of the 965-cm -1 absorption band (trans RCH=CRH') to the 909-cm -1 band (RCH=CH 2 ) increased with increasing radiation dosage, up to 18 Mrad. Gel contents reached a maximum of 75% at the 13.5 Mrad dosage, indicating that other reactions, in addition to cross-linking, occurred at the highest (18 Mrad) dosage level. 15 references, 5 figures, 4 tables

  2. Wear of a 5 megarad cross-linked polyethylene liner: a 6-year RSA study.

    Science.gov (United States)

    Callary, Stuart A; Campbell, David G; Mercer, Graham; Nilsson, Kjell G; Field, John R

    2013-07-01

    One cross-linked polyethylene (XLPE) liner is manufactured using a lower dose of radiation, 5 Mrad, which may result in less cross-linking. The reported in vivo wear rate of this XLPE liner in patients undergoing THA has varied, and has included some patients in each reported cohort who had greater than 0.1 mm/year of wear, which is an historical threshold for osteolysis. Previous studies have measured wear on plain radiographs, an approach that has limited sensitivity. We therefore measured the amount and direction of wear at 6 years using Radiostereometric analysis (RSA) in patients who had THAs that included a cross-linked polyethylene liner manufactured using 5 Mrad radiation. We prospectively reviewed wear in 30 patients who underwent primary THAs with the same design of cross-linked acetabular liner and a 28-mm articulation. Tantalum markers were inserted during surgery and all patients had RSA radiographic examinations at 1 week, 6 months, 1, 2, and 6 years postoperatively. The mean proximal, two-dimensional (2-D) and three-dimensional (3-D) wear rates calculated between 1 year and 6 years were 0.014, 0.014, and 0.018 mm/per year, respectively. The direction of the head penetration recorded between 1 week and 6 years was in a proximal direction for all patients, proximolateral for 16 of 24 patients, and proximomedial for eight of 24 patients. The proximal, 2-D and 3-D wear of a XLPE liner produced using 5 Mrad of radiation was low but measurable by RSA after 6 years. No patients had proximal 2-D or 3-D wear rates exceeding 0.1 mm/year. Further followup is needed to evaluate the effect of XLPE wear particles on the development of long-term osteolysis.

  3. Radiostereometric analysis comparison of wear of highly cross-linked polyethylene against 36- vs 28-mm femoral heads.

    Science.gov (United States)

    Bragdon, Charles R; Greene, Meridith E; Freiberg, Andrew A; Harris, William H; Malchau, Henrik

    2007-09-01

    This study used radiostereometric analysis (RSA) to compare the femoral head penetration of 28- vs 36-mm-diameter femoral heads into highly cross-linked polyethylene in 2 groups of total hip arthroplasty patients. Thirty patients were enrolled in this RSA study using highly cross-linked polyethylene (Longevity, Zimmer Inc, Warsaw, Idaho) against either 28- or 36-mm-diameter cobalt chrome femoral heads. At 3-year follow-up, there was no significant difference in the total average femoral head penetration, including both creep and wear, using 3 methods of RSA measurement between the 2 groups. Importantly, after bedding-in, there was no further significant increase in the amount of femoral head penetration (ie, wear) with either head size between years 1 and 3. There were no radiographic signs of lysis or radiolucencies at a minimum 3-year follow-up.

  4. DFT Modeling of Cross-Linked Polyethylene: Role of Gold Atoms and Dispersion Interactions.

    Science.gov (United States)

    Blaško, Martin; Mach, Pavel; Antušek, Andrej; Urban, Miroslav

    2018-02-08

    Using DFT modeling, we analyze the concerted action of gold atoms and dispersion interactions in cross-linked polyethylene. Our model consists of two oligomer chains (PEn) with 7, 11, 15, 19, or 23 carbon atoms in each oligomer cross-linked with one to three Au atoms through C-Au-C bonds. In structures with a single gold atom the C-Au-C bond is located in the central position of the oligomer. Binding energies (BEs) with respect to two oligomer radical fragments and Au are as high as 362-489 kJ/mol depending on the length of the oligomer chain. When the dispersion contribution in PEn-Au-PEn oligomers is omitted, BE is almost independent of the number of carbon atoms, lying between 293 and 296 kJ/mol. The dispersion energy contributions to BEs in PEn-Au-PEn rise nearly linearly with the number of carbon atoms in the PEn chain. The carbon-carbon distance in the C-Au-C moiety is around 4.1 Å, similar to the bond distance between saturated closed shell chains in the polyethylene crystal. BEs of pure saturated closed shell PEn-PEn oligomers are 51-187 kJ/mol. Both Au atoms and dispersion interactions contribute considerably to the creation of nearly parallel chains of oligomers with reasonably high binding energies.

  5. Electron beam cross-linking of natural rubber/linear-low density polyethylene blends

    International Nuclear Information System (INIS)

    Ahmad, A.; Mohd, D. H.; Abdullah, I.

    2005-01-01

    Effects of electron beam irradiation on the mechanical properties and morphological structure of natural rubber/linear-low density polyethylene blend was investigated The natural rubber/linear-low density polyethylene blend was prepared by melt blending in a Haake internal mixer at 140 d ig C , rotor speed of 50 rpm, and in 15 min Liquid natural rubber was incorporated into the blend as a compatibilizer Samples in the form of 1 mm sheets were exposed to 50-300 kGy of electron beam irradiation and analyzed for swelling index and gel content, tensile strength, and surface morphology. The result Indicated that gel content and mechanical properties of the samples increased with radiation dosage. The honey-comb structure of the surface morphology in low dosage irradiated samples slowly transformed into a continuous matrix on increasing radiation dose The variation of mechanical and physical properties was due to Increase in cross-linking density in the rubber and plastic phases and rubber-plastic Interaction on irradiation

  6. Electric long-term behaviour of polyethylene insulations for medium-voltage cables cross-linked chemically or by radiation

    International Nuclear Information System (INIS)

    Scharff, C.; Eberhardt, M.

    1989-01-01

    The electric long-term behaviour of cross-linked polyethylene (CLPE) was studied at room temperature by measuring the channel operating time under needling and the total charge before channel operation. It is found that the decomposition products formed in CLPE act as tension stabilizers. They have a dominating influence on the electric long-term behaviour

  7. Radiation-induced linking reactions in polyethylene

    International Nuclear Information System (INIS)

    Zoepfl, F.J.

    1983-01-01

    Three types of measurements are reported relating to chemical reactions in polyethylene induced by ionizing radiation: 1) viscometric and low-angle laser light scattering measurements to determine the effect of a radical scavenger on the yield of links; 2) calorimetric measurements to determine the effect of radiation-induced linking on the melting behavior of polyethylene; and 3) high-resolution solution carbon 13 nuclear magnetic resonance (NMR) spectrometry measurements to determine the nature of the links and the method of their formation. The NMR results present the first direct detection of radiation-induced long-chain branching (Y links) in polyethylene, and place an apparent upper limit on the yield of H-shaped crosslinks that are formed when polyethylene is irradiated to low absorbed doses. The effect of radiation-induced linking on the melting behavior of polyethylene was examined using differential scanning calorimetry (DSC). It was found that radiation-induced links do not change the heat of fusion of polythylene crystals, but decrease the melt entropy and increase the fold surface free energy per unit area of the crystals. The carbon 13 NMR results demonstrate that long-chain branches (Y links) are formed much more frequently than H-shaped crosslinks at low absorbed doses. The Y links are produced by reactions of alkyl free radicals with terminal vinyl groups in polyethylene

  8. Single-sided Nuclear Magnetic Resonance for condition monitoring of cross-linked polyethylene exposed to aggressive media

    Energy Technology Data Exchange (ETDEWEB)

    Adams, A., E-mail: Alina.Adams@itmc.rwth-aachen.de [Institut für Technische und Makromolekulare Chemie, RWTH Aachen University, Templergraben 55, 52056 Aachen (Germany); Piechatzek, A.; Schmitt, G. [Institut für Instandhaltung und Korrosionsschutztechnik gGmbH, Kalkofen 4, 58638 Iserlohn (Germany); Siegmund, G. [ExxonMobil Production Germany, Riethorst 12, 30659 Hannover (Germany)

    2015-08-05

    The potential of single-sided Nuclear Magnetic Resonance (NMR) to monitor truly non-invasive changes in polymer materials during aging under aggressive media is for the first time evaluated. For this, the NMR method is used in combination with other condition monitoring methods including mechanical measurements, mass uptake, and differential scanning calorimetry. It is validated by studying for the first time the aging kinetics of silane cross-linked polyethylene (PEX) exposed to media used in oil and gas production and transportation, including aliphatic and aromatic hydrocarbons, sulphur solvents, and corrosion inhibitors in combination with CO{sub 2} and H{sub 2}S. All investigated parameters changed, with the strongest effects detected for the NMR chain mobility and in the presence of hydrocarbons. Furthermore, a universal linear correlation curve could be established between the depression of the tensile strength and the chain mobility. This result represents a fundamental step towards establishing single-sided NMR as a new analytical tool for in situ condition monitoring of polyethylene working under sour conditions. The proposed approach can be easily extended to other polymer materials. - Highlights: • The changes in PEX exposed to sour media were quantified for the first time. • The strongest morphological changes in PEX were detected under exposure to hydrocarbon media. • The chain mobility measured truly non-destructively by single-sided NMR showed the highest sensitivity to the aging process. • A universal linear correlation curve was found between the chain mobility and the tensile strength. • Single-sided NMR was validated as a condition monitoring tool.

  9. New Aptes Cross-linked Polymers from Poly(ethylene oxide)s and Cyanuric Chloride for Lithium Batteries

    Science.gov (United States)

    Tigelaar, Dean M.; Meador, Mary Ann B.; Kinder, James D.; Bennett, William R.

    2005-01-01

    A new series of polymer electrolytes for use as membranes for lithium batteries are described. Electrolytes were made by polymerization between cyanuric chloride and diamino-terminated poly(ethylene oxide)s, followed by cross-linking via a sol-gel process. Thermal analysis and lithium conductivity of freestanding polymer films were studied. The effects of several variables on conductivity were investigated, such as length of backbone PEO chain, length of branching PEO chain, extent of branching, extent of cross-linking, salt content, and salt counterion. Polymer films with the highest percentage of PEO were found to be the most conductive, with a maximum lithium conductivity of 3.9 x 10(exp -5) S/cm at 25 C. Addition of plasticizer to the dry polymers increased conductivity by an order of magnitude.

  10. Vitamin C and Poly(ethylene glycol) Protect Concentrated Poly(vinyl alcohol) Solutions against Radiation Cross-linking

    International Nuclear Information System (INIS)

    Oral, E.

    2006-01-01

    There is a need for an injectable material to augment damaged cartilage. We propose to make such self-associating poly(vinyl alcohol) (PVA) hydrogels. Physical associations can be formed in PVA using a gellant such as polyethylene glycol (PEG). The injectability of PVA solutions is compromised when sterilized due to chemical cross-linking. We hypothesized that an anticross-linking agent could prevent cross-linking of irradiated PVA solutions. PVA (17.5 wt/v %, MW= 115,000 g/mol) was prepared in water at 90 degree. PEG (MW=400 g/mol) was added at a ratio of PEG unit to PVA unit of 17, 86, 290, and 639 mol/mol. PVA solutions (17.5 wt/v %, MW= 16,000, 61,000, 81,000 and 115,000 g/mol) were also prepared. Vitamin C was added at a molar ratio of vitamin C to PVA unit of 0.75-10.4. Solutions were poured into syringes and γ-irradiated. The viscosity of injectable solutions was determined by using the bubble tube. Gel content of cross-linked samples was measured by boiling gels in water for 6 hours, drying at 90 degree and calculating the ratio of dry weight to 'as is' weight

  11. Hydrogels Prepared from Cross-Linked Nanofibrillated Cellulose

    Science.gov (United States)

    Sandeep S. Nair; J.Y. Zhu; Yulin Deng; Arthur J. Ragauskas

    2014-01-01

    Nanocomposite hydrogels were developed by cross-linking nanofibrillated cellulose with poly(methyl vinyl ether-co-maleic acid) and polyethylene glycol. The cross-linked hydrogels showed enhanced water absorption and gel content with the addition of nanocellulose. In addition, the thermal stability, mechanical strength, and modulus increased with an increase in the...

  12. Differences in Femoral Head Penetration Between Highly Cross-Linked Polyethylene Cemented Sockets and Uncemented Liners.

    Science.gov (United States)

    Morita, Daigo; Seki, Taisuke; Higuchi, Yoshitoshi; Takegami, Yasuhiko; Ishiguro, Naoki

    2017-12-01

    This study aimed at investigating differences in femoral head penetration between highly cross-linked polyethylene (HXLPE) cemented sockets and uncemented liners during 5 years postoperatively. Ninety-six patients (106 hips) with a mean age of 64.4 (range, 35-83) years underwent total hip arthroplasty using a HXLPE cemented socket or liner and were respectively divided into cemented (35 patients [37 hips]) and uncemented (61 patients [69 hips]) groups. Femoral head penetrations were evaluated on both anteroposterior (AP)-view and Lauenstein-view radiographs, and mean polyethylene (PE) wear rates were calculated based on femoral head penetration from 2 to 5 years. Multivariate analyses were performed to assess risk factors for PE wear. At 5 years postoperatively, the cemented and uncemented groups exhibited proximal direction femoral head penetrations of 0.103 mm and 0.124 mm (P = .226) and anterior direction penetrations of 0.090 mm and 0.151 mm (P = .002), respectively. The corresponding mean PE wear rates were 0.004 mm/y and 0.009 mm/y in the AP-view (P = .286) and 0.005 mm/y and 0.012 mm/y in the Lauenstein-view (P = .168), respectively. Left-side operation and high activity were independent risk factors for PE wear on AP-view. When HXLPE was used, all mean PE wear rates were very low and those of cemented sockets and uncemented liners were very similar. PE particle theory suggests that the occurrence of osteolysis and related aseptic loosening might consequently decrease. Copyright © 2017 Elsevier Inc. All rights reserved.

  13. Low-friction arthroplasty of the hip using alumina ceramic and cross-linked polyethylene. A 17-year follow-up report.

    Science.gov (United States)

    Wroblewski, B M; Siney, P D; Fleming, P A

    2005-09-01

    We report the results of our continued review of 11 total hip arthroplasties using 22.225 mm alumina ceramic femoral heads on a Charnley flanged stem, articulating with chemically cross-linked polyethylene. There was an initial bedding-in of up to 0.41 mm at the articular surface in the first two years. This had not progressed further, at a minimum follow-up of 15 years. Radiographically no femoral or acetabular component showed loosening or osteolysis.

  14. Preparation of protein- and cell-resistant surfaces by hyperthermal hydrogen induced cross-linking of poly(ethylene oxide).

    Science.gov (United States)

    Bonduelle, Colin V; Lau, Woon M; Gillies, Elizabeth R

    2011-05-01

    The functionalization of surfaces with poly(ethylene oxide) (PEO) is an effective means of imparting resistance to the adsorption of proteins and the attachment and growth of cells, properties that are critical for many biomedical applications. In this work, a new hyperthermal hydrogen induced cross-linking (HHIC) method was explored as a simple one-step approach for attaching PEO to surfaces through the selective cleavage of C-H bonds and subsequent cross-linking of the resulting carbon radicals. In order to study the effects of the process on the polymer, PEO-coated silicon wafers were prepared and the effects of different treatment times were investigated. Subsequently, using an optimized treatment time and a modified butyl polymer with increased affinity for PEO, the technique was applied to butyl rubber surfaces. All of the treated surfaces exhibited significantly reduced protein adsorption and cell growth relative to control surfaces and compared favorably with surfaces that were functionalized with PEO using conventional chemical methods. Thus HHIC is a simple and effective means of attaching PEO to non-functional polymer surfaces.

  15. Wear performance of neat and vitamin E blended highly cross-linked PE under severe conditions: The combined effect of accelerated ageing and third body particles during wear test.

    Science.gov (United States)

    Affatato, Saverio; De Mattia, Jonathan Salvatore; Bracco, Pierangiola; Pavoni, Eleonora; Taddei, Paola

    2016-12-01

    The objective of this study is to evaluate the effects of third-body particles on the in vitro wear behaviour of three different sets of polyethylene acetabular cups after prolonged testing in a hip simulator and accelerated ageing. Vitamin E-blended, cross-linked polyethylene (XLPE_VE), cross-linked polyethylene (XLPE) and conventional polyethylene (STD_PE) acetabular cups were simulator tested for two million cycles under severe conditions (i.e. by adding third-body particles to the bovine calf serum lubricant). Micro-Fourier Transform Infrared and micro-Raman spectroscopic analyses, differential scanning calorimetry, and crosslink density measurements were used to characterize the samples at a molecular level. The STD_PE cups had twice mass loss than the XLPE_VE components and four times than the XLPE samples; statistically significant differences were found between the mass losses of the three sets of cups. The observed wear trend was justified on the basis of the differences in cross-link density among the samples (XLPE>XLPE_VE>STD_PE). FTIR crystallinity profiles, bulk DSC crystallinity and surface micro-Raman crystallinity seemed to have a similar behaviour upon testing: all of them (as well as the all-trans and ortho-trans contents) revealed the most significant changes in XLPE and XLPE_VE samples. The more severe third-body wear testing conditions determined more noticeable changes in all spectroscopic markers with respect to previous tests. Unexpectedly, traces of bulk oxidation were found in both STD_PE (unirradiated) and XLPE (remelting-stabilized), which were expected to be stable to oxidation; on the contrary, XLPE_VE demonstrated a high oxidative stability in the present, highly demanding conditions. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Five-Year Experience of Vitamin E-Diffused Highly Cross-Linked Polyethylene Wear in Total Hip Arthroplasty Assessed by Radiostereometric Analysis

    DEFF Research Database (Denmark)

    Nebergall, Audrey K; Troelsen, Anders; Rubash, Harry E

    2016-01-01

    BACKGROUND: Vitamin E-diffused highly cross-linked polyethylene (VEPE) was developed to reduce oxidation without compromising mechanical strength. The purpose of this study was to evaluate VEPE in vivo using radiostereometric analysis (RSA) and patient-reported outcome measures (PROMs). METHODS......: Fifty-one hips were enrolled. Each patient received a VEPE liner, a porous titanium shell, and an uncemented stem with a 32-mm cobalt-chrome femoral head. Tantalum beads were inserted into the VEPE to measure femoral head penetration using RSA. RSA radiographs and PROMs were obtained preoperatively...

  17. Process for molding improved polyethylene

    International Nuclear Information System (INIS)

    Kanai, Masanori; Aine, Norio; Nakada, Shinsaku.

    1962-01-01

    Various configurations in size and shape of polyethylene are molded by: (a) irradiating powders of polyethylene with ionizing radiations in the presence of oxygen to the extent of producing substantially no cross-linking among the molecules of polyethylene, and thereafter (b) molding the thus irradiated powders of polyethylene at 100-250 0 C to cross-link the molding. In this process, a uniform and desirable degree of cross-linking and any desirable configuration are provided for the polyethylene molding. Any extruder and any molding machine producing heat can be employed in this process. In embodiments, the radiation dose units may preferably be 1x10 6 to 1.5x10 7 roentgen. The ionizing radiations may be X-rays, gamma-rays or electron beams, but preferably gamma-rays. The preheating prior to molding may be effected in vacuum, in inert gas, or in oxygen at 100-250 0 C, but preferably in oxygen at 100 0 C. In an example, a polyethylene powder of 100 mesh was irradiated with gamma-rays from a Co-60 source with a dose of 3.1x10 6 r at a dose rate of 5.5x10 4 r/hr in air, then preheated in air at 80 0 C for 1 hr, and finally extruded to form a rod of 5 mm phi at 200 0 C. max. The degree of product cross-linking was 0% after irradiation in step (a), and 38% after heating in step (b). (Iwakiri, K.)

  18. Dually actuated triple shape memory polymers of cross-linked polycyclooctene-carbon nanotube/polyethylene nanocomposites.

    Science.gov (United States)

    Wang, Zhenwen; Zhao, Jun; Chen, Min; Yang, Minhao; Tang, Luyang; Dang, Zhi-Min; Chen, Fenghua; Huang, Miaoming; Dong, Xia

    2014-11-26

    In this work, electrically and thermally actuated triple shape memory polymers (SMPs) of chemically cross-linked polycyclooctene (PCO)-multiwalled carbon nanotube (MWCNT)/polyethylene (PE) nanocomposites with co-continuous structure and selective distribution of fillers in PCO phase are prepared. We systematically studied not only the microstructure including morphology and fillers' selective distribution in one phase of the PCO/PE blends, but also the macroscopic properties including thermal, mechanical, and electrical properties. The co-continuous window of the immiscible PCO/PE blends is found to be the volume fraction of PCO (vPCO) of ca. 40-70 vol %. The selective distribution of fillers in one phase of co-continuous blends is obtained by a masterbatch technique. The prepared triple SMP materials show pronounced triple shape memory effects (SMEs) on the dynamic mechanical thermal analysis (DMTA) and the visual observation by both thermal and electric actuations. Such polyolefin samples with well-defined microstructure, electrical actuation, and triple SMEs might have potential applications as, for example, multiple autochoke elements for engines, self-adjusting orthodontic wires, and ophthalmic devices.

  19. Effects of Surface Modification and Bulk Geometry on the Biotribological Behavior of Cross-Linked Polyethylene: Wear Testing and Finite Element Analysis.

    Science.gov (United States)

    Watanabe, Kenichi; Kyomoto, Masayuki; Saiga, Kenichi; Taketomi, Shuji; Inui, Hiroshi; Kadono, Yuho; Takatori, Yoshio; Tanaka, Sakae; Ishihara, Kazuhiko; Moro, Toru

    2015-01-01

    The wear and creep deformation resistances of polymeric orthopedic bearing materials are both important for extending their longevity. In this study, we evaluated the wear and creep deformation resistances, including backside damage, of different polyethylene (PE) materials, namely, conventional PE, cross-linked PE (CLPE), and poly(2-methacryloyloxyethyl phosphorylcholine)- (PMPC-) grafted CLPE, through wear tests and finite element analysis. The gravimetric and volumetric degrees of wear of disks (3 or 6 mm in thickness) of these materials against a cobalt-chromium-molybdenum alloy pin were examined using a multidirectional pin-on-disk tester. Cross-linking and PMPC grafting decreased the gravimetric wear of the PE disks significantly. The volumetric wear at the bearing surface and the volumetric penetration in the backside of the 3-mm thick PE disk were higher than those of the 6-mm thick PE disk, regardless of the bearing material. The geometrical changes induced in the PE disks consisted of creep, because the calculated internal von Mises stress at the bearing side of all disks and that at the backside of the 3-mm thick disks exceeded their actual yield strengths. A highly hydrated bearing surface layer, formed by PMPC grafting, and a cross-linking-strengthened substrate of adequate thickness are essential for increasing the wear and creep deformation resistances.

  20. Core Cross-Linked Multiarm Star Polymers with Aggregation-Induced Emission and Temperature Responsive Fluorescence Characteristics

    KAUST Repository

    Zhang, Zhen; Bilalis, Panagiotis; Zhang, Hefeng; Gnanou, Yves; Hadjichristidis, Nikolaos

    2017-01-01

    Aggregation-induced emission (AIE) active core cross-linked multiarm star polymers, carrying polystyrene (PS), polyethylene (PE), or polyethylene-b-polycaprolactone (PE-b-PCL) arms, have been synthesized through an “arm-first” strategy, by atom

  1. Thermal stability of radiation-modified polyethylene

    International Nuclear Information System (INIS)

    Vinogradova, T.B.; Sirota, A.G.; Bal'tenas, R.A.; Stanyavichus, V.I.; Knebel'man, A.M.; Sil'chenko, S.A.

    1989-01-01

    In the work reported here, the authors investigated the thermooxidative resistance, at temperatures from 373 to 473 K, of polyethylene that had been cross-linked by exposure to radiation and formulated with various heat stabilizers. Thus, these studies of the thermooxidative resistance of polyethylene-based compositions that have been cross-linked by the radiation-chemical method have shown that, in this particular series of heat-stabilizers, the greatest effect at temperatures of 373-473 K is given by the FAU-13. The DTPhDMI has the greatest heat-stabilizing effect in the temperature interval 448-473 K, whereas the heat resistance of materials containing Diaphen NN or Phenozan-23 is higher at 373-423 K. These comparative results are in agreement with data for unirradiated and chemically cross-linked polyethylene

  2. Heat shrinkable behavior, physico-mechanical and structure properties of electron beam cross-linked blends of high-density polyethylene with acrylonitrile-butadiene rubber

    International Nuclear Information System (INIS)

    Reinholds, Ingars; Kalkis, Valdis; Merijs-Meri, Remo; Zicans, Janis; Grigalovica, Agnese

    2016-01-01

    In this study, heat-shrinkable composites of electron beam irradiated high-density polyethylene (HDPE) composites with acrylonitrile-butadiene rubber (NBR) were investigated. HDPE/NBR blends at a ratio of components 100/0, 90/10, 80/20, 50/50 and 20/80 wt% were prepared using a two-roll mill. The compression molded films were irradiated high-energy (5 MeV) accelerated electrons up to irradiation absorbed doses of 100–300 kGy. The effect of electron beam induced cross-linking was evaluated by the changes of mechanical properties, gel content and by the differences of thermal properties, detected by differential scanning calorimetry. The thermo-shrinkage forces were determined as the kinetics of thermorelaxation and the residual shrinkage stresses of previously oriented (stretched up to 100% at above melting temperature of HDPE and followed by cooling to room temperature) specimens of irradiated HDPE/NBR blends under isometric heating–cooling mode. The compatibility between the both components was enhanced due to the formation of cross-linked sites at amorphous interphase. The results showed increase of mechanical stiffness of composites with increase of irradiation dose. The values of gel fraction compared to thermorelaxation stresses increased with the growth of irradiation dose level, as a result of formation cross-linked sites in amorphous PP/NBR interphase. - Highlights: • Binary blends of HDPE/NBR have been irradiated with 5 MeV accelerated electrons. • Increase of NBR content and irradiation dose improves cross-linking efficiency. • Thermo-shrinkage and residual stresses are investigated for oriented specimens. • Cross-linked HDPE/NBR composites can be successfully used as thermos-shrinkable materials.

  3. Heat shrinkable behavior, physico-mechanical and structure properties of electron beam cross-linked blends of high-density polyethylene with acrylonitrile-butadiene rubber

    Science.gov (United States)

    Reinholds, Ingars; Kalkis, Valdis; Merijs-Meri, Remo; Zicans, Janis; Grigalovica, Agnese

    2016-03-01

    In this study, heat-shrinkable composites of electron beam irradiated high-density polyethylene (HDPE) composites with acrylonitrile-butadiene rubber (NBR) were investigated. HDPE/NBR blends at a ratio of components 100/0, 90/10, 80/20, 50/50 and 20/80 wt% were prepared using a two-roll mill. The compression molded films were irradiated high-energy (5 MeV) accelerated electrons up to irradiation absorbed doses of 100-300 kGy. The effect of electron beam induced cross-linking was evaluated by the changes of mechanical properties, gel content and by the differences of thermal properties, detected by differential scanning calorimetry. The thermo-shrinkage forces were determined as the kinetics of thermorelaxation and the residual shrinkage stresses of previously oriented (stretched up to 100% at above melting temperature of HDPE and followed by cooling to room temperature) specimens of irradiated HDPE/NBR blends under isometric heating-cooling mode. The compatibility between the both components was enhanced due to the formation of cross-linked sites at amorphous interphase. The results showed increase of mechanical stiffness of composites with increase of irradiation dose. The values of gel fraction compared to thermorelaxation stresses increased with the growth of irradiation dose level, as a result of formation cross-linked sites in amorphous PP/NBR interphase.

  4. Three Year RSA Evaluation of Vitamin E Diffused Highly Cross-linked Polyethylene Liners and Cup Stability.

    Science.gov (United States)

    Sillesen, Nanna H; Greene, Meridith E; Nebergall, Audrey K; Nielsen, Poul T; Laursen, Mogens B; Troelsen, Anders; Malchau, Henrik

    2015-07-01

    Vitamin E diffusion into highly cross-linked polyethylene (E-XLPE) is a method for enhancing oxidative stability of acetabular liners. The purpose of this study was to evaluate in vivo penetration of E-XLPE using radiostereometric analysis (RSA). Eighty-four hips were recruited into a prospective 10-year RSA. This is the first evaluation of the multicenter cohort after 3-years. All patients received E-XLPE liners (E1, Biomet) and porous-titanium coated cups (Regenerex, Biomet). There was no difference (P=0.450) in median femoral head penetration into the E-XLPE liners at 3-years comparing cobalt-chrome heads (-0.028mm; inter-quartile range (IQR) - 0.065 to 0.047) with ceramic heads (-0.043mm, IQR - 0.143to0.042). The 3-year follow-up indicates minimal E-XLPE liner penetration regardless of head material and minimal early cup movement. Copyright © 2015 Elsevier Inc. All rights reserved.

  5. Seasonal and interannual cross-shelf transport over the Texas and Louisiana continental shelf

    Science.gov (United States)

    Thyng, Kristen M.; Hetland, Robert D.

    2018-05-01

    Numerical drifters are tracked in a hydrodynamic simulation of circulation over the Texas-Louisiana shelf to analyze patterns in cross-shelf transport of materials. While the important forcing mechanisms in the region (wind, river, and deep eddies) and associated flow patterns are known, the resultant material transport is less well understood. The primary metric used in the calculations is the percent of drifters released within a region that cross the 100 m isobath. Results of the analysis indicate that, averaged over the eleven years of the simulation, there are two regions on the shelf - over the Texas shelf during winter, and over the Louisiana shelf in summer - with increased seasonal probability for offshore transport. Among the two other distinct regions, the big bend region in Texas has increased probability for onshore transport, and the Mississippi Delta region has an increase in offshore transport, for both seasons. Some of these regions of offshore transport have marked interannual variability. This interannual variability is correlated to interannual changes in forcing conditions. Winter transport off of the Texas shelf is correlated with winter mean wind direction, with more northerly winds enhancing offshore transport; summer transport off the Louisiana shelf is correlated with Mississippi River discharge.

  6. Collagen cross-linking in sun-exposed and unexposed sites of aged human skin

    Science.gov (United States)

    Yamauchi, M.; Prisayanh, P.; Haque, Z.; Woodley, D. T.

    1991-01-01

    A recently described nonreducible, acid-heat stable compound, histidinohydroxylysinonorleucine (HHL), is a collagen cross-link isolated from mature skin tissue. Its abundance is related to chronologic aging of skin. The present communication describes the quantity of HHL from aged human skin of the same individuals in sun-exposed (wrist) and unexposed (buttock) sites. Punch biopsies were obtained from these sites from nine people of age 60 or older. HHL contents (moles/mole of collagen) at these sites were for wrist 0.13 +/- 0.07 and for buttock 0.69 +/- 0.17 (mean +/- SD, p less than 0.001). In addition, it was found that acute irradiation of the cross-linked peptides with UVA (up to 250 J/cm2) and UVB (up to 1 J/cm2) had no effect on HHL structure. The same treatment significantly degraded another nonreducible, stable collagen cross-link, pyridinoline. The results suggest that chronic sunlight exposure may be associated with an impediment to normal maturation of human dermal collagen resulting in tenuous amount of HHL. Thus, the process of photoaging in dermal collagen is different from that of chronologic aging in human skin.

  7. Wear resistant performance of highly cross-linked and annealed ultra-high molecular weight polyethylene against ceramic heads in total hip arthroplasty.

    Science.gov (United States)

    Sato, Taishi; Nakashima, Yasuharu; Akiyama, Mio; Yamamoto, Takuaki; Mawatari, Taro; Itokawa, Takashi; Ohishi, Masanobu; Motomura, Goro; Hirata, Masanobu; Iwamoto, Yukihide

    2012-12-01

    The purpose of this study was to examine the effects of ceramic femoral head material, size, and implantation periods on the wear of annealed, cross-linked ultra-high molecular weight polyethylene (UHMWPE) (XLPE) in total hip arthroplasty compared to non-cross-linked conventional UHMWPE (CPE). XLPE was fabricated by cross-linking with 60 kGy irradiation and annealing. Femoral heads made from zirconia and alumina ceramics and cobalt-chrome (CoCr) of 22 or 26 mm diameter were used. In this retrospective cohort study, the femoral head penetration into the cup was measured digitally on radiographs of 367 hips with XLPE and 64 hips with CPE. The average follow-up periods were 6.3 and 11.9 years, respectively. Both XLPE creep and wear rates were significantly lower than those of CPE (0.19 mm vs. 0.44 mm, 0.0001 mm/year vs. 0.09 mm/year, respectively). Zirconia displayed increased wear rates compared to alumina in CPE; however, there was no difference among head materials in XLPE (0.0008, 0.00007, and -0.009 mm/year for zirconia, alumina, and CoCr, respectively). Neither head size or implantation period impacted XLPE wear. In contrast to CPE, XLPE displayed low wear rates surpassing the effects of varying femoral head material, size, implantation period, and patient demographics. Further follow-up is required to determine the long-term clinical performance of the annealed XLPE. Copyright © 2012 Orthopaedic Research Society.

  8. Reactive electrospinning and biodegradation of cross-linked methacrylated polycarbonate nanofibers

    Energy Technology Data Exchange (ETDEWEB)

    Wu Ruizhi; Zhang Jianfeng; Fan Yuwei; Xu Xiaoming [Department of Comprehensive Dentistry and Biomaterials, Louisiana State University Health Sciences Center, 1100 Florida Avenue, Box 137, New Orleans, LA 70119 (United States); Stoute, Diana; Lallier, Thomas, E-mail: xxu@lsuhsc.edu [Department of Cell Biology and Anatomy, Louisiana State University Health Science Center, 1100 Florida Avenue, Box 137, New Orleans, LA 70119 (United States)

    2011-06-15

    The objectives of this study were to fabricate cross-linked biodegradable polycarbonate nanofibers and to investigate their biodegradability by different enzymes. Poly(2,3-dihydroxycarbonate) was synthesized from naturally occurring l-tartaric acid. The hydroxyl groups on the functional polycarbonate were converted to methacrylate groups to enable the polymer to cross-link under UV irradiation. Smooth cross-linked methacrylated polycarbonate nanofibers (300-1800 nm) were fabricated by a reactive electrospinning process with in situ UV radiation from a mixed solution of linear methacrylated polycarbonate (MPC) and poly(ethylene oxide) (PEO) (MPC:PEO = 9:1) in methanol/chloroform (50/50). These cross-linked nanofibers have shown excellent solvent resistance and their solubility decreases with increasing degree of cross-linking. The thermal properties of linear and cross-linked polycarbonate nanofibers were investigated by differential scanning calorimetry and thermogravimetric analysis. The cross-linked polycarbonate nanofibers show no melting point below 200 {sup 0}C and their decomposition temperature increases with increasing cross-linking degree. Their biodegradation products by five different enzymes were analyzed using liquid chromatography-mass spectrometry (LC-MS). The biodegradability of the polycarbonate nanofibers decreases with increasing cross-linking degree. These nanofibers were found to support human fibroblast survival and to promote cell attachment. This study demonstrates that cross-linked biodegradable polycarbonate nanofibers with different chemical properties and biodegradability can be fabricated using the novel reactive electrospinning technology to meet the needs of different biomedical applications.

  9. Observations of radiation damage effects in paraffin and polyethylene crystals

    International Nuclear Information System (INIS)

    Petermann, J.; Gleiter, H.; Bochum Univ.

    1973-01-01

    A report is given on electron microscopic observations on n-paraffin and polyethylene monocrystals after irradiating with electrons. The observations show that the cross-links in n-paraffin monocrystals form agglomerates which preferably occur in the neighbourhood of lattice defects. In polyethylene monocrystals, the cross-links line up in long rows parallel to the [100] or [010] direction. (orig./LH) [de

  10. Polyethylene as a possible hvdc cable insulant

    Energy Technology Data Exchange (ETDEWEB)

    Hawley, W.G.; Body, R.S.; Mason, J.H.

    1966-10-01

    Many cable authorities have expressed the view that polyethylene would be attractive for this application. The dc conductivity of polyethylene is lower than that of impregnated paper, and varies less with temperature and stress. Polyethylene also has higher thermal conductivity and is resistant to moisture and electrochemical deterioration. Furthermore, processing polyethylene cables should ultimately involve lower capital and manufacturing costs. However, polyethylene has a lower limiting short circuit temperature unless it is cross linked.

  11. Equal channel angular extrusion of ultra-high molecular weight polyethylene

    Energy Technology Data Exchange (ETDEWEB)

    Reinitz, Steven D., E-mail: Steven.D.Reinitz.TH@Dartmouth.edu; Engler, Alexander J.; Carlson, Evan M.; Van Citters, Douglas W.

    2016-10-01

    Ultra-high molecular weight polyethylene (UHMWPE), a common bearing surface in total joint arthroplasty, is subject to material property tradeoffs associated with conventional processing techniques. For orthopaedic applications, radiation-induced cross-linking is used to enhance the wear resistance of the material, but cross-linking also restricts relative chain movement in the amorphous regions and hence decreases toughness. Equal Channel Angular Extrusion (ECAE) is proposed as a novel mechanism by which entanglements can be introduced to the polymer bulk during consolidation, with the aim of imparting the same tribological benefits of conventional processing without complete inhibition of chain motion. ECAE processing at temperatures near the crystalline melt for UHMWPE produces (1) increased entanglements compared to control materials; (2) increasing entanglements with increasing temperature; and (3) mechanical properties between values for untreated polyethylene and for cross-linked polyethylene. These results support additional research in ECAE-processed UHMWPE for joint arthroplasty applications. - Highlights: • A new processing method for ultra-high molecular weight polyethylene is introduced. • The process produces a highly entangled polyethylene material. • Entanglements are hypothesized to enhance the wear resistance of polyethylene. • This process eliminates the trade-off between mechanical and wear properties.

  12. Controlled swollen and drug release from urea-cross-linked polyether/siloxane hybrids

    International Nuclear Information System (INIS)

    Santilli, Celso V.; Lopes, Leandro; Pulcinelli, Sandra H.; Chiavacci, Leila A.; Oliveira, Anselmo G.

    2009-01-01

    From a simple synthesis method we produced transparent ureasil cross-linked polyether (poly(ethylene oxide), PEO, or poly (propylene oxide), PPO) networks, whose designed inter cross-linking distance and tunable swell ability was assessed by small angle X-ray scattering on the D11A-SAXS1 beamline of the LNLS, we demonstrated that the controlled drug release from swell able hydrophilic ureasil-PEO materials can be sustained during some days, while from the unswell able ureasil-PPO ones, during some weeks. This outstanding feature conjugated with the bio medically safe formulation of the ureasil cross-linked polyether/siloxane hybrid widen their scope of application to include the domain of soft and implantable drug delivery devices. (author)

  13. Cross-shore flow on the inner-shelf off southwest Portugal

    Science.gov (United States)

    Lamas, L.; Peliz, A.; Oliveira, P.; Dias, J.

    2012-04-01

    Velocity measurements from 4 bottom-mounted ADCP deployments (summers of 2006, 2007, 2008 and 2011) at a 12-m depth site off Sines, Portugal, complemented with time series of winds, waves and tides, are used to study the inner-shelf cross-shore flow dependence on wave, tidal and wind forcings. During these four summers, the dominating winds are from the north (upwelling-favorable), with strong diurnal sea breeze cycle throughout these periods. This quasi-steady wind circulation is sometimes interrupted by short event-like reversals. The observed records were split in different subsets according to tidal amplitude, wave height, cross- and along-shore wind magnitudes, and the vertical structure of the cross-shore flow was studied for each of these subsets. Despite different forcing conditions, the cross-shore velocity profiles usually show a vertical parabolic structure with maximum onshore flow at mid-depth, resembling the upwelling return flow for mid-shelf conditions, but atypical for the inner-shelf and in disagreement with other inner-shelf studies from other sites. We compare the observations with simplified 2D inner-shelf models and with results from other studies.

  14. Process for producing chlorinated polyethylene

    International Nuclear Information System (INIS)

    Nose, Shinji; Takayama, Shin-ichi; Kodama, Takashi.

    1970-01-01

    A process for chlorinated polyethylene by the chlorination of an aqueous suspension of polyethylene without the use catalysts is given, using 5-55% by gel content of cross-linked polyethylene powders. The products have favorable material workability, transparency, impact strength and tensile properties. In the case of peroxide cross-linking, a mixture of peroxides with polyethylene must be ground after heat treatment. The polyethylene may preferably have a gel content of 5-55%. The chlorination temperature may be 40 0 C or more, preferably 60 0 to 160 0 C. In one example, high pressure polymerized fine polyethylene powders of 15μ having a density of 0.935 g/cc, a softening point of 114 0 C, an average molecular weight of 35,000 were irradiated in air with 40 Mrad electron beams from a 2 MV Cockcroft-Walton type accelerator at room temperature. The thus irradiated polyethylene had a gel content of 55% and a softening point of 119 0 C. It was chlorinated upto a chlorine content of 33% at 100 0 C. Products were white crystals having a melting point of 122 0 C and a melting heat value of 32 mcal/mg. A sheet formed from this product showed a tensile strength of 280 kg/cm 2 , an elongation of 370% and a hardness of 90. (Iwakiri, K.)

  15. Thermally stimulated current of electron beam irradiation cross-linked polyethylene, (3)

    International Nuclear Information System (INIS)

    Aihara, Mitsugu; Aida, Fumio; Shiono, Takeo

    1984-01-01

    In the past, electron-beam irradiation was for the most part applied to rather thin insulation electric cables. Considering application to thick insulation, high voltage power cables (6.6 kV or more), the authors experimented on the charge accumulation and crystallizing properties of polyethylene due to irradiation, using three differently crystallizing samples, high and low density polyethylenes (HDPE and LDPE) and straight chain low density polyethylene (LLDPE), and have obtained some findings. Those are summarized as follows. (1) The crystallizing properties (crystallinity, the size of spherulite, etc.) of polyethylene varied according to the cooling condition, and affected the thermally stimulated current (TSC). (2) In HDPE and LDPE, the behaviour of crystallization differed. In HDPE, fine crystals decreased, and spherulites significantly grew in slow cooling, but in LDPE, the generation of fine crystals and the growth of spherulites simultaneously progressed. (3) The TSC peak area for HDPE was scarcely affected by slow cooling, but that for LDPE greatly increased. (4) The TSC of irradiated polyethylene showed peaks corresponding to the melting temperatures of fine crystals and spherulites when collecting voltage Vc was lowered. (5) The above facts suggest that fine crystals and spherulites took part as charge trap sites, but the aspect of participation was different in HDPE and LDPE. (6) LLDPE has the properties of both HDPE and LDPE in view of the crystallinity, charge accumulation was small, and it was hard to be affected by cooling condition. Accordingly, it seemed to be an interesting material as the PE for irradiation. A differential scanning calorimeter and laser small angle scattering method were used for the analysis of the measured results of TSC. (Wakatsuki, Y.)

  16. Influence of irradiation conditions on the gamma irradiation effect in polyethylene

    International Nuclear Information System (INIS)

    Kacarevic-Popovic, Z.; Gal, O.; Novakovic, L.J.; Secerov, B.

    2002-01-01

    Complete text of publication follows. The radiation cross-linking of polyethylene, due to its high cross-linking yield, has resulted in the radiation technology that has found application in radiation production of heat shrinkable structures and in improvement of mechanical and thermo-physical properties of oriented polyethylene objects. It is observed that the cross-linking efficiency decreases when the irradiation is carried out in the presence of oxygen. In order to estimate the conditions that improve cross-linking efficiency, gamma irradiation effect in two types of polyethylene, irradiated in water and air was investigated. The polyethylene samples used were the low density (LDPE) Lotrene CdF 0302 with 45% crystallinity and the high density (HDPE) Hiplex EHM 6003 with 73% crystallinity. Both kinds of samples, fixed in the Pyrex glass tubes, were simultaneously irradiated with 60 Co gamma rays in distilled water and air, at a doses rate of 9,5 kGy/h (determined by the Fricke dosimeter) at room temperature. Radiation induced oxidative degradation was followed through oxygen containing group formation by the carbonyl group band (1720 cm -1 ) and transvinylene group formation by the band at 966 cm -1 in the infrared spectra. Cross-linking efficiency was determined by gel content using the procedure of the extraction in xylene. The monitored effects of gamma irradiation in water and air point to the conclusion that irradiation in water leads to the lower oxidative degradation and higher cross-linking compared with the effects measured after irradiation in air

  17. Rheological behaviour of polyethylene with peroxide crosslinking agent. Ismaeil Ghasemi, Peter Szabo and Henrik Koblitz Rasmussen

    DEFF Research Database (Denmark)

    Rasmussen, Henrik K.; Ghasemi, Ismaeil; Szabo, Peter

    2003-01-01

    One of the most important post-reactor modifications of polyethylene is cross-linking. Cross-linking improves some properties of polyethylene such as: environmental stress cracking resistance (ECSR), chemical and abrasion resistance, service temperature etc. In this study the rheological variation...

  18. Polymeric micelles with ionic cores containing biodegradable cross-links for delivery of chemotherapeutic agents.

    Science.gov (United States)

    Kim, Jong Oh; Sahay, Gaurav; Kabanov, Alexander V; Bronich, Tatiana K

    2010-04-12

    Novel functional polymeric nanocarriers with ionic cores containing biodegradable cross-links were developed for delivery of chemotherapeutic agents. Block ionomer complexes (BIC) of poly(ethylene oxide)-b-poly(methacylic acid) (PEO-b-PMA) and divalent metal cations (Ca(2+)) were utilized as templates. Disulfide bonds were introduced into the ionic cores by using cystamine as a biodegradable cross-linker. The resulting cross-linked micelles with disulfide bonds represented soft, hydrogel-like nanospheres and demonstrated a time-dependent degradation in the conditions mimicking the intracellular reducing environment. The ionic character of the cores allowed to achieve a very high level of doxorubicin (DOX) loading (50% w/w) into the cross-linked micelles. DOX-loaded degradable cross-linked micelles exhibited more potent cytotoxicity against human A2780 ovarian carcinoma cells as compared to micellar formulations without disulfide linkages. These novel biodegradable cross-linked micelles are expected to be attractive candidates for delivery of anticancer drugs.

  19. Novel chemically cross-linked solid state electrolyte for dye-sensitized solar cells

    International Nuclear Information System (INIS)

    Yin Xiong; Tan Weiwei; Xiang Wangchun; Lin Yuan; Zhang Jingbo; Xiao Xurui; Li Xueping; Zhou Xiaowen; Fang Shibi

    2010-01-01

    Poly(vinylpyridine-co-ethylene glycol methyl ether methacrylate) (P(VP-co-MEOMA)) and α,ω-diiodo poly(ethylene oxide-co-propylene oxide) (I[(EO) 0.8 -co-(PO) 0.2 ] y I) were synthesized and used as chemically cross-linked precursors of the electrolyte for dye-sensitized solar cells. Meanwhile, α-iodo poly(ethylene oxide-co-propylene oxide) methyl ether (CH 3 O[(EO) 0.8 -co-(PO) 0.2 ] x I) was synthesized and added into the electrolyte as an internal plasticizer. Novel polymer electrolyte resulting from chemically cross-linked precursors was obtained by the quaterisation at 90 o C for 30 min. The characteristics for this kind of electrolyte were investigated by means of ionic conductivity, thermogravimetric and photocurrent-voltage. The ambient ionic conductivity was significantly enhanced to 2.3 x 10 -4 S cm -1 after introducing plasticizer, modified-ionic liquid. The weight loss of the solid state electrolyte at 200 o C was 1.8%, and its decomposition temperature was 287 o C. Solid state dye-sensitized solar cell based on chemically cross-linked electrolyte presented an overall conversion efficiency of 2.35% under AM1.5 irradiation (100 mW cm -2 ). The as-fabricated device maintained 88% of its initial performance at room temperature even without sealing for 30 days, showing a good stability.

  20. Core Cross-Linked Multiarm Star Polymers with Aggregation-Induced Emission and Temperature Responsive Fluorescence Characteristics

    KAUST Repository

    Zhang, Zhen

    2017-05-19

    Aggregation-induced emission (AIE) active core cross-linked multiarm star polymers, carrying polystyrene (PS), polyethylene (PE), or polyethylene-b-polycaprolactone (PE-b-PCL) arms, have been synthesized through an “arm-first” strategy, by atom transfer radical copolymerization (ATRP) of a double styrene-functionalized tetraphenylethene (TPE-2St) used as a cross-linker with linear arm precursors possessing terminal ATRP initiating moieties. Polyethylene macroinitiator (PE–Br) was prepared via the polyhomologation of dimethylsulfoxonium methylide with triethylborane followed by oxidation/hydrolysis and esterification of the produced PE–OH with 2-bromoisobutyryl bromide; polyethylene-block-poly(ε-caprolactone) diblock macroinitiator was derived by combining polyhomologation with ring-opening polymerization (ROP). All synthesized star polymers showed AIE-behavior either in solution or in bulk. At high concentration in good solvents (e.g., THF, or toluene) they exhibited low photoluminescence (PL) intensity due to the inner filter effect. In sharp contrast to the small molecule TPE-2St, the star polymers were highly emissive in dilute THF solutions. This can be attributed to the cross-linked structure of poly(TPE-2St) core which restricts the intramolecular rotation and thus induces emission. In addition, the PL intensity of PE star polymers in THF(solvent)/n-hexane(nonsolvent) mixtures, due to their nearly spherical shape, increased when the temperature decreased from 55 to 5 °C with a linear response in the range 40–5 °C.

  1. Links between phytoplankton dynamics and shell growth of Arctica islandica on the Faroe Shelf

    Science.gov (United States)

    Bonitz, Fabian Georg Wulf; Andersson, Carin; Trofimova, Tamara; Hátún, Hjálmar

    2018-03-01

    The phytoplankton dynamics on the Faroe Shelf are strongly connected to higher trophic levels, and their inter-annual variability has great importance for many organisms, including the principal fish stocks. Hence, information on the marked phytoplankton variability is scientifically and economically valuable. We show here that the shell growth variability in Arctica islandica shells has the potential to identify periods of increased and decreased phytoplankton concentrations on the Faroe Shelf and in the wider Faroese region in previous centuries. The growth of A. islandica has often been linked to changes in phytoplankton concentrations, i.e., food availability. By cross-matching life-collected and sub-fossil A. islandica shells from two separate locations on the Faroe Shelf, we have built a master chronology, which reaches back to the 17th century. This master chronology correlates well with a Primary Production index for the Faroe Shelf (r = 0.65; p phytoplankton concentrations over the wider Faroese Channel Region, as represented in the Continuous Plankton Recorder surveys, especially for the months June-September (r = 0.39; p < 0.01). In addition, an inverse relationship is observed between the master chronology and on-shelf water temperatures from June-September (r = - 0.29; p < 0.01), which is likely associated with a previously reported inverse relationship between temperatures and the on-shelf primary production. An analysis of the δ18O in the shells shows that the main growing season of the shells presumably occurs during the spring and summer months, which concurs with the main spring bloom.

  2. Radiation modification and interaction mechanism of polypropylene and polyethylene by protons and electrons

    International Nuclear Information System (INIS)

    Wang Guanghou

    1988-10-01

    A systematic investigation of radiation effects on isotactic polypropylene (PP) and low-density polyethylene (PE) films by protons and electrons is reported. Electrons can make polyethylene cross-linked and polypropylene crached while protons can improve the PP mechanical properties and deteriorate polyethylene with increasing the irradiation dose. The structural analysis shows that conversion between α and β phases occurs and the crystallinity remains constant in the electron-irradiated polypropylene whereas the network structure is formed by allyl-type radicals in the e - -irradiated polyethylene. The infrared spectra indicate that conformational changes have taken place in the polypropylene under proton bombardment, such as the transition from an ordered to a disordered state in the crystalline region, the formation of double bonds as well as trans-conformations. This leads to the cross-linking between macromolecules of polypropylene at the proper irradiation doses, thus enhancing its mechanical properties. The cross-linking of polypropylene by proton bombardment observed and its properties may have some potential applications

  3. Epoxides cross-linked hexafluoropropylidene polybenzimidazole membranes for application as high temperature proton exchange membranes

    International Nuclear Information System (INIS)

    Yang, Jingshuai; Xu, Yixin; Liu, Peipei; Gao, Liping; Che, Quantong; He, Ronghuan

    2015-01-01

    Covalently cross-linked hexafluoropropylidene polybenzimidazole (F 6 PBI) was prepared and used to fabricate high temperature proton exchange membranes with enhanced mechanical strength against thermoplastic distortion. Three different epoxides, i.e. bisphenol A diglycidyl ether (R 1 ), bisphenol A propoxylate diglycidyl ether (R 2 ) and poly(ethylene glycol) diglycidyl ether (R 3 ), were chosen as the cross-linkers to investigate the influence of their structures on the properties of the cross-linked F 6 PBI membranes. All the cross-linked F 6 PBI membranes displayed excellent stability towards the radical oxidation. Comparing with the pure F 6 PBI membrane, the cross-linked F 6 PBI membranes showed high acid doping level but less swelling after doping phosphoric acid at elevated temperatures. The mechanical strength at 130 °C was improved from 0.4 MPa for F 6 PBI membrane to a range of 0.8–2.0 MPa for the cross-linked F 6 PBI membranes with an acid doping level as high as around 14, especially for that crosslinking with the epoxide (R 3 ), which has a long linear structure of alkyl ether. The proton conductivity of the cross-linked membranes was increased accordingly due to the high acid doping levels. Fuel cell tests demonstrated the technical feasibility of the acid doped cross-linked F 6 PBI membranes for high temperature proton exchange membrane fuel cells

  4. Smart surface coating of drug nanoparticles with cross-linkable polyethylene glycol for bio-responsive and highly efficient drug delivery

    Science.gov (United States)

    Wei, Weijia; Zhang, Xiujuan; Chen, Xianfeng; Zhou, Mengjiao; Xu, Ruirui; Zhang, Xiaohong

    2016-04-01

    Many drug molecules can be directly used as nanomedicine without the requirement of any inorganic or organic carriers such as silica and liposome nanostructures. This new type of carrier-free drug nanoparticles (NPs) has great potential in clinical treatment because of its ultra-high drug loading capacity and biodegradability. For practical applications, it is essential for such nanomedicine to possess robust stability and minimal premature release of therapeutic molecules during circulation in the blood stream. To meet this requirement, herein, we develop GSH-responsive and crosslinkable amphiphilic polyethylene glycol (PEG) molecules to modify carrier-free drug NPs. These PEG molecules can be cross-linked on the surface of the NPs to endow them with greater stability and the cross-link is sensitive to intracellular environment for bio-responsive drug release. With this elegant design, our experimental results show that the liberation of DOX from DOX-cross-linked PEG NPs is dramatically slower than that from DOX-non-cross-linked PEG NPs, and the DOX release profile can be controlled by tuning the concentration of the reducing agent to break the cross-link between PEG molecules. More importantly, in vivo studies reveal that the DOX-cross-linked PEG NPs exhibit favorable blood circulation half-life (>4 h) and intense accumulation in tumor areas, enabling effective anti-cancer therapy. We expect this work will provide a powerful strategy for stabilizing carrier-free nanomedicines and pave the way to their successful clinical applications in the future.Many drug molecules can be directly used as nanomedicine without the requirement of any inorganic or organic carriers such as silica and liposome nanostructures. This new type of carrier-free drug nanoparticles (NPs) has great potential in clinical treatment because of its ultra-high drug loading capacity and biodegradability. For practical applications, it is essential for such nanomedicine to possess robust stability

  5. Alumina-on-Polyethylene Bearing Surfaces in Total Hip Arthroplasty.

    Science.gov (United States)

    Jung, Yup Lee; Kim, Shin-Yoon

    2010-02-11

    The long-term durability of polyethylene lining total hip arthroplasty (THA) mainly depends on periprosthetic osteolysis due to wear particles, especially in young active patients. In hip simulator study, reports revealed significant wear reduction of the alumina ceramic-on-polyethylene articulation of THA compared with metal-on-polyethylene bearing surfaces. However, medium to long-term clinical studies of THA using the alumina ceramic-on-polyethylene are few and the reported wear rate of this articulation is variable. We reviewed the advantages and disadvantages of ceramicon- polyethylene articulation in THA, hip simulator study and retrieval study for polyethylene wear, in vivo clinical results of THA using alumina ceramic-on-polyethylene bearing surfaces in the literature, and new trial alumina ceramic-onhighly cross linked polyethylene bearing surfaces.

  6. Light-induced cross-linking and post-cross-linking modification of polyglycidol.

    Science.gov (United States)

    Marquardt, F; Bruns, M; Keul, H; Yagci, Y; Möller, M

    2018-02-08

    The photoinduced radical generation process has received renewed interest due to its economic and ecological appeal. Herein the light-induced cross-linking of functional polyglycidol and its post-cross-linking modification are presented. Linear polyglycidol was first functionalized with a tertiary amine in a two-step reaction. Dimethylaminopropyl functional polyglycidol was cross-linked in a UV-light mediated reaction with camphorquinone as a type II photoinitiator. The cross-linked polyglycidol was further functionalized by quaternization with various organoiodine compounds. Aqueous dispersions of the cross-linked polymers were investigated by means of DLS and zeta potential measurements. Polymer films were evaluated by DSC and XPS.

  7. Photocrosslinker technology: An antimicrobial efficacy of cinnamaldehyde cross-linked low-density polyethylene (Cin-C-LDPE) as a novel food wrapper.

    Science.gov (United States)

    Manukumar, H M; Umesha, S

    2017-12-01

    In recent years much attention has been devoted to active packaging technologies that offer new opportunities for the food industry and food preservation. The spoilage of food products during post process handling leads to food contamination and causes life-threatening food-borne illness. The methicillin-resistant Staphylococcus aureus (MRSA) 090 is one of the food-borne pathogens associated with food poisoning that leads to an outbreak of perilous human infections worldwide. The development of resistance in bacteria and diffusion of coated synthetic preservatives into food are the major problem in food packaging industries. In the present work, we have developed a new food wrap method by cross-linking cinnamaldehyde on low-density polyethylene (Cin-C-LDPE) using novel photocrosslinker technology. The cinnamaldehyde showed potent antimicrobial activity (145mg/mL of MIC) against MRSA 090 and radical scavenging activity (RSA). The cinnamaldehyde was successfully cross-linked to LDPE and exhibited excellent antibiofilm properties against MRSA090 compared to bare LDPE. This positive interaction of developed Cin-C-LDPE against MRSA090 biofilm was confirmed by SEM and FT-IR studies, and results showed the damaged cell membrane architecture, inturn abridged adherence of MRSA090. The Cin-C-LDPE wrapped chicken, mutton, cheese, and grapes showed 2.5±0.15 log MRSA 090 reduction at the end of 10th day compared to the bare LDPE wrapped food samples. This clearly concludes that for the first time we have developed a novel Cin-C-LDPE food wrap technology effectively involved in biocidal activity against MRSA090. Applying this new strategy to develop food wrap containing nontoxic natural antimicrobial to target cell membrane components is the upcoming challenging and promising research gap remains in the food packaging industry for the future world. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Effect of shelf aging on vibration transmissibility of anti-vibration gloves

    Science.gov (United States)

    SHIBATA, Nobuyuki

    2017-01-01

    Anti-vibration gloves have been used in real workplaces to reduce vibration transmitted through hand-held power tools to the hand. Generally materials used for vibration attenuation in gloves are resilient materials composed of certain synthetic and/or composite polymers. The mechanical characteristics of the resilient materials used in anti-vibration gloves are prone to be influenced by environmental conditions such as temperature, humidity, and photo-irradiation, which cause material degradation and aging. This study focused on the influence of shelf aging on the vibration attenuation performance of air-packaged anti-vibration gloves following 2 yr of shelf aging. Effects of shelf aging on the vibration attenuation performance of anti-vibration gloves were examined according to the Japan industrial standard JIS T8114 test protocol. The findings indicate that shelf aging induces the reduction of vibration attenuation performance in air-packaged anti-vibration gloves. PMID:28978817

  9. Dynamics of internal waves on the Southeast Florida shelf: Implications for cross-shelf exchange and turbulent mixing on a barrier reef system

    Science.gov (United States)

    Davis, Kristen Alexis

    The dynamics of internal waves shoaling on the Southeast Florida shelf and the resulting stratified turbulence in the shelf bottom boundary layer are investigated using observational studies completed during the summers of 2003-2005. This work is driven by a desire to understand the effects of internal wave-driven flow and the shoreward transport of cool, nutrient-rich water masses on cross-shelf exchange, vertical mixing, and mass transfer to benthic reef organisms. Shelf sea internal wave fields are typically highly variable and dominated by wind and tidal forces. However, this is not necessarily true for outer shelf regions or very narrow shelves where remote physical processes originating over the slope or deep ocean may exert a strong influence on the internal wave climate. During the summers of 2003 and 2004 observational studies were conducted to examine the effects of a western boundary current (the Florida Current), tides, and wind on the mean currents and internal wave field on the outer Southeast Florida shelf. We present evidence that suggests that the Florida Current plays as large a role in the determination of the high frequency internal wave field as tidal forces. These observations and analyses show that it is necessary to include the forcing from the Florida Current meanders and instabilities in order to predict accurately the episodic nature of the internal wave field on the Southeast Florida shelf. Deep ocean and continental shelf processes intersect at the shelf edge and influence the exchange of water masses and their associated characteristics including heat, nutrients, sediment, and larvae across the shelf. Thus, the dynamics of cross-shelf circulation have important consequences for organisms living on the shelf. In the second phase of this work, we investigate physical mechanisms controlling the exchange of water masses during the summer season across the Southeast Florida shelf. A time series of cross-shelf transport from May to August

  10. Modification of mature non-reducible collagen cross-link concentrations in bovine m. gluteus medius and semitendinosus with steer age at slaughter, breed cross and growth promotants.

    Science.gov (United States)

    Roy, B C; Sedgewick, G; Aalhus, J L; Basarab, J A; Bruce, H L

    2015-12-01

    Increased meat toughness with animal age has been attributed to mature trivalent collagen cross-link formation. Intramuscular trivalent collagen cross-link content may be decreased by reducing animal age at slaughter and/or inducing muscle re-modeling with growth promotants. This hypothesis was tested in m. gluteus medius (GM) and m. semitendinosus (ST) from 112 beef steers finished at either 12 to 13 (rapid growth) or 18 to 20 (slow growth) months of age. Hereford-Aberdeen Angus (HAA) or Charolais-Red Angus (CRA) steers were randomly assigned to receive implants (IMP), ractopamine (RAC), both IMP and RAC, or none (control). RAC decreased pyridinoline (mol/mol collagen) and IMP increased Ehrlich chromogen (EC) (mol/mol collagen) in the GM. In the ST, RAC increased EC (mol/mol collagen) but decreased EC (nmol/g raw muscle) in slow growing CRA steers. Also, IMP increased ST pyridinoline (nmol/g raw muscle) of slow-growing HAA steers. Results indicated alteration of perimysium collagen cross-links content in muscle in response to growth promotants. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Product analysis for polyethylene degradation by radiation and thermal ageing

    International Nuclear Information System (INIS)

    Sugimoto, Masaki; Shimada, Akihiko; Kudoh, Hisaaki; Tamura, Kiyotoshi; Seguchi, Tadao

    2013-01-01

    The oxidation products in crosslinked polyethylene for cable insulation formed during thermal and radiation ageing were analyzed by FTIR-ATR. The products were composed of carboxylic acid, carboxylic ester, and carboxylic anhydride for all ageing conditions. The relative yields of carboxylic ester and carboxylic anhydride increased with an increase of temperature for radiation and thermal ageing. The carboxylic acid was the primary oxidation product and the ester and anhydride were secondary products formed by the thermally induced reactions of the carboxylic acids. The carboxylic acid could be produced by chain scission at any temperature followed by the oxidation of the free radicals formed in the polyethylene. The results of the analysis led to formulation of a new oxidation mechanism which was different from the chain reactions via peroxy radicals and peroxides. - Highlights: ► Products analysis of polyethylene degradation by radiation and thermal ageing. ► Components of carbonyl compounds produced in polyethylene by thermal and radiation oxidation were determined by FTIR. ► Carbonyl compounds comprised carboxylic acid, carboxylic ester, and carboxylic anhydride. ► Carboxylic acid was the primary oxidation product of chain scission at any oxidation temperature. ► Carboxylic ester and carboxylic anhydride are secondary products formed from carboxylic acid at higher temperature.

  12. Surface grafting of poly(ethylene glycol) onto poly(acrylamide-co-vinyl amine) cross-linked films under mild conditions.

    Science.gov (United States)

    Yamamoto, Y; Sefton, M V

    1998-01-01

    Poly(ethylene glycol) (PEG) was grafted onto poly(acrylamide-co-vinyl amine) (poly(AM-co-VA)) film using tresylated PEG (TPEG) at 37 degrees C in aqueous buffers (pH 7.4) with a view to surface-modifying microencapsulated mammalian cells. Poly(AM-co-VA) film was synthesized by Hofmann degradation of a cross-linked poly(acrylamide) film. Conversion to vinyl amine on the surface of the film was approximately 50%, but bulk conversion was not observed; surface specificity was thought to be the result of cleavage of aminated polymer chains at the surface due to chain scission. Reaction between primary amine and TPEG gave a graft yield of 2 mol% (based on XPS) with respect to available surface amine groups, equivalent to 54 mol% ethylene oxide based on monomer units. Physical adsorption of non-activated polymer was done under identical conditions as a control and the difference in oxygen content was significant compared to TPEG. The type of buffer agent and buffer concentration did not influence graft yields. This graft reaction, which was completed in as little as 2 h was considered to be mild enough to be used for a surface modification of microcapsules containing cells without affecting their viability. Such a surface modification technique may prove to be a useful means of enhancing the biocompatibility of microcapsules (or any tissue engineering construct) even after cell encapsulation or seeding.

  13. Thirteen-Year Evaluation of Highly Cross-Linked Polyethylene Articulating With Either 28-mm or 36-mm Femoral Heads Using Radiostereometric Analysis and Computerized Tomography

    DEFF Research Database (Denmark)

    Nebergall, Audrey K; Greene, Meridith E; Rubash, Harry E

    2016-01-01

    BACKGROUND: The objective of this 13-year prospective evaluation of highly cross-linked ultra high molecular weight polyethylene (HXLPE) was to (1) assess the long-term wear of HXLPE articulating with 2 femoral head sizes using radiostereometric analysis (RSA) and to (2) determine if osteolysis...... is a concern with this material through the use of plain radiographs and computerized tomography (CT). METHODS: All patients received a Longevity HXLPE liner with tantalum beads and either a 28-mm or 36-mm femoral head. Twelve patients (6 in each head size group) agreed to return for 13-year RSA, plain...... scan revealed areas of remodeling of this graft. One patient's 13-year plain radiographs showed evidence of cup loosening and linear radiolucencies in zones 2 and 3. CONCLUSION: There was no evidence of significant wear over time using RSA. The CT scans did not show evidence of osteolysis due to wear...

  14. Application of polymers cross-linked by electron beam irradiation to electric wire industry

    International Nuclear Information System (INIS)

    Oda, Eisuke

    1976-01-01

    Applications of the polymers cross-linked by electron beam irradiation to electric wire industry as an example of dully developed utilization are reviewed. The report is divided into five parts, namely 1) radiation sources and irradiation processes, 2) development of crosslinking materials, 3) accumulation of electric charge and accumulation of heat, 4) examples of application, and 5) future prospect. Such a phenomenon as discharge destruction pattern (Lichtenberg figure) must be solved, when cable insulation materials are cross-linked by electron beam irradiation. The measures for preventing the discharge destruction are required, especially when the layers of polyethylene insulation for high voltage cables are irradiated. The accumulation of heat causes the troubles in foaming, degeneration and wire running of high potential cables, when the layers of insulation are thick. Effective promoters for cross-linking must be studied to reduce the radiation dose. The irradiators capable of irradiating wires uniformly are desirable. Electron beam accelerators will be used, as far as the radiation dose of 10 or more Mrad is required for cross-linking irradiation. If the dose of one tenth or less of the above value is required, gamma-ray sources (RI) are rather easily applicable than focused strong beam. The utilization of spent nuclear fuel is desirable. (Iwakiri, K.)

  15. Lack of cross-shelf transport of sediments on the western margin of India: Evidence from clay mineralogy

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaswamy, V.; Nair, R.R.

    transported long distances along the shelf, cross-shelf transport appears to be minimal. Confirmatory evidence of qualitative differences in outer and inner shelf clays is provided by sediment trap clay mineralogy on the outer shelf. Clay bound pollutant...

  16. Compartmentalization Technologies via Self-Assembly and Cross-Linking of Amphiphilic Random Block Copolymers in Water.

    Science.gov (United States)

    Matsumoto, Mayuko; Terashima, Takaya; Matsumoto, Kazuma; Takenaka, Mikihito; Sawamoto, Mitsuo

    2017-05-31

    Orthogonal self-assembly and intramolecular cross-linking of amphiphilic random block copolymers in water afforded an approach to tailor-make well-defined compartments and domains in single polymer chains and nanoaggregates. For a double compartment single-chain polymer, an amphiphilic random block copolymer bearing hydrophilic poly(ethylene glycol) (PEG) and hydrophobic dodecyl, benzyl, and olefin pendants was synthesized by living radical polymerization (LRP) and postfunctionalization; the dodecyl and benzyl units were incorporated into the different block segments, whereas PEG pendants were statistically attached along a chain. The copolymer self-folded via the orthogonal self-assembly of hydrophobic dodecyl and benzyl pendants in water, followed by intramolecular cross-linking, to form a single-chain polymer carrying double yet distinct hydrophobic nanocompartments. A single-chain cross-linked polymer with a chlorine terminal served as a globular macroinitiator for LRP to provide an amphiphilic tadpole macromolecule comprising a hydrophilic nanoparticle and a hydrophobic polymer tail; the tadpole thus self-assembled into multicompartment aggregates in water.

  17. Multi-stimulus-responsive shape-memory polymer nanocomposite network cross-linked by cellulose nanocrystals.

    Science.gov (United States)

    Liu, Ye; Li, Ying; Yang, Guang; Zheng, Xiaotong; Zhou, Shaobing

    2015-02-25

    In this study, we developed a thermoresponsive and water-responsive shape-memory polymer nanocomposite network by chemically cross-linking cellulose nanocrystals (CNCs) with polycaprolactone (PCL) and polyethylene glycol (PEG). The nanocomposite network was fully characterized, including the microstructure, cross-link density, water contact angle, water uptake, crystallinity, thermal properties, and static and dynamic mechanical properties. We found that the PEG[60]-PCL[40]-CNC[10] nanocomposite exhibited excellent thermo-induced and water-induced shape-memory effects in water at 37 °C (close to body temperature), and the introduction of CNC clearly improved the mechanical properties of the mixture of both PEG and PCL polymers with low molecular weights. In addition, Alamar blue assays based on osteoblasts indicated that the nanocomposites possessed good cytocompatibility. Therefore, this thermoresponsive and water-responsive shape-memory nanocomposite could be potentially developed into a new smart biomaterial.

  18. Radiation cross-linked plastics: a versatile material solution for packaging, automotive, Electrotechnic and Electronics

    International Nuclear Information System (INIS)

    Rouif, Sophie

    2004-01-01

    Used since the beginning of the 1970s for the production of halogen-free and heat-resistant cables and wires, for conditioning polyethylene hot-water pipes or for the manufacture of heat shrinkable tubes and of tyres, radiation cross-linking is developing fastly today on the scale of plastic-moulded parts, and not only by the mean of EB, but also under gamma rays. Indeed, it improves considerably the performances of a great number of plastics among thermoplastics, elastomers and thermoplastic elastomers (TPE). Radiation cross-linking reinforces the dimensional stability of polymers in chemically aggressive and high-temperature conditions. Radiation cross-linked-based engineering plastics offers OEM and end users in many branches of industry both technical and economical advantages in comparison with high-performances plastics. They constitute a technical and economical compromise between engineering plastics that failed and high-performances plastic, often over-tailored and expensive. This modern industrial technology gives way to new applications and perspectives in various sectors (packaging, automotive, electrotechnic and electronics, including connectors, surface-mounted devices, integrated circuits, 3D-MID, etc.) that are described in the paper

  19. Supercritical CO2 impregnation of polyethylene components for medical purposes

    Directory of Open Access Journals (Sweden)

    Gamse Thomas

    2007-01-01

    Full Text Available Modem hip and knee endoprosthesis are produced in titanium and to reduce the friction at the contact area polymer parts, mainly ultra-high molecular weight polyethylene (UHMW-PE, are installed. The polyethylene is impregnated with a-tocopherol (vitamin E before processing for remarkable decrease of oxidative degradation. Cross linked UHMW-PE offers much higher stability, but a-tocopherol cannot be added before processing, because a-tocopherol hinders the cross linking process accompanied by a heavy degradation of the vitamin. The impregnation of UHMW-PE with a-tocopherol has to be performed after the cross linking process and an accurate concentration has to be achieved over the cross section of the whole material. In the first tests UHMW-PE-cubes were stored in pure a-tocopherol under inert atmosphere at temperatures from 100 to 150 °C resulting in a high mass fraction of a-tocopherol in the edge zones and no constant concentration over the cross section. For better distribution and for regulating the mass fraction of a-tocopherol in the cross linked UHMW-PE material supercritical CO2 impregnation tests were investigated. Again UHMW-PE-cubes were impregnated in an autoclave with a-tocopherol dissolved in supercritical CO2 at different pressures and temperatures with variable impregnation times and vitamin E concentrations. Based on the excellent results of supercritical CO2 impregnation standard hip and knee cups were stabilized nearly homogeneously with varying mass fraction of a-tocopherol.

  20. Polyethylene Glycol Modified, Cross-Linked Starch Coated Iron Oxide Nanoparticles for Enhanced Magnetic Tumor Targeting

    Science.gov (United States)

    Cole, Adam J.; David, Allan E.; Wang, Jianxin; Galbán, Craig J.; Hill, Hannah L.; Yang, Victor C.

    2010-01-01

    While successful magnetic tumor targeting of iron oxide nanoparticles has been achieved in a number of models, the rapid blood clearance of magnetically suitable particles by the reticuloendothelial system (RES) limits their availability for targeting. This work aimed to develop a long-circulating magnetic iron oxide nanoparticle (MNP) platform capable of sustained tumor exposure via the circulation and, thus, enhanced magnetic tumor targeting. Aminated, cross-linked starch (DN) and aminosilane (A) coated MNPs were successfully modified with 5 kDa (A5, D5) or 20 kDa (A20, D20) polyethylene glycol (PEG) chains using simple N-Hydroxysuccinimide (NHS) chemistry and characterized. Identical PEG-weight analogues between platforms (A5 & D5, A20 & D20) were similar in size (140–190 nm) and relative PEG labeling (1.5% of surface amines – A5/D5, 0.4% – A20/D20), with all PEG-MNPs possessing magnetization properties suitable for magnetic targeting. Candidate PEG-MNPs were studied in RES simulations in vitro to predict long-circulating character. D5 and D20 performed best showing sustained size stability in cell culture medium at 37°C and 7 (D20) to 10 (D5) fold less uptake in RAW264.7 macrophages when compared to previously targeted, unmodified starch MNPs (D). Observations in vitro were validated in vivo, with D5 (7.29 hr) and D20 (11.75 hr) showing much longer half-lives than D (0.12 hr). Improved plasma stability enhanced tumor MNP exposure 100 (D5) to 150 (D20) fold as measured by plasma AUC0-∞ Sustained tumor exposure over 24 hours was visually confirmed in a 9L-glioma rat model (12 mg Fe/kg) using magnetic resonance imaging (MRI). Findings indicate that both D5 and D20 are promising MNP platforms for enhanced magnetic tumor targeting, warranting further study in tumor models. PMID:21176955

  1. Cross-shelf transport into nearshore waters due to shoaling internal tides in San Pedro Bay, CA

    Science.gov (United States)

    Noble, Marlene A.; Burt Jones,; Peter Hamilton,; Xu, Jingping; George Robertson,; Rosenfeld, Leslie; John Largier,

    2009-01-01

    In the summer of 2001, a coastal ocean measurement program in the southeastern portion of San Pedro Bay, CA, was designed and carried out. One aim of the program was to determine the strength and effectiveness of local cross-shelf transport processes. A particular objective was to assess the ability of semidiurnal internal tidal currents to move suspended material a net distance across the shelf. Hence, a dense array of moorings was deployed across the shelf to monitor the transport patterns associated with fluctuations in currents, temperature and salinity. An associated hydrographic program periodically monitored synoptic changes in the spatial patterns of temperature, salinity, nutrients and bacteria. This set of measurements show that a series of energetic internal tides can, but do not always, transport subthermocline water, dissolved and suspended material from the middle of the shelf into the surfzone. Effective cross-shelf transport occurs only when (1) internal tides at the shelf break are strong and (2) subtidal currents flow strongly downcoast. The subtidal downcoast flow causes isotherms to tilt upward toward the coast, which allows energetic, nonlinear internal tidal currents to carry subthermocline waters into the surfzone. During these events, which may last for several days, the transported water remains in the surfzone until the internal tidal current pulses and/or the downcoast subtidal currents disappear. This nonlinear internal tide cross-shelf transport process was capable of carrying water and the associated suspended or dissolved material from the mid-shelf into the surfzone, but there were no observation of transport from the shelf break into the surfzone. Dissolved nutrients and suspended particulates (such as phytoplankton) transported from the mid-shelf into the nearshore region by nonlinear internal tides may contribute to nearshore algal blooms, including harmful algal blooms that occur off local beaches.

  2. Long-term study of migration of volatile organic compounds from cross-linked polyethylene (PEX) pipes and effects on drinking water quality.

    Science.gov (United States)

    Lund, Vidar; Anderson-Glenna, Mary; Skjevrak, Ingun; Steffensen, Inger-Lise

    2011-09-01

    The objectives of this study were to investigate migration of volatile organic compounds (VOCs) from cross-linked polyethylene (PEX) pipes used for drinking water produced by different production methods, and to evaluate their potential risk for human health and/or influence on aesthetic drinking water quality. The migration tests were carried out in accordance with EN-1420-1, and VOCs were analysed by gas chromatography-mass spectrometry. The levels of VOC migrating from new PEX pipes were generally low, and decreasing with time of pipe use. No association was found between production method of PEX pipes and concentration of migration products. 2,4-di-tert-butyl phenol and methyl tert-butyl ether (MTBE) were two of the major individual components detected. In three new PEX pipes, MTBE was detected in concentrations above the recommended US EPA taste and odour value for drinking water, but decreased below this value after 5 months in service. However, the threshold odour number (TON) values for two pipes were similar to new pipes even after 1 year in use. For seven chemicals for which conclusions on potential health risk could be drawn, this was considered of no or very low concern. However, odour from some of these pipes could negatively affect drinking water for up to 1 year.

  3. Antimicrobial compounds in polyethylene films - characterization and content measurement techniques

    International Nuclear Information System (INIS)

    Pires, Marcia; Santos, Ramon V.; Perao, Leandro; Ellwangler, Manoela W.; Nonemacher, Regina F.; Moraes, Lilian T. de; Gorski, Sandro; Staub, Simone; Petzhold, Cesar L.

    2009-01-01

    Developments have been done in the packaging market to attend the continuous changes in consumer demands and also to keep safety and shelf life of products during transportation and storage. Active packaging is the most innovative concepts in the market. It has been defined as a packaging that changes its conditions to extend shelf life. The objective of this work is the production and characterization of active polyethylene films with antimicrobial compounds. The initial results show that analytical techniques as RX fluorescence and FTIR can be used to characterize and quantify these compounds in polyethylene films. (author)

  4. A Multicenter Approach Evaluating the Impact of Vitamin E-Blended Polyethylene in Cementless Total Hip Replacement

    Science.gov (United States)

    Jäger, Marcus; van Wasen, Andrea; Warwas, Sebastian; Landgraeber, Stefan; Haversath, Marcel; Group, VITAS

    2014-01-01

    Since polyethylene is one of the most frequently used biomaterials as a liner in total hip arthroplasty, strong efforts have been made to improve design and material properties over the last 50 years. Antioxidants seems to be a promising alternative to further increase durability and reduce polyethylene wear in long term. As of yet, only in vitro results are available. While they are promising, there is yet no clinical evidence that the new material shows these advantages in vivo. To answer the question if vitamin-E enhanced ultra-high molecular weight polyethylene (UHMWPE) is able to improve long-term survivorship of cementless total hip arthroplasty we initiated a randomized long-term multicenter trial. Designed as a superiority study, the oxidation index assessed in retrieval analyses of explanted liners was chosen as primary parameter. Radiographic results (wear rate, osteolysis, radiolucency) and functional outcome (Harris Hip Scores, University of California-Los Angeles, Hip Disability and Osteoarthritis Outcome Score, Visual Analogue Scale) will serve as secondary parameters. Patients with the indication for a cementless total hip arthroplasty will be asked to participate in the study and will be randomized to either receive a standard hip replacement with a highly cross-linked UHMWPE-X liner or a highly cross-linked vitamin-E supplemented UHMWPE-XE liner. The follow-up will be 15 years, with evaluation after 5, 10 and 15 years. The controlled randomized study has been designed to determine if Vitamin-E supplemented highly cross-linked polyethylene liners are superior to standard XLPE liners in cementless total hip arthroplasty. While several studies have been started to evaluate the influence of vitamin-E, most of them evaluate wear rates and functional results. The approach used for this multicenter study, to analyze the oxidation status of retrieved implants, should make it possible to directly evaluate the ageing process and development of the implant

  5. A multicenter approach evaluating the impact of vitamin E-blended polyethylene in cementless total hip replacement

    Directory of Open Access Journals (Sweden)

    Marcus Jäger

    2014-04-01

    Full Text Available Since polyethylene is one of the most frequently used biomaterials as a liner in total hip arthroplasty, strong efforts have been made to improve design and material properties over the last 50 years. Antioxidants seems to be a promising alternative to further increase durability and reduce polyethylene wear in long term. As of yet, only in vitro results are available. While they are promising, there is yet no clinical evidence that the new material shows these advantages in vivo. To answer the question if vitamin-E enhanced ultra-high molecular weight polyethylene (UHMWPE is able to improve long-term survivorship of cementless total hip arthroplasty we initiated a randomized long-term multicenter trial. Designed as a superiority study, the oxidation index assessed in retrieval analyses of explanted liners was chosen as primary parameter. Radiographic results (wear rate, osteolysis, radiolucency and functional outcome (Harris Hip Scores, University of California-Los Angeles, Hip Disability and Osteoarthritis Outcome Score, Visual Analogue Scale will serve as secondary parameters. Patients with the indication for a cementless total hip arthroplasty will be asked to participate in the study and will be randomized to either receive a standard hip replacement with a highly cross-linked UHMWPE-X liner or a highly cross-linked vitamin-E supplemented UHMWPE-XE liner. The follow-up will be 15 years, with evaluation after 5, 10 and 15 years. The controlled randomized study has been designed to determine if Vitamin-E supplemented highly cross-linked polyethylene liners are superior to standard XLPE liners in cementless total hip arthroplasty. While several studies have been started to evaluate the influence of vitamin-E, most of them evaluate wear rates and functional results. The approach used for this multicenter study, to analyze the oxidation status of retrieved implants, should make it possible to directly evaluate the ageing process and development

  6. Dose rate effect on material aging due to radiation. [Gamma radiation

    Energy Technology Data Exchange (ETDEWEB)

    Okamoto, Shin-ichi (Radiation Center of Osaka Prefecture, Sakai (Japan)); Hayakawa, Chikara; Takeya, Chikashi

    1982-12-01

    Although many reports have been presented on the radiation aging of the organic materials for electric cables, those have been based on the experiments carried out at high dose rate near 1 x 10/sup 6/ rad/h, assuming that aging effect depends on only radiation dose. Therefore, to investigate the aging behaviour in low dose rate range is an important subject to predict their practical life time. In this report, the results of having investigated the aging behaviour of six types of materials are described, (polyethylene for general insulation purpose, chemically cross-linked polyethylene, fire-retardant chemically cross-linked polyethylene, fire-retardant ethylene-propylene rubber, fire-retardant chloro-sulfonated polyethylene for sheaths, and fire-retardant, low hydrochloric acid, special heat-resistant vinyl for insulation purpose or chloroclean). They were irradiated with /sup 60/Co ..gamma..-ray at the dose from 5 x 10/sup 3/ to 1 x 10/sup 6/ rad/h, and their deterioration was tested for the items of elongation, tensile strength, resistivity, dielectric tangent and gel fraction. The aging mechanism and dose rate effect were also considered. The dose rate effect appeared or did not appear depending on the types of materials and also their properties. The materials that showed the dose rate effect included the typical ones whose characteristics degraded with the decreasing dose rate, and the peculiar ones whose deterioration of characteristics did not appear constantly. Aging mechanism may vary in the case of high dose rate and low dose rate. Also, if the life time at respective dose rate in relatively higher dose rate region is clarified, the life time in low dose rate region may possibly be predicted.

  7. Radiation cross-linked collagen/dextran dermal scaffolds: effects of dextran on cross-linking and degradation.

    Science.gov (United States)

    Zhang, Yaqing; Zhang, Xiangmei; Xu, Ling; Wei, Shicheng; Zhai, Maolin

    2015-01-01

    Ionizing radiation effectively cross-links collagen into network with enhanced anti-degradability and biocompatibility, while radiation-cross-linked collagen scaffold lacks flexibility, satisfactory surface appearance, and performs poor in cell penetration and ingrowth. To make the radiation-cross-linked collagen scaffold to serve as an ideal artificial dermis, dextran was incorporated into collagen. Scaffolds with the collagen/dextran (Col/Dex) ratios of 10/0, 7/3, and 5/5 were fabricated via (60)Co γ-irradiation cross-linking, followed by lyophilization. The morphology, microstructure, physicochemical, and biological properties were investigated. Compared with pure collagen, scaffolds with dextran demonstrated more porous appearance, enhanced hydrophilicity while the cross-linking density was lower with the consequence of larger pore size, higher water uptake, as well as reduced stiffness. Accelerated degradation was observed when dextran was incorporated in both the in vitro and in vivo assays, which led to earlier integration with cell and host tissue. The effect of dextran on degradation was ascribed to the decreased cross-linking density, looser microstructure, more porous and hydrophilic surface. Considering the better appearance, softness, moderate degradation rate due to controllable cross-linking degree and good biocompatibility as well, radiation-cross-linked collagen/dextran scaffolds are expected to serve as promising artificial dermal substitutes.

  8. CrossWork: Software-assisted identification of cross-linked peptides

    DEFF Research Database (Denmark)

    Rasmussen, Morten; Refsgaard, Jan; Peng, Li

    2011-01-01

    Work searches batches of tandem mass-spectrometric data, and identifies cross-linked and non-cross-linked peptides using a standard PC. We tested CrossWork by searching mass-spectrometric datasets of cross-linked complement factor C3 against small (1 protein) and large (1000 proteins) search spaces, and show...

  9. Randomized cross-over trial of polyethylene glycol electrolyte solution and water for colostomy irrigation.

    Science.gov (United States)

    O'Bichere, Austin; Green, Colin; Phillips, Robin K S

    2004-09-01

    Water for colostomy irrigation is largely absorbed by the colon, which may result in less efficient expulsion of stool. This study compared the outcome of colonic cleansing with water and polyethylene glycol solution. In a cross-over study, 41 colostomy irrigators were randomly assigned to water or polyethylene glycol solution irrigation first and then the other regimen, each for one week. Patients recorded fluid inflow time, total washout time, cramps, leakage episodes, number of stoma pouches used, and satisfaction scores (Visual Analog Scale, 1-10: 1 = poor, and 10 = excellent). The median and interquartile range for each variable was calculated, and the two treatments were compared (Wilcoxon's test). Eight patients failed to complete the study. Thirty-three patients (20 females; mean age, 55 (range, 39-73) years) provided 352 irrigation sessions: water (n = 176), and polyethylene glycol solution (n = 176). Irrigation was performed every 24, 48, and 72 hours by 17, 9, and 7 patients respectively, using 500 ml (n = 1), 750 ml (n = 2), 1,000 ml (n = 16), 1,500 ml (n = 11), 2,000 ml (n = 2), and 3,500 ml (n = 1) of fluid. The median and interquartile range for water vs. polyethylene glycol solution were: fluid inflow time (6 (range, 4.4-10.8) vs. 6.3 (range, 4.1-11) minutes; P = 0.48), total washout time (53 (range, 33-69) vs. 38 (range, 28-55) minutes; P = 0.01), leakage episodes (2.3 (range, 1.7-3.8) vs. 0.7 (range, 0.2-1); P colostomy irrigation.

  10. Cross-linking of polymeric materials

    International Nuclear Information System (INIS)

    Bloom, L.I.; Du Plessis, T.A.; Meij, G.O.

    1991-01-01

    The invention provides a method of producing a cured polymeric artifact from a polymeric thermoplastic starting material, the material of the artifact having reduced thermoplasticity relative to the starting material and exhibiting an enhanced degree of cross-linking relative to the starting material. The method includes subjecting a polymeric thermoplastic starting material, which is capable of being cross-linked by irradiation, to sufficient irradiation partially to cross-linked the starting material to produce a thermoplastic partially cross-linked intermediate material. The thermoplasticity of the intermediate material is then reduced by heating it to raise its melting point. The invention also provides a method of making a partially cross-linked feedstocks and a master batch for use in making such artifacts

  11. The salinity signature of the cross-shelf exchanges in the Southwestern Atlantic Ocean: Numerical simulations.

    Science.gov (United States)

    Matano, Ricardo P; Combes, Vincent; Piola, Alberto R; Guerrero, Raul; Palma, Elbio D; Ted Strub, P; James, Corinne; Fenco, Harold; Chao, Yi; Saraceno, Martin

    2014-11-01

    A high-resolution model is used to characterize the dominant patterns of sea surface salinity (SSS) variability generated by the freshwater discharges of the Rio de la Plata (RdlP) and the Patos/Mirim Lagoon in the southwestern Atlantic region. We identify three dominant modes of SSS variability. The first two, which have been discussed in previous studies, represent the seasonal and the interannual variations of the freshwater plumes over the continental shelf. The third mode of SSS variability, which has not been discussed hitherto, represents the salinity exchanges between the shelf and the deep ocean. A diagnostic study using floats and passive tracers identifies the pathways taken by the freshwater plumes. During the austral winter (JJA) , the plumes leave the shelf region north of the BMC. During the austral summer (DJF), the plumes are entrained more directly into the BMC. A sensitivity study indicates that the high - frequency component of the wind stress forcing controls the vertical structure of the plumes while the low-frequency component of the wind stress forcing and the interannual variations of the RdlP discharge controls the horizontal structure of the plumes. Dynamical analysis reveals that the cross-shelf flow has a dominant barotropic structure and, therefore, the SSS anomalies detected by Aquarius represent net mass exchanges between the shelf and the deep ocean. The net cross-shelf volume flux is 1.21 Sv. This outflow is largely compensated by an inflow from the Patagonian shelf.

  12. Use of Activated Carbon in Packaging to Attenuate Formaldehyde-Induced and Formic Acid-Induced Degradation and Reduce Gelatin Cross-Linking in Solid Dosage Forms.

    Science.gov (United States)

    Colgan, Stephen T; Zelesky, Todd C; Chen, Raymond; Likar, Michael D; MacDonald, Bruce C; Hawkins, Joel M; Carroll, Sophia C; Johnson, Gail M; Space, J Sean; Jensen, James F; DeMatteo, Vincent A

    2016-07-01

    Formaldehyde and formic acid are reactive impurities found in commonly used excipients and can be responsible for limiting drug product shelf-life. Described here is the use of activated carbon in drug product packaging to attenuate formaldehyde-induced and formic acid-induced drug degradation in tablets and cross-linking in hard gelatin capsules. Several pharmaceutical products with known or potential vulnerabilities to formaldehyde-induced or formic acid-induced degradation or gelatin cross-linking were subjected to accelerated stability challenges in the presence and absence of activated carbon. The effects of time and storage conditions were determined. For all of the products studied, activated carbon attenuated drug degradation or gelatin cross-linking. This novel use of activated carbon in pharmaceutical packaging may be useful for enhancing the chemical stability of drug products or the dissolution stability of gelatin-containing dosage forms and may allow for the 1) extension of a drug product's shelf-life when the limiting attribute is a degradation product induced by a reactive impurity, 2) marketing of a drug product in hotter and more humid climatic zones than currently supported without the use of activated carbon, and 3) enhanced dissolution stability of products that are vulnerable to gelatin cross-linking. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

  13. Eddy-induced cross-shelf export of high Chl-a coastal waters in the SE Bay of Biscay

    KAUST Repository

    Rubio, Anna

    2017-12-08

    Different remote sensing data were combined to characterise a winter anticyclonic eddy in the southeastern Bay of Biscay and to infer its effects on cross-shelf exchanges, in a period when typical along shelf-slope currents depict a cyclonic pattern. While the joint analysis of available satellite data (infrared, visible and altimetry) permitted the characterisation and tracking of the anticyclone properties and path, data from a coastal high-frequency radar system enabled a quantitative analysis of the surface cross-shelf transports associated with this anticyclone. The warm core anticyclone had a diameter of around 50km, maximum azimuthal velocities near 50cms−1 and a relative vorticity of up to −0.45f. The eddy generation occurred after the relaxation of a cyclonic wind-driven current regime over the shelf-slope; then, the eddy remained stationary for several weeks until it started to drift northwards along the shelf break. The surface signature of this eddy was observed by means of high-frequency radar data for 20 consecutive days, providing a unique opportunity to characterise and quantify, from a Lagrangian perspective, the associated transport and its effect on the Chl-a surface distribution. We observed the presence of mesoscale structures with similar characteristics in the area during different winters within the period 2011–2014. Our results suggest that the eddy-induced recurrent cross-shelf export is an effective mechanism for the expansion of coastal productive waters into the adjacent oligotrophic ocean basin.

  14. Evaluation of the radiation resistance of high-density polyethylene

    International Nuclear Information System (INIS)

    Dougherty, D.R.; Adams, J.W.; Barletta, R.R.

    1984-03-01

    Mechanical tests following gamma irradiation and creep tests during irradiation have been conducted on high-density polyethylene (HDPE) to provide data to help assess the adequacy of this material for use in high integrity containers (HICs). Two types of HDPE, a highly cross-linked rotationally molded material and a non-cross-linked blow molded material, were used in these tests. Gamma-ray irradiations were performed at several dose rates in environments of air, Barnwell and Hanford backfill soils, and ion-exchange resins. The results of tensile and bend tests on these materials following irradiation are presented along with results on creep during irradiation. 8 references, 9 figures, 2 tables

  15. Cross-link guided molecular modeling with ROSETTA.

    Directory of Open Access Journals (Sweden)

    Abdullah Kahraman

    Full Text Available Chemical cross-links identified by mass spectrometry generate distance restraints that reveal low-resolution structural information on proteins and protein complexes. The technology to reliably generate such data has become mature and robust enough to shift the focus to the question of how these distance restraints can be best integrated into molecular modeling calculations. Here, we introduce three workflows for incorporating distance restraints generated by chemical cross-linking and mass spectrometry into ROSETTA protocols for comparative and de novo modeling and protein-protein docking. We demonstrate that the cross-link validation and visualization software Xwalk facilitates successful cross-link data integration. Besides the protocols we introduce XLdb, a database of chemical cross-links from 14 different publications with 506 intra-protein and 62 inter-protein cross-links, where each cross-link can be mapped on an experimental structure from the Protein Data Bank. Finally, we demonstrate on a protein-protein docking reference data set the impact of virtual cross-links on protein docking calculations and show that an inter-protein cross-link can reduce on average the RMSD of a docking prediction by 5.0 Å. The methods and results presented here provide guidelines for the effective integration of chemical cross-link data in molecular modeling calculations and should advance the structural analysis of particularly large and transient protein complexes via hybrid structural biology methods.

  16. The Columbia River plume as cross-shelf exporter and along-coast barrier

    Science.gov (United States)

    Banas, N. S.; MacCready, P.; Hickey, B. M.

    2009-01-01

    An intensive Lagrangian particle-tracking analysis of the July 2004 upwelling period was conducted in a hindcast model of the US Pacific Northwest coast, in order to determine the effect of the Columbia River plume on the fate of upwelled water. The model, implemented using Regional Ocean Modeling System (ROMS), includes variable wind and atmospheric forcing, variable Columbia river flow, realistic boundary conditions from Navy Coastal Ocean Model (NCOM), and 10 tidal constituents. Model skill has been demonstrated in detail elsewhere [MacCready, P., Banas, N.S., Hickey, B.M., Dever, E.P., Liu, Y., 2008. A model study of tide- and wind-induced mixing in the Columbia River estuary and plume. Continental Shelf Research, this issue, doi:10.1016/j.csr.2008.03.015]. Particles were released in the Columbia estuary, along the Washington coastal wall, and along the model's northern boundary at 48°N. Particles were tracked in three dimensions, using both velocities from ROMS and a vertical random displacement representing turbulent mixing. When 25 h of upwelling flow is looped and particles tracked for 12 d, their trajectories highlight a field of transient eddies and recirculations on scales from 5 to 50 km both north and south of the Columbia. Not all of these features are caused by plume dynamics, but the presence of the plume increases the entrainment of inner-shelf water into them. The cumulative effect of the plume's interaction with these transient features is to increase cross-shelf dispersion: 25% more water is transported laterally past the 100 m isobath when river and estuarine effects are included than when they are omitted. This cross-shelf dispersion also disrupts the southward transport of water along the inner shelf that occurs in the model when the Columbia River is omitted. This second effect—increased retention of upwelled water on the Washington shelf—may be partly responsible for the regional-scale alongcoast gradient in chlorophyll biomass

  17. Studies of chemical interactions between chlorosulphonated polyethylene and nit rile rubber

    Directory of Open Access Journals (Sweden)

    Marković Gordana

    2005-01-01

    Full Text Available Highly polar rubbers interact with each other through their active functional groups via condensation or substitution reactions at high temperature. Chlorosulphonated polyethylene (CSM rubber is a highly reactive rubber, the reactivity of with is due to the -SO2CI groups. When CSM reacts with nit rile rubber (NBR, a chemical reaction takes place between the two rubbers at high temperature. Fourier transform infrared (FTIR studies support that CSM/NBR (50/50 w/w isothermally induces a self cross-linking blend, when cross-linking takes place via the acrylonitrile groups of NBR and the SO2CI groups or the insitu generated allyl chloride moieties of CSM. There is a loss of some -CN groups during cross-linking. This may be due to an attack on the -CN groups by HCI (produced during the heating of CSM in the presence of inherent moisture in the polymers. Amid type of linkage is formed due to cross-linking.

  18. Mechanisms of plastic deformation in highly cross-linked UHMWPE for total hip components--the molecular physics viewpoint.

    Science.gov (United States)

    Takahashi, Yasuhito; Shishido, Takaaki; Yamamoto, Kengo; Masaoka, Toshinori; Kubo, Kosuke; Tateiwa, Toshiyuki; Pezzotti, Giuseppe

    2015-02-01

    Plastic deformation is an unavoidable event in biomedical polymeric implants for load-bearing application during long-term in-vivo service life, which involves a mass transfer process, irreversible chain motion, and molecular reorganization. Deformation-induced microstructural alterations greatly affect mechanical properties and durability of implant devices. The present research focused on evaluating, from a molecular physics viewpoint, the impact of externally applied strain (or stress) in ultra-high molecular weight polyethylene (UHMWPE) prostheses, subjected to radiation cross-linking and subsequent remelting for application in total hip arthroplasty (THA). Two different types of commercial acetabular liners, which belong to the first-generation highly cross-linked UHMWPE (HXLPE), were investigated by means of confocal/polarized Raman microprobe spectroscopy. The amount of crystalline region and the spatial distribution of molecular chain orientation were quantitatively analyzed according to a combined theory including Raman selection rules for the polyethylene orthorhombic structure and the orientation distribution function (ODF) statistical approach. The structurally important finding was that pronounced recrystallization and molecular reorientation increasingly appeared in the near-surface regions of HXLPE liners with increasing the amount of plastic (compressive) deformation stored in the microstructure. Such molecular rearrangements, occurred in response to external strains, locally increase surface cross-shear (CS) stresses, which in turn trigger microscopic wear processes in HXLPE acetabular liners. Thus, on the basis of the results obtained at the molecular scale, we emphasize here the importance of minimizing the development of irrecoverable deformation strain in order to retain the pristine and intrinsically high wear performance of HXLPE components. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Folic acid-targeted disulfide-based cross-linking micelle for enhanced drug encapsulation stability and site-specific drug delivery against tumors

    Directory of Open Access Journals (Sweden)

    Zhang Y

    2016-03-01

    Full Text Available Yumin Zhang,1,* Junhui Zhou,2,* Cuihong Yang,1 Weiwei Wang,3 Liping Chu,1 Fan Huang,1 Qiang Liu,1 Liandong Deng,2 Deling Kong,3 Jianfeng Liu,1 Jinjian Liu1 1Tianjin Key Laboratory of Radiation Medicine and Molecular Nuclear Medicine, Institute of Radiation Medicine, Chinese Academy of Medical Science and Peking Union Medical College, 2Department of Polymer Science and Technology, School of Chemical Engineering and Technology, Tianjin University, 3Tianjin Key Laboratory of Biomaterial Research, Institute of Biomedical Engineering, Chinese Academy of Medical Science and Peking Union Medical College, Tianjin, People’s Republic of China *These authors contributed equally in this work Abstract: Although the shortcomings of small molecular antitumor drugs were efficiently improved by being entrapped into nanosized vehicles, premature drug release and insufficient tumor targeting demand innovative approaches that boost the stability and tumor responsiveness of drug-loaded nanocarriers. Here, we show the use of the core cross-linking method to generate a micelle with enhanced drug encapsulation ability and sensitivity of drug release in tumor. This kind of micelle could increase curcumin (Cur delivery to HeLa cells in vitro and improve tumor accumulation in vivo. We designed and synthesized the core cross-linked micelle (CCM with polyethylene glycol and folic acid-polyethylene glycol as the hydrophilic units, pyridyldisulfide as the cross-linkable and hydrophobic unit, and disulfide bond as the cross-linker. CCM showed spherical shape with a diameter of 91.2 nm by the characterization of dynamic light scattering and transmission electron microscope. Attributed to the core cross-linking, drug-loaded CCM displayed higher Nile Red or Cur-encapsulated stability and better sensitivity to glutathione than noncross-linked micelle (NCM. Cellular uptake and in vitro antitumor studies proved the enhanced endocytosis and better cytotoxicity of CCM-Cur against

  20. The Cross Surfzone/Inner-shelf Dye Exchange (CSIDE) Experiment Overview: Binational Dye Tracer Releases to Study Pollution Transport and Dilution.

    Science.gov (United States)

    Feddersen, F.; Giddings, S. N.; Kumar, N.; Grimes, D. J.; Pawlak, G. R.; Rivas, D.; Diaz, M.

    2016-02-01

    Per square km, the surfzone and inner-shelf are by far the most economically and ecologically important ocean regions, vital for recreation, food, and ecosystem services. Despite the importance of clean coastal waters to our economy and well-being, declining water quality threatens coastal ecosystem and human health worldwide. Healthy coasts are a significant priority to federal agencies, local government, and NGOs. In particular the San Diego US and Tijuana Mexico border region have unique and persistent water quality issues due to a range of pollution sources. Cross-shore exchange of tracers (e.g., pathogens, anthropogenic nutrients, harmful algal blooms - HABs, larvae) between the well-mixed surfzone and stratified inner-shelf is poorly understood. The surfzone, inner- and mid-shelf span drastically different dynamical regimes, with varying cross-shelf exchange mechanisms due to wave, wind, buoyancy, and tidal processes and intrinsic variability. The NSF funded CSIDE (Cross Surfzone/Inner-shelf Dye Exchange) experiment (Sept & Oct 2015) aims to increase our understanding of cross-shelf material exchange by performing 3 shoreline dye release experiments that are tracked for up to 20 km alongshore and over 48+ hrs. One dye release will be performed in Mexico and the dye transport tracked across the border. The dye will be tracked via a broad range of binational instrumentation. In this presentation, we present an overview of the CSIDE experiment, in particular the binational aspects of the study,

  1. Wear Performance of Sequentially Cross-Linked Polyethylene Inserts against Ion-Treated CoCr, TiNbN-Coated CoCr and Al2O3 Ceramic Femoral Heads for Total Hip Replacement

    Directory of Open Access Journals (Sweden)

    Christian Fabry

    2015-02-01

    Full Text Available The aim of the present study was to evaluate the biotribology of current surface modifications on femoral heads in terms of wettability, polyethylene wear and ion-release behavior. Three 36 mm diameter ion-treated CoCr heads and three 36 mm diameter TiNbN-coated CoCr heads were articulated against sequentially cross-linked polyethylene inserts (X3 in a hip joint simulator, according to ISO 14242. Within the scope of the study, the cobalt ion release in the lubricant, as well as contact angles at the bearing surfaces, were investigated and compared to 36 mm alumina ceramic femoral heads over a period of 5 million cycles. The mean volumetric wear rates were 2.15 ± 0.18 mm3·million cycles−1 in articulation against the ion-treated CoCr head, 2.66 ± 0.40 mm3·million cycles−1 for the coupling with the TiNbN-coated heads and 2.17 ± 0.40 mm3·million cycles−1 for the ceramic heads. The TiNbN-coated femoral heads showed a better wettability and a lower ion level in comparison to the ion-treated CoCr heads. Consequently, the low volumes of wear debris, which is comparable to ceramics, and the low concentration of metal ions in the lubrication justifies the use of coated femoral heads.

  2. Oxidation and Free Radical Decay in Vitamin E-stabilized, Radiation Cross-linked UHMWPE

    International Nuclear Information System (INIS)

    Oral, E.

    2006-01-01

    A novel a-tocopherol (vitamin E, α-T)-stabilized, cross-linked ultra-high molecular weight polyethylene (UHMWPE) (αTPE) was developed for total joint arthroplasty as a bearing surface with low wear and improved mechanical properties. Accelerated aging showed α-T protects irradiated UHMWPE against oxidation. However, accelerated aging may not truly reflect in vivo and shelf oxidation. We used real-time aging to monitor the evolution of oxidation and free radical signals of α-T to determine the mechanism of oxidative stability. UHMWPE blocks (30x30x10 mm) were machined and γ-irradiated (85 kGy) in argon. The blocks were doped in α-T for 5 hours at 120 degree and homogenized for 64 hours at 120 degree in argon, packaged in vacuum and γ-sterilized (25 kGy). Samples were aged in air at room temperature, in air at 40 degree and in water at 40 degree. Measurements were at 1, 2, 3, 4 and 7 months. Sections cut from the aged blocks (150μm) were boiled in hexane overnight to extract free species and evaluated by FTIR. Oxidation indices were calculated by taking the area under the carbonyl peak and normalizing it to a skeletal peak. ESR was used to determine the content and type of free radicals. Control was 100-kGy irradiated, unstabilized UHMWPE. αTPE showed a small amount of oxidation, which stabilized after 2 months. This indicated that the decay of the hydroperoxides formed by the reaction of the residual free radicals with oxygen was exhausted by α-T due to its ability to scavenge free radicals. In contrast, control UHMWPE continued to oxidize because the residual free radicals likely continued to form hydroperoxides and additional free radicals, furthering the oxidation reactions. There was a shift in the free radical signature of both αTPE and control from the sextet alkyl/allyl radicals to a sharp singlet during aging. Most likely, trapped free radicals move along the crystal stems until they react with another free radical or until they reach the crystal

  3. The cross linking of EPDM and NBR rubber

    Directory of Open Access Journals (Sweden)

    Samardžija-Jovanović Suzana

    2005-01-01

    Full Text Available In the process of macromolecule cross linking, the choice of type and quantity of the components and the experimental conditions are important to obtain the new cross linked materials with better mechanical and chemical characteristics. The cross linking method depends on the rubber type and structure. Intermolecular cross linking results in the formation elastomer network. The basis of the cross linking process, between ethylene propylene diene rubber (EPDM and acrylonitrile butadiene rubber (NBR, is a chemical reaction. Fillers and other additives are present in different mass ratios in the material. The exploitation properties of the cross linked materials depend on the quantity of additive in the cross linked systems.

  4. Postharvest Ripening and Shelf Life of Mango ( Mangifera indica L ...

    African Journals Online (AJOL)

    Postharvest Ripening and Shelf Life of Mango ( Mangifera indica L.) Fruit as Influenced by ... evaluate the influence of 1-Methylcyclopropene (1-MCP) and polyethylene packaging (PP) on postharvest storage of mango. ... HOW TO USE AJOL.

  5. In vivo evaluation of folate decorated cross-linked micelles for the delivery of platinum anticancer drugs.

    Science.gov (United States)

    Eliezar, Jeaniffer; Scarano, Wei; Boase, Nathan R B; Thurecht, Kristofer J; Stenzel, Martina H

    2015-02-09

    The biodistribution of micelles with and without folic acid targeting ligands were studied using a block copolymer consisting of acrylic acid (AA) and polyethylene glycol methyl ether acrylate (PEGMEA) blocks. The polymers were prepared using RAFT polymerization in the presence of a folic acid functionalized RAFT agent. Oxoplatin was conjugated onto the acrylic acid block to form amphiphilic polymers which, when diluted in water, formed stable micelles. In order to probe the in vivo stability, a selection of micelles were cross-linked using 1,8-diamino octane. The sizes of the micelles used in this study range between 75 and 200 nm, with both spherical and worm-like conformation. The effects of cross-linking, folate conjugation and different conformation on the biodistribution were studied in female nude mice (BALB/c) following intravenous injection into the tail vein. Using optical imaging to monitor the fluorophore-labeled polymer, the in vivo biodistribution of the micelles was monitored over a 48 h time-course after which the organs were removed and evaluated ex vivo. These experiments showed that both cross-linking and conjugation with folic acid led to increased fluorescence intensities in the organs, especially in the liver and kidneys, while micelles that are not conjugated with folate and not cross-linked are cleared rapidly from the body. Higher accumulation in the spleen, liver, and kidneys was also observed for micelles with worm-like shapes compared to the spherical micelles. While the various factors of cross-linking, micelle shape, and conjugation with folic acid all contribute separately to prolong the circulation time of the micelle, optimization of these parameters for drug delivery devices could potentially overcome adverse effects such as liver and kidney toxicity.

  6. Lithium polymer cell assembled by in situ chemical cross-linking of ionic liquid electrolyte with phosphazene-based cross-linking agent

    International Nuclear Information System (INIS)

    Choi, Ji-Ae; Kang, Yongku; Kim, Dong-Won

    2013-01-01

    Highlights: ► Ionic liquid-based cross-linked gel polymer electrolytes were synthesized and their electrochemical properties were investigated. ► Lithium polymer cells with in situ cross-linked gel polymer electrolytes exhibited reversible cycling behavior with good capacity retention. ► The use of ionic liquid-based cross-linked gel polymer electrolytes significantly improved the thermal stability of the cells. -- Abstract: Ionic liquid-based cross-linked gel polymer electrolytes were prepared with a phosphazene-based cross-linking agent, and their electrochemical properties were investigated. Lithium polymer cells composed of lithium anode and LiCoO 2 cathode were assembled with ionic liquid-based cross-linked gel polymer electrolyte and their cycling performance was evaluated. The interfacial adhesion between the electrodes and the electrolyte by in situ chemical cross-linking resulted in stable capacity retention of the cell. A reduction in the ionic mobility in both the electrolyte and the electrode adversely affected discharge capacity and high rate performance of the cell. DSC studies demonstrated that the use of ionic liquid-based cross-linked gel polymer electrolytes provided a significant improvement in the thermal stability of the cell

  7. Chemical cross-linking of Chlamydia trachomatis

    DEFF Research Database (Denmark)

    Birkelund, Svend; Lundemose, AG; Christiansen, Gunna

    1988-01-01

    Purified elementary bodies (EBs) of Chlamydia trachomatis serovar L2 were analyzed by chemical cross-linking with disuccinimidyl selenodipropionate. The effect of the cross-linking was analyzed by immunoblotting sodium dodecyl sulfate-polyacrylamide gel electrophoresis-separated components which...

  8. In Situ Forming, Cytocompatible, and Self-Recoverable Tough Hydrogels Based on Dual Ionic and Click Cross-Linked Alginate.

    Science.gov (United States)

    Ghanian, Mohammad Hossein; Mirzadeh, Hamid; Baharvand, Hossein

    2018-05-14

    A dual cross-linking strategy was developed to answer the urgent need for fatigue-resistant, cytocompatible, and in situ forming tough hydrogels. Clickable, yet calcium-binding derivatives of alginate were synthesized by partial substitution of its carboxyl functionalities with furan, which could come into Diels-Alder click reaction with maleimide end groups of a four arm poly(ethylene glycol) cross-linker. Tuning the cooperative viscoelastic action of transient ionic and permanent click cross-links within the single network of alginate provided a soft tough hydrogel with a set of interesting features: (i) immediate self-recovery under cyclic loading, (ii) highly efficient and autonomous self-healing upon fracture, (iii) in situ forming ability for molding and minimally invasive injection, (iv) capability for viable cell encapsulation, and (v) reactivity for on-demand biomolecule conjugation. The facile strategy is applicable to a wide range of natural and synthetic polymers by introducing the calcium binding and click reacting functional groups and can broaden the use of tough hydrogels in load-bearing, cell-laden applications such as soft tissue engineering and bioactuators.

  9. Evaluation of a new methodology to simulate damage and wear of polyethylene hip replacements subjected to edge loading in hip simulator testing.

    Science.gov (United States)

    Partridge, Susan; Tipper, Joanne L; Al-Hajjar, Mazen; Isaac, Graham H; Fisher, John; Williams, Sophie

    2018-05-01

    Wear and fatigue of polyethylene acetabular cups have been reported to play a role in the failure of total hip replacements. Hip simulator testing under a wide range of clinically relevant loading conditions is important. Edge loading of hip replacements can occur following impingement under extreme activities and can also occur during normal gait, where there is an offset deficiency and/or joint laxity. This study evaluated a hip simulator method that assessed wear and damage in polyethylene acetabular liners that were subjected to edge loading. The liners tested to evaluate the method were a currently manufactured crosslinked polyethylene acetabular liner and an aged conventional polyethylene acetabular liner. The acetabular liners were tested for 5 million standard walking cycles and following this 5 million walking cycles with edge loading. Edge loading conditions represented a separation of the centers of rotation of the femoral head and the acetabular liner during the swing phase, leading to loading of the liner rim on heel strike. Rim damage and cracking was observed in the aged conventional polyethylene liner. Steady-state wear rates assessed gravimetrically were lower under edge loading compared to standard loading. This study supports previous clinical findings that edge loading may cause rim cracking in liners, where component positioning is suboptimal or where material degradation is present. The simulation method developed has the potential to be used in the future to test the effect of aging and different levels of severity of edge loading on a range of cross-linked polyethylene materials. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1456-1462, 2018. © 2017 Wiley Periodicals, Inc.

  10. Recent advances in corneal collagen cross-linking

    Directory of Open Access Journals (Sweden)

    Gitansha Shreyas Sachdev

    2017-01-01

    Full Text Available Corneal collagen cross-linking has become the preferred modality of treatment for corneal ectasia since its inception in late 1990s. Numerous studies have demonstrated the safety and efficacy of the conventional protocol. Our understanding of the cross-linking process is ever evolving, with its wide implications in the form of accelerated and pulsed protocols. Newer advancements in technology include various riboflavin formulations and the ability to deliver higher fluence protocols with customised irradiation patterns. A greater degree of customisation is likely the path forward, which will aim at achieving refractive improvements along with disease stability. The use of cross-linking for myopic correction is another avenue under exploration. Combination of half fluence cross-linking with refractive correction for high errors to prevent post LASIK regression is gaining interest. This review aims to highlight the various advancements in the cross-linking technology and its clinical applications.

  11. Porous Cross-Linked Polyimide-Urea Networks

    Science.gov (United States)

    Meador, Mary Ann B. (Inventor); Nguyen, Baochau N. (Inventor)

    2015-01-01

    Porous cross-linked polyimide-urea networks are provided. The networks comprise a subunit comprising two anhydride end-capped polyamic acid oligomers in direct connection via a urea linkage. The oligomers (a) each comprise a repeating unit of a dianhydride and a diamine and a terminal anhydride group and (b) are formulated with 2 to 15 of the repeating units. The subunit was formed by reaction of the diamine and a diisocyanate to form a diamine-urea linkage-diamine group, followed by reaction of the diamine-urea linkage-diamine group with the dianhydride and the diamine to form the subunit. The subunit has been cross-linked via a cross-linking agent, comprising three or more amine groups, at a balanced stoichiometry of the amine groups to the terminal anhydride groups. The subunit has been chemically imidized to yield the porous cross-linked polyimide-urea network. Also provided are wet gels, aerogels, and thin films comprising the networks, and methods of making the networks.

  12. Comparison of radiation-induced and thermal oxidative aging of polyethylene in the presence of inhibitors

    International Nuclear Information System (INIS)

    Dalinkevich, A.A.; Piskarev, I.M.

    1996-01-01

    Thermal oxidative and radiation-induced oxidative aging of inhibited polyethylene of commercial brands with known properties was studied at 60, 80 and 140 deg C. Radiation-induced oxidative aging was carried out under X-ray radiation with E max = 25 keV at dose rates providing specimen oxidation in kinetic conditions. The value of activation energy of thermal oxidative destruction of inhibited polyethylene under natural conditions of its employment at 60-140 deg C (E a = 60 kJ/mol) was obtained by comparison of data for radiation-induced and thermal oxidative destruction

  13. Nitric oxide-induced interstrand cross-links in DNA.

    Science.gov (United States)

    Caulfield, Jennifer L; Wishnok, John S; Tannenbaum, Steven R

    2003-05-01

    The DNA damaging effects of nitrous acid have been extensively studied, and the formation of interstrand cross-links have been observed. The potential for this cross-linking to occur through a common nitrosating intermediate derived from nitric oxide is investigated here. Using a HPLC laser-induced fluorescence (LIF) system, the amount of interstrand cross-link formed on nitric oxide treatment of the 5'-fluorescein-labeled oligomer ATATCGATCGATAT was determined. This self-complimentary sequence contains two 5'-CG sequences, which is the preferred site for nitrous acid-induced cross-linking. Nitric oxide was delivered to an 0.5 mM oligomer solution at 15 nmol/mL/min to give a final nitrite concentration of 652 microM. The resulting concentration of the deamination product, xanthine, in this sample was found to be 211 +/- 39 nM, using GC/MS, and the amount of interstrand cross-link was determined to be 13 +/- 2.5 nM. Therefore, upon nitric oxide treatment, the cross-link is found at approximately 6% of the amount of the deamination product. Using this system, detection of the cross-link is also possible for significantly lower doses of nitric oxide, as demonstrated by treatment of the same oligomer with NO at a rate of 18 nmol/mL/min resulting in a final nitrite concentration of 126 microM. The concentration of interstrand cross-link was determined to be 3.6 +/- 0.1 nM in this sample. Therefore, using the same dose rate, when the total nitric oxide concentration delivered drops by a factor of approximately 5, the concentration of cross-link drops by a factor of about 4-indicating a qausi-linear response. It may now be possible to predict the number of cross-links in a small genome based on the number of CpG sequences and the yield of xanthine derived from nitrosative deamination.

  14. Ageing of cable insulators made of polyethylene in nuclear environment

    International Nuclear Information System (INIS)

    Khelidj, N.

    2006-10-01

    This thesis deals with lifetime prediction for polyethylene in nuclear environment. It is mainly characterised by the search for a non empirical solution. We have tried to elaborate a model describing the polymer evolution (including the skin-core heterogeneity due to the kinetic control of oxidation by oxygen diffusion) at any temperature between ambient and the melting point of the polymer, and at any dose rate between 0 and 1 kGy.h-1, with lifetimes extending to several decades of years. The main difficulty was to take into account the dual character of initiation which results from the combination of polymer radiolysis and hydroperoxide thermal decomposition. The problem was resolved considering first the asymptotic regimes where one initiation process can be neglected relatively to the other one. The kinetic parameters specific to those regimes being identified, we have built a numerical model including all the processes. In the case of un-stabilised polyethylene, this model displays excellent predictive qualities, as well in lifetime, as in thickness distribution of oxidation products. The study of stabilised polyethylenes was then initiated with samples respectively stabilised by a hindered phenol, and a thio-diester. In the case of phenol, the study of consumption kinetics reveals the existence of complex mechanisms, especially the existence of a 'reservoir effect' linked to the presence of a separated phase of phenol in excess. A kinetic model has been proposed, but we still do not know how the results can be generalised to other phenolic stabilizers. (author)

  15. DC Electrical Ageing of XLPE under Hydrostatic Pressure

    Directory of Open Access Journals (Sweden)

    Fadila Benlizidia Lalam

    2017-01-01

    Full Text Available The experimental electrical ageing, of cross-linked polyethylene films 100 μm thick, was investigated under high hydrostatic pressure of 300 bar and at atmospheric pressure. The tests are conducted on direct current (dc for up to 1000 h ageing and at temperature of 70°C. The use of the Weibull statistic, with the estimation of confidence bounds at 90%, has shown that the hydrostatic pressure has a real effect on the lifetime. These lifetime data are qualitatively analyzed with the inverse power model. It was found that thermally activated process is able to describe the pressure effect on the electrical ageing of XLPE.

  16. Preparation and properties of silk sericin/cellulose cross-linking films

    Directory of Open Access Journals (Sweden)

    Wang Kunyan

    2017-01-01

    Full Text Available Silk sericin/cellulose cross-linked films were successfully prepared using glutaraldehyde as cross-linkinger. FTIR was applied to characterize the chemical structure of films. Cross-linked silk sericin film was found the peak intensity of FTIR for cross-linked film decreased markedly compared to pure silk sericin, which indicating cross-linking reaction has been occurred. The increasing value of swelling ratio also indicated the cross-linking has been happened. The cross-linking reaction increased the thermal decomposition temperature.

  17. Cross-linked structure of network evolution

    International Nuclear Information System (INIS)

    Bassett, Danielle S.; Wymbs, Nicholas F.; Grafton, Scott T.; Porter, Mason A.; Mucha, Peter J.

    2014-01-01

    We study the temporal co-variation of network co-evolution via the cross-link structure of networks, for which we take advantage of the formalism of hypergraphs to map cross-link structures back to network nodes. We investigate two sets of temporal network data in detail. In a network of coupled nonlinear oscillators, hyperedges that consist of network edges with temporally co-varying weights uncover the driving co-evolution patterns of edge weight dynamics both within and between oscillator communities. In the human brain, networks that represent temporal changes in brain activity during learning exhibit early co-evolution that then settles down with practice. Subsequent decreases in hyperedge size are consistent with emergence of an autonomous subgraph whose dynamics no longer depends on other parts of the network. Our results on real and synthetic networks give a poignant demonstration of the ability of cross-link structure to uncover unexpected co-evolution attributes in both real and synthetic dynamical systems. This, in turn, illustrates the utility of analyzing cross-links for investigating the structure of temporal networks

  18. Cross-linked structure of network evolution

    Energy Technology Data Exchange (ETDEWEB)

    Bassett, Danielle S., E-mail: dsb@seas.upenn.edu [Department of Bioengineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States); Department of Physics, University of California, Santa Barbara, California 93106 (United States); Sage Center for the Study of the Mind, University of California, Santa Barbara, California 93106 (United States); Wymbs, Nicholas F.; Grafton, Scott T. [Department of Psychology and UCSB Brain Imaging Center, University of California, Santa Barbara, California 93106 (United States); Porter, Mason A. [Oxford Centre for Industrial and Applied Mathematics, Mathematical Institute, University of Oxford, Oxford OX2 6GG (United Kingdom); CABDyN Complexity Centre, University of Oxford, Oxford, OX1 1HP (United Kingdom); Mucha, Peter J. [Carolina Center for Interdisciplinary Applied Mathematics, Department of Mathematics, University of North Carolina, Chapel Hill, North Carolina 27599 (United States); Department of Applied Physical Sciences, University of North Carolina, Chapel Hill, North Carolina 27599 (United States)

    2014-03-15

    We study the temporal co-variation of network co-evolution via the cross-link structure of networks, for which we take advantage of the formalism of hypergraphs to map cross-link structures back to network nodes. We investigate two sets of temporal network data in detail. In a network of coupled nonlinear oscillators, hyperedges that consist of network edges with temporally co-varying weights uncover the driving co-evolution patterns of edge weight dynamics both within and between oscillator communities. In the human brain, networks that represent temporal changes in brain activity during learning exhibit early co-evolution that then settles down with practice. Subsequent decreases in hyperedge size are consistent with emergence of an autonomous subgraph whose dynamics no longer depends on other parts of the network. Our results on real and synthetic networks give a poignant demonstration of the ability of cross-link structure to uncover unexpected co-evolution attributes in both real and synthetic dynamical systems. This, in turn, illustrates the utility of analyzing cross-links for investigating the structure of temporal networks.

  19. Current status of accelerated corneal cross-linking

    Directory of Open Access Journals (Sweden)

    Michael Mrochen

    2013-01-01

    Full Text Available Corneal cross-linking with riboflavin is a technique to stabilize or reduce corneal ectasia, in diseases such as keratoconus and post-laser-assisted in situ keratomileusis (LASIK ectasia. There is an interest by patient as well as clinicians to reduce the overall treatment time. Especially, the introduction of corneal cross-linking in combination with corneal laser surgery demands a shorter treatment time to assure a sufficient patient flow. The principles and techniques of accelerated corneal cross-linking is discussed.

  20. Shaped articles of cross-linked fluorocarbon polymers

    International Nuclear Information System (INIS)

    Gotcher, A.J.; Germeraad, P.B.

    1981-01-01

    A process is described which comprises (1) contacting (a) a shaped article of a polymeric composition wherein the polymer is a fluorocarbon polymer having a melting point of at least 200 0 C, the article having a tensile strength of at least 3,000 psi, with (b) a fluid composition comprising a cross-linking agent, until the article contains at least 2.5% by weight of the cross-linking agent; and (2) irradiating the shaped article with ionising radiation to a dosage not exceeding 50 Mrads under conditions such that the composition is cross-linked sufficiently to impart thereto an M 100 value of at least 300 psi, while maintaining a tensile strength of at least 3000 psi, the shaped article containing a specified proportion of the cross-linking agent. (author)

  1. POLYETHYLENE ENCAPSULATION

    International Nuclear Information System (INIS)

    Kalb, P.

    2001-01-01

    (NRC, 1991; 1983) Because polyethylene is a relatively new material, it is difficult to predict its long-term durability. However, prior to scale-up of the microencapsulation process, a study was conducted to evaluate potential degradation mechanisms. The study examined potential effects on mechanical integrity from exposure to chemicals and solvents, thermal cycling, saturated environments, microbial attack, and high gamma-radiation fields (Kalb et al., 1991). At ambient temperatures, polyethylene is relatively inert to most chemicals, including organic solvents, acids, and alkaline solutions. Exposure to changes in temperature or saturated soil conditions have been shown to degrade the mechanical integrity of some waste forms, but had little or no measurable impact on polyethylene waste forms. Low-density polyethylene is not susceptible to growth of microbial organisms, a fact that is evidenced by the lack of plastics decomposition in municipal waste landfills. When exposed to gamma-radiation at total doses of up to lo8 rad, additional cross-linking of the polymer occurs, resulting in increased strength and lower leachability

  2. Exploring Tyrosine-Triazolinedione (TAD) Reactions for the Selective Conjugation and Cross-Linking of N-Carboxyanhydride (NCA) Derived Synthetic Copolypeptides.

    Science.gov (United States)

    Hanay, Saltuk B; Ritzen, Bas; Brougham, Dermot; Dias, Aylvin A; Heise, Andreas

    2017-07-01

    Highly efficient functionalization and cross-linking of polypeptides is achieved via tyrosine-triazolinedione (TAD) conjugation chemistry. The feasibility of the reaction is demonstrated by the reaction of 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) with tyrosine containing block copolymer poly(ethylene glycol)-Tyr 4 as well as a statistical copolymer of tyrosine and lysine (poly(Lys 40 -st-Tyr 10 )) prepared form N-carboxyanhydride polymerization. Selective reaction of PTAD with the tyrosine units is obtained and verified by size exclusion chromatography and NMR spectroscopy. Moreover, two monofunctional and two difunctional TAD molecules are synthesized. It is found that their stability in the aqueous reaction media significantly varied. Under optimized reaction conditions selective functionalization and cross-linking, yielding polypeptide hydrogels, can be achieved. TAD-mediated conjugation can offer an interesting addition in the toolbox of selective (click-like) polypeptide conjugation methodologies as it does not require functional non-natural amino acids. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Matrix association effects on hydrodynamic sorting and degradation of terrestrial organic matter during cross-shelf transport in the Laptev and East Siberian shelf seas

    Science.gov (United States)

    Tesi, Tommaso; Semiletov, Igor; Dudarev, Oleg; Andersson, August; Gustafsson, Örjan

    2016-03-01

    This study seeks an improved understanding of how matrix association affects the redistribution and degradation of terrigenous organic carbon (TerrOC) during cross-shelf transport in the Siberian margin. Sediments were collected at increasing distance from two river outlets (Lena and Kolyma Rivers) and one coastal region affected by erosion. Samples were fractionated according to density, size, and settling velocity. The chemical composition in each fraction was characterized using elemental analyses and terrigenous biomarkers. In addition, a dual-carbon-isotope mixing model (δ13C and Δ14C) was used to quantify the relative TerrOC contributions from active layer (Topsoil) and Pleistocene Ice Complex Deposits (ICD). Results indicate that physical properties of particles exert first-order control on the redistribution of different TerrOC pools. Because of its coarse nature, plant debris is hydraulically retained in the coastal region. With increasing distance from the coast, the OC is mainly associated with fine/ultrafine mineral particles. Furthermore, biomarkers indicate that the selective transport of fine-grained sediment results in mobilizing high-molecular weight (HMW) lipid-rich, diagenetically altered TerrOC while lignin-rich, less degraded TerrOC is retained near the coast. The loading (µg/m2) of lignin and HMW wax lipids on the fine/ultrafine fraction drastically decreases with increasing distance from the coast (98% and 90%, respectively), which indicates extensive degradation during cross-shelf transport. Topsoil-C degrades more readily (90 ± 3.5%) compared to the ICD-C (60 ± 11%) during transport. Altogether, our results indicate that TerrOC is highly reactive and its accelerated remobilization from thawing permafrost followed by cross-shelf transport will likely represent a positive feedback to climate warming.

  4. Interstrand cross-links arising from strand breaks at true abasic sites in duplex DNA

    Science.gov (United States)

    Yang, Zhiyu; Price, Nathan E.; Johnson, Kevin M.

    2017-01-01

    Abstract Interstrand cross-links are exceptionally bioactive DNA lesions. Endogenous generation of interstrand cross-links in genomic DNA may contribute to aging, neurodegeneration, and cancer. Abasic (Ap) sites are common lesions in genomic DNA that readily undergo spontaneous and amine-catalyzed strand cleavage reactions that generate a 2,3-didehydro-2,3-dideoxyribose sugar remnant (3’ddR5p) at the 3’-terminus of the strand break. Interestingly, this strand scission process leaves an electrophilic α,β-unsaturated aldehyde residue embedded within the resulting nicked duplex. Here we present evidence that 3’ddR5p derivatives generated by spermine-catalyzed strand cleavage at Ap sites in duplex DNA can react with adenine residues on the opposing strand to generate a complex lesion consisting of an interstrand cross-link adjacent to a strand break. The cross-link blocks DNA replication by ϕ29 DNA polymerase, a highly processive polymerase enzyme that couples synthesis with strand displacement. This suggests that 3’ddR5p-derived cross-links have the potential to block critical cellular DNA transactions that require strand separation. LC-MS/MS methods developed herein provide powerful tools for studying the occurrence and properties of these cross-links in biochemical and biological systems. PMID:28531327

  5. Donor cross-linking for keratoplasty: a laboratory evaluation.

    Science.gov (United States)

    Mukherjee, Achyut; Hayes, Sally; Aslanides, Ioannis; Lanchares, Elena; Meek, Keith M

    2015-12-01

    This laboratory-based investigation compares the topographic outcomes of conventional penetrating keratoplasty with that of a novel procedure in which donor corneas are cross-linked prior to keratoplasty. Penetrating keratoplasty procedures with continuous running sutures were carried out in a porcine whole globe model. Sixty eyes were randomly paired as 'donor' and 'host' tissue before being assigned to one of two groups. In the cross-linked group, donor corneas underwent riboflavin/UVA cross-linking prior to being trephined and sutured to untreated hosts. In the conventional keratoplasty group, both host and donor corneas remained untreated prior to keratoplasty. Topographic and corneal wavefront measurements were performed following surgery, and technical aspects of the procedure evaluated. Mean keratometric astigmatism was significantly lower in the cross-linked donor group at 3.67D (SD 1.8 D), vs. 8.43 D (SD 2.4 D) in the conventional keratoplasty group (p < 0.005). Mean wavefront astigmatism was also significantly reduced in the cross-linked donor group 4.71 D (SD 2.1) vs. 8.29D (SD 3.6) in the conventional keratoplasty group (p < 0.005). Mean RMS higher order aberration was significantly lower in the cross-linked donor group at 1.79 um (SD 0.98), vs. 3.05 um (SD 1.9) in the conventional keratoplasty group (P = 0.02). Qualitative analysis revealed less tissue distortion at the graft-host junction in the cross-linked group. Cross-linking of donor corneas prior to keratoplasty reduces intraoperative induced astigmatism and aberrations in an animal model. Further studies are indicated to evaluate the implications of this potential modification of keratoplasty surgery.

  6. Cross shelf benthic biodiversity patterns in the Southern Red Sea

    KAUST Repository

    Ellis, Joanne; Anlauf, Holger; Kurten, Saskia; Lozano-Corté s, Diego; Alsaffar, Zahra Hassan Ali; Curdia, Joao; Jones, Burton; Carvalho, Susana

    2017-01-01

    The diversity of coral reef and soft sediment ecosystems in the Red Sea has to date received limited scientific attention. This study investigates changes in the community composition of both reef and macrobenthic communities along a cross shelf gradient. Coral reef assemblages differed significantly in species composition and structure with location and depth. Inner shelf reefs harbored less abundant and less diverse coral assemblages with higher percentage macroalgae cover. Nutrient availability and distance from the shoreline were significantly related to changes in coral composition and structure. This study also observed a clear inshore offshore pattern for soft sediment communities. In contrast to the coral reef patterns the highest diversity and abundance of soft sediment communities were recorded at the inshore sites, which were characterized by a higher number of opportunistic polychaete species and bivalves indicative of mild disturbance. Sediment grain size and nutrient enrichment were important variables explaining the variability. This study aims to contribute to our understanding of ecosystem processes and biodiversity in the Red Sea region in an area that also has the potential to provide insight into pressing topics, such as the capacity of reef systems and benthic macrofaunal organisms to adapt to global climate change.

  7. Cross shelf benthic biodiversity patterns in the Southern Red Sea

    KAUST Repository

    Ellis, Joanne

    2017-03-21

    The diversity of coral reef and soft sediment ecosystems in the Red Sea has to date received limited scientific attention. This study investigates changes in the community composition of both reef and macrobenthic communities along a cross shelf gradient. Coral reef assemblages differed significantly in species composition and structure with location and depth. Inner shelf reefs harbored less abundant and less diverse coral assemblages with higher percentage macroalgae cover. Nutrient availability and distance from the shoreline were significantly related to changes in coral composition and structure. This study also observed a clear inshore offshore pattern for soft sediment communities. In contrast to the coral reef patterns the highest diversity and abundance of soft sediment communities were recorded at the inshore sites, which were characterized by a higher number of opportunistic polychaete species and bivalves indicative of mild disturbance. Sediment grain size and nutrient enrichment were important variables explaining the variability. This study aims to contribute to our understanding of ecosystem processes and biodiversity in the Red Sea region in an area that also has the potential to provide insight into pressing topics, such as the capacity of reef systems and benthic macrofaunal organisms to adapt to global climate change.

  8. Biocatalytic cross-linking of pectic polysaccharides for designed food functionality

    DEFF Research Database (Denmark)

    Zaidel, Dayang Norulfairuz Abang; Meyer, Anne S.

    2012-01-01

    the mechanisms of formation of functional pectic polysaccharide cross-links, including covalent cross-links (notably phenolic esters and uronyl ester linkages) and non-covalent, ionic cross-links (which involve calcium and borate ester links). The treatise examines how such cross-links can be designed via......Recent research has demonstrated how cross-linking of pectic polysaccharides to obtain gel formation can be promoted by enzymatic catalysis reactions, and provide opportunities for functional upgrading of pectic polysaccharides present in agro-industrial sidestreams. This review highlights...... specific enzymatic reactions, and highlights the most recent data concerning enzyme catalyzed engineering of cross-links for in situ structural design of functional properties of foods....

  9. [Biophysical principles of collagen cross-linking].

    Science.gov (United States)

    Spörl, E; Raiskup-Wolf, F; Pillunat, L E

    2008-02-01

    The reduced mechanical stability of the cornea in keratoconus or in keratectasia after Lasik may be increased by photooxidative cross-linking of corneal collagen. The biophysical principles are compiled for the safe and effective application of this new treatment method. The setting of the therapy parameters should be elucidated from the absorption behaviour of the cornea. The safety of the method for the endothelium cells and the lens will be discussed. The induced cross-links are shown to be the result of changes in the physico-chemical properties of the cornea. To reach a high absorption of the irradiation energy in the cornea, riboflavin of a concentration of 0.1% and UV light of a wavelength of 370 nm, corresponding to the relative maximum of absorption of riboflavin, were used. An irradiance of 3 mW/cm(2) and an irradiation time of 30 min lead to an increase of the mechanical stiffness. The endothelium cells will be protected due to the high absorption within the cornea, that means the damaging threshold of the endothelium cells will not be reached in a 400 microm thick stroma. As evidence for cross-links we can consider the increase of the biomechanical stiffness, the increased resistance against enzymatic degradation, a higher shrinkage temperature, a lower swelling rate and an increased diameter of collagen fibres. The therapy parameters were tested experimentally and have been proven clinically in the corneal collagen cross-linking. These parameters should be respected to reach a safe cross-linking effect without damage of the adjacent tissues.

  10. Evaluating Computer Screen Time and Its Possible Link to Psychopathology in the Context of Age: A Cross-Sectional Study of Parents and Children.

    Science.gov (United States)

    Segev, Aviv; Mimouni-Bloch, Aviva; Ross, Sharon; Silman, Zmira; Maoz, Hagai; Bloch, Yuval

    2015-01-01

    Several studies have suggested that high levels of computer use are linked to psychopathology. However, there is ambiguity about what should be considered normal or over-use of computers. Furthermore, the nature of the link between computer usage and psychopathology is controversial. The current study utilized the context of age to address these questions. Our hypothesis was that the context of age will be paramount for differentiating normal from excessive use, and that this context will allow a better understanding of the link to psychopathology. In a cross-sectional study, 185 parents and children aged 3-18 years were recruited in clinical and community settings. They were asked to fill out questionnaires regarding demographics, functional and academic variables, computer use as well as psychiatric screening questionnaires. Using a regression model, we identified 3 groups of normal-use, over-use and under-use and examined known factors as putative differentiators between the over-users and the other groups. After modeling computer screen time according to age, factors linked to over-use were: decreased socialization (OR 3.24, Confidence interval [CI] 1.23-8.55, p = 0.018), difficulty to disengage from the computer (OR 1.56, CI 1.07-2.28, p = 0.022) and age, though borderline-significant (OR 1.1 each year, CI 0.99-1.22, p = 0.058). While psychopathology was not linked to over-use, post-hoc analysis revealed that the link between increased computer screen time and psychopathology was age-dependent and solidified as age progressed (p = 0.007). Unlike computer usage, the use of small-screens and smartphones was not associated with psychopathology. The results suggest that computer screen time follows an age-based course. We conclude that differentiating normal from over-use as well as defining over-use as a possible marker for psychiatric difficulties must be performed within the context of age. If verified by additional studies, future research should integrate

  11. Shelf-life enhancement of fresh ginger rhizomes at ambient temperatures by combination of gamma-irradiation, biocontrol and closed polyethylene bag storage

    International Nuclear Information System (INIS)

    Mukherjee, P.K.; Thomas, P.; Raghu, K.

    1995-01-01

    The feasibility of a combination process involving gamma-irradiation, packing in closed polyethylene bags and biological control of fungi causing storage rot was evaluated as a means of extending the shelf-life of fresh ginger rhizomes at ambient temperatures (25–30°C). Storage in closed polyethylene bags reduced weight loss but increased sprouting and rooting, which could be prevented by gamma irradiation to 60 Gy. Rotting caused by Sclerotium rolfsii was, however, a major cause of spoilage during extended storage. Four isolates of Trichoderma sp. isolated from sclerotia of S. rolfsii infecting ginger rhizomes, one of Gliocfadium uirens, and four isolates of fluorescent Pseudomonas were tested, out of which, one isolate of Trichoderma was found to be highly effective in suppressing the growth of S. rolfsii. The efficacy of the antagonist was demonstrated under simulated market conditions using artificially inoculated rhizomes. The recommended procedure consists of dipping washed, air dried rhizomes in Trichoderma suspension (10 8 spores ml -1 ), air-drying, packing in 250 gauge LDPE bags followed by irradiation to 60 Gy. Rhizomes thus treated remained in good marketable condition for up to 2 months at ambient temperature without sprouting or significant loss of quality and less than 5% weight loss. An in vitro bioassay system was developed to demonstrate the efficacy of the antagonist to protect the cut surface of sliced rhizomes inoculated with the pathogen. The method could be used for rapid screening of antagonists

  12. Changes in mechanical properties due to gamma irradiation of high-density polyethylene (HDPE

    Directory of Open Access Journals (Sweden)

    S. S. Cota

    2007-06-01

    Full Text Available This paper presents an experimental analysis of the effect of dose and dose rate parameters during gamma irradiation of high-density polyethylene (HDPE samples. Considerations concerning the influence of these parameters on HDPE mechanical strength properties as a result of the predominance of oxidative degradation or of cross-linking are presented. The experimental results show an improvement of HDPE mechanical strength as dose increases, indicating the predominance of cross-linking over oxidative degradation and that lower doses are necessary to obtain a similar change in resistance parameters when radiation is applied at lower dose rates, showing that gamma radiation affects the HDPE in a more efficient way at lower dose rates.

  13. Changes in mechanical properties due to gamma irradiation of high-density polyethylene (HDPE)

    International Nuclear Information System (INIS)

    Cota, S.S.; Vasconcelos, V.; Senne Junior, M.; Carvalho, L.L.; Rezende, D.B.; Correa, R.F.

    2007-01-01

    This paper presents an experimental analysis of the effect of dose and dose rate parameters during gamma irradiation of high-density polyethylene (HDPE) samples. Considerations concerning the influence of these parameters on HDPE mechanical strength properties as a result of the predominance of oxidative degradation or of cross-linking are presented. The experimental results show an improvement of HDPE mechanical strength as dose increases, indicating the predominance of cross-linking over oxidative degradation and that lower doses are necessary to obtain a similar change in resistance parameters when radiation is applied at lower dose rates, showing that gamma radiation affects the HDPE in a more efficient way at lower dose rates. (author)

  14. Extrudable polymer-polymer composites based on ultra-high molecular weight polyethylene

    Science.gov (United States)

    Panin, S. V.; Kornienko, L. A.; Alexenko, V. O.; Buslovich, D. G.; Dontsov, Yu. V.

    2017-12-01

    Mechanical and tribotechnical characteristics of polymer-polymeric composites of UHMWPE are studied with the aim of developing extrudable, wear-resistant, self-lubricant polymer mixtures for Additive Manufacturing (AM). The motivation of the study is their further application as feedstocks for 3D printing. Blends of UHMWPE with graft- and block copolymers of low-density polyethylene (HDPE-g-VTMS, HDPE-g-SMA, HDPE-b-EVA), polypropylene (PP), block copolymers of polypropylene and polyamide with linear low density polyethylene (PP-b-LLDPE, PA-b-LLDPE), as well as cross-linked polyethylene (PEX-b), are examined. The choice of compatible polymer components for an ultra- high molecular weight matrix for increasing processability (extrudability) is motivated by the search for commercially available and efficient additives aimed at developing wear-resistant extrudable polymer composites for additive manufacturing. The extrudability, mechanical properties and wear resistance of UHMWPE-based polymer-polymeric composites under sliding friction with different velocities and loads are studied.

  15. Polypropylene-polyethylene blends modified by gamma radiation

    International Nuclear Information System (INIS)

    Terence, Mauro C.; Ruiz, Francisco C.

    2009-01-01

    One way to obtain a better mechanical property of polypropylene and polyethylene is to increasing the number of polymer chains cross-linked by gamma radiation. After irradiation a network is formed as a result of various chemical reactions and the radicals formed are concentrated in the amorphous phase. With the objective to improve the mechanical properties of PP, blends with PE were prepared and irradiated in doses up to 500 kGy, in atmospheric ambient. The molecular characterization of the blends was made by infrared spectroscopy and the data showed an increase in rigidity and a unique behaviour in Izod impact resistance. (author)

  16. Interstrand cross-links arising from strand breaks at true abasic sites in duplex DNA

    OpenAIRE

    Yang, Zhiyu; Price, Nathan E.; Johnson, Kevin M.; Wang, Yinsheng; Gates, Kent S.

    2017-01-01

    Abstract Interstrand cross-links are exceptionally bioactive DNA lesions. Endogenous generation of interstrand cross-links in genomic DNA may contribute to aging, neurodegeneration, and cancer. Abasic (Ap) sites are common lesions in genomic DNA that readily undergo spontaneous and amine-catalyzed strand cleavage reactions that generate a 2,3-didehydro-2,3-dideoxyribose sugar remnant (3?ddR5p) at the 3?-terminus of the strand break. Interestingly, this strand scission process leaves an electr...

  17. Interstrand cross-links arising from strand breaks at true abasic sites in duplex DNA.

    Science.gov (United States)

    Yang, Zhiyu; Price, Nathan E; Johnson, Kevin M; Wang, Yinsheng; Gates, Kent S

    2017-06-20

    Interstrand cross-links are exceptionally bioactive DNA lesions. Endogenous generation of interstrand cross-links in genomic DNA may contribute to aging, neurodegeneration, and cancer. Abasic (Ap) sites are common lesions in genomic DNA that readily undergo spontaneous and amine-catalyzed strand cleavage reactions that generate a 2,3-didehydro-2,3-dideoxyribose sugar remnant (3'ddR5p) at the 3'-terminus of the strand break. Interestingly, this strand scission process leaves an electrophilic α,β-unsaturated aldehyde residue embedded within the resulting nicked duplex. Here we present evidence that 3'ddR5p derivatives generated by spermine-catalyzed strand cleavage at Ap sites in duplex DNA can react with adenine residues on the opposing strand to generate a complex lesion consisting of an interstrand cross-link adjacent to a strand break. The cross-link blocks DNA replication by ϕ29 DNA polymerase, a highly processive polymerase enzyme that couples synthesis with strand displacement. This suggests that 3'ddR5p-derived cross-links have the potential to block critical cellular DNA transactions that require strand separation. LC-MS/MS methods developed herein provide powerful tools for studying the occurrence and properties of these cross-links in biochemical and biological systems. © The Author(s) 2017. Published by Oxford University Press on behalf of Nucleic Acids Research.

  18. bis-Nitrile and bis-Dialkylcyanamide Platinum(II) Complexes as Efficient Catalysts for Hydrosilylation Cross-Linking of Siloxane Polymers.

    Science.gov (United States)

    Islamova, Regina M; Dobrynin, Mikhail V; Ivanov, Daniil M; Vlasov, Andrey V; Kaganova, Elena V; Grigoryan, Galina V; Kukushkin, Vadim Yu

    2016-03-05

    cis- and trans-Isomers of the platinum(II) nitrile complexes [PtCl2(NCR)2] (R = NMe2, N(C₅H10), Ph, CH2Ph) were examined as catalysts for hydrosilylation cross-linking of vinyl-terminated polydimethylsiloxane and trimethylsilyl-terminated poly(dimethylsiloxane-co-ethylhydrosiloxane) producing high quality silicone rubbers. Among the tested platinum species the cis-complexes are much more active catalysts than their trans-congeners and for all studied platinum complexes cis-[PtCl2(NCCH2Ph)2] exhibits the best catalytic activity (room temperature, c = 1.0 × 10(-4) mol/L, τpot-life 60 min, τcuring 6 h). Although cis-[PtCl₂(NCCH2Ph)2] is less active than the widely used Karstedt's catalyst, its application for the cross-linking can be performed not only at room temperature (c = 1.0 × 10(-4) mol/L), but also, more efficiently, at 80 °C (c = 1.0 × 10(-4)-1.0 × 10(-5) mol/L) and it prevents adherence of the formed silicone rubbers to equipment. The usage of the cis- and trans-[PtCl2(NCR)2] complexes as the hydrosilylation catalysts do not require any inhibitors and, moreover, the complexes and their mixtures with vinyl- and trimethylsilyl terminated polysiloxanes are shelf-stable in air. Tested catalysts do not form colloid platinum particles after the cross-linking.

  19. Design, Synthesis and Characterization of Polyethylene-Based Macromolecular Architectures by Combining Polyhomologation with Powerful Linking Chemistry

    KAUST Repository

    Alkayal, Nazeeha

    2016-09-05

    Polyhomologation is a powerful method to prepare polyethylene-based materials with controlled molecular weight, topology and composition. This dissertation focuses on the discovery of new synthetic routes to prepare polyethylene-based macromolecular architectures by combining polyhomologation with highly orthogonal and efficient linking reactions such as Diels Alder, copper-catalyzed azide-alkyne cycloaddition (CuAAC), and Glaser. Taking advantage of functionalized polyhomologation initiators, as well as of the efficient coupling chemistry, we were able to synthesize various types of polymethylene (polyethylene)-based materials with complex architectures including linear co/terpolymers, graft terpolymers, and tadpole copolymers. In the first project, a facile synthetic route towards well-defined polymethylene-based co/terpolymers, by combining the anthracene/maleimide Diels–Alder reaction with polyhomologation, is presented. For the synthesis of diblock copolymers the following approach was applied: (a) synthesis of α-anthracene-ω-hydroxy-polymethylene by polyhomologation using tri (9 anthracene-methyl propyl ether) borane as the initiator, (b) synthesis of furan-protected-maleimide-terminated poly(ε-caprolactone) or polyethylene glycol and (c) Diels–Alder reaction between anthracene and maleimide-terminated polymers. In the case of triblock terpolymers, the α-anthracene-ω-hydroxy polymethylene was used as a macroinitiator for the ring-opening polymerization of D, L-lactide to afford an anthracene-terminated PM-b-PLA copolymer, followed by the Diels–Alder reaction with furan-protected maleimide-terminated poly (ε-caprolactone) or polyethylene glycol to give the triblock terpolymers. The synthetic methodology is general and potentially applicable to a range of polymers. The coupling reaction applied in the second project of this dissertation was copper-catalyzed “click” cycloaddition of azides and alkynes (CuAAC). Novel well-defined polyethylene

  20. DNA cross-linking by dehydromonocrotaline lacks apparent base sequence preference.

    Science.gov (United States)

    Rieben, W Kurt; Coulombe, Roger A

    2004-12-01

    Pyrrolizidine alkaloids (PAs) are ubiquitous plant toxins, many of which, upon oxidation by hepatic mixed-function oxidases, become reactive bifunctional pyrrolic electrophiles that form DNA-DNA and DNA-protein cross-links. The anti-mitotic, toxic, and carcinogenic action of PAs is thought to be caused, at least in part, by these cross-links. We wished to determine whether the activated PA pyrrole dehydromonocrotaline (DHMO) exhibits base sequence preferences when cross-linked to a set of model duplex poly A-T 14-mer oligonucleotides with varying internal and/or end 5'-d(CG), 5'-d(GC), 5'-d(TA), 5'-d(CGCG), or 5'-d(GCGC) sequences. DHMO-DNA cross-links were assessed by electrophoretic mobility shift assay (EMSA) of 32P endlabeled oligonucleotides and by HPLC analysis of cross-linked DNAs enzymatically digested to their constituent deoxynucleosides. The degree of DNA cross-links depended upon the concentration of the pyrrole, but not on the base sequence of the oligonucleotide target. Likewise, HPLC chromatograms of cross-linked and digested DNAs showed no discernible sequence preference for any nucleotide. Added glutathione, tyrosine, cysteine, and aspartic acid, but not phenylalanine, threonine, serine, lysine, or methionine competed with DNA as alternate nucleophiles for cross-linking by DHMO. From these data it appears that DHMO exhibits no strong base preference when forming cross-links with DNA, and that some cellular nucleophiles can inhibit DNA cross-link formation.

  1. Effect of Packaging on Shelf-life and Lutein Content of Marigold (Tagetes erecta L.) Flowers.

    Science.gov (United States)

    Pal, Sayani; Ghosh, Probir Kumar; Bhattacharjee, Paramita

    2016-01-01

    African marigold (Tagetes erecta L.) flowers are highly valued for their ornamental appeal as well as medicinal properties. However, their short shelf lives cause high post-harvest loss and limit their export potential. The review of patents and research articles revealed that different types of packaging designs/materials have been successfully employed for extension of shelf lives of cut flowers. The current work focuses on designing of different packaging configurations and selection of best configuration for preservation of marigold cut flowers. Ten packaging configurations, composed of four different packaging materials i.e., low density polyethylene (LDPE), polyethylene terephthalate, glassine paper and cellophane paper, were designed. Each pack, consisting of 20 ± 1 g of marigold flowers along with non-packaged control set were stored at 23 ± 2°C, 80% R.H., in an environmental chamber and the flowers were evaluated for their sensory attributes, phytochemical characteristics and physicochemical parameters of senescence to determine their shelf lives. Flowers packed in LDPE bag showed highest shelf life of 8 days with a lead of 4 days compared to control (shelf life - 4 days). This study also established for the first time the phenomenon of carotenogenesis in marigold cut flowers with significantly (Pshelf lives. This economically viable packaging can not only boost the export potential of this ornamental flower, but also allow utilization of nutraceutical potency of lutein.

  2. Composition of cross-linked 125I-follitropin-receptor complexes

    Energy Technology Data Exchange (ETDEWEB)

    Shin, J.; Ji, T.H.

    1985-10-15

    Both of the alpha and beta subunits of intact human follitropin (FSH) were radioiodinated with SVI-sodium iodide and chloramine-T and could be resolved on sodium dodecyl sulfate-polyacrylamide gels. Radioiodinated FSH was affinity-cross-linked with a cleavable (nondisulfide) homobifunctional reagent to its membrane receptor on the porcine granulosa cell surface as well as to a Triton X-100-solubilized form of the receptor. Cross-linked samples revealed three additional bands of slower electrophoretic mobility, corresponding to 65, 83, and 117 kDa, in addition to the hormone bands. The hormone alpha beta dimer band corresponded to 43 kDa. Formation of the three bands requires the SVI-hormone to bind specifically to the receptor with subsequent cross-linking. Binding was prevented by an excess of the native hormone but not by other hormones. A monofunctional analog of the cross-linking reagent failed to produce the three bands. Reagent concentration-dependent cross-linking revealed that their formation was sequential; smaller complexes formed first and then larger ones. When gels of cross-linked complexes were treated to cleave covalent cross-links and then electrophoresed in a second dimension, 18-, 22-, and 34-kDa components were released, in addition to the alpha and beta subunits of the hormone.

  3. Determining equilibrium osmolarity in poly(ethylene glycol)/chondrotin sulfate gels mimicking articular cartilage.

    Science.gov (United States)

    Sircar, S; Aisenbrey, E; Bryant, S J; Bortz, D M

    2015-01-07

    We present an experimentally guided, multi-phase, multi-species polyelectrolyte gel model to make qualitative predictions on the equilibrium electro-chemical properties of articular cartilage. The mixture theory consists of two different types of polymers: poly(ethylene gylcol) (PEG), chondrotin sulfate (ChS), water (acting as solvent) and several different ions: H(+), Na(+), Cl(-). The polymer chains have covalent cross-links whose effect on the swelling kinetics is modeled via Doi rubber elasticity theory. Numerical studies on equilibrium polymer volume fraction and net osmolarity (difference in the solute concentration across the gel) show a complex interplay between ionic bath concentrations, pH, cross-link fraction and the average charge per monomer. Generally speaking, swelling is aided due to a higher average charge per monomer (or a higher particle fraction of ChS, the charged component of the polymer), low solute concentration in the bath, a high pH or a low cross-link fraction. A peculiar case arises at higher values of cross-link fraction, where it is observed that increasing the average charge per monomer leads to gel deswelling. Copyright © 2014 Elsevier Ltd. All rights reserved.

  4. UV laser-induced cross-linking in peptides

    Science.gov (United States)

    Leo, Gabriella; Altucci, Carlo; Bourgoin-Voillard, Sandrine; Gravagnuolo, Alfredo M.; Esposito, Rosario; Marino, Gennaro; Costello, Catherine E.; Velotta, Raffaele; Birolo, Leila

    2013-01-01

    RATIONALE The aim of this study was to demonstrate, and to characterize by high resolution mass spectrometry, that it is possible to preferentially induce covalent cross-links in peptides by using high energy femtosecond UV laser pulses. The cross-link is readily formed only when aromatic amino acids are present in the peptide sequence. METHODS Three peptides, xenopsin, angiotensin I, interleukin, individually or in combination, were exposed to high energy femtosecond UV laser pulses, either alone or in the presence of spin trapping molecules, the reaction products being characterized by high resolution mass spectrometry. RESULTS High resolution mass spectrometry and spin trapping strategies showed that cross-linking occurs readily, proceeds via a radical mechanism, and is the highly dominant reaction, proceeding without causing significant photo-damage in the investigated range of experimental parameters. CONCLUSIONS High energy femtosecond UV laser pulses can be used to induce covalent cross-links between aromatic amino acids in peptides, overcoming photo-oxidation processes, that predominate as the mean laser pulse intensity approaches illumination conditions achievable with conventional UV light sources. PMID:23754800

  5. Paleocene Wilcox cross-shelf channel-belt history and shelf-margin growth: Key to Gulf of Mexico sediment delivery

    Science.gov (United States)

    Zhang, Jinyu; Steel, Ronald; Ambrose, William

    2017-12-01

    Shelf margins prograde and aggrade by the incremental addition of deltaic sediments supplied from river channel belts and by stored shoreline sediment. This paper documents the shelf-edge trajectory and coeval channel belts for a segment of Paleocene Lower Wilcox Group in the northern Gulf of Mexico based on 400 wireline logs and 300 m of whole cores. By quantitatively analyzing these data and comparing them with global databases, we demonstrate how varying sediment supply impacted the Wilcox shelf-margin growth and deep-water sediment dispersal under greenhouse eustatic conditions. The coastal plain to marine topset and uppermost continental slope succession of the Lower Wilcox shelf-margin sediment prism is divided into eighteen high-frequency ( 300 ky duration) stratigraphic sequences, and further grouped into 5 sequence sets (labeled as A-E from bottom to top). Sequence Set A is dominantly muddy slope deposits. The shelf edge of Sequence Sets B and C prograded rapidly (> 10 km/Ma) and aggraded modestly ( 80 m/Ma) characterizes Sequence Sets D and E, which is associated with smaller (9-10 m thick on average) and isolated channel belts. This stratigraphic trend is likely due to an upward decreasing sediment supply indicated by the shelf-edge progradation rate and channel size, as well as an upward increasing shelf accommodation indicated by the shelf-edge aggradation rate. The rapid shelf-edge progradation and large rivers in Sequence Sets B and C confirm earlier suggestions that it was the early phase of Lower Wilcox dispersal that brought the largest deep-water sediment volumes into the Gulf of Mexico. Key factors in this Lower Wilcox stratigraphic trend are likely to have been a very high initial sediment flux to the Gulf because of the high initial release of sediment from Laramide catchments to the north and northwest, possibly aided by modest eustatic sea-level fall on the Texas shelf, which is suggested by the early, flat shelf-edge trajectory, high

  6. Effects of Surface Modification and Bulk Geometry on the Biotribological Behavior of Cross-Linked Polyethylene: Wear Testing and Finite Element Analysis

    Directory of Open Access Journals (Sweden)

    Kenichi Watanabe

    2015-01-01

    phosphorylcholine- (PMPC- grafted CLPE, through wear tests and finite element analysis. The gravimetric and volumetric degrees of wear of disks (3 or 6 mm in thickness of these materials against a cobalt-chromium-molybdenum alloy pin were examined using a multidirectional pin-on-disk tester. Cross-linking and PMPC grafting decreased the gravimetric wear of the PE disks significantly. The volumetric wear at the bearing surface and the volumetric penetration in the backside of the 3-mm thick PE disk were higher than those of the 6-mm thick PE disk, regardless of the bearing material. The geometrical changes induced in the PE disks consisted of creep, because the calculated internal von Mises stress at the bearing side of all disks and that at the backside of the 3-mm thick disks exceeded their actual yield strengths. A highly hydrated bearing surface layer, formed by PMPC grafting, and a cross-linking-strengthened substrate of adequate thickness are essential for increasing the wear and creep deformation resistances.

  7. Eddy-induced cross-shelf export of high Chl-a coastal waters in the SE Bay of Biscay

    KAUST Repository

    Rubio, Anna; Caballero, Ainhoa; Orfila, Alejandro; Herná ndez-Carrasco, Ismael; Ferrer, Luis; Gonzá lez, Manuel; Solabarrieta, Lohitzune; Mader, Julien

    2017-01-01

    with similar characteristics in the area during different winters within the period 2011–2014. Our results suggest that the eddy-induced recurrent cross-shelf export is an effective mechanism for the expansion of coastal productive waters into the adjacent

  8. Estimating the Cross-Shelf Export of Riverine Materials: Part 1. General Relationships From an Idealized Numerical Model

    Science.gov (United States)

    Izett, Jonathan G.; Fennel, Katja

    2018-02-01

    Rivers deliver large amounts of terrestrially derived materials (such as nutrients, sediments, and pollutants) to the coastal ocean, but a global quantification of the fate of this delivery is lacking. Nutrients can accumulate on shelves, potentially driving high levels of primary production with negative consequences like hypoxia, or be exported across the shelf to the open ocean where impacts are minimized. Global biogeochemical models cannot resolve the relatively small-scale processes governing river plume dynamics and cross-shelf export; instead, river inputs are often parameterized assuming an "all or nothing" approach. Recently, Sharples et al. (2017), https://doi.org/10.1002/2016GB005483 proposed the SP number—a dimensionless number relating the estimated size of a plume as a function of latitude to the local shelf width—as a simple estimator of cross-shelf export. We extend their work, which is solely based on theoretical and empirical scaling arguments, and address some of its limitations using a numerical model of an idealized river plume. In a large number of simulations, we test whether the SP number can accurately describe export in unforced cases and with tidal and wind forcings imposed. Our numerical experiments confirm that the SP number can be used to estimate export and enable refinement of the quantitative relationships proposed by Sharples et al. We show that, in general, external forcing has only a weak influence compared to latitude and derive empirical relationships from the results of the numerical experiments that can be used to estimate riverine freshwater export to the open ocean.

  9. Study of the Conformational State of Non-Cross-Linked and Cross-Linked Poly(alkylmethyldiallylammonium chlorides) in Aqueous Solution by Fluorescence Probing

    NARCIS (Netherlands)

    Wang, Guang-Jia; Engberts, Jan B.F.N.

    The aggregation behaviour of novel non-cross-linked and cross-linked poly(alkylmethyldiallylammonium chlorides) in aqueous solutions has been investigated by fluorescence spectroscopy using pyrene as a probe. These copolymers were found to exhibit similar aggregate properties as the corresponding

  10. Radiation cross-linked polymers: Recent developments and new applications

    International Nuclear Information System (INIS)

    Rouif, Sophie

    2005-01-01

    The purpose of the present paper is to review the innovative and recent applications of radiation cross-linking of polymers that reinforces their dimensional stability in chemically aggressive and high temperature conditions. Radiation cross-linking can be applied to a great number of plastics: thermoplastics, elastomers and thermoplastic elastomers (TPE). Some of them can cross-link on their own, some others need to be formulated with a cross-linking agent (promoter) or to be modified during their polymerization. Some results of chemical and thermomechanical characterizations of radiation cross-linked plastics based on engineering polymers will be described, and their advantages will be emphasized in relation with their applications in various sectors: pipes and cables, packaging, automotive, electrical engineering and electronics, including connectors, surface mounted devices, integrated circuits, 3D-MID technology, etc. The paper will conclude with a short review of the industrial irradiation facilities (EB facilities and gamma plants) adapted to the treatment of such various products

  11. Interim report on assessment of cable aging for nuclear power plants

    International Nuclear Information System (INIS)

    2006-12-01

    Research on assessment of cable aging for nuclear power plants (NPPs) started in 2002 in order to obtain data of safety-related cables affected by thermal aging, simultaneous thermal and radiation aging, and Loss-of-Coolant Accident (LOCA) equivalent test, which could contribute to draft guideline on comprehensive assessment of cable aging for NPPs while taking into consideration the latest knowledge. For the cable aging test, cross-linked polyethylene, flame-retardant cross-linked polyethylene, ethylene propylene rubber, flame-retardant ethylene propylene rubber, silicone rubber and special heat-resistant polyvinyl chloride insulators were selected from the safety-related cables used in the nuclear power plants. Furthermore, 2 to 3 kinds of cables with insulators of different manufacturers were added making a total of 14 kinds of cable specimens for the test. Aging period was selected as a basic parameter while three temperature conditions for thermal aging specimen and combined nine conditions of three temperatures with three dose rates for simultaneous aging specimens. Degradation of cable aging was characterized by elongation at break of tensile test. LOCA test for 9 kinds of cables was also conducted using the simultaneous aging specimens. Furthermore, the investigation of applicability of non-destructive degradation diagnostic technologies for aged cables was conducted to confirm the validity of cable aging evaluation at actual operating plants. Interim report was issued in 2006 and based on cable aging test until 21,000 hrs maximum; 1) a significant difference might be observed at times in the aging progress depending on the insulator manufacturer even if the insulator type was identical, 2) activation energy values calculated from the thermal aging test data were smaller than those currently used and principles of calculation and application of the activation energy were developed for evaluation and 3) superposition of time dependent data was applicable to

  12. Modified gum arabic cross-linked gelatin scaffold for biomedical applications

    International Nuclear Information System (INIS)

    Sarika, P.R.; Cinthya, Kuriakose; Jayakrishnan, A.; Anilkumar, P.R.; James, Nirmala Rachel

    2014-01-01

    The present work deals with development of modified gum arabic cross-linked gelatin scaffold for cell culture. A new biocompatible scaffold was developed by cross-linking gelatin (Gel) with gum arabic, a polysaccharide. Gum arabic was subjected to periodate oxidation to obtain gum arabic aldehyde (GAA). GAA was reacted with gelatin under appropriate pH to prepare the cross-linked hydrogel. Cross-linking occurred due to Schiff's base reaction between aldehyde groups of oxidized gum arabic and amino groups of gelatin. The scaffold prepared from the hydrogel was characterized by swelling properties, degree of cross-linking, in vitro degradation and scanning electron microscopy (SEM). Cytocompatibility evaluation using L-929 and HepG2 cells confirmed non-cytotoxic and non-adherent nature of the scaffold. These properties are essential for generating multicellular spheroids and hence the scaffold is proposed to be a suitable candidate for spheroid cell culture. - Highlights: • Gum arabic cross-linked gelatin scaffold was developed for tissue engineering. • Cross-linking was achieved by Schiff's base reaction. • The scaffold is non-cytotoxic and non adherent to fibroblast and hepatocytes. • The scaffolds are potential candidates for spheroid cell culture

  13. Modified gum arabic cross-linked gelatin scaffold for biomedical applications

    Energy Technology Data Exchange (ETDEWEB)

    Sarika, P.R. [Department of Chemistry, Indian Institute of Space Science and Technology, Valiamala, Thiruvananthapuram, Kerala 695 547 (India); Cinthya, Kuriakose [Tissue Culture Laboratory, Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Poojappura, Thiruvananthapuram, Kerala 695 012 (India); Jayakrishnan, A. [Department of Biotechnology, Indian Institute of Technology Madras, Chennai 600 036 (India); Anilkumar, P.R., E-mail: anilkumarpr@sctimst.ac.in [Tissue Culture Laboratory, Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology, Poojappura, Thiruvananthapuram, Kerala 695 012 (India); James, Nirmala Rachel, E-mail: nirmala@iist.ac.in [Department of Chemistry, Indian Institute of Space Science and Technology, Valiamala, Thiruvananthapuram, Kerala 695 547 (India)

    2014-10-01

    The present work deals with development of modified gum arabic cross-linked gelatin scaffold for cell culture. A new biocompatible scaffold was developed by cross-linking gelatin (Gel) with gum arabic, a polysaccharide. Gum arabic was subjected to periodate oxidation to obtain gum arabic aldehyde (GAA). GAA was reacted with gelatin under appropriate pH to prepare the cross-linked hydrogel. Cross-linking occurred due to Schiff's base reaction between aldehyde groups of oxidized gum arabic and amino groups of gelatin. The scaffold prepared from the hydrogel was characterized by swelling properties, degree of cross-linking, in vitro degradation and scanning electron microscopy (SEM). Cytocompatibility evaluation using L-929 and HepG2 cells confirmed non-cytotoxic and non-adherent nature of the scaffold. These properties are essential for generating multicellular spheroids and hence the scaffold is proposed to be a suitable candidate for spheroid cell culture. - Highlights: • Gum arabic cross-linked gelatin scaffold was developed for tissue engineering. • Cross-linking was achieved by Schiff's base reaction. • The scaffold is non-cytotoxic and non adherent to fibroblast and hepatocytes. • The scaffolds are potential candidates for spheroid cell culture.

  14. Combination of ozone and packaging treatments maintained the quality and improved the shelf life of tomato fruit

    Science.gov (United States)

    Zainuri; Jayaputra; Sauqi, A.; Sjah, T.; Desiana, R. Y.

    2018-01-01

    Tomato is very important vegetable crop but has short shelf life. The objective of this research was to determine the effect of ozone and packaging combination treatment on the quality and the storage life of tomato fruit. There were six treatments including: control (without ozone and packaging); without ozone and packaged with polyethylene bag; without ozone and polyethylene terephtalate punnet; with ozone but without packaging; with ozone and packaged with polyethylene bag; and with ozone and polyethylene terephtalate punnet. Each treatment was made into 3 replications. Tomato samples were harvested at turning stage. Ozone treatment was applied for 60 seconds. Tomatoes were then treated with and without packaging. The fruit were then stored at room temperature for up to 12 days. The parameters for assessment were water content, color, texture, weight loss and the population of naturally contamination Escherichia coli. Each parameter was assessed on day 0, 6 and 12 of storage. The results indicated that combination of ozone and packaging treatments significantly affected the physical and biochemical changes (water content, color, texture and weight loss) of the fruit, suppressed the microbiological contamination on the fruit and maintained fruit freshness or quality after 12 days of storage. The combination of ozone and perforated polyethylene packaging treatment was the best treatment to maintain the quality and prolonged the shelf life of tomato fruit to be 12 days at room temperature.

  15. Cross-linking of wheat gluten using a water-soluble carbodiimide

    NARCIS (Netherlands)

    Tropini, V.; Lens, J.P.; Mulder, W.J.; Silvestre, F.

    2000-01-01

    Wheat gluten was cross-linked using water-soluble 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide HCl (EDC). To enhance cross-linking, N-hydroxysuccinimide (NHS) was added to the reaction mixture. The cross-linking efficiency was evaluated by the decrease in the amount of amino groups, the solubility

  16. Ageing of cable insulators made of polyethylene in nuclear environment; Vieillissement d'isolants de cables en polyethylene en ambiance nucleaire

    Energy Technology Data Exchange (ETDEWEB)

    Khelidj, N

    2006-10-15

    This thesis deals with lifetime prediction for polyethylene in nuclear environment. It is mainly characterised by the search for a non empirical solution. We have tried to elaborate a model describing the polymer evolution (including the skin-core heterogeneity due to the kinetic control of oxidation by oxygen diffusion) at any temperature between ambient and the melting point of the polymer, and at any dose rate between 0 and 1 kGy.h-1, with lifetimes extending to several decades of years. The main difficulty was to take into account the dual character of initiation which results from the combination of polymer radiolysis and hydroperoxide thermal decomposition. The problem was resolved considering first the asymptotic regimes where one initiation process can be neglected relatively to the other one. The kinetic parameters specific to those regimes being identified, we have built a numerical model including all the processes. In the case of un-stabilised polyethylene, this model displays excellent predictive qualities, as well in lifetime, as in thickness distribution of oxidation products. The study of stabilised polyethylenes was then initiated with samples respectively stabilised by a hindered phenol, and a thio-diester. In the case of phenol, the study of consumption kinetics reveals the existence of complex mechanisms, especially the existence of a 'reservoir effect' linked to the presence of a separated phase of phenol in excess. A kinetic model has been proposed, but we still do not know how the results can be generalised to other phenolic stabilizers. (author)

  17. Photoreactivities and thermal properties of psoralen cross-links

    International Nuclear Information System (INIS)

    Yeung, A.T.; Jones, B.K.; Chu, C.T.

    1988-01-01

    The authors have studied the photoreaction of 8-methoxypsoralen (8-MOP), 4,5',8-trimethylpsoralen (TMP), and 4'-(hydroxymethyl)-4,5',8-trimethylpsoralen (HMT) with a pair of 18-base-long oligonucleotides in which a 14-base region is complementary. Only one 5'TpA site, favored for both monoadduct and cross-link formation with psoralen, is present in this oligonucleotide pair. They have used this model system to demonstrate, for the first time, strand specificity in the photoreaction of psoralen with DNA. They found that the two types of cross-links which form at this site have large differences in thermal stabilities. In addition, the denaturation of each cross-links isomer duplex occurred in at least three stages, which can be visualized as three bands in thermal equilibrium under the conditions of a denaturing polyacrylamide gel. This novel observation suggests that there are several domains differing in thermal stability in a psoralen cross-link

  18. Collagen cross-linking in thin corneas

    Directory of Open Access Journals (Sweden)

    Prema Padmanabhan

    2013-01-01

    Full Text Available Collagen cross-linking (CXL has become the standard of care for progressive keratoconus, after numerous clinical studies have established its efficacy and safety in suitably selected eyes. The standard protocol is applicable in eyes which have a minimum corneal thickness of 400 μm after epithelial debridement. This prerequisite was stipulated to protect the corneal endothelium and intraocular tissues from the deleterious effect of ultraviolet-A (UVA radiation. However, patients with keratoconus often present with corneal thickness of less than 400 μm and could have otherwise benefited from this procedure. A few modifications of the standard procedure have been suggested to benefit these patients without a compromise in safety. Transepithelial cross-linking, pachymetry-guided epithelial debridement before cross-linking, and the use of hypoosmolar riboflavin are some of the techniques that have been attempted. Although clinical data is limited at the present time, these techniques are worth considering in patients with thin corneas. Further studies are needed to scientifically establish their efficacy and safety.

  19. Highly Cross-Linked Polyethylene in Total Hip and Knee Replacement: Spatial Distribution of Molecular Orientation and Shape Recovery Behavior

    Directory of Open Access Journals (Sweden)

    Yasuhito Takahashi

    2014-01-01

    Full Text Available The present study investigated effects of processing procedures on morphology of highly cross-linked and re-melted UHMWPE (XLPE in total hip and knee arthroplasty (THA, TKA. The shape recovery behavior was also monitored via uniaxial compression test at room temperature after non-destructive characterizations of the in-depth microstructure by confocal/polarized Raman spectroscopy. The goal of this study was to relate the manufacturing-induced morphology to the in vivo micromechanical performance, and ultimately to explore an optimal structure in each alternative joint bearing. It was clearly confirmed that the investigated XLPE hip and knee implants, which were produced from different orthopaedic grade resins (GUR 1050 and GUR 1020, consisted of two structural regions in the as-received states: the near-surface transitional anisotropic layer (≈100 μm thickness and the bulk isotropic structural region. These XLPEs exhibited a different crystalline anisotropy and molecular texture within the near-surface layers. In addition, the knee insert showed a slightly higher efficiency of shape recovery against the applied strain over the hip liner owing to a markedly higher percentage of the bulk amorphous phase with intermolecular cross-linking. The quantitative data presented in this study might contribute to construct manufacturing strategies for further rationalized structures as alternative bearings in THA and TKA.

  20. Elastin cross-linking in the skin from patients with amyotrophic lateral sclerosis

    Science.gov (United States)

    Ono, S.; Yamauchi, M.

    1994-01-01

    Two cross-links unique to elastin, desmosine and isodesmosine were measured and compared in skin tissue (left upper arm) from 10 patients with amyotrophic lateral sclerosis (ALS) and from seven age-matched controls. The contents of desmosine and isodesmosine were significantly decreased (p elastin is affected in ALS.

  1. Cross-linked polyelectrolyte multilayers for marine antifouling applications

    NARCIS (Netherlands)

    Zhu, X.; Janczewski, D.; Lee, S.S.C.; Teo, S.L-M.; Vancso, Gyula J.

    2013-01-01

    A polyionic multilayer film was fabricated by layer-by-layer (LbL) sequential deposition followed by cross-linking under mild conditions on a substrate surface to inhibit marine fouling. A novel polyanion, featuring methyl ester groups for an easy cross-linking was used as a generic solution for

  2. Enzymatic digestibility of peptides cross-linked by ionizing radiation

    International Nuclear Information System (INIS)

    Dizdaroglu, M.; Gajewski, E.; Simic, M.G.

    1984-01-01

    Digestibility by proteolytic enzymes of peptides cross-linked by ionizing radiation was investigated. Small peptides of alanine and phenylalanine were chosen as model compounds and aminopeptidases and carboxypeptidases were used as proteolytic enzymes. Peptides exposed to γ-radiation in aqueous solution were analysed by high-performance liquid chromatography before and after hydrolysis by aminopeptidase M, leucine aminopeptidase carboxypeptidase A and carboxypeptidase Y. The results obtained clearly demonstrate the different actions of these enzymes on cross-linked aliphatic and aromatic peptides. Peptide bonds of cross-linked dipeptides of alanine were completely resistant to enzymatic hydrolysis whereas the enzymes, except for carboxypeptidase Y, cleaved all peptide bonds of cross-linked peptides of phenylalanine. The actions of the enzymes on these particular compounds are discussed in detail. (author)

  3. Mechanical properties and collagen cross-linking of the patellar tendon in old and young men

    DEFF Research Database (Denmark)

    Couppé, C; Hansen, P; Kongsgaard, M

    2009-01-01

    were higher in OM than in YM (73 +/- 13 vs. 11 +/- 2 mmol/mol; P appreciably influence the dimensions or mechanical properties of the human patellar tendon in vivo. Collagen concentration was reduced, whereas both enzymatic......Age-related loss in muscle mass and strength impairs daily life function in the elderly. However, it remains unknown whether tendon properties also deteriorate with age. Cross-linking of collagen molecules provides structural integrity to the tendon fibrils and has been shown to change with age...... in animals but has never been examined in humans in vivo. In this study, we examined the mechanical properties and pyridinoline and pentosidine cross-link and collagen concentrations of the patellar tendon in vivo in old (OM) and young men (YM). Seven OM (67 +/- 3 years, 86 +/- 10 kg) and 10 YM (27 +/- 2...

  4. Synthesis and Catalytic Properties of Non-Cross-Linked and Cross-Linked Poly(alkylmethyldiallylammonium bromides) Having Decyl, Octyl, and Hexyl Side Chains

    NARCIS (Netherlands)

    Wang, G.J; Engberts, J.B.F.N.

    1995-01-01

    A family of non-cross-linked and cross-linked copolymers containing decyl, octyl, and hexyl groups as side chains ((CL)-CopolC1-10, (CL)-CopolC1-8, and (CL)-CopolC1-6, respectively) were synthesized by radical-initiated cyclocopolymerization of alkylmethyldiallylammonium bromide monomers without and

  5. The effect of virtual cross linking on the oxidative stability and lipid uptake of aliphatic poly(urethane urea).

    Science.gov (United States)

    Thomas, Vinoy; Jayabalan, Muthu

    2002-01-01

    In vitro oxidative degradation and lipid sorption of aliphatic, low elastic modulus and virtually cross-linked poly(urethane urea)s based on 4,4' methylene bis(cyclohexyl isocyanate), hydroxy terminated poly butadiene and hexamethylene diamine were evaluated. The aged samples revealed no weight loss in the oxidation medium. The IR spectral analyses revealed the stability of unsaturated double bonds at 964 cm(-1) (characteristic for polybutadiene soft segment) with no change in peak intensity. The poly(tetramethylene glycol) (PTMG)-added poly(ether urethane urea) polymer also revealed no disappearance of IR peaks for ether and unsaturated double bonds in samples aged in vitro oxidation medium. All the polymers have shown increase in weight due to lipid up take in lipid-rich medium (palm oil) but it was rather low in Dulbecco's modified eagle medium (DMEM) cholesterol. The slight change in mechanical properties of the present polymers in oxidation and DMEM is due to the rearrangement of molecular structure with virtual cross links of hydrogen bonding (physical cross linking) without degradation and plasticization effect of lipid. The influence of these media on the rearrangement of virtual cross links has been observed. Higher the virtual cross-link density, lesser is the loss of tensile properties of poly(urethane urea)s in the oxidation medium and vice versa. On the other hand, higher the virtual cross-link density of poly(urethane urea), higher is the loss of ultimate tensile strength and stress at 100% strain and vice versa in DMEM medium.

  6. Effect of Addition of Soybean Oil and Gamma-Ray Cross-linking on the Nanoporous HDPE Membrane

    Directory of Open Access Journals (Sweden)

    Jong-Seok Park

    2012-01-01

    Full Text Available A nanoporous high-density polyethylene (HDPE membrane was prepared by a wet process. Soybean oil and dibutyl phthalate (DBP were premixed as codiluents, and gamma-rays were used for the cross-linking of HDPE. The pore volume of the nanoporous HDPE membranes with soybean oil was affected by the extracted amount of oil. The tensile strength of the membrane improved with an increasing absorbed dose up to 60 kGy, but decreased at 80 kGy due to severe degradation. The ionic conductivity of the nanoporous HDPE membrane did not really change with an increasing absorbed dose because the pores had already been formed before the gamma-ray radiation. Finally, the electrochemical stability of the HDPE membrane increased when the absorbed dose increased up to 60 kGy.

  7. Fabrication of chemically cross-linked porous gelatin matrices.

    Science.gov (United States)

    Bozzini, Sabrina; Petrini, Paola; Altomare, Lina; Tanzi, Maria Cristina

    2009-01-01

    The aim of this study was to chemically cross-link gelatin, by reacting its free amino groups with an aliphatic diisocyanate. To produce hydrogels with controllable properties, the number of reacting amino groups was carefully determined. Porosity was introduced into the gelatin-based hydrogels through the lyophilization process. Porous and non-porous matrices were characterized with respect to their chemical structure, morphology, water uptake and mechanical properties. The physical, chemical and mechanical properties of the porous matrices are related to the extent of their cross-linking, showing that they can be controlled by varying the reaction parameters. Water uptake values (24 hours) vary between 160% and 200% as the degree of cross-linking increases. The flexibility of the samples also decreases by changing the extent of cross-linking. Young's modulus shows values between 0.188 KPa, for the highest degree, and 0.142 KPa for the lowest degree. The matrices are potential candidates for use as tissue-engineering scaffolds by modulating their physical chemical properties according to the specific application.

  8. Practical application of thermoreversibly Cross-linked rubber products

    Science.gov (United States)

    Polgar, L. M.; Picchioni, F.; de Ruiter, E.; van Duin, M.

    2017-07-01

    Currently, rubber products cannot simply be reprocessed after their product life, due to the irreversible cross-linking methods traditionally applied. The purpose of this work is to investigate how thermoreversible cross-linking of rubbers via Diels Alder chemistry can be used for the development of recyclable rubber products. Unfortunately, the applicability of the thermoreversible EPM-g-furan/BM system appears to be limited to room temperature applications, because of the rapid deterioration of the compression set at elevated temperatures compared to irreversibly cross-linked EPM. However, the use of EPM rubber modified with thiophene or cyclopentadiene moieties may extend the temperature application range and results in rubber products with acceptable properties. Finally, rubber products generally comprise fillers such as silica, carbon black or fibers. In this context, the reinforcing effect of short cut aramid fibers on the material properties of the newly developed thermoreversibly cross-linked EPM rubbers was also studied. The material properties of the resulting products were found to be comparable to those of a fiber reinforced, peroxide cured reference sample.

  9. On the Reproducibility of Label-Free Quantitative Cross-Linking/Mass Spectrometry

    Science.gov (United States)

    Müller, Fränze; Fischer, Lutz; Chen, Zhuo Angel; Auchynnikava, Tania; Rappsilber, Juri

    2018-02-01

    Quantitative cross-linking/mass spectrometry (QCLMS) is an emerging approach to study conformational changes of proteins and multi-subunit complexes. Distinguishing protein conformations requires reproducibly identifying and quantifying cross-linked peptides. Here we analyzed the variation between multiple cross-linking reactions using bis[sulfosuccinimidyl] suberate (BS3)-cross-linked human serum albumin (HSA) and evaluated how reproducible cross-linked peptides can be identified and quantified by LC-MS analysis. To make QCLMS accessible to a broader research community, we developed a workflow that integrates the established software tools MaxQuant for spectra preprocessing, Xi for cross-linked peptide identification, and finally Skyline for quantification (MS1 filtering). Out of the 221 unique residue pairs identified in our sample, 124 were subsequently quantified across 10 analyses with coefficient of variation (CV) values of 14% (injection replica) and 32% (reaction replica). Thus our results demonstrate that the reproducibility of QCLMS is in line with the reproducibility of general quantitative proteomics and we establish a robust workflow for MS1-based quantitation of cross-linked peptides.

  10. Effects of Supercritical CO 2 Conditioning on Cross-Linked Polyimide Membranes

    KAUST Repository

    Kratochvil, Adam M.

    2010-05-25

    The effects of supercritical CO2 (scCO2) conditioning on high-performance cross-linked polyimide membranes is examined through gas permeation and sorption experiments. Under supercritical conditions, the cross-linked polymers do not exhibit a structural reorganization of the polymer matrix that was observed in the non-cross-linkable, free acid polymer. Pure gas permeation isotherms and mixed gas permeabilities and selectivities show the cross-linked polymers to be much more stable to scCO2 conditioning than the free acid polymer. In fact, following scCO2 conditioning, the mixed gas CO2 permeabilities of the cross-linked polymers increased while the CO2/CH4 separation factors remained relatively unchanged. This response highlights the stability and high performance of these cross-linked membranes in aggressive environments. In addition, this response reveals the potential for the preconditioning of cross-linked polymer membranes to enhance productivity without sacrificing efficiency in practical applications which, in effect, provides another tool to \\'tune\\' membrane properties for a given separation. Finally, the dual mode model accurately describes the sorption and dilation characteristics of the cross-linked polymers. The changes in the dual mode sorption model parameters before and after the scCO2 exposure also provide insights into the alterations in the different glassy samples due to the cross-linking and scCO2 exposure. © 2010 American Chemical Society.

  11. Sequential optimization of methotrexate encapsulation in micellar nano-networks of polyethyleneimine ionomer containing redox-sensitive cross-links.

    Science.gov (United States)

    Abolmaali, Samira Sadat; Tamaddon, Ali; Yousefi, Gholamhossein; Javidnia, Katayoun; Dinarvand, Rasoul

    2014-01-01

    A functional polycation nanonetwork was developed for delivery of water soluble chemotherapeutic agents. The complexes of polyethyleneimine grafted methoxy polyethylene glycol (PEI-g-mPEG) and Zn(2+) were utilized as the micellar template for cross-linking with dithiodipropionic acid, followed by an acidic pH dialysis to remove the metal ion from the micellar template. The synthesis method was optimized according to pH, the molar ratio of Zn(2+), and the cross-link ratio. The atomic force microscopy showed soft, discrete, and uniform nano-networks. They were sensitive to the simulated reductive environment as determined by Ellman's assay. They showed few positive ζ potential and an average hydrodynamic diameter of 162±10 nm, which decreased to 49±11 nm upon dehydration. The ionic character of the nano-networks allowed the achievement of a higher-loading capacity of methotrexate (MTX), approximately 57% weight per weight, depending on the cross-link and the drug feed ratios. The nano-networks actively loaded with MTX presented some suitable properties, such as the hydrodynamic size of 117±16 nm, polydispersity index of 0.22, and a prolonged swelling-controlled release profile over 24 hours that boosted following reductive activation of the nanonetwork biodegradation. Unlike the PEI ionomer, the nano-networks provided an acceptable cytotoxicity profile. The drug-loaded nano-networks exhibited more specific cytotoxicity against human hepatocellular carcinoma cells if compared to free MTX at concentrations above 1 μM. The enhanced antitumor activity in vitro might be attributed to endocytic entry of MTX-loaded nano-networks that was found in the epifluorescence microscopy experiment for the fluorophore-labeled nano-networks.

  12. Antibiofouling hybrid dendritic Boltorn/star PEG thiol-ene cross-linked networks.

    Science.gov (United States)

    Bartels, Jeremy W; Imbesi, Philip M; Finlay, John A; Fidge, Christopher; Ma, Jun; Seppala, Jonathan E; Nystrom, Andreas M; Mackay, Michael E; Callow, James A; Callow, Maureen E; Wooley, Karen L

    2011-06-01

    A series of thiol-ene generated amphiphilic cross-linked networks was prepared by reaction of alkene-modified Boltorn polyesters (Boltorn-ene) with varying weight percent of 4-armed poly(ethylene glycol) (PEG) tetrathiol (0-25 wt%) and varying equivalents of pentaerythritol tetrakis(3-mercaptopropionate) (PETMP) (0-64 wt%). These materials were designed to present complex surface topographies and morphologies, with heterogeneity of surface composition and properties and robust mechanical properties, to serve as nontoxic antibiofouling coatings that are amenable to large-scale production for application in the marine environment. Therefore, a two-dimensional matrix of materials compositions was prepared to study the physical and mechanical properties, over which the compositions spanned from 0 to 25 wt% PEG tetrathiol and 0-64 wt% PETMP (the overall thiol/alkene (SH/ene) ratios ranged from 0.00 to 1.00 equiv), with both cross-linker weight percentages calculated with respect to the weight of Boltorn-ene. The Boltorn-ene components were prepared through the esterification of commercially available Boltorn H30 with 3-butenoic acid. The subsequent cross-linking of the Boltorn-PEG-PETMP films was monitored using IR spectroscopy, where it was found that near-complete consumption of both thiol and alkene groups occurred when the stoichiometry was ca. 48 wt% PETMP (0.75 equiv SH/ene, independent of PEG amount). The thermal properties of the films showed an increase in T(g) with an increase in 4-armed PEG-tetrathiol wt%, regardless of the PETMP concentration. Investigation of the bulk mechanical properties in dry and wet states found that the Young's modulus was the greatest at 48 wt% PETMP (0.75 equiv of SH/ene). The ultimate tensile strength increased when PETMP was constant and the PEG concentration was increased. The Young's modulus was slightly lower for wet films at constant PEG or constant PETMP amounts, than for the dry samples. The nanoscopic surface features were

  13. UV cross-linking of polypeptides associated with 3'-terminal exons

    International Nuclear Information System (INIS)

    Stolow, D.T.; Berget, S.M.

    1990-01-01

    Association of nuclear proteins with chimeric vertebrate precursor RNAs containing both polyadenylation signals and an intron was examined by UV cross-linking. One major difference in cross-linking pattern was observed between this chimeric precursor RNA and precursors containing only polyadenylation or splicing signals. The heterogeneous nuclear ribonucleoprotein (hnRNP) polypeptide C cross-linked strongly to sequences downstream of the A addition site in polyadenylation precursor RNA containing only the polyadenylation signal from the simian virus 40 (SV40) late transcription unit. In contrast, the hnRNP C polypeptide cross-linked to chimeric RNA containing the same SV40 late poly(A) cassette very poorly, at a level less than 5% of that observed with the precursor RNA containing just the poly(A) site. Observation that cross-linking of the hnRNP C polypeptide to elements within the SV40 late poly(A) site was altered by the presence of an upstream intron suggests differences in the way nuclear factors associate with poly(A) sites in the presence and absence of an upstream intron. Cross-linking of C polypeptide to chimeric RNA increased with RNAs mutated for splicing or polyadenylation consensus sequences and under reaction conditions (high magnesium) that inhibited polyadenylation. Furthermore, cross-linking of hnRNP C polypeptide to precursors containing just the SV40 late poly(A) site was eliminated in the presence of competing poly(U); polyadenylation, however, was unaffected. Correlation of loss of activity with high levels of hnRNP C polypeptide cross-linking raises questions about the specificity of the interaction between the hnRNP C polypeptide and polyadenylation precursor RNAs in vitro

  14. Tailoring the properties of cholecyst-derived extracellular matrix using carbodiimide cross-linking.

    LENUS (Irish Health Repository)

    Burugapalli, Krishna

    2009-01-01

    Modulation of properties of extracellular matrix (ECM) based scaffolds is key for their application in the clinical setting. In the present study, cross-linking was used as a tool for tailoring the properties of cholecyst-derived extracellular matrix (CEM). CEM was cross-linked with varying cross-linking concentrations of N,N-(3-dimethyl aminopropyl)-N\\'-ethyl carbodiimide (EDC) in the presence of N-hydroxysuccinimide (NHS). Shrink temperature measurements and ATR-FT-IR spectra were used to determine the degree of cross-linking. The effect of cross-linking on degradation was tested using the collagenase assay. Uniaxial tensile properties and the ability to support fibroblasts were also evaluated as a function of cross-linking. Shrink temperature increased from 59 degrees C for non-cross-linked CEM to 78 degrees C for the highest EDC cross-linking concentration, while IR peak area ratios for the free -NH(2) group at 3290 cm(-1) to that of the amide I band at 1635 cm(-1) decreased with increasing EDC cross-linking concentration. Collagenase assay demonstrated that degradation rates for CEM can be tailored. EDC concentrations 0 to 0.0033 mmol\\/mg CEM were the cross-linking concentration range in which CEM showed varied susceptibility to collagenase degradation. Furthermore, cross-linking concentrations up to 0.1 mmol EDC\\/mg CEM did not have statistically significant effect on the uniaxial tensile strength, as well as morphology, viability and proliferation of fibroblasts on CEM. In conclusion, the degradation rates of CEM can be tailored using EDC-cross-linking, while maintaining the mechanical properties and the ability of CEM to support cells.

  15. Mussel-Inspired Self-Healing Double-Cross-Linked Hydrogels by Controlled Combination of Metal Coordination and Covalent Cross-Linking

    DEFF Research Database (Denmark)

    Andersen, Amanda; Krogsgaard, Marie; Birkedal, Henrik

    2018-01-01

    a catechol-based hydrogel design that allows for the degree of oxidative covalent cross-linking to be controlled. Double cross-linked hydrogels with tunable stiffness are constructed by adding the oxidizable catechol analogue, tannic acid, to an oxidation-resistant hydrogel construct held together...... by coordination of the dihydroxy functionality of 1-(2'-carboxyethyl)-2-methyl-3-hydroxy-4-pyridinone to trivalent metal ions. By varying the amount of tannic acid, the hydrogel stiffness can be customized to a given application while retaining the self-healing capabilities of the hydrogel's coordination chemical...

  16. The spectra character of photodegraded the pyridinoline cross-links by Hypocrellin B

    International Nuclear Information System (INIS)

    Zhang Jucheng; Chen Rui; Liu Wei; Chen Zhuo; Shu Lidan; Liu Yingji

    2011-01-01

    Pyridinoline cross-links is one of the cross-link formation in collagen which in cell matrix, many research shown that this cross-link cause the fibrosis. Hypocrellin B (HB) is one of the nature photosensitizers, this work investigated the pyridinoline cross-link in collagen was photodegraded by HB. The result shown HB can degrade the pyridinoline cross-link with photo. This is to say, HB may be use as the photodynamic reagent to study the fibrosis.

  17. Effects of advanced glycation end-product inhibition and cross-link breakage in diabetic rats

    DEFF Research Database (Denmark)

    Oturai, P S; Christensen, M; Rolin, B

    2000-01-01

    ), and a breaker of already formed AGE cross-links, N-phenacylthiazolium bromide (PTB), were investigated in streptozotocin-diabetic female Wistar rats. Diabetes for 24 weeks resulted in decreased tail collagen pepsin solubility, reflecting the formation of AGE cross-linking. Collagen solubility was significantly...... ameliorated by treatment with NNC39-0028, whereas PTB had no effect. Increased urinary albumin excretion (UAE) in diabetic rats was observed in serial measurements throughout the study period, and was not reduced by any treatment. Vascular dysfunction in the eye, measured as increased clearance of 125I......-albumin, was induced by diabetes. NNC39-0028 did not affect this abnormality. This study demonstrated a pharmacological inhibition of collagen solubility alterations in diabetic rats without affecting diabetes-induced pathophysiology such as the increase in UAE or albumin clearance. Treatment with PTB, a specific...

  18. Interactions of cross-linked and uncross-linked chitosan hydrogels ...

    African Journals Online (AJOL)

    The swelling equilibrium of Chitosan and sodium tripolyphosphate (NaTPP) cross-linked chitosan hydrogels in aqueous solutions of surfactants differing in structure and hydrophobicity at 250C is reported. Anionic surfactant sodium dodecylsulfate (SDS), the cationic surfactant hexadecyltrimethylammonium bromide (HTAB) ...

  19. Cross-linking of dermal sheep collagen using a water-soluble carbodiimide

    NARCIS (Netherlands)

    Damink, LHHO; Dijkstra, PJ; vanLuyn, MJA; vanWachem, PB; Nieuwenhuis, P; Feijen, J

    A cross-linking method for collagen-based biomaterials was developed using the water-soluble carbodiimide 1-ethyl-3-(3-dimethyl aminopropyl)carbodiimide hydrochloride (EDC). Cross-linking using EDC involves the activation of carboxylic acid groups to give O-acylisourea groups, which form cross-links

  20. Cross-linking of dermal sheep collagen using a water-soluble carbodiimide

    NARCIS (Netherlands)

    Olde damink, L.H.H.; Olde Damink, L.H.H.; Dijkstra, Pieter J.; van Luyn, M.J.A.; van Wachem, P.B.; Nieuwenhuis, P.; Feijen, Jan

    1996-01-01

    A cross-linking method for collagen-based biomaterials was developed using the water-soluble carbodiimide 1-ethyl-3-(3-dimethyl aminopropyl)carbodiimide hydrochloride (EDC). Cross-linking using EDC involves the activation of carboxylic acid groups to give O-acylisourea groups, which form cross-links

  1. Formaldehyde cross-linking and structural proteomics: Bridging the gap.

    Science.gov (United States)

    Srinivasa, Savita; Ding, Xuan; Kast, Juergen

    2015-11-01

    Proteins are dynamic entities constantly moving and altering their structures based on their functions and interactions inside and outside the cell. Formaldehyde cross-linking combined with mass spectrometry can accurately capture interactions of these rapidly changing biomolecules while maintaining their physiological surroundings. Even with its numerous established uses in biology and compatibility with mass spectrometry, formaldehyde has not yet been applied in structural proteomics. However, formaldehyde cross-linking is moving toward analyzing tertiary structure, which conventional cross-linkers have already accomplished. The purpose of this review is to describe the potential of formaldehyde cross-linking in structural proteomics by highlighting its applications, characteristics and current status in the field. Copyright © 2015 Elsevier Inc. All rights reserved.

  2. Small Strain Topological Effects of Biopolymer Networks with Rigid Cross-Links

    NARCIS (Netherlands)

    Zagar, G.; Onck, P. R.; Van der Giessen, E.; Garikipati, K; Arruda, EM

    2010-01-01

    Networks of cross-linked filamentous biopolymers form topological structures characterized by L, T and X cross-link types of connectivity 2, 3 and 4, respectively. The distribution of cross-links over these three types proofs to be very important for the initial elastic shear stiffness of isotropic

  3. Cross-linked polymeric membranes for carbon dioxide separation

    Science.gov (United States)

    Hong, Tao; Chatterjee, Sabornie; Mahurin, Shannon Mark; Long, Brian Keith; Jiang, De-en; Mays, Jimmy Wayne; Sokolov, Alexei P.; Saito, Tomonori

    2018-01-23

    A membrane useful in gas separation, the membrane comprising a cross-linked polysiloxane structure having a cross-link density of about 0.1.times.10.sup.-5 mol/cm.sup.3 to about 6.times.10.sup.-5 mol/cm.sup.3, where, in particular embodiments, the cross-linked polysiloxane structure has the following general structure: ##STR00001## wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, and R.sup.6 are independently selected from hydrocarbon groups having at least 1 and up to 6 carbon atoms; A.sup.1 and A.sup.2 are independently selected from cyclic hydrocarbon groups; L.sup.1 and L.sup.2 are linking groups or covalent bonds; n is an integer of at least 1; r and s are independently selected from integers of at least 1; and p is an integer of at least 10. The invention also includes methods for making and using the above-described membranes for gas separation.

  4. A General Method for Targeted Quantitative Cross-Linking Mass Spectrometry.

    Directory of Open Access Journals (Sweden)

    Juan D Chavez

    Full Text Available Chemical cross-linking mass spectrometry (XL-MS provides protein structural information by identifying covalently linked proximal amino acid residues on protein surfaces. The information gained by this technique is complementary to other structural biology methods such as x-ray crystallography, NMR and cryo-electron microscopy[1]. The extension of traditional quantitative proteomics methods with chemical cross-linking can provide information on the structural dynamics of protein structures and protein complexes. The identification and quantitation of cross-linked peptides remains challenging for the general community, requiring specialized expertise ultimately limiting more widespread adoption of the technique. We describe a general method for targeted quantitative mass spectrometric analysis of cross-linked peptide pairs. We report the adaptation of the widely used, open source software package Skyline, for the analysis of quantitative XL-MS data as a means for data analysis and sharing of methods. We demonstrate the utility and robustness of the method with a cross-laboratory study and present data that is supported by and validates previously published data on quantified cross-linked peptide pairs. This advance provides an easy to use resource so that any lab with access to a LC-MS system capable of performing targeted quantitative analysis can quickly and accurately measure dynamic changes in protein structure and protein interactions.

  5. Collagen cross linking: Current perspectives

    Directory of Open Access Journals (Sweden)

    Srinivas K Rao

    2013-01-01

    Full Text Available Keratoconus is a common ectatic disorder occurring in more than 1 in 1,000 individuals. The condition typically starts in adolescence and early adulthood. It is a disease with an uncertain cause and its progression is unpredictable, but in extreme cases, vision deteriorates and can require corneal transplant surgery. Corneal collagen cross-linking (CCL with riboflavin (C3R is a recent treatment option that can enhance the rigidity of the cornea and prevent disease progression. Since its inception, the procedure has evolved with newer instrumentation, surgical techniques, and is also now performed for expanded indications other than keratoconus. With increasing experience, newer guidelines regarding optimization of patient selection, the spectrum of complications and their management, and combination procedures are being described. This article in conjunction with the others in this issue, will try and explore the uses of collagen cross-linking (CXL in its current form.

  6. Molecular Model for HNBR with Tunable Cross-Link Density.

    Science.gov (United States)

    Molinari, N; Khawaja, M; Sutton, A P; Mostofi, A A

    2016-12-15

    We introduce a chemically inspired, all-atom model of hydrogenated nitrile butadiene rubber (HNBR) and assess its performance by computing the mass density and glass-transition temperature as a function of cross-link density in the structure. Our HNBR structures are created by a procedure that mimics the real process used to produce HNBR, that is, saturation of the carbon-carbon double bonds in NBR, either by hydrogenation or by cross-linking. The atomic interactions are described by the all-atom "Optimized Potentials for Liquid Simulations" (OPLS-AA). In this paper, first, we assess the use of OPLS-AA in our models, especially using NBR bulk properties, and second, we evaluate the validity of the proposed model for HNBR by investigating mass density and glass transition as a function of the tunable cross-link density. Experimental densities are reproduced within 3% for both elastomers, and qualitatively correct trends in the glass-transition temperature as a function of monomer composition and cross-link density are obtained.

  7. Combined environment aging effects: radiation-thermal degradation of polyvinylchloride and polyethylene

    International Nuclear Information System (INIS)

    Clough, R.L.; Gillen, K.T.

    1981-01-01

    Results are presented for a case of polymer aging in which powerful synergisms are found between radiation and temperature. This effect was observed with formulations of polyvinylchloride and polyethylene and occurred in simultaneous and sequential radiation-thermal experiments. Dose rate dependencies, which appear to be mechanistically related to the synergism, were also found. The evidence indicates that these aging effects are mediated by a thermally induced breakdown of peroxides initially formed by the radiation. Similar effects could be important to material degradation in a variety of other types of combined-stress environment. A new technique, which uses PH 3 treatment of intact polymer specimens to test for the importance of peroxides in the pathway that leads to changes in macroscopic tensile properties, is described

  8. Mechanical properties in polypropylene-polyethylene blends modified by gamma radiation

    International Nuclear Information System (INIS)

    Ruiz, F.C.; Terence, M.C.

    2008-01-01

    One of the way to obtain a better mechanical property of polypropylene and polyethylene is related to increase the number polymer chains cross-linked by gamma radiation. After irradiation a network is formed which is the result of various chemical reactions occurred during this process, where the radicals formed are concentrated in the amorphous phase. With the objective to increase the mechanical properties of PP, blends with PE were prepared and irradiated in doses up to 100kGy, in atmospheric ambient. The tests showed increase in rigidity and a particular behaviour in Izod impact resistance. (author)

  9. Detection of introduced sessile species on the near shore continental shelf in southern Brazil

    Directory of Open Access Journals (Sweden)

    Janaína de Araújo Bumbeer

    2012-04-01

    Full Text Available Invasion by marine species, often considered a grave threat to marine ecosystems, occurs throughout the world as a consequence of many anthropogenic activities. In coastal Paraná, many factors including shipping, aquaculture and the use of artificial substrates provide suitable environments for the establishment and rapid spread of introduced marine species. To better understand this process, the encrusting community was studied on polyethylene plates (n = 120, 10 x 10 cm that were placed seasonally at fixed locations on the inner continental shelf to detect non-native species. Of the 62 taxa found, 40 were identified to species, 14 of which were native, 9 introduced and 17 cryptogenic. We found a new introduction while most introduced species were previously reported at a nearby estuary with an international port. Possible complementary explanations for these detections are 1 estuaries influence ecological processes on the inner continental shelf, 2 the study area is near the route of cargo and other ships entering the port, 3 other local vectors, such as hulls of fishing and recreational boats, and artificial reefs link the estuary to the offshore areas. Thus, not only are estuaries invaded by exotic species, but also non-indigenous marine species may be present in the open sea where they are likely to colonize artificial substrates.

  10. Studies on Cross-linking of succinic acid with chitosan/collagen

    Directory of Open Access Journals (Sweden)

    Tapas Mitra

    2013-01-01

    Full Text Available The present study summarizes the cross-linking property of succinic acid with chitosan /collagen. In detail, the chemistry behind the cross-linking and the improvement in mechanical and thermal properties of the cross-linked material were discussed with suitable instruments and bioinformatics tools. The concentration of succinic acid with reference to the chosen polymers was optimized. A 3D scaffold prepared using an optimized concentration of succinic acid (0.2% (w/v with chitosan (1.0% (w/v and similarly with collagen (0.5% (w/v, was subjected to surface morphology, FT-IR analysis, tensile strength assessment, thermal stability and biocompatibility. Results revealed, cross-linking with succinic acid impart appreciable mechanical strength to the scaffold material. In silico analysis suggested the prevalence of non-covalent interactions, which played a crucial role in improving the mechanical and thermal properties of the cross-linked scaffold. The resultant 3D scaffold may find application as wound dressing material, as an implant in clinical applications and as a tissue engineering material.

  11. X-ray-mediated cross linking of protein and DNA

    International Nuclear Information System (INIS)

    Minsky, B.D.; Braun, A.

    1977-01-01

    Using a simple filter assay for the binding of BSA or lysozyme to DNA, two mechanisms of x-ray-mediated cross linking are shown to occur. One, a fast reaction, appears to involve a radical intermediate, is inhibited by high pH and salt, and seems to be enhanced by deoxygenation. The second mechanism, a slow time-dependent component, differs from the fast reaction in its stimulation by histidine, its inhibition by catalase, and the lack of an oxygen effect. Separate irradiation of DNA or water does not lead to cross linking. However, separate irradiation of protein leads to cross linking which proceeds with slow-component kinetics

  12. Do buoyant plumes enhance cross-shelf transport in the Black Sea?

    Science.gov (United States)

    Sedakov, Roman; Zavialov, Peter; Izhitsky, Alexander

    2017-04-01

    Like many inland seas, the Black Sea is exposed to massive continental discharges on the one hand and significant anthropogenic stresses, including pollution, on the other. It is, therefore, important to understand mechanisms of advection of continental water into the sea and factors that may influence transport of such water across shelf areas. In this study, we focus on the coastal segment of the Black Sea between the Feodosia Bay, which includes nature reserve and resort areas, and the Kerch Strait. The Sea of Azov outflow penetrates into the Black Sea through the latter, forming a plume of relatively fresh, light waters with elevated concentrations of suspended matter but also pollutants, especially hydrocarbons. This plume, which can be detected via satellite imagery of the region, extends on over 70 km from the Kerch Strait outfall along Crimea shore and reaches the Feodosia Bay, making that area the most polluted of the Crimea shoreline. In situ velocity measurements were conducted at a mooring station deployed in the area at the depth of 5 and 21.5 meters during the period 17th-23rd of May 2015. These data demonstrated high correlation of the wind stress with the cross-shore component of the velocity in the surface layer and anti-correlation with that in the bottom layer during the periods when a two-layered stratification of the water column due to the occurrence of the Azov plume was present, and lack of such correlation otherwise. In order to investigate whether the buoyant plume in the surface layer is capable of fortifying the wind-driven cross-shelf exchanges, we develop a dynamical model of current forming under the influence of wind tension, pressure gradient and Earth's rotation in a simple one- and a two- layer setups. Firstly, a 2D model was investigated that did not account Coriolis effect. Secondly, a 3D model with Coriolis effect was investigated. The main parameter of the problem is the eddy diffusivity coefficient, which we choose to be

  13. Evaluation of cross-linked gelatin membranes as delivery carriers for retinal sheets

    Energy Technology Data Exchange (ETDEWEB)

    Lai, Jui-Yang, E-mail: jylai@mail.cgu.edu.tw [Institute of Biochemical and Biomedical Engineering, Chang Gung University, Taoyuan, 33302 Taiwan (China); Biomedical Engineering Research Center, Chang Gung University, Taoyuan, 33302 Taiwan (China); Molecular Medicine Research Center, Chang Gung University, Taoyuan, 33302 Taiwan (China); Li, Ya-Ting [Institute of Biochemical and Biomedical Engineering, Chang Gung University, Taoyuan, 33302 Taiwan (China)

    2010-06-15

    The delivery of intact sheet transplants to the subretinal space can prevent cell loss that is generally associated with the injection of cell suspensions or cell aggregates. The aim of this study was to develop chemically modified gelatin matrices that enhance the delivery efficiency and analyze whether the gelatin membranes cross-linked with 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC) can be considered as potential carriers for retinal sheets. The characteristics of EDC cross-linked gelatin membranes were determined by mechanical and in vitro degradation tests, melting point measurements, cell proliferation assays, cytokine expression analyses, and tissue delivery studies. Gelatin membranes without cross-linking and glutaraldehyde cross-linked gelatin samples were used for comparison. Results of this study indicated that introduction of cross-links is capable of rendering the gelatin network more stable against mechanical stresses and deformations as well as rapid hydrolysis during intraocular delivery of delicate tissue sheets. In comparison with the glutaraldehyde treated samples, the EDC cross-linked gelatin membranes showed a better degradation profile and a relatively higher cytocompatibility. In addition, after EDC cross-linking, the gelatin matrices having an acceptable melting point could be used for the fabrication of a sandwich-like carrier with a high transfer and encapsulation efficiency. These findings suggest that the cross-linking agent type gives an influence on delivery functionality of gelatin membranes. In summary, the EDC cross-linked gelatin is an ideal candidate for use as a carrier material in retinal sheet delivery applications.

  14. Analytical and Mathematical Determination of Shelf-life of Fresh-cut Red Cabbage

    Directory of Open Access Journals (Sweden)

    Fulya Şimşek

    2017-04-01

    Full Text Available Fresh-cut fruits and vegetables have longer shelf lives when appropriate packaging materials having proper permeability properties are used. For this reason eight different packaging materials having different permeability properties were used and it was aimed to determine the appropriate packaging material and analytical and mathematical shelf lives of fresh cut red cabbage. Head space analysis, microbiological and sensorial analysis together with pH, weight loss (% and colour analysis were performed. As a result of the study, it was determined that low density polyethylene (LDPE film having 20 µm of thickness and 12276 cc/m2-day of oxygen permeability was determined as the most suitable packaging material for packaging of fresh-cut red cabbage. Mathematical microbiological shelf life was determined as 12.33 days and both analytical microbiological and sensorial shelf lives were determined as 12 days. It was shown that Gompertz equation can be used in determination of microbiological shelf life of fresh-cut red cabbage since the analytical and mathematical shelf life results fit to each other. Also, the equation that can be used in calculation of shelf life of fresh-cut red cabbage when packaged with AYPE film having 12276 cc/m2-day oxygen permeability was determined as log(Nt/N0 = 6,83 × exp{-exp{[(0,80*e(6,83-t/6,83]+1}}.

  15. Redox-responsive core cross-linked prodrug micelles prepared by click chemistry for pH-triggered doxorubicin delivery

    Directory of Open Access Journals (Sweden)

    X. T. Cao

    2017-10-01

    Full Text Available A pH-triggered drug delivery system of degradable core cross-linked (CCL prodrug micelles was prepared by click chemistry. Doxorubicin conjugated block copolymers of azido functional poly(ethylene oxide-b-poly(glycidyl methacrylate were synthesized by the combination of RAFT polymerization, epoxide ring-opening reaction, and acid-cleavable hydrazone linkages. The CCL prodrug micelles were produced by the reaction of dipropargyl 3,3′-dithiodipropionate and dipropargyl adipate cross-linking agents with the azido groups of the micellar core via alkyne-azide click reaction, which were denoted as CCL/SS and CCL/noSS, respectively. The TEM images of CCL/SS prodrug micelles showed a spherical shape with the average diameter of 61.0 nm from water, and the shape was maintained with an increased diameter upon dilution with 5-fold DMF. The high DOX conjugation efficiency was 88.4%. In contrast to a very slow DOX release from CCL/SS prodrug micelles under the physiological condition (pH 7.4, the drug release is much faster (90% at pH 5.0 and 10 mM of GSH after 96 h. The cytotoxicity test and confocal laser scanning microscopy analysis revealed that CCL/SS prodrug micelles had much enhanced intracellular drug release capability in HepG2 cells than CCL/noSS prodrug micelles.

  16. Stabilized Sulfonated Aromatic Polymers by in situ Solvothermal Cross-Linking

    Energy Technology Data Exchange (ETDEWEB)

    Di Vona, Maria Luisa, E-mail: divona@uniroma2.it; Sgreccia, Emanuela [Dipartimento di Scienze e Tecnologie Chimiche, Università di Roma Tor Vergata, Rome (Italy); Narducci, Riccardo; Pasquini, Luca [Dipartimento di Scienze e Tecnologie Chimiche, Università di Roma Tor Vergata, Rome (Italy); MAtériaux Divisés, Interfaces, Réactivité, ELectrochimie (MADIREL – UMR 7246), Aix Marseille Université, Marseille (France); Hou, Hongying [Faculty of Material and Engineering, Kunming University of Science and Technology, Kunming (China); Knauth, Philippe [MAtériaux Divisés, Interfaces, Réactivité, ELectrochimie (MADIREL – UMR 7246), Aix Marseille Université, Marseille (France)

    2014-10-10

    The cross-link reaction via sulfone bridges of sulfonated polyether ether ketone (SPEEK) by thermal treatment at 180°C in presence of dimethylsulfoxide is discussed. The modifications of properties subsequent to the cross-linking are presented. The mechanical strength as well as the hydrolytic stability increased with the thermal treatment time, i.e., with the degree of cross-linking. The proton conductivity was determined as function of temperature, IEC, degree of cross-linking, and hydration number. The memory effect, which is the membrane ability to “remember” the water uptake reached at high temperature also at lower temperature, is exploited in order to achieve high values of conductivity. Membranes swelled at 110°C can reach a conductivity of 0.14 S/cm at 80°C with a hydration number (λ) of 73.

  17. Irradiation versus methyl bromide fumigation or heating as procedures for increasing shelf life of dry date varieties

    International Nuclear Information System (INIS)

    El-Samahy, S.K.; Abd El-Hady, S.A.; Swailam, H.M.

    2004-01-01

    The objective of this study is to evaluate the use of irradiation as an alternative method and comparing it with the traditional methods such as fumigation and heating for increasing shelf life dry date varieties. two varieties of dry dates, Malakaby and Gandilla, were obtained from Aswan, Upper Egypt and were used in this study. The irradiation was carried out with different doses of gamma rays to select the recommended dose to increase shelf life of dry dates. The fumigated, heated and irradiated samples were stored at room temperature after packaging in polyethylene plus cloth bags. The date characteristics such as insect infestation percent, weight loss, microbiological analyses, and firmness and chemical analyses were evaluated. The results obtained indicated that irradiation as a procedure for insect disinfestation and increasing shelf life of dry dates was better than both fumigation and heating methods. Where, irradiation of date fruits at dose of 1.0 kGy inhibited the insect infestation and improved the microbial quality of the date fruits during storage up to 18 months. Adding cloths to polyethylene packages raised the percentage of intact dry date fruits

  18. Effect of packaging materials on shelf life and quality of banana cultivars (Musa spp.).

    Science.gov (United States)

    Hailu, M; Seyoum Workneh, T; Belew, D

    2014-11-01

    This study was carried out to evaluate the effect of packaging materials on the shelf life of three banana cultivars. Four packaging materials, namely, perforated low density polyethylene bag, perforated high density polyethylene bag, dried banana leaf, teff straw and no packaging materials (control) were used with three banana cultivars, locally known as, Poyo, Giant Cavendish and Williams I. The experiment was carried out in Randomized Complete Block Design in a factorial combination with three replications. Physical parameters including weight loss, peel colour, peel thickness, pulp thickness, pulp to peel ratio, pulp firmness, pulp dry matter, decay, loss percent of marketability were assessed every 3 days. Banana remained marketable for 36 days in the high density polyethylene and low density polyethylene bags, and for 18 days in banana leaf and teff straw packaging treatments. Unpackaged fruits remained marketable for 15 days only. Fruits that were not packaged lost their weight by 24.0 % whereas fruits packaged in banana leaf and teff straw became unmarketable with final weight loss of 19.8 % and 20.9 %, respectively. Packaged fruits remained well until 36th days of storage with final weight loss of only 8.2 % and 9.20 %, respectively. Starting from green mature stage, the colour of the banana peel changed to yellow and this process was found to be fast for unpackaged fruits. Packaging maintained the peel and the pulp thickness, firmness, dry matter and pulp to peel ratio was kept lower. Decay loss for unpackaged banana fruits was16 % at the end of date 15, whereas the decay loss of fruits packaged using high density and low density polyethylene bags were 43.0 % and 41.2 %, respectively at the end of the 36th day of the experiment. It can, thus, be concluded that packaging of banana fruits in high density and low density polyethylene bags resulted in longer shelf life and improved quality of the produce followed by packaging in dried banana leaf

  19. Hydroxyl radical induced cross-linking of cytosine and tyrosine in nucleohistone

    International Nuclear Information System (INIS)

    Gajewski, E.; Dizdaroglu, M.

    1990-01-01

    Hydroxyl radical induced formation of a DNA-protein cross-link involving cytosine and tyrosine in nucleohistone in buffered aqueous solution is reported. The technique of gas chromatography-mass spectrometry was used for this investigation. A γ-irradiated aqueous mixture of cytosine and tyrosine was first investigated in order to obtain gas chromatographic-mass spectrometric properties of possible cytosine-tyrosine cross-links. One cross-link was observed, and its structure was identified as the product from the formation of a covalent bond between carbon 6 of cytosine and carbon 3 of tyrosine. With the use of gas chromatography-mass spectrometry with selected-ion monitoring, this cytosine-tyrosine cross-link was identified in acidic hydrolysates of calf thymus nucleohistone γ-irradiated in N 2 O-saturated aqueous solution. The yield of this DNA-protein cross-link in nucleohistone was found to be a linear function of the radiation dose in the range of 100-500 Gy (J·kg -1 ). This yield amounted to 0.05 nmol·J -1 . Mechanisms underlying the formation of the cytosine-tyrosine cross-link in nucleohistone were proposed to involve radical-radical and/or radical addition reactions of hydroxyl adduct radicals of cytosine and tyrosine moieties, forming a covalent bond between carbon 6 of cytosine and carbon 3 of tyrosine. When oxygen was present in irradiated solutions, no cytosine-tyrosine cross-links were observed

  20. Study of the radiosterilization dose effect on properties of poly(ethylene terephthalate) - PET recycled

    International Nuclear Information System (INIS)

    Isoldi, Ana Beatriz Godoy; Silva, Leonardo Gondim de Andrade e; Rosario, Salmo Cordeiro do

    2002-01-01

    The packing are in constant development, in function, especially, the process of globalization. The opening of the brazilian market after currency stabilization, caused technological innovations, change of habits and costumes of the population and environmental matters. Year after year, because of cost reductions, it became more extreme the hard study of the polymeric materials and their copolymers, their possible blends and their recycling, always seeking a better wrapping of the products, especially when it concerns to the food, increasing its shelf life. The process of sterilization of foods and modification of polymers through radiation are targets of growing interest by of the current industries linked to the nutrition and packing sectors. The objective of this paper is to discuss the application of the radiation (electron beam) in the sterilization of packings of recycled poly(ethylene terephthalate) PET, evaluating the possible effects on their properties. (author)

  1. Accelerated aging, natural aging, and small punch testing of gamma-air sterilized polycarbonate urethane acetabular components.

    Science.gov (United States)

    Kurtz, S M; Siskey, R; Reitman, M

    2010-05-01

    The objectives of this study were three-fold: (1) to determine the applicability of the small punch test to characterize Bionate 80A polycarbonate urethane (PCU) acetabular implants; (2) to evaluate the susceptibility of PCU acetabular implants to exhibit degradation of mechanical behavior following gamma irradiation in air and accelerated aging; and (3) to compare the oxidation of gamma-air sterilized PCU following accelerated aging and 5 years of natural shelf aging. In addition to attenuated total reflectance-Fourier transform infrared spectroscopy, we also adapted a miniature specimen mechanical test, the small punch test, for the deformable PCU cups. Accelerated aging was performed using ASTM F2003, a standard test that represents a severe oxidative challenge. The results of this study suggest that the small punch test is sufficiently sensitive and reproducible to discriminate slight differences in the large-deformation mechanical behavior of Bionate 80A following accelerated aging. The gamma-air sterilized PCU had a reduction of 9% in ultimate load after aging. Five years of shelf aging had little effect on the mechanical properties of the PCU. Overall, our findings suggest that the Bionate 80A material has greater oxidative stability than ultra-high molecular weight polyethylene following gamma irradiation in air and exposure to a severe oxidative challenge. (c) 2010 Wiley Periodicals, Inc.

  2. Long-term aging and loss-of-coolant accident (LOCA) testing of electrical cables

    International Nuclear Information System (INIS)

    Nelson, C.F.; Gauthier, G.; Carlin, F.

    1996-10-01

    Experiments were performed to assess the aging degradation and loss-of-coolant accident (LOCA) behavior of electrical cables subjected to long-term aging exposures. Four different cable types were tested in both the U.S. and France: (1) U.S. 2 conductor with ethylene propylene rubber (EPR) insulation and a Hypalon jacket. (2) U.S. 3 conductor with cross-linked polyethylene (XLPE) insulation and a Hypalon jacket. (3) French 3 conductor with EPR insulation and a Hypalon jacket. (4) French coaxial with polyethylene (PE) insulation and a PE jacket. The data represent up to 5 years of simultaneous aging where the cables were exposed to identical aging radiation doses at either 40 degrees C or 70 degrees C; however, the dose rate used for the aging irradiation was varied over a wide range (2-100 Gy/hr). Aging was followed by exposure to simulated French LOCA conditions. Several mechanical, electrical, and physical-chemical condition monitoring techniques were used to investigate the degradation behavior of the cables. All the cables, except for the French PE cable, performed acceptably during the aging and LOCA simulations. In general, cable degradation at a given dose was highest for the lowest dose rate, and the amount of degradation decreased as the dose rate was increased

  3. Stabilized sulfonated aromatic polymers by in situ solvothermal cross-linking

    Directory of Open Access Journals (Sweden)

    Maria Luisa eDi Vona

    2014-10-01

    Full Text Available The cross-link reaction via sulfone bridges of sulfonated polyetheretherketone (SPEEK by thermal treatment at 180 °C in presence of dimethylsulfoxide (DMSO is discussed. The modifications of properties subsequent to the cross-linking are presented. The mechanical strength as well as the hydrolytic stability increased with the thermal treatment time, i.e., with the degree of cross-linking. The proton conductivity was determined as function of temperature, IEC, degree of cross-linking and hydration number. The memory effect, which is the membrane ability to remember the water uptake reached at high temperature also at lower temperature, is exploited in order to achieve high values of conductivity. Membranes swelled at 110 °C can reach a conductivity of 0.14 S/cm at 80°C with a hydration number ( of 73.

  4. Characterization of solid UV cross-linked PEGDA for biological applications

    KAUST Repository

    Castro, David

    2013-10-20

    This paper reports on solid UV cross-linked Poly(ethylene)-glycol-diacrylate (PEGDA) as a material for microfluidic devices for biological applications. We have evaluated biocompatibility of PEGDA through two separate means: 1) by examining cell viability and attachment on cross-linked PEGDA surfaces for cell culture applications, and 2) by determining if cross-linked PEGDA inhibits the polymerase chain reaction (PCR) processes for on-chip PCR. Through these studies a correlation has been found between degree of curing and cell viability, attachment, as well as on PCR outcome.

  5. Fog Collection on Polyethylene Terephthalate (PET) Fibers: Influence of Cross Section and Surface Structure.

    Science.gov (United States)

    Azad, M A K; Krause, Tobias; Danter, Leon; Baars, Albert; Koch, Kerstin; Barthlott, Wilhelm

    2017-06-06

    Fog-collecting meshes show a great potential in ensuring the availability of a supply of sustainable freshwater in certain arid regions. In most cases, the meshes are made of hydrophilic smooth fibers. Based on the study of plant surfaces, we analyzed the fog collection using various polyethylene terephthalate (PET) fibers with different cross sections and surface structures with the aim of developing optimized biomimetic fog collectors. Water droplet movement and the onset of dripping from fiber samples were compared. Fibers with round, oval, and rectangular cross sections with round edges showed higher fog-collection performance than those with other cross sections. However, other parameters, for example, width, surface structure, wettability, and so forth, also influenced the performance. The directional delivery of the collected fog droplets by wavy/v-shaped microgrooves on the surface of the fibers enhances the formation of a water film and their fog collection. A numerical simulation of the water droplet spreading behavior strongly supports these findings. Therefore, our study suggests the use of fibers with a round cross section, a microgrooved surface, and an optimized width for an efficient fog collection.

  6. Mechanical Strength Improvements of Carbon Nanotube Threads through Epoxy Cross-Linking

    Directory of Open Access Journals (Sweden)

    Qingyue Yu

    2016-01-01

    Full Text Available Individual Carbon Nanotubes (CNTs have a great mechanical strength that needs to be transferred into macroscopic fiber assemblies. One approach to improve the mechanical strength of the CNT assemblies is by creating covalent bonding among their individual CNT building blocks. Chemical cross-linking of multiwall CNTs (MWCNTs within the fiber has significantly improved the strength of MWCNT thread. Results reported in this work show that the cross-linked thread had a tensile strength six times greater than the strength of its control counterpart, a pristine MWCNT thread (1192 MPa and 194 MPa, respectively. Additionally, electrical conductivity changes were observed, revealing 2123.40 S·cm−1 for cross-linked thread, and 3984.26 S·cm−1 for pristine CNT thread. Characterization suggests that the obtained high tensile strength is due to the cross-linking reaction of amine groups from ethylenediamine plasma-functionalized CNT with the epoxy groups of the cross-linking agent, 4,4-methylenebis(N,N-diglycidylaniline.

  7. Analytical characterisation of glutardialdehyde cross-linking products in gelatine-gum arabic complex coacervates

    Energy Technology Data Exchange (ETDEWEB)

    Fuguet, Elisabet [Advanced Measurement and Imaging, Unilever Food and Health Research Institute, Olivier van Noortlaan 120, 3133 AT Vlaardingen (Netherlands)], E-mail: eli.fuguet@gmail.com; Platerink, Chris van [Advanced Measurement and Imaging, Unilever Food and Health Research Institute, Olivier van Noortlaan 120, 3133 AT Vlaardingen (Netherlands); Department of Biomolecular Mass Spectrometry, Bijvoet Center for Biomolecular Research, Utrecht University, Sorbonnelaan 16, 3584 CA Utrecht (Netherlands); Janssen, Hans-Gerd [Advanced Measurement and Imaging, Unilever Food and Health Research Institute, Olivier van Noortlaan 120, 3133 AT Vlaardingen (Netherlands); van' t Hoff Institute for Molecular Sciences, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam (Netherlands)

    2007-11-26

    Encapsulates having shells of cross-linked mixtures of proteins and polysaccharides are widely used in the food and pharmaceutical industry for controlled release of actives and flavour compounds. In order to be able to predict the behaviour and the release characteristics of the microcapsules, a better understanding of the nature and extent of the cross-linking reaction is needed. Several analytical techniques were applied for the characterisation of glutardialdehyde (GDA) cross-linked encapsulates made of gelatine and gum arabic. To allow the use of sensitive, high-resolution methods such as chromatography and mass spectrometry, the sample first had to be hydrolysed. In this way, a mixture of amino acids, small peptides and the cross-link moieties was obtained. High-resolution liquid chromatography coupled to high-resolution mass spectrometry (HPLC-MS) was applied to detect possible cross-link markers through a comparison of HPLC-MS mass-chromatograms obtained for cross-linked and non-cross-linked coacervates. HPLC-MS/MS was used to identify the species responsible for the differences. Cross-linking occurred between GDA molecules and lysine and hydroxylysine {epsilon}-amino groups, and up to eight cross-link products of different nature could be identified. They included pyridinium ions and Schiff bases, and also unreacted GDA condensation products. Next, based on the insight gained in the possible chemical structures present in the cross-link markers, methods for selective labelling of these functionalities were employed to allow easier detection of related reaction products. Both liquid chromatography (LC) and gas chromatography (GC) were used in these experiments. Unfortunately, these approaches failed to detect new cross-link markers, most likely as a result of the low levels at which these are present.

  8. Analytical characterisation of glutardialdehyde cross-linking products in gelatine-gum arabic complex coacervates

    International Nuclear Information System (INIS)

    Fuguet, Elisabet; Platerink, Chris van; Janssen, Hans-Gerd

    2007-01-01

    Encapsulates having shells of cross-linked mixtures of proteins and polysaccharides are widely used in the food and pharmaceutical industry for controlled release of actives and flavour compounds. In order to be able to predict the behaviour and the release characteristics of the microcapsules, a better understanding of the nature and extent of the cross-linking reaction is needed. Several analytical techniques were applied for the characterisation of glutardialdehyde (GDA) cross-linked encapsulates made of gelatine and gum arabic. To allow the use of sensitive, high-resolution methods such as chromatography and mass spectrometry, the sample first had to be hydrolysed. In this way, a mixture of amino acids, small peptides and the cross-link moieties was obtained. High-resolution liquid chromatography coupled to high-resolution mass spectrometry (HPLC-MS) was applied to detect possible cross-link markers through a comparison of HPLC-MS mass-chromatograms obtained for cross-linked and non-cross-linked coacervates. HPLC-MS/MS was used to identify the species responsible for the differences. Cross-linking occurred between GDA molecules and lysine and hydroxylysine ε-amino groups, and up to eight cross-link products of different nature could be identified. They included pyridinium ions and Schiff bases, and also unreacted GDA condensation products. Next, based on the insight gained in the possible chemical structures present in the cross-link markers, methods for selective labelling of these functionalities were employed to allow easier detection of related reaction products. Both liquid chromatography (LC) and gas chromatography (GC) were used in these experiments. Unfortunately, these approaches failed to detect new cross-link markers, most likely as a result of the low levels at which these are present

  9. Recyclable cross-linked anion exchange membrane for alkaline fuel cell application

    Science.gov (United States)

    Hou, Jianqiu; Liu, Yazhi; Ge, Qianqian; Yang, Zhengjin; Wu, Liang; Xu, Tongwen

    2018-01-01

    Cross-linking can effectively solve the conductivity-swelling dilemma in anion exchange membranes (AEMs) but will generate solid wastes. To address this, we developed an AEM cross-linked via disulfide bonds, bearing quaternary ammonium groups, which can be easily recycled. The membrane (RC-QPPO) with IEC of 1.78 mmol g-1, when cross-linked, showed enhanced mechanical properties and good hydroxide conductivity (24.6 mS cm-1 at 30 °C). Even at higher IEC value (2.13 mmol g-1), it still has low water uptake, low swelling ratio and delivers a peak power density of 150 mW cm-2 at 65 °C. Exploiting the formation of disulfide bonds from -SH groups, the membrane can be readily cross-linked in alkaline condition and recycled by reversibly breaking disulfide bonds with dithiothreitol (DTT). The recycled membrane solution can be directly utilized to cast a brand-new AEM. By washing away the residual DTT with water and exposure to air, it can be cross-linked again and this process is repeatable. During the recycling and cross-linking processes, the membrane showed a slight IEC decrease of 5% due to functional group degradation. The strategy presented here is promising in enhancing AEM properties and reducing the impact of artificial polymers on the environment.

  10. Yield and Failure Behavior Investigated for Cross-Linked Phenolic Resins Using Molecular Dynamics

    Science.gov (United States)

    Monk, Joshua D.; Lawson, John W.

    2016-01-01

    Molecular dynamics simulations were conducted to fundamentally evaluate the yield and failure behavior of cross-linked phenolic resins at temperatures below the glass transition. Yield stress was investigated at various temperatures, strain rates, and degrees of cross-linking. The onset of non-linear behavior in the cross-linked phenolic structures was caused by localized irreversible molecular rearrangements through the rotation of methylene linkers followed by the formation or annihilation of neighboring hydrogen bonds. The yield stress results, with respect to temperature and strain rate, could be fit by existing models used to describe yield behavior of amorphous glasses. The degree of cross-linking only indirectly influences the maximum yield stress through its influence on glass transition temperature (Tg), however there is a strong relationship between the degree of cross-linking and the failure mechanism. Low cross-linked samples were able to separate through void formation, whereas the highly cross-linked structures exhibited bond scission.

  11. Preparation and properties of poly(ethylene oxide) gel filled polypropylene separators and their corresponding gel polymer electrolytes for Li-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Li Hao; Ma Xiaoting; Shi Junli; Yao Zhikan [Department of Polymer Science and Engineering, Engineering Center of Membrane and Water Treatment, Key Laboratory of Macromolecule Synthesis and Functionalization (EMC), Zhejiang University, Hangzhou 310027 (China); Zhu Baoku, E-mail: zhubk@zju.edu.c [Department of Polymer Science and Engineering, Engineering Center of Membrane and Water Treatment, Key Laboratory of Macromolecule Synthesis and Functionalization (EMC), Zhejiang University, Hangzhou 310027 (China); Zhu Liping [Department of Polymer Science and Engineering, Engineering Center of Membrane and Water Treatment, Key Laboratory of Macromolecule Synthesis and Functionalization (EMC), Zhejiang University, Hangzhou 310027 (China)

    2011-02-15

    Poly(ethylene oxide) (PEO) filled polypropylene separators (GFPSs) are designed by means of thermal cross-linking of entrapped poly(ethylene glycol) methyl ether acrylate (PEGMEA) and poly(ethylene glycol) diacrylate (PEGDA) as gel constituents. The intrinsic properties of GFPS and their corresponding gel polymer electrolytes (GPE) are characterized by DSC, SEM, contact angle and electrochemical methods. It is found the stability of liquid electrolyte uptake in GPE could be improved obviously. For the GPE prepared from GFPS with filled polyether content of 14.3 wt%, the ionic conductivity could reach 1.12 x 10{sup -3} S cm{sup -1} while the electrochemically stable window reach 5.0 V (vs. Li/Li{sup +}). These primary results show great promise of this simple method to prepare GPE for practical application in lithium ion batteries.

  12. Preparation and properties of poly(ethylene oxide) gel filled polypropylene separators and their corresponding gel polymer electrolytes for Li-ion batteries

    International Nuclear Information System (INIS)

    Li Hao; Ma Xiaoting; Shi Junli; Yao Zhikan; Zhu Baoku; Zhu Liping

    2011-01-01

    Poly(ethylene oxide) (PEO) filled polypropylene separators (GFPSs) are designed by means of thermal cross-linking of entrapped poly(ethylene glycol) methyl ether acrylate (PEGMEA) and poly(ethylene glycol) diacrylate (PEGDA) as gel constituents. The intrinsic properties of GFPS and their corresponding gel polymer electrolytes (GPE) are characterized by DSC, SEM, contact angle and electrochemical methods. It is found the stability of liquid electrolyte uptake in GPE could be improved obviously. For the GPE prepared from GFPS with filled polyether content of 14.3 wt%, the ionic conductivity could reach 1.12 x 10 -3 S cm -1 while the electrochemically stable window reach 5.0 V (vs. Li/Li + ). These primary results show great promise of this simple method to prepare GPE for practical application in lithium ion batteries.

  13. Combination of supramolecular cross-linking with covalent cross-linking through epoxide ring-opening including gel studies

    NARCIS (Netherlands)

    Hofmeier, H.; El-Ghayoury, A.; Schubert, U.S.

    2003-01-01

    Terpolymers based on poly(methyl methacrylate), containing terpyridinemoieties as well as epoxide groups, were synthesized via free-radical polymerization. The products were cross-linked non-covalently with iron(II) ions and covalently by treatment with AlCl3. Both steps could be combined in

  14. EFFECT OF PASTEURIZATION TEMPERATURE AND ASEPTIC FILLING ON THE SHELF-LIFE OF MILK

    Directory of Open Access Journals (Sweden)

    Rodrigo Rodrigues PETRUS

    2011-12-01

    Full Text Available Aseptic filling process can contribute to extend the shelf-life of pasteurized milk. However, this technology is not still commercially practiced in Brazil for this product. The aim of this study was to evaluate the effect of the pasteurization temperature and aseptic filling on the stability of milk packaged in high density polyethylene bottle (HDPE. Three batches of one hundred bottles each were processed at 72, 83, and 94ºC/15s, followed by aseptic packaging and storage at 9ºC, simulating a deficient cold chain scenario as found in the Brazilian market. Microbiological stability evaluation was based on mesophilic and psychrotrophic counts. Sensory shelf-life was estimated according to the ratings assigned to the attributes appearance, aroma, flavor and overall appreciation of milk samples. The pasteurization temperature, in the range investigated, did not affect the shelf-life of milk, which lasted up to 11 days for the three processed batches. The aseptic filling, associated to the employed thermal treatments, did not extend the shelf-life of milk stored under the abuse condition of 9°C, considering that the commercial product shelf-life in Brazil is of about 10 days.

  15. The effect of γ-ray irradiation on the water immersion and electricity application deterioration of polyethylene

    International Nuclear Information System (INIS)

    Higashimura, Yutaka; Fujioka, Norihide; Karino, Yasushi; Onuki, Tsutomu; Watanabe, Kiyoshi.

    1984-01-01

    Two types of polyethylene, that is, standard low density cross-linked polyethylene (XLPE-A) and the same with the addition of a polymer having ester radicals (XLPE-B), were used for this experiment. The water immersion and electricity application test was carried out 1) simultaneously with γ-ray irradiation, 2) after γ-ray irradiation, and 3) without γ-ray irradiation. It was found that 1) the water-immersion and electricity-application life of XLPE-A was rather elongated by γ-ray irradiation, 2) the water-immersion and electricity-application life of XLPE-B was shortened by γ-ray irradiation, which is probably attributable to the bond-rupture of ester radicals of the added polymer, 3) the life, when the irradiation of γ-ray and the application of electricity in water were simultaneously exerted, agreed well with the empirical equation which is derived on the assumption that the life is decreased proportionally to the overall dose of γ-ray, and 4) even when polyethylene was irradiated with γ-ray in hot water, the properties of polyethylene was estimated to deteriorate in the same extent as in the air. (Yoshitake, I.)

  16. Characterizing Cognitive Aging in Humans with Links to Animal Models

    Directory of Open Access Journals (Sweden)

    Gene E Alexander

    2012-09-01

    Full Text Available With the population of older adults expected to grow rapidly over the next two decades, it has become increasingly important to advance research efforts to elucidate the mechanisms associated with cognitive aging, with the ultimate goal of developing effective interventions and prevention therapies. Although there has been a vast research literature on the use of cognitive tests to evaluate the effects of aging and age-related neurodegenerative disease, the need for a set of standardized measures to characterize the cognitive profiles specific to healthy aging has been widely recognized. Here we present a review of selected methods and approaches that have been applied in human research studies to evaluate the effects of aging on cognition, including executive function, memory, processing speed, language, and visuospatial function. The effects of healthy aging on each of these cognitive domains are discussed with examples from cognitive/experimental and clinical/neuropsychological approaches. Further, we consider those measures that have clear conceptual and methodological links to tasks currently in use for non-human animal studies of aging, as well as those that have the potential for translation to animal aging research. Having a complementary set of measures to assess the cognitive profiles of healthy aging across species provides a unique opportunity to enhance research efforts for cross-sectional, longitudinal, and intervention studies of cognitive aging. Taking a cross-species, translational approach will help to advance cognitive aging research, leading to a greater understanding of associated neurobiological mechanisms with the potential for developing effective interventions and prevention therapies for age-related cognitive decline.

  17. UV-induced cross-linking of abscisic acid to binding proteins

    International Nuclear Information System (INIS)

    Cornelussen, M.H.M.; Karssen, C.M.; Loon, L.C. van

    1995-01-01

    Conditions for UV-induced cross-linking of abscisic acid (ABA) through its enone chromophore to binding proteins were evaluated. The effects of a UV-light band between 260 and 530 nm on both unconjugated and protein-conjugated ABA, as well as on anti-ABA antibodies as models of ABA-binding proteins were determined. UV irradiation caused both isomerization and photolysis of ABA, but increasing the lower irradiation boundary to 345 nm strongly reduced photolysis and largely prevented isomerization. When conjugated to alkaline phosphatase (AP), ABA remained stable when using either a 320 or a 345 nm filter. At these wavelengths both binding of ABA to antibodies as well as AP enzymatic activity were maintained. UV-induced cross-linking of monoclonal anti-ABA antibodies to immobilized ABA was analysed by immunoassays. Optimal cross-linking was achieved after a 5 min irradiation period at 0°, using a long pass, cut-on filter to quench wavelengths below 290 nm. This cross-linking faithfully reflected cognate binding activity. (author)

  18. Combination of supramolecular cross-linking with covalent cross-linking through epoxide ring-opening including gel studies

    NARCIS (Netherlands)

    Hofmeier, H.; El-Ghayoury, A.; Schubert, U.S.

    2003-01-01

    Terpolymers based on poly(methyl methacrylate), containing terpyridine-moieties as well as epoxide groups, were synthesized via free-radical polymeri-zation. The products were cross-linked non-covalently with iron(II) ions and cova-lently by treatment with AlCl3. Both steps could be combined in

  19. Highstand shelf fans: The role of buoyancy reversal in the deposition of a new type of shelf sand body

    Science.gov (United States)

    Steel, Elisabeth; Simms, Alexander R.; Warrick, Jonathan; Yokoyama, Yusuke

    2016-01-01

    Although sea-level highstands are typically associated with sediment-starved continental shelves, high sea level does not hinder major river floods. Turbidity currents generated by plunging of sediment-laden rivers at the fluvial-marine interface, known as hyperpycnal flows, allow for cross-shelf transport of suspended sand beyond the coastline. Hyperpycnal flows in southern California have deposited six subaqueous fans on the shelf of the northern Santa Barbara Channel in the Holocene. Using eight cores and nine grab samples, we describe the deposits, age, and stratigraphic architecture of two fans in the Santa Barbara Channel. Fan lobes have up to 3 m of relief and are composed of multiple hyperpycnite beds ∼5 cm to 40 cm thick. Deposit architecture and geometry suggest the hyperpycnal flows became positively buoyant and lifted off the seabed, resulting in well-sorted, structureless, elongate sand lobes. Contrary to conventional sequence stratigraphic models, the presence of these features on the continental shelf suggests that active-margin shelves may locally develop high-quality reservoir sand bodies during sea-level highstands, and that such shelves need not be solely the site of sediment bypass. These deposits may provide a Quaternary analogue to many well-sorted sand bodies in the rock record that are interpreted as turbidites but lack typical Bouma-type features.

  20. Cross-modal working memory binding and word recognition skills: how specific is the link?

    Science.gov (United States)

    Wang, Shinmin; Allen, Richard J

    2018-04-01

    Recent research has suggested that the creation of temporary bound representations of information from different sources within working memory uniquely relates to word recognition abilities in school-age children. However, it is unclear to what extent this link is attributable specifically to the binding ability for cross-modal information. This study examined the performance of Grade 3 (8-9 years old) children on binding tasks requiring either temporary association formation of two visual items (i.e., within-modal binding) or pairs of visually presented abstract shapes and auditorily presented nonwords (i.e., cross-modal binding). Children's word recognition skills were related to performance on the cross-modal binding task but not on the within-modal binding task. Further regression models showed that cross-modal binding memory was a significant predictor of word recognition when memory for its constituent elements, general abilities, and crucially, within-modal binding memory were taken into account. These findings may suggest a specific link between the ability to bind information across modalities within working memory and word recognition skills.

  1. General protein-protein cross-linking.

    Science.gov (United States)

    Alegria-Schaffer, Alice

    2014-01-01

    This protocol describes a general protein-to-protein cross-linking procedure using the water-soluble amine-reactive homobifunctional BS(3) (bis[sulfosuccinimidyl] suberate); however, the protocol can be easily adapted using other cross-linkers of similar properties. BS(3) is composed of two sulfo-NHS ester groups and an 11.4 Å linker. Sulfo-NHS ester groups react with primary amines in slightly alkaline conditions (pH 7.2-8.5) and yield stable amide bonds. The reaction releases N-hydroxysuccinimide (see an application of NHS esters on Labeling a protein with fluorophores using NHS ester derivitization). © 2014 Elsevier Inc. All rights reserved.

  2. Novel magnetic cross-linked lipase aggregates for improving the resolution of (R, S)-2-octanol.

    Science.gov (United States)

    Liu, Ying; Guo, Chen; Liu, Chun-Zhao

    2015-03-01

    Novel magnetic cross-linked lipase aggregates were fabricated by immobilizing the cross-linked lipase aggregates onto magnetic particles with a high number of -NH2 terminal groups using p-benzoquinone as the cross-linking agent. At the optimal fabrication conditions, 100% of immobilization efficiency and 139% of activity recovery of the magnetic cross-linked lipase aggregates were achieved. The magnetic cross-linked lipase aggregates were able to efficiently resolve (R, S)-2-octanol, and retained 100% activity and 100% enantioselectivity after 10 cycles of reuse, whereas the cross-linked lipase aggregates only retained about 50% activity and 70% enantioselectivity due to insufficient cross-linking. These results provide a great potential for industrial applications of the magnetic cross-linked lipase aggregates. © 2014 Wiley Periodicals, Inc.

  3. A Comparative Study of the Characteristics of Cross-Linked, Oxidized and Dual-Modified Rice Starches

    OpenAIRE

    Xiao, Hua-Xi; Lin, Qin-Lu; Liu, Gao-Qiang; Yu, Feng-Xiang

    2012-01-01

    Rice starch was cross-linked with epichlorohydrin (0.3%, w/w, on a dry starch basis) and oxidized with sodium hypochlorite (2.5% w/w), respectively. Two dual-modified rice starch samples (oxidized cross-linked rice starch and cross-linked oxidized rice starch) were obtained by the oxidation of cross-linked rice starch and the cross-linking of oxidized rice starch at the same level of reagents. The physicochemical properties of native rice starch, cross-linked rice starch and oxidized rice sta...

  4. Effects of Supercritical CO 2 Conditioning on Cross-Linked Polyimide Membranes

    KAUST Repository

    Kratochvil, Adam M.; Koros, William J.

    2010-01-01

    The effects of supercritical CO2 (scCO2) conditioning on high-performance cross-linked polyimide membranes is examined through gas permeation and sorption experiments. Under supercritical conditions, the cross-linked polymers do not exhibit a

  5. Differential neutron spectrometry in the very low neutron energy range. Neutron cross sections for Zr, Al, polyethylene and liquid fluoropolymers

    International Nuclear Information System (INIS)

    Pokotilovskij, Yu.N.; Novopol'tsev, M.I.; Geltenbort, P.; Brenner, T.

    2003-01-01

    Some results of the test of the time-of-flight neutron spectrometers in the energy range (0.05-2.5)μeV are described. The measurements of total and differential cross sections were performed for several substances relevant to the experiments in the physics of ultracold neutrons: Zr, Al, polyethylene and liquid fluoropolymers

  6. Computer simulation of randomly cross-linked polymer networks

    International Nuclear Information System (INIS)

    Williams, Timothy Philip

    2002-01-01

    In this work, Monte Carlo and Stochastic Dynamics computer simulations of mesoscale model randomly cross-linked networks were undertaken. Task parallel implementations of the lattice Monte Carlo Bond Fluctuation model and Kremer-Grest Stochastic Dynamics bead-spring continuum model were designed and used for this purpose. Lattice and continuum precursor melt systems were prepared and then cross-linked to varying degrees. The resultant networks were used to study structural changes during deformation and relaxation dynamics. The effects of a random network topology featuring a polydisperse distribution of strand lengths and an abundance of pendant chain ends, were qualitatively compared to recent published work. A preliminary investigation into the effects of temperature on the structural and dynamical properties was also undertaken. Structural changes during isotropic swelling and uniaxial deformation, revealed a pronounced non-affine deformation dependant on the degree of cross-linking. Fractal heterogeneities were observed in the swollen model networks and were analysed by considering constituent substructures of varying size. The network connectivity determined the length scales at which the majority of the substructure unfolding process occurred. Simulated stress-strain curves and diffraction patterns for uniaxially deformed swollen networks, were found to be consistent with experimental findings. Analysis of the relaxation dynamics of various network components revealed a dramatic slowdown due to the network connectivity. The cross-link junction spatial fluctuations for networks close to the sol-gel threshold, were observed to be at least comparable with the phantom network prediction. The dangling chain ends were found to display the largest characteristic relaxation time. (author)

  7. Physico-chemical/biological properties of tripolyphosphate cross-linked chitosan based nanofibers

    Energy Technology Data Exchange (ETDEWEB)

    Sarkar, Soumi Dey [School of Medical Science and Technology, Indian Institute of Technology Kharagpur, Kharagpur-721302 (India); Farrugia, Brooke L.; Dargaville, Tim R. [Institute of Health and Biomedical Innovation, Queensland University of Technology, Kelvin Groove, Queensland-4059 (Australia); Dhara, Santanu, E-mail: sdhara@smst.iitkgp.ernet.in [School of Medical Science and Technology, Indian Institute of Technology Kharagpur, Kharagpur-721302 (India)

    2013-04-01

    In this study, chitosan-PEO blend, prepared in a 15 M acetic acid, was electrospun into nanofibers (∼ 78 nm diameter) with bead free morphology. While investigating physico-chemical parameters of blend solutions, effect of yield stress on chitosan based nanofiber fabrication was clearly evidenced. Architectural stability of nanofiber mat in aqueous medium was achieved by ionotropic cross-linking of chitosan by tripolyphosphate (TPP) ions. The TPP cross-linked nanofiber mat showed swelling up to ∼ 300% in 1 h and ∼ 40% degradation during 30 day study period. 3T3 fibroblast cells showed good attachment, proliferation and viability on TPP treated chitosan based nanofiber mats. The results indicate non-toxic nature of TPP cross-linked chitosan based nanofibers and their potential to be explored as a tissue engineering matrix. - Highlights: ► Chitosan based nanofiber fabrication through electrospinning. ► Roles of solution viscosity and yield stress on spinnability of chitosan evidenced. ► Tripolyphosphate (TPP) cross-linking rendered structural stability to nanofibers. ► TPP cross-linking also improved cellular response on chitosan based nanofibers. ► Thus, chitosan based nanofibers are suitable for tissue engineering application.

  8. Physico-chemical/biological properties of tripolyphosphate cross-linked chitosan based nanofibers

    International Nuclear Information System (INIS)

    Sarkar, Soumi Dey; Farrugia, Brooke L.; Dargaville, Tim R.; Dhara, Santanu

    2013-01-01

    In this study, chitosan-PEO blend, prepared in a 15 M acetic acid, was electrospun into nanofibers (∼ 78 nm diameter) with bead free morphology. While investigating physico-chemical parameters of blend solutions, effect of yield stress on chitosan based nanofiber fabrication was clearly evidenced. Architectural stability of nanofiber mat in aqueous medium was achieved by ionotropic cross-linking of chitosan by tripolyphosphate (TPP) ions. The TPP cross-linked nanofiber mat showed swelling up to ∼ 300% in 1 h and ∼ 40% degradation during 30 day study period. 3T3 fibroblast cells showed good attachment, proliferation and viability on TPP treated chitosan based nanofiber mats. The results indicate non-toxic nature of TPP cross-linked chitosan based nanofibers and their potential to be explored as a tissue engineering matrix. - Highlights: ► Chitosan based nanofiber fabrication through electrospinning. ► Roles of solution viscosity and yield stress on spinnability of chitosan evidenced. ► Tripolyphosphate (TPP) cross-linking rendered structural stability to nanofibers. ► TPP cross-linking also improved cellular response on chitosan based nanofibers. ► Thus, chitosan based nanofibers are suitable for tissue engineering application

  9. Permanent Set of Cross-Linking Networks: Comparison of Theory with Molecular Dynamics Simulations

    DEFF Research Database (Denmark)

    Rottach, Dana R.; Curro, John G.; Budzien, Joanne

    2006-01-01

    The permanent set of cross-linking networks is studied by molecular dynamics. The uniaxial stress for a bead-spring polymer network is investigated as a function of strain and cross-link density history, where cross-links are introduced in unstrained and strained networks. The permanent set...

  10. Application of a fast sorting algorithm to the assignment of mass spectrometric cross-linking data.

    Science.gov (United States)

    Petrotchenko, Evgeniy V; Borchers, Christoph H

    2014-09-01

    Cross-linking combined with MS involves enzymatic digestion of cross-linked proteins and identifying cross-linked peptides. Assignment of cross-linked peptide masses requires a search of all possible binary combinations of peptides from the cross-linked proteins' sequences, which becomes impractical with increasing complexity of the protein system and/or if digestion enzyme specificity is relaxed. Here, we describe the application of a fast sorting algorithm to search large sequence databases for cross-linked peptide assignments based on mass. This same algorithm has been used previously for assigning disulfide-bridged peptides (Choi et al., ), but has not previously been applied to cross-linking studies. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. The conformational stability and flexibility of insulin with an additional intramolecular cross-link

    International Nuclear Information System (INIS)

    Brems, D.N.; Brown, P.L.; Nakagawa, S.H.; Tager, H.S.

    1991-01-01

    The conformational stability and flexibility of insulin containing a cross-link between the alpha-amino group of the A-chain to the epsilon-amino group of Lys29 of the B-chain was examined. The cross-link varied in length from 2 to 12 carbon atoms. The conformational stability was determined by guanidine hydrochloride-induced equilibrium denaturation and flexibility was assessed by H2O/D2O amide exchange. The cross-link has substantial effects on both conformational stability and flexibility which depend on its length. In general, the addition of a cross-link enhances conformational stability and decreases flexibility. The optimal length for enhanced stability and decreased flexibility was the 6-carbon link. For the 6-carbon link the Gibbs free energy of unfolding was 8.0 kcal/mol compared to 4.5 kcal/mol for insulin, and the amide exchange rate decreased by at least 3-fold. A very short cross-link (i.e. the 2-carbon link) caused conformational strain that was detectable by a lack of stabilization in the Gibbs free energy of unfolding and enhancement in the amide exchange rate compared to insulin. The effect of the cross-link length on insulin hydrodynamic properties is discussed relative to previously obtained receptor binding results

  12. Characteristics of recycled and electron beam irradiated high density polyethylene samples

    International Nuclear Information System (INIS)

    Cardoso, Jessica R.; Gabriel, Leandro; Geraldo, Aurea B.C.; Moura, Eduardo

    2015-01-01

    Polymers modification by irradiation is a well-known process that allows degradation and cross-linking in concurrent events; this last is expected when an increase of mechanical properties is required. Actually, the interest of recycling and reuse of polymeric material is linked to the increase of plastics ending up in waste streams. Therefore, these both irradiation and recycling process may be conducted to allow a new use to this material that would be discarded by an improvement of its mechanical properties. In this work, the High Density Polyethylene (HDPE) matrix has been recycled five times from original substrate. The electron beam irradiation process was applied from 50 kGy to 200 kGy in both original and recycled samples; in this way, mechanical properties and thermal characteristics were evaluated. The results of applied process and material characterization are discussed. (author)

  13. Characteristics of recycled and electron beam irradiated high density polyethylene samples

    Energy Technology Data Exchange (ETDEWEB)

    Cardoso, Jessica R.; Gabriel, Leandro; Geraldo, Aurea B.C.; Moura, Eduardo, E-mail: jrcardoso@ipen.br, E-mail: lgabriell@gmail.com, E-mail: ageraldo@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2015-07-01

    Polymers modification by irradiation is a well-known process that allows degradation and cross-linking in concurrent events; this last is expected when an increase of mechanical properties is required. Actually, the interest of recycling and reuse of polymeric material is linked to the increase of plastics ending up in waste streams. Therefore, these both irradiation and recycling process may be conducted to allow a new use to this material that would be discarded by an improvement of its mechanical properties. In this work, the High Density Polyethylene (HDPE) matrix has been recycled five times from original substrate. The electron beam irradiation process was applied from 50 kGy to 200 kGy in both original and recycled samples; in this way, mechanical properties and thermal characteristics were evaluated. The results of applied process and material characterization are discussed. (author)

  14. WICH, a member of WASP-interacting protein family, cross-links actin filaments

    International Nuclear Information System (INIS)

    Kato, Masayoshi; Takenawa, Tadaomi

    2005-01-01

    In yeast, Verprolin plays an important role in rearrangement of the actin cytoskeleton. There are three mammalian homologues of Verprolin, WIP, CR16, and WICH, and all of them bind actin and Wiskott-Aldrich syndrome protein (WASP) and/or neural-WASP. Here, we describe a novel function of WICH. In vitro co-sedimentation analysis revealed that WICH not only binds to actin filaments but also cross-links them. Fluorescence and electron microscopy detected that this cross-linking results in straight bundled actin filaments. Overexpression of WICH alone in cultured fibroblast caused the formation of thick actin fibers. This ability of WICH depended on its own actin cross-linking activity. Importantly, the actin cross-linking activity of WICH was modified through a direct association with N-WASP. Taken together, these data suggest that WICH induces a bundled form of actin filament with actin cross-linking activity and the association with N-WASP suppresses that activity. WICH thus appears to be a novel actin bundling protein

  15. Antimicrobial coatings on polyethylene terephthalate based on curcumin/cyclodextrin complex embedded in a multilayer polyelectrolyte architecture.

    Science.gov (United States)

    Shlar, Ilya; Droby, Samir; Rodov, Victor

    2018-04-01

    Bacterial contamination is a growing concern worldwide. The aim of this work was to develop an antimicrobial coating based on curcumin-cyclodextrin inclusion complex and using polyethylene terephthalate (PET) film as a support matrix. After a pre-treatment aimed to provide sufficient electric charge to the PET surface, it was electrostatically coated with repeated multilayers comprising alternately deposited positively-charged poly-l-lysine (PLL) and negatively-charged poly-l-glutamic acid (PLGA) and carboxymethyl-β-cyclodextrin (CMBCD). The coatings had an architecture (PLL-PLGA) 6 -(PLL-PLGA-PLL-CMBCD) n , with the number of repeated multilayers n varying from 5 to 20. The CMBCD molecules were either covalently cross-linked using carbodiimide crosslinker chemistry or left unbound. The surface morphology, structure and elemental composition of the coatings were analysed by scanning electron microscopy and energy dispersive x-ray spectroscopy. To impart antimicrobial properties to the coatings they were loaded with a natural phenolic compound curcumin forming inclusion complexes with β-cyclodextrin. The non-cross-linked coatings showed bactericidal activity towards Escherichia coli in the dark, and this activity was further enhanced upon illumination with white light. Curcumin was released from the non-cross-linked coatings into an aqueous medium in the form of cyclodextrin inclusion complex. After the cross-linking, the coating lost its dark antimicrobial activity but retained the photodynamic properties. Stabilized cross-linked curcumin-loaded coatings can serve a basis for developing photoactivated antimicrobial surfaces controlling bacterial contamination and spread. Copyright © 2018 Elsevier B.V. All rights reserved.

  16. Transglutaminase catalyzed cross-linking of sodium caseinate improves oxidative stability of flaxseed oil emulsion.

    Science.gov (United States)

    Ma, Hairan; Forssell, Pirkko; Kylli, Petri; Lampi, Anna-Maija; Buchert, Johanna; Boer, Harry; Partanen, Riitta

    2012-06-20

    Sodium caseinate was modified by transglutaminase catalyzed cross-linking reaction prior to the emulsification process in order to study the effect of cross-linking on the oxidative stability of protein stabilized emulsions. The extent of the cross-linking catalyzed by different dosages of transglutaminase was investigated by following the ammonia production during the reaction and using SDS-PAGE gel. O/W emulsions prepared with the cross-linked and non-cross-linked sodium caseinates were stored for 30 days under the same conditions. Peroxide value measurement, oxygen consumption measurement, and headspace gas chromatography analysis were used to study the oxidative stability of the emulsions. The emulsion made of the cross-linked sodium caseinate showed an improved oxidative stability with reduced formation of fatty acid hydroperoxides and volatiles and a longer period of low rate oxygen consumption. The improving effect of transglutaminase catalyzed cross-linking could be most likely attributed to the enhanced physical stability of the interfacial protein layer against competitive adsorption by oil oxidation products.

  17. Synthesis of novel bis(perfluorophenyl azides) coupling agents: Evaluation of their performance by crosslinking of poly(ethylene oxide)

    KAUST Repository

    Mehenni, Hakim

    2011-11-01

    Novel bis(perfluorophenyl azides) coupling agents, containing spacer arms from ethylene or ethylene glycol subunits, were successfully synthesized. Nitrenes photogenerated from these novel bis(PFPA) coupling agents were applied successfully to the cross-linking of poly(ethylene oxide) (PEO10,000) in either aqueous medium or at the solid state, thus, we demonstrated the potential of these bis(PFPA) molecules as promising coupling agents in surface engineering. © 2011 Elsevier Ltd. All rights reserved.

  18. A novel strategy for preparing mechanically robust ionically cross-linked alginate hydrogels

    International Nuclear Information System (INIS)

    Jejurikar, Aparna; Lawrie, Gwen; Groendahl, Lisbeth; Martin, Darren

    2011-01-01

    The properties of alginate films modified using two cross-linker ions (Ca 2+ and Ba 2+ ), comparing two separate cross-linking techniques (the traditional immersion (IM) method and a new strategy in a pressure-assisted diffusion (PD) method), are evaluated. This was achieved through measuring metal ion content, water uptake and film stability in an ionic solution ([Ca 2+ ] = 2 mM). Characterization of the internal structure and mechanical properties of hydrated films were established by cryogenic scanning electron microscopy and tensile testing, respectively. It was found that gels formed by the PD technique possessed greater stability and did not exhibit any delamination after 21 day immersion as compared to gels formed by the IM technique. The Ba 2+ cross-linked gels possessed significantly higher cross-linking density as reflected in lower water content, a more dense internal structure and higher Young's modulus compared to Ca 2+ cross-linked gels. For the Ca 2+ cross-linked gels, a large improvement in the mechanical properties was observed in gels produced by the PD technique and this was attributed to thicker pore walls observed within the hydrogel structure. In contrast, for the Ba 2+ cross-linked gels, the PD technique resulted in gels that had lower tensile strength and strain energy density and this was attributed to phase separation and larger macropores in this gel.

  19. Computational investigation of kinetics of cross-linking reactions in proteins: importance in structure prediction.

    Science.gov (United States)

    Bandyopadhyay, Pradipta; Kuntz, Irwin D

    2009-01-01

    The determination of protein structure using distance constraints is a new and promising field of study. One implementation involves attaching residues of a protein using a cross-linking agent, followed by protease digestion, analysis of the resulting peptides by mass spectroscopy, and finally sequence threading to detect the protein folds. In the present work, we carry out computational modeling of the kinetics of cross-linking reactions in proteins using the master equation approach. The rate constants of the cross-linking reactions are estimated using the pKas and the solvent-accessible surface areas of the residues involved. This model is tested with fibroblast growth factor (FGF) and cytochrome C. It is consistent with the initial experimental rate data for individual lysine residues for cytochrome C. Our model captures all observed cross-links for FGF and almost 90% of the observed cross-links for cytochrome C, although it also predicts cross-links that were not observed experimentally (false positives). However, the analysis of the false positive results is complicated by the fact that experimental detection of cross-links can be difficult and may depend on specific experimental conditions such as pH, ionic strength. Receiver operator characteristic plots showed that our model does a good job in predicting the observed cross-links. Molecular dynamics simulations showed that for cytochrome C, in general, the two lysines come closer for the observed cross-links as compared to the false positive ones. For FGF, no such clear pattern exists. The kinetic model and MD simulation can be used to study proposed cross-linking protocols.

  20. Cross-linking methods of electrospun fibrinogen scaffolds for tissue engineering applications

    International Nuclear Information System (INIS)

    Sell, Scott A; Garg, Koyal; McClure, Michael J; Bowlin, Gary L; Francis, Michael P; Simpson, David G

    2008-01-01

    The purpose of this study was to enhance the mechanical properties and slow the degradation of an electrospun fibrinogen scaffold, while maintaining the scaffold's high level of bioactivity. Three different cross-linkers were used to achieve this goal: glutaraldehyde vapour, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) in ethanol and genipin in ethanol. Scaffolds with a fibrinogen concentration of 120 mg ml -1 were electrospun and cross-linked with one of the aforementioned cross-linkers. Mechanical properties were determined through uniaxial tensile testing performed on scaffolds incubated under standard culture conditions for 1 day, 7 days and 14 days. Cross-linked scaffolds were seeded with human foreskin fibroblasts (BJ-GFP-hTERT) and cultured for 7, 14 and 21 days, with histology and scanning electron microscopy performed upon completion of the time course. Mechanical testing revealed significantly increased peak stress and modulus values for the EDC and genipin cross-linked scaffolds, with significantly slowed degradation. However, cross-linking with EDC and genipin was shown to have some negative effect on the bioactivity of the scaffolds as cell migration throughout the thickness of the scaffold was slowed.

  1. Carbonate-linked poly(ethylene oxide) polymer electrolytes towards high performance solid state lithium batteries

    International Nuclear Information System (INIS)

    He, Weisheng; Cui, Zili; Liu, Xiaochen; Cui, Yanyan; Chai, Jingchao; Zhou, Xinhong; Liu, Zhihong; Cui, Guanglei

    2017-01-01

    The classic poly(ethylene oxide) (PEO) based solid polymer electrolyte suffers from poor ionic conductivity of ambient temperature, low lithium ion transference number and relatively narrow electrochemical window (<4.0 V vs. Li + /Li). Herein, the carbonate-linked PEO solid polymer such as poly(diethylene glycol carbonate) (PDEC) and poly(triethylene glycol carbonate) (PTEC) were explored to find out the feasibility of resolving above issues. It was proven that the optimized ionic conductivity of PTEC based electrolyte reached up to 1.12 × 10 −5 S cm −1 at 25 °C with a decent lithium ion transference number of 0.39 and a wide electrochemical window about 4.5 V vs. Li + /Li. In addition, the PTEC based Li/LiFePO 4 cell could be reversibly charged and discharged at 0.05 C-rates at ambient temperature. Moreover, the higher voltage Li/LiFe 0.2 Mn 0.8 PO 4 cell (cutoff voltage 4.35 V) possessed considerable rate capability and excellent cycling performance even at ambient temperature. Therefore, these carbonate-linked PEO electrolytes were demonstrated to be fascinating candidates for the next generation solid state lithium batteries simultaneously with high energy and high safety.

  2. Dehydration of an azeotrope of ethanol/water by sodium carboxymethylcellulose membranes cross-linked with organic or inorganic cross-linker

    Directory of Open Access Journals (Sweden)

    2010-11-01

    Full Text Available To control the swelling of sodium carboxymethylcellulose (CMCNa membranes, mixtures of CMCNa and glutaraldehyde (GA and mixtures of CMCNa as an organic component and tetraethoxysilane (TEOS as an inorganic component were prepared, and CMCNa/GA cross-linked membranes and CMCNa/TEOS hybrid membranes were formed. In the separation of an ethanol/water azeotrope by pervaporation (PV, the effects of the GA or TEOS content on the water/ethanol selectivity and permeability of these CMCNa/GA cross-linked and CMCNa/TEOS hybrid membranes were investigated. Cross-linked and hybrid membranes containing up to 10 wt% GA or 10 wt% TEOS exhibited higher water/ethanol selectivity than CMCNa membrane without any cross-linker. This resulted from both increased density and depressed swelling of the membranes by the formation of a cross-linked structure. The relationship between the structure of the CMCNa/GA cross-linked membranes and CMCNa/TEOS hybrid membranes and their permeation and separation characteristics for an ethanol/water azeotrope during PV is discussed in detail.

  3. Rheological properties of dispersions of enzymatically cross-linked apo-α-lactalbumin

    NARCIS (Netherlands)

    Saricay, Yunus; Wierenga, Peter A.; Vries, de Renko

    2016-01-01

    The enzymatic cross-linking of apo-α-lactalbumin (α-LA) with horseradish peroxidase (HRP) leads to the formation of hydrophilic protein aggregates with controlled size and architecture. We explore the rheological properties of dispersions of these HRP-cross-linked α-LA aggregates with a

  4. Models for stiffening in cross-linked biopolymer networks : A comparative study

    NARCIS (Netherlands)

    van Dillen, T.; Onck, P. R.; Van der Giessen, E.

    In a recent publication, we studied the mechanical stiffening behavior in two-dimensional (2D) cross-linked networks of semiflexible biopolymer filaments under simple shear [Onck, P.R., Koeman, T., Van Dillen, T., Van der Giessen, E., 2005. Alternative explanation of stiffening in cross-linked

  5. Cross-Linked Amylose Bio-Plastic: A Transgenic-Based Compostable Plastic Alternative

    Directory of Open Access Journals (Sweden)

    Domenico Sagnelli

    2017-09-01

    Full Text Available Bio-plastics and bio-materials are composed of natural or biomass derived polymers, offering solutions to solve immediate environmental issues. Polysaccharide-based bio-plastics represent important alternatives to conventional plastic because of their intrinsic biodegradable nature. Amylose-only (AO, an engineered barley starch with 99% amylose, was tested to produce cross-linked all-natural bioplastic using normal barley starch as a control. Glycerol was used as plasticizer and citrate cross-linking was used to improve the mechanical properties of cross-linked AO starch extrudates. Extrusion converted the control starch from A-type to Vh- and B-type crystals, showing a complete melting of the starch crystals in the raw starch granules. The cross-linked AO and control starch specimens displayed an additional wide-angle diffraction reflection. Phospholipids complexed with Vh-type single helices constituted an integrated part of the AO starch specimens. Gas permeability tests of selected starch-based prototypes demonstrated properties comparable to that of commercial Mater-Bi© plastic. The cross-linked AO prototypes had composting characteristics not different from the control, indicating that the modified starch behaves the same as normal starch. The data shows the feasibility of producing all-natural bioplastic using designer starch as raw material.

  6. Cross-Linked Amylose Bio-Plastic: A Transgenic-Based Compostable Plastic Alternative

    Science.gov (United States)

    Sagnelli, Domenico; Kemmer, Gerdi Christine; Holse, Mette; Hebelstrup, Kim H.; Bao, Jinsong; Stelte, Wolfgang; Bjerre, Anne-Belinda; Blennow, Andreas

    2017-01-01

    Bio-plastics and bio-materials are composed of natural or biomass derived polymers, offering solutions to solve immediate environmental issues. Polysaccharide-based bio-plastics represent important alternatives to conventional plastic because of their intrinsic biodegradable nature. Amylose-only (AO), an engineered barley starch with 99% amylose, was tested to produce cross-linked all-natural bioplastic using normal barley starch as a control. Glycerol was used as plasticizer and citrate cross-linking was used to improve the mechanical properties of cross-linked AO starch extrudates. Extrusion converted the control starch from A-type to Vh- and B-type crystals, showing a complete melting of the starch crystals in the raw starch granules. The cross-linked AO and control starch specimens displayed an additional wide-angle diffraction reflection. Phospholipids complexed with Vh-type single helices constituted an integrated part of the AO starch specimens. Gas permeability tests of selected starch-based prototypes demonstrated properties comparable to that of commercial Mater-Bi© plastic. The cross-linked AO prototypes had composting characteristics not different from the control, indicating that the modified starch behaves the same as normal starch. The data shows the feasibility of producing all-natural bioplastic using designer starch as raw material. PMID:28973963

  7. Cross-Linked Amylose Bio-Plastic: A Transgenic-Based Compostable Plastic Alternative.

    Science.gov (United States)

    Sagnelli, Domenico; Hooshmand, Kourosh; Kemmer, Gerdi Christine; Kirkensgaard, Jacob J K; Mortensen, Kell; Giosafatto, Concetta Valeria L; Holse, Mette; Hebelstrup, Kim H; Bao, Jinsong; Stelte, Wolfgang; Bjerre, Anne-Belinda; Blennow, Andreas

    2017-09-30

    Bio-plastics and bio-materials are composed of natural or biomass derived polymers, offering solutions to solve immediate environmental issues. Polysaccharide-based bio-plastics represent important alternatives to conventional plastic because of their intrinsic biodegradable nature. Amylose-only (AO), an engineered barley starch with 99% amylose, was tested to produce cross-linked all-natural bioplastic using normal barley starch as a control. Glycerol was used as plasticizer and citrate cross-linking was used to improve the mechanical properties of cross-linked AO starch extrudates. Extrusion converted the control starch from A-type to Vh- and B-type crystals, showing a complete melting of the starch crystals in the raw starch granules. The cross-linked AO and control starch specimens displayed an additional wide-angle diffraction reflection. Phospholipids complexed with Vh-type single helices constituted an integrated part of the AO starch specimens. Gas permeability tests of selected starch-based prototypes demonstrated properties comparable to that of commercial Mater-Bi © plastic. The cross-linked AO prototypes had composting characteristics not different from the control, indicating that the modified starch behaves the same as normal starch. The data shows the feasibility of producing all-natural bioplastic using designer starch as raw material.

  8. Riboflavin/UVA Collagen Cross-Linking-Induced Changes in Normal and Keratoconus Corneal Stroma

    Science.gov (United States)

    Hayes, Sally; Boote, Craig; Kamma-Lorger, Christina S.; Rajan, Madhavan S.; Harris, Jonathan; Dooley, Erin; Hawksworth, Nicholas; Hiller, Jennifer; Terill, Nick J.; Hafezi, Farhad; Brahma, Arun K.; Quantock, Andrew J.; Meek, Keith M.

    2011-01-01

    Purpose To determine the effect of Ultraviolet-A collagen cross-linking with hypo-osmolar and iso-osmolar riboflavin solutions on stromal collagen ultrastructure in normal and keratoconus ex vivo human corneas. Methods Using small-angle X-ray scattering, measurements of collagen D-periodicity, fibril diameter and interfibrillar spacing were made at 1 mm intervals across six normal post-mortem corneas (two above physiological hydration (swollen) and four below (unswollen)) and two post-transplant keratoconus corneal buttons (one swollen; one unswollen), before and after hypo-osmolar cross-linking. The same parameters were measured in three other unswollen normal corneas before and after iso-osmolar cross-linking and in three pairs of swollen normal corneas, in which only the left was cross-linked (with iso-osmolar riboflavin). Results Hypo-osmolar cross-linking resulted in an increase in corneal hydration in all corneas. In the keratoconus corneas and unswollen normal corneas, this was accompanied by an increase in collagen interfibrillar spacing (priboflavin solutions are more likely a consequence of treatment-induced changes in tissue hydration rather than cross-linking. PMID:21850225

  9. Design and Preparation of Cross-Linked Polystyrene Nanoparticles for Elastomer Reinforcement

    Directory of Open Access Journals (Sweden)

    Ming Lu

    2010-01-01

    Full Text Available Cross-linked polystyrene (PS particles in a latex form were synthesized by free radical emulsion polymerization. The nano-PS-filled elastomer composites were prepared by the energy-saving latex compounding method. Results showed that the PS particles took a spherical shape in the size of 40–60 nm with a narrow size distribution, and the glass-transition temperature of the PS nanoparticles increased with the cross-linking density. The outcomes from the mechanical properties demonstrated that when filled into styrene-butadiene rubber (SBR, nitrile-butadiene rubber (NBR, and natural rubber (NR, the cross-linked PS nano-particles exhibited excellent reinforcing capabilities in all the three matrices, and the best in the SBR matrix. In comparison with that of the carbon black filled composites, another distinguished advantage of the cross-linked PS particles filled elastomer composites was found to be light weight in density, which could help to save tremendous amount of energy when put into end products.

  10. Cross-linking of rubber in the presence of multi-functional cross-linking aids via thermoreversible Diels-Alder chemistry

    NARCIS (Netherlands)

    Polgar, L. M.; Fortunato, G.; Araya-Hermosilla, R.; van Duin, M.; Pucci, A.; Picchioni, F.

    Furan-functionalized polyketone (PK-FU) was added to a furan-functionalized ethylene-propylene rubber (EPM-FU). The mixture was subsequently cross-linked with a bismaleimide through Diels-Alder chemistry in order to improve the mechanical properties of the rubber. Infrared spectroscopy showed the

  11. Diurnal Variability of the inner-shelf circulation in the lee of a cape under upwelling conditions

    Science.gov (United States)

    Lamas, Luisa; Peliz, Álvaro; Marchesiello, Patrick

    2013-04-01

    The circulation over the inner-shelf is a key component of shelf dynamics and an important mechanism for cross-shore exchange on most shelves. Yet our understanding of the cross-shore circulation and how it depends on different forcing conditions, bathymetry and stratification remains poor due in part to sparse observations and the difficulty of resolving spatial and temporal scales within the inner-shelf. Most studies of cross-shore transport on the inner-shelf consider only a 2D circulation, due to coastal upwelling or downwelling and assume along-shore uniformity. However, divergence in the along-shore and cross-shore flows may occur with the presence of complex coastline topography or subtle bathymetric features, and can drive substantial horizontal cross-shore exchange, with same order of magnitude as coastal upwelling and downwelling. A recent study using observational data collected near cape Sines, Portugal, showed that not only wind, waves and tides are important forcing mechanisms of the inner-shelf circulation, but also that the along-shore pressure gradient plays a major role on driving cross-shore exchange. A modeling study was conducted in order to study the complexity of the inner-shelf dynamics, in the presence of a cape. A simplified configuration was used in order to isolate the effects of individual processes: wind, heat fluxes, tides and waves. The preliminary results of the effects of these processes on the inner-shelf circulation will be presented.

  12. Ultra-high mechanical properties of porous composites based on regenerated cellulose and cross-linked poly(ethylene glycol).

    Science.gov (United States)

    Teng, Jian; Yang, Biao; Zhang, Liang-Qing; Lin, Sheng-Qiang; Xu, Ling; Zhong, Gan-Ji; Tang, Jian-Hua; Li, Zhong-Ming

    2018-01-01

    The ultra-high mechanical, biocompatible and biodegradable porous regenerated cellulose/poly(ethylene glycol) (RC/PEG) composites with double network structure were fabricated via an simple method to dissolve cellulose followed by UV irradiation. The porous structure of RC/PEG was sensitively altered by PEG contents, which led to the porous structure morphology transition from 3D fibrillar network to close-grained sheet-like-network with the loading of cross-linked PEG. The porous RC/PEG showed excellent mechanical properties, i.e., the compressive strength can reach 33 times higher than that of neat RC (0.07MPa) at the compressive strain of 30%. Porous RC/PEG also displayed outstanding properties with openly porous structure and structural stabilization. Besides, porous RC/PEG exhibited good water absorbency, which the water absorbency ratio at equilibrium state was 83% higher than that of porous RC. This work provides an environmentally friendly and simple pathway to prepare non-toxic and biocompatible porous regenerated cellulose-based composites with high strength, structural stabilization and good water absorbency, which could be useful for packaging, biomedical applications, sewage purification, etc. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Solution processed organic light-emitting diodes using the plasma cross-linking technology

    Energy Technology Data Exchange (ETDEWEB)

    He, Kongduo [Department of Light Sources and Illuminating Engineering, Fudan University, Shanghai 200433 (China); Liu, Yang [Department of Light Sources and Illuminating Engineering, Fudan University, Shanghai 200433 (China); Engineering Research Center of Advanced Lighting Technology, Ministry of Education, Shanghai 200433 (China); Gong, Junyi; Zeng, Pan; Kong, Xun; Yang, Xilu; Yang, Cheng; Yu, Yan [Department of Light Sources and Illuminating Engineering, Fudan University, Shanghai 200433 (China); Liang, Rongqing [Department of Light Sources and Illuminating Engineering, Fudan University, Shanghai 200433 (China); Engineering Research Center of Advanced Lighting Technology, Ministry of Education, Shanghai 200433 (China); Ou, Qiongrong, E-mail: qrou@fudan.edu.cn [Department of Light Sources and Illuminating Engineering, Fudan University, Shanghai 200433 (China); Engineering Research Center of Advanced Lighting Technology, Ministry of Education, Shanghai 200433 (China)

    2016-09-30

    Highlights: • Mixed acetylene and Ar plasma treatment makes the organic film surface cross-linked. • The plasma treatment for 30 s does not affect the performance of OLEDs. • Cross-linking surface can resist rinsing and corrosion of organic solvent. • The surface morphology is nearly unchanged after plasma treatment. • The plasma cross-linking method can realize solution processed multilayer OLEDs. - Abstract: Solution processed multilayer organic light-emitting diodes (OLEDs) present challenges, especially regarding dissolution of the first layer during deposition of a second layer. In this work, we first demonstrated a plasma cross-linking technology to produce a solution processed OLED. The surfaces of organic films can be cross-linked after mixed acetylene and Ar plasma treatment for several tens of seconds and resist corrosion of organic solvent. The film thickness and surface morphology of emissive layers (EMLs) with plasma treatment and subsequently spin-rinsed with chlorobenzene are nearly unchanged. The solution processed triple-layer OLED is successfully fabricated and the current efficiency increases 50% than that of the double-layer OLED. Fluorescent characteristics of EMLs are also observed to investigate factors influencing the efficiency of the triple-layer OLED. Plasma cross-linking technology may open up a new pathway towards fabrication of all-solution processed multilayer OLEDs and other soft electronic devices.

  14. Formulation and Characterization of Glutaraldehyde Cross-Linked ...

    African Journals Online (AJOL)

    ... drug/polymer ratio, volume of cross linking agent and volume of surfactant were ... The microspheres were characterized for entrapment efficiency, drug loading, ... size distribution (105 – 219 μm) and an entrapment efficiency of up to 73 %.

  15. Age differences at sexual debut and subsequent reproductive health: Is there a link?

    Directory of Open Access Journals (Sweden)

    Reynolds Heidi

    2008-10-01

    Full Text Available Abstract Background Experiences at sexual debut may be linked to reproductive health later in life. Additionally, young women with older sexual partners may be at greater risk for HIV and sexually transmitted infections. This study examines sexual debut with an older partner and subsequent reproductive health outcomes among 599 sexually experienced women aged 15–24 who utilized voluntary counseling and testing or reproductive health services in Port-au-Prince, Haiti. Methods Logistic regression models, controlling for socioeconomic and demographic factors, examined whether age differences at first sex were significantly associated with STI diagnosis in the previous 12 months and family planning method use at last intercourse. Results Sixty-five percent of women reported sexual initiation with a partner younger or less than 5 years older, 28% with a partner 5 to 10 years older, and 7% with a partner 10 or more years older. There was a trend towards decreased likelihood of recent use of family planning methods in women who had first sexual intercourse with a partner 5 to 9 years older compared to women with partners who were younger or less than 5 years older. Age differences were not linked to recent STI diagnosis. Conclusion Programs focusing on delaying sexual debut should consider age and gender-based power differentials between younger women and older men. Future research should examine whether wide age differences at sexual debut are predictive of continued involvement in cross-generational relationships and risky sexual behaviors and explore the mechanisms by which cross-generational first sex and subsequent reproductive health may be connected.

  16. Fun at Antarctic grounding lines: Ice-shelf channels and sediment transport

    Science.gov (United States)

    Drews, Reinhard; Mayer, Christoph; Eisen, Olaf; Helm, Veit; Ehlers, Todd A.; Pattyn, Frank; Berger, Sophie; Favier, Lionel; Hewitt, Ian H.; Ng, Felix; Fürst, Johannes J.; Gillet-Chaulet, Fabien; Bergeot, Nicolas; Matsuoka, Kenichi

    2017-04-01

    Meltwater beneath the polar ice sheets drains, in part, through subglacial conduits. Landforms created by such drainages are abundant in areas formerly covered by ice sheets during the last glacial maximum. However, observations of subglacial conduit dynamics under a contemporary ice sheet are lacking. We present results from ice-penetrating radar to infer the existence of subglacial conduits upstream of the grounding line of Roi Baudouin Ice Shelf, Antarctica. The conduits are aligned with ice-shelf channels, and underlain by esker ridges formed from sediment deposition due to reduced water outflow speed near the grounding line. In turn, the eskers modify local ice flow to initiate the bottom topography of the ice-shelf channels, and create small surface ridges extending onto the shelf. Relict features on the shelf are interpreted to indicate a history of these interactions and variability of past subglacial drainages. Because ice-shelf channels are loci where intense melting occurs to thin an ice shelf, these findings expose a novel link between subglacial drainage, sedimentation, and ice-shelf stability. To investigate the role of sediment transport beneath ice sheets further, we model the sheet-shelf system of the Ekstömisen catchment, Antarctica. A 3D finite element model (Elmer/ICE) is used to solve the transients full Stokes equation for isotropic, isothermal ice with a dynamic grounding line. We initialize the model with surface topography from the TanDEM-X satellites and by inverting simultaneously for ice viscosity and basal drag using present-day surface velocities. Results produce a flow field which is consitent with sattelite and on-site observations. Solving the age-depth relationship allows comparison with radar isochrones from airborne data, and gives information about the atmospheric/dynamic history of this sector. The flow field will eventually be used to identify potential sediment sources and sinks which we compare with more than 400 km of

  17. Fluorescence spectroscopic study of the aggregation behavior of non-cross-linked and cross-linked poly(alkylmethyldiallylammonium bromides) having decyl, octyl, and hexyl side chains in aqueous solution

    NARCIS (Netherlands)

    Wang, G.J; Engberts, J.B.F.N.

    1996-01-01

    The conformational state of a series of non-cross-linked and cross-linked poly(alkylmethyldiallylammonium bromides) bearing decyl, octyl, and hexyl side chains ((CL)-CopolC1-10, (CL)-CopolC1-8, and (CL)-CopolC1-6, respectively) in aqueous solutions were investigated by fluorescence spectroscopy

  18. Assessment of UVA-Riboflavin Corneal Cross-Linking Using Small Amplitude Oscillatory Shear Measurements.

    Science.gov (United States)

    Aslanides, Ioannis M; Dessi, Claudia; Georgoudis, Panagiotis; Charalambidis, Georgios; Vlassopoulos, Dimitris; Coutsolelos, Athanassios G; Kymionis, George; Mukherjee, Achyut; Kitsopoulos, Theofanis N

    2016-04-01

    The effect of ultraviolet (UV)-riboflavin cross-linking (CXL) has been measured primarily using the strip extensometry technique. We propose a simple and reliable methodology for the assessment of CXL treatment by using an established rheologic protocol based on small amplitude oscillatory shear (SAOS) measurements. It provides information on the average cross-link density and the elastic modulus of treated cornea samples. Three fresh postmortem porcine corneas were used to study the feasibility of the technique, one serving as control and two receiving corneal collagen cross-linking treatment. Subsequently, five pairs of fresh postmortem porcine corneas received corneal collagen cross-linking treatment with riboflavin and UVA-irradiation (370 nm; irradiance of 3 mW/cm2) for 30 minutes (Dresden protocol); the contralateral porcine corneas were used as control samples. After the treatment, the linear viscoelastic moduli of the corneal samples were measured using SAOS measurements and the average cross-linking densities extracted. For all cases investigated, the dynamic moduli of the cross-linked corneas were higher compared to those of the corresponding control samples. The increase of the elastic modulus of the treated samples was between 122% and 1750%. The difference was statistically significant for all tested samples (P = 0.018, 2-tailed t-test). We report a simple and accurate methodology for quantifying the effects of cross-linking on porcine corneas treated with the Dresden protocol by means of SAOS measurements in the linear regime. The measured dynamic moduli, elastic and viscous modulus, represent the energy storage and energy dissipation, respectively. Hence, they provide a means to assess the changing physical properties of the cross-linked collagen networks after CXL treatment.

  19. Carboxymethyl starch cross-linked by electron beam radiation in presence of acrylic acid sensitizer

    International Nuclear Information System (INIS)

    Doan Binh; Nguyen Thanh Duoc; Pham Thi Thu Hong

    2013-01-01

    Carboxymethyl starch (CMS) can be cross-linked by electron beam radiation to form a biocompatible and environment-friendly hydrogel at a high absorbed dose and a condensed CMS concentration. Acrylic acid (AAc) can be used as a sensitizer in order to reduce the absorbed doses to an acceptable certain level. At an absorbed dose of 3-4 kGy, the gel content of crosslinked CMS can be obtained about 50% with 5% (w/w) AAc concentration used. The compressive strength of CMS samples increased with increasing their cross-linked densities due to raising absorbed doses. The swelling ratio of cross-linked CMS was also attainable at a maximum of 50 times in the distilled water. The enzymatic degradation of cross-linked CMS was carried out in acetate buffer pH 4.6 with 0.1% α-amylase enzymatic solution incubated at 40℃ for 6 h. The crosslinked CMS samples were degraded slower than uncrosslinked CMS ones. The results indicated that the highly cross-linked CMS was almost fully degradable when the enzymatic hydrolysis was performed during 6 h. The FT IR spectra of cross-linked CMS in the presence of AAc were examined to observe the carboxyl group of AAc in the structure of cross-linked CMS. The hydrophilic of cross-linked CMS surface was determined by a contact-angle analysis. (authors)

  20. Multiscale approach for the construction of equilibrated all-atom models of a poly(ethylene glycol)-based hydrogel

    Science.gov (United States)

    Li, Xianfeng; Murthy, N. Sanjeeva; Becker, Matthew L.; Latour, Robert A.

    2016-01-01

    A multiscale modeling approach is presented for the efficient construction of an equilibrated all-atom model of a cross-linked poly(ethylene glycol) (PEG)-based hydrogel using the all-atom polymer consistent force field (PCFF). The final equilibrated all-atom model was built with a systematic simulation toolset consisting of three consecutive parts: (1) building a global cross-linked PEG-chain network at experimentally determined cross-link density using an on-lattice Monte Carlo method based on the bond fluctuation model, (2) recovering the local molecular structure of the network by transitioning from the lattice model to an off-lattice coarse-grained (CG) model parameterized from PCFF, followed by equilibration using high performance molecular dynamics methods, and (3) recovering the atomistic structure of the network by reverse mapping from the equilibrated CG structure, hydrating the structure with explicitly represented water, followed by final equilibration using PCFF parameterization. The developed three-stage modeling approach has application to a wide range of other complex macromolecular hydrogel systems, including the integration of peptide, protein, and/or drug molecules as side-chains within the hydrogel network for the incorporation of bioactivity for tissue engineering, regenerative medicine, and drug delivery applications. PMID:27013229

  1. Upper Ordovician-Lower Silurian shelf sequences of the Eastern Great Basin: Barn Hills and Lakeside Mountains, Utah

    Energy Technology Data Exchange (ETDEWEB)

    Harris, M.T. (Univ. of Wisconsin, Milwaukee, WI (United States). Dept. of Geosciences); Sheehan, P.M. (Milwaukee Public Museum, WI (United States). Dept of Geology)

    1993-04-01

    Detailed stratigraphic sections through Upper Ordovician-Lower Silurian shelf strata of the Eastern Great Basin were measured in two Utah localities, Barn Hills (Confusion Range) and Lakeside Mountains. Six major subfacies occur in these strata: mud-cracked and crinkly laminated subfacies, Laminated mudstone subfacies, cross-bedded grainstone subfacies, cross-laminated packstone subfacies, grainy bioturbated subfacies, muddy bioturbated subfacies, and thalassinoides burrowed subfacies. These occur in 1--10 m thick cycles in three facies: muddy cyclic laminite facies (tidal flats), cross-bedded facies (subtidal shoals), and bioturbated facies (moderate to low-energy shelf). The vertical facies succession, stacking patterns of meter-scale cycles, and exposure surfaces define correlatable sequences. The authors recognize four Upper Ordovician sequences (Mayvillian to Richmondian). An uppermost Ordovician (Hirnantian) sequence is missing in these sections but occurs basinward. Lower Silurian sequences are of early Llandoverian (A), middle Llandoverian (B), early late Llandoverian (C1--C3), late late Llandoverian (C4--C5), latest Llandoverian (C6) to early Wenlock age. In general, Upper Ordovician and latest Llandoverian-Wenlockian facies are muddier than intervening Llandoverian facies. The shift to muddier shelf facies in latest Llandoverian probably corresponds to the development of a rimmed shelf. The sequence framework improves correlation of these strata by combining sedimentologic patterns with the biostratigraphic data. For example, in the Lakesides, the Ordovician-Silurian boundary is shifted 37 m downward from recent suggestions. In addition, the sequence approach highlights intervals for which additional biostratigraphic information is needed.

  2. Effects of electron beam irradiation on the structural properties of polylactic acid/polyethylene blends

    Energy Technology Data Exchange (ETDEWEB)

    Bee, Soo-Tueen, E-mail: direct.beest@gmail.com [Department of Chemical Engineering, Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Jalan Genting Kelang, 53300 Setapak, Kuala Lumpur (Malaysia); Ratnam, C.T. [Radiation Processing Technology Division, Malaysian Nuclear Agency, Bangi, 43000 Kajang, Selangor (Malaysia); Sin, Lee Tin, E-mail: direct.tinsin@gmail.com [Department of Chemical Engineering, Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Jalan Genting Kelang, 53300 Setapak, Kuala Lumpur (Malaysia); Tee, Tiam-Ting; Wong, Wai-Kien; Lee, Jiuun-Xiang [Department of Chemical Engineering, Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Jalan Genting Kelang, 53300 Setapak, Kuala Lumpur (Malaysia); Rahmat, A.R. [Department of Polymer Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor (Malaysia)

    2014-09-01

    Highlights: •Electron beam irradiation on polyethylene (LDPE) and polylactic acid (PLA) blends. •Irradiated PLA/LDPE blends exhibit structural rearrangement to highly ordered structure. •Irradiated PLA/LDPE matrix extends continuity of polymer matrix with larger fibrils diameter. -- Abstract: The purpose of this research was to investigate the effects of electron beam irradiation on the properties of polylactic acid (PLA) and low density polyethylene (LDPE) blends. The PLA were compounded with 20–80% LDPE and were exposed to electron beam irradiation dosages of 20–120 kGy. The results from gel content and X-ray diffraction analyses showed that the addition of LDPE to PLA effectively increased the gel content and crystallinity. However, an increasing percentage of LDPE reduced the tensile strength and Young’s modulus of the PLA/LDPE samples due to the lower intermolecular bonding of LDPE than of PLA. Moreover, an increase in irradiation dosages gradually decreased the mechanical properties of low-LDPE PLA/LDPE. In contrast, the increasing irradiation dosage enhanced the mechanical properties of higher-LDPE PLA/LDPE. These results indicate that higher amounts of LDPE effectively react with the release of free radicals within the amorphous phase if the blends are subjected to irradiation. The higher amounts of free radicals induce the formation of three-dimensional cross-linked networks in the polymer matrix and thus increase the gel content. The irradiation-induced cross-linking in PLA/LDPE samples improves the mechanical properties and crystallinity by promoting a structural rearrangement of the polymer matrix into a highly ordered structure.

  3. Effects of electron beam irradiation on the structural properties of polylactic acid/polyethylene blends

    International Nuclear Information System (INIS)

    Bee, Soo-Tueen; Ratnam, C.T.; Sin, Lee Tin; Tee, Tiam-Ting; Wong, Wai-Kien; Lee, Jiuun-Xiang; Rahmat, A.R.

    2014-01-01

    Highlights: •Electron beam irradiation on polyethylene (LDPE) and polylactic acid (PLA) blends. •Irradiated PLA/LDPE blends exhibit structural rearrangement to highly ordered structure. •Irradiated PLA/LDPE matrix extends continuity of polymer matrix with larger fibrils diameter. -- Abstract: The purpose of this research was to investigate the effects of electron beam irradiation on the properties of polylactic acid (PLA) and low density polyethylene (LDPE) blends. The PLA were compounded with 20–80% LDPE and were exposed to electron beam irradiation dosages of 20–120 kGy. The results from gel content and X-ray diffraction analyses showed that the addition of LDPE to PLA effectively increased the gel content and crystallinity. However, an increasing percentage of LDPE reduced the tensile strength and Young’s modulus of the PLA/LDPE samples due to the lower intermolecular bonding of LDPE than of PLA. Moreover, an increase in irradiation dosages gradually decreased the mechanical properties of low-LDPE PLA/LDPE. In contrast, the increasing irradiation dosage enhanced the mechanical properties of higher-LDPE PLA/LDPE. These results indicate that higher amounts of LDPE effectively react with the release of free radicals within the amorphous phase if the blends are subjected to irradiation. The higher amounts of free radicals induce the formation of three-dimensional cross-linked networks in the polymer matrix and thus increase the gel content. The irradiation-induced cross-linking in PLA/LDPE samples improves the mechanical properties and crystallinity by promoting a structural rearrangement of the polymer matrix into a highly ordered structure

  4. Role of special cross-links in structure formation of bacterial DNA polymer

    Science.gov (United States)

    Agarwal, Tejal; Manjunath, G. P.; Habib, Farhat; Lakshmi Vaddavalli, Pavana; Chatterji, Apratim

    2018-01-01

    Using data from contact maps of the DNA-polymer of Escherichia coli (E. Coli) (at kilobase pair resolution) as an input to our model, we introduce cross-links between monomers in a bead-spring model of a ring polymer at very specific points along the chain. Via suitable Monte Carlo simulations, we show that the presence of these cross-links leads to a particular organization of the chain at large (micron) length scales of the DNA. We also investigate the structure of a ring polymer with an equal number of cross-links at random positions along the chain. We find that though the polymer does get organized at the large length scales, the nature of the organization is quite different from the organization observed with cross-links at specific biologically determined positions. We used the contact map of E. Coli bacteria which has around 4.6 million base pairs in a single circular chromosome. In our coarse-grained flexible ring polymer model, we used 4642 monomer beads and observed that around 80 cross-links are enough to induce the large-scale organization of the molecule accounting for statistical fluctuations caused by thermal energy. The length of a DNA chain even of a simple bacterial cell such as E. Coli is much longer than typical proteins, hence we avoided methods used to tackle protein folding problems. We define new suitable quantities to identify the large scale structure of a polymer chain with a few cross-links.

  5. Polyethylene glycols (PEG) and related structures

    DEFF Research Database (Denmark)

    Wenande, Emily; Kroigaard, Mogens; Mosbech, Holger

    2015-01-01

    We describe hypersensitivity to polyethylene glycols (PEGs), with cross-reactivity to a structural analog, polysorbate 80, in a 69-year-old patient with perioperative anaphylaxis and subsequent, severe anaphylactic reactions to unrelated medical products. PEGs and PEG analogs are prevalent in the...

  6. Comparative study of PBI Cross Linked Utilizing Agents of Varying Steric Configurations

    DEFF Research Database (Denmark)

    Kirkebcek, Andreas; Aili, David; Li, Qingfeng

    2016-01-01

    ionic or covalent cross linking. When considering such, little attention is devoted to explore the effect of the sterical configuration of the cross linking agent. In this contribution three different cross linking agents are utilized to evaluate how these affects final membrane properties.......The high thermal and chemical stability of poly[2,2'-(m-phenylene)-5,5' bibenzimidazole] (PBI) accounts for its wise spread use in high temperature polymer electrolyte membrane fuel cells (HT- PEMFC). By doping the membrane with phosphoric acid (PA) ionic conductivity is obtained. Thus conductivity...... is dependent on the amount of PA present within the membrane. However mechanical properties are reduced are significantly reduced due to the plasticizing effect shown by PA [1]. This effect is due to PBI chain displacement. This effect can be lessened by use of cross linking [2-4]. This can be obtained using...

  7. Biomimetic acellular detoxified glutaraldehyde cross-linked bovine pericardium for tissue engineering

    International Nuclear Information System (INIS)

    Mathapati, Santosh; Bishi, Dillip Kumar; Guhathakurta, Soma; Cherian, Kotturathu Mammen; Venugopal, Jayarama Reddy; Ramakrishna, Seeram; Verma, Rama Shanker

    2013-01-01

    Glutaraldehyde (GLUT) processing, cellular antigens, calcium ions in circulation, and phospholipids present in the native tissue are predominantly responsible for calcification, degeneration, and lack of natural microenvironment for host progenitor cell migration in tissue implants. The study presents an improved methodology for adhesion and proliferation of endothelial progenitor cells (EPCs) without significant changes in biomechanical and biodegradation properties of the processed acellular bovine pericardium. The anti-calcification potential of the processed tissue was enhanced by detoxification of GLUT-cross-linked bovine pericardium by decellularization, pretreating it with ethanol or removing the free aldehydes by citric acid treatment and lyophilization. The treated tissues were assessed for biomechanical properties, GLUT ligand quantification, adhesion, proliferation of EPCs, and biodegradability. The results indicate that there was no significant change in biomechanical properties and biodegradability when enzymatic hydrolysis (p > 0.05) is employed in detoxified acellular GLUT cross-linked tissue (DBP–G–CA–ET), compared with the native detoxified GLUT cross-linked bovine pericardium (NBP–G–CA–ET). DBP–G–CA–ET exhibited a significant (p > 0.05) increase in the viability of EPCs and cell adhesion as compared to acellular GLUT cross-linked bovine pericardium (p < 0.05). Lyophilized acellular detoxified GLUT cross-linked bovine pericardium, employed in our study as an alternative to conventional GLUT cross-linked bovine pericardium, might provide longer durability and better biocompatibility, and reduce calcification. The developed bovine pericardium patches could be used in cardiac reconstruction and repair, arteriotomy, soft tissue repair, and general surgical procedures with tissue regeneration dimensions. - Highlights: ► We improved the quality of patch biomaterial for cardiovascular surgical procedures. ► Bovine pericardium was

  8. Biomimetic acellular detoxified glutaraldehyde cross-linked bovine pericardium for tissue engineering

    Energy Technology Data Exchange (ETDEWEB)

    Mathapati, Santosh; Bishi, Dillip Kumar [Stem Cell and Molecular Biology Laboratory, Department of Biotechnology, Indian Institute of Technology Madras, Chennai (India); Frontier Lifeline Pvt Ltd. and Dr. K. M. Cherian Heart Foundation, Mogappair, Chennai (India); Healthcare and Energy Materials Laboratory, NUSNNI, Faculty of Engineering, National University of Singapore (Singapore); Guhathakurta, Soma [Departmet of Engineering Design, Indian Institute of Technology Madras, Chennai (India); Cherian, Kotturathu Mammen [Frontier Lifeline Pvt Ltd. and Dr. K. M. Cherian Heart Foundation, Mogappair, Chennai (India); Venugopal, Jayarama Reddy; Ramakrishna, Seeram [Healthcare and Energy Materials Laboratory, NUSNNI, Faculty of Engineering, National University of Singapore (Singapore); Verma, Rama Shanker, E-mail: vermars@iitm.ac.in [Stem Cell and Molecular Biology Laboratory, Department of Biotechnology, Indian Institute of Technology Madras, Chennai (India)

    2013-04-01

    Glutaraldehyde (GLUT) processing, cellular antigens, calcium ions in circulation, and phospholipids present in the native tissue are predominantly responsible for calcification, degeneration, and lack of natural microenvironment for host progenitor cell migration in tissue implants. The study presents an improved methodology for adhesion and proliferation of endothelial progenitor cells (EPCs) without significant changes in biomechanical and biodegradation properties of the processed acellular bovine pericardium. The anti-calcification potential of the processed tissue was enhanced by detoxification of GLUT-cross-linked bovine pericardium by decellularization, pretreating it with ethanol or removing the free aldehydes by citric acid treatment and lyophilization. The treated tissues were assessed for biomechanical properties, GLUT ligand quantification, adhesion, proliferation of EPCs, and biodegradability. The results indicate that there was no significant change in biomechanical properties and biodegradability when enzymatic hydrolysis (p > 0.05) is employed in detoxified acellular GLUT cross-linked tissue (DBP–G–CA–ET), compared with the native detoxified GLUT cross-linked bovine pericardium (NBP–G–CA–ET). DBP–G–CA–ET exhibited a significant (p > 0.05) increase in the viability of EPCs and cell adhesion as compared to acellular GLUT cross-linked bovine pericardium (p < 0.05). Lyophilized acellular detoxified GLUT cross-linked bovine pericardium, employed in our study as an alternative to conventional GLUT cross-linked bovine pericardium, might provide longer durability and better biocompatibility, and reduce calcification. The developed bovine pericardium patches could be used in cardiac reconstruction and repair, arteriotomy, soft tissue repair, and general surgical procedures with tissue regeneration dimensions. - Highlights: ► We improved the quality of patch biomaterial for cardiovascular surgical procedures. ► Bovine pericardium was

  9. Thermoreversible cross-linking of maleated ethylene/propylene copolymers with diamines and amino-alcohols

    NARCIS (Netherlands)

    Mee, van der M.A.J.; Goossens, J.G.P.; Duin, van M.

    2008-01-01

    Maleated ethylene/propylene copolymers (MAn-g-EPM) were thermoreversibly cross-linked using diamines and amino-alcohols. Covalent cross-links are formed via the equilibrium reaction of the grafted anhydride groups with di-functional cross-linkers containing combinations of primary (1°) and secondary

  10. SYNTHESIS AND CATALYTIC PROPERTIES OF CROSS-LINKED HYDROPHOBICALLY ASSOCIATING POLY(ALKYLMETHYLDIALLYLAMMONIUM BROMIDES)

    NARCIS (Netherlands)

    WANG, GJ; ENGBERTS, JBFN

    1994-01-01

    Cross-linked, hydrophobically associating homo- and copolymers were synthesized by free-radical cyclo(co)polymerization of alkylmethyldiallylammonium bromide monomers with a small amount of N,N'-methylenebisacrylamide in aqueous solution using ammonium persulfate as the initiator. The cross-linked

  11. Competition between dewetting and cross-linking in poly(N-vinylpyrrolidone)/polystyrene bilayer films.

    Science.gov (United States)

    Telford, Andrew M; Thickett, Stuart C; James, Michael; Neto, Chiara

    2011-12-06

    We investigated the dewetting of metastable poly(N-vinylpyrrolidone) (PNVP) thin films (45 nm) on top of polystyrene (PS) thin films (58 nm) as a function of annealing temperature and molecular weight of PS (96 and 6850 kg/mol). We focused on the competition between dewetting, occurring as a result of unfavorable intermolecular interactions at the PNVP/PS interface, and spontaneous cross-linking of PNVP, occurring during thermal annealing, as we recently reported (Telford, A. M.; James, M.; Meagher, L.; Neto, C. ACS Appl. Mater. Interfaces 2010, 2, 2399-2408). Using optical microscopy, we studied how the dewetting morphology and dynamics at different temperatures depended on the relative viscosity of the top PNVP film, which increased with cross-linking time, and of the bottom PS film. In the PNVP/PS96K system, cross-linking dominated over dewetting at temperatures below 180 °C, reducing drastically nucleated hole density and their maximum size, while above 180 °C the two processes reversed, with complete dewetting occurring at 200 °C. On the other hand, the PNVP/PS6850K system never achieved advanced dewetting stages as the dewetting was slower than cross-linking in the investigated temperature range. In both systems, dewetting of the PNVP films could be avoided altogether by thermally annealing the bilayers at temperatures where cross-linking dominated. The cross-linking was characterized quantitatively using neutron reflectometry, which indicated shrinkage and densification of the PNVP film, and qualitatively through selective removal of the bottom PS film. A simple model accounting for progressive cross-linking during the dewetting process predicted well the observed hole growth profiles and produced estimates of the PNVP cross-linking rate coefficients and of the activation energy of the process, in good agreement with literature values for similar systems. © 2011 American Chemical Society

  12. Polyethylene glycol as a promising synthetic material for repair of spinal cord injury

    Directory of Open Access Journals (Sweden)

    Xian-bin Kong

    2017-01-01

    Full Text Available Polyethylene glycol is a synthetic, biodegradable, and water-soluble polyether. Owing to its good biological and material properties, polyethylene glycol shows promise in spinal cord tissue engineering applications. Although studies have examined repairing spinal cord injury with polyethylene glycol, these compelling findings have not been recently reviewed or evaluated as a whole. Thus, we herein review and summarize the findings of studies conducted both within and beyond China that have examined the repair of spinal cord injury using polyethylene glycol. The following summarizes the results of studies using polyethylene glycol alone as well as coupled with polymers or hydrogels: (1 polyethylene glycol as an adjustable biomolecule carrier resists nerve fiber degeneration, reduces the inflammatory response, inhibits vacuole and scar formation, and protects nerve membranes in the acute stage of spinal cord injury. (2 Polyethylene glycol-coupled polymers not only promote angiogenesis but also carry drugs or bioactive molecules to the injury site. Because such polymers cross both the blood-spinal cord and blood-brain barriers, they have been widely used as drug carriers. (3 Polyethylene glycol hydrogels have been used as supporting substrates for the growth of stem cells after injury, inducing cell migration, proliferation, and differentiation. Simultaneously, polyethylene glycol hydrogels isolate or reduce local glial scar invasion, promote and guide axonal regeneration, cross the transplanted area, and re-establish synaptic connections with target tissue, thereby promoting spinal cord repair. On the basis of the reviewed studies, we conclude that polyethylene glycol is a promising synthetic material for use in the repair of spinal cord injury

  13. Polyethylene glycol as a promising synthetic material for repair of spinal cord injury

    Institute of Scientific and Technical Information of China (English)

    Xian-bin Kong; Qiu-yan Tang; Xu-yi Chen; Yue Tu; Shi-zhong Sun; Zhong-lei Sun

    2017-01-01

    Polyethylene glycol is a synthetic, biodegradable, and water-soluble polyether. Owing to its good biological and material properties, polyethylene glycol shows promise in spinal cord tissue engineering applications. Although studies have examined repairing spinal cord injury with polyethylene glycol, these compellingfindings have not been recently reviewed or evaluated as a whole. Thus, we herein review and summarize the findings of studies conducted both within and beyond China that have examined the repair of spinal cord injury using polyethylene glycol. The following summarizes the results of studies using polyethylene glycol alone as well as coupled with polymers or hydrogels: (1) polyethylene glycol as an adjustable bio-molecule carrier resists nerve fiber degeneration, reduces the inflammatory response, inhibits vacuole and scar formation, and protects nerve membranes in the acute stage of spinal cord injury. (2) Polyethylene glycol-coupled polymers not only promote angiogenesis but also carry drugs or bioactive molecules to the injury site. Because such polymers cross both the blood-spinal cord and blood-brain barriers, they have been widely used as drug carriers. (3) Polyethylene glycol hydrogels have been used as supporting sub-strates for the growth of stem cells after injury, inducing cell migration, proliferation, and differentiation. Simultaneously, polyethylene glycol hydrogels isolate or reduce local glial scar invasion, promote and guide axonal regeneration, cross the transplanted area, and re-establish synaptic connections with target tissue, thereby promoting spinal cord repair. On the basis of the reviewed studies, we conclude that polyethylene glycol is a promising synthetic material for use in the repair of spinal cord injury.

  14. Preparation of Nanocellulose Reinforced Chitosan Films, Cross-Linked by Adipic Acid.

    Science.gov (United States)

    Falamarzpour, Pouria; Behzad, Tayebeh; Zamani, Akram

    2017-02-13

    Adipic acid, an abundant and nontoxic compound, was used to dissolve and cross-link chitosan. After the preparation of chitosan films through casting technique, the in situ amidation reaction was performed at 80-100 °C as verified by Fourier transform infrared (FT-IR). The reaction was accompanied by the release of water which was employed to investigate the reaction kinetics. Accordingly, the reaction rate followed the first-order model and Arrhenius equation, and the activation energy was calculated to be 18 kJ/mol. Furthermore, the mechanical properties of the chitosan films were comprehensively studied. First, optimal curing conditions (84 °C, 93 min) were introduced through a central composite design. In order to evaluate the effects of adipic acid, the mechanical properties of physically cross-linked (uncured), chemically cross-linked (cured), and uncross-linked (prepared by acetic acid) films were compared. The use of adipic acid improved the tensile strength of uncured and chemically cross-linked films more than 60% and 113%, respectively. Finally, the effect of cellulose nanofibrils (CNFs) on the mechanical performance of cured films, in the presence of glycerol as a plasticizer, was investigated. The plasticized chitosan films reinforced by 5 wt % CNFs showed superior properties as a promising material for the development of chitosan-based biomaterials.

  15. The Colibactin Genotoxin Generates DNA Interstrand Cross-Links in Infected Cells

    Directory of Open Access Journals (Sweden)

    Nadège Bossuet-Greif

    2018-03-01

    Full Text Available Colibactins are hybrid polyketide-nonribosomal peptides produced by Escherichia coli, Klebsiella pneumoniae, and other Enterobacteriaceae harboring the pks genomic island. These genotoxic metabolites are produced by pks-encoded peptide-polyketide synthases as inactive prodrugs called precolibactins, which are then converted to colibactins by deacylation for DNA-damaging effects. Colibactins are bona fide virulence factors and are suspected of promoting colorectal carcinogenesis when produced by intestinal E. coli. Natural active colibactins have not been isolated, and how they induce DNA damage in the eukaryotic host cell is poorly characterized. Here, we show that DNA strands are cross-linked covalently when exposed to enterobacteria producing colibactins. DNA cross-linking is abrogated in a clbP mutant unable to deacetylate precolibactins or by adding the colibactin self-resistance protein ClbS, confirming the involvement of the mature forms of colibactins. A similar DNA-damaging mechanism is observed in cellulo, where interstrand cross-links are detected in the genomic DNA of cultured human cells exposed to colibactin-producing bacteria. The intoxicated cells exhibit replication stress, activation of ataxia-telangiectasia and Rad3-related kinase (ATR, and recruitment of the DNA cross-link repair Fanconi anemia protein D2 (FANCD2 protein. In contrast, inhibition of ATR or knockdown of FANCD2 reduces the survival of cells exposed to colibactin-producing bacteria. These findings demonstrate that DNA interstrand cross-linking is the critical mechanism of colibactin-induced DNA damage in infected cells.

  16. Gamma-radiation induced cross-links in ethylene-propylene rubber studied by CP-MAS NMR

    International Nuclear Information System (INIS)

    Sohma, J.; Shiotani, M.; Murakami, S.

    1983-01-01

    A new technique of 13 C-NMR, the CP-MAS method, was applied to study a chemistry of cross-links induced by #betta#-irradiation of ethylene-propylene rubber. The chemical species of cross-linking points were specified with their relative concentrations by the analysis of the CP-MAS spectra obtained before and after the irradiation. It was found that the short branches were also formed by the irradiation. A comparison was made between the cross-links detected by the CP-MAS method and those obtained by the Charlesby-Pinner analysis of the gelation caused by the #betta#-irradiation. The conventional 13 C-NMR of the cross-linked and swollen EPR provided us an information on the sol parts of the sample but little information on the cross-links in the gel parts. (author)

  17. 21 CFR 177.1211 - Cross-linked polyacrylate copolymers.

    Science.gov (United States)

    2010-04-01

    ... Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1211 Cross-linked polyacrylate... shall be determined using size exclusion chromatography or an equivalent method. When conducting the...

  18. Radiation cross-linked PVC and its applications

    International Nuclear Information System (INIS)

    Lan Junming; Chen Ruyan; Jia Chaoxing; Li Min; Li Chengxin

    1990-04-01

    The radiation cross-linking technique is adopted for improving the polyvinyl chloride (PVC) heat-resistance and reducing its thermocontractibility. For examining its properties a small insulation sheath made from modified PVC material has been tested at 260 0 5 seconds. The results obtained were satisfactory

  19. Chitosan Cross-linked Reconstituted Amniotic Collagen Membrane ...

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. Chitosan Cross-linked Reconstituted Amniotic Collagen Membrane – An Excellent Cell Substratum. The KERATINOCYTE proliferation and Differentiation into multiple layers is due to the presence of type - IV collagen in the amnion. Cultured FIBROBLASTS had good ...

  20. Optimization of Formaldehyde Cross-Linking for Protein Interaction Analysis of Non-Tagged Integrin β1

    Directory of Open Access Journals (Sweden)

    Cordula Klockenbusch

    2010-01-01

    Full Text Available Formaldehyde cross-linking of protein complexes combined with immunoprecipitation and mass spectrometry analysis is a promising technique for analysing protein-protein interactions, including those of transient nature. Here we used integrin β1 as a model to describe the application of formaldehyde cross-linking in detail, particularly focusing on the optimal parameters for cross-linking, the detection of formaldehyde cross-linked complexes, the utility of antibodies, and the identification of binding partners. Integrin β1 was found in a high molecular weight complex after formaldehyde cross-linking. Eight different anti-integrin β1 antibodies were used for pull-down experiments and no loss in precipitation efficiency after cross-linking was observed. However, two of the antibodies could not precipitate the complex, probably due to hidden epitopes. Formaldehyde cross-linked complexes, precipitated from Jurkat cells or human platelets and analyzed by mass spectrometry, were found to be composed of integrin β1, α4 and α6 or β1, α6, α2, and α5, respectively.

  1. Optimization of Formaldehyde Cross-Linking for Protein Interaction Analysis of Non-Tagged Integrin β1

    Science.gov (United States)

    Klockenbusch, Cordula; Kast, Juergen

    2010-01-01

    Formaldehyde cross-linking of protein complexes combined with immunoprecipitation and mass spectrometry analysis is a promising technique for analysing protein-protein interactions, including those of transient nature. Here we used integrin β1 as a model to describe the application of formaldehyde cross-linking in detail, particularly focusing on the optimal parameters for cross-linking, the detection of formaldehyde cross-linked complexes, the utility of antibodies, and the identification of binding partners. Integrin β1 was found in a high molecular weight complex after formaldehyde cross-linking. Eight different anti-integrin β1 antibodies were used for pull-down experiments and no loss in precipitation efficiency after cross-linking was observed. However, two of the antibodies could not precipitate the complex, probably due to hidden epitopes. Formaldehyde cross-linked complexes, precipitated from Jurkat cells or human platelets and analyzed by mass spectrometry, were found to be composed of integrin β1, α4 and α6 or β1, α6, α2, and α5, respectively. PMID:20634879

  2. Novel thermoplastic vulcanizates (TPVs based on silicone rubber and polyamide exploring peroxide cross-linking

    Directory of Open Access Journals (Sweden)

    K. Naskar

    2014-04-01

    Full Text Available Novel thermoplastic vulcanizates (TPVs based on silicone rubber (PDMS and polyamide (PA12 have been prepared by dynamic vulcanization process. The effect of dynamic vulcanization and influence of various types of peroxides as cross-linking agents were studied in detail. All the TPVs were prepared at a ratio of 50/50 wt% of silicone rubber and polyamide. Three structurally different peroxides, namely dicumyl peroxide (DCP, 3,3,5,7,7-pentamethyl 1,2,4-trioxepane (PMTO and cumyl hydroperoxide (CHP were taken for investigation. Though DCP was the best option for curing the silicone rubber, at high temperature it suffers from scorch safety. An inhibitor 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO was added with DCP to stabilize the radicals in order to increase the scorch time. Though CHP (hydroperoxide had higher half life time than DCP at higher temperature, it has no significant effect on cross-linking of silicone rubber. PMTO showed prolonged scorch safety and better cross-linking efficiency rather than the other two. TPVs of DCP and PMTO were made up to 11 minutes of mixing. Increased values of tensile strength and elongation at break of PMTO cross-linked TPV indicate the superiority of PMTO. Scanning electron micrographs correlate with mechanical properties of the TPVs. High storage modulus (E' and lower loss tangent value of the PMTO cross-linked TPV indicate the higher degree of cross-linking which is also well supported by the overall cross-link density value. Thus PMTO was found to be the superior peroxide for cross-linking of silicone rubber at high temperature.

  3. Effect of irradiation on quality, shelf life and consumer acceptance of traditional Nigerian meat and fish products

    International Nuclear Information System (INIS)

    Aworh, O.C.; Okparanta, R.N.; Oyedokun, E.O

    2002-01-01

    The effect of low dose irradiation, up to 6 kGy, on quality, shelf life and consumer acceptance of three traditional Nigerian meat and fish products was investigated. Irradiation inhibited microbial growth in 'suya' and 'kilishi' with substantial reduction in total aerobic counts, yeasts and molds and Staphylococcus aureus. Nonirradiated smoked-dried catfish (Clarias gariepinus) had a shelf life of less than one week at tropical ambient temperature (21-31 deg. C) due to insect infestation. Irradiated 'kilishi' and smoked dried catfish packed in sealed polyethylene bags (0.04 mm thick) were shelf stable for a period of 4-6 months and remained free from moldiness, infestation and were considered acceptable in sensory quality by a consumer panel of 32 assessors. There was a slight increase in TBA values of irradiated 'kilishi' stored for 4 months relative to non-irradiated controls. (author)

  4. Surface characteristics determining the cell compatibility of ionically cross-linked alginate gels

    International Nuclear Information System (INIS)

    Machida-Sano, Ikuko; Hirakawa, Makoto; Matsumoto, Hiroki; Kamada, Mitsuki; Ogawa, Sakito; Satoh, Nao; Namiki, Hideo

    2014-01-01

    In this study we investigated differences in the characteristics determining the suitability of five types of ion (Fe 3+ , Al 3+ , Ca 2+ , Ba 2+ and Sr 2+ )-cross-linked alginate films as culture substrates for cells. Human dermal fibroblasts were cultured on each alginate film to examine the cell affinity of the alginates. Since cell behavior on the surface of a material is dependent on the proteins adsorbed to it, we investigated the protein adsorption ability and surface features (wettability, morphology and charge) related to the protein adsorption abilities of alginate films. We observed that ferric, aluminum and barium ion-cross-linked alginate films supported better cell growth and adsorbed higher amounts of serum proteins than other types. Surface wettability analysis demonstrated that ferric and aluminum ion-cross-linked alginates had moderate hydrophilic surfaces, while other types showed highly hydrophilic surfaces. The roughness was exhibited only on barium ion-cross-linked alginate surface. Surface charge measurements revealed that alginate films had negatively charged surfaces, and showed little difference among the five types of gel. These results indicate that the critical factors of ionically cross-linked alginate films determining the protein adsorption ability required for their cell compatibility may be surface wettability and morphology. (paper)

  5. Physical Characterization Of High Amylose/Pectin Mixtures Cross-Linked With Sodium Trimetaphosphate

    International Nuclear Information System (INIS)

    Carbinatto, F.M.; Cury, B.S.F.; Evangelista, R.C.

    2010-01-01

    Some researches have reported that pectin and high amylose mixtures presented superior mechanical properties in relation to those of the isolated polymers. In this work, mixtures at different ratios (1:4; 1:1) of pectin and high amylose were crosslinked with sodium trimetaphosphate at different degrees by varying reaction conditions. All samples were characterized by rheological and X-ray diffraction analyses. Samples without cross-linker were prepared as control. The oscillatory dynamic tests showed that all samples exhibited predominant elastic behavior, although cross-linked samples presented higher G' values, suggesting that crosslinking by phosphorylation resulted in more strength structures. The diffractograms showed that cross-linked samples underwent structural modifications that resulted in increase of crystallinity due to cross-linking process. (author)

  6. 3-year follow-up of a long-term registry-based multicentre study on vitamin E diffused polyethylene in total hip replacement

    DEFF Research Database (Denmark)

    Sillesen, Nanna Hylleholt; Greene, Meridith E; Nebergall, Audrey K

    2016-01-01

    PURPOSE: Preclinical studies of vitamin E diffused highly cross-linked polyethylene (E-XLPE) has shown enhanced mechanical properties with less wear. The purpose of our study was to document the early clinical outcome of E-XLPE to ensure, for the safety of patients, that there are no unforeseen...... hip arthroplasty in functionality and quality of life across the centers. We have not observed any early in vivo adverse effects from diffusing the liners with vitamin E. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT00545285....... early adverse events from using this new biomaterial. METHODS: The enrolled patients (n = 977) have received either a porous titanium coated or porous plasma sprayed acetabular shell with either a E-XLPE liner or a medium cross-linked (AXL) liner. At each follow-up 5 patient-reported outcome measures...

  7. Facile synthesis of thiol-polyethylene glycol functionalized magnetic titania nanomaterials for highly efficient enrichment of N-linked glycopeptides.

    Science.gov (United States)

    Wang, Jiawen; Yao, Jizong; Sun, Nianrong; Deng, Chunhui

    2017-08-25

    As protein N-glycosylation involved in generation and development of various cancers and diseases, it is vital to capture glycopeptides from complex biological samples for biomarker discovery. In this work, by taking advantages of the interaction between titania and thiol groups, thiol-polyethylene glycol functionalized magnetic titania nanomaterials (denoted as Fe 3 O 4 @TiO 2 @PEG) were firstly fabricated as an excellent hydrophilic adsorbent of N-linked glycopeptides. On one hand, the special interaction of titanium-thiol makes the synthetic manipulation simple and provides a new idea for design and synthesis of novel nanomaterials; on the other hand, strong magnetic response could realize rapid separation and the outstanding hydrophilicity of polyethylene glycol makes Fe 3 O 4 @TiO 2 @PEG nanomaterials show superior performance for glycopeptides enrichment with ultralow limit of detection (0.1mol/μL) and high selectivity (1:100). As a result, 24 and 33 glycopeptides enriched from HRP and IgG digests were identified respectively by MALDI-TOF MS, and 300 glycopeptides corresponding to 106 glycoproteins were recognized from merely 2μL human serum, indicating a great potential of Fe 3 O 4 @TiO 2 @PEG nanomaterials for glycoproteomic research. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Discovery of undefined protein cross-linking chemistry: a comprehensive methodology utilizing 18O-labeling and mass spectrometry.

    Science.gov (United States)

    Liu, Min; Zhang, Zhongqi; Zang, Tianzhu; Spahr, Chris; Cheetham, Janet; Ren, Da; Zhou, Zhaohui Sunny

    2013-06-18

    Characterization of protein cross-linking, particularly without prior knowledge of the chemical nature and site of cross-linking, poses a significant challenge, because of their intrinsic structural complexity and the lack of a comprehensive analytical approach. Toward this end, we have developed a generally applicable workflow-XChem-Finder-that involves four stages: (1) detection of cross-linked peptides via (18)O-labeling at C-termini; (2) determination of the putative partial sequences of each cross-linked peptide pair using a fragment ion mass database search against known protein sequences coupled with a de novo sequence tag search; (3) extension to full sequences based on protease specificity, the unique combination of mass, and other constraints; and (4) deduction of cross-linking chemistry and site. The mass difference between the sum of two putative full-length peptides and the cross-linked peptide provides the formulas (elemental composition analysis) for the functional groups involved in each cross-linking. Combined with sequence restraint from MS/MS data, plausible cross-linking chemistry and site were inferred, and ultimately confirmed, by matching with all data. Applying our approach to a stressed IgG2 antibody, 10 cross-linked peptides were discovered and found to be connected via thioethers originating from disulfides at locations that had not been previously recognized. Furthermore, once the cross-link chemistry was revealed, a targeted cross-link search yielded 4 additional cross-linked peptides that all contain the C-terminus of the light chain.

  9. The exchange of inorganic carbon on the Canadian Beaufort Shelf

    Science.gov (United States)

    Mol, Jacoba; Thomas, Helmuth; Hu, Xianmin; Myers, Paul G.

    2017-04-01

    The Mackenzie Shelf in the southeastern Beaufort Sea is an area that has experienced large changes in the past several decades as warming, sea-ice loss, and increased river discharge have altered carbon cycling. Upwelling and downwelling events are common on the shelf, caused by strong, fluctuating along-shore winds and resulting cross-shelf Ekman transport. Downwelling carries inorganic carbon and other remineralization products off the shelf and into the deep basin for possible long-term storage in the world oceans. Upwelling carries water high in dissolved inorganic carbon (DIC) and nutrients from the Pacific-origin upper halocline layer (UHL) onto the shelf. Profiles of DIC and total alkalinity (TA) taken in August and September of 2014 are used to investigate the cycling of inorganic carbon on the Mackenzie Shelf. The along-shore and cross-shelf transport of inorganic carbon is quantified using velocity field output from a simulation of the Arctic and Northern Hemisphere Atlantic (ANHA4) configuration of the Nucleus of European Modelling of the Ocean (NEMO) model. A strong upwelling event prior to sampling on the Mackenzie Shelf is analyzed and the resulting influence on the carbonate system, including the saturation state of aragonite and pH levels, is investigated. TA and δ18O are used to examine water mass distributions in the study area and analyze the influence of Pacific Water, Mackenzie River freshwater, and sea-ice melt on carbon dynamics and air-sea fluxes of CO2 in the surface mixed layer. Understanding carbon transfer in this seasonally dynamic environment is key in order to quantify the importance of Arctic shelf regions to the global carbon cycle and to provide a basis for understanding how its role will respond to the aforementioned changes in the regional marine system.

  10. How ice shelf morphology controls basal melting

    Science.gov (United States)

    Little, Christopher M.; Gnanadesikan, Anand; Oppenheimer, Michael

    2009-12-01

    The response of ice shelf basal melting to climate is a function of ocean temperature, circulation, and mixing in the open ocean and the coupling of this external forcing to the sub-ice shelf circulation. Because slope strongly influences the properties of buoyancy-driven flow near the ice shelf base, ice shelf morphology plays a critical role in linking external, subsurface heat sources to the ice. In this paper, the slope-driven dynamic control of local and area-integrated melting rates is examined under a wide range of ocean temperatures and ice shelf shapes, with an emphasis on smaller, steeper ice shelves. A 3-D numerical ocean model is used to simulate the circulation underneath five idealized ice shelves, forced with subsurface ocean temperatures ranging from -2.0°C to 1.5°C. In the sub-ice shelf mixed layer, three spatially distinct dynamic regimes are present. Entrainment of heat occurs predominately under deeper sections of the ice shelf; local and area-integrated melting rates are most sensitive to changes in slope in this "initiation" region. Some entrained heat is advected upslope and used to melt ice in the "maintenance" region; however, flow convergence in the "outflow" region limits heat loss in flatter portions of the ice shelf. Heat flux to the ice exhibits (1) a spatially nonuniform, superlinear dependence on slope and (2) a shape- and temperature-dependent, internally controlled efficiency. Because the efficiency of heat flux through the mixed layer decreases with increasing ocean temperature, numerical simulations diverge from a simple quadratic scaling law.

  11. Use of cross-linked carboxymethyl cellulose for soft-tissue augmentation: preliminary clinical studies

    Directory of Open Access Journals (Sweden)

    Mauro Leonardis

    2010-11-01

    Full Text Available Mauro Leonardis1, Andrea Palange2, Rodrigo FV Dornelles3, Felipe Hund41Department of Plastic Surgery, Salvator Mundi International Hospital, Roma, Italy; 2Department of Aesthetic Medicine, Fisiobios, Roma, Italy; 3Department of Plastic Surgery, Núcleo de Plástica Avançada, São Paulo, SP, Brazil; 4Department of Plastic Surgery, Consultorio de Cirurgia Plastica, Criciuma, SC, BrazilPurpose: The continual search for new products for soft-tissue augmentation has in recent years led to the introduction of long lasting alternatives to hyaluronic acids and collagen that are composed of other polymers able to improve clinical persistence over time. This is the first report in which sodium carboxymethyl cellulose (CMC has been chemically treated by the cross-linking process and thus used as a hydrogel for soft-tissue augmentation through injection with thin needles. The study evaluates, from a clinical point of view, the behavior of cross-linked carboxymethyl cellulose hydrogel used in the aesthetic field and its side effects so as to check the safety and performance of the polymer following intradermal injections.Patients and methods: This work shows the preliminary results of an ongoing clinical study conducted between 2006 and 2009, performed on 84 healthy volunteers (62 females, 22 males aged between 18 and 72 years, for the treatment of 168 nasolabial folds, 45 perioral wrinkles, and 39 lip volume.Results: Study results show an excellent correction of facial defects. Tolerance and aesthetic quality of the correction obtained indicate considerable safety features and absence of side effects. From a clinical point of view, hydrogel is gradually absorbed into the injection site without migration issues.Conclusion: Cross-linked CMC hydrogel proves to be an ideal agent for soft tissue augmentation with regard to safety and ease of application. It did not cause infection, extrusion, migration, or adverse reactions in the patients who have been

  12. Concentration-dependent oligomerization of cross-linked complexes between ferredoxin and ferredoxin–NADP+ reductase

    International Nuclear Information System (INIS)

    Kimata-Ariga, Yoko; Kubota-Kawai, Hisako; Lee, Young-Ho; Muraki, Norifumi; Ikegami, Takahisa; Kurisu, Genji; Hase, Toshiharu

    2013-01-01

    Highlights: •Cross-linked complexes of ferredoxin (Fd) and Fd–NADP + reductase form oligomers. •In the crystal structures, Fd- and FNR moieties swap across the molecules. •The complexes exhibit concentration-dependent oligomerization at sub-milimolar order. -- Abstract: Ferredoxin–NADP + reductase (FNR) forms a 1:1 complex with ferredoxin (Fd), and catalyzes the electron transfer between Fd and NADP + . In our previous study, we prepared a series of site-specifically cross-linked complexes of Fd and FNR, which showed diverse electron transfer properties. Here, we show that X-ray crystal structures of the two different Fd–FNR cross-linked complexes form oligomers by swapping Fd and FNR moieties across the molecules; one complex is a dimer from, and the other is a successive multimeric form. In order to verify whether these oligomeric structures are formed only in crystal, we investigated the possibility of the oligomerization of these complexes in solution. The mean values of the particle size of these cross-linked complexes were shown to increase with the rise of protein concentration at sub-milimolar order, whereas the size of dissociable wild-type Fd:FNR complex was unchanged as analyzed by dynamic light scattering measurement. The oligomerization products were detected by SDS–PAGE after chemical cross-linking of these complexes at the sub-milimolar concentrations. The extent and concentration-dependent profile of the oligomerizaion were differentiated between the two cross-linked complexes. These results show that these Fd–FNR cross-linked complexes exhibit concentration-dependent oligomerization, possibly through swapping of Fd and FNR moieties also in solution. These findings lead to the possibility that some native multi-domain proteins may present similar phenomenon in vivo

  13. Seasonal circulation over the Catalan inner-shelf (northwest Mediterranean Sea)

    Science.gov (United States)

    Grifoll, Manel; Aretxabaleta, Alfredo L.; Pelegrí, Josep L.; Espino, Manuel; Warner, John C.; Sánchez-Arcilla, Agustín

    2013-01-01

    This study characterizes the seasonal cycle of the Catalan inner-shelf circulation using observations and complementary numerical results. The relation between seasonal circulation and forcing mechanisms is explored through the depth-averaged momentum balance, for the period between May 2010 and April 2011, when velocity observations were partially available. The monthly-mean along-shelf flow is mainly controlled by the along-shelf pressure gradient and by surface and bottom stresses. During summer, fall, and winter, the along-shelf momentum balance is dominated by the barotropic pressure gradient and local winds. During spring, both wind stress and pressure gradient act in the same direction and are compensated by bottom stress. In the cross-shelf direction the dominant forces are in geostrophic balance, consistent with dynamic altimetry data.

  14. Nutrient Dynamics in the Northern South China Sea Shelf-sea (NoSoCS)

    Science.gov (United States)

    Wong, G. T.; Guo, X.

    2011-12-01

    The Northern South China Sea Shelf-sea (NoSoCS) is situated in the sub-tropics along the southern Chinese coast between the southern end of the Taiwan Strait and the Hainan Island. Samples were collected in four cross-shelf transects in summer, 2010 and two cross-shelf transects in winter, 2011 in this Shelf-sea. The shelf may be sub-divided into the inner shelf (1 μM in NO3- and >0.1 μM in soluble reactive phosphate) stretched across the shelf at least to the middle shelf. Thus, vertical mixing, even to relatively shallow depths, on the shelf may supply nutrients to and play a critical role in determining the primary production in the mixed layer. At least three such processes were observed. Through the year, internal waves of various strengths generated at the Luzon Strait propagated westward along the bottom of the mixed layer and dissipated along the middle and outer shelf. The effects of these waves were especially conspicuous north of the Dongsha Atoll and their action enhances vertical mixing. In the summer, upwelling occurred in the inner/middle shelf off Dongshan in response to the along shore southwest monsoon and the topographic forcing by the ridge extending offshore from Dongshan to the Taiwan Bank. In the winter, surface cooling and the strong northeast monsoon led to complete overturn in the shelf. The maximum density, reaching 24.6, in the surface waters was found offshore in the inner and middle shelf. This density was equivalent to the density of the water at >100 m offshore. As a result, this dense water also appeared as a layer of bottom water that extended across the shelf to the shelf edge.

  15. Preparation of Nanocellulose Reinforced Chitosan Films, Cross-Linked by Adipic Acid

    Directory of Open Access Journals (Sweden)

    Pouria Falamarzpour

    2017-02-01

    Full Text Available Adipic acid, an abundant and nontoxic compound, was used to dissolve and cross-link chitosan. After the preparation of chitosan films through casting technique, the in situ amidation reaction was performed at 80–100 °C as verified by Fourier transform infrared (FT-IR. The reaction was accompanied by the release of water which was employed to investigate the reaction kinetics. Accordingly, the reaction rate followed the first-order model and Arrhenius equation, and the activation energy was calculated to be 18 kJ/mol. Furthermore, the mechanical properties of the chitosan films were comprehensively studied. First, optimal curing conditions (84 °C, 93 min were introduced through a central composite design. In order to evaluate the effects of adipic acid, the mechanical properties of physically cross-linked (uncured, chemically cross-linked (cured, and uncross-linked (prepared by acetic acid films were compared. The use of adipic acid improved the tensile strength of uncured and chemically cross-linked films more than 60% and 113%, respectively. Finally, the effect of cellulose nanofibrils (CNFs on the mechanical performance of cured films, in the presence of glycerol as a plasticizer, was investigated. The plasticized chitosan films reinforced by 5 wt % CNFs showed superior properties as a promising material for the development of chitosan-based biomaterials.

  16. Phytoplankton Distribution in Relation to Environmental Drivers on the North West European Shelf Sea.

    Science.gov (United States)

    Siemering, Beatrix; Bresnan, Eileen; Painter, Stuart C; Daniels, Chris J; Inall, Mark; Davidson, Keith

    2016-01-01

    The edge of the North West European Shelf (NWES) is characterised by a steep continental slope and a northward flowing slope current. These topographic/hydrographic features separate oceanic water and shelf water masses hence potentially separate phytoplankton communities. The slope current may facilitate the advective transport of phytoplankton, with mixing at the shelf edge supporting nutrient supply and therefore phytoplankton production. On the west Scottish shelf in particular, little is known about the phytoplankton communities in and around the shelf break and adjacent waters. Hence, to improve our understanding of environmental drivers of phytoplankton communities, biological and environmental data were collected on seven cross-shelf transects across the Malin and Hebridean Shelves during autumn 2014. Density profiles indicated that shelf break and oceanic stations had a 100 m deep mixed surface layer while stations on the shelf were generally well mixed. Analysis of similarity and multidimensional scaling of phytoplankton counts revealed that phytoplankton communities on the shelf were significantly different to those found at the shelf break and at oceanic stations. Shelf stations were dominated by dinoflagellates, with diatoms contributing a maximum of 37% of cells. Shelf break and oceanic stations were also dinoflagellate dominated but displayed a lower species diversity. Significant difference between shelf and shelf break stations suggested that the continental slope limited cross shelf phytoplankton exchange. Northern and southern phytoplankton communities on the shelf were approximately 15% dissimilar while there was no latitudinal gradient for stations along the slope current, suggesting this current provided south to north connectivity. Fitting environmental data to phytoplankton ordination showed a significant relationship between phytoplankton community dissimilarities and nutrient concentrations and light availability on the shelf compared to

  17. CLMSVault: A Software Suite for Protein Cross-Linking Mass-Spectrometry Data Analysis and Visualization.

    Science.gov (United States)

    Courcelles, Mathieu; Coulombe-Huntington, Jasmin; Cossette, Émilie; Gingras, Anne-Claude; Thibault, Pierre; Tyers, Mike

    2017-07-07

    Protein cross-linking mass spectrometry (CL-MS) enables the sensitive detection of protein interactions and the inference of protein complex topology. The detection of chemical cross-links between protein residues can identify intra- and interprotein contact sites or provide physical constraints for molecular modeling of protein structure. Recent innovations in cross-linker design, sample preparation, mass spectrometry, and software tools have significantly improved CL-MS approaches. Although a number of algorithms now exist for the identification of cross-linked peptides from mass spectral data, a dearth of user-friendly analysis tools represent a practical bottleneck to the broad adoption of the approach. To facilitate the analysis of CL-MS data, we developed CLMSVault, a software suite designed to leverage existing CL-MS algorithms and provide intuitive and flexible tools for cross-platform data interpretation. CLMSVault stores and combines complementary information obtained from different cross-linkers and search algorithms. CLMSVault provides filtering, comparison, and visualization tools to support CL-MS analyses and includes a workflow for label-free quantification of cross-linked peptides. An embedded 3D viewer enables the visualization of quantitative data and the mapping of cross-linked sites onto PDB structural models. We demonstrate the application of CLMSVault for the analysis of a noncovalent Cdc34-ubiquitin protein complex cross-linked under different conditions. CLMSVault is open-source software (available at https://gitlab.com/courcelm/clmsvault.git ), and a live demo is available at http://democlmsvault.tyerslab.com/ .

  18. Sequential optimization of methotrexate encapsulation in micellar nano-networks of polyethyleneimine ionomer containing redox-sensitive cross-links

    Directory of Open Access Journals (Sweden)

    Abolmaali SS

    2014-06-01

    Full Text Available Samira Sadat Abolmaali,1 Ali Tamaddon,1,2 Gholamhossein Yousefi,1,2 Katayoun Javidnia,3 Rasoul Dinarvand41Department of Pharmaceutics, Shiraz School of Pharmacy, 2Center for Nanotechnology in Drug Delivery, 3Medicinal and Natural Products Chemistry Research Center, Shiraz University of Medical Sciences, Shiraz, Iran; 4Nanotechnology Research Centre, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, IranAbstract: A functional polycation nanonetwork was developed for delivery of water soluble chemotherapeutic agents. The complexes of polyethyleneimine grafted methoxy polyethylene glycol (PEI-g-mPEG and Zn2+ were utilized as the micellar template for cross-linking with dithiodipropionic acid, followed by an acidic pH dialysis to remove the metal ion from the micellar template. The synthesis method was optimized according to pH, the molar ratio of Zn2+, and the cross-link ratio. The atomic force microscopy showed soft, discrete, and uniform nano-networks. They were sensitive to the simulated reductive environment as determined by Ellman's assay. They showed few positive ζ potential and an average hydrodynamic diameter of 162±10 nm, which decreased to 49±11 nm upon dehydration. The ionic character of the nano-networks allowed the achievement of a higher-loading capacity of methotrexate (MTX, approximately 57% weight per weight, depending on the cross-link and the drug feed ratios. The nano-networks actively loaded with MTX presented some suitable properties, such as the hydrodynamic size of 117±16 nm, polydispersity index of 0.22, and a prolonged swelling-controlled release profile over 24 hours that boosted following reductive activation of the nanonetwork biodegradation. Unlike the PEI ionomer, the nano-networks provided an acceptable cytotoxicity profile. The drug-loaded nano-networks exhibited more specific cytotoxicity against human hepatocellular carcinoma cells if compared to free MTX at concentrations above 1 µM. The

  19. Once again on Interregional, International and Cross-age Comparison of Unemployment

    OpenAIRE

    Gennadi Kazakevitch

    2003-01-01

    Any discussion on unemployment is never restricted with the data on unemployment only. Unemployment is linked to several key indicators such as number of employed, active population and participation rate. As we often see, increase in unemployment occurs simultaneously with increase in the number of jobs, if participation rate increases at the same time. This makes doubtful any simplistic interregional, international, inter-temporal or cross-age comparison of unemployment data taken in isolat...

  20. A general method for targeted quantitative cross-linking mass spectrometry

    Science.gov (United States)

    Chemical cross-linking mass spectrometry (XL-MS) provides protein structural information by identifying covalently linked proximal amino acid residues on protein surfaces. The information gained by this technique is complementary to other structural biology methods such as x-ray crystallography, NM...

  1. CrossLink: a novel method for cross-condition classification of cancer subtypes.

    Science.gov (United States)

    Ma, Chifeng; Sastry, Konduru S; Flore, Mario; Gehani, Salah; Al-Bozom, Issam; Feng, Yusheng; Serpedin, Erchin; Chouchane, Lotfi; Chen, Yidong; Huang, Yufei

    2016-08-22

    We considered the prediction of cancer classes (e.g. subtypes) using patient gene expression profiles that contain both systematic and condition-specific biases when compared with the training reference dataset. The conventional normalization-based approaches cannot guarantee that the gene signatures in the reference and prediction datasets always have the same distribution for all different conditions as the class-specific gene signatures change with the condition. Therefore, the trained classifier would work well under one condition but not under another. To address the problem of current normalization approaches, we propose a novel algorithm called CrossLink (CL). CL recognizes that there is no universal, condition-independent normalization mapping of signatures. In contrast, it exploits the fact that the signature is unique to its associated class under any condition and thus employs an unsupervised clustering algorithm to discover this unique signature. We assessed the performance of CL for cross-condition predictions of PAM50 subtypes of breast cancer by using a simulated dataset modeled after TCGA BRCA tumor samples with a cross-validation scheme, and datasets with known and unknown PAM50 classification. CL achieved prediction accuracy >73 %, highest among other methods we evaluated. We also applied the algorithm to a set of breast cancer tumors derived from Arabic population to assign a PAM50 classification to each tumor based on their gene expression profiles. A novel algorithm CrossLink for cross-condition prediction of cancer classes was proposed. In all test datasets, CL showed robust and consistent improvement in prediction performance over other state-of-the-art normalization and classification algorithms.

  2. Covalent-ionically cross-linked polyetheretherketone proton exchange membrane for direct methanol fuel cell

    CSIR Research Space (South Africa)

    Luo, H

    2010-08-01

    Full Text Available cross-linked PEEK-WC membrane, this covalent-ionically cross-linked PEEK-WC membrane exhibits extremely reduced water uptake and methanol permeability, but just slightly sacrificed proton conductivity. The proton conductivity of the covalent...

  3. Front-Eddy Influence on Water Column Properties, Phytoplankton Community Structure, and Cross-Shelf Exchange of Diatom Taxa in the Shelf-Slope Area off Concepción (˜36-37°S)

    Science.gov (United States)

    Morales, Carmen E.; Anabalón, Valeria; Bento, Joaquim P.; Hormazabal, Samuel; Cornejo, Marcela; Correa-Ramírez, Marco A.; Silva, Nelson

    2017-11-01

    In eastern boundary current systems (EBCSs), submesoscale to mesocale variability contributes to cross-shore exchanges of water properties, nutrients, and plankton. Data from a short-term summer survey and satellite time series (January-February 2014) were used to characterize submesoscale variability in oceanographic conditions and phytoplankton distribution across the coastal upwelling and coastal transition zones north of Punta Lavapié, and to explore cross-shelf exchanges of diatom taxa. A thermohaline front (FRN-1) flanked by a mesoscale anticyclonic intrathermocline eddy (ITE-1), or mode-water eddy, persisted during the time series and the survey was undertaken during a wind relaxation event. At the survey time, ITE-1 contributed to an onshore intrusion of warm oceanic waters (southern section) and an offshore advection of cold coastal waters (northern section), with the latter forming a cold, high chlorophyll-a filament. In situ phytoplankton and diatom biomasses were highest at the surface in FRN-1 and at the subsurface in ITE-1, whereas values in the coastal zone were lower and dominated by smaller cells. Diatom species typical of the coastal zone and species dominant in oceanic waters were both found in the FRN-1 and ITE-1 interaction area, suggesting that this mixture was the result of both offshore and onshore advection. Overall, front-eddy interactions in EBCSs could enhance cross-shelf exchanges of coastal and oceanic plankton, as well as sustain phytoplankton growth in the slope area through localized upward injections of nutrients in the frontal zone, combined with ITE-induced advection and vertical nutrient inputs to the surface layer.

  4. Laccase-Based CLEAs: Chitosan as a Novel Cross-Linking Agent

    Directory of Open Access Journals (Sweden)

    Alexandre Arsenault

    2011-01-01

    Full Text Available Laccase from Coriolopsis Polyzona was insolubilized as cross-linked enzyme aggregates (CLEAs for the first time with chitosan as the cross-linking agent. Concentrations between 0.01 and 1.867 g/L of chitosan were used and between 0.05 and 600 mM of 1-ethyl-3-(3-dimethylaminopropylcarbodiimide hydrochloride. The laccase was precipitated using ammonium sulphate and cross-linked simultaneously. Specific activity and thermal stability of these biocatalysts were measured. Activities of up to 737 U/g were obtained when 2,2-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid (ABTS was used as a substrate. Moreover, the stability of these biocatalysts was improved with regards to thermal degradation compared to free laccase when exposed to denaturing conditions of high temperature and low pH. The CLEAs stability against chemical denaturants was also tested but no significant improvement was detected. The total amount of ABTS to be oxidized during thermal degradation by CLEAs and free laccase was calculated and the insolubilized enzymes were reported to oxidize more substrate than free laccase. The formation conditions were analyzed by response surface methodology in order to determine an optimal environment for the production of efficient laccase-based CLEAs using chitosan as the cross-linking agent. After 24 hours of formation at pH 3 and at 4°C without agitation, the CLEAs exhibit the best specific activity.

  5. Dually cross-linked single network poly(acrylic acid) hydrogels with superior mechanical properties and water absorbency.

    Science.gov (United States)

    Zhong, Ming; Liu, Yi-Tao; Liu, Xiao-Ying; Shi, Fu-Kuan; Zhang, Li-Qin; Zhu, Mei-Fang; Xie, Xu-Ming

    2016-06-28

    Poly(acrylic acid) (PAA) hydrogels with superior mechanical properties, based on a single network structure with dual cross-linking, are prepared by one-pot free radical polymerization. The network structure of the PAA hydrogels is composed of dual cross-linking: a dynamic and reversible ionic cross-linking among the PAA chains enabled by Fe(3+) ions, and a sparse covalent cross-linking enabled by a covalent cross-linker (Bis). Under deformation, the covalently cross-linked PAA chains remain intact to maintain their original configuration, while the Fe(3+)-enabled ionic cross-linking among the PAA chains is broken to dissipate energy and then recombined. It is found that the mechanical properties of the PAA hydrogels are significantly influenced by the contents of covalent cross-linkers, Fe(3+) ions and water, which can be adjusted within a substantial range and thus broaden the applications of the hydrogels. Meanwhile, the PAA hydrogels have excellent recoverability based on the dynamic and reversible ionic cross-linking enabled by Fe(3+) ions. Moreover, the swelling capacity of the PAA hydrogels is as high as 1800 times in deionized water due to the synergistic effects of ionic and covalent cross-linkings. The combination of balanced mechanical properties, efficient recoverability, high swelling capacity and facile preparation provides a new method to obtain high-performance hydrogels.

  6. Multiple repair pathways mediate tolerance to chemotherapeutic cross-linking agents in vertebrate cells.

    Science.gov (United States)

    Nojima, Kuniharu; Hochegger, Helfrid; Saberi, Alihossein; Fukushima, Toru; Kikuchi, Koji; Yoshimura, Michio; Orelli, Brian J; Bishop, Douglas K; Hirano, Seiki; Ohzeki, Mioko; Ishiai, Masamichi; Yamamoto, Kazuhiko; Takata, Minoru; Arakawa, Hiroshi; Buerstedde, Jean-Marie; Yamazoe, Mitsuyoshi; Kawamoto, Takuo; Araki, Kasumi; Takahashi, Jun A; Hashimoto, Nobuo; Takeda, Shunichi; Sonoda, Eiichiro

    2005-12-15

    Cross-linking agents that induce DNA interstrand cross-links (ICL) are widely used in anticancer chemotherapy. Yeast genetic studies show that nucleotide excision repair (NER), Rad6/Rad18-dependent postreplication repair, homologous recombination, and cell cycle checkpoint pathway are involved in ICL repair. To study the contribution of DNA damage response pathways in tolerance to cross-linking agents in vertebrates, we made a panel of gene-disrupted clones from chicken DT40 cells, each defective in a particular DNA repair or checkpoint pathway, and measured the sensitivities to cross-linking agents, including cis-diamminedichloroplatinum (II) (cisplatin), mitomycin C, and melphalan. We found that cells harboring defects in translesion DNA synthesis (TLS), Fanconi anemia complementation groups (FANC), or homologous recombination displayed marked hypersensitivity to all the cross-linking agents, whereas NER seemed to play only a minor role. This effect of replication-dependent repair pathways is distinctively different from the situation in yeast, where NER seems to play a major role in dealing with ICL. Cells deficient in Rev3, the catalytic subunit of TLS polymerase Polzeta, showed the highest sensitivity to cisplatin followed by fanc-c. Furthermore, epistasis analysis revealed that these two mutants work in the same pathway. Our genetic comprehensive study reveals a critical role for DNA repair pathways that release DNA replication block at ICLs in cellular tolerance to cross-linking agents and could be directly exploited in designing an effective chemotherapy.

  7. Impact of styrenic polymer one-step hyper-cross-linking on volatile organic compound adsorption and desorption performance.

    Science.gov (United States)

    Ghafari, Mohsen; Atkinson, John D

    2018-06-05

    A novel one-step hyper-cross-linking method, using 1,2-dichloroethane (DCE) and 1,6-dichlorohexane (DCH) cross-linkers, expands the micropore volume of commercial styrenic polymers. Performance of virgin and modified polymers was evaluated by measuring hexane, toluene, and methyl-ethyl-ketone (MEK) adsorption capacity, adsorption/desorption kinetics, and desorption efficiency. Hyper-cross-linked polymers have up to 128% higher adsorption capacity than virgin polymers at P/P 0  = 0.05 due to micropore volume increases up to 330%. Improvements are most pronounced with the DCE cross-linker. Hyper-cross-linking has minimal impact on hexane adsorption kinetics, but adsorption rates for toluene and MEK decrease by 6-41%. Desorption rates decreased (3-36%) for all materials after hyper-cross-linking, with larger decreases for DCE hyper-cross-linked polymers due to smaller average pore widths. For room temperature desorption, 20-220% more adsorbate remains in hyper-cross-linked polymers after regeneration compared to virgin materials. DCE hyper-cross-linked polymers have 13-92% more residual adsorbate than DCH counterparts. Higher temperatures were required for DCE hyper-cross-linked polymers to completely desorb VOCs compared to the DCH hyper-cross-linked and virgin counterparts. Results show that the one-step hyper-cross-linking method for modifying styrenic polymers improves adsorption capacity because of added micropores, but decreases adsorption/desorption kinetics and desorption efficiency for large VOCs due to a decrease in average pore width. Copyright © 2018 Elsevier B.V. All rights reserved.

  8. Role of solvent-mediated carbodiimide cross-linking in fabrication of electrospun gelatin nanofibrous membranes as ophthalmic biomaterials

    International Nuclear Information System (INIS)

    Chou, Shih-Feng; Luo, Li-Jyuan; Lai, Jui-Yang; Ma, David Hui-Kang

    2017-01-01

    Due to their ability to mimic the structure of extracellular matrix, electrospun gelatin nanofibers are promising cell scaffolding materials for tissue engineering applications. However, the hydrophilic gelatin molecules usually need stabilization before use in aqueous physiological environment. Considering that biomaterials cross-linked via film immersion technique may have a more homogeneous cross-linked structure than vapor phase cross-linking, this work aims to investigate the chemical modification of electrospun gelatin nanofibrous membranes by liquid phase carbodiimide in the presence of ethanol/water co-solvents with varying ethanol concentrations ranging from 80 to 99.5 vol%. The results of characterization showed that increasing water content in the binary reaction solvent system increases the extent of cross-linking of gelatin nanofibers, but simultaneously promotes the effect of biopolymer swelling and distortion in fiber mat structure. As compared to non-cross-linked counterparts, carbodiimide treated gelatin nanofibrous mats exhibited better thermal and biological stability where the shrinkage temperature and resistance to enzymatic degradation varied in response to ethanol/water solvent composition-mediated generation of cross-links. Irrespective of their cross-linking density, all studied membrane samples did not induce any responses in ocular epithelial cell cultures derived from cornea, lens, and retina. Unlike many other cross-linking agents and/or methods (e.g., excessive vapor phase cross-linking) that may pose a risk of toxicity, our study demonstrated that these nanofibrous materials are well tolerated by anterior segment tissues. These findings also indicate the safety of using ethanol/water co-solvents for chemical cross-linking of gelatin to engineer nanofibrous materials with negligible biological effects. In summary, the present results suggest the importance of solvent-mediated carbodiimide cross-linking in modulating structure

  9. Role of solvent-mediated carbodiimide cross-linking in fabrication of electrospun gelatin nanofibrous membranes as ophthalmic biomaterials

    Energy Technology Data Exchange (ETDEWEB)

    Chou, Shih-Feng [Department of Mechanical Engineering, University of Texas at Tyler, Tyler, TX 75799 (United States); Luo, Li-Jyuan [Department of Chemical and Materials Engineering, Chang Gung University, Taoyuan 33302, Taiwan, ROC (China); Lai, Jui-Yang, E-mail: jylai@mail.cgu.edu.tw [Institute of Biochemical and Biomedical Engineering, Chang Gung University, Taoyuan 33302, Taiwan, ROC (China); Biomedical Engineering Research Center, Chang Gung University, Taoyuan 33302, Taiwan, ROC (China); Center for Tissue Engineering, Chang Gung Memorial Hospital, Taoyuan 33305, Taiwan, ROC (China); Department of Ophthalmology, Chang Gung Memorial Hospital, Taoyuan 33305, Taiwan, ROC (China); Department of Materials Engineering, Ming Chi University of Technology, New Taipei City 24301, Taiwan, ROC (China); Ma, David Hui-Kang [Center for Tissue Engineering, Chang Gung Memorial Hospital, Taoyuan 33305, Taiwan, ROC (China); Department of Ophthalmology, Chang Gung Memorial Hospital, Taoyuan 33305, Taiwan, ROC (China); Department of Chinese Medicine, Chang Gung University, Taoyuan 33302, Taiwan, ROC (China)

    2017-02-01

    Due to their ability to mimic the structure of extracellular matrix, electrospun gelatin nanofibers are promising cell scaffolding materials for tissue engineering applications. However, the hydrophilic gelatin molecules usually need stabilization before use in aqueous physiological environment. Considering that biomaterials cross-linked via film immersion technique may have a more homogeneous cross-linked structure than vapor phase cross-linking, this work aims to investigate the chemical modification of electrospun gelatin nanofibrous membranes by liquid phase carbodiimide in the presence of ethanol/water co-solvents with varying ethanol concentrations ranging from 80 to 99.5 vol%. The results of characterization showed that increasing water content in the binary reaction solvent system increases the extent of cross-linking of gelatin nanofibers, but simultaneously promotes the effect of biopolymer swelling and distortion in fiber mat structure. As compared to non-cross-linked counterparts, carbodiimide treated gelatin nanofibrous mats exhibited better thermal and biological stability where the shrinkage temperature and resistance to enzymatic degradation varied in response to ethanol/water solvent composition-mediated generation of cross-links. Irrespective of their cross-linking density, all studied membrane samples did not induce any responses in ocular epithelial cell cultures derived from cornea, lens, and retina. Unlike many other cross-linking agents and/or methods (e.g., excessive vapor phase cross-linking) that may pose a risk of toxicity, our study demonstrated that these nanofibrous materials are well tolerated by anterior segment tissues. These findings also indicate the safety of using ethanol/water co-solvents for chemical cross-linking of gelatin to engineer nanofibrous materials with negligible biological effects. In summary, the present results suggest the importance of solvent-mediated carbodiimide cross-linking in modulating structure

  10. The mechanism of collagen cross-linking in diabetes: a puzzle nearing resolution.

    Science.gov (United States)

    Monnier, V M; Glomb, M; Elgawish, A; Sell, D R

    1996-07-01

    Considerable interest has been focused in recent years on the mechanism of collagen cross-linking by high glucose in vitro and in vivo. Experiments in both diabetic humans and in animals have shown that over time collagen becomes less soluble, less digestible by collagenase, more stable to heat-induced denaturation, and more glycated. In addition, collagen becomes more modified by advanced products of the Maillard reaction, i.e., immunoreactive advanced glycation end products and the glycoxidation markers carboxymethyllysine and pentosidine. Mechanistic studies have shown that collagen cross-linking in vitro can be uncoupled from glycation by the use of antioxidants and chelating agents. Experiments in the authors' laboratory revealed that approximately 50% of carboxymethyllysine formed in vitro originates from pathways other than oxidation of Amadori products, i.e., most likely the oxidation of Schiff base-linked glucose. In addition, the increase in thermal stability of rat tail tendons exposed to high glucose in vitro or in vivo was found to strongly depend on H2O2 formation. The final missing piece of the puzzle is that of the structure of the major cross-link. We speculate that it is a nonfluorescent nonultraviolet active cross-link between two lysine residues, which includes a fragmentation product of glucose linked in a nonreducible bond labile to both strong acids and bases.

  11. Food losses, shelf life extension and environmental impact of a packaged cheesecake: A life cycle assessment.

    Science.gov (United States)

    Gutierrez, Michele Mario; Meleddu, Marta; Piga, Antonio

    2017-01-01

    Packaging is associated with a high environmental impact. This is also the case in the food industry despite packaging being necessary for maintaining food quality, safety assurance and preventing food waste. The aim of the present study was to identify improvements in food packaging solutions able to minimize environmental externalities while maximizing the economic sustainability. To this end, the life cycle assessment (LCA) methodology was applied to evaluate the environmental performance of new packaging solutions. The environmental impact of packaging and food losses and the balance between the two were examined in relation to a cheesecake that is normally packaged in low density polyethylene film and has a limited shelf life due to microbial growth. A shelf life extension was sought via application of the well-established modified atmosphere packaging (MAP) technique. Samples for MAP (N 2 /CO 2 : 70/30) were placed inside multilayer gas barrier trays, which were then wrapped with a multilayer gas and water barrier film (i.e. AerPack packaging); control batches were packaged in gas barrier recycled polyethylene terephthalate (XrPet) trays and wrapped with a XrPet film. Samples were then stored at 20°C and inspected at regular intervals for chemical-physical, microbiological and sensory parameters. Results show that the new packaging solution could considerably extend the shelf life of cheesecakes, thereby reducing food waste and decreasing the overall environmental impact. Moreover, the new packaging allows one to minimize transport costs and to generate economies of scale in manufacturing. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. CD24 cross-linking induces apoptosis in, and inhibits migration of, MCF-7 breast cancer cells

    International Nuclear Information System (INIS)

    Kim, Jong Bin; Bae, Ji-Yeon; Jee, Hyeon-Gun; Noh, Dong-Young; Ko, Eunyoung; Han, Wonshik; Lee, Jeong Eon; Lee, Kyung-Min; Shin, Incheol; Kim, Sangmin; Lee, Jong Won; Cho, Jihyoung

    2008-01-01

    The biological effects of CD24 (FL-80) cross-linking on breast cancer cells have not yet been established. We examined the impact of CD24 cross-linking on human breast cancer cell line MCF-7. MCF-7 and MDA-MB-231 cells were treated with anti-rabbit polyclonal IgG or anti-human CD24 rabbit polyclonal antibodies to induce cross-linking, and then growth was studied. Changes in cell characteristics such as cell cycle modulation, cell death, survival in three-dimensional cultures, adhesion, and migration ability were assayed after CD24 cross-linking in MCF-7. Expression of CD24 was analyzed by flow cytometry in MDA-MB-231 and MCF-7 cells where 2% and 66% expression frequencies were observed, respectively. CD24 cross-linking resulted in time-dependent proliferation reduction in MCF-7 cells, but no reduction in MDA-MB-231 cells. MCF-7 cell survival was reduced by 15% in three-dimensional culture after CD24 cross-linking. Increased MCF-7 cell apoptosis was observed after CD24 cross-linking, but no cell cycle arrest was observed in that condition. The migration capacity of MCF-7 cells was diminished by 30% after CD24 cross-linking. Our results showed that CD24 cross-linking induced apoptosis and inhibited migration in MCF-7 breast cancer cells. We conclude that CD24 may be considered as a novel therapeutic target for breast cancer

  13. Cross-linking in collagen by nonenzymatic glycation increases the matrix stiffness in rabbit achilles tendon.

    Science.gov (United States)

    Reddy, G Kesava

    2004-01-01

    Nonenzymatic glycation of connective tissue matrix proteins is a major contributor to the pathology of diabetes and aging. Previously the author and colleagues have shown that nonenzymatic glycation significantly enhances the matrix stability in the Achilles tendon (Reddy et al., 2002, Arch. Biochem. Biophys., 399, 174-180). The present study was designed to gain further insight into glycation-induced collagen cross-linking and its relationship to matrix stiffness in the rabbit Achilles tendon. The glycation process was initiated by incubating the Achilles tendons (n = 6) in phosphate-buffered saline containing ribose, whereas control tendons (n = 6) were incubated in phosphate-buffered saline without ribose. Eight weeks following glycation, the biomechanical attributes as well as the degree of collagen cross-linking were determined to examine the potential associations between matrix stiffness and molecular properties of collagen. Compared to nonglycated tendons, the glycated tendons showed increased maximum load, stress, strain, Young's modulus of elasticity, and toughness indicating that glycation increases the matrix stiffness in the tendons. Glycation of tendons resulted in a considerable decrease in soluble collagen content and a significant increase in insoluble collagen and pentosidine. Analysis of potential associations between the matrix stiffness and degree of collagen cross-linking showed that both insoluble collagen and pentosidine exhibited a significant positive correlation with the maximum load, stress, and strain, Young's modulus of elasticity, and toughness (r values ranging from.61 to.94) in the Achilles tendons. However, the soluble collagen content present in neutral salt buffer, acetate buffer, and acetate buffer containing pepsin showed an inverse relation with the various biomechanical attributes tested (r values ranging from.22 to.84) in the Achilles tendons. The results of the study demonstrate that glycation-induced collagen cross-linking

  14. A structural and kinetic study on myofibrils prevented from shortening by chemical cross-linking.

    Science.gov (United States)

    Herrmann, C; Sleep, J; Chaussepied, P; Travers, F; Barman, T

    1993-07-20

    In previous work, we studied the early steps of the Mg(2+)-ATPase activity of Ca(2+)-activated myofibrils [Houadjeto, M., Travers, F., & Barman, T. (1992) Biochemistry 31, 1564-1569]. The myofibrils were free to contract, and the results obtained refer to the ATPase cycle of myofibrils contracting with no external load. Here we studied the ATPase of myofibrils contracting isometrically. To prevent shortening, we cross-linked them with 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC). SDS-PAGE and Western blot analyses showed that the myosin rods were extensively cross-linked and that 8% of the myosin heads were cross-linked to the thin filament. The transient kinetics of the cross-linked myofibrils were studied in 0.1 M potassium acetate, pH 7.4 and 4 degrees C, by the rapid-flow quench method. The ATP binding steps were studied by the cold ATP chase and the cleavage and release of products steps by the Pi burst method. In Pi burst experiments, the sizes of the bursts were equal within experimental error to the ATPase site concentrations (as determined by the cold ATP chase methods) for both cross-linked (isometric) and un-cross-linked (isotonic) myofibrils. This shows that in both cases the rate-limiting step is after the cleavage of ATP. When cross-linked, the kcat of Ca(2+)-activated myofibrils was reduced from 1.7 to 0.8 s-1. This is consistent with the observation that fibers shortening at moderate velocity have a higher ATPase activity than isometric fibers.(ABSTRACT TRUNCATED AT 250 WORDS)

  15. Swelling of cross-linked polymers: interpretations and misinterpretations

    Czech Academy of Sciences Publication Activity Database

    Dušek, Karel; Dušková-Smrčková, Miroslava

    2017-01-01

    Roč. 254, 20 August (2017), s. 102 ISSN 0065-7727. [ACS National Meeting & Exposition /254./. 20.08.2017-24.08.2017, Washington] Institutional support: RVO:61389013 Keywords : swelling * cross-linked polymer Subject RIV: CD - Macromolecular Chemistry OBOR OECD: Polymer science

  16. Cross Country MetroLink Segment I Business Plan

    Science.gov (United States)

    1997-12-02

    In the St. Louis, Missouri metropolitan area, the East-West Gateway Coordinating : Council decided the route for the first MetroLink extension in the Cross-County : Corridor in September 1997. The next phase, reflected in this paper is develop, : dur...

  17. Hyper-cross-linked, hybrid membranes via interfacial polymerization

    NARCIS (Netherlands)

    Raaijmakers, Michiel

    2015-01-01

    Hyper-cross-linked, hybrid membranes consist of covalent networks of alternating organic and inorganic, or biological groups. This thesis reports on the preparation of such hybrid networks via interfacial polymerization. The structure-property relationships of the hybrid networks depend strongly on

  18. Bypass of a psoralen DNA interstrand cross-link by DNA polymerases beta, iota, and kappa in vitro

    Science.gov (United States)

    Smith, Leigh A.; Makarova, Alena V.; Samson, Laura; Thiesen, Katherine E.; Dhar, Alok; Bessho, Tadayoshi

    2012-01-01

    Repair of DNA inter-strand cross-links in mammalian cells involves several biochemically distinctive processes, including the release of one of the cross-linked strands and translesion DNA synthesis (TLS). In this report, we investigated in vitro TLS activity of psoralen DNA inter-strand cross-link by three DNA repair polymerases, DNA polymerase beta, kappa and iota. DNA polymerase beta is capable of bypassing a psoralen cross-link with a low efficiency. Cell extracts prepared from DNA polymerase beta knockout mouse embryonic fibroblast showed a reduced bypass activity of the psoralen cross-link and purified DNA polymerase beta restored the bypass activity. In addition, DNA polymerase iota mis-incorporated thymine across the psoralen cross-link and DNA polymerase kappa extended these mis-paired primer ends, suggesting that DNA polymerase iota may serve as an inserter and DNA polymerase kappa may play a role as an extender in the repair of psoralen DNA inter-strand cross-links. The results demonstrated here indicate that multiple DNA polymerases could participate in TLS steps in mammalian DNA inter-strand cross-link repair. PMID:23106263

  19. Analysis of protein-nucleic acid interactions by photochemical cross-linking and mass spectrometry

    DEFF Research Database (Denmark)

    Steen, Hanno; Jensen, Ole Nørregaard

    2002-01-01

    . Mass spectrometry (MS) has emerged as a sensitive and efficient analytical technique for determination of such cross-linking sites in proteins. The present review of the field describes a number of MS-based approaches for the characterization of cross-linked protein-nucleic acid complexes...

  20. Nanomechanics of layer-by-layer polyelectrolyte complexes: a manifestation of ionic cross-links and fixed charges.

    Science.gov (United States)

    Han, Biao; Chery, Daphney R; Yin, Jie; Lu, X Lucas; Lee, Daeyeon; Han, Lin

    2016-01-28

    This study investigates the roles of two distinct features of ionically cross-linked polyelectrolyte networks - ionic cross-links and fixed charges - in determining their nanomechanical properties. The layer-by-layer assembled poly(allylamine hydrochloride)/poly(acrylic acid) (PAH/PAA) network is used as the model material. The densities of ionic cross-links and fixed charges are modulated through solution pH and ionic strength (IS), and the swelling ratio, elastic and viscoelastic properties are quantified via an array of atomic force microscopy (AFM)-based nanomechanical tools. The roles of ionic cross-links are underscored by the distinctive elastic and viscoelastic nanomechanical characters observed here. First, as ionic cross-links are highly sensitive to solution conditions, the instantaneous modulus, E0, exhibits orders-of-magnitude changes upon pH- and IS-governed swelling, distinctive from the rubber elasticity prediction based on permanent covalent cross-links. Second, ionic cross-links can break and self-re-form, and this mechanism dominates force relaxation of PAH/PAA under a constant indentation depth. In most states, the degree of relaxation is >90%, independent of ionic cross-link density. The importance of fixed charges is highlighted by the unexpectedly more elastic nature of the network despite low ionic cross-link density at pH 2.0, IS 0.01 M. Here, the complex is a net charged, loosely cross-linked, where the degree of relaxation is attenuated to ≈50% due to increased elastic contribution arising from fixed charge-induced Donnan osmotic pressure. In addition, this study develops a new method for quantifying the thickness of highly swollen polymer hydrogel films. It also underscores important technical considerations when performing nanomechanical tests on highly rate-dependent polymer hydrogel networks. These results provide new insights into the nanomechanical characters of ionic polyelectrolyte complexes, and lay the ground for further

  1. Effects of cross-linking modification with phosphoryl chloride (POCl3 on pysiochemical properties of barely starch

    Directory of Open Access Journals (Sweden)

    Zahra Malekpour

    2016-05-01

    Full Text Available Chemical methods are one of the comon method in starch modification. This study aimed at investigating of cross-link affection of phosphoryl chloride with two different levels 0.5 and 1g.kg-1 in order to enhance funciotnal proeprties and physiochemical changes on extracted starch from barely variety Bahman which cultivates in Chahr-Mahal Bakhtiari Province of Iran. Obtained results indicated that cross-linking leads to reduce sweeling power of strach granuls compred to natural starch and the amount of reduciton increase via the substitituin level. Powerfull cross-linkingnetween starch chains casue more resistance of granules to seweeling which is increased by means of cross-linking dgree. Additioally,  investigationresults from synersis revealed that releasing water percentage in cross-linked starches increase in comparison to natural starches and this amount depends onthe amount of cross-link surface with a significantly difference in (α <0.05. Gelatinization temperature in both levels negligibly increased by modification where in low level of cross-linking was more. Furthermoe evaluating gelation temperatures of both natural and cross-linked modified starches showed that addition of phosphate groups in starch and creating extra coovalent bonds make granues more compressed reulting in slight increase of To, Tp, Tcin barely starch. Icreasing of temperature observed more in less concentration of cross-links. Evaluation of viscosity changes also revealed that this modification depending on increasing the amount of Phosphoryl Chloride led to increasing peak temperature, diminish peak and setback viscosity. Result also exhibited that in morphological level, cross-link causes to incidence changes in particles' diameter size. The comparison of diameter average and frequency between natural starch and cross-links starch exhibited that in cross-linkd treatment with 0.5% phosphoryl chloride, increase in frequency of granules with diameter of 6 - 10µm

  2. Vitamin E-diffused highly cross-linked UHMWPE particles induce less osteolysis compared to highly cross-linked virgin UHMWPE particles in vivo

    DEFF Research Database (Denmark)

    Bichara, David A; Malchau, Erik; Sillesen, Nanna H

    2014-01-01

    when compared to virgin gamma irradiated cross-linked UHMWPE. Groups received equal amount of particulate debris overlaying the calvarium for 10 days. Calvarial bone was examined using high resolution micro-CT and histomorphometric analyses. There was a statistically significant difference between...

  3. Macronutrient and carbon supply, uptake and cycling across the Antarctic Peninsula shelf during summer.

    Science.gov (United States)

    Henley, Sian F; Jones, Elizabeth M; Venables, Hugh J; Meredith, Michael P; Firing, Yvonne L; Dittrich, Ribanna; Heiser, Sabrina; Stefels, Jacqueline; Dougans, Julie

    2018-06-28

    The West Antarctic Peninsula shelf is a region of high seasonal primary production which supports a large and productive food web, where macronutrients and inorganic carbon are sourced primarily from intrusions of warm saline Circumpolar Deep Water. We examined the cross-shelf modification of this water mass during mid-summer 2015 to understand the supply of nutrients and carbon to the productive surface ocean, and their subsequent uptake and cycling. We show that nitrate, phosphate, silicic acid and inorganic carbon are progressively enriched in subsurface waters across the shelf, contrary to cross-shelf reductions in heat, salinity and density. We use nutrient stoichiometric and isotopic approaches to invoke remineralization of organic matter, including nitrification below the euphotic surface layer, and dissolution of biogenic silica in deeper waters and potentially shelf sediment porewaters, as the primary drivers of cross-shelf enrichments. Regenerated nitrate and phosphate account for a significant proportion of the total pools of these nutrients in the upper ocean, with implications for the seasonal carbon sink. Understanding nutrient and carbon dynamics in this region now will inform predictions of future biogeochemical changes in the context of substantial variability and ongoing changes in the physical environment.This article is part of the theme issue 'The marine system of the West Antarctic Peninsula: status and strategy for progress in a region of rapid change'. © 2018 The Authors.

  4. Molecular contacts for chlorosome envelope proteins revealed by cross-linking studies with chlorosomes from Chlorobium tepidum

    DEFF Research Database (Denmark)

    Li, Hui; Frigaard, Niels-Ulrik; Bryant, Donald A

    2006-01-01

    type and mutants lacking a single chlorosome protein were cross-linked with the zero-length cross-linker 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC) and analyzed by gel electrophoresis. Similar cross-linking products were observed when the time and temperature were varied or when EDC...... was replaced with glutaraldehyde. Specific interactions between chlorosome proteins in cross-linked products were identified by immunoblotting with polyclonal antibodies raised against recombinant chlorosome proteins. We confirmed these interactions by demonstrating that these products were missing...... in appropriate mutants. Confirming the location of CsmA in the paracrystalline baseplate, cross-linking showed that CsmA forms dimers, trimers, and homomultimers as large as dodecamers and that CsmA directly interacts with the Fenna-Matthews-Olson protein. Cross-linking further suggests that the precursor form...

  5. Improvement on Physical Properties of Pullulan Films by Novel Cross-Linking Strategy.

    Science.gov (United States)

    Chen, Chieh-Ting; Chen, Kuan-I; Chiang, Hsin-Han; Chen, Yu-Kuo; Cheng, Kuan-Chen

    2017-01-01

    Pullulan based films possess several advantages, including high transparency, low toxicity, good biodegradability, good mechanical properties, and low oxygen permeability, are preferable for food packaging. The application of pullulan films on food packaging, however, has inherent disadvantage of high water solubility. In this study, glutaraldehyde and glycerol were used as the cross-linking reagent and the plasticizer respectively to improve water resistance and physical properties of the pullulan films. Effects of cross-linking degree on physical properties, including water absorptions, swelling behaviors, water vapor permeability and tensile strengths of films were evaluated. FTIR results demonstrated that the pullulan films were successfully cross-linked by glutaraldehyde. The tensile strength of pullulan films could be enhanced significantly (P permeability. © 2016 Institute of Food Technologists®.

  6. Effect of gamma radiation on total antioxidant capacity, total lipid concentration and shelf life of finger millet flour

    International Nuclear Information System (INIS)

    Lathika; Manupriya, B.R.; Shenoy, K.B.; Patil, S.L.; Somashekarappa, H.M.

    2016-01-01

    The present study is an attempt to study the impact of gamma radiation on the shelf life, total antioxidant capacity and total lipid concentration of finger millet (Eleusine coracana L.) flour. Finger millet flour was procured from market. Flour samples of 50 g were taken in triplicates in a polyethylene pouch, air sealed and subjected to gamma irradiation doses ranging from 0.25 to 10 kGy and stored in polyethylene bags and plastic containers for a period of 1 year. Within 24 hours of irradiation, the samples were tested for moisture (2 ± 0.2%), total antioxidant capacity (0.12 ± 0.010 mg) and lipid concentration (15 ± 0.4 mg)

  7. All-Polyethylene Tibial Components: An Analysis of Long-Term Outcomes and Infection.

    Science.gov (United States)

    Houdek, Matthew T; Wagner, Eric R; Wyles, Cody C; Watts, Chad D; Cass, Joseph R; Trousdale, Robert T

    2016-07-01

    There is debate regarding tibial component modularity and composition in total knee arthroplasty (TKA). Biomechanical studies have suggested improved stress distribution in metal-backed tibias; however, these results have not translated clinically. The purpose of this study was to analyze the outcomes of all-polyethylene components and to compare the results to those with metal-backed components. We reviewed 31,939 patients undergoing a primary TKA over a 43-year period (1970-2013). There were 28,224 (88%) metal-backed and 3715 (12%) all-polyethylene tibial components. The metal-backed and all-polyethylene groups had comparable demographics with respect to gender, age and body mass index (BMI). Mean follow-up was 7 years. The mean survival for all primary TKAs at the 5-, 10-, 20- and 30-year time points was 95%, 89%, 73%, and 57%, respectively. All-polyethylene tibial components were found to have a significantly improved (P tibial components were also found to have a significantly lower rate of infection, instability, tibial component loosening, and periprosthetic fracture. The all-polyethylene group had improved survival rates in all age groups, except in patients 85 years old or greater, where there was no significant difference. All-polyethylene tibial components had improved survival for all BMI groups except in the morbidly obese (BMI ≥ 40) where there was no significant difference. All-polyethylene tibial components had significantly improved implant survival, reduced rates of postoperative infection, fracture, and tibial component loosening. All polyethylene should be considered for most of the patients, regardless of age and BMI. Copyright © 2016 Elsevier Inc. All rights reserved.

  8. Cross Linking Polymers (PVA & PEG with TiO2 Nanoparticles for Humidity Sensing

    Directory of Open Access Journals (Sweden)

    Monika Joshi

    2009-11-01

    Full Text Available Humidity Sensors of different types are being used for various applications. Resistive Humidity Sensor has advantage over others for being small, low cost, interchangeable and long term stable. This makes them suitable for industrial, commercial and residential applications. In the present investigation humidity sensing behavior of various composite films made of Polyvinyl Alcohol (PVA, Polyethylene glycol (PEG, alkalies and oxide nanoparticles has been studied. It was found that relationship of resistance v/s relative humidity (RH was linear from 40 RH to 60 RH for a composite film made of PVA + PEG+ alkalies .The film can work with reliable efficiency for more than 100 days for the above range of humidity at room temperature. In order to improve the efficiency of composite polymer film TiO2 nanoparticles were added in the film and studied for resistance vs. RH responses. It was found that humidity range expands from 30 RH to 65 RH indicating the proportional decrease in resistance with increase in humidity at both ends as a result of the presence of TiO2 nanoparticles. The composite film with TiO2 nanoparticles can thus be used for wider range of humidity with reasonable stability and consistency. The observed behavior of the film has been attributed to the transportation of charge through TiO2 nanoparticles enhancing the conduction with the cross linked polymers.

  9. Extremely stretchable thermosensitive hydrogels by introducing slide-ring polyrotaxane cross-linkers and ionic groups into the polymer network

    Science.gov (United States)

    Bin Imran, Abu; Esaki, Kenta; Gotoh, Hiroaki; Seki, Takahiro; Ito, Kohzo; Sakai, Yasuhiro; Takeoka, Yukikazu

    2014-01-01

    Stimuli-sensitive hydrogels changing their volumes and shapes in response to various stimulations have potential applications in multiple fields. However, these hydrogels have not yet been commercialized due to some problems that need to be overcome. One of the most significant problems is that conventional stimuli-sensitive hydrogels are usually brittle. Here we prepare extremely stretchable thermosensitive hydrogels with good toughness by using polyrotaxane derivatives composed of α-cyclodextrin and polyethylene glycol as cross-linkers and introducing ionic groups into the polymer network. The ionic groups help the polyrotaxane cross-linkers to become well extended in the polymer network. The resulting hydrogels are surprisingly stretchable and tough because the cross-linked α-cyclodextrin molecules can move along the polyethylene glycol chains. In addition, the polyrotaxane cross-linkers can be used with a variety of vinyl monomers; the mechanical properties of the wide variety of polymer gels can be improved by using these cross-linkers. PMID:25296246

  10. Collagen and elastin cross-linking is altered during aberrant late lung development associated with hyperoxia.

    Science.gov (United States)

    Mižíková, Ivana; Ruiz-Camp, Jordi; Steenbock, Heiko; Madurga, Alicia; Vadász, István; Herold, Susanne; Mayer, Konstantin; Seeger, Werner; Brinckmann, Jürgen; Morty, Rory E

    2015-06-01

    Maturation of the lung extracellular matrix (ECM) plays an important role in the formation of alveolar gas exchange units. A key step in ECM maturation is cross-linking of collagen and elastin, which imparts stability and functionality to the ECM. During aberrant late lung development in bronchopulmonary dysplasia (BPD) patients and animal models of BPD, alveolarization is blocked, and the function of ECM cross-linking enzymes is deregulated, suggesting that perturbed ECM cross-linking may impact alveolarization. In a hyperoxia (85% O2)-based mouse model of BPD, blunted alveolarization was accompanied by alterations to lung collagen and elastin levels and cross-linking. Total collagen levels were increased (by 63%). The abundance of dihydroxylysinonorleucine collagen cross-links and the dihydroxylysinonorleucine-to-hydroxylysinonorleucine ratio were increased by 11 and 18%, respectively, suggestive of a profibrotic state. In contrast, insoluble elastin levels and the abundance of the elastin cross-links desmosine and isodesmosine in insoluble elastin were decreased by 35, 30, and 21%, respectively. The lung collagen-to-elastin ratio was threefold increased. Treatment of hyperoxia-exposed newborn mice with the lysyl oxidase inhibitor β-aminopropionitrile partially restored normal collagen levels, normalized the dihydroxylysinonorleucine-to-hydroxylysinonorleucine ratio, partially normalized desmosine and isodesmosine cross-links in insoluble elastin, and partially restored elastin foci structure in the developing septa. However, β-aminopropionitrile administration concomitant with hyperoxia exposure did not improve alveolarization, evident from unchanged alveolar surface area and alveoli number, and worsened septal thickening (increased by 12%). These data demonstrate that collagen and elastin cross-linking are perturbed during the arrested alveolarization of developing mouse lungs exposed to hyperoxia. Copyright © 2015 the American Physiological Society.

  11. Comparison of Polyethylene Glycol-Electrolyte Solution vs Polyethylene Glycol-3350 for the Treatment of Fecal Impaction in Pediatric Patients.

    Science.gov (United States)

    Boles, Erin E; Gaines, Cameryn L; Tillman, Emma M

    2015-01-01

    The objective of this study was to evaluate the safety and efficacy of polyethylene glycol-electrolyte solution vs polyethylene glycol-3350 for the treatment of fecal impaction in pediatric patients. A retrospective, observational, institutional review board-approved study was conducted over a 1-year time period. Patients were included in the study if they were admitted to the hospital with a diagnosis of fecal impaction or constipation and were treated with either polyethylene glycol-electrolyte solution (PEG-ES) or polyethylene glycol-3350 (PEG-3350). Patients were excluded if they were discharged prior to resolution of treatment and/or did not receive PEG-ES or PEG-3350. Fifty-one patients (ranging in age from 1 month to 15 years) were evaluated: 23 patients received PEG-ES and 28 patients received PEG-3350. Sex, race, age, and weight were not statistically different between the 2 groups. Resolution of fecal impaction was not significantly different between PEG-ES vs PEG-3350 (87% and 86%, respectively; p = 0.87). There was only 1 reported side effect with PEG-3350, vs 11 reported side effects with PEG-ES (p PEG-3350 is as effective as PEG-ES for the treatment of fecal impaction in pediatric patients and is associated with fewer side effects.

  12. Cross-Linking in Collagen by Nonenzymatic Glycation Increases the Matrix Stiffness in Rabbit Achilles Tendon

    OpenAIRE

    Reddy, G. Kesava

    2004-01-01

    Nonenzymatic glycation of connective tissue matrix proteins is a major contributor to the pathology of diabetes and aging. Previously the author and colleagues have shown that nonenzymatic glycation significantly enhances the matrix stability in the Achilles tendon (Reddy et al., 2002, Arch. Biochem. Biophys., 399, 174–180). The present study was designed to gain further insight into glycation-induced collagen cross-linking and its relationship to matrix stiffness in the rabbit Achilles tendo...

  13. The Mechanical Properties of Recycled Polyethylene-Polyethylene Terephthalate Composites

    Directory of Open Access Journals (Sweden)

    Ehsan Avazverdi

    2015-02-01

    Full Text Available Polyethylene terephthalate (PET, one of the thermoplastic polymers, is encountered with arduous problems in its recycling. After recycling, its mechanical properties drop dramatically and therefore it cannot be used to produce the products as virgin PET does. Polyethylene is a thermoplastic polymer which can be easily recycled using the conventional recycling processes. The decreased mechanical properties of virgin polyethylene due to the environmental factors can be improved by reinforcing fillers. In this paper, we studied the effects of adding recycled polyethylene terephthalate (rPET as a filler, in various amounts with different sizes, on the physical and mechanical properties of recycled polyethylene. Composite samples were prepared using an internal mixer at temperature 185°C, well below rPET melting point (250°C, and characterized by their mechanical properties. To improve the compatibility between different components, PE grafted with maleic anhydride was added as a coupling agent in all the compositions under study. The mechanical properties of the prepared samples were performed using the tensile strength, impact strength, surface hardness and melt flow index (MFI tests. To check the dispersity of the polyethylene terephthalate powder in the polyethylene matrix, light microscopy was used. The results showed that the addition of rPET improved the tensile energy, tensile modulus and surface hardness of the composites while reduced the melt flow index, elongation-at-yield, tensile strength and fracture energy of impact test. We could conclude that with increasing rPET percentage in the recycled polyethylene matrix, the composite became brittle, in other words it decreased the plastic behavior of recycled polyethylene. Decreasing particle size led to higher surface contacts, increased the mechanical properties and made the composite more brittle. The light microscopy micrographs of the samples showed a good distribution of small r

  14. Lactoferrin binding to transglutaminase cross-linked casein micelles

    NARCIS (Netherlands)

    Anema, S.G.; de Kruif, C.G.|info:eu-repo/dai/nl/073609609

    2012-01-01

    Casein micelles in skim milk were either untreated (untreated milk) or were cross-linked using transglutaminase (TGA-milk). Added lactoferrin (LF) bound to the casein micelles and followed Langmuir adsorption isotherms. The adsorption level was the same in both milks and decreased the micellar zeta

  15. Inorganic carbon fluxes on the Mackenzie Shelf of the Beaufort Sea

    Science.gov (United States)

    Mol, Jacoba; Thomas, Helmuth; Myers, Paul G.; Hu, Xianmin; Mucci, Alfonso

    2018-02-01

    The Mackenzie Shelf in the southeastern Beaufort Sea is a region that has experienced large changes in the past several decades as warming, sea-ice loss, and increased river discharge have altered carbon cycling. Upwelling and downwelling events are common on the shelf, caused by strong, fluctuating along-shore winds, resulting in cross-shelf Ekman transport, and an alternating estuarine and anti-estuarine circulation. Downwelling carries dissolved inorganic carbon (DIC) and other remineralization products off the shelf and into the deep basin for possible long-term storage in the world's oceans. Upwelling carries DIC and nutrient-rich waters from the Pacific-origin upper halocline layer (UHL) onto the shelf. Profiles of DIC and total alkalinity (TA) taken in August and September of 2014 are used to investigate the cycling of carbon on the Mackenzie Shelf. The along-shore transport of water and the cross-shelf transport of DIC are quantified using velocity field output from a simulation of the Arctic and Northern Hemisphere Atlantic (ANHA4) configuration of the Nucleus of European Modelling of the Ocean (NEMO) framework. A strong upwelling event prior to sampling on the Mackenzie Shelf took place, bringing CO2-rich (elevated pCO2) water from the UHL onto the shelf bottom. The maximum on-shelf DIC flux was estimated at 16.9×103 mol C d-1 m-2 during the event. The maximum on-shelf transport of DIC through the upwelling event was found to be 65±15×10-3 Tg C d-1. TA and the oxygen isotope ratio of water (δ18O-H2O) are used to examine water-mass distributions in the study area and to investigate the influence of Pacific Water, Mackenzie River freshwater, and sea-ice melt on carbon dynamics and air-sea fluxes of carbon dioxide (CO2) in the surface mixed layer. Understanding carbon transfer in this seasonally dynamic environment is key to quantify the importance of Arctic shelf regions to the global carbon cycle and provide a basis for understanding how it will

  16. Inorganic carbon fluxes on the Mackenzie Shelf of the Beaufort Sea

    Directory of Open Access Journals (Sweden)

    J. Mol

    2018-02-01

    Full Text Available The Mackenzie Shelf in the southeastern Beaufort Sea is a region that has experienced large changes in the past several decades as warming, sea-ice loss, and increased river discharge have altered carbon cycling. Upwelling and downwelling events are common on the shelf, caused by strong, fluctuating along-shore winds, resulting in cross-shelf Ekman transport, and an alternating estuarine and anti-estuarine circulation. Downwelling carries dissolved inorganic carbon (DIC and other remineralization products off the shelf and into the deep basin for possible long-term storage in the world's oceans. Upwelling carries DIC and nutrient-rich waters from the Pacific-origin upper halocline layer (UHL onto the shelf. Profiles of DIC and total alkalinity (TA taken in August and September of 2014 are used to investigate the cycling of carbon on the Mackenzie Shelf. The along-shore transport of water and the cross-shelf transport of DIC are quantified using velocity field output from a simulation of the Arctic and Northern Hemisphere Atlantic (ANHA4 configuration of the Nucleus of European Modelling of the Ocean (NEMO framework. A strong upwelling event prior to sampling on the Mackenzie Shelf took place, bringing CO2-rich (elevated pCO2 water from the UHL onto the shelf bottom. The maximum on-shelf DIC flux was estimated at 16.9×103 mol C d−1 m−2 during the event. The maximum on-shelf transport of DIC through the upwelling event was found to be 65±15×10−3 Tg C d−1. TA and the oxygen isotope ratio of water (δ18O-H2O are used to examine water-mass distributions in the study area and to investigate the influence of Pacific Water, Mackenzie River freshwater, and sea-ice melt on carbon dynamics and air–sea fluxes of carbon dioxide (CO2 in the surface mixed layer. Understanding carbon transfer in this seasonally dynamic environment is key to quantify the importance of Arctic shelf regions to the global carbon cycle and provide a basis

  17. Turbulent mixing over a shelf sea bank: linking physics to fish

    Science.gov (United States)

    Palmer, Matthew; Davis, Clare; Sharples, Jonathan

    2010-05-01

    The interaction between stratified flow and topography has previously been seen to generate enhanced vertical mixing both locally and far field by breaking of an intensified wave field close to the generation point and from waves propagating energy away from the source. Here we present a new series of measurements made during the summer of 2008 that includes transect data from a Scanfish towed CTD that provides a snapshot of the vertical density structure and distribution of chlorophyll over the Celtic Sea from beyond the shelf break to 250km onshelf. The transect supports previous findings of a persistent level of primary production identifiable as a subsurface chlorophyll maximum (SCM). Intensification of chlorophyll is seen at the shelf break region and provides a biological indicator of mixing. Similarly, we identify a high concentration of chlorophyll over Jones Bank 200km from the shelf break in 120m depth. Measurements from an array of acoustic current profilers, thermistor stings and a turbulence profiler reveal that the shallow sloping bank and strong tides regularly interact to produce hydraulic jumps in the lee of the bank during spring periods identifying Jones Bank as a mixing hotspot. The energy dissipated during these events act to erode the base of the strong thermocline and result in a vertical flux of nutrients into the stable, stratified environment. We suggest that it is the spring-neap modulation of this process which promotes intensified mixing over the bank. Nutrient measurements made during the experiment reveal that the ever changing mixing environment has significant influence on the phytoplankton community at the bank and is likely the key component in promoting enhanced biological production.

  18. Collagen cross-linking: insights on the evolution of metazoan extracellular matrix.

    Science.gov (United States)

    Rodriguez-Pascual, Fernando; Slatter, David Anthony

    2016-11-23

    Collagens constitute a large family of extracellular matrix (ECM) proteins that play a fundamental role in supporting the structure of various tissues in multicellular animals. The mechanical strength of fibrillar collagens is highly dependent on the formation of covalent cross-links between individual fibrils, a process initiated by the enzymatic action of members of the lysyl oxidase (LOX) family. Fibrillar collagens are present in a wide variety of animals, therefore often being associated with metazoan evolution, where the emergence of an ancestral collagen chain has been proposed to lead to the formation of different clades. While LOX-generated collagen cross-linking metabolites have been detected in different metazoan families, there is limited information about when and how collagen acquired this particular modification. By analyzing telopeptide and helical sequences, we identified highly conserved, potential cross-linking sites throughout the metazoan tree of life. Based on this analysis, we propose that they have importantly contributed to the formation and further expansion of fibrillar collagens.

  19. Cross-shelf investigation of coral reef cryptic benthic organisms reveals diversity patterns of the hidden majority

    KAUST Repository

    Pearman, John K.

    2018-05-18

    Coral reefs harbor diverse assemblages of organisms yet the majority of this diversity is hidden within the three dimensional structure of the reef and neglected using standard visual surveys. This study uses Autonomous Reef Monitoring Structures (ARMS) and amplicon sequencing methodologies, targeting mitochondrial cytochrome oxidase I and 18S rRNA genes, to investigate changes in the cryptic reef biodiversity. ARMS, deployed at 11 sites across a near- to off-shore gradient in the Red Sea were dominated by Porifera (sessile fraction), Arthropoda and Annelida (mobile fractions). The two primer sets detected different taxa lists, but patterns in community composition and structure were similar. While the microhabitat of the ARMS deployment affected the community structure, a clear cross-shelf gradient was observed for all fractions investigated. The partitioning of beta-diversity revealed that replacement (i.e. the substitution of species) made the highest contribution with richness playing a smaller role. Hence, different reef habitats across the shelf are relevant to regional diversity, as they harbor different communities, a result with clear implications for the design of Marine Protected Areas. ARMS can be vital tools to assess biodiversity patterns in the generally neglected but species-rich cryptic benthos, providing invaluable information for the management and conservation of hard-bottomed habitats over local and global scales.

  20. Temperature dependence of electrochemical properties of cross-linked poly(ethylene oxide)–lithium bis(trifluoromethanesulfonyl)imide–N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide solid polymer electrolytes for lithium batteries

    International Nuclear Information System (INIS)

    Wetjen, Morten; Kim, Guk-Tae; Joost, Mario; Winter, Martin; Passerini, Stefano

    2013-01-01

    Highlights: ► Solid-state electrolyte for lithium batteries. ► Polymer electrolyte with improved mechanical properties by cross-linking. ► Enhanced performance of polymer electrolytes using water- and air-stable ionic liquids as co-salts. ► Polymer electrolyte with high rate capability at moderate temperatures. - Abstract: An advanced electrochemical characterization of cross-linked ternary solid polymer electrolytes (SPEs), prepared by a solvent-free hot-pressing process, is reported. Ionic conductivity, electrochemical stability window and limiting current measurements were performed as a function of the temperature by using both potentiodynamic and galvanostatic techniques. Additionally, the lithium cycleability was evaluated with respect to its dependence on both the operating temperature and the current density by using a new multi-rate Li-stripping-plating procedure. The results clearly indicate the beneficial effect of higher operating temperatures on the rate-capability, without major degradation of the electrochemical stability of the SPE. All-solid-state lithium metal polymer batteries (LMPBs), comprising a lithium metal anode, the cross-linked ternary solid polymer electrolyte and a LiFePO 4 composite cathode, were manufactured and investigated in terms of the interdependencies of the delivered capacity, operating temperature and discharge rate. The results prove quite exceptional delivered capacities both at medium current densities at ambient temperatures and even more impressive capacities above 160 mAh g −1 at high discharge rates (1 C) and temperatures above 60 °C.

  1. Cross-modal links among vision, audition, and touch in complex environments.

    Science.gov (United States)

    Ferris, Thomas K; Sarter, Nadine B

    2008-02-01

    This study sought to determine whether performance effects of cross-modal spatial links that were observed in earlier laboratory studies scale to more complex environments and need to be considered in multimodal interface design. It also revisits the unresolved issue of cross-modal cuing asymmetries. Previous laboratory studies employing simple cues, tasks, and/or targets have demonstrated that the efficiency of processing visual, auditory, and tactile stimuli is affected by the modality, lateralization, and timing of surrounding cues. Very few studies have investigated these cross-modal constraints in the context of more complex environments to determine whether they scale and how complexity affects the nature of cross-modal cuing asymmetries. Amicroworld simulation of battlefield operations with a complex task set and meaningful visual, auditory, and tactile stimuli was used to investigate cuing effects for all cross-modal pairings. Significant asymmetric performance effects of cross-modal spatial links were observed. Auditory cues shortened response latencies for collocated visual targets but visual cues did not do the same for collocated auditory targets. Responses to contralateral (rather than ipsilateral) targets were faster for tactually cued auditory targets and each visual-tactile cue-target combination, suggesting an inhibition-of-return effect. The spatial relationships between multimodal cues and targets significantly affect target response times in complex environments. The performance effects of cross-modal links and the observed cross-modal cuing asymmetries need to be examined in more detail and considered in future interface design. The findings from this study have implications for the design of multimodal and adaptive interfaces and for supporting attention management in complex, data-rich domains.

  2. Cross-linked PAN-based thin-film composite membranes for non-aqueous nanofiltration

    KAUST Repository

    Pérez-Manríquez, Liliana

    2015-01-01

    A new approach on the development of cross-linked PAN based thin film composite (TFC) membranes for non-aqueous application is presented in this work. Polypropylene backed neat PAN membranes fabricated by phase inversion process were cross-linked with hydrazine to get excellent solvent stability toward dimethylformamide (DMF). By interfacial polymerization a selective polyamide active layer was coated over the cross-linked PAN using N,N′-diamino piperazine (DAP) and trimesoyl chloride (TMC) as monomers. Permeation and molecular weight cut off (MWCO) experiments using various dyes were done to evaluate the performance of the membranes. Membranes developed by such method show excellent solvent stability toward DMF with a permeance of 1.7 L/m2 h bar and a molecular weight cut-off of less than 600 Da.

  3. Cross-linked self-assembled micelle based nanosensor for intracellular pH measurements

    DEFF Research Database (Denmark)

    Ek, Pramod Kumar; Søndergaard, Rikke Vicki; Windschiegl, Barbara

    2014-01-01

    A micelle based nanosensor was synthesized and investigated as a ratiometric pH sensor for use in measurements in living cells by fluorescent microscopy. The nanosensor synthesis was based on self-assembly of an amphiphilic triblock copolymer, which was chemically cross-linked after micelle......-linked by an amidation reaction using 3,6,9-trioxaundecandioic acid cross-linker. The cross-linked micelle was functionalized with two pH sensitive fluorophores and one reference fluorophore, which resulted in a highly uniform ratiometric pH nanosensor with a diameter of 29 nm. The use of two sensor fluorophores...... provided a sensor with a very broad measurement range that seems to be influenced by the chemical design of the sensor. Cell experiments show that the sensor is capable of monitoring the pH distributions in HeLa cells....

  4. Two-photon induced collagen cross-linking in bioartificial cardiac tissue

    Science.gov (United States)

    Kuetemeyer, Kai; Kensah, George; Heidrich, Marko; Meyer, Heiko; Martin, Ulrich; Gruh, Ina; Heisterkamp, Alexander

    2011-08-01

    Cardiac tissue engineering is a promising strategy for regenerative therapies to overcome the shortage of donor organs for transplantation. Besides contractile function, the stiffness of tissue engineered constructs is crucial to generate transplantable tissue surrogates with sufficient mechanical stability to withstand the high pressure present in the heart. Although several collagen cross-linking techniques have proven to be efficient in stabilizing biomaterials, they cannot be applied to cardiac tissue engineering, as cell death occurs in the treated area. Here, we present a novel method using femtosecond (fs) laser pulses to increase the stiffness of collagen-based tissue constructs without impairing cell viability. Raster scanning of the fs laser beam over riboflavin-treated tissue induced collagen cross-linking by two-photon photosensitized singlet oxygen production. One day post-irradiation, stress-strain measurements revealed increased tissue stiffness by around 40% being dependent on the fibroblast content in the tissue. At the same time, cells remained viable and fully functional as demonstrated by fluorescence imaging of cardiomyocyte mitochondrial activity and preservation of active contraction force. Our results indicate that two-photon induced collagen cross-linking has great potential for studying and improving artificially engineered tissue for regenerative therapies.

  5. Capacity of cognitive radio under imperfect secondary and cross link channel state information

    KAUST Repository

    Sboui, Lokman

    2011-09-01

    In this paper, we study the ergodic capacity of secondary user channel in a spectrum sharing scenario in which the secondary transmitter is instantaneously aware of estimated versions of the cross link (between the secondary transmitter and the primary receiver) and the secondary link Channel State Information (CSI). The secondary link optimal power profile along with the ergodic capacity are derived for a class of fading channels, under an average power constraint and an instantaneous interference outage constraint. We also show that our framework is rather general as it encompasses several previously studied spectrum sharing settings as special cases. In order to gain some insights on the capacity behavior, numerical results are shown for independent Rayleigh fading channels where it is found for instance, that at low SNR regime, only the secondary channel estimation matters and that the cross link CSI has no effect on the ergodic capacity; whereas at high SNR regime, the capacity is rather driven by the cross link CSI. © 2011 IEEE.

  6. Oxidative cross-linking of casein by horseradish peroxidase and its ...

    African Journals Online (AJOL)

    STORAGESEVER

    2009-10-19

    Oct 19, 2009 ... The cross-linking of casein was demonstrated by capillary zone electrophoresis analysis. .... linking reaction was started by addition of 1.0 ml 3% (w/v) H2O2 and .... by Design Expert Software (Version 7.0), keeping one variable at its ... The emulsion was immediately transferred into a 250 ml capa-.

  7. Further studies of the nature, composition and ages of contemporary phosphorite from the Namibian Shelf

    International Nuclear Information System (INIS)

    Thomson, J.; Calvert, S.E.; Mukherjee, S.; Burnett, W.C.; Bremner, J.M.

    1984-01-01

    Major and minor element and radiochemical data are examined for a set of phosphorite concretions and other phosphatic material from the Namibian Shelf. The concretions were separated on a morphological basis from grab samples taken in a transect of shallowing depth over the diatomaceous ooze belt. Compositional data indicate that the samples are fairly pure carbonate-fluorapatite, and trend towards a maximum 32% P 2 O 5 content. A range of compositional variability similar to other samples from the Namibian Shelf is observed. Radiochemical systematics confirm that pelletal phosphorite and glauconitized pelletal phosphorite from depths > 170 m are at radioactive equilibrium, and are therefore old and reworked. The concretions, collected from depths shallower than 78 m, are entirely Recent, with maximum ages in the range 500-3800 years. They may be much younger. Despite distinct textural and small compositional differences, similar are found for separates from the same grab. Samples of fish scales and an unidentified high-magnesian phosphate mineral are also shown to have incorporated uranium recently. (orig.)

  8. Conservation of RNA sequence and cross-linking ability in ribosomes from a higher eukaryote: photochemical cross-linking of the anticodon of P site bound tRNA to the penultimate cytidine of the UACACACG sequence in Artemia salina 18S rRNA

    International Nuclear Information System (INIS)

    Ciesiolka, J.; Nurse, K.; Klein, J.; Ofengand, J.

    1985-01-01

    The complex of Artemia salina ribosomes and Escherichia coli acetylvalyl-tRNA could be cross-linked by irradiation with near-UV light. Cross-linking required the presence of the codon GUU, GUA being ineffective. The acetylvalyl group could be released from the cross-linked tRNA by treatment with puromycin, demonstrating that cross-linking had occurred at the P site. This was true both for pGUU- and also for poly(U2,G)-dependent cross-linking. All of the cross-linking was to the 18S rRNA of the small ribosomal subunit. Photolysis of the cross-link at 254 nm occurred with the same kinetics as that for the known cyclobutane dimer between this tRNA and Escherichia coli 16S rRNA. T1 RNase digestion of the cross-linked tRNA yielded an oligonucleotide larger in molecular weight than any from un-cross-linked rRNA or tRNA or from a prephotolyzed complex. Extended electrophoresis showed this material to consist of two oligomers of similar mobility, a faster one-third component and a slower two-thirds component. Each oligomer yielded two components on 254-nm photolysis. The slower band from each was the tRNA T1 oligomer CACCUCCCUVACAAGp, which includes the anticodon. The faster band was the rRNA 9-mer UACACACCGp and its derivative UACACACUG. Unexpectedly, the dephosphorylated and slower moving 9-mer was derived from the faster moving dimer. Deamination of the penultimate C to U is probably due to cyclobutane dimer formation and was evidence for that nucleotide being the site of cross-linking. Direct confirmation of the cross-linking site was obtained by Z-gel analysis

  9. Cross-linking for microbial keratitis

    Directory of Open Access Journals (Sweden)

    Jayesh Vazirani

    2013-01-01

    Full Text Available The success of collagen cross-linking as a clinical modality to modify the clinical course in keratoconus seems to have fueled the search for alternative applications for this treatment. Current clinical data on its efficacy is limited and laboratory data seems to indicate that it performs poorly against resistant strains of bacteria and against slow growing organisms. However, the biological plausibility of crosslinking and the lack of effective strategies in managing infections with these organisms continue to focus attention on this potential treatment. Well-conducted experimental and clinical studies with controls are required to answer the questions of its efficacy in future.

  10. Insights into the swelling process and drug release mechanisms from cross-linked pectin/high amylose starch matrices

    Directory of Open Access Journals (Sweden)

    Fernanda M. Carbinatto

    2014-02-01

    Full Text Available Cross-linked pectin/high amylose mixtures were evaluated as a new excipient for matrix tablets formulations, since the mixing of polymers and cross-linking reaction represent rational tools to reach materials with modulated and specific properties that meet specific therapeutic needs. Objective: In this work the influence of polymer ratio and cross-linking process on the swelling and the mechanism driving the drug release from swellable matrix tablets prepared with this excipient was investigated. Methods: Cross-linked samples were characterized by their micromeritic properties (size and shape, density, angle of repose and flow rate and liquid uptake ability. Matrix tablets were evaluated according their physical properties and the drug release rates and mechanisms were also investigated. Results: Cross-linked samples demonstrated size homogeneity and irregular shape, with liquid uptake ability insensible to pH. Cross-linking process of samples allowed the control of drug release rates and the drug release mechanism was influenced by both polymer ratio and cross-linking process. The drug release of samples with minor proportion of pectin was driven by an anomalous transport and the increase of the pectin proportion contributed to the erosion of the matrix. Conclusion: The cross-linked mixtures of high amylose and pectin showed a suitable excipient for slowing the drug release rates.

  11. Characterization of ecofriendly polyethylene fiber from plastic bag waste

    Science.gov (United States)

    Soekoco, Asril S.; Noerati, Komalasari, Maya; Kurniawan, Hananto, Agus

    2017-08-01

    This paper presents the characterization of fiber morphology, fiber count and tenacity of polyethylene fiber which is made from plastic bag waste. Recycling plastic bag waste into textile fiber has not developed yet. Plastic bag waste was recycled into fiber by melt spinning using laboratory scale melt spinning equipment with single orifice nozzle and plunger system. The basic principle of melt spinning is by melting materials and then extruding it through small orifice of a spinning nozzle to form fibers. Diameter and cross section shape of Recycled polyethylene fiber were obtained by using scanning electron microscope (SEM) instrumentation. Linear density of the recycled fiber were analyzed by calculation using denier and dTex formulation and The mechanical strength of the fibers was measured in accordance with the ASTM D 3379-75 standard. The cross section of recycled fiber is circular taking the shape of orifice. Fiber count of 303.75 denier has 1.84 g/denier tenacity and fiber count of 32.52 has 3.44 g/denier tenacity. This conditions is affected by the growth of polymer chain alignment when take-up axial velocity become faster. Recycled polyethylene fiber has a great potential application in non-apparel textile.

  12. Evaluation of subbasal nerve morphology and corneal sensation after accelerated corneal collagen cross-linking treatment on keratoconus.

    Science.gov (United States)

    Ozgurhan, Engin Bilge; Celik, Ugur; Bozkurt, Ercument; Demirok, Ahmet

    2015-05-01

    The aim of this study was to report on the evaluation of corneal nerve fiber density and corneal sensation after accelerated corneal collagen cross-linking on keratoconus patients. The study was performed on 30 keratoconus eyes (30 participants: 16 M, 14 F; 17-32 years old) treated with accelerated collagen cross-linking for disease stabilization. Mean outcome measures were corneal sensation evaluation by Cochet-Bonnet esthesiometry and subbasal nerve fiber density assessment by corneal in vivo confocal microscopy. All corneal measurements were performed using scanning slit confocal microscopy (ConfoScan 4, Nidek Technologies, Padova, Italy). The accelerated corneal collagen cross-linking procedure was performed on 30 eyes of 30 patients (19 right, 63.3%; 11 left, 27.7%). The mean age was 23.93 ± 4. The preoperative mean keratometry, apex keratometry and pachymetry values were 47.19 ± 2.82 D, 56.79 ± 5.39 and 426.1 ± 25.6 μm, respectively. Preoperative mean corneal sensation was 56.3 ± 5.4 mm (with a range from 40 to 60 mm), it was significantly decreased at 1st and 3rd month visit and increased to preoperative values after 6th month visit. Preoperative mean of subbasal nerve fiber density measurements was 22.8 ± 9.7 nerve fiber/mm(2) (with a range of 5-45 mm), it was not still at the preoperative values at 6th month (p = 0.0001), however reached to the preoperative values at 12th month (p = 0.914). Subbasal nerve fibers could reach the preoperative values at the 12th month after accelerated corneal collagen cross-linking treatment although the corneal sensation was improved at 6th month. These findings imply that the subjective healing process is faster than the objective evaluation of the keratoconus patients' cornea treated with accelerated corneal collagen cross-linking.

  13. Dehydration of an ethanol/water azeotrope through alginate-DNA membranes cross-linked with metal ions by pervaporation.

    Science.gov (United States)

    Uragami, Tadashi; Banno, Masashi; Miyata, Takashi

    2015-12-10

    To obtain high dehydration membranes for an ethanol/water azeotrope, dried blend membranes prepared from mixtures of sodium alginate (Alg-Na) and sodium deoxyribonucleate (DNA-Na) were cross-linked by immersing in a methanol solution of CaCl2 or MaCl2. In the dehydration of an ethanol/water azeotropic mixture by pervaporation, the effects of immersion time in methanol solution of CaCl2 or MaCl2 on the permeation rate and water/ethanol selectivity through Alg-DNA/Ca(2+) and Alg-DNA/Mg(2+) cross-linked membranes were investigated. Alg-DNA/Mg(2+) cross-linked membrane immersed for 12h in methanol solution of MaCl2 exhibited the highest water/ethanol selectivity. This results from depressed swelling of the membranes by formation of a cross-linked structure. However, excess immersion in solution containing cross-linker led to an increase in the hydrophobicity of cross-linked membrane. Therefore, the water/ethanol selectivity of Alg-DNA/Mg(2+) cross-linked membranes with an excess immersion in cross-linking solution was lowered. The relationship between the structure of Alg-DNA/Ca(2+) and Alg-DNA/Mg(2+) cross-linked membranes and their permeation and separation characteristics during pervaporation of an ethanol/water azeotropic mixture is discussed in detail. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. SECONDARY CYTOTOXICITY OF CROSS-LINKED DERMAL SHEEP COLLAGENS DURING REPEATED EXPOSURE TO HUMAN FIBROBLASTS

    NARCIS (Netherlands)

    VANLUYN, MJA; VANWACHEM, PB; DAMINK, LHHO; DIJKSTRA, PJ; FEIJEN, J; NIEUWENHUIS, P

    1992-01-01

    We investigated commercially available dermal sheep collagen either cross-linked with hexamethylenedlisocyanate, or cross-linked with glutaraldehyde. In previous in vitro studies we could discriminate primary, i.e. extractable, and secondary cytotoxicity, due to cell-biomaterial interactions, i.e.

  15. Kinetics of enzyme-catalyzed cross-linking of feruloylated arabinan from sugar beet

    DEFF Research Database (Denmark)

    Abang Zaidel, Dayang Norulfairuz; Arnous, Anis; Holck, Jesper

    2011-01-01

    the kinetics of HRP catalyzed cross-linking of FA esterified to α-(1,5)-linked arabinans are affected by the length of the arabinan chains carrying the feruloyl substitutions. The kinetics of the HRP-catalyzed cross-linking of four sets of arabinan samples from sugar beet pulp, having different molecular...... weights and hence different degrees of polymerization, were monitored by the disappearance of FA absorbance at 316 nm. MALDI-TOF/TOF-MS analysis confirmed that the sugar beet arabinans were feruloyl-substituted, and HPLC analysis verified that the amounts of diFAs increased when FA levels decreased...

  16. Synthesis of Cross-Linked Polymeric Micelle pH Nanosensors

    DEFF Research Database (Denmark)

    Ek, Pramod Kumar; Jølck, Rasmus Irming; Andresen, Thomas Lars

    2015-01-01

    The design flexibility that polymeric micelles offer in the fabrication of optical nanosensors for ratiometric pH measurements is investigated. pH nanosensors based on polymeric micelles are synthesized either by a mixed-micellization approach or by a postmicelle modification strategy. In the mixed......-micellization approach, self-assembly of functionalized unimers followed by shell cross-linking by copper-catalyzed azide-alkyne cycloaddition (CuAAC) results in stabilized cRGD-functionalized micelle pH nanosensors. In the postmicelle modification strategy, simultaneous cross-linking and fluorophore conjugation...... at the micelle shell using CuAAC results in a stabilized micelle pH nanosensor. Compared to the postmicelle modification strategy, the mixed-micellization approach increases the control of the overall composition of the nanosensors.Both approaches provide stable nanosensors with similar pKa profiles and thereby...

  17. Covalently Cross-Linked Sulfone Polybenzimidazole Membranes with Poly(Vinylbenzyl Chloride) for Fuel Cell Applications

    DEFF Research Database (Denmark)

    Yang, Jingshuai; Aili, David; Li, Qingfeng

    2013-01-01

    Covalently cross-linked polymer membranes were fabricated from poly(aryl sulfone benzimidazole) (SO(2) PBI) and poly(vinylbenzyl chloride) (PVBCl) as electrolytes for high-temperature proton-exchange-membrane fuel cells. The cross-linking imparted organo insolubility and chemical stability against...

  18. Cell protein cross-linking by erbstatin and related compounds | Center for Cancer Research

    Science.gov (United States)

    The scheme depicts a possible mechanism of cross-linking by erbstatin and related analogues. A mechanism of action is proposed which involves initial oxidation to reactive quinone intermediates that subsequently cross-link protein nucleophiles via multiple 1,4-Michael-type additions. Similar alkylation of protein by protein-tyrosine kinase inhibitors, such as herbimycin A, has

  19. Surface functionalization of solid state ultra-high molecular weight polyethylene through chemical grafting

    Science.gov (United States)

    Sherazi, Tauqir A.; Rehman, Tayyiba; Naqvi, Syed Ali Raza; Shaikh, Ahson Jabbar; Shahzad, Sohail Anjum; Abbas, Ghazanfar; Raza, Rizwan; Waseem, Amir

    2015-12-01

    The surface of ultra-high molecular weight polyethylene (UHMWPE) powder was functionalized with styrene using chemical grafting technique. The grafting process was initiated through radical generation on base polymer matrix in the solid state by sodium thiosulfate, while peroxides formed at radical sites during this process were dissociated by ceric ammonium nitrate. Various factors were optimized and reasonably high level of monomer grafting was achieved, i.e., 15.6%. The effect of different acids as additive and divinyl benzene (DVB) as a cross-linking agent was also studied. Post-grafting sulfonation was conducted to introduce the ionic moieties to the grafted polymer. Ion-exchange capacity (IEC) was measured experimentally and is found to be 1.04 meq g-1, which is in close agreement with the theoretical IEC values. The chemical structure of grafted and functionalized polymer was characterized by attenuated total reflection infrared spectroscopy (ATR-FTIR) and thermal properties were investigated by thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Thermal analysis depicts that the presence of radicals on the polymer chain accelerates the thermal decomposition process. The results signify that the chemical grafting is an effective tool for substantial surface modification and subsequent functionalization of polyethylene.

  20. Cross-Linking Mast Cell Specific Gangliosides Stimulates the Release of Newly Formed Lipid Mediators and Newly Synthesized Cytokines

    Directory of Open Access Journals (Sweden)

    Edismauro Garcia Freitas Filho

    2016-01-01

    Full Text Available Mast cells are immunoregulatory cells that participate in inflammatory processes. Cross-linking mast cell specific GD1b derived gangliosides by mAbAA4 results in partial activation of mast cells without the release of preformed mediators. The present study examines the release of newly formed and newly synthesized mediators following ganglioside cross-linking. Cross-linking the gangliosides with mAbAA4 released the newly formed lipid mediators, prostaglandins D2 and E2, without release of leukotrienes B4 and C4. The effect of cross-linking these gangliosides on the activation of enzymes in the arachidonate cascade was then investigated. Ganglioside cross-linking resulted in phosphorylation of cytosolic phospholipase A2 and increased expression of cyclooxygenase-2. Translocation of 5-lipoxygenase from the cytosol to the nucleus was not induced by ganglioside cross-linking. Cross-linking of GD1b derived gangliosides also resulted in the release of the newly synthesized mediators, interleukin-4, interleukin-6, and TNF-α. The effect of cross-linking the gangliosides on the MAP kinase pathway was then investigated. Cross-linking the gangliosides induced the phosphorylation of ERK1/2, JNK1/2, and p38 as well as activating both NFκB and NFAT in a Syk-dependent manner. Therefore, cross-linking the mast cell specific GD1b derived gangliosides results in the activation of signaling pathways that culminate with the release of newly formed and newly synthesized mediators.

  1. Covalently cross-linked polyetheretherketone proton exchange membrane for DMFC

    CSIR Research Space (South Africa)

    Luo, H

    2009-05-01

    Full Text Available -7 cm2/s) and good electrochemical stability. The results suggested that cross-linked polyetheretherketone membrane is particularly promising to be used as proton exchange membrane for the direct methanol fuel cell application....

  2. Studies on extension of shelf-life of rawa by gamma irradiation

    International Nuclear Information System (INIS)

    Sudha Rao, V.; Srirangarajan, A.N.; Kamat, A.S.; Adhikari, H.R.; Nair, P.M.

    1994-01-01

    Semolina, a wheat product, popularly termed as rawa, was packed in 500g pouches prepared individually from high density polyethylene (HDP), biaxially oriented polypropylene : low density polyethylene laminate (BOPP/LDP), polyester : low density polyethylene laminate (PET/LDP) and irradiated using a Cobalt-60 source at dose of 0.15 to 0.50 kGy. At the end of six months' storage at room temperature, the unirradiated rawa developed infestation, whereas the irradiated samples were completely free of any infestation, thereby indicating a complete destruction of all stages of the insects due to irradiation. There was no significant difference in the moisture content and the total bacterial as well as mould counts of the irradiated and unirradiated rawa. Gamma irradiation significantly decreased the gelatinization viscosity of rawa. In sensory evaluation tests, irradiated rawa scored the same on a 9-point Hedonic scale, thereby showing that overall acceptability of the rawa was not altered due to irradiation upto 0.25 kGy. Amongst the packaging materials used, BOPP/LDP was found to be better, because of its comparatively higher resistance to penetration by insects. Gamma irradiation at 0.25 kGy could thus be recommended for effectively extending the shelf-life of rawa, prepacked in pouches made from BOPP/LDP laminate, for six months. (author). 26 refs., 1 fig., 2 tabs

  3. The role of basement inheritance faults in the recent fracture system of the inner shelf around Alboran Island, Western Mediterranean

    Science.gov (United States)

    Maestro-González, A.; Bárcenas, P.; Vázquez, J. T.; Díaz-Del-Río, V.

    2008-02-01

    Fractures associated with volcanic rock outcrops on the inner shelf of Alboran Island, Western Mediterranean, were mapped on the basis of a side-scan sonar mosaic. Absolute maximum fracture orientation frequency is NW SE to NNW SSE, with several sub-maxima oriented NNE SSW, NE SW and ENE WSW. The origin of the main fracture systems in Neogene and Quaternary rocks of the Alboran Basin (south Spain) appears to be controlled by older structures, namely NE SW and WNW ESE to NW SE faults which cross-cut the basement. These faults, pre-Tortonian in origin, have been reactivated since the early Neogene in the form of strike-slip and extensional movements linked to the recent stress field in this area. Fracture analysis of volcanic outcrops on the inner continental shelf of Alboran Island suggests that the shelf has been deformed into a narrow shear zone limited by two NE SW-trending, sub-parallel high-angle faults, the main orientation and density of which have been influenced by previous WNW ESE to NW SE basement fractures.

  4. Fabrication and characterization of hydrothermal cross-linked chitosan porous scaffolds for cartilage tissue engineering applications.

    Science.gov (United States)

    Shamekhi, Mohammad Amin; Rabiee, Ahmad; Mirzadeh, Hamid; Mahdavi, Hamid; Mohebbi-Kalhori, Davod; Baghaban Eslaminejad, Mohamadreza

    2017-11-01

    The use of various chemical cross-linking agents for the improvement of scaffolds physical and mechanical properties is a common practical method, which is limited by cytotoxicity effects. Due to exerting contract type forces, chondrocytes are known to implement shrinkage on the tissue engineered constructs, which can be avoided by the scaffold cross-linking. In the this research, chitosan scaffolds are cross-linked with hydrothermal treatment with autoclave sterilization time of 0, 10, 20 and 30min, to avoid the application of the traditional chemical toxic materials. The optimization studies with gel content and crosslink density measurements indicate that for 20min sterilization time, the gel content approaches to ~80%. The scaffolds are fully characterized by the conventional techniques such as SEM, porosity and permeability, XRD, compression, thermal analysis and dynamic mechanical thermal analysis (DMTA). FT-IR studies shows that autoclave inter-chain cross-linking reduces the amine group absorption at 1560cm -1 and increase the absorption of N-acetylated groups at 1629cm -1 . It is anticipated, that this observation evidenced by chitosan scaffold browning upon autoclave cross-linking is an indication of the familiar maillard reaction between amine moieties and carbonyl groups. The biodegradation rate analysis shows that chitosan scaffolds with lower concentrations, possess suitable degradation rate for cartilage tissue engineering applications. In addition, cytotoxicity analysis shows that fabricated scaffolds are biocompatible. The human articular chondrocytes seeding into 3D cross-linked scaffolds shows a higher viability and proliferation in comparison with the uncross-linked samples and 2D controls. Investigation of cell morphology on the scaffolds by SEM, shows a more spherical morphology of chondrocytes on the cross-linked scaffolds for 21days of in vitro culture. Copyright © 2017. Published by Elsevier B.V.

  5. The Preparation and Properties of Thermo-reversibly Cross-linked Rubber Via Diels-Alder Chemistry

    NARCIS (Netherlands)

    Polgar, Lorenzo Massimo; van Duin, Martin; Picchioni, Francesco

    2016-01-01

    A method for using Diels Alder thermo-reversible chemistry as cross-linking tool for rubber products is demonstrated. In this work, a commercial ethylene-propylene rubber, grafted with maleic anhydride, is thermo-reversibly cross-linked in two steps. The pending anhydride moieties are first modified

  6. Membrane-Based Separation of Phenol/Water Mixtures Using Ionically and Covalently Cross-Linked Ethylene-Methacrylic Acid Copolymers

    Directory of Open Access Journals (Sweden)

    Alexander Mixa

    2008-01-01

    Full Text Available Membrane-based separation of phenol/water mixtures with concentrations of phenol between 3 wt% and 8 wt% in the feed has been performed with nonmodified as well as cross-linked ethylene-methacrylic acid (E-MAA copolymers with different amounts of methacrylic acid. As cross-linking agents, aluminium acetyl acetonate, which leads to ionically cross-linked membranes, and 2,3,5,6-tetramethyl-1,4-phenylene diamine and glycerine digycidether, leading to covalently cross-linked membranes, have been used. Generally, it was found that with increasing phenol content in the feed, the total flux is increasing whereas the enrichment factor is decreasing. Using nonmodified membranes with higher methacrylic acid monomer content in the polymer, lower fluxes and higher enrichment factors were observed. Investigation of different cross-linked membranes showed that with high phenol concentration in the feed, ionic cross-linking seems to be very promising. Furthermore, variation of feed temperature shows that ionically cross-linked membranes reached higher fluxes as well as higher enrichment factors at elevated temperatures. The temperature-dependent data were fitted based on an Arrhenius-type equation, and activation energies for the permeation of phenol and water through the membrane were calculated.

  7. Effects of alginate hydrogel cross-linking density on mechanical and biological behaviors for tissue engineering.

    Science.gov (United States)

    Jang, Jinah; Seol, Young-Joon; Kim, Hyeon Ji; Kundu, Joydip; Kim, Sung Won; Cho, Dong-Woo

    2014-09-01

    An effective cross-linking of alginate gel was made through reaction with calcium carbonate (CaCO3). We used human chondrocytes as a model cell to study the effects of cross-linking density. Three different pore size ranges of cross-linked alginate hydrogels were fabricated. The morphological, mechanical, and rheological properties of various alginate hydrogels were characterized and responses of biosynthesis of cells encapsulated in each gel to the variation in cross-linking density were investigated. Desired outer shape of structure was maintained when the alginate solution was cross-linked with the applied method. The properties of alginate hydrogel could be tailored through applying various concentrations of CaCO3. The rate of synthesized GAGs and collagens was significantly higher in human chondrocytes encapsulated in the smaller pore structure than that in the larger pore structure. The expression of chondrogenic markers, including collagen type II and aggrecan, was enhanced in the smaller pore structure. It was found that proper structural morphology is a critical factor to enhance the performance and tissue regeneration. Copyright © 2014 Elsevier Ltd. All rights reserved.

  8. Immobilization of cross-linked tannase enzyme on multiwalled carbon nanotubes and its catalytic behavior.

    Science.gov (United States)

    Ong, Chong-Boon; Annuar, Mohamad S M

    2018-02-07

    Immobilization of cross-linked tannase on pristine multiwalled carbon nanotubes (MWCNT) was successfully performed. Cross-linking of tannase molecules was made through glutaraldehyde. The immobilized tannase exhibited significantly improved pH, thermal, and recycling stability. The optimal pH for both free and immobilized tannase was observed at pH 5.0 with optimal operating temperature at 30°C. Moreover, immobilized enzyme retained greater biocatalytic activities upon 10 repeated uses compared to free enzyme in solution. Immobilization of tannase was accomplished by strong hydrophobic interaction most likely between hydrophobic amino acid moieties of the glutaraldehyde-cross-linked tannase to the MWCNT.

  9. Distribution and origin of sediments on the northern Sunda Shelf, South China Sea

    Science.gov (United States)

    Wu, Shi-Guo; Wong, H. K.; Luo, You-Lang; Liang, Zhi-Rong

    1999-03-01

    Seventy-seven surface sediment samples and core samples from the outer Sunda Shelf were analyzed and a number of seismic profiles of the shelf were interpreted. The bottom sediments could be divided into six types: terrigenous sand, biogenic sand, silt-sand, clay-silt-sand, clayey silt and coral reef detritus. Our seismic data showed a thick, prograding Pleistocene deltaic sequence near the shelf-break and a thin Holocene sedimentary layer on the outer shelf. Eleven thermoluminescence (TL) ages were determined. The oldest relict sediments were derived from Late Pleistocene deposits. Based on sediment types, ages, and origins, five sedimentary areas were identified: area of modern Mekong sediments; insular shelf area receiving modern sediments from small Borneo rivers; shelf area near the Natuna-Anambas islands in the southeastern Gulf of Thailand Basin off the Malay Peninsula; area of relict sediments on the outer shelf north of the Natuna Islands, and typical coral reefs and detritus sediments.

  10. Tissue response to intraperitoneal implants of polyethylene oxide-modified polyethylene terephthalate.

    Science.gov (United States)

    Desai, N P; Hubbell, J A

    1992-01-01

    Polyethylene terephthalate films surface modified with polyethylene oxide of mol wt 18,500 g/mol (18.5 k) by a previously described technique, were implanted in the peritoneal cavity of mice, along with their respective untreated controls, for periods of 1-28 d. The implants were retrieved and examined for tissue reactivity and cellular adherence. The control polyethylene terephthalate surfaces showed an initial inflammatory reaction followed by an extensive fibrotic response with a mean thickness of 60 microns at 28 d. By contrast, polyethylene oxide-modified polyethylene terephthalate showed only a mild inflammatory response and no fibrotic encapsulation throughout the implantation period: at 28 d a cellular monolayer was observed. Apparently either the polyethylene oxide-modified surface was stimulating less inflammation, which was in turn stimulating less fibroblastic overgrowth, or the cellular adhesion to the polyethylene oxide-modified surface was too weak to support cellular multilayers.

  11. Improved cellular infiltration into nanofibrous electrospun cross-linked gelatin scaffolds templated with micrometer-sized polyethylene glycol fibers

    International Nuclear Information System (INIS)

    Skotak, Maciej; Ragusa, Jorge; Gonzalez, Daniela; Subramanian, Anuradha

    2011-01-01

    Gelatin-based nanofibrous scaffolds with a mean fiber diameter of 300 nm were prepared with and without micrometer-sized polyethylene glycol (PEG) fibers that served as sacrificial templates. Upon fabrication of the scaffolds via electrospinning, the gelatin fibers were crosslinked with glutaraldehyde, and the PEG templates were removed using tert-butanol to yield nanofibrous scaffolds with pore diameters ranging from 10 to 100 μm, as estimated with mercury intrusion porosimetry. Non-templated gelatin-based nanofibrous matrices had an average pore size of 1 μm. Fibroblasts were seeded onto both types of the gelatin-based nanofibrous surfaces and cultured for 14 days. For comparative purposes, chitosan-based and polyurethane-based macroporous scaffolds with pore sizes of 100 and 170 μm, respectively, were also included. The number of cells as a function of the depth into the scaffold was judged and quantitatively assessed using nuclei staining. Cell penetration up to a depth of 250 and 90 μm was noted in gelatin scaffolds prepared with sacrificial templates and gelatin-only nanofibrous scaffolds. Noticeably, scaffold preparation protocol presented here allowed the structural integrity to be maintained even with high template content (95%) and can easily be extended toward other classes of electrospun polymer matrices for tissue engineering.

  12. Alkali reversal of psoralen cross-link for the targeted delivery of psoralen monoadduct lesion

    International Nuclear Information System (INIS)

    Yeung, A.T.; Dinehart, W.J.; Jones, B.K.

    1988-01-01

    Psoralen intercalates into double-stranded DNA and photoreacts mainly with thymines to form monoadducts and interstrand cross-links. The authors used an oligonucleotide model to demonstrate a novel mechanism: the reversal of psoralen cross-links by base-catalyzed rearrangement at 90 0 C (BCR). The BCR reaction is more efficient than the photoreversal reaction. They show that the BCR occurs predominantly on the furan side of a psoralen cross-link. The cleavage does not result in the breaking of the DNA backbone, and the thymine based freed from the cross-link by the cleavage reaction appears to be unmodified. Similarly, BCR of the furan-side monoadduct of psoralen removed the psoralen molecule and regenerated the unaltered native oligonucleotide. The pyrone-side psoralen monoadduct is relatively resistant to BCR. One can use BCR to perform efficient oligonucleotide-directed, site-specific delivery of a psoralen monoadduct. As a demonstration of this approach, they have hybridized a 19 base long oligonucleotide vehicle containing a furan-side psoralen monoadduct to a 56 base long complementary oligonucleotide target strand and formed a specific cross-link at the target site with 365-nm UV. Subsequent BCR released the oligonucleotide vehicle and deposited the psoralen at the target site

  13. Chemical cross-linking of polypropylenes towards new shape memory polymers.

    Science.gov (United States)

    Raidt, Thomas; Hoeher, Robin; Katzenberg, Frank; Tiller, Joerg C

    2015-04-01

    In this work, syndiotactic polypropylene (sPP) as well as isotactic polypropylene (iPP) are cross-linked to gain a shape memory effect. Both prepared PP networks exhibit maximum strains of 700%, stored strains of up to 680%, and recoveries of nearly 100%. While x-iPP is stable for many cycles, x-sPP ruptures after the first shape-memory cycle. It is shown by wide-angle X-ray scattering (WAXS) experiments that cross-linked iPP exhibits homoepitaxy in the temporary, stretched shape but in contrast to previous reports it contains a higher amount of daughter than mother crystals. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Development of highly fire-retardant irradiated polyolefin cables

    Energy Technology Data Exchange (ETDEWEB)

    Ueno, Keiji; Inui, Toshifumi; Uda, Ikujiro (Sumitomo Electric Industries Ltd., Osaka (Japan))

    1982-12-01

    In recent years, motors, automobiles, heaters, etc., have been made into light weight and compact form in view of labour-saving and energy-saving. For this purpose, the wires for the electrical appliances used for these equipment are required to reduce insulation thickness and to improve heat resistance. On the other hand, the requirement for fire-retardant property has become severer than before from the viewpoint of safety. As an insulation for the wires which meets such requirement, the polyolefin cross-linked by irradiation was investigated, and the heat-resistant, highly fire-retardant, polyolefin-insulated wires have been developed, which have passed vertical combustion test (VW-1) and have the insulation thickness of 0.4 mm (voltage rating 300V) and UL standard 125 deg C and 150 deg C grades. Fire-retardant polyolefin resin is normally obtained by adding halogen series flame retarders. The selection of flame retarders requires the investigation on high thermal stability, high flame retardation, no impedance to cross-linking, and good dispersion into polymers. The evaluation of heat resistance performed on two points, thermal aging and thermal deformation. The use of oxidation inhibitors is indispensable to improve the anti-thermal aging capability, but it is important to balance the requirements well by combining oxidation inhibitors, considering thermal deformation, colouring and discolouration. By comparative test with silicone rubber, cross-linked polyethylene and cross-linked PVC-insulated wires, the characteristics of highly fire-retardant wires, insulated with polyethylene cross-linked by irradiation, are described about the fire retardation, thermal deformation, thermal aging resistance, electrical characteristics and oil resistance.

  15. An atomistic model for cross-linked HNBR elastomers used in seals

    Science.gov (United States)

    Molinari, Nicola; Sutton, Adrian; Stevens, John; Mostofi, Arash

    2015-03-01

    Hydrogenated nitrile butadiene rubber (HNBR) is one of the most common elastomeric materials used for seals in the oil and gas industry. These seals sometimes suffer ``explosive decompression,'' a costly problem in which gases permeate a seal at the elevated temperatures and pressures pertaining in oil and gas wells, leading to rupture when the seal is brought back to the surface. The experimental evidence that HNBR and its unsaturated parent NBR have markedly different swelling properties suggests that cross-linking may occur during hydrogenation of NBR to produce HNBR. We have developed a code compatible with the LAMMPS molecular dynamics package to generate fully atomistic HNBR configurations by hydrogenating initial NBR structures. This can be done with any desired degree of cross-linking. The code uses a model of atomic interactions based on the OPLS-AA force-field. We present calculations of the dependence of a number of bulk properties on the degree of cross-linking. Using our atomistic representations of HNBR and NBR, we hope to develop a better molecular understanding of the mechanisms that result in explosive decompression.

  16. Simulations of tensile failure in glassy polymers: effect of cross-link density

    International Nuclear Information System (INIS)

    Panico, M; Narayanan, S; Brinson, L C

    2010-01-01

    Molecular dynamics simulations are adopted to investigate the failure mechanisms of glassy polymers, particularly with respect to increasing density of cross-links. In our simulations thermosetting polymers, which are cross-linked, exhibit an embrittlement compared with uncross-linked thermoplastics in a similar fashion to several experimental investigations (Levita et al 1991 J. Mater. Sci. 26 2348; Sambasivam et al 1997 J. Appl. Polym. Sci. 65 1001; Iijima et al 1992 Eur. Polym. J. 28 573). We perform a detailed analysis of this phenomenon and propose an interpretation based on the predominance of chain scission process over disentanglement in thermosetting polymers. We also elucidate the brittle fracture response of the thermosetting polymers

  17. Investigation on the effect of formulation and process variables of Polyethylene Foams Production

    International Nuclear Information System (INIS)

    Barikani, H.; Sarai, M.

    2001-01-01

    Polyolefin foams such as polyethylene, polypropylene and their copolymers have been extensively used in packaging, automotive, military, marine, cable industries and sports, due to their unique properties namely: light weight, chemical resistance, thermal insulation, inertness, abrasion resistance, buoyancy and low cost. With regards to domestic mass production of polyethylene, replacement of polyurethane with polyethylene foam is very important in some applications from economical point of view. In this research preparation of high density and low density polyethylene foams were studied and the effect of formulation factors such as blowing agent, cross-linker, calcium carbonate, zinc oxide and processing factors such as heat, pressure and reaction time on density and cell size were investigated

  18. Large-Scale Ichthyoplankton and Water Mass Distribution along the South Brazil Shelf

    Science.gov (United States)

    de Macedo-Soares, Luis Carlos Pinto; Garcia, Carlos Alberto Eiras; Freire, Andrea Santarosa; Muelbert, José Henrique

    2014-01-01

    Ichthyoplankton is an essential component of pelagic ecosystems, and environmental factors play an important role in determining its distribution. We have investigated simultaneous latitudinal and cross-shelf gradients in ichthyoplankton abundance to test the hypothesis that the large-scale distribution of fish larvae in the South Brazil Shelf is associated with water mass composition. Vertical plankton tows were collected between 21°27′ and 34°51′S at 107 stations, in austral late spring and early summer seasons. Samples were taken with a conical-cylindrical plankton net from the depth of chlorophyll maxima to the surface in deep stations, or from 10 m from the bottom to the surface in shallow waters. Salinity and temperature were obtained with a CTD/rosette system, which provided seawater for chlorophyll-a and nutrient concentrations. The influence of water mass on larval fish species was studied using Indicator Species Analysis, whereas environmental effects on the distribution of larval fish species were analyzed by Distance-based Redundancy Analysis. Larval fish species were associated with specific water masses: in the north, Sardinella brasiliensis was found in Shelf Water; whereas in the south, Engraulis anchoita inhabited the Plata Plume Water. At the slope, Tropical Water was characterized by the bristlemouth Cyclothone acclinidens. The concurrent analysis showed the importance of both cross-shelf and latitudinal gradients on the large-scale distribution of larval fish species. Our findings reveal that ichthyoplankton composition and large-scale spatial distribution are determined by water mass composition in both latitudinal and cross-shelf gradients. PMID:24614798

  19. Large-scale ichthyoplankton and water mass distribution along the South Brazil Shelf.

    Directory of Open Access Journals (Sweden)

    Luis Carlos Pinto de Macedo-Soares

    Full Text Available Ichthyoplankton is an essential component of pelagic ecosystems, and environmental factors play an important role in determining its distribution. We have investigated simultaneous latitudinal and cross-shelf gradients in ichthyoplankton abundance to test the hypothesis that the large-scale distribution of fish larvae in the South Brazil Shelf is associated with water mass composition. Vertical plankton tows were collected between 21°27' and 34°51'S at 107 stations, in austral late spring and early summer seasons. Samples were taken with a conical-cylindrical plankton net from the depth of chlorophyll maxima to the surface in deep stations, or from 10 m from the bottom to the surface in shallow waters. Salinity and temperature were obtained with a CTD/rosette system, which provided seawater for chlorophyll-a and nutrient concentrations. The influence of water mass on larval fish species was studied using Indicator Species Analysis, whereas environmental effects on the distribution of larval fish species were analyzed by Distance-based Redundancy Analysis. Larval fish species were associated with specific water masses: in the north, Sardinella brasiliensis was found in Shelf Water; whereas in the south, Engraulis anchoita inhabited the Plata Plume Water. At the slope, Tropical Water was characterized by the bristlemouth Cyclothone acclinidens. The concurrent analysis showed the importance of both cross-shelf and latitudinal gradients on the large-scale distribution of larval fish species. Our findings reveal that ichthyoplankton composition and large-scale spatial distribution are determined by water mass composition in both latitudinal and cross-shelf gradients.

  20. Large-scale ichthyoplankton and water mass distribution along the South Brazil Shelf.

    Science.gov (United States)

    de Macedo-Soares, Luis Carlos Pinto; Garcia, Carlos Alberto Eiras; Freire, Andrea Santarosa; Muelbert, José Henrique

    2014-01-01

    Ichthyoplankton is an essential component of pelagic ecosystems, and environmental factors play an important role in determining its distribution. We have investigated simultaneous latitudinal and cross-shelf gradients in ichthyoplankton abundance to test the hypothesis that the large-scale distribution of fish larvae in the South Brazil Shelf is associated with water mass composition. Vertical plankton tows were collected between 21°27' and 34°51'S at 107 stations, in austral late spring and early summer seasons. Samples were taken with a conical-cylindrical plankton net from the depth of chlorophyll maxima to the surface in deep stations, or from 10 m from the bottom to the surface in shallow waters. Salinity and temperature were obtained with a CTD/rosette system, which provided seawater for chlorophyll-a and nutrient concentrations. The influence of water mass on larval fish species was studied using Indicator Species Analysis, whereas environmental effects on the distribution of larval fish species were analyzed by Distance-based Redundancy Analysis. Larval fish species were associated with specific water masses: in the north, Sardinella brasiliensis was found in Shelf Water; whereas in the south, Engraulis anchoita inhabited the Plata Plume Water. At the slope, Tropical Water was characterized by the bristlemouth Cyclothone acclinidens. The concurrent analysis showed the importance of both cross-shelf and latitudinal gradients on the large-scale distribution of larval fish species. Our findings reveal that ichthyoplankton composition and large-scale spatial distribution are determined by water mass composition in both latitudinal and cross-shelf gradients.

  1. Location of DNA-protein cross-links in mammalian cell nuclei

    International Nuclear Information System (INIS)

    Oleinick, N.L.

    1985-01-01

    DNA-protein cross-links (DPCs) occur in 1-3% of the bulk DNA of unirradiated cells, and dose-dependent increases in DPCs with γ- or UV-radiation can be detected by filter-binding. DPCs may contribute to cell lethality, since their formation is prevented by radical scavengers. Since the environment of DNA varies within eukaryotic nuclei, we have probed the composition and sub-nuclear location of DPCs. Both before and after irradiation, the major proteins cross-linked to DNA have molecular weights similar to known proteins of the nuclear matrix. The DNA cross-linked to protein is enriched in sequences which hybridize to mRNA or rRNA transcripts; such sequences are also found preferentially in preparations of nuclear matrix. When histone-depleted, matrix-associated DNA is separated from the DNA of the supercoiled ''loops'' by digestion with EcoRI and assayed for DPCs by filter binding, the frequency of DPCs is greater in the matrix. During repair of DPCs, protein-associated DNA becomes depleted in actively transcribing DNA, followed by reconstitution of the active-gene-enriched nuclear matrix. These data are consistent with known properties of the matrix and suggest the hypothesis that in intact cells, radiation-induced DPCs are primarily a product of matrix-associated DNA sequences and matrix protein

  2. Field Observations of Surf Zone-Inner Shelf Exchange on a Rip-Channeled Beach

    NARCIS (Netherlands)

    Brown, J.A.; MacMahan, J.H.; Reniers, A.J.H.M.; Thornton, E.B.

    2015-01-01

    Cross-shore exchange between the surf zone and the inner shelf is investigated using Lagrangian and Eulerian field measurements of rip current flows on a rip-channeled beach in Sand City, California. Surface drifters released on the inner shelf during weak wind conditions moved seaward due to rip

  3. Genipin Cross-Linked Glucose Oxidase and Catalase Multi-enzyme for Gluconic Acid Synthesis.

    Science.gov (United States)

    Cui, Caixia; Chen, Haibin; Chen, Biqiang; Tan, Tianwei

    2017-02-01

    In this work, glucose oxidase (GOD) and catalase (CAT) were used simultaneously to produce gluconic acid from glucose. In order to reduce the distance between the two enzymes, and therefore improve efficiency, GOD and CAT were cross-linked together using genipin. Improvements in gluconic acid production were due to quick removal of harmful intermediate hydrogen peroxide by CAT. GOD activity was significantly affected by the proportion of CAT in the system, with GOD activity in the cross-linked multi-enzyme (CLME) being 10 times higher than that in an un-cross-linked GOD/CAT mixture. The glucose conversion rate after 15 h using 15 % glucose was also 10 % higher using the CLME than was measured using a GOD/CAT mixture.

  4. Cross-linking of streptomycin to the 16S ribosomal RNA of Escherichia coli

    International Nuclear Information System (INIS)

    Gravel, M.; Melancon, P.; Barkier-Gingras, L.

    1987-01-01

    [ 3 H]Dihydrostreptomycin was cross-linked to the 30S ribosomal subunit from Escherichia coli with the bifunctional reagent nitrogen mustard. The cross-linking primarily involved the 16S RNA. To localize the site of cross-linking of streptomycin to the 16S RNA, the authors hybridized RNA labeled with streptomycin to restriction fragments of the 16S RNA gene. Labeled RNA hybridized to DNA fragments corresponding to bases 892-917 and bases 1394-1415. These two segments of the ribosomal RNA must by juxtaposed in the ribosome, since there is a single binding site for streptomycin. This region has been implicated both in the decoding site and in the binding of initiation factor IF-3, indicating its functional importance

  5. The salinity signature of the cross-shelf exchanges in the Southwestern Atlantic Ocean: Satellite observations.

    Science.gov (United States)

    Guerrero, Raul A; Piola, Alberto R; Fenco, Harold; Matano, Ricardo P; Combes, Vincent; Chao, Yi; James, Corinne; Palma, Elbio D; Saraceno, Martin; Strub, P Ted

    2014-11-01

    Satellite-derived sea surface salinity (SSS) data from Aquarius and SMOS are used to study the shelf-open ocean exchanges in the western South Atlantic near 35°S. Away from the tropics, these exchanges cause the largest SSS variability throughout the South Atlantic. The data reveal a well-defined seasonal pattern of SSS during the analyzed period and of the location of the export of low-salinity shelf waters. In spring and summer, low-salinity waters over the shelf expand offshore and are transferred to the open ocean primarily southeast of the river mouth (from 36°S to 37°30'S). In contrast, in fall and winter, low-salinity waters extend along a coastal plume and the export path to the open ocean distributes along the offshore edge of the plume. The strong seasonal SSS pattern is modulated by the seasonality of the along-shelf component of the wind stress over the shelf. However, the combined analysis of SSS, satellite-derived sea surface elevation and surface velocity data suggest that the precise location of the export of shelf waters depends on offshore circulation patterns, such as the location of the Brazil Malvinas Confluence and mesoscale eddies and meanders of the Brazil Current. The satellite data indicate that in summer, mixtures of low-salinity shelf waters are swiftly driven toward the ocean interior along the axis of the Brazil/Malvinas Confluence. In winter, episodic wind reversals force the low-salinity coastal plume offshore where they mix with tropical waters within the Brazil Current and create a warmer variety of low-salinity waters in the open ocean. Satellite salinity sensors capture low-salinity detrainment events from shelves SW Atlantic low-salinity detrainments cause highest basin-scale variability In summer low-salinity detrainments cause extended low-salinity anomalies.

  6. Higher number of pentosidine cross-links induced by ribose does not alter tissue stiffness of cancellous bone

    Energy Technology Data Exchange (ETDEWEB)

    Willems, Nop M.B.K., E-mail: n.willems@acta.nl [Dept. of Orthodontics, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University, Gustav Mahlerlaan 3004, 1081 LA Amsterdam (Netherlands); Dept. of Oral Cell Biology and Functional Anatomy, MOVE Research Institute, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University, Gustav Mahlerlaan 3004, 1081 LA Amsterdam (Netherlands); Langenbach, Geerling E.J. [Dept. of Oral Cell Biology and Functional Anatomy, MOVE Research Institute, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University, Gustav Mahlerlaan 3004, 1081 LA Amsterdam (Netherlands); Stoop, Reinout [Dept. of Metabolic Health Research, TNO, P.O. Box 2215, 2301 CE Leiden (Netherlands); Toonder, Jaap M.J. den [Dept. of Mechanical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Mulder, Lars [Dept. of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); Zentner, Andrej [Dept. of Orthodontics, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University, Gustav Mahlerlaan 3004, 1081 LA Amsterdam (Netherlands); Everts, Vincent [Dept. of Oral Cell Biology and Functional Anatomy, MOVE Research Institute, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University, Gustav Mahlerlaan 3004, 1081 LA Amsterdam (Netherlands)

    2014-09-01

    The role of mature collagen cross-links, pentosidine (Pen) cross-links in particular, in the micromechanical properties of cancellous bone is unknown. The aim of this study was to examine nonenzymatic glycation effects on tissue stiffness of demineralized and non-demineralized cancellous bone. A total of 60 bone samples were derived from mandibular condyles of six pigs, and assigned to either control or experimental groups. Experimental handling included incubation in phosphate buffered saline alone or with 0.2 M ribose at 37 °C for 15 days and, in some of the samples, subsequent complete demineralization of the sample surface using 8% EDTA. Before and after experimental handling, bone microarchitecture and tissue mineral density were examined by means of microcomputed tomography. After experimental handling, the collagen content and the number of Pen, hydroxylysylpyridinoline (HP), and lysylpyridinoline (LP) cross-links were estimated using HPLC, and tissue stiffness was assessed by means of nanoindentation. Ribose treatment caused an up to 300-fold increase in the number of Pen cross-links compared to nonribose-incubated controls, but did not affect the number of HP and LP cross-links. This increase in the number of Pen cross-links had no influence on tissue stiffness of both demineralized and nondemineralized bone samples. These findings suggest that Pen cross-links do not play a significant role in bone tissue stiffness. - Highlights: • The assessment of effects of glycation in bone using HPLC, microCT, and nanoindentation • Ribose incubation: 300‐fold increase in the number of pentosidine cross-links • 300‐fold increase in the number of pentosidine cross-links: no changes in bone tissue stiffness.

  7. Study of sorption behavior, shelf life and colour kinetics of vacuum puffed honey powder at accelerated storage conditions.

    Science.gov (United States)

    Devi, K Deepika; Paul, Sanjib Kr; Sahu, Jatindra K

    2016-05-01

    In the study, the storage life of vacuum puffed honey powder at accelerated storage environment (90 % relative humidity and 36 °C) was computed by determining the sticky-point moisture content as the critical parameter of the honey powder. The value of monolayer moisture content in the GAB model was calculated to be 0.081 kg water/kg dry solids by fitting water activity and moisture sorption data. Shelf life of the honey powder was predicted to be 222 days when the powder was packaged in aluminum foil-laminated polyethylene pouches with permeability value of 5.427X10(-8) kg/m(2)//day/Pa. Actual shelf life of honey powder was experimentally determined as 189 days and analysis of mean relative percent derivation modulus (Rd) and root mean square (RMS) established the accuracy and acceptability of the technique for the prediction of shelf life of honey powder. Overall colour deviation pattern followed first order reaction kinetics with rate constant (k1) as 0.037 day(-1). This study revealed overall colour difference of 18.1 till the end of shelf life with drastic change during initial storage period.

  8. Polypeptide nanogels with hydrophobic moieties in the cross-linked ionic cores: Synthesis, characterization and implications for anticancer drug delivery

    Science.gov (United States)

    Kim, Jong Oh; Oberoi, Hardeep S.; Desale, Swapnil; Kabanov, Alexander V.; Bronich, Tatiana K.

    2014-01-01

    Polymer nanogels have gained considerable attention as a potential platform for drug delivery applications. Here we describe the design and synthesis of novel polypeptide-based nanogels with hydrophobic moieties in the cross-linked ionic cores. Diblock copolymer, poly(ethylene glycol)-b-poly(L-glutamic acid), hydrophobically modified with L-phenylalanine methyl ester moieties was used for controlled template synthesis of nanogels with small size (ca. 70 nm in diameter) and narrow particle size distribution. Steady-state and time-resolved fluorescence studies using coumarin C153 indicated the existence of hydrophobic domains in the ionic cores of the nanogels. Stable doxorubicin-loaded nanogels were prepared at high drug capacity (30 w/w%). We show that nanogels are enzymatically-degradable leading to accelerated drug release under simulated lysosomal acidic pH. Furthermore, we demonstrate that the nanogel-based formulation of doxorubicin is well tolerated and exhibit an improved antitumor activity compared to a free doxorubicin in an ovarian tumor xenograft mouse model. Our results signify the point to a potential of these biodegradable nanogels as attractive carriers for delivery of chemotherapeutics. PMID:23998716

  9. Supermacroporous chemically cross-linked poly(aspartic acid) hydrogels.

    Science.gov (United States)

    Gyarmati, Benjámin; Mészár, E Zsuzsanna; Kiss, Lóránd; Deli, Mária A; László, Krisztina; Szilágyi, András

    2015-08-01

    Chemically cross-linked poly(aspartic acid) (PASP) gels were prepared by a solid-liquid phase separation technique, cryogelation, to achieve a supermacroporous interconnected pore structure. The precursor polymer of PASP, polysuccinimide (PSI) was cross-linked below the freezing point of the solvent and the forming crystals acted as templates for the pores. Dimethyl sulfoxide was chosen as solvent instead of the more commonly used water. Thus larger temperatures could be utilized for the preparation and the drawback of increase in specific volume of water upon freezing could be eliminated. The morphology of the hydrogels was characterized by scanning electron microscopy and interconnectivity of the pores was proven by the small flow resistance of the gels. Compression tests also confirmed the interconnected porous structure and the complete re-swelling and shape recovery of the supermacroporous PASP hydrogels. The prepared hydrogels are of interest for several biomedical applications as scaffolding materials because of their cytocompatibility, controllable morphology and pH-responsive character. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  10. Collagen Cross-Linking: Current Status and Future Directions

    Directory of Open Access Journals (Sweden)

    Marine Hovakimyan

    2012-01-01

    Full Text Available Collagen cross-linking (CXL using UVA light and riboflavin (vitamin B2 was introduced as a clinical application to stabilize the cornea by inducing cross-links within and between collagen fibers. CXL has been investigated extensively and has been shown clinically to arrest the progression of keratoconic or post-LASIK ectasia. With its minimal cost, simplicity, and proven positive clinical outcome, CXL can be regarded as a useful approach to reduce the number of penetrating keratoplasties performed. Small case series have also indicated that CXL is beneficial in corneal edema by reducing stromal swelling behavior and in keratitis by inhibiting pathogen growth. Despite these encouraging results, CXL remains a relatively new method that is potentially associated with complications. Aspects such as side effects and recurrence rates have still to be elucidated. In light of the growing interest in CXL, our paper summarizes present knowledge about this promising approach. We have intentionally endeavored to include the more relevant studies from the recent literature to provide an overview of the current status of CXL.

  11. Cross-linking e segmento de anel corneano intraestromal

    Directory of Open Access Journals (Sweden)

    Adimara da Candelaria Renesto

    2011-02-01

    Full Text Available O cross-linking corneano é um procedimento usado para a estabilização mecânica e aumento da rigidez corneana em pacientes com ceratocone (reduzindo a possibilidade de progressão, e também em processos inflamatórios de afinamento corneano. Os segmentos de anéis corneanos intraestromais têm como princípio o aplanamento central da córnea. Inicialmente utilizados para correção de baixa miopia, a principal indicação atual é em pacientes com ceratocone, para melhorar a acuidade visual não corrigida, a acuidade visual corrigida e permitir uma melhor tolerância ao uso de lentes de contato como também retardar a necessidade de um transplante de córnea. O objetivo deste artigo é revisar algumas publicações relacionadas ao cross-linking corneano e à inserção do segmento de anel intraestromal, apresentando suas indicações, resultados e complicações relatadas até o momento.

  12. Kinetics of the esterification of active pharmaceutical ingredients containing carboxylic Acid functionality in polyethylene glycol

    DEFF Research Database (Denmark)

    Schou-Pedersen, Anne Marie V; Hansen, Steen Honoré; Moesgaard, Birthe

    2014-01-01

    Polyethylene glycols (PEGs) are attractive as excipients in the manufacture of drug products because they are water soluble and poorly immunogenic. They are used in various pharmaceutical preparations. However, because of their terminal hydroxyl groups, PEGs can participate in esterification reac......, it is important to be aware of this drug-excipient interaction, as it can reduce the shelf-life of a low-average molecular weight PEG formulation considerably. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 103:2424-2433, 2014....

  13. In vitro cross-linking of elastin peptides and molecular characterization of the resultant biomaterials

    DEFF Research Database (Denmark)

    Heinz, Andrea; Ruttkies, Christoph K H; Jahreis, Günther

    2013-01-01

    -link desmosine or isodesmosine was unexpected, however, could be confirmed by tandem mass spectrometry and molecular dynamics simulations. CONCLUSIONS: The study demonstrated that it is possible to produce biopolymers containing polyfunctional cross-links characteristic of mature elastin from small elastin......BACKGROUND: Elastin is a vital protein and the major component of elastic fibers which provides resilience to many vertebrate tissues. Elastin's structure and function are influenced by extensive cross-linking, however, the cross-linking pattern is still unknown. METHODS: Small peptides containing...... and the insoluble polymers, after digestion with pancreatic elastase or trypsin, were furthermore comprehensively characterized on the molecular level using MALDI-TOF/TOF mass spectrometry. RESULTS: MS(2) data was used to develop the software PolyLinX, which is able to sequence not only linear and bifunctionally...

  14. Epithelium-on photorefractive intrastromal cross-linking (PiXL for reduction of low myopia

    Directory of Open Access Journals (Sweden)

    Lim WK

    2017-06-01

    Full Text Available Wee Kiak Lim,1,2 Zhi Da Soh,1 Harold Kah Yen Choi,1 Julian Thiam Siew Theng1,3 1Eagle Eye Centre, Mount Alvernia Hospital, 2Department of Ophthalmology, Tan Tock Seng Hospital, 3Department of Ophthalmology, Khoo Teck Puat Hospital, Singapore Purpose: To report the 9–12-month outcomes of a novel procedure for reduction of low myopia through epithelium-on photorefractive intrastromal cross-linking (PiXL with customized control of topographic distribution of ultraviolet (UV-fluence. Method: Myopic patients with normal (non-ectatic corneas underwent the PiXL procedure for reduction of low myopia. PiXL treatments were delivered through selective application of UVA light based on the refractive error of each patient. Clinical evaluation included safety (corrected distance visual acuity, endothelial cell count, central corneal thickness, anterior ocular health and efficacy (uncorrected distance visual acuity, manifest refraction, K-mean examinations. In addition, a patient satisfaction survey was conducted at 9 months post-procedure to evaluate patients’ subjective experience with the procedure. Results: Fourteen myopic eyes (mean manifest refraction spherical equivalent –1.62±0.6D; range –0.75 to –2.65D of 8 subjects (mean age 30 years old; range 24–51 years old were enrolled in the study. At 12 months post-procedure, a mean manifest refraction spherical equivalent reduction of 0.72±0.43D (P<0.001 was observed, with a corresponding gain in uncorrected visual acuity of 0.25 logMAR and mean K-mean flattening of 0.47±0.46D. All patients achieved best corrected visual acuity of 20/20 or better from 1 month onward. There were no cases of ocular infection or secondary changes to the crystalline lens and retina due to UV exposure, while transient corneal haze subsided gradually. Conclusion: The epithelium-on PiXL procedure was safe and effective in reducing myopic refractive error in this study with up to 12 months follow-up. Early results of

  15. Sodium tripolyphosphate cross-linked chitosan based sensor for enhacing sensing properties towards acetone

    Science.gov (United States)

    Nasution, T. I.; Asrosa, R.; Nainggolan, I.; Balyan, M.; Indah, R.; Wahyudi, A.

    2018-02-01

    In this report, sensing properties of sodium tripolyphosphate (TPP) cross-linked chitosan based sensor has been successfully enhanced towards acetone. Chitosan solutions were cross-linked with sodium TPP in variation of 0.1%, 0.5%, 1% and 1.5% w/v, respectively. The sensors were fabricated in film form using an electrochemical deposition method. The sensing properties of the sensors were observed by exposing the pure chitosan and sodium TPP cross-linked chitosan sensors towards acetone concentrations of 5, 10, 50, 100 and 200 ppm. The measurement results revealed that the maximum response in output voltage value of pure chitosan sensor was 0.35 V while sodium TPP crosslinked chitosan sensors were above 0.35 V towards 5 ppm acetone concentration. When the sensors were exposed towards acetone concentration of 200 ppm, the maximum response of pure chitosan was 0.45 V while sodium TPP crosslinked chitosan sensors were above 0.45 V. Amongst the variation of sodium TPP, the maximum response of 1% sodium TPP was the highest since the maximum response was 0.4 V and 0.6 V towards 5 ppm and 200 ppm acetone concentration, respectively. While the maximum responses of other sodium TPP concentrations were under 0.4 V and 0.6 V towards 5 ppm and 200 ppm acetone concentration. Moreover, 1% sodium TPP cross-linked chitosan based sensor showed good reproducibility and outstanding lifetime. Therefore, 1% sodium TPP cross-linked chitosan based sensor has exhibited remarkable sensing properties as a novel acetone sensor.

  16. Low-Temperature Cross-Linking of PEDOT:PSS Films Using Divinylsulfone.

    Science.gov (United States)

    Mantione, Daniele; Del Agua, Isabel; Schaafsma, Wandert; ElMahmoudy, Mohammed; Uguz, Ilke; Sanchez-Sanchez, Ana; Sardon, Haritz; Castro, Begoña; Malliaras, George G; Mecerreyes, David

    2017-05-31

    Recent interest in bioelectronics has prompted the exploration of properties of conducting polymer films at the interface with biological milieus. Poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) from a commercially available source has been used as a model system for these studies. Different cross-linking schemes have been used to stabilize films of this material against delamination and redispersion, but the cost is a decrease in the electrical conductivity and/or additional heat treatment. Here we introduce divinylsulfone (DVS) as a new cross-linker for PEDOT:PSS. Thanks to the higher reactiveness of the vinyl groups of DVS, the cross-linking can be performed at room temperature. In addition, DVS does not reduce electronic conductivity of PEDOT:PSS but rather increases it by acting as a secondary dopant. Cell culture studies show that PEDOT:PSS:DVS films are cytocompatible and support neuroregeneration. As an example, we showed that this material improved the transconductance value and stability of an organic electrochemical transistor (OECT) device. These results open the way for the utilization of DVS as an effective cross-linker for PEDOT:PSS in bioelectronics applications.

  17. Crosslines, fluorophores in the AGE-related cross-linked proteins.

    Science.gov (United States)

    Ienaga, K; Nakamura, K; Hochi, T; Nakazawa, Y; Fukunaga, Y; Kakita, H; Nakano, K

    1995-01-01

    We can summarize our results as follows: (1) A pair of fluorescent crosslines were isolated from the Maillard reaction mixture; (2) AGE-proteins contained crossline-like structures, and (3) crossline-like immunoreactivities were accumulated in renal tissues of diabetic rats. From these results we concluded that fluorophores in AGE proteins have crossline-like structures and we had the first indication that XLs could be markers for renal disorders.

  18. Shelf life prediction of radiation sterilized polymeric materials

    International Nuclear Information System (INIS)

    Sandford, Craig; Woo, Lecon

    1988-01-01

    The functional properties of many polymers employed in medical disposables are unaffected by sterilizing doses of ionizing radiation. However, some materials (PVC, polypropylene, cellulosics, etc.) undergo undesirable changes which continue to occur for the shelf life of the product. In many cases, conventional accelerated aging techniques do not accurately predict the real time properties of the materials. As real time aging is not generally practical, it has become necessary to develop accelerated aging techniques which can predict the functional properties of a material for the shelf life of the product. This presentation will address issues involved in developing these tests. Real time physical property data is compared to data generated by various acceleration methods. (author)

  19. Shelf life of pie caps with biodegradable films as spacers

    Directory of Open Access Journals (Sweden)

    Daniela Verónica Escobar Gianni

    2013-01-01

    Full Text Available Commonly pie caps at market use polyethylene films as spacers between them. This paper studies the conventional spacers replacement with edible and biodegradable films made with whey protein isolate (WPI and potassium sorbate as a preservative. Besides facilitating the separation of pie caps, with this application is intended to increase their shelf life. The films made by the compression molding method were used as spacers in pie caps without preservative in their formula (A and with preservative (B and they were compared with conventional polyethylene spacers (C. During four months, monthly sensory, microbiological and physicochemical (humidity evaluations were done on the pie caps, together with humidity and solubility evaluations of the films. None of the samples showed microbiological or sensory deterioration. The sensory attributes showed no or slight difference in study time. Between samples the differences were minor: the best scores were for sample A in color, sample C in flavor, and samples B and C in texture and overall liking. The edible films have an interesting potential for this application, although studies in disguise the flavor of serum should be done.

  20. Scleral lens tolerance after corneal cross-linking for keratoconus

    NARCIS (Netherlands)

    Visser, Esther Simone; Soeters, Nienke; Tahzib, Nayyirih G.

    2015-01-01

    Purpose. Subjective and objective evaluation of scleral lens tolerance and fitting before and after corneal cross-linking (CXL) for progressive keratoconus. Methods. In this prospective cohort, evaluations were made of 18 unilateral eyes in patients who underwent CXL and had been wearing scleral

  1. Mechanocatalytic polymerization and cross-linking in a polymeric matrix

    NARCIS (Netherlands)

    Jakobs, R.T.M.; Ma, Shuang; Sijbesma, R.P.

    2013-01-01

    A latent olefin metathesis catalyst, bearing two polymeric NHC ligands, was embedded in a semicrystalline polymer matrix containing cyclic olefins. The catalyst was activated by straining the solid material under compression, resulting in polymerization and cross-linking reactions of the monomers in

  2. Functionalisation of cross-linked polyethylenimine for the removal of ...

    African Journals Online (AJOL)

    ... and describe the experimental data. The thermodynamic study of the adsorption process indicated high activation energies (55.91 kJ mol-1) which confirms chemisorption as a mechanism of interaction between As and PCPEI. Keywords: Adsorption; arsenic; phosphonated cross-linked polyethylenimine, functionalisation ...

  3. Analysis of glycation induced protein cross-linking inhibitory effects of some antidiabetic plants and spices.

    Science.gov (United States)

    Perera, Handunge Kumudu Irani; Handuwalage, Charith Sandaruwan

    2015-06-09

    Protein cross-linking which occurs towards the latter part of protein glycation is implicated in the development of chronic diabetic complications. Glycation induced protein cross-linking inhibitory effects of nine antidiabetic plants and three spices were evaluated in this study using a novel, simple, electrophoresis based method. Methanol extracts of thirteen plants including nine antidiabetic plants and three spices were used. Lysozyme and fructose were incubated at 37 °C in the presence or absence of different concentrations of plant extracts up to 31 days. Standard glycation inhibitor aminoguanidine and other appropriate controls were included. A recently established sodium dodecyl polyacrylamide gel electrophoresis (SDS-PAGE) method was used to detect the products of protein cross-linking in the incubation mixtures. High molecular weight protein products representing the dimer, trimer and tetramer of lysozyme were detected in the presence of fructose. Among the nine antidiabetic plants, seven showed glycation induced protein cross-linking inhibitory effects namely Ficus racemosa (FR) stem bark, Gymnema sylvestre (GS) leaves, Musa paradisiaca (MP) yam, Phyllanthus debilis (PD) whole plant, Phyllanthus emblica (PE) fruit, Pterocarpus marsupium (PM) latex and Tinospora cordifolia (TC) leaves. Inhibition observed with Coccinia grandis (CG) leaves and Strychnos potatorum (SP) seeds were much low. Leaves of Gymnema lactiferum (GL), the plant without known antidiabetic effects showed the lowest inhibition. All three spices namely Coriandrum sativum (CS) seeds, Cinnamomum zeylanicum (CZ) bark and Syzygium aromaticum (SA) flower buds showed cross-link inhibitory effects with higher effects in CS and SA. PD, PE, PM, CS and SA showed almost complete inhibition on the formation of cross-linking with 25 μg/ml extracts. Methanol extracts of PD, PE, PM, CS and SA have shown promising inhibitory effects on glycation induced protein cross-linking.

  4. Entropic benefit of a cross-link in protein association.

    Science.gov (United States)

    Zaman, Muhammad H; Berry, R Stephen; Sosnick, Tobin R

    2002-08-01

    We introduce a method to estimate the loss of configurational entropy upon insertion of a cross-link to a dimeric system. First, a clear distinction is established between the loss of entropy upon tethering and binding, two quantities that are often considered to be equivalent. By comparing the probability distribution of the center-to-center distances for untethered and cross-linked versions, we are able to calculate the loss of translational entropy upon cross-linking. The distribution function for the untethered helices is calculated from the probability that a given helix is closer to its partner than to all other helices, the "Nearest Neighbor" method. This method requires no assumptions about the nature of the solvent, and hence resolves difficulties normally associated with calculations for systems in liquids. Analysis of the restriction of angular freedom upon tethering indicates that the loss of rotational entropy is negligible. The method is applied in the context of the folding of a ten turn helical coiled coil with the tether modeled as a Gaussian chain or a flexible amino acid chain. After correcting for loop closure entropy in the docked state, we estimate the introduction of a six-residue tether in the coiled coil results in an effective concentration of the chain to be about 4 or 100 mM, depending upon whether the helices are denatured or pre-folded prior to their association. Thus, tethering results in significant stabilization for systems with millimolar or stronger dissociation constants. Copyright 2002 Wiley-Liss, Inc.

  5. Effect of pore size and cross-linking of a novel collagen-elastin dermal substitute on wound healing.

    Science.gov (United States)

    Boekema, Bouke K H L; Vlig, Marcel; Olde Damink, Leon; Middelkoop, Esther; Eummelen, Lizette; Bühren, Anne V; Ulrich, Magda M W

    2014-02-01

    Collagen-elastin (CE) scaffolds are frequently used for dermal replacement in the treatment of full-thickness skin defects such as burn wounds. But little is known about the optimal pore size and level of cross-linking. Different formulations of dermal substitutes with unidirectional pores were tested in porcine full-thickness wounds in combination with autologous split skin mesh grafts (SSG). Effect on wound healing was evaluated both macro- and microscopically. CE scaffolds with a pore size of 80 or 100 μm resulted in good wound healing after one-stage grafting. Application of scaffolds with a larger average pore size (120 μm) resulted in more myofibroblasts and more foreign body giant cells (FBGC). Moderate crosslinking impaired wound healing as it resulted in more wound contraction, more FBGC and increased epidermal thickness compared to no cross-linking. In addition, take rate and redness were negatively affected compared to SSG only. Vascularization and the number of myofibroblasts were not affected by cross-linking. Surprisingly, stability of cross-linked scaffolds was not increased in the wound environment, in contrast to in vitro results. Cross-linking reduced the proliferation of fibroblasts in vitro, which might explain the reduced clinical outcome. The non-cross-linked CE substitute with unidirectional pores allowed one-stage grafting of SSG, resulting in good wound healing. In addition, only a very mild foreign body reaction was observed. Cross-linking of CE scaffolds negatively affected wound healing on several important parameters. The optimal non-cross-linked CE substitute is a promising candidate for future clinical evaluation.

  6. Electrode-Impregnable and Cross-Linkable Poly(ethylene oxide)-Poly(propylene oxide)-Poly(ethylene oxide) Triblock Polymer Electrolytes with High Ionic Conductivity and a Large Voltage Window for Flexible Solid-State Supercapacitors.

    Science.gov (United States)

    Han, Jae Hee; Lee, Jang Yong; Suh, Dong Hack; Hong, Young Taik; Kim, Tae-Ho

    2017-10-04

    We present cross-linkable precursor-type gel polymer electrolytes (GPEs) that have large ionic liquid uptake capability, can easily penetrate electrodes, have high ion conductivity, and are mechanically strong as high-performance, flexible all-solid-state supercapacitors (SC). Our polymer precursors feature a hydrophilic-hydrophobic poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock main-chain structure and trifunctional silane end groups that can be multi-cross-linked with each other through a sol-gel process. The cross-linked solid-state electrolyte film with moderate IL content (200 wt %) shows a well-balanced combination of excellent ionic conductivity (5.0 × 10 -3 S cm -1 ) and good mechanical stability (maximum strain = 194%). Moreover, our polymer electrolytes have various advantages including high thermal stability (decomposition temperature > 330 °C) and the capability to impregnate electrodes to form an excellent electrode-electrolyte interface due to the very low viscosity of the precursors. By assembling our GPE-impregnated electrodes and solid-state GPE film, we demonstrate an all-solid-state SC that can operate at 3 V and provides an improved specific capacitance (112.3 F g -1 at 0.1 A g -1 ), better rate capability (64% capacity retention until 20 A g -1 ), and excellent cycle stability (95% capacitance decay over 10 000 charge/discharge cycles) compared with those of a reference SC using a conventional PEO electrolyte. Finally, flexible SCs with a high energy density (22.6 W h kg -1 at 1 A g -1 ) and an excellent flexibility (>93% capacitance retention after 5000 bending cycles) can successfully be obtained.

  7. Tribology of alternative bearings.

    Science.gov (United States)

    Fisher, John; Jin, Zhongmin; Tipper, Joanne; Stone, Martin; Ingham, Eileen

    2006-12-01

    The tribological performance and biological activity of the wear debris produced has been compared for highly cross-linked polyethylene, ceramic-on-ceramic, metal-on-metal, and modified metal bearings in a series of in vitro studies from a single laboratory. The functional lifetime demand of young and active patients is 10-fold greater than the estimated functional lifetime of traditional polyethylene. There is considerable interest in using larger diameter heads in these high demand patients. Highly cross-linked polyethylene show a four-fold reduction in functional biological activity. Ceramic-on-ceramic bearings have the lowest wear rates and least reactive wear debris. The functional biological activity is 20-fold lower than with highly cross-linked polyethylene. Hence, ceramic-on-ceramic bearings address the tribological lifetime demand of highly active patients. Metal-on-metal bearings have substantially lower wear rates than highly cross-linked polyethylene and wear decreases with head diameter. Bedding in wear is also lower with reduced radial clearance. Differential hardness ceramic-on-metal bearings and the application of ceramic-like coatings reduce metal wear and ion levels.

  8. Glacigenic landforms and sediments of the Western Irish Shelf

    Science.gov (United States)

    McCarron, Stephen; Monteys, Xavier; Toms, Lee

    2013-04-01

    Vibrocoring of possible glacigenic landforms identified from high resolution bathymetric coverage of the Irish Shelf by the Irish National Seabed Survey (INSS) has provided several clusters of short (<3m) cores that, due to a regional post-glacial erosional event, comprise last glacial age stratigraphies. In addition, new shallow seismic data and sedimentological information from across the Western Irish Shelf provide new insights into aspects of the nature, timing and pattern of shelf occupation by grounded lobate extensions of the last Irish Ice Sheet. Restricted chronological control of deglacial sequences in several cores indicates that northern parts of the western mid-shelf (south of a prominent outer Donegal Bay ridge) were ice free by ~24 ka B.P., and that ice had also probably retreated from outer shelf positions (as far west as the Porcupine Bank) at or before this time.

  9. Rheological Behavior, Granule Size Distribution and Differential Scanning Calorimetry of Cross-Linked Banana (Musa paradisiaca) Starch.

    Science.gov (United States)

    Núñez-Santiago, María C.; Maristany-Cáceres, Amira J.; Suárez, Francisco J. García; Bello-Pérez, Arturo

    2008-07-01

    Rheological behavior at 60 °C, granule size distribution and Differential Scanning Calorimetry (DSC) tests were employed to study the effect of diverse reaction conditions: adipic acid concentration, pH and temperature during cross-linking of banana (Musa paradisiaca) starch. These properties were determined in native banana starch pastes for the purpose of comparison. Rheological behavior from pastes of cross-linked starch at 60 °C did not show hysteresis, probably due the cross-linkage of starch that avoided disruption of granules, elsewhere, native starch showed hysteresis in a thixotropic loop. All pastes exhibited non-Newtonian shear thinning behavior. In all cases, size distribution showed a decrease in the median diameter in cross-linked starches. This condition produces a decrease in swelling capacity of cross-linked starch. The median diameter decreased with an increase of acid adipic concentration; however, an increase of pH and Temperature produced an increase in this variable. Finally, an increase in gelatinization temperature and entalphy (ΔH) were observed as an effect of cross-linkage. An increase in acid adipic concentration produced an increase in Tonset and a decrease in ΔH. pH and temperature. The cross-linked of banana starch produced granules more resistant during the pasting procedure.

  10. An electron microscopic study of the photochemical cross-linking of DNA in guinea pig epidermis by psoralen derivatives

    International Nuclear Information System (INIS)

    Cech, T.; Pathak, M.A.; Biswas, R.K.

    1979-01-01

    Albino guinea pigs were treated with psoralen derivatives plus 320-400 nm ultraviolet radiation, and DNA was extracted from their epidermis. The DNA was assayed for the presence of interstrand cross-links by standard denaturation-renaturation assays and by a new technique, electron microscopy of the DNA under totally denaturing conditions. The latter method allows individual cross-links to be directly observed and counted. When either 4,5',8-trimethylpsoralen or 8-methoxypsoralen was applied topically to the skin (8-20 μg/cm 2 ) or administered orally (10-12 mg/kg body weight), followed by exposure to 320-400 nm ultraviolet radiation, most of the epidermal DNA was found to contain a high frequency of cross-links. For example, oral or topical trimethylpsoralen treatment gave an average of one cross-link per 250 nucleotide pairs or about 3 . 10 5 cross-links per guinea pig chromosome. When the dose of either drug was decreased 20-fold to the level used in the clinical treatment of psoriasis, however, no cross-links could be detected in the epidermal DNA. The electron microscopic assay is sensitive enough that one can put an upper limit of 1 cross-link per 10 6 nucleotide pairs (80 cross-links per chromosome) for the low dose studies. The significance of these findings to the understanding of the effectiveness of psoralens in psoriasis therapy is discussed. (Auth.)

  11. Shelf evolution along a transpressive transform margin, Santa Barbara Channel, California

    Science.gov (United States)

    Johnson, Samuel Y.; Hartwell, Stephen; Sorlien, Christopher C.; Dartnell, Peter; Ritchie, Andrew C.

    2017-01-01

    High-resolution bathymetric and seismic reflection data provide new insights for understanding the post–Last Glacial Maximum (LGM, ca. 21 ka) evolution of the ∼120-km-long Santa Barbara shelf, located within a transpressive segment of the transform continental margin of western North America. The goal is to determine how rising sea level, sediment supply, and tectonics combine to control shelf geomorphology and history. Morpho­logic, stratigraphic, and structural data highlight regional variability and support division of the shelf into three domains. (1) The eastern Santa Barbara shelf is south of and in the hanging wall of the blind south-dipping Oak Ridge fault. The broad gently dipping shelf has a convex-upward shape resulting from thick post-LGM sediment (mean = 24.7 m) derived from the Santa Clara River. (2) The ∼5–8-km-wide Ventura Basin obliquely crosses the shelf and forms an asymmetric trough with thick post-LGM sediment fill (mean = 30.4 m) derived from the Santa Clara and Ventura Rivers. The basin is between and in the footwalls of the Oak Ridge fault to the south and the blind north-dipping Pitas Point fault to the north. (3) The central and western Santa Barbara shelf is located north of and in the hanging wall of the North Channel–Pitas Point fault system. The concave-up shape of the shelf results from folding, marine erosion, and the relative lack of post-LGM sediment cover (mean = 3.8 m). Sediment is derived from small steep coastal watersheds and largely stored in the Gaviota bar and other nearshore mouth bars. Three distinct upper slope morphologies result from a mix of progradation and submarine landsliding.Ages and rates of deformation are derived from a local sea-level-rise model that incorporates an inferred LGM shoreline angle and the LGM wave-cut platform. Post-LGM slip rates on the offshore Oak Ridge fault are a mini­mum of 0.7 ± 0.1 mm/yr. Slip rates on the Pitas Point fault system are a minimum of 2.3 ± 0.3 mm

  12. Hydrogen peroxide and ferulic acid-mediated oxidative cross-linking ...

    African Journals Online (AJOL)

    STORAGESEVER

    2009-12-15

    Dec 15, 2009 ... G250 in a 4.5:4.5:1 (v/v) mixture of deionized water, methanol and glacial acetic ... mixture of 1:1:8 (v/v) methanol, glacial acetic acid and deionized water until the ..... Cross-linking of tyrosine-containing peptides by hydrogen.

  13. Electron beam induced modifications in flexible biaxially oriented polyethylene terephthalate sheets: Improved mechanical and electrical properties

    Energy Technology Data Exchange (ETDEWEB)

    Chaudhary, N. [Accelerator & Pulse Power Division, Bhabha Atomic Research Centre, Mumbai, 400 085 (India); Koiry, S.P. [Technical Physics Division, Bhabha Atomic Research Centre, Mumbai, 400 085 (India); Singh, A., E-mail: asb_barc@yahoo.com [Technical Physics Division, Bhabha Atomic Research Centre, Mumbai, 400 085 (India); Tillu, A.R. [Accelerator & Pulse Power Division, Bhabha Atomic Research Centre, Mumbai, 400 085 (India); Jha, P.; Samanta, S.; Debnath, A.K. [Technical Physics Division, Bhabha Atomic Research Centre, Mumbai, 400 085 (India); Aswal, D.K., E-mail: dkaswal@yahoo.com [Technical Physics Division, Bhabha Atomic Research Centre, Mumbai, 400 085 (India); Mondal, R.K. [Radiation Technology Development Division, Bhabha Atomic Research Centre, Mumbai, 400 085 (India); Acharya, S.; Mittal, K.C. [Accelerator & Pulse Power Division, Bhabha Atomic Research Centre, Mumbai, 400 085 (India)

    2017-03-01

    In the present work, we have studied the effects of electron beam irradiation (with dose ranging from 2 to 32 kGy) on mechanical and electrical properties of biaxially oriented polyethylene terephthalate (BOPET) sheets. The sol-gel analysis, Fourier transformation infra-red (FTIR), X-ray photoelectron spectroscopy (XPS) characterizations of the irradiated BOPET sheets suggest partial cross-linking of PET chains through the diethylene glycol (DEG). The mechanical properties of BOPET, such as, tensile strength, Young's modulus and electrical resistivity shows improvement with increasing dose and saturate for doses >10 kGy. The improved mechanical properties and high electrical resistivity of electron beam modified BOPET sheets may have additional advantages in applications, such as, packaging materials for food irradiation, medical product sterilization and electronic industries. - Graphical abstract: Irradiation of BOPET by electron beam leads to the formation of diethylene glycol that crosslink's the PET chains, resulting in improved mechanical properties and enhanced electrical resistivity. - Highlights: • BOPET exhibit improved tensile strength/Young's modulus after e-beam exposure. • Electrical resistivity of BOPET increases after e-beam exposure. • Cross-linking of PET chains through diethylene glycol was observed after e-beam exposure.

  14. Biomimetic porous high-density polyethylene/polyethylene- grafted-maleic anhydride scaffold with improved in vitro cytocompatibility.

    Science.gov (United States)

    Sharma, Swati; Bhaskar, Nitu; Bose, Surjasarathi; Basu, Bikaramjit

    2018-05-01

    A major challenge for tissue engineering is to design and to develop a porous biocompatible scaffold, which can mimic the properties of natural tissue. As a first step towards this endeavour, we here demonstrate a distinct methodology in biomimetically synthesized porous high-density polyethylene scaffolds. Co-extrusion approach was adopted, whereby high-density polyethylene was melt mixed with polyethylene oxide to form an immiscible binary blend. Selective dissolution of polyethylene oxide from the biphasic system revealed droplet-matrix-type morphology. An attempt to stabilize such morphology against thermal and shear effects was made by the addition of polyethylene- grafted-maleic anhydride as a compatibilizer. A maximum ultimate tensile strength of 7 MPa and elastic modulus of 370 MPa were displayed by the high-density polyethylene/polyethylene oxide binary blend with 5% maleated polyethylene during uniaxial tensile loading. The cell culture experiments with murine myoblast C2C12 cell line indicated that compared to neat high-density polyethylene and high-density polyethylene/polyethylene oxide, the high-density polyethylene/polyethylene oxide with 5% polyethylene- grafted-maleic anhydride scaffold significantly increased muscle cell attachment and proliferation with distinct elongated threadlike appearance and highly stained nuclei, in vitro. This has been partly attributed to the change in surface wettability property with a reduced contact angle (∼72°) for 5% PE- g-MA blends. These findings suggest that the high-density polyethylene/polyethylene oxide with 5% polyethylene- grafted-maleic anhydride can be treated as a cell growth substrate in bioengineering applications.

  15. Reorientational motion of a cross-link junction in a poly(dimethylsiloxane) network measured by time-resolved fluorescence depolarization

    International Nuclear Information System (INIS)

    Stein, A.D.; Hoffman, D.A.; Frank, C.W.; Fayer, M.D.

    1992-01-01

    The reorientational dynamics of a cross-link junction in poly(dimethylsiloxane) networks, measured by the fluorescence anisotropy decay of a chromophore tagged to the cross-link, have been investigated over a range of temperatures from T g +75 to T g +150. The probe chromophore, 1-dimethylamino-5-sulfonylnaphthalene amide (dansyl amide), is pendant to a trifunctional silane that acts as a cross-linking molecule. In cyclohexanol, the fluorescence anisotropy decay is in agreement with Debye--Stokes--Einstein hydrodynamic theory (rotational diffusion) demonstrating that the cross-linker can be used as a probe of orientational relaxation. The fluorescence anisotropy decays at a rapid rate in an end-linked poly(dimethyl siloxane) network reflecting fast reorientational motion of the cross-link junction. This reorientation appears diffusive and has a temperature dependence in accord with the Williams--Landel--Ferry equation. A model is proposed that suggests that reorientation and translational motion of the cross-link occur simultaneously and are both coupled to fluctuations of the polymer chain ends

  16. Damage and fatigue in cross-linked rubbers

    Science.gov (United States)

    Melnikov, Alexei

    Damage and fatigue of elastomers have not been fundamentally understood because of the complex nature of these materials. All currently existing models are completely phenomenological. Therefore two problems have been investigated in this research to address those fundamental issues. The first problem was creating an innovative concept with a mathematical modeling, which would be able to describe the damage using molecular characteristics of elastomers. The second problem is developing new approaches to study fatigue, and especially impact fatigue of elastomers. The following results have been obtained in this research. A theoretical model of damage has been developed which involves the basic molecular characteristics of cross-linked elastomers and takes into account the effects of viscoelasticity and stress-induced crystallization. This model was found very reliable and successful in description of numerous quasi-static simple extension experiments for monotonous and repeating loadings. It also roughly predicts in molecular terms the failure of elastomers with various degrees of cross-linking. Quasi-impact fatigue tests with different geometry of an indenter have also been performed. Some microscopic features of rubber damage have been investigated using optical microscopy and SEM. In particular, the accumulation of a completely de-vulcanized, liquid-like substance was observed under intense, multi-cycle impacts. All the findings discovered in quasi-impact experiments are consistent with the damage model predictions.

  17. Assemblages of fish larvae and mesozooplankton across the continental shelf and shelf slope of the Andaman Sea (NE Indian Ocean)

    DEFF Research Database (Denmark)

    Munk, Peter; Bjørnsen, Peter Koefoed; Boonruang, P.

    2004-01-01

    on the sampling of fish larvae and mesozooplankton. Surveys were carried out during 2 monsoon periods in March and August 1996, using 3 cross-bathymetric transects extending to the deeper part of the shelf slope of the Andaman Sea. Station distances were either 5 or 10 n miles apart, and at each station a series...... with a hydrographic front generated where the pycnocline meets the sea-bottom. An internal wave of pronounced amplitude interacts with the shelf slope at ca. 300 m bottom depth, and findings indicated another zone of enhanced abundance in this area. Analysis of the relative abundances of fish larvae within families...

  18. Glutaraldehyde cross-linking of amniotic membranes affects their nanofibrous structures and limbal epithelial cell culture characteristics.

    Science.gov (United States)

    Lai, Jui-Yang; Ma, David Hui-Kang

    2013-01-01

    Given that the cells can sense nanometer dimensions, the chemical cross-linking-mediated alteration in fibrillar structure of collagenous tissue scaffolds is critical to determining their cell culture performances. This article explores, for the first time, the effect of nanofibrous structure of glutaraldehyde (GTA) cross-linked amniotic membrane (AM) on limbal epithelial cell (LEC) cultivation. Results of ninhydrin assays demonstrated that the amount of new cross-links formed between the collagen chains is significantly increased with increasing the cross-linking time from 1 to 24 hours. By transmission electron microscopy, the AM treated with GTA for a longer duration exhibited a greater extent of molecular aggregation, thereby leading to a considerable increase in nanofiber diameter and resistance against collagenase degradation. In vitro biocompatibility studies showed that the samples cross-linked with GTA for 24 hours are not well-tolerated by the human corneal epithelial cell cultures. When the treatment duration is less than 6 hours, the biological tissues cross-linked with GTA for a longer time may cause slight reductions in 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt, and anti-inflammatory activities. Nevertheless, significant collagen molecular aggregation also enhances the stemness gene expression, indicating a high ability of these AM matrices to preserve the progenitors of LECs in vitro. It is concluded that GTA cross-linking of collagenous tissue materials may affect their nanofibrous structures and corneal epithelial stem cell culture characteristics. The AM treated with GTA for 6 hours holds promise for use as a niche for the expansion and transplantation of limbal epithelial progenitor cells.

  19. Enzymatic cross-linking of human recombinant elastin (HELP) as biomimetic approach in vascular tissue engineering.

    Science.gov (United States)

    Bozzini, Sabrina; Giuliano, Liliana; Altomare, Lina; Petrini, Paola; Bandiera, Antonella; Conconi, Maria Teresa; Farè, Silvia; Tanzi, Maria Cristina

    2011-12-01

    The use of polymers naturally occurring in the extracellular matrix (ECM) is a promising strategy in regenerative medicine. If compared to natural ECM proteins, proteins obtained by recombinant DNA technology have intrinsic advantages including reproducible macromolecular composition, sequence and molecular mass, and overcoming the potential pathogens transmission related to polymers of animal origin. Among ECM-mimicking materials, the family of recombinant elastin-like polymers is proposed for drug delivery applications and for the repair of damaged elastic tissues. This work aims to evaluate the potentiality of a recombinant human elastin-like polypeptide (HELP) as a base material of cross-linked matrices for regenerative medicine. The cross-linking of HELP was accomplished by the insertion of cross-linking sites, glutamine and lysine, in the recombinant polymer and generating ε-(γ-glutamyl) lysine links through the enzyme transglutaminase. The cross-linking efficacy was estimated by infrared spectroscopy. Freeze-dried cross-linked matrices showed swelling ratios in deionized water (≈2500%) with good structural stability up to 24 h. Mechanical compression tests, performed at 37°C in wet conditions, in a frequency sweep mode, indicated a storage modulus of 2/3 kPa, with no significant changes when increasing number of cycles or frequency. These results demonstrate the possibility to obtain mechanically resistant hydrogels via enzymatic crosslinking of HELP. Cytotoxicity tests of cross-linked HELP were performed with human umbilical vein endothelial cells, by use of transwell filter chambers for 1-7 days, or with its extracts in the opportune culture medium for 24 h. In both cases no cytotoxic effects were observed in comparison with the control cultures. On the whole, the results suggest the potentiality of this genetically engineered HELP for regenerative medicine applications, particularly for vascular tissue regeneration.

  20. Two DD-carboxypeptidases from Mycobacterium smegmatis affect cell surface properties through regulation of peptidoglycan cross-linking and glycopeptidolipids.

    Science.gov (United States)

    Pandey, Satya Deo; Pal, Shilpa; Kumar N, Ganesh; Bansal, Ankita; Mallick, Sathi; Ghosh, Anindya S

    2018-05-07

    During the peptidoglycan (PG) maturation of mycobacteria, the glycan strands are interlinked by both 3-3 (between two meso-DAP) and 4-3 cross-links (between D-ala and meso-DAP), though there is a predominance (60-80%) of 3-3 cross-links. The DD-CPases act on pentapeptides to generate tetrapeptides that are used by LD-transpeptidases as substrates to form 3-3 cross-links. Therefore, DD-CPases play a crucial role in mycobacterial PG cross-link formation. However, the physiology of DD-CPases in mycobacteria is relatively unexplored. Here, we deleted two DD-CPase genes, msmeg_2433 , and msmeg_2432 , both individually and in combination, from Mycobacterium smegmatis mc 2 155. Though the single DD-CPase deletions had no significant impact on the mycobacterial physiology, many interesting functional alterations were observed in the double deletion mutant, viz. , a predominance in PG cross-link formation was shifted from 3-3 cross-links to 4-3, cell surface glycopeptidolipid (GPL) expression was reduced and susceptibility towards β-lactams and anti-tubercular agents was enhanced. Moreover, the existence of the double mutant within murine macrophages was better as compared to the parent. Interestingly, the complementation with any one of the DD-CPase genes could restore the wild-type phenotype. In a nutshell, we infer that the altered ratio of 4-3: 3-3 PG cross-links might have influenced the expression of surface GPLs, colony morphology, biofilm formation,, drug susceptibility and subsistence of the cells within macrophages. Importance The glycan strands in mycobacterial peptidoglycan (PG) are interlinked by both 3-3 and 4-3 cross-links. The DD-CPases generate tetrapeptides by acting on the pentapeptides, and LD-transpeptidases use tetrapeptides as substrates to form 3-3 cross-links. Here, we showed that simultaneous deletions of two DD-CPases alter the nature of PG cross-linking from 3-3 cross-links to 4-3 cross-links. The deletions subsequently decrease the expression

  1. The properties of water in swollen cross-linked polystyrene sulfo acids

    Science.gov (United States)

    Gagarin, A. N.; Tokmachev, M. G.; Kovaleva, S. S.; Ferapontov, N. B.

    2008-11-01

    The properties of water in polystyrene sulfo acid gels with various cross-linking degrees were studied by optical volumetry and dynamic desorption porosimetry. The isotherms of water desorption obtained by dynamic desorption porosimetry coincided with isopiestic isotherms, which allowed this method to be recommended for the determination of the amount of water in polymer gels. Joint optical volumetry and dynamic desorption porosimetry studies showed that the interphase boundary in the cross-liked hydrophilic polymer-water system did not coincide with the visible gel boundary, because gels were two-phase systems, which contained water of two types, “free” and “bound.” The influence of the degree of polymer cross-linking on the amounts and properties of water of the two types was studied. It was shown that constants of water distribution in the polymer could be calculated from the dynamic desorption porosimetry data.

  2. Characterization of solid UV cross-linked PEGDA for biological applications

    KAUST Repository

    Castro, David; Ingram, Patrick; Kodzius, Rimantas; Conchouso Gonzalez, David; Yoon, Euisik; Foulds, Ian G.

    2013-01-01

    This paper reports on solid UV cross-linked Poly(ethylene)-glycol-diacrylate (PEGDA) as a material for microfluidic devices for biological applications. We have evaluated biocompatibility of PEGDA through two separate means: 1) by examining cell

  3. Effect of temperature and aging time on the rheological behavior of aqueous poly(ethylene glycol)/Laponite RD dispersions.

    Science.gov (United States)

    Morariu, Simona; Bercea, Maria

    2012-01-12

    The viscoelastic properties of 2% poly(ethylene glycol) aqueous solutions containing Laponite RD from 1% to 4% were investigated by oscillatory and flow measurements in the temperature range of 15-40 °C. The enhancement of the clay content from mixture causes the increase of the viscoelastic moduli and the change of the flow from liquid-like behavior (Maxwellian fluid) to a solid-like one at a set temperature. The longest relaxation times (τ(1)) of the mixtures with low clay concentrations (1% and 2%) are not affected by changes in temperature unlike the samples having high content of clay at which τ(1) increases above 30 °C and below 17.5 °C. The characteristic behavior of the mixtures with the high clay concentration could be explained by considering the effect of Brownian motion on the network structure formed in these dispersions as well as by the poor solubility of poly(ethylene glycol) in water at high temperatures. The flow activation energy was determined and discussed. An abrupt increase of the flow activation energy was evidenced between 2% and 3% Laponite RD. The rheological measurements carried out at different rest times showed a decrease of the gelation time from 1 week to 2 h when the clay concentration increases from 2% to 4%. The aging kinetics of poly(ethylene glycol)/Laponite RD/water mixtures, investigated at 25 °C, revealed the increase of the viscosity-rate kinetic constant by increasing the clay concentration.

  4. Surface and Subsurface Meltwater Ponding and Refreezing on the Bach Ice Shelf, Antarctic Peninsula

    Science.gov (United States)

    Willis, I.; Haggard, E.; Benedek, C. L.; MacAyeal, D. R.; Banwell, A. F.

    2017-12-01

    There is growing concern about the stability and fate of Antarctic ice shelves, as four major ice shelves on the Antarctic Peninsula have completely disintegrated since the 1950s. Their collapse has been linked to the southward movement of the -9 oC mean annual temperature isotherm. The proximal causes of ice shelf instability are not fully known, but an increase in surface melting leading to water ponding and ice flexure, fracture and calving has been implicated. Close to the recently collapsed Wilkins Ice Shelf, the Bach Ice Shelf (72°S 72°W) may be at risk from break up in the near future. Here, we document the changing surface hydrology of the Bach Ice Shelf between 2001 and 2017 using Landsat 7 & 8 imagery. Extensive surface water is identified across the Bach Ice Shelf and its tributary glaciers. Two types of drainage system are observed, drainage into firn via simple stream networks and drainage into the ocean via more complex networks. There are differences between the surface hydrology on the ice shelf and the tributary glaciers, as well as variations within and between summer seasons linked to surface air temperature fluctuations. We also document the changing subsurface hydrology of the ice shelf between 2014 and 2017 using Sentinel 1 A/B SAR imagery. Forty-five subsurface features are identified and analysed for their patterns and temporal evolution. Fourteen of the features show similar characteristics to previously-identified buried lakes and some occur in areas associated with surface lakes in previous years. The buried lakes show seasonal variability in area and surface backscatter, which varies with surface air temperature, and are consistent with the presence, enlargement and contraction of liquid water bodies. Buried lakes are an overlooked source of water loading on ice shelves, which may contribute to ice shelf flexure and potential fracture.

  5. Protein cross-linking by chlorinated polyamines and transglutamylation stabilizes neutrophil extracellular traps.

    Science.gov (United States)

    Csomós, Krisztián; Kristóf, Endre; Jakob, Bernadett; Csomós, István; Kovács, György; Rotem, Omri; Hodrea, Judit; Bagoly, Zsuzsa; Muszbek, Laszlo; Balajthy, Zoltán; Csősz, Éva; Fésüs, László

    2016-08-11

    Neutrophil extracellular trap (NET) ejected from activated dying neutrophils is a highly ordered structure of DNA and selected proteins capable to eliminate pathogenic microorganisms. Biochemical determinants of the non-randomly formed stable NETs have not been revealed so far. Studying the formation of human NETs we have observed that polyamines were incorporated into the NET. Inhibition of myeloperoxidase, which is essential for NET formation and can generate reactive chlorinated polyamines through hypochlorous acid, decreased polyamine incorporation. Addition of exogenous primary amines that similarly to polyamines inhibit reactions catalyzed by the protein cross-linker transglutaminases (TGases) has similar effect. Proteomic analysis of the highly reproducible pattern of NET components revealed cross-linking of NET proteins through chlorinated polyamines and ɛ(γ-glutamyl)lysine as well as bis-γ-glutamyl polyamine bonds catalyzed by the TGases detected in neutrophils. Competitive inhibition of protein cross-linking by monoamines disturbed the cross-linking pattern of NET proteins, which resulted in the loss of the ordered structure of the NET and significantly reduced capacity to trap bacteria. Our findings provide explanation of how NETs are formed in a reproducible and ordered manner to efficiently neutralize microorganisms at the first defense line of the innate immune system.

  6. Defective DNA cross-link removal in Chinese hamster cell mutants hypersensitive to bifunctional alkylating agents

    International Nuclear Information System (INIS)

    Hoy, C.A.; Thompson, L.H.; Mooney, C.L.; Salazar, E.P.

    1985-01-01

    DNA repair-deficient mutants from five genetic complementation groups isolated previously from Chinese hamster cells were assayed for survival after exposure to the bifunctional alkylating agents mitomycin C or diepoxybutane. Groups 1, 3, and 5 exhibited 1.6- to 3-fold hypersensitivity compared to the wild-type cells, whereas Groups 2 and 4 exhibited extraordinary hypersensitivity. Mutants from Groups 1 and 2 were exposed to 22 other bifunctional alkylating agents in a rapid assay that compared cytotoxicity of the mutants to the wild-type parental strain, AA8. With all but two of the compounds, the Group 2 mutant (UV4) was 15- to 60-fold more sensitive than AA8 or the Group 1 mutant (UV5). UV4 showed only 6-fold hypersensitivity to quinacrine mustard. Alkaline elution measurements showed that this compound produced few DNA interstrand cross-links but numerous strand breaks. Therefore, the extreme hypersensitivity of mutants from Groups 2 and 4 appeared specific for compounds the main cytotoxic lesions of which were DNA cross-links. Mutant UV5 was only 1- to 4-fold hypersensitive to all the compounds. Although the initial number of cross-links was similar for the three cell lines, the efficiency of removal of cross-links was lowest in UV4 and intermediate in UV5. These results suggest that the different levels of sensitivity are specifically related to different efficiencies of DNA cross-link removal. The phenotype of hypersensitivity to both UV radiation and cross-link damage exhibited by the mutants in Groups 2 and 4 appears to differ from those of the known human DNA repair syndromes

  7. Solvent Composition is Critical for Carbodiimide Cross-Linking of Hyaluronic Acid as an Ophthalmic Biomaterial

    Directory of Open Access Journals (Sweden)

    Jui-Yang Lai

    2012-10-01

    Full Text Available Hyaluronic acid (HA is one of the most important ophthalmic biomaterials, while also being used for tissue engineering and drug delivery. Although chemical cross-linking is an effective way to improve the material performance, it may as a consequence be detrimental to the living cells/tissues. Given that the cross-linking efficiency is mediated by the solvent composition during the chemical modification, this study aims to explore the stability and biocompatibility of carbodiimide cross-linked HA in relation to material processing conditions by varying the acetone/water volume ratio (from 70:30 to 95:5 at a constant 1-ethyl-3-(3-dimethyl aminopropyl carbodiimide (EDC concentration of 100 mM. Our results indicated that after the EDC treatment in the presence of an acetone/water mixture (85:15, v/v, the HA hydrogel membranes have the lowest equilibrium water content, the highest stress at break and the greatest resistance to hyaluronidase digestion. Live/Dead assays and pro-inflammatory cytokine expression analyses showed that the cross-linked HA hydrogel membranes, irrespective of the solvent composition, are compatible with human RPE cell lines without causing toxicity and inflammation. However, it should be noted that the test samples prepared by the cross-linking in the presence of acetone/water mixtures containing 70, 75, and 95 vol % of acetone slightly inhibit the metabolic activity of viable ARPE-19 cultures, probably due to the alteration in the ionic interaction between the medium nutrients and polysaccharide biomaterials. In summary, the water content, mechanical strength and RPE cell proliferative capacity strongly depends on the solvent composition for carbodiimide cross-linking of HA materials.

  8. Temperature dependence of creep compliance of highly cross-linked epoxy: A molecular simulation study

    International Nuclear Information System (INIS)

    Khabaz, Fardin; Khare, Ketan S.; Khare, Rajesh

    2014-01-01

    We have used molecular dynamics (MD) simulations to study the effect of temperature on the creep compliance of neat cross-linked epoxy. Experimental studies of mechanical behavior of cross-linked epoxy in literature commonly report creep compliance values, whereas molecular simulations of these systems have primarily focused on the Young’s modulus. In this work, in order to obtain a more direct comparison between experiments and simulations, atomistically detailed models of the cross-linked epoxy are used to study their creep compliance as a function of temperature using MD simulations. The creep tests are performed by applying a constant tensile stress and monitoring the resulting strain in the system. Our results show that simulated values of creep compliance increase with an increase in both time and temperature. We believe that such calculations of the creep compliance, along with the use of time temperature superposition, hold great promise in connecting the molecular insight obtained from molecular simulation at small length- and time-scales with the experimental behavior of such materials. To the best of our knowledge, this work is the first reported effort that investigates the creep compliance behavior of cross-linked epoxy using MD simulations

  9. Reorientational motion of a cross-link junction in a poly(dimethylsiloxane) network measured by time-resolved fluorescence depolarization

    Energy Technology Data Exchange (ETDEWEB)

    Stein, A.D. (Department of Chemistry, Stanford University, Stanford, California 94305 (United States)); Hoffman, D.A. (Department of Materials Science and Engineering, Stanford University, Stanford, California 94305 (United States)); Frank, C.W. (Department of Chemical Engineering, Stanford University, Stanford, California 94305 (United States)); Fayer, M.D. (Department of Chemistry, Stanford University, Stanford, California 94305 (United States))

    1992-02-15

    The reorientational dynamics of a cross-link junction in poly(dimethylsiloxane) networks, measured by the fluorescence anisotropy decay of a chromophore tagged to the cross-link, have been investigated over a range of temperatures from {ital T}{sub {ital g}}+75 to {ital T}{sub {ital g}}+150. The probe chromophore, 1-dimethylamino-5-sulfonylnaphthalene amide (dansyl amide), is pendant to a trifunctional silane that acts as a cross-linking molecule. In cyclohexanol, the fluorescence anisotropy decay is in agreement with Debye--Stokes--Einstein hydrodynamic theory (rotational diffusion) demonstrating that the cross-linker can be used as a probe of orientational relaxation. The fluorescence anisotropy decays at a rapid rate in an end-linked poly(dimethyl siloxane) network reflecting fast reorientational motion of the cross-link junction. This reorientation appears diffusive and has a temperature dependence in accord with the Williams--Landel--Ferry equation. A model is proposed that suggests that reorientation and translational motion of the cross-link occur simultaneously and are both coupled to fluctuations of the polymer chain ends.

  10. Sharp kink of DNA at psoralen-cross-link site deduced from crystal structure of psoralen-thymine monoadduct

    International Nuclear Information System (INIS)

    Kim, S.H.; Peckler, S.; Graves, B.; Kanne, D.; Rapoport, H.; Hearst, J.E.

    1983-01-01

    Light-induced cross-linking of double-stranded nucleic acids by psoralens has been exploited to locate, in vivo or in vitro, those double-helical regions of DNA or RNA that can accommodate any structural changes caused by the psoralen cross-links. To determine three-dimensional structural parameters of the cross-link, we have solved the crystal structure of the psoralen-thymine monoadduct formed in photoreaction between calf thymus DNA and 8-methoxypsoralen (8MOP). There are eight possible configurations for psoralen-thymine monoadducts and 64 for diadducts. We describe here the structural details of a psoralen-thymine monoadduct obtained in a biological environment and the consequences of the photo-cross-link between 8MOP and double-helical DNA

  11. Wood Sawdust/Natural Rubber Ecocomposites Cross-Linked by Electron Beam Irradiation

    Directory of Open Access Journals (Sweden)

    Elena Manaila

    2016-06-01

    Full Text Available The obtaining and characterization of some polymeric eco-composites based on wood sawdust and natural rubber is presented. The natural rubber was cross-linked using the electron beam irradiation. The irradiation doses were of 75, 150, 300 and 600 kGy and the concentrations of wood sawdust were of 10 and 20 phr, respectively. As a result of wood sawdust adding, the physical and mechanical properties such as hardness, modulus at 100% elongation and tensile strength, showed significant improvements. The presence of wood sawdust fibers has a reinforcing effect on natural rubber, similar or better than of mineral fillers. An increase in the irradiation dose leads to the increasing of cross-link density, which is reflected in the improvement of hardness, modulus at 100% elongation and tensile strength of blends. The cross-linking rates, appreciated using the Flory-Rehner equation, have increased with the amount of wood sawdust in blends and with the irradiation dose. Even if the gel fraction values have varied irregularly with the amount of wood sawdust and irradiation dose it was over 90% for all blends, except for the samples without wood sawdust irradiated with 75 kGy. The water uptake increased with increasing of fiber content and decreased with the irradiation dose.

  12. Toward a new polyethylene scattering law determined using inelastic neutron scattering

    International Nuclear Information System (INIS)

    Lavelle, C.M.; Liu, C.-Y.; Stone, M.B.

    2013-01-01

    Monte Carlo neutron transport codes such as MCNP rely on accurate data for nuclear physics cross-sections to produce accurate results. At low energy, this takes the form of scattering laws based on the dynamic structure factor, S(Q,E). High density polyethylene (HDPE) is frequently employed as a neutron moderator at both high and low temperatures, however the only cross-sections available are for ambient temperatures (∼300K), and the evaluation has not been updated in quite some time. In this paper we describe inelastic neutron scattering measurements on HDPE at 5 and 294 K which are used to improve the scattering law for HDPE. We review some of the past HDPE scattering laws, describe the experimental methods, and compare computations using these models to the measured S(Q,E). The total cross-section is compared to available data, and the treatment of the carbon secondary scatterer as a free gas is assessed. We also discuss the use of the measurement itself as a scattering law via the one phonon approximation. We show that a scattering law computed using a more detailed model for the Generalized Density of States (GDOS) compares more favorably to this experiment, suggesting that inelastic neutron scattering can play an important role in both the development and validation of new scattering laws for Monte Carlo work. -- Highlights: ► Polyethylene at 5 K and 300 K is measured using inelastic neutron scattering (INS). ► Measurements conducted at the Wide Angular-Range Chopper Spectrometer at SNS. ► Several models for Polyethylene are compared to measurements. ► Improvements to existing models for the polyethylene scattering law are suggested. ► INS is shown to be highly valuable tool for scattering law development

  13. Glutaraldehyde Cross-Linking of TendonMechanical Effects at the Level of the Tendon Fascicle and Fibril

    DEFF Research Database (Denmark)

    Hansen, P.; Svensson, R.B.; Aagaard, P.

    2009-01-01

    were examined by atomic force microscopy. Peak forces increased from 1379 to 2622 pN while an extended Hertz fit of force-indentation data showed a 24 fold increase in Young's modulus on indentation. The effect of glutaraldehyde cross-linking on the tensile properties of a single collagen fibril......Conclusive insight into the microscopic principles that govern the strength of tendon and related connective tissues is lacking and the importance of collagen cross-linking has not been firmly established. The combined application of whole-tissue mechanical testing and atomic force spectroscopy...... allowed for a detailed characterization of the effect of cross-linking in rat-tail tendon. The cross-link inducing agent glutaraldehyde augmented the tensile strength of tendon fascicles. Stress at failure increased from 8 MPa to 39 MPa. The mechanical effects of glutaraldehyde at the tendon fibril level...

  14. Effectiveness of trimethylopropane trimethacrylate for the electron-beam-irradiation-induced cross-linking of polylactic acid

    Energy Technology Data Exchange (ETDEWEB)

    Ng, Hon-Meng [Department of Chemical Engineering, Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Jalan Genting Kelang, 53300 Setapak, Kuala Lumpur (Malaysia); Bee, Soo-Tueen, E-mail: beest@utar.edu.my [Department of Chemical Engineering, Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Jalan Genting Kelang, 53300 Setapak, Kuala Lumpur (Malaysia); Ratnam, C.T. [Radiation Processing Technology Division, Malaysian Nuclear Agency, Bangi, 43000 Kajang, Selangor (Malaysia); Sin, Lee Tin; Phang, Yee-Yao; Tee, Tiam-Ting [Department of Chemical Engineering, Faculty of Engineering and Science, Universiti Tunku Abdul Rahman, Jalan Genting Kelang, 53300 Setapak, Kuala Lumpur (Malaysia); Rahmat, A.R. [Department of Polymer Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor (Malaysia)

    2014-01-15

    Highlights: • Investigation of trimethylopropane trimethacrylate (TMPTMA) on electron beam irradiated PLA. • Irradiated PLA blends were weakened by incorporation of high amount of TMPTMA. • TMPTMA interacts with polymer free radicals to build crosslinking network. -- Abstract: The purpose of this research was to investigate the effects of various loading levels of trimethylopropane trimethacrylate (TMPTMA) on the properties of polylactic acid (PLA) cross-linked via electron-beam irradiation. PLA was compounded with 3–5 wt.% of TMPTMA to induce cross-linking upon subjection to electron-beam irradiation doses of 25–250 kGy. The physical properties of the PLA samples were characterised by means of X-ray diffraction, gel fraction and scanning electron microscopy analyses on fractured surfaces after tensile tests. The presence of TMPTMA in PLA was found to effectively increase the crystallite size and gel fraction. However, higher loading levels of TMPTMA could compromise the properties of the PLA/TMPTMA samples, indicating that a larger amount of monomer free radicals might promote degradation within the substantially cross-linked amorphous phase. Irradiation-induced cross-linking in the samples could improve the cross-linking density while decreasing the elongation and interfering with the crystallisation. These effects are caused by the intensive irradiation-induced chain scission that is responsible for the deterioration of the mechanical and crystalline properties of the samples.

  15. Effectiveness of trimethylopropane trimethacrylate for the electron-beam-irradiation-induced cross-linking of polylactic acid

    International Nuclear Information System (INIS)

    Ng, Hon-Meng; Bee, Soo-Tueen; Ratnam, C.T.; Sin, Lee Tin; Phang, Yee-Yao; Tee, Tiam-Ting; Rahmat, A.R.

    2014-01-01

    Highlights: • Investigation of trimethylopropane trimethacrylate (TMPTMA) on electron beam irradiated PLA. • Irradiated PLA blends were weakened by incorporation of high amount of TMPTMA. • TMPTMA interacts with polymer free radicals to build crosslinking network. -- Abstract: The purpose of this research was to investigate the effects of various loading levels of trimethylopropane trimethacrylate (TMPTMA) on the properties of polylactic acid (PLA) cross-linked via electron-beam irradiation. PLA was compounded with 3–5 wt.% of TMPTMA to induce cross-linking upon subjection to electron-beam irradiation doses of 25–250 kGy. The physical properties of the PLA samples were characterised by means of X-ray diffraction, gel fraction and scanning electron microscopy analyses on fractured surfaces after tensile tests. The presence of TMPTMA in PLA was found to effectively increase the crystallite size and gel fraction. However, higher loading levels of TMPTMA could compromise the properties of the PLA/TMPTMA samples, indicating that a larger amount of monomer free radicals might promote degradation within the substantially cross-linked amorphous phase. Irradiation-induced cross-linking in the samples could improve the cross-linking density while decreasing the elongation and interfering with the crystallisation. These effects are caused by the intensive irradiation-induced chain scission that is responsible for the deterioration of the mechanical and crystalline properties of the samples

  16. Placement of a Non–Cross-Linked Porcine-Derived Acellular Dermal Matrix During Preperitoneal Laparoscopic Inguinal Hernia Repair

    OpenAIRE

    Alshkaki, Giath

    2013-01-01

    This retrospective chart review evaluated outcomes following laparoscopic inguinal herniorrhaphies with non–cross-linked intact porcine-derived acellular dermal matrix (PADM) by one surgeon in a community teaching facility hospital. Mesh was sutured and/or tacked in the preperitoneal space. Postoperative visits were scheduled at 2 weeks, 3 months, and 6 months, and then at 6-month intervals up to 2 years. PADM was placed in 14 male patients (mean age, 41.1 years). Seven patients had bilateral...

  17. Influence of cross-shelf water transport on nutrients and phytoplankton in the East China Sea: a model study

    Directory of Open Access Journals (Sweden)

    L. Zhao

    2011-01-01

    Full Text Available A three dimensional coupled biophysical model was used to examine the supply of oceanic nutrients to the shelf of the East China Sea (ECS and its role in primary production over the shelf. The model consisted of two parts: the hydrodynamic module was based on a nested model with a horizontal resolution of 1/18 degree, whereas the biological module was a lower trophic level ecosystem model including two types of phytoplankton, three elements of nutrients, and biogenic organic material. The model results suggested that seasonal variations occurred in the distribution of nutrients and chlorophyll a over the shelf of the ECS. After comparison with available observed nutrients and chlorophyll a data, the model results were used to calculate volume and nutrients fluxes across the shelf break. The annual mean total fluxes were 1.53 Sv for volume, 9.4 kmol s−1 for DIN, 0.7 kmol s−1 for DIP, and 18.2 kmol s−1 for silicate. Two areas, northeast of Taiwan and southwest of Kyushu, were found to be major source regions of oceanic nutrients to the shelf. Although the onshore fluxes of nutrients and volume both had apparent seasonal variations, the seasonal variation of the onshore nutrient flux did not exactly follow that of the onshore volume flux. Additional calculations in which the concentration of nutrients in Kuroshio water was artificially increased suggested that the oceanic nutrients were distributed in the bottom layer from the shelf break to the region offshore of the Changjiang estuary from spring to summer and appeared in the surface layer from autumn to winter. The calculations also implied that the supply of oceanic nutrients to the shelf can change the consumption of pre-existing nutrients from rivers. The response of primary production over the shelf to the oceanic nutrients was confirmed not only in the surface layer (mainly at the outer shelf and shelf break in winter and in the region

  18. Chemical cross-linked polyvinyl alcohol/cellulose nanocrystal composite films with high structural stability by spraying Fenton reagent as initiator.

    Science.gov (United States)

    Song, Meili; Yu, Houyong; Gu, Jiping; Ye, Shounuan; Zhou, Yuwei

    2018-07-01

    Cross-linked polyvinyl alcohol (PVA) composite films with high structural stability were prepared by free radical copolymerization between cellulose nanocrystal (CNC) and maleic anhydride (MAH) modified PVA through spraying Fenton free radical as initiator. The influence of chemical cross-linked and physical network structure on mechanical, thermal and water absorption properties of the composite films were investigated. Compared to PVA and PVA/CNC composite film, significant improvements in the mechanical, thermal and water uptake properties of the cross-linked composite film were found. The tensile strength of the cross-linked composite film was enhanced from 23.1MPa (neat PVA film) and 32.6MPa (PVA/CNC-10%) to 42.5MPa, and the maximum thermal degradation temperature was increased from 266.8°C and 281.2°C to 366.7°C (cross-linked composite film). Besides, the water absorption was reduced from 385.9% and 220.6% to 175.7% for cross-linked composite film. It indicates that compared with physical network structure in PVA/CNC composite film, the multiple cross-linked networks showed excellent thermal stability, resistance of water swelling and structural stability at the same CNC loading level. Thus, the PVA/CNC composite film with the multiple cross-linked network shows greater property reinforcements. Copyright © 2018 Elsevier B.V. All rights reserved.

  19. Identification and characterization of a pituitary corticotropin-releasing factor binding protein by chemical cross-linking

    DEFF Research Database (Denmark)

    Nishimura, E; Billestrup, Nils; Perrin, M

    1987-01-01

    appeared to have a molecular weight of approximately 70,000. The cross-linking was specific since an excess (1 microM) of an unrelated peptide (insulin) did not affect the appearance of the Mr 75,000 band. The concentration of CRF required to inhibit cross-linking by 50% was found to be similar...

  20. Genipin Cross-Linked Polymeric Alginate-Chitosan Microcapsules for Oral Delivery: In-Vitro Analysis

    Directory of Open Access Journals (Sweden)

    Hongmei Chen

    2009-01-01

    Full Text Available We have previously reported the preparation of the genipin cross-linked alginate-chitosan (GCAC microcapsules composed of an alginate core with a genipin cross-linked chitosan membrane. This paper is the further investigation on their structural and physical characteristics. Results showed that the GCAC microcapsules had a smooth and dense surface and a networked interior. Cross-linking by genipin substantially reduced swelling and physical disintegration of microcapsules induced by nongelling ions and calcium sequestrants. Strong resistance to mechanical shear forces and enzymatic degradation was observed. Furthermore, the GCAC membranes were permeable to bovine serum albumin and maintained a molecular weight cutoff at 70 KD, analogous to the widely studied alginate-chitosan, and alginate-poly-L-lysine-alginate microcapsules. The release features and the tolerance of the GCAC microcapsules in the stimulated gastrointestinal environment were also investigated. This GCAC microcapsule formulation offers significant potential as a delivery vehicle for many biomedical applications.

  1. 21 CFR 177.2710 - Styrene-divinylbenzene resins, cross-linked.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Styrene-divinylbenzene resins, cross-linked. 177.2710 Section 177.2710 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN CONSUMPTION (CONTINUED) INDIRECT FOOD ADDITIVES: POLYMERS Substances for Use Only as Components of Articles Intended...

  2. Bifunctional alkylating agent-mediated MGMT-DNA cross-linking and its proteolytic cleavage in 16HBE cells

    International Nuclear Information System (INIS)

    Cheng, Jin; Ye, Feng; Dan, Guorong; Zhao, Yuanpeng; Wang, Bin; Zhao, Jiqing; Sai, Yan; Zou, Zhongmin

    2016-01-01

    Nitrogen mustard (NM), a bifunctional alkylating agent (BAA), contains two alkyl arms and can act as a cross-linking bridge between DNA and protein to form a DNA-protein cross-link (DPC). O 6 -methylguanine–DNA methyltransferase (MGMT), a DNA repair enzyme for alkyl adducts removal, is found to enhance cell sensitivity to BAAs and to promote damage, possibly due to its stable covalent cross-linking with DNA mediated by BAAs. To investigate MGMT-DNA cross-link (mDPC) formation and its possible dual roles in NM exposure, human bronchial epithelial cell line 16HBE was subjected to different concentrations of HN2, a kind of NM, and we found mDPC was induced by HN2 in a concentration-dependent manner, but the mRNA and total protein of MGMT were suppressed. As early as 1 h after HN2 treatment, high mDPC was achieved and the level maintained for up to 24 h. Quick total DPC (tDPC) and γ-H2AX accumulation were observed. To evaluate the effect of newly predicted protease DVC1 on DPC cleavage, we applied siRNA of MGMT and DVC1, MG132 (proteasome inhibitor), and NMS-873 (p97 inhibitor) and found that proteolysis plays a role. DVC1 was proven to be more important in the cleavage of mDPC than tDPC in a p97-dependent manner. HN2 exposure induced DVC1 upregulation, which was at least partially contributed to MGMT cleavage by proteolysis because HN2-induced mDPC level and DNA damage was closely related with DVC1 expression. Homologous recombination (HR) was also activated. Our findings demonstrated that MGMT might turn into a DNA damage promoter by forming DPC when exposed to HN2. Proteolysis, especially DVC1, plays a crucial role in mDPC repair. - Highlights: • Nitrogen mustard-induced MGMT-DNA cross-linking was detected in a living cell. • Concentration- and time-dependent manners of MGMT-DNA cross-linking were revealed. • Proteolysis played an important role in protein (MGMT)-DNA cross-linking repair. • DVC1 acts as a proteolytic enzyme in cross-linking repair in a p

  3. Laser-induced corneal cross-linking upon photorefractive ablation with riboflavin

    Directory of Open Access Journals (Sweden)

    Kornilovskiy IM

    2016-04-01

    Full Text Available Igor M Kornilovskiy,1 Elmar M Kasimov,2 Ayten I Sultanova,2 Alexander A Burtsev1 1Department of Eye Diseases, Federal State Budgetary Institution “National Pirogov Medical Surgical Centre”, Ministry of Health, Moscow, Russia; 2Department of Eye Diseases, Zarifa Aliyeva National Ophthalmology Center, Ministry of Health, Baku, Azerbaijan Aim: To estimate the biomechanical effect of the laser-induced cross-linking resulting from photorefractive ablation of the cornea with riboflavin.Methods: Excimer laser ablation studies were performed ex vivo (32 eyes of 16 rabbits by phototherapeutic keratectomy (PTK and in vivo (24 eyes of 12 rabbits by transepithelial photorefractive keratectomy (TransPRK, with and without riboflavin saturation of the stroma. Then, we performed corneal optical coherence tomography on 36 eyes of 18 patients with varying degrees of myopia at different times after the TransPRK was performed with riboflavin saturation of the stroma.Results: Biomechanical testing of corneal samples saturated with riboflavin revealed cross-linking effect accompanied by the increase in tensile strength and maximum strength. PTK showed increase in tensile strength from 5.1±1.4 to 7.2±1.6 MPa (P=0.001, while TransPRK showed increase in tensile strength from 8.8±0.9 to 12.8±1.3 MPa (P=0.0004. Maximum strength increased from 8.7±2.5 to 12.0±2.8 N (P=0.005 in PTK and from 12.8±1.6 to 18.3±1.2 N (P=0.0004 in TransPRK. Clinical optical coherence tomography studies of the biomicroscopic transparent cornea at different times after TransPRK showed increased density in the surface layers of the stroma and membrane-like structure beneath the epithelium.Conclusion: Photorefractive ablation of the preliminary corneal stroma saturation with riboflavin causes the effect of laser-induced cross-linking, which is attended with an increase in corneal tensile strength, maximum strength, increased density in the surface layers of the stroma, and formation of

  4. In vitro cross-linking of bovine lens proteins photosensitized by promazines

    International Nuclear Information System (INIS)

    Merville, M.P.; Decuyper, J.; Piette, J.; Calberg-Bacq, C.M.; Van de Vorst, A.

    1984-01-01

    Promazine derivatives induce cross-linking of bovine lens crystallins in vitro by irradiation with near-ultraviolet (UV) light in the presence of O 2 , as revealed by electrophoresis after denaturation. With the five derivatives tested (promazine [PZ], chlorpromazine [CPZ], triflupromazine [TFPZ], methoxypromazine [MTPZ], and acepromazine [ACPZ]), single-hit kinetics are observed. Evidence implicating the cation radicals of the PZ derivatives as the causative agent of this in vitro effect is presented. Hydroxyl radicals do not appear to be involved in the photo-cross-linking reaction. Sodium ascorbate protects against damage induced either by PZ derivatives plus light or by PZ cation radicals in the dark. These findings are discussed with respect to development of cataracts induced by these drugs in vivo

  5. Photo-cross-linked small-molecule microarrays as chemical genomic tools for dissecting protein-ligand interactions.

    Science.gov (United States)

    Kanoh, Naoki; Asami, Aya; Kawatani, Makoto; Honda, Kaori; Kumashiro, Saori; Takayama, Hiroshi; Simizu, Siro; Amemiya, Tomoyuki; Kondoh, Yasumitsu; Hatakeyama, Satoru; Tsuganezawa, Keiko; Utata, Rei; Tanaka, Akiko; Yokoyama, Shigeyuki; Tashiro, Hideo; Osada, Hiroyuki

    2006-12-18

    We have developed a unique photo-cross-linking approach for immobilizing a variety of small molecules in a functional-group-independent manner. Our approach depends on the reactivity of the carbene species generated from trifluoromethylaryldiazirine upon UV irradiation. It was demonstrated in model experiments that the photogenerated carbenes were able to react with every small molecule tested, and they produced multiple conjugates in most cases. It was also found in on-array immobilization experiments that various small molecules were immobilized, and the immobilized small molecules retained their ability to interact with their binding proteins. With this approach, photo-cross-linked microarrays of about 2000 natural products and drugs were constructed. This photo-cross-linked microarray format was found to be useful not merely for ligand screening but also to study the structure-activity relationship, that is, the relationship between the structural motif (or pharmacophore) found in small molecules and its binding affinity toward a protein, by taking advantage of the nonselective nature of the photo-cross-linking process.

  6. Effect of dual modification with hydroxypropylation and cross-linking on physicochemical properties of taro starch.

    Science.gov (United States)

    Hazarika, Bidyut Jyoti; Sit, Nandan

    2016-04-20

    Dual modification of taro starch by hydroxypropylation and cross-linking was carried out and the properties of the modified starches were investigated. Two different levels of hydroxypropylation (5 and 10%) and cross-linking (0.05 and 0.10%) were used in different sequences. The amylose contents of the starch decreased due to single and dual modification. For the dual-modified starches, the swelling, solubility and clarity was found to increase with level of hydroxypropylation and decrease with level of cross-linking. The freeze-thaw stability of the dual-modified starches was also affected by the sequence of modification. The viscosities of the cross-linked and dual-modified starches were more than native and hydroxypropylated starches. The firmness of the dual-modified starches was also higher than native and single modified starches. The dual-modified starches have benefits of both type of modifications and could be used for specific purposes e.g. food products requiring high viscosity as well as freeze-thaw stability. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. Specific cross-linking of capsid proteins to virus RNA by ultraviolet irradiation of polio virus

    Energy Technology Data Exchange (ETDEWEB)

    Wetz, K.; Habermehl, K.O. (Freie Univ. Berlin (Germany, F.R.))

    1982-04-01

    Poliovirus was irradiated with u.v. light under conditions causing approx. 5% cross-linking of capsid protein to virus RNA. Cross-linked RNA-protein complexes, freed from unbound protein, were treated with nuclease, and then analysed on SDS-polyacrylamide gels. The smallest capsid polypeptide VP4 was found to be associated with the RNA to the greatest degree, followed by VP2 and VP1, while VP3 was attached only in trace amounts. Low radiation doses, which produced cross-linking of RNA to protein, did not cause breakdown of the virus particles or conformational changes of the capsid as examined physically and serologically. However, higher doses caused structural alterations of the virus capsid.

  8. Specific cross-linking of capsid proteins to virus RNA by ultraviolet irradiation of polio virus

    International Nuclear Information System (INIS)

    Wetz, K.; Habermehl, K.-O.

    1982-01-01

    Poliovirus was irradiated with u.v. light under conditions causing approx. 5% cross-linking of capsid protein to virus RNA. Cross-linked RNA-protein complexes, freed from unbound protein, were treated with nuclease, and then analysed on SDS-polyacrylamide gels. The smallest capsid polypeptide VP4 was found to be associated with the RNA to the greatest degree, followed by VP2 and VP1, while VP3 was attached only in trace amounts. Low radiation doses, which produced cross-linking of RNA to protein, did not cause breakdown of the virus particles or conformational changes of the capsid as examined physically and serologically. However, higher doses caused structural alterations of the virus capsid. (author)

  9. Rapid detection of DNA-interstrand and DNA-protein cross-links in mammalian cells by gravity-flow alkaline elution

    International Nuclear Information System (INIS)

    Hincks, J.R.; Coulombe, R.A. Jr.

    1989-01-01

    Alkaline elution is a sensitive and commonly used technique to detect cellular DNA damage in the form of DNA strand breaks and DNA cross-links. Conventional alkaline elution procedures have extensive equipment requirements and are tedious to perform. Our laboratory recently presented a rapid, simplified, and sensitive modification of the alkaline elution technique to detect carcinogen-induced DNA strand breaks. In the present study, we have further modified this technique to enable the rapid characterization of chemically induced DNA-interstrand and DNA-protein associated cross-links in cultured epithelial cells. Cells were exposed to three known DNA cross-linking agents, nitrogen mustard (HN 2 ), mitomycin C (MMC), or ultraviolet irradiation (UV). One hour exposures of HN 2 at 0.25, 1.0, and 4.0 microM or of MMC at 20, 40, and 60 microM produced a dose-dependent induction of total DNA cross-links by these agents. Digestion with proteinase K revealed that HN 2 and MMC induced both DNA-protein cross-links and DNA-interstrand cross-links. Ultraviolet irradiation induced both DNA cross-links and DNA strand breaks, the latter of which were either protein and nonprotein associated. The results demonstrate that gravity-flow alkaline elution is a sensitive and accurate method to characterize the molecular events of DNA cross-linking. Using this procedure, elution of DNA from treated cells is completed in 1 hr, and only three fractions per sample are analyzed. This method may be useful as a rapid screening assay for genotoxicity and/or as an adjunct to other predictive assays for potential mutagenic or carcinogenic agents

  10. Effects of Thermal Cross-Linking on the Structure and Property of Asymmetric Membrane Prepared from the Polyacrylonitrile

    Directory of Open Access Journals (Sweden)

    Xin Jin

    2018-05-01

    Full Text Available Improving the thermal and chemical stabilities of classical polymer membranes will be beneficial to extend their applications in the high temperature or aggressive environment. In this work, the asymmetric ultrafiltration membranes prepared from the polyacrylonitrile (PAN were used to fabricate the cross-linking asymmetric (CLA PAN membranes via thermal cross-linking in air to improve their thermal and chemical stabilities. The effects of thermal cross-linking parameters such as temperature and holding time on the structure, gas separation performance, thermal and chemical stabilities of PAN membranes were investigated by Fourier transform infrared spectroscopy (FTIR, X-ray photoelectron spectroscopy (XPS, positron annihilation lifetime spectroscopy (PALS, scanning electron microscopy (SEM, thermogravimetic analysis (TGA and gas permeation test. The thermal cross-linking significantly influences the chemical structure, microstructure and pore structure of PAN membrane. During the thermal cross-linking, the shrinkage of membrane and coalescence or collapse of pore and microstructure make large pores diminish, small pores disappear and pore volumes reduce. The gas permeances of CLA-PAN membranes increase as the increasing of cross-linking temperature and holding time due to the volatilization of small molecules. The CLA-PAN membranes demonstrate excellent thermal and chemical stabilities and present good prospects for application in ultrafiltration for water treatment and for use as a substrate for nanofiltration or gas separation with an aggressive and demanding environment.

  11. Diurnal variability of inner-shelf circulation in the lee of a cape under upwelling conditions

    Science.gov (United States)

    Lamas, L.; Peliz, A.; Dias, J.; Oliveira, P. B.; Angélico, M. M.; Castro, J. J.; Fernandes, J. N.; Trindade, A.; Cruz, T.

    2017-07-01

    The nearshore circulation in the lee of a cape under upwelling conditions was studied using in-situ data from 3 consecutive summers (2006-2008). Focus was given to a period between 20 July and 04 August 2006 to study the diurnal variability of the cross-shelf circulation. This period was chosen because it had a steady upwelling-favourable wind condition modulated by a diurnal cycle much similar to sea breeze. The daily variability of the observed cross-shelf circulation consisted of three distinct periods: a morning period with a 3-layer vertical structure with onshore velocities at mid-depth, a mid-day period where the flow is reversed and has a 2-layer structure with onshore velocities at the surface and offshore flow below, and, lastly, in the evening, a 2-layer period with intensified offshore velocities at the surface and onshore flow at the bottom. The observed cross-shelf circulation showed a peculiar vertical shape and diurnal variability different from several other systems described in literature. We hypothesize that the flow reversal of the cross-shelf circulation results as a response to the rapid change of the wind magnitude and direction at mid-day with the presence of the cape north of the mooring site influencing this response. A numerical modelling experiment exclusively forced by winds simulated successfully most of the circulation at the ADCP site, especially the mid-day reversal and the evening's upwelling-type structure. This supports the hypothesis that the cross-shelf circulation at diurnal timescales is mostly wind-driven. By analysing the 3D circulation in the vicinity of Cape Sines we came to the conclusion that the diurnal variability of the wind and the flow interaction with topography are responsible for the circulation variability at the ADCP site, though only a small region in the south of the cape showed a similar diurnal variability. The fact that the wind diurnally undergoes relaxation and intensification strongly affects the

  12. NW European shelf under climate warming: implications for open ocean – shelf exchange, primary production, and carbon absorption

    Directory of Open Access Journals (Sweden)

    M. Gröger

    2013-06-01

    Full Text Available Shelves have been estimated to account for more than one-fifth of the global marine primary production. It has been also conjectured that shelves strongly influence the oceanic absorption of anthropogenic CO2 (carbon shelf pump. Owing to their coarse resolution, currently applied global climate models are inappropriate to investigate the impact of climate change on shelves and regional models do not account for the complex interaction with the adjacent open ocean. In this study, a global ocean general circulation model and biogeochemistry model were set up with a distorted grid providing a maximal resolution for the NW European shelf and the adjacent northeast Atlantic. Using model climate projections we found that already a~moderate warming of about 2.0 K of the sea surface is linked with a reduction by ~ 30% of the biological production on the NW European shelf. If we consider the decline of anthropogenic riverine eutrophication since the 1990s, the reduction of biological production amounts is even larger. The relative decline of NW European shelf productivity is twice as strong as the decline in the open ocean (~ 15%. The underlying mechanism is a spatially well confined stratification feedback along the continental shelf break. This feedback reduces the nutrient supply from the deep Atlantic to about 50%. In turn, the reduced productivity draws down CO2 absorption in the North Sea by ~ 34% at the end of the 21st century compared to the end of the 20th century implying a strong weakening of shelf carbon pumping. Sensitivity experiments with diagnostic tracers indicate that not more than 20% of the carbon absorbed in the North Sea contributes to the long-term carbon uptake of the world ocean. The rest remains within the ocean's mixed layer where it is exposed to the atmosphere. The predicted decline in biological productivity, and decrease of phytoplankton concentration (in the North Sea by averaged 25% due to reduced nutrient imports from

  13. Technology transfer equipment qualification methodology for shelf life determination

    International Nuclear Information System (INIS)

    Anderson, J.W.

    1995-01-01

    Discussions with a number of Nuclear Utilities revealed that equipment qualified for 10 to 40 years in the harsh environment of the plant was being assigned shelf lives of only 5 to 10 years in the benign environment of the warehouse, and then the materials were being trashed. One safety-related equipment supplier was assigning a 10-year qualified life, from date of shipment, with no recognition of the difference in the aging rate in the plant vs. that in the warehouse. Many suppliers assign shelf lives based on product warranty considerations rather than actual product degradation. An EPRI program was initiated to evaluate the methods used to assign shelf lives and to adapt the Arrhenius methodology, used in equipment qualification, to assign technically justifiable shelf lives. Temperature is the main factor controlling shelf life; however, atmospheric pressure, humidity, ultraviolet light, ozone and other atmospheric contaminants were also considered. A list of 70 representative materials was addressed in the program. All of these were found to have shelf lives of 14 years to greater than 60 years, except for 19 items. For 18 of these items, there was no data available except for the manufacturer's recommendation

  14. Mapping protein structural changes by quantitative cross-linking

    Czech Academy of Sciences Publication Activity Database

    Kukačka, Zdeněk; Strohalm, Martin; Kavan, Daniel; Novák, Petr

    2015-01-01

    Roč. 89, NOV 2015 (2015), s. 112-120 ISSN 1046-2023 R&D Projects: GA MŠk(CZ) EE2.3.20.0055; GA MŠk(CZ) EE2.3.30.0003; GA MŠk(CZ) ED1.1.00/02.0109 Grant - others:OPPC(XE) CZ.2.16/3.1.00/24023 Institutional support: RVO:61388971 Keywords : Chemical cross-linking * Proteolysis * Mass spectrometry Subject RIV: CE - Biochemistry Impact factor: 3.503, year: 2015

  15. Highly conductive carbon nanotube buckypapers with improved doping stability via conjugational cross-linking.

    Science.gov (United States)

    Chen, I-Wen Peter; Liang, Richard; Zhao, Haibo; Wang, Ben; Zhang, Chuck

    2011-12-02

    Carbon nanotube (CNT) sheets or buckypapers have demonstrated promising electrical conductivity and mechanical performance. However, their electrical conductivity is still far below the requirements for engineering applications, such as using as a substitute for copper mesh, which is currently used in composite aircraft structures for lightning strike protection. In this study, different CNT buckypapers were stretched to increase their alignment, and then subjected to conjugational cross-linking via chemical functionalization. The conjugationally cross-linked buckypapers (CCL-BPs) demonstrated higher electrical conductivity of up to 6200 S cm( - 1), which is more than one order increase compared to the pristine buckypapers. The CCL-BPs also showed excellent doping stability in over 300 h in atmosphere and were resistant to degradation at elevated temperatures. The tensile strength of the stretched CCL-BPs reached 220 MPa, which is about three times that of pristine buckypapers. We attribute these property improvements to the effective and stable conjugational cross-links of CNTs, which can simultaneously improve the electrical conductivity, doping stability and mechanical properties. Specifically, the electrical conductivity increase resulted from improving the CNT alignment and inter-tube electron transport capability. The conjugational cross-links provide effective 3D conductive paths to increase the mobility of electrons among individual nanotubes. The stable covalent bonding also enhances the thermal stability and load transfer. The significant electrical and mechanical property improvement renders buckypaper a multifunctional material for various applications, such as conducting composites, battery electrodes, capacitors, etc.

  16. ROMP-based thermosetting polymers from modified castor oil with various cross-linking agents

    Science.gov (United States)

    Ding, Rui

    Polymers derived from bio-renewable resources are finding an increase in global demand. In addition, polymers with distinctive functionalities are required in certain advanced fields, such as aerospace and civil engineering. In an attempt to meet both these needs, the goal of this work aims to develop a range of bio-based thermosetting matrix polymers for potential applications in multifunctional composites. Ring-opening metathesis polymerization (ROMP), which recently has been explored as a powerful method in polymer chemistry, was employed as a unique pathway to polymerize agricultural oil-based reactants. Specifically, a novel norbornyl-functionalized castor oil alcohol (NCA) was investigated to polymerize different cross-linking agents using ROMP. The effects of incorporating dicyclopentadiene (DCPD) and a norbornene-based crosslinker (CL) were systematically evaluated with respect to curing behavior and thermal mechanical properties of the polymers. Isothermal differential scanning calorimetry (DSC) was used to investigate the conversion during cure. Dynamic DSC scans at multiple heating rates revealed conversion-dependent activation energy by Ozawa-Flynn-Wall analysis. The glass transition temperature, storage modulus, and loss modulus for NCA/DCPD and NCA/CL copolymers with different cross-linking agent loading were compared using dynamic mechanical analysis. Cross-link density was examined to explain the very different dynamic mechanical behavior. Mechanical stress-strain curves were developed through tensile test, and thermal stability of the cross-linked polymers was evaluated by thermogravimetric analysis to further investigate the structure-property relationships in these systems.

  17. Formulation and in vitro evaluation of sustained release matrix tablets using cross-linked natural gum.

    Science.gov (United States)

    Jamil, Qurratul Ain; Masood, Muhammad Irfan; Jamil, Muhammad Nauman; Masood, Imran; Iqbal, Shahid Muhammad

    2017-03-01

    Polysaccharide gums because of their biocompatibility, biodegradability and non-immunogenic properties are considered as the best choice for preparing sustained release tablets as compared to their synthetic counterpart. The cross linking of natural gums in matrix tablets increase the sustained release property of matrix tablets. Isoniazid is a first line therapy of tuberculosis, belongs to BCS I with half-life of 3-4 hours. These characteristics make isoniazid a good candidate for sustained release dosage form. Karaya gum crossed linked with trisodium tri metaphosphate was used as release rate retardant for preparing isoniazid cross-linked matrix tablet. Total 8 sustained release formulations were prepared. Both granules and tablets were evaluated under in vitro condition against different parameters. Dissolution studies were performed with all eight formulations for 12 hours using USP apparatus I. Four formulations designated as F1, F2, F3, F4 have drug and karaya gum while other four formulations F5, F6, F7, F8 have drug and crossed linked polymer in ratios of 1:1, 1:2, 1:3 and 1:4 respectively. Dissolution data was analyzed by using different kinetic models. Best fit model for most efficient formulation was zero order while release mechanism was super case I. Formulation 8 showed sufficiently slow release kinetics and about 83% of drug was released in 10 hours, indicating that cross-linked karaya gum proved efficient in preparing sustained release tablets.

  18. Cross-Linkable Polyimide Membranes for Improved Plasticization Resistance and Permselectivity in Sour Gas Separations

    KAUST Repository

    Kraftschik, Brian

    2013-09-10

    A series of cross-linkable membrane materials based on the 6FDA-DAM:DABA (3:2) polyimide backbone were synthesized for improved sour gas separation performance, in terms of both membrane stability and permselectivity. Short-chain poly(ethylene glycol) (PEG) molecules were used as cross-linking agents in an esterification-based cross-linking reaction. Pure and mixed gas permeation and pure gas sorption experiments were performed on dense films of these materials. Compared to unmodified 6FDA-DAM:DABA (3:2), higher sour gas permselectivity and membrane stability were achieved under aggressive feed conditions. H2S-induced plasticization was not evident until pure H2S feed pressures greater than approximately 6-8 bar. Pure CO 2-induced plasticization only occurred at feed pressures greater than about 25 bar. Under mixed gas feed conditions with 20% H2S, 20% CO2, and 60% CH4 at 35 C, attractive selectivities above 22 and 27 for H2S/CH4 and CO2/CH4, respectively, were observed for a feed pressure of 62 bar with both triethylene glycol and tetraethylene glycol cross-linking agents. © 2013 American Chemical Society.

  19. Cross-Linkable Polyimide Membranes for Improved Plasticization Resistance and Permselectivity in Sour Gas Separations

    KAUST Repository

    Kraftschik, Brian; Koros, William J.

    2013-01-01

    A series of cross-linkable membrane materials based on the 6FDA-DAM:DABA (3:2) polyimide backbone were synthesized for improved sour gas separation performance, in terms of both membrane stability and permselectivity. Short-chain poly(ethylene glycol) (PEG) molecules were used as cross-linking agents in an esterification-based cross-linking reaction. Pure and mixed gas permeation and pure gas sorption experiments were performed on dense films of these materials. Compared to unmodified 6FDA-DAM:DABA (3:2), higher sour gas permselectivity and membrane stability were achieved under aggressive feed conditions. H2S-induced plasticization was not evident until pure H2S feed pressures greater than approximately 6-8 bar. Pure CO 2-induced plasticization only occurred at feed pressures greater than about 25 bar. Under mixed gas feed conditions with 20% H2S, 20% CO2, and 60% CH4 at 35 C, attractive selectivities above 22 and 27 for H2S/CH4 and CO2/CH4, respectively, were observed for a feed pressure of 62 bar with both triethylene glycol and tetraethylene glycol cross-linking agents. © 2013 American Chemical Society.

  20. Accommodation space in a high-wave-energy inner-shelf during the Holocene marine transgression: Correlation of onshore and offshore inner-shelf deposits (0–12 ka) in the Columbia River littoral cell system, Washington and Oregon, USA

    Science.gov (United States)

    Peterson, C. D.; Twichell, D. C.; Roberts, M. C.; Vanderburgh, S.; Hostetler, Steven W.

    2016-01-01

    The Columbia River Littoral Cell (CRLC), a high-wave-energy littoral system, extends 160 km alongshore, generally north of the large Columbia River, and 10–15 km in across-shelf distance from paleo-beach backshores to about 50 m present water depths. Onshore drill holes (19 in number and 5–35 m in subsurface depth) and offshore vibracores (33 in number and 1–5 m in subsurface depth) constrain inner-shelf sand grain sizes (sample means 0.13–0.25 mm) and heavy mineral source indicators (> 90% Holocene Columbia River sand) of the inner-shelf facies (≥ 90% fine sand). Stratigraphic correlation of the transgressive ravinement surface in onshore drill holes and in offshore seismic reflection profiles provide age constraints (0–12 ka) on post-ravinement inner-shelf deposits, using paleo-sea level curves and radiocarbon dates. Post-ravinement deposit thickness (1–50 m) and long-term sedimentation rates (0.4–4.4 m ka− 1) are positively correlated to the cross-shelf gradients (0.36–0.63%) of the transgressive ravinement surface. The total post-ravinement fill volume of fine littoral sand (2.48 × 1010 m3) in the inner-shelf represents about 2.07 × 106 m3 year− 1 fine sand accumulation rate during the last 12 ka, or about one third of the estimated middle- to late-Holocene Columbia River bedload or sand discharge (5–6 × 106 m3 year− 1) to the littoral zone. The fine sand accumulation in the inner-shelf represents post-ravinement accommodation space resulting from 1) geometry and depth of the transgressive ravinement surface, 2) post-ravinement sea-level rise, and 3) fine sand dispersal in the inner-shelf by combined high-wave-energy and geostrophic flow/down-welling drift currents during major winter storms.

  1. Grafted Cross-Linked Polyolefin Substrates for Peptide Synthesis and Assays

    DEFF Research Database (Denmark)

    1999-01-01

    suited for use in solid-phase biosystems, notably bioassays, such as immunoassays, DNA hybridization assays or PCR amplification. The grafted chains may bear substituents which are such that the polymer-grafted cross-linked polyolefin substrate is swellable by water or aqueous media, in other words...

  2. Effect of carbon nanotube dispersion on glass transition in cross-linked epoxy-carbon nanotube nanocomposites: role of interfacial interactions.

    Science.gov (United States)

    Khare, Ketan S; Khare, Rajesh

    2013-06-20

    We have used atomistic molecular simulations to study the effect of nanofiller dispersion on the glass transition behavior of cross-linked epoxy-carbon nanotube (CNT) nanocomposites. Specific chemical interactions at the interface of CNTs and cross-linked epoxy create an interphase region, whose impact on the properties of their nanocomposites increases with an increasing extent of dispersion. To investigate this aspect, we have compared the volumetric, structural, and dynamical properties of three systems: neat cross-linked epoxy, cross-linked epoxy nanocomposite containing dispersed CNTs, and cross-linked epoxy nanocomposite containing aggregated CNTs. We find that the nanocomposite containing dispersed CNTs shows a depression in the glass transition temperature (Tg) by ~66 K as compared to the neat cross-linked epoxy, whereas such a large depression is absent in the nanocomposite containing aggregated CNTs. Our results suggest that the poor interfacial interactions between the CNTs and the cross-linked epoxy matrix lead to a more compressible interphase region between the CNTs and the bulk matrix. An analysis of the resulting dynamic heterogeneity shows that the probability of percolation of immobile domains becomes unity near the Tg calculated from volumetric properties. Our observations also lend support to the conceptual analogy between polymer nanocomposites and the nanoconfinement of polymer thin films.

  3. Hemostatic granules and dressing prepared from formulations of carboxymethyl cellulose, kappa-carrageenan and polyethylene oxide crosslinked by gamma radiation

    Science.gov (United States)

    Barba, Bin Jeremiah D.; Aranilla, Charito T.; Relleve, Lorna S.; Cruz, Veriza Rita C.; Vista, Jeanina Richelle; Abad, Lucille V.

    2018-03-01

    Uncontrolled hemorrhage remains a persistent problem especially in anatomical areas where compression and tourniquet cannot be applied. Hemostatic agents are materials which can achieve control of bleeding in acute, life-threatening traumatic coagulopathy. In this study, we prepared biocompatible hydrogel-based hemostat crosslinked by ionizing radiation. Granules made from carboxymethyl cellulose and dressing from kappa carrageenan and polyethylene oxide were characterized by FT-IR, SEM, and gel analysis. Gamma radiation with a dose of 25 kGy was used for sterilization process. Stability studies indicate that the products remain effective with a shelf life of up to 18 months based on accelerated aging. Both hemostatic agents were demonstrated to be effective in vitro blood clotting assays showing a low blood clotting index, high platelet adhesion capacity and accelerated clotting time. Hemostat granules and dressing were also used in a femoral artery rat bleeding model where hemorrhage control was achieved in 90 s without compression and resulted in 100% survival rate after a 7 and 14-day observation.

  4. Induction of SCE by DNA cross-links in human fibroblasts exposed to 8-MOP and UVA irradiation

    International Nuclear Information System (INIS)

    Bredberg, A.; Lambert, B.

    1983-01-01

    To study the SCE-inducing effect of psoralen cross-links in the DNA of normal, human fibroblasts, cell cultures were exposed to PUVA (0.2-1 μg of 8-MOP per ml, followed by UVA irradiation at 0.04 J/cm 2 ) and carefully washed to remove non-covalently bound psoralen. Some cell cultures were then given a second dose of UVA (1.1 J/cm 2 ), either immediately after PUVA or 1-3 days later. By this type of treatment, cells with different proportions of DNA cross-links are obtained. The initial PUVA treatment will mainly give rise to psoralen monoadducts and only few cross-links in the DNA, and the second UVA irradiation will convert a number of the psoralen monoadducts into cross-links. (orig./AJ)

  5. Sources, Fate and Distribution of Organic Matter on the Western Adriatic Continental Shelf, Italy

    International Nuclear Information System (INIS)

    Tesi, Tommaso; Miserocchi, Stefano; Langone, Leonardo; Boni, Laurita; Guerrini, Franca

    2006-01-01

    In the framework of the EUROSTRATAFORM projects, a multidisciplinary research was focused on processes that involve transport and deposition of riverine material in the Adriatic Sea. The aim of our contribution was to increase a more complete understanding of organic matter deposition on the Adriatic shelf, also taking into account the role of Apennine rivers beyond the Po influence. In order to characterize origin, fate and variability of sedimentary organic carbon we utilized elemental and stable carbon isotope data in surficial sediments along shallow cross-shelf transects on the western Adriatic shelf

  6. Effect of cross-linking on properties and release characteristics of sodium salicylate-loaded electrospun poly(vinyl alcohol) fibre mats

    International Nuclear Information System (INIS)

    Taepaiboon, Pattama; Rungsardthong, Uracha; Supaphol, Pitt

    2007-01-01

    Cross-linking of electrospun (e-spun) fibre mats (beaded fibre morphology with the average diameter of the fibre segments between beads being ∼108 nm) of poly(vinyl alcohol) (PVA) containing sodium salicylate (SS), used as the model drug, was achieved by exposing the fibre mats to the vapour from 5.6 M aqueous solution of either glutaraldehyde or glyoxal for various exposure time intervals, followed by a heat treatment in a vacuum oven. With increasing the exposure time in the cross-linking chamber, the morphology of the e-spun fibre mats gradually changed from a porous to dense structure. Both the degree of swelling and the percentage of weight loss of the cross-linked fibre mats (i.e. ∼200-530% and ∼15-57%, respectively) were lower than those of the untreated ones (i.e. ∼610% and ∼67%, respectively). Cross-linking was also responsible for the monotonic increase in the storage moduli of the cross-linked SS-loaded e-spun PVA fibre mats with increasing exposure time in the cross-linking chamber. The release characteristic of the model drug from the SS-loaded e-spun PVA fibre mats both before and after cross-linking was assessed by the transdermal diffusion through a pig skin method. The cumulative release of the drug from these matrices could be divided into two stages: 0-4 and 4-72 h, in which the amount of SS released in the first stage increased very rapidly, while it was much slower in the second stage. Cross-linking slowed down the release of SS from the drug-loaded fibre mats appreciably and both the rate of release and the total amount of the drug released were decreasing functions of the exposure time interval in the cross-linking chamber. Lastly, the cross-linked SS-loaded e-spun PVA fibre mats were non-toxic to normal human dermal fibroblasts

  7. Radiation Chemistry of Polyethylenes for Total Joint Applications

    International Nuclear Information System (INIS)

    Muratoglu, O.K.

    2006-01-01

    Wear and fatigue damage of polyethylene could limit the longevity of total hip and knee reconstructions used to treat end-stage joint diseases. Wear debris causes peri-prosthetic osteolysis, resulting in bone loss and component loosening ultimately necessitating revision surgery. Wear rate of polyethylene can be reduced by radiation crosslinking. Irradiation not only crosslinks the amorphous phase of polyethylene but also creates residual free radicals (RFR), the precursor to long-term oxidation. We used post-irradiation melting to eliminate the RFRs and improve oxidative stability. We determined the molecular weight between crosslinks (M c ) as a function of radiation-dose level and showed the wear rate to scale linearly with M c . Irradiated and melted polyethylene, in clinical use since 1998, show a significant reduction in wear in vivo through radiographic follow-up studies and analysis of surgically explanted acetabular liners. Irradiation and melting reduces the crystallinity and mechanical properties of polyethylene therefore it cannot be used for high demand joint applications, such as posterior stabilized knees. We replaced the post-irradiation melting step with ?-tocopherol (vitamin-E) doping to stabilize the RFRs and prevent long-term stability and at the same time prevent the loss of mechanical properties. 100kGy irradiated polyethylene was soaked in 120 degree vitamin-E followed by a homogenization step at 120degree. The ?-tocopherol doped samples showed no detectable oxidation after accelerating aging at 80degree in air for 5 weeks. The wear rate was comparable to that of 100-kGy irradiated and melted polyethylene with both clean and third body added bovine serum lubrication. The fatigue strength of ?-tocopherol doped polyethylene (ΔKi=0.9MPa.m 1 /2) were higher than that of 100-kGy irradiated and melted polyethylene (ΔKi=0.5 MPa.m 1 /2). Similarly, the ultimate tensile and yield strength of α-tocopherol doped polyethylenes were significantly

  8. Feasibility of biodegradable based packaging used for red meat storage during shelf-life: A pilot study.

    Science.gov (United States)

    Panseri, S; Martino, P A; Cagnardi, P; Celano, G; Tedesco, D; Castrica, M; Balzaretti, C; Chiesa, L M

    2018-05-30

    This study was designated to ascertain the effectiveness of polylactic acid (PLA) based packaging solution to store red fresh meat during its refrigerated shelf-life. Recently the attention in the packaging industry regarding the use of bioplastics has been shifting from compostable/biodegradable materials toward biobased materials. Steaks obtained from semimembranous muscle of Piemontese beef were packaged in PLA trays closed with a lid made of PLA film and for comparison purposed in a conventional reference package consisting of a amorphous polyethylene terephthalate/polyethylene (APET/PET) trays and wrapped in plastic film of polyvinyl chloride (PVC). The packaging under modified atmosphere MAP was carried out by using a gas mixture of 66% O 2 , 25% CO 2 and 9%N 2 . By using PLA packaging combination it was possible to maintain an optimum red colour together with a reduced content of volatile compounds associated to off-flavours of meat samples particularly related to the oxidation phenomena. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Cross-linked aromatic cationic polymer electrolytes with enhanced stability for high temperature fuel cell applications

    DEFF Research Database (Denmark)

    Ma, Wenjia; Zhao, Chengji; Yang, Jingshuai

    2012-01-01

    Diamine-cross-linked membranes were prepared from cross-linkable poly(arylene ether ketone) containing pendant cationic quaternary ammonium group (QPAEK) solution by a facile and general thermal curing method using 4,4′-diaminodiphenylmethane with rigid framework and 1,6-diaminohexane with flexible...... anchoring of the molecule. Combining the excellent thermal stability, the addition of a small amount of diamines enhanced both the chemical and mechanical stability and the phosphoric acid doping (PA) ability of membranes. Fuel cell performance based on impregnated cross-linked membranes have been...... successfully operated at temperatures up to 120 °C and 180 °C with unhumidified hydrogen and air under ambient pressure, the maximum performance of diamine-cross-linked membrane is observed at 180 °C with a current density of 1.06 A cm−2 and the peak power density of 323 mW cm−2. The results also indicate...

  10. Azide-based cross-linking of polymers of intrinsic microporosity (PIMs) for condensable gas separation

    KAUST Repository

    Du, Naiying

    2011-03-11

    Cross-linked polymers of intrinsic microporosity (PIM)s for gas separation membranes, were prepared by a nitrene reaction from a representative PIM in the presence of two different diazide cross-linkers. The reaction temperature was optimized using TGA. The homogenous membranes were cast from THF solutions of different ratios of PIM to azides. The resulting cross-linked structures of the PIMs membranes were formed at 175 °C after 7.5 h and confirmed by TGA, XPS, FT-IR spectroscopy and gel content analysis. These resulting cross-linked polymeric membranes showed excellent gas separation performance and can be used for O 2/N 2 and CO 2/N 2 gas pairs, as well as for condensable gases, such as CO 2/CH 4, propylene/propane separation. Most importantly, and differently from typical gas separation membranes derived from glassy polymers, the crosslinked PIMs showed no obvious CO 2 plasticization up to 20 atm pressure of pure CO 2 and CO 2/CH 4 mixtures. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. A novel sulfonated poly(ether ether ketone) and cross-linked membranes for fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Li, Hongtao; Zhang, Gang; Wu, Jing; Zhao, Chengji; Zhang, Yang; Shao, Ke; Han, Miaomiao; Lin, Haidan; Zhu, Jing; Na, Hui [Alan G MacDiarmid Institute, College of Chemistry, Jilin University, Qianjin Street 2699, Changchun 130012, Jilin (China)

    2010-10-01

    A novel poly(ether ether ketone) (PEEK) containing pendant carboxyl groups has been synthesized by a nucleophilic polycondensation reaction. Sulfonated polymers (SPEEKs) with different ion exchange capacity are then obtained by post-sulfonation process. The structures of PEEK and SPEEKs are characterized by both FT-IR and {sup 1}H NMR. The properties of SPEEKs as candidates for proton exchange membranes are studied. The cross-linking reaction is performed at 140 C using poly(vinyl alcohol) (PVA) as the cross-linker. In comparison with the non-cross-linked membranes, some properties of the cross-linked membranes are significantly improved, such as water uptake, methanol resistance, mechanical and oxidative stabilities, while the proton conductivity decreases. The effect of PVA content on proton conductivity, water uptake, swelling ratio, and methanol permeability is also investigated. Among all the membranes, SPEEK-C-8 shows the highest selectivity of 50.5 x 10{sup 4} S s cm{sup -3}, which indicates that it is a suitable candidate for applications in direct methanol fuel cells. (author)

  12. Azide-based cross-linking of polymers of intrinsic microporosity (PIMs) for condensable gas separation

    KAUST Repository

    Du, Naiying; Dal-Cin, Mauro M D; Pinnau, Ingo; Nicalek, Andrzej; Robertson, Gilles P.; Guiver, Michael D.

    2011-01-01

    Cross-linked polymers of intrinsic microporosity (PIM)s for gas separation membranes, were prepared by a nitrene reaction from a representative PIM in the presence of two different diazide cross-linkers. The reaction temperature was optimized using TGA. The homogenous membranes were cast from THF solutions of different ratios of PIM to azides. The resulting cross-linked structures of the PIMs membranes were formed at 175 °C after 7.5 h and confirmed by TGA, XPS, FT-IR spectroscopy and gel content analysis. These resulting cross-linked polymeric membranes showed excellent gas separation performance and can be used for O 2/N 2 and CO 2/N 2 gas pairs, as well as for condensable gases, such as CO 2/CH 4, propylene/propane separation. Most importantly, and differently from typical gas separation membranes derived from glassy polymers, the crosslinked PIMs showed no obvious CO 2 plasticization up to 20 atm pressure of pure CO 2 and CO 2/CH 4 mixtures. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Glutaraldehyde cross-linking of amniotic membranes affects their nanofibrous structures and limbal epithelial cell culture characteristics

    Directory of Open Access Journals (Sweden)

    Lai JY

    2013-10-01

    Full Text Available Jui-Yang Lai,1–3 David Hui-Kang Ma4,5 1Institute of Biochemical and Biomedical Engineering, 2Biomedical Engineering Research Center, 3Molecular Medicine Research Center, Chang Gung University, Taoyuan, Taiwan; 4Limbal Stem Cell Laboratory, Department of Ophthalmology, Chang Gung Memorial Hospital, Taoyuan, Taiwan; 5Department of Chinese Medicine, Chang Gung University, Taoyuan, Taiwan Abstract: Given that the cells can sense nanometer dimensions, the chemical cross-linking-mediated alteration in fibrillar structure of collagenous tissue scaffolds is critical to determining their cell culture performances. This article explores, for the first time, the effect of nanofibrous structure of glutaraldehyde (GTA cross-linked amniotic membrane (AM on limbal epithelial cell (LEC cultivation. Results of ninhydrin assays demonstrated that the amount of new cross-links formed between the collagen chains is significantly increased with increasing the cross-linking time from 1 to 24 hours. By transmission electron microscopy, the AM treated with GTA for a longer duration exhibited a greater extent of molecular aggregation, thereby leading to a considerable increase in nanofiber diameter and resistance against collagenase degradation. In vitro biocompatibility studies showed that the samples cross-linked with GTA for 24 hours are not well-tolerated by the human corneal epithelial cell cultures. When the treatment duration is less than 6 hours, the biological tissues cross-linked with GTA for a longer time may cause slight reductions in 3-(4,5-dimethylthiazol-2-yl-5-(3-carboxymethoxyphenyl-2-(4-sulfophenyl-2H-tetrazolium, inner salt, and anti-inflammatory activities. Nevertheless, significant collagen molecular aggregation also enhances the stemness gene expression, indicating a high ability of these AM matrices to preserve the progenitors of LECs in vitro. It is concluded that GTA cross-linking of collagenous tissue materials may affect their nanofibrous

  14. Sub- T g Cross-Linking of a Polyimide Membrane for Enhanced CO 2 Plasticization Resistance for Natural Gas Separation

    KAUST Repository

    Qiu, Wulin

    2011-08-09

    Decarboxylation-induced thermal cross-linking occurs at elevated temperatures (∼15 °C above glass transition temperature) for 6FDA-DAM:DABA polyimides, which can stabilize membranes against swelling and plasticization in aggressive feed streams. Despite this advantage, such a high temperature might result in collapse of substructure and transition layers in the asymmetric structure of a hollow fibers based on such a material. In this work, the thermal cross-linking of the 6FDA-DAM:DABA at temperatures much below the glass transition temperature (∼387 °C by DSC) was demonstrated. This sub-Tg cross-linking capability enables extension to asymmetric structures useful for large scale membranes. The resulting polymer membranes were characterized by swelling in known solvents for the un-cross-linked materials, TGA analysis, and permeation tests of aggressive gas feed stream at higher pressure. The annealing temperature and time clearly influence the degree of cross-linking of the membranes, and results in a slight difference in selectivity for membranes under various cross-linking conditions. Results indicate that the sub-Tg thermal cross-linking of 6FDA-DAM:DABA dense film membrane can be carried out completely even at a temperature as low as 330 °C. Permeabilities were tested for the polyimide membranes using both pure gases (He, O2, N2, CH4, CO2) and mixed gases (CO2/CH4). The selectivity of the cross-linked membrane can be maintained even under very aggressive CO2 operating conditions that are not possible without cross-linking. Moreover, the plasticization resistance was demonstrated up to 700 psia for pure CO 2 gas or 1000 psia for 50% CO2 mixed gas feeds. © 2011 American Chemical Society.

  15. MODIFICATION OF ERYTHROCYTE MEMBRANE PROTEINS WITH POLYETHYLENE GLYCOL 1500

    Directory of Open Access Journals (Sweden)

    N. G. Zemlianskykh

    2016-10-01

    Full Text Available The aim of the work was to study the effect of polyethylene glycol PEG-1500 on the Ca2+-ATPase activity and changes in CD44 surface marker expression in human erythrocyte membranes. Determination of the Ca2+-ATPase activity was carried out in sealed erythrocyte ghosts by the level of accumulation of inorganic phosphorus. Changes in the expression of CD44 and amount of CD44+-erythrocytes were evaluated by flow cytometry. The inhibition of Ca2+-ATPase activity and a reduction in the level of CD44 expression and also the decrease in the amount CD44+-cells were found, reflecting a fairly complex restructuring in the membrane-cytoskeleton complex of erythrocytes under the influence of PEG-1500. Effect of PEG-1500 on the surface CD44 marker could be mediated by modification of proteins of membrane-cytoskeleton complex, as indicated by accelerated loss of CD44 in erythrocyte membranes after application of protein cross-linking reagent diamide. Reduced activity of Ca2+-ATPase activity may contribute to the increase in intracellular Ca2+ level and thus leads to a modification of interactions of integral proteins with cytoskeletal components that eventually could result in membrane vesiculation and decreasing in expression of the CD44 marker, which is dynamically linked to the cytoskeleton.

  16. Self-reinforcement and protein sustained delivery of hyaluronan hydrogel by tailoring a dually cross-linked network

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Chunhong; Xu, Guoguang; Wang, Xinghui [Department of Materials Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Tu, Mei; Zeng, Rong; Rong, Jianhua [Department of Materials Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Engineering Research Center of Artificial Organs and Materials, Ministry of Education, Guangzhou 510632 (China); Zhao, Jianhao, E-mail: jhzhao@jnu.edu.cn [Department of Materials Science and Engineering, College of Science and Engineering, Jinan University, Guangzhou 510632 (China); Engineering Research Center of Artificial Organs and Materials, Ministry of Education, Guangzhou 510632 (China)

    2015-01-01

    A series of self-reinforcing hyaluronan hydrogels were developed to improve mechanical properties and protein sustained delivery thanks to a dually cross-linked network. Hyaluronan gel particles (HGPs, 1–5 μm in diameter) with different cross-linking densities, i.e. HGPs-1.5, HGPs-3 and HGPs-15, were prepared in an inverse emulsion system and used as the reinforcing phase after glycidyl methacrylation, while glycidyl methacrylated hyaluronan with a substitution degree of 45.2% was synthesized as the matrix phase. These two phases were cross-linked under ultraviolet irradiation to form self-reinforcing hyaluronan hydrogels (srHAs) that showed typical cross-linked structure of HGPs connecting the matrix phase by cross-section observation. In comparison to hyaluronan bulk gels and their blends with HGPs, srHAs distinctly enhanced the mechanical properties and BSA long-term sustained delivery, especially srHA-1.5 showed the highest compressive modulus of 220 ± 15 kPa and the slowest BSA delivery (67% release at 14 d). The 3T3 fibroblast cell culture showed that all the srHAs had no cytotoxicity. - Highlights: • New self-reinforcing HA hydrogels with a dually cross-linked network were developed. • Self-reinforcing HA hydrogels greatly enhanced the mechanical properties. • Self-reinforcing HA hydrogels prolonged the sustained delivery of BSA. • The self-reinforcing mechanism and BSA diffusion mechanism were discussed. • Self-reinforcing HA hydrogels had no cytotoxicity to 3T3 fibroblast cells.

  17. Self-reinforcement and protein sustained delivery of hyaluronan hydrogel by tailoring a dually cross-linked network

    International Nuclear Information System (INIS)

    Luo, Chunhong; Xu, Guoguang; Wang, Xinghui; Tu, Mei; Zeng, Rong; Rong, Jianhua; Zhao, Jianhao

    2015-01-01

    A series of self-reinforcing hyaluronan hydrogels were developed to improve mechanical properties and protein sustained delivery thanks to a dually cross-linked network. Hyaluronan gel particles (HGPs, 1–5 μm in diameter) with different cross-linking densities, i.e. HGPs-1.5, HGPs-3 and HGPs-15, were prepared in an inverse emulsion system and used as the reinforcing phase after glycidyl methacrylation, while glycidyl methacrylated hyaluronan with a substitution degree of 45.2% was synthesized as the matrix phase. These two phases were cross-linked under ultraviolet irradiation to form self-reinforcing hyaluronan hydrogels (srHAs) that showed typical cross-linked structure of HGPs connecting the matrix phase by cross-section observation. In comparison to hyaluronan bulk gels and their blends with HGPs, srHAs distinctly enhanced the mechanical properties and BSA long-term sustained delivery, especially srHA-1.5 showed the highest compressive modulus of 220 ± 15 kPa and the slowest BSA delivery (67% release at 14 d). The 3T3 fibroblast cell culture showed that all the srHAs had no cytotoxicity. - Highlights: • New self-reinforcing HA hydrogels with a dually cross-linked network were developed. • Self-reinforcing HA hydrogels greatly enhanced the mechanical properties. • Self-reinforcing HA hydrogels prolonged the sustained delivery of BSA. • The self-reinforcing mechanism and BSA diffusion mechanism were discussed. • Self-reinforcing HA hydrogels had no cytotoxicity to 3T3 fibroblast cells

  18. Effects of UV Aging on the Cracking of Titanium Oxide Layer on Poly(ethylene terephthalate) Substrate: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Chao; Gray, Matthew H.; Tirawat, Robert; Larsen, Ross E.; Chen, Fangliang

    2016-04-18

    Thin oxide and metal films deposited on polymer substrates is an emerging technology for advanced reflectors for concentrated solar power applications, due to their unique combination of light weight, flexibility and inexpensive manufacture. Thus far, there is little knowledge on the mechanical integrity or structural persistence of such multi-layer thin film systems under long-term environmental aging. In this paper, the cracking of a brittle titanium dioxide layer deposited onto elasto-plastic poly(ethylene terephthalate) (PET) substrate is studied through a combination of experiment and modeling. In-situ fragmentation tests have been conducted to monitor the onset and evolution of cracks both on pristine and on samples aged with ultraviolet (UV) light. An analytical model is presented to simulate the cracking behavior and to predict the effects of UV aging. Based on preliminary experimental observation, the effect of aging is divided into three aspects and analyzed independently: mechanical property degradation of the polymer substrate; degradation of the interlayer between substrate and oxide coating; and internal stress-induced cracks on the oxide coating.

  19. Dialing in the Ratio of Covalent and Coordination Cross-links in Self-healing Hydrogels

    DEFF Research Database (Denmark)

    Andersen, Amanda; Krogsgaard, Marie; Birkedal, Henrik

    -linking and as these impacts the abovementioned properties, it is of great interest to control the degree of which these are present; i.e. controlling the degree of catechol oxidation. Until now, the catechols participating in the two cross-linking types have been the same. This way the actual ratio between the two types...... cannot be either predefined or controlled, as it is determined by the oxidation rate within the hydrogel. Here, we report hydrogels in which the catechols participating in reversible (oxidation resistant catechol) and irreversible (classical catechol) cross-links are separated, enabling one to predefine...... the ratio of the two by altering the composition....

  20. Use of polyethylene glycol in functional constipation and fecal impaction.

    Science.gov (United States)

    Mínguez, Miguel; López Higueras, Antonio; Júdez, Javier

    2016-12-01

    The objective of this study was to evaluate in an analytical and descriptive manner the evidence published so far on the use of polyethylene glycol (PEG), with or without electrolytes, in the management of functional constipation and the treatment of fecal impaction. Search on MEDLINE, EMBASE and Cochrane databases until May 2016 of all publications adjusted to the following terms: constipation AND/OR fecal impaction AND (PEG OR polyethylene glycol OR macrogol OR movicol OR idralax OR miralax OR transipeg OR forlax OR golytely OR isocolan OR mulytely) NOT colonoscopy. Critical reading of selected articles (English or Spanish), sorting their description according to group age (adult/pediatric age) and within those, in accordance with study features (efficacy evaluation versus placebo, doses query, safety, comparison with other laxatives, observational studies and monographic review articles of polyethylene glycol or meta-analysis). Fifty-eight publications have been chosen for descriptive analysis; of them, 41 are clinical trials, eight are observational studies and nine are systematic reviews or meta-analysis. Twelve clinical trials evaluate PEG efficacy versus placebo, eight versus lactulose, six are dose studies, five compare polyethylene glycol with and without electrolytes, two compare its efficacy with respect to milk of magnesia, and the rest of the trials evaluate polyethylene glycol with enemas (two), psyllium (one), tegaserod (one), prucalopride (one), paraffin oil (one), fiber combinations (one) and Descurainia sophia (one). Polyethylene glycol with or without electrolytes is more efficacious than placebo for the treatment of functional constipation, either in adults or in pediatric patients, with great safety and tolerability. These preparations constitute the most efficacious osmotic laxatives (more than lactulose) and are the first-line treatment for functional constipation in the short and long-term. They are as efficacious as enemas in fecal

  1. 2006 Multibeam Mapping of cross-shelf corridor, North of Madison-Swanson - Florida

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This disk or set of disks contain high-resolution multibeam and backscatter maps of an area North of Madison-Swanson (29.1667N, 85.6667W), in the West-Florida shelf,...

  2. Characteristics of heat shrinkable high density polyethylene crosslinked by γ-irradiation

    International Nuclear Information System (INIS)

    Kang, Phil Hyun; Nho, Young Chang

    2001-01-01

    The effects of γ-irradiation on the crosslinking of high density polyethylene (HDPE) was investigated for the purpose of obtaining a suitable formulation for heat shrinkable materials. In this study the HDPE specimens were prepared by blending with cross linking agents and pressed into a 0.2 mm sheet at 180 .deg. C. γ-irradiation was conducted at 40 to 100 kGy in nitrogen. The heat shrinkable property and thermal mechanical property of the HDPE sheets have been investigated. It was found that the degree of crosslinking of the irradiated HDPE samples were increased with irradiation dose. Compared with the HDPE containing triallylisocyanurate, the HDPE containing trimethlol propane triacrylate shows a slight increase in crosslinking density. The heat transformation and dimension change of HDPE decreased with increasing radiation dose. The heat shrinkage of the samples increased with increasing annealing temperatures. The thermal resistance of HDPE increased upon the crosslinking of HDPE

  3. Highly Enriched Uranium Metal Annuli and Cylinders with Polyethylene Reflectors and/or Internal Polyethylene Moderator

    International Nuclear Information System (INIS)

    Tyler Sumner; J. Blair Briggs; Leland Montierth

    2007-01-01

    A variety of critical experiments were constructed of enriched uranium metal during the 1960s and 1970s at the Oak Ridge Critical Experiments Facility in support of criticality safety operations at the Y-12 Plant. The purposes of these experiments included the evaluation of storage, casting, and handling limits for the Y-12 Plant and providing data for verification of calculation methods and cross-sections for nuclear criticality safety applications. These included solid cylinders of various diameters, annuli of various inner and outer diameters, two and three interacting cylinders of various diameters, and graphite and polyethylene reflected cylinders and annuli. Of the hundreds of delayed critical experiments, experiments of uranium metal annuli with and without polyethylene reflectors and with the central void region either empty or filled with polyethylene were evaluated under ICSBEP Identifier HEU-MET-FAST-076. The outer diameter of the uranium annuli varied from 9 to 15 inches in two-inch increments. In addition, there were uranium metal cylinders with diameters varying from 7 to 15 inches with complete reflection and reflection on one flat surface to simulate floor reflection. Most of the experiments were performed between February 1964 and April 1964. Five partially reflected (reflected on the top only) experiments were assembled in November 1967, but are judged by the evaluators not to be of benchmark quality. Twenty-four of the twenty-five experiments have been determined to have fast spectra. The only exception has a mixed spectrum. Analyses were performed in which uncertainty associated with five different parameters associated with the uranium parts and three associated with the polyethylene parts was evaluated. Included were uranium mass, height, diameter, isotopic content, and impurity content and polyethylene mass, diameter, and impurity content. There were additional uncertainties associated with assembly alignment, support structure, and the value

  4. Simulating shelf life determination by two simultaneous criteria.

    Science.gov (United States)

    Peleg, Micha; Normand, Mark D

    2015-12-01

    The shelf life of food and pharmaceutical products is frequently determined by a marker's concentration or quality index falling below or surpassing an assigned threshold level. Naturally, different chosen markers would indicate different shelf life for the same storage temperature history. We demonstrate that if there are two markers, such as two labile vitamins, the order in which their concentrations cross their respective thresholds may depend not only on their degradation kinetic parameters but also on the particular storage temperature profile, be it isothermal or non-isothermal. Thus, at least theoretically, the order observed in accelerated storage need not be always indicative of the actual order at colder temperatures, except where the two degradation reactions follow the same kinetic order and their temperature-dependence rate parameter is also the same. This is shown with simulated hypothetical degradation reactions that follow first or zero order kinetics and whose rate constant's temperature-dependence obeys the exponential model. It is also demonstrated with simulated hypothetical Maillard reaction's products whose synthesis rather than their degradation follows pseudo zero order kinetics. The software developed to do the simulations and calculate the thresholds crossing points has been posted on the Internet as a freely downloadable interactive Wolfram Demonstration, which can be used as a tool in storage studies and shelf life prediction. In principle, the methodology can be extended from two to any number of markers. Copyright © 2015 Elsevier Ltd. All rights reserved.

  5. In vitro calcification and in vivo biocompatibility of the cross-linked polypentapeptide of elastin

    International Nuclear Information System (INIS)

    Wood, S.A.; Lemons, J.E.; Prasad, K.U.; Urry, D.W.

    1986-01-01

    The in vitro calcifiability and molecular weight dependence of calcification of the polypentapeptide, (L X Val1-L X Pro2-Gly3-L X Val4-Gly5)n, which had been gamma-irradiation cross-linked have been determined when exposed to dialyzates of normal, nonaugmented fetal bovine serum. The material was found to calcify: calcifiability was found to be highly molecular weight dependent and to be most favored when the highest molecular weight polymers (n approximately equal to 240) had been used for cross-linking. The in vivo biocompatibility, biodegradability, and calcifiability of the gamma-irradiation cross-linked polypentapeptide were examined in rabbits in both soft and hard tissue sites. The material was found to be biocompatible irrespective of its physical form and to be biodegradable but with n of 200 or less it was not shown to calcify or ossify in the rabbit tibial nonunion model

  6. Robust cross-links in molluscan adhesive gels: testing for contributions from hydrophobic and electrostatic interactions.

    Science.gov (United States)

    Smith, A M; Robinson, T M; Salt, M D; Hamilton, K S; Silvia, B E; Blasiak, R

    2009-02-01

    The cross-linking interactions that provide cohesive strength to molluscan adhesive gels were investigated. Metal-based interactions have been shown to play an important role in the glue of the slug Arion subfuscus (Draparnaud), but other types of interactions may also contribute to the glue's strength and their role has not been investigated. This study shows that treatments that normally disrupt hydrophobic or electrostatic interactions have little to no effect on the slug glue. High salt concentrations and non-ionic detergent do not affect the solubility of the proteins in the glue or the ability of the glue proteins to stiffen gels. In contrast, metal chelation markedly disrupts the gel. Experiments with gel filtration chromatography identify a 40 kDa protein that is a central component of the cross-links in the glue. This 40 kDa protein forms robust macromolecular aggregations that are stable even in the presence of high concentrations of salt, non-ionic detergent, urea or metal chelators. Metal chelation during glue secretion, however, may block some of these cross-links. Such robust, non-specific interactions in an aqueous environment are highly unusual for hydrogels and reflect an intriguing cross-linking mechanism.

  7. Application of cross-linked and hydrolyzed arabinoxylans in baking of model rye bread.

    Science.gov (United States)

    Buksa, Krzysztof; Nowotna, Anna; Ziobro, Rafał

    2016-02-01

    The role of water extractable arabinoxylan with varying molar mass and structure (cross-linked vs. hydrolyzed) in the structure formation of rye bread was examined using a model bread. Instead of the normal flour, the dough contained starch, arabinoxylan and protein, which were isolated from rye wholemeal. It was observed that the applied mixes of these constituents result in a product closely resembling typical rye bread, even if arabinoxylan was modified (by cross-linking or hydrolysis). The levels of arabinoxylan required for bread preparation depended on its modification and mix composition. At 3% protein, the maximum applicable level of poorly soluble cross-linked arabinoxylan was 3%, as higher amounts of this preparation resulted in an extensively viscous dough and diminished bread volume. On the other hand highly soluble, hydrolyzed arabinoxylan could be used at a higher level (6%) together with larger amounts of rye protein (3% or 6%). Further addition of arabinoxylan leads to excessive water absorption, resulting in a decreased viscosity of the dough during baking and insufficient gas retention. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. Glutaraldehyde cross-linking of tendon mechanical effects at the level of the tendon fascicle and fibril

    DEFF Research Database (Denmark)

    Hansen, Philip; Hassenkam, Tue; Svensson, Rene Bruggebusch

    2009-01-01

    at the tendon fibril level were examined by atomic force microscopy. Peak forces increased from approximately 1379 to approximately 2622 pN while an extended Hertz fit of force-indentation data showed a approximately 24 fold increase in Young's modulus on indentation. The effect of glutaraldehyde cross......Conclusive insight into the microscopic principles that govern the strength of tendon and related connective tissues is lacking and the importance of collagen cross-linking has not been firmly established. The combined application of whole-tissue mechanical testing and atomic force spectroscopy...... allowed for a detailed characterization of the effect of cross-linking in rat-tail tendon. The cross-link inducing agent glutaraldehyde augmented the tensile strength of tendon fascicles. Stress at failure increased from approximately 8 MPa to approximately 39 MPa. The mechanical effects of glutaraldehyde...

  9. Highly stable ionic-covalent cross-linked sulfonated poly(ether ether ketone) for direct methanol fuel cells

    Science.gov (United States)

    Lei, Linfeng; Zhu, Xingye; Xu, Jianfeng; Qian, Huidong; Zou, Zhiqing; Yang, Hui

    2017-05-01

    A novel ionic cross-linked sulfonated poly(ether ether ketone) containing equal content of sulfonic acid and pendant tertiary amine groups (TA-SPEEK) has been initially synthesized for the application in direct methanol fuel cells (DMFCs). By adjusting the ratio of p-xylene dibromide to tertiary amine groups of TA-SPEEK, a series of ionic-covalent cross-linked membranes (C-SPEEK-x) with tunable degree of cross-linking are prepared. Compared with the pristine membrane, the ionic and ionic-covalent cross-linked proton exchange membranes (PEMs) exhibit reduced methanol permeability and improved mechanical properties, dimensional and oxidative stability. The proton conductivity and methanol selectivity of protonated TA-SPEEK and C-SPEEK-x at 25 °C is up to 0.109 S cm-1 and 3.88 × 105 S s cm-3, respectively, which are higher than that of Nafion 115. The DMFC incorporating C-SPEEK-25 exhibits a maximum power density as high as 35.3 mW cm-2 with 4 M MeOH at 25 °C (31.8 mW cm-2 for Nafion 115). Due to the highly oxidative stability of the membrane, no obvious performance degradation of the DMFC is observed after more than 400 h operation, indicating such cost-effective ionic-covalent cross-linked membranes have substantial potential as alternative PEMs for DMFC applications.

  10. Studies in cross-linking PVC footwear soling compounds using gamma-irradiation

    International Nuclear Information System (INIS)

    Bloom, L.I.

    1983-01-01

    Irradiation cross-linking of polymeric materials has been known for some time, but it is only in recent years that it has been put to commercial advantage. Well known uses are the modification of PVC for higher temperature applications. Fundamental studies were carried out on amongst other materials, plasticised PVC compounds for use in cable applications. The results of this work, encouraged the author to investigate cross-linkable PVC in areas such as footwear soling

  11. An analog method of cross-talk compensation for a RGB wavelength division multiplexed optical link

    Science.gov (United States)

    Chisholm, George; Leveneur, Jérôme; Futter, John; Kennedy, John

    2018-06-01

    Pulse-width modulation (PWM) over optical fiber can be a very advantageous data transmission approach when an electrically isolated data link is required. The use of wavelength division multiplexing allows multiple data streams to be sent through a single fiber independently. The present investigation aims to demonstrate a novel approach to reduce cross-talk in a three-channel RGB optical link without the need for complex optical componentry. An op-amp circuit is developed to reduce the cross-talk so that the resolution of the PWM data is preserved. An iterative Monte-Carlo simulation approach is used to optimize the op-amp circuit. The approach is developed for a set of three PWM Hall effect magnetometers with 12-bit resolution and 128 Hz sampling rate. We show that, in these conditions, the loss of resolution due to cross-talk is prevented. We also show that the cross-talk compensation allows the RGB PWM link to outperform other transmission schemes.

  12. Photodissociative Cross-Linking of Non-covalent Peptide-Peptide Ion Complexes in the Gas Phase

    Science.gov (United States)

    Nguyen, Huong T. H.; Andrikopoulos, Prokopis C.; Rulíšek, Lubomír; Shaffer, Christopher J.; Tureček, František

    2018-05-01

    We report a gas-phase UV photodissociation study investigating non-covalent interactions between neutral hydrophobic pentapeptides and peptide ions incorporating a diazirine-tagged photoleucine residue. Phenylalanine (Phe) and proline (Pro) were chosen as the conformation-affecting residues that were incorporated into a small library of neutral pentapeptides. Gas-phase ion-molecule complexes of these peptides with photo-labeled pentapeptides were subjected to photodissociation. Selective photocleavage of the diazirine ring at 355 nm formed short-lived carbene intermediates that underwent cross-linking by insertion into H-X bonds of the target peptide. The cross-link positions were established from collision-induced dissociation tandem mass spectra (CID-MS3) providing sequence information on the covalent adducts. Effects of the amino acid residue (Pro or Phe) and its position in the target peptide sequence were evaluated. For proline-containing peptides, interactions resulting in covalent cross-links in these complexes became more prominent as proline was moved towards the C-terminus of the target peptide sequence. The photocross-linking yields of phenylalanine-containing peptides depended on the position of both phenylalanine and photoleucine. Density functional theory calculations were used to assign structures of low-energy conformers of the (GLPMG + GLL*LK + H)+ complex. Born-Oppenheimer molecular dynamics trajectory calculations were used to capture the thermal motion in the complexes within 100 ps and determine close contacts between the incipient carbene and the H-X bonds in the target peptide. This provided atomic-level resolution of potential cross-links that aided spectra interpretation and was in agreement with experimental data. [Figure not available: see fulltext.

  13. Hydrothermal growth of cross-linked hyperbranched copper dendrites using copper oxalate complex

    Science.gov (United States)

    Truong, Quang Duc; Kakihana, Masato

    2012-06-01

    A facile and surfactant-free approach has been developed for the synthesis of cross-linked hyperbranched copper dendrites using copper oxalate complex as a precursor and oxalic acid as a reducing and structure-directing agent. The synthesized particles are composed of highly branched nanostructures with unusual cross-linked hierarchical networks. The formation of copper dendrites can be explained in view of both diffusion control and aggregation-based growth model accompanied by the chelation-assisted assembly. Oxalic acid was found to play dual roles as reducing and structure-directing agent based on the investigation results. The understanding on the crystal growth and the roles of oxalic acid provides clear insight into the formation mechanism of hyperbranched metal dendrites.

  14. Adsorption equilibrium studies of uranium (VI) onto cross-linked chitosan-citric acid

    International Nuclear Information System (INIS)

    Ho Thi Yeu Ly; Nguyen Van Suc; Vo Quang Mai; Nguyen Mong Sinh

    2011-01-01

    Investigation of U(VI) adsorption by the cross- linked chitosan with citric acid was conduced by bath method. Effect of parameters such as pH, contact time, adsorbent dosage and other metal cations was determined. The maximum adsorption capacity of U(VI) at pH 4 was found to be 71.43 mg U(VI) / g cross-linked chitosan - citric acid after 300 min of contact time. The Langmuir and Freundlich isotherm models were used to describe adsorption equilibrium. The correction values, R 2 of two models were found to be 0.991 and 0.997, respectively. Therefore, it could be concluded that the adsorption equilibrium for U(VI) was followed the Langmuir and the Freundlich isotherm models. (author)

  15. Effects of welding parameters on friction stir spot welding of high density polyethylene sheets

    International Nuclear Information System (INIS)

    Bilici, Mustafa Kemal; Yukler, Ahmet Irfan

    2012-01-01

    Graphical abstract: (a) Schematic illustration of the cross section of a friction stir spot weld and (b) Geometry of the weld bonded area, x: nugget thickness and y: the thickness of the upper sheet. Highlights: → Welding parameters affect the FSSW nugget formation and the strength of the joint. → Melting of polyethylene occurred in the vicinity of the tool pin. → The joint that fractures with a pull nugget failure mode has a higher strength. -- Abstract: Friction stir spot welding parameters affect the weld strength of thermoplastics, such as high density polyethylene (HDPE) sheets. The effects of the welding parameters on static strength of friction stir spot welds of high density polyethylene sheets were investigated. For maximizing the weld strength, the selection of welding parameters is very important. In lap-shear tests two fracture modes were observed; cross nugget failure and pull nugget failure. The tool rotational speed, tool plunge depth and dwell time were determined to be important in the joint formation and its strength. The joint which had a better strength fails with a pull nugget failure morphology. Weld cross section image analysis of the joints were done with a video spectral comparator. The plunge rate of the tool was determined to have a negligible effect on friction stir spot welding.

  16. In-Culture Cross-Linking of Bacterial Cells Reveals Large-Scale Dynamic Protein-Protein Interactions at the Peptide Level.

    Science.gov (United States)

    de Jong, Luitzen; de Koning, Edward A; Roseboom, Winfried; Buncherd, Hansuk; Wanner, Martin J; Dapic, Irena; Jansen, Petra J; van Maarseveen, Jan H; Corthals, Garry L; Lewis, Peter J; Hamoen, Leendert W; de Koster, Chris G

    2017-07-07

    Identification of dynamic protein-protein interactions at the peptide level on a proteomic scale is a challenging approach that is still in its infancy. We have developed a system to cross-link cells directly in culture with the special lysine cross-linker bis(succinimidyl)-3-azidomethyl-glutarate (BAMG). We used the Gram-positive model bacterium Bacillus subtilis as an exemplar system. Within 5 min extensive intracellular cross-linking was detected, while intracellular cross-linking in a Gram-negative species, Escherichia coli, was still undetectable after 30 min, in agreement with the low permeability in this organism for lipophilic compounds like BAMG. We were able to identify 82 unique interprotein cross-linked peptides with cross-links occur in assemblies involved in transcription and translation. Several of these interactions are new, and we identified a binding site between the δ and β' subunit of RNA polymerase close to the downstream DNA channel, providing a clue into how δ might regulate promoter selectivity and promote RNA polymerase recycling. Our methodology opens new avenues to investigate the functional dynamic organization of complex protein assemblies involved in bacterial growth. Data are available via ProteomeXchange with identifier PXD006287.

  17. Effect of nordihydroguaiaretic acid cross-linking on fibrillar collagen: in vitro evaluation of fibroblast adhesion strength and migration

    Directory of Open Access Journals (Sweden)

    Ana Y. Rioja

    2017-04-01

    Full Text Available Fixation is required to reinforce reconstituted collagen for orthopedic bioprostheses such as tendon or ligament replacements. Previous studies have demonstrated that collagen fibers cross-linked by the biocompatible dicatechol nordihydroguaiaretic acid (NDGA have mechanical strength comparable to native tendons. This work focuses on investigating fibroblast behavior on fibrillar and NDGA cross-linked type I collagen to determine if NDGA modulates cell adhesion, morphology, and migration. A spinning disk device that applies a range of hydrodynamic forces under uniform chemical conditions was employed to sensitively quantify cell adhesion strength, and a radial barrier removal assay was used to measure cell migration on films suitable for these quantitative in vitro assays. The compaction of collagen films, mediated by the drying and cross-linking fabrication process, suggests a less open organization compared to native fibrillar collagen that likely allowed the collagen to form more inter-chain bonds and chemical links with NDGA polymers. Fibroblasts strongly adhered to and migrated on native and NDGA cross-linked fibrillar collagen; however, NDGA modestly reduced cell spreading, adhesion strength and migration rate. Thus, it is hypothesized that NDGA cross-linking masked some adhesion receptor binding sites either physically, chemically, or both, thereby modulating adhesion and migration. This alteration in the cell-material interface is considered a minimal trade-off for the superior mechanical and compatibility properties of NDGA cross-linked collagen compared to other fixation approaches.

  18. Cross-Linked ZnO Nanowalls Immobilized onto Bamboo Surface and Their Use as Recyclable Photocatalysts

    Directory of Open Access Journals (Sweden)

    Chunde Jin

    2014-01-01

    Full Text Available A novel recyclable photocatalyst was fabricated by hydrothermal method to immobilize the cross-linked ZnO nanowalls on the bamboo surface. The resultant samples were characterized by using scanning electron microscopy (SEM, X-ray diffraction (XRD, energy dispersive spectroscopy (EDS, and Fourier transformation infrared (FTIR techniques. FTIR spectra demonstrated that the cross-linked wurtzite ZnO nanowalls and bamboo surface were interconnected with each other by hydrogen bonds. Meanwhile, the cross-linked ZnO nanowalls modified bamboo (CZNB presented a superior photocatalytic ability and could be recycled at least 3 times with a photocatalytic efficiency up to 70%. The current research provides a new opportunity for the development of a portable and recycled biomass-based photocatalysts which can be an efficiently degraded pollutant solution and reused several times.

  19. Peer and Cross-Age Tutoring. ERIC Digest, Number 79.

    Science.gov (United States)

    Gaustad, Joan

    One-to-one tutoring programs, such as peer and cross-age tutoring, can result in emotional and learning benefits for the tutor and the tutee. Peer tutoring involves two students of the same age. In cross-age tutoring, the tutor is older than the tutee. The Willamette High School Peer Tutoring Program in Eugene, Oregon; the Coca-Cola Valued Youth…

  20. Quantitative Biostratigraphic Age Control of Glacimarine Sediments, ANDRILL 1B Drillcore, McMurdo Ice Shelf

    Science.gov (United States)

    Cody, R.; Levy, R.; Crampton, J.; Wilson, G.; Naish, T.; Harwood, D.; Winter, D.; Scherer, R.

    2008-12-01

    Interpretation of glacimarine sedimentary records from Antarctic shelf drillholes has been greatly hampered by the ambiguous age of strata where erosional unconformities and coarse diamictite deposits truncate or omit the mangetostratigraphic and biostratigraphic units used for correlation. However, new quantitative biostratigraphic techniques enable the correlation of sparse, incomplete, and reworking-prone Plio- Pleistocene records of Ross Sea fossil diatom flora with the more extensively documented but potentially diachronous offshore history of species' first and last appearances (FAs and LAs). The approach uses a comprehensive regional database of fossil records and computer-automated search algorithms to (a) find the multidimensional line of correlation (LOC) that best fits local observations, and (b) map out confidence intervals based on the full range of equally parsimonious composite FA/LA sequences and local range-end adjustments. An integrated, quantitative chronostratigraphic model for the AND-1B drillcore was constructed iteratively: the initial LOC was based solely on preliminary on-ice observations of fossil diatom highest and lowest occurrences (HOs and LOs) and their correlation with a database of other local event records from 24 DVDP, CIROS, and IODP drillcore sections. The model was subsequently updated as off-ice work yielded additional biostratigraphic marker events and revised event horizons, Ar/Ar ages for volcanic material, better- constrained magnetostratigraphic interpretations, and refinements to computational/analytical methodology. The current quantitative biostratigraphic age model for the AND-1B hole integrates the local ranges of 29 diatom taxa, 5 dated ashes, and independently constrained ages of 5 paleomagnetic reversals. Results corroborate almost all of the on-ice geomagnetic polarity reversal age interpretations, but identify a previously unrecognized major disconformity (~800kyr hiatus) near 440mbsf. It is significant to note