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Sample records for intrastrand crosslink lesion

  1. Are dinucleoside monophosphates relevant models for the study of DNA intrastrand cross-link lesions? The example of g[8-5m]T.

    Science.gov (United States)

    Garrec, Julian; Dumont, Elise

    2014-07-21

    Oxidatively generated tandem lesions such as G[8-5m]T pose a potent threat to genome integrity. Direct experimental studies of the kinetics and thermodynamics of a specific lesion within DNA are very challenging, mostly due to the variety of products that can be formed in oxidative conditions. Dinucleoside monophosphates (DM) involving only the reactive nucleobases in water represent appealing alternative models on which most physical chemistry and structural techniques can be applied. However, it is not yet clear how relevant these models are. Here, we present QM/MM MD simulations of the cyclization step involved in the formation of G[8-5m]T from the guanine-thymine (GpT) DM in water, with the aim of comparing our results to our previous investigation of the same reaction in DNA ( Garrec , J. , Patel , C. , Rothlisberger , U. , and Dumont , E. ( 2012 ) J. Am. Chem. Soc. 134 , 2111 - 2119 ). We show that, despite the different levels of preorganization of the two systems, the corresponding reactions share many energetic and structural characteristics. The main difference lies in the angle between the G and T bases, which is slightly higher in the transition state (TS) and product of the reaction in water than in the reaction in DNA. This effect is due to the Watson-Crick H-bonds, which are absent in the {GpT+water} system and restrain the relative positioning of the reactive nucleobases in DNA. However, since the lesion is accommodated easily in the DNA macromolecule, the induced energetic penalty is relatively small. The high similarity between the two reactions strongly supports the use of GpT in water as a model of the corresponding reaction in DNA.

  2. Insights into the Structure of Intrastrand Cross-Link DNA Lesion-Containing Oligonucleotides: G[8-5m]T and G[8-5]C from Molecular Dynamics Simulations

    Czech Academy of Sciences Publication Activity Database

    Dumont, E.; Dršata, Tomáš; Guerra, C. F.; Lankaš, Filip

    2015-01-01

    Roč. 54, č. 5 (2015), s. 1259-1267 ISSN 0006-2960 R&D Projects: GA ČR(CZ) GA14-21893S Institutional support: RVO:61388963 Keywords : hydrogen bonds * abasic sites * duplex DNA Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.876, year: 2015

  3. 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

  4. DNA oligonucleotide duplexes containing intramolecular platinated cross-links: energetics, hydration, sequence, and ionic effects.

    Science.gov (United States)

    Kankia, Besik I; Soto, Ana Maria; Burns, Nicole; Shikiya, Ronald; Tung, Chang-Shung; Marky, Luis A

    2002-11-05

    The anticancer activity of cisplatin arises from its ability to bind covalently to DNA, forming primarily intrastrand cross-links to adjacent purine residues; the most common adducts involve d(GpG) (65%) and d(ApG) (25%) intrastrand cross-links. The incorporation of these platinum adducts in a B-DNA helix induces local distortions, causing bending and unwinding of the DNA. In this work, we used temperature-dependent UV spectroscopy to investigate the unfolding thermodynamics, and associated ionic effects, of two sets of DNA decamer duplexes containing either cis-[Pt(NH(3))(2)[d(GpG

  5. Flanking bases influence the nature of DNA distortion by platinum 1,2-intrastrand (GG cross-links.

    Directory of Open Access Journals (Sweden)

    Debadeep Bhattacharyya

    Full Text Available The differences in efficacy and molecular mechanisms of platinum anti-cancer drugs cisplatin (CP and oxaliplatin (OX are thought to be partially due to the differences in the DNA conformations of the CP and OX adducts that form on adjacent guanines on DNA, which in turn influence the binding of damage-recognition proteins that control downstream effects of the adducts. Here we report a comprehensive comparison of the structural distortion of DNA caused by CP and OX adducts in the TGGT sequence context using nuclear magnetic resonance (NMR spectroscopy and molecular dynamics (MD simulations. When compared to our previous studies in other sequence contexts, these structural studies help us understand the effect of the sequence context on the conformation of Pt-GG DNA adducts. We find that both the sequence context and the type of Pt-GG DNA adduct (CP vs. OX play an important role in the conformation and the conformational dynamics of Pt-DNA adducts, possibly explaining their influence on the ability of many damage-recognition proteins to bind to Pt-DNA adducts.

  6. Evolutionary implications of inversions that have caused intra-strand parity in DNA

    Directory of Open Access Journals (Sweden)

    Wei John

    2007-06-01

    Full Text Available Abstract Background Chargaff's rule of DNA base composition, stating that DNA comprises equal amounts of adenine and thymine (%A = %T and of guanine and cytosine (%C = %G, is well known because it was fundamental to the conception of the Watson-Crick model of DNA structure. His second parity rule stating that the base proportions of double-stranded DNA are also reflected in single-stranded DNA (%A = %T, %C = %G is more obscure, likely because its biological basis and significance are still unresolved. Within each strand, the symmetry of single nucleotide composition extends even further, being demonstrated in the balance of di-, tri-, and multi-nucleotides with their respective complementary oligonucleotides. Results Here, we propose that inversions are sufficient to account for the symmetry within each single-stranded DNA. Human mitochondrial DNA does not demonstrate such intra-strand parity, and we consider how its different functional drivers may relate to our theory. This concept is supported by the recent observation that inversions occur frequently. Conclusion Along with chromosomal duplications, inversions must have been shaping the architecture of genomes since the origin of life.

  7. Ultraviolet irradiation produces cytotoxic synergy and increased DNA interstrand crosslinking with cis- and trans-diamminedichloroplatinum(II)

    International Nuclear Information System (INIS)

    Swinnen, L.J.; Erickson, L.C.

    1989-01-01

    The excision-repair mechanism responsible for the removal of UV-induced thymine dimers may also play a role in the repair of cis-diamminedichloroplatinum(II) (cis-DDP)-induced DNA adducts in both bacteria and mammalian cells. It was hypothesized that UV dimers and cis-DDP adducts, when present simultaneously, might compete for a common repair system. Colony survival assays were performed in HT-29 human colon carcinoma cells exposed either to cis-DDP alone or to cis-DDP immediately followed by UV exposure. Progressively greater cytotoxic synergy with both increasing UV dose and cis-DDP dose was observed, to a point of saturation beyond which further toxicity was purely additive. An approximate doubling in DNA crosslink frequency, relative to cis-DDP alone, was found in cells exposed to cis-DDP plus UV. Since cis-DDP produces both inter- and intrastrand DNA crosslinks similar studies were performed with trans-DDP, which is incapable of producing intrastrand crosslinks, but does produce interstrand crosslinks. Cytotoxic synergy and increased interstrand crosslinking again resulted from the addition of UV exposure, but not to the same extent as seen with cis-DDP. (author)

  8. DNA-crosslinker cisplatin eradicates bacterial persister cells.

    Science.gov (United States)

    Chowdhury, Nityananda; Wood, Thammajun L; Martínez-Vázquez, Mariano; García-Contreras, Rodolfo; Wood, Thomas K

    2016-09-01

    For all bacteria, nearly every antimicrobial fails since a subpopulation of the bacteria enter a dormant state known as persistence, in which the antimicrobials are rendered ineffective due to the lack of metabolism. This tolerance to antibiotics makes microbial infections the leading cause of death worldwide and makes treating chronic infections, including those of wounds problematic. Here, we show that the FDA-approved anti-cancer drug cisplatin [cis-diamminodichloroplatinum(II)], which mainly forms intra-strand DNA crosslinks, eradicates Escherichia coli K-12 persister cells through a growth-independent mechanism. Additionally, cisplatin is more effective at killing Pseudomonas aeruginosa persister cells than mitomycin C, which forms inter-strand DNA crosslinks, and cisplatin eradicates the persister cells of several pathogens including enterohemorrhagic E. coli, Staphylococcus aureus, and P. aeruginosa. Cisplatin was also highly effective against clinical isolates of S. aureus and P. aeruginosa. Therefore, cisplatin has broad spectrum activity against persister cells. Biotechnol. Bioeng. 2016;113: 1984-1992. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  9. Collagen crosslinks in chondromalacia of the patella.

    Science.gov (United States)

    Väätäinen, U; Kiviranta, I; Jaroma, H; Arokosi, J; Tammi, M; Kovanen, V

    1998-02-01

    The aim of the study was to determine collagen concentration and collagen crosslinks in cartilage samples from chondromalacia of the patella. To study the extracellular matrix alterations associated to chondromalacia, we determined the concentration of collagen (hydroxyproline) and its hydroxylysylpyridinoline and lysylpyridinoline crosslinks from chondromalacia foci of the patellae in 12 patients and 7 controls from apparently normal cadavers. The structure of the collagen network in 8 samples of grades II-IV chondromalacia was examined under polarized light microscopy. The full-thickness cartilage samples taken with a surgical knife from chondromalacia lesions did not show changes in collagen, hydroxylysylpyridinoline and lysylpyridinoline concentration as compared with the controls. Polarized light microscopy showed decreased birefringence in the superficial cartilage of chondromalacia lesions, indicating disorganization or disappearance of collagen fibers in this zone. It is concluded that the collagen network shows gradual disorganization with the severity of chondromalacia lesion of the patella without changes in the concentration or crosslinks of collagen.

  10. Polymerization by DNA polymerase eta is blocked by cis-diamminedichloroplatinum(II) 1,3-d(GpTpG) cross-link: implications for cytotoxic effects in nucleotide excision repair-negative tumor cells.

    Science.gov (United States)

    Chijiwa, Shotaro; Masutani, Chikahide; Hanaoka, Fumio; Iwai, Shigenori; Kuraoka, Isao

    2010-03-01

    cis-Diamminedichloroplatinum(II) (cisplatin) forms DNA adducts that interfere with replication and transcription. The most common adducts formed in vivo are 1,2-intrastrand d(GpG) cross-links (Pt-GG) and d(ApG) cross-links (Pt-AG), with minor amounts of 1,3-d(GpNpG) cross-links (Pt-GNG), interstrand cross-links and monoadducts. Although the relative contribution of these different adducts to toxicity is not known, literature implicates that Pt-GG and Pt-AG adducts block replication. Thus, nucleotide excision repair (NER), by which platinum adducts are excised, and translesion DNA synthesis (TLS), which permits adduct bypass, are thought to be associated with cisplatin resistance. Recent studies have reported that the clinical benefit from platinum-based chemotherapy is high if tumor cells express low levels of NER factors. To investigate the role of platinum-DNA adducts in mediating tumor cell survival by TLS, we examined whether 1,3-intrastrand d(GpTpG) platinum cross-links (Pt-GTG), which probably exist in NER-negative tumor cells but not in NER-positive tumor cells, are bypassed by the translesion DNA polymerase eta (pol eta), which is known to bypass Pt-GG. We show that pol eta can incorporate the correct deoxycytidine triphosphate opposite the first 3'-cross-linked G of Pt-GTG but cannot insert any nucleotides opposite the second intact T or the third 5'-cross-linked G of the adducts, thereby suggesting that TLS does not facilitate replication past Pt-GTG adducts. Thus, our findings implicate Pt-GNG adducts as mediating the cytotoxicity of platinum-DNA adducts in NER-negative tumors in vivo.

  11. Radiation crosslinking of polypropylene

    International Nuclear Information System (INIS)

    Nojiri, A.; Sawasaki, T.

    1984-01-01

    The radiation crosslinking of polypropylene with several kinds of polyfunctional monomers has been examined, and it has been clarified that the enhanced crosslinking may be classified into two types. In particular, the irradiation crosslinking process of polypropylene containing a polyfunctional monomer having an acryloyloxy group giving a specific gel - dose curve has been studied by infrared absorption spectrum and oxygen absorptivity measurement in comparison with the non-enhanced system. (author)

  12. Fanconi anemia (cross)linked to DNA repair.

    Science.gov (United States)

    Niedernhofer, Laura J; Lalai, Astrid S; Hoeijmakers, Jan H J

    2005-12-29

    Fanconi anemia is characterized by hypersensitivity to DNA interstrand crosslinks (ICLs) and susceptibility to tumor formation. Despite the identification of numerous Fanconi anemia (FANC) genes, the mechanism by which proteins encoded by these genes protect a cell from DNA interstrand crosslinks remains unclear. The recent discovery of two DNA helicases that, when defective, cause Fanconi anemia tips the balance in favor of the direct involvement of the FANC proteins in DNA repair and the bypass of DNA lesions.

  13. Cisplatin sensitivity of testis tumour cells is due to deficiency in interstrand-crosslink repair and low ERCC1-XPF expression

    Directory of Open Access Journals (Sweden)

    Kaina Bernd

    2010-09-01

    Full Text Available Abstract Background Cisplatin based chemotherapy cures over 80% of metastatic testicular germ cell tumours (TGCT. In contrast, almost all other solid cancers in adults are incurable once they have spread beyond the primary site. Cell lines derived from TGCTs are hypersensitive to cisplatin reflecting the clinical response. Earlier findings suggested that a reduced repair capacity might contribute to the cisplatin hypersensitivity of testis tumour cells (TTC, but the critical DNA damage has not been defined. This study was aimed at investigating the formation and repair of intrastrand and interstrand crosslinks (ICLs induced by cisplatin in TTC and their contribution to TTC hypersensitivity. Results We observed that repair of intrastrand crosslinks is similar in cisplatin sensitive TTC and resistant bladder cancer cells, whereas repair of ICLs was significantly reduced in TTC. γH2AX formation, which serves as a marker of DNA breaks formed in response to ICLs, persisted in cisplatin-treated TTC and correlated with sustained phosphorylation of Chk2 and enhanced PARP-1 cleavage. Expression of the nucleotide excision repair factor ERCC1-XPF, which is implicated in the processing of ICLs, is reduced in TTC. To analyse the causal role of ERCC1-XPF for ICL repair and cisplatin sensitivity, we over-expressed ERCC1-XPF in TTC by transient transfection. Over-expression increased ICL repair and rendered TTC more resistant to cisplatin, which suggests that ERCC1-XPF is rate-limiting for repair of ICLs resulting in the observed cisplatin hypersensitivity of TTC. Conclusion Our data indicate for the first time that the exceptional sensitivity of TTC and, therefore, very likely the curability of TGCT rests on their limited ICL repair due to low level of expression of ERCC1-XPF.

  14. Repair of DNA-polypeptide crosslinks by human excision nuclease

    Science.gov (United States)

    Reardon, Joyce T.; Sancar, Aziz

    2006-03-01

    DNA-protein crosslinks are relatively common DNA lesions that form during the physiological processing of DNA by replication and recombination proteins, by side reactions of base excision repair enzymes, and by cellular exposure to bifunctional DNA-damaging agents such as platinum compounds. The mechanism by which pathological DNA-protein crosslinks are repaired in humans is not known. In this study, we investigated the mechanism of recognition and repair of protein-DNA and oligopeptide-DNA crosslinks by the human excision nuclease. Under our assay conditions, the human nucleotide excision repair system did not remove a 16-kDa protein crosslinked to DNA at a detectable level. However, 4- and 12-aa-long oligopeptides crosslinked to the DNA backbone were recognized by some of the damage recognition factors of the human excision nuclease with moderate selectivity and were excised from DNA at relatively efficient rates. Our data suggest that, if coupled with proteolytic degradation of the crosslinked protein, the human excision nuclease may be the major enzyme system for eliminating protein-DNA crosslinks from the genome. damage recognition | nucleotide excision repair

  15. Mechanism of melphalan crosslink enhancement by misonidazole pretreatment

    International Nuclear Information System (INIS)

    Taylor, Y.C.; Sawyer, J.M.; Hsu, B.; Brown, J.M.

    1984-01-01

    Sensitization of Chinese hamster ovary cells to melphalan (L-PAM) toxicity by prior treatment with misonidazole is associated with increased levels of DNA crosslinks believed to be the critical lesion for bifunctional alkylating agent toxicity. Enhanced L-PAM crosslinking of DNA could occur by a variety of mechanisms in MISO-pretreated cells including: (1) increased transport or binding of L-PAM, (2) decreased repair of L-PAM monoadducts which would allow more time for their conversion to crosslinks, (3) decreased crosslink repair (unhooking of one arm), or (4) chemical modification of the DNA structure, presumably by bound MISO derivatives, such that crosslink formation is facilitated. Previous studies have eliminated mechanisms (1) and (3). Mechanism (4) was investigated by following MISO-pretreatments of whole cells with L-PAM treatments of the isolated DNA from these cells. Treatment of bare DNA with L-PAM modeled very well the crosslinking behavior in whole cells although it was somewhat more efficient. In the presence of double stranded DNA and absence of repair systems during and after the L-PAM exposure, it was determined that MISO-pretreatments did not increase the crosslinking efficiency of L-PAM

  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. Radiation crosslinking of elastomers

    International Nuclear Information System (INIS)

    Pearson, D.S.

    1981-01-01

    In the first part of this paper a review is presented of recent results which show that the tensile strength and fatigue life of synthetic elastomers cured by radiation are essentially equivalent to those prepared by other crosslinking techniques. An explanation for the conflict of these new results with the earlier studies on natural rubber is presented. Investigations into the mechanisms and kinetics of crosslinking mentioned above have also shown that the irradiation method should be ideal for preparing well characterized networks. Such materials are useful for testing theoretical relationships between the structure of rubber networks and their stress-strain behavior. The second part of this paper is devoted to this aspect. (author)

  18. Laser welding and collagen crosslinks

    Energy Technology Data Exchange (ETDEWEB)

    Reiser, K.M.; Last, J.A. [California Univ., Davis, CA (United States). Dept. of Medicine; Small, W. IV; Maitland, D.J.; Heredia, N.J.; Da Silva, L.B.; Matthews, D.L. [Lawrence Livermore National Lab., CA (United States)

    1997-02-20

    Strength and stability of laser-welded tissue may be influenced, in part, by effects of laser exposure on collagen crosslinking. We therefore studied effects of diode laser exposure (805 nm, 1-8 watts, 30 seconds) + indocyanine green dye (ICG) on calf tail tendon collagen crosslinks. Effect of ICG dye alone on crosslink content prior to laser exposure was investigated; unexpectedly, we found that ICG-treated tissue had significantly increased DHLNL and OHP, but not HLNL. Laser exposure after ICG application reduced elevated DHLNL and OHP crosslink content down to their native levels. The monohydroxylated crosslink HLNL was inversely correlated with laser output (p<0.01 by linear regression analysis). DHLNL content was highly correlated with content of its maturational product, OHP, suggesting that precursor-product relations are maintained. We conclude that: (1)ICG alone induces DHLNL and OHP crosslink formation; (2)subsequent laser exposure reduces the ICG-induced crosslinks down to native levels; (3)excessive diode laser exposure destroys normally occurring HLNL crosslinks.

  19. Radiation crosslinking of polymer materials

    International Nuclear Information System (INIS)

    Yoshii, Fumio

    2004-01-01

    It was found that some polyfunctional monomers (PFM) like triallyl isocyanurate (TAIC) and trimethallyl isocyanurate (TMAIC) when incorporated at low concentrations, are effective for promotion of crosslinking of biodegradable polymers such as polycaprolactone (PCL), poly(butylene succinate-co-adipate) (PBS) and poly(lactic acid) (PLA). PFM are kneaded with biodegradable polymers at molten condition before irradiation. Radiation crosslinking of PBS and PCL with 1% TAIC gave gel fractions of 80% at 20 kGy. This crosslinking is effective to improve deformation of biodegradable polymers at high temperature. The irradiated materials retained their biodegradability even after crosslinking when subjected to soil burial test. Irradiation at molten state (melting temperature, 340degC) led to crosslinking structures for polytetrafluoroethylene (PTFE). Crosslinked PTFE forms transparent films with high abrasion property and high radiation resistance. High-density polyethylene (HDPE) has a higher gel fraction in irradiation at molten state than irradiation at ordinary temperature. Crosslinked HDPE has been applied as knee joints in order to have high abrasion. Radiation crosslinked polycarbosilane (PCS) fiber gives high heat resistant silicon carbide (SiC) after firing. EB irradiation of PCS is effective to improve strength of product and to inhibit flow during carbonization. SiC, being resistant to high temperature will be applied in turbine and body of rockets. (author)

  20. DNA Photolithography with Cinnamate Crosslinkers

    Science.gov (United States)

    Feng, Lang (Inventor); Chaikin, Paul Michael (Inventor)

    2016-01-01

    The present invention relates generally to cinnamate crosslinkers. Specifically, the present invention relates to gels, biochips, and functionalized surfaces useful as probes, in assays, in gels, and for drug delivery, and methods of making the same using a newly-discovered crosslinking configuration.

  1. Characterisation of radiation crosslinked polydimethylsiloxane

    International Nuclear Information System (INIS)

    Preston, C.M.L.; Hill, D.J.T.; Pomery, P.J.; Whittaker, A.K.

    1998-01-01

    Polysiloxanes, or silicones, are used widely in industry, as lubricants and process additives, as well as in many household products. The most common of the silicones is polydimethylsiloxane (PDMS). The fact that silicones crosslink during exposure to high energy radiation is well established. However, despite the number of studies performed on these systems, the exact mechanism of crosslinking has yet to be determined. Nuclear Magnetic Resonance spectroscopy (NMR) provides a useful method for the analysis of crosslinked polymer systems. Linear uncrosslinked PDMS is easily characterised in the solution state by NMR, as PDMS is readily soluble in common organic solvents. However, the onset of gelation caused by crosslinking results in an insoluble polymer network. The use of cross-polarisation (CP) and magic-angle spinning (MAS) in conjunction with high power decoupling has been shown to greatly enhance sensitivity of the NMR technique in solids. The true mechanism of crosslinking between polymer chains will be discussed

  2. Radiation crosslinking of polymer blends

    International Nuclear Information System (INIS)

    Spenadel, L.

    1979-01-01

    Rocked by the one-two punch of rising energy costs and tougher pollution controls, a growing number of companies are looking to radiation crosslinking as a cheaper, cleaner alternative to heat and costly chemical crosslinking agents such as peroxides. With the development of larger, more powerful electron beam machines it is now possible to irradiate parts as thick as 400 mils in a single pass. Two application areas which have been investigated at our laboratory are the electron beam processing of thermoplastic elastomeric automotive parts and EPDM electrical insulation. This paper covers work carried out to develop the necessary technology base for the radiation crosslinking of ethylene propylene/polyolefin blends. Initial results indicate that EP/PE blends of electrical insulation quality cross-link quite readily when irradiated. On the other hand, EP/PP blends developed for automotive fascia require the addition of crosslinking monomers such as trimethylol propane trimethacrylate in order for crosslinking to predominate over chain scission. Crosslinking EP/PP blends improve mar resistance, flexural set and deformation at elevated temperatures. These are all key properties for automotive fascia. (author)

  3. Automobile parts by radiation crosslinking

    International Nuclear Information System (INIS)

    Yoshii, Fumio

    2008-01-01

    Radiation crosslinking, graft polymerization and degradation are useful technologies to improve polymer materials. The crosslinking causes improvement in strength, heat stability and processability to gives network structure for polymer materials and hence crosslinked materials are used in various fields, especially car parts. Electron beam (EB) of short time irradiation is used for these modifications. Irradiated (pre-vulcanized) before sulfur vulcanization rubber tires, heat resistant wires/cables, shrinkable tubes and foams of car parts are achieved by EB crosslinking. Polyethylene and polyvinyl chloride are used in cables and wires, polypropylene in plastic foams and natural rubber etc. In this paper radiation processing of tire, wire/cables, foams, shrinkable tubes and circuit protection devices (CPT) are explained. (author)

  4. Covalent crosslinking of carbon nanostructures

    Indian Academy of Sciences (India)

    Composites of the binary conjugates with polymer can be readily prepared by using the ... Besides the preparation of crosslinked ... of graphite oxide following the procedure described ... several times to remove the metal nanoparticles and.

  5. Radiation induced crosslinking of polytetrafluoroethylene

    International Nuclear Information System (INIS)

    Oshima, Akihiro; Tabata, Yoneho; Ikeda, Shigetoshi; Otsuhata, Kazushige; Kudoh, Hisaaki; Seguchi, Tadao.

    1995-01-01

    The Irradiation temperature effect on polytetrafluoroethylene (PTFE) from room temperature to 380degC was investigated by tensile test and thermal analysis. The behavior of tensile properties and changes of crystallinity on irradiation indicated the formation of a network structure in PTFE by radiation induced crosslinking in inert gas in the molten state just above the melting temperature of PTFE (327degC). The crosslinked PTFE showed a much improved radiation resistance in an atmospheric radiation field. (author)

  6. 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.

  7. 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

  8. Crosslinking of agarose bioplastic using citric acid.

    Science.gov (United States)

    Awadhiya, Ankur; Kumar, David; Verma, Vivek

    2016-10-20

    We report chemical crosslinking of agarose bioplastic using citric acid. Crosslinking was confirmed using Fourier transform infrared (FTIR) spectroscopy. The effects of crosslinking on the tensile strength, swelling, thermal stability, and degradability of the bioplastic were studied in detail. The tensile strength of the bioplastic films increased from 25.1MPa for control films up to a maximum of 52.7MPa for citric acid crosslinked films. At 37°C, the amount of water absorbed by crosslinked agarose bioplastic was only 11.5% of the amount absorbed by non-crosslinked controls. Thermogravimetric results showed that the crosslinked samples retain greater mass at high temperature (>450°C) than control samples. Moreover, while the crosslinked films were completely degradable, the rate of degradation was lower compared to non-crosslinked controls. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. EB radiation crosslinking of elastomers

    International Nuclear Information System (INIS)

    Bik, J.; Rzymski, M.; Gluszewski, W.; Zagorski, Z.P.

    2002-01-01

    Complete text of publication follows. The first paper in the series described by the general title, starts with radiation crosslinking of hydrogenated butadiene-nitrile rubber (HBNR). This high-tech elastomer is obtained by catalytic hydrogenation of >C=C 99.5 and 94.5% of starting double bonds. Samples were irradiated with 10 MeV electrons, monoenergetical, 6 kW power, used as scanned beam over the conveyor, securing homogeneity of dose distribution. The doses were up to 300 kGy, applied in 20 kGy increments to avoid radiation generated heating of the material. The influence of presence or absence of oxygen was considered. Irradiated samples were investigated for the extend of crosslinking in the function of dose and for properties important for understanding of mechanisms. Samples are transparent, what allowed conventional absorption spectrophotometry, also time resolved. The quantitative interpretation of results shows that for 100 crosslinks there are 6-9 acts of chain-scission. It is less, than expected from the participation of multi-ionization spurs, also in the solid state, as announced during the previous, 9th Tihany Conference. However, the apparent lower yield of multi-ionization spurs is explained by partial conversion of products into crosslinks of specific type. Our investigations confirm the usefulness of consideration of radiation spurs in polymers as well as in all, low LET irradiated media

  10. Microfabrication of crosslinked PTFE by synchrotron radiation

    International Nuclear Information System (INIS)

    Sato, Yasunori; Yamaguchi, Daichi; Oshima, Akihiro; Washio, Masakazu; Katoh, Takanori; Aoki, Yasushi; Ikeda, Shigetoshi; Tanaka, Shigeru

    2003-01-01

    Microfabrication of crosslinked polytetrafluoroethylene (PTFE) using synchrotron radiation (SR) has been demonstrated for production of micro-components applicable to radiation fields. The method of microfabrication was readily capable of obtaining a microstructure with aspect-ratio of 25 made of crosslinked PTFE. The etching rate of crosslinked PTFE was higher than that of non-crosslinked PTFE. The results show that the etching rate of crosslinked PTFE depends only on the degree of crosslinking. The effect of molecular motion on etching process was discussed from temperature dependence on etching rate. Moreover, in order to examine whether any change of chemical structures and crystallinity would be induced by SR-irradiation on PTFE, SR-irradiated PTFE was measured by NMR spectroscopy and DSC analysis. The results showed that the crosslinking reaction of PTFE would be induced by SR-irradiation in the solid state. (author)

  11. Synthesis of Hydrophobic, Crosslinkable Resins.

    Science.gov (United States)

    1985-12-01

    product by methanol precipitation the majority of the first oligomer was L-"- lost. 4.14 DIFFERENTIAL SCANNING CALORIMETRY. The DSC trace of a typical...polymer from the DSC traces obtained to dcte. Preliminary studies using an automated torsional pendulum indicate that the Tg of the crosslinked polymer is...enabling water to be used in the purification steps. The diethyl phosphonates are readily prepared by heating triethyl phosphite with the chloromethyl

  12. Theory of pairwise lesion interaction

    International Nuclear Information System (INIS)

    Harder, Dietrich; Virsik-Peuckert, Patricia; Bartels, Ernst

    1992-01-01

    A comparison between repair time constants measured both at the molecular and cellular levels has shown that the DNA double strand break is the molecular change of key importance in the causation of cellular effects such as chromosome aberrations and cell inactivation. Cell fusion experiments provided the evidence that it needs the pairwise interaction between two double strand breaks - or more exactly between the two ''repair sites'' arising from them in the course of enzymatic repair - to provide the faulty chromatin crosslink which leads to cytogenetic and cytolethal effects. These modern experiments have confirmed the classical assumption of pairwise lesion interaction (PLI) on which the models of Lea and Neary were based. It seems worthwhile to continue and complete the mathematical treatment of their proposed mechanism in order to show in quantitative terms that the well-known fractionation, protraction and linear energy transfer (LET) irradiation effects are consequences of or can at least be partly attributed to PLI. Arithmetic treatment of PLI - a second order reaction - has also the advantage of providing a prerequisite for further investigations into the stages of development of misrepair products such as chromatin crosslinks. It has been possible to formulate a completely arithmetic theory of PLI by consequently applying three biophysically permitted approximations - pure first order lesion repair kinetics, dose-independent repair time constants and low yield of the ionization/lesion conversion. The mathematical approach will be summarized here, including several formulae not elaborated at the time of previous publications. We will also study an application which sheds light on the chain of events involved in PLI. (author)

  13. Endothelial cell seeding on crosslinked collagen : Effects of crosslinking on endothelial cell proliferation and functional parameters

    NARCIS (Netherlands)

    Wissink, MJB; van Luyn, MJA; Dijk, F; Poot, AA; Engbers, GHM; Beugeling, T; van Aken, WG; Feijen, J

    Endothelial cell seeding, a promising method to improve the performance of small-diameter vascular grafts, requires a suitable substrate, such as crosslinked collagen. Commonly used crosslinking agents such as glutaraldehyde and formaldehyde cause, however, cytotoxic reactions and thereby hamper

  14. Radiation induced estane polymer crosslinking

    International Nuclear Information System (INIS)

    Fletcher, M.; Foster, P.

    1997-01-01

    The exposure of polymeric materials to radiation has been known to induce the effects of crosslinking and degradation. The crosslinking phenomena comes about when two long chain polymers become linked together by a primary bond that extends the chain and increases the viscosity, molecular weight and the elastic modules of the polymer. This process has been observed in relatively short periods of time with fairly high doses of radiation, on the order of several megarads/hour. This paper address low dose exposure over long periods of time to determine what the radiation effects are on the polymeric binder material in PBX 9501. An experimental sample of binder material without explosives will be placed into a thermal and radiation field produced from a W-48 put mod 0. Another sample will be placed in a thermal environment without the radiation. The following is the test plan that was submitted to the Pantex process. The data presented here will be from the first few weeks of exposure and this test will be continued over the next few years. Subsequent data will hopefully be presented in the next compatibility and aging conference

  15. 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...

  16. Poly(tetramethyleneterephthalate) crosslinked by irradiation

    International Nuclear Information System (INIS)

    Nyberg, D.D.

    1978-01-01

    Crosslinking, e.g., by irradiation, of a polymer comprising poly(tetramethyleneterephthalate) is made possible by the addition of a member selected from the group consisting of triallyl cyanurate and N,N'-m-phenylenedimaleimide. The resulting crosslinked modified polymer may be rendered heat recoverable

  17. 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

  18. The radiation crosslinking of ethylene copolymers

    International Nuclear Information System (INIS)

    Burns, N.M.

    1979-01-01

    The enhanced radiation crosslinking tendency of ethylene-vinyl acetate and ethylene-ethyl acrylate copolymers over ethylene homopolymer is proportional to the comonomer content. This is caused by an increase in the amorphous polymer content and by structure-related factors. The copolymers crosslink by a random process that for ethylene-vinyl acetate copolymer involves some crosslinking through the acetoxy group of the comonomer. While knowledge of the process for the crosslinking of ethylene-ethyl acrylate copolymer is less certain, it is currently believed to occur primarily at the branch point on the polymer backbone. Data relating comonomer content and the molecular weight of the copolymers to the radiation crosslinking levels realized were developed to aid in resin selection by the formulator. Triallyl cyanurate cure accelerator was found to be less effective in ethylene-vinyl acetate copolymer than in homopolymer and to have no effect on gel development in ethylene-ethyl acrylate copolymer. (author)

  19. The role of crosslinkers in epoxy-amine crosslinked silicon sol-gel barrier protection coatings

    International Nuclear Information System (INIS)

    Vreugdenhil, A.J.; Gelling, V.J.; Woods, M.E.; Schmelz, J.R.; Enderson, B.P.

    2008-01-01

    The search for chromate replacements in corrosion prevention materials has identified the use of hybrid sol-gel coatings as one, very promising approach. Appropriately functionalized hybrid sol-gel materials can be crosslinked to enhance their chemical durability and mechanical strength. In this work, we evaluate three crosslinkers used in a tetramethoxysilane-glycidoxypropyltrimethoxysilane binary sol-gel system in order to identify the role of the crosslinkers in corrosion protection. The crosslinkers examined were ethylenediamine, N-aminethylepiperazine, and diethylenetriamine. The sol-gel coatings were examined by contact angle, atomic force microscopy, and electrochemical impedance spectroscopy (EIS). Circuit modeling of the EIS results yielded valuable insights into the significant differences between the durabilities of the variously crosslinked coatings. Crosslinker hydrophobicity was identified as not playing a significant role whereas the number of reactive sites per crosslinker and the resulting morphology of the material may be an important parameter

  20. Crosslinkable coatings from phosphorylcholine-based polymers.

    Science.gov (United States)

    Lewis, A L; Cumming, Z L; Goreish, H H; Kirkwood, L C; Tolhurst, L A; Stratford, P W

    2001-01-01

    2-Methacryloyloxyethyl phosphorylcholine (MPC) was synthesised and then used in the preparation of crosslinked polymer membranes with lauryl methacrylate, hydroxypropyl methacrylate and trimethoxysilylpropyl methacrylate (crosslinker) comonomers. Some physical aspects of the membrane properties were evaluated in order to establish the basis for the synthesis of a series of post-crosslinkable polymers. These materials were made by copolymerisation of the constituent monomers via a free radical method, and characterised using NMR, FT-IR, viscometry and elemental analysis. The optimum crosslink density and conditions required for curing coatings of these polymers were investigated using atomic force microscopy (AFM) and showed the inclusion of 5 mol% silyl crosslinking agent to be ideal. A nanoindentation technique was employed to determine if the coating developed elasticity upon crosslinking. The biological properties of the coatings were evaluated using a variety of protein adsorption assays and blood contacting experiments, and an enzyme immunoassay was developed to detect E. coli in order to assess the level of bacterial adhesion to these biomaterials. Polymers of this type were shown to be very useful as coating materials for improving the biocompatibility of, or reducing the levels of adherent bacteria to medical devices.

  1. Grafting functional antioxidants on highly crosslinked polyethylene

    Science.gov (United States)

    Al-Malaika, S.; Riasat, S.; Lewucha, C.

    2016-05-01

    The problem of interference of antioxidants, such as hindered phenols, with peroxide-initiated crosslinking of polyethylene was addressed through the use of functional (reactive) graftable antioxidants (g-AO). Reactive derivatives of hindered phenol and hindered amine antioxidants were synthesised, characterised and used to investigate their grafting reactions in high density polyethylene; both non-crosslinked (PE) and highly peroxide-crosslinked (PEXa). Assessment of the extent of in-situ grafting of the antioxidants, their retention after exhaustive solvent extraction in PE and PEXa, and the stabilising performance of the grafted antioxidants (g-AO) in the polymer were examined and benchmarked against conventionally stabilised crosslinked & non-crosslinked polyethylene. It was shown that the functional antioxidants graft to a high extent in PEXa, and that the level of interference of the g-AOs with the polymer crosslinking process was minimal compared to that of conventional antioxidants which bear the same antioxidant function. The much higher level of retention of the g-AOs in PEXa after exhaustive solvent extraction, compared to that of the corresponding conventional antioxidants, accounts for their superior long-term thermal stabilising performance under severe extractive conditions.

  2. 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

  3. Crosslinked polytriazole membranes for organophilic filtration

    KAUST Repository

    Chisca, Stefan

    2016-12-30

    We report the preparation of crosslinked membranes for organophilic filtration, by reacting a new polytriazole with free OH groups, using non-toxic poly (ethylene glycol) diglycidyl ether (PEGDE). The OH-functionalized polymer was obtained by converting the oxadiazole to triazole rings with high yield (98%). The maximum degree of crosslinking is achieved after 6 h of reaction. The crosslinked polytriazole membranes are stable in a wide range of organic solvents and show high creep recovery, indicating the robustness of crosslinked membranes. The influence of different casting solutions and different crosslinking time on the membrane morphology and membrane performance was investigated. The membranes performance was studied in dimethylformamide (DMF) and (tetrahydrofuran) THF. We achieved a permeance for THF of 49 L m−2 h−1 bar−1 for membranes with molecular weight cut off (MWCO) of 7 kg mol−1 and a permeance for THF of 17.5 L m−2 h−1 bar−1 for membranes with MWCO of 3 kg mol−1. Our data indicate that by using the new polytriazole is possible to adjust the pore dimensions of the membranes to have a MWCO, which covers ultra- and nanofiltration range.

  4. Radiation crosslinking of highly plasticized PVC

    Science.gov (United States)

    Mendizabal, E.; Cruz, L.; Jasso, C. F.; Burillo, G.; Dakin, V. I.

    1996-02-01

    To improve the physical properties of highly plasticized PVC, the polymer was crosslinked by gamma irradiation using a dose rate of 91 kGy/h. The effect of plasticizer type was studied by using three different plasticizers, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB), di(2-ethyl hexyl) phthalate (DOP), and di(2-ethylhexyl terephthalate) (DOTP), and varying irradiation doses. Gel content was determined by soxhlet extraction, tensile measurements were made on a universal testing machine and the mechano-dynamic measurements were made in a dynamic rheometer. It was found that a considerable bonding of plasticizer molecules to macromolelcules takes place along with crosslinking, so that the use of the solvent extraction method for measuring the degree of crosslinking can give erroneous information. Radiation-chemical crosslinking yield ( Gc) and molecular weight of interjunctions chains ( Mc), were calculated for different systems studied. Addition of ethylene glycol dimethacrylate (EGDM) as a crosslinking coagent and dioctyl tin oxide (DOTO) as a stabilizer was also studied. Plasticizers extraction resistance was increased by irradiation treatment.

  5. Radiation crosslinking of highly plasticized PVC

    International Nuclear Information System (INIS)

    Mendizabal, E.; Cruz, L.; Jasso, C.F.; Burillo, G.; Dakin, V.I.

    1996-01-01

    To improve the physical properties of highly plasticized PVC, the polymer was crosslinked by gamma irradiation using a dose rate of 91 kGy/h. The effect of plasticizer type was studied by using three different plasticizers, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB), di(2-ethyl hexyl) phthalate (DOP), and di(2-ethylhexyl terephthalate) (DOTP), and varying irradiation doses. Gel content was determined by soxhlet extraction, tensile measurements were made on a universal testing machine and the mechano-dynamic measurements were made in a dynamic rheometer. It was found that a considerable bonding of plasticizer molecules to macromolecules takes place along with crosslinking, so that the use of the solvent extraction method for measuring the degree of crosslinking can give erroneous information. Radiation-chemical crosslinking yield (G c ) and molecular weight of interjunctions chains (M c ), were calculated for different systems studied. Addition of ethylene glycol dimethyacrylate (EGDM) as a crosslinking coagent and dioctyl tin oxide (DOTO) as a stabilizer was also studied. Plasticizers extraction resistance was increased by irradiation treatment. (author)

  6. Crosslinked polytriazole membranes for organophilic filtration

    KAUST Repository

    Chisca, Stefan; Falca, Gheorghe; Musteata, Valentina-Elena; Boi, Cristiana; Nunes, Suzana Pereira

    2016-01-01

    We report the preparation of crosslinked membranes for organophilic filtration, by reacting a new polytriazole with free OH groups, using non-toxic poly (ethylene glycol) diglycidyl ether (PEGDE). The OH-functionalized polymer was obtained by converting the oxadiazole to triazole rings with high yield (98%). The maximum degree of crosslinking is achieved after 6 h of reaction. The crosslinked polytriazole membranes are stable in a wide range of organic solvents and show high creep recovery, indicating the robustness of crosslinked membranes. The influence of different casting solutions and different crosslinking time on the membrane morphology and membrane performance was investigated. The membranes performance was studied in dimethylformamide (DMF) and (tetrahydrofuran) THF. We achieved a permeance for THF of 49 L m−2 h−1 bar−1 for membranes with molecular weight cut off (MWCO) of 7 kg mol−1 and a permeance for THF of 17.5 L m−2 h−1 bar−1 for membranes with MWCO of 3 kg mol−1. Our data indicate that by using the new polytriazole is possible to adjust the pore dimensions of the membranes to have a MWCO, which covers ultra- and nanofiltration range.

  7. Synthesis and Characterization of Ionically Crosslinked Elastomers

    Science.gov (United States)

    2016-01-01

    was prepared by quaternization of vinyl benzyl chloride, while a  common dicarboxylic RAFT agent was neutralized with  potassium . The ideal structure...polymerization  where each mole of RAFT agent will  produce one mole of crosslink  junctions.  Initial polymerizations of n‐butyl  acrylate  (BA) were...butyl  acrylate  was polymerized  with the RAFT crosslinking agent in  methanol to low conversion to  introduce BA units, but limit the crosslinking

  8. Crosslinked polyethylene foams, via eb radiation

    International Nuclear Information System (INIS)

    Cardoso, E.C.L.; Lugao, A. B.; Andrade e Silva, L. G.

    1998-01-01

    Polyethylene foams, produced by radio-induced crosslinking, show a smooth and homogeneous surface, when compared to chemical crosslinking method using peroxide as crosslinking agent. This process fosters excellent adhesive and printability properties. Besides that, closed cells, intrinsic to these foams, imparts optimum mechanical, shocks and insulation resistance, indicating these foams to some markets segments as: automotive and transport; buoyancy, flotation and marine; building and insulation; packaging; domestic sports and leisure goods. We were in search of an ideal foam, by adding 5 to 15% of blowing agent in LDPE. A series of preliminary trials defined 203 degree sign C as the right blowing agent decomposition temperature. At a 22.7 kGys/dose ratio, the lowest dose for providing an efficient foam was 30 kGy, for a formulation comprising 10% of azodicarbonamide in LDPE, within a 10 minutes foaming time

  9. Shell-crosslinked knedel-like nanoparticles induce lower immunotoxicity than their non-crosslinked analogs.

    Science.gov (United States)

    Elsabahy, Mahmoud; Samarajeewa, Sandani; Raymond, Jeffery E; Clark, Corrie; Wooley, Karen L

    2013-10-21

    The development of stable nanoparticles that can withstand the changing conditions experienced in a biological setting and also be of low toxicity and immunogenicity is of particular importance to address the problems associated with currently utilized nanotechnology-based therapeutics and diagnostics. The use of crosslinked nanoparticles continues to receive special impetus, due to their robust structure and high kinetic stability, and they have recently been shown to induce lower cytotoxicity than their non-crosslinked micellar counterparts. In the current study, poly(acrylamidoethylamine)- block -poly(DL-lactide) (PAEA 90 - b -PDLLA 40 ) copolymers were synthesized, self-assembled in water to yield nanoscopic polymeric micelles, and the effects of decorating the micellar surface with poly(ethylene glycol) ( i.e. PEGylation) and crosslinking the PAEA layer to varying extents on the physicochemical characteristics, cytotoxicity and immunotoxicity of the nanoparticles were studied. Herein, we report for the first time that crosslinking can efficiently reduce the immunotoxicity of polymeric nanomaterials. In addition, increasing the degree of crosslinking further reduced the accessibility of biomolecules to the core of the nanoparticles and decreased their cytotoxicity and immunotoxicity. It is also highlighted that crosslinking can be more efficient than PEGylation in reducing the immunotoxicity of nanomaterials. Shell-crosslinking of block copolymer micelles, therefore, is expected to advance their clinical development beyond the earlier known effects, and to broaden the implications in the field of nanomedicine.

  10. 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.

  11. 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

  12. DNA interstrand cross-link repair: understanding role of Fanconi anemia pathway and therapeutic implications.

    Science.gov (United States)

    Shukla, Pallavi; Solanki, Avani; Ghosh, Kanjaksha; Vundinti, Babu Rao

    2013-11-01

    Interstrand cross-links (ICLs) are extremely toxic DNA lesions that prevent DNA double-helix separation due to the irreversible covalent linkage binding of some agents on DNA strands. Agents that induce these ICLs are thus widely used as chemotherapeutic drugs but may also lead to tumor growth. Fanconi anemia (FA) is a rare genetic disorder that leads to ICL sensitivity. This review provides update on current understanding of the role of FA proteins in repairing ICLs at various stages of cell cycle. We also discuss link between DNA cross-link genotoxicity caused by aldehydes in FA pathway. Besides this, we summarize various ICL agents that act as drugs to treat different types of tumors and highlight strategies for modulating ICL sensitivity for therapeutic interventions that may be helpful in controlling cancer and life-threatening disease, FA. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  13. The Fanconi Anemia Pathway in Replication Stress and DNA Crosslink Repair

    Science.gov (United States)

    Jones, Mathew JK.; Huang, Tony T.

    2013-01-01

    Interstand crosslinks (ICLs) are DNA lesions where the bases of opposing DNA strands are covalently linked, inhibiting critical cellular processes such as transcription and replication. Chemical agents that generate ICLs cause chromosomal abnormalities including breaks, deletions and rearrangements, making them highly genotoxic compounds. This toxicity has proven useful for chemotherapeutic treatment against a wide variety of cancer types. The majority of our understanding of ICL repair in humans has been uncovered thorough analysis of the rare genetic disorder Fanconi anemia, in which patients are extremely sensitive to crosslinking agents. Here, we discuss recent insights into ICL repair gained through new ICL repair assays and highlight the role of the Fanconi Anemia repair pathway during replication stress. PMID:22744751

  14. Densely crosslinked polycarbosiloxanes .2. Thermal and mechanical properties

    NARCIS (Netherlands)

    Flipsen, T.A C; Derks, R.; van der Vegt, H.A.; Stenekes, R.; Pennings, A.J; Hadziioannou, G

    1997-01-01

    The thermal and mechanical properties of two densely crosslinked polycarbosiloxane systems were investigated in relation to the molecular structure. The networks were prepared from functional branched prepolymers and crosslinked via a hydrosilylation curing reaction. The prepolymers having only

  15. Thermal enhancement of x-ray induced DNA crosslinking

    International Nuclear Information System (INIS)

    Bowden, G.T.; Kasunic, M.; Cress, A.E.

    1982-01-01

    Ionizing radiation appears to crosslink nuclear DNA with chromosomal proteins. Important cellular processes such as transcription and DNA replication are likely to be compromised as a result of the DNA crosslinking. Heat treatment (43/sup o/C) of mouse leukemia cells (L1210) before X irradiation (50 Gy) was found to cause a doubling of the radiation-induced DNA crosslinking as measured by alkaline elution technique. By using proteinase K, a very active protease, to eliminate DNA-protein crosslinking in the alkaline elution assay, it was shown that the thermally enhanced DNA crosslinking was attributed to an increase in DNA-protein crosslinking. However, utilizing a protein radiolabel technique under conditions of increased DNA-protein crosslinking, the amount of protein left on the filter in the elution assay was not increased. These data suggest that qualitative rather than large quantitative differences in the crosslinked chromosomal proteins exist between irradiated cells and cells treated with heat prior to irradiation

  16. Oropharynx lesion biopsy

    Science.gov (United States)

    ... as papilloma) Fungal infections (such as candida) Histoplasmosis Oral lichen planus Precancerous sore (leukoplakia) Viral infections (such as Herpes simplex) Risks Risks of the procedure may ... Throat lesion biopsy; Biopsy - mouth or throat; Mouth lesion biopsy; Oral cancer - biopsy ...

  17. Enzymatically crosslinked silk-hyaluronic acid hydrogels.

    Science.gov (United States)

    Raia, Nicole R; Partlow, Benjamin P; McGill, Meghan; Kimmerling, Erica Palma; Ghezzi, Chiara E; Kaplan, David L

    2017-07-01

    In this study, silk fibroin and hyaluronic acid (HA) were enzymatically crosslinked to form biocompatible composite hydrogels with tunable mechanical properties similar to that of native tissues. The formation of di-tyrosine crosslinks between silk fibroin proteins via horseradish peroxidase has resulted in a highly elastic hydrogel but exhibits time-dependent stiffening related to silk self-assembly and crystallization. Utilizing the same method of crosslinking, tyramine-substituted HA forms hydrophilic and bioactive hydrogels that tend to have limited mechanics and degrade rapidly. To address the limitations of these singular component scaffolds, HA was covalently crosslinked with silk, forming a composite hydrogel that exhibited both mechanical integrity and hydrophilicity. The composite hydrogels were assessed using unconfined compression and infrared spectroscopy to reveal of the physical properties over time in relation to polymer concentration. In addition, the hydrogels were characterized by enzymatic degradation and for cytotoxicity. Results showed that increasing HA concentration, decreased gelation time, increased degradation rate, and reduced changes that were observed over time in mechanics, water retention, and crystallization. These hydrogel composites provide a biologically relevant system with controllable temporal stiffening and elasticity, thus offering enhanced tunable scaffolds for short or long term applications in tissue engineering. Copyright © 2017 Elsevier Ltd. All rights reserved.

  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. 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

  20. Mesoscopic simulations of crosslinked polymer networks

    NARCIS (Netherlands)

    Megariotis, G.; Vogiatzis, G.G.; Schneider, L.; Müller, M.; Theodorou, D.N.

    2016-01-01

    A new methodology and the corresponding C++ code for mesoscopic simulations of elastomers are presented. The test system, crosslinked ds-1'4-polyisoprene' is simulated with a Brownian Dynamics/kinetic Monte Carlo algorithm as a dense liquid of soft, coarse-grained beads, each representing 5-10 Kuhn

  1. Managing Carious Lesions

    DEFF Research Database (Denmark)

    Schwendicke, F; Frencken, J E; Bjørndal, L

    2016-01-01

    should be prioritized, while in shallow or moderately deep lesions, restoration longevity becomes more important. For teeth with shallow or moderately deep cavitated lesions, carious tissue removal is performed according toselective removal to firm dentine.In deep cavitated lesions in primary......The International Caries Consensus Collaboration undertook a consensus process and here presents clinical recommendations for carious tissue removal and managing cavitated carious lesions, including restoration, based on texture of demineralized dentine. Dentists should manage the disease dental...

  2. Crosslinking of viral nanoparticles with “clickable” fluorescent crosslinkers at the interface

    Institute of Scientific and Technical Information of China (English)

    KAUR; Gagandeep; BARNHILL; Hannah

    2010-01-01

    Cu (I) catalyzed alkyne-azide cycloaddition (CuAAC) reaction,a typical "click" reaction,is one of the modular synthetic approaches which has been broadly used in various organic syntheses,medicinal chemistry,materials development and bioconjugation applications.We have for the first time synthesized two dialkyne derivatized fluorescent crosslinkers which could be applied to crosslink two biomolecules using CuAAC reaction.Turnip yellow mosaic virus,a plant virus with unique structural and chemical properties,was used as a prototypical scaffold to form a 2D single layer at the interface of two immiscible liquids and crosslinked with these two linkers by the CuAAC reaction.Upon crosslinking,the fluorescence of both linkers diminished,likely due to the distortion of the polymethylene backbone,which therefore could be used to indicate the completion of the reaction.

  3. ESR study on free radicals trapped in crosslinked polytetrafluoroethylene (PTFE)

    International Nuclear Information System (INIS)

    Oshima, Akihiro; Tabata, Yoneho; Seguchi, Tadao

    1997-01-01

    Free radicals in crosslinked PTFE which formed by 60 Co γ-rays irradiation at 77 K and at room temperature were studied by electron spin resonance (ESR) spectroscopy. The crosslinked PTFE specimens with different crosslinking density were prepared by electron beam irradiation in the molten state. The ESR spectra observed in the irradiated crosslinked PTFE are much different from those in non-crosslinked PTFE (virgin); a broad singlet component increases with increasing the crosslinking density, G-value of radicals is much higher in crosslinked PTFE than in non-crosslinked one. Free radicals related to the broad component are trapped in the non-crystalline region of crosslinked PTFE and rather stable at room temperature, whereas radicals trapped in amorphous non-crosslinked PTFE are unstable at room temperature. It is thought that most of free radicals trapped in the crosslinked PTFE are formed in the crosslinked amorphous region. The trapped radicals decays around 383 K (110 o C) due to the molecular motion of α-relaxation. (Author)

  4. [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.

  5. Periodontal bone lesions

    International Nuclear Information System (INIS)

    Linden, L.W.J. van der.

    1985-01-01

    In the course of life the periodontum is subject to changes which may be physiological or pathological. Intraoral radiographs give insight into the hard structures of the dentomaxillar region and provides information on lesions in the bone of the periodontum in that they show radiopacities and radiolucencies caused by such lesions. In this thesis the relation is investigated between the true shape and dimensions of periodontal bone lesions and their radiographic images. A method is developed and tested of making standardized and reproducible radiographs suitable for longitudinal studies of periodontal lesions. Also the possibility is demonstrated of an objective and reproducible interpretation of radiographic characteristics of periodontal bone lesions. (Auth.)

  6. Radiation cross-linking of fluoropolymers: Pt.2

    International Nuclear Information System (INIS)

    Sun Jiazhen; Zhu Xianglin; Zhang Yuefang

    1987-01-01

    On the basis of the results of IR analysis, ESR, ESCA and chemical anlaysis, the mechanism of radiation crosslinking of fluoropolymer Fs-46 was suggested. The crosslinking point of Fs-46 is not on the side chain-CF 3 -group, as Bowers suggest with their theoretical analysis, it may carried out with recombination of two side chain radicals directly, crosslinking with H type, or recombination of side chain radicals and chain end radicals through branching and then crosslinking. It is crosslinking with T type or Y type. The later one is the probable mechanism

  7. Desmosine-Inspired Cross-Linkers for Hyaluronan Hydrogels

    Science.gov (United States)

    Hagel, Valentin; Mateescu, Markus; Southan, Alexander; Wegner, Seraphine V.; Nuss, Isabell; Haraszti, Tamás; Kleinhans, Claudia; Schuh, Christian; Spatz, Joachim P.; Kluger, Petra J.; Bach, Monika; Tussetschläger, Stefan; Tovar, Günter E. M.; Laschat, Sabine; Boehm, Heike

    2013-06-01

    We designed bioinspired cross-linkers based on desmosine, the cross-linker in natural elastin, to prepare hydrogels with thiolated hyaluronic acid. These short, rigid cross-linkers are based on pyridinium salts (as in desmosine) and can connect two polymer backbones. Generally, the obtained semi-synthetic hydrogels are form-stable, can withstand repeated stress, have a large linear-elastic range, and show strain stiffening behavior typical for biopolymer networks. In addition, it is possible to introduce a positive charge to the core of the cross-linker without affecting the gelation efficiency, or consequently the network connectivity. However, the mechanical properties strongly depend on the charge of the cross-linker. The properties of the presented hydrogels can thus be tuned in a range important for engineering of soft tissues by controlling the cross-linking density and the charge of the cross-linker.

  8. Crosslinking of wire and cable insulation using electron accelerators

    International Nuclear Information System (INIS)

    Feng Yongxiang; Ma Zueteh

    1992-01-01

    Radiation crosslinking of wire and cable insulation is a well-established technology that is widely used in industry. The advantages of radiation crosslinking over chemical crosslinking have helped maintain its steady growth. Since successful utilization of electron beam processing relies on the formulation of compounds used in insulation, the radiation crosslinking of various polymers is reviewed. The handling technology for crosslinking wire and cable insulation and the throughput capacity of electron beam processors are also discussed. More than 30% of the industrial electron accelerators in the world are used for the radiation crosslinking of wire and cable insulation. Prospects of increased use of electron accelerators for crosslinking of wire and cable insulation are very good. (orig.)

  9. Induction and repair of DNA cross-links induced by sulfur mustard in the A-549 cell line followed by a comet assay.

    Science.gov (United States)

    Jost, Petr; Svobodova, Hana; Stetina, Rudolf

    2015-07-25

    Sulfur mustard is a highly toxic chemical warfare agent with devastating impact on intoxicated tissues. DNA cross-links are probably the most toxic DNA lesions induced in the cell by sulfur mustard. The comet assay is a very sensitive method for measuring DNA damage. In the present study using the A-549 lung cell line, the comet assay protocol was optimized for indirect detection of DNA cross-links induced by sulfur mustard. The method is based on the additional treatment of the assayed cells containing cross-links with the chemical mutagen, styrene oxide. Alkali-labile adducts of styrene oxide cause DNA breaks leading to the formation of comets. A significant dose-dependent reduction of DNA migration of the comet's tail was found after exposing cells to sulfur mustard, indicative of the amount of sulfur mustard induced cross-links. The remarkable decrease of % tail DNA could be observed as early as 5min following exposure to sulfur mustard and the maximal effect was found after 30min, when DNA migration was reduced to the minimum. Sulfur mustard preincubated in culture medium without cells lost its ability to induce cross-links and had a half-life of about 15min. Pre-incubation longer than 30min does not lead to a significant increase in cross-links when applied to cells. However, the amount of cross-links is decreased during further incubation due to repair. The current modification of the comet assay provides a useful tool for detecting DNA cross-links induced by sulfur mustard and could be used for detection of other DNA cross-linking agents such as chemotherapeutic drugs. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  10. Crosslinked polyurethanes based on hyperbranched polymers

    Directory of Open Access Journals (Sweden)

    Vuković Jasna

    2008-01-01

    Full Text Available In this paper, two samples of polyurethane (PU crosslinked with hydroxy -functonal hyperbranched aliphatic polyester of the second pseudo generation were investigated. For the synthesis of these crosslinked PUs two different macrodiols were used: poly(tetramethyleneoxide (PTMO for PUPTMO and ethylene oxide-poly(dimethylsiloxane-ethylene oxide (PDMS-EO for PUPDMS-EO sample. Synthesized samples behave as elastomers and have yellow color. Obtained results show that swelling degree of the sample PUPDMS-EO in N-methyl-2-pyrrolidinon (NMP determined at room temperature is higher than for the sample PUPTMO. It has been also observed that thermal properties of these polyurethane networks can be changed by incorporation of siloxane sequences in their structure.

  11. 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.

  12. [Riboflavin UVA crosslinking in progressive keratoconus].

    Science.gov (United States)

    Maier, P; Reinhard, T

    2017-06-01

    In patients with keratoconus, a progressive, ectatic disease of the cornea, the shape of the cornea is continuously changing leading to a reduction in visual acuity by progressive myopia and more and more (irregular) astigmatism. The symptomatic treatment consists of the prescription of glasses or special gas-permeable rigid contact lenses. Corneal tomography is generally used for diagnosis. After initial diagnosis of keratoconus, regular tomographic follow-ups should be performed. If clinically significant progression is found and confirmed by repeated measurements, riboflavin UVA collagen crosslinking should be offered to the patients. The aim of riboflavin UVA collagen crosslinking is to halt the progression of the disease to avoid further complications. The therapeutic principle is a combined effect of the photosensitizer riboflavin and UVA light. This stiffening effect of the corneal tissue halts the progression of keratoconus. The efficacy of this treatment has been demonstrated in various randomized, controlled trials.

  13. Mesoscopic Simulations of Crosslinked Polymer Networks

    Science.gov (United States)

    Megariotis, Grigorios; Vogiatzis, Georgios G.; Schneider, Ludwig; Müller, Marcus; Theodorou, Doros N.

    2016-08-01

    A new methodology and the corresponding C++ code for mesoscopic simulations of elastomers are presented. The test system, crosslinked ds-1’4-polyisoprene’ is simulated with a Brownian Dynamics/kinetic Monte Carlo algorithm as a dense liquid of soft, coarse-grained beads, each representing 5-10 Kuhn segments. From the thermodynamic point of view, the system is described by a Helmholtz free-energy containing contributions from entropic springs between successive beads along a chain, slip-springs representing entanglements between beads on different chains, and non-bonded interactions. The methodology is employed for the calculation of the stress relaxation function from simulations of several microseconds at equilibrium, as well as for the prediction of stress-strain curves of crosslinked polymer networks under deformation.

  14. Radiation crosslinking of PVC with polyfunctional monomers

    International Nuclear Information System (INIS)

    Dobo, J.; Takacs, E.; Csato, P.

    1984-01-01

    The radiation crosslinking of PVC in the presence of ethylene glycol dimethacrylate (EGDM) and of trimethylol propane trimethacrylate (TMPTM) was investigated. The effect of PVC powders of different types on the polymerization rate of these monomers was studied by a Calvet-type microcalorimeter. In the milled PVC sheets containing 50 part EGDM a high concentration of trapped free radicals was found by ESR after 16 months storage. (author)

  15. Intrastromal crosslinking in post-LASIK ectasia

    Directory of Open Access Journals (Sweden)

    Bernardo Kaplan Moscovici

    2014-06-01

    Full Text Available Descrevemos um caso de ectasia de córnea precoce após cirurgia de LASIK, detectado no primeiro semestre pós-operatório. Nós optamos tratar este paciente com "crosslinking" embaixo do "flap" , sem desepitelização com bons resultados. A paciente permaneceu sem progressão da ectasia até o momento atual, dois anos após o procedimento.

  16. Adhesion between Polydimethylsiloxane Layers by Crosslinking

    DEFF Research Database (Denmark)

    Yu, Liyun; Daugaard, Anders Egede; Skov, Anne Ladegaard

    2013-01-01

    Adhesion between two surfaces may be strongly improved by chemical crosslinking of the interfaces. Polydimethylsiloxane (PDMS) is a widely used polymer that has received considerable attention due to its unique properties, such as relatively low price, biocompatibility, flexibility, high thermal...... investigated by rheology and microscopy. The objective of this work was to create adhesion of two layers without destroying the original viscoelastic properties of the PDMS films....

  17. Electron beam crosslinked PVC : structure property relationships

    International Nuclear Information System (INIS)

    Gupta, Neeraj K.; Sabharwal, Sunil

    2001-01-01

    PVC is used extensively for its insulating properties for the manufacture of wires and cables and for other applications. Its gradual degradation, oxidation and even dehydro chlorination restricts use for long lasting period in installations such as high temperature zones, underground cables, communication systems, electro-nuclear facilities, etc. The technological properties and performance characteristics of PVC based insulation can be improved via crosslinking by high-energy electrons. PVC is however a polymer, which on irradiation predominantly undergoes degradation. To avoid degradation, it needs to be compounded with sensitizing agents or multifunctional monomers so that crosslinking is the predominant reaction. Radiation cross linkable formulations are complex mixtures of resin and various additives incorporated for achieving desired technological and performance characteristics, ease of processing and improving quality. The proper choice of additives and sensitizing agents enable low dose requirements for efficient crosslinking and improvements in various technological properties. The purposes of this work was to investigate the effect of using a binary sensitizer blend of a trifunctional monomer and a rubber in PVC, and develop suitable electron beam cross linkable formulations for wire insulation. This paper presents some aspects of the investigations and development of insulation demonstrated at industrial scale

  18. Epoxy Crosslinked Silica Aerogels (X-Aerogels)

    Science.gov (United States)

    fabrizio, Eve; Ilhan, Faysal; Meador, Mary Ann; Johnston, Chris; Leventis, Nicholas

    2004-01-01

    NASA is interested in the development of strong lightweight materials for the dual role of thermal insulator and structural component for space vehicles; freeing more weight for useful payloads. Aerogels are very-low density materials (0.010 to 0.5 g/cc) that, due to high porosity (meso- and microporosity), can be, depending on the chemical nature of the network, ideal thermal insulators (thermal conductivity approx. 15 mW/mK). However, aerogels are extremely fragile. For practical application of aerogels, one must increase strength without compromising the physical properties attributed to low density. This has been achieved by templated growth of an epoxy polymer layer that crosslinks the "pearl necklace" network of nanoparticles: the framework of a typical silica aerogel. The requirement for conformal accumulation of the epoxy crosslinker is reaction both with the surface of silica and with itself. After cross-linking, the strength of a typical aerogel monolith increases by a factor of 200, in the expense of only a 2-fold increase in density. Strength is increased further by coupling residual unreacted epoxides with diamine.

  19. 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.

  20. Crosslinked anion exchange membranes with primary diamine-based crosslinkers for vanadium redox flow battery application

    Science.gov (United States)

    Cha, Min Suc; Jeong, Hwan Yeop; Shin, Hee Young; Hong, Soo Hyun; Kim, Tae-Ho; Oh, Seong-Geun; Lee, Jang Yong; Hong, Young Taik

    2017-09-01

    A series of polysulfone-based crosslinked anion exchange membranes (AEMs) with primary diamine-based crosslinkers has been prepared via simple a crosslinking process as low-cost and durable membranes for vanadium redox flow batteries (VRFBs). Chloromethylated polysulfone is used as a precursor polymer for crosslinked AEMs (CAPSU-x) with different degrees of crosslinking. Among the developed AEMs, CAPSU-2.5 shows outstanding dimensional stability and anion (Cl-, SO42-, and OH-) conductivity. Moreover, CAPSU-2.5 exhibits much lower vanadium ion permeability (2.72 × 10-8 cm2 min-1) than Nafion 115 (2.88 × 10-6 cm2 min-1), which results in an excellent coulombic efficiency of 100%. The chemical and operational stabilities of the membranes have been investigated via ex situ soaking tests in 0.1 M VO2+ solution and in situ operation tests for 100 cycles, respectively. The excellent chemical, physical, and electrochemical properties of the CAPSU-2.5 membrane make it suitable for use in VRFBs.

  1. Ghost cell lesions

    Directory of Open Access Journals (Sweden)

    E Rajesh

    2015-01-01

    Full Text Available Ghost cells have been a controversy for a long time. Ghost cell is a swollen/enlarged epithelial cell with eosnophilic cytoplasm, but without a nucleus. In routine H and E staining these cells give a shadowy appearance. Hence these cells are also called as shadow cells or translucent cells. The appearance of these cells varies from lesion to lesion involving odontogenic and nonodontogenic lesions. This article review about the origin, nature and significance of ghost cells in different neoplasms.

  2. Corneal collagen crosslinking for keratoconus. A review

    Directory of Open Access Journals (Sweden)

    M. M. Bikbov

    2014-10-01

    Full Text Available Photochemical crosslinking is widely applied in ophthalmology. Its biochemical effect is due to the release of singlet oxygen that promotes anaerobic photochemical reaction. Keratoconus is one of the most common corneal ectasia affecting 1 in 250 to 250 000 persons. Currently, the rate of iatrogenic ectasia following eximer laser refractive surgery increases due to biomechanical weakening of the cornea. Morphologically and biochemically, ectasia is characterized by corneal layers thinning, contact between the stroma and epithelium resulting from Bowman’s membrane rupture, chromatin fragmentation in keratocyte nuclei, phagocytosis, abnormal staining and arrangement of collagen fibers, enzyme system disorders, and keratocyte apoptosis. In corneal ectasia, altered enzymatic processes result in the synthesis of abnormal collagen. Collagen packing is determined by the activity of various extracellular matrix enzymes which bind amines and aldehydes of collagen fiber amino acids. In the late stage, morphological changes of Descemet’s membrane (i.e., rupture and detachment develop. Abnormal hexagonal-shaped keratocytes and their apoptosis are the signs of endothelial dystrophy. The lack of analogs in domestic ophthalmology encouraged the scientists of Ufa Eye Research Institute to develop a device for corneal collagen crosslinking. The parameters of ultraviolet (i.e., wavelength, exposure time, power to achieve the desired effect were identified. The specifics of some photosensitizers in the course of the procedure were studied. UFalink, a device for UV irradiation of cornea, and photosensitizer Dextralink were developed and adopted. Due to the high risk of endothelial damage, this treatment is contraindicated in severe keratoconus (CCT less than 400 microns. Major effects of corneal collagen crosslinking are the following: Young’s modulus (modulus of elasticity increase by 328.9 % (on average, temperature tolerance increase by 5

  3. 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.

  4. Lesion activity assessment

    DEFF Research Database (Denmark)

    Ekstrand, K R; Zero, D T; Martignon, S

    2009-01-01

    in response to cariogenic plaque as well as lesion arrest. Based on this understanding, different clinical scoring systems have been developed to assess the severity/depth and activity of lesions. A recent system has been devised by the International Caries Detection and Assessment System Committee...

  5. New crosslinked polyvinyl chloride insulated wire by electron beam irradiation

    International Nuclear Information System (INIS)

    Takahata, Norio; Shingyouchi, Kazuo; Sato, Masakatsu; Sasaki, Hidemi; Terunuma, Haruji

    1978-01-01

    The polyvinyl chloride-coated wires crosslinked by electron beam irradiation have made rapid progress as electric and electronic wiring material and grown to hold a firm position in this field. In response to the requirements for wires with the advance of electronic equipments, Hitachi Cable Ltd. developed a peculiar graft polymer consisting of chlorinated polyethylene and polyvinyl chloride. To this polymer, the characteristics of a very wide range from toughness to flexibility can be given, and the crosslinked polyvinyl chloride wires utilizing these characteristics were put in practical use. Many kinds of the wires were developed as follows; 105 deg. C rating crosslinked vinyl-coated wires authorized by UL and CSA standards, crosslinked vinyl-coated wires with excellent flexibility, high strength crosslinked vinyl-coated wires with thin coating and crosslinked vinyl-coated wires for automobiles. They are expected to be developed into other new fields and applications. (Kobatake, H.)

  6. Crosslinking of thermoplastic composites using electron beam radiation

    International Nuclear Information System (INIS)

    Strong, A.B.; Black, S.R.; Bryce, G.R.; Olcott, D.D.

    1991-01-01

    The crosslinking of thermoset materials has been clearly demonstrated to improve many desirable physical and chemical properties for composite applications. While thermoplastic resins also offer many advantages for composite applications, they are not crosslinked and, therefore, may not meet the same property criteria as crosslinked thermosets. Electron beams have been used successfully for crosslinking non-reinforced thermoplastic materials. Electron beams have also been used for curing composite thermoset materials. This research utilizes electron beams to crosslink high performance thermoplastic composite materials (PEEK and PPS with glass and carbon fibers). The tensile strength and tensile modulus are compared under various crosslinking conditions. The method is found to have some advantages in potentially improving physical properties of thermoplastic composite materials

  7. A NOVEL APPROACH TO SYNTHESIZE CHITOSAN BEADS CROSSLINKED BY EPICHLOROHYDRIN

    Institute of Scientific and Technical Information of China (English)

    WANG Yongjian; BAI Shu; SUN Yan

    2001-01-01

    The present investigation describes a novel method for preparing spherical chitosan particles based on crosslinking with epichlorohydrin. Certain amount of pre-crosslinking agent was added to form chitosan gels by traditional inverse phase suspension polymerization. Then the gels were crosslinked by epichlorohydrin at basic condition to obtain chitosan beads. The effects of reaction conditions, such as crosslinking time, the amount of crosslinking agent and the NaOtt concentration,on the physical properties of the chitosan beads were investigated. The beads were found to have more amino groups in the polymer chains than the beads crosslinked by glutaraldehyde. The capacity for copper ions is as high as 40mg/g. The beads have good mechanical strength and can be reused.

  8. A NOVEL APPROACH TO SYNTHESIZE CHITOSAN BEADS CROSSLINKED BY EPICHLOROHYDRIN

    Institute of Scientific and Technical Information of China (English)

    WANGYongjina; BAIShu; 等

    2001-01-01

    The present investigation describes a novel method for preparing spherical chitosan particles based on crosslinking with epichlorohydrin.Certain amount of pre-crosslinking agent was added to form chitosan gels by traditional inverse phase suspension polymerization.Then the gels were crosslinked by epichlorohydrin at basic condition to obtain chitosan beads.The effects of reaction conditions,such as crosslinking time,the amount of crosslinking agent and the NaOH concentration,on the physical properties of the chitosan beads were investigated.The beads were found to have more amino groups in the polymer chains than the beads crosslinked by glutaraldehyde.The capacity for copper ions in as high as 40mg/g,The beads have good mechanical strength and can be reused.

  9. Crosslinkers of Different Types in Precipitation Polymerization of Acrylic Acid

    Directory of Open Access Journals (Sweden)

    H. Eshaghi

    2013-01-01

    Full Text Available Crosslinked poly(acrylic acids were prepared using two types of crosslinker by precipitation polymerization method in a binary organic solvent. N,N’-methylenebisacrylamide (MBA and polyethylene glycol dimethacrylate (PEGDMA-330 were used as low-molecular weight and long-chain crosslinkers, respectively. The effect of various types of crosslinkers on polymer characteristics (i.e., gel content, equilibrium swelling, glass transition temperature, and rheological properties was investigated. Maximum amount of viscosity was obtained by using long-chain crosslinker. The Flory-Rehner equation and rubber elasticity theory were used to discuss the network structure of polymer. It was observed that, the glass transition temperature (Tg of the synthesized polymer containing PEGDMA-330 is higher than that of polymer containing MBA. Apparent and rotational viscosity were used to determine the optimal crosslinker type. In addition, the consistencycoefficient (m and flow behavior index (n parameter of Ostwald equation were investigated as well.

  10. Interstrand DNA crosslinks due to AP (apurinic/apyrimidinic) sites

    International Nuclear Information System (INIS)

    Goffin, C.; Verly, W.G.

    1983-01-01

    Storage of a solution of DNA containing apurinic sites, even at 4 0 C leads to the appearance of interstrand crosslinks. Possible consequences of these crosslinks, when they appear in cell DNA, are briefly discussed. Formation of interstrand crosslinks in DNA containing tritium-labelled thymine and kept in an aqueous solution might be due, at least partly, to the loss of bases by the autoirradiated DNA. (Auth.)

  11. Covalent DNA-protein crosslinking occurs after hyperthermia and radiation

    International Nuclear Information System (INIS)

    Cress, A.E.; Bowden, G.T.

    1983-01-01

    Covalent DNA-protein crosslinks occur in exponentially growing mouse leukemia cells (L1210) after exposure to ionizing radiation. The amount of DNA-protein crosslinks as measured by a filter binding assay is dose dependent upon X irradiation. Although hyperthermia and radiation in combination are synergistic with respect to cell lethality, the combination does not result in an increase of DNA-protein crosslinks when assayed immediately following treatments. Hyperthermia (43 degrees C/15 min) given prior to radiation does not alter the radiation dose dependency of the amount of initial crosslinking. In addition, the amount of DNA-protein crosslinking produced by heat plus radiation is independent of the length of heating the cells at 43 degrees C. The DNA-protein crosslinks produced by 50-Gy X ray alone are removed after 2 hr at 37 degrees C. However, if hyperthermia (43 degrees C/15 min) is given prior to 100-Gy X ray, the removal of DNA-protein crosslinks is delayed until 4.0 hr after radiation. Phospho-serine and phospho-threonine bonds are not produced with either radiation or the combination of hyperthermia plus radiation as judged by the resistance of the bonds to guanidine hydrochloride. However, hyperthermia plus radiation causes an increase in phosphate to nitrogen type bonding. These results show that radiation alone causes covalent DNA-protein crosslinks. Hyperthermia in combination with radiation does not increase the total amount of the crosslinks but delays the removal of the crosslinks and alters the distribution of the types of chemical bonding. These data suggest that the synergistic action on hyperthermia with radiation is more related to the rate of removal and the type of chemical bonding involved in the covalent DNA-protein crosslinks rather than the amount of DNA-protein crosslinks

  12. Transepithelial photorefractive keratectomy with crosslinking for keratoconus.

    Science.gov (United States)

    Mukherjee, Achyut N; Selimis, Vasilis; Aslanides, Ioannis

    2013-01-01

    To analyse visual, refractive and topographic outcomes of combining transepithelial photorefractive keratectomy (tPRK) with simultaneous corneal crosslinking for the visual rehabilitation of contact lens intolerant keratoconus patients. Patients with topographically significant keratoconus, limited corrected vision and intolerant of contact lenses were prospectively recruited, subject to ethical approval and consent. All patients underwent single step aspheric tPRK and sequential crosslinking. Preoperative vision, refraction, corneal topography and wavefront were assessed, with postoperative assessment at 1, 3, 6, and 12 months. 22 eyes of 14 patients were included in the pilot study. Mean age was 32 years (SD 6.8, range 24 to 43). Mean preoperative unaided vision was 1.39 LogMAR (SD 0.5) best corrected 0.31 LogMAR (SD 0.2). Mean preoperative spherical equivalent was -2.74 Diopters (D) (SD 4.1 range -12.25 to +7.75), and mean cylinder -2.9 D (SD 1.2, range 0 to -5.5). Mean central corneal thickness was 461um (SD 29, range 411 to 516). Vision improved postoperatively; unaided 0.32 LogMAR (SD 0.4), best corrected 0.11 (SD 0.13) (P=<0.005). Mean postoperative cylinder was -1.4D (SD1.2), significantly reduced (p<0.005). Maximum keratometry (Kmax) was stable throughout postoperative follow up. (p<0.05). Non topographic transepithelial PRK with simultaneous crosslinking improves vision, and may offer an alternative to keratoplasty in contact lens intolerant keratoconus. Further comparative studies to topographic PRK techniques are indicated.

  13. Radiation-induced DNA-protein cross-links: Mechanisms and biological significance.

    Science.gov (United States)

    Nakano, Toshiaki; Xu, Xu; Salem, Amir M H; Shoulkamy, Mahmoud I; Ide, Hiroshi

    2017-06-01

    Ionizing radiation produces various DNA lesions such as base damage, DNA single-strand breaks (SSBs), DNA double-strand breaks (DSBs), and DNA-protein cross-links (DPCs). Of these, the biological significance of DPCs remains elusive. In this article, we focus on radiation-induced DPCs and review the current understanding of their induction, properties, repair, and biological consequences. When cells are irradiated, the formation of base damage, SSBs, and DSBs are promoted in the presence of oxygen. Conversely, that of DPCs is promoted in the absence of oxygen, suggesting their importance in hypoxic cells, such as those present in tumors. DNA and protein radicals generated by hydroxyl radicals (i.e., indirect effect) are responsible for DPC formation. In addition, DPCs can also be formed from guanine radical cations generated by the direct effect. Actin, histones, and other proteins have been identified as cross-linked proteins. Also, covalent linkages between DNA and protein constituents such as thymine-lysine and guanine-lysine have been identified and their structures are proposed. In irradiated cells and tissues, DPCs are repaired in a biphasic manner, consisting of fast and slow components. The half-time for the fast component is 20min-2h and that for the slow component is 2-70h. Notably, radiation-induced DPCs are repaired more slowly than DSBs. Homologous recombination plays a pivotal role in the repair of radiation-induced DPCs as well as DSBs. Recently, a novel mechanism of DPC repair mediated by a DPC protease was reported, wherein the resulting DNA-peptide cross-links were bypassed by translesion synthesis. The replication and transcription of DPC-bearing reporter plasmids are inhibited in cells, suggesting that DPCs are potentially lethal lesions. However, whether DPCs are mutagenic and induce gross chromosomal alterations remains to be determined. Copyright © 2017 Elsevier Inc. All rights reserved.

  14. Comparison study of crosslink density determination in cured rubber

    International Nuclear Information System (INIS)

    El-sabbagh, S.H.; Yehia, A.A.

    2005-01-01

    The crosslink density is an important property affecting the major characteristics of cured rubber. The crosslink density can be determined by different methods such as: 1. Dynamic mechanical method using the data of stress-strain relationship. 2. Mooney-Rivlin equation 3. Swelling in organic solvents measurements using Flory-Rehner equation. The crosslink density calculated by the previous methods were discussed and compared with each other for cured NR, SBR and NBR. The obtained data showed that the dynamic-mechanical method can be considered as a simple and reliable method for determination of crosslink density for cured rubbers

  15. Irradiation Crosslinking of Polyamides for the Electrical and Automotive Industry

    International Nuclear Information System (INIS)

    Gehring, J.

    2006-01-01

    Irradiation crosslinking of electrical cables and heat shrinkable tubes have been widely accepted in the automotive and electrical industry for a long time. Due higher demands regarding temperature resistance, arc resistance and good chemical resistance against oil and greases crosslinked injection moulded parts made out of polyamid and polybutylentherephtalate become also more and more interesting. Crosslinked polyamide can also replace thermosets for switches and offers therefore additional financial benefits. It will be shown on the basis of already realized projects, which basic requirements exist and how irradiation crosslinking can fulfil these demands

  16. Intraosseous osteolytic lesions

    Energy Technology Data Exchange (ETDEWEB)

    Adler, C.P.; Wenz, W.

    1981-10-01

    Any pathological damage occurring in a bone will produce either an osteolytic or osteosclerotic lesion which can be seen in the macroscopic specimen as well as in the roentgenogram. Various bone lesions may lead to local destructions of the bone. An osteoma or osteoplastic osteosarcoma produces an osteosclerotic lesion showing a dense mass in the roentgenogram; a chondroblastoma or an osteoclastoma, on the other hand, induces an osteolytic focal lesion. This paper presents examples of different osteolytic lesions of the humerus. An osteolytic lesion seen in the roentgenogram may be either produced by an underlying non-ossifying fibroma of the bone, by fibrous dysplasia, osteomyelitis or Ewing's sarcoma. Differential diagnostic considerations based on the radiological picture include eosinophilic bone granuloma, juvenile or aneurysmal bone cyst, multiple myeloma or bone metastases. Serious differential diagnostic problems may be involved in case of osteolytic lesions occurring in the humerus. Cases of this type involving complications have been reported and include the presence of an teleangiectatic osteosarcoma as well as that of a hemangiosarcoma of the bone.

  17. Modification of radiation-induced DNA lesions by oxygen

    International Nuclear Information System (INIS)

    Meyn, R.E.; Jenkins, W.T.

    1984-01-01

    The efficiency of DNA strand break production by radiation under aerated and hypoxic conditions was determined in CHO cells using the technique of alkaline elution. The resulting oxygen enhancement ratio was surprisingly high, 7.8. When the pH of the elution was increased from 12.1, the normally used pH, to 12.8, a substantial increase in the strand breaks produced in the hypoxic cells was observed, resulting in an OER of 4.8. This difference in susceptibility of DNA strand break detection as a function of pH suggested a difference in the type of lesions produced in DNA when irradiated under aerated and hypoxic conditions. Further experiments to examine the DNA-protein crosslinks produced by radiation suggested that the apparent lower level of strand breaks in hypoxic cells may be due to a higher level of DNA-protein crosslinks produced under hypoxic conditions. Thus, oxygen may not only act by modifying the quantity of radiation-induced DNA lesions but may also cause qualitative changes. If the different types of DNA lesions have different contributions to lethality, the OER for cell survival may represent a complex composite of these changes at the molecular level

  18. Properties of sericin films crosslinking with dimethylolurea

    International Nuclear Information System (INIS)

    Turbiani, Franciele R.B.; Stroher, Gylles Ricardo; Tomadon Junior, Jose; Seixas, Fernanda L.; Stroher, Gylles Ricardo; Gimenes, Marcelino L.

    2011-01-01

    Sericin is a natural silk protein which is removed from silk in a process called degumming. Thus, finding a use for the extracted sericin as a bio polymer film will create added value product which will benefit both the economy and society. The films were manufactured with silk sericin, using different dimethylolurea (DMU) concentrations as cross-linking agent and glycerol as plasticizer. Sericin films produced by crosslinking method were light yellow, homogeneous, transparent and visually attractive. The average film thickness was 0.10 ± 0.02 mm. The bio films show low water solubility (up to 30% of total dry mass), good tension strength and high elongation ability. The water vapor permeability is moderate, typical of highly hydrophilic films. Structural transformations in silk sericin films were analyzed using Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy and X-ray diffraction. This resulted in aggregated β-sheet structure (peak at 1616 cm-1 in the amide I absorption) by FTIR studies and increasing the DMU concentration in film decreased the peak intensity at 2θ = 20 degree. Sericin-based film properties are dependent on components used to form film, which can used to tailor the desired film flexibility and minimize permeability of films. (author)

  19. Properties of sericin films crosslinking with dimethylolurea

    Energy Technology Data Exchange (ETDEWEB)

    Turbiani, Franciele R.B.; Stroher, Gylles Ricardo [Federal Technology University - UTFPR, Campus Apucarana, PR (Brazil); Tomadon, Junior, Jose; Seixas, Fernanda L; Stroher, Gylles Ricardo; Gimenes, Marcelino L., E-mail: francieler@utfpr.edu.br [State University of Maringa. UEM, Campus Maringa, PR (Brazil)

    2011-07-01

    Sericin is a natural silk protein which is removed from silk in a process called degumming. Thus, finding a use for the extracted sericin as a bio polymer film will create added value product which will benefit both the economy and society. The films were manufactured with silk sericin, using different dimethylolurea (DMU) concentrations as cross-linking agent and glycerol as plasticizer. Sericin films produced by crosslinking method were light yellow, homogeneous, transparent and visually attractive. The average film thickness was 0.10 {+-} 0.02 mm. The bio films show low water solubility (up to 30% of total dry mass), good tension strength and high elongation ability. The water vapor permeability is moderate, typical of highly hydrophilic films. Structural transformations in silk sericin films were analyzed using Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy and X-ray diffraction. This resulted in aggregated {beta}-sheet structure (peak at 1616 cm-1 in the amide I absorption) by FTIR studies and increasing the DMU concentration in film decreased the peak intensity at 2{theta} = 20 degree. Sericin-based film properties are dependent on components used to form film, which can used to tailor the desired film flexibility and minimize permeability of films. (author)

  20. Diffuse cavitary lung lesions

    Energy Technology Data Exchange (ETDEWEB)

    Grunzke, Mindy; Garrington, Timothy [University of Colorado Denver, Department of Pediatrics, Aurora, CO (United States); The Children' s Hospital, Rick Wilson Center for Cancer and Blood Disorders, Aurora, CO (United States); Hayes, Kari [The Children' s Hospital, Pediatric Radiology, Aurora, CO (United States); Bourland, Wendy [Children' s Hospital at St. Francis, Warren Clinic, Inc., Tulsa, OK (United States)

    2010-02-15

    An 11-year-old girl presented with a 2-month history of progressively worsening cough, daily fevers, and weight loss. A chest radiograph revealed multiple cystic cavitary lung lesions. An extensive infectious work-up was negative. Chest CT verified multiple cavitary lung lesions bilaterally, and [F-18]2-fluoro-2-deoxy-D-glucose ({sup 18}F-FDG) positron emission tomography with CT (PET/CT) showed increased uptake in the lung lesions as well as regional lymph nodes. Subsequent biopsy of an involved lymph node confirmed classical Hodgkin lymphoma, nodular sclerosis type. This case represents an unusual presentation for a child with Hodgkin lymphoma and demonstrates a role for {sup 18}F-FDG PET/CT in evaluating a child with cavitary lung lesions. (orig.)

  1. Diffuse cavitary lung lesions

    International Nuclear Information System (INIS)

    Grunzke, Mindy; Garrington, Timothy; Hayes, Kari; Bourland, Wendy

    2010-01-01

    An 11-year-old girl presented with a 2-month history of progressively worsening cough, daily fevers, and weight loss. A chest radiograph revealed multiple cystic cavitary lung lesions. An extensive infectious work-up was negative. Chest CT verified multiple cavitary lung lesions bilaterally, and [F-18]2-fluoro-2-deoxy-D-glucose ( 18 F-FDG) positron emission tomography with CT (PET/CT) showed increased uptake in the lung lesions as well as regional lymph nodes. Subsequent biopsy of an involved lymph node confirmed classical Hodgkin lymphoma, nodular sclerosis type. This case represents an unusual presentation for a child with Hodgkin lymphoma and demonstrates a role for 18 F-FDG PET/CT in evaluating a child with cavitary lung lesions. (orig.)

  2. Uterine Vascular Lesions

    Science.gov (United States)

    Vijayakumar, Abhishek; Srinivas, Amruthashree; Chandrashekar, Babitha Moogali; Vijayakumar, Avinash

    2013-01-01

    Vascular lesions of the uterus are rare; most reported in the literature are arteriovenous malformations (AVMs). Uterine AVMs can be congenital or acquired. In recent years, there has been an increasing number of reports of acquired vascular lesions of the uterus following pregnancy, abortion, cesarean delivery, and curettage. It can be seen from these reports that there is confusion concerning the terminology of uterine vascular lesions. There is also a lack of diagnostic criteria and management guidelines, which has led to an increased number of unnecessary invasive procedures (eg, angiography, uterine artery embolization, hysterectomy for abnormal vaginal bleeding). This article familiarizes readers with various vascular lesions of the uterus and their management. PMID:24340126

  3. Male breast lesions

    International Nuclear Information System (INIS)

    Matushita, J.P.K.; Andrade, L.G. de; Carregal, E.; Marimatsu, R.I.; Matushita, J.S.

    1989-01-01

    Roentgenographic examination of the male breast is an important aspect of the continued, intensive investigation of the radiologic morphology of the normal and diseased breast conducted in 17 cases examined at the Instituto Nacional do Cancer - RJ. It is purpose of this report to present the Roentgen appearance of various lesions of the male breast as they have been found in our practice and also to stress some of the difficulties in the differential diagnosis of these lesions. (author) [pt

  4. Benign fibroosseous lesions

    Directory of Open Access Journals (Sweden)

    Cansu Köseoğlu Seçgin

    2016-05-01

    Full Text Available Benign fibroosseous lesions represent a group of lesions that share the same basic evolutive mechanism and are characterized by replacement of normal bone with a fibrous connective tissue that gradually undergoes mineralization. These lesions are presented by a variety of diseases including developmental, reactive-dysplastic processes and neoplasms. Depending on the nature and amount of calcified tissue, they can be observed as radiolucent, mixed or radiopaque. Their radiographic features could be well-defined or indistinguishable from the surrounding bone tissue. They can be asymptomatic as in osseous dysplasias and can be detected incidentally on radiographs, or they can lead to expansion in the affected bone as in ossifying fibroma. All fibroosseous lesions seen in the jaws and face are variations of the same histological pattern. Therefore, detailed clinical and radiographic evaluation in differential diagnosis is important. In this review, fibroosseous benign lesions are classified as osseous dysplasia, fibrous dysplasia and fibroosseous tumors; and radiographic features and differential diagnosis of these lesions are reviewed taking into account this classification.

  5. 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

  6. Characterization of Aldehyde Crosslinked Kenaf Regenerated Cellulose Film

    Directory of Open Access Journals (Sweden)

    Hatika Kaco

    2015-08-01

    Full Text Available Regenerated cellulose film with better mechanical properties was successfully produced by introducing aldehyde crosslinker during the regeneration process. The cellulose source material was derived from kenaf core powder and dissolved in LiOH/urea solvent at −13 °C to form a cellulose solution. The cellulose solution was cast and coagulated in a crosslinker bath at different percentages of glutaraldehyde (GA and glyoxal (GX to form a regenerated cellulose film. According to Fourier transform infrared spectroscopy (FTIR spectra, the hydroxyl group of the cellulose was reduced, reducing the percentage of swelling as the percentage of crosslinker was increased. X-ray diffraction (XRD patterns showed that the crystallinity index of the crosslinked film was decreased. The pore size of the films decreased as the percentage of crosslinker was increased, resulting in decreased film transparency. The pore volume and percentage of swelling in water of the films also increased with decreases in the pore size as the percentage of crosslinker was increased. The tensile strengths of the GA- and GX-crosslinked films increased by 20 and 15% with the addition of 20% of each crosslinker, respectively.

  7. 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...

  8. Fabrication of homobifunctional crosslinker stabilized collagen for biomedical application

    International Nuclear Information System (INIS)

    Lakra, Rachita; Kiran, Manikantan Syamala; Sai, Korrapati Purna

    2015-01-01

    Collagen biopolymer has found widespread application in the field of tissue engineering owing to its excellent tissue compatibility and negligible immunogenicity. Mechanical strength and enzymatic degradation of the collagen necessitates the physical and chemical strength enhancement. One such attempt deals with the understanding of crosslinking behaviour of EGS (ethylene glycol-bis (succinic acid N-hydroxysuccinimide ester)) with collagen to improve the physico-chemical properties. The incorporation of a crosslinker during fibril formation enhanced the thermal and mechanical stability of collagen. EGS crosslinked collagen films exhibited higher denaturation temperature (T d ) and the residue left after thermogravimetric analysis was about 16  ±  5.2%. Mechanical properties determined by uniaxial tensile tests showed a threefold increase in tensile strength and Young’s modulus at higher concentration (100 μM). Water uptake capacity reduced up to a moderate extent upon crosslinking which is essential for the transport of nutrients to the cells. Cell viability was found to be 100% upon treatment with 100 μM EGS whereas only 30% viability could be observed with glutaraldehyde. Rheological studies of crosslinked collagen showed an increase in shear stress and shear viscosity at 37 °C. Crosslinking with EGS resulted in the formation of a uniform fibrillar network. Trinitrobenzene sulfonate (TNBS) assay confirmed that EGS crosslinked collagen by forming a covalent interaction with ε-amino acids of collagen. The homobifunctional crosslinker used in this study enhanced the effectiveness of collagen as a biomaterial for biomedical application. (paper)

  9. Cross-Linked Fluorescent Supramolecular Nanoparticles as Finite Tattoo Pigments with Controllable Intradermal Retention Times.

    Science.gov (United States)

    Choi, Jin-Sil; Zhu, Yazhen; Li, Hongsheng; Peyda, Parham; Nguyen, Thuy Tien; Shen, Mo Yuan; Yang, Yang Michael; Zhu, Jingyi; Liu, Mei; Lee, Mandy M; Sun, Shih-Sheng; Yang, Yang; Yu, Hsiao-Hua; Chen, Kai; Chuang, Gary S; Tseng, Hsian-Rong

    2017-01-24

    Tattooing has been utilized by the medical community for precisely demarcating anatomic landmarks. This practice is especially important for identifying biopsy sites of nonmelanoma skin cancer (NMSC) due to the long interval (i.e., up to 3 months) between the initial diagnostic biopsy and surgical treatment. Commercially available tattoo pigments possess several issues, which include causing poor cosmesis, being mistaken for a melanocytic lesion, requiring additional removal procedures when no longer desired, and potentially inducing inflammatory responses. The ideal tattoo pigment for labeling of skin biopsy sites for NMSC requires (i) invisibility under ambient light, (ii) fluorescence under a selective light source, (iii) a finite intradermal retention time (ca. 3 months), and (iv) biocompatibility. Herein, we introduce cross-linked fluorescent supramolecular nanoparticles (c-FSNPs) as a "finite tattoo" pigment, with optimized photophysical properties and intradermal retention time to achieve successful in vivo finite tattooing. Fluorescent supramolecular nanoparticles encapsulate a fluorescent conjugated polymer, poly[5-methoxy-2-(3-sulfopropoxy)-1,4-phenylenevinylene] (MPS-PPV), into a core via a supramolecular synthetic approach. FSNPs which possess fluorescent properties superior to those of the free MPS-PPV are obtained through a combinatorial screening process. Covalent cross-linking of FSNPs results in micrometer-sized c-FSNPs, which exhibit a size-dependent intradermal retention. The 1456 nm sized c-FSNPs display an ideal intradermal retention time (ca. 3 months) for NMSC lesion labeling, as observed in an in vivo tattoo study. In addition, the c-FSNPs induce undetectable inflammatory responses after tattooing. We believe that the c-FSNPs can serve as a "finite tattoo" pigment to label potential malignant NMSC lesions.

  10. Nuclear magnetic resonance structure investigations on crosslinked polyesters

    International Nuclear Information System (INIS)

    Grobelny, J.

    1999-01-01

    Styrene-crosslinked mixed polyesters derived from maleic anhydride, 2,2-di(4-hydroxypropoxyphenyl)propane, oligo(propylene oxide) and 1,2-propylene glycol were investigated by high-resolution solid-state 13 C NMR spectroscopy. The structural modifications accompanying crosslinking were characterized in terms of spin-lattice relaxation times as a function of unsaturated polyester composition. Copolymerization and crosslinking effects were individually evaluated and the latter effect was related to variations in crosslinking density associated with the chemical structure of the unsaturated prepolymer. As the crosslinking effect is suppressed, the mechanical properties undergo expected changes, e.g., impact strength is increased and modulus of elasticity in tension is decreased. (author)

  11. 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.

  12. Carboxymethylcellulose hydrogel crosslinked with citric acid for biomedical application

    International Nuclear Information System (INIS)

    Capanema, Nadia S.V.; Mansur, Alexandra A.P.; Mansur, Herman S.; Universidade Federal de Minas Gerais

    2016-01-01

    The carboxymethylcellulose (CMCel) has been extensively used in order application as flexible polymer membrane. Biopolymers crosslinked have been studied to optimize their performance in biomedical applications. In this work, CMCel films with a degree of substitution (DS = 0.77) were prepared by evaporation of solvent and crosslinked with different concentrations of citric acid (CA). The synthesized CMCel was characterized by Infrared Spectroscopy by Fourier Transform X-ray spectroscopy (FTIR), and morphology assessed by scanning electron microscopy (SEM). Morphological analysis performed using the SEM indicated the crosslinked CMCel and not crosslinked with a very smooth and uniform appearance. The FTIR results indicated the modification of existing bands and appearance of a new band 1715 cm"-"1 suggesting that there has been change in the structure of the crosslinked CMCel. (author)

  13. Radiation-induced crosslinking of poly(vinylidene fluoride)

    International Nuclear Information System (INIS)

    Makuuchi, Keizo

    1977-07-01

    The factors influencing radiation-induced crosslinking efficiency of poly(vinylidene fluoride) (PVdF) have been studied. Results of the basic research on irradiation conditions (dose rate and atmosphere) and initial physical properties of PVdF (structure of molecular chain and molecular mobility of chain segment) showed that crosslinking efficiency is raised in irradiation at high temperature above 50 0 C under vacuum in the presence of an absorbent for the evolved hydrogen fluoride. The crosslinking reaction is also accelerated with irregular molecular structure such as head-to-head bond in main chain. High crosslinking efficiency is obtained by addition of a polyfunctional monomer having good solubility with PVdF. Mechanical properties of PVdF, the strength at high temperature near the melting point in particular, are improved by crosslinking in the presence of a polyfunctional monomer. (auth.)

  14. Covalent DNA-protein crosslinking occurs after hyperthermia and radiation

    International Nuclear Information System (INIS)

    Cress, A.E.; Bowden, G.T.

    1983-01-01

    Covalent DNA-protein crosslinks occur in exponentially growing mouse leukemia cells (L1210) after exposure to ionizing radiation. The amount of DNA-protein crosslinks as measured by a filter binding assay is dose dependent upon x irradiation. Although hyperthermia and radiation in combination are synergistic with respect to cell lethality, the combination does not result in an increase of DNA-protein crosslinks when assayed immediately following treatments. Hyperthermia (43 0 C/15 min) given prior to radiation dose not alter the radiation dose dependency of the amount of initial crosslinking. In addition, the amount of DNA-protein crosslinking produced by heat plus radiation is independent of the length of heating the cells at 43 0 C. The DNA-protein crosslinks produced y 50-Gy x ray alone are removed after 2 hr at 37 0 C. However, if hyperthermia (43 0 C/15 min) is given prior to 100-Gy x ray, the removal of DNA-protein crosslinks is delayed until 4.0 hr after radiation. Phospho-serine and phospho-threonine bonds are not produced with either radiation or the combination of hyperthermia plus radiation as judged by the resistance of the bonds to guanidine hydrochloride. However, hyperthermia plus radiation causes an increase in phosphate to nitrogen type bonding. These results show that radiation alone causes covalent DNA-protein crosslinks. Hyperthermia in combination with radiation does not increase the total amount of the crosslinks but delays the removal of the crosslinks and alters the distribution of the types of chemical bonding

  15. DNA-to-protein crosslinks and backbone breaks caused by far- and near-ultraviolet, and visible light radiations in mammalian cells

    International Nuclear Information System (INIS)

    Peak, M.J.; Peak, J.G.

    1986-01-01

    Spectral responses for DNA damages caused by far-uv, near-uv, and visible light radiations have been studied. The near congruence of the spectra for far-uv damages and the spectrum of DNA is good evidence that the mechanism is the same for the induction of breaks, crosslinks, and pyrimidine dimers. For near-uv, the different spectra imply that at least several nonDNA sensitizer molecules act as primary chromophores, but that DNA damage eventually results. With the understanding that near-uv and visible radiations produce a variety of chemically potent reactive oxygen species within the cell, we recognize the possibility for many types of DNA damage. If we assume that SSBs and DNA-to-protein crosslinks are random single events along the genome, it is possible to compute the number of events per cell genome per lethal event caused by the different energies used. In the near-uv and visible region, many more breaks and crosslinks are formed per lethal event than by far-uv. About 20 times more SSBs per lethal event are caused by 365-nm radiation than by x-rays, strong evidence that these breaks are effectively repaired. It is therefore likely that SSBs are not a serious event with regard to cellular lethality. The role of crosslinks and their repair in lethal events is less clear. The lack of any correlation at all between the action spectra for SSBs, or crosslinks, and lethality and mutagenesis in the same cells is evidence that another lesion or lesions are involved in these events. The multitude of chemical events that can be caused in cellular metabolites by the reactive species generated by these long wavelengths of radiation means that death is attributable to the total spectrum of changed chemicals delivered by a lethal dose, only some of which are DNA changes leading to SSBs and crosslinks. 43 refs., 3 figs., 2 tabs

  16. Gamma irradiation Effect on the Non-Crosslinked and Crosslinked Poly(vinyl alcohol) Films

    International Nuclear Information System (INIS)

    El-Sawy, N.M.; El-Arnaouty, M.B.; Abdel Ghaffar, A.M.

    2008-01-01

    The non-crosslinked and crosslinked poly(vinyl alcohol) (PVA) films were prepared by the cast method then irradiated with gamma rays for various doses up to 300 kGy. The structure and characterization of PVA were determined by using Infrared spectroscopy (FTIR), ultraviolet spectroscopy (UV). Swelling behaviour was also investigated. Mechanical properties have been examined with respect to the absorbed dose. The color of the films changed to yellowish-white after irradiation. Additional changes were observed using FTIR analysis on the degradation products demonstrated that the radiolysis of PVA was initiated by liberation of H and OH groups leading to scission of the main chains and formation of carbonyl and double bond groups. Thermogravimetric analysis (TGA) was performed

  17. Radiation crosslinked materials with antithrombotical properties

    International Nuclear Information System (INIS)

    Schunk, W.; Kloecking, H.P.; Merkmann, G.; Giessmann, C.; Knoll, H.; Borgmann, S.

    1991-01-01

    Described is a flexible drainage tube of good tissue tolerance developed for the postoperative continuous withdrawal of secretions from wounds which - owing to the addition of an active ingredient in sustained release dosage form (pentosanpolysulfate stored in the molecular sieve) - inhibits or considerably delays clogging as a result of coagulation processes. The tube is made of a mixture of natural or silicone rubbers and 4% coagulation inhibitor that is extruded onto a metal mandrel, crosslinked using electron rays (100 kGy, 20 s) and simultaneously sterilised. The mandrel is subsequently removed. In vitro trials (using blood plasm for open flow systems and blood for circulatory flow systems) provided evidence in confirmation of a continuous regular release of active ingredient that inhibited coagulation processes over prolonged periods of time. (orig.) [de

  18. Corneal collagen crosslinking and pigment dispersion syndrome.

    Science.gov (United States)

    LaHood, Benjamin R; Moore, Sacha

    2017-03-01

    We describe the case of a keratoconus patient with pigment dispersion syndrome (PDS) who was treated for progressive corneal ectasia with corneal collagen crosslinking (CXL). Pigment dispersion syndrome has been shown to have associated morphologic changes of the corneal endothelium. Corneal CXL has the potential to cause toxicity to the corneal endothelium, and adjacent pigment might increase the likelihood of damage. In this case, the presence of PDS had no detrimental effect on the outcome of treatment, and no complications were observed at 12 months follow-up, indicating that it may be safe to perform corneal CXL in the setting of PDS. This is an important observation as the number of indications for corneal CXL grows. Copyright © 2017 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  19. In vivo biocompatibility of carbodiimide-crosslinked collagen matrices : Effects of crosslink density, heparin immobilization, and bFGF loading

    NARCIS (Netherlands)

    van Wachem, PB; Plantinga, JA; Wissink, MJB; Poot, AA; Engbers, GHM; Beugeling, T; van Aken, WG; Feijen, J; van Luyn, MJA

    2001-01-01

    Collagen matrices, crosslinked using N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide (E) and N-hydroxvsuccinimide (N), were previously developed as a substrate for endothelial cell seeding of small-diameter vascular grafts. In the present study, the biocompatibility of various EN-crosslinked collagen

  20. The Modification of PVDF Membrane via Crosslinking with Chitosan and Glutaraldehyde as the Crosslinking Agent

    OpenAIRE

    Silitonga, Romaya Sitha; Widiastuti, Nurul; Jaafar, Juhana; Ismail, Ahmad Fauzi; Abidin, Muhammad Nidzhom Zainol; Azelee, Ihsan Wan; Naidu, Mahesan

    2018-01-01

    Poly(vinylidene fluoride) (PVDF) has outstanding properties such as high thermal stability, resistance to acid solvents and good mechanical strength. Due to its properties, PVDF is widely used as a membrane matrix. However, PVDF membrane is hydrophobic properties, so as for specific applications, the surface of membrane needs to be modified to become hydrophilic. This research aims to modify PVDF membrane surface with chitosan and glutaraldehyde as a crosslinker agent. The FTIR spectra showed...

  1. 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)

  2. Precancerous Skin Lesions.

    Science.gov (United States)

    Ferrándiz, C; Malvehy, J; Guillén, C; Ferrándiz-Pulido, C; Fernández-Figueras, M

    Certain clinically and histologically recognizable skin lesions with a degree of risk of progression to squamous cell carcinoma have been traditionally grouped as precancerous skin conditions but now tend to be classified as in situ carcinomas. This consensus statement discusses various aspects of these lesions: their evaluation by means of clinical and histopathologic features, the initial evaluation of the patient, the identification of risk factors for progression, and the diagnostic and treatment strategies available today. Copyright © 2016 AEDV. Publicado por Elsevier España, S.L.U. All rights reserved.

  3. Moisture curable toughened poly(lactide utilizing vinyltrimethoxysilane based crosslinks

    Directory of Open Access Journals (Sweden)

    J. Schneider

    2016-10-01

    Full Text Available Vinyltrimethoxysilane (VTMOS was grafted on to the backbone of poly(lactide (PLA through a free radical grafting reaction using reactive extrusion (REX processing. The methoxy groups of the silane provide the modified PLA sites for crosslinking through a moisture induced pathway. VTMOS grafting efficiencies of up to 90% were obtained. The newly created methoxy functionality of the modified PLA readily undergoes hydrolysis and condensation forming siloxane crosslinks in the material. Crosslinking with VTMOS exhibited improved modulus, strength, and impact toughness while showing a decrease in ductility. Incorporating silanol-terminated poly(dimethylsiloxane (OH-PDMS resulted in the formation of longer siloxane crosslinks. These samples showed an increase in modulus and impact toughness due to the crosslinking, while the longer siloxane linkages resulted in improved ductility and tensile toughness. This is unusual for polymers toughened through crosslinking reactions. Scanning Electron Microscopy (SEM of the fractured surfaces showed the presence of these elongated siloxane crosslinks. This enhanced ability for the modified PLA to deform and absorb energy results in the increase in both impact and tensile toughness.

  4. Development of new materials by utilizing radiation crosslinking

    International Nuclear Information System (INIS)

    Ueno, Keiji; Uda, Yujiro; Suzuki, Shizuo

    1989-01-01

    About 30 years have elapsed since the cables by electron beam crosslinking were developed as the first industrial utilization of radiation in Japan. At present about 200 electron beam accelerators are used industrially in Japan, and cable industry ranks at the top, followed by foaming polyethylene and curing, and the preliminary vulcanization of tires. The effect of these irradiations is the reforming of polymers by radiation crosslinking. In cables, the heat resistance and chemical resistance of insulators are improved by radiation crosslinking. By applying radiation crosslinking to polyurethane elastomer, its weakest point, waterproof property, was improved. Moreover, by using this crosslinked polyurethane elastomer for cable coating, the reliability of the sensor cables for brake system was able to be remarkably improved. As another new application of radiation crosslinking process, the improvement of the heat resistance of engineering plasties was examined. The structure of radiation crosslinked urethane elastomer cables, their endurance in hot water and oil, and the life, and the characteristics of sensor cables are reported. Multi-functional monomers, the molecular structure, and the various characteristics of engineering plastics are described. (K.I.)

  5. 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.)

  6. Theoretical studies of ionic conductivity of crosslinked chitosan membranes

    Energy Technology Data Exchange (ETDEWEB)

    Chavez, Ernesto Lopez [Programa de Ingenieria Molecular y Nuevos Materiales, Universidad Autonoma de la Ciudad de Mexico, Fray Servando Teresa de Mier 92, 1er. Piso, Col Centro, Mexico D.F. CP 06080 (Mexico); Oviedo-Roa, R.; Contreras-Perez, Gustavo; Martinez-Magadan, Jose Manuel [Instituto Mexicano del Petroleo, Eje Central Lazaro Cardenas Norte 152, Col. San Bartolo Atepehuacan, CP 07730 Mexico D.F. (Mexico); Castillo-Alvarado, F.L. [Escuela Superior de Fisica y Matematicas del Instituto Politecnico Nacional, Edificio 9 de la UPALM, Colonia Lindavista, Mexico D.F. CP 07738 (Mexico)

    2010-11-15

    Ionic conductivity of crosslinked chitosan membranes was studied using techniques of molecular modeling and simulation. The COMPASS force field was used. The simulation allows the description of the mechanism of ionic conductivity along the polymer matrix. The theoretical results obtained are compared with experimental results for chitosan membranes. The analysis suggests that the conduction mechanism is portrayed by the overlapping large Polaron tunneling model. In addition, when the chitosan membrane was crosslinked with an appropriate degree of crosslinking its ionic conductivity, at room temperature, was increased by about one order of magnitude. The chitosan membranes can be used as electrolytes in solid state batteries, electric double layer capacitors and fuel cells. (author)

  7. Crosslinking of commercial polyethylenes by 10 MeV electrons

    International Nuclear Information System (INIS)

    Singh, A.; Lopata, V.J.; Kremers, W.; Sze, Yu-keung

    1995-08-01

    Commercial polyethylenes were irradiated with 10 MeV electrons to induce crosslinking. The gel fraction data measured as a function of total dose suggests that crosslinking proceeds on irradiation, as expected. A number of the properties of the irradiated polyethylenes, such as the degree of oxidation, crystallinity and thermal degradation, were studied by Fourier transform infrared/photo acoustic spectroscopy, X-ray diffraction, and a pyrolysis technique coupled with gas chromatography and mass spectrometry. The results of this study suggest that commercial polyethylenes can be crosslinked to a gel fraction of ∼70%, required for wire and cable applications, by 10 MeV electrons. (author). 35 refs., 6 figs

  8. Nitrile crosslinked polyphenyl-quinoxaline/graphite fiber composites

    Science.gov (United States)

    Alston, W. B.

    1976-01-01

    Studies were performed to reduce the 600 F thermoplasticity of polyphenylquinoxaline (PPQ) matrix resins by introducing crosslinking by the reaction of terminal nitrile groups. Seven solvents and solvent mixtures were studied as the crosslinking catalysts and used to fabricate crosslinked PPQ/HMS graphite fiber composites. The room temperature and 600 F composite mechanical properties after short time and prolonged 600 F air exposure and the 600 F composite weight loss were determined and compared to those properties of high molecular weight, linear PPQ/HMS graphite fiber composites.

  9. 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.

  10. Radiation degradation and crosslinking of polytetrafluoroethylene and its application

    International Nuclear Information System (INIS)

    Wu Guozhong; Wang Mouhua; Tang Zhongfeng

    2009-01-01

    Polytetrafluoroethylene (PTFE) is a high-performance engineering plastic and known as a typical material of radiation degradation. PTFE can be degraded by radiation under various conditions and PTFE micro-powder is usually fabricated by a combination of radiation and milling. PTFE can also be crosslinked by irradiation in the melt state (330∼340 degree C). The materials can be applied as a special additive due to its excellent wear resistance. Crosslinked PTFE may also be applied in lithography and fuel cell membrane in the future. In this paper, history and application of PTFE degradation and crosslinking products are reviewed. (authors)

  11. Production of radiation crosslinked polymeric compositions using diacetylenes

    International Nuclear Information System (INIS)

    Patel, G.N.

    1979-01-01

    Crosslinked polymeric compositions, useful as electrical insulators, heat shrinkable packaging, and lightweight foam plastics, are described. The crosslinked polymeric compositions are produced by admixing a diacetylene monomer, oligomer, polymer or mixture thereof, wherein the monomer has the formula, RNHCO-O-CH 2 -C==C-C==C-CH- 2 -O-OCNHR' in which R and R' are the same or different and are alkyl containing 1 to 20 carbon atoms, with a thermoplastic crosslinkable polymer and then subjecting the resulting mixture to actinic radiation

  12. Common conjunctival lesions

    African Journals Online (AJOL)

    Conjunctival lesions are frequently seen in the eye clinic, because the conjunctiva is readily ... anti-histamine drops and mast cell stabilisers can be used. e more severe cases have to be .... Ehlers J, Shah C . The Wills Eye Manual. Office and.

  13. Skin lesion removal

    Science.gov (United States)

    ... likely to be done when there is a concern about a skin cancer. Most often, an area the shape of an ellipse is removed, as this makes it easier to close with stitches. The entire lesion is removed, going as deep as the fat, if needed, to ...

  14. Genital lesions following bestiality

    Directory of Open Access Journals (Sweden)

    Mittal A

    2000-01-01

    Full Text Available A 48-year-old man presented with painful genital lesions with history of bestiality and abnor-mal sexual behaviour. Examination revealed multiple irregular tender ulcers and erosions, with phimosis and left sided tender inguinal adenopathy. VDRL, TPHA, HIV-ELISA were negative. He was treated with ciprofloxacin 500mg b.d. along with saline compresses with complete resolution.

  15. A Molecular Dynamics Study of Crosslinked Phthalonitrile Polymers: The Effect of Crosslink Density on Thermomechanical and Dielectric Properties

    Directory of Open Access Journals (Sweden)

    Janel Chua

    2018-01-01

    Full Text Available In this work, molecular dynamics (MD and molecular mechanics (MM simulations are used to study well-equilibrated models of 4,4′-bis(3,4-dicyanophenoxybiphenyl (BPh–1,3-bis(3-aminophenoxybenzene (m-APB phthalonitrile (PN system with a range of crosslink densities. A cross-linking technique is introduced to build a series of systems with different crosslink densities; several key properties of this material, including thermal expansion, mechanical properties and dielectric properties are studied and compared with experimental results. It is found that the coefficient of linear thermal expansion predicted by the model is in good agreement with experimental results and indicative of the good thermal stability of the PN polymeric system. The simulation also shows that this polymer has excellent mechanical property, whose strength increases with increasing crosslink density. Lastly and most importantly, the calculated dielectric constant—which shows that this polymer is an excellent insulating material—indicates that there is an inverse relation between cross-linking density and dielectric constant. The trend gave rise to an empirical quadratic function which can be used to predict the limits of attainable dielectric constant for highly crosslinked polymer systems. The current computational work provides strong evidence that this polymer is a promising material for aerospace applications and offers guidance for experimental studies of the effect of cross-linking density on the thermal, mechanical and dielectric properties of the material.

  16. Morel-Lavallee lesion.

    Science.gov (United States)

    Li, Hui; Zhang, Fangjie; Lei, Guanghua

    2014-01-01

    To review current knowledge of the Morel-Lavallee lesion (MLL) to help clinicians become familiar with this entity. Familiarization may decrease missed diagnoses and misdiagnoses. It could also help steer the clinician to the proper treatment choice. A search was performed via PubMed and EMBASE from 1966 to July 2013 using the following keywords: Morel-Lavallee lesion, closed degloving injury, concealed degloving injury, Morel-Lavallee effusion, Morel-Lavallee hematoma, posttraumatic pseudocyst, posttraumatic soft tissue cyst. Chinese and English language literatures relevant to the subject were collected. Their references were also reviewed. Morel-Lavallee lesion is a relatively rare condition involving a closed degloving injury. It is characterized by a filled cystic cavity created by separation of the subcutaneous tissue from the underlying fascia. Apart from the classic location over the region of the greater trochanter, MLLs have been described in other parts of the body. The natural history of MLL has not yet been established. The lesion may decrease in volume, remain stable, enlarge progressively or show a recurrent pattern. Diagnosis of MLL was often missed or delayed. Ultrasonography, computed tomography, and magnetic resonance imaging have great value in the diagnosis of MLL. Treatment of MLL has included compression, local aspiration, open debridement, and sclerodesis. No standard treatment has been established. A diagnosis of MLL should be suspected when a soft, fluctuant area of skin or chronic recurrent fluid collection is found in a region exposed to a previous shear injury. Clinicians and radiologists should be aware of both the acute and chronic appearances to make the correct diagnosis. Treatment decisions should base on association with fractures, the condition of the lesion, symptom and desire of the patient.

  17. Maxillomandibular giant osteosclerotic lesions

    Directory of Open Access Journals (Sweden)

    Constantino LEDESMA-MONTES

    2018-06-01

    Full Text Available Abstract Giant Osteosclerotic Lesions (GOLs are a group of rarely reported intraosseous lesions. Their precise diagnosis is important since they can be confused with malignant neoplasms. Objective This retrospective study aimed to record and analyze the clinical and radiographic Giant Osteosclerotic Lesions (GOLs detected in the maxillomandibular area of patients attending to our institution. Materials and Methods: Informed consent from the patients was obtained and those cases of 2.5 cm or larger lesions with radiopaque or mixed (radiolucid-radiopaque appearance located in the maxillofacial bones were selected. Assessed parameters were: age, gender, radiographic aspect, shape, borders, size, location and relations to roots. Lesions were classified as radicular, apical, interradicular, interradicular-apical, radicular-apical or located in a previous teeth extraction area. Additionally, several osseous and dental developmental alterations (DDAs were assessed. Results Seventeen radiopacities in 14 patients were found and were located almost exclusively in mandible and were two types: idiopathic osteosclerosis and condensing osteitis. GOLs were more frequent in females, and in the anterior and premolar zones. 94.2% of GOLs were qualified as idiopathic osteosclerosis and one case was condensing osteitis. All studied cases showed different osseous and dental developmental alterations (DDAs. The most common were: Microdontia, hypodontia, pulp stones, macrodontia and variations in the mental foramina. Conclusions GOLs must be differentiated from other radiopaque benign and malignant tumors. Condensing osteitis, was considered an anomalous osseous response induced by a chronic low-grade inflammatory stimulus. For development of idiopathic osteosclerosis, two possible mechanisms could be related. The first is modification of the normal turnover with excessive osseous deposition. The second mechanism will prevent the normal bone resorption, arresting the

  18. Relationship of DNA lesions and their repair to chromosomal aberration production

    International Nuclear Information System (INIS)

    Bender, M.A.

    1979-01-01

    Recent work on the roles of specific kinds of DNA lesions and their enzymatic repair systems in the production of chromosomal aberrations seems consistent with a simple molecular model of chromosomal aberrations formation. Evidence from experiments with the human repair-deficient genetic diseases xeroderma pigmentosom, ataxia telangiectasia, and Fanconi's anemia is reviewed in the light of the contributions to aberration production of single and double polynucleotide strand breaks, base damage, polynucleotide strand crosslinks, and pyrimidine cyclobutane dimers

  19. Relationship of DNA lesions and their repair to chromosomal aberration production

    Energy Technology Data Exchange (ETDEWEB)

    Bender, M.A.

    1979-01-01

    Recent work on the roles of specific kinds of DNA lesions and their enzymatic repair systems in the production of chromosomal aberrations seems consistent with a simple molecular model of chromosomal aberrations formation. Evidence from experiments with the human repair-deficient genetic diseases xeroderma pigmentosom, ataxia telangiectasia, and Fanconi's anemia is reviewed in the light of the contributions to aberration production of single and double polynucleotide strand breaks, base damage, polynucleotide strand crosslinks, and pyrimidine cyclobutane dimers.

  20. Measurement of DNA-protein crosslinks in mammalian cells without X-irradiation

    International Nuclear Information System (INIS)

    Gantt, R.; Stephens, E.V.; Davis, S.R.

    1985-01-01

    To study the mechanisms of formation and repair of DNA-protein crosslinks in mammalian cells, the best general method to assay these lesions is the Kohn membrane alkaline elution procedure. Use of this sensitive technique requires the introduction of random strand breaks in the DNA by X-irradiation to reduce the very high molecular weight so that it elutes off the filter at an appropriate rate. This report describes an alternative method for fragmenting the DNA in the absence of X-irradiation equipment. Convenient reproducible elution rates of DNA from various mouse and human cells in culture without X-irradiation result from elution through polyvinyl chloride filters with 75 mM sodium hydroxide (0.33 ml/min) instead of the standard 20 mM EDTA-tetrapropylammonium hydroxide, pH 12.2 (0.03 to 0.04 ml/min). Dose-dependent retardation of the DNA elution was observed over the range 0 to 30 microM trans-platinum(II)diamminedichloride, and proteinase K treatment during cell lysis restored the elution rate to that of the untreated control cell DNA. In the absence of X-irradiation, this elution method measures DNA-protein crosslinks with higher sensitivity and equivalent reproducibility as the air-burst procedure

  1. Radiation crosslinking of poly(butyl acrylate) during polymerization and grafted copolymerization with Cr(III) crosslinked collagen

    International Nuclear Information System (INIS)

    Pietrucha, K.; Kroh, J.

    1984-01-01

    Enhanced crosslinking of synthetic polymer simultaneous with grafting and homopolymerization processes have been observed in irradiated leather tanned with Cr(III) and embedded with aqueous emulsions of butyl acrylate. Extent of poly(butyl acrylate) crosslinking during copolymerization was found to be approximately one order higher than in the case of radiation polymerization of butyl acrylate in emulsion. New method for isolation of grafted copolymer based on degradation of collagen has been developed. The extent of crosslinking was calculated from the swelling data. (author)

  2. Radiation crosslinking of poly(butyl acrylate) during polymerization and grafted copolymerization with Cr(III) crosslinked collagen

    International Nuclear Information System (INIS)

    Pietrucha, K.; Kroh, J.

    1986-01-01

    Enhanced crosslinking of synthetic polymer simultaneously with grafting and homopolymerization processes has been observed in irradiated leather tanned with Cr(III) and embedded with aqueous emulsions of butyl acrylate. The extent of poly(butyl acrylate) crosslinking during copolymerization was found to be approximately one order higher than in the case of radiation polymerization of butyl acrylate in emulsion. A new method for isolation of grafted copolymer based on degradation of collagen has been developed. The extent of crosslinking was calculated from the swelling data. (author)

  3. Riboflavin for corneal cross-linking.

    Science.gov (United States)

    O'Brart, D P S

    2016-06-01

    Corneal collagen cross-linking (CXL) with riboflavin and ultraviolet A (UVA) radiation is the first therapeutic modality that appears to arrest the progression of keratoconus and other corneal ectasias. Riboflavin is central to the process, acting as a photosensitizer for the production of oxygen singlets and riboflavin triplets. These free radicals drive the CXL process within the proteins of the corneal stroma, altering its biomechanical properties. Riboflavin also absorbs the majority of the UVA radiation, which is potentially cytotoxic and mutagenic, within the anterior stroma, preventing damage to internal ocular structures, such as the corneal endothelium, lens and retina. Clinical studies report cessation of ectatic progression in over 90% of cases and the majority document significant improvements in visual, keratometric and topographic parameters. Clinical follow-up is limited to 5-10 years, but suggests sustained stability and enhancement in corneal shape. Sight-threatening complications are rare. The optimal stromal riboflavin dosage for CXL is as yet undetermined. Copyright 2016 Prous Science, S.A.U. or its licensors. All rights reserved.

  4. Radiation induced crosslinking of cellulose ethers

    International Nuclear Information System (INIS)

    Wach, A.R.; Mitomo, H.; Yoshii, F.; Kume, T.

    2002-01-01

    The effects of high-energy radiation on four ethers of cellulose: carboxymethyl (CMC); hydroxypropyl (HPC), hydroxyethyl (HEC) and methylcellulose (MC) were investigated. Polymers are irradiated in solid state and in aqueous solutions at various concentrations. Degree of substitution (DS) of the derivatives, the concentration of their aqueous solutions and irradiation conditions had a significant impact on the obtained products. Irradiation of polymers in solid state and in diluted aqueous solutions resulted in their degradation. However, it was found that for concentrated solutions gel formation occurred. Paste-like form of the initial material, when water plasticizes the bulk of polymer as well as the high dose rate, what prevents oxygen penetration of the polymer during irradiation, have been found favourable for hydrogel formation. Up to 95% of gel fraction was obtained from solutions of CMC with concentration over 50% irradiated by γ-rays or electron beam. It was pointed out that the ability to the formation of the three-dimensional network is related to the DS of anhydroglucose units and a type of chemical group introduced to main chain of cellulose. Produced hydrogels swelled markedly in water. Despite of the crosslinked structure they underwent degradation by the action of cellulase enzyme or microorganisms from compost, and can be included into the group of biodegradable materials. (author)

  5. Crosslinked polyimide electro-optic materials

    Energy Technology Data Exchange (ETDEWEB)

    Kowalczyk, T.C.; Kosc, T.Z.; Singer, K.D. [Case Western Reserve University, Department of Physics, Cleveland, Ohio 44106-7079 (United States); Beuhler, A.J.; Wargowski, D.A. [Amoco Research Center, Amoco Chemical Co., Naperville, Illinois 60566 (United States); Cahill, P.A.; Seager, C.H.; Meinhardt, M.B. [Sandia National Laboratories, Division 1811, Albuquerque, New Mexico 87185-1407 (United States); Ermer, S. [Lockheed Research and Development Division, Palo Alto, California 94304 (United States)

    1995-11-15

    We report studies of the optical and electro-optic properties of guest--host polymeric nonlinear optical materials based on aromatic, fluorinated, fully imidized, organic soluble, thermally, and photochemically crosslinkable, guest--host polyimides. We have introduced temperature stable nonlinear optical chromophores into these polyimides and studied optical losses, electric field poling, electro-optic properties, and orientational stability. We measured electro-optic coefficients of 5.5 and 12.0 pm/V for ((2,6-Bis(2-(3-(9-(ethyl)carbazolyl))ethenyl)4H-pyran-4-ylidene)propanedinitrile) (4-(Dicyanomethylene)-2-methyl-6-(p -dimethylaminostyryl)-4H-pyran) DCM-doped guest--host systems at 800 nm using a poling field of 1.3 MV/cm. Poling induced nonlinearities in single-layer films were in agreement with the oriented gas model, but were lower in three-layer films due to voltage division across the layers. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  6. Covalently crosslinked diels-alder polymer networks.

    Energy Technology Data Exchange (ETDEWEB)

    Bowman, Christopher (University of Colorado, Boulder, CO); Adzima, Brian J. (University of Colorado, Boulder, CO); Anderson, Benjamin John

    2011-09-01

    This project examines the utility of cycloaddition reactions for the synthesis of polymer networks. Cycloaddition reactions are desirable because they produce no unwanted side reactions or small molecules, allowing for the formation of high molecular weight species and glassy crosslinked networks. Both the Diels-Alder reaction and the copper-catalyzed azide-alkyne cycloaddition (CuAAC) were studied. Accomplishments include externally triggered healing of a thermoreversible covalent network via self-limited hysteresis heating, the creation of Diels-Alder based photoresists, and the successful photochemical catalysis of CuAAC as an alternative to the use of ascorbic acid for the generation of Cu(I) in click reactions. An analysis of the results reveals that these new methods offer the promise of efficiently creating robust, high molecular weight species and delicate three dimensional structures that incorporate chemical functionality in the patterned material. This work was performed under a Strategic Partnerships LDRD during FY10 and FY11 as part of a Sandia National Laboratories/University of Colorado-Boulder Excellence in Science and Engineering Fellowship awarded to Brian J. Adzima, a graduate student at UC-Boulder. Benjamin J. Anderson (Org. 1833) was the Sandia National Laboratories point-of-contact for this fellowship.

  7. The Fanconi anemia pathway promotes replication-dependent DNA interstrand cross-link repair.

    Science.gov (United States)

    Knipscheer, Puck; Räschle, Markus; Smogorzewska, Agata; Enoiu, Milica; Ho, The Vinh; Schärer, Orlando D; Elledge, Stephen J; Walter, Johannes C

    2009-12-18

    Fanconi anemia is a human cancer predisposition syndrome caused by mutations in 13 Fanc genes. The disorder is characterized by genomic instability and cellular hypersensitivity to chemicals that generate DNA interstrand cross-links (ICLs). A central event in the activation of the Fanconi anemia pathway is the mono-ubiquitylation of the FANCI-FANCD2 complex, but how this complex confers ICL resistance remains enigmatic. Using a cell-free system, we showed that FANCI-FANCD2 is required for replication-coupled ICL repair in S phase. Removal of FANCD2 from extracts inhibits both nucleolytic incisions near the ICL and translesion DNA synthesis past the lesion. Reversal of these defects requires ubiquitylated FANCI-FANCD2. Our results show that multiple steps of the essential S-phase ICL repair mechanism fail when the Fanconi anemia pathway is compromised.

  8. 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...

  9. Syntheses of crosslinked latex nanoparticles using differential microemulsion polymerization

    Science.gov (United States)

    Hassmoro, N. F.; Rusop, M.; Abdullah, S.

    2013-06-01

    The differential microemulsion polymerization was used to synthesize latex nanoparticles. In this paper, 1, 3-butylene glycol dimethacrylate (1, 3-BGDMA) was used as a crosslinker respectively 1-5 weight% of monomer total. Butyl acrylate (BA), butyl methacrylate (BMA), and methacrylic acid (MAA) was used as the monomer. The thin film of latex nanoparticles were prepared by using spin coating method and have been dried at 100°C for 5 minutes. The amount of the crosslinker added in the polymerization was optimized and we found that the particle sizes fall in the range of 30-60 nm. The structural morphology of the uncrosslinked latex represented the most homogeneous image compared to the crosslinked latex. The effect of the amount of crosslinker on the particle sizes investigated by the Zeta-sizer Nano series while Atomic Force microscopy (AFM) was used to study the structural properties of latex nanoparticles.

  10. Syntheses of crosslinked latex nanoparticles using differential microemulsion polymerization

    International Nuclear Information System (INIS)

    Hassmoro, N F; Abdullah, S; Rusop, M

    2013-01-01

    The differential microemulsion polymerization was used to synthesize latex nanoparticles. In this paper, 1, 3-butylene glycol dimethacrylate (1, 3-BGDMA) was used as a crosslinker respectively 1–5 weight% of monomer total. Butyl acrylate (BA), butyl methacrylate (BMA), and methacrylic acid (MAA) was used as the monomer. The thin film of latex nanoparticles were prepared by using spin coating method and have been dried at 100°C for 5 minutes. The amount of the crosslinker added in the polymerization was optimized and we found that the particle sizes fall in the range of 30–60 nm. The structural morphology of the uncrosslinked latex represented the most homogeneous image compared to the crosslinked latex. The effect of the amount of crosslinker on the particle sizes investigated by the Zeta-sizer Nano series while Atomic Force microscopy (AFM) was used to study the structural properties of latex nanoparticles.

  11. 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

  12. 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)

  13. 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....

  14. Biocompatibility and tissue regenerating capacity of crosslinked dermal sheep collagen

    NARCIS (Netherlands)

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

    1994-01-01

    The biocompatibility and tissue regenerating capacity of four crosslinked dermal sheep collagens (DSC) was studied. In vitro, the four DSC versions were found to be noncytotoxic or very low in cytoxicity. After subcutaneous implantation in rats, hexamethylenediisocyanatecrcrosslinked DSC (HDSC)

  15. 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.

  16. Multiple molecular forms of pyridinoline crosslinks generated by the ...

    African Journals Online (AJOL)

    molecular forms of pyridinoline crosslinks from insoluble bone type I collagen, and we studied ... resorbed in a dynamic process during ... proteins at 4 C for 24H in 4 mol/L .... fragments was merely due to interactions ... completely elucidated.

  17. The Effect of Polymer Molecular Weight on Citrate Crosslinked ...

    African Journals Online (AJOL)

    Erah

    Purpose: To develop citrate crosslinked chitosan films using chitosan of different molecular weights. (MW) in .... left to stand until trapped air bubbles ... blotted out carefully with filter paper from the .... potential as biodegradable stent coatings. J.

  18. 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)

  19. Highly efficient perovskite solar cells with crosslinked PCBM interlayers

    KAUST Repository

    Qiu, W.

    2017-01-09

    Commercially available phenyl-C-butyric acid methyl ester (PCBM) is crosslinked with 1,6-diazidohexane (DAZH), resulting in films resistant to common solvents used in perovskite solar cell processing. By using crosslinked PCBM as an interlayer and (HC(NH))(CHNH)PbIBr as the active layer, we achieve small area devices and modules with a maximum steady-state power conversion efficiency of 18.1% and 14.9%, respectively.

  20. 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.

  1. Lesion progression in post-treatment persistent endodontic lesions.

    Science.gov (United States)

    Yu, Victoria Soo Hoon; Messer, Harold Henry; Shen, Liang; Yee, Robert; Hsu, Chin-ying Stephen

    2012-10-01

    Radiographic lesions related to root-filled teeth may persist for long periods after treatment and are considered to indicate failure of initial treatment. Persistent lesions are found in a proportion of cases, but information on lesion progression is lacking. This study examined the incidence of lesion improvement, remaining unchanged, and deterioration among persistent lesions in a group of patients recruited from a university-based clinic and identified potential predictors for lesion progression. Patients of a university clinic with persistent endodontic lesions at least 4 years since treatment and with original treatment radiographs available were recruited with informed consent. Data were obtained by interview and from dental records and clinical and radiographic examinations. Univariate and multivariate statistical analyses were carried out by using SPSS (version 19). One hundred fifty-one persistent lesions were identified in 114 patients. A majority of the lesions (107, 70.9%) received treatment between 4 and 5 years prior. Eighty-six lesions (57.0%) improved, 18 (11.9%) remained unchanged, and 47 (31.1%) deteriorated since treatment. Potential predictors for lesions that did not improve included recall lesion size, pain on biting at recall examination, history of a postobturation flare-up, and a non-ideal root-filling length (P < .05). Lesions that had persisted for a longer period appeared less likely to be improving (relative risk, 1.038; 95% confidence interval, 1.000-1.077). A specific time interval alone should not be used to conclude that a lesion will not resolve without intervention. This study identified several clinical factors that are associated with deteriorating persistent lesions, which should aid in identifying lesions that require further intervention. Copyright © 2012 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  2. Radiation crosslinking of polymer materials and its functional properties

    International Nuclear Information System (INIS)

    Yoshii, Fumio

    2006-01-01

    It was found out that radiation crosslinking of biodegradable polymer such as poly (butylene succinate, PBS) and poly(ε-caprolactone, PCL) could be achieved by radiation in the presence of small amount of trimethallyl isocyanurate (TMAIC) or 1% triallyl isocyanurate (TAIC). Such modification is very effective to improve heat resistance for PBS and PCL. Poly (lactic acid, PLA) undergoes crosslinking effectively with 3% TAIC by radiation. Outstanding feature of these polymers is their biodegradability even after crosslinking. Radiation crosslinking of polysaccharide derivatives such as carboxymethyl-cellulose (CMC) is also achieved in aqueous solution at high concentration (paste-like state). The crosslinking behavior was largely affected by the degree of substitution (DS) and polymer concentration. After removal of water the dry CMC gel is used as water absorbent material. This dry gel is the most effective for removal of large amounts of water from organic wastes, resulting in the acceleration of their fermentation. Measurement of swelling ratio of the dry CMC gel in 0.9% NaCl aqueous solution was carried out to expand application fields for this material. Radiation crosslinked poly (vinyl alcohol) hydrogel was successfully commercialized from July 2004 as wound dressing for accelerated healing. Furthermore, this material was also used as gel protector to prevent shore sore and was further commercialized. (author)

  3. 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.

  4. Acute periodontal lesions.

    Science.gov (United States)

    Herrera, David; Alonso, Bettina; de Arriba, Lorenzo; Santa Cruz, Isabel; Serrano, Cristina; Sanz, Mariano

    2014-06-01

    This review provides updates on acute conditions affecting the periodontal tissues, including abscesses in the periodontium, necrotizing periodontal diseases and other acute conditions that cause gingival lesions with acute presentation, such as infectious processes not associated with oral bacterial biofilms, mucocutaneous disorders and traumatic and allergic lesions. A periodontal abscess is clinically important because it is a relatively frequent dental emergency, it can compromise the periodontal prognosis of the affected tooth and bacteria within the abscess can spread and cause infections in other body sites. Different types of abscesses have been identified, mainly classified by their etiology, and there are clear differences between those affecting a pre-existing periodontal pocket and those affecting healthy sites. Therapy for this acute condition consists of drainage and tissue debridement, while an evaluation of the need for systemic antimicrobial therapy will be made for each case, based on local and systemic factors. The definitive treatment of the pre-existing condition should be accomplished after the acute phase is controlled. Necrotizing periodontal diseases present three typical clinical features: papilla necrosis, gingival bleeding and pain. Although the prevalence of these diseases is not high, their importance is clear because they represent the most severe conditions associated with the dental biofilm, with very rapid tissue destruction. In addition to bacteria, the etiology of necrotizing periodontal disease includes numerous factors that alter the host response and predispose to these diseases, namely HIV infection, malnutrition, stress or tobacco smoking. The treatment consists of superficial debridement, careful mechanical oral hygiene, rinsing with chlorhexidine and daily re-evaluation. Systemic antimicrobials may be used adjunctively in severe cases or in nonresponding conditions, being the first option metronidazole. Once the acute

  5. Localization of lesions in aphasia

    International Nuclear Information System (INIS)

    Hojo, Kei; Watanabe, Shunzo; Tasaki, Hiroichi; Sato, Tokijiro; Metoki, Hirobumi.

    1984-01-01

    Using a microcomputer, the locus and extent of the lesions, as demonstrated by computed tomography for 127 cases with various types of aphasia were superimposed onto standardized marices. The relationship between the foci of the lesions and the types of aphasia was investigated. Broca aphasics (n=39) : Since the accumulated site of the lesions highly involved the deep structures of the lower part of the precentral gyrus as well as the insula and lenticular nucleus, only 60% of the Broca aphasics had lesions on these areas. This finding has proved to have little localizing value. Wernicke aphasics (n=23) : The size of the lesion was significantly smaller than Broca's aphasia. At least 70% of the patients had the superior temporal lesions involving Wernicke's area and subcortical lesions of the superior and middle temporal gyri. Amnestic aphasics (n=18) : The size of the lesion was smaller than any other types. While there was some concentration of the lesions (maximum 40%) in the area of the subcortical region of the anterior temporal gyrus adjacent to Wernicke's area and the lenticular nucleus, the lesions were distributed throughout the left hemisphere. Amnestic aphasia was thought to be the least localizable. Conduction aphasics (n=11) : The lesions were relatively small in size. Many patients had posterior speech area lesions involving at least partially Wernicke's area. In particular, more than 80% of the conduction aphasics had lesions of the supramarginal gyrus and it's adjacent deep structures. Global aphasics (n=36) : In general, the size of the lesion was very large and 70% of the global aphasics had extensive lesions involving both Broca's and Wernicke's areas. However, there were observations showing that the lesions can be small and confined. (J.P.N.)

  6. Comparison of radiation-induced DNA-protein cross-links formed in oxic, hypoxic, and glutathione depleted cells

    International Nuclear Information System (INIS)

    Xue, L.; Friedman, L.R.; Chiu, S.; Ramakrishnan, N.; Oleinick, N.L.

    1987-01-01

    Treatment of cells with L-buthionine sulfoximine (BSO) inhibits the synthesis of glutathione (GSH). Subsequent metabolism depletes the cells of GSH. GSH-depletion sensitizes both oxic and hypoxic cells to the lethal effects of ionizing radiation. DNA-protein cross-links (DPC) are formed preferentially between DNA sequences active in transcription and a subset of proteins of the nuclear matrix. Thus, DPC may be an indicator lesion of damage in sensitive regions of the genome. The interrelationships between GSH level, oxic vs. hypoxic status, and the yield of DPC have been studied in terms of number of lesions and repair rate in Chinese hamster V79 and in human lung carcinoma A549 cells. The data suggest that elevated background levels of DPC are indicative of a reduced repair capacity, and greater radiation-induced yields of DPC in hypoxia may also be indicative of a compromised repair mechanism

  7. 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.

  8. A disappearing neonatal skin lesion.

    LENUS (Irish Health Repository)

    Hawkes, Colin Patrick

    2012-01-31

    A preterm baby girl was noted at birth to have a firm, raised, non-tender skin lesion located over her right hip. She developed three similar smaller lesions on her ear, buttock and right knee. All lesions had resolved by 2 months of age.

  9. In vitro evaluation of crosslinked electrospun fish gelatin scaffolds

    International Nuclear Information System (INIS)

    Gomes, S.R.; Rodrigues, G.; Martins, G.G.; Henriques, C.M.R.; Silva, J.C.

    2013-01-01

    Gelatin from cold water fish skin was electrospun, crosslinked and investigated as a substrate for the adhesion and proliferation of cells. Gelatin was first dissolved in either water or concentrated acetic acid and both solutions were successfully electrospun. Cross-linking was achieved via three different routes: glutaraldehyde vapor, genipin and dehydrothermal treatment. Solution's properties (surface tension, electrical conductivity and viscosity) and scaffold's properties (chemical bonds, weight loss and fiber diameters) were measured. Cellular viability was analyzed culturing 3T3 fibroblasts plated on the scaffolds and grown up to 7 days. The cells were fixed and observed with SEM or stained for DNA and F-actin and observed with confocal microscopy. In all scaffolds, the cells attached and spread with varying degrees. The evaluation of cell viability showed proliferation of cells until confluence in scaffolds crosslinked by glutaraldehyde and genipin; however the rate of growth in genipin crosslinked scaffolds was slow, recovering only by day five. The results using the dehydrothermal treatment were the less satisfactory. Our results show that glutaraldehyde treated fish gelatin is the most suitable substrate, of the three studied, for fibroblast adhesion and proliferation. - Highlights: ► Electrospinning of fish gelatin dissolved in both water or concentrated acetic acid ► Glutaraldehyde, genipin and dehydrothermal treatment effectively crosslink the fish gelatin fibers ► Fibroblasts effectively adhere to and propagate on all scaffolds ► Cell population is highest for glutaraldehyde crosslinked scaffolds ► Cells exhibit more filopodia and stress fibers on glutaraldehyde crosslinked scaffolds

  10. In vitro evaluation of crosslinked electrospun fish gelatin scaffolds

    Energy Technology Data Exchange (ETDEWEB)

    Gomes, S.R. [Centro de Física e Investigação Tecnológica / Departamento de Física, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Rodrigues, G.; Martins, G.G. [Centro de Biologia Ambiental / Departamento de Biologia Animal, Faculdade de Ciências da Universidade de Lisboa, FCUL, 1749-016 Campo Grande, Lisboa (Portugal); Henriques, C.M.R. [Centro de Física e Investigação Tecnológica / Departamento de Física, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Silva, J.C., E-mail: jcs@fct.unl.pt [Centro de Física e Investigação Tecnológica / Departamento de Física, Faculdade de Ciências e Tecnologia, FCT, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal)

    2013-04-01

    Gelatin from cold water fish skin was electrospun, crosslinked and investigated as a substrate for the adhesion and proliferation of cells. Gelatin was first dissolved in either water or concentrated acetic acid and both solutions were successfully electrospun. Cross-linking was achieved via three different routes: glutaraldehyde vapor, genipin and dehydrothermal treatment. Solution's properties (surface tension, electrical conductivity and viscosity) and scaffold's properties (chemical bonds, weight loss and fiber diameters) were measured. Cellular viability was analyzed culturing 3T3 fibroblasts plated on the scaffolds and grown up to 7 days. The cells were fixed and observed with SEM or stained for DNA and F-actin and observed with confocal microscopy. In all scaffolds, the cells attached and spread with varying degrees. The evaluation of cell viability showed proliferation of cells until confluence in scaffolds crosslinked by glutaraldehyde and genipin; however the rate of growth in genipin crosslinked scaffolds was slow, recovering only by day five. The results using the dehydrothermal treatment were the less satisfactory. Our results show that glutaraldehyde treated fish gelatin is the most suitable substrate, of the three studied, for fibroblast adhesion and proliferation. - Highlights: ► Electrospinning of fish gelatin dissolved in both water or concentrated acetic acid ► Glutaraldehyde, genipin and dehydrothermal treatment effectively crosslink the fish gelatin fibers ► Fibroblasts effectively adhere to and propagate on all scaffolds ► Cell population is highest for glutaraldehyde crosslinked scaffolds ► Cells exhibit more filopodia and stress fibers on glutaraldehyde crosslinked scaffolds.

  11. Properties of crosslinked ultra-high-molecular-weight polyethylene.

    Science.gov (United States)

    Lewis, G

    2001-02-01

    Substantially reducing the rate of generation of wear particles at the surfaces of ultra-high-molecular-weight polyethylene (UHMWPE) orthopedic implant bearing components, in vivo, is widely regarded as one of the most formidable challenges in modern arthroplasty. In the light of this, much research attention has been paid to the myriad of endogenous and exogenous factors that have been postulated to affect this wear rate, one such factor being the polymer itself. In recent years, there has been a resurgence of interest in crosslinking the polymer as a way of improving its properties that are considered relevant to its use for fabricating bearing components. Such properties include wear resistance, fatigue life, and fatigue crack propagation rate. Although a large volume of literature exists on the topic on the impact of crosslinking on the properties of UHMWPE, no critical appraisal of this literature has been published. This is one of the goals of the present article, which emphasizes three aspects. The first is the trade-off between improvement in wear resistance and depreciation in other mechanical and physical properties. The second aspect is the presentation of a method of estimating the optimal value of a crosslinking process variable (such as dose in radiation-induced crosslinking) that takes into account this trade-off. The third aspect is the description of a collection of under- and unexplored research areas in the field of crosslinked UHMWPE, such as the role of starting resin on the properties of the crosslinked polymer, and the in vitro evaluation of the wear rate of crosslinked tibial inserts and other bearing components that, in vivo, are subjected to nearly unidirectional motion.

  12. Lesiones deportivas Sports injuries

    Directory of Open Access Journals (Sweden)

    Isabel Cristina Gallego Ching

    2007-04-01

    Full Text Available El estrés generado por la práctica deportiva ha originado una mayor probabilidad de que los atletas presenten lesiones agudas y crónicas. En el ámbito mundial existen diferentes investigaciones acerca de la incidencia de lesiones deportivas. La comparación de sus resultados es difícil por las diferencias en las características de la población y en la forma de reportar los datos, que varía ampliamente entre los estudios (proporciones o tasas de incidencia o tasas por cada 100 ó 1.000 participantes o tasas por horas de juego o por número de partidos jugados. Las tasas varían entre 1,7 y 53 lesiones por 1.000 horas de práctica deportiva, entre 0,8 y 90,9 por 1.000 horas de entrenamiento, entre 3,1 y 54,8 por 1.000 horas de competición y de 6,1 a 10,9 por 100 juegos. La gran variación entre las tasas de incidencia se explica por las diferencias existentes entre los deportes, los países, el nivel competitivo, las edades y la metodología empleada en los estudios. Se ha definido la lesión deportiva como la que ocurre cuando los atletas están expuestos a la práctica del deporte y se produce alteración o daño de un tejido, afectando el funcionamiento de la estructura. Los deportes de contacto generan mayor riesgo de presentar lesiones; se destacan al respecto los siguientes: fútbol, rugby, baloncesto, balonmano, artes marciales y jockey. Las lesiones ocurren con mayor probabilidad en las competencias que en el entrenamiento. Stress generated by sports practice has increased the probability that athletes suffer from acute and chronic injuries. Worldwide, there have been many different investigations concerning the incidence of sport injuries. The different ways in which results have been presented makes it difficult to compare among them. Rates of sports injuries vary between 1.7 and 53 per 1.000 hours of sports practice; 0.8 and 90.9 per 1.000 hours of training; 3.1 and 54.8 per 1.000 hours of competition, and 6.1 and 10.9 per 100

  13. Analysis of pulmonary coin lesions

    International Nuclear Information System (INIS)

    Kim, O; Kim, K. H.; Oh, K. K.; Park, C. Y.

    1979-01-01

    For A long time the solitary pulmonary nodule has remained a difficult problem to solve and has attracted a great deal of attension in recent years. Circumscribed coin lesions of the lung were generally peripheral in location with respect to the pulmonary hilus. Because of this, important clinical problem in management and diagnosis arise. Such a lesion is discovered through roentgenologic examination. So the roentgenologists is the first be in a position to offer advise. This presentation is an attempt to correlate a useful diagnosis with roentgenologic findings of pulmonary coin lesion which enables us to get differential diagnosis of benign and malignant lesion. Histologically proven 120 cases of the pulmonary coin lesion during the period of 8 years were reviewed through plain film, tomogram, bronchoscopy, variable laboratory findings, and clinical history. The results are as follows: 1. Male to female sex ratio was 3 : 1. In age distribution, most of the malignant pulmonary coin lesion appeared in 6th decade (39%) and 5th decade (27%). In benign lesion, the most cases were in 3 rd decade. 2. Pathological cell type are as follows: Primary bronchogenic cancer 43.3%, tuberculoma 25.8%, inflammatory lesion 17.5%, benign tumor 10%, and bronchial adenoma, harmartoma, A.V. malformation, mesothelioma, are 1 case respectively. As a result benign and malignant lesion showed equal distribution (49.1% : 50.3%). 3. In symptom analysis ; cough is the most common (43.5%) symptom in malignant lesion, next follows hemoptysis (20.9%) and chest pain (14.5%). In benign lesion, most of the patient (32.7%) did not complain any symptom. 4. In malignant lesion, the most common nodular size was 4 cm (32.3%), and in benign lesion 2 cm sized coin was most common (39.3%). 5. In general, margin of nodule was very sharp and well demarcated in benign lesion (83.3%), and in malignant lesion that was less demarcated and poorly defined. 6. Most case of calcification (82.7%) was seen in benign

  14. Managing Carious Lesions

    DEFF Research Database (Denmark)

    Innes, N P T; Frencken, J E; Bjørndal, L

    2016-01-01

    Variation in the terminology used to describe clinical management of carious lesions has contributed to a lack of clarity in the scientific literature and beyond. In this article, the International Caries Consensus Collaboration presents 1) issues around terminology, a scoping review of current...... manifestations to the histopathology, we have based the terminology around the clinical consequences of disease (soft, leathery, firm, and hard dentine). Approaches to carious tissue removal are defined: 1)selective removal of carious tissue-includingselective removal to soft dentineandselective removal to firm...

  15. Study of genital lesions

    Directory of Open Access Journals (Sweden)

    Anand Kumar B

    2003-03-01

    Full Text Available A total of one hundred patients (75 males and 25 females age ranged from 17-65 years with genital lesions attending the STD clinic of Bowring and LC Hospitals Bangalore constituted the study group. Based on clinical features, the study groups were classified as syphilis (39, chancroid (30, herpes genitolis (13, condylomato lato (9, LGV (7t condylomata acuminata (5, genital scabies (3, granuloma inguinole (2 and genital candidiasis (1. In 68% microbiological findings confirmed the clinical diagnosis. Of the 100 cases 13% and 2% were positive for HIV antibodies and HbsAg respectively.

  16. Mechano-responsive hydrogels crosslinked by reactive block copolymer micelles

    Science.gov (United States)

    Xiao, Longxi

    Hydrogels are crosslinked polymeric networks that can swell in water without dissolution. Owing to their structural similarity to the native extracelluar matrices, hydrogels have been widely used in biomedical applications. Synthetic hydrogels have been designed to respond to various stimuli, but mechanical signals have not incorporated into hydrogel matrices. Because most tissues in the body are subjected to various types of mechanical forces, and cells within these tissues have sophisticated mechano-transduction machinery, this thesis is focused on developing hydrogel materials with built-in mechano-sensing mechanisms for use as tissue engineering scaffolds or drug release devices. Self-assembled block copolymer micelles (BCMs) with reactive handles were employed as the nanoscopic crosslinkers for the construction of covalently crosslinked networks. BCMs were assembled from amphiphilic diblock copolymers of poly(n-butyl acrylate) and poly(acrylic acid) partially modified with acrylate. Radical polymerization of acrylamide in the presence of micellar crosslinkers gave rise to elastomeric hydrogels whose mechanical properties can be tuned by varying the BCM composition and concentration. TEM imaging revealed that the covalently integrated BCMs underwent strain-dependent reversible deformation. A model hydrophobic drug, pyrene, loaded into the core of BCMs prior to the hydrogel formation, was dynamically released in response to externally applied mechanical forces, through force-induced reversible micelle deformation and the penetration of water molecules into the micelle core. The mechano-responsive hydrogel has been studied for tissue repair and regeneration purposes. Glycidyl methacrylate (GMA)-modified hyaluronic acid (HA) was photochemically crosslinked in the presence of dexamethasone (DEX)-loaded crosslinkable BCMs. The resultant HA gels (HAxBCM) contain covalently integrated micellar compartments with DEX being sequestered in the hydrophobic core. Compared

  17. 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.)

  18. 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

  19. Sorption characteristics of technetium on crosslinked chitosan from aqueous solution

    International Nuclear Information System (INIS)

    Pivarciova, L.; Rosskopfova, O.; Galambos, M.; Rajec, P.

    2014-01-01

    Sorption of technetium on crosslinked chitosan was studied using batch techniques in static arrangement of experiment under aerobic conditions at laboratory temperature. The adsorption of technetium was rapid and the percentage of the technetium sorption was > 98 %. In the pH range of 3-11 adsorption of technetium on crosslinked chitosan was > 98 %. The competition effect of Fe 3+ towards TcO 4 - sorption on crosslinked chitosan was stronger than the competition effect of other observed cations. The selectivity of crosslinked chitosan for these cations in solution with the concentration above 1·10 -3 mol·dm -3 was in the order Fe 3+ > Ca 2+ > Na + > Fe 2+ . The competition effect of (ClO 4 ) - towards TcO 4 - sorption was stronger than the competition effect of (SO 4 ) 2 - ions. From these results it can be expected that crosslinked chitosan could be a suitable sorbent for the immobilization of technetium in the liquid radioactive waste. (authors)

  20. Vascular lesions following radiation

    International Nuclear Information System (INIS)

    Fajardo, L.F.; Berthrong, M.

    1988-01-01

    The special radiation sensitivity of the vascular system is mainly linked to that of endothelial cells, which are perhaps the most radiation-vulnerable elements of mesenchymal tissues. Within the vascular tree, radiation injures most often capillaries, sinusoids, and small arteries, in that order. Lesions of veins are observed less often, but in certain tissues the veins are regularly damaged (e.g., intestine) or are the most affected structures (i.e., liver). Large arteries do suffer the least; however, when significant damage does occur in an elastic artery (e.g., thrombosis or rupture), it tends to be clinically significant and even fatal. Although not always demonstrable in human tissues, radiation vasculopathy generally is dose and time dependent. Like other radiation-induced lesions, the morphology in the vessels is not specific, but it is characteristic enough to be often recognizable. Vascular injury, especially by therapeutic radiation is not just a morphologic marker. It is a mediator of tissue damage; perhaps the most consistent pathogenetic mechanism in delayed radiation injury

  1. Pulsed Light Accelerated Crosslinking versus Continuous Light Accelerated Crosslinking: One-Year Results

    Directory of Open Access Journals (Sweden)

    Cosimo Mazzotta

    2014-01-01

    Full Text Available Purpose. To compare functional results in two cohorts of patients undergoing epithelium-off pulsed (pl-ACXL and continuous light accelerated corneal collagen crosslinking (cl-ACXL with dextran-free riboflavin solution and high-fluence ultraviolet A irradiation. Design. It is a prospective, comparative, and interventional clinical study. Methods. 20 patients affected by progressive keratoconus were enrolled in the study. 10 eyes of 10 patients underwent an epithelium-off pl-ACXL by the KXL UV-A source (Avedro Inc., Waltham, MS, USA with 8 minutes (1 sec. on/1 sec. off of UV-A exposure at 30 mW/cm2 and energy dose of 7.2 J/cm2; 10 eyes of 10 patients underwent an epithelium-off cl-ACXL at 30 mW/cm2 for 4 minutes. Riboflavin 0.1% dextran-free solution was used for a 10-minutes corneal soaking. Patients underwent clinical examination of uncorrected distance visual acuity and corrected distance visual acuity (UDVA and CDVA, corneal topography and aberrometry (CSO EyeTop, Florence, Italy, corneal OCT optical pachymetry (Cirrus OCT, Zeiss Meditec, Jena, Germany, endothelial cells count (I-Conan Non Co Robot, and in vivo scanning laser confocal microscopy (Heidelberg, Germany at 1, 3, 6, and 12 months of follow-up. Results. Functional results one year after cl-ACXL and pl-ACXL demonstrated keratoconus stability in both groups. Functional outcomes were found to be better in epithelium-off pulsed light accelerated treatment together with showing a deeper stromal penetration. No endothelial damage was recorded during the follow-up in both groups. Conclusions. The study confirmed that oxygen represents the main driver of collagen crosslinking reaction. Pulsed light treatment optimized intraoperative oxygen availability improving postoperative functional outcomes compared with continuous light treatment.

  2. Chemical structure and physical properties of radiation-induced crosslinking of polytetrafluoroethylene

    International Nuclear Information System (INIS)

    Oshima, Akihiro; Ikeda, Shigetoshi; Katoh, Etsuko; Tabata, Yoneho

    2001-01-01

    The chemical structure and physical properties of polytetrafluoroethylene (PTFE) that has been crosslinked by radiation have been studied by various methods. It has been found that a Y-type crosslinking structure and a Y-type structure incorporating a double bond (modified Y-type) is formed in PTFE by radiation-crosslinking in the molten state. In addition, various types of double bond structures, excluding the crosslinking site, have been identified. The crosslinked PTFE has a good light transparency due to the loss of crystallites, whilst it retains the excellent properties of electrical insulation and heat resistance. The coefficient of abrasion and the permanent creep are also greatly improved by crosslinking

  3. 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.

  4. Photo-crosslinkable polymers for fabrication of photonic multilayer sensors

    Science.gov (United States)

    Chiappelli, Maria; Hayward, Ryan C.

    2013-03-01

    We have used photo-crosslinkable polymers to fabricate photonic multilayer sensors. Benzophenone is utilized as a covalently incorporated pendent photo-crosslinker, providing a convenient means of fabricating multilayer films by sequential spin-coating and crosslinking processes. Colorimetric temperature sensors were designed from thermally-responsive, low-refractive index poly(N-isopropylacrylamide) (PNIPAM) and high-refractive index poly(para-methyl styrene) (P pMS). Copolymer chemistries and layer thicknesses were selected to provide robust multilayer sensors which show color changes across nearly the full visible spectrum due to changes in temperature of the hydrated film stack. We have characterized the uniformity and interfacial broadening within the multilayers, the kinetics of swelling and de-swelling, and the reversibility over multiple hydration/dehydration cycles. We also describe how the approach can be extended to alternative sensor designs through the ability to tailor each layer independently, as well as to additional stimuli by selecting alternative copolymer chemistries.

  5. 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.

  6. White matter lesion progression

    DEFF Research Database (Denmark)

    Hofer, Edith; Cavalieri, Margherita; Bis, Joshua C

    2015-01-01

    10 cohorts. To assess the relative contribution of genetic factors to progression of WML, we compared in 7 cohorts risk models including demographics, vascular risk factors plus single-nucleotide polymorphisms that have been shown to be associated cross-sectionally with WML in the current......BACKGROUND AND PURPOSE: White matter lesion (WML) progression on magnetic resonance imaging is related to cognitive decline and stroke, but its determinants besides baseline WML burden are largely unknown. Here, we estimated heritability of WML progression, and sought common genetic variants...... associated with WML progression in elderly participants from the Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) consortium. METHODS: Heritability of WML progression was calculated in the Framingham Heart Study. The genome-wide association study included 7773 elderly participants from...

  7. Management of Preinvasive Lesions.

    Science.gov (United States)

    Patrono, Maria G; Corzo, Camila; Iniesta, Maria; Ramirez, Pedro T

    2017-12-01

    Serous tubal intraepithelial carcinoma is considered the precursor lesion of high-grade serous carcinoma, and found in both low-risk and high-risk populations. Isolated serous tubal intraepithelial carcinomas in patients with BRCA1/2 mutations are detected in ∼2% of patients undergoing risk-reducing bilateral salpingo-oophorectomy and even with removal of the tubes and ovaries the rate of developing primary peritoneal carcinoma following remains up to 7.5%. Postoperative recommendations after finding incidental STICs remain unclear and surgical staging, adjuvant chemotherapy, or observation have been proposed. Discovery of STIC should prompt consideration of hereditary cancer program referral for BRCA1/2 mutation screening.

  8. 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

  9. Nanoporous Crosslinked Polyisoprene from Polyisoprene-Polydimethylsiloxane Block Copolymer

    DEFF Research Database (Denmark)

    Hansen, Michael Steffen; Vigild, Martin Etchells; Berg, Rolf Henrik

    2004-01-01

    The polyisoprene block of a polyisoprene-polydimethylsiloxane (PI-PDMS) diblock copolymer with 0.68 volume fraction of PI was tightly crosslinked with dicumylperoxide. The PDMS part of the obtained glassy material was subsequently quantitatively etched with anhydrous hydrogen fluoride or tetrabut......The polyisoprene block of a polyisoprene-polydimethylsiloxane (PI-PDMS) diblock copolymer with 0.68 volume fraction of PI was tightly crosslinked with dicumylperoxide. The PDMS part of the obtained glassy material was subsequently quantitatively etched with anhydrous hydrogen fluoride...

  10. MALIGNANCY IN LARGE COLORECTAL LESIONS

    Directory of Open Access Journals (Sweden)

    Carlos Eduardo Oliveira dos SANTOS

    2014-09-01

    Full Text Available Context The size of colorectal lesions, besides a risk factor for malignancy, is a predictor for deeper invasion Objectives To evaluate the malignancy of colorectal lesions ≥20 mm. Methods Between 2007 and 2011, 76 neoplasms ≥20 mm in 70 patients were analyzed Results The mean age of the patients was 67.4 years, and 41 were women. Mean lesion size was 24.7 mm ± 6.2 mm (range: 20 to 50 mm. Half of the neoplasms were polypoid and the other half were non-polypoid. Forty-two (55.3% lesions were located in the left colon, and 34 in the right colon. There was a high prevalence of III L (39.5% and IV (53.9% pit patterns. There were 72 adenomas and 4 adenocarcinomas. Malignancy was observed in 5.3% of the lesions. Thirty-three lesions presented advanced histology (adenomas with high-grade dysplasia or early adenocarcinoma, with no difference in morphology and site. Only one lesion (1.3% invaded the submucosa. Lesions larger than 30 mm had advanced histology (P = 0.001. The primary treatment was endoscopic resection, and invasive carcinoma was referred to surgery. Recurrence rate was 10.6%. Conclusions Large colorectal neoplasms showed a low rate of malignancy. Endoscopic treatment is an effective therapy for these lesions.

  11. A review of crosslinked fracturing fluids prepared with produced water

    Directory of Open Access Journals (Sweden)

    Leiming Li

    2016-12-01

    Full Text Available The rapidly increasing implementations of oilfield technologies such as horizontal wells and multistage hydraulic fracturing, particularly in unconventional formations, have expanded the need for fresh water in many oilfield locations. In the meantime, it is costly for services companies and operators to properly dispose large volumes of produced water, generated annually at about 21 billion barrels in the United States alone. The high operating costs in obtaining fresh water and dealing with produced water have motivated scientists and engineers, especially in recent years, to use produced water in place of fresh water to formulate well treatment fluids. The objective of this brief review is to provide a summary of the up-to-date technologies of reusing oilfield produced water in preparations of a series of crosslinked fluids implemented mainly in hydraulic fracturing operations. The crosslinked fluids formulated with produced water include borate- and metal-crosslinked guar and derivatized guar fluids, as well as other types of crosslinked fluid systems such as crosslinked synthetic polymer fluids and crosslinked derivatized cellulose fluids. The borate-crosslinked guar fluids have been successfully formulated with produced water and used in oilfield operations with bottomhole temperatures up to about 250 °F. The produced water sources involved showed total dissolved solids (TDS up to about 115,000 mg/L and hardness up to about 11,000 mg/L. The metal-crosslinked guar fluids prepared with produced water were successfully used in wells at bottomhole temperatures up to about 250 °F, with produced water TDS up to about 300,000 mg/L and hardness up to about 44,000 mg/L. The Zr-crosslinked carboxymethyl hydroxypropyl guar (CMHPG fluids have been successfully made with produced water and implemented in operations with bottomhole temperatures at about 250+ °F, with produced water TDS up to about 280,000 mg/L and hardness up to about 91,000

  12. a study of the kinetic of synthesis and crosslinking of methylol ...

    African Journals Online (AJOL)

    Nurudeen

    The reaction was carried out in ... temperature of reaction medium reduced the time of formation and subsequent crosslinking to the ... The experiment was repeated using 3, 4, 5 and 6 ... increase the rate of the crosslinking in the formation of.

  13. 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.

  14. Permanent antistatic phthalocyanine/epoxy nanocomposites – Influence of crosslinking agent, solvent and processing temperature

    NARCIS (Netherlands)

    Yuan, M.; Brokken-Zijp, J.C.M.; With, de G.

    2010-01-01

    Cross-linked epoxy matrices containing small amounts of semi-conductive phthalocyanine (Phthalcon) nanoparticles were prepared using different crosslinking agents and processing temperatures. A starting mixture containing an optimum dispersion of these nanoparticles and with an almost equal and

  15. Stable and biocompatible genipin-inducing interlayer-crosslinked micelles for sustained drug release

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Yu; Zhang, Xiaojin, E-mail: zhangxj@cug.edu.cn [China University of Geosciences, Faculty of Materials Science and Chemistry (China)

    2017-05-15

    To develop the sustained drug release system, here we describe genipin-inducing interlayer-crosslinked micelles crosslinked via Schiff bases between the amines of amphiphilic linear-hyperbranched polymer poly(ethylene glycol)-branched polyethylenimine-poly(ε-caprolactone) (PEG-PEI-PCL) and genipin. The generation of Schiff bases was confirmed by the color changes and UV-Vis absorption spectra of polymeric micelles after adding genipin. The particle size, morphology, stability, in vitro cytotoxicity, drug loading capacity, and in vitro drug release behavior of crosslinked micelles as well as non-crosslinked micelles were characterized. The results indicated that genipin-inducing interlayer-crosslinked micelles had better stability and biocompatibility than non-crosslinked micelles and glutaraldehyde-inducing interlayer-crosslinked micelles. In addition, genipin-inducing interlayer-crosslinked micelles were able to improve drug loading capacity, reduce the initial burst release, and achieve sustained drug release.

  16. 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

  17. Theoretical approach of complex DNA lesions: from formation to repair

    International Nuclear Information System (INIS)

    Bignon, Emmanuelle

    2017-01-01

    This thesis work is focused on the theoretical modelling of DNA damages, from formation to repair. Several projects have been led in this framework, which can be sorted into three different parts. One on hand, we studied complex DNA reactivity. It included a study about 8-oxo-7,8-dihydro-guanine (8oxoG) mechanisms of formation, a project concerning the UV-induced pyrimidine 6-4 pyrimidone (6-4PP) endogenous photo-sensitizer features, and another one about DNA photo-sensitization by nonsteroidal anti-inflammatory drugs (i.e. ketoprofen and ibuprofen). On the other hand, we investigated mechanical properties of damaged DNA. The structural signature of a DNA lesion is of major importance for their repair, unfortunately only few NMR and X-ray structures of such systems are available. In order to gain insights into their dynamical structure, we investigated a series of complex damages: clustered abasic sites, interstrand cross-links, and the 6-4PP photo-lesion. Likewise, we studied the interaction modes DNA with several polyamines, which are well known to interact with the double helix, but also with the perspective to model DNA-protein cross-linking. The third part concerned the study of DNA interactions with repair enzymes. In line with the structural study about clustered abasic sites, we investigated the dynamics of the same system, but this time interacting with the APE1 endonuclease. We also studied interactions between the Fpg glycosylase with an oligonucleotides containing tandem 8-oxoG on one hand and 8-oxoG - abasic site as multiply damaged sites. Thus, we shed new lights on damaged DNA reactivity, structure and repair, which provides perspectives for biomedicine and life's mechanisms understanding as we begin to describe nucleosomal DNA. (author)

  18. Tunable photonic multilayer sensors from photo-crosslinkable polymers

    Science.gov (United States)

    Chiappelli, Maria; Hayward, Ryan

    2014-03-01

    The fabrication of tunable photonic multilayer sensors from stimuli-responsive, photo-crosslinkable polymers will be described. Benzophenone is covalently incorporated as a pendent photo-crosslinker, allowing for facile preparation of multilayer films by sequential spin-coating and crosslinking processes. Copolymer chemistries and layer thicknesses are selected to provide robust multilayer sensors which can show color changes across nearly the full visible spectrum due to the specific stimulus-responsive nature of the hydrated film stack. We will describe how this approach is extended to alternative sensor designs by tailoring the thickness and chemistry of each layer independently, allowing for the preparation of sensors which depend not only on the shift in wavelength of a reflectance peak, but also on the transition between Bragg mirrors and filters. Device design is optimized by photo-patterning sensor arrays on a single substrate, providing more efficient fabrication time as well as multi-functional sensors. Finally, radiation-sensitive multilayers, designed by choosing polymers which will preferentially degrade or crosslink under ionizing radiation, will also be described.

  19. 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.

  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. Effects of genipin corneal crosslinking in rabbit corneas.

    Science.gov (United States)

    Avila, Marcel Y; Narvaez, Mauricio; Castañeda, Juan P

    2016-07-01

    To evaluate the effect of genipin, a natural crosslinking agent, in rabbit eyes. Department of Ophthalmology, Universidad Nacional de Colombia Centro de Tecnologia Oftalmica, Bogotá, Colombia. Experimental study. Ex vivo rabbit eyes (16; 8 rabbits) were treated with genipin 1.00%, 0.50%, and 0.25% for 5 minutes with a vacuum device to increase corneal permeability. Penetration was evaluated using Scheimpflug pachymetry (Pentacam). In the in vivo model (20 rabbits; 1 eye treated, 1 eye with vehicle), corneas were crosslinked with genipin as described. Corneal curvature, corneal pachymetry, and intraocular pressure (IOP) assessments as well as slitlamp examinations were performed 0, 7, 30, and 60 days after treatment. In the ex vivo model, Scheimpflug pachymetry showed deep penetration in the rabbit corneas with an increase in corneal density and a dose-dependent relationship. Corneal flattening was observed in treated eyes (mean 4.4 diopters ± 0.5 [SD]) compared with the control eyes. Pachymetry and IOP were stable in all evaluations. No eye showed toxicity in the anterior chamber or in the lens. Corneal crosslinking induced by genipin produced significant flattening of the cornea with no toxicity in rabbit eyes. This crosslinking could be useful in the treatment of corneal ectasia and in the modification of corneal curvature. None of the authors has a financial or proprietary interest in any material or method mentioned. Copyright © 2016 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  2. 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.

  3. 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 ...

  4. Epoxy-crosslinked sulfonated poly (phenylene) copolymer proton exchange membranes

    Science.gov (United States)

    Hibbs, Michael; Fujimoto, Cy H.; Norman, Kirsten; Hickner, Michael A.

    2010-10-19

    An epoxy-crosslinked sulfonated poly(phenylene) copolymer composition used as proton exchange membranes, methods of making the same, and their use as proton exchange membranes (PEM) in hydrogen fuel cells, direct methanol fuel cell, in electrode casting solutions and electrodes, and in sulfur dioxide electrolyzers. These improved membranes are tougher, have higher temperature capability, and lower SO.sub.2 crossover rates.

  5. 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

  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. 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

  8. Cholesterol Removal from Whole Egg by Crosslinked β-Cyclodextrin

    Directory of Open Access Journals (Sweden)

    H. J. Jeong

    2014-04-01

    Full Text Available This study was carried out to optimize cholesterol removal in whole egg using crosslinked β-cyclodextrin (β-CD and to recycle the β-CD. Various factors for optimizing conditions were concentration of the β-CD, mixing temperature, mixing time, mixing speed and centrifugal speed. In the result of this study, the optimum conditions of cholesterol removal were 25% crosslinked β-CD, 40°C mixing temperature, 30 min mixing time, 1,200 rpm mixing speed and 2,810×g centrifugal speed. The recycling was repeated five times. The cholesterol removal was 92.76% when treated with the optimum conditions. After determining the optimum conditions, the recyclable yields of the crosslinked β-CD ranged from 86.66% to 87.60% in the recycling and the percentage of cholesterol removal was over 80% until third recycling. However, the cholesterol removal efficiency was decreased when the number of repeated recycling was increased. Based on the result of this study, it was concluded that the crosslinked β-CD was efficient for cholesterol removal in whole egg, and recycling is possible for only limited repeating times due to the interaction of the β-CD and egg protein.

  9. Crosslink Radio Occultation for the Remote Sensing of Planetary Atmospheres

    Science.gov (United States)

    Mannucci, A. J.; Ao, C. O.; Asmar, S.; Edwards, C. D.; Kahan, D. S.; Paik, M.; Pi, X.; Williamson, W.

    2015-12-01

    Radio occultation utilizing deep space telecommunication signals has been used with great success in the profiling of planetary atmospheres and ionospheres since the 1960s. A shortcoming of this technique, however, is the limited temporal and spatial sampling that it provides. We consider a different approach where radio occultation measurements are taken between two spacecraft orbiting an extra-terrestrial body. Such "crosslink" radio occultations between the Global Positioning System satellites and low-earth orbiting spacecraft have been routinely acquired to provide global observations of the Earth's atmosphere and ionosphere that are used for weather forecast, climate analysis, and space weather applications. The feasibility of applying this concept to other planets has recently been demonstrated for the first time, where crosslink occultation measurements have been acquired between the Mars Odyssey and Mars Reconnaissance Orbiter spacecraft. These measurements leverage the proximity link telecommunication payloads on each orbiter, which are nominally used to provide relay communication and navigation services to Mars landers and rovers. In this presentation, we will describe the Mars crosslink experiments and the corresponding data analysis in detail. In addition, we will discuss how the crosslink occultation concepts can be effectively applied in future space exploration missions.

  10. In vitro evaluation of crosslinked electrospun fish gelatin scaffolds.

    Science.gov (United States)

    Gomes, S R; Rodrigues, G; Martins, G G; Henriques, C M R; Silva, J C

    2013-04-01

    Gelatin from cold water fish skin was electrospun, crosslinked and investigated as a substrate for the adhesion and proliferation of cells. Gelatin was first dissolved in either water or concentrated acetic acid and both solutions were successfully electrospun. Cross-linking was achieved via three different routes: glutaraldehyde vapor, genipin and dehydrothermal treatment. Solution's properties (surface tension, electrical conductivity and viscosity) and scaffold's properties (chemical bonds, weight loss and fiber diameters) were measured. Cellular viability was analyzed culturing 3T3 fibroblasts plated on the scaffolds and grown up to 7 days. The cells were fixed and observed with SEM or stained for DNA and F-actin and observed with confocal microscopy. In all scaffolds, the cells attached and spread with varying degrees. The evaluation of cell viability showed proliferation of cells until confluence in scaffolds crosslinked by glutaraldehyde and genipin; however the rate of growth in genipin crosslinked scaffolds was slow, recovering only by day five. The results using the dehydrothermal treatment were the less satisfactory. Our results show that glutaraldehyde treated fish gelatin is the most suitable substrate, of the three studied, for fibroblast adhesion and proliferation. Copyright © 2012 Elsevier B.V. All rights reserved.

  11. Jack of all trades: Versatile catechol crosslinking mechanisms

    NARCIS (Netherlands)

    Yang, J.; Cohen Stuart, M.A.; Kamperman, M.M.G.

    2014-01-01

    Catechols play an important role in many natural systems. They are known to readily interact with both organic (e.g., amino acids) and inorganic (e.g., metal ions, metal oxides) compounds, thereby providing a powerful system for protein curing. Catechol crosslinked protein networks, such as

  12. Mitosis, diffusible crosslinkers, and the ideal gas law.

    Science.gov (United States)

    Odde, David J

    2015-03-12

    During mitosis, molecular motors hydrolyze ATP to generate sliding forces between adjacent microtubules and form the bipolar mitotic spindle. Lansky et al. now show that the diffusible microtubule crosslinker Ase1p can generate sliding forces between adjacent microtubules, and it does so without ATP hydrolysis. Copyright © 2015 Elsevier Inc. All rights reserved.

  13. 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

  14. The Effect of Polymer Molecular Weight on Citrate Crosslinked ...

    African Journals Online (AJOL)

    SEM), dissolution studies and differential scanning calorimetry (DSC) for surface ... Conclusion: The citrate-crosslinked chitosan films can be modulated to vary swelling and drug release at pH 3.5 and 6.2; this feature makes them useful tools for ...

  15. 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.

  16. 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

  17. Synthesis of crosslinked poly (styrene-co-divinylbenzene-co ...

    Indian Academy of Sciences (India)

    Synthesis of crosslinked poly(styrene--divinylbenzene--sulfopropyl methacrylate) nanoparticles by emulsion polymerization: Tuning the particle size and surface charge density. Dhamodaran Arunbabu Mousumi Hazarika Somsankar Naik Tushar Jana. Polymers Volume 32 Issue 6 December 2009 pp 633-641 ...

  18. Radiation crosslinked block copolymer blends with improved impact resistance

    International Nuclear Information System (INIS)

    Saunders, F.L.; Pelletier, R.R.

    1976-01-01

    Polymer blends having high impact resistance after mechanical working are produced by blending together a non-elastomeric monovinylidene aromatic polymer such as polystyrene with an elastomeric copolymer, such as a block copolymer of styrene and butadiene, in the form of crosslinked, colloidal size particles

  19. 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

  20. 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 ...

  1. Vision Restoration with a Collagen Crosslinked Boston Keratoprosthesis Unit

    Science.gov (United States)

    2016-09-01

    ex vivo using vitamin B2 (riboflavin) and ultraviolet light. The overall objective of this study is to prevent sight-threatening keratoprosthesis...keratoprosthesis carrier cornea using tissue that has been cross-linked using vitamin B2 (riboflavin) and ultraviolet light prior to prosthesis

  2. Effects of the nature of the antioxidant on the radiation crosslinking of polyethylene

    Energy Technology Data Exchange (ETDEWEB)

    Gal, O S; Markovic, V M; Novakovic, L R; Stannett, V T

    1985-01-01

    The effects of three antioxidants, a hindered phenolic, a secondary amine and a thioester on the radiation crosslinking efficiency of low-density polyethylene were studied. Both gel content and thermomechanical analysis were used to follow the crosslinking. All three antioxidants decreased the amount of crosslinking at a given dose, the thioester being the most effective. The ratios of G (scission) to G (X linking) increased with all three antioxidants. This is attributed to the antioxidants only interfering with the crosslinking reaction. (author).

  3. The effects of the nature of the antioxidant on the radiation crosslinking of polyethylene

    International Nuclear Information System (INIS)

    Gal, O.S.; Markovic, V.M.; Novakovic, L.R.; Stannett, V.T.

    1985-01-01

    The effects of three antioxidants, a hindered phenolic, a secondary amine and a thioester on the radiation crosslinking efficiency of low-density polyethylene were studied. Both gel content and thermomechanical analysis were used to follow the crosslinking. All three antioxidants decreased the amount of crosslinking at a given dose, the thioester being the most effective. The ratios of G (scission) to G (X linking) increased with all three antioxidants. This is attributed to the antioxidants only interfering with the crosslinking reaction. (author)

  4. Preoperative nonpalpable breast lesions localization

    Energy Technology Data Exchange (ETDEWEB)

    Gardellin, G; Natale, F; Perin, B

    1986-01-01

    The effectiveness of real time sonography and mammography are examined in localizing with a hookwire (introduced via a straight needle) the nonpalpable breast lesions. The method, used for surgery or biopsy, was successful in a series of 13 patients with nonpalpable breast lesions, 4 affectd by carcinoma. 18 refs.

  5. Crosslinking of oriented polyethylene by electron beam radiation. Influence of morphology induced by drawing

    International Nuclear Information System (INIS)

    Aerle, N.A.J.M. van; Crevecoeur, G.; Lemstra, P.J.

    1988-01-01

    The influence of drawing on the crosslinking efficiency for electron beam radiation is reported for solution-crystallized ultra-high molecular weight polyethylene. A maximum in crosslinking efficiency is found at a draw ratio of approximately five, indicating an optimum morphology for inducing crosslinks during the hot-drawing process. (author)

  6. 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

  7. 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

  8. 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...

  9. 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

  10. 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

  11. 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

  12. Newly identified interfibrillar collagen crosslinking suppresses cell proliferation and remodelling.

    Science.gov (United States)

    Marelli, Benedetto; Le Nihouannen, Damien; Hacking, S Adam; Tran, Simon; Li, Jingjing; Murshed, Monzur; Doillon, Charles J; Ghezzi, Chiara E; Zhang, Yu Ling; Nazhat, Showan N; Barralet, Jake E

    2015-06-01

    Copper is becoming recognised as a key cation in a variety of biological processes. Copper chelation has been studied as a potential anti-angiogenic strategy for arresting tumour growth. Conversely the delivery of copper ions and complexes in vivo can elicit a pro-angiogenic effect. Previously we unexpectedly found that copper-stimulated intraperitoneal angiogenesis was accompanied by collagen deposition. Here, in hard tissue, not only was healing accelerated by copper, but again enhanced deposition of collagen was detected at 2 weeks. Experiments with reconstituted collagen showed that addition of copper ions post-fibrillogenesis rendered plastically-compressed gels resistant to collagenases, enhanced their mechanical properties and increased the denaturation temperature of the protein. Unexpectedly, this apparently interfibrillar crosslinking was not affected by addition of glucose or ascorbic acid, which are required for crosslinking by advanced glycation end products (AGEs). Fibroblasts cultured on copper-crosslinked gels did not proliferate, whereas those cultured with an equivalent quantity of copper on either tissue culture plastic or collagen showed no effect compared with controls. Although non-proliferative, fibroblasts grown on copper-cross-linked collagen could migrate, remained metabolically active for at least 14 days and displayed a 6-fold increase in Mmps 1 and 3 mRNA expression compared with copper-free controls. The ability of copper ions to crosslink collagen fibrils during densification and independently of AGEs or Fenton type reactions is previously unreported. The effect on MMP susceptibility of collagen and the dramatic change in cell behaviour on this crosslinked ECM may contribute to shedding some light on unexplained phenomena as the apparent benefit of copper complexation in fibrotic disorders or the enhanced collagen deposition in response to localised copper delivery. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. Proton conducting sulphonated fluorinated poly(styrene) crosslinked electrolyte membranes

    Energy Technology Data Exchange (ETDEWEB)

    Soules, A.; Ameduri, B.; Boutevin, B.; David, G. [Institut Charles Gerhardt UMR CNRS 5253 Equipe, Ingenierie et Architectures Macromoleculaires,' ' Ecole Nationale Superieure de Chimie de Montpellier, 8 rue de l' Ecole Normale, 34296 Montpellier, Cedex 05 (France); Perrin, R. [CEA Le Ripault Departement des Materiaux, DMAT/SCMF/LSTP, BP16 - 37260 Monts (France); Gebel, G. [Structure et Proprietes des Architectures Moleculaires UMR 5819 (CEA-CNRS-UJF), INAC, SPrAM, CEA Grenoble, 17 Rue des Martyrs, 38054 Grenoble, Cedex 9 (France)

    2011-10-15

    Potential membranes for polymer electrolyte membrane fuel cell based on crosslinked sulphonated fluorinated polystyrenes (PS) were synthesised in two steps. First, azide-telechelic polystyrene was obtained by iodine transfer polymerisation of styrene in the presence of 1,6-diiodoperfluorohexane followed by azido chain-end functionalisation. Then azide-telechelic polystyrene was efficiently crosslinked with 1,10-diazido-1H,1H,2H,2H,9H,9H,10H,10H-perfluorodecane under UV irradiation. After 45 min only, almost completion of azide crosslinking could be achieved, resulting in crosslinked membranes with insoluble fractions higher than 95%. The sulphonation of the crosslinked membranes afforded ionic exchange capacities (IECs) ranging from 2.2 to 3.2 meq g{sup -1}. The hydration number was shown to be very high (from 30 to 75), depending on both the content of perfluorodecane and of sulphonic acid groups. The morphology of the membranes, assessed by small-angle X-ray scattering, was found to be a lamellar-type structure with two types of ionic domains. For the membrane that exhibited an IEC value of 2.2 meq.g{sup -1}, proton conductivity was in the same range as that of Nafion {sup registered} (120-135 mS.cm{sup -1}), whereas the membrane IEC value of 3.2 meq.g{sup -1} showed a proton conductivity higher than that of Nafion {sup registered} in liquid water from 25 to 80 C, though a high water uptake. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  14. 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

  15. 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

  16. Study of the direct detection of crosslinking in hydrocarbons by 13C-NMR. II. Identification of crosslink in model compound and application to irradiate paraffins

    International Nuclear Information System (INIS)

    Bennett, R.L.; Keller, A.; Stejny, H.H.; Murray, M.

    1976-01-01

    A 13 C-NMR investigation was carried out in aid of direct detection of crosslinks in hydrocarbons with the future objective of studying radiation-induced crosslinking in polyethylene by a direct method. The resonance signal due to a tertiary carbon atom appropriate to a crosslink far remote from molecular ends has been identified in a definitive manner with the aid of the H-shaped model compound 1,1,2,2-tetra(tridecyl)ethane synthetized in Part I of this study. This identification was then put to use in the examination of the irradiated linear paraffins n-hexadecane and n-eicosane, where it enabled the detection of radiation-induced crosslinks. This crosslinking could then be associated with corresponding changes in molecular weight (dimer, trimer formation) as revealed by discrete peaks in the gel-permeation chromatograms of the same samples and randomness of the crosslinking process in the liquid state of these compounds being inferred

  17. UVA photoactivation of DNA containing halogenated thiopyrimidines induces cytotoxic DNA lesions

    Science.gov (United States)

    Brem, Reto; Zhang, Xiaohui; Xu, Yao-Zhong; Karran, Peter

    2015-01-01

    Photochemotherapy, the combination of a photosensitiser and ultraviolet (UV) or visible light, is an effective treatment for skin conditions including cancer. The high mutagenicity and non-selectivity of photochemotherapy regimes warrants the development of alternative approaches. We demonstrate that the thiopyrimidine nucleosides 5-bromo-4-thiodeoxyuridine (SBrdU) and 5-iodo-4-thiodeoxyuridine (SIdU) are incorporated into the DNA of cultured human and mouse cells where they synergistically sensitise killing by low doses of UVA radiation. The DNA halothiopyrimidine/UVA combinations induce DNA interstrand crosslinks, DNA-protein crosslinks, DNA strand breaks, nucleobase damage and lesions that resemble UV-induced pyrimidine(6-4)pyrimidone photoproducts. These are potentially lethal DNA lesions and cells defective in their repair are hypersensitive to killing by SBrdU/UVA and SIdU/UVA. DNA SIdU and SBrdU generate lethal DNA photodamage by partially distinct mechanisms that reflect the different photolabilities of their C–I and C–Br bonds. Although singlet oxygen is involved in photolesion formation, DNA SBrdU and SIdU photoactivation does not detectably increase DNA 8-oxoguanine levels. The absence of significant collateral damage to normal guanine suggests that UVA activation of DNA SIdU or SBrdU might offer a strategy to target hyperproliferative skin conditions that avoids the extensive formation of a known mutagenic DNA lesion. PMID:25747491

  18. Intracellular Crosslinking of Filoviral Nucleoproteins with Xintrabodies Restricts Viral Packaging

    Directory of Open Access Journals (Sweden)

    Tamarand Lee Darling

    2017-09-01

    Full Text Available Viruses assemble large macromolecular repeat structures that become part of the infectious particles or virions. Ribonucleocapsids (RNCs of negative strand RNA viruses are a prime example where repetition of nucleoprotein (NP along the genome creates a core polymeric helical scaffold that accommodates other nucleocapsid proteins including viral polymerase. The RNCs are transported through the cytosol for packaging into virions through association with viral matrix proteins at cell membranes. We hypothesized that RNC would be ideal targets for crosslinkers engineered to promote aberrant protein–protein interactions, thereby blocking their orderly transport and packaging. Previously, we had generated single-domain antibodies (sdAbs against Filoviruses that have all targeted highly conserved C-terminal regions of NP known to be repetitively exposed along the length of the RNCs of Marburgvirus (MARV and Ebolavirus (EBOV. Our crosslinker design consisted of dimeric sdAb expressed intracellularly, which we call Xintrabodies (X- for crosslinking. Electron microscopy of purified NP polymers incubated with purified sdAb constructs showed NP aggregation occurred in a genus-specific manner with dimeric and not monomeric sdAb. A virus-like particle (VLP assay was used for initial evaluation where we found that dimeric sdAb inhibited NP incorporation into VP40-based VLPs whereas monomeric sdAb did not. Inhibition of NP packaging was genus specific. Confocal microscopy revealed dimeric sdAb was diffuse when expressed alone but focused on pools of NP when the two were coexpressed, while monomeric sdAb showed ambivalent partition. Infection of stable Vero cell lines expressing dimeric sdAb specific for either MARV or EBOV NP resulted in smaller plaques and reduced progeny of cognate virus relative to wild-type Vero cells. Though the impact was marginal at later time-points, the collective data suggest that viral replication can be reduced by crosslinking

  19. Effect of Structure Change on Radiation Crosslinking of Unsaturated Polyesters

    International Nuclear Information System (INIS)

    Ranogajec, F.

    2006-01-01

    During the course of crosslinking of unsaturated polyesters reacting system, that was liquid prior to reaction, gels, and becomes solid. Crosslinking reaction begins to be controlled by the change of the physical state of the system at an early stage of reaction. The kinetics can not be studied by the usual kinetical methods. In-source 60 C o gamma rays induced crosslinking of unsaturated polyester with styrene was followed directly and continuously by measuring electrical conductivity change. The results of extraction analysis proved good correlation between the change of electrical conductivity and the extent of curing. The gel content was inversely proportional to conductivity and free styrene content directly proportional to conductivity. DC-electrical conductivity has shown high sensitivity toward structural changes and enabled us to detect liquid-liquid transitions in unsaturated polyester. The upper liquid-liquid transition (T l ρ) is less known transition caused by a stepwise decrease of intramolecular short-range local order that remains above the glass and lower liquid-liquid transitions. The local order is based on secondary valent interactions and is enhanced by hydrogen bonding. The linear temperature dependence of the viscosity and dc electrical conductivity of unsaturated polyesters showed a change of slope caused by the (T l ρ). Those changes were the result of the diminishing of the local order (which includes several bond lengths) caused by breaking of the intramolecular interactions. The intramolecular nature of the (T l ρ) in the polyesters under consideration was proved by its insensitivity to crosslinking and dilution with solvents. In the corresponding temperature range, DSC thermograms shoved expected endothermic changes. The structure changes related to the (T l ρ) in the investigated polyesters were determined by 1 H NMR and NIR spectroscopy. The proton NMR indicated that the stepwise change in hydrogen bonding occurred in the

  20. Changing activity in MS lesions

    International Nuclear Information System (INIS)

    Kermode, A.G.; Tofts, P.S.; Thompson, A.J.; Rudge, P.; MacManus, D.G.; Kendall, B.E.; Moseley, I.F.; Kingsley, D.P.E.; McDonald, W.I.

    1989-01-01

    Gd-DTPA enhanced T1 weighted MRI is a discriminating test for a defective blood-brain barrier, with MS lesions showing considerable variation in the pattern of enhancement. Since little is known of the changes in the blood-brain barrier in the active plaque over time, the natural history of blood-brain barrier disturbance in the MS lesion was examined to confirm earlier reports that Gd-DTPA enhancement is a consistent early event in new lesions of relapsing/remitting MS. This knowledge is essential for the use of MRI in monitoring treatment. (author). 9 refs

  1. PHAEOHYPHOMYCOSIS: CUTANEOUS, SUBCUTANEOUS, NASOPHARYNGEAL LESIONS

    Directory of Open Access Journals (Sweden)

    M. Rasoolinejad

    1999-06-01

    Full Text Available Phaeohyphomycosis is an amalgam of clinical diseases caused by a wide variety of dematiaceous fungi. We are reporting on a 16 year-old patient from Amol with subcutaneous cervical nodes and nasopharyngeal lesions of phaeohypho"nmycosis that were confirmed by pathological examination, direct smear, and culture. After treatment with an oral triazole (Itraconazole for 4 months, all nodes and lesions disappeared and treatment was stopped A new lesion appeared on his chest wall 8 months, therapy with itraconazole was restarted and commuted for a long time.

  2. OCT investigation of dental lesions

    Science.gov (United States)

    Osiac, Eugen; Popescu, Sanda Mihaela; Scrieciu, Monica; Mercuţ, Rǎzvan; Mercuţ, Veronica; Vǎtu, Mihaela

    2018-03-01

    There are several important non carious lesions affecting the tooth structure, lesions which may be classified into four clinical forms of dental wear: abfraction, erosion, attrition and abrasion, and different types of root resorption. Search for new, non-invasive and fast methods able to detect and describe such injuries is of utmost importance. Optical coherence tomography (OCT) proved itself as an appropriate investigation method for several medical fields including ophthalmology, dermatology, cardiology etc. Our study reveals OCT preliminary investigations as a promising tool for detecting and evaluating of the mentioned lesions.

  3. Upregulated ATM gene expression and activated DNA crosslink-induced damage response checkpoint in Fanconi anemia: implications for carcinogenesis.

    Science.gov (United States)

    Yamamoto, Kazuhiko; Nihrane, Abdallah; Aglipay, Jason; Sironi, Juan; Arkin, Steven; Lipton, Jeffrey M; Ouchi, Toru; Liu, Johnson M

    2008-01-01

    Fanconi anemia (FA) predisposes to hematopoietic failure, birth defects, leukemia, and squamous cell carcinoma of the head and neck (HNSCC) and cervix. The FA/BRCA pathway includes 8 members of a core complex and 5 downstream gene products closely linked with BRCA1 or BRCA2. Precancerous lesions are believed to trigger the DNA damage response (DDR), and we focused on the DDR in FA and its putative role as a checkpoint barrier to cancer. In primary fibroblasts with mutations in the core complex FANCA protein, we discovered that basal expression and phosphorylation of ATM (ataxia telangiectasia mutated) and p53 induced by irradiation (IR) or mitomycin C (MMC) were upregulated. This heightened response appeared to be due to increased basal levels of ATM in cultured FANCA-mutant cells, highlighting the new observation that ATM can be regulated at the transcriptional level in addition to its well-established activation by autophosphorylation. Functional analysis of this response using gamma-H2AX foci as markers of DNA double-stranded breaks (DSBs) demonstrated abnormal persistence of only MMC- and not IR-induced foci. Thus, we describe a processing defect that leads to general DDR upregulation but specific persistence of DNA crosslinker-induced damage response foci. Underscoring the significance of these findings, we found resistance to DNA crosslinker-induced cell cycle arrest and apoptosis in a TP53-mutant, patient-derived HNSCC cell line, whereas a lymphoblastoid cell line derived from this same individual was not mutated at TP53 and retained DNA crosslinker sensitivity. Our results suggest that cancer in FA may arise from selection for cells that escape from a chronically activated DDR checkpoint.

  4. Link establishment criterion and topology optimization for hybrid GPS satellite communications with laser crosslinks

    Science.gov (United States)

    Li, Lun; Wei, Sixiao; Tian, Xin; Hsieh, Li-Tse; Chen, Zhijiang; Pham, Khanh; Lyke, James; Chen, Genshe

    2018-05-01

    In the current global positioning system (GPS), the reliability of information transmissions can be enhanced with the aid of inter-satellite links (ISLs) or crosslinks between satellites. Instead of only using conventional radio frequency (RF) crosslinks, the laser crosslinks provide an option to significantly increase the data throughput. The connectivity and robustness of ISL are needed for analysis, especially for GPS constellations with laser crosslinks. In this paper, we first propose a hybrid GPS communication architecture in which uplinks and downlinks are established via RF signals and crosslinks are established via laser links. Then, we design an optical crosslink assignment criteria considering the practical optical communication factors such as optical line- of-sight (LOS) range, link distance, and angular velocity, etc. After that, to further improve the rationality of establishing crosslinks, a topology control algorithm is formulated to optimize GPS crosslink networks at both physical and network layers. The RF transmission features for uplink and downlink and optical transmission features for crosslinks are taken into account as constraints for the optimization problem. Finally, the proposed link establishment criteria are implemented for GPS communication with optical crosslinks. The designs of this paper provide a potential crosslink establishment and topology control algorithm for the next generation GPS.

  5. Structure of E. coli 16S RNA elucidated by psoralen crosslinking

    International Nuclear Information System (INIS)

    Thompson, J.F.; Hearst, J.E.

    1983-01-01

    E. coli 16S RNA in solution was photoreacted with hydroxymethyltrimethylpsoralen and long wave ultraviolet light. Positions of crosslinks were determined to high resolution by partially digesting the RNA with T 1 RNase, separating the crosslinked fragments by two-dimensional gel electrophoresis, reversing the crosslink, and sequencing the separated fragments. This method yielded the locations of crosslinks to +/-15 nucleotides. Even finer placement has been made on the basis of our knowledge of psoralen reactivity. Thirteen unique crosslinks were mapped. Seven crosslinks confirmed regions of secondary structure which had been predicted in published phylogenetic models, three crosslinks discriminated between phylogenetic models, and three proved the existence of new structures. The new structures were all long-range interactions which appear to be in dynamic equilibrium with local secondary structure. Because this technique yields direct information about the secondary structure of large RNAs, it should prove invaluable in studying the structure of other RNAs of all sizes

  6. 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.

  7. 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.

  8. Shape memory behaviour of radiation-crosslinked PCL/PMVS blends

    International Nuclear Information System (INIS)

    Zhu Guangming; Xu Shuogui; Wang Jinhua; Zhang Longbin

    2006-01-01

    The performance and radiation crosslinking of polycaprolactone (PCL) and polymethylvinylsiloxane (PMVS) blends has been investigated. Radiation crosslinking of PCL/PMVS blends followed the Charlesby-Pinner equation, and PMVS promoted the radiation crosslinking of the blends. As the concentration of PMVS increased, the gelation dose and the ratio of degradation to crosslinking (p 0 /q 0 ) decreased and the efficiency of radiation crosslinking increased. The elastic modulus below the melting point of PCL of radiation-crosslinked PCL/PMVS blends decreased with the increase of PMVS, and increased above the melting point. The crosslinked PCL/PMVS blends exhibited excellent shape memory effects, and the ratios of deformation to recovery were more than 95%

  9. Exposure of tropoelastin to peroxynitrous acid gives high yields of nitrated tyrosine residues, di-tyrosine cross-links and altered protein structure and function

    DEFF Research Database (Denmark)

    Degendorfer, Georg; Chuang, Christine Yu-Nung; Mariotti, Michele

    2018-01-01

    Elastin is an abundant extracellular matrix protein in elastic tissues, including the lungs, skin and arteries, and comprises 30–57% of the aorta by dry mass. The monomeric precursor, tropoelastin (TE), undergoes complex processing during elastogenesis to form mature elastic fibres. Peroxynitrous......-protein di-tyrosine cross-links have been characterized by mass spectrometry. Examination of human atherosclerotic lesions shows colocalization of 3-nitroTyr with elastin epitopes, consistent with TE or elastin modification in vivo, and also an association of 3-nitroTyr containing proteins and elastin...

  10. Post-radiotherapeutic heart lesions

    International Nuclear Information System (INIS)

    Testart, F.M.

    1979-05-01

    Heart structures have traditionally been considered radioresistant. In fact all tissues subjected to radiotherapy can develop lesions. Possible damage includes: - pericardiac fibrosis, the commonest and best individualized, associated with a constriction this leads to a stoppage pattern usually occurring late, around the 18th month. Its frequency depends directly on the total radiation dose; - fibrous myocarditis by direct damage to the heart muscle; - stenosis type lesions of the large coronary trunks; - in exceptional cases lesions of the aorta: hyperplastic degenerescence of the intima and adventitia or of the aortic sigmoid valvules and the mitral valves. Three observations are reported, concerning a coronary, a pericardiac and a coronary, myocardiac and pericardiac lesion. Following this account the irradiation techniques and main experimental data are reviewed and the prophylactic and therapeutic consequences to be derived from our observations and those of the literature are examined [fr

  11. Atypical idiopathic inflammatory demyelinating lesions

    DEFF Research Database (Denmark)

    Wallner-Blazek, Mirja; Rovira, Alex; Fillipp, Massimo

    2013-01-01

    Atypical lesions of a presumably idiopathic inflammatory demyelinating origin present quite variably and may pose diagnostic problems. The subsequent clinical course is also uncertain. We, therefore, wanted to clarify if atypical idiopathic inflammatory demyelinating lesions (AIIDLs) can be class......Atypical lesions of a presumably idiopathic inflammatory demyelinating origin present quite variably and may pose diagnostic problems. The subsequent clinical course is also uncertain. We, therefore, wanted to clarify if atypical idiopathic inflammatory demyelinating lesions (AIIDLs) can...... be classified according to previously suggested radiologic characteristics and how this classification relates to prognosis. Searching the databases of eight tertiary referral centres we identified 90 adult patients (61 women, 29 men; mean age 34 years) with ≥1 AIIDL. We collected their demographic, clinical...

  12. Crosslinking in the diglycidyl ether oligoepichlorhydrin-piperazine

    Directory of Open Access Journals (Sweden)

    Konstantyn E. Varlan

    2014-03-01

    Full Text Available The possibility of acquiring film material from a mixture of oligoepichlorhydrin diglycidylether and piperazyne discussed. The process involves elongation of the chain by means of reaction of the oligomer terminal oxyran cycles with piperazine aminogrups, and the subsequent formation of crosslinked by tertiary amine alongthe chainsalkylation whis chlorometyl dand groups of macromolecules. With this purpose, the model system investigated: epichlorohydrin−piperidine, epichlorohydrin−piperazine, oligoetylenglikol glicidyl ether−piperazine. The possibility of regulating the contributions of reactions of epoxy group and alkylation on crosslinking primary stage is disclosed, as well as material properties. Taking into account the found regularities receive elastic film structured materials with quaternary nitrogen atoms in the nodes. The ratio of tertiary and quaternary structure of nitrogen depends on the process conditions. Films swell in polar solvents and has ion-exchange properties.

  13. Natural polyphenols enhance stability of crosslinked UHMWPE for joint implants.

    Science.gov (United States)

    Shen, Jie; Gao, Guorong; Liu, Xincai; Fu, Jun

    2015-03-01

    Radiation-crosslinked UHMWPE has been used for joint implants since the 1990s. Postirradiation remelting enhances oxidative stability, but with some loss in strength and toughness. Vitamin E-stabilized crosslinked UHMWPE has shown improved strength and stability as compared with irradiated and remelted UHMWPE. With more active phenolic hydroxyl groups, natural polyphenols are widely used in the food and pharmaceutical industries as potent stabilizers and could be useful for oxidative stability in crosslinked UHMWPE. We asked whether UHMWPE blended with polyphenols would (1) show higher oxidation resistance after radiation crosslinking; (2) preserve the mechanical properties of UHMWPE after accelerated aging; and (3) alter the wear resistance of radiation-crosslinked UHMWPE. The polyphenols, gallic acid and dodecyl gallate, were blended with medical-grade UHMWPE followed by consolidation and electron beam irradiation at 100 kGy. Radiation-crosslinked virgin and vitamin E-blended UHMWPEs were used as reference materials. The UHMWPEs were aged at 120 °C in air with oxidation levels analyzed by infrared spectroscopy. Tensile (n = 5 per group) and impact (n = 3 per group) properties before and after aging as per ASTM F2003 were evaluated. The wear rates were examined by pin-on-disc testing (n = 3 per group). The data were reported as mean ± SDs. Statistical analysis was performed by using Student's t-test for a two-tailed distribution with unequal variance for tensile and impact data obtained with n ≥ 3. A significant difference is defined with p Accelerated aging of these polyphenol-blended UHMWPEs resulted in ultimate tensile strength of 50.4 ± 1.4 MPa and impact strength of 53 ± 5 kJ/m(2) for 100 kGy-irradiated UHMWPE with 0.05 wt% dodecyl gallate, for example, in comparison to 51.2 ± 0.7 MPa (p = 0.75) and 58 ± 5 kJ/m(2) (p = 0.29) before aging. The pin-on-disc wear rates of 100 kGy-irradiated UHMWPE with 0.05 wt% dodecyl gallate and 0.05 wt% gallic acid

  14. Preparation of micro-pored silicone elastomer through radiation crosslinking

    International Nuclear Information System (INIS)

    Gao Xiaoling; Gu Mei; Xie Xubing; Huang Wei

    2013-01-01

    The radiation crosslinking was adopted to prepare the micro-pored silicone elastomer, which was performed by vulcanization and foaming respectively. Radiation crosslinking is a new method to prepare micro-pored material with high performance by use of radiation technology. Silicon dioxide was used as filler, and silicone elastomer was vulcanized by electron beams, then the micro-pored material was made by heating method at a high temperature. The effects of absorbed dose and filler content on the performance and morphology were investigated. The structure and distribution of pores were observed by SEM. The results show that the micro-pored silicon elastomer can be prepared successfully by controlling the absorbed dose and filler content. It has a smooth surface similar to a rubber meanwhile the pores are round and unconnected to each other with the minimum size of 14 μm. And the good mechanical performance can be suitable for further uses. (authors)

  15. Absorbed energy for radiation crosslinking in stabilized PE systems

    International Nuclear Information System (INIS)

    Novakovic, Lj.; Gal, O.; Charlesby, A.

    1990-01-01

    A quantitative consideration on the absorbed energy consumption in various γ-irradiated polyethylene systems is given. On the base of the increased gel dose values for the PE systems containing antioxidant, relative to the gel doses for the pure polymers, the surplus of the absorbed energy due to the presence of the particular antioxidant is calculated. The increasing of the energy consumption in the stabilized systems depends on both the type and the content of the basic polymer. The surplus in the absorbed energy decreases with the radiation dose increasing, reflecting both the diminishing of the antioxidant concentration in the irradiating PE systems and the crosslinking level. The findings can be of interest in the estimation of the absorbed doses for the specific radiation crosslinking processes. (author)

  16. Absorbed energy for radiation crosslinking in stabilized PE systems

    Energy Technology Data Exchange (ETDEWEB)

    Novakovic, Lj; Gal, O [Institut za Nuklearne Nauke Boris Kidric, Belgrade (Yugoslavia); Charlesby, A

    1990-01-01

    A quantitative consideration on the absorbed energy consumption in various {gamma}-irradiated polyethylene systems is given. On the base of the increased gel dose values for the PE systems containing antioxidant, relative to the gel doses for the pure polymers, the surplus of the absorbed energy due to the presence of the particular antioxidant is calculated. The increasing of the energy consumption in the stabilized systems depends on both the type and the content of the basic polymer. The surplus in the absorbed energy decreases with the radiation dose increasing, reflecting both the diminishing of the antioxidant concentration in the irradiating PE systems and the crosslinking level. The findings can be of interest in the estimation of the absorbed doses for the specific radiation crosslinking processes. (author).

  17. Comparison of glutaraldehyde and carbodiimides to crosslink tissue engineering scaffolds fabricated by decellularized porcine menisci

    International Nuclear Information System (INIS)

    Gao, Shuang; Yuan, Zhiguo; Guo, Weimin; Chen, Mingxue; Liu, Shuyun; Xi, Tingfei; Guo, Quanyi

    2017-01-01

    The objectives of this study were to fabricate porous scaffolds using decellularized meniscus, and to explore a preferable crosslinking condition to enhance mechanical properties of scaffolds. Moreover, the microstructure, porosity, biodegradation and cytotoxicity were also evaluated. EDAC or GTA in different concentration was used to crosslink scaffolds. FTIR demonstrated functional groups change in crosslinking process. SEM photography showed that crosslinked scaffolds had blurry edges, which resulted scaffolds crosslinked by 1.2 mol/l EDAC had smaller porosity than other groups. The structure change enhanced antidegradation property. After immersing in enzyme solution for 96 h, scaffolds crosslinked by GTA and EDAC could maintain their mass > 70% and 80%. Most importantly, mechanical properties of crosslinked scaffolds were also improved. Uncrosslinked Scaffolds had only 0.49 kPa in compression modulus and 12.81 kPa in tensile modulus. The compression and tensile modulus of scaffolds crosslinked by 1.0% GTA were 1.42 and 567.44 kPa respectively. The same value of scaffolds crosslinked by 1.2 mol/l EDAC were 1.49 and 532.50 kPa. Scaffolds crosslinked by 1.0% and 2.5% GTA were toxic to cells, while EDAC groups showed no cytotoxicity. Chondrocytes could proliferate and infiltrate within scaffolds after seeding. Overall, 1.2 mol/l EDAC was a preferable crosslinking condition. - Highlights: • Porous meniscus scaffolds were fabricated using decellularized meniscus tissue. • Mechanical properties of meniscus scaffolds were enhanced by chemical crosslinking. • The crosslinked scaffold showed enhanced anti-degradation properties. • Chondrocytes could infiltrate and proliferate within crosslinked scaffolds.

  18. Comparison of glutaraldehyde and carbodiimides to crosslink tissue engineering scaffolds fabricated by decellularized porcine menisci

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Shuang [Center for Biomedical Material and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871 (China); Yuan, Zhiguo; Guo, Weimin; Chen, Mingxue; Liu, Shuyun [Beijing Key Lab of Regenerative Medicine in Orthopaedics, Institute of Orthopaedics, Chinese PLA General Hospital, Beijing 100853 (China); Key Laboratory of Musculoskeletal Trauma & War Injuries, Institute of Orthopaedics, Chinese PLA General Hospital, Beijing 100853 (China); Xi, Tingfei, E-mail: tingfeixi@163.com [Center for Biomedical Material and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871 (China); Shenzhen Institute, Peking University, Shenzhen 518057 (China); Guo, Quanyi, E-mail: doctorguo_301@163.com [Beijing Key Lab of Regenerative Medicine in Orthopaedics, Institute of Orthopaedics, Chinese PLA General Hospital, Beijing 100853 (China); Key Laboratory of Musculoskeletal Trauma & War Injuries, Institute of Orthopaedics, Chinese PLA General Hospital, Beijing 100853 (China)

    2017-02-01

    The objectives of this study were to fabricate porous scaffolds using decellularized meniscus, and to explore a preferable crosslinking condition to enhance mechanical properties of scaffolds. Moreover, the microstructure, porosity, biodegradation and cytotoxicity were also evaluated. EDAC or GTA in different concentration was used to crosslink scaffolds. FTIR demonstrated functional groups change in crosslinking process. SEM photography showed that crosslinked scaffolds had blurry edges, which resulted scaffolds crosslinked by 1.2 mol/l EDAC had smaller porosity than other groups. The structure change enhanced antidegradation property. After immersing in enzyme solution for 96 h, scaffolds crosslinked by GTA and EDAC could maintain their mass > 70% and 80%. Most importantly, mechanical properties of crosslinked scaffolds were also improved. Uncrosslinked Scaffolds had only 0.49 kPa in compression modulus and 12.81 kPa in tensile modulus. The compression and tensile modulus of scaffolds crosslinked by 1.0% GTA were 1.42 and 567.44 kPa respectively. The same value of scaffolds crosslinked by 1.2 mol/l EDAC were 1.49 and 532.50 kPa. Scaffolds crosslinked by 1.0% and 2.5% GTA were toxic to cells, while EDAC groups showed no cytotoxicity. Chondrocytes could proliferate and infiltrate within scaffolds after seeding. Overall, 1.2 mol/l EDAC was a preferable crosslinking condition. - Highlights: • Porous meniscus scaffolds were fabricated using decellularized meniscus tissue. • Mechanical properties of meniscus scaffolds were enhanced by chemical crosslinking. • The crosslinked scaffold showed enhanced anti-degradation properties. • Chondrocytes could infiltrate and proliferate within crosslinked scaffolds.

  19. MRI atlas of MS lesions

    Energy Technology Data Exchange (ETDEWEB)

    Sahraian, Mohammad Ali [Tehran Univ. of Medical Sciences Sina Hospital (Iran). Dept. of Neurology; Radue, Ernst-Wilhelm [Univ. Hospital Basel (Switzerland). Dept. of Neuroradiology

    2008-07-01

    MRI has become the main paraclinical test in the diagnosis and management of multiple sclerosis. We have demonstrated more than 400 pictures of different typical and atypical MS lesions in this atlas. Each image has a teaching point. New diagnostic criteria and differential diagnosis are discussed and the book is supported by a teaching DVD where the reader can see MS lesions in different slices and sequences. (orig.)

  20. 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)

  1. Heterobifunctional crosslinkers for tethering single ligand molecules to scanning probes

    International Nuclear Information System (INIS)

    Riener, Christian K.; Kienberger, Ferry; Hahn, Christoph D.; Buchinger, Gerhard M.; Egwim, Innocent O.C.; Haselgruebler, Thomas; Ebner, Andreas; Romanin, Christoph; Klampfl, Christian; Lackner, Bernd; Prinz, Heino; Blaas, Dieter; Hinterdorfer, Peter; Gruber, Hermann J.

    2003-01-01

    Single molecule recognition force microscopy (SMRFM) is a versatile atomic force microscopy (AFM) method to probe specific interactions of cognitive molecules on the single molecule level. It allows insights to be gained into interaction potentials and kinetic barriers and is capable of mapping interaction sites with nm positional accuracy. These applications require a ligand to be attached to the AFM tip, preferably by a distensible poly(ethylene glycol) (PEG) chain between the measuring tip and the ligand molecule. The PEG chain greatly facilitates specific binding of the ligand to immobile receptor sites on the sample surface. The present study contributes to tip-PEG-ligand tethering in three ways: (i) a convenient synthetic route was found to prepare NH 2 -PEG-COOH which is the key intermediate for long heterobifunctional crosslinkers; (ii) a variety of heterobifunctional PEG derivatives for tip-PEG-ligand linking were prepared from NH 2 -PEG-COOH; (iii) in particular, a new PEG crosslinker with one thiol-reactive end and one terminal nitrilotriacetic acid (NTA) group was synthesized and successfully used to tether His 6 -tagged protein molecules to AFM tips via noncovalent NTA-Ni 2+ -His 6 bridges. The new crosslinker was applied to link a recombinant His 6 -tagged fragment of the very-low density lipoprotein receptor to the AFM tip whereupon specific docking to the capsid of human rhinovirus particles was observed by force microscopy. In a parallel study, the specific interaction of the small GTPase Ran with the nuclear import receptor importin β1 was studied in detail by SMRFM, using the new crosslinker to link His 6 -tagged Ran to the measuring tip [Nat. Struct. Biol. (2003), 10, 553-557

  2. Studies on flame retardancy of radiation crosslinked PE foam

    International Nuclear Information System (INIS)

    Yang Huili; Yao Zhanhai; Xu Jun

    1996-01-01

    CPE, DBDPO and Sb 2 O 3 were used as flame-retardant of PE foam. Effect of CPE on PE foam under radiation and it's flame-retardancy were studied. The result showed that CPE can enhance radiation cross-linking of PE, and trinary of addition being made of CPE, DBDPO and Sb 2 O 3 made oxygen index of PE foam achieve over 30, and self-extinguish, it did not influence manufacture and mechanical properties of PE foam

  3. The effects of trioctyl trimellitate concentration on crosslinking

    International Nuclear Information System (INIS)

    Jamaliah Sharif; Rozana Abu Bakar

    1997-01-01

    The effects of trimellitate type plasticizer concentration on PVC formulation were investigated. The results show that the degree of crosslinking is higher in the PVC compounds containing lower concentration of plasticizer compared to others. The tensile properties were decreased with the increase of plasticizer. However, the ageing properties of the lower concentration samples were very poor. The electrical properties of the compounds were acceptable with the volume resistivity value above 1014 . The heat deformation properties of the samples also improved after irradiation

  4. The Evaluation of Corneal Fragility After UVA/Riboflavin Crosslinking.

    Science.gov (United States)

    Li, Zhiwei; Wang, Yumeng; Xu, Yanyun; Jhanji, Vishal; Zhang, Chunxiao; Mu, Guoying

    2017-03-01

    To evaluate the fragility of cornea after UVA/riboflavin crosslinking (CXL). Sixty New Zealand rabbits received UVA/riboflavin crosslinking treatment (wavelength 365 nm, irradiance 3.0 mW/cm, and total dose 5.4 J/cm) on right eyes. Animals were sacrificed before and immediately after treatment (day 0), day 1, 3, 7, and 28 after treatment. A 4×10 mm corneal strip for biomechanical evaluation was harvested after sacrifice. The corneal fragility was evaluated by measurement of elongation rate, whereby the elongation rate equals elongation length/baseline length. The Youngs modulus and maximal stress were 1.41±0.51 MPa and 5.56±1.84 MPa before CXL, and increased to 2.31±0.68 MPa (P=0.008) and 9.25±2.74 MPa (P=0.04), respectively, on day 0, then maintained a stable level within a 28 days follow-up. The elongation rate was 62.04±9.34% before CXL and decreased to 48.95%±8.24% (P=0.02) on day 0, then maintained a stable level within a 28 days follow-up. This study showed an increase in the corneal fragility after UVA/riboflavin crosslinking along with an increase in the corneal stiffness. A long-term follow-up should be taken to evaluate the potential deleterious effect of the increasing corneal fragility after UVA/riboflavin crosslinking.

  5. Recycling tires? Reversible crosslinking of poly(butadiene).

    Science.gov (United States)

    Trovatti, Eliane; Lacerda, Talita M; Carvalho, Antonio J F; Gandini, Alessandro

    2015-04-01

    Furan-modified poly(butadiene) prepared by the thiol-ene click reaction is crosslinked with bismaleimides through the Diels-Alder reaction, giving rise to a novel recyclable elastomer. This is possible because of the thermal reversibility of the adducts responsible for the formation of the network. The use of this strategy provides the possibility to produce recyclable tires. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Histomorphological spetrum of breast lesions.

    Science.gov (United States)

    Parajuli, S; Koirala, U; Khatri, R; Acharya, L; Suwal, A

    2011-04-01

    Cancer of the breast is the second most common cause of cancer in women. Mass in the breast, whether benign or malignant is a cause of anxiety to the patients and the family members. All breast lumps are considered to be carcinomas until proved otherwise and are the causes of concern both for the patient and surgeon. This is a retrospective study conducted in Kathmandu Model Hospital for a total duration of three years from August 2007 to August 2010. 114 sample of breast tissue sent for histopathology were studied. Peak incidence of benign lesion was in between 21-30 years and malignant lesions in between 31-50 years. No breast lesions were seen in the first decade of life. Cancer of the breast was seen in 12.28% of cases. Fibroadenoma and fibrocystic disease were the commonest benign lesion and infiltrating ductal carcinoma was the commonest malignant lesion. Specimens from 10 male breasts were received. Gynaecomastia was the most common lesion encountered in males. Infiltrating ductal carcinoma was seen in a 70 year old male. Breast cancer is one of the commonest causes of breast lump particularly in women and is growing public health problem in Nepal.

  7. Premalignant Lesions in the Kidney

    Directory of Open Access Journals (Sweden)

    Ziva Kirkali

    2001-01-01

    Full Text Available Renal cell carcinoma (RCC is the most malignant urologic disease. Different lesions, such as dysplasia in the tubules adjacent to RCC, atypical hyperplasia in the cyst epithelium of von Hippel-Lindau syndrome, and adenoma have been described for a number of years as possible premalignant changes or precursor lesions of RCC. In two recent papers, kidneys adjacent to RCC or removed from other causes were analyzed, and dysplastic lesions were identified and defined in detail. Currently renal intraepithelial neoplasia (RIN is the proposed term for classification. The criteria for a lesion to be defined as premalignant are (1 morphological similarity; (2 spatial association; (3 development of microinvasive carcinoma; (4 higher frequency, severity, and extent then invasive carcinoma; (5 progression to invasive cancer; and (6 similar genetic alterations. RIN resembles the neoplastic cells of RCC. There is spatial association. Progression to invasive carcinoma is described in experimental cancer models, and in some human renal tumors. Similar molecular alterations are found in some putative premalignant changes. The treatment for RCC is radical or partial nephrectomy. Preneoplastic lesions may remain in the renal remnant in patients treated by partial nephrectomy and may be the source of local recurrences. RIN seems to be a biologic precursor of some RCCs and warrants further investigation. Interpretation and reporting of these lesions would reveal important resources for the biological nature and clinical significance. The management of RIN diagnosed in a renal biopsy and partial nephrectomy needs to be answered.

  8. Optical and structural behaviors of crosslinked polyvinyl alcohol thin films

    Science.gov (United States)

    Pandit, Subhankar; Kundu, Sarathi

    2018-04-01

    Polyvinyl Alcohol (PVA) has excellent properties like uniaxial tensile stress, chemical resistance, biocompatibility, etc. The properties of PVA further can be tuned by crosslinking process. In this work, a simple heat treatment method is used to find out the optimum crosslinking of PVA and the corresponding structural and optical responses are explored. The PVA crosslinking is done by exposing the films at different temperatures and time intervals. The optical property of pure and heat treated PVA films are investigated by UV-Vis absorption and photoluminescence emission spectroscopy and structural modifications are studied by Fourier Transform Infrared Spectroscopy (FTIR). The absorption peaks of pure PVA are observed at ≈ 280 and 335 nm and the corresponding emission is observed at ≈ 424 nm. The pure PVA showed modified optical behaviors after the heat treatment. In addition, dipping the PVA films in hot water (85°C) for nearly 20 minutes also show impact on both structural and optical properties. From FTIR spectroscopy, the changes in vibrational band positions confirm the structural modifications of PVA films.

  9. 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.

  10. Radiation crosslinking of methylcellulose and hydroxyethylcellulose in concentrated aqueous solutions

    International Nuclear Information System (INIS)

    Wach, Radoslaw A.; Mitomo, Hiroshi; Nagasawa, Naotsugu; Yoshii, Fumio

    2003-01-01

    The effects of ionizing radiation on aqueous solutions of cellulose ethers, methylcellulose (MC) and hydroxyethylcellulose (HEC) were investigated. The well-established knowledge states that cellulose and its derivatives belong to degrading type of polymers. However, in our study intermolecular crosslinking initiated by gamma rays or electron beam leaded to the formation of insoluble gel. This is an opposite effect of irradiation to the degradation. Paste-like form of the initial specimen, i.e. concentration 20-30%, when water plasticizes the bulk of polymer; and a high dose rate were favorable for hydrogel formation. Gel fraction up to 60% and 70% was obtained from solutions of HEC and MC, respectively. Produced hydrogels swell markedly in aqueous media by imbibing and holding the solvent. Radiation parameters of irradiation, such as yields of degradation and crosslinking and the gelation dose, were evaluated by sol-gel analysis on the basis of Charlesby-Rosiak equation. Despite of the crosslinked structure, obtained hydrogels can be included into the group of biodegradable materials. They undergo decomposition by the action of cellulase enzyme or microorganisms from compost

  11. Crosslinked ionic polysaccharides for stimuli-sensitive drug delivery.

    Science.gov (United States)

    Alvarez-Lorenzo, Carmen; Blanco-Fernandez, Barbara; Puga, Ana M; Concheiro, Angel

    2013-08-01

    Polysaccharides are gaining increasing attention as components of stimuli-responsive drug delivery systems, particularly since they can be obtained in a well characterized and reproducible way from the natural sources. Ionic polysaccharides can be readily crosslinked to render hydrogel networks sensitive to a variety of internal and external variables, and thus suitable for switching drug release on-off through diverse mechanisms. Hybrids, composites and grafted polymers can reinforce the responsiveness and widen the range of stimuli to which polysaccharide-based systems can respond. This review analyzes the state of the art of crosslinked ionic polysaccharides as components of delivery systems that can regulate drug release as a function of changes in pH, ion nature and concentration, electric and magnetic field intensity, light wavelength, temperature, redox potential, and certain molecules (enzymes, illness markers, and so on). Examples of specific applications are provided. The information compiled demonstrates that crosslinked networks of ionic polysaccharides are suitable building blocks for developing advanced externally activated and feed-back modulated drug delivery systems. Copyright © 2013 Elsevier B.V. All rights reserved.

  12. Structures of DNA containing psoralen crosslink and thymine dimer

    International Nuclear Information System (INIS)

    Kim, S.H.; Pearlman, D.A.; Holbrook, S.R.; Pirkle, D.

    1985-01-01

    UV irradiation by itself or in conjunction with other chemicals can cause covalent damages to DNA in living cells. To overcome the detrimental effect of DNA damage, cells developed a repair mechanism by which damaged DNA is repaired. In the absence of such repair, cell malfunction or cell death can occur. Two most studied radiation-induced DNA damage are thymine dimer formation by UV irradiation and psoralen crosslink by combination of psoralens and UV: In the former, two adjacent thymine bases on a strand of DNA are fused by forming cyclobutane ring, and in the latter, one pyrimidine on one DNA strand is crosslinked to another pyrimidine on the other strand via a psoralen. The authors' objective is to deduce the structure of DNA segment which contains a psoralen crosslink or a thymine dimer using the combination of results of X-ray crystallographic studies, molecular model building, and energy minimization. These structural features may be important for understanding the biological effects of such damages and for the recognition by the repair enzymes

  13. Crosslinking and corneal cryotherapy in acanthamoeba keratitis -- a histological study.

    Science.gov (United States)

    Hager, Tobias; Hasenfus, A; Stachon, T; Seitz, B; Szentmáry, N

    2016-01-01

    Acanthamoeba keratitis is rare, but difficult to treat. Penetrating keratoplasty is performed in therapy-resistant cases. Nevertheless, subsequent recurrences occur in 40 % of the cases. In addition to triple-topical therapy (polyhexamid, propamidinisoethionat, neomycin), treatment alternatives are corneal cryotherapy and/or crosslinking (CXL). The aim of our present histological study was to analyze the persistence of acanthamoebatrophozoites and cysts, the persistence of bacteria, and activation of keratocytes in corneas of acanthamoeba keratitis patients following corneal cryotherapy and/or CXL. We analyzed histologically corneal buttons (from penetrating keratoplasties) of nine patients with acanthamoeba keratitis, following corneal cryotherapy (two patients) or a combination of crosslinking and corneal cryotherapy (seven patients), using haematoxilin–eosin, periodic acid Schiff (PAS), Gram and alpha-smooth muscle actin (alpha-SMA) stainings. Acanthamoeba trophozoites persisted in three corneas after cryotherapy and CXL. Cysts persisted in one of two corneas following corneal cryotherapy and in six of seven corneas after a combination of CXL and cryotherapy. One cornea showed positive Gram staining, but there were no alpha-SMA positive keratocytes in any of the corneas. Crosslinking and corneal cryotherapy have only limited impact on killing of acanthamoeba trophozoites, cysts, or bacteria. Corneal cryotherapy and CXL did not stimulate myofibroblastic transformation of keratocytes.

  14. Radiation-induced crosslinking of syndiotactic 1,2-polybutadiene

    International Nuclear Information System (INIS)

    Iwai, Tadashi; Hoshino, Sadao; Yamamoto, Rokuro; Okamoto, Hidemasa; Obana, Kazuyoshi.

    1978-01-01

    Crystalline syndiotactic 1, 2-polybutadiene (hereafter abbreviated as 1, 2-PB) developed in Ube Industries, Ltd. by its own technology is a new thermoplastic resin belonging to the intermediate region between rubber and plastics in its flexibility. By selecting appropriate catalyst composition, 1, 2-PB having the melting point of 90 to 200 deg. C and crystallization of 10 to 65% can be obtained. These 1, 2-PBs can be worked to formed products by general thermoplastic forming methods such as injection molding, extrusion forming and blow forming. Radiation-crosslinked 1, 2-PB changed to very hard polymers through heat treatment. This change has been found to be radical chain reaction of cyclic polymerization. The relation of radiation-induced crosslinking and thermal expansion behavior, and the changes of appearance and structural and physical properties with heat treatment of these polymers are described. That is, specific gravity has increased, tensile strength has been enhanced, and elongation has decreased. While dielectric strength and arc resistivity have been upgraded. Therefore, these polymers can be used for the following applications: food wrapping film, molded notions, molded low foaming material for the soles of footwears, highly foaming moldings such as sponges, electric insulation material such as cable coating and adhesives for many materials. It is considered that crosslinking contributes to the application to electric insulation materials and heat curing to heat-resistant materials and parts. (Wakatsuki, Y.)

  15. Superficial corneal crosslinking during laser in situ keratomileusis.

    Science.gov (United States)

    Seiler, Theo G; Fischinger, Isaak; Koller, Tobias; Derhartunian, Viktor; Seiler, Theo

    2015-10-01

    To determine the safety of superficial corneal crosslinking after laser in situ keratomileusis (LASIK). Institut für Refraktive und Ophthalmo-Chirurgie, Zurich, Switzerland. Prospective study. Eyes with an ectasia risk score of 2 or higher were treated with standard LASIK (90 μm flap) for myopia correction, after which a rapid corneal crosslinking was performed in the interface (riboflavin 0.5% for 2 minutes, 9 mW/cm(2) for 5 minutes) (Group 1). The follow-up was up to 1 year. The prevalence of complications was statistically compared with that in a group of eyes matched regarding age, sex, and attempted refractive correction that were treated with standard LASIK only (Group 2). One month postoperatively, 5 eyes in Group 1 lost 1 line of corrected distance visual acuity (CDVA) compared with 1 eye in Group 2 (P rate of less than 5%. The refractive success was identical in both groups. Early postoperative complications such as erosions (16%), diffuse lamellar keratitis (DLK) stage 1 (38%), and DLK stage 2 (5%) were statistically significantly more frequent after superficial corneal crosslinking, leading to a statistically significantly reduced uncorrected distance visual acuity at 1 month (P interest in any material or method mentioned. Copyright © 2015 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

  16. Induction of corneal collagen cross-linking in experimental corneal alkali burns in rabbits

    Directory of Open Access Journals (Sweden)

    Marcello Colombo-Barboza

    2014-10-01

    Full Text Available Objective: To evaluate the effect of riboflavin-ultraviolet-A-induced cross-linking (CXL following corneal alkali burns in rabbits. Methods: The right corneas and limbi of ten rabbits were burned using a 1N solution of NaOH and the animals were then divided into two groups: a control group submitted to clinical treatment alone and an experimental group that was treated 1 h after injury with CXL, followed by the same clinical treatment as administered to the controls. Clinical parameters were evaluated post-injury at 1, 7, 15, and 30 days by two independent observers. Following this evaluation, the corneas were excised and examined histologically. Results: There were no statistically significant differences in clinical parameters, such as hyperemia, corneal edema, ciliary injection, limbal ischemia, secretion, corneal neovascularization, symblepharon, or blepharospasm, at any of the time-points evaluated. However, the size of the epithelial defect was significantly smaller in the CXL group (p<0.05 (day 15: p=0.008 and day 30: p=0.008 and the extent of the corneal injury (opacity lesion was also smaller (day 30: p=0.021. Histopathology showed the presence of collagen bridges linking the collagen fibers in only the CXL group. Conclusions: These results suggest that the use of CXL may improve the prognosis of acute corneal alkali burns.

  17. FFA STUDY OF MACULAR LESIONS

    Directory of Open Access Journals (Sweden)

    K. Vinayagamurthy

    2017-08-01

    Full Text Available BACKGROUND Macula is an important portion of retina that occupies the posterior pole of retina. Any disease that affects macula results in significant loss of central vision, form vision and colour vision to an extent. Macular lesions can be hereditary as well as acquired. Macular lesions occur in both younger and older individuals. Anatomically, a macular lesions can vary from a simple lesion like an RPF defect to a vision-threatening lesions like choroidal neovascular membrane. Many screening tests that are sensitive and specific are available to assess the functioning of macula called as ‘macular function test’. But, the greater understanding of the retinal vascular led to the usage of fluorescein angiogram in the detection and screening of macular, retinovascular and optic disc lesions. Through fundus fluorescein angiogram is a thirty-year-old procedure; it is still in vogue in almost all parts of the world. It has its own merits. The aim of the study is to study the role of fluorescein angiography in the evaluation of macular lesions. MATERIALS AND METHODS A hospital-based prospective randomised study was done, which included 50 patients. Detailed patient history was taken and thorough ocular and systemic examination was done. All patients were examined by ophthalmoscopy (direct and indirect and slit-lamp examination with 90D followed by fluorescein angiography. Ophthalmoscopic and fluorescein angiography findings were analysed and categorised. Patients were advised proper ocular and systemic treatment and follow up. RESULTS 50 cases with macular lesions were analysed and categorised into conditions like ARMD, CSR, macular oedema, CME, degenerations and dystrophies and miscellaneous conditions. FFA altered the diagnosis in 8% cases and categorised the cases in all cases. 16% patients developed adverse reactions like allergy, vomiting and nausea. On statistical analysis, FFA proved to be cheap and superior diagnostic tool in confirming

  18. 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

  19. Oxidation resistant peroxide cross-linked UHMWPE produced by blending and surface diffusion

    International Nuclear Information System (INIS)

    Gul, Rizwan M; Oral, Ebru; Muratoglu, Orhun K

    2014-01-01

    Ultra-high molecular weight polyethylene (UHMWPE) has been widely used as acetabular cup in total hip replacement (THR) and tibial component in total knee replacement (TKR). Crosslinking of UHMWPE has been successful used to improve its wear performance leading to longer life of orthopedic implants. Crosslinking can be performed by radiation or organic peroxides. Peroxide crosslinking is a convenient process as it does not require specialized equipment and the level of crosslinking can be manipulated by changing the amount of peroxide added. However, there is concern about the long-term stability of these materials due to possible presence of by-products. Vitamin E has been successfully used to promote long-term oxidative stability of UHMWPE. In this study, UHMWPE has been crosslinked using organic peroxide in the presence of Vitamin E to produce an oxidation resistant peroxide crosslinked material. Crosslinking was performed both in bulk by mixing peroxide and resin, and only on the surface using diffusion of peroxides.The results show that UHMWPE can be crosslinked using organic peroxides in the presence of vitamin E by both methods. However, the level of crosslinking decreases with the increase in vitamin E content. The wear resistance increases with the increase in crosslink density, and oxidation resistance significantly increases due to the presence of vitamin E

  20. Oxidation resistant peroxide cross-linked UHMWPE produced by blending and surface diffusion

    International Nuclear Information System (INIS)

    Gul, R. M.; Oral, E.; Muratoglu, O. K.

    2013-01-01

    Ultra-high molecular weight polyethylene (UHMWPE) has been widely used as acetabular cup in total hip replacement (THR) and tibial component in total knee replacement (TKR). Crosslinking of UHMWPE has been successful used to improve its wear performance leading to longer life of orthopedic implants. Crosslinking can be performed by radiation or organic peroxides. Peroxide crosslinking is a convenient process as it does not require specialized equipment and the level of crosslinking can be manipulated by changing the amount of peroxide added. However, there is concern about the long-term stability of these materials due to possible presence of by-products. Vitamin E has been successfully used to promote long-term oxidative stability of UHMWPE. In this study, UHMWPE has been crosslinked using organic peroxide in the presence of Vitamin E to produce an oxidation resistant peroxide crosslinked material. Crosslinking was performed both in bulk by mixing peroxide and resin, and only on the surface using diffusion of peroxides.The results show that UHMWPE can be crosslinked using organic peroxides in the presence of vitamin E by both methods. However, the level of crosslinking decreases with the increase in vitamin E content. The wear resistance increases with the increase in crosslink density, and oxidation resistance significantly increases due to the presence of vitamin E. (author)

  1. 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.

  2. 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)

  3. 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.

  4. Radiation-induced strand-breaks and DNA-protein crosslinks depend predominantly on the dose, oxygen concentration and repair time

    International Nuclear Information System (INIS)

    Wheeler, K.T.; Miyagi, Y.; Zhang, H.

    1995-01-01

    It has been known for many years that the DNA damage produced by ionizing radiation depends upon the oxygen concentration around the DNA. For example, the number of DNA strand-breaks (SBs) formed per unit dose decreases at low oxygen concentrations, and the number of DNA-protein crosslinks formed per unit dose increases at low oxygen concentrations. If radiation-induced SBs and DPCs are to be useful for detecting and/or quantifying hypoxic cells in solid tumors, the formation of these lesions must depend predominantly on the oxygen concentration around the DNA. All other physical, biological, and physiological factors must either be controllable or have little influence on the assay used to measure these lesions. This paper is a summary of the authors' recent experiments to determine if the radiation-induced SBs and DPCs measured by alkaline elution may be used to estimate the hypoxic fraction or fractional hypoxic volume of solid tumors

  5. MRI of the stener lesion

    International Nuclear Information System (INIS)

    Haramati, N.; Hiller, N.; Dowdle, J.; Jacobson, M.; Barax, C.N.; Lieberfarb, R.I.; Lester, B.; Kulick, R.G.

    1995-01-01

    Six cadaver thumbs had ulnar collateral ligament (UCL) tears created surgically. MR examinations (2D STIR and 3D GRASS) were performed identically on all specimens both before displacement (non-Stener) and after displacement (Stener lesion) of the UCL. The MR images were then randomly numbered. Each image was evaluated separately in blinded fashion by four musculoskeletal radiologists for the presence or absence of a Stener lesion. Each radiologist reinterpreted the images after an interval of several days. The interpretation was based on previously published criteria for Stener lesion diagnosis by MR. The sensitivity of GRASS ranged from 0.17 to 0.67 with the most experienced reader scoring the lowest. The specificity of GRASS ranged from 0.33 to 1.0 (most experienced reader 0.67, 0.83). STIR had a sensitivity of 0.00-0.17 and a specificity of 0.53-0.83. The K values for inter- and intraobserver agreement were measured. The intraobserver K for GRASS was 0.27-0.75 (most experienced reader 0.75). 2D imaging is probably inadequate for the evaluation of Stener lesions. The most likely reason is that the STIR slice thickness of 3 mm limits resolution of small UCLs. The poor sensitivity and specificity of GRASS as well as poor interobserver agreement suggest that MR may not be sufficiently accurate for Stener lesion evaluation. (orig./MG)

  6. The Arabidopsis thaliana Homolog of the Helicase RTEL1 Plays Multiple Roles in Preserving Genome Stability[C][W

    Science.gov (United States)

    Recker, Julia; Knoll, Alexander; Puchta, Holger

    2014-01-01

    In humans, mutations in the DNA helicase Regulator of Telomere Elongation Helicase1 (RTEL1) lead to Hoyeraal-Hreidarsson syndrome, a severe, multisystem disorder. Here, we demonstrate that the RTEL1 homolog in Arabidopsis thaliana plays multiple roles in preserving genome stability. RTEL1 suppresses homologous recombination in a pathway parallel to that of the DNA translocase FANCM. Cytological analyses of root meristems indicate that RTEL1 is involved in processing DNA replication intermediates independently from FANCM and the nuclease MUS81. Moreover, RTEL1 is involved in interstrand and intrastrand DNA cross-link repair independently from FANCM and (in intrastrand cross-link repair) parallel to MUS81. RTEL1 contributes to telomere homeostasis; the concurrent loss of RTEL1 and the telomerase TERT leads to rapid, severe telomere shortening, which occurs much more rapidly than it does in the single-mutant line tert, resulting in developmental arrest after four generations. The double mutant rtel1-1 recq4A-4 exhibits massive growth defects, indicating that this RecQ family helicase, which is also involved in the suppression of homologous recombination and the repair of DNA lesions, can partially replace RTEL1 in the processing of DNA intermediates. The requirement for RTEL1 in multiple pathways to preserve genome stability in plants can be explained by its putative role in the destabilization of DNA loop structures, such as D-loops and T-loops. PMID:25516598

  7. The Arabidopsis thaliana homolog of the helicase RTEL1 plays multiple roles in preserving genome stability.

    Science.gov (United States)

    Recker, Julia; Knoll, Alexander; Puchta, Holger

    2014-12-01

    In humans, mutations in the DNA helicase Regulator of Telomere Elongation Helicase1 (RTEL1) lead to Hoyeraal-Hreidarsson syndrome, a severe, multisystem disorder. Here, we demonstrate that the RTEL1 homolog in Arabidopsis thaliana plays multiple roles in preserving genome stability. RTEL1 suppresses homologous recombination in a pathway parallel to that of the DNA translocase FANCM. Cytological analyses of root meristems indicate that RTEL1 is involved in processing DNA replication intermediates independently from FANCM and the nuclease MUS81. Moreover, RTEL1 is involved in interstrand and intrastrand DNA cross-link repair independently from FANCM and (in intrastrand cross-link repair) parallel to MUS81. RTEL1 contributes to telomere homeostasis; the concurrent loss of RTEL1 and the telomerase TERT leads to rapid, severe telomere shortening, which occurs much more rapidly than it does in the single-mutant line tert, resulting in developmental arrest after four generations. The double mutant rtel1-1 recq4A-4 exhibits massive growth defects, indicating that this RecQ family helicase, which is also involved in the suppression of homologous recombination and the repair of DNA lesions, can partially replace RTEL1 in the processing of DNA intermediates. The requirement for RTEL1 in multiple pathways to preserve genome stability in plants can be explained by its putative role in the destabilization of DNA loop structures, such as D-loops and T-loops. © 2014 American Society of Plant Biologists. All rights reserved.

  8. Hyaluronan microgel as a potential carrier for protein sustained delivery by tailoring the crosslink network

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Chunhong [Department of Materials Science and Engineering, College of Science and Engineering, Jinan University, 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); 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)

    2014-03-01

    Hyaluronan (HA) microgels with different crosslink network, i.e. HGPs-1, HGPs-1.5, HGPs-3, HGPs-6 and HGPs-15, were synthesized using divinyl sulfone (DVS) as the crosslinker in an inverse microemulsion system for controlling the sustained delivery of bovine serum albumin (BSA). With increasing the crosslinker content, the average particle size slightly increased from 1.9 ± 0.3 μm to 3.6 ± 0.5 μm by dynamic laser scattering analysis. However, the crosslinker content had no significant effect on the morphology of HA microgels by scanning and transmission electron microscopes. Fourier transform infrared spectroscopy and elemental analysis proved more sulfur participated in the crosslink reaction when raising the crosslinker amount. The water swelling test confirmed the increasing crosslink density with the crosslinker content by calculating the average molecular weight between two crosslink points to be 8.25 ± 2.51 × 10{sup 5}, 1.26 ± 0.43 × 10{sup 5}, 0.96 ± 0.09 × 10{sup 5}, 0.64 ± 0.03 × 10{sup 5}, and 0.11 ± 0.01 × 10{sup 5} respectively. The degradation of HA microgels by hyaluronidase slowed down by enhancing the crosslink density, only about 5% of HGPs-15 was degraded as opposed to over 90% for HGPs-1. BSA loading had no obvious influence on the surface morphology of HA microgels but seemed to induce their aggregation. The increase of crosslink density decreased the BSA loading capacity but facilitated its long-term sustained delivery. When the molar ratio of DVS to repeating unit of HA reached 3 or higher, similar delivery profiles were obtained. Among all these HA microgels, HGPs-3 was the optimal carrier for BSA sustained delivery in this system because it possessed both high BSA loading capacity and long-term delivery profile simultaneously. - Highlights: • HA microgels with different crosslink densities were prepared. • The crosslinker content had little effect on the morphology and size of HA microgels. • The crosslink density

  9. Abfraction lesions reviewed: current concepts

    Directory of Open Access Journals (Sweden)

    Adriana de Fátima Vasconcelos Pereira

    2008-01-01

    Full Text Available Non-carious cervical lesions are characterized by structural loss near the cementoenamel junction, without the presence of caries. Anumber of theories have arisen to explain the etiology of such lesions, although the real causes remain obscure, as is reflected by the contradictory terminology used in the literature. In addition to describing acidic and abrasive processes documented as etiological factors, attention is given to the role of mechanical stress from occlusal load, which is the most accepted theory for the development of abfraction lesions. Considering that tensile stress leads to the failure of restorations in the cervical region and that this is a fruitful area for future research, the present study has highlighted diagnosis, prognosis and the criteria for treatment.

  10. Ultrasonography of chest wall lesion

    Energy Technology Data Exchange (ETDEWEB)

    Park, Cheol Min; Kim, C. H.; Cha, I. H.; Chung, K. B.; Ser, W. H.; Choi, Y. H. [Seoul National University College of Medicine, Seoul (Korea, Republic of)

    1989-12-15

    Thirty-one patients with chest wall diseases were studied with ultrasound to evaluate its role in chest wall lesions. There were eight infectious conditions, 9 benign tumors, 11 malignant lesions and 3 miscellaneous cases. Diffuse chest wall thickening with heterogeneous echogenicity and obliteration of subcutaneous fat layer are findings of acute infection. In cases of tuberculous smpyema necessitates, pleural abnormality extended to the chest wall through intercostal space. Benign tumors were well demarcated, except in 4 cases of lipoma/lipomatosis. Malignant lesions showed irregular soft tissue masses, bone destruction, pleural effusion and subcutaneous invasion. Multiple enlarged lymph nodes were also shown. Ultrasound can demonstrate te internal structure, extent, depth and associated findings such as pleural effusion, bone destruction and peripheral lung involvement. Ultrasound is not only safe, non-invasive and an effective diagnostic imaging modality for chest wall disease, but can also guide aspiration or biopsy for pathologic diagnosis

  11. Ultrasonography of chest wall lesion

    International Nuclear Information System (INIS)

    Park, Cheol Min; Kim, C. H.; Cha, I. H.; Chung, K. B.; Ser, W. H.; Choi, Y. H.

    1989-01-01

    Thirty-one patients with chest wall diseases were studied with ultrasound to evaluate its role in chest wall lesions. There were eight infectious conditions, 9 benign tumors, 11 malignant lesions and 3 miscellaneous cases. Diffuse chest wall thickening with heterogeneous echogenicity and obliteration of subcutaneous fat layer are findings of acute infection. In cases of tuberculous smpyema necessitates, pleural abnormality extended to the chest wall through intercostal space. Benign tumors were well demarcated, except in 4 cases of lipoma/lipomatosis. Malignant lesions showed irregular soft tissue masses, bone destruction, pleural effusion and subcutaneous invasion. Multiple enlarged lymph nodes were also shown. Ultrasound can demonstrate te internal structure, extent, depth and associated findings such as pleural effusion, bone destruction and peripheral lung involvement. Ultrasound is not only safe, non-invasive and an effective diagnostic imaging modality for chest wall disease, but can also guide aspiration or biopsy for pathologic diagnosis

  12. The radiology in the solitary bone lesions

    International Nuclear Information System (INIS)

    Veloso, G.A.; Cardoso, V.M.

    1985-01-01

    Three methods of radiologic analysis of the solitary bone lesions are reviewed. 1. Radiological analysis of the lesions with the objective to suppose the histologic type; 2. To appreciate the velocity of growth and aggressiveness of the lesions. 3. To appreciate the biological behaviour of the bone lesions, making the diagnosis necessary for the treatment. (M.A.C.) [pt

  13. [The treatment of decubitus lesions].

    Science.gov (United States)

    Fugazza, G; Moroni, S; Bona, F

    1995-01-01

    The authors present a plan for pharmacological treatment of pressure sores in patients affected by neurological pathologies: cerebrovascular accidents, head injuries, spinal cord injuries. This plan is easily applicable to all pressure sores included between first and third degree of the Reuler and Cooney classification. Authors identified some drugs specifically usefull in different cutaneous lesion degrees. Skin lesions and employed medicines are described as follows: Erythema: semi occlusive bandage with porous adsorbing membrane. This dressing must be left in for five days at least. Excoriation: bactericidal or bacteriostatic medicines if it's situated in a non pressed area while the same dressing utilized for erythema if it's localized in a pressed area. Pressure sores: if there is local infection cleanse the wound from bacterial defilement using topic antibiotics apply compresses with vitamin C if the cutaneous lesion is larger than deeper, Cadexomero lodico if it's deeper than larger. Fistulas: wadding with tablets of collagen. Necrobiosis: complete or partial surgical removal of eschar preceded by the use of enzymatic drugs when eschar is firmly adherent to subcutaneous tissues. The first group collects 9 patients with stroke and head injury: 8 with sacral and 1 with heel pressure sores. First degree pressure sores heal within 45 days and third degree lesions within 160 days. The second group collects 10 spinal cord injury patients mostly with complete lesion among which: 7 sacral, 1 heel, 1 ischiatic and 1 malleolar lesions. First degree pressure sores heal within 30 days, third degree pressure sores heal within 200 days. Healing time are considered acceptable. Pressure sores recovery swiftness can be related to different factors such as pressure sores sterness, neurological pathology and arising of clinical complication (hyperthermia, infections, low serum albumin values, etc).

  14. Improvement of radiation resistance for polytetrafluoroethylene(PTFE) by radiation cross-linking

    International Nuclear Information System (INIS)

    Oshima, Akihiro; Tabata, Yoneho; Ikeda, Shigetoshi; Seguchi, Tadao.

    1996-01-01

    The crosslinked polytetrafluoroethylene(PTFE) was prepared by electron beams irradiation technique in the molten state at 340degC ± 3degC in inert gas atmosphere. The crosslinking density was changed by the irradiation dose. The radiation resistance of crosslinked PTFE was investigated on the mechanical properties after irradiation by γ-rays at room temperature under vacuum and in air. The dose at half value of elongation at break was about 1MGy for 500kGy-crosslinked PTFE, while the dose for non-crosslinked PTFE was only 3.5kGy. It was found that the radiation resistance of PTFE was extremely improved by crosslinking. (author)

  15. 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)

  16. 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....

  17. Interstrand DNA crosslinking by 4,5',8-trimethylpsoralen plus monochromatic ultraviolet light

    International Nuclear Information System (INIS)

    Cohen, L.F.; Ewig, R.A.G.; Kohn, K.W.; Glaubiger, D.

    1980-01-01

    DNA crosslinking by 4,5',8-trimethylpsoralen plus monochromatic ultraviolet light of wavelength 365 nm was studied in mouse L1210 leukemia cells. DNA breaks and crosslinking were evaluated by alkaline elution of DNA from poly(vinyl chloride) filters. Trimethylpsoralen plus 365 nm light produced DNA crosslinks but not breaks. The kinetics of crosslinging were linear with respect to concentration and second-order with respect to light exposure time. The latter finding supports the proposed two photon mechanism for the formation of diadducts. In contrast to DNA crosslinking agents such as nitrogen mustard, nitrosoureas and platinums, trimethylpsoralen crosslinks were resistant to proteolytic digestion. Thus, trimethylpsoralen plus 365 nm light produced interstrand crosslinks, as proposed for a bifunctional agent binding to bases on opposite DNA strands. (Auth.)

  18. The effect of chain flexibility and chain mobility on radiation crosslinking reactions of polymers

    International Nuclear Information System (INIS)

    Sun Jiazhen

    2003-01-01

    Flexibility of polymer chains is an important factor to effects of radiation crosslinking of the polymer. Polymers with flexible chains are easier to be crosslinked, with lower dose of gelation, than polymers with more rigid chains. And it is known that most polymers with abnormal rigidity can be radiation-crosslinked only at high temperatures when the molecular chains get enough mobility. The flexibility of polymer chains also influences the relationship between degree of degradation and radiation dose. A chain flexibility factor β has been introduced to modify the Charlesby-Pinner equation of sol-fraction and radiation dose. The new relationship equation applies to a wider range of polymers in radiation crosslinking. Studies also show that for flexible polymers with lower T g and molecular internal rotating factor, mechanism of radiation crosslinking is mainly in H type, whereas for rigid polymers with higher T g and molecular internal rotating factor, mechanism of radiation crosslinking is mainly in T type

  19. Lesions of juxtacortical origin (surface lesions of bone)

    International Nuclear Information System (INIS)

    Kenan, S.; Abdelwahab, I.F.; Klein, M.J.; Hermann, G.; Lewis, M.M.

    1993-01-01

    A large variety of tumor and tumor-like conditions have been shown to originate from the surface of bone. Most surface lesions are associated with periosteal reaction. The periosteum is a multipotential membrane. Its cellular composition may give rise to a variety of both neoplasms and tumor-like conditions. To avoid misinterpretation, the orthopedist, radiologist, and pathologist should be familiar with the entire spectrum of surface lesions. A better understanding of the natural history and biological behavior at different lesional maturity stages and correlation of the history with the radiographic and pathological findings is essential to establish the correct diagnosis. A history of injury of blunt trauma is very important. A stress fracture may produce a periosteal reaction acd callus that can be difficult to distinguish from osteosarcoma. In this review article, the authors wish to describe and define each term by its anatomy and radiographic features while discussing the entire spectrum of surface lesions. All the illustrative cases in this review article have been proven histologically. (orig.)

  20. Periapical lesions: diagnosis and treatment

    OpenAIRE

    García-Rubio, A.; Bujaldón-Daza, A.L.; Rodríguez-Archilla, A.

    2015-01-01

    Las lesiones periapicales resultado de la necrosis de la pulpa dental son las patologías que más frecuentemente ocurren encontradas en el hueso alveolar. El tratamiento consiste en la eliminación de los agentes infecciosos mediante el tratamiento del canal radicular, permitiendo la cicatrización de la lesión. Periapical lesions, which are a result of the necrosis of the dental pulp, are the most frequently occurring diseases found in the alveolar bone. The treatment involves the removal of...

  1. Localized lesions in secondary syphillis

    International Nuclear Information System (INIS)

    Rasid, N.; Syphilis, S.

    2008-01-01

    The clinical manifestations of secondary syphilis are variable and can mimic many skin diseases, mostly being generalized and symmetrical in distribution. Localized lesions of secondary syphilis are rarely seen in dermatology clinics. We report an unusual presentation wherein a patient had localized lesions over face and soles only. There is a need for increased awareness on the part of physicians to recognize new patterns of syphilitic infection, together with a willingness to consider the diagnosis of syphilis in patients with unusual clinical features. (author)

  2. Effect of crosslinking agents on chitosan microspheres in controlled release of diclofenac sodium

    OpenAIRE

    Gonçalves,Vanessa L.; Laranjeira,Mauro C. M.; Fávere,Valfredo T.; Pedrosa,Rozângela C.

    2005-01-01

    In this work chitosan microspheres were prepared by the simple coacervation method and crosslinked using epichlorhydrin or glutaraldehyde for the controlled release of diclofenac sodium. The effects of the crosslinking agents on chitosan microspheres over a 12-hour period were assessed with regard to swelling, hydrolysis, porosity, crosslinking, impregnation of diclofenac sodium (DS), and consequently to the release of DS in buffer solutions, simulating the gastrointestinal tract. The degree ...

  3. Effect of crosslink torsional stiffness on elastic behavior of semiflexible polymer networks

    Science.gov (United States)

    Hatami-Marbini, H.

    2018-02-01

    Networks of semiflexible filaments are building blocks of different biological and structural materials such as cytoskeleton and extracellular matrix. The mechanical response of these systems when subjected to an applied strain at zero temperature is often investigated numerically using networks composed of filaments, which are either rigidly welded or pinned together at their crosslinks. In the latter, filaments during deformation are free to rotate about their crosslinks while the relative angles between filaments remain constant in the former. The behavior of crosslinks in actual semiflexible networks is different than these idealized models and there exists only partial constraint on torques at crosslinks. The present work develops a numerical model in which two intersecting filaments are connected to each other by torsional springs with arbitrary stiffness. We show that fiber networks composed of rigid and freely rotating crosslinks are the limiting case of the present model. Furthermore, we characterize the effects of stiffness of crosslinks on effective Young's modulus of semiflexible networks as a function of filament flexibility and crosslink density. The effective Young's modulus is determined as a function of the mechanical properties of crosslinks and is found to vanish for networks composed of very weak torsional springs. Independent of the stiffness of crosslinks, it is found that the effective Young's modulus is a function of fiber flexibility and crosslink density. In low density networks, filaments primarily bend and the effective Young's modulus is much lower than the affine estimate. With increasing filament bending stiffness and/or crosslink density, the mechanical behavior of the networks becomes more affine and the stretching of filaments depicts itself as the dominant mode of deformation. The torsional stiffness of the crosslinks significantly affects the effective Young's modulus of the semiflexible random fiber networks.

  4. Polymeric Micelles with Ionic Cores Containing Biodegradable Crosslinks for Delivery of Chemotherapeutic Agents

    OpenAIRE

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

    2010-01-01

    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 (Ca2+) 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 n...

  5. Covalent Crosslinking of Porous Poly(Ionic Liquid) Membrane via a Triazine Network

    OpenAIRE

    Täuber, Karoline; Dani, Alessandro; Yuan, Jiayin

    2017-01-01

    Porous poly(ionic liquid) membranes that were prepared via electrostatic cross-linking were subsequently covalently cross-linked via formation of a 1,3,5-triazine network. The additional covalent cross-links do not affect the pore size and pore size distribution of the membranes and stabilize them towards salt solutions of high ionic strength, enabling the membranes to work in a broader environmental window.

  6. Molecular and macro-scale analysis of enzyme-crosslinked silk hydrogels for rational biomaterial design.

    Science.gov (United States)

    McGill, Meghan; Coburn, Jeannine M; Partlow, Benjamin P; Mu, Xuan; Kaplan, David L

    2017-11-01

    Silk fibroin-based hydrogels have exciting applications in tissue engineering and therapeutic molecule delivery; however, their utility is dependent on their diffusive properties. The present study describes a molecular and macro-scale investigation of enzymatically-crosslinked silk fibroin hydrogels, and demonstrates that these systems have tunable crosslink density and diffusivity. We developed a liquid chromatography tandem mass spectroscopy (LC-MS/MS) method to assess the quantity and order of covalent tyrosine crosslinks in the hydrogels. This analysis revealed between 28 and 56% conversion of tyrosine to dityrosine, which was dependent on the silk concentration and reactant concentration. The crosslink density was then correlated with storage modulus, revealing that both crosslinking and protein concentration influenced the mechanical properties of the hydrogels. The diffusive properties of the bulk material were studied by fluorescence recovery after photobleaching (FRAP), which revealed a non-linear relationship between silk concentration and diffusivity. As a result of this work, a model for synthesizing hydrogels with known crosslink densities and diffusive properties has been established, enabling the rational design of silk hydrogels for biomedical applications. Hydrogels from naturally-derived silk polymers offer versitile opportunities in the biomedical field, however, their design has largely been an empirical process. We present a fundamental study of the crosslink density, storage modulus, and diffusion behavior of enzymatically-crosslinked silk hydrogels to better inform scaffold design. These studies revealed unexpected non-linear trends in the crosslink density and diffusivity of silk hydrogels with respect to protein concentration and crosslink reagent concentration. This work demonstrates the tunable diffusivity and crosslinking in silk fibroin hydrogels, and enables the rational design of biomaterials. Further, the characterization methods

  7. The Effect of Double Crosslinker on Precipitation Polymerization of Poly(acrylic acid

    Directory of Open Access Journals (Sweden)

    Hajar Es-haghi

    2014-06-01

    Full Text Available Cross-linked poly(acrylic acids were prepared by dual cross-linkers via precipitation polymerization method in a binary organic solvent. Polyethylene glycol diacrylate (PEGDA-400 as a long-chain cross-linker and di(trimethylol propane tetraacrylate (DTMPTA as multifunctional cross-linker were used. PEGDA-400 was utilized to increase thickening properties and DTMPTA was used to improve the gel strength. The dual cross-linkers effect on the sample features (i.e., equilibrium swelling, thickening properties and rheological properties was investigated. Maximum amount of swelling was obtained by a high percentage of long-chain cross-linker. The apparent viscosity of the microgels was measured to determine their thickening properties for aqueous media. Maximum viscosity occurred at DT25-PE75 which was dependent on the type of cross-linkers in the polymer structure. The Flory-Rehner equation (from swelling ratio data and rubber elasticity theory (from rheometry data were used to discuss the network structure of the polymer. Increasing density of the network was shown by a sample containing high percentage of a four-functional cross-linker. The rheological properties of the cross-linked polymers were measured to determine storage modulus (strength network. The rheological behaviors demonstrated that the synthesized polymer containing a high amount of four-functional cross-linker had higher storage modulus (G′ than other samples. In addition the consistency coefficient (m and flow behavior index (n parameters of Ostwald equation were investigated as well. As a result, n values in each sample were found to be smaller than 1 and these results were fitted clearly with the pseudoplastic model. Apparent and rotational viscosities were used to determine the optimal cross-linker type (synthesized sample contained a high percentage of long-chain cross-linker.

  8. Radiation polymerization and crosslinking of N-isopropylacrylamide in aqueous solution and in solid state

    International Nuclear Information System (INIS)

    Safranj, A.; Yoshida, Masaru; Omichi, Hideki; Nagaoka, Noriyasu; Kubota, Hitoshi; Katakai, Ryoichi.

    1995-01-01

    Poly(N-isopropylacrylamide) hydrogels were synthesized by radiation induced simultaneous polymerization and cross-linking. Aqueous monomer solutions and pure monomer, without crosslinker, were irradiated in nitrogen atmosphere at a 60 Co gamma source. The conversion from monomer to polymer and cross-linked gel was investigated as a function of temperature and monomer concentration. The swelling behavior of the gels showed clear dependence on the synthesis conditions. (author)

  9. 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.

  10. Disseminated paracoccidioidomycosis diagnosis based on oral lesions

    Directory of Open Access Journals (Sweden)

    Liana Preto Webber

    2014-01-01

    Full Text Available Paracoccidioidomycosis (PCM is a deep mycosis with primary lung manifestations that may present cutaneous and oral lesions. Oral lesions mimic other infectious diseases or even squamous cell carcinoma, clinically and microscopically. Sometimes, the dentist is the first to detect the disease, because lung lesions are asymptomatic, or even misdiagnosed. An unusual case of PCM with 5 months of evolution presenting pulmonary, oral, and cutaneous lesions that was diagnosed by the dentist based on oral lesions is presented and discussed.

  11. Identification of potentially cytotoxic lesions induced by UVA photoactivation of DNA 4-thiothymidine in human cells

    Science.gov (United States)

    Reelfs, Olivier; Macpherson, Peter; Ren, Xiaolin; Xu, Yao-Zhong; Karran, Peter; Young, Antony R.

    2011-01-01

    Photochemotherapy—in which a photosensitizing drug is combined with ultraviolet or visible radiation—has proven therapeutic effectiveness. Existing approaches have drawbacks, however, and there is a clinical need to develop alternatives offering improved target cell selectivity. DNA substitution by 4-thiothymidine (S4TdR) sensitizes cells to killing by ultraviolet A (UVA) radiation. Here, we demonstrate that UVA photoactivation of DNA S4TdR does not generate reactive oxygen or cause direct DNA breakage and is only minimally mutagenic. In an organotypic human skin model, UVA penetration is sufficiently robust to kill S4TdR-photosensitized epidermal cells. We have investigated the DNA lesions responsible for toxicity. Although thymidine is the predominant UVA photoproduct of S4TdR in dilute solution, more complex lesions are formed when S4TdR-containing oligonucleotides are irradiated. One of these, a thietane/S5-(6-4)T:T, is structurally related to the (6-4) pyrimidine:pyrimidone [(6-4) Py:Py] photoproducts induced by UVB/C radiation. These lesions are detectable in DNA from S4TdR/UVA-treated cells and are excised from DNA more efficiently by keratinocytes than by leukaemia cells. UVA irradiation also induces DNA interstrand crosslinking of S4TdR-containing duplex oligonucleotides. Cells defective in repairing (6-4) Py:Py DNA adducts or processing DNA crosslinks are extremely sensitive to S4TdR/UVA indicating that these lesions contribute significantly to S4TdR/UVA cytotoxicity. PMID:21890905

  12. Radiation Induced Grafting of Styrene onto ETFE: Influence of Crosslinker

    International Nuclear Information System (INIS)

    Gursel, S. A.

    2006-01-01

    Polymer electrolyte fuel cells are promising types of electrochemical devices for future power production with low operation temperature. In order to make this technology attractive, further cost reduction and improved reliability are required. These can be achieved in part by means of radiation induced grafting for the preparation of low cost proton-conducting polymer membranes. Indeed, the method can be performed with low-cost starting materials (fluorinated and partially fluorinated polymers). In our laboratory at Paul Scherrer Institut, most of the work has been performed using styrene and DVB as the monomers and poly (tetrafluoroethylene-co-hexafluoropropylene) as the base material. Performance comparable to Nafion 112 membranes and durability of several thousands hours at steady-state conditions have been achieved for this type of membranes under fuel cell operation conditions. Previously, poly(ethylene-alt-tetrafluoroethylene) (ETFE) based membranes have been prepared in the presence of divinylbenzene (DVB) as the crosslinking agent and found to exhibit encouraging fuel cell performance. However, the synthesis parameters were not optimized in detail to further improve the membrane properties. Recently, we have investigated the parameters of ETFE based grafting without crosslinking agent. In this study, proton-exchange membranes were prepared by pre-irradiation grafting of styrene onto ETFE and subsequent sulfonation in the presence of DVB containing different isomers (m- and p-isomer of DVB and m- and p-ethylvinylbenzene) as the crosslinker. The grafted films and membranes with varying DVB concentrations and similar degree of grafting (25%) were characterized by Fourier transform infrared spectroscopy (FTIR-ATR) and differential scanning calorimetry (DSC). In addition, dimensional changes and fuel cell relevant properties were examined. FTIR-ATR measurements revealed that the p- isomers are more reactive than m-isomers, and the grafted films are more highly

  13. Segregation effect of radiation induced crosslinking of HDPE: morphology change

    International Nuclear Information System (INIS)

    Deng Pengyang; Zhong Xiaoguang

    2000-01-01

    Scanning Electronic Microscopy has been used to study morphology of pure gel; sol-gel blend and sol-gel segregation samples of radiation induced crosslinking of HDPE. The results show that the morphology of segregation sample is the same as that of pure gel and different from that of sol-gel blend. This kind of morphology change proves that the sol-gel blend have occurred a liquid---solid phase segregation in the melting state. The liquid phase (sol) will naturally immersed in the network of the gel. (author)

  14. Cross-Linked Hydrogel for Pharmaceutical Applications: A Review

    Directory of Open Access Journals (Sweden)

    Rabinarayan parhi

    2017-12-01

    Full Text Available Hydrogels are promising biomaterials because of their important qualities such as biocompatibility, biodegradability, hydrophilicity and non-toxicity. These qualities make hydrogels suitable for application in medical and pharmaceutical field. Recently, a tremendous growth of hydrogel application is seen, especially as gel and patch form, in transdermal drug delivery. This review mainly focuses on the types of hydrogels based on cross-linking and; secondly to describe the possible synthesis methods to design hydrogels for different pharmaceutical applications. The synthesis and chemistry of these hydrogels are discussed using specific pharmaceutical examples. The structure and water content in a typical hydrogel have also been discussed.

  15. Radiation-induced crosslinking of aromatic polymers with cardo group

    International Nuclear Information System (INIS)

    Xu Jun; Zhang Wanxi

    1991-01-01

    The effects of irradiation on the aromatic polymers with cardo group, such as polyetherketone with cardo group (PEK-C) and polyethersulfone with cardo group (PES-C) were studied. It was found that PEK-C and PES-C can be crosslinked by irradiation under vacuum. Moreover, it was also found that the intensity of the shake-up peak of X-ray photoelectron spectroscopy (XPS) for PEK-C and PES-C varies as irradiation dose. Gelation doses (Rg) of PEK-C and PES-C were estimated by shake-up peaks of XPS. (author) 6 refs.; 8 figs.; 3 tabs

  16. 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

  17. Peripheral hepatic arterial embolization with cross-linked collagen fibers

    International Nuclear Information System (INIS)

    Daniels, J.R.; Kerlan, R.K. Jr.; Dodds, L.; McLaughlin, P.; La Berge, J.M.; Harrington, D.; Daniels, A.M.; Ring, E.J.

    1986-01-01

    Hepatic artery embolization with a nonimmunogenic, cross-linked collagen preparation (Angiostat, collagen for embolization, Target Therapeutics) was studied in mongrel dogs. Flow-directed technique was used to achieve complete distal arterial occlusion. Serial liver function evaluation demonstrated marked alterations at 48 to 72 hours, partial correction at 1 week, and resolution of abnormalities by 1 month. Restoration of large-vessel blood flow was angiographically demonstrable at 1 week. Recanalization, achieved by migration of endothelial cells around the collagen, resulted in complete restoration of normal hepatic vascular and tissue anatomy at 1 month. Repeated embolization at biweekly intervals was well tolerated

  18. Dipolar cross-linkers for PDMS networks with enhanced dielectric permittivity and low dielectric loss

    DEFF Research Database (Denmark)

    Bahrt, Frederikke; Daugaard, Anders Egede; Hvilsted, Søren

    2013-01-01

    -(4-((4-nitrophenyl)diazenyl)phenoxy)-prop-1-yn-1-ylium, with a synthesized silicone compatible azide-functional cross-linker by click chemistry. The thermal, mechanical and electromechanical properties were investigated for PDMS films with 0 to 3.6 wt% of dipole-cross-linker. The relative dielectric permittivity......Dipole grafted cross-linkers were utilized to prepare polydimethylsiloxane (PDMS) elastomers with various chain lengths and with various concentrations of functional cross-linker. The grafted cross-linkers were prepared by reaction of two alkyne-functional dipoles, 1-ethynyl-4-nitrobenzene and 3...

  19. 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.

  20. 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

  1. Imaging inflammatory acne: lesion detection and tracking

    Science.gov (United States)

    Cula, Gabriela O.; Bargo, Paulo R.; Kollias, Nikiforos

    2010-02-01

    It is known that effectiveness of acne treatment increases when the lesions are detected earlier, before they could progress into mature wound-like lesions, which lead to scarring and discoloration. However, little is known about the evolution of acne from early signs until after the lesion heals. In this work we computationally characterize the evolution of inflammatory acne lesions, based on analyzing cross-polarized images that document acne-prone facial skin over time. Taking skin images over time, and being able to follow skin features in these images present serious challenges, due to change in the appearance of skin, difficulty in repositioning the subject, involuntary movement such as breathing. A computational technique for automatic detection of lesions by separating the background normal skin from the acne lesions, based on fitting Gaussian distributions to the intensity histograms, is presented. In order to track and quantify the evolution of lesions, in terms of the degree of progress or regress, we designed a study to capture facial skin images from an acne-prone young individual, followed over the course of 3 different time points. Based on the behavior of the lesions between two consecutive time points, the automatically detected lesions are classified in four categories: new lesions, resolved lesions (i.e. lesions that disappear completely), lesions that are progressing, and lesions that are regressing (i.e. lesions in the process of healing). The classification our methods achieve correlates well with visual inspection of a trained human grader.

  2. Cystic Lesions in Autoimmune Pancreatitis

    Directory of Open Access Journals (Sweden)

    Macarena Gompertz

    2015-11-01

    Full Text Available Autoimmune pancreatitis (AIP can be chronic or recurrent, but frequently completely reversible after steroid treatment. A cystic lesion in AIP is a rare finding, and it can mimic a pancreatic cystic neoplasm. Difficulties in an exact diagnosis interfere with treatment, and surgery cannot be avoided in some cases. We report the history of a 63-year-old male presenting with jaundice and pruritus. AIP was confirmed by imaging and elevated IgG4 blood levels, and the patient completely recovered after corticosteroid therapy. One year later, he presented with a recurrent episode of AIP with elevated IgG4 levels, accompanied by the appearance of multiple intrapancreatic cystic lesions. All but 1 of these cysts disappeared after steroid treatment, but the remaining cyst in the pancreatic head was even somewhat larger 1 year later. Pancreatoduodenectomy was finally performed. Histology showed the wall of the cystic lesion to be fibrotic; the surrounding pancreatic tissue presented fibrosis, atrophy and lymphoplasmacytic infiltration by IgG4-positive cells, without malignant elements. Our case illustrates the rare possibility that cystic lesions can be part of AIP. These pseudocysts appear in the pancreatic segments involved in the autoimmune disease and can be a consequence of the local inflammation or related to ductal strictures. Steroid treatment should be initiated, after which these cysts can completely disappear with recovery from AIP. Surgical intervention may be necessary in some exceptional cases.

  3. Stereotactic lesioning for mental illness

    International Nuclear Information System (INIS)

    Kim, M.-C.; Lee, T.-K.

    2008-01-01

    The authors report stereotactically created lesioning by radiofrequency or Cyberknife radiosurgery for patients with mental illness. Since 1993, thirty-eight patients have undergone stereotactic psychosurgery for medically intractable mental illnesses. Two patients had aggressive behavior. Twenty-five patients suffered from Obsessive-Compulsive Disorder (OCD) and ten patients had depression. Another patient suffered from atypical psychosis. Bilateral amygdalotomy and subcaudate tractotomy were done for aggressive behavior. Limbic leucotomy or anterior cingulotomy was done for CCD and subcaudate tractotomy with or without cingulotomy was done for depression. In twenty-three patients, the lesions were made by a radiofrequency (RF) lesion generator. In fifteen cases, the lesions were made with Cyberknife Radiosurgery (CKRS). The Overt Aggression Scale (OAS) declined from 8 to 2 with clinical improvement during follow up period. With long-term follow up (meaning 57 months) in 25 OCDs, the mean Yale Brown Obsessive Compulsive Score (YBOCS) declined from 34 to 13 (n = 25). The Hamilton Depression scale (HAMD) for ten patients with depression declined from 38.5 to 10.5 (n = 10). There was no operative mortality and no significant morbidity except one case with transient urinary incontinence. Authors suggest that stereotactic psychosurgery by RF and CKRS could be a safe and effective means of treating some medically intractable mental illnesses. (author)

  4. Secondary syphilis lesions resembling pityriasis

    International Nuclear Information System (INIS)

    Dar, N.R.; Ali, L.; Nawaz, M.A.

    2007-01-01

    This case report describes a male patient who presented with generalized, centrally-ulcerated papules with crusts and hypopigmented macules. Initially, differential diagnostic considerations included pityriasis lichenoides but the serology for syphilis was positive and there was a rapid response to penicillin with clearing of the lesions at the end of three weeks treatment. (author)

  5. Characterization of non-dimer DNA lesions and cellular damages caused by ultraviolet light

    International Nuclear Information System (INIS)

    Nakao, Kumi

    1989-01-01

    To understand the mechanisms of carcinogenicity and cytotoxicity induced by ultraviolet (UV) light, non-dimer DNA damages produced by near UV light (wave-length: 290∼320 nm) were examined by alkaline elution using Chinese hamster V-79 cells. UV exposure produced a dose-dependent induction of DNA single strand breaks and DNA-protein crosslinks. However, neither of these DNA lesions were repaired within a 24 hr incubation of the cells following UV exposure. Rather the number of these lesions increased. Also, UV exposure inhibited DNA and RNA synthesis. In addition, UV induced both cytotoxicity and chromosomal aberration. Electron spin resornance (ESR) studies showed that the exposure of cells to UV light resulted in the appearance of an ESR signal at -120degC. The roles of glutathione, vitamin E and vitamin B 2 , which were celluar antioxidant, on the induction of cytotoxicity by UV exposure were also examined. Pretreatment with vitamin E reduced the cytotoxicty caused by UV, whereas neither preteatment with vitamin B 2 nor the alteration of cellular gluthaione content affected the cytotoxicity. These results suggest that non-dimer DNA damages, such as DNA single strand breaks and DNA-protein crosslinks play an important role in inducing UV-carcinogenicity and UV-cytotoxicity, and that the mechanisms of these damages may be associated with the generation of free radicals. (author)

  6. 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.

  7. Synthesis of silver nanoparticles in hydrogels crosslinked by ionizing radiation

    International Nuclear Information System (INIS)

    Alcantara, Maria Tania S.; Oliani, Washington L.; Brant, Antonio J.C.; Oliveira, Maria Jose A. de; Riella, Humberto Gracher; Lugao, Ademar B.

    2013-01-01

    Hydrogel is defined as a polymeric material which exhibits the ability to swell and retain a significant fraction of water within its structure without dissolving the polymeric network. Silver nanoparticles (AgNPs) are used in a range of medicinal products based on hydrogels and diverse other products due to their antibacterial properties at low concentrations. The use of ionizing radiation in the production process of hydrogels of poly(N-vinyl-2-pyrrolidone) (PVP) and poly(vinyl alcohol) (PVA) in aqueous solutions enables the crosslinking of their polymer chains. If polymer solutions contain Ag + ions, these can be reduced radiolytically to nanocrystalline silver. The objective of this study was to investigate the reduction of Ag + ions by gamma-irradiation for the synthesis of AgNPs in hydrogels of PVA and PVP as main polymers and to make a comparison of the performance of the two polymeric matrices, chiefly focusing on the effect of the AgNPs' synthesis on the crosslinking of both polymers. The properties of the hydrogel matrices obtained were evaluated from tests of gel fraction, swelling in water, and stress-strain. The results of mechanical properties of PVA matrix were higher than those of PVP one whereas the latter exhibited a higher swelling degree. The reduction of silver ions was confirmed by UV-visible absorption spectrum, whose characteristics also indicated the formation of silver nanoparticles in both arrays. (author)

  8. Glucantime drug delivery comparison between crosslinked membranes irradiation versus esterification

    International Nuclear Information System (INIS)

    Oliveira, Maria J.A.; Parra, Duclerc F.; Lugao, Ademar B.; Amato, Valdir S.

    2009-01-01

    Pentavalent Antimony (Glucantime) is the drug of choice for the treatment of Leishmaniasis. The disease is transmitted by the female bite of Phlebotomine sandflies. The sandflies inject the infective stage, metacyclic promastigotes, during blood meals. The protozoan parasite causes a spectrum of clinical diseases afflicting 12 million people worldwide. The use of hydrogels matrices for particular drug-release applications has been investigated with the synthesis of modified polymeric hydrogel of poly (vinyl alcohol) (PVAl), poly (N-viny-2- pyrrolidone) (PVP) and poly (ethylene glycol). They were processed using gamma radiation from Cobalt-60 source at 25 kGy dose. The characterization of the hydrogels was conducted and toxicity was evaluated. The dried hydrogel was analyzed for differential scanning calorimetry (DSC), thermogravimetry (TGA), swelling and gel content determinations. The membranes have no toxicity and gel content has revealed the crosslink degree. The chemical crosslinking depends on the acid concentration. Increase of the acid concentration increases the gel content, the thermal stability of the PVAl component and decreases the swelling capacity. The thermal stability of irradiated membranes is decreased in the presence of plasticizer. In contrast to ionizing radiation membranes described in the literature and formulated with PVAl/PEG, our new membranes composed by PVAl/PVP/PEG are more flexible and presents higher swelling capacity. The drug was immobilized in the hydrogels structures and the glucantime drug delivery was determined. (author)

  9. The improvement of polyethylene prostheses through radiation crosslinking

    International Nuclear Information System (INIS)

    Du Plessis, T.A.; Grobbelaar, C.J.; Marais, F.

    1977-01-01

    During the past decade, remarkable progress has been made in the utilization of high-density polyethylene (HDPE) as a material for the manufacture of prostheses used in orthopaedic operations. This polymer contributes largely to the success of total hip replacement. In the case of total knee replacement it was considered imperative that a more hard-wearing polymer should be developed if at all possible, because not only are the cold-flow characteristics of ordinary high-density polyethylene at high pressures a limiting factor, but particle formation from friction can furthermore lead to physiological side-effects which adversely affect the efficacy of joints made from this material, especially so in the case of knee-joints. Bearing in mind the excellent improvements to be obtained through the radiation crosslinking of polyethylene film, the radiation crosslinking of high-density polyethylene prostheses seemed to be a logical avenue to investigate. Experimental details are presented. Gamma radiation was used. Impact strength and tensile strength measurements were made on specimens irradiated over a dose range of 0 to 80 Mrad. The results are discussed. (U.K.)

  10. Glucantime drug delivery comparison between crosslinked membranes irradiation versus esterification

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Maria J.A.; Parra, Duclerc F.; Lugao, Ademar B., E-mail: mariajhho@yahoo.com.b, E-mail: dfparra@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN/SP), Sao Paulo, SP (Brazil). Centro de Quimica e Meio Ambiente (CQMA); Amato, Valdir S. [Hospital das Clinicas (HC/USP), Sao Paulo, SP (Brazil). Div. de Clinica de Molestias Infecciosas e Parasitarias

    2009-07-01

    Pentavalent Antimony (Glucantime) is the drug of choice for the treatment of Leishmaniasis. The disease is transmitted by the female bite of Phlebotomine sandflies. The sandflies inject the infective stage, metacyclic promastigotes, during blood meals. The protozoan parasite causes a spectrum of clinical diseases afflicting 12 million people worldwide. The use of hydrogels matrices for particular drug-release applications has been investigated with the synthesis of modified polymeric hydrogel of poly (vinyl alcohol) (PVAl), poly (N-viny-2- pyrrolidone) (PVP) and poly (ethylene glycol). They were processed using gamma radiation from Cobalt-60 source at 25 kGy dose. The characterization of the hydrogels was conducted and toxicity was evaluated. The dried hydrogel was analyzed for differential scanning calorimetry (DSC), thermogravimetry (TGA), swelling and gel content determinations. The membranes have no toxicity and gel content has revealed the crosslink degree. The chemical crosslinking depends on the acid concentration. Increase of the acid concentration increases the gel content, the thermal stability of the PVAl component and decreases the swelling capacity. The thermal stability of irradiated membranes is decreased in the presence of plasticizer. In contrast to ionizing radiation membranes described in the literature and formulated with PVAl/PEG, our new membranes composed by PVAl/PVP/PEG are more flexible and presents higher swelling capacity. The drug was immobilized in the hydrogels structures and the glucantime drug delivery was determined. (author)

  11. 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.

  12. Photo-crosslinked hyaluronic acid coated upconverting nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Mrazek, Jiri, E-mail: jiri.mrazek@contipro.com; Kettou, Sofiane; Matuska, Vit; Svozil, Vit; Huerta-Angeles, Gloria; Pospisilova, Martina; Nesporova, Kristina; Velebny, Vladimir [Contipro a. s. (Czech Republic)

    2017-02-15

    Hyaluronic acid (HA)-coated inorganic nanoparticles display enhanced interaction with the CD44 receptors which are overexpressed in many types of cancer cells. Here, we describe a modification of core-shell β-NaY{sub 0.80}Yb{sub 0.18}Er{sub 0.02}F{sub 4}@NaYF{sub 4} nanoparticles (UCNP) by HA derivative bearing photo-reactive groups. UCNP capped with oleic acid were firstly transferred to aqueous phase by an improved protocol using hydrochloric acid or lactic acid treatment. Subsequently, HA bearing furanacryloyl moieties (HA-FU) was adsorbed on the nanoparticle surface and crosslinked by UV irradiation. The crosslinking resulted in stable HA coating, and no polymer desorption was observed. As-prepared UCNP@HA-FU show a hydrodynamic diameter of about 180 nm and are colloidally stable in water and cell culture media. The cellular uptake by normal human fibroblasts and MDA MB-231 cancer cell line was investigated by upconversion luminescence imaging.

  13. Autoclavable physically-crosslinked chitosan cryogel as a wound dressing.

    Science.gov (United States)

    Takei, Takayuki; Danjo, So; Sakoguchi, Shogo; Tanaka, Sadao; Yoshinaga, Takuma; Nishimata, Hiroto; Yoshida, Masahiro

    2018-04-01

    Moist wounds were known to heal more rapidly than dry wounds. Hydrogel wound dressings were suitable for the moist wound healing because of their hyperhydrous structure. Chitosan was a strong candidate as a base material for hydrogel wound dressings because the polymer had excellent biological properties that promoted wound healing. We previously developed physically-crosslinked chitosan cryogels, which were prepared solely by freeze-thawing of a chitosan-gluconic acid conjugate (CG) aqueous solution, for wound treatment. The CG cryogels were disinfected by immersing in 70% ethanol before applying to wounds in our previous study. In the present study, we examined the influence of autoclave sterilization (121°C, 20 min) on the characteristics of CG cryogel because complete sterilization was one of the fundamental requirements for medical devices. We found that optimum value of gluconic acid content of CG, defined as the number of the incorporated gluconic acid units per 100 glucosamine units of chitosan, was 11 for autoclaving. An increased crosslinking level of CG cryogel on autoclaving enhanced resistance of the gels to enzymatic degradation. Furthermore, the autoclaved CG cryogels retained favorable biological properties of the pre-autoclaved CG cryogels in that they showed the same hemostatic activity and efficacy in repairing full-thickness skin wounds as the pre-autoclaved CG cryogels. These results showed the great potential of autoclavable CG cryogels as a practical wound dressing. Copyright © 2017 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  14. 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.

  15. Thermally Stable Gold Nanoparticles with a Crosslinked Diblock Copolymer Shell

    Science.gov (United States)

    Jang, Se Gyu; Khan, Anzar; Hawker, Craig J.; Kramer, Edward J.

    2010-03-01

    The use of polymer-coated Au nanoparticles prepared using oligomeric- or polymeric-ligands tethered by Au-S bonds for incorporation into block copolymer templates under thermal processing has been limited due to dissociation of the Au-S bond at T > 100^oC where compromises their colloidal stability. We report a simple route to prepare sub-5nm gold nanoparticles with a thermally stable polymeric shell. An end-functional thiol ligand consisting of poly(styrene-b-1,2&3,4-isoprene-SH) is synthesized by anionic polymerization. After a standard thiol ligand synthesis of Au nanoparticles, the inner PI block is cross-linked through reaction with 1,1,3,3-tetramethyldisiloxane. Gold nanoparticles with the cross-linked shell are stable in organic solvents at 160^oC as well as in block copolymer films of PS-b-P2VP annealed in vacuum at 170^oC for several days. These nanoparticles can be designed to strongly segregate to the PS-P2VP interface resulting in very large Au nanoparticle volume fractions φp without macrophase separation as well as transitions between lamellar and bicontinuous morphologies as φp increases.

  16. 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.

  17. Petrous apex lesions in the pediatric population

    Energy Technology Data Exchange (ETDEWEB)

    Radhakrishnan, Rupa [University of Cincinnati College of Medicine, Department of Radiology, Cincinnati, OH (United States); Cincinnati Children' s Hospital Medical Center, Department of Radiology, Cincinnati, OH (United States); Son, Hwa Jung [University of Cincinnati College of Medicine, Department of Otolaryngology-Head and Neck Surgery, Cincinnati, OH (United States); Koch, Bernadette L. [Cincinnati Children' s Hospital Medical Center, Department of Radiology, Cincinnati, OH (United States)

    2014-03-15

    A variety of abnormal imaging findings of the petrous apex are encountered in children. Many petrous apex lesions are identified incidentally while images of the brain or head and neck are being obtained for indications unrelated to the temporal bone. Differential considerations of petrous apex lesions in children include ''leave me alone'' lesions, infectious or inflammatory lesions, fibro-osseous lesions, neoplasms and neoplasm-like lesions, as well as a few rare miscellaneous conditions. Some lesions are similar to those encountered in adults, and some are unique to children. Langerhans cell histiocytosis (LCH) and primary and metastatic pediatric malignancies such as neuroblastoma, rhabomyosarcoma and Ewing sarcoma are more likely to be encountered in children. Lesions such as petrous apex cholesterol granuloma, cholesteatoma and chondrosarcoma are more common in adults and are rarely a diagnostic consideration in children. We present a comprehensive pictorial review of CT and MRI appearances of pediatric petrous apex lesions. (orig.)

  18. 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...

  19. Imaging review of lipomatous musculoskeletal lesions

    Directory of Open Access Journals (Sweden)

    Burt Ashley M.

    2017-01-01

    Full Text Available Lipomatous lesions are common musculoskeletal lesions that can arise within the soft tissues, bone, neurovascular structures, and synovium. The majority of these lesions are benign, and many of the benign lesions can be diagnosed by radiologic evaluation. However, radiologic differences between benign and malignant lipomatous lesions may be subtle and pathologic correlation is often needed. The use of sonography, computed tomography (CT, and magnetic resonance imaging (MRI is useful not only in portraying fat within the lesion, but also for evaluating the presence and extent of soft tissue components. Lipomas make up most soft tissue lipomatous lesions, but careful evaluation must be performed to distinguish these lesions from a low-grade liposarcoma. In addition to the imaging appearance, the location of the lesion and the patient demographics can be utilized to help diagnose other soft tissue lipomatous lesions, such as elastofibroma dorsi, angiolipoma, lipoblastoma, and hibernoma. Osseous lipomatous lesions such as a parosteal lipoma and intraosseous lipoma occur less commonly as their soft tissue counterpart, but are also benign. Neurovascular and synovial lipomatous lesions are much rarer lesions but demonstrate more classic radiologic findings, particularly on MRI. A review of the clinical, radiologic, and pathologic characteristics of these lesions is presented.

  20. Hock lesions and free-stall design.

    Science.gov (United States)

    Weary, D M; Taszkun, I

    2000-04-01

    We compared the prevalence and severity of skin lesions on the hocks of lactating dairy cows in southern British Columbia, comparing 20 farms using three common bedding surfaces: sawdust, sand, and geotextile mattresses. Skin lesions were scored at five positions on the hock. For each position we noted if the lesion showed inflammatory attributes, and then assigned a severity score. Of the 1752 lactating cows scored, 1267 cows (73%) had at least one hock lesion. Of those cows with lesions, 87% had lesions on both legs, 76% had lesions on more than one location on the hock, and 78% had a lesion of at least moderate severity (i.e., evidence of skin breakage or an area of hair loss >10 cm2). Lesions were most prevalent on farms that used geotextile mattresses (91% of cows) and least common on farms that used sand (24% of cows). Moreover, lesions on cows from farms using mattresses were more numerous and more severe than those on cows from sand-bedded farms. The prevalence and severity of lesions on farms using sawdust was intermediate. Lesions also varied in relation to location on the hock. For farms using geotextile mattresses, lesions were more common and more severe on the lateral surfaces of both the tuber calcis and the tarsal joint. On farms using sawdust, lesions were common on the dorsal surface of the tuber calcis and the lateral surfaces of both the tuber calcis and the tarsal joint. Lesions were rare on all five positions for cows from sand-bedded farms. Among the 10 farms sampled using sawdust, we found a significant negative relationship between the length of the stall and severity of lesions. For cows with lesions, the number and severity of lesions increased with age.

  1. Structure-based non-canonical amino acid design to covalently crosslink an antibody–antigen complex

    Science.gov (United States)

    Xu, Jianqing; Tack, Drew; Hughes, Randall A.; Ellington, Andrew D.; Gray, Jeffrey J.

    2014-01-01

    Engineering antibodies to utilize non-canonical amino acids (NCAA) should greatly expand the utility of an already important biological reagent. In particular, introducing crosslinking reagents into antibody complementarity determining regions (CDRs) should provide a means to covalently crosslink residues at the antibody–antigen interface. Unfortunately, finding the optimum position for crosslinking two proteins is often a matter of iterative guessing, even when the interface is known in atomic detail. Computer-aided antibody design can potentially greatly restrict the number of variants that must be explored in order to identify successful crosslinking sites. We have therefore used Rosetta to guide the introduction of an oxidizable crosslinking NCAA, l-3,4-dihydroxyphenylalanine (l-DOPA), into the CDRs of the anti-protective antigen scFv antibody M18, and have measured crosslinking to its cognate antigen, domain 4 of the anthrax protective antigen. Computed crosslinking distance, solvent accessibility, and interface energetics were three factors considered that could impact the efficiency of l-DOPA-mediated crosslinking. In the end, 10 variants were synthesized, and crosslinking efficiencies were generally 10% or higher, with the best variant crosslinking to 52% of the available antigen. The results suggest that computational analysis can be used in a pipeline for engineering crosslinking antibodies. The rules learned from l-DOPA crosslinking of antibodies may also be generalizable to the formation of other crosslinked interfaces and complexes. PMID:23680795

  2. Long-Chain Diacrylate Crosslinkers and Use of PEG Crosslinks in Poly(potassium acrylate-acrylic acid)/Kaolin Composite Superabsorbents

    OpenAIRE

    Koroush Kabiri; Siavash Nafisi; Mohammad jalaledin Zohuriaan-Mehr; Ali Akbar Yousefi

    2013-01-01

    Long-chain diacrylate crosslinkers based on linear α,ω-diols were synthesized and characterized using FTIR and 1H NMR spectroscopy. The highest reaction yield (99.5%) was due to polyethylene glycol diacrylate 1000 (PEGDA-1000). Then, kaolin-containing poly(potassium acrylate-acrylic acid) superabsorbent composites and kaolin-free counterparts were synthesized using PEGDA-1000.The effect of the crosslinker concentration on swelling, rheological and thermo-mechanical properties was investigated...

  3. A zwitterionic macro-crosslinker for durable non-fouling coatings.

    Science.gov (United States)

    Wang, Wei; Lu, Yang; Xie, Jinbing; Zhu, Hui; Cao, Zhiqiang

    2016-03-28

    A novel zwitterionic macro-crosslinker was developed and applied to fabricate durable non-fouling coatings on a polyurethane substrate. The zwitterionic macro-crosslinker coating exhibited superior durability over the traditional brush polymer coating and was able to retain its non-fouling property even after weeks of shearing in flowing liquid.

  4. 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.

  5. 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...

  6. 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

  7. Immobilization of heparin to EDC/NHS-crosslinked collagen. Characterization and in vitro evaluation

    NARCIS (Netherlands)

    Wissink, M.J.B.; Beernink, R.; Pieper, J.S.; Poot, Andreas A.; Engbers, G.H.M.; Beugeling, T.; Beugeling, T.; van Aken, W.G.; Feijen, Jan

    2001-01-01

    In the present study, heparin immobilization to a non-cytotoxic crosslinked collagen substrate for endothelial cell seeding was investigated. Crosslinking of collagen using N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide (EDC) and N-hydroxysuccinimide (NHS) resulted in a material containing 14 free

  8. Radiation-induced crosslinking of polyethylene in the presence of bifunctional vinyl monomers

    Energy Technology Data Exchange (ETDEWEB)

    Joshi, M.S.

    1976-10-06

    The apparent crosslinking produced by the radiation grafting of two monomers to polyethylene, acrylic acid and acrylonitrile, was investigated. Evidence is presented to show that covalent crosslinks are not produced during the radiation grafting step; covalent crosslinks are produced by the post-irradiation heat treatment associated with measurements of gel; the enhancement in gel fraction and physical properties arises from true crosslinks rather than chain entanglements; and there may be practical value associated with the sensitization of crosslinking produced by the methods employed in this work. The effect of monomer-solvent composition on the graft and gel yield was studied. Viscoelastic properties of grafted films were determined above the melting point of pure polyethylene. The kinetic data, infrared spectra, and viscoelastic properties are the bases for the following mechanism: (1) Acrylic acid-g-PE: Acrylic acid enters the film in the form of a hydrogen bonded dimer and undergoes a grafting reaction that produces hydrogen-bond crosslinks. The heat treatment during the conventional methods for determining of crosslinks convert them into intermolecular anhydride bonds. (2) Acrylonitrile-g-PE: In this, the post-grafting crosslinking is the result of a thermally induced chain reaction leading to an uninterrupted conjugated sequence. The length of the ring structure increases with time and temperature, and the intensity of color increases with the length of the ring structure.

  9. 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...

  10. Radiation-induced crosslinking of polyethylene in the presence of bifunctional vinyl monomers

    International Nuclear Information System (INIS)

    Joshi, M.S.

    1976-01-01

    The apparent crosslinking produced by the radiation grafting of two monomers to polyethylene, acrylic acid and acrylonitrile, was investigated. Evidence is presented to show that covalent crosslinks are not produced during the radiation grafting step; covalent crosslinks are produced by the post-irradiation heat treatment associated with measurements of gel; the enhancement in gel fraction and physical properties arises from true crosslinks rather than chain entanglements; and there may be practical value associated with the sensitization of crosslinking produced by the methods employed in this work. The effect of monomer-solvent composition on the graft and gel yield was studied. Viscoelastic properties of grafted films were determined above the melting point of pure polyethylene. The kinetic data, infrared spectra, and viscoelastic properties are the bases for the following mechanism: (1) Acrylic acid-g-PE: Acrylic acid enters the film in the form of a hydrogen bonded dimer and undergoes a grafting reaction that produces hydrogen-bond crosslinks. The heat treatment during the conventional methods for determining of crosslinks convert them into intermolecular anhydride bonds. (2) Acrylonitrile-g-PE: In this, the post-grafting crosslinking is the result of a thermally induced chain reaction leading to an uninterrupted conjugated sequence. The length of the ring structure increases with time and temperature, and the intensity of color increases with the length of the ring structure

  11. Crosslinked electrospun PVA nanofibrous membranes: elucidation of their physicochemical, physicomechanical and molecular disposition

    International Nuclear Information System (INIS)

    Shaikh, Rubina P; Kumar, Pradeep; Choonara, Yahya E; Du Toit, Lisa C; Pillay, Viness

    2012-01-01

    The effects of modifying electrospun poly(vinyl alcohol) (PVA) nanofibers through crosslinking using glutaraldehyde (GA) are explored in this paper. Various concentrations of PVA solutions containing model drugs rifampicin (RIF) and isoniazid (INH) were electrospun and thereafter crosslinked using GA vapors. PVA nanofibers demonstrated high drug entrapment efficiency of 98.77% ± 1.384% and 95.07% ± 1.988% for the INH- and RIF-loaded PVA nanofibers, respectively. The surface morphology, molecular vibrational transitions, tensile attributes and in vitro drug release were characterized and supported by in silico molecular mechanics simulations. Results indicated that crosslinking caused a significant reduction in the rate of drug release where 81.11% ± 2.35% of INH and 59.31% ± 2.57% of RIF were released after 12 h. Tensile properties such as the ultimate strength and Young's modulus increased after crosslinking, caused by crosslinks forming between PVA nanofibers as was revealed through scanning electron microscopy analysis. Fourier Transform infrared analysis was conducted to further support the mode of crosslinking. Additionally, image processing analysis was carried out to quantify the effect of formulation variables on the morphology of nanofibers. Furthermore, the effect of GA-induced crosslinking and addition of drugs on the performance of electrospun fibers was further elucidated and conceptualized using a molecular mechanics assisted model building and energy refinement approach via molecular mechanics energy relationships by exploring the spatial disposition of energy-minimized molecular structures of the polymer, crosslinker and the drugs. (paper)

  12. 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

  13. Enhancing the antimony sorption properties of nano titania-chitosan beads using epichlorohydrin as the crosslinker.

    Science.gov (United States)

    Nishad, Padala Abdul; Bhaskarapillai, Anupkumar; Velmurugan, Sankaralingam

    2017-07-15

    Antimony is classified as a pollutant of priority importance by USEPA. We have earlier reported the synthesis of nano-titania impregnated epichlorohydrin crosslinked chitosan (TA-Cts-Epi) beads, in a format suitable for large scale applications with high sorption capacity for antimony. To understand the sorption mechanism, and to fine tune the bead composition, the effect of crosslinking density on the swelling and sorption properties of the beads was investigated in detail. Epichlorohydrin effected significant changes in physical and sorption properties of the beads. The antimony sorption capacity of the TA-Cts-Epi beads prepared by crosslinking 0.3g non-crosslinked titania-chitosan beads (TA-Cts-NCL) with 6.4mmol epichlorohydrin was 493μmol/g, while those crosslinked with 0.64mmol showed a capacity of 133μmol/g. Whereas, TA-Cts-NCL beads showed a capacity of 75μmol/g. The increase in uptake capacity with increase in crosslinking demonstrated the active involvement of the epichlorohydrin moieties in antimony binding leading to enhanced sorption. Apart from altering the stability, swelling behaviour and sorption kinetics of the beads, crosslinking significantly increased the uptake of the anionic species via electrostatic interactions. Epichlorohydrin crosslinked chitosan beads prepared without TiO 2 also showed similar behaviour. The results demonstrated the involvement of chitosan, TiO 2 and epichlorohydrin in sorption. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Pathways and Mechanisms Underlying the Photophysics and Photochemistry of Riboflavin induced cornea crosslinking

    DEFF Research Database (Denmark)

    Breitenbach, Thomas; Ogilby, Peter Remsen

    In this talk, we will describe general pathways involved in the photophysics of a photosensitized process, which can lead to crosslinking due to light excitation of Riboflavin in the cornea. Furthermore, we will elucidate different aspects of reactions that can produce crosslinks, with respect...

  15. 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...

  16. Novel silicone compatible cross-linkers for controlled functionalization of PDMS networks

    DEFF Research Database (Denmark)

    Madsen, Frederikke Bahrt; Daugaard, Anders Egede; Hvilsted, Søren

    2013-01-01

    . In order to improve the dielectric properties of PDMS a novel system is developed where push-pull dipoles are grafted to a new silicone compatible cross-linker. The grafted cross-linkers are prepared by reaction of two different push-pull dipole alkynes as well as a fluorescent alkyne with the new azide...

  17. Secondary cytotoxicity of (crosslinked) dermal sheep collagen during repeated exposure to human fibroblasts

    NARCIS (Netherlands)

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

    1992-01-01

    We investigated commercially available dermal sheep collagen either cross-linked with hexamethylenediisocyanate, 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.

  18. 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

  19. Sequence-Dependent Diastereospecific and Diastereodivergent Crosslinking of DNA by Decarbamoylmitomycin C.

    Science.gov (United States)

    Aguilar, William; Paz, Manuel M; Vargas, Anayatzinc; Clement, Cristina C; Cheng, Shu-Yuan; Champeil, Elise

    2018-04-20

    Mitomycin C (MC), a potent antitumor drug, and decarbamoylmitomycin C (DMC), a derivative lacking the carbamoyl group, form highly cytotoxic DNA interstrand crosslinks. The major interstrand crosslink formed by DMC is the C1'' epimer of the major crosslink formed by MC. The molecular basis for the stereochemical configuration exhibited by DMC was investigated using biomimetic synthesis. The formation of DNA-DNA crosslinks by DMC is diastereospecific and diastereodivergent: Only the 1''S-diastereomer of the initially formed monoadduct can form crosslinks at GpC sequences, and only the 1''R-diastereomer of the monoadduct can form crosslinks at CpG sequences. We also show that CpG and GpC sequences react with divergent diastereoselectivity in the first alkylation step: 1"S stereochemistry is favored at GpC sequences and 1''R stereochemistry is favored at CpG sequences. Therefore, the first alkylation step results, at each sequence, in the selective formation of the diastereomer able to generate an interstrand DNA-DNA crosslink after the "second arm" alkylation. Examination of the known DNA adduct pattern obtained after treatment of cancer cell cultures with DMC indicates that the GpC sequence is the major target for the formation of DNA-DNA crosslinks in vivo by this drug. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. BIOCOMPATIBILITY AND TISSUE REGENERATING CAPACITY OF CROSS-LINKED DERMAL SHEEP COLLAGEN

    NARCIS (Netherlands)

    VANWACHEM, PB; VANLUYN, MJA; DAMINK, LHHO; DIJKSTRA, PJ; FEIJEN, J; NIEUWENHUIS, P

    The biocompatibility and tissue regenerating capacity of four crosslinked dermal sheep collagens (DSC) was studied. In vitro, the four DSC versions were found to be noncytotoxic or very low in cytoxicity. After subcutaneous implantation in rats, hexamethylenediisocyanate-crosslinked DSC (HDSC)

  1. 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.

  2. 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...

  3. Thermoreversible covalent crosslinking of maleated ethylene/propylene copolymers with diols

    NARCIS (Netherlands)

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

    2008-01-01

    Maleated ethylene/propylene copolymer (MAn-g-EPM) was thermoreversibly cross-linked using different routes, i.e. ionic interactions (ionomers), hydrogen bonding and a combination thereof. Microphase separation into polar MAn-rich aggregates occurs for MAn-g-EPM and all cross-linked materials, which

  4. In vitro degradation behaviour of biodegradable soy plastics : effects of crosslinking with glyoxal and thermal treatment

    NARCIS (Netherlands)

    Vaz, C.M.; Graaf, de L.A.; Reis, R.L.; Cunha, A.M.

    2003-01-01

    In-vitro degradation of soy-derived protein materials, non-crosslinked (SItp), crosslinked with glyoxal (X-SItp) or submitted to heat treatment (24TT-SItp), was studied with either an isotonic saline solution without enzymatic activity or containing bacterial collagenase. The changes in weight of

  5. 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...

  6. Design of polymer networks by variation of precursor structure and crosslinking regime

    Czech Academy of Sciences Publication Activity Database

    Dušek, Karel; Dušková, Miroslava; Huybrecht, J.

    2003-01-01

    Roč. 44, č. 1 (2003), s. 62-63 ISSN 0032-3934. [ACS National Meeting "Crosslinking Materials and Processes"/254./. New Orleans, 23.03.2003-27.03.2003] R&D Projects: GA AV ČR KSK4050111 Keywords : polymer networks * designed precursor * crosslinking Subject RIV: CD - Macromolecular Chemistry

  7. DNA double strand breaks but not interstrand crosslinks prevent progress through meiosis in fully grown mouse oocytes.

    Directory of Open Access Journals (Sweden)

    Wai Shan Yuen

    Full Text Available There is some interest in how mammalian oocytes respond to different types of DNA damage because of the increasing expectation of fertility preservation in women undergoing chemotherapy. Double strand breaks (DSBs induced by ionizing radiation and agents such as neocarzinostatin (NCS, and interstrand crosslinks (ICLs induced by alkylating agents such as mitomycin C (MMC, are toxic DNA lesions that need to be repaired for cell survival. Here we examined the effects of NCS and MMC treatment on oocytes collected from antral follicles in mice, because potentially such oocytes are readily collected from ovaries and do not need to be in vitro grown to achieve meiotic competency. We found that oocytes were sensitive to NCS, such that this ionizing radiation mimetic blocked meiosis I and caused fragmented DNA. In contrast, MMC had no impact on the completion of either meiosis I or II, even at extremely high doses. However, oocytes treated with MMC did show γ-H2AX foci and following their in vitro maturation and parthenogenetic activation the development of the subsequent embryos was severely compromised. Addition of MMC to 1-cell embryos caused a similarly poor level of development, demonstrating oocytes have eventual sensitivity to this ICL-inducing agent but this does not occur during their meiotic division. In oocytes, the association of Fanconi Anemia protein, FANCD2, with sites of ICL lesions was not apparent until entry into the embryonic cell cycle. In conclusion, meiotic maturation of oocytes is sensitive to DSBs but not ICLs. The ability of oocytes to tolerate severe ICL damage and yet complete meiosis, means that this type of DNA lesion goes unrepaired in oocytes but impacts on subsequent embryo quality.

  8. Eye lesions in pet birds.

    Science.gov (United States)

    Tsai, S S; Park, J H; Hirai, K; Itakura, C

    1993-03-01

    Amongst eye lesions in birds that died in quarantine, cataracts were the most common disorders (37/241, 15.4%), being prevalent in the annular pads of cockatiels (Nymphicus hollandicus), Amazon parrots (Amazona aestiva aestiva) and budgerigars (Melopsittacus undulatus). The incidence in male birds was more than twice that in females. Deposition of crystals, mostly in the cornea, was the second most frequent lesion (21/293, 8.7%), mainly found in cockatiels, parakeets (Psittacula krameri manillensis), Amazon parrots (Amazona aestiva aestiva), budgerigars and finches (Poephila gouldiae gouldiae). These corneal crystals were negative to PAS and Kossa's stains. Six parakeets (Psittacula krameri manillensis) had calcium salts deposited in the inner plexiform layer of the retina and occasionally in the iris and ciliary body. Neither inflammation nor neo-vascularization was observed when cataracts, corneal crystalline deposition, and retinal and ciliary calcification were present. Intranuclear inclusion bodies typical for papovavirus infection were found in the eyelids of six budgerigars (2.5%). Similar inclusions were simultaneously found in the pars ciliaris retinae (4, 1.7%), inner plexiform of retina (1, 0.4%) and anterior epithelium of the cornea (1, 0.4%). Other lesions such as candidial endophthalmitis, conjunctival cryptosporidiosis, corneal dystrophy, keratitis, corneal perforation and iridocyclitis, were occasional findings.

  9. Automatic segmentation of psoriasis lesions

    Science.gov (United States)

    Ning, Yang; Shi, Chenbo; Wang, Li; Shu, Chang

    2014-10-01

    The automatic segmentation of psoriatic lesions is widely researched these years. It is an important step in Computer-aid methods of calculating PASI for estimation of lesions. Currently those algorithms can only handle single erythema or only deal with scaling segmentation. In practice, scaling and erythema are often mixed together. In order to get the segmentation of lesions area - this paper proposes an algorithm based on Random forests with color and texture features. The algorithm has three steps. The first step, the polarized light is applied based on the skin's Tyndall-effect in the imaging to eliminate the reflection and Lab color space are used for fitting the human perception. The second step, sliding window and its sub windows are used to get textural feature and color feature. In this step, a feature of image roughness has been defined, so that scaling can be easily separated from normal skin. In the end, Random forests will be used to ensure the generalization ability of the algorithm. This algorithm can give reliable segmentation results even the image has different lighting conditions, skin types. In the data set offered by Union Hospital, more than 90% images can be segmented accurately.

  10. NEOPLASTIC LESIONS OF THE APPENDIX

    Directory of Open Access Journals (Sweden)

    Piotr Bryk

    2013-11-01

    Full Text Available The aim of the research was to present the clinical observations of neoplastic lesions of the appendix (one carcinoid and two mucous cysts and to discuss various manners of treatment and prognosis. Material and methods: The authors of the following paper present a description of three cases of appendix tumours, two patients with a mucous cyst and a patient with carcinoid, against the background of all the appendectomies performed at the Clinical Department of General, Endocrine and Oncological Surgery of the Provincial Polyclinical Hospital in Kielce in the years 2005–2011. Results : Within the 7-year period, a total of 11 719 surgical operations have been performed, where 834 (7.1% were that of appendectomy. Among all of the removed vermiform appendixes, neoplastic lesions occurred in three cases constituting a mere 0.3% of all of the appendectomies performed within that period. In two of the cases there was a suspicion of mucous cysts before the surgical operation. In none of the above-mentioned cases was is possible to ultimately establish the diagnosis before the operation. The patients were subjected to a simple appendectomy. The patients are in good clinical health, with no signs of relapse. Conclusions : The presented cases of patients with appendix tumours illustrate the difficulty of preoperative detection of a neoplastic lesion. This is mainly due to a scantily symptomatic course or symptoms typical of appendicitis. In light of this, histopathological examination of each appendix should be treated as obligatory.

  11. 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.

  12. Cross-linked hyaluronic acid in pressure ulcer prevention.

    Science.gov (United States)

    Beniamino, P; Vadalà, M; Laurino, C

    2016-07-02

    Long-term bedridden patients are at high risk of acquring pressure ulcers (PUs). In this group of patients, prevention is necessary to cut the health costs, improve quality of life and reduce the mortality. Here, we evaluated the effectiveness of a cross-linked hyaluronic acid (HA) as plastic bulking-agent filling and remodelling the deep dermis and subcutaneous space of the skin areas exposed to the risk of necrosis. Our work hypothesis has been to inflate a sub-dermal elastic cushion, filled with a natural ECM component, with the aim to induce a stronger tissue background resistant to the ulcerative process. All the patients had an increased risk of PUs, at the sacral, ileum or heel skin. Patients were being nursed accordingly to the standard orthopaedic ward management with a pressure relieveing air mattress. The standard protocol consisted in body mobilisation every 3 hours, 24 hours a day and accurate cleaning of the skin with liquid soap and water without any towel friction and without adding any cream or lotion for the skin protection. Our filling protocol enclosed: accurate disinfection of the skin to be injected with povidone-iodine solution, followed by a local anaesthesia with 28G 13 mm needle, injecting 1.5 ml of 1% xylocaine. Then slow, deep, subcutaneous injection of cross-linked HA was performed with a 18G long needle, in order to deliver a homogeneous, soft gel layer underneath and around the whitish erythematous skin edges at risk of ulceration. Patients' tolerability of the compound and adverse events were also recorded. There were 15 patients (78-94 years old) who participated in the study. All tolerated the procedure very well and no serious side effects were declared. No skin pressure ulceration was detected in the four weeks follow-up Conclusion: We have demonstrated the safety and tolerability of a cross-linked HA subdermal injection in PUs prevention. The compound stratifies in a soft, elastic, interstitial bulk into the deep dermis, thus

  13. Corneal collagen cross-linking and liposomal amphotericin B combination therapy for fungal keratitis in rabbits

    Directory of Open Access Journals (Sweden)

    Zhao-Qin Hao

    2016-11-01

    Full Text Available AIM: To observe the therapeutic effect of corneal collagen cross-linking (CXL in combination with liposomal amphotericin B in fungal corneal ulcers. METHODS: New Zealand rabbits were induced fungal corneal ulcers by scratching and randomly divided into 3 groups, i.e. control, treated with CXL, and combined therapy of CXL with 0.25% liposomal amphotericin B (n=5 each. The corneal lesions were documented with slit-lamp and confocal microscopy on 3, 7, 14, 21 and 28d after treatment. The corneas were examined with transmission electron microscopy (TEM at 4wk. RESULTS: A rabbit corneal ulcer model of Fusarium was successfully established. The corneal epithelium defect areas in the two treatment groups were smaller than that in the control group on 3, 7, 14 and 21d (P<0.05. The corneal epithelium defect areas of the combined group was smaller than that of the CXL group (P<0.05 on 7 and 14d, but there were no statistical differences on 3, 21 and 28d. The corneal epithelium defects of the two treatment groups have been healed by day 21. The corneal epithelium defects of the control group were healed on 28d. The diameters of the corneal collagen fiber bundles (42.960±7.383 nm in the CXL group and 37.040±4.160 nm in the combined group were thicker than that of the control group (24.900±1.868 nm, but there was no difference between the two treatment groups. Some corneal collagen fiber bundles were distorted and with irregular arrangement, a large number of fibroblasts could be seen among them but no inflammatory cells in both treatment groups. CONCLUSION: CXL combined with liposomal amphotericin B have beneficial effects on fungal corneal ulcers. The combined therapy could alleviate corneal inflammattions, accelerate corneal repair, and shorten the course of disease.

  14. High Performance Polymer Field-Effect Transistors Based on Thermally Crosslinked Poly(3-hexylthiophene)

    International Nuclear Information System (INIS)

    Jiang Chun-Xia; Yang Xiao-Yan; Zhao Kai; Wu Xiao-Ming; Yang Li-Ying; Cheng Xiao-Man; Yin Shou-Gen; Wei Jun

    2011-01-01

    The performance of polymer field-effect transistors is improved by thermal crosslinking ofpoly(3-hexylthiophene), using ditert butyl peroxide as the crosslinker. The device performance depends on the crosslinker concentration significantly. We obtain an optimal on/off ratio of 10 5 and the saturate field-effect mobility of 0.34cm 2 V −1 s −1 , by using a suitable ratios of ditert butyl peroxide, 0.5 wt% ofpoly(3-hexylthiophene). The microstructure images show that the crosslinked poly(3-hexylthiophene) active layers simultaneously possess appropriate crystallinity and smooth morphology. Moreover, crosslinking of poly(3-hexylthiophene) prevents the transistors from large threshold voltage shifts under ambient bias-stressing, showing an advantage in encouraging device environmental and operating stability. (cross-disciplinary physics and related areas of science and technology)

  15. A comparison of thiolated and disulfide-crosslinked polyethylenimine for nonviral gene delivery.

    Science.gov (United States)

    Aravindan, Latha; Bicknell, Katrina A; Brooks, Gavin; Khutoryanskiy, Vitaliy V; Williams, Adrian C

    2013-09-01

    Branched polyethylenimine (25 kDa) is thiolated and compared with redox-sensitive crosslinked derivatives. Both polymers thiol contents are assessed; the thiolated polymers have 390-2300 mmol SH groups/mol, whereas the crosslinked polymers have lower thiol contents. Cytotoxicity assays show that both modified polymers give lower hemolysis than unmodified PEI. Increased thiol content increases gene transfer efficiency but also elevates cytotoxicity. Crosslinking improves plasmid DNA condensation and enhances transfection efficiency, but extensive crosslinking overstabilizes the polyplexes and decreases transfection, emphasizing the need to balance polyplex stabilization and unpacking. Thus, at low levels of crosslinking, 25 kDa PEI can be an efficient redox-sensitive carrier system. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Crosslinked polymeric nanocapsules with controllable structure via a 'self-templating' approach

    International Nuclear Information System (INIS)

    Liu Peng; Liu Guangfeng; Zhang Wei; Jiang Fan

    2010-01-01

    We developed a novel strategy for the near-monodispersed crosslinked polymeric nanocapsules with controllable structure via the 'self-templating' approach by the following four steps: (i) preparation of the PVAc lattices by the emulsion polymerization of VAc; (ii) surface hydrolysis of the PVAc lattices; (iii) crosslinking the PVA segments on the surface of the surface-hydrolyzed PVAc lattices and (iv) removal of the PVAc core of the core-shell structures by being dissolved by methanol. The strategy developed was confirmed with Fourier-transform infrared, transmission electron microscopy and dynamic light scattering techniques. In the strategy developed, the particle size, the thickness and the crosslinking degree of the nanocapsules could be controlled with the lattice's size, relative molecular weight of PVAc and the crosslinking degree of the crosslinked shell.

  17. Modification of liposomes with proteins by dansyl-labeled heterobifunctional crosslinker.

    Science.gov (United States)

    Chen, Tao; Wang, Rutao; Lu, Tingting; Liang, Guozheng; Lu, Tingli

    2011-07-01

    The introduction of a fluorescent chromaphore into bifunctional crosslinkers results in a molecule with normal crosslinker properties and a fluorescent group for straightforward quantification. This work describes the synthesis of the dansyl-labeled heterobifunctional crosslinker N-succinimidyl ε-N-dansyl α-N-(acetylthio)acetyllysine (dansyl-ATA-lysine-NHS) containing reactive N-hydroxysuccinimidyl (NHS) ester and sulfhydryl groups. The application of this crosslinker to conjugation of bovine serum albumin (BSA) protein to the surface of a liposome containing maleimide functions is also demonstrated. BSA was modified with the dansyl-labeled crosslinker and subsequently conjugated to liposomes containing reactive phospholipid derivative N-[4-(p-maleimidophenyl)butyryl]phosphatidylethanolamine and the degree of modification and conjugation were quantitatively determined by measuring the fluorescence emission of the dansyl group. The reliability of the fluorescence quantification was confirmed by a micro bio-barcode assay protein assay.

  18. Influence of crosslinking process on the mechanical behavior of Poly(Dimethylsiloxane) (PDMS)

    International Nuclear Information System (INIS)

    Fernandes, Barbara Monteiro Pessoa; Weber, Ricardo Ponde; Elzubair, Amal; Suarez, Joao Carlos Miguez

    2010-01-01

    In the present work was studied the influence of the crosslinking process on the mechanical behavior of a composite with a poly(dimethylsiloxane) (PDMS) matrix filled with inorganic particles, used as dental impression material. The material was crosslinked chemically and by exposition to 400kGy gamma radiation dose. The material properties, before and after crosslinking, were analyzed through physical chemical and mechanical tests and microscopic exam. The results showed that the gamma irradiation, as compared to chemical cure process, produced higher degree of crosslinking, better wettability, adjusted hardness and low fragility. However, the microscopic exam showed that the gamma irradiated PDMS presents, as compared with the chemical cure, a greater number of defaults which resulted from the large concentration of released gases. The results allowed us to conclude that gamma irradiation is an adequate process to crosslink the studied PDMS composite, since we can reduce the quantity of gases formed in this process. (author)

  19. The degree of collagen crosslinks in medical collagen membranes determined by water absorption

    International Nuclear Information System (INIS)

    Braczko, M.; Tederko, A.; Grzybowski, J.

    1994-01-01

    Collagen membranes were crosslinked by using three agents: glutaraldehyde, hexametylenediisocyanate, and UV irradiation. The increasing concentrations of above chemical agents or longer time of UV exposition resulted in the higher cross-links degree and in the decrease of collagen membranes swelling (measured as water absorption), their elasticity and mechanical resistance. According to American standards, the degree of collagen biomaterial cross-links is determined by measuring of the digestion time by pepsin. However, that method is very time-consuming. In our study, we have that a simple, linear regression between logarithm of digestion time by pepsin exists and it was identical for all three cross-linking agents used. We have concluded that determination of water absorption can be an alternative, simple and fast method for examination of collagen membrane cross-links degree. (author). 16 refs, 7 figs, 1 tab

  20. Excision and crosslink repair of DNA and sister chromatid exchanges in cultured human fibroblasts with different repair capacities

    Energy Technology Data Exchange (ETDEWEB)

    Fujiwara, Y; Kano, Y; Paul, P; Goto, K; Yamamoto, K [Kobe Univ. (Japan). School of Medicine

    1981-01-01

    Xeroderma pigmentosum (XP) groups A to G lacked the initial stage of ultraviolet (UV) excision repair in the order of A = G > C > D > E asymptotically equals F, while the XP variant was weakly defective in the later repair steps. Killing sensitivities were in the orders of A >= G > D > C > E asymptotically equals F asymptotically equals variant > normal to UV, A = G > D > F > C = E > variant > normal to 4-nitroquinoline-1-oxide (4NQO), and A > C > D = E = F = variant > G = normal to decarbamoyl mitomycin-C(DCMC). The induced sister chromatid exchange (SCE) frequency was unrelated to the extent of repair deficiency. The SCE induction rate was consistently 3 - 6 fold higher by these UV-like mutagens in XP group A cells than in normal cells. However, repair-proficient Cockayne's syndrome (CS) cells showed a higher SCE induction by UV, which was normalized by NAD/sup +/, suggesting that chromatin lesions as well as DNA damage contribute to SCE. Two-step crosslink repair involves a first rapid half-excision and a second slow nucleotide-excision repair. Fanconi's anemia (FA) cells had an impaired first half-excision and were supersensitive to MC, but not to UV and DCMC. The SCE frequency induced by MC (1 hr) was higher in FA cells than in normal cells despite their normal response to DCMC, and vice versa in XP cells. FA cells lacked the first rapid decline and showed higher remaining SCEs. Thus, part of the crosslink seems to lead to SCE formation. Caffeine synergistically elevated UV-induced SCEs, but not UV induced mutations in V79 cells, implying that SCE may not necessarily involve mutation.

  1. Excision and crosslink repair of DNA and sister chromatid exchanges in cultured human fibroblasts with different repair capacities

    International Nuclear Information System (INIS)

    Fujiwara, Yoshisada; Kano, Yoshio; Paul, P.; Goto, Kaoru; Yamamoto, Kazuo

    1981-01-01

    Xeroderma pigmentosum (XP) groups A to G lacked the initial stage of ultraviolet (UV) excision repair in the order of A = G > C > D > E asymptotically equals F, while the XP variant was weakly defective in the later repair steps. Killing sensitivities were in the orders of A >= G > D > C > E asymptotically equals F asymptotically equals variant > normal to UV, A = G > D > F > C = E > variant > normal to 4-nitroquinoline-1-oxide (4NQO), and A > C > D = E = F = variant > G = normal to decarbamoyl mitomycin-C(DCMC). The induced sister chromatid exchange (SCE) frequency was unrelated to the extent of repair deficiency. The SCE induction rate was consistently 3 - 6 fold higher by these UV-like mutagens in XP group A cells than in normal cells. However, repair-proficient Cockayne's syndrome (CS) cells showed a higher SCE induction by UV, which was normalized by NAD + , suggesting that chromatin lesions as well as DNA damage contribute to SCE. Two-step crosslink repair involves a first rapid half-excision and a second slow nucleotide-excision repair. Fanconi's anemia (FA) cells had an impaired first half-excision and were supersensitive to MC, but not to UV and DCMC. The SCE frequency induced by MC (1 hr) was higher in FA cells than in normal cells despite their normal response to DCMC, and vice versa in XP cells. FA cells lacked the first rapid decline and showed higher remaining SCEs. Thus, part of the crosslink seems to lead to SCE formation. Caffeine synergistically elevated UV-induced SCEs, but not UV induced mutations in V79 cells, implying that SCE may not necessarily involve mutation. (J.P.N.)

  2. Excision and crosslink repair of DNA and sister chromatid exchanges in cultured human fibroblasts with different repair capacities

    Energy Technology Data Exchange (ETDEWEB)

    Fujiwara, Y.; Kano, Y.; Paul, P.; Goto, K.; Yamamoto, K. (Kobe Univ. (Japan). School of Medicine)

    1981-01-01

    Xeroderma pigmentosum (XP) groups A to G lacked the initial stage of ultraviolet (UV) excision repair in the order of A = G > C > D > E asymptotically equals F, while the XP variant was weakly defective in the later repair steps. Killing sensitivities were in the orders of A >= G > D > C > E asymptotically equals F asymptotically equals variant > normal to UV, A = G > D > F > C = E > variant > normal to 4-nitroquinoline-1-oxide (4NQO), and A > C > D = E = F = variant > G = normal to decarbamoyl mitomycin-C(DCMC). The induced sister chromatid exchange (SCE) frequency was unrelated to the extent of repair deficiency. The SCE induction rate was consistently 3 - 6 fold higher by these UV-like mutagens in XP group A cells than in normal cells. However, repair-proficient Cockayne's syndrome (CS) cells showed a higher SCE induction by UV, which was normalized by NAD/sup +/, suggesting that chromatin lesions as well as DNA damage contribute to SCE. Two-step crosslink repair involves a first rapid half-excision and a second slow nucleotide-excision repair. Fanconi's anemia (FA) cells had an impaired first half-excision and were supersensitive to MC, but not to UV and DCMC. The SCE frequency induced by MC (1 hr) was higher in FA cells than in normal cells despite their normal response to DCMC, and vice versa in XP cells. FA cells lacked the first rapid decline and showed higher remaining SCEs. Thus, part of the crosslink seems to lead to SCE formation. Caffeine synergistically elevated UV-induced SCEs, but not UV induced mutations in V79 cells, implying that SCE may not necessarily involve mutation.

  3. 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.

  4. Chemical crosslinking and mass spectrometry studies of the structure and dynamics of membrane proteins and receptors.

    Energy Technology Data Exchange (ETDEWEB)

    Haskins, William E.; Leavell, Michael D.; Lane, Pamela; Jacobsen, Richard B.; Hong, Joohee; Ayson, Marites J.; Wood, Nichole L.; Schoeniger, Joseph S.; Kruppa, Gary Hermann; Sale, Kenneth L.; Young, Malin M.; Novak, Petr

    2005-03-01

    Membrane proteins make up a diverse and important subset of proteins for which structural information is limited. In this study, chemical cross-linking and mass spectrometry were used to explore the structure of the G-protein-coupled photoreceptor bovine rhodopsin in the dark-state conformation. All experiments were performed in rod outer segment membranes using amino acid 'handles' in the native protein sequence and thus minimizing perturbations to the native protein structure. Cysteine and lysine residues were covalently cross-linked using commercially available reagents with a range of linker arm lengths. Following chemical digestion of cross-linked protein, cross-linked peptides were identified by accurate mass measurement using liquid chromatography-fourier transform mass spectrometry and an automated data analysis pipeline. Assignments were confirmed and, if necessary, resolved, by tandem MS. The relative reactivity of lysine residues participating in cross-links was evaluated by labeling with NHS-esters. A distinct pattern of cross-link formation within the C-terminal domain, and between loop I and the C-terminal domain, emerged. Theoretical distances based on cross-linking were compared to inter-atomic distances determined from the energy-minimized X-ray crystal structure and Monte Carlo conformational search procedures. In general, the observed cross-links can be explained by re-positioning participating side-chains without significantly altering backbone structure. One exception, between C3 16 and K325, requires backbone motion to bring the reactive atoms into sufficient proximity for cross-linking. Evidence from other studies suggests that residues around K325 for a region of high backbone mobility. These findings show that cross-linking studies can provide insight into the structural dynamics of membrane proteins in their native environment.

  5. 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.

  6. 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.

  7. 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

  8. Thermally reversible cross-linked poly(ether-urethanes

    Directory of Open Access Journals (Sweden)

    V. Gaina

    2013-07-01

    Full Text Available Cross-linked poly(ether-urethanes were prepared by Diels-Alder (DA reaction of the furan-containing poly(ether-urethane to bismaleimides and showed thermal reversibility evidenced by differential scanning calorimetry and attenuated total reflectance in conjunction with Fourier transform infrared spectroscopy (ATR-FTIR. The furan-containing poly(ether-urethanes were synthesized by the polyaddition reaction of 1,6-hexamethylene diisocyanate (HMDI or 4,4'- dibenzyl diisocyanate (DBDI to poly(tetramethylene ether glycol (PTMEG having Mn = 250, 650, 1000, 1500 and 2000 and 2-[N,N-bis(2-methyl-2-hydroxyethylamino]furfuryl as chain extender by the solution prepolymer method. The molar ratio of isocyanate: PTMEG:chain extender varied from 2:1:1 to 4:1:3, which produces a molar concentration of furyl group ranging between 3.65•10–4 and 1.25•10–3 mol/g.

  9. Eco-friendly Crosslinking Agent for Acid Functional Acrylic Resin

    Directory of Open Access Journals (Sweden)

    Archana Shah

    2009-01-01

    Full Text Available Oil from J. multifida was extracted and it was first converted into N,N-bis(2-hydroxyethyl Jatropha fatty amide (HEJFA. HEJFA has been synthesized by reaction between Jatropha oil and diethanol amine in presence of zinc oxide as a catalyst. The reaction is relatively rapid and proceeded to high yield at 200±5 OC. The resulting HEJFA was used to formulate thermosetting coating compositions. Films were cured at ambient (air drying and elevated (stove drying temperatures using N, N-bis(2-hydroxyethyl Jatropha fatty amide (HEJFA as eco-friendly crosslinking agent for acrylic resin. The coating performance of the various compositions was tested by measurement of scratch hardness, impact strength and chemical resistance. The results show better performance of the HEJFA based compositions compared to butylated melamine formaldehyde (MF based compositions.

  10. Degradation and crosslinking of PTFE due to irradiation

    International Nuclear Information System (INIS)

    Tutiya, Mituaki

    1995-01-01

    In this report, we summarized all our experimental results concerning about the effects of Co-60 γ rays irradiation on polytetrafluoroethylene (PTFE). The NMR spectra, the mechanical properties and others of PTFE were measured. The increase in the degree of crystallinity, the lowering of the 19degC transition temperature and that of the melting temperature due to irradiation were observed. The effect of post-irradiation heat treatment were also observed. In each case, the main causes of these effects were attributed to the radiation-induced main chain scission. In the case of PTFE irradiated at 320-360degC in vacuum, we found that the effect of radiation-induced crosslinking were observed. By using our new theories, these experimental results which were measured in the crystalline and the amorphous regions of the irradiated PTFE were discussed, and a satisfactory agreement between the theories and the experiments was obtained. (author)

  11. Organic photovoltaics: Crosslinking for optimal morphology and stability

    KAUST Repository

    Rumer, Joseph W.

    2015-04-25

    Organic solar cells now exceed 10% efficiency igniting interest not only in the fundamental molecular design of the photoactive semiconducting materials, but also in overlapping fields such as green chemistry, large-scale processing and thin film stability. For these devices to be commercially useful, they must have lifetimes in excess of 10 years. One source of potential instability, is that the two bicontinuous phases of electron donor and acceptor materials in the photoactive thin film bulk heterojunction, change in dimensions over time. Photocrosslinking of the π-conjugated semiconducting donor polymers allows the thin film morphology to be ‘locked’ affording patterned and stable blends with suppressed fullerene acceptor crystallization. This article reviews the performance of crosslinkable polymers, fullerenes and additives used to-date, identifying the most promising.

  12. High temperature concrete composites containing organosiloxane crosslinked copolymers

    Science.gov (United States)

    Zeldin, A.; Carciello, N.; Kukacka, L.; Fontana, J.

    High temperature polymer concrete composites comprising about 10 to 30% by weight of a liquid monomer mixture is described. It consists essentially of an organosiloxane polymer crosslinked with an olefinically unsaturated monomer selected from the group consisting of styrene, methyl methacrylate, trimethylolpropane trimethacrylate, triallyl cyanurate, n-phenylmalimide, divinyl benzene and mixtures thereof. About 70 to 90% by weight of an inert inorganic filler system containing silica sand and portland cement, Fe/sub 2/O/sub 3/, carbon black or mixtures thereof. Optionally a free radical initiator such as di-tert-butyl peroxide, azobisisobyutyronitrile, benzoyl peroxide, lauryl peroxide and other organic peroxides are used to initiate crosspolymerization of the monomer mixture in the presence of the inorganic filler.

  13. Organic photovoltaics: Crosslinking for optimal morphology and stability

    KAUST Repository

    Rumer, Joseph W.; McCulloch, Iain

    2015-01-01

    Organic solar cells now exceed 10% efficiency igniting interest not only in the fundamental molecular design of the photoactive semiconducting materials, but also in overlapping fields such as green chemistry, large-scale processing and thin film stability. For these devices to be commercially useful, they must have lifetimes in excess of 10 years. One source of potential instability, is that the two bicontinuous phases of electron donor and acceptor materials in the photoactive thin film bulk heterojunction, change in dimensions over time. Photocrosslinking of the π-conjugated semiconducting donor polymers allows the thin film morphology to be ‘locked’ affording patterned and stable blends with suppressed fullerene acceptor crystallization. This article reviews the performance of crosslinkable polymers, fullerenes and additives used to-date, identifying the most promising.

  14. Radiation cross-linking of PTC conductive polymers

    International Nuclear Information System (INIS)

    Doljack, F.A.; Jacobs, S.M.; Taylor, J.M.; McTavish, M.S.

    1982-01-01

    An electrical device comprising a PTC conductive polymer is irradiated so that it is very highly cross-linked. A dosage of at least 50 Mrads, preferably at least 80 Mrads, especially at least 120 Mrads is used except that where the device includes planar electrodes which are present during irradiation the minimum dose is 120 Mrads. In this way, for example, it is possible to make a circuit protection device which will continue to provide effective protection even after repeated exposure to a voltage of 200 volts. A PTC protection device may be produced by moulding carbon loaded polymer round three electrodes the centre one of which is then removed to leave an aperture between the other two electrodes. (author)

  15. Lesion Contrast Enhancement in Medical Ultrasound Imaging

    DEFF Research Database (Denmark)

    Stetson, Paul F.; Sommer, F.G.; Macovski, A.

    1997-01-01

    Methods for improving the contrast-to-noise ratio (CNR) of low-contrast lesions in medical ultrasound imaging are described. Differences in the frequency spectra and amplitude distributions of the lesion and its surroundings can be used to increase the CNR of the lesion relative to the background...

  16. Synthesis of EVA/MWNT nanocomposites by radiation induced crosslinking

    International Nuclear Information System (INIS)

    Dubey, K.A.; Bhardwaj, Y.K.; Chaudhari, C.V.; Sabharwal, S.

    2008-01-01

    Full text: EVA is widely used as an insulating material for high voltage cables and in the footwear and toy industries due to its high flexibility and chemical inertness. The nano-composites of EVA with MWNT are of the special interest because incorporation of suitable amount of MWNT in EVA matrix is expected to significantly enhance EVA's thermal and mechanical properties, and open a new domain of applications. The modification of EVA by using high-energy radiation and with particulate filler has been widely practiced; however, there is not much information available on the radiation processing of EVA nanocomposites. To understand the effect of radiation and of MWNT addition on the physico-mechanical characteristics of EVA, different compositions of ethylene vinyl acetate (EVA)/multiple walled carbon nanotube (MWNT) nanocomposites were prepared by mixing in Brabender and subjected to different doses of gamma radiation. The efficiency of radiation vulcanization was analyzed by gel-content, Charlesby-Pinner parameter and crosslinking density measurements. Gamma radiation induced crosslinking was found to increase with MWNT fraction in EVA/MWNT nanocomposites (P o /q o range: 1.15-0.98). These results ruled out the possibility of a significant neutralization of single ionization spurs by MWNT addition. The polymer-filler interaction parameter determined from Kraus plot indicated good interaction between EVA and MWNTs. Storage modulus changed from 7 x 10 7 Pa to 1.8 x 10 8 Pa with incorporation of 5% (wt/wt) MWNT while density increased from 0.78 g/cc to 0.80 g/cc

  17. Crosslinking of tRNA containing a long extra arm to elongation factor Tu by trans-diamminedichloroplatinum(II)

    DEFF Research Database (Denmark)

    Rasmussen, Nils-Jørgen; Wikman, Friedrik; Clark, Brian F. C.

    1990-01-01

    A tRNA containing a long extra arm, namely E. coli tRNA1Leu has been crosslinked to elongation factor Tu, with the crosslinking reagent trans-diamminedichloroplatinum(II). The nucleotide involved in the crosslinking was identified to be a guanosine in the variable region at position 47F or 47G....

  18. Benign clavicular lesions that may mimic malignancy

    International Nuclear Information System (INIS)

    Gerscovich, E.G.; Greenspan, A.; Szabo, R.M.

    1991-01-01

    Nontraumatic lesions of the clavicle are infrequent. Of these, malignant tumors are more common than benign lesions. From January 1988 to January 1990, we examined 17 patients with benign lesions of the clavicle; in 8, the morphologic appearance of the lesion raised the possibility of malignancy in the differential diagnosis. The radiologic findings in these patients are presented. We propose that the unique shape and embryologic development of the clavicle may contribute to the atypical, aggressive presentation of some benign lesions in that bone. (orig.)

  19. Quantitative angiography methods for bifurcation lesions

    DEFF Research Database (Denmark)

    Collet, Carlos; Onuma, Yoshinobu; Cavalcante, Rafael

    2017-01-01

    Bifurcation lesions represent one of the most challenging lesion subsets in interventional cardiology. The European Bifurcation Club (EBC) is an academic consortium whose goal has been to assess and recommend the appropriate strategies to manage bifurcation lesions. The quantitative coronary...... angiography (QCA) methods for the evaluation of bifurcation lesions have been subject to extensive research. Single-vessel QCA has been shown to be inaccurate for the assessment of bifurcation lesion dimensions. For this reason, dedicated bifurcation software has been developed and validated. These software...

  20. Solitary lucent epiphyseal lesions in children

    Energy Technology Data Exchange (ETDEWEB)

    Gardner, D.J.; Azouz, E.M.

    1988-10-01

    We evaluated retrospectively the varying radiographic appearances of 15 solitary lucent epiphyseal lesions occurring in children. Imaging modalities used included plain films, conventional tomography, nuclear scintigraphy, and computed tomography. 40% of the lesions (6) were due to osteomyelitis. The remaining lesions included tuberculosis (1), foreign body granuloma (1), chondroblastoma (2), chondromyoxid fibroma (1), enchondroma (1), osteoid osteoma (2), and eosinophilic granuloma (1). Although the radiographic appearances of such lesions may be particularly characteristic, pathologic correlation is frequently necessary. The high incidence of osteomyelitis in our cases emphasizes its importance as a cause for a lucent epiphyseal lesion.

  1. Computerized tomography of orbital lesions

    International Nuclear Information System (INIS)

    Kuroiwa, Mayumi

    1981-01-01

    Two different types of computerized tomography scanners (CT scanner), i.e. a whole-body CT scanner (GE-CT/T8800) and a cerebral CT scanner (EMI-1010), were compared in the assessment and diagnosis of various orbital lesions. The whole-body CT scanner was found to be advantageous over the cerebral CT scanner for the following reasons: (1) CT images were more informative due to thinner slices associated with smaller-sized and larger-numbered matrices; (2) less artifacts derived from motion of the head or eyeball were produced because of the shorter scanning time; (3) with a devised gantry, coronal dissections were available whenever demanded. (author)

  2. Induction of DNA–protein cross-links by ionizing radiation and their elimination from the genome

    Energy Technology Data Exchange (ETDEWEB)

    Nakano, Toshiaki; Mitsusada, Yusuke [Department of Mathematical and Life Sciences, Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526 (Japan); Salem, Amir M.H. [Department of Mathematical and Life Sciences, Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526 (Japan); Department of Pathology, Medical Research Division, National Research Centre, El-Bohouth St., Dokki, Giza 12311 (Egypt); Shoulkamy, Mahmoud I. [Department of Mathematical and Life Sciences, Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526 (Japan); Department of Zoology, Biological Science Building, Faculty of Science, Minia University, Minia 61519 (Egypt); Sugimoto, Tatsuya [Department of Mathematical and Life Sciences, Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526 (Japan); Hirayama, Ryoichi; Uzawa, Akiko [Research Center for Charged Particle Therapy, National Institute of Radiological Sciences (NIRS), Chiba 263-8555 (Japan); Furusawa, Yoshiya [Development and Support Center, National Institute of Radiological Sciences (NIRS), Chiba 263-8555 (Japan); Ide, Hiroshi, E-mail: ideh@hiroshima-u.ac.jp [Department of Mathematical and Life Sciences, Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526 (Japan)

    2015-01-15

    Highlights: • Normoxic and hypoxic mouse tumors were irradiated with X-rays and C-ion beams. • DNA–protein cross-links (DPCs) and DNA double-strand breaks (DSBs) were analyzed. • C-ion beams produced more DPCs than did X-rays in normoxic and hypoxic tumor cells. • DPCs were eliminated from the genome much more slowly than DSBs. • Persisting DPCs may have deleterious effects on cells in conjunction with DSBs. - Abstract: Ionizing radiation produces various types of DNA lesions, such as base damage, single-strand breaks, double-strand breaks (DSBs), and DNA–protein cross-links (DPCs). Of these, DSBs are the most critical lesions underlying the lethal effects of ionizing radiation. With DPCs, proteins covalently trapped in DNA constitute strong roadblocks to replication and transcription machineries, and hence can be lethal to cells. The formation of DPCs by ionizing radiation is promoted in the absence of oxygen, whereas that of DSBs is retarded. Accordingly, the contribution of DPCs to the lethal events in irradiated cells may not be negligible for hypoxic cells, such as those present in tumors. However, the role of DPCs in the lethal effects of ionizing radiation remains largely equivocal. In the present study, normoxic and hypoxic mouse tumors were irradiated with X-rays [low linear energy transfer (LET) radiation] and carbon (C)-ion beams (high LET radiation), and the resulting induction of DPCs and DSBs and their removal from the genome were analyzed. X-rays and C-ion beams produced more DPCs in hypoxic tumors than in normoxic tumors. Interestingly, the yield of DPCs was slightly but statistically significantly greater (1.3- to 1.5-fold) for C-ion beams than for X-rays. Both X-rays and C-ion beams generated two types of DPC that differed according to their rate of removal from the genome. This was also the case for DSBs. The half-lives of the rapidly removed components of DPCs and DSBs were similar (<1 h), but those of the slowly removed components

  3. Intramolecularly Protein-Crosslinked DNA Gels: New Biohybrid Nanomaterials with Controllable Size and Catalytic Activity.

    Science.gov (United States)

    Zhou, Li; Morel, Mathieu; Rudiuk, Sergii; Baigl, Damien

    2017-07-01

    DNA micro- and nanogels-small-sized hydrogels made of a crosslinked DNA backbone-constitute new promising materials, but their functions have mainly been limited to those brought by DNA. Here a new way is described to prepare sub-micrometer-sized DNA gels of controllable crosslinking density that are able to embed novel functions, such as an enzymatic activity. It consists of using proteins, instead of traditional base-pairing assembly or covalent approaches, to form crosslinks inside individual DNA molecules, resulting in structures referred to as intramolecularly protein-crosslinked DNA gels (IPDGs). It is first shown that the addition of streptavidin to biotinylated T4DNA results in the successful formation of thermally stable IPDGs with a controllable crosslinking density, forming structures ranging from elongated to raspberry-shaped and pearl-necklace-like morphologies. Using reversible DNA condensation strategies, this paper shows that the gels can be reversibly actuated at a low crosslinking density, or further stabilized when they are highly crosslinked. Finally, by using streptavidin-protein conjugates, IPDGs with various enzymes are successfully functionalized. It is demonstrated that the enzymes keep their catalytic activity upon their incorporation into the gels, opening perspectives ranging from biotechnologies (e.g., enzyme manipulation) to nanomedicine (e.g., vectorization). © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Crosslinking of a Peritrophic Matrix Protein Protects Gut Epithelia from Bacterial Exotoxins

    Science.gov (United States)

    Shibata, Toshio; Maki, Kouki; Hadano, Jinki; Fujikawa, Takumi; Kitazaki, Kazuki; Koshiba, Takumi; Kawabata, Shun-ichiro

    2015-01-01

    Transglutaminase (TG) catalyzes protein-protein crosslinking, which has important and diverse roles in vertebrates and invertebrates. Here we demonstrate that Drosophila TG crosslinks drosocrystallin, a peritrophic matrix protein, to form a stable fiber structure on the gut peritrophic matrix. RNA interference (RNAi) of the TG gene was highly lethal in flies and induced apoptosis of gut epithelial cells after oral infection with Pseudomonas entomophila. Moreover, AprA, a metalloprotease secreted by P. entomophila, digested non-crosslinked drosocrystallin fibers, but not drosocrystallin fibers crosslinked by TG. In vitro experiments using recombinant drosocrystallin and monalysin proteins demonstrated that monalysin, a pore-forming exotoxin of P. entomophila, was adsorbed on the crosslinked drosocrystallin fibers in the presence of P. entomophila culture supernatant. In addition, gut-specific TG-RNAi flies had a shorter lifespan than control flies after ingesting P. entomophila, whereas the lifespan after ingesting AprA-knockout P. entomophila was at control levels. We conclude that drosocrystallin fibers crosslinked by TG, but not non-crosslinked drosocrystallin fibers, form an important physical barrier against exotoxins of invading pathogenic microbes. PMID:26506243

  5. Crosslinking of a Peritrophic Matrix Protein Protects Gut Epithelia from Bacterial Exotoxins.

    Directory of Open Access Journals (Sweden)

    Toshio Shibata

    2015-10-01

    Full Text Available Transglutaminase (TG catalyzes protein-protein crosslinking, which has important and diverse roles in vertebrates and invertebrates. Here we demonstrate that Drosophila TG crosslinks drosocrystallin, a peritrophic matrix protein, to form a stable fiber structure on the gut peritrophic matrix. RNA interference (RNAi of the TG gene was highly lethal in flies and induced apoptosis of gut epithelial cells after oral infection with Pseudomonas entomophila. Moreover, AprA, a metalloprotease secreted by P. entomophila, digested non-crosslinked drosocrystallin fibers, but not drosocrystallin fibers crosslinked by TG. In vitro experiments using recombinant drosocrystallin and monalysin proteins demonstrated that monalysin, a pore-forming exotoxin of P. entomophila, was adsorbed on the crosslinked drosocrystallin fibers in the presence of P. entomophila culture supernatant. In addition, gut-specific TG-RNAi flies had a shorter lifespan than control flies after ingesting P. entomophila, whereas the lifespan after ingesting AprA-knockout P. entomophila was at control levels. We conclude that drosocrystallin fibers crosslinked by TG, but not non-crosslinked drosocrystallin fibers, form an important physical barrier against exotoxins of invading pathogenic microbes.

  6. Crosslinking of SAVY-4000 O-rings as a Function of Aging Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Van Buskirk, Caleb Griffith [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-09-08

    SAVY-4000 containers were developed as a part of DOE M 441.1-1 to protect workers who handle stored nuclear material from exposure due to loss of containment.1 The SAVY-4000 is comprised of three parts: a lid, a container, and a cross-linked fluoropolymer O-ring. Degradation of the O-ring during use could limit the lifetime of the SAVY-4000. In order to quantify the chemical changes of the Oring over time, the molecular weight between crosslinks was determined as a function of aging conditions using a swelling technique. Because the O-ring is a cross-linked polymer, it will absorb solvent into its matrix without dissolving. The relative amount of solvent uptake can be related to the degree of crosslinking using an equation developed by Paul Flory and John Rehner Jr3. This method was used to analyze O-ring samples aged under thermal and ionizing-radiation conditions. It was found that at the harsher thermal gaining conditions in absence of ionizing-radiation the average molecular weight between crosslinks decreased, indicating a rise in crosslinks, which may be attributable to advanced aging with no ionizing radiation present. Inversely, in the presence of ionizing radiation it was found that material has a higher level of cross-linking with age. This information could be used to help predict the lifetime of the O-rings in SAVY-4000 containers under service conditions.

  7. Crosslinked poly(ether block amide) composite membranes for organic solvent nanofiltration applications

    KAUST Repository

    Aburabie, Jamaliah; Peinemann, Klaus-Viktor.

    2016-01-01

    Poly(ether block amide) – Pebax® – based membranes are well described for gas separation applications. But only a few publications exist for their application in pressure driven liquid applications like ultrafiltration and nanofiltration. Here we use the commercially available Pebax® 1657 for the preparation of membranes for the filtration of organic solvents. Porous polyacrylonitrile membranes were coated with Pebax® 1657 which was then crosslinked. Toluene diisocyanate (TDI) was used as a crosslinker agent for the coating. Reaction time and crosslinker concentration were optimized for the aimed application. The Pebax® coating and the impact of the TDI on the resulting crosslinked membranes were investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). SEM analysis shows a uniform thin coating of the PEBAX that covers the pores of the PAN membranes. FTIR and DSC analysis confirm the crosslinking reaction. Crosslinked Pebax® membranes show high stability toward ethanol propanol, acetone and even dimethylformamide (DMF). In the case of DMF applications, the standard PAN was replaced by crosslinked PAN developed in our laboratory. In order to increase the membranes permeances, graphene oxide (GO) nanosheets were incorporated in the Pebax® coating. These GO containing membranes showed strongly increased permeances for selected solvents. © 2016 Elsevier B.V.

  8. Rubber mixing process and its relationship with bound rubber and crosslink density

    Science.gov (United States)

    Hasan, A.; Rochmadi; Sulistyo, H.; Honggokusumo, S.

    2017-06-01

    This research studied the relationship between bound rubber and crosslink density based on rubber mixing process. Bound rubber was obtained after natural rubber was masticated and mixed with rubber chemicals and filler while crosslink density was collected after rubber compound was vulcanized. Four methods are used and each method refers to four ways of incorporating carbon black during mixing. The first method, after rubber was masticated for 5 minutes, the addition of rubber chemicals and filler was done simultaneously. Rubber was masticated for 1 minute and continued mixing of rubber chemicals and filler where mixing was different from first method. This was the second method. The third method was the same as the second method but the filler used N 660 while in the second method N 330. The last method is not the same as the first and second, the rubber is only masticated for 3 minutes and then mixed with filler and followed by rubber chemicals sequentially. The results showed that bound rubber and crosslink density were influenced by mixing and mastication process. Bound rubber dropped and crosslink density was relatively stable in the first three mixing methods for increasing carbon black at the beginning of the mixing process. Bound rubber and crosslink density stated opposite results in the fourth mixing method. The higher the bound rubber the lower the crosslink density. Without regard to mixing methods, there is a non-linear relationship between bound rubber formation and crosslink density determination

  9. 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

  10. Redundancy and cooperativity in the mechanics of compositely crosslinked filamentous networks.

    Directory of Open Access Journals (Sweden)

    Moumita Das

    Full Text Available The cytoskeleton of living cells contains many types of crosslinkers. Some crosslinkers allow energy-free rotations between filaments and others do not. The mechanical interplay between these different crosslinkers is an open issue in cytoskeletal mechanics. Therefore, we develop a theoretical framework based on rigidity percolation to study a generic filamentous system containing both stretching and bond-bending forces to address this issue. The framework involves both analytical calculations via effective medium theory and numerical simulations on a percolating triangular lattice with very good agreement between both. We find that the introduction of angle-constraining crosslinkers to a semiflexible filamentous network with freely rotating crosslinks can cooperatively lower the onset of rigidity to the connectivity percolation threshold-a result argued for years but never before obtained via effective medium theory. This allows the system to ultimately attain rigidity at the lowest concentration of material possible. We further demonstrate that introducing angle-constraining crosslinks results in mechanical behaviour similar to just freely rotating crosslinked semflexible filaments, indicating redundancy and universality. Our results also impact upon collagen and fibrin networks in biological and bio-engineered tissues.

  11. 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.

  12. Effect of Crosslinking Agent Concentration on the Properties of Unmedicated Hydrogels

    Directory of Open Access Journals (Sweden)

    Rachel Shet Hui Wong

    2015-09-01

    Full Text Available Novel polyethylene oxide (PEO hydrogel films were synthesized via UV crosslinking with varying concentrations of pentaerythritol tetra-acrylate (PETRA as crosslinking agent. The aim was to study the effects of the crosslinking agent on the material properties of hydrogel films intended for dermatological applications. Fabricated film samples were characterized using swelling studies, scanning electron microscopy, tensile testing and rheometry. Films showed rapid swelling and high elasticity. The increase of PETRA concentration resulted in significant increase in the gel fraction and crosslinking density (ρc, while causing a significant decrease in the equilibrium water content (EWC, average molecular weight between crosslinks (\\({\\overline{M}}_{c}\\, and mesh size (ζ of films. From the scanning electron microscopy, cross-linked PEO hydrogel network appeared as cross-linked mesh-like structure with interconnected micropores. Rheological studies showed PEO films required a minimum of 2.5% w/w PETRA to form stable viscoelastic solid gels. Preliminary studies concluded that a minimum of 2.5% w/w PETRA is required to yield films with desirable properties for skin application.

  13. Procyanidins-crosslinked aortic elastin scaffolds with distinctive anti-calcification and biological properties.

    Science.gov (United States)

    Wang, Xiaoya; Zhai, Wanyin; Wu, Chengtie; Ma, Bing; Zhang, Jiamin; Zhang, Hongfeng; Zhu, Ziyan; Chang, Jiang

    2015-04-01

    Elastin, a main component of decellularized extracellular matrices and elastin-containing materials, has been used for tissue engineering applications due to their excellent biocompatibility. However, elastin is easily calcified, leading to the decrease of life span for elastin-based substitutes. How to inhibit the calcification of elastin-based scaffolds, but maintain their good biocompatibility, still remains significantly challenging. Procyanidins (PC) are a type of natural polyphenols with crosslinking ability. To investigate whether pure elastin could be crosslinked by PC with anti-calcification effect, PC was first used to crosslink aortic elastin. Results show that PC can crosslink elastin and effectively inhibit elastin-initiated calcification. Further experiments reveal the possible mechanisms for the anti-calcification of PC crosslinking including (1) inhibiting inflammation cell attachment, and secretion of inflammatory factors such as MMPs and TNF-α, (2) preventing elastin degradation by elastase, and (3) direct inhibition of mineral nucleation in elastin. Moreover, the PC-crosslinked aortic elastin maintains natural structure with high pore volume (1111 μL/g), large pore size (10-300 μm) and high porosity (75.1%) which facilitates recellularization of scaffolds in vivo, and displays excellent hemocompatibility, anti-thrombus and anti-inflammatory potential. The advantages of PC-crosslinked porous aortic elastin suggested that it can serve as a promising scaffold for tissue engineering. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  14. Influences of poly (vinyl alcohol molecular weight and carbon nanotubes on radiation crosslinking shape memory polymers

    Directory of Open Access Journals (Sweden)

    Aamer A.M. Alfayyadh

    2017-06-01

    Full Text Available Polyvinyl alcohol (PVA of two molecular weights was used to prepare shape memory polymers based on chemical-crosslinking by glutaraldehyde. The chemical-crosslinking was done in the presence of 2-carboxyethyl acrylate oligomers (CEA and nano-filler [multi-wall carbon nanotubes (MWCNT and functionalized carbon nanotubes (MWCNT-NH2] followed by radiation-induced crosslinking. The analysis of the material revealed an increase in the gel fraction and a significant reduction in swelling of the nanocomposite material that was crosslinked with both glutaraldehyde and ionizing radiation. The radiation crosslinked nanocomposites demonstrated approximately a 90% gelation over a range of 50–300 kGy irradiation doses. The scanning electron microscopy (SEM analysis showed a homogeneous distribution of nanocomposites in the composite matrix. The thermal properties of radiation crosslinked (PVA/CEA and (PVA-CEA-nano-fillers were investigated by a thermogravimetric analysis (TGA. The mechanical properties were examined via dynamic mechanical analysis (DMA which showed significant variation because of the addition of nanocomposites. This radiation crosslinked materials show good shape memory behavior that may be useful in many applications based on the range of temperatures at which Tan δ appears.

  15. Synthesis and characterization of crosslinked gellan/PVA nanofibers for tissue engineering application.

    Science.gov (United States)

    Vashisth, Priya; Pruthi, Vikas

    2016-10-01

    Electrospun nanofibers based on gellan are considered as promising biomaterial for tissue engineering and wound healing applications. However, major hurdles in usage of these nanofibers are their poor stability and deprived structural consistency in aqueous medium which is a prerequisite for their application in the biomedical sector. In this investigation, three dimensional nanofibers, consisting of gellan and PVA have been fabricated and then stabilized under various crosslinking conditions in order to improve their physiochemical stability. The impacts of different crosslinking procedures on the gellan/PVA nanofibers were examined in terms of changes in morphological, mechanical, swelling and biological properties. Superior tensile strength and strain was recorded in case of crosslinked nanofibers as compared to non-crosslinked nanofibers. Contact angles and swelling properties of fabricated gellan/PVA nanofibers were found to vary with the crosslinking method. All crosslinking conditions were evaluated with regard to their response towards human dermal fibroblast (3T3L1) cells. Biocompatibility studies suggested that the fabricated crosslinked gellan/PVA nanofibers hold a great prospective in the biomedical engineering arena. Copyright © 2016 Elsevier B.V. All rights reserved.

  16. Charged Triazole Cross-Linkers for Hyaluronan-Based Hybrid Hydrogels

    Directory of Open Access Journals (Sweden)

    Maike Martini

    2016-09-01

    Full Text Available Polyelectrolyte hydrogels play an important role in tissue engineering and can be produced from natural polymers, such as the glycosaminoglycan hyaluronan. In order to control charge density and mechanical properties of hyaluronan-based hydrogels, we developed cross-linkers with a neutral or positively charged triazole core with different lengths of spacer arms and two terminal maleimide groups. These cross-linkers react with thiolated hyaluronan in a fast, stoichiometric thio-Michael addition. Introducing a positive charge on the core of the cross-linker enabled us to compare hydrogels with the same interconnectivity, but a different charge density. Positively charged cross-linkers form stiffer hydrogels relatively independent of the size of the cross-linker, whereas neutral cross-linkers only form stable hydrogels at small spacer lengths. These novel cross-linkers provide a platform to tune the hydrogel network charge and thus the mechanical properties of the network. In addition, they might offer a wide range of applications especially in bioprinting for precise design of hydrogels.

  17. Influence of Crosslink Density and Stiffness on Mechanical Properties of Type I Collagen Gel

    Directory of Open Access Journals (Sweden)

    Shengmao Lin

    2015-02-01

    Full Text Available The mechanical properties of type I collagen gel vary due to different polymerization parameters. In this work, the role of crosslinks in terms of density and stiffness on the macroscopic behavior of collagen gel were investigated through computational modeling. The collagen fiber network was developed in a representative volume element, which used the inter-fiber spacing to regulate the crosslink density. The obtained tensile behavior of collagen gel was validated against published experimental data. Results suggest that the cross-linked fiber alignment dominated the strain stiffening effect of the collagen gel. In addition, the gel stiffness was enhanced approximately 40 times as the crosslink density doubled. The non-affine deformation was reduced with the increased crosslink density. A positive bilinear correlation between the crosslink density and gel stiffness was obtained. On the other hand, the crosslink stiffness had much less impact on the gel stiffness. This work could enhance our understanding of collagen gel mechanics and shed lights on designing future clinical relevant biomaterials with better control of polymerization parameters.

  18. Preparation and adsorption behavior for metal ions and humic acid of chitosan derivatives crosslinked by irradiation

    International Nuclear Information System (INIS)

    Zhao Long; Wasikiewicz, J.M.; Mitomo, H.; Nagasawa, N.; Yoshii, F.

    2007-01-01

    This article deals with the determination of the adsorption properties of metal ions and humic acid in wa- ter on crosslinked chitosan derivatives (carboxymethylchitosan) which were formed using the irradiation technique without any additives. The solubility test of these crosslinked materials were investigated in acidic, alkaline media, distilled water, and certain organic solvents. Scanning electron microscopic (SEM) images showed that the crosslinked chitosan derivatives possessed a porous morphological structure. Charged characteristic analyses demonstrated typically pH-dependent properties of the crosslinked materials. The adsorption studies were carded out by the batch method at room temperature. Adsorption of heavy metal ions (such as Cu 2+ , Cd 2+ ) and humic acid onto crosslinked samples was found to be strongly pH-dependent. Adsorption kinetic studies indicated the rapid removal of metal ions, and humic acid from the aqueous solutions. Moreover, isothermal adsorption data revealed that Cu 2+ , Cd 2+ , and humic acid were removed by these crosslinked materials with high efficiency. Adsorption isothermal data were interpreted well by the Langmuir equation. These crosslinked carboxymethylated chitosan derivatives indicate favorable adsorption of metal ions and humic acid. (authors)

  19. 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.

  20. Formation of DNA-protein crosslinks in gamma-irradiated chromatin

    International Nuclear Information System (INIS)

    Mee, L.K.

    1985-01-01

    Gamma-irradiation of chromatin in vitro and in vivo induces DNA-protein crosslinks which are stable to salt and detergent treatment. The efficiency of crosslink formation is 100 times greater in irradiated isolated chromatin than in chromatin irradiated in cells before isolation. Gamma-irradiation of isolated chromatin in the presence of radical scavengers shows that OH . is the most effective radical for the promotion of crosslinking whereas e/sub aq//sup -/ and O/sub 2//sup -/ are essentially ineffective. For chromatin irradiated in the cell before isolation, fewer crosslinks are formed in air than in an atmosphere of nitrogen; the greatest effect is found in cells irradiated in an atmosphere of nitrous oxide, suggesting that OH . may be involved in the formation of crosslinks in vivo. On the basis of comparing radiation-induced crosslinking in whole chromating (DNA, H1 histone, the core histones - H2A, H2B, H3 and H4 - and non-histone chromosomal proteins) and in a chromatin subunit (DNA and the core histones), the authors identified the core histones as the specific chromosomal proteins predominantly involved in crosslinking to DNA

  1. Crosslinked poly(ether block amide) composite membranes for organic solvent nanofiltration applications

    KAUST Repository

    Aburabie, Jamaliah

    2016-10-01

    Poly(ether block amide) – Pebax® – based membranes are well described for gas separation applications. But only a few publications exist for their application in pressure driven liquid applications like ultrafiltration and nanofiltration. Here we use the commercially available Pebax® 1657 for the preparation of membranes for the filtration of organic solvents. Porous polyacrylonitrile membranes were coated with Pebax® 1657 which was then crosslinked. Toluene diisocyanate (TDI) was used as a crosslinker agent for the coating. Reaction time and crosslinker concentration were optimized for the aimed application. The Pebax® coating and the impact of the TDI on the resulting crosslinked membranes were investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). SEM analysis shows a uniform thin coating of the PEBAX that covers the pores of the PAN membranes. FTIR and DSC analysis confirm the crosslinking reaction. Crosslinked Pebax® membranes show high stability toward ethanol propanol, acetone and even dimethylformamide (DMF). In the case of DMF applications, the standard PAN was replaced by crosslinked PAN developed in our laboratory. In order to increase the membranes permeances, graphene oxide (GO) nanosheets were incorporated in the Pebax® coating. These GO containing membranes showed strongly increased permeances for selected solvents. © 2016 Elsevier B.V.

  2. 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

  3. Effect of crosslinking UHMWPE on its tensile and compressive creep performance.

    Science.gov (United States)

    Lewis, G; Carroll, M

    2001-01-01

    The in vitro quasi-static tensile and compressive creep properties of three sets of GUR 1050 ultra-high-molecular-weight polyethylene (UHMWPE) specimens were obtained. These sets were: control (as-received stock); "low-gamma" (specimens were crosslinked using gamma radiation, with a minimum dose of 5 Mrad); and "high-gamma" (specimens were crosslinked using gamma radiation, with a minimum dose of 15 Mrad). The % crystallinity (%C) and crosslink density (rho(x)) of the specimens in the three sets were also obtained. It was found that, in both tension and compression, crosslinking resulted in a significant depreciation in the creep properties, relative to control. The trend in the creep results is explained in terms of the impact of crosslinking on the polymer's %C and rho(x). The present results are in contrast to literature reports that show that crosslinking enhances the wear resistance of the polymer. The implications of the present results, taken together with the aforementioned literature results, are fully discussed vis-a-vis the use of crosslinked UHMWPE for fabricating articular components for arthroplasties.

  4. Comparison of femtosecond laser and continuous wave UV sources for protein-nucleic acid crosslinking.

    Science.gov (United States)

    Fecko, Christopher J; Munson, Katherine M; Saunders, Abbie; Sun, Guangxing; Begley, Tadhg P; Lis, John T; Webb, Watt W

    2007-01-01

    Crosslinking proteins to the nucleic acids they bind affords stable access to otherwise transient regulatory interactions. Photochemical crosslinking provides an attractive alternative to formaldehyde-based protocols, but irradiation with conventional UV sources typically yields inadequate product amounts. Crosslinking with pulsed UV lasers has been heralded as a revolutionary technique to increase photochemical yield, but this method had only been tested on a few protein-nucleic acid complexes. To test the generality of the yield enhancement, we have investigated the benefits of using approximately 150 fs UV pulses to crosslink TATA-binding protein, glucocorticoid receptor and heat shock factor to oligonucleotides in vitro. For these proteins, we find that the quantum yields (and saturating yields) for forming crosslinks using the high-peak intensity femtosecond laser do not improve on those obtained with low-intensity continuous wave (CW) UV sources. The photodamage to the oligonucleotides and proteins also has comparable quantum yields. Measurements of the photochemical reaction yields of several small molecules selected to model the crosslinking reactions also exhibit nearly linear dependences on UV intensity instead of the previously predicted quadratic dependence. Unfortunately, these results disprove earlier assertions that femtosecond pulsed laser sources provide significant advantages over CW radiation for protein-nucleic acid crosslinking.

  5. Food Simulating Organic Solvents for Evaluating Crosslink Density of Bulk Fill Composite Resin

    Directory of Open Access Journals (Sweden)

    Neveen M. Ayad

    2017-01-01

    Full Text Available Objectives. To evaluate crosslink densities of two bulk fill composite resins and determine if the used Food Simulating Organic Solvent (FSOS affected them. Methods. Forty specimens were prepared from SureFill and SonicFill bulk fill composite resins, 20 each. All specimens were stored dry for 24 h. Each group was divided into 2 subgroups: stored in ethanol (E 75% or in methyl ethyl ketone (MEK 100% for 24 h. Crosslink density was evaluated by calculating the difference between the Vickers hardness numbers of the specimens stored dry and after their storage in FSOS. The data were statistically analyzed using t-test. Results. The means of crosslink density in E and MEK were 6.99% and 9.44% for SureFill and 10.54% and 11.92% for SonicFill, respectively. t-test displayed significant differences between crosslink densities of SureFill and SonicFill: (P<0.0001 in E and (P=0.02 in MEK and between crosslink densities of SureFill in E and MEK (P=0.02. Conclusions. Crosslink density of bulk fill composite resin can be evaluated using E or MEK. SureFill has higher crosslink density than SonicFill in both E and MEK.

  6. Recyclable crosslinked polymer networks with full property recovery made via one-step controlled radical polymerization

    Science.gov (United States)

    Jin, Kailong; Li, Lingqiao; Torkelson, John

    Rubber tires illustrate well the issues ranging from economic loss to environmental problems and sustainability issues that arise with spent, covalently crosslinked polymers. A nitroxide-mediated polymerization (NMP) strategy has been developed that allows for one-step synthesis of recyclable crosslinked polymers from monomers or polymers that contain carbon-carbon double bonds amenable to radical polymerization. Resulting materials possess dynamic alkoxyamine crosslinks that undergo reversible decrosslinking as a function of temperature. Using polybutadiene as starting material, and styrene, an appropriate nitroxide molecule and bifunctional initiator for initial crosslinking, a model for tire rubber can be produced by reaction at temperatures comparable to those employed in tire molding. Upon cooling, the crosslinks are made permanent due to the extraordinarily strong temperature dependence of the reverisible nitroxide capping and uncapping reaction. Based on thermomechanical property characterization, when the original crosslinked model rubber is chopped into bits and remolded in the melt state, a well-consolidated material is obtained which exhibits full recovery of properties reflecting crosslink density after multiple recycling steps.

  7. Effect of polyfunctional monomers on properties of radiation crosslinked EPDM/waste tire dust blend

    International Nuclear Information System (INIS)

    Yasin, Tariq; Khan, Sajid; Nho, Young-Chang; Ahmad, Rashid

    2012-01-01

    In this study, waste tire dust is recycled as filler and blended with ethylene-propylene diene monomer (EPDM) rubber. Three different polyfuntional monomers (PFMs) are incorporated into the standard formulation and irradiated under electron beam at different doses up to maximum of 100 kGy. The combined effects of PFMs and absorbed dose on the physical properties of EPDM/WTD blend are measured and compared with sulfur crosslinked formulation. Thermogravimetric analysis showed that radiation developed better crosslinked network with higher thermal stability than sulfur crosslinked structure. The physical properties of radiation crosslinked blend are similar to the sulfur crosslinked blend. The absence of toxic chemicals/additives in radiation crosslinked blends made them an ideal candidate for many applications such as roof sealing sheets, water retention pond, playground mat, sealing profile for windows etc. - Highlights: ► We have recycled waste tire dust and blended it with EPDM. ► EB crosslinking is carried in the presence of polyfuntional monomers. ► Radiation gave better network with higher thermal stability than sulfur. ► The absence of toxic chemicals in EB blends will increase its acceptability.

  8. Ultrasonographic findings of breast lesions

    International Nuclear Information System (INIS)

    Hwang, In Sung; Kim, Yang Soo; Suh, Hyoung Sim

    1990-01-01

    Authors retrospectively analyzed ultrasonographic findings of 61 cases of breast lesions which were proven pathologically at Daerim St. Mary's Hospital from May 1987 to February 1990. The results were as follows : 1. Of all 61 cases, there were 27 fibroadenomas, 13 fibrocystic diseases, 11 carcinomas, 8 abscesses, 1 sclerosing adenosis, and 1 intraductal papilloma. 2. Findings suggesting benignancy were smooth contour, round or oval shape, homogeneously echolucent internal echo, echogenic boundary echo, and posterior enhancement. In the cases of abscess, the findings were rather irregular contour, strong posterior enhancement, and dirty, inhomogeneous internal echo. While irregular and lobulated shape, inhomogeneous and mixed internal echo and pectoral muscle invasion were suggested for malignancy. 3. The sensitivity was 98% and the specificity 58% in benign mass excluding abscesses, 63% and 98% in abscesses, and 55% and 98% in carcinomas. In conclusion, ultrasonography is one of the excellent imaging modality for detecting breast lesions larger than 5 mm in size, but unfortunately some of the malignant tumors simulated benignancy, thus we considered fine needle aspiration biopsy and adjunctive imaging modalities such as film mammography must be followed for better detection of breast cancer

  9. Ultrasonographic findings of breast lesions

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, In Sung; Kim, Yang Soo; Suh, Hyoung Sim [College of Medicine, Daerim St. Mary' s Hospital, Seoul (Korea, Republic of)

    1990-07-15

    Authors retrospectively analyzed ultrasonographic findings of 61 cases of breast lesions which were proven pathologically at Daerim St. Mary's Hospital from May 1987 to February 1990. The results were as follows : 1. Of all 61 cases, there were 27 fibroadenomas, 13 fibrocystic diseases, 11 carcinomas, 8 abscesses, 1 sclerosing adenosis, and 1 intraductal papilloma. 2. Findings suggesting benignancy were smooth contour, round or oval shape, homogeneously echolucent internal echo, echogenic boundary echo, and posterior enhancement. In the cases of abscess, the findings were rather irregular contour, strong posterior enhancement, and dirty, inhomogeneous internal echo. While irregular and lobulated shape, inhomogeneous and mixed internal echo and pectoral muscle invasion were suggested for malignancy. 3. The sensitivity was 98% and the specificity 58% in benign mass excluding abscesses, 63% and 98% in abscesses, and 55% and 98% in carcinomas. In conclusion, ultrasonography is one of the excellent imaging modality for detecting breast lesions larger than 5 mm in size, but unfortunately some of the malignant tumors simulated benignancy, thus we considered fine needle aspiration biopsy and adjunctive imaging modalities such as film mammography must be followed for better detection of breast cancer.

  10. Imaging in cardiac mass lesions

    International Nuclear Information System (INIS)

    Mundinger, A.; Gruber, H.P.; Dinkel, E.; Geibel, A.; Beck, A.; Wimmer, B.; Schlosser, V.

    1992-01-01

    In 26 patients with cardiac mass lesions confirmed by surgery, diagnostic imaging was performed preoperatively by means of two-dimensional echocardiography (26 patients), angiography (12 patients), correlative computed tomography (CT, 8 patients), and magnetic resonance imaging (MRI, 3 patients). Two-dimensional echocardiography correctly identified the cardiac masses in all patients. Angiography missed two of 12 cardiac masses; CT missed one of eight. MRI identified three of three cardiac masses. Although the sensitivity of two-dimensional echocardiography was high (100%), all methods lacked specificity. None of the methods allowed differentiation between myxoma (n=13) and thrombus (n=7). Malignancy of the lesions was successfully predicted by noninvasive imaging methods in all six patients. However, CT and MRI provided additional information concerning cardiac mural infiltration, pericardial involvement, and extracardiac tumor extension, and should be integrated within a preoperative imaging strategy. Thus two-dimensional echocardiography is the method of choice for primary assessment of patients with suspected cardiac masses. Further preoperative imaging by CT or MRI can be limited to patients with malignancies suspected on the grounds of pericardial effusion or other clinical results. (author)

  11. Genipin cross-linked electrospun chitosan-based nanofibrous mat as tissue engineering scaffold

    Directory of Open Access Journals (Sweden)

    Esmaeil Mirzaei

    2014-04-01

    Full Text Available   Objective(s: To improve water stability of electrospun chitosan/ Polyethylene oxide (PEO nanofibers, genipin, a biocompatible and nontoxic agent, was used to crosslink chitosan based nanofibers.   Materials and Methods: Different amounts of genipin were added to the chitosan/PEO solutions, chitosan/PEO weight ratio 90/10 in 80 % acetic acid, and the solutions were then electrospun to form nanofibers. The spun nanofibers were exposed to water vapor to complete crosslinking. The nanofibrous membranes were subjected to detailed analysis by scanning electron microscopy (SEM, Fourier transform infrared-attenuated total reflection (FTIR-ATR spectroscopy, swelling test, MTT cytotoxicity, and cell attachment. Results: SEM images of electrospun mats showed that genipin-crosslinked nanofibers retained their fibrous structure after immerging in PBS (pH=7.4 for 24 hours, while the uncrosslinked samples lost their fibrous structure, indicating the water stability of genipin-crosslinked nanofibers. The genipin-crosslinked mats also showed no significant change in swelling ratio in comparison with uncrosslinked ones. FTIR-ATR spectrum of uncrosslinked and genipin-crosslinked chitosan nanofibers revealed the reaction between genipin and amino groups of chitosan. Cytotoxicity of genipin-crosslinked nanofibers was examined by MTT assay on human fibroblast cells in the presence of nanofibers extraction media. The genipin-crosslinked nanofibers did not show any toxic effects on fibroblast cells at the lowest and moderate amount of genipin. The fibroblast cells also showed a good adhesion on genipin-crosslinked nanofibers. Conclusion: This electrospun matrix would be used for biomedical applications such as wound dressing and scaffold for tissue engineering without the concern of toxicity.

  12. 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.

  13. Rational design of molecularly imprinted polymer: the choice of cross-linker.

    Science.gov (United States)

    Muhammad, Turghun; Nur, Zohre; Piletska, Elena V; Yimit, Osmanjan; Piletsky, Sergey A

    2012-06-07

    The paper describes a rational approach for the selection of cross-linkers during the development of molecularly imprinted polymers (MIPs). As a model system for this research MIPs specific for the drug zidovudine (AZT) were designed and tested. Three cross-linkers trimethylolpropane trimethacrylate (TRIM), ethylene glycol dimethacrylate (EGDMA) and divinylbenzene (DVB) were studied. The analogue of zidovudine (AZT) ester (AZT-ES) was used as a dummy template. The imprinting factors for all of the polymers in the static adsorption experiments were calculated. The data on the AZT adsorption by control polymers (CP), which were prepared with different cross-linkers without a functional monomer, was also analyzed. DVB was found to be more inert towards zidovudine than EGDMA and TRIM, which was confirmed by both molecular modelling and adsorption experiments. It was demonstrated that DVB-based polymers had a higher imprinting factor (I = 1.85) compared with other tested cross-linked polymers. It was suggested that the selection of the cross-linker should be based on the strength of the interaction with the template: the cross-linker which displays lower binding of the template should be preferential because it generates MIPs with lower non-specific binding and a higher imprinting factor, and therefore specificity. Which cross-linker to use for the preparation of any particular MIP can be determined by analysis of the interactions between the cross-linker and template. This could be done either virtually using computational modelling or by template adsorption using a small library of polymers prepared using different cross-linkers.

  14. In situ crosslinking of surface-initiated ring opening metathesis polymerization of polynorbornene for improved stability.

    Science.gov (United States)

    Fursule, Ishan A; Abtahi, Ashkan; Watkins, Charles B; Graham, Kenneth R; Berron, Brad J

    2018-01-15

    In situ crosslinking is expected to increase the solvent stability of coatings formed by surface-initiated ring opening metathesis polymerization (SI ROMP). Solvent-associated degradation limits the utility of SI ROMP coatings. SI ROMP coatings have a unique capacity for post-functionalization through reaction of the unsaturated site on the polymer backbone. Any post-reaction scheme which requires a liquid solvent has the potential to degrade the coating and lower the thickness of the resulting film. We designed a macromolecular crosslinking group based on PEG dinorbornene. The PEG length is tailored to the expected mean chain to chain distance during surface-initiated polymerization. This crosslinking macromer is randomly copolymerized with norbornene through SI ROMP on a gold coated substrate. The solvent stability of polynorbornene coatings with and without PEG dinorbornene is quantitatively determined, and the mechanism of degradation is further supported through XPS and AFM analyses. The addition of the 0.25mol% PEG dinorbornene significantly increases the solvent stability of the SI ROMP coatings. The crosslinker presence in the more stable films is supported with observable PEG absorbances by FTIR and an increase in contact angle hysteresis when compared to non-crosslinked coatings. The oxidation of the SI ROMP coatings is supported by the observation of carbonyl oxygen in the polynorbornene coatings. The rapid loss of the non-crosslinked SI ROMP coating corresponds to nanoscale pitting across the surface and micron-scale regions of widespread film loss. The crosslinked coatings have uniform nanoscale pitting, but the crosslinked films show no evidence of micron-scale film damage. In all, the incorporation of minimal crosslinking content is a simple strategy for improving the solvent stability of SI ROMP coatings. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. Photo-crosslinkable cyanoacrylate bioadhesive: shrinkage kinetics, dynamic mechanical properties, and biocompatibility of adhesives containing TMPTMA and POSS nanostructures as crosslinking agents.

    Science.gov (United States)

    Ghasaban, S; Atai, M; Imani, M; Zandi, M; Shokrgozar, M-A

    2011-11-01

    The study investigates the photo-polymerization shrinkage behavior, dynamic mechanical properties, and biocompatibility of cyanoacrylate bioadhesives containing POSS nanostructures and TMPTMA as crosslinking agents. Adhesives containing 2-octyl cyanoacrylate (2-OCA) and different percentages of POSS nanostructures and TMPTMA as crosslinking agents were prepared. The 1-phenyl-1, 2-propanedione (PPD) was incorporated as photo-initiator into the adhesive in 1.5, 3, and 4 wt %. The shrinkage strain of the specimens was measured using bonded-disk technique. Shrinkage strain, shrinkage strain rate, maximum and time at maximum shrinkage strain rate were measured and compared. Mechanical properties of the adhesives were also studied using dynamic mechanical thermal analysis (DMTA). Biocompatibility of the adhesives was examined by MTT method. The results showed that shrinkage strain increased with increasing the initiator concentration up to 3 wt % in POSS-containing and 1.5 wt % in TMPTMA-containing specimens and plateaued out at higher concentrations. By increasing the crosslinking agent, shrinkage strain, and shrinkage strain rate increased and the time at maximum shrinkage strain rate decreased. The study indicates that the incorporation of crosslinking agents into the cyanoacrylate adhesives resulted in improved mechanical properties. Preliminary MTT studies also revealed better biocompatibility profile for the adhesives containing crosslinking agents comparing to the neat specimens. Copyright © 2011 Wiley Periodicals, Inc.

  16. Fanconi anaemia and the repair of Watson and Crick DNA crosslinks.

    Science.gov (United States)

    Kottemann, Molly C; Smogorzewska, Agata

    2013-01-17

    The function of Fanconi anaemia proteins is to maintain genomic stability. Their main role is in the repair of DNA interstrand crosslinks, which, by covalently binding the Watson and the Crick strands of DNA, impede replication and transcription. Inappropriate repair of interstrand crosslinks causes genomic instability, leading to cancer; conversely, the toxicity of crosslinking agents makes them a powerful chemotherapeutic. Fanconi anaemia proteins can promote stem-cell function, prevent tumorigenesis, stabilize replication forks and inhibit inaccurate repair. Recent advances have identified endogenous aldehydes as possible culprits of DNA damage that may induce the phenotypes seen in patients with Fanconi anaemia.

  17. Preparation of Citric Acid Crosslinked Chitosan/Poly(Vinyl Alcohol Blend Membranes for Creatinine Transport

    Directory of Open Access Journals (Sweden)

    Retno Ariadi Lusiana

    2016-08-01

    Full Text Available Preparation of membrane using crosslinking reaction between chitosan and citric acid showed that functional group modification increased the number of active carrier groups which lead to better transport capacity of the membrane. In addition, the substitution of the carboxyl group increased creatinine permeation of chitosan membrane. The transport capacity of citric acid crosslinked chitosan membrane for creatinine was found to be 6.3 mg/L. The presence of cyanocobalamin slightly hindered the transport of creatinine although compounds did not able to pass through citric acid crosslinked chitosan/poly(vinyl alcohol blend membrane, as compounds no found in the acceptor phase.

  18. Pressure effects on the crosslinking by gamma radiation of commercial vinil polymers

    International Nuclear Information System (INIS)

    Lopez V, D.; Burillo, G.

    1991-01-01

    Gamma-ray induced crosslinking of some commercial polymers was investigated. Polypropylene, polystyrene, polyvinilchloride, polyacrylamide and polyvinilalcohol were compressed to disks and the effect to pressure on the crosslinking was studied. In all the cases, the crosslinking yield increased significantly by compressing the polymers. This is probably because oxygen is removed from polymer by the effect of the pressure and therefore the chain scission is prevented. The effect of pressure is also due to the decrease in the intermolecular distance and thus the coupling of polymer radicals is facilitated. (Author)

  19. Melt-processable, radiation cross-linkable E--CTFE copolymer compositions

    International Nuclear Information System (INIS)

    Robertson, A.B.; Schaffhauser, R.J.

    1976-01-01

    Melt-processable, radiation cross-linkable ethylene/chlorotrifluoroethylene copolymer compositions are provided which contain about 0.1 to 5 percent by weight of the copolymer of a radiation cross-linking promoter, about 0.01 to 5 percent by weight of an anti-oxidant and about 0.1 to 30 precent by weight of an acid scavenger. Such compositions do not give off odors when irradiated to cross-link the copolymer and do not develop bubbles after irradiation. 15 claims, no drawings

  20. Crosslinked Hexafluoropropylidene Polybenzimidazole Membranes with Chloromethyl Polysulfone for Fuel Cell Applications

    DEFF Research Database (Denmark)

    Yang, Jingshuai; Li, Qingfeng; Cleemann, Lars Nilausen

    2013-01-01

    Hexafluoropropylidene polybenzimidazole (F6PBI) was synthesized with excellent chemical stability and improved solubility. When doped with phosphoric acid, however, the F6PBI membranes showed plastic deformation at elevated temperatures. Further efforts were made to covalently crosslink F6PBI...... membranes with chloromethyl polysulfone as a polymeric crosslinker. Comparing with linear F6PBI and mPBI membranes, the polymer crosslinked F6PBI membranes exhibited little organo solubility, excellent stability towards the radical oxidation, high resistance to swelling in concentrated phosphoric acid...... with the linear F6PBI and mPBI membranes....

  1. 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.

  2. Hardness enhancement and crosslinking mechanisms in polystyrene irradiated with high energy ion-beams

    International Nuclear Information System (INIS)

    Lee, E.H.; Rao, G.R.; Mansur, L.K.

    1996-01-01

    Surface hardness values several times larger than steel were produced using high energy ion beams at several hundred keV to MeV. High LET is important for crosslinking. Crosslinking is studied by analyzing hardness variations in response to irradiation parameter such as ion species, energy, and fluence. Effective crosslinking radii at hardness saturation are derived base on experimental data for 350 keV H + and 1 MeV Ar + irradiation of polystyrene. Saturation value for surface hardness is about 20 GPa

  3. Preliminary histopathological study of intra-articular injection of a novel highly cross-linked hyaluronic acid in a rabbit model of knee osteoarthritis.

    Science.gov (United States)

    Iannitti, Tommaso; Elhensheri, Mohamed; Bingöl, Ali O; Palmieri, Beniamino

    2013-04-01

    Osteoarthritis is a degenerative joint disease mostly occurring in the knee and commonly seen in middle-aged and elderly adults. Intra-articular injection of hyaluronic acid has been widely used for treatment of knee osteoarthritis. The aim of this study was to evaluate the efficacy of intra-articular injection of a novel highly cross-linked hyaluronic acid, alone or in combination with ropivacaine hydrochloride and triamcinolone acetonide, on knee articular cartilage in a rabbit model of collagenase-induced knee osteoarthritis. After induction of experimental osteoarthritis by intra-articular injection of collagenase, adult New Zealand white rabbits (n = 12) were divided into 3 groups. Group 1 (control group) received 0.3 ml phosphate buffered saline into the right knee joint. Group 2 received 0.3 ml cross-linked hyaluronic acid (33 mg/ml) into the right knee joint. Group 3 received a mixture of 0.15 ml cross-linked hyaluronic acid (33 mg/ml), 0.05 ml ropivacaine hydrochloride 1 % and 0.1 ml triamcinolone acetonide (10 mg/ml) into the right knee joint. Intra-articular injections were given 4 weeks after first collagenase injection and were administered once a week for 3 weeks. Gross pathology and histological evaluation of rabbits' knee joints were performed after 16 weeks following initial collagenase injection. Histological analysis of sections of right knee joints at lesion sites showed a significant decrease in Mankin's score in groups treated with hyaluronic acid alone or in combination with ropivacaine hydrochloride and triamcinolone acetonide versus control group (p hyaluronic acid, alone or in combination with ropivacaine hydrochloride and triamcinolone acetonide, produces a significant improvement in knee articular cartilage degeneration in a rabbit model of collagenase-induced osteoarthritis.

  4. Evaluation of corneal symmetry after UV corneal crosslinking for keratoconus

    Directory of Open Access Journals (Sweden)

    Mofty H

    2017-11-01

    Full Text Available Hanan Mofty,1,2 Khaled Alzahrani,2 Fiona Carley,3 Sophie Harper,3 Arun Brahma,3 Leon Au,3 Debbie Morley,3 M Chantal Hillarby2 1Optometry Department, College of Applied Medical Science, King Saud University, Riyadh, Kingdom of Saudi Arabia; 2Division of Pharmacy and Optometry, School of Health Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, 3Manchester Royal Eye Hospital, Manchester, UK Purpose: The purpose of this study was to assess UV corneal crosslinking (CXL treatment outcomes for keratoconus by evaluating the corneal regularity in patients through follow-up using the Oculus Pentacam.Patients and methods: A total of 18 eyes from CXL patients with keratoconus were studied before and after CXL treatment, and six eyes from six patients who were not treated with CXL served as controls. Treated patients had Pentacam images taken before CXL treatment and regularly 3 months post treatment up to the 12th month. Controls were imaged during their first appointment and after 12 months. Symmetry and asphericity were evaluated and correlated with both best-corrected visual acuity (BCVA and maximum K-readings.Results: In the CXL-treated group, there was a significant improvement in the index of symmetrical variation (ISV and keratoconus index (KI at 3 months and in the index of height asymmetry (IHA and minimum radius of curvature (Rmin at 9 months post treatment. On the contrary, the untreated group’s indices showed some significant worsening in ISV, KI, central keratoconus index (CKI, and Rmin. A novel finding in our study was a slight positive shift of anterior asphericity in the 6 mm, 7 mm, and 8 mm 3 months after treatment, which had a correlation with BCVA (R2=0.390, p=0.053 and a strong correlation with maximum K-reading (R2=0.690, p=0.005. However, the untreated group had no significant changes after 1 year.Conclusion: The corneal asymmetrical shape is associated with the spherical aberration alteration

  5. Mechanically Strong, Polymer Cross-linked Aerogels (X-Aerogels)

    Science.gov (United States)

    Leventis, Nicholas

    2006-01-01

    Aerogels comprise a class of low-density, high porous solid objects consisting of dimensionally quasi-stable self-supported three-dimensional assemblies of nanoparticles. Aerogels are pursued because of properties above and beyond those of the individual nanoparticles, including low thermal conductivity, low dielectric constant and high acoustic impedance. Possible applications include thermal and vibration insulation, dielectrics for fast electronics, and hosting of functional guests for a wide variety of optical, chemical and electronic applications. Aerogels, however, are extremely fragile materials, hence they have found only limited application in some very specialized environments, for example as Cerenkov radiation detectors in certain types of nuclear reactors, aboard spacecraft as collectors of hypervelocity particles (refer to NASA's Stardust program) and as thermal insulators on planetary vehicles on Mars (refer to Sojourner Rover in 1997 and Spirit and Opportunity in 2004). Along these lines, the X-Aerogel is a new NASA-developed strong lightweight material that has resolved the fragility problem of traditional (native) aerogels. X-Aerogels are made by applying a conformal polymer coating on the surfaces of the skeletal nanoparticles of native aerogels (see Scanning Electron Micrographs). Since the relative amounts of the polymeric crosslinker and the backbone are comparable, X-Aerogels can be viewed either as aerogels modified by the templated accumulation of polymer on the skeletal nanoparticles, or as nanoporous polymers made by remplated casting of polymer on a nanostructured framework. The most striking feature of X-Aerogels is that for a nominal 3-fold increase in density (still a ultralighweight material), the mechanical strength can be up to 300 times higher than the strength of the underlying native aerogel. Thus, X-Aerogels combine a multiple of the specific compressive strength of steel, with the the thermal conductivity of styrofoam. X

  6. Friedel–Crafts Crosslinked Highly Sulfonated Polyether Ether Ketone (SPEEK Membranes for a Vanadium/Air Redox Flow Battery

    Directory of Open Access Journals (Sweden)

    Géraldine Merle

    2013-12-01

    Full Text Available Highly conductive and low vanadium permeable crosslinked sulfonated poly(ether ether ketone (cSPEEK membranes were prepared by electrophilic aromatic substitution for a Vanadium/Air Redox Flow Battery (Vanadium/Air-RFB application. Membranes were synthesized from ethanol solution and crosslinked under different temperatures with 1,4-benzenedimethanol and ZnCl2 via the Friedel–Crafts crosslinking route. The crosslinking mechanism under different temperatures indicated two crosslinking pathways: (a crosslinking on the sulfonic acid groups; and (b crosslinking on the backbone. It was observed that membranes crosslinked at a temperature of 150 °C lead to low proton conductive membranes, whereas an increase in crosslinking temperature and time would lead to high proton conductive membranes. High temperature crosslinking also resulted in an increase in anisotropy and water diffusion. Furthermore, the membranes were investigated for a Vanadium/Air Redox Flow Battery application. Membranes crosslinked at 200 °C for 30 min with a molar ratio between 2:1 (mol repeat unit:mol benzenedimethanol showed a proton conductivity of 27.9 mS/cm and a 100 times lower VO2+ crossover compared to Nafion.

  7. Friedel–Crafts Crosslinked Highly Sulfonated Polyether Ether Ketone (SPEEK) Membranes for a Vanadium/Air Redox Flow Battery

    Science.gov (United States)

    Merle, Géraldine; Ioana, Filipoi Carmen; Demco, Dan Eugen; Saakes, Michel; Hosseiny, Seyed Schwan

    2014-01-01

    Highly conductive and low vanadium permeable crosslinked sulfonated poly(ether ether ketone) (cSPEEK) membranes were prepared by electrophilic aromatic substitution for a Vanadium/Air Redox Flow Battery (Vanadium/Air-RFB) application. Membranes were synthesized from ethanol solution and crosslinked under different temperatures with 1,4-benzenedimethanol and ZnCl2 via the Friedel–Crafts crosslinking route. The crosslinking mechanism under different temperatures indicated two crosslinking pathways: (a) crosslinking on the sulfonic acid groups; and (b) crosslinking on the backbone. It was observed that membranes crosslinked at a temperature of 150 °C lead to low proton conductive membranes, whereas an increase in crosslinking temperature and time would lead to high proton conductive membranes. High temperature crosslinking also resulted in an increase in anisotropy and water diffusion. Furthermore, the membranes were investigated for a Vanadium/Air Redox Flow Battery application. Membranes crosslinked at 200 °C for 30 min with a molar ratio between 2:1 (mol repeat unit:mol benzenedimethanol) showed a proton conductivity of 27.9 mS/cm and a 100 times lower VO2+ crossover compared to Nafion. PMID:24957118

  8. Friedel-Crafts Crosslinked Highly Sulfonated Polyether Ether Ketone (SPEEK) Membranes for a Vanadium/Air Redox Flow Battery.

    Science.gov (United States)

    Merle, Géraldine; Ioana, Filipoi Carmen; Demco, Dan Eugen; Saakes, Michel; Hosseiny, Seyed Schwan

    2013-12-30

    Highly conductive and low vanadium permeable crosslinked sulfonated poly(ether ether ketone) (cSPEEK) membranes were prepared by electrophilic aromatic substitution for a Vanadium/Air Redox Flow Battery (Vanadium/Air-RFB) application. Membranes were synthesized from ethanol solution and crosslinked under different temperatures with 1,4-benzenedimethanol and ZnCl2 via the Friedel-Crafts crosslinking route. The crosslinking mechanism under different temperatures indicated two crosslinking pathways: (a) crosslinking on the sulfonic acid groups; and (b) crosslinking on the backbone. It was observed that membranes crosslinked at a temperature of 150 °C lead to low proton conductive membranes, whereas an increase in crosslinking temperature and time would lead to high proton conductive membranes. High temperature crosslinking also resulted in an increase in anisotropy and water diffusion. Furthermore, the membranes were investigated for a Vanadium/Air Redox Flow Battery application. Membranes crosslinked at 200 °C for 30 min with a molar ratio between 2:1 (mol repeat unit:mol benzenedimethanol) showed a proton conductivity of 27.9 mS/cm and a 100 times lower VO2+ crossover compared to Nafion.

  9. Treatment of metastatic brain lesion

    Directory of Open Access Journals (Sweden)

    A. M. Zaytsev

    2015-01-01

    Full Text Available Objective. Increasing survival in patients with secondary brain damage, and identifying the factors of favorable and adverse prognosis.Material and method. In P. A. Hertsen Moscow Oncology Research Institute from 2007 to 2013 there were treated 268 patients with brain metastases. The mean age was 55.8 years (from 24 to 81 years. Metastases of colorectal cancer identified in 7.8%, cases of lung cancer in 34%, melanoma 9.3 %, breast cancer in 26%, kidney cancer in 11%, with non-identified primary tumor in 4.5%, other tumors accounted for 6.7%. Solitary metastasis was diagnosed in 164 (61,19% patients, oligometastasis (2-3 - 72 (26,87% patients with polymetastasis (more than 3 – 32 (11,94% patients. In 106 (39,55% of patients with brain metastases it was the only manifestation of the generalization process. To control the radical removal of the tumor in 93 (34,7% patients we used the method of fluorescence navigation (FN with the drug Alasens. In 66 (24,6% patients intraoperatively was held a session of photodynamic therapy (PDT. In 212 (79,1% cases, the removal of metastasis performed totally, 55 (20,9% patients stated Subtotal removal.Results. The observation period for the patients ranged from 3 to 79 months. Survival median among the entire group of patients with metastatic brain lesion was 12 months. Overall survival was significantly dependent on RPA class, the volume of postoperative treatment, histological type of primary tumor, number of intracerebral metastases and the timing of the relapse-free period.Conclusions. Factors that affects the overall survival are the features of the histology of the primary lesion, multiplicity of metastatic lesions, RPA class and the synchronous nature of the metastasis. The median of overall survival of patients who did not receive after surgical treatment of a particular type of therapy was only 4 months. If to use the combined treatment (surgical treatment with the irradiation of the whole brain median

  10. Reduction-responsive interlayer-crosslinked micelles prepared from star-shaped copolymer via click chemistry for drug controlled release

    Science.gov (United States)

    Dai, Yu; Wang, Hongquan; Zhang, Xiaojin

    2017-12-01

    To improve the stability of polymeric micelles, here we describe interlayer-crosslinked micelles prepared from star-shaped copolymer via click chemistry. The formation of interlayer-crosslinked micelles was investigated and confirmed by proton nuclear magnetic resonance, Fourier-transform infrared spectroscopy, and fluorescence spectroscopy. The morphology of un-crosslinked micelles and crosslinked micelles observed by transmission electron microscope is both uniform nano-sized spheres (approximately 20 nm). The crosslinking enhances the stability of polymeric micelles and improves the drug loading capacity of polymeric micelles. The interlayer-crosslinked micelles prepared from star-shaped copolymer and a crosslinker containing a disulfide bond are reduction-responsive and can release the drug quickly in the presence of the reducing agents such as glutathione (GSH).

  11. Downregulation of SWI/SNF chromatin remodeling factor subunits modulates cisplatin cytotoxicity

    International Nuclear Information System (INIS)

    Kothandapani, Anbarasi; Gopalakrishnan, Kathirvel; Kahali, Bhaskar; Reisman, David; Patrick, Steve M.

    2012-01-01

    Chromatin remodeling complex SWI/SNF plays important roles in many cellular processes including transcription, proliferation, differentiation and DNA repair. In this report, we investigated the role of SWI/SNF catalytic subunits Brg1 and Brm in the cellular response to cisplatin in lung cancer and head/neck cancer cells. Stable knockdown of Brg1 and Brm enhanced cellular sensitivity to cisplatin. Repair kinetics of cisplatin DNA adducts revealed that downregulation of Brg1 and Brm impeded the repair of both intrastrand adducts and interstrand crosslinks (ICLs). Cisplatin ICL-induced DNA double strand break repair was also decreased in Brg1 and Brm depleted cells. Altered checkpoint activation with enhanced apoptosis as well as impaired chromatin relaxation was observed in Brg1 and Brm deficient cells. Downregulation of Brg1 and Brm did not affect the recruitment of DNA damage recognition factor XPC to cisplatin DNA lesions, but affected ERCC1 recruitment, which is involved in the later stages of DNA repair. Based on these results, we propose that SWI/SNF chromatin remodeling complex modulates cisplatin cytotoxicity by facilitating efficient repair of the cisplatin DNA lesions. -- Highlights: ► Stable knockdown of Brg1 and Brm enhances cellular sensitivity to cisplatin. ► Downregulation of Brg1 and Brm impedes the repair of cisplatin intrastrand adducts and interstrand crosslinks. ► Brg1 and Brm deficiency results in impaired chromatin relaxation, altered checkpoint activation as well as enhanced apoptosis. ► Downregulation of Brg1 and Brm affects recruitment of ERCC1, but not XPC to cisplatin DNA lesions.

  12. Long-Chain Diacrylate Crosslinkers and Use of PEG Crosslinks in Poly(potassium acrylate-acrylic acid/Kaolin Composite Superabsorbents

    Directory of Open Access Journals (Sweden)

    Koroush Kabiri

    2013-01-01

    Full Text Available Long-chain diacrylate crosslinkers based on linear α,ω-diols were synthesized and characterized using FTIR and 1H NMR spectroscopy. The highest reaction yield (99.5% was due to polyethylene glycol diacrylate 1000 (PEGDA-1000. Then, kaolin-containing poly(potassium acrylate-acrylic acid superabsorbent composites and kaolin-free counterparts were synthesized using PEGDA-1000.The effect of the crosslinker concentration on swelling, rheological and thermo-mechanical properties was investigated. Absorption capacity of the composite hydrogels (having ~38% kaolin was unexpectedly higher than that of kaolin-free hydrogels. This was attributed to an interfering effect of kaolin during the polymerization. Glass transition temperature was increased with crosslinker concentration enhancement and addition of kaolin up to about 10oC and 28oC, respectively. Making such K-containing superabsorbents may be taken as an effective action to achieve more durable and cheaper superabsorbents for agricultural uses.

  13. Crystal structure of a Fanconi anemia-associated nuclease homolog bound to 5' flap DNA: basis of interstrand cross-link repair by FAN1

    Energy Technology Data Exchange (ETDEWEB)

    Gwon, Gwang Hyeon; Kim, Youngran; Liu, Yaqi; Watson, Adam T.; Jo, Aera; Etheridge, Thomas J.; Yuan, Fenghua; Zhang, Yanbin; Kim, YoungChang; Carr, Anthony M.; Cho, Yunje

    2014-10-15

    Fanconi anemia (FA) is an autosomal recessive genetic disorder caused by defects in any of 15 FA genes responsible for processing DNA interstrand cross-links (ICLs). The ultimate outcome of the FA pathway is resolution of cross-links, which requires structure-selective nucleases. FA-associated nuclease 1 (FAN1) is believed to be recruited to lesions by a monoubiquitinated FANCI–FANCD2 (ID) complex and participates in ICL repair. Here, we determined the crystal structure of Pseudomonas aeruginosa FAN1 (PaFAN1) lacking the UBZ (ubiquitin-binding zinc) domain in complex with 5' flap DNA. All four domains of the right-hand-shaped PaFAN1 are involved in DNA recognition, with each domain playing a specific role in bending DNA at the nick. The six-helix bundle that binds the junction connects to the catalytic viral replication and repair (VRR) nuclease (VRR nuc) domain, enabling FAN1 to incise the scissile phosphate a few bases distant from the junction. The six-helix bundle also inhibits the cleavage of intact Holliday junctions. PaFAN1 shares several conserved features with other flap structure-selective nucleases despite structural differences. A clamping motion of the domains around the wedge helix, which acts as a pivot, facilitates nucleolytic cleavage. The PaFAN1 structure provides insights into how archaeal Holliday junction resolvases evolved to incise 5' flap substrates and how FAN1 integrates with the FA complex to participate in ICL repair.

  14. 'Emotional Intelligence': Lessons from Lesions.

    Science.gov (United States)

    Hogeveen, J; Salvi, C; Grafman, J

    2016-10-01

    'Emotional intelligence' (EI) is one of the most highly used psychological terms in popular nomenclature, yet its construct, divergent, and predictive validities are contentiously debated. Despite this debate, the EI construct is composed of a set of emotional abilities - recognizing emotional states in the self and others, using emotions to guide thought and behavior, understanding how emotions shape behavior, and emotion regulation - that undoubtedly influence important social and personal outcomes. In this review, evidence from human lesion studies is reviewed in order to provide insight into the necessary brain regions for each of these core emotional abilities. Critically, we consider how this neuropsychological evidence might help to guide efforts to define and measure EI. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Imaging of extradural spinal lesions

    International Nuclear Information System (INIS)

    Ahlhelm, F.; Schulte-Altedorneburg, G.; Naumann, N.; Reith, W.; Nabhan, A.

    2006-01-01

    There is a wide variety of spinal extradural tumors. In addition to real neoplasms, degenerative diseases, congenital abnormalities and inflammatory disorders can be causes of extradural masses. Due to the bony boundary of the spinal canal, both benign as well as malignant masses can cause progressive neurological deficits including paraplegia. Most of the spinal tumors are benign (hemangioma of the vertebral body, degenerative diseases). In younger patients congenital abnormalities and primary tumors of the spine have to be considered, whereas in adults the list of differential diagnoses should include secondary malignancies such as metastases and lymphomas as well as metabolic disorders such as osteoporotic vertebral compression fracture and Paget's disease. Cross-sectional imaging techniques such as magnetic resonance imaging (MRI) and computed tomography (CT) of the spine often help to make a specific diagnosis of extradural spinal lesions and represent important tools for tumor staging and preoperative evaluation. (orig.) [de

  16. Chemometric, physicomechanical and rheological analysis of the sol-gel dynamics and degree of crosslinking of glycosidic polymers

    International Nuclear Information System (INIS)

    Choonara, Y E; Pillay, V; Singh, N; Ndesendo, V M K; Khan, R A

    2008-01-01

    The influence of calcium (Ca 2+ ), zinc (Zn 2+ ) and barium (Ba 2+ ) ions on the sol-gel interconversion dynamics, degree of crosslinking and the matrix resilience of crosslinked alginate gelispheres was determined. The dependent compositional and operational variables of crosslinking make it a challenging task to optimize the degree of crosslinking and the physicomechanical properties of alginate gelispheres. The combinatory approach of textural profiling, assessing pertinent rheological descriptors and chemometric model analysis of the sol-gel interconversion mechanisms and energy paradigms involved during crosslinking, hydration and erosion of gelispheres was explored. Molecular structural modelling of the gelispheres provided a mechanistic understanding of the sol-gel interconversion phenomena and their influence on the degree of crosslinking, the hydrational dynamics and gelisphere formation. Rheological analysis revealed offset yield point values of 6.1 mg ml -1 and 8.0 mg ml -1 were computed from fitted regression curves for determining the crosslinker concentration required for combinatory crosslinkers such as Ca/Zn/Ba ions and Ba/Zn, respectively. The influence of hydration on the erosion was a direct function of the gelispheres physicomechanical strength. Textural profiling characterized the gelisphere matrices for their resilience. The various crosslinkers interacted with monomeric units at varying intensities. Ba-crosslinked gelispheres were brittle with dense polymeric networks. Zn-crosslinked gelispheres produced permeable resilient matrices when hydrated and Ca-crosslinked gelispheres demonstrated intermediate resilience with greater G/M ratio alginate grades. Chemometrical analysis explicated a potential link between several phenomena such as the type of crosslinkers employed, the static shear-rate viscosity attained, the matrix resilience and the associated sol-gel mechanisms and energy paradigms of crosslinked gelispheres

  17. Cutaneous lesions in new born

    Directory of Open Access Journals (Sweden)

    Sachdeva Meenakshi

    2002-11-01

    Full Text Available Five hundred unselected newborn babies delivered in the Department of Obstetrics and Gynaecology, Unit II of SGBT Hospital attached to Government Medical College, Amritsar during April 2000 to October 2000 were examined for cutaneous lesions daily for the first five days after birth. Different cutaneous lesions were seen in 474(94. 8% newborns. The physiological skin changes observed in order of frequency were Epstein pearls in 305(61%, Mongolian spot in 301(60. 2%, superficial cutaneous desquamation in 200(40%, icterus in 128(25. 6%, milia in 119(23. 8%, sebaceous gland hyperplasia in 107 (21. 4%, occipital alopecia in 94(18. 8%, lanugo in 72(14. 4%, peripheral cyanosis in 47(9. 4%, breast hypertrophy in 29(5. 8% and miniature puberty in 28(5. 6% newborns. Of the transient non-infective skin diseases, erythema toxicum neonatorum was observed most commonly in 105(21 %, followed by miliaria rubra in 103(20. 6% and acne neonatorum in 27(5. 4% newborns. The naevi and other developmental defects in the descending order were salmon patch in 69(13. 8%, congenital melanocytic noevi in 10(2%, accessory tragi in 3(0.6%, spina bifida in 2(0.4%, hydrocephalus in 1(0.2% and poliosis in 1(0.2% newborns. Cradle cap was the only dermatitis observed in 50(10% newborns. One (0.2% case each of Harlequin ichthyosis and labial cyst was seen.

  18. Energy harvesting from vibration with cross-linked polypropylene piezoelectrets

    Directory of Open Access Journals (Sweden)

    Xiaoqing Zhang

    2015-07-01

    Full Text Available Piezoelectret films are prepared by modification of the microstructure of polypropylene foam sheets cross-linked by electronic irradiation (IXPP, followed by proper corona charging. Young’s modulus, relative permittivity, and electromechanical coupling coefficient of the fabricated films, determined by dielectric resonance spectra, are about 0.7 MPa, 1.6, and 0.08, respectively. Dynamic piezoelectric d33 coefficients up to 650 pC/N at 200 Hz are achieved. The figure of merit (FOM, d33 ⋅ g33 for a more typical d33 value of 400 pC/N is about 11.2 GPa−1. Vibration-based energy harvesting with one-layer and two-layer stacks of these films is investigated at various frequencies and load resistances. At an optimum load resistance of 9 MΩ and a resonance frequency of 800 Hz, a maximum output power of 120 μW, referred to the acceleration g due to gravity, is obtained for an energy harvester consisting of a one-layer IXPP film with an area of 3.14 cm2 and a seismic mass of 33.7 g. The output power can be further improved by using two-layer stacks of IXPP films in electric series. IXPP energy harvesters could be used to energize low-power electronic devices, such as wireless sensors and LED lights.

  19. Energy harvesting from vibration with cross-linked polypropylene piezoelectrets

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiaoqing [Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology & School of Physics Science and Engineering, Tongji University, Shanghai 200092 (China); Institute for Telecommunications Technology, Merckstrasse 25, 64283 Darmstadt (Germany); Wu, Liming [Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology & School of Physics Science and Engineering, Tongji University, Shanghai 200092 (China); Sessler, Gerhard M., E-mail: g.sessler@nt.tu-darmstadt.de [Institute for Telecommunications Technology, Merckstrasse 25, 64283 Darmstadt (Germany)

    2015-07-15

    Piezoelectret films are prepared by modification of the microstructure of polypropylene foam sheets cross-linked by electronic irradiation (IXPP), followed by proper corona charging. Young’s modulus, relative permittivity, and electromechanical coupling coefficient of the fabricated films, determined by dielectric resonance spectra, are about 0.7 MPa, 1.6, and 0.08, respectively. Dynamic piezoelectric d{sub 33} coefficients up to 650 pC/N at 200 Hz are achieved. The figure of merit (FOM, d{sub 33} ⋅ g{sub 33}) for a more typical d{sub 33} value of 400 pC/N is about 11.2 GPa{sup −1}. Vibration-based energy harvesting with one-layer and two-layer stacks of these films is investigated at various frequencies and load resistances. At an optimum load resistance of 9 MΩ and a resonance frequency of 800 Hz, a maximum output power of 120 μW, referred to the acceleration g due to gravity, is obtained for an energy harvester consisting of a one-layer IXPP film with an area of 3.14 cm{sup 2} and a seismic mass of 33.7 g. The output power can be further improved by using two-layer stacks of IXPP films in electric series. IXPP energy harvesters could be used to energize low-power electronic devices, such as wireless sensors and LED lights.

  20. Elasticity in Physically Cross-Linked Amyloid Fibril Networks

    Science.gov (United States)

    Cao, Yiping; Bolisetty, Sreenath; Adamcik, Jozef; Mezzenga, Raffaele

    2018-04-01

    We provide a constitutive model of semiflexible and rigid amyloid fibril networks by combining the affine thermal model of network elasticity with the Derjaguin-Landau-Vervey-Overbeek (DLVO) theory of electrostatically charged colloids. When compared to rheological experiments on β -lactoglobulin and lysozyme amyloid networks, this approach provides the correct scaling of elasticity versus both concentration (G ˜c2.2 and G ˜c2.5 for semiflexible and rigid fibrils, respectively) and ionic strength (G ˜I4.4 and G ˜I3.8 for β -lactoglobulin and lysozyme, independent from fibril flexibility). The pivotal role played by the screening salt is to reduce the electrostatic barrier among amyloid fibrils, converting labile physical entanglements into long-lived cross-links. This gives a power-law behavior of G with I having exponents significantly larger than in other semiflexible polymer networks (e.g., actin) and carrying DLVO traits specific to the individual amyloid fibrils.

  1. Adjuvant corneal crosslinking to prevent hyperopic LASIK regression.

    Science.gov (United States)

    Aslanides, Ioannis M; Mukherjee, Achyut N

    2013-01-01

    To report the long term outcomes, safety, stability, and efficacy in a pilot series of simultaneous hyperopic laser assisted in situ keratomileusis (LASIK) and corneal crosslinking (CXL). A small cohort series of five eyes, with clinically suboptimal topography and/or thickness, underwent LASIK surgery with immediate riboflavin application under the flap, followed by UV light irradiation. Postoperative assessment was performed at 1, 3, 6, and 12 months, with late follow up at 4 years, and results were compared with a matched cohort that received LASIK only. The average age of the LASIK-CXL group was 39 years (26-46), and the average spherical equivalent hyperopic refractive error was +3.45 diopters (standard deviation 0.76; range 2.5 to 4.5). All eyes maintained refractive stability over the 4 years. There were no complications related to CXL, and topographic and clinical outcomes were as expected for standard LASIK. This limited series suggests that simultaneous LASIK and CXL for hyperopia is safe. Outcomes of the small cohort suggest that this technique may be promising for ameliorating hyperopic regression, presumed to be biomechanical in origin, and may also address ectasia risk.

  2. Adjuvant corneal crosslinking to prevent hyperopic LASIK regression

    Directory of Open Access Journals (Sweden)

    Aslanides IM

    2013-03-01

    Full Text Available Ioannis M Aslanides, Achyut N MukherjeeEmmetropia Mediterranean Eye Clinic, Heraklion, Crete, GreecePurpose: To report the long term outcomes, safety, stability, and efficacy in a pilot series of simultaneous hyperopic laser assisted in situ keratomileusis (LASIK and corneal crosslinking (CXL.Method: A small cohort series of five eyes, with clinically suboptimal topography and/or thickness, underwent LASIK surgery with immediate riboflavin application under the flap, followed by UV light irradiation. Postoperative assessment was performed at 1, 3, 6, and 12 months, with late follow up at 4 years, and results were compared with a matched cohort that received LASIK only.Results: The average age of the LASIK-CXL group was 39 years (26–46, and the average spherical equivalent hyperopic refractive error was +3.45 diopters (standard deviation 0.76; range 2.5 to 4.5. All eyes maintained refractive stability over the 4 years. There were no complications related to CXL, and topographic and clinical outcomes were as expected for standard LASIK.Conclusion: This limited series suggests that simultaneous LASIK and CXL for hyperopia is safe. Outcomes of the small cohort suggest that this technique may be promising for ameliorating hyperopic regression, presumed to be biomechanical in origin, and may also address ectasia risk.Keyword: CXL

  3. Cross-linking da cornea: protocolo padrão

    Directory of Open Access Journals (Sweden)

    Marcony R. Santhiago

    Full Text Available RESUMO O objetivo desta revisão é de determinar as indicações e eficácia da cirurgia que promove novas ligações covalentes entre as fibras de colágeno da córnea, conhecida como Cross-Linking (CXL, assim como esclarecer seus objetivos. O ceratocone é uma doença ectasica da córnea, bilateral, assimétrica, que, principalmente, cursa com encurvamento e afinamentos progressivo, e se inicia em geral na segunda década de vida. O uso primário do CXL tem sido na interrupção da progressão do Ceratocone. Apesar do conhecido encurvamento no estroma da córnea ocorrer nesses pacientes, a fisiopatologia por trás do ceratocone ainda é desconhecida e parece ser multifatorial. Pela evidencia literária disponível até o momento, o CXL da córnea esta, portanto indicado nos pacientes com doença em progressão. Concluímos que existe evidencia suficiente para afirmar que o CXL da córnea é eficaz na estabilização da doença ectásica da cornea.

  4. Synthesis and Properties of Cross-Linked Polyamide Aerogels

    Science.gov (United States)

    Williams, Jarrod C.; Meador, Mary Ann; McCorkle, Linda

    2015-01-01

    We report the first synthesis of cross-linked polyamide aerogels through step growth polymerization using a combination of diamines, diacid chloride and triacid chloride. Polyamide oligomers endcapped with amines are prepared as stable solutions in N-methylpyrrolidinone from several different diamine precursors and 1,3-benzenedicarbonyl dichloride. Addition of 1,3,5-benzenetricarbonyl trichloride yields gels which form in under five minutes according to the scheme shown. Solvent exchange of the gels into ethanol, followed by drying using supercritical CO2 extraction gives colorless aerogels with densities around 0.1 to 0.2 gcm3. Thicker monolithes of the polyamide aerogels are stiff and strong, while thin films of certain formulations are highly flexible, durable, and even translucent. These materials may have use as insulation for deployable space structures, rovers, habitats or extravehicular activity suits as well as in many terrestrial applications. Strucure property relationships of the aerogels, including surface area, mechanical properties, and thermal conductivity will be discussed.

  5. Electrochemical behavior of ionically crosslinked polyampholytic gel electrolytes

    International Nuclear Information System (INIS)

    Chen Wanyu; Tang Haitao; Ou Ziwei; Wang Hong; Yang Yajiang

    2007-01-01

    An ionic complex of anionic and cationic monomers was obtained by protonation of (N,N-diethylamino)ethylmethacrylate (DEA) with acrylic acid (AAc). Free radical copolymerization of the ionic complex and acrylamide (AAm), yielded the ionically crosslinked polyampholytic gel electrolytes [poly(AAc-DEA-AAm), designated as PADA] using two types of organic solvents containing a lithium salt. The PADA gel electrolyte exhibited good thermal stability shown by the DSC thermogram. The impedance analysis at temperatures ranging from -30 to 75 deg. C indicated that the ionic conductivities of the PADA gel electrolytes were rather close to those of liquid electrolytes. The temperature dependence of the ionic conductivities was found to be in accord with the Arrhenius equation. Moreover, the ionic conductivities of PADA gel electrolytes increased with an increase of the molar ratios of cationic/anionic monomers. The ionic conductivities of PADA gels prepared in solvent mixtures of propylene carbonate, ethyl methyl ether and dioxolane (3:1:1, v/v) were higher than those of PADA gels prepared in propylene carbonate only. Significantly, the ionic conductivities of two kinds of PADA gel electrolytes were in the range of 10 -3 and 10 -4 S cm -1 even at -30 deg. C. The electrochemical windows of PADA gel electrolytes measured by cyclic voltammetry were in the range from -1 V to 4.5 V

  6. Fabrication of superhydrophobic cotton fabrics using crosslinking polymerization method

    Science.gov (United States)

    Jiang, Bin; Chen, Zhenxing; Sun, Yongli; Yang, Huawei; Zhang, Hongjie; Dou, Haozhen; Zhang, Luhong

    2018-05-01

    With the aim of removing and recycling oil and organic solvent from water, a facile and low-cost crosslinking polymerization method was first applied on surface modification of cotton fabrics for water/oil separation. Micro-nano hierarchical rough structure was constructed by triethylenetetramine (TETA) and trimesoyl chloride (TMC) that formed a polymeric layer on the surface of the fabric and anchored Al2O3 nanoparticles firmly between the fabric surface and the polymer layer. Superhydrophobic property was further obtained through self-assembly grafting of hydrophobic groups on the rough surface. The as-prepared cotton fabric exhibited superoleophilicity in atmosphere and superhydrophobicity both in atmosphere and under oil with the water contact angle of 153° and 152° respectively. Water/oil separation test showed that the as-prepared cotton fabric can handle with various oil-water mixtures with a high separation efficiency over 99%. More importantly, the separation efficiency remained above 98% over 20 cycles of reusing without losing its superhydrophobicity which demonstrated excellent reusability in oil/water separation process. Moreover, the as-prepared cotton fabric possessed good contamination resistance ability and self-cleaning property. Simulation washing process test showed the superhydrophobic cotton fabric maintained high value of water contact angle above 150° after 100 times washing, indicating great stability and durability. In summary, this work provides a brand-new way to surface modification of cotton fabric and makes it a promising candidate material for oil/water separation.

  7. Imaging pattern of calvarial lesions in adults

    Energy Technology Data Exchange (ETDEWEB)

    Garfinkle, Jarred; Melancon, Denis; Cortes, Maria; Tampieri, Donatella [Montreal Neurological Institute and Hospital-McGill University Health Center, Department of Diagnostic and Interventional Neuroradiology, Montreal, Quebec (Canada)

    2011-10-15

    Calvarial lesions often present themselves as clinically silent findings on skull radiographs or as palpable masses that may cause localized pain or soreness. This review aims to explore the radiographic, computed tomography (CT), and magnetic resonance imaging (MRI) characteristics of calvarial neoplastic, inflammatory, and congenital lesions that are common in adults in order to facilitate a structured approach to their diagnosis and limit the differential diagnosis. In addition to reviewing the literature, we reviewed the records of 141 patients of the Montreal Neurological Institute and Hospital with radiologically documented calvarial lesions between 2001 and June 2009. CT is ideal for detecting bony lesions and is helpful in precisely localizing a lesion pre-surgically. MRI is best at identifying intradiploic lesions before they affect the cortical tables and is able to establish extraosseous involvement, especially when paramagnetic contrast is employed. (orig.)

  8. Detection of Fundus Lesions Using Classifier Selection

    Science.gov (United States)

    Nagayoshi, Hiroto; Hiramatsu, Yoshitaka; Sako, Hiroshi; Himaga, Mitsutoshi; Kato, Satoshi

    A system for detecting fundus lesions caused by diabetic retinopathy from fundus images is being developed. The system can screen the images in advance in order to reduce the inspection workload on doctors. One of the difficulties that must be addressed in completing this system is how to remove false positives (which tend to arise near blood vessels) without decreasing the detection rate of lesions in other areas. To overcome this difficulty, we developed classifier selection according to the position of a candidate lesion, and we introduced new features that can distinguish true lesions from false positives. A system incorporating classifier selection and these new features was tested in experiments using 55 fundus images with some lesions and 223 images without lesions. The results of the experiments confirm the effectiveness of the proposed system, namely, degrees of sensitivity and specificity of 98% and 81%, respectively.

  9. Induction of DNA damage in γ-irradiated nuclei stripped of nuclear protein classes: differential modulation of double-strand break and DNA-protein crosslink formation

    International Nuclear Information System (INIS)

    Xue, L.-Y.; Friedman, L.R.; Oleinick, N.L.; Chiu, S.-M.

    1994-01-01

    The influence of chromatin proteins on the induction of DNA double-strand breaks (dsb) and DNA-protein crosslinks (dpc) by γ-radiation was investigated. Low molecular weight non-histone proteins and classes of histones were extracted with increasing concentrations of NaC1, whereas nuclear matrix proteins were not extractable even by 2.0 M NACl. The yield of dsb increased with progressive removal of proteins from chromatin. The data support our previous conclusion that nuclear matrix protein rather than the majority of the histones are the predominant substrates for dpc production, although the involvement of a subset of tightly bound histones (H3 and H4) has not been excluded. This finding demonstrates that chromatin proteins can differentially modify the yield of two types of radiation-induced DNA lesions. (author)

  10. Multifunctional Peroxidegas Alternative Crosslink Agents for Dynamically Vulcanized Expoxidized Natural Rubber/Polypropylene Blends

    NARCIS (Netherlands)

    Thitithammawong, A.; Thitithammawong, A.; Sahakaro, Kannika; Noordermeer, Jacobus W.M.

    2009-01-01

    Commonly used dicumyl peroxide (DCP) in combination with coagent, triallyl cyanurate (TAC), as a crosslinking agent is well acceptable for dynamically vulcanized rubber phase of thermoplastic vulcanizates (TPVs). However, it generally produces volatile decomposition products, which cause a typical

  11. Preparation and characterization of porous crosslinked collagenous matrices containing bioavailable chondroitin sulphate

    NARCIS (Netherlands)

    Pieper, J.S.; Oosterhof, A.; Dijkstra, Pieter J.; Veerkamp, J.H.; van Kuppevelt, T.H.

    1999-01-01

    Porous collagen matrices with defined physical, chemical and biological characteristics are interesting materials for tissue engineering. Attachment of glycosaminoglycans (GAGs) may add to these characteristics and valorize collagen. In this study, porous type I collagen matrices were crosslinked

  12. Chitosan coatings crosslinked with genipin for corrosion protection of AZ31 magnesium alloy sheets.

    Science.gov (United States)

    de Y Pozzo, Ludmila; da Conceição, Thiago F; Spinelli, Almir; Scharnagl, Nico; Pires, Alfredo T N

    2018-02-01

    In this study, coatings of chitosan crosslinked with genipin were prepared on sheets of AZ31 magnesium alloy and their corrosion protection properties were characterized by means of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The coatings were also characterized by means of FTIR and XPS. It was observed that the crosslinking process decreases the corrosion current and shifts the corrosion potential of the alloy to less negative values. The EIS analysis demonstrated that the crosslinking process increases the maximum impedance after short and long exposure times. The superior performance of the crosslinked coatings is related to a lower degree of swelling, as observed in the swelling tests carried out on free-standing films. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Thin-film composite crosslinked polythiosemicarbazide membranes for organic solvent nanofiltration (OSN)

    KAUST Repository

    Aburabie, Jamaliah; Neelakanda, Pradeep; Karunakaran, Madhavan; Peinemann, Klaus-Viktor

    2015-01-01

    In this work we report a new class of solvent stable thin-film composite (TFC) membrane fabricated on crosslinked polythiosemicarbazide (PTSC) as substrate that exhibits superior stability compared with other solvent stable polymeric membranes

  14. 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.

  15. Preliminary study on radiation crosslinking of PE-NBR multiple phase system

    International Nuclear Information System (INIS)

    Wang Hong; Zhang Wanxi; Sun Jiazhen

    1989-01-01

    The effect of radiation crosslinking on the structure and properties of PE-NBR (polyethylene-acrylonitrile-butadiene rubber) multiple phase system was studied in this paper. The relationship of sol fraction and irradiated dose to multiplephase system was demonstrated

  16. Reduction-Triggered Transformation of Crosslinking Modules of Disulfide-Containing Micelles with Chemically Tunable Rates.

    Science.gov (United States)

    Deng, Zhengyu; Yuan, Shuai; Xu, Ronald X; Liang, Haojun; Liu, Shiyong

    2018-05-16

    A dilemma exists between the circulation stability and cargo release/mass diffusion at desired sites for designing delivery nanocarriers and in vivo nanoreactors. We herein report disulfide-crosslinked (DCL) micelles exhibiting reduction-triggered switching of crosslinking modules and synchronized hydrophobic-to-hydrophilic transition. Tumor cell-targeted DCL micelles undergo cytoplasmic milieu-triggered disulfide cleavage and cascade self-immolative decaging reactions at chemically adjustable rates, generating primary amine moieties. Extensive amidation reactions with neighboring ester moieties then occur due to high local concentrations and suppression of apparent amine pKa within hydrophobic cores, leading to the transformation of crosslinking modules and formation of tracelessly crosslinked (TCL) micelles with hydrophilic cores inside live cells. We further integrate this design principle with theranostic nanocarriers for selective intracellular drug transport guided by enhanced magnetic resonance (MR) imaging performance. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Preparation and physical properties of enhanced radiation induced crosslinking of ethylene-vinyl alcohol copolymer (EVOH)

    International Nuclear Information System (INIS)

    Deng Pengyang; Liu Meihua; Zhang Wanxi; Sun Jiazhen

    2007-01-01

    Preparation and physical properties of ethylene-vinyl alcohol copolymer (EVOH) crosslinked by enhanced radiation have been studied through various methods. It was found that the most effective agent for irradiation-crosslinking was triallyl isocyanurate (TAIC) among four kinds of polyfunctional monomers. Gel content (65.6%) was formed for EVOH-44 (content of ethylene is 44 mol%) at 200 kGy with 5% TAIC, but for EVOH-32 (content of ethylene is 32 mol%), only 37.4% gel content was formed under the same conditions. This result showed that the more the content of ethylene units comprised in EVOH, the easier the chemical bonds could be formed between different molecular chains. Tensile strength and elastic modulus increased after crosslinking at high test temperature and elongation at break decreased at the same time. Hygroscopicity of EVOH showed noticeable decrease after enhancement radiation-crosslinking

  18. Porcine skin as a source of biodegradable matrices: alkaline treatment and glutaraldehyde crosslinking

    Directory of Open Access Journals (Sweden)

    Fabiana T. Rodrigues

    2010-06-01

    Full Text Available In this work, the modifications promoted by alkaline hydrolysis and glutaraldehyde (GA crosslinking on type I collagen found in porcine skin have been studied. Collagen matrices were obtained from the alkaline hydrolysis of porcine skin, with subsequent GA crosslinking in different concentrations and reaction times. The elastin content determination showed that independent of the treatment, elastin was present in the matrices. Results obtained from in vitro trypsin degradation indicated that with the increase of GA concentration and reaction time, the degradation rate decreased. From thermogravimetry and differential scanning calorimetry analysis it can be observed that the collagen in the matrices becomes more resistant to thermal degradation as a consequence of the increasing crosslink degree. Scanning electron microscopy analysis indicated that after the GA crosslinking, collagen fibers become more organized and well-defined. Therefore, the preparations of porcine skin matrices with different degradation rates, which can be used in soft tissue reconstruction, are viable.

  19. Biobased composites from thermoplastic polyurethane elastomer and cross-linked acrylated-epoxidized soybean oil

    Science.gov (United States)

    Soybean oil is an important sustainable material. Crosslinked acrylated epoxidized soybean oil (AESO) is brittle without flexibility and the incorporation of thermoplastic polyurethane improves its toughness for industrial applications. The hydrophilic functional groups from both oil and polyurethan...

  20. Swelling of radiation crosslinked acrylamide-based microgels and their potential applications

    Energy Technology Data Exchange (ETDEWEB)

    Abd El-Rehim, H.A. [National Center for Radiation Research and Technology, Atomic Energy Authority, P.O. Box 29 Nasr City, Cairo (Egypt)]. E-mail: ha_rehim@hotmail.com

    2005-10-01

    Crosslinked polyacrylamide PAAm and acrylamide-Na-acrylate P(AAm-Na-AAc) microgels were prepared by electron beam irradiation. It was found that the dose required for crosslinking depends on the polymer moisture content, so that the dose to obtain PAAm of maximum gel fraction was over 40 and 20 kGy for dry and moist PAAm, respectively. The structural changes in irradiated PAAm were investigated using FTIR and SEM. The swelling property of such microgels in distilled water and real urine solution was determined and crosslinked polymers reached their equilibrium swelling state in a few minutes. As the gel content and crosslinking density decrease, the swelling of the microgels increases. The ability of the microgels to absorb and retain large amount of solutions suggested their possible uses in horticulture and in hygienic products such as disposable diapers.

  1. Swelling of radiation crosslinked acrylamide-based microgels and their potential applications

    International Nuclear Information System (INIS)

    Abd El-Rehim, H.A.

    2005-01-01

    Crosslinked polyacrylamide PAAm and acrylamide-Na-acrylate P(AAm-Na-AAc) microgels were prepared by electron beam irradiation. It was found that the dose required for crosslinking depends on the polymer moisture content, so that the dose to obtain PAAm of maximum gel fraction was over 40 and 20 kGy for dry and moist PAAm, respectively. The structural changes in irradiated PAAm were investigated using FTIR and SEM. The swelling property of such microgels in distilled water and real urine solution was determined and crosslinked polymers reached their equilibrium swelling state in a few minutes. As the gel content and crosslinking density decrease, the swelling of the microgels increases. The ability of the microgels to absorb and retain large amount of solutions suggested their possible uses in horticulture and in hygienic products such as disposable diapers

  2. Photochemical Acceleration of DNA Strand Displacement by Using Ultrafast DNA Photo-crosslinking.

    Science.gov (United States)

    Nakamura, Shigetaka; Hashimoto, Hirokazu; Kobayashi, Satoshi; Fujimoto, Kenzo

    2017-10-18

    DNA strand displacement is an essential reaction in genetic recombination, biological processes, and DNA nanotechnology. In particular, various DNA nanodevices enable complicated calculations. However, it takes time before the output is obtained, so acceleration of DNA strand displacement is required for a rapid-response DNA nanodevice. Herein, DNA strand displacement by using DNA photo-crosslinking to accelerate this displacement is evaluated. The DNA photo-crosslinking of 3-cyanovinylcarbazole ( CNV K) was accelerated at least 20 times, showing a faster DNA strand displacement. The rate of photo-crosslinking is a key factor and the rate of DNA strand displacement is accelerated through ultrafast photo-crosslinking. The rate of DNA strand displacement was regulated by photoirradiation energy. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. 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...

  4. Anisotropically Swelling Gels Attained through Axis-Dependent Crosslinking of MOF Crystals.

    Science.gov (United States)

    Ishiwata, Takumi; Kokado, Kenta; Sada, Kazuki

    2017-03-01

    Anisotropically deforming objects have attracted considerable interest for use in molecular machines and artificial muscles. Herein, we focus on a new approach based on the crystal crosslinking of organic ligands in a pillared-layer metal-organic framework (PLMOF). The approach involves the transformation from crosslinked PLMOF to polymer gels through hydrolysis of the coordination bonds between the organic ligands and metal ions, giving a network polymer that exhibits anisotropic swelling. The anisotropic monomer arrangement in the PLMOF underwent axis-dependent crosslinking to yield anisotropically swelling gels. Therefore, the crystal crosslinking of MOFs should be a useful method for creating actuators with designable deformation properties. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. 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

  6. 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

  7. 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.

  8. Study on the DNA-protein crosslinks induced by chromium (VI) in SPC-A1

    Science.gov (United States)

    Liu, Yanqun; Ding, Jianjun; Lu, Xiongbing; You, Hao

    2018-01-01

    Objective: This study was designed to investigate the effect of chromium (VI) on DNA-protein crosslinks (DPC) of SPC-A1 cells. Methods: We exposed SPC-A1 cells were cultured in 1640 medium and treated with the SPC-A1 cells in vitro to different concentrations of Hexavalent chromium Cr(VI) for 2h, the KC1-SDS precipitation assay were used to measure the DNA-protein cross-linking effect. Results: All the different concentrations of Cr(VI) could cause the increase of DPC coefficient in SPC-A1 cells. But this effect was not significant (P>0.05) at low concentrations; while in high concentration Cr(VI) induced SPC-A1 cells could produce DNA-protein cross-linking effect significantly (P<0.05). Conclusions: chromium (VI) could induce DNA-protein crosslink.

  9. Ouabain, a cardiac glycoside, inhibits the Fanconi anemia/BRCA pathway activated by DNA interstrand cross-linking agents.

    Directory of Open Access Journals (Sweden)

    Dong Wha Jun

    Full Text Available Modulation of the DNA repair pathway is an emerging target for the development of anticancer drugs. DNA interstrand cross-links (ICLs, one of the most severe forms of DNA damage caused by anticancer drugs such as cisplatin and mitomycin C (MMC, activates the Fanconi anemia (FA/BRCA DNA repair pathway. Inhibition of the FA/BRCA pathway can enhance the cytotoxic effects of ICL-inducing anticancer drugs and can reduce anticancer drug resistance. To find FA/BRCA pathway inhibitory small molecules, we established a cell-based high-content screening method for quantitating the activation of the FA/BRCA pathway by measuring FANCD2 foci on DNA lesions and then applied our method to chemical screening. Using commercial LOPAC1280 chemical library screening, ouabain was identified as a competent FA/BRCA pathway inhibitory compound. Ouabain, a member of the cardiac glycoside family, binds to and inhibits Na(+/K(+-ATPase and has been used to treat heart disease for many years. We observed that ouabain, as well as other cardiac glycoside family members--digitoxin and digoxin--down-regulated FANCD2 and FANCI mRNA levels, reduced monoubiquitination of FANCD2, inhibited FANCD2 foci formation on DNA lesions, and abrogated cell cycle arrest induced by MMC treatment. These inhibitory activities of ouabain required p38 MAPK and were independent of cellular Ca(2+ ion increase or the drug uptake-inhibition effect of ouabain. Furthermore, we found that ouabain potentiated the cytotoxic effects of MMC in tumor cells. Taken together, we identified an additional effect of ouabain as a FA/BRCA pathway-inhibiting chemosensitization compound. The results of this study suggest that ouabain may serve as a chemosensitizer to ICL-inducing anticancer drugs.

  10. Hybrid Odontogenic Lesion: A Rare Entity

    Directory of Open Access Journals (Sweden)

    Reza Imani

    2017-03-01

    Full Text Available Hybrid tumors are very rare tumors composed of two different tumor entities, each of which conforms to an exactly defined tumor category. A 14-year-old boy was referred for an intraosseous painless lesion with a histopathological feature of multiple odontogenic lesions including calcifying odontogenic cyst, complex odontoma and ameloblastic fibro-odontoma. The final diagnosis considered to be a hybrid odontogenic lesion.

  11. Space Occupying Lesions in the Liver

    OpenAIRE

    Nasser Ebrahimi Daryani

    2009-01-01

    "nRadiology (imaging) plays a pivotal role for the diagnosis, staging, treatment planning, and follow-up of focal liver lesions. The differential diagnosis in patients presenting with a focal liver lesion is broad. "nThe size of the liver mass is an important consideration in guiding the evaluation. Lesions smaller than approximately 1.0 cm are commonly benign incidental findings on imaging studies, and in most cases represent small cysts, hemangiomas, or biliary hamartomas. Further...

  12. Benign Lesions of The Vocal Fold

    Directory of Open Access Journals (Sweden)

    Ozgur Surmelioglu

    2013-02-01

    Full Text Available Benign lesions of vocal folds are common disorders. Fifty percent of patients who have sound complaints are found to have these lesions after endoscopic and stroboscopic examinations. Benign vocal fold diseases are primarily caused by vibratory trauma. However they may also occur as a result of viral infections and congenital causes. These lesions are often presented with the complaints of dysphonia. [Archives Medical Review Journal 2013; 22(1.000: 86-95

  13. 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

  14. Preparation and adsorption behavior for metal ions and humic acid of chitosan derivatives crosslinked by irradiation

    International Nuclear Information System (INIS)

    Zhao Long; Mitomo, H.; Yoshii, F.

    2006-01-01

    Introduction: Removing metal ions and humic acid from water in water treatment has attracted much environment and health interests. Adsorbents, derived from a nature polymer, are desired in the viewpoints of environment-conscious technologies. Recently, some nature materials such as chitin, chitosan and their derivatives have been identified as an attractive option due to their distinctive properties. For an insoluble adsorbent based on these polymers to be obtained over a broad pH range, modification through crosslinking is required. Crosslinking agents such as glutaric dialdehyde and ethylene glycol diglycidyl ether are frequently used for modification. However, these crosslinking agents are not preferred because of their physiological toxicity. Radiation-crosslinking without any additive in the fabrication process results in a high-purity product. In a previous work, we applied ionizing radiation to induce the crosslinking of carboxymethylchitosan under highly concentrated paste-like conditions. The aim of this study is to investigate the adsorption behavior of metal ions, humic acid on irradiation-crosslinked carboxymethylchitosan. Experimental: Irradiation of chitosan samples at paste-like state was done with an electron beam. The solubility test of these crosslinked materials were investigated in acidic, alkaline media, and some organic solvents. Swelling and charged characteristic analyses demonstrated typically pH-sensitive properties of these crosslinked materials. Scanning electron microscopic images showed that the crosslinked samples possessed porous morphological structure. The adsorption studies were carried out by the batch method at room temperature. Adsorption of heavy metal ions (such as Cu 2+ , Cd 2+ ) and humic acid onto crosslinked samples was found to be strongly pH-dependent. Adsorption kinetic studies indicated the rapid removal of metal ions, and humic acid from the aqueous solutions. Also, isothermal adsorption data revealed that Cu 2

  15. Cross-linked polybenzimidazole membranes for high temperature proton exchange membrane fuel cells with dichloromethyl phosphinic acid as a cross-linker

    DEFF Research Database (Denmark)

    Noye, Pernille; Li, Qingfeng; Pan, Chao

    2008-01-01

    Phosphoric acid doped polybenzimidazole (PBI) membranes have been covalently cross-linked with dichloromethyl phosphinic acid (DCMP). FT-IR measurements showed new bands originating from bonds between the hydrogen bearing nitrogen in the imidazole group of PBI and the CH2 group in DCMP. The produ......Phosphoric acid doped polybenzimidazole (PBI) membranes have been covalently cross-linked with dichloromethyl phosphinic acid (DCMP). FT-IR measurements showed new bands originating from bonds between the hydrogen bearing nitrogen in the imidazole group of PBI and the CH2 group in DCMP.......e. within the temperature range of operation of PBI-based fuel cells....

  16. Biohybrid Fibro-Porous Vascular Scaffolds: Effect of Crosslinking on Properties

    OpenAIRE

    Thomas, Vinoy; Nozik, Danna; Patel, Harsh; Singh, Raj K.; Vohra, Yogesh K.

    2015-01-01

    Tubular grafts were fabricated from blends of polycaprolactone (PCL) and poly(glycolide -co-caprolactone) (PGC) polymers and coated with an extracellular matrix containing collagens, laminin, and proteoglycans, but not growth factors (HuBiogel™). Multifunctional scaffolds from polymer blends and membrane proteins provide the necessary biomechanics and biological functions for tissue regeneration. Two crosslinking agents, a natural crosslinker namely genipin (Gp) and a carbodiimide reagent nam...

  17. Study on the kinetics of gel formation in the radiation crosslinking reaction

    International Nuclear Information System (INIS)

    Wang Mingjun; Liu Yuming

    1988-01-01

    From the kinetic equation of gel formation obtained by the authors, the mechanism of gel formation may be interpreted clearly as follows: (1) When the degree of crosslinking q g , the system is sol and the crosslinking reaction is only carried out between the sol molecules. (q g is the gel point). (2) When q=q g , there exists a beginning point where the gel is coexisted with the sol, and the system is still sol, and the crosslinking reaction is still carried out between the sol molecules. (3) When q>q g , the crosslinking reaction exceeds the gel point and the gel is coexisted with the sol. The kinetic equation shows clearly that the transformation from sol into gel is caused by crosslinking reaction of the uncrosslinked chain units between the sol and gel molecules. As a result the sol molecules are transformed into the gel molecules gradually, and the sol fraction is reduced. When the chain units P-barw(s)S(1-s)dq in sol are crosslinked with gel, the sol fraction in the system is reduced ds (where P-barw(s) is a function of the radiation dose and s is sol frection). The degree of crosslinking per unit dose (q 0 ) is a reduced function of dose (R). The equation for calculating its value for every irradiation dose is obtained. After knowing the correlation between P-bar W(s) vs R and q 0 vs R, the distribution of gel and sol in the process of radiation crosslinking can be discussed as well

  18. 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

  19. 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

  20. DNA-protein crosslinks in peripheral lymphocytes of individuals exposed to hexavalent chromium compounds.

    Science.gov (United States)

    Zhitkovich, A; Lukanova, A; Popov, T; Taioli, E; Cohen, H; Costa, M; Toniolo, P

    1996-01-01

    Abstract DNA-protein crosslinks were measured in peripheral blood lymphocytes of chrome-platers and controls from Bulgaria in order to evaluate a genotoxic effect of human exposure to carcinogenic Cr(VI) compounds. Chrome-platers and most of the unexposed controls were from the industrial city of Jambol; some additional controls were recruited from the seaside town of Burgas. The chrome-platers had significantly elevated levels of chromium in pre- and post-shift urine, erythrocytes and lymphocytes compared with the control subjects. The largest differences between the two groups were found in erythrocyte chromium concentrations which are considered to be indicative of Cr(VI) exposure. Despite the significant differences in internal chromium doses, levels of DNA-protein crosslinks were not significantly different between the combined controls and exposed workers. Individual DNA-protein crosslinks, however, correlated strongly with chromium in erythrocytes at low and moderate doses but at high exposures, such as among the majority of chrome-platers, these DNA adducts were saturated at maximum levels. The saturation of DNA-protein crosslinks seems to occur at 7-8 μg I-(1) chromium in erythrocytes whereas a mean erythrocyte chromium among the chrome platers was as high as 22.8 μg l(-1). Occupationally unexposed subjects exhibited a significant variability with respect to the erythrocyte chromium concentration, however erythrocyte chromium levels correlated closely with DNA-protein crosslinks in lymphocytes. The controls from Jambol had higher chromium concentrations in erythrocytes and elevated levels of DNA-protein crosslinks compared with Burgas controls. Occupational exposure to formaldehyde among furniture factory workers did not change levels of DNA-protein crosslinks in peripheral lymphocytes. DNA-protein crosslink measurements showed a low intraindividual variability and their levels among both controls and exposed indivduals were not affected by smoking, age