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Sample records for antibiotic-loaded cement spacers

  1. Antibiotic-loaded acrylic cement: current concepts.

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    Buchholz, H W; Elson, R A; Heinert, K

    1984-11-01

    Antibiotic-loaded acrylic cement has been used routinely since 1972 at the authors' hospitals, where a series of some 22,000 joint arthroplasty operations was performed from 1964-1983. The current status of the material is presented with up-to-date follow-up statistics on prophylactic therapy and on established deep infections. The results of 869 exchange arthroplasties are compared with results published in 1981. In the future, results will be presented in the form of survival curves. The method by which survival tables and curves are constructed is critical. Investigators should use survival curves for ease of comparison and because of the wide range of possibilities in an analysis of covariable factors. A retrospective actuarial analysis was made of 825 one-stage reimplantations in which antibiotic-loaded acrylic cement was used for infected total hip arthroplasties. Staphylococcus aureus was the most commonly encountered organism. Failure rates of prostheses infected by S. aureus, S. species, and anaerobic corynebacteria did not differ statistically. A factor that significantly contributed to failure of this method of treatment was Pseudomonas infection. By actuarial analysis five years after operation, a success (survival) rate of 77% was calculated.

  2. Backgrounds of antibiotic-loaded bone cement and prosthesis-related infection

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    Hendriks, JGE; van Horn, [No Value; van der Mei, HC; Busscher, HJ

    2004-01-01

    Antibiotic-loaded bone cement has been in use for over 30 years for the fixation of total joint arthroplasties, although its mechanism of action is still poorly understood. This review presents the backgrounds of bone cements, prosthesis-related infection and antibiotic-loaded bone cements. It is sh

  3. The economics of using prophylactic antibiotic-loaded bone cement in total knee replacement.

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    Gutowski, C J; Zmistowski, B M; Clyde, C T; Parvizi, J

    2014-01-01

    The rate of peri-prosthetic infection following total joint replacement continues to rise, and attempts to curb this trend have included the use of antibiotic-loaded bone cement at the time of primary surgery. We have investigated the clinical- and cost-effectiveness of the use of antibiotic-loaded cement for primary total knee replacement (TKR) by comparing the rate of infection in 3048 TKRs performed without loaded cement over a three-year period versus the incidence of infection after 4830 TKRs performed with tobramycin-loaded cement over a later period of time of a similar duration. In order to adjust for confounding factors, the rate of infection in 3347 and 4702 uncemented total hip replacements (THR) performed during the same time periods, respectively, was also examined. There were no significant differences in the characteristics of the patients in the different cohorts. The absolute rate of infection increased when antibiotic-loaded cement was used in TKR. However, this rate of increase was less than the rate of increase in infection following uncemented THR during the same period. If the rise in the rate of infection observed in THR were extrapolated to the TKR cohort, 18 additional cases of infection would have been expected to occur in the cohort receiving antibiotic-loaded cement, compared with the number observed. Depending on the type of antibiotic-loaded cement that is used, its cost in all primary TKRs ranges between USD $2112.72 and USD $112 606.67 per case of infection that is prevented.

  4. Temporary total hip arthroplasty-like spacer for treating an infected periprosthetic femoral fracture using a long stem: A case report

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    Youngwoo Kim

    2017-01-01

    Conclusions: Temporary antibiotic-loaded cement-coated THA-like spacer using a long stem facilitated the eradication of infection, fracture stabilization, and enables partial weight bearing without pain.

  5. Definitive Treatment of Infected Shoulder Arthroplasty With a Cement Spacer.

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    Mahure, Siddharth A; Mollon, Brent; Yu, Stephen; Kwon, Young W; Zuckerman, Joseph D

    2016-09-01

    Infection in the setting of shoulder arthroplasty can result in significant pain, loss of function, and the need for additional surgery. As the use of shoulder arthroplasty increases, the medical and economic burdens of periprosthetic joint infection increase as well. The ideal management of infected shoulder prostheses has not been established. This report describes 9 patients from a single institution who had an infected shoulder arthroplasty that was definitively managed with a cement spacer. All patients had a minimum of 2 years of follow-up. Of the 9 patients in this study, 6 were men. Mean age was 73±9 years. Of the study patients, 1 had diabetes, 2 presented with Parkinson's disease, and 5 had a history of tobacco use. Average body mass index was 27.9±7 kg/m(2). After mean follow-up of 4 years, none of the patients had clinical or radiographic evidence of infection. Functional outcomes, as measured by American Shoulder and Elbow Surgeons scores, were good or fair in 89% of patients, and the average American Shoulder and Elbow Surgeons score was 57. A review of recent literature suggested that the current findings were similar to those in studies reporting 1- or 2-stage revision procedures. Although cement spacers are typically used as part of a 2-stage revision procedure, the current findings suggest that cement spacers can be used effectively to eradicate infection and allow for acceptable functional recovery and range of motion in patients who have severe medical comorbidities and cannot tolerate additional surgery. [Orthopedics. 2016; 39(5):e924-e930.].

  6. Acute Delayed or Late Infection of Revision Total Hip Arthroplasty Treated with Debridement/Antibiotic-loaded Cement Beads and Retention of the Prosthesis

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    Chang, Jun-Dong; Kim, In-Sung; Lee, Sang-Soo

    2017-01-01

    Purpose The treatment of infected revision total hip arthroplasty (THA) is very challenging due to retained revision prosthesis, poor bone stock and soft tissue condition derived from previous revision surgeries, and comorbidities. The purpose of this study was to investigate the effectiveness and short-term outcomes of aggressive debridement and use of antibiotic-loaded cement beads with retention of the prosthesis for acute delayed or late infection of revision THAs. Materials and Methods Ten consecutive patients with symptoms or signs of less than one-week evolution and well-fixed prostheses, were treated with this procedure and a postoperative course of organism-specific antibiotics for a minimum of 6 weeks. All hips presented with acute delayed or late infection of revision THAs. Patients with a mean age of 68.1 years (range, 59-78 years) underwent an average of 1.9 previous revision THAs (1-4) before the index surgery. The minimal follow-up was 2 years with a mean of 46.2 months (range, 24-64 months). Results There were 8 cures (80.0%) and 2 failures with no mortality during the study period. The 2 failures involved the same and resistant bacteria implicated in the primary infection (methicillin-resistant Staphylococcus aureus and Prevotella oralis, respectively). The mean Harris hip score was 65.2 (range, 26-83) and the mean visual analogue scale was 2.6 (range, 1-4) at final follow-up. Conclusion With a favorable success rate and no mortality, our procedure may be considered a safe and effective alternative for the treatment of acute delayed or late infection of revision THAs with well-fixed prostheses. PMID:28316961

  7. Current status of the application of antibiotic-loaded bone cements in primary arthroplasty%初次关节置换中抗生素骨水泥的应用现状

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    王晓楠; 王金成

    2013-01-01

    Infection is considered to be a serious complication of artificial arthroplasty. Accordingly, infection control becomes a research focus in recent years. In order to reduce its incidence, many doctors use antibiotic-loaded bone cements in primary arthroplasty, especially in those special cases, such as surgery with a long period, or with a high risk of pollution, revision surgery, and for patients with idiopathic or acquired immunodeficiency, patients with rheumatoid diseases or systemic lupus erythematosus, patients treated with radiotherapy or chemotherapy, obese patients, diabetic patients, especially patients with poor glucose control, and patients with previous joint infection or malignancy. However, there exists such problems as higher costs and a single kind of antibiotics in use. At the same time, the release time of antibiotics in bone cements is limited, which determines that the infection is mainly prevented in the introduced pathway after artificial arthroplasty. So it is uncertain whether all types of bacteria entering the human body through the introduced pathway can be included by the antibacterial spectrum of antibiotics in bone cements, and further experiments and studies are needed for doctors to verify the results. In this article, we reviewed the application of antibiotic-loaded bone cements in primary arthroplasty for reference.

  8. Antibiotic-loaded cement femoral prosthesis in treatment of hip arthroplasty infection%抗生素骨水泥股骨头临时假体治疗髋关节置换术后感染

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    何爱珊; 廖威明; 傅明; 盛璞义; 孟繁纲

    2012-01-01

    Objective To evaluate the effectiveness of antibiotic-loaded cement femoral prosthesis implantation after primary debridement and two-stage hip prosthesis revision in the treatment of hip arthroplasty infection. Methods Between January 2006 and November 2010, 11 cases(12 hips) of hip arthroplasty infection were treated by two-stage revision. There were seven men (eight hips) and four women (four hips) with a mean age of 60 years (range, 29 -80years). The Harris scores was (32 ± 7. 63) (range, 17-45) . All the patients were treated as follows: in the first stage, the infected prosthesis was removed, debridement was performed, and an antibiotic-loaded cement femoral prosthesis was then implanted for 4 to 20 months (average, 12 months). When the results of C reactive protein, leukocyte count and erythorocyte sedimentation rate were back to normal and no infective sign was found around the incision, a two-stage revision was performed. All cases were regularly followed up for 4 to 40 months (average, 20 months). Results All 11 patients achieved healing of incision by first intention, and no complications occurred. No reinfection was found in the follow-up. The function of hip was improved. The Harris score was (87 ± 7. 72) (range, 65 - 96) in the follow-up, showing significant improvement compared with preoperative score (t =38.81, P < 0. 01) . Conclusions The implantation of antibiotic-loaded cement femoral prosthesis in the first stage after surgical debridement is effective for treatment of hip arthroplasty infection. The antibiotic-loaded cement femoral prosthesis can also help to reduce shortening deformity in extremities. According to the patients' conditions, cement or cementless hip prosthesis may be used in the two-stage hip prosthesis revision to get satisfactory clinical effect.%目的 总结评估Ⅰ期清创后采用自制抗生素骨水泥股骨头假体控制感染,Ⅱ期翻修重建治疗人工髋关节置换术后感染的临床效果.方法 自2006

  9. Treatment of persistent extraarticular infection using a temporary cement spacer on the tibia after ACL reconstruction.

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    Jung, Kwang Am; Lee, Soo Chan; Song, Moon Bok; Lee, Choon Key

    2008-01-01

    Postoperative infection after anterior cruciate ligament (ACL) reconstruction is an uncommon but serious complication. Although several treatments for intraarticular infection have been reported, no report has been recorded on the treatment of persistent extraarticular infections. The authors experienced reconstructed graft removal due to a refractory extraarticular infection on tibia. Early ACL reimplantation was performed using a temporary cement spacer containing antibiotics and a irradiated bone patellar tendon bone allograft.

  10. A new device designed for direct yield stress measurements of cement spacer

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    Gordon, C.L.; Tonmukayakul, P.; Morgan, R.L. [Halliburton Energy Services, Houston, TX (United States)

    2007-07-01

    The rheological properties of spacer fluids and cement slurries have a significant impact on the hydraulic shear stress of well casing walls. This paper described experimental studies and numerical models of a device designed to measure the yield stress and rheological properties of spacer and cement samples. The device was designed using the Couette principle for rheological measurements, and measured the yield stress of particle-laden samples between 4 and 150 degrees C. A sample contained in a gap between a stator and a blade located along the inside wall of a steel cup was analyzed using the device. A stator was attached to a torque device and remained static during the rheological measurement. Yield stress was measured by rotating the device at a low speed at 3 rpm and at steady state torque. Torque was recorded when the rotation stopped. Two aqueous mixtures of titanium oxide (TiO{sub 2}) particles were used for the experiment. A cement spacer comprised of a blend of barite, citric acid and water was also measured. A volume-averaged shear method was used to calculate shear rate and shear stress. Key dimensionless variables were the impeller Reynolds number; the Froude number; the Weber number; and the Weissenberg number. Accuracy was assessed by examining the data obtained with a model fluid where yield stress data was already determined. Results of the comparison showed that values obtained using the device were consistent and comparable with results obtained using other techniques. It was concluded that further research is needed to characterize the elastic fluids in the device. 13 refs., 2 tabs., 3 figs.

  11. Patella tendon injuries secondary to cement spacers used at first-stage revision of infected total knee replacement

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    Wasim S Khan

    2015-04-01

    Full Text Available We describe a series of three patients who sustained patella tendon injuries in infected TKAs following the use of a static cement spacer at first-stage knee revision. The patella tendon injuries resulted in significant compromise to wound healing and knee stability requiring multiple surgeries. The mid-term function was poor with an Oxford score at 24 months ranging from 12-20. Based on our experience, we advise caution in the use of static cement spacer blocks. If they are to be used, we recommend that they should be keyed in the bone to prevent patella tendon injuries.

  12. Choice and doses of antibacterial agents for cement spacers in treatment of prosthetic joint infections: review of published studies.

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    Iarikov, D; Demian, H; Rubin, D; Alexander, J; Nambiar, S

    2012-12-01

    Addition of antibacterial drugs to interim antibacterial cement spacers (ACSs) is considered to be standard of care for surgical revision in prosthetic joint infections (PJIs). We reviewed published studies evaluating the choice and doses of antibacterials in spacers. We conducted a PubMed search of all clinical study reports evaluating the use of ACSS in a 2-stage hip or knee arthroplasty for treatment of PJI (1988 through August 2011). The trial design, antibacterials used, and end points studied were analyzed. No randomized trials were found comparing either ACSs with different concentrations of antibacterials or ACSs with or without antibacterials. Most of the studies were uncontrolled and used various time points to evaluate the outcome. Twenty publications that reported doses of antibacterials in spacers and had a follow-up of ≥ 24 months after the second stage were selected for review. Most ACSs included vancomycin and aminoglycosides. The doses of aminoglycosides and vancomycin ranged from 0.25 to 4.8 g and from 1 to 4 g, respectively, per 4 g of cement. No association between reported eradication of the infection and antibacterial load was found. Published data do not allow evaluation of whether antibacterials in temporary cement spacers provide additional benefits in the treatment of PJI, compared with systemic antibacterials, and are not sufficient to support recommendations on dosages. Complications of ACSs have not been consistently analyzed. Prospective randomized trials comparing spacers with and without antibacterials or spacers with different loads of antibacterials are needed to evaluate the safety and efficacy of ACSs.

  13. Influence of the interposition of ceramic spacers on the degree of conversion and the hardness of resin cements

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    Patricia Angelica Milani Calgaro

    2013-09-01

    Full Text Available This study evaluated: I the effect of photo-activation through ceramics on the degree of conversion (DC and on the Knoop hardness (KHN of light- and dual-cured resin cements; and II two different protocols for obtaining the spectra of uncured materials, to determine the DC of a dual-cured resin cement. Thin films of cements were photo-activated through ceramics [feldspathic porcelain (FP; lithium disilicate glass-ceramics of low translucency (e.max-LT, medium opacity (e.max-MO and high translucency (e.max-HT; glass-infiltrated alumina composite (IC and polycrystalline zirconia (ZR] with thicknesses of 1.5 and 2.0 mm. DC was analyzed by Fourier transform infrared (FTIR spectroscopy. Two protocols were used to obtain the spectra of the uncured materials: I base and catalyst pastes were mixed, and II thin films of base and catalyst pastes were obtained separately, and an average was obtained. KHN assessment was performed with cylindrical specimens. The results were analyzed by ANOVA and Tukey's test (α= 0.05. The light-cured cement showed higher DC (61.9% than the dual-cured cement (55.7%. The DC varied as follows: FP (65.4%, e.max-HT (65.1%, e.max-LT (61.8%, e.max-MO (60.9%, ZR (54.8%, and IC (44.9%. The light-cured cement showed lower KHN (22.0 than the dual-cured (25.6 cement. The cements cured under 1.5 mm spacers showed higher KHN (26.2 than when polymerized under 2.0 mm ceramics (21.3. Regarding the two protocols, there were significant differences only in three groups. Thus, both methods can be considered appropriate. The physical and mechanical properties of resin cements may be affected by the thickness and microstructure of the ceramic material interposed during photo-activation.

  14. Outcome of total knee replacement following explantation and cemented spacer therapy

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    Ghanem, Mohamed

    2016-03-01

    Full Text Available Background: Infection after total knee replacement (TKR is one of the serious complications which must be pursued with a very effective therapeutic concept. In most cases this means revision arthroplasty, in which one-setting and two-setting procedures are distinguished. Healing of infection is the conditio sine qua non for re-implantation. This retrospective work presents an assessment of the success rate after a two-setting revision arthroplasty of the knee following periprosthetic infection. It further considers drawing conclusions concerning the optimal timing of re-implantation.Patients and methods: A total of 34 patients have been enclosed in this study from September 2005 to December 2013. 35 re-implantations were carried out following explantation of total knee and implantation of cemented spacer. The patient’s group comprised of 53% (18 males and 47% (16 females. The average age at re-implantation time was 72.2 years (ranging from 54 to 85 years. We particularly evaluated the microbial spectrum, the interval between explantation and re-implantation, the number of surgeries that were necessary prior to re-implantation as well as the postoperative course. Results: We reported 31.4% (11 reinfections following re-implantation surgeries. The number of the reinfections declined with increasing time interval between explantation and re-implantation. Patients who developed reinfections were operated on (re-implantation after an average of 4.47 months. Those patients with uncomplicated course were operated on (re-implantation after an average of 6.79 months. Nevertheless, we noticed no essential differences in outcome with regard to the number of surgeries carried out prior to re-implantation. Mobile spacers proved better outcome than temporary arthrodesis with intramedullary fixation.Conclusion: No uniform strategy of treatment exists after peri-prosthetic infections. In particular, no optimal timing can be stated concerning re

  15. Antibiotic elution from acrylic bone cement loaded with high doses of tobramycin and vancomycin.

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    Slane, Joshua; Gietman, Bradley; Squire, Matthew

    2017-09-06

    Two-stage revision treatment of prosthetic joint infection (PJI) frequently employs the use of a temporary bone cement spacer loaded with multiple antibiotic types. Tobramycin and vancomycin are commonly used antibiotics in cement spacers, however, there is no consensus on the relative concentrations and combinations that should be used. Therefore, the purpose of this study was to investigate the influence of dual antibiotic loading on the total antibiotic elution and compressive mechanical properties of acrylic bone cement. Varying concentrations of tobramycin (0-3 g) and vancomycin (0-3 g) were added either alone or in combination to acrylic cement (Palacos R), resulting in 12 experimental groups. Samples were submerged in 37°C saline for 28 d and sampled at specific time points. The collected eluent was analyzed to determine the cumulative antibiotic release. In addition, the cement's compressive mechanical properties and porosity were characterized. Interestingly, the cement with the highest concentration of antibiotics did not possess the best elution properties. Cement samples containing both 3 g of tobramycin and 2 g vancomycin demonstrated the highest cumulative antibiotic release after 28 d, which was coupled with a significant decrease in the mechanical properties and an increased porosity. The collected data also suggests that tobramycin elutes more effectively than vancomycin from cement. In conclusion, this study demonstrates that high antibiotic loading in cement does not necessarily lead to enhanced antibiotic elution. Clinically this information may be used to optimize cement spacer antibiotic loading so that both duration and amount of antibiotics eluted are optimized. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

  16. Two-stage revision total hip arthroplasty for periprosthetic infections using antibiotic-impregnated cement spacers of various types and materials.

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    Uchiyama, Katsufumi; Takahira, Naonobu; Fukushima, Kensuke; Moriya, Mitsutoshi; Yamamoto, Takeaki; Minegishi, Yojiro; Sakai, Rina; Itoman, Moritoshi; Takaso, Masashi

    2013-01-01

    Antibiotic-impregnated hip cement spacers of various types and materials have been used in the treatment of periprosthetic hip infections. We developed a handmade spacer by using polymethylmethacrylate (PMMA) and/or α -tricalcium phosphate ( α -TCP). In this study, we retrospectively reviewed the surgical outcomes in 36 consecutive patients treated with 2-stage revision total hip arthroplasty by using our antibiotic-impregnated hip cement spacers. We aimed to analyze the infection control and reinfection rates after revision surgery. Moreover, we analyzed the possible predictors of postoperative reinfection. After exclusion of 1 patient who died immediately after the first-stage surgery, infection was controlled in 33 of the 36 hips (success rate, 91.7%). Two of these 33 hips underwent resection arthroplasty. Of the 36 hips that had been treated with the antibiotic-cement spacer, 31 hips (86.1%) were eligible for the second-stage prosthesis re-implantation. The 31 protocol hip joints of patients followed up for >6 months (mean, 48.6 months). Ten of these 31 hips (32.3%) became reinfected. No possible predictor examined differed significantly between the reinfection-positive and reinfection-negative groups. However, spacers consisting of PMMA cement alone were associated with the highest risk of reinfection. Therefore, α -TCP-containing antibiotic-impregnated hip cement spacers might decrease the reinfection rate in patients undergoing re-implantation.

  17. RELEASE OF GENTAMICIN FROM CEMENT SPACERS IN TWO-STAGE PROCEDURES FOR HIP AND KNEE PROSTHETIC INFECTION: AN IN VIVO PHARMACOKINETIC STUDY WITH CLINICAL FOLLOW-UP.

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    Balato, G; Ascione, T; Rosa, D; Pagliano, P; Solarino, G; Moretti, B; Mariconda, M

    2015-01-01

    Eighteen patients undergoing two-stage exchange arthroplasty for infected total hip or knee arthroplasty using gentamicin-loaded bone cement spacers (80g bone cement, 2 g gentamicin and 2 g clindamycin) were studied. The concentration of gentamicin eluted from the spacers was assessed on samples of blood, urine, and drainage fluid that were collected from each patient at set intervals during the 48 hours following the first-stage surgery. The hip and knee cement spacers showed similar curve of release over the first postoperative hours (early peak followed by slow release), but the mean gentamicin concentration in the drainage fluid was higher in patients with hip spacers compared to patients with knee spacers (30.61±19.47 mg/L vs 17.43±13,63 mg/L, p less than 0.05). In patients with hip spacers, the mean, maximum, and minimum concentration of gentamicin was higher with respect to the minimum inhibitory concentration (MIC) break point for Staphylococcus spp, Pseudomonas Aeruginosa and Enterobacteriaceae throughout the first postoperative 48 h. Conversely, in 25% of patients with a knee spacer a drug concentration below the MIC break point for Gram negative bacteria was found in the drainage fluid after 12 h. Gentamicin levels in the blood samples were negligible over the entire time interval and were steadily well below the renal toxicity reference. The highest urinary concentration of gentamicin was observed between 4 and 9 h postoperatively. Subsequently, it gradually declined until 48 h. Clinically, the rate of cure was 100% at a mean follow-up of 113 weeks (range 90-182). Gentamicin-loaded cement spacers offer the advantage of achieving early high concentrations of the antibiotic directly at the site of infection but especially in the knee a systemic antibiotic therapy must be given as a complement to the spacer implantation to eradicate periprosthetic joint infection (PJI).

  18. Acetabular spacers in 2-stage hip revision: is it worth it? A single-centre retrospective study.

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    Burastero, Giorgio; Basso, Marco; Carrega, Giuliana; Cavagnaro, Luca; Chiarlone, Francesco; Salomone, Carlo; Papa, Gabriele; Felli, Lamberto

    2017-03-31

    The aim of this work is to evaluate an acetabular antibiotic loaded bone cement spacer in 2-stage revision surgery as a potential approach able to reduce complications during the inter-stage period (i.e. dislocation, acetabular wear), as well as simplify 2-stage hip revision surgery and improve hip biomechanics. We performed a retrospective comparative study and evaluated clinical, radiological and surgical data of 71 patients affected by periprosthetic hip infection who were treated with 2-stage exchange. 31 patients were treated using an acetabular spacer in addition to the femoral (group A) while 40 underwent a standard revision surgery (femoral spacer only, group B). Mean time of surgery for the first stage was 148 ± 59 minutes and 142 ± 45 minutes for group A and B respectively; we noted a statistically significant reduction (26 min, p = 0.015) in the same parameter for the second stage (83 ± 35 minutes for group A and 109 ± 36 minutes for group B). We observed the following interstage complications: 5 femoral spacer dislocations (1 for group A and 4 for group B); 1 spacer fracture (group B), 1 spacer fracture (group A), 2 periprosthetic fractures (group B) and 2 patients with acetabular spacer instability (group B). Additionally, we observed a significant improvement in leg length restoration for group A (p = 0.03). Our data show that the acetabular spacer technique is able to reduce the interstage complication rate and allow improved hip biomechanics restoration.

  19. Temporary total hip arthroplasty-like spacer for treating an infected periprosthetic femoral fracture using a long stem: A case report.

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    Kim, Youngwoo; Katsura, Yoshiaki; Kasahara, Nina; Kasahara, Takashi; Kanamura, Masashi; Kawanabe, Keiichi

    2017-01-01

    Infected periprosthetic femoral fractures are among the most complex and significant complications of total hip arthroplasty (THA). We report the novel use of a temporary THA-like spacer for treating an infected periprosthetic femoral fracture after revision surgery using a long stem. We present a 72-year-old woman sustained a left infected periprosthetic femoral fracture after revi - streptococci in the culture sample. On suspicion of a periprosthetic joint infection, we planned a two-stage procedure. We used a temporary THA-like spacer comprising the removed femoral long stem, which was autoclaved and then reimplanted, and applied a new polyethylene acetabular liner. Both components were cemented in place with antibioticloaded bone cement, without applying strong pressure. Pain control waseasily achieved postoperatively because the fracture had been stabilized early. The THA-like spacer was stable, and allowed a good range of motion without pain. She was allowed to move with a wheelchair and was walk with partial weight bearing without pain. Seven week after the initial THAlike spacer placement, we performed a revision THA after successful control of infection. At the 1-year follow-up, the patient remained free of infection. Temporary antibiotic-loaded cement-coated THA-like spacer using a long stem facilitated the eradication of infection, fracture stabilization, and enables partial weight bearing without pain. Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.

  20. 初次全膝关节置换术抗生素骨水泥应用的回顾性队列研究%A retrospective cohort study on prophylactic use of antibiotic-loaded bone cement in primary total knee arthroplasty

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    张雷; 吴宇黎; 符培亮; 付奇伟; 丁喆如

    2012-01-01

    Objective To confirm whether antibiotic-loaded bone cement (ALBC) may reduce infection rates of primary total knee arthroplasty (TKA) by a retrospective cohort study. Methods All cases of primary TKA from 1994 to 2009 were divided into two groups based on whether received ALBC. Differences of age, BMI, diabetes, HSS score and operation time were compared. Logistic analysis was performed to confirm the factors causing infection. Further analysis of all infection cases was also performed. Results The rates of infection between ALBC group and non-ALBC group had no difference (8/945 vs 5/701, χ2 =0.0913, P > 0. 05). The result of logistic analysis also showed ALBC was not predictive of a lower incidence of infection ( OR = 1. 241 , 95% CI (0. 402, 3. 834) , (χ2 =0. 140, P >0. 05). Further analysis of 13 infection cases showed coagulase-negative staphylococcus ( CNS) was most prevalent (38% ), while traditional staphylococcus aureus (SA) was only 23%. The commonly used antibiotic gentamicin may not cover the entire spectrum of organisms. Conclusions A prudential attitude should be held on prophylactic use of ALBC to avoid overuse which may cause waste of medical resources and increase frequency of related complications.%目的 回顾性分析初次全膝关节置换术的合适病例,探讨抗生素骨水泥的应用是否可以降低其术后感染率.方法 对1994年至2009年本组所有接受初次全膝关节置换术的患者按是否使用抗生素骨水泥分为两组,分析年龄、性别、BMI、糖尿病、基础疾病、HSS评分、手术时间的差别,对其中的差异项目进行Logistic回归分析以找出影响TKA术后感染的因素,并对感染病例进行感染时间、致病菌、药敏结果等分析.结果 抗生素骨水泥组相比于非抗生素骨水泥组,其感染率方面并无统计学差异(8/945 vs 5/701,x2=0.0913,P>0.05).相关性Logistic回归分析显示抗生素骨水泥应用并不能降低感染率[OR=1.241,95%CI(0

  1. Approach to osteomyelitis treatment with antibiotic loaded PMMA.

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    Wentao, Zhang; Lei, Guangyu; Liu, Yang; Wang, Wei; Song, Tao; Fan, Jinzhu

    2017-01-01

    To reduce the incidence of osteomyelitis infection, local antibiotic impregnated delivery systems are commonly used as a promising and effective approach to deliver high antibiotic concentrations at the infection site. The objective of this review was to provide a literature review regarding approach to osteomyelitis treatment with antibiotic loaded PMMA. Literature study regarding osteomyelitis treatment with antibiotic loaded carriers using key terms Antibiotic, osteomyelitis, biodegradable PMMA through published articles. Hands searching of bibliographies of identified articles were also undertaken. We concluded that Antibiotic-impregnated PMMA beads are useful options for the treatment of osteomyelitis for prolonged drug therapy. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. Acute renal failure after high-dose antibiotic bone cement: case report and review of the literature.

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    James, Alexia; Larson, Trent

    2015-07-01

    High-dose antibiotic-loaded bone cement (ALBC) spacers are commonly used to treat prosthetic joint infections following total hip and knee arthroplasties. This methodology can provide high local antibiotic concentrations while minimizing systemic exposure and toxicity. The occurrence of acute kidney injury (AKI) is rarely reported. Available literature suggests that the rate may be higher than previously thought. We report a case of significant systemic tobramycin absorption with concomitant acute renal failure in a 69-year-old female following the implantation of a high-dose ALBC spacer containing both tobramycin and vancomycin. The tobramycin level 24 h post-surgery was 5.8 mcg/mL. Due to concomitant renal failure, antibiotic clearance was poor and resulted in prolonged exposure to elevated aminoglycoside levels. Recovery of renal function occurred, but clinicians should be vigilant in considering the potential impact ALBC spacers can have on post-operative renal function if antibiotic elution is higher than expected.

  3. Antibiotic-loaded phosphatidylcholine inhibits staphylococcal bone infection

    Science.gov (United States)

    Jennings, Jessica Amber; Beenken, Karen E; Skinner, Robert A; Meeker, Daniel G; Smeltzer, Mark S; Haggard, Warren O; Troxel, Karen S

    2016-01-01

    AIM To test antibiotic-loaded coating for efficacy in reducing bacterial biofilm and development of osteomyelitis in an orthopaedic model of implant infection. METHODS Phosphatidylcholine coatings loaded with 25% vancomycin were applied to washed and sterilized titanium wires 20 mm in length. A 10 mm segment was removed from rabbit radius (total = 9; 5 coated, 4 uncoated), and the segment was injected with 1 × 106 colony forming units (CFUs) of Staphylococcus aureus (UAMS-1 strain). Titanium wires were inserted through the intramedullary canal of the removed segment and into the proximal radial segment and the segment was placed back into the defect. After 7 d, limbs were removed, X-rayed, swabbed for tissue contamination. Wires were removed and processed to determine attached CFUs. Tissue was swabbed and streaked on agar plates to determine bacteriological score. RESULTS Antibiotic-loaded coatings resulted in significantly reduced biofilm formation (4.7 fold reduction in CFUs; P < 0.001) on titanium wires and reduced bacteriological score in surrounding tissue (4.0 ± 0 for uncoated, 1.25 ± 0.5 for coated; P = 0.01). Swelling and pus formation was evident in uncoated controls at the 7 d time point both visually and radiographically, but not in antibiotic-loaded coatings. CONCLUSION Active antibiotic was released from coated implants and significantly reduced signs of osteomyelitic symptoms. Implant coatings were well tolerated in bone. Further studies with additional control groups and longer time periods are warranted. Antibiotic-loaded phosphatidylcholine coatings applied at the point of care could prevent implant-associated infection in orthopaedic defects. PMID:27622146

  4. Durable infection control and function with the PROSTALAC spacer in two-stage revision for infected knee arthroplasty.

    Science.gov (United States)

    Gooding, Christopher R; Masri, Bassam A; Duncan, Clive P; Greidanus, Nelson V; Garbuz, Donald S

    2011-04-01

    A two-stage revision total knee arthroplasty is recognized as the gold standard in the treatment of infection. However, traditional spacers limit function in the interval between the two stages and may cause instability, scarring, and bone erosion. The PROSTALAC knee spacer is an antibiotic-loaded cement articulating spacer that allows some movement of the knee between stages. Whether motion enhances long-term function is unknown. We therefore identify the rate of control of infection using the PROSTALAC exchange spacer and to assess the clinical outcome after implantation with a definitive implant. We retrospectively reviewed 115 knees that underwent two-stage exchange with the PROSTALAC spacer. Forty-eight of these had a minimum followup of 5 years (mean, 9 years; range, 5-12 years). At last review, 101 of the 115 knees (88%) had no evidence of infection. Of the 14 knees that became reinfected, four were from the same organism and 10 were with a different organism. After further intervention, using the two-stage approach again, the infection was controlled in 12 of the 14 initially reinfected cases, resulting in a failure to cure in only two cases. We observed improvements in mean WOMAC, Oxford, UCLA, and Patient Satisfaction scores at last review. The PROSTALAC functional spacer was associated with a 98% rate of control of infection and improvements in the quality-of-life outcomes in the treatment of chronically infected total knee arthroplasties. Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

  5. Bone cement spacers and Link spacers for treatment of infection due to total hip arthroplasty:a comparative study%两种占位器治疗人工全髋关节置换术后感染的疗效比较

    Institute of Scientific and Technical Information of China (English)

    孙立; 田晓滨; 胡如印; 田家亮; 韩伟; 刘兆成

    2012-01-01

    目的 比较自制含万古霉素的骨水泥占位器和Link感染治疗型占位器的疗效,探讨人工髋关节置换术后慢性感染Ⅱ期翻修中占位器的选择.方法 26例人工髋关节置换术后感染患者,年龄32~82岁,平均69.5岁.彻底清创、取出假体后,14例置入含万古霉素的骨水泥占位器,12例采用Link感染治疗型占位器.术后静脉滴注抗生素2周后,改为口服抗生素6周;术后定期复查血白细胞、红细胞沉降率(ESR)和C-反应蛋白(CRP).Ⅱ期行人工髋关节翻修术.手术前、后以Harris髋关节评分标准评估临床治疗效果.结果 26例患者在彻底清创、取出假体、自制含万古霉素的骨水泥占位器或Link感染治疗型占位器置入后,伤口均Ⅰ期愈合.Ⅱ期翻修手术间隔时间平均5.2个月(3~11.5个月),翻修术后随访平均20.8个月(12~33个月),未出现感染复发征象.Harris髋关节评分Ⅰ期术前平均27.9分,Ⅱ期术前平均52.9分,最后随访时平均83.6分(P<0.05).含万古霉素骨水泥占位器患者Ⅱ期术前有1例断裂,Link感染治疗型占位器患者Ⅱ期术前无断裂.结论 (1)Ⅱ期翻修术具有感染清除率高、缓解疼痛、有效保留关节功能等优点,是治疗人工髋关节置换术后感染的有效方法;(2)使用自制含万古霉素的骨水泥占位器和Link感染治疗型占位器,均能有效感染控制和恢复部分患肢功能;(3)Link感染治疗型占位器术中操作简便,治疗间歇期患肢功能恢复较好,但置管易堵,不能长期缓释抗生素,费用较高,适用于体质较好、感染不严重、两次手术间隔期患肢功能要求较高的患者.%Objective To compare the efficacy of self-made bone cement spacers containing vancomycin(vancomycin spacer)and Link infection-treating spacers(Link type spacer)for chronic infection after total hip arthroplasty(HTA)and investigate the choice of spacers for the two-stage revision of infection.Methods The study

  6. Two-stage revision surgery with preformed spacers and cementless implants for septic hip arthritis: a prospective, non-randomized cohort study

    Directory of Open Access Journals (Sweden)

    Logoluso Nicola

    2011-05-01

    Full Text Available Abstract Background Outcome data on two-stage revision surgery for deep infection after septic hip arthritis are limited and inconsistent. This study presents the medium-term results of a new, standardized two-stage arthroplasty with preformed hip spacers and cementless implants in a consecutive series of adult patients with septic arthritis of the hip treated according to a same protocol. Methods Nineteen patients (20 hips were enrolled in this prospective, non-randomized cohort study between 2000 and 2008. The first stage comprised femoral head resection, debridement, and insertion of a preformed, commercially available, antibiotic-loaded cement hip spacer. After eradication of infection, a cementless total hip arthroplasty was implanted in the second stage. Patients were assessed for infection recurrence, pain (visual analog scale [VAS] and hip joint function (Harris Hip score. Results The mean time between first diagnosis of infection and revision surgery was 5.8 ± 9.0 months; the average duration of follow up was 56.6 (range, 24 - 104 months; all 20 hips were successfully converted to prosthesis an average 22 ± 5.1 weeks after spacer implantation. Reinfection after total hip joint replacement occurred in 1 patient. The mean VAS pain score improved from 48 (range, 35 - 84 pre-operatively to 18 (range, 0 - 38 prior to spacer removal and to 8 (range, 0 - 15 at the last follow-up assessment after prosthesis implantation. The average Harris Hip score improved from 27.5 before surgery to 61.8 between the two stages to 92.3 at the final follow-up assessment. Conclusions Satisfactory outcomes can be obtained with two-stage revision hip arthroplasty using preformed spacers and cementless implants for prosthetic hip joint infections of various etiologies.

  7. Infection of orthopedic implants and the use of antibiotic-loaded bone cements - A review

    NARCIS (Netherlands)

    van de Belt, H; Neut, D; Schenk, W; van Horn, [No Value; van der Mei, HC; Busscher, HJ

    2001-01-01

    Infections by bacteria are a serious complication following orthopedic implant surgery, that can usually only be cured by removing the implant, since the biofilm mode of growth of infecting bacteria on an implant surface protects the organisms from the host immune system and antibiotic therapy. Over

  8. The influence of cyclic loading on gentamicin release from acrylic bone cements

    NARCIS (Netherlands)

    Hendriks, JGE; Neut, D; Hazenberg, JG; Verkerke, GJ; van Horn, [No Value; van der Mei, HC; Busscher, HJ

    2005-01-01

    Antibiotic-loaded acrylic bone cement is widely used in total joint replacement to reduce infections. Walking results in cyclic loading, which has been suggested to stimulate antibiotic release. The goal of this study is to compare antibiotic release from cyclically loaded bone cement with the relea

  9. Effect of gentamicin loaded PMMA bone cement on Staphylococcus aureus biofilm formation

    NARCIS (Netherlands)

    Poelstra, KA; Busscher, HJ; Schenk, W; van Horn, [No Value; van der Mei, HC

    1999-01-01

    PMMA (poly-methyl-methacrylate) bone cement is widely used in prosthetic implant surgery and is currently prepared with vacuum-mixing for improved mechanical properties. Revision of implants due to infection occurs in about 1% of cases, mostly involving staphylococcal strains. Antibiotic loaded ceme

  10. Antibacterial Efficacy of a New Gentamicin-Coating for Cementless Prostheses Compared to Gentamicin-Loaded Bone Cement

    NARCIS (Netherlands)

    Neut, Danielle; Dijkstra, Rene J. B.; Thompson, Jonathan I.; van der Mei, Henny C.; Busscher, Henk J.

    2011-01-01

    Cementless prostheses are increasingly popular but require alternative prophylactic measures than the use of antibiotic-loaded bone cements. Here, we determine the 24-h growth inhibition of gentamicin-releasing coatings from grit-blasted and porous-coated titanium alloys, and compare their antibacte

  11. Patient satisfaction and functional status after treatment of infection at the site of a total knee arthroplasty with use of the PROSTALAC articulating spacer.

    Science.gov (United States)

    Meek, R M Dominic; Masri, Bassam A; Dunlop, David; Garbuz, Donald S; Greidanus, Nelson V; McGraw, Robert; Duncan, Clive P

    2003-10-01

    Two-stage exchange arthroplasty remains the standard treatment of infection at the site of a total knee arthroplasty. The clinical and functional outcomes associated with the use of an articulating antibiotic spacer for two-stage revision for infection are not well established. We conducted a retrospective study to evaluate the outcomes associated with the use of the PROSTALAC articulating spacer between the first and second stages. Fifty-eight patients underwent two-stage revision total knee arthroplasty for infection between January 1997 and December 1999. Of these, fifty-four were alive at the time of follow-up and forty-seven were available for inclusion in the present retrospective study. In all patients, a prosthesis of antibiotic-loaded acrylic cement (the PROSTALAC system) was implanted during the first stage after débridement. The amount of osteolysis that occurred between the stages and the range of motion of the knee joint were measured. After two years of follow-up, outcomes were assessed with use of the WOMAC, Oxford-12, and SF-12 instruments as well as a satisfaction questionnaire. At a minimum of two years (average, forty-one months) after revision arthroplasty, two patients (4%) had had a recurrence of infection. The amount of bone loss was unchanged between stages, and the range of movement of the knee improved from 78.2 degrees before the first stage to 87.1 degrees at two years. The average normalized WOMAC function and pain scores were 68.9 and 77.1, respectively; the average Oxford-12 score was 67.3; the average SF-12 mental and physical scores were 53.7 and 41.2, respectively; and the average satisfaction score was 71.7. A revision operation for infection at the site of a total knee replacement with use of an articulating spacer was associated with reasonable function and satisfaction scores. These findings may be related to the articulating features of the PROSTALAC system, which permits full active movement of the knee in the early

  12. Structural Stator Spacers

    DEFF Research Database (Denmark)

    Rasmussen, Peter Omand; Andreasen, Jens H.; Pijanowski, J. M.

    2001-01-01

    This paper presents a powerful new design aspect to reduce acoustic noise and vibration of electro-magnetic origin for electrical machines, by introducing improved slot wedges referred to as "Structural Stator Spacers". These spacers, by using a very stiff dielectric and non magnetic material...... drawbacks usually associated with other noise reduction methods or interdict other noise control methods. Design models and practical prototypes are detailed which are used to verify the effectiveness of the spacers......., a modified shape and small modifications to the stator laminations not only secure the windings and reduce windage losses but also make it possible to increase the stiffness of the stator structure significantly thereby reducing the generation of audible noise. This new method does not incur the significant...

  13. Development and Evaluation of a New Nanometer Based Spacer NMS-I

    Institute of Scientific and Technical Information of China (English)

    Cheng Rongchao; Wang Ruihe; Cao Huilian; Bu Yuhuan; Cheng Yuanfang

    2007-01-01

    In view of the inadequate cementing quality in the cementation for long isolation intervals of oil and gas wells,and considering the field practice in Tarim Oilfield,a nanometer material LC-212 was introduced as the base stock to experimentally develop a new spacer system NMS-I,in combination with other materials,including a chemical gel plugging agent,carboxymethyl cellulose and barite. Experimental results indicated that the system had a wide adjustable range of density,good rheological property,static stability and compatibility with cement slurry. It also showed no flocculating or thickening effect on the water-base drilling fluid and low-density cement system. Meanwhile,the capacity of lost circulation control and the influence of the spacer on the second interfacial cementing strength were evaluated by a self-made lost circulation simulator and shearing test facility. The results showed that the spacer had favorable plugging and flushing effect,and the second interfacial cementing strength can be greatly improved. Moreover,based on the experiments,the mechanisms of spacer function were analyzed. The results obtained from the investigation offer a novel approach to resolving some practical problems in cementing jobs.

  14. Cement Conundrum

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    China aims to streamline the crowded cement industry Policymakers are looking to build a concrete wall around the cement-making industry as they seek to solidify the fluid cement market and cut excessive production.

  15. Laboratory development and field application of novel cement system for cementing high-temperature oil wells

    Energy Technology Data Exchange (ETDEWEB)

    Wan, X.; Zhang, H.; Li, Y.; Yang, Y. [SINOPEC, Beijing (China); Shan, H.; Xiao, Z. [OPT, Beijing (China)

    2010-07-01

    The challenges that oil and gas well engineers face when cementing mid-to-high temperature exploration oil and gas wells were discussed. A newly developed cement system with an effective laminar-flow spacer was presented along with case histories that document the system's effectiveness for cementing high temperature exploration wells. The problems associated with cementing high temperature exploration wells include high bottom hole static temperature; very low pump rates; and very long job times. These challenges contribute to the operational risks during cement slurry placement in the wellbore as well as during cement sheath setting during the life of the well. The new cement formulation presented in this paper addresses these challenges. Eight jobs have been completed in the field with much success. The combination of a new retarder and fluid loss control additive improves the system performance considerably in terms of low fluid loss rate, minimal free water, proper rheology, predictable thickening time, high resistance to salt contaminations and no adverse effect on set cement strength. The drilling muds are effectively displaced by the laminar flow spacer, thus improving the cementing bond. 9 refs., 5 tabs., 6 figs.

  16. Cement Formation

    DEFF Research Database (Denmark)

    Telschow, Samira; Jappe Frandsen, Flemming; Theisen, Kirsten

    2012-01-01

    Cement production has been subject to several technological changes, each of which requires detailed knowledge about the high multiplicity of processes, especially the high temperature process involved in the rotary kiln. This article gives an introduction to the topic of cement, including...... an overview of cement production, selected cement properties, and clinker phase relations. An extended summary of laboratory-scale investigations on clinkerization reactions, the most important reactions in cement production, is provided. Clinker formations by solid state reactions, solid−liquid and liquid...

  17. Controlled drug release from antibiotic-loaded layered double hydroxide coatings on porous titanium implants in a mouse model.

    Science.gov (United States)

    Badar, Muhammad; Rahim, Muhammad Imran; Kieke, Marc; Ebel, Thomas; Rohde, Manfred; Hauser, Hansjörg; Behrens, Peter; Mueller, Peter P

    2015-06-01

    As an alternative to degradable organic coatings the possibility of using layered double hydroxides (LDHs) to generate implant coatings for controlled drug delivery was evaluated in vivo and in vitro. Coatings prepared from LDH suspensions dissolved slowly and appeared compatible with cultured cells. LDH coatings loaded with an antibiotic resulted in antibacterial effects in vitro. The LDH coating prolonged the drug release period and improved the proliferation of adherent cells in comparison to pure drug coatings. However, during incubation in physiological solutions the LDH coatings became brittle and pieces occasionally detached from the surface. For stress protection porous titanium implants were investigated as a substrate for the coatings. The pores prevented premature detachment of the coatings. To evaluate the coated porous implants in vivo a mouse model was established. To monitor bacterial infection of implants noninvasive in vivo imaging was used to monitor luminescently labeled Pseudomonas aeruginosa. In this model porous implants with antibiotic-loaded LDH coatings could antagonize bacterial infections for over 1 week. The findings provide evidence that delayed drug delivery from LDH coatings could be feasible in combination with structured implant surfaces.

  18. Ertapenem Articulating Spacer for the Treatment of Polymicrobial Total Knee Arthroplasty Infection

    Directory of Open Access Journals (Sweden)

    Dragan Radoicic

    2016-01-01

    Full Text Available Introduction. Periprosthetic joint infections (PJIs are the primary cause of early failure of the total knee arthroplasty (TKA. Polymicrobial TKA infections are often associated with a higher risk of treatment failure. The aim of the study was to assess the efficacy of ertapenem loaded spacers in the treatment of polymicrobial PJI. Methods. There were 18 patients enrolled; nine patients with polymicrobial PJI treated with ertapenem loaded articulating spacers were compared to the group of 9 patients treated with vancomycin or ceftazidime loaded spacers. Results. Successful reimplantation with revision implants was possible in 66.67%. Ertapenem spacers were used in 6 cases in primary two-stage procedure and in 3 cases in secondary spacer exchange. Successful infection eradication was achieved in all cases; final reimplantation with revision knee arthroplasty implants was possible in 6 cases. Conclusion. Ertapenem can be successfully used as antimicrobial addition to the cement spacers in two-stage revision treatment of polymicrobial PJIs. However, this type of spacer may also be useful in the treatment of infections caused by monomicrobial extended spectrum beta-lactamases producing gram-negative bacilli. Further clinical studies are required to evaluate the efficacy and safety of ertapenem spacers in the treatment of polymicrobial and monomicrobial PJIs.

  19. Loading and release of doxycycline hyclate from strontium-substituted calcium phosphate cement.

    Science.gov (United States)

    Alkhraisat, M Hamdan; Rueda, C; Cabrejos-Azama, J; Lucas-Aparicio, J; Mariño, F Tamimi; Torres García-Denche, J; Jerez, L Blanco; Gbureck, U; Cabarcos, E Lopez

    2010-04-01

    Novel Sr-substituted calcium phosphate cement (CPC) loaded with doxycycline hyclate (DOXY-h) was employed to elucidate the effect of strontium substitution on antibiotic delivery. The cement was prepared using as reactants Sr-substituted beta-tricalcium phosphate (Sr-beta-TCP) and acidic monocalcium phosphate monohydrate. Two different methods were used to load DOXY-h: (i) the adsorption on CPC by incubating the set cement in drug-containing solutions; and (ii) the use of antibiotic solution as the cement liquid phase. The results revealed that the Sr-substituted cement efficiently adsorbs the antibiotic, which is attributed to an enhanced accessibility to the drug-binding sites within this CPC. DOXY-h desorption is influenced by the initial adsorbed amount and the cement matrix type. Furthermore, the fraction of drug released from CPCs set with DOXY-h solution was higher, and the release rate was faster for the CPC prepared with 26.7% Sr-beta-TCP. The analysis of releasing profiles points to Fickian diffusion as the mechanism responsible for antibiotic delivery. We can conclude that Sr substitution in secondary calcium phosphate cements improves their efficiency for DOXY-h adsorption and release. The antibiotic loading method provides a way to switch from rapid and complete to slower and prolonged drug release. Copyright 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  20. Spacer lock of roof bolting

    Energy Technology Data Exchange (ETDEWEB)

    Shirokov, A.P.; Boronov, N.N.; Isachenko, V.M.; Kuntsevich, V.I.

    1980-04-05

    The object of the invention is a spacer joint of anchor bolting, which includes a wedge-shaped head and half-coupling, which are beveled on the inner side of the walls, and have ribs on the outer sides of the walls. It is characterized in that in order to reduce cost of the joint by reducing the amount of steel and manufacturing costs, the walls of the half-couplings hae identical thickness lengthwise, and the ribs are of varying height with corresponding projections on the inner side of the half-couplings.

  1. CRISPR interference directs strand specific spacer acquisition.

    Directory of Open Access Journals (Sweden)

    Daan C Swarts

    Full Text Available BACKGROUND: CRISPR/Cas is a widespread adaptive immune system in prokaryotes. This system integrates short stretches of DNA derived from invading nucleic acids into genomic CRISPR loci, which function as memory of previously encountered invaders. In Escherichia coli, transcripts of these loci are cleaved into small RNAs and utilized by the Cascade complex to bind invader DNA, which is then likely degraded by Cas3 during CRISPR interference. RESULTS: We describe how a CRISPR-activated E. coli K12 is cured from a high copy number plasmid under non-selective conditions in a CRISPR-mediated way. Cured clones integrated at least one up to five anti-plasmid spacers in genomic CRISPR loci. New spacers are integrated directly downstream of the leader sequence. The spacers are non-randomly selected to target protospacers with an AAG protospacer adjacent motif, which is located directly upstream of the protospacer. A co-occurrence of PAM deviations and CRISPR repeat mutations was observed, indicating that one nucleotide from the PAM is incorporated as the last nucleotide of the repeat during integration of a new spacer. When multiple spacers were integrated in a single clone, all spacer targeted the same strand of the plasmid, implying that CRISPR interference caused by the first integrated spacer directs subsequent spacer acquisition events in a strand specific manner. CONCLUSIONS: The E. coli Type I-E CRISPR/Cas system provides resistance against bacteriophage infection, but also enables removal of residing plasmids. We established that there is a positive feedback loop between active spacers in a cluster--in our case the first acquired spacer--and spacers acquired thereafter, possibly through the use of specific DNA degradation products of the CRISPR interference machinery by the CRISPR adaptation machinery. This loop enables a rapid expansion of the spacer repertoire against an actively present DNA element that is already targeted, amplifying the

  2. CEMENT SLURRIES FOR GEOTHERMAL WELLS CEMENTING

    Directory of Open Access Journals (Sweden)

    Nediljka Gaurina-Međimurec

    1994-12-01

    Full Text Available During a well cementing special place belongs to the cement slurry design. To ensure the best quality of cementing, a thorough understanding of well parameters is essential, as well as behaviour of cement slurry (especially at high temperatures and application of proven cementing techniques. Many cement jobs fail because of bad job planning. Well cementing without regarding what should be accomplished, can lead to well problems (channels in the cement, unwanted water, gas or fluid production, pipe corrosion and expensive well repairs. Cementing temperature conditions are important because bot-tomhole circulating temperatures affect slurry thickening time, arheology, set time and compressive strength development. Knowing the actual temperature which cement encounters during placement allows the selection of proper cementing materials for a specific application. Slurry design is affected by well depth, bottom hole circulating temperature and static temperature, type or drilling fluid, slurry density, pumping time, quality of mix water, fluid loss control, flow regime, settling and free water, quality of cement, dry or liquid additives, strength development, and quality of the lab cement testing and equipment. Most Portland cements and Class J cement have shown suitable performances in geot-hermal wells. Cement system designs for geothermal wells differ from those for conventional high temperature oil and gas wells in the exclusive use of silica flour instead of silica sand, and the avoidance of fly ash as an extender. In this paper, Portland cement behaviour at high temperatures is described. Cement slurry and set cement properties are also described. Published in literature, the composition of cement slurries which were tested in geothermal conditions and which obtained required compressive strength and water permeability are listed. As a case of our practice geothermal wells Velika Ciglena-1 and Velika Ciglena-la are described.

  3. Development of a High Performance Spacer Grid

    Energy Technology Data Exchange (ETDEWEB)

    Song, Kee Nam; Song, K. N.; Yoon, K. H. (and others)

    2007-03-15

    A spacer grid in a LWR fuel assembly is a key structural component to support fuel rods and to enhance the heat transfer from the fuel rod to the coolant. In this research, the main research items are the development of inherent and high performance spacer grid shapes, the establishment of mechanical/structural analysis and test technology, and the set-up of basic test facilities for the spacer grid. The main research areas and results are as follows. 1. 18 different spacer grid candidates have been invented and applied for domestic and US patents. Among the candidates 16 are chosen from the patent. 2. Two kinds of spacer grids are finally selected for the advanced LWR fuel after detailed performance tests on the candidates and commercial spacer grids from a mechanical/structural point of view. According to the test results the features of the selected spacer grids are better than those of the commercial spacer grids. 3. Four kinds of basic test facilities are set up and the relevant test technologies are established. 4. Mechanical/structural analysis models and technology for spacer grid performance are developed and the analysis results are compared with the test results to enhance the reliability of the models.

  4. Lunar cement

    Science.gov (United States)

    Agosto, William N.

    1992-01-01

    With the exception of water, the major oxide constituents of terrestrial cements are present at all nine lunar sites from which samples have been returned. However, with the exception of relatively rare cristobalite, the lunar oxides are not present as individual phases but are combined in silicates and in mixed oxides. Lime (CaO) is most abundant on the Moon in the plagioclase (CaAl2Si2O8) of highland anorthosites. It may be possible to enrich the lime content of anorthite to levels like those of Portland cement by pyrolyzing it with lunar-derived phosphate. The phosphate consumed in such a reaction can be regenerated by reacting the phosphorus product with lunar augite pyroxenes at elevated temperatures. Other possible sources of lunar phosphate and other oxides are discussed.

  5. LISA telescope spacer design investigations

    Science.gov (United States)

    Sanjuan, Josep; Mueller, Guido; Livas, Jeffrey; Preston, Alix; Arsenovic, Petar; Castellucci, Kevin; Generie, Joseph; Howard, Joseph; Stebbins, Robin

    ) and materials such as Silicon Carbide (SiC) and Carbon Fiber Reinforced Plastic (CFRP) are considered to be used in the telescope spacer structure. We will describe our experimental efforts to understand and quantify the behavior of different materials and also discuss a first investigation of a specific on-axis SiC telescope spacer for LISA. This work is supported by NASA contract 00069955.

  6. ULTRA-LIGHTWEIGHT CEMENT

    Energy Technology Data Exchange (ETDEWEB)

    Fred Sabins

    2002-07-30

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report includes results from laboratory testing of ULHS systems along with other lightweight cement systems, including foamed and sodium silicate slurries. During this project quarter, a comparison study of the three cement systems examined the effect that cement drillout has on the three cement systems. Testing to determine the effect of pressure cycling on the shear bond properties of the cement systems was also conducted. This report discusses testing that was performed to analyze the alkali-silica reactivity of ULHS in cement slurries.

  7. A New Type of Biphasic Calcium Phosphate Cement as a Gentamicin Carrier for Osteomyelitis

    Directory of Open Access Journals (Sweden)

    Wen-Yu Su

    2013-01-01

    Full Text Available Osteomyelitis therapy is a long-term and inconvenient procedure for a patient. Antibiotic-loaded bone cements are both a complementary and alternative treatment option to intravenous antibiotic therapy for the treatment of osteomyelitis. In the current study, the biphasic calcium phosphate cement (CPC, called α-TCP/HAP (α-tricalcium phosphate/hydroxyapatite biphasic cement, was prepared as an antibiotics carrier for osteomyelitis. The developed biphasic cement with a microstructure of α-TCP surrounding the HAP has a fast setting time which will fulfill the clinical demand. The X-ray diffraction and Fourier transform infrared spectrometry analyses showed the final phase to be HAP, the basic bone mineral, after setting for a period of time. Scanning electron microscopy revealed a porous structure with particle sizes of a few micrometers. The addition of gentamicin in α-TCP/HAP would delay the transition of α-TCP but would not change the final-phase HAP. The gentamicin-loaded α-TCP/HAP supplies high doses of the antibiotic during the initial 24 hours when they are soaked in phosphate buffer solution (PBS. Thereafter, a slower drug release is produced, supplying minimum inhibitory concentration until the end of the experiment (30 days. Studies of growth inhibition of Staphylococcus aureus and Pseudomonas aeruginosa in culture indicated that gentamicin released after 30 days from α-TCP/HAP biphasic cement retained antibacterial activity.

  8. Investigation and analysis of dual-k spacer with different materials and spacer lengths for nanowire-FET performance

    Science.gov (United States)

    Ko, Hyungwoo; Kim, Jongsu; Kang, Myounggon; Shin, Hyungcheol

    2017-10-01

    In this work, dual-k spacer structures are investigated using a variety of materials along the high-k spacer length in detail. It is known that not only the higher permittivity materials of high-k spacer boost the on-current but also lower permittivity materials of low-k spacer effectively reduce the off-current. By compared the results of other various single spacers and dual-k spacers, it is HfO2/Vacuum dual-k spacer that shows relatively higher ION, ION/IOFF, better immunity of short channel effects and outstanding device performances.

  9. The ribosomal gene spacer region in archaebacteria

    Science.gov (United States)

    Achenbach-Richter, L.; Woese, C. R.

    1988-01-01

    Sequences for the spacer regions that separate the 16S and 23S ribosomal RNA genes have been determined for four more (strategically placed) archaebacteria. These confirm the general rule that methanogens and extreme halophiles have spacers that contain a single tRNAala gene, while tRNA genes are not found in the spacer region of the true extreme thermophiles. The present study also shows that the spacer regions from the sulfate reducing Archaeglobus and the extreme thermophile Thermococcus (both of which cluster phylogenetically with the methanogens and extreme halophiles) contain each a tRNAala gene. Thus, not only all methanogens and extreme halophiles show this characteristic, but all organisms on the "methanogen branch" of the archaebacterial tree appear to do so. The finding of a tRNA gene in the spacer region of the extreme thermophile Thermococcus celer is the first known phenotypic property that links this organism with its phylogenetic counterparts, the methanogens, rather than with its phenotypic counterparts, the sulfur-dependent extreme thermophiles.

  10. Effect of rheology on flow displacement during cementing process in oil wells

    Energy Technology Data Exchange (ETDEWEB)

    Braghini, Andre; Naccache, Monica F.; Fonseca, Marcos I. [Dept. Mechanical Engineering. Pontificia Universidade Catolica (PUR-Rio), Rio de Janeiro, RJ (Brazil)], e-mails: mnaccache@puc-rio.br; Miranda, Cristiane R. de; Martins, Andre L.; Aranha, Pedro E. [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil)], e-mails: crisrichard@petrobras.com.br, aleibsohn@petrobras.com.br, pearanha@petrobras.com.br

    2010-07-01

    This paper describes a set of numerical simulations of the displacement flow of three non-Newtonian fluids through annular eccentric wells. The main application of this work is the studying of drilling and completion processes of oil wells where a cement slurry pushes the drilling mud, used in the drilling process to lubricate the drill and to remove the produced drilling cuts. To avoid contamination, a spacer fluid is usually inserted between them. Both drilling mud and cement slurry behave as non-Newtonian fluids, and the spacer fluid can be Newtonian or non-Newtonian. The analysis of flow and interface configuration between these fluids helps to determine contamination, and is an important tool for the process optimization. The numerical solution of the governing conservation equations of mass and momentum is obtained with the Fluent software, using the finite volume technique and the volume of fluid method. The effects of rheological parameters, density ratios and pumped volume of the spacer fluid are investigated. The results obtained show that the displacement is better when a more viscous spacer fluid is used. The results also show that using lower amounts of the spacer fluid can lead to contamination, which is worse in the smaller gap region of the annular space, in the case of non-rectilinear well. It was also observed that the density ratios play a major role in the cementing operation. (author)

  11. Separator-spacer for electrochemical systems

    Science.gov (United States)

    Grimes, Patrick G.; Einstein, Harry; Newby, Kenneth R.; Bellows, Richard J.

    1983-08-02

    An electrochemical cell construction features a novel co-extruded plastic electrode in an interleaved construction with a novel integral separator-spacer. Also featured is a leak and impact resistant construction for preventing the spill of corrosive materials in the event of rupture.

  12. ULTRA-LIGHTWEIGHT CEMENT

    Energy Technology Data Exchange (ETDEWEB)

    Fred Sabins

    2001-04-15

    The objective of this project is to develop an improved ultra-lightweight cement using ultralight hollow glass spheres (ULHS). Work reported herein addresses Task 1: Assess Ultra-Lightweight Cementing Problems and Task 3: Test Ultra-Lightweight Cements. Results reported this quarter include a review and summary of Halliburton Energy Services (HES) and BJ Services historical performance data for lightweight cement applications. These data are analyzed and compared to ULHS cement and foamed cement performances. Similar data is expected from Schlumberger, and an analysis of this data will be completed in the following phases of the project. Quality control testing of materials used to formulate ULHS cements in the laboratory was completed to establish baseline material performance standards. A testing protocol was developed employing standard procedures as well as procedures tailored to evaluate ULHS and foamed cement. This protocol is presented and discussed. Results of further testing of ULHS cements are presented along with an analysis to establish cement performance design criteria to be used during the remainder of the project. Finally, a list of relevant literature on lightweight cement performance is compiled for review during the next quarter.

  13. Heterogeneous diversity of spacers within CRISPR

    Science.gov (United States)

    Deem, Michael; He, Jiankui

    2011-03-01

    Clustered regularly interspaced short palindromic repeats (CRISPR) in bacterial and archaeal DNA have recently been shown to be a new type of anti-viral immune system in these organisms. We here study the diversity of spacers in CRISPR under selective pressure. We propose a population dynamics model that explains the biological observation that the leader-proximal end of CRISPR is more diversified and the leader-distal end of CRISPR is more conserved. This result is shown to be in agreement with recent experiments. Our results show that the CRISPR spacer structure is influenced by and provides a record of the viral challenges that bacteria face. 1) J. He and M. W. Deem, Phys. Rev. Lett. 105 (2010) 128102

  14. ULTRA-LIGHTWEIGHT CEMENT

    Energy Technology Data Exchange (ETDEWEB)

    Fred Sabins

    2002-01-23

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report includes results from laboratory testing of ULHS systems along with other lightweight cement systems: foamed and sodium silicate slurries. Comparison studies of the three cement systems examined several properties: tensile strength, Young's modulus, water permeability, and shear bond. Testing was also done to determine the effect that temperature cycling has on the shear bond properties of the cement systems. In addition, analysis was carried out to examine alkali silica reactivity of slurries containing ULHS. Data is also presented from a study investigating the effects of mixing and pump circulation on breakage of ULHS. Information is also presented about the field application of ULHS in cementing a 7-in. intermediate casing in south Texas.

  15. Effect of Spacer and the Enzyme-Linked Immunosorbent Assay

    Directory of Open Access Journals (Sweden)

    Manisha Sathe

    2016-09-01

    Full Text Available The effect of spacers and the enzyme-linked immunosorbent assay (ELISA formats on the functional parameters of assays such as lower detection limit, inhibitory concentration at 50 per cent (IC50, and specificity were studied. Enzyme conjugates having hydrophobic and hydrophilic spacers were prepared using O-isopropyl methylphosphonic acid (IMPA and horseradish peroxidase (HRP as an enzyme label. Comparison was made with reference to enzyme conjugate without any spacer. The present investigation revealed that the presence of a hydrophilic spacer in the enzyme conjugate significantly improves the sensitivity of assays. An enhanced IC50 value achieved was 0.01 μg mL−1 for free antigen detection by direct immunoassay using hydrophilic spacers and precoating of ELISA plates by secondary antibody. The use of a hydrophilic spacer might have helped in projecting the hapten in the aqueous phase, leading to enhanced antibody binding signal and improved sensitivity of the assay.

  16. Cement and concrete

    Science.gov (United States)

    Corley, Gene; Haskin, Larry A.

    1992-01-01

    To produce lunar cement, high-temperature processing will be required. It may be possible to make calcium-rich silicate and aluminate for cement by solar heating of lunar pyroxene and feldspar, or chemical treatment may be required to enrich the calcium and aluminum in lunar soil. The effects of magnesium and ferrous iron present in the starting materials and products would need to be evaluated. So would the problems of grinding to produce cement, mixing, forming in vacuo and low gravity, and minimizing water loss.

  17. POZZOLAN AND CEMENTS WITH POZZOLAN

    OpenAIRE

    Hasan KAPLAN; Hanifi BİNİCİ

    1995-01-01

    Cement, one of the basic material of construction engineering, has an important place in view of strength and cost of structures. Cement consumption is increasing parallel to development of building construction sector. For cement producers, minimal cost is desired by using new and economical material sources. On the other hand, the controllers and contractors need cheaper, safer and higher strength materials. From this respect cement industry tends to use cement with pozzolan. In Türkiye, ce...

  18. Molecular recordings by directed CRISPR spacer acquisition.

    Science.gov (United States)

    Shipman, Seth L; Nivala, Jeff; Macklis, Jeffrey D; Church, George M

    2016-07-29

    The ability to write a stable record of identified molecular events into a specific genomic locus would enable the examination of long cellular histories and have many applications, ranging from developmental biology to synthetic devices. We show that the type I-E CRISPR (clustered regularly interspaced short palindromic repeats)-Cas system of Escherichia coli can mediate acquisition of defined pieces of synthetic DNA. We harnessed this feature to generate records of specific DNA sequences into a population of bacterial genomes. We then applied directed evolution so as to alter the recognition of a protospacer adjacent motif by the Cas1-Cas2 complex, which enabled recording in two modes simultaneously. We used this system to reveal aspects of spacer acquisition, fundamental to the CRISPR-Cas adaptation process. These results lay the foundations of a multimodal intracellular recording device.

  19. Mask specification guidelines in spacer patterning technology

    Science.gov (United States)

    Hashimoto, Kohji; Mukai, Hidefumi; Miyoshi, Seiro; Yamaguchi, Shinji; Mashita, Hiromitsu; Kobayashi, Yuuji; Kawano, Kenji; Hirano, Takashi

    2008-11-01

    We have studied both the mask CD specification and the mask defect specification for spacer patterning technology (SPT). SPT has the possibility of extending optical lithography to below 40nm half-pitch devices. Since SPT necessitates somewhat more complicated wafer process flow, the CD error and mask defect printability on wafers involve more process factors compared with conventional single-exposure process (SEP). This feature of SPT implies that it is very important to determine mask-related specifications for SPT in order to select high-end mask fabrication strategies; those are for mask writing tools, mask process development, materials, inspection tools, and so on. Our experimental studies reveal that both mask CD specification and mask defect specification are somehow relaxed from those in ITRS2007. This is most likely because SPT reduces mask CD error enhanced factor (MEF) and the reduction of line-width roughness (LWR).

  20. Stress Analysis of Single Spacer Grid Support considering Fuel Rod

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Y. G.; Jung, D. H.; Kim, J. H. [Chungnam National University, Daejeon (Korea, Republic of); Park, J. K.; Jeon, K. L. [Korea Nuclear Fuel, Daejeon (Korea, Republic of)

    2010-10-15

    Pressurized water reactor (PWR) nuclear fuel assembly is mainly composed of a top-end piece, a bottom-end piece, lots of fuel rods, and several spacer grids. Among them, the main function of spacer grid is protecting fuel rods from Fluid Induced Vibration (FIV). The cross section of spacer grid assembled by laser welding in upper and lower point. When the fuel rod inserted in spacer gird, spring and dimple and around of welded area got a stresses. The main hypothesis of this analysis is the boundary area of HAZ and base metal can get a lot of damage than other area by FIV. So, design factors of spacer grid mainly considered to preventing the fatigue failure in HAZ and spring and dimple of spacer grid. From previous researching, the environment in reactor verified. Pressure and temperature of light water observed 15MPa and 320 .deg. C, and vibration of the fuel rod observed within 0 {approx} 50Hz. In this study, mechanical properties of zirconium alloy that extracted from the test and the spacer grid model which used in the PWR were applied in stress analyzing. General-purpose finite element analysis program was used ANSYS Workbench 12.0.1 version. 3-D CAD program CATIA was used to create spacer grid model

  1. Orthognathic model surgery with LEGO key-spacer.

    Science.gov (United States)

    Tsang, Alfred Chee-Ching; Lee, Alfred Siu Hong; Li, Wai Keung

    2013-12-01

    A new technique of model surgery using LEGO plates as key-spacers is described. This technique requires less time to set up compared with the conventional plaster model method. It also retains the preoperative setup with the same set of models. Movement of the segments can be measured and examined in detail with LEGO key-spacers.

  2. Spacer effect on nanostructures and self-assembly in organogels via some bolaform cholesteryl imide derivatives with different spacers

    Science.gov (United States)

    Jiao, Tifeng; Gao, Fengqing; Zhang, Qingrui; Zhou, Jingxin; Gao, Faming

    2013-10-01

    In this paper, new bolaform cholesteryl imide derivatives with different spacers were designed and synthesized. Their gelation behaviors in 23 solvents were investigated, and some of them were found to be low molecular mass organic gelators. The experimental results indicated that these as-formed organogels can be regulated by changing the flexible/rigid segments in spacers and organic solvents. Suitable combination of flexible/rigid segments in molecular spacers in the present cholesteryl gelators is favorable for the gelation of organic solvents. Scanning electron microscopy and atomic force microscopy observations revealed that the gelator molecules self-assemble into different aggregates, from wrinkle and belt to fiber with the change of spacers and solvents. Spectral studies indicated that there existed different H-bond formations between imide groups and assembly modes, depending on the substituent spacers in molecular skeletons. The present work may give some insight into the design and character of new organogelators and soft materials with special molecular structures.

  3. ULTRA-LIGHTWEIGHT CEMENT

    Energy Technology Data Exchange (ETDEWEB)

    Fred Sabins

    2001-10-23

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). Work reported herein addresses tasks performed in the fourth quarter as well as the other three quarters of the past year. The subjects that were covered in previous reports and that are also discussed in this report include: Analysis of field laboratory data of active cement applications from three oil-well service companies; Preliminary findings from a literature review focusing on problems associated with ultra-lightweight cements; Summary of pertinent information from Russian ultra-lightweight cement literature review; and Comparison of compressive strengths of ULHS systems using ultrasonic and crush methods Results reported from the fourth quarter include laboratory testing of ULHS systems along with other lightweight cement systems--foamed and sodium silicate slurries. These comparison studies were completed for two different densities (10.0 and 11.5 lb/gal) and three different field application scenarios. Additional testing included the mechanical properties of ULHS systems and other lightweight systems. Studies were also performed to examine the effect that circulation by centrifugal pump during mixing has on breakage of ULHS.

  4. Advanced hole patterning technology using soft spacer materials (Conference Presentation)

    Science.gov (United States)

    Park, Jong Keun; Hustad, Phillip D.; Aqad, Emad; Valeri, David; Wagner, Mike D.; Li, Mingqi

    2017-03-01

    A continuing goal in integrated circuit industry is to increase density of features within patterned masks. One pathway being used by the device manufacturers for patterning beyond the 80nm pitch limitation of 193 immersion lithography is the self-aligned spacer double patterning (SADP). Two orthogonal line space patterns with subsequent SADP can be used for contact holes multiplication. However, a combination of two immersion exposures, two spacer deposition processes, and two etch processes to reach the desired dimensions makes this process expensive and complicated. One alternative technique for contact hole multiplication is the use of an array of pillar patterns. Pillars, imaged with 193 immersion photolithography, can be uniformly deposited with spacer materials until a hole is formed in the center of 4 pillars. Selective removal of the pillar core gives a reversal of phases, a contact hole where there was once a pillar. However, the highly conformal nature of conventional spacer materials causes a problem with this application. The new holes, formed between 4 pillars, by this method have a tendency to be imperfect and not circular. To improve the contact hole circularity, this paper presents the use of both conventional spacer material and soft spacer materials. Application of soft spacer materials can be achieved by an existing coating track without additional cost burden to the device manufacturers.

  5. PART II. HYDRATED CEMENTS

    Directory of Open Access Journals (Sweden)

    Milan Drabik

    2014-09-01

    Full Text Available Essential focus of the study has been to acquire thermoanalytical events, incl. enthalpies of decompositions - ΔH, of technological materials based on two types of Portland cements. The values of thermoanalytical events and also ΔH of probes of technological compositions, if related with the data of a choice of minerals of calcium-silicate-sulfate-aluminate hydrates, served as a valued input for the assessment of phases present and phase changes due to the topical hydraulic processes. The results indicate mainly the effects of "standard humidity" or "wet storage" of the entire hydration/hydraulic treatment, but also the presence of cement residues alongside calcium-silicate-sulfate-aluminate hydrates (during the tested period of treatment. "A diluting" effect of unhydrated cement residues upon the values of decomposition enthalpies in the studied multiphase system is postulated and discussed

  6. The mechanical effect of the existing cement mantle on the in-cement femoral revision.

    LENUS (Irish Health Repository)

    Keeling, Parnell

    2012-08-01

    Cement-in-cement revision hip arthroplasty is an increasingly popular technique to replace a loose femoral stem which retains much of the original cement mantle. However, some concern exists regarding the retention of the existing fatigued and aged cement in such cement-in-cement revisions. This study investigates whether leaving an existing fatigued and aged cement mantle degrades the mechanical performance of a cement-in-cement revision construct.

  7. Preclinical Evaluation of Bioabsorbable Polyglycolic Acid Spacer for Particle Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Akasaka, Hiroaki [Division of Radiation Oncology, Kobe University Graduate School of Medicine, Hyogo Japan (Japan); Sasaki, Ryohei, E-mail: rsasaki@med.kobe-u.ac.jp [Division of Radiation Oncology, Kobe University Graduate School of Medicine, Hyogo Japan (Japan); Miyawaki, Daisuke; Mukumoto, Naritoshi; Sulaiman, Nor Shazrina Binti [Division of Radiation Oncology, Kobe University Graduate School of Medicine, Hyogo Japan (Japan); Nagata, Masaaki [Division of Gastroenterology, Kobe University Graduate School of Medicine, Hyogo Japan (Japan); Yamada, Shigeru [Research Center Hospital, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Chiba (Japan); Murakami, Masao [Radiation Oncology Center, Dokkyo Medical University, Tochigi (Japan); Demizu, Yusuke [Department of Radiology, Hyogo Ion Beam Medical Center, Hyogo (Japan); Fukumoto, Takumi [Division of Hepato-Biliary-Pancreatic Surgery, Kobe University Graduate School of Medicine, Hyogo Japan (Japan)

    2014-12-01

    Purpose: To evaluate the efficacy and safety of a polyglycolic acid (PGA) spacer through physical and animal experiments. Methods and Materials: The spacer was produced with surgical suture material made of PGA, forming a 3-dimensional nonwoven fabric. For evaluation or physical experiments, 150-MeV proton or 320-MeV carbon-ion beams were used to generate 60-mm width of spread-out Bragg peak. For animal experiments, the abdomens of C57BL/6 mice, with or without the inserted PGA spacers, were irradiated with 20 Gy of carbon-ion beam (290 MeV) using the spread-out Bragg peak. Body weight changes over time were scored, and radiation damage to the intestine was investigated using hematoxylin and eosin stain. Blood samples were also evaluated 24 days after the irradiation. Long-term thickness retention and safety were evaluated using crab-eating macaques. Results: No chemical or structural changes after 100 Gy of proton or carbon-ion irradiation were observed in the PGA spacer. Water equivalency of the PGA spacer was equal to the water thickness under wet condition. During 24 days' observation after 20 Gy of carbon-ion irradiation, the body weights of mice with the PGA spacer were relatively unchanged, whereas significant weight loss was observed in those mice without the PGA spacer (P<.05). In mice with the PGA spacer, villus and crypt structure were preserved after irradiation. No inflammatory reactions or liver or renal dysfunctions due to placement of the PGA spacer were observed. In the abdomen of crab-eating macaques, thickness of the PGA spacer was maintained 8 weeks after placement. Conclusions: The absorbable PGA spacer had water-equivalent, bio-compatible, and thickness-retaining properties. Although further evaluation is warranted in a clinical setting, the PGA spacer may be effective to stop proton or carbon-ion beams and to separate normal tissues from the radiation field.

  8. Cement Mason's Curriculum. Instructional Units.

    Science.gov (United States)

    Hendirx, Laborn J.; Patton, Bob

    To assist cement mason instructors in providing comprehensive instruction to their students, this curriculum guide treats both the skills and information necessary for cement masons in commercial and industrial construction. Ten sections are included, as follow: related information, covering orientation, safety, the history of cement, and applying…

  9. Reducing cement's CO2 footprint

    Science.gov (United States)

    van Oss, Hendrik G.

    2011-01-01

    The manufacturing process for Portland cement causes high levels of greenhouse gas emissions. However, environmental impacts can be reduced by using more energy-efficient kilns and replacing fossil energy with alternative fuels. Although carbon capture and new cements with less CO2 emission are still in the experimental phase, all these innovations can help develop a cleaner cement industry.

  10. Technology Roadmaps: Cement

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2009-07-01

    To support its roadmap work focusing on key technologies for emissions reductions, the International Energy Agency (IEA) also investigated one particular industry: cement. Cement production includes technologies that are both specific to this industry and those that are shared with other industries (e.g., grinding, fuel preparation, combustion, crushing, transport). An industry specific roadmap provides an effective mechanism to bring together several technology options. It outlines the potential for technological advancement for emissions reductions in one industry, as well as potential cross-industry collaboration.

  11. Cementing a wellbore using cementing material encapsulated in a shell

    Energy Technology Data Exchange (ETDEWEB)

    Aines, Roger D.; Bourcier, William L.; Duoss, Eric B.; Floyd, III, William C.; Spadaccini, Christopher M.; Vericella, John J.; Cowan, Kenneth Michael

    2017-03-14

    A system for cementing a wellbore penetrating an earth formation into which a pipe extends. A cement material is positioned in the space between the wellbore and the pipe by circulated capsules containing the cement material through the pipe into the space between the wellbore and the pipe. The capsules contain the cementing material encapsulated in a shell. The capsules are added to a fluid and the fluid with capsules is circulated through the pipe into the space between the wellbore and the pipe. The shell is breached once the capsules contain the cementing material are in position in the space between the wellbore and the pipe.

  12. Cementing a wellbore using cementing material encapsulated in a shell

    Science.gov (United States)

    Aines, Roger D.; Bourcier, William L.; Duoss, Eric B.; Spadaccini, Christopher M.; Cowan, Kenneth Michael

    2016-08-16

    A system for cementing a wellbore penetrating an earth formation into which a pipe extends. A cement material is positioned in the space between the wellbore and the pipe by circulated capsules containing the cement material through the pipe into the space between the wellbore and the pipe. The capsules contain the cementing material encapsulated in a shell. The capsules are added to a fluid and the fluid with capsules is circulated through the pipe into the space between the wellbore and the pipe. The shell is breached once the capsules contain the cementing material are in position in the space between the wellbore and the pipe.

  13. Cementing a wellbore using cementing material encapsulated in a shell

    Energy Technology Data Exchange (ETDEWEB)

    Aines, Roger D.; Bourcier, William L.; Duoss, Eric B.; Spadaccini, Christopher M.; Cowan, Kenneth Michael

    2016-08-16

    A system for cementing a wellbore penetrating an earth formation into which a pipe extends. A cement material is positioned in the space between the wellbore and the pipe by circulated capsules containing the cement material through the pipe into the space between the wellbore and the pipe. The capsules contain the cementing material encapsulated in a shell. The capsules are added to a fluid and the fluid with capsules is circulated through the pipe into the space between the wellbore and the pipe. The shell is breached once the capsules contain the cementing material are in position in the space between the wellbore and the pipe.

  14. Technique for adapting a spacer for a custom impression tray.

    Science.gov (United States)

    Kaur, Harsimran; Nanda, Aditi; Verma, Mahesh; Koli, Dheeraj

    2016-12-01

    A method of adapting a spacer for the custom trays used to make a definite impression for complete dentures is presented. The technique can be used under a variety of conditions and offers several advantages.

  15. Response of an electrostatic probe for a right cylindrical spacer

    DEFF Research Database (Denmark)

    Rerup, T; Crichton, George C; McAllister, Iain Wilson

    1994-01-01

    During the last decade many experimental studies of surface charge phenomena have been undertaken employing right cylindrical spacers. Measurement of the surface charge was performed using small electrostatic field probes to scan across the dielectric surface. Charges are electrostatically induced...

  16. Osteotransductive bone cements.

    Science.gov (United States)

    Driessens, F C; Planell, J A; Boltong, M G; Khairoun, I; Ginebra, M P

    1998-01-01

    Calcium phosphate bone cements (CPBCs) are osteotransductive, i.e. after implantation in bone they are transformed into new bone tissue. Furthermore, due to the fact that they are mouldable, their osteointegration is immediate. Their chemistry has been established previously. Some CPBCs contain amorphous calcium phosphate (ACP) and set by a sol-gel transition. The others are crystalline and can give as the reaction product dicalcium phosphate dihydrate (DCPD), calcium-deficient hydroxyapatite (CDHA), carbonated apatite (CA) or hydroxyapatite (HA). Mixed-type gypsum-DCPD cements are also described. In vivo rates of osteotransduction vary as follows: gypsum-DCPD > DCPD > CDHA approximately CA > HA. The osteotransduction of CDHA-type cements may be increased by adding dicalcium phosphate anhydrous (DCP) and/or CaCO3 to the cement powder. CPBCs can be used for healing of bone defects, bone augmentation and bone reconstruction. Incorporation of drugs like antibiotics and bone morphogenetic protein is envisaged. Load-bearing applications are allowed for CHDA-type, CA-type and HA-type CPBCs as they have a higher compressive strength than human trabecular bone (10 MPa).

  17. Bioinformatics analyses of Shigella CRISPR structure and spacer classification.

    Science.gov (United States)

    Wang, Pengfei; Zhang, Bing; Duan, Guangcai; Wang, Yingfang; Hong, Lijuan; Wang, Linlin; Guo, Xiangjiao; Xi, Yuanlin; Yang, Haiyan

    2016-03-01

    Clustered regularly interspaced short palindromic repeats (CRISPR) are inheritable genetic elements of a variety of archaea and bacteria and indicative of the bacterial ecological adaptation, conferring acquired immunity against invading foreign nucleic acids. Shigella is an important pathogen for anthroponosis. This study aimed to analyze the features of Shigella CRISPR structure and classify the spacers through bioinformatics approach. Among 107 Shigella, 434 CRISPR structure loci were identified with two to seven loci in different strains. CRISPR-Q1, CRISPR-Q4 and CRISPR-Q5 were widely distributed in Shigella strains. Comparison of the first and last repeats of CRISPR1, CRISPR2 and CRISPR3 revealed several base variants and different stem-loop structures. A total of 259 cas genes were found among these 107 Shigella strains. The cas gene deletions were discovered in 88 strains. However, there is one strain that does not contain cas gene. Intact clusters of cas genes were found in 19 strains. From comprehensive analysis of sequence signature and BLAST and CRISPRTarget score, the 708 spacers were classified into three subtypes: Type I, Type II and Type III. Of them, Type I spacer referred to those linked with one gene segment, Type II spacer linked with two or more different gene segments, and Type III spacer undefined. This study examined the diversity of CRISPR/cas system in Shigella strains, demonstrated the main features of CRISPR structure and spacer classification, which provided critical information for elucidation of the mechanisms of spacer formation and exploration of the role the spacers play in the function of the CRISPR/cas system.

  18. Sidewall spacer optimization for steep switching junctionless transistors

    Science.gov (United States)

    Gupta, Manish; Kranti, Abhinav

    2016-06-01

    In this work, we analyze the impact of a high permittivity (high-κ) sidewall spacer and gate dielectric on the occurrence of sub-60 mV/decade subthreshold swing (S-swing) in symmetrical junctionless (JL) double gate (DG) transistors. It is shown that steep S-swing values (≤10 mV/decade) can be achieved in JL devices with a combination of a high permittivity (high-κ) gate dielectric and a narrow low permittivity (low-κ) sidewall spacer. Implementation of a wider high-κ spacer will diminish the degree of impact ionization by the influence of the fringing component of the gate electric field, and will not be useful for steep off-to-on current transition. A wider spacer with low-κ and a narrow spacer with high-κ permittivity will be useful to limit the latching effect that can occur at lower temperatures (250 K). For high temperature operation, the decrease in the impact ionization rate can be compensated by designing a JL transistor with a thicker silicon film. The work demonstrates opportunities to enhance impact ionization at sub bandgap voltages, and proposes optimal guidelines for selecting a sidewall spacer to facilitate steep switching in JL transistors.

  19. The potential of standard and modified feed spacers for biofouling control

    KAUST Repository

    Araújo, Paula A.

    2012-06-01

    The impact of feed spacers on initial feed channel pressure (FCP) drop, FCP increase and biomass accumulation has been studied in membrane fouling simulators using feed spacers applied in commercially available nanofiltration and reverse osmosis spiral wound membrane modules. All spacers had a similar geometry.Our studies showed that biofouling was not prevented by (i) variation of spacer thickness, (ii) feed spacer orientation, (iii) feed spacer coating with silver, copper or gold and (iv) using a biostatic feed spacer. At constant feed flow, a lower FCP and FCP increase were observed for a thicker feed spacer. At constant linear flow velocity, roughly the same FCP development and biomass accumulation were found irrespective of the feed spacer thickness: hydrodynamics and substrate load were more important for development and impact of biofouling than the thickness of currently applied spacers. Use of biostatic and metal coated spacers were not effective for biofouling control. The same small reduction of biofouling rate was observed with copper and silver coated spacers as well as uncoated 45° rotated spacers.The studied modified spacers were not effective for biofouling prevention and control. The impact of biofouling on FCP increase was reduced significantly by a lower linear flow velocity, while spacer orientation and spacer thickness in membrane modules had a smaller but still significant effect. © 2012 Elsevier B.V.

  20. The effect of cement creep and cement fatigue damage on the micromechanics of the cement-bone interface.

    NARCIS (Netherlands)

    Waanders, D.; Janssen, D.; Mann, K.A.; Verdonschot, N.J.J.

    2010-01-01

    The cement-bone interface provides fixation for the cement mantle within the bone. The cement-bone interface is affected by fatigue loading in terms of fatigue damage or microcracks and creep, both mostly in the cement. This study investigates how fatigue damage and cement creep separately affect

  1. Mineral resource of the month: hydraulic cement

    Science.gov (United States)

    van Oss, Hendrik G.

    2012-01-01

    Hydraulic cements are the binders in concrete and most mortars and stuccos. Concrete, particularly the reinforced variety, is the most versatile of all construction materials, and most of the hydraulic cement produced worldwide is portland cement or similar cements that have portland cement as a basis, such as blended cements and masonry cements. Cement typically makes up less than 15 percent of the concrete mix; most of the rest is aggregates. Not counting the weight of reinforcing media, 1 ton of cement will typically yield about 8 tons of concrete.

  2. POZZOLAN AND CEMENTS WITH POZZOLAN

    Directory of Open Access Journals (Sweden)

    Hasan KAPLAN

    1995-02-01

    Full Text Available Cement, one of the basic material of construction engineering, has an important place in view of strength and cost of structures. Cement consumption is increasing parallel to development of building construction sector. For cement producers, minimal cost is desired by using new and economical material sources. On the other hand, the controllers and contractors need cheaper, safer and higher strength materials. From this respect cement industry tends to use cement with pozzolan. In Türkiye, cement with pozzolan is produced by adding the pozzolan, which has a large reservoir in the country, in cement in sertain amount. However this type of cement is consumed in the construction sector, sortage of scientific investigation and speculative news on the subject.are worried the users and producers. In this paper, prior to an experimental study on the cements having pozzolan additive, historical development of pozzolan, reservoir of Turkiye, and comparison with portland cement is carried out. Advantages and disadvantages of pozzolan are also discussed in some points.

  3. Cement from magnesium substituted hydroxyapatite.

    Science.gov (United States)

    Lilley, K J; Gbureck, U; Knowles, J C; Farrar, D F; Barralet, J E

    2005-05-01

    Brushite cement may be used as a bone graft material and is more soluble than apatite in physiological conditions. Consequently it is considerably more resorbable in vivo than apatite forming cements. Brushite cement formation has previously been reported by our group following the mixture of nanocrystalline hydroxyapatite and phosphoric acid. In this study, brushite cement was formed from the reaction of nanocrystalline magnesium-substituted hydroxyapatite with phosphoric acid in an attempt to produce a magnesium substituted brushite cement. The presence of magnesium was shown to have a strong effect on cement composition and strength. Additionally the presence of magnesium in brushite cement was found to reduce the extent of brushite hydrolysis resulting in the formation of HA. By incorporating magnesium ions in the apatite reactant structure the concentration of magnesium ions in the liquid phase of the cement was controlled by the dissolution rate of the apatite. This approach may be used to supply other ions to cement systems during setting as a means to manipulate the clinical performance and characteristics of brushite cements.

  4. Research and Application of MS Spacer Fluid for Plugging%MS型堵漏隔离液的研究与应用

    Institute of Scientific and Technical Information of China (English)

    初永涛

    2013-01-01

    为了解决易漏失井固井施工中水泥浆的漏失问题,研究开发了一种堵漏隔离液.首先运用颗粒级配理论确定堵漏材料的粒径范围,然后根据堵漏材料物理性能的要求,优选了蛭石颗粒和丙纶纤维作为堵漏材料.使用MS隔离液化学剂、高温隔离液助剂和堵漏材料配制得到MS型堵漏隔离液,对MS型堵漏隔离液的流变性、稳定性、纤维分布情况、相容性和冲洗能力等进行了评价,利用缝隙板堵漏试验和砂床堵漏试验对MS型堵漏隔离液的堵漏性能进行评价.结果表明,MS型堵漏隔离液各项性能指标完全满足固井施工要求,堵漏承压能力达到8 MPa.MS型堵漏隔离液在河坝107井φ219.1 mm尾管固井中成功应用,并在川东北地区和塔河油田进行了53井次的现场应用,取得了良好的堵漏效果.%In order to solve the leakage problem in cementing operation,a new plugging spacer fluid has been developed.The particle size and range of plugging material were determined according to the theory of grain composition,and Vermiculite particles and Polypropylene fiber selected as plugging materials.Taking MS spacer as a base fluid,made by MS chemicals and high temperature additive,the rheological property,stability,distribution of fiber,compatibility and flushing ability were evaluated.Plugging ability of the spacer was also evaluated with crack-plate plugging and sand bed plugging experiment.The results show that the performance of the MS plugging spacer fluid meets all the requirements for cementing,and its plugging pressure-bearing ability reaches 8 MPa.The MS plugging spacer fluid was applied successfully during φ219.1 mm liner cementation in Well Heba107.Field applications of 53 wells in northeastern Sichuan area and Tahe Oilfield have got good plugging results.

  5. US cement industry

    Energy Technology Data Exchange (ETDEWEB)

    Nisbet, M.A.

    1997-12-31

    This paper describes the cement and concrete industry, and provides data on energy use and carbon dioxide emissions. The potential impact of an energy tax on the industry is briefly assessed. Opportunities identified for reducing carbon dioxide emissions include improved energy efficiency, alternative fuels, and alternative materials. The key factor in determining CO{sub 2} emissions is the level of domestic production. The projected improvement in energy efficiency and the relatively slow growth in domestic shipments indicate that CO{sub 2} emissions in 2000 should be about 5% above the 1990 target. However, due to the cyclical nature of cement demand, emissions will probably be above target levels during peak demand and below target levels during demand troughs. 7 figs., 2 tabs.

  6. Performance of Cement Containing Laterite as Supplementary Cementing Material

    Directory of Open Access Journals (Sweden)

    Abbas Bukhari, Z. S.

    2013-03-01

    Full Text Available The utilization of different industrial waste, by-products or other materials such as ground granulated blast furnace slag, silica fume, fly ash, limestone, and kiln dust, etc. as supplemen- tary cementing materials has received considerable attention in recent years. A study has been conducted to look into the performance of laterite as Supplementary Cementing Materials (SCM. The study focuses on compressive strength performance of blended cement containing different percentage of laterite. The cement is replaced accordingly with percentage of 2 %, 5 %, 7 % and 10 % by weight. In addition, the effect of use of three chemically different laterites have been studied on physical performance of cement as in setting time, Le-Chatlier expansion, loss on ignition, insoluble residue, free lime and specifically compressive strength of cement cubes tested at the age of 3, 7, and 28 days. The results show that the strength of cement blended with laterite as SCM is enhanced. Key words: Portland cement, supplementary cementing materials (SCM, laterite, compressive strength KUI – 6/2013 Received January 4, 2012 Accepted February 11, 2013

  7. Advances in Glass Ionomer Cements

    OpenAIRE

    KAYA, Dt. Tuğba; TİRALİ, Yard. Doç. Dr. Resmiye Ebru

    2013-01-01

    In recent years there have been a number of innovations and developments with respect to glass ionomer cements and their applications in clinical dentistry. This article considers some of the recent outstanding studies regarding the field of glass ionomer cement applications, adhesion and setting mechanisms, types, advantage and disadvantages among themselves and also to enhance the physical and antibacterial properties under the title of 'Advances in Glass Ionomer Cements'. As their biologic...

  8. Cement penetration after patella venting.

    Science.gov (United States)

    Jones, Christopher W; Lam, Li-On; Butler, Adam; Wood, David J; Walsh, William R

    2009-01-01

    There is a high rate of patellofemoral complications following total knee arthroplasty. Optimization of the cement-bone interface by venting and suction of the tibial plateau has been shown to improve cement penetration. Our study was designed to investigate if venting the patella prior to cementing improved cement penetration. Ten paired cadaver patellae were allocated prior to resurfacing to be vented or non-vented. Bone mineral density (BMD) was measured by DEXA scanning. In vented specimens, a 1.6 mm Kirschner wire was used to breach the anterior cortex at the center. Specimens were resurfaced with standard Profix instrumentation and Versabond bone cement (Smith and Nephew PLC, UK). Cement penetration was assessed from Faxitron and sectioned images by a digital image software package (ImageJ V1.38, NIH, USA). Wilcoxon rank sum test was used to assess the difference in cement penetration between groups. The relationship between BMD and cement penetration was analyzed by Pearson correlation coefficient. There was a strong negative correlation between peak BMD and cement penetration when analyzed independent of experimental grouping (r(2)=-0.812, p=0.004). Wilcoxon rank sum testing demonstrated no significant difference (rank sum statistic W=27, p=0.579) in cement penetration between vented (10.53%+/-4.66; mean+/-std dev) and non-vented patellae (11.51%+/-6.23; mean+/-std dev). Venting the patella using a Kirschner wire does not have a significant effect on the amount of cement penetration achieved in vitro using Profix instrumentation and Versabond cement.

  9. [Haemotoxicity of dental luting cements].

    Science.gov (United States)

    Anders, A; Welker, D

    1989-06-01

    A glass ionomer luting cement (AquaCem) shows a relatively low haemolytic activity in comparison with two zinc phosphate cements. Especially the initial irritation by this cement is smaller. Although it is possible that AquaCem particularly, in unfavourable cases, may damage the pulpa dentin system; this is due to the slowly decrease of the haemolytic activity with increasing of the probes. We found that Adhesor showed in dependence of the batches a varying quality.

  10. Final design of a spacer grid using axiomatic design

    Energy Technology Data Exchange (ETDEWEB)

    Park, Gyung-Jin; Lee, Hyun-Ah; Kim, Chong-Ki [Hanyang Univ., Seoul (Korea, Republic of); Song, Gi-Nam [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2007-03-15

    The spacer grid set is a component in the nuclear fuel assembly. The set supports the fuel rod safely. The spacer grid set must have enough strength to sustain external loads such as earthquake. The fretting wear occurs between the spring of the fuel rod and the spacer grid due to the flow-induced vibration after the fuel rod is inserted to the spacer grid set. Design of the spring is carried out by using the independence axiom in axiomatic design to solve the two problems. The spacer grid is divided into two parts for sustaining the impact load and reducing fretting wear based on the function requirements. The design for the impact load is performed through non-linear analysis and the homology theory is adopted to reduce fretting wear achieved for shape optimization. The objective function to be minimized ids the maximum stress and constraints are defined to increase the contact area between the fuel rod and the spring using the homology theory. In the design results, the contact area becomes large and it is conformed by nonlinear static analysis. The final design shows that larger impact loads can be sustained compared to the current model.

  11. Impact of spacer thickness on biofouling in forward osmosis

    KAUST Repository

    Valladares Linares, Rodrigo

    2014-06-01

    Forward osmosis (FO) indirect desalination systems integrate wastewater recovery with seawater desalination. Niche applications for FO systems have been reported recently, due to the demonstrated advantages compared to conventional high-pressure membrane processes such as nanofiltration (NF) and reverse osmosis (RO). Among them, wastewater recovery has been identified to be particularly suitable for practical applications. However, biofouling in FO membranes has rarely been studied in applications involving wastewater effluents. Feed spacers separating the membrane sheets in cross-flow systems play an important role in biofilm formation. The objective of this study was to determine the influence of feed spacer thickness (28, 31 and 46mil) on biofouling development and membrane performance in a FO system, using identical cross-flow cells in parallel studies. Flux development, biomass accumulation, fouling localization and composition were determined and analyzed. For all spacer thicknesses, operated at the same feed flow and the same run time, the same amount of biomass was found, while the flux reduction decreased with thicker spacers. These observations are in good agreement with biofouling studies for RO systems, considering the key differences between FO and RO. Our findings contradict previous cross-flow studies on particulate/colloidal fouling, where higher cross-flow velocities improved system performance. Thicker spacers reduced the impact of biofouling on FO membrane flux. © 2014 Elsevier Ltd.

  12. Impact of spacer thickness on biofouling in forward osmosis.

    Science.gov (United States)

    Valladares Linares, R; Bucs, Sz S; Li, Z; AbuGhdeeb, M; Amy, G; Vrouwenvelder, J S

    2014-06-15

    Forward osmosis (FO) indirect desalination systems integrate wastewater recovery with seawater desalination. Niche applications for FO systems have been reported recently, due to the demonstrated advantages compared to conventional high-pressure membrane processes such as nanofiltration (NF) and reverse osmosis (RO). Among them, wastewater recovery has been identified to be particularly suitable for practical applications. However, biofouling in FO membranes has rarely been studied in applications involving wastewater effluents. Feed spacers separating the membrane sheets in cross-flow systems play an important role in biofilm formation. The objective of this study was to determine the influence of feed spacer thickness (28, 31 and 46 mil) on biofouling development and membrane performance in a FO system, using identical cross-flow cells in parallel studies. Flux development, biomass accumulation, fouling localization and composition were determined and analyzed. For all spacer thicknesses, operated at the same feed flow and the same run time, the same amount of biomass was found, while the flux reduction decreased with thicker spacers. These observations are in good agreement with biofouling studies for RO systems, considering the key differences between FO and RO. Our findings contradict previous cross-flow studies on particulate/colloidal fouling, where higher cross-flow velocities improved system performance. Thicker spacers reduced the impact of biofouling on FO membrane flux.

  13. CRISPR interference and priming varies with individual spacer sequences.

    Science.gov (United States)

    Xue, Chaoyou; Seetharam, Arun S; Musharova, Olga; Severinov, Konstantin; Brouns, Stan J J; Severin, Andrew J; Sashital, Dipali G

    2015-12-15

    CRISPR-Cas (clustered regularly interspaced short palindromic repeats-CRISPR associated) systems allow bacteria to adapt to infection by acquiring 'spacer' sequences from invader DNA into genomic CRISPR loci. Cas proteins use RNAs derived from these loci to target cognate sequences for destruction through CRISPR interference. Mutations in the protospacer adjacent motif (PAM) and seed regions block interference but promote rapid 'primed' adaptation. Here, we use multiple spacer sequences to reexamine the PAM and seed sequence requirements for interference and priming in the Escherichia coli Type I-E CRISPR-Cas system. Surprisingly, CRISPR interference is far more tolerant of mutations in the seed and the PAM than previously reported, and this mutational tolerance, as well as priming activity, is highly dependent on spacer sequence. We identify a large number of functional PAMs that can promote interference, priming or both activities, depending on the associated spacer sequence. Functional PAMs are preferentially acquired during unprimed 'naïve' adaptation, leading to a rapid priming response following infection. Our results provide numerous insights into the importance of both spacer and target sequences for interference and priming, and reveal that priming is a major pathway for adaptation during initial infection.

  14. A non-electrostatic spacer for aerosol delivery

    DEFF Research Database (Denmark)

    Bisgaard, H; Anhøj, J; Klug, B;

    1995-01-01

    A pear shaped non-electrostatic spacer, composed of steel with a volume of 250 ml and equipped with a facemask containing integrated inlet and outlet valves for inspiration and expiration, was compared with three plastic spacers. The plastic spacers were primed with repeated puffs from a budesonide...... pressurised metered dose inhaler (p-MDI) to minimise the electrostatic charge on the plastic. The procedure prolonged the half life (t1/2) of the aerosol in the Nebuhaler from nine to 32 seconds. A normal cleaning procedure reduced the aerosol t1/2 back to baseline. The t1/2 of the aerosol in the metal spacer...... was 27 seconds and independent of the use of p-MDI. In vitro the maximum dose of budesonide from a p-MDI, expressed as a percentage of the nominal dose, was 56% from the non-electrostatic spacer, 61% from the Nebuhaler, 45% from the Babyhaler, and 30% from the AeroChamber. In 124 children, age 6 months...

  15. Routine use of antibiotic laden bone cement for primary total knee arthroplasty: impact on infecting microbial patterns and resistance profiles.

    Science.gov (United States)

    Hansen, Erik N; Adeli, Bahar; Kenyon, Robert; Parvizi, Javad

    2014-06-01

    Antibiotic-laden bone cement (ALBC) is used in primary arthroplasties throughout Europe. In North America, ALBC is only FDA approved for revision arthroplasty after periprosthetic joint infection (PJI). No article has evaluated whether infecting microbial profile and resistance has changed with the introduction of ALBC. We hypothesized that prophylactic use of ALBC in primary total knee arthroplasty (TKA) has not had a significant impact on infecting pathogens, and antibiotic resistance profiles. A retrospective cohort analysis was conducted of all PJI patients undergoing primary TKA and total hip arthroplasty (THA) between January 2000 and January 2009. No significant change in the patterns of infecting PJI pathogens, and no notable increase in percentage resistance was found among organisms grown from patients with PJI that had received prophylactic antibiotic-loaded cement in their primary joint arthroplasty. Early findings suggest that routine prophylactic use of ALBC has not led to changes in infecting pathogen profile, nor has led to the emergence of antimicrobial resistance at our institution.

  16. Effect of a spacer moiety on radiometal labelled Neurotensin derivatives

    Energy Technology Data Exchange (ETDEWEB)

    Mascarin, A.; Valverde, I.E.; Mindt, T.L. [Univ. of Basel Hospital (Switzerland). Div. of Radiopharmaceutical Chemistry

    2013-07-01

    The binding sequence of the regulatory peptide Neurotensin, NT(8-13), represents a promising tumour-specific vector for the development of radiopeptides useful in nuclear oncology for the diagnosis (imaging) and therapy of cancer. A number of radiometal-labelled NT(8-13) derivatives have been reported, however, the effect of the spacer which connects the vector with the radiometal complex has yet not been investigated systematically. Because a spacer moiety can influence potentially important biological characteristics of radiopeptides, we synthesized three [DOTA({sup 177}Lu)]-X-NT(8-13) derivatives and evaluated the effect of a spacer (X) on the physico-chemical properties of the conjugate including lipophilicity, stability, and in vitro receptor affinity and cell internalization. (orig.)

  17. Phosphate based oil well cements

    Science.gov (United States)

    Natarajan, Ramkumar

    The main application of the cement in an oil well is to stabilize the steel casing in the borehole and protect it from corrosion. The cement is pumped through the borehole and is pushed upwards through the annulus between the casing and the formation. The cement will be exposed to temperature and pressure gradients of the borehole. Modified Portland cement that is being used presently has several shortcomings for borehole sealant. The setting of the Portland cement in permafrost regions is poor because the water in it will freeze even before the cement sets and because of high porosity and calcium oxide, a major ingredient it gets easily affected by the down hole gases such as carbon dioxide. The concept of phosphate bonded cements was born out of considerable work at Argonne National Laboratory (ANL) on their use in stabilization of radioactive and hazardous wastes. Novel cements were synthesized by an acid base reaction between a metal oxide and acid phosphate solution. The major objective of this research is to develop phosphate based oil well cements. We have used thermodynamics along with solution chemistry principles to select calcined magnesium oxide as candidate metal oxide for temperatures up to 200°F (93.3°C) and alumina for temperatures greater than 200°F (93.3°C). Solution chemistry helped us in selecting mono potassium phosphate as the acid component for temperatures less than 200°F (93.3°C) and phosphoric acid solution greater than 200°F (93.3°C). These phosphate cements have performance superior to common Portland well cements in providing suitable thickening time, better mechanical and physical properties.

  18. Thermal Shock-resistant Cement

    Energy Technology Data Exchange (ETDEWEB)

    Sugama T.; Pyatina, T.; Gill, S.

    2012-02-01

    We studied the effectiveness of sodium silicate-activated Class F fly ash in improving the thermal shock resistance and in extending the onset of hydration of Secar #80 refractory cement. When the dry mix cement, consisting of Secar #80, Class F fly ash, and sodium silicate, came in contact with water, NaOH derived from the dissolution of sodium silicate preferentially reacted with Class F fly ash, rather than the #80, to dissociate silicate anions from Class F fly ash. Then, these dissociated silicate ions delayed significantly the hydration of #80 possessing a rapid setting behavior. We undertook a multiple heating -water cooling quenching-cycle test to evaluate the cement’s resistance to thermal shock. In one cycle, we heated the 200 and #61616;C-autoclaved cement at 500 and #61616;C for 24 hours, and then the heated cement was rapidly immersed in water at 25 and #61616;C. This cycle was repeated five times. The phase composition of the autoclaved #80/Class F fly ash blend cements comprised four crystalline hydration products, boehmite, katoite, hydrogrossular, and hydroxysodalite, responsible for strengthening cement. After a test of 5-cycle heat-water quenching, we observed three crystalline phase-transformations in this autoclaved cement: boehmite and #61614; and #61543;-Al2O3, katoite and #61614; calcite, and hydroxysodalite and #61614; carbonated sodalite. Among those, the hydroxysodalite and #61614; carbonated sodalite transformation not only played a pivotal role in densifying the cementitious structure and in sustaining the original compressive strength developed after autoclaving, but also offered an improved resistance of the #80 cement to thermal shock. In contrast, autoclaved Class G well cement with and without Class F fly ash and quartz flour failed this cycle test, generating multiple cracks in the cement. The major reason for such impairment was the hydration of lime derived from the dehydroxylation of portlandite formed in the autoclaved

  19. PCR-Internal Transcribed Spacer (ITS) genes sequencing and ...

    African Journals Online (AJOL)

    2. Department of Pure and Applied Zoology, Federal University of Agriculture, Abeokuta, Nigeria. 3. ... Keywords: Internal transcribed spacer genes, phylogenetic, genetic ... ization of fungi by polymerase chain reaction (PCR) am- .... Basic Local Alignment search Tool (BLAST) to establish ..... Population structure and.

  20. CRISPR interference and priming varies with individual spacer sequences

    NARCIS (Netherlands)

    Xue, Chaoyou; Seetharam, Arun S.; Musharova, Olga; Severinov, Konstantin; Brouns, Stan J.J.; Severin, Andrew J.; Sashital, Dipali G.

    2015-01-01

    CRISPR-Cas (clustered regularly interspaced short palindromic repeats-CRISPR associated) systems allow bacteria to adapt to infection by acquiring 'spacer' sequences from invader DNA into genomic CRISPR loci. Cas proteins use RNAs derived from these loci to target cognate sequences for

  1. Shelf life of pie caps with biodegradable films as spacers

    Directory of Open Access Journals (Sweden)

    Daniela Verónica Escobar Gianni

    2013-01-01

    Full Text Available Commonly pie caps at market use polyethylene films as spacers between them. This paper studies the conventional spacers replacement with edible and biodegradable films made with whey protein isolate (WPI and potassium sorbate as a preservative. Besides facilitating the separation of pie caps, with this application is intended to increase their shelf life. The films made by the compression molding method were used as spacers in pie caps without preservative in their formula (A and with preservative (B and they were compared with conventional polyethylene spacers (C. During four months, monthly sensory, microbiological and physicochemical (humidity evaluations were done on the pie caps, together with humidity and solubility evaluations of the films. None of the samples showed microbiological or sensory deterioration. The sensory attributes showed no or slight difference in study time. Between samples the differences were minor: the best scores were for sample A in color, sample C in flavor, and samples B and C in texture and overall liking. The edible films have an interesting potential for this application, although studies in disguise the flavor of serum should be done.

  2. CRISPR interference and priming varies with individual spacer sequences

    NARCIS (Netherlands)

    Xue, Chaoyou; Seetharam, Arun S.; Musharova, Olga; Severinov, Konstantin; Brouns, Stan J.J.; Severin, Andrew J.; Sashital, Dipali G.

    2015-01-01

    CRISPR-Cas (clustered regularly interspaced short palindromic repeats-CRISPR associated) systems allow bacteria to adapt to infection by acquiring 'spacer' sequences from invader DNA into genomic CRISPR loci. Cas proteins use RNAs derived from these loci to target cognate sequences for destructio

  3. Filter holder assembly having extended collar spacer ring

    Science.gov (United States)

    Alvin, Mary Anne; Bruck, Gerald J.

    2002-01-01

    A filter holder assembly is provided that utilizes a fail-safe regenerator unit with an annular spacer ring having an extended metal collar for containment and positioning of a compliant ceramic gasket used in the assembly. The filter holder assembly is disclosed for use with advanced composite, filament wound, and metal candle filters.

  4. Magnesium oxychloride cement concrete

    Indian Academy of Sciences (India)

    A K Misra; Renu Mathur

    2007-06-01

    The scope of magnesium oxychloride (MOC) cement in concrete works has been evaluated. MOC cement concrete compositions of varying strengths having good placing and finishing characteristics were prepared and investigated for their compressive and flexural strengths, -values, abrasion resistance etc. The durability of MOC concrete compositions against extreme environmental conditions viz. heating–cooling, freezing–thawing, wetting–drying and penetration and deposition of salts etc were investigated. The results reveal that MOC concrete has high compressive strength associated with high flexural strength and the ratio of compressive to flexural strength varies between 6 and 8. The elastic moduli of the compositions studied are found to be 23–85 GPa and the abrasion losses between 0.11 and 0.20%. While alternate heating–cooling cycles have no adverse effect on MOC concrete, it can be made durable against freezing–thawing and the excessive exposure to water and salt attack by replacing 10% magnesium chloride solution by magnesium sulphate solution of the same concentration.

  5. Cemented total hip arthroplasty with Boneloc bone cement.

    Science.gov (United States)

    Markel, D C; Hoard, D B; Porretta, C A

    2001-01-01

    Boneloc cement (WK-345, Biomet Inc, Warsaw, Ind) attempted to improve cement characteristics by reducing exotherm during polymerization, lowering residual monomer and solubility, raising molecular weight, and lowering airborne monomer and aromatic amines. To study the efficacy of this cement, a selected group of 20 patients were prospectively enrolled and followed up after hip arthroplasty. All components were cemented. During the enrollment period, approximately 70 other hip arthroplasties were performed. Clinical evaluation was based on the Harris hip score. Radiographic evaluation was based on assessment of position of the components, subsidence, and/or presence of radiolucencies. Patients had follow-up for an average of 42 months (11 to 58 months); 1 was lost to follow-up. Of these, 7 (35%) had failure at last follow-up. Despite its initial promise, Boneloc cement had an unacceptably high failure rate over a relatively short follow-up period and is not recommended for use. Despite the longevity and odor toxicity problems with conventional bone cement, new cement technologies must be approached with caution.

  6. Grout cement. ; Grout cement to fill ground/grout cement to fill cracks. Chunyuyo cement. ; Jiban chunyuyo cement /hibiware chunyuyo cement

    Energy Technology Data Exchange (ETDEWEB)

    Okaue, H. (Nittetsu Cement Co. Ltd., Hokkaido (Japan))

    1991-09-01

    Ground grout cement is grouted into the ground under high pressure in high water ratio (100 to 1000%) in the form of milk differing from concrete in terms of the water-cement ratio. The grouted milk is governed by characteristics of the cement the milk itself possesses, resulting in variable grouting modes, which are divided in fracture grouting, permeation grouting and boundary grouting. Their applications include cutting off of water in dams, ground reinforcement, prevention of water gushing in tunnel excavation, natural ground reinforcement, improvement of sandy soil and prevention of its collapse, and stabilization of ground for urban civil engineering works such as subway, water supply and sewerage constructions. Grout cement to fill cracks in concrete structures is so grouted into cracks that the slurry fills up contiguous cracks to a certain level and goes upward while pushing out air or water existing in the cracks. The slurry filled into the cracks solidifies and hardens while being absorbed into the concrete, and finally integrates with the concrete. The grout cement is used to rework such concrete structures as dams, tunnels, and bridge bases. 6 figs., 4 tabs.

  7. Implementation of spacer therapy for acute asthma in children.

    LENUS (Irish Health Repository)

    Vandeleur, M

    2009-09-01

    The aim was to develop and implement an evidence based guideline for the treatment of acute asthma using a metered dose inhaler and spacer combination. Children admitted to Cork University Hospital Paediatric Department with acute asthma were identified during two identical 2 month seasonal periods before (2005) and after (2006) implementation of the new guidelines in September 2006. Pre-intervention and post-intervention audits by case note review were performed to determine the impact of and compliance with this evidence-based guideline emphasising patient assessment, spacer delivered bronchodilator and specific discharge criteria. Patients had similar characteristics during the two study periods. There was a raised threshold for admission after guideline implementation with 11\\/52 patients having mild exacerbations in 2006, compared to 21\\/36 in 2005. Duration of admission was less in the post-implementation group for equivalent exacerbation severity e.g. for moderate severity; 28 hours in 2005, 23 hours in 2006. Duration of bronchodilator therapy was shorter in 2006 and more likely to be given by spacer device earlier for equivalent levels of severity e.g. for moderate exacerbations, in 2006 the average length of salbutamol therapy was 18 hours with 12 hours by spacer device, in 2005 the average length of therapy was 25 hours with 3 hours by spacer. There was earlier initiation of oral corticosteroids; the average time to administration was 56 minutes in 2006 and 227 minutes in 2005. There was an improved documentation of asthma education in 2006 e.g. inhaler technique was reviewed in 37\\/52 in 2006, 21\\/35 in 2005 and better use of written action plans.

  8. 21 CFR 888.4200 - Cement dispenser.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cement dispenser. 888.4200 Section 888.4200 Food... DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4200 Cement dispenser. (a) Identification. A cement dispenser is a nonpowered syringe-like device intended for use in placing bone cement (§ 888.3027)...

  9. HYDROELASTIC VIBRATIONS AND LIQUID SLOSHING SUPPRESSION IN A RECTANGULAR TANK WITH ELASTIC SPACER

    Institute of Scientific and Technical Information of China (English)

    CHENG Xu-duo; LIANG Yong; WEN Ji-hua

    2004-01-01

    In this paper, the couple vibration of liquid and elastic spacer in a rectangular tank is investigated. Two different velocity potential functions corresponding respectively to the liquid above and below the elastic spacer are assumed. Complicated boundary conditions corresponding to two velocity potential functions and vibrations of elastic spacer are given. Using the method of energy, the equation of couple frequency is obtained. Through numerical computation the natural frequencies that change according to the location and stiffness of the spacer are shown.

  10. Cements containing by-product gypsum

    Energy Technology Data Exchange (ETDEWEB)

    Bensted, J. [University of Greenwich, London (United Kingdom). School of Biological and Chemical Sciences

    1995-12-31

    Chemical by-product gypsum can readily replace natural gypsum in Portland cements and in blended cements like Portland pfa cement and Portland blast furnace cement without technical detriment in many instances. Indeed, sometimes the technical performance of the cement can be enhanced. The hydration chemistry is often changed, in that where there is at least some retardation of setting, more AFT phase (ettringite) is formed during early hydration at the expense of calcium silicate hydrates. By-product gypsum can also replace natural gypsum in speciality products like calcium aluminate cement-Portland cement mixes for producing quick setting cements and in calcium sulphoaluminate-type expansive cements. However, by-products gypsum have proved to be less successful for utilization in API Classes of oilwell cements, because of the greater difficulty in obtaining batch-to-batch consistency in properties like thickening time and slurry rheology. 11 refs., 3 figs., 5 tabs.

  11. Cement for Oil Well Cementing Operations in Ghana

    African Journals Online (AJOL)

    Michael

    This research evaluates the ... The paper details results of API specification tests and the physical ... Keywords: Compressive strength, Free fluid, Portland cement, Rheology, Thickening time ..... Geothermal Well Cementing” Proceedings of.

  12. Biofouling Control in Spiral-Wound Membrane Systems: Impact of Feed Spacer Modification and Biocides

    KAUST Repository

    Siddiqui, Amber

    2016-12-01

    High-quality drinking water can be produced with membrane-based filtration processes like reverse osmosis and nanofiltration. One of the major problems in these membrane systems is biofouling that reduces the membrane performance, increasing operational costs. Current biofouling control strategies such as pre-treatment, membrane modification, and chemical cleaning are not sufficient in all cases. Feed spacers are thin (0.8 mm), complex geometry meshes that separate membranes in a module. The main objective of this research was to evaluate whether feed spacer modification is a suitable strategy to control biofouling. Membrane fouling simulator studies with six feed spacers showed differences in biofouled spacer performance, concluding that (i) spacer geometry influences biofouling impact and (ii) biofouling studies are essential for evaluation of spacer biofouling impact. Computed tomography (CT) was found as a suitable technique to obtain three-dimensional (3D) measurements of spacers, enabling more representative mathematical modeling of hydraulic behavior of spacers in membrane systems. A strategy for developing, characterizing, and testing of spacers by numerical modeling, 3D printing of spacers and experimental membrane fouling simulator studies was developed. The combination of modeling and experimental testing of 3D printed spacers is a promising strategy to develop advanced spacers aiming to reduce the impact of biofilm formation on membrane performance and to improve the cleanability of spiral-wound membrane systems.

  13. Magnesium substitution in brushite cements.

    Science.gov (United States)

    Alkhraisat, Mohammad Hamdan; Cabrejos-Azama, Jatsue; Rodríguez, Carmen Rueda; Jerez, Luis Blanco; Cabarcos, Enrique López

    2013-01-01

    The use of magnesium-doped ceramics has been described to modify brushite cements and improve their biological behavior. However, few studies have analyzed the efficiency of this approach to induce magnesium substitution in brushite crystals. Mg-doped ceramics composed of Mg-substituted β-TCP, stanfieldite and/or farringtonite were reacted with primary monocalcium phosphate (MCP) in the presence of water. The cement setting reaction has resulted in the formation of brushite and newberyite within the cement matrix. Interestingly, the combination of SAED and EDX analyses of single crystal has indicated the occurrence of magnesium substitution within brushite crystals. Moreover, the effect of magnesium ions on the structure, and mechanical and setting properties of the new cements was characterized as well as the release of Ca(2+) and Mg(2+) ions. Further research would enhance the efficiency of the system to incorporate larger amounts of magnesium ions within brushite crystals.

  14. Intergenic spacer length variants in Old Portuguese bread wheat cultivars

    Indian Academy of Sciences (India)

    Ana Carvalho; Henrique Guedes-Pinto; José Lima-Brito

    2011-08-01

    The intergenic spacer of the ribosomal DNA is highly variable, but is location specific in the nucleolar organizer region of the chromosomes. This study provides an event of high level of polymorphism / size variation and occurrence of 14 unique phenotypes in 48 landraces of Portuguese bread wheat cultivars for IGS-amplified products obtained by PCR-RFLP technique performed with TaqI. The attendant IGS polymorphism has been used to deduce affinities between landraces. Some of the high molecular weight IGS allelic variants were also probed for their chromosomal localization by sequential silver nitrate staining and fluorescence in situ hybridization. However, only the intergenic spacer allelic variant of 3.1 kb could be successfully hybridized, and was observed to be physically located on the chromosome pair 1B in the NOR loci of the cultivar ‘Magueija’.

  15. Portland cement-blast furnace slag blends in oilwell cementing applications

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, D.T.; DiLullo, G.; Hibbeler, J. [and others

    1995-12-31

    Recent investigations of blast furnace slag cementing technologies. have been expanded to include Portland cement/blast furnace slag blends. Mixtures of Portland cement and blast furnace slag, while having a long history of use in the construction industry, have not been used extensively in oilwell cementing applications. Test results indicate that blending blast furnace slag with Portland cement produces a high quality well cementing material. Presented are the design guidelines and laboratory test data relative to mixtures of blast furnace slag and Portland cements. Case histories delineating the use of blast furnace slag - Portland cement blends infield applications are also included.

  16. Calcium Orthophosphate Cements and Concretes

    Directory of Open Access Journals (Sweden)

    Sergey V. Dorozhkin

    2009-03-01

    Full Text Available In early 1980s, researchers discovered self-setting calcium orthophosphate cements, which are a bioactive and biodegradable grafting material in the form of a powder and a liquid. Both phases form after mixing a viscous paste that after being implanted, sets and hardens within the body as either a non-stoichiometric calcium deficient hydroxyapatite (CDHA or brushite, sometimes blended with unreacted particles and other phases. As both CDHA and brushite are remarkably biocompartible and bioresorbable (therefore, in vivo they can be replaced with newly forming bone, calcium orthophosphate cements represent a good correction technique for non-weight-bearing bone fractures or defects and appear to be very promising materials for bone grafting applications. Besides, these cements possess an excellent osteoconductivity, molding capabilities and easy manipulation. Furthermore, reinforced cement formulations are available, which in a certain sense might be described as calcium orthophosphate concretes. The concepts established by calcium orthophosphate cement pioneers in the early 1980s were used as a platform to initiate a new generation of bone substitute materials for commercialization. Since then, advances have been made in the composition, performance and manufacturing; several beneficial formulations have already been introduced as a result. Many other compositions are in experimental stages. In this review, an insight into calcium orthophosphate cements and concretes, as excellent biomaterials suitable for both dental and bone grafting application, has been provided.

  17. Surgical spacer placement and proton radiotherapy for unresectable hepatocellular carcinoma

    Institute of Scientific and Technical Information of China (English)

    Shohei; Komatsu; Yuichi; Hori; Takumi; Fukumoto; Masao; Murakami; Yoshio; Hishikawa; Yonson; Ku

    2010-01-01

    Few potentially curative treatment options exist apart from hepatic resection for patients with huge hepatocellular carcinoma (HCC). Proton radiotherapy is a promising new modality which has an inherent antitumor effect against HCC. However, the application of proton radiotherapy for tumors adjacent to the gastrointestinal tract is restricted because the tolerance dose of the intestine is extremely low. A novel two-step treatment was developed with surgical spacer placement and subsequent proton radiotherap...

  18. Effects of interspinous spacers on lumbar degenerative disease.

    Science.gov (United States)

    Zhou, Dong; Nong, Lu-Ming; DU, Rui; Gao, Gong-Ming; Jiang, Yu-Qing; Xu, Nan-Wei

    2013-03-01

    The present study aimed to evaluate the early effects of interspinous spacers on lumbar degenerative disease. The clinical outcomes of 23 patients with lumbar degenerative disease, treated using interspinous spacer implantation alone or combined with posterior lumbar fusion, were retrospectively studied and assessed with a visual analogue scale (VAS) and the Oswestry Disability Index (ODI). Pre-operative and post-operative interspinous distance, disc space height, foraminal width and height and segmental lordosis were determined. The early effects and complications associated with the interspinous spacers were recorded. The surgical procedures performed with the in-space treatment were easy and minimally invasive. The VAS scores and ODI were improved post-operatively compared with pre-operatively. Significant changes in the interspinous distance, disc space height, foraminal width and height and segmental lordosis were noted. In-space treatment for degenerative lumbar disease is easy and safe, with good early effects. The in-space system provides an alternative treatment for lumbar degenerative disease.

  19. Impact of feed spacer and membrane modification by hydrophilic, bactericidal and biocidal coating on biofouling control

    KAUST Repository

    Araújo, Paula A.

    2012-06-01

    The influence of polydopamine- and polydopamine-. graft-poly(ethylene glycol)-coated feed spacers and membranes, copper-coated feed spacers, and commercially-available biostatic feed spacers on biofouling has been studied in membrane fouling simulators. Feed spacers and membranes applied in practical membrane filtration systems were used; biofouling development was monitored by feed channel pressure drop increase and biomass accumulation. Polydopamine and polydopamine-. g-PEG are hydrophilic surface modification agents expected to resist protein and bacterial adhesion, while copper feed spacer coatings and biocides infused in feed spacers are expected to restrict biological growth. Our studies showed that polydopamine and polydopamine-. g-PEG coatings on feed spacers and membranes, copper coatings on feed spacers, and a commercial biostatic feed spacer did not have a significant impact on feed channel pressure drop increase and biofilm accumulation as measured by ATP and TOC content. The studied spacer and membrane modifications were not effective for biofouling control; it is doubtful that feed spacer and membrane modification, in general, may be effective for biofouling control regardless of the type of applied coating. © 2012 Elsevier B.V.

  20. Low pH Cements

    Energy Technology Data Exchange (ETDEWEB)

    Savage, David; Benbow, Steven [Quintessa Ltd., Henley-on-Thames (United Kingdom)

    2007-05-15

    The development of low-pH cements for use in geological repositories for radioactive waste stems from concerns over the potential for deleterious effects upon the host rock and other EBS materials (notably bentonite) under the hyperalkaline conditions (pH > 12) of cement pore fluids. Low pH cement (also known as low heat cement) was developed by the cement industry for use where large masses of cement (e.g. dams) could cause problems regarding heat generated during curing. In low pH cements, the amount of cement is reduced by substitution of materials such as fly ash, blast furnace slag, silica fume, and/or non-pozzolanic silica flour. SKB and Posiva have ruled out the use of blast furnace slag and fly-ash and are focusing on silica fume as a blending agent. Currently, no preferred composition has been identified by these agencies. SKB and Posiva have defined a pH limit {<=} 11 for cement grout leachates. To attain this pH, blending agents must comprise at least 50 wt % of dry materials. Because low pH cement has little, or no free portlandite, the cement consists predominantly of calcium silicate hydrate (CSH) gel with a Ca/Si ratio {<=} 0.8. Although there are potential implications for the performance of the spent fuel and cladding due to the presence of hyperalkaline fluids from cement, the principal focus for safety assessment lies with the behaviour of bentonite. There are a number of potential constraints on the interaction of hyperalkaline cement pore fluids with bentonite, including mass balance, thermodynamic issues, mass transport, and kinetics, but none of these is likely to be limiting if conventional OPC cements are employed in repository construction. Nevertheless: Low-pH cements may supply approximately 50 % less hydroxyl ions than conventional OPC for a given volume of cement, but mass balance constraints are complicated by the uncertainty concerning the type of secondary minerals produced during cement-bentonite interaction. The change of aqueous

  1. Low pH Cements

    Energy Technology Data Exchange (ETDEWEB)

    Savage, David; Benbow, Steven [Quintessa Ltd., Henley-on-Thames (United Kingdom)

    2007-05-15

    The development of low-pH cements for use in geological repositories for radioactive waste stems from concerns over the potential for deleterious effects upon the host rock and other EBS materials (notably bentonite) under the hyperalkaline conditions (pH > 12) of cement pore fluids. Low pH cement (also known as low heat cement) was developed by the cement industry for use where large masses of cement (e.g. dams) could cause problems regarding heat generated during curing. In low pH cements, the amount of cement is reduced by substitution of materials such as fly ash, blast furnace slag, silica fume, and/or non-pozzolanic silica flour. SKB and Posiva have ruled out the use of blast furnace slag and fly-ash and are focusing on silica fume as a blending agent. Currently, no preferred composition has been identified by these agencies. SKB and Posiva have defined a pH limit {<=} 11 for cement grout leachates. To attain this pH, blending agents must comprise at least 50 wt % of dry materials. Because low pH cement has little, or no free portlandite, the cement consists predominantly of calcium silicate hydrate (CSH) gel with a Ca/Si ratio {<=} 0.8. Although there are potential implications for the performance of the spent fuel and cladding due to the presence of hyperalkaline fluids from cement, the principal focus for safety assessment lies with the behaviour of bentonite. There are a number of potential constraints on the interaction of hyperalkaline cement pore fluids with bentonite, including mass balance, thermodynamic issues, mass transport, and kinetics, but none of these is likely to be limiting if conventional OPC cements are employed in repository construction. Nevertheless: Low-pH cements may supply approximately 50 % less hydroxyl ions than conventional OPC for a given volume of cement, but mass balance constraints are complicated by the uncertainty concerning the type of secondary minerals produced during cement-bentonite interaction. The change of aqueous

  2. Development and characterization of 3D-printed feed spacers for spiral wound membrane systems

    KAUST Repository

    Siddiqui, Amber Siddiqui Shahnawaz

    2016-01-02

    Feed spacers are important for the impact of biofouling on the performance of spiral-wound reverse osmosis (RO) and nanofiltration (NF) membrane systems. The objective of this study was to propose a strategy for developing, characterizing, and testing of feed spacers by numerical modeling, three-dimensional (3D) printing of feed spacers and experimental membrane fouling simulator (MFS) studies. The results of numerical modeling on the hydraulic behavior of various feed spacer geometries suggested that the impact of spacers on hydraulics and biofouling can be improved. A good agreement was found for the modeled and measured relationship between linear flow velocity and pressure drop for feed spacers with the same geometry, indicating that modeling can serve as first step in spacer characterization. An experimental comparison study of a feed spacer currently applied in practice and a 3D printed feed spacer with the same geometry showed (i) similar hydraulic behavior, (ii) similar pressure drop development with time and (iii) similar biomass accumulation during MFS biofouling studies, indicating that 3D printing technology is an alternative strategy for development of thin feed spacers with a complex geometry. Based on the numerical modeling results, a modified feed spacer with low pressure drop was selected for 3D printing. The comparison study of the feed spacer from practice and the modified geometry 3D printed feed spacer established that the 3D printed spacer had (i) a lower pressure drop during hydraulic testing, (ii) a lower pressure drop increase in time with the same accumulated biomass amount, indicating that modifying feed spacer geometries can reduce the impact of accumulated biomass on membrane performance. The combination of numerical modeling of feed spacers and experimental testing of 3D printed feed spacers is a promising strategy (rapid, low cost and representative) to develop advanced feed spacers aiming to reduce the impact of biofilm formation on

  3. Development and characterization of 3D-printed feed spacers for spiral wound membrane systems.

    Science.gov (United States)

    Siddiqui, Amber; Farhat, Nadia; Bucs, Szilárd S; Linares, Rodrigo Valladares; Picioreanu, Cristian; Kruithof, Joop C; van Loosdrecht, Mark C M; Kidwell, James; Vrouwenvelder, Johannes S

    2016-03-15

    Feed spacers are important for the impact of biofouling on the performance of spiral-wound reverse osmosis (RO) and nanofiltration (NF) membrane systems. The objective of this study was to propose a strategy for developing, characterizing, and testing of feed spacers by numerical modeling, three-dimensional (3D) printing of feed spacers and experimental membrane fouling simulator (MFS) studies. The results of numerical modeling on the hydrodynamic behavior of various feed spacer geometries suggested that the impact of spacers on hydrodynamics and biofouling can be improved. A good agreement was found for the modeled and measured relationship between linear flow velocity and pressure drop for feed spacers with the same geometry, indicating that modeling can serve as the first step in spacer characterization. An experimental comparison study of a feed spacer currently applied in practice and a 3D printed feed spacer with the same geometry showed (i) similar hydrodynamic behavior, (ii) similar pressure drop development with time and (iii) similar biomass accumulation during MFS biofouling studies, indicating that 3D printing technology is an alternative strategy for development of thin feed spacers with a complex geometry. Based on the numerical modeling results, a modified feed spacer with low pressure drop was selected for 3D printing. The comparison study of the feed spacer from practice and the modified geometry 3D printed feed spacer established that the 3D printed spacer had (i) a lower pressure drop during hydrodynamic testing, (ii) a lower pressure drop increase in time with the same accumulated biomass amount, indicating that modifying feed spacer geometries can reduce the impact of accumulated biomass on membrane performance. The combination of numerical modeling of feed spacers and experimental testing of 3D printed feed spacers is a promising strategy (rapid, low cost and representative) to develop advanced feed spacers aiming to reduce the impact of

  4. 21 CFR 888.3027 - Polymethylmethacrylate (PMMA) bone cement.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Polymethylmethacrylate (PMMA) bone cement. 888... Polymethylmethacrylate (PMMA) bone cement. (a) Identification. Polymethylmethacrylate (PMMA) bone cement is a device...: Polymethylmethacrylate (PMMA) Bone Cement.”...

  5. Cementation of Loose Sand Particles based on Bio-cement

    Institute of Scientific and Technical Information of China (English)

    RONG Hui; QIAN Chunxiang

    2014-01-01

    Loose sand particles could be cemented to sandstone by bio-cement (microbial induced magnesium carbonate). The bio-sandstone was firstly prepared, and then the compressive strength and the porosity of the sandstone cemented by microbial induced magnesium carbonate were tested to characterize the cementation effectiveness. In addition, the formed mineral composition and the microstructure of bio-sandstone were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The experimental results show that the feasibility of binding loose sand particles using microbial induced magnesium carbonate precipitation is available and the acquired compressive strength of bio-sandstone can be excellent at certain ages. Moreover, the compressive strength and the porosity could be improved with the increase of microbial induced magnesium carbonate content. XRD results indicate that the morphology of magnesium carbonate induced by microbe appears as needles and SEM results show that the cementation of loose sand particles to sandstone mainly relies on the microbial induced formation of magnesium carbonate precipitation around individual particles and at particle-particle contacts.

  6. New Development and Research Area of Cementing Material and Technology%固井材料技术新进展及研究方向

    Institute of Scientific and Technical Information of China (English)

    齐奉忠; 杜建平; 魏群宝

    2015-01-01

    As the exploration and development work is extending into the fields of deep layers, low-pressure, low permeability and low abundance as well as offshore areas and non-conventional reservoirs, oil and gas well cementing becomes more and more difficult and calls for higher requirements on long-term cementing quality. Research and development of cementing materials face new challenges. This paper summarizes the technological achievements of cement slurry systems and materials made in recent years in the areas of ultra-high density cement slurry, ultra-low density cement slurry, large temperature difference cement slurry, salt-resistant latex cement slurry, lfexible cement, CO2 corrosion-resistant cement, phosphate cement, and low hydrate heat and low temperature cement. It also briefs about technological development of high temperature-resistant spacer lfuid, high-efifciency lfushing spacer lfuid and oil displacement high-density spacer lfuid. Based on the company’s cementing service business, the paper idienifes the future research areas –study of cementing material mechanism, improvement of cement slurry formula and additive performance, and development of new-type cementing materials.%随着勘探开发工作的逐步深入以及向“深(深层)、低(低压、低渗透、低丰度)、海(海洋)、非(非常规储层)”领域的拓展,油气井固井难度显著增加,对长期封固质量的要求越来越高,固井材料研发及应用面临新的挑战。文章从超高密度水泥浆、超低密度水泥浆、大温差水泥浆、抗盐胶乳水泥浆、韧性水泥、防C O2腐蚀水泥、磷酸盐水泥、低水化热低温水泥等方面总结了近来水泥浆体系和材料的技术进展,以及抗高温隔离液、高效冲洗隔离液、驱油型高密度隔离液等方面取得的技术进步。根据公司固井作业面临的形势,从固井材料机理研究、水泥浆配方及外加剂性能完善、新型固井

  7. Hydration of fly ash cement

    Energy Technology Data Exchange (ETDEWEB)

    Etsuo Sakai; Shigeyoshi Miyahara; Shigenari Ohsawa; Seung-Heun Lee; Masaki Daimon [Tokyo Institute of Technology, Tokyo (Japan). Department of Metallurgy and Ceramics Science, Graduate School of Science and Engineering

    2005-06-01

    It is necessary to establish the material design system for the utilization of large amounts of fly ash as blended cement instead of disposing of it as a waste. Cement blended with fly ash is also required as a countermeasure to reduce the amount of CO{sub 2} generation. In this study, the influences of the glass content and the basicity of glass phase on the hydration of fly ash cement were clarified and hydration over a long curing time was characterized. Two kinds of fly ash with different glass content, one with 38.2% and another with 76.6%, were used. The hydration ratio of fly ash was increased by increasing the glass content in fly ash in the specimens cured for 270 days. When the glass content of fly ash is low, the basicity of glass phase tends to decrease. Reactivity of fly ash is controlled by the basicity of the glass phase in fly ash during a period from 28 to 270 days. However, at an age of 360 days, the reaction ratios of fly ash show almost identical values with different glass contents. Fly ash also affected the hydration of cement clinker minerals in fly ash cement. While the hydration of alite was accelerated, that of belite was retarded at a late stage.

  8. Biodeterioration of the Cement Composites

    Science.gov (United States)

    Luptáková, Alena; Eštoková, Adriana; Mačingová, Eva; Kovalčíková, Martina; Jenčárová, Jana

    2016-10-01

    The destruction of natural and synthetic materials is the spontaneous and irreversible process of the elements cycling in nature. It can by accelerated or decelerated by physical, chemical and biological influences. Biological influences are represented by the influence of the vegetation and microorganisms (MO). The destruction of cement composites by different MO through the diverse mechanisms is entitled as the concrete biodeterioration. Several sulphur compounds and species of MO are involved in this complex process. Heterotrophic and chemolithotrophic bacteria together with fungi have all been found in samples of corroding cement composites. The MO involved in the process metabolise the presented sulphur compounds (hydrogen sulphide, elemental sulphur etc.) to sulphuric acid reacting with concrete. When sulphuric acid reacts with a concrete matrix, the first step involves a reaction between the acid and the calcium hydroxide forming calcium sulphate. This is subsequently hydrated to form gypsum, the appearance of which on the surface of concrete pipes takes the form of a white, mushy substance which has no cohesive properties. In the continuing attack, the gypsum would react with the calcium aluminate hydrate to form ettringite, an expansive product. The use supplementary cementing composite materials have been reported to improve the resistance of concrete to biodeterioration. The aim of this work was the study of the cement composites biodeterioration by the bacteria Acidithiobacillus thiooxidans. Experimental works were focused on the comparison of special cement composites and its resistance affected by the activities of used sulphur-oxidising

  9. Impact of ZnO embedded feed spacer on biofilm development in membrane systems.

    Science.gov (United States)

    Ronen, Avner; Semiat, Raphael; Dosoretz, Carlos G

    2013-11-01

    The concept of suppressing biofouling formation using an antibacterial feed spacer was investigated in a bench scale-cross flow system mimicking a spiral wound membrane configuration. An antibacterial composite spacer containing zinc oxide-nanoparticles was constructed by modification of a commercial polypropylene feed spacer using sonochemical deposition. The ability of the modified spacers to repress biofilm development on membranes was evaluated in flow-through cells simulating the flow conditions in commercial spiral wound modules. The experiments were performed at laminar flow (Re = 300) with a 200 kDa molecular weight cut off polysulfone ultrafiltration membrane using Pseudomonas putida S-12 as model biofilm bacteria. The modified spacers reduced permeate flux decrease at least by 50% compared to the unmodified spacers (control). The physical properties of the modified spacer and biofilm development were evaluated using high resolution/energy dispersive spectrometry-scanning electron microscopy, atomic force microscopy and confocal laser scanning microscopy imaging (HRSEM, EDS, AFM and CLSM). HRSEM images depicted significantly less bacteria attached to the membranes exposed to the modified spacer, mainly scattered and in a sporadic monolayer structure. AFM analysis indicated the influence of the modification on the spacer surface including a phase change on the upper surface. Dead-live staining assay by CLSM indicated that most of the bacterial cells attached on the membranes exposed to the modified spacer were dead in contrast to a developed biofilm which was predominant in the control samples.

  10. Seating load parameters impact on dental ceramic reinforcement conferred by cementation with resin-cements.

    LENUS (Irish Health Repository)

    Addison, Owen

    2010-09-01

    Cementation of all-ceramic restorations with resin-cements has been demonstrated to reduce the incidence of fracture in service. The aim was to investigate the influence of loading force and loading duration applied during cementation on the reinforcement conferred by a resin-cement on a leucite reinforced glass-ceramic.

  11. 76 FR 76760 - Gray Portland Cement and Cement Clinker From Japan

    Science.gov (United States)

    2011-12-08

    ... Portland Cement and Cement Clinker From Japan Determination On the basis of the record \\1\\ developed in the... antidumping duty order on gray Portland cement and cement clinker from Japan would be likely to lead to... the Commission are contained in USITC Publication 4281 (December 2011), entitled Gray Portland...

  12. Freezing resistance of high iron phoasphoaluminate cement

    Science.gov (United States)

    Zhang, S. X.; Lu, L. C.; Wang, S. D.; Zhao, P. Q.; Gong, C. C.

    2017-03-01

    The influence of freeze-thaw cycle on the mechanical properties of high iron phoasphoaluminate cement was investigated in the present study. The visual examination was conducted to evaluate the surface damage. The deterioration considering the weight loss, modulus loss of relative dynamic elastic and strength loss of mortar were also investigated. The morphology of hydration products were analysed by SEM. Compared with ordinary Portland cement and sulphoaluminate cement, the frost resistance of high iron phosphoraluminate cement is better. Hydration products of high iron phoasphoaluminate cement contain sheet crystals, and a lot of gel form a dense three-dimensional network structure, which results in a lower porosity. Different from ordinary Portland cement, the hydration product of high iron phoasphoaluminate cement does not contain Ca(OH)2, and low alkalinity reduces its osmotic pressure. The lower porosity and osmotic pressure are the two main reasons which causes in the higher frost resistance of high iron phoasphoaluminate cement.

  13. Antibacterial potential of contemporary dental luting cements.

    Science.gov (United States)

    Daugela, Povilas; Oziunas, Rimantas; Zekonis, Gediminas

    2008-01-01

    The aims of this investigation were to evaluate the antibacterial activities of different types of dental luting cements and to compare antibacterial action during and after setting. Agar diffusion testing was used to evaluate the antibacterial properties of seven types of dental luting cements (glass ionomer cements (GICs), resin modified GICs, resin composite, zinc oxide eugenol, zinc oxide non-eugenol, zinc phosphate, zinc polycarboxylate cements) on Streptococcus mutans bacteria. Instantly mixed zinc phosphate cements showed the strongest antibacterial activity in contrast to the non-eugenol, eugenol and resin cements that did not show any antibacterial effects. Non-hardened glass ionomer, resin modified and zinc polycarboxylate cements exhibited moderate antibacterial action. Hardened cements showed weaker antibacterial activities, than those ones applied right after mixing.

  14. 76 FR 24519 - Gray Portland Cement and Cement Clinker From Japan; Institution of a Five-Year Review Concerning...

    Science.gov (United States)

    2011-05-02

    ... COMMISSION Gray Portland Cement and Cement Clinker From Japan; Institution of a Five-Year Review Concerning the Antidumping Duty Order on Gray Portland Cement and Cement Clinker From Japan AGENCY: United States... determine whether revocation of the antidumping duty order on gray portland cement and cement clinker...

  15. 76 FR 50252 - Gray Portland Cement and Cement Clinker From Japan; Scheduling of an Expedited Five-Year Review...

    Science.gov (United States)

    2011-08-12

    ... COMMISSION Gray Portland Cement and Cement Clinker From Japan; Scheduling of an Expedited Five-Year Review Concerning the Antidumping Duty Order on Gray Portland Cement and Cement Clinker From Japan AGENCY: United... cement and cement clinker from Japan would be likely to lead to continuation or recurrence of...

  16. An insulating grid spacer for large-area MICROMEGAS chambers

    CERN Document Server

    Bernard, D; D'Enterria, D G; Le Guay, M; Martínez, G; Mora, M J; Pichot, P; Roy, D; Schutz, Y; Gandi, A; De Oliveira, R

    2002-01-01

    We present an original design for large area gaseous detectors based on the MICROMEGAS technology. This technology incorporates an insulating grid, sandwiched between the micro-mesh and the anode-pad plane, which provides an uniform 200 $\\mu$m amplification gap. The uniformity of the amplification gap thickness has been verified under several experimental conditions. The gain performances of the detector are presented and compared to the values obtained with detectors using cylindrical micro spacers. The new design presents several technical and financial advantages.

  17. Synthesis and properties of novel gemini surfactant with short spacer

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Cationic gemini surfactant dimethylene-1,2-bis(dodecyldiethylammonium bromide), referred to as C12C2C12(Et) was synthesized, and its surface property and aggregation behavior in aqueous solution were studied. The value of γat the critical micelle concentration (γcmc) is much smaller than that of the surfactant homologues with longer spacer. Spherical and elongated micelles were formed in the aqueous solution of this gemini surfactant,and the spherical micelles were absolutely dominant compared to the elongated micelles at our studied concentration quantitatively.

  18. PERFORMANCE OF PULVERIZED SLAG-SUBSTITUTED CEMENT

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The Portland cement is equivalently substituted by slag micropowders with various specific areas. The workability,activity and acid-corrosion resistance of the slag-substituted cements are investigated,the activation of gypsum is discussed,also the porosity and pore distribution of mortars of the slag micropowders cement are determined by mercury intrusion porosimetry.

  19. Cementation in adhesive dentistry: the weakest link

    NARCIS (Netherlands)

    Jongsma, L.A.

    2012-01-01

    Het succesvol bevestigen van tandrestauraties is een belangrijke en veeleisende procedure. Met behulp van cement wordt het restauratiemateriaal aan de tandstructuur verbonden. Op die manier worden twee hechtvlakken gecreëerd: het raakvlak tussen tand en cement, en het raakvlak tussen cement en resta

  20. 21 CFR 872.3275 - Dental cement.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Dental cement. 872.3275 Section 872.3275 Food and... DENTAL DEVICES Prosthetic Devices § 872.3275 Dental cement. (a) Zinc oxide-eugenol—(1) Identification... filling or as a base cement to affix a temporary tooth filling, to affix dental devices such as crowns or...

  1. ADVANCED CEMENTS FOR GEOTHERMAL WELLS

    Energy Technology Data Exchange (ETDEWEB)

    SUGAMA,T.

    2007-01-01

    Using the conventional well cements consisting of the calcium silicate hydrates (CaO-SiO{sub 2}-H{sub 2}O system) and calcium aluminum silicate hydrates (CaO-Al{sub 2}O{sub 3}-SiO{sub 2}-H{sub 2}O system) for the integrity of geothermal wells, the serious concern confronting the cementing industries was their poor performance in mechanically supporting the metallic well casing pipes and in mitigating the pipe's corrosion in very harsh geothermal reservoirs. These difficulties are particularly acute in two geological regions: One is the deep hot downhole area ({approx} 1700 m depth at temperatures of {approx} 320 C) that contains hyper saline water with high concentrations of CO{sub 2} (> 40,000 ppm) in conjunction with {approx} 100 ppm H{sub 2}S at a mild acid of pH {approx} 5.0; the other is the upper well region between the well's surface and {approx} 1000 m depth at temperatures up to 200 C. The specific environment of the latter region is characterized by highly concentrated H{sub 2}SO{sub 4} (pH < 1.5) brine containing at least 5000 ppm CO{sub 2}. When these conventional cements are emplaced in these harsh environments, their major shortcoming is their susceptibility to reactions with hot CO{sub 2} and H{sub 2}SO4, thereby causing their deterioration brought about by CO{sub 2}-catalyzed carbonation and acid-initiated erosion. Such degradation not only reduced rapidly the strength of cements, lowering the mechanical support of casing pipes, but also increased the extent of permeability of the brine through the cement layer, promoting the rate of the pipe's corrosion. Severely carbonated and acid eroded cements often impaired the integrity of a well in less than one year; in the worst cases, casings have collapsed within three months, leading to the need for costly and time-consuming repairs or redrilling operations. These were the reasons why the geothermal well drilling and cementing industries were concerned about using conventional well

  2. Transcriptional regulator-mediated activation of adaptation genes triggers CRISPR de novo spacer acquisition

    DEFF Research Database (Denmark)

    Liu, Tao; Li, Yingjun; Wang, Xiaodi;

    2015-01-01

    , it was demonstrated that the transcription level of csa1, cas1, cas2 and cas4 was significantly enhanced in a csa3a-overexpression strain and, moreover, the Csa1 and Cas1 protein levels were increased in this strain. Furthermore, we demonstrated the hyperactive uptake of unique spacers within both CRISPR loci......Acquisition of de novo spacer sequences confers CRISPR-Cas with a memory to defend against invading genetic elements. However, the mechanism of regulation of CRISPR spacer acquisition remains unknown. Here we examine the transcriptional regulation of the conserved spacer acquisition genes in Type I...... in the presence of the csa3a overexpression vector. The spacer acquisition process is dependent on the CCN PAM sequence and protospacer selection is random and non-directional. These results suggested a regulation mechanism of CRISPR spacer acquisition where a single transcriptional regulator senses the presence...

  3. Effect of plastic spacer handling on salbutamol lung deposition in asthmatic children

    DEFF Research Database (Denmark)

    Lipworth, Brian J; Lee, Daniel K C; Anhøj, Jacob

    2002-01-01

    AIMS: To study the effects of electrostatics in a plastic spacer on the lung deposition of salbutamol in asthmatic children. METHODS: Twenty-five children (5-12 years) with mild asthma were given salbutamol hydrofluoroalkane pressurized metered dose inhaler 400 micro g via a 750 ml plastic spacer...... use (Used ), a spacer rinsed after repeated use (UsedRinsed ) and a spacer primed with benzalkonium chloride to avoid electrostatics (Primed1). In addition, spacers were evaluated using a 15 s inhalation delay following actuation with primed (PrimedDelay) and rinsed (RinsedDelay) spacers. Data were...... log transformed and expressed as geometric mean fold difference for the average plasma salbutamol concentration (Cav) over 20 min. RESULTS: There were significant differences (P Primed1 vs NewRinsed 1.92 fold (95% CI 1.15, 3...

  4. Transcriptional regulator-mediated activation of adaptation genes triggers CRISPR de novo spacer acquisition

    DEFF Research Database (Denmark)

    Liu, Tao; Li, Yingjun; Wang, Xiaodi

    2015-01-01

    Acquisition of de novo spacer sequences confers CRISPR-Cas with a memory to defend against invading genetic elements. However, the mechanism of regulation of CRISPR spacer acquisition remains unknown. Here we examine the transcriptional regulation of the conserved spacer acquisition genes in Type I......, it was demonstrated that the transcription level of csa1, cas1, cas2 and cas4 was significantly enhanced in a csa3a-overexpression strain and, moreover, the Csa1 and Cas1 protein levels were increased in this strain. Furthermore, we demonstrated the hyperactive uptake of unique spacers within both CRISPR loci...... in the presence of the csa3a overexpression vector. The spacer acquisition process is dependent on the CCN PAM sequence and protospacer selection is random and non-directional. These results suggested a regulation mechanism of CRISPR spacer acquisition where a single transcriptional regulator senses the presence...

  5. Successful Treatment of Candida Albicans-Infected Total Hip Prosthesis With Staged Procedure Using an Antifungal-Loaded Cement Spacer

    NARCIS (Netherlands)

    Deelstra, Jenneke J.; Neut, Danielle; Jutte, Paul C.

    We present a rare case of an immunocompetent host who developed a Candida albicans-infected total hip prosthesis. The infection could not be eradicated with debridement and extensive antifungal therapy. Our patient first underwent a resection of the proximal femur and local treatment with

  6. Packaging design criteria modified fuel spacer burial box. Revision 1

    Energy Technology Data Exchange (ETDEWEB)

    Stevens, P.F.

    1994-09-13

    Various Hanford facilities must transfer large radioactively contaminated items to burial/storage. Presently, there are eighteen Fuel Spacer Burial Boxes (FSBBs) available on the Hanford Site for transport of such items. Previously, the FSBBS were transported from a rail car to the burial trench via a drag-off operation. To allow for the lifting of the boxes into the burial trench, it will be necessary to improve the packagings lifting attachments and provide structural reinforcement. Additional safety improvements to the packaging system will be provided by the addition of a positive closure system and package ventilation. FSBBs that are modified in such a manner are referred to as Modified Fuel Spacer Burial Boxes (MFSBs). The criteria provided by this PDC will be used to demonstrate that the transfer of the MFSB will provide an equivalent degree of safety as would be provided by a package meeting offsite transportation requirements. This fulfills the onsite transportation safety requirements implemented in WHC-CM-2-14, Hazardous Material Packaging and Shipping. A Safety Analysis Report for Packaging (SARP) will be prepared to evaluate the safety of the transfer operation. Approval of the SARP is required to authorize transfer. Criteria are also established to ensure burial requirements are met.

  7. Thoughts on the Current Cement Industry Development

    Institute of Scientific and Technical Information of China (English)

    Gan Zhihe

    2003-01-01

    According to the analysis of cement capacity andits relations with macro economy running index, the mainreasons for the present rapid development of cement capacityare the rapid development of economy and the shot up ofwhole society fixed asset investment. According to the presentspeed of economy development, cement still enjoys a po-tential increase, So here has not been an overall excessivepopularity of cement industry. The best way to prevent lowlevel repeated construction is to promote the development ofnew dry- process cement as well as try to get rid of blindness.

  8. Nanoparticle-Based Brachytherapy Spacers for Delivery of Localized Combined Chemoradiation Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Rajiv, E-mail: r.kumar@neu.edu [Nanomedicine Science and Technology Center, Northeastern University, Boston, Massachusetts (United States); Department of Radiation Oncology, Brigham and Women' s Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts (United States); Belz, Jodi [Nanomedicine Science and Technology Center, Northeastern University, Boston, Massachusetts (United States); Markovic, Stacey [Department of Electrical and Computer Engineering, Northeastern University, Boston, Massachusetts (United States); Jadhav, Tej; Fowle, William [Nanomedicine Science and Technology Center, Northeastern University, Boston, Massachusetts (United States); Niedre, Mark [Department of Electrical and Computer Engineering, Northeastern University, Boston, Massachusetts (United States); Cormack, Robert; Makrigiorgos, Mike G. [Department of Radiation Oncology, Brigham and Women' s Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts (United States); Sridhar, Srinivas [Nanomedicine Science and Technology Center, Northeastern University, Boston, Massachusetts (United States); Department of Radiation Oncology, Brigham and Women' s Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts (United States)

    2015-02-01

    Purpose: In radiation therapy (RT), brachytherapy-inert source spacers are commonly used in clinical practice to achieve high spatial accuracy. These implanted devices are critical technical components of precise radiation delivery but provide no direct therapeutic benefits. Methods and Materials: Here we have fabricated implantable nanoplatforms or chemoradiation therapy (INCeRT) spacers loaded with silica nanoparticles (SNPs) conjugated containing a drug, to act as a slow-release drug depot for simultaneous localized chemoradiation therapy. The spacers are made of poly(lactic-co-glycolic) acid (PLGA) as matrix and are physically identical in size to the commercially available brachytherapy spacers (5 mm × 0.8 mm). The silica nanoparticles, 250 nm in diameter, were conjugated with near infrared fluorophore Cy7.5 as a model drug, and the INCeRT spacers were characterized in terms of size, morphology, and composition using different instrumentation techniques. The spacers were further doped with an anticancer drug, docetaxel. We evaluated the in vivo stability, biocompatibility, and biodegradation of these spacers in live mouse tissues. Results: The electron microscopy studies showed that nanoparticles were distributed throughout the spacers. These INCeRT spacers remained stable and can be tracked by the use of optical fluorescence. In vivo optical imaging studies showed a slow diffusion of nanoparticles from the spacer to the adjacent tissue in contrast to the control Cy7.5-PLGA spacer, which showed rapid disintegration in a few days with a burst release of Cy7.5. The docetaxel spacers showed suppression of tumor growth in contrast to control mice over 16 days. Conclusions: The imaging with the Cy7.5 spacer and therapeutic efficacy with docetaxel spacers supports the hypothesis that INCeRT spacers can be used for delivering the drugs in a slow, sustained manner in conjunction with brachytherapy, in contrast to the rapid clearance of the drugs when

  9. Cervical interfacet spacers and maintenance of cervical lordosis.

    Science.gov (United States)

    Tan, Lee A; Straus, David C; Traynelis, Vincent C

    2015-05-01

    OBJECT The cervical interfacet spacer (CIS) is a relatively new technology that can increase foraminal height and area by facet distraction. These offer the potential to provide indirect neuroforaminal decompression while simultaneously enhancing fusion potential due to the relatively large osteoconductive surface area and compressive forces exerted on the grafts. These potential benefits, along with the relative ease of implantation during posterior cervical fusion procedures, make the CIS an attractive adjuvant in the management of cervical pathology. One concern with the use of interfacet spacers is the theoretical risk of inducing iatrogenic kyphosis. This work tests the hypothesis that interfacet spacers are associated with loss of cervical lordosis. METHODS Records from patients undergoing posterior cervical fusion at Rush University Medical Center between March 2011 and December 2012 were reviewed. The FacetLift CISs were used in all patients. Preoperative and postoperative radiographic data were reviewed and the Ishihara indices and cervical lordotic angles were measured and recorded. Statistical analyses were performed using STATA software. RESULTS A total of 64 patients were identified in whom 154 cervical levels were implanted with machined allograft interfacet spacers. Of these, 15 patients underwent anterior-posterior fusions, 4 underwent anterior-posterior-anterior fusions, and the remaining 45 patients underwent posterior-only fusions. In the 45 patients with posterior-only fusions, a total of 110 levels were treated with spacers. There were 14 patients (31%) with a single level treated, 16 patients (36%) with two levels treated, 5 patients (11%) with three levels treated, 5 patients (11%) with four levels treated, 1 patient (2%) with five levels treated, and 4 patients (9%) with six levels treated. Complete radiographic data were available in 38 of 45 patients (84%). On average, radiographic follow-up was obtained at 256.9 days (range 48-524 days

  10. CO2 Capture by Cement Raw Meal

    DEFF Research Database (Denmark)

    Pathi, Sharat Kumar; Lin, Weigang; Illerup, Jytte Boll

    2013-01-01

    The cement industry is one of the major sources of CO2 emissions and is likely to contribute to further increases in the near future. The carbonate looping process has the potential to capture CO2 emissions from the cement industry, in which raw meal for cement production could be used...... as the sorbent. Cyclic experiments were carried out in a TGA apparatus using industrial cement raw meal and synthetic raw meal as sorbents, with limestone as the reference. The results show that the CO2 capture capacities of the cement raw meal and the synthetic raw meal are comparable to those of pure limestone...... that raw meal could be used as a sorbent for the easy integration of the carbonate looping process into the cement pyro process for reducing CO2 emissions from the cement production process....

  11. Understanding cement mechanical behavior in SAGD wells

    Energy Technology Data Exchange (ETDEWEB)

    Xie, J.; Zahacy, T. A. [C-FER Technologies (Canada)

    2011-07-01

    In the heavy oil industry, the steam assisted gravity drainage process is often used to enhance oil recovery but it can cause cracks in the cement sheath. These cracks are the result of high steam temperatures and thermal expansion. In order to mitigate this risk, improved well designs are required. The aim of this paper is to present the mechanical behavior of the cement sheath during the heating phase. An analysis of the impact of design and operating parameters was conducted through thermal hydraulic and thermal mechanical analyses to assess cement integrity. These analyses were then performed on an example of an SAGD project in the southern part of the Athabasca oilsands region to assess the performance of the cement sheath. Results showed that potential damage to the cement can be reduced by slow heating and a lower Young's modulus cement blend. This paper makes recommendations for optimizing cement design in thermal recovery wells.

  12. Some durability aspects of hybrid alkaline cements

    Directory of Open Access Journals (Sweden)

    Donatello S.

    2014-04-01

    Full Text Available Blended cements that contain a high content of fly ash and a low content of Portland cement typically suffer from low early strength development and long setting times. Recently, one method of overcoming these problems has been to use an alkali activator to enhance the reactivity of fly ash particles at early ages. Such cements can be grouped under the generic term “hybrid alkaline cements”, where both cement clinker and fly ash, encouraged by the presence of alkalis, are expected to contribute to cementitious gel formation. The work presented here examines some of the durability aspects of high fly ash content hybrid alkaline cement. Specifically, the aspects investigated were: exposure at high temperatures (up to 1000°C, resistance to immersion in aggressive solutions and susceptibility to the alkali aggregate reaction. All tests were repeated with a commercially available sulfate resistant Portland cement for comparison. When exposed to high temperatures, the hybrid alkaline cement showed strikingly different behaviour compared to the control Portland cement, showing fewer micro-cracks and maintaining residual compressive strengths at least equal to original strengths. Beyond 700°C, the hybrid alkaline cement began to sinter, which resulted in shrinkage of around 5% and a 100% increase in residual compressive strengths. No such sintering event was noted in the control Portland cement, which showed a drastic loss in residual compressive strengths upon heating. In immersion tests, the hybrid alkaline cement possessed excellent resistance to sulfate and seawater attack, similar to the control sulfate resistant cement. Both cements were however severely degraded by immersion in 0.1M HCl for 90 days. Both binders complied with the accelerated alkali-aggregate test but when this test was extended, the hybrid alkaline binder showed much greater dimensional stability. Possible reasons for the differences in durability behaviour in both cements

  13. Synthesis and Properties of Gemini Cationic Surfactants with Amide Spacers

    Institute of Scientific and Technical Information of China (English)

    DENG Qi-gang; YU Hong-wei; LIN Hong; JIA Li-hua; GUO Xiang-feng; ZHOU De-rui

    2005-01-01

    Four gemini cationic surfactants {N,N'-di[2-(lauryldimethylamino)acetyl]polymethylenediamine dichloride, LAA-s-LAA, s=2,3,4,6} were synthesized by using four bis(α-chloroacetamide)s and N,N-dimethyllaurylamine, respectively. The molecular structures were characterized by means of IR, 1H NMR, 13C NMR and MS, and the behavior of their aqueous solutions was studied. The critical micell concentrations(CMC) of LAA-s-LAA were one order of magnitude lower than that of dodecyltrimethyl ammonium chloride(DTAC). With the change of the length of spacer chain(s), their CMC values change, and CMC reaches the top value at s=4.

  14. Vibration of the Package of Rods Linked by Spacer Grids

    Science.gov (United States)

    Zeman, V.; Hlaváč, Z.

    This paper deals with modelling and vibration analysis of the large package of identical parallel rods which are linked by transverse springs (spacer grids) placed on several level spacings. The vibration of rods is caused by the support plate motion. The rod discretization by FEM is based on Rayleigh beam theory. With respect to cyclic and central package rod symmetry, the system is decomposed to identical revolved rod segments. The modal synthesis method with condensation of the rod segments is used for modelling and determination of steady forced vibration of the whole system. The presented method is the first step to modelling of the nuclear fuel assembly vibration caused by kinematical excitation determined by motion of the support plates which are part of the reactor core.

  15. Research of magnesium phosphosilicate cement

    Science.gov (United States)

    Ding, Zhu

    Magnesium phosphosilicate cement (MPSC) is a novel phosphate bonded cement, which consists mainly of magnesia, phosphate and silicate minerals. The traditional magnesium phosphate cements (MPCs) usually composed by ammonium phosphate, and gaseous ammonia will emit during mixing and in service. There is no noxious ammonia released from MPSC, furthermore, it can recycle a large volume of the non-hazardous waste. The goal of this research is to investigate the composition, reaction products, reaction mechanism, microstructure, properties, durability and applications of the MPSC. MPSC sets rapidly and has high early strength. It reacts better with solid industrial waste when compared to Portland cement. Many solid industrial wastes, such as fly ash, steel slag, coal gangue, red coal gangue, red mud, barium-bearing slag, copper slag, silica fume, and ground granulated blast furnace slag, have been used as the main component (40% by weight) in MPSC. The research has found that these aluminosilicate (or ironsilicate, or calciumsilicate) minerals with an amorphous or glass structure can enhance the performance of MPSC. The disorganized internal structure of amorphous materials may make it possess higher reactivity compared to the crystalline phases. Chemical reaction between phosphate and these minerals may form an amorphous gel, which is favorable to the cementing. Borax, boric acid and sodium tripolyphosphate have been used as retardants in the MPSC system. It is found that boric acid has a higher retarding effect on the setting of cement, than borax does. However, sodium polyphosphate accelerates the reaction of MPSC. The hydration of MPSC is exothermic reaction. The heat evolution may prompt hydrates formation, and shorten the setting process. Modern materials characterization techniques, XRD, DSC, TG-DTA FTIR, XPS, MAS-NMR, SEM, TEM, MIP, etc. were used to analyze the phase composition, micro morphology, and microstructure of hardened MPSC. The main hydration product

  16. Solution-processed organic tandem solar cells with embedded optical spacers

    NARCIS (Netherlands)

    Hadipour, Afshin; de Boer, Bert; Blom, Paul W. M.

    2007-01-01

    We demonstrate a solution-processed polymer tandem solar cell in which the two photoactive single cells are separated by an optical spacer. The use of an optical spacer allows for an independent optimization of both the electronic and optical properties of the tandem cell. The optical transmission

  17. Variability of aerosol delivery via spacer devices in young asthmatic children in daily life

    NARCIS (Netherlands)

    H.M. Janssens (Hettie); S.G. Devadason; W.C.J. Hop (Wim); P.N. LeSouef; J.C. de Jongste (Johan); H.A.W.M. Tiddens (Harm)

    1999-01-01

    textabstractPressurized metered dose inhalers (pMDI) are widely used together with spacers for the treatment of asthma in children. However, the variability of daily medication dose for pMDI/spacer combinations is not known. Electrostatic charge is a potential source of

  18. Occupational hand dermatitis among cement workers in Taiwan

    Directory of Open Access Journals (Sweden)

    Bour-Jr Wang

    2011-12-01

    Conclusion: We conclude that occupational cement hand dermatitis among cement workers is an important and severe issue in Taiwan, and the most common allergens among cement workers are potassium dichromate, thiuram mix, fragrance mix and cobalt chloride. The high positive rate of chromium hypersensitivity among cement workers reflects the urgency to regulate the addition of ferrous sulfate to cement in Taiwan.

  19. A Study of Neutronics Effects of the Spacer Grids in a Typical PWR via Monte Carlo Calculation

    Energy Technology Data Exchange (ETDEWEB)

    Bach, Tran Xuan; Cho, Nam Zin [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

    2014-10-15

    Neutronics analysis, the spacer grids which support fuel rods are not explicitly described, but they are homogenized with coolant. However, the effects of neglecting or simplifying the spacer grids are not reported in the literature to the best of our knowledge. In this paper, to investigate the effects of spacer grids in neutronics analysis, a detailed description of spacer grids is added to the KAIST benchmark problem 1B. Then, the effective multiplication factor, spatial distributions of neutron flux, and its energy spectrum are obtained for the two cases (with and without spacer grids). Numerical results show that the effects of spacer grids are not negligible. In this paper, to investigate the effect of spacer grids, the spacer grid geometry is described in detail in the Monte Carlo calculation. In the numerical test, the two cases are compared in the context of a modified KAIST benchmark problem 1B. Case 1 does not have spacer grids, while the space is filled by coolant instead. Case 2 includes the spacer grids. The difference in neutron flux spectra is also observed. Thus, the effect of the spacer grids should be considered in the whole-core reactor analysis. In practice, the spacer grids are homogenized into coolant to consider its effect. As a further study, therefore, it would be worthwhile to investigate the differences between the homogenization and the explicit description of the spacer grids.

  20. Hydrophobic spacers enhance the helicity and lectin binding of synthetic, pH-responsive glycopolypeptides.

    Science.gov (United States)

    Mildner, Robert; Menzel, Henning

    2014-12-08

    The influence of different hydrophobic spacers on the structural and lectin binding properties of well-defined glycopolypeptides decorated with galactose moieties was investigated. All glycopolypeptides were prepared from a poly(α,l-glutamic acid) (PGA) precursor via a polymer-analogous aqueous amide coupling reaction. Thereby, two alkyl spacers of different length (C6 and C11) as well as an aromatic spacer were introduced between the backbone and the galactose moieties, as confirmed by (1)H NMR spectroscopy. The secondary structure was investigated as a function of the sugar density and the pH by circular dichroism (CD) spectroscopy. It was found that the helicity in acidic medium and thus the typical coil-to-helix transition is strongly enhanced by the hydrophobic spacers. Preliminary lectin binding tests via turbidimetric assay revealed that the spacers also significantly enhance the interaction of the glycopolypeptides with the lectin RCA120.

  1. Alternative Fuels in Cement Production

    OpenAIRE

    2007-01-01

    Substitutionen af fossilt med alternativt brændsel i cement produktionen er steget betydeligt i den sidste dekade. Af disse nye alternative brændsler, udgør de faste brændsler p.t. den største andel, hvor kød- og benmel, plastic og dæk i særdeleshed har været de alternative brændsler der har bidraget med mest alternativ brændsels energi til den tyske cement industri. De nye alternative brændsler er typisk karakteriseret ved et højt indhold af flygtige bestanddele og adskiller sig typisk fra t...

  2. A Twofold Comparison between Dual Cure Resin Modified Cement and Glass Ionomer Cement for Orthodontic Band Cementation

    Science.gov (United States)

    Attar, Hanaa El; Elhiny, Omnia; Salem, Ghada; Abdelrahman, Ahmed; Attia, Mazen

    2016-01-01

    AIM: To test the solubility of dual cure resin modified resin cement in a food simulating solution and the shear bond strength compared to conventional Glass ionomer cement. MATERIALS AND METHOD: The materials tested were self-adhesive dual cure resin modified cement and Glass Ionomer (GIC). Twenty Teflon moulds were divided into two groups of tens. The first group was injected and packed with the modified resin cement, the second group was packed with GIC. To test the solubility, each mould was weighed before and after being placed in an analytical reagent for 30 days. The solubility was measured as the difference between the initial and final drying mass. To measure the Shear bond strength, 20 freshly extracted wisdom teeth were equally divided into two groups and embedded in self-cure acrylic resin. Four mm sections of stainless steel bands were cemented to the exposed buccal surfaces of teeth under a constant load of 500 g. Shear bond strength was measured using a computer controlled materials testing machine and the load required to deband the samples was recorded in Newtons. RESULTS: GIC showed significantly higher mean weight loss and an insignificant lower Shear bond strength, compared to dual cure resin Cement. CONCLUSION: It was found that dual cure resin modified cement was less soluble than glass ionomer cement and of comparable bond strength rendering it more useful clinically for orthodontic band cementation. PMID:28028417

  3. Influence of the temperature on the cement disintegration in cement-retained implant restorations.

    Science.gov (United States)

    Linkevicius, Tomas; Vindasiute, Egle; Puisys, Algirdas; Linkeviciene, Laura; Svediene, Olga

    2012-01-01

    The aim of this study was to estimate the average disintegration temperature of three dental cements used for the cementation of the implant-supported prostheses. One hundred and twenty metal frameworks were fabricated and cemented on the prosthetic abutments with different dental cements. After heat treatment in the dental furnace, the samples were set for the separation to test the integration of the cement. Results have shown that resin-modified glass-ionomer cement (RGIC) exhibited the lowest disintegration temperature (pcement (ZPC) and dual cure resin cement (RC) (p>0.05). Average separation temperatures: RGIC - 306 ± 23 °C, RC - 363 ± 71 °C, it could not be calculated for the ZPC due to the eight unseparated specimens. Within the limitations of the study, it could be concluded that RGIC cement disintegrates at the lowest temperature and ZPC is not prone to break down after exposure to temperature.

  4. ROTARY SCREW SYSTEMS IN CEMENT

    OpenAIRE

    2016-01-01

    The article presents results of research of rotary-screw systems in relation to the creation of rotary kilns for the annealing of-cuttings in the preparation of cement clinker. Using the proposed design, in comparison with known designs of similar purpose, it significantly improves performance, reduces size and power consumption through the use of rotary screw systems in the form of screw rotors and drums made hollow with sidewalls assembled from separate strips or plates of different geometr...

  5. Center for Cement Composite Materials

    Science.gov (United States)

    1990-01-31

    pastes have shown that the matrix is microporous; mesopores are absent unless the material is allowed to dry out. This results in water adsorption at low...only to water. When subsequently dried a portion of3 the porosity is converted to larger mesopores . • Only about one third of the cement reacts in a...Frictional sliding, in this case was characterized by a decreasing slope in the loading curve followed by hysteresis in the unload/reloading curves

  6. The cement solidification systems at LANL

    Energy Technology Data Exchange (ETDEWEB)

    Veazey, G.W.

    1990-01-01

    There are two major cement solidification systems at Los Alamos National Laboratory. Both are focused primarily around treating waste from the evaporator at TA-55, the Plutonium Processing Facility. The evaporator receives the liquid waste stream from TA-55's nitric acid-based, aqueous-processing operations and concentrates the majority of the radionuclides in the evaporator bottoms solution. This is sent to the TA-55 cementation system. The evaporator distillate is sent to the TA-50 facility, where the radionuclides are precipitated and then cemented. Both systems treat TRU-level waste, and so are operated according to the criteria for WIPP-destined waste, but they differ in both cement type and mixing method. The TA-55 systems uses Envirostone, a gypsum-based cement and in-drum prop mixing; the TA-50 systems uses Portland cement and drum tumbling for mixing.

  7. WHITE CEMENT IN SUSTAINABLE DEVELOPMENT

    Directory of Open Access Journals (Sweden)

    Y.C.P RAMANA BABU

    2013-04-01

    Full Text Available India is one among the fast developing countries in the world in the areas of Infrastructure. Now a day, Carbon monoxide (CO and carbon dioxide (CO2 are the temporary atmospheric pollutants in the environment chiefly emitted from the fuel burning vehicles and street lights which lead to global warming and pose a major threat tothe survival and sustainable development. This paper deals with the principal purpose of use of white cement in pavement design which will take care of the Green house gases (i.e., CO and CO2 and also saves lot of money in the long run process. A small amount of these gases in environment can cause major problems over time. Use of white cement in composite pavement design where there is heavy traffic loads are acting as well as number of vehicles are more such as junctions, bus stops, check posts etc., can perform better and acts asenvironment friendly. Its light colour reflects more than bituminous pavement so that it can be easily identified and avoid accidents to some extent. White cement helps to lower the average bus stop, junction temperature providing comfort to the people because it has high solar reflectance there by reducing “urban heat island” effect. In addition to this it has some more advantages which increase the sustainability, durability and workability of the pavements.

  8. Sustainable Development of the Cement Industry and Blended Cements to Meet Ecological Challenges

    OpenAIRE

    Konstantin Sobolev

    2003-01-01

    The world production of cement has greatly increased in the past 10 years. This trend is the most significant factor affecting technological development and the updating of manufacturing facilities in the cement industry. Existing technology for the production of cement clinker is ecologically damaging; it consumes much energy and natural resources and also emits pollutants. A new approach to the production of blended or high-volume mineral additive (HVMA) cement helps to improve its ecologi...

  9. Water dynamics in glass ionomer cements

    Science.gov (United States)

    Berg, M. C.; Jacobsen, J.; Momsen, N. C. R.; Benetti, A. R.; Telling, M. T. F.; Seydel, T.; Bordallo, H. N.

    2016-07-01

    Glass ionomer cements (GIC) are an alternative for preventive dentistry. However, these dental cements are complex systems where important motions related to the different states of the hydrogen atoms evolve in a confined porous structure. In this paper, we studied the water dynamics of two different liquids used to prepare either conventional or resin-modified glass ionomer cement. By combining thermal analysis with neutron scattering data we were able to relate the water structure in the liquids to the materials properties.

  10. Pulmonary Cement Embolism following Percutaneous Vertebroplasty

    Directory of Open Access Journals (Sweden)

    Ümran Toru

    2014-01-01

    Full Text Available Percutaneous vertebroplasty is a minimal invasive procedure that is applied for the treatment of osteoporotic vertebral fractures. During vertebroplasty, the leakage of bone cement outside the vertebral body leads to pulmonary cement embolism, which is a serious complication of this procedure. Here we report a 48-year-old man who was admitted to our hospital with dyspnea after percutaneous vertebroplasty and diagnosed as pulmonary cement embolism.

  11. Effects of cement flue dusts from a Nigerian cement plant on air, water and planktonic quality.

    Science.gov (United States)

    Olaleye, Victor F; Oluyemi, Emmanuel A

    2010-03-01

    Effects of cement flue dust from Ewekoro cement Kilns were monitored at some aquatic receptor locations. High levels of total suspended particulates (TSPs) and atmospheric deposition rates (ADRs) were recorded within the factory compared to ancillary locations outside the factory. The TSP and ADR levels which were location dependent were significantly higher (P cement factory catchment areas.

  12. The mechanical effects of different levels of cement penetration at the cement-bone interface.

    NARCIS (Netherlands)

    Waanders, D.; Janssen, D.; Mann, K.A.; Verdonschot, N.J.J.

    2010-01-01

    The mechanical effects of varying the depth of cement penetration in the cement-bone interface were investigated using finite element analysis (FEA) and validated using companion experimental data. Two FEA models of the cement-bone interface were created from micro-computed tomography data and the p

  13. The influence of ultrasound on removal of prefabricated metal post cemented with different resin cements

    Directory of Open Access Journals (Sweden)

    Atiyeh Feiz

    2013-01-01

    Conclusion: Ultrasonic energy did not decrease the retention of posts cemented with Panavia or Maxcem Elite cements. Furthermore, it seems that there is no significant difference between removal force of self-etch (Panavia and the self-etch self-adhesive (Maxcem Elite resin cements.

  14. Frozen delivery of brushite calcium phosphate cements.

    Science.gov (United States)

    Grover, Liam M; Hofmann, Michael P; Gbureck, Uwe; Kumarasami, Balamurgan; Barralet, Jake E

    2008-11-01

    Calcium phosphate cements typically harden following the combination of a calcium phosphate powder component with an aqueous solution to form a matrix consisting of hydroxyapatite or brushite. The mixing process can be very important to the mechanical properties exhibited by cement materials and consequently when used clinically, since they are usually hand-mixed their mechanical properties are prone to operator-induced variability. It is possible to reduce this variability by pre-mixing the cement, e.g. by replacing the aqueous liquid component with non-reactive glycerol. Here, for the first time, we report the formation of three different pre-mixed brushite cement formulations formed by freezing the cement pastes following combination of the powder and liquid components. When frozen and stored at -80 degrees C or less, significant degradation in compression strength did not occur for the duration of the study (28 days). Interestingly, in the case of the brushite cement formed from the combination of beta-tricalcium phosphate with 2 M orthophosphoric acid solution, freezing the cement paste had the effect of increasing mean compressive strength fivefold (from 4 to 20 MPa). The increase in compression strength was accompanied by a reduction in the setting rate of the cement. As no differences in porosity or degree of reaction were observed, strength improvement was attributed to a modification of crystal morphology and a reduction in damage caused to the cement matrix during manipulation.

  15. Substantial global carbon uptake by cement carbonation

    Science.gov (United States)

    Xi, Fengming; Davis, Steven J.; Ciais, Philippe; Crawford-Brown, Douglas; Guan, Dabo; Pade, Claus; Shi, Tiemao; Syddall, Mark; Lv, Jie; Ji, Lanzhu; Bing, Longfei; Wang, Jiaoyue; Wei, Wei; Yang, Keun-Hyeok; Lagerblad, Björn; Galan, Isabel; Andrade, Carmen; Zhang, Ying; Liu, Zhu

    2016-12-01

    Calcination of carbonate rocks during the manufacture of cement produced 5% of global CO2 emissions from all industrial process and fossil-fuel combustion in 2013. Considerable attention has been paid to quantifying these industrial process emissions from cement production, but the natural reversal of the process--carbonation--has received little attention in carbon cycle studies. Here, we use new and existing data on cement materials during cement service life, demolition, and secondary use of concrete waste to estimate regional and global CO2 uptake between 1930 and 2013 using an analytical model describing carbonation chemistry. We find that carbonation of cement materials over their life cycle represents a large and growing net sink of CO2, increasing from 0.10 GtC yr-1 in 1998 to 0.25 GtC yr-1 in 2013. In total, we estimate that a cumulative amount of 4.5 GtC has been sequestered in carbonating cement materials from 1930 to 2013, offsetting 43% of the CO2 emissions from production of cement over the same period, not including emissions associated with fossil use during cement production. We conclude that carbonation of cement products represents a substantial carbon sink that is not currently considered in emissions inventories.

  16. Hidration kinetics study of tlie mixed cements

    OpenAIRE

    Duque Fernández, Gabriel . L; Díaz Quintanilla, David; Zapata Sierra, Manuel; Rubio Frías, Ester

    1993-01-01

    A study of the hydration process of cements with 10% and 20% addition of a tuff from "Las Carolinas" quarry (Cienfuegos, Cuba) by different methods was done. The results obtained by different methods showed a good agreement. It was proved an increment of the hydration products, an acceleration of alite hydration and a swelling of the fixed water in mixed cements. The resistance of the cement with 10% addition is similar to that of the pure cement for ages of 28 days, whereas with 20% addition...

  17. In vitro performance of three combinations of spacers and pressurized metered dose inhalers for treatment in children

    DEFF Research Database (Denmark)

    Berg, E; Madsen, J; Bisgaard, H

    1998-01-01

    The performance of pressurized metered dose inhalers (pMDIs) and spacers in correct dose recommendations is important, but limited information on dose delivery and fine-particle dose from different combinations of spacers and pMDIs is available. In this study, three combinations of spacers and pM...

  18. Occult spinous process fractures associated with interspinous process spacers.

    Science.gov (United States)

    Kim, David H; Tantorski, Mark; Shaw, Jeremy; Martha, Juli; Li, Ling; Shanti, Nael; Rencu, Tal; Parazin, Stephen; Kwon, Brian

    2011-07-15

    Prospective observational study. To provide a more accurate estimate of the rate of acute spinous process fractures associated with IPS surgery. Biomechanical cadaveric studies have suggested adequate spinous process strength to support placement of interspinous process spacers (IPS). Postoperative spinous process fractures have been reported in one%-to 5.8% of patients in previous series based on routine biplanar radiographic evaluation. However, most fractures occur between the base and midportion of the spinous process in an area that is typically difficult to visualize on plain radiographs due to device design. All patients underwent preoperative biplanar plain radiographs and computed tomography (CT) of the lumbar spine to confirm anatomy favorable for IPS placement and rule out fracture or spondylolysis. Postoperatively, all patients underwent repeat CT imaging within six months of surgery, biplanar radiographs at two weeks, six weeks, three months, six months, and one year. All studies were reviewed independently by a neuroradiologist and two orthopedic spine surgeons. Fifty implants (38 L4-5, 12 L3-4) were placed in 38 patients who completed follow-up and were included in final analysis. Three IPS designs were included (34 Medtronic X-STOP titanium, 8 X-STOP PEEK, 8 Lanx Aspen). Postoperative CT revealed 11 nondisplaced spinous process fractures in 11 patients (28.9% of patients, 22% of levels). Five fractures were associated with mild to moderate lumbar back pain and six fractures were asymptomatic. No patient reported a traumatic incident. No fracture was identifiable on plain radiographs. One fracture displaced during follow-up evaluation. Three patients underwent IPS removal and laminectomy. Three fractures healed by CT in one year. Overall, patients with fractures tended toward poorer outcomes by Zurich Claudication Questionnaire (ZCQ) (28.5% vs. 34.8% improvement in symptom severity, P = 0.496; 21.4% vs. 30.7% improvement in physical function, P = 0

  19. A study on provisional cements, cementation techniques, and their effects on bonding of porcelain laminate veneers.

    Science.gov (United States)

    Vinod Kumar, G; Soorya Poduval, T; Bipin Reddy; Shesha Reddy, P

    2014-03-01

    Minimal tooth preparation is required for porcelain laminate veneers, but interim restorations are a must to protect their teeth against thermal insult, chemical irritation, and to provide aesthetics. Cement remaining after the removal of the provisional restoration can impair the etching quality of the tooth surface and fit and final bonding of the porcelain laminate veneer. This in vitro study examined the tooth surface for remaining debris of cement after removal of a provisional restoration. Determine the presence of cement debris on prepared tooth surface subsequent to the removal of provisional restoration. Determine the cement with the least residue following the cleansing procedures. Determine the effect of smear layer on the amount of residual luting cement. Eighty-four extracted natural anterior teeth were prepared for porcelain laminate veneers. For half of the teeth, the smear layer was removed before luting provisional restorations. Veneer provisional restorations were fabricated and luted to teeth with six bonding methods: varnish combined with glass ionomer cement (GIC), varnish combined with resin modified GIC, varnish, spot etching combined with dual-cure luting cement, adhesive combined with GIC, adhesive combined with resin modified GIC, and adhesive, spot etching combined with dual-cure luting cement. After removal of provisional restorations 1 week later, the tooth surface was examined for residual luting material with SEM. Traces of cement debris were found on all the prepared teeth surfaces for all six groups which were cemented with different methods. Cement debris was seen on teeth subsequent to the removal of provisional's. Dual-cure cement had the least residue following the cleansing procedures. Presence of smear layer had no statistical significance in comparison with cement residue. With the use of adhesive the cement debris was always found to be more than with the use of varnish. GIC showed maximum residual cement followed by dual-cure.

  20. Antibacterial activity of selected glass ionomer cements

    Directory of Open Access Journals (Sweden)

    Elżbieta Łuczaj-Cepowicz

    2014-01-01

    Full Text Available Introduction: The aim of the paper was to determine the antibacterial activity of four glass ionomer cements against bacteria of the genera Streptococcus and Lactobacillus.Material and methods: Four capsulated glass ionomer cements were applied in the study: Fuji Triage (GC, Fuji IX (GC, Ketac Molar (3M Espe and Ketac Silver (3M Espe. Four standard bacterial strains were used to assess the antibacterial activity of the studied cements: Streptococcus mutans, S. sanguis, S. salivarius and Lactobacillus casei. The antibacterial activity was determined by the agar diffusion method. The bacterial suspension was spread with a cotton swab on TSA plates. For each material six wells (7 mm diameter, 5 mm deep were made with a cork borer. Each well was then filled with freshly prepared cements. The results were obtained by measuring the bacterial growth inhibition zone after 1, 2, 3 and 7 days. Results: Fuji Triage cement inhibited the growth of all bacterial strains. Fuji IX cement demonstrated the most potent antibacterial activity against S. sanguis. Ketac Molar showed antibacterial activity against S. sanguis and S. salivarius, whereas Ketac Silver was efficient against S. mutans as well. Neither of the Ketac cements inhibited growth of the standard L. casei strain. Discussion: Antibacterial activity of glass ionomer cements has attracted the interest of scientists in recent years. Most authors, including us, carried out experiments using the agar diffusion method and demonstrated antibacterial activity of glass ionomer cements. Different antibacterial activity of glass ionomer cements, observed in our study and studies of other authors, depended on the evaluated cement, bacterial strain and period of evaluation.

  1. Antibacterial activity of selected glass ionomer cements.

    Science.gov (United States)

    Luczaj-Cepowicz, Elżbieta; Marczuk-Kolada, Grażyna; Zalewska, Anna; Pawińska, Małgorzata; Leszczyńska, Katarzyna

    2014-01-22

    The aim of the paper was to determine the antibacterial activity of four glass ionomer cements against bacteria of the genera Streptococcus and Lactobacillus. Four capsulated glass ionomer cements were applied in the study: Fuji Triage (GC), Fuji IX (GC), Ketac Molar (3M Espe) and Ketac Silver (3M Espe). Four standard bacterial strains were used to assess the antibacterial activity of the studied cements: Streptococcus mutans, S. sanguis, S. salivarius and Lactobacillus casei. The antibacterial activity was determined by the agar diffusion method. The bacterial suspension was spread with a cotton swab on TSA plates. For each material six wells (7 mm diameter, 5 mm deep) were made with a cork borer. Each well was then filled with freshly prepared cements. The results were obtained by measuring the bacterial growth inhibition zone after 1, 2, 3 and 7 days. Fuji Triage cement inhibited the growth of all bacterial strains. Fuji IX cement demonstrated the most potent antibacterial activity against S. sanguis. Ketac Molar showed antibacterial activity against S. sanguis and S. salivarius, whereas Ketac Silver was efficient against S. mutans as well. Neither of the Ketac cements inhibited growth of the standard L. casei strain. Antibacterial activity of glass ionomer cements has attracted the interest of scientists in recent years. Most authors, including us, carried out experiments using the agar diffusion method and demonstrated antibacterial activity of glass ionomer cements. Different antibacterial activity of glass ionomer cements, observed in our study and studies of other authors, depended on the evaluated cement, bacterial strain and period of evaluation.

  2. Characterization of feed channel spacer performance using geometries obtained by X-ray computed tomography

    KAUST Repository

    Haaksman, Viktor A.

    2016-09-09

    Spiral-wound membrane modules used in water treatment for water reuse and desalination make use of spacer meshes for keeping the membrane leaves apart and for enhancing the mass transfer. Computational fluid dynamics (CFD) has gained importance in the design of new spacers with optimized hydrodynamic characteristics, but this requires a precise description of the spacer geometry. This study developed a method to obtain accurate three-dimensional (3-D) geometry representations for any given spacer design from X-ray computed tomography (CT) scans. The method revealed that the filaments of industrial spacers have a highly variable cross-section size and shape, which impact the flow characteristics in the feed channel. The pressure drop and friction factors were calculated from numerical simulations on five commercially available feed spacers used in practice. Model solutions compared well to experimental data measured using a flow cell for average velocities up to 0.2 m/s, as used in industrial reverse osmosis and nanofiltration membrane operations. A newly-proposed spacer geometry with alternating strand thickness was tested, which was found to yield a lower pressure drop while being highly efficient in converting the pumping power into membrane shear. Numerical model solutions using CFD with geometries from CT scans were closer to measurements than those obtained using the traditional circular cross-section strand simplification, indicating that CT scans are very well suitable to approximate real feed spacer geometries. By providing detailed insight on the spacer filament shape, CT scans allow better quantification of local distribution of velocity and shear, possibly leading to more accurate estimations of fouling and concentration polarization. © 2016 Elsevier B.V.

  3. Optimization of Radiation Therapy Techniques for Prostate Cancer With Prostate-Rectum Spacers: A Systematic Review

    Energy Technology Data Exchange (ETDEWEB)

    Mok, Gary [Department of Radiation Oncology, Geneva University Hospital, Geneva (Switzerland); Department of Radiation Oncology, Centre Intégré de Cancérologie de Laval, Centre de Santé et de Services Sociaux de Laval, Laval, Québec (Canada); Department of Radiology, Radiation Oncology, and Nuclear Medicine, Centre Hospitalier Universitaire de Montréal, Montréal, Québec (Canada); Benz, Eileen [Department of Radiation Oncology, Geneva University Hospital, Geneva (Switzerland); Vallee, Jean-Paul [Department of Radiology, Geneva University Hospital, Geneva (Switzerland); Miralbell, Raymond [Department of Radiation Oncology, Geneva University Hospital, Geneva (Switzerland); Zilli, Thomas, E-mail: Thomas.Zilli@hcuge.ch [Department of Radiation Oncology, Geneva University Hospital, Geneva (Switzerland)

    2014-10-01

    Dose-escalated radiation therapy for localized prostate cancer improves disease control but is also associated with worse rectal toxicity. A spacer placed between the prostate and rectum can be used to displace the anterior rectal wall outside of the high-dose radiation regions and potentially minimize radiation-induced rectal toxicity. This systematic review focuses on the published data regarding the different types of commercially available prostate-rectum spacers. Dosimetric results and preliminary clinical data using prostate-rectum spacers in patients with localized prostate cancer treated by curative radiation therapy are compared and discussed.

  4. APPLICATIONS OF SPACERS MADE WITH DOUBLE BAR RASCHEL MACHINE

    Directory of Open Access Journals (Sweden)

    DÍAZ-GARCÍA Pablo

    2016-05-01

    Full Text Available Nowadays, textile technologies develop to adapt their different techniques for creating new products for the different sectors of application every day. Particularly, warp knitted fabrics and warp-knitting technology have applications in all different groups of technical textiles. It could be the most applied technique, the most versatile technology to develop new textile products for the new textile market. Warp knitted fabrics play the most important role among the technical textile fabrics. This technology is used in different product groups such as mobile textiles (car seat covers, dashboard cover, industrial textiles (composites, medical textiles (anti-decubitus blankets, sports textiles and foundation garments (bra cups, pads for swimwear. This study presents some examples of the application of this technology in some markets Within the market of technical textile, medical textile has an increasing relevance and knitted fabrics and knitting technology, at the same time, play a very important role in the fields of technical and medical textiles. Studies have demonstrated that knitted structures possess excellent mechanical properties and can promote more effective regenerative medicine, tissue repair, ligament, tendon cartilage, reconstruction, etc. The aim of this paper is to present different possibilities of textiles developed with this kind of structures, to present different alternatives, different examples of products obtained with this kind of textile structure combined with the correct kind of textile fiber. In this kind of technology, double-bar Raschel machines used for producing three-dimensional textiles, spacers, play an important role.

  5. Modulation of porphyrin photoluminescence by nanoscale spacers on silicon substrates

    Science.gov (United States)

    Fang, Y. C.; Zhang, Y.; Gao, H. Y.; Chen, L. G.; Gao, B.; He, W. Z.; Meng, Q. S.; Zhang, C.; Dong, Z. C.

    2013-11-01

    We investigate photoluminescence (PL) properties of quasi-monolayered tetraphenyl porphyrin (TPP) molecules on silicon substrates modulated by three different nanoscale spacers: native oxide layer (NOL), hydrogen (H)-passivated layer, and Ag nanoparticle (AgNP) thin film, respectively. In comparison with the PL intensity from the TPP molecules on the NOL-covered silicon, the fluorescence intensity from the molecules on the AgNP-covered surface was greatly enhanced while that for the H-passivated surface was found dramatically suppressed. Time-resolved fluorescence spectra indicated shortened lifetimes for TPP molecules in both cases, but the decay kinetics is believed to be different. The suppressed emission for the H-passivated sample was attributed to the weaker decoupling effect of the monolayer of hydrogen atoms as compared to the NOL, leading to increased nonradiative decay rate; whereas the enhanced fluorescence with shortened lifetime for the AgNP-covered sample is attributed not only to the resonant excitation by local surface plasmons, but also to the increased radiative decay rate originating from the emission enhancement in plasmonic "hot-spots".

  6. Microbial analysis of biofilms on cement surfaces: An investigation in cement-associated peri-implantitis.

    Science.gov (United States)

    Korsch, Michael; Walther, Winfried; Marten, Silke-Mareike; Obst, Ursula

    2014-09-05

    The cementation of implant-supported restorations always poses the risk of excess cement retained in the peri-implant sulcus despite careful clinical control. Excess cement can become the basis of colonization by oral microorganisms. As a result of the biofilm formation peri-mucositis or peri-implantitis may develop. Complications were observed in the routine prosthetic restoration of implants when a methacrylate-based cement was used. These developed a few weeks after cementation of the suprastructure and caused bleeding on probing as well as suppuration from the peri-implant tissue. In the revision therapy, excess cement in the peri-implant sulcus was found in many cases. This excess cement was sampled from ten patients and investigated for biofilm formation. For this purpose, the cement samples were collected and analyzed for bacterial in situ colonization by 16S rDNA-based methods. In laboratory experiments, the methacrylate-based cement and two other dental cements were then investigated for their proneness to form biofilm. The results of the in situ and in vitro investigations revealed a strong tendency towards bacterial invasion of the methacrylate-based cement by opportunistic species and pathogens.

  7. Copper Slag Blended Cement: An Environmental Sustainable Approach for Cement Industry in India

    Directory of Open Access Journals (Sweden)

    Jagmeet Singh

    2016-04-01

    Full Text Available Indian cement industry is facing environmental issue of emission of carbon dioxide (CO2, a greenhouse gas. Blended cements including supplementary cementitious materials are substitute of Portland cement to reduce CO2 emission. The present paper investigates theappropriateness of copper slag (CS as supplementary cementitious material. Strength properties and hydration of mixes were determined at different replacement levels of CS with cement. Compressive, flexural and tensile strength of each mix was found out at different curing periods. The hydration of cement was investigated through X-ray diffraction (XRD. The strength test results showed that substitution of up to 20% of CS can significantly replace Portland cement.XRD test results were corresponding to strength test results. The present study encourages the utilization of CS as supplementary cementitious material to make economical and environmentally sustainable blended cement

  8. The influence of cement type and temperature on chloride binding in cement paste

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede; Korzen, Migge Sofie Hoffmann; Skibsted, Jørgen

    1998-01-01

    This paper describes effects of cement type and temperature on chloride binding in cement paste, which is an important subject in relation to life-time modelling of reinforced concrete structures. The influence of cement type on chloride binding is investigated by substituting cement with pure...... cement clinker. Both theoretical considerations and experimental data for chloride binding in cement pastes are presented. A physico-chemically based model to describe the influence of temperature on physical binding of chloride is presented. Solid-state 27Al and 29Si magic-angle spinning (MAS) nuclear...... magnetic resonance (NMR) spectroscopy has been used for quantification of the anhydrous and hydrated aluminate and silicate phases in the chloride exposed cement pastes. The 27Al isotropic chemical shift and nuclear quadrupole coupling is reported for a synthetic sample of Friedel's salt, Ca2Al(OH)6Cl×2H2O....

  9. A Pause for China's Cement Industry

    Institute of Scientific and Technical Information of China (English)

    Li Zhen

    2009-01-01

    @@ Cement industry suffers excess productionWith the advent of global financial crisis,the Chinese government has laid out a stimulus package on infrastructure construction.Driven by the investment spree,China's cement makers are flocking to expand output capacity,which is now leading the industry into a much-higher-thanneeded state.

  10. Contact dermatitis in cement workers in Isfahan

    Directory of Open Access Journals (Sweden)

    Iraji Fariba

    2006-01-01

    Full Text Available BACKGROUND: Due to recent industrialization and inadequately protected workers or in other words poor supervision on constructive workers habits in our large city of Isfahan cement contact dermatitis is relatively high especially among cement factory workers and constructive personnel. PURPOSES: To investigate the prevalence rate of cement contact dermatitis in cement factory workers in Isfahan. METHODS: A case-control clinical study was carried out by randomly selecing 150 factory workders and 150 official clerks in a cement factory in Isfahan in 2001. After a complete physical examination, data was recorded in observational checklists. FINDINGS: The percentages of contact dermatitis prevalences in the first and the second groups were 22% and 5.3% respectively. About 60% of cement workers with contact dermatitis were between 30-40 years of age. There was a direct relationship with age in both groups of the workers. In the high-exposure group, the hand eczema along was 70% but in the other group the percentage of involvement was the same in exposed and unexposed anatomical areas. CONCLUSIONS: There was a direct relationship between occurrence and the severity of involvement and duration of contact in the first group. Cent percent of cement workers had contact dermatitis after 10 or less years, but the percentage among the other group was 35%. LIMITATION: Irritant contact dermatitis to cement has not been detected.

  11. Basic Chemistry for the Cement Industry.

    Science.gov (United States)

    Turner, Mason

    This combined student workbook and instructor's guide contains nine units for inplant classes on basic chemistry for employees in the cement industry. The nine units cover the following topics: chemical basics; measurement; history of cement; atoms; bonding and chemical formulas; solids, liquids, and gases; chemistry of Portland cement…

  12. Investigation of a Hardened Cement Paste Grout

    DEFF Research Database (Denmark)

    Esteves, Luis Pedro; Sørensen, Eigil Verner

    This report documents a series of tests performed on a hardened cement paste grout delivered by the client, Det Norske Veritas A/S.......This report documents a series of tests performed on a hardened cement paste grout delivered by the client, Det Norske Veritas A/S....

  13. Chloride ingress in cement paste and mortar

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede; Hansen, Per Freiesleben; Coats, Alison M.

    1999-01-01

    In this paper chloride ingress in cement paste and mortar is followed by electron probe microanalysis. The influence of several paste and exposure parameters on chloride ingress are examined (e.g., water-cement ratio, silica fume addition, exposure time, and temperature), The measurements...

  14. TECHNOLOGICAL CHANGES IN THE CEMENT MANUFACTURING INDUSTRY.

    Science.gov (United States)

    WESSON, CARL E.

    THE PURPOSE OF THIS STUDY IS TO PRESENT A PRELIMINARY PICTURE OF OCCUPATIONAL CHANGES BROUGHT ABOUT IN THE MANUFACTURE OF CEMENT AS A RESULT OF INTRODUCING AUTOMATED EQUIPMENT. ONE AUTOMATED AND SEVERAL CONVENTIONAL TYPE CEMENT PLANTS WERE STUDIED. ANALYSIS OF DATA OBTAINED THROUGH RESEARCH AND DATA COLLECTED DURING THE STUDY REVEALED THAT…

  15. A note on cement in asteroids

    CERN Document Server

    Bilalbegovic, G

    2016-01-01

    Cement mineral tobermorite was formed in hydrothermal experiments on alternation of calcium-aluminum-rich inclusions (CAIs) in carbonaceous chondrite meteorites. Unidentified bands at 14 microns were measured for CAIs and the matrix of the Allende meteorite sample, as well as for Hektor and Agamemnon asteroids. The presence of cement nanoparticles may explain the feature at 14 microns.

  16. A note on cement in asteroids

    Science.gov (United States)

    Bilalbegović, G.

    2016-09-01

    Cement mineral tobermorite was formed in hydrothermal experiments on alternation of calcium-aluminum-rich inclusions (CAIs) in carbonaceous chondrite meteorites. Unidentified bands at 14 μm were measured for CAIs and the matrix of the Allende meteorite sample, as well as for Hektor and Agamemnon asteroids. The presence of cement nanoparticles may explain the feature at 14 μm.

  17. Effect of hydrogen sulfide emissions on cement mortar specimens

    Energy Technology Data Exchange (ETDEWEB)

    Idriss, A. F. [Alberta Environment, Science and Technology Branch, Edmonton, AB (Canada); Negi, S. C.; Jofriet, J. C.; Haywoard, G. L. [Guelph Univ., Guelph, ON (Canada)

    2001-07-01

    Six different cement mortar specimens used in animal buildings, where they were exposed to hydrogen sulfide generated from anaerobic fermentation of manure during a period of one year, were investigated. Primary interest was on comparing the corrosion resistance of different cement mortar specimens under long term exposure to hydrogen sulfide. The impressed voltage technique was used to test the specimens in the laboratory. Results revealed that test specimens made with eight per cent silica fume cement replacement performed best and similar Portland cement mortar specimens with a water-cement ratio of 0.55 (PC55) the poorest. All other treatments, (Portland cement with a water to cement ratio of 045, Portland cement Type 50, Portland cement with fibre mesh and Portland cement Type 10 coated with linseed oil) all with water-cement ratios of 0.45, were less effective in preventing corrosion than silica fume replacement.

  18. Energetically Modified Cement (EMC) - Performance Mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Ronin, Vladimir; Elfgren, Lennart [Luleaa Univ. of Technology (Sweden). Centre for High Performance Cement

    2003-03-01

    Energetically Modified Cements, EMC, made of intensively milled cement (50%) and fillers (50%) of quartz or fly ash have been compared to blends of Ordinary Portland Cement, OPC, and fillers. The EMCs have better properties than other blends and are comparable to unblended OPC. This remarkable fact can probably be explained as follows. The grinding process reduces the size of both cement grains and fillers. This combined with the creation of micro defects gives the ground cement a very high degree of hydration. The increased early hydration and a better distribution of hydration products results in an extensive pore size refinement of the hardened binder. This pore size refinement leads to a favorably reduced permeability and diffusivity and very good mechanical properties.

  19. Shrinkage Properties of Cement Stabilized Gravel

    DEFF Research Database (Denmark)

    Lund, Mia Schou Møller; Hansen, Kurt Kielsgaard

    2014-01-01

    Cement stabilized gravel is an attractive material in road construction because its strength prop-erties are accommodating the increasingly higher requirements to the bearing capacity of a base course. However, reflection cracking of cement stabilized gravel is a major concern. In this pa......-per the shrinkage properties of cement stabilized gravel have been documented under various temperature and relative humidity conditions. Two cement contents corresponding to a 28-days compressive strength of 6.2 MPa and 12.3 MPa have been tested and compared. It is found that the coefficient of linear expansion...... for the two cement contents is 9.9 × 10-6 ⁰C-1 and 11.3 × 10-6 ⁰C-1, respectively. Furthermore, it is found that reflecting cracking can mainly be explained by temperature dependent shrinkage rather than moisture dependent shrinkage....

  20. Energetically Modified Cement (EMC) - Performance Mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Ronin, Vladimir; Elfgren, Lennart [Luleaa Univ. of Technology (Sweden). Centre for High Performance Cement

    2003-03-01

    Energetically Modified Cements, EMC, made of intensively milled cement (50%) and fillers (50%) of quartz or fly ash have been compared to blends of Ordinary Portland Cement, OPC, and fillers. The EMCs have better properties than other blends and are comparable to unblended OPC. This remarkable fact can probably be explained as follows. The grinding process reduces the size of both cement grains and fillers. This combined with the creation of micro defects gives the ground cement a very high degree of hydration. The increased early hydration and a better distribution of hydration products results in an extensive pore size refinement of the hardened binder. This pore size refinement leads to a favorably reduced permeability and diffusivity and very good mechanical properties.

  1. CO2 Capture by Cement Raw Meal

    DEFF Research Database (Denmark)

    Pathi, Sharat Kumar; Lin, Weigang; Illerup, Jytte Boll

    2013-01-01

    The cement industry is one of the major sources of CO2 emissions and is likely to contribute to further increases in the near future. The carbonate looping process has the potential to capture CO2 emissions from the cement industry, in which raw meal for cement production could be used...... as the sorbent. Cyclic experiments were carried out in a TGA apparatus using industrial cement raw meal and synthetic raw meal as sorbents, with limestone as the reference. The results show that the CO2 capture capacities of the cement raw meal and the synthetic raw meal are comparable to those of pure limestone....... The CO2 capture capacity of limestone in the raw meal is lower than for pure limestone. The difference in the CO2 capture capacity decreases with an increase in cycle number. The calcination conditions and composition are major factors that influence the CO2 capture capacity of limestone. At 850 °C in N2...

  2. [Interspinous spacers and disc herniation. Geomorphometric and clinical study of 71 cases treated by L4-L5 microdiscectomy associated to spacer placement].

    Science.gov (United States)

    Aso Escario, José; Aso Vizán, Alberto; Martínez Quiñones, José Vicente; Consolini, Fabian; Martín Gallego, Álvaro; Arregui Calvo, Ricardo

    2015-01-01

    A controversial indication of interspinous spacers is their use as a complement to discectomy. At the present time, there is no solid clinical evidence of effectiveness of that association, which might result from variability in spacer positioning, restricting its correct biomechanical actions. In this study our goal was to identify and analyse the variability in the placement of an interspinous spacer, and to investigate its relationship with the clinical results. We performed a retrospective study on X-ray films from 71 patients suffering from disc herniation in L4-L5 who underwent surgery in our hospital, consisting of: microdiscectomy and biomed interspinous spacer implantation. The geomorphometric techniques used to analyse the data were procrustes superimposition and principal components analysis. We compared the clinical results (using the Herron and Turner scale), segmental lordosis and surgical distraction with the geomorphometric parameters. Significant morphological variability was found in the implant position showing cephalo-caudal translation and clockwise-counterclockwise rotations. This variability did not correlate with clinical results. A relationship with anatomical features (lordosis) and additional surgical distraction was identified. A different morphology of implant-segment configuration was identified in cases with recurrence of disc herniation. Geometric morphometrics allowed identifying high variability in the final placement of interspinous spacers. Nevertheless, it seems not to be related to the clinical outcome, depending rather on the degree of lordosis and distraction. Some differences in segment-implant morphology were identified in cases with recurrences. To assess the effectiveness of spacers, larger studies including morphological and clinical variables are required. Copyright © 2013 Sociedad Española de Neurocirugía. Published by Elsevier España. All rights reserved.

  3. Effects of grid spacer with mixing vane on entrainments and depositions in two-phase annular flows

    Directory of Open Access Journals (Sweden)

    Akimaro Kawahara

    2015-06-01

    Full Text Available The effects of mixing vanes (MVs attached to a grid spacer on the characteristics of air–water annular flows were experimentally investigated. To know the effects, a grid spacer with or without MV was inserted in a vertical circular pipe of 16-mm internal diameter. For three cases (i.e., no spacer, spacer without MV, and spacer with MV, the liquid film thickness, liquid entrainment fraction, and deposition rate were measured by the constant current method, single liquid film extraction method, and double liquid film extraction method, respectively. The MVs significantly promote the re-deposition of liquid droplets in the gas core flow into the liquid film on the channel walls. The deposition mass transfer coefficient is three times higher for the spacer with MV than for the spacer without MV, even for cases 0.3-m downstream from the spacer. The liquid film thickness becomes thicker upstream and downstream for the spacer with MV, compared with the thickness for the spacer without MV and for the case with no spacer.

  4. CONCRETE BASED ON MODIFIED DISPERSE CEMENT SYSTEM

    Directory of Open Access Journals (Sweden)

    D. V. Rudenko

    2016-08-01

    Full Text Available Purpose. The article considers definition of the bond types occurring in a modified cement concrete matrix, and the evaluation of the quality of these links in a non-uniform material to determine the geometrical and physical relationships between the structure and the cement matrix modifiers. Methodology. To achieve this purpose the studies covered the microstructure of dispersed modified concrete cement matrix, the structure formation mechanism of the modified cement concrete system of natural hardening; as well as identification of the methods of sound concrete strength assessment. Findings. The author proposed a model of the spatial structure of the concrete cement matrix, modified by particulate reinforcement crystal hydrates. The initial object of study is a set of volume elements (cells of the cement matrix and the system of the spatial distribution of reinforcing crystallohydrates in these volume elements. It is found that the most dangerous defects such as cracks in the concrete volume during hardening are formed as a result of internal stresses, mainly in the zone of cement matrix-filler contact or in the area bordering with the largest pores of the concrete. Originality. The result of the study is the defined mechanism of the process of formation of the initial strength and stiffness of the modified cement matrix due to the rapid growth of crystallohydrates in the space among the dispersed reinforcing modifier particles. Since the lack of space prevents from the free growth of crystals, the latter cross-penetrate, forming a dense structure, which contributes to the growth of strength. Practical value. Dispersed modifying cement matrix provides a durable concrete for special purposes with the design performance characteristics. The developed technology of dispersed cement system modification, the defined features of its structure formation mechanism and the use of congruence principle for the complex of technological impacts of physical

  5. Computer-Aided Design Method of Warp-Knitted Jacquard Spacer Fabrics

    Directory of Open Access Journals (Sweden)

    Li Xinxin

    2016-06-01

    Full Text Available Based on a further study on knitting and jacquard principles, this paper presents a mathematical design model to make computer-aided design of warp-knitted jacquard spacer fabrics more efficient. The mathematical model with matrix method employs three essential elements of chain notation, threading and Jacquard designing. With this model, the processing to design warp-knitted jacquard spacer fabrics with CAD software is also introduced. In this study, the sports shoes which have separated functional areas according to the feet structure and characteristics of movement are analysed. The results show the different patterns on Jacquard spacer fabrics that are seamlessly stitched with jacquard technics. The computer-aided design method of warp-knitted jacquard spacer fabrics is efficient and simple.

  6. Enhanced charge trapping in bipolar spacer oxides during low-dose-rate irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Fleetwood, D.M.; Reber, R.A. Jr.; Winokur, P.S. [Sandia National Labs., Albuquerque, NM (United States); Kosier, S.L.; Schrimpf, R.D. [Arizona Univ., Tucson, AZ (United States). Dept. of Electrical and Computer Engineering; Nowlin, R.N. [Air Force Phillips Laboratory, Albuquerque, NM (United States); Pease, R.L. [RLP Research, Inc., Albuquerque, NM (United States); DeLaus, M. [Analog Devices, Wilmington, MA (United States)

    1994-03-01

    Thermally-stimulated-current and capacitance-voltage measurements reveal enhanced hole trapping in bipolar spacer-oxide capacitors irradiated at 0 V at low dose rates. Possible mechanisms and implications for bipolar low-rate response are discussed.

  7. Cholesterol-containing liquid crystal dimmers with ether linkages between the spacer and mesogenic units

    NARCIS (Netherlands)

    Marcelis, A.T.M.; Koudijs, A.; Karczmarzyk, Z.; Sudhölter, E.J.R.

    2003-01-01

    Three series of chiral liquid crystalline dimers were investigated, having a cholesteryl and a cyanobiphenylyl, butoxybiphenylyl or hexyloxybiphenylyl group connected to a variable alkyl spacer through ether linkages. Their properties were compared with those of the corresponding ester derivatives.

  8. Very strong antiferromagnetic interlayer exchange coupling with iridium spacer layer for perpendicular magnetic tunnel junctions

    Science.gov (United States)

    Yakushiji, Kay; Sugihara, Atsushi; Fukushima, Akio; Kubota, Hitoshi; Yuasa, Shinji

    2017-02-01

    We systematically studied the interlayer exchange coupling (IEC) in a perpendicular synthetic antiferromagnetically coupled structure having an Ir spacer layer for perpendicular magnetic tunnel junctions (p-MTJs). We found a broader peak in IEC energy density (Jex) versus spacer thickness (tIr) compared with the case of using a Ru spacer. The highest IEC energy density was 2.6 erg/cm2 at a tIr of about 5 nm. The p-MTJ nanopillars had a high magnetoresistance ratio (131%) as well as a high spin-transfer torque (STT) switching efficiency (about 2). An Ir spacer can be used to make a stable reference layer for STT magnetoresistive random access memory.

  9. Cholesterol-containing liquid crystal dimmers with ether linkages between the spacer and mesogenic units

    NARCIS (Netherlands)

    Marcelis, A.T.M.; Koudijs, A.; Karczmarzyk, Z.; Sudhölter, E.J.R.

    2003-01-01

    Three series of chiral liquid crystalline dimers were investigated, having a cholesteryl and a cyanobiphenylyl, butoxybiphenylyl or hexyloxybiphenylyl group connected to a variable alkyl spacer through ether linkages. Their properties were compared with those of the corresponding ester derivatives.

  10. Manufacturing and Process-based Property Analysis of Textile-Reinforced Thermoplastic Spacer Composites

    Science.gov (United States)

    Hufenbach, Werner; Adam, Frank; Füßel, René; Krahl, Michael; Weck, Daniel

    2012-12-01

    Novel woven spacer fabrics based on hybrid yarns are suitable for an efficient fabrication of three-dimensional composite structures in high volume production. In this paper, an innovative manufacturing process with short cycle times and high automatisation is introduced for textile-reinforced thermoplastic spacer structures suited for bending load cases. The different process steps hybrid yarn fabrication, weaving technology for three-dimensional textile preforms and consolidation with unique kinematics and hot pressing technology are described in detail. The bending properties of the manufactured spacer structures are evaluated by means of experiments as well as finite element simulations. Numerical parametric studies are performed in order to validate the influence of manufacturing tolerances on the bending stiffness of the spacer structures.

  11. Spacer geometry and particle deposition in spiral wound membrane feed channels

    KAUST Repository

    Radu, A.I.

    2014-11-01

    Deposition of microspheres mimicking bacterial cells was studied experimentally and with a numerical model in feed spacer membrane channels, as used in spiral wound nanofiltration (NF) and reverse osmosis (RO) membrane systems. In-situ microscopic observations in membrane fouling simulators revealed formation of specific particle deposition patterns for different diamond and ladder feed spacer orientations. A three-dimensional numerical model combining fluid flow with a Lagrangian approach for particle trajectory calculations could describe very well the in-situ observations on particle deposition in flow cells. Feed spacer geometry, positioning and cross-flow velocity sensitively influenced the particle transport and deposition patterns. The deposition patterns were not influenced by permeate production. This combined experimental-modeling approach could be used for feed spacer geometry optimization studies for reduced (bio)fouling. © 2014 Elsevier Ltd.

  12. CRISPR Spacer Arrays for Detection of Viral Signatures from Acidic Hot Springs

    Science.gov (United States)

    Snyder, J. C.; Bateson, M. M.; Suciu, D.; Young, M. J.

    2010-04-01

    Viruses are the most abundant life-like entities on the planet Earth. Using CRISPR spacer sequences, we have developed a microarray-based approach to detecting viral signatures in the acidic hot springs of Yellowstone.

  13. Pack cementation coatings for alloys

    Energy Technology Data Exchange (ETDEWEB)

    He, Yi-Rong; Zheng, Minhui; Rapp, R.A. [Ohio State Univ., Columbus, OH (United States)

    1996-08-01

    The halide-activated pack cementation process was modified to produce a Ge-doped silicide diffusion coating on a Cr-Cr{sub 2}Nb alloy in a single processing step. The morphology and composition of the coating depended both on the composition of the pack and on the composition and microstructure of the substrate. Higher Ge content in the pack suppressed the formation of CrSi{sub 2} and reduced the growth kinetics of the coating. Ge was not homogeneously distributed in the coatings. In cyclic and isothermal oxidation in air at 700 and 1050{degrees}C, the Ge-doped silicide coating protected the Cr-Nb alloys from significant oxidation by the formation of a Ge-doped silica film. The codeposition and diffusion of aluminum and chromium into low alloy steel have been achieved using elemental Al and Cr powders and a two-step pack cementation process. Sequential process treatments at 925{degrees}C and 1150{degrees}C yield dense and uniform ferrite coatings, whose compositions are close to either Fe{sub 3}Al or else FeAl plus a lower Cr content, when processed under different conditions. The higher content of Al in the coatings was predicted by thermodynamic calculations of equilibrium in the gas phase. The effect of the particle size of the metal powders on the surface composition of the coating has been studied for various combinations of Al and Cr powders.

  14. Cements with low Clinker Content

    Science.gov (United States)

    García-Lodeiro, I.; Fernández-Jiménez, A.; Palomo, A.

    2015-11-01

    Hybrid alkaline cements are multi-component systems containing a high percentage of mineral additions (fly ash, blast furnace slag), low proportions (clinker and scarce amounts of alkaline activators. The substantially lower amount of clinker needed to manufacture these binders in comparison to ordinary Portland cement is both economically and ecologically beneficial. Their enormous versatility in terms of the raw materials used has made them the object of considerable interest. The present study explored the mechanical strength of binary blends mixes; B1= 20% clinker (CK) + 80% fly ash (FA) and B2=20% clinker + 80% blast furnace slag (BFS), both hydrated in the presence and absence of an alkaline activator specifically designed for this purpose. The use of the activator enhanced the development of early age strength considerably. All the hydrated matrices were characterised with XRD, SEM/EDX and (29Si and 27Al) NMR. The use of the alkaline activator generated reaction products consisting primarily of a mix of gels ((N,C)-A-S-H and C-A-S-H) whose respective proportions were found to depend upon system composition and initial reactivity.

  15. Dentin-cement Interfacial Interaction

    Science.gov (United States)

    Atmeh, A.R.; Chong, E.Z.; Richard, G.; Festy, F.; Watson, T.F.

    2012-01-01

    The interfacial properties of a new calcium-silicate-based coronal restorative material (Biodentine™) and a glass-ionomer cement (GIC) with dentin have been studied by confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), micro-Raman spectroscopy, and two-photon auto-fluorescence and second-harmonic-generation (SHG) imaging. Results indicate the formation of tag-like structures alongside an interfacial layer called the “mineral infiltration zone”, where the alkaline caustic effect of the calcium silicate cement’s hydration products degrades the collagenous component of the interfacial dentin. This degradation leads to the formation of a porous structure which facilitates the permeation of high concentrations of Ca2+, OH-, and CO32- ions, leading to increased mineralization in this region. Comparison of the dentin-restorative interfaces shows that there is a dentin-mineral infiltration with the Biodentine, whereas polyacrylic and tartaric acids and their salts characterize the penetration of the GIC. A new type of interfacial interaction, “the mineral infiltration zone”, is suggested for these calcium-silicate-based cements. PMID:22436906

  16. Cement compositions for cementing wells, allowing pressure gas-channeling in the cemented annulus to be controlled

    Energy Technology Data Exchange (ETDEWEB)

    Parcevaux, P.A.; Piot, B.M.; Vercaemer, C.J.

    1987-01-27

    The invention relates to cement compositions for cementing oil and geothermal wells. These compositions allow pressure gas-channeling to be effectively controlled up to more than about 485/sup 0/F. The compositions according to the invention comprise four essential constituents: a cement, a styrene-butadiene latex, a latex stabilizer, and water. The cement is a hydraulic cement belonging to any class among those currently used for cementing oil wells. The useful stabilizers according to the invention are anionic polyelectrolytes such as lignosulfanates and their desulfonated and/or resulfonated derivatives; sulfonated lignin-Kraft products; melamine-formaldehyde resins modified by a sulfonic acid or sulfite; formaldehyde/sulfonated naphthalene resins; or the condensation products of bi-nuclear sulfonated phenols and of formaldehyde. Preferred are the sodium salts of the condensation product of mononaphthalenesulfonic acid and of formaldehyde. The patent also includes a description of tests of various cement compositions of the invention, plus scanning electron microscope observations. 10 figs., 7 tabs.

  17. The effect of flexible spacers on the h-shaped dimesogenic liquid crystalline compounds

    Energy Technology Data Exchange (ETDEWEB)

    Park, Joo Hoon; Lee, Hwan Myoung; Choi, Ok Byung; Lee, Chang Joon [Hoseo Univ., Asan (Korea, Republic of); So, Bong Keun; Lee, Soo Min [Hannam Univ., Daejon (Korea, Republic of)

    2001-12-01

    A homologous series of new H-shaped twin liquid crystal molecules (PPPA-n) with flexible spacers, oxypolymethyleneoxy, has been prepared by esterification of acid chloride of {alpha}, {omega}-bis(2,5-dicar-boxyphenoxy)alkanes with p-phenylphenol. The length of spacer was varied from oxyethyleneoxy (n=2) to oxydecamethyleneoxy (n=10). Their thermodynamic data were measured by differential scanning calorimetry and liquid crystalline properties were investigated by a hot-stage polarizing microscope.

  18. Biofouling patterns in spacer filled channels: High resolution imaging for characterization of heterogeneous biofilms

    KAUST Repository

    Staal, Marc

    2017-08-15

    Biofilms develop in heterogeneous patterns at a µm scale up to a cm scale, and patterns become more pronounced when biofilms develop under complex hydrodynamic flow regimes. Spatially heterogeneous biofilms are especially known in spiral wound reverse osmosis (RO) and nanofiltration (NF) membrane filtration systems used for desalination and wastewater reuse to produce high quality (drinking) water. These spiral wound membrane modules contain mesh-like spacer structures used to create an intermembrane space and improve water mixing. Spacers create inhomogeneous water flow patterns resulting in zones favouring biofilm growth, possibly leading to biofouling thus hampering water production. Oxygen sensing planar optodes were used to visualize variations in oxygen decrease rates (ODR). ODR is an indication of biofilm activity. In this study, ODR images of multiple repetitive spacer areas in a membrane fouling simulator were averaged to produce high resolution, low noise ODR images. Averaging 40 individual spacer areas improved the ODR distribution image significantly and allowed comparison of biofilm patterning over a spacer structure at different positions in an RO filter. This method clearly showed that most active biofilm accumulated on and in direct vicinity of the spacer. The averaging method was also used to calculate the deviation of ODR patterning from individual spacer areas to the average ODR pattern, proposing a new approach to determine biofilm spatial heterogeneity. This study showed that the averaging method can be applied and that the improved, averaged ODR images can be used as an analytical, in-situ, non-destructive method to assess and quantify the effect of membrane installation operational parameters or different spacer geometries on biofilm development in spiral wound membrane systems characterized by complex hydrodynamic conditions.

  19. The CRISPRdb database and tools to display CRISPRs and to generate dictionaries of spacers and repeats

    OpenAIRE

    Vergnaud Gilles; Grissa Ibtissem; Pourcel Christine

    2007-01-01

    Abstract Background In Archeae and Bacteria, the repeated elements called CRISPRs for "clustered regularly interspaced short palindromic repeats" are believed to participate in the defence against viruses. Short sequences called spacers are stored in-between repeated elements. In the current model, motifs comprising spacers and repeats may target an invading DNA and lead to its degradation through a proposed mechanism similar to RNA interference. Analysis of intra-species polymorphism shows t...

  20. 骨水泥不同时相负载抗生素%Bone cement mixed with different antibiotics using different methods

    Institute of Scientific and Technical Information of China (English)

    魏波; 王宸; 李贺

    2012-01-01

    BACKGROUND: In artificial joint replacement surgery, which antibiotic mixed with bone cement can play an effective prevention against postoperative infection is still controversial.OBJECTIVE: To study the release characteristics of antibiotic in animals and the mechanical properties of bone cement based on the observation of bone cement mixed with different antibiotics using different mixture methods.METHODS: Thirty-six white rabbits were randomly divided into six groups: gentamicin group Ⅰ, vancomycin group ,, cefuroxime sodium group Ⅰ, gentamicin group Ⅱ, vancomycin group Ⅱ, cefuroxime sodium group Ⅱ. In the former three groups, 2 g of gentamicin sulfate, 1 g of vancomycin and 1.5 g of cefuroxime sodium were added into 40 g of bone cement at different phases, respectively, to prepare antibiotic-loaded bone cements that were then implanted into the rabbits. In the latter three groups, 2 g of gentamicin sulfate, 1 g of vancomycin and 1.5 g of cefuroxime sodium were respectively added before the solid-phase and liquid-phase mixture of 40 g bone cement.RESULTS AND CONCLUSION: The average release time of three antibiotics was over 31 days in rabbits. The elution volume of antibiotics in the former three groups was higher than that in the latter three groups (P < 0.05). The elution volume in the vancomycin group I was higher than that in the other groups (P < 0.05). The mechanical properties of antibiotic-loaded bone cements in each group were better than international standard ISO 5833, and there was no significant difference among the groups. These findings indicate that antibiotics can release from bone cement effectively; bone cements containing 1-2 g of antibiotics cannot affect the mechanical strength of bone cements; the elution effect of vancomycin is better; the method to add antibiotics after the solid-phase and liquid-phase bone cement mixture is more conducive to the release of antibiotics.%背景:在人工关节置换中,骨水泥与何种抗生

  1. Sustainable Development of the Cement Industry and Blended Cements to Meet Ecological Challenges

    Directory of Open Access Journals (Sweden)

    Konstantin Sobolev

    2003-01-01

    Full Text Available The world production of cement has greatly increased in the past 10 years. This trend is the most significant factor affecting technological development and the updating of manufacturing facilities in the cement industry. Existing technology for the production of cement clinker is ecologically damaging; it consumes much energy and natural resources and also emits pollutants. A new approach to the production of blended or high-volume mineral additive (HVMA cement helps to improve its ecological compatibility. HVMA cement technology is based on the intergrinding of portland cement clinker, gypsum, mineral additives, and a special complex admixture. This new method increases the compressive strength of ordinary cement, improves durability of the cement-based materials, and - at the same time - uses inexpensive natural mineral additives or industrial by-products. This improvement leads to a reduction of energy consumption per unit of the cement produced. Higher strength, better durability, reduction of pollution at the clinker production stage, and decrease of landfill area occupied by industrial by-products, all provide ecological advantages for HVMA cement.

  2. Sustainable development of the cement industry and blended cements to meet ecological challenges.

    Science.gov (United States)

    Sobolev, Konstantin

    2003-05-05

    The world production of cement has greatly increased in the past 10 years. This trend is the most significant factor affecting technological development and the updating of manufacturing facilities in the cement industry. Existing technology for the production of cement clinker is ecologically damaging; it consumes much energy and natural resources and also emits pollutants. A new approach to the production of blended or high-volume mineral additive (HVMA) cement helps to improve its ecological compatibility. HVMA cement technology is based on the intergrinding of portland cement clinker, gypsum, mineral additives, and a special complex admixture. This new method increases the compressive strength of ordinary cement, improves durability of the cement-based materials, and--at the same time--uses inexpensive natural mineral additives or industrial by-products. This improvement leads to a reduction of energy consumption per unit of the cement produced. Higher strength, better durability, reduction of pollution at the clinker production stage, and decrease of landfill area occupied by industrial by-products, all provide ecological advantages for HVMA cement.

  3. Clinical Evaluation of Indirect Composite Resin Restorations Cemented with Different Resin Cements.

    Science.gov (United States)

    Marcondes, Maurem; Souza, Niélli; Manfroi, Fernanda Borguetti; Burnett, Luiz Henrique; Spohr, Ana Maria

    2016-01-01

    To clinically evaluate the performance of indirect composite resin restorations cemented with conventional and self-adhesive resin cements over a 12-month period. Ten patients fulfilled all the inclusion criteria. Twenty-four composite resin restorations were performed using an indirect technique and cemented with a resin cement (RelyX ARC) or a self-adhesive resin cement (RelyX U100). Two independent evaluators analyzed the restorations using modified USPHS criteria after periods of two weeks and 6 and 12 months. Statistical significance between the cements at each timepoint was evaluated with the Wilcoxon test and between timepoints with the Mann-Whitney test, both at a significance level of 5%. Fisher's exact test was used to assess the occurrence of absolute failures. No statistically significant differences were found between the groups at the same timepoint nor between groups at different timepoints. The only significant difference was found for color match for both groups after 12 months. After 12 months, indirect composite resin restorations cemented with self-adhesive resin cement performed similarly to those cemented with conventional resin cement.

  4. INFLUENCE OF ELECTRICAL AND STRUCTURAL PARAMETERS ON THE PERFORMANCE OF THE SPACERS IN HOPFED

    Institute of Scientific and Technical Information of China (English)

    Zhong Xuefei; Wilbert van der Poel; Daniel den Engelsen; Yin Hanchun

    2006-01-01

    The HOPping Field Emission Display (HOPFED) is a new architecture for field emission displays.The main difference between a conventional Field Emission Display (FED) device and a HOPFED lies in the spacer structure. In a HOPFED, two dielectric plates, named hop and flu spacer, are sandwiched between the emitter and the front plate. The objective of this spacer structure is to improve the performance of a FED substantially with notable contrast, color purity and luminance uniformity. In order to optimize the structure of the device and to make the electron spot on the screen match the requirement of the phosphor dot dimension,the influence of electrical and structural parameters of the device on the electron spot profile was studied by numerical simulation in this paper. Monte Carlo method was employed to calculate the potential distribution inside hop and flu spacers due to secondary electrons mechanism plays an important role in HOPFED. The results indicated that the potential distribution in the spacers and spot profile depended strongly on the hop voltage, anode voltage and spacer's layout. This study may provide a useful theoretical support for optimizing the structure in HOPFED.

  5. Shape memory alloy smart knee spacer to enhance knee functionality: model design and finite element analysis.

    Science.gov (United States)

    Gautam, Arvind; Rani, A Bhargavi; Callejas, Miguel A; Acharyya, Swati Ghosh; Acharyya, Amit; Biswas, Dwaipayan; Bhandari, Vasundhra; Sharma, Paresh; Naik, Ganesh R; Gautam, Arvind; Rani, A Bhargavi; Callejas, Miguel A; Acharyya, Swati Ghosh; Acharyya, Amit; Biswas, Dwaipayan; Bhandari, Vasundhra; Sharma, Paresh; Naik, Ganesh R; Acharyya, Swati Ghosh; Sharma, Paresh; Bhandari, Vasundhra; Rani, A Bhargavi; Gautam, Arvind; Biswas, Dwaipayan; Callejas, Miguel A; Acharyya, Amit

    2016-08-01

    In this paper we introduce Shape Memory Alloy (SMA) for designing the tibial part of Total Knee Arthroplasty (TKA) by exploiting the shape-memory and pseudo-elasticity property of the SMA (e.g. NiTi). This would eliminate the drawbacks of the state-of-the art PMMA based knee-spacer including fracture, sustainability, dislocation, tilting, translation and subluxation for tackling the Osteoarthritis especially for the aged people of 45-plus or the athletes. In this paper a Computer Aided Design (CAD) model using SolidWorks for the knee-spacer is presented based on the proposed SMA adopting the state-of-the art industry-standard geometry that is used in the PMMA based spacer design. Subsequently Ansys based Finite Element Analysis is carried out to measure and compare the performance between the proposed SMA based model with the state-of-the art PMMA ones. 81% more bending is noticed in the PMMA based spacer compared to the proposed SMA that would eventually cause fracture and tilting or translation of spacer. Permanent shape deformation of approximately 58.75% in PMMA based spacer is observed compared to recoverable 11% deformation in SMA when same load is applied on both separately.

  6. Dehydration kinetics of Portland cement paste at high temperature

    NARCIS (Netherlands)

    Zhang, Q.; Ye, G.

    2012-01-01

    Portland cement paste is a multiphase compound mainly consisting of calcium-silicate-hydrate (CSH) gel, calcium hydroxide (CH) crystal, and unhydrated cement core. When cement paste is exposed to high temperature, the dehydration of cement paste leads to not only the decline in strength, but also

  7. Dehydration kinetics of Portland cement paste at high temperature

    NARCIS (Netherlands)

    Zhang, Q.; Ye, G.

    2012-01-01

    Portland cement paste is a multiphase compound mainly consisting of calcium-silicate-hydrate (CSH) gel, calcium hydroxide (CH) crystal, and unhydrated cement core. When cement paste is exposed to high temperature, the dehydration of cement paste leads to not only the decline in strength, but also th

  8. Environmental Assessment of Different Cement Manufacturing ...

    Science.gov (United States)

    Due to its high environmental impact and energy intensive production, the cement industry needs to adopt more energy efficient technologies to reduce its demand for fossil fuels and impact on the environment. Bearing in mind that cement is the most widely used material for housing and modern infrastructure, the aim of this paper is to analyse the Emergy and Ecological Footprint of different cement manufacturing processes for a particular cement plant. There are several mitigation measures that can be incorporated in the cement manufacturing process to reduce the demand for fossil fuels and consequently reduce the CO2 emissions. The mitigation measures considered in this paper were the use of alternative fuels and a more energy efficient kiln process. In order to estimate the sustainability effect of the aforementioned measures, Emergy and Ecological Footprint were calculated for four different scenarios. The results show that Emergy, due to the high input mass of raw material needed for clinker production, stays at about the same level. However, for the Ecological Footprint, the results show that by combining the use of alternative fuels together with a more energy efficient kiln process, the environmental impact of the cement manufacturing process can be lowered. The research paper presents an analysis of the sustainability of cement production , a major contributor to carbon emissions, with respect to using alternative fuels and a more efficient kiln. It show

  9. Dermatoses in cement workers in southern Taiwan.

    Science.gov (United States)

    Guo, Y L; Wang, B J; Yeh, K C; Wang, J C; Kao, H H; Wang, M T; Shih, H C; Chen, C J

    1999-01-01

    Construction workers are known to have occupational dermatoses. The prevalence of such dermatoses was unknown in Taiwanese construction workers. The objective of this study was to determine the work exposure, prevalence of skin manifestations, and sensitivity to common contact allergens in cement workers of southern Taiwan. A total of 1147 current regular cement workers were telephone-interviewed about skin problems during the past 12 months, work exposure, and personal protection. Among those interviewed, 166 were examined and patch tested with common contact allergens. A high % of cement workers reported skin problems in the past 12 months. More men (13.9%) reported skin problems possibly related to work than women (5.4%). Prevalence was associated with lower use of gloves, duration of work as cement worker, and more time in jobs involving direct manual handling of cement, especially tiling. A high % of dermatitis was noted in the 166 workers examined, which correlated with reported skin problems. On patch testing, construction workers had a high frequency of sensitivity to chromate. Sensitivity to chromate or cobalt was associated with reported skin problems, or dorsal hand dermatitis on examination. These workers' dermatitis was under-diagnosed and inadequately managed. It is concluded that cement workers in southern Taiwan had a high prevalence of skin problems related to cement use. Protective measures, work practice, and physician education should be improved to prevent or manage such problems.

  10. International development trends in low-energy cements

    Energy Technology Data Exchange (ETDEWEB)

    Stark, J.; Mueller, A.

    1988-04-01

    Besides the currently dominant tendency to increase the proportion of interground additive in cement, the following development trends are internationally emerging in the material composition of so-called low-energy cements with a view to minimizing energy input for cement manufacture: (1) active belite cement with the principal clinker minerals a'C/sub 2/S and C/sub 3/S; (2) belite sulphoaluminate cement (..beta.. C/sub 2/S, C/sub 4/A/sub 3/S); (3) belite sulphoferrite cement (..beta.. C/sub 2/S, C/sub 4/AF, C/sub 4/A/sub 3/S); (4) NTS cement (alinite).

  11. Holocene cemented beach deposits in Belize

    Science.gov (United States)

    Gischler, Eberhard; Lomando, Anthony J.

    1997-06-01

    Two types of cemented beach deposits occur on reef islands off the coast of Belize. These are (1) intertidal beachrock that is dominantly cemented by marine aragonite and high-magnesium-calcite cements, and (2) supratidal cayrock that is cemented mainly by vadose low-magnesium-calcite cements. Besides differences in position relative to present sea level and resulting early diagenesic features, beachrock and cayrock can be distinguished on the basis of differences in composition, texture, geographical position, and age. Whereas the composition of beachrock is similar to that of the adjacent marginal reef sediments, cayrock is enriched in benthic foraminifera. Intertidal beachrock is moderately to well sorted and well cemented, while supratidal cayrock is very well sorted, poorly cemented and friable. Beachrock occurs preferentially on windward beaches of sand-shingle Gays on the middle and southern barrier reefs and on the isolated platforms Glovers and Lighthouse Reefs. Cayrock only occurs on larger mangrove-sand Gays of the isolated platforms Turneffe Islands, Lighthouse Reef, and the northern barrier reef. 14C-dating of ten whole-rock and mollusk shell samples produced calibrated dates between AD 345 and AD 1435 for beachrock and between BC 1085 and AD 1190 for cayrock. The large-scale distribution of beachrock in Belize supports the contention that physical processes such as water agitation rather than biological processes control beachrock formation and distribution. Only on windward sides of cays that are close to the reef crest, where large amounts of seawater flush the beaches, considerable amounts of cements can be precipitated to produce beachrock. Cayrock forms due to cementation in the vadose zone and is only preserved on larger, stable mangrove-sand cays.

  12. Time spans and spacers : Molecular phylogenetic explorations in the Cladophora complex (Chlorophyta) from the perspective of rDNA gene and spacer sequences

    NARCIS (Netherlands)

    Bakker, Frederik Theodoor

    1995-01-01

    In this study, phylogenetic relationships among genera, species and biogeographic representatives of single Cladophora species within the Cladophorales were analyzed using rDNA gene and spacer sequences. Based on phylogenetic analysis of 18S rRNA gene sequences, the Cladophora complex is shown to be

  13. Comparison of Temperature Field Distribution between Cement Preclinkering Technology and Cement Precalcining Technology

    Institute of Scientific and Technical Information of China (English)

    XU Xun; WANG Lan

    2016-01-01

    Through the comparison of calcination conditions between cement preclinkering technology and cement precalcining technology, we studied the characteristics of temperature ifeld distribution of cement preclinkering technology systems including cyclone preheater, preclinkering furnace, and rotary kiln. We used numerical simulation method to obtain data of temperature ifeld distribution.Some results are found by system study. The ratio of tail coal of cement preclinkering technology is about 70%, and raw meal temperature can reach 1070℃. ShorterL/D kiln type of preclinkering technology can obtain more stable calcining zone temperature. The highest solid temperature of cement preclinkering technology is higher than 80℃, and high temperature region (>1450℃) length is 2 times, which is beneifcial for calcining clinker and higher clinker quality. So cement preclinkering technology can obtain more performance temperature ifled, which improves both the solid-phase reaction and liquid-phase reaction.

  14. The behavior of the micro-mechanical cement-bone interface affects the cement failure in total hip replacement

    NARCIS (Netherlands)

    Waanders, D.; Janssen, D.; Mann, K.A.; Verdonschot, N.J.J.

    2011-01-01

    In the current study, the effects of different ways to implement the complex micro-mechanical behavior of the cement-bone interface on the fatigue failure of the cement mantle were investigated. In an FEA-model of a cemented hip reconstruction the cement-bone interface was modeled and numerically im

  15. Effect of cementing technique and cement type on thermal necrosis in hip resurfacing arthroplasty - a numerical study

    NARCIS (Netherlands)

    Janssen, D.; Srinivasan, P.; Scheerlinck, T.; Verdonschot, N.J.J.

    2012-01-01

    Femoral fractures within resurfacing implants have been associated with bone necrosis, possibly resulting from heat generated by cement polymerization. The amount of heat generated depends on cement mantle volume and type of cement. Using finite element analysis, the effect of cement type and volume

  16. Synthesis of pure Portland cement phases

    DEFF Research Database (Denmark)

    Wesselsky, Andreas; Jensen, Ole Mejlhede

    2009-01-01

    Pure phases commonly found in Portland cement clinkers are often used to test cement hydration behaviour in simplified experimental conditions. The synthesis of these phases is covered in this paper, starting with a description of phase relations and possible polymorphs of the four main phases...... in Portland cement, i.e. tricalcium silicate, dicalcium silicate, tricalcium aluminate and tetracalcium alumino ferrite. Details of the The process of solid state synthesis are is described in general including practical advice on equipment and techniques. Finally In addition, some exemplary mix compositions...

  17. INFLUENCE OF GLASS CULLET IN CEMENT PASTES

    Institute of Scientific and Technical Information of China (English)

    A.Karamberi; E.Chaniotakis; D.Papageorgiou; A.Moutsatsou

    2006-01-01

    The present study investigates glass and cement compatibility with a view to use glass as a cement replacement. Amber, flint and green glasses were chosen due to their prevalence in the Greek market as packaging materials. The factors under investigation were the pozzolanicity of the glass cullet, the hydration rate and the mechanical strength development of the cement pastes, as well as the expansion of the specimens due to alkali-silica reaction.Moreover, the potential enhancement of glass pozzolanic activity was examined. The results of the study were encouraging to show the potentiality of utilising glass cullet in cementitious products.

  18. Alternative Fuels in Cement Production

    DEFF Research Database (Denmark)

    Larsen, Morten Boberg

    The substitution of alternative for fossil fuels in cement production has increased significantly in the last decade. Of these new alternative fuels, solid state fuels presently account for the largest part, and in particular, meat and bone meal, plastics and tyre derived fuels (TDF) accounted...... of the fuel heating value. In addition, the devolatilization time of alternative fuels cannot be neglected in kiln system process analyses, as these fuels are typically in the cm-size with devolatilization times in the order of minutes. The devolatilization characteristics of large particles of tyre rubber...... time, where increased particle size increased the devolatilization time. Model analyses demonstrated that the overall devolatilization kinetics of large particles of tyre rubber is mainly controlled by heat transfer and intrinsic pyrolysis kinetics, whereas mass transfer has negligible influence...

  19. Predicting the impact of feed spacer modification on biofouling by hydraulic characterization and biofouling studies in membrane fouling simulators

    KAUST Repository

    Siddiqui, A.

    2016-12-22

    Feed spacers are an essential part of spiral-wound reverse osmosis (RO) and nanofiltration (NF) membrane modules. Geometric modification of feed spacers is a potential option to reduce the impact of biofouling on the performance of membrane systems. The objective of this study was to evaluate the biofouling potential of two commercially available reference feed spacers and four modified feed spacers. The spacers were compared on hydraulic characterization and in biofouling studies with membrane fouling simulators (MFSs). The virgin feed spacer was characterized hydraulically by their resistance, measured in terms of feed channel pressure drop, performed by operating MFSs at varying feed water flow rates. Short-term (9 days) biofouling studies were carried out with nutrient dosage to the MFS feed water to accelerate the biofouling rate. Long-term (96 days) biofouling studies were done without nutrient dosage to the MFS feed water. Feed channel pressure drop was monitored and accumulation of active biomass was quantified by adenosine tri phosphate (ATP) determination. The six feed spacers were ranked on pressure drop (hydraulic characterization) and on biofouling impact (biofouling studies). Significantly different trends in hydraulic resistance and biofouling impact for the six feed spacers were observed. The same ranking for biofouling impact on the feed spacers was found for the (i) short-term biofouling study with nutrient dosage and the (ii) long-term biofouling study without nutrient dosage. The ranking for hydraulic resistance for six virgin feed spacers differed significantly from the ranking of the biofouling impact, indicating that hydraulic resistance of clean feed spacers does not predict the hydraulic resistance of biofouled feed spacers. Better geometric design of feed spacers can be a suitable approach to minimize impact of biofouling in spiral wound membrane systems.

  20. Cement Manufacturing Plant Guidelines: An Approach to Reconciling the Financing of Cement with Climate Change Objectives

    OpenAIRE

    2010-01-01

    Cement manufacturing is an energy-intensive process, requiring high fuel consumption to operate cement kilns, which in turn generates carbon dioxide (CO2). These Guidelines aim to provide clear and quantitative Minimum Climate Change Performance Criteria necessary for IDB to support projects, as well as guidance on assessing and reducing the greenhouse gas (GHG) emissions of projects. The purpose of the Cement Manufacturing Plant guidelines is to set forth an approach for the financing of new...

  1. The mineralogy and chemistry of cement and cement raw materials In the united arab emirates

    OpenAIRE

    Nasir, Sobhi J. [صبحي جابر نصر; El Etr, H.

    1996-01-01

    The raw materials, clinkers and cements from different cement factories in the United Arab Emirates have been investigated using polarizing microscopy, X-ray diffraction (XRD), Scanning electron microscopy (SEM), and chemical analyses. The chemical and mineralogical analyses indicate that the local raw materials are suitable for cement industry. Geological review shows that there is a good potential for industrial-grade local occurrences of limestone, marl, gypsum and iron oxide, that may be ...

  2. Chromium content in human skin after in vitro application of ordinary cement and ferrous-sulphate-reduced cement

    DEFF Research Database (Denmark)

    Fullerton, A; Gammelgaard, Bente; Avnstorp, C

    1993-01-01

    The amount of chromium found in human skin after in vitro application of cement suspensions on full-thickness human skin in diffusion cells was investigated. Cement suspensions made from ordinary Portland cement or Portland cement with the chromate reduced with added ferrous sulphate were used....... The cement suspensions were either applied on the skin surface under occlusion for 48 h or applied repeatedly every 24 h for 96 h. No statistically significant difference in chromium content of skin layers between skin exposed to ordinary Portland cement, skin exposed to cement with added ferrous sulphate...

  3. [Our experiences with anterior cervical cages and spacer].

    Science.gov (United States)

    Szabó, József; Lapis, István; Marik, László; Kondacs, András; Rusznyák, Csaba

    2007-11-30

    Between 2001 and 2005 86 patients were treated for cervical disc herniations and spondylosis at our department. Stabilization was performed with different cervical cages or spacer after discectomy and decompression. The aim of the study was to examine the changes of the patients' pain, quality of life and work ability, fusion rate, the intervertebral disc height, changes of under and upper segments and finally curvature of cervical spine. Patients were followed by the authors, clinical examination, lateral and antero-posterior radiographic examinations were performed. They were asked to fill in a questionnaire, concerning their pre- and postoperative pain, quality of life and work ability. The patients' pain was graded using a 10-point analog scale (VAS) and with a simplified, McGill-Melzak analog scale. The quality of life was measured with a 10-graduated analog scale as well. More than 77% of our patients appeared at follow up examination. The fusion rate was 89.3%, operated spaces were held in 61%. In the upper segment of operated space 7%, and in the under-segment 14% were found increasingly degenerated. The curvature of cervical spine of the patients' were 64.51% lordotic, 27.42% straight and 8.07% kyphotic. On average the patients' pain changed on VAS from 8.179 to 5.015; on McGill-Melzak scale from 3.89 to 2.80; quality of life changed from 8.045 to 5.463. By the advantage of using cages, the operative approach has become smaller than before, consequently the operative pain has become less too. In addition operation time and hospital stay were significantly shorter (p work and 5 patients do easier work. The majority of our patients were disabled before the operation, but from that time many of them became disabled, in some cases the grade of disability increased. There can be some reasons for it: the majority of the patients have other diseases for example: lumbar spondylosis and disc herniation, hypertension, diabetes, asthma and depression. There is just a

  4. Radiographic appearance of commonly used cements in implant dentistry.

    Science.gov (United States)

    Pette, Gregory A; Ganeles, Jeffrey; Norkin, Frederic J

    2013-01-01

    Cement-retained restorations allow for a conventional fixed partial denture approach to restoring dental implants. However, inadequate removal of excess cement at the time of cementation may introduce a severe complication: cement-induced peri-implantitis. Radiopaque cements are more easily detected on radiographs and should improve the recognition of extravasated cement at the time of insertion. The purpose of this study was to evaluate the radiopacity of commercially available cements in vitro. Eighteen different cements commonly used for luting restorations to implants were tested at both 0.5- and 1.0-mm thicknesses. The cements examined were zinc oxide eugenol, zinc oxide, zinc polycarboxylate, zinc phosphate, resin-reinforced glass ionomer, urethane resin, resin, and composite resin. Two samples of each cement thickness underwent standardized radiography next to an aluminum step wedge as a reference. The mean grayscale value of each of the nine 1-mm steps in the step wedge were used as reference values and compared to each of the cement samples. Temp Bond Clear (resin), IMProv (urethane resin), Premier Implant Cement (resin), and Temrex NE (resin) were not radiographically detectable at either sample thickness. Cements containing zinc were the most detectable upon radiographic analysis. There are significant differences in the radiopacity of many commonly used cements. Since cementinduced peri-implantitis can lead to late implant failure, cements that can be visualized radiographically may reduce the incidence of this problem.

  5. Slagment Cement Improve the Cement Resistance Toward Acids Attack During Acidizing Treatment

    Directory of Open Access Journals (Sweden)

    Nik Khairul Irfan Bin Nik Ab. Lah.

    2013-05-01

    Full Text Available Acidizing treatment in past experience shows several zonal isolation problems after the treatment. This study presents the effect of the acid treatment toward class G cement and slagment cement as the improvement method to improve the cement resistance toward the acid. Lab experiments were conducted by immerge the respective cement cubes into 12% HCl/3% HF solution for 40 min before several analysis were conducted. Based on the result, the mass loss and compressive strength loss of the cement cubes decrease as the curing temperature and pressure increase due to more evenly distributed cement chemical composition crystal in high curing condition as shown in Scanning Electron Microscopy (SEM analysis. From X-Ray Diffraction (XRD and X-Ray Fluorescence (XRF analysis, only the first layer of the cement cubes shows chemical component change due to the reaction between the acid. This study found that, replacing class G cement to slagment cement can reduce the mass loss and compressive strength loss up to 72% and 82%, respectively.

  6. Effect of Cement Type on Autogenous Deformation of Cement-Based Materials

    DEFF Research Database (Denmark)

    Pietro, Lura; Ye, Guang; van Breugel, Klaas

    2004-01-01

    (BFS) cement pastes. Self-desiccation shrinkage of the BFS cement paste was modeled based on the RH measurements, following the capillary-tension approach. The main findings of this study are: 1) self-desiccation shrinkage can be related to self-desiccation both for Portland and for BFS cement pastes......, taking into account the influence of the dissolved salts in the pore solution, 2) the BFS cement paste studied shows pronounced self-desiccation and self-desiccation shrinkage, mainly caused by its very fine pore structure....

  7. INFLUENCE OF WINE ACID ON RHEOLOGICAL PROPERTIES OF WELL BORE CEMENT SLURRIES AND HARDENED CEMENT PROPERTIES

    Directory of Open Access Journals (Sweden)

    Nediljka Gaurina-Međimurec

    1989-12-01

    Full Text Available Adaptation of commercial types of domestic cements for use in cementing the deep wells is a process by which Yugoslav oil industry tends to solve problems of completion of those wells independently. In order to design a domestic, cheep and effective retarder, tests of applicability of wine acid on cement slurries have been carried out. Besides examining the necessary wine acid content to achieve desirable Theological properties, the influence of this additive on properties of hardened cement samples has been tested too (the paper is published in Croatian.

  8. A functional analysis of the spacer of V(DJ recombination signal sequences.

    Directory of Open Access Journals (Sweden)

    Alfred Ian Lee

    2003-10-01

    Full Text Available During lymphocyte development, V(DJ recombination assembles antigen receptor genes from component V, D, and J gene segments. These gene segments are flanked by a recombination signal sequence (RSS, which serves as the binding site for the recombination machinery. The murine Jbeta2.6 gene segment is a recombinationally inactive pseudogene, but examination of its RSS reveals no obvious reason for its failure to recombine. Mutagenesis of the Jbeta2.6 RSS demonstrates that the sequences of the heptamer, nonamer, and spacer are all important. Strikingly, changes solely in the spacer sequence can result in dramatic differences in the level of recombination. The subsequent analysis of a library of more than 4,000 spacer variants revealed that spacer residues of particular functional importance are correlated with their degree of conservation. Biochemical assays indicate distinct cooperation between the spacer and heptamer/nonamer along each step of the reaction pathway. The results suggest that the spacer serves not only to ensure the appropriate distance between the heptamer and nonamer but also regulates RSS activity by providing additional RAG:RSS interaction surfaces. We conclude that while RSSs are defined by a "digital" requirement for absolutely conserved nucleotides, the quality of RSS function is determined in an "analog" manner by numerous complex interactions between the RAG proteins and the less-well conserved nucleotides in the heptamer, the nonamer, and, importantly, the spacer. Those modulatory effects are accurately predicted by a new computational algorithm for "RSS information content." The interplay between such binary and multiplicative modes of interactions provides a general model for analyzing protein-DNA interactions in various biological systems.

  9. Basalt waste added to Portland cement

    Directory of Open Access Journals (Sweden)

    Thiago Melanda Mendes

    2016-08-01

    Full Text Available Portland cement is widely used as a building material and more than 4.3 billion tons were produced in 2014, with increasing environmental impacts by this industry, mainly through CO2 emissions and consumption of non-removable raw materials. Several by-products have been used as raw materials or fuels to reduce environmental impacts. Basaltic waste collected by filters was employed as a mineral mixture to Portland cement and two fractions were tested. The compression strength of mortars was measured after 7 days and Scanning Electron Microscopy (SEM and Electron Diffraction Scattering (EDS were carried out on Portland cement paste with the basaltic residue. Gains in compression strength were observed for mixtures containing 2.5 wt.% of basaltic residue. Hydration products observed on surface of basaltic particles show the nucleation effect of mineral mixtures. Clinker substitution by mineral mixtures reduces CO2 emission per ton of Portland cement.

  10. The Setting Chemistry of Glass Ionomer Cement

    Institute of Scientific and Technical Information of China (English)

    CHENG Hanting; LIU Hanxing; ZHANG Guoqing

    2005-01-01

    The setting chemistry of glass ionomer cement was investigated by using mechanical determination of compressive strength at predetermined intervals, and measurement of structure changes of corresponding fracture sample by means of IR spectra and differential scanning calorimetry ( DSC). Zinc polycarboxylate cement was used as a comparison sample. The compressive strength of glass ionomer cement (GIC) increases with aging. IR spectra and DSC of corresponding fracture sample show the structure changes of the matrix and interface layer comprising of silica gel during the predetermined intervals studied, however, no significant changes occur in the zinc polycarxyolate cement. Hence the structure changes of the matrix and/or interface layer are responsible for compressive strength increasing with aging. The structure changes include the crosslink density, the ratio of complex form to ionic form, the content ratio of Al-PAA to Ca-PAA, the forming and mauring process of the interface layer comprising of silica gel.

  11. Dicalcium phosphate cements: brushite and monetite.

    Science.gov (United States)

    Tamimi, Faleh; Sheikh, Zeeshan; Barralet, Jake

    2012-02-01

    Dicalcium phosphate cements were developed two decades ago and ever since there has been a substantial growth in research into improving their properties in order to satisfy the requirements needed for several clinical applications. The present paper presents an overview of the rapidly expanding research field of the two main dicalcium phosphate bioceramics: brushite and monetite. This review begins with a summary of all the different formulae developed to prepare dicalcium phosphate cements, and their setting reaction, in order to set the scene for the key cement physical and chemical properties, such as compressive and tensile strength, cohesion, injectability and shelf-life. We address the issue of brushite conversion into either monetite or apatite. Moreover, we discuss the in vivo behavior of the cements, including their ability to promote bone formation, biodegradation and potential clinical applications in drug delivery, orthopedics, craniofacial surgery, cancer therapy and biosensors.

  12. The case of Mugher cement facto

    African Journals Online (AJOL)

    Thomas

    based on emission test and mass balance performed. Yet it accounts for ... Hydraulic (chiefly portland) cement, the binding agent in concrete and most .... phenolphthalein were used for end-point detection of the acid-base titration. Materials.

  13. Low-cycle fatigue of surgical cements

    Directory of Open Access Journals (Sweden)

    A. Balin

    2007-01-01

    Full Text Available Purpose: In case when surgical cement is used to fix endoprostheses of joints the fatigue character of mechanicalinterraction in the cement seems to be a significant importance. The paper suggests to adapt the research methodof low cycle fatigue for modelling the loads on surgical cements in an artificial hip joint. Surgical cements havealso been modified in order to improve their functional properties.Design/methodology/approach: Low cycle fatigue tests were conducted on samples made from Palamedcement without an addition and on samples modified with glassy carbon and titanium. The tests were conductedon a servohydraulic fatigue testing machine, MTS-810, with displacement control.Findings: Fatigue tests proved viscoelastic character of all the tested materials. During the fatigue tests, thephenomenon of stress cyclic relaxation was observed.Research limitations/implications: Modelling the loadings of cement in endoprostheses of joints with the lowcycle fatigue method takes into account all high value stresses, while cement is being used for endoprosthesesfor many years in the conditions of random stress and deformation courses. Therefore the obtained stress anddeformation values are bigger than those which would have been obtained in real conditions in the same time.Practical implications: The low cycle fatigue tests carried out showed how important is the factor of timefor the behavior of surgical cement in the conditions of changeable loadings. This fact is essential to assessits usability for endoprosthesoplasty of joints, specially of a hip joint. Post deformation return which is acharacteristic feature for material viscoelasticity enables its regeneration conditioning expected durability ofendoprosthesis of joints.Originality/value: Low cycle fatigue testing method for modelling of loads on surgical cement in artificial hipjoint enables to carry out the tests in a shorter period of time.

  14. Continued stabilization of Triathlon cemented TKA

    OpenAIRE

    Molt, Mats; Ryd, Leif; Toksvig-Larsen, Sören

    2016-01-01

    Background and purpose There is a general call for phased introduction of new implants, and one step in the introduction is an early evaluation of micromotion. We compared the micromotion in the Triathlon and its predecessor, the Duracon total knee prosthesis, concentrating especially on continuous migration over 5 years of follow-up. Patients and methods 60 patients were randomized to receive either a cemented Triathlon total knee prosthesis or a cemented Duracon total knee prosthesis. 3-D t...

  15. Cement stratigraphy: Image probes of cathodoluminescent facies.

    OpenAIRE

    Vuillemin, Aurèle; Ndiaye, Mapathe; Martini, Rossana; Davaud, Eric Jean

    2011-01-01

    Cement stratigraphy of carbonates aims to establish the chronology of processes involved in the rock diagenesis. Regional cement stratigraphy allows correlations and understanding of the petrological heterogeneities in reservoirs and aquifers, but is a long and rigorous approach. This article exposes a methodology of image analysis that facilitates the spatial correlation of diagenetic events in carbonate rocks. Based on the statistical comparison of signals extracted from the red spectrum em...

  16. Physical Properties of Acidic Calcium Phosphate Cements

    OpenAIRE

    2014-01-01

    The gold standard for bone replacement today, autologous bone, suffers from several disadvantages, such as the increased risk of infection due to the need for two surgeries. Degradable synthetic materials with properties similar to bone, such as calcium phosphate cements, are a promising alternative. Calcium phosphate cements are suited for a limited amount of applications and improving their physical properties could extend their use into areas previously not considered possible. For example...

  17. Dynamic properties of composite cemented clay

    Institute of Scientific and Technical Information of China (English)

    蔡袁强; 梁旭

    2004-01-01

    In this work,the dynamic properties of composite cemented clay under a wide range of strains were studied considering the effect of different mixing ratio and the change of confining pressures through dynamic triaxial test. A simple and practical method to estimate the dynamic elastic modulus and damping ratio is proposed in this paper and a related empirical normalized formula is also presented. The results provide useful guidelines for preliminary estimation of cement requirements to improve the dynamic properties of clays.

  18. Knitting Technologies And Tensile Properties Of A Novel Curved Flat-Knitted Three-Dimensional Spacer Fabrics

    Directory of Open Access Journals (Sweden)

    Li Xiaoying

    2015-09-01

    Full Text Available This paper introduces a knitting technique for making innovative curved three-dimensional (3D spacer fabrics by the computer flat-knitting machine. During manufacturing, a number of reinforcement yarns made of aramid fibres are inserted into 3D spacer fabrics along the weft direction to enhance the fabric tensile properties. Curved, flat-knitted 3D spacer fabrics with different angles (in the warp direction were also developed. Tensile tests were carried out in the weft and warp directions for the two spacer fabrics (with and without reinforcement yarns, and their stress–strain curves were compared. The results showed that the reinforcement yarns can reduce the fabric deformation and improve tensile stress and dimensional stability of 3D spacer fabrics. This research can help the further study of 3D spacer fabric when applied to composites.

  19. Case Study of the California Cement Industry

    Energy Technology Data Exchange (ETDEWEB)

    Coito, Fred; Powell, Frank; Worrell, Ernst; Price, Lynn; Friedmann, Rafael

    2005-05-01

    California is the largest cement producing state in theU.S., accounting for between 10 percent and 15 percent of U.S. cementproduction and cement industry employment. The cement industry inCalifornia consists of 31 sites that consume large amounts of energy,annually: 1,600 GWh of electricity, 22 million therms of natural gas, 2.3million tons of coal, 0.25 tons of coke, and smaller amounts of wastematerials, including tires. The case study summarized in this paperfocused on providing background information, an assessment ofenergy-efficiency opportunities and barriers, and program recommendationsthat can be used by program planners to better target products to thecement industry. The primary approach to this case study involvedwalk-through surveys of customer facilities and in depth interviews withcustomer decision makers and subsequent analysis of collected data. Inaddition, a basic review of the cement production process was developed,and summary cement industry energy and economic data were collected, andanalyzed. The analysis of secondary data provides background informationon the cement industry and identification of potential energy-efficiencyopportunities. The interviews provide some understanding of the customerperspective about implementation of energy-efficiencyprojects.

  20. Development of an innovative spacer grid model utilizing computational fluid dynamics within a subchannel analysis tool

    Science.gov (United States)

    Avramova, Maria

    In the past few decades the need for improved nuclear reactor safety analyses has led to a rapid development of advanced methods for multidimensional thermal-hydraulic analyses. These methods have become progressively more complex in order to account for the many physical phenomena anticipated during steady state and transient Light Water Reactor (LWR) conditions. The advanced thermal-hydraulic subchannel code COBRA-TF (Thurgood, M. J. et al., 1983) is used worldwide for best-estimate evaluations of the nuclear reactor safety margins. In the framework of a joint research project between the Pennsylvania State University (PSU) and AREVA NP GmbH, the theoretical models and numerics of COBRA-TF have been improved. Under the name F-COBRA-TF, the code has been subjected to an extensive verification and validation program and has been applied to variety of LWR steady state and transient simulations. To enable F-COBRA-TF for industrial applications, including safety margins evaluations and design analyses, the code spacer grid models were revised and substantially improved. The state-of-the-art in the modeling of the spacer grid effects on the flow thermal-hydraulic performance in rod bundles employs numerical experiments performed by computational fluid dynamics (CFD) calculations. Because of the involved computational cost, the CFD codes cannot be yet used for full bundle predictions, but their capabilities can be utilized for development of more advanced and sophisticated models for subchannel-level analyses. A subchannel code, equipped with improved physical models, can be then a powerful tool for LWR safety and design evaluations. The unique contributions of this PhD research are seen as development, implementation, and qualification of an innovative spacer grid model by utilizing CFD results within a framework of a subchannel analysis code. Usually, the spacer grid models are mostly related to modeling of the entrainment and deposition phenomena and the heat

  1. Detection and characterization of spacer integration intermediates in type I-E CRISPR-Cas system.

    Science.gov (United States)

    Arslan, Zihni; Hermanns, Veronica; Wurm, Reinhild; Wagner, Rolf; Pul, Ümit

    2014-07-01

    The adaptation against foreign nucleic acids by the CRISPR-Cas system (Clustered Regularly Interspaced Short Palindromic Repeats and CRISPR-associated proteins) depends on the insertion of foreign nucleic acid-derived sequences into the CRISPR array as novel spacers by still unknown mechanism. We identified and characterized in Escherichia coli intermediate states of spacer integration and mapped the integration site at the chromosomal CRISPR array in vivo. The results show that the insertion of new spacers occurs by site-specific nicking at both strands of the leader proximal repeat in a staggered way and is accompanied by joining of the resulting 5'-ends of the repeat strands with the 3'-ends of the incoming spacer. This concerted cleavage-ligation reaction depends on the metal-binding center of Cas1 protein and requires the presence of Cas2. By acquisition assays using plasmid-located CRISPR array with mutated repeat sequences, we demonstrate that the primary sequence of the first repeat is crucial for cleavage of the CRISPR array and the ligation of new spacer DNA.

  2. Numerical investigation on the characteristics of two-phase flow in fuel assemblies with spacer grid

    Energy Technology Data Exchange (ETDEWEB)

    Chen, D.; Yang, Z.; Zhong, Y.; Xiao, Y.; Hu, L. [Chongqing Univ. (China). Key Lab. of Low-grade Energy Utilization Technologies and Systems

    2016-07-15

    In pressurized water reactors (PWRs), the spacer grids of the fuel assembly has significant impact on the thermal-hydraulic performance of the fuel assembly. Particularly, the spacer grids with the mixing vanes can dramatically enhance the secondary flow and have significant effect on the void distribution in the fuel assembly. In this paper, the CFD study has been carried out to analyze the effects of the spacer grid with the steel contacts, dimples and mixing vanes on the boiling two-phase flow characteristics, such as the two-phase flow field, the void distribution, and so on. Considered the influence of the boiling phase change on two-phase flow, a boiling model was proposed and applied in the CFD simulation by using the UDF (User Defined Function) method. Furthermore, in order to analyze the effects of the spacer grid with mixing vanes, the adiabatic (without boiling) two-phase flow has also been investigated as comparison with the boiling two-phase flow in the fuel assembly with spacer grids. The CFD simulation on two-phase flow in the fuel assembly with the proposed boiling model can predict the characteristics of two-phase flow better.

  3. CFD study of isothermal water flow in rod bundle with split-type spacer grid

    Science.gov (United States)

    Batta, A.; Class, A. G.

    2014-06-01

    The design of rod bundles in nuclear application nowadays is assessed by CFD (computational fluid dynamics). The accuracy of CFD models need validation. Within the OECD/NEA benchmark MATiS-H (Measurement and Analysis of Turbulent Mixing in Sub-channels - Horizontal) a single-phase water flow in a 5x5 rod bundle is studied. In the benchmark, two types of spacer grids are tested, the swirl type and the split type, where the current study focuses on the split type spacer grid. Comparison of CFD results obtained at Karlsruhe Institut of Technology (KIT) with experimental results of KAERI (Korea Atomic Energy Research Institute) are presented. In the benchmark velocities components along selected lines downstream of the spacer grid are measured and compared to CFD results. The CFD code STAR CCM+ with the Realized k-ɛ model is used. Comparisons with experimental results show quantitative and qualitative agreement for the averaged values of velocity components. Comparisons of results to other benchmark partners using different modeling show that the selected mesh size and models for the analysis of the current case gives relatively accurate results. However, the used turbulent model (Realized k-ɛ does not capture the turbulent intensity correctly. Computation shows that the flow has very high mixing due to the spacer grid, which does not decay within the measurements domain (z/ DH =0-10 downstream of spacer grid). The same conclusion can be drawn from experimental data.

  4. Effect of different commercial feed spacers on biofouling of reverse osmosis membrane systems: A numerical study

    KAUST Repository

    Bucs, Szilard

    2014-06-01

    Feed spacers and hydrodynamics have been found relevant for the impact of biofouling on performance in reverse osmosis (RO) and nanofiltration (NF) membrane systems.The objectives of this study on biofouling development were to determine the impact of (i) linear flow velocity and bacterial cell load, (ii) biomass location and (iii) various feed spacer geometries as applied in practice as well as a modified geometry spacer.A three-dimensional mathematical model for biofouling of feed spacer channels including hydrodynamics, solute mass transport and biofilm formation was developed in COMSOL Multiphysics and MATLAB software.Results of this study indicate that the feed channel pressure drop increase caused by biofilm formation can be reduced by using thicker and/or modified feed spacer geometry and/or a lower flow rate in the feed channel. The increase of feed channel pressure drop by biomass accumulation is shown to be strongly influenced by the location of biomass. Results of numerical simulations are in satisfactory agreement with experimental data, indicating that this micro-scale mechanistic model is representative for practice. The developed model can help to understand better the biofouling process of spiral-wound RO and NF membrane systems and to develop strategies to reduce and control biofouling. © 2013 Elsevier B.V.

  5. Using cathode spacers to minimize reactor size in air cathode microbial fuel cells

    KAUST Repository

    Yang, Qiao

    2012-04-01

    Scaling up microbial fuel cells (MFCs) will require more compact reactor designs. Spacers can be used to minimize the reactor size without adversely affecting performance. A single 1.5mm expanded plastic spacer (S1.5) produced a maximum power density (973±26mWm -2) that was similar to that of an MFC with the cathode exposed directly to air (no spacer). However, a very thin spacer (1.3mm) reduced power by 33%. Completely covering the air cathode with a solid plate did not eliminate power generation, indicating oxygen leakage into the reactor. The S1.5 spacer slightly increased columbic efficiencies (from 20% to 24%) as a result of reduced oxygen transfer into the system. Based on operating conditions (1000ς, CE=20%), it was estimated that 0.9Lh -1 of air would be needed for 1m 2 of cathode area suggesting active air flow may be needed for larger scale MFCs. © 2012 Elsevier Ltd.

  6. In Silico Study of Spacer Arm Length Influence on Drug Vectorization by Fullerene C60

    Directory of Open Access Journals (Sweden)

    Haifa Khemir

    2015-01-01

    Full Text Available This work studies theoretically the effect of spacer arm lengths on the characteristics of a fullerene C60-based nanovector. The spacer arm is constituted of a carbon chain including a variable number of methylene groups (n = 2–11. To improve the ability of the fullerene carriage, two arms are presented simultaneously through a malonyl bridge. Then the evolution of selected physicochemical parameters is monitored as a function of the spacer arm length and the angle between the two arms. We show here that while the studied characteristics are almost independent of the spacer arm length or vary monotonically with it, the dipole moment and its orientation vary periodically with the parity of the number of carbon atoms. This periodicity is related to both modules and orientations of dipole moments of the spacer arms. In the field of chemical synthesis, these results highlight the importance of theoretical calculations for the optimization of operating conditions. In the field of drug discovery, they show that theoretical calculations of the chemical properties of a drug candidate can help predict its in vivo behaviour, notably its bioavailability and biodistribution, which are known to be tightly dependent of its polarity.

  7. Influence of length and flexibility of spacers on the binding affinity of divalent ligands

    Directory of Open Access Journals (Sweden)

    Susanne Liese

    2015-05-01

    Full Text Available We present a quantitative model for the binding of divalent ligand–receptor systems. We study the influence of length and flexibility of the spacers on the overall binding affinity and derive general rules for the optimal ligand design. To this end, we first compare different polymeric models and determine the probability to simultaneously bind to two neighboring receptor binding pockets. In a second step the binding affinity of divalent ligands in terms of the IC50 value is derived. We find that a divalent ligand has the potential to bind more efficiently than its monovalent counterpart only, if the monovalent dissociation constant is lower than a critical value. This critical monovalent dissociation constant depends on the ligand-spacer length and flexibility as well as on the size of the receptor. Regarding the optimal ligand-spacer length and flexibility, we find that the average spacer length should be equal or slightly smaller than the distance between the receptor binding pockets and that the end-to-end spacer length fluctuations should be in the same range as the size of a receptor binding pocket.

  8. Influence of length and flexibility of spacers on the binding affinity of divalent ligands.

    Science.gov (United States)

    Liese, Susanne; Netz, Roland R

    2015-01-01

    We present a quantitative model for the binding of divalent ligand-receptor systems. We study the influence of length and flexibility of the spacers on the overall binding affinity and derive general rules for the optimal ligand design. To this end, we first compare different polymeric models and determine the probability to simultaneously bind to two neighboring receptor binding pockets. In a second step the binding affinity of divalent ligands in terms of the IC50 value is derived. We find that a divalent ligand has the potential to bind more efficiently than its monovalent counterpart only, if the monovalent dissociation constant is lower than a critical value. This critical monovalent dissociation constant depends on the ligand-spacer length and flexibility as well as on the size of the receptor. Regarding the optimal ligand-spacer length and flexibility, we find that the average spacer length should be equal or slightly smaller than the distance between the receptor binding pockets and that the end-to-end spacer length fluctuations should be in the same range as the size of a receptor binding pocket.

  9. Detection and characterization of spacer integration intermediates in type I-E CRISPR–Cas system

    Science.gov (United States)

    Arslan, Zihni; Hermanns, Veronica; Wurm, Reinhild; Wagner, Rolf; Pul, Ümit

    2014-01-01

    The adaptation against foreign nucleic acids by the CRISPR–Cas system (Clustered Regularly Interspaced Short Palindromic Repeats and CRISPR-associated proteins) depends on the insertion of foreign nucleic acid-derived sequences into the CRISPR array as novel spacers by still unknown mechanism. We identified and characterized in Escherichia coli intermediate states of spacer integration and mapped the integration site at the chromosomal CRISPR array in vivo. The results show that the insertion of new spacers occurs by site-specific nicking at both strands of the leader proximal repeat in a staggered way and is accompanied by joining of the resulting 5′-ends of the repeat strands with the 3′-ends of the incoming spacer. This concerted cleavage-ligation reaction depends on the metal-binding center of Cas1 protein and requires the presence of Cas2. By acquisition assays using plasmid-located CRISPR array with mutated repeat sequences, we demonstrate that the primary sequence of the first repeat is crucial for cleavage of the CRISPR array and the ligation of new spacer DNA. PMID:24920831

  10. Towards a rational spacer design for bivalent inhibition of estrogen receptor

    Science.gov (United States)

    Bujotzek, Alexander; Shan, Min; Haag, Rainer; Weber, Marcus

    2011-03-01

    Estrogen receptors are known drug targets that have been linked to several kinds of cancer. The structure of the estrogen receptor ligand binding domain is available and reveals a homodimeric layout. In order to improve the binding affinity of known estrogen receptor inhibitors, bivalent compounds have been developed that consist of two individual ligands linked by flexible tethers serving as spacers. So far, binding affinities of the bivalent compounds do not surpass their monovalent counterparts. In this article, we focus our attention on the molecular spacers that are used to connect the individual ligands to form bivalent compounds, and describe their thermodynamic contribution during the ligand binding process. We use computational methods to predict structural and entropic parameters of different spacer structures. We find that flexible spacers introduce a number of effects that may interfere with ligand binding and possibly can be connected to the low binding affinities that have been reported in binding assays. Based on these findings, we try to provide guidelines for the design of novel molecular spacers.

  11. Influence of Cellulose Ethers on Hydration Products of Portland Cement

    Institute of Scientific and Technical Information of China (English)

    MA Baoguo; OU Zhihua; JIAN Shouwei; XU Rulin

    2011-01-01

    Cellulose ethers are widely used to mortar formulations, and it is significant to understand the interaction between cellulose ethers and cement pastes. FT-IR spectra, thermal analysis and SEM are used to investigate hydration products in the cement pastes modified by HEMC and HPMC in this article. The results show that the hydration products in modified cement pastes were finally identical with those in the unmodified cement paste, but the major hydration products, such as CH (calcium hydroxide), ettringite and C-S-H, appeared later in the modified cement pastes than in the unmodified cement paste. The cellulose ethers decrease the outer products and increase inner products of C-S-H gels. Compared to unmodified cement pastes, no new products are found in the modified cement pastes in the present experiment. The HEMC and HPMC investigation shows almost the same influence on the hydration products of Portland cement.

  12. Investigation of Possible Wellbore Cement Failures During Hydraulic Fracturing Operations

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jihoon; Moridis, George

    2014-11-01

    We model and assess the possibility of shear failure, using the Mohr-Coulomb model ? along the vertical well by employing a rigorous coupled flow-geomechanic analysis. To this end, we vary the values of cohesion between the well casing and the surrounding cement to representing different quality levels of the cementing operation (low cohesion corresponds to low-quality cement and/or incomplete cementing). The simulation results show that there is very little fracturing when the cement is of high quality.. Conversely, incomplete cementing and/or weak cement can causes significant shear failure and the evolution of long fractures/cracks along the vertical well. Specifically, low cohesion between the well and cemented areas can cause significant shear failure along the well, but the same cohesion as the cemented zone does not cause shear failure. When the hydraulic fracturing pressure is high, low cohesion of the cement can causes fast propagation of shear failure and of the resulting fracture/crack, but a high-quality cement with no weak zones exhibits limited shear failure that is concentrated near the bottom of the vertical part of the well. Thus, high-quality cement and complete cementing along the vertical well appears to be the strongest protection against shear failure of the wellbore cement and, consequently, against contamination hazards to drinking water aquifers during hydraulic fracturing operations.

  13. Diagraphies de cimentation : vers une analyse de la qualité du contact ciment-formation Cement Logging: Toward an Analysis of the Quality of Cement-Formation Bonding

    Directory of Open Access Journals (Sweden)

    Isambourg P.

    2006-11-01

    example, promote the premature arrival of gas in the oil produced. The cementing defects that can disturb this seal are:(a Cement-casing micro- or macro-annulus. (b Mud channel at the level of the casing. (c Cement-formation micro- or macro-annulus. (d Mud channel at the level of the formation. (e Gas percolation in the cement sheath. (f Gas channel in the cement sheath. The aim of these logs is to determine whether one of these defect is present in the cement sheath. The causes of these defects may be numerous and varied:(a Poor displacement of the drilling mud. (b Improper spacer formulation. (c Cement formulation not conforming to the requirements of the well. (d Cracks in the cemented annulus as the result of thermal and hydraulic shocks and aging. (e Variation of the permeability during aging. With the battery of logs now available, we know how to detect defects quite accurately at the level of the cement-casing contact as well as any gas percolation in the cement. On the contrary, local defects at the level of the cement-formation contact can be assessed only very qualitatively by a log of the VDL type. In addition, a VDL analysis requires serious expertise. The present challenge is thus to obtain a cementing log capable of making the same analysis at the level of the formation as what is now done at the level of the casing. This is all the more important as the percentage of risk in the presence of a defect is greater at the level of the cement-formation interface. We have thus worked on the possibility of making use of ultrasonic echo techniques for analyzing the quality of the cement-formation contact.

  14. Interference-driven spacer acquisition is dominant over naive and primed adaptation in a native CRISPR–Cas system

    Science.gov (United States)

    Staals, Raymond H. J.; Jackson, Simon A.; Biswas, Ambarish; Brouns, Stan J. J.; Brown, Chris M.; Fineran, Peter C.

    2016-01-01

    CRISPR–Cas systems provide bacteria with adaptive immunity against foreign nucleic acids by acquiring short, invader-derived sequences called spacers. Here, we use high-throughput sequencing to analyse millions of spacer acquisition events in wild-type populations of Pectobacterium atrosepticum. Plasmids not previously encountered, or plasmids that had escaped CRISPR–Cas targeting via point mutation, are used to provoke naive or primed spacer acquisition, respectively. The origin, location and order of spacer acquisition show that spacer selection through priming initiates near the site of CRISPR–Cas recognition (the protospacer), but on the displaced strand, and is consistent with 3′–5′ translocation of the Cas1:Cas2-3 acquisition machinery. Newly acquired spacers determine the location and strand specificity of subsequent spacers and demonstrate that interference-driven spacer acquisition (‘targeted acquisition') is a major contributor to adaptation in type I-F CRISPR–Cas systems. Finally, we show that acquisition of self-targeting spacers is occurring at a constant rate in wild-type cells and can be triggered by foreign DNA with similarity to the bacterial chromosome. PMID:27694798

  15. Characterization of cement minerals, cements and their reaction products at the atomic and nano scale

    DEFF Research Database (Denmark)

    Skibsted, Jørgen; Hall, Christopher

    2008-01-01

    Recent advances and highlights in characterization methods are reviewed for cement minerals, cements and their reaction products. The emphasis is on X-ray and neutron diffraction, and on nuclear magnetic resonance methods, although X-ray absorption and Raman spectroscopies are discussed briefly...

  16. Color difference of composite resins after cementation with different shades of resin luting cement.

    Science.gov (United States)

    Cengiz, Esra; Kurtulmus-Yilmaz, Sevcan; Karakaya, Izgen; Aktore, Huseyin

    2017-07-26

    The purpose of this study was to evaluate the color difference of nanohybrid and ormocer-based composite resins with different thicknesses when 4 different shades of resin luting cement were used. 56 disc specimens of each composite resin (Aelite aesthetic enamel, Ceram-X mono) with 0.5 and 1 mm thicknesses were fabricated. Baseline color measurements were performed using a clinical spectrophotometer. The specimens of each thicknesses of each resin were randomly divided into 4 groups according to the shades of resin luting cement (white/A1, yellow/universal/A3, transparent and white opaque) (n = 7). Mixed resin cement was applied onto the resin specimens using a Teflon mold in 0.1 mm thickness. Color measurements of cemented composite resin specimens were repeated and color difference (∆E) between baseline and after cementation measurements was calculated. ANOVA and Tukey's test were used for statistical analysis. The opaque shade had significantly increased ∆E values as compared to the other shades (p resins in terms of ∆E values. The shade of resin cement and the type of the resin affected the final color; however, the thickness of composite resin had no influence on the final color of restoration. Selecting the shade of resin luting cement before cementation of indirect composite laminate restoration is important to achieve final color match.

  17. Revision Total Hip Arthroplasty Using the Cement-in-Cement Technique.

    Science.gov (United States)

    Amanatullah, Derek F; Pallante, Graham D; Floccari, Lorena V; Vasileiadis, George I; Trousdale, Robert T

    2017-03-01

    The cement-in-cement technique is useful in the setting of revision total hip arthroplasty (THA), especially to gain acetabular exposure, change a damaged or loose femoral component, or change the version, offset, or length of a fixed femoral component. The goal of this retrospective study was to assess the clinical and radiographic characteristics of revision THA using the cement-in- cement technique. Between 1971 and 2013, a total of 63 revision THAs used an Omnifit (Osteonics, Mahwah, New Jersey) or Exeter (Howmedica, Mahwah, New Jersey) stem and the cement-in-cement technique at the senior author's institution. Aseptic loosening (74%) was the predominant preoperative diagnosis followed by periprosthetic fracture (14%), instability (8%), and implant fracture (6%). Mean clinical follow-up was 5.5±3.8 years. The Harris Hip Score had a statistically significant increase of 18.5 points (Pfracture, or circumferential lucent lines at final follow-up. The patients who underwent cement-in-cement revision THA at the senior author's institution had good restoration of function but a high complication rate. [Orthopedics. 2017; 40(2):e348-e351.]. Copyright 2016, SLACK Incorporated.

  18. [Burns caused by cement mortar (based on expert opinion)].

    Science.gov (United States)

    Kleinhans, D

    1984-01-01

    A 35-year-old farmer with scars on his right arm, following erosion obviously due to wet cement (case of an expert opinion), was examined. Cement water had continuously soaked his shirt while he was planing a freshly applied wet cement ceiling with his right arm upwards. The cement did not contain special additives, so the normal alkalinity of wet cement and occlusion effects caused the erosion. The farmer sued the manufacturer of the cement for damages because of missing warning notices. The court decided in his favor.

  19. A Blended Cement Containing Blast Furnace Slag and Phosphorous Slag

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Blended cement containing blast furnace slag(BFS) and phosphorous slag(PS) is a new kind of cement.The total content of blended materials could increase if two additives were used. Using the same admixtures, the properties of the blended cement with 70% additives could reach the standard of 525-grade slag cement according to GB.The strength of cement with 80% additives could reach the standard of 425-grade slag cement.The tests of strength, pore structure,hydration products,inhibiting alkali-aggregate reaction, resistance to sulfate corrosion of BFS-PSC were performed.

  20. Carbonation Resistance of Sulphoaluminate Cement-based High Performance Concrete

    Institute of Scientific and Technical Information of China (English)

    ZHANG Decheng; XU Dongyu; CHENG Xin; CHEN Wen

    2009-01-01

    The influences of water/cement ratio and admixtures on carbonation resistance of sulphoaluminate cement-based high performance concrete(HPC)were investigated.The experimental results show that with the decreasing water/cement ratio,the carbonation depth of sulphoaluminate cement-based HPC is decreased remarkably,and the carbonation resistance capability is also improved with the adding admixtures.The morphologies and structure characteristics of sulphoaluminate cement hydration products before and after carbonation were analyzed using SEM and XRD.The analysis results reveal that the main hydration product of sulphoaluminate cement,that is ettringite(AFt),de-composes after carbonation.

  1. Effect of Weld Properties on the Crush Strength of the PWR Spacer Grid

    Directory of Open Access Journals (Sweden)

    Kee-nam Song

    2012-01-01

    Full Text Available Mechanical properties in a weld zone are different from those in the base material because of different microstructures. A spacer grid in PWR fuel is a structural component with an interconnected and welded array of slotted grid straps. Previous research on the strength analyses of the spacer grid was performed using base material properties owing to a lack of mechanical properties in the weld zone. In this study, based on the mechanical properties in the weld zone of the spacer grid recently obtained by an instrumented indentation technique, the strength analyses considering the mechanical properties in the weld zone were performed, and the analysis results were compared with the previous research.

  2. Stable inverted small molecular organic solar cells using a p-doped optical spacer.

    Science.gov (United States)

    Lee, Sang-Hoon; Seo, Ji-Won; Lee, Jung-Yong

    2015-01-07

    We report inverted small molecular organic solar cells using a doped window layer as an optical spacer. The optical spacer was used to shift the optical field distribution inside the active layers, generating more charge carriers from sunlight. In this report, N,N,N',N'-tetrakis(4-methoxyphenyl)-benzidine (MeO-TPD) was doped with 2,2-(perfluoronaphthalene-2,6-diylidene)dimalononitrile (F6-TCNNQ), a p-type dopant material. P-doped MeO-TPD was adopted as an optical spacer because it has a large energy band gap, and its conductivity can be increased by several orders of magnitude through a doping process. As a result, a power conversion efficiency of 4.15% was achieved with the doped window layer of optimized thickness. Lastly, we present significantly improved stability of the inverted devices with the MeO-TPD layer.

  3. Staged Custom, Intramedullary Antibiotic Spacers for Severe Segmental Bone Loss in Infected Total Hip Arthroplasty

    Directory of Open Access Journals (Sweden)

    Atul F. Kamath

    2011-01-01

    Full Text Available Introduction. Total hip arthroplasty (THA infections with severe bone loss pose significant reconstructive challenges. We present our experience with two-stage hip reimplantation using an intramedullary, antibiotic-impregnated nail. Methods. Three patients with infected THA with severe proximal femoral bone loss (Mallory type IIIB or greater were treated using a custom antibiotic spacer. Clinical outcomes and any complications were recorded. Average followup was 49 months from final reimplantation. Results. Mean age at spacer placement (stage 1 was 53 years. The mean Harris Hip Score at final followup was 80. Two patients had asymptomatic heterotopic ossification, and one patient had a 2 cm leg-length discrepancy. Conclusions. A custom intramedullary nail antibiotic spacer is a reliable option in the staged management of the infected THA with severe proximal femoral bone loss. Benefits of this technique include limb salvage with maintenance of leg length, soft tissue tension, and functional status.

  4. Binding of Streptavidin to Surface-attached Biotin with Different Spacer Thicknesses

    Institute of Scientific and Technical Information of China (English)

    LI Yifei; ZHANG Haining

    2015-01-01

    The specific binding of receptor to ligand covalently attached to surface with different surface densities was studied using streptavidin-biotin model pair. Biotinylated substrates with different spacer thicknesses as formed through a simple reaction between amine immobilized surfaces and N-hydroxysucciimide groups at the end of biotin modiifed PEG in anhydrous organic solutions (“grafting to”technique). The amount of the speciifcally adsorbed protein was measured as a function of spacer thickness between hard surface and biotin moieties. It has been shown that the amount of specifically adsorbed streptavidin decreases with the increase spacer thickness and the protein adsorbs onto the functionalized surfaces in a single molecular manner. It provides an interesting model system for studying single molecular interactions.

  5. RISSC: a novel database for ribosomal 16S-23S RNA genes spacer regions.

    Science.gov (United States)

    García-Martínez, J; Bescós, I; Rodríguez-Sala, J J; Rodríguez-Valera, F

    2001-01-01

    A novel database, under the acronym RISSC (Ribosomal Intergenic Spacer Sequence Collection), has been created. It compiles more than 1600 entries of edited DNA sequence data from the 16S-23S ribosomal spacers present in most prokaryotes and organelles (e.g. mitochondria and chloroplasts) and is accessible through the Internet (http://ulises.umh.es/RISSC), where systematic searches for specific words can be conducted, as well as BLAST-type sequence searches. Additionally, a characteristic feature of this region, the presence/absence and nature of tRNA genes within the spacer, is included in all the entries, even when not previously indicated in the original database. All these combined features could provide a useful documentation tool for studies on evolution, identification, typing and strain characterization, among others.

  6. Custom Anatomical 3D Spacer for Temporomandibular Joint Resection and Reconstruction

    Science.gov (United States)

    Green, John Marshall; Lawson, Sarah T.; Liacouras, Peter C.; Wise, Edward M.; Gentile, Michael A.; Grant, Gerald Thomas

    2015-01-01

    Two cases are presented using a two-stage approach and a custom antibiotic spacer placement. Temporomandibular reconstruction can be very demanding and accomplished with a variety of methods in preparation of a total joint and ramus reconstruction with total joint prostheses (TMJ Concepts, Ventura, CA). Three-dimensional reconstructions from diagnostic computed tomography were used to establish a virtually planned resection which included the entire condyle-ramus complex. From these data, digital designs were used to manufacture molds to facilitate intraoperative fabrication of precise custom anatomic spacers from rapidly setting antibiotic-impregnated polymethyl methacrylate. Molds were manufactured using vat polymerization (stereolithography) with a photopolymer in the first case and powder bed fusion (electron beam melting) with Ti6AL4V for the second. Surgical methodology and the use of molds for intraoperative spacer fabrication for each case are discussed. PMID:26889353

  7. Petroleum Sludge as gypsum replacement in cement plants: Its Impact on Cement Strength

    Science.gov (United States)

    Benlamoudi, Ali; Kadir, Aeslina Abdul; Khodja, Mohamed

    2017-08-01

    Due to high cost of cement manufacturing and the huge amount of resources exhaustion, companies are trying to incorporate alternative raw materials or by-products into cement production so as to produce alternative sustainable cement. Petroleum sludge is a dangerous waste that poses serious imparts on soil and groundwater. Given that this sludge contains a high percentage of anhydrite (CaSO4), which is the main component of gypsum (CaSO4.2H2O), it may play the same gypsum role in strength development. In this research, a total replacement of gypsum (100%) has been substituted by petroleum sludge in cement production and has led to an increase of 28.8% in UCS values after 28 curing days. Nevertheless, the burning of this waste has emitted a considerable amount of carbon monoxide (CO) gas that needs to be carefully considered prior to use petroleum sludge within cement plants.

  8. Alternative Fuel for Portland Cement Processing

    Energy Technology Data Exchange (ETDEWEB)

    Schindler, Anton K; Duke, Steve R; Burch, Thomas E; Davis, Edward W; Zee, Ralph H; Bransby, David I; Hopkins, Carla; Thompson, Rutherford L; Duan, Jingran; ; Venkatasubramanian, Vignesh; Stephen, Giles

    2012-06-30

    The production of cement involves a combination of numerous raw materials, strictly monitored system processes, and temperatures on the order of 1500 °C. Immense quantities of fuel are required for the production of cement. Traditionally, energy from fossil fuels was solely relied upon for the production of cement. The overarching project objective is to evaluate the use of alternative fuels to lessen the dependence on non-renewable resources to produce portland cement. The key objective of using alternative fuels is to continue to produce high-quality cement while decreasing the use of non-renewable fuels and minimizing the impact on the environment. Burn characteristics and thermodynamic parameters were evaluated with a laboratory burn simulator under conditions that mimic those in the preheater where the fuels are brought into a cement plant. A drop-tube furnace and visualization method were developed that show potential for evaluating time- and space-resolved temperature distributions for fuel solid particles and liquid droplets undergoing combustion in various combustion atmospheres. Downdraft gasification has been explored as a means to extract chemical energy from poultry litter while limiting the throughput of potentially deleterious components with regards to use in firing a cement kiln. Results have shown that the clinkering is temperature independent, at least within the controllable temperature range. Limestone also had only a slight effect on the fusion when used to coat the pellets. However, limestone addition did display some promise in regards to chlorine capture, as ash analyses showed chlorine concentrations of more than four times greater in the limestone infused ash as compared to raw poultry litter. A reliable and convenient sampling procedure was developed to estimate the combustion quality of broiler litter that is the best compromise between convenience and reliability by means of statistical analysis. Multi-day trial burns were conducted

  9. Thermal reactions of brushite cements.

    Science.gov (United States)

    Bohner, M; Gbureck, U

    2008-02-01

    The thermal reactions of a brushite cement made of beta-tricalcium phosphate (beta-TCP), monocalcium phosphate monohydrate (MCPM), and an aqueous solution were followed in situ with an isothermal calorimeter at 37 degrees C. The investigated parameters were the beta-TCP/MCPM weight ratio, the liquid-to-powder ratio, the synthesis route and milling duration of the beta-TCP powder, as well as the presence of sulfate, citrate, and pyrophosphate ions in the mixing liquid. The thermograms were complex, particularly for mixtures containing an excess of MCPM or additives in the mixing solution. Results suggested that the endothermic MCPM dissolution and the highly exothermic beta-TCP dissolution occurred simultaneously, thereby leading to the formation of a large exothermic peak at early reaction time. Both reactions were followed by the exothermic crystallization of brushite and in the presence of an excess of MCPM by the endothermic crystallization of monetite. Additives generally widened the main exothermic reaction peak, or in some cases with pyrophosphate ions postponed the main exothermic peak at late reaction time. Generally, the results could be well explained and understood based on thermodynamic and solubility data.

  10. Flunisolide hydrofluoroalkane with integrated spacer for treating asthma: an updated review.

    Science.gov (United States)

    Berger, William E; Tashkin, Donald P

    2015-01-01

    Flunisolide hydrofluoroalkane (HFA) with integrated spacer is the most recent reformulated inhaled corticosteroid (ICS) for asthma available in the United States. It is the only product that combines a corticosteroid extrafine aerosol with a built-in spacer. The potential clinical benefit of the flunisolide HFA formulation and its integrated spacer for treating persistent asthma was assessed through a comprehensive review of the published literature and data from the past 10 years focusing on (1) flunisolide, the molecule, and the impact of the HFA reformulation; (2) updated information on the anti-inflammatory response to flunisolide HFA, particularly in the distal airways; and (3) the usefulness of an integrated spacer. Flunisolide HFA was found effective and safe in clinical studies and comparable with the chlorofluorocarbon (CFC) formulation, but at about one-third the dose of flunisolide CFC, likely reflecting both the device and the particle size of the reformulated product. Compared with the CFC formulation, the extrafine aerosol and smaller particle size of flunisolide HFA substantially increased pulmonary deposition and decreased oropharyngeal deposition. The integrated spacer further enhanced the pulmonary/oropharyngeal deposition ratio. Examination of lung biopsy specimens indicated a favorable anti-inflammatory response to flunisolide HFA in peripheral airways. Pediatric studies showed no significant effects on growth. The data indicate that flunisolide HFA is a safe and effective maintenance therapy for asthma patients. The integrated spacer may provide an added advantage for patients, especially those who may be more likely to experience adverse effects of ICSs, both local and systemic, including children susceptible to adverse effects on growth.

  11. Quality control of cemented waste forms

    Energy Technology Data Exchange (ETDEWEB)

    Slate, L.J.

    1994-12-31

    To insure that cemented radwaste remains immobilized after disposal, certain standards have been set in Europe by the Commission of the European Communities. One such standard is compressive strength. If the compressive strength can be predicted during the early curing stages, time and money can be saved and the quality of the final waste form guaranteed. It was determined that the 7- and 28-day compressive strength from radwaste cementation can be predicted during the mixing and early curing stages by at least three methods. The three that were studied were maturity, rheology, and impedance. Maturity is a temperature-to-time measurement, rheology is a shear stress-to-shear rate measurement, and impedance is the opposition offered to the flow of alternating current. These three methods were employed on five different cemented radwaste concentrations with three different water-to-cement ratios; thus, a total of 15 different mix designs were considered. The results showed that the impedance was the easiest to employ for an on-line process. The results of the impedance method showed a very good relationship between impedance and water-to-cement ratio; therefore, an accurate prediction of compressive strength of cemented radwaste can be drawn from this method. The results of the theology method were very good. The method showed that concrete conforms to the Bingham plastic rheologic model, and the theology method can be used to predict the compressive strength of cemented radwaste, but may be too cumbersome. The results of the maturity method were shown to be limited in accuracy for determining compressive strength.

  12. New clustered regularly interspaced short palindromic repeat locus spacer pair typing method based on the newly incorporated spacer for Salmonella enterica.

    Science.gov (United States)

    Li, Hao; Li, Peng; Xie, Jing; Yi, Shengjie; Yang, Chaojie; Wang, Jian; Sun, Jichao; Liu, Nan; Wang, Xu; Wu, Zhihao; Wang, Ligui; Hao, Rongzhang; Wang, Yong; Jia, Leili; Li, Kaiqin; Qiu, Shaofu; Song, Hongbin

    2014-08-01

    A clustered regularly interspaced short palindromic repeat (CRISPR) typing method has recently been developed and used for typing and subtyping of Salmonella spp., but it is complicated and labor intensive because it has to analyze all spacers in two CRISPR loci. Here, we developed a more convenient and efficient method, namely, CRISPR locus spacer pair typing (CLSPT), which only needs to analyze the two newly incorporated spacers adjoining the leader array in the two CRISPR loci. We analyzed a CRISPR array of 82 strains belonging to 21 Salmonella serovars isolated from humans in different areas of China by using this new method. We also retrieved the newly incorporated spacers in each CRISPR locus of 537 Salmonella isolates which have definite serotypes in the Pasteur Institute's CRISPR Database to evaluate this method. Our findings showed that this new CLSPT method presents a high level of consistency (kappa = 0.9872, Matthew's correlation coefficient = 0.9712) with the results of traditional serotyping, and thus, it can also be used to predict serotypes of Salmonella spp. Moreover, this new method has a considerable discriminatory power (discriminatory index [DI] = 0.8145), comparable to those of multilocus sequence typing (DI = 0.8088) and conventional CRISPR typing (DI = 0.8684). Because CLSPT only costs about $5 to $10 per isolate, it is a much cheaper and more attractive method for subtyping of Salmonella isolates. In conclusion, this new method will provide considerable advantages over other molecular subtyping methods, and it may become a valuable epidemiologic tool for the surveillance of Salmonella infections. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

  13. Assessment of Natural Radioactivity Levels of Cements and Cement Composites in the Slovak Republic

    Directory of Open Access Journals (Sweden)

    Adriana Eštoková

    2013-12-01

    Full Text Available The radionuclide activities of 226Ra, 232Th and 40K and radiological parameters (radium equivalent activity, gamma and alpha indices, the absorbed gamma dose rate and external and internal hazard indices of cements and cement composites commonly used in the Slovak Republic have been studied in this paper. The cement samples of 8 types of cements from Slovak cement plants and five types of composites made from cement type CEM I were analyzed in the experiment. The radionuclide activities in the cements ranged from 8.58–19.1 Bq·kg−1, 9.78–26.3 Bq·kg−1 and 156.5–489.4 Bq·kg−1 for 226Ra, 232Th and 40K, respectively. The radiological parameters in cement samples were calculated as follows: mean radium equivalent activity Raeq = 67.87 Bq·kg−1, gamma index Iγ = 0.256, alpha index Iα = 0.067, the absorbed gamma dose rate D = 60.76 nGy·h−1, external hazard index Hex = 0.182 and internal hazard index Hin was 0.218. The radionuclide activity in composites ranged from 6.84–10.8 Bq·kg−1 for 226Ra, 13.1–20.5 Bq·kg−1 for 232Th and 250.4–494.4 Bq·kg−1 for 40K. The calculated radiological parameters of cements were lower than calculated radiological parameters of cement composites.

  14. The Effect of Various Fabric Parameters on the Sound Absorption Properties of Circular Knitted Spacer Fabrics

    Directory of Open Access Journals (Sweden)

    Arzu Marmaralı

    2014-07-01

    Full Text Available Spacer fabrics which can be produced through weaving or nonwoven technique beside warp knitting and weft knitting processes, can be used for functional applications such as automotive textiles, medical textiles, geotextiles, sportswear, protective textiles and composites due to the possibility of using a variety of different materials, flexible product range and the three dimensional construction. Additionally they can also be used for sound absorption applications with different pore geometry. In this study, the effect of fabric parameters like material type, fabric thickness and surface structures on the sound absorption properties of circular knitted spacer fabrics was investigated and aimed to determine the optimum fabric parameters for better sound absorption.

  15. Microbial fuel cells with an integrated spacer and separate anode and cathode modules

    KAUST Repository

    He, Weihua

    2016-01-01

    A new type of scalable MFC was developed based on using alternating graphite fiber brush array anode modules and dual cathode modules in order to simplify construction, operation, and maintenance of the electrodes. The modular MFC design was tested with a single (two-sided) cathode module with a specific surface area of 29 m2 m−3 based on a total liquid volume (1.4 L; 20 m2 m−3 using the total reactor volume of 2 L), and two brush anode modules. Three different types of spacers were used in the cathode module to provide structural stability, and enhance air flow relative to previous cassette (combined anode–cathode) designs: a low-profile wire spacer; a rigid polycarbonate column spacer; and a flexible plastic mesh spacer. The best performance was obtained using the wire spacer that produced a maximum power density of 1100 ± 10 mW m−2 of cathode (32 ± 0.3 W m−3 based on liquid volume) with an acetate-amended wastewater (COD = 1010 ± 30 mg L−1), compared to 1010 ± 10 mW m−2 for the column and 650 ± 20 mW m−2 for the mesh spacers. Anode potentials were unaffected by the different types of spacers. Raw domestic wastewater produced a maximum of 400 ± 8 mW m−2 under fed batch conditions (wire-spacers), which is one of the highest power densities for this fuel. Over time the maximum power was reduced to 300 ± 10 mW m−2 and 275 ± 7 mW m−2 for the two anode compartments, with only slightly less power of 250 ± 20 mW m−2 obtained under continuous flow conditions. In fixed-resistance tests, the average COD removal was 57 ± 5% at a hydraulic retention time of 8 h. These results show that this modular MFC design can both simplify reactor construction and enable relatively high power generation from even relatively dilute wastewater.

  16. Role of the conjugated spacer in the optimization of second-order nonlinear chromophores

    Science.gov (United States)

    Pérez-Moreno, Javier; Clays, Koen; Kuzyk, Mark G.

    2009-08-01

    We investigate the role of the conjugated spacer in the optimization of the first hyperpolarizability of organic chromophores. We propose a novel strategy for the optimization of the first hyperpolarizability that is based on the variation of the degree of conjugation for the bridge that separates the donor and acceptors at the end of push-pull type chromophores. The correlation between the type of conjugated spacer and the experimental nonlinear performance of the chromophores is investigated and interpreted in the context of the quantum limits.

  17. Heterogeneous Diversity of Spacers within CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)

    Science.gov (United States)

    He, Jiankui; Deem, Michael W.

    2010-09-01

    Clustered regularly interspaced short palindromic repeats (CRISPR) in bacterial and archaeal DNA have recently been shown to be a new type of antiviral immune system in these organisms. We here study the diversity of spacers in CRISPR under selective pressure. We propose a population dynamics model that explains the biological observation that the leader-proximal end of CRISPR is more diversified and the leader-distal end of CRISPR is more conserved. This result is shown to be in agreement with recent experiments. Our results show that the CRISPR spacer structure is influenced by and provides a record of the viral challenges that bacteria face.

  18. Hole-transfer induced energy transfer in perylene diimide dyads with a donor-spacer-acceptor motif.

    Science.gov (United States)

    Kölle, Patrick; Pugliesi, Igor; Langhals, Heinz; Wilcken, Roland; Esterbauer, Andreas J; de Vivie-Riedle, Regina; Riedle, Eberhard

    2015-10-14

    We investigate the photoinduced dynamics of perylene diimide dyads based on a donor-spacer-acceptor motif with polyyne spacers of varying length by pump-probe spectroscopy, time resolved fluorescence, chemical variation and quantum chemistry. While the dyads with pyridine based polyyne spacers undergo energy transfer with near-unity quantum efficiency, in the dyads with phenyl based polyyne spacers the energy transfer efficiency drops below 50%. This suggests the presence of a competing electron transfer process from the spacer to the energy donor as the excitation sink. Transient absorption spectra, however, reveal that the spacer actually mediates the energy transfer dynamics. The ground state bleach features of the polyyne spacers appear due to the electron transfer decay with the same time constant present in the rise of the ground state bleach and stimulated emission of the perylene energy acceptor. Although the electron transfer process initially quenches the fluorescence of the donor it does not inhibit energy transfer to the perylene energy acceptor. The transient signatures reveal that electron and energy transfer processes are sequential and indicate that the donor-spacer electron transfer state itself is responsible for the energy transfer. Through the introduction of a Dexter blocker unit into the spacer we can clearly exclude any through bond Dexter-type energy transfer. Ab initio calculations on the donor-spacer and the donor-spacer-acceptor systems reveal the existence of a bright charge transfer state that is close in energy to the locally excited state of the acceptor. Multipole-multipole interactions between the bright charge transfer state and the acceptor state enable the energy transfer. We term this mechanism coupled hole-transfer FRET. These dyads represent a first example that shows how electron transfer can be connected to energy transfer for use in novel photovoltaic and optoelectronic devices.

  19. Salts slurries using in 'offshore' recent cementation in Campos Basin; Pastas salinas utilizadas em cimentacoes recentes 'offshore' na Bacia de Santos

    Energy Technology Data Exchange (ETDEWEB)

    Garzon, Ricardo [BJ Services, Macae, RJ (Brazil); Simao, Cristina Aiex; Sledz, Marcelo [PETROBRAS S.A., RJ (Brazil)

    2008-07-01

    PETROBRAS has recently begun active drilling on locations where the interest zone is below salt formations, which can be as thick as 2000 meters, formation that may contain mobile salts as taquihydryte. This paper refers to the slurries used on the first well drilled under those conditions and to slurry designs used in other similar wells. The challenge is to avoid the open hole closure by the taquihydryte before the next phase is drilled and cased. In order to do so, it was programmed to use a heavy spacer to maintain the wells stability for at least 30 days, due to hydrostatic pressure. This spacer and the heavy salt slurry (18,5 lb/gal) were used for the first time in Brazil. To cement the production casings, similar formulations were used, although with 15,8 lb/gal density slurries and a minimum of 10% bwow salt (NaCl). On the surface cementing operations, light slurries with sea water, salt, and, silicate and aluminate based additives, were designed and used, followed by the 15,8 lb/gal with 18% bwow salt slurry. Information about the different slurries are presented. (author)

  20. Chemical and Physical Reactions of Wellbore Cement under CO2 Storage Conditions: Effects of Cement Additives

    Science.gov (United States)

    Kutchko, B. G.; Strazisar, B. R.; Huerta, N.; Lowry, G. V.; Dzombak, D. A.; Thaulow, N.

    2008-12-01

    Sequestration of CO2 into geologic formations requires long-term storage and low leakage rates to be effective. Active and abandoned wells in candidate storage formations must be evaluated as potential leakage points. Wellbore integrity is an important part of an overall integrated assessment program being developed at NETL to assess potential risks at CO2 storage sites. Such a program is needed for ongoing policy and regulatory decisions for geologic carbon sequestration. The permeability and integrity of the cement in the well is a primary factor affecting its ability to prevent leakage. Cement must be able to maintain low permeability over lengthy exposure to reservoir conditions in a CO2 injection and storage scenario. Although it is known that cement may be altered by exposure to CO2, the results of ongoing research indicate that cement curing conditions, fluid properties, and cement additives play a significant role in the rate of alteration and reaction. The objective of this study is to improve understanding of the factors affecting wellbore cement integrity for large-scale geologic carbon sequestration projects. Due to the high frequency use of additives (pozzolan) in wellbore cement, it is also essential to understand the reaction of these cement-pozzolan systems upon exposure to CO2 under sequestration conditions (15.5 MPa and 50°C). Laboratory experiments were performed to determine the physical and chemical changes, as well as the rate of alteration of commonly used pozzolan-cement systems under simulated sequestration reservoir conditions, including both supercritical CO2 and CO2-saturated brine. The rate of alteration of the cement-pozzolan systems is considerably faster than with neat cement. However, the alteration of physical properties is much less significant with the pozzolanic blends. Permeability of a carbonated pozzolanic cement paste remains sufficiently small to block significant vertical migration of CO2 in a wellbore. All of the

  1. The fluid-compensated cement bond log

    Energy Technology Data Exchange (ETDEWEB)

    Nayfeh, T.H.; Leslie, H.D.; Wheelis, W.B.

    1984-09-01

    An experimental and numerical wave mechanics study of cement bond logs demonstrated that wellsite computer processing can now segregate wellbore fluid effects from the sonic signal response to changing cement strength. Traditionally, cement logs have been interpreted as if water were in the wellbore, without consideration of wellbore fluid effects. These effects were assumed to be negligible. However, with the increasing number of logs being run in completion fluids such as CaCl/sub 2/, ZnBr/sub 2/, and CaBr/sub 2/, large variations in cement bond logs became apparent. A Schlumberger internal paper showing that bond log amplitude is related to the acoustic impedance of the fluid in which the tool is run led to a comprehensive study of wellbore fluid effects. Numerical and experimental models were developed simulating wellbore geometry. Measurements were conducted in 5-, 7-, and 95/8-in. casings by varying the wellbore fluid densities, viscosities, and fluid types (acoustic impedance). Parallel numerical modeling was undertaken using similar parameters. The results showed that the bond log amplitude varied dramatically with the wellbore fluid's acoustic impedance; for example, there was a 70 percent increase in the signal amplitude for 11.5-lb/ gal CaCl/sub 2/ over the signal amplitude in water. This led to the development of a Fluid-Compensated Bond log that corrects the amplitude for acoustic impedance of varying wellbore fluids, thereby making the measurements more directly related to the cement quality.

  2. EFFECT OF NANOMATERIALS IN CEMENT MORTAR CHARACTERISTICS

    Directory of Open Access Journals (Sweden)

    WAIL N. AL-RIFAIE

    2016-09-01

    Full Text Available Concrete is considered as brittle materials and widely used due to high compressive strength but unfortunately having and has low tensile strength that has a numerous negative impacts on the lifespan of concrete made structures. Therefore, mechanical properties of cement mortar have been investigated experimentally using different types and ratios of nano material to improve the properties. Since the strength of the concrete is of high importance, different materials have been used to enhance the compressive and the tensile characteristics of the cement mortar compressive and tensile strength. Mainly, this objective has been implemented through using micro cement, micro sand, nano silica, and nano clay in developing a nano-cement mortar which can to improve the concrete for the constructional applications. The samples were prepared and tested under tensile and compressive mode according to ASTM-2011 regulations for concrete. The parameters that are taken consideration during the investigation were micro sand, micro cement, nano silica, developed nano clay, and naphthalene sulphonate as super- plasticizers. In general, it has been observed that the results showed a significant increase in both compressive and tensile strength of the mortar at early stages of hardening, where a maximum increase of 22% in the compressive strength was achieved , whereas 3.7 time increase in the compressive strength was recorded over the tradition levels of the concrete strength.

  3. Clinical applications of glass-ionomer cements.

    Science.gov (United States)

    McLean, J W

    1992-01-01

    The use of glass-ionomer cements in clinical dentistry is now well established. They have a number of unique properties, including adhesion to moist tooth structure, biological compatibility, and anticariogenic properties due to their fluoride release. Their use in treating early carious or erosion lesions has been widely investigated. Established techniques include fissure filling and sealing, restoration of class 5 erosion lesions without cavity preparation, and the internal occlusal fossa or tunnel restoration. The "sandwich" technique using glass-ionomer cements as "dentin substitutes" has enabled composite restorations to be used with greater safety where pulpal damage may occur. The future probably lies in using a laminate technique where materials that attach to dentin and form a biological seal can be covered by tougher and harder enamel veneers, thus mimicking the structure of the tooth. The deficiencies of glass-ionomer cements are well known, including lack of toughness, early water sensitivity, low abrasion resistance, and porosity leading to poor surface polish. Solving these problems is formidable, since inherently the strength of these cements is related to their water content. The clinician should be aware of these deficiencies and stay within the parameters of the techniques outlined in this paper. In particular, clinical success depends upon early protection of the cement from hydration or dehydration, and the current use of light-cured bonding agents has largely solved this problem.

  4. Stimuli-responsive cement-reinforced rubber.

    Science.gov (United States)

    Musso, Simone; Robisson, Agathe; Maheshwar, Sudeep; Ulm, Franz-Josef

    2014-05-14

    In this work, we report the successful development of a cement-rubber reactive composite with reversible mechanical properties. Initially, the composite behaves like rubber containing inert filler, but when exposed to water, it increases in volume and reaches a stiffness that is intermediate between that of hydrogenated nitrile butadiene rubber (HNBR) and hydrated cement, while maintaining a relatively large ductility characteristic of rubber. After drying, the modulus increases even further up to 400 MPa. Wet/drying cycles prove that the elastic modulus can reversibly change between 150 and 400 MPa. Utilizing attenuated total reflection Fourier transform infrared spectroscopy), we demonstrate that the high pH produced by the hydration of cement triggers the hydrolysis of the rubber nitrile groups into carboxylate anions. Thus, the salt bridges, generated between the carboxylate anions of the elastomer and the cations of the filler, are responsible for the reversible variations in volume and elastic modulus of the composite as a consequence of environmental moisture exposure. These results reveal that cement nanoparticles can successfully be used to accomplish a twofold task: (a) achieve an original postpolymerization modification that allows one to work with carboxylate HNBR (HXNBR) not obtained by direct copolymerization of carboxylate monomers with butadiene, and (b) synthesize a stimuli-responsive polymeric composite. This new type of material, having an ideal behavior for sealing application, could be used as an alternative to cement for oil field zonal isolation applications.

  5. Durability of Alite-calcium Barium Sulphoaluminate Cement

    Institute of Scientific and Technical Information of China (English)

    LU Lingchao; LU Zeye; LIU Shiquan; WANG Shoude; CHENG Xin

    2009-01-01

    The durability of the cement was mainly studied.Under 1.0 MPa of hydraulic pressure for 8 hours,water could penetrate completely through the sample made by portland cement,but could not penetrate through that by alite-barium sulphoaluminate cement.Under the condition of freezing and thawing cycle,the loss ratio of compressive strength of the cement was only about 17.3%at curing 28 d ages,but the loss of portland cement was as high as 29.5%.Alite-calcium bar-ium sulphoaluminate cement also has an excellent resistance to sulfate attack.The coefficients of resistance to sulfate attack of the cement exceeded 1.0.Meanwhile,the composition and microstructure of the hardened paste of alite-calcium barium sulphoaluminate cement were analyzed by XRD and SEM.

  6. Migration of ions in cement paste as studied by SIMS

    Energy Technology Data Exchange (ETDEWEB)

    Prince, K.E.; Aldridge, L.P. [Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, NSW (Australia); Rougeron, P. [Electricite de France Direction des Etudes et Recherches, Les Renardiers (France)

    1998-06-01

    Cement is often used to condition and encapsulate low level radioactive waste before it is disposed of in a repository. Ground water can attack these waste-forms by transporting aggressive ions into the cement paste and by removing radioactive ions from the paste. The extent of the attack will be governed by the diffusion of the ions in the cement paste. In this study we examine the migration of aggressive carbonate ions and inactive Cs and Sr through cement pastes. The use of SIMS for establishing the penetration depths and diffusion profiles for Cs and Sr in cement will be explored. The penetration profiles of Cs and Sr in a non-zeolite cement paste were examined and compared to those of a paste made with zeolite. The effects of the non-homogeneous nature of the cement was most pronounced in the study of the zeolite rich cement; Cs being preferentially accumulated in the zeolite material. (authors). 4 refs., 2 figs.

  7. Effect of aluminium phosphate as admixture on oxychloride cement

    Indian Academy of Sciences (India)

    M P S Chandrawat; R N Yadav

    2000-02-01

    The effect of admixing of aluminium phosphate on oxychloride cement in the matrix has been investigated. It is shown that aluminium phosphate retards the setting process of the cement and improves water-tightness.

  8. The use of limestone powder as an alternative cement replacement ...

    African Journals Online (AJOL)

    The use of limestone powder as an alternative cement replacement material: An ... The laboratory test results revealed that up to 15% replacement of clinker by fine ... Early strength, Limestone filler, Loss on ignition, Portland limestone cement ...

  9. Assessment of Pollution Potentialities of some Portland Cement 1H ...

    African Journals Online (AJOL)

    ABSTRACT: Chemical analysis of some Portland cement commonly used in Nigeria was carried out. All the cement studies ... Determination of Loss on Ignition. 1g of each ... the specifications of American Standard for testing materials (ASTM ...

  10. Present Situation and Perspective of Chinese Cement Industry

    Institute of Scientific and Technical Information of China (English)

    Gao Changming

    2003-01-01

    @@ Totally, there are 12 types of cement kiln pro-duction lines in China and running with a quite differenttechnical- economical levels. The cement productionof different types product lines in 1997 ~ 2002 is shownin Table 1.

  11. the use of limestone powder as an alternative cement replacement ...

    African Journals Online (AJOL)

    user

    properties of cement paste and hardened mortar in two ranges of blain fineness .... shrinkage as compared to siliceous additives. It is ... 100LSF (Lime. Saturation Factor) ..... production of Portland limestone cement were free from impurities or ...

  12. Characteristics of Portland blast-furnace slag cement containing cement kiln dust and active silica

    Directory of Open Access Journals (Sweden)

    A. Abdel Rahman

    2016-09-01

    Full Text Available This investigation dealt with the effect of active silica, silica fume (SF or rice husk ash (RHA, on the mechanical and physico-chemical characteristics of the hardened blended cement pastes made of Portland blast-furnace slag cement (PSC containing cement kiln dust (CKD cured under normal conditions. Two blends made of PSC and CKD, improved by SF and two blends made of PSC and CKD improved by RHA were investigated. Hardened blended cement pastes were prepared from each cement blend by using water/cement ratio (W/C of 0.30 by weight and hydrated for various curing ages of 1, 3, 7, 28 and 90 days at the normal curing conditions under tap water at room temperature. Each cement paste was tested for its physico-chemical and mechanical characteristics; these characteristics include: compressive strength and kinetics of hydration. The phase composition of the formed hydration products was identified using X-ray diffraction (XRD and differential thermal analysis (DTA. It was found that the partial substitution of PSC by 10% and 15% of CKD is associated with an increase in the rate of hydration and a subsequent improvement of compressive strength of hardened PSC–CKD pastes. In addition, the replacement of PSC, in PSC–CKD blends, by 5% active silica was accompanied by further improvement of the physico-mechanical characteristics of the hardened PSC–CKD pastes.

  13. Coupled effect of cement hydration and temperature on hydraulic behavior of cemented tailings backfill

    Institute of Scientific and Technical Information of China (English)

    WU Di; CAI Si-jing

    2015-01-01

    Cemented tailings backfill (CTB) is made by mixing cement, tailings and water together, thus cement hydration and water seepage flow are the two crucial factors affecting the quality of CTB. Cement hydration process can release significant amount of heat to raise the temperature of CTB and in turn increase the rate of cement hydration. Meanwhile, the progress of cement hydration consumes water and produces hydration products to change the pore structures within CTB, which further influences the hydraulic behavior of CTB. In order to understand the hydraulic behavior of CTB, a numerical model was developed by coupling the hydraulic, thermal and hydration equations. This model was then implemented into COMSOL Multiphysics to simulate the evolutions of temperature and water seepage flow within CTB versus curing time. The predicted outcomes were compared with correspondent experimental results, proving the validity and availability of this model. By taking advantage of the validated model, effects of various initial CTB and curing temperatures, cement content, and CTB's geometric shapes on the hydraulic behavior of CTB were demonstrated numerically. The presented conclusions can contribute to preparing more environmentally friendly CTB structures.

  14. Exposure to cement dust at a Portland cement factory and the risk of cancer.

    Science.gov (United States)

    Vestbo, J; Knudsen, K M; Raffn, E; Korsgaard, B; Rasmussen, F V

    1991-01-01

    The relation between exposure to cement dust and cancer was examined in a population of 546 cement workers and a reference population of 858 randomly sampled men of similar age and area of residence. In 1974 all men gave lifelong occupational and smoking histories; information on incidence of cancer in the period 1974-85 was obtained from the Danish Cancer Registry. No increased risk of overall cancer was found among cement workers. Among men with more than 20 years exposure to cement dust, 14 cases of respiratory cancer were observed (observed/expected (O/E) 1.52, 95% confidence interval (95% CI) 0.90-2.57) when compared with all Danish men. Men with 1-20 years exposure had O/E 1.14 (95% CI 0.59-2.19) based on nine cases of cancer. After excluding all men with documented exposure to asbestos during employment in an asbestos cement factory no increased risk of overall cancer or respiratory cancer was found among cement workers compared with white collar workers from the local reference population, using a Cox regression model controlling for age and smoking habits. Relative risks were 0.5 (95% CI 0.1-1.5) and 1.0 (95% CI 0.4-2.6) for men with 1-20 and more than 20 years of exposure to cement dust respectively compared with white collar workers. PMID:1772795

  15. Sequence analysis of rDNA intergenic spacer region (IGS) as a tool for phylogenetic studies in Trichoderma spp.

    Institute of Scientific and Technical Information of China (English)

    Mercatelli Elisabetta; Pecchia Susanna; Ciliegi Sandro; Vannacci Giovanni

    2004-01-01

    @@ Different from ribosomal genes, which contain highly conserved sequences that are detected in all organisms, the intergenic spacer of rDNA (IGS) appears to be the most rapidly-evolving spacer region. For this reason we tested this region for phylogenetic studies.

  16. pH-dependent phase behavior of carbohydrate-based gemini surfactants. Effect of the length of the hydrophobic spacer

    NARCIS (Netherlands)

    Klijn, Jaap E.; Stuart, Marc C. A.; Scarzello, Marco; Wagenaar, Anno; Engberts, Jan B. F. N.

    2006-01-01

    The phase behavior of a series of carbohydrate-based gemini surfactants with varying spacer lengths was studied using static and dynamic light scattering between pH 2 and 12. Cryo-electron microscopy pictures provide evidence for the different morphologies present in solution. The spacer length of

  17. Effect of electrostatic charge in plastic spacers on the lung delivery of HFA-salbutamol in children

    DEFF Research Database (Denmark)

    Anhøj, J; Bisgaard, H; Lipworth, B J

    1999-01-01

    was delivered on 3 different study days from plastic spacers with mouthpiece. Pre-treatment of the spacers differed between study days: (a) Non-electrostatic 350 ml Babyhaler (coated with benzalkonium chloride) (b) New 350 ml Babyhaler (rinsed in water), and (c) New 145 ml AeroChamber (rinsed in water). Plasma...

  18. Interference-driven spacer acquisition is dominant over naive and primed adaptation in a native CRISPR-Cas system

    NARCIS (Netherlands)

    Staals, Raymond H.J.; Jackson, Simon A.; Biswas, Ambarish; Brouns, Stan J.J.; Brown, Chris M.; Fineran, Peter C.

    2016-01-01

    CRISPR-Cas systems provide bacteria with adaptive immunity against foreign nucleic acids by acquiring short, invader-derived sequences called spacers. Here, we use high-throughput sequencing to analyse millions of spacer acquisition events in wild-type populations of Pectobacterium atrosepticum.

  19. Unusual low-energy near-infrared bands for ferrocenyl-naphthalimide donor-acceptor dyads with aromatic spacer groups

    DEFF Research Database (Denmark)

    Tagg, Tei; Kjærgaard, Henrik Grum; Lane, Joseph R.

    2015-01-01

    Time-dependent density functional theory (TDDFT) calculations for a series of donor-spacer-acceptor (D-S-A) molecules with phenyl (1), biphenyl (2), and anthryl (3) spacers interpolated between the ferrocenylalkene donor and -C≡C-4-naphthalimido acceptor components predicted the presence of weak,...

  20. A Study of Neutronics Effects of the Spacer Grids in a Typical PWR via Monte Carlo Calculation

    Directory of Open Access Journals (Sweden)

    Xuan Bach Tran

    2016-02-01

    Full Text Available Spacer grids play an important role in maintaining the proper form of the fuel assembly structure and ensuring the safety of reactor core design. This study applies the Monte Carlo method to the analysis of the neutronics effects of spacer grids in a typical pressurized water reactor (PWR. The core problem used to analyze the neutronics effects of spacer grids is a modified version of Korea Advanced Institute of Science and Technology benchmark problem 1B, based on an Advanced Power Reactor 1400 (APR1400 core model. The spacer grids are modeled and added to this test problem in various ways. Then, by running MCNP5 for all cases of spacer grid modeling, some important numerical results, such as the effective multiplication factor, the spatial distributions of neutron flux, and its energy spectrum are obtained. The numerical results of each case of spacer grid modeling are analyzed and compared to assess which type has more advantages in accuracy of numerical results and effectiveness in terms of geometry building. The conclusion is that the most realistic modeling for Monte Carlo calculation is the “volume-preserving” streamlined heterogeneous spacer grids, but the “banded” dissolution spacer grids modeling is a more practical yet accurate model for routine (deterministic analysis.

  1. STUDY ON HIGH CONTENT OF BLENDS IN CEMENT

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The technology of activation by a]dding few activators(<1%) to increase the amount of blends in cement was investigated.The results show that outer activation has a remarkable effect on improving the physical properties of slag cement,flyash cement and volcanic cement.For example,the compressive strength was increased by 5-10 MPa.Morever,the application of activation is beneficial to grind-aiding,early strength and water-reducing etc.

  2. Comparison of creep of the cement pastes included fly ash

    Directory of Open Access Journals (Sweden)

    Padevět Pavel

    2017-01-01

    Full Text Available The paper is devoted to comparison of creep of cement pastes containing fly ash admixture. The size of creep in time depends on the amount of components of the cement paste. Attention is paid to the content of classical fly ash in cement paste and its impact on the size of creep. The moisture of cement pastes is distinguished because it significantly affects the rheological properties of the material.

  3. Heavy cement slurries; Pastas pesadas de cimento

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Francisco Avelar da; Conceicao, Antonio C. Farias [PETROBRAS, XX (Brazil). Distrito de Perfuracao do Nordeste. Div. de Tecnicas de Perfuracao; Marins, Carlos Cesar Silva [PETROBRAS, XX (Brazil). Dept. de Perfuracao. Div. de Revestimento e Cimentacao

    1989-12-31

    When going deeper in a high pressure well, the only way to successfully cement your casing or linear is through the use of heavy cement slurry. In 1987 PETROBRAS geologists presented to the Drilling Department a series of deep, hot and high pressure wells to be drilled. The Casing and Cement Division of this department then started a program to face this new challenge. This paper introduces the first part of this program and shows how PETROBRAS is dealing with heavy weight slurries. We present the slurry formulations tested in laboratory, the difficulties found in mixing them in the field, rheology measurements, API free water and API fluid loss from both laboratory and field samples. (author) 3 tabs.

  4. Performance of cemented coal gangue backfill

    Institute of Scientific and Technical Information of China (English)

    ZHANG Qin-li; WANG Xin-min

    2007-01-01

    Possibility of cemented gangue backfill was studied with gangue of Suncun Coal Mine, Xinwen Coal Group, Shandong,and fly ash of nearby thermal power plant, in order to treat enormous coal gangue on a large scale and to recovery safety coal pillars.The results indicate that coal gangue is not an ideal aggregate for pipeline gravity flow backfill, but such disadvantages of gangue as bad fluidity and serious pipe wear can be overcome by addition of fly ash. It is approved that quality indexes such as strength and dewatering ratio and piping feature of slurry can satisfy requirement of cemented backfill if mass ratio of cement to fly ash to gangue higher middle and long term comprehensive strength.

  5. Cementing Properties of Oil Shale Ash

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The oil crisis has prompted renewed interest in direct burning of oil shale as an alternative energy source.A major problem in this process is the large portion of ash produced.The cementing properties of this ash were investigated to determine its applicability as a building material.By means of XRD, IR, NMR and ICP, we have studied the effects of burning temperature on the reactivity of ash.Maximum reactivity was obtained with ash samples produced at 700 °C to 900 °C.In this range, the strength of oil-shale-based material, with properties similar to cement, which is composed of oil shale and several other kinds of solid wastes, can achieve the standard of 42.5# cement.Our study has provided an experimental foundation and theoretical base for a massive utilization of oil shale.

  6. Microstructure and Properties of Activated Slag Cement

    Institute of Scientific and Technical Information of China (English)

    GUO Jun-cai; XIANG Xin; XU Yan-wu

    2004-01-01

    Activation of theslag cement was performed using a composite activator. Experimental resultsshow that the performance of the cement is remarkably improved. The fineness and specific surface area of the ce-ment are increased by 23.7% and 1.4% , and 3d flexural strength and compressive strength are enhanced by20.9% and 22.9% , respectively. Microstructure and phase composition of the hydrates were analysed by X- raydiffraction(XRD) and scanning electron microscopy(SEM). The results indicate that Ca( OH)2 in the hydratesdecrease obviously. The morphology of the other hydrates appears to be flocculent, with a dense structure. The im-provements of the properties is related to the microstructural changes.

  7. Experimental techniques for cement hydration studies

    Directory of Open Access Journals (Sweden)

    Andreas Luttge

    2011-10-01

    Full Text Available Cement hydration kinetics is a complex problem of dissolution, nucleation and growth that is still not well understood, particularly in a quantitative way. While cement systems are unique in certain aspects they are also comparable to natural mineral systems. Therefore, geochemistry and particularly the study of mineral dissolution and growth may be able to provide insight and methods that can be utilized in cement hydration research. Here, we review mainly what is not known or what is currently used and applied in a problematic way. Examples are the typical Avrami approach, the application of Transition State Theory (TST to overall reaction kinetics and the problem of reactive surface area. Finally, we suggest an integrated approach that combines vertical scanning interferometry (VSI with other sophisticated analytical techniques such as atomic force microscopy (AFM and theoretical model calculations based on a stochastic treatment.

  8. Pore structure in blended cement pastes

    DEFF Research Database (Denmark)

    Canut, Mariana Moreira Cavalcanti

    Supplementary cementitious materials (SCMs), such as slag and fly ash, are increasingly used as a substitute for Portland cement in the interests of improvement of engineering properties and sustainability of concrete. According to studies improvement of engineering properties can be explained...... supplement each other. Cement pastes (w/b=0.4) with and without slag and fly ash cured at two moisture (sealed and saturated) and temperature (20 and 55ºC) conditions were used to investigate the combined impact of SCMs addition and curing on the pore structure of pastes cured up to two years. Also...... volume and threshold pore size were found when comparing with plain cement paste at the same curing conditions. The porosity methods MIP, LTC and SEM have been shown to be suitable to characterise pore parameters of the pastes. MIP is a simple and fast method which covers a large range of pore sizes...

  9. Application of Carbonate Looping to Cement Industry

    DEFF Research Database (Denmark)

    Lin, Weigang; Illerup, Jytte Boll; Dam-Johansen, Kim

    2012-01-01

    In the present work, cycle experiments of different types of limestone, cement raw meal and a mixture of limestone and clay were carried out in laboratory scale setups at more realistic conditions (i.e. calcination temperature is 950°C and CO2 concentration is 80%) to simulate the performance...... with an increase in the CO2 partial pressure during calcination, indicating enhancement of sintering by the presence of CO2. As sorbents, cement raw meal and the mixture of limestone and clay show a similar trend as limestone with respect to the decay of the CO2 carrying capacity and this capacity is lower than...... that of limestone at the same conditions in most cases. SEM and XRD analyses indicate that a combination of severe sintering and formation of calcium silicates attributes to the poor performance of the cement raw meal....

  10. Organic Additive Implantation onto Cement Hydration Products

    Institute of Scientific and Technical Information of China (English)

    ZHU Jipeng; LI Zongjin; YANG Ruochong; ZHANG Yamei

    2014-01-01

    In polymer modified cementitious materials, it is hard to set up a chemical connection between the added polymer and the cement moiety. In this study FS (functional silane) was adopted to form this connection as a bridge component which has the functional group forming bonds with polymer. To testify the connection between FS and cement moiety, Q2/Q1 ratio (Qx:intensity ratio) investigation was carried out by the means of quantitative solid state 29Si MAS NMR. The results show that the Q2/Q1 ratio has increased with the addition of FS which indicates that the silicon chain length has increased, and the quantity of silicon atoms at site of Q2, chain site, has enhanced, showing that the silicon atom of FS has connected to the silicon chain of cement moiety by the bond“-Si-O-Si-”formation.

  11. Recovery of knee mobility after a static or mobile spacer in total knee infection

    NARCIS (Netherlands)

    Brunnekreef, J.J.; Hannink, G.; Mde, W. Malefijt

    2013-01-01

    The purpose of the study was to compare the recovery of knee mobility after two-stage revision of an infected total knee arthroplasty using a static or mobile spacer. At 12 months follow-up, none of the patients had a recurrent infection of their new prosthesis. Knee flexion was lower in the static

  12. Treatment of an old infection in a total hip replacement with an interim spacer prosthesis.

    Science.gov (United States)

    Zilkens, K W; Casser, H R; Ohnsorge, J

    1990-01-01

    When treating a septic hip-joint prosthesis with bone loss of the proximal femur secondary to osteomyelitis, we implanted a specially designed prosthesis to act as a local antibiotic and spacer between the acetabulum and femur until the infection abated. Arthroplasty could then be carried out with no trouble and there was no recurrence of infection.

  13. Bending of the Flexible Spacer Chain of Gemini Surfactant Induced by Hydrophobic Interaction

    Institute of Scientific and Technical Information of China (English)

    YOU,Yi; JIANG,Rong; LING,Tingting; ZHAO,Jianxi

    2009-01-01

    In order to understand the special role of the flexible alkylene spacer of gemini surfactant in the self-assembly,three gemini surfactants,alkylene-α,ω-bis(didodecylmethylammonium bromide)that is designated as 2C12-s-2C12·2Br (s=3,6,8),were synthesized.When the spread films of 2C12-s-2C12·2Br on the surface of water were con-structed,they form the dense layer of the alkyl tails owing to four dodecyl chains per molecule.This induced the bending of the spacer chain toward the air-side at the s smaller than that of C12-s-C12·2Br adsorbed on the air/water interface owing to the enhanced hydrophobic interaction between the alkyl tails and the spacer chain, where C12-s-C12·2Br has only two alkyl tails per molecule. Conclusively.,the enhanced hydrophobic interaction between the alkyl tails and the spacer chain can effectively induce the bending of the latter toward the air-side.

  14. Mechanical Properties Of 3D-Structure Composites Based On Warp-Knitted Spacer Fabrics

    Directory of Open Access Journals (Sweden)

    Chen Si

    2015-06-01

    Full Text Available In this paper, the mechanical properties (compression and impact behaviours of three-dimension structure (3D-structure composites based on warp-knitted spacer fabrics have been thoroughly investigated. In order to discuss the effect of fabric structural parameters on the mechanical performance of composites, six different types of warp-knitted spacer fabrics having different structural parameters (such as outer layer structure, diameter of spacer yarn, spacer yarn inclination angle and thickness were involved for comparison study. The 3D-structure composites were fabricated based on a flexible polyurethane foam. The produced composites were characterised for compression and impact properties. The findings obtained indicate that the fabric structural parameters have strong influence on the compression and impact responses of 3D-structure composites. Additionally, the impact test carried out on the 3D-structure composites shows that the impact loads do not affect the integrity of composite structure. All the results reveal that the product exhibits promising mechanical performance and its service life can be sustained.

  15. Aerosol delivery from spacers in wheezy infants: a daily life study

    NARCIS (Netherlands)

    H.M. Janssens (Hettie); E.M. Heijnen; V.M. de Jong; W.C.J. Hop (Wim); W.P. Holland (Wim); J.C. de Jongste (Johan); H.A.W.M. Tiddens (Harm)

    2000-01-01

    textabstractThe aims of this study were to assess and compare dose delivery and dose variability of pressurized metered dose inhalers (pMDI)/spacers in wheezy infants in daily life and to investigate factors influencing aerosol delivery. In an open randomized crossover

  16. Electrochemical behavior and dioxygen reactivity of tripodal dinuclear copper complexes linked by unsaturated rigid spacers.

    Science.gov (United States)

    Gomila, Antoine; Le Poul, Nicolas; Kerbaol, Jean-Michel; Cosquer, Nathalie; Triki, Smaïl; Douziech, Bénédicte; Conan, Françoise; Le Mest, Yves

    2013-02-14

    New dinucleating ligands based on two tripodal tris(2-pyridylmethyl)amine (TMPA) units linked by a series of delocalized π-electrons spacers have been synthesized. Their di-Cu(II) complexes have been prepared and structurally characterized. As compared to the corresponding monotopic complexes, these dinuclear Cu(II) complexes reveal spectroscopic and voltammetric features ascribable to weakly perturbed electronic interactions. In the case of the anthracenyl spacer, observation both in the solid and in solution suggests that the existence of intramolecular π-π stacking interactions influences the geometry of the complex and hence its electronic properties. The bis-Cu(I) complexes were prepared electrochemically. In the specific case of the complex bearing a mono-alkyne spacer, addition of dioxygen in acetonitrile leads to the slow formation of a trans-μ-1,2 peroxo Cu(2) complex which shows good stability at 268 K (t(1/2) = 240 s). Analysis of the kinetics of the peroxo formation by UV-vis spectroscopy suggests that the increased activation barrier for intramolecular binding of dioxygen is due to the rigidity of the spacer.

  17. Usefulness of a radiolucent spacer in radiation therapy for cancer of the tongue

    Energy Technology Data Exchange (ETDEWEB)

    Yokoi, Motoo (Nagoya City Univ. (Japan). Hospital); Ito, Yoshiyuki; Fuwa, Nobukazu; Kato, Eriko; Murao, Takayuki; Morita, Kozo

    1993-05-01

    For the purpose of preventing osteonecrosis following interstitial irradiation for tongue cancer, a Radiolucent Spacer was prepared with the intention of reducing bone dose by keeping the mandible at a distance from the source. Because of its radiolucency, the Spacer made of silicone enables to perform X-P while inserted, and more exact dose calculation. For 6 cases in which 8 mm-spacer was used, dose reduction rate for surface of lower gingiva corresponded to 42.3%, average of tumor dose for TDF. For 51 cases in which the observation of course was practicable for 2 years--9 years and 4 months, averaging 5 years and 7 months, the incidence of osteonecrosis was 0%, and therefore, Spacer of not less than 8 mm-thickness is thought useful as prosthesis. Extraction of the tooth was done at the start of irradiation, but the healing course was always favorable. The most aseptic possible alveolectomy and complete closure of the wound are necessary for tooth extraction. (author).

  18. Development of Finite Element Model for the Static Buckling Behavior of the Spacer Grid

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Young Ik; Park, Nam Gyu; Kim, Kyoung Ju; Suh, Jung Min [Kepco Nuclear Fuel, Daejeon (Korea, Republic of)

    2013-10-15

    In this study, finite element model was proposed to evaluate the buckling characteristics and structural behavior of partial spacer grids. A two-dimensional model was developed to simplify a real spacer gird model and save analysis time. And it was validated for comparison with experimental tests. A non-linear analysis method was introduced to perform realistic simulation. Later, the buckling analysis of the full size grid will be performed based on the analysis results of partial spacer grids. A study was conducted to develop the simplified model of a spacer grid and provide a prediction of buckling behavior. The FE analysis results are quite similar to the experimental tests. · The deformed geometry of FE model after compression is consistent and very similar to that of real situation, and the non-linear analysis method used in this model can simulate buckling and post-buckling behavior well. · The buckling strength obtained by FEM shows a very good agreement with the physical tests.

  19. Aerosol delivery from spacers in wheezy infants: a daily life study

    NARCIS (Netherlands)

    H.M. Janssens (Hettie); E.M. Heijnen; V.M. de Jong; W.C.J. Hop (Wim); W.P. Holland (Wim); J.C. de Jongste (Johan); H.A.W.M. Tiddens (Harm)

    2000-01-01

    textabstractThe aims of this study were to assess and compare dose delivery and dose variability of pressurized metered dose inhalers (pMDI)/spacers in wheezy infants in daily life and to investigate factors influencing aerosol delivery. In an open randomized crossover

  20. Effect of spacer dielectric engineering on Asymmetric Source Underlapped Double Gate MOSFET using Gate Stack

    Science.gov (United States)

    Chattopadhyay, Ankush; Dasgupta, Arpan; Das, Rahul; Kundu, Atanu; Sarkar, Chandan K.

    2017-01-01

    In this paper, the use of high-k spacers in a source underlapped nMOSFET is explored. The effects have been reported by varying the dielectric constant of the spacer from 3.9 to 22.5 and the study includes a comparison of analog parameters such as transconductance, transconductance generation factor, intrinsic gain, and RF parameters such as parasitic capacitances, resistances, and cut-off frequency. The RF parameters are calculated using the Non-Quasi Static (NQS) Approach which is required for sub 20 nm technology node. The device with high-k spacers features an improvement of 33% in DIBL, significantly increases the on current and reducing the off current by 60%. However, there is a slight compromise in the RF performance of the device, owing to an increase in intrinsic capacitance by about 0.35 fF. The Voltage Transfer Characteristics (VTC) and AC gain analysis of the circuit is also done in this paper. The circuit performance using single stage amplifier with the proposed device as the driver MOS has been analysed. High-k spacers also account for 19% improvement in small signal gain when used in a single stage amplifier circuit.

  1. The Interspinous Spacer: A New Posterior Dynamic Stabilization Concept for Prevention of Adjacent Segment Disease

    Directory of Open Access Journals (Sweden)

    Antoine Nachanakian

    2013-01-01

    Full Text Available Introduction. Posterior Dynamic stabilization using the interspinous spacer device is a known to be used as an alternative to rigid fusion in neurogenic claudication patients in the absence of macro instability. Actually, it plays an important in the management of adjacent segment disease in previously fused lumbar spine. Materials and Method. We report our experience with posterior dynamic stabilization using an interspinous spacer. 134 cases performed in our institution between September 2008 and August 2012 with different lumbar spine pathologies. The ages of our patients were between 40 and 72 years, with a mean age of 57 years. After almost 4 years of follow up in our patient and comparing their outcome to our previous serious we found that in some case the interspinous distracter has an important role not only in the treatment of adjacent segment disease but also in its prevention. Results and Discussion. Clinical improvement was noted in ISD-treated patients, with high satisfaction rate. At first, radicular pain improves with more than 3/10 reduction of the mean score on visual analog scale (VAS. In addition, disability score as well as disc height and lordotic angle showed major improvement at 3 to 6 months post operatively. And, no adjacent segment disease was reported in the patient operated with interspinous spacer. Conclusion. The interspinous spacer is safe and efficient modality to be used not only as a treatment of adjacent segment disease but also as a preventive measure in patients necessitating rigid fusion.

  2. A New Pyrene-Spacer-Maleimide Dyad for Sensing Molecules with One or Two Thiol Groups

    Institute of Scientific and Technical Information of China (English)

    WANG,Zhuo; ZHANG,De-Qing; ZHU,Dao-Ben

    2006-01-01

    A new pyrene-spacer-maleimide dyad 1 was used to selectively detect cysteine in the presence of other amino acids, and sequentially react with dithiols to generate the molecule with two pyrene units showing typical excimer fluorescence. Accordingly, dyad 1 was able to differentiate molecules with one or two thiol groups.

  3. Structural analysis of two length variants of the rDNA intergenic spacer from Eruca sativa.

    Science.gov (United States)

    Lakshmikumaran, M; Negi, M S

    1994-03-01

    Restriction enzyme analysis of the rRNA genes of Eruca sativa indicated the presence of many length variants within a single plant and also between different cultivars which is unusual for most crucifers studied so far. Two length variants of the rDNA intergenic spacer (IGS) from a single individual E. sativa (cv. Itsa) plant were cloned and characterized. The complete nucleotide sequences of both the variants (3 kb and 4 kb) were determined. The intergenic spacer contains three families of tandemly repeated DNA sequences denoted as A, B and C. However, the long (4 kb) variant shows the presence of an additional repeat, denoted as D, which is a duplication of a 224 bp sequence just upstream of the putative transcription initiation site. Repeat units belonging to the three different families (A, B and C) were in the size range of 22 to 30 bp. Such short repeat elements are present in the IGS of most of the crucifers analysed so far. Sequence analysis of the variants (3 kb and 4 kb) revealed that the length heterogeneity of the spacer is located at three different regions and is due to the varying copy numbers of repeat units belonging to families A and B. Length variation of the spacer is also due to the presence of a large duplication (D repeats) in the 4 kb variant which is absent in the 3 kb variant. The putative transcription initiation site was identified by comparisons with the rDNA sequences from other plant species.

  4. Response of an annular electrostatic probe for a right cylindrical spacer

    DEFF Research Database (Denmark)

    Johansson, Torben; MacAllister, I. W.

    2002-01-01

    The response of an annular electrostatic probe mounted in an electrode is examined with reference to a right cylindrical spacer. The study involves using the probe λ function to derive characteristic parameters. These parameters enable the response of the probe to different charge distributions...

  5. Dynamic simulation of universal spacer in Dynesys dynamic stabilization system for human vertebra

    Institute of Scientific and Technical Information of China (English)

    Sung-Min KIM; In-Chul YANG; Seung-Yeol LEE; Sung-Youn CHO

    2009-01-01

    The aim of this study is to analyze the simulated behavior of universal spacer in Dynesys dynamic stabilization system inserted in human vertebra. Dynesys, so-called "Dynamic neutralization system for the spine", dynamic stabilization system is a new concept in the surgical treatment of lower back pain recently. Universal spacer used as flexible material is to stabilize the spine and the material property of universal spacer is polycarbonate urethane. Universal spacer may apply different kinematic behaviors at implanted level in vertebra. Spinal range of motion(SROM) of inter-vertebra with installed Dynesys dynamic stabilization system was studied using Adams+LifeMOD as simulation software package. The vertebra model was set up to closely resemble the in-vivo conditions. Inter-vertebra rotations were measured by post processor of Adams and compared with the intact values. SROMs of the flexion, extension, lateral bending, and axial rotation of human virtual models were measured, where three spinal fixation systems such as rigid system, Dynesys system, and fused system were installed. As a result, the value of SROM is decreased in flexion-extension and lateral bending when the spinal fixation system is implanted. The movement of Dynesys system is similar to that of intact model by allowing the movement of lumbar. This means that the Dynesys system is proved to be safe and effective in the treatment of unstable spinal condition.

  6. Investigations in Number, Data, and Space[R]. What Works Clearinghouse Intervention Report

    Science.gov (United States)

    What Works Clearinghouse, 2013

    2013-01-01

    "Investigations in Number, Data, and Space"[R], published by Pearson Scott Foresman, is an activity-based K-5 mathematics curriculum designed to help students understand number and operations, geometry, data, measurement, and early algebra. Each instructional unit focuses on a particular content area and lasts from two to five-and-a-half…

  7. Investigations in Number, Data, and Space[R]. WWC Intervention Report

    Science.gov (United States)

    What Works Clearinghouse, 2009

    2009-01-01

    Investigations in Number, Data, and Space[R], published by Pearson Scott Foresman, is an activity-based K-5 mathematics curriculum designed to help students understand the fundamental ideas of number and operations, geometry, data, measurement, and early algebra. The curriculum encourages students to use prior knowledge to develop an understanding…

  8. Influence of the spacer on the inhibitory effect of different polycarbophil-protease inhibitor conjugates.

    Science.gov (United States)

    Marschütz, M K; Veronese, F M; Bernkop-Schnürch, A

    2001-09-01

    Within the present study various polycarbophil (PCP)-serine protease inhibitor conjugates were synthesized and the influence of different spacers on their inhibitory efficacy was evaluated in vitro. Results demonstrated that 4.2+/-0.15 units (n=3; +/-SD) of alpha-chymotrypsin were inhibited by 50% utilizing 0.86% (w/v) of a PCP-tetramethylenediamine (TMDA)-chymostatin 20:1 conjugate. In contrast, only 0.6+/-0.05 units (n=3; +/-SD) of alpha-chymotrypsin were inhibited by a corresponding PCP-poly(ethylene glycol) (PEG)-chymostatin conjugate. Inhibitory effects of PCP-TMDA-antipain and -elastatinal conjugates towards trypsin and elastase, respectively, were also significantly higher (P<0.05) than those of corresponding PCP-PEG-inhibitor conjugates. Hence, the great impact of the molecular size as well as the structure of the spacer on resulting polymer-inhibitor conjugates could be demonstrated. The small and rigid C4-spacer TMDA (molecular weight (MW) 161.1) was thereby shown to be highly advantageous over a long, hydrophilic and flexible PEG-diamine spacer (MW 3400). Results obtained should provide helpful basic knowledge for the development of mucoadhesive polymer-inhibitor conjugates used as auxiliary agents for the oral administration of peptide drugs.

  9. DYNAMIC CHARACTERISTICS OF LIQUID SLOSHING IN A TRANS-VERSELY VIBRATING SPHERICAL TANK WITH A SPACER UNDER LOW GRAVITY

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The dynamic characteristics of liquid sloshing in a transversely vibrating spherical tank with spacer under low gravity were investigated. By expanding the characteristic functions, the frequencies and velocity potentials of liquid free-sloshing were obtained. The dynamic equations and boundary conditions of liquid sloshing in the traverse vibrational spherical tank with spacer under low gravity were derived. By modifying the velocity potentials of liquid free-sloshing, the velocity potentials of liquid sloshing in the traverse vibrating spherical tank with a spacer were obtained. Furthermore, the forces and the moments acting on tank wall were given. The numerical results show when a spacer is inserted in the tank, the sloshing frequencies of liquid and the forces acting on tank wall will decrease, but the moment of force to the centre of the tank which is caused by the force of liquid acting on the spacer will occur.

  10. Velocity and turbulence distributions in wall subchannels of a road bundle in three axial planes downstream of a spacer grid

    Science.gov (United States)

    Rehme, K.

    1987-03-01

    The velocity, turbulence, and temperature distributions in nuclear fuel element bundles of nuclear reactors were investigated. The mean velocity, the wall shear stresses, and the turbulence were measured in two wall subchannels of a rod bundle of four parallel rods, arranged in a rectangular channel, for three axial planes. A spacer grid was inserted in the rod bundle, for ratios between the distance spacer grid/measuring plane and the hydraulic diameter (LIDh) of 40.4, 32.8 and 16.9. The Reynolds number was 145,000. The results show that the distributions of the velocity and the turbulence are affected by the spacer grid, already for LIDh = 40.4. The effects of the spacer grid increase with decreasing distance to the spacer grid.

  11. 3D laser inspection of fuel assembly grid spacers for nuclear reactors based on diffractive optical elements

    Science.gov (United States)

    Finogenov, L. V.; Lemeshko, Yu A.; Zav'yalov, P. S.; Chugui, Yu V.

    2007-06-01

    Ensuring the safety and high operation reliability of nuclear reactors takes 100% inspection of geometrical parameters of fuel assemblies, which include the grid spacers performed as a cellular structure with fuel elements. The required grid spacer geometry of assembly in the transverse and longitudinal cross sections is extremely important for maintaining the necessary heat regime. A universal method for 3D grid spacer inspection using a diffractive optical element (DOE), which generates as the structural illumination a multiple-ring pattern on the inner surface of a grid spacer cell, is investigated. Using some DOEs one can inspect the nomenclature of all produced grids. A special objective has been developed for forming the inner surface cell image. The problems of diffractive elements synthesis, projecting optics calculation, adjusting methods as well as calibration of the experimental measuring system are considered. The algorithms for image processing for different constructive elements of grids (cell, channel hole, outer grid spacer rim) and the experimental results are presented.

  12. Influence of Calcium Sulfate State and Fineness of Cement on Hydration of Portland Cements Using Electrical Measurement

    Institute of Scientific and Technical Information of China (English)

    WEI Xiaosheng; LI Zongjin; XIAO Lianzhen; THONG Wangfai

    2006-01-01

    The influence of calcium sulfate state and fineness of cement on hydration of Portland cement was studied using electrical resistivity measurement. The bulk resistivity curve of the paste from the abnormal cement mainly with hemihydrate had a characteristic abnormal peak and rapid increase in early period. The resistivity measurement technique can be used to discriminate abnormal setting. For normal cement with gypsum, the increase in fineness of the Portland cement decreases the minimum resistivity due to a higher ionic concentration and increases the 24 hour resistivity due to a reduction in macroscopic pore size. Thesetting time, compressive strength, pore structure of pastes made from different cements were carried out to compare the influence of water to cement ratio, calcium sulfate state and fineness. It is found that the electrical and mechanical properties are strongly affected by the initial porosity, the presence of hemihydrate or gypsum, and the fineness of cement.

  13. ASSESSMENT OF DEFORMATION AND STRENGTH OF SOILS STRENGTHENED BY CEMENTING

    Directory of Open Access Journals (Sweden)

    Sainov Mihail Petrovich

    2014-09-01

    Full Text Available Currently there are few studies of deformation and strength properties of loose soils strengthened by cementing. Based on the data of already arranged grout curtains it was determined that in cemented gravel-pebble soil there are 7...9 % of cement, which is less than in concrete. To assess deformation and strength of such soils it is possible to use the data of tests conducted by other authors, where the effect of cement contents on sand-cement mix properties was studied. Analysis of experimental data showed that cemented soil may be identified with concrete only with high content of cement (more than 10 %. At cement content 7...9 % in soil the strength deformation of cemented soil varies to a small extent. Its deformation becomes 2-3 times less. It greatly depends on compression stresses. The formulae are proposed which permit assessing the effect of compression and cement content on deformation of cemented soil. It is shown that strength of cemented soil is less than that even of the weakest concrete. It has a sufficiently high cohesion, but the friction angle is approximately the same as that of the initial soil.

  14. Glass Ionomer Cements with Improved Bioactive and Antibacterial Properties

    OpenAIRE

    2016-01-01

    Dental restorative cements are placed in a harsh oral environment where they are subjected to thermal shock, chemical degradation, and repeating masticatory force. The ideal restorative dental cements should have superior mechanical properties, chemical stability, aesthetic, good handling properties, biocompatibility, antibacterial properties, and preferably bioactivity. This thesis presents research on dental restorative cements with enhanced properties. The overall aim was to increase the b...

  15. The suitability of a supersulfated cement for nuclear waste immobilisation

    Science.gov (United States)

    Collier, N. C.; Milestone, N. B.; Gordon, L. E.; Ko, S.-C.

    2014-09-01

    Composite cements based on ordinary Portland cement are used in the UK as immobilisation matrices for low and intermediate level nuclear wastes. However, the high pore solution pH causes corrosion of some metallic wastes and undesirable expansive reactions, which has led to alternative cementing systems being examined. We have investigated the physical, chemical and microstructural properties of a supersulfated cement in order to determine its applicability for use in nuclear waste encapsulation. The hardened supersulfated cement paste appeared to have properties desirable for use in producing encapsulation matrices, but the high powder specific surface resulted in a matrix with high porosity. Ettringite and calcium silicate hydrate were the main phases formed in the hardened cement paste and anhydrite was present in excess. The maximum rate of heat output during hydration of the supersulfated cement paste was slightly higher than that of a 9:1 blastfurnace slag:ordinary Portland cement paste commonly used by the UK nuclear waste processing industry, although the total heat output of the supersulfated cement paste was lower. The pH was also significantly lower in the supersulfated cement paste. Aluminium hydroxide was formed on the surface of aluminium metal encapsulated in the cement paste and ettringite was detected between the aluminium hydroxide and the hardened cement paste.

  16. Control of in vivo mineral bone cement degradation.

    Science.gov (United States)

    Kanter, Britta; Geffers, Martha; Ignatius, Anita; Gbureck, Uwe

    2014-07-01

    The current study aimed to prevent the formation of hydroxyapatite reprecipitates in brushite-forming biocements by minimizing the availability of free Ca(2+) ions in the cement matrix. This was achieved by both maximizing the degree of cement setting to avoid unreacted, calcium-rich cement raw materials which can deliver Ca(2+) directly to the cement matrix after dissolution, and by a reduction in porosity to reduce Ca(2+) diffusion into the set cement matrix. In addition, a biocement based on the formation of the magnesium phosphate mineral struvite (MgNH4PO4·6H2O) was tested, which should prevent the formation of low-solubility hydroxyapatite reprecipitates due to the high magnesium content. Different porosity levels were fabricated by altering the powder-to-liquid ratio at which the cements were mixed and the materials were implanted into mechanically unloaded femoral defects in sheep for up to 10 months. While the higher-porosity brushite cement quantitatively transformed into crystalline octacalcium phosphate after 10 months, slowing down cement resorption, a lower-porosity brushite cement modification was found to be chemically stable with the absence of reprecipitate formation and minor cement resorption from the implant surface. In contrast, struvite-forming cements were much more degradable due to the absence of mineral reprecipitates and a nearly quantitative cement degradation was found after 10 months of implantation.

  17. 21 CFR 888.4220 - Cement monomer vapor evacuator.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cement monomer vapor evacuator. 888.4220 Section... (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4220 Cement monomer vapor evacuator. (a) Identification. A cement monomer vapor evacuator is a device intended for use during surgery to contain or...

  18. Experimental Investigation of Second Interface Cement Bond Evaluation

    Institute of Scientific and Technical Information of China (English)

    Che Xiaohua; Qiao Wenxiao

    2007-01-01

    Cement bond model wells (1:10 scaled-down) were made with a gradually degrading cement annulus for cement bond evaluation of the first interface (between the casing and the cement annulus) and the second interface (between the cement annulus and the formation).Experimental simulation on cement bond logging was carried out with these model wells.The correlation of acoustic waveforms,casing wave energy and free casing area before and after cement bonding of the second interface was established.The experimental results showed that the arrival of the casing waves had no relationship with the cement bonding of the second interface,but the amplitude of the casing head wave decreased obviously after the second interface was bonded.So,cement bonding of the second interface had little effect on the evaluation of the cement bond quality of the first interface by using casing head wave arrivals.Strong cement annulus waves with early arrivals were observed before the second interface was bonded,while obvious "formation waves" instead of cement annulus waves were observed after the second interface was bonded.

  19. 21 CFR 888.4230 - Cement ventilation tube.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cement ventilation tube. 888.4230 Section 888.4230...) MEDICAL DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4230 Cement ventilation tube. (a) Identification. A cement ventilation tube is a tube-like device usually made of plastic intended to be inserted...

  20. Research of dynamic mechanical performance of cement rock

    Institute of Scientific and Technical Information of China (English)

    WANG Qiang; WANG Tong; WANG Xiang-lin

    2007-01-01

    As Daqing Oilfield is developing oil layer with a big potential, the requirement for the quality of well cementation is higher than ever before. Cement rock is a brittle material containing a great number of microcracks and defects. In order to reduce the damage to cement ring and improve sealed cementing property at the interface, it is necessary to conduct research on the modification of the cement rock available. According to the principle of super mixed composite materials, various fillers are added to the ingredients of cement rock. Dynamic fracture toughness of cement rock will be changed under the influence of filler. In order to study the damage mechanism of the cement circle during perforation and carry out comprehensive experiments on preventing and resisting connection, a kind of comprehensive experiment equipment used to simulate perforation and multifunctional equipment for testing the dynamic properties of the material are designed. Experimental study of the dynamical mechanical performance of original and some improved cement rock and experiment used to simulate the well cementation and perforation are carried out. Standard for dynamical mechanical performance of the cement rock with fine impact resistance and mechanical properties of some improved cement rock are also given.

  1. 21 CFR 888.4210 - Cement mixer for clinical use.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cement mixer for clinical use. 888.4210 Section... (CONTINUED) MEDICAL DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4210 Cement mixer for clinical use. (a) Identification. A cement mixer for clinical use is a device consisting of a container intended for use in...

  2. Hydration of Portoguese cements, measurement and modelling of chemical shrinkage

    DEFF Research Database (Denmark)

    Maia, Lino; Geiker, Mette Rica; Figueiras, Joaquim A.

    2008-01-01

    Development of cement hydration was studied by measuring the chemical shrinkage of pastes. Five types of Portuguese Portland cement were used in cement pastes with . Chemical shrinkage was measured by gravimetry and dilatometry. In gravimeters results were recorded automatically during at least...

  3. Influence of surface pretreatment of fiber posts on cement delamination

    NARCIS (Netherlands)

    Jongsma, L.A.; Kleverlaan, C.J.; Feilzer, A.J.

    2010-01-01

    Objectives To evaluate the influence of post surface pretreatment on the delamination strength of different cements from a prefabricated FRC post tested in a three-point bending test. Methods Three cements were tested; RelyX Unicem, DC Core Automix, and Panavia F2.0. Per cement, 40 posts (D.T. Light

  4. Modeling the effect of spacers and biofouling on forward osmosis performance

    KAUST Repository

    Mosqueira Santillán, María José

    2014-11-01

    Currently, the most utilized desalination technology is reverse osmosis (RO), where a membrane is used as a physical barrier to separate the salts from the seawater, using high hydraulic pressure as driving force. A major problem in RO systems is biofouling, caused by severe growth of bacterial biofilms. Both, the need of an external energy input, as well as biofouling, impose a high cost on RO operation. Forward osmosis (FO) is an alternative membrane process that uses an osmotic pressure difference as driving force. FO uses a concentrated draw solution to generate high osmotic pressure, which extracts water across a semi permeable membrane from a feed solution. One of the main advantages of FO is the limited amount of external energy required to extract water from the feed solution. The objective of this research is the assessment of the impact of spacers, separating the membrane sheets, and biofouling on the FO system performance. This type of studies allow the optimization of membrane devices and operational conditions. For this, a two dimensional numerical model for FO systems was developed using computational fluid dynamics (CFD). This model allowed the evaluation of the impact of (i) spacers and (ii) biofilm, and (iii) the combined impact of spacers and biofilm on the performance of FO systems. The results obtained showed that the presence of spacers improved the performance of FO systems. Cavity configuration spacer gave the higher water flux across the membrane in clean systems; whereas for biofouled systems, the submerged configuration showed a better performance. In absence of spacers, the thickness or amount of biofilm is inversely proportional with the water flux. Furthermore, membrane surface coverage of the biofilm is more important than the amount of biofilm in terms of the impact on the performance. The numerical model can be adapted with other parameters (e.g. membrane and spacer thickness, feed and draw solution, solution concentration, etc.) to

  5. CO2 Capture for Cement Technology

    OpenAIRE

    2013-01-01

    Production of cement is an energy intensive process and is the source of considerable CO2emissions. Itis estimated that the cement industry contributes around 8% of total global CO2emissions. CO2is oneof the major greenhouse gases. In the atmosphere, the CO2concentration has increased from 310 ppmvin 1960 to 390 ppmv in 2012, probably due to human activity. A lot of research is being carried out forreducing CO2emissions from large stationary sources. Ofwhich, the carbonate looping process is ...

  6. Porosity and liquid absorption of cement paste

    DEFF Research Database (Denmark)

    Krus, M.; Hansen, Kurt Kielsgaard; Kunzel, H. M.

    1997-01-01

    be a slowing-down effect which is related to water because the absorption of organic liquids, such as hexane, is quite normal. Measurements of the porosity of hardened cement paste determined by helium pycnometry and water saturation show that water molecules can enter spaces in the microstructure which...... are not accessible to the smaller helium atoms. Considering the results of dilatation tests both before and after water and hexane saturation, it seems possible that a contraction of capillary pores due to moisture-related swelling of the cement gel leads to the non-linear water absorption over the square root...

  7. Durability of pulp fiber-cement composites

    Science.gov (United States)

    Mohr, Benjamin J.

    Wood pulp fibers are a unique reinforcing material as they are non-hazardous, renewable, and readily available at relatively low cost compared to other commercially available fibers. Today, pulp fiber-cement composites can be found in products such as extruded non-pressure pipes and non-structural building materials, mainly thin-sheet products. Although natural fibers have been used historically to reinforce various building materials, little scientific effort has been devoted to the examination of natural fibers to reinforce engineering materials until recently. The need for this type of fundamental research has been emphasized by widespread awareness of moisture-related failures of some engineered materials; these failures have led to the filing of national- and state-level class action lawsuits against several manufacturers. Thus, if pulp fiber-cement composites are to be used for exterior structural applications, the effects of cyclical wet/dry (rain/heat) exposure on performance must be known. Pulp fiber-cement composites have been tested in flexure to examine the progression of strength and toughness degradation. Based on scanning electron microscopy (SEM), environmental scanning electron microscopy (ESEM), energy dispersive spectroscopy (EDS), a three-part model describing the mechanisms of progressive degradation has been proposed: (1) initial fiber-cement/fiber interlayer debonding, (2) reprecipitation of crystalline and amorphous ettringite within the void space at the former fiber-cement interface, and (3) fiber embrittlement due to reprecipitation of calcium hydroxide filling the spaces within the fiber cell wall structure. Finally, as a means to mitigate kraft pulp fiber-cement composite degradation, the effects of partial portland cement replacement with various supplementary cementitious materials (SCMs) has been investigated for their effect on mitigating kraft pulp fiber-cement composite mechanical property degradation (i.e., strength and toughness

  8. Chloride ingress in cement paste and mortar

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, O.M.; Hansen, P.F.; Coats, A.M.; Glasser, F.P.

    1999-09-01

    In this paper chloride ingress in cement paste and mortar is followed by electron probe microanalysis. The influence of several paste and exposure parameters on chloride ingress are examined (e.g., water-cement ratio, silica fume addition, exposure time, and temperature). The measurements are modelled on Fick's law modified by a term for chloride binding. Inclusion of chloride binding significantly improves the profile shape of the modelled ingress profiles. The presence of fine aggregate and formation of interfacial transition zones at paste-aggregate boundaries does not significantly affect diffusion rates.

  9. Barriers and supports to implementation of MDI/spacer use in nine Canadian pediatric emergency departments: a qualitative study

    Directory of Open Access Journals (Sweden)

    Graham Ian D

    2009-10-01

    Full Text Available Abstract Background Despite recent research supporting the use of metered dose inhalers with spacer devices (MDI/spacers in pediatric emergency departments (PEDs for acute exacerbations of asthma, uptake of this practice has been slow. The objectives of this study were to determine the barriers and supports to implementing MDI/spacer research and to identify factors associated with early and late adoption of MDI/spacers in Canadian PEDs. Methods Using a comparative case study design, we classified nine tertiary care pediatric hospital PEDs based on their stage of implementation. Data were collected using focus group interviews with physicians, registered nurses (RNs, and respiratory therapists (RTs, and individual interviews with both patient care and medical directors at each site. Initial coding was based on the Ottawa Model of Research Use (OMRU categories of elements known to influence the uptake of innovations. Results One hundred and fifty healthcare professionals from nine different healthcare institutions participated in this study. Lack of leadership in the form of a research champion, a lack of consensus about the benefits of MDI/spacers among staff, perceived resistance from patients/parents, and perceived increased cost and workload associated with MDI/spacer use were the most prevalent barriers to the adoption of the MDI/spacer. Common strategies used by early-adopting sites included the active participation of all professional groups in the adoption process in addition to a well-planned and executed educational component for staff, patients, and families. Early adopter sites were also more likely to have the MDI/spacer included in a clinical protocol/pathway. Conclusion Potential barriers and supports to implementation have been identified that will help EDs adopt MDI/spacer use. Future interventions intended to increase MDI/spacer use in PEDs will need to be sensitive to the barriers identified in this study.

  10. Cement Formation:A Success Story in a Black Box: High Temperature Phase Formation of Portland Cement Clinker

    OpenAIRE

    2012-01-01

    Cement production has been subject to several technological changes, each of which requires detailed knowledgeabout the high multiplicity of processes, especially the high temperature process involved in the rotary kiln. This article gives an introduction to the topic of cement, including an overview of cement production, selected cement properties, and clinker phase relations. An extended summary of laboratory-scale investigations on clinkerization reactions, the most important reactions in ...

  11. Hydrogel Spacer Prospective Multicenter Randomized Controlled Pivotal Trial: Dosimetric and Clinical Effects of Perirectal Spacer Application in Men Undergoing Prostate Image Guided Intensity Modulated Radiation Therapy

    Energy Technology Data Exchange (ETDEWEB)

    Mariados, Neil, E-mail: nmariados@ampofny.com [Associated Medical Professionals of New York, Syracuse, New York (United States); Sylvester, John [21st Century Oncology, East Bradenton, Florida (United States); Shah, Dhiren [Western New York Urology Associates, Cancer Care of WNY, Cheektowaga, New York (United States); Karsh, Lawrence [The Urology Center of Colorado, Denver, Colorado (United States); Hudes, Richard [Chesapeake Urology Research Associates, The Prostate Center, Owings Mills, Maryland (United States); Beyer, David [Arizona Oncology Services Foundation, Phoenix, Arizona (United States); Kurtzman, Steven [Urological Surgeons of Northern California, Campbell, California (United States); Bogart, Jeffrey [The Research Foundation of State University of New York, SUNY Upstate Medical University, Syracuse, New York (United States); Hsi, R. Alex [Peninsula Cancer Center, Poulsbo, Washington (United States); Kos, Michael [Urology Nevada, Reno, Nevada (United States); Ellis, Rodney [University Hospitals Case Medical Center, Cleveland, Ohio (United States); Logsdon, Mark [Sutter Health Sacramento Sierra Region, Sutter Institute for Medical Research, Sacramento, California (United States); Zimberg, Shawn [Advanced Radiation Centers of New York, Lake Success, New York (United States); Forsythe, Kevin [Oregon Urology Institute, Springfield, Oregon (United States); Zhang, Hong [University of Rochester, Rochester, New York (United States); Soffen, Edward [CentraState Medical Center, Freehold, New Jersey (United States); Francke, Patrick [Carolina Regional Cancer Center, 21st Century Oncology, Myrtle Beach, South Carolina (United States); Mantz, Constantine [21st Century Oncology, Fort Meyers, Florida (United States); Rossi, Peter [Emory University, Atlanta, Georgia (United States); DeWeese, Theodore [The Johns Hopkins University, Baltimore, Maryland (United States); and others

    2015-08-01

    Purpose: Perirectal spacing, whereby biomaterials are placed between the prostate and rectum, shows promise in reducing rectal dose during prostate cancer radiation therapy. A prospective multicenter randomized controlled pivotal trial was performed to assess outcomes following absorbable spacer (SpaceOAR system) implantation. Methods and Materials: Overall, 222 patients with clinical stage T1 or T2 prostate cancer underwent computed tomography (CT) and magnetic resonance imaging (MRI) scans for treatment planning, followed with fiducial marker placement, and were randomized to receive spacer injection or no injection (control). Patients received postprocedure CT and MRI planning scans and underwent image guided intensity modulated radiation therapy (79.2 Gy in 1.8-Gy fractions). Spacer safety and impact on rectal irradiation, toxicity, and quality of life were assessed throughout 15 months. Results: Spacer application was rated as “easy” or “very easy” 98.7% of the time, with a 99% hydrogel placement success rate. Perirectal spaces were 12.6 ± 3.9 mm and 1.6 ± 2.0 mm in the spacer and control groups, respectively. There were no device-related adverse events, rectal perforations, serious bleeding, or infections within either group. Pre-to postspacer plans had a significant reduction in mean rectal V70 (12.4% to 3.3%, P<.0001). Overall acute rectal adverse event rates were similar between groups, with fewer spacer patients experiencing rectal pain (P=.02). A significant reduction in late (3-15 months) rectal toxicity severity in the spacer group was observed (P=.04), with a 2.0% and 7.0% late rectal toxicity incidence in the spacer and control groups, respectively. There was no late rectal toxicity greater than grade 1 in the spacer group. At 15 months 11.6% and 21.4% of spacer and control patients, respectively, experienced 10-point declines in bowel quality of life. MRI scans at 12 months verified spacer absorption. Conclusions: Spacer

  12. Effect of a spacer on pulmonary aerosol deposition from a jet nebuliser during mechanical ventilation.

    Science.gov (United States)

    Harvey, C. J.; O'Doherty, M. J.; Page, C. J.; Thomas, S. H.; Nunan, T. O.; Treacher, D. F.

    1995-01-01

    BACKGROUND--Several factors have been identified which improve nebulised aerosol delivery in vitro. One of these is the addition of a spacer to the ventilator circuit which improves aerosol delivery from a jet nebuliser to a model lung by approximately 30%. The current study was designed to demonstrate whether similar improvements could be demonstrated in vivo. METHODS--Ten patients (seven men) were studied during mechanical ventilation (Siemens Servo 900C) after open heart surgery. Aerosol was delivered using a Siemens Servo 945 nebuliser system (high setting) driving a System 22 Acorn jet nebuliser (Medic-Aid) containing 3 ml technetium-99m labelled human serum albumin (99mTc-HSA (50 micrograms); activity in the first nebulisation, 90 MBq; in the second nebulisation, 185 MBq). Central and peripheral lung aerosol deposition and the time to complete deposition were measured using a gamma camera and compared when the nebuliser was connected to the inspiratory limb using a simple T-piece or a 600 ml spacer. RESULTS--The addition of the spacer increased total lung deposition (mean (SD) percentage initial nebuliser activity) from 2.2 (0.7)% to 3 (0.8)%. There was no difference in the time required to complete nebulisation (18.2 min v 18.3 min respectively for T-piece and spacer) or in the retention of activity in the nebuliser (46.2% v 47.1% respectively). CONCLUSIONS--The combination of a spacer with a jet nebuliser increased lung deposition by 36% in mechanically ventilated patients and is a simple way of increasing drug deposition or reducing the amount of an expensive drug required for nebulisation. Images PMID:7886649

  13. Glass powder blended cement hydration modelling

    Science.gov (United States)

    Saeed, Huda

    The use of waste materials in construction is among the most attractive options to consume these materials without affecting the environment. Glass is among these types of potential waste materials. In this research, waste glass in powder form, i.e. glass powder (GP) is examined for potential use in enhancing the characteristics of concrete on the basis that it is a pozzolanic material. The experimental and the theoretical components of the work are carried out primarily to prove that glass powder belongs to the "family" of the pozzolanic materials. The chemical and physical properties of the hydrated activated glass powder and the hydrated glass powder cement on the microstructure level have been studied experimentally and theoretically. The work presented in this thesis consists of two main phases. The first phase contains experimental investigations of the reaction of glass powder with calcium hydroxide (CH) and water. In addition, it includes experiments that are aimed at determining the consumption of water and CH with time. The reactivity, degree of hydration, and nature of the pore solution of the glass powder-blended cement pastes and the effect of adding different ratios of glass powder on cement hydration is also investigated. The experiments proved that glass powder has a pozzolanic effect on cement hydration; hence it enhances the chemical and physical properties of cement paste. Based on the experimental test results, it is recommended to use a glass powder-to-cement ratio (GP/C) of 10% as an optimum ratio to achieve the best hydration and best properties of the paste. Two different chemical formulas for the produced GP C-S-H gel due to the pure GP and GP-CH pozzolanic reaction hydration are proposed. For the pure GP hydration, the produced GP C-S-H gel has a calcium-to-silica ratio (C/S) of 0.164, water-to-silica ratio (H/S) of 1.3 and sodium/silica ratio (N/S) of 0.18. However, for the GP-CH hydration, the produced GP C-S-H gel has a C/S ratio of 1

  14. Analysis of Chemical Composition of Portland Cement in Ghana: A Key to Understand the Behavior of Cement

    Directory of Open Access Journals (Sweden)

    Mark Bediako

    2015-01-01

    Full Text Available The performance of Portland cement in concrete or mortar formation is very well influenced by chemical compositions among other factors. Many engineers usually have little information on the chemical compositions of cement in making decisions for the choice of commercially available Portland cement in Ghana. This work analyzed five different brands of Portland cement in Ghana, namely, Ghacem ordinary Portland cement (OPC and Portland limestone cement (PLC, CSIR-BRRI Pozzomix, Dangote OPC, and Diamond PLC. The chemical compositions were analyzed with X-Ray Fluorescence (XRF spectrometer. Student’s t-test was used to test the significance of the variation in chemical composition between standard literature values and each of the commercial cement brands. Analysis of variance (ANOVA was also used to establish the extent of variations between chemical compositions and brand name of the all commercial Portland cement brands. Student’s t-test results showed that there were no significant differences between standard chemical composition values and that of commercial Portland cement. The ANOVA results also indicated that each brand of commercial Portland cement varies in terms of chemical composition; however, the specific brands of cement had no significant differences. The study recommended that using any brand of cement in Ghana was good for any construction works be it concrete or mortar formation.

  15. The suitability of a supersulfated cement for nuclear waste immobilisation

    Energy Technology Data Exchange (ETDEWEB)

    Collier, N.C., E-mail: nick.collier@sheffield.ac.uk [Immobilisation Science Laboratory, Department of Materials Science and Engineering, The University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom); Milestone, N.B. [Immobilisation Science Laboratory, Department of Materials Science and Engineering, The University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom); Callaghan Innovation, 69 Gracefield Road, PO Box 31310, Lower Hutt 5040 (New Zealand); Gordon, L.E. [Immobilisation Science Laboratory, Department of Materials Science and Engineering, The University of Sheffield, Mappin Street, Sheffield S1 3JD (United Kingdom); Geopolymer and Minerals Processing Group, Department of Chemical and Biomolecular Engineering, University of Melbourne, Parkville, Victoria 3010 (Australia); Ko, S.-C. [Holcim Technology Ltd, Hagenholzstrasse 85, CH-8050 Zurich (Switzerland)

    2014-09-15

    Highlights: • We investigate a supersulfated cement for use as a nuclear waste encapsulant. • High powder fineness requires a high water content to satisfy flow requirements. • Heat generation during hydration is similar to a control cement paste. • Typical hydration products are formed resulting in a high potential for waste ion immobilisation. • Paste pH and aluminium corrosion is less than in a control cement paste. - Abstract: Composite cements based on ordinary Portland cement are used in the UK as immobilisation matrices for low and intermediate level nuclear wastes. However, the high pore solution pH causes corrosion of some metallic wastes and undesirable expansive reactions, which has led to alternative cementing systems being examined. We have investigated the physical, chemical and microstructural properties of a supersulfated cement in order to determine its applicability for use in nuclear waste encapsulation. The hardened supersulfated cement paste appeared to have properties desirable for use in producing encapsulation matrices, but the high powder specific surface resulted in a matrix with high porosity. Ettringite and calcium silicate hydrate were the main phases formed in the hardened cement paste and anhydrite was present in excess. The maximum rate of heat output during hydration of the supersulfated cement paste was slightly higher than that of a 9:1 blastfurnace slag:ordinary Portland cement paste commonly used by the UK nuclear waste processing industry, although the total heat output of the supersulfated cement paste was lower. The pH was also significantly lower in the supersulfated cement paste. Aluminium hydroxide was formed on the surface of aluminium metal encapsulated in the cement paste and ettringite was detected between the aluminium hydroxide and the hardened cement paste.

  16. Development of an Improved Cement for Geothermal Wells

    Energy Technology Data Exchange (ETDEWEB)

    Trabits, George [Trabits Group, LLC, Wasilla, AK (United States)

    2015-04-20

    After an oil, gas, or geothermal production well has been drilled, the well must be stabilized with a casing (sections of steel pipe that are joined together) in order to prevent the walls of the well from collapsing. The gap between the casing and the walls of the well is filled with cement, which locks the casing into place. The casing and cementing of geothermal wells is complicated by the harsh conditions of high temperature, high pressure, and a chemical environment (brines with high concentrations of carbon dioxide and sulfuric acid) that degrades conventional Portland cement. During the 1990s and early 2000s, the U.S. Department of Energy’s Geothermal Technologies Office (GTO) provided support for the development of fly-ash-modified calcium aluminate phosphate (CaP) cement, which offers improved resistance to degradation compared with conventional cement. However, the use of CaP cements involves some operational constraints that can increase the cost and complexity of well cementing. In some cases, CaP cements are incompatible with chemical additives that are commonly used to adjust cement setting time. Care must also be taken to ensure that CaP cements do not become contaminated with leftover conventional cement in pumping equipment used in conventional well cementing. With assistance from GTO, Trabits Group, LLC has developed a zeolite-containing cement that performs well in harsh geothermal conditions (thermal stability at temperatures of up to 300°C and resistance to carbonation) and is easy to use (can be easily adjusted with additives and eliminates the need to “sterilize” pumping equipment as with CaP cements). This combination of properties reduces the complexity/cost of well cementing, which will help enable the widespread development of geothermal energy in the United States.

  17. Cytotoxicity evaluation of five different dual-cured resin cements used for fiber posts cementation

    Science.gov (United States)

    Dioguardi, M; Perrone, D; Troiano, G; Laino, L; Ardito, F; Lauritano, F; Cicciù, M; Muzio, L Lo

    2015-01-01

    Custom-cast posts and cores are usually used to treat endodontically treated teeth. However, several researches have underlined how these devices may be a much higher elastic modulus than the supporting dentine and the difference in the modulus could lead to stress concentrating in the cement lute, leading to failure. The role of the cement seems to play a fundamental role in order to transfer the strength during the chewing phases. Aim of this research is to record the rate of cytotoxicity of five different dual-cured resin cements used for fiber posts cementation. We tested the cytotoxicity of this five materials on MG63 osteoblast-like cells through two different methods: MTT ([3-4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide succinate) assay which tests for mitochondrial enzyme activity6 and xCELLigence® system. PMID:26309592

  18. Dental Cements for Luting and Bonding Restorations: Self-Adhesive Resin Cements.

    Science.gov (United States)

    Manso, Adriana P; Carvalho, Ricardo M

    2017-10-01

    Self-adhesive resin cements combine easy application of conventional luting materials with improved mechanical properties and bonding capability of resin cements. The presence of functional acidic monomers, dual cure setting mechanism, and fillers capable of neutralizing the initial low pH of the cement are essential elements of the material and should be understood when selecting the ideal luting material for each clinical situation. This article addresses the most relevant aspects of self-adhesive resin cements and their potential impact on clinical performance. Although few clinical studies are available to establish solid clinical evidence, the information presented provides clinical guidance in the dynamic environment of material development. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. Design of Fit-for-Purpose Cement to Restore Cement-Caprock Seal Integrity

    Science.gov (United States)

    Provost, R.

    2015-12-01

    This project aims to study critical research needs in the area of rock-cement interfaces, with a special focus on crosscutting applications in the Wellbore Integrity Pillar of the SubTER initiative. This study will focus on design and test fit-for-purpose cement formulations. The goals of this project are as follows: 1) perform preliminary study of dispersing nanomaterial admixtures in Ordinary Portland Cement (OPC) mixes, 2) characterize the cement-rock interface, and 3) identify potential high-performance cement additives that can improve sorption behavior, chemical durability, bond strength, and interfacial fracture toughness, as appropriate to specific subsurface operational needs. The work presented here focuses on a study of cement-shale interfaces to better understand failure mechanisms, with particular attention to measuring bond strength at the cement-shale interface. Both experimental testing and computational modeling were conducted to determine the mechanical behavior at the interface representing the interaction of cement and shale of a typical wellbore environment. Cohesive zone elements are used in the finite element method to computationally simulate the interface of the cement and rock materials with varying properties. Understanding the bond strength and mechanical performance of the cement-formation interface is critical to wellbore applications such as sequestration, oil and gas production and exploration and nuclear waste disposal. Improved shear bond strength is an indication of the capability of the interface to ensure zonal isolation and prevent zonal communication, two crucial goals in preserving wellbore integrity. Understanding shear bond strength development and interface mechanics will provide an idea as to how the cement-formation interface can be altered under environmental changes (temperature, pressure, chemical degradation, etc.) so that the previously described objectives can be achieved. Sandia National Laboratories is a multi

  20. Development of Clinical Cement of Nanoapatite and Polyamide Composite

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A new type of inorganicorganic biomimetic bone cement consisting of nanohydroxyapatite and polyamide 66 composite was investigated. This cement can be handled as paste and easily shaped into any contour. Nanoapatite and polyamide composite cement has a reasonable setting time, excellent washout resistance, high mechanical strength and bioactivity, and it is easily handled and shaped, which can be developed as a clinical cement. It can be predicted that nanoapatite/polymer composite cement would be a new trend of biomedical material, showing a promising prospect.

  1. Serviceability and Reinforcement of Low Content Whisker in Portland Cement

    Institute of Scientific and Technical Information of China (English)

    CAO Mingli; WEI Jianqiang; WANG Lijiu

    2011-01-01

    In order to explore the serviceability and reinforcement of CaCO3 whisker in portland cement matrix,the durability of CaCO3 whisker and effect of low whisker content(0%-4.0%)on the working performance and mechanical properties of portland cement were investigated.The experimental results show that CaCO3 whiskers have a good stability and serviceability in cement,and should not significantly alter the rheological properties of the cement paste.The flexural and compressive strength of portland cement reinforced by CaCO3 whiskers was increased by 33.3% and 12.83%,respectively.

  2. A Study on Provisional Cements, Cementation Techniques, and Their Effects on Bonding of Porcelain Laminate Veneers

    OpenAIRE

    Vinod Kumar, G.; Soorya Poduval, T.; Bipin Reddy; Shesha Reddy, P.

    2013-01-01

    Minimal tooth preparation is required for porcelain laminate veneers, but interim restorations are a must to protect their teeth against thermal insult, chemical irritation, and to provide aesthetics. Cement remaining after the removal of the provisional restoration can impair the etching quality of the tooth surface and fit and final bonding of the porcelain laminate veneer. This in vitro study examined the tooth surface for remaining debris of cement after removal of a provisional restorati...

  3. Alkali binding in hydrated Portland cement paste

    NARCIS (Netherlands)

    Chen, W.; Brouwers, H.J.H.

    2010-01-01

    The alkali-binding capacity of C–S–H in hydrated Portland cement pastes is addressed in this study. The amount of bound alkalis in C–S–H is computed based on the alkali partition theories firstly proposed by Taylor (1987) and later further developed by Brouwers and Van Eijk (2003). Experimental data

  4. Advances in glass-ionomer cements

    OpenAIRE

    Davidson, Carel Leon

    2006-01-01

    This article describes the properties, advances and shortcomings of glass-ionomer cement as a restorative material. The adhesion of glass-ionomer to tooth structure is less technique sensitive than composite resins and its quality increases with time. Therefore glass-ionomer might turn out to the more reliable restorative material in minimal invasive dentistry based on adhesive techniques.

  5. Formulation of an injectable phosphocalcium cement

    Energy Technology Data Exchange (ETDEWEB)

    Goncalves, S. [CIRIMAT Equipe de Physico-Chimie des Phosphates ENSCT INP, Toulouse (France); TEKNIMED, Vic en Bigorre (France); Brouchet, A.; Delisle, B. [CHU Rangueil, Toulouse (France). Service d' Anatomie Pathologie; Freche, M.; Lacout, J.L. [CIRIMAT Equipe de Physico-Chimie des Phosphates ENSCT INP, Toulouse (France); Rodriguez, F. [Lab. de Galenique, Chmin des Maraichers, Toulouse (France)

    2001-07-01

    In orthopedic surgery, the loss or the reinforcement of osseous substance often requires filling of the defective part. In order to make the surgical operations easier we sought to make an injectable form. This study examined the effect of silicone and polyglycol on the injectability, setting time and mechanical properties of the cement. The basic solid phase was composed of a mixture of tetracalcium phosphate (Ca{sub 4}(PO{sub 4}){sub 2}O), {alpha}-tricalcium phosphate (Ca{sub 3}(PO{sub 4}){sub 2}) and sodium glycerophosphate. The basic liquid phase was made up of lime, orthophosphoric acid and water. Silicone was previously dissolved in cyclohexane and introduced in the solid phase. Polyglycol is a water-soluble compound so it is introduced in the liquid phase. For the mechanical properties, the strong increase in the percentage of additives decreased the compressive strength. Silicone and polyglycol made it possible to improve viscosity without modifying the basic setting time. The rate of evolution was different with the two different additives. From the data it was possible to optimize the formulation of cements to give predicted properties. Testing the in vivo implantation of the cement has already started. Preliminary results show the perfect osteointegration of the new cements without reactions to the foreign body in spite of the presence of silicone. (orig.)

  6. [A new hydroxyapatite cement for craniofacial surgery].

    Science.gov (United States)

    Pistner, H; Reuther, J; Reinhart, E; Kübler, N; Priessnitz, B

    1998-05-01

    A new stoechiometric mixture of 27% dicalcium-phosphate (DCPA) and 73% tetra-calcium-phosphate (TTCP) can be prepared with water intraoperatively to a paste that subsequently sets to a structurally stabile implant composed of hydroxyapatite (HA). Primary setting time is about 20 min; pH during setting ranges from 6.5 to 8.5. There is no relevant curing heat or expansion or contraction. Compressive strength is about 50 MPa, tensile strength about 8 MPa. Over a period of about 4 h in physiological milieu, the cement converts to hydroxyapatite. This product is no longer redissolvable in normal body fluid. This cement can be used for non-load-bearing applications especially in craniofacial bone surgery. Cranial defects due to tumour or trauma as well as deficits in the facial skeleton may be reconstructed using this new biomaterial. In nine of ten patients we used the hydroxyapatite cement successfully for reconstructions in the craniofacial area. Fluid control of the operation field and implant site is extremely important and sometimes difficult to achieve. Further applications could be all non-load-bearing augmentations such as filling of blocked paranasal sinuses, of dentoalveolar cysts and defects following dental apectomy or fixation of implanted hearing-aid electrodes. The perspectives for the hydroxyapatite cement include its application as a carrier for osteogenic protein preparations, especially because of its isothermic reaction and intrinsic osteoconductive characteristics.

  7. [New hydroxylapatite cement for craniofacial surgery].

    Science.gov (United States)

    Pistner, H; Reuther, J; Reinhart, E; Kübler, N; Priessnitz, B

    1998-05-01

    A new stoechiometric mixture of 27% dicalcium-phosphate (DCPA) and 73% tetra-calcium-phosphate (TTCP) can be prepared with water intraoperatively to a paste that subsequently sets to a structurally stabile implant composed of hydroxyapatite (HA). Primary setting time is about 20 min; pH during setting ranges from 6.5 to 8.5. There is no relevant curing heat or expansion or contraction. Compressive strength is about 50 MPa, tensile strength about 8 MPa. Over a period of about 4 h in physiological milieu, the cement converts to hydroxyapatite. This product is no longer redissolvable in normal body fluid. This cement can be used for non-load-bearing applications especially in craniofacial bone surgery. Cranial defects due to tumour or trauma as well as deficits in the facial skeleton may be reconstructed using this new biomaterial. In nine of ten patients we used the hydroxyapatite cement successfully for reconstructions in the craniofacial area. Fluid control of the operation field and implant site is extremely important and sometimes difficult to achieve. Further applications could be all non-load-bearing augmentations such as filling of blocked paranasal sinuses, of dentoalveolar cysts and defects following dental apectomy or fixation of implanted hearing-aid electrodes. The perspectives for the hydroxyapatite cement include its application as a carrier for osteogenic protein preparations, especially because of its isothermic reaction and intrinsic osteoconductive characteristics.

  8. Advances in glass-ionomer cements.

    Science.gov (United States)

    Davidson, Carel Leon

    2006-01-01

    This article describes the properties, advances and shortcomings of glass-ionomer cement as a restorative material. The adhesion of glass-ionomer to tooth structure is less technique sensitive than composite resins and its quality increases with time. Therefore glass-ionomer might turn out to the more reliable restorative material in minimal invasive dentistry based on adhesive techniques.

  9. Hidration kinetics study of tlie mixed cements

    Directory of Open Access Journals (Sweden)

    Duque Fernández, Gabriel . L

    1993-09-01

    Full Text Available A study of the hydration process of cements with 10% and 20% addition of a tuff from "Las Carolinas" quarry (Cienfuegos, Cuba by different methods was done. The results obtained by different methods showed a good agreement. It was proved an increment of the hydration products, an acceleration of alite hydration and a swelling of the fixed water in mixed cements. The resistance of the cement with 10% addition is similar to that of the pure cement for ages of 28 days, whereas with 20% addition they were similar only after 180 days.

    Se hizo un estudio por diferentes métodos de la hidratación de cementos con 10% y 20% de adición de una toba del yacimiento "Las Carolinas", en la provincia de Cien fuegos (Cuba. Hubo una buena correspondencia entre las diferentes técnicas de análisis utilizadas, comprobándose que en los cementos mezclados se incrementan los productos de hidratación, se acelera la hidratación de la alita, aumenta el contenido de agua fija, así como que la resistencia del cemento, con hasta 10% de adición, es similar al cemento puro para tiempos de curado de 3 y 28 días, mientras que con 20% de adición sólo se igualan después de los 180 días.

  10. [Pain after cementation of cast restorations

    NARCIS (Netherlands)

    Gerritsen, A.E.

    2004-01-01

    Some patients experience pain after cementation of a cast restoration on a vital tooth. Limited data are available on the prevalence of this pain. In many cases the pain disappears within two weeks. The major cause of the pain might be attributed to more permeability of the dentine after

  11. Marginal adaptation of ceramic inserts after cementation

    NARCIS (Netherlands)

    Ozcan, M; Pfeiffer, P; Nergiz, [No Value

    2002-01-01

    The advantage of using ceramic inserts is to prevent major drawbacks of composite resins such as polymerization shrinkage, wear and microleakage. This in vitro study evaluated the marginal adaptation of two approximal ceramic insert systems after cementation to the cavities opened with ultrasonic ti

  12. Kinetics of strength gain of biocidal cements

    Directory of Open Access Journals (Sweden)

    Rodin Aleksandr Ivanovich

    Full Text Available Biocorrosion becomes the determinative durability factor of buildings and constructions. Damages of construction materials caused by bacteria, filamentous fungi, actinomycetes constitute a serious danger to the constructions of a building or a structure and to the health of people. Biodeteriorations are typical both in old and new constructions. A great quantity of destruction factors of industrial and residential buildings under the influence of microorganisms was established in practice. Providing products and constructions based on concretes fungicidal and bactericidal properties is an important direction of modern construction material science. The most efficient way to solve this task is creation of biocidal cements. The article presents the results of experimental studies of kinetic dependences of strength gain by biocidal cements by physico-mechanical and physico-chemical analysis methods. The identical velocity character of initial hydration of the developed compositions of biocidal cements is set, as well as a more calm behavior of hardening processes at later terms. It has been established that the compositions of biocidal cements modified by sodium sulfate and sodium fluoride possess the greatest strength.

  13. The effect of hyaluronic acid on brushite cement cohesion.

    Science.gov (United States)

    Alkhraisat, M H; Rueda, C; Mariño, F T; Torres, J; Jerez, L B; Gbureck, U; Cabarcos, E L

    2009-10-01

    The improvement of calcium phosphate cement (CPC) cohesion is essential for its application in highly blood perfused regions. This study reports the effectiveness of hyaluronic acids of different molecular weights in the enhancement of brushite cement cohesion. The cement was prepared using a powder phase composed of a mixture of beta-tricalcium phosphate and monocalcium phosphate monohydrate, whereas the liquid phase was formed by 0.5M citric acid solution modified by the addition of hyaluronic acid of different molecular weights. It was found that medium and high molecular weight hyaluronic acid enhances the cement cohesion and scarcely affects the cement mechanical properties. However, concentrations >0.5% (w/v) were less efficient to prevent the cement disintegration. It is concluded that hyaluronic acid could be applied efficiently to reduce brushite cement disintegration.

  14. Mechanical Properties and Decay Resistance of Hornbeam Cement Bonded Particleboards

    Directory of Open Access Journals (Sweden)

    Antonios N. Papadopoulos

    2008-01-01

    Full Text Available Cement bonded particleboards were manufactured from hornbeam (Carpinus betulus L. wood particles. Hydration tests were carried out to determine the inhibitory index in order to characterise wood-cement compatibility. The results revealed that the mixture of hornbeam-cement can be classified as moderate inhibition. Two wood: cement ratios were applied in this study, namely, 1 : 3 and 1 : 4, for the board manufacture. It was found that an increase of cement-wood ratio resulted in an improvement in all properties examined, except MOR. All properties of the boards made from 1 : 4 wood: cement ratio surpassed the minimum requirements set forth by the building type HZ code. Boards were exposed to brown and white rot fungi, Coniophora puteana, and Trametes versicolor, respectively. Overall, both fungi failed to attack the cement-bonded boards.

  15. Constitutive Response of Microbial Induced Calcite Precipitation Cemented Sands

    Science.gov (United States)

    Feng, Kai

    In the last decade, microbial induced calcite precipitation (MICP) emerged as a novel technique for implementing soil improvement in an environmentally-friendly and economically beneficial manner. However, the mechanical behavior and constitutive response of these materials are still not fully explored by researchers. In this dissertation, the characteristics of MICP cemented sands are investigated through numerical modelling and experimental tests, including macro and micro tests under both static and dynamic loading. In the first part, the mechanical behavior of MICP cemented sands were probed using monotonic load testing and the existence of calcite precipitation was verified by scanning electron microscopy, with this behavior compared to traditionally cemented soil and naturally cemented soil. Both MICP cementation and traditional cementation were verified to be effective in the increase of stiffness and strength, and unique characteristic of MICP cemented soil was highlighted.

  16. Quality of life after intensity-modulated radiotherapy for prostate cancer with a hydrogel spacer. Matched-pair analysis

    Energy Technology Data Exchange (ETDEWEB)

    Pinkawa, M.; Piroth, M.D.; Holy, R.; Escobar-Corral, N.; Caffaro, M.; Djukic, V.; Klotz, J.; Eble, M.J. [RWTH Aachen Univ. (Germany). Dept. of Radiation Oncology

    2012-10-15

    Background: Hydrogel spacer is an innovative method to protect the rectal wall during prostate cancer radiotherapy. Clinical effects are not well known. Methods: Patients have been surveyed before, at the last day, and 2-3 months after radiotherapy using a validated questionnaire (Expanded Prostate Cancer Index Composite). Median dose to the prostate in the spacer subgroup (SP) was 78 Gy in 2 Gy fractions. The results were independently compared with two matched-pair subgroups (treated conventionally without spacer): 3D conformal 70.2 Gy in 1.8 Gy fractions (3DCRT) and intensity-modulated radiotherapy (IMRT) 76 Gy in 2 Gy fractions. There were 28 patients in each of the three groups. Results: Baseline mean bowel bother scores were 96 points in all subgroups. Similar mean changes (SP 16, 3DCRT 14, IMRT 17 points) were observed at the end of radiotherapy. The smallest difference resulted in the spacer subgroup 2-3 months after radiotherapy (SP 2, 3DCRT 8, IMRT 6 points). Bowel bother scores were only significantly different in comparison to baseline levels in the spacer subgroup. The percentage of patients reporting moderate/big bother with specific symptoms did not increase for any item (urgency, frequency, diarrhoea, incontinence, bloody stools, pain). Conclusion: Moderate bowel quality-of-life changes can be expected during radiotherapy irrespective of spacer application or total dose. Advantages with a spacer can be expected a few weeks after treatment. (orig.)

  17. Asymmetric underlap spacer layer enabled nanoscale double gate MOSFETs for design of ultra-wideband cascode amplifiers

    Science.gov (United States)

    Roy, Debapriya; Biswas, Abhijit

    2017-10-01

    Using extensive numerical analysis we investigate effects of asymmetric sidewall spacers on various device parameters of 20-nm double gate MOSFETs associated with analog/RF applications. Our studies show that the device with underlap drain-side spacer length LED of 10 nm and source-side spacer length LES of 5 nm shows improvement in terms of the peak value of transconductance efficiency, voltage gain Av, unity-gain cut-off frequency fT and maximum frequency of oscillations fMAX by 8.6%, 51.7%, 5% and 10.3%, respectively compared to the symmetric 5 nm underlap spacer device with HfO2 spacer of dielectric constant k = 22. Additionally, a higher spacer dielectric constant increases the peak Av while decreasing both peak fT and fMAX. The detailed physical insight is exploited to design a cascode amplifier which yields an ultra-wide gain bandwidth of 2.48 THz at LED = 10 nm with a SiO2 spacer.

  18. Influence of Portland Cement Class on the Corrosion Rate of Steel Reinforcement in Cement Mortar Caused by Penetrating Chloride and Sulfate from the Environment

    OpenAIRE

    Bikić, F.; Cacan, M.; Rizvanović, M.

    2013-01-01

    The influence of portland cement class on the corrosion rate of steel reinforcement in cement mortar caused by penetrating chloride or sulfate from the environment in already hardened cement mortar is investigated in this paper. Three classes of portland cement have been used for the tests, PC 35, PC 45 and PC 55. Cylindrical samples of cement mortar with steel reinfor- cement in the middle were treated 6 months at room temperature in the follow...

  19. On the Origin of Reverse Transcriptase-Using CRISPR-Cas Systems and Their Hyperdiverse, Enigmatic Spacer Repertoires

    Directory of Open Access Journals (Sweden)

    Sukrit Silas

    2017-07-01

    Full Text Available Cas1 integrase is the key enzyme of the clustered regularly interspaced short palindromic repeat (CRISPR-Cas adaptation module that mediates acquisition of spacers derived from foreign DNA by CRISPR arrays. In diverse bacteria, the cas1 gene is fused (or adjacent to a gene encoding a reverse transcriptase (RT related to group II intron RTs. An RT-Cas1 fusion protein has been recently shown to enable acquisition of CRISPR spacers from RNA. Phylogenetic analysis of the CRISPR-associated RTs demonstrates monophyly of the RT-Cas1 fusion, and coevolution of the RT and Cas1 domains. Nearly all such RTs are present within type III CRISPR-Cas loci, but their phylogeny does not parallel the CRISPR-Cas type classification, indicating that RT-Cas1 is an autonomous functional module that is disseminated by horizontal gene transfer and can function with diverse type III systems. To compare the sequence pools sampled by RT-Cas1-associated and RT-lacking CRISPR-Cas systems, we obtained samples of a commercially grown cyanobacterium—Arthrospira platensis. Sequencing of the CRISPR arrays uncovered a highly diverse population of spacers. Spacer diversity was particularly striking for the RT-Cas1-containing type III-B system, where no saturation was evident even with millions of sequences analyzed. In contrast, analysis of the RT-lacking type III-D system yielded a highly diverse pool but reached a point where fewer novel spacers were recovered as sequencing depth was increased. Matches could be identified for a small fraction of the non-RT-Cas1-associated spacers, and for only a single RT-Cas1-associated spacer. Thus, the principal source(s of the spacers, particularly the hypervariable spacer repertoire of the RT-associated arrays, remains unknown.

  20. Vacuum-mixing cement does not decrease overall porosity in cemented femoral stems: AN IN VITRO LABORATORY INVESTIGATION

    Science.gov (United States)

    Messick, K. J.; Miller, M. A.; Damron, L. A.; Race, A.; Clarke, M. T.; Mann, K. A.

    2008-01-01

    The role of vacuum mixing on the reduction of porosity and on the clinical performance of cemented total hip replacements remains uncertain. We have used paired femoral constructs prepared with either hand-mixed or vacuum-mixed cement in a cadaver model which simulated intra-operative conditions during cementing of the femoral component. After the cement had cured, the distribution of its porosity was determined, as was the strength of the cement-stem and cement-bone interfaces. The overall fraction of the pore area was similar for both hand-mixed and vacuum-mixed cement (hand 6%; vacuum 5.7%; paired t-test, p = 0.187). The linear pore fractions at the interfaces were also similar for the two techniques. The pore number-density was much higher for the hand-mixed cement (paired t-test, p = 0.0013). The strength of the cement-stem interface was greater with the hand-mixed cement (paired t-test, p = 0.0005), while the strength of the cement-bone interface was not affected by the conditions of mixing (paired t-test, p = 0.275). The reduction in porosity with vacuum mixing did not affect the porosity of the mantle, but the distribution of the porosity can be affected by the technique of mixing used. PMID:17785755

  1. Estimation of the energy flow through the spacer in a DGU during calorimetric g-value measurement

    DEFF Research Database (Denmark)

    Duer, Karsten

    1997-01-01

    The edge-construction of a glazing has an impact on the g-value of the glazing, measured by calorimetric devices. If no insulation is applied on the glazing edges (inside and outside) during measurements, heat will be transferred by conduction through the glass panes and through the spacer....... The amount of energy transferred and the direction of the energy flow depends on the construction of the glazing (types of glass, coatings and spacer) and on the interieur and exterieur temperatures during the measurements. This paper gives an evaluation of the amount of energy transferred through the spacer...

  2. CFD analysis of pressure drop across grid spacers in rod bundles compared to correlations and heavy liquid metal experimental data

    Energy Technology Data Exchange (ETDEWEB)

    Batta, A., E-mail: batta@kit.edu; Class, A.G., E-mail: class@kit.edu

    2017-02-15

    Early studies of the flow in rod bundles with spacer grids suggest that the pressure drop can be decomposed in contributions due to flow area variations by spacer grids and frictional losses along the rods. For these shape and frictional losses simple correlations based on theoretical and experimental data have been proposed. In the OECD benchmark study LACANES it was observed that correlations could well describe the flow behavior of the heavy liquid metal loop including a rod bundle with the exception of the core region, where different experts chose different pressure-loss correlations for the losses due to spacer grids. Here, RANS–CFD simulations provided very good data compared to the experimental data. It was observed that the most commonly applied Rehme correlation underestimated the shape losses. The available correlations relate the pressure drop across a grid spacer to the relative plugging of the spacer i.e. solidity e{sub max}. More sophisticated correlations distinct between spacer grids with round or sharp leading edge shape. The purpose of this study is to (i) show that CFD is suitable to predict pressure drop across spacer grids and (ii) to access the generality of pressure drop correlations. By verification and validation of CFD results against experimental data obtained in KALLA we show (i). The generality (ii) is challenged by considering three cases which yield identical pressure drop in the correlations. First we test the effect of surface roughness, a parameter not present in the correlations. Here we compare a simulation assuming a typical surface roughness representing the experimental situation to a perfectly smooth spacer surface. Second we reverse the flow direction for the spacer grid employed in the experiments which is asymmetric. The flow direction reversal is chosen for convenience, since an asymmetric spacer grid with given blockage ratio, may result in different flow situations depending on flow direction. Obviously blockage

  3. Transcriptome changes in STSV2-infected Sulfolobus islandicus REY15A undergoing continuous CRISPR spacer acquisition

    DEFF Research Database (Denmark)

    León Sobrino, Carlos; Kot, W.P.; Garrett, Roger Antony

    2016-01-01

    A transcriptome study was performed on Sulfolobus islandicus REY15A actively undergoing CRISPR spacer acquisition from the crenarchaeal monocaudavirus STSV2 in rich and basal media over a 6 day period. Spacer acquisition preceded strong host growth retardation, altered transcriptional activity...... of four different CRISPR-Cas modules and changes in viral copy numbers, and with significant differences in the two media. Transcript levels of proteins involved in the cell cycle were reduced, while those of DNA replication, DNA repair, transcriptional regulation, and some antitoxin-toxin pairs...... and transposases were unchanged or enhanced. Antisense RNAs were implicated in the transcriptional regulation of adaptation and interference modules of the type I-A CRISPR-Cas system and evidence was found for the occurrence of functional coordination between the single CRISPR-Cas adaptation module...

  4. Analysis of sound absorption of tuck spacer fabrics to reduce automotive noise

    Science.gov (United States)

    Dias, Tilak; Monaragala, Ravindra; Needham, Peter; Lay, Edward

    2007-08-01

    Textiles are widely used in the automotive industry to provide both comfort to the passengers and an aesthetic appearance to the automotive interior. They can also be used to reduce automotive interior noise, which can make automotive travel safer and more comfortable. Knitted fabrics are used widely in automotive upholstery; however, the sound absorbency of a single layer of a knitted fabric is inadequate for the reduction of automotive interior noise. This paper investigates the sound absorbency of a novel knitted spacer fabric, which can be used in automotive upholstery and has the potential for greater sound absorbency than a conventional plain knitted fabric and its derivatives. The spacer fabric is modelled as a porous sound absorber and its sound absorbency is studied with regard to its structural parameters.

  5. Metagenomic data of fungal internal transcribed spacer from serofluid dish, a traditional Chinese fermented food

    Directory of Open Access Journals (Sweden)

    Peng Chen

    2016-03-01

    Full Text Available Serofluid dish (or Jiangshui, in Chinese, a traditional food in the Chinese culture for thousands of years, is made from vegetables by fermentation. In this work, microorganism community of the fermented serofluid dish was investigated by the culture-independent method. The metagenomic data in this article contains the sequences of fungal internal transcribed spacer (ITS regions of rRNA genes from 12 different serofluid dish samples. The metagenome comprised of 50,865 average raw reads with an average of 8,958,220 bp and G + C content is 45.62%. This is the first report on metagenomic data of fungal ITS from serofluid dish employing Illumina platform to profile the fungal communities of this little known fermented food from Gansu Province, China. The Metagenomic data of fungal internal transcribed spacer can be accessed at NCBI, SRA database accession no. SRP067411.

  6. Metagenomic data of fungal internal transcribed spacer from serofluid dish, a traditional Chinese fermented food.

    Science.gov (United States)

    Chen, Peng; Zhao, Yang; Wu, Zhengrong; Liu, Ronghui; Xu, Ruixiang; Yan, Lei; Li, Hongyu

    2016-03-01

    Serofluid dish (or Jiangshui, in Chinese), a traditional food in the Chinese culture for thousands of years, is made from vegetables by fermentation. In this work, microorganism community of the fermented serofluid dish was investigated by the culture-independent method. The metagenomic data in this article contains the sequences of fungal internal transcribed spacer (ITS) regions of rRNA genes from 12 different serofluid dish samples. The metagenome comprised of 50,865 average raw reads with an average of 8,958,220 bp and G + C content is 45.62%. This is the first report on metagenomic data of fungal ITS from serofluid dish employing Illumina platform to profile the fungal communities of this little known fermented food from Gansu Province, China. The Metagenomic data of fungal internal transcribed spacer can be accessed at NCBI, SRA database accession no. SRP067411.

  7. Development and Manufacture of the Coil End Spacers of the LHC Pre-series Dipoles

    CERN Document Server

    Farina, E; Perini, D; Schiappapietra, A; Seneé, L

    2002-01-01

    The coil end spacers play an important role in the performance of superconducting coils, as their shape and location determine the mechanical stability of the conductors in the coil ends (and hence the overall coil training performance) and the local field quality. The dipole end spacers are often of a size and a geometry difficult to be industrially series manufactured and measured. Efficiency of the production and related costs are a key issue to achieve the required production rate of the LHC main dipoles at an affordable price. For the latter reasons, a design approach integrating state-of-the-art CAD/CAM optimization techniques allowing to considerably decrease design and machining time was implemented. This paper gives examples and describes the design criteria, the computation methods, the machining and measuring procedures adopted to carry out the pre-series production.

  8. MOLECULAR FIELD THEORY FOR NEMATIC LIQUID CRYSTAL POLYMER COMPRISING FLEXIBLE SPACER

    Institute of Scientific and Technical Information of China (English)

    WANG Xiaogong; LIU Deshan; ZHOU Qixiang

    1993-01-01

    Based on the new model and concept of intramolecular orientational order parameter, a molecular field theory was built up for main chain liquid crystalline polymer (MC-LCPs) with flexible spacers. The theory takes account of orientational correlation among all mesogens in a polymer chain and the relationship between the intramolecular orientation and spatial orientation of the mesogens. The free energy, temperature and entropy of the nematic-isotropic transition were determined with the theory and compared with experiments in current work. It was found that many unique transition properties of the MC-LCPs comprising flexible spacer are correctly predicted by the theory and the agreement of the theory with the experiments is impressive.

  9. Pressurised metered dose inhaler-spacer technique in young children improves with video instruction.

    Science.gov (United States)

    Shaw, Nicole; Le Souëf, Peter; Turkovic, Lidija; McCahon, Lucy; Kicic, Anthony; Sly, Peter D; Devadason, Sunalene; Schultz, André

    2016-07-01

    The importance of good device technique to maximise delivery of aerosolised medications is widely recognised. Pressurised metered dose inhaler (pMDI)-spacer technique was investigated in 122 children, aged 2-7 years, with asthma. Eight individual steps of device technique were evaluated before and after viewing an instructional video for correct device technique. Video measurements were repeated every three months for nine months. Device technique improved directly after video instruction at the baseline study visit (p children scoring maximal (p = 0.02) and near-maximal (p = 0.04) scores. Repeated video instruction over time improves inhaler technique in young children. • Correct device technique is considered essential for sufficient delivery of inhaled medication. • Poor inhaler use is common in young asthmatic children using pressurised metered dose inhalers and spacers. What is New: • Video instruction could be used as a strategy to improve device technique in young children.

  10. Transcriptome changes in STSV2-infected Sulfolobus islandicus REY15A undergoing continuous CRISPR spacer acquisition

    DEFF Research Database (Denmark)

    León-Sobrino, Carlos; Kot, Witold P; Garrett, Roger A

    2016-01-01

    A transcriptome study was performed on Sulfolobus islandicus REY15A actively undergoing CRISPR spacer acquisition from the crenarchaeal monocaudavirus STSV2 in rich and basal media over a 6 day period. Spacer acquisition preceded strong host growth retardation, altered transcriptional activity...... of four different CRISPR-Cas modules and changes in viral copy numbers, and with significant differences in the two media. Transcript levels of proteins involved in the cell cycle were reduced, while those of DNA replication, DNA repair, transcriptional regulation, and some antitoxin-toxin pairs...... and transposases were unchanged or enhanced. Antisense RNAs were implicated in the transcriptional regulation of adaptation and interference modules of the type I-A CRISPR-Cas system and evidence was found for the occurrence of functional coordination between the single CRISPR-Cas adaptation module...

  11. SYNTHESIS OF NOVEL LIQUID CRYSTALLINE POLY(METH)ACRYLATES CONTAINING SILOXANE SPACER AND TERPHENYLENE MESOGENIC UNIT

    Institute of Scientific and Technical Information of China (English)

    Zhi-qian Zang; Yu-fei Luo; Dong Zhang; Xin-hua Wan; Qi-feng Zhou

    2000-01-01

    Novel side-chain liquid-crystalline poly(meth)acrylates were synthesized using 1-(3-hydroxyl-propyl)-3-[(4"cyano-p-terphenyloxycarbonyl)alkyl]-1, 1,3,3-tetramethyldisiloxane as the key intermediate. The polymers used a disiloxane moiety as decoupling spacer with cyano-p-terphenyl as mesogenic unit. The products were characterized by NMR, GPC,DSC and polarizing optical microscopy. All the polymers with cyano-p-terphenyl mesogens formed a stable mesophase.However, if the mesogenic unit is replaced by cyano-p-biphenyl, the liquid crystalline character will be lost. The results also showed that the decoupling is incomplete even if a complex and very flexible decoupling spacer is deliberately incorporated to obtain the highest possible decoupling effect.

  12. The sequence of spacers between the consensus sequences modulates the strength of procaryotic promoters

    DEFF Research Database (Denmark)

    Jensen, Peter Ruhdal; Hammer, Karin

    1998-01-01

    than 2000 relative units, which is among the strongest promoters known for this organism. The ranking of the promoter activities was somewhat different when assayed in E. coli, but the promoters are efficient for modulating gene expression in this bacteria as well. DNA sequencing revealed...... the spacers, at least a 400 fold change in activity can be obtained. Interestingly, the entire range of promoter activities is covered in small steps of activity increase, which makes these promoters very suitable for quantitative physiological studies and for fine tuning of gene expression in industrial bio......A library of synthetic promoters for Lactococcus lactis was constructed, in which the known consensus sequences were kept constant while the sequences of the separating spacers were randomized. The library consists of 38 promoters which differ in strength from 0.3 relative units, and up to more...

  13. Influence of Spacer Grid Outer Strap on Fuel Assembly Thermal Hydraulic Performance

    Directory of Open Access Journals (Sweden)

    Jingwen Yan

    2014-01-01

    Full Text Available The outer strap as a typical structure of a spacer grid enhances the mechanical strength, decreases hang-up susceptibility, and also influences thermal hydraulic performance, for example, pressure loss, mixing performance, and flow distribution. In the present study, a typical grid spacer with different outer strap designs is adopted to investigate the influence of outer strap design on fuel assembly thermal hydraulic performance by using a commercial computational fluid dynamics (CFD code, ANSYS CFX, and a subchannel analysis code, FLICA. To simulate the outer straps’ influence between fuel assemblies downstream, four quarter-bundles from neighboring fuel assemblies are constructed to form the computational domain. The results show that the outer strap design has a major impact on cross-flow between fuel assemblies and temperature distribution within the fuel assembly.

  14. Numerical Simulation for Flow Distribution in ACE7 Fuel Assemblies affected by a Spacer Grid Deformation

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jongpil; Jeong, Ji Hwan [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-05-15

    In spite of various efforts to understand hydraulic phenomena in a rod bundle containing deformed rods due to swelling and/or ballooning of clad, the studies for flow blockage due to spacer grid deformation have been limited. In the present work, 3D CFD analysis for flow blockage was performed to evaluate coolant flow within ACE7 fuel assemblies (FAs) containing a FA affected by a spacer grid deformation. The real geometry except for inner grids was used in the simulation and the region including inner grid was replaced by porous media. In the present work, the numerical simulation was performed to predict coolant flow within ACE7 FAs affected by a Mid grid deformation. The 3D CFD result shows that approximately 60 subchannel hydraulic diameter is required to fully recover coolant flow under normal operating condition.

  15. Automatic actuation of a dry powder inhaler into a nonelectrostatic spacer

    DEFF Research Database (Denmark)

    Bisgaard, H

    1998-01-01

    This article describes a new "automatic spacer" device, which has been developed to improve the delivery of inhaled medication to young children. In the device, a dry powder inhaler (DPI) is mechanically actuated into a nonelectrostatic spacer, producing an aerosol cloud of fine drug particles...... of the patient to the additives and propellants used in pressurized metered dose inhalers. Studies with the prototype device show a high yield of fine drug particles in the aerosol (mass median aerodynamic diameter, 2.8 microm), a high repeatability of drug delivery owing to the mechanical nature...... of the actuation (relative standard deviation, 12%), and a prolonged residence time of the fine particle aerosol (half-life of the fallout of the fine particles, 82 s). These features should prove advantageous in the treatment of young children with inhaled medication....

  16. Effect of spacer layer on the magnetization dynamics of permalloy/rare-earth/permalloy trilayers

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Chen, E-mail: ronanluochen@gmail.com; Yin, Yuli; Zhang, Dong; Jiang, Sheng; Yue, Jinjin; Zhai, Ya, E-mail: yazhai@seu.edu.cn [Physics Department, Southeast University, Nanjing 211189 (China); Du, Jun; Zhai, Hongru [National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China)

    2015-05-07

    The permalloy/rare-earth/permalloy trilayers with different types (Gd and Nd) and thicknesses of spacer layer are investigated using frequency dependence of ferromagnetic resonance (FMR) measurements at room temperature, which shows different behaviors with different rare earth spacer layers. By fitting the frequency dependence of the FMR resonance field and linewidth, we find that the in-plane uniaxial anisotropy retains its value for all samples, the perpendicular anisotropy remains almost unchanged for different thickness of Gd layer but the values are tailored by different thicknesses of Nd layer. The Gilbert damping is almost unchanged with different thicknesses of Gd; however, the Gilbert damping is significantly enhanced from 8.4×10{sup −3} to 20.1×10{sup −3} with 6 nm of Nd and then flatten out when the Nd thickness rises above 6 nm.

  17. Enhanced spin-torque in double tunnel junctions using a nonmagnetic-metal spacer

    Energy Technology Data Exchange (ETDEWEB)

    Chen, C. H.; Cheng, Y. H.; Ko, C. W.; Hsueh, W. J., E-mail: hsuehwj@ntu.edu.tw [Nanomagnetism Group, Department of Engineering Science and Ocean Engineering, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei 10660, Taiwan (China)

    2015-10-12

    This study proposes an enhancement in the spin-transfer torque of a magnetic tunnel junction (MTJ) designed with double-barrier layer structure using a nonmagnetic metal spacer, as a replacement for the ferromagnetic material, which is traditionally used in these double-barrier stacks. Our calculation results show that the spin-transfer torque and charge current density of the proposed double-barrier MTJ can be as much as two orders of magnitude larger than the traditional double-barrier one. In other words, the proposed double-barrier MTJ has a spin-transfer torque that is three orders larger than that of the single-barrier stack. This improvement may be attributed to the quantum-well states that are formed in the nonmagnetic metal spacer and the resonant tunneling mechanism that exists throughout the system.

  18. TiNi Shape Memory Alloy Foams Synthesized by Spacer Sintering and their Properties

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Titanium (Ti) andnickel (Ni) elemental powders were blended by ball milling and the ball milled powders were employed to fabricate TiNi shape memory alloy (SMA) foams by spacer sintering. Effect of ball milling time on phase constitutes of the sintered TiNi alloy foams was studied by X-ray diffraction (XRD) analysis. Scanning electron microscopy (SEM) was used to characterize the porous structure, and compressive tests were carried out to evaluate the mechanical properties ofthe foams. Results indicate that porosities of the TiNi alloy foams can be controlled by using the spacer sintering method, and the porosities show a significant effect on the mechanical properties and shape memory effect (SME).

  19. Environmental CRIteria for CEMent based products, ECRICEM. Phase I. Ordinary Portland Cements. Phase II. Blended Cements. Executive Summary

    Energy Technology Data Exchange (ETDEWEB)

    Van der Sloot, H.A.; Van Zomeren, A. [ECN Biomass, Coal and Environmetal Research, Petten (Netherlands); Stenger, R. [Holcim Group Support Ltd, Holderbank (Switzerland); Schneider, M.; Spanka, G. [VDZ, Duesseldorf (Germany); Stoltenberg-Hansson, A. [NORCEM, HeidelbergCement Group, Brevik (Norway); Dath, P. [Holcim Belgium, Obourg (Belgium)

    2008-01-15

    The protection of the immediate environment of structural works is one of the essential requirements of the European Construction Products Directive (CPD). According to the CPD, construction products can only be put on the market, if the structural works built with them fulfil the relevant requirements for hygiene, and the protection of health and the environment. These essential requirements in the respective standards are specified at the national level by the individual member states. Cement and cementitious materials are considered to fulfil the fundamental requirements of the European Construction Products Directive and the corresponding national regulations. Therefore a technical regulation like the cement standard EN 197 in general does not cover separate requirements for determining compliance of cementitious materials with criteria on hygiene, health and environmental protection. Further regulations are laid down in cases where it appears necessary for constructive applications requiring a particular protection of water, soil and air.

  20. Stimulation of the mouse rRNA gene promoter by a distal spacer promoter.

    OpenAIRE

    Paalman, M H; Henderson, S L; Sollner-Webb, B

    1995-01-01

    We show that the mouse ribosomal DNA (rDNA) spacer promoter acts in vivo to stimulate transcription from a downstream rRNA gene promoter. This augmentation of mammalian RNA polymerase I transcription is observed in transient-transfection experiments with three different rodent cell lines, under noncompetitive as well as competitive transcription conditions, over a wide range of template concentrations, whether or not the enhancer repeats alone stimulate or repress expression from the downstre...

  1. Fluid dynamics evaluation of split vane grid spacer in a small modular reactor

    Energy Technology Data Exchange (ETDEWEB)

    Nazififard, Mohammad [Kashan Univ (Iran, Islamic Republic of). Dept. of Energy System Engineering; Seoul National Univ. (Korea, Republic of). Dept. of Nuclear Engineering; Philosophia, Seoul (Korea, Republic of); Nematollahi, Mohammadreza [Shiraz Univ. (Iran, Islamic Republic of). Dept. of Nuclear Engineering; Suh, Kune Y. [Seoul National Univ. (Korea, Republic of). Dept. of Nuclear Engineering; Philosophia, Seoul (Korea, Republic of)

    2015-12-15

    This paper numerically evaluates the effect of a split vane grid spacer on thermohydrodynamics in a subchannel of a typical small modular pressurized water reactor. The turbulent convective heat transfer and pressure drop are numerically calculated. Thermohydrodynamics and neutronics coupling would indeed be interesting for more quantitative analyses of the fuel assembly design, heat transfer correlation and mixing coefficient for the System-Integrated Modular Advanced Reactor (SMART) being developed by the Korea Atomic Energy Research Institute (KAERI).

  2. Contamination effects of drilling fluid additives on cement slurry

    Directory of Open Access Journals (Sweden)

    Youzhi Zheng

    2015-10-01

    Full Text Available During the cementation of deep wells, contamination at the contact surface between cement slurry and drilling fluid will present a technical challenge, which may threaten operation safety. To deal with the problem, lab tests and analysis were performed specifically on the compatibility of fluids during cementation in Sichuan and Chongqing gas fields. Impacts of commonly used additives for drilling fluids were determined on fluidity and thickening time of conventional cement slurry. Through the infrared spectrum analysis, SEM and XRD, infrared spectrum data of kalium polyacrylamide (KPAM and bio-viscosifier were obtained, together with infrared spectrum, SEM and XRD data of cement slurry with additives. Contamination mechanisms of the cement slurry by conventional additives for drilling fluid were reviewed. Test results show that both KPAM and bio-viscosifier are such high-molecular materials that the long chains in these materials may easily absorb cement particles in the slurry to form mixed network structures; as a result, cement particles were prone to agglomeration and eventually lost their pumpability. Finally, assessment of and testing methods for the contamination effects of drilling fluid additives on cement slurry were further improved to form standards and codes that may help solve the said problems. This study will provide technological supports for the preparation of drilling fluids with desirable properties prior to cementation, the selection of optimal drilling fluids additives, and the development of innovative drilling fluids additives.

  3. Development of monetite-nanosilica bone cement: a preliminary study.

    Science.gov (United States)

    Zhou, Huan; Luchini, Timothy J F; Agarwal, Anand K; Goel, Vijay K; Bhaduri, Sarit B

    2014-11-01

    In this paper, we reported the results of our efforts in developing DCPA/nanosilica composite orthopedic cement. It is motivated by the significances of DCPA and silicon in bone physiological activities. More specifically, this paper examined the effects of various experimental parameters on the properties of such composite cements. In this work, DCPA cement powders were synthesized using a microwave synthesis technique. Mixing colloidal nanosilica directly with synthesized DCPA cement powders can significantly reduce the washout resistance of DCPA cement. In contrast, a DCPA-nanosilica cement powder prepared by reacting Ca(OH)2 , H3 PO4 and nanosilica together showed good washout resistance. The incorporation of nanosilica in DCPA can improve compressive strength, accelerate cement solidification, and intensify surface bioactivity. In addition, it was observed that by controlling the content of NaHCO3 during cement preparation, the resulting composite cement properties could be modified. Allowing for the development of different setting times, mechanical performance and crystal features. It is suggested that DCPA-nanosilica composite cement can be a potential candidate for bone healing applications.

  4. Development of fluorapatite cement for dental enamel defects repair.

    Science.gov (United States)

    Wei, Jie; Wang, Jiecheng; Shan, Wenpeng; Liu, Xiaochen; Ma, Jian; Liu, Changsheng; Fang, Jing; Wei, Shicheng

    2011-06-01

    In order to restore the badly carious lesion of human dental enamel, a crystalline paste of fluoride substituted apatite cement was synthesized by using the mixture of tetracalcium phosphate (TTCP), dicalcium phosphate anhydrous (DCPA) and ammonium fluoride. The apatite cement paste could be directly filled into the enamel defects (cavities) to repair damaged dental enamel. The results indicated that the hardened cement was fluorapatite [Ca(10)(PO(4))(6)F(2), FA] with calcium to phosphorus atom molar ratio (Ca/P) of 1.67 and Ca/F ratio of 5. The solubility of FA cement in Tris-HCl solution (pH = 5) was slightly lower than the natural enamel, indicating the FA cement was much insensitive to the weakly acidic solutions. The FA cement was tightly combined with the enamel surface, and there was no obvious difference of the hardness between the FA cement and natural enamel. The extracts of FA cement caused no cytotoxicity on L929 cells, which satisfied the relevant criterion on dental biomaterials, revealing good cytocompatibility. In addition, the results showed that the FA cement had good mechanical strength, hydrophilicity, and anti-bacterial adhesion properties. The study suggested that using FA cement was simple and promising approach to effectively and conveniently restore enamel defects.

  5. The contemporary cement cycle of the United States

    Science.gov (United States)

    Kapur, A.; Van Oss, H. G.; Keoleian, G.; Kesler, S.E.; Kendall, A.

    2009-01-01

    A country-level stock and flow model for cement, an important construction material, was developed based on a material flow analysis framework. Using this model, the contemporary cement cycle of the United States was constructed by analyzing production, import, and export data for different stages of the cement cycle. The United States currently supplies approximately 80% of its cement consumption through domestic production and the rest is imported. The average annual net addition of in-use new cement stock over the period 2000-2004 was approximately 83 million metric tons and amounts to 2.3 tons per capita of concrete. Nonfuel carbon dioxide emissions (42 million metric tons per year) from the calcination phase of cement manufacture account for 62% of the total 68 million tons per year of cement production residues. The end-of-life cement discards are estimated to be 33 million metric tons per year, of which between 30% and 80% is recycled. A significant portion of the infrastructure in the United States is reaching the end of its useful life and will need to be replaced or rehabilitated; this could require far more cement than might be expected from economic forecasts of demand for cement. ?? 2009 Springer Japan.

  6. Heat transfer enhancement with mixing vane spacers using the field synergy principle

    Science.gov (United States)

    Yang, Lixin; Zhou, Mengjun; Tian, Zihao

    2017-01-01

    The single-phase heat transfer characteristics in a PWR fuel assembly are important. Many investigations attempt to obtain the heat transfer characteristics by studying the flow features in a 5 × 5 rod bundle with a spacer grid. The field synergy principle is used to discuss the mechanism of heat transfer enhancement using mixing vanes according to computational fluid dynamics results, including a spacer grid without mixing vanes, one with a split mixing vane, and one with a separate mixing vane. The results show that the field synergy principle is feasible to explain the mechanism of heat transfer enhancement in a fuel assembly. The enhancement in subchannels is more effective than on the rod's surface. If the pressure loss is ignored, the performance of the split mixing vane is superior to the separate mixing vane based on the enhanced heat transfer. Increasing the blending angle of the split mixing vane improves heat transfer enhancement, the maximum of which is 7.1%. Increasing the blending angle of the separate mixing vane did not significantly enhance heat transfer in the rod bundle, and even prevented heat transfer at a blending angle of 50°. This finding testifies to the feasibility of predicting heat transfer in a rod bundle with a spacer grid by field synergy, and upon comparison with analyzed flow features only, the field synergy method may provide more accurate guidance for optimizing the use of mixing vanes.

  7. Relative lung bioavailability of generic sodium cromoglycate inhalers used with and without a spacer device.

    Science.gov (United States)

    Aswania, O; Chrystyn, H

    2001-01-01

    The relative lung bioavailability of sodium cromoglycate following inhalation has been evaluated using urinary drug excretion in nine healthly volunteers. Each inhaled four 5 mg sodium cromoglycate doses from a generic metered dose inhaler (MDI) and when it was attached to large volume spacer (MDI + VOL). A breath-actuated MDI was also evaluated either used on its own (EB) or attached to a small volume spacer tube (EBO). The mean (SD) urinary excretion of sodium cromoglycate in the first 30 min post-inhalation was 34.1 (20.2), 211.7 (123.5), 29.3 (19.5) and 52.8 (36.0) microg following MDI, MDI+VOL, EB and EBO, respectively. The cumulative mean (SD) urinary excretion of sodium cromoglycate over the 24 h post-inhalation was 364.7 (266.2), 1227.1 (459.0), 280.2 (155.4) and 429.5 (176.7) microg. A metered dose inhaler attached to a large volume spacer delivers more sodium cromoglycate to the lungs than any other inhalation method.

  8. MetaCRAST: reference-guided extraction of CRISPR spacers from unassembled metagenomes

    Science.gov (United States)

    Moller, Abraham G.

    2017-01-01

    Clustered regularly interspaced short palindromic repeat (CRISPR) systems are the adaptive immune systems of bacteria and archaea against viral infection. While CRISPRs have been exploited as a tool for genetic engineering, their spacer sequences can also provide valuable insights into microbial ecology by linking environmental viruses to their microbial hosts. Despite this importance, metagenomic CRISPR detection remains a major challenge. Here we present a reference-guided CRISPR spacer detection tool (Metagenomic CRISPR Reference-Aided Search Tool—MetaCRAST) that constrains searches based on user-specified direct repeats (DRs). These DRs could be expected from assembly or taxonomic profiles of metagenomes. We compared the performance of MetaCRAST to those of two existing metagenomic CRISPR detection tools—Crass and MinCED—using both real and simulated acid mine drainage (AMD) and enhanced biological phosphorus removal (EBPR) metagenomes. Our evaluation shows MetaCRAST improves CRISPR spacer detection in real metagenomes compared to the de novo CRISPR detection methods Crass and MinCED. Evaluation on simulated metagenomes show it performs better than de novo tools for Illumina metagenomes and comparably for 454 metagenomes. It also has comparable performance dependence on read length and community composition, run time, and accuracy to these tools. MetaCRAST is implemented in Perl, parallelizable through the Many Core Engine (MCE), and takes metagenomic sequence reads and direct repeat queries (FASTA or FASTQ) as input. It is freely available for download at https://github.com/molleraj/MetaCRAST. PMID:28894651

  9. MetaCRAST: reference-guided extraction of CRISPR spacers from unassembled metagenomes

    Directory of Open Access Journals (Sweden)

    Abraham G. Moller

    2017-09-01

    Full Text Available Clustered regularly interspaced short palindromic repeat (CRISPR systems are the adaptive immune systems of bacteria and archaea against viral infection. While CRISPRs have been exploited as a tool for genetic engineering, their spacer sequences can also provide valuable insights into microbial ecology by linking environmental viruses to their microbial hosts. Despite this importance, metagenomic CRISPR detection remains a major challenge. Here we present a reference-guided CRISPR spacer detection tool (Metagenomic CRISPR Reference-Aided Search Tool—MetaCRAST that constrains searches based on user-specified direct repeats (DRs. These DRs could be expected from assembly or taxonomic profiles of metagenomes. We compared the performance of MetaCRAST to those of two existing metagenomic CRISPR detection tools—Crass and MinCED—using both real and simulated acid mine drainage (AMD and enhanced biological phosphorus removal (EBPR metagenomes. Our evaluation shows MetaCRAST improves CRISPR spacer detection in real metagenomes compared to the de novo CRISPR detection methods Crass and MinCED. Evaluation on simulated metagenomes show it performs better than de novo tools for Illumina metagenomes and comparably for 454 metagenomes. It also has comparable performance dependence on read length and community composition, run time, and accuracy to these tools. MetaCRAST is implemented in Perl, parallelizable through the Many Core Engine (MCE, and takes metagenomic sequence reads and direct repeat queries (FASTA or FASTQ as input. It is freely available for download at https://github.com/molleraj/MetaCRAST.

  10. Design, Synthesis and Hydrolytic Behavior of Mutual Prodrugs of NSAIDs with Gabapentin Using Glycol Spacers

    Directory of Open Access Journals (Sweden)

    Hiba Najeh Alsaad

    2012-10-01

    Full Text Available The free –COOH present in NSAIDs is thought to be responsible for the GI irritation associated with all traditional NSAIDs. Exploitation of mutual prodrugs is an approach wherein the NSAID is covalently bounded to a second pharmacologically active carrier/drug with the ultimate aim of reducing the gastric irritation. In this study some NSAIDs were conjugated with gabapentin via ester bonds using glycol spacers with the expectation of reducing gastric adverse effects and obtaining synergistic analgesic effects. The kinetics of ester hydrolysis were studied in two different non enzymatic buffer solutions at pH 1.2 and 7.4, as well as in 80% human plasma using HPLC with chloroform -methanol as mobile phase. Compounds 9a–c with ethylene glycol spacers showed significant stability at buffer solutions with half lives ranging from about 8–25 h, while the underwent a reasonable plasma hydrolysis (49%–88% in 2 h. Compound 9d with a propylene glycol spacer shows a higher rate of enzymatic hydrolysis than the corresponding ethylene glycol compound 9c. The result of compounds 9a-c indicate that these compounds may be stable during their passage through the GIT until reaching the blood circulation.

  11. FIVPET Flow-Induced Vibration Test Report (1) - Candidate Spacer Grid Type I (Optimized H Type)

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Kang Hee; Kang, Heung Seok; Yoon, Kyung Ho; Song, Kee Nam; Kim, Jae Yong

    2006-03-15

    The flow-induced vibration (FIV) test using a 5x5 partial fuel assembly was performed to evaluate mechanical/structural performance of the candidate spacer grid type I (Optimized H shape). From the measured vibration response of the test bundle and the flow parameters, design features of the spacer strap can be analyzed in the point of vibration and hydraulic aspect, and also compared with other spacer strap in simple comparative manner. Furthermore, the FIV test will contributes to understand behaviors of nuclear fuel in operating reactor. The FIV test results will be used to verify the theoretical model of fuel rod and assembly vibration. The aim of this report is to present the results of the FIV test of partial fuel assembly and to introduce the detailed test methodology and analysis procedure. In chapter 2, the overall configuration of test bundle and instrumented tube is remarked and chapter 3 will introduce the test facility (FIVPET) and test section. Chapter 4 deals with overall test condition and procedure, measurement and data acquisition devices, instrumentation equipment and calibration, and error analysis. Finally, test result of vibration and pressure fluctuation is presented and discussed in chapter 5.

  12. Investigation of DNA-cationic bolaform surfactants interaction with different spacer length.

    Science.gov (United States)

    Sohrabi, Beheshteh; Khani, Vahid; Moosavi-Movahedi, Ali Akbar; Moradi, Parviz

    2013-10-01

    In this paper interaction of DNA with cationic bolaform surfactants is investigated. The structural formula for synthesized bolaforms is as follows: bolaform B1 with structural formula Br(-)(CH3)3N(+)(CH2)3N(+)(CH3)Br(-) and bolaform B2 with structural formula of Br(-)(CH3)3N(+)(CH2)12N(+)(CH3)Br(-). There are stronger electrostatic interactions in bolaform B1 due to shorter spacer length, while there are stronger hydrophobic interactions in bolaform B2 compared to bolaform B1 due to existence of 12 carbons in hydrocarbonic chain. The structure of bolaforms consists of two polar head groups which play important role in DNA compaction. Surface tension change in aqueous solution of bolaform surfactants is measured using tensiometer. Electrical conductivity of surfactants aqueous solution is examined with and without DNA. DNA compaction is tracked in the presence of bolaforms by dynamic light scattering (DLS) technique. Results of DLS indicate bolaforms with shorter spacer length (dominant electrostatic interactions) are more influential in compressing DNA compared to bolaforms with longer spacer length (stronger hydrophobic interactions). UV-vis and fluorescence spectroscopies specify the binding mechanism of bolaform surfactants to DNA.

  13. Role of spacer lengths of gemini surfactants in the synthesis of silver nanorods in micellar media.

    Science.gov (United States)

    Bhattacharya, Santanu; Biswas, Joydeep

    2011-07-01

    In this work, we have prepared Ag-nanorods using biscationic gemini surfactant micelles as the media by a seed-mediated wet synthesis method. Towards this end, we first synthesized Ag-nanoseeds of diameter ~7 nm stabilized by trisodium citrate (as the capping agent). Then these Ag-nanoseeds were used to synthesize Ag-nanorods of different aspect ratios. With decreasing Ag-nanoseed concentration, the aspect ratios of the Ag-nanorods stabilized by these gemini surfactants increased gradually. Various Ag-nanoseeds and Ag-nanospecies were characterized using UV-Vis spectroscopy (to know the surface plasmon bands), transmission electron microscopy (to find out their particle sizes and distribution), energy-dispersive X-ray spectroscopy and X-ray diffraction. When we used micelles derived from gemini surfactants of shorter spacer -(CH(2))(n)- (n = 2 or 4) to stabilize the Ag-nanorods, the λ(max) of the longitudinal band shifted more towards the blue region compared to that of the gemini surfactant micelles with a longer spacer -(CH(2))(n)- (n = 5, 12) at a given amount of the Ag-nanoseed solution. So, the growth of Ag-nanorods in the gemini micellar solutions depends on the spacer-chain length of gemini surfactants employed.

  14. Review and Comparison of simulation software for additive manufacturing process: the practical case of dipole End-Spacers

    CERN Document Server

    Vevers, Arturs

    2017-01-01

    Project was made to compare and benchmark simulation software for additive manufacturing. Simulations for End-spacers and HOM crab cavity were made to compare simulation results with 3D scanned data for these parts.

  15. Visible light dynamical diffraction in a 1-D photonic crystal-based interferometer with an extremely thin spacer layer

    Science.gov (United States)

    Prudnikov, I. R.

    2016-01-01

    Properties of light diffraction in a Fabry-Pérot-like interferometer composed of two 1-D photonic crystals and a nanometer-thick spacer layer are analytically investigated. It is shown that the resonant enhancement of light wave intensity in such a layer is possible because of light dynamical diffraction from the photonic crystals of the interferometer. Numerical simulations of (i) light reflectivity and transmittance curves of the interferometer having an ultra-thin spacer layer (its thickness changes from less than 1 nm to about 10 nm) and (ii) the resonant distribution of the light wave intensity in the vicinity of the layer are performed. Based on the numerical simulations, potentialities for the determination of the structural parameters (e.g., thicknesses and refraction indexes) of ultra-thin spacer films are discussed. A difference is found to appear in resonant intensity enhancements inside the ultra-thin spacer layers between s- and p-polarized light waves.

  16. INFLUENCE OF THE SIZE OF METHYLENE SPACERS ON THE THERMAL BEHAVIOR OF SEVERAL ALIPHATIC-AROMATIC POLYESTERS

    Directory of Open Access Journals (Sweden)

    NATALIA HURDUC

    2014-04-01

    Full Text Available Polyesters have a wide range of technical applications and therefore their processing is of the utmost importance. Since polyesters are usually processed by melting, their thermal stability is an extremely important characteristic for the exact determination of the operational parameters. The thermal analysis was carried out using a MOM-Budapest derivatograph at the 10 C/min heating speed, aluminum oxide the reference material, and the air conditions were static. The study lead to conclusions on the thermal stability and degradation mechanism depending on the number of methylene groups in the spacer. Thermal stability is supported by the increase in the number of methylene groups in the spacer. The degradation mechanism is complex through successive reactions. The spacer size influences the nature of the micromolecules formed by spacer fragmenting and by the number of carbon atoms, respectively.

  17. Spacer Thickness-Dependent Electron Transport Performance of Titanium Dioxide Thick Film for Dye-Sensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Reda E. El-Shater

    2015-01-01

    Full Text Available A titanium dioxide (P25 film was deposited by cast coating as conductive photoelectrode and subsequently immersed in dye solution (N719 to fabricate the photoanode of dye-sensitized solar cells (DSSCs. A plastic spacer was used as a separation and sealant layer between the photoanode and the counter electrode. The effect of the thickness of this spacer on the transfer of electrons in the liquid electrolyte of the DSSCs was studied by means of both IV curves and electrochemical impedance. Using a spacer thickness range of 20 μm to 50 μm, efficiency ranges from 3.73% to 7.22%. The highest efficiency of 7.22% was obtained with an optimal spacer thickness of 40 μm.

  18. Binding of 12-s-12 dimeric surfactants to calf thymus DNA: Evaluation of the spacer length influence.

    Science.gov (United States)

    Sarrión, Beatriz; Bernal, Eva; Martín, Victoria Isabel; López-López, Manuel; López-Cornejo, Pilar; García-Calderón, Margarita; Moyá, María Luisa

    2016-08-01

    Several cationic dimeric surfactants have shown high affinity towards DNA. Bis-quaternary ammonium salts (m-s-m) have been the most common type of dimeric surfactants investigated and it is generally admitted that those that posses a short spacer (s≤3) show better efficiency to bind or compact DNA. However, experimental results in this work show that 12-s-12 surfactants with long spacers make the surfactant/ctDNA complexation more favorable than those with short spacers. A larger contribution of the hydrophobic interactions, which control the binding Gibbs energy, as well as a higher average charge of the surfactant molecules bound to the nucleic acid, which favors the electrostatic attractions, could explain the experimental observations. Dimeric surfactants with intermediate spacer length seem to be the less efficient for DNA binding.

  19. Identification of Swertia mussotii and its adulterant Swertia species by 5S rRNA gene spacer.

    Science.gov (United States)

    Yu, Man-Tang; Wong, Ka-Lok; Zong, Yu-Ying; Shaw, Pang-Chui; Che, Chun-Tao

    2008-03-01

    This research focused on analyzing the differences of 5S rRNA gene spacer sequences on Swertia mussotii and its commonly used adulterants, including S. franchetiana, S. wolfangiana and S. chirayita. DNA was extracted from the collected Swertia samples. 5S rRNA intergenic spacers were amplified by PCR, sequenced and analyzed. 5S rRNA gene spacer sequences were different between S. mussotii and its other three adulterants. Sequence divergence among species ranged from 30.6% to 65.0%. 5S rRNA spacers may be used as molecular authentication markers to differentiate S. mussotii and other commonly used Swertia adulterants. This result provides reliable and simple reference for the authentication of Swertia genus species.

  20. Review of the correlation developments and a new concept based on mixing mechanism for heat transfer enhancement of spacer grids

    Energy Technology Data Exchange (ETDEWEB)

    Mao, H.; Yang, B.W.; Liu, X. [Xi' an Jiaotong Univ., Shaanxi (China). Science and Technology Center for Advanced Nuclear Fuel Research

    2016-07-15

    Spacer grids could cause heat transfer enhancement both at the spacer grid regions and downstream of the spacer grids as a result of mixing promoted by the spacer grids in the rod bundle. This phenomenon has been demonstrated by many experiments, and several correlations have been developed based on these experimental data. This paper gives a review of the grid-enhanced heat transfer correlation developments in single phase flow. Following the exploration of the correlation development history, a predictive formulation of grid-enhanced heat transfer in single phase flow is established taking into account the effect of both swirl flow and crossflow. With emphasis on modeling of the mixing mechanism associated with the mixing vane grid, the new correlation could better reflect the physical process of the heat transfer augmentation, while a large number of experimental data are needed to determine the coefficients of the new correlation.

  1. Autopsy studies of the bone-cement interface in well-fixed cemented total hip arthroplasties.

    Science.gov (United States)

    Schmalzried, T P; Maloney, W J; Jasty, M; Kwong, L M; Harris, W H

    1993-04-01

    Although knowledge of the clinical status of the implant is important, only instrumented mechanical testing of retrieved specimens provides quantitative assessment of implant fixation. This measurement allows placement of the implant along a continuum of loosening and is the foundation for the interpretation of subsequent findings. Analysis of implants that have been proven to be well fixed by instrumented testing reveals significant differences in the initial events in the loosening of femoral and acetabular components. Although radiolucencies were observed around all of these well-fixed femoral and acetabular components, the histology (and therefore the etiology) of the radiolucency is different and variable on the two sides of the articulation. The majority of femoral radiolucencies appear to be due to age and stress-related remodeling while particulate-induced bone resorption plays an important role in acetabular radiolucencies. A finding common to both sides of the articulation in these stable components, however, was intimate contact of bone with cement without any interposed soft tissue even after 17.5 years of service. Primary incompatibility and/or failure of the cement was not identified as a factor in initiating either femoral or acetabular component loosening. These studies document the long-term compatibility of bone with cement in bulk form. Improvements in cemented femoral component fixation should focus on stem design and cementing technique. Long-term acetabular component fixation can be improved by reduction or elimination of polyethylene wear and optimization of the bone-implant interface.

  2. Cement clinker structure during plasma-chemical synthesis and its influence on cement properties

    Science.gov (United States)

    Sazonova, N.; Skripnikova, N.; Lucenko, A.; Novikova, L.

    2015-01-01

    The aim of this study was to determine the degree of influence of cement clinker cooling modes, synthesized in a low-temperature plasma, its structure and physico-mechanical properties. The raw mixture consisting of marble, sand, ash from thermal power plants and py- rite cinders were used, which are characterized by saturation factor (1,045); silicate (2,35) and alumina (1,22) modules. It was found that the use of different cooling rates of fused cement clinker entails changes associated with the mineralogical composition (increase of alite of 8.719,2 %), morphology (variation of the mineral alite aspect ratio of 6,7-17,5), density of the structure (change in distance between the minerals from 1 to 7,5 microns), grindability, specific surface area (2600-3650 cm2/g) and, in consequence, the activity of cement (56,973,2 MPa). Disorientation of alite mineral blocks against each other, a significant amount of microcracks, affect the increase in cement specific surface area of 14,3-21,6 %, which leads to activity growth of the system. Along with this, with the rapid cooling of the samples, alite 54CaO- 16SiO2-Al2O3 MgO is formed, with single units of the structure, more deformed relatively to C3S, which has a positive effect on the hydraulic cement activity.

  3. Hydrothermal Characteristics of Blended Cement Pastes Containing Silica Sand Using Cement Kiln Dust as an Activator

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The hydrothermal reactivity of silica sand was studied using cement kiln dust (CKD) as an activator in addition to the Portlandcement fraction of El-Karnak cement (a blend of ordinary Portland cement and ground sand). Autoclaved El-Karnak cementpastes were studied at pressures of 0.507, 1.013 and 1.520 MPa of saturated steam with respect to their compressive strength,kinetics of hydrothermal reaction and the phase composition of the formed hydrates. The role of CKD in affecting thephysicochemical and mechanical properties of El-Karnak cement pastes was studied by autoclaving of several pastes containing5, 7.5, 10 and 20% CKD at a pressure of 1.013 MPa of saturated steam. CKD was added either as a raw CKD (unwashed) orafter washing with water (washed CKD). The results of these physicochemical studies obtained could be related as much aspossible to the role of CKD (raw or washed) in affecting the hydrothermal reactivity of silica sand in El-Karnak cement pastes.

  4. Glass ionomer restorative cement systems: an update.

    Science.gov (United States)

    Berg, Joel H; Croll, Theodore P

    2015-01-01

    Glass ionomer cements have been used in pediatric restorative dentistry for more than two decades. Their usefulness in clinical dentistry is preferential to other materials because of fluoride release from the glass component, biocompatibility, chemical adhesion to dentin and enamel, coefficient of thermal expansion similar to that of tooth structure, and versatility. The purpose of this paper was to review the uses of glass ionomer materials in pediatric dentistry, specifically as pit and fissure sealants, dentin and enamel replacement repair materials, and luting cements, and for use in glass ionomer/resin-based composite stratification tooth restoration (the sandwich technique). This article can also be used as a guide to research and clinical references regarding specific aspects of the glass ionomer systems and how they are used for young patients.

  5. Scrap tire ashes in portland cement production

    Directory of Open Access Journals (Sweden)

    Mónica Adriana Trezza

    2009-01-01

    Full Text Available Scrap tires are not considered harmful waste, but their stocking and disposal are a potential health and environmental risk. Properly controlled calcinations at high temperatures make tire combustion an interesting alternative due to its high calorific power, comparable to that of fuel-oil. Consequently, using them as an alternative combustible material in cement kilns makes it possible to give it a valuable use. However, it remains to be assured whether the impurities added to the clinker through these fuels do not affect its structure or properties.This paper shows the studies carried out on different clinkers under laboratory conditions with different levels of addition of scrap tire ashes, added by partially replacing traditional fuel in cement kilns.

  6. Underground void filling by cemented mill tailings

    Institute of Scientific and Technical Information of China (English)

    Choudhary Bhanwar Singh; Kumar Santosh

    2013-01-01

    Underground mining always create voids. These voids can cause subsidence of surface. So it is always a demand to fill the void in such a manner that the effect of underground mining can be minimized. Void filling using mill tailings especially in metal mining is one of the best techniques. The tailings produced in milling process have traditionally been disposed in tailing ponds creating a waste disposal and environ-mental problems in terms of land degradation, air and water pollution, etc. This disposal practice is more acute in the metal milling industry where the fine grinding, required for value liberation, results in the production of very fine tailings in large percentage. This paper includes discussions on the effectiveness of different paste mixes with varying cement contents in paste backfilling operations. The results revealed that material composition and use of super plasticizer strongly influenced the strength of cemented backfill.

  7. [Environment load from China's cement production].

    Science.gov (United States)

    Zhu, Tian-le; He, Wei; Zeng, Xiao-lan; Huang, Xin; Ma, Bao-guo

    2006-10-01

    Based on the life-cycle theory, a quantitative evaluation of the environment load caused by cement manufacturing in China was carried out with the application of the CML. environmental impact assessment method. The results show that global warming potential, energy depletion potential and abiotic depletion potential make the main contribution to the environment impact, their environmental loads corresponding to identical environmental impact sorts being 2.76%, 2.34% and 1.39% of the overall load of the whole world, respectively. In 2004, the environment load from cement manufacturing in China is roughly 1.28% of the overall load of the whole world, in which the environmental loads from the shaft kiln processing, wet rotary processing and new-type dry processing being 0.84%, 0.12% and 0.32%, respectively. And it can be reduced to about 1% by replacing backward production processes with the dry method production process.

  8. High temperature cement raw meal flowability

    DEFF Research Database (Denmark)

    Maarup, Claus; Hjuler, Klaus; Dam-Johansen, Kim

    2014-01-01

    The flowability of cement raw meal is investigated at temperatures up to 850°C in a specially designed monoaxial shear tester. Consolidation stresses of 0.94, 1.87 and 2.79kPa are applied. The results show that the flowability is reduced as temperature is increased above 550°C, indicated by incre......The flowability of cement raw meal is investigated at temperatures up to 850°C in a specially designed monoaxial shear tester. Consolidation stresses of 0.94, 1.87 and 2.79kPa are applied. The results show that the flowability is reduced as temperature is increased above 550°C, indicated...

  9. DESIGN OF CEMENT COMPOSITES WITH INCREASED IMPERMEABILITY

    Directory of Open Access Journals (Sweden)

    Fedyuk Roman Sergeevich

    2016-05-01

    Full Text Available The paper deals with the development of composite binders for producing concrete with improved characteristics of gas, water and vapor permeability. The authors investigate the processes of composite materials formation in order of decreasing scale levels from macro to nanostructures. The criteria for optimization of the volume of dispersed additives in concrete are offered. The authors theoretically studied the technological features of the formation of hydrated cement stone structure. A positive effect of nanodispersed additives on the structure and physico-mechanical properties of cement composite materials are predicted. Thanks to its improved features, such as good ratio of strength and body density, high density and lifetime, the modified concrete may be used when solving various practical tasks of the construction branch.

  10. Development of a novel cement by conversion of hopeite in set zinc phosphate cement into biocompatible apatite.

    Science.gov (United States)

    Horiuchi, Shinya; Asaoka, Kenzo; Tanaka, Eiji

    2009-01-01

    Synthetic bone cement that has zinc oxide core particles covered with hydroxyapatite (HAP) was developed; that is, the conversion of hopeite, the traditional zinc phosphate cement, into HAP was attempted. Here, hopeite is the final product of the reaction between powders and trituration liquid of the traditional zinc phosphate cement. This cement may have many advantages not only in terms of biological functions but also the setting process of the traditional cement and the mechanical properties of the developed compact if the hopeite can be converted into calcium phosphate (CP). In this study, calcium nitrate solutions of various concentrations were used for the conversion of hopeite crystals into CP. The products after the solution treatment were analyzed by X-ray diffractometry (XRD), Fourier transform infrared spectrometry (FTIR), and scanning electron microscope (SEM) observation. These results indicated that the converted scholzite crystals could be partially detected. Several types of set zinc phosphate cement with different P/L ratios were arranged. The surface products of the set cement after the solution treatment were analyzed by XRD. However, the crystal phase such as hopeite was not detected except for zinc oxide. The set cement, which was treated with the calcium nitrate solution, was immersed in simulated body fluid (SBF). HAP-like crystals on the set cement could be detected for the specimens immersed for 4 weeks. These findings suggested that the binding phase in the set cement could be converted into HAP by immersion in SBF.

  11. Preclinical investigations towards the first spacer gel application in prostate cancer treatment during particle therapy at HIT

    OpenAIRE

    Ruciński, Antoni; Bauer, Julia; Campbell, Patrick; Brons, Stephan; Unholtz, Daniel; Habl, Gregor; Herfarth, Klaus; Debus, Jürgen; Bert, Christoph; Parodi, Katia; Jäkel, Oliver; Haberer, Thomas

    2013-01-01

    Background The application of spacer gel represents a promising approach to reliably spare the rectal frontal wall during particle therapy (IJROBP 76:1251-1258, 2010). In order to qualify the spacer gel for the clinical use in particle therapy, a variety of measurements were performed in order to ensure the biological compatibility of the gel, its physical stability during and after the irradiation, and a proper definition of the gel in terms of the Hounsfield Unit (HU) values for the treatme...

  12. Distribution of CRISPR spacer matches in viruses and plasmids of crenarchaeal acidothermophiles and implications for their inhibitory mechanism

    DEFF Research Database (Denmark)

    Shah, Shiraz Ali; Hansen, Niels R; Garrett, Roger A

    2009-01-01

    Transcripts from spacer sequences within chromosomal repeat clusters [CRISPRs (clusters of regularly interspaced palindromic repeats)] from archaea have been implicated in inhibiting or regulating the propagation of archaeal viruses and plasmids. For the crenarchaeal thermoacidophiles, the chromo......Transcripts from spacer sequences within chromosomal repeat clusters [CRISPRs (clusters of regularly interspaced palindromic repeats)] from archaea have been implicated in inhibiting or regulating the propagation of archaeal viruses and plasmids. For the crenarchaeal thermoacidophiles...

  13. Understanding acoustic methods for cement bond logging.

    Science.gov (United States)

    Wang, Hua; Tao, Guo; Shang, Xuefeng

    2016-05-01

    Well cementation is important for oil/gas production, underground gas storage, and CO2 storage, since it isolates the reservoir layers from aquifers to increase well integrity and reduce environmental footprint. This paper analyzes wave modes of different sonic/ultrasonic methods for cement bonding evaluation. A Two dimensional finite difference method is then used to simulate the wavefield for the ultrasonic methods in the cased-hole models. Waveforms of pulse-echo method from different interfaces in a good bonded well are analyzed. Wavefield of the pitch-catch method for free casing, partial or full bonded models with ultra-low density cement are studied. Based on the studies, the modes in different methods are considered as follows: the zero-order symmetric Leaky-Lamb mode (S0) for sonic method, the first-order symmetric Leaky-Lamb mode (S1) for the pulse-echo method, and the zero-order anti-symmetric Leaky-Lamb mode (A0) for the pitch-catch method. For the sonic method, a directional transmitter in both the azimuth and axial directions can generate energy with a large incidence angle and azimuth resolution, which can effectively generate S0 and break out the azimuth limitation of the conventional sonic method. Although combination of pulse-echo and pitch-catch methods can determine the bonding condition of the third interface for the ultra-low density cement case, the pitch-catch cannot tell the fluid annulus thickness behind casing for the partial bonded cased-hole.

  14. Polypropylene Fibers in Portland Cement Concrete Pavements.

    Science.gov (United States)

    1992-08-01

    Bibliography on Fiber- Reinforced Cement and Concrete," Miscellaneous Paper C-76-6, with supplements 1, 2, 3, and 4 ( 1977 , 1979, 1980, and 1982), US Army... Mindess , S., Bentur, A., Yan, C., and Vondran, G., "Impact Resistance of Concrete Containing Both Conventional Steel Reinforcement and Fibrillated...Roads, Streets, Walks, and Open Storage Areas," TM 5-822-6/AFM 88-7, Chap. 7, Washington, DC, 1977 . 18. __ , "Concrete Floor Slabs on Grade Subjected

  15. Estimating the chloride transport in cement paste

    Directory of Open Access Journals (Sweden)

    Princigallo, A.

    2012-06-01

    Full Text Available A method was developed to measure the diffusion coefficient of chloride ions in cement paste based on an analytical solution to Fick’s 2nd law in a cylindrical coordinate system. This natural method yielded diffusivity results within as little as a month. Testing time was reduced by exploiting the three-dimensional inward flux in the specimen. In an attempt to determine the saturation concentration, dense portland cement pastes were exposed to a concentrated chloride solution. The method proved to be useful for exploring cement hydration-induced changes in the diffusion coefficient of cement paste.

    Se ha desarrollado un método para medir el coeficiente de difusión de los iones cloruro en la pasta de cemento, partiendo de una aplicación analítica de la segunda ley de Fick en un sistema de coordinadas cilíndrico. Este método, que es natural, demostró ser capaz de producir resultados de difusividad en tan solo un mes. Se consiguió reducir el tiempo de ensayo mediante el aprovechamiento de la tridimensionalidad del flujo desde el exterior al interior de la probeta. A fin de determinar la concentración de saturación, se sometieron las pastas de cemento Portland a una disolución de cloruros concentrada. Este método resultó ser útil en el estudio de los cambios del coeficiente de difusión de la pasta de cemento provocados por las reacciones de hidratación que tienen lugar en esta.

  16. Application of Magnetic Force Generator in Cementation

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The paper introduces a new behavior of the heat treatment technique that is cementation with magnetic force generator (MFHS). The result shows that due to the strong magnetic field action of MFHS on seep means, the energy and activity of active atom are increased, which accelerates interface activating and atoms diffusing, forms action of speed-up seeping. This technique features are Iow in energy consuming, and high in seeping efficiency.

  17. EQUIVALENT MODEL OF EXPANSION OF CEMENT MORTAR UNDER SULPHATE EROSION

    Institute of Scientific and Technical Information of China (English)

    Jue Zhu; Minqiang Jiaug; Jiankang Chen

    2008-01-01

    The expansion property of cement mortar under the attack of sulfate ions is studied by experimental and theoretical methods.First,cement mortars are fabricated with the ratio of water to cement of 0.4,0.6,and 0.8.Secondly,the expansion of specimen immerged in sulphate solution is measured at different times.Thirdly,a theoretical model of expansion of cement mortar under sulphate erosion is suggested by virtue of represent volume element method.In this model, the damage evolution due to the interaction between delayed ettringite and cement mortar is taken into account.Finally,the numerical calculation is performed.The numerical and experimental results indicate that the model perfectly describes the expansion of the cement mortar.

  18. Injectable bioactive calcium-magnesium phosphate cement for bone regeneration.

    Science.gov (United States)

    Wu, Fan; Su, Jiacan; Wei, Jie; Guo, Han; Liu, Changsheng

    2008-12-01

    Novel injectable and degradable calcium-magnesium phosphate cement (CMPC) with rapid-setting characteristic was developed by the introduction of magnesium phosphate cement (MPC) into calcium phosphate cement (CPC). The calcium-magnesium phosphate cement prepared under the optimum P/L ratio exhibited good injectability and desired workability. It could set within 10 min at 37 degrees C in 100% relative humidity and the compressive strength could reach 47 MPa after setting for 48 h, indicating that the prepared cement has relatively high initial mechanical strength. The results of in vitro degradation experiments demonstrated the good degradability of the injectable CMPC, and its degradation rate occurred significantly faster than that of pure CPC in simulated body fluid (SBF) solution. It can be concluded that the novel injectable calcium-magnesium phosphate cement is highly promising for a wide variety of clinical applications, especially for the development of minimally invasive techniques.

  19. Test on Sensor Effect of Cement Matrix Piezoelectric Composite

    Institute of Scientific and Technical Information of China (English)

    YANG Xiaoming; LI Zhongxian; DING Yang; LI Zongjin

    2005-01-01

    A novel cement matrix smart piezoelectric composite and its application as sensing element are presented.A cement matrix smart piezoelectric composite piece encapsulated in a cement mortar formed a practical sensor, and it was tested on material test system with cyclic loading.According to the theoretical analysis, the function of the cement matrix piezoelectric sensor output voltage was expressed in terms of the magnitude of the input cyclic loading amplitude and frequency.The curve fitting of gain function that is defined as sensor′s gain factor under different frequencies of input loading was carried out. From the results of curve fitting, it is found that the cement matrix smart piezoelectric composite has a simple relationship between input loading and output voltage.Therefore the cement matrix piezoelectric composite sensor is suitable to be applied in structural health monitoring.

  20. Solidification of Spent Ion Exchange Resin Using ASC Cement

    Institute of Scientific and Technical Information of China (English)

    周耀中; 云桂春; 叶裕才

    2002-01-01

    Ion exchange resins (IERs) have been widely used in nuclear facilities. However, the spent radioactive IERs result in major quantities of low and intermediate level radioactive wastes. This article describes a laboratory experimental study on solidification processing of IERs using a new type of cement named ASC cement. The strength of the cementation matrix is in the range of 18-20 MPa (28 d); the loading of the spent IER in the cement-resin matrix is over 45% and leaching rates of 137Cs, 90Sr and 60Co are 7.92×10-5, 5.7×10-6, and 1.19×10-8 cm/d. The results show that ASC cement can be a preferable cementation material for immobilization of radioactive spent IER.

  1. Utilization of red mud in cement production: a review.

    Science.gov (United States)

    Liu, Xiaoming; Zhang, Na

    2011-10-01

    Red mud is a solid waste residue of the digestion of bauxite ores with caustic soda for alumina production. Its disposal remains a worldwide issue in terms of environmental concerns. During the past decades, extensive work has been done by a lot of researchers to develop various economic ways for the utilization of red mud. One of the economic ways is using red mud in cement production, which is also an efficient method for large-scale recycling of red mud. This paper provides a review on the utilization of red mud in cement production, and it clearly points out three directions for the use of red mud in cement production, namely the preparation of cement clinkers, production of composite cements as well as alkali-activated cements. In the present paper, the chemical and mineralogical characteristics of red mud are summarized, and the current progresses on these three directions are reviewed in detail.

  2. Chemical and physical properties of bone cement for vertebroplasty

    Directory of Open Access Journals (Sweden)

    Po-Liang Lai

    2013-08-01

    Full Text Available Vertebral compression fracture is the most common complication of osteoporosis. It may result in persistent severe pain and limited mobility, and significantly impacts the quality of life. Vertebroplasty involves a percutaneous injection of bone cement into the collapsed vertebrae by fluorescent guide. The most commonly used bone cement in percutaneous vertebroplasty is based on the polymerization of methylmethacrylate monomers to polymethylmethacrylate (PMMA polymers. However, information on the properties of bone cement is mostly published in the biomaterial sciences literature, a source with which the clinical community is generally unfamiliar. This review focuses on the chemistry of bone cement polymerization and the physical properties of PMMA. The effects of altering the portions and contents of monomer liquid and polymer powders on the setting time, polymerization temperature, and compressive strength of the cement are also discussed. This information will allow spine surgeons to manipulate bone cement characteristics for specific clinical applications and improve safety.

  3. Injectable Premixed Cement of Nanoapatite and Polyamide Composite

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A new type of injectable premixed bone cement consisting of nano-hydroxyapatite (n-HA) and polyamide 66(PA66) composite is investigated. This cement can be handled as paste and easily shaped, which can set in air, in physiological saline solution and in blood. The setting time, injectability and compressive strength of the cement largely depend on the ratio of liquid to powder (L/P). Moreover, the content of n-HA in composite also affects the compressive strength and injectability of the cement. The premixed composite cement can remain stable in the package for a long period and harden only after delivery to the defects site. The results suggest that injectable premixed cement has a reasonable setting time, reasonable viscosity for injecting, excellent washout resistance and high mechanical strength, which can be developed for root canal filling, sealing and various bone defects augmentation.

  4. The Pore Structure and Hydration Performance of Sulphoaluminate MDF Cement

    Institute of Scientific and Technical Information of China (English)

    HUANG Cong-yun; YUAN Run-zhang; LONG Shi-zong

    2004-01-01

    The hydration and pore structure of sulphoaluminate MDF cement were studied by X-ray diffractometer ( XRD ), scanning electron microscope (SEM) and mercury intrusion porosimeter ( MIP ) etc. The ex-perimental results indicate that hydration products of the materials are entringites ( Aft ), aluminium hydroxide andCSH (Ⅰ) gel etc. Due to its very low water-cement ratio, hydration function is only confined to the surfaces of ce-ment grains, and there is a lot of sulphoaluminate cement in the hardenite which is unhydrated yet. Hydration re-action was rapidly carried under the condition of the heat-pressing. Therefore cement hydrates Aft, CSH (Ⅰ) andaluminium hydroxide gel fill in pores. The expansibility of Aft makes the porosity of MDF cement lower ( less than1 percent ) and the size of pore smaller (80 percent pore was less than 250A), and enhances its strength.

  5. Cement-Based Materials for Nuclear Waste Storage

    CERN Document Server

    Cau-di-Coumes, Céline; Frizon, Fabien; Lorente, Sylvie

    2013-01-01

    As the re-emergence of nuclear power as an acceptable energy source on an international basis continues, the need for safe and reliable ways to dispose of radioactive waste becomes ever more critical. The ultimate goal for designing a predisposal waste-management system depends on producing waste containers suitable for storage, transportation and permanent disposal. Cement-Based Materials for Nuclear-Waste Storage provides a roadmap for the use of cementation as an applied technique for the treatment of low- and intermediate-level radioactive wastes.Coverage includes, but is not limited to, a comparison of cementation with other solidification techniques, advantages of calcium-silicate cements over other materials and a discussion of the long-term suitability and safety of waste packages as well as cement barriers. This book also: Discusses the formulation and production of cement waste forms for storing radioactive material Assesses the potential of emerging binders to improve the conditioning of problemati...

  6. Formulating a low-alkalinity cement for radioactive waste repositories

    Energy Technology Data Exchange (ETDEWEB)

    Coumes, C. Cau Dit; Courtois, S.; Leclercq, S.; Bourbon, X

    2004-07-01

    A multi-annual research program has been launched in January 2003 by CEA, EDF and ANDRA in order to formulate and characterize low-alkalinity and low-heat cements which would be compatible with an underground waste repository environment. Four types of bindings have been investigated: binary blends of Portland cement and silica fume or metakaolin, as well as ternary blends of Portland cement, fly ash and silica fume or metakaolin. Promising results have been obtained with a mixture comprising 37.5% Portland cement, 32.5% silica fume, and 30% fly ash: pH of water in equilibrium with fully hydrated cement is below 11. Moreover, silica fume compensates for the low reactivity of fly ash, while fly ash allows to reduce water demand, heat release, and dimensional variations of cement pastes and mortars. (authors)

  7. Effective Permeability Change in Wellbore Cement with Carbon Dioxide Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Um, Wooyong; Jung, Hun Bok; Martin, Paul F.; McGrail, B. Peter

    2011-11-01

    Portland cement, a common sealing material for wellbores for geological carbon sequestration was reacted with CO{sub 2} in supercritical, gaseous, and aqueous phases at various pressure and temperature conditions to simulate cement-CO{sub 2} reaction along the wellbore from carbon injection depth to the near-surface. Hydrated Portland cement columns (14 mm diameter x 90 mm length; water-to-cement ratio = 0.33) including additives such as steel coupons and Wallula basalt fragments were reacted with CO{sub 2} in the wet supercritical (the top half) and dissolved (the bottom half) phases under carbon sequestration condition with high pressure (10 MPa) and temperature (50 C) for 5 months, while small-sized hydrated Portland cement columns (7 mm diameter x 20 mm length; water-to-cement ratio = 0.38) were reacted with CO{sub 2} in dissolved phase at high pressure (10 MPa) and temperature (50 C) for 1 month or with wet CO{sub 2} in gaseous phase at low pressure (0.2 MPa) and temperature (20 C) for 3 months. XMT images reveal that the cement reacted with CO{sub 2} saturated groundwater had degradation depth of {approx}1 mm for 1 month and {approx}3.5 mm for 5 month, whereas the degradation was minor with cement exposure to supercritical CO{sub 2}. SEM-EDS analysis showed that the carbonated cement was comprised of three distinct zones; the innermost less degraded zone with Ca atom % > C atom %, the inner degraded zone with Ca atom % {approx} C atom % due to precipitation of calcite, the outer degraded zone with C atom % > Ca atom % due to dissolution of calcite and C-S-H, as well as adsorption of carbon to cement matrix. The outer degraded zone of carbonated cement was porous and fractured because of dissolution-dominated reaction by carbonic acid exposure, which resulted in the increase in BJH pore volume and BET surface area. In contrast, cement-wet CO{sub 2}(g) reaction at low P (0.2 MPa)-T (20 C) conditions for 1 to 3 months was dominated by precipitation of micron

  8. Cements and adhesives for all-ceramic restorations.

    Science.gov (United States)

    Manso, Adriana P; Silva, Nelson R F A; Bonfante, Estevam A; Pegoraro, Thiago A; Dias, Renata A; Carvalho, Ricardo M

    2011-04-01

    Dental cements are designed to retain restorations, prefabricated or cast posts and cores, and appliances in a stable, and long-lasting position in the oral environment. Resin-based cements were developed to overcome drawbacks of nonresinous materials, including low strength, high solubility, and opacity. Successful cementation of esthetic restorations depends on appropriate treatment to the tooth substrate and intaglio surface of the restoration, which in turn, depends on the ceramic characteristics. A reliable resin cementation procedure can only be achieved if the operator is aware of the mechanisms involved to perform the cementation and material properties. This article addresses current knowledge of resin cementation concepts, exploring the bonding mechanisms that influence long-term clinical success of all-ceramic systems. Copyright © 2011 Elsevier Inc. All rights reserved.

  9. The fluid-compensated cement bond log

    Energy Technology Data Exchange (ETDEWEB)

    Nayfeh, T.H.; Wheelis, W.B. Jr.; Leslie, H.D.

    1986-08-01

    Simulations of cement bond logging (CBL) have shown that wellbore fluid effects can be segregated from sonic-signal response to changing cement strengths. Traditionally, the effects have been considered negligible and the CBL's have been interpreted as if water were in the wellbore. However, large variations in CBL's have become apparent with the increasing number of logs run in completion fluids, such as CaCl/sub 2/, ZnBr/sub 2/, and CaBr/sub 2/. To study wellbore fluid effects, physical and numerical models were developed that simulated the wellbore geometry. Measurements were conducted in 5-, 7-, and 9 5/8-in. casings for a range of wellbore fluid types and for both densities and viscosities. Parallel numerical modeling used similar parameters. Results show that bond-log amplitudes varied dramatically with the wellbore fluid acoustic impedance-i.e., there was a 70% increase in signal amplitudes for 11.5 lbm/gal (1370-kg/m/sup 3/) CaCl/sub 2/ over the signal amplitude in water. This led to the development of a fluid-compensated bond log that corrects the amplitude for acoustic impedance of various wellbore fluids, thereby making the measurements more directly related to the cement quality.

  10. Tunisian gypsums: Characteristics and use in cement

    Science.gov (United States)

    Mahmoudi, Salah; Bennour, Ali; Chalwati, Youssef; Souidi, Khouloud; Thabet, Manel; Srasra, Ezzedine; Zargouni, Fouad

    2016-09-01

    Gypsum materials of hundred meters thickness and interbedded with marine claystones and limestones from different paleogeographic sectors in the Tunisian territory are studied to assess their suitability for cement production. For this reason, thirty representative samples are analysed by chemical, physical and geotechnical tests. The obtained results for the studied gypsum materials are compared to Tunisian and European norms and with the local cements, currently marketed and which obey international norms. Indeed, for all samples hydraulic modulus HM, silica modulus SM and alumina modulus AM vary from (2.37-2.44), (2.48-2.68) and (1.45-2.5), respectively; whereas the required values for these modulus are (1.5-2.5), (2-3) and (1.5-2.5). The same behavior is observed for mineralogical analyses of C3S, C2S, C3A and C4AF and compressive strength at different ages. Briefly, Tunisia contains important reserves of gypsum scattered and spread over the Tunisian territory and can be used for cement production.

  11. A Comparison of Flow Field Characteristics from PIV Experiment Measurement to Numerical Simulation behind a Spacer in a Vertical Pipe

    Directory of Open Access Journals (Sweden)

    Lávička D.

    2010-07-01

    Full Text Available This paper describes the topic of measurement using a modern laser method (PIV in an annular channel of very small dimensions. The annular channel simulates the flow area around a model of a fuel rod in the VVER nuclear reactor. The annular channel holds spacers which create obstacles to fluid flow. The spacers serve a number of important purposes. In the real nuclear reactor, the spacer holds a fuel rod in the fuel rod bundle. Another important function of the spacer is to influence the flow field characteristics, especially turbulence size, by the shape of the spacer. The value of the turbulence regulates the intensity of heat transfer between the fuel rod and the fluid. Therefore, it is very important to provide a correct description and analysis of the flow field behind the obstacle the spacer generates. The paper further looks into the solution of the same task using numerical simulation. The solution of this task consisted of setting the suitable boundary conditions and of setting the turbulence model for the numerical simulation. The result is a comparison of the flow field characteristics from the experimental measurement and the findings of the numerical simulation. The numerical simulation was carried out using commercial CFD software package, FLUENT.

  12. A Rationale for Going Back to the Future: Use of Disposable Spacers for Pressurised Metered Dose Inhalers

    Directory of Open Access Journals (Sweden)

    Mark Sanders

    2015-01-01

    Full Text Available The introduction of pressurised metered dose inhalers (MDIs in the mid-1950s completely transformed respiratory treatment. Despite decades of availability and healthcare support and development of teaching aids and devices to promote better use, poor pMDI user technique remains a persistent issue. The main pMDI user aid is the spacer/valved holding chamber (VHC device. Spacer/chamber features (size, shape, configuration, construction material, and hygiene considerations can vie with clinical effectiveness (to deliver the same dose as a correctly used pMDI, user convenience, cost, and accessibility. Unsurprisingly, improvised, low-cost alternatives (plastic drink bottles, paper cups, and paper towel rolls have been pressed into seemingly effective service. A UK law change permitting schools to hold emergency inhalers and spacers has prompted a development project to design a low-cost, user-friendly, disposable, and recyclable spacer. This paper spacer requires neither preuse priming nor washing, and has demonstrated reproducible lung delivery of salbutamol sulphate pMDI, comparable to an industry-standard VHC, an alternative paperboard VHC, and pMDI alone. This new device appears to perform better than these other VHC devices at the low flow rates thought achievable by paediatric patients. The data suggest that this disposable spacer may have a place in the single-use emergency setting.

  13. Carbonate Looping for De-Carbonization of Cement Plants

    OpenAIRE

    2011-01-01

    Cement industry is one of the largest emitter of CO2 other than power generation plants, which includes the emissions from combustion of fuel and also from calcination of limestone for clinker production. In order to reduce CO2 emissions from the cement industry an effective an economically feasible technology is to be developed. The carbonate looping process is a promising technology, which is particularly suitable for the cement industry as limestone could be used for capture and release of...

  14. Personal exposure to inhalable cement dust among construction workers.

    Science.gov (United States)

    Peters, Susan; Thomassen, Yngvar; Fechter-Rink, Edeltraud; Kromhout, Hans

    2009-01-01

    Objective- A case study was carried out to assess cement dust exposure and its determinants among construction workers and for comparison among workers in cement and concrete production.Methods- Full-shift personal exposure measurements were performed and samples were analysed for inhalable dust and its cement content. Exposure variability was modelled with linear mixed models.Results- Inhalable dust concentrations at the construction site ranged from 0.05 to 34 mg/m(3), with a mean of 1.0 mg/m(3). Average concentration for inhalable cement dust was 0.3 mg/m(3) (GM; range 0.02-17 mg/m(3)). Levels in the ready-mix and pre-cast concrete plants were on average 0.5 mg/m(3) (GM) for inhalable dust and 0.2 mg/m(3) (GM) for inhalable cement dust. Highest concentrations were measured in cement production, particularly during cleaning tasks (inhalable dust GM = 55 mg/m(3); inhalable cement dust GM = 33 mg/m(3)) at which point the workers wore personal protective equipment. Elemental measurements showed highest but very variable cement percentages in the cement plant and very low percentages during reinforcement work and pouring. Most likely other sources were contributing to dust concentrations, particularly at the construction site. Within job groups, temporal variability in exposure concentrations generally outweighed differences in average concentrations between workers. 'Using a broom', 'outdoor wind speed' and 'presence of rain' were overall the most influential factors affecting inhalable (cement) dust exposure.Conclusion- Job type appeared to be the main predictor of exposure to inhalable (cement) dust at the construction site. Inhalable dust concentrations in cement production plants, especially during cleaning tasks, are usually considerably higher than at the construction site.

  15. Beta-tricalcium phosphate release from brushite cement surface.

    Science.gov (United States)

    Alkhraisat, M Hamdan; Mariño, F Tamimi; Retama, J Rubio; Jerez, L Blanco; López-Cabarcos, E

    2008-03-01

    Different in vivo studies demonstrated that brushite cements are biocompatible, bioresorbable, and osteoconductive. However, the decay of brushite cements has been scarcely studied even though it may be of great concern for clinical applications in highly blood-perfused regions. This work was elaborated to elucidate factors that determine brushite cement surface disintegration. For that, brushite cements were modified using in their preparation different aqueous solutions of phosphoric, glycolic, tartaric, and citric acids in concentrations that were reported to improve the cement properties. Two-viscosity enhancing polysaccharides, chondroitin-4 sulfate and hyaluronic acid, were also assayed. Thereafter, pre- and set cement samples were immersed in distilled water for 24 h. The cement-solid weight loss, microstructure, liquid phase viscosity, mean size of the released particles, and zeta potential were analyzed using X-ray diffraction, FTIR spectroscopy, light scattering, scanning electron microscopy and optical microscopy. It was found that the particles released from the cement surface were beta-TCP, and their amount depends on the carboxylic acid used in the preparation of the cement. The addition of hyaluronic acid and chondroitin-4 sulfate decreased the amount of released particles from the surface of the set brushite cement made with citric acid. Furthermore, the hyaluronic acid increased significantly the viscosity of the citric acid solution and the cement paste prepared with this liquid phase showed a pronounced step down in particle release. In this study, we showed that the water solubility of calcium carboxylate and the viscosity of mixing liquid may dictate the superficial disintegration of brushite cements.

  16. Bone cement flow analysis by stepwise injection through medical cannulas.

    Science.gov (United States)

    Zderic, Ivan; Steinmetz, Philipp; Windolf, Markus; Richards, R Geoff; Boger, Andreas; Gueorguiev, Boyko

    2016-12-01

    Cement leakage is a serious adverse event potentially occurring during vertebroplasty. Pre-operative in-silico planning of the cement filling process can help reducing complication rates related to leakage. This requires a better understanding of the cement flow along the whole injection path. Therefore, the aim of the present study was to analyze bone cement flow behavior by stepwise injections through medical cannulas. Sixteen cannulas were assigned to four groups for stepwise injection of differently colored cement portions of 1ml volume. Each group differed in the amount of injected cement portions with a range of 1-4ml. After cement curing longitudinal cross-sections of the cannulas were performed and high-resolution pictures taken. Based on these pictures, quadratic polynomial interpolation was applied to the marked intersections between the last two injected cement portions to calculate the leading coefficients. Leading coefficients in the groups with three cement portions (0.287 ± 0.078), four portions (0.243 ± 0.041) and two portions (0.232 ± 0.050) were comparable and significantly higher than the group with one cement portion (0.0032 ± 0.0004), p ≤ 0.016. Based on these findings, cement flow through medical cannulas can be considered as predictable and can therefore be excluded as a source of risk for possible cement leakage complications during vertebroplasty procedures. Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.

  17. Physical, mechanical, and durability properties of gypsum-Portland cement-natural pozzolan blends

    National Research Council Canada - National Science Library

    Colak A

    2001-01-01

    This paper deals with the effect of gypsum Portland cement and gypsum Portland cement natural pozzolan ratios on the physical, mechanical, and durability properties of gypsum Portland cement natural pozzolan blends...

  18. Correlation between the cytotoxicity of self-etching resin cements and the degree of conversion

    Directory of Open Access Journals (Sweden)

    Luís FSA Morgan

    2015-01-01

    Conclusion: These results indicate that photopolymerization of dual cure self-etching resin cements decrease toxic effects on cell culture. Adequate photopolymerization should be considered during cementation when using dual polymerization self-etching resin cements.

  19. A prospective clinical study of polycarboxylate cement in periapical surgery

    National Research Council Canada - National Science Library

    Peñarrocha-Diago, M-A; Ortega-Sánchez, B; García-Mira, B; Maestre-Ferrín, L; Peñarrocha-Oltra, D; Gay-Escoda, C

    .... A prospective clinical study was made of 25 patients subjected to periapical surgery with ultrasound and magnifying loupes, in which polycarboxylate cement was used as retrograde filling material...

  20. Leaching of metals from cement under simulated environmental conditions.

    Science.gov (United States)

    Lu, Huixia; Wei, Fang; Tang, Jingchun; Giesy, John P

    2016-03-15

    Leaching of metals from cement under various environmental conditions was measured to evaluate their environmental safety. A cement product containing clinker, which was produced from cement kiln co-processing of hazardous wastes, was solidified and leaching of metals was characterized using the 8-period test. Concentrations and speciation of metals in cements were determined. Effects of ambient environment and particle size on leachability of metals and mineralogical phases of cement mortars were evaluated by use of XRD and SEM. Results indicated that metals in cements were leachable in various media in descending order of: sea water, groundwater and acid rain. Cr, Ni, As, Co and V were leached by simulated sea water, while Cu, Cd, Pb, Zn, Mn, Sb and Tl were not leached in simulated sea water, groundwater or acid rain. When exposed to simulated acid rain or groundwater, amounts of Cr, Ni, As and V leached was inversely proportional to particle size of cement mortar. According to the one-dimensional diffusion equation, Cr was most leachable and the cumulative leached mass was predicted to be 9.6 mg kg(-1) after 20 years. Results of this study are useful in predicting releases of metals from cement products containing ash and clinkers cement kiln co-processing of hazardous wastes, so that they can be safely applied in the environment.

  1. Corrosion-resistant Foamed Cements for Carbon Steels

    Energy Technology Data Exchange (ETDEWEB)

    Sugama T.; Gill, S.; Pyatina, T., Muraca, A.; Keese, R.; Khan, A.; Bour, D.

    2012-12-01

    The cementitious material consisting of Secar #80, Class F fly ash, and sodium silicate designed as an alternative thermal-shock resistant cement for the Enhanced Geothermal System (EGS) wells was treated with cocamidopropyl dimethylamine oxide-based compound as foaming agent (FA) to prepare numerous air bubble-dispersed low density cement slurries of and #61603;1.3 g/cm3. Then, the foamed slurry was modified with acrylic emulsion (AE) as corrosion inhibitor. We detailed the positive effects of the acrylic polymer (AP) in this emulsion on the five different properties of the foamed cement: 1) The hydrothermal stability of the AP in 200 and #61616;C-autoclaved cements; 2) the hydrolysis-hydration reactions of the slurry at 85 and #61616;C; 3) the composition of crystalline phases assembled and the microstructure developed in autoclaved cements; 4) the mechanical behaviors of the autoclaved cements; and, 5) the corrosion mitigation of carbon steel (CS) by the polymer. For the first property, the hydrothermal-catalyzed acid-base interactions between the AP and cement resulted in Ca-or Na-complexed carboxylate derivatives, which led to the improvement of thermal stability of the AP. This interaction also stimulated the cement hydration reactions, enhancing the total heat evolved during cement’s curing. Addition of AP did not alter any of the crystalline phase compositions responsible for the strength of the cement. Furthermore, the AP-modified cement developed the porous microstructure with numerous defect-free cavities of disconnected voids. These effects together contributed to the improvement of compressive-strength and –toughness of the cured cement. AP modification of the cement also offered an improved protection of CS against brine-caused corrosion. There were three major factors governing the corrosion protection: 1) Reducing the extents of infiltration and transportation of corrosive electrolytes through the cement layer deposited on the underlying CS

  2. Development and clinical trial of a novel bioactive bone cement

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Strontium(Sr)and related compounds have become more attractive in the prevention and treatment of osteoporosis.Previously,we developed a novel bioactive bone cement which is mainly composed of strontium-containing hydroxyapatite(Sr-HA)filler and bisphenol A diglycidylether dimethacrylate(Bis-GMA)resin.This bone cement is superior to conventional polymethylmethacrylate (PMMA)bone cement in bioactivity,biocompatibility,and osseointegration.It also has shown sufficient mechanical strength properties for its use in percutaneous vertebroplasty(PVP)and total hip replacement(THR).In this paper,we review the in vitro,in vivo and clinical evidence for the effectiveness of this bioactive bone cement.

  3. Development of nanosilica bonded monetite cement from egg shells

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Huan, E-mail: huanzhou@cczu.edu.cn [Institute of Biomedical Engineering and Health Sciences, Changzhou University, Changzhou, Jiangsu (China); Department of Mechanical, Industrial and Manufacturing Engineering, The University of Toledo, Toledo, OH (United States); Luchini, Timothy J.F.; Boroujeni, Nariman Mansouri [Department of Mechanical, Industrial and Manufacturing Engineering, The University of Toledo, Toledo, OH (United States); Agarwal, Anand K.; Goel, Vijay K. [Department of Bioengineering, The University of Toledo, Toledo, OH (United States); Bhaduri, Sarit B. [Department of Mechanical, Industrial and Manufacturing Engineering, The University of Toledo, Toledo, OH (United States); Division of Dentistry, The University of Toledo, Toledo, OH (United States)

    2015-05-01

    This work represents further effort from our group in developing monetite based calcium phosphate cements (CPC). These cements start with a calcium phosphate powder (MW-CPC) that is manufactured using microwave irradiation. Due to the robustness of the cement production process, we report that the starting materials can be derived from egg shells, a waste product from the poultry industry. The CPC were prepared with MW-CPC and aqueous setting solution. Results showed that the CPC hardened after mixing powdered cement with water for about 12.5 ± 1 min. The compressive strength after 24 h of incubation was approximately 8.45 ± 1.29 MPa. In addition, adding colloidal nanosilica to CPC can accelerate the cement hardening (10 ± 1 min) process by about 2.5 min and improve compressive strength (20.16 ± 4.39 MPa), which is more than double the original strength. The interaction between nanosilica and CPC was monitored using an environmental scanning electron microscope (ESEM). While hardening, nanosilica can bond to the CPC crystal network for stabilization. The physical and biological studies performed on both cements suggest that they can potentially be used in orthopedics. - Highlights: • Cement raw powder is derived from egg shells. • A microwave assisted system is used for preparing monetite bone cement. • Colloidal silica is used to reinforce cement.

  4. Accuracy of Image Analysis in Quantitative Study of Cement Paste

    Directory of Open Access Journals (Sweden)

    Feng Shu-Xia

    2016-01-01

    Full Text Available Quantitative study on cement paste especially blended cement paste has been a hot and difficult issue over the years, and the technique of backscattered electron image analysis showed unique advantages in this field. This paper compared the test results of cement hydration degree, Ca(OH2 content and pore size distribution in pure pastes by image analysis and other methods. Then the accuracy of qualitative study by image analysis was analyzed. The results showed that image analysis technique had displayed higher accuracy in quantifying cement hydration degree and Ca(OH2 content than non-evaporable water test and thermal analysis respectively.

  5. Hydration process in Portland cement blended with activated coal gangue

    Institute of Scientific and Technical Information of China (English)

    Xian-ping LIU; Pei-ming WANG; Min-ju DING

    2011-01-01

    This paper deals with the hydration of a blend of Portland cement and activated coal gangue in order to determine the relationship between the degree of hydration and compressive strength development.The hydration process was investigated by various means:isothermal calorimetry,thermal analysis,non-cvaporable water measurement,and X-ray diffraction analysis.The results show that the activated coal gangue is a pozzolanic material that contributes to the hydration of the cement blend.The pozzolanic reaction occurs over a period of between 7 and 90 d,consuming portlandite and forming both crystal hydrates and ill-crystallized calcium silicate hydrates.These hydrates are similar to those found in pure Portland cement.The results show that if activated coal gangue is substituted for cement at up to 30% (w/w),it does not significantly affect the final compressive strength of the blend.A long-term compressive strength improvement can in fact be achieved by using activated coal gangue as a supplementary cementing material.The relationship between compressive strength and degree of hydration for both pure Portland cement and blended cement can be described with the same equation.However,the parameters are different since blended cement produces fewer calcium silicate hydrates than pure Portland cement at the same degree of hydration.

  6. Production of cement requiring low energy expenditure. An industrial test

    Energy Technology Data Exchange (ETDEWEB)

    Gimenez, S.; Blanco, M.T.; Palomo, A.; Puertas, F. (Instituto de Ciencias de la Construccion, Madrid (Spain))

    1991-01-01

    A new method for making cement is proposed. It is based on the use of CaF{sub 2} and CaSO{sub 4} for partial replacement of the usual raw materials in cement manufacturing. This paper shows the feasibility of the proposed method on an industrial scale. A test carried out in a Spanish cement factory (1500 t yield of the new cement) has revealed that the mehtod can not only be adapted to the current technology but also requires a much lower energy expenditure. The final product is shown to have excellent properties in comparison with OPC. (orig.).

  7. Hydration of Portoguese cements, measurement and modelling of chemical shrinkage

    DEFF Research Database (Denmark)

    Maia, Lino; Geiker, Mette Rica; Figueiras, Joaquim A.

    2008-01-01

    form of the dispersion model. The development of hydration varied between the investigated cements; based on the measured data the degree of hydration after 24 h hydration at 20 C varied between 40 and 50%. This should be taken into account when comparing properties of concrete made from the different......Development of cement hydration was studied by measuring the chemical shrinkage of pastes. Five types of Portuguese Portland cement were used in cement pastes with . Chemical shrinkage was measured by gravimetry and dilatometry. In gravimeters results were recorded automatically during at least...

  8. Measuring techniques for autogenous strain of cement paste

    DEFF Research Database (Denmark)

    Lura, Pietro; Jensen, Ole Mejlhede

    2006-01-01

    Volumetric measurement of autogenous strain is frequently performed by placing the fresh cement paste in a rubber membrane submerged in water. The volume change of the cement paste is measured by the amount of water displaced by the submerged sample. Volumetric and linear measurements of autogenous...... of the volumetric method. Water absorption is driven by a lowering of the water activity in the cement paste due to dissolved salts in the pore fluid and to self-desiccation. From the moment of casting, significant water uptake was registered in all experiments. This water uptake influenced the volumetric...... on the same cement pastes....

  9. Measuring techniques for autogenous strain of cement paste

    DEFF Research Database (Denmark)

    Lura, Pietro; Jensen, Ole Mejlhede

    2007-01-01

    Volumetric measurement of autogenous strain is frequently performed by placing the fresh cement paste in a rubber membrane submerged in water. The volume change of the cement paste is measured by the amount of water displaced by the submerged sample. Volumetric and linear measurements of autogenous...... of the volumetric method. Water absorption is driven by a lowering of the water activity in the cement paste due to dissolved salts in the pore fluid and to self-desiccation. From the moment of casting, significant water uptake was registered in all experiments. This water uptake influenced the volumetric...... on the same cement pastes....

  10. Study on the hardening mechanism of cement asphalt binder

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The hydration and hardening mechanism of cement asphalt binder(CAB) was studied.The early hydration process,hydration products and paste microstructure of CAB made by Portland cement and anionic asphalt emulsion were investigated by calorimetry,X-ray diffraction,and environmental scanning electron microscopy.The early hydration process of CAB can be characterized as 5 stages similar to those of Portland cement.There is no chemical reaction detected between cement and asphalt,hence no new hydration products other than those of Portland cement are produced.The hardening of CAB begins with the hydration of cement.When the hydration of cement comes into the acceleration period and its exothermic rate comes to the maximum,the coalescence of asphalt particles in asphalt emulsion is triggered.In the hardened system of CAB,it was found that the hydration products of cement form the skeleton and are covered by the continuous asphalt film.They formed an interpenetrating network system.The emulsifiers in the asphalt emulsion may retard the hydration process of cement.

  11. Sodium diethyldithiocarbamate as accelerator of the rate of copper cementation

    Directory of Open Access Journals (Sweden)

    Abeer A. El-Saharty

    2015-12-01

    Full Text Available The effects of Cu2+ ion concentration and temperature on the cementation rate of copper from copper sulphate on zinc and the effect of additives of the organic compound “sodium diethyldithiocarbamate” (NaDDC were studied. It was noticed that the cementation increases significantly by increasing the concentrations of NaDDC. The rate of cementation increased by 58.58−100.31%. Our data showed that sodium diethyldithiocarbamate reacts with the Cu2+ solution giving a complex of copper diethyldithiocarbamate, which enhances the rate of cementation.

  12. Statistical Study on Cement-Soil Mixture Strength

    Institute of Scientific and Technical Information of China (English)

    YU Zhiqiang; CAO Yonghua; YAN Shuwang

    2005-01-01

    This paper presents an investigation on strength of cement deep mixing (CDM) mixture. Four typical works of offshore or land-based projects are introduced. With samples from these projects and laboratory tests, statistical analysis is made on the increment law of the strength of cement-soil mixture with different amount of cement, and strengths under different working conditions are compared. It is found that the amount of cement in the cement-soil mixture is closely related to the unconfined compressive strength of the mixture. At the age of 90 d,the unconfined compressive strength of the cement-soil mixture increased by 0.054 Mpa-0.124 Mpa with each cement increasing 10 kg/m3 in the cement-soil mixture, averagely increased by 0.085 Mpa, while that at the age of 120 d increased by 11% in comparison.The quality of the cement-soil mixture should be comprehensively evaluated in accordance with the trimmed average of strength, coefficient of variation and rock quality designation (RQD) indicators of sampling ratio.

  13. DEVELOPING A NEW GENERATION OF HIGH PERFORMANCE COMPOSITE CEMENT

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    This paper proposed a new generation of high performance composite cement which is designed according to the optimization of composition and structure of cement paste and is manufactured by blending the different components with special composite techniques. Each of these components has its different special property, and should be compatible with each other and match each other, and the properties of them are complementary mutually. At present, such kind of high performance composite cement can be manufactured with high reactivity cement clinker, ground granulated blast-furnace slag, high grade fly ash, silica fume etc.

  14. Magnesia Modification of Alkali-Activated Slag Fly Ash Cement

    Institute of Scientific and Technical Information of China (English)

    SHEN Weiguo; WANG Yiheng; ZHANG Tao; ZHOU Mingkai; LI Jiasheng; CUI Xiaoyu

    2011-01-01

    A new type of magnesia modification alkali-activated cement was prepared, the strength, setting time, shrinkage ratio and cracking behavior, as well as the composition and structure of the hydration product were investigated. The results indicate that the setting time of this cement is similar to that of the ordinary commercial cements; its strength reaches the standard of 42.5 degree cement, its cracking resistance has been remarkably improved because of the micro-aggregate effect of fly ash and shrinkage compensating of magnesia.

  15. Microindentation of Polymethyl Methacrylate (PMMA Based Bone Cement

    Directory of Open Access Journals (Sweden)

    F. Zivic

    2011-12-01

    Full Text Available Characterization of polymethyl methacrylate (PMMA based bone cement subjected to cyclical loading using microindentation technique is presented in this paper. Indentation technique represents flexible mechanical testing due to its simplicity, minimal specimen preparation and short time needed for tests. The mechanical response of bone cement samples was studied. Realised microindentation enabled determination of the indentation testing hardness HIT and indentation modulus EIT of the observed bone cement. Analysis of optical photographs of the imprints showed that this technique can be effectively used for characterization of bone cements.

  16. Minerals of expansive and non-shrinkage sulfomineral cements

    Directory of Open Access Journals (Sweden)

    Samchenko Svetlana V.

    2017-01-01

    Full Text Available Usually to obtain expansive cements sulfoaluminate clinker or mix aluminate clinker with calcium sulfates (gypsum, hemihydrate, anhydrate are used. For these cements ettringite is an important hydration product and kinetic reaction of this phase plays an important role in determinаting performance. The alternative aluminate phases may be ferrite containing ones. This article deals with the composition and properties of solid solution of calcium sulfoaluminate, sulfoferrite and sulfoaluminoferrite cements. It was studied an influence of calcium sulfate on structure and properties of calcium aluminate and ferrite phases, and their stability under high temperatures. Beside that the properties of cements containing these phases were studied. The investigation of hydration and properties of sulfomineral cements shows that ettringite and its analogies are formed in such way to provide expansion and compression of cement stone. Degree of expansion and self-stressing of cement stone depends not only on composition of sulfated minerals but on ratio and types of clinkers. The higher expansion is reached by the use of high alite containing Portland cement clinker together with sulfoaluminate or sulfoalumoferrite one, the lower expansion is reached by addition of sulfoalumoferrite and sulfoferrite clinkers. These cements are classified as self-stressing, expansive or shrinkage-compensating ones depend on the degree of their expansion after 28 days of curing.

  17. Cementing and formation damage; Cimentacao e dano a formacao

    Energy Technology Data Exchange (ETDEWEB)

    Souza, David Soares de [PETROBRAS, BA (Brazil). Distrito de Perfuracao da Bahia. Div. de Tecnicas e Operacoes

    1994-07-01

    This work presents a general perspective on cementing and formation damage. Few relative experiments to the damage to the formation, that they involve the casing activity and cementing, consider all the factors that affect these operations. So that she can analyze the contribution of a primary cementing has in the formation damage , it should be considered, also, the contribution of the drilling fluid and of the operation of the perforation. With base in experimental data of several accomplished studies, it can be concluded that a primary cementing has small, or any, contribution in the decrease of the productivity of an oil well.

  18. Influence of relationship water/cement upon the processing of cements with pozzolana in standard mortar

    Directory of Open Access Journals (Sweden)

    Gener Rizo, M.

    2002-03-01

    Full Text Available The processing of standard mortar is completed following different methods in accordance with the country, but they exist two fundamental tendecies, the ISO and the ASTM. The cuban norm for mechanic-physic tests is based in ISO, and so they use a constant relationship water/cement in the processing of standard mortar a great problem concerning the cement users when they tested those mixed with puzzolanes, because they don't take care of the bigger water needs of those materials. In this work we present an study of the behaviour of Pozzolanic Portland cements (PP-250 elaborates with a fix and changeable relationship water/cement, obtained starting from the fluidity of the pure Portland cement. (P-350 The results obtained shows that the mechanical resistance decreased in cement mortars PP-250 realised with changeable relationship water/cement. So we recommend the adoption of an optional procedure to elaborate a quality mortar with pozzolana cements.

    La elaboración del mortero normalizado se realiza internacionalmente por diferentes métodos, pero existen dos tendencias fundamentales, la enunciada por ISO y por ASTM. La norma cubana de ensayos físico-mecánicos de cemento se basa en la norma ISO, por lo que para la elaboración del mortero normalizado se utiliza una relación agua/cemento constante. Esto ha provocado discrepancias con los usuarios del cemento, especialmente cuando se ensayan los cementos que contienen puzolanas, ya que se plantea que no se tiene en cuenta la mayor demanda de agua de estos materiales. En el presente trabajo se presenta un estudio del comportamiento de cementos Portland Puzolánicos (PP-250 elaborados con una relación agua/ cemento fija y variable, lograda a partir de la fluidez de la pasta de cemento Portland puro (P-350. Los resultados obtenidos indican que se producen disminuciones en la resistencia mecánica en los morteros de cemento PP-250 elaborados con agua/ cemento variable y recomienda la

  19. Conduction calorimetric studies of ternary binders based on Portland cement, calcium aluminate cement and calcium sulphate

    OpenAIRE

    Torrens Martín, David; Fernández Carrasco, Lucía; Blanco Varela, M.Teresa

    2013-01-01

    Different binders of Portland cement, calcium aluminate cement and calcium sulphate (PC/CAC/CS) have been investigated to determinate the in¿uence the CAC and CS amount in the reactions mechanism. Several mixtures were studied, ratios of 100, 85/15 and 75/25 of PC/CAC with 0, 3 and 5 % of CS. Conduction calorimetric technique was used to follow the hydration during 100 h. The XRD and FTIR techniques were used as support in the analysis of the hydration products. The results have shown tha...

  20. Influence of Temporary Cements on the Bond Strength of Self-Adhesive Cement to the Metal Coronal Substrate.

    Science.gov (United States)

    Peixoto, Raniel Fernandes; De Aguiar, Caio Rocha; Jacob, Eduardo Santana; Macedo, Ana Paula; De Mattos, Maria da Gloria Chiarello; Antunes, Rossana Pereira de Almeida

    2015-01-01

    This research evaluated the influence of temporary cements (eugenol-containing [EC] or eugenol-free [EF]) on the tensile strength of Ni-Cr copings fixed with self-adhesive resin cement to the metal coronal substrate. Thirty-six temporary crowns were divided into 4 groups (n=9) according to the temporary cements: Provy, Dentsply (eugenol-containing), Temp Cem, Vigodent (eugenol-containing), RelyX Temp NE, 3M ESPE (eugenol-free) and Temp Bond NE, Kerr Corp (eugenol-free). After 24 h of temporary cementation, tensile strength tests were performed in a universal testing machine at a crosshead speed of 0.5 mm/min and 1 kN (100 kgf) load cell. Afterwards, the cast metal cores were cleaned by scraping with curettes and air jet. Thirty-six Ni-Cr copings were cemented to the cast metal cores with self-adhesive resin cement (RelyX U200, 3M ESPE). Tensile strength tests were performed again. In the temporary cementation, Temp Bond NE (12.91 ± 2.54) and Temp Cem (12.22 ± 2.96) presented the highest values of tensile strength and were statistically similar to each other (p>0.05). Statistically significant difference (pcementation of Ni-Cr copings with self-adhesive resin cement. In addition, Temp Cem (120.68 ± 48.27) and RelyX Temp NE (103.04 ± 26.09) showed intermediate tensile strength values. In conclusion, the Provy eugenol-containing temporary cement was associated with the highest bond strength among the resin cements when Ni-Cr copings were cemented to cast metal cores. However, the eugenol cannot be considered a determining factor in increased bond strength, since the other tested cements (1 eugenol-containing and 2 eugenol-free) were similar.