Second and first-derivative spectrophotometry for efficient simultaneous and individual determination of palladium and cobalt using 1-(2-pyridylazo)-2-naphthol in sodium dodecylsulfate micellar media.
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1-(2-Pyridylazo)-2-naphthol (PAN) has been used for the simultaneous and individual determination of palladium and cobalt at trace levels. PAN complexes of palladium and cobalt at neutral pH form green-color neutral complexes, which are soluble in aqueous SDS micellar media. Under optimum conditions, calibration graphs for individual determinations by zero and first-derivative spectrophotometry, and also for simultaneous determinations by second-derivative spectrophotometry were obtained. A zero-crossing method using second-derivative spectrophotometry at 628 or 578 and 614 nm, respectively, for cobalt and palladium was used for simultaneous determinations. The method is able to determine the cobalt-to-palladium ratio, 5:1 to 1:10 (Wt/Wt), accurately. The accuracy and reproducibility of the determination method for various known amounts of cobalt and palladium in their binary mixtures were tested. The effects of diverse ions on the determination of cobalt and palladium to investigate the selectivity of the method were also studied. The recommended procedures were applied to a synthetic binary alloy, cobalt in vitamin B12 and B-complex ampoules, a Co2O3-Co3O4 laboratorial chemical mixture, some synthetic cobalt-alloy samples, a Pd-charcoal catalyst, and some synthetic palladium alloys. (+info)
A facile spectrophotometric method for cobalt determination using alpha-benzilmonoxime in sodium dodecylsulfate micellar solutions.
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Alpha-benzilmonoxime in sodium dodecylsulfate micellar media has been used for the spectrophotometric determination of cobalt at pH 9.0. The linear range of calibration is 0.05-1.50 microg cm(-3) of cobalt at 380 nm with molar absorptivity of 3.72 x 10(4) dm3 mol(-1) cm(-1), which is about 1.5-times greater than that of the alpha-benzilmonoxime extraction based method. The relative standard deviations, recoveries, detection limit and effects of diverse ions on the determination of cobalt were studied. These analytical results were satisfactory. The method was successfully applied to the determination of cobalt in the various samples. (+info)
Efficacious use of nitinol stents in the femoral and popliteal arteries.
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OBJECTIVE: To evaluate the performance and identify predictors of outcome after the use of self-expanding nitinol stents in the treatment of femoropopliteal arterial occlusive disease. METHODS: A retrospective analysis of a prospectively collected database was performed. Outcomes of patients who underwent placement of a nitinol stent in the femoral or above-knee popliteal arteries between 1999 and 2002 were studied. Patency, limb salvage, and patient survival were determined by Kaplan-Meier estimation and intergroup comparisons by log-rank test and Cox proportional hazards model. To define individual factors associated with clinical outcomes, stepwise regression analysis was performed. RESULTS: A total of 41 patients (mean age, 70 +/- 10 years; gender, 26 men and 15 women) underwent percutaneous placement of nitinol stents. Limb salvage was the indication for intervention in 68% of patients. Diabetes was present in 54%, and 36% had end-stage renal disease. Nitinol stents were placed in the superficial femoral (35 patients) or the above-knee popliteal (6 patients) arteries. The mean postprocedural increase in ankle-brachial index was 0.32 +/- 0.19. The 6-month, 1-year, and 2-year primary patency and limb-salvage rates were 95%, 84%, and 84%, and 92%, 89%, and 89%, respectively. Major amputations occurred only in patients undergoing limb-salvage procedures presenting with major tissue loss. No statistically significant differences in patency were seen with regard to diabetes, end-stage renal disease, runoff score, length of vessel stented (median, 80 mm), hypertension, or smoking. CONCLUSIONS: Our initial experience with self-expanding nitinol stents for femoropopliteal occlusive disease appears to demonstrate acceptable patency and limb-salvage rates at these early time points. Further evaluation of clinical outcome with these devices in this and larger groups of patients is warranted. (+info)
An in vitro study into the corrosion of intra-oral magnets in the presence of dental amalgam.
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The aim of this investigation was to study the corrosion behaviour and products of uncoated neodymium-iron-boron magnets in the presence of dental amalgam. Microcosm plaques were grown on discs of neodymium-iron-boron magnets or amalgam in a constant depth film fermentor. The biofilms were supplied with artificial saliva and growth was determined by viable counting. The results showed that the neodymium-iron-boron magnets corroded with an average daily weight loss of 0.115 +/- 0.032 per cent. However, when the magnets were in close proximity to the amalgam the amount of corrosion was reduced to a daily loss of 0.066 +/- 0.023 per cent. The highest loss of constituent elements from the corrosion products of the magnets was observed for iron. The composition of the microcosm plaques altered markedly between the two materials with less streptococci and more Veillonella spp. present in the biofilms grown on magnets in the presence of amalgam. The corrosion of neodymium-iron-boron magnets is limited and in the presence of amalgam is reduced further. This suggests that amalgam present in the mouth will not cause an increased clinical risk in terms of biocompatibility with neodymium-iron-boron magnets. (+info)
Virus-based toolkit for the directed synthesis of magnetic and semiconducting nanowires.
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We report a virus-based scaffold for the synthesis of single-crystal ZnS, CdS, and freestanding chemically ordered CoPt and FePt nanowires, with the means of modifying substrate specificity through standard biological methods. Peptides (selected through an evolutionary screening process) that exhibit control of composition, size, and phase during nanoparticle nucleation have been expressed on the highly ordered filamentous capsid of the M13 bacteriophage. The incorporation of specific, nucleating peptides into the generic scaffold of the M13 coat structure provides a viable template for the directed synthesis of semiconducting and magnetic materials. Removal of the viral template by means of annealing promoted oriented aggregation-based crystal growth, forming individual crystalline nanowires. The unique ability to interchange substrate-specific peptides into the linear self-assembled filamentous construct of the M13 virus introduces a material tunability that has not been seen in previous synthetic routes. Therefore, this system provides a genetic toolkit for growing and organizing nanowires from semiconducting and magnetic materials. (+info)
Disappointing results with a new commercially available thoracic endograft.
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INTRODUCTION: New devices for endovascular treatment of thoracic aortic diseases were recently approved for clinical use by European authorities, obtaining the Conformite Europeenne (CE) mark. In all patients who underwent endovascular treatment of a thoracic aortic disease in 2002, we used a new CE-marked device, the Endofit stent graft. The device is constituted of nitinol stents and polytetrafluoroethylene fabric, and has a simple design and delivery system. METHODS: During 2002, 11 patients (mean age, 75 years; range, 66-85 years) underwent treatment of atherosclerotic aneurysm (n = 9), chronic type B dissection (n = 1), and intramural hematoma (n = 1). Disease involved the descending thoracic aorta in 7 patients and the distal aortic arch in 4 patients. RESULTS: In all cases the Endofit stent grafts were successfully deployed in the intended position. No postoperative paraplegia or paraparesis was recorded. There were two in-hospital deaths: 1 patient died in the operating room (postmortem examination showed a kinked graft); and the other patient died in the intensive care unit on postoperative day 30, after an intraoperative stroke. One surgical conversion was performed 2 weeks after the procedure, because of total collapse of the graft due to rupture of three stents. Other graft-related complications included type I endoleak (n = 2), type II endoleak (n = 1), and incomplete opening of the device (n = 1). CONCLUSION: Endovascular treatment of thoracic disease with the Endofit graft in this small heterogeneous group of patients resulted in several complications, which may arise from both the delivery system and the graft itself. At present, other commercially available endografts may be safer for endovascular treatment of thoracic aortic diseases. (+info)
Pain in the well-fixed, aseptic titanium hip replacement. The role of corrosion.
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We have investigated nine patients with cemented Furlong (JRI, London, UK) titanium hip replacements who presented with early pain despite a well-fixed, aseptic prosthesis. All were followed up clinically and radiologically at regular intervals. Pain was located in the thigh and was worse at night. Radiographs showed cortical hypertrophy of the femur around the tip of the stem. Eight of the nine patients subsequently required single-stage revision using an uncemented prosthesis, which relieved the pain. At revision, the pH of the tip of the stem was found to be highly acidic with macroscopic evidence of corrosion consisting of multiple layers of titanium oxides when studied by X-ray dispersive analysis. Cemented titanium implants have a potential for crevice corrosion leading to cortical hypertrophy and intractable pain. (+info)
Mortality of workers at a plant manufacturing nickel alloys, 1958-2000.
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BACKGROUND: Excess risks of respiratory cancer have been demonstrated in some groups of nickel-exposed workers. It is clear, however, that not all forms of nickel exposure are implicated in these excess risks. Aim To determine whether occupational exposures received in the manufacture of nickel alloys lead to increased risks of cancer, in particular nasal cancer and lung cancer. METHODS: The mortality experienced by a cohort of 1999 workers employed at a plant manufacturing nickel alloys has been investigated. Study subjects were all those male workforce employees first employed in the period 1953-1992 who had at least 5 years employment with the company. Observed numbers of cause-specific deaths were compared with expectations based on national mortality rates. Standardized mortality ratios (SMRs) were calculated by period from commencing employment and by operating area of first job. In addition, rate ratios derived from Poisson regression and based on an internal standard were calculated by levels of duration of employment. RESULTS: SMRs were significantly below 100 for all causes (observed 557, expected 704.3, SMR 79), all neoplasms (observed 169, expected 209.4, SMR 81) non-malignant diseases of the respiratory system (observed 50, expected 73.0, SMR 69) and diseases of the circulatory system (observed 261, expected 335.5, SMR 78). Significantly elevated SMRs were not shown for any cause of death and mortality was below expectation for stomach cancer (observed 8, expected 16.0, SMR 50), lung cancer (observed 64, expected 73.6, SMR 87) and bladder cancer (observed 3, expected 8.0, SMR 38). There were no deaths from nasal cancer (expected 0.33). More detailed findings were unexceptional. CONCLUSIONS: The analyses did not suggest the presence of an occupational cancer hazard in the mortality experience of the cohort. (+info)