Speciation of arsenic metabolites in the urine of occupational workers and experimental rats using an optimised hydride cold-trapping method

A hydride cold-trapping technique was developed and optimised for the measurement of urinary arsenic metabolites. The analytical precision of the method was found to be 6.1, 4.0 and 4.8% (n = 5) for inorganic arsenic (ASi), monomethylarsonate (MMA) and dimethylarsinate (DMA), respectively, with recoveries close to 100%. The detection limits were 1.0, 1.3 and 3 ng for ASi, MMA and DMA, respectively. The method was then used to analyse urine samples obtained from three groups of workers for occupational exposure in three companies where copper chrome arsenate was used for timber treatment. The results were compared with those for a normal control group of laboratory workers. Arsenic and its metabolites were also measured in experimental rats given 5 mg As kg-1 body mass by oral gavage in the form of sodium arsenite, calcium arsenite or sodium arsenate. Occupational workers showed a significantly higher excretion of ASi. Up to two fold increases of urinary ASi excretion in rats compared with control rats were also observed in animals dosed with various forms of arsenicals. The method is suitable for the measurement of arsenic metabolites in urine of both humans and experimental animals.     

Computing network flow on a multiple processor pipeline

We demonstrate the feasibility of a distributed implementation of the Goldberg-Tarjan algorithm for finding the maximum flow in a network. Unlike other parallel implementations of this algorithm, where the network graph is partitioned among many processors, we partition the algorithm among processors arranged in a pipeline. The network graph data are distributed among the processors according to local requirements. The partitioned algorithm is implemented on six processors within a 15-processor pipelined message-passing multicomputer operating at 5 MHz. We used randomly generated networks with integer capacities as examples. Performance estimates based upon a six-processor pipelined implementation indicated a speedup between 3.8 and 5.9 over a single processor     

Memory characteristics of MOSFETs with densely stacked silicon nanocrystal Layers in the gate oxide synthesized by low-energy ion beam

Densely stacked silicon nanocrystal layers embedded in the gate oxide of MOSFETs are synthesized with Si ion implantation into an SiO/sub 2/ layer at an implantation energy of 2 keV. In this letter, the memory characteristics of MOSFETs with 7-nm tunnel oxide and 20-nm control oxide at various temperatures have been investigated. A threshold voltage window of /spl sim/ 0.5 V is achieved under write/erase (W/E) voltages of +12 V/-12 V for 1 ms. The devices exhibit good endurance up to 10/sup 5/ W/E cycles even at a high operation temperature of 150/spl deg/C. They also have good retention characteristics with an extrapolated ten-year memory window of /spl sim/ 0.3 V at 100/spl deg/C.     

An insight into cathode options for microbial fuel cells.

Microbial fuel cell (MFC) is an emerging and promising technology, particularly in the field of wastewater treatment. The MFC capability of achieving organic removal and generating in situ electricity could make it an attractive alternative wastewater treatment technology over conventional treatment technologies. However, MFC is still far from being economically viable, especially because of the cost of the platinum (Pt) catalyst that makes possible the reaction at the cathode. In this study, we tested alternative cathode catalysts, namely sputter-deposited Cobalt (Co) and denitrifying bacteria (biocathode). The performance of these innovative cathodes was compared with that of classic Pt-cathodes. Co competed well with Pt, but further research is still required for biocathodes. However, biocathodes MFC have showed promise.     

Kinetic analysis of the sorption of copper(II) ions on chitosan

The removal of copper ions from aqueous effluents by chitosan was studied in equilibrium and agitated batch contacting systems. The sorption capacities of chitosan for copper ions are 1.26 and 1.12 mmol g^?1 at pH 3.5 and 4.5, respectively. The equilibrium experimental data were best correlated by the Langmuir equation. The kinetics of sorption were studied at an initial solution pH of 4.5 and a chitosan particle size of 355–500 µm. The kinetics were analyzed using four models: the pseudo‐first‐order, pseudo‐second‐order, modified second‐order and Elovich equations. The rate parameters for the four models were determined and the Elovich equation provided the best correlation of the experimental kinetic data. Copyright © 2003 Society of Chemical Industry     

Partial oxidation of methane over Y1Ba2Cu3O6+X−ZFZ

In this communication we report our study on using high-temperature superconductors as partial oxidation catalysts. We have also investigated fluorinated superconducting materials, since the presence of a strong oxidizing agent should favor partial oxidation selectivities.     

Mobility improvement of n-MOSFET's with nitrided gate oxide bybacksurface Ar+ bombardment

Low-energy (550 eV) argon-ion beam was used to bombard directly, the backsurface of nitrided n-MOSFET's after the completion of all conventional nMOS processing steps. The interface characteristics and inversion layer mobility of the MOS devices were investigated. The results show that, as bombardment time increases, interface state density and fixed charge density decrease first, and then the change slows down or even turns around. Correspondingly, the carrier mobility and drain conductance of the MOS devices are found to enhance first, and then saturate or turn around. Therefore, this simple technique, which is readily compatible with existing IC processing, is effective for restoring some of the lost device performance associated with gate-oxide nitridation     

Leg manifestation in alien hand syndrome

In this article, I review various causes of exogenous myoglobinuria(MU) and its pathogenesis in 26 consecutive patients admitted to emergency room, Asan Medical Center and determine whether there is a relationship between concentration of urine myoglobin(Mb) and acute renal failure(ARF) as a complication of MU. Serum and urine Mb were measured by RIA using myoglobin kit(Daiichi, Inc., Tokyo, Japan). The most common disorder of MU was septic shock with hypotension, followed by crush syndrome, major arterial occlusion by thormbosis, alcohol intoxication with status epilepticus, intoxication of unidentified snake venom and drug ingestion. On the basis of this limited amount of data, there is a significant association between high concentration in urine Mb(> 300 ng/ml) and ARF(Fisher's exact test, p < 0.005). To minimize the chances of development of ARF, routine urine Mb levels should be checked on patients at risk, especially septic shock with hypotension.     

Micro-spike EEG electrode and the vacuum-casting technology for mass production

An innovative dry electroencephalography (EEG) electrode has been successfully designed and tested, in which multiple micro-spike electrodes, each of them consisting of a micro-pillar with a micro-tip on top of it, were designed to pass through the hairs and establish electrical conduction at the skin-electrode interface by penetrate into the stratum corneum of the skin. For hygiene reasons, such electrodes should be made disposable, at the same time, should be cost effective. Therefore, a mass production technology, including the processing methods, such as casting, has to be designed and developed. In this project, the micro-spike dry electrodes were fabricated by a vacuum casting method using a master pattern piece made by CNC micro-machining, in which silicone rubber moulds are created and then used to vacuum cast polyurethane (PU), epoxy or epoxy-carbon micro-spike electrodes. In order to obtain a harder polymeric material, varying amount of carbon fillers were added to the epoxy resin, and the hardness of the resulting material were measured and compared. It was found that a higher concentration of added carbon fillers resulted in a harder cast polymer composite. Further to the vacuum casting, to create an electrically conductive layer on the vacuum-casted electrode, an Ag/AgCl electroless deposition method has been developed. The sputtering of the conductive layer was also carried out for comparison. The developed micro-spike electrodes showed better performance in terms of the impedance level and stability as well as a much higher efficiency in EEG measurement.     

Analysis of free intracellular nucleotides using high-performance capillary electrophoresis.

High-performance capillary electrophoresis (HPCE) with UV absorbance detection (254 nm) has been applied for analyzing intracellular free ribonucleotides. The nucleotide profiles obtained from peripheral blood lymphocytes differ from those obtained from Molt4 human leukemic cells. With a 140 mM borate buffer, pH 9.4, a nearly complete profile can be obtained in 25 min. HPCE has comparable resolution to that of high-performance liquid chromatography (HPLC) but is faster in terms of time per sample run (25 min vs 45 min) and requires much less sample (nanoliter range for HPCE vs microliter range for HPLC).