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Three nominally identical cohorts of NMC/graphite automotive Li-ion cells aged zero, one, and two years were obtained from an automotive Li-ion cell producer. The aged cells were stored at 50% state of charge at room temperature without cycling. High precision coulometry and differential voltage analysis (dV/dQ vs. Q) were used to probe the fresh and aged cells to learn about the parasitic reactions occurring. The stored cells had developed a mature SEI which led to virtually no capacity loss during testing but precision coulometry still showed evidence for significant electrolyte oxidation at the positive electrode. The fresh cells showed SEI growth at the negative electrode leading to initial capacity fading which accelerated with temperature. They also showed electrolyte oxidation at the positive electrode which increased dramatically with cycling temperature or upper cutoff potential. All cells showed virtually no evidence for loss of active material during storage or cycling. These results strongly suggest that electrolyte additives which limit electrolyte oxidation at the positive electrode side are required to improve the longevity of these cells. [ABSTRACT FROM AUTHOR]

In order to develop Li-ion batteries with improved lifetimes, a means of quickly and accurately estimating battery life is required. The use of coulombic efficiency (CE) is an important tool which provides a way to quantify parasitic reactions occurring within cells. As more stable battery chemistries are developed, the rates of parasitic reactions become smaller and differences in CE among cells with different electrolyte additives become increasingly smaller. In order to resolve these differences, charger systems must be developed which can measure CE with increased precision and accuracy. This paper investigates various ways to improve the precision and accuracy of CE measurements. Using the high-precision charger (HPC) at Dalhousie University (built in 2009) as a starting point, a new prototype charger was built with several modifications to the design of the existing HPC. The effect of each of these modifications is investigated in detail to provide a blueprint for the development of next-generation charger systems. This prototype charger shows greatly improved precision and accuracy, with CE results that are approximately four times more precise than those of the existing HPC and over an order of magnitude more precise than high-end commercially available charger systems. [ABSTRACT FROM AUTHOR]

A user-friendly differential voltage analysis software has been developed and is described here. The user must supply high-precision reference potential-specific capacity data for Li/negative electrode and Li/positive electrodes, as well as the cycled full cell potential-specific capacity. From these, the differential voltage versus capacity, dV/dQ vs. Q, of a full Li-ion cell is calculated and compared to experiment. The calculated dV/dQ vs. Q curve has four adjustable parameters, which are optimized manually with slider bars or automatically by least squares fitting of the calculation to experiment. The parameters are the positive electrode mass, the negative electrode mass, the positive electrode slippage and the negative electrode slippage. Examples of the use of the program are given for graphite/LiCoO2 wound cells cycled for hundreds of cycles. The variation of the four parameters with cycle number give insights into the mechanisms of cell failure equivalent to that which could be obtained with a Li reference electrode inserted within the cell. The software is available free of charge by contacting the authors. [ABSTRACT FROM AUTHOR]

The electrochemical behavior of Pt1-xMnx (0.1 < x < 0.8) catalysts prepared by magnetron sputtering were studied extensively using the rotating disk electrode technique, electron microprobe, X-ray photoelectron spectroscopy and X-ray diffraction. The data suggests that Mn forms an oxide layer at the surface of the catalyst upon contact with air. Mn is preferentially drawn out of the intermixed catalyst into the oxide layer, depleting the core of Mn content. Without significant amounts of Mn present at the core of the catalyst, de-alloying reactions have less effect on the electrochemically active surface area compared to the case of Pt1-xNix, for example. High and low Mn content alloys have about the same Pt-area specific current densities, jspecific, so it is likely that all samples have the same catalytic surface composition, namely Pt. [ABSTRACT FROM AUTHOR]

Pt and intermixed Pt1-xNix (0.65 < x < 0.75) catalysts were sputtered-deposited onto both bare and nanostructured thin film (NSTF)-coated glassy carbon disks. The oxygen reduction reaction (ORR) activities of the disks were determined from Rotating Disk Electrode (RDE) measurements. Experiments on the NTSF-coated disks examined both catalytic activities and the effects of high surface area supports in a single measurement. The RDE measurement protocols were designed to examine changes in catalyst properties and performance during de-alloying and thus did not include the typical "electrochemical cleaning" procedure at the beginning. Instead, a continuous CV-ORR measurement protocol was used to monitor the electrochemical performance indicators such as active surface area (SEF) and ORR kinetic current density of the catalysts over the course of 9 h. As an example, the SEF of Pt25Ni75 on the NSTF-support was initially 20 cm/cm and the SEF increased rapidly at the beginning of the experiment, then stabilized near ∼50 cm²/cm² as Ni de-alloyed. This is compared with sputtered Pt on NSTF support that showed SEF ∼15 cm²/cm². De-alloying is an effective way to create Pt-transition metal catalysts on NSTF with extremely high active surface area. [ABSTRACT FROM AUTHOR]

Nanostructured thin film catalysts (NSTF) with widely varying compositions of PtxMy and PtxMyNz (M, N = Ni, Co, Zr, Hf, Fe, Mn) have been evaluated for 0 x, y, z < 1. The catalysts' activity for oxygen reduction (ORR) was measured in 50 cm² fuel cell membrane electrode assemblies. Pt1-xNix was found to be unique in showing an extraordinarily sharp peak in ORR activity as a function of the as-made composition around x = 0.69 ± 0.02 determined gravimetrically. This composition gave a corresponding fcc lattice parameter of 3.71 Angstroms and a grain size of 7.5 nm. Both surface area and specific activity increases contribute to the increased mass activity of the resultant dealloyed films. The ORR mass activity of the Pt3Ni7 is 60% higher than for the NSTF standard Pt68Co29Mn3 alloy. Rotating disk electrode measurements of a Pt1-xNix series on NSTF coated glassy carbon disks show a similar large and sharp peak in activity. In contrast, PtCo shows a diminished but still sharply peaked mass activity in 50 cm² tests near x = 0.62 by electron microprobe over the 0 < x < 0.7 range examined. [ABSTRACT FROM AUTHOR]

Three Pt1-xNix catalyst compositions, with high Ni content, were sputter deposited onto 3M Company's Nano-Structured Thin Film catalyst support to determine whether the high oxygen reduction reaction (ORR) activities recently reported are a surface phenomenon or require bulk Ni dissolution. The electrodes with Pt0.27Ni0.73 throughout had the highest mass specific ORR activity of the samples tested. When some of the Pt0.27Ni0.73 was replaced with either Pt or Pt0.75Ni0.25, the mass activity dropped. These results confirmed that continuous high Ni content is required to obtain high mass activity. [ABSTRACT FROM AUTHOR]

Three Pt1-xMx composition spreads were prepared, characterized, and then tested in 64-electrode proton exchange membrane fuel cells. The spreads were prepared by sputter-depositing a linear gradient of Re. Nb, or Bi with a constant amount of Pt in a manner that allowed for atomic level mixing of the elements. Re and Nb were selected as elements likely to be resistant to corrosion; Bi was selected because it was likely to dissolve. The spreads were deposited onto a range of different substrates including 3M Company's nanostructured thin-film catalyst support. Electron microprobe data showed that the composition spreads contained up to 60 atom % of the intermix element of interest. X-ray diffraction measurements showed that face-centered cubic lattices were retained Out to relatively high amounts of the intermix element. Acid exposure testing results showed that essentially all of the Bi initially present dissolved, some Nb was lost from the surface, and almost all of the Re was retained. It is likely that the same changes would have occurred during fuel cell operation. Pt surface areas as measured by cyclic voltammetry increased with increasing atomic fraction of the additive. High potential cycling was used to assess the stability of the Pt1-x (under-potential deposition) surface area; the Pt1-xNbx composition spread was the most stable. [ABSTRACT FROM AUTHOR]

Layered Pt1-xIrx (0 1-xIrx film was prepared by depositing alternating layers of Pt (constant thickness) and Jr (gradient), finished with a 5 nm Pt top layer. The NSTP-supported catalysts had much higher active surface areas and reached the diffusion-limited current at higher potentials than the bare GC supported catalysts. The surface enhancement factor (SEF) of Pt on NSTF-coated disks was approximately 14. The SEP increased (reaching a maximum of 22 at x = 0.2 in Pt1-xIrx) as the Jr content increased for the Pt1-xIrxsamples on NSTF. The kinetic ORR current density also increased with increasing Jr content. A similar trend was not observed for the same cataJyst coated onto bare GC disks. All of the cataJystlsupport combinations had identical Tafel slopes and area-specific current densities, suggesting that Pt is the active catalytic ingredient. Catalysts coated on NSTFcoated GC disks can be used to accurately examine both catalytic activities and the effects of high surface area supports in a single measurement. [ABSTRACT FROM AUTHOR]

The catalytic activity of a templated catalyst material (Fe-N-C). prepared using FeCl3, pyrrole. and a mesoporous silica gel as template, was investigated. The oxygen reduction reaction activity of the catalyst material was measured using the rotating ring-disk electrode technique, revealing an onset potential of about 0.85 V vs a reversible hydrogen electrode. The catalytic activity of the prepared sample was also tested in a 5 cm2 fuel cell for different catalyst loadings using oxygen or air atmospheres. Fuel cell polarization measurements were recorded at 75°C. The power densities varied between 0.032 and 0.095 W/cm2 for different catalyst loadings when oxygen was used. In addition, durability tests were carried Out by keeping the cell at 0.6 V for 16 h. The current densities decayed to about 25% of the initial value during this period. The results are compared to state-of-the-art results from the literature. The templated catalyst shows comparable activity to the best catalysts in the literature but its durability requires improvement. [ABSTRACT FROM AUTHOR]

A ternary composition spread, (Pt1-xRux)1-yMoy, 0 < x < 1; 0 < y < 0.3, was prepared through sputter deposition onto a nano-structured thin film support. The film was found to be reasonably stable when exposed to acid at 80°C, although there was evidence for loss of some Mo, presumably through a corrosion mechanism. The catalytic activity towards hydrogen oxidation of this composition range was measured simultaneously in a 64-electrode proton exchange membrane fuel cell with emphasis on performance in the presence of CO. The addition of either Mo or Ru to Pt led to a reduction in hydrogen oxidation overpotential for a simulated reformate gas stream containing up to 50 ppm CO. The best performance under CO-containing reformate was found for compositions containing both Ru and Mo, e.g., Pt0.40Ru0.35Mo0.25. The performance observed was significantly better than that measured on compositions containing Pt and Ru only. The use of air bleed was found to be most beneficial for compositions containing predominantly Pt and Ru. [ABSTRACT FROM AUTHOR]

Pt1-xMx (M = Ru,Mo,Co,Ta,Au,Sn) random alloy samples, covering most of the binary composition range, have been prepared via magnetron sputtering. The alloys were deposited through shadow masks onto 3M nanostructured thin-film catalyst support for testing in a 64-electrode polymer electron membrane fuel cell (PEMFC). CO stripping voltammograms and hydrogen oxidation polarization curves with pure hydrogen and with reformate containing up to 50 ppm CO were measured on all the samples. In agreement with reports in the literature, Ru, Mo, and Sn were found to improve the CO tolerance of Pt, although the intrinsic hydrogen oxidation activity of Pt decreased significantly as the Sn content increased. The addition of Co to Pt had no impact on CO tolerance, possibly because of loss of surface Co through dissolution in the fuel cell. The addition of Au to Pt led to an increase in hydrogen oxidation overpotential when CO was present. Small amounts of Ta gave a small reduction in hydrogen oxidation overpotential in the presence of CO, but the overpotentials were still too high for practical application in a reformate-fed fuel cell. [ABSTRACT FROM AUTHOR]

Chelator-buffered hydroponic solutions provide low and buffered free-metal concentrations and allow the easy calculation of nutrient species expected in these solutions. Some researchers suspect that the solutions allow plant uptake of chelates and that this uptake explains the failure of the free-ion activity model using these solutions. To determine the amount and method of chelate uptake, swiss chard was grown in solution culture in growth chambers for about three wks and then transferred to solutions containing 14C-EDTA, 14C-citrate, or 14C-L-histidine for a 21-hour assay. Much higher root and shoot 14C were found from treatments containing metabolites histidine (2706 097 shoot Bq 14C) or citrate (2241 953 shoot Bq 14C) than EDTA (280 110 shoot Bq 14C). Passive transpirational flow could explain all of the EDTA uptake, but active uptake would be required to explain most of the citrate and histidine uptake even assuming some adsorption of ligand bound to roots. Swiss chard grown in solutions with the same total EDTA concentrations, but different amounts of Fe bound to EDTA, had ≥3-fold differences in root and shoot 14C concentrations. In a second experiment, swiss chard roots removed more EDTA from solutions containing mostly M-EDTA0 than M-EDTA1- or M-EDTA2- (288 140, 245 051, and 192 559 Bq 14C, respectively) suggesting plant selectivity for EDTA and a non-apoplastic route of uptake or an effect resulting from root cell-wall adsorption. Results indicated buffering of metals by ligands allowed some ligand uptake with much more uptake occurring with metabolites citrate and histidine than EDTA. A passive or indiscriminate form of uptake does not appear to explain all EDTA uptake with a selectivity by swiss chard for M-EDTA complexes of lower charge. [ABSTRACT FROM AUTHOR]

PURPOSE Interferon-alfa, 2'-deoxycoformycin, and 2-chlorodeoxyadenosine (2-CdA) are effective in the management of patients with hairy cell leukemia. These agents produce remissions in most patients, but relapses occur with all three drugs. The optimal means to follow patients for relapse alter treatment has not been determined. METHODS We retrospectively examined serial serum soluble interleukin-2 receptor levels (sIL-2R) and absolute granulocyte counts in eight patients with relapsed hairy cell leukemia. All were treated with 2-CdA at the time of relapse. Serum samples were available at 3- to 6-month intervals from 5 to 9 years before relapse and 2-CdA treatment. RESULTS sIL-2R levels increase only in patients who go on to relapse. sIL-2R levels doubled a mean of 17.1 months (range, 4-36 months) before absolute granulocyte count decreased by 50%. DISCUSSION Demonstration of a rising serum sIL-2R level in patients with hairy cell leukemia identified those with an increased risk of relapse who need more frequent observation than patients who maintain a stable sIL-2R level. Early intervention may ameliorate the toxicity of salvage therapy because disease-related neutropenia may be anticipated. (Cancer J Sci Am 2000;6:21-24) [ABSTRACT FROM AUTHOR]

On the 29 July 1984 archaeologists engaged in a survey of the later Prehistoric and Romano-British landscape around Holme-on-Spalding Moor in East Yorkshire visited land at Hasholme which was being drained. Examination of the drainage works led to the discovery fragments of a substantial logboat amongst timbers which had been removed from the fenland by the contractors after fouling their mole drainer. These fragments were rescued and their findspot (SE S22326 ) identified by the workmen. An excavation was organized by the first author in conjunction with Hull City Museums, to examine the remainder q/the vessel, to investigate its context and establish its date. The spectacular and substantially intact remains o fan oak logboat were located, excavated and recorded 'in situ' in co-operation with a team from the Archaeological Research Centre of the National Maritime Museum under the direction of the second author. The boat was raised and taken to the National Maritime Museum for study before being returned to Hull for conservation and permanent display. Post-excavation research demonstrates that the late Iron Age logboat is unique both in its preservation and in some of its constructional features. An examination of its context allows conclusions to be drawn about the changing environment of the area from the beginning of the fourth millennium B.C. to the first millennium A.D., and provides important new information about the coastline of the Humber area during the Iron Age. A tree-ring study has produced a new dendrochronological sequence for Eastern England for the years 699 to 323 B.C. [ABSTRACT FROM AUTHOR]

Objective: To describe the educational experiences of students in managed care settings and to compare these with recommendations for preparing physicians to practice in managed care.Design: We searched MEDLINE using the keywords "medical education," "managed care," "health maintenance organization," and others; we manually checked the reference lists of identified articles and reports from 1969 to 1996. Survey information was obtained from all US medical schools in 1995 and 1996. Site visits were made to 6 managed care organizations selected according to size, geographic region, and involvement in education.Main Outcome Measures: The extent to which schools use managed care settings for clinical education, the types of settings used, and the kinds of educational programs experienced.Results: In 1995 and 1996, an average of 16% of schools required all students to have clerkships or other clinical experiences in a group/staff model HMO, and some students from another 46% of schools spent time in an HMO for clerkships or physical diagnosis/introduction to clinical medicine courses. About 85% of schools potentially exposed students to other types of managed care during 1 or more required clinical experiences in ambulatory, community-based settings. The learning objectives of these experiences did not explicitly address features unique to managed care such as cost containment and disease prevention.Conclusion: The selection of managed care settings for undergraduate education is based on general clinical objectives rather than explicit goals tied to managed care. Whether these experiences in managed care settings help students to develop competencies for future practice in a managed care environment has not been demonstrated. While the feasibility of medical education in nonprofit group/staff model HMOs is well documented, it is not certain whether these models can be adapted to for-profit managed care settings. [ABSTRACT FROM AUTHOR]

The salt tolerances of plants from natural populations of Trifolium repens L. (White Clover) growing in saline and non-saline sites were compared by root growth tests at a range of NaCl concentrations. Plants from three salt-marsh sites showed high or very high salt tolerance, with relatively vigorous root growth in 150-200 mM NaCl. Plants with two non-saline inland sites showed little or no tolerance. A sea-cliff population and plants of cv. Gwenda showed intermediate levels of tolerance at low salt concentrations. Halophytic maritime populations may provide material for the development of salt tolerant cultivars of T. repens, a crop plant in which most existing cultivars are thought to be salt-sensitive. [ABSTRACT FROM AUTHOR]

The interaction of the intestinal phases of Giardia muris and Trichinella spiralis was investigated in Swiss albino mice. Intraoesophageal inoculation of G. muris cysts seven days before, or seven days after, similar inoculation of T. spiralis larvae resulted in significant reduction in the numbers of Giardia trophozoites in small bowel and Giardia cysts in stools. This effect was not observed when G. muris cysts were administered after resolution of the intestinal phase of trichinosis. Giardiasis had no effect on trichinosis as assessed by numbers of adult worms in small bowel and larvae in skeletal muscles. Studies of small bowel morphology showed that the intestinal phase of trichinosis was associated with increased numbers of inflammatory cells in the lamina propria, a significant increase in Paneth cells in crypts, and a marked reduction in the villus:crypt ratio of jejunum. These observations suggest that the intestinal phase of trichinosis induced environmental changes in small bowel, perhaps related to inflammation, which resulted in suppression of proliferation of Giardia trophozoites. [ABSTRACT FROM PUBLISHER]

Describes the application of the Problem-Oriented Medical Synopsis approach to medical records in a hospital medical ward and patient care. Principles of the problem-oriented medical synopsis; Procedure on patient's admission and discharge; Mechanism used during assessment of patient in hospital.