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Abstract-An important goal in rehabilitation engineering is to develop technology that allows individuals with severe motor impairment to practice arm movement without continuous supervision from a rehabilitation therapist. This paper describes the development of such a system, called Therapy WREX or ("T-WREX"). The system consists of an orthosis that assists in arm movement across a large workspace, a grip sensor that detects hand grip pressure, and software that simulates functional activities. The arm orthosis is an instrumented, adult-sized version of the Wilmington Robotic Exoskeleton (WREX), which is a five degrees-of-freedom mechanism that passively counterbalances the weight of the arm using elastic bands. After providing a detailed design description of T-WREX, this paper describes two pilot studies of the system's capabilities. The first study demonstrated that individuals with chronic stroke whose arm function is compromised in a normal gravity environment can perform reaching and drawing movements while using T-WREX. The second study demonstrated that exercising the affected arm of five people with chronic stroke with T-WREX over an eight week period improved unassisted movement ability (mean change in Fugl-Meyer score was 5 points 2 SD; mean change in range of motion of reaching was 10%, 0 001). These results demonstrate the feasibility of automating upper-extremity rehabilitation therapy for people with severe stroke using passive gravity assistance, a grip sensor, and simple virtual reality software.

Denitrification is an important net sink for NO 3 -in streams, but direct measurements are limited and in situ controlling factors are not well known. We measured denitrification at multiple scales over a range of flow conditions and NO 3 -concentrations in streams draining agricultural land in the upper Mississippi River basin. Comparisons of reach-scale measurements (in-stream mass transport and tracer tests) with local-scale in situ measurements (pore-water profiles, benthic chambers) and laboratory data (sediment core microcosms) gave evidence for heterogeneity in factors affecting benthic denitrification both temporally (e.g., seasonal variation in NO 3 -concentrations and loads, flood-related disruption and re-growth of benthic communities and organic deposits) and spatially (e.g., local stream morphology and sediment characteristics). When expressed as vertical denitrification flux per unit area of streambed (U denit , in), results of different methods for a given set of conditions commonly were in agreement within a factor of 2-3. At approximately constant temperature (*20 ± 4°C) and with minimal benthic disturbance, our aggregated data indicated an overall positive relation between U denit (*0-4,000 lmol N m -2 h -1 ) and stream NO 3 -concentration (*20-1,100 lmol L -1 ) representing seasonal variation from spring high flow (high NO 3 -) to late summer low flow (low NO 3 -). The temporal dependence of U denit on NO 3-was less than first-order and could be described about equally well with power-law or saturation equations (e.g., for the unweighted dataset, -008-9282-8 in m day -1 ) at seasonal and possibly event time scales; (2) although k1 denit was relatively large at low flow (low NO 3 -), its impact on annual loads was relatively small because higher concentrations and loads at high flow were not fully compensated by increases in U denit ; and (3) although NO 3 -assimilation and denitrification were linked through production of organic reactants, rates of NO 3 -loss by these processes may have been partially decoupled by changes in flow and sediment transport. Whereas k1 denit and v f,denit are linked implicitly with stream depth, NO 3 -concentration, and(or) NO 3 -load, estimates of U denit may be related more directly to field factors (including NO 3 -concentration) affecting denitrification rates in benthic sediments. Regional regressions and simulations of benthic denitrification in stream networks might be improved by including a non-linear relation between U denit and stream NO 3 -concentration and accounting for temporal variation.

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A microbial community analysis using 16S rRNA gene sequencing was performed on borehole water and a granite rock core from Henderson Mine, a >1,000-meter-deep molybdenum mine near Empire, CO. Chemical analysis of borehole water at two separate depths (1,044 m and 1,004 m below the mine entrance) suggests that a sharp chemical gradient exists, likely from the mixing of two distinct subsurface fluids, one metal rich and one relatively dilute; this has created unique niches for microorganisms. The microbial community analyzed from filtered, oxic borehole water indicated an abundance of sequences from iron-oxidizing bacteria (Gallionella spp.) and was compared to the community from the same borehole after 2 weeks of being plugged with an expandable packer. Statistical analyses with UniFrac revealed a significant shift in community structure following the addition of the packer. Phospholipid fatty acid (PLFA) analysis suggested that Nitrosomonadales dominated the oxic borehole, while PLFAs indicative of anaerobic bacteria were most abundant in the samples from the plugged borehole. Microbial sequences were represented primarily by Firmicutes, Proteobacteria, and a lineage of sequences which did not group with any identified bacterial division; phylogenetic analyses confirmed the presence of a novel candidate division. This "Henderson candidate division" dominated the clone libraries from the dilute anoxic fluids. Sequences obtained from the granitic rock core (1,740 m below the surface) were represented by the divisions Proteobacteria (primarily the family Ralstoniaceae) and Firmicutes. Sequences grouping within Ralstoniaceae were also found in the clone libraries from metal-rich fluids yet were absent in more dilute fluids. Lineage-specific comparisons, combined with phylogenetic statistical analyses, show that geochemical variance has an important effect on microbial community structure in deep, subsurface systems.

Doctors are exhorted to practice evidence based medicine, and the British government says that it wants public policy to be based on evidence. 1 We share the government's enthusiasm, but can it become a reality rather than an aspiration? How much do we know about what works, and are researchers, government ministers, and civil servants truly committed to developing and using the best evidence?We had an opportunity to learn about the realities of evidence based policy making when we were invited in late 1997 to become an "evaluation group" to assist the independent inquiry into inequalities in health. 2Our reflections concern the material submitted and the evaluation process, not the final report.

Open surgical treatment of acute Achilles tendon ruptures significantly reduces the risk of rerupture compared with non-surgical treatment, but produces significantly higher risks of other complications, including wound infection. The latter may be reduced by performing surgery percutaneously.

Bacterial abundance, distribution, and heterotrophic uptake in a freshwater aquifer contaminated by treated sewage were determined from analyses of groundwater and sediment-core samples. The number of free-living (unattached) bacteria in contaminated groundwater declined steadily with increasing distance from the source of sewage infiltration, from 1.94 (±0.20) x 106 ml-' at 0.21 km to 0.25 (±0.02) x 106 ml-' at 0.97 km. Bacterial abundance in groundwater sampled at 0.31 km correlated strongly with specific conductance and increased sharply from 4.0 (±0.3) x 104 ml-' at a depth of 6 m to 1.58 (±0.12) x 0l m-1 at 14 m, then declined at 20 and 31 m to 1.29 (+0.12) x 106 and 0.96 (±0.12) x 106 ml-', respectively. A majority of the bacteria in contaminated and uncontaminated zones of the aquifer were bound to the surfaces of particulates, <60 ,um in diameter. The glucose uptake rate, assayed at in situ and 5 ,uM concentrations, declined steadily in contaminated groundwater sampled along a transect. A preparative wet-sieving technique for use in processing core samples for bacterial enumeration is described and evaluated.