Role of Sediment Resuspension on Estuarine Suspended Particulate Mercury Dynamics

Coastal sediments are an important site for transient and long-term mercury (Hg) storage, and they foster a geochemical environment optimal for Hg methylation. Therefore, efforts have been taken to constrain the role of sediments as a source of methylmercury (MeHg) to the estuarine water column. This study employed the Gust Microcosm Erosion Core system capable of quantifying particle removal from undisturbed cores under measurable shear stress conditions to assess particulate Hg and MeHg exchange between sediments and the water column. Samples were collected from organic-rich and organic-poor sediment types from the mid- and lower Delaware Bay. It was found that bulk sediment samples from organic-rich systems overpredict total Hg and MeHg release to the water column, whereas organic-poor sediments underpredict the exchange. In general, organic-rich sediments in shallow environments have the most impact on surface particle dynamics. There is little evidence to suggest that MeHg formed in the sediments is released to the water column via particulate exchange, and therefore, nonsedimentary sources likely control MeHg levels in this estuarine water column

Technology-assisted training of arm-hand skills in stroke: concepts on reacquisition of motor control and therapist guidelines for rehabilitation technology design

<p>Abstract</p> <p>Background</p> <p>It is the purpose of this article to identify and review criteria that rehabilitation technology should meet in order to offer arm-hand training to stroke patients, based on recent principles of motor learning.</p> <p>Methods</p> <p>A literature search was conducted in PubMed, MEDLINE, CINAHL, and EMBASE (1997–2007).</p> <p>Results</p> <p>One hundred and eighty seven scientific papers/book references were identified as being relevant. Rehabilitation approaches for upper limb training after stroke show to have shifted in the last decade from being analytical towards being focussed on environmentally contextual skill training (task-oriented training). Training programmes for enhancing motor skills use patient and goal-tailored exercise schedules and individual feedback on exercise performance. Therapist criteria for upper limb rehabilitation technology are suggested which are used to evaluate the strengths and weaknesses of a number of current technological systems.</p> <p>Conclusion</p> <p>This review shows that technology for supporting upper limb training after stroke needs to align with the evolution in rehabilitation training approaches of the last decade. A major challenge for related technological developments is to provide engaging patient-tailored task oriented arm-hand training in natural environments with patient-tailored feedback to support (re) learning of motor skills.</p

The biogeochemical balance of oceanic nickel cycling

Nickel is a biologically essential element for marine life, with the potential to influence diverse processes, including methanogenesis, nitrogen uptake and coral health, in both modern and past oceans. However, an incomplete view of oceanic Ni cycling has stymied understanding of how Ni may impact marine life in these modern and ancient oceans. Here we combine data-constrained global biogeochemical circulation modelling with culture experiments and find that Ni in oligotrophic gyres is both chemically and biologically labile and only minimally incorporated into diatom frustules. We then develop a framework for understanding oceanic Ni distributions, and in particular the two dominant features of the global marine Ni distribution: the deep concentration maximum and the residual pool of approximately 2 nM Ni in subtropical gyres. We suggest that slow depletion of Ni relative to macronutrients in upwelling regions can explain the residual Ni pool, and reversible scavenging or slower regeneration of Ni compared with macronutrients contributes to the distinct Ni vertical distribution. The strength of these controls may have varied in the past ocean, impacting Ni bioavailability and setting a fine balance between Ni feast and famine for phytoplankton, with implications for both ocean chemistry and climate state

Demographics of the Dutch multicenter prospective cohort study 'Restoration of mobility in spinal cord injury rehabilitation'

Study design: A multicenter prospective cohort study. Objective: To compare the demographic data of the included population with other studied spinal cord injury (SCI) populations in the international literature. Setting: Eight Dutch rehabilitation centers with a specialized SCI unit. Methods: A total of 205 individuals with SCI participated in this study. Information about personal, lesion and rehabilitation characteristics were collected at the beginning of active rehabilitation by means of a questionnaire. Results: The research group mainly consisted of men (74%), of individuals with a paraplegia (59%), and had a complete lesion (68%). The SCI was mainly caused by a trauma (75%), principally due to a traffic accident (42%). The length of clinical rehabilitation varied between 2 months and more than a year, which seemed to be dependent on the lesion characteristics and related comorbidity. Conclusions: The personal and lesion characteristics of the subjects of the multi-center study were comparable to data of other studies, although fewer older subjects and subjects with an incomplete lesion were included due to the inclusion criteria'age' and 'wheelchair-dependent'. The length of stay in rehabilitation centers in The Netherlands was longer compared to Denmark but much longer than in eg Australia and the USA. © 2006 International Spinal Cord Society. All rights reserved