Estimation of crank angle for cycling with a powered prosthesis

In order for a prosthesis to restore power generation during cycling, it must supply torque in a manner that is coordinated with the motion of the bicycle crank. This paper outlines an algorithm for the real time estimation of the angular position of a bicycle crankshaft using only measurements internal to an intelligent knee and ankle prosthesis. The algorithm assumes that the rider/prosthesis/bicycle system can be modeled as a four-bar mechanism. Assuming that a prosthesis can generate two independent angular measurements of the mechanism (in this case the knee angle and the absolute orientation of the shank), Freudenstein's equation can be used to synthesize the mechanism continuously. A recursive least-squares algorithm is implemented to estimate the Freudenstein coefficients, and the resulting link lengths are used to reformulate the equation in terms of input-output relationships mapping both measured angles to the crank angle. Using two independent measurements allows the algorithm to uniquely determine the crank angle from multi-valued functions. In order to validate the algorithm, a bicycle was mounted on a trainer and configured with the prosthesis using an artificial hip joint attached to the seat post. Motion capture was used to monitor the mechanism for forward and backward pedaling and the results are compared to the output of the presented algorithm. Once the parameters have converged, the algorithm is shown to predict the crank angle within 15° of the externally measured value throughout the entire crank cycle during forward rotation.

Long term prospective of the Seine River system: confronting climatic and direct anthropogenic changes

To explore the evolution of a human impacted river, the Seine (France), over the 21st century, three driving factors were examined: climate, agriculture, and point source inputs of domestic and industrial origin. Three future scenarios were constructed, by modification of a baseline representative of recent conditions. A climate change scenario, based on simulations by a general circulation model driven by the SRES-A2 scenario of radiative forcing, accounts for an average warming of +3.3 degrees C over the watershed and marked winter increase and summer decrease in precipitation. To illustrate a possible reduction in nitrate pollution from agricultural origin, a scenario of good agricultural practices was considered, introducing catch crops and a 20% decrease in nitrogen fertilisation. Future point source pollution was estimated following the assumptions embedded in scenario SRES-A2 regarding demographic, economic and technologic changes, leading to reductions of 30 to 75% compared to 2000, depending on the pollutants. Four models, addressing separate components of the river system (agronomical model, hydrogeological model, land surface model and water quality model), were used to analyse the relative impact of these scenarios on water quality, in light of their impact on hydrology and crop production. The first-order driving factor of water quality over the 21st century is the projected reduction of point source pollution, inducing a noticeable decrease in eutrophication and oxygen deficits downstream from Paris. The impact of climate change on these terms is driven by the warming of the water column. It enhances algal growth in spring and the loss factors responsible for phytoplankton mortality in late summer (grazers and viruses). In contrast, increased seasonal contrasts in river discharge have a negligible impact on river water quality, as do the changes in riverine nitrate concentration, which never gets limiting. The latter changes have a similar magnitude under the three scenarios. Under climate change, riverine and groundwater nitrate concentrations increase and crop production is advantaged with reduced growing cycles and increased yields. In contrast, nitrate concentrations decrease under the good agricultural practices scenario, with a limited decrease in crop production. When these two scenarios are combined, the changes in nitrate concentrations balance each other and crop yields increase. The results of this numerical exercise indicate that the potential changes to the Seine River system during the 21st century will not lead to severely degraded water quality.

Agriculture and groundwater nitrate contamination in the Seine basin. The STICS-MODCOU modelling chain

A software package is presented here to predict the fate of nitrogen fertilizers and the transport of nitrate from the rooting zone of agricultural areas to surface water and groundwater in the Seine basin, taking into account the long residence times of water and nitrate in the unsaturated and aquifer systems. Information on pedological characteristics, land use and farming practices is used to determine the spatial units to be considered. These data are converted into input data for the crop model STICS which simulates the water and nitrogen balances in the soil-plant system with a daily time-step. A spatial application of STICS has been derived at the catchment scale which computes the water and nitrate fluxes at the bottom of the rooting zone. These fluxes are integrated into a surface and groundwater coupled model MODCOU which calculates the daily water balance in the hydrological system, the flow in the rivers and the piezometric variations in the aquifers, using standard climatic data (rainfall, PET). The transport of nitrate and the evolution of nitrate contamination in groundwater and to rivers is computed by the model NEWSAM. This modelling chain is a valuable tool to predict the evolution of crop productivity and nitrate contamination according to various scenarios modifying farming practices and/or climatic changes. Data for the period 1970-2000 are used to simulate the past evolution of nitrogen contamination. The method has been validated using available data bases of nitrate concentrations in the three main aquifers of the Paris basin (Oligocene, Eocene and chalk). The approach has then been used to predict the future evolution of nitrogen contamination up to 2015. A statistical approach allowed estimating the probability of transgression of different concentration thresholds in various areas in the basin. The model is also used to evaluate the cost of the damage resulting of the treatment of drinking water at the scale of a groundwater management unit in the Seine river basin.

Uranium transport around the reactor zone at Bangombé and Okélobondo (Oklo): examples of hydrogeological and geochemical model integration and data evaluation

The sites at Bangombé and Okélobondo (Oklo) in Gabon provide a unique opportunity to study the behaviour of products from natural nuclear reactions in the vicinity of reactor zones which were active around two billion years ago. The Commission of the European Communities initiated the Oklo Natural Analogue Programme. One of the principal aims was to study indications of present time migration of elements from the reactor zones under ambient conditions. The hydrogeological and hydrochemical data from the Oklo sites were modelled in order to better understand the geochemical behaviour of radionuclides in the natural system, by using independent models and by comparing the modelling outcome. Two modelling approaches were used: M3 code (hydrochemical mixing and mass balance model), developed by the Swedish Nuclear Fuel and Waste Management Company (SKB) and HYTEC (reactive transport model) developed by Ecole des Mines de Paris. Two different reactor zones were studied: Bangombé, a shallow site, the reactor being at 11 m depth, and OK84 at Okélobondo, situated at about 450 m depth, more comparable with a real repository location. This allowed the validation of modelling tools in two different sedimentary environments: one shallow, with a more homogeneous layering situated in an area of meteoric alteration, and the other offering the opportunity to study radionuclide migration from the reaction zone over a distance of 450 m through very heterogeneous sedimentary layers. The modeling results indicate that the chemical reactions retarding radionuclide transport are very different at the two sites. At Bangombé, the decomposition of organic material consumes oxygen and at Okélobondo the oxygen is consumed by inorganic reactions resulting, in both cases, in uranium retardation. Both modelling approaches (statistic with M3 code and deterministic with HYTEC code) could describe this situation. The goal of this exercise is to test codes which can help to describe and understand the processes taking place at the sites, validate the models with in situ data, and thus build confidence in the tools used for future site characterization. Ultimately, this allows identifying and selecting processes and parameters that can be used as input into repository performance assessment calculations and modelling exercises.

Subsurface transfer of chloride after a lake retreat in the central Andes

The area under study covers 3500 km2 in the upstream part of the closed catchment basin of the salt crust of Uyuni. This crust is a remnant of the saline Lake Tauca, which covered the area about 15,000 years ago. In the downstream part of the aquifer, the Cl concentration of ground water and Cl content in the unsaturated zone exceed 20 meq/L and 18 kg/m2, respectively. With the present hydrological conditions under semiarid conditions, the ground water residence time in the study area exceeds 3000 years. Transient simulations over 11,000 years were made using initial conditions as the retreat of Lake Tauca and taking into account a low recharge during the arid mid-Holocene period. The modeling simulates ground water flow, Cl transport, and ground water residence time. It includes the evaporation from the aquifer that leads to the accumulation of chloride in the unsaturated zone. Results of the modeling are consistent with the observations if it is assumed that the Cl previously accumulated in the unsaturated zone was flushed back into the aquifer around 2000 years B.P., contemporaneously with the end of the arid period.

Using standardized patients to teach end-of-life skills to clinical clerks

BACKGROUND

This study examines the use of standardized patients to teach end-of-life skills to clinical clerks.

METHODS

Forty-four third-year clinical medical students participated in a half-day standardized patient workshop that was precepted by faculty members. The students were asked to report on their perceived abilities prior to the workshop and these were compared with post-workshop responses. The students were also asked to provide an overall evaluation of the standardized patient workshop as a learning experience.

RESULTS

The students uniformly found the workshop to be realistic, found the faculty facilitators to be helpful, and found the workshop effective in enhancing their end-of-life skills. Following participation in the workshop, students reported significant improvements in their perceived abilities to deal with pain, to appreciate cultural differences in the dying process, to deliver bad news, and to understand the legalities of do-not-resuscitate orders.

CONCLUSIONS

Standardized patient workshops are useful for teaching end-of-life skills.

Comparison of spinal health indicators in predicting spinal status in a 1-year longitudinal study

A 1-year longitudinal study was performed to assess and compare the predictive qualities of spinal health indicators (excluding the cervical spine) among aircraft assembly workers having at least 1 year seniority in a large assembly plant. Ten health indicators were compared to determine their sensitivity and predictive power with regard to back compensation and absenteeism in 12 months follow-up, and the presence of any limitation at work due to the back, or symptoms to the back at the end of the interval. The initial response to a self-administered questionnaire was obtained from 269 male workers, of whom 205 (76.2%) completed the follow-up questionnaire. Initial prevalence of symptoms to the back was 42.3%, limitation in performing at work was 28.1%, consultation of a health professional was 7.3%, and a history of compensation for the back (ever) was reported by 30.4%. During the year of follow-up, 16 (6%) of the 269 workers initially enrolled were granted 17 compensated episodes. Of the 205 workers who responded to the follow-up, 33 (16.1%) have been absent from work (with or without compensation) because of their back. The presence, at the beginning of the study, of a limitation in performing at work or in activities of daily living and a history of compensation (ever) were the three indicators independently associated with the occurrence of compensation or absenteeism (total work disability) related to a back problem during the following year.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of French and English versions of the American Thoracic Society respiratory questionnaire in a bilingual working population

Standardized French and English versions of the American Thoracic Society (ATS) respiratory disease questionnaire were administered to 204 English-speaking and 406 French-speaking male blue-collar aviation workers unexposed to occupational respiratory hazards. After adjusting for smoking status, age, years of education, foreign birth and maternal language other than French or English, no significant differences between the two questionnaires were found for response rates to usual cough, usual phlegm, mild or moderate dyspnoea, and chronic bronchitis. French-speaking workers reported significantly less wheeze with colds (OR = 0.60, p less than 0.02) and wheeze apart from colds (OR = 0.55, p less than 0.05) than the English-speaking group, but, the occurrence of wheeze on most days or nights was similar for both groups (OR = 1.02, NS). For 66 bilingual workers who completed both French and English questionnaires at a time interval of approximately two months, highly consistent results were found for sociodemographic data, smoking habits, cough, phlegm, breathlessness and chronic bronchitis, but not for wheeze with or apart from colds (agreement less than 90%; Kappa less than 0.50). These results reflect the difficulties in translating the concept of 'wheeze' from English to French. We conclude that most symptoms elicited by the French questionnaire may be generalized to English-speaking populations, but that questions pertaining to wheeze on most days or nights may be preferable to other questions concerning wheeze.