Sampling method, storage and pretreatment of sediment affect AVS concentrations with consequences for bioassay responses.

Sediment treatment and sediment storage may alter sediment toxicity, and consequently biotic response. Purpose of our study was to combine these three aspects (treatment-toxicity-biotic response) in one integrated approach. We used Acid Volatile Sulfide (AVS) concentrations as a proxy of the disturbance of the sediment. AVS and Simultaneously Extracted Metal (SEM) concentrations were compared to bioassay responses with the freshwater benthic macroinvertebrate Asellus aquaticus. Storage conditions and sediment treatment affected AVS but not SEM levels. AVS can be used as a proxy for sediment disturbance. The best way to pretreat the sediment for use in a bioassay in order to maintain initial AVS conditions was to sample the sediment with an Ekman grab, immediately store it in a jar without headspace, and freeze it as soon as possible. In a survey using seven different sediments, bioassay responses of A. aquaticus were correlated with SEM and AVS characteristics.

Measuring acid volatile sulphide in floodplain lake sediments: effect of reaction time, sample size and aeration.

For the routine measurement of acid volatile sulphide (AVS) in floodplain lake sediments, an earlier published diffusion method was adapted and optimised. We evaluated the effect of reaction time, sample weight and passive sample aeration on AVS recovery, and determined the method's reproducibility. The optimal reaction time was 4 h. Losses of AVS due to sample aeration did not occur within 15 min of sample-air contact. Relative standard deviation was <2.5% for known sulphide solutions, was between 10% and 15% for AVS concentrations in sediments and <12% for SEM concentrations in sediments, generally. Sediment samples with known SEM and AVS content were used to compare results of the developed method with the purge-and-trap method. There is a good agreement with the purge-and-trap method for SEM concentrations. AVS concentrations measured with the diffusion method are higher than with the purge-and-trap method. We conclude that the adapted diffusion method is well suited for the routine measurement of AVS concentrations in floodplain sediments.

Biomechanical Analysis of Patient Using FES Peroneal Brace and Further Developments.

The effect of functional electrical stimulation on gait and postural sway of hemiplegics was studied. Patients utilizing the Underknee Peroneal Stimulator were studied and compared to patients receiving conventional physiotherapy and to normal subjects. Several patients treated with electrical stimulation showed marked improvement in postural sway and ankle control during locomotion. Additional studies on the effect of various stimulation waveforms and pain sensation in a computer-controlled double blind evaluation are discussed.

Biomechanics of functional electrical stimulation.

Patients with hemiplegia frequently have difficulty in walking due to lack of eversion and dorsiflexion capability of the foot. One method of treating these patients utilizes functional electrical stimulation (FES). The effect of FES on locomotion, co-ordination, proprioception and balance sense was assessed using instrumented gait analysis and a postural sway test. In general patients treated with FES showed either a marked improvement or very little change. Any improvement was reflected in postural sway and ankle control during locomotion. Changes in hip and knee control were insignificant.