A quantitative approach to modeling mammalian myelinated nervefibers for electrical prosthesis design

Presents an upgraded cable model of mammalian myelinated nerve fibers in an extracellularly applied field. The kinetics of the nodes is based upon voltage clamp data in rat motor fibers at 37°C (J.R. Schwartz and G. Eikhof, 1987), while the resting membrane potential is computed with the Goldman equation. The resulting spike shape, conduction velocity, strength/duration behavior, and absolute and relative refractory period are in good quantitative agreement with published experimental data in mammals at normal body temperature and at 20°C. Results at intermediate temperatures however, suggest that the widely used concept of a constant Q₁₀ for the rate constants is invalid. In addition, the model generates realistic abortive spikes towards the end of the absolute refractory period and it can describe the consequences of repetitive firing. The results stress the advantages of a multiple nonlinear node model even if only time aspects of nerve behavior are under study. It turned out, that the model presented here describes in vivo neural properties relevant for electrical prosthesis design better than previous models in literature     

Towards a common carbon footprint assessment methodology for the water sector

This paper describes the carbon footprint methodology used in assessing the global warming potential of the Dutch water sector. The assessment includes CO₂ emissions from energy consumption and methane and nitrous oxide emissions from water treatment processes. There is, however, debate on the amounts and mechanism of greenhouse gas (GHG) emissions, and a standardised approach is discussed. As a result of this approach, the contribution of GHG emissions to the total carbon footprint of the Dutch water sector appeared to be relatively high. Next to the lack of common emission factors for GHG and chemicals used, there is also no agreed‐upon approach related to the system boundaries and scope of carbon footprinting of the water cycle. For reasons of benchmarking and monitoring of climate change reduction targets, a common carbon footprint assessment methodology for the water sector will be required.     

Nonlinear dynamics in Nasdaq dealer quotes

A nonlinear dynamic model for the quotes issued by Nasdaq dealers is considered. The model focusses on the top two electronic communication networks (ECNs), Island and Instinet, and the three most active market makers for a sample of twenty stocks. The model extends the standard linear vector error correction model for price discovery in three different ways. First, quote adjustments are set relative to the inside quote, i.e. the best bid and ask in the market. Second, dealers react to the inside spread. Third, adjustments differ according to which dealer is currently at the inside. Adjustments are different if an ECN is currently at the inside compared to an individual dealer. This difference is attributed to the asymmetric information among dealers. Price discovery dynamics are studied using generalized impulse response functions.     

Psychogenic pseudoptosis

Three patients with psychogenic pseudoptosis of one eyelid are reported. All showed depression of the eyebrow on the affected side. The clinical course varied: in two patients the symptom resolved spontaneously after positive reassurance; in the third patient it remained unchanged for 2 years.     

Application of astigmatism μ-PTV to analyze the vortex structure of AC electroosmotic flows

The three-dimensional (3D) flow due to AC electroosmotic (ACEO) forcing on an array of interdigitated symmetric electrodes in micro-channels is experimentally analyzed using astigmatism micro-particle tracking velocimetry (astigmatism μ-PTV). Upon application of the AC electric field with a frequency of 1,000 Hz and a voltage of 2 Volts peak–peak, the obtained 3D particle trajectories exhibit a vortical structure of ACEO flow above the electrodes. Two alternating time delays (0.03 and 0.37 s) were used to measure the flow field with a wide range of velocities, including error analysis. Presence and properties of the vortical flow were quantified. The steady nature and the quasi-2D character of the vortices can combine the results from a series of measurements into one dense data set. This facilitates accurate evaluation of the velocity field by data-processing methods. The primary circulation of the vortices due to ACEO forcing is given in terms of the spanwise component of vorticity. The outline of the vortex boundary is determined via the eigenvalues of the strain-rate tensor. Overall, astigmatism μ-PTV is proven to be a reliable tool for quantitative analysis of ACEO flow.     

Multibody interactions of actuated magnetic particles used as fluid drivers in microchannels

The forced motion of superparamagnetic particles and their multibody interactions are studied in view of the application as integrated fluid drivers in microchannel systems. Previous studies on particle manipulation in open fluid volumes serve as our starting point for the analysis of particle dynamics and interplay effects in confined fluid volumes. An experimental setup is designed that offers a constant force field on all individual particles dispersed in a microchannel. Distinguishable multi-particle configurations are observed and analyzed on the basis of magnetic and hydrodynamic particle interaction mechanisms. The fluid driving performance and the efficiency of the particles are evaluated on system level by means of numerical simulation models.     

Negativity in problematic and nonproblematic families: A multigroup social relations model analysis with structured means.

The aim of the study was to determine whether there are differences in patterns of negativity between families with and without an adolescent with externalizing problem behavior. We used a structured means Social Relations Model in order to examine negativity in multiple levels of the family system. The sample consisted of 120 problematic and 153 nonproblematic families (two parents, two children), who rated the level of negativity in the relationship with each family member. Although a simple mean differences test would lead us to believe that differences in negativity between groups of families can be ascribed to the interaction between parent and adolescent, the results of the present study indicate that these differences are actually related to the characteristics of a problematic child. (PsycINFO Database Record (c) 2011 APA, all rights reserved)