			Home About us Contact

Spatial Requirements (spatial + requirement)

Distribution by Scientific Domains

Life Sciences	60%

Selected Abstracts

Improvement of the Accuracy in the Optical Hematocrit Measurement by Optimizing Mean Optical Path Length

ARTIFICIAL ORGANS, Issue 9 2009
Shiori Oshima
Abstract Optical techniques have been developed to acquire blood information (e.g., hematocrit [Hct], saturation of oxygen, thrombus) noninvasively and continuously in an artificial heart. For the practical use of an optical Hct measurement, Twersky's theory has been shown to be useful and have a good agreement in forward-scattered measurements. However, it was not applied to backward-scattered measurements, which can provide the measurement with a less demanding spatial requirement. Additionally, optimal measurement for accuracy is not well examined. Therefore, we developed an accurate Hct measurement in an artificial heart using current optical devices. To this end, we focused on optimizing an emitter,detector distance to provide a maximum optical path length. We attached optical emitter and detector fibers on Tygon tubing at various distances to measure forward- and backward-scattered light. Fresh bovine blood (Hct: 30,50%) was circulated in the tubing by a nonpulsatile artificial heart. We calculated the optical path length at various emitter,detector distances by fitting the measured optical outputs and the reference Hcts to Twersky's theory. Then, we performed Hct measurements. As a result, Twersky's theory is applicable not only to forward- but also to backward-scattered measurements in the physiogical Hct range. In both forward- and backward-scattered measurements, calculated optical path lengths become maximum at the same emitter,detector distance. The accuracy of Hct measurement is improved two to three times with the emitter,detector distance compared with other distances. The mean error is less than 1 Hct%. This result shows that an accurate Hct measurement is realized by selecting the optimal emitter,detector distance, which provides maximum optical path length defined by Twersky's theory. Our study provides a framework for the practical and less restrictive application of the optical Hct measurement to patients with an artificial heart. [source]

A pragmatic approach to estimating the distributions and spatial requirements of the medium- to large-sized mammals in the Cape Floristic Region, South Africa

DIVERSITY AND DISTRIBUTIONS, Issue 1-2 2001
A. F. Boshoff
Conservation planning in the Cape Floristic Region, a recognized world plant diversity hotspot, required systematic information on the estimated distributions and spatial requirements of the medium- to large-sized mammals within each of 102 Broad Habitat Units delineated according to key biophysical parameters. As a consequence of a general lack of data, we derived a pragmatic approach for obtaining estimates of these two parameters. Distribution estimates were based on a combination of a literature survey (with emphasis on early texts) and the ecological requirements of the species. Spatial requirement estimates were derived from a simple spreadsheet model that is based on forage availability estimates and the metabolic requirements of the mammals in question. Our analysis incorporated adaptations of the agriculture-based Large Stock Unit or Animal Unit approach. The predictions of the model were tested by comparing them with actual density data. The outcomes provided realistic estimates of the two parameters. However, they should be considered as testable hypotheses and the concept of adaptive management , or management by hypothesis , must apply. Examples of the outcomes are provided in the form of maps and tables. [source]

Nonaqueous Aluminum Nitride Extrusion: I, Die-Entry Flow Behavior

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2002
John F. Jr. Wight
Simultaneous orifice and capillary rheometry at 160°C was used to determine flow parameters of aluminum nitride extrudates plasticized with a polyethylene,mineral-oil binder. Data were analyzed using the Benbow model for square-entry ram extrusion. Variables included the powder concentration, polymer molecular weight and concentration, and lubricant concentration. Die-entry rheology was explained in terms of the mean interparticle separation, polymer spatial requirements, and lubricant adsorption. Particles and polymer were observed to not pack independently. The yield stress of the body increased rapidly as the solids loading approached the critical volume limit of extrudability. An increase in polymer molecular weight or partial decrease of adsorbed lubricant increased the yield stress of the body and produced a satisfactory extrudate. [source]

Detection of human neutrophil elastase with peptide-bound cross-linked ethoxylate acrylate resin analogs

CHEMICAL BIOLOGY & DRUG DESIGN, Issue 4 2005
J.V. Edwards
Abstract:, An assessment of elastase-substrate kinetics and adsorption at the solid,liquid interface of peptide-bound resin was made in an approach to the solid-phase detection of human neutrophil elastase (HNE), which is found in high concentration in chronic wound fluid. N-succinyl-alanine-alanine-proline-valine- p -nitroanilide (suc-Ala-Ala-Pro-Val- pNA), a chromogenic HNE substrate, was attached to glycine-cross-linked ethoxylate acrylate resins (Gly-CLEAR) by a carbodiimide reaction. To assess the enzyme-substrate reaction in a two-phase system, the kinetic profile of resin-bound peptide substrate hydrolysis by HNE was obtained. A glycine and di-glycine spacer was placed between the resin polymer and substrate to assess the steric and spatial requirements of resin to substrate with enzyme hydrolysis. The enzymatic activities of suc-Ala-Ala-Pro-Val- pNA and suc-Ala-Ala-Pro-Ala- pNA on the solid-phase resin were compared with similar analogs in solution. An increase in visible wavelength absorbance was observed with increasing amounts of substrate-resin and enzyme concentration. Enzyme hydrolysis of the resin-bound substrate was also demonstrated on a polypropylene surface, which was employed for visible absorbance of released chromophore. A soluble active substrate analog was released from the resin through saponification of the ethoxylate ester linkages in the resin polymer. The resin-released conjugate of the HNE substrate demonstrated an increased dose response with increasing enzyme concentration. The synthesis and assay of elastase substrates bound to CLEAR resin gives an understanding of substrate-elastase adsorption and activity at the resin's solid,liquid interface for HNE detection with a solid-phase peptide. [source]