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Engineering	50%

Selected Abstracts

H, feedback-control theory in biochemical systems

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 1 2008
E. Gershon
Abstract In this paper we study the possible optimality of biochemical pathways in the H, sense. We start by presenting simple linearized models of single enzymatic reaction systems, where we apply classical and modern tools of feedback-control theory. We then apply the results obtained by our analysis to a linearly unbranched enzyme pathway system, where we explore the effect of a negative feedback loop internally exerted on the system by a self-product of the pathway. We then probe the sensitivity of the enzymatic system to variations in certain variables and we deal with the problem of assessing the optimality of the static-output feedback control, in the H, sense, inherent to the closed-loop system. In this point we demonstrate the applicability of our results via a theoretical example that provides an open-loop and closed-loop analysis of a four-block enzymatic system. We then apply the various tools we developed to the optimal analysis of the Threonine synthesis pathway which is regulated by three feedback loops. We demonstrate that this pathway is optimal in the H, sense, in the face of considerable uncertainties in the various enzyme concentrations of the pathway. Copyright © 2007 John Wiley & Sons, Ltd. [source]

UV-induced immune suppression and sunscreen

PHOTODERMATOLOGY, PHOTOIMMUNOLOGY & PHOTOMEDICINE, Issue 3 2000
E. M. Gil
Sun protection factor (SPF) that measures sunscreen protection against erythema and edema may not be enough to measure a sunscreen's activity against many other biologic reactions induced by ultraviolet radiation (UV). It may be better to evaluate sunscreen efficacy using various tools including immune protection factor (IPF), mutation protection factor (MPF) and protection against photocarcinogenesis. In terms of immune protection, sunscreens protected against UV-induced immune suppression significantly. But protection in some cases was partial and often the IPF of sunscreens were less than the SPF. IPF may differ with various immunological endpoints, and it may be better to use a couple of different assays to measure sunscreen protection more objectively. Sunscreen use protects against most UV-induced non-melanoma skin cancers and actinic keratoses but its activity against melanoma is not clear. More studies with broad-spectrum stable sunscreens and better models for the investigation of malignant melanoma are required. [source]

An Application of Six Sigma to Reduce Waste

QUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 6 2005
Ricardo Bañuelas
Abstract Six Sigma has been considered a powerful business strategy that employs a well-structured continuous improvement methodology to reduce process variability and drive out waste within the business processes using effective application of statistical tools and techniques. Although there is a wider acceptance of Six Sigma in many organizations today, there appears to be virtually no in-depth case study of Six Sigma in the existing literature. This involves how the Six Sigma methodology has been used, how Six Sigma tools and techniques have been applied and how the benefits have been generated. This paper presents a case study illustrating the effective use of Six Sigma to reduce waste in a coating process. It describes in detail how the project was selected and how the Six Sigma methodology was applied. It also shows how various tools and techniques within the Six Sigma methodology have been employed to achieve substantial financial benefits. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Bridging the educational research-teaching practice gap

BIOCHEMISTRY AND MOLECULAR BIOLOGY EDUCATION, Issue 1 2010
Tools for evaluating the quality of assessment instruments
Abstract Student assessment is central to the educational process and can be used for multiple purposes including, to promote student learning, to grade student performance and to evaluate the educational quality of qualifications. It is, therefore, of utmost importance that assessment instruments are of a high quality. In this article, we present various tools that instructors could use, both to improve instrument design and validity before presentation to students and, to evaluate the reliability and quality of the assessment after students have answered the questions. In keeping with our goals of the Bridging-the-Gap series, we also present various ideas from the educational literature regarding the evaluation of assessment quality and end with a list of criteria that instructors could use to guide their evaluation process. [source]