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Chemical Laboratories (chemical + laboratory)

Distribution by Scientific Domains

Chemistry	50%

Selected Abstracts

Bench,shelf system dynamic characteristics and their effects on equipment and contents

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 13 2006
Tara C. Hutchinson
Abstract Economic losses during past earthquakes are strongly associated with damage and failure to nonstructural equipment and contents. Among the vast types of nonstructural elements, one important category, is scientific equipment in biological or chemical laboratories. These equipment are often mounted on heavy ceramic bench-tops of bench,shelf systems, which in turn may amplify the dynamic motions imposed. To investigate the seismic response of these types of systems, a series of shake table and field experiments were conducted considering different representative bench and shelf-mounted equipment and contents. Results from shake table experiments indicate that these equipment are generally sliding-dominated. In addition, the bench,shelf system is observed to be very stiff and when lightly loaded, has a fundamental frequency between 10 and 16 Hz. An approximate 50% reduction in the first and second fundamental frequencies is observed considering practical loading conditions. Insight into a broader range of system response is provided by conducting eigenvalue and time history analyses. Non-linear regression through the numerical data indicate acceleration amplification ratios , range from 2.6 to 1.4 and from 4.3 to 1.6, for fixed,fixed and pinned,pinned conditions, respectively. Both the experimental and numerical results support the importance of determining the potential dynamic amplification of motion in the context of accurately determining the maximum sliding displacement of support equipment and contents. Copyright © 2006 John Wiley & Sons, Ltd. [source]

New and old trends in chemometrics.

JOURNAL OF CHEMOMETRICS, Issue 8-10 2002
How to deal with the increasing data volumes in R&D&P (research, development, process modeling, production), with examples from pharmaceutical research
Abstract Chemometrics was started around 30 years ago to cope with and utilize the rapidly increasing volumes of data produced in chemical laboratories. The methods of early chemometrics were mainly focused on the analysis of data, but slowly we came to realize that it is equally important to make the data contain reliable information, and methods for design of experiments (DOE) were added to the chemometrics toolbox. This toolbox is now fairly adequate for solving most R&D problems of today in both academia and industry, as will be illustrated with a few examples. However, with the further increase in the size of our data sets, we start to see inadequacies in our multivariate methods, both in their efficiency and interpretability. Drift and non-linearities occur with time or in other directions in data space, and models with masses of coefficients become increasingly difficult to interpret and use. Starting from a few examples of some very complicated problems confronting chemical researchers today, possible extensions and generalizations of the existing chemometrics methods, as well as more appropriate preprocessing of the data before the analysis, will be discussed. Criteria such as scalability of methods to increasing size of problems and data, increasing sophistication in the handling of noise and non-linearities, interpretability of results, and relative simplicity of use will be held as important. The discussion will be made from a perspective of the evolution of the scientific methodology as driven by new technology, e.g. computers, and constrained by the limitations of the human brain, i.e. our ability to understand and interpret scientific and data analytical results. Quilt-PCA and Quilt-PLS presented here address and offer a possible solution to these problems. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Gazing at the Hand: A Foucaultian View of the Teaching of Manipulative Skills to Introductory Chemistry Students in the United States and the Potential for Transforming Laboratory Instruction

CURRICULUM INQUIRY, Issue 3 2005
STEPHEN DEMEO
ABSTRACT Many studies of chemistry have described the rise of the academic chemical laboratory and laboratory skills in the United States as a result of famous men, important discoveries, and international influences. What is lacking is a perspective of the manifestations of the balances of power and knowledge between teacher and student. A Foucaultian analysis of the teaching of manipulative skills to the introductory student in high school and college in the United States during the later half of the 19th and into the 20th century has provided such a perspective. The analysis focuses on the body, specifically students' hands, and how this body has been redescribed in terms of time, space, activity, and their combinations. It is argued in the first part of this article that the teaching of manipulative skills in the chemistry laboratory can be characterized by effects of differential forms of power and knowledge, such as those provided by Foucault's ideas of hierarchical observation, normalization, and the examination. Moreover, it is evident that disciplinary techniques primarily focused on the physical hands of the student have been recast to include a new cognitive-physiological space in which the teaching of manipulative skills currently takes place. In the second part of this article, the author describes his own professional development as a laboratory instructor through a series of reflective statements that are critiqued from a Foucaultian perspective. The personal narratives are presented in order to pro- vide science educators with an alternative way for their students to think about the relationship between one's manipulative skills and the quality of their data. The pedagogical approach is related to the maturation process of the chemist and contextualized in the current paradigm of laboratory practice, inquiry-based science education. [source]

Modular Microreaction Systems for Homogeneously and Heterogeneously Catalyzed Chemical Synthesis

HELVETICA CHIMICA ACTA, Issue 1 2005
Daniel
Until now, microreaction devices designed for a specific type of reaction were used mainly for highly exothermic, very fast reactions. Described is a modular microreaction system and its application to representative homogeneous and heterogeneous reactions important in organic synthesis. The modular microreaction system allows continuous flow processes to be optimized and employed effectively in the chemical laboratory. The modular microreaction systems proved also versatile for syntheses requiring moderate reaction times, thus extending their application to a large fraction of organic reactions. The use of the modular and cleanable microreaction systems to rapidly develop optimized reaction conditions provides an excellent basis for the development of many chemical transformations scalable from milligram to ton production quantities. [source]