316. Using Work Practice Simulation and a Physical-Chemical Mathematical Exposure Model for Determination of Occupational Exposure

2004 ◽  
Author(s):  
M. Plisko ◽  
J. Spencer ◽  
L. Burrelli
Keyword(s):  
Occupational Exposure ◽  
Work Practice ◽  
Exposure Model ◽  
Physical Chemical

Transmission Electron Microscopy of Protein Macromolecules

1971 ◽  
Vol 29 ◽  
pp. 424-425
Author(s):  
Henry S. Slayter
Keyword(s):  
Biological Systems ◽  
Metal Vapor ◽  
Resolving Power ◽  
Electron Microscopic ◽  
Chemical Methods ◽  
Molecular Weights ◽  
The Past ◽  
Physical Chemical ◽  
Transmission Electron

Electron microscopic methods have been applied increasingly during the past fifteen years, to problems in structural molecular biology. Used in conjunction with physical chemical methods and/or Fourier methods of analysis, they constitute powerful tools for determining sizes, shapes and modes of aggregation of biopolymers with molecular weights greater than 50, 000. However, the application of the e.m. to the determination of very fine structure approaching the limit of instrumental resolving power in biological systems has not been productive, due to various difficulties such as the destructive effects of dehydration, damage to the specimen by the electron beam, and lack of adequate and specific contrast. One of the most satisfactory methods for contrasting individual macromolecules involves the deposition of heavy metal vapor upon the specimen. We have investigated this process, and present here what we believe to be the more important considerations for optimizing it. Results of the application of these methods to several biological systems including muscle proteins, fibrinogen, ribosomes and chromatin will be discussed.

scholarly journals Born out of Fire and Ice: Polymorph Studies of the Antiviral Famciclovir

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 129
Author(s):  
Liana Vella-Zarb ◽  
Ulrich Baisch
Keyword(s):  
Variable Temperature ◽  
Chemical Properties ◽  
Crystal Form ◽  
X Ray Diffraction ◽  
Crystal Forms ◽  
X Ray ◽  
Physical Chemical ◽  
Diffraction Patterns ◽  
Crystalline Forms

There is much interest and focus on solid forms of famciclovir. However, in spite of the abundance of reported differences in oral bioavailability, compressibility, and other physical–chemical properties of the various crystal forms of this drug, very little precise structural analysis is available in the literature to date. The form used in the commercial formulation is the anhydrous form I. Patents and patent applications report three different anhydrous crystalline forms on the basis of unindexed powder diffraction patterns. Single-crystal and variable-temperature X-ray diffraction experiments using the commercially available anhydrous form of famciclovir were carried out and led not only to the crystal structure determination of the anhydrous form I, but also to discovery of a new crystal form of anhydrous famciclovir from powder data.

scholarly journals Determination of trace metals in water from Mangueira Lagoon – RS, Brazil

2018 ◽  
Vol 13 (3) ◽  
pp. 612-620
Author(s):  
Filipe Sousa dos Santos ◽  
Eduarda Medran Rangel ◽  
Pedro José Sanches Filho
Keyword(s):  
Trace Metals ◽  
Atomic Emission ◽  
Atomic Absorption Spectrophotometry ◽  
Emission Spectrometry ◽  
Chemical Parameters ◽  
Chelex 100 ◽  
Physical Chemical ◽  
Low Degree ◽  
Copper Zinc

Abstract Determination of trace metals was carried out in Mangueira Lagoon, in the southern zone of Rio Grande do Sul. Samples were collected at five points to evaluate the concentrations of the following trace metals: copper, zinc, lead, chromium, nickel and iron. Metals were determined by digestion with concentrated nitric acid and pre-concentrated in Chelex 100 resin analyzed by atomic absorption spectrophotometry. In parallel, the physical-chemical parameters pH, chlorides, alkalinity, hardness and organic matter in the water were determined. Potassium and sodium metals were analyzed by atomic emission spectrometry. The analyzes of pH and conductance were analyzed in the field while the others were done in the laboratory of the research group of environmental contaminants (GPCA). Through the results of physical-chemical parameters of the water, the Mangueira Lagoon exhibits a low degree of contamination, but in the future may compromise the biota of the lagoon. Regarding the focus of this work, of Cu, Cr, Fe, Ni, Pb, and Zn (heavy metals), only lead and iron obtained the values above that are established in CONAMA 357/2005.

Determination of an Occupational Exposure Guideline for Manganese Using the Benchmark Method

Risk Analysis ◽  
2003 ◽  
Vol 23 (5) ◽  
pp. 1031-1046 ◽  
Author(s):  
Harvey J. Clewell ◽  
Gregory A. Lawrence ◽  
Donald B. Calne ◽  
Kenny S. Crump
Keyword(s):  
Occupational Exposure

scholarly journals The multivariate calculation of material balances of flowsheets for separating ternary mixtures of different physical-chemical nature

2016 ◽  
Vol 11 (3) ◽  
pp. 47-57 ◽  
Author(s):  
A. V. Frolkova ◽  
M. A. Ablizin ◽  
M. A. Mayevskiy ◽  
A. K. Frolkova
Keyword(s):  
Phase Diagrams ◽  
Chemical Nature ◽  
Material Balance ◽  
Ternary Systems ◽  
Butyl Alcohol ◽  
Ternary Mixtures ◽  
Two Phase ◽  
Physical Chemical ◽  
Alcohol Water

An approach to the determination of free variables required for calculating the material balance of the flowsheet of ternary mixtures separation is presented. Phase diagrams of the considered ternary systems are characterized by the presence of a two-phase splitting area and by the presence of different amounts of azeotropes (classes 3.1.0, 3.1.1, 3.2.1 and 3.3.1). For all the systems flowsheets containing three rectification columns and a florentine vessel for separation were suggested. The multivariance of the solution of the balance problem was shown. The approach was illustrated by the example of real ternary systems characterized by different phase diagrams (methanol - chloroform - water, butyl alcohol - water - toluene, nitromethane - hexane - water). The parameters of the rectification columns were presented.

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