The Influence of the Cell Geometry on the Signal Shape in Electron Drift Velocity Measurements

1986 ◽  
Vol 41 (7) ◽  
pp. 912-920 ◽  
Author(s):  
A. F. Borghesani ◽  
L. Bruschi ◽  
M. Santini ◽  
G. Torzo
Keyword(s):  
Edge Effects ◽  
Accurate Determination ◽  
Finite Size ◽  
High Mobility ◽  
Drift Chamber ◽  
Cell Geometry ◽  
Experimental Conditions ◽  
Drift Cell ◽  
Cell Dimensions

An accurate determination of the “time-of-flight” in swarm experiments with a parallel plate drift chamber requires that the time evolution of the charge induced on the collector is linear. This is obtained in very large chambers where the edge effects can be neglected. However, the experimental conditions of high-mobility carriers and highly pressurized gases impose some constraints on the acceptable drift cell dimensions. We have numerically calculated the effects of the finite size of the collector by exploiting the methods of the images. The numerical results have been experimentally checked using a suitable drift cell of variable geometry. As a result, a quantitative limit on the ratio between the collector radius and the drift distance has been established in order to design drift cells for which the edge effects can be neglected. P.A.C.S. numbers: 2940. 4110 D, 3480 B

Factors affecting constancy of acetate concentration and correct determination of methanogenic activity in pH-stat experiments

2003 ◽  
Vol 48 (6) ◽  
pp. 111-118
Author(s):  
M. Mösche ◽  
U. Meyer
Keyword(s):  
Accurate Determination ◽  
Original Method ◽  
Experimental Conditions ◽  
Methanogenic Activity ◽  
Factors Affecting ◽  
Acetate Concentration ◽  
Correct Determination ◽  
Ph Stat ◽  
The Stability

The determination of methanogenic activity with a pH-stat titration bioassay is evaluated utilising a mathematical model of this system. For given kinetic parameters and experimental conditions the model calculates the development of titrant flow and acetate concentration during experiments. Simulations of experiments under various conditions are compared. They show that the original method inherently causes a strong drift of acetate concentration during the experiments and a misestimation of methanogenic activity. As a solution to these disadvantages the addition of sodium hydroxide to the titrant and a careful control of pH during flushing the reactor with gas prior to the experiment are recommended. In this way a better constancy of acetate concentration and a more accurate determination of methanogenic activity should be achievable. The accuracy of this method is limited by the stability of pH-electrode calibration parameters.

Relation between outer and luminal diameter in cannulated arteries

1999 ◽  
Vol 277 (5) ◽  
pp. H1745-H1753 ◽  
Author(s):  
Gilles Faury ◽  
Gail M. Maher ◽  
Dean Y. Li ◽  
Mark T. Keating ◽  
Robert P. Mecham ◽  
...  
Keyword(s):  
Accurate Determination ◽  
Experimental Conditions ◽  
Cross Sectional ◽  
Luminal Diameter ◽  
Fluorescent Marker ◽  
Wide Range ◽  
Before And After ◽  
Single Determination ◽  
Knockout Animals

Resistance in blood vessels is directly related to the inner (luminal) diameter (ID). However, ID can be difficult to measure during physiological experiments because of poor transillumination of thick-walled or tightly constricted vessels. We investigated whether the wall cross-sectional area (WCSA) in cannulated arteries is nearly constant, allowing IDs to be calculated from outer diameters (OD) using a single determination of WCSA. With the use of image analysis, OD and ID were directly measured using either transillumination or a fluorescent marker in the lumen. IDs from a variety of vessel types were calculated from WCSA at several reference pressures. Calculated IDs at all of the reference WCSA were within 5% (mean <1%) of the corresponding measured IDs in all vessel types studied, including vessels from heterozygote elastin knockout animals. This was true over a wide range of transmural pressures, during treatment with agonists, and before and after treatment with KCN. In conclusion, WCSA remains virtually constant in cannulated vessels, allowing accurate determination of ID from OD measurement under a variety of experimental conditions.

An accurate determination of the cell dimensions of bultfonteinite, Ca4Si2O10H6F2

1955 ◽  
Vol 30 (228) ◽  
pp. 569-573 ◽  
Author(s):  
Helen D. Megaw ◽  
C. H. Kelsey
Keyword(s):  
South Africa ◽  
Optical Properties ◽  
Calcium Silicate ◽  
Accurate Determination ◽  
Unit Cell ◽  
Accurate Evaluation ◽  
Cell Dimensions ◽  
Approximate Composition ◽  
Unit Cell Dimensions

Bultfonteinite from Bultfontein mine, Kimberley, South Africa, is a hydrated fluorine-containing calcium silicate, of approximate composition Ca4Si2O10H6F2. It was first described in 1932 by Parry, Williams, and Wright,1 who gave an account of its morphology, optical properties, composition, and chemical relationships. It is triclinic but markedly pseudo-orthorhombic. The present work consists primarily of a determination of the unit-cell dimensions, involving a more accurate evaluation of the interaxial angles than the earlier one; this is followed by some tentative suggestions about the structure.

Accurate determination of the cell dimensions of magnetite

1957 ◽  
Vol 31 (237) ◽  
pp. 431-442 ◽  
Author(s):  
E. Z. Basta
Keyword(s):  
Accurate Determination ◽  
Precise Determination ◽  
Defect Structures ◽  
Precision Data ◽  
X Ray ◽  
Cell Dimensions ◽  
Glass Tubes ◽  
Ideal Composition ◽  
The Ideal

SummaryAn analysed magnetite from Bisperg, Säter, Dalecarlia, Sweden, gave the formula , which corresponds closely to the ideal composition. A precise determination of the cell dimensions gave a 8·3963±0·0005 Å. at 18° C. Gentle heating of the powdered magnetite in evacuated silica glass tubes, before X-ray examination, resulted in sharply defined lines with high Bragg angles; an improvement which enabled precision data to be obtained. Four other new analyses of magnetites are also given and their lattice parameters are determined in the same way and are found to range from 8·3960 Å. to 8·3970 Å. The Bisperg magnetite being the purest sample examined, the value of its cell edge is taken as representative of pure magnetite.The effect of the different ionic substitutions on the cell dimensions of natural magnetites is discussed. An attempt is also made to explain the great variations among the published values of cell dimensions of artificial preparations; one main reason being the presence of defect structures with varying oxygen contents in excess of the formula requirements.

Trace Organic Silicon Analysis Using Atomic Absorption Spectroscopy

1968 ◽  
Vol 22 (5) ◽  
pp. 520-526 ◽  
Author(s):  
Concetta M. Paralusz
Keyword(s):  
Atomic Absorption ◽  
Accurate Determination ◽  
Organic Matrix ◽  
Absorption Spectrometry ◽  
Polydimethyl Siloxane ◽  
Experimental Conditions ◽  
Silicon Compounds ◽  
Organic Silicon ◽  
Organic Matrices

Trace silicon analysis in organic matrix materials is complicated by time-consuming concentration schemes and/or a lack of suitable organic standards. This paper describes an improved technique for quantitative determination of trace amounts of silicon in organic matrices. The method utilizes recent improvements in atomic absorption spectrometry and can be used to determine silicon in levels as low as 0.1 μg/ml in organic solution. Matrix interferences have been overcome by controlling solids of polymers and preparing standards using Si-free matrix materials. Suitable instrumentation and experimental conditions are described. Model organic silicon compounds and polydimethyl siloxane oils have been examined for use as standards. Experimental data, including a comparison of this method with wet-chemical and x-ray results, is presented. This method can be used for accurate determination of trace silicone contamination in the 1–10 ppm range in (1) paper products, (2) resinous and elastomeric polymers, and (3) oils.

Determination of Concentration Dependent Diffusion Coefficients of Carbon in Expanded Austenite

2008 ◽  
Vol 273-276 ◽  
pp. 306-311 ◽  
Author(s):  
Thomas S. Hummelshøj ◽  
Thomas L. Christiansen ◽  
Marcel A.J. Somers
Keyword(s):  
Diffusion Coefficient ◽  
Weight Change ◽  
Diffusion Coefficients ◽  
Input Data ◽  
Accurate Determination ◽  
Experimental Conditions ◽  
Thin Foils ◽  
Expanded Austenite ◽  
Aisi 316

In the present paper various experimental procedures to experimentally determine the concentration dependent diffusion coefficient of carbon in expanded austenite are evaluated. To this end thermogravimetric carburization was simulated for various experimental conditions and the evaluated composition dependent diffusivity of carbon derived from the simulated experiments was compared with the input data. The most promising procedure for an accurate determination is shown to be stepwise gaseous carburizing of thin foils in a gaseous atmosphere; the finer the stepsize, the more accurate the approximation of the diffusivity. Thermogravimetry was applied to continuously monitor the weight change of thin foils of AISI 316 during carburizing in CO-H2 gas mixtures for one of the simulated experimental procedures.

FIRST ORDER PHASE TRANSITIONS IN A SOLID WITH FINITE SIZE

1990 ◽  
Vol 04 (10) ◽  
pp. 1671-1692 ◽  
Author(s):  
G.G. CABRERA
Keyword(s):  
Phase Transitions ◽  
Spontaneous Magnetization ◽  
Accurate Determination ◽  
Finite Size ◽  
Finite Width ◽  
Variable Boundary ◽  
First Order ◽  
Mass Gap ◽  
First Order Phase

First order phase transitions are rounded in solids of finite size. It is shown here that the above rounding is monitored by the correlation length ξL of the finite system, or equivalently by the so-called mass gap for the quantum Hamiltonian version of the model. Scaling with size is studied as a function of variable boundary conditions for the cylinder geometry (infinite strips with finite width), and a striking crossover is found in the mass gap behavior when the coupling g along the boundary becomes anti-periodic. For g>0, the rounding is exponential with size and an accurate determination of the spontaneous magnetization (order parameter) of the infinite system is obtained from numerical extrapolations.

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