scholarly journals The absorption coefficient for slow electrons in the vapours of mercury, cadmium and zinc

1925 ◽  
Vol 109 (750) ◽  
pp. 397-405 ◽  
Keyword(s):  
Absorption Coefficient ◽  
Electric Fields ◽  
Single Molecule ◽  
Unit Volume ◽  
Effective Area ◽  
Classical Dynamics ◽  
The Common ◽  
The Mean ◽  
Slow Electrons ◽  
Unit Pressure

According to the classical dynamics, the molecules in the path of a beam of electrons will, by virtue of their electric fields, deflect the electrons constituting the beam. This deflection, while not perceptible for the electrons which pass at large distances from the molecule, may cause those which approach more closely to disappear from the beam. The effective area, within which an electron will be deflected from the beam, can be calculated from the equation I = I 0 e -α xp , where I 0 is the number of electrons initially present in the beam, I the number remaining at the end of the path x , p the pressure of the gas, and α the absorption coefficient or the effective stopping area of all the molecules in a unit volume of gas at unit pressure. The mean effective area of a single molecule is obtained by dividing a by 3·56 × 10 16 , when the units chosen are millimetres of Hg and centimetres. Using this equation, Lenard and others have determined the absorption coefficients for most of the common gases.

scholarly journals Experimental and theoretical studies of the behaviour of slow electrons in air. I

1949 ◽  
Vol 196 (1046) ◽  
pp. 402-426 ◽  
Keyword(s):  
Drift Velocity ◽  
Mean Free Path ◽  
Free Electrons ◽  
Direct Measurements ◽  
Electronic Motion ◽  
The Mean ◽  
Gas Molecules ◽  
Slow Electrons ◽  
Experimental And Theoretical Studies ◽  
Unit Pressure

This paper is an account of an experimental investigation of the motions of free electrons in air by the method developed by Townsend. An improved form of apparatus is described with the appropriate theory. The following parameters of the electronic motion were determined as functions of the ratio Z/p of the electric field strength Z to the gas pressure p : Townsend’s energy factor k r the drift velocity W , the mean free path at unit pressure L and the mean proportion n of its energy lost in collisions with gas molecules. The experimental data are given in the form of tables and curves. The drift velocity W is found by a new procedure based on the Hall effect and by comparing the velocities W so obtained with the direct measurements of W by Nielsen & Bradbury it is seen that the velocities of agitation are distributed approximately according to Druyvesteyn’s law when Z/p exceeds 0.5. Bailey’s factor G , which is of importance in ionospheric studies, is obtained from the experimental dependence of η on k r . Theoretical formulae are derived for k r and W in terms of L, G and Z/p . The theory of the new method for measuring W is given in an appendix.

scholarly journals The Diffusion of Slow Electrons in Deuterium

1955 ◽  
Vol 8 (4) ◽  
pp. 468 ◽  
Author(s):  
Barbara IH Hall
Keyword(s):  
Cross Section ◽  
Mean Free Path ◽  
Lateral Spread ◽  
Electron Stream ◽  
Collisional Cross Section ◽  
The Mean ◽  
Energy Coefficient ◽  
Slow Electrons ◽  
Deuterium Molecule ◽  
Unit Pressure

The agitational energies and drift velocities of slow electrons diffusing in deuterium are measured as a function of the ratio Z/p of the electric field strength Z to the gas pressure p. The lateral spread of the diffusing electron stream is measured, which enables Townsend's energy coefficient to be calculated. Drift velocities are measured using a magnetic deflection method. On the basis of the kinetic theory of gases these measurements are used to calculate values for the mean free path L of the electrons at unit pressure, the mean proportion η of the energy lost by an electron in a collision with a deuterium molecule, and the collisional cross section A of the molecules in collisions with the electrons. The values obtained are compared with those of Crompton and Sutton (1952) for hydrogen.

scholarly journals The absorption coefficient for slow electrons in mercury vapour

1929 ◽  
Vol 125 (796) ◽  
pp. 134-142 ◽  
Keyword(s):  
Absorption Coefficient ◽  
Path Length ◽  
Mean Free Path ◽  
Mercury Vapour ◽  
Cross Sectional ◽  
Original Apparatus ◽  
Maximum Angle ◽  
The Mean ◽  
Slow Electrons ◽  
Good Agreement

The effective cross-sectional area of an atom is defined in this paper as that area within which a passing electron is deflected so that it can no longer go through a system of slits defining a beam of electrons. The sum of all these areas in a cubic centimetre of the gas defines the absorption coefficient, the reciprocal of which is the mean free path. The absorption coefficient is a function of the atom studied and the velocity of the electron. It way also depend on the geometry of the apparatus which defines the maximum angle of deflection. From the agreement of the results obtained by several observers with different limiting angles, the variation of the observed absorption coefficient with size of the limiting angle appears to be small. The absorption coefficient is compound from the equation I = I 0 e -α xp , where I is the electron current at the end of the path, I 0 the current at the beginning of the path, x the path length, p the pressure of the gas α the absorption coefficient. Apparatus .—For the measurement of the absorption coefficient a modification of Ramsauer's original apparatus was used. The same modification was previously used for the measurement of the absorption coefficient in other gases giving results in good agreement with those by Ramsauer's more complicated apparatus.

Comparison of Heffner Criteria and Light Criteria in Differentiating Exudative and Transudative Pleural Effusion

2020 ◽  
Vol 22 (3) ◽  
pp. 141-145
Author(s):  
Krishna Chandra Devkota ◽  
S Hamal ◽  
PP Panta
Keyword(s):  
Pleural Effusion ◽  
Cross Sectional Study ◽  
Pleural Space ◽  
Sectional Study ◽  
Inclusion Criteria ◽  
Cross Sectional ◽  
Medical College ◽  
The Common ◽  
The Mean ◽  
Exudative Pleural Effusion

Pleural effusion is present when there is >15ml of fluid is accumulated in the pleural space. It can be divided into two types; exudative and transudative pleural effusion. Tuberculosis and parapneumonic effusion are the common cause of exudative pleural effusion whereas heart failure accounts for most of the cases of transudative pleural effusion. This study was a hospital based cross sectional study performed at Nepal Medical College during the period of January 2016-December 2016. A total of 50 patients who fulfilled the inclusion criteria were enrolled. Pleural effusion was confirmed by clinical examination and radiology. After confirmation of pleural effusion, pleural fluid was aspirated and was analysed for protein, LDH, cholesterol. The Heffner criteria was compared with Light criteria to classify exudative or transudative pleural effusion. Among 50 patients, 30 were male and 20 were female. The mean age of patient was 45.4±21.85 years. The sensitivity and specificity of using Light criteria to detect the two type of pleural effusion was 100% and 90.9%, whereas using Heffner criteria was 94.87%, 100% respectively(P<0.01). There are variety of causes for development of pleural effusion and no one criteria is definite to differentiate between exudative or transudative effusion. In this study Light criteria was more sensitive whereas Heffner criteria was more specific to classify exudative pleural effusion. Hence a combination of criteria might be useful in case where there is difficulty to identify the cause of pleural effusion.

Of Reformed Versifying

2018 ◽  
Author(s):  
Neil Rhodes
Keyword(s):  
Sixteenth Century ◽  
Faerie Queene ◽  
Classical Literature ◽  
Native Form ◽  
Christian Doctrine ◽  
English Verse ◽  
The Common ◽  
The Mean ◽  
The Faerie Queene ◽  
Stylistic Ideal

This chapter examines how the development of English poetry in the second half of the sixteenth century is characterized by the search for an appropriate style. In this context, ‘reformed versifying’ may be understood as a reconciliation of high and low in which the common is reconfigured as a stylistic ideal of the mean. That development can be traced in debates about prosody where an alternative sense of ‘reformed versifying’ as adapting classical metres to English verse is rejected in favour of native form. At the same time Sidney recuperates poetry by reforming it as an agent of virtue. Reformation and Renaissance finally come together in Spenser, who realizes Erasmus’ aim of harmonizing the values of classical literature with Christian doctrine, and reconciles the foreign and the ‘homewrought’. The Faerie Queene of 1590 represents the triumph of the mean in both style and, through its celebration of marriage, in substance.

scholarly journals Tuning Single-Molecule Conductance by Controlled Electric Field-Induced trans-to-cis Isomerisation

2021 ◽  
Vol 11 (8) ◽  
pp. 3317
Author(s):  
C.S. Quintans ◽  
Denis Andrienko ◽  
Katrin F. Domke ◽  
Daniel Aravena ◽  
Sangho Koo ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Single Molecule ◽  
Quantum Interference ◽  
Single Molecule Level ◽  
Wet Chemical Synthesis ◽  
Single Molecule Junctions ◽  
Tunnelling Microscopy ◽  
The Difference

External electric fields (EEFs) have proven to be very efficient in catalysing chemical reactions, even those inaccessible via wet-chemical synthesis. At the single-molecule level, oriented EEFs have been successfully used to promote in situ single-molecule reactions in the absence of chemical catalysts. Here, we elucidate the effect of an EEFs on the structure and conductance of a molecular junction. Employing scanning tunnelling microscopy break junction (STM-BJ) experiments, we form and electrically characterize single-molecule junctions of two tetramethyl carotene isomers. Two discrete conductance signatures show up more prominently at low and high applied voltages which are univocally ascribed to the trans and cis isomers of the carotenoid, respectively. The difference in conductance between both cis-/trans- isomers is in concordance with previous predictions considering π-quantum interference due to the presence of a single gauche defect in the trans isomer. Electronic structure calculations suggest that the electric field polarizes the molecule and mixes the excited states. The mixed states have a (spectroscopically) allowed transition and, therefore, can both promote the cis-isomerization of the molecule and participate in electron transport. Our work opens new routes for the in situ control of isomerisation reactions in single-molecule contacts.

scholarly journals Genetic gain in the breeding program of common beans at IAC from 1989 to 2007

2010 ◽  
Vol 10 (4) ◽  
pp. 329-336 ◽  
Author(s):  
Alisson Fernando Chiorato ◽  
Sérgio Augusto Morais Carbonell ◽  
Roland Vencovsky ◽  
Nelson da Silva Fonseca Júnior ◽  
José Baldin Pinheiro
Keyword(s):  
Grain Yield ◽  
Common Bean ◽  
Genetic Gain ◽  
Grain Quality ◽  
The State ◽  
Breeding Program ◽  
Common Beans ◽  
The Common ◽  
The Mean ◽  
Second Period

The goal of the present work was to evaluate the genetic gain obtained in grain yield for the common bean genotypes from 1989 until 2007, at the Instituto Agronômico de Campinas, in the state of São Paulo. Genetic gain has been separated into two research periods; the first, from 1989 to 1996, and the second, from 1997 to 2007. In the first period, a genetic gain of 1.07 % per year was obtained, whereas for the second period, the gain was zero. However, the mean yield of the evaluated lines was approximately 1000 kg ha-1 superior to the figures obtained in the first period. The main cause for the absence of genetic gain in the second period is that the focus of the breeding program was changed to grain quality. The individualized analysis of the genotypes with carioca grains in the second period indicated the lack of genetic gain during the investigated period.

Addressing common errors and misconceptions in integral calculus with clickers and classroom voting

2019 ◽  
Vol 39 (2) ◽  
pp. 71-85
Author(s):  
Kelly Cline ◽  
Holly Zullo ◽  
David A Huckaby
Keyword(s):  
Correct Answer ◽  
Group Discussion ◽  
Multiple Choice ◽  
Small Group Discussion ◽  
Multiple Choice Questions ◽  
Integral Calculus ◽  
Common Features ◽  
Incorrect Answer ◽  
The Common ◽  
The Mean

Abstract Common student errors and misconceptions can be addressed through the method of classroom voting, in which the instructor presents a multiple-choice question to the class, and after a few minutes for consideration and small-group discussion, each student votes on the correct answer, using a clicker or a phone. If a large number of students have voted for one particular incorrect answer, the instructor can recognize and address the issue. In order to identify multiple-choice questions that are especially effective at provoking common errors and misconceptions, we recorded the percentages of students voting for each option on each question used in 25 sections of integral calculus, taught by 7 instructors, at 4 institutions, over the course of 12 years, on a collection of 172 questions. We restricted our analysis to the 115 questions which were voted on by at least 5 different classes. We present the six questions that caused the largest percentages of students to vote for a particular incorrect answer, discuss how we used these questions in the classroom, and examine the common features of these questions. Further, we look for correlations between question characteristics and the mean percentage of students voting for common errors on these questions, and we find that questions based on general cases have higher percentages of students voting for common errors.

scholarly journals Distribution of twin kHz QPOs in LMXBs

2012 ◽  
Vol 8 (S290) ◽  
pp. 327-328
Author(s):  
D. H. Wang ◽  
L. Chen
Keyword(s):  
Common Property ◽  
Periodic Oscillation ◽  
Quasi Periodic Oscillation ◽  
Mean Values ◽  
Orbital Frequency ◽  
Low Mass ◽  
The Common ◽  
The Mean ◽  
X Ray Binaries ◽  
Z Sources

AbstractWith kilohertz quasi-periodic oscillation (kHz QPO) sources in neutron star low mass X-ray binaries (NS-LMXBs) published up to now, we analyze the centroid frequency (ν) distribution of twin kHz QPOs. We find that Atoll and Z sources show the similar distributions of ν1 and ν2, which indicate that twin kHz QPOs may be the common property of NS-LXMBs and have the similar physical origins. The mean values of ν1 and ν2 in Atoll sources are higher than those in Z sources, and we consider that this may because the QPO signals are sheltered by the thicken accretion disk or corona in Z sources. The maximums of ν2 in both Atoll and Z sources are the same order as the Keplerian orbital frequency of the NS surface, so kHz QPOs could occur near the NS surface.

scholarly journals On tho proportions of the prevailing winds, the mean temperature, and depth of rain in the climate of London, computed through a cycle of Eighteen Years, or periods of the Moon’s declination

1843 ◽  
Vol 4 ◽  
pp. 300-300
Keyword(s):  
The Moon ◽  
Fair Weather ◽  
North West ◽  
West Wind ◽  
North East ◽  
East Wind ◽  
The North ◽  
The Common ◽  
The Mean ◽  
Solar Influence

In this paper the author investigates the periodical variations of the winds, rain and temperature, corresponding to the conditions of the moon’s declination, in a manner similar to that he has already followed in the case of the barometrical variations, on a period of years extending from 1815 to 1832 inclusive. In each case he gives tables of the average quantities for each week, at the middle of which the moon is in the equator, or else has either attained its maximum north or south declination. He thus finds that a north-east wind is most promoted by the constant solar influence which causes it, when the moon is about the equator, going from north to south; that a south-east wind, in like manner, prevails most when the moon is proceeding to acquire a southern declination ; that winds from the south and west blow more when the moon is in her mean degrees of declination, going either way, than with a full north or south declination ; and that a north-west wind, the common summer and fair weather wind of the climate, affects, in like manner, the mean declination, in either direction, in preference to the north or south, and most when the moon is coming north. He finds the average annual depth of rain, falling in the neighbourhood of London, is 25’17 inches.

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