scholarly journals On experiments relating to the spectrum of nitrogen

1925 ◽  
Vol 107 (743) ◽  
pp. 411-422 ◽  
Keyword(s):  
Nitrogen Atom ◽  
Atmospheric Pressure ◽  
Negative Band ◽  
Discharge Tubes ◽  
In Series ◽  
Striking Change ◽  
The Subject ◽  
Band Spectra ◽  
Low Pressures ◽  
Conventional Type

It is somewhat remarkable that the spectrum of the neutral nitrogen atom, nitrogen arc or NI spectrum, should be the least known of the spectra associated with nitrogen. The positive and negative band spectra, associated with nitrogen molecules, have been the subject of many investigations, and the line spectra which are developed when condensed discharges are passed rough nitrogen at atmospheric pressure or through nitrogen contained in ancuum tubes, the spectrum of singly ionised nitrogen, the NII spectrum, has recently been arranged in series by Fowler ( ‘Roy. Soc. Proc.,' vol. 107, A, p. 31,25), who has in an earlier investigation (‘Monthly Notices R. A. S.,’ vol. 80, 692, 1920) assigned a number of lines which have not yet been arranged in series to the doubly ionised nitrogen atom. It would appear that under ordinary conditions of excitation the lines of the arc or nitrogen I spectrum are not conspicuous, and we are indebted to Hardtke (‘Ann. der Phys.,’ vol. 3, p. 363, 1918) for the information at present available with respect to this Spectrum. Hardtke found that with discharge tubes of special construction containing nitrogen a number of lines were predominant in the spectrum of the positive rays observed in certain regions of the discharge tubes, and that the same lines were relatively enhanced in vacuum tubes of the conventional type when they were excited by condensed discharges of feeble moderate intensities. Hardtke gave approximate measurements of a Number of these lines, which he assigned to the arc spectrum. In a series of previous investigations (Merton, ‘ Roy. Soc. Proc.,’ A, vol. 96, 382, 1920; Merton and Barratt, ‘ Phil. Trans.,’ A, vol. 222, p. 369, 1922; Merton and Johnson, ‘ Roy. Soc. Proc.,’ A, vol. 103. p. 383, 1923) it has been Shown that profound modifications are sometimes observed in the spectrum of a substance when a very small quantity of that substance is present in a discharge tube containing helium at a comparatively high pressure, and the tube is excited by condensed or uncondensed discharges. Thus with uncondensed discharges there is a striking change in the distribution of intensity the lines of the secondary spectrum of hydrogen; a trace of carbon is recognised by the appearance of the ‘‘comet tail” spectrum, first observed by Fowler (‘Monthly Notices R. A. S.,’ vol. 70, p. 484, 1910) at very low pressures and when both carbon and hydrogen are present a new triplet series of band: are developed.

scholarly journals Further spectra associated with carbon

1925 ◽  
Vol 108 (746) ◽  
pp. 343-355 ◽  
Keyword(s):  
Visible Spectrum ◽  
Ultra Violet ◽  
Line Spectrum ◽  
Band Spectrum ◽  
Comet Tail ◽  
Experimental Conditions ◽  
Negative Band ◽  
In Series ◽  
Condensed Discharge ◽  
Band Spectra

In a recent paper by Professor Merton and myself, an investigation was made of the experimental conditions effecting the isolation of some familiar band-spectra of Carbon. In particular, we made a study of the action of Helium in isolating and modifying spectra associated with this element. It was found that under appropriate conditions some new spectra of Carbon were isolated. With a trace of an oxide of Carbon in some 20 to 30 mm. of Helium an uncondensed discharge produced a band system identical with that found by Pluvinet and Baldet in the spectrum of comet tails, and which was afterwards discovered by Fowler to be characteristic of CO at extreme low pressures. Tubes prepared in this way and subjected to a mild condensed discharge yielded a spectrum consisting only of the lines and bands of Helium, and a number of new lines which were attributed to Carbon. A notable feature of the latter spectrum was the bright line at λ 5380, recorded previously only as a Carbon line of small intensity. The characteristic spark lines λλ 6583, 6578, 4267, were also absent, or of very doubtful occurrence, and the conditions of excitation led us to suggest that this line spectrum might be the true “arc” spectrum of Carbon, which the energy of the ordinary arc was insufficient to produce, and that of the condensed spark sufficient to repress. Both the line-spectrum and the Comet-Tail bands were investigated only in the visible spectrum; in the present paper observations and measurements of these spectra in the ultra-violet are recorded. In addition, a new band-spectrum apparently associated with the Comet-Tail bands has been measured and expressed by a series formula. The opportunity afforded by the exceptionally strong development of the first negative band-spectrum of Carbon has been taken to re-measure these bands and dispose them in series. Finally, the significance of some of these phenomena is discussed.

The Townend Ring

1930 ◽  
Vol 34 (238) ◽  
pp. 813-848 ◽  
Author(s):  
H. C. H. Townend
Keyword(s):  
Subject Matter ◽  
Air Resistance ◽  
The Subject ◽  
Conventional Type

The work which forms the subject matter of this paper relates to a device for reducing the air resistance of an air-cooled radial engine. It can be added to the engine without completely enclosing the cylinders, either singly or collectively, in streamline casings of the conventional type, which usually render the engine inaccessible.

scholarly journals IV. On the nature of the streamers in the electric spark

1909 ◽  
Vol 209 (441-458) ◽  
pp. 71-87 ◽  
Keyword(s):  
Incident Light ◽  
Close Relation ◽  
Actual Process ◽  
Metal Vapour ◽  
New Era ◽  
Spark Gap ◽  
In Series ◽  
The Subject ◽  
The Doppler Effect ◽  
The Individual

When the oscillating electric spark is examined in a rapidly rotating mirror, the successive oscillations render themselves evident in the image as a series of lumnious curved streamers which emanate from the poles and extend towards the centre of the spark gap. These streamers were first observed by Feddersen in 1862, but the work of Schuster and Hemsalech in 1900 may be said to have opened up a new era in the subject. These workers threw the image of the spark on the slit of a spectroscope, and photographed the resulting spectrum on a film which was maintained in rapid rotation in a direction at right angles to that of the incident light. In their photographs they found that the air lines extended straight across from pole to pole, but that the metal lines were represented by curved bands drawn out in the centre of the spark gap. There is a close relation between these bands and the streamers seen in the unanalysed inductive spark. Schuster and Hemsalech carried out their experiments with the smallest possible inductance in series with the spark, and thus made the period of the oscillations so small that the drawing out on the film was insufficient to separate the individual oscillations from each other. Thus their curved lines represent a composite structure, consisting of all the streamers due to the successive oscillations superposed on each other. It follows from their results that the light of the streamers in the spark is entirely produced by the glowing of the metallic vapour of the electrodes, and that, while the luminosity of the air is practically instantaneous in its occurrence, that due to the metal vapour occurs in the centre of the spark gap an appreciable time later than near the poles. The actual process which goes on in the spark and gives rise to this delay in the arrival of the metallic vapour at the centre of the gap is not yet thoroughly understood. Schuster and Hemsalech make the natural supposition that it is due to the fact that the metal of the electrode is vaporised and rendered incandescent by the heat of the spark, and that the vapour takes an appreciable time to diffuse from the electrodes to the centre of the gap. The exception which has been taken to this view has arisen in part from the difficulty of observing the Doppler effect on the metallic lines which should be a concomitant of the diffusion of the vapour from the poles, and in part from the extraordinary results which the authors themselves obtained in some metals for the velocity of the diffusion corresponding to the different lines. In the case of bismuth and, in a less degree, of cadmium the different metallic lines could be divided into groups of different curvatures which indicated different velocities of diffusion towards the centre of the gap. As regards the former matter, there does not seem to be involved any real difficulty to the explanation, as Dr. Schuster has himself recently shown. The curious effect of the different curvatures of the lines of the same element has, however, always remained more or less of a difficulty in the way of a complete acceptance of their view. Schuster and Hemsalech themselves refer to the possibility in the case of bismuth that the metal may be a compound, and that the two kinds of molecules give rise to the differently curved lines. Other explanations have been made by different writers, but it cannot be said that any explanation adequately supported by experiment has been forthcoming. In view of this incompleteness in our knowledge of the constitution of the streamers it seemed to me that further observations with a rotating mirror would possibly be of value, and the investigations recorded below succeed, I think, in throwing a clearer light on the nature of the streamers, and on certain other phenomena which are characteristic of the spark.

scholarly journals The rate of evaporation of droplets. Evaporation and diffusion coefficients, and vapour pressures of dibutyl phthalate and butyl stearate

1946 ◽  
Vol 186 (1006) ◽  
pp. 368-390 ◽  
Keyword(s):  
Diffusion Coefficients ◽  
Atmospheric Pressure ◽  
Dibutyl Phthalate ◽  
Droplet Evaporation ◽  
Medium Size ◽  
Good Accordance ◽  
Butyl Stearate ◽  
Rate Of Evaporation ◽  
Low Pressures ◽  
And Diffusion

The rate of evaporation of drops of dibutyl phthalate and butyl stearate of radius approx. 0.5 mm. has been studied by means of a microbalance over a range of atmospheric pressures down to approx. 0*1 mm. of mercury. Wide departures from Langmuir’s evaporation formula were found to occur at these low pressures, but results are in good accordance with the theory of droplet evaporation advanced by Fuchs which hitherto has not been tested experimentally. This experimental verification of Fuch’s theory for droplets of medium size evaporating at low pressures shows that the theory can be applied to the evaporation of very small drops at atmospheric pressure. The vapour pressures of the above liquids have been measured by Knudsen’s method and the evaporation and diffusion coefficients calculated fro n the experimental data.

scholarly journals The influence of pressure on the boiling points of metals

1910 ◽  
Vol 83 (565) ◽  
pp. 483-491 ◽  
Keyword(s):  
Atmospheric Pressure ◽  
Boiling Point ◽  
High Vacuum ◽  
Similar Type ◽  
Exact Relation ◽  
Reduced Pressure ◽  
Boiling Points ◽  
Experimental Values ◽  
Low Pressures ◽  
Very High

Part I. — Pressures below 760 mm . In a previous communication (‘Proc.’, A, vol. 82, 1909, p. 396) the approximate boiling points of a number of metals were determined at atmospheric pressure. Apart from the question of finding the exact relation between the boiling point and pressure, it is an important criterion of any method for fixing the temperatures of ebullition to demonstrate that the experimental values obtained are dependent on the pressure. It is specially desirable when dealing with substances boiling at temperatures above 2000° to have some evidence that the points indicated are true boiling points. Previous work on the vaporisation of metals at different pressures has been confined to experiments in a very high vacuum except for metals like bismuth, cadmium, and zinc, which boil at relatively low temperatures under atmospheric pressure. The observations were limited to very low pressures on account of the difficulty of obtaining any material capable of withstanding a vacuum at temperatures over 1400° and the consequent necessity for keeping the boiling point below this limit by using very low pressures. Moreover in the case of the majority of the metals, e. g. , copper, tin, ebullition under reduced pressure has never been observed. The difficulties indicated above were avoided by using a similar type of apparatus to that previously described, and arranging the whole furnace inside a vacuum enclosure, thus permitting of the use of graphite crucibles to contain the metal.

scholarly journals Bands in the secondary spectrum of hydrogen

1927 ◽  
Vol 114 (767) ◽  
pp. 293-313 ◽  
Keyword(s):  
Quantum Theory ◽  
Static Model ◽  
Moment Of Inertia ◽  
Initial Moment ◽  
A Value ◽  
Starting Point ◽  
Band Spectra ◽  
The University ◽  
Low Pressures ◽  
Complete Account

Fulcher’s discovery of bands in the secondary spectrum of hydrogen at low pressures proved the starting point of a number of investigations, including those, based on the valuable tables of Merton and Barratt, which have been carried out in the University of St. Andrews. The application of the quantum theory to these bands has been discussed by one of us (H. S. A.), by Curtis, and in particular by Richardson who, partly in association with Tanaka, has added greatly to the number of known regularities and done much to bring them into line with the theory of band spectra. Nevertheless, apart from the Fulcher system, of which Richardson has recently given a very complete account, there remains a very large number of lines which have not yet been classified. One of the present writers (I. S.) has been engaged in a study of the secondary spectrum at higher pressures, and among the regularities which have been selected by this method is a band with head at 4582·58 A. U. and shading towards the violet, which has been described in a recent communication. This band yielded an initial moment of inertia agreeing closely with a value deduced from a static model of triatomic hydrogen, H 3 . This band has since been found to be one of a large number of similar bands which it will be the purpose of this paper to describe. We shall refer to it for convenience as “Band II A , a .”

In-phase rejection requirements for measuring respiratory input impedance

1984 ◽  
Vol 56 (3) ◽  
pp. 804-809 ◽  
Author(s):  
R. Peslin ◽  
P. Jardin ◽  
C. Duvivier ◽  
P. Begin
Keyword(s):  
Pressure Difference ◽  
Input Impedance ◽  
Pressure Transducer ◽  
Absolute Pressure ◽  
Impedance Measurements ◽  
Differential Pressure Transducer ◽  
Rejection Ratio ◽  
Respiratory Flow ◽  
In Series ◽  
The Subject

Respiratory flow is commonly obtained by measuring the pressure difference across a pneumotachograph. When respiratory input impedance is studied, that pressure difference may be very small with respect to the absolute pressure swings inside the pneumotachograph. Then the in-phase rejection of the differential pressure transducer is expected to markedly influence the accuracy of the data. The problem was investigated by computer simulation and by measurements on a mechanical analog of the respiratory system made of a resistance, an inertance, and a compliance arranged in series. Both studies demonstrated that comparatively small differences in the volumes of the chambers or in the lengths or diameters of the connecting tubes led to artifactual frequency dependence of resistance and serious misestimation of compliance and inertance. Errors were larger when the resistance of the pneumotachograph was smaller and the impedance of the subject larger. In practice, with usual pneumotachographs accurate impedance measurements require using the most symmetrical transducers presently available (common-mode rejection ratio of about 70 dB at 30 Hz).

Numerical Investigation of Multistage Viscous Micropump Configurations

2005 ◽  
Vol 127 (4) ◽  
pp. 734-742 ◽  
Author(s):  
M. Abdelgawad ◽  
I. Hassan ◽  
N. Esmail ◽  
P. Phutthavong
Keyword(s):  
Flow Rate ◽  
Numerical Data ◽  
Future Research ◽  
Shear Stresses ◽  
Vertical Rotor ◽  
Viscous Micropump ◽  
Study Results ◽  
In Series ◽  
The Subject ◽  
Drag And Lift

The viscous micropump consists of a cylinder placed eccentrically inside a microchannel, where the rotor axis is perpendicular to the channel axis. When the cylinder rotates, a net force is transferred to the fluid because of the unequal shear stresses on the upper and lower surfaces of the rotor. Consequently, this causes the surrounding fluid in the channel to displace toward the microchannel outlet. The simplicity of the viscous micropump renders it ideal for micropumping; however, previous studies have shown that its performance is still less than what is required for various applications. The performance of the viscous micropump, in terms of flow rate and pressure capabilities, may be enhanced by implementing more than one rotor into the configuration either horizontally or vertically oriented relative to each other. This is analogous to connecting multiple pumps in parallel or in series. The present study will numerically investigate the performance of various configurations of the viscous micropumps with multiple rotors, namely, the dual-horizontal rotor, triple-horizontal rotor, symmetrical dual-vertical rotor, and eight-shaped dual-vertical rotor. The development of drag-and-lift forces with time, as well as the viscous resisting torque on the cylinders were studied. In addition, the corresponding drag, lift, and moment coefficients were calculated. The flow pattern and pressure distribution on the cylinders’ surfaces are also included in the study. Results show that the symmetrical dual-vertical rotor configuration yields the best efficiency and generates the highest flow rate. The steady-state performance of the single-stage micropump was compared to the available experimental and numerical data and found to be in very good agreement. This work provides a foundation for future research on the subject of fluid phenomena in viscous micropumps.

On the Action of the Geiger α-particle Counter

1928 ◽  
Vol 24 (2) ◽  
pp. 251-258 ◽  
Author(s):  
James Taylor
Keyword(s):  
General Problem ◽  
Mode Of Action ◽  
The Self ◽  
Particle Counter ◽  
Discharge Tubes ◽  
The Subject

A very great deal has been published upon the subject of the electrical counter and its mode of action. Most explanations are incomplete in that they neglect some of the factors involved. The question of the self-restoring property of the system has also received attention, but this property has not been properly related to the general problem of intermittency in discharge tubes.

Null referential subjects in the history of Swedish

2013 ◽  
Vol 3 (2) ◽  
pp. 155-191 ◽  
Author(s):  
David Håkansson
Keyword(s):  
Subject Position ◽  
Verb Second ◽  
Common Assumption ◽  
Subordinate Clauses ◽  
Movement Strategies ◽  
Old Swedish ◽  
History Of ◽  
Striking Change ◽  
The Subject ◽  
Person Agreement

This article is concerned with null referential subjects in Old Swedish (ca. 1225–1526), and addresses the problem of why the scope for such subjects has been reduced during the history of Swedish. Within diachronic syntax it has been a common assumption that syntactic change is caused by changes in morphology. However, this study shows that deflexion only to a limited extent can explain the loss of null referential subjects in Old Swedish, since the most striking change in their use seems to take place during Early Old Swedish (ca. 1225–1375) before the loss of person agreement: whereas referential subjects could be omitted from verb-second main clauses and subordinate clauses in Early Old Swedish, in Late Old Swedish corresponding subjectless clauses are uncommon. Within the framework of generative grammar it is argued that this is an effect of changes in movement strategies to the subject position, [Spec, IP]: whereas movement to the subject position is syntactically determined in Modern Swedish, in Early Old Swedish the corresponding move is pragmatically determined. The study is based on a corpus of approximately 193,400 words, collected from 12 Old Swedish texts.

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