scholarly journals An experimental determination of the ionisation potential for electrons in helium

1919 ◽  
Vol 95 (671) ◽  
pp. 408-429 ◽  
Keyword(s):  
Direct Determination ◽  
Complete Removal ◽  
The Other ◽  
Ionisation Potential ◽  
Electron Collisions ◽  
Positive Ions ◽  
Positive Nucleus ◽  
Quantum Theory Of Radiation ◽  
The One

Bohr has developed a theory of atomic structure by applying a system of mechanics based on the quantum theory of radiation to the theory of the nucleus atom proposed by Rutherford. In the case of certain simple atoms he has calculated the minimum voltages through which an electron must fall in order to be able to produce ionisation by collision, and a comparison of the calculated values with those obtained experimentally serves as a check on the validity of the theory. Next to the hydrogen atom, that of helium has the simplest constitution, and this, for the normal atom, consists of two electrons rotating in non-radiating orbits round a doubly charged positive nucleus. The application of Bohr’s formula to helium indicates that the minimum velocity necessary to remove one electron from the helium atom is about 29 volts, but the direct experimental determinations of several observers agree in fixing the value at about 20 volts. Bohr has attempted to explain this by the assumption that the ionisation potential measured does not correspond to the complete removal of the electron from the atom, but only to a transition from the normal state of the atom to some other stationary state, where the one electron rotates outside the other. When the outer electron falls back to its original orbit, radiation of sufficiently high frequency to liberate electrons by photo-electric action from the metal parts of the apparatus is produced, and Bohr has suggested that such a secondary effect has been mistaken for a genuine ionisation of helium by electron collisions. The first direct determination of the minimum ionisation potential for helium was made by Franck and Hertz, using the method originally devised by Lenard. In their experiments, electrons from a glowing filament were accelerated towards a platinum gauze, on the other side of which they encountered an opposing field, which prevented any of them from reaching a collecting electrode. If, however, the electrons on passing through the gauze possessed sufficient energy to ionise the gas present by collisions, the positive ions liberated were driven towards the collecting electrode, and the ionisation was measured by an electrometer in connection with it. The experiment consisted in gradually increasing the potential difference accelerating the electrons until positive ions were detected by the electrometer. The accelerating voltage at which this occurred was increased by the experimentally determined velocity of emission of the electrons from the glowing filament, and the value 20·5 volts was obtained for the ionisation potential.

scholarly journals Determination of the Height of Hard X-Ray Sources in the Solar Atmosphere by Measurement of Photospheric Albedo Photons

1975 ◽  
Vol 68 ◽  
pp. 239-241
Author(s):  
John C. Brown ◽  
H. F. Van Beek
Keyword(s):  
Solar Atmosphere ◽  
The Other ◽  
X Ray ◽  
Theoretical Predictions ◽  
Source Models ◽  
The One

SummaryThe importance and difficulties of determining the height of hard X-ray sources in the solar atmosphere, in order to distinguish source models, have been discussed by Brown and McClymont (1974) and also in this Symposium (Brown, 1975; Datlowe, 1975). Theoretical predictions of this height, h, range between and 105 km above the photosphere for different models (Brown and McClymont, 1974; McClymont and Brown, 1974). Equally diverse values have been inferred from observations of synchronous chromospheric EUV bursts (Kane and Donnelly, 1971) on the one hand and from apparently behind-the-limb events (e.g. Datlowe, 1975) on the other.

Augustus and the Senate: 23 B.C.

Antichthon ◽  
1985 ◽  
Vol 19 ◽  
pp. 57-67 ◽  
Author(s):  
W.K. Lacey
Keyword(s):  
The Other ◽  
The One ◽  
Res Publica

While the exact meaning of Res Gestae 34, the powers of Augustus at various moments in his principate, and the significance of his auctoritas have been extensively argued, more practical questions about how his political arrangements might have been set into action have not generally excited much interest. In 1974 I put forward a suggestion about how the so-called first settlement of 27 B.C. came about. It was, in brief, that Octavian, as he then was, used the traditional consular mechanisms, and proposed for debate in the Senate a motion, de provinciis consularibus, and this explains why, on the one hand, the result of the debate was that he had provinces allocated to him, and, on the other, claims could be made that the res publica was restored, because one of the things which characterized res publica (as distinct from dictatorship or triumviral rule) was that the determination of who should command which army stationed in the provinces now lay, ostensibly at least, with the publicum consilium, the Senate.

Table II : Quantitative determination of carbonyl compounds at different odour sources (concentrations in ppb) Rendering plant Gelatine plant neighbourhood neighbourhood Formaldehyde 40 16 Acetaldehyde 39 24 Acetone 36 73 Prcpanal 10 -Isobutyraldehyde 10 30 Pentanal 15 19 Hexanal 3.52 Heptanal 12.5 Octanal 10.5 Nonanal 1 2 acids (figure 7). However extractions always involve a serious decrease in sensitivity, while evaporation of the extract produces a solution in 0.1-0.5 ml of solvent, and only 1 pi of it can be brought in the gas chromatograph. Therefore work is in progress to enhance sensitivity by converting acids in­ to halogenated derivatives, which can be GC-analysed with the more sensitive electron-capture detector. For thiols a similar procedure is investigated as with aldehydes. One possibility is absorption of thiols in an alkaline solution and reaction with 2,4-dinitrochlorobenzene, yielding 2,4-dinitrofenylsulfides, which are analysed by HPLC (9). Sane improvements on removal of reagents at the one hand and on separation of sane by-products on the other hand have to be achieved in order to in­ crease the sensitivity with another factor of ten. 5. CONCLUSION The actual scope and limitations of chemical analysis of odour show that all problems can be tackled as far as emission is concerned. For iititiission measurements seme progress is necessary, but there is no essential reason why chemical analysis would be unable to attain the desired sensitivity for all types of odorants. There is no doubt that in a few years the last dif­ ficulties will be solved. In order to achieve real control of odour nui­ sance, automatic measurement is necessary on a long time basis. There again seme technical development is to be expected. Does this mean that machines are going to decide if an odour is pre­ sent or not? By no means, while the population will always be the reference, and psychophysical measurements will be necessary to make chemical analysis possible.

1986 ◽  
pp. 171-171
Keyword(s):  
Chemical Analysis ◽  
Quantitative Determination ◽  
Alkaline Solution ◽  
Automatic Measurement ◽  
The Other ◽  
Long Time ◽  
Time Basis ◽  
The One ◽  
By Products

scholarly journals On the magnetic power of soft iron

1837 ◽  
Vol 3 ◽  
pp. 187-188
Keyword(s):  
Electric Current ◽  
Copper Wire ◽  
Complete Removal ◽  
The Other ◽  
Present Communication ◽  
Hard Steel ◽  
Electric Current Passing ◽  
Good Contact ◽  
The One ◽  
Single Helix

When free magnetism is developed by induction, and is not retained in that state by what has been termed the coercive force of hard steel, it has generally been considered that all the phenomena due to the existence of free magnetism cease on the removal of the inducing cause. The object of the present communication is to show that such is not the fact. From a variety of experiments described by the author, it appears that soft iron continued to exhibit strongly the attraction due to the developement of magnetism long after the means by which the magnetism had been originally excited had ceased to act. In these experiments, bars of soft iron, in the form of a horseshoe, had a single helix of copper wire wound round them, so that on the ends of the wire being brought into contact with the poles of a voltaic battery, the iron became an electromagnet. With one of these horse-shoes, while the connexion between the ends of the helix and the poles of the battery existed, the soft iron, having a keeper applied to its poles, supported 125 pounds it supported 56 pounds after that connexion had been broken, and continued to retain the power of supporting the same weight after an interval of several days, care having been taken not to disturb, during the time, the contact between the horse-shoe and its keeper. On this contact, however, being broken, nearly the whole attractive power appeared to be immediately lost. The author describes several instances of the same kind, particularly one in which the contact between the ends of the horse-shoe of soft iron and its keeper having been undisturbed during fifteen weeks, the attractive power continued undiminished. Although the interposition of a substance, such as mica or paper, between the ends of the horse-shoe and its keeper necessarily diminished the force of attraction, it did not appear to diminish the power of retaining that force. In a case where the electromagnet of soft iron and its keeper were equal semi-circles, the author found, what may appear singular, that the arrangement of the magnetism during the time that the electric current traversed the helix, appeared not to be the same as after the cessation of that current; in the one case similar, and in the other dissimilar, poles being opposed to each other at the opposite extremities of the two semi-circles. Whether the magnetism was originally developed in the soft iron by means of an electric current passing round it, or by passing over its surface the poles of an electromagnet, or those of a common magnet of hard steel, it appeared to possess the same power of retaining a large portion of the magnetism thus developed. The retention of the magnetism does not appear to depend upon the relative positions of the ends of the horse-shoe and the keeper remaining undisturbed, but on their contact remaining unbroken: for one keeper was substituted for another without diminution of this power; care being taken that the second should be in good contact with both ends of the horse-shoe before the complete removal of the first.

scholarly journals XXII. On the extensive atmosphere of Mars

1831 ◽  
Vol 121 ◽  
pp. 417-422 ◽  
Keyword(s):  
The Other ◽  
Astronomical Observations ◽  
Royal Observatory ◽  
Formed Part ◽  
The One

That several of the planets as well as that which we inhabit are surrounded by atmosphere, astronomical observations have long since established; the extent, however, to which in particular planets such atmospheres are diffused, is as yet not satisfactorily determined. The former rests principally upon phenomena observed on the planets’ discs, whilst the latter derives its support chiefly from those detected at or near their respective limbs. Every night, nay almost every hour, may give us indication of the one, whilst years are sometimes necessary, as in the case of planets unattended by satellites, to help us to the other; thus the hypothesis of the extensive atmosphere of Mars derives its origin from the observations of Cassini and Roëmer, and has stood more than a century and a half without refutation or support. The observations to which I allude formed part of a series undertaken for the determination of the parallax of Mars, and are recorded in the Mémoires de l’Académie des Sciences. Cassini’s were made at Briare and at La Charité sur Loire; whilst Roémer’s was obtained at the Royal Observatory of Paris.

Serological characteristics of Streptomyces species using cell wall immunizing antigens

1970 ◽  
Vol 16 (2) ◽  
pp. 107-115 ◽  
Author(s):  
Gerald R. Taylor ◽  
Rufus K. Guthrie ◽  
Elwood B. Shirling
Keyword(s):  
Cell Wall ◽  
Morphological Characteristics ◽  
The Other ◽  
Streptomyces Species ◽  
Dichotomous Key ◽  
Specific Antisera ◽  
Combination Of Methods ◽  
The One ◽  
Taxonomic Studies

A dichotomous key for determination of serological groups among Streptomyces is described. This key is limited in that only seven specific antisera are used for testing. The utility and reliability of the application of this key were tested and compared to the results of previous taxonomic studies reported on the basis of biochemical and morphological characteristics of these organisms. Results indicate the desirability of using a combination of methods including serological characteristics on the one hand, and biochemical–morphological characteristics on the other, to increase the reliability of taxonomic studies.

scholarly journals An investigation of the effects of electron collisions with platinum and with hydrogen, to ascertain whether the production of ionisation from platinum is due to occluded hydrogen

1920 ◽  
Vol 97 (681) ◽  
pp. 23-43 ◽  
Keyword(s):  
Metal Surface ◽  
Metal Surfaces ◽  
Direct Proof ◽  
Ionisation Potential ◽  
Electron Collisions ◽  
Electron Stream ◽  
Positive Ions ◽  
Minimum Velocity ◽  
Positively Charged ◽  
Made In

In the course of an investigation of the effects of electron collisions with helium atoms, it was found that positive ions were produced from a positively charged platinum gauze when this was bombarded by electrons with a minimum velocity of about 11 volts. The production of positive ions in this way does not appear to have been observed before for such small velocities of the impacting electrons, though their detection with primary rays of 30 volts speed is recorded by Campbell in the account of his experiments on ionisation by charged particles. In this paper Campbell gives an excellent summary of the work which has been done in connection with the bombardment of metal surfaces by slow cathode rays. The work of Lenard, Baeyer, Gehrts, Campbell, and others has established the facts that, when such rays fall on a negatively charged metal surface, electrons leave the surface, and that the number and the speed of these electrons depends on the velocity of impact of the primary stream. When the velocity of the incident rays is less than 11 volts, the electrons leaving the plate are those of the primary stream which have been reflected at the metal surface, the characteristic of these reflected rays being that most of them have a velocity comparable with that of the incident rays. When the velocity of impact reaches 11 volts, in addition to reflexion, an excitation of secondary rays begins and gradually increases in amount as the speed is further increased up to about 200 volts. On this account the curve showing the relation between the velocity of impact and the number of electrons leaving the plate takes an upward turn at 11 volts, but no other bend occurs until 200 volts is reached. It has therefore been concluded that the two processes mentioned above, viz., reflexion, and excitation of secondary rays beginning at 11 volts, are the only causes of electrons leaving the impacted surface. It was found by Baeyer that with a minimum velocity of impact of about 25 volts more electrons leave the plate than fall on it, and this result, combined with the fact that Campbell detected a positive current (presumably from a positively charged plate) when the bombarding electrons had a minimum velocity of 30 volts, has given rise to the view that the second process—that which is operative above 11 volts—is an ionisation at the metal surface, the material ionised being either the metal itself or gas attached to it. On this view it is concluded that the critical velocity of 11 volts is the “ionisation potential ” of the material ionised. This velocity was found to be the same for all the metal surfaces tested, and as it agreed with the usually accepted value of the “ionisation potential” for hydrogen, it has been suggested that the material ionised is hydrogen present in the surface of the metal. Some confirmation of this view has been obtained by Campbell from experiments with metal surfaces subjected to treatment designed to modify the amount of hydrogen present, but the evidence hitherto produced cannot be said to prove conclusively that the process which begins at 11 volts is a genuine ionisation by electron collisions. That ionisation occurs ultimately can hardly be doubted, for it has been observed that when the velocity of the electron stream is sufficiently increased, the number of electrons leaving a bombarded electrode is in some cases as much as twenty times as great as the number arriving at it, but the first direct proof that ionisation occurs at the metal surface when the impacting electrons have a velocity as small as 11 volts seems to be that given by the experiments made in the course of our investigation of the ionisation of helium. The present research is a fuller investigation of this effect, undertaken in order to ascertain whether the evidence of ionisation at 11 volts could be substantiated, and, if so, to determine whether it should be attributed to the metal itself or to hydrogen attached to the metal surface.

scholarly journals IX. Remarks concerning the Natural-Historical Determination of Diallage

1826 ◽  
Vol 10 (1) ◽  
pp. 127-147
Author(s):  
W. Haidinger
Keyword(s):  
Fixed Point ◽  
Natural History ◽  
Distinct Species ◽  
The Other ◽  
Accurate Information ◽  
External Appearance ◽  
Slight Degree ◽  
The One

The following paper contains the results of a series of inquiries, which lead to the conclusion, that the mineral called Smaragdite by Saussure, does not form a species of its own; but that this name has been given to a compound of certain varieties of two distinct species, Augite and Hornblende, the natural-historical species of paratomous and hemiprismatic Augite-spar.Owing in part to the slight degree of resemblance prevailing among its varieties, the authors who have described them differ so essentially in opinion, that I am obliged to go into various details, both respecting the external appearance of the mineral itself, and of the opinions of mineralogists, in order to afford a correct view of the natural-historical species, to which these varieties belong, since this is the basis upon which every system, and, indeed, all accurate information in natural history, is founded, and the fixed point to which the one and the other must be referred.

Determination of Enemy Character of Corporations

1930 ◽  
Vol 24 (2) ◽  
pp. 310-336 ◽  
Author(s):  
Ralph A. Nohem
Keyword(s):  
The Other ◽  
Separate Entity ◽  
Entity Theory ◽  
Long Period ◽  
Corporate Entity ◽  
Sovereign Authority ◽  
The Subject ◽  
The One ◽  
Independent Person

Much controversy has raged for a long period of time over the precise nature of what Wormser refers to as the “anatomy” of a corporation. Wormser himself defines a corporation as a “group of one or more persons authorized by sovereign authority to act as a unit and a personality in the eye of the law.” The definition indicates, on the one hand, that the act of incorporation creates a new person or entity, on the other that this new entity is in fact composite, made up of one or more pre-existing entities. The question arises, at what times will the court regard the corporate entity, and at what times will it look to the real persons who compose it ? A key to the solution of the problem is offered by Lord Mansfield. “A fiction of law shall never be contradicted so as to defeat the end for which it was invented, but for every other purpose it may be contradicted.” By the separate entity theory is meant that a corporation is to be regarded as an entity separate and apart from its corporators and that it is to be treated like any other independent person. That this is the theory of corporations generally accepted by the courts need hardly be proved. It will only be noted that the ruling English case on the subject is that of Salomon and Co. v. Salomon. In his opinion in that case Lord Halsbury said: “Once the company is legally incorporated it must be treated like any other independent person.”

scholarly journals Element-for-Element Replacement? Beware! There Might Be a "No-Entry" Sign

2002 ◽  
Vol 45 (4) ◽  
pp. 622-627
Author(s):  
Kazem Lotfipour-Saedi
Keyword(s):  
The Other ◽  
Language System ◽  
Direct Route ◽  
The One ◽  
The Relationship ◽  
Replacement Operation

Abstract Various definitions have been offered for translation, each assuming a different orientation to the nature of meaning and language but all sharing the notion of replacement of one sort or another. The commonsensically perceived framework of translation operation is also basically founded upon the notion of replacement, mostly leading to the illusion that translation is just a matter of replacing SL elements by TL ones. But due to the uniqueness of each language system on the one hand and the non-isomorphic nature of the relationship between form and meaning across language on the other, this replacement operation faces challenging problems. This paper argues that there is no direct route in this operation and the replacement becomes possible only through the determination of the value of the elements to be replaced.

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