scholarly journals LV. On the distribution of energy in the different types of γ rays emitted from certain radioactive substances

1914 ◽  
Vol 28 (166) ◽  
pp. 527-539 ◽  
Author(s):  
Jadwiga Szmidt
Keyword(s):  
Radioactive Substances ◽  
Different Types ◽  
Γ Rays

scholarly journals The γ-rays from actinium emanation and their origin

1932 ◽  
Vol 136 (829) ◽  
pp. 407-412 ◽  
Keyword(s):  
Fine Structure ◽  
Experimental Evidence ◽  
Long Range ◽  
Strong Evidence ◽  
The Other ◽  
Homogeneous Groups ◽  
Radioactive Substances ◽  
Complex Transformation ◽  
Γ Rays ◽  
The Individual

As a result of recent experiments, evidence is accumulating that the pene­trating γ -rays from radioactive substances have their origin not in the movement of electrons but in the transitions of α -particles in an excited nucleus. Strong evidence in support of this view was obtained by Rutherford, Ward and Lewis from their analysis of the groups of long range α -particles from radium C', and a more detailed discussion of the results was given by Rutherford and Ellis. This problem of the origin of the γ -rays can be attacked in another direction from a consideration of the so-called fine structure shown by the groups of α -particles emitted by certain radioactive substances. In particular, Rosenblum found that the transformation of thorium C was accompanied by the appearance of five homogeneous groups of α -particles. In explanation of these results, Gamow suggested that γ -rays should be emitted as a result of such a complex transformation, the energies of the individual γ -rays corre­sponding to the differences of energies between the α -particles in the various groups. Unfortunately it is a difficult matter to give a decisive answer on this important question. In a recent paper, Ellis concludes that the experimental evidence is in support of Gamow’s theory, but on the other hand, Meitner as a result of her investigations, has expressed a contrary opinion. It is thus of much impor­tance to examine all methods of obtaining evidence on this question.

scholarly journals The excitation of γ -rays by β -rays

1914 ◽  
Vol 90 (621) ◽  
pp. 521-531 ◽  
Keyword(s):  
Atomic Weight ◽  
Balance Method ◽  
The Other ◽  
Characteristic Radiation ◽  
Definite Evidence ◽  
Radioactive Substances ◽  
Γ Rays ◽  
The Impact ◽  
First Time ◽  
Soft Radiation

The excitation of γ -rays by the impact of β -rays on different substances has been investigated by several observers. The question was first systematically examined by J. A. Gray. He showed that penetrating γ -rays are produced by the β -rays of radium E when they impinge on different materials, the amount of γ -radiation increasing with increase of atomic weight of the material. The particular disposition used in his first experiments was not suitable for the examination of any soft types of radiation which might have been excited, but in later work he showed, for the first time, that characteristic radiations were excited in the case of silver, tin, barium and cerium. Chadwick, using the balance method of Rutherford and Chadwick, examined whether the β -rays from radium B and radium C excite penetrating γ -rays in different kinds of matter. Definite evidence was obtained that an excited radiation amounting to about 0.5 per cent, of the primary γ -radiation is produced. This method, however, was not suitable for the detection of soft characteristic radiations. These general results have recently been confirmed by Starke, using the β -rays from a strong preparation of mesothorium. In previous papers by Rutherford and the author on the analysis of the γ -rays from radioactive substances, it has been shown that the γ -rays emitted by the different products can be separated into groups differing widely in penetrating power. Some of these radiations appear to be characteristic of the elements by which they are emitted and fall into one or other of the series given by Barkla. On the other hand, some of the groups of rays found do not appear to belong to either series. It was further shown in previous work that when radium C is deposited on nickel a soft radiation is given out which is entirely absorbed by 2 mm. of aluminium. This soft radiation was much more readily absorbed than that emitted by radium B, and for which μ = 40 (cm. -1 ), but it was appreciably harder than the characteristic radiation of nickel. Moreover, when radium C was deposited on silver, little, if any, soft radiation appeared to be emitted. It seemed of importance, therefore, to examine in detail the nature of the radiation excited by the β - and γ -rays from radium B and radium C, and to examine the bearing of the results on the type of radiation emitted by different materials on which radium C is deposited.

Study on grafting of different types of acrylic monomers onto natural rubber by γ-rays

2006 ◽  
Vol 75 (1) ◽  
pp. 168-172 ◽  
Author(s):  
N.C. Dafader ◽  
M.E. Haque ◽  
F. Akhtar ◽  
M.U. Ahmad
Keyword(s):  
Natural Rubber ◽  
Acrylic Monomers ◽  
Different Types ◽  
Γ Rays

scholarly journals Analysis of α-rays by an annular magnetic field

1933 ◽  
Vol 139 (839) ◽  
pp. 617-637 ◽  
Keyword(s):  
Magnetic Field ◽  
Long Range ◽  
Resolving Power ◽  
Counting Method ◽  
Range Measurements ◽  
Considerable Uncertainty ◽  
Radioactive Substances ◽  
Γ Rays ◽  
The Mean ◽  
Α Particles

In previous papers an account has been given of a new counting method for analysing the groups of α-rays emitted by radioactive substances, and for measuring directly their mean range in air. In the course of these experiments, we showed that the long range groups of α-particles from radium C' are very complex, consisting of at least nine groups, with mean ranges lying between 7·7 and 11·6 cm. of air. As it is believed that the energies of these long range groups are intimately connected with those of the γ-rays from radium C', it has become of great importance to determine the energies of these groups of particles with precision. As, however, the seven groups with ranges between 9·5 and 11·6 cm. differ so little in velocity that they can only be partially resolved in range measurements, it was very difficult in our experiments to determine the mean ranges with accuracy. Moreover, there has been considerable uncertainty as to the precise relation between the range and velocity of such long range particles. A much greater resolving power can be obtained by a direct velocity determination, using a magnet to bend the α-rays into a circle. The great Paris electromagnet has been used in this way by Rosenblum, who photographed the α-ray spectra produced by the well-known focussing method. He has demonstrated the complexity of a number of α-ray groups, and has measured their velocities with an accuracy of at least 1 in 1000.

The extinction time of a general birth and death process with catastrophes

1986 ◽  
Vol 23 (04) ◽  
pp. 851-858 ◽  
Author(s):  
P. J. Brockwell
Keyword(s):  
Laplace Transform ◽  
Size Distribution ◽  
Sufficient Conditions ◽  
Necessary And Sufficient Conditions ◽  
Death Process ◽  
Extinction Time ◽  
Birth And Death Process ◽  
Different Types ◽  
The Laplace Transform ◽  
Necessary And Sufficient

The Laplace transform of the extinction time is determined for a general birth and death process with arbitrary catastrophe rate and catastrophe size distribution. It is assumed only that the birth rates satisfyλ0= 0,λj> 0 for eachj> 0, and. Necessary and sufficient conditions for certain extinction of the population are derived. The results are applied to the linear birth and death process (λj=jλ, µj=jμ) with catastrophes of several different types.

Differentiating between different forms of moral obligations

2020 ◽  
Vol 43 ◽  
Author(s):  
Rajen A. Anderson ◽  
Benjamin C. Ruisch ◽  
David A. Pizarro
Keyword(s):  
Moral Character ◽  
Moral Obligations ◽  
Different Types

Abstract We argue that Tomasello's account overlooks important psychological distinctions between how humans judge different types of moral obligations, such as prescriptive obligations (i.e., what one should do) and proscriptive obligations (i.e., what one should not do). Specifically, evaluating these different types of obligations rests on different psychological inputs and has distinct downstream consequences for judgments of moral character.

Ultrastructural Investigations of the Contractile Filaments of Amoebae

1974 ◽  
Vol 32 ◽  
pp. 188-189
Author(s):  
P.L. Moore
Keyword(s):  
Cytoplasmic Streaming ◽  
Three Dimensional ◽  
Freeze Fracture ◽  
Amoeboid Movement ◽  
Different Types ◽  
Chemical Conditions ◽  
Complete Interpretation

Previous freeze fracture results on the intact giant, amoeba Chaos carolinensis indicated the presence of a fibrillar arrangement of filaments within the cytoplasm. A complete interpretation of the three dimensional ultrastructure of these structures, and their possible role in amoeboid movement was not possible, since comparable results could not be obtained with conventional fixation of intact amoebae. Progress in interpreting the freeze fracture images of amoebae required a more thorough understanding of the different types of filaments present in amoebae, and of the ways in which they could be organized while remaining functional.The recent development of a calcium sensitive, demembranated, amoeboid model of Chaos carolinensis has made it possible to achieve a better understanding of such functional arrangements of amoeboid filaments. In these models the motility of demembranated cytoplasm can be controlled in vitro, and the chemical conditions necessary for contractility, and cytoplasmic streaming can be investigated. It is clear from these studies that “fibrils” exist in amoeboid models, and that they are capable of contracting along their length under conditions similar to those which cause contraction in vertebrate muscles.

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