scholarly journals THE ABSORPTION OF ULTRA-VIOLET RADIATION BY CRYSTALLINE PEPSIN

1934 ◽  
Vol 18 (2) ◽  
pp. 265-278 ◽  
Author(s):  
Frederick L. Gates
Keyword(s):  
Absorption Spectrum ◽  
Absorption Spectra ◽  
Energy Flux ◽  
Ultra Violet ◽  
Total Absorption ◽  
Absorbed Energy ◽  
Violet Light ◽  
Ultra Violet Radiation ◽  
Violet Radiation

Determination of the absorption spectra of pure preparations of Northrop's crystalline pepsin inactivated by irradiation with ultra-violet light shows that the total absorption in the ultra-violet region of the spectrum increases with the degree of inactivation. This increase is especially marked between 2400 and 2750 Å.u. The rate of photoinactivation is shown to be sensitive to changes in pH, increasing with lower values, and evidently bears a one-quantum relationship to the energy flux. Tests of the rate of inactivation of pepsin exposed to several different bands of the ultra-violet spectrum, in relation to the absorbed energy, indicate that the destruction spectrum of the enzyme agrees essentially with its absorption spectrum and is similar to that of urease.

Properties of Higher Polymers in Solution. III. The Action of Ultra-Violet Light on Dissolved Rubber

1936 ◽  
Vol 9 (4) ◽  
pp. 570-572 ◽  
Author(s):  
Kurt H. Meyer ◽  
Cesare Ferri
Keyword(s):  
Physical Properties ◽  
Wave Length ◽  
Ultra Violet ◽  
The Other ◽  
Ultra Violet Light ◽  
Violet Light ◽  
Ultra Violet Radiation ◽  
Gutta Percha ◽  
Other Hand ◽  
Violet Radiation

Abstract The action of ultra-violet radiation on rubber has been the object of a long series of investigations. According to van Rossem, rubber is depolymerized under the action of light. Asano on the other hand thinks that ultra-violet light, is able to bring about either polymerization or depolymerization according to its wave-length. More recently Dogadkin and Pantschenkov have carried out experiments in an atmosphere of nitrogen, during the course of which they have found a strong diminution in the viscosity. From this fact they have concluded that light is able to cause depolymerization and micellar degradation. We have undertaken a study of the action of ultra-violet light on rubber in order to prove whether the double cis-linkages of rubber undergo a transposition into trans-linkages, for numerous instances are known where light causes these cis-trans-transpositions. In the case of rubber, one should obtain, therefore, either a hydrocarbon of the gutta-percha type or, if light causes a sort of cis-trans-equilibrium, a hydrocarbon with double cis-linkages distributed irregularly. In our experiments we were extremely careful to exclude oxygen, since some years ago Henri proved that ultra-violet light activates greatly the oxidation of rubber. On the other hand it is known that oxidation causes a diminution in the length of the chains which modifies considerably the physical properties, for example, the viscosity, and which may mask the effect produced by light.

scholarly journals The action of ultra-violet radiation on barium and strontium azides

1939 ◽  
Vol 172 (950) ◽  
pp. 299-314 ◽  
Keyword(s):  
Induction Period ◽  
Alkaline Earth ◽  
Room Temperature ◽  
Wave Length ◽  
Ultra Violet ◽  
Ultra Violet Light ◽  
Violet Light ◽  
Ultra Violet Radiation ◽  
Pre Treatment ◽  
Violet Radiation

The alkaline earth azides decompose at appreciable rates at temperatures above 100° C, and the reactions which occur are of the accelerating type increasing in speed as the 6th-8th power of the time, there being a marked induction period during which the reaction occurs at a negligible rate (Harvey 1933; Marke 1937; Maggs 1939). The decomposition is accelerated and the length of the induction period shortened when the solid is acted upon by β -rays at room temperature before the heat treatment (Garner and Moon 1933; Maggs 1939). It was, therefore, possible that ultra-violet light would cause an acceleration of these reactions in a similar manner. Muller and Brous (1933) have shown that sodium azide is decomposed by ultra-violet light at a rate which is proportional to the intensity and that the threshold wave-length for the decomposition is around 405 m µ . In the present investigation it is shown that barium and strontium azides are decomposed by ultra-violet light at room temperature and that the thermal decomposition of these substances is accelerated by pre-treatment with this radiation.

scholarly journals RESULTS OF IRRADIATING SACCHAROMYCES WITH MONOCHROMATIC ULTRA-VIOLET LIGHT

1935 ◽  
Vol 18 (3) ◽  
pp. 351-355 ◽  
Author(s):  
R. H. Oster ◽  
W. A. Arnold
Keyword(s):  
Cell Division ◽  
Ultra Violet ◽  
Sufficient Data ◽  
Ultra Violet Light ◽  
Violet Light ◽  
Ultra Violet Radiation ◽  
Degree Of Damage ◽  
Multiple Hit ◽  
Violet Radiation

Data obtained on yeast irradiated with monochromatic ultra-violet radiation has been analyzed for the number of quantum hits involved in the production of different degrees of inhibition of cell division, according to the method proposed by Mme. Curie (1929). Sufficient data are not available for a rigorous determination, but the calculated results tend to indicate that a multiple hit to kill relation is followed, that different numbers of hits are involved in the production of different degrees of inhibition, and that this number increases with increase in the degree of damage sustained.

The influence of physical factors on the survival and infectivity of miracidia ofSchistosoma mansoniandS. haematobiumI. Effect of temperature and ultra-violet light

1977 ◽  
Vol 51 (1) ◽  
pp. 73-85 ◽  
Author(s):  
S. K. Prah ◽  
C. James
Keyword(s):  
Low Temperature ◽  
Old Age ◽  
Ultra Violet ◽  
Effect Of Temperature ◽  
Physical Factors ◽  
Influence Of Temperature ◽  
Violet Light ◽  
Ultra Violet Radiation ◽  
Turbid Waters ◽  
Violet Radiation

ABSTRACTThe influence of temperature and ultra-violet radiation on the degree of activity, survival and infectivity of schistosome miracidia is profound. Miracidia ofSchistosoma mansoniandS. haematobiumwere affected equally. Only miracidia classified as “active” or “slow” were capable of penetration, a capacity they retained for about 17 hours at 19°C. Miracidia that were “lethargic” as a result of low temperature, old age or ultra-violet radiation lost their infective capacity. The conclusion, however, is that neither the temperatures encountered in the field nor the solar ultra-violet radiation penetrating turbid waters are likely to be harmful to miracidia and thus have no effect on the level of transmission.

XXII.—Deficiency Effects of Ultra-violet Light in Drosophila melanogaster

1942 ◽  
Vol 61 (3) ◽  
pp. 297-315
Author(s):  
B. M. Slizynski
Keyword(s):  
Drosophila Melanogaster ◽  
Ultra Violet ◽  
Maize Pollen ◽  
X Ray ◽  
Ultra Violet Light ◽  
Violet Light ◽  
Ultra Violet Radiation ◽  
Chromosomal Changes ◽  
Ray Series ◽  
Violet Radiation

Stadler and Sprague in a series of papers (1936) succeeded in demonstrating by a genetical method the effect of ultra-violet radiation in maize pollen, and found that in their experiments in the X-ray series the chromosomal changes are very common, while in the ultra-violet series they are rare.

scholarly journals THE INFLUENCE OF ULTRA-VIOLET RADIATION ON THE WEIGHT OF ADULT RABBITS, NORMAL AND SYPHILITIC

1930 ◽  
Vol 52 (2) ◽  
pp. 253-266 ◽  
Author(s):  
Alvin R. Harnes
Keyword(s):  
Initial Period ◽  
Ultra Violet ◽  
Total Darkness ◽  
Lower Body ◽  
Control Groups ◽  
Violet Light ◽  
Ultra Violet Radiation ◽  
Lower Body Weight ◽  
Rate Of Increase ◽  
Violet Radiation

In summarizing the results obtained for these 6 groups of animals, the following conclusions may be drawn: Normal rabbits living in total darkness and exposed to ultra-violet radiation at regular intervals showed a more rapid rate of increase in weight than animals living under the same condition, but after an initial period of rapid increase, the irradiated animals maintained a lower body weight than those living in the dark. Under the same conditions, animals inoculated with T. pallidum and exposed to ultra-violet light maintained a lower weight than the corresponding control groups living in total darkness. Furthermore, the mortality rate from pneumonic infection was found to be greater in animals exposed to ultra-violet radiation than in those living entirely in the dark. It is evident, therefore, that, under the conditions given, ultra-violet radiation was detrimental rather than beneficial.

scholarly journals The absorption spectrum of vitamin D

1929 ◽  
Vol 104 (733) ◽  
pp. 561-583 ◽  
Keyword(s):  
Vitamin D ◽  
Absorption Spectrum ◽  
Absorption Band ◽  
Ultra Violet ◽  
Maximum Absorption ◽  
Characteristic Absorption Band ◽  
Simultaneous Formation ◽  
Ultra Violet Radiation ◽  
Vitamin D 3 ◽  
Violet Radiation

Numerous studies have been made of the absorption spectrum of the products of ultra-violet radiation of ergosterol (1). These studies have shown that such radiation causes a decrease and final disappearance of the characteristic absorption band of ergosterol (maximum 280 m μ). Several workers have reported the simultaneous formation of a new absorption band (maximum 240), and have attributed this band to vitamin D. Our own observations, however, have shown (2) that the first effect of ultra-violet radiation on ergosterol, and we have suggested that this is due to the formation of a new substance with an absorption maximum at 280, and that this substance is vitamin D (3). It has also shown that the product having maximum absorption at 240 has no detectable antirachitic activity (4). We have compared the antirachitic activity of irradiated ergosterol solutions with their absorption spectra, both before and after removal of unchanged ergosterol, and have obtained evidence pointing to the successive formation of three substances (or mixtures of substances). Of these, the first has maximum absorption at 280, and is, we believe, vitamin D; the second shows maximum absorption at 240, and has no antirachitic action; the third is similarly inactive, and shows no intense absorption. We propose to refer to these substances as A, B, and C, respectively.

A comparison of the effects of ultra-violet and gamma radiation in polymethylmethacrylate

1962 ◽  
Vol 269 (1336) ◽  
pp. 104-124 ◽  
Keyword(s):  
Room Temperature ◽  
Significant Contribution ◽  
Main Chain ◽  
Ultra Violet ◽  
High Energy ◽  
Electron Radiation ◽  
High Energy Radiation ◽  
Violet Light ◽  
Ultra Violet Radiation ◽  
Violet Radiation

The exposure of polymethylmethacrylate ( PMM ) and many other macromolecules to high-energy y- or electron radiation produces a degradation of the molecular chains. This may result from either ionization or excitation. Ultra-violet light results in excitation only. This paper compares the effects of these forms of radiation. The degradation of PMM has been studied in thick or thin films, and in solutions in benzene. It is found that at room temperature degradation (random main chain fracture) occurs with ultra-violet radiation, whereas at higher temperatures the reaction is one of chain depolymerization. The energy absorbed per main chain fracture is about 550 eV with ultra ­ violet radiation, so that less than 1 % of the quanta absorbed are effective; this compares with about 65 eV of γ-energy absorbed per fracture. Apart from this difference in efficiency, the two reactions are very similar. In both cases the number of fractures is proportional to dose and the radicals formed (as seen by e.s.r.) are identical in character. Somewhat similar changes also appear in the optical spectrum, although these may be modified by surface oxygen. These results show no significant contribution from any ionization produced by high-energy radiation.

Ultra-Violet Radiation and Varicose Ulcers

BMJ ◽  
1927 ◽  
Vol 2 (3479) ◽  
pp. 472-472
Author(s):  
M. Weinbren
Keyword(s):  
Ultra Violet ◽  
Ultra Violet Radiation ◽  
Violet Radiation
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