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.

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 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.

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.

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.

scholarly journals Studies on air-borne virus infections: II. the killing of virus aerosols by ultra-violet radiation

1943 ◽  
Vol 43 (1) ◽  
pp. 11-15 ◽  
Author(s):  
D. G. ff. Edward ◽  
Dora Lush ◽  
R. B. Bourdillon
Keyword(s):  
Influenza Virus ◽  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Wave Length ◽  
Ultra Violet ◽  
Virus Infections ◽  
Ultra Violet Radiation ◽  
Vaccinia Viruses ◽  
Simplex Virus ◽  
Violet Radiation

The experiments show that rapid and effective sterilization of atmospheres containing atomized particles of influenza and vaccinia viruses, and probably also of herpes simplex virus, can be obtained by ultra-violet radiation of wave-length 2537 A. At least 99 % and probably more of an aerosol of influenza virus was killed by exposure for 6 sec. at. a distance of 2 cm. from either a Hanovia lamp or a G.E.C. ‘Sterilamp’. These findings confirm the work of Wells and his associates who first demonstrated the susceptibility of this virus to ultra-violet radiation (Wells & Brown, 1936; Wells & Henle, 1941). At the same distance the ‘Sterilamp’ produced more than a 99 % kill of vaccinia virus with an exposure of 1 sec. and about a 90 % kill in 0·5 sec. The experiments with herpes were less satisfactory but suggested a similar sensitivity. These results support the view that ‘germicidal’ lamps are likely to be useful in reducing the infectivity of air contaminated with particles from persons suffering from virus infections of the respiratory tract.We wish to acknowledge our indebtedness to the late Sir Patrick Laidlaw who, although his name does not appear as author, largely inspired the investigation and took an active part in it until his death.

scholarly journals The coagulation of protein by sunlight

1922 ◽  
Vol 93 (651) ◽  
pp. 235-248 ◽  
Keyword(s):  
Temperature Coefficient ◽  
Tap Water ◽  
Wave Length ◽  
Ultra Violet ◽  
Protein Molecule ◽  
Mercury Vapour ◽  
Absorption Bands ◽  
Ultra Violet Light ◽  
Violet Light ◽  
Mercury Vapour Lamp

It was first shown by Dreyer and Hanssen (1) in 1917 that ultra-violet light produced a change in protein solutions which appeared to be similar to coagulation by heat. They exposed various solutions in quartz chambers to the light of a Bang lamp with iron and silver electrodes. Vitellin was found most easily coagulated, while globulin, albumin and fibrinogen showed a decreasing sensitivity to ultra-violet rays in the order mentioned. These investigators also discovered that acids markedly increase the rate of precipitation. Soret (2) had shown in 1883 that there are absorption bands in the extreme ultra-violet region of the spectrum of various proteins, e. g. , casein, ovalbumin, mucin and globulin. Tyrosine likewise has this band in the ultra-violet and Soret attributed to this constituent of the protein molecule its power of absorbing ultra-violet rays. In this connection Harris and Hoyt (3) carried out some interesting experiments on the protective power of various substances for paramœcium cultures exposed to ultra-violet radiations. They found that gelatin peptone, amino-benzoic acid, cystine, leucine and especially tyrosine possessed the power of detoxicating ultra-violet rays when placed as a thin layer of aqueous solution over paramœcium cultures under a quartz-mercury lamp. The toxicity of the radiations for paramœcia or protoplasm in general can be understood in the light of the discovery of Dreyer and Hanssen coupled with that of Soret. From a physico- chemical standpoint Bovie (4) has published a study of the coagulation of proteins by ultra-violet light. By exposing solutions of crystalline ovalbumin, both dialysed and containing electrolytes, to the light of a mercury-vapour lamp, he came to the conclusion that there were two reactions involved in the coagulation of ovalbumin by ultra-violet light. The first is a photochemical one with a low temperature coefficient,—denaturation; and the second is one with a higher temperature coefficient of two and is dependent upon the electrolytes present,—coagulation. While using solutions dialysed against tap water Bovie made the observation that the protein appeared to become sensitive to light of longer wave-length, for his control tubes in glass were slowly coagulated.

scholarly journals A STUDY OF THE BACTERICIDAL ACTION OF ULTRA VIOLET LIGHT

1929 ◽  
Vol 13 (2) ◽  
pp. 249-260 ◽  
Author(s):  
Frederick L. Gates
Keyword(s):  
Direct Action ◽  
Wave Length ◽  
Ultra Violet ◽  
Ion Concentration ◽  
Appreciable Effect ◽  
Bactericidal Action ◽  
Hydrogen Ion Concentration ◽  
Ultra Violet Light ◽  
Violet Light ◽  
Reciprocity Law

1. Wide differences in the intensity of incident ultra violet energy are not accurately compensated by corresponding changes in the exposure time, so that the Bunsen-Roscoe reciprocity law does not hold, strictly, especially for bactericidal action on young, metabolically and genetically active bacteria. In the present series of experiments, however, the energies used at various wave lengths did not differ by so much as to cause a significant error in the reported reactions. 2. The longer wave length limit of a direct bactericidal action on S. aureus was found to be between 302 and 313 mµ. The shorter limit was not determined because the long exposures required vitiate quantitative results. Bactericidal action was observed at λ225 mµ. 3. The temperature coefficient of the bactericidal reaction approaches 1 and thus furnishes empirical evidence that the direct action of ultra violet light on bacteria is essentially physical or photochemical in character. 4. The hydrogen ion concentration of the environment has no appreciable effect upon the bactericidal reaction between the limits of pH 4.5 and 7.5. At pH 9 and 10 evidence of a slight but definite increase in bacterial susceptibility was noted, but this difference may have been due to a less favorable environment for subsequent recovery and multiplication of injured organisms. 5. Plane polarization of incident ultra violet radiation has no demonstrable effect upon its bactericidal action. In a third paper of this group the ratios of incident to absorbed ultra violet energy at various wave lengths and the significance of these relations in an analysis of the bactericidal reaction will be discussed.

scholarly journals Certain pathological effects of ultra-violet radiation on mosquito larvæ and pupæ

1932 ◽  
Vol 112 (774) ◽  
pp. 27-38 ◽  
Keyword(s):  
Ovarian Function ◽  
Wave Length ◽  
Ultra Violet ◽  
Mercury Vapour ◽  
Mosquito Larvae ◽  
Wave Band ◽  
Ultra Violet Radiation ◽  
Quartz Mercury ◽  
Mercury Vapour Lamp ◽  
Violet Radiation

In the course of recent work on the possible effect the ultra-violet wave-band may have on the activation of ovarian function in female mosquitoes, it became apparent that mosquito larvae are highly susceptible to a remarkable form of injury by radiations from the unshielded mercury-arc generated by the ordinary Cooper-Hewitt vacuum type of quartz mercury-vapour lamp. This effect upon the larvae has been studied, and an attempt was made (1) to determine the wave-length of the radiations responsible for the injury by means of screens interposed between the lamp and the larvae; and (2) to ascertain the physiological and histological nature of the injury.

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.

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