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

1929 ◽  
Vol 13 (2) ◽  
pp. 231-248 ◽  
Author(s):  
Frederick L. Gates
Keyword(s):  
Energy Level ◽  
Metabolic Activity ◽  
Wave Length ◽  
Ultra Violet ◽  
Bactericidal Action ◽  
Ultra Violet Light ◽  
Violet Light ◽  
General Similarity ◽  
Monomolecular Reactions

In this first paper of a series on the bactericidal action of ultra violet light the methods of isolating and measuring monochromatic radiations, of preparing and exposing the bacteria, and of estimating the effects of exposure, are given in detail. At all the different wave lengths studied the reactions of S. aureus followed similar curves, but occurred, at each wave length, at a different energy level. The general similarity of these curves to those for monomolecular reactions provokes a discussion of their signifiance, and emphasis is laid upon variations in susceptibility of individual organisms, due especially to age and metabolic activity, so that the typical curve seems to be best interpreted as one of probability.

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 A STUDY OF THE BACTERICIDAL ACTION OF ULTRA VIOLET LIGHT

1930 ◽  
Vol 14 (1) ◽  
pp. 31-42 ◽  
Author(s):  
Frederick L. Gates
Keyword(s):  
Characteristic Curve ◽  
Wave Length ◽  
Ultra Violet ◽  
Close Relation ◽  
Energy Curve ◽  
Bactericidal Action ◽  
Ultra Violet Light ◽  
Violet Light ◽  
Specific Substance ◽  
Lethal Reaction

The simple conclusion of former investigators that the shorter the wave length of ultra violet light the greater the bactericidal action is in error. A study with measured monochromatic energy reveals a characteristic curve of bactericidal effectiveness with a striking maximum between 260 and 270 m.µ. The reciprocal of this abiotic energy curve suggests its close relation to specific light absorption by some single essential substance in the cell. Methods are described for determining the absorption curve, or absorption coefficients, of intact bacteria. These curves for S. aureus and B. coli have important points of similarity and of difference with the reciprocals of the curves of bactericidal incident energy, and point the way in a further search for the specific substance, or substances, involved in the lethal reaction.

scholarly journals The bactericidal action of ultra-violet light

1940 ◽  
Vol 40 (2) ◽  
pp. 162-171 ◽  
Author(s):  
D. E. Lea ◽  
R. B. Haines
Keyword(s):  
Survival Curve ◽  
Wave Length ◽  
Chemical Change ◽  
Monochromatic Light ◽  
Ultra Violet ◽  
X Rays ◽  
Bactericidal Action ◽  
Survival Curves ◽  
Ultra Violet Light ◽  
Violet Light

Experiments on the bactericidal action of ultra-violet light have been made to determine the shape of the survival curve and the dependence upon radiation intensity of the rate of death.Bact. coli, Bact. prodigiosumand spores ofB. mesentericuswere irradiated with approximately monochromatic light of wave-length 2537 A. The survival curves obtained were exponential and the rate of death was accurately proportional to the intensity over an intensity range of 500:1.By comparing these results with data previously obtained of the action of X-rays on the same organisms it was established that one ionization produced by X-rays is as effective as some hundreds of ultra-violet quanta. This is interpreted to mean that the quantum yield in whatever chemical change leads to the loss of viability in the irradiated bacteria is, for 2537 A., between 0·01 and 0·001.

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 On the fluorescence of iodine vapour excited by ultra-violet light

1914 ◽  
Vol 91 (623) ◽  
pp. 23-29 ◽  
Keyword(s):  
Fluorescence Spectrum ◽  
Wave Length ◽  
Ultra Violet ◽  
Quartz Tube ◽  
Glass Tubing ◽  
Ultra Violet Light ◽  
Violet Light ◽  
Fused Quartz ◽  
Quartz Spectrograph ◽  
Narrow Bands

In a recent communication by the writer a new fluorescence spectrum of iodine vapour was described which could be stimulated by the light from the mercury arc. This fluorescence spectrum consisted of a set of narrow bands extending from λ 4600 down to λ 2100. While of this spectrum was clearly defined, the most intensely marked portion of it was made up of a set of seven equally spaced bands between λ 3315 and λ 3175. in obtaining the spectrum a highly exhausted tube of fused quartz containing a few iodine crystals was inserted axially in an ordinary glass Cooper-Hewitt mercury are lamp, with a lateral anode and provided with a short extension at the positive end, to which the quartz tube was sealed with mastic wax. The quartz iodine vapour tube was provided with a window of clear fused quartz, towards which the collimator of quartz spectrograph was directed in taking the photographs. When the Copper-Hewitt tube was in action the are played directly upon the inserted quartz tube and so subjected the vapour contained in it to intense illumination. In the paper describing this fluorescence spectrum of iodine vapour it was pointed out that it was impossible to obtain the spectrum when the inserted tube containing the iodine vapour was made of combustion glass tubing. It was also pointed out that this glass tubing was found to be transparent to the light from the mercury are down to λ 2893∙7, and on account of this fact the conclusion was drawn that the light which stimulated the iodine vapour to the flurescence referred to must have had a shorter wave-length than λ 2893∙7.

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.

V.—The Ionisation of Iodine Vapour by Ultra-Violet Light

1926 ◽  
Vol 45 (1) ◽  
pp. 34-41
Author(s):  
W. West ◽  
E.B. Ludlam
Keyword(s):  
Quantum Theory ◽  
Electron Impact ◽  
Wave Length ◽  
Ultra Violet ◽  
Short Wave ◽  
Ultra Violet Light ◽  
Violet Light ◽  
Negative Results ◽  
Short Wave Length ◽  
Effect Of Light

The ionisation of iodine vapour by light has been sought by several investigators with negative results. Nevertheless, the application of the quantum theory, which has proved so fruitful with respect to the relation between electron impact on gaseous molecules and the emission of light, leads to the expectation that the ionisation of a gas should be affected by light of sufficiently short wave-length. This ionisation was first observed by Lenard, who investigated the effect of light in the extreme ultra-violet on air and other gases.

Studies on the Responses of the Female Aëdes Mosquito. Part VI.—The Attractiveness of coloured Cloths to Canadian Species

1954 ◽  
Vol 45 (1) ◽  
pp. 67-78 ◽  
Author(s):  
A. W. A. Brown
Keyword(s):  
Wave Length ◽  
Ultra Violet ◽  
Aedes Mosquito ◽  
Ultra Violet Light ◽  
Violet Light ◽  
Infra Red ◽  
Associated Species

A series of 32 cloths, including 8 flannels dyed to Munsell standard colours, seven coloured satins and 17 service fabrics, were tested for their attractiveness to northern Canadian Aëdes mosquitos, and were assessed for their reflectivity of visible and ultra-violet light.Their attractiveness was found to vary inversely with their reflectivity or brightness, although the different textures represented in the series tended to obscure the generalised relationship.When comparisons were made within a series of identical texture, the correlation was good in the range between 475 and 625 mμ wave-length, but was not present in the red or infra-red, nor in the violet and ultra-violet ranges of wavelength.Green tended to be less attractive, and white more attractive, than was expected from this relationship. For colour values of similar lightness or darkness, the order of attractiveness to Aëdes punctor and associated species was black, red, blue, brown, green, white, yellow.

Clouds produced in an expansion chamber by ultra-violet light

1951 ◽  
Vol 207 (1091) ◽  
pp. 527-539 ◽  
Keyword(s):  
Water Vapour ◽  
Atomic Oxygen ◽  
Wave Length ◽  
Charged Particles ◽  
Ultra Violet ◽  
Expansion Chamber ◽  
Quartz Window ◽  
Ultra Violet Light ◽  
Violet Light ◽  
Intense Beam

Clouds are produced in an expansion chamber filled with air and water vapour by irradiating with ultra-violet light through a quartz window, and expanding shortly afterwards. It is shown that the condensation does not occur upon charged particles, but on certain electrically neutral nuclei, not yet identified. By varying the wave-length of the ultra-violet light it is shown that the condensation is initiated by atomic oxygen, liberated by the action of the radiation on oxygen molecules. Similar effects are produced when an intense beam of deuterons is passed into the chamber.

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.

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