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 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

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

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.

Studies on Rubber in Solution. I. Studies on the Aging of Rubber Solutions

1932 ◽  
Vol 5 (4) ◽  
pp. 618-625
Author(s):  
Takeo Fujihara
Keyword(s):  
Chemical Change ◽  
Ultra Violet ◽  
Preliminary Test ◽  
Dispersed Phase ◽  
Colloidal Solutions ◽  
Ultra Violet Light ◽  
Violet Light ◽  
Dispersed Particles ◽  
Dispersed Medium ◽  
Constant Viscosity

Abstract It is well known that raw rubber in colloidal solutions with different dispersion mediums shows the general characteristics of aging such as a decrease in its viscosity, whether aged by natural or artificial methods, and especially when exposed to ultra-violet light. Whitby and Jane (Colloid Symposium Monograph, Vol. 2, page 16) pointed out this phenomenon, and Asano (Mem. Coll. Eng. Kyoto Imp. Univ., Vol. 3, page 267) noticed that dispersed rubber sols decreased in viscosity and the rubber depolymerized and became insoluble by exposure to ultra-violet light. This effect was particularly noticeable with light of 2250 A. U.; however, light of longer wave lengths caused oxidation of the rubber and formed a transparent insoluble substance. Recently Hada (Rubber Ind., 1931, 147) demonstrated the curves of decrease in viscosity of rubber sols by exposure to ultra-violet light, and pointed out that the sols reached a definite viscosity after long exposure. The theory generally accepted to explain the mechanism of the lowering of the viscosity of rubber sols on aging is that depolymerization results from the oxidation of rubber molecules, and thereby increases the degree of dispersion. The process as a whole involves the formation of a dispersed phase from the absorption of the dispersion medium, and after passing the stages of solvation the viscosity of sols thus formed decreases on aging. The principal cause of these phenomena is considered to be due to a change in the structure of the dispersed particles by a chemical change of the dispersed phase itself. Whether or not it is possible to obtain, in the laboratory, a stable rubber sol by the process of long aging is not certain. It is, however, no exaggeration to say that the oxidation of the dispersed phase causes a decrease in its affinity for the dispersed medium, i. e., the oxidation changes the emulsoid to a supersoid or, in other words, there is a decrease in the size of the particles in the dispersed phase if the theory of the aging of rubber sols is that there is an increase in the dispersity by depolymerization. The author subjected rubber sols to long exposure to ultra-violet light and measured the lowering of their viscosity. The results show that (1) rubber sols in benzene reached a constant viscosity, and (2) the use of different solvents causes marked differences in rubber sols. The Brownian movement of the particles in aged rubber sols was observed with a cardioid ultra-microscope. These experiments were made as a preliminary test to explain the mechanism of dispersion of raw rubber in solvents.

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 excitation of characteristic X-rays from light elements

1923 ◽  
Vol 102 (717) ◽  
pp. 389-410 ◽  
Keyword(s):  
Ultra Violet ◽  
Critical Values ◽  
X Rays ◽  
Light Elements ◽  
X Ray ◽  
Ultra Violet Light ◽  
Violet Light ◽  
Light Waves ◽  
Electric Effect ◽  
Electric Action

In an attempt to fill up the gap between the shortest ultra-violet light waves hitherto produced and the longest X-ray waves known, Hughes recently made a study of the characteristic X-rays emitted by carbon and by boron when bombarded by electrons. In this investigation the energy of the bombarding electrons was increased by steps, and the critical values were determined that were necessary and just sufficient to cause the bombarded element to emit its characteristic radiations with measurable intensities. These characteristic radiations were detected, and their intensities measured, by their photo-electric action on an insulated electrode of nickel or of silver. The method followed by Hughes in recording his results was to plot curves with the values of the accelerating potentials of the electrons as abscissæ and the measures of the photo-electric effect divided by the corresponding electronic currents as ordinates. At certain critical accelerating voltages it was found that these curves showed marked and abrupt kinks or changes of curvature, and these changes were taken to connote the beginning of the emission by the bombarded element of its characteristic radiations.

An Ultra-Violet Light Method for Producing Haploid Amphibian Embryos

Development ◽  
1958 ◽  
Vol 6 (4) ◽  
pp. 634-637
Author(s):  
G. G. Selman
Keyword(s):  
Toluidine Blue ◽  
Filter Paper ◽  
Ultra Violet ◽  
Alternative Methods ◽  
X Rays ◽  
Ultra Violet Light ◽  
Violet Light ◽  
Amphibian Embryos ◽  
Petri Dishes ◽  
Transplantation Experiments

For several years in this laboratory, ultra-violet light has been used to produce haploid amphibian embryos, sometimes to provide haploid nuclei for transplantation experiments, as in Pantelouris & Jacob (1958). The ultra-violet method gives a high proportion of haploids, is very simple and speedy to carry out and involves the use of only inexpensive apparatus. Our method and results are described here to help others choose between this and alternative methods such as the use of toluidine blue by Briggs (1952), or X-rays by Lehman (1955) and Rugh (1939). Other methods are reviewed in Fankhauser (1937) and Drebinger (1951). Eggs were taken from the oviducts of newt females and were placed close together in groups on cellophane squares to which they adhered by their jelly coats so that their animal surfaces were uppermost. The cellophane squares of unfertilized eggs were then placed in Petri dishes in air kept moist with a piece of damp filter paper at one side.

William H. Bragg's Corpuscular Theory of X-Rays and γ-Rays

1971 ◽  
Vol 5 (3) ◽  
pp. 258-281 ◽  
Author(s):  
Roger H. Stuewer
Keyword(s):  
Ultra Violet ◽  
Black Body ◽  
Black Body Radiation ◽  
Electromagnetic Spectrum ◽  
Light Quantum ◽  
X Rays ◽  
Ultra Violet Light ◽  
Violet Light ◽  
History Of ◽  
Γ Rays

The modern corpuscular theory of radiation was born in 1905 when Einstein advanced his light quantum hypothesis; and the steps by which Einstein's hypothesis, after years of profound scepticism, was finally and fully vindicated by Arthur Compton's 1922 scattering experiments constitutes one of the most stimulating chapters in the history of recent physics. To begin to appreciate the complexity of this chapter, however, it is only necessary to emphasize an elementary but very significant point, namely, that while Einstein based his arguments for quanta largely on the behaviour of high-frequency black body radiation or ultra-violet light, Compton experimented with X-rays. A modern physicist accustomed to picturing ultra-violet light and X-radiation as simply two adjacent regions in the electromagnetic spectrum might regard this distinction as hair-splitting. But who in 1905 was sure that X-rays and γ-rays are far more closely related to ultra-violet light than to α-particles, for example ? This only became evident after years of painstaking research, so that moving without elaboration from Einstein's hypothesis to Compton's experiments automatically eliminates from consideration an important segment of history—a segment in which a major role was played by William Henry Bragg.

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