摘要:

Experiments were performed onColletotrichum phomoides, a fungus which is a common cause of ripe-rot on tomatoes.The lines of the mercury arc spectrum may be grouped into three classes on the basis of their effect on the growth ofColletotrichum: those which cause constant retardation, those which cause constant stimulation and those which cause primary retardation followed by stimulation.On the basis of the effect on the production of spores, there are two classes of lines in the mercury arc spectrum,i.e., those which hasten spore development and those which have no apparent effect. Spore production is generally hastened by monochromatic light causing retardation or extreme stimulation of growth, and is apparently not affected by light which moderately stimulates growth; moreover, an optimum duration is shown for the illumination causing the accelerated development of spores.Evidence is given that the effect of monochromatic light is upon the protoplasm and not the culture, since cultures grown on non-irradiated media from irradiated spores show the same effects as those obtained by irradiating three-day cultures. In many cases, inColletotrichum, the effect of irradiation is evident in the culture 10 days after the spores have been illuminated.There is a marked similarity in the effect upon the growth ofColletotrichum,YeastandParamoecium.

ISSN:1923-4287    

DOI:10.1139/cjr30-054

出版商:NRC Research Press    

年代:1930

数据来源: NRC

摘要:

A cultural study was made of an organism of theEscherichia-Aërobactergroup in connection with the production of an alleged feed flavor or stable odor in milk. A tentative classification of the organism as an atypical strain ofAërobacter oxytocum, (Migula) Bergey et al., is based on the sum of its characteristics. The suggestion is made that the organism may be defined as a new species within the genusAërobacter, but until other characteristically identical strains have been isolated, this is merely tentative.

ISSN:1923-4287    

DOI:10.1139/cjr30-055

出版商:NRC Research Press    

年代:1930

数据来源: NRC

摘要:

Values for the heat capacities of ice and resulting water from initial temperatures of between 0 °C. and − 78.5 °C. to a final temperature of + 25.00 °C. are measured to ± 0.05% or better with an improved adiabatic calorimeter previously described. The specific heats of ice over the temperature range 0° C. to − 80 °C. are found and the latent heat of fusion of ice at 0 °C. is obtained from these heat capacity determinations.

ISSN:1923-4287    

DOI:10.1139/cjr30-056

出版商:NRC Research Press    

年代:1930

数据来源: NRC

摘要:

In the preparation of dihydroxy maleic acid from tartaric acid by hydrogen peroxide in the presence of ferrous sulphate, the very small yields are the result of inactivation of the catalyst by the production of the relatively strong dihydroxy maleic acid; this reaction product undergoes such rearrangement to an isomer as prevents quantitative separation. By means of conductivity measurements of the reaction mixture, the course of the reaction is accurately followed.The existence of the tautomeric keto form of dihydroxy maleic acid, first suggested by Nef as an alternative formula, has been clearly indicated.The search for a procedure which will improve the yield of dihydroxy maleic acid is now restricted to the discovery of some compound which will at the same time reduce the hydrogen ion concentration and shift the equilibrium in favor of the enol form.

ISSN:1923-4287    

DOI:10.1139/cjr30-057

出版商:NRC Research Press    

年代:1930

数据来源: NRC

摘要:

In this investigation the heating of solutions of simple electrolytes of varying concentrations when irradiated by short electromagnetic waves from 10 to 200 metres in length was measured. It was found that for a given wave-length there is a maximum heating effect produced in a medium, the specific conductivity and dielectric constant of which are connected with the frequency by a simple law. This law, proved theoretically as well as shown experimentally to hold for dilute solutions iswhereC= specific conductivity in absolute units,K= dielectric constant andn= frequency of wave."Skin effect" was shown theoretically and experimentally to be negligible for substances having the low conductivities studied and deep-seated heating effects were shown to be attainable with the radio waves used. The possibility of directed selective heating effects is suggested and illustrated by experiments on blood. The law shown to apply in these experiments was used to evaluate the dielectric constant of water.

ISSN:1923-4287    

DOI:10.1139/cjr30-058

出版商:NRC Research Press    

年代:1930

数据来源: NRC

摘要:

This paper deals with the action of cathode rays on gases and gas mixtures. Methane, methane-oxygen mixtures, carbon monoxide and carbon monoxide-oxygen mixtures were examined. Methane gave small percentages of hydrogen and ethane. Methane and oxygen mixtures gave as gaseous products, carbon monoxide, carbon dioxide and hydrogen, the only other products being water and formic acid. The relative proportions of the products do not vary widely under a wide variation of conditions.The reaction was found to be of the first order with respect to pressure. The reaction rate increases linearly with the voltage up to a certain value, after which it becomes nearly independent of the voltage.The action of cathode rays on carbon monoxide produces carbon dioxide and a solid brown suboxide which is extremely soluble in water, and its composition corresponds to a formula (C3O)n. If the carbon monoxide is moist, no visible amount of solid or liquid is found and there is less carbon dioxide.Carbon monoxide-oxygen mixtures under the action of cathode rays form carbon dioxide. Presence of water vapor has a retarding effect on the reaction. For mixtures of the same composition the reaction rate is proportional to the total pressure. For dry mixtures the product increases with the carbon monoxide present; when moist it is much less, and independent of the carbon monoxide.

ISSN:1923-4287    

DOI:10.1139/cjr30-059

出版商:NRC Research Press    

年代:1930

数据来源: NRC

摘要:

A new observation regarding the visual characters of penumbral shadows is recorded. It is pointed out that penumbral shadows appear to be laid down as a series of bands arranged serially as to density. This occurrence results in far-reaching effects in radiography as well as in other sciences concerned with the observation of images.

ISSN:1923-4287    

DOI:10.1139/cjr30-060

出版商:NRC Research Press    

年代:1930

数据来源: NRC

摘要:

A mathematical theory is developed for the distribution of stress in welded joints with parallel fillets, in the case where each of the members connected by the weld is of uniform cross section. The theory is verified by strain measurements on two specimens of the type of joint considered.

ISSN:1923-4287    

DOI:10.1139/cjr30-061

出版商:NRC Research Press    

年代:1930

数据来源: NRC

摘要:

The information contained in this report is the result of a detailed investigation of the characteristics of a variety of modified corners in a wind tunnel. The modification of the corner was effected by the insertion of banks or cascades of vanes along the diagonal, the intention being to secure minimum losses due to turbulence, coupled with uniformity in the issuing air stream. Apart from the specific application of this research to the design of wind tunnel corners, it has a real value in assisting the solution of the problem of corner losses in water, steam and air systems.The report includes data on vane shape, spacing and incidence, on the variation of the accompanying air flow, and on the resulting influence on corner resistance. A variety of methods have been employed to analyse the conditions existing in the air stream at the vanes and, from the information so obtained, it is possible to select the vane section and method of use which will lead to the most desirable features in the flow at the corner.

ISSN:1923-4287    

DOI:10.1139/cjr30-062

出版商:NRC Research Press    

年代:1930

数据来源: NRC