ISSN:0021-8979    

DOI:10.1063/1.1707347

出版商:AIP    

年代:1939

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1707348

出版商:AIP    

年代:1939

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1707349

出版商:AIP    

年代:1939

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1707350

出版商:AIP    

年代:1939

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1707351

出版商:AIP    

年代:1939

数据来源: AIP

ISSN:0021-8979    

DOI:10.1063/1.1707352

出版商:AIP    

年代:1939

数据来源: AIP

摘要:

The killing effect of 2537A radiation has been studied, both for bacteria suspended in air and bacteria and molds on surfaces. A 15‐watt sterilizing lamp (giving 25 &mgr;w/cm of 2537A radiation at 1 meter from the lamp) will kill 97–99 percent of B. Coli suspended in air at a distance of 24 inches in 10 seconds. Accordingly in an air duct a 15‐watt lamp can sterilize approximately 200 cu. ft. of air per minute. A 15‐watt sterilizing lamp will kill B. Coli on the surface of agar at a distance of 10″ in 20 seconds. The Bunsen Roscoe reciprocity law applies to the killing of bacteria by ultraviolet radiation between the intensities of 2000 &mgr;w/cm2and 1.3 &mgr;w/cm2. The lethal dose of 2537A radiation for B. Coli on agar is 6600 &mgr;w sec./cm2. For practical purposes the effect of temperature may be neglected. A film of grease is very effective in shielding bacteria from radiation. The lethal dose of 2537A radiation for black mold spores is about 45 times that for B. Coli. The reciprocity law applies. The sensitivity of mold spores decreases with increasing wave‐length and is negligible for 3650A. Low pressure lamps in ultraviolet transmitting glass produce concentrations of ozone of the order of 0.1 part per million. From these experiments it may be concluded that low pressure mercury vapor lamps when used under the proper conditions are very powerful bactericidal agents if the bacteria are directly exposed to the radiation, but that the effectiveness is greatly reduced by even such slight shielding as is offered by a film of grease.

ISSN:0021-8979    

DOI:10.1063/1.1707353

出版商:AIP    

年代:1939

数据来源: AIP

摘要:

An oscillographic study of arcs formed between silver contacts in the rupturing of 120‐volt a.c. circuits containing resistive loads shows that reignition of the arc occurs at low speeds of contact separation. Data have been obtained by means of a ballistic wattmeter showing the effect of current and line voltage on arc energy for silver contacts opening at speeds from 0.024 to 16.7 inches per second. In the low speed range reignition is more prevalent at 225 volts than at 115 volts, and restriking of the arc occurs at higher speeds for higher currents. The formation of an arc in reigniting cycles is believed to be due to field emission of electrons, an average field of 0.30×106volts/cm being found for all cases of reignition observed. Reignition occurred at potentials as low as 72 volts and the intermediate glow discharge normally observed in the interruption of inductive circuits did not appear.

ISSN:0021-8979    

DOI:10.1063/1.1707354

出版商:AIP    

年代:1939

数据来源: AIP

摘要:

The operation of beam power tubes in regenerative ultra‐high frequency oscillators is investigated experimentally. Wave‐length characteristics of oscillating 6Y6‐G and 6V6‐G tubes are displayed and compared with a corresponding curve for a type 56 triode. Wave‐lengths as low as 150 cm were obtained. Current and wave‐length characteristics of the oscillating 6Y6‐G are given as functions of plate, screen and control grid voltages. The efficiency of the generator is investigated near its lowest wave‐length limit. Means for preventing oscillation in amplifier circuits using beam tubes are suggested.

ISSN:0021-8979    

DOI:10.1063/1.1707355

出版商:AIP    

年代:1939

数据来源: AIP

摘要:

The gradientE, total voltagee, and current densityIin the one‐atmosphere hydrogen arc between pure carbon electrodes in the 0–10‐ampere range are measured by an oscillographic method. An abrupt change inetakes place at 2 and 0.6 ampere, and inEat 2 amperes, leading to the identification of three states of the hydrogen discharge in this current range and pressure. Rapid motion pictures of this arc at pressures above atmospheric show violent arc movements originating from convection forces. The exponent of theE‐irelation is found to be 0.70 for the normal arc state atp= 1 atmos.

ISSN:0021-8979    

DOI:10.1063/1.1707356

出版商:AIP    

年代:1939

数据来源: AIP