Document v1kgEEQ1yNM7Oxe7BEqVNwX3E

590 HEINZ SPECHT The temperature of the atmosphere is due mainly to the energy absorb from solar radiation, secondarily to that added by conduction or convec|| For our consideration, the distribution of temperature in the two zones o| atmosphere nearest the earth is of interest. From the ground up to about 3flg feet there is found a variable temperature, the average value falling increase in altitude, and above this level there is a region of uniform tempetp| known as the isothermal layer. This uniform temperature, which extends excessively high altitudes, is reported to be relatively constant at --5ggg (--67 F.).6 It is in this upper region that the ozone produced by abso|* of ultraviolet radiation by oxygen in the outer layers is observed to gravitat appreciable concentration. Because of the filtering action of these superiors! there is relatively little absorption of energy by the gases in the isothermal|l||||| Below the lower boundary of this layer, at about 36,000 feet, water vapojlat! solids in the atmosphere absorb energy in an appreciable amount, aii'3 temperature rises gradually as the earth is approached until the charact||| temperature of the latitude is attained. On the other hand, owing to the! displacement of air masses by convection and conduction of heat and mm absorption of reradiated energy from the earth's surface, there is often dyfc deal of random distribution of temperature. Thus, surface temperature iff|||f colder than at several thousand feet directly above the ground, and several! inversions may be found above each other. These are found mainly oyeW masses and are part and parcel of the "weather." The mechanism is not imf|p(gj to this discussion. Further details may be found in Humphreys." Local tures below the tropopause, or iower strato'sphere' level^' aFlbw as -- 12ub^|| been recorded. It is important to point out that in contradistinction-|^p previous fact, aeronautical tables are calculated on the assumption that^JtmpL^ a constant temperature in the so-called isothermal region and that a jeglilar increase in temperature on descent from this level to the ground is founcIvTim the effect of the temperature variations on "pressure altitudes" in the atmosplfipj is of interest to the physiologist, who is concerned with the barometric valucV" any linear altitude and not with the actual height above sea level. .. As far as increased pressures are concerned, it is evident that, except jior, heat added by compressing equipment, the temperature of the air or othcr^giisc will tend to equal that of the environment; for example, in sea...y;at.e'sffi|^ range upward from 28.6 F., which is the freezing point of sea water .of salinity. While the .heat conductivity of gases is not affected by pressure.,c6? changes in heat loss from the body are to be expected from changeg^>|gB ~6f~tlTF~atmospherfe, since tte~hSHiryapa'cltynof^he~air~rs~ghanieii~an3:j!!;tegt alter the temperature differential necessary to maintain constant heat|j|||ni from the body to the environmental gases. This effect is very marked for vabjJjP EFFECTS , OP ABNORMAL ATMOSPHERIC PRES8TJRE 591 JawipreSSUre chambers at "altitude," and may cause wrong interpretation of gPEin^'crature sensations. C. CHEMICAL ACTIVITY KWph|inical activity of the gases of the atmosphere relevant to the OTcSgVpS atmospheric pressure in mammals is limited to that of oxygen and frgllfpi&ie. This limitation is mainly due to the fact that the energy levels ^tokdirect chemical reaction are not feasible in living systems. All reactions , under these circumstances, either primarily or secondarily on fipjisfffisome type. The metabolic involvement of hydrogen agd nitrogen has re^^^stantiated for living forms as high as bacteria,28,24 but mammals have |f|fflee!ttf<iund to possess the systems necessary for either hydrogen or nitrogen Kvctmu'ipWin the gaseous state. Enzymes for the activation of gaseous oxygen and 'wfiPnaiifecide are integral to the metabolic process of all mammals.25 In common s^ip^CTfons of other substances, the rate and equilibrium of the reaction of igplwsdep^nd, among other factors, on the concentration of the gas, both relatiWyJB.ud|absolutely; that is, the systems are pressure-labile within limits. This utmost importance in the physiological analysis of the effects frllifiKwpheric pressure. inlljellin'g aside, at the beginning of Section B.5, the fact that chemical the solution of gases, it was intended only to reserve this comf^rosfurther discussion because, as will be seen in subsequent sections, ,s'^Saji!importance-in-.the_exchange,..of .gases..between, the atmosphere and |g|||j|iuicis. jMKbe. fitting to point out at this time that the widely publicized,29 JmmarlTMbetween the status of flames and metabolic oxidations at altitude is a Wfl-bircitjus lone, flames having actually only minor response to even extensive but being markedly sensitive to relative concentration, while meiSljm^aoHdations behave quite the opposite. The difference is in part due to -Suie^fa'ct-lt.hAt' in metabolic activities there exists always a solution phase between the substance oxidized. Contrary to popular accounts28,27 a s3cui'Ile$lan?e will continue to burn in air up to a simulated' altitude of 57,000 CT"5pro.viaed a large enough volume of air is used for the environment of the SMSSErac^Sgeiin-the-character.. of...flames at altitude6 led to .'errbneous con- ^niaioi^roni' experimental engineering data cited above.28 The ultimate limita^;pn'a"rini^Se: stability in the case of the candle results from the flame's being ^^/.Vluc;n.` Laurie, Discovery Repts., 7, 365 (1933). gS^^KrVgh^flturg, 133, 635 '(1934). JulSfl*' pmaf&l941. //'urnan"P/iv8ioZoffV"-8th-ed--bea-and--Febiger lOmrinstrong and M. C. Grow, Fit to Fly, a Medical Handbook for Fliers. Appleton- 7TM,';r>:,,'.`Ne'w,<York, 1941. ' , K. Byerts, Eng. Min, J., 141, No. 10, 44 (1940). , .. su'if ,m <r7 tic