High-altitude Conditions Research Articles

Claiming the high ground: Sherpas, subsistence, and environmental change in the highest Himalaya

Stanley Stevens brings a new historical perspective to his study of a subsistence society in ever-increasing contact with the outside world. The Khumbu Sherpas, famous for their mountaineering exploits, have frequently been depicted as victims of the world's highest-altitude tourist boom. But has the flow of outsiders to Mt Everest and the heights of Nepal in fact destroyed a stable, finely-balanced relationship between the Sherpas and their environment? Steven's innovative use of oral history and cultural ecology suggests that tourism is not the watershed circumstance many have considered it to be. Drawing on extensive interviews and data gathered during three years of fieldwork, he documents the Sherpas' ingenious adaptation to high-altitude conditions, their past and present agricultural, pastoral, trade and forest management practices, and their own perspectives on the environmental history of their homeland.

Blood types in cattle of Iberian ancestry and in Holsteins at various altitudes

Summary Gene frequencies of rbc antigens were determined in Holsteins and Colombian (criollas) cattle living at 3,000 m, and in cattle descended from fighting bulls (Vacas de lidia) living at 2,500 m. These frequencies were compared with those of Holsteins, cattle native to Florida (scrub cattle), longhorns, and native cattle from Brazil (caracu cattle) living at sea level. The criollas, Vacas de lidia, scrub cows, longhorns, and caracu are descendants of original Iberian stock introduced to the Americas. We found that despite common ancestry (scrub cattle, longhorns, criollas, and caracu), genetic differences may have been derived through years of demographic isolation. The most remarkable blood-group differences were found in the high prevalence of the B system phenogroup (heritable group of antigenic factors) BQA'G'34 in the Vacas de lidia, and of the S system phenogroup U1H' in these cattle and in caracu. Furthermore, the gene frequencies differed in the Holsteins maintained at moderately high altitude (descended from Holsteins kept at sea level), and may have been reflective of the need to adapt to moderately high altitude and chronic hypoxemic conditions. Blood group polymorphism was found in all groups of cattle, although it was reduced in the Vacas de lidia, possibly because their breeding has been carefully controlled and they appear to be highly inbred.

A comparison of the heart rate at different ambient temperatures during long-term hibernation in the garden dormouse, Eliomys quercinus L

Heart rate in hibernating garden dormice, Eliomys quercinus, was studied by means of permanently implanted electrodes; ambient temperatures ( T A's) were maintained at 0, 4, 6.5, and 9 °C during the 6-month test period in each winter study. The animals were kept under constant conditions in darkness and without food or water. Heart rate remained at a low level during deep hibernation at all T A's studied. There were no differences in midwinter values between the T A's of 6.5 and 9 °C: the means were 9–12 beats/min during apnea. Heart rate thus differs from other hibernation parameters studied simultaneously, which were strongly T A dependent. However, the optimal T A of 4 °C could be distinguished and heart rate was significantly lower, 8–10 beats/min. At 0 °C the values were slightly higher: 12–13 beats/min. The T A of 0 °C was exceptional for all parameters studied. At the beginning of the hibernation season was a transition period with elevated heart rate values. Respiratory-related heart-rate changes appeared during periodic respiration, heart rate being significantly higher during respiratory periods at all T A's. At 0, 6.5, and 9 °C tachycardia occurred also during apnea, very close to the respiratory period. There are responses that are comparable to hypoxic environmental conditions during hibernation, diving, and pregnancy and under high-altitude conditions. Parallel adaptations appear in heart rate and respiration, i.e., bradycardia and periodic respiration. In conclusion, heart-rate values were low during deep hibernation, and compared with other parameters measured at different T A's heart rate is maintained inside narrow limits during deep hibernation.

Hematological Indices of Turkey Embryos Incubated at High Altitude as Affected by Oxygen and Shell Permeability

Turkey eggs (Meleagris gallopavo) were incubated at altitude of 1,707 m to test the effects of oxygen supplementation and increased eggshell permeability by removal of shell cuticle on embryonic hematology. Turkey embryo hematological indices measured were red blood cell count (RBC), hemoglobin concentration, packed cell volume, mean cellular volume, mean cellular hemoglobin, and percentage of reticulocytes. Although hemoglobin concentration measured during pipping increased as expected by increasing RBC, no significant differences were observed between oxygenation, or permeability treatments, or their interaction. Under the high altitude conditions of the present experiment, increased hemoglobin concentrations in all treatments corresponded to increased numbers of erythrocytes with constant mean cellular hemoglobin. None of the remaining hematological indices examined was affected by oxygen or permeability treatments. It was concluded that turkey embryos incubating at 1,707-m elevation make no additional changes in hemoglobin concentrations during the plateau stage in oxygen consumption (25, 26, and 27 days of incubation) when exposed to increased oxygen tension (151 mm Hg versus 135 mm Hg) or increased eggshell permeability (19.9 mg H2 O/day per mm Hg versus 23.2 mg H2 O/day per mm Hg).

Altered cardiac tissue gene expression during acute hypoxic exposure.

Anoxia has been shown to induce the expression of one or more "stress proteins' in mammalian cells and tissues. A less severe form of oxygen depletion, hypoxic hypoxia, occurs in response to hypobaric decompression which simulates high altitude conditions. Under these conditions mouse hearts accumulate mRNAs for at least two polypeptides at substantially elevated levels. The molecular weights of these proteins, 85 kDa and 95 kDa, are similar to those reported for other mammalian stress proteins or glucose-regulated proteins. Time course experiments suggest that mRNAs for these species increase continuously for up to 16 hours of treatment, while mRNA for 71 kDa and 79 kDa polypeptides are elevated early in the treatment, but later decrease to control values. Total heart mRNA template activity is also increased by the hypobaric treatment. These results demonstrate that mouse cardiac tissue is capable of mounting a cellular stress-like response when exposed to moderately stressful conditions. It also provides a model for studying the direct effects of acute hypoxic stress on cellular gene expression, and its relationship to physiological adaptation.

The Effect of Atmospheric Conditions on the Performance of an Air-Borne Two-Stroke Spark-Ignition Engine

The effect of changes in atmospheric pressure and temperature on the performance of a crankcase-scavenged spark-ignition two-stroke cycle engine has been investigated. A detailed computer code has been developed to simulate the two-stroke cycle and was used to evaluate an optimal engine design for best performances at high altitude conditions. The model which includes detailed computations of the scavenging process, calculations of the flows into and out of the engine, empirical expressions for the combustion process, and a practical approach for the heat transfer has been calibrated by using experimental results. An empirical correlation has been devised for the prediction of the indicated power and for the specific fuel consumption of an engine at any pressure and temperature using information obtained at normal atmospheric conditions. These are [Formula: see text] The correlations have been compared with some other suggested correlations and were found to best fit experimental observations for three different makes of engine.

Changes in epithelium of the nasal mucosa during adaptation to high-altitude conditions

Changes in epithelium of the nasal mucosa during adaptation to high-altitude conditions

Effect of Oxygen Addition on Ignition of Aero-Gas Turbine at Simulated Altitude Facility

An experimental investigation was made of the effect of oxygen addition on the altitude ignition performance of an aero-gas turbine engine (a J69-T41-A) under steady windmilling operation at a simulated high-altitude condition. The results show that the injection of oxygen can improve altitude light-up performance significantly. In general, compared with the previous engine test data without oxygen addition, the increase in maximum light-up altitude was about 5000-7000 m, the maximum light-up flight Mach number was varied roughly at 0.361.1, and the maximum combustor inlet velocity for successful ignition was increased from 25-30 to 60-90 m/s. With oxygen addition, the maximum flow velocity for ignition at low pressure was higher than that at high pressure. A series of ignition tests was carried out at subatmospheric pressure on a prechamber taken from an existing engine. Oxygen was uniformly injected into the airstream. In order to explore the effect of oxygen addition on ignition performance of a single igniter, various parameters such as airflow pressure, velocity, air-fuel ratio, and oxygen flow rate were individually varied. Finally, a preliminary analysis of the effect of oxygen addition on minimum ignition energy reduction in a static and uniform mixture was made.

実験的高々所環境下の人の心拍出量変化に対するセンソ含有製剤の効果

In order to evaluate the efficacy of Ch'an Su containing drug in improvement of acutemountain sickness, the effect on the cardiac output (CO) was examined in 19 experiments with five healthy, 21 to 29 years old, males during exposure to 7, 000 maltitude conditions simulated by a decompression chamber. The subjects were also loaded by exercise with bicycle ergometer during the stay. Five minutes after exercise the single oral administration of the drug (5 mg) or its placebo was taken, then the impedance changes of chest wall, by which the stroke volume (SV) was estimated, and the heart rate (HR) were recorded every 3 or 5 minutes- during the subsequent 20 minutes. CO could be obtained as the product of SV and HR. Although there were considerably large individual differences, the average SV and CO at the 6, 10 and 15 post-drug minutes demonstrated statistically significant increase in comparison with those obtained from the placebo experiments. Further, the data obtained in these increasing periods gave the correlation coefficient of 0.891 for SV to CO relation, while only 0.416 for HR to CO, showing that the CO increase is highly dependent to that of SV. The results suggested that drug acts effectively, and rapidly as well, to improve the cardiac muscle activity against to the hypoxic impairment experienced under extreme high altitude conditions.

4334533 Breathing method and apparatus for simulating high altitude conditions: M L Henkin

4334533 Breathing method and apparatus for simulating high altitude conditions: M L Henkin

Fertilizer response of cold-tolerant sorghums under semi-arid high-altitude conditions.

5 fertilizer trials were carried out in 1974-5 at 3 different high-alt. locations in Kenya. In 3 of the 5 trials the yield response of a grain-type sorghum cv. was compared with the response of a forage-type cv. to N and P. In the other 2 trials the yield response of a grain-type sorghum to N, P, K and Mg + Zn, B and Cu was studied. Rainfall during the field period of the crop varied from 225 mm to 811 mm. There was no interaction with yr, but the responses varied greatly with trial site. Although DM yields obtained from the grain type in the driest trials were considered good (4.9 t DM/ha on 255 mm and 7.2 t DM/ha on 294 mm), no response to N or P was observed. Under wetter conditions it appeared that N increased the total DM yield of the forage-type cv. and the grain yield of the grain-type cv.; the type was accentuated. P increased the grain yield and total DM yield of the grain-type cv. Both N and P increased the CP content of the forage sorghum, but with the grain sorghum only N increased CP content whereas P decreased it. K and trace elements had a positive influence on yield in 2 experiments, but more work is needed to evaluate this effect in detail. Yield and forage quality differences resulting from different fertilizer applications were small. One possible reason for this is N-fixation in the soil, but more research is needed to substantiate this. In the trials with the lowest rainfall, the earlier maturing grain type outyielded the forage type, but if rainfall was less limited the forage type had a clear advantage over the grain type. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Splenic Infarction in Sickle Cell-Hemoglobin C Disease

Splenic infarction with consequent splenic fibrosis and functional asplenia is a common occurrence in patients who have sickle-cell anemia during childhood. It occasionally occurs in adults with the sickle-cell trait under high-altitude conditions where Po 2 is decreased, such as during airflight 1-9 or mountaineering. 10 A number of instances of splenic infarction have been reported in patients with sickle cell-hemoglobin C disease during air travel. 2,5,7,9,11-13 The diagnosis of splenic infarction is frequently based on the clinical features of sudden onset of pain in the left upper quadrant of the abdomen with or without associated fever, nausea, vomiting, splenomegaly, or localized friction rub. At times, however, the bedside diagnosis of splenic infarction is difficult and may not be easily differentiated from thromboembolism or infarction of the lower part of the left lung or left kidney. Recently, radioisotope scintillation scanning of the spleen has been found useful in establishing the

Solar space heating at high altitude conditions

Results of field trials on a solar space heating device at an altitude of 3·5 km and under sub-zero ambient conditions, down to −17°C are presented. The equipment does not require auxiliary power. It is based on automatic thermosiphon circulation of anti-freeze solution and subsequent radiant heating of living space. The equipment has been tried on a living room of dimensions 3·75 × 2·40 × 2·40 m and results compared with those of kerosene and electrically-heated control rooms. A solar collector area of 6·5 m 2 provides heat equivalent to 17 kWh of electricity or 71. of kerosene per day. Apart from economic advantage, the device avoids air pollution and fire hazards.

262. Experimental action of steroids, in hypobaric conditions of high altitude, upon the dynamics of ocular striated and smooth musculature

262. Experimental action of steroids, in hypobaric conditions of high altitude, upon the dynamics of ocular striated and smooth musculature

Non-gaseous layer combustions: Part 2. The effects of reduced pressure and rotational motion

The aim of this work was to establish the influence of reduced pressure and high speeds of rotation upon the combustion of chemical compositions. The compositions that were studied are of use in rocket propellant and related technology, and reduced pressure was used to simulate high-altitude conditions. Similarly, high speeds of rotation reproduce conditions of tracing compositions in the bases of spinning projectiles. Reduced pressure decreased the combustion rate of a ferro-titanium/barium peroxide ( 30 70 ) mixture, and rotation increased up to a point the combustion rate of magnesium/cupric oxide and magnesium/barium sulphate compositions (both 30 70 ). In other respects the essential mode of propagation followed the mechanism of the Mallard-le Chatelier theory.

Strategies for Control of the Space Shuttle Transition

The space shuttle will re-enter the Earth's atmosphere at high angle of attack, in order to minimize total heat load, and will perform a transition to low angle of attack for increased trajectory control. The timing and shaping of this angle transition are affected by specific-control-moment boundaries, attitude instability, angle of attack, limits on various flight parameters, and the establishment of a trimmed condition for flight to the landing site. Transitions to altitudes between 45,000 and 150,000 ft are investigated here, with particular attention given to suitable terminal conditions and to stability and control boundaries. Angle of attack is the control variable; hence, the short-period dynamics are not modeled. Two degree-of-freedom trajectories are optimized using a steepest descent algorithm with automatic step-sizing and open end-time. It is found that trim-glide flight-path angle y becomes very steep as altitude increases and that trajectories to such flight conditions are difficult to achieve. High-altitude equilibrium conditions (y = 0) at zero y are readily obtained, and they provide suitable way points for a continued glide to low altitude. Dynamic pressure and load factor peaks associated with both types of transition are not excessive. Stability and control boundaries have significant effects on the trajectories, although peak load, dynamic pressure and load factor are not materially altered. Gliding trajectories from high to low altitude are found to be sensitive to phugoid mode excitation, and the dynamic pressure peak which occurs prior to the terminal flight condition may be excessive.

Comment on “Preignition Products from Propellants at Simulated High Altitude Conditions”

Engine pressure spiking restart preignition products, determining hydrazine nitrate and dinitrate presence by spectrum analysis

Rocket plume /N2O4/MMH/ impingement on aluminum surface

T combustion of bipropellant motors under high-altitude conditions using dinitrogen tetroxide and hydrazine fuels has been reported to result in the formation of nonvolatile residues. The partial oxidation of the fuel is particularly evident during the pulse mode operation of the motor where high-combustion temperatures are not attained. Two major problems resulting from the use of these restartable space environmental engines are the contamination of vehicle surfaces from bipropellant rocket exhaust products and the occurrence of large transient ignition overpressures, which could have deleterious effects on engine operation. The latter results from the sudden detonation of the combustion residues which had accumulated on the rocket chamber wall. Both problems result from the incomplete combustion of the oxidizer and the fuel. The major product from the partial oxidation of hydrazine type fuels by N204 has been identified as fuel nitrates. Although the chemical nature of the combustion residues has been studied by several investigators, no information is available on the particle size and distribution of residues in the plume. In this study, a polished aluminum bar was placed in the plume of a N2O4-monomethylhydrazine (MMH) bipropellant motor during pulse mode firings under highaltitude conditions to obtain the imprint of residues striking the metal surface at very high velocity.

Approximate far-field flow description for a nozzle exhausting into a vacuum

References 1 Burch, B. A., of Contamination on Spacecraft Surfaces Exposed to Rocket Exhausts/' AEDC-TR-68-23, April 1968. ARO Inc., Tullahoma, Tenn. 2 Hill, D. W., Jr. and Smith, D. K., and Control of Contamination from a Scaled MOL Altitude Control Thruster in a Tangential Orientation/' AEDC-TR-69-146, Oct. 1969, ARO Inc., Tullahoma, Tenn. 3 Borson, E. N. and Landsbaum, E. M., A Review of Available Rocket Contamination Results, TR-0200(4250-20)-2, Dec. 1969. Aerospace Corp., El Segundo, Calif. 4 Valentine, R. S., Rossi, F. S., and Kromfrey, R. K., Fluid Dynamic Effects on Apollo Engine Pressure Spikes, Journal of Spacecraft and Rockets, Vol. 5, No. 1, Jan. 1968, pp. 31-35. 5 Christos, T. et al., Characteristics of Condensed-Phase Hydrazine-Type Fuels with Nitrogen Tetroxide/' Journal of Spacecraft and Rockets, Vol. 4, No. 9, Sept. 1967, pp. 1224-1229. 6 Per lee, H. E. et al., Preignition Phenomena in Small A-50/NTO Pulsed Rocket Engines, Journal of Spacecraft and Rockets, Vol. 5, No. 2, Feb. 1968, pp. 233-235. 7 Mayer, S. W., Taylor, D., and Schieler, L., Preignition Products from Propellants at Simulated High-Altitude Conditions, Combustion Science and Technology, Vol. 1, 1969, pp. 119-129. 8 Seamans, T. F. and Dawson, B. E., Hyperbolic Ignition at Reduced Pressures, Rept. RMD 5809-Q1, 1966, Thiokol Chemical Corp. 9 Takimoto, H. H. and Denault, G. C., Residues from N2O4-MMH Motors, TR-0066(5210-10)-1, Sept. 1969, Aerospace Corp., El Segundo, Calif.

Preignition Products from Propellants at Simulated High-Altitude Conditions

Abstract In view of the destructive ignitions that occur in hypergolic test firings of attitude-control motors under simulated high-altitude conditions, the preignition behavior of MMH, UDMH, A-50 and N2H4 with N2O4 was examined at low pressures and temperatures in the laboratory. At low NO2 pressures and temperatures, such as those that would be encountered in combustion chambers during starts in space, the ignition of these fuels was significantly delayed. During the preignition period, relatively involatile reaction products were formed between NO2. and the fuels. Infrared spectrophotometry, mass spectrometry, differential thermal analysis, and other techniques were used to examine these preignition residues. The IR absorption curves were consistent with the view that the major component in the MMH residue that could behave as an explosive monopropellant was MMH.nitrate, IR spectra of the preignition residues formed with N2H4 or A-50 suggest that hydrazine nitrate was the major constitutent of these re...