Severe Temperature Changes Research Articles

Seasonal reproduction in the eastern rock elephant‐shrew: influenced by rainfall and ambient temperature?

AbstractBecause environmental conditions vary seasonally in most regions, many small mammals reproduce at a specific time of the year to maximize their reproductive success. In the tropics and subtropics, the breeding season is usually determined by the extent of the dry and rainy seasons. We investigated the seasonality of reproduction in the eastern rock elephant‐shrew (Elephantulus myurus), over a 12‐month period and attempted to elucidate the factors that may influence seasonal reproduction in this endemic African mammal. E. myurus breeds seasonally during the warm and wet spring and summer months and cessation of breeding occurs during the cold and dry winter months of the southern hemisphere. Pregnant females were only collected from August through to January. Ovarian size and plasma progesterone started to increase a few months prior to the first rains, were highest in October and decreased thereafter. Follicular growth and corpora body numbers corresponded to this seasonal reproductive pattern. Testes and seminiferous tubule size and plasma testosterone concentration has already started to increase during the coldest months, 2 months prior to reproductive onset in females. We propose that seasonal reproduction evolved in E. myurus because of seasonally changing food availability brought about by severe seasonal changes in rainfall and ambient temperature. The direct effects of rainfall and ambient temperature on reproduction of E. myurus are ambiguous, and we discuss other environmental factors that may trigger reproductive onset in this species.

Assessment of cumulative damage by using ultrasonic C-scan on carbon fiber/epoxy composites under thermal cycling

In recent years, structural composites manufactured by carbon fiber/epoxy laminates have been employed in large scale in aircraft industries. These structures require high strength under severe temperature changes of -56° until 80 °C. Regarding this scenario, the aim of this research was to reproduce thermal stress in the laminate plate developed by temperature changes and tracking possible cumulative damages on the laminate using ultrasonic C-scan inspection. The evaluation was based on attenuation signals and the C-scan map of the composite plate. The carbon fiber/epoxy plain weave laminate underwent temperatures of -60° to 80 °C, kept during 10 minutes and repeated for 1000, 2000, 3000 and 4000 times. After 1000 cycles, the specimens were inspected by C-scanning. A few changes in the laminate were observed using the inspection methodology only in specimens cycled 3000 times, or so. According to the found results, the used temperature range did not present enough conditions to cumulative damage in this type of laminate, which is in agreement with the macro - and micromechanical theory.

Improving the Durability of Straw-Reinforced Clay Plaster Cladding for Earthen Buildings

Many historic earthen structures in the Middle East, Central Asia, and parts of Africa and Latin America are traditionally protected against the rain by straw-reinforced clay-plaster applied as a protective layer to the exterior of the building. The plaster is effective in keeping the building dry and can sustain the severe temperature changes of the regions; however, the plaster is susceptible to relatively fast water erosion. This article presents the results of a program of experiments, aimed at enhancing the durability of this traditional plaster against rain erosion. Hydrated lime and a very fine-grained aggregate (crusher dust) are used to improve the resistance of the straw-reinforced plaster. Samples made of the improved plaster mixes are tested for compressive and flexural strengths, water tightness, and resistance to water erosion; the results are used to obtain an optimum mix proportion for the improved clay soil plaster. The results indicate a substantial increase in the strength and durability of the plaster by using small quantities of these low-cost additives.

Thermomechanical behavior of pseudoelastic NiTi shape memory alloys

AbstractThe thermomechanical behavior of polycrystalline Ni‐rich pseudoelastic NiTi shape memory alloys is analyzed. Special focus is on regions within the stress strain diagram which are regarded as linear elastic in common phenomenological material models, i.e. the region between zero stress and the beginning of the pseudoelastic plateau as well as the region within the hysteresis. In both cases, severe temperature changes can be observed. A possible explanation for this effect is twofold: On the one hand, it might be explained by the presence of an R‐phase transformation. On the other hand, unstructured martensite of the B19' phase may form. However, the assumption of a purely thermo‐elastic material behavior in those regions does not seem to hold true in general. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Rodent paleofaunas as indicators of climatic change in Europe during the last 125,000 years

This paper presents a quantitative reconstruction of the European late Pleistocene paleoclimate based on 72 rodent assemblages of five sequences from France, Germany and Bulgaria, covering the last interglacial–glacial cycle. They show a pattern of severe changes in temperature, with reduced precipitation during the coldest periods. A tentative correlation between the isotopic and palynological records and the paleotemperature changes is shown. These changes are consistent with variations in atmospheric circulation patterns in response to an expanding–retracting Fennoscandian ice-sheet. They can be attributed to the enhancement–weakening of the Scandinavian-Polar anticyclone and its associated dry winds, the south–north shifting of the North Atlantic Polar Front, and the varying supply of moist air from the Atlantic. Qualitative paleoenvironmental analysis shows broadleaved-deciduous forests in France and Bulgaria during most of the studied period. Taiga and tundra appeared in eastern France during the lower Würm. The German sequence indicates the presence of coniferous forests. These results are broadly consistent with other paleobiological records (mammalian, avian and insect faunas, isotopic record in dental tissue, palynology). The main discrepancies with the paleoclimate inferred from the palynological record are found during the coldest periods and are probably due to the interaction between vegetation, climate, and atmospheric CO 2 levels.

Biological constraints in algal biotechnology

In the past decade, considerable progress has been made in developing the appropriate biotechnology for microalgal mass cultivation aimed at establishing a new agro-industry. This review points out the main biological constraints affecting algal biotechnology outdoors and the requirements for making this biotechnology economically viable. One of them is the availability of a wide variety of algal species and improved strains that favorably respond to varying environmental conditions existing outdoors. It is thus just a matter of time and effort before a new methodology like genetic engineering can and will be applied in this field as well. The study of stress physiology and adaptation of microalgae has also an important application in further development of the biotechnology for mass culturing of microalgae. In outdoor cultures, cells are exposed to severe changes in light and temperature much faster than the time scale required for the cells to acclimate. A better understanding of those parameters and the ability to rapidly monitor those conditions will provide the growers with a better knowledge on how to optimize growth and productivity. Induction of accumulation of high value products is associated with stress conditions. Understanding the physiological response may help in providing a better production system for the desired product and, at a later stage, give an insight of the potential for genetic modification of desired strains. The potential use of microalgae as part of a biological system for bioremediation/detoxification and wastewater treatment is also associated with growing the cells under stress conditions. Important developments in monitoring and feedback control of the culture behavior through application of on-line chlorophyll fluorescence technique are in progress. Understanding the process associated with those unique environmental conditions may help in choosing the right culture conditions as well as selecting strains in order to improve the efficiency of the biological process.

振動工具取扱い作業の温度負荷試験への検討

振動工具取扱い作業の温度負荷試験への検討

Simulation of the Hot Ring Rolling Process by Using a Thermo-Coupled Three-Dimensional Rigid-Viscoplastic Finite Element Method

During hot metal forming, the temperature variation and plastic deformation affect each other considerably. In the present investigation, ring rolling of hot steel is simulated by using a three-dimensional thermo-coupled rigid-viscoplastic finite element method. A new term is added to the functional in the variational approach to consider the influence of the frictional torque of the mandrel bearing, and the coupled thermal-mechanical simulation is performed by the iteration between the rigid-viscoplastic finite element analysis and the thermal finite element analysis. Since the deformation region and the severe temperature changes are restricted to the vicinity of the roll gap, only a ring segment and parts of the rolls are analyzed using a steady-state treatment to save computation time. Roll force and torque, width spread, temperature distributions, the distributions of strain and strain rate and the distributions of relative velocity and stress at the roll surfaces are obtained. The results show that the angular velocity of the driven roll has a significant influence on the temperature variations in the ring and the rolls, to which attention should be paid in the design of the process. The method presented can also be used to analyze other forming processes such as unsymmetrical plate rolling, symmetric rolling, and extrusion.

Morphology of Apollo 11 and 12 Soil Samples and the Quest for Biogenic Forms

The Apollo 11 and 12 missions to the moon returned valuable samples for scientific study. The morphology of the loose sediment and breccia from Apollo 11 have been studied extensively in our laboratory using light microscopy, electron microscopy, scanning electron microscopy and the electron probe. The Apollo 12 sample is now undergoing similar treatment.Even though conditions on the moon, especially on the surface, are known to be extremely hostile to life as we know it, an extensive search was carried out for evidence of past life. Since numerous reports exist purporting evidence of life forms in carbonaceous chondrites coming to the Earth from outer space, such material would also be expected to be embedded in the lunar surface. Enders calculates about 2% carbonaceous chondrites on the lunar surface and Keil had measured nickel iron meteoritic ratios in his sample as about 1%. Thus influx to the surface and undetermined past history add interest to the search. However, an estimated turnover rate of 120 million years for a few inches of lunar soil does mean long exposure of this material to radiation, severe temperature changes, high vacuum, etc.

Elastoplastic Composites in the Transportation Industry

This article describes a process for fabricating an improved urethane skin—microcellular foam elastoplastic composite. The resulting composite can be used where thin skins are subjected to severe weathering and temperature changes. An automotive fen der extension was selected to show the softskin M-E concept. Skins for the fender extension may be screw-injection molded, however to avoid the cost of metal molds, wood molds were built to permit vacuum drape forming of the demonstration samples.

Pleistocene Paleotemperature Record Based on Planktonic Foraminifers, Gulf of Mexico: ABSTRACT

ABSTRACT Study of planktonic foraminifers from deep-water sediment cores in the northern Gulf of Mexico indicates the presence of alternating cold-- and warm--water faunas which are interpreted to represent glacial and interglacial stages of the Pleistocene. Globorotalia menardii (warm) and Globorotalia inflata (cold) are the most sensitive indicators for delineating severe changes in Pleistocene temperature in the Gulf of Mexico. On the basis of planktonic datums the cold-warm cycles are correlated with water-depth changes in the shallower shelf environment which are interpreted to represent eustatic sea-level changes. The cold intervals represent times of lowered sea level and are correlated with the glacial stages of North America. Age relationships between the glacially related events recognized in the marine Pleistocene section and the continental glacial stages are well documented to about 35,000 years ago on the basis of carbon 14 dates. Age relationships between the older part of the marine Pleistocene and the continental glacial stages are not so well documented but can be inferred from correlation between the glacial-interglacial cycles and paleomagnetic reversal events, which are well dated by potassium-argon. Onset of severe climatic deterioration and beginning of the Quaternary (Nebraskan Stage) in the Gulf of Mexico correspond with the extinction horizon of Globoquadrina altispira. Correlation of this horizon with the paleomagnetic reversal events gives an age of about 2.8 m.y. ago for the Pliocene-Pleistocene boundary. Placement of the Pliocene-Pleistocene boundary at 2.8 m.y. ago allows recognition of five major glacially related events in the marine Pleistocene based on climatic and eustatic criteria. Faunal data indicate that the Nebraskan, Illinoian, and Wisconsinan were severely cold periods, whereas the Aftonian, Kansan, Yarmouthian and Sangamonian were warmer, with the Aftonian the warmest. Carbon 13/12 isotope data support these conclusions. Foraminifers and discoasters from the marine Calabrian Stage of southern Italy at Santa Maria di Catanzaro indicate a correlation with the marine Nebraskan Stage, as here defined, in the Gulf of Mexico. Paleontological evidence indicates that the Pliocene-Pleistocene boundary of Glass et al. (1967), Berggren et al. (1967), and Ericson and Wollin (1968) falls near the base of the Kansan. The cold and warm intervals shown below the Pliocene-Pleistocene boundary of Glass et al. (1967) are interpreted to represent the Nebraskan and Aftonian Stages. Paleomagnetic evidence suggests that the Olduvai magnetic event of these authors probably represents the Gilsa event at about 1.6 to 1.8 m.y. ago. Advances in paleomagnetic stratigraphy indicate that the magnetic reversals facilitate dating and correlating marine stages at latitudes where differing paleontologic criteria must be used to delineate the glacial and interglacial episodes. Seemingly, the major paleomagnetic epochs are reliable for stratigraphic correlation; however, the minor events of relatively short duration appear to be less reliable as unique stratigraphic markers. Globorotalia pertenuis, n. sp., a right-coiling member of the Globorotalia menardii group, is described.

INFLUENCE OF WATER TEMPERATURE ON HEART RATE AND RECTAL TEMPERATURE OF SWIMMING RATS.

The heart rate and rectal temperature of 12 adult male hooded rats were studied during 10-min swims in water of 37, 20, and 42 C. Both the heart rate and the rectal temperature stabilized in water of 37 C, suggesting that swimming in thermoneutral water is a submaximal exercise for rats. In water of 20 C, rectal temperature and heart rate of swimming animals fell exponentially to 28 C and 251 beats/min, respectively. The relationship of heart rate to rectal temperature in these swimming, cooling animals was not different from that reported in the literature for unanesthetized, inactive, hypothermic rats. It appeared that exercise had no effect on the heart rate of rats when the body temperature was dropping. In water of 42 C the rectal temperature rose exponentially to 42.2 C. The heart rate rose to 521 beats/min at the 8th min of swimming and remained stable thereafter. It is suggested that inadequate cardiac output resulting from severe changes in body temperature may be one factor which limits swimming capacity of small animals in hot and cold water.

INFLUENCE OF WATER TEMPERATURE ON OXYGEN UPTAKE BY SWIMMING RATS.

Oxygen uptake and rectal temperature of ten rats forced to swim to exhaustion or for 45 min in cold, hot, and thermoneutral water were measured during swimming. In 20 C water rats swam for 12.6 min and had a final rectal temperature of 26.9 C. In 42 C water the mean swimming time was 14.1 min and the final rectal temperature was 42.6 C. All rats swam for 45 min in water of 37 C, and the final rectal temperature was not different from the preswim temperature. Oxygen uptake during swimming in 37 C water rose and stabilized at a rate of about three times basal in a pattern suggesting that the swimming work was moderate. Animals swimming in cold and hot water were exhausted before their oxygen uptakes stabilized, but the increasing oxygen uptakes during the early parts of these swims were similar to that in neutral water. It appeared that while the metabolic rate was adjusted to the level of work and was not greatly affected by severe changes in body temperature, alterations in body temperature profoundly influenced the duration of work in the hot or cold environments. exercise and thermal stress; exercise metabolism Submitted on March 23, 1964

OCULAR EFFECTS OF ALTITUDE FLYING AND OF DEEP SEA DIVING

The subject assigned refers primarily to changes brought about by alterations in atmospheric pressure and in partial pressure of oxygen, to rapid and severe changes in temperature and to protection of the eyes against glare, air blast, dust and flying debris. Changes in atmos1 pheric pressure in flying are within the range between the pressure at sea level (1 atmosphere—about 15 pounds per square inch [1,050 Gm. per square centimeter], or 760 mm. of mercury) and a pressure of about ⅙ atmosphere (2½ pounds per square inch [170 Gm. per square centimeter], or 127 mm. of mercury) at the maximum altitudes now attainable by military aircraft. Pressures encountered in deep sea diving can also be expressed in terms of pressure at sea level. These pressures range from 1 to 6, 7 or 8 atmospheres. The physiologic effects of variations in pressure are brought about in several ways : By