Slow Temperature Changes Research Articles

Growth of buffer multilayers on nickel for deposition of YBa 2Cu 3O 7− δ-layers

The growth of buffer layers for YBa 2Cu 3O 7− δ deposition on Ni-tapes was studied under idealized conditions on epitaxial Ni-films covered with a Pd protection layer. The subsequent films were CeO 2 and YSZ. The greatest obstacle in the growth was crack formation and (1 1 1) orientated NiO growth even through CeO 2-films. Good crystallographic properties of the upper layer with in-plane and out-of-plane mosaic spreads below 2° were achieved at high deposition rates and slow temperature changes for YSZ deposition.

温度履歴に伴う砂岩の間隙構造の変化

Changes in pore spaces and microcracks in Shirahama sandstone subjected to slow and uniform temperature changes up to 1,000 °C have been examined using a fluorescent technique. A specimen heated up to a certain temperature was kept at the constant for 24 hours, and then cooled down to a room temperature. Texture of the specimen was observed with a microscope. Above 500 °C, new microcracks were observed along grain boundaries. The widening of grain boundary microcracks was recognized with increasing temperature. Thermal expansion caused by the α to β transition of quartz plays the dominant role in the development of grain boundary microcracks. Above 500 °C, increase and enlargement of pore spaces in the matrix were also observed. The changes in matrix are caused by thermal reactions in the matrix constituent materials such as dehydration and formation of new minerals. At high temperatures, these reactions and the quartz expansion may occur simultaneously, so that microcracks and pore spaces significantly increase. Changes in physical properties such as porosity and elastic wave velocity show good agreement with the results obtained by microscopic observations.

Molecular Dynamics Simulations of Polyampholytes

The dynamical and equilibrium properties of charged polymers of random copolymerization (polyampholytes) are studied for both the single-chain and multichain cases with the use of molecular dynamics simulations. Single-chain polyampholyte has three temperature regimes under neutral conditions, which are characterized by an elongated Gaussian coil and a very dense globule for high and low temperatures, respectively, and by a transition between them at medium temperature. The gyration radius of single-chain polyampholyte shows a hysteresis against slow cyclic changes in temperature under the Coulomb force and short-range attraction force. The multichain polyampholyte takes a segregated globular phase at low temperatures and the wall-bound one-phase state with separated chains at high temperatures. The polyampholyte chains overlap significantly below critical temperature, at which glass transition takes place because of the Coulomb force. Added salt ions screen the electric field between the monomers and make the polyampholyte soluble when their density is comparable to that of the polyampholyte.

Temperature profiles for the expression of endogenous rhythmicity and arrhythmicity of CO 2 exchange in the CAM plant Kalanchoë daigremontiana can be shifted by slow temperature changes

The crassulacean acid metabolism (CAM) plant Kalanchoe daigremontiana Hamet et Perrier de la Bâthie shows an endogenous circadian rhythm of net CO2 exchange (JCO2) under constant conditions in continuous light. Previous studies have shown, however, that above a certain threshold temperature JCO2 changes from rhythmic to arrhythmic behaviour and that this is reversible when the temperature is lowered again. It is now demonstrated here, that this re-initiation of rhythmic JCO2 from arrhythmicity needs a sufficiently strong temperature signal as defined by its abruptness. Rhythmicity reappears only if the temperature is reduced rather rapidly. If the temperature is reduced slowly then arrhythmicity is retained even at a low temperature level which normally would allow rhythmicity. Under these circumstances, however, a distinct temperature increase followed by an abrupt temperature decrease immediately elicits regular oscillations of JCO2 at this lower temperature. We suggest that the strong temperature signals function as a definite synchronizer (“zeitgeber”) which synchronizes different cells and/or different leaf areas which remain desynchronized after application of only slow temperature changes. This is further supported by Fourier transform analyses, revealing a harmonic structure of the superficially arrhythmic time series of JCO2 after application of slow temperature reductions. This conclusion adds a spatial dimension to the otherwise purely time-dependent rhythmicity and arrhythmicity of JCO2 in CAM.

TEMPERATURE EFFECTS ON AIR-POCKET TENSIOMETERS

Air-pocket tensiometers with pressure transducer sensors are used widely in routine monitoring of soil water potential and in studies of soil water movement. Air temperature fluctuations in the exposed head space of the tensiometer can cause large air pressure changes leading to misinterpretation of the soil water potential. Treating the tensiometer head space as an ideal gas with water vapor in dynamic equilibrium, a set of coupled equations is derived that describes the relationship between head space air pressure, the rate of temperature change, the conductance of the tensiometer cup, and the head space volume. The interaction of these factors is illustrated through a series of simulations and then demonstrated with laboratory and field experiments. Air pressure deviations as large as ±80% were observed in tensiometers of low cup conductance and large head space when exposed to rapid temperature change. When the temperature change is slow relative to the cup conductance, changes in air-pocket pressure are corrected by water flow across the cup, and interpretation errors are small. Air pressure deviations from both rapid and slow temperature change may be estimated with the simulation equations using an approximation for the water pressure gradient across the tensiometer cup. The most practical outcome of this research is the theoretical and experimental confirmation that air temperature effects are reduced by maintaining high water levels in the tensiometer (that is, minimizing the air-pocket volume) and by maximizing the tensiometer cup conductance. In the field, insulating or shading tensiometers reduces temperature-related errors in general but may aggravate the problem if removal of the insulation (as might be necessary to read the tensiometer) causes a sudden temperature change in the air-pocket.

Thermal threshold determination in alcoholic polyneuropathy: an improvement of diagnosis

Reports on the incidence of alcoholic polyneuropathies are variable depending on diagnostic tools. In this study, 50 chronic alcoholics with positive MALT (Munich Alcoholism Test) and greater than seven years history of excessive alcohol abuse were examined neurologically. Tibial and peroneal motor and sural nerve conduction velocities (NCV) were studied. Warm and cold perception was evaluated in the area behind the internal malleolus using a Somedic-Thermotest. Thresholds were determined by the method of limits. The effect of a slow, medium and fast temperature change rate on thermal perception was tested. Thirty-eight patients (76%) showed signs of neuropathy. Thermal perception was more often abnormal (62%) than NCV (42%) and clinical examination (56%). A medium temperature change rate of 2.0-2.5 degrees C/s was the most sensitive index of small fiber neuropathy. Thermal threshold measurement proved to be a reliable, sensitive and easy to perform method that should become standard in the examination of polyneuropathies.

Phase change and viscosity effects on a quartz crystal microbalance

The mass–frequency dependence for various materials deposited onto the surface of a resonating quartz crystal was investigated. The relationship is linear, but the constant of proportionality is different for different materials deposited. Such frequency changes are commonly described by the Sauerbrey equation, but in this experiment the equation was found to be in error by factors of up to 23. This can be accounted for by changes in surface viscosity. Slow temperature changes of a resonating quartz crystal coated with the polymer Antarox CO-880 revealed a significant frequency minimum at the phase-transition points. This is also attributed to a change in the viscosity of the coating at transition. The phase-transition temperature for this polymer was verified by differential scanning calorimetry. Quartz crystal techniques may provide a simple, accurate method for the measurements of phase-transition temperatures.

Threshold temperature responses of thermosensitive neurons in guinea-pig hypothalamic slices

1. 1.|Neuronal activity in slices of the preoptic and anterior hypothalamic area of guinea-pigs during slow low-amplitude temperature changes analogous to temperature changes in the brain of endothermic animals, was extracellularly recorded. 2. 2.|42% of neurons showed threshold temperature responses. The threshold of response averaged 37.4°C for warm-sensitive neurons during warming and 37.0°C for cold-sensitive neurons during cooling. 3. 3.|The thresholds differed, on average, by 0.1°C in the same neuron at repeated temperature changes. 4. 4.|With temperatures 0.8°C above threshold on average (0.2°C in some units) neuronal activity reached a new high level that did not change either during a further exceeding of the threshold or prolonged maintenance of suprathreshold temperature. 5. 5.|The characteristics of the threshold temperature response of a hypothalamic neuron meet the criteria of thermoinduced structural rearrangements of cell membranes, caused by phase transitions of lipids, changes in protein conformation and cytoskeletal activity.

When Climate Twitches, Evolution Takes Great Leaps

Earth's climate system has ridden a slow roller coaster for the past 60 million years. It warmed gradually until about 53 million years ago, reaching a peak that brought crocodiles to northern Canada; then it entered a long, undulating downgrade toward the ice-age world of the past few million years. Because the same span of time brought major evolutionary changes, including the rise of modern mammals, paleontologists have long assumed that these slow temperature changes helped spur the processes of evolution. But recent findings have suggested that another, more potent mechanisms was also at work: Abrupt climate excursions, superimposed on these long-term trends, have now been linked to rapid periods of mammal evolution. The evidence for short, sharp evolutionary shocks comes from studies of a pair of mirror-image climate shifts at opposite ends of the Eocene epoch, 55 million and 33.5 million years ago. In both cases, researchers studying the record of climate preserved in sea-floor sediments have found that a gradual climate change-warming in the first case, cooling in the second - suddenly steepened into a short-lived pulse of extreme warming or cooling. The short time scale of these events and their clear coincidence with turning points in themore » evolution of mammals are providing the tightest links yet between global climate change and evolution on land.« less

The collapse temperature in freeze drying: Dependence on measurement methodology and rate of water removal from the glassy phase

Accurate determination of the maximum allowable product temperature during primary drying is critical to optimization of the freeze drying process. For an amorphous solute system, this maximum temperature is normally the collapse temperature. Methodologies for determining the collapse temperature involve direct microscopic observation of collapse during freeze drying and methods which, in effect, determine the glass transition temperature of the amorphous phase. While one might be tempted to assume that the collapse temperature is a property only of the material, and independent of details of the measurement method, both theoretical concepts and limited experimental observations suggest that this assumption may not be wholly correct. The main objective of this research is to determine the magnitude of variations in measured collapse temperature caused by variations in experimental methodology. The approach taken is both experimental, using moxalactam di-sodium formulated with 12% mannitol as a model, and theoretical. The theoretical analysis is based on two fundamental concepts. Firstly, for collapse to be observed, viscous flow of the amorphous phase must occur over a finite distance during the measurement time. Secondly, during a freeze drying process, water is removed from the amorphous phase once the ice-vapor boundary recedes past the region of interest. Since water removal increases viscosity, viscous flow, and therefore, collapse is partially arrested, and the effective collapse temperature will be increased, the effect being greater the faster the sublimation rate. A quantitative model based on these concepts is developed with key parameters being evaluated by experimental studies. The observed variation in collapse temperature of moxalactam di-sodium with sublimation rate is quantitatively predicted by the theory. The theory is used to investigate differences between collapse temperatures determined by laboratory procedures and the observation of collapse in production processes. The collapse temperature will increase as the sublimation rate increases (i.e., as the solute concentration decreases), and at constant sublimation rate, the collapse temperature may increase as the surface area of the solid increases. In general, product freeze drying in a vial will collapse at a slightly higher temperature than collapse measured by the microscopic method. However, the calculated variations in collapse temperatures are modest (1–3°C). Collapse temperature and glass transition temperature, T ′ g , are not identical, the latter being slightly lower when measured at low rates of temperature increase. A secondary but important experimental result is that, contrary to some opinion in the literature, water in a glassy system has sufficient mobility to be in approximate ‘equilibrium’ with the ice phase during the relatively slow temperature changes relevant to freeze drying operations.

岩石のＰ波速度に及ぼす温度の影響

P wave velocities of both dry and saturated rocks were measured during a slow temperature change (0.5K/min.) between 110K and 370K. Their thermal expansions were measured simultaneously. The change of P wave velocity was larger by about one or two orders than that expected from the net change of sample length due to thermal expansion. In the dry condition, hysteresis in the temperature-P wave velocity relation was observed in only granite among various kinds of rocks, which is explained by frictional sliding at the surface of microcracks and crushing of microcrack asperities. In the saturated condition, however, hysteresis was observed in all rocks due to the temperature difference between freezing and thawing of water within pores and microcracks. A large increase in P wave velocity was observed in all rocks between 273K and 230K during cooling. A sharp decrease in P wave velocity coincided with thermal cracking detected by the changes of both the activity of acoustic emission (AE) and thermal expansion. These observations suggest that the temperature effect on P wave velocity of rock is strongly affected by (1) thermal cracking, and (2) the phase change of water within pores and microcracks.

加熱・冷却にともなう大島花こう岩のＡＥと熱膨張

AE and thermal expansion of both stressed and unstressed Oshima granite were investigated. The samples were subjected to slow cyclic temperature change (0.5K/min) between 290K and 370K or between 210K and 290K. A large number of AE events occurred only during the first cycle both heating and cooling. Under unstressed conditions, the thermal expansion coefficient became highly temperature dependent when the occurrence of AE events was observed. When the rock was subjected to thermal cycling under uniaxial stress conditions, the thermal expansion coefficient in the axial (loading) direction became temperature independent, while that in the circumferential direction was unchanged. The reactivation of the AE events was observed during the first heating after the removal of stress. These observations suggest that microcracks are produced by the mismatch of thermal expansion of individual mineral grains and cause the temperature dependency of the thermal expansion coefficient of Oshima granite. The anisotropy of thermal expansion observed when the samples were uniaxially compressed, is explained by the closure of microcracks perpen-dicular to the axial direction.

Behaviour of granites and limestones subjected to slow and homogeneous temperature changes : Homand-Etienne, F; Troalen, J P Engng GeolV20, N3, Aug 1984, P219–233

Behaviour of granites and limestones subjected to slow and homogeneous temperature changes : Homand-Etienne, F; Troalen, J P Engng GeolV20, N3, Aug 1984, P219–233

低温で熱サイクルをうける乾燥岩石の熱膨張について

Thermal expansions of 11 dry rocks were investigated. These rocks were subjected to slow cyclic temperature change (0.5K/min) between 110K and 300K. They were divided into 2 groups according to their thermal expension behavior; existence of a hysteresis in the thermal expansion and a residual strain after the thermal cycling. (1) Nongranitic rocks (sedimentary and volcanic rocks) showed neither residual strain nor hysteresis. (2) Granitic rocks and Akiyoshi marble showed the residual strain and the hysteresis. Thermal expansion coefficient of the marble was negative at almost all temperatures. The difference in the thermal expansion between these groups was explained by the thermal cracking and the cracks in the rocks. Thermal cracking which is the cause of the residual strain can be produced by the mismatch of thermal expansion among the mineral grains. Cracks are responsible for the hysteresis by frictional sliding at crack surfaces and partial crushing of asperities. Decreasing temperature cannot provide the local strain sufficient to produce the cracking in the nongranitic rocks which consist of small grains and glassy matrix. On the contrary, the granitic rocks contain large grains and a large amont of quartz that shows larger expansion than other minerals. Akiyoshi marble is the aggregation of polycrystalline calcite that expands anisotropically. Themal cracking is therefore produced in these rocks during the first cooling stage.

Body Temperature and Information Processing Capability

Typically, human performance is projected to fluctuate in a circadian manner, usually in association with body temperature rhythm. Such sinusoidal relationships are isomorphic in that they are, under most normal circumstances, phase-locked in environmental time. As body temperature rises so performance is improved. However, increase in temperature above the zenith does not result in increased capability. Rather, such elevation has the dual and opposing action of speeding performance while elevating error rate to produce an overall diminution of efficiency (e.g., Allan and Gibson, 1979; Nunneley, Reader, and Maldonado, 1982). It has been suggested that deep body temperature controls the speed of performance, while skin temperature mediates error through the control of comfort associated with peripheral variation. To overcome distress connected with peripheral increase, yet to utilize the superior speed elicited by alteration of central temperature change, the use of selective head heating has been explored. The present paper synthesizes data from selective heating studies and indicates the potential gains which may be realized in complex machine operation. Results from this paradigm have suggested facilitation in stimulus assimilation, decision making capability and response selection and execution (e.g., Hancock, 1983; Hancock and Dirkin, 1982; Holt and Brainard, 1976). This facilitation is not linear in temperature change. To a 1°C increase there appears a change in decision criterion such that individuals become more conservative in response. Above this threshold value, veridical gains in performance are manifest with a reduction in both task latency and error rate. Simple physiological accounts of such behavior are largely inadequate as the precise physiological effect has yet to be thoroughly documented. An initial outgrowth of this work is the potential usage of fluctuation in head temperature as a dynamic physiological reflection of imposed mental workload (e.g., Hancock, Meshkati, and Robertson, 1984). These performance facilitations under relatively slow temperature changes are contrasted with decrement observed under rapid temperature fluctuation. A potential relationship with the notion of attentional resource capacity is explored.

Unlimited phase compensator for fiber-optic interferometric detection of slow temperature change

Measurement of slow temperature change by means of a Michelson-type fiber-optic interferometric sensor exploiting unlimited phase compensation is presented. A new simple phase demodulation system, based on a rotating half-wave retarder controlled by a feedback loop, permits real-time detection of a slowly induced phase change of any magnitude. A theoretical analysis of the demodulator is given, together with experimental data showing that a precision better than l/10 degrees C was achieved on a 1-h thermic cycle.

Behaviour of granites and limestones subjected to slow and homogeneous temperature changes

We have studied the evolution of the texture in two granites and two limestones subjected to slow and uniform temperature change. Each granite has a different grain size and each limestone a different texture: Carrare crystalline limestone and Crepey oolitic limestone. Temperature was varied from 200°C to 700°C. Scanning Electron Microscope observations of different rock samples show that during thermal cycling intercrystalline boundaries in granites widen out progressively and porosity increases. New microcracks appear in crystals between 500°C and 600°C. In Carrare crystalline limestone, intercrystalline cracks appear at temperatures as low as 200°C. Due to its heterogeneous cracks appear at temperatures as low as 200°C. Due to its heterogeneous increasing temperature. Longitudinal wave velocity and intrinsic permeability show good correlation with the Scanning Electron Microscope observations.

マスコンクリートの温度ひびわれ発生条件 : 第二報 温度変化速度が小さい場合のコンクリートの温度ひびわれ

マスコンクリートの温度ひびわれ発生条件 : 第二報 温度変化速度が小さい場合のコンクリートの温度ひびわれ

1-anilinonaphthalene-8-sulphonate as a fluorescent probe for temperature-induced changes in Escherichia coli membranes.

Slow temperature changes of anEscherichia coli 15 TAU suspension caused only insignificant shifts in the fluorescence of 1-anilinonaphthalene-8-sulphonate. A rapid temperature shock enhanced the fluorescence substantially, particularly from 37.0 to 46.2 °C, when optimum synchronization of culture is achieved. Methionine suppressed both synchronization and fluorescence shift. It is conjectured that the degree of synchrony is related to the extent of fluorescence enhancement in these cells.

Temperature dependence of courtship in male guppies, Poecilia reticulata Peters (Pisces, Cyprinidae)

In poikilothermal animals, modes of behaviour as well as other physiological functions are dependent on the environmental temperature. Individual adaptation can decrease or cancel out this dependency. In experiments involving abrupt and slow temperature changes, we were able to prove temperature compensations and stress effects in the courting behaviour of the male Poecilia reticulata.