Temperature-induced Variation Research Articles

Microthermal Probing of Ultrathin Polymer Films

We present the results of microthermal studies of ultrathin polymeric films deposited on a silicon substrate. We propose the procedure for microthermal analysis of ultrathin polymer films, elucidate limits of applicability of this technique to study their microthermal properties, and observe the thermomechanical response during local heating for films with thicknesses above 10 nm. The glass transition temperature of ultrathin polystyrene (PS) films deduced from experiments decreases for film thicknesses below 200 nm. For the thinnest PS film with clearly detectable response(25nm), the glass transition temperature is 20 °C below its bulk value. Our estimation of heat dissipation in the tip–surface contact area supports the conclusion that the observed micro-thermal-analysis response for polymer films is associated mainly with temperature-induced elastic variation of the contact area.

Effects of temperature-induced variation in anuran larval growth rate on head width and leg length at metamorphosis.

We tested whether temperature-induced variation in the growth rate of Rana cascadae tadpoles caused any variation in head width or leg length at metamorphosis, independent of the effects of temperature on body size. Body-size-adjusted head width appears to be insensitive to even large variations in tadpole growth rate. This result mirrors previous observations on the effects of variation in food level and temperature on metric shape in frogs and other ectothermic vertebrates. Leg length, on the other hand, showed a small but statistically significant response to the temperature treatment. Fast-growing tadpoles attained slightly longer legs than slowly growing tadpoles at a common metamorphic body size. This example is the first to show that variation in growth rate per se can influence metric shape (i.e., the rate at which individuals reach a common body size determines their shape at that size). Nevertheless, the induced effects were small, and our results taken together with those of previous studies suggest that environmentally induced variation in growth rate is not a major source of variation in metric shape of skeletal characters in ectothermic vertebrates.

Linear techniques to correct for temperature-induced spectral variation in multivariate calibration

The influence of external physical variation such as temperature fluctuations on near-infrared (NIR) spectra and their effect on the predictive power of calibration models such as PLS have been studied. Different methods to correct for the temperature effect by explicitly including the temperature in a calibration model have been tested. The results are compared to the implicit inclusion, which takes the temperature into account only through the calibration design. Two data sets are used, one well-designed data set measured in the laboratory and one industrial data set consisting of measurements for process samples. For both data sets, the explicit inclusion of the temperature in the calibration models did not result in an improvement of the prediction accuracy compared to implicit inclusion.

Microstructure analysis using temperature-induced contrast variation in small-angle scattering

We propose to introduce Temperature-Induced Contrast Variation (TICV) as a technique for improving the specificity of microstructure analyses obtained using small-angle scattering methods. TICV exploits the fact that, at temperatures well removed from melting or annealing regimes, the scattering contrast in many multicomponent systems exhibits a significant temperature dependence while the form factors for the scattering processes change only slightly. Difference scattering patterns formed by subtracting the pattern measured at a suitable reference temperature from the pattern obtained at another temperature emphasize those components of the microstructure that vary most strongly with temperature over the chosen range. This can facilitate an effective separation of the observed scattering patterns into separate components for differing scattering mechanisms. Examples of distinct scattering mechanisms commonly found in polymers include liquid-like scattering from amorphous components, contributions from the intramolecular amorphous halo, Guinier scattering from inclusions, and the scattering from ordered stacks of crystalline lamellae. The experimental data presented here provide qualitative demonstrations of general features of the method. Further work is needed to obtain improved descriptors to characterize microstructure in these systems.

Correction of temperature-induced spectral variation by continuous piecewise direct standardization

In process analytical applications it is not always possible to keep the measurement conditions constant. However, fluctuations in external variables such as temperature can have a strong influence on measurement results. For example, nonlinear temperature effects on near-infrared (NIR) spectra may lead to a strongly biased prediction result from multivariate calibration models such as PLS. A new method, called Continuous Piecewise Direct Standardization (CPDS) has been developed for the correction of such external influences. It represents a generalization of the discrete PDS calibration transfer method and is able to adjust for continuous nonlinear influences such as the temperature effects on spectra. It was applied to shortwave NIR spectra of ethanol/water/2-propanol mixtures measured at different temperatures in the range 30-70 degrees C. The method was able to remove, almost completely, the temperature effects on the spectra, and prediction of the mole fractions of the chemical components was close to the results obtained at constant temperature.

Hall effect ofYBa2Cu3O7−δsingle crystals

For a number of ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ single crystals with various oxygen concentrations and differing values of the zero magnetic-field critical temperature ${T}_{c0},$ the Hall effect has been investigated between 10 and 300 K by applying magnetic fields $\mathbf{H}\ensuremath{\parallel}c$ and currents $\mathbf{I}\ensuremath{\perp}c,$ where $c$ denotes the direction perpendicular to the Cu-O planes of this material. These measurements yield that the sign change of the Hall voltage close to ${T}_{c0}$ varies with \ensuremath{\delta} and eventually disappears in heavily oxygen-depleted ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ single crystals. Such behavior can qualitatively be explained by a model calculation based on the time-dependent Ginsburg-Landau theory. In the normal state, we find that the Hall coefficient ${R}_{H}$ and the Hall angle ${\ensuremath{\theta}}_{H}$ vary as ${R}_{H}^{\ensuremath{-}1}\ensuremath{\propto}T$ and $\mathrm{cot}{\ensuremath{\theta}}_{H}\ensuremath{\propto}{T}^{2}$ in an extended temperature range, as has previously been found for fully oxygenated ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7}$ and ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3\ensuremath{-}y}{M}_{y}{\mathrm{O}}_{7}$ ($M=\mathrm{Ni},$ Zn). Deviations from these behaviors for both ${R}_{H}^{\ensuremath{-}1}$ and $\mathrm{cot}{\ensuremath{\theta}}_{H}$ are observed below a characteristic temperature ${T}^{*},$ whereby ${T}^{*}$ increases with decreasing ${T}_{c0},$ i.e., increasing oxygen depletion. This implies a temperature-induced variation of the normal-state electronic spectrum and/or the scattering parameters governing the electronic transport of this material.

Spontaneous photorefractive effect in Sr1−x CaxTiO3 (x=0.014)

The temperature dependence of the principal values of the refractive index in Sr1−xCaxTiO3 (x=0.014) has been measured in the 17–275 K range under various conditions of sample illumination with 1.96 eV photons. The spontaneous photorefractive contribution δnph to the temperature-induced variation of the refractive index of Sr1−xCaxTiO3, which appears after illumination of the sample in the ferrophase (transition temperature Tc=32 K) and persists in the paraphase under heating up to 150 K, has been separated. The photoinduced polarization has been estimated.

A COMPARISON OF TEMPERATURE-INDUCED POLYPHENISM IN AFRICAN BICYCLUS BUTTERFLIES FROM A SEASONAL SAVANNAH-RAINFOREST ECOTONE.

Temperature-induced variation and norms of reaction have been analyzed for wing pattern elements of six species belonging to the African butterfly genus Bicyclus (Lepidoptera, Nymphalidae, Satyrinae). Five of these species are sympatric in Malawi and exhibit seasonal polyphenism in the savannah-rainforest ecotone. The sixth species originated from Cameroonian equatorial rainforest. The organisms were laboratory reared under four different temperature conditions ranging from 17-28°C. The variation in response to temperature is described by principal component analysis (PCA). Discrimination on the basis of plastic wing pattern characters was performed by discriminant function analysis (DFA) and unweighed pair-group method algorithm (UPGMA) clustering. A phylogenetic reconstruction based on adaptive plastic wing characters was compared with a cladogram built on "nonadaptive" characters. Results demonstrate that: (1) Phenotypic plasticity of wing pattern characters in response to temperature in laboratory-reared organisms is reminiscent of variation induced by seasonal change in the field. (2) Different wing pattern characters are under different control: "exposed" characters of butterflies at rest position are highly sensitive to temperature variation, whereas "hidden" characters, only visible during active behavior, are dominated by species differences. In general the sensitivity of the former can be attributed to their proposed function in deflecting predators. (3) The sexes differ especially in the size of those eyespots that are displayed during active behavior. (4) Species from seasonal and aseasonal environments react in a broadly similar manner to temperature variation. However, savannah species and species of aseasonal rainforest exhibit relatively shallow reaction norms, whereas reaction norms are steeper in species from the savannah-rainforest ecotone. Such a strong response was also apparent in so-called correlation networks between principal components for these species. (5) Phylogenetic distances are to some extent reflected in ordination in both PCA-space and DFA-space: closely related species of the safitza group remain close in both ordinations. The more distantly related species differ in ordination from a pattern as suggested by a phylogenetic reconstruction. It is argued that the wing pattern variation of these species reflects both adaptive processes and historical relationships.

Spectra of water in the near- and mid-infrared region

Spectra of water have been acquired in the mid-infrared (MIR) and the near-infrared (NIR) region in the temperature range 2–96°C and 4–52°C, respectively. Loading plots from partial-least-squares regression were used to locate isosbestic points in the spectra bands of water. By means of least-squares, the original spectral profiles have been resolved into two spectra, one increasing and the other decreasing with temperature. Concentration profiles of the two structurally different water associations, for the investigated temperature range, were obtained by use of evolutionary curve resolution and first-order differentiation of the MIR spectra. Utilising information from the concentration profiles obtained in the MIR, the NIR spectra were resolved. Relative concentrations were obtained using spectral intensities from the isosbestic points. The complexity in both the fundamental and overtone region of the spectra shows that both structures of water are involved in H-bonding. This result indicates a pseudo-first-order reaction in water, either between an open and a more dense state, or between a rigid, strongly H-bonded state and a more loosely H-bonded state. The cross-correlation pattern between the two regions can be ascribed to the temperature-induced variation in the concentration of the two associations.

Measurement of Significant Marine Paleotemperature Variation Using Black Abalone Shells from Prehistoric Middens

The archaeological record from the last millennium in southern California indicates that a period of significant cultural change was associated with a reported marine paleoenvironmental disruption ca. 1150-1250 A.D. A lengthy warm-water anomaly may have in part precipitated more complex sociopolitical and economic responses. We develop independent verification of the perturbation (originally deduced from sediment core data) using archaeological data. Respiratory pore number allometry in the black abalone shell is known to vary clinally in modern populations in response to temperature-induced variation in rate of growth. We use developmental trajectories of abalone from dated, stratified archaeological deposits to reconstruct prehistoric seawater temperatures.

Dielectric and EPR measurements of a main-chain liquid crystalline polyazine. Advanced tools to study thermal behavior

The thermal behaviour of the nematic main-chain polyazine [OPh(OH)-CH=NN=CH-Ph(OH)O(CH 2 ) 12 ] n is investigated. The conductivity contribution to dielectric measurements and the temperature-induced variation of paramagnetic units seen by EPR spectroscopy suggest the thermal generation of active intermediates. Changes in polymer inherent viscosity on heating show an increase in the degree of polymerization in the solid state

Long-term growth dynamics of young Pacific halibut: evidence of temperature-induced variation

The first five otolith growth zones of 744 Pacific halibut from 26 year-classes (1953–1978) were analyzed to identify patterns of annual growth and the sources of temporal variation. Sexual differences in growth appeared at an early age, and size selectivity of the gear types was shown to influence the perception of past growth. We adjusted the growth record for these two effects by removing variation in annual otolith growth that was linearly related to the size of the fish at capture. Correlation patterns of the otolith zones at the youngest ages suggested a general uncoupling of individual growth from one year to the next. Temporal variation was examined by developing a linear model to partition growth at different ages into both year and year-class effects. Randomization tests indicated that both effects are significant when all five ages are included, but when subsets of the data are examined, the year effect is strongest for youngest juveniles, whereas the year-class effect is significant for older juveniles. The year effect is probably attributable to interannual temperature changes, as indicated by a strong linear relationship between sea surface temperature (SST) and otolith growth from ages 0 to 2 years. However, analysis of residuals indicated a remaining year effect, suggesting that SST is an imperfect measure of the actual environment that regulates juvenile growth. The year-class effect observed in older juveniles was not present in the data adjusted for size selectivity, suggesting that this effect could be influenced by sampling bias, though intrinsic influences cannot be ruled out. Density-dependent growth did not appear to be a factor accounting for growth variation; instead, there appeared to be a slight positive correlation between otolith growth at ages 1 and 2 years and estimated year-class abundance (at age 8 years), suggesting that early growth is a factor in determining year-class strength.

Temperature-induced variation in reproductive success: field and control experiments with the C4 grass Echinochloa crus-galli

To examine the influence of weather patterns on the flowering of a C4 plant, 11 transplant gardens were sown with seeds of Echinochloa crus-galli var. crus-galli within and beyond the species range. Both the isolated effect of climate and the joint effect of competition and soil quality on the flowering of E. crus-galli were analyzed. Although vegetative growth was significantly more vigorous in the southernmost site, Echinochloa plants were able to grow actively even at high latitudes. Conversely, flowering decreased gradually from south to north. The maximum temperature in August was the best predictor of floral emergence. Data from controlled experiments confirmed that flowering of E. crus-galli was size independent, and temperature was shown to have an effect on biomass accumulation and allocation as well as on floral emergence. Plants grown in the coolest thermoperiod produced a small number of heavy seeds, whose germinability was superior to that of plants grown in the other temperature treatments. Finally, the results indicate that maternal families represent a significant source of variability for reproductive characteristics. The presence of genetic effects suggests that E. crus-galli has the potential for further evolution with regard to temperature. Key words: flowering, reproduction, low temperature, C4 plants, Echinochloa crus-galli.

A 300-MHz digitally compensated SAW oscillator

A method for compensating for the inherent temperature sensitivity of surface-acoustic-wave (SAW) oscillators is described. Results for a 300-MHz digitally compensated SAW oscillator (DCSO) show a reduction of temperature-induced frequency variation from +/-125 parts per million to +/-1.4 parts per million over the temperature range of -23 to 75 degrees C. This is accomplished using simple digital circuitry and microprocessor control. The temperature-sensing scheme, using a SAW structure with two delay paths of different temperature sensitivity on the same AT-cut quartz substrate, virtually eliminates thermal resistance and time-constant problems. Advantages over ovenized systems include fast warmup; reduced size, weight, and power dissipation; low cost potential; and the ability to compensate for other sources of frequency drift.

Thermoexcited dipole glasslike phase in the crystals with Jahn-Teller ions

Abstract The rare-earth ions in crystals have as a rule some low laying excited energy levels. Properties of the ion on the ground or excited states are generally different, so the temperature variations of excited states population can change polarization properties of crystals remarkably. Such effect should be particularly important in the case of the crystals with Jahn-Teller ions, because of the strong coupling between the electron state and the ligand distortion for these ions. In this connection Eu+3 containing compounds are of the most interest. The ground state of Eu+3 ions is nondegenerate (7F0), but the lowest excited one in the contrary is degenerate (7F1). The energy splitting of 7F0−7F1 states is 300 cm−1. Therefore, for such crystals the changes of properties caused by temperature-induced variation of population of excited (7F1) state, may be strong. Besides, such changes have to be observed over the convenient temperature range.

Effects of temperature on the body form, growth, electron transport system activity, and development rate of an echinopluteus

The development rate from fertilization to the six-armed pluteus stage in Dendraster excentricus (Eschscholtz, 1829) was markedly temperature-dependent. It took three times as long to reach the six-armed stage at 12°C as it did at 22°C. The respiratory electron transport system (ETS) activity of six-armed plutei was also temperature-dependent between 12 and 22°C at a limiting substrate concentration. In spite of temperature-induced variation in development rate and metabolism, body size (length and protein content) and shape (ciliated band length and body symmetry) of the six-armed plutei did not vary with culture temperature. The sequence of form changes during larval development from the two-armed to the eight-armed stage were also independent of temperature (10–15°C). Plutei, given excess food, maintained the correspondence between growth rate and development rate. An important consequence of form constancy is the lack of change in ciliated band length with temperature. Band length determines larval feeding capability, defined as the maximal volume of water cleared of particles per unit time per larva. Since ETS activity is temperature-dependent, metabolic demand should increase with increasing temperature. It might be difficult for plutei (and other organisms that feed with the single band, upstream particle capture mechanism) to maintain energy balance under natural, food limiting conditions at high temperature. This could result in smaller larvae or modification of larval shape.

Advertisement Call Variation and Observations on Breeding Behavior of Bufo debilis and B. punctatus

ABsTRAcr.-Advertisement calls of Bufo debilis and B. punctatus were analyzed to determine if variation in calls was correlated with body size and temperature. Advertisement call variables (frequency, pulse rate or call duration) were not significantly correlated with male snout-vent length in either species. All three call variables, as well as call rate, were significantly correlated with body temperature in B. punctatus; analysis of temperature-induced variation was not possible for B. debilis. Observations revealed that males of neither species employ satellite or active-searching strategies to locate females in choruses. To initiate amplexus a female approaches a calling male and the male continues to vocalize until the female makes physical contact. These results are discussed in relation to previous work with bufonids. Breeding behavior of a number of anurans has recently been subjected to sociobiological analysis (see reviews by Wells, 1977; Sullivan, 1983a). These and other studies have generated considerable controversy concerning the means by which non-random mating can arise in anuran breeding aggregations (Woodward, 1982; Sullivan, 1983a).

Injection photoconductivity and photovoltage in metal/tetracene/metal sandwich systems

Steady state and pulsed photoconduction ( i ) and photovoltaic ( U oc , i sc measurements were made on vacuum-evaporated tetracene films sandwiched between two aluminium or two gold semitransparent electrodes. The properties of the cells are shown to be strongly dependent on whether the substrate (S) or the non-substrate (NS) electrode is illuminated. A theoretical model is presented to explain the photoconduction and photovoltaic characteristics of the cells. The model is based on the assumption that charge carriers (holes) are injected into the band and to surface traps at the contacts by triplet excitons created by the exciting light in the tetracene layer. The charge introduced into the sample, in turn, affects the diffusion flux of triplet excitons reaching the electrodes. The energy and space distributions of traps are different at the S and the NS electrode. This causes triplet excitons to be more strongly quenched on their way to the S electrode than to the NS electrode. Predictions of the model are shown to agree with the experimental action spectra and the dependence of i , U oc and i sc on the light intensity I o . In particular, it allows the sublinear dependence of the emission-limited photocurrent on I o and the characteristic reversals of sign in the action spectra and in the dependence of U oc on I o to be explained. The cells studied entirely under vacuum (2 x 10 -3 Pa) showed no chane in the shape of the action spectra but the value of U oc decreased by a maximum of about one order of magnitude. The influence of the temperature could be rationalized by a temperature-induced variation in the trap parameter l and a change in the ratio of the dark to the photoinjection efficiency.

Oxygen isotope variation on a lagoonal platform reef, Heron island, Great Barrier Reef

A survey of temperature, salinity and oxygen isotope ratio was conducted on the reefal waters of a lagoonal platform reef, Heron Reef, situated near the southern end of the Great Barrier Reef. The oxygen isotope ratio of the water changed by nearly 2‰ during a 3-week period. Daily variations of 1.4‰ were detected. As the maximum oxygen isotope ratios occurred at low tide, during times of high temperature and high salinity, temperature-induced variation in oxygen isotope ratios of skeletal material was masked. Such a phenomenon can easily explain why previous workers have failed to detect the full range of oxygen isotope ratios in coral skeletons and other calcareous organisms.

A temperature-induced variation in the intrinsic hyperfine separation of a tightly bound nitroxide spin label

A temperature-induced variation in the intrinsic hyperfine separation of a tightly bound nitroxide spin label