Behavioural fever is a synergic signal amplifying the innate immune response.

PubMed

Boltaña, Sebastian; Rey, Sonia; Roher, Nerea; Vargas, Reynaldo; Huerta, Mario; Huntingford, Felicity Anne; Goetz, Frederick William; Moore, Janice; Garcia-Valtanen, Pablo; Estepa, Amparo; Mackenzie, S

2013-09-07

Behavioural fever, defined as an acute change in thermal preference driven by pathogen recognition, has been reported in a variety of invertebrates and ectothermic vertebrates. It has been suggested, but so far not confirmed, that such changes in thermal regime favour the immune response and thus promote survival. Here, we show that zebrafish display behavioural fever that acts to promote extensive and highly specific temperature-dependent changes in the brain transcriptome. The observed coupling of the immune response to fever acts at the gene-environment level to promote a robust, highly specific time-dependent anti-viral response that, under viral infection, increases survival. Fish that are not offered a choice of temperatures and that therefore cannot express behavioural fever show decreased survival under viral challenge. This phenomenon provides an underlying explanation for the varied functional responses observed during systemic fever. Given the effects of behavioural fever on survival and the fact that it exists across considerable phylogenetic space, such immunity-environment interactions are likely to be under strong positive selection.

Potentially exploitable supercritical geothermal resources in the ductile crust

USGS Publications Warehouse

Watanabe, Noriaki; Numakura, Tatsuya; Sakaguchi, Kiyotoshi; Saishu, Hanae; Okamoto, Atsushi; Ingebritsen, Steven E.; Tsuchiya, Noriyoshi

2017-01-01

The hypothesis that the brittle–ductile transition (BDT) drastically reduces permeability implies that potentially exploitable geothermal resources (permeability >10−16 m2) consisting of supercritical water could occur only in rocks with unusually high transition temperatures such as basalt. However, tensile fracturing is possible even in ductile rocks, and some permeability–depth relations proposed for the continental crust show no drastic permeability reduction at the BDT. Here we present experimental results suggesting that the BDT is not the first-order control on rock permeability, and that potentially exploitable resources may occur in rocks with much lower BDT temperatures, such as the granitic rocks that comprise the bulk of the continental crust. We find that permeability behaviour for fractured granite samples at 350–500 °C under effective confining stress is characterized by a transition from a weakly stress-dependent and reversible behaviour to a strongly stress-dependent and irreversible behaviour at a specific, temperature-dependent effective confining stress level. This transition is induced by onset of plastic normal deformation of the fracture surface (elastic–plastic transition) and, importantly, causes no ‘jump’ in the permeability. Empirical equations for this permeability behaviour suggest that potentially exploitable resources exceeding 450 °C may form at depths of 2–6 km even in the nominally ductile crust.

On the heterogeneity of fluorescence lifetime of room temperature ionic liquids: onset of a journey for exploring red emitting dyes.

PubMed

Ghosh, Anup; Chatterjee, Tanmay; Mandal, Prasun K

2012-06-25

An excitation and emission wavelength dependent non-exponential fluorescence decay behaviour of room temperature ionic liquids (RTILs) has been noted. Average fluorescence lifetimes have been found to vary by a factor of three or more. Red emitting dyes dissolved in RTILs are found to follow hitherto unobserved single exponential fluorescence decay behaviour.

Field induced polarization and magnetization behaviour of Gd-doped lead magnesium niobate ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pandey, Adityanarayan, E-mail: apandey@rrcat.gov.in, E-mail: padityanarayan5@gmail.com; Laser Materials Development and Devices Division, Raja Ramanna Centre for Advanced Technology, Indore – 452013; Gupta, Surya Mohan

2016-05-23

Both superparaelectric and superparamagnetic behaviour has been observed in rare earth magnetic ion Gd{sup 3+} doped Lead Magnesium Niobate (Gd-PMN). Field induced polarization and magnetization studies reveal hystresis loss free P-E and M-H loop at 300 K and 5 K, respectively. Temperature dependence of inverse susceptibility plot shows deviation at a temperature “t{sub d}” when fitted with the Curie-Weiss law. This deviation has been attributed to transition from paramagnetic to superparamagnetic behaviour as reported in amorphous Pd-Ni-Fe-P alloys.

Influence of smooth temperature variation on hotspot ignition

NASA Astrophysics Data System (ADS)

Reinbacher, Fynn; Regele, Jonathan David

2018-01-01

Autoignition in thermally stratified reactive mixtures originates in localised hotspots. The ignition behaviour is often characterised using linear temperature gradients and more recently constant temperature plateaus combined with temperature gradients. Acoustic timescale characterisation of plateau regions has been successfully used to characterise the type of mechanical disturbance that will be created from a plateau core ignition. This work combines linear temperature gradients with superelliptic cores in order to more accurately account for a local temperature maximum of finite size and the smooth temperature variation contained inside realistic hotspot centres. A one-step Arrhenius reaction is used to model a H2-air reactive mixture. Using the superelliptic approach a range of behaviours for temperature distributions are investigated by varying the temperature profile between the gradient only and plateau and gradient bounding cases. Each superelliptic case is compared to a respective plateau and gradient case where simple acoustic timescale characterisation may be performed. It is shown that hot spots equivalent with excitation-to-acoustic timescale ratios sufficiently greater than unity exhibit behaviour very similar to a simple plateau-gradient model. However, for larger hot spots with timescale ratios sufficiently less than unity the reaction behaviour is highly dependent on the smooth temperature profile contained within the core region.

Host-pathogen interactions in a varying environment: temperature, behavioural fever and fitness.

PubMed Central

Elliot, Sam L; Blanford, Simon; Thomas, Matthew B

2002-01-01

We demonstrate how variable temperatures, mediated by host thermoregulation and behavioural fever, critically affect the interaction between a host (the desert locust, Schistocerca gregaria) and a pathogen (the fungus Metarhizium anisopliae var. acridum). By means of behavioural thermoregulation, infected locusts can raise their body temperatures to fever levels. The adaptive value of this behaviour was examined using three thermal regimes wherein maximum body temperatures achievable were: (i) below, or (ii) at normally preferred temperatures, or were (iii) unrestricted, allowing heightened fever temperatures. All infected locusts ultimately succumbed to disease, with median survival times of 8, 15 and 21 days post-infection, respectively. Crucially, only those locusts able to fever produced viable offspring. This represents, to our knowledge, the first demonstration of the adaptive value of behavioural fever following infection with a naturally occurring pathogen. By contrast, although normal host thermoregulation moderately reduced pathogen reproduction (by 35%), there was no additional negative effect of fever, resulting in an asymmetry in the fitness consequences of fever for the host and the pathogen. The dependency of the host-pathogen interaction upon external abiotic conditions has implications for how virulence and resistance are treated both theoretically and in the management of pests and diseases. PMID:12184830

Warming increases chlorpyrifos effects on predator but not anti-predator behaviours.

PubMed

Dinh Van, Khuong; Janssens, Lizanne; Debecker, Sara; Stoks, Robby

2014-07-01

Recent insights indicate that negative effects of pesticides on aquatic biota occur at concentrations that current legislation considers environmentally protective. We here address two, potentially interacting, mechanisms that may contribute to the underestimation of the impact of sublethal pesticide effects in single species tests at room temperature: the impairment of predator and antipredator behaviours and the stronger impact of organophosphate pesticides at higher temperatures. To address these issues we assessed the effects of chlorpyrifos on the predator and antipredator behaviours of larvae of the damselfly Ischnura elegans, important intermediate predators in aquatic food webs, in a common-garden warming experiment with replicated low- and high-latitude populations along the latitudinal gradient of this species in Europe. Chlorpyrifos reduced the levels of predator behavioural endpoints, and this reduction was stronger at the higher temperature for head orientations and feeding strikes. Chlorpyrifos also impaired two key antipredator behavioural endpoints, activity reductions in response to predator cues were smaller in the presence of chlorpyrifos, and chlorpyrifos caused a lower escape swimming speed; these effects were independent of temperature. This suggests chlorpyrifos may impact food web interactions by changing predator-prey interactions both with higher (predators) and lower trophic levels (food). Given that only the interaction with the lower trophic level was more impaired at higher temperatures, the overall pesticide-induced changes in food web dynamics may be strongly temperature-dependent. These findings were consistent in damselflies from low- and high-latitude populations, illustrating that thermal adaptation will not mitigate the increased toxicity of pesticides at higher temperatures. Our study not only underscores the relevance of including temperature and prey-predator interactions in ecological risk assessment but also their potential interplay and thereby highlights the complexity of contaminant effects on predator-prey interactions being differentially temperature-dependent pending on the trophic level. Copyright © 2014 Elsevier B.V. All rights reserved.

Compensation for environmental change by complementary shifts of thermal sensitivity and thermoregulatory behaviour in an ectotherm.

PubMed

Glanville, E J; Seebacher, F

2006-12-01

Thermoregulating animals are thought to have evolved a preferred body temperature at which thermally sensitive performance is optimised. Even during thermoregulation, however, many animals experience pronounced variability in body temperature, and may regulate to different body temperatures depending on environmental conditions. Here we test the hypothesis that there is a trade-off between regulating to lower body temperatures in cooler conditions and locomotory and metabolic performance. Animals (estuarine crocodiles, Crocodylus porosus) acclimated to cold (N=8) conditions had significantly lower maximum and mean daily body temperatures after 33 days than warm-acclimated animals (N=9), despite performing characteristic thermoregulatory behaviours. Concomitant with behavioural changes, maximum sustained swimming speed (U(crit)) shifted to the respective mean body temperatures during acclimation (cold=20 degrees C, warm=29 degrees C), but there was no difference in the maxima between acclimation groups. Mitochondrial oxygen consumption changed significantly during acclimation, and maximum respiratory control ratios coincided with mean body temperatures in liver, muscle and heart tissues. There were significant changes in the activities of regulatory metabolic enzymes (lactate dehydrogenase, citrate synthase, cytochrome c oxidase) and these were tissue specific. The extraordinary shift in behaviour and locomotory and metabolic performance shows that within individuals, behaviour and physiology covary to maximise performance in different environments.

Grain boundary-dominated electrical conduction and anomalous optical-phonon behaviour near the Neel temperature in YFeO3 ceramics

NASA Astrophysics Data System (ADS)

Raut, Subhajit; Babu, P. D.; Sharma, R. K.; Pattanayak, Ranjit; Panigrahi, Simanchalo

2018-05-01

We investigated the anomalous behaviour in the dielectric properties, occurring nearly at room temperature and at elevated temperatures (near the Neel temperature TN) of the polycrystalline samples of YFeO3 (YFO) ceramics. On the prepared YFO ceramics, the magnetic measurements showed the Neel temperature of YFO to be 650 K, below which the compound exhibited the weak ferromagnetic behaviour. X-ray photoelectron spectroscopy (XPS) shows the presence of Fe ions (Fe2+ and Fe3+ states) and also revealed the formation of the oxygen vacancies. The frequency dependence of the complex dielectric constant within the frequency domain of 100 Hz-1 MHz shows the presence of grain dominated dielectric relaxation over the thermal window of 300-373 K. The activation energy Eact.ɛ=0.611 eV extracted from the imaginary permittivity spectrum indicates the involvement of oxygen vacancies in the relaxation process. Above 493 K, the ac conductivity, complex impedance, and modulus studies revealed appreciable conduction and relaxation processes occurring in YFO ceramics with respective activation energies Eac t . σ=1.362 eV and Eac t . Z=1.345 eV , which suggests that the oxygen vacancies are also involved for the anomalous behaviour of the dielectric constant at elevated temperatures. The temperature dependent Raman spectroscopic measurements within the thermal window of 298-698 K showed anomalous variations of the line widths and frequencies of several Raman active modes above 473 K up to the vicinity of TN pointing towards the presence of admixtures of the electron-phonon and spin-phonon coupling in the system. A further study on the thermal variation of the B2g(4) mode frequency with [M(T)/MS]2 shows the occurrence of strong spin-phonon (s-p) coupling, while the line shape shows the presence of the Fano asymmetry, suggesting spin dependent electron-phonon (e-p) coupling in the system below TN.

Influence of smooth temperature variation on hotspot ignition

DOE PAGES

Reinbacher, Fynn; Regele, Jonathan David

2017-10-06

Autoignition in thermally stratified reactive mixtures originates in localised hotspots. The ignition behaviour is often characterised using linear temperature gradients and more recently constant temperature plateaus combined with temperature gradients. Acoustic timescale characterisation of plateau regions has been successfully used to characterise the type of mechanical disturbance that will be created from a plateau core ignition. This work combines linear temperature gradients with superelliptic cores in order to more accurately account for a local temperature maximum of finite size and the smooth temperature variation contained inside realistic hotspot centres. A one-step Arrhenius reaction is used to model a H 2–airmore » reactive mixture. Using the superelliptic approach a range of behaviours for temperature distributions are investigated by varying the temperature profile between the gradient only and plateau and gradient bounding cases. Each superelliptic case is compared to a respective plateau and gradient case where simple acoustic timescale characterisation may be performed. It is shown that hot spots equivalent with excitation-to-acoustic timescale ratios sufficiently greater than unity exhibit behaviour very similar to a simple plateau-gradient model. Furthermore, for larger hot spots with timescale ratios sufficiently less than unity the reaction behaviour is highly dependent on the smooth temperature profile contained within the core region.« less

Influence of smooth temperature variation on hotspot ignition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reinbacher, Fynn; Regele, Jonathan David

Autoignition in thermally stratified reactive mixtures originates in localised hotspots. The ignition behaviour is often characterised using linear temperature gradients and more recently constant temperature plateaus combined with temperature gradients. Acoustic timescale characterisation of plateau regions has been successfully used to characterise the type of mechanical disturbance that will be created from a plateau core ignition. This work combines linear temperature gradients with superelliptic cores in order to more accurately account for a local temperature maximum of finite size and the smooth temperature variation contained inside realistic hotspot centres. A one-step Arrhenius reaction is used to model a H 2–airmore » reactive mixture. Using the superelliptic approach a range of behaviours for temperature distributions are investigated by varying the temperature profile between the gradient only and plateau and gradient bounding cases. Each superelliptic case is compared to a respective plateau and gradient case where simple acoustic timescale characterisation may be performed. It is shown that hot spots equivalent with excitation-to-acoustic timescale ratios sufficiently greater than unity exhibit behaviour very similar to a simple plateau-gradient model. Furthermore, for larger hot spots with timescale ratios sufficiently less than unity the reaction behaviour is highly dependent on the smooth temperature profile contained within the core region.« less

Highly Conducting Molecular Crystals.

NASA Astrophysics Data System (ADS)

Whitehead, Roger James

Available from UMI in association with The British Library. Requires signed TDF. As the result of a wide ranging effort towards the preparation of new electrically conducting molecular crystals, high quality samples were prepared of the organic radical-ion salt (TMTSF)_2SbCl _2F_4 {bis-tetramethyltetraselenafulvalene-dichlorotetrafluoroantimonate(V) }. A collaborative effort to investigate the electronic and structural properties of this material has yielded the necessary depth of information required to give a satisfactory understanding of its rather complicated behaviour. The combination of x-ray structural studies with d.c. transport, reflectance and magnetic measurements has served to underline the importance of crystalline perfection, electronic dimensionality and conduction electron correlation in determining the materials overall behaviour. This thesis describes the method of preparation and characterization of (TMTSF)_2SbCl _2F_4 and the experimental arrangements used to determine the temperature dependence of its ambient pressure electrical conductivity, thermopower and electron spin resonance spectra. The crystal structure and optical reflectance measurements at room temperature are also presented. The results into a study of the low temperature diffraction pattern are described along with the temperature dependence in the static magnetic susceptibility and in the conductivity behaviour under elevated hydrostatic pressures. These findings are rationalized by reference to other materials which show similar behaviour in their electronic and/or structural properties, and also to the various theoretical models currently enjoying favour.

Organometallic macromolecules with piano stool coordination repeating units: chain configuration and stimulated solution behaviour.

PubMed

Cao, Kai; Ward, Jonathan; Amos, Ryan C; Jeong, Moon Gon; Kim, Kyoung Taek; Gauthier, Mario; Foucher, Daniel; Wang, Xiaosong

2014-09-11

Theoretical calculations illustrate that organometallic macromolecules with piano stool coordination repeating units (Fe-acyl complex) adopt linear chain configuration with a P-Fe-C backbone surrounded by aromatic groups. The macromolecules show molecular weight-dependent and temperature stimulated solution behaviour in DMSO.

Influence of the particle size and intrinsic magnetic characteristics on the coercivity of sintered magnets

NASA Astrophysics Data System (ADS)

Turilli, G.; Paoluzi, A.; Lucenti, M.; Pareti, L.

1992-02-01

Using sintered specimens of Ba-hexaferrite powders as a model system, a study was made of the dependence of coercivity on the particle dimensions and on the temperature from RT up to the Curie temperature. The temperature behaviour of the coercive and anisotropy field are the same in single-domain particle specimens while they are rather different in polydomain particle specimens. However, the coercivity behaviour of both systems can be fitted well up to 350°C using a simple relation between Hc, HA, and Ms. Further contributions to the coercivity have to be taken into account at higher temperatures.

Does sex-ratio selection influence nest-site choice in a reptile with temperature-dependent sex determination?

PubMed

Mitchell, Timothy S; Maciel, Jessica A; Janzen, Fredric J

2013-12-07

Evolutionary theory predicts that dioecious species should produce a balanced primary sex ratio maintained by frequency-dependent selection. Organisms with environmental sex determination, however, are vulnerable to maladaptive sex ratios, because environmental conditions vary spatio-temporally. For reptiles with temperature-dependent sex determination, nest-site choice is a behavioural maternal effect that could respond to sex-ratio selection, as mothers could adjust offspring sex ratios by choosing nest sites that will have particular thermal properties. This theoretical prediction has generated decades of empirical research, yet convincing evidence that sex-ratio selection is influencing nesting behaviours remains absent. Here, we provide the first experimental evidence from nature that sex-ratio selection, rather than only viability selection, is probably an important component of nest-site choice in a reptile with temperature-dependent sex determination. We compare painted turtle (Chrysemys picta) neonates from maternally selected nest sites with those from randomly selected nest sites, observing no substantive difference in hatching success or survival, but finding a profound difference in offspring sex ratio in the direction expected based on historical records. Additionally, we leverage long-term data to reconstruct our sex ratio results had the experiment been repeated in multiple years. As predicted by theory, our results suggest that sex-ratio selection has shaped nesting behaviour in ways likely to enhance maternal fitness.

Does sex-ratio selection influence nest-site choice in a reptile with temperature-dependent sex determination?

PubMed Central

Mitchell, Timothy S.; Maciel, Jessica A.; Janzen, Fredric J.

2013-01-01

Evolutionary theory predicts that dioecious species should produce a balanced primary sex ratio maintained by frequency-dependent selection. Organisms with environmental sex determination, however, are vulnerable to maladaptive sex ratios, because environmental conditions vary spatio-temporally. For reptiles with temperature-dependent sex determination, nest-site choice is a behavioural maternal effect that could respond to sex-ratio selection, as mothers could adjust offspring sex ratios by choosing nest sites that will have particular thermal properties. This theoretical prediction has generated decades of empirical research, yet convincing evidence that sex-ratio selection is influencing nesting behaviours remains absent. Here, we provide the first experimental evidence from nature that sex-ratio selection, rather than only viability selection, is probably an important component of nest-site choice in a reptile with temperature-dependent sex determination. We compare painted turtle (Chrysemys picta) neonates from maternally selected nest sites with those from randomly selected nest sites, observing no substantive difference in hatching success or survival, but finding a profound difference in offspring sex ratio in the direction expected based on historical records. Additionally, we leverage long-term data to reconstruct our sex ratio results had the experiment been repeated in multiple years. As predicted by theory, our results suggest that sex-ratio selection has shaped nesting behaviour in ways likely to enhance maternal fitness. PMID:24266033

Structure-dependent water transport across nanopores of carbon nanotubes: toward selective gating upon temperature regulation.

PubMed

Zhao, Kuiwen; Wu, Huiying

2015-04-28

Determining water structure in nanopores and its influence on water transport behaviour is of great importance for understanding and regulating the transport across nanopores. Here we report an ultrafast-slow flow transition phenomenon for water transport across nanopores of carbon nanotubes owing to the change in water structure in nanopores induced by temperature. By performing extensive molecular dynamics simulations, we show the dependence of water transport behaviours on water structures. Our results indicate that owing to the change in water structure in nanopores, water flux across nanopores with certain pore sizes decreases sharply (nearly 3 orders of magnitude) with the decreasing temperature. This phenomenon is very sensitive to the pore size. The threshold temperatures for the occurrence of the ultrafast-slow flow transition for water transport are also determined for various pore sizes. These findings suggest a novel protocol for selective gating of water and proton conduction across nanopores and temperature-controlled drug release.

Temperature and pressure dependence of the optical properties of Cr3+-doped Gd3Ga5O12 nanoparticles.

PubMed

Martín-Rodríguez, R; Valiente, R; Rodríguez, F; Bettinelli, M

2011-07-01

Since the crystal-field strength at the Cr(3+) site is very close to the excited-state crossover (ESCO), this work investigates the optical properties of Cr(3+)-doped Gd(3)Ga(5)O(12) (GGG) nanoparticles as a function of temperature and pressure in order to establish the effect of the ESCO on the optical behaviour of nanocrystalline GGG. Luminescence, time-resolved emission and lifetime measurements have been performed on GGG:0.5% Cr(3+) nanoparticles in the 25-300 K temperature range, as well as under hydrostatic pressure up to 20 GPa. We show how low temperature and high pressure progressively transforms Cr(3+)(4)T(2) --> (4)A(2) broadband emission into a ruby-like (2)E --> (4)A(2) luminescence. This behaviour together with the lifetime dependence on pressure and temperature are explained on the basis of the spin-orbit interaction between the (4)T(2) and (2)E states of Cr(3+).

Thermoelastic behaviour of martensitic alloy in the vicinity of critical point in the stress-temperature phase diagram

NASA Astrophysics Data System (ADS)

L'vov, V. A.; Matsishin, N.; Glavatska, N.

2010-04-01

The theoretical phase diagram of the shape memory alloy, which exhibits the first-order martensitic phase transition of the cubic-tetragonal type, has been considered. The thermoelastic behaviour of the ultra-soft Ni-Mn-Ga alloy in the vicinity of the endpoint of the phase transitions line has been modelled. To this end, the strain-temperature and stress-strain dependencies have been computed with the account of the temperature dependence of the elastic modulus of the alloy. Two important features of thermoelastic behaviour of the alloy have been disclosed: (1) even in the case of complete stress-induced martensitic transformation (MT), the MT strain determined from the length of the plateaus at the stress-strain curves is smaller than the 'spontaneous' tetragonal distortion of the crystal lattice, which arises on cooling of the alloy and (2) the stress-strain loops may include the plateau-like segment even at temperatures above the critical temperature, which corresponds to the endpoint of the stress-strain phase diagram. These features render the observation of the endpoint of phase transitions line impossible with the help of the stress-strain tests and make preferable the direct structural studies of MTs in the stressed single-crystalline specimens.

Influence of strain rate and temperature on tensile properties and flow behaviour of a reduced activation ferritic-martensitic steel

NASA Astrophysics Data System (ADS)

Vanaja, J.; Laha, K.; Sam, Shiju; Nandagopal, M.; Panneer Selvi, S.; Mathew, M. D.; Jayakumar, T.; Rajendra Kumar, E.

2012-05-01

Tensile strength and flow behaviour of a Reduced Activation Ferritic-Martensitic (RAFM) steel (9Cr-1W-0.06Ta-0.22V-0.08C) have been investigated over a temperature range of 300-873 K at different strain rates. Tensile strength of the steel decreased with temperature and increased with strain rate except at intermediate temperatures. Negative strain rate sensitivity of flow stress of the steel at intermediate temperatures revealed the occurrence of dynamic strain ageing in the steel, even though no serrated flow was observed. The tensile flow behaviour of the material was well represented by the Voce strain hardening equation for all the test conditions. Temperature and strain rate dependence of the various parameters of Voce equation were interpreted with the possible deformation mechanisms. The equivalence between the saturation stress at a given strain rate in tensile test and steady state deformation rate at a given stress in creep test was found to be satisfied by the RAFM steel.

Analysis of different forward current-voltage behaviours of Al implanted 4H-SiC vertical p-i-n diodes

NASA Astrophysics Data System (ADS)

Megherbi, M. L.; Pezzimenti, F.; Dehimi, L.; Rao, S.; Della Corte, F. G.

2015-07-01

In this work different experimental current-voltage behaviours of several Al implanted 4H-SiC p-i-n diodes are investigated by means of numerical simulations in a wide range of currents and temperatures. Some devices for which recombination and tunneling are the dominant current processes at all biases are classified as "leaky" diodes. The well behaved diodes, instead, show good rectifying characteristics with a current conduction due to tunneling below 1.7 V, recombination between 1.7 V and 2.5 V, and diffusion processes above 2.5 V. At higher current regimes, a series resistance in excess of 1 mΩ cm2 becomes the main current limiting factor. Depending on the relative weight between the contact resistances and the internal diode resistance, different temperature dependencies of the current are obtained. A good agreement between numerical and measured data is achieved employing temperature-dependent carrier lifetime and mobility as fitting parameters.

Antisite disorder induced spin glass and exchange bias effect in Nd2NiMnO6 epitaxial thin film

NASA Astrophysics Data System (ADS)

Singh, Amit Kumar; Chauhan, Samta; Chandra, Ramesh

2017-03-01

We report the observation of the exchange bias effect and spin glass behaviour at low temperature in a ferromagnetic Nd2NiMnO6 epitaxial thin film. Along with the ferromagnetic transition at ˜194 K, an additional transition is observed at lower temperature (˜55 K) as seen from M-T curves of the sample. A shift in the ac susceptibility peak with frequency has been observed at low temperature, which is a signature of a glassy phase within the sample. The detailed investigation of the memory effect and time dependent magnetic relaxation measurements reveals the presence of a spin glass phase in the Nd2NiMnO6 thin film. The exchange bias effect observed at low temperature in the sample has been associated with an antisite disorder induced spin glass phase, which results in a ferromagnetic/spin glass interface at low temperature. The exchange bias behaviour has been further confirmed by performing cooling field and temperature dependence of exchange bias along with training effect measurements.

Abiotic factors influencing embryonic development, egg hatching, and larval orientation in the reindeer warble fly, Hypoderma tarandi.

PubMed

Karter, A J; Folstad, I; Anderson, J R

1992-10-01

Wild-caught, tethered females of the reindeer warble fly, Hypoderma tarandi (L.) (= Oedemagena tarandi (L.)), (Diptera, Oestridae) were stimulated to oviposit on hairs of a reindeer hide. Newly laid eggs incubated at constant temperatures and relative humidities hatched within 3 days to 2 weeks, depending on the experimental conditions. Over a range of 7-40 degrees C, hatching only occurred between 20 and 37 degrees C. Eggs held at 100% relative humidity had lower hatchability and longer time to hatch relative to eggs held at 77% relative humidity. The average number of degree-days for hatching was 50.35. Between 20 and 33 degrees C there was a temperature-dependent linear trend in developmental rate, and the proportion of eggs hatching was highest, and least variable, at the mid-temperature ranges. The temperature range found in the natural host micro-habitat where H. tarandi commonly affix their eggs (close to the skin at the base of a host hair) was consistent with the experimental temperature treatments that produced the highest hatching rate. Newly emerged larvae displayed positive thermotaxis, while showing no phototaxic or geotaxic behaviour. Results indicate that constraints of the host environment, coupled with temperature-dependent hatching success, may impose a selective pressure on oviposition behaviour.

Polarization behaviour of polyvinylidenefluoride-polysulfone (PVDF: PSF) blends under high field and high temperature condition

NASA Astrophysics Data System (ADS)

Shrivas, Sandhya; Patel, Swarnim; Dubey, R. K.; Keller, J. M.

2018-05-01

Thermally stimulated discharge currents of PVDF: PSF blend samples in ratio 80:20 and 95:05 prepared by the solution cast technique have been studied as a function of polarizing field and polarizing temperature, the temperature corresponding to a peak in TSDC is found to be independent of polarizing field but dependent on the polarizing temperature.

Temperature behaviour of optical parameters in (Ag3AsS3)0.3(As2S3)0.7 thin films

NASA Astrophysics Data System (ADS)

Kutsyk, Mykhailo M.; Ráti, Yosyp Y.; Izai, Vitalii Y.; Makauz, Ivan I.; Studenyak, Ihor P.; Kökényesi, Sandor; Komada, Paweł; Zhailaubayev, Yerkin; Smailov, Nurzhigit

2015-12-01

(Ag3AsS3)0.3(As2S3)0.7 thin films were deposited onto a quartz substrate by rapid thermal evaporation. The optical transmission spectra of thin films were measured in the temperature range 77-300 K. It is shown that the absorption edge spectra are described by the Urbach rule. The temperature behaviour of absorption spectra was studied, the temperature dependences of energy position of absorption edge and Urbach energy were investigated. The influence of transition from three-dimensional glass to the two-dimensional thin film as well as influence of Ag3AsS3 introduction into As2S3 on the optical parameters of (Ag3AsS3)0.3(As2S3)0.7 were analysed. The spectral and temperature behaviour or refractive index for (Ag3AsS3)0.3(As2S3)0.7 thin film were studied.

Temperature behaviour of the average size of nanoparticle lattices co-deposited with an amorphous matrix. Analysis of Ge + Al2O3 and Ni + Al2O3 thin films

NASA Astrophysics Data System (ADS)

Mezzasalma, Stefano A.; Car, Tihomir; Nekić, Nikolina; Jerčinović, Marko; Buljan, Maja

2017-11-01

We theoretically interpret the thermal behaviour of the average radius versus substrate temperature of regular quantum dot/nanocluster arrays formed by sputtering semiconductor/metal atoms with oxide molecules. The analysis relies on a continuum theory for amorphous films with given surface quantities, perturbed by a nanoparticle lattice. An account of the basic thermodynamic contributions is given in terms of force-flux phenomenological coefficients of each phase (Ge, Ni, Al2O3). Average radii turn out to be expressible by a characteristic length scale and a dimensionless parameter, which mainly depend upon temperature through diffusion lengths, film pressures and finite-size corrections to interfacial tensions. The numerical agreement is good in both Ge (4 % ) and Ni (15.4 % ) lattices grown at temperatures ≤slant 800 K, despite the lower temperature behaviour of quantum dots seeming to suggest further driving forces taking part in such processes.

Low temperature magneto-morphological characterisation of coronene and the resolution of previously observed unexplained phenomena

NASA Astrophysics Data System (ADS)

Potticary, Jason; Boston, Rebecca; Vella-Zarb, Liana; Few, Alex; Bell, Christopher; Hall, Simon R.

2016-12-01

The polyaromatic hydrocarbon coronene has been the molecule of choice for understanding the physical properties of graphene for over a decade. The modelling of the latter by the former was considered to be valid, as since it was first synthesised in 1932, the physical behaviour of coronene has been determined extremely accurately. We recently discovered however, an unforeseen polymorph of coronene, which exists as an enantiotrope with the previously observed crystal structure. Using low-temperature magnetisation and crystallographic measurements, we show here for the first time that the electronic and magnetic properties of coronene depend directly on the temperature at which it is observed, with hysteretic behaviour exhibited between 300 K and 100 K. Furthermore we determine that this behaviour is a direct result of the appearance and disappearance of the newly-discovered polymorph during thermal cycling. Our results not only highlight the need for theoretical models of graphene to take into account this anomalous behaviour at low temperatures, but also explain puzzling experimental observations of coronene dating back over 40 years.

Drosophila Ionotropic Receptor 25a mediates circadian clock resetting by temperature.

PubMed

Chen, Chenghao; Buhl, Edgar; Xu, Min; Croset, Vincent; Rees, Johanna S; Lilley, Kathryn S; Benton, Richard; Hodge, James J L; Stanewsky, Ralf

2015-11-26

Circadian clocks are endogenous timers adjusting behaviour and physiology with the solar day. Synchronized circadian clocks improve fitness and are crucial for our physical and mental well-being. Visual and non-visual photoreceptors are responsible for synchronizing circadian clocks to light, but clock-resetting is also achieved by alternating day and night temperatures with only 2-4 °C difference. This temperature sensitivity is remarkable considering that the circadian clock period (~24 h) is largely independent of surrounding ambient temperatures. Here we show that Drosophila Ionotropic Receptor 25a (IR25a) is required for behavioural synchronization to low-amplitude temperature cycles. This channel is expressed in sensory neurons of internal stretch receptors previously implicated in temperature synchronization of the circadian clock. IR25a is required for temperature-synchronized clock protein oscillations in subsets of central clock neurons. Extracellular leg nerve recordings reveal temperature- and IR25a-dependent sensory responses, and IR25a misexpression confers temperature-dependent firing of heterologous neurons. We propose that IR25a is part of an input pathway to the circadian clock that detects small temperature differences. This pathway operates in the absence of known 'hot' and 'cold' sensors in the Drosophila antenna, revealing the existence of novel periphery-to-brain temperature signalling channels.

Phase behaviour, thermal expansion and compressibility of SnMo2O8

NASA Astrophysics Data System (ADS)

Araujo, Luiza R.; Gallington, Leighanne C.; Wilkinson, Angus P.; Evans, John S. O.

2018-02-01

The phase behaviour and thermoelastic properties of SnMo2O8, derived from variable temperature and pressure synchrotron powder diffraction data, are reported. SnMo2O8 is a member of the AM2O8 family of negative thermal expansion (NTE) materials, but unexpectedly, has positive thermal expansion. Over the P-T space explored (298-513 K, ambient to 310 MPa) four different forms of SnMo2O8 are observed: α, β, γ and γ‧. The γ to β transition is temperature-, pressure-, and time-dependent. SnMo2O8 is a much softer material (α and γ form have BT = 29 and 26 GPa at 298 K) than other members of the AM2O8 family. Counter-intuitively, its high temperature β phase becomes stiffer with increasing temperature (BT ∼36 GPa at 490 K). The pressure dependence of the thermal expansion for each phase is reported.

Phase behaviour, thermal expansion and compressibility of SnMo 2 O 8

DOE Office of Scientific and Technical Information (OSTI.GOV)

Araujo, Luiza R.; Gallington, Leighanne C.; Wilkinson, Angus P.

The phase behaviour and thermoelastic properties of SnMo2O8, derived from variable temperature and pressure synchrotron powder diffraction data, are reported. SnMo2O8 is a member of the AM2O8 family of negative thermal expansion (NTE) materials, but unexpectedly, has positive thermal expansion. Over the P-T space explored (298–513 K, ambient to 310 MPa) four different forms of SnMo2O8 are observed: α, β, γ and γ'. The γ to β transition is temperature-, pressure-, and time-dependent. SnMo2O8 is a much softer material (α and γ form have BT = 29 and 26 GPa at 298 K) than other members of the AM2O8 family.more » Counter-intuitively, its high temperature β phase becomes stiffer with increasing temperature (BT ~36 GPa at 490 K). The pressure dependence of the thermal expansion for each phase is reported.« less

An equation of state based upon a ratio of polynomials (rational) form for the residual Helmholtz energy: application to nitrogen, argon and methane

NASA Astrophysics Data System (ADS)

Gomez-Osorio, Martin A.; Browne, Robert A.; Cristancho, Diego E.; Holste, James C.; Hall, Kenneth R.; Bell, Ian H.

2017-06-01

This work presents an equation of state that contains the residual Helmholtz free energy as a ratio of polynomials in density with temperature-dependent coefficients and demonstrates that it is a viable alternative for describing thermodynamic properties accurately. The specific form of the equation in this work has six density terms in the numerator, three density terms in the denominator, and five temperature parameters for each temperature-dependent coefficient. Nitrogen, argon, and methane serve as prototype fluids to demonstrate the capability of the form to describe p-ρ-T behaviour, vapour pressures, speeds of sound, and isochoric heat capacities up to 1000 MPa. Characteristic curves for several properties of nitrogen generated using the equation exhibit proper behaviour at high temperatures and pressures. Because the equation contains no exponential terms or non-integer exponents, the computational time associated with the new equation is more than a factor of 10 less than that required for similar equations with comparable accuracy.

Time and temperature dependent adsorption-desorption behaviour of pretilachlor in soil.

PubMed

Kaur, Paawan; Kaur, Pervinder

2018-06-04

Understanding and quantifying the adsorption-desorption behaviour of herbicide in soil is imperative for predicting their fate and transport in the environment. In the present study, the effect of time and temperature on the adsorption-desorption behaviour of pretilachlor in soils was investigated using batch equilibration technique. The adsorption-desorption kinetics of pretilachlor in soils was two step process and was well described by pseudo-second-order kinetic model. Freundlich model accurately predicted the sorption behaviour of pretilachlor. The adsorption-desorption of pretilachlor varied significantly with the concentration, temperature and properties of soil viz. organic matter and clay content. All the studied soils had non-linear slopes (n < 1) and degree of nonlinearity increased with increase in clay, organic matter content and temperature (p < 0.05). Desorption of pretilachlor was hysteretic in studied soils and hysteresis coefficient varied from 0.023 to 0.275. Thermodynamic analysis showed that pretilachlor adsorption onto soils was a feasible, spontaneous and endothermic process which becomes more favourable at high temperature. It could be inferred that the adsorption of pretilachlor on soils was physical in nature. Copyright © 2018 Elsevier Inc. All rights reserved.

Influences of the manufacturing process chain design on the near surface condition and the resulting fatigue behaviour of quenched and tempered SAE 4140

NASA Astrophysics Data System (ADS)

Klein, M.; Eifler, D.

2010-07-01

To analyse interactions between single steps of process chains, variations in material properties, especially the microstructure and the resulting mechanical properties, specimens with tension screw geometry were manufactured with five process chains. The different process chains as well as their parameters influence the near surface condition and consequently the fatigue behaviour in a characteristic manner. The cyclic deformation behaviour of these specimens can be benchmarked equivalently with conventional strain measurements as well as with high-precision temperature and electrical resistance measurements. The development of temperature-values provides substantial information on cyclic load dependent changes in the microstructure.

Out of the frying pan into the air—emersion behaviour and evaporative heat loss in an amphibious mangrove fish (Kryptolebias marmoratus)

PubMed Central

Gibson, Daniel J.; Sylvester, Emma V. A.; Turko, Andy J.; Tattersall, Glenn J.; Wright, Patricia A.

2015-01-01

Amphibious fishes often emerse (leave water) when faced with unfavourable water conditions. How amphibious fishes cope with the risks of rising water temperatures may depend, in part, on the plasticity of behavioural mechanisms such as emersion thresholds. We hypothesized that the emersion threshold is reversibly plastic and thus dependent on recent acclimation history rather than on conditions during early development. Kryptolebias marmoratus were reared for 1 year at 25 or 30°C and acclimated as adults (one week) to either 25 or 30°C before exposure to an acute increase in water temperature. The emersion threshold temperature and acute thermal tolerance were significantly increased in adult fish acclimated to 30°C, but rearing temperature had no significant effect. Using a thermal imaging camera, we also showed that emersed fish in a low humidity aerial environment (30°C) lost significantly more heat (3.3°C min−1) than those in a high humidity environment (1.6°C min−1). In the field, mean relative humidity was 84%. These results provide evidence of behavioural avoidance of high temperatures and the first quantification of evaporative cooling in an amphibious fish. Furthermore, the avoidance response was reversibly plastic, flexibility that may be important for tropical amphibious fishes under increasing pressures from climatic change. PMID:26490418

Out of the frying pan into the air--emersion behaviour and evaporative heat loss in an amphibious mangrove fish (Kryptolebias marmoratus).

PubMed

Gibson, Daniel J; Sylvester, Emma V A; Turko, Andy J; Tattersall, Glenn J; Wright, Patricia A

2015-10-01

Amphibious fishes often emerse (leave water) when faced with unfavourable water conditions. How amphibious fishes cope with the risks of rising water temperatures may depend, in part, on the plasticity of behavioural mechanisms such as emersion thresholds. We hypothesized that the emersion threshold is reversibly plastic and thus dependent on recent acclimation history rather than on conditions during early development. Kryptolebias marmoratus were reared for 1 year at 25 or 30°C and acclimated as adults (one week) to either 25 or 30°C before exposure to an acute increase in water temperature. The emersion threshold temperature and acute thermal tolerance were significantly increased in adult fish acclimated to 30°C, but rearing temperature had no significant effect. Using a thermal imaging camera, we also showed that emersed fish in a low humidity aerial environment (30°C) lost significantly more heat (3.3°C min(-1)) than those in a high humidity environment (1.6°C min(-1)). In the field, mean relative humidity was 84%. These results provide evidence of behavioural avoidance of high temperatures and the first quantification of evaporative cooling in an amphibious fish. Furthermore, the avoidance response was reversibly plastic, flexibility that may be important for tropical amphibious fishes under increasing pressures from climatic change. © 2015 The Author(s).

Magnetic relaxation behaviour in Pr{sub 2}NiSi{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pakhira, Santanu, E-mail: santanupakhira20006@gmail.com; Mazumdar, Chandan; Ranganathan, R.

2016-05-06

Time dependent isothemal remanent magnetizatin (IRM) behaviour for polycrystalline compound Pr{sub 2}NiSi{sub 3} have been studied below its characteristic temperature. The compound undergoes slow magnetic relaxation with time. Along with competing interaction, non-magnetic atom disorder plays an important role in formation of non-equilibrium glassy like ground state for this compound.

Temperature induced phonon behaviour in germanium selenide thin films probed by Raman spectroscopy

NASA Astrophysics Data System (ADS)

Taube, A.; Łapińska, A.; Judek, J.; Wochtman, N.; Zdrojek, M.

2016-08-01

Here we report a detailed study of temperature-dependent phonon properties of exfoliated germanium selenide thin films (several tens of nanometers thick) probed by Raman spectroscopy in the 70-350 K temperature range. The temperature-dependent behavior of the positions and widths of the Raman modes was nonlinear. We concluded that the observed effects arise from anharmonic phonon-phonon interactions and are explained by the phenomenon of optical phonon decay into acoustic phonons. At temperatures above 200 K, the position of the Raman modes tended to be linearly dependent, and the first order temperature coefficients χ were  -0.0277, -0.0197 and  -0.031 cm-1 K-1 for B 3g , A g(1) and A g(2) modes, respectively.

Flow behaviour and constitutive modelling of a ferritic stainless steel at elevated temperatures

NASA Astrophysics Data System (ADS)

Zhao, Jingwei; Jiang, Zhengyi; Zu, Guoqing; Du, Wei; Zhang, Xin; Jiang, Laizhu

2016-05-01

The flow behaviour of a ferritic stainless steel (FSS) was investigated by a Gleeble 3500 thermal-mechanical test simulator over the temperature range of 900-1100 °C and strain rate range of 1-50 s-1. Empirical and phenomenological constitutive models were established, and a comparative study was made on the predictability of them. The results indicate that the flow stress decreases with increasing the temperature and decreasing the strain rate. High strain rate may cause a drop in flow stress after a peak value due to the adiabatic heating. The Zener-Hollomon parameter depends linearly on the flow stress, and decreases with raising the temperature and reducing the strain rate. Significant deviations occur in the prediction of flow stress by the Johnson-Cook (JC) model, indicating that the JC model cannot accurately track the flow behaviour of the FSS during hot deformation. Both the multiple-linear and the Arrhenius-type models can track the flow behaviour very well under the whole hot working conditions, and have much higher accuracy in predicting the flow behaviour than that of the JC model. The multiple-linear model is recommended in the current work due to its simpler structure and less time needed for solving the equations relative to the Arrhenius-type model.

Climate warming causes life-history evolution in a model for Atlantic cod (Gadus morhua).

PubMed

Holt, Rebecca E; Jørgensen, Christian

2014-01-01

Climate change influences the marine environment, with ocean warming being the foremost driving factor governing changes in the physiology and ecology of fish. At the individual level, increasing temperature influences bioenergetics and numerous physiological and life-history processes, which have consequences for the population level and beyond. We provide a state-dependent energy allocation model that predicts temperature-induced adaptations for life histories and behaviour for the North-East Arctic stock (NEA) of Atlantic cod (Gadus morhua) in response to climate warming. The key constraint is temperature-dependent respiratory physiology, and the model includes a number of trade-offs that reflect key physiological and ecological processes. Dynamic programming is used to find an evolutionarily optimal strategy of foraging and energy allocation that maximizes expected lifetime reproductive output given constraints from physiology and ecology. The optimal strategy is then simulated in a population, where survival, foraging behaviour, growth, maturation and reproduction emerge. Using current forcing, the model reproduces patterns of growth, size-at-age, maturation, gonad production and natural mortality for NEA cod. The predicted climate responses are positive for this stock; under a 2°C warming, the model predicted increased growth rates and a larger asymptotic size. Maturation age was unaffected, but gonad weight was predicted to more than double. Predictions for a wider range of temperatures, from 2 to 7°C, show that temperature responses were gradual; fish were predicted to grow faster and increase reproductive investment at higher temperatures. An emergent pattern of higher risk acceptance and increased foraging behaviour was also predicted. Our results provide important insight into the effects of climate warming on NEA cod by revealing the underlying mechanisms and drivers of change. We show how temperature-induced adaptations of behaviour and several life-history traits are not only mediated by physiology but also by trade-offs with survival, which has consequences for conservation physiology.

Climate warming causes life-history evolution in a model for Atlantic cod (Gadus morhua)

PubMed Central

Holt, Rebecca E.; Jørgensen, Christian

2014-01-01

Climate change influences the marine environment, with ocean warming being the foremost driving factor governing changes in the physiology and ecology of fish. At the individual level, increasing temperature influences bioenergetics and numerous physiological and life-history processes, which have consequences for the population level and beyond. We provide a state-dependent energy allocation model that predicts temperature-induced adaptations for life histories and behaviour for the North-East Arctic stock (NEA) of Atlantic cod (Gadus morhua) in response to climate warming. The key constraint is temperature-dependent respiratory physiology, and the model includes a number of trade-offs that reflect key physiological and ecological processes. Dynamic programming is used to find an evolutionarily optimal strategy of foraging and energy allocation that maximizes expected lifetime reproductive output given constraints from physiology and ecology. The optimal strategy is then simulated in a population, where survival, foraging behaviour, growth, maturation and reproduction emerge. Using current forcing, the model reproduces patterns of growth, size-at-age, maturation, gonad production and natural mortality for NEA cod. The predicted climate responses are positive for this stock; under a 2°C warming, the model predicted increased growth rates and a larger asymptotic size. Maturation age was unaffected, but gonad weight was predicted to more than double. Predictions for a wider range of temperatures, from 2 to 7°C, show that temperature responses were gradual; fish were predicted to grow faster and increase reproductive investment at higher temperatures. An emergent pattern of higher risk acceptance and increased foraging behaviour was also predicted. Our results provide important insight into the effects of climate warming on NEA cod by revealing the underlying mechanisms and drivers of change. We show how temperature-induced adaptations of behaviour and several life-history traits are not only mediated by physiology but also by trade-offs with survival, which has consequences for conservation physiology. PMID:27293671

The costs of keeping cool in a warming world: implications of high temperatures for foraging, thermoregulation and body condition of an arid-zone bird.

PubMed

du Plessis, Katherine L; Martin, Rowan O; Hockey, Philip A R; Cunningham, Susan J; Ridley, Amanda R

2012-10-01

Recent mass mortalities of bats, birds and even humans highlight the substantial threats that rising global temperatures pose for endotherms. Although less dramatic, sublethal fitness costs of high temperatures may be considerable and result in changing population demographics. Endothermic animals exposed to high environmental temperatures can adjust their behaviour (e.g. reducing activity) or physiology (e.g. elevating rates of evaporative water loss) to maintain body temperatures within tolerable limits. The fitness consequences of these adjustments, in terms of the ability to balance water and energy budgets and therefore maintain body condition, are poorly known. We investigated the effects of daily maximum temperature on foraging and thermoregulatory behaviour as well as maintenance of body condition in a wild, habituated population of Southern Pied Babblers Turdoides bicolor. These birds inhabit a hot, arid area of southern Africa where they commonly experience environmental temperatures exceeding optimal body temperatures. Repeated measurements of individual behaviour and body mass were taken across days varying in maximum air temperature. Contrary to expectations, foraging effort was unaffected by daily maximum temperature. Foraging efficiency, however, was lower on hotter days and this was reflected in a drop in body mass on hotter days. When maximum air temperatures exceeded 35.5 °C, individuals no longer gained sufficient weight to counter typical overnight weight loss. This reduction in foraging efficiency is likely driven, in part, by a trade-off with the need to engage in heat-dissipation behaviours. When we controlled for temperature, individuals that actively dissipated heat while continuing to forage experienced a dramatic decrease in their foraging efficiency. This study demonstrates the value of investigations of temperature-dependent behaviour in the context of impacts on body condition, and suggests that increasingly high temperatures will have negative implications for the fitness of these arid-zone birds. © 2012 Blackwell Publishing Ltd.

Dynamics of a molecular glass former: Energy landscapes for diffusion in ortho-terphenyl

NASA Astrophysics Data System (ADS)

Niblett, S. P.; de Souza, V. K.; Stevenson, J. D.; Wales, D. J.

2016-07-01

Relaxation times and transport processes of many glass-forming supercooled liquids exhibit a super-Arrhenius temperature dependence. We examine this phenomenon by computer simulation of the Lewis-Wahnström model for ortho-terphenyl. We propose a microscopic definition for a single-molecule cage-breaking transition and show that, when correlation behaviour is taken into account, these rearrangements are sufficient to reproduce the correct translational diffusion constants over an intermediate temperature range in the supercooled regime. We show that super-Arrhenius behaviour can be attributed to increasing negative correlation in particle movement at lower temperatures and relate this to the cage-breaking description. Finally, we sample the potential energy landscape of the model and show that it displays hierarchical ordering. Substructures in the landscape, which may correspond to metabasins, have boundaries defined by cage-breaking transitions. The cage-breaking formulation provides a direct link between the potential energy landscape and macroscopic diffusion behaviour.

The tribology of rosin

NASA Astrophysics Data System (ADS)

Smith, J. H.; Woodhouse, J.

2000-08-01

Rosin is well known for its ability to excite stick-slip vibration on a violin string but the precise characteristics of the material which enable it to exhibit this behaviour have not been studied in any detail. A method is described in which the coefficient of friction of rosin is measured during individual cycles of a stick-slip vibration. Friction versus sliding velocity characteristics deduced in this way exhibit hysteresis, similar to that found in other investigations using different materials. No part of the hysteresis loops follow the friction/velocity curve found from steady-sliding experiments. Possible constitutive laws are examined to describe this frictional behaviour. It is suggested by a variety of evidence that contact temperature plays an important role. Friction laws are developed by considering that the friction arises primarily from the shear of a softened or molten layer of rosin, with a temperature-dependent viscosity or shear strength. The temperature of the rosin layer is calculated by modelling the heat flow around the sliding contact. The temperature-based models are shown to reproduce some features of the measurements which are not captured in the traditional model, in which friction depends only on sliding speed. A model based on viscous behaviour of a thin melted layer of rosin gives predictions at variance with observations. However, a model based on plastic yielding at the surface of the rosin gives good agreement with these observations.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dan, K.; Roy, M.; Datta, A.

The present manuscript describes the role of entropic and enthalpic forces mediated by organic non-polar (hexane) and polar (methanol) solvents on the bulk and microscopic phase transition of a well known nematic liquid crystalline material MBBA (N-(4-methoxybenzylidene)-4-butylaniline) through Differential Scanning calorimetry (DSC), UV-Visible (UV–Vis), and Fourier Transform Infrared (FTIR) spectroscopy. DSC study indicates continuous linear decreases in both nematic-isotropic (N-I) phase transition temperature and enthalpy of MBBA in presence of hexane while both these parameters show a saturation after an initial decay in methanol. These distinct transitional behaviours were explained in terms of the “depletion force” model for entropic screeningmore » in hexane and “screening-self-screening” model for methanol. Heating rate dependent DSC studies find that non-Arrhenius behaviour, characteristic of pristine MBBA and a manifestation of non-equilibrium nature [Dan et al., J. Chem. Phys. 143, 094501 (2015)], is preserved in presence of entropic screening in the hexane solution, while it changes to Arrhenius behaviour (signifying equilibrium behaviour) in presence of enthalpic screening in methanol solution. FTIR spectra show similar dependence on the solvent induced screening in the intensities of the imine (—C = N) stretch and the out-of-plane distortion vibrations of the benzene rings of MBBA with hexane and methanol as in DSC, further establishing our entropic and enthalpic screening models. UV–Vis spectra of the electronic transitions in MBBA as a function of temperature also exhibit different dependences of intensities on the solvent induced screening, and an exponential decrease is observed in presence of hexane while methanol completely changes the nature of interaction to follow a linear dependence.« less

Plasticity of preferred body temperatures as means of coping with climate change?

PubMed Central

Gvoždík, Lumír

2012-01-01

Thermoregulatory behaviour represents an important component of ectotherm non-genetic adaptive capacity that mitigates the impact of ongoing climate change. The buffering role of behavioural thermoregulation has been attributed solely to the ability to maintain near optimal body temperature for sufficiently extended periods under altered thermal conditions. The widespread occurrence of plastic modification of target temperatures that an ectotherm aims to achieve (preferred body temperatures) has been largely overlooked. I argue that plasticity of target temperatures may significantly contribute to an ectotherm's adaptive capacity. Its contribution to population persistence depends on both the effectiveness of acute thermoregulatory adjustments (reactivity) in buffering selection pressures in a changing thermal environment, and the total costs of thermoregulation (i.e. reactivity and plasticity) in a given environment. The direction and magnitude of plastic shifts in preferred body temperatures can be incorporated into mechanistic models, to improve predictions of the impact of global climate change on ectotherm populations. PMID:22072284

Plasticity of preferred body temperatures as means of coping with climate change?

PubMed

Gvozdík, Lumír

2012-04-23

Thermoregulatory behaviour represents an important component of ectotherm non-genetic adaptive capacity that mitigates the impact of ongoing climate change. The buffering role of behavioural thermoregulation has been attributed solely to the ability to maintain near optimal body temperature for sufficiently extended periods under altered thermal conditions. The widespread occurrence of plastic modification of target temperatures that an ectotherm aims to achieve (preferred body temperatures) has been largely overlooked. I argue that plasticity of target temperatures may significantly contribute to an ectotherm's adaptive capacity. Its contribution to population persistence depends on both the effectiveness of acute thermoregulatory adjustments (reactivity) in buffering selection pressures in a changing thermal environment, and the total costs of thermoregulation (i.e. reactivity and plasticity) in a given environment. The direction and magnitude of plastic shifts in preferred body temperatures can be incorporated into mechanistic models, to improve predictions of the impact of global climate change on ectotherm populations.

Effects of kainic acid on rat body temperature: unmasking by dizocilpine.

PubMed

Ahlenius, S; Oprica, M; Eriksson, C; Winblad, B; Schultzberg, M

2002-07-01

The effects of intraperitoneal (i.p.) administration of kainic acid (KA) and dizocilpine, alone or in combination, on body temperature of freely moving rats were examined. Injection of saline or dizocilpine (3.0 or 5.0 mg/kg) was followed after an hour by injection of saline or KA (10 mg/kg) and the body temperature was measured at different time points during the first 5 h. KA alone produced an initial short-lasting hypothermia followed by a longer-lasting hyperthermic effect. Administration of dizocilpine alone produced an early increase in core temperature. Pretreatment of KA-injected rats with dizocilpine potentiated the KA-induced hypothermic effect at 30 min and dose-dependently reduced the temperature measured at 1 h after KA-injection without influencing the ensuing hyperthermia.These data suggest that the KA-induced changes in body temperature do not necessarily involve the activation of NMDA-receptors as opposed to KA-induced behavioural changes that are blocked by dizocilpine in a dose-dependent manner. It is unlikely, therefore, that the KA-induced hyperthermia is a result of the KA-induced seizure motor activity. Furthermore, our findings indicate that KA-induced changes in core temperature may be used as a criterion of drug-responsiveness when the behavioural changes are blocked, e.g. with dizocilpine.

The behavioural consequences of sex reversal in dragons

PubMed Central

Li, Hong; Holleley, Clare E.; Elphick, Melanie; Georges, Arthur

2016-01-01

Sex differences in morphology, physiology, and behaviour are caused by sex-linked genes, as well as by circulating sex-steroid levels. Thus, a shift from genotypic to environmental sex determination may create an organism that exhibits a mixture of male-like and female-like traits. We studied a lizard species (Central Bearded Dragon, Pogona vitticeps), in which the high-temperature incubation of eggs transforms genetically male individuals into functional females. Although they are reproductively female, sex-reversed dragons (individuals with ZZ genotype reversed to female phenotype) resemble genetic males rather than females in morphology (relative tail length), general behaviour (boldness and activity level), and thermoregulatory tactics. Indeed, sex-reversed ‘females’ are more male-like in some behavioural traits than are genetic males. This novel phenotype may impose strong selection on the frequency of sex reversal within natural populations, facilitating rapid shifts in sex-determining systems. A single period of high incubation temperatures (generating thermally induced sex reversal) can produce functionally female individuals with male-like (or novel) traits that enhance individual fitness, allowing the new temperature-dependent sex-determining system to rapidly replace the previous genetically based one.

Magnetic dynamic properties of electron-doped La(0.23)Ca(0.77)MnO3 nanoparticles.

PubMed

Dolgin, B; Puzniak, R; Mogilyansky, D; Wisniewski, A; Markovich, V; Jung, G

2013-02-20

Magnetic properties of basically antiferromagnetic La(0.23)Ca(0.77)MnO(3) particles with average sizes of 12 and 60 nm have been investigated in a wide range of magnetic fields and temperature. Particular attention has been paid to magnetization dynamics through measurements of the temperature dependence of ac-susceptibility at various frequencies, the temperature and field dependence of thermoremanent and isothermoremanent magnetization originating from nanoparticles shells, and the time decay of the remanent magnetization. Experimental results and their analysis reveal the major role in magnetic behaviour of investigated antiferromagnetic nanoparticles played by the glassy component, associated mainly with the formation of the collective state formed by ferromagnetic clusters in frustrated coordination at the surfaces of interacting antiferromagnetic nanoparticles. Magnetic behaviour of nanoparticles has been ascribed to a core-shell scenario. Magnetic transitions have been found to play an important role in determining the dynamic properties of the phase separated state of coexisting different magnetic phases.

Crystallization behaviour of nanostructured hybrid SiO2-TiO2 gel glasses to nanocomposites.

PubMed

Tsvetelina, Gerganova; Yordanka, Ivanova; Yuliya, Vueva; Miranda, Salvado Isabel M; Helena, Fernandes Maria

2010-04-01

The crystallization behaviour of hybrid SiO2-TiO2 nanocomposites derived from titanosiloxanes by sol-gel method has been investigated depending on the type of siloxane precursor and the pirolysis temperature. The resulting hybrid titanosiloxanes, crosslinked with trimethylsilil isocyanate (nitrogen-modified) or methyltrietoxisilane (carbon-modified), were pirolyzed in an inert atmosphere in the temperature range between 600 to 1100 degrees C in order to form C-(N)-Si-O-TiO2 nanocomposites. By means of XRD, FTIR, 29Si NMR, SEM, TEM and AFM investigations have been established that the transformation of the nanostructured SiO2-TiO2 hybrid materials into nanocomposites as well as the crystalline size depend on the titanium content and the type of cross-linking agents used in the synthesizes.

Experimental Characterization and Material Modelling of an AZ31 Magnesium Sheet Alloy at Elevated Temperatures under Consideration of the Tension-Compression Asymmetry

NASA Astrophysics Data System (ADS)

Behrens, B.-A.; Bouguecha, A.; Bonk, C.; Dykiert, M.

2017-09-01

Magnesium sheet alloys have a great potential as a construction material in the aerospace and automotive industry. However, the current state of research regarding temperature dependent material parameters for the description of the plastic behaviour of magnesium sheet alloys is scarce in literature and accurate statements concerning yield criteria and appropriate characterization tests to describe the plastic behaviour of a magnesium sheet alloy at elevated temperatures in deep drawing processes are to define. Hence, in this paper the plastic behaviour of the well-established magnesium sheet alloy AZ31 has been characterized by means of convenient mechanical tests (e. g. tension, compression and biaxial tests) at temperatures between 180 and 230 °C. In this manner, anisotropic and hardening behaviour as well as differences between the tension-compression asymmetry of the yield locus have been estimated. Furthermore, using the evaluated data from the above mentioned tests, two different yield criteria have been parametrized; the commonly used Hill’48 and an orthotropic yield criterion, CPB2006, which was developed especially for materials with hexagonal close packed lattice structure and is able to describe an asymmetrical yielding behaviour regarding tensile and compressive stress states. Numerical simulations have been finally carried out with both yield functions in order to assess the accuracy of the material models.

Characterising the thermoforming behaviour of glass fibre textile reinforced thermoplastic composite materials

NASA Astrophysics Data System (ADS)

Kuhtz, M.; Maron, B.; Hornig, A.; Müller, M.; Langkamp, A.; Gude, M.

2018-05-01

Textile reinforced thermoplastic composites are predestined for highly automated medium- and high-volume production processes. The presented work focusses on experimental studies of different types of glass fibre reinforced polypropylene (GF-PP) semi-finished thermoplastic textiles to characterise the forming behaviour. The main deformation modes fabric shear, tension, thought-thickness compression and bending are investigated with special emphasis on the impact of the textile structure, the deformation temperature and rate dependency. The understanding of the fundamental forming behaviour is required to allow FEM based assessment and improvement of thermoforming process chains.

Low-temperature thermal conductivity of ferroelastic Gd 2(MoO 4) 3

NASA Astrophysics Data System (ADS)

Mielcarek, S.; Mróz, B.; Tylczyński, Z.; Piskunowicz, P.; Trybuła, Z.; Bromberek, M.

2001-05-01

Thermal conductivity, k, of GMO crystal has been measured in temperatures from 0.5 to 80 K. The maximum of k appears at 18 K and its value depends on the current domain state of the sample. The ferroelastic domain walls and antiphase boundaries, characterised by elastic inhomogeneities, are responsible for additional phonon scattering and a decrease in the thermal conductivity. The deviation of the temperature dependence of thermal conductivity from the classical Debye theory observed below 4 K is related to the anomalous behaviour of specific heat in the region of the antiferromagnetic transition at T N=0.3 K .

Thermomechanical properties of polyurethane shape memory polymer-experiment and modelling

NASA Astrophysics Data System (ADS)

Pieczyska, E. A.; Maj, M.; Kowalczyk-Gajewska, K.; Staszczak, M.; Gradys, A.; Majewski, M.; Cristea, M.; Tobushi, H.; Hayashi, S.

2015-04-01

In this paper extensive research on the polyurethane shape memory polymer (PU-SMP) is reported, including its structure analysis, our experimental investigation of its thermomechanical properties and its modelling. The influence of the effects of thermomechanical couplings on the SMP behaviour during tension at room temperature is studied using a fast and sensitive infrared camera. It is shown that the thermomechanical behaviour of the SMP significantly depends on the strain rate: at a higher strain rate higher stress and temperature values are obtained. This indicates that an increase of the strain rate leads to activation of different deformation mechanisms at the micro-scale, along with reorientation and alignment of the molecular chains. Furthermore, influence of temperature on the SMP’s mechanical behaviour is studied. It is observed during the loading in a thermal chamber that at the temperature 20 °C below the glass transition temperature (Tg) the PU-SMP strengthens about six times compared to the material above Tg but does not exhibit the shape recovery. A finite-strain constitutive model is formulated, where the SMP is described as a two-phase material composed of a hyperelastic rubbery phase and elastic-viscoplastic glassy phase. The volume content of phases is governed by the current temperature. Finally, model predictions are compared with the experimental results.

Bio-physical model provides insight into dispersal of plaice (Pleuronectes platessa L.) from putative spawning grounds to nursery areas on the west coast of Ireland

NASA Astrophysics Data System (ADS)

Zölck, Melanie; Brophy, Deirdre; Mohn, Christian; Minto, Cóilín; McGrath, David

2015-05-01

In this study we use an individual-based coupled physical biological model (ICPBM) to reconstruct the dispersal pathways of 0-group juveniles (young of the year) collected from nursery grounds in Galway Bay and to identify probable spawning ground locations for plaice on the west coast of Ireland. The relative importance of passive transport, behaviour and individual growth rates on successful larval delivery, from three putative spawning grounds to suitable nursery areas, was also investigated. Using a hydrodynamic Regional Ocean Modelling System (ROMS), combined with a particle tracking model, three model scenarios were tested: a passive tracer scenario (PTS), a linear growth scenario (LGS) and a temperature-dependent growth scenario (TDS). Hydrodynamic conditions were modelled and biological information (pelagic larval durations and size at settlement) incorporated. The LGS and TDS included vertical migration and tidally synchronised behaviour. Generalized Linear Model (GLM) comparisons showed that incorporation of behaviour and temperature-dependent growth, resulted in approximately two to three times more particles being delivered to sites of suitable depth for settlement (≤ 10 m), compared to passive transport alone (p < 0.001, LGS 19-78%; TDS 40-81%). The probability of successful delivery also varied significantly depending on the location, year and week of release (p < 0.05). A comparison of temperature histories between particles that were delivered to shallow inshore areas and those that failed to reach depths suitable for settlement indicated that dispersal to coastal nursery areas is facilitated by entrainment into a cool coastal current system. This study identifies a probable plaice spawning area in western Ireland and reconfirms the importance of including behaviour and growth in dispersal simulations. The model results suggest that differences in growth can influence larval delivery to potentially suitable nursery areas.

Low temperature magnetic behaviour near 35 K in unmetamorphosed claystones

NASA Astrophysics Data System (ADS)

Kars, Myriam; Aubourg, Charles; Pozzi, Jean-Pierre

2011-09-01

There is growing evidence that the magnetic assemblage of claystones, illustrated by low-temperature magnetic transitions at ˜120 K and ˜35 K, may be representative of the peak burial temperature in the so-called oil-window (60-150°C). In previous studies, it was proposed that this magnetic assemblage is characterized by fine-grained pyrrhotite (Fe7S8) and magnetite (Fe3O4). However, evidence of pyrrhotite was not so obvious and the magnetic transition near 35 K of fine-grained pyrrhotite has similarities with those of siderite (FeCO3) or rhodochrosite (MnCO3). Here, we propose some diagnostic tests to distinct <50 K behaviours by studying claystones from Netherlands borehole and Borneo Prism that experienced different peak burial temperatures. We perform magnetic susceptibility, temperature dependency of SIRM (ZFC, RT-SIRM) and field cooled hysteresis loops. On cooling of RT-SIRM (300 K to 10 K), we applied a magnetic field of 5 μT to enhance Néel type magnetic transition. It is found that our samples can be classified in two categories based on the shape of the RT-SIRM curve: one displaying an abrupt break-in-slope in the remanence at ˜30 K, called N-behaviour, and the other one characterized by a progressive increase of the remanent magnetization by 80 K, named P-behaviour. The first category contains essentially magnetite and Fe-Mn carbonates, the second one magnetite and probably iron sulphides.

Beyond body size: muscle biochemistry and body shape explain ontogenetic variation of anti-predatory behaviour in the lizard Salvator merianae.

PubMed

de Barros, Fábio Cury; de Carvalho, José Eduardo; Abe, Augusto Shinya; Kohlsdorf, Tiana

2016-06-01

Anti-predatory behaviour evolves under the strong action of natural selection because the success of individuals avoiding predation essentially defines their fitness. Choice of anti-predatory strategies is defined by prey characteristics as well as environmental temperature. An additional dimension often relegated in this multilevel equation is the ontogenetic component. In the tegu Salvator merianae, adults run away from predators at high temperatures but prefer fighting when it is cold, whereas juveniles exhibit the same flight strategy within a wide thermal range. Here, we integrate physiology and morphology to understand ontogenetic variation in the temperature-dependent shift of anti-predatory behaviour in these lizards. We compiled data for body shape and size, and quantified enzyme activity in hindlimb and head muscles, testing the hypothesis that morphophysiological models explain ontogenetic variation in behavioural associations. Our prediction is that juveniles exhibit body shape and muscle biochemistry that enhance flight strategies. We identified biochemical differences between muscles mainly in the LDH:CS ratio, whereby hindlimb muscles were more glycolytic than the jaw musculature. Juveniles, which often use evasive strategies to avoid predation, have more glycolytic hindlimb muscles and are much smaller when compared with adults 1-2 years old. Ontogenetic differences in body shape were identified but marginally contributed to behavioural variation between juvenile and adult tegus, and variation in anti-predatory behaviour in these lizards resides mainly in associations between body size and muscle biochemistry. Our results are discussed in the ecological context of predator avoidance by individuals differing in body size living at temperature-variable environments, where restrictions imposed by the cold could be compensated by specific phenotypes. © 2016. Published by The Company of Biologists Ltd.

Temperature limits trail following behaviour through pheromone decay in ants

NASA Astrophysics Data System (ADS)

van Oudenhove, Louise; Billoir, Elise; Boulay, Raphaël; Bernstein, Carlos; Cerdá, Xim

2011-12-01

In Mediterranean habitats, temperature affects both ant foraging behaviour and community structure. Many studies have shown that dominant species often forage at lower temperature than subordinates. Yet, the factors that constrain dominant species foraging activity in hot environments are still elusive. We used the dominant ant Tapinoma nigerrimum as a model species to test the hypothesis that high temperatures hinder trail following behaviour by accelerating pheromone degradation. First, field observations showed that high temperatures (> 30°C) reduce the foraging activity of T. nigerrimum independently of the daily and seasonal rhythms of this species. Second, we isolated the effect of high temperatures on pheromone trail efficacy from its effect on worker physiology. A marked substrate was heated during 10 min (five temperature treatments from 25°C to 60°C), cooled down to 25°C, and offered in a test choice to workers. At hot temperature treatments (>40°C), workers did not discriminate the previously marked substrate. High temperatures appeared therefore to accelerate pheromone degradation. Third, we assessed the pheromone decay dynamics by a mechanistic model fitted with Bayesian inference. The model predicted ant choice through the evolution of pheromone concentration on trails as a function of both temperature and time since pheromone deposition. Overall, our results highlighted that the effect of high temperatures on recruitment intensity was partly due to pheromone evaporation. In the Mediterranean ant communities, this might affect dominant species relying on chemical recruitment, more than subordinate ant species, less dependent on chemical communication and less sensitive to high temperatures.

Supramolecular motifs in dynamic covalent PEG-hemiaminal organogels

PubMed Central

Fox, Courtney H.; ter Hurrne, Gijs M.; Wojtecki, Rudy J.; Jones, Gavin O.; Horn, Hans W.; Meijer, E. W.; Frank, Curtis W.; Hedrick, James L.; García, Jeannette M.

2015-01-01

Dynamic covalent materials are stable materials that possess reversible behaviour triggered by stimuli such as light, redox conditions or temperature; whereas supramolecular crosslinks depend on the equilibrium constant and relative concentrations of crosslinks as a function of temperature. The combination of these two reversible chemistries can allow access to materials with unique properties. Here, we show that this combination of dynamic covalent and supramolecular chemistry can be used to prepare organogels comprising distinct networks. Two materials containing hemiaminal crosslink junctions were synthesized; one material is comprised of dynamic covalent junctions and the other contains hydrogen-bonding bis-hemiaminal moieties. Under specific network synthesis conditions, these materials exhibited self-healing behaviour. This work reports on both the molecular-level detail of hemiaminal crosslink junction formation as well as the macroscopic behaviour of hemiaminal dynamic covalent network (HDCN) elastomeric organogels. These materials have potential applications as elastomeric components in printable materials, cargo carriers and adhesives. PMID:26174864

Thermal and damping behaviour of magnetic shape memory alloy composites

NASA Astrophysics Data System (ADS)

Glock, Susanne; Michaud, Véronique

2015-06-01

Single crystals of ferromagnetic shape memory alloys (MSMA) exhibit magnetic field and stress induced strains via energy dissipating twinning. Embedding single crystalline MSMA particles into a polymer matrix could thus produce composites with enhanced energy dissipation, suitable for damping applications. Composites of ferromagnetic, martensitic or austenitic Ni-Mn-Ga powders embedded in a standard epoxy matrix were produced by casting. The martensitic powder composites showed a crystal structure dependent damping behaviour that was more dissipative than that of austenitic powder or Cu-Ni reference powder composites and than that of the pure matrix. The loss ratio also increased with increasing strain amplitude and decreasing frequency, respectively. Furthermore, Ni-Mn-Ga powder composites exhibited an increased damping behaviour at the martensite/austenite transformation temperature of the Ni-Mn-Ga particles in addition to that at the glass transition temperature of the epoxy matrix, creating possible synergetic effects.

Influence of temperature on fatigue life or reinforced pavement by whitetopping

NASA Astrophysics Data System (ADS)

Szydło, A.; Mackiewicz, P.

2018-05-01

The article presents the influence of temperature on the fatigue strength of concrete slabs used for reinforcing susceptible flexible pavement. In Poland, so far, there is no research on thermal interactions on concrete pavement. The article presents an analysis of various climatic conditions occurring in Poland and temperature distribution in concrete pavement. The dependence of daily temperature fluctuations on the temperatures appearing in the concrete slab was demonstrated. An analysis of thermal stresses in concrete slabs depending on their parameters was shown, and then fatigue life was determined. The applied 3DFEM model includes elements of contact, friction, and gravity in order to better approximate the behaviour of the board from temperature change. On this basis, the significant influence of cyclical daily temperature changes on the durability of the concrete pavement was indicated. The presented analyses can be applied to reinforcements of existing flexible pavements.

Low temperature IR spectroscopic study of torsional vibrations of taurine

NASA Astrophysics Data System (ADS)

Bajaj, Naini; Bhatt, Himal; Vishwakarma, S. R.; Thomas, Susy; Murli, C.; Deo, M. N.

2018-04-01

The hydrogen bonding network in amino acids can give information about the structural stability under varying thermodynamic conditions such as temperature and pressure. We have carried out low temperature IR spectroscopic studies on Taurine, an amino acid with various bio-chemical applications in physiology and synthesis, in order to observe the behaviour of torsional modes, i.e. τ(CSH) and τ(NH3), which are very sensitive to the hydrogen bonding interactions. It was observed that the CSH torsional mode showed splitting at low temperature of nearly 250 K and the bandwidth shows linear temperature dependence, which can be attributed to anharmonicity. Another torsional mode, τ(NH3) showed no splitting, but the bandwidth has non-linear temperature dependence. This can be due to orientational changes at low temperature. These observations are strong evidences for a hydrogen bond reorientation induced phase transition at 250 K.

Understanding Biological Rates and their Temperature Dependence, from Enzymes to Ecosystems

NASA Astrophysics Data System (ADS)

Prentice, E.; Arcus, V. L.

2017-12-01

Temperature responses over various scales in biological systems follow a similar pattern; negative curvature results in an optimum temperature (Topt) for activity/growth/turnover, with decreases in rates on either side of Topt. Previously this downturn in rates at high temperatures has been attributed to enzyme denaturation, where a failing of the basic driving units of metabolism was used to describe curvature at the enzyme and organism level. However, recent developments in our understanding of the factors governing enzyme rates at different temperatures have guided a new understanding of the responses of biological systems. Enzymes catalyse reactions by driving the substrate through a high energy species, which is tightly bound to the enzyme. Macromolecular rate theory (MMRT) has recently been developed to account for the changes in the system brought about by this tight binding, specifically the change in the physical parameter heat capacity (ΔCǂp), and the effect this has on the temperature dependence of enzyme reactions. A negative ΔCǂp imparts the signature negative curvature to rates in the absence of denaturation, and finds that Topt, ΔCǂp and curvature are all correlated, placing constraints on biological systems. The simplest of cells comprise thousands of enzymatically catalysed reactions, functioning in series and in parallel in metabolic pathways to determine the overall growth rate of an organism. Intuitively, the temperature effects of enzymes play a role in determining the overall temperature dependence of an organism, in tandem with cellular level regulatory responses. However, the effect of individual Topt values and curvature on overall pathway behaviour is less apparent. Here, this is investigated in the context of MMRT through the in vitro characterisation of a six-step metabolic pathway to understand the steps in isolation and functioning in series. Pathway behaviour is found to be approximately an average of the properties of the individual steps, indicating all enzymes have an influence on organism temperature dependence. This has implications for our understanding of how organisms respond to fluctuations in environmental temperature.

Rate of egg maturation in marine turtles exhibits 'universal temperature dependence'.

PubMed

Weber, Sam B; Blount, Jonathan D; Godley, Brendan J; Witt, Matthew J; Broderick, Annette C

2011-09-01

1. The metabolic theory of ecology (MTE) predicts that, after correcting for body mass variation among organisms, the rates of most biological processes will vary as a universal function of temperature. However, empirical support for 'universal temperature dependence' (UTD) is currently equivocal and based on studies of a limited number of traits. 2. In many ectothermic animals, the rate at which females produce mature eggs is temperature dependent and may be an important factor in determining the costs of reproduction. 3. We tested whether the rate of egg maturation in marine turtles varies with environmental temperature as predicted by MTE, using the time separating successive clutches of individual females to estimate the rate at which eggs are formed. We also assessed the phenotypic contribution to this rate, by using radio telemetry to make repeated measurements of interclutch intervals for individual green turtles (Chelonia mydas). 4. Rates of egg maturation increased with seasonally increasing water temperatures in radio-tracked green turtles, but were not repeatable for individual females, and did not vary according to maternal body size or reproductive investment (number and size of eggs produced). 5. Using a collated data set from several different populations and species of marine turtles, we then show that a single relationship with water temperature explains most of the variation in egg maturation rates, with a slope that is statistically indistinguishable from the UTD predicted by MTE. However, several alternative statistical models also described the relationship between temperature and egg maturation rates equally parsimoniously. 6. Our results offer novel support for the MTE's predicted UTD of biological rates, although the underlying mechanisms require further study. The strong temperature dependence of egg maturation combined with the apparently weak phenotypic contribution to this rate has interesting behavioural implications in ectothermic animals. We suggest that maternal thermoregulatory behaviour in marine turtles, and many other reptiles, is consistent with a strategy of adaptively increasing body temperatures to accelerate egg maturation. © 2011 The Authors. Journal of Animal Ecology © 2011 British Ecological Society.

Thermoregulatory behaviour affects prevalence of chytrid fungal infection in a wild population of Panamanian golden frogs

PubMed Central

Richards-Zawacki, Corinne L.

2010-01-01

Predicting how climate change will affect disease dynamics requires an understanding of how the environment affects host–pathogen interactions. For amphibians, global declines and extinctions have been linked to a pathogenic chytrid fungus, Batrachochytrium dendrobatidis. Using a combination of body temperature measurements and disease assays conducted before and after the arrival of B. dendrobatidis, this study tested the hypothesis that body temperature affects the prevalence of infection in a wild population of Panamanian golden frogs (Atelopus zeteki). The timing of first detection of the fungus was consistent with that of a wave of epidemic infections spreading south and eastward through Central America. During the epidemic, many golden frogs modified their thermoregulatory behaviour, raising body temperatures above their normal set point. Odds of infection decreased with increasing body temperature, demonstrating that even slight environmental or behavioural changes have the potential to affect an individual's vulnerability to infection. The thermal dependency of the relationship between B. dendrobatidis and its amphibian hosts demonstrates how the progression of an epidemic can be influenced by complex interactions between host and pathogen phenotypes and the environments in which they are found. PMID:19864287

High temperature impact on fatigue life of asphalt mixture in Slovakia

NASA Astrophysics Data System (ADS)

Mandula, Ján; Olexa, Tomáš

2017-09-01

Temperature dependence of materials bonded with bitumen is a well-known fact. The impact of temperature changes the behaviour of asphalt mixtures from elastic to viscous state, and it also influences the complex modulus, phase angle and other properties of asphalt mixtures. This study observed the summer temperature influence on fatigue behaviour of an asphalt mixture for the surface course of roads in conditions of Slovakia. Measurements were made using the four-point bending method on the asphalt mixture with maximum grain size of 11 mm bonded with polymer modified bitumen. Summer conditions were represented by environmental temperature of 27 °C according to the Slovakian pavement design method. Ordinary temperatures for fatigue measurements are 10 °C, 15 °C and 20 °C according to European standards for asphalt mixture testing. Structural changes in the material were observed by dissipation energy calculations for each loading cycle. The aim of the study was to find out if the influence of high environmental temperature is positive or negative for the lifespan of asphalt mixtures.

Chemical degradation and morphological instabilities during focused ion beam prototyping of polymers.

PubMed

Orthacker, A; Schmied, R; Chernev, B; Fröch, J E; Winkler, R; Hobisch, J; Trimmel, G; Plank, H

2014-01-28

Focused ion beam processing of low melting materials, such as polymers or biological samples, often leads to chemical and morphological instabilities which prevent the straight-forward application of this versatile direct-write structuring method. In this study the behaviour of different polymer classes under ion beam exposure is investigated using different patterning parameters and strategies with the aim of (i) correlating local temperatures with the polymers' chemistry and its morphological consequences; and (ii) finding a way of processing sensitive polymers with lowest chemical degradation while maintaining structuring times. It is found that during processing of polymers three temperature regimes can be observed: (1) at low temperatures all polymers investigated show stable chemical and morphological behaviour; (2) very high temperatures lead to strong chemical degradation which entails unpredictable morphologies; and (3) in the intermediate temperature regime the behaviour is found to be strongly material dependent. A detailed look reveals that polymers which rather cross-link in the proximity of the beam show stable morphologies in this intermediate regime, while polymers that rather undergo chain scission show tendencies to develop a creeping phase, where material follows the ion beam movement leading to instable and unpredictable morphologies. Finally a simple, alternative patterning strategy is suggested, which allows stable processing conditions with lowest chemical damage even for challenging polymers undergoing chain scission.

Structural and Magnetic Properties of {Eu}(3+) Eu 3 + -Doped {CdNb}_{2} {O}_{6} CdNb 2 O 6 Powders

NASA Astrophysics Data System (ADS)

Topkaya, Ramazan; Boyraz, Cihat; Ekmekçi, Mete Kaan

2018-03-01

Europium-doped CdNb2O6 powders with the molar concentration of Eu^{3+} (0.5, 3 and 6 mol%) were successfully prepared at 900°C by using molten salt synthesis method. The effect of europium (Eu) molar concentration on the structural and temperature-dependent magnetic properties of CdNb2O6 powders has been investigated by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), vibrating sample magnetometer (VSM) and ferromagnetic resonance (FMR) techniques in the temperature range of 10-300 K. XRD results confirm that all the powders have orthorhombic crystal structure. It has been confirmed from VSM and FMR measurements that Eu^{3+}-doped CdNb2O6 powders have ferromagnetic behaviour for each Eu^{3+} molar concentration between 10 and 300 K. XRD and EDX analyses indicate that there is no magnetic impurity in Eu^{3+}-doped CdNb_2O_6 powders, supporting that the ferromagnetic behaviour of the powders arises from Eu^{3+} ions. The observed ferromagnetism was elucidated with the intrinsic exchange interactions between the magnetic moments associated with the unpaired 4 f electrons in Eu^{3+} ions. The saturation magnetization decreases with increasing Eu^{3+} molar concentration. The temperature-dependent magnetization behaviour was observed not to agree with Curie-Weiss law because europium obeys Van Vleck paramagnetism. Broad FMR spectra and a g-value higher than 2 were observed from FMR measurements, indicating the ferromagnetic behaviour of the powders. It was found that while the resonance field of FMR spectra decreases, the linewidth increases as a function of Eu^{3+} molar concentration.

Studies on a.c. conductivity behaviour of milled carbon fibre reinforced epoxy gradient composites

NASA Astrophysics Data System (ADS)

Nigrawal, Archana; Sharma, Arun Kumar; Ojha, Pragya

2018-05-01

Temperature and frequency dependence of a.c. conductivity (σa.c) of milled carbon fibre (MCF) reinforced epoxy gradient composites has been studied in a wide temperature (30 to 150°C) and frequency range (1 to 10kHz). It is observed that the ac conductivity of composites increases with increase in temperature. Activation energy decreases from 0.55 eV to 0.43 eV on increase of MCF content from 0.45to 1.66 Vol%.

The temporal behaviour of MHD waves in a partially ionized prominence-like plasma: Effect of heating and cooling

NASA Astrophysics Data System (ADS)

Ballester, J. L.; Carbonell, M.; Soler, R.; Terradas, J.

2018-01-01

Context. During heating or cooling processes in prominences, the plasma microscopic parameters are modified due to the change of temperature and ionization degree. Furthermore, if waves are excited on this non-stationary plasma, the changing physical conditions of the plasma also affect wave dynamics. Aims: Our aim is to study how temporal variation of temperature and microscopic plasma parameters modify the behaviour of magnetohydrodynamic (MHD) waves excited in a prominence-like hydrogen plasma. Methods: Assuming optically thin radiation, a constant external heating, the full expression of specific internal energy, and a suitable energy equation, we have derived the profiles for the temporal variation of the background temperature. We have computed the variation of the ionization degree using a Saha equation, and have linearized the single-fluid MHD equations to study the temporal behaviour of MHD waves. Results: For all the MHD waves considered, the period and damping time become time dependent. In the case of Alfvén waves, the cut-off wavenumbers also become time dependent and the attenuation rate is completely different in a cooling or heating process. In the case of slow waves, while it is difficult to distinguish the slow wave properties in a cooling partially ionized plasma from those in an almost fully ionized plasma, the period and damping time of these waves in both plasmas are completely different when the plasma is heated. The temporal behaviour of the Alfvén and fast wave is very similar in the cooling case, but in the heating case, an important difference appears that is related with the time damping. Conclusions: Our results point out important differences in the behaviour of MHD waves when the plasma is heated or cooled, and show that a correct interpretation of the observed prominence oscillations is very important in order to put accurate constraints on the physical situation of the prominence plasma under study, that is, to perform prominence seismology.

Study of rheological behaviour of wines

NASA Astrophysics Data System (ADS)

Trávníček, Petr; Burg, Patrik; Krakowiak-Bal, Anna; Junga, Petr; Vítěz, Tomáš; Ziemiańczyk, Urszula

2016-10-01

This study deals with rheological properties of various wine varieties. Samples of the following wines were used for this experiment: André, Cabernet Moravia, Laurot, Saint Laurent, Gruner Veltliner, Pinot Blanc, Müller Thurgau, and Riesling Italico. These samples were obtained from wine produced from the grapes collected in the Czech Republic (Morava region, subregion Velke Pavlovice). In the first phase, the chemical composition of the samples was determined. The following chemical parameters were determined: total acidity, pH, content of the alcohol, reduced sugars, free SO2, total SO2, and volatile acids. In the second phase of the study, the physical properties of the samples were determined and the samples of the wines were subjected to rheological tests. These tests consisted in determination of apparent viscosity in relation to temperature, hysteresis loop tests, and apparent viscosity related to time. The dependence of the shear rate on the shear stress was described with the Herschel-Bulkley mathematical model. The experiment yielded the following findings: seven out of the eight samples behaved as non-Newtonian fluids at low temperature (5°C); non-Newtonian behaviour was changed into Newtonian at the temperature higher than 10°C; non-Newtonian behaviour was characterised as thixotropic behaviour; the degree of thixotropy is relatively small and reaches 1.85 Pa s-1 ml-1.

Folded fabric tunes rock deformation and failure mode in the upper crust.

PubMed

Agliardi, F; Dobbs, M R; Zanchetta, S; Vinciguerra, S

2017-11-10

The micro-mechanisms of brittle failure affect the bulk mechanical behaviour and permeability of crustal rocks. In low-porosity crystalline rocks, these mechanisms are related to mineralogy and fabric anisotropy, while confining pressure, temperature and strain rates regulate the transition from brittle to ductile behaviour. However, the effects of folded anisotropic fabrics, widespread in orogenic settings, on the mechanical behaviour of crustal rocks are largely unknown. Here we explore the deformation and failure behaviour of a representative folded gneiss, by combining the results of triaxial deformation experiments carried out while monitoring microseismicity with microstructural and damage proxies analyses. We show that folded crystalline rocks in upper crustal conditions exhibit dramatic strength heterogeneity and contrasting failure modes at identical confining pressure and room temperature, depending on the geometrical relationships between stress and two different anisotropies associated to the folded rock fabric. These anisotropies modulate the competition among quartz- and mica-dominated microscopic damage processes, resulting in transitional brittle to semi-brittle modes under P and T much lower than expected. This has significant implications on scales relevant to seismicity, energy resources, engineering applications and geohazards.

Non-equilibrium phase transitions in a liquid crystal

NASA Astrophysics Data System (ADS)

Dan, K.; Roy, M.; Datta, A.

2015-09-01

The present manuscript describes kinetic behaviour of the glass transition and non-equilibrium features of the "Nematic-Isotropic" (N-I) phase transition of a well known liquid crystalline material N-(4-methoxybenzylidene)-4-butylaniline from the effects of heating rate and initial temperature on the transitions, through differential scanning calorimetry (DSC), Fourier transform infrared and fluorescence spectroscopy. Around the vicinity of the glass transition temperature (Tg), while only a change in the baseline of the ΔCp vs T curve is observed for heating rate (β) > 5 K min-1, consistent with a glass transition, a clear peak for β ≤ 5 K min-1 and the rapid reduction in the ΔCp value from the former to the latter rate correspond to an order-disorder transition and a transition from ergodic to non-ergodic behaviour. The ln β vs 1000/T curve for the glass transition shows convex Arrhenius behaviour that can be explained very well by a purely entropic activation barrier [Dan et al., Eur. Phys. Lett. 108, 36007 (2014)]. Fourier transform infrared spectroscopy indicates sudden freezing of the out-of-plane distortion vibrations of the benzene rings around the glass transition temperature and a considerable red shift indicating enhanced coplanarity of the benzene rings and, consequently, enhancement in the molecular ordering compared to room temperature. We further provide a direct experimental evidence of the non-equilibrium nature of the N-I transition through the dependence of this transition temperature (TNI) and associated enthalpy change (ΔH) on the initial temperature (at fixed β-values) for the DSC scans. A plausible qualitative explanation based on Mesquita's extension of Landau-deGennes theory [O. N. de Mesquita, Braz. J. Phys. 28, 257 (1998)] has been put forward. The change in the molecular ordering from nematic to isotropic phase has been investigated through fluorescence anisotropy measurements where the order parameter, quantified by the anisotropy, goes to zero from nematic to isotropic phase. To a point below the transition temperature, the order parameter is constant but decreases linearly with increase in temperature below that indicating the dependence of nematic ordering on the initial temperature during heating consistent with the non-equilibrium nature of nematic-isotropic phase transition.

Direct evidence for a pressure-induced nodal superconducting gap in the Ba0.65Rb0.35Fe2As2 superconductor

PubMed Central

Guguchia, Z.; Amato, A.; Kang, J.; Luetkens, H.; Biswas, P. K.; Prando, G.; von Rohr, F.; Bukowski, Z.; Shengelaya, A.; Keller, H.; Morenzoni, E.; Fernandes, Rafael M.; Khasanov, R.

2015-01-01

The superconducting gap structure in iron-based high-temperature superconductors (Fe-HTSs) is non-universal. In contrast to other unconventional superconductors, in the Fe-HTSs both d-wave and extended s-wave pairing symmetries are close in energy. Probing the proximity between these very different superconducting states and identifying experimental parameters that can tune them is of central interest. Here we report high-pressure muon spin rotation experiments on the temperature-dependent magnetic penetration depth in the optimally doped nodeless s-wave Fe-HTS Ba0.65Rb0.35Fe2As2. Upon pressure, a strong decrease of the penetration depth in the zero-temperature limit is observed, while the superconducting transition temperature remains nearly constant. More importantly, the low-temperature behaviour of the inverse-squared magnetic penetration depth, which is a direct measure of the superfluid density, changes qualitatively from an exponential saturation at zero pressure to a linear-in-temperature behaviour at higher pressures, indicating that hydrostatic pressure promotes the appearance of nodes in the superconducting gap. PMID:26548650

Direct evidence for a pressure-induced nodal superconducting gap in the Ba 0.65Rb 0.35Fe 2As 2 superconductor

DOE PAGES

Guguchia, Z.; Amato, A.; Kang, J.; ...

2015-11-09

The superconducting gap structure in iron-based high-temperature superconductors (Fe-HTSs) is non-universal. Contrasting with other unconventional superconductors, in the Fe-HTSs both d-wave and extended s-wave pairing symmetries are close in energy. Probing the proximity between these very different superconducting states and identifying experimental parameters that can tune them is of central interest. Here we report high-pressure muon spin rotation experiments on the temperature-dependent magnetic penetration depth in the optimally doped nodeless s-wave Fe-HTS Ba 0.65Rb 0.35Fe 2As 2. Upon pressure, a strong decrease of the penetration depth in the zero-temperature limit is observed, while the superconducting transition temperature remains nearly constant.more » More importantly, the low-temperature behaviour of the inverse-squared magnetic penetration depth, which is a direct measure of the superfluid density, changes qualitatively from an exponential saturation at zero pressure to a linear-in-temperature behaviour at higher pressures, indicating that hydrostatic pressure promotes the appearance of nodes in the superconducting gap.« less

Immersion freezing of ice nucleation active protein complexes

NASA Astrophysics Data System (ADS)

Hartmann, S.; Augustin, S.; Clauss, T.; Wex, H.; Šantl-Temkiv, T.; Voigtländer, J.; Niedermeier, D.; Stratmann, F.

2013-06-01

Utilising the Leipzig Aerosol Cloud Interaction Simulator (LACIS), the immersion freezing behaviour of droplet ensembles containing monodisperse particles, generated from a Snomax™ solution/suspension, was investigated. Thereto ice fractions were measured in the temperature range between -5 °C to -38 °C. Snomax™ is an industrial product applied for artificial snow production and contains Pseudomonas syringae} bacteria which have long been used as model organism for atmospheric relevant ice nucleation active (INA) bacteria. The ice nucleation activity of such bacteria is controlled by INA protein complexes in their outer membrane. In our experiments, ice fractions increased steeply in the temperature range from about -6 °C to about -10 °C and then levelled off at ice fractions smaller than one. The plateau implies that not all examined droplets contained an INA protein complex. Assuming the INA protein complexes to be Poisson distributed over the investigated droplet populations, we developed the CHESS model (stoCHastic modEl of similar and poiSSon distributed ice nuclei) which allows for the calculation of ice fractions as function of temperature and time for a given nucleation rate. Matching calculated and measured ice fractions, we determined and parameterised the nucleation rate of INA protein complexes exhibiting class III ice nucleation behaviour. Utilising the CHESS model, together with the determined nucleation rate, we compared predictions from the model to experimental data from the literature and found good agreement. We found that (a) the heterogeneous ice nucleation rate expression quantifying the ice nucleation behaviour of the INA protein complex is capable of describing the ice nucleation behaviour observed in various experiments for both, Snomax™ and P. syringae bacteria, (b) the ice nucleation rate, and its temperature dependence, seem to be very similar regardless of whether the INA protein complexes inducing ice nucleation are attached to the outer membrane of intact bacteria or membrane fragments, (c) the temperature range in which heterogeneous droplet freezing occurs, and the fraction of droplets being able to freeze, both depend on the actual number of INA protein complexes present in the droplet ensemble, and (d) possible artifacts suspected to occur in connection with the drop freezing method, i.e., the method frequently used by biologist for quantifying ice nucleation behaviour, are of minor importance, at least for substances such as P. syringae, which induce freezing at comparably high temperatures. The last statement implies that for single ice nucleation entities such as INA protein complexes, it is the number of entities present in the droplet population, and the entities' nucleation rate, which control the freezing behaviour of the droplet population. Quantities such as ice active surface site density are not suitable in this context. The results obtained in this study allow a different perspective on the quantification of the immersion freezing behaviour of bacterial ice nucleation.

On rate-dependent polycrystal deformation: the temperature sensitivity of cold dwell fatigue

PubMed Central

Zhang, Zhen; Cuddihy, M. A.; Dunne, F. P. E.

2015-01-01

A temperature and rate-dependent crystal plasticity framework has been used to examine the temperature sensitivity of stress relaxation, creep and load shedding in model Ti-6Al polycrystal behaviour under dwell fatigue conditions. A temperature close to 120°C is found to lead to the strongest stress redistribution and load shedding, resulting from the coupling between crystallographic slip rate and slip system dislocation hardening. For temperatures in excess of about 230°C, grain-level load shedding from soft to hard grains diminishes because of the more rapid stress relaxation, leading ultimately to the diminution of the load shedding and hence, it is argued, the elimination of the dwell debit. Under conditions of cyclic stress dwell, at temperatures between 20°C and 230°C for which load shedding occurs, the rate-dependent accumulation of local slip by ratcheting is shown to lead to the progressive cycle-by-cycle redistribution of stress from soft to hard grains. This phenomenon is termed cyclic load shedding since it also depends on the material's creep response, but develops over and above the well-known dwell load shedding, thus providing an additional rationale for the incubation of facet nucleation. PMID:26528078

The evolution of γ-Mg17Al12 intermetallic compound during accumulative back extrusion and subsequent ageing treatment

NASA Astrophysics Data System (ADS)

Maghsoudi, M. H.; Zarei-Hanzaki, A.; Abedi, H. R.; Shamsolhodaei, A.

2015-11-01

Accumulative back extrusion (ABE) processing, as a novel severe plastic deformation (SPD) method, has been recently justified to be capable of modifying the microstructural characteristics of alloys. In line to its ongoing researches, the present work has been planned to study the evolution of γ-Mg17Al12 intermetallic phase during ABE and subsequent ageing treatment in a high Al-bearing Mg-Al-Zn alloy. The behaviour of γ intermetallic has been systematically examined as following points of view: (i) strain-temperature-dependent morphology changes, (ii) strain-induced dissolution, and (iii) re-ageing behaviour as a function of time and temperature. Aiming to analyse the morphology of eutectic γ compound with respect to the strain and temperature, 2D projections of effective diameter, shape factor and globularity have been made in strain/temperature graphs. The processing conditions (strain and temperature) corresponding to the desired and undesired morphologies are introduced and microstructurally explained through underlying plasticity mechanisms, i.e., 'necking-thinning-particle separation' and 'brittle fragmentation.' The former mechanism is suggested to be in relation with partial strain-induced dissolution of eutectic γ phase, leading to generation of a supersaturated solid solution. This has resulted to the observation of 'off-stoichiometry' phenomena in Mg17Al12 phase and has been justified through dislocation-assisted deformation mechanism at elevated temperature. Surprisingly, a unique re-ageing behaviour has been found for the obtained solid solutions, where a modified kinetics and morphology of γ phase precipitation were characterized. The altered precipitation behaviour is attributed to the specific defect structure achieved by SPD acting as fast diffusion channel for Al solutes.

Effect of NiO substitution on the structural and dielectric behaviour of NaNbO3

NASA Astrophysics Data System (ADS)

George, R. T.; Joshi, D. C.; Nayak, S.; Tiwari, N.; Chauhan, R. N.; Pramanik, P.; Dar, T. A.; Ghosh, S.; Thota, S.

2018-02-01

The structural and dielectric properties of NiO substituted NaNbO3 ceramics are reported. The orthorhombic (Pmna) crystal structure of NaNbO3 transforms to a lower symmetry monoclinic phase (Pbma) after the dilute dispersion of NiO. X-ray photoelectron spectroscopy reveals pentavalent "Nb," monovalent "Na," and divalent "Ni" states along with the signatures of non-local screening effects. The antiferroelectric to paraelectric transition (TAFE) accompanied by a structural change from the orthorhombic to the tetragonal phase shifts by 55 °C toward the low-temperature side, whereas the morphotropic phase boundary (TO-M) moves toward a higher temperature by 28 °C for nominal substitutions ( x ≤0.10 ). The generalized Lyddane-Sachs-Teller expression (ε0/-S'ε∞)= (ωl/ωt ) 2 and thermodynamic free energy models are employed to explain the anomalous behaviour of the temperature dependence of relative dielectric permittivity ( εr (T)) across TAFE and TO-M. The frequency dependence of ac-conductivity σac(ω) follows the Jonscher power law (σac = σ(0) + Aωs), suggesting the dominance of the phonon-assisted hopping mechanism, whereas the frequency independent term (σ(0)) was explained by Funke's Jump-Relaxation Model.

Can temperate insects take the heat? A case study of the physiological and behavioural responses in a common ant, Iridomyrmex purpureus (Formicidae), with potential climate change.

PubMed

Andrew, Nigel R; Hart, Robert A; Jung, Myung-Pyo; Hemmings, Zac; Terblanche, John S

2013-09-01

Insects in temperate regions are predicted to be at low risk of climate change relative to tropical species. However, these assumptions have generally been poorly examined in all regions, and such forecasting fails to account for microclimatic variation and behavioural optimisation. Here, we test how a population of the dominant ant species, Iridomyrmex purpureus, from temperate Australia responds to thermal stress. We show that ants regularly forage for short periods (minutes) at soil temperatures well above their upper thermal limits (upper lethal temperature = 45.8 ± 1.3°C; CT(max) = 46.1°C) determined over slightly longer periods (hours) and do not show any signs of a classic thermal performance curve in voluntary locomotion across soil surface temperatures of 18.6-57°C (equating to a body temperature of 24.5-43.1°C). Although ants were present all year round, and dynamically altered several aspects of their thermal biology to cope with low temperatures and seasonal variation, temperature-dependence of running speed remained invariant and ants were unable to elevate high temperature tolerance using plastic responses. Measurements of microclimate temperature were higher than ant body temperatures during the hottest part of the day, but exhibited a stronger relationship with each other than air temperatures from the closest weather station. Generally close associations of ant activity and performance with microclimatic conditions, possibly to maximise foraging times, suggest I. purpureus displays highly opportunistic thermal responses and readily adjusts behaviour to cope with high trail temperatures. Increasing frequency or duration of high temperatures is therefore likely to result in an immediate reduction in foraging efficiency. In summary, these results suggest that (1) soil-dwelling temperate insect populations may be at higher risks of thermal stress with increased frequency or duration of high temperatures resulting from climate change than previously thought, however, behavioural cues may be able to compensate to some extent; and (2) indices of climate change-related thermal stress, warming tolerance and thermal safety margin, are strongly influenced by the scale of climate metrics employed. Copyright © 2013 Elsevier Ltd. All rights reserved.

Context dependency and generality of fever in insects.

PubMed

Stahlschmidt, Z R; Adamo, S A

2013-07-01

Fever can reduce mortality in infected animals. Yet, despite its fitness-enhancing qualities, fever often varies among animals. We used several approaches to examine this variation in insects. Texas field crickets (Gryllus texensis) exhibited a modest fever (1 °C increase in preferred body temperature, T pref) after injection of prostaglandin, which putatively mediates fever in both vertebrates and invertebrates, but they did not exhibit fever during chronic exposure to heat-killed bacteria. Further, chronic food limitation and mating status did not affect T pref or the expression of behavioural fever, suggesting limited context dependency of fever in G. texensis. Our meta-analysis of behavioural fever studies indicated that behavioural fever occurs in many insects, but it is not ubiquitous. Thus, both empirical and meta-analytical results suggest that the fever response in insects 'is widespread, although certainly not inevitable' (Moore 2002). We highlight the need for future work focusing on standardizing an experimental protocol to measure behavioural fever, understanding the specific mechanism(s) underlying fever in insects, and examining whether ecological or physiological costs often outweigh the benefits of fever and can explain the sporadic nature of fever in insects.

Context dependency and generality of fever in insects

NASA Astrophysics Data System (ADS)

Stahlschmidt, Z. R.; Adamo, S. A.

2013-07-01

Fever can reduce mortality in infected animals. Yet, despite its fitness-enhancing qualities, fever often varies among animals. We used several approaches to examine this variation in insects. Texas field crickets ( Gryllus texensis) exhibited a modest fever (1 °C increase in preferred body temperature, T pref) after injection of prostaglandin, which putatively mediates fever in both vertebrates and invertebrates, but they did not exhibit fever during chronic exposure to heat-killed bacteria. Further, chronic food limitation and mating status did not affect T pref or the expression of behavioural fever, suggesting limited context dependency of fever in G. texensis. Our meta-analysis of behavioural fever studies indicated that behavioural fever occurs in many insects, but it is not ubiquitous. Thus, both empirical and meta-analytical results suggest that the fever response in insects `is widespread, although certainly not inevitable' (Moore 2002). We highlight the need for future work focusing on standardizing an experimental protocol to measure behavioural fever, understanding the specific mechanism(s) underlying fever in insects, and examining whether ecological or physiological costs often outweigh the benefits of fever and can explain the sporadic nature of fever in insects.

Thermal shock tests to qualify different tungsten grades as plasma facing material

NASA Astrophysics Data System (ADS)

Wirtz, M.; Linke, J.; Loewenhoff, Th; Pintsuk, G.; Uytdenhouwen, I.

2016-02-01

The electron beam device JUDITH 1 was used to establish a testing procedure for the qualification of tungsten as plasma facing material. Absorbed power densities of 0.19 and 0.38 GW m-2 for an edge localized mode-like pulse duration of 1 ms were chosen. Furthermore, base temperatures of room temperature, 400 °C and 1000 °C allow investigating the thermal shock performance in the brittle, ductile and high temperature regime. Finally, applying 100 pulses under all mentioned conditions helps qualifying the general damage behaviour while with 1000 pulses for the higher power density the influence of thermal fatigue is addressed. The investigated reference material is a tungsten product produced according to the ITER material specifications. The obtained results provide a general overview of the damage behaviour with quantified damage characteristics and thresholds. In particular, it is shown that the damage strongly depends on the microstructure and related thermo-mechanical properties.

Synthesis and characterization of electrical conducting porous carbon structures based on resorcinol-formaldehyde

NASA Astrophysics Data System (ADS)

Najeh, I.; Ben Mansour, N.; Mbarki, M.; Houas, A.; Nogier, J. Ph.; El Mir, L.

2009-10-01

Electrical conducting carbon (ECC) porous structures were explored by changing the pyrolysis temperature of organic xerogel compounds prepared by sol-gel method from resorcinol-formaldehyde (RF) mixtures in acetone using picric acid as catalyst. The effect of this preparation parameter on the structural and electrical properties of the obtained ECCs was studied. The analysis of the obtained results revealed that the polymeric insulating xerogel phase was transformed progressively with pyrolysis temperature into carbon conducting phase; this means the formation of long continuous conducting path for charge carriers to move inside the structure with thermal treatment and the samples exhibited tangible percolation behaviour where the percolation threshold can be determined by pyrolysis temperature. The temperature-dependent conductivity of the obtained ECC structures shows a semi-conducting behaviour and the I( V) characteristics present a negative differential resistance. The results obtained from STM micrographs revealed that the obtained ECC structures consist of porous electrical conducting carbon materials.

Modelling Viscoelastic Behaviour of Polymer by A Mixed Velocity, Displacement Formulation - Numerical and Experimental Results

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pham, VT.; Silva, L.; Digonnet, H.

2011-05-04

The objective of this work is to model the viscoelastic behaviour of polymer from the solid state to the liquid state. With this objective, we perform experimental tensile tests and compare with simulation results. The chosen polymer is a PMMA whose behaviour depends on its temperature. The computation simulation is based on Navier-Stokes equations where we propose a mixed finite element method with an interpolation P1+/P1 using displacement (or velocity) and pressure as principal variables. The implemented technique uses a mesh composed of triangles (2D) or tetrahedra (3D). The goal of this approach is to model the viscoelastic behaviour ofmore » polymers through a fluid-structure coupling technique with a multiphase approach.« less

Temperature dependence of ice-on-rock friction at realistic glacier conditions

PubMed Central

Savage, H.; Nettles, M.

2017-01-01

Using a new biaxial friction apparatus, we conducted experiments of ice-on-rock friction in order to better understand basal sliding of glaciers and ice streams. A series of velocity-stepping and slide–hold–slide tests were conducted to measure friction and healing at temperatures between −20°C and melting. Experimental conditions in this study are comparable to subglacial temperatures, sliding rates and effective pressures of Antarctic ice streams and other glaciers, with load-point velocities ranging from 0.5 to 100 µm s−1 and normal stress σn = 100 kPa. In this range of conditions, temperature dependences of both steady-state friction and frictional healing are considerable. The friction increases linearly with decreasing temperature (temperature weakening) from μ = 0.52 at −20°C to μ = 0.02 at melting. Frictional healing increases and velocity dependence shifts from velocity-strengthening to velocity-weakening behaviour with decreasing temperature. Our results indicate that the strength and stability of glaciers and ice streams may change considerably over the range of temperatures typically found at the ice–bed interface. This article is part of the themed issue ‘Microdynamics of ice’. PMID:28025297

Thermoelectric power of PrMg3

NASA Astrophysics Data System (ADS)

Isikawa, Yosikazu; Somiya, Kazuya; Koyanagi, Huruto; Mizushima, Toshio; Kuwai, Tomohiko; Tayama, Takashi

2010-01-01

PrMg3 is supposed to be one of the strongly correlated electron systems originated from the hybridization between the Pr 4f and conduction electrons, because the gigantic electronic specific heat coefficient C/T was observed at low temperatures. However, a typical behaviour of - ln T dependence was not observed in the temperature dependence of the electrical resistivity. The thermoelectric power S is a powerful tool to investigate the density of states at the Fermi energy. We measured carefully the thermoelectric power of PrMg3 in the temperature range between 2 and 300 K. S is extremely small, ranged within ±1 μV/K over the whole temperature. The value of S/T at low temperature limit was also significantly smaller than expected from the specific heat results. We therefore conclude that the density of state at the Fermi level is not enhanced in PrMg3.

Thermal plasticity in young snakes: how will climate change affect the thermoregulatory tactics of ectotherms?

PubMed

Aubret, F; Shine, R

2010-01-15

Climate change will result in some areas becoming warmer and others cooler, and will amplify the magnitude of year-to-year thermal variation in many areas. How will such changes affect animals that rely on ambient thermal heterogeneity to behaviourally regulate their body temperatures? To explore this question, we raised 43 captive-born tiger snakes Notechis scutatus in enclosures that provided cold (19-22 degrees C), intermediate (19-26 degrees C) or hot (19-37 degrees C) thermal gradients. The snakes adjusted their diel timing of thermoregulatory behaviour so effectively that when tested 14 months later, body temperatures (mean and maximum), locomotor speeds and anti-predator behaviours did not differ among treatment groups. Thus, the young snakes modified their behaviour to compensate for restricted thermal opportunities. Then, we suddenly shifted ambient conditions to mimic year-to-year variation. In contrast to the earlier plasticity, snakes failed to adjust to this change, e.g. snakes raised at cooler treatments but then shifted to hot conditions showed a higher mean body temperature for at least two months after the onset of the new thermal regime. Hence, thermal conditions experienced early in life influenced subsequent thermoregulatory tactics; the mean selected temperature of a snake depended more upon its prior raising conditions than upon its current thermoregulatory opportunities. Behavioural plasticity thus allows snakes to adjust to suboptimal thermal conditions but this plasticity is limited. The major thermoregulatory challenge from global climate change may not be the shift in mean values (to which our young snakes adjusted) but the increased year-to-year variation (with which our snakes proved less able to deal).

The first example of erbium triple-stranded helicates displaying SMM behaviour.

PubMed

Gorczyński, Adam; Kubicki, Maciej; Pinkowicz, Dawid; Pełka, Robert; Patroniak, Violetta; Podgajny, Robert

2015-10-14

A series of isostructural C3-symmetrical triple stranded dinuclear lanthanide [Ln2L3](NO3)3 molecules have been synthesized using subcomponent self-assembly of Ln(NO3)3 with 2-(methylhydrazino)benzimidazole and 4-tert-butyl-2,6-diformylphenol, where Ln = Tb (1), Dy (2), Ho (3), Er (4), Tm (5), and Yb (6). The temperature dependent and field dependent magnetic properties of 1-6 were modeled using the van Vleck approximation including the crystal field term HCF, the super-exchange term HSE and the Zeeman term HZE. Ferromagnetic interactions were found in 1, 2, 4 and 6, while antiferromagnetic interactions were found in 3 and 5. The erbium analogue reveals field induced SMM behaviour.

Multi-year behaviour of the midnight OH∗ temperature according to observations at Zvenigorod over 2000-2016

NASA Astrophysics Data System (ADS)

Perminov, V. I.; Semenov, A. I.; Pertsev, N. N.; Medvedeva, I. V.; Dalin, P. A.; Sukhodoev, V. A.

2018-04-01

Using spectral measurements of the hydroxyl airglow at the Zvenigorod station (56° N, 37° E), Moscow region, over 2000-2016, we obtained the long-term set of data comprising 1822 midnight values of the OH∗ temperature in the mesopause region. These data revealed a 17-year series of its mean annual values, as well as amplitudes and phases of the first two harmonics of its annual variation. The obtained parameters were analyzed to determine statistically relevant characteristics of their long-term variations. As a result, we found that the long-term behaviour of the mean annual OH∗ temperature features a small negative linear trend (-0.07 ± 0.03 K/year) over the addressed period. Besides, its dependence on solar activity is shown to be 4.1 ± 0.5 K/100 SFU. Regarding the long-term behaviour of the mean annual OH∗ temperature, we revealed the existence of two oscillations with 3-year (the amplitude being 1.3 ± 0.2 K) and 4.1-year (the amplitude being 0.6 ± 0.2 K) periods. We obtained empirical relations describing year-to-year variations in the amplitudes and phases of the annual and semi-annual harmonics.

Influence of nanotube length and density on the plasmonic terahertz response of single-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Karlsen, P.; Shuba, M. V.; Beckerleg, C.; Yuko, D. I.; Kuzhir, P. P.; Maksimenko, S. A.; Ksenevich, V.; Viet, Ho; Nasibulin, A. G.; Tenne, R.; Hendry, E.

2018-01-01

We measure the conductivity spectra of thin films comprising bundled single-walled carbon nanotubes (CNTs) of different average lengths in the frequency range 0.3-1000 THz and temperature interval 10-530 K. The observed temperature-induced changes in the terahertz conductivity spectra are shown to depend strongly on the average CNT length, with a conductivity around 1 THz that increases/decreases as the temperature increases for short/long tubes. This behaviour originates from the temperature dependence of the electron scattering rate, which we obtain from Drude fits of the measured conductivity in the range 0.3-2 THz for 10 μm length CNTs. This increasing scattering rate with temperature results in a subsequent broadening of the observed THz conductivity peak at higher temperatures and a shift to lower frequencies for increasing CNT length. Finally, we show that the change in conductivity with temperature depends not only on tube length, but also varies with tube density. We record the effective conductivities of composite films comprising mixtures of WS2 nanotubes and CNTs versus CNT density for frequencies in the range 0.3-1 THz, finding that the conductivity increases/decreases for low/high density films as the temperature increases. This effect arises due to the density dependence of the effective length of conducting pathways in the composite films, which again leads to a shift and temperature dependent broadening of the THz conductivity peak.

New WC-Cu thermal barriers for fusion applications: High temperature mechanical behaviour

NASA Astrophysics Data System (ADS)

Tejado, E.; Dias, M.; Correia, J. B.; Palacios, T.; Carvalho, P. A.; Alves, E.; Pastor, J. Y.

2018-01-01

The combination of tungsten carbide and copper as a thermal barrier could effectively reduce the thermal mismatch between tungsten and copper alloy, which are proposed as base armour and heat sink, respectively, in the divertor of future fusion reactors. Furthermore, since the optimum operating temperature windows for these divertor materials do not overlap, a compatible thermal barrier interlayer between them is required to guarantee a smooth thermal transition, which in addition may mitigate radiation damage. The aim of this work is to study the thermo-mechanical properties of WC-Cu cermets fabricated by hot pressing. Focus is placed on the temperature effect and composition dependence, as the volume fraction of copper varies from 25 to 50 and 75 vol%. To explore this behaviour, fracture experiments are performed within a temperature range from room temperature to 800 °C under vacuum. In addition, elastic modulus and thermal expansion coefficient are estimated from these tests. Results reveal a strong dependence of the performance on temperature and on the volume fraction of copper and, surprisingly, a slight percent of Cu (25 vol%) can effectively reduce the large difference in thermal expansion between tungsten and copper alloy, which is a critical point for in service applications. The thermal performance of these materials, together with their mechanical properties could indeed reduce the heat transfer from the PFM to the underlying element while supporting the high thermal stresses of the joint. Thus, the presence of these cermets could allow the reactor to operate above the ductile to brittle transition temperature of tungsten, without compromising the underlying materials.

Critical behaviour and filed dependence of magnetic entropy change in K-doped manganites Pr0.8Na0.2-xKxMnO3 (x = 0.10 and 0.15)

NASA Astrophysics Data System (ADS)

Ben Khlifa, H.; M'nassri, R.; Tarhouni, S.; Regaieg, Y.; Cheikhrouhou-Koubaa, W.; Chniba-Boudjada, N.; Cheikhrouhou, A.

2018-01-01

The orthorhombic Pr0.8Na0.2-xKxMnO3 (x = 0.10 and 0.15) manganites are prepared by using the solid state reaction at high temperatures. The critical exponents (β, γ, δ) are investigated through various techniques such as modified Arrott plot, Kouvel-Fisher method and critical isotherm analysis based on the data of the magnetic measurements recorded around the Curie temperature. The critical exponents are derived from the magnetization data using the Kouvel-Fisher method, are found to be β = 0.32(4) and γ = 1.29(2) at TC 123 K for x = 0.10 and β = 0.31(1) and γ = 1.25(2) at TC 133 K for x = 0.15. The critical exponent values obtained for both samples are comparable to the values predicted by the 3D-Ising model, and have also been verified by the scaling equation of state. Such results demonstrate the existence of ferromagnetic short-range order in our materials. The magnetic entropy changes of polycrystalline samples with a second-order phase transition are investigated. A large magnetic entropy change deduced from isothermal magnetization curves, is observed in our samples with a peak centered on their respective Curie temperatures (TC). The field dependence of the magnetic entropy changes are analyzed, which show power law dependence ΔSmax ≈ a(μ0 H) n at transition temperature. The values of n obey to the Curie Weiss law above the transition temperature. It is shown that for the investigated materials, the magnetic entropy change follow a master curve behaviour. The rescaled magnetic entropy change curves for different applied fields collapse onto a single curve for both samples.

Interface interactions in benzophenone doped by multiwalled carbon nanotubes

NASA Astrophysics Data System (ADS)

Lebovka, N. I.; Goncharuk, A.; Melnyk, V. I.; Puchkovska, G. A.

2009-08-01

The interface interactions were studied by methods of conductometry, low-temperature phosphorescence and differential scanning calorimetry (DSC) in multiwalled carbon nanotubes (MWCNT) and benzophenone (BP) composite. The concentration of MWCNTs was varied within 0-1 wt%. A percolative threshold was found at MWCNT concentrations exceeding 0.1 wt%. The integration of MWCNTs caused melting temperature increase (≈3 K for 1 wt% of MWCNTs). The effect of positive thermal resistively coefficient, as well as substantial hysteretic behaviour of electrical conductivity σ in a heating-cooling cycle, was observed near the melting point of BP ( T m=321.5 K). The activation-type temperature behaviour of electrical conductivity was observed in the temperature range of supercooled BP. The activation energy was decreasing with increase of MWCNT concentration. The observed nonlinear dependencies of electrical conductivity σ vs. applied voltage U reflect the transport mechanism of the charge carriers through amorphous interface films formed near the surface of the MWCNTs. The thermal shifts of phosphorescence spectra measured within the temperature range 5-200 K evidence existence of such interface films of amorphous BP with width of the order of 0.1 μm.

The effect of ambient temperature, habitat quality and individual age on incubation behaviour and incubation feeding in a socially monogamous songbird.

PubMed

Amininasab, Seyed Mehdi; Kingma, Sjouke A; Birker, Martje; Hildenbrandt, Hanno; Komdeur, Jan

Incubation is an important aspect of avian life history. The behaviour is energetically costly, and investment in incubation strategies within species, like female nest attentiveness and the feeding by the non-incubating partner during incubation, can therefore vary depending on environmental and individual characteristics. However, little is known about the combined effect of these characteristics. We investigated the importance of ambient temperature, habitat quality, and bird age on female incubation behaviour and male feeding of the incubating female (incubation feeding) in blue tits Cyanistes caeruleus , a socially monogamous songbird. An increase in ambient temperature resulted in a higher nest temperature, and this enabled females to increase the time off the nest for self-maintenance activities. Probably as a consequence of this, an increase in ambient temperature was associated with fewer incubation feedings by the male. Moreover, in areas with more food available (more deciduous trees), females had shorter incubation recesses and males fed females less often. Additionally, males fed young females more, presumably to increase such females' investment in their eggs, which were colder on average (despite the length of recesses and female nest attentiveness being independent of female age). Male age did not affect incubation feeding rate. In conclusion, the patterns of incubation behaviour were related to both environmental and individual characteristics, and male incubation feeding was adjusted to females' need for food according these characteristics, which can facilitate new insights to the study of avian incubation energetics. Parents often invest a substantial amount of energy in raising offspring. How much they do so depends on several environmental factors and on the extent they cooperate to raise the offspring. In birds, males can feed incubating females, which may allow females to stay longer on the nest, which, in turn, may ultimately improve reproductive success. The interplay between environmental factors and such incubation feeding on incubation attendance has, however, received little attention. Here, we show that favourable circumstances (higher ambient temperature and food availability) allowed incubating blue tit females to increase the time off the nest to improve self-maintenance and males to feed them less, whereas males also fed inexperienced partners more often. Thus, we show a concerted effect of several environmental and intrinsic factors on parental effort during incubation, which will help to improve the general understanding of avian incubation and parental care.

Effect of pyrolysis temperature on polycyclic aromatic hydrocarbons toxicity and sorption behaviour of biochars prepared by pyrolysis of paper mill effluent treatment plant sludge.

PubMed

Devi, Parmila; Saroha, Anil K

2015-09-01

The polycyclic aromatic hydrocarbons (PAHs) toxicity and sorption behaviour of biochars prepared from pyrolysis of paper mill effluent treatment plant (ETP) sludge in temperature range 200-700 °C was studied. The sorption behaviour was found to depend on the degree of carbonization where the fractions of carbonized and uncarbonized organic content in the biochar act as an adsorption media and partition media, respectively. The sorption and partition fractions were quantified by isotherm separation method and isotherm parameters were correlated with biochar properties (aromaticity, polarity, surface area, pore volume and ash content). The risk assessment for the 16 priority EPA PAHs present in the biochar matrix was performed and it was found that the concentrations of the PAHs in the biochar were within the permissible limits prescribed by US EPA (except BC400 and BC500 for high molecular weight PAHs). Copyright © 2015 Elsevier Ltd. All rights reserved.

Salmonella enterica isolates from layer farm environments are able to form biofilm on eggshell surfaces.

PubMed

Pande, Vivek V; McWhorter, Andrea R; Chousalkar, Kapil K

2016-08-01

This study examined the eggshell biofilm forming ability of Salmonella enterica isolates recovered from egg farms. Multicellular behaviour and biofilm production were examined at 22 and 37°C by Congo red morphology and the crystal violet staining assay. The results indicated that the biofilm forming behaviour of Salmonella isolates was dependent on temperature and associated with serovars. Significantly greater biofilm production was observed at 22°C compared with 37°C. The number of viable biofilm cells attached to eggshells after incubation for 48 h at 22°C was significantly influenced by serovar. Scanning electron microscopic examination revealed firm attachment of bacterial cells to the eggshell surface. The relative expression of csgD and adrA gene was significantly higher in eggshell biofilm cells of S. Mbandaka and S. Oranienburg. These findings demonstrate that Salmonella isolates are capable of forming biofilm on the eggshell surface and that this behaviour is influenced by temperature and serovar.

Stress-induced behaviour in adult and old rats: effects of neonatal asphyxia, body temperature and chelation of iron.

PubMed

Rogalska, J; Caputa, M; Wentowska, K; Nowakowska, A

2006-11-01

Perinatal asphyxia in mammals leads to iron accumulation in the brain, which results in delayed neurobehavioural disturbances, including impaired learning and abnormal alertness over their entire life span. The aim of this investigation was to verify our hypothesis that newborn rats, showing reduced normal body temperature, are protected against neurotoxicity of the asphyxia up to senescence. Alertness was studied in adult and old male Wistar rats after exposure to critical neonatal anoxia: (i) at physiological neonatal body temperature of 33 degrees C, (ii) at body temperature elevated to 37 degrees C, or (iii) at body temperature elevated to 39 degrees C (the thermal conditions remained unchanged both during anoxia and for 2 h postanoxia). To elucidate the effect of iron-dependent postanoxic oxidative damage to the brain, half of the group (iii) was injected with deferoxamine, a chelator of iron. Postanoxic behavioural disturbances were recorded in open-field, elevated plus-maze, and sudden silence tests when the rats reached the age of 12 and 24 months. Open-field stress-induced motor activity was reduced in rats subjected to neonatal anoxia under hyperthermic conditions. In contrast, these rats were hyperactive in the plus-maze test. Both the plus-maze and sudden silence tests show reduced alertness of these rats to external stimuli signalling potential dangers. The behavioural disturbances were prevented by body temperature of 33 degrees C and by administration of deferoxamine.

Trapping and desorption of complex organic molecules in water at 20 K

NASA Astrophysics Data System (ADS)

Burke, Daren J.; Puletti, Fabrizio; Woods, Paul M.; Viti, Serena; Slater, Ben; Brown, Wendy A.

2015-10-01

The formation, chemical, and thermal processing of complex organic molecules (COMs) is currently a topic of much interest in interstellar chemistry. The isomers glycolaldehyde, methyl formate, and acetic acid are particularly important because of their role as pre-biotic species. It is becoming increasingly clear that many COMs are formed within interstellar ices which are dominated by water. Hence, the interaction of these species with water ice is crucially important in dictating their behaviour. Here, we present the first detailed comparative study of the adsorption and thermal processing of glycolaldehyde, methyl formate, and acetic acid adsorbed on and in water ices at astrophysically relevant temperatures (20 K). We show that the functional group of the isomer dictates the strength of interaction with water ice, and hence the resulting desorption and trapping behaviour. Furthermore, the strength of this interaction directly affects the crystallization of water, which in turn affects the desorption behaviour. Our detailed coverage and composition dependent data allow us to categorize the desorption behaviour of the three isomers on the basis of the strength of intermolecular and intramolecular interactions, as well as the natural sublimation temperature of the molecule. This categorization is extended to other C, H, and O containing molecules in order to predict and describe the desorption behaviour of COMs from interstellar ices.

Investigation of conduction and relaxation phenomena in BaZrxTi1-xO3 (x=0.05) by impedance spectroscopy

NASA Astrophysics Data System (ADS)

Mahajan, Sandeep; Haridas, Divya; Ali, S. T.; Munirathnam, N. R.; Sreenivas, K.; Thakur, O. P.; Prakash, Chandra

2014-10-01

In present study we have prepared ferroelectric BaZrxTi1-xO3 (x=0.05) ceramic by conventional solid state reaction route and studied its electrical properties as a function of temperature and frequency. X-ray diffraction (XRD) analysis shows single-phase formation of the compound with orthorhombic crystal structure at room temperature. Impedance and electric modulus spectroscopy analysis in the frequency range of 40 Hz-1 MHz at high temperature (200-600 °C) suggests two relaxation processes with different time constant are involved which are attributed to bulk and grain boundary effects. Frequency dependent dielectric plot at different temperature shows normal variation with frequency while dielectric loss (tanδ) peak was found to obey an Arrhenius law with activation energy of 1.02 eV. The frequency-dependent AC conductivity data were also analyzed in a wide temperature range. In present work we have studied the role of grain and grain boundaries on the electrical behaviour of Zr-doped BaTiO3 and their dependence on temperature and frequency by complex impedance and modulus spectroscopy (CIS) technique in a wide frequency (40 Hz-1 MHz) and high temperature range.

The Gassmann-Burgers Model to Simulate Seismic Waves at the Earth Crust And Mantle

NASA Astrophysics Data System (ADS)

Carcione, José M.; Poletto, Flavio; Farina, Biancamaria; Craglietto, Aronne

2017-03-01

The upper part of the crust shows generally brittle behaviour while deeper zones, including the mantle, may present ductile behaviour, depending on the pressure-temperature conditions; moreover, some parts are melted. Seismic waves can be used to detect these conditions on the basis of reflection and transmission events. Basically, from the elastic-plastic point of view the seismic properties (seismic velocity and density) depend on effective pressure and temperature. Confining and pore pressures have opposite effects on these properties, such that very small effective pressures (the presence of overpressured fluids) may substantially decrease the P- and S-wave velocities, mainly the latter, by opening of cracks and weakening of grain contacts. Similarly, high temperatures induce the same effect by partial melting. To model these effects, we consider a poro-viscoelastic model based on Gassmann equations and Burgers mechanical model to represent the properties of the rock frame and describe ductility in which deformation takes place by shear plastic flow. The Burgers elements allow us to model the effects of seismic attenuation, velocity dispersion and steady-state creep flow, respectively. The stiffness components of the brittle and ductile media depend on stress and temperature through the shear viscosity, which is obtained by the Arrhenius equation and the octahedral stress criterion. Effective pressure effects are taken into account in the dry-rock moduli using exponential functions whose parameters are obtained by fitting experimental data as a function of confining pressure. Since fluid effects are important, the density and bulk modulus of the saturating fluids (water and steam) are modeled using the equations provided by the NIST website, including supercritical behaviour. The theory allows us to obtain the phase velocity and quality factor as a function of depth and geological pressure and temperature as well as time frequency. We then obtain the PS and SH equations of motion recast in the velocity-stress formulation, including memory variables to avoid the computation of time convolutions. The equations correspond to isotropic anelastic and inhomogeneous media and are solved by a direct grid method based on the Runge-Kutta time stepping technique and the Fourier pseudospectral method. The algorithm is tested with success against known analytical solutions for different shear viscosities. An example shows how anomalous conditions of pressure and temperature can in principle be detected with seismic waves.

Moisture uptake of polyoxyethylene glycol glycerides used as matrices for drug delivery: kinetic modelling and practical implications.

PubMed

Qi, Sheng; Belton, Peter; McAuley, William; Codoni, Doroty; Darji, Neerav

2013-04-01

Gelucire 50/13, a polyoxyethylene glycol glyceride mixture, has been widely used in drug delivery, but its moisture uptake behaviour is still poorly understood. In this study, the effects of relative humidity, temperature, and drug incorporation on the moisture uptake of Gelucire are reported in relation to their practical implications for preparation of solid dispersions using this material. DVS combined with kinetics modelling was used as the main experimental method to study the moisture uptake behaviour of Gelucire. Thermal and microscopic methods were employed to investigate the effect of moisture uptake on the physical properties of the material and drug loaded solid dispersions. The moisture uptake by Gelucire 50/13 is temperature and relative humidity dependent. At low temperatures and low relative humidities, moisture sorption follows a GAB model. The model fitting indicated that at high relative humidities the sorption is a complex process, potentially involving PEG being dissolved and the PEG solution acting as solvent to dissolve other components. Careful control of the storage and processing environmental conditions are required when using Gelucire 50/13. The incorporation of model drugs not only influences the moisture uptake capacity of Gelucire 50/13 but also the solidification behaviour.

Temperature Effects on the Magnetization and Magnetoimpedance in Ferromagnetic Glass-Covered microwires

NASA Astrophysics Data System (ADS)

Uddin, A.; Evstigneeva, S. A.; Dzhumazoda, A.; Salem, M. M.; Nematov, M. G.; Adam, A. M.; Panina, LV; Morchenko, A. T.

2017-11-01

The effect of temperature on static and dynamic magnetization in Co-based amorphous microwires was investigated with the aim of potential applications in miniature temperature sensors. The wires of two compositions with different magnetostriction and Curie temperature in glass-cover and after removing the glass layer demonstrated very different temperature behaviour of the magnetization loops and magnetoimpedance. The mechanisms of the temperature effects are related to the residual stress distribution due to fast solidification, the difference in thermal expansion coefficient of metal and glass and the proximity to the Curie temperature. The interplay of these factors may result in a very strong temperature dependence of magnetoimpedance in a moderate temperature range (room temperature -373K). Such elements may be incorporated in various composite materials for a local temperature monitoring.

Temperature dependence of quantized states in an InGaAs/GaAs strained asymmetric triangular quantum well

NASA Astrophysics Data System (ADS)

Chi, W. S.; Lin, D. Y.; Huang, Y. S.; Qiang, H.; Pollak, F. H.; Mathine, D. L.; Maracas, G. N.

1996-03-01

Photoreflectance (PR), contactless electroreflectance (CER) and piezoreflectance (PzR) measurements of an InGaAs/GaAs strained asymmetric triangular quantum well (ATQW) heterostructure as a function of temperature in the range of 20 to 300 K have been carried out. The structure was fabricated by molecular beam epitaxy using the digital alloy compositional grading method. A careful analysis of the PR, CER and PzR spectra has led to the identification of various excitonic transitions, mnH(L), between the mth conduction band state to the nth heavy(light)-hole band state. Comparison of the observed intersubband transitions with a theoretical calculation based on the envelope function model, including the effects of strain, provide a self-consistent check of the ATQW composition profile. The detailed study of the temperature dependence of the excitonic transition energies indicates that the potential profile of the ATQW varies at different temperatures. The parameters that describe the temperature dependence of 0268-1242/11/3/012/img8 are evaluated. The anomalous behaviour of the temperature dependence of the linewidth of 11H, 0268-1242/11/3/012/img9, is compared with recent results for GaAs/AlGaAs and InGaAs/GaAs symmetric rectangular quantum wells of comparable dimensions.

Dependence of the critical temperature in overdoped copper oxides on superfluid density

NASA Astrophysics Data System (ADS)

Božović, I.; He, X.; Wu, J.; Bollinger, A. T.

2016-08-01

The physics of underdoped copper oxide superconductors, including the pseudogap, spin and charge ordering and their relation to superconductivity, is intensely debated. The overdoped copper oxides are perceived as simpler, with strongly correlated fermion physics evolving smoothly into the conventional Bardeen-Cooper-Schrieffer behaviour. Pioneering studies on a few overdoped samples indicated that the superfluid density was much lower than expected, but this was attributed to pair-breaking, disorder and phase separation. Here we report the way in which the magnetic penetration depth and the phase stiffness depend on temperature and doping by investigating the entire overdoped side of the La2-xSrxCuO4 phase diagram. We measured the absolute values of the magnetic penetration depth and the phase stiffness to an accuracy of one per cent in thousands of samples; the large statistics reveal clear trends and intrinsic properties. The films are homogeneous; variations in the critical superconducting temperature within a film are very small (less than one kelvin). At every level of doping the phase stiffness decreases linearly with temperature. The dependence of the zero-temperature phase stiffness on the critical superconducting temperature is generally linear, but with an offset; however, close to the origin this dependence becomes parabolic. This scaling law is incompatible with the standard Bardeen-Cooper-Schrieffer description.

Behavioural responses to thermal conditions affect seasonal mass change in a heat-sensitive northern ungulate.

PubMed

van Beest, Floris M; Milner, Jos M

2013-01-01

Empirical tests that link temperature-mediated changes in behaviour (activity and resource selection) to individual fitness or condition are currently lacking for endotherms yet may be critical to understanding the effect of climate change on population dynamics. Moose (Alces alces) are thought to suffer from heat stress in all seasons so provide a good biological model to test whether exposure to non-optimal ambient temperatures influence seasonal changes in body mass. Seasonal mass change is an important fitness correlate of large herbivores and affects reproductive success of female moose. Using GPS-collared adult female moose from two populations in southern Norway we quantified individual differences in seasonal activity budget and resource selection patterns as a function of seasonal temperatures thought to induce heat stress in moose. Individual body mass was recorded in early and late winter, and autumn to calculate seasonal mass changes (n = 52 over winter, n = 47 over summer). We found large individual differences in temperature-dependent resource selection patterns as well as within and between season variability in thermoregulatory strategies. As expected, individuals using an optimal strategy, selecting young successional forest (foraging habitat) at low ambient temperatures and mature coniferous forest (thermal shelter) during thermally stressful conditions, lost less mass in winter and gained more mass in summer. This study provides evidence that behavioural responses to temperature have important consequences for seasonal mass change in moose living in the south of their distribution in Norway, and may be a contributing factor to recently observed declines in moose demographic performance. Although the mechanisms that underlie the observed temperature mediated habitat-fitness relationship remain to be tested, physiological state and individual variation in thermal tolerance are likely contributory factors. Climate-related effects on animal behaviour, and subsequently fitness, are expected to intensify as global warming continues.

Behavioural Responses to Thermal Conditions Affect Seasonal Mass Change in a Heat-Sensitive Northern Ungulate

PubMed Central

van Beest, Floris M.; Milner, Jos M.

2013-01-01

Background Empirical tests that link temperature-mediated changes in behaviour (activity and resource selection) to individual fitness or condition are currently lacking for endotherms yet may be critical to understanding the effect of climate change on population dynamics. Moose (Alces alces) are thought to suffer from heat stress in all seasons so provide a good biological model to test whether exposure to non-optimal ambient temperatures influence seasonal changes in body mass. Seasonal mass change is an important fitness correlate of large herbivores and affects reproductive success of female moose. Methodology/Principal Findings Using GPS-collared adult female moose from two populations in southern Norway we quantified individual differences in seasonal activity budget and resource selection patterns as a function of seasonal temperatures thought to induce heat stress in moose. Individual body mass was recorded in early and late winter, and autumn to calculate seasonal mass changes (n = 52 over winter, n = 47 over summer). We found large individual differences in temperature-dependent resource selection patterns as well as within and between season variability in thermoregulatory strategies. As expected, individuals using an optimal strategy, selecting young successional forest (foraging habitat) at low ambient temperatures and mature coniferous forest (thermal shelter) during thermally stressful conditions, lost less mass in winter and gained more mass in summer. Conclusions/Significance This study provides evidence that behavioural responses to temperature have important consequences for seasonal mass change in moose living in the south of their distribution in Norway, and may be a contributing factor to recently observed declines in moose demographic performance. Although the mechanisms that underlie the observed temperature mediated habitat-fitness relationship remain to be tested, physiological state and individual variation in thermal tolerance are likely contributory factors. Climate-related effects on animal behaviour, and subsequently fitness, are expected to intensify as global warming continues. PMID:23776584

Temperature-dependent plastic hysteresis in highly confined polycrystalline Nb films

NASA Astrophysics Data System (ADS)

Waheed, S.; Hao, R.; Zheng, Z.; Wheeler, J. M.; Michler, J.; Balint, D. S.; Giuliani, F.

2018-02-01

In this study, the effect of temperature on the cyclic deformation behaviour of a confined polycrystalline Nb film is investigated. Micropillars encapsulating a thin niobium interlayer are deformed under cyclic axial compression at different test temperatures. A distinct plastic hysteresis is observed for samples tested at elevated temperatures, whereas negligible plastic hysteresis is observed for samples tested at room temperature. These results are interpreted using planar discrete dislocation plasticity incorporating slip transmission across grain boundaries. The effect of temperature-dependent grain boundary energy and dislocation mobility on dislocation penetration and, consequently, the size of plastic hysteresis is simulated to correlate with the experimental results. It is found that the decrease in grain boundary energy barrier caused by the increase in temperature does not lead to any appreciable change in the cyclic response. However, dislocation mobility significantly affects the size of plastic hysteresis, with high mobilities leading to a larger hysteresis. Therefore, it is postulated that the experimental observations are predominantly caused by an increase in dislocation mobility as the temperature is increased above the critical temperature of body-centred cubic niobium.

Daytime avoidance of chemosensory alarm cues by adult sea lamprey (Petromyzon marinus)

USGS Publications Warehouse

Di Rocco, Richard; Belanger, Cowan; Imre, István; Brown, Grant; Johnson, Nicholas S.

2014-01-01

Sea lamprey (Petromyzon marinus) avoid damage-released and predator chemosensory cues at night, but their response to these cues during the day is unknown. Here, we explored (i) whether sea lamprey avoid these cues during the day and (ii) the effect of water temperature on the avoidance of chemosensory alarm cues in two diurnal laboratory experiments. We hypothesized that daytime activity would be temperature-dependent and that only sea lamprey vulnerable to predation (i.e., not hiding) would behaviourally respond to chemosensory alarm cues. Ten groups of ten sea lamprey were exposed to one of a variety of potential chemosensory cues. The experiments were conducted over a range of temperatures to quantify the effect of temperature on avoidance behaviour. Consistent with our hypothesis, a higher proportion of animals were active during daytime as water temperature increased. Moving sea lamprey showed an avoidance response to 2-phenylethylamine (a compound found in mammalian urine) and human saliva once water temperatures had risen to mean (±SD) = 13.7 (±1.4) °C. Resting and hiding sea lamprey did not show an avoidance response to any of the experimental stimuli.

Thermo-mechanical Modelling of Pebble Beds in Fusion Blankets and its Implementation by a Return-Mapping Algorithm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gan, Yixiang; Kamlah, Marc

In this investigation, a thermo-mechanical model of pebble beds is adopted and developed based on experiments by Dr. Reimann at Forschungszentrum Karlsruhe (FZK). The framework of the present material model is composed of a non-linear elastic law, the Drucker-Prager-Cap theory, and a modified creep law. Furthermore, the volumetric inelastic strain dependent thermal conductivity of beryllium pebble beds is taken into account and full thermo-mechanical coupling is considered. Investigation showed that the Drucker-Prager-Cap model implemented in ABAQUS can not fulfill the requirements of both the prediction of large creep strains and the hardening behaviour caused by creep, which are of importancemore » with respect to the application of pebble beds in fusion blankets. Therefore, UMAT (user defined material's mechanical behaviour) and UMATHT (user defined material's thermal behaviour) routines are used to re-implement the present thermo-mechanical model in ABAQUS. An elastic predictor radial return mapping algorithm is used to solve the non-associated plasticity iteratively, and a proper tangent stiffness matrix is obtained for cost-efficiency in the calculation. An explicit creep mechanism is adopted for the prediction of time-dependent behaviour in order to represent large creep strains in high temperature. Finally, the thermo-mechanical interactions are implemented in a UMATHT routine for the coupled analysis. The oedometric compression tests and creep tests of pebble beds at different temperatures are simulated with the help of the present UMAT and UMATHT routines, and the comparison between the simulation and the experiments is made. (authors)« less

Are there evidences of altitudinal effects of air temperature trends in the European Alps 1820-2013?

NASA Astrophysics Data System (ADS)

Schoener, W.; Auer, I.; Chimani, B.; Garnekind, M.; Haslinger, K.

2013-12-01

We use the HISTALP data set (www.zamg.ac.at/histalp) in order to assess the elevation dependency of air temperature trends within the European Alps. The evidence of altitudinal effects of the climate warming (with higher sensitivity of high mountain regions to warming) is a key statement, or at least key hypothesis, in many studies. The high relevance of such statement resp. hypothesis is obvious if one consider the impacts resulting from such fact, such as snow- and glacier melting and related effects for mountain hydrology. The HISTALP data set stands out with respect to its series lengths and its high level of homogenisation. Interestingly, the HISTALP temperature data show no clear altitudinal dependency of warming or cooling trends within the period 1820-2013. Additionally, a rather homogenous temporal trend could be observed within the entire Greater Alpine Region (GAR). Because HISTALP include also air pressure and vapour pressure series, we could compare our measured air temperatures with mean-column air temperatures, computed by the barometric formula, which were derived from the independently measured air pressure data (using vapour pressure to account for the atmospheric water content) at low resp. high elevations. Computed mean column temperatures are in good agreement with observed temperatures, indicating generally homogenous temporal temperature trend behaviour at different elevations. Our finding contradicts several results from climate modelling attempts and also other studies investigating Alpine temperature trends. We conclude that, whereas modelling results are still limited in the assessment of altitudinal effect of temperature trends from missing atmospheric processes captured by the models, the difference of the trend behaviour compared to other analyses of instrumental air temperatures comes from the seasonal base taken as the basis for trend estimation. It appears that opposite trend in spring and autumn for the period 1980-2000, respectively, levels each other out for the annual temperature trend.

Strong temperature effect on the sizes of the Cooper pairs in a two-band superconductor

NASA Astrophysics Data System (ADS)

Örd, Teet; Rägo, Küllike; Vargunin, Artjom; Litak, Grzegorz

2018-01-01

We study the temperature dependencies of the mean sizes of the Cooper pairs in a two-band BCS-type s-wave superconductivity model with coupling cut-off in the momentum space. It is found that, in contrast to single-band systems, the size of Cooper pairs in the weaker superconductivity band can significantly decrease with a temperature increase due to an interband proximity effect. The relevant spatial behaviour of the wave functions of the Cooper pairs is analyzed. The results also indicate a possibility that the size of Cooper pairs in two-band systems may increase with an increase in temperature.

Electrodynamics in cylindrical symmetry in the magnetic plasma state

NASA Astrophysics Data System (ADS)

López-Bara, F. I.; López-Aguilar, F.

2018-05-01

Excited states in magnetic structures of the so-called spin-ices and in some artificial magnetic materials present a behaviour as being a magnetic neutral plasma. In this state the electromagnetic waves in confined systems (waveguides) filled with materials with magnetic charges are able to transmit information and energy. In the natural spin-ices, the difficulty is the very low temperature for which these magnetic entities appear, whose phenomenology under the electromagnetic interaction is that of solids containing magnetic charges. However, similar behaviour may be present in other compounds at higher temperatures, even at room temperature and they are named artificial spin-ice compounds. This analysis is addressed to obtain theoretical results about magnetic responses and frequency-dependent magnetricity. The key physical magnitudes are the plasmon frequency () which is related to the cut-off frequency in a wave guide and the effective inertial masses () of these magnetic charges. All properties of the electromagnetic propagation in these compounds with effective magnetic monopoles depend on and m. This is carried out including the dissipative forces among magnetic charges which give new characteristic features to the electromagnetic propagation. The main goal of this work is the analysis of these electromagnetic properties in order to find possible circuital applications of these materials to be utilized by devices.

Design and experimental validation of an adaptive phononic crystal using highly dissipative polymeric material interface

NASA Astrophysics Data System (ADS)

Billon, K.; Ouisse, M.; Sadoulet-Reboul, E.; Collet, M.; Chevallier, G.; Khelif, A.

2017-04-01

In this paper, some numerical tools for dispersion analysis of periodic structures are presented, with a focus on the ability of the methods to deal with dissipative behaviour of the systems. An adaptive phononic crystal based on the combination of metallic parts and highly dissipative polymeric interface is designed. The system consists in an infinite periodic bidirectional waveguide. The periodic cylindrical pillars include a layer of shape memory polymer and Aluminum. The mechanical properties of the polymer depend on both temperature and frequency and can radically change from glassy to rubbery state, with various combination of high/low stiffness and high/low dissipation. A fractional derivative Zener model is used for the description of the frequency-dependent behaviour of the polymer. A 3D finite element model of the cell is developed for the design of the metamaterial. The "Shifted-Cell Operator" technique consists in a reformulation of the PDE problem by "shifting" in terms of wave number the space derivatives appearing in the mechanical behaviour operator inside the cell, while imposing continuity boundary conditions on the borders of the domain. Damping effects can easily be introduced in the system and a quadratic eigenvalue problem yields to the dispersion properties of the periodic structure. In order to validate the design and the adaptive character of the metamaterial, results issued from a full 3D model of a finite structure embedding an interface composed by a distributed set of the unit cells are presented. Various driving temperature are used to change the behaviour of the system. After this step, a comparison between the results obtained using the tunable structure simulation and the experimental results is presented. Two states are obtained by changing the temperature of the polymeric interface: at 25°C, the bandgap is visible around a selected frequency. Above the glass transition, the phononic crystal tends to behave as an homogeneous plate.

EFFECTS OF LASER RADIATION ON MATTER: Laser damage behaviour of titania coatings

NASA Astrophysics Data System (ADS)

Skvortsov, L. A.

2010-01-01

A model is proposed for the generation of defects responsible for laser damage in thin titania films during repetitive exposure to nanosecond near-IR laser pulses. The model relies on the hypothesis that there is charge transfer between two point defect centres differing in photoionisation cross section, one of which has an adsorptive nature. The model's predictions agree well with the experimentally determined accumulation curve and the temperature dependence of the damage threshold at low temperatures and clarify the role of protective coatings.

Internal quantum efficiency and tunable colour temperature in monolithic white InGaN/GaN LED

NASA Astrophysics Data System (ADS)

Titkov, Ilya E.; Yadav, Amit; Zerova, Vera L.; Zulonas, Modestas; Tsatsulnikov, Andrey F.; Lundin, Wsevolod V.; Sakharov, Alexey V.; Rafailov, Edik U.

2014-03-01

Internal Quantum Efficiency (IQE) of two-colour monolithic white light emitting diode (LED) was measured by temperature dependant electro-luminescence (TDEL) and analysed with modified rate equation based on ABC model. External, internal and injection efficiencies of blue and green quantum wells were analysed separately. Monolithic white LED contained one green InGaN QW and two blue QWs being separated by GaN barrier. This paper reports also the tunable behaviour of correlated colour temperature (CCT) in pulsed operation mode and effect of self-heating on device performance.

High pressure ferroelastic phase transition in SrTiO3

NASA Astrophysics Data System (ADS)

Salje, E. K. H.; Guennou, M.; Bouvier, P.; Carpenter, M. A.; Kreisel, J.

2011-07-01

High pressure measurements of the ferroelastic phase transition of SrTiO3 (Guennou et al 2010 Phys. Rev. B 81 054115) showed a linear pressure dependence of the transition temperature between the cubic and tetragonal phase. Furthermore, the pressure induced transition becomes second order while the temperature dependent transition is near a tricritical point. The phase transition mechanism is characterized by the elongation and tilt of the TiO6 octahedra in the tetragonal phase, which leads to strongly nonlinear couplings between the structural order parameter, the volume strain and the applied pressure. The phase diagram is derived from the Clausius-Clapeyron relationship and is directly related to a pressure dependent Landau potential. The nonlinearities of the pressure dependent strains lead to an increase of the fourth order Landau coefficient with increasing pressure and, hence, to a tricritical-second order crossover. This behaviour is reminiscent of the doping related crossover in isostructural KMnF3.

Wear Mechanism Maps for Magnesium Alloy AM60 and Composite AM60-9% (Al2O3)f

NASA Astrophysics Data System (ADS)

Ullah Khan, Muhammad Zafar

The purpose of this work was to study the tribological behaviour of squeeze cast Mg alloy AM60 and its composite AM60-9% (Al2O3) f. Dry sliding wear tests were performed on specimens of these materials using a block-on-ring tribometer which was equipped with a COF and temperature measurement system. Wear, COF and temperature maps were constructed to illustrate the effect of temperature and COF on the wear behaviour of the Mg alloy and it's composite. Four wear regimes namely low, mild, transient and severe wear were identified. The transition from mild to severe wear regime was found to be dependent on the bulk temperature of the specimen. Oxidational wear prevailed in low and mild wear whereas plastic deformation induced wear and melt wear controlled the wear rates in transient and severe wear regimes, respectively. This study shows that the incorporation of Al2O3 fibres in AM60 alloy improved the wear resistance of the resulting composite by delaying the transition from mild to severe wear.

Tree-hugging koalas demonstrate a novel thermoregulatory mechanism for arboreal mammals

PubMed Central

Briscoe, Natalie J.; Handasyde, Kathrine A.; Griffiths, Stephen R.; Porter, Warren P.; Krockenberger, Andrew; Kearney, Michael R.

2014-01-01

How climate impacts organisms depends not only on their physiology, but also whether they can buffer themselves against climate variability via their behaviour. One of the way species can withstand hot temperatures is by seeking out cool microclimates, but only if their habitat provides such refugia. Here, we describe a novel thermoregulatory strategy in an arboreal mammal, the koala Phascolarctos cinereus. During hot weather, koalas enhanced conductive heat loss by seeking out and resting against tree trunks that were substantially cooler than ambient air temperature. Using a biophysical model of heat exchange, we show that this behaviour greatly reduces the amount of heat that must be lost via evaporative cooling, potentially increasing koala survival during extreme heat events. While it has long been known that internal temperatures of trees differ from ambient air temperatures, the relevance of this for arboreal and semi-arboreal mammals has not previously been explored. Our results highlight the important role of tree trunks as aboveground ‘heat sinks’, providing cool local microenvironments not only for koalas, but also for all tree-dwelling species. PMID:24899683

H-modulated microwave absorption and resistive transition in the high- Tc superconductor YBa 2Cu 3O 7

NASA Astrophysics Data System (ADS)

Buluggiu, E.; Vera, A.; Amoretti, G.

1990-11-01

The derivative microwave absorption near Tc in presence of a sufficiently high field ( H⩾1 kOe) is related to the temperature variation of resistivity. This idea, originally proposed by Kim et al. (1988), is extended to take into account the effects of the anomalous resistive tail by using the thermoactivated flux-creep model proposed by Tinkham (1988). This gives a simple explanation for some relevant features observed in the temperature behaviour of the ESR absorption, as the asymmetry of the peak at Tc, with the long tail extending toward low temperatures, and the field dependence of height and linewidth, for which the model provides H-1 and H2/3 behaviour, respectively, ESR data on YBa 2Cu 3O 7 powder are in satisfactory agreement with this picture, when the role of the intrinsic 2D-character of this compound is properly taken into account. This allows us to deduce consistent values for the parameters a‖ and a⊥ of the anisotropic resistivity.

Dust silicate emission in FIR/submm

NASA Astrophysics Data System (ADS)

Coupeaud, A.; Demyk, K.; Mény, C.; Nayral, C.

2010-12-01

The far-infrared to millimeter wavelength (FIR-mm) range in astronomical observations is dominated by the thermal emission from large (10-100 nm) and cold (10-20 K) dust grains, which are in thermal equilibrium with the interstellar radiation field. However, the physics of the FIR-mm emission from such cold matter is not well understood as shown by the observed dependence with the temperature of the spectral index of the dust emissivity β and by the observed far infrared excess. Interestingly, a similar behaviour is observed in experiments of characterization of the spectral properties of dust analogues. We present a study of the optical properties of analogues of interstellar silicate grains at low temperature in the FIR/submm range aiming to understand their peculiar behaviour. Such studies are essential for the interpretation of the Herschel and Planck data.

Microstructural dependence on relevant physical-mechanical properties on SiO2-Na2O-CaO-P2O5 biological glasses.

PubMed

Rajendran, V; Begum, A Nishara; Azooz, M A; el Batal, F H

2002-11-01

Bioactive glasses of the system SiO2-Na2O-CaO-P2O5 have been prepared by the normal melting and annealing technique. The elastic moduli, attenuation, Vickers hardness, fracture toughness and fracture surface energy have been obtained using the known method at room temperature. The temperature dependence of elastic moduli and attenuation measurements have been extended over a wide range of temperature from 150 to 500 K. The SiO2 content dependence of velocities, attenuation, elastic moduli, and other parameters show an interesting observation at 45 wt% of SiO2 by exhibiting an anomalous behaviour. A linear relation is developed for Tg, which explores the influence of Na2O on SiO2-Na2O-CaO-P2O5 bioactive glasses. The measured hardness, fracture toughness and fracture surface energy show a linear relation with Young's modulus. It is also interesting to note that the observed results are functions of polymerisation and the number of non-bridging oxygens (NBO) prevailing in the network with change in SiO2 content. The temperature dependence of velocities, attenuation and elastic moduli show the existence of softening in the glass network structure as temperature increases.

Graphitic carbon nanospheres: A Raman spectroscopic investigation of thermal conductivity and morphological evolution by pulsed laser irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agarwal, Radhe; Sahoo, Satyaprakash, E-mail: satya504@gmail.com, E-mail: rkatiyar@hpcf.upr.edu; Chitturi, Venkateswara Rao

2015-12-07

Graphitic carbon nanospheres (GCNSs) were prepared by a unique acidic treatment of multi-walled nanotubes. Spherical morphology with a narrow size distribution was confirmed by transmission electron microscopy studies. The room temperature Raman spectra showed a clear signature of D- and G-peaks at around 1350 and 1591 cm{sup −1}, respectively. Temperature dependent Raman scattering measurements were performed to understand the phonon dynamics and first order temperature coefficients related to the D- and G-peaks. The temperature dependent Raman spectra in a range of 83–473 K were analysed, where the D-peak was observed to show a red-shift with increasing temperature. The relative intensity ratio ofmore » D- to G-peaks also showed a significant rise with increasing temperature. Such a temperature dependent behaviour can be attributed to lengthening of the C-C bond due to thermal expansion in material. The estimated value of the thermal conductivity of GCNSs ∼0.97 W m{sup −1} K{sup −1} was calculated using Raman spectroscopy. In addition, the effect of pulsed laser treatment on the GCNSs was demonstrated by analyzing the Raman spectra of post irradiated samples.« less

radiation and electric field induced effects on the order-disorder phase in lithium sodium sulphate crystals

NASA Astrophysics Data System (ADS)

Hamed, A. E.; Kassem, M. E.; El-Wahidy, E. F.; El-Abshehy, M. A.

1995-03-01

The temperature dependence of specific heat at constant pressure, Cp(T), has been measured for lithium sodium sulphate, LiNaSo4 crystals, at different ?-radiation doses and external bias electric field (Eb), in the temperature range 300-900 K. A nonlinear dependence of transition temperature, T1 and a remarkable change in the thermodynamic parameters, were obtained as the effect of both electric field and ?-radiation. The effect of ?-radiation doses on the phase transition in LiNaSO4 crystals was explained as due to an internal bias field, Eb, originating from the interaction of polar defects with the order parameter of the host lattice. The internal bias field effect on the behaviour of Cp(T) in LiNaSO4 crystals was similar to that of the external electric field (E).

Double path integral method for obtaining the mobility of the one-dimensional charge transport in molecular chain.

PubMed

Yoo-Kong, Sikarin; Liewrian, Watchara

2015-12-01

We report on a theoretical investigation concerning the polaronic effect on the transport properties of a charge carrier in a one-dimensional molecular chain. Our technique is based on the Feynman's path integral approach. Analytical expressions for the frequency-dependent mobility and effective mass of the carrier are obtained as functions of electron-phonon coupling. The result exhibits the crossover from a nearly free particle to a heavily trapped particle. We find that the mobility depends on temperature and decreases exponentially with increasing temperature at low temperature. It exhibits large polaronic-like behaviour in the case of weak electron-phonon coupling. These results agree with the phase transition (A.S. Mishchenko et al., Phys. Rev. Lett. 114, 146401 (2015)) of transport phenomena related to polaron motion in the molecular chain.

Delocalized and localized states of eg electrons in half-doped manganites.

PubMed

Winkler, E L; Tovar, M; Causa, M T

2013-07-24

We have studied the magnetic behaviour of half-doped manganite Y0.5Ca0.5MnO3 in an extended range of temperatures by means of magnetic susceptibility, χ(T), and electron spin resonance (ESR) experiments. At high temperature the system crystallizes in an orthorhombic structure. The resistivity value, ρ ≃ 0.05 Ω cm at 500 K, indicates a metallic behaviour, while the Curie-Weiss dependence of χ(T) and the thermal evolution of the ESR parameters are very well described by a model that considers a system conformed by localized Mn(4+) cores, [Formula: see text], and itinerant, eg, electrons. The strong coupling between t2g and eg electrons results in an enhanced Curie constant and an FM Curie-Weiss temperature that overcomes the AFM interactions between the [Formula: see text] cores. A transition to a more distorted phase is observed at T ≈ 500 K and signatures of localization of the eg electrons appear in the χ(T) behaviour below 300 K. A new Curie-Weiss regime is observed, where the Curie-constant value is consistent with dimer formation. Based on mean-field calculations, the dimer formation is predicted as a function of the interaction strength between the t2g and eg electrons.

Analysis of the internal temperature of the cells in a battery pack during SOC balancing

NASA Astrophysics Data System (ADS)

Mizanur, R.; Rashid, M. M.; Rahman, A.; Zahirul Alam, A. H. M.; Ihsan, S.; Mollik, M. S.

2017-03-01

Lithium-ion batteries are more suitable for the application of electric vehicle due to high energy and power density compared to other rechargeable batteries. However, the battery pack temperature has a great impact on the overall performance, cycle life, normal charging-discharging behaviour and even safety. During rapid charge transferring process, the internal temperature may exceed its allowable limit (460C). In this paper, an analysis of internal temperature during charge balancing and discharging conditions is presented. Specific interest is paid to the effects of temperature on the different rate of ambient temperature and discharging current. Matlab/Simulink Li-ion battery model and quasi-resonant converter base balancing system are used to study the temperature effect. Rising internal temperature depends on the rate of balancing current and ambient temperature found in the simulation results.

Temperature-dependent, behavioural, and transcriptional variability of a tritrophic interaction consisting of bean, herbivorous mite, and predator.

PubMed

Ozawa, Rika; Nishimura, Osamu; Yazawa, Shigenobu; Muroi, Atsushi; Takabayashi, Junji; Arimura, Gen-ichiro

2012-11-01

Different organisms compensate for, and adapt to, environmental changes in different ways. In this way, environmental changes affect animal-plant interactions. In this study, we assessed the effect of temperature on a tritrophic system of the lima bean, the herbivorous spider mite Tetranychus urticae and the predatory mite Phytoseiulus persimilis. In this system, the plant defends itself against T. urticae by emitting volatiles that attract P. persimilis. Over 20-40 °C, the emission of volatiles by infested plants and the subsequent attraction of P. persimilis peaked at 30 °C, but the number of eggs laid by T. urticae adults and the number of eggs consumed by P. persimilis peaked at 35 °C. This indicates that the spider mites and predatory mites performed best at a higher temperature than that at which most volatile attractants were produced. Our data from transcriptome pyrosequencing of the mites found that P. persimilis up-regulated gene families for heat shock proteins (HSPs) and ubiquitin-associated proteins, whereas T. urticae did not. RNA interference-mediated gene suppression in P. persimilis revealed differences in temperature responses. Predation on T. urticae eggs by P. persimilis that had been fed PpHsp70-1 dsRNA was low at 35 °C but not at 25 °C when PpHsp70-1 expression was very high. Overall, our molecular and behavioural approaches revealed that the mode and tolerance of lima bean, T. urticae and P. persimilis are distinctly affected by temperature variability, thereby making their tritrophic interactions temperature dependent. © 2012 Blackwell Publishing Ltd.

Implications of extreme sexual size dimorphism for thermoregulation in a freshwater turtle.

PubMed

Bulté, Grégory; Blouin-Demers, Gabriel

2010-02-01

Sexual size dimorphism (SSD) is a common phenomenon in animals. In many species females are substantially larger than males. Because body size plays a central role in modulating the body temperature (T (b)) of ectotherms, intersexual differences in body size may lead to important intersexual differences in thermoregulation. In addition, because SSD is realized by differences in growth rate and because growth rate is strongly temperature dependent in ectotherms, a conflict between male reproductive behaviour and thermoregulation may affect the expression of SSD. In this study, we investigated the thermal implications of SSD in a reptile exhibiting spectacular female-biased SSD: the northern map turtle (Graptemys geographica). Over three seasons, we collected >150,000 measurements of T (b) in free-ranging adult and juvenile northern map turtles using surgically implanted miniature temperature loggers. Northern map turtles exhibited seasonal patterns of thermoregulation typical of reptiles in northern latitudes, but we found that large adult females experienced a lower daily maximum T (b) and a narrower daily range of T (b) than adult males and small juvenile females. In addition, despite more time spent basking, large adult females were not able to thermoregulate as accurately as small turtles. Our findings strongly suggest that body size limits the ability to thermoregulate accurately in large females. By comparing thermoregulatory patterns between adult males and juvenile females of similar body size, we found no evidence that male reproductive behaviours are an impediment to thermoregulation. We also quantified the thermal significance of basking behaviour. We found, contrary to previous findings, that aerial basking allows northern map turtles to raise their T (b) substantially above water temperature, indicating that basking behaviour likely plays an important role in thermoregulation.

Facing the Heat: Thermoregulation and Behaviour of Lowland Species of a Cold-Dwelling Butterfly Genus, Erebia

PubMed Central

Kleckova, Irena; Klecka, Jan

2016-01-01

Understanding the potential of animals to immediately respond to changing temperatures is imperative for predicting the effects of climate change on biodiversity. Ectothermic animals, such as insects, use behavioural thermoregulation to keep their body temperature within suitable limits. It may be particularly important at warm margins of species occurrence, where populations are sensitive to increasing air temperatures. In the field, we studied thermal requirements and behavioural thermoregulation in low-altitude populations of the Satyrinae butterflies Erebia aethiops, E. euryale and E. medusa. We compared the relationship of individual body temperature with air and microhabitat temperatures for the low-altitude Erebia species to our data on seven mountain species, including a high-altitude population of E. euryale, studied in the Alps. We found that the grassland butterfly E. medusa was well adapted to the warm lowland climate and it was active under the highest air temperatures and kept the highest body temperature of all species. Contrarily, the woodland species, E. aethiops and a low-altitude population of E. euryale, kept lower body temperatures and did not search for warm microclimates as much as other species. Furthermore, temperature-dependence of daily activities also differed between the three low-altitude and the mountain species. Lastly, the different responses to ambient temperature between the low- and high-altitude populations of E. euryale suggest possible local adaptations to different climates. We highlight the importance of habitat heterogeneity for long-term species survival, because it is expected to buffer climate change consequences by providing a variety of microclimates, which can be actively explored by adults. Alpine species can take advantage of warm microclimates, while low-altitude grassland species may retreat to colder microhabitats to escape heat, if needed. However, we conclude that lowland populations of woodland species may be more severely threatened by climate warming because of the unavailability of relatively colder microclimates. PMID:27008409

Sun Basking in Red Wood Ants Formica polyctena (Hymenoptera, Formicidae): Individual Behaviour and Temperature-Dependent Respiration Rates

PubMed Central

Kadochová, Štěpánka; Frouz, Jan; Roces, Flavio

2017-01-01

In early spring, red wood ants Formica polyctena are often observed clustering on the nest surface in large numbers basking in the sun. It has been hypothesized that sun-basking behaviour may contribute to nest heating because of both heat carriage into the nest by sun-basking workers, and catabolic heat production from the mobilization of the workers’ lipid reserves. We investigated sun-basking behaviour in laboratory colonies of F. polyctena exposed to an artificial heat source. Observations on identified individuals revealed that not all ants bask in the sun. Sun-basking and non-sun-basking workers did not differ in body size nor in respiration rates. The number of sun-basking ants and the number of their visits to the hot spot depended on the temperature of both the air and the hot spot. To investigate whether sun basking leads to a physiological activation linked with increased lipolysis, we measured respiration rates of individual workers as a function of temperature, and compared respiration rates of sun-basking workers before and two days after they were allowed to expose themselves to a heat source over 10 days, at self-determined intervals. As expected for ectothermic animals, respiration rates increased with increasing temperatures in the range 5 to 35°C. However, the respiration rates of sun-basking workers measured two days after a long-term exposure to the heat source were similar to those before sun basking, providing no evidence for a sustained increase of the basal metabolic rates after prolonged sun basking. Based on our measurements, we argue that self-heating of the nest mound in early spring has therefore to rely on alternative heat sources, and speculate that physical transport of heat in the ant bodies may have a significant effect. PMID:28114396

The Burgers/squirt-flow seismic model of the crust and mantle

NASA Astrophysics Data System (ADS)

Carcione, José M.; Poletto, Flavio; Farina, Biancamaria

2018-01-01

Part of the crust shows generally brittle behaviour while areas of high temperature and/or high pore pressure, including the mantle, may present ductile behaviour. For instance, the potential heat source of geothermal fields, overpressured formations and molten rocks. Seismic waves can be used to detect these conditions on the basis of reflection and transmission events. Basically, from the elastic-plastic point of view the seismic properties (seismic velocity, quality factor and density) depend on effective pressure and temperature. Confining and pore pressures have opposite effects on these properties, and high temperatures may induce a similar behaviour by partial melting. In order to model these effects, we consider a poro-viscoelastic model based on the Burgers mechanical element and the squirt-flow model to represent the properties of the rock frame to describe ductility in which deformation takes place by shear plastic flow, and to model local and global fluid flow effects. The Burgers element allows us to model the effects of the steady-state creep flow on the dry-rock frame. The stiffness components of the brittle and ductile media depend on stress and temperature through the shear viscosity, which is obtained by the Arrhenius equation and the octahedral stress criterion. Effective pressure effects are taken into account in the dry-rock moduli by using exponential functions whose parameters are obtained by fitting experimental data as a function of confining pressure. Since fluid effects are important, the density and bulk modulus of the saturating fluids (water at sub- and supercritical conditions) are modeled by using the equations provided by the NIST website. The squirt-flow model has a single free parameter represented by the aspect ratio of the grain contacts. The theory generalizes a preceding theory based on Gassmann (low-frequency) moduli to the more general case of the presence of local (squirt) flow and global (Biot) flow, which contribute with additional attenuation mechanisms to the wave propagation.

Takahasi Nearest-Neighbour Gas Revisited II: Morse Gases

NASA Astrophysics Data System (ADS)

Matsumoto, Akira

2011-12-01

Some thermodynamic quantities for the Morse potential are analytically evaluated at an isobaric process. The parameters of Morse gases for 21 substances are obtained by the second virial coefficient data and the spectroscopic data of diatomic molecules. Also some thermodynamic quantities for water are calculated numerically and drawn graphically. The inflexion point of the length L which depends on temperature T and pressure P corresponds physically to a boiling point. L indicates the liquid phase from lower temperature to the inflexion point and the gaseous phase from the inflexion point to higher temperature. The boiling temperatures indicate reasonable values compared with experimental data. The behaviour of L suggests a chance of a first-order phase transition in one dimension.

cAMP signalling in mushroom bodies modulates temperature preference behaviour in Drosophila.

PubMed

Hong, Sung-Tae; Bang, Sunhoe; Hyun, Seogang; Kang, Jongkyun; Jeong, Kyunghwa; Paik, Donggi; Chung, Jongkyeong; Kim, Jaeseob

2008-08-07

Homoiotherms, for example mammals, regulate their body temperature with physiological responses such as a change of metabolic rate and sweating. In contrast, the body temperature of poikilotherms, for example Drosophila, is the result of heat exchange with the surrounding environment as a result of the large ratio of surface area to volume of their bodies. Accordingly, these animals must instinctively move to places with an environmental temperature as close as possible to their genetically determined desired temperature. The temperature that Drosophila instinctively prefers has a function equivalent to the 'set point' temperature in mammals. Although various temperature-gated TRP channels have been discovered, molecular and cellular components in Drosophila brain responsible for determining the desired temperature remain unknown. We identified these components by performing a large-scale genetic screen of temperature preference behaviour (TPB) in Drosophila. In parallel, we mapped areas of the Drosophila brain controlling TPB by targeted inactivation of neurons with tetanus toxin and a potassium channel (Kir2.1) driven with various brain-specific GAL4s. Here we show that mushroom bodies (MBs) and the cyclic AMP-cAMP-dependent protein kinase A (cAMP-PKA) pathway are essential for controlling TPB. Furthermore, targeted expression of cAMP-PKA pathway components in only the MB was sufficient to rescue abnormal TPB of the corresponding mutants. Preferred temperatures were affected by the level of cAMP and PKA activity in the MBs in various PKA pathway mutants.

From global change to a butterfly flapping: biophysics and behaviour affect tropical climate change impacts.

PubMed

Bonebrake, Timothy C; Boggs, Carol L; Stamberger, Jeannie A; Deutsch, Curtis A; Ehrlich, Paul R

2014-10-22

Difficulty in characterizing the relationship between climatic variability and climate change vulnerability arises when we consider the multiple scales at which this variation occurs, be it temporal (from minute to annual) or spatial (from centimetres to kilometres). We studied populations of a single widely distributed butterfly species, Chlosyne lacinia, to examine the physiological, morphological, thermoregulatory and biophysical underpinnings of adaptation to tropical and temperate climates. Microclimatic and morphological data along with a biophysical model documented the importance of solar radiation in predicting butterfly body temperature. We also integrated the biophysics with a physiologically based insect fitness model to quantify the influence of solar radiation, morphology and behaviour on warming impact projections. While warming is projected to have some detrimental impacts on tropical ectotherms, fitness impacts in this study are not as negative as models that assume body and air temperature equivalence would suggest. We additionally show that behavioural thermoregulation can diminish direct warming impacts, though indirect thermoregulatory consequences could further complicate predictions. With these results, at multiple spatial and temporal scales, we show the importance of biophysics and behaviour for studying biodiversity consequences of global climate change, and stress that tropical climate change impacts are likely to be context-dependent. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

From global change to a butterfly flapping: biophysics and behaviour affect tropical climate change impacts

PubMed Central

Bonebrake, Timothy C.; Boggs, Carol L.; Stamberger, Jeannie A.; Deutsch, Curtis A.; Ehrlich, Paul R.

2014-01-01

Difficulty in characterizing the relationship between climatic variability and climate change vulnerability arises when we consider the multiple scales at which this variation occurs, be it temporal (from minute to annual) or spatial (from centimetres to kilometres). We studied populations of a single widely distributed butterfly species, Chlosyne lacinia, to examine the physiological, morphological, thermoregulatory and biophysical underpinnings of adaptation to tropical and temperate climates. Microclimatic and morphological data along with a biophysical model documented the importance of solar radiation in predicting butterfly body temperature. We also integrated the biophysics with a physiologically based insect fitness model to quantify the influence of solar radiation, morphology and behaviour on warming impact projections. While warming is projected to have some detrimental impacts on tropical ectotherms, fitness impacts in this study are not as negative as models that assume body and air temperature equivalence would suggest. We additionally show that behavioural thermoregulation can diminish direct warming impacts, though indirect thermoregulatory consequences could further complicate predictions. With these results, at multiple spatial and temporal scales, we show the importance of biophysics and behaviour for studying biodiversity consequences of global climate change, and stress that tropical climate change impacts are likely to be context-dependent. PMID:25165769

The automated analysis of clustering behaviour of piglets from thermal images in response to immune challenge by vaccination.

PubMed

Cook, N J; Bench, C J; Liu, T; Chabot, B; Schaefer, A L

2018-01-01

An automated method of estimating the spatial distribution of piglets within a pen was used to assess huddling behaviour under normal conditions and during a febrile response to vaccination. The automated method was compared with a manual assessment of clustering activity. Huddling behaviour was partly related to environmental conditions and clock time such that more huddling occurred during the night and at lower ambient air temperatures. There were no positive relationships between maximum pig temperatures and environmental conditions, suggesting that the narrow range of air temperatures in this study was not a significant factor for pig temperature. Spatial distribution affected radiated pig temperature measurements by IR thermography. Higher temperatures were recorded in groups of animals displaying huddling behaviour. Huddling behaviour was affected by febrile responses to vaccination with increased huddling occurring 3 to 8 h post-vaccination. The automated method of assessing spatial distribution from an IR image successfully identified periods of huddling associated with a febrile response, and to changing environmental temperatures. Infrared imaging could be used to quantify temperature and behaviour from the same images.

Mechanistic basis of temperature-dependent dwell fatigue in titanium alloys

NASA Astrophysics Data System (ADS)

Zheng, Zebang; Balint, Daniel S.; Dunne, Fionn P. E.

2017-10-01

The temperature-dependent dwell sensitivity of Ti-6242 and Ti-6246 alloys has been assessed over a temperature range from - 50∘ C to 390 °C using discrete dislocation plasticity which incorporates both thermal activation of dislocation escape from obstacles and slip transfer across grain boundaries. The worst-case load shedding in Ti-6242 alloy is found to be at or close to 120 °C under dwell fatigue loading, which diminishes and vanishes at temperatures lower than - 50∘ C or higher than 230 °C. Load shedding behaviour is predicted to occur in alloy Ti-6246 also but over a range of higher temperatures which are outside those relevant to in-service conditions. The key controlling dislocation mechanism with respect to load shedding in titanium alloys, and its temperature sensitivity, is shown to be the time constant associated with the thermal activation of dislocation escape from obstacles, with respect to the stress dwell time. The mechanistic basis of load shedding and dwell sensitivity in dwell fatigue loading is presented and discussed in the context of experimental observations.

Deformation-mechanism map for nanocrystalline metals by molecular-dynamics simulation.

PubMed

Yamakov, V; Wolf, D; Phillpot, S R; Mukherjee, A K; Gleiter, H

2004-01-01

Molecular-dynamics simulations have recently been used to elucidate the transition with decreasing grain size from a dislocation-based to a grain-boundary-based deformation mechanism in nanocrystalline f.c.c. metals. This transition in the deformation mechanism results in a maximum yield strength at a grain size (the 'strongest size') that depends strongly on the stacking-fault energy, the elastic properties of the metal, and the magnitude of the applied stress. Here, by exploring the role of the stacking-fault energy in this crossover, we elucidate how the size of the extended dislocations nucleated from the grain boundaries affects the mechanical behaviour. Building on the fundamental physics of deformation as exposed by these simulations, we propose a two-dimensional stress-grain size deformation-mechanism map for the mechanical behaviour of nanocrystalline f.c.c. metals at low temperature. The map captures this transition in both the deformation mechanism and the related mechanical behaviour with decreasing grain size, as well as its dependence on the stacking-fault energy, the elastic properties of the material, and the applied stress level.

A Rigorous Temperature-Dependent Stochastic Modelling and Testing for MEMS-Based Inertial Sensor Errors.

PubMed

El-Diasty, Mohammed; Pagiatakis, Spiros

2009-01-01

In this paper, we examine the effect of changing the temperature points on MEMS-based inertial sensor random error. We collect static data under different temperature points using a MEMS-based inertial sensor mounted inside a thermal chamber. Rigorous stochastic models, namely Autoregressive-based Gauss-Markov (AR-based GM) models are developed to describe the random error behaviour. The proposed AR-based GM model is initially applied to short stationary inertial data to develop the stochastic model parameters (correlation times). It is shown that the stochastic model parameters of a MEMS-based inertial unit, namely the ADIS16364, are temperature dependent. In addition, field kinematic test data collected at about 17 °C are used to test the performance of the stochastic models at different temperature points in the filtering stage using Unscented Kalman Filter (UKF). It is shown that the stochastic model developed at 20 °C provides a more accurate inertial navigation solution than the ones obtained from the stochastic models developed at -40 °C, -20 °C, 0 °C, +40 °C, and +60 °C. The temperature dependence of the stochastic model is significant and should be considered at all times to obtain optimal navigation solution for MEMS-based INS/GPS integration.

Atomistic study on shock behaviour of NiTi shape memory alloy

NASA Astrophysics Data System (ADS)

Yin, Qiuyun; Wu, Xianqian; Huang, Chenguang

2017-06-01

The shock behaviour of NiTi shape memory alloy is investigated by using molecular dynamics simulation. The nano-pillar samples of the alloy are subjected to the impact of a piston with a velocity of 350 m/s at initial environment temperatures of 325 and 500 K. At 325 K, we observe two different pathways of the formation of BCO phase, the gradient twins, and the detwinning phenomena, strongly depending on the local stress and the deformation state. As the initial temperature increases to 500 K, the plasticity is dominated by the dislocation movements rather than the twinning at 325 K. The phase transformation and plasticity result in stress attenuation when the stress wave propagates through the nano-pillar. Furthermore, it is interesting to note that multiple stress peaks occur due to the formation of local complex atomic structures with various wave speeds, leading to the catch up and overlap of the stress waves.

Multi-temperature state-dependent equivalent circuit discharge model for lithium-sulfur batteries

NASA Astrophysics Data System (ADS)

Propp, Karsten; Marinescu, Monica; Auger, Daniel J.; O'Neill, Laura; Fotouhi, Abbas; Somasundaram, Karthik; Offer, Gregory J.; Minton, Geraint; Longo, Stefano; Wild, Mark; Knap, Vaclav

2016-10-01

Lithium-sulfur (Li-S) batteries are described extensively in the literature, but existing computational models aimed at scientific understanding are too complex for use in applications such as battery management. Computationally simple models are vital for exploitation. This paper proposes a non-linear state-of-charge dependent Li-S equivalent circuit network (ECN) model for a Li-S cell under discharge. Li-S batteries are fundamentally different to Li-ion batteries, and require chemistry-specific models. A new Li-S model is obtained using a 'behavioural' interpretation of the ECN model; as Li-S exhibits a 'steep' open-circuit voltage (OCV) profile at high states-of-charge, identification methods are designed to take into account OCV changes during current pulses. The prediction-error minimization technique is used. The model is parameterized from laboratory experiments using a mixed-size current pulse profile at four temperatures from 10 °C to 50 °C, giving linearized ECN parameters for a range of states-of-charge, currents and temperatures. These are used to create a nonlinear polynomial-based battery model suitable for use in a battery management system. When the model is used to predict the behaviour of a validation data set representing an automotive NEDC driving cycle, the terminal voltage predictions are judged accurate with a root mean square error of 32 mV.

pH and heat-dependent behaviour of glucose oxidase down to single molecule level by combined fluorescence spectroscopy and molecular modelling.

PubMed

Dumitraşcu, Loredana; Stănciuc, Nicoleta; Bahrim, Gabriela Elena; Ciumac, Alexandrina; Aprodu, Iuliana

2016-04-01

In the food industry, glucose oxidase (GOX) is used to improve the shelf life of food materials. The pH- and heat-induced conformational changes of glucose oxidase from Aspergillus niger were quantified by means of fluorescence spectroscopy and molecular dynamics simulations. The phase diagram showed an all-or-none transition process, indicating that pH and temperature largely influence the conformational state of GOX. Shifts in maximum wavelength of Trp, Tyr were registered as the protein encounters a lower pH (pH 4.0), suggesting significant changes of the polarity around the chromophore molecule. Quenching experiments using KI showed higher quenching constants of Trp and flavin adenine dinucleotide upon heating or by changing pH value, and were mainly correlated with the conformational changes upon protein matrix. Finally, valuable insights into the thermal behaviour of GOX were obtained from molecular modelling results. The conformation and structure of GOX protein is dependent upon the pH and heat treatment applied. Molecular dynamics simulation indicated significant changes in the substrate binding region at temperatures over 60 °C that might affect enzyme activity. Moreover, an important alteration of the small pocket hosting the positively charged His(516) residue responsible for oxygen activation appears evident at high temperatures. © 2015 Society of Chemical Industry.

Iron oxide particles in large pore zeolites

NASA Astrophysics Data System (ADS)

García, J. L.; López, A.; Lázaro, F. J.; Martínez, C.; Corma, A.

1996-05-01

The magnetic properties of iron-containing ETS-10 zeolite and its calcined variety have been studied by magnetic measurements. The results are consistent with the presence of paramagnetic ions and superparamagnetic clusters. Calcination results in a shift of the blocking temperatures, although their frequency dependence cannot be ascribed to non-interacting clusters. The hypothesis of cluster-glass like behaviour is discussed.

Influence of small DC bias field on the electrical behaviour of Sr- and Mg-doped lanthanum gallate

NASA Astrophysics Data System (ADS)

Raghvendra; Singh, Rajesh Kumar; Singh, Prabhakar

2014-09-01

One of the promising electrolyte materials for solid oxide fuel cells application, Sr- and Mg-doped lanthanum gallate La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM), is synthesized by conventional solid state ceramic route. X-ray Rietveld analysis confirms the formation of main orthorhombic phase at room temperature along with a few minor secondary phases. SEM micrograph reveals the grain and grainboundary morphology of the system. Electrical conductivity of the LSGM sample is measured in the temperature range 573-873 K and in the frequency range 20 Hz-1 MHz at a few small DC bias fields (at 0.0, 0.5, 1.0, 1.5 and 2.0 V). The conductivity spectra show power-law behaviour. Electrical conductivity of the sample is found to be weakly dependent on DC bias field. This is attributed to field-dependent bulk and grainboundary conduction processes. In the present system, under investigated bias field range, the possibility of formation of Schottky barrier is ruled out. The concept of grainboundary channel (pathway) modulation on the application of bias field is proposed.

Intrinsic inhomogeneous barrier height at the n-TiO2/p-Si hole-blocking junction

NASA Astrophysics Data System (ADS)

Kumar, Mohit; Singh, Ranveer; Som, Tapobrata

2018-01-01

Using Kelvin probe force microscopy (KPFM) and temperature-dependent current-voltage characteristics, we study the charge transport across an n-TiO2/p-Si heterojunction. In particular, the KPFM result shows a variation in the work function at the TiO2 surface. On the other hand, temperature-dependent current-voltage characteristics depict a non-ideal hole-blocking behaviour of the same. In addition, the measured barrier height is found to decrease with temperature and does not follow the thermionic emission theory, strongly suggesting an inhomogeneous nature of the barrier. The observed barrier inhomogeneity is attributed to the nanoscale height modulation, arising due to the growth dynamics of TiO2 and corroborates well with the KPFM map. The presented results will open a new avenue to understand the charge transport in TiO2-based nanoscale devices.

The temperature-dependence of adenylate cyclase from baker's yeast.

PubMed Central

Londesborough, J; Varimo, K

1979-01-01

The Michaelis constant of membrane-bound adenylate cyclase increased from 1.1 to 1.8 mM between 7 and 38 degrees C (delta H = 13 kJ/mol). Over this temperature range, the maximum velocity increased 10-fold, and the Arrhenius plot was nearly linear, with an average delta H* of 51 kJ/mol. The temperature-dependence of the reaction rate at 2 mM-ATP was examined in more detail: for Lubrol-dispersed enzyme, Arrhenius plots were nearly linear with average delta H* values of 45 and 68 kJ/mol, respectively, for untreated and gel-filtered enzymes; for membrane-bound enzyme, delta H changed from 40 kJ/mol above about 21 degrees C to 62 kJ/mol below 21 degrees C, but this behaviour does not necessarily indicate an abrupt, lipid-induced, transition in the reaction mechanism. PMID:391221

Influence of temperature on the corticosterone stress-response: an experiment in the Children's python (Antaresia childreni).

PubMed

Dupoué, Andréaz; Brischoux, François; Lourdais, Olivier; Angelier, Frédéric

2013-11-01

To cope with environmental challenges, organisms have to adjust their behaviours and their physiology to the environmental conditions they face (i.e. allostasis). In vertebrates, such adjustments are often mediated through the secretion of glucocorticoids (GCs) that are well-known to activate and/or inhibit specific physiological and behavioural traits. In ectothermic species, most processes are temperature-dependent and according to previous studies, low external temperatures should be associated with low GC concentrations (both baseline and stress-induced concentrations). In this study, we experimentally tested this hypothesis by investigating the short term influence of temperature on the GC stress response in a squamate reptile, the Children's python (Antaresia childreni). Snakes were maintained in contrasting conditions (warm and cold groups), and their corticosterone (CORT) stress response was measured (baseline and stress-induced CORT concentrations), within 48h of treatment. Contrary to our prediction, baseline and stress-induced CORT concentrations were higher in the cold versus the warm treatment. In addition, we found a strong negative relationship between CORT concentrations (baseline and stress-induced) and temperature within the cold treatment. Although it remains unclear how cold temperatures can mechanistically result in increased CORT concentrations, we suggest that, at suboptimal temperature, high CORT concentrations may help the organism to maintain an alert state. Copyright © 2013 Elsevier Inc. All rights reserved.

A thermodynamic approach to model the caloric properties of semicrystalline polymers

NASA Astrophysics Data System (ADS)

Lion, Alexander; Johlitz, Michael

2016-05-01

It is well known that the crystallisation and melting behaviour of semicrystalline polymers depends in a pronounced manner on the temperature history. If the polymer is in the liquid state above the melting point, and the temperature is reduced to a level below the glass transition, the final degree of crystallinity, the amount of the rigid amorphous phase and the configurational state of the mobile amorphous phase strongly depend on the cooling rate. If the temperature is increased afterwards, the extents of cold crystallisation and melting are functions of the heating rate. Since crystalline and amorphous phases exhibit different densities, the specific volume depends also on the temperature history. In this article, a thermodynamically based phenomenological approach is developed which allows for the constitutive representation of these phenomena in the time domain. The degree of crystallinity and the configuration of the amorphous phase are represented by two internal state variables whose evolution equations are formulated under consideration of the second law of thermodynamics. The model for the specific Gibbs free energy takes the chemical potentials of the different phases and the mixture entropy into account. For simplification, it is assumed that the amount of the rigid amorphous phase is proportional to the degree of crystallinity. An essential outcome of the model is an equation in closed form for the equilibrium degree of crystallinity in dependence on pressure and temperature. Numerical simulations demonstrate that the process dependences of crystallisation and melting under consideration of the glass transition are represented.

Modelling and measurement of bandgap behaviour in medium-wavelength IR InAs/InAs0.815Sb0.185 strained-layer superlattices

NASA Astrophysics Data System (ADS)

Letka, Veronica; Keen, James; Craig, Adam; Marshall, Andrew R. J.

2017-10-01

InAs/InAs1-xSbx type-II strained-layer superlattices (SLS) are a structure with potential infrared detection applications, owing to its tunable bandgap and suppressed Auger recombination. A series of medium-wavelength infrared (MWIR) InAs/InAs0.815Sb0.185 SLS structures, grown as undoped absorption epilayers on GaAs, were fabricated using molecular beam epitaxy in order to study the dependence of the ground state transitions on temperature and superlattice period thickness. Photoluminescence peaks at 4 K were obtained with the use of a helium-cooled micro-PL system and an InSb detector, and temperature-dependent absorption spectra were measured in the range 77 K - 300 K on a Fourier Transform Infrared (FTIR) spectrometer, equipped with a 1370 K blackbody source and a DTGS detector. An nBn device sample with the absorber structure identical to one of the undoped samples was also grown and processed with the goal of measuring temperature-dependent spectral response. A model for superlattice band alignment was also devised, incorporating the Bir-Pikus transformation results for uniaxial and biaxial strain, and the Einstein oscillator model for bandgap temperature dependence. Absorption coefficients of several 1000 cm-1 throughout the entire MWIR range are found for all samples, and temperature dependence of the bandgaps is extracted and compared to the model. This and photoluminescence data also demonstrate bandgap shifts consistent with the different superlattice periods of the three samples.

The effect of temperature mixing on the observable (T, β)-relation of interstellar dust clouds

NASA Astrophysics Data System (ADS)

Juvela, M.; Ysard, N.

2012-03-01

Context. Detailed studies of the shape of dust emission spectra are possible thanks to the current instruments capable of simultaneous observations in several sub-millimetre bands (e.g., Herschel and Planck). The relationship between the observed spectra and the intrinsic dust grain properties is known to be affected by the noise and the line-of-sight temperature variations. However, some controversy remains even on the basic effects resulting from the mixing of temperatures along the line-of-sight or within the instrument beam. Aims: Regarding the effect of temperature variations, previous studies have suggested either a positive or a negative correlation between the colour temperature TC and the observed spectral index βObs. Our aim is to show that both cases are possible and to determine the principal factors leading to either behaviour. Methods: We start by studying the behaviour of the sum of two or three modified black bodies at different temperatures. Then, with radiative transfer models of spherical clouds, we examine the probability distributions of the dust mass as a function of the physical dust temperature. With these results as a guideline, we examine the (TC, βobs) relations for different sets of clouds. Results: Even in the simple case of models consisting of two blackbodies at temperatures T0 and T0 + ΔT0, the correlation between TC and βobs can be either positive or negative. If one compares models where the temperature difference ΔT0 between the two blackbodies is varied, the correlation is negative. If the models differ in their mean temperature T0 rather than in ΔT0, the correlation remains positive. Radiative transfer models show that externally heated clouds have different mean temperatures but the widths of their temperature distributions are rather similar. Thus, in observations of samples of such clouds the correlation between TC and βObs is expected to be positive. The same result applies to clouds illuminated by external radiation fields of different intensity. For internally heated clouds a negative correlation is the more likely alternative. Conclusions: Previous studies of the (TC,β) relation have been correct in that, depending on the cloud sample, both positive and negative correlations are possible. For externally heated clouds the effect is opposite to the negative correlation seen in the observations. If the signal-to-noise ratio is high, the observed negative correlation could be explained by the temperature dependence of the dust optical properties but that intrinsic dependence could be even steeper than the observed one.

Frequency dependent polarisation switching in h-ErMnO3

NASA Astrophysics Data System (ADS)

Ruff, Alexander; Li, Ziyu; Loidl, Alois; Schaab, Jakob; Fiebig, Manfred; Cano, Andres; Yan, Zewu; Bourret, Edith; Glaum, Julia; Meier, Dennis; Krohns, Stephan

2018-04-01

We report an electric-field poling study of the geometrically-driven improper ferroelectric h-ErMnO3. From a detailed dielectric analysis, we deduce the temperature and the frequency dependent range for which single-crystalline h-ErMnO3 exhibits purely intrinsic dielectric behaviour, i.e., free from the extrinsic so-called Maxwell-Wagner polarisations that arise, for example, from surface barrier layers. In this regime, ferroelectric hysteresis loops as a function of frequency, temperature, and applied electric fields are measured, revealing the theoretically predicted saturation polarisation on the order of 5-6 μC/cm2. Special emphasis is put on frequency dependent polarisation switching, which is explained in terms of domain-wall movement similar to proper ferroelectrics. Controlling the domain walls via electric fields brings us an important step closer to their utilization in domain-wall-based electronics.

Mechanical behaviour of TWIP steel under shear loading

NASA Astrophysics Data System (ADS)

Vincze, G.; Butuc, M. C.; Barlat, F.

2016-08-01

Twinning induced plasticity steels (TWIP) are very good candidate for automotive industry applications because they potentially offer large energy absorption before failure due to their exceptional strain hardening capability and high strength. However, their behaviour is drastically influenced by the loading conditions. In this work, the mechanical behaviour of a TWIP steel sheet sample was investigated at room temperature under monotonic and reverse simple shear loading. It was shown that all the expected features of load reversal such as Bauschinger effect, transient strain hardening with high rate and permanent softening, depend on the prestrain level. This is in agreement with the fact that these effects, which occur during reloading, are related to the rearrangement of the dislocation structure induced during the predeformation. The homogeneous anisotropic hardening (HAH) approach proposed by Barlat et al. (2011) [1] was successfully employed to predict the experimental results.

Temperature-dependent resetting of the molecular circadian oscillator in Drosophila

PubMed Central

Goda, Tadahiro; Sharp, Brandi; Wijnen, Herman

2014-01-01

Circadian clocks responsible for daily time keeping in a wide range of organisms synchronize to daily temperature cycles via pathways that remain poorly understood. To address this problem from the perspective of the molecular oscillator, we monitored temperature-dependent resetting of four of its core components in the fruitfly Drosophila melanogaster: the transcripts and proteins for the clock genes period (per) and timeless (tim). The molecular circadian cycle in adult heads exhibited parallel responses to temperature-mediated resetting at the levels of per transcript, tim transcript and TIM protein. Early phase adjustment specific to per transcript rhythms was explained by clock-independent temperature-driven transcription of per. The cold-induced expression of Drosophila per contrasts with the previously reported heat-induced regulation of mammalian Period 2. An altered and more readily re-entrainable temperature-synchronized circadian oscillator that featured temperature-driven per transcript rhythms and phase-shifted TIM and PER protein rhythms was found for flies of the ‘Tim 4’ genotype, which lacked daily tim transcript oscillations but maintained post-transcriptional temperature entrainment of tim expression. The accelerated molecular and behavioural temperature entrainment observed for Tim 4 flies indicates that clock-controlled tim expression constrains the rate of temperature cycle-mediated circadian resetting. PMID:25165772

Droplet bubbling evaporatively cools a blowfly.

PubMed

Gomes, Guilherme; Köberle, Roland; Von Zuben, Claudio J; Andrade, Denis V

2018-04-19

Terrestrial animals often use evaporative cooling to lower body temperature. Evaporation can occur from humid body surfaces or from fluids interfaced to the environment through a number of different mechanisms, such as sweating or panting. In Diptera, some flies move tidally a droplet of fluid out and then back in the buccopharyngeal cavity for a repeated number of cycles before eventually ingesting it. This is referred to as the bubbling behaviour. The droplet fluid consists of a mix of liquids from the ingested food, enzymes from the salivary glands, and antimicrobials, associated to the crop organ system, with evidence pointing to a role in liquid meal dehydration. Herein, we demonstrate that the bubbling behaviour also serves as an effective thermoregulatory mechanism to lower body temperature by means of evaporative cooling. In the blowfly, Chrysomya megacephala, infrared imaging revealed that as the droplet is extruded, evaporation lowers the fluid´s temperature, which, upon its re-ingestion, lowers the blowfly's body temperature. This effect is most prominent at the cephalic region, less in the thorax, and then in the abdomen. Bubbling frequency increases with ambient temperature, while its cooling efficiency decreases at high air humidities. Heat transfer calculations show that droplet cooling depends on a special heat-exchange dynamic, which result in the exponential activation of the cooling effect.

Current-voltage hysteresis and dielectric properties of PVA coated MWCNT film

NASA Astrophysics Data System (ADS)

Das, Amit Kumar; Meikap, Ajit Kumar

2017-12-01

In this work, we have prepared polyvinyl alcohol (PVA) coated multiwall carbon nanotube (MWCNT) film by an in situ chemical oxidative preparation technique. The thermogravimetric analysis clearly explains the thermal degradation of pure polymer and polymer nanocomposite film. We have studied the AC electrical transport properties and current-voltage (I-V) characteristic of PVA-MWCNT composites within the temperature range 300 ≤ T ≤ 423 K and frequency range 150 Hz ≤ f ≤ 2 MHz. It is observed that the dielectric constant of the composite film increases significantly. The frequency variation of AC conductivity follows the power law ( ωS ) and a sharp transition from small polaron tunneling to correlated barrier hopping model is found. The imaginary part of electric modulus shows non-Debye type asymmetric behaviour. The impedance spectroscopy shows the negative temperature coefficient of resistance of the composite film. Nyquist plot of the composite film at different temperatures is established from impedance measurement. The current-voltage characteristic (under ± 20 V) shows hysteresis behaviour and field dependent resistance. We simulate the experimentally observed current density-electric field data with the established theory.

Current-voltage hysteresis and dielectric properties of PVA coated MWCNT film

NASA Astrophysics Data System (ADS)

Das, Amit Kumar; Meikap, Ajit Kumar

2018-06-01

In this work, we have prepared polyvinyl alcohol (PVA) coated multiwall carbon nanotube (MWCNT) film by an in situ chemical oxidative preparation technique. The thermogravimetric analysis clearly explains the thermal degradation of pure polymer and polymer nanocomposite film. We have studied the AC electrical transport properties and current-voltage (I-V) characteristic of PVA-MWCNT composites within the temperature range 300 ≤ T ≤ 423 K and frequency range 150 Hz ≤ f ≤ 2 MHz. It is observed that the dielectric constant of the composite film increases significantly. The frequency variation of AC conductivity follows the power law ( ωS ) and a sharp transition from small polaron tunneling to correlated barrier hopping model is found. The imaginary part of electric modulus shows non-Debye type asymmetric behaviour. The impedance spectroscopy shows the negative temperature coefficient of resistance of the composite film. Nyquist plot of the composite film at different temperatures is established from impedance measurement. The current-voltage characteristic (under ± 20 V) shows hysteresis behaviour and field dependent resistance. We simulate the experimentally observed current density-electric field data with the established theory.

Detailed study of the magnetic behaviour at low scale in La2/3Sr1/3MnO3

NASA Astrophysics Data System (ADS)

Arango, I. C.; E Ordoñez, J.; Dominguez, C.; Arango, C.; E Gomez, M.

2017-12-01

The La2/3Sr1/3MnO3 (LSMO) with Curie temperature above room temperature is the leading compound of the manganite perovskite family. Therefore, the physical properties are desirable for practical applications as magnetic sensors. However, when the dimensions are reduced the ferromagnetic properties of material are weakened. In this research, we have grown La2/3Sr1/3MnO3/SrTiO3 thin films by sputtering DC at high oxygen pressure at 830°C. X-Ray Diffraction (XRD) analysis reveals that only (0 0 2) LSMO peak are present, indicating a textured growth. The samples morphology was characterized by Atomic Force Microscopy (AFM). Additionally, LSMO microwires were patterned by UV lithography; the devices are a well-defined channel with current and voltage leads enabling four points resistance measurements. Resistivity versus temperature curves displays typical manganite behaviour with metal-insulator transition ∼350K. We study the electric and magnetotransport properties in LSMO film and in wire channel and their dependence with size (width and length) for potential applications like magnetic sensors.

Moisture Sorption Behaviour and Mould Ecology of Trade Garri Sold in South Eastern Nigeria

PubMed Central

Samuel, Tochukwu; Ugwuanyi, J. Obeta

2014-01-01

Garri is a creamy white or yellow starchy grit produced by roasting to gelatinization and dryness of peeled, washed, mashed, and fermented dewatered cassava roots. It is the most important product of cassava in West and Central Africa. Mean moisture content of yellow and white garri was 11.11% and 10.81% within 24 hrs of sampling from the market, increasing to 17.27% and 16.14%, respectively, following 3 months of storage at room temperature. The water activity of samples varied from initial 0.587 to 0.934 following storage. Moisture sorption isotherms, determined by static gravimetric techniques at 20° and 30°C, showed temperature dependent BET Sigmoidal type II behaviour typical of carbohydrate rich foods but modulated very slightly by the content of palm oil. Equilibrium moisture content decreased with increase in temperature at constant water activity. A total of 10 fungal species belonging to the genera Mucor, Penicillium, Cephalosporium, Aspergillus, Scopulariopsis, Rhizopus, and Paecilomyces were identified, with range increasing with water activity of samples. PMID:26904621

Development of Modified Incompressible Ideal Gas Model for Natural Draft Cooling Tower Flow Simulation

NASA Astrophysics Data System (ADS)

Hyhlík, Tomáš

2018-06-01

The article deals with the development of incompressible ideal gas like model, which can be used as a part of mathematical model describing natural draft wet-cooling tower flow, heat and mass transfer. It is shown, based on the results of a complex mathematical model of natural draft wet-cooling tower flow, that behaviour of pressure, temperature and density is very similar to the case of hydrostatics of moist air, where heat and mass transfer in the fill zone must be taken into account. The behaviour inside the cooling tower is documented using density, pressure and temperature distributions. The proposed equation for the density is based on the same idea like the incompressible ideal gas model, which is only dependent on temperature, specific humidity and in this case on elevation. It is shown that normalized density difference of the density based on proposed model and density based on the nonsimplified model is in the order of 10-4. The classical incompressible ideal gas model, Boussinesq model and generalised Boussinesq model are also tested. These models show deviation in percentages.

Temperature studies of optical parameters of (Ag3AsS3)0.6(As2S3)0.4 thin films prepared by rapid thermal evaporation and pulse laser deposition

NASA Astrophysics Data System (ADS)

Studenyak, I. P.; Kutsyk, M. M.; Buchuk, M. Yu.; Rati, Y. Y.; Neimet, Yu. Yu.; Izai, V. Yu.; Kökényesi, S.; Nemec, P.

2016-02-01

(Ag3AsS3)0.6(As2S3)0.4 thin films were deposited using rapid thermal evaporation (RTE) and pulse laser deposition (PLD) techniques. Ag-enriched micrometre-sized cones (RTE) and bubbles (PLD) were observed on the thin film surface. Optical transmission spectra of the thin films were studied in the temperature range 77-300 K. The Urbach behaviour of the optical absorption edge in the thin films due to strong electron-phonon interaction was observed, the main parameters of the Urbach absorption edge were determined. Temperature dependences of the energy position of the exponential absorption edge and the Urbach energy are well described in the Einstein model. Dispersion and temperature dependences of refractive indices were analysed; a non-linear increase of the refractive indices with temperature was revealed. Disordering processes in the thin films were studied and compared with bulk composites, the differences between the thin films prepared by RTE and PLD were analysed.

Dielectric relaxation in complex perovskite oxide In(Ni{sub 1/2}Zr{sub 1/2})O{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agrawal, Lata, E-mail: lata_agrawal84@yahoo.com; Singh, B.P.; Sinha, T.P.

2009-09-15

The dielectric study of indium nickel zirconate, In(Ni{sub 1/2}Zr{sub 1/2})O{sub 3} (INZ) synthesized by solid state reaction technique is performed in a frequency range from 500 Hz to 1 MHz and in a temperature range from 303 to 493 K. The X-ray diffraction analysis shows that the compound is monoclinic. A relaxation is observed in the entire temperature range as a gradual decrease in {epsilon}'({omega}) and as a broad peak in {epsilon}''({omega}) in the frequency dependent real and imaginary parts of dielectric constant, respectively. The frequency dependent electrical data are analyzed in the framework of conductivity and electric modulus formalisms.more » The frequencies corresponding to the maxima of the imaginary electric modulus at various temperatures are found to obey an Arrhenius law with activation energy of 0.66 eV. The Cole-Cole model is used to study the dielectric relaxation of INZ. The scaling behaviour of imaginary part of electric modulus suggests that the relaxation describes the same mechanism at various temperatures. The frequency dependent conductivity spectra follow the universal power law.« less

Time dependent viscoelastic rheological response of pure, modified and synthetic bituminous binders

NASA Astrophysics Data System (ADS)

Airey, G. D.; Grenfell, J. R. A.; Apeagyei, A.; Subhy, A.; Lo Presti, D.

2016-08-01

Bitumen is a viscoelastic material that exhibits both elastic and viscous components of response and displays both a temperature and time dependent relationship between applied stresses and resultant strains. In addition, as bitumen is responsible for the viscoelastic behaviour of all bituminous materials, it plays a dominant role in defining many of the aspects of asphalt road performance, such as strength and stiffness, permanent deformation and cracking. Although conventional bituminous materials perform satisfactorily in most highway pavement applications, there are situations that require the modification of the binder to enhance the properties of existing asphalt material. The best known form of modification is by means of polymer modification, traditionally used to improve the temperature and time susceptibility of bitumen. Tyre rubber modification is another form using recycled crumb tyre rubber to alter the properties of conventional bitumen. In addition, alternative binders (synthetic polymeric binders as well as renewable, environmental-friendly bio-binders) have entered the bitumen market over the last few years due to concerns over the continued availability of bitumen from current crudes and refinery processes. This paper provides a detailed rheological assessment, under both temperature and time regimes, of a range of conventional, modified and alternative binders in terms of the materials dynamic (oscillatory) viscoelastic response. The rheological results show the improved viscoelastic properties of polymer- and rubber-modified binders in terms of increased complex shear modulus and elastic response, particularly at high temperatures and low frequencies. The synthetic binders were found to demonstrate complex rheological behaviour relative to that seen for conventional bituminous binders.

Phase transition in lithium ammonium sulphate doped with cesium metal ions

NASA Astrophysics Data System (ADS)

Gaafar, M.; Kassem, M. E.; Kandil, S. H.

2000-07-01

Effects of doped cesium (C s+) metal ions (with different molar ratios n) on the phase transition of lithium ammonium sulphate LiNH 4SO 4 system have been studied by measuring the specific heat Cp( T) of the doped systems in the temperature range from 400 to 480 K. The study shows a peculiar phase transition of the pure system ( n=0) characterized by double distinct peaks, changed to a single sharp and narrow one as a result of the doping process. The measurements exhibit different effects of enhanced molar ratios of dopants on the phase transition behaviour of this system. At low dopant content ( n≤3%), the excess specific heat (Δ Cp) max at the transition temperature T1 decreases till a minimum value at n=0.8%, then it increases gradually. In this case, Δ Cp( T) behaviour is varied quantitatively and not modified. Enhanced dopant content ( n>3%) has a pronounced effect on the critical behaviour, which is significantly changed and considerably modified relative to the pure system. In addition, broadening of the critical temperature region, and decrease of (Δ Cp) max associated with changes of the Landau expansion coefficients are obtained and discussed. The study deals with the contribution of the thermally excited dipoles to the specific heat in the ferroelectric region and shows that their energy depends on doping.

Predicting organismal vulnerability to climate warming: roles of behaviour, physiology and adaptation.

PubMed

Huey, Raymond B; Kearney, Michael R; Krockenberger, Andrew; Holtum, Joseph A M; Jess, Mellissa; Williams, Stephen E

2012-06-19

A recently developed integrative framework proposes that the vulnerability of a species to environmental change depends on the species' exposure and sensitivity to environmental change, its resilience to perturbations and its potential to adapt to change. These vulnerability criteria require behavioural, physiological and genetic data. With this information in hand, biologists can predict organisms most at risk from environmental change. Biologists and managers can then target organisms and habitats most at risk. Unfortunately, the required data (e.g. optimal physiological temperatures) are rarely available. Here, we evaluate the reliability of potential proxies (e.g. critical temperatures) that are often available for some groups. Several proxies for ectotherms are promising, but analogous ones for endotherms are lacking. We also develop a simple graphical model of how behavioural thermoregulation, acclimation and adaptation may interact to influence vulnerability over time. After considering this model together with the proxies available for physiological sensitivity to climate change, we conclude that ectotherms sharing vulnerability traits seem concentrated in lowland tropical forests. Their vulnerability may be exacerbated by negative biotic interactions. Whether tropical forest (or other) species can adapt to warming environments is unclear, as genetic and selective data are scant. Nevertheless, the prospects for tropical forest ectotherms appear grim.

Mechanical properties and fracture behaviour of defective phosphorene nanotubes under uniaxial tension

NASA Astrophysics Data System (ADS)

Liu, Ping; Pei, Qing-Xiang; Huang, Wei; Zhang, Yong-Wei

2017-12-01

The easy formation of vacancy defects and the asymmetry in the two sublayers of phosphorene nanotubes (PNTs) may result in brand new mechanical properties and failure behaviour. Herein, we investigate the mechanical properties and fracture behaviour of defective PNTs under uniaxial tension using molecular dynamics simulations. Our simulation results show that atomic vacancies cause local stress concentration and thus significantly reduce the fracture strength and fracture strain of PNTs. More specifically, a 1% defect concentration is able to reduce the fracture strength and fracture strain by as much as 50% and 66%, respectively. Interestingly, the reduction in the mechanical properties is found to depend on the defect location: a defect located in the outer sublayer has a stronger effect than one located in the inner layer, especially for PNTs with a small diameter. Temperature is also found to strongly influence the mechanical properties of both defect-free and defective PNTs. When the temperature is increased from 0 K to 400 K, the fracture strength and fracture strain of defective PNTs with a defect concentration of 1% are reduced further by 71% and 61%, respectively. These findings are of great importance for the structural design of PNTs as building blocks in nanodevices.

High pressure study of Pu(0.92)Am(0.08) binary alloy.

PubMed

Klosek, V; Griveau, J C; Faure, P; Genestier, C; Baclet, N; Wastin, F

2008-07-09

The phase transitions (by means of x-ray diffraction) and electrical resistivity of a Pu(0.92)Am(0.08) binary alloy were determined under pressure (up to 2 GPa). The evolution of atomic volume with pressure gives detailed information concerning the degree of localization of 5f electronic states and their delocalization process. A quasi-linear V = f(P) dependence reflects subtle modifications of the electronic structure when P increases. The electrical resistivity measurements reveal the very high stability of the δ phase for pressures less than 0.7 GPa, since no martensitic-like transformation occurs at low temperature. Remarkable electronic behaviours have also been observed. Finally, resistivity curves have shown the temperature dependence of the phase transformations together with unexpected kinetic effects.

Fibre systems for future astronomy: anomalous wavelength-temperature effects

NASA Astrophysics Data System (ADS)

Poppett, C. L.; Allington-Smith, J. R.

2007-07-01

Focal ratio degradation is an important property of optical fibres that determines the design and cost of instruments using fibres. Motivated by the importance of fibres in feeding instruments on Extremely Large Telescopes, the need for cryogenic-cooling to reduce thermal background and the desire for broad-band performance, we have studied the dependency of focal ratio degradation (FRD) on both temperature and wavelength. This shows a small but significant reduction in performance when cooled as expected from previous work. We also find an increase in FRD with wavelength broadly consistent with theory at room temperature but this dependency reverses in sign when the fibres are cooled to 77K, contrary to existing theory. We parameterize the wavelength dependency by an ad hoc extension to an existing model but it is clear that existing theory does not provide a good description of the operation of fibres in astronomical systems. This unexpected behaviour, which may relate to frozen-in stress from the manufacturing process, will need to be taken into account when designing future fibre systems.

Temperature dependence of gas sensing behaviour of TiO2 doped PANI composite thin films

NASA Astrophysics Data System (ADS)

Srivastava, Subodh; Sharma, S. S.; Sharma, Preetam; Sharma, Vinay; Rajura, Rajveer Singh; Singh, M.; Vijay, Y. K.

2014-04-01

In the present work we have reported the effect of temperature on the gas sensing properties of TiO2 doped PANI composite thin film based chemiresistor type gas sensors for hydrogen gas sensing application. PANI and TiO2 doped PANI composite were synthesized by in situ chemical oxidative polymerization of aniline at low temperature. The electrical properties of these composite thin films were characterized by I-V measurements as function of temperature. The I-V measurement revealed that conductivity of composite thin films increased as the temperature increased. The changes in resistance of the composite thin film sensor were utilized for detection of hydrogen gas. It was observed that at room temperature TiO2 doped PANI composite sensor shows higher response value and showed unstable behavior as the temperature increased. The surface morphology of these composite thin films has also been characterized by scanning electron microscopy (SEM) measurement.

Age-related changes in core body temperature and activity in triple-transgenic Alzheimer’s disease (3xTgAD) mice

PubMed Central

Knight, Elysse M.; Brown, Timothy M.; Gümüsgöz, Sarah; Smith, Jennifer C. M.; Waters, Elizabeth J.; Allan, Stuart M.; Lawrence, Catherine B.

2013-01-01

SUMMARY Alzheimer’s disease (AD) is characterised, not only by cognitive deficits and neuropathological changes, but also by several non-cognitive behavioural symptoms that can lead to a poorer quality of life. Circadian disturbances in core body temperature and physical activity are reported in AD patients, although the cause and consequences of these changes are unknown. We therefore characterised circadian patterns of body temperature and activity in male triple transgenic AD mice (3xTgAD) and non-transgenic (Non-Tg) control mice by remote radiotelemetry. At 4 months of age, daily temperature rhythms were phase advanced and by 6 months of age an increase in mean core body temperature and amplitude of temperature rhythms were observed in 3xTgAD mice. No differences in daily activity rhythms were seen in 4- to 9-month-old 3xTgAD mice, but by 10 months of age an increase in mean daily activity and the amplitude of activity profiles for 3xTgAD mice were detected. At all ages (4–10 months), 3xTgAD mice exhibited greater food intake compared with Non-Tg mice. The changes in temperature did not appear to be solely due to increased food intake and were not cyclooxygenase dependent because the temperature rise was not abolished by chronic ibuprofen treatment. No β-amyloid (Aβ) plaques or neurofibrillary tangles were noted in the hypothalamus of 3xTgAD mice, a key area involved in temperature regulation, although these pathological features were observed in the hippocampus and amygdala of 3xTgAD mice from 10 months of age. These data demonstrate age-dependent changes in core body temperature and activity in 3xTgAD mice that are present before significant AD-related neuropathology and are analogous to those observed in AD patients. The 3xTgAD mouse might therefore be an appropriate model for studying the underlying mechanisms involved in non-cognitive behavioural changes in AD. PMID:22864021

Age-related changes in core body temperature and activity in triple-transgenic Alzheimer's disease (3xTgAD) mice.

PubMed

Knight, Elysse M; Brown, Timothy M; Gümüsgöz, Sarah; Smith, Jennifer C M; Waters, Elizabeth J; Allan, Stuart M; Lawrence, Catherine B

2013-01-01

Alzheimer's disease (AD) is characterised, not only by cognitive deficits and neuropathological changes, but also by several non-cognitive behavioural symptoms that can lead to a poorer quality of life. Circadian disturbances in core body temperature and physical activity are reported in AD patients, although the cause and consequences of these changes are unknown. We therefore characterised circadian patterns of body temperature and activity in male triple transgenic AD mice (3xTgAD) and non-transgenic (Non-Tg) control mice by remote radiotelemetry. At 4 months of age, daily temperature rhythms were phase advanced and by 6 months of age an increase in mean core body temperature and amplitude of temperature rhythms were observed in 3xTgAD mice. No differences in daily activity rhythms were seen in 4- to 9-month-old 3xTgAD mice, but by 10 months of age an increase in mean daily activity and the amplitude of activity profiles for 3xTgAD mice were detected. At all ages (4-10 months), 3xTgAD mice exhibited greater food intake compared with Non-Tg mice. The changes in temperature did not appear to be solely due to increased food intake and were not cyclooxygenase dependent because the temperature rise was not abolished by chronic ibuprofen treatment. No β-amyloid (Aβ) plaques or neurofibrillary tangles were noted in the hypothalamus of 3xTgAD mice, a key area involved in temperature regulation, although these pathological features were observed in the hippocampus and amygdala of 3xTgAD mice from 10 months of age. These data demonstrate age-dependent changes in core body temperature and activity in 3xTgAD mice that are present before significant AD-related neuropathology and are analogous to those observed in AD patients. The 3xTgAD mouse might therefore be an appropriate model for studying the underlying mechanisms involved in non-cognitive behavioural changes in AD.

Electrical properties of Ba(Dy{sub 1/2}Nb{sub 1/2})O{sub 3} ceramic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nath, K. Amar, E-mail: karn190@gmail.com; Chandra, K. P., E-mail: kpchandra23@gmail.com; Dubey, K., E-mail: kirandubey45@yahoo.com

2016-05-06

Polycrystalline Ba(Dy{sub 1/2}Nb{sub 1/2})O{sub 3} was prepared using a high-temperature solid-state reaction method. X-ray diffraction analysis indicated the formation of a single-phase cubic structure having space group Pm3m. AC impedance plots as a function of frequency at different temperatures were used to analyse the electrical behaviour of the sample, which indicated the negative temperature coefficient of resistance character. Complex impedance analysis targeted non-Debye type dielectric relaxation. Frequency dependent ac conductivity data obeyed Jonscher’s power law. The apparent activation energy was estimated to be 0.97 eV at 1 kHz.

Dielectric study of chalcogenide (Se80Te20)94Ge6 glass

NASA Astrophysics Data System (ADS)

Sharma, Neha; Patial, Balbir Singh; Thakur, Nagesh

2018-04-01

In the present study, dielectric characteristics specifically dielectric constant (ɛ'), dielectric loss (ɛ″) and AC conductivity (σAC) have been investigated for chalcogenide (Se80Te20)94Ge6 glass in the frequency range from 1Hz to 1MHz and within the temperature range from 300 K to 380 K. ɛ'(ω) and ɛ″(ω) are found to be frequency and temperature dependent. This behaviour is interpreted on the basis of Guintini's theory of dielectric dispersion. The investigated glass obeys the power law ωs (s<1) and decreases as temperature rises. The obtained results are discussed in terms of the correlation barrier hopping (CBH) model proposed by Elliot.

Corrosion behaviour of electropolished AISI 316L austenitic biomaterial in physiological solution

NASA Astrophysics Data System (ADS)

Zatkalíková, V.; Markovičová, L.; Škorvanová, M.

2017-11-01

Due to suitable mechanical properties, satisfactory corrosion resistance and relatively low cost, austenitic stainless steels are important biomaterials for manufacture of implants and various medical instruments and devices. Their corrosion properties and biocompatibility are significantly affected by protective passive surface film quality, which depends on used mechanical and chemical surface treatment. This article deals with corrosion resistance of AISI 316L stainless steel, which is the most widely used Cr-Ni-Mo austenitic biomaterial. Corrosion behaviour of five various surfaces (original, electropolished, three surfaces with combined treatment finished by electropolishing) is evaluated on the bases of cyclic potentiodynamic polarization tests performed in physiological solution at the temperature of 37± 0.5 °C.

Evidence of dilute ferromagnetism in rare-earth doped yttrium aluminium garnet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farr, Warrick G.; Goryachev, Maxim; Le Floch, Jean-Michel

This work demonstrates strong coupling regime between an erbium ion spin ensemble and microwave hybrid cavity-whispering gallery modes in a yttrium aluminium garnet dielectric crystal. Coupling strengths of 220 MHz and mode quality factors in excess of 10{sup 6} are demonstrated. Moreover, the magnetic response of high-Q modes demonstrates behaviour which is unusual for paramagnetic systems. This behaviour includes hysteresis and memory effects. Such qualitative change of the system's magnetic field response is interpreted as a phase transition of rare earth ion impurities. This phenomenon is similar to the phenomenon of dilute ferromagnetism in semiconductors. The clear temperature dependence of themore » phenomenon is demonstrated.« less

The Reverse Thermal Effect in Epoxy Resins and Moisture Absorption in Semi-Interpenetrating Polymer Networks.

NASA Astrophysics Data System (ADS)

El-Sa'Ad, Leila

1989-12-01

Available from UMI in association with The British Library. Requires signed TDF. Epoxy resins exhibit many desirable properties which make them ideal subjects for use as matrices of composite materials in many commercial, military and space applications. However, due to their high cross-link density they are often brittle. Epoxy resin networks have been modified by incorporating tough, ductile thermoplastics. Such systems are referred to as Semi-Interpenetrating Polymer Networks (Semi-IPN). Systematic modification to the thermoplastics backbone allowed the morphology of the blend to be controlled from a homogeneous one-phase structure to fully separated structures. The moisture absorption by composites in humid environments has been found to lead to a deterioration in the physical and mechanical properties of the matrix. Therefore, in order to utilize composites to their full potential, their response to hot/wet environments must be known. The aims of this investigation were two-fold. Firstly, to study the effect of varying the temperature of exposure at different stages in the absorption process on the water absorption behaviour of a TGDDM/DDS epoxy resin system. Secondly, to study water absorption characteristics, under isothermal conditions, of Semi-Interpenetrating Polymer Networks possessing different morphologies, and develop a theoretical model to evaluate the diffusion coefficients of the two-phase structures. The mathematical treatment used in this analysis was based on Fick's second law of diffusion. Tests were performed on specimens immersed in water at 10 ^circ, 40^circ and 70^circC, their absorption behaviour and swelling behaviour, as a consequence of water absorption, were investigated. The absorption results of the variable temperature absorption tests indicated a saturation dependence on the absorption behaviour. Specimens saturated at a high temperature will undergo further absorption when transferred to a lower temperature. This behaviour was termed the "reverse thermal effect". The swelling results suggested that it is more tightly bound water in the polymer which takes part in the reverse thermal effect. The absorption results for the Semi-Interpenetrating Polymer Networks suggested that the two key parameters which affected the moisture uptake were the morphology of the network and the percentage of epoxy resin in the system.

Effect of ripples on the finite temperature elastic properties of hexagonal boron nitride using strain-fluctuation method

NASA Astrophysics Data System (ADS)

Thomas, Siby; Ajith, K. M.; Valsakumar, M. C.

2017-11-01

This work intents to put forth the results of a classical molecular dynamics study to investigate the temperature dependent elastic constants of monolayer hexagonal boron nitride (h-BN) between 100 and 1000 K for the first time using strain fluctuation method. The temperature dependence of out-of-plane fluctuations (ripples) is quantified and is explained using continuum theory of membranes. At low temperatures, negative in-plane thermal expansion is observed and at high temperatures, a transition to positive thermal expansion has been observed due to the presence of thermally excited ripples. The decrease of Young's modulus, bulk modulus, shear modulus and Poisson's ratio with increase in temperature has been analyzed. The thermal rippling in h-BN leads to strong anharmonic behaviour that causes large deviation from the isotropic elasticity. A detailed study shows that the strong thermal rippling in large systems is also responsible for the softening of elastic constants in h-BN. From the determined values of elastic constants and elastic moduli, it has been elucidated that 2D h-BN sheets meet the Born's mechanical stability criterion in the investigated temperature range. The variation of longitudinal and shear velocities with temperature is also calculated from the computed values of elastic constants and elastic moduli.

Magneto-photoconductivity of three dimensional topological insulator bismuth telluride

NASA Astrophysics Data System (ADS)

Cao, Bingchen; Eginligil, Mustafa; Yu, Ting

2018-03-01

Magnetic field dependence of the photocurrent in a 3D topological insulator is studied. Among the 3D topological insulators bismuth telluride has unique hexagonal warping and spin texture which has been studied by photoemission, scanning tunnelling microscopy and transport. Here, we report on low temperature magneto-photoconductivity, up to 7 T, of two metallic bismuth telluride topological insulator samples with 68 and 110 nm thicknesses excited by 2.33 eV photon energy along the magnetic field perpendicular to the sample plane. At 4 K, both samples exhibit negative magneto-photoconductance below 4 T, which is as a result of weak-antilocalization of Dirac fermions similar to the previous observations in electrical transport. However the thinner sample shows positive magneto-photoconductance above 4 T. This can be attributed to the coupling of surface states. On the other hand, the thicker sample shows no positive magneto-photoconductance up to 7 T since there is only one surface state at play. By fitting the magneto-photoconductivity data of the thicker sample to the localization formula, we obtain weak antilocalization behaviour at 4, 10, and 20 K, as expected; however, weak localization behaviour at 30 K, which is a sign of surface states masked by bulk states. Also, from the temperature dependence of phase coherence length bulk carrier-carrier interaction is identified separately from the surface states. Therefore, it is possible to distinguish surface states by magneto-photoconductivity at low temperature, even in metallic samples.

Measurement and interpretation of fluorescence polarisations in phospholipid dispersions.

PubMed

Bashford, C L; Morgan, C G; Radda, G K

1976-03-05

An instrument that measures the temperature dependence of fluorescence polarisation and intensity directly and continuously is described. The behaviour of four fluorescent probes bound to a number of well characterised model systems was then examined. The motional properties of the probes were determined from the polarisation and intensity data and were found to be sensitive to the crystalline-liquid crystalline phase transitions in phospholipid vesicles of dimyristoly and dipalmitoly phosphatidylcholine. Binary mixture of dilauroyl and dipalmitoyl phosphatidylcholine show lateral phase separation and in this system the probes parition preferentially into the more 'fluid' phase. In systems that have been reported to contain 'short range order' or 'liquid clustering', such as dioleoyl phosphatidylcholine and liquid paraffin, the motion of the probes was found to have anomalous Arrhenius behaviour consistent with the idea that homogeneous phases were not being sampled. The significance of these findings for the interpretation of the behaviour of fluorescent probes bound to natural membranes is discussed.

Nonlinear microwave response of an MgB2 thin film

NASA Astrophysics Data System (ADS)

Purnell, A. J.; Cohen, L. F.; Zhai, H. Y.; Christen, H. M.; Paranthaman, M. P.; Lowndes, D. H.; Hao, Ling; Gallop, J. C.

2004-04-01

MgB2 is a two-gap superconductor and as a result may manifest unusual physical properties. The performance of MgB2 films at microwave frequencies has so far been rather poor compared to that of Nb alloys and this may result from intrinsic behaviour related to the double-gap structure or extrinsic properties due to non-optimized thin films. Here we give a detailed report on the microwave magnetic field dependent surface impedance of an MgB2 thin film, using a parallel plate resonator, as a function of temperature. We discuss whether the framework used to analyse nonlinear behaviour for other superconductors, both low and high Tc, but single-gap, has any validity for MgB2 and whether the films are limited by intrinsic or extrinsic behaviour. The key result is the observation of junction-type switching effects at high microwave power.

Symbiodinium identity alters the temperature-dependent settlement behaviour of Acropora millepora coral larvae before the onset of symbiosis

PubMed Central

Winkler, Natalia S.; Pandolfi, John M.; Sampayo, Eugenia M.

2015-01-01

The global distribution of marine species, many of which disperse during the larval stages, is influenced by ocean temperature regimes. Here, we test how temperature and the coral symbionts (Symbiodinium) affect survival, symbiont uptake, settlement success and habitat choice of Acropora millepora larvae. Experiments were conducted at Heron Island (Australia), where larvae were exposed to 22.5, 24.5, 26.5 and 28.5°C. Within each temperature treatment, larvae were offered symbionts with distinct characteristics: (i) homologous Symbiodinium type C3, (ii) regionally homologous thermo-tolerant type D1, and (iii) heterologous thermo-tolerant type C15, as well as controls of (iv) un-filtered and (v) filtered seawater. Results show that lower instead of higher temperatures adversely affected recruitment by reducing larval survival and settlement. Low temperatures also reduced recruit habitat choice and initial symbiont densities, both of which impact on post-settlement survival. At lower temperatures, larvae increasingly settle away from preferred vertical surfaces and not on crustose coralline algae (CCA). Surprisingly, substrate preference to CCA was modified by the presence of specific symbiont genotypes that were present ex-hospite (outside the coral larvae). When different symbionts were mixed, the outcomes were non-additive, indicating that symbiont interactions modify the response. We propose that the observed influence of ex-hospite symbionts on settlement behaviour may have evolved through ecological facilitation and the study highlights the importance of biological processes during coral settlement. PMID:25589607

Water temperatures influence the marine area use of Salvelinus alpinus and Salmo trutta.

PubMed

Jensen, J L A; Rikardsen, A H; Thorstad, E B; Suhr, A H; Davidsen, J G; Primicerio, R

2014-06-01

The migratory behaviour and spatial area use of sympatric Arctic charr Salvelinus alpinus and brown trout Salmo trutta were investigated during their marine feeding migration. The likelihood of finding individuals of both species in the inner or outer fjord areas was dependent on water temperature in the inner area (especially for S. alpinus), the temperature difference between the inner and outer areas (especially for S. trutta) and fish fork length (both species). The strongest predictor was the water temperature in the inner area, and particularly S. alpinus left this area and moved to the outer areas with increasing temperatures in the inner area. At 8° C in the inner area, the likelihood of finding S. alpinus in the outer areas was >50%. This predictor had a smaller effect on S. trutta, and the likelihood of finding S. trutta in the outer areas only started to increase at around 14° C. The relationships between temperature and area use did not correspond to the species' optimal growth temperatures, but to their previously documented temperature preferences. Individuals of both species used mainly the littoral fjord areas, and to a lesser extent the pelagic areas. In conclusion, temperature differences between the inner and outer marine areas probably resulted in the segregated area use between the species, because water temperatures or factors influenced by temperature affected their migratory behaviour and habitat use differently. The results indicate that increased marine temperatures with global warming may lead to increased spatial overlap between S. trutta and S. alpinus, which again may lead to increased interspecific competition during their marine phase, and with S. alpinus probably being the more negatively affected. © 2014 The Fisheries Society of the British Isles.

Specific absorption rate dependence on temperature in magnetic field hyperthermia measured by dynamic hysteresis losses (ac magnetometry)

NASA Astrophysics Data System (ADS)

Garaio, Eneko; Sandre, Olivier; Collantes, Juan-Mari; Garcia, Jose Angel; Mornet, Stéphane; Plazaola, Fernando

2015-01-01

Magnetic nanoparticles (NPs) are intensively studied for their potential use for magnetic hyperthermia, a treatment that has passed a phase II clinical trial against severe brain cancer (glioblastoma) at the end of 2011. Their heating power, characterized by the ‘specific absorption rate (SAR)’, is often considered temperature independent in the literature, mainly because of the difficulties that arise from the measurement methodology. Using a dynamic magnetometer presented in a recent paper, we measure here the thermal dependence of SAR for superparamagnetic iron oxide (maghemite) NPs of four different size-ranges corresponding to mean diameters around 12 nm, 14 nm, 15 nm and 16 nm. The article reports a parametrical study extending from 10 to 60 {}^\\circ C in temperature, from 75 to 1031 kHz in frequency, and from 2 to 24 kA m-1 in magnetic field strength. It was observed that SAR values of smaller NPs decrease with temperature whereas for the larger sample (16 nm) SAR values increase with temperature. The measured variation of SAR with temperature is frequency dependent. This behaviour is fully explained within the scope of linear response theory based on Néel and Brown relaxation processes, using independent magnetic measurements of the specific magnetization and the magnetic anisotropy constant. A good quantitative agreement between experimental values and theoretical values is confirmed in a tri-dimensional space that uses as coordinates the field strength, the frequency and the temperature.

Behaviour during elevated water temperatures: can physiology explain movement of juvenile Atlantic salmon to cool water?

PubMed

Breau, Cindy; Cunjak, Richard A; Peake, Stephan J

2011-07-01

1. Temperature governs most physiological processes in animals. Ectotherms behaviourally thermoregulate by selecting habitats with temperatures regulating their body temperature for optimal physiological functioning. However, ectotherms can experience temperature extremes forcing the organisms to seek temperature refuge. 2. Fish actively avoid potentially lethal temperatures by moving to cool-water sites created by inflowing tributaries and groundwater seeps. Juvenile Atlantic salmon (Salmo salar) of different age classes exhibit different behavioural responses to elevated temperatures (>23 °C). Yearling (1+) and 2-year-old (2+) Atlantic salmon often cease feeding, abandon territorial behaviour and swim continuously in aggregations in cool-water sites; whereas young-of-the-year (0+) fish continue defending territories and foraging. 3. This study determined whether the behavioural shift in older individuals (2+) occurred when basal metabolic rate, driven by increasing water temperature, reached the maximum metabolic rate such that anaerobic pathways were recruited to provide energy to support vital processes. Behaviour (feeding and stress responses), oxygen consumption, muscle lactate and glycogen, and circulating blood lactate and glucose concentrations were measured in wild 0+ and 2+ Atlantic salmon acclimated to water temperatures between 16 and 28 °C. 4. Results indicate that oxygen consumption of the 2+ fish increased with temperature and reached a plateau at 24 °C, a temperature that corresponded to cessation of feeding and a significant increase in muscle and blood lactate levels. By contrast, oxygen consumption in 0+ fish did not reach a plateau, feeding continued and muscle lactate did not increase, even at the highest temperatures tested (28 °C). 5. To conclude, the experiment demonstrated that the 0+ and 2+ fish had different physiological responses to the elevated water temperatures. The results suggest that wild 2+ Atlantic salmon employ behavioural responses (e.g. movement to cool-water sites) at elevated temperatures in an effort to mitigate physiological imbalances associated with an inability to support basal metabolism through aerobic metabolic processes. © 2011 The Authors. Journal of Animal Ecology © 2011 British Ecological Society.

Modelling Behaviour of a Carbon Epoxy Composite Exposed to Fire: Part II—Comparison with Experimental Results

PubMed Central

Tranchard, Pauline; Samyn, Fabienne; Duquesne, Sophie; Estèbe, Bruno; Bourbigot, Serge

2017-01-01

Based on a phenomenological methodology, a three dimensional (3D) thermochemical model was developed to predict the temperature profile, the mass loss and the decomposition front of a carbon-reinforced epoxy composite laminate (T700/M21 composite) exposed to fire conditions. This 3D model takes into account the energy accumulation by the solid material, the anisotropic heat conduction, the thermal decomposition of the material, the gas mass flow into the composite, and the internal pressure. Thermophysical properties defined as temperature dependant properties were characterised using existing as well as innovative methodologies in order to use them as inputs into our physical model. The 3D thermochemical model accurately predicts the measured mass loss and observed decomposition front when the carbon fibre/epoxy composite is directly impacted by a propane flame. In short, the model shows its capability to predict the fire behaviour of a carbon fibre reinforced composite for fire safety engineering. PMID:28772836

Thermal modelling of Li-ion polymer battery for electric vehicle drive cycles

NASA Astrophysics Data System (ADS)

Chacko, Salvio; Chung, Yongmann M.

2012-09-01

Time-dependent, thermal behaviour of a lithium-ion (Li-ion) polymer cell has been modelled for electric vehicle (EV) drive cycles with a view to developing an effective battery thermal management system. The fully coupled, three-dimensional transient electro-thermal model has been implemented based on a finite volume method. To support the numerical study, a high energy density Li-ion polymer pouch cell was tested in a climatic chamber for electric load cycles consisting of various charge and discharge rates, and a good agreement was found between the model predictions and the experimental data. The cell-level thermal behaviour under stressful conditions such as high power draw and high ambient temperature was predicted with the model. A significant temperature increase was observed in the stressful condition, corresponding to a repeated acceleration and deceleration, indicating that an effective battery thermal management system would be required to maintain the optimal cell performance and also to achieve a full battery lifesapn.

The influence of implanted yttrium on the cyclic oxidation behaviour of 304 stainless steel

NASA Astrophysics Data System (ADS)

Riffard, F.; Buscail, H.; Caudron, E.; Cueff, R.; Issartel, C.; Perrier, S.

2006-03-01

High-temperature alloys are frequently used in power plants, gasification systems, petrochemical industry, combustion processes and in aerospace applications. Depending on the application, materials are subjected to corrosive atmospheres and thermal cycling. In the present work, thermal cycling was carried out in order to study the influence of implanted yttrium on the oxide scale adherence on 304 steel specimens oxidised in air at 1273 K. In situ X-ray diffraction indicates that the oxides formed at 1273 K are different on blank specimens compared to implanted specimens. Glancing angle XRD allows to analyse the oxide scale composition after cooling to room temperature. Experimental results show that yttrium implantation at a nominal dose of 10 17 ions cm -2 does not improve significantly the cyclic oxidation behaviour of the austenitic AISI 304 steel. However, it appears that yttrium implantation remarkably enhance the oxidation resistance during isothermal oxidation. It reduces the transient oxidation stage and the parabolic oxidation rate constant by one order of magnitude.

Modelling Behaviour of a Carbon Epoxy Composite Exposed to Fire: Part II-Comparison with Experimental Results.

PubMed

Tranchard, Pauline; Samyn, Fabienne; Duquesne, Sophie; Estèbe, Bruno; Bourbigot, Serge

2017-04-28

Based on a phenomenological methodology, a three dimensional (3D) thermochemical model was developed to predict the temperature profile, the mass loss and the decomposition front of a carbon-reinforced epoxy composite laminate (T700/M21 composite) exposed to fire conditions. This 3D model takes into account the energy accumulation by the solid material, the anisotropic heat conduction, the thermal decomposition of the material, the gas mass flow into the composite, and the internal pressure. Thermophysical properties defined as temperature dependant properties were characterised using existing as well as innovative methodologies in order to use them as inputs into our physical model. The 3D thermochemical model accurately predicts the measured mass loss and observed decomposition front when the carbon fibre/epoxy composite is directly impacted by a propane flame. In short, the model shows its capability to predict the fire behaviour of a carbon fibre reinforced composite for fire safety engineering.

Ferrian Ilmenites: Investigating the Magnetic Phase Diagram

NASA Astrophysics Data System (ADS)

Lagroix, F.

2007-12-01

The main objective of this study is to investigate the magnetic phase changes within the hematite-ilmenite solid solution, yFeTiO3·(1-y)·Fe2O3. Two sets of synthetic ferrian ilmenites of y-values equal to 0.7, 0.8, 0.9, and 1.0 were available for this study. As currently drawn, the magnetic phase diagram, proposed by Ishikawa et al. [1985, J. Phys. Soc. Jpn. v.54, 312-325], predicts for increasing y values (0.5

Ultrasonic Characterization of Superhard Material: Osmium Diboride

NASA Astrophysics Data System (ADS)

Yadawa, P. K.

2012-12-01

Higher order elastic constants have been calculated in hexagonal structured superhard material OsB2 at room temperature following the interaction potential model. The temperature variation of the ultrasonic velocities is evaluated along different angles with unique axis of the crystal using the second order elastic constants. The ultrasonic velocity decreases with the temperature along particular orientation with the unique axis. Temperature variation of the thermal relaxation time and Debye average velocities are also calculated along the same orientation. The temperature dependency of the ultrasonic properties is discussed in correlation with elastic, thermal and electrical properties. It has been found that the thermal conductivity is the main contributor to the behaviour of ultrasonic attenuation as a function of temperature and the responsible cause of attenuation is phonon-phonon interaction. The mechanical properties of OsB2 at low temperature are better than at high temperature, because at low temperature it has low ultrasonic velocity and ultrasonic attenuation. Superhard material OsB2 has many industrial applications, such as abrasives, cutting tools and hard coatings.

Interparticle interactions mediated superspin glass to superferromagnetic transition in Ni-bacterial cellulose aerogel nanocomposites

NASA Astrophysics Data System (ADS)

Thiruvengadam, V.; Vitta, Satish

2016-06-01

The interparticle interactions in the magnetic nanocomposites play a dominant role in controlling phase transitions: superparamagnetic to superspin glass and to superferromagnetic. These interactions can be tuned by controlling the size and number density of nanoparticles. The aerogel composites, 0.3Ni-BC and 0.7Ni-BC, consisting of Ni nanoparticles distributed in the bacterial cellulose have been used as a model system to study these interactions. Contrary to conventional approach, size of Ni-nanoparticles is not controlled and allowed to form naturally in bacterial cellulose template. The uncontrolled growth of Ni results in the formation of nanoparticles with 3 different size distributions - <10 nm particles along the length of fibrils, 50 nm particles in the intermediate spaces between the fibrils, and >100 nm particles in voids formed by reticulate structure. At room temperature, the composites exhibit a weakly ferromagnetic behaviour with a coercivity of 40 Oe, which increases to 160 Oe at 10 K. The transition from weakly ferromagnetic state to superferromagnetic state at low temperatures is mediated by the superspin glass state at intermediate temperatures via the interparticle interactions aided by nanoparticles present along the length of fibres. A temperature dependent microstructural model has been developed to understand the magnetic behaviour of nanocomposite aerogels.

Critical behaviour and vapour-liquid coexistence of 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ionic liquids via Monte Carlo simulations.

PubMed

Rai, Neeraj; Maginn, Edward J

2012-01-01

Atomistic Monte Carlo simulations are used to compute vapour-liquid coexistence properties of a homologous series of [C(n)mim][NTf2] ionic liquids, with n = 1, 2, 4, 6. Estimates of the critical temperatures range from 1190 K to 1257 K, with longer cation alkyl chains serving to lower the critical temperature. Other quantities such as critical density, critical pressure, normal boiling point, and accentric factor are determined from the simulations. Vapour pressure curves and the temperature dependence of the enthalpy of vapourisation are computed and found to have a weak dependence on the length of the cation alkyl chain. The ions in the vapour phase are predominately in single ion pairs, although a significant number of ions are found in neutral clusters of larger sizes as temperature is increased. It is found that previous estimates of the critical point obtained from extrapolating experimental surface tension data agree reasonably well with the predictions obtained here, but group contribution methods and primitive models of ionic liquids do not capture many of the trends observed in the present study

Body temperature changes during simulated bacterial infection in a songbird: fever at night and hypothermia during the day.

PubMed

Sköld-Chiriac, Sandra; Nord, Andreas; Tobler, Michael; Nilsson, Jan-Åke; Hasselquist, Dennis

2015-09-01

Although fever (a closely regulated increase in body temperature in response to infection) typically is beneficial, it is energetically costly and may induce detrimentally high body temperatures. This can increase the susceptibility to energetic bottlenecks and risks of overheating in some organisms. Accordingly, it could be particularly interesting to study fever in small birds, which have comparatively high metabolic rates and high, variable body temperatures. We therefore investigated two aspects of fever and other sickness behaviours (circadian variation, dose dependence) in a small songbird, the zebra finch. We injected lipopolysaccharide (LPS) at the beginning of either the day or the night, and subsequently monitored body temperature, body mass change and food intake for the duration of the response. We found pronounced circadian variation in the body temperature response to LPS injection, manifested by (dose-dependent) hypothermia during the day but fever at night. This resulted in body temperature during the peak response being relatively similar during the day and night. Day-to-night differences might be explained in the context of circadian variation in body temperature: songbirds have a high daytime body temperature that is augmented by substantial heat production peaks during activity. This might require a trade-off between the benefit of fever and the risk of overheating. In contrast, at night, when body temperature is typically lower and less variable, fever can be used to mitigate infection. We suggest that the change in body temperature during infection in small songbirds is context dependent and regulated to promote survival according to individual demands at the time of infection. © 2015. Published by The Company of Biologists Ltd.

Magnetic and magnetocaloric properties of the exactly solvable mixed-spin Ising model on a decorated triangular lattice in a magnetic field

NASA Astrophysics Data System (ADS)

Gálisová, Lucia; Strečka, Jozef

2018-05-01

The ground state, zero-temperature magnetization process, critical behaviour and isothermal entropy change of the mixed-spin Ising model on a decorated triangular lattice in a magnetic field are exactly studied after performing the generalized decoration-iteration mapping transformation. It is shown that both the inverse and conventional magnetocaloric effect can be found near the absolute zero temperature. The former phenomenon can be found in a vicinity of the discontinuous phase transitions and their crossing points, while the latter one occurs in some paramagnetic phases due to a spin frustration to be present at zero magnetic field. The inverse magnetocaloric effect can also be detected slightly above continuous phase transitions following the power-law dependence | - ΔSisomin | ∝hn, where n depends basically on the ground-state spin ordering.

Obsessive passion: a dependency associated with injury-related risky behaviour in dancers.

PubMed

Akehurst, Sally; Oliver, Emily J

2014-01-01

Grounded in self-determination theory, obsessive passion for an activity has been associated with increased risky behaviour and rigid persistence, both symptomatic of dependence. However, it is unknown whether obsessive passion may predict the development of dependence, and furthermore, theoretically important relationships between basic need satisfaction, passion, exercise dependence and subsequent risky behaviour have not been fully explored. A sample of 100 professional dancers (50(fs); 50(ms); Mage = 20.88; SD = 2.69) completed self-ratings of risk-related behaviours (doctor visits; following treatment, and warming up), passion for dance and dance dependence. Findings supported the maladaptive nature of obsessive passion in relation to risky behaviour and as predicted dance dependence mediated this relationship. Interestingly, need satisfaction was positively related to both obsessive passion and harmonious passion. Results are discussed in the light of self-determination theory and dysfunctions of obsessive passion, suggesting that professional dancers are at risk of employing maladaptive behaviours if high in obsessive passion, which may be detectable via symptoms of dance dependence.

Can crayfish take the heat? Procambarus clarkii show nociceptive behaviour to high temperature stimuli, but not low temperature or chemical stimuli

PubMed Central

Puri, Sakshi; Faulkes, Zen

2015-01-01

Nociceptors are sensory neurons that are tuned to tissue damage. In many species, nociceptors are often stimulated by noxious extreme temperatures and by chemical agonists that do not damage tissue (e.g., capsaicin and isothiocyanate). We test whether crustaceans have nociceptors by examining nociceptive behaviours and neurophysiological responses to extreme temperatures and potentially nocigenic chemicals. Crayfish (Procambarus clarkii) respond quickly and strongly to high temperatures, and neurons in the antenna show increased responses to transient high temperature stimuli. Crayfish showed no difference in behavioural response to low temperature stimuli. Crayfish also showed no significant changes in behaviour when stimulated with capsaicin or isothiocyanate compared to controls, and neurons in the antenna did not change their firing rate following application of capsaicin or isothiocyanate. Noxious high temperatures appear to be a potentially ecologically relevant noxious stimulus for crayfish that can be detected by sensory neurons, which may be specialized nociceptors. PMID:25819841

Electrical, structural and surface morphological properties of thermally stable low-resistance W/Ti/Au multilayer ohmic contacts to n-type GaN

NASA Astrophysics Data System (ADS)

Jyothi, I.; Reddy, V. Rajagopal

2010-10-01

A W/Ti/Au multilayer scheme has been fabricated for achieving thermally stable low-resistance ohmic contact to n-type GaN (4.0 × 10 18 cm -3). It is shown that the as-deposited W/Ti/Au contact exhibits near linear I- V behaviour. However, annealing at temperature below 800 °C the contacts exhibit non-linear behaviour. After annealing at a temperature in excess of 850 °C, the W/Ti/Au contact showed ohmic behaviour. The W/Ti/Au contact produced specific contact resistance as low as 6.7 × 10 -6 Ω cm 2 after annealing at 900 °C for 1 min in a N 2 ambient. It is noted that the specific contact resistance decreases with increase in annealing temperature. It is also noted that annealing the contacts at 900 °C for 30 min causes insignificant degradation of the electrical and thermal properties. It is further shown that the overall surface morphology of the W/Ti/Au stayed fairly smooth even after annealing at 900 °C. The W/Ti/Au ohmic contact showed good edge sharpness after annealing at 900 °C for 30 min. Based on the Auger electron spectroscopy and glancing angle X-ray diffraction results, possible explanation for the annealing dependence of the specific contact resistance of the W/Ti/Au contacts are described and discussed.

Locally preserved α  →  β phase transition in natural radiation-damaged titanite (CaTiSiO5): evidence from laser-induced photoluminescence and dielectric measurements

NASA Astrophysics Data System (ADS)

Beirau, Tobias; Murawski, Dawid; Behrens, Harald; Salje, Ekhard K. H.; Groat, Lee A.; Kaden, Ronny; Pöllmann, Herbert; Bismayer, Ulrich

2018-01-01

In situ temperature-dependent laser-induced photoluminescence and dielectric measurements provide new evidence for the local occurrence of the α  →  β phase transition near 500 K in the preserved crystalline parts of natural radiation-damaged titanite (sample E2335 with ~24% amorphous fraction, containing Fe and Al impurities). Photoluminescence spectroscopic measurements show an anomaly in the vicinity of 500 K. The temperature-dependent evolution of the real part of the electrical conductivity (σ) and the real (ɛ‧) and the imaginary (ɛ″) part of the complex dielectric permittivity (ɛ *) of titanite have been measured at various AC frequencies (~1.2-96.8 kHz). Despite the masking and smearing effect of impurities and defects, the temperature-dependent behaviour of ɛ‧ and ɛ″ around the transition temperature of the investigated natural titanite E2335 shows a remarkable similarity to that of the synthetic end-member material (see Zhang et al (1995 Phys. Chem. Miner. 22 41-9)). This study indicates the suitability of photoluminescence and impedance spectroscopy for the detection of phase transitions, even in heavily disordered systems.

Transverse crack initiation under combined thermal and mechanical loading of Fibre Metal Laminates and Glass Fibre Reinforced Polymers

NASA Astrophysics Data System (ADS)

van de Camp, W.; Dhallé, M. M. J.; Warnet, L.; Wessel, W. A. J.; Vos, G. S.; Akkerman, R.; ter Brake, H. J. M.

2017-02-01

The paper describes a temperature-dependent extension of the classical laminate theory (CLT) that may be used to predict the mechanical behaviour of Fibre Metal Laminates (FML) at cryogenic conditions, including crack initiation. FML are considered as a possible alternative class of structural materials for the transport and storage of liquified gasses such as LNG. Combining different constituents in a laminate opens up the possibility to enhance its functionality, e.g. offering lower specific weight and increased damage tolerance. To explore this possibility, a test programme is underway at the University of Twente to study transverse crack initiation in different material combinations under combined thermal and mechanical loading. Specifically, the samples are tested in a three-point bending experiment at temperatures ranging from 77 to 293 K. These tests will serve as a validation of the model presented in this paper which, by incorporating temperature-dependent mechanical properties and differential thermal expansion, will allow to select optimal material combinations and laminate layouts. By combining the temperature-dependent mechanical properties and the differential thermal contraction explicitly, the model allows for a more accurate estimate of the resulting thermal stresses which can then be compared to the strength of the constituent materials.

Does dependency make a difference? The role of convenience, social influence, facilitating condition and self-efficacy on student's purchase behaviour of smartphone

NASA Astrophysics Data System (ADS)

Jaganathan, Mathivannan; Mustapa, Azrain Nasyrah; Hasan, Wan Azlina Wan; Mat, Nik Kamariah Nik; Alekam, Jamal Mohammed Esmail

2014-12-01

It is an undeniable fact that penetration level and usage and sales of Smartphone dramatically increased past few years, whereby; it has increased to almost 60 percent of total population. Despite the high penetration of smartphone, previous studies have exhibited inconsistent findings towards understanding the behavioural intention to use smartphone especially among university students. Thus, the purpose of this study is to examine purchasing behaviour of Smartphone among students. From the literature, five antecedents of purchasing behaviour were identified. Each variable is measured using 7-point Likert scale: convenience (10 items), social influence (6 items), self-efficacy (10 items), facilitating condition (11 items), dependency (14 items) and purchasing behaviour (4 items). Using the primary data collection method, 400 questionnaires were distributed to the target respondents of one of the public higher education in the northern region. The responses collected were 350 completed questionnaires representing 87.5 percent response rate. The data were analysed using Structural Equation Modeling (SEM) using AMOS. Confirmatory factor analysis of measurement models indicates adequate goodness or fit after few items were eliminated through modification indices verifications. Therefore, goodness of fit for the generated structural model shows the adequate fit. This study has established four direct significant causal effects and two significant mediating effects: (1) convenience and dependency, (2) social influence and dependency, (3) facilitating condition and purchase behaviour, (4), dependency and purchase behaviour. The significant mediating results are: (1). Dependency mediates the relationship between convenience and purchase behaviour; (2) dependency mediates social influence and purchase behaviour. Thus, findings suggested that convenience, social influence and dependency play a role in determining students purchase behaviour of smartphone. The researchers hope the findings of this study will contribute theoretically and practically to scholars, marketers and smartphone manufacturers.

Grain size effect on the permittivity of La1.5Sr0.5NiO4 nanoparticles

NASA Astrophysics Data System (ADS)

Dang Thanh, Tran; Van Hong, Le

2009-09-01

Using the annealing at different temperatures the La1.5Sr0.5NiO4 ceramic samples with different mean grain size were manufactured. Mean grain size () of the samples was evaluated by Warren-Averbach method and their SEM images. The obtained results of both methods are almost the same, changing from 16.2 to 95 nm in dependence on the annealing temperature. The frequency dependence of dielectric constant in the frequency range of (1-13 MHz) was recorded for all samples. The real (ɛ') and the imaginary parts (ɛ") of the permittivity of La1.5Sr0.5NiO4 samples abnormally depend on the frequency, exhibiting a dielectric resonance around 500 kHz. R-L-C in series equivalent-circuit fitted well for the obtained result. It was supposed that there exists magnetic contribution in material that suggests the material is a multiferroic one. Dependence of the (ɛ') on the mean grain size supposed that the colossal dielectric property is an intrinsic behaviour of La1.5Sr0.5NiO4 material.

Magnetic properties of the new π -d organic superconductor β -(BDA-TTP){2}FeCl{4}

NASA Astrophysics Data System (ADS)

Tokumoto, M.; Ishii, K.; Tanaka, H.; Akutsu, H.; Yamada, J.; Choi, E. S.; Brooks, J. S.; Ishida, K.

2004-04-01

We have investigated complete anisotropy in the magnetic properties of the charge transfer salt β -(BDA-TTP){2}FeCl{4} [BDA-TTP = 2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene] and revealed that the anisotropy in both the temperature and the field dependences of magnetization below TN show behaviours different from those for typical antiferromagnets. Key words. Antiferromagnet anisotropy Smagnetization.

A new apparatus for testing the delayed mechanical behaviour of interfaces: The Shearing Interfaces Creep box (SInC box)

NASA Astrophysics Data System (ADS)

Stavropoulou, Eleni; Briffaut, Matthieu; Dufour, Frédéric; Camps, Guillaume; Boulon, Marc

2017-06-01

A new experimental apparatus is presented for testing the time-dependent behaviour of interfaces, including in particular interfaces of geomaterials, under constant loading. This apparatus allows the application of two orthogonal loads normal and tangential to the mean plane of the interface, as well as the measurement of the axial and tangential relative displacements. The sample is moulded inside two half shear boxes and the system is designed in such a way that the shear force is applied along the mean plane of the interface. Some preliminary testing was carried out on a clay rock/concrete interface, under a controlled temperature environment. Preliminary results are presented, showing the evolution of the delayed displacements.

Predicting organismal vulnerability to climate warming: roles of behaviour, physiology and adaptation

PubMed Central

Huey, Raymond B.; Kearney, Michael R.; Krockenberger, Andrew; Holtum, Joseph A. M.; Jess, Mellissa; Williams, Stephen E.

2012-01-01

A recently developed integrative framework proposes that the vulnerability of a species to environmental change depends on the species' exposure and sensitivity to environmental change, its resilience to perturbations and its potential to adapt to change. These vulnerability criteria require behavioural, physiological and genetic data. With this information in hand, biologists can predict organisms most at risk from environmental change. Biologists and managers can then target organisms and habitats most at risk. Unfortunately, the required data (e.g. optimal physiological temperatures) are rarely available. Here, we evaluate the reliability of potential proxies (e.g. critical temperatures) that are often available for some groups. Several proxies for ectotherms are promising, but analogous ones for endotherms are lacking. We also develop a simple graphical model of how behavioural thermoregulation, acclimation and adaptation may interact to influence vulnerability over time. After considering this model together with the proxies available for physiological sensitivity to climate change, we conclude that ectotherms sharing vulnerability traits seem concentrated in lowland tropical forests. Their vulnerability may be exacerbated by negative biotic interactions. Whether tropical forest (or other) species can adapt to warming environments is unclear, as genetic and selective data are scant. Nevertheless, the prospects for tropical forest ectotherms appear grim. PMID:22566674

Temperature-dependent conformational variation of chromophoric dissolved organic matter and its consequent interaction with phenanthrene.

PubMed

Chen, Wei; Liu, Xiao-Yang; Yu, Han-Qing

2017-03-01

Temperature variation caused by climate change, seasonal variation and geographic locations affects the physicochemical compositions of chromophoric dissolved organic matter (CDOM), resulting in difference in the fates of CDOM-related environmental pollutants. Exploration into the thermal induced structural transition of CDOM can help to better understand their environmental impacts, but information on this aspect is still lacking. Through integrating fluorescence excitation-emission matrix coupled parallel factor analysis with synchronous fluorescence two-dimensional correlation spectroscopy, this study provides an in-depth insight into the temperature-dependent conformational transitions of CDOM and their impact on its hydrophobic interaction with persistent organic pollutants (with phenanthrene as an example) in water. The fluorescence components in CDOM change linearly to water temperature with different extents and different temperature regions. The thermal induced transition priority in CDOM is protein-like component → fulvic-like component → humic-like component. Furthermore, the impact of thermal-induced conformational transition of CDOM on its hydrophobic interaction with phenanthrene is observed and explored. The fluorescence-based analytic results reveal that the conjugation degree of the aromatic groups in the fulvic- and humic-like substances, and the unfolding of the secondary structure in the protein-like substances with aromatic structure, contribute to the conformation variation. This integrated approach jointly enhances the characterization of temperature-dependent conformational variation of CDOM, and provides a promising way to elucidate the environmental behaviours of CDOM. Copyright © 2017 Elsevier Ltd. All rights reserved.

High temperature (900-1300 C) mechanical behaviour of dendritic web grown silicon ribbons - Strain rate and temperature dependence of the yield stress

NASA Technical Reports Server (NTRS)

Mathews, V. K.; Gross, T. S.

1987-01-01

The mechanical behavior of dendritic web Si ribbons close the melting point was studied experimentally. The goal of the study was to generate data for modeling the generation of stresses and dislocation structures during growth of dendritic web Si ribbons, thereby permitting modifications to the production process, i.e., the temperature profile, to lower production costs for the photovoltaic ribbons. A laser was used to cut specimens in the direction of growth of sample ribbons, which were then subjected to tensile tests at temperatures up to 1300 C in an Ar atmosphere. The tensile strengths of the samples increased when the temperature rose above 1200 C, a phenomena which was attributed to the diffusion of oxygen atoms to the quasi-dislocation sites. The migration to the potential dislocations sites effectively locked the dislocations.

Temperature effect on the acid-base behaviour of Na-montmorillonite.

PubMed

Duc, Myriam; Carteret, Cédric; Thomas, Fabien; Gaboriaud, Fabien

2008-11-15

We report a study of the acid-base properties of Na-montmorillonite suspensions at temperatures from 25 degrees C to 80 degrees C, by continuous and batch potentiometric methods, combined with analysis of the dissolved and readsorbed species. The batch titration curves reveal that the dissolution processes of Na-montmorillonite and silica-rich secondary phases are increasingly predominant, respectively at acid and basic pH, and according to the temperature. The continuous titration curves are less affected by these side reactions. In the absence of a common intersection point, the thermodynamic analysis of the curves was based on the shift of the PZNPC with the ionic strength. This shift was not significantly altered by the temperature, by comparison with the dissociation product of water in the same conditions. Therefore we concluded that protonation-deprotonation of the dissociable sites at the edges of the clay platelets is not significantly temperature dependent.

Myelin basic protein reduces molecular motions in DMPA, an elastic neutron scattering study

NASA Astrophysics Data System (ADS)

Natali, F.; Gliozzi, A.; Rolandi, R.; Cavatorta, P.; Deriu, A.; Fasano, A.; Riccio, P.

2001-07-01

We have studied the effect of physiological amounts of myelin basic protein (MBP) on pure dimyristoyl L- α-phosphatidic acid (DMPA) vesicles using the elastic neutron scattering technique. Elastic scans have been performed in a wide temperature range (20-300 K). In the lower temperature region the behaviour of the integrated elastic intensity was the typical one of harmonic systems. The analysis of the Q and T dependence performed in terms of an asymmetric double well potential clearly showed that the effect of the protein consisted in a significant reduction of the conformational mobility of the DMPA bilayers and in the stabilisation of the membrane.

First-principles investigations into the thermodynamics of cation disorder and its impact on electronic structure and magnetic properties of spinel Co(Cr1-x Mn x )2O4.

PubMed

Das, Debashish; Ghosh, Subhradip

2017-02-08

Cation disorder over different crystallographic sites in spinel oxides is known to affect their properties. Recent experiments on Mn doped multiferroic [Formula: see text] indicate that a possible distribution of Mn atoms among tetrahedrally and octahedrally coordinated sites in the spinel lattice give rise to different variations in the structural parameters and saturation magnetisations in different concentration regimes of Mn atoms substituting the Cr. A composition dependent magnetic compensation behaviour points to the role conversions of the magnetic constituents. In this work, we have investigated the thermodynamics of cation disorder in [Formula: see text] system and its consequences on the structural, electronic and magnetic properties, using results from first-principles electronic structure calculations. We have computed the variations in the cation-disorder as a function of Mn concentration and the temperature and found that at the annealing temperature of the experiment many of the systems exhibit cation disorder. Our results support the interpretations of the experimental results regarding the qualitative variations in the sub-lattice occupancies and the associated magnetisation behaviour, with composition. We have analysed the variations in structural, magnetic and electronic properties of this system with variations in the compositions and the degree of cation disorder from the variations in their electronic structures and by using the ideas from crystal field theory. Our study provides a complete microscopic picture of the effects that are responsible for composition dependent behavioural differences of the properties of this system. This work lays down a general framework, based upon results from first-principles calculations, to understand and analyse the substitutional magnetic spinel oxides [Formula: see text] in presence of cation disorder.

Investigation of the stochastic nature of temperature and humidity for energy management

NASA Astrophysics Data System (ADS)

Hadjimitsis, Evanthis; Demetriou, Evangelos; Sakellari, Katerina; Tyralis, Hristos; Iliopoulou, Theano; Koutsoyiannis, Demetris

2017-04-01

Atmospheric temperature and dew point, in addition to their role in atmospheric processes, influence the management of energy systems since they highly affect the energy demand and production. Both temperature and humidity depend on the climate conditions and geographical location. In this context, we analyze numerous of observations around the globe and we investigate the long-term behaviour and periodicities of the temperature and humidity processes. Also, we present and apply a parsimonious stochastic double-cyclostationary model for these processes to an island in the Aegean Sea and investigate their link to energy management. Acknowledgement: This research is conducted within the frame of the undergraduate course "Stochastic Methods in Water Resources" of the National Technical University of Athens (NTUA). The School of Civil Engineering of NTUA provided moral support for the participation of the students in the Assembly.

Adsorption parameters and phase behaviour of non-ionic surfactants at liquid interfaces.

PubMed

Slavchov, Radomir Iliev; Ivanov, Ivan Boyanov

2017-11-29

A reasonable adsorption model is one that allows all adsorption parameters (adsorption constant, hard-disc area α, attraction parameter β) of a surfactant at a liquid interface to be predicted accurately as a function of the molecular structure and medium conditions. However, the established adsorption models of van der Waals and Frumkin lead to inconsistencies, such as negative β at water|oil, α significantly larger than the crystallographic area of the molecule, and phase behaviour that contradicts the experimental observations. Several less popular models that are better suited for liquid interfaces are investigated. It is shown that the sticky disc model agrees with the observed adsorption behaviour of several homologous series of surfactants, both at water|air and water|oil interfaces. The area α is independent of the interface and agrees within 6% to what follows from collapse and crystallographic data. A model of the lateral attraction is proposed, from which it follows that β has a strongly non-linear dependence on the hydrocarbon chain length, the area of the head group and the temperature. Using the model of β, experimental data, and the law of corresponding states, the critical point of the adsorbed layer could be determined. Depending on the value of β, the adsorption behaviour of the surfactants at liquid interfaces can be classified into distinct categories: cohesive or non-cohesive, based on their Boyle points (where β = 2), and sub-critical or super-critical, based on their critical points (where β = 38.1).

Risk, resources and state-dependent adaptive behavioural syndromes

PubMed Central

Luttbeg, Barney; Sih, Andrew

2010-01-01

Many animals exhibit behavioural syndromes—consistent individual differences in behaviour across two or more contexts or situations. Here, we present adaptive, state-dependent mathematical models for analysing issues about behavioural syndromes. We find that asset protection (where individuals with more ‘assets’ tend be more cautious) and starvation avoidance, two state-dependent mechanisms, can explain short-term behavioural consistency, but not long-term stable behavioural types (BTs). These negative-feedback mechanisms tend to produce convergence in state and behaviour over time. In contrast, a positive-feedback mechanism, state-dependent safety (where individuals with higher energy reserves, size, condition or vigour are better at coping with predators), can explain stable differences in personality over the long term. The relative importance of negative- and positive-feedback mechanisms in governing behavioural consistency depends on environmental conditions (predation risk and resource availability). Behavioural syndromes emerge more readily in conditions of intermediate ecological favourability (e.g. medium risk and medium resources, or high risk and resources, or low risk and resources). Under these conditions, individuals with higher initial state maintain a tendency to be bolder than individuals that start with low initial state; i.e. later BT is determined by state during an early ‘developmental window’. In contrast, when conditions are highly favourable (low risk, high resources) or highly unfavourable (high risk, low resources), individuals converge to be all relatively bold or all relatively cautious, respectively. In those circumstances, initial differences in BT are not maintained over the long term, and there is no early developmental window where initial state governs later BT. The exact range of ecological conditions favouring behavioural syndromes depends also on the strength of state-dependent safety. PMID:21078650

Light Effects on Behavioural Performance Depend on the Individual State of Vigilance

PubMed Central

Barba, Antonio; Padilla, Francisca

2016-01-01

Research has shown that exposure to bright white light or blue-enriched light enhances alertness, but this effect is not consistently observed in tasks demanding high-level cognition (e.g., Sustained Attention to Response Task—SART, which measures inhibitory control). Individual differences in sensitivity to light effects might be mediated by variations in the basal level of arousal. We tested this hypothesis by measuring the participants’ behavioural state of vigilance before light exposure, through the Psychomotor Vigilance Task. Then we compared the effects of a blue-enriched vs. dim light at nighttime on the performance of the auditory SART, by controlling for individual differences in basal arousal. The results replicated the alerting effects of blue-enriched light, as indexed by lower values of both proximal temperature and distal-proximal gradient. The main finding was that lighting effects on SART performance were highly variable across individuals and depended on their prior state of vigilance. Specifically, participants with higher levels of basal vigilance before light exposure benefited most from blue-enriched lighting, responding faster in the SART. These results highlight the importance of considering basal vigilance to define the boundary conditions of light effects on cognitive performance. Our study adds to current research delineating the complex and reciprocal interactions between lighting effects, arousal, cognitive task demands and behavioural performance. PMID:27820822

Light Effects on Behavioural Performance Depend on the Individual State of Vigilance.

PubMed

Correa, Ángel; Barba, Antonio; Padilla, Francisca

2016-01-01

Research has shown that exposure to bright white light or blue-enriched light enhances alertness, but this effect is not consistently observed in tasks demanding high-level cognition (e.g., Sustained Attention to Response Task-SART, which measures inhibitory control). Individual differences in sensitivity to light effects might be mediated by variations in the basal level of arousal. We tested this hypothesis by measuring the participants' behavioural state of vigilance before light exposure, through the Psychomotor Vigilance Task. Then we compared the effects of a blue-enriched vs. dim light at nighttime on the performance of the auditory SART, by controlling for individual differences in basal arousal. The results replicated the alerting effects of blue-enriched light, as indexed by lower values of both proximal temperature and distal-proximal gradient. The main finding was that lighting effects on SART performance were highly variable across individuals and depended on their prior state of vigilance. Specifically, participants with higher levels of basal vigilance before light exposure benefited most from blue-enriched lighting, responding faster in the SART. These results highlight the importance of considering basal vigilance to define the boundary conditions of light effects on cognitive performance. Our study adds to current research delineating the complex and reciprocal interactions between lighting effects, arousal, cognitive task demands and behavioural performance.

Exploring electrical resistance: a novel kinesthetic model helps to resolve some misconceptions

NASA Astrophysics Data System (ADS)

Cottle, Dan; Marshall, Rick

2016-09-01

A simple ‘hands on’ physical model is described which displays analogous behaviour to some aspects of the free electron theory of metals. Using it students can get a real feel for what is going on inside a metallic conductor. Ohms Law, the temperature dependence of resistivity, the dependence of resistance on geometry, how the conduction electrons respond to a potential difference and the concepts of mean free path and drift speed of the conduction electrons can all be explored. Some quantitative results obtained by using the model are compared with the predictions of Drude’s free electron theory of electrical conduction.

Effect of internal stress on the electro-optical behaviour of Al-doped ZnO transparent conductive thin films

NASA Astrophysics Data System (ADS)

Proost, J.; Henry, F.; Tuyaerts, R.; Michotte, S.

2016-08-01

In this work, we will report on scientific efforts aimed at unraveling the quantitative effect of elastic strain on the electro-optical behaviour of Al-doped zinc oxide (AZO). AZO thin films have been deposited by reactive magnetron sputtering to thicknesses from 300 to 500 nm, both on extra-clear glass substrates as well as on oxidised Si wafers. This resulted in both cases in polycrystalline, strongly textured (002) films. During deposition, the internal stress evolution in the growing film was monitored in-situ using high resolution curvature measurements. The resulting growth-induced elastic strain, which was found to depend heavily on the oxygen partial pressure, could further be modulated by appropriately choosing the deposition temperature. The latter also induces an additional extrinsic thermal stress component, whose sign depends on the substrate used. As such, a wide range of biaxial internal stresses could be achieved, from -600 MPa in compression up to 800 MPa in tension. The resulting charge carrier mobilities, obtained independently from room temperature Hall measurements, were found to range between 5 and 25 cm2/V s. Interestingly, the maximum mobility occurred at the zero-stress condition, and together with a charge carrier concentration of about 8 × 1020 cm-3, this gave rise to a resistivity of only 300 μΩ cm. From the stress-dependent optical transmission spectra in the range of 200-1000 nm, the pressure coefficient of the optical bandgap was estimated from the corresponding Tauc plots to be 31 meV/GPa, indicating a very high strain-sensitivity as well.

Specific heat in the pure gauge SU(2) theory

NASA Astrophysics Data System (ADS)

Mitrjushkin, V. K.; Zadorozhny, A. M.

1989-12-01

We calculated the specific heat Cv in pure gauge SU(2) theory. Calculations were done on the 3·8 3 lattice in the vicinity of the phase transition temperature. It is shown that the dependence of its electric ( CEv) and magnetic ( CMV) compone nts differ drastically near the phase transition point. Their behaviour is in full agreement with our previous calculations of the electric and magnetic components of the internal energy density and pressure.

The smell of change: warming affects species interactions mediated by chemical information.

PubMed

Sentis, Arnaud; Ramon-Portugal, Felipe; Brodeur, Jacques; Hemptinne, Jean-Louis

2015-10-01

Knowledge of how temperature influences an organism's physiology and behaviour is of paramount importance for understanding and predicting the impacts of climate change on species' interactions. While the behaviour of many organisms is driven by chemical information on which they rely on to detect resources, conspecifics, natural enemies and competitors, the effects of temperature on infochemical-mediated interactions remain largely unexplored. Here, we experimentally show that temperature strongly influences the emission of infochemicals by ladybeetle larvae, which, in turn, modifies the oviposition behaviour of conspecific females. Temperature also directly affects female perception of infochemicals and their oviposition behaviour. Our results suggest that temperature-mediated effects on chemical communication can influence flows across system boundaries (e.g. immigration and emigration) and thus alter the dynamics and stability of ecological networks. We therefore argue that investigating the effects of temperature on chemical communication is a crucial step towards a better understanding of the functioning of ecological communities facing rapid environmental changes. © 2015 John Wiley & Sons Ltd.

Frictional behaviour of exhumed subduction zone sediments from the Shimanto Belt, Japan, at in-situ P-T conditions and implications for megathrust seismogenesis

NASA Astrophysics Data System (ADS)

den Hartog, Sabine; Niemeijer, Andre; Saffer, Demian; Marone, Chris

2014-05-01

Seismogenesis on subduction zone megathrusts is generally thought to be limited to a region between the ~100-150°C isotherms, at ~5-15 km depth, and the ~350°C isotherm, typically at ~40 km depth. This zone is bounded at its up-dip and down-dip limits by aseismic zones. However, in recent years it has been discovered that very low frequency earthquakes (VLFE) and non-destructive Slow Slip Events (SSEs) or slow earthquakes nucleate in these presumed aseismic regions. Slip on megathrusts is likely to localize in the weak subducted sediments along the plate interface, which implies that the fault material is derived at least in part from these sediments. Therefore, understanding the depth distribution of seismicity and SSEs on megathrusts requires knowledge of the frictional behaviour of metapelites. We investigated such behaviour by performing shear experiments on natural megathrust fault gouges, derived from exhumed subduction zone sediments and faults exposed in the Shimanto Belt on Shikoku Island, Japan. These gouges correspond to peak paleo-temperatures of 105°C to 280°C, representing different stages in the diagenetic and metamorphic evolution of the subducted sediments, covering the shallow aseismic zone as well as the seismogenic zone. The composition of all gouges was dominated by illite/muscovite, with smaller amounts of quartz, feldspar and chlorite. We sheared these gouges at low displacement rates (0.1-100 micron/s) to address the nucleation of megathrust earthquakes and SSEs, using either a double-direct (biaxial) shear machine or a rotary shear machine. The double-direct shear experiments were performed at room temperature, 5% relative humidity and 50 MPa normal stress. The rotary shear experiments, in turn, were conducted at the sample-specific, approximate peak in-situ P-T conditions, i.e. the P-T conditions corresponding to the maximum burial depth of these samples. At room temperature, samples from different peak paleo-temperatures showed similar frictional behaviour, with near-neutral velocity dependence, i.e. stable or aseismic behaviour. When deformed at their approximate in-situ peak P-T conditions, on the other hand, the samples showed a progressive transition from strong velocity-strengthening (stable) behaviour at 105°C (notably at 10-100 micron/s), to velocity-weakening (unstable) behaviour at 280°C. The results at elevated P-T conditions match previous results on simulated illite-quartz analogue fault gouges and imply a broad transition in the slip stability of subduction megathrusts from stable (velocity-strengthening), to unstable (velocity-weakening) with increasing depth, in agreement with seismological observations.

Some like it hot: factors impacting thermal preferences of two Ponto-Caspian amphipods Dikerogammarus villosus (Sovinsky, 1894) and Dikerogammarus haemobaphes (Eichwald, 1841).

PubMed

Rachalewski, Michał; Kobak, Jarosław; Szczerkowska-Majchrzak, Eliza; Bącela-Spychalska, Karolina

2018-01-01

Temperature is a crucial factor determining biology and ecology of poikilothermic animals. It often constitutes an important barrier for invasive species originating from different climate zones but, on the other hand, may facilitate the invasion process of animals with wide thermal preferences and high resistance to extreme temperatures. In our experimental study, we investigated the thermal behaviour of two Ponto-Caspian amphipod crustaceans- Dikerogammarus villosus and Dikerogammarus haemobaphes . Both species are known to live under a wide range of thermal conditions which may promote their invasion. Moreover, both these amphipods are hosts for microsporidian parasites which co-evolved with them within the Ponto-Caspian region and spread in European waters. As the presence of a parasite may influence the thermal preferences of its host, we expected to observe behavioural changes in infected individuals of the studied amphipods leading to (1) behavioural fever (selecting a warmer habitat) or (2) anapyrexia (selecting a colder habitat). The experiment ( N  = 20) was carried out for 30 min in a 100 cm. 20 cm from boths sides were not avaliable for amphipods long thermal gradient (0-40 °C), using 30 randomly selected adult amphipod individuals of one species. At the end of each trial, we checked the position of amphipods along the gradient and determined their sex and infection status (uninfected or infected by one of microsporidium species). D. villosus was infected with Cucumispora dikerogammari whereas D. haemobaphes was a host for C. dikerogammari , Dictyocoela muelleri or D. berillonum . Thermal preferences of amphipods depended on their species and sex. Females of D. villosus preferred warmer microhabitats (often much above 30 °C) than conspecific males and females of D. haemobaphes , whereas no significant differences were found among males of both species and both sexes of D. haemobaphes . Moreover, infected males of D. villosus stayed in warmer water more often than uninfected males of this species, selecting temperatures higher than 30 °C, which may be explained either as a behavioural fever constituting a defence mechanism of a host against the infection, or as a parasite manipulation of the host behaviour increasing the parasite fitness. On the other hand, none of the parasite species affected the thermal preferences of D. haemobaphes , including also C. dikerogammari , changing the behaviour of D. villosus . Our research presents the complexity of the thermal behaviour of studied amphipods and the evidence that microsporidia may trigger a change in temperature preferendum of their host species and those observations may be the result of different host-parasite coevolution time which may vary for the two host species (Poulin, 2010).

Analysis of corrosion layers on protective coatings and high temperature materials in simulated service environments of modern power plants using SNMS, SIMS, SEM, TEM, RBS and X-ray diffraction studies.

PubMed

Nickel, H; Quadakkers, W J; Singheiser, L

2002-10-01

In three different examples, the effects of the oxidation behaviour as well as the microstructural stability of high temperature materials and protective coatings was determined by combining the results of kinetic studies with extensive analytical investigations using, among other techniques, SNMS, SIMS, SEM, TEM, Rutherford back scattering (RBS) as well as X-ray diffraction. 1). The effect of water vapour on the oxidation behaviour of 9% Cr steels in simulated combustion gases has been determined. The effects of O2 and H2O content on the oxidation behaviour of 9% Cr steel in the temperature range 600-800 degrees C showed that in dry oxygen a protective scale was formed with an oxidation rate controlled by diffusion in the protective scale. In the presence of water vapour, after an incubation period, the scales became non-protective as a result of a change in the oxidation limiting process. The destruction of the protective scale by water vapour does not only depend on H2O content but also on the H2O/O2-ratio. 2). The increase of component surface temperature in modern gas turbines leads to an enhanced oxidation attack of the blade coating. Improvements in corrosion resistance and longer lifetime thermal barrier coatings in gas turbines have been achieved by improvement of the high temperature properties of MCrAlY coatings by additions of minor alloying elements such as yttrium, silicon and titanium. 3). The use of oxide dispersion strengthened (ODS) alloys provides excellent creep resistance up to much higher temperatures than can be achieved with conventional wrought or cast alloys in combination with suitable high temperature oxidation/corrosion resistance. Investigation of the growth mechanisms of protective chromia and alumina scales were examined by a two-stage oxidation method with 18O tracer. The distribution of the oxygen isotopes in the oxide scale was determined by SIMS and SNMS. The results show the positive influence of a Y2O3 dispersion on the oxidation resistance of the ODS alloys and its effect on growth mechanisms.

Nonlinear dynamics under varying temperature conditions of the resonating beams of a differential resonant accelerometer

NASA Astrophysics Data System (ADS)

Zhang, Jing; Wang, Yagang; Zega, Valentina; Su, Yan; Corigliano, Alberto

2018-07-01

In this work the nonlinear dynamic behaviour under varying temperature conditions of the resonating beams of a differential resonant accelerometer is studied from the theoretical, numerical and experimental points of view. A complete analytical model based on the Hamilton’s principle is proposed to describe the nonlinear behaviour of the resonators under varying temperature conditions and numerical solutions are presented in comparison with experimental data. This provides a novel perspective to examine the relationship between temperature and nonlinearity, which helps predicting the dynamic behaviour of resonant devices and can guide their optimal design.

Activation energy and entropy for viscosity of wormlike micelle solutions.

PubMed

Chandler, H D

2013-11-01

The viscosities of two surfactant solutions which form wormlike micelles (WLMs) were studied over a range of temperatures and strain rates. WLM solutions appear to differ from many other shear thinning systems in that, as the shear rate increases, stress-shear rate curves tend to converge with temperature rather than diverge and this can sometimes lead to higher temperature curves crossing those at lower. Behaviour was analysed in terms of activation kinetics. It is suggested that two mechanisms are involved: Newtonian flow, following an Arrhenius law superimposed on a non-Newtonian flow described by a stress assisted kinetic law, this being a more general form of the Arrhenius law. Anomalous flow is introduced into the kinetic equation via a stress dependent activation entropy term. Copyright © 2013 Elsevier Inc. All rights reserved.

Alternative Splicing of Barley Clock Genes in Response to Low Temperature

PubMed Central

Calixto, Cristiane P. G.; Simpson, Craig G.; Waugh, Robbie; Brown, John W. S.

2016-01-01

Alternative splicing (AS) is a regulated mechanism that generates multiple transcripts from individual genes. It is widespread in eukaryotic genomes and provides an effective way to control gene expression. At low temperatures, AS regulates Arabidopsis clock genes through dynamic changes in the levels of productive mRNAs. We examined AS in barley clock genes to assess whether temperature-dependent AS responses also occur in a monocotyledonous crop species. We identify changes in AS of various barley core clock genes including the barley orthologues of Arabidopsis AtLHY and AtPRR7 which showed the most pronounced AS changes in response to low temperature. The AS events modulate the levels of functional and translatable mRNAs, and potentially protein levels, upon transition to cold. There is some conservation of AS events and/or splicing behaviour of clock genes between Arabidopsis and barley. In addition, novel temperature-dependent AS of the core clock gene HvPPD-H1 (a major determinant of photoperiod response and AtPRR7 orthologue) is conserved in monocots. HvPPD-H1 showed a rapid, temperature-sensitive isoform switch which resulted in changes in abundance of AS variants encoding different protein isoforms. This novel layer of low temperature control of clock gene expression, observed in two very different species, will help our understanding of plant adaptation to different environments and ultimately offer a new range of targets for plant improvement. PMID:27959947

Observation of relaxor ferroelectricity and multiferroic behaviour in nanoparticles of the ferromagnetic semiconductor La2NiMnO6

NASA Astrophysics Data System (ADS)

Masud, Md G.; Ghosh, Arijit; Sannigrahi, J.; Chaudhuri, B. K.

2012-07-01

We report a diffuse phase transition (extending over a finite temperature range of ˜50 K) in sol-gel derived nanoparticles (˜25 nm) of the ferromagnetic double perovskite La2NiMnO6. The macroscopic polarization (P-E hysteresis loop), validity of the Vogel-Fulcher relation and high dielectric permittivity (˜9 × 102) confirm relaxor ferroelectric phenomena in these magnetic nanoparticles. Compared to the corresponding bulk sample, appreciably large enhancement of the magnetocapacitive effect (MC ˜ 30%) is observed even under low magnetic field (0.5 T) around the broad relaxor dielectric peak temperature (˜220 K), which is close to the ferromagnetic transition temperature (θf ˜ 196 K). All of these features establish the multiferroic character of the La2NiMnO6 nanoparticles. The inhomogeneities arising from chemical and valence mixing in the present La2NiMnO6 nanoparticles and the inter-site, Ni/Mn-site disorder along with surface disorder of the individual nanoparticles resulting in local polar regions are attributed to the observed dielectric behaviour of the nanoparticles. The wave vector dependent spin-pair correlation is considered to be the plausible cause of the colossal magnetocapacitive response near the transition temperature. High permittivity and large magnetocapacitive properties make these ferromagnetic La2NiMnO6 nanoparticles technologically important.

Tensile stress-strain and work hardening behaviour of P9 steel for wrapper application in sodium cooled fast reactors

NASA Astrophysics Data System (ADS)

Christopher, J.; Choudhary, B. K.; Isaac Samuel, E.; Mathew, M. D.; Jayakumar, T.

2012-01-01

Tensile flow behaviour of P9 steel with different silicon content has been examined in the framework of Hollomon, Ludwik, Swift, Ludwigson and Voce relationships for a wide temperature range (300-873 K) at a strain rate of 1.3 × 10 -3 s -1. Ludwigson equation described true stress ( σ)-true plastic strain ( ɛ) data most accurately in the range 300-723 K. At high temperatures (773-873 K), Ludwigson equation reduces to Hollomon equation. The variations of instantaneous work hardening rate ( θ = dσ/ dɛ) and θσ with stress indicated two-stage work hardening behaviour. True stress-true plastic strain, flow parameters, θ vs. σ and θσ vs. σ with respect to temperature exhibited three distinct temperature regimes and displayed anomalous behaviour due to dynamic strain ageing at intermediate temperatures. Rapid decrease in flow stress and flow parameters, and rapid shift in θ- σ and θσ- σ towards lower stresses with increase in temperature indicated dominance of dynamic recovery at high temperatures.

Thermo-mechanical modelling of salt caverns due to fluctuating loading conditions.

NASA Astrophysics Data System (ADS)

Böttcher, N.

2015-12-01

This work summarizes the development and application of a numerical model for the thermo-mechanical behaviour of salt caverns during cyclic gas storage. Artificial salt caverns are used for short term energy storage, such as power-to-gas or compressed air energy storage. Those applications are characterized by highly fluctuating operation pressures due to the unsteady power levels of power plants based on renewable energy. Compression and expansion of the storage gases during loading and unloading stages lead to rapidly changing temperatures in the host rock of the caverns. This affects the material behaviour of the host rock within a zone that extends several meters into the rock mass adjacent to the cavern wall, and induces thermo-mechanical stresses and alters the creep response.The proposed model features the thermodynamic behaviour of the storage medium, conductive heat transport in the host rock, as well as temperature dependent material properties of rock salt using different thermo-viscoplastic material models. The utilized constitutive models are well known and state-of-the-art in various salt mechanics applications. The model has been implemented into the open-source software platform OpenGeoSys. Thermal and mechanical processes are solved using a finite element approach, coupled via a staggered coupling scheme. The simulation results allow the conclusion, that the cavern convergence rate (and thus the efficiency of the cavern) is highly influenced by the loading cycle frequency and the resulting gas temperatures. The model therefore allows to analyse the influence of operation modes on the cavern host rock or on neighbouring facilities.

Successful despite poor flight performance: range expansion is associated with enhanced exploratory behaviour and fast development.

PubMed

Reim, Elisabeth; Blesinger, Simone; Förster, Lisa; Fischer, Klaus

2018-05-29

Anthropogenic interference forces species to respond to changing environmental conditions. One possible response is dispersal and concomitant range shifts, allowing individuals to escape unfavourable conditions or to track the shifting climate niche. Range expansions depend on both dispersal capacity and the ability to establish populations beyond the former range. We here compare well-established core populations with recently established edge populations in the currently northward expanding butterfly Lycaena tityrus. Edge populations were characterized by shorter development times and smaller size, a higher sensitivity to high temperature and an enhanced exploratory behaviour. The differences between core and edge populations found suggest adaptation to local climates and an enhanced dispersal ability in edge populations. In particular, enhanced exploratory behaviour may be advantageous in all steps of the dispersal process and may have facilitated the current range expansion. This study describes differences associated with a current range expansion, knowledge which might be useful for a better understanding of species responses to environmental change. We further report on variation between males and females in morphology and flight behaviour, with males showing a longer flight endurance and more pronounced exploratory behaviour than females. © 2018 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2018 European Society For Evolutionary Biology.

Preliminary investigation of thermal behaviour of PCM based latent heat thermal energy storage

NASA Astrophysics Data System (ADS)

Pop, Octavian G.; Fechete Tutunaru, Lucian; Bode, Florin; Balan, Mugur C.

2018-02-01

Solid-liquid phase change is used to accumulate and release cold in latent heat thermal energy storage (LHTES) in order to reduce energy consumption of air cooling system in buildings. The storing capacity of the LHTES depends greatly on the exterior air temperatures during the summer nights. One approach in intensifying heat transfer is by increasing the air's velocity. A LHTES was designed to be integrated in the air cooling system of a building located in Bucharest, during the month of July. This study presents a numerical investigation concerning the impact of air inlet temperatures and air velocity on the formation of solid PCM, on the cold storing capacity and energy consumption of the LHTES. The peak amount of accumulated cold is reached at different air velocities depending on air inlet temperature. For inlet temperatures of 14°C and 15°C, an increase of air velocity above 50% will not lead to higher amounts of cold being stored. For Bucharest during the hottest night of the year, a 100 % increase in air velocity will result in 5.02% more cold being stored, at an increase in electrical energy consumption of 25.30%, when compared to the reference values.

Effect of trap states and microstructure on charge carrier conduction mechanism through semicrystalline poly(vinyl alcohol) granular film

NASA Astrophysics Data System (ADS)

Das, A. K.; Bhowmik, R. N.; Meikap, A. K.

2018-05-01

We report a comprehensive study on hysteresis behaviour of current-voltage characteristic and impedance spectroscopy of granular semicrystalline poly(vinyl alcohol) (PVA) film. The charge carrier conduction mechanism and charge traps of granular PVA film by measuring and analyzing the temperature dependent current-voltage characteristic indicate a bi-stable electronic state in the film. A sharp transformation of charge carrier conduction mechanism from Poole-Frenkel emission to space charge limited current mechanism has been observed. An anomalous oscillatory behaviour of current has been observed due to electric pulse effect on the molecular chain of the polymer. Effect of microstructure on charge transport mechanism has been investigated from impedance spectroscopy analysis. An equivalent circuit model has been proposed to explain the result.

Neutral and charged gallium clusters: structures, physical properties and implications for the melting features

NASA Astrophysics Data System (ADS)

Núñez, Sara; López, José M.; Aguado, Andrés

2012-09-01

We report the putative Global Minimum (GM) structures and electronic properties of GaN+, GaN and GaN- clusters with N = 13-37 atoms, obtained from first-principles density functional theory structural optimizations. The calculations include spin polarization and employ an exchange-correlation functional which accounts for van der Waals dispersion interactions (vdW-DFT). We find a wide diversity of structural motifs within the located GM, including decahedral, polyicosahedral, polytetrahedral and layered structures. The GM structures are also extremely sensitive to the number of electrons in the cluster, so that the structures of neutral and charged clusters differ for most sizes. The main magic numbers (clusters with an enhanced stability) are identified and interpreted in terms of electronic and geometric shell closings. The theoretical results are consistent with experimental abundance mass spectra of GaN+ and with photoelectron spectra of GaN-. The size dependence of the latent heats of melting, the shape of the heat capacity peaks, and the temperature dependence of the collision cross-sections, all measured for GaN+ clusters, are properly interpreted in terms of the calculated cohesive energies, spectra of configurational excitations, and cluster shapes, respectively. The transition from ``non-melter'' to ``magic-melter'' behaviour, experimentally observed between Ga30+ and Ga31+, is traced back to a strong geometry change. Finally, the higher-than-bulk melting temperatures of gallium clusters are correlated with a more typically metallic behaviour of the clusters as compared to the bulk, contrary to previous theoretical claims.We report the putative Global Minimum (GM) structures and electronic properties of GaN+, GaN and GaN- clusters with N = 13-37 atoms, obtained from first-principles density functional theory structural optimizations. The calculations include spin polarization and employ an exchange-correlation functional which accounts for van der Waals dispersion interactions (vdW-DFT). We find a wide diversity of structural motifs within the located GM, including decahedral, polyicosahedral, polytetrahedral and layered structures. The GM structures are also extremely sensitive to the number of electrons in the cluster, so that the structures of neutral and charged clusters differ for most sizes. The main magic numbers (clusters with an enhanced stability) are identified and interpreted in terms of electronic and geometric shell closings. The theoretical results are consistent with experimental abundance mass spectra of GaN+ and with photoelectron spectra of GaN-. The size dependence of the latent heats of melting, the shape of the heat capacity peaks, and the temperature dependence of the collision cross-sections, all measured for GaN+ clusters, are properly interpreted in terms of the calculated cohesive energies, spectra of configurational excitations, and cluster shapes, respectively. The transition from ``non-melter'' to ``magic-melter'' behaviour, experimentally observed between Ga30+ and Ga31+, is traced back to a strong geometry change. Finally, the higher-than-bulk melting temperatures of gallium clusters are correlated with a more typically metallic behaviour of the clusters as compared to the bulk, contrary to previous theoretical claims. Electronic supplementary information (ESI) available: Atomic coordinates (in xyz format and Å units) and point group symmetries for the global minimum structures reported in this paper. See DOI: 10.1039/c2nr31222k

Seasonal variations in behaviour of thermoregulation in juveniles and adults Liolaemus lutzae (Squamata, Liolaemidae) in a remnant of Brazilian restinga.

PubMed

Maia-Carneiro, Thiago; Rocha, Carlos Frederico Duarte

2013-11-01

Adaptations of lizards inhabiting hot arid environments should include mechanisms of behavioural thermoregulation. In contrast, in environments with lower temperatures lizards tend to behave as thermoconformers. Herein we aim to infer thermoregulatory behaviours exhibited by Liolaemus lutzae (a lizard species endemic to restingas in the coast of the state of Rio de Janeiro, Brazil) in two different seasonal thermal environments. In the dry season, the body temperatures (Tb) of the lizards were higher than air temperature (Ta) and similar to substrate temperature (Ts), suggesting thermoconformer thermoregulatory behaviour using Ts. During the rainy season, the higher percentage of negative values of ΔTs (=Tb-Ts) and ΔTa (=Tb-Ta) and the tendency for lower Tb compared to Ts suggest a more active behavioural thermoregulation in that season. The ΔTs was higher for juveniles in the rainy season, suggesting that youngest lizards tended to thermoregulate more actively regarding to Ts than adults. L. lutzae probably survives under high Ts due to the behaviour of the individuals sheltering inside burrows or under detritus and burying themselves into the sand. This behavioural flexibility may potentially reduce variations in Tb of active lizards in changing thermal environments both during the daily cycle and between seasons. Copyright © 2013 Elsevier B.V. All rights reserved.

Anomalous low-temperature Coulomb drag in graphene-GaAs heterostructures.

PubMed

Gamucci, A; Spirito, D; Carrega, M; Karmakar, B; Lombardo, A; Bruna, M; Pfeiffer, L N; West, K W; Ferrari, A C; Polini, M; Pellegrini, V

2014-12-19

Vertical heterostructures combining different layered materials offer novel opportunities for applications and fundamental studies. Here we report a new class of heterostructures comprising a single-layer (or bilayer) graphene in close proximity to a quantum well created in GaAs and supporting a high-mobility two-dimensional electron gas. In our devices, graphene is naturally hole-doped, thereby allowing for the investigation of electron-hole interactions. We focus on the Coulomb drag transport measurements, which are sensitive to many-body effects, and find that the Coulomb drag resistivity significantly increases for temperatures <5-10 K. The low-temperature data follow a logarithmic law, therefore displaying a notable departure from the ordinary quadratic temperature dependence expected in a weakly correlated Fermi-liquid. This anomalous behaviour is consistent with the onset of strong interlayer correlations. Our heterostructures represent a new platform for the creation of coherent circuits and topologically protected quantum bits.

Dependence of viscosity of suspensions of ceramic nanopowders in ethyl alcohol on concentration and temperature

PubMed Central

2012-01-01

This work presents results of measurements of viscosity of suspensions including yttrium oxide (Y2O3), yttrium aluminum garnet (Y3Al5O12) and magnesium aluminum spinel (MgAl2O4) nanopowders in ethanol. Nanoparticles used in our research were either commercially available (Baikowski) or nanopowders newly developed in the Institute of Ceramics and Building Materials in Warsaw, Poland. The study was conducted in a wide range of shear rates (0.01 to 2,000 s−1) and temperature interval from -15°C to 20°C. A Haake Mars 2 rheometer from Thermo Fisher, Germany, was used in the Biophysics Laboratory at Rzeszów University of Technology. Most of the samples show a non-Newtonian behaviour. It was confirmed with a Rheo-NMR system from Bruker that 10% by weight of Y2O3 suspension is a non-Newtonian fluid. In this work, we also report an unexpected behaviour of the viscosity of some samples (Y2O3 and Y3Al5O12) due to sedimentation effect. PMID:22824064

Pronounced non-Arrhenius behaviour of hydrogen-abstractions from toluene and derivatives by phthalimide-N-oxyl radicals: a theoretical study.

PubMed

Hermans, Ive; Jacobs, Pierre; Peeters, Jozef

2008-02-28

Abstraction of hydrogen atoms by pthalimide-N-oxyl radicals is an important step in the N-hydroxyphthalimide catalyzed autoxidation of hydrocarbons. In this contribution, the temperature dependency of this reaction is evaluated by a detailed transition state theory based kinetic analysis for the case of toluene. Tunneling was found to play a very important role, enhancing the rate constant by a factor of 20 at room temperature. As a result, tunneling, in combination with the existence of two distinct rotamers of the transition state, causes a pronounced temperature dependency of the pre-exponential frequency factor, and, as a consequence, marked curvature of the Arrhenius plot. This explains why earlier experimental studies over a limited temperature range around 300 K found formal Arrhenius activation energies and pre-factors that are 4 kcal mol(-1) and three orders of magnitude smaller than the actual energy barrier and the corresponding frequency factor, respectively. Also as a consequence of tunneling, substitution of a deuterium atom for a hydrogen atom causes a large decrease in the rate constant, in agreement with the measured kinetic isotope effects. The present theoretical analysis, complementary to the experimental rate coefficient data, allows for a reliable prediction of the rate coefficient at higher temperatures, relevant for actual autoxidation processes.

Behavioural response of juvenile Chinook salmon Oncorhynchus tshawytscha during a sudden temperature increase and implications for survival

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bellgraph, Brian J.; McMichael, Geoffrey A.; Mueller, Robert P.

2010-01-01

The behaviours of juvenile Chinook salmon Oncorhynchus tshawytscha were evaluated during a temperature increase from 8.8 to 23.2°C, which was designed to simulate unique thermal conditions present in a hydroelectric reservoir. The percent of fish with an active swimming behaviour increased from 26 to 93 % and mean opercular beat rates increased from 76 to 159 beats per minute between basal and maximum temperatures. Fish equilibrium did not change significantly throughout the experiment and relatively little mortality (12 %) occurred. Thermal stress is likely incurred by juvenile salmon experiencing a temperature change of this magnitude; however, stress induced in thismore » study was primarily sublethal. Behavioural changes accompanying thermal stress (e.g., erratic swimming) may increase predation potential in the wild despite being sublethal during laboratory experiments.« less

Deformation of phospholipid vesicles in an optical stretcher.

PubMed

Delabre, Ulysse; Feld, Kasper; Crespo, Eleonore; Whyte, Graeme; Sykes, Cecile; Seifert, Udo; Guck, Jochen

2015-08-14

Phospholipid vesicles are common model systems for cell membranes. Important aspects of the membrane function relate to its mechanical properties. Here we have investigated the deformation behaviour of phospholipid vesicles in a dual-beam laser trap, also called an optical stretcher. This study explicitly makes use of the inherent heating present in such traps to investigate the dependence of vesicle deformation on temperature. By using lasers with different wavelengths, optically induced mechanical stresses and temperature increase can be tuned fairly independently with a single setup. The phase transition temperature of vesicles can be clearly identified by an increase in deformation. In the case of no heating effects, a minimal model for drop deformation in an optical stretcher and a more specific model for vesicle deformation that takes explicitly into account the angular dependence of the optical stress are presented to account for the experimental results. Elastic constants are extracted from the fitting procedures, which agree with literature data. This study demonstrates the utility of optical stretching, which is easily combined with microfluidic delivery, for the future serial, high-throughput study of the mechanical and thermodynamic properties of phospholipid vesicles.

Assessing the Nature of the Distribution of Localised States in Bulk GaAsBi.

PubMed

Wilson, Tom; Hylton, Nicholas P; Harada, Yukihiro; Pearce, Phoebe; Alonso-Álvarez, Diego; Mellor, Alex; Richards, Robert D; David, John P R; Ekins-Daukes, Nicholas J

2018-04-24

A comprehensive assessment of the nature of the distribution of sub band-gap energy states in bulk GaAsBi is presented using power and temperature dependent photoluminescence spectroscopy. The observation of a characteristic red-blue-red shift in the peak luminescence energy indicates the presence of short-range alloy disorder in the material. A decrease in the carrier localisation energy demonstrates the strong excitation power dependence of localised state behaviour and is attributed to the filling of energy states furthest from the valence band edge. Analysis of the photoluminescence lineshape at low temperature presents strong evidence for a Gaussian distribution of localised states that extends from the valence band edge. Furthermore, a rate model is employed to understand the non-uniform thermal quenching of the photoluminescence and indicates the presence of two Gaussian-like distributions making up the density of localised states. These components are attributed to the presence of microscopic fluctuations in Bi content, due to short-range alloy disorder across the GaAsBi layer, and the formation of Bi related point defects, resulting from low temperature growth.

Mechanism of nucleation and growth of catalyst-free self-organized GaN columns by MOVPE

NASA Astrophysics Data System (ADS)

Wang, Xue; Li, Shunfeng; Fündling, Sönke; Wehmann, Hergo-H.; Strassburg, Martin; Lugauer, Hans-Jürgen; Steegmüller, Ulrich; Waag, Andreas

2013-05-01

The growth mechanism of catalyst-free self-organized GaN nuclei and three-dimensional columns on sapphire by metal organic vapour phase epitaxy (MOVPE) is investigated. Temperature- and time-dependent growth is performed. The growth behaviour can be characterized by two different kinetic regimes: mass-transport-limited growth and thermodynamically limited growth. The sum of activation energies for thermodynamic barrier of nucleation and for surface diffusion/mass-transport limitation, i.e. Whet +Ed, is 0.57 eV in the ‘low’-temperature region and 2.43 eV in the ‘high’-temperature region. GaN columns grown under the same conditions have very comparable height, which is not dependent on their diameter or the distance to other columns. Therefore, the growth rate is presumably limited by the incorporation rate on the top surface of columns. The height and diameter at the top of the GaN columns increase linearly with time and no height limit is observed. The GaN columns can reach more than 40 µm in height. Moreover, the investigated GaN columns are Ga-polar.

Uniaxial creep property and viscoelastic-plastic modelling of ethylene tetrafluoroethylene (ETFE) foil

NASA Astrophysics Data System (ADS)

Li, Yintang; Wu, Minger

2015-02-01

Ethylene tetrafluoroethylene (ETFE) foil has been widely used in spatial structures for its light weight and high transparency. This paper studies short- and long-term creep properties of ETFE foil. Two series of short-term creep and recovery tests were performed, in which residual strain was observed. A long-term creep test of ETFE foil was also conducted and lasted about 400 days. A viscoelastic-plastic model was then established to describe short-term creep and recovery behaviour of ETFE foil. This model contains a traditional generalised Kelvin part and an added steady-flow component to represent viscoelastic and viscoplastic behaviour, respectively. The model can fit tests' data well at three stresses and six temperatures. Additionally, time-temperature superposition was adopted to simulate long-term creep behaviour of ETFE foil. Horizontal shifting factors were determined by W.L.F. equation in which transition temperature was simulated by shifting factors. Using this equation, long-term creep behaviours at three temperatures were predicted. The results of the long-term creep test showed that a short-term creep test at identical temperatures was insufficient to predict additional creep behaviour, and the long-term creep test verified horizontal shifting factors which were derived from the time-temperature superposition.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blackstone, R.; Graham, L.W.

The dimensional changes observed in a range of graphitic materials following irradiation at 600, 900, and 1200 deg C are reported. The results are discussed in the light of current models for irradiation damage in graphite and it is concluded that for conventional materials the dimensional behaviour can be related to the material properties. Further confirmation of the extreme dependence of the dimensional changes on the crystallite size has been obtained. The way in which the rate of dimensional change varies with temperature is compatible with this effect being caused by vacancy loss at crystallite boundaries. For a given crystallitemore » size there appears to be a breakaway temperature above which the rate of dimensional change accelerates rapidly. (auth)« less

Microwave dielectric properties of inorganic fullerene-like tungsten disulfide nanoparticles

NASA Astrophysics Data System (ADS)

Chang, Hong; Dimitrakis, Georgios; Xu, Fang; Yi, Chenbo; Kingman, Samuel; Zhu, Yanqiu

2013-01-01

The dielectric response of inorganic fullerene-like (IF) tungsten disulfide (WS2) nanoparticles prepared by a sulfidization reaction of WO3 nanoparticles has been investigated, against commercial platelet 2H-WS2 particles, using a cavity perturbation technique at microwave frequencies at temperatures ranging from 20 to 750 °C. The IF-WS2 nanoparticles showed both temperature and frequency dependent dielectric properties. The different dielectric behaviour between the IF-WS2 and 2H-WS2 can be attributed to the different conductivity and structure peculiar to the materials. The microstructure and thermal stability of the IF-WS2 and 2H-WS2 were thoroughly examined, to correlate with the resulting dielectric responses.

Real-time dielectric studies of polymerizing systems

NASA Astrophysics Data System (ADS)

Williams, G.; Smith, I. K.; Holmes, P. A.; Varma, S.

1999-03-01

The use of real-time dielectric relaxation spectroscopy (DRS) for monitoring changes in molecular mobility during reaction for thermosetting systems is described together with phenomenological and molecular theories of the time-dependent relaxation functions that are involved. Reduced molecular mobility normally leads to the diffusion control of a reaction and ultimately to glass formation at the polymerization temperature 0953-8984/11/10A/004/img7. We present new DRS results for a boroxine/epoxide system that show glass formation below a `floor temperature' 0953-8984/11/10A/004/img8 and very different behaviour above 0953-8984/11/10A/004/img8, when the dielectric properties become independent of time and an elastomer is formed.

Hydrodynamic behaviour and comparison of technologies for the removal of excess biomass in gas-phase biofilters.

PubMed

Mendoza, J A; Prado, O J; Veiga, M C; Kennes, C

2004-01-01

The hydrodynamic behaviour of a biofilter fed toluene and packed with an inert carrier was evaluated on start-up and after long-term operation, using both methane and styrene as tracers in Residence Time Distribution experiments. Results indicated some deviation from ideal plug flow behaviour after 2-year operation. It was also observed that the retention time of VOCs gradually increased with time and was significantly longer than the average residence time of the bulk gas phase. Non-ideal hydrodynamic behaviour in packed beds may be due to excess biomass accumulation and affects both reactor modeling and performance. Therefore, several methods were studied for the removal of biomass after long-term biofilter operation: filling with water and draining, backwashing, and air sparging. Several flow rates and temperatures (20-60 degrees C) were applied using either water or different chemicals (NaOH, NaOCl, HTAB) in aqueous solution. Usually, higher flow rates and higher temperatures allowed the removal of more biomass, but the efficiency of biomass removal was highly dependent on the pressure drop reached before the treatment. The filling/draining method was the least efficient for biomass removal, although the treatment did basically not generate any biological inhibition. The efficiency of backwashing and air sparging was relatively similar and was more effective when adding chemicals. However, treatments with chemicals resulted in a significant decrease of the biofilter's performance immediately after applying the treatment, needing periods of several days to recover the original performance. The effect of manually mixing the packing material was also evaluated in duplicate experiments. Quite large amounts of biomass were removed but disruption of the filter bed was observed. Batch assays were performed simultaneously in order to support and quantify the observed inhibitory effects of the different chemicals and temperatures used during the treatments.

Unconventional high-Tc superconductivity in fullerides.

PubMed

Takabayashi, Yasuhiro; Prassides, Kosmas

2016-09-13

A3C60 molecular superconductors share a common electronic phase diagram with unconventional high-temperature superconductors such as the cuprates: superconductivity emerges from an antiferromagnetic strongly correlated Mott-insulating state upon tuning a parameter such as pressure (bandwidth control) accompanied by a dome-shaped dependence of the critical temperature, Tc However, unlike atom-based superconductors, the parent state from which superconductivity emerges solely by changing an electronic parameter-the overlap between the outer wave functions of the constituent molecules-is controlled by the C60 (3-) molecular electronic structure via the on-molecule Jahn-Teller effect influence of molecular geometry and spin state. Destruction of the parent Mott-Jahn-Teller state through chemical or physical pressurization yields an unconventional Jahn-Teller metal, where quasi-localized and itinerant electron behaviours coexist. Localized features gradually disappear with lattice contraction and conventional Fermi liquid behaviour is recovered. The nature of the underlying (correlated versus weak-coupling Bardeen-Cooper-Schrieffer theory) s-wave superconducting states mirrors the unconventional/conventional metal dichotomy: the highest superconducting critical temperature occurs at the crossover between Jahn-Teller and Fermi liquid metal when the Jahn-Teller distortion melts.This article is part of the themed issue 'Fullerenes: past, present and future, celebrating the 30th anniversary of Buckminster Fullerene'. © 2016 The Author(s).

Unconventional high-Tc superconductivity in fullerides

PubMed Central

Takabayashi, Yasuhiro; Prassides, Kosmas

2016-01-01

A3C60 molecular superconductors share a common electronic phase diagram with unconventional high-temperature superconductors such as the cuprates: superconductivity emerges from an antiferromagnetic strongly correlated Mott-insulating state upon tuning a parameter such as pressure (bandwidth control) accompanied by a dome-shaped dependence of the critical temperature, Tc. However, unlike atom-based superconductors, the parent state from which superconductivity emerges solely by changing an electronic parameter—the overlap between the outer wave functions of the constituent molecules—is controlled by the C603− molecular electronic structure via the on-molecule Jahn–Teller effect influence of molecular geometry and spin state. Destruction of the parent Mott–Jahn–Teller state through chemical or physical pressurization yields an unconventional Jahn–Teller metal, where quasi-localized and itinerant electron behaviours coexist. Localized features gradually disappear with lattice contraction and conventional Fermi liquid behaviour is recovered. The nature of the underlying (correlated versus weak-coupling Bardeen–Cooper–Schrieffer theory) s-wave superconducting states mirrors the unconventional/conventional metal dichotomy: the highest superconducting critical temperature occurs at the crossover between Jahn–Teller and Fermi liquid metal when the Jahn–Teller distortion melts. This article is part of the themed issue ‘Fullerenes: past, present and future, celebrating the 30th anniversary of Buckminster Fullerene’. PMID:27501971

Behavioural response to combined insecticide and temperature stress in natural populations of Drosophila melanogaster.

PubMed

Fournier-Level, A; Neumann-Mondlak, A; Good, R T; Green, L M; Schmidt, J M; Robin, C

2016-05-01

Insecticide resistance evolves extremely rapidly, providing an illuminating model for the study of adaptation. With climate change reshaping species distribution, pest and disease vector control needs rethinking to include the effects of environmental variation and insect stress physiology. Here, we assessed how both long-term adaptation of populations to temperature and immediate temperature variation affect the genetic architecture of DDT insecticide response in Drosophila melanogaster. Mortality assays and behavioural assays based on continuous activity monitoring were used to assess the interaction between DDT and temperature on three field-derived populations from climate extremes (Raleigh for warm temperate, Tasmania for cold oceanic and Queensland for hot tropical). The Raleigh population showed the highest mortality to DDT, whereas the Queensland population, epicentre for derived alleles of the resistance gene Cyp6g1, showed the lowest. Interaction between insecticide and temperature strongly affected mortality, particularly for the Tasmanian population. Activity profiles analysed using self-organizing maps show that the insecticide promoted an early response, whereas elevated temperature promoted a later response. These distinctive early or later activity phases revealed similar responses to temperature and DDT dose alone but with more or less genetic variance depending on the population. This change in genetic variance among populations suggests that selection particularly depleted genetic variance for DDT response in the Queensland population. Finally, despite similar (co)variation between traits in benign conditions, the genetic responses across population differed under stressful conditions. This showed how stress-responsive genetic variation only reveals itself in specific conditions and thereby escapes potential trade-offs in benign environments. © 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.

The influence of dielectric relaxation on intramolecular electron transfer

NASA Astrophysics Data System (ADS)

Heitele, H.; Michel-Beyerle, M. E.; Finckh, P.

1987-07-01

An unusually strong temperature dependence on the intramolecular electron-transfer rate has been observed for bridged donor-acceptor compounds in propylene glycol solution. In the frame of recent electron-transfer theories this effect reflects the influence of dielectric relaxation dynamics on electron transfer. With increasing dielectric relaxation time a smooth transition from non-adiabatic to solvent-controlled adiabatic behaviour is observed. The electron transfer rate in the solvent-controlled adiabatic limit is dominated by an inhomogeneous distribution of relaxation times.

Modeling Plasticity of Ni3Al-Based L12 Intermetallic Single Crystals-I. Anomalous Temperature Dependence of the Flow Behavior (Preprint)

DTIC Science & Technology

2006-07-01

dislocation-loop expansion . The new model was used to simulate the thermally reversible flow behaviour for C-S type two-step deformation, and the results are...implemented into the finite element software ABAQUS through a User MATerial subroutine (UMAT). A tangent modulus method [48] was used for the time...locking under a dislocation loop- expansion configuration. This approach was motivated by modern understanding of dislocation mechanisms for Ni3Al

High temperature Oxidation of ODS alloy with zirconia dispersions synthesized using Arc Plasma Sintering

NASA Astrophysics Data System (ADS)

Bandriyana; Sujatno, A.; Salam, R.; Sugeng, B.; Dimyati, A.

2017-02-01

Microstructure formation and oxidation behaviour of the Oxide Dispersion Strengthened (ODS) steels for application as structure material in Nuclear Power Plant was investigated. A mixture composed of Fe and 12 wt. % Cr powder with addition of 0.5 and 1 wt.% ZrO2 particles was milled and isostatic pressed to form a sample coin. The coin was then consolidated in the Arc Plasma Sintering (APS) for 4 minutes. The samples were subjected to the high temperature oxidation test in the Magnetic Suspension Balance (MSB). The oxidation test was carried out at 700°C for 6 hours to evaluate the oxide growth in the early stage of it formation by extraction the mass gain curve. The Scanning Electron Microscope (SEM) imaging and X-ray Diffraction Spectroscopy (EDX) elemental mapping were performed to study the microstructure change and compositional distribution. SEM and EDX observation revealed the time dependent development of the Fe-Cr-phases during consolidation. The oxidation rate behaviour of the samples followed the parabolic rate characteristic for inward oxidation process driven by oxygen inward diffusion through the oxide scale with the maximum weight gain around of 60 g/m2. The oxidation resistance was strongly affected by the formation of the oxide protective layer on the surface. In so far, addition of zirconia particles has played no significant role to the oxidation behaviour.

Atomistic modelling of magnetic nano-granular thin films

NASA Astrophysics Data System (ADS)

Agudelo-Giraldo, J. D.; Arbeláez-Echeverry, O. D.; Restrepo-Parra, E.

2018-03-01

In this work, a complete model for studying the magnetic behaviour of polycrystalline thin films at nanoscale was processed. This model includes terms as exchange interaction, dipolar interaction and various types of anisotropies. For the first term, exchange interaction dependence of the distance n was used with purpose of quantify the interaction, mainly in grain boundaries. The third term includes crystalline, surface and boundary anisotropies. Special attention was paid to the disorder vector that determines the loss of cubic symmetry in the crystalline structure. For the case of the dipolar interaction, a similar implementation of the fast multiple method (FMM) was performed. Using these tools, modelling and simulations were developed varying the number of grains, and the results obtained presented a great dependence of the magnetic properties on this parameter. Comparisons between critical temperature and magnetization of saturation depending on the number of grains were performed for samples with and without factors as the surface and boundary anisotropies, and the dipolar interaction. It was observed that the inclusion of these parameters produced a decrease in the critical temperature and the magnetization of saturation; furthermore, in both cases, including and not including the disorder parameters, not only the critical temperature, but also the magnetization of saturation exhibited a range of values that also depend on the number of grains. This presence of a critical interval is due to each grain can transit toward the ferromagnetic state at different values of critical temperature. The processes of Zero field cooling (ZFC), Field cooling (FCC) and field cooling in warming mode (FCW) were necessary for understanding the mono-domain regime around of transition temperature, due to the high probabilities of a Super-paramagnetic (SPM) state.

Low-temperature transport properties of TaxN thin films (0.72 <= x <= 0.83)

NASA Astrophysics Data System (ADS)

Očko, Miroslav; Žonja, Sanja; Nelson, G. L.; Freericks, J. K.; Yu, Lei; Newman, N.

2010-11-01

We report on low-temperature (4-320 K) transport properties of TaxN thin films deposited on an amorphous SiO2 substrate. In this work, TaxN thin films were restricted to a narrow range of x: 0.72 <= x <= 0.83 yet show considerable and nonmonotonic variation of their transport properties with Ta concentration. This behaviour is consistent with a local minimum in the density of electronic states at the Fermi level, as calculated for the rock salt intermetallic Ta4N5, and a rigid band model for describing the transport. The temperature dependence of the resistivity is best fit to the unusual form exp(-T/T0). Interestingly enough, the fit parameter T0 correlates well with the temperature of the maximum of the corresponding thermopower. Both of these characteristics, the fit and the correlation with the thermopower, are consistent with the Jonson-Mahan many-body formalism for charge and thermal transport when one has a nontrivial temperature dependence of the chemical potential. At the lowest temperatures measured, we have also found that the resistivity and thermopower show signatures of electron-electron interactions. We discuss also our results in the light of some theories usually used for describing transport of thin films and to other experimental investigations that have been performed on TaxN.

Orthotropic creep in polyethylene glycol impregnated archaeological oak from the Vasa ship - Results of creep experiments in a museum-like climate

NASA Astrophysics Data System (ADS)

Vorobyev, Alexey; van Dijk, Nico P.; Kristofer Gamstedt, E.

2018-02-01

Creep in archaeological oak samples and planks from the Vasa ship impregnated with polyethylene glycol (PEG) has been studied in museum-like climate. Creep studies of duration up to three years have been performed in nearly constant relative humidity and temperature of the controlled museum climate. Cubic samples were subjected to compressive creep tests in all orthotropic directions. Additionally, the creep behaviour of planks with and without PEG and of recent oak was tested in four-point bending. The experimental results have been summarised and also compared with reference results from recent oak wood. The effect of variable ambient conditions on creep and mass changes is discussed. The experimental results of creep in the longitudinal direction showed deformations even for the low stresses. There is relatively much more scatter in creep behaviour, and not all samples showed linear viscoelastic response. The creep in radial and tangential directions of the cubes and the plank samples showed a strong dependency on the ambient conditions. Some samples showed expansion for decreasing moisture content, possibly caused by the thermal expansion of the PEG component. For the planks, increasing creep deformation was observed induced by changing ambient conditions. Such behaviour may be related to e.g. oscillations in ambient conditions and presence of PEG in the wood cell wall and cell lumen. The behaviour of PEG archaeological wood depends on the level of deterioration that occurred over centuries. However, although the findings presented here apply to this specific case, they provide a unique view on such wood.

A new approach to the current distribution in field cooled superconductors disks

NASA Astrophysics Data System (ADS)

Bernstein, P.; Colson, L.; Dupont, L.; Noudem, J.

2018-01-01

The Bean model considers that in field cooled superconducting cylinders with diameter R, the currents flow over all the thickness of the superconductor along circular paths, the minimum radius of which depends on the magnetizing field and the critical current density. A combination of trapped field and levitation force measurements reported recently has shown, however, that in YBCO and MgB2 disks the current flows in fact in a restricted region with thickness t of the superconductor. In this contribution, from measurements carried out on two YBCO and two MgB2 disks, we report the dependence on temperature of t and J p, the current density in this region, as well as that of the field trapped by the samples. The results confirm that t decreases as the temperature decreases. This behaviour is ascribed to the conservation of the magnetic energy stored in the superconductor, which depends on the magnetizing source and not on the measurement temperature. As a consequence, t behaves as {{J}{{p}}}-2/3, while the field trapped along the axis of the cylinder behaves as {{J}{{p}}}1/3. These claims are substantiated by the experimental results. The possibility that J p is equal to the depairing current is investigated.

Isoprene-styrene copolymer elastomer and tetrahydrofurfuryl methacrylate mixtures for soft prosthetic applications.

PubMed

Nazhat, S N; Parker, S; Patel, M P; Braden, M

2001-09-01

Novel elastomer/methacrylate systems have been developed for potential soft prosthetic applications. Mixtures of varying compositions of an isoprene-styrene copolymer elastomer and tetrahydrofurfuryl methacrylate (SIS/THFMA) formed one-gel systems and were heat cured with a peroxide initiator. The blends were characterised in terms of sorption in deionised water and simulated body fluids (SBF), tensile properties and viscoelastic parameters of storage modulus and tan delta, as well as glass transition temperatures using dynamic mechanical analysis (DMA). DMA data gave two distinct peaks in tan delta, a lower temperature transition due to the isoprene phase in SIS and one at high temperature thought to be a combination of THFMA and the styrene phase in SIS. The tensile data showed a clear phase inversion within the mid range compositions changing from plastic to elastomeric behaviour. The sorption studies in deionised water showed a two stage uptake with an initial Fickian region that was linear to t 1/2 followed by a droplet growth/clustering system. The slope of the linear region was dependent on the composition ratio. The extent of overall uptake was osmotically dependent as all materials equilibrated at a much lower uptake in SBF. The diffusion coefficients were found to be concentration dependent.

Simultaneous degumming and production of a natural gum from Crotalaria juncea seeds: Physicochemical and rheological characterization.

PubMed

Sadhukhan, Suvra; Bhattacharjee, Annesha; Sarkar, Ujjaini; Baidya, Pabitra Kumar; Baksi, Sibashish

2018-05-01

The oil extracted from Crotalaria juncea (Sunn-hemp) contains 70% of gum. Several methods of degumming are attempted in order to maximize the yield of gum. During appropriate water induced degumming, about 95-98% of phosphatides are separated. The maximum oil yield for two types of degummimg processes are 0.59% and 0.69% corresponding to hot water and pure O-phosphoric acid (19.88 N) treatment respectively. The % oil yield obtained for TOP degumming is about 0.78%. Physico-chemical characteristics of the isolated gum such as moisture, ash, protein, fat and aqueous solubility along with FTIR and TGA analysis are studied in order to evaluate the effect of extraction process. The behaviour of gum on the molecular scale is evaluated through alcohol treatment. Chromatographic analysis determines the monosaccharide content of the gum with glucose: xylose: arabinose::54: 34:1. Rheological characterization shows that the juncea gum solutions are shear rate dependent and the behaviour is shear-thinning (or pseudoplastic). Results show that the temperature dependent viscosity decreases with increasing shear rate. Copyright © 2018 Elsevier B.V. All rights reserved.

FE calculations on a three stage metal forming process of Sandvik Nanoflex™

NASA Astrophysics Data System (ADS)

Voncken, R. M. J.; van der Sluis, O.; Post, J.; Huétink, J.

2004-06-01

Sandvik Nanoflex™ combines good corrosion resistance with high strength. This steel has good deformability in austenitic conditions. It belongs to the group of metastable austenites, which means that during deformation a strain-induced transformation into martensite takes place. After deformation, transformation continues as a result of internal stresses. Both transformations are stress-state and temperature dependent. A constitutive model for this steel has been formulated, based on the macroscopic material behaviour measured by inductive measurements. Both the stress-assisted and the strain-induced transformation into martensite have been incorporated in this model. Path-dependent work hardening has also been taken into account. This article describes how the model is implemented in an internal Philips FE code called Crystal, which is a dedicated robust and accurate finite element solver. The implementation is based on lookup tables in combination with feed-forward neural networks. The radial return method is used to determine the material state during and after plastic flow, however, it has been extended to cope with the stiff character of the partial differential equation that describes the transformation behaviour.

Behavioural thermoregulation in a temperature-sensitive coral reef fish, the five-lined cardinalfish ( Cheilodipterus quinquelineatus)

NASA Astrophysics Data System (ADS)

Nay, Tiffany J.; Johansen, Jacob L.; Habary, Adam; Steffensen, John F.; Rummer, Jodie L.

2015-12-01

As global temperatures increase, fish populations at low latitudes are thought to be at risk as they are adapted to narrow temperature ranges and live at temperatures close to their thermal tolerance limits. Behavioural movements, based on a preference for a specific temperature ( T pref), may provide a strategy to cope with changing conditions. A temperature-sensitive coral reef cardinalfish ( Cheilodipterus quinquelineatus) was exposed to 28 °C (average at collection site) or 32 °C (predicted end-of-century) for 6 weeks. T pref was determined using a shuttlebox system, which allowed fish to behaviourally manipulate their thermal environment. Regardless of treatment temperature, fish preferred 29.5 ± 0.25 °C, approximating summer average temperatures in the wild. However, 32 °C fish moved more frequently to correct their thermal environment than 28 °C fish, and daytime movements were more frequent than night-time movements. Understanding temperature-mediated movements is imperative for predicting how ocean warming will influence coral reef species and distribution patterns.

Post-irradiation examinations of THERMHET composite fuels for transmutation

NASA Astrophysics Data System (ADS)

Noirot, J.; Desgranges, L.; Chauvin, N.; Georgenthum, V.

2003-07-01

The thermal behaviour of composite targets dedicated to minor actinide transmutation was studied using THERMHET (thermal behaviour of heterogeneous fuel) irradiation in the SILOE reactor. Three inert matrix fuel designs were tested (macro-mass, jingle and microdispersion) all with a MgAl 2O 4 spinel inert matrix and around 40% weight of UO 2 to simulate minor actinide inclusions. The post-irradiation examinations led to a new interpretation of the temperature measurement by thermocouples located in the central hole of the pellets. A major change in the micro-dispersed structure was detected. The examinations enabled us to understand the behaviour of the spinel during the different stages of irradiation. They revealed an amorphisation at low temperature and then a nano re-crystallisation at high temperature of the spinel in the micro-dispersed case. These results, together with those obtained in the MATINA irradiation of an equivalent structure, show the importance of the irradiation temperature on spinel behaviour.

Determination of the swelling velocity of different wood species and tissues depending on the cutting direction on microtome section level

NASA Astrophysics Data System (ADS)

Stuckenberg, Peter; Wenderdel, Christoph; Zauer, Mario

2018-06-01

Swelling velocity in dependence on the anatomical cutting direction of yew [Taxus baccata L.] and boxwood [Buxus sempervirens L.] was determined at temperature of 20 °C and at relative humidity of 10% and 100%. The investigations, conducted on a microtome section level, showed a similar behaviour for specimens of both wood species. It was possible to determine that the swelling velocity for yew and boxwood increases in its anatomical cutting directions. The longitudinal direction showed the lowest value, the tangential direction, by distinction, the highest value. Furthermore, a significant influence of early wood and late wood content on the swelling velocity for yew was detected.

Non-monotonic temperature dependence of chaos-assisted diffusion in driven periodic systems

NASA Astrophysics Data System (ADS)

Spiechowicz, J.; Talkner, P.; Hänggi, P.; Łuczka, J.

2016-12-01

The spreading of a cloud of independent Brownian particles typically proceeds more effectively at higher temperatures, as it derives from the commonly known Sutherland-Einstein relation for systems in thermal equilibrium. Here, we report on a non-equilibrium situation in which the diffusion of a periodically driven Brownian particle moving in a periodic potential decreases with increasing temperature within a finite temperature window. We identify as the cause for this non-intuitive behaviour a dominant deterministic mechanism consisting of a few unstable periodic orbits embedded into a chaotic attractor together with thermal noise-induced dynamical changes upon varying temperature. The presented analysis is based on extensive numerical simulations of the corresponding Langevin equation describing the studied setup as well as on a simplified stochastic model formulated in terms of a three-state Markovian process. Because chaos exists in many natural as well as in artificial systems representing abundant areas of contemporary knowledge, the described mechanism may potentially be discovered in plentiful different contexts.

Evidence of spin phonon coupling in magnetoelectric NiFe{sub 2}O{sub 4}/PMN-PT composite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahlawat, Anju; Satapathy, S., E-mail: srinu73@rrcat.gov.in, E-mail: srinusatapathy@gmail.com; Gupta, P. K.

2013-12-16

The coupling of phonon with spin in strain coupled magnetoelectric NiFe{sub 2}O{sub 4} (NFO)/0.65Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}–0.35PbTiO{sub 3} (PMN-PT) composite was investigated by temperature-dependent Raman spectroscopy and magnetic measurements in the range 30–350 °C. Pure NFO shows usual ferromagnetic behaviour in this temperature range while NFO/PMN-PT composite show dramatic change in magnetic moment across ferroelectric transition temperature (T{sub c} ∼ 180 °C) of PMN-PT. The temperature evolution of the Raman spectra for the composite shows significant phonon anomalies in T-site (Fe-O) and O-site (Ni/Fe-O) phonon modes at ferroelectric transition temperature is attributed to spin phonon coupling in NFO/PMN-PT composite. The strain mediated magnetoelectric couplingmore » mechanism in this composite is apparent from the observed spin phonon interaction.« less

Thermogravimetric analysis for rapid assessment of moisture diffusivity in polydisperse powder and thin film matrices.

PubMed

Thirunathan, Praveena; Arnz, Patrik; Husny, Joeska; Gianfrancesco, Alessandro; Perdana, Jimmy

2018-03-01

Accurate description of moisture diffusivity is key to precisely understand and predict moisture transfer behaviour in a matrix. Unfortunately, measuring moisture diffusivity is not trivial, especially at low moisture values and/or elevated temperatures. This paper presents a novel experimental procedure to accurately measure moisture diffusivity based on thermogravimetric approach. The procedure is capable to measure diffusivity even at elevated temperatures (>70°C) and low moisture values (>1%). Diffusivity was extracted from experimental data based on "regular regime approach". The approach was tailored to determine diffusivity from thin film and from poly-dispersed powdered samples. Subsequently, measured diffusivity was validated by comparing to available literature data, showing good agreement. Ability of this approach to accurately measure diffusivity at a wider range of temperatures provides better insight on temperature dependency of diffusivity. Thus, this approach can be crucial to ensure good accuracy of moisture transfer description/prediction especially when involving elevated temperatures. Copyright © 2017 Elsevier Ltd. All rights reserved.

Medium effects and parity doubling of hyperons across the deconfinement phase transition

NASA Astrophysics Data System (ADS)

Aarts, Gert; Allton, Chris; Boni, Davide De; Hands, Simon; Jäger, Benjamin; Praki, Chrisanthi; Skullerud, Jon-Ivar

2018-03-01

We analyse the behaviour of hyperons with strangeness S = -1,-2,-3 in the hadronic and quark gluon plasma phases, with particular interest in parity doubling and its emergence as the temperature grows. This study uses our FASTSUM anisotropic Nf = 2+1 ensembles, with four temperatures below and four above the deconfinement transition temperature, Tc. The positive-parity groundstate masses are found to be largely temperature independent below Tc, whereas the negative-parity ones decrease considerably as the temperature increases. Close to the transition, the masses are almost degenerate, in line with the expectation from chiral symmetry restoration. This may be of interest for heavy-ion phenomenology. In particular we show an application of this effect to the Hadron Resonance Gas model. A clear signal of parity doubling is found above Tc in all hyperon channels, with the strength of the effect depending on the number of s-quarks in the baryons. Presented at 35th International Symposium on Lattice Field Theory, 18-24 June 2017, Granada, Spain

Endocrine differences among colour morphs in a lizard with alternative behavioural strategies.

PubMed

Yewers, Madeleine St Clair; Jessop, Tim S; Stuart-Fox, Devi

2017-07-01

Alternative behavioural strategies of colour morphs are expected to associate with endocrine differences and to correspond to differences in physical performance (e.g. movement speed, bite force in lizards); yet the nature of correlated physiological and performance traits in colour polymorphic species varies widely. Colour morphs of male tawny dragon lizards Ctenophorus decresii have previously been found to differ in aggressive and anti-predator behaviours. We tested whether known behavioural differences correspond to differences in circulating baseline and post-capture stress levels of androgen and corticosterone, as well as bite force (an indicator of aggressive performance) and field body temperature. Immediately after capture, the aggressive orange morph had higher circulating androgen than the grey morph or the yellow morph. Furthermore, the orange morph maintained high androgen following acute stress (30min of capture); whereas androgen increased in the grey and yellow morphs. This may reflect the previously defined behavioural differences among morphs as the aggressive response of the yellow morph is conditional on the colour of the competitor and the grey morph shows consistently low aggression. In contrast, all morphs showed an increase in corticosterone concentration after capture stress and morphs did not differ in levels of corticosterone stress magnitude (CSM). Morphs did not differ in size- and temperature-corrected bite force but did in body temperature at capture. Differences in circulating androgen and body temperature are consistent with morph-specific behavioural strategies in C. decresii but our results indicate a complex relationship between hormones, behaviour, temperature and bite force within and between colour morphs. Copyright © 2017 Elsevier Inc. All rights reserved.

Infrared spectra of the ammonium ion in ammonium metavanadate NH 4VO 3

NASA Astrophysics Data System (ADS)

de Waal, D.; Heyns, A. M.; Range, K.-J.; Eglmeier, C.

The ND stretching modes of isotopically dilute NH 3D + ions in NH 4VO 3 are in agreement with the predicted splitting into C s, C s and C1(2) components under C s site symmetry for the NH +4 ion. The three bands observed represent the three NH bonding distances in the crystal, and the position, shape and low temperature behaviour of each band confirms the existence of two types of hydrogen bonding in NH 4VO 3. The low temperature infrared modes of NH +4 and ND +4 in NH 4VO 3 and ND 4VO 3, respectively, can be assigned under space group Pbcm. Temperature dependence of these modes also reflects the presence of both normal and bifurcated hydrogen bonds in NH 4VO 3.

Characterisation of an Al-BN nanocomposite prepared by ball milling and hot extrusion

NASA Astrophysics Data System (ADS)

Arlic, U.; Drozd, Z.; Trojanová, Z.; Molnárová, O.; Kasakewitsch, A.

2017-07-01

Aluminium-matrix-nanocomposites were manufactured by ball milling of microscale aluminium powder with BN nanoparticles in air, followed by subsequent consolidation by hot extrusion. The microstructure of the samples was studied using scanning electron microscopy. Vickers microhardness measurements were used to probe the mechanical properties of the samples. The amplitude dependent damping of the nanocomposites was measured at room temperature after thermal treatment of samples, and the linear thermal expansion was measured over a wide temperature range from room temperature up to 670K in the as-extruded state. The experimental results give a comprehensive picture of the behaviour of this nanocomposite system over the range of thermomechanical treatment conditions examined in this study. Based on these experimental data some possible influences of BN nanoparticles on the anelastic, plastic and thermal properties of microcrystalline aluminium are discussed.

Hemorheology and oxygen transport in vertebrates. A role in thermoregulation?

PubMed

Viscor, G; Torrella, J R; Fouces, V; Pagés, T

2003-12-01

We studied the effect of temperature on blood rheology in three vertebrate species with different thermoregulation and erythrocyte characteristics. Higher fibrinogen proportion to total plasma protein was found in turtles (20%) than in pigeons (5.6%) and rats (4.2%). Higher plasma viscosity at room temperature than at homeotherm body temperature was observed in rats (1.69 mPa x s at 20 degrees C vs. 1.33 mPa x s at 37 degrees C), pigeons (3.40 mPa x s at 20 degrees C vs. 1.75 mPa x s at 40 degrees C), and turtles (1.74 mPa x s at 20 degrees C vs. 1.32 mPa x s at 37 degrees C). This fact allow us to hypothesize that thermal changes in protein structure may account for an adjustment of the plasma viscosity. Blood viscosity was dependent on shear rate, temperature and hematocrit in the three species. A different behaviour in apparent and relative viscosities between rat and pigeon at environmental temperature was found. Moreover, the blood oxygen transport capacity seems more affected by a reduction of temperature in rats than in pigeons. Both findings indicate a greater influence of temperature on mammalian erythrocyte than on nucleated red cells, possibly as a consequence of differences in thermal sensitivity and mechanical stability between them. A comparison between the three species revealed that apparent blood viscosity measured at homeotherm physiological temperature was linearly related to the hematocrit level of each species. However, when measured at environmental temperature, rat blood showed a higher apparent viscosity than those found in species with non-nucleated red cells, thus indicating a higher impact of temperature decrease on blood viscosity in mammals. This suggest that regional hypothermia caused by cold exposure may affect mammalian blood rheological behaviour in a higher extent than in other vertebrate species having nucleated red cells and, consequently, influencing circulatory function and oxygen transport.

Comparison of three approaches to model grapevine organogenesis in conditions of fluctuating temperature, solar radiation and soil water content.

PubMed

Pallas, B; Loi, C; Christophe, A; Cournède, P H; Lecoeur, J

2011-04-01

There is increasing interest in the development of plant growth models representing the complex system of interactions between the different determinants of plant development. These approaches are particularly relevant for grapevine organogenesis, which is a highly plastic process dependent on temperature, solar radiation, soil water deficit and trophic competition. The extent to which three plant growth models were able to deal with the observed plasticity of axis organogenesis was assessed. In the first model, axis organogenesis was dependent solely on temperature, through thermal time. In the second model, axis organogenesis was modelled through functional relationships linking meristem activity and trophic competition. In the last model, the rate of phytomer appearence on each axis was modelled as a function of both the trophic status of the plant and the direct effect of soil water content on potential meristem activity. The model including relationships between trophic competition and meristem behaviour involved a decrease in the root mean squared error (RMSE) for the simulations of organogenesis by a factor nine compared with the thermal time-based model. Compared with the model in which axis organogenesis was driven only by trophic competition, the implementation of relationships between water deficit and meristem behaviour improved organogenesis simulation results, resulting in a three times divided RMSE. The resulting model can be seen as a first attempt to build a comprehensive complete plant growth model simulating the development of the whole plant in fluctuating conditions of temperature, solar radiation and soil water content. We propose a new hypothesis concerning the effects of the different determinants of axis organogenesis. The rate of phytomer appearance according to thermal time was strongly affected by the plant trophic status and soil water deficit. Furthermore, the decrease in meristem activity when soil water is depleted does not result from source/sink imbalances.

An internal thermal sensor controlling temperature preference in Drosophila.

PubMed

Hamada, Fumika N; Rosenzweig, Mark; Kang, Kyeongjin; Pulver, Stefan R; Ghezzi, Alfredo; Jegla, Timothy J; Garrity, Paul A

2008-07-10

Animals from flies to humans are able to distinguish subtle gradations in temperature and show strong temperature preferences. Animals move to environments of optimal temperature and some manipulate the temperature of their surroundings, as humans do using clothing and shelter. Despite the ubiquitous influence of environmental temperature on animal behaviour, the neural circuits and strategies through which animals select a preferred temperature remain largely unknown. Here we identify a small set of warmth-activated anterior cell (AC) neurons located in the Drosophila brain, the function of which is critical for preferred temperature selection. AC neuron activation occurs just above the fly's preferred temperature and depends on dTrpA1, an ion channel that functions as a molecular sensor of warmth. Flies that selectively express dTrpA1 in the AC neurons select normal temperatures, whereas flies in which dTrpA1 function is reduced or eliminated choose warmer temperatures. This internal warmth-sensing pathway promotes avoidance of slightly elevated temperatures and acts together with a distinct pathway for cold avoidance to set the fly's preferred temperature. Thus, flies select a preferred temperature by using a thermal sensing pathway tuned to trigger avoidance of temperatures that deviate even slightly from the preferred temperature. This provides a potentially general strategy for robustly selecting a narrow temperature range optimal for survival.

Urbanisation shapes behavioural responses to a pesticide.

PubMed

Tüzün, Nedim; Debecker, Sara; Op de Beeck, Lin; Stoks, Robby

2015-06-01

The degree of urbanisation is rapidly increasing worldwide. Due to anthropogenic impact, urban populations are exposed to higher levels of contaminants and higher temperatures. Despite this, urbanisation is a largely overlooked spatial component in ecotoxicology. We tested in a common garden rearing experiment whether replicated urban and rural populations of the damselfly Coenagrion puella differ in their vulnerability to sublethal levels of a widespread pesticide, chlorpyrifos, in terms of ecologically relevant behaviours (exploration behaviour, activity, boldness and food intake), and to what extent these patterns are affected by temperature (20 and 24°C). Except boldness, all behaviours were affected by previous pesticide exposure. While the pesticide did not affect exploration behaviour at 20°C, it was associated with increased exploration at 24°C, which may reflect an increased toxicity of chlorpyrifos at higher temperatures. Importantly, rural and urban larvae showed consistently different, sometimes even opposite behavioural responses to pesticide exposure. When exposed to the pesticide, rural larvae decreased activity and food intake at both temperatures; urban larvae instead increased activity at both temperatures and only reduced food intake at the high temperature. This suggests that urban larvae were less affected by the pesticide, which would be consistent with a scenario of local adaptation to higher contaminant levels. Our results highlight that urbanisation may be an important factor to arrive at a spatially explicit ecological risk assessment, and may be an ignored reason why studies on the same species may generate widely different vulnerabilities to pesticides. Copyright © 2015 Elsevier B.V. All rights reserved.

Thermo-elastic behaviour of liquid crystal elastomer

NASA Astrophysics Data System (ADS)

J, Jessy P.; Mani, Santosh A.; Amare, Jyoti R.; Gharde, Rita A.

2015-06-01

The effect of temperature on Liquid Crystal Elastomer was studied to understand thermo-elastic behaviour of these fantastic soft materials. The investigations were performed using Polarizing Microscopy Studies (PMS) and Differential Thermal Analysis (DTA). The relative length shows hysteresis as function of temperature. As temperature increases, the length shrinks, while it returns to original shape on cooling.

Controlled nanopatterning & modifications of materials by energetic ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sinha, O. P.

Compound semiconductors (InP, InAs and GaSb) has been exposed to energetic 3 keV Ar{sup +} ions for a varying fluence range of 10{sup 13} ions/cm{sup 2} to 10{sup 18} ions/cm{sup 2} at room temperature. Morphological modifications of the irradiated surfaces have been investigated by Scanning Tunneling Microscopy (STM) in UHV conditions. It is observed that InP and GaSb have fluence dependent nanopattering e.g. nanoneedle, aligned nanodots, superimposed nanodots ripple like structures while InAs has little fluence dependent behaviour indicating materials dependent growth of features on irradiated surfaces. Moreover, surface roughness and wavelength of the features are also depending on themore » materials and fluences. The RMS surface roughness has been found to be increased rapidly in the early stage of irradiation followed by slower escalate rate and later tends to saturate indicating influence of the nonlinear processes.« less

A dynamic tester to evaluate the thermal and moisture behaviour of the surface of textiles.

PubMed

Li, Wenbin; Xu, Weilin; Wang, Hao; Wang, Xin

2016-01-01

The thermal and moisture behaviour of the microclimate of textiles is crucial in determining the physiological comfort of apparel, but it has not been investigated sufficiently due to the lack of particular evaluation techniques. Based on sensing, temperature controlling and wireless communicating technology, a specially designed tester has been developed in this study to evaluate the thermal and moisture behaviour of the surface of textiles in moving status. A temperature acquisition system and a temperature controllable hotplate have been established to test temperature and simulate the heat of human body, respectively. Relative humidity of the surface of fabric in the dynamic process has been successfully tested through sensing. Meanwhile, wireless communication technology was applied to transport the acquired data of temperature and humidity to computer for further processing. Continuous power supply was achieved by intensive contact between an elastic copper plate and copper ring on the rotating shaft. This tester provides the platform to evaluate the thermal and moisture behaviour of textiles. It enables users to conduct a dynamic analysis on the temperature and humidity together with the thermal and moisture transport behaviour of the surface of fabric in moving condition. Development of this tester opens the door of investigation on the micro-climate of textiles in real time service, and eventually benefits the understanding of the sensation comfort and wellbeing of apparel wearers. Copyright © 2015 Elsevier Ltd. All rights reserved.

Steric hindrances create a discrete linear Dy4 complex exhibiting SMM behaviour.

PubMed

Lin, Shuang-Yan; Zhao, Lang; Ke, Hongshan; Guo, Yun-Nan; Tang, Jinkui; Guo, Yang; Dou, Jianmin

2012-03-21

Two linear tetranuclear lanthanide complexes of general formula [Ln(4)(L)(2)(C(6)H(5)COO)(12)(MeOH)(4)], where HL = 2,6-bis((furan-2-ylmethylimino)methyl)-4-methylphenol, () and Ln(III) = Dy(III) (1) and Gd(III) (2), have been synthesized and characterized. The crystal structural analysis demonstrates that two Schiff-base ligands inhibit the growth of benzoate bridged 1D chains, leading to the isolation of discrete tetranuclear complexes due to their steric hindrances. Every Ln(III) ion is coordinated by eight donor atoms in a distorted bicapped trigonal-prismatic arrangement. Alternating current (ac) susceptibility measurements of complex 1 reveal a frequency- and temperature-dependent out-of-phase signal under zero dc field, typical of single-molecule magnet (SMM) behaviour with an anisotropic barrier Δ(eff) = 17.2 K.

Carbon nanotube dry adhesives with temperature-enhanced adhesion over a large temperature range.

PubMed

Xu, Ming; Du, Feng; Ganguli, Sabyasachi; Roy, Ajit; Dai, Liming

2016-11-16

Conventional adhesives show a decrease in the adhesion force with increasing temperature due to thermally induced viscoelastic thinning and/or structural decomposition. Here, we report the counter-intuitive behaviour of carbon nanotube (CNT) dry adhesives that show a temperature-enhanced adhesion strength by over six-fold up to 143 N cm -2 (4 mm × 4 mm), among the strongest pure CNT dry adhesives, over a temperature range from -196 to 1,000 °C. This unusual adhesion behaviour leads to temperature-enhanced electrical and thermal transports, enabling the CNT dry adhesive for efficient electrical and thermal management when being used as a conductive double-sided sticky tape. With its intrinsic thermal stability, our CNT adhesive sustains many temperature transition cycles over a wide operation temperature range. We discover that a 'nano-interlock' adhesion mechanism is responsible for the adhesion behaviour, which could be applied to the development of various dry CNT adhesives with novel features.

Single-backscattering and quasi-single-backscattering of low energy ions from a cold nickel surface: contribution to the ICISS method

NASA Astrophysics Data System (ADS)

Soszka, W.

1992-09-01

Energy spectra of 5 keV Ne+ and He+ ions backscattered from the cold (100) nickel surface for chosen values of the incidence angles were measured. It was found that the occurrence of the isotope structure of the so-called "single-scattering" peak as well as its position on the energy scale depend on the incidence angle and the target temperature. In comparison to the case of room temperature the "ICISS curve" (the intensity of the single-scattering peak versus the incidence angle) at low temperatures increases up to relatively large angles. The curve in its part shows some structure which is not observed at room temperatures. It has been shown [E.S. Parilis et al., Atomic Collisions in Gases and on Solid Surfaces (FAN, Tashkent, 1988) in Russian] that the doubly scattered ions can have the same energy and exit angle as the singly scattered ions and both components create the quasi-single-scattering peak. The double-scattering component depends in a complex manner on the incidence angle and the target temperature. It is shown that at low temperatures (below 80 K) the intensity of the single-scattering component decreases (a decrease of thermal cross section), and the intensity of the double-scattering component relatively increases. This determines the behaviour of the ICISS curve, which, for low temperatures and light projectiles cannot be treated as a real ICISS curve.

High temperature radiance spectroscopy measurements of solid and liquid uranium and plutonium carbides

NASA Astrophysics Data System (ADS)

Manara, D.; De Bruycker, F.; Boboridis, K.; Tougait, O.; Eloirdi, R.; Malki, M.

2012-07-01

In this work, an experimental study of the radiance of liquid and solid uranium and plutonium carbides at wavelengths 550 nm ⩽ λ ⩽ 920 nm is reported. A fast multi-channel spectro-pyrometer has been employed for the radiance measurements of samples heated up to and beyond their melting point by laser irradiation. The melting temperature of uranium monocarbide, soundly established at 2780 K, has been taken as a radiance reference. Based on it, a wavelength-dependence has been obtained for the high-temperature spectral emissivity of some uranium carbides (1 ⩽ C/U ⩽ 2). Similarly, the peritectic temperature of plutonium monocarbide (1900 K) has been used as a reference for plutonium monocarbide and sesquicarbide. The present spectral emissivities of solid uranium and plutonium carbides are close to 0.5 at 650 nm, in agreement with previous literature values. However, their high temperature behaviour, values in the liquid, and carbon-content and wavelength dependencies in the visible-near infrared range have been determined here for the first time. Liquid uranium carbide seems to interact with electromagnetic radiation in a more metallic way than does the solid, whereas a similar effect has not been observed for plutonium carbides. The current emissivity values have also been used to convert the measured radiance spectra into real temperature, and thus perform a thermal analysis of the laser heated samples. Some high-temperature phase boundaries in the systems U-C and Pu-C are shortly discussed on the basis of the current results.

The effect of pH on the rheology of mixed gels containing whey protein isolate and xanthan-curdlan hydrogel.

PubMed

Shiroodi, Setareh Ghorban; Lo, Y Martin

2015-11-01

The ultimate goal of this work was to examine the effect of xanthan-curdlan hydrogel complex (XCHC) on the rheology of whey protein isolate (WPI) within the pH range of 4-7 upon heating and cooling. Dynamic rheological properties of WPI and XCHC were studied individually and in combination, as a function of time or temperature. For pure WPI, gels were pH-dependent, and in all pH values except 7, gels formed upon first heating from 40 to 90 °C. At pH 7, WPI did not form gel upon first heating, and the storage modulus (G') started to increase during the holding time at 90 °C. The onset of gelation temperature of WPI was lower in acidic pH ranges compared to the neutral pH. In mixed gels, the presence of XCHC increased the G' of the gels. The rheological behaviour was pH-dependent and initially was controlled by XCHC; however, after the consolidation of WPI network, the behaviour was led by the whey protein isolate. Results showed that XCHC had a synergistic effect on enhancing the elastic modulus of the gels after the consolidation of WPI network. Based on the results of this study, it is possible to use these biopolymers in the formulation of frozen dairy-based products and enable food manufactures to improve the textural and physicochemical properties, and as a result the consumer acceptance of the food product.

Observation of relaxor ferroelectricity and multiferroic behaviour in nanoparticles of the ferromagnetic semiconductor La(2)NiMnO(6).

PubMed

Masud, Md G; Ghosh, Arijit; Sannigrahi, J; Chaudhuri, B K

2012-07-25

We report a diffuse phase transition (extending over a finite temperature range of ∼50 K) in sol-gel derived nanoparticles (∼25 nm) of the ferromagnetic double perovskite La(2)NiMnO(6). The macroscopic polarization (P-E hysteresis loop), validity of the Vogel-Fulcher relation and high dielectric permittivity (∼9 × 10(2)) confirm relaxor ferroelectric phenomena in these magnetic nanoparticles. Compared to the corresponding bulk sample, appreciably large enhancement of the magnetocapacitive effect (MC  ∼ 30%) is observed even under low magnetic field (0.5 T) around the broad relaxor dielectric peak temperature (∼220 K), which is close to the ferromagnetic transition temperature (θ(f) ∼ 196 K). All of these features establish the multiferroic character of the La(2)NiMnO(6) nanoparticles. The inhomogeneities arising from chemical and valence mixing in the present La(2)NiMnO(6) nanoparticles and the inter-site, Ni/Mn-site disorder along with surface disorder of the individual nanoparticles resulting in local polar regions are attributed to the observed dielectric behaviour of the nanoparticles. The wave vector dependent spin-pair correlation is considered to be the plausible cause of the colossal magnetocapacitive response near the transition temperature. High permittivity and large magnetocapacitive properties make these ferromagnetic La(2)NiMnO(6) nanoparticles technologically important.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, J.; Bollinger, A. T.; He, X.

The origin of high-temperature superconductivity in copper oxides and the nature of the ‘normal’ state above the critical temperature are widely debated. In underdoped copper oxides, this normal state hosts a pseudogap and other anomalous features; and in the overdoped materials, the standard Bardeen–Cooper–Schrieffer description fails, challenging the idea that the normal state is a simple Fermi liquid. To investigate these questions, we have studied the behaviour of single-crystal La 2–xSr xCuO 4 films through which an electrical current is being passed. Here we report that a spontaneous voltage develops across the sample, transverse (orthogonal) to the electrical current. The dependence of this voltage on probe current, temperature, in-plane device orientation and doping shows that this behaviour is intrinsic, substantial, robust and present over a broad range of temperature and doping. If the current direction is rotated in-plane by an anglemore » $$\\phi$$, the transverse voltage oscillates as sin(2$$\\phi$$), breaking the four-fold rotational symmetry of the crystal. The amplitude of the oscillations is strongly peaked near the critical temperature for superconductivity and decreases with increasing doping. We find that these phenomena are manifestations of unexpected in-plane anisotropy in the electronic transport. The films are very thin and epitaxially constrained to be tetragonal (that is, with four-fold symmetry), so one expects a constant resistivity and zero transverse voltage, for every $$\\phi$$. The origin of this anisotropy is purely electronic—the so-called electronic nematicity. Unusually, the nematic director is not aligned with the crystal axes, unless a substantial orthorhombic distortion is imposed. The fact that this anisotropy occurs in a material that exhibits high-temperature superconductivity may not be a coincidence.« less

Temperature-dependent changes in the swimming behaviour of Tetrahymena pyriformis-NT1 and their interrelationships with electrophysiology and the state of membrane lipids.

PubMed

Connolly, J G; Brown, I D; Lee, A G; Kerkut, G A

1985-01-01

The swimming velocity and the amplitude of the helical swimming path of T. pyriformis-NT1 cells grown at 20 degrees C (Tg 20 degrees C) and 38 degrees C (Tg 38 degrees C) were monitored between 0 and 40 degrees C in the presence and absence of electric fields. Within physiological limits the swimming velocity increased and the amplitude decreased as temperature was raised. The temperature profiles of these properties were not linear, and showed discontinuities at different temperatures for the different cultures. The break points in Arrhenius plots of the resting potential, regenerative spike magnitude, repolarization time, swimming velocity and swimming amplitude are tabulated and compared. The initial breakpoints upon cooling were clustered about the breakpoints in fluorescence polarization of D.P.H. in extracted phospholipids, and around the transition temperatures estimated from the literature for the pellicular membrane of these cells. The average of the initial breakpoints on cooling was 22.9 degrees C for Tg 38 degrees C cells and 13.7 degrees C for Tg 20 degrees C cells, a shift of 9.2 degrees C. Unlike Paramecium there is no depolarizing receptor potential in Tetrahymena upon warming. It is suggested that this may be the basis of a behavioural difference between Tetrahymena and Paramecium--namely that in Tetrahymena maximum swimming velocity occurs above growth temperature whereas in Paramecium the two points coincide. Swimming velocity and resting potential were correlated with membrane fluidity within physiological limits, but for other parameters the relationship with fluidity was more complex.(ABSTRACT TRUNCATED AT 250 WORDS)

Accelerated aging tests on ENEA-ASE solar coating for receiver tube suitable to operate up to 550 °C

NASA Astrophysics Data System (ADS)

Antonaia, A.; D'Angelo, A.; Esposito, S.; Addonizio, M. L.; Castaldo, A.; Ferrara, M.; Guglielmo, A.; Maccari, A.

2016-05-01

A patented solar coating for evacuated receiver, based on innovative graded WN-AlN cermet layer, has been optically designed and optimized to operate at high temperature with high performance and high thermal stability. This solar coating, being designed to operate in solar field with molten salt as heat transfer fluid, has to be thermally stable up to the maximum temperature of 550 °C. With the aim of determining degradation behaviour and lifetime prediction of the solar coating, we chose to monitor the variation of the solar absorptance αs after each thermal annealing cycle carried out at accelerated temperatures under vacuum. This prediction method was coupled with a preliminary Differential Thermal Analysis (DTA) in order to give evidence for any chemical-physical coating modification in the temperature range of interest before performing accelerated aging tests. In the accelerated aging tests we assumed that the temperature dependence of the degradation processes could be described by Arrhenius behaviour and we hypothesized that a linear correlation occurs between optical parameter variation rate (specifically, Δαs/Δt) and degradation process rate. Starting from Δαs/Δt values evaluated at 650 and 690 °C, Arrhenius plot gave an activation energy of 325 kJ mol-1 for the degradation phenomenon, where the prediction on the coating degradation gave a solar absorptance decrease of only 1.65 % after 25 years at 550 °C. This very low αs decrease gave evidence for an excellent stability of our solar coating, also when employed at the maximum temperature (550 °C) of a solar field operating with molten salt as heat transfer fluid.

Spontaneous breaking of rotational symmetry in copper oxide superconductors

DOE PAGES

Wu, J.; Bollinger, A. T.; He, X.; ...

2017-07-26

The origin of high-temperature superconductivity in copper oxides and the nature of the ‘normal’ state above the critical temperature are widely debated. In underdoped copper oxides, this normal state hosts a pseudogap and other anomalous features; and in the overdoped materials, the standard Bardeen–Cooper–Schrieffer description fails, challenging the idea that the normal state is a simple Fermi liquid. To investigate these questions, we have studied the behaviour of single-crystal La 2–xSr xCuO 4 films through which an electrical current is being passed. Here we report that a spontaneous voltage develops across the sample, transverse (orthogonal) to the electrical current. The dependence of this voltage on probe current, temperature, in-plane device orientation and doping shows that this behaviour is intrinsic, substantial, robust and present over a broad range of temperature and doping. If the current direction is rotated in-plane by an anglemore » $$\\phi$$, the transverse voltage oscillates as sin(2$$\\phi$$), breaking the four-fold rotational symmetry of the crystal. The amplitude of the oscillations is strongly peaked near the critical temperature for superconductivity and decreases with increasing doping. We find that these phenomena are manifestations of unexpected in-plane anisotropy in the electronic transport. The films are very thin and epitaxially constrained to be tetragonal (that is, with four-fold symmetry), so one expects a constant resistivity and zero transverse voltage, for every $$\\phi$$. The origin of this anisotropy is purely electronic—the so-called electronic nematicity. Unusually, the nematic director is not aligned with the crystal axes, unless a substantial orthorhombic distortion is imposed. The fact that this anisotropy occurs in a material that exhibits high-temperature superconductivity may not be a coincidence.« less

Thermoregulation of foraging honeybees on flowering plants: seasonal variability and influence of radiative heat gain

PubMed Central

Kovac, Helmut; Stabentheiner, Anton

2011-01-01

1. During nectar and pollen foraging in a temperate climate, honeybees are exposed to a broad range of ambient temperatures, challenging their thermoregulatory ability. The body temperature that the bees exhibit results from endothermic heat production, exogenous heat gain from solar radiation, and heat loss. In addition to profitability of foraging, season was suggested to have a considerable influence on thermoregulation. To assess the relative importance of these factors, the thermoregulatory behaviour of foragers on 33 flowering plants in dependence on season and environmental factors was investigated. 2. The bees (Apis mellifera carnica Pollman) were always endothermic. On average, the thorax surface temperature (Tth) was regulated at a high and rather constant level over a broad range of ambient temperatures (Tth = 33.7–35.7°C, Ta = 10–27°C). However, at a certain Ta, Tth showed a strong variation, depending on the plants from which the bees were foraging. At warmer conditions (Ta = 27–32°C) the Tth increased nearly linearly with Ta to a maximal average level of 42.6 °C. The thorax temperature excess decreased strongly with increasing Ta (Tth−Ta = 21.6 − 3.6°C). 3. The bees used the heat gain from solar radiation to elevate the temperature excess of thorax, head, and abdomen. Seasonal dependance was reflected in a 2.7 °C higher mean Tth in the spring than in the summer. An anova revealed that season had the greatest effect on Tth, followed by Ta and radiation. 4. It was presumed the foragers' motivational status to be the main factor responsible for the variation of Tth between seasons and different plants. PMID:22419834

Mathematical models for prediction of rheological parameters in vinasses derived from sugar cane

NASA Astrophysics Data System (ADS)

Chacua, Leidy M.; Ayala, Germán; Rojas, Hernán; Agudelo, Ana C.

2016-04-01

The rheological behaviour of vinasses derived from sugar cane was studied as a function of time (0 and 600 s), soluble solids content (44 and 60 °Brix), temperature (10 and 50°C), and shear rate (0.33 and 1.0 s-1). The results indicated that vinasses were time-independent at 25°C, where shear stress values ranged between 0.01 and 0.08 Pa. Flow curves showed a shear-thinning rheological behaviour in vinasses with a flow behaviour index between 0.69 and 0.89, for temperature between 10 and 20°C. With increasing temperature, the flow behaviour index was modified, reaching values close to 1.0. The Arrhenius model described well the thermal activation of shear stress and the consistency coefficient as a function of temperature. Activation energy from the Arrhenius model ranged between 31 and 45 kJ mol-1. Finally, the consistency coefficient as a function of the soluble solids content and temperature was well fitted using an exponential model (R2 = 0.951), showing that the soluble solids content and temperature have an opposite effect on consistency coefficient values.

Could behaviour and not physiological thermal tolerance determine winter survival of aphids in cereal fields?

PubMed

Alford, Lucy; Andrade, Thiago Oliveira; Georges, Romain; Burel, Françoise; van Baaren, Joan

2014-01-01

Traits of physiological thermotolerance are commonly measured in the laboratory as predictors of the field success of ectotherms at unfavourable temperatures (e.g. during harsh winters, heatwaves, or under conditions of predicted global warming). Due to being more complicated to measure, behavioural thermoregulation is less commonly studied, although both physiology and behaviour interact to explain the survival of ectotherms. The aphids Metopolophium dirhodum, Rhopalosiphum padi and Sitobion avenae are commercially important pests of temperate cereal crops. Although coexisting, these species markedly differ in winter success, with R. padi being the most abundant species during cold winters, followed by S. avenae and lastly M. dirhodum. To better understand the thermal physiology and behavioural factors contributing to differential winter success, the lethal temperature (physiological thermotolerance) and the behaviour of aphids in a declining temperature regime (behavioural thermotolerance) of these three species were investigated. Physiological thermotolerance significantly differed between the three species, with R. padi consistently the least cold tolerant and S. avenae the most cold tolerant. However, although the least cold tolerant of the study species, significantly more R. padi remained attached to the host plant at extreme sub-zero temperatures than S. avenae and M. dirhodum. Given the success of anholocyclic R. padi in harsh winters compared to its anholocyclic counterparts, this study illustrates that behavioural differences could be more important than physiological thermotolerance in explaining resistance to extreme temperatures. Furthermore it highlights that there is a danger to studying physiological thermotolerance in isolation when ascertaining risks of ectotherm invasions, the establishment potential of exotic species in glasshouses, or predicting species impacts under climate change scenarios.

Diffusion anisotropy of poor metal solute atoms in hcp-Ti

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scotti, Lucia, E-mail: lxs234@bham.ac.uk; Mottura, Alessandro, E-mail: a.mottura@bham.ac.uk

2015-05-28

Atom migration mechanisms influence a wide range of phenomena: solidification kinetics, phase equilibria, oxidation kinetics, precipitation of phases, and high-temperature deformation. In particular, solute diffusion mechanisms in α-Ti alloys can help explain their excellent high-temperature behaviour. The purpose of this work is to study self- and solute diffusion in hexagonal close-packed (hcp)-Ti, and its anisotropy, from first-principles using the 8-frequency model. The calculated diffusion coefficients show that diffusion energy barriers depend more on bonding characteristics of the solute rather than the size misfit with the host, while the extreme diffusion anisotropy of some solute elements in hcp-Ti is a resultmore » of the bond angle distortion.« less

Blue phase liquid crystal phase transition for cyano compound chiral nematic liquid crystal mixtures with three two-ring core structures and chiral dopant concentrations

NASA Astrophysics Data System (ADS)

Shin, Jaesun; Kim, Beomjong; Jung, Wansu; Fahad, Mateen; Park, SangJin; Hong, Sung-Kyu

2017-05-01

Blue phase (BP) temperature range of a chiral nematic liquid crystal (LC) mixture is dependent upon the host nematic LC chemical structure and chiral dopant concentration. In this study, we investigated BP phase transition behaviour and helical twisting power (HTP) using three chiral dopant concentrations of cyano compound chiral nematic LC mixtures incorporating three two-ring core structures in the host nematic LCs. The effect of the host nematic LC core structure, HTP and chiral dopant concentrations were considered on BP temperature ranges, for two types of complete BPI and BPII without isotropic phase (Iso) and two types of coexistence state of BPI+Iso and BPII+Iso.

The Drosophila TRPA1 Channel and Neuronal Circuits Controlling Rhythmic Behaviours and Sleep in Response to Environmental Temperature.

PubMed

Roessingh, Sanne; Stanewsky, Ralf

2017-10-03

trpA1 encodes a thermosensitive transient receptor potential channel (TRP channel) that functions in selection of preferred temperatures and noxious heat avoidance. In this review, we discuss the evidence for a role of TRPA1 in the control of rhythmic behaviours in Drosophila melanogaster . Activity levels during the afternoon and rhythmic temperature preference are both regulated by TRPA1. In contrast, TRPA1 is dispensable for temperature synchronisation of circadian clocks. We discuss the neuronal basis of TRPA1-mediated temperature effects on rhythmic behaviours, and conclude that they are mediated by partly overlapping but distinct neuronal circuits. We have previously shown that TRPA1 is required to maintain siesta sleep under warm temperature cycles. Here, we present new data investigating the neuronal circuit responsible for this regulation. First, we discuss the difficulties that remain in identifying the responsible neurons. Second, we discuss the role of clock neurons (s-LNv/DN1 network) in temperature-driven regulation of siesta sleep, and highlight the role of TRPA1 therein. Finally, we discuss the sexual dimorphic nature of siesta sleep and propose that the s-LNv/DN1 clock network could play a role in the integration of environmental information, mating status and other internal drives, to appropriately drive adaptive sleep/wake behaviour.

Electrical conductivity and dielectric properties of TlInS2 single crystals

NASA Astrophysics Data System (ADS)

El-Nahass, M. M.; Youssef, S. B.; Ali, H. A. M.; Hassan, A.

2011-07-01

TlInS2 single crystals were grown by using Bridgman-Stockbauer technique. Measurements of DC conductivity were carried out in parallel (σ//) and perpendicular (σ⊥) directions to the c-axis over a temperature range from 303 to 463 K. The anisotropic behaviour of the electrical conductivity was also detected. AC conductivity and dielectric measurements were studied as a function of both frequency (102-106 Hz) and temperature (297-375 K). The frequency dependence of the AC conductivity revealed that σac(ω) obeys the universal law: σac(ω) = Aωs. The mechanism of the ac charge transport across the layers of TlInS2 single crystals was referred to the hopping over localized states near the Fermi level in the frequency range >3.5 × 103 Hz. The temperature dependence of σac(ω) for TlInS2 showed that σac is thermally activated process. Both of ɛ1 and ɛ2 decrease by increasing frequency and increase by increasing temperature. Some parameters were calculated as: the density of localized states near the Fermi level NF = 1.5 × 1020 eV-1 cm-3, the average time of charge carrier hoping between localized states τ = 3.79 μs and the average hopping distance R = 6.07 nm.

Growth of raspberry-, prism- and flower-like ZnO particles using template-free low-temperature hydrothermal method and their application as humidity sensors

NASA Astrophysics Data System (ADS)

Pál, Edit; Hornok, Viktória; Kun, Robert; Chernyshev, Vladimir; Seemann, Torben; Dékány, Imre; Busse, Matthias

2012-08-01

Zinc oxide particles with different morphologies were prepared by hydrothermal method at 60-90 °C. The structure formation was controlled by the addition rate and temperature of hydrolyzing agent, while the particles size (10 nm-2.5 μm) was influenced by the preparation (hydrothermal) temperature. Scanning electron microscopy studies showed that raspberry-, prism- and flower-like ZnO particles were prepared, whose average size decreased with increasing reaction temperature. X-ray diffraction investigations confirmed that ZnO particles with hexagonal crystal structure formed in all syntheses. The raspberry-, prism- and flower-like ZnO particles showed a weak UV-emission in the range of 390-395 nm and strong visible emission with a maximum at 586, 593 and 598 nm, respectively. Morphology effect on electrical and water vapour sensing properties of ZnO samples was investigated by impedance spectroscopy and quartz crystal microbalance, respectively. The absolute impedance of raspberry-, prism- and flower-like ZnO particles was found to be strong dependent on the morphology. Space-charge-limited conductivity transport mechanism was proved by the oscillatory behaviour of impedance. Humidity sensor tests also revealed morphology and specific surface area dependency on the sensitivity and water vapour adsorption property.

First-principles investigations into the thermodynamics of cation disorder and its impact on electronic structure and magnetic properties of spinel Co(Cr1-x Mn x )2O4

NASA Astrophysics Data System (ADS)

Das, Debashish; Ghosh, Subhradip

2017-02-01

Cation disorder over different crystallographic sites in spinel oxides is known to affect their properties. Recent experiments on Mn doped multiferroic \\text{CoC}{{\\text{r}}2}{{\\text{O}}4} indicate that a possible distribution of Mn atoms among tetrahedrally and octahedrally coordinated sites in the spinel lattice give rise to different variations in the structural parameters and saturation magnetisations in different concentration regimes of Mn atoms substituting the Cr. A composition dependent magnetic compensation behaviour points to the role conversions of the magnetic constituents. In this work, we have investigated the thermodynamics of cation disorder in \\text{Co}{{≤ft(\\text{C}{{\\text{r}}1-x}\\text{M}{{\\text{n}}x}\\right)}2}{{\\text{O}}4} system and its consequences on the structural, electronic and magnetic properties, using results from first-principles electronic structure calculations. We have computed the variations in the cation-disorder as a function of Mn concentration and the temperature and found that at the annealing temperature of the experiment many of the systems exhibit cation disorder. Our results support the interpretations of the experimental results regarding the qualitative variations in the sub-lattice occupancies and the associated magnetisation behaviour, with composition. We have analysed the variations in structural, magnetic and electronic properties of this system with variations in the compositions and the degree of cation disorder from the variations in their electronic structures and by using the ideas from crystal field theory. Our study provides a complete microscopic picture of the effects that are responsible for composition dependent behavioural differences of the properties of this system. This work lays down a general framework, based upon results from first-principles calculations, to understand and analyse the substitutional magnetic spinel oxides A{{≤ft({{B}1-x}{{C}x}\\right)}2}{{\\text{O}}4} in presence of cation disorder.

Interfacial coupling in multiferroic BiFeO3 and ferromagnetic La2/3Sr1/3MnO3 thin films

NASA Astrophysics Data System (ADS)

Dominguez, C.; E Ordoñez, J.; E Gomez, M.

2017-12-01

Antiferromagnetic/Ferromagnetic coupling mechanics have been studying by growing successfully BiFeO3/La2/3Sr1/3MnO3 bilayers on SrTiO3 single crystals by using rf and dc sputtering technique at pure oxygen pressures. We have investigated the magnetic behaviour of this samples, field cooling loops evidence interfacial coupling effect when antiferromagnetic ferroelectric BiFeO3 is placed in contact with ferromagnetic La2/3Sr1/3MnO3 indicate by the shift of the magnetization loop to negative values of the applied magnetic field. Our samples exhibited an exchange bias of 76Oe at 5K after field cooling the sample under 5000Oe. Temperature dependence of the exchange bias field showed exponential decay. The BFO/LSMO bilayer exhibits excellent ferroelectric behaviour (Ps=65μC/cm2 at 4V and 100Hz). Coexistence of ferroelectric and ferromagnetic properties in the BFO/LSMO bilayer make it a promising candidate system for applications where the magnetoelectric behaviour is required.

AC electrical characterisation and insight to charge transfer mechanisms in DNA molecular wires through temperature and UV effects.

PubMed

Kassegne, Sam; Wibowo, Denni; Chi, James; Ramesh, Varsha; Narenji, Alaleh; Khosla, Ajit; Mokili, John

2015-06-01

In this study, AC characterisation of DNA molecular wires, effects of frequency, temperature and UV irradiation on their conductivity is presented. λ-DNA molecular wires suspended between high aspect-ratio electrodes exhibit highly frequency-dependent conductivity that approaches metal-like behaviour at high frequencies (∼MHz). Detailed temperature dependence experiments were performed that traced the impedance response of λ-DNA until its denaturation. UV irradiation experiments where conductivity was lost at higher and longer UV exposures helped to establish that it is indeed λ-DNA molecular wires that generate conductivity. The subsequent renaturation of λ-DNA resulted in the recovery of current conduction, providing yet another proof of the conducting DNA molecular wire bridge. The temperature results also revealed hysteretic and bi-modal impedance responses that could make DNA a candidate for nanoelectronics components like thermal transistors and switches. Further, these experiments shed light on the charge transfer mechanism in DNA. At higher temperatures, the expected increase in thermal-induced charge hopping may account for the decrease in impedance supporting the 'charge hopping mechanism' theory. UV light, on the other hand, causes damage to GC base-pairs and phosphate groups reducing the path available both for hopping and short-range tunneling mechanisms, and hence increasing impedance--this again supporting both the 'charge hopping' and 'tunneling' mechanism theories.

Deeply torpid bats can change position without elevation of body temperature.

PubMed

Bartonička, Tomáš; Bandouchova, Hana; Berková, Hana; Blažek, Ján; Lučan, Radek; Horáček, Ivan; Martínková, Natália; Pikula, Jiri; Řehák, Zdeněk; Zukal, Jan

2017-01-01

Because body temperature is tightly coupled to physiological function, hibernating animals entering deep torpor are typically immobile. We analysed thermal behaviour and locomotory activity of hibernating greater mouse-eared bats Myotis myotis and found two types of movement behaviour related to body temperature, i.e. movement at high fur temperature and at low fur temperatures (Tflow; <5°C). First Tflow movements appeared at the beginning of March and often occurred during long torpor bouts. In most cases, Tflow events represented slow displacements between clusters of bats. In several cases, however, departure or arrivals from and into clusters was also recorded without any elevation in body temperature. Distance travelled, flight duration and speed of locomotion during Tflow events was lower than in high fur temperature events. Such behaviour could allow bats to save energy long-term and prolong torpor bouts. Tflow movement in torpid bats significantly changes our understanding of basic hibernation principles and we strongly recommend further studies on the subject. Copyright © 2016. Published by Elsevier Ltd.

Shell colour, temperature, (micro)habitat structure and predator pressure affect the behaviour of Cepaea nemoralis

NASA Astrophysics Data System (ADS)

Rosin, Zuzanna M.; Kwieciński, Zbigniew; Lesicki, Andrzej; Skórka, Piotr; Kobak, Jarosław; Szymańska, Anna; Osiejuk, Tomasz S.; Kałuski, Tomasz; Jaskulska, Monika; Tryjanowski, Piotr

2018-06-01

Although shell colour polymorphism of the land snail Cepaea nemoralis is a well-known phenomenon, proximate and ultimate factors driving its evolution remain uncertain. Polymorphic species show variation in behavioural responses to selective forces. Therefore, we estimated effects of various environmental factors (temperature, humidity, food availability, (micro)habitat structure and predatory pressure) on behavioural response (frequency of locomotion, climbing and hiding) of C. nemoralis morphs, in experimental and natural conditions. In the experimental part of study, the frequency of locomotion was negatively affected by temperature and the presence of food and positively influenced by the presence of light. Morphs significantly differed in behavioural responses to environmental variability. Pink mid-banded and yellow five-banded morphs climbed less often and hide in shelter more often than yellow and pink unbanded individuals when temperature was low and food was absent. Snails fed most often at moderate temperature compared to low and high temperatures. Field investigations partially confirmed differences among morphs in frequency of climbing, but not in terms of probability of hiding in sheltered sites. In natural colonies, temperature and (micro)habitat structure significantly affected frequency of climbing as well as hiding in shelter. Snails more often hid in sheltered sites where thrushes preyed on Cepaea. Tendency of unbanded morphs to climb trees may have evolved under avian predatory pressure as thrushes forage on a ground. Tendency of banded morphs to hide in sheltered sites may reflect prey preferences for cryptic background. The results implicate that differential behaviour of C. nemoralis morphs compensate for their morphological and physiological limitations of adaptation to habitat.

Shell colour, temperature, (micro)habitat structure and predator pressure affect the behaviour of Cepaea nemoralis.

PubMed

Rosin, Zuzanna M; Kwieciński, Zbigniew; Lesicki, Andrzej; Skórka, Piotr; Kobak, Jarosław; Szymańska, Anna; Osiejuk, Tomasz S; Kałuski, Tomasz; Jaskulska, Monika; Tryjanowski, Piotr

2018-05-09

Although shell colour polymorphism of the land snail Cepaea nemoralis is a well-known phenomenon, proximate and ultimate factors driving its evolution remain uncertain. Polymorphic species show variation in behavioural responses to selective forces. Therefore, we estimated effects of various environmental factors (temperature, humidity, food availability, (micro)habitat structure and predatory pressure) on behavioural response (frequency of locomotion, climbing and hiding) of C. nemoralis morphs, in experimental and natural conditions. In the experimental part of study, the frequency of locomotion was negatively affected by temperature and the presence of food and positively influenced by the presence of light. Morphs significantly differed in behavioural responses to environmental variability. Pink mid-banded and yellow five-banded morphs climbed less often and hide in shelter more often than yellow and pink unbanded individuals when temperature was low and food was absent. Snails fed most often at moderate temperature compared to low and high temperatures. Field investigations partially confirmed differences among morphs in frequency of climbing, but not in terms of probability of hiding in sheltered sites. In natural colonies, temperature and (micro)habitat structure significantly affected frequency of climbing as well as hiding in shelter. Snails more often hid in sheltered sites where thrushes preyed on Cepaea. Tendency of unbanded morphs to climb trees may have evolved under avian predatory pressure as thrushes forage on a ground. Tendency of banded morphs to hide in sheltered sites may reflect prey preferences for cryptic background. The results implicate that differential behaviour of C. nemoralis morphs compensate for their morphological and physiological limitations of adaptation to habitat.

Influence of temperature on patch residence time in parasitoids: physiological and behavioural mechanisms

NASA Astrophysics Data System (ADS)

Moiroux, Joffrey; Abram, Paul K.; Louâpre, Philippe; Barrette, Maryse; Brodeur, Jacques; Boivin, Guy

2016-04-01

Patch time allocation has received much attention in the context of optimal foraging theory, including the effect of environmental variables. We investigated the direct role of temperature on patch time allocation by parasitoids through physiological and behavioural mechanisms and its indirect role via changes in sex allocation and behavioural defences of the hosts. We compared the influence of foraging temperature on patch residence time between an egg parasitoid, Trichogramma euproctidis, and an aphid parasitoid, Aphidius ervi. The latter attacks hosts that are able to actively defend themselves, and may thus indirectly influence patch time allocation of the parasitoid. Patch residence time decreased with an increase in temperature in both species. The increased activity levels with warming, as evidenced by the increase in walking speed, partially explained these variations, but other mechanisms were involved. In T. euproctidis, the ability to externally discriminate parasitised hosts decreased at low temperature, resulting in a longer patch residence time. Changes in sex allocation with temperature did not explain changes in patch time allocation in this species. For A. ervi, we observed that aphids frequently escaped at intermediate temperature and defended themselves aggressively at high temperature, but displayed few defence mechanisms at low temperature. These defensive behaviours resulted in a decreased patch residence time for the parasitoid and partly explained the fact that A. ervi remained for a shorter time at the intermediate and high temperatures than at the lowest temperature. Our results suggest that global warming may affect host-parasitoid interactions through complex mechanisms including both direct and indirect effects on parasitoid patch time allocation.

Factors that influence effective perioperative temperature management by anesthesiologists: a qualitative study using the Theoretical Domains Framework.

PubMed

Boet, Sylvain; Patey, Andrea M; Baron, Justine S; Mohamed, Karim; Pigford, Ashlee-Ann E; Bryson, Gregory L; Brehaut, Jamie C; Grimshaw, Jeremy M

2017-06-01

Inadvertent perioperative hypothermia (IPH) is associated with a range of adverse outcomes. Safe and effective warming techniques exist to prevent IPH; however, IPH remains common. This study aimed to identify factors that anesthesiologists perceive may influence temperature management during the perioperative period. After Research Ethics Board approval, semi-structured interviews were conducted with staff anesthesiologists at a Canadian academic hospital. An interview guide based on the Theoretical Domains Framework (TDF) was used to capture 14 theoretical domains that may influence temperature management. The interview transcripts were coded using direct content analysis to generate specific beliefs and to identify relevant TDF domains perceived to influence temperature management behaviour. Data saturation was achieved after 15 interviews. The following nine theoretical domains were identified as relevant to designing an intervention for practices in perioperative temperature management: knowledge, beliefs about capabilities, beliefs about consequences, reinforcement, memory/attention/decision-making, environmental context and resources, social/professional role/identity, social influences, and behavioural regulation. Potential target areas to improve temperature management practices include interventions that address information needs about individual temperature management behaviour as well as patient outcome (feedback), increasing awareness of possible temperature management strategies and guidelines, and a range of equipment and surgical team dynamics that influence temperature management. This study identified several potential target areas for future interventions from nine of the TDF behavioural domains that anesthesiologists perceive to drive their temperature management practices. Future interventions that aim to close the evidence-practice gap in perioperative temperature management may include these targets.

Larger corpus callosum and reduced orbitofrontal cortex homotopic connectivity in codeine cough syrup-dependent male adolescents and young adults.

PubMed

Qiu, Ying-Wei; Lv, Xiao-Fei; Jiang, Gui-Hua; Su, Huan-Huan; Ma, Xiao-Fen; Tian, Jun-Zhang; Zhuo, Fu-Zhen

2017-03-01

To characterize interhemispheric functional and anatomical connectivity and their relationships with impulsive behaviour in codeine-containing cough syrup (CCS)-dependent male adolescents and young adults. We compared volumes of corpus callosum (CC) and its five subregion and voxel-mirrored homotopic functional connectivity (VMHC) in 33 CCS-dependent male adolescents and young adults and 38 healthy controls, group-matched for age, education and smoking status. Barratt impulsiveness scale (BIS.11) was used to assess participant impulsive behaviour. Abnormal CC subregions and VMHC revealed by group comparison were extracted and correlated with impulsive behaviour and duration of CCS use. We found selective increased mid-posterior CC volume in CCS-dependent male adolescents and young adults and detected decreased homotopic interhemispheric functional connectivity of medial orbitofrontal cortex (OFC). Moreover, impairment of VMHC was associated with the impulsive behaviour and correlated with the duration of CCS abuse in CCS-dependent male adolescents and young adults. These findings reveal CC abnormalities and disruption of interhemispheric homotopic connectivity in CCS-dependent male adolescents and young adults, which provide a novel insight into the impact of interhemispheric disconnectivity on impulsive behaviour in substance addiction pathophysiology. • CCS-dependent individuals (patients) had selective increased volumes of mid-posterior corpus callosum • Patients had attenuated interhemispheric homotopic FC (VMHC) of bilateral orbitofrontal cortex • Impairment of VMHC correlated with impulsive behaviour in patients • Impairment of VMHC correlated with the CCS duration in patients.

High temperatures disrupt Artemia franciscana mating patterns and impact sexual selection intensity

NASA Astrophysics Data System (ADS)

Santos, Maria R.; Vieira, Natividade; Monteiro, Nuno M.

2018-07-01

Temperature plays a critical role in survival and reproduction, especially in ectotherms. Therefore, it is important to understand the mechanisms influencing life history traits and reproductive behaviours in order to predict climate change impacts on species' occurrence and performance. Here, we used the crustacean Artemia franciscana to investigate the potential impacts of temperature on life history traits, mating patterns and intensity of sexual selection. We reared A. franciscana at three temperatures 20 °C, 25 °C, and 30 °C and measured life history traits such as growth, mortality or development of sexual traits. Our observations confirmed a clear link between life history traits and temperature, with advanced sexual maturity and increased mortality rates following temperature rises. Also, we found that mating is size assortative close to the ideal developmental temperature. Nevertheless, when temperatures deviate from the optimum, mating patterns were altered. Although selection intensity for females remained similar at all tested temperatures, as males preferentially mated with the larger females, size assortative mating disappeared at the highest temperature. Overall, our results highlight the potential for a temperature-dependent disruption of A. franciscana mating patterns. This disruption is especially pronounced under high temperatures as reproduction becomes progressively more random, thus entailing a relaxation of sexual selection intensity.

Influence of traps on the deuterium behaviour in the low activation martensitic steels F82H and Batman

NASA Astrophysics Data System (ADS)

Serra, E.; Perujo, A.; Benamati, G.

1997-06-01

A time dependent permeation method is used to measure the permeability, diffusivity and solubility of deuterium in the low activation martensitic steels F82H and Batman. The measurements cover the temperature range from 373 to 743 K which includes the onset of deuterium trapping effects on diffusivity and solubility. The results are interpreted using a trapping model. The number of trap sites and their average energies for deuterium in F82H and Batman steels are determined.

Heisenberg spin-glass behaviour in Ga0.99Yb0.01FeO3

NASA Astrophysics Data System (ADS)

Neacsa, Daniela Maria; Gruener, Gisèle; Hebert, Sylvie; Soret, Jean-Claude

2017-06-01

The dynamic and static magnetic properties of Ga0.99Yb0.01FeO3 are studied in detail using ac susceptibility and dc magnetization measurements. The study shows that the compound undergoes a spin-glass freezing at Tg ≈ 213 K . The dynamic scaling analysis of ac susceptibility data reveals typical features characteristic of canonical spin-glasses, i.e., relaxation time τ∗ ∼10-14 s , critical exponent νz = 4.1 ± 0.2 , and frequency sensitivity parameter δf ∼10-3 within three frequency decades. The analysis of the critical behaviour of the static nonlinear susceptibility yields the critical exponents γ = 4.3 ± 0.1, β = 1.0 ± 0.1 , and δ = 5.5 ± 0.5 , which lie between those typical of three-dimensional (3D) weakly anisotropic Heisenberg and Ising spin glasses. The analysis of the field-cooled and zero-field-cooled magnetization data allows to define two characteristic temperatures depending on the applied magnetic field. The upper one, Tirr(H) , is the threshold temperature corresponding to the appearance of weak irreversibility, whereas the lower one, Ts(H) , marks the onset of strong irreversibility. The resulting field-temperature phase diagram turns out to be in good quantitative agreement with the mean-field predictions for 3D Heisenberg spin-glass with random magnetic anisotropy, and appears consistent with the chiral driven freezing scenario.

Survival of Verwey transition in gadolinium-doped ultrasmall magnetite nanoparticles.

PubMed

Yeo, Sunmog; Choi, Hyunkyung; Kim, Chul Sung; Lee, Gyeong Tae; Seo, Jeong Hyun; Cha, Hyung Joon; Park, Jeong Chan

2017-09-28

We have demonstrated that the Verwey transition, which is highly sensitive to impurities, survives in anisotropic Gd-doped magnetite nanoparticles. Transmission electron microscopy analysis shows that the nanoparticles are uniformly distributed. X-ray photoelectron spectroscopy and EDS mapping analysis confirm Gd-doping on the nanoparticles. The Verwey transition of the Gd-doped magnetite nanoparticles is robust and the temperature dependence of the magnetic moment (zero field cooling and field cooling) shows the same behaviour as that of the Verwey transition in bulk magnetite, at a lower transition temperature (∼110 K). In addition, irregularly shaped nanoparticles do not show the Verwey transition whereas square-shaped nanoparticles show the transition. Mössbauer spectral analysis shows that the slope of the magnetic hyperfine field and the electric quadrupole splitting change at the same temperature, meaning that the Verwey transition occurs at ∼110 K. These results would provide new insights into understanding the Verwey transition in nano-sized materials.

Intrinsic Josephson junction behaviour of the low Tc superconductor (LaSe) 1.14(NbSe 2)

NASA Astrophysics Data System (ADS)

Kačmarčík, J.; Szabó, P.; Samuely, P.; Rodrigo, J. G.; Suderow, H.; Vieira, S.; Lafond, A.; Meerschaut, A.

2008-04-01

Interlayer magnetotransport measurements on the highly anisotropic (LaSe)1.14(NbSe2) superconductor with Tc ∼ 1.2 K have indicated that this layered compound represents a model system of intrinsic Josephson junctions [P. Szabó et al., Phys. Rev. Lett. 86 (2001) 5990]. Scanning tunneling microscopy at room temperature and tunneling spectroscopy measurements at very low temperatures are presented in this work. STM imaging has revealed the presence of two types of surfaces which can be attributed to the appearance of LaSe or NbSe2 layers on the surface. The use of STM tip made of superconducting lead enabled a precise measurement of the temperature dependence of the superconducting energy gap Δ(T) on the NbSe2 layer. Δ(T) obtained from the surface sensitive STS data support the scenario obtained from our previous interlayer - ergo bulk sensitive magnetotransport measurements.

Hardness and wear analysis of Cu/Al2O3 composite for application in EDM electrode

NASA Astrophysics Data System (ADS)

Hussain, M. Z.; Khan, U.; Jangid, R.; Khan, S.

2018-02-01

Ceramic materials, like Aluminium Oxide (Al2O3), have high mechanical strength, high wear resistance, high temperature resistance and good chemical durability. Powder metallurgy processing is an adaptable method commonly used to fabricate composites because it is a simple method of composite preparation and has high efficiency in dispersing fine ceramic particles. In this research copper and novel material aluminium oxide/copper (Al2O3/Cu) composite has been fabricated for the application of electrode in Electro-Discharge Machine (EDM) using powder metallurgy technique. Al2O3 particles with different weight percentages (0, 1%, 3% and 5%) were reinforced into copper matrix using powder metallurgy technique. The powders were blended and compacted at a load of 100MPa to produce green compacts and sintered at a temperature of 574 °C. The effect of aluminium oxide content on mass density, Rockwell hardness and wear behaviour were investigated. Wear behaviour of the composites was investigated on Die-Sink EDM (Electro-Discharge Machine). It was found that wear rate is highly depending on hardness, mass density and green protective carbonate layer formation at the surface of the composite.

Statistical thermodynamics of aligned rigid rods with attractive lateral interactions: Theory and Monte Carlo simulations

NASA Astrophysics Data System (ADS)

dos Santos, G. J.; Linares, D. H.; Ramirez-Pastor, A. J.

2018-04-01

The phase behaviour of aligned rigid rods of length k (k-mers) adsorbed on two-dimensional square lattices has been studied by Monte Carlo (MC) simulations and histogram reweighting technique. The k-mers, containing k identical units (each one occupying a lattice site) were deposited along one of the directions of the lattice. In addition, attractive lateral interactions were considered. The methodology was applied, particularly, to the study of the critical point of the condensation transition occurring in the system. The process was monitored by following the fourth order Binder cumulant as a function of temperature for different lattice sizes. The results, obtained for k ranging from 2 to 7, show that: (i) the transition coverage exhibits a decreasing behaviour when it is plotted as a function of the k-mer size and (ii) the transition temperature, Tc, exhibits a power law dependence on k, Tc ∼k 0 , 4, shifting to higher values as k increases. Comparisons with an analytical model based on a generalization of the Bragg-Williams approximation (BWA) were performed in order to support the simulation technique. A significant qualitative agreement was obtained between BWA and MC results.

On the molecular origin of the cooperative coil-to-globule transition of poly(N-isopropylacrylamide) in water† †Electronic supplementary information (ESI) available: Stereochemistry and initial conformation of PNIPAM 30-mer; pair distribution functions of PNIPAM methyl groups; average time of transitions of dihedral angles; distribution of methyl dihedral angles; temperature dependence of average number of hydration water molecules; correlation between hydrogen bonding of water molecules per repeating unit in the FHS and end to end distance and correlation between PNIPAM–water hydrogen bonding and end to end distance. Time evolution of PNIPAM with the first hydration shell: movie FHSpnipam.avi. See DOI: 10.1039/c8cp00537k

PubMed Central

Zaccarelli, E.

2018-01-01

By means of atomistic molecular dynamics simulations we investigate the behaviour of poly(N-isopropylacrylamide), PNIPAM, in water at temperatures below and above the lower critical solution temperature (LCST), including the undercooled regime. The transition between water soluble and insoluble states at the LCST is described as a cooperative process involving an intramolecular coil-to-globule transition preceding the aggregation of chains and the polymer precipitation. In this work we investigate the molecular origin of such cooperativity and the evolution of the hydration pattern in the undercooled polymer solution. The solution behaviour of an atactic 30-mer at high dilution is studied in the temperature interval from 243 to 323 K with a favourable comparison to available experimental data. In the water soluble states of PNIPAM we detect a correlation between polymer segmental dynamics and diffusion motion of bound water, occurring with the same activation energy. Simulation results show that below the coil-to-globule transition temperature PNIPAM is surrounded by a network of hydrogen bonded water molecules and that the cooperativity arises from the structuring of water clusters in proximity to hydrophobic groups. Differently, the perturbation of the hydrogen bond pattern involving water and amide groups occurs above the transition temperature. Altogether these findings reveal that even above the LCST PNIPAM remains largely hydrated and that the coil-to-globule transition is related with a significant rearrangement of the solvent in the proximity of the surface of the polymer. The comparison between the hydrogen bonding of water in the surrounding of PNIPAM isopropyl groups and in the bulk displays a decreased structuring of solvent at the hydrophobic polymer–water interface across the transition temperature, as expected because of the topological extension along the chain of such interface. No evidence of an upper critical solution temperature behaviour, postulated in theoretical and thermodynamics studies of PNIPAM aqueous solution, is observed in the low temperature domain. PMID:29619464

Current-voltage characteristics of a cathodic plasma contactor with discharge chamber for application in electrodynamic tether propulsion

NASA Astrophysics Data System (ADS)

Xie, Kan; Martinez, Rafael A.; Williams, John D.

2014-04-01

This paper focuses on the net electron-emission current as a function of bias voltage of a plasma source that is being used as the cathodic element in a bare electrodynamic tether system. An analysis is made that enables an understanding of the basic issues determining the current-voltage (C-V) behaviour. This is important for the efficiency of the electrodynamic tether and for low impedance performance without relying on the properties of space plasma for varying orbital altitudes, inclinations, day-night cycles or the position of the plasma contactor relative to the wake of the spacecraft. The cathodic plasma contactor considered has a cylindrical discharge chamber (10 cm in diameter and ˜11 cm in length) and is driven by a hollow cathode. Experiments and a 1D spherical model are both used to study the contactor's C-V curves. The experiments demonstrate how the cathodic contactor would emit electrons into space for anode voltages in the range of 25-40 V, discharge currents in the range of 1-2.5 A, and low xenon gas flows of 2-4 sccm. Plasma properties are measured and compared with (3 A) and without net electron emission. A study of the dependence of relevant parameters found that the C-V behaviour strongly depends on electron temperature, initial ion energy and ion emission current at the contactor exit. However, it depended only weakly on ambient plasma density. The error in the developed model compared with the experimental C-V curves is within 5% at low electron-emission currents (0-2 A). The external ionization processes and high ion production rate caused by the discharge chamber, which dominate the C-V behaviour at electron-emission currents over 2 A, are further highlighted and discussed.

Local geology controlled the feasibility of vitrifying Iron Age buildings.

PubMed

Wadsworth, Fabian B; Heap, Michael J; Damby, David E; Hess, Kai-Uwe; Najorka, Jens; Vasseur, Jérémie; Fahrner, Dominik; Dingwell, Donald B

2017-01-12

During European prehistory, hilltop enclosures made from polydisperse particle-and-block stone walling were exposed to temperatures sufficient to partially melt the constituent stonework, leading to the preservation of glassy walls called 'vitrified forts'. During vitrification, the granular wall rocks partially melt, sinter viscously and densify, reducing inter-particle porosity. This process is strongly dependent on the solidus temperature, the particle sizes, the temperature-dependence of the viscosity of the evolving liquid phase, as well as the distribution and longevity of heat. Examination of the sintering behaviour of 45 European examples reveals that it is the raw building material that governs the vitrification efficiency. As Iron Age forts were commonly constructed from local stone, we conclude that local geology directly influenced the degree to which buildings were vitrified in the Iron Age. Additionally, we find that vitrification is accompanied by a bulk material strengthening of the aggregates of small sizes, and a partial weakening of larger blocks. We discuss these findings in the context of the debate surrounding the motive of the wall-builders. We conclude that if wall stability by bulk strengthening was the desired effect, then vitrification represents an Iron Age technology that failed to be effective in regions of refractory local geology.

Misoriented grain boundaries vicinal to the (1 1 1) <1 1¯0> twin in nickel Part I: Thermodynamics & temperature-dependent structure

DOE PAGES

O’Brien, Christopher J.; Medlin, Douglas L.; Foiles, Stephen M.

2016-03-30

Here, grain boundary-engineered materials are of immense interest for their corrosion resistance, fracture resistance and microstructural stability. This work contributes to a larger goal of understanding both the structure and thermodynamic properties of grain boundaries vicinal (within ±30°) to the Σ3(1 1 1) <1 1¯0> (coherent twin) boundary which is found in grain boundary-engineered materials. The misoriented boundaries vicinal to the twin show structural changes at elevated temperatures. In the case of nickel, this transition temperature is substantially below the melting point and at temperatures commonly reached during processing, making the existence of such boundaries very likely in applications. Thus,more » the thermodynamic stability of such features is thoroughly investigated in order to predict and fully understand the structure of boundaries vicinal to twins. Low misorientation angle grain boundaries (|θ| ≲ 16°) show distinct ±1/3(1 1 1) disconnections which accommodate misorientation in opposite senses. The two types of disconnection have differing low-temperature structures which show different temperature-dependent behaviours with one type undergoing a structural transition at approximately 600 K. At misorientation angles greater than approximately ±16°, the discrete disconnection nature is lost as the disconnections merge into one another. Free energy calculations demonstrate that these high-angle boundaries, which exhibit a transition from a planar to a faceted structure, are thermodynamically more stable in the faceted configuration.« less

Influence des conditions climatiques saisonnières sur quelques paramètres physiologiques dès boucs Créoles alimentés avec de l'ensilage de banane

NASA Astrophysics Data System (ADS)

Fauconneau, B.; Xande, A.

1986-06-01

Response of three groups of 12 male creole goats (weighing about 10 kg) to environmental variations was tested in Guadeloupe (French West Indies) respectively at three times in the year: end of humid season (October November), dry season (February March) and beginning of humid season (July August). Voluntary free intake of banana silage (silage of mixed green banana, bagassa, wheat bran and urea complemented with molasse) was not significantly affected by climatic variations. Three physiological parameters: rectal temperature, respiratory frequency and cardiac frequency were measured. These parameters were correlated with heat production dependent factors such as metabolic body weight, body weight gain and voluntary free intake. Rectal temperature increased all through the day until sunset and then decreased during the night. Both minimal rectal temperature and daily increase of rectal temperature were correlated with ambient temperature. Cardiac frequency increased during feeding. Generally cardiac frequency seemed to be correlated with activity of animals and so with behavioural response to environmental variations. Respiratory frequency was the most sensitive index of goat response to climate. The daily increase of respiratory frequency was important at the end of the humid season but was not observed in dry season. This increase was dependent on ambient temperature increase but also on air humidity characteristics and air velocity. These points are discussed according to integration of those physiological parameters in thermoregulation.

Driving force for indentation cracking in glass: composition, pressure and temperature dependence

PubMed Central

Rouxel, Tanguy

2015-01-01

The occurrence of damage at the surface of glass parts caused by sharp contact loading is a major issue for glass makers, suppliers and end-users. Yet, it is still a poorly understood problem from the viewpoints both of glass science and solid mechanics. Different microcracking patterns are observed at indentation sites depending on the glass composition and indentation cracks may form during both the loading and the unloading stages. Besides, we do not know much about the fracture toughness of glass and its composition dependence, so that setting a criterion for crack initiation and predicting the extent of the damage yet remain out of reach. In this study, by comparison of the behaviour of glasses from very different chemical systems and by identifying experimentally the individual contributions of the different rheological processes leading to the formation of the imprint—namely elasticity, densification and shear flow—we obtain a fairly straightforward prediction of the type and extent of the microcracks which will most likely form, depending on the physical properties of the glass. Finally, some guidelines to reduce the driving force for microcracking are proposed in the light of the effects of composition, temperature and pressure, and the areas for further research are briefly discussed. PMID:25713446

Persistence and long-term memories of daily maximum and minimum temperatures in southern South America

NASA Astrophysics Data System (ADS)

Naumann, Gustavo; Vargas, Walter M.; Minetti, Juan L.

2011-10-01

The persistence and long-term memories in daily maximum and minimum temperature series during the instrumental period in southern South America were analysed. Here, we found a markedly seasonal pattern both for short- and long-term memories that can lead to enhanced predictability on intraseasonal timescales. In addition, well-defined spatial patterns of these properties were found in the region. Throughout the entire region, the strongest dependence was observed in autumn and early winter. In the Patagonia region only, the temperatures exhibited more memory during the spring. In general, these elements indicate that nonlinear interactions exist between the annual cycles of temperature and its anomalies. Knowledge of the spatiotemporal behaviour of these long-term memories can be used in the building of stochastic models that only use persistence. It is possible to propose two objective forecast models based on linear interactions associated with persistence and one that allows for the use of information from nonlinear interactions that are manifested in the form of forerunners.

Probing transport mechanisms of BaFe₂As₂ superconducting films and grain boundary junctions by noise spectroscopy.

PubMed

Barone, C; Romeo, F; Pagano, S; Adamo, M; Nappi, C; Sarnelli, E; Kurth, F; Iida, K

2014-08-22

An important step forward for the understanding of high-temperature superconductivity has been the discovery of iron-based superconductors. Among these compounds, iron pnictides could be used for high-field magnet applications, resulting more advantageous over conventional superconductors, due to a high upper critical field as well as its low anisotropy at low temperatures. However, the principal obstacle in fabricating high quality superconducting wires and tapes is given by grain boundaries. In order to study these effects, the dc transport and voltage-noise properties of Co-doped BaFe₂As₂ superconducting films with artificial grain boundary junctions have been investigated. A specific procedure allows the separation of the film noise from that of the junction. While the former shows a standard 1/f behaviour, the latter is characterized by an unconventional temperature-dependent multi-Lorentzian voltage-spectral density. Moreover, below the film superconducting critical temperature, a peculiar noise spectrum is found for the grain boundary junction. Possible theoretical interpretation of these phenomena is proposed.

Temperature influence on the cladding mode distribution in highly localized point-by-point fibre Bragg gratings

NASA Astrophysics Data System (ADS)

Caucheteur, C.; Gonzalez-Vila, A.; Chikh-Bled, H.; Lasri, B.; Kinet, D.; Chah, K.

2016-05-01

An infrared femtosecond pulses laser is used to manufacture point-by-point gratings in telecommunication-grade optical fibres. The refractive index modulations are localized close to the core-cladding interface, yielding a strong coupling to cladding mode resonances together with an important photo-induced birefringence. Such gratings have been recently used for refractrometric measurements. In this work, their transmitted amplitude spectrum is measured with polarized light while they are exposed to temperature changes up to 900 °C. Despite an overall good thermal stability of the gratings that confirms their robustness for high-temperature refractometry, we report an interesting polarization effect depending on both the cladding mode resonance family (radially- and azimuthally-polarized modes) and mode order. While the birefringence of the core mode resonance decreases with the temperature, certain cladding mode resonances show an increase of the wavelength splitting between their orthogonally-polarized components. This differential behaviour can be of high interest to develop high-resolution multiparametric sensing platforms.

Temperature dependence of electrical properties of mixture of exogenous neurotransmitters dopamine and epinephrine

NASA Astrophysics Data System (ADS)

Patki, Mugdha; Patil, Vidya

2016-05-01

Neurotransmitters are chemical messengers that support the communication between the neurons. In vitro study of exogenous neurotransmitters Dopamine and Epinephrine and their mixture, carried out to learn about their electrical properties being dielectric constant and conductivity amongst others. Dielectric constant and conductivity of the selected neurotransmitters are found to increase with temperature. As a result, the time constant of the system increases with temperature. This change leads to increase in the time taken by the synapse to transport the action potential. The correlation between physical properties of exogenous neurotransmitters and psychological and physiological behaviour of human being may be understood with the help of current study. The response time of Epinephrine is in microseconds whereas response time of Dopamine is in milliseconds. The response time for both the neurotransmitters and their mixture is found to be increasing with temperature indicating the symptoms such as depression, apathy, chronic fatigue and low physical energy with no desire to exercise the body, which are observed during the fever.

Free volume study on the miscibility of PEEK/PEI blend using positron annihilation and dynamic mechanical thermal analysis

NASA Astrophysics Data System (ADS)

Ramani, R.; Alam, S.

2015-06-01

High performance polymer blend of poly(ether ether ketone) (PEEK) and poly(ether imide) (PEI) was examined for their free volume behaviour using positron annihilation lifetime spectroscopy and dynamic mechanical thermal analysis methods. The fractional free volume obtained from PALS shows a negative deviation from linear additivity rule implying good miscibility between PEEK and PEI. The dynamic modulus and loss tangent were obtained for the blends at three different frequencies 1, 10 and 100 Hz at temperatures close to and above their glass transition temperature. Applying Time-Temperature-Superposition (TTS) principle to the DMTA results, master curves were obtained at a reference temperature To and the WLF coefficients c01 and c02 were evaluated. Both the methods give similar results for the dependence of fractional free volume on PEI content in this blend. The results reveal that free volume plays an important role in determining the visco-elastic properties in miscible polymer blends.

High temperature tensile and creep behaviour of low pressure plasma-sprayed Ni-Co-Cr-Al-Y coating alloy

NASA Technical Reports Server (NTRS)

Hebsur, M. G.; Miner, R. V.

1986-01-01

The high temperature tensile and creep behavior of low pressure plasma-sprayed plates of a typical Ni-Co-Cr-Al-Y alloy has been studied. From room temperature to 800 K, the Ni-Co-Cr-Al-Y alloy studied has nearly a constant low ductility and a high strength. At higher temperatures, it becomes weak and highly ductile. At and above 1123 K, the behavior is highly dependent on strain rate and exhibits classic superplastic characteristics with a high ductility at intermediate strain rates and a strain rate sensitivity of about 0.5. At either higher or lower strain rates, the ductility decreases and the strain rate sensitivities are about 0.2. In the superplastic deformation range, the activation energy for creep is 120 + or - 20 kJ/mol, suggesting a diffusion-aided grain boundary sliding mechanism. Outside the superplastic range, the activation energy for creep is calculated to be 290 + or - 20 kJ/mol.

Temperature control of the ultra-short laser pulse compression in a one-dimensional photonic band gap structure with nematic liquid crystal as a defect layer

NASA Astrophysics Data System (ADS)

Shiri, Ramin; Safari, Ebrahim; Bananej, Alireza

2018-04-01

We investigate numerically the controllable chirped pulse compression in a one-dimensional photonic structure containing a nematic liquid crystal defect layer using the temperature dependent refractive index of the liquid crystal. We consider the structure under irradiation by near-infrared ultra-short laser pulses polarized parallel to the liquid crystal director at a normal angle of incidence. It is found that the dispersion behaviour and consequently the compression ability of the system can be changed in a controlled manner due to the variation in the defect temperature. When the temperature increased from 290 to 305 K, the transmitted pulse duration decreased from 75 to 42 fs in the middle of the structure, correspondingly. As a result, a novel low-loss tunable pulse compressor with a really compact size and high compression factor is achieved. The so-called transfer matrix method is utilized for numerical simulations of the band structure and reflection/transmission spectra of the structure under investigation.

Interfacial control of oxygen vacancy doping and electrical conduction in thin film oxide heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Veal, Boyd W.; Kim, Seong Keun; Zapol, Peter

2016-06-10

Oxygen vacancies in proximity to surfaces and heterointerfaces in oxide thin film heterostructures have major effects on properties, resulting, for example, in emergent conduction behaviour, large changes in metal-insulator transition temperatures or enhanced catalytic activity. Here we report the discovery of a means of reversibly controlling the oxygen vacancy concentration and distribution in oxide heterostructures consisting of electronically conducting In2O3 films grown on ionically conducting Y2O3-stabilized ZrO2 substrates. Oxygen ion redistribution across the heterointerface is induced using an applied electric field oriented in the plane of the interface, resulting in controlled oxygen vacancy (and hence electron) doping of the filmmore » and possible orders-of-magnitude enhancement of the film's electrical conduction. The reversible modified behaviour is dependent on interface properties and is attained without cation doping or changes in the gas environment.« less

Behaviour of implanted arsenic during rapid thermal annealing of Ti on Si

NASA Astrophysics Data System (ADS)

Ponpon, J. P.; Saulnier, A.; Stuck, R.

1987-11-01

The reaction during rapid thermal annealing of the Ti-Si couple with arsenic implanted either into titanium or into silicon has been investigated from the point of view of suicide formation kinetics and impurity redistribution. In contrast with similar experiments on other refractory metals, tungsten for example, the reaction is not blocked by the presence of arsenic but a temperature and dose dependent impurity effect leading to a lowering of the growth rate of the disilicide phase is observed. This has been attributed to arsenic segregation in the grain boundaries of the growing suicide which reduces the transport of silicon via easy diffusion paths towards the unreacted metal or a metal rich suicide phase. Arsenic, when present in the metal, has been found to produce the same effects as oxygen at the early beginning of the annealing. However, after the reaction has started the respective behaviour and influence of arsenic and oxygen become completely different.

Mechanical behaviour of Arabica coffee (Coffea arabica) beans under loading compression

NASA Astrophysics Data System (ADS)

Sigalingging, R.; Herak, D.; Kabutey, A.; Sigalingging, C.

2018-02-01

The uniformity of the product of the grinding process depends on various factors including the brittleness of the roasted coffee bean and it affects the extraction of soluble solids to obtain the coffee brew. Therefore, the reaching of a certain degree of brittleness is very important for the grinding to which coffee beans have to be subjected to before brewing. The aims of this study to show the mechanical behaviour of Arabica coffee beans from Tobasa (Indonesia) with roasted using different roasting time (40, 60 and 80 minutes at temperature 174 °C) under loading compression 225 kN. Universal compression testing machine was used with pressing vessel diameter 60 mm and compression speed 10 mm min-1 with different initial pressing height ranging from 20 to 60 mm. The results showed that significant correlation between roasting time and the brittleness.

Accelerated Post-Weld Natural Ageing in Ultrasonic Welding Aluminium 6111-T4 Automotive Sheet

NASA Astrophysics Data System (ADS)

Chen, Ying-Chun; Prangnell, Phil

In contrast to previously published reports, it is shown that there is an observable HAZ when ultrasonic spot welding (USW) automotive alloys, like AA6111-T4, the severity of which depends on the welding energy. Immediately after welding, softening is seen relative to the T4 condition, but this is rapidly recovered by natural ageing, which masks the presence of a HAZ, and the weld strength eventually exceeds that of the parent material. This behaviour is caused by dissolution of the solute clusters/GPZs in the T4 sheet, due to the high weld temperatures (> 400 °C), combined with accelerated post-weld natural ageing to a more advanced state than in the parent material. Modelling has demonstrated that this accelerated natural ageing behaviour can be attributed to an excess vacancy concentration generated by the USW process.

Untangling the roles of microclimate, behaviour and physiological polymorphism in governing vulnerability of intertidal snails to heat stress.

PubMed

Dong, Yun-Wei; Li, Xiao-Xu; Choi, Francis M P; Williams, Gray A; Somero, George N; Helmuth, Brian

2017-05-17

Biogeographic distributions are driven by cumulative effects of smaller scale processes. Thus, vulnerability of animals to thermal stress is the result of physiological sensitivities to body temperature ( T b ), microclimatic conditions, and behavioural thermoregulation. To understand interactions among these variables, we analysed the thermal tolerances of three species of intertidal snails from different latitudes along the Chinese coast, and estimated potential T b in different microhabitats at each site. We then empirically determined the temperatures at which heart rate decreased sharply with rising temperature (Arrhenius breakpoint temperature, ABT) and at which it fell to zero (flat line temperature, FLT) to calculate thermal safety margins (TSM). Regular exceedance of FLT in sun-exposed microhabitats, a lethal effect, was predicted for only one mid-latitude site. However, ABTs of some individuals were exceeded at sun-exposed microhabitats in most sites, suggesting physiological impairment for snails with poor behavioural thermoregulation and revealing inter-individual variations (physiological polymorphism) of thermal limits. An autocorrelation analysis of T b showed that predictability of extreme temperatures was lowest at the hottest sites, indicating that the effectiveness of behavioural thermoregulation is potentially lowest at these sites. These results illustrate the critical roles of mechanistic studies at small spatial scales when predicting effects of climate change. © 2017 The Author(s).

High-Temperature Creep Behaviour and Positive Effect on Straightening Deformation of Q345c Continuous Casting Slab

NASA Astrophysics Data System (ADS)

Guo, Long; Zhang, Xingzhong

2018-03-01

Mechanical and creep properties of Q345c continuous casting slab subjected to uniaxial tensile tests at high temperature were considered in this paper. The minimum creep strain rate and creep rupture life equations whose parameters are calculated by inverse-estimation using the regression analysis were derived based on experimental data. The minimum creep strain rate under constant stress increases with the increase of the temperature from 1000 °C to 1200 °C. A new casting machine curve with the aim of fully using high-temperature creep behaviour is proposed in this paper. The basic arc segment is cancelled in the new curve so that length of the straightening area can be extended and time of creep behaviour can be increased significantly. For the new casting machine curve, the maximum straightening strain rate at the slab surface is less than the minimum creep strain rate. So slab straightening deformation based on the steel creep behaviour at high temperature can be carried out in the process of Q345c steel continuous casting. The effect of creep property at high temperature on slab straightening deformation is positive. It is helpful for the design of new casting machine and improvement of old casting machine.

Untangling the roles of microclimate, behaviour and physiological polymorphism in governing vulnerability of intertidal snails to heat stress

PubMed Central

Li, Xiao-xu; Choi, Francis M. P.; Williams, Gray A.; Somero, George N.; Helmuth, Brian

2017-01-01

Biogeographic distributions are driven by cumulative effects of smaller scale processes. Thus, vulnerability of animals to thermal stress is the result of physiological sensitivities to body temperature (Tb), microclimatic conditions, and behavioural thermoregulation. To understand interactions among these variables, we analysed the thermal tolerances of three species of intertidal snails from different latitudes along the Chinese coast, and estimated potential Tb in different microhabitats at each site. We then empirically determined the temperatures at which heart rate decreased sharply with rising temperature (Arrhenius breakpoint temperature, ABT) and at which it fell to zero (flat line temperature, FLT) to calculate thermal safety margins (TSM). Regular exceedance of FLT in sun-exposed microhabitats, a lethal effect, was predicted for only one mid-latitude site. However, ABTs of some individuals were exceeded at sun-exposed microhabitats in most sites, suggesting physiological impairment for snails with poor behavioural thermoregulation and revealing inter-individual variations (physiological polymorphism) of thermal limits. An autocorrelation analysis of Tb showed that predictability of extreme temperatures was lowest at the hottest sites, indicating that the effectiveness of behavioural thermoregulation is potentially lowest at these sites. These results illustrate the critical roles of mechanistic studies at small spatial scales when predicting effects of climate change. PMID:28469014

The Drosophila TRPA1 Channel and Neuronal Circuits Controlling Rhythmic Behaviours and Sleep in Response to Environmental Temperature

PubMed Central

2017-01-01

trpA1 encodes a thermosensitive transient receptor potential channel (TRP channel) that functions in selection of preferred temperatures and noxious heat avoidance. In this review, we discuss the evidence for a role of TRPA1 in the control of rhythmic behaviours in Drosophila melanogaster. Activity levels during the afternoon and rhythmic temperature preference are both regulated by TRPA1. In contrast, TRPA1 is dispensable for temperature synchronisation of circadian clocks. We discuss the neuronal basis of TRPA1-mediated temperature effects on rhythmic behaviours, and conclude that they are mediated by partly overlapping but distinct neuronal circuits. We have previously shown that TRPA1 is required to maintain siesta sleep under warm temperature cycles. Here, we present new data investigating the neuronal circuit responsible for this regulation. First, we discuss the difficulties that remain in identifying the responsible neurons. Second, we discuss the role of clock neurons (s-LNv/DN1 network) in temperature-driven regulation of siesta sleep, and highlight the role of TRPA1 therein. Finally, we discuss the sexual dimorphic nature of siesta sleep and propose that the s-LNv/DN1 clock network could play a role in the integration of environmental information, mating status and other internal drives, to appropriately drive adaptive sleep/wake behaviour. PMID:28972543

Optimization of tribological behaviour on Al- coconut shell ash composite at elevated temperature

NASA Astrophysics Data System (ADS)

Siva Sankara Raju, R.; Panigrahi, M. K.; Ganguly, R. I.; Srinivasa Rao, G.

2018-02-01

In this study, determine the tribological behaviour of composite at elevated temperature i.e. 50 - 150 °C. The aluminium matrix composite (AMC) are prepared with compo casting route by volume of reinforcement of coconut shell ash (CSA) such as 5, 10 and 15%. Mechanical properties of composite has enhances with increasing volume of CSA. This study details to optimization of wear behaviour of composite at elevated temperatures. The influencing parameters such as temperature, sliding velocity and sliding distance are considered. The outcome response is wear rate (mm3/m) and coefficient of friction. The experiments are designed based on Taguchi [L9] array. All the experiments are considered as constant load of 10N. Analysis of variance (ANOVA) revealed that temperature is highest influencing factor followed by sliding velocity and sliding distance. Similarly, sliding velocity is most influencing factor followed by temperature and distance on coefficient of friction (COF). Finally, corroborates analytical and regression equation values by confirmation test.

Communally breeding bats use physiological and behavioural adjustments to optimise daily energy expenditure

NASA Astrophysics Data System (ADS)

Pretzlaff, Iris; Kerth, Gerald; Dausmann, Kathrin H.

2010-04-01

Small endotherms must change roosting and thermoregulatory behaviour in response to changes in ambient conditions if they are to achieve positive energy balance. In social species, for example many bats, energy expenditure is influenced by environmental conditions, such as ambient temperature, and also by social thermoregulation. Direct measurements of daily fluctuations in metabolic rates in response to ambient and behavioural variables in the field have not been technologically feasible until recently. During different reproductive periods, we investigated the relationships between ambient temperature, group size and energy expenditure in wild maternity colonies of Bechstein’s bats ( Myotis bechsteinii). Bats used behavioural and physiological adjustments to regulate energy expenditure. Whether bats maintained normothermia or used torpor, the number of bats in the roosts as well changed with reproductive status and ambient temperature. During pregnancy and lactation, bats remained mostly normothermic and daily group sizes were relatively large, presumably to participate in the energetic benefits of social thermoregulation. In contrast, smaller groups were formed on days when bats used torpor, which occurred mostly during the post-lactation period. Thus, we were able to demonstrate on wild animals under natural conditions the significance of behavioural and physiological flexibility for optimal thermoregulatory behaviour in small endotherms.

Thermal Detection Thresholds of Aδ- and C-Fibre Afferents Activated by Brief CO2 Laser Pulses Applied onto the Human Hairy Skin

PubMed Central

Churyukanov, Maxim; Plaghki, Léon; Legrain, Valéry; Mouraux, André

2012-01-01

Brief high-power laser pulses applied onto the hairy skin of the distal end of a limb generate a double sensation related to the activation of Aδ- and C-fibres, referred to as first and second pain. However, neurophysiological and behavioural responses related to the activation of C-fibres can be studied reliably only if the concomitant activation of Aδ-fibres is avoided. Here, using a novel CO2 laser stimulator able to deliver constant-temperature heat pulses through a feedback regulation of laser power by an online measurement of skin temperature at target site, combined with an adaptive staircase algorithm using reaction-time to distinguish between responses triggered by Aδ- and C-fibre input, we show that it is possible to estimate robustly and independently the thermal detection thresholds of Aδ-fibres (46.9±1.7°C) and C-fibres (39.8±1.7°C). Furthermore, we show that both thresholds are dependent on the skin temperature preceding and/or surrounding the test stimulus, indicating that the Aδ- and C-fibre afferents triggering the behavioural responses to brief laser pulses behave, at least partially, as detectors of a change in skin temperature rather than as pure level detectors. Most importantly, our results show that the difference in threshold between Aδ- and C-fibre afferents activated by brief laser pulses can be exploited to activate C-fibres selectively and reliably, provided that the rise in skin temperature generated by the laser stimulator is well-controlled. Our approach could constitute a tool to explore, in humans, the physiological and pathophysiological mechanisms involved in processing C- and Aδ-fibre input, respectively. PMID:22558230

Normal state transport studies of Bi2Sr2 Ca n-1CunOy thin films at different doping levels and manifestation of the pseudogap

NASA Astrophysics Data System (ADS)

Raffy, H.

2002-03-01

We have studied the evolution of the transport properties of Bi2Sr2 Ca n-1CunOy (n=1, 2) epitaxial thin films as function of doping p. For each phase, this was done on a single film by changing the oxygen content going from a maximally overdoped to a strongly underdoped non superconducting state(Z. Konstantinovic, Z.Z. Li and H. Raffy, Physica C 351, 163 (2001)). The behaviour of the resistance versus T and of the Hall effect will be described in the different regions of the phase diagram. In the underdoped region the pseudogap manifests itself on R(T) by a more rapid decrease or a reduction of the scattering rate below a temperature T*, representing an energy /temperature scale. It is observed that the resistivity curves can be scaled to a universal curve as a function of T/T*. Magnetoresistance measurements performed up to 20 Teslas do not show any significant change of this curve or of T*. The Hall constant RH(T) shows similar temperature dependence for both phases, with a broad maximum around 100K. The cotangent of the Hall angle can be described, above a temperature T0 (p), by a law of the form a+bT^m with 1.65

Adaptive capacity at the northern front: sockeye salmon behaviourally thermoregulate during novel exposure to warm temperatures

PubMed Central

Armstrong, Jonathan B.; Ward, Eric J.; Schindler, Daniel E.; Lisi, Peter J.

2016-01-01

As climate change increases maximal water temperatures, behavioural thermoregulation may be crucial for the persistence of coldwater fishes, such as salmonids. Although myriad studies have documented behavioural thermoregulation in southern populations of salmonids, few if any have explored this phenomenon in northern populations, which are less likely to have an evolutionary history of heat stress, yet are predicted to experience substantial warming. Here, we treated a rare heat wave as a natural experiment to test whether wild sockeye salmon (Oncorhynchus nerka) at the northern extent of their primary range (60° latitude) can thermoregulate in response to abnormally high thermal conditions. We tagged adult sockeye salmon with temperature loggers as they staged in a lake epilimnion prior to spawning in small cold streams (n = 40 recovered loggers). As lake surface temperatures warmed to physiologically suboptimal levels (15–20°C), sockeye salmon thermoregulated by moving to tributary plumes or the lake metalimnion. A regression of fish body temperature against lake surface temperature indicated that fish moved to cooler waters when the epilimnion temperature exceeded ~12°C. A bioenergetics model suggested that the observed behaviour reduced daily metabolic costs by as much as ~50% during the warmest conditions (18–20°C). These results provide rare evidence of cool-seeking thermoregulation at the poleward extent of a species range, emphasizing the potential ubiquity of maximal temperature constraints and the functional significance of thermal heterogeneity for buffering poikilotherms from climate change. PMID:27729980

Investigating Low Temperature Properties of Rubber Seals - 13020

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jaunich, M.; Wolff, D.; Stark, W.

To achieve the required tightness levels of containers for low and intermediate level radioactive wastes rubbers are widely applied as main sealing materials. The save encapsulation of the radioactive container contents has to be guaranteed according to legislation and appropriate guidelines for long storage periods as well as down to temperatures of -40 deg. C during transportation. Therefore the understanding of failure mechanisms that lead to leakage at low temperatures is of high importance. It is known that the material properties of rubbers are strongly influenced by temperature. At low temperatures this is caused by the rubber-glass transition (abbr. glassmore » transition). During continuous cooling the material changes from rubber-like entropy-elastic to stiff energy-elastic behaviour, that allows nearly no strain or retraction. Therefore, rubbers are normally used above their glass transition but the minimum working temperature limit is not defined precisely, what can cause problems during application. The temperature range where full functionality is possible is strongly dependent on the application conditions and the material. For this investigation mainly ethylene propylene diene (EPDM) and fluorocarbon rubbers (FKM) were selected as they are often used for radioactive waste containers. Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA) are typically used for the determination of the temperature range of the glass transition process. The standardized compression set measurement according to ISO 815 is common for investigation of rubber sealing materials as the test simulates the seal behaviour after release. To reduce the test time of the standard tests a faster technique giving the same information was developed. Additionally, the breakdown temperature of the sealing function of complete O-ring seals is measured in a component test setup to compare it with the results of the other tests. The experimental setup is capable of measuring the leakage rate at low temperatures by the pressure rise method. A model was developed that allows calculating the minimum working temperature limit of a seal by combining the results of the applied methods. (authors)« less

Linking models of human behaviour and climate alters projected climate change

DOE PAGES

Beckage, Brian; Gross, Louis J.; Lacasse, Katherine; ...

2018-01-01

Although not considered in climate models, perceived risk stemming from extreme climate events may induce behavioural changes that alter greenhouse gas emissions. Here, we link the C-ROADS climate model to a social model of behavioural change to examine how interactions between perceived risk and emissions behaviour influence projected climate change. Our coupled climate and social model resulted in a global temperature change ranging from 3.4–6.2 °C by 2100 compared with 4.9 °C for the C-ROADS model alone, and led to behavioural uncertainty that was of a similar magnitude to physical uncertainty (2.8 °C versus 3.5 °C). Model components with themore » largest influence on temperature were the functional form of response to extreme events, interaction of perceived behavioural control with perceived social norms, and behaviours leading to sustained emissions reductions. Lastly, our results suggest that policies emphasizing the appropriate attribution of extreme events to climate change and infrastructural mitigation may reduce climate change the most.« less

Linking models of human behaviour and climate alters projected climate change

NASA Astrophysics Data System (ADS)

Beckage, Brian; Gross, Louis J.; Lacasse, Katherine; Carr, Eric; Metcalf, Sara S.; Winter, Jonathan M.; Howe, Peter D.; Fefferman, Nina; Franck, Travis; Zia, Asim; Kinzig, Ann; Hoffman, Forrest M.

2018-01-01

Although not considered in climate models, perceived risk stemming from extreme climate events may induce behavioural changes that alter greenhouse gas emissions. Here, we link the C-ROADS climate model to a social model of behavioural change to examine how interactions between perceived risk and emissions behaviour influence projected climate change. Our coupled climate and social model resulted in a global temperature change ranging from 3.4-6.2 °C by 2100 compared with 4.9 °C for the C-ROADS model alone, and led to behavioural uncertainty that was of a similar magnitude to physical uncertainty (2.8 °C versus 3.5 °C). Model components with the largest influence on temperature were the functional form of response to extreme events, interaction of perceived behavioural control with perceived social norms, and behaviours leading to sustained emissions reductions. Our results suggest that policies emphasizing the appropriate attribution of extreme events to climate change and infrastructural mitigation may reduce climate change the most.

Linking models of human behaviour and climate alters projected climate change

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beckage, Brian; Gross, Louis J.; Lacasse, Katherine

Although not considered in climate models, perceived risk stemming from extreme climate events may induce behavioural changes that alter greenhouse gas emissions. Here, we link the C-ROADS climate model to a social model of behavioural change to examine how interactions between perceived risk and emissions behaviour influence projected climate change. Our coupled climate and social model resulted in a global temperature change ranging from 3.4–6.2 °C by 2100 compared with 4.9 °C for the C-ROADS model alone, and led to behavioural uncertainty that was of a similar magnitude to physical uncertainty (2.8 °C versus 3.5 °C). Model components with themore » largest influence on temperature were the functional form of response to extreme events, interaction of perceived behavioural control with perceived social norms, and behaviours leading to sustained emissions reductions. Lastly, our results suggest that policies emphasizing the appropriate attribution of extreme events to climate change and infrastructural mitigation may reduce climate change the most.« less

A quantum mechanical alternative to the Arrhenius equation in the interpretation of proton spin-lattice relaxation data for the methyl groups in solids.

PubMed

Bernatowicz, Piotr; Shkurenko, Aleksander; Osior, Agnieszka; Kamieński, Bohdan; Szymański, Sławomir

2015-11-21

The theory of nuclear spin-lattice relaxation in methyl groups in solids has been a recurring problem in nuclear magnetic resonance (NMR) spectroscopy. The current view is that, except for extreme cases of low torsional barriers where special quantum effects are at stake, the relaxation behaviour of the nuclear spins in methyl groups is controlled by thermally activated classical jumps of the methyl group between its three orientations. The temperature effects on the relaxation rates can be modelled by Arrhenius behaviour of the correlation time of the jump process. The entire variety of relaxation effects in protonated methyl groups have recently been given a consistent quantum mechanical explanation not invoking the jump model regardless of the temperature range. It exploits the damped quantum rotation (DQR) theory originally developed to describe NMR line shape effects for hindered methyl groups. In the DQR model, the incoherent dynamics of the methyl group include two quantum rate (i.e., coherence-damping) processes. For proton relaxation only one of these processes is relevant. In this paper, temperature-dependent proton spin-lattice relaxation data for the methyl groups in polycrystalline methyltriphenyl silane and methyltriphenyl germanium, both deuterated in aromatic positions, are reported and interpreted in terms of the DQR model. A comparison with the conventional approach exploiting the phenomenological Arrhenius equation is made. The present observations provide further indications that incoherent motions of molecular moieties in the condensed phase can retain quantum character over much broader temperature range than is commonly thought.

Cadmium and high temperature effects on brain and behaviour of Lymantria dispar L. caterpillars originating from polluted and less-polluted forests.

PubMed

Perić-Mataruga, Vesna; Petković, Branka; Ilijin, Larisa; Mrdaković, Marija; Dronjak Čučaković, Slađana; Todorović, Dajana; Vlahović, Milena

2017-10-01

Insects brain as a part of nervous system is the first-line of fast stress response that integrate stress signals to regulate all aspects of insect physiology and behaviour. The cadmium (Cd) bioaccumulation factor (BF), activity of the neurotoxicity biomarker acetylcholinesterase (AChE), dopamine content, expression and amount of Hsp70 in the brain and locomotor activity were evaluated in the 4th instar of Lymantria dispar L. caterpillars fed a Cd supplemented diet and reared in an optimal temperature regime (23 °C) and/or exposed to high temperature (28 °C). The insects originated from two forests, one close to "Nikola Tesla" thermoelectric power plant, Obrenovac (polluted population), and the other Kosmaj mountain (less-polluted population, far from any industrial region). The Cd BF was higher in the less-polluted than in the polluted population especially at the high ambient temperature. AChE activity and dopamine content were changed in the brains of L. dispar from both populations in the same manner. Hsp70 concentration in caterpillar brains showed opposite trends, a decrease in the less-polluted and an increase in the polluted population. Locomotor activity was modified in both Lymantria dispar populations, but the pattern of changes depended on the stressors and their combined effect. ACh activity and dopamine content are sensitive parameters to Cd exposure, regardless of pollutant experience, and might be promising biomarkers in monitoring forest ecosystems. Copyright © 2017 Elsevier Ltd. All rights reserved.

Ion-irradiation-induced damage of steels characterized by means of nanoindentation

NASA Astrophysics Data System (ADS)

Heintze, C.; Recknagel, C.; Bergner, F.; Hernández-Mayoral, M.; Kolitsch, A.

2009-05-01

Self-ion irradiation was used to simulate the damage caused by fast neutrons in the austenitic stainless steel SS 304 SA, the ferritic/martensitic steel Eurofer'97 and a Fe-9 at.%Cr model alloy. The irradiation-induced hardness change in the damage layer was evaluated by means of nanoindentation. Three-step irradiations were performed at room temperature and 300 °C up to 1 and 10 dpa. An irradiation-induced hardness change was shown for all materials. No influence of irradiation temperature could be resolved. Irradiation-induced hardening exhibits different fluence dependencies in Eurofer'97 and Fe-9 at.%Cr. While the data indicate a saturation-like behaviour for Fe-9 at.%Cr, an increase of hardness with fluence up to 10 dpa was found for Eurofer'97.

Superconductivity and anomalous normal state in the CePd 2Si 2/CeNi 2Ge 2 system

NASA Astrophysics Data System (ADS)

Grosche, F. M.; Lister, S. J. S.; Carter, F. V.; Saxena, S. S.; Haselwimmer, R. K. W.; Mathur, N. D.; Julian, S. R.; Lonzarich, G. G.

1997-02-01

The unconventional nonmagnetic metal CeNi 2Ge 2 is characterised at ambient pressure by temperature dependences of the specific heat and of the resistivity which deviate strongly from standard Fermi-liquid predictions and are reminiscent of the behaviour observed in its sibling system CePd 2Si 2 above the critical pressure at which magnetic order is suppressed. We have explored the CePd 2Si 2/CeNi 2Ge 2 phase diagram in a series of resistivity measurements under high hydrostatic pressure, p. At p > 15 kbar, a new superconducting transition appears below 220 mK in CeNi 2Ge 2 and shifts to higher temperatures with increasing pressure, reaching ≈400 mK at p ≈ 26 kbar.

Quantum interference magnetoconductance of polycrystalline germanium films in the variable-range hopping regime

NASA Astrophysics Data System (ADS)

Li, Zhaoguo; Peng, Liping; Zhang, Jicheng; Li, Jia; Zeng, Yong; Zhan, Zhiqiang; Wu, Weidong

2018-06-01

Direct evidence of quantum interference magnetotransport in polycrystalline germanium films in the variable-range hopping (VRH) regime is reported. The temperature dependence of the conductivity of germanium films fulfilled the Mott VRH mechanism with the form of ? in the low-temperature regime (?). For the magnetotransport behaviour of our germanium films in the VRH regime, a crossover, from negative magnetoconductance at the low-field to positive magnetoconductance at the high-field, is observed while the zero-field conductivity is higher than the critical value (?). In the regime of ?, the magnetoconductance is positive and quadratic in the field for some germanium films. These features are in agreement with the VRH magnetotransport theory based on the quantum interference effect among random paths in the hopping process.

A case study of the long-term retention of 137Cs after inhalation of high temperature reactor fuel element ash.

PubMed

Froning, M; Kozielewski, T; Schläger, M; Hill, P

2004-01-01

In 1987, a worker was internally contaminated with 137Cs as a result of an accident during the handling of high temperature reactor fuel element ash. In the long-term follow-up monitoring an unusual retention behaviour was found. The observed time dependence of caesium retention does not agree with the standard models of ICRP Publication 30. The present case can be better explained by assuming an intake of a mixture of type F and type S compounds. However, experimental data can be best described by a four-exponential retention function with two long-lived components, which was used as an ad hoc model for dose calculation. The resulting dose is compared with doses calculated on the basis of ICRP Publication 66.

Insight into Temperature Dependence of GTPase Activity in Human Guanylate Binding Protein-1

PubMed Central

Rahman, Safikur; Deep, Shashank; Sau, Apurba Kumar

2012-01-01

Interferon-γ induced human guanylate binding protein-1(hGBP1) belongs to a family of dynamin related large GTPases. Unlike all other GTPases, hGBP1 hydrolyzes GTP to a mixture of GDP and GMP with GMP being the major product at 37°C but GDP became significant when the hydrolysis reaction was carried out at 15°C. The hydrolysis reaction in hGBP1 is believed to involve with a number of catalytic steps. To investigate the effect of temperature in the product formation and on the different catalytic complexes of hGBP1, we carried out temperature dependent GTPase assays, mutational analysis, chemical and thermal denaturation studies. The Arrhenius plot for both GDP and GMP interestingly showed nonlinear behaviour, suggesting that the product formation from the GTP-bound enzyme complex is associated with at least more than one step. The negative activation energy for GDP formation and GTPase assay with external GDP together indicate that GDP formation occurs through the reversible dissociation of GDP-bound enzyme dimer to monomer, which further reversibly dissociates to give the product. Denaturation studies of different catalytic complexes show that unlike other complexes the free energy of GDP-bound hGBP1 decreases significantly at lower temperature. GDP formation is found to be dependent on the free energy of the GDP-bound enzyme complex. The decrease in the free energy of this complex at low temperature compared to at high is the reason for higher GDP formation at low temperature. Thermal denaturation studies also suggest that the difference in the free energy of the GTP-bound enzyme dimer compared to its monomer plays a crucial role in the product formation; higher stability favours GMP but lower favours GDP. Thus, this study provides the first thermodynamic insight into the effect of temperature in the product formation of hGBP1. PMID:22859948

High-Temperature Microindentation Tests on Olivine and Clinopyroxene

NASA Astrophysics Data System (ADS)

Dorner, D.; Schellewald, M.; Stöckhert, B.

2001-12-01

The perspectives of microindentation techniques for the investigation of the mechanical behaviour of minerals at high temperatures are explored. The technique offers the following advantages: (1) natural specimens with small grain size can be used, (2) preparation is simple, (3) a reasonable number of experiments can be performed within a short period of time. The strength of single crystals as a function of orientation and the activated glide systems are studied using scanning electron microscopy (SEM) combined with electron backscatter diffraction (EBSD) facilities. Furthermore, the effects of compositional variations on the flow strength of solid solutions are explored. The indentation hardness tests are performed on selected grains within natural polycrystalline aggregates. The surface of the specimen is polished mechanically and chemically. The orientation of the crystals is determined using EBSD. The indentation tests are performed with a diamond pyramid (Vickers indenter) at temperatures of 25 ° C to 900 ° C. Loading is done with a constant displacement rate up to a force of 0.5 N, followed by a creep period of 10 s at constant load. SEM is used to measure the size of the indents and to examine their morphology in detail. The microhardness obtained for olivine depends on crystal and indenter orientation and decreases slightly with temperature. Slip steps are observed on the surface around the indents. Their orientation with respect to the crystal orientation indicates that the predominant glide system activated in the indentation process is \\{110\\}[001]. The Schmid factors for this glide system correlate with the observed orientation dependence of the hardness. Indentation hardness of clinopyroxene solid solutions depends on composition with jadeite being stronger than diopside. This is inverse to what is expected for dislocation creep. The high yield stresses inferred from the hardness data and the weak dependence of hardness on temperature are consistent with plasticity being the deformation regime explored in indentation hardness tests.

The tell-tale: what do heart rate; skin temperature and skin conductance reveal about emotions of people with severe and profound intellectual disabilities?

PubMed

Vos, Pieter; De Cock, Paul; Munde, Vera; Petry, Katja; Van Den Noortgate, Wim; Maes, Bea

2012-01-01

Identifying emotions in people with severe and profound intellectual disabilities is a difficult challenge. Since self-reports are not available, behaviour is the most used source of information. Given the limitations and caveats associated with using behaviour as the sole source of information about their emotions, it is important to supplement behavioural information with information from another source. As it is accepted that emotions consist of language, behaviour and physiology, in this article we investigated if physiology could give information about the emotions of people with severe and profound intellectual disabilities. To this aim we tested hypotheses derived from the motivational model of Bradley, Codispoti, Cuthbert, and Lang (2001) about the relation between heart rate and the valence of emotions and between heart rate, skin conductance and skin temperature and behavioural expressions of emotions of people with severe and profound intellectual disability. We presented 27 participants with 4 staff-selected negative and 4 staff-selected positive stimuli. The situations were videotaped and their heart rate, skin conductance and skin temperature was measured. Each behaviour of the participant was coded using the observational method developed by Petry and Maes (2006). As hypothesized, we found a lower heart rate when participants were presented with negative stimuli than when they were presented with positive stimuli in the first 6s of stimuli presentation. Their skin temperature was higher for the expression of low intensity negative emotions compared to the expression of low intensity positive emotions. The results suggest that, as with people without disability, heart rate and skin temperature can give information about the emotions of persons with severe and profound ID. Copyright © 2012 Elsevier Ltd. All rights reserved.

Evolutionary stasis and lability in thermal physiology in a group of tropical lizards.

PubMed

Muñoz, Martha M; Stimola, Maureen A; Algar, Adam C; Conover, Asa; Rodriguez, Anthony J; Landestoy, Miguel A; Bakken, George S; Losos, Jonathan B

2014-03-07

Understanding how quickly physiological traits evolve is a topic of great interest, particularly in the context of how organisms can adapt in response to climate warming. Adjustment to novel thermal habitats may occur either through behavioural adjustments, physiological adaptation or both. Here, we test whether rates of evolution differ among physiological traits in the cybotoids, a clade of tropical Anolis lizards distributed in markedly different thermal environments on the Caribbean island of Hispaniola. We find that cold tolerance evolves considerably faster than heat tolerance, a difference that results because behavioural thermoregulation more effectively shields these organisms from selection on upper than lower temperature tolerances. Specifically, because lizards in very different environments behaviourally thermoregulate during the day to similar body temperatures, divergent selection on body temperature and heat tolerance is precluded, whereas night-time temperatures can only be partially buffered by behaviour, thereby exposing organisms to selection on cold tolerance. We discuss how exposure to selection on physiology influences divergence among tropical organisms and its implications for adaptive evolutionary response to climate warming.

Evolutionary stasis and lability in thermal physiology in a group of tropical lizards

PubMed Central

Muñoz, Martha M.; Stimola, Maureen A.; Algar, Adam C.; Conover, Asa; Rodriguez, Anthony J.; Landestoy, Miguel A.; Bakken, George S.; Losos, Jonathan B.

2014-01-01

Understanding how quickly physiological traits evolve is a topic of great interest, particularly in the context of how organisms can adapt in response to climate warming. Adjustment to novel thermal habitats may occur either through behavioural adjustments, physiological adaptation or both. Here, we test whether rates of evolution differ among physiological traits in the cybotoids, a clade of tropical Anolis lizards distributed in markedly different thermal environments on the Caribbean island of Hispaniola. We find that cold tolerance evolves considerably faster than heat tolerance, a difference that results because behavioural thermoregulation more effectively shields these organisms from selection on upper than lower temperature tolerances. Specifically, because lizards in very different environments behaviourally thermoregulate during the day to similar body temperatures, divergent selection on body temperature and heat tolerance is precluded, whereas night-time temperatures can only be partially buffered by behaviour, thereby exposing organisms to selection on cold tolerance. We discuss how exposure to selection on physiology influences divergence among tropical organisms and its implications for adaptive evolutionary response to climate warming. PMID:24430845

Adolescent-onset alcohol abuse exacerbates the influence of childhood conduct disorder on late adolescent and early adult antisocial behaviour.

PubMed

Howard, Richard; Finn, Peter; Jose, Paul; Gallagher, Jennifer

2011-12-16

This study tested the hypothesis that adolescent-onset alcohol abuse (AOAA) would both mediate and moderate the effect of childhood conduct disorder on antisocial behaviour in late adolescence and early adulthood. A sample comprising 504 young men and women strategically recruited from the community were grouped using the criteria of the Diagnostic and Statistical Manual (DSM-IV, American Psychiatric Association. (1994). Diagnostic and statistical manual of mental disorders (4th ed.). Washington, DC: APA), as follows: neither childhood conduct disorder (CCD) nor alcohol abuse/dependence; CCD but no alcohol abuse or dependence; alcohol abuse/dependence but no CCD; both CCD and alcohol abuse/dependence. The outcome measure was the sum of positive responses to 55 interview items capturing a variety of antisocial behaviours engaged in since age 15. Severity of lifetime alcohol-related and CCD problems served as predictor variables in regression analysis. Antisocial behaviour problems were greatest in individuals with a history of co-occurring conduct disorder (CD) and alcohol abuse/dependence. While CCD was strongly predictive of adult antisocial behaviour, this effect was both mediated and moderated (exacerbated) by AOAA.

Adolescent-onset alcohol abuse exacerbates the influence of childhood conduct disorder on late adolescent and early adult antisocial behaviour

PubMed Central

Howard, Richard; Finn, Peter; Jose, Paul; Gallagher, Jennifer

2012-01-01

This study tested the hypothesis that adolescent-onset alcohol abuse (AOAA) would both mediate and moderate the effect of childhood conduct disorder on antisocial behaviour in late adolescence and early adulthood. A sample comprising 504 young men and women strategically recruited from the community were grouped using the criteria of the Diagnostic and Statistical Manual (DSM-IV, American Psychiatric Association. (1994). Diagnostic and statistical manual of mental disorders (4th ed.). Washington, DC: APA), as follows: neither childhood conduct disorder (CCD) nor alcohol abuse/dependence; CCD but no alcohol abuse or dependence; alcohol abuse/dependence but no CCD; both CCD and alcohol abuse/dependence. The outcome measure was the sum of positive responses to 55 interview items capturing a variety of antisocial behaviours engaged in since age 15. Severity of lifetime alcohol-related and CCD problems served as predictor variables in regression analysis. Antisocial behaviour problems were greatest in individuals with a history of co-occurring conduct disorder (CD) and alcohol abuse/dependence. While CCD was strongly predictive of adult antisocial behaviour, this effect was both mediated and moderated (exacerbated) by AOAA. PMID:23459369

Handedness and lateralised tympanic membrane temperature in relation to approach-avoidance behaviour in Garnett's bushbaby (Otolemur garnettii).

PubMed

Hanbury, David B; Edens, Kyle D; Fontenot, M Babette; Greer, Tammy F; McCoy, John G; Watson, Sheree L

2013-01-01

Studies of handedness suggest a relationship between hemispheric specialisation and emotional processing. Recently measures of lateralised tympanic membrane temperature (TMT) have identified similar relationships (i.e., the left hemisphere is involved in approach behaviour and the right hemisphere avoidance behaviour). In the present study we examined lateralised changes in TMT in response to social interaction in 10 Garnett's bushbabies. Additionally, we examined whether handedness could be used as a predictor of approach-avoidance tendencies. We found a positive association between temperature change and both allogrooming and affiliative approach. Social behaviour did not differ between right- and left-handed bushbabies. These findings are discussed in terms of existing theories of asymmetric emotional processing. Overall, the data suggest that there is a left hemisphere specialisation for processing approach-related behaviours, which is consistent with existing models of lateralised emotional processing. Our data also indicate that TMT is a reliable, cost-effective measure of cerebral activation that is less invasive and more practical than alternative measures such as EEG, PET, and fMRI.

Differences in neurochemical profiles of two gadid species under ocean warming and acidification.

PubMed

Schmidt, Matthias; Windisch, Heidrun Sigrid; Ludwichowski, Kai-Uwe; Seegert, Sean Lando Levin; Pörtner, Hans-Otto; Storch, Daniela; Bock, Christian

2017-01-01

Exposure to future ocean acidification scenarios may alter the behaviour of marine teleosts through interference with neuroreceptor functioning. So far, most studies investigated effects of ocean acidification on the behaviour of fish, either isolated or in combination with environmental temperature. However, only few physiological studies on this issue were conducted despite the putative neurophysiological origin of the CO 2 -induced behavioural changes. Here, we present the metabolic consequences of long-term exposure to projected ocean acidification (396-548 μatm P CO 2 under control and 915-1272 μatm under treatment conditions) and parallel warming in the brain of two related fish species, polar cod ( Boreogadus saida , exposed to 0 °C, 3 °C, 6 °C and 8 °C) and Atlantic cod ( Gadus morhua , exposed to 3 °C, 8 °C, 12 °C and 16 °C). It has been shown that B. saida is behaviourally vulnerable to future ocean acidification scenarios, while G. morhua demonstrates behavioural resilience. We found that temperature alters brain osmolyte, amino acid, choline and neurotransmitter concentrations in both species indicating thermal responses particularly in osmoregulation and membrane structure. In B. saida, changes in amino acid and osmolyte metabolism at the highest temperature tested were also affected by CO 2 , possibly emphasizing energetic limitations. We did not observe changes in neurotransmitters, energy metabolites, membrane components or osmolytes that might serve as a compensatory mechanism against CO 2 induced behavioural impairments. In contrast to B. saida , such temperature limitation was not detected in G. morhua ; however, at 8 °C, CO 2 induced an increase in the levels of metabolites of the glutamate/GABA-glutamine cycle potentially indicating greater GABAergic activity in G.morhua . Further, increased availability of energy-rich substrates was detected under these conditions. Our results indicate a change of GABAergic metabolism in the nervous system of Gadus morhua close to the optimum of the temperature range. Since a former study showed that juvenile G. morhua might be slightly more behaviourally resilient to CO 2 at this respective temperature, we conclude that the observed change of GABAergic metabolism could be involved in counteracting OA induced behavioural changes. This may serve as a fitness advantage of this respective species compared to B. saida in a future warmer, more acidified polar ocean.

Validation of a biotelemetric technique, using ambulatory miniature black globe thermometers, to quantify thermoregulatory behaviour in ungulates.

PubMed

Hetem, Robyn S; Maloney, Shane K; Fuller, Andrea; Meyer, Leith C R; Mitchell, Duncan

2007-06-01

Behavioural thermoregulation is an animal's primary defence against changes in the thermal environment. We aimed to validate a remote technique to quantify the thermal environment behaviourally selected by free-ranging ungulates. First, we demonstrated that the temperature of miniature, 30 mm diameter, black globes (miniglobes) could be converted to standard, 150 mm diameter, black globe temperatures. Miniglobe temperature sensors subsequently were fitted to collars on three free-ranging ungulates, namely blue wildebeest (Connochaetes taurinus), impala (Aepyceros melampus) and horse (Equus caballus). Behavioural observations were reflected in animal miniglobe temperatures which differed from those recorded by an identical miniglobe on a nearby exposed weather station. The wildebeest often selected sites protected from the wind, whereas the impala and the horse sheltered from the sun. Nested analysis of variances revealed that the impala and horse selected significantly less variable environments than those recorded at the weather station (P<0.001) over a 20-min time interval, whereas, the microclimates selected by wildebeest tended to be more variable (P=0.08). Correlation of animal miniglobe against weather station miniglobe temperature resulted in regression slopes significantly less than one (P<0.001) for all species studied, implying that, overall, the animals selected cooler microclimates at high environmental heat loads and/or warmer microclimates at low environmental heat loads. We, therefore, have developed an ambulatory device, which can be attached to free-ranging animals, to remotely quantify thermoregulatory behaviour and selected microclimates. (c) 2007 Wiley-Liss, Inc.

Modeling FBG sensors sensitivity from cryogenic temperatures to room temperature as a function of metal coating thickness

NASA Astrophysics Data System (ADS)

Vendittozzi, Cristian; Felli, Ferdinando; Lupi, Carla

2018-05-01

Fiber optics with photo-imprinted Bragg grating have been studied in order to be used as temperature sensors in cryogenic applications. The main disadvantage presented by Fiber Bragg Grating (FBG) sensors is the significant drop in sensitivity as temperature decreases, mainly due to the critical lowering of the thermo-optic coefficient of the fiber and the very low thermal expansion coefficient (CTE) of fused silica at cryogenic temperatures. Thus, especially for the latter, it is important to enhance sensitivity to temperature by depositing a metal coating presenting higher CTE. In this work the thermal sensitivity of metal-coated FBG sensors has been evaluated by considering their elongation within temperature variations in the cryogenic range, as compared to bare fiber sensors. To this purpose, a theoretical model simulating elongation of metal-coated sensors has been developed. The model has been used to evaluate the behaviour of different metals which can be used as coating (Ni, Cu, Al, Zn, Pb and In). The optimal coating thickness has been calculated at different fixed temperature (from 5 K to 100 K) for each metal. It has been found that the metal coating effectiveness depends on thickness and operating temperature in accordance to our previous experimental work and theory suggest.

Comparison of kinetic and air temperatures in Budapest aiming applications in weather forecasting

NASA Astrophysics Data System (ADS)

Mika, Janos; Nemeth, Akos; Bela Olah, Andras; Dezso, Zsuzsanna

2010-05-01

Moderate Resolution Imaging Spectroradiometer (MODIS) based kinetic temperature data are compared with the surface air temperature data at the four weather stations in Budapest, Hun-gary. Dependence of these temperature characteristics on weather conditions, characterised by macrosynoptic types and by objective weather types, is in the focus of the study. Day- and night-time kinetic temperature series are used from the period 2001-2008. Four automatic stations are also used as the surface-based control variables. The four MODIS-pixels, covering one station, each, are the sites of our comparison. One of the four stations has strictly urban situation at the roof level in a strongly built-in region of Budapest. Another one, used as background rural station is at the east-west edge of the town with gar-dened environment. Two other stations are positioned near the river Danube at the northern and southern edges of Budapest, still under mezo-scale effect of the city. The number of elaborated hourly values is 4300-4400 above each pixel, depending on the cloudiness. At the four station automatic observations on air temperature, cloudiness (=0), relative humidity and wind-speed are observed in the hours of the MODIS observations. From these elements air temperature is used for comparison with the satellite-based kinetic temperature, and also as the main components of the Physiologically Equivalent Temperature (PET), de-rived to characterise usefulness of the kinetic temperature. Our first aim is to specify detailed relationship between the two temperatures consider-ing the seasonal and diurnal cycles and synoptic situation. This comparison is also performed by using the PET to establish which kind of temperature reminds this human bioclimatic in-dex better. If we could establish effective relationships with the synoptic situations (or weather types) we could use them in two further applications. The first one is the everyday forecasting of dangerous situations within the city on the days when the rural weather forecast claims about extreme temperature even at the rural sites. On summer hot days the weather-dependent UHI increases but on cold winter days decreases the risks on human health and technical equipments. The other scientific problem is whether the long-term season-dependent changes of the atmospheric circulation can modify the behaviour of the UHI even without fur-ther changes in the building in of the city. To answer this question the established relation-ships are combined with regional climate change projections of the circulation conditions.

Behavioural and Physiological Responses of Gammarus pulex Exposed to Cadmium and Arsenate at Three Temperatures: Individual and Combined Effects

PubMed Central

Vellinger, Céline; Felten, Vincent; Sornom, Pascal; Rousselle, Philippe; Beisel, Jean-Nicolas; Usseglio-Polatera, Philippe

2012-01-01

This study aimed at investigating both the individual and combined effects of cadmium (Cd) and arsenate (AsV) on the physiology and behaviour of the Crustacean Gammarus pulex at three temperatures (5, 10 and15°C). G. pulex was exposed during 96 h to (i) two [Cd] alone, (ii) two [AsV] alone, and (iii) four combinations of [Cd] and [AsV] to obtain a complete factorial plane. After exposure, survival, [AsV] or [Cd] in body tissues, behavioural (ventilatory and locomotor activities) and physiological responses (iono-regulation of [Na+] and [Cl−] in haemolymph) were examined. The interactive effects (antagonistic, additive or synergistic) of binary mixtures were evaluated for each tested temperature using a predictive model for the theoretically expected interactive effect of chemicals. In single metal exposure, both the internal metal concentration in body tissues and the mortality rate increased along metallic gradient concentration. Cd alone significantly impaired both [Na+] and [Cl−] while AsV alone had a weak impact only on [Cl−]. The behavioural responses of G. pulex declined with increasing metal concentration suggesting a reallocation of energy from behavioural responses to maintenance functions. The interaction between AsV and Cd was considered as ‘additive’ for all the tested binary mixtures and temperatures (except for the lowest combination at 10°C considered as “antagonistic”). In binary mixtures, the decrease in both ventilatory and locomotor activities and the decline in haemolymphatic [Cl−] were amplified when respectively compared to those observed with the same concentrations of AsV or Cd alone. However, the presence of AsV decreased the haemolymphatic [Na+] loss when G. pulex was exposed to the lowest Cd concentration. Finally, the observed physiological and behavioural effects (except ventilation) in G. pulex exposed to AsV and/or Cd were exacerbated under the highest temperature. The discussion encompasses both the toxicity mechanisms of these metals and their interaction with rising temperature. PMID:22761731

Sibutramine-induced anorexia: potent, dose-dependent and behaviourally-selective profile in male rats.

PubMed

Tallett, A J; Blundell, J E; Rodgers, R J

2009-03-17

The serotonin and noradrenaline reuptake inhibitor sibutramine has been licensed as an anti-obesity treatment for more than a decade. However, while inhibitory effects on food intake and weight gain are well documented, surprisingly little published detail exists regarding its influence on feeding and related behaviours. The present study was therefore designed to assess the effects of acute sibutramine treatment on food intake, the behavioural satiety sequence (BSS) and post-treatment weight gain. Subjects were 10 non-deprived adult male Lister hooded rats, tested with 0.5-3.0 mg/kg sibutramine hydrochloride during 1-h DVD-recorded test sessions with palatable mash. Our results show that sibutramine dose-dependently reduced food intake, an effect significant at all doses tested. Ethological analysis revealed very few behavioural effects, except for a dose-dependent reduction in time spent feeding and an increase in the frequency of resting. Behavioural specificity was further supported by time-bin analysis which confirmed both the structural integrity and dose-dependent acceleration of the BSS. Single dosing with sibutramine (3.0 mg/kg) also suppressed daily weight gain over the 24-72 h period post-dosing. Current data support the conclusion that the acute anorectic and weight loss efficacy of sibutramine in adult male rats is not secondary to behavioural disruption but, instead, is due largely to an acceleration in behavioural satiety.

Critical behaviour in DOPC/DPPC/cholesterol mixtures: static (2)H NMR line shapes near the critical point.

PubMed

Davis, James H; Schmidt, Miranda L

2014-05-06

Static (2)H NMR spectroscopy is used to study the critical behavior of mixtures of 1,2-dioleoyl-phosphatidylcholine/1,2-dipalmitoyl-phosphatidylcholine (DPPC)/cholesterol in molar proportion 37.5:37.5:25 using either chain perdeuterated DPPC-d62 or chain methyl deuterated DPPC-d6. The temperature dependence of the first moment of the (2)H spectrum of the sample made with DPPC-d62 and of the quadrupolar splittings of the chain-methyl-labeled DPPC-d6 sample are directly related to the temperature dependence of the critical order parameter η, which scales as [Formula: see text] near the critical temperature. Analysis of the data reveals that for the chain perdeuterated sample, the value of Tc is 301.51 ± 0.1 K, and that of the critical exponent, βc = 0.391 ± 0.02. The line shape analysis of the methyl labeled (d6) sample gives Tc = 303.74 ± 0.07 K and βc = 0.338 ± 0.009. These values obtained for βc are in good agreement with the predictions of a three-dimensional Ising model. The difference in critical temperature between the two samples having nominally the same molar composition arises because of the lowering of the phase transition temperature that occurs due to the perdeuteration of the DPPC. Copyright © 2014 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Superposed epoch analysis of vertical ion velocity, electron temperature, field-aligned current, and thermospheric wind in the dayside auroral region as observed by DMSP and CHAMP

NASA Astrophysics Data System (ADS)

Kervalishvili, G.; Lühr, H.

2016-12-01

This study reports on the results obtained by a superposed epoch analysis (SEA) method applied to the electron temperature, vertical ion velocity, field-aligned current (FAC), and thermospheric zonal wind velocity at high-latitudes in the Northern Hemisphere. The SEA study is performed in a magnetic latitude versus magnetic local time (MLat-MLT) frame. The obtained results are based on observations collected during the years 2001-2005 by the CHAMP and DMSP (F13 and F15) satellites. The dependence on interplanetary magnetic field (IMF) orientations is also investigated using data from the NASA/GSFC's OMNI database. Further, the obtained results are subdivided into three Lloyd seasons of 130 days each, which are defined as follows: local winter (1 January ± 65 days), combined equinoxes (1 April and 1 October ± 32days), and local summer (1 July ± 65 days). A period of 130 days is needed by the CHAMP satellite to pass through all local times. The time and location of the electron temperature peaks from CHAMP measurements near the cusp region are used as the reference parameter for the SEA method to investigate the relationship between the electron temperature and other ionospheric quantities. The SEA derived MLat profiles of the electron temperature show a seasonal dependence, increasing from winter to summer, as expected. But, the temperature rise (difference between the reference temperature peak and the background electron temperature) strongly decreases towards local summer. The SEA derived MLat profiles of the ion vertical velocity at DMSP altitude show the same seasonal behaviour as the electron temperature rice. There exists a clear linear relation between these two variables with a quiet large correlation coefficient value, >0.9. The SEA derived MLat profiles of both, thermospheric zonal wind velocity and FAC, show a clear IMF By orientation dependence for all local seasons. The zonal wind velocity is prominently directed towards west in the MLat-MLT frame for both signs of IMF By, but speeds are larger for positive By. FAC shows a systematic imbalance between downward (upward) and upward (downward) peaks equatorward and poleward of the reference point for positive (negative) IMF By. The influence of upflow events depends strongly on the amplitude of IMF By, to a lesser extend on Bz.

Study of the Dependency on Magnetic Field and Bias Voltage of an AC-Biased TES Microcalorimeter

NASA Technical Reports Server (NTRS)

Gottardi, L.; Bruijn, M.; denHartog, R.; Hoevers, H.; deKorte, P.; vanderKuur, J.; Linderman, M.; Adams, J.; Bailey, C.; Bandler, S.;

Study of the Dependence on Magnetic Field and Bias Voltage of an AC-Biased TES Microcalorimeter

NASA Technical Reports Server (NTRS)

Bandler, Simon

2011-01-01

At SRON we are studying the performance of a Goddard Space Flight Center single pixel TES microcalorimeter operated in the AC bias configuration. For x-ray photons at 6keV the AC biased pixel shows a best energy resolution of 3.7eV, which is about a factor of 2 worse than the energy resolution observed in identical DC-biased pixels. To better understand the reasons of this discrepancy, we investigated the detector performance as a function of temperature, bias working point and applied magnetic field. A strong periodic dependence of the detector noise on the TES AC bias voltage is measured. We discuss the results in the framework of the recent weak-link behaviour observed inTES microcalorimeters.

Coupled grain boundary motion in aluminium: the effect of structural multiplicity

NASA Astrophysics Data System (ADS)

Cheng, Kuiyu; Zhang, Liang; Lu, Cheng; Tieu, Kiet

2016-05-01

The shear-induced coupled grain boundary motion plays an important role in the deformation of nanocrystalline (NC) materials. It has been known that the atomic structure of the grain boundary (GB) is not necessarily unique for a given set of misorientation and inclination of the boundary plane. However, the effect of the structural multiplicity of the GB on its coupled motion has not been reported. In the present study we investigated the structural multiplicity of the symmetric tilt Σ5(310) boundary in aluminium and its influence on the GB behaviour at a temperature range of 300 K-600 K using molecular dynamic simulations. Two starting atomic configurations were adopted in the simulations which resulted in three different GB structures at different temperatures. Under the applied shear deformation each GB structure exhibited its unique GB behaviour. A dual GB behaviour, namely the transformation of one GB behaviour to another during deformation, was observed for the second starting configuration at a temperature of 500 K. The atomistic mechanisms responsible for these behaviour were analysed in detail. The result of this study implicates a strong relationship between GB structures and their behaviour, and provides a further information of the grain boundary mediated plasticity in nanocrystalline materials.

Effect of butorphanol on thermal nociceptive threshold in healthy pony foals.

PubMed

McGowan, K T; Elfenbein, J R; Robertson, S A; Sanchez, L C

2013-07-01

Pain management is an important component of foal nursing care, and no objective data currently exist regarding the analgesic efficacy of opioids in foals. To evaluate the somatic antinociceptive effects of 2 commonly used doses of intravenous (i.v.) butorphanol in healthy foals. Our hypothesis was that thermal nociceptive threshold would increase following i.v. butorphanol in a dose-dependent manner in both neonatal and older pony foals. Seven healthy neonatal pony foals (age 1-2 weeks), and 11 healthy older pony foals (age 4-8 weeks). Five foals were used during both age periods. Treatments, which included saline (0.5 ml), butorphanol (0.05 mg/kg bwt) and butorphanol (0.1 mg/kg bwt), were administered i.v. in a randomised crossover design with at least 2 days between treatments. Response variables included thermal nociceptive threshold, skin temperature and behaviour score. Data within each age period were analysed using a 2-way repeated measures ANOVA, followed by a Holm-Sidak multiple comparison procedure if warranted. There was a significant (P<0.05) increase in thermal threshold, relative to Time 0, following butorphanol (0.1 mg/kg bwt) administration in both age groups. No significant time or treatment effects were apparent for skin temperature. Significant time, but not treatment, effects were evident for behaviour score in both age groups. Butorphanol (0.1 mg/kg bwt, but not 0.05 mg/kg bwt) significantly increased thermal nociceptive threshold in neonatal and older foals without apparent adverse behavioural effects. Butorphanol shows analgesic potential in foals for management of somatic painful conditions. © 2012 EVJ Ltd.

Strain effect on the photoluminescence property of gold nanoclusters

NASA Astrophysics Data System (ADS)

Saravanan, K.; David, C.; Jayalakshmi, G.; Panigrahi, B. K.; Avasthi, D. K.

2018-02-01

Herein, we report the temperature-dependent photoluminescence (PL) properties of Au nanoclusters (NCs) embedded in a Si matrix. Gold NCs have been synthesized in Si by a multistep procedure that involves ion implantation and gold decoration by drive in annealing. Transmission electron microscopic studies reveal profuse nucleation of Au NCs, with mean sizes of ˜8 nm in the near-surface region. PL measurements in the range of 2 eV to 3.65 eV were carried out in the temperature range of 5 K to 300 K. The Au NCs exhibit PL emissions at 3 eV and 2.5 eV; these are attributed to the recombination of sp-band electrons with the holes of a deep lying d-band below the Fermi level in the vicinity of the L symmetry point of the Brillouin zone and the recombination of sp band electrons with the holes of the first d band below the Fermi level in the vicinity of the X symmetry point of the Brillouin zone, respectively. Temperature-dependent PL measurements show that the PL intensity of Au NCs initially decreases with the increase of temperature up to 50 K, and, thereafter, the intensity starts to increase and reaches a maximum at 150 K. A further increase in temperature causes the intensity to decrease. However, the PL intensity of Au NCs embedded in a sapphire matrix monotonically decreases with the increase of temperature. The present work discusses the plausible mechanism behind this unusual PL behaviour by invoking the role of strain at the NC-matrix interface.

Doping concentration dependence of microstructure and magnetic behaviours in Co-doped TiO2 nanorods

PubMed Central

2014-01-01

Co-doped titanium dioxide (TiO2) nanorods with different doping concentrations were fabricated by a molten salt method. It is found that the morphology of TiO2 changes from nanorods to nanoparticles with increasing doping concentration. The mechanism for the structure and phase evolution is investigated in detail. Undoped TiO2 nanorods show strong ferromagnetism at room temperature, whereas incorporating of Co deteriorates the ferromagnetic ordering. X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) results demonstrate that the ferromagnetism is associated with Ti vacancy. PMID:25593558

Electron beam irradiation effects on ethylene-tetrafluoroethylene copolymer films

NASA Astrophysics Data System (ADS)

Nasef, Mohamed Mahmoud; Saidi, Hamdani; Dahlan, Khairul Zaman M.

2003-12-01

The effects of electron beam irradiation on ethylene-tetrafluoroethylene copolymer (ETFE) films were studied. Samples were irradiated in air at room temperature by a universal electron beam accelerator for doses ranging from 100 to 1200 kGy. Irradiated samples were investigated with respect to their chemical structure, thermal characteristics, crystallinity and mechanical properties using FTIR, differential scanning calorimeter (DSC) and universal mechanical tester. The interaction of electron irradiation with ETFE films was found to induce dose-dependent changes in all the investigated properties. A mechanism for electron-induced reactions is proposed to explain the structure-property behaviour of irradiated ETFE films.

The link between behavioural type and natal dispersal propensity reveals a dispersal syndrome in a large herbivore

PubMed Central

Debeffe, L.; Morellet, N.; Bonnot, N.; Gaillard, J. M.; Cargnelutti, B.; Verheyden-Tixier, H.; Vanpé, C.; Coulon, A.; Clobert, J.; Bon, R.; Hewison, A. J. M.

2014-01-01

When individuals disperse, they modify the physical and social composition of their reproductive environment, potentially impacting their fitness. The choice an individual makes between dispersal and philopatry is thus critical, hence a better understanding of the mechanisms involved in the decision to leave the natal area is crucial. We explored how combinations of behavioural (exploration, mobility, activity and stress response) and morphological (body mass) traits measured prior to dispersal were linked to the subsequent dispersal decision in 77 roe deer Capreolus capreolus fawns. Using an unusually detailed multi-trait approach, we identified two independent behavioural continuums related to dispersal. First, a continuum of energetic expenditure contrasted individuals of low mobility, low variability in head activity and low body temperature with those that displayed opposite traits. Second, a continuum of neophobia contrasted individuals that explored more prior to dispersal and were more tolerant of capture with those that displayed opposite traits. While accounting for possible confounding effects of condition-dependence (body mass), we showed that future dispersers were less neophobic and had higher energetic budgets than future philopatric individuals, providing strong support for a dispersal syndrome in this species. PMID:25030983

Magnetism from Fe2O3 nanoparticles embedded in amorphous SiO2 matrix

NASA Astrophysics Data System (ADS)

Sendil Kumar, A.; Bhatnagar, Anil K.

2018-02-01

Fe2O3 nanoparticles are embedded in amorphous SiO2 matrix by coprecipitation method with varying concentrations. Conditions are optimized to get almost monodispersed Fe2O3 nanoparticles with high chemical stability. Microstructure of synthesized nanoparticles is well characterized and found that Fe2O3 is in nanocrystalline form and embedded uniformly in amorphous SiO2 matrix. Enhanced surface reactivity is found for nanoparticles which influences physical properties of the SiO2 supported Fe2O3 system due to adsorption. In oxide nanoparticles, significant number of defect sites at the surface is expected but when supported medium such as SiO2 it reduces this defect concentration. Field- and temperature-dependent magnetisation studies on these samples show superparamagnetic behaviour. Superparamagnetic behaviour is seen in all the concentration systems but the coercivity observed in the lower concentration systems is found to be anomalous compared to that of higher concentrations. The observed magnetic behaviour comes from either unsaturated bond existing due to the absence of anions at the surface of nanoparticles or reconstruction of atomic orbitals taking place at interface of Fe2O3-SiO2 system.

Formulation of steam-methane reforming rate in Ni-YSZ porous anode of solid oxide fuel cells

NASA Astrophysics Data System (ADS)

Sugihara, Shinichi; Kawamura, Yusuke; Iwai, Hiroshi

2018-02-01

The steam-methane reforming reaction on a Ni-YSZ (yttria-stabilized zirconia) cermet was experimentally investigated under atmospheric pressure and in the temperature range from 650 to 750 °C. We examined the effects of the partial pressures of methane and steam in the supply gas on the reaction rate. The experiments were conducted with a low Ni contained Ni-YSZ cermet sheet of thickness 0.1 mm. Its porous microstructure and accompanied parameters were quantified using the FIB-SEM (focused ion beam scanning electron microscopy) technique. A power-law-type rate equation incorporating the reaction-rate-limiting conditions was obtained on the basis of the unit surface area of the Ni-pore contact surface in the cermet. The kinetics indicated a strong positive dependence on the methane partial pressure and a negative dependence on the steam partial pressure. The obtained rate equation successfully reproduced the experimental results for Ni-YSZ samples having different microstructures in the case of low methane consumption. The equation also reproduced the limiting-reaction behaviours at different temperatures.

"Anomalous" excitation in hydrogen-bonded molecular crystals - a Raman scattering study of specifically deuterated acetanilide (C 6D 5-CONH-CD 3)

NASA Astrophysics Data System (ADS)

Sauvajol, J. L.; De Nunzio, G.; Almairac, R.; Moret, J.; Barthés, M.; Bataillon, Place E.

1991-01-01

The focus of experimental and theoretical works about crystalline Acetanilide has been the "anomalous" temperature-dependent ir absorption and Raman peaks at about 1650 cm -1 and the multiband structure in the N-H stretch region. A lively discussion about the assignment of these "anomalous" bands has arisen and is still in progress. The present Raman experiments should be placed in this context as an attempt to identify the molecular degrees of freedom which originate the "anomalous" bands. In this aim Raman experiments have been performed on specifically deuterated Acetanilide [C 6D 5-CONH-CD 3] single crystal in the low-frequency (phonon) and C=O stretching regions. On cooling a distinct band at about 1495 cm -1 increases in intensity. We assign this peak to the equivalent of the 1650 cm -1 band in Acetanilide. The temperature dependence of this Raman line was studied. The results are discussed in the light of the models proposed to explain the anomalous behaviour of the 1650 cm -1 Raman line in Acetanilide.

Predicted global warming scenarios impact on the mother plant to alter seed dormancy and germination behaviour in Arabidopsis.

PubMed

Huang, Z; Footitt, S; Tang, A; Finch-Savage, W E

2018-01-01

Seed characteristics are key components of plant fitness that are influenced by temperature in their maternal environment, and temperature will change with global warming. To study the effect of such temperature changes, Arabidopsis thaliana plants were grown to produce seeds along a uniquely designed polyethylene tunnel having a thermal gradient reflecting local global warming predictions. Plants therefore experienced the same variations in temperature and light conditions but different mean temperatures. A range of seed-related plant fitness estimates were measured. There were dramatic non-linear temperature effects on the germination behaviour in two contrasting ecotypes. Maternal temperatures lower than 15-16 °C resulted in significantly greater primary dormancy. In addition, the impact of nitrate in the growing media on dormancy was shown only by seeds produced below 15-16 °C. However, there were no consistent effects on seed yield, number, or size. Effects on germination behaviour were shown to be a species characteristic responding to temperature and not time of year. Elevating temperature above this critical value during seed development has the potential to dramatically alter the timing of subsequent seed germination and the proportion entering the soil seed bank. This has potential consequences for the whole plant life cycle and species fitness. © 2017 John Wiley & Sons Ltd.

Thermal games in crayfish depend on establishment of social hierarchies.

PubMed

Tattersall, Glenn J; Luebbert, Joshua P; LePine, Olivia K; Ormerod, Kiel G; Mercier, A Joffre

2012-06-01

An unequal resource distribution is commonly seen in dominance hierarchies, in which the individual with the higher status is more successful in obtaining the resource. One possible resource is preferred temperature. When situations allow, ectotherms regulate their body temperature by behaviourally selecting different environmental conditions, achieving, when possible, a preferred temperature. Using a shuttlebox, the preferred temperature for Procambarus clarkii was determined to be 23.9°C with upper and lower voluntary escape temperatures of 25.9 and 21.8°C, respectively. If this preferred temperature zone (21.8-25.9°C) was valued as a resource, given the choice between a preferred temperature and a non-preferred temperature, crayfish should compete over the preferred temperature, with the dominant individual of dyadic pairs achieving the preferred temperature more often than the subordinate. Using a dual-choice experimental tank, competition over a binary temperature choice between rank-established paired crayfish was determined under both warm and cold challenge conditions (warm vs preferred temperature and cold vs preferred temperature, respectively). In naive pairings, similar levels of competition over the preferred temperature occurred in both warm and cold challenge trials, as predicted by game theory. In established pairings, however, dominant crayfish gained significantly greater access to preferred temperature in both warm and cold challenge conditions. These results demonstrate that crayfish engage in a cost-benefit assessment during their initial agonistic contests over temperature, but as hierarchies mature, these thermal games are decided by the dominant animal gaining primary access to the temperature resource.

Dilution and non-Fermi-liquid effects in the CePtIn Kondo lattice.

PubMed

Ragel, F C; Plessis, P de V du; Strydom, A M

2009-01-28

Measurements of electrical resistivity (ρ(T)), magnetoresistivity (MR), magnetic susceptibility (χ(T)) and heat capacity (C(P)(T)) are presented for the (Ce(1-x)La(x))PtIn alloy system of which the CePtIn parent is a known dense Kondo compound that does not order magnetically down to 50 mK. χ(T) for alloys 0≤x≤0.8 exhibits Curie-Weiss behaviour. ρ(T) results indicate a transition from a dense Kondo behaviour for 0≤x≤0.2 to a single-ion Kondo region (0.3≤x≤0.8). The Kondo energy scale as given by T(K) values calculated from MR studies and by the temperature T(max)(ρ(mag)) where the magnetic contribution to ρ(T) exhibits a maximum value, is compared with theoretical models. It is shown that the experimental results not only depend on a volume effect as given by the compressible Kondo lattice model of Lavagna but in addition confirm the more complex behaviour recently presented by Burdin and Fulde for a Kondo alloy system in which the magnetic (Ce) and non-magnetic (La) atoms are distributed randomly. Non-Fermi-liquid behaviour is predicted by Burdin and Fulde at certain critical concentrations of the alloy system and experimental evidence for this is presented through χ(T), ρ(T) and C(P)(T) measurements.

Review of NMR studies of nanoscale molecular magnets composed of geometrically frustrated antiferromagnetic triangles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Furukawa, Yuji

This paper presents a comprehensive review of nuclear magnetic resonance (NMR) studies performed on three nanoscale molecular magnets with different novel configurations of geometrically frustrated antiferromagnetic (AFM) triangles: (1) the isolated single AFM triangle K 6[V 15As 6O 42(H 2O)]·8H 2O (in short V15), (2) the spin ball [Mo 72Fe 30O 252(Mo 2O 7(H 2O)) 2(Mo 2O 8H 2(H 2O)) (CH 3COO) 12(H 2O) 91]·150H 2O (in short Fe30 spin ball), and (3) the twisted triangular spin tube [(CuCl 2tachH) 3Cl]Cl 2 (in short Cu3 spin tube). In V15t, from 51V NMR spectra, the local spin configurations were directly determinedmore » in both the nonfrustrated total spin S T = 3/2 state at higher magnetic fields (H ge; 2.7 T) and the two nearly degenerate S T = 1/2 ground states at lower magnetic fields (H ≤ 2.7 T). The dynamical magnetic properties of V15 were investigated by proton spin-lattice relaxation rate (1/T 1) measurements. In the S T = 3/2 state, 1/T 1 shows thermally activated behaviour as a function of temperature. On the other hand, the temperature independent behaviour of 1/T 1 at very low temperatures is observed in the frustrated S T = 1/2 ground state. Possible origins for the peculiar behaviour of 1/T 1 will be discussed in terms of magnetic fluctuations due to spin frustrations. In Fe30, static and dynamical properties of Fe 3+ (s = 5/2) have been investigated by proton NMR spectra and 1/T 1 measurements. From the temperature dependence of 1/T 1, the fluctuation frequency of the Fe 3+ spins is found to decrease with decreasing temperature, indicating spin freezing at low temperatures. The spin freezing is also evidenced by the observation of a sudden broadening of 1H NMR spectra below 0.6 K. Finally, 1H NMR data in Cu3 will be described. An observation of magnetic broadening of 1H NMR spectra at low temperatures below 1 K directly revealed a gapless ground state. The 1/T 1 measurements revealed a usual slow spin dynamics in the Cu3 spin tube.« less

Review of NMR studies of nanoscale molecular magnets composed of geometrically frustrated antiferromagnetic triangles

DOE PAGES

Furukawa, Yuji

2016-10-01

This paper presents a comprehensive review of nuclear magnetic resonance (NMR) studies performed on three nanoscale molecular magnets with different novel configurations of geometrically frustrated antiferromagnetic (AFM) triangles: (1) the isolated single AFM triangle K 6[V 15As 6O 42(H 2O)]·8H 2O (in short V15), (2) the spin ball [Mo 72Fe 30O 252(Mo 2O 7(H 2O)) 2(Mo 2O 8H 2(H 2O)) (CH 3COO) 12(H 2O) 91]·150H 2O (in short Fe30 spin ball), and (3) the twisted triangular spin tube [(CuCl 2tachH) 3Cl]Cl 2 (in short Cu3 spin tube). In V15t, from 51V NMR spectra, the local spin configurations were directly determinedmore » in both the nonfrustrated total spin S T = 3/2 state at higher magnetic fields (H ge; 2.7 T) and the two nearly degenerate S T = 1/2 ground states at lower magnetic fields (H ≤ 2.7 T). The dynamical magnetic properties of V15 were investigated by proton spin-lattice relaxation rate (1/T 1) measurements. In the S T = 3/2 state, 1/T 1 shows thermally activated behaviour as a function of temperature. On the other hand, the temperature independent behaviour of 1/T 1 at very low temperatures is observed in the frustrated S T = 1/2 ground state. Possible origins for the peculiar behaviour of 1/T 1 will be discussed in terms of magnetic fluctuations due to spin frustrations. In Fe30, static and dynamical properties of Fe 3+ (s = 5/2) have been investigated by proton NMR spectra and 1/T 1 measurements. From the temperature dependence of 1/T 1, the fluctuation frequency of the Fe 3+ spins is found to decrease with decreasing temperature, indicating spin freezing at low temperatures. The spin freezing is also evidenced by the observation of a sudden broadening of 1H NMR spectra below 0.6 K. Finally, 1H NMR data in Cu3 will be described. An observation of magnetic broadening of 1H NMR spectra at low temperatures below 1 K directly revealed a gapless ground state. The 1/T 1 measurements revealed a usual slow spin dynamics in the Cu3 spin tube.« less

Theory of the milieu dependent isomerisation dynamics of reducing sugars applied to d-erythrose.

PubMed

Kaufmann, Martin; Mügge, Clemens; Kroh, Lothar W

2015-12-11

Quantitative (1)H selective saturation transfer NMR spectroscopy ((1)H SST qNMR) was used to fully describe the milieu dependent dynamics of the isomeric system of d-erythrose. Thermodynamic activation parameters are calculated for acidic as well as for basic catalysis combining McConnell's modified Bloch equations for the chemical exchange solved for the constraint of saturating the non-hydrated acyclic isomer, the Eyring equation and Hudson's equation for pH dependent catalysis. A detailed mathematical examination describing the milieu dependent dynamics of sugar isomerisation is provided. Thermodynamic data show evidence that photo-catalysed sugar isomerisation as well as degradation has to be considered. Approximations describing the pH and temperature dependence of thermodynamic activation parameters are derived that indicate the possibility of photo-affecting equilibrium constants. Moreover, the results show that isomerisation dynamics are closely related to degradation kinetics and that sugars' reactivities are altered by the concentration of acyclic carbonyl isomer and the sum of its ring closing rate constants. Additionally, it is concluded that sugar solutions show a limited self-stabilising behaviour. Copyright © 2015 Elsevier Ltd. All rights reserved.

Fatigue damage characterization of braided and woven fiber reinforced polymer matrix composites at room and elevated temperatures

NASA Astrophysics Data System (ADS)

Montesano, John

The use of polymer matrix composites (PMC) for manufacturing primary load-bearing structural components has significantly increased in many industrial applications. Specifically in the aerospace industry, PMCs are also being considered for elevated temperature applications. Current aerospace-grade composite components subjected to fatigue loading are over-designed due to insufficient understanding of the material failure processes, and due to the lack of available generic fatigue prediction models. A comprehensive literature survey reveals that there are few fatigue studies conducted on woven and braided fabric reinforced PMC materials, and even fewer at elevated temperatures. It is therefore the objective of this study to characterize and subsequently model the elevated temperature fatigue behaviour of a triaxial braided PMC, and to investigate the elevated temperature fatigue properties of two additional woven PMCs. An extensive experimental program is conducted using a unique test protocol on the braided and woven composites, which consists of static and fatigue testing at various test temperatures. The development of mechanically-induced damage is monitored using a combination of non-destructive techniques which included infrared thermography, fiber optic sensors and edge replication. The observed microscopic damage development is quantified and correlated to the exhibited macroscopic material behaviour at all test temperatures. The fiber-dominated PMC materials considered in this study did not exhibit notable time- or temperature-dependent static properties. However, fatigue tests reveal that the local damage development is in fact notably influenced by temperature. The elevated temperature environment increases the toughness of the thermosetting polymers, which results in consistently slower fatigue crack propagation rates for the respective composite materials. This has a direct impact on the stiffness degradation rate and the fatigue lives for the braided and woven composites under investigation. The developed analytical fatigue damage prediction model, which is based on actual observed damage mechanisms, accurately predicted the development of damage and the corresponding stiffness degradation for the braided PMC, for all test temperatures. An excellent correlation was found between the experimental and the predicted results to within a 2% accuracy. The prediction model adequately captured the local temperature-induced phenomenon exhibited by the braided PMC material. The results presented in this study are novel for a braided composite material subjected to elevated temperature fatigue.

Local geology controlled the feasibility of vitrifying Iron Age buildings

USGS Publications Warehouse

Fabian B Wadsworth,; Michael J Heap,; Damby, David; Kai-Uwe Hess,; Jens Najorka,; Jérémie Vasseur,; Dominik Fahrner,; Donald B Dingwell,

2017-01-01

During European prehistory, hilltop enclosures made from polydisperse particle-and-block stone walling were exposed to temperatures sufficient to partially melt the constituent stonework, leading to the preservation of glassy walls called ‘vitrified forts’. During vitrification, the granular wall rocks partially melt, sinter viscously and densify, reducing inter-particle porosity. This process is strongly dependent on the solidus temperature, the particle sizes, the temperature-dependence of the viscosity of the evolving liquid phase, as well as the distribution and longevity of heat. Examination of the sintering behaviour of 45 European examples reveals that it is the raw building material that governs the vitrification efficiency. As Iron Age forts were commonly constructed from local stone, we conclude that local geology directly influenced the degree to which buildings were vitrified in the Iron Age. Additionally, we find that vitrification is accompanied by a bulk material strengthening of the aggregates of small sizes, and a partial weakening of larger blocks. We discuss these findings in the context of the debate surrounding the motive of the wall-builders. We conclude that if wall stability by bulk strengthening was the desired effect, then vitrification represents an Iron Age technology that failed to be effective in regions of refractory local geology.

Long-term effects of warming and ocean acidification are modified by seasonal variation in species responses and environmental conditions

PubMed Central

Godbold, Jasmin A.; Solan, Martin

2013-01-01

Warming of sea surface temperatures and alteration of ocean chemistry associated with anthropogenic increases in atmospheric carbon dioxide will have profound consequences for a broad range of species, but the potential for seasonal variation to modify species and ecosystem responses to these stressors has received little attention. Here, using the longest experiment to date (542 days), we investigate how the interactive effects of warming and ocean acidification affect the growth, behaviour and associated levels of ecosystem functioning (nutrient release) for a functionally important non-calcifying intertidal polychaete (Alitta virens) under seasonally changing conditions. We find that the effects of warming, ocean acidification and their interactions are not detectable in the short term, but manifest over time through changes in growth, bioturbation and bioirrigation behaviour that, in turn, affect nutrient generation. These changes are intimately linked to species responses to seasonal variations in environmental conditions (temperature and photoperiod) that, depending upon timing, can either exacerbate or buffer the long-term directional effects of climatic forcing. Taken together, our observations caution against over emphasizing the conclusions from short-term experiments and highlight the necessity to consider the temporal expression of complex system dynamics established over appropriate timescales when forecasting the likely ecological consequences of climatic forcing. PMID:23980249

High Pressure and Temperature Effects in Polymers

NASA Astrophysics Data System (ADS)

Bucknall, David; Arrighi, Valeria; Johnston, Kim; Condie, Iain

Elastomers are widely exploited as the basis for seals in gas and fluid pipelines. The underlying behaviour of these elastomer at the high pressure, elevated temperatures they experience in operation is poorly understood. Consequently, the duty cycle of these materials is often deliberately limited to a few hours, and in order to prevent failure, production is stopped in order to change the seals in critical joints. The result is significant time lost due to bringing down production to change the seals as well as knock on financial costs. In order to address the fundamental nature of the elastomers at their intended operating conditions, we are studying the gas permeation behaviour of hydrogenated natural butyl rubber (HNBR) and fluorinated elastomers (FKM) at a high pressure and elevated temperature. We have developed a pressure system that permits gas permeation studies at gas pressures of up to 5000 psi and operating temperatures up to 150° C. In this paper, we will discuss the nature of the permeation behaviour at these extreme operating conditions, and how this relates to the changes in the polymer structure. We will also discuss the use of graphene-polymer thin layer coatings to modify the gas permeation behaviour of the elastomers.

Chaotic, informational and synchronous behaviour of multiplex networks

NASA Astrophysics Data System (ADS)

Baptista, M. S.; Szmoski, R. M.; Pereira, R. F.; Pinto, S. E. De Souza

2016-03-01

The understanding of the relationship between topology and behaviour in interconnected networks would allow to charac- terise and predict behaviour in many real complex networks since both are usually not simultaneously known. Most previous studies have focused on the relationship between topology and synchronisation. In this work, we provide analytical formulas that shows how topology drives complex behaviour: chaos, information, and weak or strong synchronisation; in multiplex net- works with constant Jacobian. We also study this relationship numerically in multiplex networks of Hindmarsh-Rose neurons. Whereas behaviour in the analytically tractable network is a direct but not trivial consequence of the spectra of eigenvalues of the Laplacian matrix, where behaviour may strongly depend on the break of symmetry in the topology of interconnections, in Hindmarsh-Rose neural networks the nonlinear nature of the chemical synapses breaks the elegant mathematical connec- tion between the spectra of eigenvalues of the Laplacian matrix and the behaviour of the network, creating networks whose behaviour strongly depends on the nature (chemical or electrical) of the inter synapses.

Effects of ambient temperature and early open-field response on the behaviour, feed intake and growth of fast- and slow-growing broiler strains.

PubMed

Nielsen, B L

2012-09-01

Increased activity improves broiler leg health, but also increases the heat production of the bird. This experiment investigated the effects of early open-field activity and ambient temperature on the growth and feed intake of two strains of broiler chickens. On the basis of the level of activity in an open-field test on day 3 after hatching, fast-growing Ross 208 and slow-growing i657 chickens were allocated on day 13 to one of the 48 groups. Each group included either six active or six passive birds from each strain and the groups were housed in floor-pens littered with wood chips and fitted with two heat lamps. Each group was fed ad libitum and subjected to one of the three temperature treatments: two (HH; 26°C), one (HC; 16°C to 26°C) or no (CC; 16°C) heat lamps turned on. Production and behavioural data were collected every 2 weeks until day 57. For both strains, early open-field activity had no significant effects on their subsequent behaviour or on any of the production parameters measured, and overall, the slow-growing strain was more active than the fast-growing strain. Ambient temperature had significant effects on production measures for i657 broilers, with CC chickens eating and weighing more, and with a less efficient feed conversion than HH chickens, with HC birds intermediate. A similar effect was found for Ross 208 only for feed intake from 27 to 41 days of age. Ross 208 chickens distributed themselves in the pen with a preference for cooler areas in the hottest ambient temperature treatments. In contrast, the behaviour of the slow-growing strain appeared to be relatively unaffected by the ambient temperature. In conclusion, fast-growing broilers use behavioural changes when trying to adapt to warm environments, whereas slow-growing broilers use metabolic changes to adapt to cooler ambient temperatures.

Experimental investigations on thermo mechanical behaviour of aluminium alloys subjected to tensile loading and laser irradiation

NASA Astrophysics Data System (ADS)

Jelani, Mohsan; Li, Zewen; Shen, Zhonghua; Sardar, Maryam; Tabassum, Aasma

2017-05-01

The present work reports the investigation of the thermal and mechanical behaviour of aluminium alloys under the combined action of tensile loading and laser irradiations. The two types of aluminium alloys (Al-1060 and Al-6061) are used for the experiments. The continuous wave Ytterbium fibre laser (wavelength 1080 nm) was employed as irradiation source, while tensile loading was provided by tensile testing machine. The effects of various pre-loading and laser power densities on the failure time, temperature distribution and on deformation behaviour of aluminium alloys are analysed. The experimental results represents the significant reduction in failure time and temperature for higher laser powers and for high load values, which implies that preloading may contribute a significant role in the failure of the material at elevated temperature. The reason and characterization of material failure by tensile and laser loading are explored in detail. A comparative behaviour of under tested materials is also investigated. This work suggests that, studies considering only combined loading are not enough to fully understand the mechanical behaviour of under tested materials. For complete characterization, one must consider the effect of heating as well as loading rate.

Intermediate valence to Kondo behaviour in Ce(Pt1-xIrx)2Si2 (0≤x≤1)

NASA Astrophysics Data System (ADS)

Tchoula Tchokonté, M. B.; du Plessis, P. de V.; Kaczorowski, D.

2009-10-01

Measurements of X-ray diffraction (XRD), resistivity ( ρ(T)), magnetic susceptibility ( χ(T)) and magnetization ( σ(μ0H)) are reported for the polycrystalline Ce(Pt1-xIrx)2Si2 alloy system. The unit cell volume derived from the XRD results deviates from Vegard's rule around x=0.2-0.3. χ(T) measurements show a Curie-Weiss behaviour at high temperatures for the x= 0, 0.1 and 0.2 alloys whereas the alloys with x≥0.4 exhibit broad maxima in χ(T) at intermediate temperature (e.g. at 170 K for x=0.4). The latter behaviour due to valence fluctuations as described by Sales and Wohlleben. ρ(T) data indicate Kondo lattice behaviour for x≤0.2 and fluctuating valency for x≥0.3. σ(μ0H) data indicate metamagnetic behaviour for the x=0.4 alloy.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Banerjee, D.; Sankaranarayanan, S.; Khachariya, D.

We demonstrate a method for nanowire formation by natural selection during wet anisotropic chemical etching in boiling phosphoric acid. Nanowires of sub-10 nm lateral dimensions and lengths of 700 nm or more are naturally formed during the wet etching due to the convergence of the nearby crystallographic hexagonal etch pits. These nanowires are site controlled when formed in augmentation with dry etching. Temperature and power dependent photoluminescence characterizations confirm excitonic transitions up to room temperature. The exciton confinement is enhanced by using two-dimensional confinement whereby enforcing greater overlap of the electron-hole wave-functions. The surviving nanowires have less defects and a small temperaturemore » variation of the output electroluminescent light. We have observed superluminescent behaviour of the light emitting diodes formed on these nanowires. There is no observable efficiency roll off for current densities up to 400 A/cm{sup 2}.« less

Weak cooperativity in selected iron(II) 1D coordination polymers

NASA Astrophysics Data System (ADS)

Dîrtu, Marinela M.; Gillard, Damien; Naik, Anil D.; Rotaru, Aurelian; Garcia, Yann

2012-03-01

The spin crossover behaviour of a new class of FeII coordination polymers [Fe(phtptrz)3]I2 ( 1), [Fe(phtptrz)3](ReO4)2•CH3OH ( 2) and [Fe(phtptrz)3]TaF7•6H2O ( 3) based on a novel ligand 4-(3' -N-phtalimido-propyl)-1,2,4-triazole (phtptrz), were investigated by temperature dependent 57Fe Mössbauer spectroscopy and magnetic susceptibility measurements. The adverse effect of bulky substituent on 1,2,4-triazole, favorable supramolecular interactions and influence of increasing anion size on spin crossover profile is discussed. 1 and 2 show thermally induced spin conversions of gradual and incomplete nature with associated thermochromism, and transition temperatures T1/2 ~ 163 K and 137 K, respectively. A spin state crossover is also identified for 3.

The Nosé–Hoover looped chain thermostat for low temperature thawed Gaussian wave-packet dynamics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coughtrie, David J.; Tew, David P.

2014-05-21

We have used a generalised coherent state resolution of the identity to map the quantum canonical statistical average for a general system onto a phase-space average over the centre and width parameters of a thawed Gaussian wave packet. We also propose an artificial phase-space density that has the same behaviour as the canonical phase-space density in the low-temperature limit, and have constructed a novel Nosé–Hoover looped chain thermostat that generates this density in conjunction with variational thawed Gaussian wave-packet dynamics. This forms a new platform for evaluating statistical properties of quantum condensed-phase systems that has an explicit connection to themore » time-dependent Schrödinger equation, whilst retaining many of the appealing features of path-integral molecular dynamics.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khan, Shabana

This paper reports the precipitation behaviour of γ′ phase in the newly developed Ni-base superalloy Alloy 693. Precipitation of γ′ particles is studied at different temperatures ranging from 800 °C to 950 °C under isothermal conditions for various time periods. Monomodal, bimodal and trimodal size distributions of γ′ precipitates have been observed depending on the temperature of annealing and the cooling rates. These studies have been carried out using scanning and transmission electron microscopy. Results are compared with existing literature and explained on the basis of classical nucleation and growth theory. - Highlights: •The alloy exhibits multi-modal distribution of γ′more » precipitates formed in aged Alloy 693. •The γ′ phase has been found contain up to 4 at% of Nb. •Results have been explained on the basis of classical nucleation and growth models.« less

Deriving strain from crystallographic preferred orientation for a ductile shear zone in north western Turkey.

NASA Astrophysics Data System (ADS)

Farrell, K.; Lloyd, G. E. E.; Wallis, D.; Phillips, R. J.

2015-12-01

Understanding the behaviour of active continental-scale fault zones at depth, and in particular how displacements observed at the Earth's surface are accommodated through the crust, is crucial to improving understanding of the earthquake cycle. This behaviour can be inferred by study of exhumed portions of ductile shear zones using methods such as recording strain profile(s) across the fault zone. However, due to the nature of mid-crustal rocks, strain markers tend to be rare and/or discontinuously distributed. The intensity (I) of crystallographic preferred orientation (CPO) of deformed minerals provides a proxy for strain that is continuous across fault zones. CPO are collected via electron back scattered diffraction in the scanning electron microscope. The strength of the CPO can be quantified using eigenvalue-based intensity parameters. Calibration of intensity with strain is achieved via comparison with visco-plastic self-consistency models of CPO evolution, although the temperature-dependent critical resolved shear stresses of potential crystal slip systems must be known. As an example, we consider the dextral strike-slip Eskişehir shear zone, NW Turkey, which was active during the Oligocene and accommodated ~100km of displacement, including a component of late oblique-normal slip. An exhumed mid-crustal section of this fault zone is exposed in the Uludağ Massif, comprising of high-grade metamorphic rocks of the Uludağ Group, intruded by the Central and South Uludağ granites. Sample transects focussed on the pure calcic marbles that dominate the stratigraphy. Fortunately, the availability of experimental data for calcite crystal slip behaviour at different temperatures makes the application of the CPO intensity strain proxy method relatively straightforward. The Uludağ Massif and Eskişehir shear zone provide a field based analogue for the ductile shear zone beneath the currently active North Anatolian Fault. The results of our CPO intensity-based strain profiles allow us to speculate on the current behaviour of the North Anatolian Fault, a major seismogenic feature, at depth.

Probing transport mechanisms of BaFe2As2 superconducting films and grain boundary junctions by noise spectroscopy

PubMed Central

Barone, C.; Romeo, F.; Pagano, S.; Adamo, M.; Nappi, C.; Sarnelli, E.; Kurth, F.; Iida, K.

2014-01-01

An important step forward for the understanding of high-temperature superconductivity has been the discovery of iron-based superconductors. Among these compounds, iron pnictides could be used for high-field magnet applications, resulting more advantageous over conventional superconductors, due to a high upper critical field as well as its low anisotropy at low temperatures. However, the principal obstacle in fabricating high quality superconducting wires and tapes is given by grain boundaries. In order to study these effects, the dc transport and voltage-noise properties of Co-doped BaFe2As2 superconducting films with artificial grain boundary junctions have been investigated. A specific procedure allows the separation of the film noise from that of the junction. While the former shows a standard 1/f behaviour, the latter is characterized by an unconventional temperature-dependent multi-Lorentzian voltage-spectral density. Moreover, below the film superconducting critical temperature, a peculiar noise spectrum is found for the grain boundary junction. Possible theoretical interpretation of these phenomena is proposed. PMID:25145385

Cardiorespiratory performance during prolonged swimming tests with salmonids: a perspective on temperature effects and potential analytical pitfalls.

PubMed

Farrell, A P

2007-11-29

A prolonged swimming trial is the most common approach in studying steady-state changes in oxygen uptake, cardiac output and tissue oxygen extraction as a function of swimming speed in salmonids. The data generated by these sorts of studies are used here to support the idea that a maximum oxygen uptake is reached during a critical swimming speed test. Maximum oxygen uptake has a temperature optimum. Potential explanations are advanced to explain why maximum aerobic performance falls off at high temperature. The valuable information provided by critical swimming tests can be confounded by non-steady-state swimming behaviours, which typically occur with increasing frequency as salmonids approach fatigue. Two major concerns are noted. Foremost, measurements of oxygen uptake during swimming can considerably underestimate the true cost of transport near critical swimming speed, apparently in a temperature-dependent manner. Second, based on a comparison with voluntary swimming ascents in a raceway, forced swimming trials in a swim tunnel respirometer may underestimate critical swimming speed, possibly because fish in a swim tunnel respirometer are unable to sustain a ground speed.

Degradation kinetic modelling of ascorbic acid and colour intensity in pasteurised blood orange juice during storage.

PubMed

Remini, Hocine; Mertz, Christian; Belbahi, Amine; Achir, Nawel; Dornier, Manuel; Madani, Khodir

2015-04-15

The stability of ascorbic acid and colour intensity in pasteurised blood orange juice (Citrus sinensis [L.] Osbeck) during one month of storage was investigated at 4-37 °C. The effects of ascorbic acid fortification (at 100, 200 mg L(-1)) and deaeration, temperature/time storage on the kinetic behaviour were determined. Ascorbic acid was monitored by HPLC-DAD and colour intensity by spectrophotometric measurements. Degradation kinetics were best fitted by first-order reaction models for both ascorbic acid and colour intensity. Three models (Arrhenius, Eyring and Ball) were used to assess the temperature-dependent degradation. Following the Arrhenius model, activation energies were ranged from 51 to 135 kJ mol(-1) for ascorbic acid and from 49 to 99 kJ mol(-1) for colour intensity. The effect of storage temperature and deaeration are the most influent factors on kinetics degradation, while the fortification revealed no significant effect on ascorbic acid content and colour intensity. Copyright © 2014 Elsevier Ltd. All rights reserved.

Effect of Electromagnetic Interactions on the Undulatory Temperature Dependent Behaviour of Non-Resonant Microwave Absorption Signal Amplitude in Bi2Sr2CaCu2O8+x

NASA Astrophysics Data System (ADS)

Padam, Gursharan K.; Ekbote, Shrikant N.; Sharma, Mukul; Tripathy, Malay R.; Srivastava, Ganesh P.; Das, Bijoy K.

2006-01-01

Variation of non-resonant microwave absorption (NRMA) signal amplitude in single-phase Bi-2212 (5 wt % Ag) sintered pellets (Tc\\circ ˜ 96 K) while increasing temperature from 15 to 105 K has been investigated and discussed. These studies show an undulatory behavior of an initial fall in the amplitude (15-71.8 K) with a subsequent narrow weak temperature independent region (71.8-75.6 K) and then a rise peaking at ˜82.5 K followed by a final exponential fall (82.5-105 K). A detailed discussion on earlier reported data has suggested that this undulatory behavior cannot be understood in terms of existing approaches involving effect of Josephson interactions (JI) alone among vortices. In our opinion, the entire undulatory behavior observed in the present samples can be explained with the inclusion of electromagnetic interaction (EMI) along with JI.

A study on specific heat capacities of Li-ion cell components and their influence on thermal management

NASA Astrophysics Data System (ADS)

Loges, André; Herberger, Sabrina; Seegert, Philipp; Wetzel, Thomas

2016-12-01

Thermal models of Li-ion cells on various geometrical scales and with various complexity have been developed in the past to account for the temperature dependent behaviour of Li-ion cells. These models require accurate data on thermal material properties to offer reliable validation and interpretation of the results. In this context a thorough study on the specific heat capacities of Li-ion cells starting from raw materials and electrode coatings to representative unit cells of jelly rolls/electrode stacks with lumped values was conducted. The specific heat capacity is reported as a function of temperature and state of charge (SOC). Seven Li-ion cells from different manufactures with different cell chemistry, application and design were considered and generally applicable correlations were developed. A 2D thermal model of an automotive Li-ion cell for plug-in hybrid electric vehicle (PHEV) application illustrates the influence of specific heat capacity on the effectivity of cooling concepts and the temperature development of Li-ion cells.

Supercooling of water confined in reverse micelles

NASA Astrophysics Data System (ADS)

Spehr, T.; Frick, B.; Grillo, I.; Stühn, B.

2008-03-01

We report on the temperature dependence of the nanosecond-timescale dynamics of the ternary mixture water/AOT/oil with deuterated heptane, toluene or decane as the oil. Water-swollen reverse micelles as formed in such microemulsions allow us to investigate the freezing behaviour of water confined in a soft environment. We report here on the first neutron scattering studies in which the freezing of the confined water and of the oil is followed down to temperatures at which the whole system is frozen. We focus on studies of water confined in three different droplet sizes: by means of small-angle neutron scattering we have determined the radii to be 46, 18, and 7 Å for water to surfactant ratios ω = 40, 12, and 3. From elastic temperature scans by neutron backscattering we deduce a strong supercooling of water confined in the reverse swollen micelles which increases with decreasing droplet size. For the smallest droplets we find a supercooling of more than 45 K compared to bulk water.

Strong room-temperature ferromagnetism in VSe2 monolayers on van der Waals substrates

NASA Astrophysics Data System (ADS)

Bonilla, Manuel; Kolekar, Sadhu; Ma, Yujing; Diaz, Horacio Coy; Kalappattil, Vijaysankar; Das, Raja; Eggers, Tatiana; Gutierrez, Humberto R.; Phan, Manh-Huong; Batzill, Matthias

2018-04-01

Reduced dimensionality and interlayer coupling in van der Waals materials gives rise to fundamentally different electronic1, optical2 and many-body quantum3-5 properties in monolayers compared with the bulk. This layer-dependence permits the discovery of novel material properties in the monolayer regime. Ferromagnetic order in two-dimensional materials is a coveted property that would allow fundamental studies of spin behaviour in low dimensions and enable new spintronics applications6-8. Recent studies have shown that for the bulk-ferromagnetic layered materials CrI3 (ref. 9) and Cr2Ge2Te6 (ref. 10), ferromagnetic order is maintained down to the ultrathin limit at low temperatures. Contrary to these observations, we report the emergence of strong ferromagnetic ordering for monolayer VSe2, a material that is paramagnetic in the bulk11,12. Importantly, the ferromagnetic ordering with a large magnetic moment persists to above room temperature, making VSe2 an attractive material for van der Waals spintronics applications.

Magnetic moments induce strong phonon renormalization in FeSi.

PubMed

Krannich, S; Sidis, Y; Lamago, D; Heid, R; Mignot, J-M; Löhneysen, H v; Ivanov, A; Steffens, P; Keller, T; Wang, L; Goering, E; Weber, F

2015-11-27

The interactions of electronic, spin and lattice degrees of freedom in solids result in complex phase diagrams, new emergent phenomena and technical applications. While electron-phonon coupling is well understood, and interactions between spin and electronic excitations are intensely investigated, only little is known about the dynamic interactions between spin and lattice excitations. Noncentrosymmetric FeSi is known to undergo with increasing temperature a crossover from insulating to metallic behaviour with concomitant magnetic fluctuations, and exhibits strongly temperature-dependent phonon energies. Here we show by detailed inelastic neutron-scattering measurements and ab initio calculations that the phonon renormalization in FeSi is linked to its unconventional magnetic properties. Electronic states mediating conventional electron-phonon coupling are only activated in the presence of strong magnetic fluctuations. Furthermore, phonons entailing strongly varying Fe-Fe distances are damped via dynamic coupling to the temperature-induced magnetic moments, highlighting FeSi as a material with direct spin-phonon coupling and multiple interaction paths.

Modelling and simulation of thermal behaviour of vanadium redox flow battery

NASA Astrophysics Data System (ADS)

Yan, Yitao; Li, Yifeng; Skyllas-Kazacos, Maria; Bao, Jie

2016-08-01

This paper extends previous thermal models of the vanadium redox flow battery to predict temperature profiles within multi-cell stacks. This involves modelling the thermal characteristics of the stack as a whole to modelling each individual cell. The study investigates the thermal behaviour for two different scenarios: during standby periods when the pumps are turned off, and in a residential power arbitrage scenario for two types of membranes. It was found that the temperature gradient across the cells is most significant during the standby case, with the simulation results showing completely different thermal behaviours between the two systems.

Acoustic emission: A useful tool for damage evaluation in composite materials

NASA Astrophysics Data System (ADS)

Mouzakis, Dionysios E.; Dimogianopoulos, Dimitrios G.

2018-02-01

High performance composites for aviation-related structures are prone to constant aging by environmental agents. Previous data from our work reported on the stiffening behaviour of glass fibre polyester composites used in the manufacturing of wind turbine blades. Airplanes from such composites are already on service nowadays. This justifies the detailed study of the exposure of high performance materials to environmental conditions such as varying temperature, humidity, ultraviolet radiation, in order to assess the impact of these important aging factors on their mechanical behaviour. The dramatic changes in the dynamic mechanical response of polymer matrix carbon fibre composites upon exposure to acceleration aging has been assessed in the present study. In order to assess the synergistic effect action of temperature and humidity on composites subjected to changes of temperature from -35 to +40 °C and humidity variations from <10% to 95% RH (non-condensing) specimens were stored in a climatic chamber for 60 days. Conditions were cycled, as if actual flight cycles of 3-4 hours per flight, were to be simulated. Dynamic mechanical analysis tests were performed in three point bending mode. Scanning of frequency and temperature were performed in order to determine both the viscoelastic response as well as the time-dependent behaviour of the aged materials. All tests were run both for aged and pristine materials for comparison purposes. Three point bending testing was performed in both static as well as in Dynamic mechanical analysis, for a range of temperatures and frequencies. Acoustic Emission damage detection was also performed during the three point bending test both in static and dynamic mode. The aged materials had gained in dynamic stiffness. In addition, that, the gain in the storage moduli, was accompanied by a decrease in the material damping ability, as determined by the tanδ parameter. In the final stages of the study, impact testing was performed on both pristine and aged specimens. The experimentally recorded force/time signals were utilized for concluding on the specimens' condition, by means of signal based damage detection methodologies. Effort was invested in utilizing signal analysis in order to get comparative aging-related information on the tested specimens in order to ultimately validate results of mechanical testing.

Chemical reactivity of nitrates and nitrites towards TBP and potassium nickel ferrocyanide between 30 and 300 deg

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lambertin, D.; Chartier, D.; Joussot-Dubien, C.

2007-07-01

Since the late sixties, bitumen has been widely used by the nuclear industry as a matrix for the immobilization of low- and intermediate level radioactive waste originating mainly from the nuclear activities: precipitation or evaporator concentrates, ion exchange resins, incinerator ashes, and filter materials. Depending on bitumen and operating conditions, bituminization of radioactive waste can be operated between 130 and 180 deg. C, so chemical reaction can be induced with nitrate or nitrite towards elements contained in waste (TPB, potassium nickel ferrocyanide and cobalt compound) and bitumen. These reactions are mainly exothermic this is the reason why the enthalpy reactionmore » and their temperature of initiation have to be determined independently of their concentration in waste. In this work, we have studied by Calvet Calorimetry at 0.1 deg. C/min heating rates, the behaviour of chemical elements especially oxido-reduction couples that can react at a temperature range 100- 300 deg. C (Nitrate/PPFeNi, Nitrite/PPFeNi, Nitrate/TBP, Nitrite/TBP, Nitrate/bitumen and Nitrite/bitumen). The initial temperature reaction of nitrates or nitrites towards potassium nickel ferrocyanide (PPFeNi) has been studied and is equal respectively to 225 deg. C and 175 deg. C. Because of the large scale temperature reaction of nitrate and PPFeNi, enthalpy reaction can not be calculated, although enthalpy reaction of nitrite and PPFeNi is equal to 270 kJ/mol of nitrite. Sodium Nitrate and TBP behaviour has been investigated, and an exothermic reaction at 135 deg. C until 250 deg. C is evidenced. The exothermic energy reaction is a function of TBP concentration and the enthalpy reaction has been determined. (authors)« less

Warmer weather as a risk factor for hospitalisations due to urinary tract infections.

PubMed

Simmering, J E; Cavanaugh, J E; Polgreen, L A; Polgreen, P M

2018-02-01

The incidence of urinary tract infections (UTIs) is seasonal, and this seasonality may be explained by changes in weather, specifically, temperature. Using data from the Nationwide Inpatient Sample, we identified the geographic location for 581 813 hospital admissions with the primary diagnosis of a UTI and 56 630 773 non-UTI hospitalisations in the United States. Next, we used data from the National Climatic Data Center to estimate the monthly average temperature for each location. Using a case-control design, we modelled the odds of a hospital admission having a primary diagnosis of UTI as a function of demographics, payer, location, patient severity, admission month, year and the average temperature for the admission month. We found, after controlling for patient factors and month of admission, the odds of a UTI diagnosis increased with higher temperatures in a dose-dependent manner. For example, relative to months with average temperatures of 5-7.5 °C, an admission in a month with an average temperature of 27.5-30 °C has 20% higher odds of a primary diagnosis of UTI. However, in months with extremely high average temperatures (above 30 °C), the odds of a UTI admissions decrease, perhaps due to changes in behaviour. Thus, at a population level, UTI-related hospitalisations are associated with warmer weather.

Magnetic anisotropy behaviour of pyrrhotite as determined by low- and high-field experiments

NASA Astrophysics Data System (ADS)

Martín-Hernández, F.; Dekkers, M. J.; Bominaar-Silkens, I. M. A.; Maan, J. C.

2008-07-01

Here we report on the sources of magnetic anisotropy in pyrrhotite, an iron sulphide present in many rocks as an important carrier of the Natural Remanent Magnetization. While the magnetic hysteresis parameters of pyrrhotite are well known, the existing database concerning its anisotropy behaviour is patchy and ambiguous. Therefore, a collection of 11 seemingly single crystals of natural pyrrhotite was scrutinized. Before embarking on the anisotropy determinations the set of single crystals was extensively characterized rock magnetically by measuring Curie temperatures, hysteresis loops, IRM acquisition curves, and FORC diagrams (the latter three all at room temperature). First the variation of the low-field susceptibility as function of applied field and grain size was evaluated for fields ranging from 1 to 450 A m-1. Existing grain size dependent data and the present larger crystals show a logarithmic grain size dependence. This enables estimating the grain size for unimodal pyrrhotite distributions in rocks. Measured trends are better fitted with an exponential function than with a Rayleigh Law style function. Based on the rock magnetic characterization and the behaviour of the anisotropy of magnetic susceptibility six samples (of the original 11) were selected for the high-field anisotropy determinations within the basal plane. Those data were acquired with a torque cantilever-type magnetometer. As expected, most single crystals showed a pure 6-θ curve within their basal plane because of the easy axis configuration. In some crystals, however, lower harmonic terms overlapped the 6-θ term. This may be the dominant source of the observed variation in magnetic anisotropy properties. Torque data of three of the six samples were of sufficient quality to allow evaluation of K1. Re-evaluation of existing torque data and including the present newly derived determinations, yields for the anisotropy constant of pyrrhotite within the basal plane K1: (2.7 +/- 0.2) 104 Jm-3. This is over an order of magnitude more precise than the sparse existing K1 data; only the value reported by Mikami and co-authors in 1959 agrees with the new determination. With this firmly established K1 value meaningful anisotropy models are now possible for pyrrhotite-bearing rocks.

Acyl chain conformational ordering of individual components in liquid-crystalline bilayers of mixtures of phosphatidylcholines and phosphatidic acids. A comparative FTIR and 2H NMR study

NASA Astrophysics Data System (ADS)

Ziegler, Wolfgang; Blume, Alfred

1995-09-01

The conformational ordering of the acyl chains of all possible binary 1:1 mixtures containing the phospholipids DMPC, DMPA, DPPC, and DPPA was investigated using FTIR and 2H NMR spectroscopy. One of the components was always labelled with perdeuterated chains to be able to observe the individual behaviour of the two components. From the temperature dependence of the frequencies of the symmetric and antisymmetric CH 2- and CD 2-stretching vibrations the transition temperatures were determined. The integral intensities of the conformation sensitive CH 2-wagging bands at ca. 1368 cm -1(gtg' and gtg sequences), 1356 cm -1 (double gauche), and 1342 cm -1 (end gauche) can be converted to numbers of gauche conformers per acyl chain using calibration factors published by Senak et al. J. Phys. Chem. 95 (1991) 2565. The 2H NMR quadrupolar splittings of the CD 2-segments of the perdeuterated lipid components are affected not only by trans-gauche isomerizations but also by long axis rotations and restricted wobbling motions of the acyl chains. The values of the average gauche probability overlinep3 from FTIR spectroscopy and the average order parameters overlineSCD, the order parameter of the terminal methyl groups SCDCD 3 and the average order parameter for the plateau region overlineSCDPlat of components in the mixtures are compared to those of the pure lipids evaluated in a previous publication Tuchtenhagen et al. Eur. Biophys. J. 23 (1994) 323. The conformational behaviour of lipids in mixtures is mainly influenced by head groups interactions, PAs always being more ordered than the corresponding PCs. Depending on absolute chain length and on chain length differences between the two components different conformational behaviour is observed for the two components in the mixtures, indicating non-ideal mixing and formation of micro-domains in the liquid-crystalline phase. Increases in order at the chain ends with a concomitant decrease in probabilities for end gauche conformations give hints to chain interdigitation in the liquid-crystalline phase.

On transitions in the behaviour of tabu search algorithm TabuCol for graph colouring

NASA Astrophysics Data System (ADS)

Chalupa, D.

2018-01-01

Even though tabu search is one of the most popular metaheuristic search strategies, its understanding in terms of behavioural transitions and parameter tuning is still very limited. In this paper, we present a theoretical and experimental study of a popular tabu search algorithm TabuCol for graph colouring. We show that for some instances, there are sharp transitions in the behaviour of TabuCol, depending on the value of tabu tenure parameter. The location of this transition depends on graph structure and may also depend on its size. This is further supported by an experimental study of success rate profiles, which we define as an empirical measure of these transitions. We study the success rate profiles for a range of graph colouring instances, from 2-colouring of trees and forests to several instances from the DIMACS benchmark. These reveal that TabuCol may exhibit a spectrum of different behaviours ranging from simple transitions to highly complex probabilistic behaviour.

Henry constant and isosteric heat at zero-loading for gas adsorption in carbon nanotubes.

PubMed

Do, D D; Do, H D; Wongkoblap, A; Nicholson, D

2008-12-28

The Henry constant and the isosteric heat of adsorption at zero loading in a carbon nanotube bundle are studied with Monte Carlo integration for the adsorption of gases over a range of temperatures. The spacing between nanotubes in a bundle is determined from the minimization of potential energy of interaction between these tubes. We study different tube configurations with bundles of 2, 3, 4 and 7 tubes. Depending on the configuration it is found that the spacing is of between 0.31 to 0.333 nm, and this falls within the range reported in the literature. The Henry constant has been carefully defined so that it will not become negative at high temperatures. This is done with the aid of accessible volume, rather than the usual absolute void volume. We show that linearity of the van't Hoff plot for the Henry constant is not strictly followed. Furthermore the slope of this plot is not equal to the isosteric heat of adsorption at zero loading, which is found to be a strong function of temperature. From the results we find that the Henry constant and the heat of adsorption depend on the tube configuration. In general the adsorption in the cusp interstices is strongest followed by that inside the tube and finally on the outer surface. However for very small tubes adsorption occurs inside the tube first. For molecules with orientation, the behaviour is even more interesting and the shape of the isosteric heat versus temperature depends on the degree of orientation, tube configuration and the domain of adsorption (interstices, inside the tube and on the outer surface).

The autumn effect: timing of physical dormancy break in seeds of two winter annual species of Geraniaceae by a stepwise process

PubMed Central

Gama-Arachchige, N. S.; Baskin, J. M.; Geneve, R. L.; Baskin, C. C.

2012-01-01

Background and Aims The involvement of two steps in the physical dormancy (PY)-breaking process previously has been demonstrated in seeds of Fabaceae and Convolvulaceae. Even though there is a claim for a moisture-controlled stepwise PY-breaking in some species of Geraniaceae, no study has evaluated the role of temperature in the PY-breaking process in this family. The aim of this study was to determine whether a temperature-controlled stepwise PY-breaking process occurs in seeds of the winter annuals Geranium carolinianum and G. dissectum. Methods Seeds of G. carolinianum and G. dissectum were stored under different temperature regimes to test the effect of storage temperature on PY-break. The role of temperature and moisture regimes in regulating PY-break was investigated by treatments simulating natural conditions. Greenhouse (non-heated) experiments on seed germination and burial experiments (outdoors) were carried out to determine the PY-breaking behaviour in the natural habitat. Key Results Irrespective of moisture conditions, sensitivity to the PY-breaking step in seeds of G. carolinianum was induced at temperatures ≥20 °C, and exposure to temperatures ≤20 °C made the sensitive seeds permeable. Sensitivity of seeds increased with time. In G. dissectum, PY-break occurred at temperatures ≥20 °C in a single step under constant wet or dry conditions and in two steps under alternate wet–dry conditions if seeds were initially kept wet. Conclusions Timing of seed germination with the onset of autumn can be explained by PY-breaking processes involving (a) two temperature-dependent steps in G. carolinianum and (b) one or two moisture-dependent step(s) along with the inability to germinate under high temperatures in G. dissectum. Geraniaceae is the third of 18 families with PY in which a two-step PY-breaking process has been demonstrated. PMID:22684684

Problematic Internet Use, Excessive Alcohol Consumption, Their Comorbidity and Cardiovascular and Cortisol Reactions to Acute Psychological Stress in a Student Population

PubMed Central

Bibbey, Adam; Phillips, Anna C.; Ginty, Annie T.; Carroll, Douglas

2015-01-01

Background and Aims Problematic Internet use and excessive alcohol consumption have been associated with a host of maladaptive outcomes. Further, low (blunted) cardiovascular and stress hormone (e.g. cortisol) reactions to acute psychological stress are a feature of individuals with a range of adverse health and behavioural characteristics, including dependencies such as tobacco and alcohol addiction. The present study extended this research by examining whether behavioural dependencies, namely problematic Internet use, excessive alcohol consumption, and their comorbidity would also be associated with blunted stress reactivity. Methods A large sample of university students (N = 2313) were screened using Internet and alcohol dependency questionnaires to select four groups for laboratory testing: comorbid Internet and alcohol dependence (N = 17), Internet dependence (N = 17), alcohol dependence (N = 28), and non-dependent controls (N = 26). Cardiovascular activity and salivary cortisol were measured at rest and in response to a psychological stress protocol comprising of mental arithmetic and public speaking tasks. Results Neither problematic Internet behaviour nor excessive alcohol consumption, either individually or in combination, were associated with blunted cardiovascular or cortisol stress reactions. Discussion It is possible that problematic Internet behaviour and excessive alcohol consumption in a student population were not related to physiological reactivity as they may not reflect ingrained addictions but rather an impulse control disorder and binging tendency. Conclusions The present results serve to indicate some of the limits of the developing hypothesis that blunted stress reactivity is a peripheral marker of the central motivational dysregulation in the brain underpinning a wide range of health and behavioural problems. PMID:26014670

Modelling of the mechanical behaviour of the single-crystal turbine alloy CMSX-4 during thermomechanical loading

NASA Astrophysics Data System (ADS)

Schubert, F.; Fleury, G.; Steinhaus, T.

2000-11-01

Turbine blades in gas turbine engines are subjected during operation to triaxial stress fields. For the description of the deformation behaviour of anisotropic single-crystal blades, constitutive equations are required which take account of modifications to the deformation processes caused by evolution of the γ/γ' microstructure during service (γ' rafting). A microstructure-dependent, orthotropic Hills potential, whose anisotropy coefficients are connected to the edge length of γ' particles, has been applied. The shape of γ' particles remains cubic below exposures at 700 °C. At high temperatures (above 850 °C) the γ' particles coalesce to rafts, and the viscoplastic response of the superalloy is continuously modified. This reduces the creep resistance of <001> orientated specimen. After tensile loading of the <001>-orientated specimens at 1000 °C, the rafting of γ' in the (100) plane was observed as expected, whereas the <111> specimens did not reveal γ' rafting. Torsionally loaded specimens exhibited rafting only in the near <100>-orientated surface regions of the specimen. The deformation in the <111> tensile and <001> torsion specimens occurred by octahedral slip of dislocations and not by cubic slip, as expected from theoretical considerations. Rafting did not occur in the <111>-orientated specimens. This anisotropy change is simulated successfully by the microstructure-dependent model.

Magnetic, electronic transport and magneto-transport behaviours of (Co1-xMnx)2P compounds

NASA Astrophysics Data System (ADS)

Sun, N. K.; Zhang, Y. Q.; Li, Y. B.; Li, D.; Li, W. F.; Liu, W.; Zhao, X. G.; Zhang, Z. D.

2006-10-01

Magnetic, electronic transport and magneto-transport behaviours of (Co1-xMnx)2P (0.55 <= x <= 0.675) compounds have been systematically investigated. A typical metallic-conductivity behaviour is observed in the ferromagnetic compound (Co0.45Mn0.55)2P. The increase in the Mn concentration gives rise to dramatic changes in magnetic, electronic transport and magneto-transport behaviours. With increasing temperature, a first-order phase transition from antiferromagnetism to ferromagnetism takes place at about 145 K, 185 K and 240 K for x = 0.60, 0.625 and 0.65, respectively. (Co0.4Mn0.6)2P and (Co0.375Mn0.625)2P compounds experience a metal-insulator transition (Anderson transition) with decreasing temperature. An external magnetic field of 5 T strongly influences the Anderson transition, lowering the transition temperature from 80 to 55 K for (Co0.4Mn0.6)2P and from 115 to 70 K for (Co0.375Mn0.625)2P. In contrast with this metal-insulator transition, an insulating behaviour appears in the temperature range from 10 to 300 K for (Co0.35Mn0.65)2P and (Co0.325Mn0.675)2P compounds. Below the antiferromagnetic-ferromagnetic transition temperature TAF-F, a metamagnetic transition can be induced by an external magnetic field. The metamagnetic transition is accompanied by a maximum magnetoresistance ratio of -7%, -6.3% or -3.7% at 5 T in the (Co0.4Mn0.6)2P, (Co0.375Mn0.625)2P or (Co0.35Mn0.65)2P compound at 10 K. The mechanisms of magnetoresistive behaviours are discussed in terms of the formation of a super-zone gap in the antiferromagnetic state.

Context dependency of trait repeatability and its relevance for management and conservation of fish populations

PubMed Central

Killen, S S; Adriaenssens, B; Marras, S; Claireaux, G; Cooke, S J

2016-01-01

Abstract Repeatability of behavioural and physiological traits is increasingly a focus for animal researchers, for which fish have become important models. Almost all of this work has been done in the context of evolutionary ecology, with few explicit attempts to apply repeatability and context dependency of trait variation toward understanding conservation-related issues. Here, we review work examining the degree to which repeatability of traits (such as boldness, swimming performance, metabolic rate and stress responsiveness) is context dependent. We review methods for quantifying repeatability (distinguishing between within-context and across-context repeatability) and confounding factors that may be especially problematic when attempting to measure repeatability in wild fish. Environmental factors such temperature, food availability, oxygen availability, hypercapnia, flow regime and pollutants all appear to alter trait repeatability in fishes. This suggests that anthropogenic environmental change could alter evolutionary trajectories by changing which individuals achieve the greatest fitness in a given set of conditions. Gaining a greater understanding of these effects will be crucial for our ability to forecast the effects of gradual environmental change, such as climate change and ocean acidification, the study of which is currently limited by our ability to examine trait changes over relatively short time scales. Also discussed are situations in which recent advances in technologies associated with electronic tags (biotelemetry and biologging) and respirometry will help to facilitate increased quantification of repeatability for physiological and integrative traits, which so far lag behind measures of repeatability of behavioural traits. PMID:27382470

Primary School Teachers' Views about Supervisional Deviant Behaviours

ERIC Educational Resources Information Center

Aksu, Ali; Gucer, Halil; Orcan, Asli

2015-01-01

This research examines supervisional deviant behaviours depending on the primary school teachers' view in Izmir, Turkey. Organizational or workplace deviant behaviours have been studied in number of studies and these types of behaviours are determined. It is obvious that solving the problems of orgaizational deviance contribute to meet…

Statistical Physics of Colloidal Dispersions.

NASA Astrophysics Data System (ADS)

Canessa, E.

Available from UMI in association with The British Library. Requires signed TDF. This thesis is concerned with the equilibrium statistical mechanics of colloidal dispersions which represent useful model systems for the study of condensed matter physics; namely, charge stabilized colloidal dispersions and polymer stabilized colloidal dispersions. A one-component macroparticle approach is adopted in order to treat the macroscopic and microscopic properties of these systems in a simple and comprehensive manner. The thesis opens with the description of the nature of the colloidal state before reviewing some basic definitions and theory in Chapter II. In Chapter III a variational theory of phase equilibria based on the Gibbs-Bogolyobov inequality is applied to sterically stabilized colloidal dispersions. Hard spheres are chosen as the reference system for the disordered phases while an Einstein model is used for the ordered phases. The new choice of pair potential, taken for mathematical convenience, is a superposition of two Yukawa functions. By matching a double Yukawa potential to the van der Waals attractive potential at different temperatures and introducing a purely temperature dependent coefficient to the repulsive part, a rich variety of observed phase separation phenomena is qualitatively described. The behaviour of the potential is found to be consistent with a small decrease of the polymer layer thickness with increasing temperature. Using the same concept of a collapse transition the non-monotonic second virial coefficient is also explained and quantified. It is shown that a reduction of the effective macroparticle diameter with increasing temperature can only be partially examined from the point of view of a (binary-) polymer solution theory. This chapter concludes with the description of the observed, reversible, depletion flocculation behaviour. This is accomplished by using the variational formalism and by invoking the double Yukawa potential to allow changes of the depletion attraction with free polymer concentration. Chapter IV deals with the contributions of pairwise additive and volume dependent forces to the free energy of charge stabilized colloidal dispersions. To a first approximation the extra volume dependent contributions due to the chemical equilibrium and counterion-macroion coupling are treated in a one-component plasma approach. Added salt is treated as an ionized gas within the Debye-Huckel theory of electrolytes. In order to set this approach on a quantitative basis the existence of an equilibrium lattice with a small shear modulus is examined. Structural phase transitions in these systems are also analysed theoretically as a function of added electrolyte.

Estimation of thermodynamic parameters for Au- and Mg-based metallic glasses

NASA Astrophysics Data System (ADS)

Gaur, Jitendra; Mishra, R. K.

2017-10-01

The study of temperature dependent thermodynamic parameters; Gibb's free energy difference (ΔG), entropy difference (ΔS) and enthalpy difference (ΔH) between the undercooled liquid and the corresponding equilibrium solid phases has been proved to be extremely advantageous in the study of the thermodynamic behaviour of Metallic glass (MG) forming melts. In last two decades, Au- and Mg-based alloys were found to form glass phases. In present study, the three thermodynamic parameters viz., ΔG, ΔS and ΔH are calculated theoretically in the entire temperature range Tm (melting temperature) to Tg (glass transition temperature) for both Au- and Mg-based five samples of MGs; Au77Ge13.6Si9.4, Au53.2Pb27.5Sb19.3, Au81.4Si18.6, Mg85.5Cu14.5 and Mg81.6Ga18.4 on the basis of Taylor's series expansion. A relative study is also made between the present result and the result obtained experimentally as well as on the basis of expressions projected by the earlier researchers. An attempt is also been made to narrate the reduced glass transition temperature with glass forming ability for all five MGs.

Effects of Composite Pions on the Chiral Condensate within the PNJL Model at Finite Temperature

NASA Astrophysics Data System (ADS)

Blaschke, D.; Dubinin, A.; Ebert, D.; Friesen, A. V.

2018-05-01

We investigate the effect of composite pions on the behaviour of the chiral condensate at finite temperature within the Polyakov-loop improved NJL model. To this end we treat quark-antiquark correlations in the pion channel (bound states and scattering continuum) within a Beth-Uhlenbeck approach that uses medium-dependent phase shifts. A striking medium effect is the Mott transition which occurs when the binding energy vanishes and the discrete pion bound state merges the continuum. This transition is triggered by the lowering of the continuum edge due to the chiral restoration transition. This in turn also entails a modification of the Polyakov-loop so that the SU(3) center symmetry gets broken at finite temperature and dynamical quarks (and gluons) appear in the system, taking over the role of the dominant degrees of freedom from the pions. At low temperatures our model reproduces the chiral perturbation theory result for the chiral condensate while at high temperatures the PNJL model result is recovered. The new aspect of the current work is a consistent treatment of the chiral restoration transition region within the Beth-Uhlenbeck approach on the basis of mesonic phase shifts for the treatment of the correlations.

A comparative study of texture and rheology of Argentinian honeys from two regions.

PubMed

Maldonado, Ezequiel; Navarro, Alba S; Yamul, Diego K

2018-06-23

The rheological and textural properties of 26 eastern Argentinian honeys from two different regions (North and Central) were investigated. The viscosity curves of the samples were obtained using a rotational rheometer over a temperature range of 10 to 50°C. The viscosity decreased with temperature and all honeys showed a Newtonian behaviour. The temperature dependence of viscosity was described using the Arrhenius, Williams- Landel-Ferry, Vogel-Taumman-Fulcher and Power Law models. The glass transition temperatures of honeys were measured with differential scanning calorimetry and values ranged from -42.63 to -47.71°C. The glass transition temperature was also predicted with the Williams- Landel-Ferry model and no significant differences were observed with the experimental results. Rheological parameters were obtained by small amplitude oscillation experiments. Results indicated that the viscous modulus was higher than the storage modulus within all the frequency ranges assayed and honeys from the North region were more viscous. Results of the back extrusion test showed that honeys from the Central region are harder and both groups of honeys (North and Central) exhibited the same consistency and adhesivity. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Ultrasonic Investigations on Polonides of Ba, Ca, and Pb

NASA Astrophysics Data System (ADS)

Singh, Devraj; Bhalla, Vyoma; Bala, Jyoti; Wadhwa, Shikha

2017-10-01

The temperature-dependent mechanical and ultrasonic properties of barium, calcium, and lead polonides (BaPo, CaPo, and PbPo) were investigated in the temperature range 100-300 K. The second- and third-order elastic constants (SOECs and TOECs) were computed using Coulomb and Born-Mayer potential and these in turn have been used to estimate other secondary elastic properties such as strength, anisotropy, microhardness, etc. The theoretical approach followed the prediction that BaPo, CaPo, and PbPo are brittle in nature. PbPo is found to be the hardest amongst the chosen compounds. Further the SOECs and TOECs are applied to determine ultrasonic velocities, Debye temperature, and acoustic coupling constants along <100>, <110>, and <111> orientations at room temperature. Additionally thermal conductivity has been computed using Morelli and Slack's approach along different crystallographic directions at room temperature. Finally ultrasonic attenuation due to phonon-phonon interaction and thermoelastic relaxation mechanisms has been computed for BaPo, CaPo, and PbPo. The behaviour of these compounds is similar to that of semi-metals with thermal relaxation time of the order 10-11 s. The present computation study is reasonably in agreement with the available theoretical data for the similar type of materials.

Initiation of the ice phase by marine biogenic surfaces in supersaturated gas and supercooled aqueous phases.

PubMed

Alpert, Peter A; Aller, Josephine Y; Knopf, Daniel A

2011-11-28

Biogenic particles have the potential to affect the formation of ice crystals in the atmosphere with subsequent consequences for the hydrological cycle and climate. We present laboratory observations of heterogeneous ice nucleation in immersion and deposition modes under atmospherically relevant conditions initiated by Nannochloris atomus and Emiliania huxleyi, marine phytoplankton with structurally and chemically distinct cell walls. Temperatures at which freezing, melting, and water uptake occur are observed using optical microscopy. The intact and fragmented unarmoured cells of N. atomus in aqueous NaCl droplets enhance ice nucleation by 10-20 K over the homogeneous freezing limit and can be described by a modified water activity based ice nucleation approach. E. huxleyi cells covered by calcite plates do not enhance droplet freezing temperatures. Both species nucleate ice in the deposition mode at an ice saturation ratio, S(ice), as low as ~1.2 and below 240 K, however, for each, different nucleation modes occur at warmer temperatures. These observations show that markedly different biogenic surfaces have both comparable and contrasting effects on ice nucleation behaviour depending on the presence of the aqueous phase and the extent of supercooling and water vapour supersaturation. We derive heterogeneous ice nucleation rate coefficients, J(het), and cumulative ice nuclei spectra, K, for quantification and analysis using time-dependent and time-independent approaches, respectively. Contact angles, α, derived from J(het)via immersion freezing depend on T, a(w), and S(ice). For deposition freezing, α can be described as a function of S(ice) only. The different approaches yield different predictions of atmospheric ice crystal numbers primarily due to the time evolution allowed for the time-dependent approach with implications for the evolution of mixed-phase and ice clouds.

Thermal preference predicts animal personality in Nile tilapia Oreochromis niloticus.

PubMed

Cerqueira, Marco; Rey, Sonia; Silva, Tome; Featherstone, Zoe; Crumlish, Margaret; MacKenzie, Simon

2016-09-01

Environmental temperature gradients provide habitat structure in which fish orientate and individual thermal choice may reflect an essential integrated response to the environment. The use of subtle thermal gradients likely impacts upon specific physiological and behavioural processes reflected as a suite of traits described by animal personality. In this study, we examine the relationship between thermal choice, animal personality and the impact of infection upon this interaction. We predicted that thermal choice in Nile tilapia Oreochromis niloticus reflects distinct personality traits and that under a challenge individuals exhibit differential thermal distribution. Nile tilapia were screened following two different protocols: 1) a suite of individual behavioural tests to screen for personality and 2) thermal choice in a custom-built tank with a thermal gradient (TCH tank) ranging from 21 to 33 °C. A first set of fish were screened for behaviour and then thermal preference, and a second set were tested in the opposite fashion: thermal then behaviour. The final thermal distribution of the fish after 48 h was assessed reflecting final thermal preferendum. Additionally, fish were then challenged using a bacterial Streptococcus iniae model infection to assess the behavioural fever response of proactive and reactive fish. Results showed that individuals with preference for higher temperatures were also classified as proactive with behavioural tests and reactive contemporaries chose significantly lower water temperatures. All groups exhibited behavioural fever recovering personality-specific thermal preferences after 5 days. Our results show that thermal preference can be used as a proxy to assess personality traits in Nile tilapia and it is a central factor to understand the adaptive meaning of animal personality within a population. Importantly, response to infection by expressing behavioural fever overrides personality-related thermal choice. © 2016 The Authors. Journal of Animal Ecology © 2016 British Ecological Society.

The Directive 2010/63/EU on animal experimentation may skew the conclusions of pharmacological and behavioural studies.

PubMed

Macrì, Simone; Ceci, Chiara; Altabella, Luisa; Canese, Rossella; Laviola, Giovanni

2013-01-01

All laboratory animals shall be provided some form of environmental enrichment (EE) in the nearest future (Directive 2010/63/EU). Displacing standard housing with EE entails the possibility that data obtained under traditional housing may be reconsidered. Specifically, while EE often contrasts the abnormalities of consolidated disease models, it also indirectly demonstrates that their validity depends on housing conditions. We mimicked a situation in which the consequences of a novel pharmacological compound were addressed before and after the adoption of the Directive. We sub-chronically exposed standard- or EE-reared adolescent CD1 mice (postnatal days 23-33) to the synthetic compound JWH-018, and evaluated its short- and long-term potential cannabinoid properties on: weight gain, locomotion, analgesia, motor coordination, body temperature, brain metabolism ((1)H MRI/MRS), anxiety- and depressive-related behaviours. While several parameters are modulated by JWH-018 independently of housing, other effects are environmentally mediated. The transition from standard housing to EE shall be carefully monitored.

Symplasmata are a clonal, conditional, and reversible type of bacterial multicellularity

DOE PAGES

Tecon, Robin; Leveau, Johan H. J.

2016-08-18

Microorganisms are capable of remarkable social behaviours, such as forming transient multicellular assemblages with properties and adaptive abilities exceeding those of individual cells. Here, we report on the formation and structure of genets known as symplasmata produced by Pantoea eucalypti bacteria. Each symplasmatum develops clonally and stochastically from a single bacterium into a membrane-delimited, capsule-embedded cluster of progeny cells and with a frequency that depends on temperature, pH, and nutrient availability. Transposon mutagenesis identified several gene products required for symplasmata formation, including master regulator LrhA, replication inhibitor CspD, polysaccharide transporter RfbX3, and autoinducer synthase PhzI. We also show that bacteriamore » inside symplasmata are shaped irregularly with punctuated cell-to-cell contacts, metabolically responsive to environmental stimuli, dispersal-ready, and transcriptionally reprogrammed to anticipate multiple alternative futures in terms of carbon source availability. In conclusion, the structured and conditionable nature of symplasmata offers exciting prospects towards a mechanistic understanding of multicellular behaviours and their ecological significance.« less

Measurements and tests of HTS bulk material in resistive fault current limiters

NASA Astrophysics Data System (ADS)

Noe, M.; Juengst, K.-P.; Werfel, F. N.; Elschner, S.; Bock, J.; Wolf, A.; Breuer, F.

2002-08-01

The application of superconducting fault current limiters (SCFCL) depends highly on their technical and economical benefits. Therefore it is obvious that the main requirements on the SCFCL are a reliable, fail-safe and rapid current limitation, low losses, and an inexpensive production. As a potential candidate material we have investigated HTS bulk material in resistive fault current limiters. Our report focuses on the E- j-curves, the AC-losses and the quench behaviour of melt cast processed-BSCCO 2212 and melt textured polycrystalline-YBCO 123. Within a temperature range from 64 to 80 K E- j-curves and AC losses of HTS elements were measured. The measurement results show that HTS bulk material meets the SCFCL specifications. In order to avoid hot spots during limitation and to improve mechanical stability a metallic bypass is needed. First test results of the quench behaviour of HTS bulk material with metallic bypass demonstrate safe limitation up to the specified electrical field of 100 V/m.

Fracture Properties of Polystyrene Aggregate Concrete after Exposure to High Temperatures

PubMed Central

Tang, Waiching; Cui, Hongzhi; Tahmasbi, Soheil

2016-01-01

This paper mainly reports an experimental investigation on the residual mechanical and fracture properties of polystyrene aggregate concrete (PAC) after exposure to high temperatures up to 800 degrees Celsius. The fracture properties namely, the critical stress intensity factor (KICS), the critical crack tip opening displacement (CTODC) for the Two-Parameter Model, and the fracture energy (GF) for the Fictitious Crack Model were examined using the three-point bending notched beam test, according to the RILEM recommendations. The effects of polystyrene aggregate (PA) content and temperature levels on the fracture and mechanical properties of concrete were investigated. The results showed that the mechanical properties of PAC significantly decreased with increase in temperature level and the extent of which depended on the PA content in the mixture. However, at a very high temperature of 800 °C, all samples showed 80 percent reduction in modulus of elasticity compared to room temperature, regardless of the level of PA content. Fracture properties of control concrete (C) and PAC were influenced by temperature in a similar manner. Increasing temperature from 25 °C to 500 °C caused almost 50% reduction of the fracture energy for all samples while 30% increase in fracture energy was occurred when the temperature increased from 500 °C to 800 °C. It was found that adding more PA content in the mixture lead to a more ductile behaviour of concrete. PMID:28773752

Study of the Dependency on Magnetic Field and Bias Voltage of an AC-Biased TES Microcalorimeter.

PubMed

Gottardi, L; Adams, J; Bailey, C; Bandler, S; Bruijn, M; Chervenak, J; Eckart, M; Finkbeiner, F; den Hartog, R; Hoevers, H; Kelley, R; Kilbourne, C; de Korte, P; van der Kuur, J; Lindeman, M; Porter, F; Sadlier, J; Smith, S

At SRON we are studying the performance of a Goddard Space Flight Center single pixel TES microcalorimeter operated in an AC bias configuration. For x-ray photons at 6 keV the pixel shows an x-ray energy resolution Δ E FWHM =3.7 eV, which is about a factor 2 worse than the energy resolution observed in an identical DC-biased pixel. In order to better understand the reasons for this discrepancy we characterised the detector as a function of temperature, bias working point and applied perpendicular magnetic field. A strong periodic dependency of the detector noise on the TES AC bias voltage is measured. We discuss the results in the framework of the recently observed weak-link behaviour of a TES microcalorimeter.

How does the composition affect the mechanical behaviour of simulated clay-rich fault gouges?

NASA Astrophysics Data System (ADS)

Bakker, Elisenda; Spiers, Christopher J.; Hangx, Suzanne J. T.

2014-05-01

CO2 capture and storage (CCS) in depleted oil and gas reservoirs is seen as one of the most promising large-scale CO2-mitigation strategies. Prediction of the effect of fluid-rock interaction on the mechanical integrity and sealing capacity of a reservoir-seal system, on timescales of the order of 1,000 or 10,000 years, is important to ensure the safety and containment of a reservoir in relation to long-term CO2 storage. However, most chemical reactions in rock/CO2/brine systems are slow, which means that long-term effects of fluids on rock composition, microstructure, mechanical properties and transport properties cannot be easily reproduced under laboratory conditions. One way to overcome this problem is to use simulated fault gouges in experiments, investigating a range of possible mineralogical compositions resulting from CO2-exposure. Previous studies have shown that the mechanical and transport properties of clay-rich fault gouges are significantly influenced by the mineralogy, particularly by the presence and relative amount of secondary phases, such as quartz and/or carbonate. In CCS settings, where dissolution and/or precipitation of carbonates may play an important role, the carbonate:clay ratio is expected to influence fault frictional behaviour. This is supported by the different behaviour of phyllosilicates, which generally show stable slip behaviour (aseismic), compared to carbonates, which have shown to become prone to unstable slip (potentially seismic) with increasing temperature. However, little is known about the mechanical and transport properties of carbonate/clay mixtures. We investigated the effect of the carbonate:clay ratio on fault friction, fault reactivation potential and slip stability, i.e. seismic vs. aseismic behaviour, as well as transmissivity evolution during and after fault reactivation. We used two types of starting material, derived from crushed Opalinus Claystone (Mont Terri, Switzerland): i) untreated samples consisting mainly of phyllosilicates (60%), quartz (~20%) and calcite (~15-25%) and ii) "leached" samples consisting of phyllosilicate (65%) and quartz (35%), where the removal of the calcite represents a worst-case scenario for rock/CO2/brine (dissolution) reactions. We performed triaxial direct shear experiments at relevant in-situ temperatures (60-120°C) under saturated conditions (Pp = 25 MPa), using demineralized water as pore fluid, at an effective normal stress (σn) of 50 MPa and shear velocities of 0.22 to 10.9 μm/s. Preliminary results show that the shear strength of the leached samples decreases by ~10-15% with respect to the natural, untreated clay samples. Typical steady-state friction coefficient values obtained for the natural samples are in the range 0.27-0.33, whereas for the leached samples they vary between 0.24 and 0.27. These values are significantly lower than typical friction coefficient values obtained for pure calcite (i.e. 0.62 to 0.71). Both natural and leached samples show velocity strengthening behaviour. The slip stability of the natural gouge appears to be slightly more temperature dependent, showing somewhat higher values of the stability (rate and state friction) parameter (a-b) for lower temperatures.

Indicators of drug-seeking aberrant behaviours: the feasibility of use in observational post-marketing cohort studies for risk management.

PubMed

Layton, Deborah; Osborne, Vicki; Al-Shukri, Mohammad; Shakir, Saad A W

2014-08-01

Problematic prescription drug use is reflected by or associated with drug-seeking aberrant behaviours. Research gaps include lack of post-marketing evidence and instruments. As part of the pharmacovigilance requirements, a risk management plan was developed for fentanyl buccal tablets (FEBT) by the manufacturer, with an additional pharmacovigilance activity requested by the regulatory authority, to investigate the risks of misuse, abuse, criminal use, off-label use and accidental exposure to FEBT after the product became commercially available. A Modified Prescription-Event Monitoring (M-PEM), observational, post-authorisation safety surveillance (PASS) study was conducted, with an overall aim to examine the use of FEBT in relation to their safety as prescribed in primary care in England. One of the exploratory objectives included estimating the prevalence of aberrant behaviours during FEBT treatment. To determine the feasibility of estimating the prevalence of risk factors associated with dependence on starting treatment and aberrant behaviours in patients during treatment with a prototypical abuse liable substance (fentanyl), as based on the application of an existing index (the Chabal criteria). Data were collected as part of the M-PEM PASS study; exposure and outcome data (including risk factors for dependence and aberrant behaviours based on behavioural not clinical manifestations) were derived from questionnaires sent to primary care physicians in England during April 2008 to June 2011. For the exploratory objective of interest, descriptive statistics and simple (non-weighted) risk scores were constructed on aggregate counts (score ≥3 considered 'high-risk'). Supplementary analyses explored the relationship between the two indices and the characteristics of patients with aberrant behaviours and those without (crude odds ratios plus 95% confidence interval (CI) were calculated). In a cohort of 551 patients, the prevalence of at least one pre-existing risk factor for dependence was 26% (n = 145), whilst the frequency of aberrant behaviours observed during treatment was 8% (n = 46). Patients with aberrant behaviours had several different characteristics to patients without. The two indices were associated (χ (2) df (20) = 58.72, p < 0.001), but a high-dependence risk-factor score provided a poor indication of high aberrant behaviour risk; the area under the receiver operating characteristic curve was 0.58 (95% CI 0.41, 0.74). Study limitations included subjectivity in relation to physicians identifying aberrant behaviours, and under-reporting thereof in PASS observational study designs. The presence of these criteria does not confirm misuse, but should be considered as a signal of problematic opioid misuse, which requires investigation. Further research is needed to develop a more robust analytical construct. In this PASS study, the prevalence of at least one pre-existing risk factor for dependence was 26%, whilst the frequency of aberrant behaviours observed during treatment was 8%. Patients with aberrant behaviours had several different characteristics to patients without. This study demonstrates the feasibility of the systematic collection of physician reports of risk factors for dependence and aberrant behaviours to facilitate the development of risk scores, using these reports to support the post-marketing risk management of products with misuse potential.

Temperature, but Not Available Energy, Affects the Expression of a Sexually Selected Ultraviolet (UV) Colour Trait in Male European Green Lizards

PubMed Central

Bajer, Katalin; Molnár, Orsolya; Török, János; Herczeg, Gábor

2012-01-01

Background Colour signals are widely used in intraspecific communication and often linked to individual fitness. The development of some pigment-based (e.g. carotenoids) colours is often environment-dependent and costly for the signaller, however, for structural colours (e.g. ultraviolet [UV]) this topic is poorly understood, especially in terrestrial ectothermic vertebrates. Methodology/Principal Findings In a factorial experiment, we studied how available energy and time at elevated body temperature affects the annual expression of the nuptial throat colour patch in male European green lizards (Lacerta viridis) after hibernation and before mating season. In this species, there is a female preference for males with high throat UV reflectance, and males with high UV reflectance are more likely to win fights. We found that (i) while food shortage decreased lizards' body condition, it did not affect colour development, and (ii) the available time for maintaining high body temperature affected the development of UV colour without affecting body condition or other colour traits. Conclusions/Significance Our results demonstrate that the expression of a sexually selected structural colour signal depends on the time at elevated body temperature affecting physiological performance but not on available energy gained from food per se in an ectothermic vertebrate. We suggest that the effect of high ambient temperature on UV colour in male L. viridis makes it an honest signal, because success in acquiring thermally favourable territories and/or effective behavioural thermoregulation can both be linked to individual quality. PMID:22479611

A novel method for delivering ramped cooling reveals rat behaviours at innocuous and noxious temperatures: A comparative study of human psychophysics and rat behaviour.

PubMed

Dunham, James P; Hulse, Richard P; Donaldson, Lucy F

2015-07-15

Thermal sensory testing in rodents informs human pain research. There are important differences in the methodology for delivering thermal stimuli to humans and rodents. This is particularly true in cold pain research. These differences confound extrapolation and de-value nociceptive tests in rodents. We investigated cooling-induced behaviours in rats and psychophysical thresholds in humans using ramped cooling stimulation protocols. A Peltier device mounted upon force transducers simultaneously applied a ramped cooling stimulus whilst measuring contact with rat hind paw or human finger pad. Rat withdrawals and human detection, discomfort and pain thresholds were measured. Ramped cooling of a rat hind paw revealed two distinct responses: Brief paw removal followed by paw replacement, usually with more weight borne than prior to the removal (temperature inter-quartile range: 19.1 °C to 2.8 °C). Full withdrawal was evoked at colder temperatures (inter quartile range: -11.3 °C to -11.8 °C). The profile of human cool detection threshold and cold pain threshold were remarkably similar to that of the rat withdrawals behaviours. Previous rat cold evoked behaviours utilise static temperature stimuli. By utilising ramped cold stimuli this novel methodology better reflects thermal testing in patients. Brief paw removal in the rat is driven by non-nociceptive afferents, as is the perception of cooling in humans. This is in contrast to the nociceptor-driven withdrawal from colder temperatures. These findings have important implications for the interpretation of data generated in older cold pain models and consequently our understanding of cold perception and pain. Copyright © 2015. Published by Elsevier B.V.

Collective thermoregulation in bee clusters

PubMed Central

Ocko, Samuel A.; Mahadevan, L.

2014-01-01

Swarming is an essential part of honeybee behaviour, wherein thousands of bees cling onto each other to form a dense cluster that may be exposed to the environment for several days. This cluster has the ability to maintain its core temperature actively without a central controller. We suggest that the swarm cluster is akin to an active porous structure whose functional requirement is to adjust to outside conditions by varying its porosity to control its core temperature. Using a continuum model that takes the form of a set of advection–diffusion equations for heat transfer in a mobile porous medium, we show that the equalization of an effective ‘behavioural pressure’, which propagates information about the ambient temperature through variations in density, leads to effective thermoregulation. Our model extends and generalizes previous models by focusing the question of mechanism on the form and role of the behavioural pressure, and allows us to explain the vertical asymmetry of the cluster (as a consequence of buoyancy-driven flows), the ability of the cluster to overpack at low ambient temperatures without breaking up at high ambient temperatures, and the relative insensitivity to large variations in the ambient temperature. Our theory also makes testable hypotheses for the response of the cluster to external temperature inhomogeneities and suggests strategies for biomimetic thermoregulation. PMID:24335563

Effect of ageing temperatures on pseudoelasticity of Ni-rich NiTi shape memory alloy

NASA Astrophysics Data System (ADS)

Mohamad, Hishamiakim; Mahmud, Abdus Samad; Nashrudin, Muhammad Naqib; Razali, Muhammad Fauzinizam

2018-05-01

The shape memory behavior of NiTi alloy is very sensitive to alloy composition and heat treatments, particularly annealing and ageing. This paper analysed the effect of ageing towards the thermomechanical behaviour of Ti-51at%Ni wire. The analysis focused on the effect of ageing at the different temperature on thermal transformation sequence and tensile deformation behaviour with respect to the recoverability of the alloy. It was found that B2-R transformation peak appeared in the differential scanning calorimetry (DSC) measurement when the alloys were aged at the temperature between 400°C to 475°C for 30 minutes. Further ageing at 500°C to 550°C yielded two stage transformation, B2-R-B19' in cooling. All aged wires exhibited good pseudoelastic behaviour when deformed at room temperature and yielded below 1% residual strain upon unloading. Ageing at 450°C resulted the smallest unrecovered strain of about 0.4%.

Behavioural Thermoregulatory Tactics in Lacustrine Brook Charr, Salvelinus fontinalis

PubMed Central

Bertolo, Andrea; Pépino, Marc; Adams, Julie; Magnan, Pierre

2011-01-01

The need to vary body temperature to optimize physiological processes can lead to thermoregulatory behaviours, particularly in ectotherms. Despite some evidence of within-population phenotypic variation in thermal behaviour, the occurrence of alternative tactics of this behaviour is rarely explicitly considered when studying natural populations. The main objective of this study was to determine whether different thermal tactics exist among individuals of the same population. We studied the behavioural thermoregulation of 33 adult brook charr in a stratified lake using thermo-sensitive radio transmitters that measured hourly individual temperature over one month. The observed behavioural thermoregulatory patterns were consistent between years and suggest the existence of four tactics: two “warm” tactics with both crepuscular and finer periodicities, with or without a diel periodicity, and two “cool” tactics, with or without a diel periodicity. Telemetry data support the above findings by showing that the different tactics are associated with different patterns of diel horizontal movements. Taken together, our results show a clear spatio-temporal segregation of individuals displaying different tactics, suggesting a reduction of niche overlap. To our knowledge, this is the first study showing the presence of behavioural thermoregulatory tactics in a vertebrate. PMID:21490935

Climate collective risk dilemma with feedback of real-time temperatures

NASA Astrophysics Data System (ADS)

Du, Jinming; Wu, Bin; Wang, Long

2014-09-01

Controlling global warming through collective cooperation is a non-optional threshold public goods game. Previous models assume that the disaster is a sudden event and it happens with a given probability. It is shown that high risk can pave the way for reaching the cooperative target. These models, however, neglect the temperature dynamics, which is influenced by the collective behaviours. Here, we establish a temperature dynamics, and introduce the feedback between human strategy updating and the temperature change: high temperature will discount individuals' payoffs; while sufficient public goods may decrease the ever-rising temperature. We investigate how the temperature is affected by human behaviour and vice versa. It is found that, on the one hand, the temperature can be stabilized to a relatively safe level in the long run. On the other hand, the cooperation can be promoted and be maintained at a higher level, compared with public goods game models with no such feedback.

Environment-dependence of behavioural consistency in adult male European green lizards (Lacerta viridis).

PubMed

Horváth, Gergely; Mészáros, Boglárka; Urszán, Tamás János; Bajer, Katalin; Molnár, Orsolya; Garamszegi, László Zsolt; Herczeg, Gábor

2017-01-01

Understanding the background mechanisms affecting the emergence and maintenance of consistent between-individual variation within population in single (animal personality) or across multiple (behavioural syndrome) behaviours has key importance. State-dependence theory suggests that behaviour is 'anchored' to individual state (e.g. body condition, gender, age) and behavioural consistency emerges through behavioural-state feedbacks. A number of relevant state variables are labile (e.g. body condition, physiological performance) and expected to be affected by short-term environmental change. Yet, whether short-term environmental shifts affect behavioural consistency during adulthood remains questionable. Here, by employing a full-factorial laboratory experiment, we explored if quantity of food (low vs. high) and time available for thermoregulation (3h vs. 10h per day) had an effect on activity and risk-taking of reproductive adult male European green lizards (Lacerta viridis). We focussed on different components of behavioural variation: (i) strength of behavioural consistency (repeatability for animal personality; between-individual correlation for behavioural syndrome), (ii) behavioural type (individual mean behaviour) and (iii) behavioural predictability (within-individual behavioural variation). Activity was repeatable in all treatments. Risk-taking was repeatable only in the low basking treatments. We found significant between-individual correlation only in the low food × long basking time group. The treatments did not affect behavioural type, but affected behavioural predictability. Activity predictability was higher in the short basking treatment, where it also decreased with size (≈ age). Risk-taking predictability in the short basking treatment increased with size under food limitation, but decreased when food supply was high. We conclude that short-term environmental change can alter various components of behavioural consistency. The effect could be detected in the presence/absence patterns of animal personality and behavioural syndrome and the level of individual behavioural predictability, but not in behavioural type.

Evidence that long-lasting potentiation in limbic circuits mediating defensive behaviour in the right hemisphere underlies pharmacological stressor (FG-7142) induced lasting increases in anxiety-like behaviour: role of benzodiazepine receptors.

PubMed

Adamec, R E

2000-01-01

The hypothesis that benzodiazepine receptors mediate initiation of lasting behavioural changes induced by FG-7142 was supported in this study. Behavioural changes normally induced by FG-7142 were blocked by prior administration of the competitive benzodiazepine receptor blocker, Flumazenil. When cats were subsequently given FG-7142 alone, the drug produced lasting behavioural changes in species characteristic defensive responses to rodent and cat vocal threat. FG-7142 also induced long-lasting potentiation (LLP) of evoked potentials in a number of efferent pathways from the amygdala in both hemispheres. Flumazenil given prior to FG-7142 blocked LLP in all but one of the amygdala efferent pathways, suggesting benzodiazepine receptor dependence of initiation of LLP. Three physiological changes were most closely correlated with behavioural changes. LLP in the right amygdalo-ventromedial hypothalamic (VMH) and amygdalo-periacqueductal gray (PAG) pathways coincided closely with behavioural changes, as did a reduced threshold for the right amygdalo-VMH evoked potential. Administration of Flumazenil after FG-7142 returned defensive behaviour to pre FG-7142 baseline levels in a drug-dependent manner. At the same time LLP only in the right amygdalo-PAG pathway was reduced by Flumazenil. LLP in other pathways and amygdalo-VMH threshold were unaltered by Flumazenil. Moreover, covariance analyses indicated that increased defensiveness depended solely on LLP in the right amygdalo-PAG. These findings support the view that maintenance of lasting increases in defensive behaviour depend upon LLP of excitatory neural transmission between amygdala and lateral column of the PAG in the right hemisphere. Moreover, FG-7142 may be a useful model of the effects of traumatic stressors on limbic system function in anxiety, especially in view of the recent data in humans implicating right hemispheric function in persisting negative affective states in post-traumatic stress disorder.

Pathways for diffusion in the potential energy landscape of the network glass former SiO2

NASA Astrophysics Data System (ADS)

Niblett, S. P.; Biedermann, M.; Wales, D. J.; de Souza, V. K.

2017-10-01

We study the dynamical behaviour of a computer model for viscous silica, the archetypal strong glass former, and compare its diffusion mechanism with earlier studies of a fragile binary Lennard-Jones liquid. Three different methods of analysis are employed. First, the temperature and time scale dependence of the diffusion constant is analysed. Negative correlation of particle displacements influences transport properties in silica as well as in fragile liquids. We suggest that the difference between Arrhenius and super-Arrhenius diffusive behaviour results from competition between the correlation time scale and the caging time scale. Second, we analyse the dynamics using a geometrical definition of cage-breaking transitions that was proposed previously for fragile glass formers. We find that this definition accurately captures the bond rearrangement mechanisms that control transport in open network liquids, and reproduces the diffusion constants accurately at low temperatures. As the same method is applicable to both strong and fragile glass formers, we can compare correlation time scales in these two types of systems. We compare the time spent in chains of correlated cage breaks with the characteristic caging time and find that correlations in the fragile binary Lennard-Jones system persist for an order of magnitude longer than those in the strong silica system. We investigate the origin of the correlation behaviour by sampling the potential energy landscape for silica and comparing it with the binary Lennard-Jones model. We find no qualitative difference between the landscapes, but several metrics suggest that the landscape of the fragile liquid is rougher and more frustrated. Metabasins in silica are smaller than those in binary Lennard-Jones and contain fewer high-barrier processes. This difference probably leads to the observed separation of correlation and caging time scales.

Rock-magnetic analyses as a tool to investigate archaeological fired sediments: a case study of Mirador cave (Sierra de Atapuerca, Spain)

NASA Astrophysics Data System (ADS)

Carrancho, Á.; Villalaín, J. J.; Angelucci, D. E.; Dekkers, M. J.; Vallverdú, J.; Vergès, J. M.

2009-10-01

Here we report a detailed mineral magnetic study of Neolithic burnt levels in the Mirador Cave (Sierra de Atapuerca, Burgos, Spain) to reconstruct the burning history and to investigate their suitability for archaeomagnetic purposes. As a consequence of the ancient burning, a characteristic facies sequence was developed along the Holocene stratigraphy. From top to bottom it includes: (i) 2-10 cm ash layers, (ii) ~2 cm underlying rubefied layers and (iii) clay, mainly unburnt and of variable thickness. In some cases a thermally altered facies (2-6 cm) with a heterogeneous texture was identified (facies TF), usually between rubefactions and the unburnt levels. 126 oriented samples from 4 units (MIR12, 15, 18 and 21) and a 2 m section, all comprised between units MIR21 (6380 +/- 40 14C BP) and MIR9 (5090 +/- 40 14C BP) were analysed with rock magnetic methods. In addition, bulk sediment from each facies that comprise the Neolithic sequence was investigated. Measurements included: stepwise alternating field and thermal demagnetization of natural remanent magnetization (NRM), viscosity experiments, determination of the anisotropy of the magnetic susceptibility (AMS), the susceptibility frequency dependence at room temperature and determination of the temperature dependence of the susceptibility. Additional experiments consisted in the determination of the behaviour of anhysteretic and isothermal (IRM) remanences, magnetic hysteresis loops, first-order-reversal-curve diagrams, and thermal demagnetization of three-axial IRM. It appeared that the facies all show a fairly similar magnetic mineralogy and grain size dominated by low-titanium magnetite that is often partially maghaemitized. Main differences constitute the amount of superparamagnetic particles that is higher in unburnt strata concurring with a less well-defined NRM behaviour. The magnetic mineral concentration is notably higher in ashes. This homogeneity strongly suggests that similar sources and burial conditions prevailed during Neolithic times. Agreeing with archaeological observations and favoured by rapid burial conditions, very limited alterations have been deduced. AMS data revealed the absence of fluid flow in the ash lenses sampled. Demagnetization revealed a stable single NRM component in ashes, a single or two-component NRM in rubefactions and less stable multicomponent behaviour in clays. In ashes, magnetic minerals are likely secondary in origin formed by low-temperature oxidization soon after burning. Although this thermochemical nature of the NRM invalidates the use of these sediments for palaeointensity studies, archaeomagnetic (directional) data can be successfully obtained because the burning and oxidation are closely confined in time.

Distributed dynamic load on composite laminates

NASA Astrophysics Data System (ADS)

Langella, A.; Lopresto, V.; Caprino, G.

2016-05-01

An experimental activity conducted in order to assess the impact behavior at room and low temperature of carbon fibre in vinylester resin laminates used in the shipbuilding industry, was reported. The conditions which reproduce the impact of a hull at low temperature with a solid body suspended in the water was reproduced. A test equipment was designed and realized to reproduce the real material behaviour in water to obtain a load distribution on the entire surface of the specimen. The results were obtained impacting the laminates placed between the cilyndrical steel impactor and a bag containing water. A falling weight machine, equipped with an instrumented steel impactor and a thermal chamber, was adopted for the experimental tests. The impact behaviour in hostile environments was compared to the behaviour at room temperature and the data obtained under distributed load conditions were compared with the results from concentrated loads: a completely different behaviour was observed between the two different loading conditions in terms of load-displacement curve. The effect of the impact on the laminates has been related with the delaminations, evaluated by ultrasonic scanning, and the indentation.

Self-assembling N-(9-Fluorenylmethoxycarbonyl)-l-Phenylalanine hydrogel as novel drug carrier.

PubMed

Snigdha, Kirti; Singh, Brijesh K; Mehta, Abijeet Singh; Tewari, R P; Dutta, P K

2016-12-01

Supramolecular hydrogel as a novel drug carrier was prepared from N-(9-Fluorenylmethoxycarbonyl) (Fmoc) modified l-phenylalanine. Its different properties like stability at different pH, temperature and rheology were evaluated in reference to salicylic acid (SA) as a model drug, entrapped in the supramolecular hydrogel network. The release behaviour of SA drug in supramolecular hydrogel was investigated by UV-vis spectroscopy. The influence of hydrogelator, pH values of the accepting media, temperature and concentration of SA drug on the release behaviour was investigated under static conditions. The results indicated that the release rate of SA in the supramolecular hydrogels was slightly retarded with an increase of the hydrogelator concentration. Also, the release rates of SA increased with an increase of temperature and its concentration. Furthermore, the release behaviour of SA was found to be different at various pH values in buffers. The study of the release kinetics indicated that the release behaviour of SA from the carrier was in accord with the Peppas model and the diffusion controlled mechanism involved in the Fickian model. Copyright © 2016 Elsevier B.V. All rights reserved.

The effect of leaf beetle herbivory on the fire behaviour of tamarisk (Tamarix ramosissima Lebed.)

USGS Publications Warehouse

Drus, Gail M.; Dudley, Tom L.; Brooks, Matthew L.; Matchett, John R.

2012-01-01

The non-native tree, Tamarix spp. has invaded desert riparian ecosystems in the south-western United States. Fire hazard has increased, as typically fire-resistant native vegetation is replaced by Tamarix. The tamarisk leaf beetle, Diorhabda carinulata Desbrochers, introduced for biological control, may affect fire behaviour by converting hydrated live Tamarix leaves and twigs into desiccated and dead fuels. This potentially increases fire hazard in the short term before native vegetation can be re-established. This study investigates how fire behaviour is altered in Tamarix fuels desiccated by Diorhabda herbivory at a Great Basin site, and by herbivory simulated by foliar herbicide at a Mojave Desert site. It also evaluates the influence of litter depth on fire intensity. Fire behaviour was measured with a fire intensity index that integrates temperature and duration (degree-minutes above 70°C), and with maximum temperature, duration, flame lengths, rates of spread and vegetation removal. Maximum temperature, flame length and rate of spread were enhanced by foliar desiccation of Tamarix at both sites. At only the Mojave site, there was a trend for desiccated trees to burn with greater fire intensity. At both sites, fire behaviour parameters were influenced to a greater degree by litter depth, vegetation density and drier and windier conditions than by foliar desiccation.

Thermal quality influences effectiveness of thermoregulation, habitat use, and behaviour in milk snakes.

PubMed

Row, Jeffrey R; Blouin-Demers, Gabriel

2006-05-01

We investigated the link between thermal quality and the effectiveness of thermoregulation in milk snakes in a thermally challenging environment. We defined thermoregulatory effectiveness as the extent to which an individual maintains its body temperature (Tb) closer to the preferred range (Tset) than allowed by the thermal quality of its environment. We defined thermal quality as the magnitude of the difference between operative environmental temperatures (Te) and Tset. Because ectotherms regulate body temperatures through choice of habitat and behavioural adjustments, we also examined the link between thermoregulation, habitat use and behaviour. During 2003-2004, we located 25 individuals 890 times, and recorded their Tb. Thermal quality was lower in the spring and fall than in the summer, and was lower in forests than in open habitats. Milk snakes thermoregulated more effectively in the spring than in the summer and fall, and more effectively in the forest than in open habitats. Milk snakes had a strong preference for open habitats in all seasons, which was likely to facilitate behavioural thermoregulation. The preference for open habitats was equally strong in all seasons and, therefore, the higher effectiveness of thermoregulation was not a result of altered habitat use. Instead, milk snakes modified their behaviour and were seen basking more and moved less in the spring than in the summer.

Time-resolved study of formate on Ni( 1 1 1 ) by picosecond SFG spectroscopy

NASA Astrophysics Data System (ADS)

Kusafuka, K.; Noguchi, H.; Onda, K.; Kubota, J.; Domen, K.; Hirose, C.; Wada, A.

2002-04-01

Time-resolved vibrational measurements were carried out on formate (HCOO) adsorbed on Ni(1 1 1) surface by combining the sum-frequency generation method and picosecond laser system (time resolution of 6 ps). Rapid intensity decrease (within the time resolution) followed by intensity recovery (time constant of several tens of ps) of CH stretching signal was observed when picosecond 800 nm pulse was irradiated on the sample surface. From the results of temperature and pump fluence dependences of temporal behaviour of signal intensity, we concluded that the observed intensity change was induced by non-thermal process. Mechanism of the temporal intensity change was discussed.

Notizen: Non-coincidence of Isotropic and Anisotropic Raman Spectra of the v3 Mode of the CH3F/CD3F System

NASA Astrophysics Data System (ADS)

Newberg, I. L.; Gee, C. M.; Thurmond, G. D.; Yen, H. W.

1990-12-01

It has been proved with the aid of CH3F/CD3F mixtures that the remarkably large non-coincidence effect in the Raman scattering spectrum of the v3 mode of liquid methyl fluoride is due to intermolecular vibrational coupling mediated mainly by transition dipole interaction. The amount of the effect and its temperature and mole fraction dependence are - at least qualitatively - in agreement with Logan's theoretical concept. The rather different behaviour of the isotopic species and the asymmetry and narrow width of the isotropic band, however, raise new questions which require further investigations.

Thermal behaviour of GdCo1-xMnxO3 cobaltates

NASA Astrophysics Data System (ADS)

Thakur, Rasna; Thakur, Rajesh K.; Gaur, N. K.

2018-05-01

With the objective of exploring the unknown thermodynamic behavior of GdCo1-xMnxO3 family, we present here an investigation of the temperature-dependent (10K≤T≤1000K) thermodynamic properties of GdCo1-xMnxO3 (x=0.1 to 0.8). The specific heat of GdCoO3 with Mn doping in the perovskite structure at B-site has been studied by means of a Modified Rigid Ion Model (MRIM). The cohesive energy, specific heat (C), volume thermal expansion (α) and Gruneisen parameter (γ) of GdCo1-xMnxO3 compounds are also discussed.

Vortex properties of two-dimensional superconducting Pb films.

PubMed

Ning, Y X; Song, C L; Wang, Y L; Chen, Xi; Jia, J F; Xue, Q K; Ma, X C

2010-02-17

Using low temperature scanning tunnelling microscopy/spectroscopy (STM/STS) we have investigated the vortex behaviours of two-dimensional superconducting Pb films at different thicknesses. STS at the vortex core shows an evolution of electronic states with film thickness. Transition from the clean limit to the dirty limit of superconductivity is identified, which can be ascribed to the decreased electronic mean free path induced by stronger scattering from the disordered interface at smaller thicknesses. A magnetic field dependent vortex core size is observed even for such a low- κ superconductor. The weak pinning induced by surface defects leads to the formation of a distorted hexagonal vortex lattice.

Diel time-courses of leaf growth in monocot and dicot species: endogenous rhythms and temperature effects.

PubMed

Poiré, Richard; Wiese-Klinkenberg, Anika; Parent, Boris; Mielewczik, Michael; Schurr, Ulrich; Tardieu, François; Walter, Achim

2010-06-01

Diel (24 h) leaf growth patterns were differently affected by temperature variations and the circadian clock in several plant species. In the monocotyledon Zea mays, leaf elongation rate closely followed changes in temperature. In the dicotyledons Nicotiana tabacum, Ricinus communis, and Flaveria bidentis, the effect of temperature regimes was less obvious and leaf growth exhibited a clear circadian oscillation. These differences were related neither to primary metabolism nor to altered carbohydrate availability for growth. The effect of endogenous rhythms on leaf growth was analysed under continuous light in Arabidopsis thaliana, Ricinus communis, Zea mays, and Oryza sativa. No rhythmic growth was observed under continuous light in the two monocotyledons, while growth rhythmicity persisted in the two dicotyledons. Based on model simulations it is concluded that diel leaf growth patterns in mono- and dicotyledons result from the additive effects of both circadian-clock-controlled processes and responses to environmental changes such as temperature and evaporative demand. Apparently very distinct diel leaf growth behaviour of monocotyledons and dicotyledons can thus be explained by the different degrees to which diel temperature variations affect leaf growth in the two groups of species which, in turn, depends on the extent of the leaf growth control by internal clocks.

Ceramic materials under high temperature heat transfer conditions

NASA Astrophysics Data System (ADS)

Mittenbühler, A.; Jung, J.

1990-04-01

Ceramic materials for application in a High-Temperature Reactor coupled with the steam gasification of coal were investigated. The study concentrated on the hot gas duct and their thermal insulation. Materials examined for the inner lining of the tubes were graphite, carbon fibre reinforced carbon and amorphous silica, while fibres, porous alumina and bonded alumina fibres were tested as insulating materials. During material investigations qualification was performed on samples and in component tests. For two carbon fibre reinforced carbon qualities with different graphitizing temperatures, the bending strength was determined as a function of volume corrosion. Devitrification of amorphous silica can be tolerated up to operating temperatures of about 950°C. The resilience of fibre materials depends on the Al2O3/ SiO2 ratio. It decreases according to the different fibre composition with increasing temperature and limits the maximum operating temperature for long term operation. The porous hollow spherical corundum inserted in the form of bricks fulfilled the thermal shock and mechanical requirements but led to an insulation exhibiting gaps in component tests. An advanced insulation on the basis of bonded alumina fibre showed a quasi-elastic material behaviour. Resistance to abrasion was achieved with a protective ceramic coating. The different materials and design concepts are compared and the results provide a good solution for the project.

Allelic association of a dopamine transporter gene polymorphism with antisocial behaviour in heroin-dependent patients.

PubMed

Gerra, Gilberto; Garofano, Luciano; Pellegrini, Caterina; Bosari, Silvano; Zaimovic, Amir; Moi, Gabriele; Avanzini, Paola; Talarico, Enrica; Gardini, Federica; Donnini, Claudia

2005-09-01

Polymorphism of a variable number of tandem repeats (VNTR) in the 3' untranslated region of exon 15 of the SLC6A3 gene, coding for the dopamine transporter (DAT), was analysed to test whether length variation contributes to differences in the individual susceptibility to aggressive - criminal behaviour and liability to heroin dependence. The repeat number of the DAT polymorphism was assessed in 125 healthy subjects and 104 heroin-dependent subjects (including 52 addicted individuals with violent behaviour and criminal records). There was no significant difference in the frequencies of genotypes and alleles between heroin-dependent subjects and control subjects. On the contrary, there was a significant difference between offenders and non-offenders, p = 0.004 and p = 0.002, respectively, among heroin-dependent subjects. No association was found between DAT polymorphism and history of suicide. Buss - Durkee Hostility Inventory (BDHI) mean total scores were significantly higher in heroin addicts than in controls (p < 0.001) and in antisocial - violent heroin addicts in comparison with addicted individuals without antisocial behaviour (p < 0.005). The regression analysis of BDHI subscales, performed to provide an estimate of the magnitude of any potential effect on the risk of aggressiveness associated with the variants in DAT VNTR, showed that the presence of the 9 - 9 genotype significantly increases the risk of irritability and direct aggressiveness more than six and 10 times with respect to the 9 - 10 genotype. Our findings suggest that the 9-repeat allele of the DAT polymorphism confers increased susceptibility to antisocial - violent behaviour and aggressiveness, rather than drug dependence per se in heroin-dependent males.

Anxiety profile in morphine-dependent and withdrawn rats: effect of voluntary exercise.

PubMed

Miladi-Gorji, Hossein; Rashidy-Pour, Ali; Fathollahi, Yaghoub

2012-01-18

Withdrawal from chronic opiates is associated with an increase in anxiogenic-like behaviours, but the anxiety profile in the morphine-dependent animals is not clear. Thus, one of the aims of the present study was to examine whether morphine-dependent rats would increase the expression of anxiogenic-like behaviours in novel and stressful conditions. Additionally, recent studies have shown that voluntary exercise can reduce anxiety levels in rodents. Therefore, another aim of this study was to examine the effect of voluntary exercise on the anxiety profile in both morphine-dependent animals and animals experiencing withdrawal. Rats were injected with bi-daily doses (10 mg/kg, at 12 h intervals) of morphine over a period of 10 days in which they were also allowed voluntary exercise. Following these injections, anxiety-like behaviours were tested in the elevated plus-maze (EPM) model and the light/dark (L/D) box. We found reductions in time spent in, and entries into, the EPM open arms and reductions in time spent in the lit side of the L/D box for both sedentary morphine-dependent and withdrawn rats as compared to the sedentary control groups. The exercising morphine-dependent and withdrawn rats exhibited an increase in EPM open arm time and entries and L/D box lit side time as compared with the sedentary control groups. We conclude that voluntary exercise decreases the severity of the anxiogenic-like behaviours in both morphine-dependent and withdrawn rats. Thus, voluntary exercise could be a potential natural method to ameliorate some of the deleterious behavioural consequences of opiate abuse. Copyright © 2011 Elsevier Inc. All rights reserved.

NCAM deficiency in the mouse forebrain impairs innate and learned avoidance behaviours.

PubMed

Brandewiede, J; Stork, O; Schachner, M

2014-06-01

The neural cell adhesion molecule (NCAM) has been implicated in the development and plasticity of neural circuits and the control of hippocampus- and amygdala-dependent learning and behaviour. Previous studies in constitutive NCAM null mutants identified emotional behaviour deficits related to disturbances of hippocampal and amygdala functions. Here, we studied these behaviours in mice conditionally deficient in NCAM in the postmigratory forebrain neurons. We report deficits in both innate and learned avoidance behaviours, as observed in elevated plus maze and passive avoidance tasks. In contrast, general locomotor activity, trait anxiety or neophobia were unaffected by the mutation. Altered avoidance behaviour of the conditional NCAM mutants was associated with a deficit in serotonergic signalling, as indicated by their reduced responsiveness to (±)-8-hydroxy-2-(dipropylamino)-tetralin-induced hypothermia. Another serotonin-dependent behaviour, namely intermale aggression that is massively increased in constitutively NCAM-deficient mice, was not affected in the forebrain-specific mutants. Our data suggest that genetically or environmentally induced changes of NCAM expression in the late postnatal and mature forebrain determine avoidance behaviour and serotonin (5-HT)1A receptor signalling. © 2014 John Wiley & Sons Ltd and International Behavioural and Neural Genetics Society.

New thermoelastic parameters of natural C2/ c omphacite

NASA Astrophysics Data System (ADS)

Pandolfo, Francesco; Nestola, Fabrizio; Cámara, Fernando; Domeneghetti, M. Chiara

2012-04-01

The compressibility at room temperature and the thermal expansion at room pressure of two disordered crystals (space group C2/ c) obtained by annealing a natural omphacite sample (space group P2/ n) of composition close to Jd56Di44 and Jd55Di45, respectively, have been studied by single-crystal X-ray diffraction. Using a Birch-Murnaghan equation of state truncated at the third order [BM3-EoS], we have obtained the following coefficients: V 0 = 421.04(7) Å3, K T0 = 119(2) GPa, K' = 5.7(6). A parameterized form of the BM3 EoS was used to determine the axial moduli of a, b and c. The anisotropy scheme is β c ≤ β a ≤ β b , with an anisotropy ratio 1.05:1.00:1.07. A fitting of the lattice variation as a function of temperature, allowing for linear dependency of the thermal expansion coefficient on the temperature, yielded αV(1bar,303K) = 2.64(2) × 10-5 K-1 and an axial thermal expansion anisotropy of α b ≫ α a > α c . Comparison of our results with available data on compressibility and thermal expansion shows that while a reasonable ideal behaviour can be proposed for the compressibility of clinopyroxenes in the jadeite-diopside binary join [ K T0 as a function of Jd molar %: K T0 = 106(1) GPa + 0.28(2) × Jd(mol%)], the available data have not sufficient quality to extract the behaviour of thermal expansion for the same binary join in terms of composition.

Insights into the crystal-packing effects on the spin crossover of [Fe(II)(1-bpp)](2+)-based materials.

PubMed

Vela, Sergi; Novoa, Juan J; Ribas-Arino, Jordi

2014-12-28

Iron(II) complexes of the [Fe(II)(1-bpp2)](2+) type (1-bpp = 2,6-di(pyrazol-1-yl)pyridine) have been intensively investigated in the context of crystal engineering of switchable materials because their spin-crossover (SCO) properties dramatically depend on the counterions. Here, by means of DFT + U calculations at the molecular and solid state levels we provide a rationale for the different SCO behaviour of the BF4(-) and ClO4(-) salts of the parent complex; the former features Fe(II) complexes with a regular coordination geometry and undergoes a spin transition, whereas the Fe(II) complexes of the latter adopt a distorted structure and remain in the high-spin state at all temperatures. The different SCO behaviour of both salts can be explained on the basis of a combination of thermodynamic and kinetic effects. The shape of the SCO units at high temperature is thermodynamically controlled by the intermolecular interactions between the SCO units and counterions within the crystal. The spin trapping at low temperatures in the ClO4(-) salt, in turn, is traced back to a kinetic effect because our calculations have revealed the existence of a more stable polymorph having SCO units in their low-spin state that feature a regular structure. From the computational point of view, it is the first time that the U parameter is fine-tuned on the basis of CASPT2 calculations, thereby enabling an accurate description of the energetics of the spin transition at both molecular and solid-state levels.

Stage- and sex-specific heat tolerance in the yellow dung fly Scathophaga stercoraria.

PubMed

Blanckenhorn, Wolf U; Gautier, Roland; Nick, Marcel; Puniamoorthy, Nalini; Schäfer, Martin A

2014-12-01

Thermal tolerance varies at all hierarchical levels of biological organization: among species, populations, individuals, and even within individuals. Age- or developmental stage- and sex-specific thermal effects have received relatively little attention in the literature, despite being crucial for understanding thermal adaptation in nature and responses to global warming. We document stage- and sex- specific heat tolerance in the yellow dung fly Scathophaga stercoraria (Diptera: Scathophagidae), a species common throughout the northern hemisphere that generally favours cool climates. Exposure of eggs to temperatures up to 32°C did not affect larval hatching rate, but subsequent egg-to-adult survival at a benign temperature was reduced. Permanent transfer from benign (18°C) to hot temperatures (up to 31°C) at different larval and pupal stages strongly decreased egg-to-adult survival, though survival continuously improved the later the transfer occurred. Temporary transfer for only two days increased mortality more weakly, survival being lowest when temperature stress was imposed early during the larval or pupal stages. Adult flies provided with sugar and water tolerated 31°C longer than previously thought (5 days in males to 9 days in females). Eggs were thus less susceptible to thermal stress than larvae, pupae or adults, in agreement with the hypothesis that more mobile stages require less physiological protection against heat because they can behaviourally thermoregulate. The probability of mating, of laying a clutch, and hatching success were generally independently reduced by exposure of females or males to warm temperatures (24°C) during the juvenile or adult stages, with some interactions evident. High temperature stress thus affects survival differentially depending on when it occurs during the juvenile or the pre-reproductive adult life stage, and affects reproductive success via the mating behaviour of both sexes, female physiology in terms of oviposition, and fertility via sperm and/or egg quality. Our results illustrate that temperature stress, even when moderate and temporary, during early development can have profound lethal and non-lethal fitness-consequences later in life. Copyright © 2014 Elsevier Ltd. All rights reserved.

Behavioural thermoregulation by subyearling fall (autumn) Chinook salmon oncorhynchus tshawytscha in a reservoir

USGS Publications Warehouse

Tiffan, K.F.; Kock, T.J.; Connor, W.P.; Steinhorst, R.K.; Rondorf, D.W.

2009-01-01

This study investigated behavioural thermoregulation by subyearling fall (autumn) Chinook salmon Oncorhynchus tshawytscha in a reservoir on the Snake River, Washington, U.S.A. During the summer, temperatures in the reservoir varied from 23?? C on the surface to 11?? C at 14 m depth. Subyearlings implanted with temperature-sensing radio transmitters were released at the surface at temperatures >20?? C during three blocks of time in summer 2004. Vertical profiles were taken to measure temperature and depth use as the fish moved downstream over an average of 5??6-7??2 h and 6??0-13??8 km. The majority of the subyearlings maintained average body temperatures that differed from average vertical profile temperatures during most of the time they were tracked. The mean proportion of the time subyearlings tracked within the 16-20?? C temperature range was larger than the proportion of time this range was available, which confirmed temperature selection opposed to random use. The subyearlings selected a depth and temperature combination that allowed them to increase their exposure to temperatures of 16-20?? C when temperatures 20?? C were available at lower and higher positions in the water column. A portion of the subyearlings that selected a temperature c. 17??0?? C during the day, moved into warmer water at night coincident with an increase in downstream movement rate. Though subyearlings used temperatures outside of the 16-20?? C range part of the time, behavioural thermoregulation probably reduced the effects of intermittent exposure to suboptimal temperatures. By doing so, it might enhance growth opportunity and life-history diversity in the population of subyearlings studied.

Strength of the repulsive part of the interatomic potential determines fragility in metallic liquids

NASA Astrophysics Data System (ADS)

Pueblo, Christopher E.; Sun, Minhua; Kelton, K. F.

2017-08-01

The dynamical behaviour of liquids is frequently characterized by the fragility, which can be defined from the temperature dependence of the shear viscosity, η (ref. ). For a strong liquid, the activation energy for η changes little with cooling towards the glass transition temperature, Tg. The change is much greater in fragile liquids, with the activation energy becoming very large near Tg. While fragility is widely recognized as an important concept--believed, for example, to play an important role in glass formation--the microscopic origin of fragility is poorly understood. Here, we present new experimental evidence showing that fragility reflects the strength of the repulsive part of the interatomic potential, which can be determined from the steepness of the pair distribution function near the hard-sphere cutoff. On the basis of an analysis of scattering data from ten different metallic alloy liquids, we show that stronger liquids have steeper repulsive potentials.

Bending effects and temperature dependence of magnetic properties in a Fe-rich amorphous wire

NASA Astrophysics Data System (ADS)

Bordin, G.; Buttino, G.; Poppi, M.

2001-08-01

Amorphous wires with composition Fe 77.5Si 7.5B 15 exhibit a very peculiar magnetization process characterized by a single and quite large Barkhausen jump. This gives rise to a squared hysteresis loop at a critical magnetic field. The bistable behaviour, widely studied in wires with typical length of 10 cm and diameter of 125 μm, appears above a length of about 7 cm in straight wires and disappears for curvature radius within the range 2-12 cm in bent wires. In this work it is shown that bistability occurs in bent wires, whatever their curvature is, provided the wires are long enough. To this purpose spiral-shaped samples with several turns are considered. However, when the wire length is not a integer number of turns the magnetization reverses through many large Barkhausen jumps. In this condition, varying the measuring temperature can activate the energy barriers for the jumps.

Study of multi-functionality of lanthanum ferrite (LaFeO{sub 3})

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gaikwad, Vishwajit M.; Uikey, Pankaj; Acharya, Smita A., E-mail: saha275@yahoo.com

2015-06-24

In the present work, multifunctional behaviors of LaFeO{sub 3} (LFO) are investigated by studying its dielectric and photocatalytic properties, respectively. LFO is synthesized by microwave-assisted co-precipitation route. Orthorhombic structure is confirmed by X-ray diffraction (XRD) and data is well fitted using Rietveld refinement by Full-Prof suite. Frequency and Temperature dependence dielectric behavior are systematically studied. The dielectric constant of LFO was found to be 2500 – 3000 with dissipation factor less than 5%. Photodegradation of toxic dye (Methylene Blue) using as-prepared LFO is also investigated. UV-visible absorption spectra are used to study the photodegradation behaviour. Photodegradation of methylene blue (MB)more » taken from textile industries by LFO are reported. The colossal value of dielectric constant of LFO exhibits high potential to use as room temperature capacitive component for device miniaturization in microelectronics as well as photodegradation ability shows good photocatalyst.« less

A correlated nickelate synaptic transistor.

PubMed

Shi, Jian; Ha, Sieu D; Zhou, You; Schoofs, Frank; Ramanathan, Shriram

2013-01-01

Inspired by biological neural systems, neuromorphic devices may open up new computing paradigms to explore cognition, learning and limits of parallel computation. Here we report the demonstration of a synaptic transistor with SmNiO₃, a correlated electron system with insulator-metal transition temperature at 130°C in bulk form. Non-volatile resistance and synaptic multilevel analogue states are demonstrated by control over composition in ionic liquid-gated devices on silicon platforms. The extent of the resistance modulation can be dramatically controlled by the film microstructure. By simulating the time difference between postneuron and preneuron spikes as the input parameter of a gate bias voltage pulse, synaptic spike-timing-dependent plasticity learning behaviour is realized. The extreme sensitivity of electrical properties to defects in correlated oxides may make them a particularly suitable class of materials to realize artificial biological circuits that can be operated at and above room temperature and seamlessly integrated into conventional electronic circuits.

Investigation of structural, optical and electrical properties of Co3O4 nanoparticles

NASA Astrophysics Data System (ADS)

Bhargava, Richa; Khan, Shakeel; Ahmad, Naseem; Ansari, Mohd Mohsin Nizam

2018-05-01

In the current work, we report the synthesis of Cobalt oxide (Co3O4) NPs (NPs) by co-precipitation method. The structural analysis was confirmed by using X-ray diffractometer (XRD) which shows that the Co3O4 NPs have cubic phase. The average crystallite size and the lattice parameter were calculated for Co3O4 NPs. The functional groups of the as-synthesized sample were examined by Fourier transform infrared spectroscopy (FTIR). The optical band gap of Co3O4 NPs was estimated by using UV diffuse reflectance spectroscopy and the Band gap was evaluated by using Tauc relation. The temperature dependence of dielectric constant and dielectric loss were studied over a range of temperature 50-300 °C. The DC electrical resistivity of Co3O4 NPs shows a semiconducting behaviour and the value of activation energy was calculated by using Arrhenius equation.

Model of two-temperature convective transfer in porous media

NASA Astrophysics Data System (ADS)

Gruais, Isabelle; Poliševski, Dan

2017-12-01

In this paper, we study the asymptotic behaviour of the solution of a convective heat transfer boundary problem in an ɛ -periodic domain which consists of two interwoven phases, solid and fluid, separated by an interface. The fluid flow and its dependence with respect to the temperature are governed by the Boussinesq approximation of the Stokes equations. The tensors of thermal diffusion of both phases are ɛ -periodic, as well as the heat transfer coefficient which is used to describe the first-order jump condition on the interface. We find by homogenization that the two-scale limits of the solutions verify the most common system used to describe local thermal non-equilibrium phenomena in porous media (see Nield and Bejan in Convection in porous media, Springer, New York, 1999; Rees and Pop in Transport phenomena in porous media III, Elsevier, Oxford, 2005). Since now, this system was justified only by volume averaging arguments.

Development and Characterization of Poly(1-vinylpyrrolidone-co-vinyl acetate) Copolymer Based Polymer Electrolytes

PubMed Central

Sa'adun, Nurul Nadiah; Subramaniam, Ramesh; Kasi, Ramesh

2014-01-01

Gel polymer electrolytes (GPEs) are developed using poly(1-vinylpyrrolidone-co-vinyl acetate) [P(VP-co-VAc)] as the host polymer, lithium bis(trifluoromethane) sulfonimide [LiTFSI] as the lithium salt and ionic liquid, and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide [EMImTFSI] by using solution casting technique. The effect of ionic liquid on ionic conductivity is studied and the optimum ionic conductivity at room temperature is found to be 2.14 × 10−6 S cm−1 for sample containing 25 wt% of EMImTFSI. The temperature dependence of ionic conductivity from 303 K to 353 K exhibits Arrhenius plot behaviour. The thermal stability of the polymer electrolyte system is studied by using thermogravimetric analysis (TGA) while the structural and morphological properties of the polymer electrolyte is studied by using Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction analysis (XRD), respectively. PMID:25431781

Thermodynamics of emergent magnetic charge screening in artificial spin ice

DOE PAGES

Farhan, Alan; Scholl, Andreas; Petersen, Charlotte F.; ...

2016-09-01

Electric charge screening is a fundamental principle governing the behaviour in a variety of systems in nature. Through reconfiguration of the local environment, the Coulomb attraction between electric charges is decreased, leading, for example, to the creation of polaron states in solids or hydration shells around proteins in water. Here, we directly visualize the real-time creation and decay of screened magnetic charge configurations in a two-dimensional artificial spin ice system, the dipolar dice lattice. By comparing the temperature dependent occurrence of screened and unscreened emergent magnetic charge defects, we determine that screened magnetic charges are indeed a result of localmore » energy reduction and appear as a transient minimum energy state before the system relaxes towards the predicted ground state. These results highlight the important role of emergent magnetic charges in artificial spin ice, giving rise to screened charge excitations and the emergence of exotic low-temperature configurations.« less

Thermodynamics of emergent magnetic charge screening in artificial spin ice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farhan, Alan; Scholl, Andreas; Petersen, Charlotte F.

Electric charge screening is a fundamental principle governing the behaviour in a variety of systems in nature. Through reconfiguration of the local environment, the Coulomb attraction between electric charges is decreased, leading, for example, to the creation of polaron states in solids or hydration shells around proteins in water. Here, we directly visualize the real-time creation and decay of screened magnetic charge configurations in a two-dimensional artificial spin ice system, the dipolar dice lattice. By comparing the temperature dependent occurrence of screened and unscreened emergent magnetic charge defects, we determine that screened magnetic charges are indeed a result of localmore » energy reduction and appear as a transient minimum energy state before the system relaxes towards the predicted ground state. These results highlight the important role of emergent magnetic charges in artificial spin ice, giving rise to screened charge excitations and the emergence of exotic low-temperature configurations.« less

Cross-sectional and prospective relation of cannabis potency, dosing and smoking behaviour with cannabis dependence: an ecological study.

PubMed

van der Pol, Peggy; Liebregts, Nienke; Brunt, Tibor; van Amsterdam, Jan; de Graaf, Ron; Korf, Dirk J; van den Brink, Wim; van Laar, Margriet

2014-07-01

Increased delta-9-tetrahydrocannabinol (THC) concentrations in cannabis may lead to higher THC exposure, cannabis dependence and treatment need, but users may also adapt the actual intake of THC through reduced inhalation of THC containing smoke (titration). We investigated whether consumers of stronger cannabis use less cannabis per joint or inhale less smoke than those using less potent cannabis and whether these factors predict cannabis dependence severity. Heavy cannabis users (n = 98) brought their own cannabis, rolled a joint and smoked it ad libitum in a naturalistic setting. We analysed the content of the joint, its association with smoking behaviour and the cross-sectional and prospective (1.5-year follow-up) relations between smoking behaviour and cannabis dependence severity (total number of DSM-IV dependence symptoms). THC concentration in cannabis (range 1.10-24.70%) was correlated positively with cannabis dose per joint (b = 0.008, P = 0.01), but the resulting THC concentration per joint (range 0.24-15.72%) was associated negatively with inhalation volume (b = -0.05, P = 0.03). Smoking behaviour measures (number of puffs, inhaled volume, reduction of puff volume and puff duration while smoking) predicted follow-up dependence severity, independently of baseline dependence severity and monthly THC dose (number of joints × cannabis dose × cannabis THC concentration). Monthly THC dose only predicted follow-up dependence severity when unadjusted for baseline severity. Cannabis users titrate their delta-9-tetrahydrocannabinol intake by inhaling lower volumes of smoke when smoking strong joints, but this does not fully compensate for the higher cannabis doses per joint when using strong cannabis. Thus, users of more potent cannabis are generally exposed to more delta-9-tetrahydrocannabinol. Smoking behaviour appears to be a stronger predictor for cannabis dependence severity than monthly delta-9-tetrahydrocannabinol dose. © 2014 Society for the Study of Addiction.

Within-season variability of fighting behaviour in an Australian alpine grasshopper

PubMed Central

Muschett, Giselle; Umbers, Kate D. L.; Herberstein, Marie E.

2017-01-01

Throughout the breeding season, changing environmental and biological conditions can lead to variation in the reproductive landscape of many species. In alpine environments temperature is a key driver of behaviour for small ectotherms such as insects, but variable biotic factors such as mate quality and availability can also influence behaviour. Kosicuscola tristis is a small semelparous grasshopper of the Australian alpine region. In a rare behaviour among grasshoppers, K. tristis males engage in vigorous fights over access to females, involving mandible displays, kicking, biting and grappling. In this study we describe the variation in fighting behaviour of K. tristis throughout the breeding season and test several hypotheses related to temperature, body size, mating behaviour, and female quality. We show that K. tristis males are more aggressive toward each other at the end of the breeding season than at the beginning. This increased aggression is associated with decreased daily average temperatures (from ~20°C to ~9°C), decreased mating activity, increased female fecundity, and an unexpected trend toward an increase in female-to-male aggression. These results suggest that K. tristis is likely under increased selective pressure to time key life cycle events with favourable biological and climatic conditions. The stochastic nature of alpine environments combined with a relatively short life span and breeding season, as well as limited mating opportunities toward the end of the season may have contributed to the evolution of this extraordinary mating system. PMID:28403243

Energy and Transmissibility in Nonlinear Viscous Base Isolators

NASA Astrophysics Data System (ADS)

Markou, Athanasios A.; Manolis, George D.

2016-09-01

High damping rubber bearings (HDRB) are the most commonly used base isolators in buildings and are often combined with other systems, such as sliding bearings. Their mechanical behaviour is highly nonlinear and dependent on a number of factors. At first, a physical process is suggested here to explain the empirical formula introduced by J.M. Kelly in 1991, where the dissipated energy of a HDRB under cyclic testing, at constant frequency, is proportional to the amplitude of the shear strain, raised to a power of approximately 1.50. This physical process is best described by non-Newtonian fluid behaviour, originally developed by F.H. Norton in 1929 to describe creep in steel at high-temperatures. The constitutive model used includes a viscous term, that depends on the absolute value of the velocity, raised to a non-integer power. The identification of a three parameter Kelvin model, the simplest possible system with nonlinear viscosity, is also suggested here. Furthermore, a more advanced model with variable damping coefficient is implemented to better model in this complex mechanical process. Next, the assumption of strain-rate dependence in their rubber layers under cyclic loading is examined in order to best interpret experimental results on the transmission of motion between the upper and lower surfaces of HDRB. More specifically, the stress-relaxation phenomenon observed with time in HRDB can be reproduced numerically, only if the constitutive model includes a viscous term, that depends on the absolute value of the velocity raised to a non-integer power, i. e., the Norton fluid previously mentioned. Thus, it becomes possible to compute the displacement transmissibility function between the top and bottom surfaces of HDRB base isolator systems and to draw engineering-type conclusions, relevant to their design under time-harmonic loads.

Migration by soaring or flapping: numerical atmospheric simulations reveal that turbulence kinetic energy dictates bee-eater flight mode

PubMed Central

Sapir, Nir; Horvitz, Nir; Wikelski, Martin; Avissar, Roni; Mahrer, Yitzhak; Nathan, Ran

2011-01-01

Aerial migrants commonly face atmospheric dynamics that may affect their movement and behaviour. Specifically, bird flight mode has been suggested to depend on convective updraught availability and tailwind assistance. However, this has not been tested thus far since both bird tracks and meteorological conditions are difficult to measure in detail throughout extended migratory flyways. Here, we applied, to our knowledge, the first comprehensive numerical atmospheric simulations by mean of the Regional Atmospheric Modeling System (RAMS) to study how meteorological processes affect the flight behaviour of migrating birds. We followed European bee-eaters (Merops apiaster) over southern Israel using radio telemetry and contrasted bird flight mode (flapping, soaring–gliding or mixed flight) against explanatory meteorological variables estimated by RAMS simulations at a spatial grid resolution of 250 × 250 m2. We found that temperature and especially turbulence kinetic energy (TKE) determine bee-eater flight mode, whereas, unexpectedly, no effect of tailwind assistance was found. TKE during soaring–gliding was significantly higher and distinct from TKE during flapping. We propose that applying detailed atmospheric simulations over extended migratory flyways can elucidate the highly dynamic behaviour of air-borne organisms, help predict the abundance and distribution of migrating birds, and aid in mitigating hazardous implications of bird migration. PMID:21471116

A crystallographic and thermal study of pridinol mesylate and its monohydrated solvate.

PubMed

Gaztañaga, Pablo; Baggio, Ricardo; Vega, Daniel Roberto

2018-06-01

Herein are reported the crystal and molecular structures of the pridinol mesylate salt (C 20 H 25 NO + ·CH 3 O 3 S - ) (I) and its monohydrated solvate form (C 20 H 25 NO + ·CH 3 O 3 S - ·H 2 O) (II). A comparison of both with the already reported structure of pure pridinol [1,1-diphenyl-3-piperidino-1-propanol, C 20 H 25 NO; Tacke et al. (1980). Chem. Ber. 113, 1962-1980] is made. Molecular structures (I) and (II) are alike in bond distances and bond angles, but differ in their spatial conformation, and, more relevant still, in their hydrogen-bonding motifs. This gives rise to quite different packing schemes, in the form of simple dimers in (I) but water-mediated hydrogen-bonded chains in (II). The dehydration behaviour of form (II) is highly dependent on the heating rate, with slow rates leading to a clear endothermic dehydration step, towards anhydrous (I), with subsequent melting of this latter phase. Increased heating rates result in a more unclear behaviour ending in a structural collapse (melting of the hydrated phase), at temperatures significantly lower than the melting point of the anhydrous phase. The eventual relevance of the water link in the structure of (II) is discussed in regard to this behaviour.

Behavioural adaptations of Rana temporaria to cold climates.

PubMed

Ludwig, Gerda; Sinsch, Ulrich; Pelster, Bernd

2015-01-01

Environmental conditions at the edge of a species' ecological optimum can exert great ecological or evolutionary pressure at local populations. For ectotherms like amphibians temperature is one of the most important abiotic factors of their environment as it influences directly their metabolism and sets limits to their distribution. Amphibians have evolved three ways to cope with sub-zero temperatures: freeze tolerance, freeze protection, freeze avoidance. The aim of this study was to assess which strategy common frogs at mid and high elevation use to survive and thrive in cold climates. In particular we (1) tested for the presence of physiological freeze protection, (2) evaluated autumnal activity and overwintering behaviour with respect to freeze avoidance and (3) assessed the importance of different high-elevation microhabitats for behavioural thermoregulation. Common frogs did not exhibit any signs of freeze protection when experiencing temperatures around 0 °C. Instead they retreated to open water for protection and overwintering. High elevation common frogs remained active for around the same period of time than their conspecifics at lower elevation. Our results suggest that at mid and high elevation common frogs use freeze avoidance alone to survive temperatures below 0 °C. The availability of warm microhabitats, such as rock or pasture, provides high elevation frogs with the opportunity of behavioural thermoregulation and thus allows them to remain active at temperatures at which common frogs at lower elevation cease activity. Copyright © 2015 Elsevier Ltd. All rights reserved.

How Does Cognitive Behaviour Therapy Work with Opioid-Dependent Clients? Results of the UKCBTMM Study

ERIC Educational Resources Information Center

Kouimtsidis, Christos; Reynolds, Martina; Coulton, Simon; Drummond, Colin

2012-01-01

Introduction: Process research in psychotherapy is important to understand how treatment works. The National Institute of Clinical Excellence guidelines suggest that in methadone maintenance treatment (MMT) for opioid dependence, drug key-working should be based on cognitive behavioural therapy (CBT) principles. This article reports the findings…

Dimensions of dependence and their influence on the outcome of cognitive behaviour therapy for health anxiety: randomized controlled trial.

PubMed

Tyrer, Peter; Wang, Duolao; Tyrer, Helen; Crawford, Mike; Cooper, Sylvia

2016-05-01

The personality trait of dependence is common in health-seeking behaviour. We therefore examined its impact in a large randomized controlled trial of psychological treatment for health anxiety. To test whether dependent personality traits were positive or negative in determining the outcome of an adapted form of cognitive behaviour therapy for health anxiety (CBT-HA) over the course of 5 years and whether dependent personality dysfunction could be viewed dimensionally in a similar way to the new ICD-11 diagnostic system for general personality disorder. Dependent personality dysfunction was assessed using a self-rated questionnaire, the Dependent Personality Questionnaire, at baseline in a randomized controlled trial of 444 patients from medical clinics with pathological health anxiety treated with a modified form of CBT-HA or standard treatment in the medical clinics, with assessment on five occasions over 5 years. Dependent personality dysfunction was assessed using four severity groups. Patients with mild and moderate dependent personality disorder treated with CBT-HA showed the greatest reduction in health anxiety compared with standard care, and those with no dependent dysfunction showed the least benefit. Patients with higher dependent traits received significantly more treatment sessions (8.6) than those with low trait levels (5.4) (p < 0.01). The results suggest that patients treated with cognitive behaviour therapy for health anxiety respond better if they have moderate dependent personality. The reasons for this may be related to better adherence to psychological treatment and greater negative effects of frequent reassurance and excessive consultation in those treated in standard care. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Experimental and numerical characterisation of the elasto-plastic properties of bovine trabecular bone and a trabecular bone analogue.

PubMed

Kelly, Nicola; McGarry, J Patrick

2012-05-01

The inelastic pressure dependent compressive behaviour of bovine trabecular bone is investigated through experimental and computational analysis. Two loading configurations are implemented, uniaxial and confined compression, providing two distinct loading paths in the von Mises-pressure stress plane. Experimental results reveal distinctive yielding followed by a constant nominal stress plateau for both uniaxial and confined compression. Computational simulation of the experimental tests using the Drucker-Prager and Mohr-Coulomb plasticity models fails to capture the confined compression behaviour of trabecular bone. The high pressure developed during confined compression does not result in plastic deformation using these formulations, and a near elastic response is computed. In contrast, the crushable foam plasticity models provide accurate simulation of the confined compression tests, with distinctive yield and plateau behaviour being predicted. The elliptical yield surfaces of the crushable foam formulations in the von Mises-pressure stress plane accurately characterise the plastic behaviour of trabecular bone. Results reveal that the hydrostatic yield stress is equal to the uniaxial yield stress for trabecular bone, demonstrating the importance of accurate characterisation and simulation of the pressure dependent plasticity. It is also demonstrated in this study that a commercially available trabecular bone analogue material, cellular rigid polyurethane foam, exhibits similar pressure dependent yield behaviour, despite having a lower stiffness and strength than trabecular bone. This study provides a novel insight into the pressure dependent yield behaviour of trabecular bone, demonstrating the inadequacy of uniaxial testing alone. For the first time, crushable foam plasticity formulations are implemented for trabecular bone. The enhanced understanding of the inelastic behaviour of trabecular bone established in this study will allow for more realistic simulation of orthopaedic device implantation and failure. Copyright © 2011 Elsevier Ltd. All rights reserved.

Affective dependence and aggression: an exploratory study.

PubMed

Petruccelli, Filippo; Diotaiuti, Pierluigi; Verrastro, Valeria; Petruccelli, Irene; Federico, Roberta; Martinotti, Giovanni; Fossati, Andrea; Di Giannantonio, Massimo; Janiri, Luigi

2014-01-01

Emotionally dependent subjects may engage in controlling, restrictive, and aggressive behaviours, which limit their partner's autonomy. The underlying causes of such behaviours are not solely based on levels of aggression, but act as a mean of maintaining the subject's own sense of self-worth, identity, and general functioning. The aim of the paper is to explore the correlation between affective dependency and reactive/proactive aggression and to evaluate individual differences as predisposing factors for aggressive behaviour and emotional dependency. The Spouse-Specific Dependency Scale (SSDS) and the Reactive Proactive Questionnaire (RPQ) were administered to a sample of 3375 subjects. In the whole sample, a positive correlation between emotional dependency and proactive aggression was identified. Differences with regard to sex, age group, and geographical distribution were evidenced for the scores of the different scales. A fundamental distinction between reactive and proactive aggression was observed, anchoring proactive aggression more strictly to emotional dependency. Sociocultural and demographical variables, together with the previous structuring of attachment styles, help to determine the scope, frequency, and intensity of the demands made to the partner, as well as to feed the fears of loss, abandonment, or betrayal.

Temperature Insensitivity and Behavioural Reduction of the Physiological Stress Response to Longline Capture by the Gummy Shark, Mustelus antarcticus.

PubMed

Guida, Leonardo; Walker, Terence I; Reina, Richard D

2016-01-01

Many factors influence the physiological stress response to fisheries capture in elasmobranchs. However, the influence of sea surface temperatures (SST) and behaviour are unknown and crucial considering global fishing pressures. We investigated the effect of SST and behaviour on the physiological stress response to capture of the gummy shark, Mustelus antarcticus, and compared our results to a laboratory study using similar conditions to test whether stress responses of in situ capture are consistent with those from laboratory simulations. Capture time for 23 M. antarcticus ranged 32-241 min as measured by hook timers or time depth recorders (TDR) in SSTs ranging 12-20°C. TDR data from 13 M. antarcticus were analysed to quantify capture behaviour as the percentage of time spent moving during capture. Several physiological variables measured from blood samples obtained immediately upon the animals' landing indicated that although warmer SSTs increased metabolic rate, the stress response to capture was not exacerbated by capture duration. During capture movement occurred for an average of 10% of the time and since M. antarcticus can respire whilst stationary, restricted movement probably mitigated potential influences of increased SSTs and capture duration on the stress response. Previous laboratory findings were also shown to be indicative of in situ conditions and we thus advise that studies control for water temperature given the influence it has on variables (e.g. lactate) used to measure capture stress in elasmobranchs. We highlight the importance of seasonal water temperatures and capture behaviour when assessing the resilience to fisheries capture and the implementation of appropriate fisheries management strategies.

Effects of aspect ratio of multi-walled carbon nanotubes on coal washery waste water treatment.

PubMed

Aliyu, Ahmed; Kariim, Ishaq; Abdulkareem, Saka Ambali

2017-11-01

The dependency of adsorption behaviour on the aspect ratio of multi-walled carbon nanotubes (MWCNTs) has been explored. In this study, effect of growth temperature on yield and aspect ratio of MWCNTs by catalytic chemical vapour deposition (CCVD) method is reported. The result revealed that yield and aspect ratio of synthesised MWCNTs strongly depend on the growth temperature during CCVD operation. The resulting MWCNTs were characterized by High Resolution Transmission Electron Microscope (HRTEM), Dynamic Light Scattering (DLS) and X-ray diffraction (XRD) techniques to determine it diameter, hydrodynamic diameter and crystallinity respectively. Aspect ratio and length of the grown MWCNTs were determined from the HRTEM images with the hydrodynamic diameter using the modified Navier-Stokes and Stokes-Einstein equations. The effect of the prepared MWCNTs dosage were investigated on the Turbidity, Iron (Fe) and Lead (Pb) removal efficiency of coal washery effluent. The MWCNTs with higher length (58.17 μm) and diameter (71 nm) tend to show high turbidity and Fe removal, while MWCNTs with lower length (38.87 μm) and diameter (45 nm) tend to show high removal of Pb. Hence, the growth temperature during CCVD operation shows a great effluence on the aspect ratio of MWCNTs which determines it area of applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

Thermally induced fracture for core-veneered dental ceramic structures.

PubMed

Zhang, Zhongpu; Guazzato, Massimiliano; Sornsuwan, Tanapon; Scherrer, Susanne S; Rungsiyakull, Chaiy; Li, Wei; Swain, Michael V; Li, Qing

2013-09-01

Effective and reliable clinical uses of dental ceramics necessitate an insightful analysis of the fracture behaviour under critical conditions. To better understand failure characteristics of porcelain veneered to zirconia core ceramic structures, thermally induced cracking during the cooling phase of fabrication is studied here by using the extended finite element method (XFEM). In this study, a transient thermal analysis of cooling is conducted first to determine the temperature distributions. The time-dependent temperature field is then imported to the XFEM model for viscoelastic thermomechanical analysis, which predicts thermally induced damage and cracking at different time steps. Temperature-dependent material properties are used in both transient thermal and thermomechanical analyses. Three typical ceramic structures are considered in this paper, namely bi-layered spheres, squat cylinders and dental crowns with thickness ratios of either 1:2 or 1:1. The XFEM fracture patterns exhibit good agreement with clinical observation and the in vitro experimental results obtained from scanning electron microscopy characterization. The study reveals that fast cooling can lead to thermal fracture of these different bi-layered ceramic structures, and cooling rate (in terms of heat transfer coefficient) plays a critical role in crack initiation and propagation. By exploring different cooling rates, the heat transfer coefficient thresholds of fracture are determined for different structures, which are of clear clinical implication. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Modelling West Nile virus transmission risk in Europe: effect of temperature and mosquito biotypes on the basic reproduction number.

PubMed

Vogels, Chantal B F; Hartemink, Nienke; Koenraadt, Constantianus J M

2017-07-10

West Nile virus (WNV) is a mosquito-borne flavivirus which has caused repeated outbreaks in humans in southern and central Europe, but thus far not in northern Europe. The main mosquito vector for WNV, Culex pipiens, consists of two behaviourally distinct biotypes, pipiens and molestus, which can form hybrids. Differences between biotypes, such as vector competence and host preference, could be important in determining the risk of WNV outbreaks. Risks for WNV establishment can be modelled with basic reproduction number (R 0 ) models. However, existing R 0 models have not differentiated between biotypes. The aim of this study was, therefore, to explore the role of temperature-dependent and biotype-specific effects on the risk of WNV establishment in Europe. We developed an R 0 model with temperature-dependent and biotype-specific parameters, and calculated R 0 values using the next-generation matrix for several scenarios relevant for Europe. In addition, elasticity analysis was done to investigate the contribution of each biotype to R 0 . Global warming and increased mosquito-to-host ratios can possibly result in more intense WNV circulation in birds and spill-over to humans in northern Europe. Different contributions of the Cx. pipiens biotypes to R 0 shows the importance of including biotype-specific parameters in models for reliable WNV risk assessments.

Toward continuous glucose monitoring with planar modified biosensors and microdialysis. Study of temperature, oxygen dependence and in vivo experiment.

PubMed

Ricci, Francesco; Caprio, Felice; Poscia, Alessandro; Valgimigli, Francesco; Messeri, Dimitri; Lepori, Elena; Dall'Oglio, Giorgio; Palleschi, Giuseppe; Moscone, Danila

2007-04-15

Glucose biosensors based on the use of planar screen-printed electrodes modified with an electrochemical mediator and with glucose oxidase have been optimised for their application in the continuous glucose monitoring in diabetic patients. A full study of their operative stability and temperature dependence has been accomplished, thus giving useful information for in vivo applications. The effect of dissolved oxygen concentration in the working solution was also studied in order to evaluate its effect on the linearity of the sensors. Glucose monitoring performed with serum samples was performed to evaluate the effect of matrix components on operative stability and demonstrated an efficient behaviour for 72 h of continuous monitoring. Finally, these studies led to a sensor capable of detecting glucose at concentrations as low as 0.04 mM and with a good linearity up to 2.0 mM (at 37 degrees C) with an operative stability of ca. 72 h, thus demonstrating the possible application of these sensors for continuous glucose monitoring in conjunction with a microdialysis probe. Moreover, preliminary in vivo experiments for ca. 20 h have demonstrated the feasibility of this system.

[Youth drinking as en example of relationship between risk behaviour and knowledge on its effects].

PubMed

Wrona-Wolny, Weronika; Brudecki, Janusz

2006-01-01

Using psychoactive substances like smoking, drinking or drugs are most common risky behaviour. In the article only drinking as an examples was analysed. Knowledge about alcohol health effects and its dependence on undertaking risky behaviour, alcohol-advertisement perception, sex and group were analysed. Between 2001 and 2005 343 sportsmen and 400 students as a control group were participated in research. Questionnaire diagnosed alcohol-related behaviour and alcohol-advertisement perceptions were used. Knowledge about effects of alcohol acting contains 11 questions. Chi-square test and multifactor analysis of variances were used. Results show that knowledge level depends only from group belonging and is higher in students than sportsmen. Susceptibility to undertaking risky behaviour occurs more frequently in control than in sport group, in man then woman, and in person with who pay attention to alcohol advertisements.

Application of predictive models to assess the influence of thyme essential oil on Salmonella Enteritidis behaviour during shelf life of ready-to-eat turkey products.

PubMed

Possas, Arícia; Posada-Izquierdo, Guiomar D; Pérez-Rodríguez, Fernando; Valero, Antonio; García-Gimeno, Rosa M; Duarte, Marta C T

2017-01-02

Consumers' demand for ready-to-eat (RTE) turkey meat is attributed to its convenience and healthy properties. However, as cooked meat product it is subjected to post-process contamination, thus allowing presence and growth of microbial pathogens, such as Salmonella spp.. The aim of this study was to include a natural antimicrobial, thyme essential oil (TEO), on RTE turkey products in order to evaluate its effectiveness throughout the shelf life. To do so, the effect of four different formulations of cooked RTE turkey products on Salmonella Enteritidis behaviour was investigated. Products' slices were surface inoculated with S. Enteritidis (ca. 4 to 5logcfu/g), subsequently stored at 10 and 25°C and microbiologically analysed during 18 and 12days, respectively. Predictive microbiology models fitted to count data were used to evaluate microbial behaviour. Results showed that S. Enteritidis behaviour on RTE turkey products slices during storage was strongly dependent on temperature. The pathogen was able to grow on slices at all tested conditions during storage at 25°C and no statistical differences were detected (p>0.05) between growth parameters. At 10°C, different behaviour patterns were observed. The application of TEO led to higher Salmonella inactivation rates on a product exempt of chemical preservatives. The addition of this novel antimicrobial on meat products or its incorporation on meat active packaging systems as a part of hurdle technology could increase RTE turkey products safety while satisfying the demand of more natural foods. Copyright © 2016 Elsevier B.V. All rights reserved.

Is the time-dependent behaviour of the aortic valve intrinsically quasi-linear?

NASA Astrophysics Data System (ADS)

Anssari-Benam, Afshin

2014-05-01

The widely popular quasi-linear viscoelasticity (QLV) theory has been employed extensively in the literature for characterising the time-dependent behaviour of many biological tissues, including the aortic valve (AV). However, in contrast to other tissues, application of QLV to AV data has been met with varying success, with studies reporting discrepancies in the values of the associated quantified parameters for data collected from different timescales in experiments. Furthermore, some studies investigating the stress-relaxation phenomenon in valvular tissues have suggested discrete relaxation spectra, as an alternative to the continuous spectrum proposed by the QLV. These indications put forward a more fundamental question: Is the time-dependent behaviour of the aortic valve intrinsically quasi-linear? In other words, can the inherent characteristics of the tissue that govern its biomechanical behaviour facilitate a quasi-linear time-dependent behaviour? This paper attempts to address these questions by presenting a mathematical analysis to derive the expressions for the stress-relaxation G( t) and creep J( t) functions for the AV tissue within the QLV theory. The principal inherent characteristic of the tissue is incorporated into the QLV formulation in the form of the well-established gradual fibre recruitment model, and the corresponding expressions for G( t) and J( t) are derived. The outcomes indicate that the resulting stress-relaxation and creep functions do not appear to voluntarily follow the observed experimental trends reported in previous studies. These results highlight that the time-dependent behaviour of the AV may not be quasi-linear, and more suitable theoretical criteria and models may be required to explain the phenomenon based on tissue's microstructure, and for more accurate estimation of the associated material parameters. In general, these results may further be applicable to other planar soft tissues of the same class, i.e. with the same representation for fibre recruitment mechanism and discrete time-dependent spectra.