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Author(s): G. G. Guzmán-Verri [sup.1] [sup.2] [sup.3] , R. T. Brierley [sup.4] , P. B. Littlewood [sup.3] [sup.5] Author Affiliations: (1) Centro de Investigación en Ciencia e Ingeniería de Materiales [...], Metal-to-insulator transitions.sup.1 driven by strong electronic correlations occur frequently in condensed matter systems, and are associated with remarkable collective phenomena in solids, including superconductivity and magnetism. Tuning and control of the transition holds the promise of low-power, ultrafast electronics.sup.2, but the relative roles of doping, chemistry, elastic strain and other applied fields have made systematic understanding of such transitions difficult. Here we show that existing data.sup.3-5 on the tuning of metal-to-insulator transitions in perovskite transition-metal oxides through ionic size effects provides evidence of large systematic effects on the phase transition owing to dynamical fluctuations of the elastic strain, which have usually been neglected.sup.6. We illustrate this using a simple yet quantitative statistical mechanical calculation in a model that incorporates cooperative lattice distortions coupled to the electronic degrees of freedom. We reproduce the observed dependence of the transition temperature on the cation radius in the well studied manganite.sup.7 and nickelate.sup.8 materials. Because elastic couplings are generally strong, we anticipate that these conclusions will generalize to all metal-to-insulator transitions that couple to a change in lattice symmetry. Theoretical modelling shows that elastic fluctuations can enable the tuning of metal-to-insulator transitions, potentially also explaining the dependence of the transition temperature on cation radius in perovskite transition-metal oxides.

PRS® paraffin wax was encapsulated by means of suspension-like copolymerization of methyl methacrylate (MMA) with butyl acrylate (BA). The effects of the polymeric shell dry glass transition temperature ([T.sub.g]) and [...]

The poly ethylene terephthalate near the glass transition temperature highlights a strongly non linear elastic and viscous behaviour when biaxially stretched at high strain rates representative of the injection stretch blow moulding process. A non linear visco-hyperelastic model, where characteristics are coupled to the temperature, has already been identified from equi-biaxial tension experimental results. The weak form of the mechanical part of the model is presented and implemented into a finite element code developed in the Matlab environment and validated by comparing numerical simulation of equi-biaxial testing with the analytical solution in the isothermal case. Considering the thermal aspects, an experimental study, where PET sheets are heated using infrared (IR for short) lamps is also presented. The modeling of the IR radiation of the sheet helps to identify the thermal properties of the PET. The thermal model is then implemented in the finite element code, coupled to the 2D viscoelastic model. A discussion is made to justify the accuracy of the assumption made on homogeneity of the temperature field through the thickness. The simulation of the 20 plane stress equibiaxial test shows the important influence of the thermal aspects and the coupled thermo-mechanical software is used to quantify the self-heating phenomenon in the case of the biaxial elongations of PET sheets at high strain rates. POLYM. ENG. SCI., 53:2683-2695, 2013. © 2013 Society of Plastics Engineers, INTRODUCTION The injection stretch blow molding (ISBM) process that is managed at a temperature near or slightly above the glass transition temperature ([T.sub.g]) involves multiaxial large strains at high strain [...]

Poly(methyl methacrylate)-based copolymers were prepared by solution copolymerization of methyl methacrylate (MMA) with methacrylamide (MAAM) or methacrylic acid (MAA) in dioxane. The blends of poly (methyl methacrylate-co-methacrylamide) (MMA- MAAM) with poly(methyl methacrylate-co-methacrylic acid) (MMA-MAA) were prepared by solution blending. The thermal properties of the blends were studied by differential scanning calorimetry. A large positive deviation in the glass transition temperature (TO from the Fox equation was observed. The existence of strong hydrogen-bonding interaction between the two copolymers was indicated based on the Kwei equation and conformed by Fourier transform infrared spectroscopy. The contact angle measurements showed that the hydrophilicity of the blends is lower than the corresponding copolymers. POLYM. ENG. SCI., 53:2370-2377, 2013. 0 2013 Society of Plastics Engineers, INTRODUCTION Poly(methyl methacrylate) (PMMA) is a nonpoisonous, environmental polymeric material possessing many admirable advantages, such as high light transmittance, ease of processing, excellent dimensional stability, colorlessness, resistance to weathering corrosion, [...]

In this article, we analyzed the influence of isosorbide content on glass transition temperature and crystallinity of poly(L-lactide). Different synthesis methods were applied to determine optimal procedure for polymerization of L-lactide in the presence of isosorbide. Two procedures were performed with tin(II) 2-ethylhexa-noate as the catalyst: first, using the vacuum sealed vessel, and second, using microwave reactor bulk polymerizations. The solution polymerization (with trifluoromethanesulfonic acid as catalyst) was possible at the temperature of 40°C. Obtained polyesters had number average molecular weights ranging from 20,000 to 65,000 g [mol.sup.1], according to the gel permeation chromatography measurements. The polymer structure was characterized by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy. Thermal properties of the obtained polymers were analyzed using thermogravimetry (TG) and differential scanning calorimetry (DSC). According to DSC measurements, the addition of isosorbide in the polyesters influenced the increase in both glass transition temperature and degree of crystallization for all samples. The results obtained by thermogravimetric analysis confirmed the strong influence of polymerization mechanism on synthesized poly(L-lactides) thermal properties. POLYM. ENG. SCI., 53:1374-1382, 2013. © 2012 Society of Plastics Engineers, INTRODUCTION Because of concerns for the global environment biodegradable polymers became appropriate alternatives for many petrochemical-based polymers. Bio-renewable and biodegradable materials, such as lactide (1) or isosorbide, are becoming more [...]

The cadmium sulfide/polystyrene (CdS/PS) nanocomposites with concentration (0, 2, 4, 6, and 8) wt% of CdS nanoparticles were prepared by solution casting method and characterized through fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM) measurements. The particle size of nanoparticles is found to be around 15 nm. Glass transition and mechanical behavior of CdS/PS nanocomposites were investigated using dynamic mechanical analyzer (DMA). The mechanical properties such as Young's modulus and tensile strength were determined at room, as well as at elevated temperatures through their stress-strain curves. The result shows that glass transition temperature ([T.sub.g]) is shifted toward the higher temperature after the addition of CdS nanoparticles. The mechanical properties increased at low wt% loading of CdS nanoparticles and decreased for higher wt% loading of CdS nanoparticles. It was also found that mechanical properties decline with increase in the temperature. POLYM. ENG. SC1., 53:1223-1229, 2013. © 2012 Society of Plastics Engineers, INTRODUCTION As a result of the insatiable demand for new materials in emerging field like nanotechnology, the preparation and characterization of semiconductor-polymer nanocomposites is a rapidly evolving area of research [...]

Hot-embossing (HE) experiments were conducted on polymethyl methacrylate (PMMA) across its glass transition temperature from 92 to 142 ° C. The glass transition temperature (Tg) of the PMMA used in this study was ~ 102 ° C. The polymer samples were embossed to a depth of 0.8 mm (800 µm). The experiments were carried out at various temperatures for different hold times of 30, 90, and 180 sec during the embossing process. A few additional experiments were conducted at 142 ° C with cooling of the samples as well. The force required for embossing and the final depth of the embossed features were analyzed. Polymers, including PMMA, show significantly different material behavior around and above [T.sub.g]. The same was seen in the aforementioned tests; the trends observed for the force as well as the final depth changed considerably around 122 ° C ([T.sub.g] + 20). These findings will be used in developing material models for use in simulating the hot-embossing process. POLYM. ENG. SCI., 52:1284-1292, 2012. © 2012 Society of Plastics Engineers, INTRODUCTION Polymethyl methacrylate (PMMA) is an amorphous thermoplastic used in various industrial applications. PMMA is compatible with human tissues and allows for high-resolution features to be embossed onto it, thus [...]

We synthesized series of shape memory polyurethanes with amorphous reversible phase [(T.sub.g]-SMPUs) and systematically studied their microphase structure and shape memory properties. The (T.sub.g]-SMPUs having no or less hard phase showed lower shape recovery. When the volume fraction of hard phase was in the range of 20-30%, the (T.sub.g]-SMPUs exhibited the highest shape recovery. As the fraction of hard phase increased further the shape recovery decreased, because more polymer components with higher glass transition temperatures ((T.sub.g]s) would participate in strain storage. For the (T.sub.g]-SMPUs having similar (T.sub.g]s, those polymers having higher volume fraction of hard phase exhibited higher shape fixity, broader shape recovery region, and larger recovery stress. Increasing deformation strain could raise shape fixity and recovery stress but broaden shape recovery region. The highest recovery stress of a material could be achieved when the deformation occurred at its glass transition temperature below which decreasing deformation temperature could not increase recovery stress further. POLYM. ENG. SCI., 52:1015-1026, 2012. @ 2011 Society of Plastics Engineers, INTRODUCTION Shape memory polyurethanes (SMPUs) aroused increasing interests from both academia and industry in the past decades because of their extensive application potential in many fields [1-11]. SMPUs are the [...]

Phenolic and amine epoxy systems are widely used as hardeners in underfill materials for. flip chip packaging. A comparison was made between these two systems in order to evaluate the reliability performance of a flip chip plastic ball grid array (FC-PBGA). The coefficient of thermal expansion, glass transition temperature ([T.sub.g]), Young's modulus (E), and fracture toughness were revealed by using a thermal mechanical analyzer, a dynamic mechanical analyzer, and a single-edge notch three-point bending test, while moisture absorption study was performed using an 85[degrees]C/85% relative humidity chamber. The adhesion strength with different conditions of temperature and humidity was performed using a die shear test. The series of standard reliability tests such as accelerated temperature cycle test, pressure cooker test, thermal humidity storage test, and high temperature storage test were executed upon the FC-PBGA, which was filled by phenolic and amine epoxy systems of underfill materials. It was found that the adhesion strength of phenolic-based underfills is better than that of amine-based underfills in almost all test conditions. Phenolic-based underfills also demonstrated better reliability compared with amine-based underfills. [DOI: 10.1115/1.4002741] Keywords: amine-based, phenolic-based, reliability, underfill

Most polymers solidify into a glassy amorphous state, accompanied by a rapid increase in the viscosity when cooled below the glass transition temperature ([T.sub.g]). There is an ongoing debate on whether the [T.sub.g] changes with decreasing polymer film thickness and on the origin of the changes. We measured the viscosity of unentangled, short-chain polystyrene films on silicon at different temperatures and found that the transition temperature for the viscosity decreases with decreasing film thickness, consistent with the changes in the [T.sub.g] of the films observed before. By applying the hydrodynamic equations to the films, the data can be explained by the presence of a highly mobile surface liquid layer, which follows an Arrhenius dynamic and is able to dominate the flow in the thinnest films studied. 10.1126/science.1184394

Four scenarios have been proposed for the low-temperature phase behavior of liquid water, each predicting different thermodynamics. The physical mechanism that leads to each is debated. Moreover, it is still unclear which of the scenarios best describes water, because there is no definitive experimental test. Here we address both open issues within the framework of a microscopic cell model by performing a study combining mean-field calculations and Monte Carlo simulations. We show that a common physical mechanism underlies each of the four scenarios, and that two key physical quantities determine which of the four scenarios describes water: (i) the strength of the directional component of the hydrogen bond and (ii) the strength of the cooperative component of the hydrogen bond. The four scenarios may be mapped in the space of these two quantities. We argue that our conclusions are model independent. Using estimates from experimental data for H-bond properties the model predicts that the low-temperature phase diagram of water exhibits a liquid-liquid critical point at positive pressure. anomalous liquids | liquid-liquid transition | liquid water | mean field | Monte Carlo simulations doi/ 10.1073/pnas.0912756107

The new topological indices (Sh indices) based on the distance sum and connectivity of a molecular graph, previously developed by our team, were extended to predict the two physicochemical properties, including normal boiling point (NBP) and molar refractivity (MR), of a large set of organic compounds consisting of alkanes, alkenes, ethers, amines, alcohols, alkylbenzenes, and alkylhalides. The sets of molecular descriptors were derived directly from the two-dimensional molecular structure of the compounds based on graph theory. Both linear and nonlinear modelings were implemented by using principal component regression (PCR) and principal component -- artificial neural network (PC--ANN) with back-propagation learning algorithm, respectively. Eigenvalue and correlation-ranking procedures were used to rank the principal components and entered them into the models. Principal component analysis of Sh data matrix showed that the respective six and seven PCs could explain 97.49% and 99.22% of variances in the Sh indices. PCR analysis of the NBP and MR data demonstrated that the proposed Sh indices could explain about 97.52% and 99.52% of variations, while the variations explained by the PC--ANN modeling were more than 99.00% and 99.82%, respectively. The predictive ability of the models were evaluated using an external test set for NBP and MR of the molecules with the respective root-mean-square errors lower than 9.69 K and 0.660 [cm.sup.3] [mol.sup.-1] for the linear model and 6.17 K and 0.416 [cm.sup.3] [mol.sup.-1] for the nonlinear model. Key words: topological Sh indices, eigenvalue ranking, correlation ranking, normal boiling point, molar refractivity, principal component analysis, principal component regression (PCR), principal component-artificial neural network (PC-ANN). Les nouveaux indices topologiques (indices Sh) bases sur la somme de la distance et la connectivite d'un graphe moleculaire et developpes anterieurement par notre equipe ont ete etendus afin de pouvoir predire deux proprietes physicochimiques, dont le point d'ebullition normal (PEN) et la refractivite molaire (RM) d'un large ensemble de composes organiques formes d'alcanes, d'alcenes, d'amines, d'alkylbenzenes et d'halogenures d'alkyle. Les ensembles de descripteurs moleculaires ont ete derives directement de la structure moleculaire bidimensionnelle des composes basee sur la theorie des graphes. On a developpe des modeles lineaires et non lineaires en utilisant l'algorithme d'apprentissage en retropropagation respectivement avec une regression du composant principal (RCP) et avec le reseau neural artificiel du composant principal (RNA--CP). On a fait appel aux methodes de la valeur de eigen et du classement des correlations pour classer les composants principaux qui ont ensuite ete introduits dans les modeles. L'analyse du composant principal d'une matrice de donnees Sh a permis de montrer que respectivement six ou sept composants principaux (CP) peuvent expliquer 97,49 % et 99,22 % des variances dans les indices Sh. L'analyse de la RCP des donnees relatives aux PEN et aux RM a permis de demontrer que les indices Sh peuvent expliquer environ 97,52 % et 99,52 % des variations alors que les variations expliquees par me modele RNA-CP expliquent respectivement 99,00 % et 99,82 % des variations. On a evalue l'habilite des modeles a faire des predictions relatives aux PEN et aux RM des molecules en utilisant un ensemble externe et les erreurs quadratiques moyennes respectives etaient inferieures reseau neural artificiel du composant principal (RNA--CP) a 9,69 K et 0,660 [cm.sup.3] [m.sup.-1] pour le modele lineaire et de 6,17 K et 0,416 [cm.sup.3] [m.sup.-1] pour le modele non lineaire. Mots-cles : indices SH topologiques, classement de valeurs de eigen, classement de correlation, point d'ebullition normal (PEN), refractivite moleculaire (RM), analyse du composant principal, regression du composant principal (RCP), reseau neural artificiel du composant principal (RNA-CP). [Traduit par la Redaction], Introduction One of the most fundamental ideas of chemistry is that the physicochemical properties, for instance, normal boiling point and molar refractivity, for chemical and chemical engineering substances are determined [...]

Ceramic superconductors (cuprates, pnictides, etc.) exhibit universal features in both [T.sub.c.sup.max] and in their planar lattice disordering measured by EXAFS, as reflected by three phase transitions. The two highest temperature transitions are known to be associated with formation of Jahn--Teller pseudogaps and superconductive gaps, with corresponding Landau order parameters, but no new gap is associated with the third transition below [T.sub.c], and its origin is mysterious. It is argued that the third sub[T.sub.c] transition is a dopant glass transition, which is remarkably similar to topological transitions previously observed in chalcogenide and oxide alloy network glasses (like window glass). EXAFS | superconductivity | topological

Frozen fraction measurements made using a droplet free-fall freezing tube apparatus are presented and used, along with other recent laboratory measurements, to evaluate how well both the water activity idea and the translated melting-point curve idea of Koop et al. predict homogeneous freezing-point temperatures for aqueous ammonium sulfate and sulfuric acid solution droplets. The new freezing-point temperature datasets agree with the previous lowest-temperature results for both solutes. The lowest measured freezing-point temperatures for aqueous ammonium sulfate solutions agree with a curve shaped like the translated melting-point curve. However, those for aqueous sulfuric acid solutions are significantly lower than predicted by the translated melting-point curve idea, and a single water activity freezing-point temperature curve does not represent the lowest-temperature freezing-point temperature data for both solutes. A linear extrapolation of the new aqueous sulfuric acid solution freezing data to low temperatures predicts that high critical supersaturations in cloud-free regions of the upper troposphere will occur when homogeneous ice nucleation in ah aqueous sulfuric acid aerosol is the primary ice formation mechanism.

I suggest that the origin of the Mpemba effect (the freezing of hot water before cold) is due to freezing-point depression by solutes, either gaseous or solid, whose solubility decreases with increasing temperature so that they are removed when water is heated. The solutes are concentrated ahead of the freezing front by zone refining in water that has not been heated, reducing the temperature of the freezing front, and thereby reducing the temperature gradient and heat flux, slowing the progress of the freezing front. I present a simple calculation of this effect, and suggest experiments to test this hypothesis. [DOI: 10.1119/1.2996187]

The temperature-dependent phase transition and supersonic conductivity of silver-iodide (AgI) are analyzed. The array-structures nanocomposite AgI-anodic-aluminum-oxide (AAO) is developed for usage as a new type of battery with individual AgI nanowires as basic elements.

Glass transition of low-density amorphous water is studied which provides insight into the thermodynamics of water transition.

Establishing phase relationships between earth-system components during periods of rapid global change is vital to understanding the underlying processes. It requires records of each component with independent and accurate chronologies. Until now, no continental record extending from the present to the penultimate glacial had such a chronology to our knowledge. Here, we present such a record from the annually laminated sediments of Lago Grande di Monticchio, southern Italy. Using this record we determine the duration (17.70 [+ or -] 0.20 ka) and age of onset (127.20 [+ or -] 1.60 ka B.P.) of the last interglacial, as reflected by terrestrial ecosystems. This record also reveals that the transitions at the beginning and end of the interglacial spanned only [approximately equal to] 100 and 150 years, respectively. Comparison with records of other earthsystem components reveals complex leads and lags. During the penultimate deglaciation phase relationships are similar to those during the most recent deglaciation, peaks in Antarctic warming and atmospheric methane both leading Northern Hemisphere terrestrial warming. It is notable, however, that there is no evidence at Monticchio of a Younger Dryas-like oscillation during the penultimate deglaciation. Warming into the first major interstadial event after the last interglacial is characterized by markedly different phase relationships to those of the deglaciations, warming at Monticchio coinciding with Antarctic warming and leading the atmospheric methane increase. Diachroneity is seen at the end of the interglacial; several global proxies indicate progressive cooling after [approximately equal to] 115 ka B.P., whereas the main terrestrial response in the Mediterranean region is abrupt and occurs at 109.50 [+ or -] 1.40 ka B.P. Eemian | phase relationships | pollen | varves

Discovery of the Thermus aquaticus and other microbes thriving at temperatures close to water's boiling point change the perception that life could not exist much above 70 degrees Celsius and polar studies have also revealed robust communities of psychrophiles, microbes that spend their lives near 0 degrees Celsius. If life can persist over the vast range from minus 20 to more than 150 degrees Celsius, then it is time to rethink the view of habitable zones on Earth, in the solar system and throughout the galaxy.

A hexagonal diethynylbenzene macrocycle having exterior octyloxymethyl groups undergoes spontaneous polymerization at room temperature to form hardly soluble materials, in contrast to the corresponding dehydrotetramer and dehydrooctamer, which are stable to show their melting points at higher than 140 degree Celsius.

Abstract: The existence of finite phase transition temperatures is proved for a classical double-well potential of a nonhomogeneous anisotropic two-phase elastic medium with general boundary conditions. Bibliography: 6 titles. Article History: Registration Date: 30/12/2005 Article note: Translated from Problemy Matematicheskogo Analiza, No. 31, 2005, pp. 59--66.

Byline: V. G. Osmolovski (1) Abstract: Dependence of the phase transition temperature on the domain size is investigated for a double-well quadratic potential. It is shown that for a domain whose boundary is subjected to a hydrostatical pressure, the temperature of phase transitions is independent of the domain and the surface tension coefficient and depends exclusively on the properties of the elastic media. If the displacement field vanishes on the boundary, then for sufficiently small domains, the temperature also does not depend on the surface tension and domain size and is determined by properties of the elastic media only. Bibliography: 8 titles. Author Affiliation: (1) St. Petersburg State University, St. Petersburg, Russia Article History: Registration Date: 12/12/2005 Received Date: 15/03/2004 Article note: Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 310, 2004, pp. 98--113.

Several experiments have suggested that newly synthesized polypeptide chains can adopt helical structures deep within the ribosome exit tunnel. We hypothesize that confinement in the roughly cylindrical tunnel can entropically stabilize [alpha]-helices. The hypothesis is validated by using theory and simulations of coarse-grained off-lattice models. The model helix, which is unstable in the bulk, is stabilized in a cylindrical cavity provided the diameter (D) of the cylinder exceeds a critical value D *. When D < D * both the helical content and the helix-coil transition temperature ([T.sub.f]) decrease abruptly. Surprisingly, we find that the stability of the [alpha]-helix depends on the number (N) of amino acid residues. Entropic stabilization, as measured by changes in [T.sub.f], increases nonlinearly as N increases. The simulation results are in quantitative agreement with a standard helix-coil theory that takes into account entropy cost of confining a polypeptide chain in a cylinder. The results of this work are in qualitative accord with most of the findings of a recent experiment in which N-dependent ribosome-induced helix stabilization of transmembrane sequences was measured by fluorescence resonance energy transfer. confinement effects | cylindrical pores | entropic stabilization folding

We investigate, for two water models displaying a liquid--liquid critical point, the relation between changes in dynamic and thermodynamic anomalies arising from the presence of the liquid--liquid critical point. We find a correlation between the dynamic crossover and the locus of specific heat maxima [C.sup.max.sub.p] ('Widom line') emanating from the critical point. Our findings are consistent with a possible relation between the previously hypothesized liquid-liquid phase transition and the transition in the dynamics recently observed in neutron scattering experiments on confined water. More generally, we argue that this connection between [C.sup.max.sub.p] and dynamic crossover is not limited to the case of water, a hydrogen bond network-forming liquid, but is a more general feature of crossing the Widom line. Specifically, we also study the Jagla potential, a spherically symmetric two-scale potential known to possess a liquid-liquid critical point, in which the competition between two liquid structures is generated by repulsive and attractive ramp interactions. liquid--liquid critical point | low-density liquid | high-density liquid | [C.sup.max.sub.p] line | [K.sup.max.sub.T] line

The nucleation behavior of n-alkane droplets with carbon numbers ranging from 14 to 17 is observed in an electrodynamic balance. The changes in the elastic light-scattering pattern of the single levitated microdroplets indicate the phase transition from liquid to solid. Cooling/heating experiments showed larger supercooling temperatures than expected for alkane droplets with an alkane/air interface.

Experimental structure-I clathrate hydrate equilibrium and ice-melting data for mesoporous silica glass is presented. The Gibbs-Thomson relationship is used to describe the temperature depression of clathrate dissociation conditions in cylindrical pores. It is observed that in both cases, high capillary pressures result in depressed solid decomposition temperatures, as a function of pore diameter.

The features of the clathrate hydrate equilibria in mesoporous media are discussed in terms of a conceptual model, with the aim of resolving current inconsistencies concerning experimental and interpretative methods employed in studies of such systems. It is concluded that the Gibbs-Thomson (or Kelvin) relationship used to model clathrate inhibition in porous media must be modified correctly to reflect the hysteries between growth and dissociation.

The transformation of a crystalline solid into a liquid, seeming to have no precursor and no intermediate states, has challenged scientists for over a century. The search for the fundamental mechanism stimulated the development of quantum mechanics, concepts of the roles of dimensionality and topological order in condensed matter, and experimental techniques to test the theories. We now understand that the transition begins at lower temperatures than the melting point of the bulk. It starts at the edges of crystal planes, progresses across the surface, evolves into the successive melting of atomic layers, and ends in bulk phase coexistence. The memory of the process remains within a few molecular distances at the crystal--melt interface.

The rate constants for the gas-phase reactions of phenanthrene, phenanthrene-d10, and 1-, 2-, 3-, and 9-methyphenanthrenes with the hydroxyl radical are measured using the relative rate technique over the temperature range of 323-403 K and at a total pressure of 760 Torr. The Arrhenius parameters determined here are the first to be presented.

Rate equations to describe electron densities were solved to calculate carrier transition rates and subband populations for GaAs/A1GaAs quantum cascade lasers.

Glass transition temperature prediction of fruit powders is examined using a mathematical model.

This paper discusses the dependence of Fe thickness on the temperature transition and compensation in Fe/Tb multilayers using Heisenberg bilayer model and Monte Carlo simulations.

A study of the glass transition temperature and viscosity of aqueous trehalose and its mixtures with borax and sodium chloride is presented with measurements taken over a wide range of concentration.

The paper describes microwave differential thermal analysis, a new technique that combines the advantages of microwave heating with the benefits of differential temperature measurement to give a sensitive means of probing the thermal properties of materials as a function of temperature. Details are given of the theoretical background, equipment, design of sample cells, and different modes of operation. Examples are given for a wide range of thermal transitions including fusions, solid-solid phase transitions, and thermal decompositions. The results are discussed in the context of conventional differential thermal techniques.

Research was conducted to examine second harmonic generation for the 30ZnO*70TeO2 glass with a two-step poling procedure. The objective was to gain a new insight into the explanation for the decline in second harmonic intensity just below the glass transition temperature. Results indicate that the decrease in second harmonic intensity with an increase in poling temperature is caused not by a reversible process like a thermal fluctuation of dipoles, but by an irreversible method.

Close to optimal doping, the copper oxide superconductors show 'strange metal' behaviour (1,2), suggestive of strong fluctuations associated with a quantum critical point (3-6). Such a critical point requires a [...]

Despite its ubiquity and long history of investigation, the nature of the glass transition still remains one of the most interesting and puzzling unsolved problems in the physics of condensed matter. However, significant progress in this field has been achieved during the past decade. In this article new ideas formulated in this field and some of the unexpected implications of these ideas are briefly discussed.

The powder-in-tube (PIT) and surface-coated conductor methods were utilized in fabricating Tl-1223 conductors. Short monofilament tapes and meter-long 37-filament tapes exhibited current densities of 20,000 A/cm2 and 12,000 A/cm2 at 77 K, respectively. A new method was also proposed for the development of PIT Tl-1223 conductors with grain alignment. The approach successfully fabricated conductors with critical currents of 18 A and a 19,000A/cm2 Jc.

The laser ablation method was used for NdBa2Cu3O7-delta thin film deposition on (100) SrTiO3 substrates. The thin films' transition temperature were influenced by such deposition parameters as chamber pressure, substrate temperature and the distance between target and substrate. Deposition at 770-degrees celsius and 800 mTorr of oxygen pressure resulted in thin films with temperatures of -93 K.

Molecular dynamic simulation of surface-induced diamond-to-graphite transition generates a microscopic model for the initial stages of graphitization. The transition results in the formation of a diamond/graphite interface. Graphitization involves the breaking of adjacent bonds aligned along the z direction. Direct transformation forms graphite microcrystals at the diamond interface in the presence of large activation energy. Diamond deposited on graphite through chemical vapor deposition exhibits an epitaxial relationship between graphite and diamond.

The classic experiments carried out by Thomas Andrews in Belfast in the 1870s on the continuity of the gaseous and liquid states, and his concept of critical temperature, are familiar to most scientists. Very few, however, have actually seen the transition taking place. This article reviews the phenomenon in the light of current theory, and illustrates it by photographs taken of the transition of Freon 115 in a specially constructed glass and steel cell.

The solid-fluid transition zone that occurs during the melting and solidifying of binary alloys is studied. Several sets ofequations are used to account for solid-fluid mixture's fundamental parameters,such as true density, average density, volume fraction and average velocity. A finite element program is then employed to solve the stress and temperature fields for both the solid and liquid phases. The results show fair agreement with experimental data.

A low temperature radiation damage study of first-generation passive microwave devices fabricated from high temperature cuprate superconductors has been performed in order to examine the effects of nonionizing radiation damage. Changes in performance due to radiation-induced shifts in the transition temperature and to film erosion are discussed. The results show that if these relatively simple passive devices are reasonably well shielded, they should survive in typical five-year space applications.

A study was conducted to determine the thermal transition, mechanical properties, phase morphology and blending of poly(phenylene sulfide) (PPS)/polyamides mixtures. It was found that semicrystalline aliphatic polyamides exhibit crystalline melting points while amorphous polyamides show a glass transition temperature. Experiments showed that a smaller viscosity difference between the blend components produces a finer dispersed phase. Most PPS/semicrystalline, aliphatic polyamide blends have poor strength, while PPS/amorphous polyamide blends are stronger than the pure PPS resin.

A Diamond Anvil Cell (DAC) coupled with a high-energy dispersive synchrotron radiation is used to carry out in situ X-ray diffraction study of AIN nanocrystals with an average particle size of 10nm, at a pressure 36.9 GPa. The results suggest that the combination of the volume expansion and the softening of the Poisson ratio, and shear modulus result in reduction of the phase transition pressure, and a higher surface energy casts crucial effect on the enhanced bulk modulus of AIN nanocrystals.