The equation of state of triolein up to 1 GPa

In this paper, the compressibility studies of triolein up to 1 GPa at temperature range from 10°C to 50°C have been presented. The discontinuity of V(p) relation, characteristic for the first-order phase transition was observed. At higher temperatures (40°C and above), the time necessary for the phase transition rises considerably. Also the pressure–volume hysteresis due to the phase formation–decomposition cycle was enlarged.     

A Spin Label Study of the Effects of Hydrostatic Pressure and Temperature on Cellular Lipids

Rabbit alveolar macrophages were labeled with fatty acid-derived spin labels and the effects of both hydrostatic pressure and temperature upon the fluidity of cell lipids were observed. The alveolar macrophage membrane is significantly more fluid than the erythrocyte membrane, with a value of 2T of 52.1 ± 0.7 gauss as compared to a literature value of 56.2 ± 0.8 gauss for erythrocyte ghosts. Arrhenius plots of the effects of temperature upon membrane lipids exhibit a constant slope as the temperature is reduced until a temperature of 2–3°C is obtained, at which point an abrupt change of slope is encountered indicating a lipid phase transition. When the temperature is held constant and hydrostatic pressure is applied in increasing increments, membrane lipids again exhibit a gradual, consistent decrease in fluidity. Moderate pressures in the range of atmospheric to 4000 psi were employed; and for the cells studied, an increase in pressure of 1000 psi appears roughly equivalent to a temperature reduction of 1°C. When hydrostatic pressure is applied in combination with reduced temperature, the temperature at which the lipid phase transition takes place is shifted from 2–3°C to approximately 10°C.     

Substitution and proton doping effect on SrZrO3 behaviour: high‐pressure Raman study

The high‐pressure Raman studies of pure, Yb‐modified, protonated and non‐protonated SrZrO₃ dense ceramics were performed between 0.1 and 40 GPa using a diamond anvil cell. Lanthanide‐modified, protonated SrZrO₃ perovskites are potential materials for electrolytic membrane in fuel cells and electrolysers working at medium temperature. The comparison of the Raman spectra shows important differences in the pressure behaviour between the pure and Yb‐modified SrZrO₃ ceramics. SrZrO₃ exhibits a rigid structure without any structural modification, whereas for both SrZr_0.93 Yb_0.07 O_2.965 and SrZr_0.93 Yb_0.07 O_2.962 H_0.003 a sequence of structural modifications at 10, 20 and 35 GPa is revealed. The character of these structural modifications is very similar to that observed as a function of the temperature (orthorhombic Pnma 750 °C → pseudo‐tetragonal Imma 840 °C → tetragonal I4/mcm 1070 °C → cubic Pm3m), which suggests that they can be considered as the phase transitions. Despite the low level of proton content (0.3% mole/mole), significant difference between protonated and non‐protonated compounds is observed for the 700–750 cm⁻¹ doublet assigned to the Zr O octahedron stretching mode, perturbed by an oxygen atom vacancy and/or neighbouring Yb ion. The location of proton is discussed. Copyright © 2011 John Wiley & Sons, Ltd.     

Defect centres and thermoluminescence in SrS:Bi phosphor

Thermoluminescence (TL) and electron spin resonance studies have been carried out on SrS:Bi phosphor. The TL glow curve is broad and indicates a dominant peak at 120 ^°C with two additional peaks, not clearly resolved, appearing as shoulders at around 180 and 250 ^°C. Two defect centres are observed at room temperature. One of them is characterized by an isotropic g-value 2.0034 and is assigned to an F⁺ centre. Step annealing measurements indicate a possible association between the F⁺ centre and the three TL peaks.     

Brillouin light scattering in likso4

Brillouin shift for LIkSO₄ was measured as a function of temperature inthe range 300–363°K. Elastic stiffness coefficients C₁₁, C₃₃ and C₆₆ were also evaluated in this range. A discontinuity of their values was observed at 333°K, suggesting thereby a structural phase transition.     

TL,OA and ESR of spessartine garnet

Thermoluminescence (TL), optical absorption (OA), electron spin resonance (ESR) and their relation to point defects in spessartine have been investigated. The TL glow curve presented four peaks at 150, 220, 260 and 335 °C. The 150 and 335 °C TL peaks growth curves presented a linear growth with radiation dose up to about 400 Gy, supralinearity above this dose, and saturation around 800–1000 Gy. The OA spectrum presented allowed spin transition bands due to Fe³⁺ and Mn²⁺ in dodecahedral environment. Absorption bands due to ultraviolet charge transfer of Fe³⁺ in octahedral and tetrahedral positions were also observed. Two ESR, a strong one around g?～?2 due to Fe³⁺ in octahedral position, and another weaker one at g?～?4 due to Fe³⁺ in tetrahedral position, have been detected. The effect of high temperature annealing (600–900 °C) before irradiation was also investigated.     

Investigation of the alterations induced in erythrocyte membrane physical characteristics of non-insulin-dependent type II diabetic Patients: an ESR study

The physical and dynamic properties of intact erythrocyte membranes of two groups, diabetic patients treated by diet alone (27 women and 41 men, 40–75 years old) and healthy subjects (controls) (25 women and 35 men, 35–75 years old) were investigated by electron spin resonance (ESR) spectroscopy. 5-doxyl stearic acid (5-DSA) and 4-maleimido-2,2,6,6-tetramethyl-piperidine-1-oxyl (MAL-6) are employed as spin labels throughout the experiments. While 5-DSA monitors the membrane surface region and gives information about the order of lipids in this region through the order parametersS′, MAL-6 binds thiol groups S-H to the membrane protein and gives information about possible protein conformational changes. Order parameters were calculated from room temperature spectra recorded for intact erythrocytes labeled with 5-DSA and the values of 0.682±0.004 and 0.666±0.004 were obtained for diabetic patients and controls, respectively. Variations of theh ₍₋₁₎,h ₍₀₎,h ₍₊₁₎ and 2A ₁₁ parameters in the temperature range of 10–50 °C were also studied and fairly different behaviors were observed for both groups, especially for theh ₍₋₁₎ parameter. Line intensitiesW andS characterizing the concentrations of weakly and strongly immobilized MAL-6 species bound to S-H groups of intact erythrocyte membrane proteins were used to calculate theW/S ratios. They were found to be 34.1±1.9 and 30.5±2.4 for diabetic patients and controls, respectively. While line intensitiesT, those of theM ₁=−1 high-field resonance line associated with the weakly immobilized S-H sites, of both groups exhibit a very similar microwave saturation behavior in the range of 0.5–20 mW, line intensitiesW of both groups saturated differently. Variations of line intensitiesS, W andT with temperature were also investigated in the temperature range of 10–50 °C and characteristic differences were observed to exist between two groups implying a less fluid erythrocyte membrane for diabetic patients. Increases in the order parameterS′ and in theW/S ratio are considered as major factors attributable to the alteration in the physical and dynamic properties of erythrocyte membrane in the diabetic state.     

Synthesis and characterization of Ce-doped SrS phosphors

SrS:Ce phosphor was prepared by a solid-state diffusion method. Powder X-ray diffraction, transmission electron microscopy, and thermogravimetric analysis were used to characterize the as-prepared product, and the optical properties were studied by photoluminescence spectra. In addition, thermoluminescence and electron spin resonance studies have been carried out on SrS:Ce phosphor. The TL glow curve is broad and indicates two dominant peaks at 137 and 275^°C, with an additional peak, not clearly resolved, appearing as shoulder at ～362^°C. Two defect centers are observed at room temperature. One of them is characterized by an isotropic g-value of 2.0039 and is assigned to an F⁺ center. Step annealing measurements indicate a possible association between the F⁺ center and the 137^°C TL peak.     

Investigation of domain behaviour in 0.7Pb(Mg1/3Nb2/3) O3-0.3PbTiO3 single crystals at different temperatures in the transmission electron microscope

Using transmission electron microscopy, in-situ changes in ferroelastic domains in 0.7Pb(Mg_1/3Nb_2/3)O₃-0.3PbTiO₃ single crystals were observed at 60 to -163°C. At -163°C, the microscopic tweed morphology of the ferroelastic domains rotated by 90°, and certain orientation changes in the mesoscopic sawtooth domains took place. At this temperature, the ferroelastic domains became coarsened and certain S-shaped mesoscopic domains were reshaped. The disappearance and/or changes in the orientations of both the sawtooth and the ferroelastic domains were reversible upon return to room temperature. On heating to 60°C, both the mesoscopic sawtooth and the microscopic tweed domains were stable below 53°C. Above 53°C, the mesoscopic walls disappeared and the contrast of the tweed domains became blurred. Upon return to room temperature from 60°C, the mesoscopic domain patterns could not be retrieved, indicating that the transformation was irreversible. The morphology of the tweeds at this temperature indicated a structural transition from a two-variant domain state to a multivariant state, eliminating mesoscopic boundaries.     

Structural evolution of ZrO2–mullite nanocomposites from the Si–Al–Zr–O amorphous bulk

ZrO₂–mullite nanocomposites were fabricated by in-situ-controlled crystallization of Si–Al–Zr–O amorphous bulk at 800–1250°C. The structural evolution of the Si–Al–Zr–O amorphous, annealed at different temperatures, was studied by X-ray diffraction, infrared, Laser Raman spectroscopy, field emission scanning electron microscopy, and high-resolution transmission electron microscopy. The materials consisted of an amorphous phase up to 920°C at which phase separation of Si-rich and Al, Zr-rich clusters occurred. The crystalline phases of t-ZrO₂ and mullite were observed at 950°C and 1000°C, respectively. Mullite with a tetragonal structure, formed by the reaction between Al–Si spinel and amorphous silica at low temperature, changed into an orthorhombic structure with the increase of temperature. It was the phase segregation that improved crystallization of the Si–Al–Zr–O amorphous bulk. The anisotropic growth of mullite was observed and the phase transformation from t-ZrO₂ to m-ZrO₂ occurred when the temperature was higher than 1100°C.     

Specific features of the structural states in Pb2CdWO6 in the temperature range 15 ≤ T ≤ 770°C

In the temperature range 15–770°C, a correlation between the dielectric and structural specific features of lead cadmium tungstate is established. When studying the structure of Pb₂CdWO₆ in the temperature range 15 ≤ T ≤ 770°C, the unit-cell parameters and atomic parameters of the orthorhombic phase with space group Pmc2₁ (15 ≤ T ≤ 380°C) and cubic phase with space group Fm3m (380 ≤ T ≤ 770°C) are determined. It is revealed that the antiferroelectric state observed in of Pb₂CdWO₆ in the orthorhombic phase is associated with antiparallel displacements of Pb atoms. In the cubic phase, the Cd atoms are found to have disordered static displacements along [100]-type directions.     

Dielectric anomalous response of water at 60 °C

Recently, the paraelectric response of water was investigated in the range 0–100 °C. It showed an almost perfect Curie–Weiss behaviour up to 60 °C, but a slight change in slope of 1/ε_d versus T at 60 °C was overlooked. In this work, we report optical extinction measurements on metallic (gold and silver) nanoparticles dispersed in water, annealed at various temperatures in the range from 20 to 90 °C. An anomalous response at 60 °C is clearly detectable, which we associate to a subtle structural transformation in the water molecules at that temperature. This water anomaly is also manifested by means of a blue shift in the longitudinal surface plasmon resonance of the metallic nanoparticles for the solutions annealed at temperatures higher than about 60 °C. A reanalysis of 1/ε_d (T) for water in the whole temperature range leads us to conclude that the water molecule undergoes a subtle transformation from a low temperature (0–60 °C) configuration with a dipole moment μ₁ = 2.18 D (close to the molecular dipole moment of ice) to a high temperature (60–100 °C) configuration with μ₂ = 1.87 D (identical to the molecular dipole moment in water vapour).     

SAXS ANALYSIS OF THE TRANSITION INDUCED BY ANNEALING QUENCHED ISOTACTIC POLYPROPYLENE

The morphologic and structural behavior of isotactic polypropylene (i-PP), quenched in a mixture of dry ice and acetone (?78°C), cold-stretched, and then annealed with fixed ends at 70°C, 80°C, 110°C, 140°C, and 150°C, was analyzed by small-angle X-ray scattering (SAXS). The study of the transition induced by annealing, from the quenched form to the well-crystallized one, was carried out through the analysis of the changes that occurred in the macrolattice parameters. The SAXS patterns showed, for all the samples, a meridional interference peak, indicating a coherent macroreticular sequence in the fiber axis direction. The analysis of the meridional spots was performed two dimensionally; that is, the intensity profiles both along the meridian and normal to it were analyzed according to paracrystal theory. The best fit between the calculated and observed intensities of these profiles is evidence of larger paracrystalline fluctuations in the equatorial direction with respect to the meridional one. The equatorial intensity profiles are continuous-like; from the iterative Guinier-Warren analysis of these profiles, three Gaussian components resulted for all the samples except the one annealed at 150°C, for which only two Gaussian components were found. The morphology of the i-PP samples studied here was interpreted on the basis of ultrafibrils, partially isolated and partially packed into two different kinds of aggregates, with the larger one disappearing at the higher annealing temperature. The more remarkable changes occurring in the transition progress concerned the macroreticular parameters in the fiber axis direction. In the temperature range 80°C–110°C, a discontinuity appeared in the changes of the parameters that we interpret in terms of a latent disorder released at this energy level.     

Proton transport through aqueous Nafion membrane

We introduce a new model for proton transport through a single proton-conducting channel of an aqueous Nafion membrane based on a mechanism in which protons move under electrostatic effect provided by the sulfonate ( SO₃ ^-groups of the Nafion side chains, the spin effect of active components, the hydrogen bonding effect with water molecules, and the screening effect of water media. This model can describe the proton transport within various levels of humidification ranging from the low humidity to the high humidity as a function of operating temperature. At low humidity, this model approaches to the so-called surface mechanism, while at high humidity, it approaches the well-known Grotthuss one. Proton motion is considered as the transfer from cluster to cluster under a potential energy. A proton-proton interaction is comprised in the calculation. Using Green function method, we obtained the proton current as a function of the Nafion membrane temperature. We found that the lower the temperature, the higher the proton current transfer through the Nafion membrane in low temperatures compared to the critical point 10K, which separates magnetic regime from non-magnetic regime. The increasing of proton current at very low temperatures is attributed to the spin effect. As the membrane temperature is higher than 40 ^° C , the decreasing of proton current is attributed to the loss of water uptake and the polymer contraction. The results of this study are qualitatively in good agreement with experiments. The expression for the critical temperature is also presented as a function of structural and tunable parameters, and interpreted by experimental data.     

Evidence for ordered regions in poly(n-butyl)methacrylate from light-scattering studies

From light-scattering studies on polybutylmethacrylate, a polymeric glass, the variation of the velocity and attenuation of thermally excited hypersonic phonons with temperature has been measured. Measurement of the temperature dependence of the ratio of the intensity of the Rayleigh line to the Brillouin lines is interpreted as due to a configurational rearrangement within the glass above the glass transition temperature, T_g . Only light scattered from longitudinal phonons was observed. The distinct change in the temperature dependence of the velocity, attenuation and intensity ratio identified the glass transition.

For samples annealed well above T_g, T_g was found to be about 0°C from the light-scattering studies, 12°C from differential scanning calorimetry (DSC), and 20°C from refractive index measurements. For an unannealed sample the behaviour of the above parameters with temperature was found to be different. T_g for the unannealed sample was 14°C from light-scattering, 18°C from DSC and 20°C from index of refraction measurements.     

Birefringence of SbSI and SbSeI crystals at the region of antiferroelectric phase transition

Anomalous behavior has been observed in the temperature range of T = 140–145 °C. The electric current I(T) of SbSI and SbSeI crystals along the c(z) axis changes significantly at the region of the antiferroelectric phase transition when DC voltage is applied. The peak positions are observed at 140 °C and 145 °C for SbSI and SbSeI, respectively. The birefringence spectra show temperature-dependent changes upon retardation m, confirming the antiferroelectric phase transition for both crystals. The peak positions observed from the optical measurements do not differ from the electrical measurements, showing the transition point at 140?°C and 145?°C for SbSI and SbSeI, respectively.     

Piezoelectric activity and phase transitions in (PMN)0.69(PT)0.31 single crystal

Piezoelectric and dielectric investigations have been performed on a (PMN)_0.69(PT)_0.31 single crystal. Low frequency (100?Hz) dielectric permittivity measurements revealed distinct anomaly at 129°C (T _εmax) corresponding to the structural transformation from the tetragonal to cubic phase. Two other anomalies have been detected at 90 and 96°C. After preliminary polarization in the d.c. electric field, switched on above T _εmax and switched off inside the tetragonal phase, the piezoelectric activity has been observed in function of temperature. Values of the piezoelectric resonance frequencies changed markedly at 96°C (on cooling) and 124°C (on heating) showing clear softening of the elastic properties near these temperatures. Values of the piezoelectric and electromechanical coupling coefficients obtained were respectively of the order of 800?pCN^?1 (d ₃₁) and 0.35?(k ₃₁). Piezoelectric activity was detected tens of degrees above the temperature T _εmax and disappeared at temperature at which the dispersion of the dielectric permittivity due to the presence of polar nanoregions is negligible. It was found that strong softening of the elastic properties accompanies phase transitions to the tetragonal and monoclinic phase.     

Annealing Induced Degradation of Thermal SiO2 On (100)Si: Point Defect Generation

The structural degradation of thermal SiO₂ on (100)Si under isochronal post oxidation vacuum annealing (POVA) has been probed by electron spin resonance (ESR). The degradation process, studied in the range T_an = 950–1250 °C, is established as intense point defect generation including E′_γ, E′_δ, EX and the elusive predominant degradation center S. Thermally activated generation is revealed over broad T_an ranges for the two most populous defects, S and E′_γ, with a common activation energy ～1.6eV. Depth profiling after heating at 1200°C shows that the S centers predominantly reside near the oxide borders, generally in anticorrelation with the E′_γ distribution. The S center susceptibility has been inferred from conventional ESR signal intensity monitoring as well as from revealed anisotropic demagnetisation effects. It is found Curie-Weiss type with critical temperature of ～ 1.3 K. Newly observed weak hyperfine structure may comply with the S center being an E′-like defect.     

Structural,spectroscopic and dielectric properties of KVO3

Polycrystalline samples of KVO₃, a member of the pyroxene structural family have been synthesised with high-temperature solid-state reaction technique. Preliminary structural and spectroscopic and detailed dielectric properties have been studied in different conditions. No dielectric anomaly or hysteresis loop has been observed in a wide temperature range (30°C to 450°C). Basic structural and spectroscopic (IR and Raman) studies suggest that at room temperature, KVO₃ is centrosymmetric as reported earlier. This and other observations do not support the recent report of ferroelectric phase transition in the compound.     

Electrolyte interaction with DPPC vesicles: An ESR study

Summary The partition of the spin probe TEMPO between the fluid lipid phase of single-walled vesicles of dipalmitoylphosphatidylcholine and the aqueous bulk solution have been used to investigate the interaction of monovalent ions with polar head of neutral phospholipids. The study has been performed by electron spin resonance (ESR) spectroscopy in the temperature range of (20÷60)°C and in the presence of (0÷3) M 1∶1 electrolyte. In the absence of electrolyte the spin probe TEMPO reveals the characteristic order→disorder DPPC main phase transition atT _m≈37°C, while the pretransition occurs atT _p≈27.5°C. On increasing the ionic strength of the dispersion medium it results for the partition coefficient,P _C, that, at each temperature,P _C(3)>P _C(2)>P _C(1)>P _C(0). Correspondingly, the pretransition disappears and theT _m value downshifts from ≈37°C with 0 M electrolyte to ≈34°C with 3M salt in the order:T _m(3)>T _m(2)>T _m(1)>T _m(0). The results suggest an increase in the net surface charge density of vesicles due to high ionic-strength values. The alteration of the electric interactions occurring into the polar zone of DPPC bilayer reduces the hindrances which, in turn, favour the enhancement of TEMPO partitioning in the hydrophobic core of phospholipid bilayers. The authors of this paper have agreed to not receive the proofs for correction.