This paper is an attempt to investigate the STRUCTURAL properties, PHASE TRANSITION, and thermodynamic and phonon properties of AlAs. Quasi-harmonic Debye- Einstein model was used to obtain lattice constant and static Bulk modulus B0 for B3, B8 and B1PHASEs. These results showed good consistency with experimental results and other theoretical data. Afterwards, the PHASE TRANSITIONs of B3 to B1 and B3 to B8 obtained were equal to 7.9 GPa and 11.2 GPa respectively, which also indicated a good consistency with the theoretical and experimental results. In addition, phonon properties of B3 PHASE were compared with experimental data, and the results demonstrated a good consistency with experimental results especially in the gamma point that is the basis of thermodynamic calculations. Furthermore, the diagrams of heat capacity at constant volume and heat capacity at constant pressure were investigated in terms of temperature for B3 PHASE, and the results showed their significant consistency with theoretical and experimental results.

Obtaining the superconductor samples or mainly, STRUCTURAL PHASE controlling in 123 systems is a matter of special importance. As decreasing of oxygen in this structure has special effects, and mainly causing STRUCTURAL PHASE TRANSITION, by investigating the structure and thermal analysis of the system, tetragonal-orthorhombic STRUCTURAL PHASE TRANSITION was observed and optimum contents of STRUCTURAL PHASE TRANSITION temperature and oxygen were gained (tC630±5oC) and (7-dC @ 6.6), respectively, that are in good agreement with others’ work. In addition by band structure and density of states calculations of YBa2Cu3O7 we gained the equilibrium position, the role and contribution of ions, especially oxygen, in total system’s density of state. It shows that the conductivity of orthorhombic PHASE is more in compare with tetragonal PHASE in normal states of 123 systems.

In this study, we investigated the PHASE behavior of rods with square ( ) and circular (diameter D) cross sections between two hard walls using the Parsons-Lee theory and applying the Zwanzig approximation. Our focus is to find wall-to-wall separations (H) and the size of particles in which the PHASE of the system changes without occurring a PHASE TRANSITION. It was determined that if the distance between the plates is smaller than the length of the particles, for any particle whose length (L) to diameter ratio is greater than 1, the second order PHASE TRANSITION occurs, and most of the particles are placed in a certain direction parallel to the plates, which this type of PHASE TRANSITION takes place at lower densities with increasing particle’s aspect ratio. We also came to the conclusion that if the distance between the plates is greater than and , despite the PHASE change of the system with increasing particle density, no PHASE TRANSITION will occur. In addition, it was found that the cylindrical shaped particles show some unexpected behaviors, which could be due to the inappropriate performance of the applied theory or their real physical behavior, which requires more detailed studies to resolve the ambiguity.

In this paper, we consider a spin chain with cluster interaction which is under the transverse magnetic field. We also study its dynamical behavior as the magnetic field changes suddenly. This system has an exact solution by means of Jordan-Wigner transformations. We show that if the magnetic field changes in such a way that its initial and finial value are in two different equilibrium PHASEs, then the rate function of return probability diverges periodically in time. In case this divergence is in time, it is called dynamical PHASE TRANSITION. If the quench has been done within the same PHASE, dynamical PHASE TRANSITION will not occur. Furthermore, we have shown that Fisher zero lines cross the imaginary axes when the dynamical PHASE TRANSITION occurs.

Sleep is an essential process to maintain and improve human activities, while many details related to sleep are still not well understood. Decreased or fragmented sleep is a health risk that might result in heart disease or diabetes on one hand and degradation of consciousness and cognition on the other hand. Sleep fragmentation is a phenomenon in which an individual's sleep is intermittently disrupted by arousal caused by external factors (noise) or internal factors (apnea) although sleep deprivation does not completely occur. Computational modeling is a suitable framework for understanding complex biological mechanisms. In this paper, the fundamental phenomena underlying the sleep-wake TRANSITION was reviewed and simulated. The dynamical behavior of model was then investigated and afterwards the factors that might cause obstructive sleep apnea were implemented and evaluated. The model includes two main neuronal populations: the ascending arousal system in the brain stem that is responsible for awakening and a neuronal population in the hypothalamus, called VLPO, which mediates sleep. These populations have mutual inhibition on each other causing a fl ip-fl op or switching behavior between sleep and wake. The results of modeling in this paper showed hysteresis in the sleep-wake cycle, the size of which is affected by factors causing arousal. In OSA, intermittent and unstable TRANSITIONs as well as the shrinking of bistable zone is expected. The model could reproduce some experimental results related to obstructive apneas.

In this article, we have employed GSAS software to do Reitveld profile refinement on XRD patterns from H-Tc superconductor powder YBa2-xKxCu3O7-y (0<x,y<1) samples. Increasing the Potassium doping content of the sample, x, causes some changes in the XRD patterns such as creating new peaks and also deteriorating of goodness of the refinement, c2. On the other hand, substituting of K instead of Ba led to oxygen depletion and also lowering the Ba (K) plane position along the Z direction (||c). The STRUCTURAL PHASE ratio of tetragonal to orthorhombic increased and it means that the superconductivity exist even in samples with dominant tetragonal PHASE.

STRUCTURAL, electronic, mechanical and optical properties of half-Heusler alloy TiPdSn were investigated from first-principles calculation as well as the STRUCTURAL PHASE TRANSITION under pressure. The projected augmented wave (PAW) type of pseudopotential within the generalized gradient approximation (GGA) was used during the calculation. The obtained results revealed that TiPdSn is a semiconductor with an indirect band gap. Also the results from the mechanical property showed that TiPdSn is ductile and mechanically stable. TiPdSn is seen to undergo STRUCTURAL PHASE TRANSITION from cubic to two different structures namely type1 and type2 which crystallize in hexagonal structure and the TRANSITION pressures recorded were 4.53GPa for type 1 and 25.3 GPa for type 2. Optical properties revealed that TiPdSn has a static dielectric function of 21.47 and a refractive index of 4.63. The band gap of the alloy decreases and later increases as pressure increases.

In this paper, we have studied the PHASE TRANSITION of nucleons, between a paired PHASE and a Fermi gas state, in 89Y and 208Pb nuclei. In order to conduct this study, the nuclear level density parameters of 89Y and 208Pb nuclei in the constant temperature model were extracted by the using of experimental data from Oslo group. The extracted results were used in the calculation of the cross sections of 208Pb (n, el), 208Pb(p, el), 89Y(n, el) and 89Y(p, el) nuclear reactions. According to the good agreement between the extracted results and corresponding experimental values for the cross sections, a constant temperature behavior, which can be interpreted as an evidence for the pairing PHASE TRANSITION, is confirmed for the nuclei. In addition, heat capacity of 89Y and 208Pb nuclei has been extracted from the experimental level densities and the effect of pairing PHASE TRANSITION of nucleons is studied within this thermodynamic quantity.