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 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.

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.

The collapse of antiferromagnetic order as a function of some quantum tuning parameter such as carrier density or hydrostatic pressure is often accompanied by a region of superconductivity. The corresponding phenomenon in the potentially simpler case of itinerant-electron ferromagnetism, however, remains more illusive. In this paper we consider the reasons why this may be so and summaries evidence suggesting that the obstacles to observing the phenomenon are apparently overcome in a few metallic ferromagnets. A new twist to the problem presented by the recent discoveries in ferroelectric symmetric systems and new graphite intercalate superconductors will also be discussed.

High magneto- crystalline anisotropy AWT IMAGE of L10-FePt nanoparticles are an excellent candidate for ultra high-density magnetic recording. The 4 nm FePt nanocrystals were prepared by superhydride reduction of FeCl2.4H2O and Pt (acac) 2 precursors in the phenyl ether by reduction of the 1, 2-hexadecanediol and LiBEt3H superhydride. The crystal and magnetic structures were studied by XRD and VSM analysis. By TEM and EDS analyses the size distribution and molar concentration of Fe/Pt of the nanoparticles were determined. The results showed that the particles are first superparamagnetic before heat treatment and then a PHASE TRANSITION accrue from disorder fcc to order fct structure after annealing. Finally, the PHASE TRANSITION leads the magnetic anisotropy of hard FePt nanoparticles to increase to 7 kOe.

In this letter, we consider static black hole in f(R) gravity. We take advan-tage from corrected entropy and temperature and investigate such black hole. Finally, we study the P 􀀀 V critically and PHASE TRANSITION of corrected black hole with respect to entropy and temperature. Here also, we obtain the heat capacity for the static black hole in f(R) gravity. This calculation helps us to investigate some singularity. We have shown that the corrections exist for any black hole, but they are important for a small black holes and negligible for the large black holes. The advantage of a static black hole in f(R) gravity is its holographic picture, which is a van der Waals uid. Then, We have shown that in the presence of corrections there is still a van der Waals uid as a dual picture. The critical values of event horizon radius for PHASE TRANSITIONs are shown due to the corrections of entropy and temperature. We have some  gures which show the PHASE TRANSITION and P 􀀀 V critically.

The melting of zigzag, armchair and chiral single walled boron nitride nanotubes (SWBNs) investigated using molecular dynamics (MD) simulation based on Tersoff-like many body potential. The MD simulation has been employed in the constant pressure, constant temperature (NPT) ensemble. The temperature and pressure of the system were controlled by Nose-Hoover thermostat and Berendsen barostat, respectively. We have computed the variation of the melting temperature with the radius of BN nanotube. The results show that the melting temperature of nanotubes increase with increasing in the size of radii, but this dependence is not the same for the various chiral angle of nanotubes. The relation of the melting point with radius for three types of nanotubes i. e. zigzag, armchair and chiral obtained. Moreover, our results show that the melting temperature of nanotubes approach a constant value at larger radii.

In this research, the magnetic PHASE TRANSITION and anisotropic magnetoelastic effects of a polycrystalline sample of Ndl4Dy2Fe78sB6 were studied by susceptibility and magnetostriction measurements. The composition was prepared by casting method. SEM pictures and XRD analysis showed that it was composed of polycrystalline magnetic PHASEs with the main PHASE of 2-14-1.Results of ac susceptibility measurements show that the sample undergoes a magnetic PHASE TRANSITION at about 130 K, which is due to a gradual spin reorientation accompanied with crystal structure distortion. Magnetostriction measurements in three orthogonal directions of the main body of the sample were performed in the range of 77 K to 300 K and if the field up to 1.5 T. At temperatures below 125 K, the magnetostriction values in three orthogonal directions differ by a factor of two to three. This anisotropy in magnetostriction indicates preferential orientation of the crystalline grains in the volume of the sample. In addition, magnetostriction curves show minimum values near the PHASE TRANSITION temperature with different values in the different directions. Minimum values of magnetostriction can be explained by the critical behavior of the orbital magnetic moments of the Fe atoms at the PHASE TRANSITION temperature.

Clinoptiloite transforms to analcime under hydrothermal condition in presence of alkaline fluids. The effect of Na+ and K+ concentrations, temperature and run duration are being considered as the variable parameters in the present study. Alkaline solutions were used in concentration of 1.25 up to 7.5mol/lit under temperatures of 100 and 150˚C. Results of this study show that analcime is synthesized at 150ºC and high concentration of Na+. With increasing Na+ content of the fluids and reaction time, the amount of analcime increases drastically.  Powder X-ray diffraction study has revealed an orthorhombic symmetry with the unit-cell parameter of a: 13.731 Å, b: 13.726 Å, c: 13.769 Å.

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.