The effect of the surface field on the phase diagrams of a transverse Ising thin film

Within an effective field theory (EFT), the phase diagrams of a transverse Ising thin film (TIM) has been investigated. The effects of the Ωs on the critical temperature are discussed by including the modification of surface exchange interaction. The phase diagrams are also determinated as function of the transverse field for different values of the film thickness n and for same value of ∆sWithin an effective field theory (EFT), the phase diagrams of a transverse Ising thin film (TIM) has been investigated. The effects of the Ωs on the critical temperature are discussed by including the modification of surface exchange interaction. The phase diagrams are also determinated as function of the transverse field for different values of the film thickness n and for same value of ∆

Growth of homopolymer chain

Thermodynamic and kinetic properties of an homopolymer chain, in two dimensional square lattice, are studied by the use of chain growth algorithm based on the self avoiding walks process. Which is in accord with what happen in nature. All monomers are considered to be hydrophobic. In the thermodynamical study we examine the critical behaviour of the chain by following the evolution of the chain geometry with temperature. This is done by studying the behaviour of the mean distance R chosen to describe the homopolymer structure. Moreover, we give the behaviour of thermodynamic quantities such as conformational energy and specific heat. The effect of a force applied, in a fixed direction, on the chain when it is growing is also investigated. Finally, in a kinetic study, we analyse the evolution with temperature of the mean time necessarily for a given conformation to reach its native state.Thermodynamic and kinetic properties of an homopolymer chain, in two dimensional square lattice, are studied by the use of chain growth algorithm based on the self avoiding walks process. Which is in accord with what happen in nature. All monomers are considered to be hydrophobic. In the thermodynamical study we examine the critical behaviour of the chain by following the evolution of the chain geometry with temperature. This is done by studying the behaviour of the mean distance R chosen to describe the homopolymer structure. Moreover, we give the behaviour of thermodynamic quantities such as conformational energy and specific heat. The effect of a force applied, in a fixed direction, on the chain when it is growing is also investigated. Finally, in a kinetic study, we analyse the evolution with temperature of the mean time necessarily for a given conformation to reach its native state

Ising-Like Model For Ferroelectric Phase Transitions In Tetragonal Tungsten Bronze Compounds

The two-component anisotropic Ising-like model was proposed to model the ferroelectric phase transitions in Tetragonal Tungsten Bronze (TTB) compounds. Using the mean-field approach we reconstructed the phase diagram of the TTB system and showed that depending on he relative strength of the interaction parameters there ferroelectric states are possible: (i) the state with y-directed polarization that corresponds to the tetragonal ferroelectric phase in TTB compounds, (ii) the state with x-directed polarization that corresponds to the orthorhombic TTB phase and (iii)  the state with superposition of x- and y- polarization components that can correspond to the not yet discovered mixed phase.The two-component anisotropic Ising-like model was proposed to model the ferroelectric phase transitions in Tetragonal Tungsten Bronze (TTB) compounds. Using the mean-field approach we reconstructed the phase diagram of the TTB system and showed that depending on he relative strength of the interaction parameters there ferroelectric states are possible: (i) the state with y-directed polarization that corresponds to the tetragonal ferroelectric phase in TTB compounds, (ii) the state with x-directed polarization that corresponds to the orthorhombic TTB phase and (iii)  the state with superposition of x- and y- polarization components that can correspond to the not yet discovered mixed phase

Mean field theory and Monte Carlo simulation of Phase transitions and Magnetic Properties of a tridimensional Fe7S8 Compound

The structural, electronic and magnetic properties of Fe7S8 material have been studied within the framework of the ab-initio calculations, the mean field approximation (MFA) and Monte Carlo simulation (MCS). Our study shows that two forms of the iron atoms, Fe2+ with spin S=2, and Fe3+ with spin {\sigma}=5/2 are the most probable configurations. A mixed Ising model with ferromagnetic spin coupling between Fe2+ and Fe3+ ions and between Fe3+ and Fe3+ ions, and with antiferromagnetic spin coupling between Fe2+ ions of adjacent layers has been used to study the magnetic properties of this compound. We demonstrated that the magnetic phase transition can be either of the first or of the second order, depending on the value of the exchange interaction and crystal field. The presence of vacancies in every second iron layer leads to incomplete cancellation of magnetic moments, hence to the emergence of the ferrimagnetism. Anomalies in the magnetization behavior have been found and compared with the experimental results.Comment: 18 pages, 14 Figures, 4 Table

Elaboration and characterization by XRD and SEM of the glass-ceramics in BaTiO3 – NaPO3 system

There is a strong need for low cost glass-ceramic materials whose high chemical stability and dielectric properties can be engineered flexibly in bulk and fiber forms. Therefore we have manufactured transparent ferroelectric glass-ceramics consisting of barium titanate (BT) crystallites in a chain metaphosphate glass matrix. Several glass compositions, in the series (1-x) NaPO3 – x BaTiO3 have been prepared by a conventional melt quenching method. The compositions have been selected on the basis of chemical stability. X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicate the formation of small particle size of BaTiO3 in the glass network when its amount is above 4 mol%.There is a strong need for low cost glass-ceramic materials whose high chemical stability and dielectric properties can be engineered flexibly in bulk and fiber forms. Therefore we have manufactured transparent ferroelectric glass-ceramics consisting of barium titanate (BT) crystallites in a chain metaphosphate glass matrix. Several glass compositions, in the series (1-x) NaPO3 – x BaTiO3 have been prepared by a conventional melt quenching method. The compositions have been selected on the basis of chemical stability. X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicate the formation of small particle size of BaTiO3 in the glass network when its amount is above 4 mol%

Characterization of the Drosophila Ortholog of the Human Usher Syndrome Type 1G Protein Sans

BACKGROUND: The Usher syndrome (USH) is the most frequent deaf-blindness hereditary disease in humans. Deafness is attributed to the disorganization of stereocilia in the inner ear. USH1, the most severe subtype, is associated with mutations in genes encoding myosin VIIa, harmonin, cadherin 23, protocadherin 15, and sans. Myosin VIIa, harmonin, cadherin 23, and protocadherin 15 physically interact in vitro and localize to stereocilia tips in vivo, indicating that they form functional complexes. Sans, in contrast, localizes to vesicle-like structures beneath the apical membrane of stereocilia-displaying hair cells. How mutations in sans result in deafness and blindness is not well understood. Orthologs of myosin VIIa and protocadherin 15 have been identified in Drosophila melanogaster and their genetic analysis has identified essential roles in auditory perception and microvilli morphogenesis, respectively. PRINCIPAL FINDINGS: Here, we have identified and characterized the Drosophila ortholog of human sans. Drosophila Sans is expressed in tubular organs of the embryo, in lens-secreting cone cells of the adult eye, and in microvilli-displaying follicle cells during oogenesis. Sans mutants are viable, fertile, and mutant follicle cells appear to form microvilli, indicating that Sans is dispensable for fly development and microvilli morphogenesis in the follicle epithelium. In follicle cells, Sans protein localizes, similar to its vertebrate ortholog, to intracellular punctate structures, which we have identified as early endosomes associated with the syntaxin Avalanche. CONCLUSIONS: Our work is consistent with an evolutionary conserved function of Sans in vesicle trafficking. Furthermore it provides a significant basis for further understanding of the role of this Usher syndrome ortholog in development and disease