Stress in physical education teachers in Qatar

Stress is an area of interest among researchers and practitioners in many fields – including teaching. Much of the research on causes of stress for teachers has focused on teachers in general; only a few studies have focused on physical education teachers. Although there have been a few studies of causes of stress for physical education teachers in the Middle East, no studies have been conducted on physical education teachers in Qatar. Thus, the purpose of this study was to identify causes of stress for physical education teachers in Qatar at the beginning and end of the school year as well as any changes over the course of the year. A second purpose was to try to explain any differences in causes of stress according to: gender; nationality; type of school; and amount of experience. Results showed that there were different causes of stress for different groups of teachers which could be related to different backgrounds and experiences and different roles and responsibilities in society as a result of different cultural and social expectations and environmental factors

Evolution of the vorticity-area density during the formation of coherent structures in two-dimensional flows

It is shown: 1) that in two-dimensional, incompressible, viscous flows the vorticity-area distribution evolves according to an advection-diffusion equation with a negative, time dependent diffusion coefficient and 2) how to use the vorticity-streamfunction relations, i.e., the so-called scatter-plots, of the quasi-stationary coherent structures in order to quantify the experimentally observed changes of the vorticity distribution moments leading to the formation of these structures.Comment: LaTeX, 15 pp., 2 eps figures. Some sections have been rewritten; referees' Comments have been include

Energy dependence of non-local potentials

Recently a variety of studies have shown the importance of including non-locality in the description of reactions. The goal of this work is to revisit the phenomenological approach to determining non-local optical potentials from elastic scattering. We perform a $\chi^2$ analysis of neutron elastic scattering data off $^{40}$Ca, $^{90}$Zr and $^{208}$Pb at energies $E \approx 5-40$ MeV, assuming a Perey and Buck or Tian, Pang, and Ma non-local form for the optical potential. We introduce energy and asymmetry dependencies in the imaginary part of the potential and refit the data to obtain a global parameterization. Independently of the starting point in the minimization procedure, an energy dependence in the imaginary depth is required for a good description of the data across the included energy range. We present two parameterizations, both of which represent an improvement over the original potentials for the fitted nuclei as well as for other nuclei not included in our fit. Our results show that, even when including the standard Gaussian non-locality in optical potentials, a significant energy dependence is required to describe elastic-scattering data.Comment: 6 pages, 3 figures, accepted by Phys. Rev. C Rapid Communicatio

Switching dynamics between metastable ordered magnetic state and nonmagnetic ground state - A possible mechanism for photoinduced ferromagnetism -

By studying the dynamics of the metastable magnetization of a statistical mechanical model we propose a switching mechanism of photoinduced magnetization. The equilibrium and nonequilibrium properties of the Blume-Capel (BC) model, which is a typical model exhibiting metastability, are studied by mean field theory and Monte Carlo simulation. We demonstrate reversible changes of magnetization in a sequence of changes of system parameters, which would model the reversible photoinduced magnetization. Implications of the calculated results are discussed in relation to the recent experimental results for prussian blue analogs.Comment: 12 pages, 13 figure

Data to support study of Iron(II) Complexes of 2,4-Dipyrazolyl-1,3,5-Triazine Derivatives ‒ the Influence of Ligand Geometry on Metal Ion Spin State

Seven derivatives of [FeL2]2+ (L = 2,4-di{pyrazol-1-yl}-1,3,5-triazine) are all high-spin. DFT calculations imply this can be attributed to the geometry of the L ligand

Coulomb corrected eikonal description of the breakup of halo nuclei

The eikonal description of breakup reactions diverges because of the Coulomb interaction between the projectile and the target. This divergence is due to the adiabatic, or sudden, approximation usually made, which is incompatible with the infinite range of the Coulomb interaction. A correction for this divergence is analysed by comparison with the Dynamical Eikonal Approximation, which is derived without the adiabatic approximation. The correction consists in replacing the first-order term of the eikonal Coulomb phase by the first-order of the perturbation theory. This allows taking into account both nuclear and Coulomb interactions on the same footing within the computationally efficient eikonal model. Excellent results are found for the dissociation of 11Be on lead at 69 MeV/nucleon. This Coulomb Corrected Eikonal approximation provides a competitive alternative to more elaborate reaction models for investigating breakup of three-body projectiles at intermediate and high energies.Comment: 19 pages, 9 figures, accepted for publication in Phys. Rev.

Global persistence exponent of the two-dimensional Blume-Capel model

The global persistence exponent $\theta_g$ is calculated for the two-dimensional Blume-Capel model following a quench to the critical point from both disordered states and such with small initial magnetizations. Estimates are obtained for the nonequilibrium critical dynamics on the critical line and at the tricritical point. Ising-like universality is observed along the critical line and a different value $\theta_g =1.080(4)$ is found at the tricritical point.Comment: 7 pages with 3 figure

Spin Chains as Perfect Quantum State Mirrors

Quantum information transfer is an important part of quantum information processing. Several proposals for quantum information transfer along linear arrays of nearest-neighbor coupled qubits or spins were made recently. Perfect transfer was shown to exist in two models with specifically designed strongly inhomogeneous couplings. We show that perfect transfer occurs in an entire class of chains, including systems whose nearest-neighbor couplings vary only weakly along the chain. The key to these observations is the Jordan-Wigner mapping of spins to noninteracting lattice fermions which display perfectly periodic dynamics if the single-particle energy spectrum is appropriate. After a half-period of that dynamics any state is transformed into its mirror image with respect to the center of the chain. The absence of fermion interactions preserves these features at arbitrary temperature and allows for the transfer of nontrivially entangled states of several spins or qubits.Comment: Abstract extended, introduction shortened, some clarifications in the text, one new reference. Accepted by Phys. Rev. A (Rapid Communications

Investigation of the long effective conjugation length in defect-free insulated molecular wires

Due to the “insulation” of the π-conjugated backbones, insulated molecular wires (IMWs) are expected to be applied to various optoelectronic applications and nanotechnology.[1] Recently, Kazunori et al have succeeded in the synthesis of a self-threading polythiophene with a polyrotaxane-like 3D architecture (PSTB, see Figure 1), for which an intrawire hole mobility of 0.9 cm2 V−1 s−1 has been measured.[2] Here, we aim to evaluate the extent of π-conjugation along polythiophene backbones sheathed within defect-free “insulating” layers. A comparison between the experimental Raman spectra of the self-threading oligomers (i.e. 2STB-5STB) and the corresponding PSTB polymer indicates that: (i) the ratio of relative intensities of the two most intense Raman bands (I1375/1445) increases with the elongation of the size chain but does not saturate up to the pentamer, and (ii) π-conjugation spreads over 17–18 thiophene units in the polymer. Whether the effective conjugation length of the polymer is better described by using the long oligomer extrapolation approach[3] or periodic DFT calculations of the polymer is discussed in detailed by exploiting the very recent potentialities of state-of-the-art quantum chemical simulations of vibrational properties for crystalline solids.[Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Extended gaussian ensemble solution and tricritical points of a system with long-range interactions

The gaussian ensemble and its extended version theoretically play the important role of interpolating ensembles between the microcanonical and the canonical ensembles. Here, the thermodynamic properties yielded by the extended gaussian ensemble (EGE) for the Blume-Capel (BC) model with infinite-range interactions are analyzed. This model presents different predictions for the first-order phase transition line according to the microcanonical and canonical ensembles. From the EGE approach, we explicitly work out the analytical microcanonical solution. Moreover, the general EGE solution allows one to illustrate in details how the stable microcanonical states are continuously recovered as the gaussian parameter $\gamma$ is increased. We found out that it is not necessary to take the theoretically expected limit $\gamma \to \infty$ to recover the microcanonical states in the region between the canonical and microcanonical tricritical points of the phase diagram. By analyzing the entropy as a function of the magnetization we realize the existence of unaccessible magnetic states as the energy is lowered, leading to a treaking of ergodicity.Comment: 8 pages, 5 eps figures. Title modified, sections rewritten, tricritical point calculations added. To appear in EPJ