Parameter study of in-situ grown superconducting YBaCuO thin films prepared by laser ablation

A parameter study has been made of YBaCuO thin films prepared by laser oblation. The films were deposited on SrTiO3, MgO, and Si with ZrO2 buffer layer at substrate temperatures between 600°C – 800°C. With optimization of different parameters like substrate temperature, pulse frequency, target-substrate distance, and oxygen pressure, zero resistivity was derived for the in-situ grown films on SrTiO3 at 89.5 K, on MgO at 84.6 K, and on Si (ZrO2) at 83.5 K

Admixtures to d-wave gap symmetry in untwinned YBa2Cu3O7 superconducting films measured by angle-resolved electron tunneling

We report on an \textit{ab}-anisotropy of $J_{c \parallel b}/J_{c \parallel a}$ and $I_{c}R_{n \parallel b}/I_{c}R_{n \parallel a}\cong 1.2$ in ramp-edge junctions between untwinned YBa$_{2}$Cu$_{3}$O$_{7}$ and $s$% -wave Nb. For these junctions, the angle $\theta$ with the YBa$_{2}$Cu$_{3}$O$_{7}$ crystal b-axis is varied as a single parameter. The $R_{n}$A($\theta$)-dependence presents 2-fold symmetry. The minima in $I_{c}R_{n}$ at $\theta \cong 50^{\circ}$ suggest a real s-wave subdominant component and negligible $d_{xy}$-wave or imaginary s-wave admixtures. The $I_{c}R_{n}$($\theta$)-dependence is well-fitted by 83% $d_{x^{2}-y^{2}}$-, 15% isotropic $s$- and 2% anisotropic s-wave order parameter symmetry, consistent with $\Delta_{b}/\Delta_{a} \cong 1.5$.Comment: 4 pages, 3 figures, to be published in Physical Review Letter

Hysteresis phenomenon in deterministic traffic flows

We study phase transitions of a system of particles on the one-dimensional integer lattice moving with constant acceleration, with a collision law respecting slower particles. This simple deterministic ``particle-hopping'' traffic flow model being a straightforward generalization to the well known Nagel-Schreckenberg model covers also a more recent slow-to-start model as a special case. The model has two distinct ergodic (unmixed) phases with two critical values. When traffic density is below the lowest critical value, the steady state of the model corresponds to the ``free-flowing'' (or ``gaseous'') phase. When the density exceeds the second critical value the model produces large, persistent, well-defined traffic jams, which correspond to the ``jammed'' (or ``liquid'') phase. Between the two critical values each of these phases may take place, which can be interpreted as an ``overcooled gas'' phase when a small perturbation can change drastically gas into liquid. Mathematical analysis is accomplished in part by the exact derivation of the life-time of individual traffic jams for a given configuration of particles.Comment: 22 pages, 6 figures, corrected and improved version, to appear in the Journal of Statistical Physic

Is charisma hyper-romanticism? Empirical evidence from new data and a meta-analysis

In prior research, mixed results were obtained with respect to the relationship between Romance of Leadership and the perception of transformational leadership. In this paper, we first present new studies originating from different contexts (students and employees) and different countries and, second, we meta-analyse these studies together with prior studies in order to shed light on the relationship between Romance of Leadership and the perception of transformational leadership. In the meta-analysis, we considered the following moderators: field/employees vs. experimental/student samples, geographical region, and type of assessment of transformational leadership. The results indicate a positive relationship between Romance of Leadership and the perception of transformational leadership. Only the moderating effect of region of origin was significant. In line with social constructivism and information processing approaches of leadership, our results indicate that the perception of leadership comprises more than merely the actual behaviour the leader exhibits. Des résultats contradictoires ont été obtenus dans le passé en ce qui concerne la relation entre la Romance du Leadership et la perception du leadership transformationnel. Dans cet article, nous présentons d’abord de nouvelles recherches portant sur des populations différentes (des étudiants ou des salariés) provenant de plusieurs pays, puis dans un second temps nous effectuons une méta-analyse regroupant ces travaux et des études antérieures afin d’y voir plus clair dans la relation entre la Romance du Leadership et la perception du leadership transformationnel. On a, dans la méta-analyse, pris en considération les variables régulatrices suivantes: l’origine géographique des échantillons d’étudiants (travaux expérimentaux) ou de salariés (enquêtes sur le terrain) et le type d’évaluation du leadership transformationnel. Les résultats vont dans le sens d’une relation positive entre la Romance du Leadership et la perception du leadership transformationnel. Il n’y a que la région d’origine qui présente un effet régulateur significatif. Dans la continuité du constructivisme social et des travaux concevant le leadership comme un traitement de l’information, nos résultats indiquent que la perception du leadership dépasse le comportement observable du leader

Precision measurement of the half-life and the decay branches of 62Ga

In an experiment performed at the Accelerator Laboratory of the University of Jyvaskyla, the beta-decay half-life of 62Ga has been studied with high precision using the IGISOL technique. A half-life of T1/2 = 116.09(17)ms was measured. Using beta-gamma coincidences, the gamma intensity of the 954keV transition and an upper limit of the beta-decay feeding of the 0+_2 state have been extracted. The present experimental results are compared to previous measurements and their impact on our understanding of the weak interaction is discussed.Comment: 7 pages, 7 figures, submitted to EPJ

Redistribution of fast ions during sawtooth reconnection

In a tokamak-based fusion power plant, possible scenarios may include regulated sawtooth oscillations to remove thermalized helium from the core of the plasma. During a sawtooth crash, the helium ash and other impurities trapped in the core are driven by the instability to an outer region. However, in a fusion plasma, high energy ions will represent a significant population. We thus study the behaviour of these energetic particles during a sawtooth. This paper presents the modelling of the redistribution of fast ions during a sawtooth reconnection event in a tokamak plasma. Along the lines of the model for the evolution of the flux surfaces during a sawtooth collapse described in Ya.I. Kolesnichenko and Yu.V. Yakovenko 1996 Nucl. Fusion 36 159, we have built a time-dependent electromagnetic model of a sawtooth reconnection. The trajectories of the ions are described by a complete gyro-orbit integration. The fast particles were evolved from specific initial parameters (given energy and uniform spread in pitch) or distributed initially according to a slowing-down distribution created by fusion reactions. Our modelling is used to understand the main equilibrium parameters driving the motions during the collapse and to determine the evolution of the distribution function of energetic ions when different geometries of reconnection are considered.</p

Arms Control and European Security

The following three papers comprise one of the panels from a conference on U.S.-Russia relations that SSI co-sponsored with the Carnegie Council at Pocantico, NY, from June 1-3, 2011: Carnegie Council\u27s Program on “U.S. Global Engagement: A Two-Year Retrospective.” The papers offer three contrasting looks at one of the major issues in today’s arms control agenda, namely the future of the Conventional Forces in Europe Treaty (CFE). The three papers were written by leading experts in the field from the United States, the United Kingdom, and Russia and provide a revealing glimpse into the very different assessments that are being made by those three governments and the difficult issues involved in attempting to regenerate the process that led to the original treaty in 1990. These three chapters also implicitly contribute to a better understanding of the intractabilities facing the major players in any effort to advance not only arms control but also European stability.https://press.armywarcollege.edu/monographs/1549/thumbnail.jp