Fragile-glass behavior of a short range pp-spin model

In this paper we propose a short range generalization of the $p$-spin interaction spin-glass model. The model is well suited to test the idea that an entropy collapse is at the bottom-line of the dynamical singularity encountered in structural glasses. The model is studied in three dimensions through Monte Carlo simulations, which put in evidence fragile glass behavior with stretched exponential relaxation and super-Arrhenius behavior of the relaxation time. Our data are in favor of a Vogel-Fulcher behavior of the relaxation time, related to an entropy collapse at the Kauzmann temperature. We however encounter difficulties analogous to those found in experimental systems when extrapolating thermodynamical data at low temperatures. We study the spin glass susceptibility investigating the behavior of the correlation length in the system. We find that the the increase of the relaxation time is not accompanied by any growth of the correlation length. We discuss the scaling properties of off-equilibrium dynamics in the glassy regime, finding qualitative agreement with the mean-field theory.Comment: 8 pages, LaTeX, 8 postscript figure

Transient pupils: the induction and support of Key Stage 3 late entrants .

Little UK research has been undertaken into the experiences of pupils who move between secondary schools after the normal year 7 entry date. This thesis builds on a major research study on pupil mobility in English schools undertaken by Dobson, Henthorne and Lewis (2000) which investigated its impact on school and pupil performance, and school and LEA responses to this. The purpose of the study described in this thesis was to identify the circumstances and characteristics associated with late entrants to secondary school, to investigate their experience of late entry and to see whether additional induction and support could assist them in making a successful transfer. The study investigated the experiences of Key Stage 3 late entrants to Coventry LEA schools who participated in a programme of induction and support provided by Connexions Service personal advisers. The research, which was conducted in two phases, involved myself, an LEA adviser, and Connexions personal advisers in collecting data. First, personal advisers collected data about personal background and school transfer experience from all late entrants who were referred to them by year heads for induction interviews. At the end of the same school year, I conducted in- depth interviews with nine pupils, their year heads and personal advisers; personal advisers also completed questionnaires. Data analysis revealed a multiplicity of circumstances and characteristics associated with moving schools during the secondary phase that made it an individual and sometimes isolated experience. Pupils used a variety of strategies to assist them in managing this transition and they valued the support of the Connexions personal adviser. School induction and support systems for late entrants varied in their effectiveness and appeared rarely to be consistently implemented within over-stretched pastoral and curriculum systems

Apparent slow dynamics in the ergodic phase of a driven many-body localized system without extensive conserved quantities

We numerically study the dynamics on the ergodic side of the many-body localization transition in a periodically driven Floquet model with no global conservation laws. We describe and employ a numerical technique based on the fast Walsh-Hadamard transform that allows us to perform an exact time evolution for large systems and long times. As in models with conserved quantities (e.g., energy and/or particle number) we observe a slowing down of the dynamics as the transition into the many-body localized phase is approached. More specifically, our data is consistent with a subballistic spread of entanglement and a stretched-exponential decay of an autocorrelation function, with their associated exponents reflecting slow dynamics near the transition for a fixed system size. However, with access to larger system sizes, we observe a clear flow of the exponents towards faster dynamics and can not rule out that the slow dynamics is a finite-size effect. Furthermore, we observe examples of non-monotonic dependence of the exponents with time, with dynamics initially slowing down but accelerating again at even larger times, consistent with the slow dynamics being a crossover phenomena with a localized critical point.Comment: 9 pages, 8 figures; added details on the level statistics and the energy absorptio

STUDY OF XIAO JUNFENG'S FRONT HANDSPRING TO SOMERSAULT FORWARD STRETCHED WITH 900 DEGREE TWIST BY BIOMECHANICAL ANALYSIS

It is well known that new and difficult performances occur constantly and stimulate the development of gymnastics. The focuses in performance are the connection and all kinds of somersault and twist technique. Lately, no matter whether in domestic or international competition, the front handspring to somersault with certain difficulty has been used frequently. It is worth mention that from 1993 to 1996 the international rules of gymnastics were changed, increasing the difficulty value of the front somersault. That means that the front somersault gets more points than the back somersault, even for a performance turn of the same degree. The front handspring connecting somersault forward stretched and twist performance is being concentrated on by coaches and athletics. Even some experts considered the front handspring to somersault forward stretched with twist performance as part of the future of free gymnastics. Xiao Junfeng was one of the athletes of the Chinese gymnastic team. He was the first athlete to perform the front handspring to somersault forward with a 900 degree twist. He won the title champion of the world gymnastics championships in 1997. The purpose of this study is to analyze the technique of his performance by biomechanical methods. The subject was Xiao Junfeng ( age: 17 years old, Height: 1.60 m, Weight: 50 kg). HUAHANG KS 16-mm camera and TP-301 film analysis systems and a KISTLER 3-dimensional testing force platform were use to collect the data of the front handspring to somersault forward stretched with a 900 degree twist performance

Memory effects and KWW relaxation of the interacting magnetic nano-particles

The nano-particle systems under theoretically and experimentally investigation because of the potential applications in the nano-technology such as drug delivery, ferrofluids mechanics, magnetic data storage, sensors, magnetic resonance imaging, and cancer therapy. Recently, it is reported that interacting nano-particles behave as spin-glasses and experimentally show that the relaxation of these systems obeys stretched exponential i.e., KWW relaxation. Therefore, in this study, considering the interacting nano-particle systems we model the relaxation and investigate frequency and temperature behaviour depends on slow relaxation by using a simple operator formalism. We show that relaxation deviates from Debye and obeys to KWW in the presence of the memory effects in the system. Furthermore, we obtain the frequency and temperature behaviour depend on KWW relaxation. We conclude that the obtained results are consistent with experimental results and the simple model, presented here, is very useful and pedagogical to discuss the slow relaxation of the interacting nano-particles.Comment: Accepted in Physica