Diffractive dissociation into KsK±π∓π−K_sK^{\pm}\pi^{\mp}\pi^{-} final states

The COMPASS fixed-target experiment at CERN/SPS is dedicated to the study of hadron structure and spectroscopy, especially the search for spin-exotic states. After having started to study the existence of the spin-exotic $\pi_1(1600)$ resonance in the 2004 pilot-run data, the new 2008/09 data will enable us to further clarify the situation. Apart from the $\pi_1(1600)$ resonance, also a spin-exotic $\pi_1(2000)$ was reported in the past in the $f_1(1285)\pi$ decay channel by the E852/BNL experiment, however, this state still lacks confirmation. We present a first event selection of the diffractively produced $(K\bar{K}\pi\pi)^{-}$ system showing clean $f_1(1285)$ and $f_1(1420)$ resonances at competing statistics. A partial-wave analysis started on $f_1(1285)\pi$ and $f_1(1420)\pi$ decay channels will further complete the search for spin-exotics in the 2008/09 COMPASS data.Comment: 4 pages, 6 figures, Hadron2011 Conference Proceedings, to appear in the proceedings of the XIV International Conference on Hadron Spectroscopy: Hadron 2011, Munich, Germany, 13-17 June 201

Concurrence of dynamical phase transitions at finite temperature in the fully connected transverse-field Ising model

We construct the finite-temperature dynamical phase diagram of the fully connected transverse-field Ising model from the vantage point of two disparate concepts of dynamical criticality. An analytical derivation of the classical dynamics and exact diagonalization simulations are used to study the dynamics after a quantum quench in the system prepared in a thermal equilibrium state. The different dynamical phases characterized by the type of non-analyticities that emerge in an appropriately defined Loschmidt-echo return rate directly correspond to the dynamical phases determined by the spontaneous breaking of $\mathbb{Z}_2$ symmetry in the long-time steady state. The dynamical phase diagram is qualitatively different depending on whether the initial thermal state is ferromagnetic or paramagnetic. Whereas the former leads to a dynamical phase diagram that can be directly related to its equilibrium counterpart, the latter gives rise to a divergent dynamical critical temperature at vanishing final transverse-field strength.Comment: journal article, 15 pages, 12 figures. Final versio

Epistemic and Social Scripts in Computer-Supported Collaborative Learning

Collaborative learning in computer-supported learning environments typically means that learners work on tasks together, discussing their individual perspectives via text-based media or videoconferencing, and consequently acquire knowledge. Collaborative learning, however, is often sub-optimal with respect to how learners work on the concepts that are supposed to be learned and how learners interact with each other. Therefore, instructional support needs to be implemented into computer-supported collaborative learning environments. One possibility to improve collaborative learning environments is to conceptualize scripts that structure epistemic activities and social interactions of learners. In this contribution, two studies will be reported that investigated the effects of epistemic and social scripts in a text-based computer-supported learning environment and in a videoconferencing learning environment in order to foster the individual acquisition of knowledge. In each study the factors "epistemic script" and "social script" have been independently varied in a 2×2-factorial design. 182 university students of Educational Science participated in these two studies. Results of both studies show that social scripts can be substantially beneficial with respect to the individual acquisition of knowledge, whereas epistemic scripts apparently do not lead to the expected effects.Unter kooperativem Lernen in computerunterstützten Lernumgebungen versteht man typischerweise, dass Lernende Wissen erwerben indem sie gemeinsam Aufgaben bearbeiten und dabei ihre individuellen Perspektiven mittels textbasierter Medien oder in Videokonferenzen diskutieren. Kooperatives Lernen scheint aber häufig suboptimal zu sein in Bezug auf die inhaltliche Bearbeitung der zu lernenden Konzepte sowie hinsichtlich der sozialen Interaktionen der Lernenden. Eine Möglichkeit kooperative Lernumgebungen zu verbessern besteht darin, Skripts zu konzeptualisieren, die epistemische Aktivitäten und soziale Interaktionen von Lernenden unterstützen. In diesem Beitrag werden zwei Studien berichtet, die die Wirkungen epistemischer und sozialer Skripts auf den individuellen Wissenserwerb in einer text- bzw. einer videobasierten computerunterstützten Lernumgebung untersuchen. In beiden Studien wurden die Faktoren "epistemisches Skript" und "soziales Skript" unabhängig voneinander in einem 2×2-faktoriellen Design miteinander variiert. 182 Studierende der Pädagogik der LMU München nahmen an diesen beiden Studien teil. Die Ergebnisse beider Studien deuten darauf hin, dass soziale Skripts individuellen Wissenserwerb substanziell fördern können, während epistemische Skripts scheinbar nicht zu den erwarteten Ergebnissen führen

Chromospherically active stars in the ROTSE-1 database: paper 6. Variables 126 - 149

Another 24 new chromospherically active stars are presented, which were found in the ROTSE-1 database: GSC 02268-00394, GSC 01224-00894, GSC 00648-00579, GSC 02865-01987, GSC 01851-01202, GSC 00124-00551, GSC 00150-01109, GSC 01339-00572, GSC 02968-01511, GSC 03005-00885, GSC 01083-00698, GSC 03941-00354, GSC 04450-00134, GSC 05163-01764, GSC 01095-00848, GSC 04459-00659, USNO A2.0 1275-14029063, GSC 04247-00903, GSC 01656-01276, GSC 02197-01430, GSC 02227-01294, GSC 04480-00965, GSC 01159-00245, GSC 02237-01574. For one of these stars (GSC 00124-00551), further observations were made using a TeleView 509/5.0 telescope with a CCD camera SIGMA1603 and IR-cutting filter in Velden, Germany

A Riemannian approach to strain measures in nonlinear elasticity

The isotropic Hencky strain energy appears naturally as a distance measure of the deformation gradient to the set SO(n) of rigid rotations in the canonical left-invariant Riemannian metric on the general linear group GL(n). Objectivity requires the Riemannian metric to be left-GL(n)-invariant, isotropy requires the Riemannian metric to be right-O(n)-invariant. The latter two conditions are satisfied for a three-parameter family of Riemannian metrics on the tangent space of GL(n). Surprisingly, the final result is basically independent of the chosen parameters. In deriving the result, geodesics on GL(n) have to be parametrized and a novel minimization problem, involving the matrix logarithm for non-symmetric arguments, has to be solved

Artificial environments for the co-translational stabilization of cell-free expressed proteins

An approach for designing individual expression environments that reduce or prevent protein aggregation and precipitation is described. Inefficient folding of difficult proteins in unfavorable translation environments can cause significant losses of overexpressed proteins as precipitates or inclusion bodies. A number of chemical chaperones including alcohols, polyols, polyions or polymers are known to have positive effects on protein stability. However, conventional expression approaches can use such stabilizing agents only post-translationally during protein extraction and purification. Proteins that already precipitate inside of the producer cells cannot be addressed. The open nature of cell-free protein expression systems offers the option to include single chemicals or cocktails of stabilizing compounds already into the expression environment. We report an approach for systematic screening of stabilizers in order to improve the solubility and quality of overexpressed proteins co-translationally. A comprehensive list of representative protein stabilizers from the major groups of naturally occurring chemical chaperones has been analyzed and their concentration ranges tolerated by cell-free expression systems have been determined. As a proof of concept, we have applied the method to improve the yield of proteins showing instability and partial precipitation during cell-free synthesis. Stabilizers that co-translationally improve the solubility and functional folding of human glucosamine 6-phosphate N-acetyltransferase have been identified and cumulative effects of stabilizers have been studied