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Many stormy events in astrophysics occur due to the sudden magnetic energy release. This is possible if a magnetic configuration abruptly changes its topology, an event usually referred to as magnetic reconnection. It is known that pure Ohmic decay is inefficient, occurring during cosmological times (due to the huge characteristic scales $L$). It is recognized that the presence of current sheets speeds up the process, but still insufficiently$^{1,2,3,4,5}$. We show that, in highly compressible and substantially gravitational media, the reconnection is fast enough to account for stormy events. Thus, highly compressible situations offer exiting opportunities in explanations of violent events, although full-scale compressible and gravitational simulations proved to be quite challenging., Comment: 10 pages, 4 figures

This paper performs a comprehensive investigation of dynamic selection for long atomic traces. It introduces a classification of trace selection methods and discusses existing and novel dynamic selection approaches - including loop unrolling, procedure in-lining and incremental merging of traces based on dynamic bias. The paper empirically analyzes a number of selection schemes in an idealized framework. Observations based on the SPEC-CPU2000 benchmarks show that: (a) selection based on dynamic bias is necessary to achieve the best performance across all benchmarks, (b) the best selection scheme is benchmark and maximum trace-length specific, (c) simple selection, based on program structure information only, is sufficient to achieve the best performance for several benchmarks. Consequently, two alternatives for the trace selection mechanism are established: (a) a "best performance" approach relying on complex dynamic criteria (b) a "value" approach that provides the best performance (and potentially the best power consumption) based on simpler static criteria. Another emerging alternative advocates adaptive based mechanisms to adjust selection criteria. 2 11 Sponsors: ACM/SIGARCH Intel Corporation Florida State University Conference code: 62275 Cited By :6

The study of X-ray emission of stellar clusters, allows to decouple the influence of some individual stellar parameters, as initial conditions, composition and age, on the stellar X-ray luminosity function.

Exergaming can be effective to improve physical and cognitive functions, motor-cognitive per-formances, and psychological outcomes in older persons with or without cognitive impairment. However, little is known about the training volume required to achieve positive effects. The aim of this study was to evaluate the time course of improvements in motor-cognitive game performances during an exergame intervention in Persons with Dementia (PwD). Fifty-six PwD (mean age = 82.7 ± 6.2, MMSE = 22.2 ± 2.8) took part in a 10-week task-specific training program (2/week = 20 sessions) on an interactive, exergame-based balance training system (Physiomat®), combining postural control tasks with cognitive tasks of an established neuropsychological test (modified Trail-Making-Test). Physiomat® performance was assessed at baseline (T1), after training session 7 (TS7) and 14 (TS14), and at post-intervention after 20 training sessions (T2) as the time required to complete different Physiomat®-Trail-Making-Tasks (PTMT). Significant improvements with large effect sizes in all PTMT were observed from T1 to TS7 (p ≤ 0.001–0.003; Cohen’s d = 0.80–1.40 for effect sizes). Physiomat® performance in most PTMT did not significantly improve from TS7 to TS14, nor from TS14 to T2. Across all PTMT, significant improvements with moderate-to-large effect sizes (p ≤ 0.001–0.036; Cohen’s d = 0.43–1.07) were found from TS7 to T2. Results suggest that large task-specific improvements in complex motor-cognitive performances can be achieved in PwD within a surprisingly short exergame intervention. For further increase of the performance level, a higher training volume may to be necessary to fully exploit rehabilitation potential in this vulnerable population.

We look at the spreading of localized temperature perturbations in the accreted fuel layer of a non-rotating neutron star. The pressure at the base of the accreted fuel layer is large and the material is only partially degenerate. Any temperature perturbations and resulting pressure gradients will lead to enormous accelerations (both laterally and vertically) of the material in the fuel layer. If the burning of this fuel cannot proceed more rapidly than the spreading of this perturbation, then localized burning cannot take place, and it is likely that the ignition would have to proceed simultaneously throughout the envelope. We present some multidimensional simulations of the spreading of temperature perturbations in a helium atmosphere on a neutron star., Comment: 7 pages, to appear in the Proceedings of the 3D Stellar Evolution Workshop, Livermore, CA, July 2002

Recently X-ray emission from protostellar jets has been detected with both XMM-Newton and Chandra satellites, but the physical mechanism which can give rise to this emission is still unclear. We performed an extensive exploration of a wide space of the main parameters influencing the jet/ambient interaction. Aims include: 1) to constrain the jet/ambient interaction regimes leading to the X-ray emission observed in Herbig-Haro objects in terms of the emission by a shock forming at the interaction front between a continuous supersonic jet and the surrounding medium; 2) to derive detailed predictions to be compared with optical and X-ray observations of protostellar jets; 3) to get insight into the protostellar jet's physical conditions. We performed a set of bidimensional hydrodynamic numerical simulations, in cylindrical coordinates, modeling supersonic jets ramming a uniform ambient medium. The model takes into account the most relevant physical effects, namely the thermal conduction and the radiative losses. Our model explains the observed X-ray emission from protostellar jets in a natural way. In particular we find that the case of a protostellar jet less dense than the ambient medium reproduces well the observations of the nearest Herbig-Haro object, HH154, and allows us to make detailed predictions of a possible X-ray source proper motion (vsh = 500 km/s), detectable with Chandra. Furthermore our results suggest that the simulated protostellar jets which best reproduce the X-rays observations cannot drive molecular outflows., 13 pages, 10 figures, accepted for publication in Astronomy and Astrophysics

Zusammenfassung. Bislang wurden in der Psychotherapieforschung vornehmlich Therapieergebnisse und nicht Therapieverläufe untersucht. Dies hat neben inhaltlichen auch methodische Gründe, da die in der Psychotherapieforschung üblicherweise kurzen Zeitreihen statistisch aufwendiger handzuhaben sind. In dieser Studie wurden die BDI-Verläufe von 63 unipolar depressiven Patienten mithilfe Hierarchischer Linearer Modelle (HLM) untersucht. Die Patienten hatten randomisiert an einer von drei ambulant durchgeführten Psychotherapieformen (Kognitive Verhaltenstherapie, Gestalttherapie und unterstützende selbstadministrierte Bibliotherapie) mit je zwanzig wöchentlichen Sitzungen teilgenommen. Neben dem Einfluß der Therapieform auf den Verlauf wurden auch differentielle Effekte nach Geschlecht und Schweregrad untersucht. Schwer depressive Patienten zeigten eine schnellere Verbesserung als weniger depressive Patienten. Während über alle Patienten hinweg kein globaler Vorteil für eine der Therapieformen sicherbar war, zeigte sich bei den schwer depressiven Patienten ein günstigerer Verlauf unter Verhaltenstherapie im Vergleich zur Gestalttherapie, sowie unter Gestalttherapie im Vergleich zur selbstdirektiven Therapie.

AIMS. We study and discuss the time-dependent X-ray emission predicted by hydrodynamic modeling of the interaction of a SNR shock wave with an interstellar gas cloud. The scope includes: 1) to study the correspondence between modeled and X-ray emitting structures, 2) to explore two different physical regimes in which either thermal conduction or radiative cooling plays a dominant role, and 3) to investigate the effects of the physical processes at work on the emission of the shocked cloud in the two different regimes. METHODS. We use a detailed hydrodynamic model, including thermal conduction and radiation, and explore two cases characterized by different Mach numbers of the primary shock: M = 30 in which the cloud dynamics is dominated by radiative cooling and M = 50 dominated by thermal conduction. From the simulations, we synthesize the expected X-ray emission, using available spectral codes. RESULTS. The morphology of the X-ray emitting structures is significantly different from that of the flow structures originating from the shock-cloud interaction. The hydrodynamic instabilities are never clearly visible in the X-ray band. Shocked clouds are preferentially visible during the early phases of their evolution. Thermal conduction and radiative cooling lead to two different phases of the shocked cloud: a cold cooling dominated core emitting at low energies and a hot thermally conducting corona emitting in the X-ray band. The thermal conduction makes the X-ray image of the cloud smaller, more diffuse, and shorter-lived than that observed when thermal conduction is neglected., Comment: 9 pages, 8 Figures; paper accepted for publication in A&A; the paper with high-resolution figures can be downloaded at http://www.astropa.unipa.it/Library/OAPA_preprints/shock_cloud2.pdf

We model hydrodynamic interactions of an old supernova remnant shock wave with a small interstellar gas cloud, taking into account the effects of thermal conduction and radiative losses. In particular, we consider a representative case of a Mach 30 shock impacting on an isolated cloud with density contrast χ = 10 with respect to the ambient medium. Thermal conduction appears to be effective in suppressing the Kelvin-Helmholtz and Rayleigh-Taylor instabilities which would develop at the cloud boundaries. We demonstrate that the radiative losses play a crucial role in the dynamics of the shock-cloud interaction, dominating evolution of the shocked cloud medium.