Local heat flux and energy loss in a 2D vibrated granular gas

We performed event-driven simulations of a two-dimensional granular gas between two vibrating walls and directly measured the local heat flux and energy dissipation rate in the stationary state. Describing the local heat flux as a function of the coordinate x in the direction perpendicular to the driving walls, we use a generalization of Fourier's law, q_x(x) = kappa d_x T(x) + mu d_x rho(x), to relate the local heat flux to the local gradients of the temperature and density. This ansatz accounts for the fact that density gradients also generate heat flux, not only temperature gradients. The transport coefficients kappa and mu are assumed to be independent of x, and we check the validity of this assumption in the simulations. Both kappa and mu are determined for different system parameters, in particular, for a wide range of coefficients of restitution. We also compare our numerical results to existing hydrodynamic theories. Agreement is found for kappa for very small inelasticities only. Beyond this region, kappa and mu exhibit a striking non-monotonic behavior.Comment: 8 pages, 5 figure

Indirect observation of unobservable interstellar molecules

It is suggested that the abundances of neutral non-polar interstellar molecules unobservable by radio astronomy can be systematically determined by radio observation of the protonated ions. As an example, observed N2H(+) column densities are analyzed to infer molecular nitrogen abundances in dense interstellar clouds. The chemistries and expected densities of the protonated ions of O2, C2, CO2, C2H2 and CH4 are then discussed. Microwave transition frequencies fo HCO2(+) and C2H3(+) are estimated, and a preliminary astronomical search for HCO2(+) is described

Results of the ROTOR-program. I. The long-term photometric variability of classical T Tauri stars

We present a unique, homogeneous database of photometric measurements for Classical T Tauri stars extending up to 20 years. The database contains more than 21,000 UBVR observations of 72 CTTs. All the data were collected within the framework of the ROTOR-program at Mount Maidanak Observatory (Uzbekistan) and together they constitute the longest homogeneous, accurate record of TTS variability ever assembled. We characterize the long term photometric variations of 49 CTTs with sufficient data to allow a robust statistical analysis and propose an empirical classification scheme. Several patterns of long term photometric variability are identified. The most common pattern, exhibited by a group of 15 stars which includes T Tau itself, consists of low level variability (Delta(V)<=0.4mag) with no significant changes occurring from season to season over many years. A related subgroup of 22 stars exhibits a similar stable long term variability pattern, though with larger amplitudes (up to Delta(V)~1.6 mag). Besides these representative groups, we identify three smaller groups of 3-5 stars each which have distinctive photometric properties. The long term variability of most CTTs is fairly stable and merely reflects shorter term variability due to cold and hot surface spots. Only a small fraction of CTTs undergo significant brightness changes on the long term (months, years), which probably arise from slowly varying circumstellar extinction.Comment: 16 pages, 11 figures. Astron. Astrophys., in pres

Testing the Disk-Locking Paradigm: An Association Between U-V Excess and Rotation in NGC 2264

We present some results from a UVI photometric study of a field in the young open cluster NGC 2264 aimed, in part, at testing whether accretion in pre-main sequence stars is linked to rotation. We confirm that U-V excess is well correlated with H-alpha equivalent width for the stars in our sample. We show that for the more massive stars in the cluster sample (roughly 0.4-1.2 M_sun) there is also a significant association between U-V excess and rotation, in the sense that slow rotators are more likely to show excess U-band emission and variability. This constitutes significant new evidence in support of the disk-locking paradigm.Comment: Accepted by ApJ Letter

Experimental Test bed to De-Risk the Navy Advanced Development Model

This paper presents a reduced scale demonstration test-bed at the University of Texas’ Center for Electromechanics (UT-CEM) which is well equipped to support the development and assessment of the anticipated Navy Advanced Development Model (ADM). The subscale ADM test bed builds on collaborative power management experiments conducted as part of the Swampworks Program under the US/UK Project Arrangement as well as non-military applications. The system includes the required variety of sources, loads, and controllers as well as an Opal-RT digital simulator. The test bed architecture is described and the range of investigations that can be carried out on it is highlighted; results of preliminary system simulations and some initial tests are also provided. Subscale ADM experiments conducted on the UT-CEM microgrid can be an important step in the realization of a full-voltage, full-power ADM three-zone demonstrator, providing a test-bed for components, subsystems, controls, and the overall performance of the Medium Voltage Direct Current (MVDC) ship architecture.Center for Electromechanic

Evidence for Differential Rotation on a T Tauri Star

Five years of photometric monitoring of the T Tauri star HBC 338 in NGC 1333 has revealed that it is a periodic variable, but the period has changed significantly with time. From 2000-2003, a period near 5.6 days was observed, while in the last two seasons, the dominant period is near 4.6 days. No other T Tauri star has been seen to change its period by such a large percentage. We propose a model in which a differentially rotating star is seen nearly equator-on and a high latitude spot has gradually been replaced by a low latitude spot. We show that this model provides an excellent fit to the observed shapes of the light curves at each epoch. The amplitude and sense of the inferred differential rotation is similar to what is seen on the Sun. This may be surprising given the likely high degree of magnetic surface activity on the star relative to the Sun but we note that HBC 338 is clearly an exceptional T Tauri star.Comment: Acepted for publication in PAS

From structure to ae tiology: a new window on the biology of leucine-rich repeat kinase 2 and Parkinson's disease

Since the discovery of mutations in leucine-rich repeat kinase 2 (LRRK2) as an underlying genetic cause for the development of Parkinson's disease (PD) in 2004 (Neuron 44, 601–607; Neuron 44, 595–600), and subsequent efforts to develop LRRK2 kinase inhibitors as a therapy for Parkinson's (Expert Opin. Ther. Targets 21, 751–753), elucidating the atomic resolution structure of LRRK2 has been a major goal of research into this protein. At over 250 kDa, the large size and complicated domain organisation of LRRK2 has made this a highly challenging target for structural biologists, however, a number of recent studies using both in vitro and in situ approaches (Nature 588, 344–349; Cell 182, 1508–1518.e1516; Cell 184, 3519–3527.e3510) have provided important new insights into LRRK2 structure and the complexes formed by this protein

Effective superpotentials for B-branes in Landau-Ginzburg models

We compute the partition function for the topological Landau-Ginzburg B-model on the disk. This is done by treating the worldsheet superpotential perturbatively. We argue that this partition function as a function of bulk and boundary perturbations may be identified with the effective D-brane superpotential in the target spacetime. We point out the relationship of this approach to matrix factorizations. Using these methods, we prove a conjecture for the effective superpotential of Herbst, Lazaroiu and Lerche for the A-type minimal models. We also consider the Landau-Ginzburg theory of the cubic torus where we show that the effective superpotential, given by the partition function, is consistent with the one obtained by summing up disk instantons in the mirror A-model. This is done by explicitly constructing the open-string mirror map.Comment: 57p, 7 figs, harvma

Simulation System for the Wendelstein 7-X Safety Control System

The Wendelstein 7-X (W7-X) Safety Instrumented System (SIS) ensures personal safety and investment protection. The development and implementation of the SIS are based on the international safety standard for the process industry sector, IEC 61511. The SIS exhibits a distributed and hierarchical organized architecture consisting of a central Safety System (cSS) on the top and many local Safety Systems (lSS) at the bottom. Each technical component or diagnostic system potentially hazardous for the staff or for the device is equipped with an lSS. The cSS is part of the central control system of W7-X. Whereas the lSSs are responsible for the safety of each individual component, the cSS ensures safety of the whole W7-X device. For every operation phase of the W7-X experiment hard- and software updates for the SIS are mandatory. New components with additional lSS functionality and additional safety signals have to be integrated. Already established safety functions must be adapted and new safety functions have to be integrated into the cSS. Finally, the safety programs of the central and local safety systems have to be verified for every development stage and validated against the safety requirement specification. This contribution focuses on the application of a model based simulation system for the whole SIS of W7-X. A brief introduction into the development process of the SIS and its technical realization will be give followed by a description of the design and implementation of the SIS simulation system using the framework SIMIT (Siemens). Finally, first application experiences of this simulation system for the preparation of the SIS for the upcoming operation phase OP 1.2b of W7-X will be discussed