Trotter Derivation of Algorithms for Brownian and Dissipative Particle Dynamics

This paper focuses on the temporal discretization of the Langevin dynamics, and on different resulting numerical integration schemes. Using a method based on the exponentiation of time dependent operators, we carefully derive a numerical scheme for the Langevin dynamics, that we found equivalent to the proposal of Ermak, and not simply to the stochastic version of the velocity-Verlet algorithm. However, we checked on numerical simulations that both algorithms give similar results, and share the same ``weak order two'' accuracy. We then apply the same strategy to derive and test two numerical schemes for the dissipative particle dynamics (DPD). The first one of them was found to compare well, in terms of speed and accuracy, with the best currently available algorithms.Comment: to be published in J.Chem.Phy

Chromospheric evaporation flows and density changes deduced from Hinode/EIS during an M1.6 flare

We analyzed high-cadence sit-and-stare observations acquired with the Hinode/EIS spectrometer and HXR measurements acquired with RHESSI during an M-class flare. During the flare impulsive phase, we observe no significant flows in the cooler Fe XIII line but strong upflows, up to 80-150 km/s, in the hotter Fe XVI line. The largest Doppler shifts observed in the Fe XVI line were co-temporal with the sharp intensity peak. The electron density obtained from a Fe XIII line pair ratio exhibited fast increase (within two minutes) from the pre-flare level of 5.01x10^(9) cm^(-3) to 3.16x10^(10) cm^(-3) during the flare peak. The nonthermal energy flux density deposited from the coronal acceleration site to the lower atmospheric layers during the flare peak was found to be 1.34x10^(10) erg/s/cm^(2) for a low-energy cut-off that was estimated to be 16 keV. During the decline flare phase, we found a secondary intensity and density peak of lower amplitude that was preceded by upflows of 15 km/s that were detected in both lines. The flare was also accompanied by a filament eruption that was partly captured by the EIS observations. We derived Doppler velocities of 250-300 km/s for the upflowing filament material.The spectroscopic results for the flare peak are consistent with the scenario of explosive chromospheric evaporation, although a comparatively low value of the nonthermal energy flux density was determined for this phase of the flare. This outcome is discussed in the context of recent hydrodynamic simulations. It provides observational evidence that the response of the atmospheric plasma strongly depends on the properties of the electron beams responsible for the heating, in particular the steepness of the energy distribution.Comment: 13 pages, 11 figures, accepted for publication in Astronomy and Astrophysic

High-contrast Imaging with Spitzer: Deep Observations of Vega, Fomalhaut, and epsilon Eridani

Stars with debris disks are intriguing targets for direct imaging exoplanet searches, both due to previous detections of wide planets in debris disk systems, as well as commonly existing morphological features in the disks themselves that may be indicative of a planetary influence. Here we present observations of three of the most nearby young stars, that are also known to host massive debris disks: Vega, Fomalhaut, and eps Eri. The Spitzer Space Telescope is used at a range of orientation angles for each star, in order to supply a deep contrast through angular differential imaging combined with high-contrast algorithms. The observations provide the opportunity to probe substantially colder bound planets (120--330 K) than is possible with any other technique or instrument. For Vega, some apparently very red candidate point sources detected in the 4.5 micron image remain to be tested for common proper motion. The images are sensitive to ~2 Mjup companions at 150 AU in this system. The observations presented here represent the first search for planets around Vega using Spitzer. The upper 4.5 micron flux limit on Fomalhaut b could be further constrained relative to previous data. In the case of eps Eri, planets below both the effective temperature and the mass of Jupiter could be probed from 80 AU and outwards, although no such planets were found. The data sensitively probe the regions around the edges of the debris rings in the systems where planets can be expected to reside. These observations validate previous results showing that more than an order of magnitude improvement in performance in the contrast-limited regime can be acquired with respect to conventional methods by applying sophisticated high-contrast techniques to space-based telescopes, thanks to the high degree of PSF stability provided in this environment.Comment: 11 pages, 12 figures, accepted for publication in A&

Lymphadenektomie im Rahmen der radikalen Zystektomie: Aktueller Stand und Kontroversen

Zusammenfassung: Die pelvine Lymphadenektomie (LAD) ist ein entscheidender Bestandteil der radikalen Zystektomie bei muskelinvasiven Harnblasentumoren. Die optimale Ausdehnung der LAD, insbesondere die proximale Ausdehnung, wird weiterhin kontrovers diskutiert. Aufgrund der vorliegenden Mapping- sowie retrospektiven Studien scheint die ausgedehnte LAD bis zum oberen Drittel der iliakal kommunen Gefäße einen prognostischen wie auch therapeutischen Benefit mit sich zu bringen und sollte deshalb als Standard definiert werden. Dies gilt gleichermaßen für die offene wie auch für die minimal-invasive Chirurgie. Dabei ist die alleinige Lymphknoten- (LK-)Anzahl kein hinlängliches Qualitätskriterium für eine LAD, da die LK-Zahl zu sehr durch anatomische Variabilität, chirurgische Technik, Wahl des Templates, histopathologische Aufarbeitung etc. beeinflusst wird und daraus konsekutiv beträchtliche interinstitutionelle Unterschiede resultieren, welche keinen Vergleich zulassen. Die LK-Density wird als besserer prognostischer Faktor postuliert, wird aber in gleichem Ausmaß von denselben Faktoren beeinflusst. Hinsichtlich molekularer Diagnostik zur Verbesserung der Sensitivität des LK-Stagings ist weitere Forschungstätigkeit notwendig. Es wird sich zeigen, inwieweit die Ergebnisse der beiden groß angelegten prospektiv randomisierten Studien zur Klärung der optimalen Ausdehnung der LAD beitragen werde

Towards agent-based crowd simulation in airports using games technology

We adapt popular video games technology for an agent-based crowd simulation in an airport terminal. To achieve this, we investigate the unique traits of airports and implement a virtual crowd by exploiting a scalable layered intelligence technique in combination with physics middleware and a socialforces approach. Our experiments show that the framework runs at interactive frame-rate and evaluate the scalability with increasing number of agents demonstrating navigation behaviour

Characteristics of long-duration inhibitory postsynaptic potentials in rat neocortical neurons in vitro

1. The characteristics of long-duration inhibitory postsynaptic potentials (l-IPSPs) which are evoked in rat frontal neocortical neurons by local electrical stimulation were investigated with intracellular recordings from anin vitro slice preparation. 2. Stimulation with suprathreshold intensities evoked l-IPSPs with typical durations of 600–900 msec at resting membrane potential. Conductance increases of 15–60% were measured at the peak amplitude of l-IPSPs (150–250 msec poststimulus). 3. The duration of the conductance increases during l-IPSPs displayed a significant voltage dependence, decreasing as the membrance potential was depolarized and increasing with hyperpolarization. 4. The reversal potential of l-IPSPs is significantly altered by reductions in the extracellular potassium concentration. Therefore it is concluded that l-IPSPs in rat neocortical neurons are generated by the activation of a potassium conductance. 5. l-IPSPs exhibit stimulation fatigue. Stimulation with a frequency of 1 Hz produces a complete fatigue of the conductance increases during l-IPSPs after approximately 20 consecutive stimuli. Recovery from this fatigue requires minutes. 6. l-IPSPs are not blocked by bicuculline but are blocked by baclofen

Nachhaltigkeit von drei graslandbasierten Milchproduktionssystemen in der Schweiz mit der Bewertungsmethode RISE

Dairy farming is a key sector for Swiss agriculture and the food industry. Therefore, sustainability of dairy farms is important. Grassland-based farming systems are the most common production system, combining the indoor feeding of fresh grass with partial grazing. The effects of three dairy production systems (VW: full grazing plus on avg. 46±93 SD kg concentrate (KF), GFKF: indoor feeding/partial grazing plus on avg. 345±204 SD kg KF and GFKFplus: indoor feeding/partial grazing plus on avg. 1007±353 SD kg KF) on sustainability, according to RISE, were studied on 12 pilot farms in the lowland of Switzerland. In most of the sustainability themes, the farms performed medium to good according to the RISE evaluation scale. The GFKFplus farms produced the highest output of milk by low N- and P-self-sufficiency, showed the highest energy input and the lowest greenhouse gas output per kg milk. The GFKF group achieved remarkable results by moderate N-, P- and energy inputs. The VW farms showed a lower milk output but a higher level of feed self-sufficiency and a lower energy consumption. In the search for the optimal production strategy, farms should consider the individual farm structure (contiguous areas), the market potential but also social aspects such as the preferences of the farmer`s family

A Review of the "Digital Turn" in the New Literacy Studies

Digital communication has transformed literacy practices and assumed great importance in the functioning of workplace, recreational, and community contexts. This article reviews a decade of empirical work of the New Literacy Studies, identifying the shift toward research of digital literacy applications. The article engages with the central theoretical, methodological, and pragmatic challenges in the tradition of New Literacy Studies, while highlighting the distinctive trends in the digital strand. It identifies common patterns across new literacy practices through cross-comparisons of ethnographic research in digital media environments. It examines ways in which this research is taking into account power and pedagogy in normative contexts of literacy learning using the new media. Recommendations are given to strengthen the links between New Literacy Studies research and literacy curriculum, assessment, and accountability in the 21st century

Stable Real-Time Interaction Between Virtual Humans and Real Scenes

We present an augmented reality system that relies on purely passive techniques to solve the real-time registration problem. It can run on a portable PC and does not require engineering of the environment, for example by adding markers. To achieve this result, we have integrated robust computer vision techniques into a powerful VR framework. The resulting AR system allows us to produce complex rendering and animation of virtual human characters, and to blend them into the real world. The system tracks the 3D camera position by means of a natural features tracker, which, given a rough CAD model, can deal with complex 3D objects. The tracking method can handle both large camera displacements and aspect changes. We will show that our system works in the cluttered environment of a real industrial facility and can, therefore, be used to enhance manufacturing and industrial processe