1,654 research outputs found
Recent applications of the Tübingen-Vienna Smooth Particle Hydrodynamics code
Here, we present the latest improvements and applications
of the Tübingen-Vienna Smooth Particle Hydrodynamics
(SPH) code. By the use of modern graphics processing units
(GPUs), we have increased the performance of astrophysical
simulations in the field of hydrodynamics and solid mechanics by
porting an OpenMP code to the GPU with CUDA™. Recently, we
have added a porosity module and a soil module to our existing
framework. The code is freely available upon request
Search for dark matter in the hidden-photon sector with a large spherical mirror
If dark matter consists of hidden-sector photons which kinetically mix with
regular photons, a tiny oscillating electric-field component is present
wherever we have dark matter. In the surface of conducting materials this
induces a small probability to emit single photons almost perpendicular to the
surface, with the corresponding photon frequency matching the mass of the
hidden photons. We report on a construction of an experimental setup with a
large ~14 m2 spherical metallic mirror that will allow for searches of
hidden-photon dark matter in the eV and sub-eV range by application of
different electromagnetic radiation detectors. We discuss sensitivity and
accessible regions in the dark matter parameter space.Comment: 9 pages, proceeding of the 34th International Cosmic Ray Conference
(ICRC), July 30 - August 6, 2015, The Hague, The Netherland
Momentum Enhancement during Kinetic Impacts in the Low-intermediate-strength Regime: Benchmarking and Validation of Impact Shock Physics Codes
In 2022 September, the DART spacecraft (NASA’s contribution to the Asteroid Impact & Deflection Assessment (AIDA) collaboration) will impact the asteroid Dimorphos, the secondary in the Didymos system. The crater formation and material ejection will affect the orbital period. In 2027, Hera (ESA’s contribution to AIDA) will investigate the system, observe the crater caused by DART, and characterize Dimorphos. Before Hera’s arrival, the target properties will not be well-constrained. The relationships between observed orbital change and specific target properties are not unique, but Hera’s observations will add additional constraints for the analysis of the impact event, which will narrow the range of feasible target properties. In this study, we use three different shock physics codes to simulate momentum transfer from impactor to target and investigate the agreement between the results from the codes for well-defined target materials. In contrast to previous studies, care is taken to use consistent crushing behavior (e.g., distension as a function of pressure) for a given porosity for all codes. First, we validate the codes against impact experiments into a regolith simulant. Second, we benchmark the codes at the DART impact scale for a range of target material parameters (10%–50% porosity, 1.4–100 kPa cohesion). Aligning the crushing behavior improves the consistency of the derived momentum enhancement between the three codes to within +/−5% for most materials used. Based on the derived mass–velocity distributions from all three codes, we derive scaling parameters that can be used for studies of the ejecta curtain
Insulin Receptor in Pancreatic Cancer-Crown Witness in Cross Examination
Background The proximity of pancreatic cancer (PDAC) to the physiological source of the growth promoting hormone insulin might be exploited by this highly malignant cancer entity. We investigated if (I) PDACs express the insulin receptor (IR) in cancer cells and cancer vasculature, (II) if IR correlates with clinicopathological patient characteristics, including survival, and hence is involved in PDAC biology, (III) if IR is already expressed in precursor lesions, if (IV) the IGF1 receptor (IGF1R) is associated with clinicopathological patient characteristics and survival and (V) is linked to IR expression. Methods 160 PDAC samples were examined for IR and IGF1R expression by immunohistochemistry. A modified HistoScore was correlated with clinicopathological characteristics and survival. Results IR overexpression was already observed in pancreatic intraepithelial neoplasia. Furthermore, it was more frequently observed in advanced disease and associated with distant metastasis, UICC stage, lymphatic invasion and an increased lymph node ratio, but without impacting survival in the end. IGF1R expression was not associated with clinicopathological parameters or survival, in contrast to former paradigms. Conclusions We hypothesize that the close proximity to the pancreatic islets might be advantageous for cancer growth at first, but it experiences self-limitation due to surgical removal or local destruction following accelerated cancer growth
Experimental Research in Synthetic Molecular Communications -- Part I: Overview and Short-Range Systems
Since its emergence from the communication engineering community around one
and a half decades ago, the field of Synthetic Molecular Communication (SMC)
has experienced continued growth, both in the number of technical contributions
from a vibrant community and in terms of research funding. Throughout this
process, the vision of SMC as a novel, revolutionary communication paradigm has
constantly evolved, driven by feedback from theoretical and experimental
studies, respectively. It is believed that especially the latter ones will be
crucial for the transition of SMC towards a higher technology readiness level
in the near future. In this spirit, we present here a comprehensive survey of
experimental research in SMC. In particular, this survey focuses on
highlighting the major drivers behind different lines of experimental research
in terms of the respective envisioned applications. This approach allows us to
categorize existing works and identify current research gaps that still hinder
the development of practical SMC-based applications. Our survey consists of two
parts; this paper and a companion paper. While the companion paper focuses on
SMC with relatively long communication ranges, this paper covers SMC over short
distances of typically not more than a few millimeters.Comment: 10 pages, 1 table, 5 figures. Accepted for publication in the IEEE
Nanotechnology Magazin
Experimental Research in Synthetic Molecular Communications -- Part II: Long-Range Communication
In this second part of our survey on experimental research in Synthetic
Molecular Communication (SMC), we review works on long-range SMC systems, i.e.,
systems with communication ranges of more than a few millimeters. Despite the
importance of experimental research for the evolution of SMC towards a mature
communication paradigm that will eventually support revolutionary applications
beyond the reach of today's prevalent communication paradigms, the existing
body of literature is still comparatively sparse. Long-range SMC systems have
been proposed in the literature for information transmission in two types of
fluid media, liquid and air. While both types of SMC systems, liquid-based and
air-based systems, rely on encoding and transmitting information using
molecules, they differ substantially in terms of the physical system designs
and in the type of applications they are intended for. In this paper, we
present a systematic characterization of experimental works on long-range SMC
that reveals the major drivers of these works in terms of the respective target
applications. Furthermore, the physical designs for long-range SMC proposed in
the literature are comprehensively reviewed. In this way, our survey will
contribute to making experimental research in this field more accessible and
identifying novel directions for future research.Comment: 10 pages, 2 tables, 4 figures. Accepted for publication in the IEEE
Nanotechnology Magazin
Species‐specific transpiration responses to intermediate disturbance in a northern hardwood forest
Intermediate disturbances shape forest structure and composition, which may in turn alter carbon, nitrogen, and water cycling. We used a large‐scale experiment in a forest in northern lower Michigan where we prescribed an intermediate disturbance by stem girdling all canopy‐dominant early successional trees to simulate an accelerated age‐related senescence associated with natural succession. Using 3 years of eddy covariance and sap flux measurements in the disturbed area and an adjacent control plot, we analyzed disturbance‐induced changes to plot level and species‐specific transpiration and stomatal conductance. We found transpiration to be ~15% lower in disturbed plots than in unmanipulated control plots. However, species‐specific responses to changes in microclimate varied. While red oak and white pine showed increases in stomatal conductance during postdisturbance (62.5 and 132.2%, respectively), red maple reduced stomatal conductance by 36.8%. We used the hysteresis between sap flux and vapor pressure deficit to quantify diurnal hydraulic stress incurred by each species in both plots. Red oak, a ring porous anisohydric species, demonstrated the largest mean relative hysteresis, while red maple, bigtooth aspen, and paper birch, all diffuse porous species, had the lowest relative hysteresis. We employed the Penman‐Monteith model for LE to demonstrate that these species‐specific responses to disturbance are not well captured using current modeling strategies and that accounting for changes to leaf area index and plot microclimate are insufficient to fully describe the effects of disturbance on transpiration.Key PointsPlot level scaling of evaporation from sap flux evaluated with eddy fluxDisturbance changes intradaily transpiration dynamicsHydraulic strategy causes species‐specific transpiration differencesPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/110637/1/jgrg20315.pd
A microscopic semiclassical confining field equation for lattice gauge theory in 2+1 dimensions
We present a semiclassical nonlinear field equation for the confining field
in 2+1--dimensional lattice gauge theory (compact QED). The equation is
derived directly from the underlying microscopic quantum Hamiltonian by means
of truncation. Its nonlinearities express the dynamic creation of magnetic
monopole currents leading to the confinement of the electric field between two
static electric charges. We solve the equation numerically and show that it can
be interpreted as a London relation in a dual superconductor.Comment: 21 pages, epsf postscript figures included, full postscript available
at ftp://ftp.th.physik.uni-frankfurt.de/pub/cbest/micro.ps.Z or
http://www.th.physik.uni-frankfurt.de/~cbest/pub.htm
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