Technische Universität Darmstadt

About: Technische Universität Darmstadt is a education organization based out in Darmstadt, Germany. It is known for research contribution in the topics: Computer science & Context (language use). The organization has 17316 authors who have published 40619 publications receiving 937916 citations. The organization is also known as: Darmstadt University of Technology & University of Darmstadt.

Probing eV-scale axions with CAST

Abstract: We have searched for solar axions or other pseudoscalar particles that couple to two photons by using the CERN Axion Solar Telescope (CAST) setup. Whereas we previously have reported results from CAST with evacuated magnet bores (Phase I), setting limits on lower mass axions, here we report results from CAST where the magnet bores were filled with 4He gas (Phase II) of variable pressure. The introduction of gas generates a refractive photon mass mγ, thereby achieving the maximum possible conversion rate for those axion masses ma that match mγ. With 160 different pressure settings we have scanned ma up to about 0.4 eV, taking approximately 2 h of data for each setting. From the absence of excess x-rays when the magnet was pointing to the Sun, we set a typical upper limit on the axion-photon coupling of gaγ2.2 × 10−10 GeV−1 at 95% CL for ma0.4 eV, the exact result depending on the pressure setting. The excluded parameter range covers realistic axion models with a Peccei-Quinn scale in the neighborhood of fa ~ 107 GeV. Currently in the second part of CAST Phase II, we are searching for axions with masses up to about 1.2 eV using 3He as a buffer gas.

Effects of salt treatment and osmotic stress on V-ATPase and V-PPase in leaves of the halophyte Suaeda salsa

Abstract: The Chenopodiaceae Suaeda salsa L. was grown under different salt concentrations and under osmotic stress. The fresh weight was markedly stimulated by 0.1 M NaCl, 0.4 M NaCl and 0.1 M KCl and reduced by osmotic stress (PEG iso-osmotic to 0.1 M NaCl). Treatment with 0.4 M KCl severely damaged the plants. Membrane vesicle fractions containing tonoplast vesicles were isolated by sucrose gradient from leaves of the S. salsa plants and modulations of V-ATPase and V-PPase depending on the growth conditions were determined. Western blot analysis revealed that V-ATPase of S. salsa consists of at least nine subunits (apparent molecular masses 66, 55, 52, 48, 36, 35, 29, 18, and 16 kDa). This polypeptide pattern did not depend on culture conditions. V-PPase is composed of a single polypeptide (69 kDa). An additional polypeptide (54 kDa) was detected in the fractions of NaCl-, KCl- and PEG-treated plants. It turned out that the main strategy of salt-tolerance of S. salsa seems to be an up-regulation of V-ATPase activity, which is required to energize the tonoplast for ion uptake into the vacuole, while V-PPase plays only a minor role. The increase in V-ATPase activity is not obtained by structural changes of the enzyme, but by an increase in V-ATPase protein amount.

Mining apps for abnormal usage of sensitive data

Abstract: What is it that makes an app malicious? One important factor is that malicious apps treat sensitive data differently from benign apps. To capture such differences, we mined 2,866 benign Android applications for their data flow from sensitive sources, and compare these flows against those found in malicious apps. We find that (a) for every sensitive source, the data ends up in a small number of typical sinks; (b) these sinks differ considerably between benign and malicious apps; (c) these differences can be used to flag malicious apps due to their abnormal data flow; and (d) malicious apps can be identified by their abnormal data flow alone, without requiring known malware samples. In our evaluation, our mudflow prototype correctly identified 86.4% of all novel malware, and 90.1% of novel malware leaking sensitive data.