RWTH Aachen University

About: RWTH Aachen University is a education organization based out in Aachen, Nordrhein-Westfalen, Germany. It is known for research contribution in the topics: Population & Catalysis. The organization has 49754 authors who have published 96212 publications receiving 2581377 citations. The organization is also known as: Rheinisch-Westfälische Technische Hochschule Aachen & Technical University of Aachen.

Temperature dependence of the permittivity and loss tangent of high-permittivity materials at terahertz frequencies

Abstract: An analysis including the temperature dependence of the permittivity and loss tangent of three low-cost and high-permittivity materials (zirconium-tin-titanate, alumina, and titanium-dioxide) in the terahertz frequency range is presented. Such dielectric materials find varied applications in microwave and terahertz systems and components. Their effective use under varying environmental conditions or in space applications requires a detailed knowledge about temperature dependencies. Here, measurements using broad-band terahertz time-domain spectroscopy are presented in the temperature range from 10 to 323 K. It is shown that zirconium-tin-titanate and alumina provide a good thermal stability of the permittivity, whereas the permittivity of titanium-dioxide exhibits a strong dependence on the temperature.

Tactile frequency discrimination is enhanced by circumventing neocortical adaptation

Abstract: Neocortical responses typically adapt to repeated sensory stimulation, improving sensitivity to stimulus changes, but possibly also imposing limitations on perception. For example, it is unclear whether information about stimulus frequency is perturbed by adaptation or encoded by precise response timing. We addressed this question in rat barrel cortex by comparing performance in behavioral tasks with either whisker stimulation, which causes frequency-dependent adaptation, or optical activation of cortically expressed channelrhodopsin-2, which elicits non-adapting neural responses. Circumventing adaption by optical activation substantially improved cross-hemispheric discrimination of stimulus frequency. This improvement persisted when temporal precision of optically evoked spikes was reduced. We were able to replicate whisker-driven behavior only by applying adaptation rules mimicking sensory-evoked responses to optical stimuli. Conversely, in a change-detection task, animals performed better with whisker than optical stimulation. Our results directly demonstrate that sensory adaptation critically governs the perception of stimulus patterns, decreasing fidelity under steady-state conditions in favor of change detection.

Qualification tests of 474 photomultiplier tubes for the inner detector of the Double Chooz experiment

Abstract: The hemispherical 10'' photomultiplier tube (PMT) R7081 from Hamamatsu Photonics K.K. (HPK) is used in various experiments in particle and astroparticle physics. We describe the test and calibration of 474 PMTs for the reactor antineutrino experiment Double Chooz. The unique test setup at Max-Planck-Institut fur Kernphysik Heidelberg (MPIK) allows one to calibrate 30 PMTs simultaneously and to characterize the single photoelectron response, transit time spread, linear behaviour and saturation effects, photon detection efficiency and high voltage calibration.

Commissioning of the CMS experiment and the cosmic run at four tesla

Abstract: The CMS Collaboration conducted a month-long data-taking exercise known as the Cosmic Run At Four Tesla in late 2008 in order to complete the commissioning of the experiment for extended operation. The operational lessons resulting from this exercise were addressed in the subsequent shutdown to better prepare CMS for LHC beams in 2009. The cosmic data collected have been invaluable to study the performance of the detectors, to commission the alignment and calibration techniques, and to make several cosmic ray measurements. The experimental setup, conditions, and principal achievements from this data-taking exercise are described along with a review of the preceding integration activities.