Nitrogen fluorescence in air for observing extensive air showers

Extensive air showers initiate the fluorescence emissions from nitrogen molecules in air. The UV-light is emitted isotropically and can be used for observing the longitudinal development of extensive air showers in the atmosphere over tenth of kilometers. This measurement technique is well-established since it is exploited for many decades by several cosmic ray experiments. However, a fundamental aspect of the air shower analyses is the description of the fluorescence emission in dependence on varying atmospheric conditions. Different fluorescence yields affect directly the energy scaling of air shower reconstruction. In order to explore the various details of the nitrogen fluorescence emission in air, a few experimental groups have been performing dedicated measurements over the last decade. Most of the measurements are now finished. These experimental groups have been discussing their techniques and results in a series of Air Fluorescence Workshops commenced in 2002. At the 8$^{\rm{th}}$ Air Fluorescence Workshop 2011, it was suggested to develop a common way of describing the nitrogen fluorescence for application to air shower observations. Here, first analyses for a common treatment of the major dependences of the emission procedure are presented. Aspects like the contributions at different wavelengths, the dependence on pressure as it is decreasing with increasing altitude in the atmosphere, the temperature dependence, in particular that of the collisional cross sections between molecules involved, and the collisional de-excitation by water vapor are discussed.Comment: 12 pages, 17 figures, 2 tables, International Symposium on Future Directions in UHECR Physics, 13-16 February 2012, CERN, Geneva (Switzerland); the updated version corrects for a typo in Eq. (1

Development of driving simulator for the experiment of tsunami evacuation using automobile

The 2011 off the Pacific coast of Tohoku Earthquake, which occurred on March 11, 2011, triggered an extremely large tsunami. More than 15,000 deaths and 3,400 people missing were confirmed and 92.4% of the fatalities in Iwate, Miyagi, and Fukushima prefectures resulted from drowning. In Japan, it is basically prohibited to evacuate by automobile in case of tsunami because there may occur traffic congestions and accidents. However, Central Disaster Management Council of Japan reported that about 57% of evacuees used their automobiles to reach the upland refuges. This resulted from the social situations in the coastal residential areas in Japan. Aging of population is rather fast especially in the affected areas by the 2011 Tohoku earthquake, and the number of people in need of nursing care is increasing. Based on these circumstances, many people drove to the elevated areas after the 2011 Tohoku earthquake although the use of automobile was prohibited. This study aims to reveal the permissible limits of tsunami evacuation using automobile based on a series of driving simulator experiments. The authors perform numerical simulation of tsunami propagation, and the results are visualized from driver???s point of view using 3D computer graphics (CG). The CG is installed to a driving simulator, which consists of three LCDs, steering wheel, and brake and accelerator pedals. Several tsunami scenarios are employed in the driving simulator experiments to reveal the effectiveness of evacuation using automobile quantitatively

Very high two-dimensional hole gas mobilities in strained silicon germanium

We report on the growth by solid source MBE and characterization of remote doped Si/SiGe/Si two-dimensional hole gas structures. It has been found that by reducing the Ge composition to <=13% and limiting the thickness of the alloy layer, growth temperatures can be increased up to 950 °C for these structures while maintaining good structural integrity and planar interfaces. Record mobilities of 19 820 cm2 V−1 s−1 at 7 K were obtained in normal structures. Our calculations suggest that alloy scattering is not important in these structures and that interface roughness and interface charge scattering limit the low temperature mobilities

Green's function approach to transport through a gate-all-around Si nanowire under impurity scattering

We investigate transport properties of gate-all-around Si nanowires using non-equilibrium Green's function technique. By taking into account of the ionized impurity scattering we calculate Green's functions self-consistently and examine the effects of ionized impurity scattering on electron densities and currents. For nano-scale Si wires, it is found that, due to the impurity scattering, the local density of state profiles loose it's interference oscillations as well as is broaden and shifted. In addition, the impurity scattering gives rise to a different transconductance as functions of temperature and impurity scattering strength when compared with the transconductance without impurity scattering.Comment: 8 pages, 4 figure

Exchange interaction effects in inter-Landau level Auger scattering in a two-dimensional electron gas

We consider the influence of spin effects on the inter-Landau level electron-electron scattering rate in a two-dimensional electron gas. Due to the exchange spin splitting, the Landau levels are not equidistant. This leads to the suppresion of Auger processes and a nonlinear dependence of the lifetime on the concentration of the excited electrons even at very low excitation levels.Comment: 10 pages, 3 figure