Braunschweig University of Technology

About: Braunschweig University of Technology is a education organization based out in Braunschweig, Germany. It is known for research contribution in the topics: Population & Computer science. The organization has 13268 authors who have published 26707 publications receiving 611590 citations.

The nanorod approach: GaN NanoLEDs for solid state lighting

Abstract: Vertically aligned GaN nanorods have recently obtained substantial interest as a new approach to solid state lighting. In comparison to conventional planar LEDs, 3D NanoLEDs are expected to offer substantial advantageous: very low defect density, quasi free-standing, no strain due to mismatch of thermal expansion coefficients, no substrate bending even when grown on large area silicon. Core-shell strategies are another very interesting aspect. The active LED surface per wafer could be increased by more than one order of magnitude. However, most of these advantages have not yet been proven in real devices, which would include a quantitative comparison of light emission. Related to the 3D character, there are also technological risks. In the following we will discuss the main developments which have paved the way up to this point, including a detailed discussion of possible benefits and risks connected with the NanoLED approach (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Evidence for the formation of comet 67P/Churyumov-Gerasimenko through gravitational collapse of a bound clump of pebbles

Abstract: The processes that led to the formation of the planetary bodies in the Solar system are still not fully understood. Using the results obtained with the comprehensive suite of instruments onboard the European Space Agency's Rosetta mission, we present evidence that comet 67P/Churyumov-Gerasimenko likely formed through the gentle gravitational collapse of a bound clump of mm-sized dust aggregates ('pebbles'), intermixed with microscopic ice particles. This formation scenario leads to a cometary make-up that is simultaneously compatible with the global porosity, homogeneity, tensile strength, thermal inertia, vertical temperature profiles, sizes and porosities of emitted dust and the steep increase in water-vapour production rate with decreasing heliocentric distance, measured by the instruments onboard the Rosetta spacecraft and the Philae lander. Our findings suggest that the pebbles observed to be abundant in protoplanetary discs around young stars provide the building material for comets and other minor bodies. (Less)

Cosmic Ray Impact on Extrasolar Earth-Like Planets in Close-in Habitable Zones

Abstract: Because of their different origins, cosmic rays can be subdivided into galactic cosmic rays and solar/stellar cosmic rays. The flux of cosmic rays to planetary surfaces is mainly determined by two planetary parameters: the atmospheric density and the strength of the internal magnetic moment. If a planet exhibits an extended magnetosphere, its surface will be protected from high-energy cosmic ray particles. We show that close-in extrasolar planets in the habitable zone of M stars are synchronously rotating with their host star because of the tidal interaction. For gravitationally locked planets the rotation period is equal to the orbital period, which is much longer than the rotation period expected for planets not subject to tidal locking. This results in a relatively small magnetic moment. We found that an Earth-like extrasolar planet, tidally locked in an orbit of 0.2 AU around an M star of 0.5 solar masses, has a rotation rate of 2% of that of the Earth. This results in a magnetic moment of less than 1...

Environmental changes since 8.4 ka reflected in the lacustrine core sediments from Nam Co, central Tibetan Plateau, China

Abstract: The Tibetan Plateau induces and enhances the Asian monsoon that influences the plateau itself, East China and even the whole of Asia. Pursuing the changing monsoon history and its impact in this environment- sensitive area is a key for understanding the climatic changes. Here, we present the initial results from core sed- iments in Nam Co, central Tibet, to elucidate the Holocene environment changes in this area. The studied lake (Nam Co) is the second largest lake, with an elevation of 4718 m, water area of 2015 km 2 and catchment area of 10 610 km 2 . By using echo-seismic profiling and hydro-echosounding, we investigated the bathymetric dis- tribution of the whole lake. One 332 cm long PISTON core was successfully taken in the east part of the lake at 60 m water depth. Twelve AMS 14 C dates from top to bottom of this core established a good time sequence. TOC, TN, n-alkanes, grain size, clay minerals, Fe/Mn, Sr/Ba and CaCO3 content were analysed with sampling intervals from 1 cm to 10 cm. Results showed that since 8400 yr BP, the environment changes in this region indicate three stages. The early stage (8400-6900 yr BP) was characterized by slight shifting from warm to cold with a cold-dry interval at 8100-7800 yr BP. The middle stage was from 6900 to 2900 yr BP, during which cli- mate changed from warm-humid to cold-dry. However, around 2900 yr BP, the climate once was slightly cold but strongly dry. The late stage, from 2900 yr BP to present, was characterized by a general tendency toward cold-dry: the first temperature decline was around 1700-1500 yr BP, following which temperature increased once, before decreasing again around 600-300 yr BP, which might be the result of the 'Little Ice Age'.