Start-Up incubators - an analysis of two leading incubators and their performance

Accelerators are a modern phenomenon of start-up support. The first accelerator was founded in 2005 and several hundred have been created all over the world since then. The concept of acceleration itself is not new but the recent programs take a different approach. How well do these perform and what is the best method to accelerate start-ups? Two leading accelerators YC and Techstars are being analysed in this paper to evaluate their differences in performance and their approaches

Bromoform and dibromomethane above the Mauritanian upwelling: Atmospheric distributions and oceanic emissions

Natural sources of bromoform (CHBr3) and dibromomethane (CH2Br2), including oceanic emissions, contribute to stratospheric and tropospheric O3 depletion. Convective transport over tropical oceans could deliver large amounts of these short-lived organic bromine species to the upper atmosphere. High mixing ratios of atmospheric CHBr3 in air masses from the northwest African coast have been hypothesized to originate from the biologically active Mauritanian upwelling. During a cruise into the upwelling source region in spring 2005 the atmospheric mixing ratios of the brominated compounds CHBr3 and CH2Br2 were found to be elevated above the marine background and comparable to measurements in other coastal regions. The shelf waters were identified as a source of both compounds for the atmosphere. The calculated sea-to-air emissions support the hypothesis of a strong upwelling source for reactive organic bromine. However, calculated emissions were not sufficient to explain the elevated concentrations observed in the coastal atmosphere. Other strong sources that could contribute to the large atmospheric mixing ratios previously observed over the Atlantic Ocean must exist within or near West Africa

Rates and controls of the air-sea flux of bromoform (CHBr3): a review and synthesis

Bromoform (CHBr3) is the largest single source of atmospheric organic bromine and therefore of importance as a source of reactive halogens to the troposphere and lower stratosphere. The sea-to-air flux, originating with macroalgal and planktonic sources, is the main source for atmospheric bromoform. We review bromoform's contribution to atmospheric chemistry, its atmospheric and oceanic distributions and its oceanic sources and sinks. We have reassessed oceanic emissions, based on published aqueous and airborne concentration data, global climatological parameters, and information concerning coastal and biogenic sources. The goals are to attempt an estimate of the global source strength and partly to identify key regions that require further investigation. The sea-to-air flux is spatially and temporally variable with tropical, subtropical and shelf waters identified as potentially important source regions. We obtain an annual global flux of bromoform of ∼10 Gmol Br yr−1 (3–22 Gmol Br yr−1). This estimate is associated with significant uncertainty, arising from data precision and coverage, choice of air-sea exchange parameterizations and model assumptions. Anthropogenic sources of ∼0.3 (to 1.1) Gmol Br yr−1 (as CHBr3) can be locally significant, but are globally negligible. Our estimate of the global oceanic source is three to four times higher than recent estimates based on the modeling of atmospheric sinks. The reasons for this discrepancy could lie with the limited regional and temporal data available and the broad assumptions that underlie our flux calculations. Alternatively, atmospheric sink calculations, often made on the basis of background CHBr3 levels, may neglect the influence of strong but highly localized sources (e.g., from some coastal and shelf regions). The strongly variable and poorly characterized source of CHBr3, together with its short atmospheric lifetime, complicates model-based estimation of the distribution of reactive Br resulting from its atmospheric degradation. An integrated program of marine and atmospheric observations, atmospheric modeling and mechanistic studies of oceanic bromoform production is required to better constrain present and future Br delivery to the atmosphere

Test and characterization of a plastic printed Ka-band slotted waveguide antenna

With the Ka-band PolInSAR system, the German Aerospace Center is taking a first step towards SAR technology in Ka-band. Thereby, high demands on the mechanical accuracy of complex antenna components require new manufacturing methods such as 3D printing. Due to a higher coefficient of thermal expansion, an increased sensitivity of the plastic printed antenna against temperature changes is expected. The aim of this work is to investigate the behavior of two antenna prototypes manufactured of brass and plastic in the temperature range of airborne SAR systems. The investigation is carried out by simulations as well as by practical measurements. The theoretical investigation is performed to analyze the impact of temperature variation on the electrical performance of the prototypes. After the development of a suitable measuring setup, the characteristic of the antennas is measured at different temperatures. The comparison of a plastic printed and a classical milled antenna showed only minor differences in the electrical behavior and confirms that plastic is suitable for slotted waveguide antennas. Furthermore, a method to detect changes in antenna characteristics within a wide temperature range using simple measuring and processing methods could be introduced