ALBERT

Description: This study investigates growth processes of raindrops and the role of recirculation of raindrops for the formation of precipitation in shallow cumulus. Two related cases of fields of lightly precipitating shallow cumulus are simulated using Large-Eddy Simulation combined with a Lagrangian drop model for raindrop growth and a cloud tracking algorithm. Statistics from the Lagrangian drop model yield that most raindrops leave the cloud laterally and then evaporate in the subsaturated cloud environmental air. Only 1 % to 3 % of the raindrops contribute to surface precipitation. Among this subsample of raindrops that contribute to surface precipitation two growth regimes are identified: those raindrops that are dominated by accretional growth from cloud water, and those raindrops that are dominated by selfcollection among raindrops. The mean cloud properties alone are not decisive for the growth of an individual raindrop but the in-cloud variability is crucial. Recirculation of raindrops is found to be common in shallow cumulus, especially for those raindrops that contribute to surface precipitation. The fraction of surface precipitation that is attributed to recirculating raindrops differs from cloud to cloud but can be larger than 50 %. This implies that simple conceptual models of raindrop growth that neglect the effect of recirculation disregard a substantial portion of raindrop growth in shallow cumulus. This article is protected by copyright. All rights reserved.

Description: In this study, we introduce a Lagrangian drop (LD) model to study warm rain microphysical processes in shallow cumulus. The approach combines Large-Eddy Simulations (LES) including a bulk microphysics parameterization with an LD model for raindrop growth. The LD model is one-way coupled with the Eulerian LES and represents all relevant rain microphysical processes such as evaporation, accretion and selfcollection among LDs as well as dynamical effects such as sedimentation and inertia. To test whether the LD model is fit for purpose, a sensitivity study for isolated shallow cumulus clouds is conducted. We show that the surface precipitation rate and the development of the raindrop size distribution are sensitive to the treatment of selfcollection in the LD model. Some uncertainty remains for the contribution of the subgrid-scale turbulence to the relative velocity difference of a pair of LDs, which appears as a factor in the collision kernel. Sensitivities to other model parameters such as the initial multiplicity or the initial mass distribution are small. Overall, sensitivities of the LD model are small compared to the uncertainties in the assumptions of the bulk rain microphysics scheme and the LD model is well suited for particle-based studies of raindrop growth and dynamics. This opens up the opportunity to study effects like recirculation, deviations from terminal fall velocity and other microphysical phenomena that so far were not accessible for bin, bulk or parcel models. This article is protected by copyright. All rights reserved.

Description: Pronuclear microinjection of bacterial artificial chromosomes (BACs)is the preferred way to generate transgenic mice because the transgene accurately recapitulates expression of the endogenous gene. However, the method is demanding and the integrity and copy number of the BAC transgene is difficult to control. Here we describe a simpler pronuclear injection method that relies on transpositionto introducefull-length BACs into the mouse genome. The bacterial backbone of a hPAX6-GFP reporter BAC was retrofitted with PiggyBac transposon inverted repeats(ITRs) andco-injectedwith PiggyBac transposase mRNA. Both the frequency of transgenic founders as well as intact, full-length, single copy integrations was increased.Transposition was determined by a rapid PCR screen for a transpositional signature and confirmation by splinkerette sequencing to show that the BACs were integrated as a single copy either in one or two different genomic sites. BAC transposons displayed improved functional accuracy over random integrants as evaluated by expression of the hPAX6-GFP reporter in embryonic neural tube and absence of ectopic expression. This method involves less work to achieve increased frequencies of both transgenesis and single copy, full-length integrations. These advantages are not only relevant to rodents but also for transgenesis in all systems. © 2012 Wiley-Liss, Inc.

Description: MeTe R f ( R f = CF 3 , C 2 F 5 ) can easily be prepared via the reactions of methyl iodide and the corresponding tetramethylammonium perfluoroalkyltellurates(0), [NMe 4 ]Te R f ( R f = CF 3 , C 2 F 5 ). Both compounds are easily oxidized by xenon difluoride and the heavier halogens to yield the corresponding dihalides, MeTe( R f ) X 2 ( X = F, Cl, Br, I) and by ArI(OCOCF 3 ) 2 to give the corresponding trifluoroacetates, MeTe( R f )(OCOCF 3 ) 2 . All compounds are characterized byspectroscopic means. The molecular structures of MeTe( R f )F 2 ,MeTe( R f )Cl 2 , MeTe( R f )Br 2 , and of 4-MeC 6 H 4 I(OCOCF 3 ) 2 were elucidated by XRD methods.

Description: . MeTe R f ( R f = CF 3 , C 2 F 5 ) can easily be prepared via the reactions of methyl iodide and the corresponding tetramethylammonium perfluoroalkyltellurates(0), [NMe 4 ]Te R f ( R f = CF 3 , C 2 F 5 ). Both compounds are easily oxidized by xenon difluoride and the heavier halogens to yield the corresponding dihalides, MeTe( R f ) X 2 ( X = F, Cl, Br, I) and by ArI(OCOCF 3 ) 2 to give the corresponding trifluoroacetates, MeTe( R f )(OCOCF 3 ) 2 . All compounds are characterized byspectroscopic means. The molecular structures of MeTe( R f )F 2 ,MeTe( R f )Cl 2 , MeTe( R f )Br 2 , and of 4-MeC 6 H 4 I(OCOCF 3 ) 2 were elucidated by XRD methods.

Description: ABSTRACT In the context of climate change characterized by rising temperature and more extreme precipitation regimes, drought is one of the most relevant natural disasters. This paper presents maps of global drought frequency, duration, and severity for the periods 1951–1970, 1971–1990, and 1991–2010, to give an overview of the respective drought hot spots. Drought frequency is defined as the number of drought events occurred, drought duration as the number of months in drought conditions, and drought severity as the sum of the integral area below zero of each event. Because drought is mainly driven by rainfall deficits, we chose the Standardized Precipitation Index (SPI) as the base indicator to derive drought-related quantities. SPI-12 has been calculated on a monthly basis using a Gamma distribution fitted to a 60-year baseline period (1951–2010). Global grids (0.5° × 0.5°) of the Full Data Reanalysis Version 6.0 dataset provided by the Global Precipitation Climatology Centre (GPCC) have been used as precipitation data input. The regions most exposed to prolonged and severe droughts during 1951–1970 were the Central United States, the Argentinian Pampas, Russia, and Central Australia; during 1971–1990 they were Southern Chile, the Sahel, and Siberia; during 1991–2010 they were the Amazon Forest, the Congo River Basin, Mongolia, North Eastern China, and Borneo. A linear trend analysis between 1951 and 2010 shows a small global increase in each drought component, but drought frequency decreased in the Northern Hemisphere. The increase in drought frequency, duration, and severity is found to be significant in Africa, Eastern Asia, Mediterranean region, and Southern Australia, while the Americas and Russia show a decrease in each drought component.

Description: ABSTRACT Over the past decades, a continuous rise in global air temperatures resulted in significant changes in the global hydrological cycle. Regionally increased frequencies of extreme weather events and changes in the regional extent of drylands resulted in new areas at risk of desertification, a complex process driven by socio-economic and climate-related factors. Although desertification is not confined to drylands, they are the most vulnerable to land degradation processes. To investigate possible changes in climate patterns over the past 60 years, we couple the information obtained from the Köppen–Geiger (KG) climate classification and the FAO aridity index (AI), providing an overview of the most evident global changes in climate regimes from 1951–1980 to 1981–2010 and focussing on the modifications of the extent of drylands. KG and AI indicators have been computed on a 0.5° × 0.5° global grid using precipitation data from the Full Data Reanalysis (v6.0) of the Global Precipitation Climatology Centre, and mean temperature and potential evapotranspiration data from the Climate Research Unit of the University of East Anglia (CRUTSv3.20). Both KG and AI show that the arid areas globally increased between 1951–1980 and 1981–2010, but decreased on average in the Americas. North-Eastern Brazil, Southern Argentina, the Sahel, Zambia and Zimbabwe, the Mediterranean area, North-Eastern China and Sub-Himalayan India have been identified as areas with a significant increase of drylands extent. An analysis of the scientific literature gives evidence that most of the areas identified are effectively undergoing desertification, thus confirming the validity of AI and KG to highlight the areas under risk of desertification. We also discuss the global decrease of cold areas, the progressive change from continental to temperate climate in Central Europe, the shift from tundra to continental climate in Alaska, Canada and North-Eastern Russia and the widening of the tropical belt.

Description: ABSTRACT We have undertaken petrographic, mineralogical, geochemical and isotopic investigations on carbonate minerals found within a 10-m-long core from Lonar Lake, central India, with the aim of evaluating their potential as palaeoenvironmental proxies. The core encompasses the entire Holocene and is the first well-dated high-resolution record from central India. While calcite and/or aragonite were found throughout the core, the mineral gaylussite was found only in two specific intervals (4630–3890 and 2040–560 cal a BP). Hydrochemical and isotope data from inflowing streams and lake waters indicate that evaporitic processes play a dominant role in the precipitation of carbonates within this lake. Isotopic (δ 18 O and δ 13 C) studies on the evaporative gaylussite crystals and residual bulk carbonates (calcite) from the long core show that evaporation is the major control on δ 18 O enrichment in both the minerals. However, in case of δ 13 C additional mechanisms, for example methanogenesis (gaylussite) and phytoplankton productivity (calcium carbonate), play an additional important role in some intervals. We also discuss the relevance of our investigation for palaeoclimate reconstruction and late Holocene monsoon variability. Copyright © 2013 John Wiley & Sons, Ltd.

Description: In this contribution a new specimen, which enables high precision tension-compression testing, is presented. Due to a special mounting geometry, tests from a compression strain of −45 % up to a tension strain of 400 % can be performed with a nearly homogeneous deformation field within the measuring zone. Consequently, the mechanical behavior of rubber, which exhibits phenomena like Mullins effect, Payne effect, recovery and relaxation behavior, can be characterized within experimental investigations. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)