A spintronic source of circularly polarized single photons

We present a spintronic single photon source which emits circularly polarized light, where the helicity is determined by an applied magnetic field. Photons are emitted from an InGaAs quantum dot inside an electrically operated spin light-emitting diode, which comprises the diluted magnetic semiconductor ZnMnSe. The circular polarization degree of the emitted light is high, reaching 83% at an applied magnetic field of 2T and 96% at 6 T. Autocorrelation traces recorded in pulsed operation mode prove the emitted light to be antibunched. The two circular polarization states could be used for representing quantum states |0> and |1> in quantum cryptography implementations

Mikrowellen-Spinmanipulation in Spin-LEDs

Diese Arbeit verfolgt den Ansatz der ESR für die Anwendung in spintronischen Bauteilen. Dabei werden spinpolarisierte Elektronen in einer Spin-LED in InGaAs Quantenpunkte injiziert und der Spinzustand optisch ausgelesen. Die Spinmanipulation wird durch den verwendeten Spinausrichter (ZnMnSe) ermöglicht. Die Arbeit beweist damit, dass ein schnelles Schalten von Elektronenspins durch die gezielte resonante Anregung von Übergängen zwischen Spinzuständen möglich ist

Progress towards continuous aqueous two-phase extraction via TAPPIR

At ICB II, we presented Aqueous Two-Phase Extraction (ATPE) as a non-chromatographic alternative for protein purification. We had developed an aqueous two-phase system with inexpensive and biocompatible PEG 1500 or 4000 and ammonium citrate. We purified several enzymes, more specifically a series of dehydrogenases [1], to near homogeneity after forward extraction into a PEG-heavy top phase at pH \u3e 9 and back extraction into a bottom phase at pH 4-6; in selected cases, we were able to obtain pure protein in the bottom phase without forward extraction into the top phase. Scale-up of the PEG 1500/4000-ammonium citrate to 5-10 L scale still often gave phase separation times of less than five minutes.[2] However, ATPE technology is characterized by complex phase separation and very limited number of separation stages not offering enough separation efficiency. Furthermore, conventional ATPE does not lend itself to continuous operation. Please click Additional Files below to see the full abstract

Electrochemical reduction of allyl halides in nonaqueous solvents - a reinvestigation

Abstract: The electrochemical reduction of allyl iodide (la), allyl bromide (lb), (E)-3-bromo-l-phenyl-l-propene (IC), and (E)-5-bromo-2,2,6,6-tetramethyl-3-heptene (Id) was studied in dry acetonitrile with TBAP as supporting electrolyte by means of cyclic voltammetry and coulometry at mercury, platinum, and vitreous carbon electrodes. Compounds la-c showed multiple waves on platinum and mercury because of halide surface effects. However on vitreous carbon la-d gave single reduction waves, with half-peak potentials of -1.38, -1.64, -1.1 I , and -1.89 V (vs. SCE), respectively. Apparent coulometric n values of 1 for la-c were shown to arise from rapid nucleophilic substitution of the allyl anion intermediates with starting halide to give electroinactive dimers. Sterically hindered Id showed an napp of 2 and did not exhibit surface interactions with Hg and Pt. Thus allyl halides, contrary to previous statements in the literature, are reduced via a two-electron electrode reaction and the reduction of the allyl radical to the allyl anion cannot be seen as a separate step. Evidence was also obtained for the formation of the allyl anion by reduction of l a and I b with solvated electrons in liquid ammonia; the electrochemical oxidation of this species in this medium occurred at ca. -1.2 V. Introduction The electrochemical reduction of organic halogen compounds has been widely investigated and several reviews are available.* As was first shown by von Stackelberg and S t r a~k e ,~ the overall reaction involves cleavage of the carbon-halogen bond in a single two-electron polarographic wave to give a carbanion which is subsequently protonated (Schem

Three-dimensional architecture and biogenesis of membrane structures associated with hepatitis C virus replication

All positive strand RNA viruses are known to replicate their genomes in close association with intracellular membranes. In case of the hepatitis C virus (HCV), a member of the family Flaviviridae, infected cells contain accumulations of vesicles forming a membranous web (MW) that is thought to be the site of viral RNA replication. However, little is known about the biogenesis and three-dimensional structure of the MW. In this study we used a combination of immunofluorescence- and electron microscopy (EM)-based methods to analyze the membranous structures induced by HCV in infected cells. We found that the MW is derived primarily from the endoplasmic reticulum (ER) and contains markers of rough ER as well as markers of early and late endosomes, COP vesicles, mitochondria and lipid droplets (LDs). The main constituents of the MW are single and double membrane vesicles (DMVs). The latter predominate and the kinetic of their appearance correlates with kinetics of viral RNA replication. DMVs are induced primarily by NS5A whereas NS4B induces single membrane vesicles arguing that MW formation requires the concerted action of several HCV replicase proteins. Three-dimensional reconstructions identify DMVs as protrusions from the ER membrane into the cytosol, frequently connected to the ER membrane via a neck-like structure. In addition, late in infection multi-membrane vesicles become evident, presumably as a result of a stress-induced reaction. Thus, the morphology of the membranous rearrangements induced in HCV-infected cells resemble those of the unrelated picorna-, corona- and arteriviruses, but are clearly distinct from those of the closely related flaviviruses. These results reveal unexpected similarities between HCV and distantly related positive-strand RNA viruses presumably reflecting similarities in cellular pathways exploited by these viruses to establish their membranous replication factories

Market value margin via mean-variance hedging

We use mean–variance hedging in discrete time in order to value an insurance liability. The prediction of the insurance liability is decomposed into claims development results, that is, yearly deteriorations in its conditional expected values until the liability is finally settled. We assume the existence of a tradeable derivative with binary pay-off written on the claims development result and available in each development period. General valuation formulas are stated and, under additional assumptions, these valuation formulas simplify to resemble familiar regulatory cost-of-capital-based formulas. However, adoption of the mean–variance framework improves upon the regulatory approach by allowing for potential calibration to observed market prices, inclusion of other tradeable assets, and consistent extension to multiple periods. Furthermore, it is shown that the hedging strategy can also lead to increased capital efficiency

The Many Faces of FKBP51

The FK506-binding protein 51 (FKBP51) has emerged as a key regulator of endocrine stress responses in mammals and as a potential therapeutic target for stress-related disorders (depression, post-traumatic stress disorder), metabolic disorders (obesity and diabetes) and chronic pain. Recently, FKBP51 has been implicated in several cellular pathways and numerous interacting protein partners have been reported. However, no consensus on the underlying molecular mechanisms has yet emerged. Here, we review the protein interaction partners reported for FKBP51, the proposed pathways involved, their relevance to FKBP51’s physiological function(s), the interplay with other FKBPs, and implications for the development of FKBP51-directed drugs

Warm Greenland during the last interglacial: the role of regional changes in sea ice cover

The last interglacial, also known as the Eemian, is characterized by warmer than present conditions at high latitudes. This is implied by various Eemian proxy records as well as by climate model simulations, though the models mostly underestimate the warming with respect to proxies. Simulations of Eemian surface air temperatures (SAT) in the Northern Hemisphere extratropics further show large variations between different climate models, and it has been hypothesized that this model spread relates to diverse representations of the Eemian sea ice cover. Here we use versions 3 and 4 of the Community Climate System Model (CCSM3 and CCSM4) to highlight the crucial role of sea ice and sea surface temperatures changes for the Eemian climate, in particular in the North Atlantic sector and in Greenland. A substantial reduction in sea ice cover results in an amplified atmospheric warming and thus a better agreement with Eemian proxy records. Sensitivity experiments with idealized lower boundary conditions reveal that warming over Greenland is mostly due to a sea ice retreat in the Nordic Seas. In contrast, sea ice changes in the Labrador Sea have a limited local impact. Changes in sea ice cover in either region are transferred to the overlying atmosphere through anomalous surface energy fluxes. The large-scale spread of the warming resulting from a Nordic Seas sea ice retreat is mostly explained by anomalous heat advection rather than by radiation or condensation processes. In addition, the sea ice perturbations lead to changes in the hydrological cycle. Our results consequently imply that both temperature and snow accumulation records from Greenland ice cores are sensitive to sea ice changes in the Nordic Seas but insensitive to sea ice changes in the Labrador Sea. Moreover, the simulations suggest that the uncertainty in the Eemian sea ice cover accounts for 1.6 °C of the Eemian warming at the NEEM ice core site. The estimated Eemian warming of 5 °C above present day based on the NEEM δ15N record can be reconstructed by the CCSM4 model for the scenario of a substantial sea ice retreat in the Nordic Seas combined with a reduced Greenland ice sheet

Dependence of Eemian Greenland temperature reconstructions on the ice sheet topography

The influence of a reduced Greenland Ice Sheet (GrIS) on Greenland's surface climate during the Eemian interglacial is studied using a set of simulations with different GrIS realizations performed with a comprehensive climate model. We find a distinct impact of changes in the GrIS topography on Greenland's surface air temperatures (SAT) even when correcting for changes in surface elevation, which influences SAT through the lapse rate effect. The resulting lapse-rate-corrected SAT anomalies are thermodynamically driven by changes in the local surface energy balance rather than dynamically caused through anomalous advection of warm/cold air masses. The large-scale circulation is indeed very stable among all sensitivity experiments and the Northern Hemisphere (NH) flow pattern does not depend on Greenland's topography in the Eemian. In contrast, Greenland's surface energy balance is clearly influenced by changes in the GrIS topography and this impact is seasonally diverse. In winter, the variable reacting strongest to changes in the topography is the sensible heat flux (SHF). The reason is its dependence on surface winds, which themselves are controlled to a large extent by the shape of the GrIS. Hence, regions where a receding GrIS causes higher surface wind velocities also experience anomalous warming through SHF. Vice-versa, regions that become flat and ice-free are characterized by low wind speeds, low SHF, and anomalous low winter temperatures. In summer, we find surface warming induced by a decrease in surface albedo in deglaciated areas and regions which experience surface melting. The Eemian temperature records derived from Greenland proxies, thus, likely include a temperature signal arising from changes in the GrIS topography. For the Eemian ice found in the NEEM core, our model suggests that up to 3.1 °C of the annual mean Eemian warming can be attributed to these topography-related processes and hence is not necessarily linked to large-scale climate variations

Safety and security of drones in the oil and gas industry

This paper describes safety and security challenges and best practices of the use of drones in the oil and gas industry, with consideration of the harsh weather conditions in the Northern Territories of Norway. We have described the present status of the use of drones in air, on water (surface) and under water. Drones are being used in the industry to reduce or remove dangerous, dirty or dull operations from humans and to increase quality of data collection. The Norwegian oil and gas industry and authorities have a high focus on continuous improvement of safety, security and environmental issues. This has for instance resulted in the offshore helicopter transport in Norway to be among the safest offshore transport worldwide. Use of drones in the safety conscious oil and gas industry, should help us to improve the safety practices of drone use in general. Our suggestions are to focus on systematic data reporting of the use of drones, establish guidelines for risk assessments and operations, improve the use and testing of drones in the industry (i.e. build more experience) and support improved robustness and resilience of drone use. In addition, we see the need for improved quality of the interfaces between human operators and drones to ensure meaningful human control.publishedVersio