2,425 research outputs found
Spin injection across magnetic/non-magnetic interfaces with finite magnetic layers
We have reconsidered the problem of spin injection across
ferromagnet/non-magnetic-semiconductor (FM/NMS) and
dilute-magnetic-semiconductor/non-magnetic-semiconductor interfaces, for
structures with \textit{finite} magnetic layers (FM or DMS). By using
appropriate physical boundary conditions, we find expressions for the
resistances of these structures which are in general different from previous
results in the literature. When the magnetoresistance of the contacts is
negligible, we find that the spin-accumulation effect alone cannot account for
the dependence observed in recent magnetoresistance data. In a limited
parameter range, our formulas predict a strong dependence arising from the
magnetic contacts in systems where their magnetoresistances are sizable.Comment: 6 pages, 3 eps figs. (extended version- new title + two new figures
added
Focusing a deterministic single-ion beam
We focus down an ion beam consisting of single 40Ca+ ions to a spot size of a
few mum using an einzel-lens. Starting from a segmented linear Paul trap, we
have implemented a procedure which allows us to deterministically load a
predetermined number of ions by using the potential shaping capabilities of our
segmented ion trap. For single-ion loading, an efficiency of 96.7(7)% has been
achieved. These ions are then deterministically extracted out of the trap and
focused down to a 1sigma-spot radius of (4.6 \pm 1.3)mum at a distance of 257mm
from the trap center. Compared to former measurements without ion optics, the
einzel-lens is focusing down the single-ion beam by a factor of 12. Due to the
small beam divergence and narrow velocity distribution of our ion source,
chromatic and spherical aberration at the einzel-lens is vastly reduced,
presenting a promising starting point for focusing single ions on their way to
a substrate.Comment: 16 pages, 7 figure
Conditional Allocation of Control Rights in Venture Capital Finance
When a young entrepreneurial firm matures, it is often necessary to replace the founding entrepreneur by a professional manager. This replacement decision can be affected by the private benefits of control enjoyed by the entrepreneur which gives rise to a conflict of interest between the entrepreneur and the venture capitalist. We show that a combination of convertible securities and contingent control rights can be used to resolve this conflict efficiently. This contractual arrangement is frequently observed in venture capital finance
Genetic analysis of rab7 mutants in zebrafish
Vascular network formation requires the fusion of newly formed blood vessels and the emergence of a patent lumen between the newly established connections so that blood flow can start. Lumen formation has been shown to depend on the late endosomal/lysosomal pathway in various organs of animal tubular systems. Here, we identified a late endosomal/lysosomal vesicular fraction (Rab7/Lamp2) in early zebrafish angiogenic sprouts, which appears to contribute to apical membrane growth during lumen formation. To study the effect of the late endocytic pathway on vascular development, we generated mutant alleles for all three rab7 genes in zebrafish ( rab7a, rab7ba, rab7bb ). All rab7 genes are expressed in wild-type zebrafish and we did not detect any compensatory effects by the other rab7 isoforms in single knockout mutants, which were all viable. Only the triple mutant was lethal suggesting some functional redundancy. However, the different rab7 isoforms fulfil also at least partially independent functions because eggs laid from mothers lacking two rab7 ( rab7a and/or rab7bb ). showed reduced survival and contained enlarged yolk granules, suggesting maternal contribution of these two rab7 . Finally, we observed minor effects on lumen formation in embryos which still express one copy of rab7 . Our results support the notion that the late endocytic/lysosomal compartment contributes to lumen expansion
Exploiting Locally Imposed Anisotropies in (Ga,Mn)As: a Non-volatile Memory Device
Progress in (Ga,Mn)As lithography has recently allowed us to realize
structures where unique magnetic anisotropy properties can be imposed locally
in various regions of a given device. We make use of this technology to
fabricate a device in which we study transport through a constriction
separating two regions whose magnetization direction differs by 90 degrees. We
find that the resistance of the constriction depends on the flow of the
magnetic field lines in the constriction region and demonstrate that such a
structure constitutes a non-volatile memory device
Saturated Ferromagnetism and Magnetization Deficit in Optimally Annealed (Ga,Mn)As Epilayers
We examine the Mn concentration dependence of the electronic and magnetic
properties of optimally annealed Ga1-xMnxAs epilayers for 1.35% < x < 8.3%. The
Curie temperature (Tc), conductivity, and exchange energy increase with Mn
concentration up to x ~ 0.05, but are almost constant for larger x, with Tc ~
110 K. The ferromagnetic moment per Mn ion decreases monotonically with
increasing x, implying that an increasing fraction of the Mn spins do not
participate in the ferromagnetism. By contrast, the derived domain wall
thickness, an important parameter for device design, remains surprisingly
constant.Comment: 8 pages, 4 figures, submitted for Rapid Communication in Phys Rev
Growth of 1T ' MoTe2 by thermally assisted conversion of electrodeposited tellurium films
Molybdenum ditelluride (MoTe2) is a transition metal dichalcogenide (TMD) which has two phases stable under ambient conditions, a semiconducting (2H) and semimetallic (1T') phase. Despite a host of interesting properties and potential applications, MoTe2 is one of the less-studied TMDs, perhaps due its relatively low abundance in nature or challenges associated with its synthesis, such as the toxicity of most precursors. In this report, we describe the fabrication of thin films of phase-pure IT' MoTe2 using predeposited molybdenum and electrodeposited tellurium layers, at the relatively low temperature of 450 C. This method allows control over film geometry and over the tellurium concentration during the conversion. The MoTe2 films are characterized by Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, atomic force microscopy, and electron microscopies. When applied as a catalyst for the hydrogen evolution reaction, the films display promising initial results. The MoTe2 films have a Tafel slope of below 70 mV dec(-1) and compare favorably with other MoTe2 catalysts reported in the literature, especially considering the inherently scalable fabrication method. The variation in electrocatalytic behavior with thickness and morphology of the films is also investigated
Photo-production of Nucleon Resonances and Nucleon Spin Structure Function in the Resonance Region
The photo-production of nucleon resonances is calculated based on a chiral
constituent quark model including both relativistic corrections H{rel} and
two-body exchange currents, and it is shown that these effects play an
important role. We also calculate the first moment of the nucleon spin
structure function g1 (x,Q^2) in the resonance region, and obtain a
sign-changing point around Q^2 ~ 0.27 {GeV}^2 for the proton.Comment: 23 pages, 5 figure
ADAM10 and ADAM17 promote SARSâCoVâ2 cell entry and spike proteinâmediated lung cell fusion
The severeâacuteârespiratoryâsyndromeâcoronavirusâ2 (SARSâCoVâ2) is the causative agent of COVIDâ19, but host cell factors contributing to COVIDâ19 pathogenesis remain only partly understood. We identify the host metalloprotease ADAM17 as a facilitator of SARSâCoVâ2 cell entry and the metalloprotease ADAM10 as a host factor required for lung cell syncytia formation, a hallmark of COVIDâ19 pathology. ADAM10 and ADAM17, which are broadly expressed in the human lung, cleave the SARSâCoVâ2 spike protein (S) in vitro, indicating that ADAM10 and ADAM17 contribute to the priming of S, an essential step for viral entry and cell fusion. ADAM proteaseâtargeted inhibitors severely impair lung cell infection by the SARSâCoVâ2 variants of concern alpha, beta, delta, and omicron and also reduce SARSâCoVâ2 infection of primary human lung cells in a TMPRSS2 proteaseâindependent manner. Our study establishes ADAM10 and ADAM17 as host cell factors for viral entry and syncytia formation and defines both proteases as potential targets for antiviral drug development
Rhenium-doped MoS2 films
Tailoring the electrical properties of transition metal dichalcogenides by doping is one of the biggest challenges for the application of 2D materials in future electronic devices. Here, we report on a straightforward approach to the n-type doping of molybdenum disulfide (MoS2) films with rhenium (Re). High-Resolution Scanning Transmission Electron Microscopy and Energy-Dispersive X-ray spectroscopy are used to identify Re in interstitial and lattice sites of the MoS2 structure. Hall-effect measurements confirm the electron donating influence of Re in MoS2, while the nominally undoped films exhibit a net p-type doping. Density functional theory (DFT) modelling indicates that Re on Mo sites is the origin of the n-type doping, whereas S-vacancies have a p-type nature, providing an explanation for the p-type behaviour of nominally undoped MoS2 films
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