The Williams-Beuren syndrome is a genomic disorder (prevalence: 1/7,500 to 1/20,000), caused by a hemizygous contiguous gene deletion on chromosome 7q11.23. Typical symptoms comprise supravalvular ...aortic stenosis, mental retardation, overfriendliness and visuospatial impairment. The common deletion sizes range of 1.5-1.8 mega base pairs (Mb), encompassing app. 28 genes. For a few genes, a genotype-phenotype correlation has been established. The best-explored gene within this region is the elastin gene; its haploinsufficiency causes arterial stenosis. The region of the Williams-Beuren syndrome consists of a single copy gene region (~1.2 Mb) flanked by repetitive sequences - Low Copy Repeats (LCR). The deletions arise as a consequence of misalignment of these repetitive sequences during meiosis and a following unequal crossing over due to high similarity of LCRs. This review presents an overview of the Williams-Beuren syndrome region considering the genomic assembly, chromosomal rearrangements and their mechanisms (i.e. deletions, duplications, inversions) and evolutionary and historical aspects.
The divalent cation, zinc is the second most abundant metal in the human body and is indispensable for life. Zinc concentrations must however, be tightly regulated as deficiencies are associated with ...multiple pathological conditions while an excess can be toxic.
Zinc plays an important role as a cofactor in protein folding and function, e.g. catalytic interactions, DNA recognition by zinc finger proteins and modulation ion channel activity. There are 24 mammalian proteins specific for zinc transport that are subdivided in two groups with opposing functions: ZnT proteins reduce cytosolic zinc concentration while ZIP proteins increase it. The mammalian brain contains a significant amount of zinc, with 5–15% concentrated in synaptic vesicles of glutamatergic neurons alone. Accumulated in these vesicles by the ZnT3 transporter, zinc is released into the synaptic cleft at concentrations from nanomolar at rest to high micromolar during active neurotransmission.
Low concentrations of zinc modulate the activity of a multitude of voltage- or ligand-gated ion channels, indicating that this divalent cation must be taken into account in the analysis of the pathophysiology of CNS disorders including epilepsy, schizophrenia and Alzheimer's disease.
In the context of the latest findings, we review the role of zinc in the central nervous system and discuss the relevance of the most recent association between the zinc transporter, ZIP8 and schizophrenia. An enhanced understanding of zinc transporters in the context of ion channel modulation may offer new avenues in identifying novel therapeutic entities that target neurological disorders.
Although the power conversion efficiency of perovskite solar cells has increased from 3.81% to 22.1% in just 7 years, they still suffer from stability issues, as they degrade upon exposure to ...moisture, UV light, heat, and bias voltage. We herein examined the degradation of perovskite solar cells in the presence of UV light alone. The cells were exposed to 365 nm UV light for over 1,000 h under inert gas at <0.5 ppm humidity without encapsulation. 1-sun illumination after UV degradation resulted in recovery of the fill factor and power conversion efficiency. Furthermore, during exposure to consecutive UV light, the diminished short circuit current density (J
) and EQE continuously restored. 1-sun light soaking induced recovery is considered to be caused by resolving of stacked charges and defect state neutralization. The J
and EQE bounce-back phenomenon is attributed to the beneficial effects of PbI
which is generated by the decomposition of perovskite material.
We propose a very long baseline atom interferometer test of Einstein's equivalence principle (EEP) with ytterbium and rubidium extending over 10 m of free fall. In view of existing parametrizations ...of EEP violations, this choice of test masses significantly broadens the scope of atom interferometric EEP tests with respect to other performed or proposed tests by comparing two elements with high atomic numbfers. In the first step, our experimental scheme will allow us to reach an accuracy in the Eötvös ratio of 7 10−13. This achievement will constrain violation scenarios beyond our present knowledge and will represent an important milestone for exploring a variety of schemes for further improvements of the tests as outlined in the paper. We will discuss the technical realisation in the new infrastructure of the Hanover Institute of Technology (HITec) and give a short overview of the requirements needed to reach this accuracy. The experiment will demonstrate a variety of techniques, which will be employed in future tests of EEP, high-accuracy gravimetry and gravity gradiometry. It includes operation of a force-sensitive atom interferometer with an alkaline earth-like element in free fall, beam splitting over macroscopic distances and novel source concepts.
Atom-Chip Fountain Gravimeter Abend, S; Gebbe, M; Gersemann, M ...
Physical review letters,
11/2016, Letnik:
117, Številka:
20
Journal Article
Recenzirano
We demonstrate a quantum gravimeter by combining the advantages of an atom chip for the generation, delta-kick collimation, and coherent manipulation of freely falling Bose-Einstein condensates ...(BECs) with an innovative launch mechanism based on Bloch oscillations and double Bragg diffraction. Our high-contrast BEC interferometer realizes tens of milliseconds of free fall in a volume as little as a one centimeter cube and paves the way for measurements with sub-μGal accuracies in miniaturized, robust devices.
Recent proposals for space-borne gravitational wave detectors based on atom interferometry rely on extremely narrow single-photon transition lines as featured by alkaline-earth metals or atomic ...species with similar electronic configuration. Despite their similarity, these species differ in key parameters such as abundance of isotopes, atomic flux, density and temperature regimes, achievable expansion rates, density limitations set by interactions, as well as technological and operational requirements. In this study, we compare viable candidates for gravitational wave detection with atom interferometry, contrast the most promising atomic species, identify the relevant technological milestones and investigate potential source concepts towards a future gravitational wave detector in space.
A
bstract
In the first-quantised worldline approach to quantum field theory, a long-standing problem has been to extend this formalism to amplitudes involving open fermion lines while maintaining the ...efficiency of the well-tested closed-loop case. In the present series of papers, we develop a suitable formalism for the case of quantum electrodynamics in vacuum (part one and two) and in a constant external electromagnetic field (part three), based on second-order fermions and the symbol map. We derive this formalism from standard field theory, but also give an alternative derivation intrinsic to the worldline theory. In this first part, we use it to obtain a Bern-Kosower type master formula for the fermion propagator, dressed with
N
photons, in terms of the “
N
-photon kernel,” where off-shell this kernel appears also in “subleading” terms involving only
N −
1 of the
N
photons. Although the parameter integrals generated by the master formula are equivalent to the usual Feynman diagrams, they are quite different since the use of the inverse symbol map avoids the appearance of long products of Dirac matrices. As a test we use the
N
= 2 case for a recalculation of the one-loop fermion self energy, in
D
dimensions and arbitrary covariant gauge, reproducing the known result. We find that significant simplification can be achieved in this calculation by choosing an unusual momentum-dependent gauge parameter.
This paper gives an overview on the current understanding of a technologically relevant defect group in crystalline silicon related to the presence of boron and oxygen. It is commonly addressed as ...boron-oxygen defects and has been found to affect silicon devices, whose performance depends on minority charge carrier diffusion lengths-such as solar cells. The defects are a common limitation in Czochralski-grown p-type silicon, and their recombination activity develops under charge carrier injection and is, thus, commonly referred to as light-induced degradation. A multitude of studies investigating the effect have been published and introduced various trends and interpretations. This review intends to summarize established trends and provide a consistent nomenclature for the defect transitions in order to simplify discussion.
A
bstract
In the first part of this series, we employed the second-order formalism and the “symbol” map to construct a particle path-integral representation of the electron propagator in a background ...electromagnetic field, suitable for open fermion-line calculations. Its main advantages are the avoidance of long products of Dirac matrices, and its ability to unify whole sets of Feynman diagrams related by permutation of photon legs along the fermion lines. We obtained a Bern-Kosower type master formula for the fermion propagator, dressed with
N
photons, in terms of the “
N
-photon kernel,” where this kernel appears also in “subleading” terms involving only
N −
1 of the
N
photons.
In this sequel, we focus on the application of the formalism to the calculation of on-shell amplitudes and cross sections. Universal formulas are obtained for the fully polarised matrix elements of the fermion propagator dressed with an arbitrary number of photons, as well as for the corresponding spin-averaged cross sections. A major simplification of the on-shell case is that the subleading terms drop out, but we also pinpoint other, less obvious simplifications.
We use integration by parts to achieve manifest transversality of these amplitudes at the integrand level and exploit this property using the spinor helicity technique. We give a simple proof of the vanishing of the matrix element for “all +” photon helicities in the massless case, and find a novel relation between the scalar and spinor spin-averaged cross sections in the massive case. Testing the formalism on the standard linear Compton scattering process, we find that it reproduces the known results with remarkable efficiency. Further applications and generalisations are pointed out.
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