1,084 research outputs found
Direct observation of irradiation-induced nanocavity shrinkage in Si
Nanocavities in Si substrates, formed by conventional H implantation and thermal annealing, are shown to evolve in size during subsequent Si irradiation. Both ex situ and in situ analytical techniques were used to demonstrate that the mean nanocavity diameter decreases as a function of Si irradiation dose in both the crystalline and amorphous phases. Potential mechanisms for this irradiation-induced nanocavity evolution are discussed. In the crystalline phase, the observed decrease in diameter is attributed to the gettering of interstitials. When the matrix surrounding the cavities is amorphized, cavity shrinkage may be mediated by one of two processes: nanocavities can supply vacancies into the amorphous phase and/or the amorphous phase may flow plastically into the nanocavities. Both processes yield the necessary decrease in density of the amorphous phase relative to crystalline material
Androgenetic alopecia: a review
Androgenetic alopecia, commonly known as male pattern baldness, is the most common type of progressive hair loss disorder in men. The aim of this paper is to review recent advances in understanding the pathophysiology and molecular mechanism of androgenetic alopecia.Using the PubMed database, we conducted a systematic review of the literature, selecting studies published from 1916 to 2016.The occurrence and development of androgenetic alopecia depends on the interaction of endocrine factors and genetic predisposition. Androgenetic alopecia is characterized by progressive hair follicular miniaturization, caused by the actions of androgens on the epithelial cells of genetically susceptible hair follicles in androgen-dependent areas. Although the exact pathogenesis of androgenetic alopecia remains to be clarified, research has shown that it is a polygenetic condition. Numerous studies have unequivocally identified two major genetic risk loci for androgenetic alopecia, on the X-chromosome ARa"EDA2R locus and the chromosome 20p11 locus.Candidate gene and genome-wide association studies have reported that single-nucleotide polymorphisms at different genomic loci are associated with androgenetic alopecia development. A number of genes determine the predisposition for androgenetic alopecia in a polygenic fashion. However, further studies are needed before the specific genetic factors of this polygenic condition can be fully explained
Geometry-related magnetic interference patterns in long SNS Josephson junctions
We have measured the critical current dependence on the magnetic flux of two
long SNS junctions differing by the normal wire geometry. The samples are made
by a Au wire connected to W contacts, via Focused Ion Beam assisted deposition.
We could tune the magnetic pattern from the monotonic gaussian-like decay of a
quasi 1D normal wire to the Fraunhofer-like pattern of a square normal wire. We
explain the monotonic limit with a semiclassical 1D model, and we fit both
field dependences with numerical simulations of the 2D Usadel equation.
Furthermore, we observe both integer and fractional Shapiro steps. The magnetic
flux dependence of the integer steps reproduces as expected that of the
critical current Ic, while fractional steps decay slower with the flux than Ic.Comment: 5 pages, 4 figure
Straight motion of half-integer topological defects in thin Fe-N magnetic films with stripe domains
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Hubbard band or oxygen vacancy states in the correlated electron metal SrVO?
We study the effect of oxygen vacancies on the electronic structure of the
model strongly correlated metal SrVO. By means of angle-resolved
photoemission (ARPES) synchrotron experiments, we investigate the systematic
effect of the UV dose on the measured spectra. We observe the onset of a
spurious dose-dependent prominent peak at an energy range were the lower
Hubbard band has been previously reported in this compound, raising questions
on its previous interpretation. By a careful analysis of the dose dependent
effects we succeed in disentangling the contributions coming from the oxygen
vacancy states and from the lower Hubbard band. We obtain the intrinsic ARPES
spectrum for the zero-vacancy limit, where a clear signal of a lower Hubbard
band remains. We support our study by means of state-of-the-art ab initio
calculations that include correlation effects and the presence of oxygen
vacancies. Our results underscore the relevance of potential spurious states
affecting ARPES experiments in correlated metals, which are associated to the
ubiquitous oxygen vacancies as extensively reported in the context of a
two-dimensional electron gas (2DEG) at the surface of insulating
transition metal oxides.Comment: Manuscript + Supplemental Material, 12 pages, 9 figure
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