8,552 research outputs found
Fractional vortices and composite domain walls in flat nanomagnets
We provide a simple explanation of complex magnetic patterns observed in
ferromagnetic nanostructures. To this end we identify elementary topological
defects in the field of magnetization: ordinary vortices in the bulk and
vortices with half-integer winding numbers confined to the edge. Domain walls
found in experiments and numerical simulations in strips and rings are
composite objects containing two or more of the elementary defects.Comment: Minor changes: updated references and fixed typo
Tunneling magnetoresistance in Fe3Si/MgO/Fe3Si(001) magnetic tunnel junctions
published_or_final_versio
Design and Testing of Cesium Atomic Concentration Detection System Based on TDLAS
In order to better build the Neutral Beam Injector with Negative Ion Source
(NNBI), the pre-research on key technologies has been carried out for the
Comprehensive Research Facility for Fusion Technology (CRAFT). Cesium seeding
into negative-ion sources is a prerequisite to obtain the required negative
hydrogen ion. The performance of ion source largely depends on the cesium
conditions in the source. It is very necessary to quantitatively measure the
amount of cesium in the source during the plasma on and off periods (vacuum
stage). This article uses the absorption peak of cesium atoms near 852.1nm to
build a cesium atom concentration detection system based on Tunable Diode Laser
Absorption Spectroscopy (TDLAS) technology. The test experiment based on the
cesium cell is carried out, obtained the variation curve of cesium
concentration at different temperatures. The experimental results indicate
that: the system detection range is within 5*10E6-2.5*10E7 pieces/cm3 and the
system resolution better than 1*10E6 pieces/cm3.Comment: 8 pages,7 figures, the 20th International Symposium on Laser-Aided
Plasma Diagnostic
First direct observation of the Van Hove singularity in the tunneling spectra of cuprates
In two-dimensional lattices the electronic levels are unevenly spaced, and
the density of states (DOS) displays a logarithmic divergence known as the Van
Hove singularity (VHS). This is the case in particular for the layered cuprate
superconductors. The scanning tunneling microscope (STM) probes the DOS, and is
therefore the ideal tool to observe the VHS. No STM study of cuprate
superconductors has reported such an observation so far giving rise to a debate
about the possibility of observing directly the normal state DOS in the
tunneling spectra. In this study, we show for the first time that the VHS is
unambiguously observed in STM measurements performed on the cuprate Bi-2201.
Beside closing the debate, our analysis proves the presence of the pseudogap in
the overdoped side of the phase diagram of Bi-2201 and discredits the scenario
of the pseudogap phase crossing the superconducting dome.Comment: 4 pages, 4 figure
Surgical management and outcome of rectal carcinoids in a university hospital
Abstract Background: Rectal carcinoids are an uncommon entity comprising only 1%-2% of all rectal tumors. Rectal carcinoids are frequently diagnosed during colonoscopy, but management after polypectomy is still controversial. The aims of this study were to review the surgical procedures for rectal carcinoids and to compare the outcomes of patients after different treatment modalities in a university hospital in Hong Kong. Methods: All rectal carcinoids diagnosed between January 2003 and September 2012 were reviewed retrospectively, including clinicopathological characteristics, their management, and surgical outcomes. Results: There were 54 patients with a median age of 60 years, and 32 were males (59.3%). All patients underwent colonoscopy, and the most had rectal bleeding (53.7%). Two patients were diagnosed incidentally in the surgical specimens of rectal tissues. Eighteen patients were diagnosed to have rectal carcinoids after snaring polypectomy, and no further intervention was required. Twenty-five patients had local resection either by means of transanal resection or transanal endoscopic operation. Radical resection was performed in seven patients in which one had T3N1 disease and the others did not have any lymph node metastasis. In the median follow-up of 30 months (10-108 months), there was no recurrence in the "incidental" or post-polypectomy group. However, two patients with transanal resection and two patients with radical resection developed hepatic metastases after 13-24 months post-treatment. The 5-year overall survival was 100% in patients having snaring polypectomy only, 83% for those with local resection, and 63% in patients who underwent radical surgery (p = 0.04)
Atomic-scale images of charge ordering in a mixed-valence manganite
Transition-metal perovskite oxides exhibit a wide range of extraordinary but
imperfectly understood phenomena. Charge, spin, orbital, and lattice degrees of
freedom all undergo order-disorder transitions in regimes not far from where
the best-known of these phenomena, namely high-temperature superconductivity of
the copper oxides, and the 'colossal' magnetoresistance of the manganese
oxides, occur. Mostly diffraction techniques, sensitive either to the spin or
the ionic core, have been used to measure the order. Unfortunately, because
they are only weakly sensitive to valence electrons and yield superposition of
signals from distinct mesoscopic phases, they cannot directly image mesoscopic
phase coexistence and charge ordering, two key features of the manganites. Here
we describe the first experiment to image charge ordering and phase separation
in real space with atomic-scale resolution in a transition metal oxide. Our
scanning tunneling microscopy (STM) data show that charge order is correlated
with structural order, as well as with whether the material is locally metallic
or insulating, thus giving an atomic-scale basis for descriptions of the
manganites as mixtures of electronically and structurally distinct phases.Comment: 8 pages, 4 figures, 19 reference
Epigenetics as a mechanism driving polygenic clinical drug resistance
Aberrant methylation of CpG islands located at or near gene promoters is associated with inactivation of gene expression during tumour development. It is increasingly recognised that such epimutations may occur at a much higher frequency than gene mutation and therefore have a greater impact on selection of subpopulations of cells during tumour progression or acquisition of resistance to anticancer drugs. Although laboratory-based models of acquired resistance to anticancer agents tend to focus on specific genes or biochemical pathways, such 'one gene : one outcome' models may be an oversimplification of acquired resistance to treatment of cancer patients. Instead, clinical drug resistance may be due to changes in expression of a large number of genes that have a cumulative impact on chemosensitivity. Aberrant CpG island methylation of multiple genes occurring in a nonrandom manner during tumour development and during the acquisition of drug resistance provides a mechanism whereby expression of multiple genes could be affected simultaneously resulting in polygenic clinical drug resistance. If simultaneous epigenetic regulation of multiple genes is indeed a major driving force behind acquired resistance of patients' tumour to anticancer agents, this has important implications for biomarker studies of clinical outcome following chemotherapy and for clinical approaches designed to circumvent or modulate drug resistance
Emerging pharmacotherapy of tinnitus
Tinnitus, the perception of sound in the absence of an auditory stimulus, is perceived by about 1 in 10 adults, and for at least 1 in 100, tinnitus severely affects their quality of life. Because tinnitus is frequently associated with irritability, agitation, stress, insomnia, anxiety and depression, the social and economic burdens of tinnitus can be enormous. No curative treatments are available. However, tinnitus symptoms can be alleviated to some extent. The most widespread management therapies consist of auditory stimulation and cognitive behavioral treatment, aiming at improving habituation and coping strategies. Available clinical trials vary in methodological rigor and have been performed for a considerable number of different drugs. None of the investigated drugs have demonstrated providing replicable long-term reduction of tinnitus impact in the majority of patients in excess of placebo effects. Accordingly, there are no FDA or European Medicines Agency approved drugs for the treatment of tinnitus. However, in spite of the lack of evidence, a large variety of different compounds are prescribed off-label. Therefore, more effective pharmacotherapies for this huge and still growing market are desperately needed and even a drug that produces only a small but significant effect would have an enormous therapeutic impact. This review describes current and emerging pharmacotherapies with current difficulties and limitations. In addition, it provides an estimate of the tinnitus market. Finally, it describes recent advances in the tinnitus field which may help overcome obstacles faced in the pharmacological treatment of tinnitus. These include incomplete knowledge of tinnitus pathophysiology, lack of well-established animal models, heterogeneity of different forms of tinnitus, difficulties in tinnitus assessment and outcome measurement and variability in clinical trial methodology. © 2009 Informa UK Ltd.Fil: Langguth, Berthold. Universitat Regensburg; AlemaniaFil: Salvi, Richard. State University of New York; Estados UnidosFil: Elgoyhen, Ana Belen. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Instituto de Investigaciones en IngenierÃa Genética y BiologÃa Molecular "Dr. Héctor N. Torres"; Argentin
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