348 research outputs found
Direct electronic measurement of the spin Hall effect
The generation, manipulation and detection of spin-polarized electrons in
nanostructures define the main challenges of spin-based electronics[1]. Amongst
the different approaches for spin generation and manipulation, spin-orbit
coupling, which couples the spin of an electron to its momentum, is attracting
considerable interest. In a spin-orbit-coupled system, a nonzero spin-current
is predicted in a direction perpendicular to the applied electric field, giving
rise to a "spin Hall effect"[2-4]. Consistent with this effect,
electrically-induced spin polarization was recently detected by optical
techniques at the edges of a semiconductor channel[5] and in two-dimensional
electron gases in semiconductor heterostructures[6,7]. Here we report
electrical measurements of the spin-Hall effect in a diffusive metallic
conductor, using a ferromagnetic electrode in combination with a tunnel barrier
to inject a spin-polarized current. In our devices, we observe an induced
voltage that results exclusively from the conversion of the injected spin
current into charge imbalance through the spin Hall effect. Such a voltage is
proportional to the component of the injected spins that is perpendicular to
the plane defined by the spin current direction and the voltage probes. These
experiments reveal opportunities for efficient spin detection without the need
for magnetic materials, which could lead to useful spintronics devices that
integrate information processing and data storage.Comment: 5 pages, 4 figures. Accepted for publication in Nature (pending
format approval
Human Pancreatic Acinar Cells Do Not Respond to Cholecystokinin
Pancreatic secretion can be influenced by cholecystokinin (CCK) either directly via actions on acinar cells or indirectly via actions on nerves. The presence and functional roles of CCK receptors on human pancreatic acinar cells remains unclear. In the current study human pancreatic acini were isolated and then treated with CCK-8, gastrin and/or carbachol. Functional parameters were measured including intracellular [Ca2+] and amylase secretion. It was observed that human acini did not respond to CCK agonists but did respond to carbachol with robust increases in functional parameters. Adenoviral-mediated gene transfer of CCK1 or CCK2 receptors to the human cells resulted in cell responses to CCK agonists. In order to determine the reason for the lack of responsiveness of the human acini, expression of receptor mRNAs was determined using quantitative RT-PCR and localized by in situ hybridization. mRNA levels for CCK1 receptors were ∼30 times lower than those of CCK2 receptors, which were ∼10 times lower than those of m3 Ach receptors as measured by quantitative PCR. Neither CCK1 nor CCK2 receptors were localized in adult human pancreas by i n situ hybridization. These results indicate that human pancreatic acinar cells do not respond directly to CCK receptor activation and this is likely due to an insufficient level of receptor expression.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73903/1/j.1600-0773.2002.910610.x.pd
A Case of Recurrent Schneiderian Papilloma of the Lacrimal Sac Invading the Nasal Cavity
A 44-year-old man presented with a history of chronic epiphora, discharge from the right eye, and a palpable mass in the medial canthal area. Irrigation of the lacrimal system revealed bloody discharge. Orbital magnetic resonance imaging (MRI) showed a well-defined heterogeneous enhanced mass filling the lacrimal sac and upper nasolacrimal duct (NLD). A wide excision and surgical biopsy were performed. Histopathology showed the tumor to be an exophytic Schneiderian papilloma with moderate to severe dysplasia. Three months later, the mass was found to be invading the nasal cavity through the NLD. Endoscopic histopathological evaluation confirmed that it was identical to the originally identified papilloma
Experimental demonstration of a magnetically induced warping transition in a topological insulator mediated by rare-earth surface dopants
Magnetic topological insulators (MTI) constitute a novel class of materials
where the topologically protected band structure coexists with long-range
ferromagnetic order, which can lead to the breaking of time-reversal symmetry
(TRS), introducing a bandgap in the Dirac cone-shaped topological surface state
(TSS). The gap opening in MITs has been predicted to be accompanied by a
distortion in the TSS, evolving its warped shape from hexagonal to trigonal. In
this work, we demonstrate such a transition by means of angle-resolved
photoemission spectroscopy after the deposition of low concentrations of
magnetic rare earths, namely Er and Dy, on the ternary three-dimensional
prototypical topological insulator BiSeTe. Signatures of the gap
opening occurring as a consequence of the TRS breaking have also been observed,
whose existence is supported by the observation of the aforementioned
transition. Moreover, increasing the Er coverage results in a tunable p-type
doping of the TSS. As a consequence, the Fermi level (E) of our
BiSeTe crystals can be gradually tuned towards the TSS Dirac point, and
therefore to the magnetically induced bandgap; thus fulfilling two of the
necessary prerequisites for the realization of the quantum anomalous Hall
effect (QAHE) in this system. The experimental results are rationalized by a
theoretical model where a magnetic Zeeman out-of-plane term is introduced in
the hamiltonian governing the TSS band dispersion. Our results offer new
strategies to control magnetic interactions with TSSs based on a simple
approach and open up viable routes for the realization of the QAHE
A Novel Electrochemical Sensor for Probing Doxepin Created on a Glassy Carbon Electrode Modified with Poly(4-Amino- benzoic Acid)/Multi-Walled Carbon Nanotubes Composite Film
A novel electrochemical sensor for sensitive detection of doxepin was prepared, which was based on a glassy carbon electrode modified with poly(4-aminobenzoic acid)/multi-walled carbon nanotubes composite film [poly(4-ABA)/MWNTs/GCE]. The sensor was characterized by scanning electron microscopy and electrochemical methods. It was observed that poly(4-ABA)/MWNTs/GCE showed excellent preconcentration function and electrocatalytic activities towards doxepin. Under the selected conditions, the anodic peak current was linear to the logarithm of doxepin concentration in the range from 1.0 × 10−9 to 1.0 × 10−6 M, and the detection limit obtained was 1.0 × 10−10 M. The poly(4-ABA)/MWNTs/GCE was successfully applied in the measurement of doxepin in commercial pharmaceutical formulations, and the analytical accuracy was confirmed by comparison with a conventional ultraviolet spectrophotometry assay
Integrative genomic analysis of human ribosomal DNA
The transcription of ribosomal RNA (rRNA) is critical to life. Despite its importance, ribosomal DNA (rDNA) is not included in current genome assemblies and, consequently, genomic analyses to date have excluded rDNA. Here, we show that short sequence reads can be aligned to a genome assembly containing a single rDNA repeat. Integrated analysis of ChIP-seq, DNase-seq, MNase-seq and RNA-seq data reveals several novel findings. First, the coding region of active rDNA is contained within nucleosome-depleted open chromatin that is highly transcriptionally active. Second, histone modifications are located not only at the rDNA promoter but also at novel sites within the intergenic spacer. Third, the distributions of active modifications are more similar within and between different cell types than repressive modifications. Fourth, UBF, a positive regulator of rRNA transcription, binds to sites throughout the genome. Lastly, the insulator binding protein CTCF associates with the spacer promoter of rDNA, suggesting that transcriptional insulation plays a role in regulating the transcription of rRNA. Taken together, these analyses confirm and expand the results of previous ChIP studies of rDNA and provide novel avenues for exploration of chromatin-mediated regulation of rDNA
Belle II Technical Design Report
The Belle detector at the KEKB electron-positron collider has collected
almost 1 billion Y(4S) events in its decade of operation. Super-KEKB, an
upgrade of KEKB is under construction, to increase the luminosity by two orders
of magnitude during a three-year shutdown, with an ultimate goal of 8E35 /cm^2
/s luminosity. To exploit the increased luminosity, an upgrade of the Belle
detector has been proposed. A new international collaboration Belle-II, is
being formed. The Technical Design Report presents physics motivation, basic
methods of the accelerator upgrade, as well as key improvements of the
detector.Comment: Edited by: Z. Dole\v{z}al and S. Un
Carnitine reduces the lipoperoxidative damage of the membrane and apoptosis after induction of cell stress in experimental glaucoma
The pathological damage caused by glaucoma is associated to a high intraocular pressure. The ocular hypertone is most likely due to a defective efflux of aqueous humor from the anterior chamber of the eye. Ocular hypertension causes apoptotic death of retinal ganglion cells and overexpression of molecular markers typical of cell stress response and apoptosis. In this work, we report on the neuroprotective, antiapoptotic and antioxidant action of a natural substance, -carnitine. This compound is known for its ability to improve the mitochondrial performance. We analyze a number of cellular and molecular markers, typical of ocular hypertension and, in general, of the cell stress response. In particular, -carnitine reduces the expression of glial fibrillary acidic protein, inducible nitric oxide synthase, ubiquitin and caspase 3 typical markers of cell stress. In addition, the morphological analysis of the optic nerve evidenced a reduction of the pathological excavation of the optic disk. This experimental hypertone protocol induces a severe lipoperoxidation, which is significantly reduced by -carnitine. The overall interpretation is that mortality of the retinal cells is due to membrane damage
Magnesium Ferrite (MgFe2O4) Nanostructures Fabricated by Electrospinning
Magnesium ferrite (MgFe2O4) nanostructures were successfully fabricated by electrospinning method. X-ray diffraction, FT-IR, scanning electron microscopy, and transmission electron microscopy revealed that calcination of the as-spun MgFe2O4/poly(vinyl pyrrolidone) (PVP) composite nanofibers at 500–800 °C in air for 2 h resulted in well-developed spinel MgFe2O4nanostuctures. The crystal structure and morphology of the nanofibers were influenced by the calcination temperature. Crystallite size of the nanoparticles contained in nanofibers increased from 15 ± 4 to 24 ± 3 nm when calcination temperature was increased from 500 to 800 °C. Room temperature magnetization results showed a ferromagnetic behavior of the calcined MgFe2O4/PVP composite nanofibers, having their specific saturation magnetization (Ms) values of 17.0, 20.7, 25.7, and 31.1 emu/g at 10 Oe for the samples calcined at 500, 600, 700, and 800 °C, respectively. It is found that the increase in the tendency ofMsis consistent with the enhancement of crystallinity, and the values ofMsfor the MgFe2O4samples were observed to increase with increasing crystallite size
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