1,661 research outputs found
Toward an artificial Mott insulator: Correlations in confined, high-density electron liquids in SrTiO3
We investigate correlation physics in high-density, two-dimensional electron
liquids that reside in narrow SrTiO3 quantum wells. The quantum wells are
remotely doped via an interfacial polar discontinuity and the three-dimensional
(3D) carrier density is modulated by changing the width of the quantum well. It
is shown that even at 3D densities well below one electron per site,
short-range Coulomb interactions become apparent in transport, and an
insulating state emerges at a critical density. We also discuss the role of
disorder in the insulating state.Comment: Accepted for publication in Physical Review B (Rapid Communication
Ultra-low loss single-mode silica tapers manufactured by a microheater
Using a ceramic thermoelectric heater, we show highly reproducible
fabrication of single-mode sub-wavelength silica tapers with ultra-low loss
level. The reproducibility of the process is studied statistically, leading to
an average taper transmission of 94%. The best tapers have a transmission
superior to 99%, above common level reached by other fabrication methods. The
taper profile is inspected along its length and closely follows the exponential
profile predicted by the model of Birks and Li. This high degree of control
over the taper shape allows a detailed analysis of the transition to the
single-mode regime during tapering. As an application of this fabrication
method, we present a micro-looped taper probe for evanescent coupling
experiments requiring fine spatial selectivity
Antioxidant and Anti-Apoptotic Effect of Melatonin on the Vestibular Hair Cells of Rat Utricles
ObjectivesAminoglycosides are commonly used antibiotic agents, and they are known to generate free oxygen radicals within the inner ear and to cause vestibulo-cochlear toxicity and permanent damage to the sensory hair cells and neurons. Melatonin, a pineal secretory product, has the properties of being a powerful direct and indirect antioxidant. The aim of the present study was to prove the antioxidant effect of melatonin against gentamicin-induced ototoxicty.MethodsThe utricular maculae of Sprague-Dawley rats were prepared from postnatal day 2-4, and these maculae were were divided into 6 groups as follows: 1) control, 2) melatonin only, 3) gentamicin only, and 4), 5), and 6) gentamicin plus melatonin (10, 50, and 100 ”M, respectively). To count the number of hair cells, 5 utricles from each group were stained with phalloidin-FITC on the 1st, 4th, and 7th days after drug administration. Reactive oxygen species (ROS) was assessed by using the fluorescent probe hydrofluorescent diacetate acetyl ester. The caspase-3 activity was also examined with using the fluorescent caspase-3 substrate and performing Western blotting.ResultsThe result of this study showed that gentamicin induced the loss of utricular hair cells, and this loss of hair cells was significantly attenuated by co-administration of melatonin. Melatonin reduced ROS production and caspase-3 activation in the gentamicin treated utricular hair cells.ConclusionOur findings conclusively reveal that melatonin has protective effects against gentamicin-induced hair cell loss in the utricles of rat by inhibiting both ROS production and caspase-3 activity
Structure and Spin Dynamics of LaSrMnO
Neutron scattering has been used to study the structure and spin dynamics of
LaSrMnO. The magnetic structure of this system is
ferromagnetic below T_C = 235 K. We see anomalies in the Bragg peak intensities
and new superlattice peaks consistent with the onset of a spin-canted phase
below T_{CA} = 205 K, which appears to be associated with a gap at q = (0, 0,
0.5) in the spin-wave spectrum. Anomalies in the lattice parameters indicate a
concomitant lattice distortion. The long-wavelength magnetic excitations are
found to be conventional spin waves, with a gapless (< 0.02 meV) isotropic
dispersion relation . The spin stiffness constant D has a
dependence at low T, and the damping at small q follows . An
anomalously strong quasielastic component, however, develops at small wave
vector above 200 K and dominates the fluctuation spectrum as T -> T_C. At
larger q, on the other hand, the magnetic excitations become heavily damped at
low temperatures, indicating that spin waves in this regime are not eigenstates
of the system, while raising the temperature dramatically increases the
damping. The strength of the spin-wave damping also depends strongly on the
symmetry direction in the crystal. These anomalous damping effects are likely
due to the itinerant character of the electrons.Comment: 8 pages (RevTex), 9 figures (encapsulated postscript
Implantable Cardioverter-Defibrillator Implantation in a Patient with Atrial Standstill
We report a 55-year-old female patient who presented with no P waves but with a wide QRS complex escape rhythm at 44 beats/min and prolonged QTc of 0.55 seconds on ECG. The patient had recurrence of ventricular fibrillations and loss of consciousness, and underwent defibrillation and cardiopulmonary resuscitation (CPR) several times because of cardiac arrest. The transthoracic echocardiography showed dilated cardiomyopathy and enlargement of both atria. The Doppler echocardiography documented the absence of A wave in the tricuspid and mitral valve flow. An electrophysiologic study demonstrated electrical inactivity in the right and left atria. Atrial pacing with maximum output did not capture the atria. These findings together with her electrocardiographic finding indicated atrial standstill. Sudden cardiac death was her first clinical manifestation of ventricular arrhythmia. The patient remained asymptomatic after receiving a single chamber implantable cardioverter-defibrillator (ICD) with VVI pacemaker function
Carcinoembryonic Antigen Gene Family
The carcinoembryonic antigen (CEA) gene family belongs to the immunoglobulin supergene family and can be divided into two main subgroups based on sequence comparisons. In humans it is clustered on the long arm of chromosome 19 and consists of approximately 20 genes. The CEA subgroup genes code for CEA and its classical crossreacting antigens, which are mainly membrane-bound, whereas the other subgroup genes encode the pregnancy-specific glycoproteins (PSG), which are secreted. Splice variants of individual genes and differential post-translational modifications of the resulting proteins, e.g., by glycosylation, indicate a high complexity in the number of putative CEA-related molecules. So far, only a limited number of CEA-related antigens in humans have been unequivocally assigned to a specific gene. Rodent CEA-related genes reveal a high sequence divergence and, in part, a completely different domain organization than the human CEA gene family, making it difficult to determine individual gene counterparts. However, rodent CEA-related genes can be assigned to human subgroups based on similarity of expression patterns, which is characteristic for the subgroups. Various functions have been determined for members of the CEA subgroup in vitro, including cell adhesion, bacterial binding, an accessory role for collagen binding or ecto-ATPases activity. Based on all that is known so far on its biology, the clinical outlook for the CEA family has been reassessed
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