Optically Imaged Striped Domains of Nonequilibrium Electronic and Nuclear Spins in a Fractional Quantum Hall Liquid

Using photoluminescence microscopy enhanced by magnetic resonance, we visualize in real space both electron and nuclear polarization occurring in nonequilibrium fraction quantum Hall (FQH) liquids. We observe stripelike domain regions comprising FQH excited states which discretely form when the FQH liquid is excited by a source-drain current. These regions are deformable and give rise to bidirectionally polarized nuclear spins as spin-resolved electrons flow across their boundaries.

Direct visualization of the N impurity state in dilute GaNAs using scanning tunneling microscopy

The interaction between nitrogen (N) impurity states in III-V compounds plays a key role in controlling optoelectronic properties of the host materials. Here, we use scanning tunneling microscopy to characterize the spatial distribution and electronic properties of N impurity states in dilute GaNAs. We demonstrated that the N impurity states can be directly visualized by taking empty state current images using the multipass scanning method. The N impurity states broadened over several nanometers and exhibited a highly anisotropic distribution with a bowtie-like shape on the GaAs(110) surface, which can be explained by anisotropic propagation of strain along the zigzag chains of Ga and As atoms in the {110} plane. Our experimental findings provide strong insights into a possible role of N impurity states in modifying properties of the host materials.

Biologic and therapeutic effects of 1 alpha-hydroxycholecalciferol in different types of Fanconi syndrome

The plasma 1,25-(OH)2VD3 level in Fanconi syndrome was low but rose rapidly following the administration of 1 alpha-OHVD3. 1 alpha-OHVD3 was administered to 6 patients with different types of Fanconi syndrome. The effect of 1 alpha-OHVD3 proved to be 200-250 times as great as that of vitamin D2. From our results it was suggested that Ca malabsorption due to failure of 1 alpha-hydroxylation of vitamin D in the kidney, together with renal tubular acidosis and hypophosphatemia, is involved in the pathogenesis of the rickets of Fanconi syndrome.

Nuclear magnetization in gallium arsenide quantum dots at zero magnetic field

Optical and electrical control of the nuclear spin system allows enhancing the sensitivity of NMR applications and spin-based information storage and processing. Dynamic nuclear polarization in semiconductors is commonly achieved in the presence of a stabilizing external magnetic field. Here we report efficient optical pumping of nuclear spins at zero magnetic field in strain-free GaAs quantum dots. The strong interaction of a single, optically injected electron spin with the nuclear spins acts as a stabilizing, effective magnetic field (Knight field) on the nuclei. We optically tune the Knight field amplitude and direction. In combination with a small transverse magnetic field, we are able to control the longitudinal and transverse components of the nuclear spin polarization in the absence of lattice strain--that is, in dots with strongly reduced static nuclear quadrupole effects, as reproduced by our model calculations.

A new method for determining the optimal CT threshold for extracting the upper airway

OBJECTIVES

The purpose of this study was to evaluate the optimal upper threshold levels of a number of individuals and determine the most suitable upper threshold.

METHODS

A phantom model and ten patients were used in this study. The phantom was made of acrylic resin and urethane resin and had nine pillar-shaped air spaces. The subjects were ten female patients with jaw deformities who were not affected by respiratory disease. The optimal threshold levels were determined using the "calculation of CT value disparities" (CCTD) technique, which we devised. In other words, the mean CT values along two lines (air space and soft tissue) were calculated and the optimal threshold level was determined as the level that produced the maximum difference between the CT values measured inside and outside of the air-space border.

RESULTS

The optimal upper threshold levels of the nine phantom holes calculated using the CCTD technique in the front-on standing position and side-on standing position were -434 HU and -456 HU, respectively. The optimal upper threshold level of the ten patients calculated using the CCTD technique was -472 HU. The true threshold level of each patient was defined as the optimal threshold level calculated using the CCTD technique. The mean threshold level was defined as -472 HU. The absolute differences between the volume measurements obtained with these two measures were considered. Therefore, the no error values were -460 HU and -470 HU.

CONCLUSIONS

We consider that the most suitable upper threshold level for extracting the airway is from -460 HU to -470 HU.

Dark-bright mixing of interband transitions in symmetric semiconductor quantum dots

In photoluminescence spectra of symmetric [111] grown GaAs/AlGaAs quantum dots in longitudinal magnetic fields applied along the growth axis, we observe in addition to the expected bright states also nominally dark transitions for both charged and neutral excitons. We uncover a strongly nonmonotonic, sign-changing field dependence of the bright neutral exciton splitting resulting from the interplay between exchange and Zeeman effects. Our theory shows quantitatively that these surprising experimental results are due to magnetic-field-induced ±3/2 heavy-hole mixing, an inherent property of systems with C(3v) point-group symmetry.

Lasing in ultra-narrow emission from GaAs quantum dots coupled with a two-dimensional layer

We report electrically injected lasing in GaAs quantum dots (QDs) grown on GaAs(001) by droplet epitaxy. High-quality GaAs QDs with superior uniformity are formed using improved growth techniques involving the insertion of a two-dimensional layer, control of the As flux for GaAs crystallization, and thin AlGaAs layer capping with high-temperature annealing. The QDs show ultra-narrow luminescence with a linewidth of 20 meV. Ground-state lasing from a laser diode containing fivefold-stacked QD layers is observed at low temperature under pulsed operation.

Scanning Fabry-Pérot interferometer with largely tuneable free spectral range for high resolution spectroscopy of single quantum dots

We report on the implementation of a scanning Fabry-Pérot interferometer for photoluminescence spectroscopy investigation. We choose a conveniently small reflectivity of the two planar semitransparent mirrors which, in spite of a moderate cavity finesse, ensures a good mechanical stability over a long time. We also exploit the large tuneability of the cavity length (i.e., of the free spectral range) for changing the spectral resolution over two order of magnitude (from ~300 μeV to ~4 μeV in full width at half maximum). Such a characteristic easily allows to scan both sharp and broad luminescence bands. We test our Fabry-Pérot interferometer on sharp photoluminescence lines resulting from excitonic recombination in self-assembled GaAs quantum dots. We demonstrate the ability of our system to resolve linewidth as small as 4 μeV.

Effects of low-temperature capping on the optical properties of GaAs/AlGaAs quantum wells

We study the effects of low-temperature capping (200-450°C) on the optical properties of GaAs/AlGaAs quantum wells. Photoluminescence measurements clearly show the formation of abundant nonradiative recombination centers in an AlGaAs capping layer grown at 200°C, while there is a slight degradation of the optical quality in AlGaAs capping layers grown at temperatures above 350°C compared to that of a high-temperature capping layer. In addition, the optical quality can be restored by post-growth annealing without any structural change, except for the 200°C-capped sample.

Allelic diversity of the MHC class II DRB genes in brown bears (Ursus arctos) and a comparison of DRB sequences within the family Ursidae

The allelic diversity of the DRB locus in major histocompatibility complex (MHC) genes was analyzed in the brown bear (Ursus arctos) from the Hokkaido Island of Japan, Siberia, and Kodiak of Alaska. Nineteen alleles of the DRB exon 2 were identified from a total of 38 individuals of U. arctos and were highly polymorphic. Comparisons of non-synonymous and synonymous substitutions in the antigen-binding sites of deduced amino acid sequences indicated evidence for balancing selection on the bear DRB locus. The phylogenetic analysis of the DRB alleles among three genera (Ursus, Tremarctos, and Ailuropoda) in the family Ursidae revealed that DRB allelic lineages were not separated according to species. This strongly shows trans-species persistence of DRB alleles within the Ursidae.

Ultra-narrow emission from single GaAs self-assembled quantum dots grown by droplet epitaxy

We realized ultra-narrow excitonic emission from single GaAs/AlGaAs quantum dots (QDs) grown by a refined droplet epitaxy technique. We found that uncapped quantum dots can be annealed at 400 degrees C without major changes in their morphology, thus enabling an AlGaAs capping layer to be grown at that temperature. Consequently, we demonstrate a fourfold reduction of the linewidth of the emission together with an increased recombination lifetime, compared to the conventional droplet epitaxial QDs. The averaged linewidth of neutral excitons measured by micro-photoluminescence on single quantum dots was around 35 microeV.

Edaravone (MCI-186) is effective as a free radical scavenger following arteriovenous sheathotomy for treatment of macular oedema associated with branch retinal vein occlusion

Aims:

To determine whether edaravone (MCI-186), a free radical scavenger, can reduce macular oedema and improve the visual acuity after arteriovenous sheathotomy in eyes with a branch retinal vein occlusion (BRVO).

Methods:

Forty-seven eyes of 47 consecutive patients with a BRVO who were treated with arteriovenous sheathotomy were studied. The patients were assigned prospectively to either Group R who received 30 mg of edaravone (Radicut) systemically during the vitrectomy or Group N who did not receive any drugs. The postoperative visual acuity was measured before and 12 months after the operation.

Results:

At 12 months postoperatively, the best-corrected visual acuity (BCVA) in logarithm of the minimum angle of resolution (logMAR) units improved significantly from 0.22 to 0.56 logMAR units in Group R and from 0.20 to 0.27 units in Group N (p = 0.016). Twenty-three of 27 cases (85%) in Group R and four of 15 cases (27%) in Group N showed an improvement in BCVA of >0.2 logMAR units (p = 0.0025).

Conclusion:

The better visual acuity in patients given edaravone than those without endaravone during the arteriovenous sheathotomy suggests that edaravone improved the physiology of the retinal cells after the arteriovenous sheathotomy.