Experimental and Atomistic Theoretical Study of Degree of Polarization from Multi-layer InAs/GaAs Quantum Dots

Recent experimental measurements, without any theoretical guidance, showed that isotropic polarization response can be achieved by increasing the number of QD layers in a QD stack. Here we analyse the polarization response of multi-layer quantum dot stacks containing up to nine quantum dot layers by linearly polarized PL measurements and by carrying out a systematic set of multi-million atom simulations. The atomistic modeling and simulations allow us to include correct symmetry properties in the calculations of the optical spectra: a factor critical to explain the experimental evidence. The values of the degree of polarization (DOP) calculated from our model follows the trends of the experimental data. We also present detailed physical insight by examining strain profiles, band edges diagrams and wave function plots. Multi-directional PL measurements and calculations of the DOP reveal a unique property of InAs quantum dot stacks that the TE response is anisotropic in the plane of the stacks. Therefore a single value of the DOP is not sufficient to fully characterize the polarization response. We explain this anisotropy of the TE-modes by orientation of hole wave functions along the [-110] direction. Our results provide a new insight that isotropic polarization response measured in the experimental PL spectra is due to two factors: (i) TM[001]-mode contributions increase due to enhanced intermixing of HH and LH bands, and (ii) TE[110]-mode contributions reduce significantly due to hole wave function alignment along the [-110] direction. We also present optical spectra for various geometry configurations of quantum dot stacks to provide a guide to experimentalists for the design of multi-layer QD stacks for optical devices. Our results predict that the QD stacks with identical layers will exhibit lower values of the DOP than the stacks with non-identical layers.Comment: 10 pages, 7 figures, and 1 tabl

Wide frequency tuning of continuous terahertz wave generated by difference frequency mixing under exciton-excitation conditions in a GaAs/AlAs multiple quantum well

Continuous terahertz wave sources with narrow bandwidth and wide frequency tunability enable high-resolution terahertz spectroscopy and high-speed information communication. In this study, using the optical nonlinearity of excitons as the source of second-order nonlinear polarization, we realize a continuous terahertz electromagnetic wave demonstrating wide frequency tunability from 0.1 to 18 THz without a decrease in intensity due to phonon scattering. Because of excitation of two exciton states in a Ga As / Al As multiple quantum well using two continuous-wave lasers, terahertz waves are emitted as a result of difference-frequency mixing, where the intensity shows a square dependence on the excitation intensity. Using the inhomogeneous width of exciton lines, we achieve wide frequency tunability without phonon effects

Effects of Choto-san (Diao-Teng-San) on microcirculation of bulbar conjunctiva and hemorheological factors in patients with asymptomatic cerebral infarction

In this study, the effects of Choto-san ( 釣藤散 ) on the microcirculation of bulbar conjunctiva in 16 patients with asymptornatic cerebral infarction were investigated with a video-microscopic system. After the administration of Choto-san for four weeks, variables of microcirculatory flow of the bulbar conjunctiva, that is, the internal diameter of vessels, flow velocity and flow volume rate were increased (p<0.05) . Erythrocyte aggregability, evaluated by measuring the maximum diameter of a column of intravascular erythrocyte aggregation, was also improved (p<0.05) . Simultaneously, hemorheological factors such as whole blood viscosity, plasrna viscosity, erythrocyte deformability and leukocyte deformability were examined. Choto-san improved deformability of both erythrocytes and leukocytes (p<0.05) , but not blood viscosity. These results suggest that Choto-san may have favorable effects on cerebrovascular disorders through changes in microcirculatory flow, erythrocyte aggregability and blood cell deformability. 今回,無症候性脳梗塞患者16名を対象に,眼球結膜微小循環に及ぼす釣藤散の効果をビデオ顕徴鏡システムを用いて検討した。釣藤散を4週間投与後,眼球結膜微小循環の血管内径,血流速度,血流量が増加した(p<0.05)。血管内赤血球集合現象を認める血管の最大内径で評価ざれる赤血球集合能も改善した(p<0.05)。同時に,血液レオロジー因子である全血粘度,血漿粘度,赤血球変形能,白血球変形能も検討したところ,釣藤散は赤血球と白血球の変形能を改善したが(p<0.05),血液粘度は改善しなかった。以上の結果から,釣藤散は徴小循環血流や赤血球集合能,血球変形能を改善することで,脳血管障害に好影響を与える可能性が示唆された

Methemoglobinemia induced by chlorphenamidine

A 76-year old farmer ingested 100 g of chlorphenamidine (Galectron), a plant acaricle, for the purpose of suicide. Gastric lavage was performed and the patient survived. Methemoglobinemia was noted after emergency treatment and was still present at 20 hours after ingestion of the compound. The patient was lethargic for at least 50 hours. Moderate neutrophilic leukocytosis and kidney injury were observed.</p

Clinical profile of reading ability and reading and writing achievement of children with borderline full-scale intellectual quotient : a prospective study

Background Poor reading ability is one of the common causes of low academic performance. In previous studies, children with dyslexia were found to demonstrate poor academic achievement due to poor reading ability. However, the relationship between academic achievement and reading ability in children with a borderline full-scale intellectual quotient (FSIQ) is unknown. This study aimed to clarify the clinical characteristics of children with borderline FSIQ and poor reading ability, and differentiate these characteristics from those of children with higher FSIQ and poor reading ability. Methods A total of 126 children (aged 6-15 years) identified as having low academic performance were enrolled. The reading ability of children was assessed through their performance on the hiragana (Japanese syllabary) reading task, while their reading and writing achievement was assessed through their reading and writing score on the Kaufman Assessment Battery for Children, Second Edition. Children were categorized into two groups based on their FSIQ score (FSIQ > 85 and 85 >= FSIQ >= 70). Reading ability in children was evaluated by referring to the linear relationship between FSIQ and the standard deviation value of reading tasks in typically developing children. A one-way analysis of variance (ANOVA) was performed to examine clinical characteristics between higher and lower FSIQ groups. Associations between reading and writing achievement, reading ability, and ages of children were assessed using Pearson's product-moment correlation coefficients for the higher and lower FSIQ groups. Results Poorer reading and writing achievement was associated with poorer reading ability in the higher FSIQ group. Conversely, poorer reading and writing achievement and poor reading ability were associated with older age in the lower FSIQ group. Conclusions Poor reading and writing achievement were associated with older age, not with poor reading ability in the lower FSIQ group. Children with lower FSIQ need appropriate educational interventions based on independent assessments to further their academic achievement and reading ability. Moreover, they need more frequent evaluations of their academic achievement than do children with higher FSIQ and poor reading ability since they are more likely to be at a lower academic achievement level at an older age.Peer reviewe

An extremely basic monoclonal IgG in an aged apoplectic patient with prolonged bacterial infection

A case with prolonged bacterial infection accompanied by an abnormal serum protein which migrated in the post-gamma region on electrophoresis is presented. The abnormal protein was identified as IgG with gamma-type light chain moiety. The patient suffered from prolonged pneumonia and cholecystitis, Bone marrow aspiration and skeletal x-rays did not indicate multiple myeloma.</p

A case of alcaptonuria with fatal cardiovascular disturbance

A case of alcaptonuria combined with aortic insufficiency was found in a 28-year-old male. The patient was palpitating at admission. The daily excretion of homogentisic acid was 2.0-6.0 g. Electrocardiography indicated atrial fibrillation and left ventricular hypertrophy with a ST-T change and right axis deviation. Cartilage tissues in the knee-joints showed no pigmentation. Vertebral X-ray revealed no calcification. The patient's history disclosed a family intermarriage in his grandparents. The patient's mother noticed the presence of black stains on diapers in his infancy and brown pigmentation on the skin and sclera in childhood. No kin had similar symptoms.</p