Search

Metalorganic chemical vapor deposition (MOCVD) is a critical process and is widely used for the epitaxial growth of light-emitting diode (LED) wafers. The key component, a gas injection system, delivers the gas into the reactor by using a nozzle or showerhead. In this paper, the numerical simulation method was applied to investigate the thermal fluid field and to design a new gas injection system for MOCVD. In this study, we developed a new gas injection system with inlet barriers. The inlet barriers can separate the various reactive gases, reduce the prereaction, and prevent adducted particles from forming and blocking the inlet gas system. The barrier geometry, including the barrier length, the barrier inclination angle, and the V/III precursor ratio was systematically studied to determine the optimal design conditions. Higher growth rate and improved uniformity were demonstrated using the new optimal gas inlet barrier design.

Spintronic phenomena and devices have evolved from exploiting spin-polarized current to pure spin current. A pure spin current can more efficiently deliver spin angular momentum with fewer or no charge carriers, enabling spin–orbit torque switching in ferromagnets. The prospects of antiferromagnetic spintronics, especially electrical switching, remain perplexing and controversial. We describe some recent advances, outstanding issues, challenges, and prospects of pure spin current.

Geophysical data through electrical resistivity tomography (ERT) and induced polarization (IP) can be assisted to understanding hydrogeological characteristic of groundwater aquifer. By knowing the difference in electrical resistivity and induced polarization values in alluvium deposition will facilitate to identify any groundwater occurrence. In agriculture sector, shallow tube well will be option to farmers due to more economic. The resistivity measurements proved to be a good tool for mapping the subsurface in the Alluvium, especially when used in combination with Induced Polarization parameters. Alluvial deposits or fluvial deposits are composed of particles of gravel, sand, silt or clay size that are not bound or hardened by permeable mineral, by pressure, or thermal alteration of the grains. Consideration of gravelly deposition is the higher hydraulic conductivity. Furthermore, coarse to fine sand are the second higher followed by silt and clay are the lowest values. From the case study, the electrical resistivity tomography of these deposits ranged from 40 to 1000 Ωm, while the values of chargeability were 0 to 20 mS/m. The bottom of the aquifer consisted of a layer with gravelly sandy silt, and the resistivity was 260 Ωm, while the chargeability was 6.5 mS/m. The shallow tube well in quaternary aquifer was constructed at 51 m depth with thickness of aquifer was 24 m to 51 m depth into the ground will consider for groundwater resources. The groundwater discharge from tubewell is 6.53 m3/hr in mixed gravel, sandy and silt.

BACKGROUND AND PURPOSE: SWI is a high-resolution 3D, fully velocity-compensated gradient-echo sequence that uses both magnitude and phase data. The purpose of this study was to investigate the phase behavior of the capsule of pyogenic brain abscesses with noncontrast SWI. MATERIALS AND METHODS: Fourteen patients with pyogenic brain abscesses were studied at 1.5T. In all of the patients, SWI images were obtained and reviewed in addition to conventional MR images. Phase values within the abscess capsule were measured and compared with those from the abscess cavities and contralateral normal white matter using 1-way repeated measures ANOVA with post hoc Bonferroni analysis. RESULTS: SWI phase images showed mild hypointesity in 6 patients, isointensity in 3 patients, and mixed iso- to mild hypointensity in 5 patients. The means of phase in the cavity, rim of abscesses, and contralateral normal white matter were –7.552 × 10 −3 ± 0.024, –0.105 ± 0.080, and +0.029 ± 0.011 radians, respectively. Post hoc comparisons showed significant differences between any pair of the 3 regions (abscess cavity, rim capsule, and normal white matter) in SWI (all P s CONCLUSIONS: SWI phase imaging shows evidence of paramagnetic substances in agreement with the presence of free radicals from phagocytosis. SWI may provide additional information valuable in the characterization of pyogenic brain abscesses.

Optimum intermediate temperatures are evaluated for two-stage Gifford-McMahon (GM) coolers including shield coolers protecting cryostats with low-boiling-point liquids, e.g. liquid Helium-4 (He I) baths near 4 K. Recent cooler progress has raised refrigeration loads to the 1-watt order of magnitude at 4 K. Thus, present three-stage systems with two-stage GM and single-stage Joule-Thomson (JT) expanders are potentially replaceable as two-stage GMs reach the refrigeration power of the three-stage GM/JT systems. We have extended earlier studies with the objective of evaluating realistic optimum intermediate temperatures, e.g. of two-stage GMs, in order to replace previous ideal limits. Our present extended model includes previous components such as the cascade-shunt model. Its optimum temperatures are found to be lower than ideal values, consistent with cooler data, in the range of parameters covered. This feature relates in part to higher loss parameters in the low temperature stage exceeding those of the elevated temperature stage.

The two most common causes of hypercalcemia are malignancy and primary hyperparathyroidism (1 degree HPT). The radiographic presentations and the histological findings on bone biopsy are important for differential diagnosis of underlying diseases. We report a patient with hypercalcemia who presented unusual bone manifestations. A 43 y/o woman was admitted due to right femoral fracture. X-ray on the right tibia revealed several osteolytic cystic lesions with sclerotic rims. Blood biochemistry showed anemia, impaired renal function and hypercalcemia. Multiple osteolytic lesions on the skull and bilateral forearms were also noted. Malignancy, such as multiple myeloma or metastatic cancer was suspected. However, this was excluded because of the absence of M-component on serum protein electrophoresis and the negative finding of plasma cells or other malignant cell on bone biopsy examination. Abdominal sonography demonstrated bilateral medullary nephrocalcinosis. The final diagnosis of 1 degree HPT was made, based on the findings of classic pathological pictures (brown tumor) and the markedly elevated intact parathyroid hormone (1267.4 pg/ml) level. Sonography on the neck and 201Tl/99mTc parathyroid subtraction scan localized a left lower parathyroid tumor and fine needle aspiration confirmed the parathyroid origin. Diagnosis of 1 degree HPT could only be made from recurrent urolithiasis and X-ray picture of osteitis fibrosa cystica in the past. This patient presented the full-blown skeletal changes which are uncommonly seen nowadays. The characteristic sclerotic rims suggesting increased bone formation provides a further important clue for differential diagnosis of 1 degree HPT from other malignancies with osteolytic bone lesions.

Neocarzinostatin is an enediyne antitumor antibiotic. Upon attack by a thiol, the enediyne nucleus is cycloaromatized into two stable 1:1 thiol adducts. After analyzing products from various thiols, the chromatographic and spectroscopic characters that associate only with the cyclized aromatic moiety from enediyne nucleus were assigned. Based on HPLC analysis we have derived, products from picomole ranges of the drug sample can be detected. Confirming the type of cycloaromatization at nanomole ranges can be achieved by photodiode array UV spectroscopy. Three-dimensional fluorogram presents ten times more sensitive identification. The method provides a sensitive tool for massive screening study in microscale.

Hereditary nonpolyposis colorectal cancer is associated with defects in DNA mismatch repair. Here, we characterize tumor susceptibility of the recently described Msh2-deficient mouse model. Within the first year of observation, all homozygous mice succumbed to disease, with lymphomas observed in at least 80% of the cases. The majority (70%) of animals 6 months or older developed intestinal neoplasms associated with APC inactivation. Microsatellite instability was more common in carcinomas than in adenomas, but uncommon in normal tissues. Some animals (7%) developed a variety of skin neoplasms analogous to the Muir-Torre syndrome. Msh2-/- mice implicate a direct role for mismatch repair in several neoplasms with striking phenotypic similarities to humans.