Structural Characterization of Porous Silicon Fabricated by Electrochemical and Chemical Dissolution of Si Wafers

The structure of porous silicon exhibiting efficient visible photoluminescence has been characterized by using Fourier transformed infrared absorption, Raman scattering and x-ray diffraction. It is shown that the lattice spacing in the porous Si layer expands by about 0.3% in the direction perpendicular to the surface and also a partially disordered structure is existing. Electron beam irradiation causes desorption of hydrogen and fluorine bonds which terminate the surface, resulting in the quenching of the visible luminescence. The chemical etching of such layer has led to complete recovery of the luminescence intensity as well as the hydrogen and fluorine bonds termination.

First-principles study of blue silicate phosphors

First-principles calculations were performed to investigate the optical property of blue silicate phosphor, CMS:Eu. The optical absorption property is discussed based on electronic band structure and density of states. Our calculation results indicate that hybridization of the wavefunction plays an important role for nonradiative migration of electrons and holes. The calculated optical absorption spectrum could reproduce the optical features of the experimental excitation spectrum. It is also demonstrated that a practical approach using computational materials screening is effective in phosphor materials development.

[Simulation of thoracoscopic esophagectomy for esophageal cancer by three-dimensional computed tomography and usefulness for preservation of bronchial arteries]

Thoracoscopic esophagectomy for esophageal cancer was simulated preoperatively by 3-dimensional computed tomography (3D-CT). The anatomical structures such as major vessels, bone, trachea and bronchi, esophagus, lymph nodes, and broncial arteries were extracted from multi-detector row CT scanning and integrated to build the virtual operative field by multi-volume fusion. The virtual thoracoscopy was helpful to understand the location of lymph nodes and bronchial arteries in relation to the adjacent anatomical structures. Preservation of bronchial arteries is important to avoid tracheobronchial ischemia which is a fatal complication in salvage esophagectomy after definitive chemoradiotherapy. 3D-CT revealed anatomical variations of bronchial arteries and was useful for identification and preservation of bronchial arteries in thoracoscopic esophagectomy.

The effects of seasonal and interannual variability of oceanic structure in the western Pacific North Equatorial Current on larval transport of the Japanese eel Anguilla japonica

As the North Equatorial Current (NEC)-bifurcation is known to be related to El Niño-Southern Oscillation (ENSO) events, the influence of the position of the NEC bifurcation on transport success of the larval Japanese eel Anguilla japonica was investigated. Using a Lagrangian modelling approach, larval transport was simulated and the relative influence of El Niño and La Niña events and the NEC-bifurcation position on the success of particle transport analysed. The number of particles transported from the NEC to the Kuroshio tended to be lowest during El Niño years, and differences between La Niña and regular years were small. The transport success observed in simulations showed some relationships to annual A. japonica glass eel recruitment to Tanegashima Island over 1993 to 2001, but not in 2002. The study shows that particle tracking simulations can be used to improve knowledge of the oceanic migration of A. japonica but further studies are required, including comparisons with the effects on larval survival of fluctuations in temperature and food availability.

Behavior of solutions of the Hodgkin-Huxley equations and its relation to properties of mechanoreceptors

The membrane current in the Hodgkin-Huxley equations is considered to be a stimulus to the membrane and the responses to the simulus are numerically calculated. Responses of the Hodgkin-Huxley model to an alternating current superimposed upon a constant bias current show qualitative analogy to responses of biological mechanoreceptors. The intensity of the bias current seems to correspond to the degree of adaptation of actual receptors.

[Perioperative management and prevention of complication for salvage esophagectomy after definitive chemoradiotherapy]

Salvage esophagectomy has been increasing as a second-line treatment after failure of definitive chemoradiotherapy (CRT) for esophageal cancer. A number of patients who have received CRT, especially those who have residual tumors and shorter waiting times until operation, have developed malnutrition and problems in their immunologic condition because of decreasing oral intake and bone marrow suppression. Because high-dose radiation causes inflammation, fibrosis and peripheral circulatory disturbance of various tissues in the treatment fields, salvage surgery can be a technically difficult operation. In our previous experience, postoperative complications of salvage esophagectomy are more frequent and more serious than that of planned esophagectomy. For example, we have experienced necrosis of the reconstructed gastric tube, esophago-tracheal fistula, mediastinal abscess, hard-to-treat acute respiratory distress syndrome (ARDS) and so on. In particular, respiratory tract necrosis or perforation is the most critical complication and frequently becomes lethal. Patients who undergo a salvage esophagectomy have a significantly higher risk of pulmonary and cardiac complication, and have high rates of repeated surgery. Rapid diagnosis and appropriate treatment of complications are necessary to reduce postoperative mortality. To improve the overall outcome, it is very important to better understand the condition of patients after CRT, so appropriate surgery can be carefully planned. Furthermore, it is absolutely essential to perform the operation with great care and to meticulously manage the perioperative care for salvage esophagectomy.

A quantitative method for estimating hepatic blood flow using a dual-input single-compartment model

The purpose of this study was to investigate the accuracy of a quantitative method for estimating arterial hepatic blood flow and portal hepatic blood flow separately using a dual-input single-compartment model compared with the maximum slope method using computer simulations and clinical data. In computer simulations, the rate constants for the transfer of contrast agent (CA) from the hepatic artery to the liver (K(1a)), from the portal vein to the liver (K(1p)) and from the liver to the blood (k(2)) were estimated from simulated time-density curves with various transit times of CA from the aorta to the liver (tau(a)) and from the portal vein to the liver (tau(p)) using the linear least-squares (LLSQ) method. In clinical studies, dynamic CT data were acquired from 27 patients, and parametric maps of K(1a), K(1p) and k(2) were generated by applying the LLSQ method pixel by pixel. In simulation studies, tau(a) and tau(p) were found to have a large and a small effect on the estimates of K(1a) and K(1p), respectively. In clinical studies, the K(1a) and K(1p) values estimated with the maximum slope method were underestimated by 60+/-29% and 37+/-12%, respectively, compared with those estimated by the LLSQ method. In conclusion, our results suggest that correction of tau(a) is necessary for accurately estimating K(1a) and K(1p). Our method is therefore promising for the evaluation of hepatic blood flow in various liver diseases because it allows us to evaluate arterial hepatic blood flow and portal hepatic blood flow separately and visually.

Pdx-1-independent differentiation of mouse embryonic stem cells into insulin-expressing cells

To investigate whether insulin-producing cells obtained from ES cells via the nestin-positive cell-mediated method are of the pancreatic lineage, we established a pdx-1 knockout ES cell line and analyzed its differentiation into insulin-producing cells. As a result, pdx-1 knockout ES cell expressed insulin 2 gene at the final differentiated cells. Thus, our study demonstrated that pdx-1 is not essential for insulin gene expression, at least in cells differentiated from this population of nestin-expression enriched ES cells, and suggested that the insulin-producing cells derived from ES cells may be different from the pancreatic beta cells in terms of their lineage.

Calcium signalling during mammalian fertilization

The fertilized mammalian egg is a nice model system for analysing spatiotemporal Ca2+ signalling in the intact cell. Hamster eggs show repetitive Ca2+ transients, associated in the initial response with Ca2+ waves which begin from the site of sperm attachment and are propagated across the deep cytoplasm to the opposite pole. In unfertilized eggs, a regenerative Ca2+ wave is induced by injection of either inositol 1,4,5-trisphosphate (InsP3) or Ca2+, and Ca2+ oscillations are produced by continuous injection of InsP3. These Ca2+ waves and oscillations in both fertilized and unfertilized eggs are inhibited in a dose-dependent manner by a monoclonal antibody to the type 1 InsP3 receptor. Ryanodine receptors (both skeletal and cardiac types) are not detected by physiological or immunoblot analyses. Positive and negative feedback between cytosolic Ca2+ and Ca2+ release from InsP3-sensitive pools accounts for the spatiotemporal Ca2+ signalling. In addition to intracellular Ca2+ release, Ca2+ entry from outside the egg is necessary to refill the Ca2+ pools and maintain Ca2+ oscillations. Evidence suggests that inositol 1,3,4,5-tetrakisphosphate activates the Ca2+ influx. The signal transduction process leading to the production of InsP3 and the mechanism of egg activation following the Ca2+ response still remain to be elucidated.