Apoptotic cells induce immunosuppression through dendritic cells: Critical roles of IFN-gamma and nitric oxide

Apoptotic cells induce immunosuppression through unknown mechanisms. To identify the underlying molecular mediators, we examined how apoptotic cells induce immunoregulation by dendritic cells (DC). We found that administration of DC exposed to apoptotic c

Changes of tissue endothelin-1 and nitric oxide synthase in a sheep model of large intestinal obstruction

Large intestinal obstruction (LIO) in farm animals can cause a ischaemic necrosis of intestinal tissue, eventually leading to death. The roles of endothelin-1 (ET-1) and nitric oxide (NO) are not well understood in the process of LIO, but evidence suggests that endothelial-derived mediators may participate. In the present study, ET-1 concentration and total nitric oxide synthase (NOS) activity were measured in heart, liver, pancreas, lung and kidney in a model of LIO in sheep. Our data demonstrated that ET-1 concentration and NOS activity were altered, with significant increases of ET-1 in heart, lung and kidney and of NOS activity in pancreas and kidney, but a marked decline of NOS activity in liver (p<0.05). It is postulated that these alterations in NOS activity and ET-1 concentration may contribute to the progressive loss of organ function, and finally lead to death in LIO in sheep.

Fracture Properties of LPCVD Silicon Nitride and Thermally Grown Silicon Oxide Thin Films From the Load-Deflection of Long Si3N4 and SiO2/Si3N4 Diaphragms

The bulge test is successfully extended to the determination of the fracture properties of silicon nitride and oxide thin films. This is achieved by using long diaphragms made of silicon nitride single layers and oxide/nitride bilayers, and applying comprehensive mechanical model that describes the mechanical response of the diaphragms under uniform differential pressure. The model is valid for thin films with arbitrary z-dependent plane-strain modulus and prestress, where z denotes the coordinate perpendicular to the diaphragm. It takes into account the bending rigidity and stretching stiffness of the layered materials and the compliance of the supporting edges. This enables the accurate computation of the load-deflection response and stress distribution throughout the composite diaphragm as a function of the load, in particular at the critical pressure leading to the fracture of the diaphragms. The method is applied to diaphragms made of single layers of 300-nm-thick silicon nitride deposited by low-pressure chemical vapor deposition and composite diaphragms of silicon nitride grown on top of thermal silicon oxide films produced by wet thermal oxidation at 950 degrees C and 1050 degrees C with target thicknesses of 500, 750, and 1000 mn. All films characterized have an amorphous structure. Plane-strain moduli E-ps and prestress levels sigma(0) of 304.8 +/- 12.2 GPa and 1132.3 +/- 34.4 MPa, respectively, are extracted for Si3N4, whereas E-ps = 49.1 +/- 7.4 GPa and sigma(0) = -258.6 +/- 23.1 MPa are obtained for SiO2 films. The fracture data are analyzed using the standardized form of the Weibull distribution. The Si3N4 films present relatively high values of maximum stress at fracture and Weibull moduli, i.e., sigma(max) = 7.89 +/- 0.23 GPa and m = 50.0 +/- 3.6, respectively, when compared to the thermal oxides (sigma(max) = 0.89 +/- 0.07 GPa and m = 12.1 +/- 0.5 for 507-nm-thick 950 degrees C layers). A marginal decrease of sigma(max) with thickness is observed for SiO2, with no significant differences between the films grown at 950 degrees C and 1050 degrees C. Weibull moduli of oxide thin films are found to lie between 4.5 +/- 1.2 and 19.8 +/- 4.2, depending on the oxidation temperature and film thickness.

Influence of electron irradiation on hydrothermally grown zinc oxide single crystals

The resistivity of hydrothermally grown ZnO single crystals increased from similar to 10(3) Omega cm to similar to 10(6) Omega cm after 1.8 MeV electron irradiation with a fluence of similar to 10(16) cm(-2), and to similar to 10(9) Omega cm as the fluence increased to similar to 10(18) cm(-2). Defects in samples were studied by thermally stimulated current (TSC) spectroscopy and positron lifetime spectroscopy (PLS). After the electron irradiation with a fluence of 10(18) cm(-2), the normalized TSC signal increased by a factor of similar to 100. A Zn vacancy was also introduced by the electron irradiation, though with a concentration lower than expected. After annealing in air at 400 degrees C, the resistivity and the deep traps concentrations recovered to the levels of the as-grown sample, and the Zn vacancy was removed.

Multiple valley couplings in nanometer Si metal-oxide-semiconductor field-effect transistors

We investigate the couplings between different energy band valleys in a metal-oxide-semiconductor field-effect transistor (MOSFET) device using self-consistent calculations of million-atom Schrodinger-Poisson equations. Atomistic empirical pseudopotentials are used to describe the device Hamiltonian and the underlying bulk band structure. The MOSFET device is under nonequilibrium condition with a source-drain bias up to 2 V and a gate potential close to the threshold potential. We find that all the intervalley couplings are small, with the coupling constants less than 3 meV. As a result, the system eigenstates derived from different bulk valleys can be calculated separately. This will significantly reduce the simulation time because the diagonalization of the Hamiltonian matrix scales as the third power of the total number of basis functions. (C) 2008 American Institute of Physics.

A comparison of silicon oxide and nitride as host matrices on the photoluminescence from Er3+ ions

This paper compares the properties of silicon oxide and nitride as host matrices for Er ions. Erbium-doped silicon nitride films were deposited by a plasma-enhanced chemical-vapour deposition system. After deposition, the films were implanted with Er3+ at different doses. Er-doped thermal grown silicon oxide films were prepared at the same time as references. Photoluminescence features of Er3+ were inspected systematically. It is found that silicon nitride films are suitable for high concentration doping and the thermal quenching effect is not severe. However, a very high annealing temperature up to 1200 degrees C is needed to optically activate Er3+ which may be the main obstacle to impede the application of Er-doped silicon nitride.

Quantum mechanical simulation of nanosized metal-oxide-semiconductor field-effect transistor using empirical pseudopotentials: A comparison for charge density occupation methods

The atomistic pseudopotential quantum mechanical calculations are used to study the transport in million atom nanosized metal-oxide-semiconductor field-effect transistors. In the charge self-consistent calculation, the quantum mechanical eigenstates of closed systems instead of scattering states of open systems are calculated. The question of how to use these eigenstates to simulate a nonequilibrium system, and how to calculate the electric currents, is addressed. Two methods to occupy the electron eigenstates to yield the charge density in a nonequilibrium condition are tested and compared. One is a partition method and another is a quasi-Fermi level method. Two methods are also used to evaluate the current: one uses the ballistic and tunneling current approximation, another uses the drift-diffusion method. (C) 2009 American Institute of Physics. [doi:10.1063/1.3248262]

Single-electron multiple-valued memory using ultra-small floating gate metal-oxide-semiconductor field effect transistor

This paper proposes a novel single-electron multiple-valued memory. It is a metal-oxide-semiconductor field effect transistor (MOS)-type memory with multiple separate control gates and floating gate layer, which consists of nano-crystal grains. The electron can tunnel among the grains (floating gates) and between the floating gate layer and the MOS channel. The memory can realize operations of 'write', 'store' and 'erase' of multiple-valued signals exceeding three values by controlling the single electron tunneling behavior. We use Monte Carlo method to simulate the operation of single-electron four-valued memory. The simulation results show that it can operate well at room temperature.

Properties of high k gate dielectric gadolinium oxide deposited on Si(100) by dual ion beam deposition (DIBD)

Gadolinium oxide thin films have been prepared on silicon (100) substrates with a low-energy dual ion-beam epitaxial technique. Substrate temperature was an important factor to affect the crystal structures and textures in an ion energy range of 100-500 eV. The films had a monoclinic Gd2O3 structure with preferred orientation ((4) over bar 02) at low substrate temperatures. When the substrate temperature was increased, the orientation turned to (202), and finally, the cubic structure appeared at the substrate temperature of 700 degreesC, which disagreed with the previous report because of the ion energy. The AES studies found that Gadolinium oxide shared Gd2O3 structures, although there were a lot of oxygen deficiencies in the films, and the XPS results confirmed this. AFM was also used to investigate the surface images of the samples. Finally, the electrical properties were presented. (C) 2004 Elsevier B.V. All rights reserved.

Chemical liquid phase deposition of thin aluminum oxide films

Thin aluminum oxide films were deposited by a new and simple physicochemical method called chemical liquid phase deposition (CLD) on semiconductor materials. Aluminum sulfate with crystallized water and sodium bicarbonate were used as precursors for film growth, and the control of the system's pH value played an important role in this experiment. The growth rate is 12 nm/h with the deposition at [Al-2(SO4)(3)]=0.0837 mol.L-1, [NaHCO3]=0.214 mol.L-1, 15 degreesC. Post-growth annealing not only densifies and purifies the films, but results in film crystallization as well. Excellent quality of Al2O3 films in this work is supported by electron dispersion spectroscopy, Fourier transform infrared spectrum, X-ray diffraction spectrum and scanning electron microscopy photograph.

Characteristics of oxide-free InGaAlAs layers grown by narrow stripe selective MOVPE

Narrow stripe selective MOVPE has been used to grow high quality oxide-free InGaAlAs layers on an InP substrate patterned with SiO2 masks at optimized growth conditions. Mirror-like surface morphologies and abrupt cross sections are obtained in all samples without spike growth at the mask edge. For the narrow stripe selectively grown InGaAlAs layers with a mesa width of about 1.2 mu m, a bandgap wavelength shift of 70 nm, a photoluminescence (PL) intensity of more than 80% and a PL full width at half maximum (FWHM) of less than 60 meV are obtained simultaneously with a small mask width variation from 0 to 40 mu m. The characteristics of the thickness enhancement ratio and the PL spectrum dependence on the mask width are presented and explained by considering both the migration effect from a masked region and the lateral vapour diffusion effect.