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The influence of a sputter-deposited titanium adhesion layer on glass and Si (1 1 1) substrates with or without exposure of titanium layer surface to the atmosphere on the growth mode of the tantalum films was studied. It was found that, because of the well match of the cell constants between the deposited Ta and the underlying Ti, the tantalum films continuously deposited on the adhesion layer of titanium grown without breaking vacuum always grew with the orientation following that of the bottom titanium layer and nucleated bcc α phase of tantalum with low degrees of orientation. After exposure of the bottom titanium layer surface to atmosphere, the absorption and diffusion of oxygen and other impurity atoms on the surface would promote a higher lever of oxidation and favor to form more and more titanium suboxides at the Ti surface. The increase of titanium suboxides at the Ti surface change the lattice mismatch between the underlying titanium film and the bcc-Ta film, which disturbed the nucleation of α-Ta and promoted the growth of β-Ta. Consequently, the electrical properties of the Ta/Ti bi-layer films were significantly changed.

In order to provide the equivalent of a human anti-human protein antibody as positive control in ELISAs, a goat-human antibody complex was created using chemical cross-linking. The resulting hybrid complex had a larger molecular size on HPLC and SDS-PAGE. In ELISA, the goat-human complex bound to human antigen and was detectable by a secondary anti-human conjugate. The method to make the hybrid complex is simple, cost-effective and can be used to make human-like antibodies to many human proteins.

The topography and size of damage on the surface of HOPG (Highly Oriented Pyrolitic Graphite) bombarded by high fluence (1x10(16) ions/cm(2)) of H+ ions were observed and studied. In this work, 457 STM images of each one with 9x9 nm(2) area were obtained. From 163 of these pictures visible damage was found. In these 163 STM images the diameter of most damage is from 0.2 to 0.8 nm. In this study the number density of visible damage is much less than the ion fluence. The probability of damage is only about 1.8x10(-4). The possible mechanism of damage formation is also analyzed and discussed.

In order to shorten the design cycle of FOPS and improve the pass rate of FOPS laboratory destructive tests, nonlinear finite element methods of elastic-plastic large displacement were presented to simulate the dynamic displacement, velocity and acceleration of drop hammer during impact process, and the dynamic changing law of these parameters during the whole collision were analyzed. At the same time, the stress and deformation of FOPS happened in the collision process were obtained. Associated with changing law of drop hammer parameters, stress and deformation in FOPS, several laboratory destructive impact tests were conducted, and FOPS deformation patterns and failure modes were acquired. The simulation methods for FOPS were proved to be reasonable and can be the guidance of FOPS design and test.

DX center-like traps were detected and characterized by DLTS in the n + -Ga 0.7 Al 0.3 As buffer layers of PIN heterostructures. Their thermal capture barriers were measured by an original method that used the intrinsic superlattice layer as a light source to photoionize the captured electrons. The traps are very close to the conduction band edge, and have a large capture barrier. They are located at 0.04 eV and 0.01 eV under the conduction band.

Theoretically studied current self-oscillations and spatiotemporal current patterns in quantum-well (QW) negative-effective-mass (NEM) p/sup +/pp/sup +/ diodes when the electric field is applied along the direction of the well. The origin of current self-oscillations is the formation and traveling of electric-field domains in the well. In the calculations we have accurately considered scattering contributions from carrier-impurity, carrier-acoustic phonon, and carrier-optic phonon. It is indicated that, both the applied bias and the doping concentration in the well largely influence the current patterns and self-oscillating frequencies, which lie in the THz range for the NEM p/sup +/pp/sup +/ diode having a submicrometer p-base. The NEM p/sup +/pp/sup +/ diode presented here may therefore be used as an electrically tunable THz source.

Trace elements are involved in chronic liver diseases because these elements may have a direct hepatic toxicity or may be decreased as a consequence of the impaired liver function, particularly in patients with alcoholic cirrhosis and/or malnutrition. In this study, we determined plasma and erythrocytes trace elements in 50 inpatients with nonalcoholic chronic liver disease (11 with biopsy-proven chronic hepatitis, 39 with cirrhosis [16 in stage A according to Child-Pugh criteria, 23 Child B+C]), and in a control group of 10 healthy subjects by the proton induced x-ray emission method. The relationship between trace element concentration and the extent of liver damage, the nutritional status (by anthropometric evaluations), and various blood markers of oxidative stress--reduced glutathione, total lipoperoxides and malonyldialdehyde--was investigated. We found that cirrhotics had a significant decrease of Fe, Zn, Se, and GSH levels in the plasma and of GSH and Se in the erythrocytes with respect to the control and chronic hepatitis groups. GSH levels were related to the degree of liver damage; a significant direct correlation was observed among Se, Zn, and GSH plasma values and between GSH and Se in the erythrocytes. The trace element decrease was, on the contrary, independent of the degree of liver function impairment and only partially affected by the nutritional status. Data indicate that liver cirrhosis, even if not alcohol related, induces a decrease of Se and Zn and that, in these patients, an oxidative stress is present, as documented by the significant correlation between Se and GSH. The plasma Br level was higher in cirrhotics with respect to the control and chronic hepatitis groups.

We evaluated the effect of one year of supplementation with iron plus zinc (12 mg/day of Fe+++ and 12.5 mg/day of Zn++), zinc alone (12.5 mg/day of Zn++) and placebo on growth and on the iron, zinc, copper and selenium tissue contents in 30 well-selected children of short stature (16 M and 14 F; 4-11 years old). Before and after supplementation, we measured the concentrations of iron, transferrin, ferritin, zinc and copper in serum, of zinc in erythrocytes and leukocytes, and of zinc, copper and selenium in hair, as well as glutathione peroxidase activity in erythrocytes. Before supplementation, ferritin and serum, erythrocyte and hair zinc contents were significantly lower than in age-matched controls, while the other measured indices were in the normal range. Iron plus zinc supplementation caused an improvement in growth rate in all subjects, i.e., the median Z-score increased from -2.22 +/- 0.45 to -0.64 +/- 0.55; (p < 0.01). In the zinc-supplemented group, only the subjects whose ferritin levels were higher than 20 ng/L before supplementation showed a similar improvement of growth rate. Iron plus zinc supplementation could be a reasonable treatment in short, prepubertal children affected by marginal zinc and iron deficiency.

We have studied the behaviour of electron irradiation induced defects in δ-doping GaAs superlattices, using capacitance-voltage and deep level transient spectroscopy. For the planar doping used (10 11 SSi cm −2 ) with a distance of 70 a between each plane, we observed a delocalization of the carriers, in agreement with theoretical calculation. The defects created by the irradiation are identical to the defects created in bulk GaAs. However, we observed in addition two new defects which are tentatively ascribed to a complex formed between the silicon dopant and the arsenic vacancy.

We first show how the characteristical properties of defects (energy level capture cross-sections) in systems such as single heterostructures and superlattices can be deduced from the corresponding properties in a bulk material. Concluding that these characteristics can be obtained once the band structure of the system is known we discuss as illustration the problems encountered with the two principal defects present in GaAs and related alloys namely the EL2 defect and the DX center.

We describe how the electrical characteristics (energy level in the gap, electron capture cross section) a defect has in a bulk material are modified when this defect is placed in the well or the barrier of a superlattice. The relations between these characteristics we deduce are verified in GaAs-GaAlAs superlattices using electron irradiation induced defects as test. The implications of these considerations to the characterization of deep levels in superlattices as well as of the superlattices themselves are discussed.

In Si doped GaAlAs layers and two different types of GaAs-AlAs superlattices grown by molecular beam epitaxy we detect using deep level transient spectroscopy the DX center. The energetical location of the DX level is compared to the band structures of these superlattices allowing us to conclude that the DX state is linked to the L band.

Transient capacitance spectroscopy can be used to characterize superlattices and the defects they contain. Here, we describe the measurement of electron capture cross-sections of deep levels introduced by electron irradiation. The variation of the capture rate versus temperature indicates that this capture occurs through a multiphonon emission process whose characteristics can be predicted in taking into account the superlattice band structure.

The capture kinetics of electrons on DX centers are interpreted in terms of a simple model taking only into account the fact that the concentrations of the DX centers and of the doping impurities are equal. It is shown that there is no need to introduce an alloying effect in order to explain the capture as well as the emission kinetics, in agreement with the nonobservation of this effect in optical transitions. This is understood if the DX center is itself the donor impurity.

We present data which show that electron emission from the DX center is sensitive to the Poole-Frenkel effect. We demonstrate that this result implies that the DX center is an L effective-mass state of the donor impurity accompanied by a small lattice relaxation. We show that all the observations so far obtained on this center are in agreement with this model.