Fast instrumental conversion of line frequency fluctuations

Instrumental conversion of fluctuations of electric power system frequency is described, using the well-known properties of instantaneous values of sinusoidal electric quantities and the method of least squares. Digital implementation of the method is proposed. The results of simulation of line frequency fluctuations and their instrumental conversion are presented. Translated from Izmeritel'naya Tekhnika, No. 3, pp. 42–44, March, 1997.     

Surface-enhanced Raman scattering detection of chemical and biological agent simulants

Surface-enhanced Raman scattering spectra of chemical and biological agent simulants, such as dimethyl methylphonate, pinacolyl methylphosphonate, diethyl phosphoramidate, 2-chloroethyl ethylsulfide, bacillus globigii, erwinia herbicola, and bacillus thuringiensis were obtained from silver-oxide film-deposited substrates. Thin AgO films ranging in thickness from 50 to 250 nm were produced by chemical bath deposition onto glass slides. Further Raman intensity enhancements were noticed in UV irradiated surfaces due to photo-induced Ag nanocluster formation, which may provide a possible route to producing highly useful plasmonic sensors for the detection of chemical and biological agents upon visible-light illumination.     

Hole-effective masses in the transport calculation of Si nanowire pMOSFETs

The full-quantum, self-consistent simulation of p-type silicon nanowire field effect transistors based on the k * p method is performed and their device characteristics are examined in the light of the hole-effective masses. An attempt is made in this study to assess the role of the hole-effective masses by devising simple, single-band parabolic effective mass (PEM) Hamiltonians and comparing the transport characteristics with the ones from the k * p method. It is found that the PEM Hamiltonian with isotropic effective masses fails to correctly produce both the scaling behavior of the subthreshold currents and the behavior of the on-currents with respect to the silicon orientation. A modified PEM model with light-hole effective mass in the transport direction and quantization effective mass in the perpendicular direction greatly improve the subthreshold behavior for all the silicon orientations, which shows that the top-most light-hole subband dominantly determines the subthreshold behavior. The modified PEM model however overestimates the on-currents, indicating the limitation of the model.     

The preparation of AI2O3/Ni composites by a powder coating technique

In the present study, nickel particles are coated onto the surface of alumina powder by an impregnation technique. The densification behaviour and the microstructural evolution of the nickel coated alumina powder during sintering are investigated. The strength and the toughness of the resulting Al₂O₃/Ni composites are determined. As the nickel content is less than 13 vol%, fully dense composites can be prepared by pressureless sintering. The matrix grain size decreases as nickel inclusions are added. The strength and the toughness of alumina can be increased by 23 and 42% by adding 5 and 8vol% nickel, respectively. The toughening effect is attributed to plastic deformation of ductile inclusions and crack deflection by the inclusions. The strengthening effect is attributed to microstructural refinement.     

Numerical resolution of the boundary integral equations for elastic scattering by a plane crack

The problem of wave scattering by a plane crack is solved, either in the case of acoustic waves or in the case of elastic waves incidence using the boundary integral equation method. A collocation method is often used to solve that equation, but here we will use a variational method, first writing the problem of Fourier variables, and then writing the associated integrals in the sesquilinear form with weak singularity kernels. This representation is used in the numerical approach, made with a finite element method in the surface of the crack. Numerical tests were made with circular and elliptical cracks, but this method can be extended to other shapes, with the same convergence profiles. Extensive results are given concerning the crack opening displacement, the scattering cross-section, the back-scattered amplitude and far-field patterns.     

Histomorphometric evidence for echistatin inhibition of bone resorption in mice with secondary hyperparathyroidism

Echistatin, an RGD-containing peptide, was shown to inhibit the acute calcemic response to exogenous PTH or PTH-related protein (PTH-rP) in thyroparathyroidectomized rats, suggesting that echistatin inhibits bone resorption. In this study: 1) we present histological evidence for echistatin inhibition of bone resorption in mice with secondary hyperparathyroidism, and show that 2) echistatin binds to osteoclasts in vivo, 3) increases osteoclast number, and 4) does not detectably alter osteoclast morphology. Infusion of echistatin (30 microg/kg x min) for 3 days prevented the 2.6-fold increase in tibial cancellous bone turnover and the 36% loss in bone volume, produced by a low calcium diet. At the light microscopy level, echistatin immunolocalized to osteoclasts and megakaryocytes. Echistatin treatment increased osteoclast-covered bone surface by about 50%. At the ultrastructural level, these osteoclasts appeared normal, and the fraction of cells containing ruffled borders and clear zones was similar to controls. Echistatin was found on the basolateral membrane and in intracellular vesicles of actively resorbing osteoclasts. Weak labeling was found in the ruffled border, and no immunoreactivity was detected at the clear zone/bone surface interface. These findings provide histological evidence for echistatin binding to osteoclasts and for inhibition of bone resorption in vivo, through reduced osteoclast efficacy, without apparent changes in osteoclast morphology.     

Localization and functional analysis of the cytosolic and extracellular CuZn superoxide dismutases in the human parasitic nematode Onchocerca volvulus

This study describes the histological localization of two CuZn superoxide dismutases (SOD1 and SOD2) in the parasitic nematode Onchocerca volvulus, and a functional characterization of the 'extracellular' form of this enzyme (SOD2) which provides evidence that it is involved in the defense against environmental superoxide anion radicals. These essential enzymes are detected in larval and adult stages of the parasite, determined at the mRNA and protein levels by in situ hybridization and immunolocalization studies. These proteins are distributed throughout the worm, at various concentrations with particularly high levels produced in the hypodermis. In vitro maintenance of parasites indicated that SOD2 was secreted outside the parasite into the medium. Baculovirus constructs designed to test the ability of the SOD2 hydrophobic N-terminal region to function in processing and secretion confirmed the ability of this polypeptide sequence to direct the secretion of a marker protein, as well as of the mature SOD2 enzyme. Analyses of the native, mature SOD2 enzyme molecular mass, and the primary and quaternary structure, indicate that unlike other extracellular SODs, the SOD2 is active as a non-glycosylated dimer, rather than as a tetrameric glycoprotein. The detection of SOD2 outside of the parasite maintained in vitro, and the confirmation that the SOD2 is a secreted enzyme, indicate that this enzyme plays a role in the interactive biology of parasitic nematodes with their hosts.     

高炉转型稀土渣盐酸化选除杂工艺研究

稀土转型渣经过化学选矿,在合适的酸度、反应时间和固液比等条件下,稀土渣品位由18.6%提高到31%左右,稀土收率大于98%。