Small-signal equivalent ? networks for carrier generation?recombination?trapping at imperfection centres in semiconductors

A ? network for carrier generation?recombination?trapping processes under arbitrary steady-state conditions is obtained, which has the following features which are useful for computer calculations of the admittance functions of semiconductor devices: the admittances are positive real, the voltage-controlled current sources are connected between the hole and electron quasi-Fermi potential nodes, and the current sources vanish at zero external excitation.     

Exact large-signal lumped-network representation of a semiconductor

An exact 1-lump integral representation of a semiconductor layer of thickness w and its circuit model are obtained for large-signal and arbitrary steady-state levels. The dielectric capacitance is isolated from the distributed network. The application to p-n junctions is given as an illustration.     

Microstructure and creep resistance of a diffusionally aluminized Ni-base superalloy

An aluminide layer was formed on a wrought Ni-base superalloy by the diffusional aluminizing method, which involves a physical vapor deposition of Al followed by two-step heat treatment in vacuum. Microstructural analysis revealed the presence of an aluminide layer, inter-diffusion zone (IDZ), and affected substrate, all of which developed due to the inter-diffusion of deposited Al and elements in the matrix. In addition, a wide carbide free zone, in which grain boundaries were mostly denuded of carbides, was found below the IDZ. Depth profiling analysis using a glow discharge spectrometer confirmed the reduced carbon content in the carbide free zone. At 900 °C, the diffusionally aluminized specimens showed a decrease in creep-rupture life caused by the presence of the carbide free zone. Fracture surface and cross-section microstructure observation confirmed the detrimental effect of the carbide free zone on the creep resistance of the diffusionally aluminized Alloy 617.     

Senescence mutants of Saccharomyces cerevisiae with a defect in telomere replication identify three additional EST genes

The primary determinant for telomere replication is the enzyme telomerase, responsible for elongating the G-rich strand of the telomere. The only component of this enzyme that has been identified in Saccharomyces cerevisiae is the TLC1 gene, encoding the telomerase RNA subunit. However, a yeast strain defective for the EST1 gene exhibits the same phenotypes (progressively shorter telomeres and a senescence phenotype) as a strain deleted for TLC1, suggesting that EST1 encodes either a component of telomerase or some other factor essential for telomerase function. We designed a multitiered screen that led to the isolation of 22 mutants that display the same phenotypes as est1 and tlc1 mutant strains. These mutations mapped to four complementation groups: the previously identified EST1 gene and three additional genes, called EST2, EST3 and EST4. Cloning of the EST2 gene demonstrated that it encodes a large, extremely basic novel protein with no motifs that provide clues as to function. Epistasis analysis indicated that the four EST genes function in the same pathway for telomere replication as defined by the TLC1 gene, suggesting that the EST genes encode either components of telomerase or factors that positively regulate telomerase activity.     

Influence of temperature on threshold stress for reorientation of hydrides and residual stress variation across thickness of Zr-2.5Nb alloy pressure tube

Threshold stress, σ_th, for reorientation of hydrides in cold worked and stress-relieved (CWSR) Zr-2.5Nb pressure tube material was determined in the temperature range of 523-673 K. Using tapered gage tensile specimen, mean value of σ_th was experimentally determined by two methods, half thickness method and area compensation method. The difference between local values of σ_th measured across the thickness of the tube and the mean σ_th values yielded the residual stress variation across the tube thickness. It was observed that both the mean threshold stress and residual stress decrease with increase in reorientation temperature. Also, the maximum value of residual stresses was observed near the midsection of the tube.     

Interface edge effect and its contribution to the frequency dispersion of metal-oxide-semiconductor admittance

Room temperature frequency dispersion of the admittance of Metal-Oxide-Semiconductor (MOS) capacitors made on non-degenerate n-type silicon substrate with (111) surface orientation was studied. A simplified lumped equivalent circuit model which takes into account the interface edge effect, i.e. carrier generation-recombination-trapping via interface states near the edge of the surface inversion region, is proposed and found to be in good agreement with experimental data. Our model also suggests another method of calculating the density of interface states. Fundamental properties of interface states are estimated from experimental data. A self-consistency check is made among the values of equivalent circuit elements to substantiate our model.     

MOS Capacitance–Voltage Characteristics: IV. Trapping Capacitance from 3-Charge-State Impurities

Metal-Oxide-Semiconductor Capacitance-Voltage (MOSCV) characteristics containing giant carrier trapping capacitances from 3-charge-state or 2-energy-level impurities are presented for not-doped, n-doped, p-doped and compensated silicon containing the double-donor sulfur and iron, the double-acceptor zinc, and the amphoteric or one-donor and one-acceptor gold and silver impurities. These impurities provide giant trapping capacitances at trapping energies from 200 to 800 meV (50 to 200 THz and 6 to 1.5 μm), which suggest potential sub-millimeter, far-infrared and spin electronics applications.     

Soluble‐eggshell‐membrane‐protein‐modified porous silk fibroin scaffolds with enhanced cell adhesion and proliferation properties

In this study, a porous silk fibroin (SF) scaffold was modified with soluble eggshell membrane protein (SEP) with the aim of improving the cell affinity properties of the scaffold for tissue regeneration. The pore size and porosity of the prepared scaffold were in the ranges 200–300 μm and 85–90%, respectively. The existence of SEP on the scaffold surface and the structural and thermal stability were confirmed by energy‐dispersive X‐ray spectroscopy, X‐ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. The cell culture study indicated a significant improvement in the cell adhesion and proliferation of mesenchymal stem cells (MSCs) on the SF scaffold modified with SEP. The cytocompatibility of the SEP‐conjugated SF scaffold was confirmed by a 3‐(4,5‐dimethyltriazol‐2‐y1)‐2,5‐diphenyl tetrazolium assay. Thus, this study demonstrated that the biomimic properties of the scaffold could be enhanced by surface modification with SEP. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40138.