A study of hillock formation on Al---Ta alloy films for interconnections of TFT-LCDs

The relationship between hillock formation and microstructure was studied in Al---Ta alloy films for interconnections of thin-film transistor-liquid-crystal displays. In-situ scanning electron microscopy observation of hillock formation, transmission electron microscopy studies of microstructures of both the hillock and film, and in-situ stress measurements during isothermal annealing were carried out on Al-2at.%Ta alloy films deposited on glass substrates by d.c. magnetron sputtering. Hillock size increased with annealing temperature and time during variable temperature and isothermal annealing, respectively. Macroscopic hillock number density saturated soon after the appearance of hillocks. New hillocks were observed on the outer perimeter of old hillocks. The distance between hillocks ranged from 20 μm to 100 μm, an extremely large distance in comparison with the grain size. The relationship between hillock formation and microstructures on Al---Ta alloy films can be explained by a model in which hillock formation due to lateral diffusion, i.e. diffusion in the film plane, results in compressive stress relaxation in a large area around the hillock. The fine-grained film structure caused by the addition of Ta plays an important role in reducing hillock density.     

Activation of complement in quails bearing Rous sarcoma virus-induced tumors

The concentration of serum C3 in quails bearing tumors induced by Rous sarcoma virus (RSV) was elevated in parallel with tumor growth, whereas serum C3 levels in quails inoculated with avian leukosis virus, which lacks transforming activity, showed a pattern similar to that in mock-infected quails. C3 deposition was also observed in almost all tumor cells at the tumor developing stage. These findings obtained in vivo suggest that the cells transformed by RSV activated the C3 on their surfaces.     

Molecular Dynamics Study of Na-Si-O-N Oxynitride Glasses

The structure and properties of Na-Si-O-N oxynitride glasses have been studied by molecular dynamics calculations using a pair potential of the Busing approximation of the Born-Mayer-Huggins type. Nitrogen atoms bonded to one, two, and three silicon atoms coexist in the glass structure. The mean of the number of silicon atoms bonded to a nitrogen atom ranges from 2.4 to 2.1, decreasing with increasing Na₂O content from 15 to 30 mol%. It has been assumed that nitrogen atoms bonded to two or fewer silicon atoms are formed when nitrogen atoms substitute for non-bridging atoms. The bond angle ∠Si-N-Si exhibits a bimodal distribution around 105–135° and 140–170°, roughly corresponding to the nitrogen atoms bonded to three and two silicon atoms, respectively. The dependences of the density, the bulk thermal expansion, and the bulk modulus on the nitrogen content are consistent with those observed in real systems.     

Reduction of n-C5H11N3 Catalyzed by [Mo2Fe6S8(OMe)3(SC6H4-p-n-C8H17)6]3– in an Aqueous Micellar Solution

Reduction of n-C₅H₁₁N₃ by Na₂S₂O₄ was performed in the presence of (n-Bu₄N)₃ [Mo₂Fe₆S₈(OMe)₃(SC₆H4-p-n-C₈H₁₇)₆] ((n-Bu₄N)₃ [Mo-Fe]) as a catalyst in aqueous Triton X-100 micellar solutions. The rate of the reduction is enhanced efficiently by the addition of methyl viologen (MV²⁺). The methyl viologen radical cation (MV⁺) produced by the reaction of MV²⁺ with Na₂S₂O₄ undergoes a disproportionation reaction to afford MV²⁺ and MV° in the micellar solution. The resultant MV° formed in the micelle transfers two electrons to [Mo-Fe]³⁻ effectively to give [Mo-Fe]⁵⁻, which reduces n-C₅H₁₁N₃ with two electrons to produce n-C₅H₁₁NH₂ and N₂.     

Breakdown Process in Rod-to-Plane Gaps with DC Voltages

The breakdown process in rod-to-plane gaps, of which gap spacings were up to 80 cm under dc voltage, was investigated with multiple techniques using an image converter camera, five photomultipliers, and two still cameras, as well as with the measurements of voltage and current. The combination of a photomultiplier with an image converter camera allowed us to view for the first time the leader development with dc voltage. It is shown that breakdown proceeds, after well-known corona discharges, through streamers bridging the gap, leader development, and their bridging the gap to induce the intense return ionizing waves, to lead the formation of a spark channel. The charge density was estimated to be 2.7-24.5 pC/cm in corona discharges for the applied voltage of 170-410 kV and to be on the order of 10-8 C/ cm in the leader head.     

Natriuretic peptide family as a novel antimigration factor of vascular smooth muscle cells

Vascular smooth muscle cell (SMC) migration is proposed to be an important process in the initiation and/or progression of atherosclerosis. The present study examined the effects of the natriuretic peptide family (atrial, brain, and C-type natriuretic peptides; ANP, BNP, and CNP) on the migration of cultured rat SMCs, using Boyden's chamber methods. Fetal calf serum (FCS) and platelet-derived growth factor (PDGF)-BB potently stimulated SMC migration. Rat ANP(1-28), rat BNP-45, and rat CNP-22 clearly inhibited SMC migration stimulated with FCS or PDGF-BB in a concentration-dependent manner. CNP-22 had the most potent inhibitory effect compared with other natriuretic peptides. When PDGF-BB-induced migration was separated into chemotactic and chemokinetic activities, the chemotactic component was strongly inhibited by these natriuretic peptides. Such inhibition by these natriuretic peptides was paralleled by an increase in the cellular level of cyclic GMP. The addition of a cyclic GMP analogue, 8-bromo cyclic GMP, and an activator of the cytosolic guanylate cyclase, sodium nitroprusside, significantly inhibited FCS- and PDGF-BB-stimulated migration in a concentration-dependent manner. These results suggest that natriuretic peptides, especially CNP-22, inhibit FCS- or PDGF-BB-stimulated SMC migration at least in part through a cyclic GMP-dependent process. Thus, the natriuretic peptide family may play a role as an antimigration factor of SMCs under certain circumstances.     

Revolving magnet wheels with permanent magnets

A new type of actuator with both magnetic levitation and linear drive is proposed. The actuator, called magnet wheel, has a rotating magnetic field obtained by revolving permanent magnets with high coercivity mechanically. The induction repulsive-type magnetic lift force with self-stabilization can be obtained by linking the rotating flux to a conducting plate. The induced simultaneous drag torque, which causes power loss, is used to obtain thrust in two proposed ways. These are called “tilt type” and “partial overlap type,” respectively. In the tilt type, the magnet wheel is tilted against the surface of a conducting plate. In the partial overlap type, the magnet wheel operates near the edge of a conducting plate. In this paper, the fundamentals of the structure of proposed magnet wheels are described. The basic characteristics at parallel to the conductor are shown by using a numerical three-dimensional electromagnetic analysis and measured results. The generation of both lift force and thrust in tilt type and partial overlap type magnet wheel are proved by experiments, respectively.     

Formation of a thin III-VI compound interfacial layer at ZnTe/znse heterojunction and its effect on energy band discontinuity

Interfacial layers were inserted at the interface of ZnSe and ZnTe in order to reduce both (1) the effect of strain and (2) the valence band discontinuity. The interfacial layer adapted in this study is the III-VI compound (Ga,Se). The layered structure GaSe is favorable for the present work, because it can be a buffer layer to relax the lattice mismatch at the interface. All layers including ZnTe, (Ga,Se) and ZnSe were grown on (100) GaAs substrate by conventional molecular beam epitaxy. The crystal structure of the (Ga,Se) on ZnSe was investigated. The growth of the layered structure GaSe layer on (100) ZnSe was very difficult, though the defect zinc-blende structure Ga₂Se₃ layer could be easily grown. The defect zinc-blende structure Ga₂Se₃ was inserted at the interface of ZnSe and ZnTe so that the valence band discontinuity could be modified. The discontinuity was decreased to about 0.1 eV when the thickness of the interfacial layer was about 8Å. The current-voltage characteristics were measured for the sample with Ga₂Se₃ interfacial layer. The structure with Ga₂Se₃ exhibited the ohmic property. These results suggest that the valence band discontinuity between ZnTe and ZnSe can be reduced by introducing the Ga₂Se₃ interfacial layer.