Control of ultrafine microstructure by single-pass heavy deformation and cold forging of metal

A hot extrusion system with controlled cooling is investigated in this study. This system is used with the aim of manufacturing steel and other metal products with ultrafine microstructures by single-pass heavy deformation followed by controlled cooling. The continuous formation of bulk materials with the desired geometry and microstructure could be realized using the proposed system or by adding hot rolling stands after processing using the proposed system. Microstructure evolution during and after heavy single-pass deformation is examined through a series of experiments involving the hot extrusion of plain carbon steel followed by controlled cooling. The effects of severe plastic deformation on grain refinement and the mechanical properties of the formed products are discussed. It is clear that the use of the proposed system is helpful for the grain refinement of a cast microstructure. Also, ultrafine-grain steel with a grain diameter of 3 μm can be formed using the proposed system. Finally, the formability of the ultrafine-grain steel manufactured using the proposed system is examined by a cold-forging experiment.     

Physical random number generator based on MOS structure after soft breakdown

We present a novel physical random number generator (RNG) that uses a metal-oxide semiconductor (MOS) capacitor after soft breakdown (SBD) as a random source. It is known that the electrical properties of MOS capacitors after SBD show large fluctuation. When the resistor in an astable multivibrator is replaced with an MOS capacitor after SBD, the multivibrator converts the noise signal into a rectangular wave whose period fluctuates randomly. A 1-bit counter and a flip-flop are used to generate random numbers from the fluctuating rectangular wave. Some high-level tests indicate that the generated random numbers have excellent quality for cryptographic applications. Even though our circuit is small and can be constructed using about 20 complementary-MOS logic gates and several passive devices, high-quality random numbers such as those generated by large physical RNGs can be obtained.     

Selective oxidation of methanol in exhaust gas containing aromatic compounds

The activity of exhaust catalysts of methanol and gasoline mixture fueled automobiles is inhibited by coexistent aromatic compounds contained in the exhaust stream. One approach to avoid this inhibition could be the utilization of a molecular-sieve effect. It seems probable that the migration of aromatic compounds, which have larger molecular sizes than that of methanol, will be blocked by these supports and methanol will selectively reach the active sites of the catalysts. Thus, we examined the simultaneous oxidation of methanol and toluene over some ion-exchanged Pt/zeolite catalysts. Experimental results showed that ion-exchanged Pt/zeolite catalysts are less affected by coexistent toluene and have a higher selectivity for methanol oxidation compared with an alumina-supported platinum catalyst, suggesting that the use of these catalysts is effective for oxidizing methanol in the exhaust stream containing aromatic compounds. Among the catalysts tested, a Pt/H-MOR catalyst was found to be the most effective for the oxidation of methanol and effectively catalyzed the reaction in the presence of toluene even at low temperature.     

Subacute multifocal painful neuropathy with spontaneous remission

We present the cases of two patients with subacute onset of multifocal painful neuropathy with spontaneous remission and no relapse. The distribution of pain in patient 1 was hands (median > ulnar nerve region) and feet (peroneal and terminal tibial nerve regions), and in patient 2, hands (ulnar nerve region) and feet, left worse than in right. Both patients experienced facial numbness. Deep tendon reflexes were intact except for absent ankle jerks in patient 2. Motor nerve conduction studies demonstrated a marked prolongation of the distal motor latencies with normal proximal segment conduction velocities, suggesting distal demyelination. Cerebrospinal fluid protein concentration was elevated in patient 2, but no definite abnormality was found on sural nerve biopsy. A demyelinating neuropathy with a monophasic self-limited course may be consistent with Guillain-Barre syndrome (GBS). However, the multifocal painful sensory symptoms with facial numbness and the marked distal nerve conduction slowing in our cases are not consistent with GBS.     

Study on behavior of tritium in concrete wall

It is required to understand the tritium behavior in concrete for establishment of tritium safety technology of a fusion reactor or a tritium handling facility because the concrete wall is used as the final containment to prevent tritium release to the environment. This paper discusses about the effect of adsorption and diffusion of water and isotope exchange reaction between physically adsorbed water and chemically adsorbed water or structural water. It is known in this study that a large amount of tritium can be trapped to the concrete wall because cement paste has the nature of porous hydrophilic material.     

Human papillomavirus infection and risk determinants for squamous intraepithelial lesion and cervical cancer in Japan

Smooth muscle cell (SMC) proliferation is inhibited both in vivo and in vitro by heparin. However, the precise mechanisms of action are still not understood. The analogy between two sulfated polysaccharides, heparin and fucan, has led us to compare in detail their effects on SMC growth. We have prepared and characterized a 19 kDa fucan fraction from brown seaweed, Ascophyllum nodosum. Fucan affects the growth of SMCs in a time- and dose-dependent, reversible and non-toxic fashion. As determined by cell counting, [3H]thymidine incorporation, and microcytofluorimetry analysis, heparin was less active than fucan in inhibiting SMC growth. Fucan and heparin act by preferential blocking of G0/G1, thus decreasing the G0/S transition. Binding experiments with [125I]fucan indicated saturable, unlabeled-fucan displaceable binding sites with an apparent Kd of 30 nM. Moreover, displacement experiments performed with various polysaccharides revealed that antiproliferative compounds interacted with these membrane sites, but non-antiproliferative polysaccharides (dextran, chondroitin sulfate) did not, providing evidence of a correlation between binding to SMCs and their antiproliferative activity. When cells were exposed at 37 degrees C to a fluorescent 5-([4,6-dichlorotriazin-2-yl]-amino)fluorescein (DTAF)-fucan, internalization occurred and punctate vesicles were observed which accumulated rapidly in the perinuclear region as previously reported for heparin. Nuclear preparations (membranes + contents) of cultured SMCs previously incubated with radiolabeled heparin or fucan indicated the presence of radioactivity, suggesting an antiproliferative action of both polysaccharides at the nuclear level. Collectively, these observations indicated that fucan and heparin share some similar mechanisms of action, such as SMC growth inhibition, binding, and internalization. In the accompanying paper (Logeart et al., Eur. J. Cell Biol. 74, 1997, this issue), we describe the effect of fucans of different molecular weights and conclude that there is no direct link between polysaccharide degradation and the antiproliferative effect on SMCs.     

Low-temperature (77 K) BJT model with temperature dependences onthe injected condition and base resistance

A low-temperature (77-K) bipolar transistor model based on physical analysis by considering the temperature dependences of the injection condition and base resistance modulation is described. A charge-based injection factor which describes the temperature dependence of the ideality factor n is introduced by taking into account the electron and hole concentration ratios at the edges of the emitter-base depletion layer. The temperature dependence of base resistance modulation is explained by using the temperature dependences of the conductivity modulation effect, the base pushout effect, and the emitter current-crowding effect. Calculations using the model are compared with measurements, revealing excellent agreement over a wide temperature range from 50 to 298 K     

Low-loss multifibre connectors with plug-guide-grooved silicon

Low-loss interchangable multifibre connectors have been developed using plugs consisting of large guiding grooved and fibre-fixing V-grooved silicon chips. Guiding grooves etched on silicon chips accomplish extremely small average fibre offset less than 2 ?m. A 6-fibre connector plug pair selected from the same wafer exhibits 0.14 dB average connection loss. Connector plugs from different wafers exhibit 0.17 dB and 0.24 dB average connection losses.