Three-dimensional shaping by dot-matrix electrical discharge machining

This paper deals with a new prototyping method called dot-matrix electrical discharge machining (EDM) with scanning motion. The machining process by the dot-matrix method is similar to printing motion with a dot-impact printer. This method can be applied not only to EDM but also electrochemical machining and forming. A prototype of the machining unit for the dot-matrix method has six feeding devices for thin wire electrodes. The electrodes of 300 μm in diameter are arranged with the pitches of 760 μm. To obtain a smooth surface, a planetary motion in the x-y-plane is added to the feeding of the machining unit in the z-direction, the same area is machined repeatedly, or the machining unit is moved with fine feed. By compensating for the wear of the electrode during the scanning EDM, various shapes with the accuracy of micrometers order can be obtained without a formed tool electrode.     

Applications of phase-transfer catalytic reactions to fatty acids and their derivatives: Present state and future potential

Phase-transfer catalysts (PTC), which accelerate reactions between liquid(organic)-liquid(water) and liquidsolid heterogeneous states, have been investigated and developed. Several processes with PTC have succeeded in industrial processes involving fatty acids and their derivatives. For example, preparation of fatty alkyl glycidyl ethers, from which fatty alkyl glyceryl ethers and their derivatives can be obtained, has been carried out with PTC. However, some problems remain to be solved. For example, preparation of the fatty alkyl glycidyl ether by a PTC reaction was considered, but typical problems to be solved included: (i) how to reuse or recover the catalysts; (ii) how to control the heterogeneous reaction without obstacles to produce useful chemical materials; (iii) how to satisfy the environmental requirements for the catalysts; and (iv) are there more effective catalysts? We address these problems based on our own experiences with phase-transfer catalytic Williamson ether syntheses of fatty alkyl glycidyl ethers. Moreover, we describe recent developments in phase-transfer catalytic reactions related to oleochemistry, such as transition metal-catalyzed reactions of long-chain olefins in liquid(organic)-liquid(water) or liquid-solid heterogeneous states. Based on these results, we have considered the potential of PTC as a synthetic tool in oleochemistry.     

Internal photoemission spectroscopy measurement of Alq3/cathode interface by three layered electron only device

We have investigated the Schottky barrier height for electrons at aluminum tris (8-hydroxyquinoline) (Alq₃)/cathode interfaces by internal photoemission (IPE) measurement. A three layered device consisting of ITO/TiO₂/intermediate layer (IL)/Alq₃/cathode structure was used to fabricate the “electron-only device” and to reduce the equivalent thickness of TiO₂ and IL stack. The measured barrier heights were 0.86, 1.05, 1.3 and 1.55 eV for MgAg, Al, Ag and Au electrodes, and it gradually decreased with external voltage and it was explained as Schottky effect. Barrier height showed linear relationship with work-function and electronegativity of cathode materials. The slope parameter of 0.6 with electronegativity was attributed to the interfacial charge transfer through the metal-induced gap states at the cathode/Alq₃ interface.     

Control of mechanical deformation of a laminate by electrical load to piezoelectric actuator considering the effects of damping and transverse shear

In this paper, we treat the control of dynamic deformation of a laminate by applying electrical load to piezoelectric actuators. Dynamic behavior of the laminate is analyzed considering the effect of damping due to interlaminar shear and the effect of transverse shear. The analytical model is a rectangular laminate composed of fiber-reinforced laminae and piezoelectric layers. The model is assumed to be a symmetric cross-ply laminate with all edges simply supported and to be subjected to unavoidable mechanical load and to electrical loads to piezoelectric actuators. Behavior of the laminate is analyzed based on the first-order shear deformation theory. The effect of damping due to interlaminar shear is incorporated into our analysis by introducing the interlaminar shear stresses which satisfy the Newton’s law of viscosity. The following quantities are obtained: (1) natural frequencies of the laminate, (2) weight functions for the deflection and rotations and (3) transient deflection due to loads varying arbitrarily with time. Moreover, the methods to control the deflection due to mechanical load by applying electrical voltage to the piezoelectric actuator are shown.     

Self-Sharpening of Thin Tungsten Electrode in Single, High-Current Discharge: Its Dynamics and Mechanism

Self-sharpening of a thin tungsten electrode occurs in single, high-current discharge. This phenomenon has been observed with a custom-made, high-speed imaging system. The system allowed us to take one hundred images of the electrode shape during and after the discharge with 16 μs intervals. The following selfs-harpening mechanism has been proposed based on observations: (1) During the discharge, when the melt front descends towards the axis of the electrode, while the melt forms a sphere and moves along it due to the surface tension. (2) The melt continues moving even after the discharge, revealing a needle-shaped unmelted part and then solidifies. Detailed studies of discharge conditions to the diameter of the needle-shape formed by the process have been carried out. Results supporting the proposed mechanism are obtained.     

A case of herpes simplex encephalitis presenting complete destruction of the medial portions in the bilateral temporal lobes

A 57-year old man, who had suffered from herpes simplex encephalitis and had been cured without antiviral agents, was admitted to our hospital three years after the encephalitis. He had a complete loss of memory for events subsequent to the encephalitis and a retrograde amnesia for the several years leading up the encephalitis. MRI revealed the abnormalities located in the limbic system, especially the medial portions in the bilateral temporal lobes of the cerebrum were completely destroyed. We consider that this case suggests the specific affinity of herpes simplex virus especially for the medial portions in the temporal lobes of the cerebrum.     

The dynamic balance of import and export of zinc in Escherichia coli suggests a heterogeneous population response to stress

Zinc is essential for life, but toxic in excess. Thus all cells must control their internal zinc concentration. We used a systems approach, alternating rounds of experiments and models, to further elucidate the zinc control systems in Escherichia coli. We measured the response to zinc of the main specific zinc import and export systems in the wild-type, and a series of deletion mutant strains. We interpreted these data with a detailed mathematical model and Bayesian model fitting routines. There are three key findings: first, that alternate, non-inducible importers and exporters are important. Second, that an internal zinc reservoir is essential for maintaining the internal zinc concentration. Third, our data fitting led us to propose that the cells mount a heterogeneous response to zinc: some respond effectively, while others die or stop growing. In a further round of experiments, we demonstrated lower viable cell counts in the mutant strain tested exposed to excess zinc, consistent with this hypothesis. A stochastic model simulation demonstrated considerable fluctuations in the cellular levels of the ZntA exporter protein, reinforcing this proposal. We hypothesize that maintaining population heterogeneity could be a bet-hedging response allowing a population of cells to survive in varied and fluctuating environments.