Mechanism of photoconductivity gain and persistent photoconductivity for diamond photodetector

Photoconductivity gain (PG) and persistent photoconductivity (PPC) properties observed in diamond photodetector are theoretically explained by solving rate equations which describe capture and emission processes of photo-generated hole and electron through a boron acceptor and a hole trap in a diamond epilayer and a nitrogen donor in a diamond substrate. Formation of one-sided pn-junction between the epilayer and substrate and slow hole capture rate of acceptor and hole trap levels provide accumulation of photo-generated hole in the epilayer, which produces the PG larger than the ideal responsivity. The PPC current after turning off the deep ultraviolet light is interpreted as due to the slow hole capture rate of the acceptor and trap levels.     

Estimation of the deep-drawability of aluminum square cups by fracture forces

Several fracture forces for the evaluation of the forming limit are investigated. The influence of flange lubrication, blank shapes, blank materials and tool shapes on the fracture forces is examined. The increase in the critical fracture force (the ability to sustain deep-drawing forces) is required for the improvement in the deep-drawability of square cups. Constant fracture force and transitional fracture force are used as target values for the increase in the critical fracture force. Both the fracture forces are independent of the blank shapes, and influenced by the flange lubrication, the blank materials and the tool shapes. The deep-drawability of square cups is evaluated by means of the fracture forces.     

On the increase of the intensity ratio of doubly charged ions to singly charged ions for liquid gold and copper ion sources.

The reason for the increase of R21 which is defined by the intensity ratio of the doubly charged ions to the singly charged ions, was studied. Based on the conventional field evaporation theory, an increase in the electric field and/or the source temperature is considered to be attributable. We took the fact that R21 turned to decrease at the higher current regime into consideration and examined whether the change of R21 due to change in the field or temperature would finally meet the criterion for the decrease of R21. It was concluded that an increase of the source temperature may be a possible reason for the increase of R21.     

Source-Field Relationships for Cardiac Generators on the Heart Surface Based on Their Transfer Coefficients

We consider three different types of equivalent sources over a closed surface enclosing all the electrical cardiac generators: the (in situ) potential, the (in situ) normal current density, and the (macroscopic) transmembrane potential on the heart surface. The last equivalent source, which behaves as a double layer, is derived from the bidomain (bisyncytia) model for anisotropic cardiac muscle. This model predicts that if ratios of intracellular to interstitial conductivity along all directions are equal, field potential can be calculated only using surface integrals. The volume integral arising from the tissue anisotropy of cardiac muscle vanishes in that case. For each type of source under study, we give the field potential in a bounded inhomogeneous volume conductor in the form of an integral equation. We also derive the conditions which the lead field (or the transfer coefficients) must satisfy. The in situ potential and normal current are related to the cardiac sources in a complex way, but their lead fields are independent of conductivity of heart muscle, whereas the transmembrane potential is directly involved as a source term, but the lead field depends on the anisotropy of the heart muscle.     

Reduced incidence of Helicobacter pylori infection in young Japanese persons between the 1970s and the 1990s

The activity of eight topoisomerase inhibitors was investigated against five clinical isolates of Pneumocystis carinii. Susceptibility tests were performed by inoculation of the organisms on to a cell monolayer and parasites were counted after 72 h incubation at 37 degrees C. Culture plates were added with Dulbecco's modified Eagle's medium containing serial dilutions of lomefloxacin, norfloxacin, ofloxacin, pefloxacin, rufloxacin, camptothecin, amsacrine and etoposide. Atovaquone, pentamide isethionate and co-trimoxazole were used as control drugs. Etoposide gave inhibition comparable to that observed with atovaquone. Poor activity was demonstrated by pefloxacin, while the other topoisomerase inhibitors had no significant effect.     

Apatite crystal in hard tissue of conodont fossils

The present study was aimed at examining the nature of apatite crystal in the tooth apparatus of a conodont fossil using transmission electron microscopy (TEM), scanning electron microscopy (SEM), laser Raman microprobe spectrometry and electron-probe microanalysis (EPMA). The hard tissue of the condont consisted of 2 layers and the organization varied with the size of the crystal. Higher magnification showed that the crystals were observed in the lattice of (100) and the central dark lines were not present. Ca, P, and F were detected in the crystal using EPMA. Our results indicate that the apatite crystal in conodont fossils is not hydroxyapatite but fluorapatite.     

Determination of the Temperature Coefficient Distribution of Dielectric Ceramics Using Scanning Photothermal Dielectric Microscopy

Two-dimensional images of the distribution showing the temperature coefficient of the dielectric constant for two types of two-phase composite ceramics composed of TiO₂-Bi₂Ti₄O₁₁ and BaTi₄O₉-BaPr₂Ti₄O₁₂ were obtained using scanning photothermal dielectric microscopy. The images of the TiO₂-Bi₂Ti₄O₁₁ ceramic showed that the TiO₂ and Bi₂Ti₄O₁₁ grains had negative and positive temperature coefficients, respectively, and that the macroscopic averaged temperature coefficient of the ceramic was relatively low because of the cancellation of the opposite signs of the coefficients. On the other hand, the images of the BaTi₄O₉-BaPr₂Ti₄O₁₂ ceramic showed that the temperature coefficient of both grains had the same sign (negative), although their absolute values were quite different.