Oblique semi-elliptical surface crack in semi-infinite solid subjected to tension

This note is concerned with a semi-elliptical surface crack arbitrarily inclined to the free surface of a semi-infinite solid subjected to tension. The analysis is performed by the body force method, and the stress intensity factor at the maximum depth point on the crack front are given for various shapes and inclination angles of the crack. The numerical results are fitted to a reliable polynomial for convenience in engineering applications.     

A New Method for the Stereoselective Synthesis of Nucleosides by Means of Sodium Borohydride Mediated Reductive C-C or C-N Bond Cleavage Reaction

New dienophiles, dimethyl acetoxymethylenemalonate and its analogues, have been synthesized. These dienophiles reacted with cyclopentadiene to give Diels-Alder adducts, which served as versatile synthetic precursors for carbocyclic C-nucleosides. The method has the following three characteristics: (1) the C-C bond in the adduct originated from the dienophile can be cleaved stereoselectively by the reductive retrograde aldol (RRA) reaction, (2) the CC bond in the adduct serves as a latent functionality of 2′- and 3′- positions of the nucleoside, and (3) the malonate unit can be transformed to a variety of heterocycles. The high pressure mediated Diels-Alder reaction of furan with the same dienophiles also gave the cycloadducts, which served as synthons for C-nucleosides. Use of chiral dienophiles, such as di-1-menthyl acetoxymethylenemalonate, for the above Diels-Alder reactions has offered a new route to the enantioselective synthesis of C-nucleosides and their carbocyclic analogues. Essentially the same methodology has also been applied to the synthesis of carbocyclic nucleosides from 2-azabicyclo[2.2.1]hept-5-en-3-one, in which a reductive amido bond cleavage reaction similar to (1) is involved. Synthesis of carbocyclic oxetanocin and its analogues is also described.     

Tension of a finite-thickness plate with a pair of semi-elliptical surface cracks

This paper deals with the tension of a finite-thickness plate with a pair of semi-elliptical cracks on both of the free surfaces. The analysis is performed in a similar manner to the previous single crack problem, by using the body force method and the boundary conditions expressed in terms of resultant forces and displacements of the boundary elements. The stress intensity factor at the maximum depth of the crack front is calculated for various values of the parameters and these results are fitted by a reliable polynomial formula for convenience of engineering applications.     

The effect of nonstoichiometry on the positive temperature dependence of strength of Ni3AI and Ni3Ga

Compression tests have been carried out on the polycrystalline Ni₃Al and Ni₃Ga alloys over the temperature range 77 ~ 1000 K. The flow stress and the temperature dependence of strength are found to be sensitive to small composition change within the phase field. The anomalous strengthening of these compounds with temperature is more significant for Al-and Ga-rich deviations than for Ni-rich deviations from stoichiometry. The change in activation constant of these compounds derived from the flow stress increment appears to be discontinuous at the stoichiometric composition. The influence of deviations from stoichiometry on the temperature dependence of strength could be accounted for by the phase stability concept proposed by the present authors. It is concluded that the phase stability of the Ni₃Al and Ni₃Ga alloys with respect to the D0₂₂ phase as well as the D0₁₉ phase are reduced as the composition of the minority component is increased. This change leads to the relatively reduced {100} antiphase boundary energy which increases the propensity for the cross slip onto cube plane. formerly graduate student, Department of Material Science and Engineering, Tokyo Institute of Technology.     

Decomposition of water by a CaTiO3 photocatalyst under UV light irradiation

Platinized CaTiO₃ powder (band gap 3.5 eV) had a high photocatalytic activity of decomposing water into H₂ and O₂ under the irradiation of UV light, especially with photon energies above 3.8 eV. The existence of this photocatalytic activity is further supported on electrochemical grounds in that the photoinduced current spectrum measured between a CaTiO₃ single crystal and a Pt electrode without applied voltage in water showed a maximum near 4.1 eV. This result indicates that the direct measurement of the spectrum corresponding to the efficiency of water decomposition is an effective method to survey photocatalytic activities of materials.     

A leukotriene receptor antagonist, ONO-1078, modulates drug sensitivity and leukotriene C4 efflux in lung cancer cells expressing multidrug resistance protein

In this preliminary observation, a group of seven mentally and physically handicapped persons of chronological ages ranging from 15.4 yr. to 26.8 yr. experienced 15 sec. of physical rocking. For the further analysis, the poststimulus periods were classified into either those when the subjects' spontaneous head, mouth, and body movements had increased from the prestimulus period or those decreased. The median heart rates recorded in the poststimulus period were not significantly different from those in the prestimulus period on trials on which there was an observable increase in the rates of spontaneous head, mouth, and body movements; however, the median heart rates decreased during those trials on which a decrease in the rates of the movements occurred. Since it is said that rocking heightens arousal of persons with mental and physical handicaps, it is suggested that spontaneously emitted, aimless head, mouth, and body movements attributed to low arousal were reduced by heightened arousal rather than by a decline in participants' activities.     

Preparation of Y-type Barium Hexaferrite by the Glass–Ceramic Method

Y-type Ba-hexaferrites (Ba₂Zn₂Fe₁₂O₂₂), which have been identified as electromagnetic wave absorbers, were prepared by the glass–ceramic method. Glasses with the composition 0.1ZnO·0.9( x B₂O₃· y BaO·(1− x − y )Fe₂O₃) were prepared, and the precipitation of Y-type Ba-hexaferrite from the glass matrix was investigated. Y-type Ba-hexaferrite were precipitated by heating glass specimens with roughly the composition 0.1ZnO·0.9(0.2B₂O₃·0.5BaO·0.3Fe₂O₃) at temperatures above about 1073 K. The lower temperature limit at which single-phase Y-type powder was obtained after leaching with a dilute HCl solution was about 1093 K. The low-temperature formation of Y-type Ba-hexaferrite was linked to the generation of a liquid phase. The shape of Y-type crystals depended strongly on the heating temperature and changed from a plate-like hexagon to a complex polyhedron with increasing heating temperature.     

Microstructure of Strontium Titanate Thin Film Grown by the Hydrothermal-Electrochemical Method

Microstructures of SrTiO₃ thin films grown on Ti substrates by the hydrothermal-electrochemical method have been studied by transmission electron microscopy. The grown films consisted of a thin surface layer having an isotropic polycrystalline structure and a thick inner layer having a columnar structure. Pores of the order of several tens of nanometers were found at boundaries of columnar grains constituting the inner layer. A 20- or 30-nm-thick polycrystalline layer of Ti oxides contaminated with a small amount of Sr was also found at the SrTiO₃ film/Ti substrate interface. During the film growth at this interface, the observed pores are considered to act as short-circuit paths for mass transport from the film surface to the interface.     

1.55 ?m narrow-linewidth multielectrode DFB laser for coherent FSK transmission

A 1.55?m multielectrode DFB laser, with both flat FM response characteristic and spectral linewidth as narrow as 4.5 MHz, has been fabricated by an MOVPE/LPE hybrid growth method. Since this device is relatively easy to fabricate, the multielectrode DFB laser is most promising as a coherent FSK transmission light source