Mössbauer spectroscopic study of half-Heusler compounds

The family of half-Heusler compounds offers a variety of half-metallic ferromagnetic materials. We have applied the Mössbauer spectroscopy to study the atomic order, local surroundings and hyperfine fields to several half-Heusler compounds. ¹²¹Sb Mössbauer study of the compound CoMnSb revealed the presence of two nonequivalent antimony positions in the elementary cell and enabled to identify the structure. ^119mSn, ¹⁵⁵Gd and ¹⁹⁷Au Mössbauer spectroscopic studies were used to characterize the properties of ferromagnetic granular material based on the half-Heusler ferromagnet MnAuSn in the antiferromagnetic GdAuSn matrix.     

Study by X-ray crystallography and Mössbauer spectroscopy of CeFe(CN)6·5H2O and GdFe(CN)6·4H2O

From the X-ray crystallographic point of view, the environment of Fe in CeFe(CN)₆·5H₂O has higher octahedral symmetry than that in GdFe(CN)₆·4H₂O. The single Mössbauer absorption peak for CeFe(CN)₆·5H₂O indicates that the three t_2g levels are close to each other in energy due to a near-perfect octahedral Fe(CN)₆ unit. The doublet peak of of GdFe(CN)₆·4H₂O can be explained by assuming that the three t_2g levels are widely separated as a result of the distortion of the octahedral Fe(CN)₆ unit.     

False Hyperelliptic Surfaces with Section

Let X be a nonsingular relatively minimal projective surface over an algebraically closed field of characteristic p > 0. We call X a false hyperelliptic surface if X satisfies the following conditions: (1) c₂(X) = 0, c₁(X)² = 0, dim Alb (X) = 1, and (2) All fibres of the Albanese mapping of X are rational curves with only one cusp of type xp^v + yⁿ = 0. In this article, we consider a false hyperelliptic surface whose Albanese mapping has a cross-section. We prove that every false hyperellyptic surface with section arises from an elliptic ruled surface and that every false hyperelliptic surface has an elliptic fibration with multiple fibre. Moreover, we construct an example of false hyperelliptic surface with section, whose elliptic fibration has a multiple fibre of supersingular elliptic curve of multiplicity p^v (v > 1).     

Temperature-disturbance free magnetic field sensor based on double fiber optic polarimetry

A double fiber-optic Mach-Zehnder interferometer for sensing magnetic fields is devised using two polarization maintaining single-mode fibers. This sensor achieves not only highly sensitive performance but also excellent immunity from temperature disturbance. The sensitivity attains 243 deg/mT (mT=10^-3N/A) for the sensing part of the 5 cm long fiber.     

A finite difference method for 3D flows about bodies of complex geometry in rectangular co-ordinate systems

A finite difference simulation method is developed for 3D flow about a body of complex geometry. The Navier–Stokes equation is approximated by a high-order-accurate difference scheme in the framework of rectangular co-ordinate systems. The configuration of the 3D body is represented by use of both surface porosity and volume porosity and the no-slip body boundary conditions are approximately implemented on the boundary cells. The validity of the method is demonstrated by a numerical test of flow past a sphere at a Reynolds number of 1000. The complicated structure of separated vortices is well revealed by this test computation. The versatility of the method is shown by application to an ocean-engineering problem of flow about a bay with an island.     

Statistical evaluation of accelerated stability data obtained at a single temperature. II. Estimation of shelf-life from remaining drug content

Accelerated stability data obtained at a single temperature (40 degrees C) is statistically evaluated and the utility of the actual value of remaining drug content observed in the test for estimation of shelf-life is discussed. The distribution of the time required for 10% degradation at 25 degrees C, t90(25), is calculated from the observed drug content, taking the experimental errors into consideration. The probability that the t90(25) is longer than a specified shelf-life, which is calculated from the distribution, is represented as a function of the observed drug content. The probability was found to depend on the experimental errors in the assay and temperature control as well as in the activation energy of degradation (Ea). The relationship between the observed drug content and the shelf-life assured with a certain probability is shown graphically, so that one can reasonably predict the expected shelf-life as a function of Ea if the accuracy and precision of the assay and temperature control are known.     

Highly Sensitive and Widely Dynamic Fiber-Coiled Deformation Sensor Immune from External Disturbances

This paper describes a double fiber-coiled interferometric deformation sensor fabricated using paired polarization maintaining single-mode fibers. A change in bending-induced birefringence plays a fundamental role in the sensor performance as the fiber-coil is being deformed across its cross-section. Differential optical heterodyne detection processes allow us to implement two-mode operations; one is widely dynamic operation and the other highly sensitive operation around a target region. The deformation sensitivity for one-turn fiber-coil is 2.5 deg/mm for the widely dynamic operation, whereas 9.5X10 deg/mm for the highly sensitive operation. The double fiber-coiled deformation sensor can eliminate external, undesirable temperature disturbances.     

The structures of eumitrins A1, A2 and B: The yellow pigments of the lichen,Usnea bayleyi(Stirt.)Zahlbr.

The yellow pigments named eumitrins A₁, A₂ and B were isolated from the lichen, Usnea bayleyi(Stirt.)Zahlbr. The modified bixanthone structures of these compounds were deduced mainly from their spectral data, and their absolute structures (2a, 3a and 4a) were established on the basis of X-ray crystallographic analysis of a transformed product (6) of tribromo-eumitrin B (5).     

Enhanced piezoelectric properties of off-stoichiometric strontium bismuth tantalate Sr0.8Bi2.2Ta2O9 ceramics

The piezoelectric properties of strontium bismuth tantalate SrBi₂Ta₂O₉ (SBT) ceramics were enhanced by introducing off-stoichiometry into the starting materials. Sr-deficient and Bi-excess SBT, Sr_0.8Bi_2.2Ta₂O₉ (S_0.8B_2.2T), ceramic samples were prepared by a conventional ceramic technique. The optimum poling conditions (temperature T_p, time t_p, and electric field E_p) were investigated for the piezoelectric measurement. All the obtained independent electromechanical coupling factors of the S_0.8B_2.2T dense ceramics were as follows: k_p=10.6, k₃₁=6.8, k₃₃=14.0, k₁₅=7.8, and k_t=16.2%. The physical constants of the S_0.8B_2.2T ceramics were also determined. The piezoelectric constants were d₃₃=13.0, d₃₁=6.0, and d₁₅=10.2 pC/N. PACS 77.84.Dy; 61.66.Fn; 77.65.-j