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  • 1995-1999  (19)
  • 1990-1994  (9)
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  • 1
    Electronic Resource
    Electronic Resource
    MEED: a program package for electron-density-distribution calculation by the maximum-entropy method (1993)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 26 (1993), S. 453-457 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: MEED (maximum-entropy electron density) is a program package to calculate the electron-density distribution from a set of structure-factor data by the maximum-entropy method. MEED is an upgraded version of the original maximum-entropy program, MEMTARO, which was used in the first study to use the maximum-entropy method (MEM) on silicon [Sakata & Sato (1990). Acta Cryst. A46, 263–270]. MEED is applicable to any space group and can cope with both single-crystal and powder X-ray diffraction data, whereas MEMTARO can only after modification. Another upgraded feature is the speed of calculation. By employing a new algorithm, MEED is much faster than MEMTARO for the same calculation. Computing time depends on various factors, such as the number of reflection data, accuracy of data and the number of symmetry operations. It is estimated that MEED is typically 100 times faster than MEMTARO. In an extreme case like the beryllium powder-data case, MEED is 600 times faster than MEMTARO. MEED is coded in Fortran77 for both a scaler computer, FACOM M780, and a vector computer, FACOM VP2600, which are mainframe computers at the Computation Center of Nagoya University. MEED enables the electron-density distribution to be calculated for any crystalline material, with a fine pixel size, e.g. with 128 × 128 × 128 pixels to a unit cell, provided that accurate diffraction data are available. MEED can overcome, to some extent, one of the biggest drawbacks of MEM analysis, the vast computing time required.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889892012883
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  • 2
    Electronic Resource
    Electronic Resource
    Gamma-ray sensitivity and shielding of a neutron imaging plate (1999)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 32 (1999), S. 878-882 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The energy dependence of gamma-ray sensitivity of a neutron imaging plate (NIP) has been measured. The gamma-ray sensitivity is equivalent to one half that of a thermal neutron at a gamma-ray energy less than 300 keV, and 1/40 at greater than 300 keV. The shielding of the NIP, by lead, from gamma rays in the experimental hall of the reactor JRR-3M of the Japan Atomic Energy Research Institute (JAERI) was measured. It was found that lead of thickness 40 mm is sufficient to reduce the gamma-ray background to 1/10 on a normalized scale. Covering the NIP with lead foil of thickness 1 mm results in a decrease of the gamma-ray background without reduction of the neutron signal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889899005701
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  • 3
    Electronic Resource
    Electronic Resource
    The multiple-diffraction effect in accurate structure-factor measurements of PtP2 crystals (1994)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 50 (1994), S. 246-252 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Accurate X-ray intensities of a PtP2 crystal were measured with the multiple-diffraction effect avoided by using the ψ rotation of the crystal around the scattering vector. The results were compared with those of a measurement made without avoiding the effect. The extinction parameters were more isotropic and the peaks of the deformation density were significantly smaller when multiple diffraction was avoided. In the measurement made without avoiding the effect, the number of structure factors affected by more than 1% was 403 from 936 reflections measured. Of 272 strong reflections with sin &thgr;/λ 〈 0.6 Å−1 and Fobs 〉 200, 27 reflections were affected by more than 1%. These facts, as well as the smaller R values, indicate that the multiple-diffraction effect cannot be neglected in electron-density studies of crystals including heavy atoms. To assess the intensity fluctuation calculated in the present study, the intensities of 200 reflections were measured at intervals of 0.5° from 0 to 180° in ψ and compared with the calculated values. The variations of the measured and calculated intensities with ψ correspond to each other, which indicates that the present method can be used effectively to identify the reflections affected significantly by multiple diffraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767393008876
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  • 4
    Electronic Resource
    Electronic Resource
    A direct investigation of thermal vibrations of beryllium in real space through the maximum-entropy method applied to single-crystal neutron diffraction data (1994)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 50 (1994), S. 330-337 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The thermal vibrations of beryllium metal were determined directly from the nuclear densities obtained by the maximum-entropy method (MEM) using neutron single-crystal data. A high-resolution nuclear density distribution of beryllium was obtained by applying the MEM to the 48 structure factors with sin θ/λ 〈 1.41 Å−1 from a previous study [Larsen, Lehmann & Merisalo (1980). Acta Cryst. A36, 159–163], which showed small but significant cubic anharmonicity in beryllium by least-squares refinement of the structure factors. In the present study, quartic as well as cubic anharmonicities are clearly visible in the MEM nuclear density. In order to determine anharmonic thermal-vibration parameters, a three-dimensional function was fitted to the MEM nuclear density around the atom site. The one-particle potential was used to model the thermal vibrations up to quartic terms. The least-squares-fit values were γ = −0.306 eV Å−3 for the third- and α40 = − 1.02, β20 = 2.95 and γ00 = − 3.28 eV Å−4 for the fourth-order anharmonic parameters. Thus, the atomic potential in the basal plane is hardened against the bipyramidal space around the tetrahedral holes of the hexagonal-close-packed structure. It is softened towards the center of the octahedral voids. Least-squares refinement of the MEM nuclear density gives a standard deviation of about 5 for the last digit of the anharmonic parameters. However, there is added uncertainty in the parameters because of the relationship of the reliability of the MEM density distribution to the standard deviations of the measured intensities. Judging from previous studies of the thermal parameters for beryllium based on least-squares refinement of observed structure factors, it is estimated that values determined here for the anharmonic parameters are reliable to the first digit after the decimal point.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767393011523
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  • 5
    Electronic Resource
    Electronic Resource
    On the single-pixel approximation in maximum-entropy analysis (1995)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 51 (1995), S. 47-53 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: By a recent development of the maximum-entropy method (MEM) following Sakata & Sato [Acta Cryst. (1990), A46, 263–270], electron- (or nuclear-) density distributions have been obtained for crystalline materials of simple structures from single-crystal or powder diffraction data. In order to obtain a ME density map, the ME equation is solved iteratively under the zeroth-order single-pixel approximation (ZSPA) starting from the uniform density. The purpose of this paper is to examine the validity of the ZSPA by using a one-dimensional two-pixel model for which the exact solution can be analytically obtained. For this model, it is also possible to solve the ME equation numerically without ZSPA by the same iterative procedure as in the case of ZSPA. By comparison of these three solutions for a one-dimensional two-pixel model, it is found that the solutions obtained iteratively both with and without ZSPA always converge to the exact solution so long as the value of the Lagrange undetermined multiplier, λ, is chosen to be sufficiently small. This means the ZSPA solution does not depend on λ when the convergence is attained. When, λ exceeds a critical value, iteration with ZSPA gives oscillatory divergence but iteration without ZSPA converges to a different value from the exact solution. It is concluded that the introduction of ZSPA does not cause any serious problem in the solution of the ME equation, when a sufficiently small λ value is used in the ME analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767394006173
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  • 6
    Electronic Resource
    Electronic Resource
    An accurate determination of the thermal vibration of rutile from the nuclear density distribution of the maximum-entropy analysis (1995)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 51 (1995), S. 651-658 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The maximum-entropy method (MEM) can provide a high-resolution nuclear density distribution purely from experimental neutron diffraction data. The distribution expresses thermal smearing, which is caused by all kinds of thermal-vibration modes both harmonic and anharmonic. If the effective one-particle potential (OPP) is assumed to describe thermal smearing of nuclei, the potential parameters can be determined by least-squares refinement of the nuclear density distribution. By this method, the OPP parameters of rutile (TiO2) are directly determined from the nuclear density distribution originally derived by Sakata, Uno, Takata & Howard [J. Appl. Cryst. (1993), 26, 159–164]. In the rutile case, the x coordinate of the O atom located at (x, x, 0) has to be determined before the OPP parameters are analysed. The atomic position is defined as the position where the first-order moment of the nuclear density becomes zero. The obtained x coordinate is 0.30477, which shows excellent agreement with the previous study of Rietveld analysis by Howard, Sabine & Dickson [Acta Cryst. (1991), B47, 462–468], i.e. 0.30478 (6). The higher-order moments of nuclear density are calculated in order to build an adequate OPP model. Among these values, none of the sixth order is significant and hence the OPP model up to fourth-order anharmonicity is employed. The potential parameters are refined by least-squares analysis using the above OPP model. For the Ti atom, nine OPP parameters (three harmonic and six fourth-order anharmonic) are determined with reliability factor R = 0.73%. For the O atom, twelve OPP parameters (three harmonic, three third- and six fourth-order anharmonic) are determined with R = 3.83%. The nuclear density of the O atom shows substantial skewness in rutile owing to the third-order anharmonicities. It is shown that the present method is a very powerful technique to determine the precise values for both harmonic and anharmonic potential parameters based on the OPP model in comparison with conventional structure analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767395001206
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  • 7
    Electronic Resource
    Electronic Resource
    In vitro electrochemical detection of wheat allergen using rat basophilic leukaemia (RBL-1) cells (1995)
    Springer
    Applied microbiology and biotechnology 43 (1995), S. 622-625 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract We have investigated an electrochemical method of detecting foods that cause an allergic reaction. Rat basophilic leukaemia (RBL-1) cells were sensitized with serum from a rat that was allergic to wheat. A sample containing the protein fraction of a food was added to the cells and incubated. The cells were immobilized on a membrane filter and attached to a basalplane pyrolytic graphite electrode. When a potential was applied in the range 0–1.0 V relative to a saturated calomel electrode, an anodic peak current appeared at around 0.33 V. This peak current, attributed to serotonin, increased with time, and the maximum current (0.5 μA) was obtained 20–25 min of incubation. The response of the RBL-1 cells was specific to the protein fraction of wheat. The peak current increased linearly with increasing protein concentration in the range of 0.01–0.5 μg ml−1. These results suggest that the concentration of the protein bringing about the allergic reaction can be determined by cyclic voltammetry within 25 min. This method is more sensitive than the conventional skin tests.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00164764
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  • 8
    Electronic Resource
    Electronic Resource
    In vitro electrochemical detection of wheat allergen using rat basophilic leukaemia (RBL-1) cells (1995)
    Springer
    Applied microbiology and biotechnology 43 (1995), S. 622-625 
    Details
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  We have investigated an electrochemical method of detecting foods that cause an allergic reaction. Rat basophilic leukaemia (RBL-1) cells were sensitized with serum from a rat that was allergic to wheat. A sample containing the protein fraction of a food was added to the cells and incubated. The cells were immobilized on a membrane filter and attached to a basal-plane pyrolytic graphite electrode. When a potential was applied in the range 0–1.0 V relative to a saturated calomel electrode, an anodic peak current appeared at around 0.33 V. This peak current, attributed to serotonin, increased with time, and the maximum current (0.5 μA) was obtained 20–25 min of incubation. The response of the RBL-1 cells was specific to the protein fraction of wheat. The peak current increased linearly with increasing protein concentration in the range of 0.01–0.5 μg ml-1. These results suggest that the concentration of the protein bringing about the allergic reaction can be determined by cyclic voltammetry within 25 min. This method is more sensitive than the conventional skin tests.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00164764
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  • 9
    Electronic Resource
    Electronic Resource
    Structural study of amorphous Pd41Ni41Si18 alloy associated with structural relaxation by anomalous X-ray scattering (1997)
    Springer
    Journal of materials science 16 (1997), S. 1157-1160 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Abstracts are not published in this journal
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018596623870
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  • 10
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    Recent technical advances in thin-film CdS/CdTe solar cells (1996)
    Elsevier
    Details
    Publication Date: 1996-05-01
    Print ISSN: 0960-1481
    Electronic ISSN: 1879-0682
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by Elsevier
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