bluuebunny/crossref_metadata_2025 huggingface dataset:
Crystal structure of moganite-type phosphorus oxynitride: relationship to other twinned-quartz-based structures
Authors: Haines J. , Chateau C. , Léger J. M. , Le Sauze A. , Diot N. , Marchand R. , Hull S.
Published: July 2002

The structure of moganite-type phosphorus oxynitride quenched from high-pressure high-temperature conditions has been refined using neutron powder diffraction data. This moganite-type structure, space group I2/a, Z = 12, is slightly less distorted with respect to the Imab aristotype than is moganite (a monoclinic form of silica). A close topological relationship has been identified between the moganite-type and orthorhombic BeH2 structures indicating that SiO2, PON and BeH2 all adopt structures belonging to the twinned-quartz-based group. This group represents another possible structure type for systems composed of corner-sharing AX
4 tetrahedra. Structures of this group are obvious candidates for intermediate phases between the cristobalite and quartz types.
Structure of and electron density in RbTiOAsO4 at 9.6 K
Authors: Almgren Jenni , Streltsov Victor A. , Sobolev Alexander N. , Figgis Brian N. , Albertsson Jörgen
Published: July 2002

Structure factors for rubidium titanyl arsenate, RbTiOAsO4, were measured with Mo Kα radiation (λ = 0.71069 Å) at 9.6 and 295 K. The data show that there is no phase transition between room temperature and 9.6 K. The space group is Pna2
1. Unit-cell parameters are a = 13.218 (1), b = 6.6500 (9) and c = 10.761 (1) Å at 9.6 K, and a = 13.261 (2), b = 6.6791 (8) and c = 10.769 (1) Å at 295 K. As the temperature was lowered from 295 to 9.6 K the Rb atoms moved along the c axis in the direction of the polarization vector, while no significant change was noted for the Ti–O–As network. Strong accumulation and polarization of the difference electron density (Δρ) in exceptionally short covalent Ti—O bonds alternates with the depleted density in long Ti—O bonds. The Δρ near the Ti atoms is polarized and aligned in the negative c direction in accordance with the ferroelectric properties of this material. However, the electron density near the Rb atoms is depleted in this direction and the excess Δρ is moved further away from the nuclei along the c vector.
Structure and molecular modelling of protected dipeptide fragment (Boc–Phe–Leu–OBzl) of enkephalin
Authors: Antolić S. , Teichert M. , Sheldrick G. , Kojić-Prodić B. , Čudić M. , Horvat Š.
Published: July 2002

The conformational characteristics of a flexible totally protected C-terminal dipeptide fragment (Boc–Phe–Leu–OBzl) of enkephalin are studied using X-ray data, molecular modelling and data retrieved from the Cambridge Structural Database. The dipeptide crystallizes with seven conformers in the asymmetric unit. C27H36N2O5, T = 133 K, monoclinic, P21, a = 13.706 (3), b = 22.800 (3), c = 30.674 (5) Å, β = 97.15 (3)°, V = 9511 (3) Å3, Z = 14, D

c
= 1.145 Mg m−3. Six of the seven molecules exhibit folded conformations with hydrophobic groups disposed at the opposite side of the peptide backbone. The characteristic Φ1 and Ψ1 angles of the Phe residue and Φ2 of the Leu fragment are in the allowed region defined in the Ramachandran diagram. However, they do not belong to the family of the lowest energy conformations. In the crystal, molecules are interconnected via N—H...O hydrogen bonds of peptide groups forming an infinite sheet similar to a parallel β-sheet. Molecular dynamics simulations performed in vacuo reproduce the conformers and rotamers detected in the solid state.
Structure of ν-Al80.61Cr10.71Fe8.68, a giant hexagonal approximant of a quasicrystal determined by a combination of electron microscopy and X-ray diffraction
Authors: Mo Z. M. , Zhou H. Y. , Kuo K. H.
Published: July 2002

ν-Al80.61Cr10.71Fe8.68, P63/m (No. 176), a = 40.68 (7), c = 12.546 (1) Å, V = 17 983 (8) Å3, atoms/cell = 1184.56, D

x
 = 3.518 g cm−3, λ(Mo Kα) = 0.71069 Å, μ = 5.032 mm−1, F(000) = 18 433, T = 293 K, final R = 0.075 for 3854 reflections with F

o
 > 4σ(F

o
). The [001] high-resolution electron-microscopic image of the ν-AlCrFe phase clearly shows similar local characteristics to those given by the complex icosahedral cluster found in somewhat smaller hexagonal approximant structures, such as κ-Al76Cr18Ni6 [a = 17.674 (3), c = 12.516 (3) Å; Sato et al. (1997). Acta Cryst. C53, 1531–1533; Marsh (1998). Acta Cryst. B54, 925–926] and λ-Al4.32Mn [a = 28.382 (9), c = 12.389 (2) Å; Kreiner & Franzen (1997). J. Alloys Compd.
261, 83–104]. Using the known atomic distribution of this icosahedral cluster in the κ and λ phases as the starting point, the structure of the ν phase, a hexagonal intermetallic compound with probably the largest a parameter, was solved by X-ray single-crystal diffraction using direct methods. As in κ and λ phases, almost all TM (transition metal) atoms in the complex icosahedral cluster are icosahedrally coordinated. However, contrary to the λ structure in which about 98% of the TM atoms have icosahedral coordination, the TM atoms in the ν structure also form capped pentagonal prisms in the region between these complex icosahedral clusters, yielding an average icosahedral coordination of about 70% for TM atoms. After rapid solidification, the ν phase occurs together with a decagonal quasicrystal with a periodicity of about 12.5 Å along its tenfold axis and thus also consists of six layers, two flat ones each sandwiched between two puckered layers in mirror reflection, stacked along the c axis.
Structure correlation study of four-coordinate copper(I) and (II) complexes
Authors: Raithby Paul R. , Shields Gregory P. , Allen Frank H. , Motherwell W. D. Samuel
Published: July 2002

The geometries of four-coordinate CuI and CuII complexes in the Cambridge Structural Database (CSD) have been analysed systematically and compared using symmetry-deformation coordinates and principal component analysis. The observed stereochemistries have been rationalized in terms of the d-electron configurations, interligand repulsion and π-bonding effects. The results confirm that the majority of four-coordinate copper(I) complexes in the CSD adopt tetrahedral geometries and deviations from tetrahedral symmetry are caused by the presence of chelating ligands or by the incorporation of copper centres into dimeric or polymeric structures. Four-coordinate copper(II) complexes generally adopt geometries close to square planar; this is particularly evident for bis(chelate) complexes where π-bonding is important. Distortions towards tetrahedral geometries are attributable to steric interactions of bulky substituents in the bidentate ligands.
Bragg's influence on progress in optical computations
Authors: McLachlan D.
Published: July 2002

An attempt is made in this paper to indicate the impact that one small part of Sir Lawrence Bragg's gross contributions have had upon crystallography during his lifetime up to the age of eighty. The small part referred to is the growing field of optical computation. Since this paper is partly for the enlightenment of the reader as well as a salute to history, descriptions of five basic optical operations are given: I, addition; II, multiplication; III, reciprocation; IV, convolution and V, diffraction. The role of Bragg and his co-workers is woven into each description. Finally as an extrapolation, a further process is described: VI, inverse imaging.
A method, based upon `bond-strength' calculations, for finding probable lithium sites in crystal structures
Authors: Waltersson K.
Published: July 2002

A method for finding probable Li positions in a given oxygen matrix in crystals is described. It is formally based upon bond strength-bond length discussions. The sums of bond strengths for simulated Li atoms are calculated and printed in three-dimensional maps. The method is tested on nine structures containing Li atoms. In five of these the Li sites are known from neutron diffraction studies, in two from X-ray powder diffraction data sets, and in the other two from X-ray single-crystal investigations. The calculated Li coordinates in all the tests are in fair agreement with the experimentally observed positions. The method is therefore likely to provide an auxiliary tool for determining Li sites in X-ray crystal structure studies.
In-house low-resolution X-ray crystallography
Authors: Evans Gwyndaf , Roversi Pietro , Bricogne Gérard
Published: July 2002

It is demonstrated that standard in-house protein crystal X-ray diffraction apparatus can be used to measure very low resolution reflections with only a few modifications. The apparatus and modifications are described in detail and tested on two different macromolecular crystal samples: lysozyme and the 30S ribosomal subunit. Contrast-variation measurements on tetragonal hen egg-white lysozyme demonstrate the potential usefulness of the apparatus in providing accurate data for the determination of macromolecular envelopes. In contrast, the measurement of very low resolution diffraction from crystals of the 30S ribosome subunit illustrates how in-house facilities can provide data from small weakly diffracting crystals of a very large macromolecule.
The Nucleic Acid Database
Authors: Berman Helen M. , Westbrook John , Feng Zukang , Iype Lisa , Schneider Bohdan , Zardecki Christine
Published: July 2002

The Nucleic Acid Database was established in 1991 as a resource to assemble and distribute structural information about nucleic acids. Over the years, the NDB has developed generalized software for processing, archiving, querying and distributing structural data for nucleic acid-containing structures. The architecture and capabilities of the Nucleic Acid Database, as well as some of the research enabled by this resource, are presented in this article.
Crystals of bovine heart ubiquinol–cytochrome c reductase diffracting X-rays up to 2.8 Å resolution at 276 K
Authors: Murakami Satoshi , Shinzawa-Itoh Kyoko , Yoshikawa Shinya
Published: July 2002

Bovine heart ubiquinol–cytochrome c reductase stabilized with sucrose monocaplate was crystallized with polyethylene glycol as the precipitant at 277 K. X-rays diffracted by the crystal were detected up to 2.8 Å resolution at 266 K, without using a synchrotron source. The space group and cell dimensions are P61 or P65 and a = b = 128.5 and c = 715.7 Å, respectively.
An improved procedure for the preparation of X-ray diffraction-quality crystals of cytochrome P450cam
Authors: Nickerson Darren , Wong Luet-Lok , Rao Zihe
Published: July 2002

A procedure for the crystallization of recombinant cytochrome P450cam has been developed which avoids the difficulties inherent in the glass-capillary free-interface diffusion method reported previously. The surface mutation, Cys334→Ala (C334A), originally designed to prevent dimer formation and thus improve routine handling of the enzyme, facilitates crystallization by the hanging-drop vapour-diffusion technique. Crystals of (C334A)P450cam grow within 48 h and diffract to beyond 1.2 Å at 100 K in-house on a Siemens multiwire area detector. Data have been collected from the camphor-bound form to 1.35 Å.
Preliminary X-ray analysis of a new crystal form of the vanadium-dependent bromoperoxidase from Corallina officinalis
Authors: Brindley Amanda A. , Dalby Andrew R. , Isupov Michail N. , Littlechild Jennifer A.
Published: July 2002

A new crystal form of the vanadium-dependent bromoperoxidase from Corallina officinalis has been obtained. The crystals exhibit a `teardrop' morphology and are grown from 2 M ammonium dihydrogen phosphate pH 5 and diffract to beyond 1.7 Å resolution. They are in tetragonal space group P4222 with unit-cell dimensions of a = b = 201.9, c = 178.19 Å, α = β = γ = 90°. A 2.3 Å resolution native data set has been collected at the Hamburg Synchrotron. A mercury derivative data set has also been collected, and the heavy-atom positions have been determined. The self-rotation function and the positions of the heavy atoms are consistent with the molecule being a dodecamer with local 23 symmetry.
Crystallization of two related lectins from the legume plant Dolichos biflorus
Authors: Dao-Thi Minh-Hoa , Hamelryck Thomas W. , Bouckaert Julie , Körber Fritjof , Burkow Valentina , Poortmans Freddy , Etzler Marilynn , Strecker Gerard , Wyns Lode , Loris Remy
Published: July 2002

The seed lectin DBL and the related stem and leaves lectin DB58 of the tropical legume Dolichos biflorus were crystallized, as well as complexes of DBL with adenine and with GalNAc(α1-3)[Fuc(α1-2)]Gal. The different crystal forms of DBL diffract to about 2.8 Å, while DB58 crystals diffract to 3.3 Å.
Crystallization and preliminary X-ray analysis of the unliganded recombinant catalytic subunit of cAMP-dependent protein kinase
Authors: Narayana Narendra , Akamine Pearl , Xuong Nguyen-Huu , Taylor Susan S.
Published: July 2002

X-ray diffraction-quality crystals of the unliganded mouse recombinant catalytic subunit of cAMP-dependent protein kinase were grown by the hanging-drop vapour-diffusion technique using 2-methyl-2,4-pentanediol as precipitant. The crystals belong to the monoclinic space group P21 with unit-cell parameters a = 48.9, b = 147.4, c = 54.2 Å, β = 110.2°. A data set to 3.0 Å resolution with 92% completeness has been collected using synchrotron radiation. The unit cell contains four molecules of molecular weight 40 kDa with a corresponding volume solvent content of 45%.
Crystallization and preliminary X-ray analysis of a chitinase from the fungal pathogen Coccidioides immitis
Authors: Hollis Thomas , Monzingo Arthur F. , Bortone Kara , Schelp Elisabeth , Cox Rebecca , Robertus Jon D.
Published: July 2002

Chitinase is necessary for fungal growth and cell division and, therefore, is an ideal target for the design of inhibitors which may act as antifungal agents. A chitinase from the fungal pathogen Coccidioides immitis has been expressed as a fusion protein with gluathione-S-transferase (GST), which aids in purification. After cleavage from GST, chitinase was crystallized from 30% PEG 4000 in 0.1 M sodium acetate pH 4.6. The crystals have a tetragonal crystal lattice and belong to space group P41212 or P43212 and diffract to 2.2 Å resolution. The unit-cell parameters are a = b = 91.2, c = 95.4 Å; there is only one chitinase molecule in the asymmetric unit.
Initiating a crystallographic study of UDP-galactopyranose mutase from Escherichia coli
Authors: McMahon Stephen A. , Leonard Gordon A. , Buchanan Louise V. , Giraud Marie-France , Naismith James H.
Published: July 2002

UDP-galactopyranose mutase, the enzyme responsible for the conversion of UDP-galactopyranose to UDP-galactofuranose, has been crystallized in a form suitable for X-ray diffraction studies. UDP-galactofuranose is a key component of mycobacterial cell walls. Crystals of both the native protein and a selenomethionine variant have been grown by the vapour-diffusion method in hanging drops, and diffract to beyond 3.0 Å using synchrotron radiation. Equilibration was against a solution of 20%(w/v) polyethylene glycol (4K), 12%(v/v) 2-propanol, 0.1 M HEPES pH 7.6 at 293.5 K. Crystals grow as thin plates of dimensions 0.4 × 0.2 × ∼0.02 mm. They are orthorhombic, space group P21, with unit-cell dimensions a = 71.12, b = 58.42, c = 96.38 Å, β = 96.38°. 92% (native) and 94% (selenomethionine) complete data sets have been recorded to 2.9 Å (R
merge = 5.0%) and 3.0 Å (R
merge = 6.9%), respectively. The Matthews coefficient is 2.35 Å3 Da−1 for a dimer in the asymmetric unit, the solvent content being 47%. Diffraction data have also been recorded on a putative platinum derivative to 3.5 Å.
Crystallization and preliminary analysis of a DNA dodecamer of d(CGCGmo6AATCCGCG) containing 2′-deoxy-N
6-methoxyadenosine: change in crystal packing with different humidity
Authors: Chatake Toshiyuki , Sunami Tomoko , Ono Akira , Ueno Yoshihito , Matsuda Akira , Takenaka Akio
Published: July 2002

The DNA dodecamer of (CGCGmo6AATCCGCG) containing 2′-deoxy-N
6-methoxyadenosine has been crystallized for X-ray analysis in order to investigate the effects of the modified adenosine on base pairing. It has been found that the crystal changes from one form to another during data collection in a manner similar to a phase transition. The two crystal structures show that this phenomenon, ascribed to differences in humidity, is correlated with a change in the contact angle between the two duplexes.
Combining direct methods with isomorphous replacement or anomalous scattering data. VIII. Phasing experimental SIR data with the replacing atoms in a centrosymmetric arrangement
Authors: Liu Yu-Dong , Gu Yuan-Xin , Zheng Chao-De , Hao Q. , Fan Hai-Fu
Published: July 2002

A multisolution direct method has been proposed to resolve the phase ambiguity intrinsic in single isomorphous replacement data of proteins with the replacing atoms in a centrosymmetric arrangement. The phase ambiguity of each reflection is in fact a `sign ambiguity' of the phase difference between the phase of the native protein and that of the replacing atoms, i.e. ± |Δφ| = φ − φ′. The P
+ probability formula can be used to derive the signs. The multisolution phasing procedure is initiated using random starting values of P
+. A cluster analysis is used instead of figures of merit to find the correct solution. The direct-method phases can be further improved by density-modification techniques. The method was tested with the experimental SIR data at 2 Å resolution from a known protein aPP; satisfactory results were obtained.
The structure of mouse tumour-necrosis factor at 1.4 Å resolution: towards modulation of its selectivity and trimerization
Authors: Baeyens K. J. , De Bondt H. L. , Raeymaekers A. , Fiers W. , De Ranter C. J.
Published: July 2002

The 1.4 Å resolution structure of recombinant mouse tumour-necrosis factor α (mTNF) at 100 K has been determined. The crystals are triclinic, space group P1, with unit-cell parameters a = 48.06, b = 48.18, c = 51.01 Å, α = 114.8, β = 103.6, γ = 91.1°. The structure was refined to a final crystallographic R value of 19.7% (R
free = 23.3%), including 3477 protein atoms, one 2-propanol molecule, one Tris molecule and 240 water molecules. Throughout the crystal lattice, the trimers are differently packed compared with human TNF, which was crystallized in the tetragonal space group P41212 and refined to 2.6 Å resolution. The structures of mTNF and human TNF are very similar, diverging mainly in regions that are either flexible and/or involved in crystal packing. Some loops in mTNF which contain residues important for receptor binding are better resolved than in human TNF, such as the surface-exposed loops 30–34 and 144–147, which are also important for receptor specificity. Compared with human TNFs, the channel formed by the three monomers in mTNF is narrower. One 2-propanol molecule trapped in the trimeric channel could be a lead compound for the design of TNF inhibitors.
Crystallization and preliminary diffraction data of a platelet-aggregation inhibitor from the venom of Agkistrodon piscivorus piscivorus (North American water moccasin)
Authors: Arni R. K. , Padmanabhan K.P. , Tulinsky A.
Published: July 2002

Applaggin (Agkistrodon piscivorus piscivorus platelet-aggregation inhibitor) is a potent inhibitor of blood platelet aggregation derived from the venom of the North American water moccasin. The protein consists of 71 amino acids, is rich in cysteines, contains the sequence-recognition site of adhesion proteins at positions 50–52 (Arg-Gly-Asp) and shares high sequence homology with other snake-venom disintegrins such as echistatin, kistrin and trigramin. Single crystals of applaggin have been grown and X-ray diffraction data have been collected to a resolution of 3.2 Å. The crystals belong to space group P41212 (or its enantiomorph), with unit-cell dimensions a = b = 63.35, c = 74.18 Å and two molecules per asymmetric unit. Molecular replacement using models constructed from the NMR structures of echistatin and kistrin has not been successful in producing a trial structure for applaggin.
Crystallization and X-ray crystallographic analysis of m-calpain, a Ca2+-dependent protease
Authors: Hosfield Christopher M. , Ye Qilu , Arthur J. Simon C. , Hegadorn Carol , Croall Dorothy E. , Elce John S. , Jia Zongchao
Published: July 2002

The absolute requirement of Ca2+ for proteolytic activity is a feature unique to the calpains, a family of heterodimeric cysteine proteases. Conditions are described which give rise to diffraction-quality crystals of m-calpain in two crystal forms, P1 and P21. Data have been collected from native crystals of m-calpain in both P1 and P21 forms, to 2.6 and 2.15 Å, respectively. Selenomethionine-containing crystals have been grown in both forms, and anomalous data from the P21 selenomethionine enzyme provided the location of 17 of the 19 Se atoms in the protein.
Analysis and characterization of data from twinned crystals
Authors: Chandra N. , Acharya K. Ravi , Moody P. C. E.
Published: July 2002

It is difficult but not impossible to determine a macromolecular structure using X-ray data obtained from twinned crystals, providing it is noticed and corrected. For perfectly twinned crystals, the structure can probably only be solved by molecular replacement. It is possible to detect and characterize twinning from an analysis of the intensity statistics and crystal packing density. Tables of likely twinning operators and some examples are discussed here.
Crystallization and preliminary X-ray analysis of birch-pollen allergen Bet v 1 in complex with a murine monoclonal IgG Fab′ fragment
Authors: Spangfort Michael D. , Mirza Osman , Svensson L. Anders , Larsen Jørgen N. , Gajhede Michael , Ipsen Henrik
Published: July 2002

The human type I allergic response is characterized by the presence of allergen-specific serum immunoglobulin E (IgE). Allergen-mediated cross-linking of receptor-bound IgE on the surface of mast cells and circulating basophils triggers the release of mediators, resulting in the development of the clinical symptoms of allergy. In order to study the structural basis of allergen–antibody interaction, a complex between the major birch-pollen allergen Bet v 1 and a Fab′ fragment isolated from the murine monoclonal Bet v 1 antibody BV16 has been crystallized. Complex crystals belong to space group P1, with unit-cell parameters a = 91.65, b = 99.14, c = 108.90 Å, α = 105.7, β = 98.32, γ = 97.62°, and diffract to 2.9 Å resolution when analyzed at 100 K using synchrotron-generated X-rays.
Crystallization and preliminary crystal analysis of yeast hexokinase PI and PII
Authors: Kuser Paula R. , Golubev Alexander M. , Polikarpov Igor
Published: July 2002

Hexokinase is the prime enzyme of the Embden–Meyerhof pathway and is responsible for the first stage of energy conversion. It catalyzes the transfer of a phosphate to glucose to form glucose-6-phosphate. Yeast hexokinase PII is also known to play an important role in glucose signal transduction. Crystals of yeast hexokinase isoforms PI and PII were obtained by vapour-diffusion techniques using the hanging-drop method. Isoform PI crystals belong to the space group P212121, with unit-cell parameters a = 62.12, b = 78.87, c = 144.74 Å. Unit-cell parameters for isoform PII crystals are a = b = 142.81, c = 58.46 Å and the space group is I4. Synchrotron diffraction data have been collected to 2.2 Å resolution from the isoform PII crystal, whereas isoform PI diffracted to 3.1 Å.
Crystallization and preliminary crystallographic studies of ribosome recycling factor from Escherichia coli
Authors: Yun Jungmin , Kim Wookhyun , Ha Sung Chul , Eom Soo-Hyun , Suh Se Won , Kim Kyeong Kyu
Published: July 2002

Ribosome recycling factor (RRF) catalyzes the disassembly of a termination complex during the final stage of protein synthesis. RRF from Escherichia coli has been crystallized with PEG 400 as precipitant at 287 K. The crystal belongs to the trigonal space group P3121 (or P3221), with unit-cell parameters a = b = 48.08, c = 141.67 Å. Native data were collected from a frozen crystal to a resolution of 3.0 Å on a Cu Kα rotating-anode X-ray source.
Comparison between resonant Lα emission spectra and resonant LMM Auger spectra of yttrium compounds
Authors: Nakai Shun-Ichi , Kashiwakura Takayuki , Sasaki Katsuhiro , Watanabe Tohru
Published: July 2002

Resonant Lα x-ray emission spectra (RXES) and resonant LMM Auger emission spectra (RAES) of Yttrium compounds were measured across YLIII absorption threshold. When the incident photon energy is bellow the absorption threshold, only Raman scattering component is commonly observed in both spectra. Above the absorption threshold, Raman and normal Lα (or normal LMM Auger) emission peaks are observed in insulator samples. These spectral features are almost same in both RXES and RAES processes, except for the relative intensity ratio between these Raman peaks and normal Lα (or normal LMM Auger) emission peaks. Comparing these two spectra, useful information about the deexcitation of core hole can be obtained.
XAFS analysis of corroded metal surfaces with molten salts by conversion-electron-yield method
Authors: Yanase Etsuya , Arai Kazuo , Watanabe Iwao , Takahashi Masao , Dake Yoshinori
Published: July 2002

We have measured XAFS spectra of metal surfaces corroded with melting salt (NaCl, KCl, and Na2SO4). Steel samples used were S45C, SCM435, SUS310S, and SUS304. We measured the Fe K-edge XAFS spectra for all samples and the Ni K-edge for SUS310S and SUS304 samples before and after the corrosion. The XANES spectra of samples before the corrosion show metallic structure because surface oxide thickness is thinner than probing depth with a conversion yield XAFS method. Each result of these XAFS spectra gives good agreements with the FEFF calculation in the assumption of bcc and/or fcc structure. The Fe K-edge spectra of steel samples except SUS310S after corroded treatment show existence bonding between Fe and another light element although the spectra of SUS310S samples before and after corroded treatment are much the same. Keywords: metal, molten salts, corrosion.
XAFS study of the additive cation effect on the oxidation-resistance of platinum catalyst
Authors: Yazawa Yoshiteru , Yoshida Hisao , Hattori Tadashi
Published: July 2002

The additive cation effect on the oxidation-resistance of platinum supported on alumina was investigated by Pt LIII and LII-edge XAFS. The white line intensity at Pt LIII-edge of oxidized catalysts decreased with an increase in the electronegativity of the additive cation in the same way as the support effect previously reported: The addition of electrophilic cations make the supported platinum less oxidized state compared with the original Pt/Al2O3 and vice versa. Thus, it was revealed that the addition of more electrophilic cations provides the higher oxidation-resistance to platinum catalyst, even when platinum is supported on basic oxides.
XANES spectra of mechanical alloyed Y–Cu system
Authors: Nakai Ikuo , Murakami Yoshiyuki , Shibai Yoshifumi
Published: July 2002

Changes in the structure and the electronic states of YCu2 during mechanical alloying are reported. The x-ray diffraction shows that milling for about 60 h transforms mixture of elemental powders of Y and Cu into an amorphous alloy. We have measured the x-ray absorption near edge structure (XANES) spectra of mechanically alloyed YCu2 at Cu K and Y K edges at various milling time. The pre-edge peak near the Cu K threshold grows remarkably and its central energy decreases with increasing the milling time. The absorption near the Y K threshold, on the other hand, decreases with milling time. We discuss these features of XANES spectra in connection with the phase transformation from the crystalline to amorphous states.
QEXAFS study of the sulfidation of NiMo/Al2O3 hydrotreating catalysts
Authors: Cattaneo Riccardo , Shido Takafumi , Prins Roel
Published: July 2002

Quick-scanning extended X-ray absorption fine structure (QEXAFS) spectroscopy was employed to investigate in situ the sulfidation of Mo and Ni in γ-Al2O3-supported hydrotreating catalysts modified with chelating ligands. Mo K-edge QEXAFS enabled the detection of an intermediate product in the sulfidation of Mo. The parameters obtained from the fits of the QEXAFS spectra showed that this product consists of compounds similar to Mo2S{}_{12}^{2-} or Mo3S{}_{13}^{2-}. QEXAFS also demonstrated that the sulfidation of Ni is strongly influenced by the presence of chelating ligands. Classical EXAFS spectra of the sulfided catalysts showed that Ni forms small sulfided clusters, the size of which is influenced by the presence or absence of the chelating agents.
EXAFS study of crystal structures of (Ba1−xLax)2In2O5+x and their oxide ion conductivity
Authors: Uchimoto Yoshiharu , Takagi Hiromitsu , Yao Takeshi , Ozawa Naoshi , Inagaki Toru , Yoshida Hiroyuki
Published: July 2002

Crystal structures of (Ba1−xLax)2In2O5+x (x=0.00, 0.20, 0.30, 0.40, 0.50) were analyzed by EXAFS and the powder X-ray Rietveld method. A Fourier transform of In K-edge EXAFS data from (Ba1−xLax)2In2O5+x showed a peak between 1.2 and 2.0 Å attributed to the nearest oxide ions around In3+ cation. The peak was back-Fourier transformed, and the structural parameters were refined by the least square fitting. The coordination number of In3+ cation increases with increasing La3+ cation content. This means oxygen is introduced at interstitial site by keeping an electroneutrality. As a result of the oxygen distribution, the oxide ion vacancies distribute randomly. The electrical conductivities of (Ba1−xLax)2In2O5 rapidly increased above 1203 K due to the order–disorder transition of oxygen vacancy. On the other hand, the electrical conductivities of (Ba1−xLax)2In2O5+x (x=0.20, 0.30, 0.35, 0.40, 0.45, 0.50) did not show the sharp discontinuity in the conductivity because the disorder phase of defective perovskite type structure was stabilized by doping La3+ cations at A-site even at low temperature.
XAFS study of LiCo1-x
Fe
x
O2 cathode for rechargeable lithium battery by laboratory XAFS spectrometer
Authors: Kageyama Hiroyuki , Shigemura Hikari , Tabuchi Mitsuharu , Ado Kazuaki , Kobayashi Hironori
Published: July 2002

The change of local structure in layered-rock-salt-type iron doped lithium cobaltate LiCo1-xFexO2 under electrochemical Li de-intercalation (charge) /re-intercalation (discharge) was studied by a laboratory type XAFS spectrometer. In Co K-XANES and Fe K-XANES of LiCo0.85Fe0.15O2 the absorption peak shifted to higher energy by 1.5-2eV for Co K-edge and by 2-2.5eV for Fe K-edge, respectively, after the first charge. The spectra returned close to initial position and had almost original shape after the first discharge. In Co K- and Fe K-EXAFS of LiCo0.85Fe0.15O2 during the first charge and discharge the reversible change of the local structure was observed mainly around the Co atoms although the partly irreversible change of the local structure was found around the Fe atoms. The variation of local structure occurred in similar manner for the samples with x=0.05 and 0.25. This indicates that both Co3+/Co4+ and Fe3+/Fe4+ redox reactions occur reversibly during the first charge and discharge.
X-ray refraction-enhanced imaging and a method for phase retrieval for a simple object
Authors: Suzuki Yoshio , Yagi Naoto , Uesugi Kentaro
Published: July 2002

Refraction-enhanced imaging is now widely used for imaging low-absorption-contrast specimens in the hard X-ray region. However, the interpretation of the details of a refraction-enhanced image is not always clear. In this paper the theoretical treatment of refraction-enhanced imaging and a method for phase retrieval from refraction-contrast images are discussed in comparison with angular-deflection mapping of the transmitting beam. The problems of thick and complicated objects are also discussed.
2-Amino-5-(4-methoxybenzyl)-4-methyl-1,3-thiazolium chloride
Authors: Lynch Daniel E. , McClenaghan Ian
Published: July 2002

The structure of the title compound, C12H15ClN2OS, (I), comprises a twisted thiazolium base that associates to a free Cl ionviaN—H...Cl hydrogen-bonding interactions. The dihedral angle between the two ring systems is 79.65 (7)°.
Dibromo(N,N,N′,N′-tetramethylethane-1,2-diamine)zinc(II)
Authors: Citeau Helene , Conrad Olaf , Giolando Dean M.
Published: July 2002

The structure of the title compound, [ZnBr2(C6H16N2)], which is interesting from the metal coordination point of view, was determined by direct methods on 15672 observed reflections with MoKα radiation. The asymmetric unit contains two molecules on general positions.
trans-Tetraaquabis(pyridine-4-carboxylate-κN)nickel(II)
Authors: Batten Stuart R. , Harris Alexander R.
Published: July 2002

The title complex, [Ni(C6H4NO2)2(H2O)4], consists of Ni atoms coordinated to twotranspyridylcarboxylate ligands, coordinated through the N atoms, and four water ligands. The Ni atom lies on a centre of symmetry. Extensive inter-complex hydrogen bonding occurs between the water ligands and the carboxylate groups, resulting in a three-dimensional network.
trans-Dinitro(1,4,8,11-tetraazacyclotetradecane-N,N′,N′′,N′′′)cobalt(III) perchlorate
Authors: Ohba Shigeru , Yamada Naoki , Eishima Makoto
Published: July 2002

In the title compound,trans-[Co(NO2)2(cyclam)]ClO4, (I), where cyclam is 1,4,8,11-tetraazacyclotetradecane (C10H24N4), the CoIIIcomplex has a distorted octahedral coordination. The O atoms of each nitro ligand are disordered over two sites with 65:35% occupancy.
2-Chloro-4-methylquinoline
Authors: Lynch Daniel E. , McClenaghan Ian
Published: July 2002

The structure of the title compound, C10H8ClN, comprises planar molecules that form stacked columns parallel to thebcell direction. Two symmetry-related molecules associateviaC—H...N interactions to form a non-planarR22(8) dimer.
Tris(1,2-dimethoxyethane-O,O′)sodium pentaphenylcyclopentadienide
Authors: Holl Sven , Bock Hans , Gharagozloo-Hubmann Katayoun
Published: July 2002

The title compound, [Na(C4H10O2)3](C35H25), is the first pentaphenylcyclopentadienide salt with an isolated anion. Solvent-separated sodium cations and pentaphenylcyclopentadienide anions alternate with each other in stacks parallel to thebaxis and are arranged in segregated stacks along theadirection.
Vulgarone B
Authors: Yokochi Alex F. T. , White James D. , Sturtz George
Published: July 2002

The crystal structure of vulgarone B (2,6,6,11-tetramethyltricyclo[5.4.0.02,8]undec-10-en-9-one), a carbocyclic sesquiterpene with the formula C15H22O, is reported. All intramolecular geometric parameters are as expected. The molecule contains a four-membered ring, in which all atoms are stereogenic. The 1,3 and 2,4 atoms of this cyclobutane are bridgehead C atoms which form part of six-membered and seven-membered rings.
Laser surface melting for improving intergranular corrosion resistance of cold‐worked and sensitised type 316 stainless steel
Authors: Kamachi Mudali U. , Dayal R.K. , Goswami G.L.
Published: July 2002

This study used laser melting techniques to improve the intergranular corrosion resistance of cold worked and sensitised stainless steel surfaces. Type 316 stainless steel specimens, cold worked to 5 per cent, 10 per cent and 20 per cent reductions in thickness values, were sensitised at 923K for 25 hours. These specimens were laser‐surface‐melted by using a 300W Nd:YAG pulsed laser, and tested according to ASTM A262 practice A and practice E tests. The results of the practice A test showed that a cellular‐dendritic structure was present in the laser‐melted region in contrast to a typical ditch microstructure observed for sensitised unmelted specimens and a ditch structure was not present in the melt‐affected zone (MAZ). The hardness measurements across the melted, MAZ, and unmelted zones showed significant variations in their values. The results of the practice E tests showed no intergranular cracks for laser‐melted specimens while the unmelted specimens (5 and 10 per cent cold working) failed the test through significant cracking. The improvement in IGC resistance is attributed to the dissolution of M23C6 carbides and the homogenisation of chromium‐depleted regions.
Interpersonal skills training for quality service interactions
Authors: Garavan Thomas N.
Published: July 2002

Achieving improvements in customer service is now recognized as a major challenge facing manufacturing and service industries throughout the world. This challenge is particularly pertinent to the tourism and hospitality sector. Notions of quality in the tourism and hospitality sector have changed dramatically in the past 25 years: it was once synonymous with luxury and personalized service; it now counts at all levels of price. Service quality is often presented in the literature as primarily a marketing‐oriented concept; however, it has major implications for the quality of human resources and specifically for training and development activities. Focuses on the human resource dimension, specifically the behaviours which hinder and facilitate transactions between people in a service environment. Begins with a discussion of the concepts of quality, customer and service improvement, then considers the factors influencing interpersonal relationships and discusses alternative approaches to the development of interpersonal skills. Considers the nature of services and, finally, reports a study which evaluates the impact of an interpersonal training and development intervention on the quality of service provided by front‐office staff in a medium‐sized hotel.
Knowledge management in the learning organization
Authors: Hong Jon‐Chao , Kuo Chia‐Ling
Published: July 2002

Businesses have to go through constant innovations on management, and innovation principles must be acquired through constant learning. Learning principles are realized through knowledge and wisdom sharing with colleagues, clients, and others in such learning activities as instruction, sharing, and self‐study. Such knowledge and wisdom sharing activities include study circles, on the job training, and technology exhibitions. Different learning activities such as survival learning, benchmark learning and leading learning are subject to different sharing mechanisms. Moreover the mastery of each sharing function is fundamental to enhancing the performance of knowledge management in a learning organization.
Solution of quasi‐static, force‐driven problems by means of a dynamic‐explicit approach and an adaptive loading procedure
Authors: Mattiasson Kjell , Bernspång Lars , Samuelsson Alf
Published: July 2002

Argues that the dynamic‐explicit approach has in recent years been successfully applied to the solution of various quasi‐static, elastic‐plastic problems, especially in the metal forming area. A condition for the success has, however, been that the problems have been displacement‐driven. The solution of similar force‐driven problems, using this approach, has been shown to be much more complicated and computationally time consuming because of the difficulties in controlling the unphysical dynamic forces. Describes a project aiming to develop a methodology by which a force‐driven problem can be analysed with similar computational effort as a corresponding displacement‐driven one. To this end an adaptive loading procedure has been developed, in which the loading rate is controlled by a prescribed velocity norm. Presents several examples in order to exhibit the merits of the proposed procedure.
Managerial stress in Hong Kong and Taiwan: a comparative study
Authors: Siu Oi‐ling , Lu Luo , Cooper Cary L.
Published: July 2002

This study investigated occupational stress in managers in Hong Kong and Taiwan using the Occupational Stress Indicator‐2 (OSI‐2). The results showed the reliabilities and predictive validity of the OSI‐2 subscales were reasonably high in both samples. The logical relationships between job satisfaction, mental and physical well‐being found in the two samples have provided support to findings obtained in Western countries. Moreover, the direct impacts of coping strategies, Type A behaviour and locus of control on job strains also corroborated previous studies in Western societies. Further, there were gender differences in managerial stress in Hong Kong: female managers scored higher in sources of stress and quitting intention; but had lower job satisfaction, worse mental and physical well‐being than male managers. These differences could not be found in Taiwanese managers, yet Taiwanese female managers did report more stress related to the “managerial role” than their male counterparts.
Professional development for heads: the role of mentoring
Authors: Bush Tony , Coleman Marianne
Published: July 2002

Mentoring is an important mode of professional development in many
countries. It involves an experienced colleague supporting the
development of a new principal. Reports the findings of one aspect of a
major national research project on mentoring and teacher education in
England and Wales. Considers the nature and purpose of mentoring and
examines the “match” between mentor and the new headteacher.
Reports on the benefits of mentoring for new principals, mentors and the
educational system, and discusses certain limitations of this approach
to professional development. Presents several conceptual models of the
mentor relationship and reports that the dominant normative conception
is that of peer support. Concludes that mentoring is valuable in
supporting principals as they adapt to their new role but it may lack
the rigour to be a really effective mode of professional development.
Timing and structural consideration for the processing of mitochondrial matrix space proteins by the mitochondrial processing peptidase (MPP)
Authors: Mukhopadhyay Abhijit , Hammen Philip , Waltner‐Law Mary , Weiner Henry
Published: July 2002

Most mitochondrial matrix space proteins are synthesized as a precursor protein, and the N‐terminal extension of amino acids that served as the leader sequence is removed after import by the action of a metalloprotease called mitochondrial processing peptidase (MPP). The crystal structure of MPP has been solved very recently, and it has been shown that synthetic leader peptides bind with MPP in an extended conformation. However, it is not known how MPP recognizes hundreds of leader peptides with different primary and secondary structures or when during import the leader is removed. Here we took advantage of the fact that the structure of the leader from rat liver aldehyde dehydrogenase has been determined by 2D‐NMR to possess two helical portions separated by a three amino acid (RGP) linker. When the linker was deleted, the leader formed one long continuous helix that can target a protein to the matrix space but is not removed by the action of MPP. Repeats of two and three leaders were fused to the precursor protein to determine the stage of import at which processing occurs, if MPP could function as an endo peptidase, and if it would process if the cleavage site was part of a helix. Native or linker deleted constructs were used. Import into isolated yeast mitochondria or processing with recombinantly expressed MPP was performed. It was concluded that processing did not occur as the precursor was just entering the matrix space, but most likely coincided with the folding of the protein. Further, finding that hydrolysis could not take place if the processing site was part of a stable helix is consistent with the crystal structure of MPP. Lastly, it was found that MPP could function at sites as far as 108 residues from the N terminus of the precursor protein, but its ability to process decreases exponentially as the distance increases.
Control of the allosteric equilibrium of hemoglobin by cross‐linking agents
Authors: Marden Michael C. , Cabanes‐Macheteau Marion , Babes Alexandru , Kiger Laurent , Griffon Nathalie , Poyart Claude , Boyiri Telih , Safo Martin K. , Abraham Donald J.
Published: July 2002

The kinetics of ligand rebinding have been studied for modified or cross‐linked hemoglobins (Hbs). Several compounds were tested that interact with α Val 1 or involve a cross‐link between α Val 1 and α Lys 99 of the opposite dimer. By varying the length of certain cross‐linking molecules, a wide range in the allosteric equilibrium could be obtained. Several of the mono‐aldehyde modified Hbs show a shift toward the high affinity conformation of Hb. At the other extreme, for certain di‐aldehyde cross‐linked Hbs, the CO kinetics are typical of binding to deoxy Hb, even at low photodissociation levels, with which the dominant photoproduct is the triply liganded species; in these cases the hemoglobin does not switch from the low to high affinity state until after the fourth ligand is bound. Although each modified Hb shows only two distinct rates, the kinetic data as a function of dissociation level cannot be simulated with a simple two‐state model. A critical length is observed for the maximum shift toward the low affinity T‐state. Longer or shorter lengths of the cross‐linker yielded more high affinity R‐state. Unlike native Hb, which is in equilibrium with free dimers, the cross‐linked Hbs maintain the fraction slow kinetics, which is unique to Hb tetramers, even at 0.5 μM (total heme). Addition of HbCN to unmodified HbCO solutions results in dimer exchange, which decreases the relative fraction of slow bimolecular kinetics; the cross‐linked Hbs did not show such an effect, indicating that they do not participate in dimer exchange.
Hypocretin‐2 (orexin‐B) modulation of superficial dorsal horn activity in rat
Authors: Grudt Timothy J. , van den Pol Anthony N. , Perl Edward R.
Published: July 2002

The hypothalamic peptides hypocretin‐1 (orexin A) and hypocretin‐2 (Hcrt‐2; orexin B) are important in modulating behaviours demanding arousal, including sleep and appetite. Fibres containing hypocretin project from the hypothalamus to the superficial dorsal horn (SDH) of the spinal cord (laminae I and II); however, the effects produced by hypocretins on SDH neurones are unknown. To study the action of Hcrt‐2 on individual SDH neurones, tight‐seal, whole‐cell recordings were made with biocytin‐filled electrodes from rat lumbar spinal cord slices. In 19 of 63 neurones, Hcrt‐2 (30 nm to 1 μm) evoked an inward (excitatory) current accompanied by an increase in baseline noise. The inward current and noise were unaffected by TTX but were blocked by the P2X purinergic receptor antagonist suramin (300–500 μm). Hcrt‐2 (30 nm to 1 μm) increased the frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) in the majority of neurones. The sIPSC increase was blocked by strychnine (1 μm) and by TTX (1 μm), suggesting that the increased sIPSC frequency was glycine and action potential dependent. Hcrt‐2 increased the frequency of spontaneous excitatory postsynaptic currents (sEPSCs) in a few neurones but had no effect on dorsal root‐evoked EPSCs in these or in other neurones. Neurones located in outer lamina II, particularly radial and vertical cells, were most likely to respond to Hcrt‐2. We conclude that Hcrt‐2 has excitatory effects on certain SDH neurones, some of which exert inhibitory influences on other cells of the region, consistent with the perspective that hypocretin has a role in orchestrating reactions related to arousal, including nociception, pain and temperature sense.
An Analytical and Experimental Analysis for a One-Dimensional Passive Stand-Off Layer Damping Treatment
Authors: Yellin Jessica M. , Shen I. Y. , Reinhall Per G. , Huang Peter Y. H.
Published: July 2002

Passive stand-off layer (PSOL) damping treatments are presently being implemented in many commercial and defense designs. In a passive stand-off layer damping treatment, a stand-off or spacer layer is added to a conventional passive constrained layer (PCL) damping treatment. An analytical model which quantifies the bending and shearing contributions of the stand-off layer has been developed for a passive stand-off layer damping treatment applied to a beam. The equations of motion were derived and solved in order to simulate the frequency responses of several beams treated with passive stand-off layer damping. A series of experiments was conducted in order to test this analytical model. These experiments measured the frequency responses of a variety of beams treated with passive stand-off layer damping treatments. The experimentally measured results were normalized and calibrated and then compared with the theoretical predictions using the new analytical model. This comparison showed that the analytical model was able to predict very accurately the frequency responses of the beams treated with passive stand-off layer damping. [S0739-3717(00)01004-7]