bluuebunny/crossref_metadata_2025 huggingface dataset:
Indexing approximants of icosahedral quasicrystals
Authors: Quiquandon M. , Katz A. , Puyraimond F. , Gratias D.
Published: July 2002

It is well known that the crystallography of approximants is directly related to that of the parent quasicrystal, once its unit-cell vectors are identified as parallel projections of certain N-dimensional lattice nodes {\bf A}^{i}. Derived here are explicit simple relations for calculating the shear matrices {\boldvarepsilon} and the related crystallographic properties of the corresponding approximants, including diffraction indexing and the determination of the lattice in perpendicular space. Applied to low-dimensional approximants, the derivation shows that the systematic `accidental' extinction rules observed in the pentagonal phases are generic extinctions that are due to the geometrical properties of the projected 1D lattice and are independent of the actual model of the quasicrystal.
Structure of Nd10W22O81 from high-resolution electron microscopy and X-ray powder diffraction
Authors: Grenthe Carl , Guagliardi Antonietta , Sundberg Margareta , Werner Per-Erik
Published: July 2002

The crystal structure of Nd10W22O81, neodymium tungstate, has been determined using a combination of high-resolution transmission electron microscopy and X-ray powder diffraction methods. The unit-cell dimensions determined from X-ray data are a  =  3.8613 (1), b  =  35.9431 (1), c  =  21.8900 (1) Å, V = 3038.05 Å3, Z  =  2, space group Pbcm. The structure is built up of pentagonal columns (PCs) connected to ReO3-type fragments consisting of three octahedra, thus forming W9O32 units. These units form `pillars' along a. These `pillars' are joined by pairs of tilted octahedra (W2O11 groups) to form corrugated layers perpendicular to b. The Nd atoms are located in the space between these layers and form the only link between them. Interstitial O atoms are located between two of the Nd atoms. The formula Nd10W22O81 can thus be alternatively given as Nd5W11O39 + x
(x ≃ 1.5), where x represents the interstitial O atoms. Nd10W22O81 is a new type of PC structure.
Modification of crystal structure of ammonium Rochelle salt [NaNH4(+)-C4H4O6.4H2O] owing to the replacement of NH4 ions with K ions
Authors: Suzuki E. , Muta T. , Nozaki R. , Shiozaki Y.
Published: July 2002

The crystal structures of NaK1−x
(NH4)
x
(+)-C4H4O6.4H2O (RS1−x
ARS
x
, x = 0.90, 0.94 and 1.00) have been determined in the paraelectric phase (T = 294 K). The crystal data are: for ARS, orthorhombic, P21212, R = 0.038, wR = 0.032, no. of reflections = 3373, a = 12.206 (7), b = 14.451 (6), c = 6.250 (4) Å, V = 1102 (1) Å3, Z = 4, Dx
= 1.573 g cm−3, λ(MoKα) = 0.70926 Å, F(000) = 552.00; for RS0.06ARS0.94, orthorhombic, P21212, R = 0.040, wR = 0.030, no. of reflections = 2446, a = 12.172 (4), b = 14.421 (4), c = 6.239 (2) Å, V = 1095.2 (6) Å3, Z = 4, Dx
= 1.592 g cm−3, λ(Mo Kα1) = 0.70926 Å, F(000) = 553.92; for RS0.10ARS0.90, orthorhombic, P21212, R = 0.036, wR = 0.027, no. of reflections = 1898, a = 12.165 (9), b = 14.420 (7), c = 6.239 (4) Å, V = 1094 (1) Z = 4, Dx
= 1.598 g cm−3, λ(Mo Kα1) = 0.70926 Å, F(000) = 555.20. In the crystals there are two crystallographically nonequivalent cation sites occupied by K/NH4 ions. The accommodation ratios of sites (1) [(2a) by the Wyckoff notation] and (2) [(2b)] are 0.94 (1) and 0.92 (1), respectively, in RS0.06ARS0.94, and 0.90 (1) and 0.93 (1), respectively, in RS0.10ARS0.90. As x increases, the location of site (2) displaces towards the origin. The hydrogen bonds around sites (1) and (2) are classified into two types: one is that the distances become longer as x increases, due to the difference in the ionic radii of K and NH4 ions, while the other is that the distances are equal. Comparing the crystal structure of ARS to that of RS, the following differences occur: the position of site (2), the interatomic distances between cations of sites (1) and (2) and O atoms, the form of the tartrate molecule and the position of some water molecules. These differences seem to be mainly caused by the replacement of NH4 ions by K.
Structure of ammonium hydrogen succinate above and below the phase transition around 170K
Authors: Hirano A. , Kubozono Y. , Maeda H. , Ishida H. , Kashino S.
Published: July 2002

For crystals of ammonium hydrogen succinate it is known that the space group is P{\bar 1} with Z = 2 at 293 K and the second-order phase transition occurs around 170 K. X-ray crystal structure analyses above and below 170 K have been carried out in order to study the change in mode of short hydrogen bonds between the hydrogen succinate ions. The space group was determined to be P{\bar 1} at 150 and 190 K by structure analysis. No ordering of the H-atom positions in the short hydrogen bonds occurs by the phase transition. The hydrogen bonds show a decrease in the O...O distances with a decrease in temperature from 290 to 190 K, but no significant change in the geometries between 190 and 150 K. Disorder of the NH4
+ ion is not observed at 297, 190 and 150 K. Significant change through the phase transition is found only in the geometry of one of the N—H...O hydrogen bonds between ammonium and hydrogen succinate ions.
Theoretical and experimental (113 K) electron-density study of lithium bis(tetramethylammonium) hexanitrocobaltate(III)
Authors: Bianchi R. , Gatti C. , Adovasio V. , Nardelli M.
Published: July 2002

This paper presents an analysis of the crystal structure and the charge density, ρ(r), for lithium bis(tetramethylammonium) hexanitrocobaltate(III) determined by the rigid pseudoatom model from accurate X-ray data measured at 113 K. This compound has also been investigated by an ab initio Hartree–Fock fully periodic approach. A comparison of the topological properties between the experimentally and theoretically derived density is also given. A notable agreement between experiment and theory is observed in the topological properties of the metal-ligand interaction and a close parallel between the orbital model description and the shape of the Laplacian distribution around the Co atom is outlined. The results confirm the typical 3d-electron distribution of octahedral CoIII complexes in a low-spin state and the presence of four C—H...O hydrogen bonds in the crystal structure. Important differences between experiment and theory remain for the Laplacian and the parallel curvature (λ
3) values at the C—N and N—O bond critical points. The atomic charges derived from the Quantum Theory of Atoms in Molecules are remarkably close to the formal values.
Statistical analysis of noncovalent interactions of anion groups in crystal structures. I. Hydrogen bonding of sulfate anions
Authors: Chertanova L. , Pascard C.
Published: July 2002

The hydrogen-bond acceptor characteristics of sulfate dianions are analyzed in crystal structures of small molecules. For 85 anions, neither coordinated to metal ions nor covalently bonded, 697 hydrogen bonds are faund. Of these, 266 (38%) are the O...H—O type and 431 (62%) are the O...H—N type, proportions that correspond well to the stoichiometry of the compounds studied and indicate no preference for a particular donor. The analysis of the data set, after classifying the hydrogen bonds according to the different types of donors, shows that O...H—O bonds are more linear than O...H—N. The anion oxygen–acceptor function is characterized by multiple hydrogen bonding. Only in 56 cases does a sulfate oxygen participate in a single hydrogen bond. In most cases every sulfate oxygen is coordinated by two (187 cases) or three (89 cases) hydrogen bonds. For three H donors, the preferred coordination geometry of the sulfate oxygen is pyramidal. The most frequent coordination around a sulfate dianion is with eight to ten H donors. Thus, sulfate dianions can play a significant cohesive role in molecular aggregation.
Definitive Structural Characterization of the Conventional Low-Temperature Host Structure in Urea Inclusion Compounds
Authors: Yeo L. , Harris K. D. M.
Published: July 2002

Structural properties of the 1,10-dibromodecane/urea and 1,12-dibromododecane/urea inclusion compounds have been determined by single-crystal X-ray diffraction for both the high- and low-temperature phases. In the high-temperature phase both inclusion compounds have the conventional hexagonal urea tunnel structure, with substantial orientational disorder of the guest molecules. In the low-temperature phase the urea tunnel structure distorts to an orthorhombic structure, based on a distorted form of the orthohexaganol cell of the high-temperature structure and with the loss of the C centre. Within this tunnel structure there is evidence that the guest molecules have a narrow distribution of orientations (with respect to rotation about the tunnel axis) and the preferred orientation of the guest molecules correlates well with the observed distortion of the host tunnel. This represents the first accurate and reliable report of the conventional low-temperature structure of urea inclusion compounds. Previous powder X-ray diffraction studies have confirmed that the host structure in the low-temperature phase of 1,10-dibromodecane/urea is the same as that in the low-temperature phase of the alkane/urea inclusion compounds.
Low-Temperature Synchrotron Radiation Study of a Twinned Disordered Crystal of Bis(4,4'-bromophenyl)-61,61-diyl Methano Fullerene C60
Authors: Iversen B. B. , Darovsky A. , Bolotovsky R. , Coppens P.
Published: July 2002

Synchrotron radiation diffraction measurements at 100 (5) K have been carried out on bis(4,4′-bromophenyl)-61,61-diyl methano fullerene C60 using area detector technology. In order to obtain a satisfactory description of the data it is necessary to introduce both a twinning model of the crystal and a disorder model consisting of two different isomers of the title compound. The study provides the first solid-state characterization of a 6–5 isomer of a methano fullerene. For the 6–6 isomer the geometry is in good agreement with recent literature on methano fullerenes. Unfortunately, the present study cannot resolve the bond lengths in the transannular region. The fact that the structure can be solved from diffraction data measured on a minute poorly scattering crystal shows that the low-temperature single-crystal synchrotron radiation technique is an indispensable tool in chemical crystallography.
Structures of Homoleptic Benzyl Derviatives of Zirconium
Authors: Tedesco C. , Immirzi A. , Proto A.
Published: July 2002

Crystals of Zr(p-CH2C6H4CMe3)4, tetra(4-tert-butylbenzyl)zirconium (1), have been studied by X-ray diffraction. The crystals belong to the tetragonal system, space group I4¯, with a = 16.481 (2), c = 7.131 (4) Å, so that chemically equivalent ligands are also structurally equivalent, unlike other known homoleptic M(CH2C6H5)4 compounds. Zr—CH2—C
ipso
bond angles of 90.0 (2)° suggest that ligands are η2-bonded. The structure is discussed along with that of Zr(CH2C6H5)4, tetrabenzylzirconium (2) (redetermined), which is crystallographically unsymmetrical but also of approximate S
4 symmetry. The distortion of (2) from tetragonal symmetry (the four Zr—CH2—C
ipso
bond angles being rather different) is discussed along with crystal packing.
Calculation of Structural Parameters in Isostructural Series: the Kieserite Group
Authors: Aleksovska S. , Petrusevski V. M. , Soptrajanov B.
Published: July 2002

In order to demonstrate the possibility of predicting the structural parameters of members in a sequence of isostructural compounds, the kieserite group isotypes (with the general formula M
II
XO4.H2O) were chosen since a number of them have accurately refined crystal structures. The unit-cell parameters and the fractional atomic coordinates were shown to vary linearly with both cation and anion size. This makes it possible to calculate the structural parameters of a particular member, taking into account only the effective ionic radii of the constituent atoms. Agreement between the calculated and experimentally refined (by X-ray diffraction) structural parameters is good. The cell constants and atomic coordinates of FeSeO4.H2O, iron selenate monohydrate, are predicted in this way.
Determination of the site of incorporation of cobalt in CoZnPO-CZP by multiple-wavelength anomalous-dispersion crystallography
Authors: Helliwell M. , Helliwell J. R. , Kaucic V. , Zabukovec Logar N. , Barba L. , Busetto E. , Lausi A.
Published: July 2002

Data were collected from a crystal of CoZnPO-CZP {sodium cobalt–zinc phosphate hydrate, Na6[Co0.2Zn0.8PO4]6.6H2O} using synchrotron radiation at ELETTRA at the inflection point and `white line' for both the cobalt and zinc K edges, and at 1.45 Å, a wavelength remote from the K edges of both metals. The data were processed using the programs DENZO and SCALEPACK. The CCP4 program suite was used for the scaling of data sets and the subsequent calculation of dispersive difference Fourier maps. Optimal scaling was achieved by using a subset of reflections with little or no contribution from the metal atoms (i.e. which were essentially wavelength independent in their intensities) and using weights based on the σ's to obtain an overall scale factor in each case. Phases were calculated with SHELXL97 based on the refined structure using a much higher resolution and complete Cu Kα data set. An occupancy of 100% by zinc at the two metal-atom sites was assumed. The dispersive difference Fourier map calculated for zinc gave two peaks above the background of similar heights at the expected metal-atom sites. The peak height at the Zn1 site was a little higher than at the Zn2 site. The dispersive difference Fourier map calculated for cobalt gave just one peak above the background, at the Zn1 site, and only a small peak at the Zn2 site, thus indicating that incorporation of cobalt takes place mainly at one site. Refinement of the zinc occupancies using MLPHARE reinforces this conclusion. The chemical environment of each site is discussed.
Topological analysis of the electron density in hydrogen bonds
Authors: Espinosa E. , Souhassou M. , Lachekar H. , Lecomte C.
Published: July 2002

Topological analysis of the experimental electron density ρ(r) in hydrogen-bonding regions has been carried out for a large number of organic compounds using different multipole models and techniques. Relevant systematic relationships between topological properties at the critical points and the usual geometric parameters are pointed out. Results involving X-ray data only and joint X-ray and neutron data, as well as special hydrogen bonding cases (symmetric, bifurcated, peptide bonds, etc.) are included and analysed in the same framework. A new classification of hydrogen bonds using the positive curvature of the electron density at the critical point [\lambda_3({\bf r}_{\rm CP})] is proposed.
Crystallization of the NADP-dependent β-keto acyl carrier protein reductase from Escherichia coli
Authors: Rafferty John B. , Fisher Martin , Langridge Sarah J. , Martindale Wayne , Thomas Neil C. , Simon J. William , Bithell Siàn , Slabas Antoni R. , Rice David W.
Published: July 2002

The NADP-dependent β-keto acyl carrier protein reductase (BKR) from E. coli has been crystallized by the hanging-drop method of vapour diffusion using poly(ethylene glycol) of average molecular weight 1450. The crystals belong to the hexagonal space group P6122 or P6522 with unit-cell dimensions a = b = 67.8, c = 355.8 Å. Calculated values for Vm
and consideration of the packing suggest that the asymmetric unit contains a dimer. BKR catalyses the first reductive step in the elongation cycle of fatty-acid biosynthesis. It shares extensive sequence homology with the enzyme which catalyzes the second reductive step in the cycle, enoyl acyl carrier protein reductase (ENR), and thus provides an opportunity to study the evolution of enzyme function in a metabolic pathway. The structure determination will permit the analysis of the molecular basis of its catalytic mechanism and substrate specificity.
Envelope skeletonization as a means to determine monomer masks and non-crystallographic symmetry relationships: application in the solution of the structure of fibrinogen fragment D
Authors: Spraggon Glen
Published: July 2002

An algorithm is described which utilizes the solvent mask generated by the solvent-flattening technique to calculate a monomer molecular envelope. In the case where non-crystallographic symmetry (NCS) is present in the crystal and self-rotation angles are known from a self-rotation function, the resultant monomer envelopes can be used to search for the translation component of the NCS element by a three-dimensional search in real space. In the absence of self-rotation angles, the monomer envelope may be used to derive the NCS operators by reciprocal-space techniques. Thus, an automatic procedure for averaging directly from the solvent-flattening stage can be implemented. The procedure was instrumental in the structure solution of fibrinogen fragment D, which is presented as an example.
Crystallization and preliminary X-ray diffraction of Trypanosoma cruzi dUTPase
Authors: Bernier-Villamor V. , Camacho A. , González-Pacanowska D. , Cedergren-Zeppezauer E. , Antson A. , Wilson K. S.
Published: July 2002

Crystals of Trypanosoma cruzi dUTPase have been grown. Two different morphologies are observed, depending on the molecular weight of the PEG used as precipitating agent in the mother liquor, both having a hexagonal unit cell with similar dimensions. Complete X-ray diffraction data have been collected to low resolution for one of the forms. The space group is P6322, with unit-cell dimensions a = 134.15, c = 147.05 Å. Peaks in the self-rotation function and the solvent content are consistent with two molecules of dUTPase per asymmetric unit.
Crystallization of importin α, the nuclear-import receptor
Authors: Teh Trazel , Tiganis Tony , Kobe Bostjan
Published: July 2002

Crystals of recombinant importin α, the nuclear-import receptor, have been obtained at two different pH conditions by vapour diffusion using sodium citrate as precipitant and dithiothreitol as an additive. At pH 4–5, the crystals have the symmetry of the trigonal space group P3121 or P3221 (a = b = 78.0, c = 255.8 Å, γ = 120°); at pH 6–7, the crystals have the symmetry of the orthorhombic space group P212121 (a = 78.5, b = 89.7, c = 100.5 Å). In both cases, there is probably one molecule of importin α in the asymmetric unit. At least one of the crystal forms diffracts to a resolution higher than 3 Å using the laboratory X-ray source; the crystals are suitable for crystal structure determination.
The structures of α2u-globulin and its complex with a hyaline droplet inducer
Authors: Chaudhuri Barnali N. , Kleywegt Gerard J. , Björkman Joakim , Lehman-McKeeman Lois D. , Oliver Joel D. , Jones T. Alwyn
Published: July 2002

α2u-Globulin (A2U) is the major urinary protein excreted by adult male rats. The structure of a monoclinic crystal form of A2U was reported in 1992 [Böcskei et al. (1992). Nature (London),
360, 186–188]. The structures of an orthorhombic crystal form of A2U at 2.5 Å resolution (refined to an R factor of 0.248; R
free = 0.264) and of a complex between A2U and d-limonene 1,2-epoxide (DLO) at 2.9 Å resolution (R factor = 0.248; R
free = 0.260) are presented here. DLO is one of a diverse group of chemicals which cause a male rat-specific renal carcinogenesis called hyaline-droplet nephropathy. The rate-determining step in the development of this disorder is the binding of the toxin to A2U. Comparison of the cavities in A2U and in the corresponding mouse urinary protein (MUP) reveal that the former is tailor-made for small oval hydrophobic ligands such as DLO. The cavity in MUP is more shallow and elongated and cannot easily accommodate such ligands.
Three-dimensional structure of β-momorcharin at 2.55 Å resolution
Authors: Yuan Yu-Ren , He Yong-Ning , Xiong Jian-Ping , Xia Zong-Xiang
Published: July 2002

β-Momorcharin (Mr
≃ 29 kDa) is a single-chained ribosome-inactivating protein (RIP) with a branched hexasaccharide bound to Asn51. The crystal structure of β-momorcharin has been determined using the molecular-replacement method and refined to 2.55 Å resolution. The final structural model gave an R factor of 17.2% and root-mean-square deviations of 0.016 Å and 1.76° from ideal bond lengths and bond angles, respectively. β-Momorcharin contains nine α-helices, two 310 helices and three β-sheets, and its overall structure is similar to those of other single-chained RIPs. Residues Tyr70, Tyr109, Glu158 and Arg161 are expected to define the active site of β-momorcharin as an rRNA N-glycosidase. The oligosaccharide is linked to the protein through an N-glycosidic bond, β-GlcNAc–(1-N)-Asn51, and stretches from the surface of the N-terminal domain far from the active site, which suggests that it should not play a role in enzymatic function. The oligosaccharide of each β-momorcharin molecule interacts with the protein through hydrogen bonds, although in the crystals most of these are intermolecular interactions with the protein atoms in an adjacent unit cell. This is the first example of an RIP structure which provides information about the three-dimensional structure and binding site of the oligosaccharide in the active chains of RIPs.
B-DNA at atomic resolution reveals extended hydration patterns
Authors: Vlieghe Dominique , Turkenburg Johan P. , Van Meervelt Luc
Published: July 2002

Despite the importance of hydration around DNA in the understanding of its conformation and interactions with other molecules in many biological processes, only limited atomic resolution information is available. Crystal-engineering techniques, which were originally developed to mimic DNA base triplets in a crystal lattice, also eliminate the rotational disorder of oligonucleotides around their helical axis and thereby enhance the resolution of the structure analysis. The low-temperature crystal structure of the synthetic DNA decamer d(GGCCAATTGG) has been determined at atomic resolution (1.15 Å) using 17700 reflections and the highly organized hydration patterns in both grooves have been characterized. The narrow d(AATT) minor groove is occupied by an `extended hydration spine' alternately bridging base pairs and phosphate O1P atoms of opposite strands, while a distinctive pattern of parallel water ribbons is observed in the major groove. This analysis provides structural insight into the correlation found between narrow minor-groove width and occurrence of the BI conformation and can be used to design new minor-groove binders. By their location between adjacent helices, two fully hydrated magnesium ions further stabilize the crystal packing. The structure also provides details of the hydration and conformation of G·GC triple helices.
Structure of oxalate-substituted diferric mare lactoferrin at 2.7 Å resolution
Authors: Sharma Ashwani K. , Singh Tej P.
Published: July 2002

Lactoferrin binds two Fe3+ and two CO^{2-}_{3} ions with high affinity. It can also bind other metal ions and anions. In order to determine the perturbations in the environments of the binding sites in the N and C lobes and elsewhere in the protein, the crystal structure of oxalate-substituted diferric mare lactoferrin has been determined at 2.7 Å resolution. The final model has a crystallographic R factor of 21.3% for all data in the resolution range 17.0–2.7 Å. The substitution of an oxalate anion does not perturb the overall structure of the protein, but produces several significant changes at the metal-binding and anion-binding sites. The binding of the oxalate anion is symmetrical in both the N and C lobes, unlike in diferric dioxalate human lactoferrin, where the oxalate anion binds the metal ion symmetrically in the C lobe and asymmetrically in the N lobe.
1.35 and 2.07 Å resolution structures of the red abalone sperm lysin monomer and dimer reveal features involved in receptor binding
Authors: Kresge Nicole , Vacquier Victor D. , Stout C. David
Published: July 2002

Abalone sperm use lysin to make a hole in the egg's protective vitelline envelope (VE). When released from sperm, lysin first binds to the VE receptor for lysin (VERL) then dissolves the VE by a non-enzymatic mechanism. The structures of the monomeric and dimeric forms of Haliotis rufescens (red abalone) lysin, previously solved at 1.90 and 2.75 Å, respectively, have now been refined to 1.35 and 2.07 Å, respectively. The monomeric form of lysin was refined using previously obtained crystallization conditions, while the dimer was solved in a new crystal form with four molecules (two dimers) per asymmetric unit. These high-resolution structures reveal alternate residue conformations, enabling a thorough analysis of the conserved residues contributing to the amphipathic nature of lysin. The availability of five independent high-resolution copies of lysin permits comparisons leading to insights on the local flexibility of lysin and alternative conformations of the hypervariable N-terminus, thought to be involved in species-specific receptor recognition. The new analysis led to the discovery of the basic nature of a cleft formed upon dimerization and a patch of basic residues in the dimer interface. Identification of these features was not possible at lower resolution. In light of this new information, a model explaining the binding of sperm lysin to egg VERL and the subsequent dissolution of the egg VE is proposed.
Anisotropic features in XMCD spectra
Authors: Nagamatsu Shin-ichi , Fujikawa Takashi
Published: July 2002

The angular dependent K-edge X-ray magnetic circular dichroism (XMCD) spectra based on the semi-relativistic full multiple scattering theory are discussed, where 2-spinor formalism is used to describe spin-orbit coupling. So far most of theoretical approaches have been limited to the simplest case where the circularly polarized X-ray propagation coincides with the direction of the magnetic field. Here we discuss more general cases, using the above theoretical approaches. We separately discuss atomic, single and full multiple scattering XMCD spectra; in particular anisotropic features of them are studied in detail.
Standard Transport Channels of X-ray Beamlines at SPring-8
Authors: Goto Shunji , Yabashi Makina , Ohashi Haruhiko , Kimura Hiroaki , Takeshita Kunikazu , Uruga Tomoya , Mochizuki Tetsuro , Kohmura Yoshiki , Kuroda Masanori , Yamamoto Masaki , Furukawa Yukito , Kamiya Nobuo , Ishikawa Tetsuya
Published: July 2002

SPring-8 is constructing most of its beamlines using a combination of standardized components. The structures of the beamlines are also standardized according to the light-source characteristics. Specifications of components as well as the unified method of assembly and alignment are described.
Supplier knowledge exchange in aerospace product engineering
Authors: Fan Ip‐Shing , Russell Steve , Lunn Richard
Published: July 2002

With the high level of outsourcing in aerospace engineering and manufacture, the effective use of knowledge across the supply chain is acknowledged to be crucial to the success of any projects. “Knowledge”, however, may have different meanings and context. Presents a view of the supplier knowledge in relation to the product engineering process. The different types of supplier knowledge in the five key stages of the aerospace product development process are explained. An existing joint supplier improvement information system is used to illustrate best practice in supply‐base management. Tools that could be used in the different modes of supplier involvement are briefly introduced. Represents part of the results of three industrial research projects that interacted with the supply bases of two large British aerospace companies.
Metal spray Invar tooling for composites
Authors: Ian Wimpenny David , Gibbons Gregory John
Published: July 2002

This work was performed within IMI Spray Mould, an EPSRC joint funded programme, aimed at developing a manufacturing route for large aerospace composite forming tooling, based on metal spray technologies. Assesses the mechanical properties of Invar steel coatings, deposited using electric arc spraying, and correlates these properties to the spray parameters and processes used so as to offer coatings with characteristics appropriate to the tooling requirements. In particular, two processing methods, inert and air atomisation, and three arc spray gun configurations (air cap design) are evaluated. The mechanical properties of the coatings are found to be low compared to bulk Invar, regardless of the spray parameters and hardware used. Inert arc spraying affords more consistent coating characteristics but this comes with a compromised durability. The spray hardware is found to be more significant in determining the coating properties than the parameters employed.
Inhibition by phosphonic acids ‐ an overview
Authors: Gunasekaran G. , Natarajan R. , Muralidharan V.S. , Palaniswamy N. , Appa Rao B.V.
Published: July 2002

Phosphonic acids are good complexing agents. However, they are not good as inhibitors except for a very few. Synergistic inhibition is offered in the presence of metal cations like Ca2+, Mg2+, Zn2+and others in neutral media. The zinc ion is an ideal choice. The part of zinc ions are now replaced by polymers, azoles to prepare eco‐friendly inhibitor formulations. They are also used as corrosion inhibitors in concrete, coatings, rubber blends, acid cleaners, anti‐freeze coolants, etc. Discusses the various applications of phosphonic acids and their action mechanisms.
Employment relations in local government: strategic choice and the case of Brent
Authors: Kessler Ian , Purcell John , Coyle Shapiro Jackie
Published: July 2002

Systematically evaluates changes in people management in one case study, the London Borough of Brent, as the major arena for the regulation of employment relations in local government moves from the national to the authority level. Considers the impact of upstream decisions on mission, purpose and structure and of downstream decisions on employment relations, as they relate to the structure of the personnel function, the role of line managers in personnel activities, the way staff are treated and the role of the unions, based upon a strategic choice model. Argues that there are, indeed, strong linkages between Brent’s upstream decision to become a “competitive market” authority and devolve decision making to business units and the dimensions of employment relations distinguished. However, the consequences of the upstream‐downstream relationship were not necessarily as intended by the Borough, with some of the results having highly dysfunctional consequences for the organization.
Robot control system for safe and rapid programming of grinding applications
Authors: Thomessen Trygve , Lien Terje K.
Published: July 2002

Presents a robot control system dedicated for grinding and deburring robots. The control system is based on an active force feedback system using three axes force sensor attached to the robot’s end effector. This system offers new functionality in rapid programming of the robot by applying automatic programming and force supervision. The system is implemented and tested experimentally on a MultiCraft 560 robot with parallel kinematics. The experimental results show a significant reduction in the programming and set up time compared to conventional robot control systems.
Optical fibre strain sensing for practical structural load monitoring
Authors: Everall L. , Gallon A. , Roberts D.
Published: July 2002

This paper describes state‐of‐the‐art optical technology, employing Bragg gratings, which has been used to develop an Optical Fibre Strain Sensing System. This system is capable of providing actual strain and temperature information for new and existing structures. The sensors, written into the core of standard single mode optical fibre, are embedded into the composite material, or surface bonded on to the structure for load monitoring. The system can be used as a design tool for engineers, for composite cure‐monitoring, setting up of rigs etc., or can be used as a health monitoring tool to periodically monitor loading of bridges, buildings and pipelines.
Numerical modelling of double diffusion driven reactive flow transport in deformable fluid‐saturated porous media with particular consideration of temperature‐dependent chemical reaction rates
Authors: Zhao Chongbin , Hobbs B.E. , Mühlhaus H.B. , Ord A. , Lin Ge
Published: July 2002

Numerical methods are used to solve double diffusion driven reactive flow transport problems in deformable fluid‐saturated porous media. In particular, the temperature dependent reaction rate in the non‐equilibrium chemical reactions is considered. A general numerical solution method, which is a combination of the finite difference method in FLAC and the finite element method in FIDAP, to solve the fully coupled problem involving material deformation, pore‐fluid flow, heat transfer and species transport/chemical reactions in deformable fluid‐saturated porous media has been developed. The coupled problem is divided into two sub‐problems which are solved interactively until the convergence requirement is met. Owing to the approximate nature of the numerical method, it is essential to justify the numerical solutions through some kind of theoretical analysis. This has been highlighted in this paper. The related numerical results, which are justified by the theoretical analysis, have demonstrated that the proposed solution method is useful for and applicable to a wide range of fully coupled problems in the field of science and engineering.
Thermo‐hydro‐mechanical analysis of partially saturated porous materials
Authors: Gawin Dariusz , Schrefler Bernhard A. , Galindo M.
Published: July 2002

Presents a fully coupled numerical model to simulate the slow transient phenomena involving heat and mass transfer in deforming partially saturated porous materials. Makes use of the modified effective stress concept together with the capillary pressure relationship. Examines phase changes (evaporation‐condensation(, heat transfer through conduction and convection, as well as latent heat transfer. The governing equations in terms of gas pressure, capillary pressure, temperature and displacements are coupled non‐linear differential equations and are discretized by the finite element method in space and by finite differences in the time domain. The model is further validated with respect to a documented experiment on partially saturated soil behaviour, and the effects of two‐phase flow, as compared to the one‐phase flow solution, are analysed. Two other examples involving drying of a concrete wall and thermoelastic consolidation of partially saturated clay demonstrate the importance of proper physical modelling and of appropriate choice of the boundary conditions.
Putting the stress back into role stress: improving the measurement of role conflict and role ambiguity
Authors: Siegall Marc
Published: July 2002

Traditional measures of role conflict and role ambiguity assess the frequency with which a person experiences issues with role expectations. The cognitive model of stress developed by Lazarus and Folkman in 1984 emphasizes that a potentially stressful episode does not actually create distress unless it is appraised as threatening. This study takes the first step towards integrating these two approaches, by adding threat appraisals to the traditional measures of conflict and ambiguity. Surveys were distributed to all employees of an electronics/software firm, measuring role stress, physical and psychological strain, several work related attitudes, and withdrawal behaviors. The new measure of role conflict was more predictive of the strain outcomes than was the traditional measure of role conflict, and in general shows promise as a better way of measuring role stress.
Segment‐based mass customization: an exploration of a new conceptual marketing framework
Authors: Jiang Pingjun
Published: July 2002

In this paper, it is argued that the concept of mass customization should not be treated as an alternative strategy to market segmentation. It should be seen as an integral part of market segmentation theory which offers the best way to satisfy individual consumer’s unique needs and wants while yielding profits to companies. Though the overall objective of the concept of mass customization is to recognize individual differences among customers and modify the offerings accordingly, by using the logic of the segmentation theory, this paper argues that mass customization is also not simply equal to segmenting‐to‐one. If all the relevant variables that affect buyer behavior are taken into account, the result is an untenably large number of market segments (finally segment of one). However, practically, creating separate marketing programs for each individual in most circumstances will become extremely difficult, even not feasible, and less profitable. In response to this dilemma, this paper proposes a new concept of “Segment‐based mass customization”. The basic idea behind this concept is that, mass customization is the efforts of reaching a segment unit efficiently and profitably. The efficiency and profitability will be determined by whether the mass customization is based on an optimal segment size, which is subject to the market situation and company resources. Finally, this paper comes up with a series of propositions which are relevant to developing a good customization strategy.
Toward a holistic theory of strategic problem solving
Authors: O’Loughlin Andrew , McFadzean Elspeth
Published: July 2002

To date, many of the models and theories that seek to explain problem solving and decision making, have tended to adopt an overly reductionist view of the processes involved. As a consequence, most theories and models have proved unsuitable in providing managers with a practical explanation of the dynamics that underpin problem solving. A substantial part of a manager’s time is taken up with problem solving and decision making issues. The question of whether managers possess the necessary problem solving skills, or have access to “tools”, which can be used to manage different types of problems, has become an issue of some importance for managers and organisations alike. This paper seeks to contribute to the current literature on problem solving and decision making, by presenting a conceptual model of problem solving, which is intended to assist managers in developing a more holistic framework for managing problem solving issues.
Post‐processing of selective laser sintered metal parts
Authors: Agarwala Mukesh , Bourell David , Beaman Joseph , Marcus Harris , Barlow Joel
Published: July 2002

Gives a brief overview of post‐processing of selective laser sintered (SLS) metal parts to improve structural integrity and/or to induce a material transformation. Presents results which show the effect of post‐processing liquid phase sintering temperature and time on material properties. Describes the hot isostatic pressing process, and discusses its application to SLS metal parts. Results gained from using this process show that it is suitable for achieving almost full‐density parts.
Double Lookbacks
Authors: He Hua , Keirstead William P. , Rebholz Joachim
Published: July 2002

A new class of options, double lookbacks, where the payoffs depend on the maximum and/or minimum prices of one or two traded assets is introduced and analyzed. This class of double lookbacks includes calls and puts with the underlying being the difference between the maximum and minimum prices of one asset over a certain period, and calls or puts with the underlying being the difference between the maximum prices of two correlated assets over a certain period. Analytical expressions of the joint probability distribution of the maximum and minimum values of two correlated geometric Brownian motions are derived and used in the valuation of double lookbacks. Numerical results are shown, and prices of double lookbacks are compared to those of standard lookbacks on a single asset.
Calcium and calcium‐activated currents in vagotomized rat primary vagal afferent neurons
Authors: Lancaster Eric , Oh Eun Joo , Gover Tony , Weinreich Daniel
Published: July 2002

Adult inferior vagal ganglion neurons (nodose ganglion neurons, NGNs) were acutely isolated 4–6 days after section of their peripheral axons (vagotomy) and examined with the whole‐cell patch‐clamp technique. A subset (∼25 %) of vagotomized NGNs displayed depolarizing after‐potentials (DAPs), not present in control NGNs. DAPs were inhibited by niflumic acid (125 μm) or cadmium (100 μm), and had a reversal potential near ECl, indicating that they were due to Ca2+‐activated chloride current (ICl(Ca)). N‐type, L‐type, T‐/R‐ and other types of voltage‐dependent Ca2+ channels provided about 43, 2, 16 and 40 % of the trigger Ca2+ for DAP generation, respectively. Intracellular Ca2+ concentration ([Ca2+]i) was estimated using fura‐2 fluorescence. Resting [Ca2+]i and peak [Ca2+]i elevation induced by activating Ca2+‐induced Ca2+ release (CICR) stores with 10 mm caffeine were not significantly different among control NGNs, vagotomized NGNs with DAPs and vagotomized NGNs without DAPs, averaging 54 ± 7.9 (n= 19; P= 0.49) and 2022 ± 1059 nm (n= 19; P= 0.44), respectively. Blocking CICR with 10 μm ryanodine reduced DAP amplitude by ∼37 %. Ca2+ influx induced by action potential waveforms was increased by over 250 % in vagotomized NGNs with DAPs (19.0 ± 2.1 pC) compared to control NGNs (5.0 ± 0.8 pC) or vagotomized NGNs without DAPs (7.0 ± 0.8 pC). L‐type, N‐type, T‐/R‐type and other types of Ca2+ influx were increased proportionately in vagotomized NGNs with DAPs. In conclusion, a subset of vagotomized NGNs have increased Ca2+ currents and express ICl(Ca). These NGNs respond electrically to increases in [Ca2+]i during regeneration.
A Gro¨bner-Sylvester Hybrid Method for Closed-Form Displacement Analysis of Mechanisms
Authors: Dhingra A. K. , Almadi A. N. , Kohli D.
Published: July 2002

The displacement analysis problem for planar and spatial mechanisms can be written as a system of multivariate polynomial equations. Elimination theory based on resultants and polynomial continuation are some of the methods that have been used to solve this problem. This paper presents a new approach to displacement analysis using the reduced Gro¨bner basis form of a system of equations under degree lexicographic (dlex) term ordering of its monomials and Sylvester’s Dialytic elimination method. Using the Gro¨bner-Sylvester hybrid approach, a finitely solvable system of equations F is transformed into its reduced Gro¨bner basis G using dlex term ordering. Next, using the entire or a subset of the set of generators in G, the Sylvester’s matrix is assembled. The vanishing of the resultant, given as the determinant of Sylvester’s matrix, yields the necessary condition for polynomials in G (as well as F) to have a common factor. The proposed approach appears to provide a systematic and rational procedure to the problem discussed by Roth, dealing with the generation of (additional) equations for constructing the Sylvester’s matrix. Three examples illustrating the applicability of the proposed approach to displacement analysis of planar and spatial mechanisms are presented. The first and second examples address the forward displacement analysis of the general 6-6 Stewart mechanism and the 6-6 Stewart platform, whereas the third example deals with the determination of the I/O polynomial of an 8-link 1-DOF mechanism that does not contain any 4-link loop. [S1050-0472(00)01204-6]
The Use of Hot-Wire Anemometry to Investigate Unsteady Wake-Induced Boundary-Layer Development on a High-Lift LP Turbine Cascade
Authors: Wolff Stefan , Brunner Stefan , Fottner Leonhard
Published: July 2002

Recent research has revealed positive effects of unsteady flow on the development of boundary layers in turbine cascades, especially at conditions with a laminar suction side separation bubble at low Reynolds numbers. Compared to steady flow, a reduction of total pressure loss coefficient over a broad range of Reynolds numbers has been shown. Taking into account the positive effects of wake-induced transition already during the design process, new high lift bladings with nearly the same low losses at unsteady inlet flow conditions could be achieved. This leads to a reduction of weight and cost of the whole turbine module for a constant stage loading. Unsteady flow in turbomachines is caused by the relative motion of rotor and stator rows. For simulating a moving blade row upstream of a linear cascade in the High-Speed Cascade Wind Tunnel of the Universita¨t der Bundeswehr Mu¨nchen, a wake generator has been designed and built. The wakes are generated with bars, moving with a velocity of up to 40 m/s in the test section upstream of the cascade inlet plane. Unsteady flow causes the transition on the surface of the suction side of a low-pressure turbine blade to move upstream whenever an incoming wake is present on the surface; moreover, a laminar separation bubble can be diminished or even suppressed. In order to detect the effects of wakes on the boundary layer development a new hot wire data acquisition system is required. Due to the fact that hot wires give a good insight into boundary layer development, a new hot-wire data acquisition system has been set up. The anemometry system can acquire four channels simultaneously, therefore being capable of logging a triple hot-wire sensor and a bar trigger simultaneously. One further channel is utilized for a once-per-revolution trigger. The once-per-revolution trigger is used to start the measurement of one data block. Using the well-established ensemble-averaging technique, 300 ensembles each consisting of five wake passing periods have been acquired. Ensemble averaging can be directly performed without any data reduction. The adaptation of this new hot-wire anemometry data acquisition system to the High-Speed Cascade Wind Tunnel of the Universita¨t der Bundeswehr Mu¨nchen is pointed out. First, results on unsteady periodic boundary layer development of a highly loaded low-pressure turbine cascade under unsteady inlet flow conditions are presented. During the present investigation four boundary layer traverses, ranging from x/lax=0.82 to x/lax=0.99 (suction side), at steady and unsteady inlet flow conditions Ubar=10 m/s at an outlet Reynolds number of Re2th=100,000 have been conducted. [S0889-504X(00)00204-X]
A Biphasic, Anisotropic Model of the Aortic Wall
Authors: Johnson Mark , Tarbell John M.
Published: July 2002

A biphasic, anisotropic elastic model of the aortic wall is developed and compared to literature values of experimental measurements of vessel wall radii, thickness, and hydraulic conductivity as a function of intraluminal pressure. The model gives good predictions using a constant wall modulus for pressures less than 60 mmHg, but requires a strain-dependent modulus for pressures greater than this. In both bovine and rabbit aorta, the tangential modulus is found to be approximately 20 times greater than the radial modulus. These moduli lead to predictions that, when perfused in a cylindrical geometry, the aortic volume and its specific hydraulic conductivity are relatively independent of perfusion pressure, in agreement with experimental measurements. M, the parameter that relates specific hydraulic conductivity to tissue dilation, is found to be a positive quantity correcting a previous error in the literature.