bluuebunny/crossref_metadata_2025 huggingface dataset:
Meis homeoproteins directly regulate Pax6 during vertebrate lens morphogenesis
Authors: Zhang Xin , Friedman Adam , Heaney Shaun , Purcell Patricia , Maas Richard L.
Published: October 2002

Pax6 is a pivotal regulator of eye development throughout Metazoa, but the direct upstream regulators of vertebrate Pax6expression are unknown. In vertebrates, Pax6 is required for formation of the lens placode, an ectodermal thickening that precedes lens development. Here we show that the Meis1 and Meis2 homeoproteins are direct regulators of Pax6 expression in prospective lens ectoderm. In mice, Meis1 and Meis2 are developmentally expressed in a pattern remarkably similar to Pax6 and their expression isPax6-independent. Biochemical and transgenic experiments reveal that Meis1 and Meis2 bind a specific sequence in the Pax6 lens placode enhancer that is required for its activity. Furthermore,Pax6 and Meis2 exhibit a strong genetic interaction in lens development, and Pax6 expression is elevated in lenses ofMeis2-overexpressing transgenic mice. When expressed in embryonic lens ectoderm, dominant-negative forms of Meis down-regulate endogenous Pax6. These results contrast with those inDrosophila, where the single Meis homolog, Homothorax, has been shown to negatively regulate eye formation. Therefore, despite the striking evolutionary conservation of Pax6 function,Pax6 expression in the vertebrate lens is uniquely regulated.
Shh establishes an Nkx3.2/Sox9 autoregulatory loop that is maintained by BMP signals to induce somitic chondrogenesis
Authors: Zeng Li , Kempf Hervé , Murtaugh L. Charles , Sato Mie Elissa , Lassar Andrew B.
Published: October 2002

Prior work has established that transient Shh signals from the notochord and floor plate confer a competence in somitic tissue for subsequent BMP signals to induce chondrogenesis. We have therefore proposed that Shh induces a factor(s) that renders somitic cells competent to chondrify in response to subsequent BMP signals. Recently, we have shown that forced expression of Nkx3.2, a transcriptional repressor induced by Shh, is able to confer chondrogenic competence in somites. In this work, we show that administration of Shh or forced Nkx3.2 expression induces the expression of the transcription factor Sox9 in the somitic tissue. Forced expression of Sox9 can, in turn, induce robust chondrogenesis in somitic mesoderm, provided that BMP signals are present. We have found that in the presence of BMP signals, Sox9 and Nkx3.2 induce each other's expression. Thus, Nkx3.2 may promote axial chondrogenesis by derepressing the expression of Sox9 in somitic mesoderm. Furthermore, forced expression of either Sox9 or Nkx3.2 not only activates expression of cartilage-specific genes in somitic mesoderm, but also promotes the proliferation and survival of the induced chondrocytes in the presence of BMP signals. However, unlike Nkx3.2, Sox9 is able to induce de novo cartilage formation in non-cartilage-forming tissues. Our findings suggest that Shh and BMP signals work in sequence to establish a positive regulatory loop between Sox9 and Nkx3.2, and that Sox9 can subsequently initiate the chondrocyte differentiation program in a variety of cellular environments.
Default repression and Notch signaling: Hairless acts as an adaptor to recruit the corepressors Groucho and dCtBP to Suppressor of Hairless
Authors: Barolo Scott , Stone Tammie , Bang Anne G. , Posakony James W.
Published: October 2002

The DNA-binding transcription factor Suppressor of Hairless [Su(H)] functions as an activator during Notch (N) pathway signaling, but can act as a repressor in the absence of signaling. Hairless (H), a novel Drosophila protein, binds to Su(H) and has been proposed to antagonize N signaling by inhibiting DNA binding by Su(H). Here we show that, in vitro, H directly binds two corepressor proteins, Groucho (Gro) and dCtBP. Reduction of gro or dCtBP function enhances H mutant phenotypes and suppresses Nphenotypes in the adult mechanosensory bristle. This activity ofgro is surprising, because it is directed oppositely to its traditionally defined role as a neurogenic gene. We find that Su(H)-H complexes can bind to DNA with high efficiency in vitro. Furthermore, a H-VP16 fusion protein causes dominant-negative phenotypes in vivo, a result consistent with the proposal that H functions in transcriptional repression. Taken together, our findings indicate that “default repression” of N pathway target genes by an unusual adaptor/corepressor complex is essential for proper cell fate specification during Drosophila peripheral nervous system development.
RNAi is activated during Drosophila oocyte maturation in a manner dependent on aubergine and spindle-E
Authors: Kennerdell Jason R. , Yamaguchi Shinji , Carthew Richard W.
Published: October 2002

Gene silencing by double-stranded RNA is a widespread phenomenon called RNAi, involving homology-dependent degradation of mRNAs. Here we show that RNAi is established in the Drosophila female germ line. mRNA transcripts are translationally quiescent at the arrested oocyte stage and are insensitive to RNAi. Upon oocyte maturation, transcripts that are translated become sensitive to degradation while untranslated transcripts remain resistant. Mutations inaubergine and spindleE, members of the PIWI/PAZ and DE-H helicase gene families, respectively, block RNAi activation during egg maturation and perturb translation control during oogenesis, supporting a connection between gene silencing and translation in the oocyte.
Minimal Introns Are Not “Junk”
Authors: Yu Jun , Yang Zhiyong , Kibukawa Miho , Paddock Marcia , Passey Douglas A. , Wong Gane Ka-Shu
Published: October 2002

Intron-size distributions for most multicellular (and some unicellular) eukaryotes have a sharp peak at their “minimal intron” size. Across the human population, these minimal introns exhibit an abundance of insertion-deletion polymorphisms, the effect of which is to maintain their optimal size. We argue that minimal introns affect function by enhancing the rate at which mRNA is exported from the cell nucleus.
From Acquisition to Consolidation: On the Role of Brain-Derived Neurotrophic Factor Signaling in Hippocampal-Dependent Learning
Authors: Tyler William J. , Alonso Mariana , Bramham Clive R. , Pozzo-Miller Lucas D.
Published: October 2002

One of the most rigorously investigated problems in modern neuroscience is to decipher the mechanisms by which experience-induced changes in the central nervous system are translated into behavioral acquisition, consolidation, retention, and subsequent recall of information. Brain-derived neurotrophic factor (BDNF) has recently emerged as one of the most potent molecular mediators of not only central synaptic plasticity, but also behavioral interactions between an organism and its environment. Recent experimental evidence indicates that BDNF modulates synaptic transmission and plasticity by acting across different spatial and temporal domains. BDNF signaling evokes both short- and long-term periods of enhanced synaptic physiology in both pre- and postsynaptic compartments of central synapses. Specifically, BDNF/TrkB signaling converges on the MAP kinase pathway to enhance excitatory synaptic transmission in vivo, as well as hippocampal-dependent learning in behaving animals. Emerging concepts of the intracellular signaling cascades involved in synaptic plasticity induced through environmental interactions resulting in behavioral learning further support the contention that BDNF/TrkB signaling plays a fundamental role in mediating enduring changes in central synaptic structure and function. Here we review recent literature showing the involvement of BDNF/TrkB signaling in hippocampal-dependent learning paradigms, as well as in the types of cellular plasticity proposed to underlie learning and memory.
The Contextual Modulation of Conditioned Taste Aversions by the Physical Environment and Time of Day Is Similar
Authors: Morón Ignacio , Manrique Tatiana , Molero Andrés , Ballesteros M ª Angeles , Gallo Milagros , Fenton Andre
Published: October 2002

In a pair of experiments, we have compared the ability of changes of place (Exp. 1) and changes of time of day (Exp. 2) to separately modulate learned saline-aversion memory phenomena in rats. Neither a spatial nor a temporal change disrupted latent inhibition using the present behavioral procedure. However, pre-exposure to the taste increased the contextual control of the learned aversion expression. The aversion reappeared in the place or at the time of conditioning after extinction in a different context. The results indicate that environmental and temporal contexts can independently, but similarly modulate taste aversion learning.
High-Level and Ubiquitous Expression of the Rice CytochromecGeneOsCc1and Its Promoter Activity in Transgenic Plants Provides a Useful Promoter for Transgenesis of Monocots
Authors: Jang In-Cheol , Choi Won-Bin , Lee Kyung-Hee , Song Sang Ik , Nahm Baek Hie , Kim Ju-Kon
Published: October 2002

Expression patterns of a rice (Oryza sativa) cytochrome c gene OsCc1 and its promoter activity were characterized in transgenic rice plants.OsCc1 transcripts accumulate in most cell types, but to varying levels. Large amounts of OsCc1 transcripts are found in the roots, calli, and suspension cells, but relatively lower in mature leaves, demonstrating its higher levels of expression in non-photosynthetic tissues. Unlike the human cytochromec gene, which is responsive to cAMP,OsCc1 expression is not enhanced in various rice tissues after dibutyryl cAMP treatments. OsCc1 promoter was linked to the sgfp gene and its activities in different tissues and cell types of transgenic rice plants were analyzed in comparison with the Act1 and RbcSpromoters. OsCc1 promoter directs expression in virtually all organs of transgenic plants including roots, leaves, calli, embryos, and suspension cells, showing a particularly high activity in calli and roots. Activity of the OsCc1promoter was 3-fold higher than Act1 in calli and roots and comparable with RbcS in leaves, representing a useful alternative to the maize (Zea mays)Ubi1 and the rice Act1 promoters for transgene expression in monocots.
How Closely Do the δ13C Values of Crassulacean Acid Metabolism Plants Reflect the Proportion of CO2 Fixed during Day and Night?
Authors: Winter Klaus , Holtum Joseph A.M.
Published: October 2002

The extent to which Crassulacean acid metabolism (CAM) plant δ13C values provide an index of the proportions of CO2 fixed during daytime and nighttime was assessed. Shoots of seven CAM species (Aloe vera, Hylocereus monocanthus, Kalanchoe beharensis,Kalanchoe daigremontiana, Kalanchoe pinnata, Vanilla pauciflora, andXerosicyos danguyi) and two C3 species (teak [Tectona grandis] and Clusia sp.) were grown in a cuvette, and net CO2 exchange was monitored for up to 51 d. In species exhibiting net dark CO2fixation, between 14% and 73.3% of the carbon gain occurred in the dark. δ13C values of tissues formed inside the cuvette ranged between −28.7‰ and −11.6‰, and correlated linearly with the percentages of carbon gained in the light and in the dark. The δ13C values for new biomass obtained solely during the dark and light were estimated as −8.7‰ and −26.9‰, respectively. For each 10% contribution of dark CO2 fixation integrated over the entire experiment, the δ13C content of the tissue was, thus, approximately 1.8‰ less negative. Extrapolation of the observations to plants previously surveyed under natural conditions suggests that the most commonly expressed version of CAM in the field, “the typical CAM plant,” involves plants that gain about 71% to 77% of their carbon by dark fixation, and that the isotopic signals of plants that obtain one-third or less of their carbon in the dark may be confused with C3 plants when identified on the basis of carbon isotope content alone.
Transgenic Plant Cells Lacking Mitochondrial Alternative Oxidase Have Increased Susceptibility to Mitochondria-Dependent and -Independent Pathways of Programmed Cell Death
Authors: Robson Christine A. , Vanlerberghe Greg C.
Published: October 2002

The plant mitochondrial electron transport chain is branched such that electrons at ubiquinol can be diverted to oxygen via the alternative oxidase (AOX). This pathway does not contribute to ATP synthesis but can dampen the mitochondrial generation of reactive oxygen species. Here, we establish that transgenic tobacco (Nicotiana tabacum L. cv Petit Havana SR1) cells lacking AOX (AS8 cells) show increased susceptibility to three different death-inducing compounds (H2O2, salicylic acid [SA], and the protein phosphatase inhibitor cantharidin) in comparison with wild-type cells. The timing and extent of AS8 cell death are very similar among the three treatments and, in each case, are accompanied by the accumulation of oligonucleosomal fragments of DNA, indicative of programmed cell death. Death induced by H2O2 or SA occurs by a mitochondria-dependent pathway characterized by cytochrome c release from the mitochondrion. Conversely, death induced by cantharidin occurs by a pathway without any obvious mitochondrial involvement. The ability of AOX to attenuate these death pathways may relate to its ability to maintain mitochondrial function after insult with a death-inducing compound or may relate to its ability to prevent chronic oxidative stress within the mitochondrion. In support of the latter, long-term treatment of AS8 cells with an antioxidant compound increased the resistance of AS8 cells to SA- or cantharidin-induced death. The results indicate that plants maintain both mitochondria-dependent and -independent pathways of programmed cell death and that AOX may act as an important mitochondrial “survival protein” against such death.
O-Methyltransferases Involved in the Biosynthesis of Volatile Phenolic Derivatives in Rose Petals
Authors: Lavid Noa , Wang Jihong , Shalit Moshe , Guterman Inna , Bar Einat , Beuerle Till , Menda Naama , Shafir Sharoni , Zamir Dani , Adam Zach , Vainstein Alexander , Weiss David , Pichersky Eran , Lewinsohn Efraim
Published: October 2002

Rose (Rosa hybrida) flowers produce and emit a diverse array of volatiles, characteristic to their unique scent. One of the most prominent compounds in the floral volatiles of many rose varieties is the methoxylated phenolic derivative 3,5-dimethoxytoluene (orcinol dimethyl ether). Cell-free extracts derived from developing rose petals displayedO-methyltransferase (OMT) activities toward several phenolic substrates, including 3,5-dihydroxytoluene (orcinol), 3-methoxy,5-hydroxytoluene (orcinol monomethyl ether), 1-methoxy, 2-hydroxy benezene (guaiacol), and eugenol. The activity was most prominent in rose cv Golden Gate, a variety that produces relatively high levels of orcinol dimethyl ether, as compared with rose cv Fragrant Cloud, an otherwise scented variety but which emits almost no orcinol dimethyl ether. Using a functional genomics approach, we have identified and characterized two closely related cDNAs from a rose petal library that each encode a protein capable of methylating the penultimate and immediate precursors (orcinol and orcinol monomethyl ether, respectively) to give the final orcinol dimethyl ether product. The enzymes, designated orcinol OMTs (OOMT1 and OOMT2), are closely related to other plant methyltransferases whose substrates range from isoflavones to phenylpropenes. The peak in the levels ofOOMT1 and OOMT2 transcripts in the flowers coincides with peak OMT activity and with the emission of orcinol dimethyl ether.
Physiological and Molecular Biological Characterization of Intracellular Carbonic Anhydrase from the Marine DiatomPhaeodactylum tricornutum
Authors: Satoh Dan , Hiraoka Yasutaka , Colman Brian , Matsuda Yusuke
Published: October 2002

A single intracellular carbonic anhydrase (CA) was detected in air-grown and, at reduced levels, in high CO2-grown cells of the marine diatom Phaeodactylum tricornutum (UTEX 642). No external CA activity was detected irrespective of growth CO2 conditions. Ethoxyzolamide (0.4 mm), a CA-specific inhibitor, severely inhibited high-affinity photosynthesis at low concentrations of dissolved inorganic carbon, whereas 2 mm acetazolamide had little effect on the affinity for dissolved inorganic carbon, suggesting that internal CA is crucial for the operation of a carbon concentrating mechanism in P. tricornutum. Internal CA was purified 36.7-fold of that of cell homogenates by ammonium sulfate precipitation, and two-step column chromatography on diethylaminoethyl-sephacel andp-aminomethylbenzene sulfone amide agarose. The purified CA was shown, by SDS-PAGE, to comprise an electrophoretically single polypeptide of 28 kD under both reduced and nonreduced conditions. The entire sequence of the cDNA of this CA was obtained by the rapid amplification of cDNA ends method and indicated that the cDNA encodes 282 amino acids. Comparison of this putative precursor sequence with the N-terminal amino acid sequence of the purified CA indicated that it included a possible signal sequence of up to 46 amino acids at the N terminus. The mature CA was found to consist of 236 amino acids and the sequence was homologous to β-type CAs. Even though the zinc-ligand amino acid residues were shown to be completely conserved, the amino acid residues that may constitute a CO2-binding site appeared to be unique among the β-CAs so far reported.
Modification of Expansin Transcript Levels in the Maize Primary Root at Low Water Potentials
Authors: Wu Yajun , Thorne Eleanor T. , Sharp Robert E. , Cosgrove Daniel J.
Published: October 2002

We previously demonstrated that maintenance of cell elongation in the apical region of maize primary roots at low water potentials (ψw) was associated with an increase in expansin activity and extractable expansin protein. Here, we characterized the spatial pattern of expansin gene expression along the growing maize root and studied the effect of low ψw on expansin gene expression. Roots were divided into three segments: apical 0 to 5 mm, subapical 5 to 10 mm, and non-growing 10 to 20 mm. Of the five expansin genes expressed in control roots, two α-expansins (Exp1 andExp5) and two β-expansins (ExpB2 andExpB8) are expressed specifically in the growing region, whereas expression of β-expansin ExpB6 is shifted basipetally. After seedlings were transplanted to vermiculite with a ψw of −1.6 MPa, transcripts forExp1, Exp5, and ExpB8rapidly accumulated in the apical region of the root. These mRNA changes correlated with the maintenance of root elongation and increases in wall extensibility found previously. The β-expansinsExpB2 and ExpB6 showed distinctive patterns of expression and responses to low ψw,indicative of distinctive functions. Inhibition of abscisic acid (ABA) accumulation at low ψw (by fluridone treatment) had no effect on expansin expression, except that ExpB2transcript level showed a minor dependence on ABA. Gene-specific regulation of α- and β-expansin mRNA pools likely contributes to growth alterations of the maize (Zea mays) root as it adapts to a low ψw, but these changes do not appear to be mediated by changes in ABA content.
Plasma Membrane Phosphatidylinositol 4,5-Bisphosphate Levels Decrease with Time in Culture
Authors: Heilmann Ingo , Perera Imara Y. , Gross Wolfgang , Boss Wendy F.
Published: October 2002

During the stationary phase of growth, after 7 to 12 d in culture, the levels of phosphatidylinositol 4,5-bisphosphate (PtdInsP2) decreased by 75% in plasma membranes of the red alga Galdieria sulphuraria. Concomitant with the decrease in PtdInsP2 levels in plasma membranes, there was an increase in PtdInsP2 in microsomes, suggesting that the levels of plasma membrane PtdInsP2 are regulated differentially. The decline of PtdInsP2 in plasma membranes was accompanied by a 70% decrease in the specific activity of PtdInsP kinase and by reduced levels of protein cross-reacting with antisera against a conserved PtdInsP kinase domain. Upon osmotic stimulation, the loss of PtdInsP2from the plasma membrane increased from 10% in 7-d-old cells to 60% in 12-d-old cells, although the levels of inositol 1,4,5-trisphosphate (InsP3) produced in whole cells were roughly equal at both times. When cells with low plasma membrane PtdInsP2 levels were osmotically stimulated, a mild osmotic stress (12.5 mm KCl) activated PtdInsP kinase prior to InsP3 production, whereas in cells with high plasma membrane PtdInsP2, more severe stress (250 mm KCl) was required to induce an increase in PtdInsP kinase activity. The differential regulation of a plasma membrane signaling pool of PtdInsP2 is discussed with regard to the implications for understanding the responsive state of cells.
Expression of 35S::Pto Globally Activates Defense-Related Genes in Tomato Plants
Authors: Xiao Fangming , Tang Xiaoyan , Zhou Jian-Min
Published: October 2002

The tomato (Lycopersicon esculentum) resistance genePto confers resistance to the bacterial pathogenPseudomonas syringae pv tomato carrying the avirulent gene avrPto. OverexpressingPto under the control of the cauliflower mosaic virus 35S promoter constitutively activates defense responses in the absence of pathogen infection and nonspecifically enhances disease resistance. To elucidate the mechanisms underlying this resistance, we isolated cDNAs corresponding to transcripts that accumulated in 35S::Pto plants. By using suppression subtractive hybridization, we isolated 82 unique cDNA clones, most of which corresponded to differentially expressed transcripts. Most of the genes examined were also induced by pathogen inoculation. Sequence analysis showed that a large number of genes encode defense-related proteins, and most had not been previously isolated from tomato. The isolated cDNAs also include those with a putative role in the oxidative burst, proteolysis, the hypersensitive response, signal transduction, and a number of genes with unknown functions. The isolation of these cDNAs of diverse functions will assist in the characterization of defense pathways activated during disease resistance.
Symmetrieverwandtschaften bei Varianten des Perowskit-Typs
Authors: Bock Oliver , Müller Ulrich
Published: October 2002

The relationships among the huge number of derivative structures of the perovskite type are rationalized in a concise manner using group–subgroup relations between space groups. One family tree of such relations is given for perovskites having tilted coordination octahedra. Further group–subgroup relations are concerned with distortions of the octahedra, such as Jahn–Teller distortions or with atoms shifted from the octahedron centres. In these cases, the space-group symmetry reductions must allow site symmetry reductions of the occupied sites in the perovskite structure. On the other hand, subgroups in which the perovskite sites split into different independent sites are necessary for derivative structures with atom substitutions, such as in the elpasolites A
2
EMX
6. In addition, substitutions and distortions can be combined in adequate subgroups. Substitutions may also involve the occupation of atom sites of perovskite by molecular groups such as N(CH3)4
+ or other organic cations, or by molecules like acetonitrile. If they are ordered, their molecular symmetry requires further space-group symmetry reductions. The anions can be replaced by cyanide ions or by NO2
− ions; space-group symmetry then depends on the temperature-dependent degree of order. The relationships can be used to predict if and what kind of twinning may occur in phase transitions and whether second-order phase transitions are possible.
On the influence of thermal motion on the crystal structures and polymorphism of even n-alkanes
Authors: van de Streek Jacco , Verwer Paul , Bennema Piet , Vlieg Elias
Published: October 2002

Discrepancies between the crystal structures of short n-alkanes as obtained from experiment and as obtained from molecular mechanics tended to worsen at longer chain lengths. The same holds for the relative stabilities of the two experimentally observed polymorphs. In this paper it is argued that the discrepancies are caused by thermal effects, and that the triclinic polymorph is the most stable polymorph for all chain lengths at 0 K. A phase transition is predicted but has yet to be found experimentally. Current force fields cannot reproduce the experimental observations without explicit introduction of temperature by means of molecular dynamics.
Asymmetric hydrogen bonds in centrosymmetric environment. II. Neutron study of very short hydrogen bonds in potassium hydrogen dichloromaleate at 90 K and 170 K
Authors: Olovsson I. , Ptasiewicz-Bak H. , Gustafsson T. , Majerz I.
Published: October 2002

In our earlier neutron diffraction study of the title compound at 30 K and 295 K an unconventional strategy in the refinement of hydrogen was applied and the same procedure has now been followed in the present investigation at 170 K and 90 K. There are two short O...H...O hydrogen bonds [2.437 (2) Å and 2.442 (2) Å at 30 K] and the `heavy-atom' structure is centrosymmetric (P\bar1) with centres of symmetry in the middle of the O...O bonds. However, statistical significance tests clearly show that an asymmetric location of both H atoms gives the most satisfactory description of the structure at all temperatures. The shift of hydrogen from the centre of symmetry is 0.15, 0.14, 0.15 and 0.15 Å for H2 at 30, 90, 170 and 295 K, respectively, and 0.15, 0.15, 0.15 and 0.12 Å for H4 (σ = 0.01 Å). Furthermore, the behaviour of H2 is very interesting: at 295 K and 170 K it is located on one side of the symmetry centre but at 90 K and 30 K it is located on the other side. A detailed determination of the unit-cell parameters by X-ray diffraction in the whole temperature range from 30 K to 295 K has revealed that the data points of the cell parameters as a function of temperature fall on two different straight lines with a sudden change in the slope around 135 K. It appears likely that the change in the location of H2 as the temperature is lowered is related to this behaviour. At 170 K, R(F) = 0.029 for 1236 reflections; at 90 K, R(F) = 0.030 for 1457 reflections.
Simulated annealing structure solution of a new phase of dicalcium silicate Ca2SiO4 and the mechanism of structural changes from α-dicalcium silicate hydrate to αL′-dicalcium silicate via the new phase
Authors: Toraya H. , Yamazaki S.
Published: October 2002

A new phase of dicalcium silicate (Ca2SiO4) was formed by heating α-dicalcium silicate hydrate [α-Ca2(SiO4H)OH = α-C2SH] at temperatures of ∼663–763 K, and it was transformed into \alpha _{\rm L} ^\prime-Ca2SiO4 (= \alpha _{\rm L} ^\prime-C2S) above ∼1193 K. The crystal structure of the new phase (hereafter called x-C2S) has been determined by simulated annealing and refined by the Rietveld method using synchrotron radiation powder diffraction data. The structure consists of isolated SiO4 tetrahedra and a three-dimensional CaO
n
polyhedral network, forming a new structural type of dicalcium silicate. A structural change from α-C2SH to x-C2S is compelled by large displacements of SiO4 tetrahedra, accompanied by dehydration, in the direction perpendicular to the two-dimensional Ca(O,OH)
n
polyhedral network in α-C2SH. With increasing temperature, sizes of CaO
n
polyhedra in x-C2S become too large to confine Ca atoms at the sixfold to eightfold coordination sites. Then the structure of x-C2S is transformed into \alpha _{\rm L} ^\prime-C2S, having eightfold to tenfold coordination sites for the Ca atoms.
Crystal structures of ecdysteroids: the role of solvent molecules in hydrogen bonding and isostructurality
Authors: Fábián László , Argay Gyula , Kálmán Alajos , Báthori Mária
Published: October 2002

Three crystal forms of the steroid 20-hydroxyecdysone were identified by single-crystal X-ray diffraction analysis: a solvent-free modification, a methanol solvate hydrate and a trihydrate. The structure of a closely related steroid, polypodine B (the 5,20-dihydroxy derivative of ecdysone), was determined in its monohydrate form. Since the unit-cell volume of unsolvated 20-hydroxyecdysone was found to be considerably smaller than that of ecdysone [Huber & Hoppe (1965). Chem. Ber.
98, 2403–2424], a new structure determination of ecdysone was performed, which confirmed the unexpected difference between the unit-cell volumes. The crystals of ecdysone and 20-hydroxyecdysone are isostructural, while the mixed solvate of 20-hydroxyecdysone is homostructural with the hydrate of polypodine B. A detailed analysis of the hydrogen-bond networks in these closely related crystal pairs highlights their packing similarities, demonstrates the role of solvent molecules, and explains the unexpectedly small cell volume of 20-hydroxyecdysone.
The structure of trititanate nanotubes
Authors: Chen Q. , Du G.H. , Zhang S. , Peng L.-M.
Published: October 2002

A comprehensive chemical and structural analysis is made of a new type of trititanate nanotube, which is synthesized via the reaction of TiO2 particles with NaOH aqueous solution. It is found that the trititanate nanotubes are multi-walled scroll nanotubes with an inter-shell spacing of about 0.78 nm and an average diameter of about 9 nm. An atomic model of the nanotube is derived based on information from powder X-ray diffraction, selective-area electron diffraction, high-resolution electron microscopy and structure simulations. A model nanotube may be constructed by wrapping a (100) sheet of H2Ti3O7 along [001] with the tube axis parallel to [010].
Diffuse X-ray scattering and reverse Monte Carlo simulation of the short-range order in ytterbium iodine phthalocyanine [YbPc2]I2
Authors: Krawczyk J. , Pietraszko A. , Łukaszewicz K.
Published: October 2002

Iodine-doped ytterbium phthalocyanine, C64H32N16YbI2, [YbPc2]I2 (YPI), presents an example of a disordered modulated crystal structure of the intergrowth type. The short-range order in YPI has been studied at ambienttemperature by the diffuse X-ray scattering technique. Both Yb and I atoms are disordered. In a unit cell of the average structure, the Yb atoms occupy two positions, \textstyle {{1} \over {2}}, \textstyle {{1} \over {2}}, \textstyle {{1} \over {4}} or \textstyle {{1} \over {2}}, \textstyle {{1} \over {2}}, \textstyle {{3} \over {4}}, with occupancy 0.5. In the neighbouring unit cells in the (001) plane there is, however, a strong tendency towards an alternating distribution of ytterbium in positions shifted by Δz = \textstyle {{1} \over {2}}. The crystal structure of YPI consists of one-dimensional columnar stacks of [{\rm YbPc} _{2} ^{2/3+}]
n
and of linear iodine chains [{\rm I} _{3} ^{-}]
n
. The modulation is commensurate since the period c
I of iodine chains [{\rm I} _{3} ^{-}]
n
in the [001] direction is equal to one-half of the period c of the [{\rm YbPc} _{2} ^{2/3+}]
n
stacks. In the crystal structure, each stack of [{\rm YbPc} _{2} ^{2/3+}]
n
may occur in two settings shifted by c/2 and each iodine chain in three settings shifted along [001] by one-third of the period c
I. The short-range order of iodine chains distributed over three settings results in a complicated pattern. Iodine chains of the same setting tend to form ribbons perpendicular to 〈100〉 and running along [001].
Vibrational genetic algorithm as a new concept in airfoil design
Authors: Hacioĝlu Abdurrahman , Özkol İbrahim
Published: October 2002

We introduce the Vibration concept for real coded Genetic Algorithm and its implementation to inverse airfoil design, which decreases the number of CFD calculations. This concept assures efficient diversity in the population and consequently gives faster solution. We used the Vibration concept as vibrational mutation and vibrational crossover. For the mutational manner, a sinusoidal wave with random amplitude is introduced into population periodically from the beginning of the initial step of the genetic process. This operation spreads out the population over the design space and increases exploration performance of the genetic process. This makes passing over local optimums for genetic algorithm easy. In order to apply this new concept at the crossover stages, Double Directional Alpha (DDA) approximation in BLX‐α as a new crossover technique which was already presented in our earlier study is used. In the developed technique, the value of α oscillates systematically during the genetic process. Implementation of the Vibration concept to the inverse airfoil design makes the convergence faster.
Pioneer probe generates “space warp”, disproves “big bang”
Authors: Keller Joseph C. , Keller Edwin C.
Published: October 2002

Apparently, all space probes, but no planets, are subject to a constant quasigravitational force that is equivalent to the force on photons that causes the Hubble red shift. Also, the surface gravity of protons, determined by the Heisenberg Uncertainty Principle, causes a barrier at about 53 astronomical units from the sun. Pioneer 10 generated a “space warp” as it crossed this barrier.
Studies on damping characteristics and parameter optimization of anisotropic laminated damped structure
Authors: Cao Yihua , Li Mingjun , Su Yuan , Sun Xiangchun
Published: October 2002

An anisotropic design is introduced to the laminated damped plates in this paper. The parameter effects on the loss factor of anisotropic laminated damped plates have been analyzed in detail. The damping analyses and control mechanism of laminated anisotropic damped plates have been carried out theoretically. Finally, through the software developed here, the parameter optimization has been conducted on the loss factors of the anisotropic laminated damped plates. The results indicate it may provide scientific basis for the new optimization anisotropic design of laminated damped plates used in Aircraft cabin structure for obtaining the maximum loss factor.
Laminar‐turbulent transition of the incompressible swept attachment‐line
Authors: Wrona M. , Tuliszka‐Sznitko E.
Published: October 2002

The linear and non‐linear stability of an incompressible swept attachment‐line boundary layer are analysed, within the Görtler‐Hämmerlin framework. The system of perturbation equations is solved using spectral collocation method based on Chebyshev polynomials. The global solution method utilised for solving the eigenproblem yields the full spectrum of the least damped waves. The influence of suction and blowing on critical Reynolds numbers is analysed. A comparison of the present paper linear solutions for both zero suction and a layer in which blowing and suction are applied with the Spalart's DNS solutions (obtained for small initial disturbances) shows very good agreement. The transition Reynolds numbers have been predicted using well known exp(n) method and results are compared with the experimental data of Powilleit.
Effects of plasma cleaning and conservation treatment on the corrosion layer of corroded steel – XRD evaluation
Authors: Kotzamanidi I. , Anastassiadis A. , Filippaki L. , Filippakis S.E. , Vassiliou P. , Sarris Em.
Published: October 2002

The application of hydrogen plasma on corroded steel and excavated iron artefacts has been studied. Transformations of the corrosion layer due to the plasma effect were investigated by means of X‐ray diffraction analysis. The reduction of iron oxides to the stable iron oxide, magnetite, was observed for all the samples. In the case of excavated objects, the reduction to magnetite did not occur throughout the whole of the bulk of the oxides, as it does (for example) in the case of steel corroded in the laboratory. Nevertheless, excavated objects, in which a metallic core remained, were stabilised against subsequent corrosion. However, objects that are completely oxidised must be treated carefully, because treatment may result in the formation of a brittle outer layer, and there is a risk of disintegration of such items, if treated using the plasma conditioning and restoration procedure.
Electrodeposition of rhodium metal on titanium substrates
Authors: Baraka A.M. , Hamed H.A. , Shaarawy H.H.
Published: October 2002

The electrodeposition of any metal over titanium substrates meets with many problems due to the formation of a non‐conductive layer of titanium oxide on the surface of substrates during the electroplating process. Trials were made to overcome these problems by the pre‐anodisation of titanium substrates in oxalic acid solution of concentration 100g/l, at high current density of 60‐95mA/cm–2, and at ambient temperature. In these conditions, a thin, porous and conductive titanium oxide film can be obtained, which will then support electroplating processes. Rhodium metal was electrodeposited over the anodised titanium substrates from a bath consisting of Rh2(SO4)3, 5.2g/l and H2SO4, 100g/l. At optimum conditions of electroplating, the rhodium electrodeposits were formed over the anodised titanium substrate with high adhesion, brightness and high current efficiency (92.05 per cent).
The use of applied library and information studies (LIS) research in New Zealand libraries
Authors: Turner Kathlyn J.
Published: October 2002

This study investigated the perceptions of New Zealand information professionals regarding LIS (library and information studies) applied research, by determining their reasons for and against consulting it, their tendency towards conducting it and encouraging others in their employ to produce it, and their opinions concerning the current relationship between LIS research and practice and how it might be improved. The study found that the amount of research consultation by information professionals is low; levels of research production, and encouragement for employees to produce research, are even lower. Participants most often consult the research to stay current with trends and developments in LIS, and to support workplace activities such as decision making, problem solving, planning and evaluation. The research is most often not consulted due to time constraints. Associational relationships were apparent between the amount of research consultation and education and employment participant variables. Respondents indicated that the most effective strategy for improving the current relationship between research and practice is the encouragement of research productions that include practical guidelines for the application of results in a workplace context.
Scotland and the Encyclopaedia Britannica
Authors: Glasgow Eric
Published: October 2002

The history of the Encyclopaedia Britannica from its inauguration in 1768 up to the ninth edition of 1888 is described. Its origins in Edinburgh during the Enlightenment are discussed and its early Edinburgh editors and contributors reviewed. Later editors and contributors and the gradual changing of the work are discussed. Its expansion from an Edinburgh to a global publication is also demonstrated.
Libraries in Sweden
Authors: Glasgow Eric
Published: October 2002

Surveys the history of the major libraries of Sweden. The Royal Library in Stockholm, Uppsala and Lund University Libraries and the City and University Libraries of Gothenburg are featured. The development of public libraries in Sweden is also considered.
Cladistics as historiography: part II – the phylogeny of automotive assembly
Authors: Leseure Michel J.
Published: October 2002

This second part of the paper presents in more detail the phylogenetic model of automotive assembly factories used in the first part of the paper. The key organizational species and their mutual relationships are described with an emphasis on the speciation points. This paper is purely descriptive.
ICT for access to information services for disabled people: an overview of projects and services at Gateshead Libraries Service
Authors: Myhill Christine E.
Published: October 2002

Providing access to information for all users, irrespective of their physical disabilities, is a requirement for all libraries and ICT can be used to assist this. The case study describes a range of projects and services that have been developed by Gateshead Libraries using ICT to enable disabled people gain access to information. These projects range from AIRS (which started with the production of a talking newspaper in 1987), to MISSISSIPPI (which uses videotelephony for sign language communication for deaf people) to the Web accessibility guidelines used for the Gateshead Grid for Learning.
Mechanism of friction of fullerenes
Authors: Rapoport L. , Leshchinsky V. , Lvovsky M. , Nepomnyashchy O. , Volovik Yu , Tenne R.
Published: October 2002

In the past few years, inorganic fullerene‐like (IF) supramolecules of metal dichalcogenide WS2 and MoS2 with structures closely related to (nested) carbon fullerenes and nanotubes have been synthesized. Recent experiments showed that IF added to oil and impregnated into the porous matrixes possess lubricating properties superior to those of layered WS2 and MoS2 (2H platelets). The main goal of this work was to analyze the mechanism of friction of fullerene‐like nanoparticles. Friction and wear behavior of IF in different contact conditions is studied. Third body model is considered. Sliding/rolling of the IF nanoparticles in the boundary of the first bodies and in between the wear particles (third body) is supposed to facilitate the shear of the lubrication film. Broken and oxidized 2H‐WS2 small pieces adhered to wear debris do not provide high tribological properties especially under high loads.
Gender and career experience in mainland Chinese state‐owned enterprises
Authors: Leung Alicia S.M.
Published: October 2002

This paper examines the career experience of Chinese male and female managers in an emerging socialist market economy. The paper is based on research carried out in a range of Chinese state‐owned enterprises. It explores managers’ attitudes toward their careers as a result of changes in enterprise governance, which limit promotion opportunities and reduce job security. In particular, this study investigates gender differences in coping strategies, when career expectations have been frustrated. The results and their implications for future studies of career experience are discussed.
Globalisation and labour market deregulation in Australia and New Zealand
Authors: Harbridge Raymond , Walsh Pat
Published: October 2002

The labour markets of Australia and New Zealand have been regulated in similar ways, through industrial conciliation and arbitration, since the early 1900s. Globalization and market deregulation generally have led to intense pressure for greater labour market flexibility in both countries. In New Zealand, flexibility was achieved by a radical dismantling of the industrial relations system. What had been essentially a multi‐employer bargaining system was replaced with a system that supported individual employment contracting. In Australia, conciliation and arbitration remained protected by the constitution; however, industrial relations reforms aimed at severely weakening the system were implemented in the 1990s. This paper compares various labour market outcomes across both countries. The trends in both countries are similar despite maintaining different systems. Collective bargaining coverage has dropped. Collective bargaining outcomes have seen reductions in benefits, and significant changes in working time arrangements. Union density has dropped, as also has public sector employment.
Multinational corporations, employers’ associations and trade union exclusion strategies in the German fast‐food industry
Authors: Royle Tony
Published: October 2002

This paper focuses on the employment practices of both multinational corporations (MNCs) and large national competitors in the German fast‐food industry, such as Burger King, Pizza Hut, Nordsee, McDonald’s, Churrasco and Blockhaus. The paper poses a number of questions. Have the activities of MNCs affected the employment practices of national companies? Are companies adopting union exclusion policies and if so why and to what extent? Does the “country of origin effect” help explain the activities of MNCs? What changes are evident in workers’ terms and conditions and how effective are statutory systems of employee representation in practice? The findings suggest that Anglo‐Saxon‐based MNCs are more likely to adopt anti‐works council and non‐union policies in the sector, suggesting that MNCs may indeed be able to transfer their management practices across borders, imposing their employer‐based systems with little regard for German institutional arrangements.
The effects of on‐the‐job training on wages in Sweden
Authors: Regnér Håkan
Published: October 2002

On‐the‐job training has a large positive effect on wages for employees in Sweden, and employees in jobs that require long on‐the‐job training earn significantly more than workers in jobs with short training requirements. The effects of training are large for recently hired and low for senior employees. There are significant wage effects of general and specific on‐the‐job training, and the effect is significantly larger for general training. Separate estimates for the public and private sectors show significant effects of specific training only for public‐sector employees and large effects of general training for private‐sector employees. The results suggest that the distinction between general and specific training matters, that firms are willing to pay for general training and that there is heterogeneity in the returns to these forms of training.
Leadership: an “alternative” view
Authors: Lloyd Bruce , Mori Mayumi
Published: October 2002

Professor Bruce Lloyd, South Bank University discusses “An ‘alternative’ view of leadership” with Dr Mayumi Mori, co‐organiser PAF (Planetary Academic Federation); director, Global Institute for Soft Technology; author “Everything makes one” (PHP Institute) and “Mother recounts: the true history of the universe” (The EVHA creation). This discussion covered the role of intuition and the need for a redefinition of knowledge management, as well as issues that relate to gender and the position of values within the changing views of what is seen as effective leadership. In addition the article discussed the need to consider broader dimensions such as the role of humanity and religion; it ended with an exploration of the key issues of the need to ensure that we are concerned with the bringing up of the next generation.
Sourcing trends in the car industry
Authors: von Corswant Fredrik , Fredriksson Peter
Published: October 2002

Intense competition and structural changes characterize the car industry. Several trends (i.e. general changes over time) concerning sourcing strategies and supplier relations can therefore be identified. The article aims to analyze how these trends correspond to the actual situation in the car industry. Based on a survey answered by both car manufacturers and first tier suppliers, this article provides facts and analyses regarding sourcing‐related trends over the past decade as well as some future predictions. The results show that both car manufacturers and suppliers continue to reduce product development time. They also increase supplier involvement in product development and the share of inbound JIT‐deliveries. However, while suppliers increase their outsourcing and globalization of production and product development activities, car manufacturers do not. Only some of the identified sourcing‐related trends are actually supported by the presented results. Hence, this article modulates the picture of the current development within the car industry.