bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phosphatidylinositol 3‐kinase and Akt participate in the FSH‐induced meiotic maturation of mouse oocytes
Authors: Hoshino Yumi , Yokoo Masaki , Yoshida Noriyuki , Sasada Hiroshi , Matsumoto Hiromichi , Sato Eimei 
Published: July 2004

AbstractPhosphatidylinositol 3‐kinase (PI3K) is known to play critical roles in signal transduction processes related to a variety of cellular activities. In the present study, we investigated the role of PI3K during meiotic maturation in mouse oocytes using a specific inhibitor,LY294002. In follicle‐stimulating hormone (FSH)‐induced reversal of hypoxanthine‐mediated meiotic arrest of cumulus oocyte complexes (COCs), LY294002 suppressed germinal vesicle breakdown (GVBD), first polar body (PB1) emission, and cumulus expansion. To examine the effect of LY294002, denuded oocytes (DOs) were cultured in medium containing follicular fluid meiosis‐activating sterol (FF‐MAS) since absence of gonadotropin receptors in oocytes has been reported and FSH did not stimulate meiotic maturation of DOs in the presence of hypoxanthine. In FF‐MAS‐induced maturation of DOs, LY294002 suppressed PB1emission, but not GVBD. In spontaneous gonadotropin‐independent oocyte maturation, LY294002 had no effect on COCs and DOs. Akt/protein kinase B, a serine‐threonine kinase, is a key downstream effector of the PI3K pathway. Therefore, we also examined the distribution of Akt during FSH‐induced meiotic maturation. The distribution of Ser473 phosphorylated Akt was similar to the localization of microtubules, while Thr308 phosphorylated Akt was present in the pericentriolar materials (PCM) in metaphase I (MI) and II (MII) oocytes. LY294002 decreased the amount of Thr308 phosphorylated Akt to very low to undetectable levels in MI and MII oocytes. Ser473 phosphorylated Akt showed aberrant distribution and very low to undetectable levels of expression in LY294002‐treated MI and MII oocytes, respectively. These results suggest that PI3K and Akt participate in mouse meiotic maturation. Mol. Reprod. Dev. 69: 77–86, 2004. © 2004 Wiley‐Liss, Inc.
The regulation of competence to replicate in meiosis by Cdc6 is conserved during evolution
Authors: Lemaître Jean‐Marc , Bocquet Stéphane , Terret Marie‐Emilie , Namdar Mandana , Aït‐Ahmed Ounissa , Kearsey Stephen , Verlhac Marie‐Hélène , Méchali Marcel 
Published: July 2004

AbstractDNA replication licensing is an important step in the cell cycle at which cells become competent for DNA replication. When the cell cycle is arrested for long periods of time, this competence is lost. This is the case for somatic cells arrested in G0 or vertebrate oocytes arrested in G2. CDC6 is a factor involved in replication initiation competence which is necessary for the recruitment of the MCM helicase complex to DNA replication origins. In Xenopus, we have previously shown that CDC6 is the only missing replication factor in the oocyte whose translation during meiotic maturation is necessary and sufficient to confer DNA replication competence to the egg before fertilization (Lemaitre et al., 2002: Mol Biol Cell 13:435–444; Whitmire et al., 2002: Nature 419:722–725). Here, we report that this oogenesis control has been acquired by metazoans during evolution and conserved up to mammals. We also show that, contrary to eukaryotic metazoans, in S. pombe cdc18 (the S. pombe CDC6 homologue), CDC6 protein synthesis is down regulated during meiosis. As such, the lack of cdc18 prevents DNA replication from occurring in spores, whereas the presence of cdc6 makes eggs competent for DNA replication. Mol. Reprod. Dev. 69: 94–100, 2004. © 2004 Wiley‐Liss, Inc.
β2‐agonist treatment enhances uterine oxytocin receptor mRNA expression in pregnant rats
Authors: Klukovits Anna , Ducza Eszter , Földesi Imre , Falkay George 
Published: July 2004

AbstractThe objective of this study was to disclose an interaction between β2‐adrenergic (β2‐ARs) and oxytocin (OT) receptors (OTRs) in the late‐pregnant rat uterus. We investigated the level of uterine OTR mRNA expression after the administration of β2‐AR agonists fenoterol and hexoprenaline to rats from day 18 to 22 of pregnancy, and also tested the effect of fenoterol on uterine explants. Hexoprenaline induced a maximum 24% increase of OTR mRNA. Fenoterol in vivo elicited a maximum 125% increase of OTR mRNA, in vitro produced a maximum fourfold increase in OTR mRNA. In fenoterol‐treated rats the maximal contractility increasing effect of OT on isolated uterine rings was significantly higher than in intact term pregnant rats, but the EC50 values were not statistically different. It was concluded that the enhanced expression of OTR mRNA induced by β2‐agonists in the late‐pregnant rat uterus may be a possible drawback to effective therapy of preterm uterine contractions with β2‐agonists. Mol. Reprod. Dev. 69: 60–65, 2004. © 2004 Wiley‐Liss, Inc.
Updated semi‐discretization method for periodic delay‐differential equations with discrete delay
Authors: Insperger Tamás , Stépán Gábor 
Published: July 2004

AbstractAn updated version of the semi‐discretization method is presented for periodic systems with a single discrete time delay. The delayed term is approximated as a weighted sum of two neighbouring discrete delayed state values and the transition matrix over a single period is determined. Stability charts are constructed for the damped and delayed Mathieu equation for different time‐period/time‐delay ratios. The convergence of the method is investigated by examples. Stability charts are constructed for 1 and 2 degree of freedom milling models. The codes of the algorithm are also attached in the appendix. Copyright © 2004 John Wiley & Sons, Ltd.
Melt processing of PA‐66/clay, HDPE/clay and HDPE/PA‐66/clay nanocomposites
Authors: Mehrabzadeh Mahmood , Kamal Musa R. 
Published: July 2004

AbstractPolyamide 66/clay, high‐density polyethylene (HDPE)/clay and HDPE/PA66/clay nanocomposites were prepared, using a twin‐screw extruder. The nanocomposites were characterized by means of transmission electron microscopy (TEM), scanning electron microscopy (SEM), wide angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), optical microscopy and tensile testing. Effects of processing conditions and clay modifier were evaluated. The results show that exfoliation in the twin‐screw extruder is enhanced by the incorporation of mixing and shearing elements and high residence times. Compatibility of the clay modifier with the polymer matrix plays an important role in exfoliation. Clay does not influence the crystal form, melting temperature or crystallinity of PA‐66 and HDPE. However, it acts as a nucleation agent, increases marginally the crystallization temperatures, and reduces the crystallite size. Clay in the blend nanocomposites acts as a compatibilizer and changes the morphology of the blend. TEM micrographs suggest the presence of an exfoliated structure in PA‐66 and an intercalated structure in HDPE. Polym. Eng. Sci. 44:1152–1161, 2004. © 2004 Society of Plastics Engineers.
Epoxy‐phenolic novolac‐montmorillonite hybrid nanocomposites: Novel synthesis methods and their characteristics
Authors: Lee Sang Min , Hwang Tae Ryong , Song Yang Sun , Lee Jae Wook 
Published: July 2004

AbstractEpoxy resin‐layered silicate nanocomposites (ER‐LSN) were successfully synthesized using pre‐intercalated novolac resin‐layered silicate nanocomposites (NR‐LSN) as epoxy hardeners to develop novel formulations for copper‐clad laminate sheets (CCLS) with enhanced properties. We used melt, melt‐ultrasonic, solution, and solution‐ultrasonic intercalation methods to prepare NR‐LSN with different kinds of novolac resins including phenolic novolac (PN), bisphenol‐A novolac (BN) and phenolic aralkyl novolac, so‐called Xylok (XK). We employed different kinds of montmorillonites (MMT) that were organically modified with benzyl dimethyl octadecyl ammonium and bis(2‐hydroxy‐ethyl)methyl tallow ammonium. It was confirmed that the synthesized NR‐LSN and ER‐LSN were intercalated or exfoliated, and exhibited stable structure owing to the effective action of high‐intensity ultrasound. These materials showed significantly improved thermal and mechanical properties suitable for halogen‐free CCLS with highly reliable performance. Polym. Eng. Sci. 44:1170–1177, 2004. © 2004 Society of Plastics Engineers.
Morphology and performance of epoxy nanocomposites modified with organoclay and rubber
Authors: Liu Weiping , Hoa Suong V. , Pugh Martin 
Published: July 2004

AbstractHybrid epoxy nanocomposites modified with carboxyl‐terminated butadiene acrylonitrile (CTBN) rubber and organoclay were synthesized. The morphology of those nanocomposites was studied with X‐ray diffraction (XRD), Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). The results showed that most of the organoclay in the nanocomposites was exfoliated and high cure temperatures benefit the formation of exfoliated nanocomposites. Organoclay simultaneously improved fracture toughness, compressive modulus, yield strength and ultimate strength of the epoxy resin. Organoclay not only enhanced Tg, yield strength and ultimate strength of rubber‐modified epoxies, but also further improved their fracture toughness. There was a superposition effect on fracture toughness of the hybrid epoxy nanocomposites modified with both rubber and organoclay. Polym. Eng. Sci. 44:1178–1186, 2004. © 2004 Society of Plastics Engineers.
Geometry and binding properties of different multiple‐state glycine–Fe+/Fe2+ complexes
Authors: Ai Hongqi , Bu Yuxiang , Li Ping , Li Zhiqiang , Hu Xiangquan , Chen Zhida 
Published: July 2004

AbstractSeveral biologically relevant glycine–Fe+/Fe2+ complexes with three different multiplicities were studied for the first time by using the hybrid three‐parameter B3LYP density functional method with different basis sets. Single‐point calculations were also carried out at the BHLYP level with a larger basis set to refine and calibrate these energy values. The results show that the most stable glycine–Fe+ isomer is the C1‐symmetric sextet NO‐16, in which Fe+ is interacted with both the amino nitrogen and carbonyl oxygen of the glycine ligand. The ground‐state structure of glycine–Fe2+ is the 5A′′ state 2O‐25, which generates from the interaction of Fe2+ with the two oxygen terminus of the zwitterionic glycine. The calculations indicate that the binding energies mainly derive from the contributions of electrostatic effects, for both the monovalent and divalent metal cation‐chelated glycine complexes. The differences in binding energies between these different multiple‐state glycine–Fe+ isomers with same combination modes mainly derive from their different electrostatic and polarized effects, and those between the isomers of different combination modes with the same multiple states mainly stem from their different deformation effects. The differences in the relative stabilities of these glycine–Fe+ isomers with different multiple states mainly come from the fact that the more electrostatic contribution of the lower spin complex cannot compensate for the loss of energy enhancement of its corresponding metal cation relative to that of the higher spin counterpart. The same is true for the glycine–Fe2+ complexes. Copyright © 2004 John Wiley & Sons, Ltd.
Acidochromism of C2‐symmetrical aza‐analogues of 1,4‐distyrylbenzene
Authors: Detert Heiner , Sadovski Oleg , Sugiono Erli 
Published: July 2004

AbstractA series of C2‐symmetrical aza‐analogous 1,4‐distyrylbenzenes were synthesised via two‐fold PO‐activated olefinations or Heck reactions. Pyridine, pyrimidine and quinoline were used as terminal rings, and the 2,5‐positions of the central benzene ring were substituted with H, alkoxy, or alkylsulfonyl groups. These strongly fluorescent compounds are freely soluble in common solvents such as toluene or chloroform. Whereas the electronic spectra of the pyridine and pyrimidine chromophores were very similar to those of the parent compound 1,4‐distyrylbenzene, the spectra of the former were altered considerably in the presence of trifluoroacetic acid. Depending on the concentration of the acid, protonation of the ground state and/or the excited state caused bathochromic shifts of the absorption and the emission spectra, accompanied by reductions in the fluorescence efficiencies. Copyright © 2004 John Wiley & Sons, Ltd.
Chemical messengers: mediated oxidations with the enzyme laccase
Authors: Galli Carlo , Gentili Patrizia 
Published: July 2004

AbstractThe use of low molecular‐weight compounds (viz., mediators) in combination with fungal laccase makes the enzyme suitable for the oxidation of ‘non‐natural’ non‐phenolic substrates. Benzyl alcohols are thus oxidised to carbonylic products by laccase/mediator systems in the presence of oxygen, although laccase cannot oxidise these substrates directly. The reaction is carried out by the oxidised form of the mediator (Medox), generated on its interaction with laccase, and the structure of the Medox species is crucial for the mechanism of the ensuing non‐enzymatic oxidation of the substrate. 1‐Hydroxybenzotriazole (HBT), N‐hydroxyphthalimide (HPI), violuric acid (VLA) and TEMPO have been investigated as mediators, and experimental evidence is provided that enables the radical hydrogen atom transfer route with the laccase/HBT, laccase/HPI and laccase/VLA systems to be assessed unambiguously, although the laccase/TEMPO system follows a different and ionic oxidation route. Copyright © 2004 John Wiley & Sons, Ltd.
Three‐centre hydrogen bonding in the complexes of syn‐2,4‐difluoroadamantane with 4‐fluorophenol and hydrogen fluoride
Authors: Adcock William , Graton Jérôme , Laurence Christian , Luçon Maryvonne , Trout Neil 
Published: July 2004

AbstractHydrogen bond enthalpies for the interaction of 4‐fluorophenol with syn‐2,4‐difluoroadamantane (5) and, for comparison, 2‐fluoroadamantane (6) and 1,3‐difluoroadamantane (7) have been determined by Fourier transform infrared spectrometry. Among a series of seven fluoroalkanes (1–7) it is found that syn‐2,4‐difluoroadamantane is the best hydrogen bond acceptor. This high hydrogen bond acceptor strength is explained, using electrostatic and ‘atoms in molecules’ properties and from density functional theory and ab initio calculations on hydrogen fluoride complexes, by the formation of an F·H·F three‐centre hydrogen bond. In this system, the three‐centre hydrogen bonding is energetically (mainly on the Gibbs energy scale) superior to the two‐centre hydrogen bonding. Copyright © 2004 John Wiley & Sons, Ltd.
Quadrupolar donor–acceptor substituted oligo(phenylenevinylene)s—synthesis and solvatochromism of the fluorescence
Authors: Detert Heiner , Schmitt Volker 
Published: July 2004

AbstractThe electronic spectra of oligo(phenylenevinylene)s with five benzene rings and an acceptor–donor–acceptor substitution pattern were investigated. Although the absorption spectra are mostly unaffected by an increasing solvent polarity, both bathochromic shifts and reduced efficiencies of the fluorescence arise with the quadrupolar electronic structure. The chromophores with the lowest oxidation or reduction potentials are the most sensitive towards the environment. The synthesis of the centrosymmetrical oligomers was performed in a sequence of two two‐fold Wittig–Horner olefinations. Copyright © 2004 John Wiley & Sons, Ltd.
Towards Optimal Descriptor Subset Selection with Support Vector Machines in Classification and Regression
Authors: Fröhlich Holger , Wegner Jörg K. , Zell Andreas 
Published: July 2004

AbstractIn this paper we present a novel method for selecting descriptor subsets by means of Support Vector Machines in classification and regression – the Incremental Regularized Risk Minimization (IRRM) algorithm. In contrast to many other wrapper methods it is fully deterministic and computationally efficient. We compare our method to existing algorithms and present results on a Human Intestinal Absorption (HIA) classification data set and the Huuskonen regression data set for aqueous solubility.
Quantitative Structure‐Retention Relationships (QSRR) of Some CNS Agents Studied on DB‐5 and DB‐17 Phases in Gas Chromatography
Authors: Hodjmohammadi M. R. , Ebrahimi P. , Pourmorad F. 
Published: July 2004

AbstractA QSRR study was performed to develop a predictive model correlating molecular structures with their RIs in gas chromatography. CNS agents included some benzodiazepines, barbiturates and phenytoin, which had been studied, previously, on two DB stationary phases with different phenyl percentages. At first, a high quality model (R=0.988, F=253.89 for DB‐5 and R=0.983, F=164.721 for DB‐17 column) was generated for two columns separately, using only calculated descriptors and multiple linear regression techniques. Then a combined model, added a polarity term of stationary phase (M), was also developed for these columns, and the result was satisfactory (R=0.989, F=232.354). The results of leave‐one‐out cross and external validation techniques showed good predictive ability of the models (R$\rm{ {_{cv}^{2}}}$=0.967, R$\rm{ {_{Prediction\ set}^{2}}}$=0.954). The results of the study indicated that a six‐parameter equation can be utilized for prediction of retention indices of compounds on DB‐5 and DB‐17 stationary phases simultaneously, for which there are no empirical RI values.
Intermolecular interaction energies for deprotonated complexes
Authors: Masamura M. 
Published: July 2004

AbstractThe intermolecular interaction energies of the deprotonated hydrogen‐bonded complexes F−(HF), F−(H2O), F−(NH3), Cl−(HF), SH−(HF), H2P−(HF), OH−(H2O), OH−(H2O)2, OH−(NH3), Cl−(H2O), SH−(H2O), H2P−(H2O), Cl−(NH3), SH−(NH3), H2P−(NH3), Cl−(HCl), Cl−(H2S), Cl−(PH3), SH−(H2S), SH−(PH3), and H2P−(PH3) in complete basis set limit at the MP2, MP4, QCISD(T), and CCSD(T) levels were calculated with correlation consistent basis sets. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Electric field integrals for Slater‐type orbitals
Authors: Fernández Rico J. , López R. , Ramírez G. , Ema I. 
Published: July 2004

AbstractGeneral algorithms for electric field integrals with Slater‐type orbitals (STO) are reported, and the efficiency of the computational procedure based in these algorithms is analyzed. An accuracy of nine decimal places, at least, is estimated for the molecular electric field computed on any point. Timing was examined for calculations with STO basis sets ranging from 30 to 300 basis functions. Computational cost was moderate, even for the largest basis set. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Chemical bond modeling with correlation effects included
Authors: Abarenkov I. V. , Smelkov K. V. 
Published: July 2004

AbstractThe one‐electron pseudo‐atom potential is developed following the chemical bond modeling method we proposed earlier 1, 2 in the HF approximation. The bond orbital, exact in the HF approximation, is the solution of the closed‐shell HF equation for two electrons in the field of two pseudo‐atoms connected with the bond. The closed shell HF bond energy reproduces the bond adiabatic potential fairly well in the vicinity of the equilibrium bond length. However, for larger distances the results are bad due to the deficiency of one closed shell approximation for the bond at large interatomic separation. The few‐to‐many configuration calculations of the two‐electron problem for the single chemical bond are reported here. The pseudo‐atom potential used in these calculations is calculated in the HF approximation at the equilibrium bond length and fixed. The results for some carbon‐containing molecules are presented and discussed here. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Zentrum Paul Klee – Entwurf und Konstruktion der Museumswelle
Authors: Lang Robert , Schmid Volker 
Published: July 2004

AbstractDas vom Renzo Piano Building Workshop entworfene “Zentrum Paul Klee” in Bern besticht durch die ungewöhnliche Wellenform des Daches. Der Aufsatz beschreibt den Entwurf und die besondere Geometrie des neuen Museumskomplexes und erläutert die Umsetzung der von gestalterischen Gesichtspunkten geprägten Dachform in ein adäquates Tragwerk. Die strukturellen Besonderheiten und die Detaillierung des aus geschweißten Stahlträgern errichteten Dachtragwerks werden dargestellt.
Wandelbares Membrandach im Innenhof des Wiener Rathauses
Authors: Bergermann Rudolf , Gugeler Jochen , Keck Thomas 
Published: July 2004

AbstractIm September 2000 wurde das wandelbare Membrandach über dem Arkadenhof des Wiener Rathauses eingeweiht. Als Regen‐ und Sonnenschutz für die zahlreichen Veranstaltungen ersetzt die neue 34 m ∞ 32 m große Konstruktion die bisher verwendeten Zelte. An den Längsseiten des Daches sind Schienen angeordnet, auf denen die Laufwagen der in Querrichtung gespannten Tragseile verfahren werden. Die Membran trägt zwischen diesen sogenannten Gratseilen praktisch einachsig in Dachlängsrichtung. Die Dachkehle – zwischen jeweils zwei Gratseilen – wurde so ballastiert, daß sich die Membran beim Verfahren wie eine Ziehharmonika zwischen Grat und Kehle auffaltet.
Hochgebirgsattraktionen aus Stahl
Authors: Huber Gerald , Aste Christian 
Published: July 2004

AbstractDie neuen Stahl‐Attraktionen im Skigebiet Sölden (Österreich) auf über 3000 m Seehöhe bringen die faszinierende Bergwelt spürbar nahe. Die extremen Belastungs‐ und Montagebedingungen im alpinen Hochgebirge sowie die sichtbar bleibenden konstruktiven Details machten diese touristisch viel beachteten Gipfelsymbole auch ingenieurtechnisch zu einer besonderen Herausforderung.
Berechnungsverfahren zur Ermittlung der Wärmedurchgangskoeffizienten von zweischaligen Wand‐ und Dachaufbauten in Leichtbauweise
Authors: Loose Tobias , Saal Helmut 
Published: July 2004

AbstractDie Energieeinsparverordnung fordert bei der Berechnung der Transmissionswärmeverluste die Berücksichtigung von Wärmebrücken. Berechnungsverfahren, die diese Wärmebrückenverluste bei der Ermittlung des Wärmedurchgangskoeffizienten berücksichtigen, werden für sechs Wand‐ und zwei Dachaufbauten vorgestellt. Diese Berechnungsverfahren, die sich an die Schwedische Norm SS 02 42 30 halten, sind sehr rechenaufwendig und werden deshalb mit Hilfe von Nomogrammen vereinfacht.
Zur sicheren Anwendung feuerverzinkter Stahlträger
Authors: Sedlacek Gerhard , Dahl Winfried , Hoffmeister Benno , Kühn Bertram , Feldmann Markus , Pinger Thomas , Langenberg Peter , Eichenmüller Helena , Grotmann Dietmar , Blum Marc 
Published: July 2004

AbstractBei feuerverzinkten Stahlträgern u.a. für den Parkhausbau sind in der Vergangenheit Risse aufgetreten, hauptsächlich Längsrisse im Steg der Träger, die von geschweißten Teil kopfplatten ausgingen, vereinzelt auch Risse am Untergurt quer zum Träger, die an lokalen Druckstellen infolge Kaltverformung zum Vorkrümmen der Träger ihren Anfang nahmen.Der Aufsatz geht den wechselseitigen Ursachen der Rißbildung bei der Verzinkung entsprechend dem derzeitigen Stand der Forschung nach und gibt vorläufige Empfehlungen zur Werkstoffwahl, konstruktiven Ausbildung sowie Fertigung und Feuerverzinkung, um in Zukunft Risse zu vermeiden.