bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cloprostenol, a prostaglandin F2α analog, induces hypoxia in rat placenta: BOLD contrast MRI
Authors: Girsh Eliezer , Plaks Vicki , Gilad Assaf A. , Nevo Nava , Schechtman Edna , Neeman Michal , Dekel Nava 
Published: August 2006

AbstractBlood oxygen level dependent (BOLD) contrast was used to monitor hypoxia induced by cloprostenol, a prostaglandin F2α (PGF2α) analog, in the rat embryo‐placental unit (EPU). It is shown that administration of cloprostenol (0.025 mg/rat) at mid‐gestation (day 16) reduced EPU oxygenation, as detected by BOLD contrast MRI, in correlation with induction of vascular endothelial growth factor (VEGF) gene (Vegfa) expression in the corresponding placenta (r = 0.56, p = 0.03). Elevated VEGF mRNA expression in response to cloprostenol treatment was also observed at early gestation (day 9) in the forming placenta (p = 0.04) and uterus (p = 0.03). Cloprostenol increased the expression levels of endothelin‐1 (ET‐1) gene (Edn1) (p = 0.03) and its corresponding peptide (p = 0.02) in the forming placenta, as well as the expression of the endothelin receptor type A (ETA) gene (Ednra) in both the forming placenta (p = 0.009) and the uterus (p = 0.01). The levels of the endothelin receptor type B (ETB) gene (Ednrb) were not affected in response to cloprostenol, but a significant elevation in the expression level of this receptor was observed in the uterus at mid‐ and late gestation (day 22) (p = 0.04 and 0.01 respectively), suggesting a role for ETB in the vasodilatory status of the pregnant uterus. It is suggested that PGF2α induces uteroplacental vasoconstriction in the rat, and that ET‐1 may take part in mediating this effect, probably via activation of ETA receptor. The uteroplacental vasoconstriction induces hypoxia, as manifested by significant changes in BOLD MRI and by upregulation of VEGF. Copyright © 2006 John Wiley & Sons, Ltd.
NMR study of the cooperative behavior of thermotropic model polypeptides
Authors: Kurková Dana , Kříž Jaroslav , Rodríguez‐Cabello José Carlos , Arias Francisco Javier 
Published: August 2006

AbstractUsing 1H and 13C 1D and 2D NMR spectra, relaxation and PFG NMR measurements, the structural changes of two genetically engineered, and thus unimolecular, elastin‐like polypentapeptides [(GVGVP)2‐(GEGVP)‐(GVGVP)2]n, n = 9 and 15, in D2O and H2O solutions and at two concentrations (5 and 0.5% wt), were studied in the temperature interval 288–330 K, i.e. below, at and above their inverse temperature transition (ITT). According to the extent of extreme signal broadening, the rigidity of both polymers increases at and above ITT. The process of polymer stiffening proceeds primarily from the polymer backbone and is accompanied by coiling of the polymer and aggregation. It is distinctly more effective in the polymer with higher molecular weight, as well as at higher concentration, which indicates intra‐ and intermolecular cooperativity of the process. According to the measured NHCH dihedral angles and chemical shifts, the conformation of the visible part of both polypeptides does not significantly differ from random coil conformation both below and above the transition temperatures. However, this could be due to fast averaging of more definite conformations. Tighter coiling of the NMR‐visible part of the polymer during thermal transition is indicated by a decrease of its hydrodynamic radius, derived from the self‐diffusion coefficient measured by PFG NMR. Lower values of HOD T1 relaxation time and lower slope of its increase compared to those of HOD in pure D2O suggest a remaining interaction of the polymer with water above ITT. Copyright © 2006 Society of Chemical Industry
Plasmonen als Lichttransporter: Nanooptik
Authors: Aussenegg Franz , Ditlbacher Harald 
Published: August 2006

AbstractMetallische Nanopartikel, Nanodrähte oder Filme können Licht in Oberflächen‐Plasmonen einfangen. Dieses Phänomen spielt sich im optischen Nahfeld und im Subwellenlängenbereich ab. Dabei entsteht ein hybrider, optoelektronischer Anregungszustand aus Licht und oszillierenden Leitungselektronen. Metallische Nanopartikel können zum Beispiel als “Hilfsantennen” die Fluoreszenz von Biomolekülen erheblich verstärken. Das ist für Fluoreszenzsensoren interessant. Experimente zeigen, dass metallische Nanodrähte in Oberflächen‐Plasmonen Licht transportieren können. Auf zweidimensionalen, strukturierten Metallfilmen wurden Bauelemente bis hin zum Interferometer für Plasmonen erfolgreich demonstriert. Das junge Feld der Plasmonik könnte wichtige Beiträge zu einer zukünftigen Nanooptik liefern.
Der Blick ins Gehirn: Bildgebende Verfahren in der Gehirnforschung
Authors: Pietrzyk Uwe , Khodaverdi Maryam 
Published: August 2006

AbstractModerne bildgebende Verfahren ermöglichen Untersuchungen am menschlichen Gehirn, ohne es in seinen Funktionen zu stören oder zu verletzten. Sie erzeugen hoch aufgelöste Abbildungen, die Medizinern die Möglichkeit geben, Krankheiten zu diagnostizieren und chirurgische Eingriffe zu planen. Aber auch die Funktion und Struktur des Gehirns lässt sich mit der Bildgebung erforschen. Die Physiker stellen dazu immer sensitivere und genauere Hilfsmittel zur Verfügung.
Ludwig Boltzmann als Experimentalphysiker: Frühe Bestätigung der Maxwell‐Theorie
Authors: Rumpf Klemens , Granitzer Petra 
Published: August 2006

AbstractAm Beispiel von Boltzmanns Experimenten zur Bestätigung der Maxwell‐Theorie wird dessen hervorragende Begabung auch als Experimentalphysiker deutlich. Die dargestellten Arbeiten fanden etwa 15 Jahre vor den Hertzschen Experimenten statt, zu einem Zeitpunkt also, als die noch junge Maxwell‐Theorie dringend experimenteller Bestätigung bedurfte. Boltzmann konnte mit seinen experimentellen Untersuchungen eine direkte Konsequenz der Maxwellschen elektromagnetischen Theorie, die so genannte Maxwell‐Relation, bestätigen. Seine Experimente stellten nicht nur lange Zeit den stärksten Beleg für die Richtigkeit der Maxwellschen Lichttheorie dar, sondern waren eine experimentelle Spitzenleistung an der Grenze des damals Möglichen. Besonders Boltzmanns Bestimmung der Dielektrizitätskonstanten von Gasen fand noch Jahrzehnte später Erwähnung in namhaften Lehrbüchern.
Was ist ein Proton?
Authors: Ziegler Thomas 
Published: August 2006

AbstractEine Gruppe am Jefferson Lab in den USA hat kürzlich neue Experimente zur Untersuchung der Protonstruktur durchgeführt. Dabei konzentrierten sich die Physiker auf die Frage nach der Existenz von Strange‐Quarks im Proton. Das Ergebnis war überraschend und lässt die Diskussion darüber, was ein Proton wirklich ist, erneut aufflammen.
Meilenstein in der Physik der B‐Mesonen
Authors: Ziegler Thomas 
Published: August 2006

AbstractIn Japan hat die Belle‐Kollaboration am KEK einen wichtigen Durchbruch erzielt. Zum ersten Mal wurde der sehr seltene, rein leptonische Zerfall eines B‐Mesons beobachtet. Er bietet die Möglichkeit, andere wichtige Größen der Elementarteilchenphysik, wie die Masse des Higgs‐Teilchens, besser vorhersagen und verstehen zu können.
Ein Phasenkontrast‐Mikroskop für Neutronen
Authors: Pfeiffer Franz 
Published: August 2006

AbstractPhasenkontrast mit sichtbarem Licht ist ein unentbehrliches Hilfsmittel der modernen Mikroskopie. Einem Forscherteam am schweizerischen Paul Scherrer Institut (PSI) ist es nun gelungen, ein entsprechendes Abbildungsverfahren auch für Neutronenstrahlen zu entwickeln. So können quantenmechanische Wechselwirkungen von Neutronen mit Materie in Form von zwei‐ und dreidimensionalen Bildern sichtbar gemacht werden.
Fragwürdiges beim Millikan‐Versuch
Authors: Heering Peter 
Published: August 2006

AbstractRobert A. Millikan erhielt 1923 als erster amerikanischer Physiker den Nobelpreis für Physik. Geehrt wurde er für seine Präzisionsmessungen zum Photoeffekt und zur experimentellen Bestimmung der elektrischen Elementarladung. Millikans Experimente zur Elementarladung sind auch heute noch ein Standardthema im schulischen Physikunterricht, gleichzeitig werfen sie aber eine Reihe von wissenschaftstheoretischen und ethisch relevanten Fragen auf.
Das Universum® in Bremen
Authors: Althans Svenja , Haller Kerstin , Wolff Tobias 
Published: August 2006

AbstractIm Universum® Science Center Bremen tauchen die Besucher mit allen Sinnen in die Welt wissenschaftlicher Phänomene ein. Auf drei Expeditionen durch die Gebiete Mensch, Erde, Kosmos wird jeder Besucher zum Forscher, kann ausprobieren und experimentieren. Die konkreten Erfahrungen bilden dabei die Basis für nachhaltiges Lernen naturwissenschaftlicher Zusammenhänge.
Das Schmoren der Tripelhelix
Authors: Vilgis Thomas 
Published: August 2006

AbstractSchmoren ist eine der beliebtesten Methoden, geschmackvolles Fleisch auf den Tisch zu zaubern, ob als Gulasch oder als klassischen Sauerbraten. Garzeiten von mehr als zwei Stunden sind keine Seltenheit. Der Grund dafür liegt in der Biophysik des durchwachsenen Schmorfleisches. Das Bindegewebe Kollagen muss zuerst in Gelatine umgewandelt werden, damit es dem Genuss keinen Widerstand mehr bietet.
Thermodynamic analysis of the reaction‐induced phase separation of solutions of random copolymers of methyl methacrylate and N,N‐dimethylacrylamide in the precursors of a polythiourethane network
Authors: Soulé E. R. , Jaffrennou B. , Méchin F. , Pascault J. P. , Borrajo J. , Williams R. J. J. 
Published: August 2006

AbstractPoly(methyl methacrylate) and random copolymers of methyl methacrylate (MMA) and N,N‐dimethylacrylamide (DMA) containing 7.5, 15, or 20 wt % DMA were dissolved in a stoichiometric mixture of m‐xylylene diisocyanate and 4‐mercaptomethyl‐3,6‐dithia‐1,8‐octanedithiol, precursors of a polythiourethane network. Phase separation, which took place during polymerizations at 60, 90, and 120 °C, exhibited a lower critical solution temperature behavior. The cloud‐point conversions, which were determined by the iodometric titration of free thiol groups of samples chilled in ice at the cloud point, increased with the weight fraction of DMA in the random copolymer. This could be used to control the cloud‐point conversion and determine the characteristic size of the dispersed domains. A thermodynamic analysis was performed with the Flory–Huggins equation, taking into account the polydispersities of both the thermoplastic and thermoset polymers and using an interaction parameter depending on the temperature and on the three binary interaction energies. A reasonable fitting of the experimental curves was obtained with negative values for the interaction energies of the MMA–thermoset and DMA–thermoset pairs and with a positive value for the MMA–DMA pair. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2821–2827, 2006
Generalized modeling of enzyme–ligand interactions using proteochemometrics and local protein substructures
Authors: Strömbergsson Helena , Kryshtafovych Andriy , Prusis Peteris , Fidelis Krzysztof , Wikberg Jarl E. S. , Komorowski Jan , Hvidsten Torgeir R. 
Published: August 2006

AbstractModeling and understanding protein–ligand interactions is one of the most important goals in computational drug discovery. To this end, proteochemometrics uses structural and chemical descriptors from several proteins and several ligands to induce interaction‐models. Here, we present a new and generalized approach in which proteins varying greatly in terms of sequence and structure are represented by a library of local substructures. Using linear regression and rule‐based learning, we combine such local substructures with chemical descriptors from the ligands to model binding affinity for a training set of hydrolase and lyase enzymes. We evaluate the predictive performance of these models using cross validation and sets of unseen ligand with unknown three‐dimensional structure. The models are shown to generalize by outperforming models using descriptors from only proteins or only ligands, or models using global structure similarities rather than local similarities. Thus, we demonstrate that this approach is capable of describing dependencies between local structural properties and ligands in otherwise dissimilar protein structures. These dependencies are often, but not always, associated with local substructures that are in contact with the ligands. Finally, we show that strongly bound enzyme–ligand complexes require the presence of particular local substructures, while weakly bound complexes may be described by the absence of certain properties. The results demonstrate that the alignment‐independent approach using local substructures is capable of describing protein–ligand interaction for largely different proteins and hence opens up for proteochemometrics‐analysis of the interaction‐space of entire proteomes. Current approaches are limited to families of closely related proteins. families of closely related proteins. Proteins 2006. © 2006 Wiley‐Liss, Inc.
Multifrequency magnetic resonance and blocking behavior of FexPt1–x nanoparticles
Authors: Antoniak C. , Lindner J. , Salgueiriño‐Maceira V. , Farle M. 
Published: August 2006

AbstractMultifrequency ferromagnetic resonance well above the blocking temperature was used to determine the composition dependent g ‐factor in wet‐chemically synthesized Fex Pt1–x nanoparticles with mean diameters around 3 nm. The magnetic relaxation process in these experiments is found to be non‐Gilbert like. To obtain the blocking temperature and the effective anisotropy, zero‐field‐cooled magnetometry data are simulated using a model of non‐interacting particles. In this simulation, the temperature dependence of the effective anisotropy has to be taken into account for accurate results. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical characterization of CuIn3Se5, CuGa3Se5 and CuGa5Se8 crystals by spectroscopic ellipsometry
Authors: León M. , Serna R. , Levcenko S. , Nateprov A. , Nicorici A. , Merino J. M. , Arushanov E. 
Published: August 2006

AbstractThe ellipsometric spectra of CuIn3Se5, CuGa3Se5 and CuGa5Se8 ordered vacancy compounds (OVC) have been studied in the spectral range from 0.8 to 4.4 eV. The structures observed in the measured spectra were analyzed by fitting the second derivative of the experimental spectrum to analytical line shapes. The energies corresponding to different electronic transitions were determined. The lowest direct gap (E 0) is characterized by 3‐dimensional critical points, while higher energy structures are characterized by 2D critical points. Optical constants related to dielectric function, such as the complex refractive index n *(ω ), extinction coefficient k (ω ), absorption coefficient α (ω ), and normal‐incidence reflectivity R (ω ), of studied OVC were determined. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The structural representation and properties of mutually incommensurate composite crystal (BiS)xTS2 (T = Ti, V, Nb and Ta)
Authors: Gotoh Y. , Fujihisa H. , Takeya S. , Yamaguchi I. 
Published: August 2006

AbstractThe structural representation of mutually incommensurate composite crystal, (BiS)x TS2 (T = Ti, V, Nb and Ta), with layered substructures has been described by superspace group approach. The incommensurate composite structures of (BiS)x TS2 have been successfully characterized by the single‐crystal X‐ray‐diffraction method. Temperature dependences of in‐plane electrical resistivity of single composite crystals of (BiS)x TS2 have been obtained by a standard d.c. four probe method in the range of 1.7–300 K. It has been found that the electronic transport properties of (BiS)x TS2 compounds show metallic behavior below room temperature. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Donor‐acceptor pair recombination luminescence from Cu2ZnSnS4 bulk single crystals
Authors: Tanaka K. , Miyamoto Y. , Uchiki H. , Nakazawa K. , Araki H. 
Published: August 2006

AbstractPhotoluminescence from Cu2ZnSnS4 bulk single crystals was studied as a function of temperature and excitation power density. The bulk single crystals showed a broad luminescence between 1.1 and 1.45 eV. The peak energy of the photoluminescence was shifted to higher energy side when the excitation power density was increased. The origon of the photoluminescence was attributed to donor–acceptor pair recombination with an activation energy of 48 meV. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic structure and exchange constants in magnetic semiconductor digital alloys: chemical and band‐gap effects
Authors: Picozzi S. , Ležaić M. , Blügel S. 
Published: August 2006

AbstractFirst‐principles simulations have been performed for [001]‐ordered Mn/Ge and Mn/GaAs “digital alloys”, focusing on the effects of (i) a larger band‐gap and (ii) a different semiconducting host on the electronic structure of the magnetic semiconductors of interest. Our results for the exchange constants in Mn/Ge, evaluated using a frozen‐magnon scheme, show that a larger band‐gap tends to give a stronger nearest‐neighbor ferromagnetic coupling and an overall enhanced in‐plane ferromagnetic coupling even for longer‐ranged coupling constants. As for the chemical effects on the exchange constants, we show that Mn/GaAs shows a smaller nearest‐neighbor ferromagnetic coupling than Mn/Ge, but exchange constants for higher Mn–Mn distance show an overall increased ferromagnetic behavior in Mn/GaAs. As a result, from the magnetic‐coupling point of view, the two systems behave on average rather similarly. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic structure of ternary thallium chalcogenide compounds
Authors: Kashida S. , Yanadori Y. , Otaki Y. , Seki Y. , Panich A. M. 
Published: August 2006

AbstractThe electronic structures of the ternary thallium chalcogenide compounds, TlGaSe2 and TlGaS2 are studied, using the linear muffin‐tin orbital (LMTO) method. The calculated band dispersion shows that both compounds are indirect gap semiconductors. For both compounds, the top of the valence bands is located at Γ. For TlGaSe2, the bottom of the conduction band is located along the Z(0, 0, –5)–L(0.5, 0.5, –0.5) line. For TlGaS2, the bottom of the conduction band is located along the Γ–Y(0, 1, 0) line. An inspection of the LMTO wave functions shows that the valence band top has the character of Tl:6s–Se:4p or S:3p antibonding state, while the conduction band bottom has the character of Tl:6p–Se:4p or S:3p antibonding state. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Microstructures and MR effects of transparent ferromagnetic chemically prepared Fe–Zn–O films
Authors: Shinagawa T. , Izaki M. , Inui H. , Murase K. , Awakura Y. 
Published: August 2006

AbstractTransparent ferromagnetic Fe–Zn–O films with an entire oxide system were prepared by chemical bath depositions followed by heat treatment. The Fe–Zn–O film was composed of two phases, where spinel‐type iron oxide particles of 20 nm in diameter were embedded in a wurtzite zinc oxide film with 240 nm thickness. The electrical properties evaluated by a Hall effects measuring system revealed that the film is an n‐type semiconductor with a resistivity of 2.6 Ω cm. The Fe–Zn–O film exhibited magnetic hysteresis at room temperature, and magnetic moment of 0.5μ B/Fe and coercive force of 172.5 Oe were observed. A negative magnetoresistance effect, probably due to a spin‐dependent scattering of carrier electrons, of about −0.35% in a 5 kOe magnetic field was detected at room temperature. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Local structure in (MnS)2x(CuInS2)1–x alloys
Authors: Pietnoczka A. , Bacewicz R. , Schorr S. 
Published: August 2006

AbstractLocal structure around Mn atoms in (MnS)2x (CuInS2)1–x alloys for x ≤ 0.09 has been determined using near‐edge and extended X‐ray absorption fine structure (XANES and EXAFS) measured at the Mn K‐edge. We found that for the Mn concentration up to 9 at% Mn atoms substitute preferentially for indium in the chalcopyrite lattice. The Mn–S bond length is 2.43 ± 0.015 Å, and is about 2% shorter than the In–S bond length. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic structures of Fe3–xVxSi probed by photoemission spectroscopy
Authors: Cui Y. T. , Kimura A. , Miyamoto K. , Sakamoto K. , Xie T. , Qiao S. , Nakatake M. , Shimada K. , Taniguchi M. , Fujimori S.‐I. , Saitoh Y. , Kobayashi K. , Kanomata T. , Nashima O. 
Published: August 2006

AbstractThe electronic structures of the Heusler type compounds Fe3–x Vx Si in the concentration range between x = 0 and x = 1 have been probed by photoemission spectroscopy (PES). The observed shift of Si 2p core‐ level and the main valence band structres indicates a chemical potential shift to higher energy with increasing x . It is also clarified that the density of state at Fermi edge is owing to the collaboration of V 3d and Fe 3d derived states. Besides the decrease of the spectral intensity near Fermi edge with increasing x suggests the formation of pseudo gap at large x . (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electronic and optical properties of zinc blende and complex crystal structured solids
Authors: Verma A. S. , Bhardwaj S. R. 
Published: August 2006

AbstractThe dielectric description of ionicity developed by Phillips and Van Vechten has been successfully employed in a wide range of semi‐conductors and insulators. However, the applicability of this Phillips and Van Vechten (PV) dielectric analysis has been limited to only the simple AN B8–N compounds, which contain only one type of bond. Levine has extended the theory of PV to multi bond and complex crystals. Levine's theory of ionicity has been used to calculate the various bond parameters for the chalcopyrites. In this paper a simple method based on the product of ionic charge and nearest‐neighbor distance of solids, is proposed for the calculation of ionic gap (E c), average energy gap (E g), crystal ionicity (f i) and dielectric constant (ϵ) of zinc blende (AIIBVI and AIIIBV) and chalcopyrite (AIBIII$ \rm C ^{\rm VI}_{2} $ and AIIBIV$ \rm C ^{\rm V}_{2} $) semiconductors. We find the ionic gap (E c) and average energy gap (E g) are inversely related to product of ionic charge and nearest‐neighbor distance. Our evaluated values are in excellent agreement with the values reported by different researchers. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Description of high‐spin restricted open‐shell molecules with the Piris natural orbital functional
Authors: Leiva P. , Piris M. 
Published: August 2006

AbstractThe Piris natural orbital functional (PNOF) based on a new approach for the two‐electron cumulant is considered for the case of high‐spin restricted open‐shell systems. The theory is applied to the calculation of molecular energies, dipole moments, vertical ionization potentials (IP), and electron affinities (EA) of 10 open‐shell molecules. Vertical values of IP and EA were used to evaluate the hardness. It was observed that the results obtained using the PNOF method are comparable to the corresponding results obtained using CCSD(T) in the case of energies and dipole moments. Best agreement between theory and experiment is achieved by PNOF for EA and hardness values. The calculated PNOF values for the mentioned properties are in good agreement with the available experimental data, considering the basis sets used (6–31 ++G**). © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
Computational approach to the blood–aluminum problem?
Authors: Exley Christopher , Beardmore James , Rugg Gordon 
Published: August 2006

AbstractAluminum has no known function in biota and, when biologically available, is inimical to life. A key to understanding its potential toxicity in humans is its transport in blood. A consensus of opinion has identified the binding of aluminum by the iron‐transport protein transferrin as the preeminent factor in the transport of aluminum in blood, although this idea has emanated from in vitro analysis of isolated blood and has never been tested in vivo. We have highlighted what we believe to be inadequacies of our present understanding of aluminum transport in blood, and we have proposed the application of computational methods to test rigorously what we have coined “the blood‐aluminum problem.” © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007