bluuebunny/crossref_metadata_2025_split huggingface dataset:
Correlated hyperspherical harmonics: Application to systems of three bosons
Authors: Zickendraht W. , Levinger J. S. 
Published: September 2010

AbstractWe study the use of expansions in correlated hyperspherical harmonics to calculate the energy of the ground state of a system of three identical spinless bosons, for a model potential. In our model the potential is the sum of a harmonic oscillator and an inverse square repulsion of variable strength. We find excellent convergence.
Strategies for reproduction and ageing
Authors: Bernardes A. T. 
Published: September 2010

AbstractThe process of accumulation of deleterious mutations is the fundamental reason of ageing, according to the evolutionary theory. In this theory, the individuals better fitted to reproduce will suffer this accumulation in adulthood or old age. We present results obtained from Monte Carlo simulations of the Penna model dealing with the influence of environmental conditions in the reproductive regimes and its consequences on the population ageing: longevity and catastrophic senescence. Moreover, the role of antagonistic pleiotropy in the time evolution is discussed. A puzzling experimental result obtained in species with gender differentiation is the existence of different survival probabilities for males and females. This matter is discussed here in the context of antagonistic pleiotropy.
Decrease of soft vibrational modes with increasing density of two‐level states in the metallic glass Zr‐Rh
Authors: Junge B. , Gey W. 
Published: September 2010

AbstractExperiments are reported on the specific heat below 1 K of 13 melt quenched ZrRh alloys in the superconducting state (Tc>4.2 K) where electronic degrees of freedom are frozen out. Large differences of the quasilinear (two‐level system, TLS) contributions given by λTLS occur with no correlation to the rhodium concentration. The coefficient α of the cubic, phonon‐type term is found to decrease with the density of TLS for this metallic glass. This is counter‐intuitive to the soft‐potential model and differs from the relation found for insulating glasses.
Optical absorption by quasiparticles in superconducting multilayers
Authors: Plehn H. , Kümmel R. 
Published: September 2010

AbstractThe absorption of photons by quasiparticles in the Bloch bands of multilayers, formed by alternating normal (N) and superconducting (S) regions, is computed for the vector of the oscillating electric field being perpendicular to the N‐S interfaces. The absorption spectrum extends down to frequencies below the gap of the S‐layers, and its structure results from the combined effects of Andreev scattering and conventional scattering at the N‐S interfaces. For not too different Fermi energies ϵFS and ϵFN in the S and N layers there is one prominent resonance peak. With increasing temperature low frequency absorption goes up. For ϵFS ≫ ϵFN, on the other hand, a sharp multipeak structure at low frequencies is found.
From sum rules to RPA: 3. Optical dipole response in metal clusters
Authors: Reinhard P.‐G. , Genzken O. , Brack M. 
Published: September 2010

AbstractThe properties of plasmon resonances in metal clusters are computed within the random phase approximation (RPA), starting from the Kohn‐Sham ground state within the jellium model. The paper aims at a systematic survey of the general trends with varying parameters such as electron number, angular momentum, Wigner‐Seitz radius etc. To this end we exploit the flexibility of a particular RPA scheme which allows to switch easily between different levels of approximation.
Critical dynamics and multifractal exponents at the Anderson transition in 3d disordered systems
Authors: Brandes T. , Huckestein B. , Schweitzer L. 
Published: September 2010

AbstractWe investigate the dynamics of electrons in the vicinity of the Anderson transition in d = 3 dimensions. Using the exact eigenstates from a numerical diagonalization, a number of quantities related to the critical behavior of the diffusion function are obtained. The relation η = d − D2 between the correlation dimension D2 of the multifractal eigenstates and the exponent η which enters into correlation functions is verified. Numerically, we have η ≈︁ 1.3. Implications of critical dynamics for experiments are predicted. We investigate the long‐time behavior of the motion of a wave packet. Furthermore, electron‐electron and electron‐phonon scattering rates are calculated. For the latter, we predict a change of the temperature dependence for low T due to η. The electron‐electron scattering rate is found to be linear in T and depends on the dimensionless conductance at the critical point.
Transport properties of quantum dots
Authors: Weinmann Dietmar , Häusler Wolfgang , Kramer Bernhard 
Published: September 2010

AbstractLinear and nonlinear transport through a quantum dot that is weakly coupled to ideal quantum leads is investigated in the parameter regime where charging and geometrical quantization effects coexist. The exact eigenstates and spins of a finite number of correlated electrons confined within the dot are combined with a rate equation. The current is calculated in the regime of sequential tunneling. The analytic solution for an Anderson impurity is given. The phenomenological charging model is compared with the quantum mechanical model for interacting electrons. The current‐voltage characteristics show Coulomb blockade. The excited states lead to additional fine‐structure in the current voltage characteristics. Asymmetry in the coupling between the quantum dot and the leads causes asymmetry in the conductance peaks which is reversed with the bias voltage. The spin selection rules can cause a ‘spin blockade’ which decreases the current when certain excited states become involved in the transport. In two‐dimensional dots, peaks in the linear conductance can be suppressed at low temperatures, when the total spins of the corresponding ground states differ by more than 1/2. In a magnetic field, an electron number parity effect due to the different spins of the many‐electron ground states is predicted in addition to the vanishing of the spin blockade effect. All of the predicted features are consistent with recent experiments.
Die Gänsebachtalbrücke, eine integrale Talbrücke der DB AG auf der Neubaustrecke Erfurt‐Leipzig/Halle
Authors: Schenkel Marcus , Goldack Arndt , Schlaich Jörg , Kraft Stefan 
Published: September 2010

AbstractDie Gänsebachtalbrücke auf der Neubaustrecke zwischen Erfurt und Leipzig/Halle, Teil des Verkehrsprojektes Deutsche Einheit Nr. 8.2, ist eine integrale, also lagerlose, Eisenbahnbrücke aus Spannbeton. Sie ist für den Hochgeschwindigkeitsverkehr mit Betriebsgeschwindigkeiten bis zu 300 km/h bestimmt. Die in der Realisierung befindliche Talbrücke basiert als alternativer Entwurf auf dem “Leitfaden: Gestalten von Eisenbahnbrücken” der DB AG. Die Gänsebachtalbrücke ist eine Rahmenbrücke, ein Spannbetonplattenbalken monolithisch auf kreisrunden Pfeilern. Am Beispiel der Gänsebachtalbrücke konnte gezeigt werden, dass die alternativen Entwürfe aus dem Leitfaden der DB AG hinsichtlich Tragfähigkeit, Gebrauchstauglichkeit und Verkehrssicherheit sowie Kosten mindestens gleichwertig und damit für den Hochgeschwindigkeitsverkehr geeignet sind. Das Abweichen von der Rahmenplanung und die integrale Bauweise erforderten eine Zustimmung im Einzelfall und damit zahlreiche weiterführende Untersuchungen, welche in diesem Aufsatz ausführlich dargestellt werden, wie die Untersuchung zum dynamischen Verhalten bei Zugüberfahrten und möglicher Resonanzerscheinungen. Mit diesem alternativen Entwurf kommt eine Talbrücke zur Ausführung, die robuster ist und sich besser in das flache Gänsebachtal einfügt als der Ausschreibungsentwurf der Rahmenplanung.The Gänsebach Valley Bridge, an Integral Valley Bridge owned by the DB AG on the New Railway Erfurt‐Leipzig/HalleThe new railway between Erfurt and Leipzig/Halle, part of the transportation project “Deutsche Einheit No. 8.2”, crosses the Gänsebach valley via an intregal (i.e. no bearings) prestressed concrete bridge. The bridge is designed for high‐speed traffic of up to 300 km/h. The bridge, currently under construction, is based on an alternative design in accordance with the guideline “Design of Railway Bridges” (“Leitfaden: Gestalten von Eisenbahnbrücken”) of the Deutsche Bahn AG. The Gänsebach valley bridge is designed as a frame bridge, a monolithical prestressed concrete double T‐beam on circular columns. The example of the Gänsebach valley bridge proved that alternative designs following the DB AG guideline are to be regarded as at least equivalent with regard to load bearing capacity, serviceability and traffic safety as well as cost and therefore suitable for high‐speed traffic. The deviation from the original plan and the integral design required a separate approval and consequently various further tests, such as examining the dynamic behavior under train crossings and possible resonance vibrations. These tests will be described in detail in this paper. This alternative design will result in a bridge which is more robust and will fit in more harmoniously with the shallow valley of the Gänsebach than the original commissioned design would have.
Korrosionsprodukte und deren Volumenfaktor bei der Korrosion von Stahl in Beton
Authors: Raupach Michael , Weizhong Gan , Wei‐Liang Jin 
Published: September 2010

AbstractKorrosion der Bewehrung ist eine der Hauptursachen für Schäden an Betonbauwerken. Das Volumen des Rostes ist i. d. R. um ein Vielfaches größer als das ursprüngliche Stahlvolumen, was zu Rissbildungen und Abplatzungen des Betons bis hin zum Verlust der Gebrauchstauglichkeit führen kann. Basierend auf gezielten Korrosionsuntersuchungen werden in diesem Beitrag die Hauptkomponenten der typischen Eisenoxide und ‐hydrate sowie deren Volumenfaktoren beschrieben, die als Basis für weiterführende Betrachtungen der Auswirkungen der Bewehrungskorrosion dienen sollen.Corrosion Products and their Volume Factor Created by Corrosion of Steel in ConcreteSteel corrosion is one of the main reasons of degradation and damage of concrete structures. The volume of rust, resulting from steel corrosion, can be several times greater than the original steel volume which leads to cracking and spalling of the concrete and may finally end in the loss of structural functionality. Based on corrosion experiments on black steel, this article presents the major components of typical oxide layers and their volume expansion and thus forms a basis for further studies on corrosion of steel in concrete.
Der Eurocode 2 für Deutschland – Erläuterungen und Hintergründe
Authors: Fingerloos Frank 
Published: September 2010

AbstractDer neue Eurocode 2: “Bemessung und Konstruktion von Stahlbeton‐ und Spannbetontragwerken – Teil 1‐1: Allgemeine Bemessungsregeln und Regeln für den Hochbau” (EC2‐1‐1) mit seinem Nationalen Anhang ist nach einer ausführlichen Erprobungsphase bereit zur bauaufsichtlichen Einführung in Deutschland. In mehreren Beiträgen sollen Erläuterungen und Hintergründe zu einigen Regelungen im Eurocode 2 und zu den Entscheidungen für Regeln im Nationalen Anhang vorgestellt werden, die entweder zu Änderungen gegenüber DIN 1045‐1 oder zu Abweichungen vom Eurocode 2 führten. Der Teil 4 enthält einige Erläuterungen zu den Bewehrungs‐ und Konstruktionsregeln.The Eurocode 2 for Germany – Explanations and Backgrounds Part 4: Detailing of Reinforcement and MembersThe new Eurocode 2 “Design of concrete structures – Part 1‐1: General rules and rules for buildings” (EC2‐1‐1) and its National Annex has undergone a phase of detailed testing and is now ready for the implementation in Germany. In some articles should be given explanations and backgrounds of some rules in Eurocode 2 and of decisions for rules in the National Annex, which have been taken either to changes compared with DIN 1045‐1 or to differences to Eurocode 2. Article 4 contains some explanations to detailing of reinforcement and members.
Nachträgliche Abdichtung von Betonbauwerken durch Gelinjektionen
Authors: Rudolph Matthias , Hornig Ute 
Published: September 2010

AbstractDer Beitrag beschäftigt sich mit den Möglichkeiten, Betonbauwerke mit anderen als den in der Instandsetzungsrichtlinie des DAfStb aufgeführten Produkten abzudichten. Dafür kommen Injektionsgele in Frage, die eine Reihe vorteilhafter Eigenschaften besitzen, durch die eine erfolgreiche Abdichtung auch dann noch möglich ist, wenn die “klassischen” Verfahren zu scheitern drohen. Wesentliche Vertreter der Injektionsgele, für die eine Reihe von praktischen Erfahrungen und Forschungsergebnissen vorliegen, sind die Acrylatgele, deren Anwendung beschrieben werden.Ausgehend von beispielhaft genannten Randbedingungen und einer Darstellung der wesentlichen Materialeigenschaften werden die Arten der mit Gelinjektionen herstellbaren Abdichtungen (Gelschleierabdichtungen, Injektion in das Bauteil, in Bauteilzwischenräume und in Risse, sowie deren Mischformen) dargestellt.Der Schwerpunkt liegt auf der Schleierinjektion, da sie die größten Besonderheiten gegenüber den üblichen Injektionen zum Füllen von Rissen und Fehlstellen aufweist. Für die Schleierinjektionen werden Grenzen der Ausführbarkeit und Möglichkeiten zum Erkennen dieser Grenzen aufgezeigt. Eine solche Möglichkeit besteht in der Ausführung von Probeinjektionen mit Wasser an vorgesehenen Injektionsstellen in den am Bauwerk anstehenden Baugrund. Neben der Darstellung der technischen Grundlagen und Anwendungsgrenzen wird für die einzelnen Arten der Gelinjektionen aufgeführt, welche baurechtlichen Anforderungen zu beachten sind.Post‐Construction Sealing of Concrete Structures by Gel GroutingThis article deals with possibilities to seal concrete structures by other products than those authorized by the DAfStb. Among those products are grout injection gels which have several favourable properties which allow the user to seal even those structures where conventional methods might fail. Particularly for acrylate gel there is already a wide range of experience. This article describes the main properties of the materials, standard boundary conditions and the resulting types of sealing: curtain grouting, injections into the structural components or joints between structural elements, in cracks and a mixture of the methods mentioned above. The focus is set on curtain grouting which differs significantly from common grouting to repair cracks and defects. The usage of curtain grouting is limited. A method is described to recognize those limitations. One possibility could be to perform test injections at the original site using water instead of the gel. Apart from technical basics and practical limitations the requirements made by the authorities are characterized.
A fluorimetric method for the determination of atmospheric hydrogen sulfide with fluorescein
Authors: He Xia , Guoquan Gong , Huaigong Wang 
Published: September 2010

AbstractA rapid, simple and sensitive fluorimetric method has been developed for the determination of hydrogen sulfide with fluorescein as fluorogenic reagent (λex=493nm, λem=518nm) at pH 6.1‐8.3. A linear calibration curve was obtained in the range 0.003‐0.25 μg H2S/25 ml. The detection limit is 0.003 μg H2S/25 ml. The method was successfully applied to the determination of atmospheric hydrogen sulfide.
Étude de la Cinétique de Décomposition des Phosphates de Djebel Onk Par l'Acide Nitrique
Authors: Mizane A. , Samar M. H. , Allal K. M. 
Published: September 2010

AbstractThe development of industrial processes designed to produce efficient fertilisers is nowadays of great importance, particularly in the field of farming. One way of producing phosphate fertilisers is by reacting phosphate rocks with nitric acid. In the present work, the kinetics of this reaction has been studied using phosphate mineral of the Djebel Onk mine (Algeria) and measurements of the conversion of P2O5 have been carried out by gravimetry. The effects of various operating parameters such as the reaction time, the reaction temperature, the nitric acid concentration and the size of the particle have been studied. The experimental conditions have been optimised and global kinetic data such as the reaction rate constant and the activation energy have been determined.
Solvent effect in the Wollgerodt‐Kindler reaction
Authors: Kanyonyo Martial R. , Ucar Huseyin , Isa Majed , Carato Pascal , Lesieur Daniel , Renard Pierre , Poupaert Jacques H. 
Published: September 2010

AbstractThe Willgerodt‐Kindler reaction was studied on three different model compounds (4‐bromo benzaldehyde, 4‐fluorobenzaldehyde, 4‐methoxyacetophenone) with particular emphasis on the influence of the solvent on the yield of the reaction. Best conditions involved the use of polar aprotic solvents such as DMF. This finding was applied to the Willgerodt‐Kindler reaction of two difficult substrates, i.e. 3‐methyl‐6‐formyl‐2 (3H)‐benzoxazolinone and 3‐methyl‐6‐formyl‐2(3H)‐benzothiazolinone with various secondary amines.
Kinetic studies of the reactions of 2‐diethylaminoethylchloride with nucleophilic reagents in N,N‐dimethylformamide
Authors: Yang H. , Thyrion F. C. 
Published: September 2010

AbstractThe kinetics of the reactions of 2‐diethylaminoethylchloride with nucleophilic reagents have been studied in N, N‐dimethylformamide from 33 to 80°. An ethyleneimmonium ion is easily formed from 2‐diethylaminoethylchloride by the participation of the neighbouring nitrogen atom. This ion is rather stable in N, N‐dimethylformamide solution and is in equilibrium with 2‐diethylaminoethylchloride. However, it reacts very rapidly with various nucleophilic reagents such as 8‐benzyltheophylline and 2‐(ethylamino)ethanol. The formation of the ethyleneimmonium ion is slower than the nucleophilic substitution reaction. The equilibrium constant and the rate constant of the formation of the ethyleneimmonium ion, as well as the rate constants of the nucleophilic substitution reactions, have been determined.
Réactions des Méthylazide et Phénylazide Avec Quelques Alcynes et Oléfines α‐Nitrées. Synthèse Régiospécifique des 1,2,3 Triazoles
Authors: Piet J. C. , Le Hetet G. , Cailleux P. , Benhaoua H. , Carrié R. 
Published: September 2010

AbstractThe reactions of alkynes and α‐nitro‐olefines with methylazide and phenylazide was studied. In contrast to known reactions with alkynes which are non‐regioselective, methylazide and phenylazide react regiospecifically with α‐nitro‐olefines and give only one type of triazole after elimination of HNO2. These reactions are very useful synthetic approaches to 1,2,3 triazoles.
Modification of surface properties due to the action of spillover species during catalytic reactions. An overview
Authors: Delmon Bernard 
Published: September 2010

AbstractWe give here an overview of new developments concerning spillover processes in catalysis. We focus on the remote control, namely the ability of spillover species to promote activity and selectivity and to act against the deactivation of catalysts. This deals both with the atomic level processes and the macroscopic description of the phenomenon, and alludes to the new chemical engineering developments the concept leads to. This summarizes several very recent reviews (1‐6).
Study of the behaviour of an autothermic catalytic reactor
Authors: Fontaine J. L. , Germain A. 
Published: September 2010

AbstractIn some cases, the mathematical expressions describing chemical problems are actually very difficult to handle. We are studying one of these systems, the non isothermal combustion of hydrogen‐oxygen‐nitrogen mixtures over Pd catalysts. Data obtained during stationary and dynamic experiments are analyzed by using neural networks, and the results are compared to results obtained on the same basis with orthogonal collocation. Neural networks analyze experimental data, in order to determine the behaviour of the system. Thanks to this tool, we are able to model the behaviour of such a difficult reactional system in a very good way. New improvements in the use of neural networks for the modelling of chemical phenomena are also showed.
Kinetics of surface reactions on the atomic scale
Authors: Kruse N. 
Published: September 2010

AbstractThe reaction of CO and NO with Rh crystals of almost hemispherical shape was studied at temperatures between 300 and 550 K. Strong morphological changes of the crystals were observed with atomic resolution in the field ion microscope (FIM). After field‐free reaction with CO at 420 K the hemispherical Rh crystal appeared to be transformed into polyhedral forms. The reaction with NO did not produce as regular forms as with CO. In particular, high‐index planes were largely absent after reaction in CO while they were still present, though redistributed, after reaction with NO. Adsorbate‐induced restructuring was found to be thermally activated. Using pulsed field desorption mass spectrometry (PFDMS), the underlying reaction mechanisms and kinetics were studied in small selected areas of up to 150 atomic sites. The interaction with CO led to the formation of Rh‐subcarbonyls, Rh(CO)x (x=1‐3). These species are most likely directly involved in the reconstruction process of the Rh sample. A reaction model is proposed according to which Rh‐dicarbonyl is liberated into the terrace parts of the surface after Rh‐Rh bond breaking in kink site positions. This is a repeatable step which ends as soon as an open chain of atoms is used up. Accordingly, kink sites are annihilated and facet structures with long chains of ledge atoms appear. The details of the reconstruction process with NO are not as clearly established as with CO. Multiple bonded NOad was not detected by PFDMS. Instead, considerable decomposition into nitrogen and oxygen atoms occurred which finding is in agreement with the catalytic activity known for Rh metal.
Hydrogen a probe molecule and a reactant on platinum catalysts
Authors: Barbier J. , Lamy‐Pitara E. , Marecot P. 
Published: September 2010

AbstractThe main results in the literature concerning the thermodynamics, the kinetics and the stoichiometry of adsorption of hydrogen in gas phase are compared to those obtained in liquid phase by transient electrochemical methods on platinum catalysts.Two states of adsorbed hydrogen are identified: one strongly bound and not very mobile, the other weakly bound and mobile on the surface of the catalyst. The difference in the binding energy of that two states is close to 50kl./mol.The catalytic hydrogenation of unsaturated compounds proves that only weakly bound hydrogen (or the most mobile) is active.The nature of the hydrogen (or the binding energy Pt‐H) involved in the reaction varies with the nature of the unsaturated compounds under consideration. By controlling the nature of the adsorbed hydrogen (by means of the potential control of the catalyst) it is possible to orient the selectivity of the hydrogenation reactions.
Contact reactions of n‐butane and 2‐Methylpentane with well characterized clean metallic, carburized or oxidized tungsten surfaces
Authors: Wanner Sonia , Hemming Florence , Wehrer Pierre , Hindermann Jean‐Paul , Maire Gilbert 
Published: September 2010

AbstractOxygen is known to change drastically the surface states and the catalytic properties of transition metal carbides. In order to better understand the mechanism of the reaction of hydrocarbons with the oxygen modified surfaces, surfaces have been prepared by controlled additions of oxygen on a clean WC carbide. 2‐methylpentane and n‐butane were reacted on these surfaces. The obtained results have been compared with those observed on metal, oxygen predosed metal, and partially reduced oxide. A bifunctional mechanism seems to be operating on the oxygen modified surfaces.