Showing papers by "Technical University of Dortmund published in 1991"
TL;DR: In this article, the authors use molecular-dynamics simulations to examine the effect of such defects on molecular mobility in water and find that they provide pathways of lower energy between different tetrahedral local arrangements, thus acting as "catalysts".
Abstract: LIQUID water is a totally connected random network of hydrogen bonds, the connectivity lying well above the percolation threshold1–3 But despite this extensive association of hydrogen bonds with strengths greater than the thermal energy, the diffusion and rotation rates of water molecules at ambient temperatures are comparable to those of non-associated simple liquids. Many experiments have indicated that the random tetrahedral network cannot be perfect but must contain defects, which are characterized geometrically by the presence of an extra (fifth) molecule in the first coordination shell, or topologically by the presence of 'bifurcated' hydrogen bonds4–7. Here we use molecular-dynamics simulations to examine the effect of such defects on molecular mobility in water. We find that they provide pathways of lower energy between different tetrahedral local arrangements, thus acting as 'catalysts'. The anomalous mobility of water under compression8,9 and the decreased mobility in hydrophobic hydration shells10,11 can be interpreted on the same basis. We suggest that our results are relevant to studies on 'stretched' water12,13.
328 citations
TL;DR: In this article, it was shown that the phonon-induced self-trapping transition is only induced by phonons, and not induced by a large class of generalized Fr\"ohlich models.
Abstract: For more than 40 years it was thought that polaron- and exciton-phonon systems exhibited unexpected localization properties. Particular attention was paid to the so-called phonon-induced self-trapping transition, which, it was believed, should manifest itself as a point of nonanalyticity in the ground-state energy as a function of the electron-phonon coupling parameter. It will be demonstrated for a large class of (generalized Fr\"ohlich) models that no such transition exists. The dimensionality of space has no qualitative influence; insofar, an application of the authors' results to problems in lower dimensions (e.g., polarons in quantum wells) is straightforward. The same holds true if homogeneous external fields are involved; for example, a discontinuous mass stripping for magnetopolarons can be excluded. On the other hand, a phase-transition-like behavior will be found, if a polaron or exciton is exposed to a short-range potential, allowing a so-called pinning transition. The authors emphasize, however, that even in this case the transition is only modified, and not induced, by phonons.
176 citations
TL;DR: In this paper, a high-statistics measurement of the differential cross-sections for neutrino-iron scattering in the wide-band Neutrino beam at the CERN SPS is presented.
Abstract: A high-statistics measurement of the differential cross-sections for neutrino-iron scattering in the wide-band neutrino beam at the CERN SPS is presented. Nucleon structure functions are extracted and theirQ
2 evolution is compared with the predictions of quantum chromodynamics.
170 citations
TL;DR: Oscillations with time-dependent period in the transmitted light intensity are quantitatively explained as resulting from quantum beats between the two branches of the exciton polariton.
Abstract: Coherent propagation of quadrupole polaritons in ${\mathrm{Cu}}_{2}$O is demonstrated by time-resolved spectroscopy. This manifests itself in a strong distortion of the temporal shape of a picosecond optical pulse which is in resonance with the 1S exciton polariton. Oscillations with time-dependent period in the transmitted light intensity are quantitatively explained as resulting from quantum beats between the two branches of the exciton polariton. The analysis yields the homogeneous linewidth and oscillator strength.
149 citations
TL;DR: In this paper, a study of events containing at least four high transverse momentum jets and a search for double parton scattering (DPS) have been performed using data collected with the UA2 detector at the CERN p p Collider (√s=630 GeV).
144 citations
01 Jun 1991
TL;DR: The main purpose of the concept is to facilitate the modeling of large real-world systems, rather than using them for theoretical considerations, and form the foundation of an editor-simulator-tool with a direct manipulation interface for this type of nets.
Abstract: This paper introduces a formal concept of hierarchical Petri nets with building blocks The hierarchy concept allows to handle the refinement of places and transitions even if they are adjacent The building blocks are introduced as slightly restricted hierarchical Petri nets with hierarchically structured interfaces The main purpose of the concept is to facilitate the modeling of large real-world systems, rather than using them for theoretical considerations This will form the foundation of an editor-simulator-tool with a direct manipulation interface for this type of nets
119 citations
TL;DR: To ensure that the predicted lumbar load during bricklaying remains below the limits, the brick-supply stack should be above 50 cm, as indicated by the moment of force and the force at the lumbosacral disc determined using a dynamic 3-D model, ‘The Dortmunder’.
99 citations
TL;DR: The highest pullulan yield was achieved at decreased constant DO in connection with decreased shear rate, and biomass production was not affected.
Abstract: Experiments were carried out withA. pullulans (ATCC 9348) at constant dissolved oxygen concentration (DO=100 and 50% related to air saturation at 1 bar) and at constant stirrer speeds (n=500 and 150 [min−1]). The highest pullulan yield was achieved at decreased constant DO in connection with decreased shear rate. Biomass production was not affected.
96 citations
TL;DR: In this article, patent competition is modeled as a dollar auction game between two firms, incumbent and entrant, whose total amount is constrained by fixed (research) budgets, and the explicit solution (subgame-perfect equilibrium) determines who wins the patent and how the winning expenditures depend on order of play and budgets of firms.
87 citations
TL;DR: A dynamical generalization of the seesaw mechanism is proposed based upon the BCS theory in which a neutrino condensate gives rise to right-handed-neutrino Majorana masses and all associated spin-zero bosons are composite.
Abstract: We consider a new mechanism for dynamical symmetry breaking of the electroweak symmetries involving condensates of fourth-generation quarks and leptons A dynamical generalization of the seesaw mechanism is proposed based upon the BCS theory in which a neutrino condensate gives rise to right-handed-neutrino Majorana masses and all associated spin-zero bosons are composite The fourth-generation neutrino is naturally heavier than {ital M}{sub {ital Z}}/2 and the scale of new physics is bounded above The renormalization-group equations for the effective Lagrangian of this model are derived and used to solve the model Implications for neutrino masses are discussed
80 citations
11 Sep 1991
TL;DR: A type system is presented with strong typing and static type checking that is not yet well supported in most existing object-oriented database systems.
Abstract: A type system is presented with strong typing and static type checking that is not yet well supported in most existing object-oriented database systems. A subtyping rule is defined for correctly structuring the inheritance hierarchy of the types. Based on the subtyping, a number of type inference rules are defined. They can be used by the type system to statically determine the types of the query results and whether a given application program is type correct. >
TL;DR: In this article, the rotating-frame nuclear magnetic relaxation time T 1 ϱ of 63 Cu as a function of temperature between 283 and 425 K was investigated and an activation enthalpy of 0.69 eV was deduced for the corresponding diffusion process.
TL;DR: In this paper, a general scheme for a construction of mean-field-like theories of itinerant lattice fermions based on solutions to the exactd=∞ grand canonical potential is presented.
Abstract: We present a general scheme for a construction of mean-field-like theories of itinerant lattice fermions based on solutions to the exactd=∞ grand canonical potential. The general construction is explicitly demonstrated on the exactly solvabled=∞ Falicov-Kimball model. A mean-field zero-temperature behaviour of this sample model is studied quantitatively.
TL;DR: In this paper, the authors show how to calculate the free energy of the spinless Falicov Kimball model exactly in the limit of infinite dimensions, and do it explicitly for the homogeneous and the chessboard phase.
Abstract: We show how to calculate the free energy of the spinless Falicov Kimball model exactly in the limit of infinite dimensions, and do it explicitly for the homogeneous and the chessboard phase. By comparing the free energies for those two cases we study the transitions between the pure phases, and by looking for concavities in the course of the free energy as a function of the meanf-particle density we examine the possibility of phase segregation.
TL;DR: In this article, the authors studied the second order U-perturbation treatment of the non-magnetic Hartree-Fock solution of the Hubbard model and showed that it is possible to compute a 2d-fold momentum integration to obtain the self-energy contribution in second order in U for a d-dimensional system.
Abstract: We study the Hubbard model within the second order U-perturbation treatment around the non-magnetic Hartree-Fock solution. When starting from the standard expression, the explicit calculations are very cumbersome, as a 2d-fold momentum integration is required to obtain the selfenergy contribution in second order in U for a d-dimensional system. We show that these computational efforts are strongly reduced when starting from the limit of infinite dimension, d=∞, and taking into account the effects of the finite dimension d by means of a 1/d-expansion.
TL;DR: In this paper, simulation experiments conducted by the International Study Group on Land-Use/Transport Interaction (ISGLUTI) for the metropolitan region of Dortmund in the Federal Republic of Germany are reported.
TL;DR: In this paper, a reine Verbindung ist zuganglich, wenn LiNH2 and Ta3N5 in Hochdruckautoklaven (550 °C; p(NH3) = 0,6 GPa; 5 Tage) zur Reaktion gebracht werden.
TL;DR: Hexamethyl- hexaethyl- and hexabutyl-ditin add to a variety of allenes in the presence of Pd(PPh34) as mentioned in this paper.
TL;DR: The observation that erythrocytes exhibit interindividual differences make binding products with haemoglobin less suitable for biological monitoring of ethylene oxide exposure than, for example, DNA adducts in lymphocytes.
Abstract: The distribution of radioactivity following the incubation of human blood with radio-labelled ethylene oxide was investigated in vitro. After incubation, the individual blood samples were separated into lymphocytes and high (Mr greater than 10,000) and low (Mr less than 10,000) molecular fractions of erythrocyte cytoplasm and blood plasma. The radioactivity was determined in each sample by liquid scintillation counting. In erythrocyte cytoplasm, the distribution of radioactivity showed marked interindividual differences and two distinct groups could be distinguished. The coincidence of these groups with 'conjugators' and 'non-conjugators', in terms of the enzymatic conjugation of methyl halides to glutathione in erythrocytes, suggests a common principle, such as enzyme polymorphism. Such polymorphism has been described for glutathione S-transferase mu in the human liver, an enzyme that efficiently conjugates epoxides. In the other blood compartments, the interindividual differences were either less significant or were not detectable. Binding products with various macromolecules in blood, such as haemoglobin or lymphocyte DNA, are being discussed as biological monitors for occupational exposure to ethylene oxide. The observation that erythrocytes exhibit interindividual differences as described above make binding products with haemoglobin less suitable for biological monitoring of ethylene oxide exposure than, for example, DNA adducts in lymphocytes.
TL;DR: In this article, the authors used the ARGUS detector at the e+ e− storage ring DORIS II at DESY to search for direct evidence for b→u transitions through reconstruction of complete events.
TL;DR: In this article, ausammenfassung Kupferpalladiumnitridphasen, Cu 3 Pd x N with x = 0,020 and 0,989, wurden durch Umsetzungen von [Cu(NH 3 ) 2 ]NO 3 and [Pd(NH 4 ](NO 3 ) 4 ], in uberkritischem Ammoniak als Losungsmittel bei T = 500 ° C and PNH 3 ≈ 6 kbar im Temperaturgefalle der eingesetzten
Abstract: Zusammenfassung Kupferpalladiumnitridphasen, Cu 3 Pd x N mit x = 0,020 und 0,989, wurden durch Umsetzungen von [Cu(NH 3 ) 2 ]NO 3 und [Pd(NH 3 ) 4 ](NO 3 ) 2 in uberkritischem Ammoniak als Losungsmittel bei T = 500 ° C und P(NH 3 ) ≈ 6 kbar im Temperaturgefalle der eingesetzten Autoklaven erhalten. Rontgenographische Strukturbestimmungen an Einkristallen fuhrten zum Perowskit-Typ (“Pd x NCu 3 ”) in Pm3m mit Z = 1: Cu 3 Pd 0,020(3) N: a = 3,810(1) A , R R w = 0,012 0,013 , Z ( F 2 0 ) ⩾ 3 σ ( F 2 0 ) = 32, Z ( Var ) = 7 Cu 3 Pd 0,989(5) N: a = 3,854(1) A , R R w = 0,016 0,018 , Z ( F 2 0 ) ⩾ 3 σ ( F 2 0 ) = 67, Z ( Var ) = 7 Cu 3 Pd 0,020 N und Cu 3 Pd 0,989 N sehen silberfarben aus und leiten den elektrischen Strom. Die Phasen sind bei Raumtemperatur metastabil und zerfallen bei 470 °C zu Cu 3 Pd x und N 2 .
TL;DR: In this article, the main components are vinyl phosphines formed via addition of the Ph 2 P. radical to the central carbon atom of the allene fragment, and the main products are Z -vinylphosphines.
TL;DR: A model of an “acid” and an "alkaline” state of the membrane has been developed, which can be applied both for cation and anion exchange membranes, which is a valuable help in optimizing the concentrations of sodium sulphate, sulphuric acid and caustic soda.
Abstract: There is an increasing interest in the electro-chemical splitting of sodium sulphate into caustic soda solution and sulphuric acid by means of ion exchange membranes. Adaptation of the product properties to the demands of recycling requires the use of cation exchange membranes, anion exchange membranes or a combination of both. Application of available membranes results in product concentrations which are below usual industrial standards. Extensive measurements prove that the current efficiency is either dependent on concentrations of the anode region (sulphuric acid, sodium sulphate) or on the concentrations of the cathode region (caustic soda, sodium sulphate) with regard to the range of concentrations. In order to explain these phenomena a model of an “acid” and an “alkaline” state of the membrane has been developed, which can be applied both for cation and anion exchange membranes. This model is a valuable help in optimizing the concentrations of sodium sulphate, sulphuric acid and caustic soda.
TL;DR: The combination of integrated optics and micromechanics on silicon offers new integration potentials for sensor applications as discussed by the authors, where the SiON optical strip waveguides are fabricated by low-temperature (570 K) PECVD and RIE processes on microbridges, cantilevers and resonators based on field oxide.
Abstract: The combination of integrated optics and micromechanics on silicon offers new integration potentials for sensor applications. Silicon oxinitride (SiON) optical strip waveguides are fabricated by low-temperature (570 K) PECVD and RIE processes on microbridges, cantilevers and resonators based on field oxide. The single-mode strip waveguides with a refractive index n=1.52 of the SiON layer show 0.5 dB/cm attenuation at 0.633 μm wavelength. The micromechanical elements are delineated by anisotropic KOH etching. They are built up with SiO2SiONSiO2 triple layers and exhibit low internal stress.
TL;DR: Charm leptroproduction asymmetries at Q2 = 0 are estimated for forthcoming experiments with polarized lepton (e, μ) beams and polarized fixed targets in this article, where they show that δG(x, Q2) is unsuitable for extracting ΔG. Other possible charm production asymmetry determinations, at higher values of Q2, as well as polarized deep inelastic large-kT jet production are furthermore critically considered for realistic experimental situations.
TL;DR: In this article, the ARGUS detector at the DESY storage ring was used to measure the production of mesons in B decays and in nonresonante+e− annihilation around 10.6 GeV.
Abstract: Using the ARGUS detector at thee+e− storage ring DORIS II at DESY, we have measured the inclusive production ofD0,D+ andD*(2010)+ mesons inB decays and in nonresonante+e− annihilation around 10.6 GeV. The inclusive branching ratios forB decays toD0,D+ andD*+ mesons are found to be (52.2±8.2±3.5)%, (27.2±6.3±3.5)% and (34.8±6.0±3.5)% respectively. Thus,D0 andD+ production account for about 70% of the charm produced inB decays, neglectingb→u contributions to the total width. The production cross sections and momentum spectra for continuume+e− annihilation are also presented.
TL;DR: Xenon NMR spectroscopy was used to characterize xenon in silver-exchanged sodium X zeolites and the materials formed by treatment with oxygen and hydrogen.
TL;DR: A quantitative estimation procedure is described for a measure K denoting the degree of perceptual constancy of background target motions noncollinear to the eye movements during ocular pursuit, which allows for quantitative comparison between experiments with a variety of parameters in visual motton displays.
Abstract: Perceptual constancy of uisual motion is usually described as the degree of correspondence between physical and perceived characteristics of motion in the external world. To study it, one has to assess the relationship between physical motion, its retinal image, and its perception. We describe a quantitative estimation procedure for a measure K denoting the degree of perceptual constancy of background target motions noncollinear to the eye movements during ocular pursuit. The calculation of K is based on three vectors describing the target motion (1) as it is physically, (2) as it is mapped to the retina, and (3) as it is perceived, but only the direction of the perceptual motion vector has to be determined experimentally. K allows for quantitative comparison between experiments with a variety of parameters in visual motton displays.
Technical University of Dortmund1, University of Erlangen-Nuremberg2, Heidelberg University3, Max Planck Society4, Natural Sciences and Engineering Research Council5, National Science Foundation6, Karlsruhe Institute of Technology7, University of Ljubljana8, Swedish Research Council9, United States Department of Energy10
TL;DR: Using the ARGUS detector at the e + e − storage ring DORIS II at DESY, a search for penguin decays of B mesons involving b→s gluon has been performed as mentioned in this paper.