Hindered motions in a ketonea-urea inclusion compound. An ESR and ENDOR study

We have studied by ESR and ENDOR spectroscopy the free radicals produced in γ-irradiated inclusion compound formed between the ketone 10-nonadecanone and urea. Only one type of long lived radical is formed by the removal of an α-proton from the ketone. The hyperfine (hf) coupling constants of the α- and β-protons of the radicals have been measured by ESR at different temperatures in the range 110–292 K and at different orientations of the crystals. The hf coupling of the γ-protons of the radical and of the urea protons have been studied by ENDOR. The temperature and angular dependences of the coupling constants have been analyzed in terms of the internal and overall motions of the radical inside the hexagonal channels formed by the urea molecules. It has been found that the radical cannot perform complete reorientations around the long molecular axis, but it undergoes restricted rotational diffusion. This process is explained by assuming a coupling between the rotational and translational degrees of freedom of the radical inside the urea channels.     

Spectra of fast π + mesons from the π − A → π + X reaction on oxygen and lithium nuclei at 0.59 GeV

The spectra of fast π ⁺ mesons from the π ^? A → π ⁺ X reaction on A=⁶Li, ⁷Li, and ¹⁶O nuclei at a primary momentum of p ₀=0.72 GeV/c (T ₀=0.59 GeV) are measured at emission-angle values in the range ?=0°–14°. The results obtained in this way are compared with experimental data taken in other studies at lower energies and with the results of model calculations. The energy dependence of the cross sections and of shadowing effects is analyzed for the reactions in question that occur on lithium isotopes.     

Gasdynamische Untersuchung des Jouleschen Überströmversuches

Zusammenfassung Es wird die zeitabhängige Strömung beim Ausgleichsvorgang zwischen zwei endlichen Behältern untersucht. Den Überlegungen wird eine eindimensionale, reibungsfreie und quasistationäre Strömung zugrunde gelegt. Während bei überkritischer Strömung eine analytische Lösung möglich ist, wird das Problem bei unterkritischer Strömung numerisch gelöst.Dem Druckausgleich zwischen den beiden Behältern folgt ein isobarer Wärme- und Massenaustausch, bis sich das thermodynamische Gleichgewicht eingestellt hat.

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Gasdynamical investigation of Joule's overflow experiment

The time-dependent flow of an exchange process between two big insulated tanks is considered. The problem is treated on the basis of a one-dimensional, inviscid and quasi-steady flow. An analytical solution is obtained for supercritical flow, while for subcritical flow the problem is solved numerically.After the pressure-equilibrium between the two-tanks an isobar heat and mass exchange follows, until the thermodynamic equilibrium is reached.

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Formelzeichen a Schallgechwindigkeit - A engster Querschnitt - c Geschwindigkeit - c _p spezifische Wärme bei konstantem Druck - c _v spezifische Wärme bei konstantem Volumen - e innere Energie - i Enthalpie - m Masse - M Machzahl - p Druck - spezielle Gaskonstante - s Stromlinie, spezifische Entropie - t dimensionsbehaftete Zeit - T Temperatur - V Volumen - Konstante - Abkürzung - Volumenverhältnis - Verhältnis der spezifischen Wärmen - Dichte - dimensionslose Zeit Indizes 0 Zustand zur Zeitt=0 - 1 Zustand im Überdruckbehälter - 2 Zustand im Überströmbehälter - * Zustand im engsten Querschnitt - K kritisch - M Zustand bei Druckausgleich - E Endzustand bei Temperaturausgleich Herrn Prof. Dr. B. Schmidt in Dankbarkeit zum 60. Geburtstag gewidmet     

An analysis on forced convection in a channel filled with a Brinkman-Darcy porous medium: Exact and approximate solutions

An analysis was made to investigate non-Darcian fully developed flow and heat transfer in a porous channel bounded by two parallel walls subjected to uniform heat flux. The Brinkmanextended Darcy model was employed to study the effect of the boundary viscous frictional drag on hydrodynamic and heat transfer characteristics. An exact expression has been derived for the Nusselt number under the uniform wall heat flux condition. Approximate results were also obtained by exploiting a momentum integral relation and an auxiliary relation implicit in the Brinkmanextended Darcy model. Excellent agreement was confirmed between the approximate and exact solutions even in details of velocity and temperature profiles.     

Ein LIFO Branch and Bound Verfahren zur optimalen Altstoffbehälterallokation

Zusammenfassung In diesem Artikel wird auf ein Problem eingegangen, das sich im Rahmen einer abfallwirtschaftlichen Studie ergab, in der die Durchführbarkeit von Altstoffsammlungen im dichtverbauten Siedlungsgebiet untersucht wurde. Als wichtige Teilaufgabe war dabei eine platzminimale Altstoffbehälterkombination für jede Altstoffart und für jedes Haus des untersuchten Sammelgebietes zu ermitteln, wobei unter anderem die Zugänglichkeit des Behälterraumes für die Sammelmannschaft und dessen topographische Gegebenheiten zu beachten waren. Zur Lösung dieser Aufgabe, deren Formalisierung auf ein ganzzahliges LP führte, wurde ein LIFO Branch and Bound Verfahren entwickelt. Dieses wird an Hand der wesentlichen Bestandteile eines jeden Algorithmus vom Branch and Bound Typ: der Branching Strategie, der Bounding Strategie und der Search Strategie dargestellt. Der Algorithmus wurde in PL/I programmiert und hat seine Leistungsfähigkeit in zahlreichen Programmläufen unter Beweis gestellt.

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Summary In this article a problem is treated which rose in the course of a research into the suitability for reconditioning used materials. This study analyzes the feasibility of scrap collection in densily populated, urban areas. One major aspect was to provide for a space saving combination of containers for every kind of scrap and for each house of the test area, bearing in mind the constraints given by the topographical conditions of the container room and its accessibility to the collection personnel. The formulation of this problem led to an all integer program. To solve this program a LIFO branch and bound algorithm was developed. The algorithm is presented by discussing its branching strategy, its bounding strategy and its search strategy, which constitute the essential parts of each procedure of the branch and bound type. The algorithm was programmed in PL/I and proved its efficiency in numerous runs.

     

Polarity effects on ZnO films grown along the nonpolar [1120] direction

The surface electrical properties of ZnO thin films grown along the nonpolar [1120] direction have been investigated by Kelvin probe microscopy on a nanometer scale. Two different charge domains, with a 75 meV work function difference, coexist within the ZnO surface, which is covered by rhombohedral pyramids whose sidewalls are shown to be {1011}-type planes. The presence and relative orientation of the two kinds of charge domains are explained in terms of the atomic arrangement at the {1011} polar surfaces.     

Influence of low intensity noise on assemblies of diffusively coupled chaotic cells

The effect of time-correlated and white Gaussian noises of low intensity on one-dimensional arrays consisting of diffusively coupled chaotic cells is analyzed. An improvement or worsening of the synchronization between cells of the array driven by low-intensity colored noise is observed for a resonant interval of time correlation values. A comparison between colored and white noise and additive and multiplicative contribution has been carried out investigating the nonlinear cooperative effects of noise strength, correlation time, and coupling strength to control spatiotemporal chaos in coupled arrays of chaotic cells. The possibility to distinguish highly correlated areas of a diffusively coupled network of cells by using low-intensity time correlated noise is discussed. (c) 2001 American Institute of Physics.     

Observation of B(s)(0) → D(s)(*)+ D(s)(*)- using e+ e- collisions and a determination of the B(s)-B(s) width difference ΔΓ(s)

We have made the first observation of B(s)(0)→D(s)(*)+ D(s)(*)- decays using 23.6 fb(-1) of data recorded by the Belle experiment running on the Υ(5S) resonance. The branching fractions are measured to be B(B(s)(0)→D(s)+ D(s)-)=(1.03(-0.32-0.25)(+0.39+0.26))%, B(B(s)(0)→D(s)(*±) D(s)(?))=(2.75(-0.71)(+0.83)±0.69)%, and B(B(s)(0)→D(s)*+ D(s)*-)=(3.08(-1.04-0.86)(+1.22+0.85))%; the sum is B[B(s)(0)→D(s)(*)+ D(s)(*)-]=(6.85(-1.30-1.80)(+1.53+1.79))%. Assuming B(s)(0)→D(s)(*)+ D(s)(*)- saturates decays to CP-even final states, the branching fraction determines the ratio ΔΓ(s)/cosφ, where ΔΓ(s) is the difference in widths between the two B(s)-B(s) mass eigenstates, and φ is a CP-violating weak phase. Taking CP violation to be negligibly small, we obtain ΔΓ(s)/Γ(s)=0.147(-0.030)(+0.036)(stat)(-0.041)(+0.042)(syst), where Γ(s) is the mean decay width.