Showing papers by "Karlsruhe Institute of Technology published in 1975"

Mechanism of Ozonolysis

Abstract: The formation of ozonides (1,2,4-trioxolanes) from alkenes and ozone can be described as a succession of three [2+3] cycloadditions or cycloreversions involving primary ozonides (1,2,3-trioxolanes) and aldehyde or ketone oxides as decisive intermediates, all of which have finite lifetimes. There is no warranted experimental basis for assuming an alternative mechanism.

New network permeability model of porous media

Abstract: In this study a new mathematical model for predicting permeabilities of porous media has been developed. The model consists of a set of cubic networks of arbitrary orientations with respect to the macroscopic flow direction. The networks consist of capillary tubes which are made up of segments of different diameters. It is shown that a cubic network of capillaries has isotropic permeability properties. The permeability model requires two pore size distributions and the porosity of the sample for the calculations. The calculated permeabilities agreed with experimental results for a wide range of permeabilities of highly compacted materials to within ± 23%, without using adjustable tortuosity factors.

Notiz über eine einfache Methode zur Darstellung von Tris(trimethylsilyl)phosphin

Abstract: Tris(trimethylsilyl)phosphin wird wegen seiner reaktiven Si P-Bindung immer mehr zum wertvollen Ausgangsprodukt für Organophosphorverbindungen. So ist durch Umsetzung dieser Verbindung mit n-Butyllithium das reaktive [(CH3hSi]2PLi· Äther I) darstellbar. Die Reaktion mit Carbonsäure-halogeniden fUhrt zu Acylphosphinen und ihren Derivaten 2), unter denen die Diacylphosphine wegen ihrer Keto-Enol-Tautomerie (zwischen PH und O-H-O) besonders hervorzuheben sind 3). Tris(trimethylsilyl)phosphin wurde lange Zeit durch Umsetzung von NaPH2 4) (aus PH3 und Na in 11. NH 3) oder Li3P 5) (aus PH3 und n-Butyllithium) mit Trimethylchlorsilan in Diglyme dargestellt. Bei allen Ansätzen muß mit größeren Mengen gasförmigen Phosphins gearbeitet werden. Zur kürzlich publizierten Methode von Schumann und Rösch 6 ) (aus Mg, (CH3hSiCI und PCI3 in HMPT A bzw. THF) ist zu bemerken, daß die von den Autoren angegebenen Ausbeuten nicht immer erreicht werden, da offenbar die Reaktionsbedingungen nicht hinreichend bekannt sind. Vor einiger Zeit berichteten Peterson und Logan 7) über die Reaktion von gelöstem weißem Phosphor in Benzol mit Na/K-Legierung zum \"Na3P/K3P\" und die anschließende Umsetzung mit Methylhalogeniden. Wir fanden, daß auf diese Weise dargestelltes \"Na3P/K3P\" (nach Abpipettieren des überstehenden Benzols) in Monoglyme oder Diglyme in befriedigender Ausbeute mit TrimethylchlorsiIan zum Tris(trimethylsilyl)phosphin reagiert. Allerdings kann auf diese Weise dargestelltes Tris(trimethylsilyl)phosphin bis zu 10% 3,6-Bis(trimethylsilyl)-I,4-cyclohexadien enthalten, das durch Reduktion des Benzols und anschließende Silylierung entsteht 8) und auch durch Destillation über eine Ringspaltkolonne nicht abzutrennen ist. Führt man auch die Reduktion des weißen Phosphors in Monoglyme durch, so unterbleibt bei gleicher Ausbeute die Bildung des Nebenproduktes.

Direct determination of pair natural orbitals

Abstract: A method is proposed to solve the two-electron Schrodinger equation by a rapidly converging iterative procedure. The wavefunction is obtained in terms of its NO's. The special features of the present method are: We further propose simplified NO-equations the solution of which requires a small fraction of computertime only. As examples of the efficiency of these methods we report applications to the 11 Sstate of He, the 11∑ g + , 13∑ u + states of H2, and IEPA,PNO-CI, and CEPA type computations on CH4.

Theoretical study of the H 5 + system

Abstract: Ab initio calculations have been carried out for the ground state of H 5 + in order to predict its equilibrium geometry, binding energy, enthalpy of formation, and the features of the H2 · H 3 + interaction at large and intermediate intermolecular distances. The extended basis set of Gaussian functions was carefully optimized to describe the various kinds of intermolecular interactions. Electron correlation was accounted for by means of CI calculations. Different from previous studies we find a D 2d equilibrium geometry with D e = 7.4 kcal/mol and ΔH 300 0 ≈−8.7 kcal/mol. The potential surface turns out to be extremely shallow in the vicinity of the D 2d structure which results in a great mobility of the central nucleus at room temperature.

Convection in boxes: an experimental investigation in vertical cylinders and annuli

Abstract: Convective flow of the cellular type has been investigated in vertical cylinders of axisymmetric and annular shape. The critical Rayleigh numbers were determined as functions of the box diameter and the gap width respectively. A distinct influence of side walls with different thermal conductivities was observed.

PNO–CI (pair‐natural‐orbital configuration interaction) and CEPA–PNO (coupled electron pair approximation with pair natural orbitals) calculations of molecular systems. IV. The molecules N2, F2, C2H2, C2H4, and C2H6

Abstract: SCF, IEPA–PNO, CEPA–PNO, and PNO–CI calculations have been performed for the molecules N2 and F2 at their experimental equilibrium distances with two basis sets, a ’’small’’ basis that contains one d set per atom and a ’’standard’’ basis with two d sets and one f set Potential curves of these molecules are calculated with the small basis sets The molecules C2H2 and C2H4 are calculated with the small basis (which contains additionally one p set on H) and with a ’’hydrocarbon’’ basis that is smaller in the s,p part, but includes the same polarization functions For C2H6 in both its staggered and eclipsed forms only the hydrocarbon basis is used The computed correlation energies are analyzed in terms of quantities defined in Part I, in particular, in terms of the IEPA pair correlation energies eμIEPA and the error ΔEIEPA of the IEPA energy A comparison is made between the results in the canonical and the localized representations and a partially localized description in which the σ–π separation is preser

Ein neuer Typ Silylphosphane; (me3Si)3P7, (me3Si)4P14, (me=CH3)

Abstract: einer Glasziehvorrichtung bis zu einem Spitzendurchmesser von < 0,2 pm reproduzierbar hergestellt wird. Die mechanische Festigkeit der Glasspitzen wird durch eine Kombination yon thermischer Behandlung, FluBsgureeinwirkung, Hfirtung durch Ionenaustausch sowie durch Elektronenbeschul3 erh6ht [4]. Auf diese Glasbzw. Quarz-Spitzen wurden mit der Hochfrequenzzerst/iubungsanlage Sputron II (Firma Balzers, Liechtenstein) Edelmetallschichten aufgebracht [5]. Die Haftfestigkeit der Edelmetallschichten wurde durch vorhergehende Glimmentladung und anschliel3endes Aufbringen einer dfinnen Tantal-Zwischenschicht erreicht. Zur elektrischen Isolierung des Elektrodenschaftes wurden, in Weiterentwicklung der f/Jr die Pn-Mikroelektrode entwikkelten Technik [6], Mehrfachschichten hochisolierender Dielektrika abwechselnd aus verschiedenen Oxiden und Nitriden mit der HF-Zerst/iubung aufgebracht. So lassen sich Elektroden mit koaxialer Anordnung der Schichten herstellen. Form und Gr6f3e der akdven Mel3oberfl/iche k6nnen durch Maskieren mit Photolack oder durch Schleifen bestimmt werden. Es entstehen entweder konusf6rmige Spitzen, z.B. mit einem Durchmesser kleiner als 1 ~tm, oder ringf6rmige ElektrodenoberfI~ichen (schriiger Anschliff im Winkel yon 3 0 4 0 °, Fig. 1). Zur Messung des absoluten Sauerstoffdruckes werden zwei gasdurchl/issige Membranen, z.B. aus Polystyrol und Kollodium, aufgebracht. Ftir Wasserstoffdruckmessungen werden die aktiven Edelmetallschichten galvanisch palladiniert [7].

Intraplate tectonics in stable Europe as related to plate tectonics in the Alpine system

Abstract: Western Europe is traversed by the Rhinegraben rift system. The stages of graben formation evolved coincidentally with the culminations of compressional folding in the Alps. Rhinegraben rifting has been controlled by mantle diapirism, but the Alpine orogeny by subduction of lithosphere. Presumably, Alpine subduction forced compensating mantle uplift in the foreland. The Middle Eocene to Oligocene crustal spreading of the Rhinegraben implies a state of stress with a maximum horizontal component parallel to the graben axis (about 20‡). In the same area, the Recent average direction of maximum compressive stress is of about 320‡ (NW), as calculated by in-situ stress measurements, fault-plane solutions of earthquakes and Recent crustal movements. The rotation of the stress components relative to the crust of stable Europe evolved subsequent to counterclockwise rotations of microplates in the Mediterranean. A model is proposed which ascribes these rotations to alterating shear motions of the Afro-Arabian macroplates relative to stable Europe exerting a ball-bearing effect to the intervenient microplates. The postulated motions are in accord with the patterns of inhomogeneous ocean floor spreading east and west of the African plate. The stages of Alpine plate collision had induced a significant readjustment of intraplate stress conditions, and deformation in the cratonic foreland of stable Europe.

Petrologic significance of rare earths distribution in granites

Abstract: Granitic rocks of various ages and composition are found in the Schwarzwald region of West Germany. These granites range in age from Upper Devonian to Upper Carboniferous (370-280 m.y.) and in composition from granodiorites to alkali feldspar granites. 14 representative samples of twelve different types were analysed for their La, Ce, Nd, Sm, Eu, Tb, Dy, Yb, Lu by instrumental neutron activation. The studies reveal that there are characteristic differences between the different types of granitic rocks both as regards to their total REE content as well as the distribution pattern of these elements. These differences can not be directly related to the variations in the major element chemistry or the mineralogy of the granites. On the other hand, a relationship is found between the age of the granitic rocks and the total REE as well as their distribution pattern. In general the ΣREE varies from 22 to 215 ppm in different types. The ΣLa-Lu increases gradually in the direction Upper Devonian→Lower Carboniferous, however, in the granitic rocks of the Upper Carboniferous this trend is reversed and there is again a marked depletion in the content of REE. The chondrite normalised patterns of all the older types give a smooth concave curve with decrease of concentration from La to Lu. All the Upper Carboniferous granites on the other hand are characterised by a progressive pronounced negative Eu anomaly. The gradual increase of the ΣREE in the older granites is related to their evolution by progressive anatexis, whereas, the decrease in the total REE content in case of the younger Upper Carboniferous granites is due to processes of magmatic differentiation. The depletion of Eu in these K-feldspar rich types of granite is probably related to the breakdown of biotite in the anatectic starting material.

Flow-invariant sets and differential inequalities in normed spaces †

Abstract: A set M in a Banach space B is said to be flow-invariant with respect to the ordinary differential equation x(t)=f(t,x) (t real, xeB,f(t,x)eB), if for each solution x(i) of this equation x(0) e M implies x(t) e M for t >0. In this paper, several theorems on flow-invariance are given. These theorems on differential inequalities in ordered Banach spaces. In particular, they apply to the important case when the interior of the positive cone of the Banach space is empty. Finally it is shown that the basic assumption for the validity of a theorem on differential inequalities, namely the quasimonotonicity property as given by Volkmann [11], is equivalent to the tangent condition of Brezis [3]with respect to the positive cone.

Rotationssymmetrisches ebenes Fließen eines granularen Modellmaterials

Abstract: Es werden grose ebene, rotationssymmetrische, plastische Formanderungen eines Kontinuums studiert, das dem Coulombschen Flieskriterium und der assoziierten Fliesregel genugt. Damit last sich die Couette-Stromung eines aus parallelen Nadeln zusammengesetzten “granularen” Materials (Schneebeli) kinematisch qualitativ zufriedenstellend vorhersagen, auch wenn man die Eigenrotation der “Korner” mit einbezieht und dementsprechend ein plastisches Cosserat-Kontinuum zugrunde legt. Hingegen sind die auftretenden Momentenspannungen ebenso wie die asymmetrischen Schubspannungsanteile grosenmasig zu vernachlassigen — ein weiterer Hinweis darauf, das verallgemeinerte Kontinua mehr von der Kinematik als von der Statik her Bedeutung besitzen.

Die PVT-Daten des Acetonitrils bis 450 °C und 2500 bar

Abstract: Die PVT-Daten des Acetonitrils (Methylcyanid) wurden im Volumenbereich von 1,140 cm3 g−1 bis 8,200 cm3 g−1 bis zu Drucken von 2400 bar und Temperaturen von 400 °C gemessen. Die Mesdaten sind fur 12 spezifische Volumen durch Temperatur- und Druckangaben dargestellt. Fur jede Isochore sind die Drucke als Funktion der Temperatur durch Polynome zweiten Grades zu beschreiben. Ausgeglichene Werte fur den Realfaktor z = PV/RT werden angegeben. Fur jede Temperatur konnen die Daten von 400 bar an durch die Tait-Gleichung dargestellt werden. Zweite Virialkoeffizienten werden angegeben. The PVT-data of acetonitrile (methyl cyanide) have been measured for specific volumes between 1.140 cm3 g−1 and 8.200 cm3 g−1 up to pressures of 2400 bar and temperatures of 400 °C. For 12 different specific volumes pairs of temperature and pressure data are given. Isochoric pressures as functions of temperature can be represented by second order polynomials. Smoothed values of the compression factor z = PV/RT are reported. The PVT-data above 400 bar for each temperature can be described by the Tail equation. Second virial coefficients are given.