Showing papers by "Karlsruhe Institute of Technology published in 1973"
TL;DR: In this paper, a detailed description of fracture phenomena, observed in comminution experiments, is followed by the derivation of a similarity law based on reasonable physical assumptions, which is extended to cover different materials and different initial flaw distributions.
155 citations
TL;DR: In this paper, a simple method of broad applicability for the preparation of ketene thioacetals was proposed for the Preparation of Ketene Thioacetal (KTE) compounds.
Abstract: Umsetzungen von 2-Lithio-2-(trimethylsilyl)-1,3-dithian und -1,3,5-trithian sowie von Bis-(methylthio- und phenylthio)(trimethylsilyl)me-thyllithium mit Aldehyden, Ketonen und Formamiden von sek. Aminen fuhren direkt und in hohen Ausbeuten zu Keten-thioacetalen der allgemeinen Formel 1.
Reaction of Metalated Trimethylsilylformaldehyde Thioacetals with Carbonyl Compounds A Simple Method of Broad Applicability for the Preparation of Ketene Thioacetals
Reactions of 2-lithio-2-(trimethylsilyl)-1,3-dithiane and -1,3,5-trithiane and of bis(methylthio- and phenylthio)(trimethylsilyl)methyllithium with aldehydes, ketones, and formamides of sec. amines furnish in one step and in high yields ketene thioacetals of the general formula 1.
118 citations
TL;DR: In this paper, the anodic dissolution of pure iron was studied in oxygen-free solutions at high concentrations of chloride and hydrogen ions at 25°C under potentiostatic steady-state conditions.
106 citations
TL;DR: From the 13C-nmr spectra of a large number of dimeric and monomeric lignin model compounds the chemical shifts of the carbon atoms of the C9-units in lignIn with different substitution patterns were determined.
105 citations
01 May 1973
TL;DR: In this paper, inkrementelle Stoffgleichungen fur trockenen Sand unter Berucksichtigung der Bezugsinvarianz (J 1), der KoordinatenInvarianz(J 2), der Einheiteninvarianzer (J 3) entwickelt.
Abstract: Es werden inkrementelle Stoffgleichungen fur trockenen Sand unter Berucksichtigung der Bezugsinvarianz (J 1), der Koordinateninvarianz (J 2) und der Einheiteninvarianz (J 3) entwickelt. Dabei sind die acht folgenden Stoffannahmen zugrundegelegt worden: Es liegt ein sogenannter einfacher Stoff vor (A 1), das Stoffunktional ist geschwindigkeitsunabhangig (A 2), das Stoffunktional ist stetig (A 3), die Fliesgrenze hangt homogen von den Spannungen ab (A 4), im elastischen Bereich gilt das Hookesche Gesetz (A 5), die Fliesregel hangt homogen von den Spannungen ab (A 6), durch Deformationszyklen kann einer Probe keine Energie entzogen werden (A 7), die Cauchy-Spannungen sind Zustandsparameter (A 8).
99 citations
01 Jan 1973
TL;DR: In this paper, the potential hypersurface of the system LiH2* is calculated in the Hartree-Fock approximation and with the IEPA PNO method (including electron correlation).
Abstract: The potential hypersurface of the system LiH2* is calculated in the Hartree—Fock approximation and with the IEPA PNO method (including electron correlation). The basis set consists of gaussian lobes. The region of HH distances considered is 0.9 to 3 ao (occasionally to 5 ao) whereas the distance of the Li nucleus to the midpoint of the H2 subunit is varied between 1 and 15 αo. The angular dependence of the hypersurface is investigated as well. The maximum overall error (except for a parallel shift of the whole hypersurface) is estimated to be less than 0.002 au and even smaller in more limited regions of space. The role of the correlation energy is discussed and the asymptotic behaviour of the Li+/H2 interaction is compared with results from perturbation theory. The results are given both as tables of numbers in the form of an analytic fit. The change of energy, equiblirium distance and force constant of the H2 as a function of the approach of the Li+ is also tabulated.
99 citations
TL;DR: In this paper, a computer simulation of the cubic SiP2O7 superstructure was applied, where the predicted distances were treated as observations in a distance least-squares refinement, in which the positional coordinates of the atoms are varied until the calculated distances conform to the predicted values.
86 citations
TL;DR: In this article, an independent-electron -pair approximation (including intra-and inter-pair correlation effects) was performed for the ground state of acetylene, ethylene and their protonated cations.
85 citations
01 Jan 1973
TL;DR: The self-diffusion coefficient D describes the nature of the erratic translational motion of water molecules as discussed by the authors, and it is shown that the time necessary for such a displacement is 6 × 10−12 sec.
Abstract: As in all liquids, so, too, in water the molecules undergo thermal motion. The self-diffusion coefficient D describes the nature of the erratic translational motion:
$$\left\langle {{r^2}} \right\rangle {\mkern 1mu} = {\mkern 1mu} 6Dt$$
(1)
where 〈r2〉 is the mean square displacement of the water molecule after a time t. For water at 25°C, D = 2.31 × 10−5 cm2 sec−1,(580) so if we consider a mean square displacement of ∼a2, where a is the diameter of the water molecule, the time necessary for such a displacement is 6 × 10−12 sec. Equation (1) only holds if the time is long enough so that we actually have random motion, that is, the instantaneous velocity of the water molecule must have suffered a large number of changes in magnitude and direction. For times t ≳ 6 × 10−12 sec this condition is fulfilled.
78 citations
TL;DR: In this paper, a model in which a layer of a second phase present between the barium titanate grains is assumed to possess acceptor character and a dependence of its permittivity on the temperature and the electric field strength is presented.
Abstract: Specimens were prepared of doped ceramic barium titanate in the form of bars which, between their metallized ends, contained only one high-resistance grain boundary running across the entire cross-section. The measurements covered the differential capacitance of these individual grain boundaries, under bias, and their d.c. current-voltage characteristics. The results can be described quite well by a model in which a layer of a second phase present between the barium titanate grains is assumed to possess, firstly, acceptor character and, secondly, a dependence of its permittivity on the temperature and the electric field strength.
69 citations
TL;DR: In this paper, temperature dependent self-diffusion coefficient measurements of glycerol by the pulsed N.M.R. technique are presented, and the authors propose a method to calculate the self-defusion coefficient of a single glycerin sample.
Abstract: (1973). Temperature dependent self-diffusion coefficient measurements of glycerol by the pulsed N.M.R. technique. Molecular Physics: Vol. 25, No. 3, pp. 735-738.
TL;DR: In this article, a near Hartree-Fock ab initio SCF and correlation energy calculations based on the IEPA-PNO approximation are reported for F−, HF, OH−, H2O, H 2F+ and H3O+ using GTO-basis sets.
Abstract: Near Hartree-Fock ab initio SCF and correlation energy calculations based on the IEPA-PNO approximation are reported for F−, HF, OH−, H2O, H2F+ and H3O+ using GTO-basis sets. The SCF values for the equilibrium geometries and harmonic force constants are corrected in the desired direction by inclusion of the correlation energy. The SCF errors are, however, always overcompensated. The agreement with experiment is improved for the symmetric stretching force constants of HF and H2O, but bond lengths are nearly the same amount too long in the IEPA approximation as they are too short in the SCF calculations. In addition thereto protonation energies are computed and compared with experimental measurements.
TL;DR: In this paper, die Zugfestigkeit von feuchten Haufwerken aus kornigen Stoffen im gesamten Bereich des FlussigkeITssattigungsgrades dargestellt und die Anwendbarkeit der Modelle durch Experimente belegt.
Abstract: Aufgrund von Modellen wird die Zugfestigkeit von feuchten Haufwerken aus kornigen Stoffen im gesamten Bereich des Flussigkeitssattigungsgrades dargestellt und die Anwendbarkeit der Modelle durch Experimente belegt. Neben einer Erklarung der unterschiedlich grosen Festigkeitswerte bei einer Be- und Entfeuchtung des Haufwerks wird gezeigt, das sich die groste Zugfestigkeit beim sog. Eintrittskapillardruck einstellt. Der Eintrittskapillardruck, der als charakteristischer Kapillardruck eines Haufwerks angesehen werden kann, last sich mittels einer Dimensionsanalyse in Abhangigkeit von seinen Einflusgrosen darstellen. Der Einflus der Porositat wird mit Hilfe einer Regressionsanalyse experimentell ermittelt und mit bekannten Modellgleichungen verglichen. Der kapillare Entfeuchtungsvorgang, der zum Verstandnis der Festigkeits- und Kapillardruckuntersuchungen notwendig ist, wird dargelegt. Es zeigt sich, das die Flussigkeit wahrend der Entfeuchtung nahezu gleichmasig aus allen Schichten des Haufwerks entfernt wird.
TL;DR: Several very unstable pigments have been isolated from the red skin of the fly agaric by chromatography on different types of sephadex: the two orange components musca-aurinI and -II, the yellow muscaflavin, the red brown muscarubrin, and the violet muscapurpurin this paper.
Abstract: Aus der roten Huthaut des Fliegenpilzes werden durch Chromatographie an verschiedenen Sephadex-Typen mehrere sehr empfindliche Farbstoffe isoliert; zwei orangefarbene: Musca-aurin-I und -II, ein gelber: Muscaflavin, ein rotbrauner: Muscarubrin und das violette Muscapurpurin. Die Elektronenspektren zeigen an, das diese Farbstoffe die gleichen Chromophore besitzen wie die Betalaine2).
Colouring Matters from Fly Agaric II. Isolation of Pigments from Amanita muscaria and their Chromophoric Systems
Several very unstable pigments have been isolated from the red skin of the fly agaric by chromatography on different types of sephadex: the two orange components musca-aurin-I and -II, the yellow muscaflavin, the red brown muscarubrin, and the violet muscapurpurin. It is concluded from the electronic spectra that these pigments belong to the same chromo-phoric systems as the betalains2) do.
TL;DR: In this article, the thermal conductivity of β- and α-FeSi2 has been investigated at low temperatures (2 K < T < 90 K) and between room temperature and the transition temperature (1200 K).
Abstract: The thermal conductivity of β- and α-FeSi2 has been investigated at low temperatures (2 K < T < 90 K) and between room temperature and the transition temperature (1200 K). For undoped β-FeSi2 results are obtained, which are typical for pure crystals. Doping with Co and Al reduces the lattice thermal conductivity. A band gap (T = 0 K) of 0.9 eV can be calculated from the ambipolar range. The lattice thermal conductivity of α-FeSi2 is determined by a high concentration of Fe-vacancies.
Die Warmeleitfahigkeit von β- und α-FeSi2 wurde bei tiefen Temperaturen (2 < T < < 90 K) und oberhalb Zimmertemperatur bis zur Phasenumwandlung bei 1200 K untersucht. Fur undotiertes β-FeSi2 wird der fur reine Kristalle typische Verlauf gefunden. Co-und Al-Dotierung setzt die Gitterwarmeleitfahigkeit herab. Aus dem ambipolaren Anteil der Warmeleitfahigkeit last sich der Bandabstand (T = 0 K) zu 0,9 eV berechnen. Die Gitterwarmeleitfahigkeit von α-FeSi2 wird durch eine hohe Fe-Leerstellenkonzentration beeinflust.
TL;DR: In this paper, a conceptual model was formulated to describe crack extension at a given stress as well as the manner in which ultimate failure of concrete takes place, and compressive tests were performed on concrete prisms to investigate the nature of crack growth at the macroscopic level.
TL;DR: The part played by true point defects (isolated vacancies and interstitial atoms) in defect solid solutions and in mixed valence non-stoichiometric phases is not clear.
Abstract: THE part played by true point defects—isolated vacancies and interstitial atoms—in defect solid solutions and in mixed valence non-stoichiometric phases is not clear. In many ionic or quasi-ionic structures there is some structural reorganization and at least incipient ordering of defect clusters. In some oxides—notably those of titanium, vanadium, molybdenum and tungsten, in which the covalent component of the bonding is probably strong—slight reduction, with a change in the ratio of oxygen to metal, is accommodated largely by crystallographic shear. A complete sheet of anion sites is eliminated from the structure, forming an extended defect and greatly diminishing the extent to which a deficit of oxygen must be compensated by anion vacancies or interstitial cations. Thus Hyde and Bursill1 found that, in slightly reduced rutile, TiO1.9986, the point defect concentration could hardly exceed 10−4. In more extensively reduced rutile, changes in stoichiometry involve only changes in the spacing between crystallographic shear planes, without detectable concentrations of localized defects.
TL;DR: In this paper, the authors defined and classified interface inhibition and electrolyte-layer inhibition in electrodeposition of metals and classified them into primary and secondary inhibition, depending on the origin of the inhibitors.
TL;DR: In this paper, the kinetics of anodic iron dissolution in sulphate ions containing solutions, which are free of oxygen, are investigated in a over potential range between active and passive states of the metal.
TL;DR: In this article, etwa 5,000 Experimente von 14 Autoren einschlieslich eigener Messungen ausgewertet wurden etwa.
Abstract: Wandwarmeubergangskoeffizienten lassen sich aus Messungen von Gesamtwarmeubergangskoeffizienten berechnen, wenn man die effektive Warmeleitfahigkeit kennt und gewisse vereinfachende Annahmen, insbesondere uber die Stromungsform, macht. Es wurden etwa 5 000 Experimente von 14 Autoren einschlieslich eigener Messungen ausgewertet. Dabei zeigte sich, das man nur bei Berucksichtigung der Tatsache, das die Stromungsgeschwindigkeit radial veranderlich ist, fur den Wandwarmeubergangskoeffizienten in allen Fallen physikalisch sinnvolle Ergebnisse erhalt. Die Wandwarmeubergangskoeffizienten hangen bei kleinen Peclet-Zahlen von der Rohrlange ab. Es wurden Gleichungen zur Vorausberechnung von Wandwarmeubergangskoeffizienten und Gesamtwarmeubergangskoeffizienten angegeben. Der Stoffubergang von der Wand an das Fluid wird als Grenzfall mitbehandelt.
TL;DR: In this paper, SCF and IEPA PNO correlation energy calculations with large gaussian basis sets are reported for H 3 O +, and the equilibrium geometry is pyramidal both from SCF, and from IEPA, and the inversion barrier is increased considerably by the inclusion of electron correlation.
TL;DR: In this paper, a reeller normierter Raum with Nullelement 0, E* the Raum der stetigen, linearen Funktionale auf E and R der Raum of reelle Zahlen.
Abstract: 1. Einleittmg. Es seien E ein reeller normierter Raum mit Nullelement 0, E* der Raum der stetigen, linearen Funktionale auf E und R der Raum der reellen Zahlen. C sei stets eine nichtleere, abgeschlossene Teilmenge von E; auBerhalb dieser Nr. wird C als konvex vorausgesetzt. Sind x e E und M c__ E, so bezeichnet dist (M, x) den Abstand zwischen x und M, dist(M,x)= inf Jlx-yll; ein Punkt psM heiBt Lotpunkt
TL;DR: In this article, the structure of Dipivaloylmethane-Mercuric-Acetate has been determined from the spectra of the titel compound and the ligands are arranged nearly linearly (1 75°) around the mercury atom.
Abstract: Die aus den Spektren abgeleitete Konstitution der Titelverbindung wird durch Rontgenanalyse bewiesen. Die Liganden sind annahernd linear (1 75°) am Quecksilber gebunden, der Dipivaloylmethanrest als Diketon uber das mittlere C-Atom (2.11 A), der Acetatrest unsymmetrisch uber ein O-Atom (2.10 A). Die Einzelheiten der Struktur und Packung im Kristall werden mit denen beim Bis(dipivaloylmethan)quecksilber (C-Hg 2.13, 2.18 A) und Quecksilberacetat (O – Hg 2.09, 2.06 A) verglichen.
Organic Metal Complexes, X. The Structure of Dipivaloylmethane-Mercuric-Acetate
X-ray analysis confirms the structure of the titel compound, which has been derived from the spectra. The ligands are arranged nearly linearly (1 75°) around the mercury atom. Dipivaloylmethane is bound in the diketone form with the central carbon atom (2.11 A), the acetate group unsymmetrically at one of the oxygens atoms (2.10 A). The details of the structure and packing in the crystals are compared with those of bis(dipivaloylmethane)mercury (C-Hg 2.13, 2.18 A) and mercuric acetate (O -Hg 2.09, 2.06 A).
TL;DR: In this paper, the electrical behavior of amorphous layers is more similar to that of the metallic high-temperature phase (α-FeSi2) than to the semiconducting one (β- FeSi2), and the observed properties of the ammorphous and crystalline layers are interpreted in terms of a crude band model.
Abstract: Thin layers of FeSi2 deposited at room temperature have an amorphous structure. These layers show a phase transformation into crystalline β-FeSi2) on heating to high temperature. The electrical behaviour of amorphous layers is more similar to that of the metallic high-temperature phase (α-FeSi2) than to that of the semiconducting one (β-FeSi2). Intrinsic absorption in amorphous and polycrystalline layers has also been investigated. The observed properties of the amorphous and crystalline layers are interpreted in terms of a crude band model.
TL;DR: In this paper, the optical conductivity of K2Pt (CN)4Br0,3 · 3H2O single crystals for phonon energies near the plasma edge is investigated.
TL;DR: The Umsetzung der Hydroperoxide verlauft enzymatisch (Isomerase) and fuhrt nach Hydrolyse zur Bildung von 9,12,13-Trihydroxy-trans-10-octadecensaure und 9,10,13 -Trihydroxyltrans-11-octacehensaure as discussed by the authors.
Abstract: Durch Haferenzymextrakte erfolgt bei Linolsaurchydroperoxiden (LHPO) sowohl ein Abbau der Hydroperoxidgruppe als auch der Dienstruktur. Die Umsetzung der Hydroperoxide verlauft enzymatisch (Isomerase) und fuhrt nach Hydrolyse zur Bildung von 9,12,13-Trihydroxy-trans-10-octadecensaure und 9,10,13-Trihydroxy-trans-11-octadecensaure.
TL;DR: In this article, a vergleichsweise geringer Anteil an 13-LHPO is established, der sich anschliesende enzymatische (Lipoperoxidase, Isomerase) und nicht-enzymatischen Abbau der beiden Hydroperoxide fuhrt zu einem hohen AntEil der aus der 9-LhpO gebildeten 9-Hydroxy-cis,trans-octadecadiensaure, 9-hydroxy
Abstract: Bei Haferenzym-Linolsaure-Incubationen wird durch Lipoxygenasekatalyse stark uberwiegend die 9-Hydroperoxyoctadecadiensaure (9-LHPO) gebildet. Daneben entsteht ein vergleichsweise geringer Anteil an 13-LHPO. Der sich anschliesende enzymatische (Lipoperoxidase, Isomerase) und nicht-enzymatische Abbau der beiden Hydroperoxide fuhrt zu einem hohen Anteil der aus der 9-LHPO gebildeten 9-Hydroxy-cis,trans-octadecadiensaure, 9-Hydroxy-cis-12,13-epoxy-trans-10-octadecensdure und 9, 12, 13-Trihydroxy-trans-10-octadecensaure.
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TL;DR: Several new types of grammars are introduced; some of them are proved to possess the same generative power as ordinary matrix Grammars; for some other types inclusion properties are obtained.
Abstract: The matrix grammar is a well-known concept of a grammar with restricted use of productions. By weakening the matrix restrictions imposed on context-free grammars several new types of grammars are introduced; some of them are proved to possess the same generative power as ordinary matrix grammars; for some other types inclusion properties are obtained.
TL;DR: In this paper, the photoelectron spectra of methyl and silyl sulfides were assigned on the basis of modified CNDO-SCF-MO calculations and the orbital sequence (2b1, 4a1, 3b2) was found independent of conformation.