Showing papers by "École Polytechnique Fédérale de Lausanne published in 1972"

Thermische Zerfallsreaktionen von Nitroverbindungen I: Dissoziation von Nitromethan

Abstract: The thermal decomposition of CH3NO2 highly diluted in Ar has been studied in shock waves at 900 < T < 1500 K and 1.5 · 10−5 < [Ar] < 3.5 · 10−4 mol/cm3. Concentration profiles of CH3NO2 and NO2 were recorded. The unimolecular reaction was found to be in its fall-off range. Limiting low pressure rate constants of k0 = [Ar] · 1017.1 exp(−42(kcal/mol)/RT) cm3/ mol sec in the range 900 < T < 1400 K and limiting high pressure rate constants of k∞ = 1016.25 exp (−(58.5 ± 0.5 kcal/mol)/RT) sec−1 have been derived. A rate constant of 1.3 · 1013 cm3/mol sec was found for the first subsequent reaction CH3+NO2 → CH3O+NO.

Ultimate Strength and Design of Reinforced Concrete Beams in Torsion and Bending

Abstract: Since about ten years experimental and theoretical research into the behavior of reinforced and prestressed concrete beams subjected to torsion and combined torsion-bending-shear has been intensified world wide (see e. g. [9]). For the past seven years such a program has been under way at the Institute of Structural Engineering, Swiss Federal Institute of Technology, Zurich. The aim of the project is to develop a failure model for reinforced and prestressed concrete beams applicable to general cross sectional shapes including on one side small solid sections used in buildings, on the other side large sections such as box sections occurring in prestressed concrete bridges. Results of the experimental and theoretical studies have been reported in references [1] to [5].

Temperaturabhängigkeit der Ultraviolett‐Spektren von H2O2 und von HO2‐Radikalen

Abstract: The absorption spectra of H2O2 and of HO2 radicals have been investigated in shock waves at 1950 ⩽ λ ⩽ 2900 A and temperatures of 650 and 1100 K. By comparison with room temperature experiments, information on the nature of electronic transitions involved may be obtained.

Markov processes and their functional in duality

Abstract: Let X and X be a pair of Markov processes in duality. Formally, this means that their transition functions are adjoint operators on L ~ of some measure space. The interpretation in terms of their paths is that X is the process X somehow run backward in time. The formal duality alone is quite powerful--after establishing some elementary results, one can prove quite amazing things just by manipulating formulae--but we want to look at the processes more from the point of view of their sample paths. In fact we backslide a bit rather quickly: the main result of w 2 is a formula which relates in a simple way quite complicated properties of the two processes, and most of the calculations in the following sections are based on it. It does make more precise in what sense X is "X run backward", however, and suggests a way to relate the functionals of one to the functionals of the other. If, for instance, A is an additive functional of one process, one can construct explicitly an additive functional A of the other which is dual to A in a quite natural sense. Because the construction is explicit, it is straightforward--given the form of the construction, "straightbackward" might be a better word--to deduce the properties of A from those of A. We consider only additive and multiplicative functionals in detail, but the method extends to other cases. The first four sections concern right continuous processes in duality and hence both A and its dual .4 must be right continuous. One could just as well consider a situation where X and A were right continuous but the dual process 2 and dual functional A were left continuous. In fact, in view of some of the complications introduced in making A right continuous, this might be not only easier, but more natural in some sense. In this spirit, the last section investigates duality without imposing continuity hypotheses. We see there that if the sample paths of one process have right limits, those of its dual must necessarily have left limits, and conversely. Let E be a locally compact separable metric space and A a point isolated from E. Let g be the topological Borel field of E u A, and b g the set of bounded g-measurable functions on E w A which vanish at A. ~2 is the space of all functions from R + to E u A which are right continuous, have left limits, and admit a lifetime ~; that is, co (t) + A if t ~ (co). As usual, we designate the coordinate variable by X~(co)=co(t), (we will often use Xt instead of X t for clarity) and let (4 ~ be the natural Borel fields of the process (Xt), with ~o = V 4 ~ Now suppose that we have two Markov processes X and X with semigroups (P~) and (4) respectively, defined canonically on ~2. This means that for each x, the semigroup (Pt) generates a measure px on (f2, ~o), and that the canonical

Analysis of Mechanical Oscillations by Speckling

Abstract: The application of the speckle phenomenon to the analysis of in-plane translations and oscillations is first reviewed briefly. Then a practical method of investigating out-of-plane rotations (tilts) even in the presence of in-plane movements is studied. This goal can be achieved by recording the speckle patterns in the Fourier transform plane before and after the tilt or as a time-average exposure for an oscillating object. Young’s fringes related to the tilts are observed in the Fraunhofer diffraction pattern when the developed photographic plate is illuminated with coherent light. This leads to a very simple engineering tool for the analysis of movements. Theoretical and experimental results will be shown.

An approach to the modeling of lakes

Abstract: Models for predicting water quality reflect the physical, chemical and biological characteristics of the particular body of water under consideration. Morphology and nutrient loading, for example, have received considerable attention in the modeling of lakes. Water quality models also depend upon the objectives of the modeling study. Just as a single map cannot represent the complete geography of a region, so a single model cannot answer all questions about a natural aquatic system. Finally, water quality models depend upon the background and experience of the investigators. Given the same objectives, an aquatic biologist and an environmental engineer will most probably construct different models for the same aquatic system. In this paper an approach to the development of predictive models for water quality in lakes is presented. This approach is intended to be somewhat general. Nevertheless, attention is directed primarily towards lake depth and nutrient loading in order to illustrate the approach in physical terms and also to provide some opportunity for comparison with existing work. The approach is biased by the background and experience of the writer; it includes physical and chemical phenomena to a greater extent than biological interactions.

Structure relaxation during internal rotation of the nitro group in nitrobenzene

Abstract: An analysis of the dependence of the observed rotational constants on the quantum number ν36 of the NO2 torsional mode of nitrobenzene is presented. It is first shown that the empirical data available cannot be explained by the exact solution of the semi-rigid rotation-internal rotation model; in particular, the decrease of the rotational constant A with increasing ν36 deviates in a characteristic way from predictions of this model. A satisfactory interpretation, however, is obtained if relaxation of the ONO angle is included in the rotation-internal rotation theory. The relaxation effects are discussed by a perturbation treatment of the rotation-internal rotation theory. Since nitrobenzene represents a C 2ν frame-C 2ν top system, either the phenyl or the nitro group may be chosen as a frame. The interrelation of the two hamiltonians is given and their symmetry groups are shown to be outer automorphs.

The use of intermediates with preformed disulfide bridge for the synthesis of oxytocin and deamino-oxytocin.

Abstract: The disulfide-bridged hexapeptides 6a and 6b have been prepared from benzyl-protected intermediates Coupling of 6a and 6b with prolyl-leucyl-glycine amide afforded deamino-oxytocin (7a) and the protected oxytocin derivative 7b, respectively; the latter was converted to oxytocin (7c) by removal of the Boc protecting group

Juvenile hormone breaks ovarian diapause in two nymphalide butterflies

Abstract: Falter des TagpfauenaugesInachis io und des kleinen FuchsesAglais urticae fallen in der Natur im Herbst, in Gefangenschaft aber zu jeder Jahreszeit in reproduktive Diapause. Die Diapause der Ovarien und der Kittdrusen der Weibchen kann jederzeit durch topicale Behandlung mit synthetischen Juvenilhormonderivaten gebrochen werden. Kopulation und Oviposition gefangener Falter werden jedoch durch das Hormon nicht stimuliert.

Exact solution to the rotation-ring-puckering problem of D 4h -D 2d four-membered ring molecules by infinite matrix diagonalization

Abstract: The rotation-ring-puckering problem of four-membered ring cyclobutane-type molecules with D 4h -D 2d conformations is formulated as a dynamical system in the eulerian angles and the polar coordinate ϑ. Classical and quantum-mechanical hamiltonians and their symmetry group O ++(3) × D ∞h are discussed. The kinetic energy matrix coefficients gmm are found to be irrational functions of the trigonometric polynomial 3 + cos 2ϑ in the internal coordinate ϑ. It is shown that the energy matrix coefficients may all be expressed as Laurent coefficients by means of the hypergeometric function 2 F 1, the convergence being determined by the roots of the kinetic determinant. Selection rules and matrix elements for rotation-ring-puckering Raman transitions are given.

Respiratory activity of Candida tropicalis during growth on hexadecane and on glucose.

Abstract: Rates of oxygen uptake and the oxygen demand during growth of Candida tropicalis on hexadecane and glucose were determined in batch experiments. Oxygen demand was 2.5 fold higher for the synthesis of one unit of cell mass from hydrocarbon than from glucose. On the other hand specific respiration is of the same order of magnitude for both substrates, e.g. 12 mmoles O2xh-1xg-1 (dry weight) and seems to be a constant of this organism. Higher rates of oxygen supply into the medium had no effect on the specific rates of respiration. Specific growth rates on hexadecane were 2.4 times lower than on glucose. It is concluded, that rates of synthesis of cell components are controlled by the overall capacity of the respiratory pathways.

Decomposition of bipartite multigraphs into matchings

Abstract: In this paper we show that a bipartite multigraphG in which no vertex is adjacent to more thann edges may be decomposed into any numbern *≥n of matchings in such a way that the number of edges in each of these matchings differ from one another by at most one unit. When the two sets of verticesX and¯X ofG are partitioned into subsetsX i and¯X j respectively, we give conditions for the existence of a decomposition ofG inton *≥n matchings such that each matching contains at mostα i edges adjacent to vertices inX i and at mostβ j edges adjacent to vertices in¯X j . There are many practical problems of scheduling with resource limitations for which such decompositions of a bipartite graph are required; some examples are given.