Showing papers by "Technical University of Berlin published in 1980"

The Fischer-Tropsch Synthesis in the Liquid Phase

Abstract: The hydrogenation of carbon monoxide by the Fischer-Tropsch (F-T) process [1] forms saturated and unsaturated compounds of the homologous hydrocarbon series. It permits the synthesis of hydrocarbons ranging from methane to high-melting paraffins with molecular weights above 20,000, depending on the catalyst, temperature, and type of process employed. By-products such as alcohols, aldehydes, ketones, acids, and esters are formed on a smaller scale. Small amounts of aromatic compounds are formed at high temperatures by secondary dehydrocyclization reactions from the primary hydrocarbons formed.

XPS measurements and structural aspects of silicate and phosphate glasses

Abstract: Detailed measurements of the shape of the 01s photoelectron lines from a range of silicate, alumino silicate, and phosphate glasses have been made. In the case of the silicate glasses contributions from bridging and non bridging oxygen atoms were separated. For phosphate glasses an additional component due to double bonded oxygen atoms could be determined by curve fitting procedures and by comparison with selected crystalline phosphates. The intensities of the photoelectrons from these oxygen types bonded in different ways and the chemical shifts between them could be correlated with alkali and alkaline earth oxide contents and with the cation field strength. The ionic binding character introduced into the glass networks is a non-localized effect because not only the non bridging oxygen atoms are influenced by the alkali and alkaline earth ions but also the bridging and double bonded oxygen atoms. In the case of the sodium alumino silicate glasses a coordination change is indicated at Al2O3/Na2O ∼ 0.4.

Induction of transfer-cell formation by iron deficiency in the root epidermis of Helianthus annuus L

Abstract: Helianthus annuus L. responds to iron deficiency by forming a thickened cortex and abundant root hairs in a zone near the root apex that corresponds to the primary developmental stage. Cytological investigations revealed that within 24 to 48 h of iron deficiency most of the peripheral cells differentiate into transfer cells. The wall labyrinth is always situated on the peripheral walls that face the external medium. The cytoplasm of these cells is characterized by numerous mitochondria, extensive rough endoplasmic reticulum, and large leucoplasts containing protein bodies. These observations are discussed in relation to the fact that Helianthus, as an “iron efficient” plant, responds physiologically to iron deficiency by extrusion of H+, production of reducing substances, and a steep increase in the uptake efficiency of Fe.

Estimation of the fatigue limit by progressively‐increasing load tests

Abstract: — On the basis of fatigue data derived from a large number of experiments, the load progression methods of Locati and Prot as well as a method operating on a thermometric basis have been comparatively evaluated in an experimental and analytical (statistical) study. The last-named thermo-method can provide useful estimates for a fatigue limit corresponding with ca. 0 to 5% probability of fracture with only 1 to 3 experiments. The Prot-method, set up and evaluated in a certain way, provides a useful estimate of the fatigue limit and, additionally, an approximate indication of the width of the transition range of the corresponding Wohler-type tests after experiments on not less than about ten specimens. The load progression, contrary to the original Prot-concept, must not necessarily be applied in a continuous mode, but can occur stepwise with increments Δσ smaller than ca. 15 Nm-2.

Semantics and Pragmatics of Sentence Connectives in Natural Language

Abstract: One need be neither a diplomat nor a lady to use the word perhaps to mean ‘yes’ one time and ‘no’ another. But what is the meaning of a word like perhaps if everyone can make it mean either ‘yes’ or ‘no’ as he pleases? Can one in any sense talk about a fixed word meaning here? But if not, what is it Voltaire is telling us when he maintains that the diplomat’s uttering “yes” as well as the lady’s uttering “no” means ‘perhaps’?

Smoluchowski's theory of coagulation in colloids holds rigorously in the Boltzmann-Grad-limit

Abstract: We consider Smoluchowski's model of coagulation in colloids: n particles move in three-dimensional euclidean space according to Brownian motions independently of each other as long as the particles are at a distance greater than R. When two particles come to within a distance R they stick together and form a “double particle”, which itself is in Brownian motion — and so on. In the Boltzmann-Grad-limit n→∞, n R=constant, we prove “propagation of chaos” and derive the kinetic equations for the densities of the k-fold particles.

Coherence time measurement of picosecond pulses by a light-induced grating method

Abstract: The temporal coherence function |Γ(τ)| of picosecond pulses from a Nd: YAG laser has been measured by diffraction at a transient grating. The coherence timetc=7 ps is small compared to the pulse widthtp=22 ps but is in correspondence with the spectral bandwidth Δv=12·1010 Hz. The new method for measuring the coherence function |Γ(τ)| is discussed and compared with a previous experiment.

Tumorhemmung durch Metallocene: Wirkung von Titanocen-, Zirconocen- und Hafnocen-dichlorid gegenüber Ehrlich-Aszites-Tumor der Maus

Abstract: Die Antitumor-Aktivitat der Metallocen-dichloride TDC, ZDC und HDC wird an Ehrlich-Aszites-Tumor-tragenden CF 1-Mausen untersucht.

The Berry-Esseen theorem for functionals of discrete Markov chains

Abstract: The error bound O(1/√n) is derived in the central limit theorem for partial sums $$\sum\limits_{j = 1}^n {f(\xi _j )} $$ where ξj is a recurrent discrete Markov chain and f is a real valued function on the state space. In particular it is shown that for bounded f and starting distribution dominated by some multiple of the stationary one, it is sufficient for the chain to have recurrence times with third moments on order to get this bound.

Tumor inhibition by metallocenes: antitumor activity of titanocene dihalides (C5H5)2TiX2 (X=F, Cl, Br, I, NCS) and their application in buffered solutions as a method for suppressing drug-induced side effects.

Abstract: The antitumor activity of titanocene dihalides (C5H5)2TiX2 with X=F, Cl, Br, I, NCS is investigated against Ehrlich ascites tumor in CF 1 mice Varying doses of the compounds are applied as single ip injections 24 h ptt both in non-buffered (pH 14–39) and buffered (pH 42–59) solutions or suspensions, all of the substances achieving in optimum doses cure rates of 100% on day 120 ptt This corresponds to ILS values of 600–750% referred to the untreated controls Some drug-induced side effects, especially the appearance of postperiotonitic symptoms several weeks after ip application of higher doses of titanocene dihalides, are strikingly reduced by pH elevation in the injected drug solutions

A model for phase transition in pseudoelastic bodies

Abstract: A model is proposed which simulates the observed properties of a pseudoelastic body or memory alloy. The statistical mechanics of the model permits the description of the first-order phase transitions which occur in this alloy. A close analogy between the behaviour of a pseudoelastic body and a ferroelectric body is described.

Mechanisms of unimolecular fragmentations of odd-electron cations in the gas phase: The importance of intramolecular hydrogen migration for [odd]+˙ → [even]+ transitions

Abstract: Eighteen quite different examples are discussed in which the unimolecular elimination of a given radical X˙ from an odd-electron cation cannot be described as a one-step process. Despite the fact that the radical X˙ eliminated is already present as a structural unit in the decomposing ions, the product analysis and structure determination of the even-electron ion formed, the investigation of the energetics of the reaction, the analysis of stereochemical factors, and the determination of kinetic isotope effects reveal that the eliminations must be characterized as two- or multi-step reactions. In all cases investigated, the process commences with a specific (intramolecular) hydrogen transfer to a suitable acceptor function. In this way a reactive radical site is created which induces the actual dissociation step (elimination of X˙) by simultaneous double bond formation. Due to the fact that the hydrogen migration takes place within the charge carrying part of the cation radical and that the migrated hydrogen atom remains there throughout the whole process, the intervention of a H-migration cannot be traced directly by appropriate mass shifts in the spectra of 2H labelled precursors. However, the methods mentioned above can be applied to reveal the details of the reaction mechanism, and the term ‘hidden’ hydrogen migration induced dissociation is suggested to recognize the particular rǒle of H-rearrangements to trigger radical eliminations from odd-electron cations in the gas phase.

Stoichiometry of Proton Translocation during Photosynthesis

Abstract: Formation of ATP in photosynthesis takes place at the expense of free energy stored in the gradient of protons across the thylakoid membrane. Set up of the proton gradient is accomplished by the light-driven electron transport reactions. The stoichiometry of H+ translocation across the thylakoid membrane is determined with respect to electron flow and ATP synthesis. Direct information is obtained on the basis of the H+ flux measurement. Depending on the experimental conditions two or three H+ are translocated from outside into the aqueous inner phase of the thylakoid vesicles for each electron which is transferred through the electron transport chain. Three H+ are translocated from inside to outside across the ATPase for each ATP molecule which is synthesized. Mechanistic and energetic consequences are discussed. Die Bildung von Adenosintriphosphat (ATP) aus Adenosindiphosphat und anorganischem Phosphat stellt eine energiespeichernde Reaktion von universeller Bedeutung im biologischen Stoffwechsel dar. Energielieferanten sind membrangebunden ablaufende Elektronentransport-Reaktionen. Die Energieubertragung erfolgt dabei bemerkenswerterweise nicht uber ein chemisches Zwischenprodukt im klassischen Sinn, sondern unter Zwischenschaltung eines transmembranen H+ -Gradienten. — An isolierten Chloroplasten ermitteln wir fur die Vorgange bei der photosynthetischen ATP-Bildung unter stationaren Bedingungen folgende Daten: 1. Pro Durchlauf eines Elektrons durch die in die Thylakoid-Membran eingebettete Elektronentransport-Kette werden 2 bis 3 H+ -Ionen uber die Membran von der wasrigen Ausenphase in die wasrige Innenphase der Thylakoid-Vesikel transportiert. 2. Die Synthese eines ATP-Molekuls an der in die Thylakoid-Membran eingebetteten ATPase erfordert die Translokation von 3 H+ -Ionen von der Innen- in die Ausenphase. Mechanistische und energetische Konsequenzen werden diskutiert.

A Comparison Between Petri-Nets and Graph Grammars

Abstract: A graph grammar is constructed from a given Petri-net so that direct derivation steps in the grammar correspond to firings of transitions in the net. This close relationship between Petri-nets and graph grammars allows to compare the concurrency concepts of the two theories. As an illustrating example the well-known dining-philosophers problem is discussed.

Density of states in amorphous silicon determined from transport experiments

Abstract: Conductivity and thermopower has been studied for a variety of glow discharge and evaporated aSi films doped by alkali ions, phosphorus, and by boron. It is shown that for all dopants and doping levels the electronic transport over a wide temperature range can be described by an activated mobility. The unusual temperature dependence of both conductivity and thermopower observed in the experiments must, therefore, be ascribed to the statistical shift of the Fermi level. A selfconsistent density of states model is proposed that accounts for the statistical temperature shift of the Fermi level as well as for the changes of the Fermi level position due to doping. It shows a deep minimum near midgap for undoped material and for evaporated films a higher density of gap states which is independent of energy.

Algorithm 562: Shortest Path Lengths [H]

Abstract: Key Words and Phrases CR Categor)es' 5 32 Language Fortran IV shortest path, shortest route problem DESCRIPTION This algorithm finds the shortest path lengths from a specific node to all other nodes in a network. It is a modification of Moore's algorithm [4], originally due to d'Esopo as reported by Pollack and Wiebenson [7] and refined by Pape [5, 6]. The algorithm does not determine the shortest paths. If a shortest path is to be determined, this algorithm may be combined with any algorithm that traces the shortest path from the root node to any other node from the list of predecessors of nodes. As the calculation of the path lengths is the most rime-consuming part of the whole process, we confine our attention to this problem. The main idea of the given algorithm centers around the \"status\" of a new-found successor node j. Ifj has not yet been reached by the process, it is entered at the end of the successor list; if it is currently in the list, no new entry is made, but if it has already been processed and removed from the list, it is entered at the top of the list so that it will be processed next. The current status of each node is recorded by the values of the list which are stored as linked deque (double-ended queue). The steps involved are as follows: top element of the deque := ]; mj := o% mjj := O; while deque ~ ~ do begin t := top element of the deque; remove top element; for all successors k of t do begin mjk := mj, + d,k if mjk < rnfi then begin mfi := mjk; wjk := t; Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage, the ACM copyright notice and the title of the publication and its date appear, and notice Is given that copying is by permission of the Association for Computing Machinery To copy otherwise, or to republish, requires a fee and/or specific permission Author's address.