Kriechverformung des Betons unter statischer und unter dynamischer Belastung

Zusammenfassung In einer früheren Arbeit wurde gezeigt, daß sich die Kriechverformung einer Betonprobe unter konstanter Last befriedigend mit den Mitteln der Reaktionskinetik beschreiben läßt. Es wird gezeigt, wie diese Überlegungen erweitert werden müssen, um auf den Fall dynamischer Belastung übertragen werden zu können. Eine Gleichung wird abgeleitet, die die Kriechverformung als Funktion der mittleren Spannung und der Spannungsamplitude angibt. Versuchsergebnisse mehrerer Autoren wurden ausgewertet und mit der Theorie verglichen. Die Übereinstimmung ist im Rahmen der Meßgenauigkeit befriedigend.

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Summary In a previous paper the author showed that the creep deformation in a concrete sample under constant load can be satisfactorily described with the means of reaction kinetics. This paper shows how these considerations must be enlarged to allow their transfer to the case of dynamic load. An equation is derived which represents the creep deformation as a function of the mean stress and the stress amplitude. Test results of several authors are evaluated and compared with the theory. Agreement is satisfactory within the scope of measuring accuracy.

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Die Arbeit ist während eines Aufenthaltes des Autors an der Universität Leeds entstanden. Herrn ProfessorA. M. Neville möchte ich an dieser Stelle herzlich dafür danken, daß er mir die Möglichkeit bot, an seinem Institut zu arbeiten. HerrnWhaley möchte ich für zahlreiche interessante Diskussionen danken.     

Device calibration impacts security of quantum key distribution

Characterizing the physical channel and calibrating the cryptosystem hardware are prerequisites for establishing a quantum channel for quantum key distribution (QKD). Moreover, an inappropriately implemented calibration routine can open a fatal security loophole. We propose and experimentally demonstrate a method to induce a large temporal detector efficiency mismatch in a commercial QKD system by deceiving a channel length calibration routine. We then devise an optimal and realistic strategy using faked states to break the security of the cryptosystem. A fix for this loophole is also suggested.     

An application of rosenthal's moment inequality to the strong law of large numbers

We apply a moment inequality of H.P. Rosenthal to get various generalizations of a theorem of Brunk-Chung-Prohoroff. In particular, we show that the strong law hols provided $\text{∑}\text{n=1}\text{∞}\text{n}{}^{\mathrm{?2p}}\text{E(X}{}_{\mathrm{n}}\text{}{}^{\mathrm{2p}}\text{) < ∞}$ and $\text{∑}\text{n=1}\text{∞}\text{n}{}^{\mathrm{?2?p}}\text{(E(}\text{X}\text{n}\text{2}\text{))}{}^{\mathrm{p}}\text{< ∞}$ for one p ? 1.     

Electrical resistivity and crystallization behaviour of icosahedral Al51Cu12.5Mg36.5

Samples consisting of icosahedral Al₅₁Cu_12.5Mg_36.5 were produced by melt-spinning and characterized by X-ray and electron diffraction. DSC measurements confirm the transition from the quasicrystalline to the crystalline state to be exothermic. The electrical conductivity shows two steps at about 600 K due to crystallization processes. The magnetoresistance at 4.2 K exhibits the typical shape of the quantum interference correction.     

Nucleophilic displacements of N-aryl and heteroaryl groups. Part 8 . Intermolecular reactions of N-aryl-pyridinium, -quinolinium,and -acridinium salts with nucleophiles

N-Aryl-mono-, -tri- and -pentacyclic pyridinium cations react with S- and C-nucleophiles to give: (i) simple addition of hydride at the α-ring position, (ii) nucleophilic addition of thiophenoxide at the γ-ring position, (iii) deprotonation at the 6-position of a 5,6-dihydroquinolinium ring followed by prototropic shift to give a 1,2-dihydroquinoline derivative, (iv) ring contraction of a pyridine to a pyrrole ring, and (v) nucleophilic displacement of the N-aryl group.     

Automated sample preparation for X-ray fluorescence, plasma emission and atomic absorption spectrometry

Summary There exists an important disparity between the high throughput of modern spectrometers for the analysis of mineral products and the weak means for the isoformation of samples. To fill this gap the French Iron and Steel Research Institute (IRSID), with the financial help of the European Community for Steel and Coal, has developed several instruments able to rapidly prepare samples for X-ray fluorescence, plasma emission and atomic absorption spectrometries. These three devices are able to prepare beads, solutions or both. Using high frequency heating, effective mixing during the fusion-dissolution process as well as a judicious choise of a number of parameters. The samples obtained are of such a quality that the preparation and measurement reproducibilities are often very similar.

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Automatische Probenvorbereitung für die Röntgenfluorescenz-, Plasmaemissions- und Atomabsorptions-SpektrometrieProbenvorbereitung mittels PERL'X-2, PLASMASOL und SOL'X

Zusammenfassung Es besteht eine große Ungleichheit zwischen dem hohen Probendurchsatz der modernen Spektrometer zur Analyse anorganischer Produkte und den unzureichenden Mitteln der Probenaufbereitung. Aus diesem Grund hat das französische Forschungsinstitut für Eisenhüttenwesen (IRSID) mit der finanziellen Hilfe der Europäischen Gemeinschaft für Kohle und Stahl einige Geräte entwickelt, die es erlauben, schnell Proben für die Röntgenfluorescenz, die mit Plasma angeregte optische Emission und die Atomabsorption aufzubereiten. Diese drei Geräte können Perlen, Lösungen, oder beide zugleich herstellen. Dank einer Hochfrequenzheizung, einer guten Durchmischung während der Aufschmelzung-Verdünnung und gezielt gewählter Parameter sind die erhaltenen Proben von einer solchen Qualität, daß die Reproduzierbarkeit von Aufbereitung und Messung in vielen Fällen nahezu gleich ist.

     

Analogues of the “zero-two” law for positive linear contractions inL p andC(X)

LetT be a positive linear contraction inL ^p (1≦p<∞), then we show that lim ‖T ^pf −T ⁿ⁺¹ f‖ _p ≦(1 − ε)2^1/p (f∈L _p ⁺ , ε>0 independent off) implies already lim_n n→∞ ‖T ⁿf −T ⁿ⁺¹ n+1f ‖_p p=0. Several other related results as well as uniform variants of these are also given. Finally some similar results inLsu/t8 andC(X) are shown.     

Spaltungen mittels Diazoniumverbindungen und Chinonimidchlorid, 8. Mitt.: Über Effekte entlang einer ungesättigten Kohlenstoffkette

Zusammenfassung Es wird über die Reaktion von Chinonimidchlorid und verschieden methylsubstituierten 1,5-Bis-(4-hydroxyphenyl)-^1,4-pentadienon-(3)-verbindungen berichtet und gezeigt, daß die Menge an Spaltungsprodukt nicht nur von den Substituenten am Benzolkern, sondern auch von der Natur der Sohlenstoffkette zwischen den aromatischen Ringen abhängig ist.

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The reaction of p-benzoquinone-monochloroimine with several methyl substituted 1,5-bis-(4-hydroxyphenyl)-^1,4-pentadienon-3-compounds has been studied. It has been shown that the yield of the cleavage products does not only depend from the substituent of the phenyl group but also from the nature of the carbon chain between the two aromatic ring systems.

     

Polyethylene–isotactic polypropylene epitaxy: Analysis of the diffraction patterns of oriented biphasic blends

Diffraction patterns of oriented blends of isotactic polypropylene (iPP) and polyethylene (PE) published recently by several authors are analyzed on the basis of a unique epitaxial relationship between the iPP and PE crystal lattices. The contact planes are (100)_PE and (010)_iPP, and the PE chains lie at 50° to the iPP chain axis, parallel to the helical path of the iPP helices, which is formed by rows of side-group methyls.     

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for metabolic flux analyses using isotope-labeled ethanol

We describe a novel method for the determination of the concentration and labeling degree of ethanol originating from 1-13C-labeling experiments. This method is suitable for high-throughput metabolic flux analysis because of the possible parallel sample preparation and fast final analysis using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). In a closed vial containing culture supernatant, ethanol is enzymatically oxidized to acetaldehyde. The acetaldehyde formed evaporates and is readily trapped in a second enclosed but open vial containing acidified 2,4-dinitrophenylhydrazine (DNPH). The 2,4-acetaldehyde dinitrophenylhydrazone (Ac-DNPH) that is formed is insoluble under these conditions. This leads to a constant conversion rate of the acetaldehyde produced from ethanol after 14 h minimum incubation time. MALDI-TOFMS was used to quantify the formed Ac-DNPH with [13C2]-ethanol as internal standard. The relative signal intensities of the unlabeled ethanol derivative as well as of [1-13C]-ethanol were linearly related to the ethanol concentration within a range of 1 to 50 mM with a limit of detection of 0.6 mM, a range which is sufficient for flux analysis in microtiter plate fermentation experiments. The method allows the estimation of the [1-13C]-ethanol originating from 1-13C-labeling experiments of Saccharomyces cerevisiae strains. In experiments where the expected flux range was exceeded, unlabeled ethanol was determined with a linear range from 30 to 500 mM. Ethanol quantification using this method was compared with enzymatic analysis and exhibited differences of less than 3.3% on average. Comparison of flux partitioning ratios between glycolysis and the pentose-phosphate pathway (PPP) based on MALDI-TOFMS and gas chromatography (GC)/MS methods showed good agreement, with differences for ethanol and alanine labeling of only 4.3%.