Ueber in den Chinarinden vorkommende Alkaloide

Ohne Zusammenfassung     

Size Effect in Concrete Intrinsic Permeability Measurements

This paper questions the possibility that the measure of concrete permeability in laboratory depends in some instances on the size of the sample, i.e. that intrinsic permeability measurements exhibit a size effect. Experiments were carried out on specimens of different size (the surface interested by the flow ranging from 2 × 10³ to 2 × 10⁵ mm ²) of an ultra high strength concrete heated at 523.15 K for 30 days. A first campaign was made using a Cembureau permeameter, with silicon masks put on the sample’s flat surfaces to reduce the areas where inlet or outlet pressures apply and otherwise standard settings and procedures. A second one was made on concrete hollow cylinders of 265 mm height and 350 mm external diameter, fixed between steel plates so as to make a canister that was filled with pressurised nitrogen (from 253 to 415 kPa in different tests) and observed during pressure decay for 2–4 days. Further Cembureau tests were made to correlate the two campaigns. Mathematical models were put forward to process the information gathered from these experiments, dealing with bending of flow lines in the first case and with unsteady flow in the second, and numerical computations made to estimate permeability starting from boundary data measured in experiments. A general analysis, based on the extreme value theory, supported the idea that a Frechet law should be adopted to possibly describe the growth of permeability with the size of the cross-section of the flow. Though explorative in principle, our results lead to the conclusion that a size effect was observed. The shape parameter of the Frechet law describing this effect was identified accordingly.     

The characterization of electronic defect states of single and double carbon vacancies in graphene sheets using molecular density functional theory

ABSTRACT

A detailed picture of the electronic states manifolds of single- and double-vacancy defects in molecular models of graphene based on polycyclic aromatic hydrocarbons (PAHs) is presented. DFT calculations using various density functionals including long-range corrected ones have been performed for pyrene, circumpyrene and 7a,7z-periacene. It has been found for pyrene defect models that DFT results reproduced well the set of closely-spaced singlet and triplet states predicted by the CCSD(T) and previous MRCI?+?Q calculations, indicating the applicability of DFT for accessing the excited states manifolds also for larger graphene models. For the single-carbon vacancy defect, all structures have a triplet ground state. As expected, in the largest system, 7a,7z-periacene-1C, the lowest lying states are much closer in energy. For all double-vacancy defect structures, a significant rearrangement of the electronic states with increasing size of the sheet is observed. The closed-shell ¹A_g state in the smallest systems is destabilised in the extended 7a,7z-periacene system, which has the ³B_2u state as the ground state. As observed for the single-vacancy defect, the lowest lying states are closer in energy for the larger systems, since there are more π orbitals close in energy available. For all states, the formation of the bridging bonds for the double vacancy leads to distances shorter than for the single vacancy defect indicating a larger rigidity of the former structure which does not allow stronger distortions.     

Определение дефекто в решетки третъего ро да и величины когерентн ых областей решетки у порошкооБразного в олъфрама

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The influence of the spectral asymmetry of X-ray emission lines on the results of studying defects in crystals by X-rays of different wavelength

Since the asymmetry of X-ray emission lines was found to influence the exact measurements of lattice parameters of powdered samples the author has revised the results she once obtained when carrying out exact measurements of the lattice parameter with radiations of various wavelengths for tungsten crystals containing admixtures of different elements. It is shown that with samples having an inhomogeneous distribution of the admixtures in the crystals the typical graphs of lattice parameter found originally remain when respecting the influence of the spectral asymmetry. On the other hand, with a sintered sample which has been homogeneized by long annealing the introduction of corrections to spectral asymmetry leads to an adjustment of the differences measured originally, for which it was difficult to find a probable explanation.

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Anisotropic diffusion of light in a strongly scattering material

Light transport in a strongly scattering, strongly anisotropic material is studied experimentally using both static and time-resolved techniques. Both the static and the dynamic results are well characterized by a diffusion equation with an anisotropic diffusion tensor and a scalar absorption term. Light diffuses 4.0 times faster along the uniaxial axis of the material compared with diffusion in the orthogonal directions.     

Violating Bell's inequality beyond Cirel'son's bound

Cirel'son inequality states that the absolute value of the combination of quantum correlations appearing in the Clauser-Horne-Shimony-Holt (CHSH) inequality is bound by 2 square root of (2). It is shown that the correlations of two qubits belonging to a three-qubit system can violate the CHSH inequality beyond 2 square root of (2). Such a violation is not in conflict with Cirel'son's inequality because it is based on postselected systems. The maximum allowed violation of the CHSH inequality, 4, can be achieved using a Greenberger-Horne-Zeilinger state.     

Communication Complexity as a Principle of Quantum Mechanics

We introduce a two-party communication complexity problem in which the probability of success by using a particular strategy allows the parties to detect with certainty whether or not some forbidden communication has taken place. We show that theprobability of success is bounded by nature; any conceivable method which gives a probability of success outside these bounds is impossible. Moreover, any conceivable method to solve the problem which gives a probability success within these bounds is possible in nature. This example suggests that a suitaby chosen set of communication complexity problems could be the basis of an information-theoretic axiomatization of quantum mechanics.     

ИЗМЕНЕНИЯ ТОНКОЙ СТР УКТУРЫ МОЛОТОГО КОБА ЛТА

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