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41.
Anthony Linden Yuehui Zhou Heinz Heimgartner 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(5):482-487
In the selenium‐containing heterocyclic title compound {systematic name: N‐[5‐(morpholin‐4‐yl)‐3H‐1,2,4‐diselenazol‐3‐ylidene]benzamide}, C13H13N3O2Se2, the five‐membered 1,2,4‐diselenazole ring and the amide group form a planar unit, but the phenyl ring plane is twisted by 22.12 (19)° relative to this plane. The five consecutive N—C bond lengths are all of similar lengths [1.316 (6)–1.358 (6) Å], indicating substantial delocalization along these bonds. The Se...O distance of 2.302 (3) Å, combined with a longer than usual amide C=O bond of 2.252 (5) Å, suggest a significant interaction between the amide O atom and its adjacent Se atom. An analysis of related structures containing an Se—Se...X unit (X = Se, S, O) shows a strong correlation between the Se—Se bond length and the strength of the Se...X interaction. When X = O, the strength of the Se...O interaction also correlates with the carbonyl C=O bond length. Weak intermolecular Se...Se, Se...O, C—H...O, C—H...π and π–π interactions each serve to link the molecules into ribbons or chains, with the C—H...O motif being a double helix, while the combination of all interactions generates the overall three‐dimensional supramolecular framework. 相似文献
42.
The ability to separate enzymes, nucleic acids, cells, and viruses is an important asset in life sciences. This can be realised by using their spontaneous asymmetric partitioning over two macromolecular aqueous phases in equilibrium with one another. Such phases can already form while mixing two different types of macromolecules in water. We investigate the effect of polydispersity of the macromolecules on the two-phase formation. We study theoretically the phase behavior of a model polydisperse system: an asymmetric binary mixture of hard spheres, of which the smaller component is monodisperse and the larger component is polydisperse. The interactions are modelled in terms of the second virial coefficient and are assumed to be additive hard sphere interactions. The polydisperse component is subdivided into sub-components and has an average size ten times the size of the monodisperse component. We calculate the theoretical liquid–liquid phase separation boundary (the binodal), the critical point, and the spinodal. We vary the distribution of the polydisperse component in terms of skewness, modality, polydispersity, and number of sub-components. We compare the phase behavior of the polydisperse mixtures with their concomittant monodisperse mixtures. We find that the largest species in the larger (polydisperse) component causes the largest shift in the position of the phase boundary, critical point, and spinodal compared to the binary monodisperse binary mixtures. The polydisperse component also shows fractionation. The smaller species of the polydisperse component favor the phase enriched in the smaller component. This phase also has a higher-volume fraction compared to the monodisperse mixture. 相似文献
43.
We address the problem of "nonlocal computation," in which separated parties must compute a function without any individual learning anything about the inputs. Surprisingly, entanglement provides no benefit over local classical strategies for such tasks, yet stronger nonlocal correlations allow perfect success. This provides intriguing insights into the limits of quantum information processing, the nature of quantum nonlocality, and the differences between quantum and stronger-than-quantum nonlocal correlations. 相似文献
44.
Greta Linden Prof. Dr. Olalla Vázquez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(44):10014-10023
Photodynamic therapy (PDT) leads to cancer remission via the production of cytotoxic species under photosensitizer (PS) irradiation. However, concomitant damage and dark toxicity can both hinder its use. With this in mind, we have implemented a versatile peptide-based platform of bioorthogonally activatable BODIPY-tetrazine PSs. Confocal microscopy and phototoxicity studies demonstrated that the incorporation of the PS, as a bifunctional module, into a peptide enabled spatial and conditional control of singlet oxygen (1O2) generation. Comparing subcellular distribution, PS confined in the cytoplasmic membrane achieved the highest toxicities (IC50=0.096±0.003 μm ) after activation and without apparent dark toxicity. Our tunable approach will inspire novel probes towards smart PDT. 相似文献
45.
Y. S. Wang P. Bennema L. W. M. Schreurs C. J. Beers J. Wunk P. Van Der Linden 《Crystal Research and Technology》1993,28(2):253-256
In this paper we present the results of recent studies on the improvement of superconductivity in PbxBi2-xSr2CaCu2Oy single crystals by preventing impurities incorporation, employing ZrO2 crucible for crystal growth and post annealing the as-grown crystals in vacuum or argon. It is realized that the superconductivity of as-grown crystals is improved. 相似文献
46.
Y. S. Wang P. Bennema M. N. Zheng C. M. Fu P. van der Linden 《Crystal Research and Technology》1993,28(7):1015-1020
A mechanism of high-Tc superconductivity related to the perovskite crystal structure is proposed by a “phonon attenuation model”, which means that in the perovskite-like crystal structure, a number of “ordering” vacancies or holes occur due to the non-stoichiometric structure features. Such a reticular “spongly-like” structure facilitates lattice thermovibration attenuation perovskite (phonon attenuation) during temperature reduction. This leads to an abrupt drop of the resistivity, owing to the conduction electrons transmitted through the media without collision with irregularities in the lattice due to the lattice thermovibration. This probably is the main reason for high-Tc superconductivity of the perovskite cuprates. 相似文献
47.
48.
On the basis of a pyrrolidine tweezer 1, a library of peptidosulfonamide tweezers (15a-e, 16a-e) was synthesized on the solid phase. This library was screened in a simultaneous substrate screening procedure for the ability to enantioselectively catalyze the Ti(O-i-Pr)(4)-mediated addition of diethylzinc to aldehydes. One of the best solid-phase tweezer catalyst (i.e., 16d, giving an ee of 32% in solid-phase catalysis) was resynthesized in solution (compounds 20 and 21). The now homogeneous solution-phase catalysis showed even better enantioselectivity (i.e., up to 66%). 相似文献
49.
We present difference-frequency generation cross-correlation frequency-resolved optical gating, a new method of characterizing the amplitude and phase of weak ultrashort pulses in the blue spectral region. The method uses the spectrally resolved downconversion signal of the blue pulse and a fully characterized reference pulse with a lower center frequency. The amplitude and phase of the blue test pulse are retrieved from the corresponding spectrogram and electric field of the reference pulse with an interactive Fourier-transform algorithm. 相似文献
50.
Adaptive anisotropic noise filtering for magnitude MR data 总被引:4,自引:0,他引:4
Sijbers J den Dekker AJ Van der Linden A Verhoye TM Van Dyck D 《Magnetic resonance imaging》1999,17(10):1211-1539
Conventional noise filtering schemes applied to magnitude magnetic resonance (MR) images tacitly assume Gauss distributed noise. Magnitude MR data, however, are Rice distributed. Not incorporating this knowledge leads inevitably to biased results, in particular when applying such filters in regions with low signal-to-noise ratio. In this work, we show how the Rice data probability distribution can be incorporated so as to construct a noise filter that is far less biased. 相似文献