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151.
152.
K. Ziegler 《Zeitschrift für Physik B Condensed Matter》1992,86(1):33-38
A model for disordered superfluids and superconductors is considered in terms of the Bogoliubov-de Gennes equation with a random order parameter field. Two characteristic cases are distinguished: model I with a real order parameter (time reversal invariant system) and model II with a complex order parameter (broken time reversal invariance). The fluctuations of the order parameter close the gap in both models, and we investigate the states at the center of the filled gap. The two models have distinctive properties in terms of the quasiparticle states due to different symmetries. Model II exhibits only localized quasiparticle states at the band center. In contrast, the fluctuations of the real order parameter of model I can be described by a nonlinear sigma model which leads to a transition from localized to extended states for dimensionsd>2. 相似文献
153.
Projective geometry is formulated in the language of geometric algebra, a unified mathematical language based on Clifford algebra. This closes the gap between algebraic and synthetic approaches to projective geometry and facilitates connections with the rest of mathematics.This work was partially supported by NSF grant MSM-8645151. 相似文献
154.
Prof. Dr. H. Ziegler 《Archive of Applied Mechanics (Ingenieur Archiv)》1982,52(1-2):105-113
Summary To account for shear in buckling pioblems, one uses either the approach of Engesser or the socalled modified approach, proposed by Haringx in connection with helical springs. Both are based on onedimensional reasoning. While most authors seem to prefer the second method, Nänni [4] has shown by means of the three-dimensional theory of elasticity that, for bars, the first one is superior. The present paper is based on a more fundamental one-dimensional approach and confirms Nänni's and hence Engesser's results. It also shows that, together with shear, shortening of the bar must be taken into account, and it improves Engesser's formulas accordingly. It finally shows why Haringx' approach is correct for springs.
Argumente für und gegen Engessers Knickformeln
Übersicht Um bei Knickproblemen den Schub zu berücksichtigen, verwendet man entweder das Engessersche oder das sogenannte modifizierte Verfahren, das von Haringx zur Behandlung von Schraubenfedern vorgeschlagen worden ist. Während die meisten Autoren die zweite Methode vorzuziehen scheinen, hat Nänni [4] mittels der dreidimensionalen Elastizitätstheorie gezeigt, daß bei Stäben die erste überlegen ist. Die vorliegende Arbeit stützt sich auf ein fundamentaleres eindimensionales Verfahren und bestätigt Nännis und damit Engessers Ergebnisse. Sie zeigt auch, daß mit dem Schub zusammen die Verkürzung des Stabes zu berücksichtigen ist, und sie verbessert Engessers Formeln dementsprechend. Schließlich zeigt sie, weshalb das Verfahren von Haringx bei Federn korrekt ist.相似文献
155.
Biology‐Oriented Synthesis of a Withanolide‐Inspired Compound Collection Reveals Novel Modulators of Hedgehog Signaling
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Dr. Jakub Švenda Dipl.‐Biochem. Michael Sheremet M. Sc. Lea Kremer Lukáš Maier Dr. Jonathan O. Bauer Prof. Dr. Carsten Strohmann Dr. Slava Ziegler Dr. Kamal Kumar Prof. Dr. Herbert Waldmann 《Angewandte Chemie (International ed. in English)》2015,54(19):5596-5602
Biology‐oriented synthesis employs the structural information encoded in complex natural products to guide the synthesis of compound collections enriched in bioactivity. The trans‐hydrindane dehydro‐δ‐lactone motif defines the characteristic scaffold of the steroid‐like withanolides, a plant‐derived natural product class with a diverse pattern of bioactivity. A withanolide‐inspired compound collection was synthesized by making use of three key intermediates that contain this characteristic framework derivatized with different reactive functional groups. Biological evaluation of the compound collection in cell‐based assays that monitored biological signal‐transduction processes revealed a novel class of Hedgehog signaling inhibitors that target the protein Smoothened. 相似文献
156.
M. Sc. Yasemin Akbulut Hannah J. Gaunt Prof. Katsuhiko Muraki Dr. Melanie J. Ludlow Dr. Mohamed S. Amer Dr. Alexander Bruns Dr. Naveen S. Vasudev Dr. Lea Radtke Dr. Matthieu Willot M. Sc. Sven Hahn M. Sc. Tobias Seitz Dr. Slava Ziegler Prof. Dr. Mathias Christmann Prof. Dr. David J. Beech Prof. Dr. Herbert Waldmann 《Angewandte Chemie (International ed. in English)》2015,54(12):3787-3791
Current therapies for common types of cancer such as renal cell cancer are often ineffective and unspecific, and novel pharmacological targets and approaches are in high demand. Here we show the unexpected possibility for the rapid and selective killing of renal cancer cells through activation of calcium‐permeable nonselective transient receptor potential canonical (TRPC) calcium channels by the sesquiterpene (?)‐englerin A. This compound was found to be a highly efficient, fast‐acting, potent, selective, and direct stimulator of TRPC4 and TRPC5 channels. TRPC4/5 activation through a high‐affinity extracellular (?)‐englerin A binding site may open up novel opportunities for drug discovery aimed at renal cancer. 相似文献
157.
Unusually Strong Long‐Distance Metal–Metal Coupling in Bis(ferrocene)‐Containing BOPHY: An Introduction to Organometallic BOPHYs
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Hannah M. Rhoda Kullapa Chanawanno Alexander J. King Yuriy V. Zatsikha Prof. Christopher J. Ziegler Prof. Victor N. Nemykin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(50):18043-18046
The first organometallic BOPHY (BOPHY=bis(difluoroboron)‐1,2‐bis{(pyrrol‐2‐yl)methylene}hydrazine) containing two ferrocene substituents was prepared through a Knoevenagel condensation between tetramethyl substituted BOPHY and ferrocene carboxaldehyde. An unprecedentedly strong long‐range (≈17.2 Å) metal–metal coupling in this new complex was investigated using electrochemical, spectroelectrochemical, and chemical oxidation methods. Electrochemical data is indicative of a 200 mV separation between the first and the second ferrocene‐centered oxidation processes. Formation of the mixed‐valence states and appearance and disappearance of two NIR bands were observed during stepwise oxidation of the first organometallic BOPHY. The electronic structure and the nature of the excited states in this new chromophore were studied by DFT and TDDFT calculations. 相似文献
158.
We show that by cutting off the vertices and then the edges of neighborly cubical polytopes, one obtains simple 4-dimensional polytopes with n vertices such that all separators of the graph have size at least Ω(n/log3/2 n). This disproves a conjecture by Kalai from 1991/2004. 相似文献
159.
160.
Qayyum H Herrick RS Ziegler CJ 《Dalton transactions (Cambridge, England : 2003)》2011,40(28):7442-7445
The aqueous one-step reaction of Re(CO)(3)(H(2)O)(3)(+) with pyridine-2-carboxyaldehyde and glycine or alanine produces a new class of cyclic dimeric products. The ligands of the chiral C(2)-symmetric products are bound via the diimine at one rhenium centre and via the pendant carboxylate to a second rhenium center. 相似文献