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51.
We compare the eigenvalues of the Dirac and Laplace operator on a two-dimensional torus with respect to the trivial spin structure.
In particular, we compute their variation up to order 4 upon deformation of the flat metric, study the corresponding Hamiltonian
and discuss several families of examples.
Received: 10 December 1998 相似文献
52.
We investigate the holonomy group of a linear metric connection with skew-symmetric torsion. In case of the euclidian space and a constant torsion form this group is always semisimple. It does not preserve any non-degenerated 2-form or any spinor. Suitable integral formulas allow us to prove similar properties in case of a compact Riemannian manifold equipped with a metric connection of skew-symmetric torsion. On the Aloff-Wallach space N(1,1) we construct families of connections admitting parallel spinors. Furthermore, we investigate the geometry of these connections as well as the geometry of the underlying Riemannian metric. Finally, we prove that any 7-dimensional 3-Sasakian manifold admits 2-parameter families of linear metric connections and spinorial connections defined by 4-forms with parallel spinors.Mathematics Subject Classification (2000):53 C 25, 81 T 30We thank Andrzej Trautman for drawing our attention to these papers by Cartan – see [27]. 相似文献
53.
54.
Blank K Lankenau A Mai T Schiffmann S Gilbert I Hirler S Albrecht C Benoit M Gaub HE Clausen-Schaumann H 《Analytical and bioanalytical chemistry》2004,379(7-8):974-981
Protein assays provide direct access to biologically and pharmacologically relevant information. To obtain a maximum of information from the very smallest amounts of complex biological samples, highly multiplexed protein assays are needed. However, at present, cross-reactions of binding reagents restrict the use of such assays to selected cases and severely limit the potential for up-scaling the technology. Here we describe a double-chip format, which can effectively overcome this specificity problem for sandwich immunoassays. This format consists of a capture array and a reference array with fluorescent labeled detection antibodies coupled to the reference array via DNA duplexes. This format allows for the local application of the labeled detection antibodies onto their corresponding specific spots on the capture array. Here we show that this double-chip format allows for the use of cross-reactive antibodies without generating false positive signals, and an assay for the parallel detection of seven different cytokines was set up. Even without further optimization, the dynamic range and the limit of detection for interleukin 8 were found to be comparable to those obtained with other types of multiplexed sandwich immunoassays. 相似文献
55.
Hans Bock Klaus Ruppert Christian Nther Zdenek Havlas Hans-Friedrich Herrmann Claudia Arad Ilka Gbel Andreas John Jochen Meuret Sabine Nick Andreas Rauschenbach Wolfgang Seitz Torsten Vaupel Bahman Solouki 《Angewandte Chemie (International ed. in English)》1992,31(5):550-581
The structure of a molecule can change considerably as its energy and thus its electron distribution within the time-domain of dynamic relaxation varies. Based on comparison of approriate measured data of related compounds and supported by quantum chemical calculations, therefore, charge-perturbed and/or sterically overcrowded molecules can be designed. Their preparation, handling, and structural characterization, frequently under extreme and especially largely aprotic conditions, provides some surprises. New structural principles become evident and old-fashioned ones are confirmed. Thus the contact-ion aggregates that form on ultrasonically supported reduction of unsaturated hydrocarbons with sodium metal partly contain dibenzene sodium sandwiches. Vicinal dimethylamino substituents or isoelectronic isopropyl groups cause steric overcrowding and facilitate oxidation to molecular cations by energetically favorable delocalization of the generated positive charge. Molecules and molecular ions in which an even number of π electrons are distributed over a σ skeleton containing an odd number of centers preferentially form cyanine subunits. This is demonstrated by the novel ethene dication and dianion salts with central C? C single bonds and molecular halves twisted relative to each other. Altogether in two years well over 50 structures have been determined. Much has been learned from them, especially about electron transfer and contact ion-pair formation in aprotic solvents. Nevertheless, we had to realize that answers to many questions, above all “what crystallizes, how, and why”, are still out of reach. 相似文献
56.
Laura Schmitt Ilka Hinxlage Pablo A. Cea Holger Gohlke Sebastian Wesselborg 《Molecules (Basel, Switzerland)》2021,26(4)
Polybrominated diphenyl ethers (PBDEs) are a group of molecules with an ambiguous background in literature. PBDEs were first isolated from marine sponges of Dysidea species in 1981 and have been under continuous research to the present day. This article summarizes the two research aspects, (i) the marine compound chemistry research dealing with naturally produced PBDEs and (ii) the environmental toxicology research dealing with synthetically-produced brominated flame-retardant PBDEs. The different bioactivity patterns are set in relation to the structural similarities and dissimilarities between both groups. In addition, this article gives a first structure–activity relationship analysis comparing both groups of PBDEs. Moreover, we provide novel data of a promising anticancer therapeutic PBDE (i.e., 4,5,6-tribromo-2-(2′,4′-dibromophenoxy)phenol; termed P01F08). It has been known since 1995 that P01F08 exhibits anticancer activity, but the detailed mechanism remains poorly understood. Only recently, Mayer and colleagues identified a therapeutic window for P01F08, specifically targeting primary malignant cells in a low µM range. To elucidate the mechanistic pathway of cell death induction, we verified and compared its cytotoxicity and apoptosis induction capacity in Ramos and Jurkat lymphoma cells. Moreover, using Jurkat cells overexpressing antiapoptotic Bcl-2, we were able to show that P01F08 induces apoptosis mainly through the intrinsic mitochondrial pathway. 相似文献
57.
Jrg Prust Kerstin Most Ilka Müller Eftichia Alexopoulos Andreas Stasch Isabel Usn Herbert W. Roesky 《无机化学与普通化学杂志》2001,627(8):2032-2037
The reaction of the β‐diketoiminate lithium complex (dipp)NacNacLi · OEt2 ((dipp)NacNac = 2‐((2,6‐diisopropylphenyl)amino)‐4‐((2,6‐diisopropylphenyl)imino)‐pent‐2‐enyl) with iPrMgCl and MgI2 yield the corresponding (dipp)NacNacMgiPr · OEt2 ( 1 ) and (dipp)NacNacMgI · OEt2 ( 2 ). The reaction of 2 with NaBH4 in diethylether gives (dipp)NacNacMg(μ‐H)3BH · OEt2 ( 3 ). The core element of compounds 1 – 3 is a six‐membered ring formed by N(1)–C(1)–C(2)–C(3)–N(2) and magnesium. The structures of 1 and 2 show the β‐diketoiminate backbone in a boat‐conformation with the tetrahedrally coordinated metal center at the prow and the opposing carbon atom at the stern. The magnesium atom in 3 is octahedrally coordinated and out of the β‐diketoiminate plane. 相似文献
58.
59.
Much recent research in the educational field has been concerned with finding out the ideas which learners typically hold to explain phenomena and fundamental ideas in chemistry. Some of these conceptions do not correspond with the scientific view, for example the transfer of properties from the level of substances onto the level of particles. Many students fall back on their original conceptions outside the classroom. Examples of those daily‐life concepts and their development are presented here. 相似文献
60.
Agricola Ilka Dileo Giulia Stecker Leander 《Annals of Global Analysis and Geometry》2021,60(1):111-141
Annals of Global Analysis and Geometry - We show that every 3- $$(\alpha ,\delta )$$ -Sasaki manifold of dimension $$4n + 3$$ admits a locally defined Riemannian submersion over a quaternionic... 相似文献