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151.
The three-loop form factors in massless QCD can be expressed as a linear combination of master integrals. Besides a number of master integrals which factorise into products of one-loop and two-loop integrals, one finds 16 genuine three-loop integrals. Of these, six have the form of a bubble insertion inside a one-loop or two-loop vertex integral. We compute all master integrals with these insertion topologies. 相似文献
152.
We comment on a Letter by Toytman et al. [Opt. Lett.32, 1941 (2007)] in which a novel setup for wide-field imaging in coherent anti-Stokes Raman scattering (CARS) microscopy is demonstrated. There the authors state that our phase-matching implementation of a wide-field CARS system [Appl. Phys. Lett.84, 816 (2004); New J. Phys.8, 36 (2006)] suffers from a strong background from the bulk medium. However, our results show quite the contrary, i.e., that our setup provides a very good signal contrast, due to an almost vanishing background level from the bulk solvent. 相似文献
153.
Rolf Jansen Heinrich Steinmetz Wolf-Dieter Schubert Simone C. Albrecht 《Tetrahedron letters》2008,49(40):5796-5799
Rhizopodin was isolated as cytostatic and weakly antifungal macrolide (1) and later characterized as potent actin-depolymerizing agent. It is produced by the myxobacterium Myxococcus stipitatus, which enables a fermentative supply of the drug for biological studies. We here report a revised structure that characterizes rhizopodin (2) as the first known dimeric bis-lactone exhibiting side chains that terminate in N-methyl-vinylformamide groups, which are otherwise found in smaller marine toxins also targeting the actin cytoskeleton. Compound 2 might function as bivalent inhibitor forming ternary complexes with actin which would explain its high efficacy. 相似文献
154.
Stephanie Kindt Prof. Dr. Markus R. Heinrich 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(47):15344-15348
The Meerwein arylation has recently become an even more powerful tool for the functionalization of alkenes. Besides the attachment of an aryl group, radical reactions of this type allow the introduction of several different heteroatoms and a broad variety of alkenes are meanwhile tolerated as substrates. Closing a long‐standing gap of the methodology, this communication describes the first intermolecular Meerwein‐type carbofluorination. In metal‐free reactions, arylalkyl fluorides were obtained from arylhydrazines and alkenes with Selectfluor acting as oxidant and as radical fluorine source. 相似文献
155.
Tris(oxalato)phosphorus acid and its lithium salt 总被引:1,自引:0,他引:1
Wietelmann U Bonrath W Netscher T Nöth H Panitz JC Wohlfahrt-Mehrens M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(10):2451-2458
The conversion of three equivalents of anhydrous oxalic acid with phosphorus pentachloride yields tris(oxalato)phosphorus acid 1, which crystallizes from diethyl ether solutions as protonated diethyl ether complex [(Et2O)2H](+)[P(C2O3)3)]-. The superacidic compound can be used as catalyst for Friedel-Crafts-type reactions. Upon neutralization with lithium hydride, the lithium salt Li[P(C2O3)3] 2 is obtained, which is highly soluble in aprotic solvents and which exhibits a wide voltage window. Thus, the lithium compound is a promising candidate as electrolyte for high performance non-aqueous batteries. 相似文献
156.
157.
Heinrich Saller 《International Journal of Theoretical Physics》2000,39(2):321-340
The linear particle-antiparticle conjugation C and position space reflection P aswell as the antilinear time reflection T are shown to be inducible by theself-duality of representations for the operation groups SU(2), SL(C2), and R forspin, Lorentz transformations, and time translations, respectively. The definitionof a color-compatible linear CP-reflection for quarks as self-duality induced isimpossible since triplet and antitriplet SU(3)-representations are not linearlyequivalent. 相似文献
158.
159.
160.
AxelG. Griesbeck Thomas Heinrich Michael Oelgemller Arne Molis Axel Heidtmann 《Helvetica chimica acta》2002,85(12):4561-4578
The synthesis of a variety of cyclic peptides from N‐phthaloyl‐protected di‐, tri‐, tetra‐, and pentapeptides with different aminocarboxylic acid tethers by photodecarboxylation – initiated by intramolecular electron transfer – has been explored in aqueous media. The progress and the chemoselectivity of the follow‐up processes after CO2 extrusion were traced by the respective pH/time‐profiles, as well as by the overall change in pH after completion of the reaction. The competition between cyclization and simple oxidative decarboxylation depends on spacer length and geometry, H‐bonding interaction between the electron accepting phthalimide C?O groups and amide H‐atoms, as well as the geometric reorganization coupled with the radical combination step and the formation of the lactam rings. With progressing reaction, hydrolysis of the phthalimide chromophore becomes an increasingly important side reaction due to the constant increase in pH. The use of phosphate‐buffered aqueous media consequently improved the cyclization yields. The ground‐state interactions between amide groups and the terminal COO? group with the imide C?O groups were studied for the model system [N‐(phthaloyl)glycyl]sarcosine ( 1 ) by NMR spectroscopy where the amide (E/Z)‐equilibrium depends on the presence of carboxylate vs. free carboxylic acid, demonstrating the role of H‐bonding and metal coordination. 相似文献