29 research outputs found
Path integral approach for superintegrable potentials on spaces of non-constant curvature: II. Darboux spaces DIII and DIV
No full textThis is the second paper on the path integral approach of superintegrable systems on Darboux spaces, spaces of non-constant curvature. We analyze five and four superintegrable potentials in the spaces D III and D IV, respectively; these potentials were first given by Kalnins et al. We are able to evaluate the path integral in most of the separating coordinate systems, leading to expressions for the Green's functions, the discrete and continuous wavefunctions, and the discrete energy spectra. In some cases, however, the discrete spectrum cannot be stated explicitly because it is determined by a higher-order polynomial equation. We also show that the free motion in a Darboux space of type III can contain bound states, provided the boundary conditions are appropriate. We can state the corresponding energy spectrum and the wavefunctions. � 2007 Pleiades Publishing, Ltd
Asymmetric synthesis of 2,2-disubstituted chromanols. novel approaches to vitamin E analogues
No full textUnsymmetrically Substituted Iridium(III)−Carbene Complexes by a CH-Activation Process<sup>†</sup>
No full textThe synthesis of the metalhydride Cp*(L‘)IrH+OTf - (L‘ = 1-(2-cyclohexenyl)-3-cyclohexylimidazolin-2-ylidene, OTf = OSO2CF3) is achieved by a cyclohexane to cyclohexene
transformation at the N-heterocyclic carbene ligand based on a CH-activation/β-hydrogen
migration process at the Ir(III) center under mild conditions. The synthetic route to Cp*(L‘)IrH+OTf - and NMR spectroscopic and X-ray structural data are presented
Separation of variables in path integrals and path integral solution of two potentials on the Poincare upper half-plane
No full textThe author discusses how to separate variables in path integrals. It is assumed that a one-dimensional problem with potential V(x) has an exact solution with energy levels Elambda and wavefunctions Psi lambda . In order to perform the separation of variables, a time transformation is performed back and forth in the path integral which allows one to insert the path integral solution corresponding to the potential V(x). The author illustrates the method by discussing some specific potential problems on the Poincare upper half-plane
Path integrals for potential problems with -function perturbation
No full textThe author presents several examples of potential problems with a δ-function perturbation by means of path integrals. The idea is to sum a perturbation series expansion resulting in an energy-dependent Green function G(E). The energy levels E of the perturbed problem are determined by the equation (one-dimensional case) iG(a, a; E)=/ gamma where G is the Green function of the unperturbed problem, gamma is the strength of the δ potential and a its location in R. In D-dimensional radial problems with a spherically shaped delta function located at r=a this equation changes into iGl(a, a; E)=/a , where l denotes the angular momentum number
Single cell genomics-based analysis of gene content and expression of prophages in a diffuse-flow deep-sea hydrothermal system
No full text© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Labonte, J. M., Pachiadaki, M., Fergusson, E., McNichol, J., Grosche, A., Gulmann, L. K., Vetriani, C., Sievert, S. M., & Stepanauskas, R. Single cell genomics-based analysis of gene content and expression of prophages in a diffuse-flow deep-sea hydrothermal system. Frontiers in Microbiology, 10, (2019): 1262, doi:10.3389/fmicb.2019.01262.Phage–host interactions likely play a major role in the composition and functioning of many microbiomes, yet remain poorly understood. Here, we employed single cell genomics to investigate phage–host interactions in a diffuse-flow, low-temperature hydrothermal vent that may be reflective of a broadly distributed biosphere in the subseafloor. We identified putative prophages in 13 of 126 sequenced single amplified genomes (SAGs), with no evidence for lytic infections, which is in stark contrast to findings in the surface ocean. Most were distantly related to known prophages, while their hosts included bacterial phyla Campylobacterota, Bacteroidetes, Chlorobi, Proteobacteria, Lentisphaerae, Spirochaetes, and Thermotogae. Our results suggest the predominance of lysogeny over lytic interaction in diffuse-flow, deep-sea hydrothermal vents, despite the high activity of the dominant Campylobacteria that would favor lytic infections. We show that some of the identified lysogens have co-evolved with their host over geological time scales and that their genes are transcribed in the environment. Functional annotations of lysogeny-related genes suggest involvement in horizontal gene transfer enabling host’s protection against toxic metals and antibacterial compounds.This work was supported by the U.S. National Science Foundation’s Dimensions of Biodiversity Program [OCE-1136488 (to RS), OCE-1136727 (to SMS) and OCE-1136451 (to CV)], as well as DEB-1441717 and OCE-1335810 (to RS), and the DOE JGI CSP project 1477
Control of Leading-Edge Flow Separation from Airfoils by Acoustic Excitation
No full textSince several years experiments are carried out at DLR Goettingen to investigate the feasibility of controlling the laminar- turbulent boundary layer transition by means of periodic, in particular acoustic, excitation of the unstable laminar boundary layer. Similar techniques can be applied to diminish the flow separation from airfoils or to shift the onset of separation to higher angles of incidence. Work on this problem has been carried out by V.V. Kozlov and A.V. Dovgal of ITAM Novosibirsk in cooperation with the first author during their stay at Goettingen as guest scientists. The paper concern mainly windtunnel experiments on the control of three-dimensional separation from a wing by external acoustic excitation
The transition frequencies of the D lines of <sup>39</sup>K, <sup>40</sup>K, and <sup>41</sup>K measured with a femtosecond laser frequency comb
No full textPracticability of investigating artifically forced instabilities in planar laminar boundary layers at Mach 5 in the Ludwieg-tube Göttingen (RWG)
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