19,343 research outputs found
Studies on · 4-Pyrones and 4-Pyridones. II. The Preparation . and Rearrangement of 3-Allyloxy-4-pyrone
Prep aration of 3-allyloxy-4-pyrone (II), the Claisen rearrangement
of II to 3 .~hydroxy -2-allyl-4 -pyrone (IV) an d synthesis of a
number of related compounds are described
An analytic Approach to Turaev's Shadow Invariant
In the present paper we extend the "torus gauge fixing approach" by Blau and
Thompson (Nucl. Phys. B408(1):345--390, 1993) for Chern-Simons models with base
manifolds M of the form M= \Sigma x S^1 in a suitable way. We arrive at a
heuristic path integral formula for the Wilson loop observables associated to
general links in M. We then show that the right-hand side of this formula can
be evaluated explicitly in a non-perturbative way and that this evaluation
naturally leads to the face models in terms of which Turaev's shadow invariant
is defined.Comment: 44 pages, 2 figures. Changes have been made in Sec. 2.3, Sec 2.4,
Sec. 3.4, and Sec. 3.5. Appendix C is ne
From simplicial Chern-Simons theory to the shadow invariant II
This is the second of a series of papers in which we introduce and study a
rigorous "simplicial" realization of the non-Abelian Chern-Simons path integral
for manifolds M of the form M = Sigma x S1 and arbitrary simply-connected
compact structure groups G. More precisely, we introduce, for general links L
in M, a rigorous simplicial version WLO_{rig}(L) of the corresponding Wilson
loop observable WLO(L) in the so-called "torus gauge" by Blau and Thompson
(Nucl. Phys. B408(2):345-390, 1993). For a simple class of links L we then
evaluate WLO_{rig}(L) explicitly in a non-perturbative way, finding agreement
with Turaev's shadow invariant |L|.Comment: 53 pages, 1 figure. Some minor changes and corrections have been mad
Small Open Reading Frames, Non-Coding RNAs and Repetitive Elements in Bradyrhizobium japonicum USDA 110
Small open reading frames (sORFs) and genes for non-coding RNAs are poorly investigated components of most genomes. Our analysis of 1391 ORFs recently annotated in the soybean symbiont Bradyrhizobium japonicum USDA 110 revealed that 78% of them contain less than 80 codons. Twenty-one of these sORFs are conserved in or outside Alphaproteobacteria and most of them are similar to genes found in transposable elements, in line with their broad distribution. Stabilizing selection was demonstrated for sORFs with proteomic evidence and bll1319_ISGA which is conserved at the nucleotide level in 16 alphaproteobacterial species, 79 species from other taxa and 49 other Proteobacteria. Further we used Northern blot hybridization to validate ten small RNAs (BjsR1 to BjsR10) belonging to new RNA families. We found that BjsR1 and BjsR3 have homologs outside the genus Bradyrhizobium, and BjsR5, BjsR6, BjsR7, and BjsR10 have up to four imperfect copies in Bradyrhizobium genomes. BjsR8, BjsR9, and BjsR10 are present exclusively in nodules, while the other sRNAs are also expressed in liquid cultures. We also found that the level of BjsR4 decreases after exposure to tellurite and iron, and this down-regulation contributes to survival under high iron conditions. Analysis of additional small RNAs overlapping with 3-UTRs revealed two new repetitive elements named Br-REP1 and Br-REP2. These REP elements may play roles in the genomic plasticity and gene regulation and could be useful for strain identification by PCR-fingerprinting. Furthermore, we studied two potential toxin genes in the symbiotic island and confirmed toxicity of the yhaV homolog bll1687 but not of the newly annotated higB homolog blr0229_ISGA in E. coli. Finally, we revealed transcription interference resulting in an antisense RNA complementary to blr1853, a gene induced in symbiosis. The presented results expand our knowledge on sORFs, non-coding RNAs and repetitive elements in B. japonicum and related bacteria
Electrotransport and magnetic properies of Cr-GaSb spintronic materials synthesized under high pressure
Electrotarnsport and magnetic properties of new phases in the system Cr-GaSb
were studied. The samples were prepared by high-pressure (P=6-8 GPa)
high-temperature treatment and identified by x-ray diffraction and scanning
electron microscopy (SEM). One of the CrGaSb phases with an
orthorhombic structure has a combination of ferromagnetic and
semiconductor properties and is potentially promising for spintronic
applications. Another high-temperature phase is paramagnetic and identified as
tetragonal
CP violation at one loop in the polarization-independent chargino production in e+e- collisions
Recently Osland and Vereshagin noticed, based on sample calculations of some
box diagrams, that in unpolarised e+e- collisions CP-odd effects in the
non-diagonal chargino-pair production process are generated at one-loop. Here
we perform a full one-loop analysis of these effects and point out that in some
cases the neglected vertex and self-energy contributions may play a dominant
role. We also show that CP asymmetries in chargino production are sensitive not
only to the phase of mu parameter in the chargino sector but also to the phase
of stop trilinear coupling A_t.Comment: 14 pages, 5 figure
Mechanisms of rolling contact spalling
The results of a study aimed at analyzing the mechanical material interactions responsible for rolling contact spalling of the 440 C steel, high pressure oxygen turbopump bearings are presented. A coupled temperature displacement finite element analysis of the effects of friction heating under the contact is presented. The contact is modelled as a stationary, heat generating, 2 dimensional indent in an elastic perfectly plastic half-space with heat fluxes up to 8.6 x 10000 KW/m sq comparable to those generated in the bearing. Local temperatures in excess of 1000 C are treated. The calculations reveal high levels of residual tension after the contact is unloaded and cools. Efforts to promote Mode 2/Mode 3 fatigue crack growth under cyclic torsion in hardened 440 C steel are described. Spalls produced on 440 C steel by a 3 ball/rod rolling contact testing machine were studied with scanning microscopy. The shapes of the cyclic, stress strain hysteresis loops displayed by hardened 440 C steel in cyclic torsion at room temperature are defined for the plastic strain amplitudes encountered in rolling/sliding contact. Results of these analyses are discussed in detail
Loopedia, a Database for Loop Integrals
Loopedia is a new database at loopedia.org for information on Feynman
integrals, intended to provide both bibliographic information as well as
results made available by the community. Its bibliometry is complementary to
that of SPIRES or arXiv in the sense that it admits searching for integrals by
graph-theoretical objects, e.g. its topology.Comment: 16 pages, lots of screenshot
Higgs Phenomenology in Warped Extra-Dimensions with a 4th Generation
We study a warped extra-dimension scenario where the Standard Model fields
lie in the bulk, with the addition of a fourth family of fermions. We
concentrate on the flavor structure of the Higgs couplings with fermions in the
flavor anarchy ansatz. Even without a fourth family, these couplings will be
generically misaligned with respect to the SM fermion mass matrices. The
presence of the fourth family typically enhances the misalignment effects and
we show that one should expect them to be highly non-symmetrical in the
inter-generational mixing. The radiative corrections from the new
fermions and their flavor violating couplings to the Higgs affect negligibly
known experimental precision measurements such as the oblique parameters and
or . On the other hand,
processes, mediated by tree-level Higgs exchange, as well as radiative
corrections to and put some generic pressure
on the allowed size of the flavor violating couplings. But more importantly,
these couplings will alter the Higgs decay patterns as well as those of the new
fermions, and produce very interesting new signals associated to Higgs
phenomenology in high energy colliders. These might become very important
indirect signals for these type of models as they would be present even when
the KK mass scale is high and no heavy KK particle is discovered.Comment: 39 pages, 6 figure
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