11,591 research outputs found
QCD Approach to B->D \pi Decays and CP Violation
The branching ratios and CP violations of the decays, including
both the color-allowed and the color-suppressed modes, are investigated in
detail within QCD framework by considering all diagrams which lead to three
effective currents of two quarks. An intrinsic mass scale as a dynamical gluon
mass is introduced to treat the infrared divergence caused by the soft
collinear approximation in the endpoint regions, and the Cutkosky rule is
adopted to deal with a physical-region singularity of the on mass-shell quark
propagators. When the dynamical gluon mass is regarded as a universal
scale, it is extracted to be around MeV from one of the
well-measured decay modes. The resulting predictions for all
branching ratios are in agreement with the current experimental measurements.
As these decays have no penguin contributions, there are no direct
asymmetries. Due to interference between the Cabibbo-suppressed and the
Cabibbo-favored amplitudes, mixing-induced CP violations are predicted in the
decays to be consistent with the experimental data at
1- level. More precise measurements will be helpful to extract weak
angle .Comment: 21pages,5 figures,3 tables, typos corrected and numerical result for
one of decay channels is improve
F(T) gravity and k-essence
Modified teleparallel gravity theory with the torsion scalar have recently
gained a lot of attention as a possible explanation of dark energy. We perform
a thorough reconstruction analysis on the so-called models, where
is some general function of the torsion term, and derive conditions for the
equivalence between of models with purely kinetic k-essence. We present
a new class models of -gravity and k-essence. We also proposed some new
models of generalized gases and knot universes as well as some generalizations
of gravity.Comment: 25 page
Searching (the) FIRST radio arcs near ACO clusters
Gravitational lensing (GL) of distant radio sources by galaxy clusters should
produce radio arc(let)s. We extracted radio sources from the FIRST survey near
Abell cluster cores and found their radio position angles to be uniformly
distributed with respect to the cluster centres. This result holds even when we
restrict the sample to the richest or most centrally condensed clusters, and to
sources with high S/N and large axial ratio. Our failure to detect GL with
statistical methods may be due to poor cluster centre positions. We did not
find convincing candidates for arcs either. Our result agrees with theoretical
estimates predicting that surveys much deeper than FIRST are required to detect
the effect. This is in apparent conflict with the detection of such an effect
claimed by Bagchi & Kapahi (1995).Comment: 6 pages; 8 figures and 1 style file are included; to appear in Proc.
"Observational Cosmology with the New Radio Surveys", eds. M. Bremer, N.
Jackson & I. Perez-Fournon, Kluwer Acad. Pres
Fabrication of Large Area Periodic Nanostructures Using Nanosphere Photolithography
Large area periodic nanostructures exhibit unique optical and electronic properties and have found many applications, such as photonic band-gap materials, high dense data storage, and photonic devices. We have developed a maskless photolithography method—Nanosphere Photolithography (NSP)—to produce a large area of uniform nanopatterns in the photoresist utilizing the silica micro-spheres to focus UV light. Here, we will extend the idea to fabricate metallic nanostructures using the NSP method. We produced large areas of periodic uniform nanohole array perforated in different metallic films, such as gold and aluminum. The diameters of these nanoholes are much smaller than the wavelength of UV light used and they are very uniformly distributed. The method introduced here inherently has both the advantages of photolithography and self-assembled methods. Besides, it also generates very uniform repetitive nanopatterns because the focused beam waist is almost unchanged with different sphere sizes
Systemic Inflammatory Cytokines Predict the Infectious Complications but Not Prolonged Postoperative Ileus after Colorectal Surgery
Micromechanical Model for Self-Organized Impurity Nanorod Arrays in Epitaxial YBCO Films
A micromechanical model based on the theory of elasticity has been developed
to study the configuration of self-assembled impurity nanostructures in high
temperature superconducting YBCO films. With the calculated equilibrium strain
and elastic energy of the impurity doped film, a phase diagram of lattice
mismatches elastic constants of the dopant was obtained for the
energetically-preferred orientation of impurity nanorods. The calculation of
the nanorod orientation and the film lattice deformation has yielded an
excellent agreement with experimental measurements
The absolute position of a resonance peak
It is common practice in scattering theory to correlate between the position
of a resonance peak in the cross section and the real part of a complex energy
of a pole of the scattering amplitude. In this work we show that the resonance
peak position appears at the absolute value of the pole's complex energy rather
than its real part. We further demonstrate that a local theory of resonances
can still be used even in cases previously thought impossible
Taxonomy and phylogeny of mud owls (Annelida: Sternaspidae), including a new synonymy and new records from the Southern Ocean, North East Atlantic Ocean and Pacific Ocean: challenges in morphological delimitation
Species delimitation in sternaspid polychaetes is currently based on the morphology of a limited suite of characters, namely characters of the ventro-caudal shield—a unique feature of the family. Sternaspid species description has increased rapidly in recent years; however, the validity of the shield as a diagnostic character has not been assessed through molecular means. This study performs the largest molecular taxonomy of Sternaspidae to date, using the nuclear gene 18S, and the mitochondrial genes 16S and cytochrome oxidase subunit I (COI) to assess phylogenetic relationships within the family, to reassess the placement of Sternaspidae within the wider polychaete tree and to investigate the effectiveness of the shield as a diagnostic morphological character. This study includes many new records and reports Sternaspis affinis Stimpson, 1864 from USA Pacific coastline and genetic connectivity between specimens identified as Sternaspis cf. annenkovae Salazar-Vallejo & Buzhinskaja, 2013 from off southeastern Australia and specimens identified as Sternaspis cf. williamsae Salazar-Vallejo & Buzhinskaja, 2013 from the northwestern Pacific. In addition, we investigate material identified as Sternaspis cf. scutata (Ranzani, 1817) in the English Channel and compare with S. scutata through both molecular and morphological means. We further perform a detailed morphological and molecular investigation of new sternaspid material collected from the Southern Ocean and Antarctic Peninsula and regard Sternaspis monroi Salazar-Vallejo, 2014 syn. n. as a junior synonym of Sternaspis sendalli Salazar-Vallejo, 2014, two species recently described from the region, raising questions concerning the validity of current morphological delimitation.© The Author(s) 2019
Open Access
This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made
Circadian patterns of Wikipedia editorial activity: A demographic analysis
Wikipedia (WP) as a collaborative, dynamical system of humans is an
appropriate subject of social studies. Each single action of the members of
this society, i.e. editors, is well recorded and accessible. Using the
cumulative data of 34 Wikipedias in different languages, we try to characterize
and find the universalities and differences in temporal activity patterns of
editors. Based on this data, we estimate the geographical distribution of
editors for each WP in the globe. Furthermore we also clarify the differences
among different groups of WPs, which originate in the variance of cultural and
social features of the communities of editors
Experiments and numerical simulations to evaluate peeling properties of polymeric coatings for degradable Mg stents
- …