1,165 research outputs found
Ambient Isotopic Meshing of Implicit Algebraic Surface with Singularities
A complete method is proposed to compute a certified, or ambient isotopic,
meshing for an implicit algebraic surface with singularities. By certified, we
mean a meshing with correct topology and any given geometric precision. We
propose a symbolic-numeric method to compute a certified meshing for the
surface inside a box containing singularities and use a modified
Plantinga-Vegter marching cube method to compute a certified meshing for the
surface inside a box without singularities. Nontrivial examples are given to
show the effectiveness of the algorithm. To our knowledge, this is the first
method to compute a certified meshing for surfaces with singularities.Comment: 34 pages, 17 Postscript figure
Impact of Subleading Corrections on Hadronic B Decays
We study the subleading corrections originating from the 3-parton (q\bar q g)
Fock states of final-state mesons in B decays. The corrections could give
significant contributions to decays involving an \omega or \eta^{(\prime)} in
the final states. Our results indicate the similarity of \omega K and \omega
\pi^- rates, of order 5\times 10^{-6}, consistent with the recent measurements.
We obtain a_2(B\to J/\psi K)\approx 0.27+0.05i, in good agreement with data.
Without resorting to the unknown singlet annihilation effects, 3-parton Fock
state contributions can enhance the branching ratios of K\eta' to the level
above 50\times 10^{-6}.Comment: 5 pages, 5 figures, revtex4; some typos corrected, a new figure and a
reference added, more explanations for the calculation provided, to appear in
Phys. Rev.
Implications of Recent Measurements of Hadronic Charmless B Decays
Implications of recent CLEO measurements of hadronic charmless B decays are
discussed. (i) Employing the Bauer-Stech-Wirbel (BSW) model for form factors as
a benchmark, the data indicate that the form factor
is smaller than that predicted by the BSW model, whereas the
data of imply that the form factors are greater than the BSW model's values. (ii) The tree-dominated
modes imply that the effective
number of colors N_c(LL) for (V-A)(V-A) operators is preferred to be smaller,
while the current limit on shows that N_c(LR)>3. The data of and clearly indicate that . (iii) In
order to understand the observed suppression of and
non-suppression of modes, both being governed by the form factor
, the unitarity angle is preferred to be greater than
. By contrast, the new measurement of no
longer strongly favors . (iv) The observed pattern K^-\pi^+\sim
\ov K^0\pi^-\sim {2\over 3}K^-\pi^0 is consistent with the theoretical
expectation: The constructive interference between electroweak and QCD penguin
diagrams in the mode explains why {\cal B}(B^-\to K^-\pi^0)>{1\over
2}{\cal B}(\ov B^0\to K^-\pi^+). (v) The observation \nc(LL)<3<\nc(LR) and
our preference for \nc(LL)\sim 2 and \nc(LR)\sim 6 are justified by a
recent perturbative QCD calculation of hadronic rare B decays in the heavy
quark limit.Comment: 21 pages; CLEO measurements of several charmless B decay modes are
updated. Discussion of the unitarity angle gamma in the \rho\pi mode is
revise
Non-renormalization of induced charges and constraints on strongly coupled theories
It is shown that global fermionic charges induced in vacuum by slowly
varying, topologically non-trivial background scalar fields are not
renormalized provided that expansion in momenta of background fields is valid.
This suggests that strongly coupled theories obey induced charge matching
conditions which are analogous, but generally not equivalent, to 't Hooft
anomaly matching conditions. We give a few examples of induced charge matching.
In particular, the corresponding constraints in softly broken supersymmetric
QCD suggest non-trivial low energy mass pattern, in full accord with the
results of direct analyses.Comment: 19 pages, LaTeX, two PS figures; Submitted to special issue of Phys.
Reports dedicated to 70th birthday of L.B.Oku
Quantification of the boron speciation in alkali borosilicate glasses by electron energy loss spectroscopy
Transmission electron microscopy and related analytical techniques have been widely used to study the microstructure of different materials. However, few research works have been performed in the field of glasses, possibly due to the electron-beam irradiation damage. In this paper, we have developed a method based on electron energy loss spectroscopy (EELS) data acquisition and analyses, which enables determination of the boron speciation in a series of ternary alkali borosilicate glasses with constant molar ratios. A script for the fast acquisition of EELS has been designed, from which the fraction of BO(4) tetrahedra can be obtained by fitting the experimental data with linear combinations of the reference spectra. The BO(4) fractions (N(4)) obtained by EELS are consistent with those from (11)B MAS NMR spectra, suggesting that EELS can be an alternative and convenient way to determine the N(4) fraction in glasses. In addition, the boron speciation of a CeO(2) doped potassium borosilicate glass has been analyzed by using the time-resolved EELS spectra. The results clearly demonstrate that the BO(4) to BO(3) transformation induced by the electron beam irradiation can be efficiently suppressed by doping CeO(2) to the borosilicate glasses
Mutations in Ehrlichia chaffeensis Causing Polar Effects in Gene Expression and Differential Host Specificities
Citation: Cheng, C. M., Nair, A. D. S., Jaworski, D. C., & Ganta, R. R. (2015). Mutations in Ehrlichia chaffeensis Causing Polar Effects in Gene Expression and Differential Host Specificities. Plos One, 10(7), 13. doi:10.1371/journal.pone.0132657Ehrlichia chaffeensis, a tick-borne rickettsial, is responsible for human monocytic ehrlichiosis. In this study, we assessed E. chaffeensis insertion mutations impacting the transcription of genes near the insertion sites. We presented evidence that the mutations within the E. chaffeensis genome at four genomic locations cause polar effects in altering gene expressions. We also reported mutations causing attenuated growth in deer (the pathogen's reservoir host) and in dog (an incidental host), but not in its tick vector, Amblyomma americanum. This is the first study documenting insertion mutations in E. chaffeensis that cause polar effects in altering gene expression from the genes located upstream and downstream to insertion sites and the differential requirements of functionally active genes of the pathogen for its persistence in vertebrate and tick hosts. This study is important in furthering our knowledge on E. chaffeensis pathogenesis
Phenomenological Analysis of B->PP Decays with QCD Factorization
In this paper, we study nonleptonic charmless B decays to two light
pseudoscalar mesons within the frame of QCD factorization, including the
contributions from the chirally enhanced power corrections and weak
annihilation. Predictions for the CP-averaged branching ratios and CP-violating
asymmetries are given. Within the reasonable range of the parameters, we find
that our predictions for the branching ratios of B -> PP are consistent with
the present experimental data. But because of the logarithmic divergences at
the endpoints in the hard spectator scatterings and weak annihilation, there
are still large uncertainties in these predictions.Comment: 34 pages, 5 figures. to appear in PR
On the Geometry of the Nodal Lines of Eigenfunctions of the Two-Dimensional Torus
The width of a convex curve in the plane is the minimal distance between a
pair of parallel supporting lines of the curve. In this paper we study the
width of nodal lines of eigenfunctions of the Laplacian on the standard flat
torus. We prove a variety of results on the width, some having stronger
versions assuming a conjecture of Cilleruelo and Granville asserting a uniform
bound for the number of lattice points on the circle lying in short arcs.Comment: 4 figures. Added some comments about total curvature and other
detail
Some Insight into the Wind-Induced Vibration of Stay Cables in the Context of Rigid Static Inclined Circular Cylinder
Wind-induced cable vibration is a contemporary issue in cable-stayed bridges, which potentially threats the safety
and durability of the structure. A thorough understanding of the fundamental physics underlying these phenomena is
a priori for developing effective remedies to resolve the issue. In the present paper, possible mechanisms associated
with two different types of wind-induced cable vibration phenomena have been studied based on a set of wind tunnel
experimental data on a rigid circular cylinder. A number of analyses were applied to the unsteady surface pressure
data sampled on the cylinder model to elucidate the possible mechanisms of these phenomena. Negative aerodynamic
damping ratios were identified in the ranges of Reynolds number and cylinder orientation where divergent galloping
type of response is expected to occur. A breakdown range of wind-cable relative angle was detected in which the
regular Karman vortex shedding was suppressed within the subcritical Reynolds number range. In the critical
Reynolds number range, however, the symmetry of surrounding flow field beyond this breakdown range could be
altered drastically, leading to considerable changes in the lift force which is responsible for the negative aerodynamic
damping ratio values. Significant increase of correlation length of sectional aerodynamic forces was also detected
within this breakdown range in the critical regime. This, combined with the negative aerodynamic damping, is
proposed to be a possible necessary onset condition for the galloping of dry inclined cables. The limited-amplitude
instability, which occurred in the subcritical Re range, on the other hand, was found to be caused by the mitigation of
regular Karman vortex shedding in the breakdown range while the spatial flow field was strongly correlated. In
addition, the decay in correlation of aerodynamic forces in the critical Re range was believed to be key to the
suppression of this unstable response
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