186 research outputs found
Application of Jain and Munczek's bound-state approach to gamma gamma-processes of pi0, eta_c and eta_b
We point out the problems affecting most quark--antiquark bound state
approaches when they are faced with the electromagnetic processes dominated by
Abelian axial anomaly. However, these problems are resolved in the consistently
coupled Schwinger-Dyson and Bethe-Salpeter approach. Using one of the most
successful variants of this approach, we find the dynamically dressed
propagators of the light u and d quarks, as well as the heavy c and b quarks,
and find the Bethe-Salpeter amplitudes for their bound states pi0, eta_c and
\eta_b. Thanks to incorporating the dynamical chiral symmetry breaking, the
pion simultaneously appears as the (pseudo)Goldstone boson. We give the
theoretical predictions for the gamma-gamma decay widths of pi0, eta_c and
eta_b, and for the pi0 gamma* -> gamma transition form factor, and compare them
with experiment. In the chiral limit, the axial-anomaly result for
pi0->gamma-gamma is reproduced analytically in the consistently coupled
Schwinger-Dyson and Bethe-Salpeter approach, provided that the quark-photon
vertex is dressed consistently with the quark propagator, so that the vector
Ward-Takahashi identity of QED is obeyed. On the other hand, the present
approach is also capable of quantitatively describing systems of heavy quarks,
concretely eta_c and possibly eta_b, and their gamma-gamma decays. We discuss
the reasons for the broad phenomenological success of the bound-state approach
of Jain and Munczek.Comment: RevTeX, 37 pages, 7 eps figures, submitted to Int. J. Mod. Phys.
Leptonic Decays of Heavy Quarks on the Lattice
The status of lattice calculations of heavy-light decay constants and of the
parameter is reviewed. After describing the lattice approach to heavy
quark systems, the main results are discussed, with special emphasis on the
systematic errors in present lattice calculations. A detailed analysis of the
continuum limit for decay constants is performed. The implications of lattice
results on studies of CP violation in the Standard Model are discussed.Comment: Invited review to be published in Int. J. Mod. Phys. A, 63 pages,
LaTeX, ijmpa1.sty (included), 8 postscript figure
Genome-wide haplotype association study identifies the SLC22A3-LPAL2-LPA gene cluster as a risk locus for coronary artery disease
Perspectives on the use of transcriptomics to advance biofuels
As a field within the energy research sector, bioenergy is continuously expanding. Although much has been achieved and the yields of both ethanol and butanol have been improved, many avenues of research to further increase these yields still remain. This review covers current research related with transcriptomics and the application of this high-throughput analytical tool to engineer both microbes and plants with the penultimate goal being better biofuel production and yields. The initial focus is given to the responses of fermentative microbes during the fermentative production of acids, such as butyric acid, and solvents, including ethanol and butanol. As plants offer the greatest natural renewable source of fermentable sugars within the form of lignocellulose, the second focus area is the transcriptional responses of microbes when exposed to plant hydrolysates and lignin-related compounds. This is of particular importance as the acid/base hydrolysis methods commonly employed to make the plant-based cellulose available for enzymatic hydrolysis to sugars also generates significant amounts of lignin-derivatives that are inhibitory to fermentative bacteria and microbes. The article then transitions to transcriptional analyses of lignin-degrading organisms, such as Phanerochaete chrysosporium, as an alternative to acid/base hydrolysis. The final portion of this article will discuss recent transcriptome analyses of plants and, in particular, the genes involved in lignin production. The rationale behind these studies is to eventually reduce the lignin content present within these plants and, consequently, the amount of inhibitors generated during the acid/base hydrolysis of the lignocelluloses. All four of these topics represent key areas where transcriptomic research is currently being conducted to identify microbial genes and their responses to products and inhibitors as well as those related with lignin degradation/formation.clos
Spin-Dependent Twist-Four Matrix Elements from g_1 Data in the Resonance Region
Matrix elements of spin-dependent twist-four operators are extracted from
recent data on the spin-dependent g_1 structure function of the proton and
deuteron in the resonance region. We emphasize the need to include the elastic
contributions to the first moments of the structure functions at Q^2 < 2 GeV^2.
The coefficients of the 1/Q^2 corrections to the Ellis-Jaffe sum rules are
found to be 0.04 \pm 0.02 and 0.03 \pm 0.04 GeV^2 for the proton and neutron,
respectively.Comment: 10 pages REVTeX, 4 figure
Structure Functions of the Nucleon and their Interpretation
The current status of measurements of the nucleon structure functions and
their understanding is reviewed. The fixed target experiments E665, CCFR and
NMC and the HERA experiments H1 and ZEUS are discussed in some detail. The
extraction of parton momentum distribution functions from global fits is
described, with particular attention paid to much improved information on the
gluon momentum distribution. The status of alpha_s measurements from deep
inelastic data is reviewed. Models and non-perturbative approaches for the
parton input distributions are outlined. The impact on the phenomenology of QCD
of the data at very low values of the Bjorken x variable is discussed in
detail. Recent advances in the understanding of the transition from deep
inelastic scattering to photoproduction are summarised. Some brief comments are
made on the recent HERA measurements of the ep NC and CC cross-sections at very
high Q2.Comment: 196 pages, 79 figures, uses ijmpa.sty and psfig.tex (included
Can Antiviral Drugs Contain Pandemic Influenza Transmission?
Antiviral drugs dispensed during the 2009 influenza pandemic generally failed to
contain transmission. This poses the question of whether preparedness for a
future pandemic should include plans to use antiviral drugs to mitigate
transmission
Point absorbers in Advanced LIGO
Published 30 April 2021Small, highly absorbing points are randomly present on the surfaces of the main interferometer optics in Advanced LIGO. The resulting nanometer scale thermo-elastic deformations and substrate lenses from these micron-scale absorbers significantly reduce the sensitivity of the interferometer directly though a reduction in the power-recycling gain and indirect interactions with the feedback control system. We review the expected surface deformation from point absorbers and provide a pedagogical description of the impact on power buildup in second generation gravitational wave detectors (dual-recycled Fabry-Perot Michelson interferometers). This analysis predicts that the power-dependent reduction in interferometer performance will significantly degrade maximum stored power by up to 50% and, hence, limit GW sensitivity, but it suggests system wide corrections that can be implemented in current and future GW detectors. This is particularly pressing given that future GW detectors call for an order of magnitude more stored power than currently used in Advanced LIGO in Observing Run 3. We briefly review strategies to mitigate the effects of point absorbers in current and future GW wave detectors to maximize the success of these enterprises.Aidan F. Brooks ... Daniel D. Brown ... Huy Tuong Cao ... Alexei A. Ciobanu ... David J. Ottaway ... Peter J. Veitch ... et al
Sensitivity and performance of the Advanced LIGO detectors in the third observing run
On April 1st, 2019, the Advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO), joined by the Advanced Virgo detector, began the third observing run, a year-long dedicated search for gravitational radiation. The LIGO detectors have achieved a higher duty cycle and greater sensitivity to gravitational waves than ever before, with LIGO Hanford achieving angle-averaged sensitivity to binary neutron star coalescences to a distance of 111 Mpc, and LIGO Livingston to 134 Mpc with duty factors of 74.6% and 77.0% respectively. The improvement in sensitivity and stability is a result of several upgrades to the detectors, including doubled intracavity power, the addition of an in-vacuum optical parametric oscillator for squeezed-light injection, replacement of core optics and end reaction masses, and installation of acoustic mode dampers. This paper explores the purposes behind these upgrades, and explains to the best of our knowledge the noise currently limiting the sensitivity of each detector.A Buikema ⊠D.D. Brown ⊠A.A. Ciobanu ⊠D.J. Ottaway ⊠P.J. Veitch ⊠et al
Slower is not always better: Response-time evidence clarifies the limited role of miserly information processing in the Cognitive Reflection Test
We report a study examining the role of `cognitive miserliness' as a determinant of poor performance on the standard three-item Cognitive Reflection Test (CRT). The cognitive miserliness hypothesis proposes that people often respond incorrectly on CRT items because of an unwillingness to go beyond default, heuristic processing and invest time and effort in analytic, reflective processing. Our analysis (N = 391) focused on people's response times to CRT items to determine whether predicted associations are evident between miserly thinking and the generation of incorrect, intuitive answers. Evidence indicated only a weak correlation between CRT response times and accuracy. Item-level analyses also failed to demonstrate predicted response time differences between correct analytic and incorrect intuitive answers for two of the three CRT items. We question whether participants who give incorrect intuitive answers on the CRT can legitimately be termed cognitive misers and whether the three CRT items measure the same general construct
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