315 research outputs found

    SMW Wall for Seepage Control in Levee Reconstruction

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    An SMW wall was installed as a cutoff wall for seepage control during high floods in a narrow levee constructed in the early 1900\u27s using sandy soils. After part of the wall was installed, difficulties were encountered in evaluating the permeability of the as-built cutoff wall according to the project specifications. Methods used to evaluate the permeability of the cutoff wall included laboratory tests on bulk samples and core samples and in-situ permeability tests. Significant differences in test results were caused by various sample preparation and handling procedures, sampling disturbance, and different testing methods. The difficulties were resolved by performing a trial mix study and installing a full scale test section that resulted in changed installation, sampling, and testing procedures

    Running coupling in Yang-Mills theory - a flow equation study -

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    The effective average action of Yang-Mills theory is analyzed in the framework of exact renormalization group flow equations. Employing the background-field method and using a cutoff that is adjusted to the spectral flow, the running of the gauge coupling is obtained on all scales. In four dimensions and for the gauge groups SU(2) and SU(3), the coupling approaches a fixed point in the infrared.Comment: 35 pages, 3 figures, v2: References added, minor improvements, version to appear in PR

    Transport Properties of the Quark-Gluon Plasma -- A Lattice QCD Perspective

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    Transport properties of a thermal medium determine how its conserved charge densities (for instance the electric charge, energy or momentum) evolve as a function of time and eventually relax back to their equilibrium values. Here the transport properties of the quark-gluon plasma are reviewed from a theoretical perspective. The latter play a key role in the description of heavy-ion collisions, and are an important ingredient in constraining particle production processes in the early universe. We place particular emphasis on lattice QCD calculations of conserved current correlators. These Euclidean correlators are related by an integral transform to spectral functions, whose small-frequency form determines the transport properties via Kubo formulae. The universal hydrodynamic predictions for the small-frequency pole structure of spectral functions are summarized. The viability of a quasiparticle description implies the presence of additional characteristic features in the spectral functions. These features are in stark contrast with the functional form that is found in strongly coupled plasmas via the gauge/gravity duality. A central goal is therefore to determine which of these dynamical regimes the quark-gluon plasma is qualitatively closer to as a function of temperature. We review the analysis of lattice correlators in relation to transport properties, and tentatively estimate what computational effort is required to make decisive progress in this field.Comment: 54 pages, 37 figures, review written for EPJA and APPN; one parag. added end of section 3.4, and one at the end of section 3.2.2; some Refs. added, and some other minor change

    Theory of finite temperature crossovers near quantum critical points close to, or above, their upper-critical dimension

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    A systematic method for the computation of finite temperature (TT) crossover functions near quantum critical points close to, or above, their upper-critical dimension is devised. We describe the physics of the various regions in the TT and critical tuning parameter (tt) plane. The quantum critical point is at T=0T=0, t=0t=0, and in many cases there is a line of finite temperature transitions at T=Tc(t)T = T_c (t), t<0t < 0 with Tc(0)=0T_c (0) = 0. For the relativistic, nn-component ϕ4\phi^4 continuum quantum field theory (which describes lattice quantum rotor (n2n \geq 2) and transverse field Ising (n=1n=1) models) the upper critical dimension is d=3d=3, and for d<3d<3, ϵ=3d\epsilon=3-d is the control parameter over the entire phase diagram. In the region TTc(t)Tc(t)|T - T_c (t)| \ll T_c (t), we obtain an ϵ\epsilon expansion for coupling constants which then are input as arguments of known {\em classical, tricritical,} crossover functions. In the high TT region of the continuum theory, an expansion in integer powers of ϵ\sqrt{\epsilon}, modulo powers of lnϵ\ln \epsilon, holds for all thermodynamic observables, static correlators, and dynamic properties at all Matsubara frequencies; for the imaginary part of correlators at real frequencies (ω\omega), the perturbative ϵ\sqrt{\epsilon} expansion describes quantum relaxation at ωkBT\hbar \omega \sim k_B T or larger, but fails for ωϵkBT\hbar \omega \sim \sqrt{\epsilon} k_B T or smaller. An important principle, underlying the whole calculation, is the analyticity of all observables as functions of tt at t=0t=0, for T>0T>0; indeed, analytic continuation in tt is used to obtain results in a portion of the phase diagram. Our method also applies to a large class of other quantum critical points and their associated continuum quantum field theories.Comment: 36 pages, 4 eps figure

    Do Instantons Like a Colorful Background?

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    We investigate chiral symmetry breaking and color symmetry breaking in QCD. The effective potential of the corresponding scalar condensates is discussed in the presence of non-perturbative contributions from the semiclassical one-instanton sector. We concentrate on a color singlet scalar background which can describe chiral condensation, as well as a color octet scalar background which can generate mass for the gluons. Whereas a non-vanishing singlet chiral field is favored by the instantons, we have found no indication for a preference of color octet backgrounds.Comment: 25 pages, 7 figure

    Myocarditis following COVID-19 vaccine: incidence, presentation, diagnosis, pathophysiology, therapy, and outcomes put into perspective. A clinical consensus document supported by the Heart Failure Association of the European Society of Cardiology (ESC) and the ESC Working Group on Myocardial and Pericardial Diseases

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    Over 10 million doses of COVID-19 vaccines based on RNA technology, viral vectors, recombinant protein, and inactivated virus have been administered worldwide. Although generally very safe, post-vaccine myocarditis can result from adaptive humoral and cellular, cardiac-specific inflammation within days and weeks of vaccination. Rates of vaccine-associated myocarditis vary by age and sex with the highest rates in males between 12 and 39 years. The clinical course is generally mild with rare cases of left ventricular dysfunction, heart failure and arrhythmias. Mild cases are likely underdiagnosed as cardiac magnetic resonance imaging (CMR) is not commonly performed even in suspected cases and not at all in asymptomatic and mildly symptomatic patients. Hospitalization of symptomatic patients with electrocardiographic changes and increased plasma troponin levels is considered necessary in the acute phase to monitor for arrhythmias and potential decline in left ventricular function. In addition to evaluation for symptoms, electrocardiographic changes and elevated troponin levels, CMR is the best non-invasive diagnostic tool with endomyocardial biopsy being restricted to severe cases with heart failure and/or arrhythmias. The management beyond. guideline-directed treatment of heart failure and arrhythmias includes non-specific measures to control pain. Anti-inflammatory drugs such as non-steroidal anti-inflammatory drugs, and corticosteroids have been used in more severe cases, with only anecdotal evidence for their effectiveness. In all age groups studied, the overall risks of SARS-CoV-2 infection-related hospitalization and death are hugely greater than the risks from post-vaccine myocarditis. This consensus statement serves as a practical resource for physicians in their clinical practice, to understand, diagnose, and manage affected patients. Furthermore, it is intended to stimulate research in this area

    The Infrared Behaviour of the Pure Yang-Mills Green Functions

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    We review the infrared properties of the pure Yang-Mills correlators and discuss recent results concerning the two classes of low-momentum solutions for them reported in literature; i.e. decoupling and scaling solutions. We will mainly focuss on the Landau gauge and pay special attention to the results inferred from the analysis of the Dyson-Schwinger equations of the theory and from "{\it quenched}" lattice QCD. The results obtained from properly interplaying both approaches are strongly emphasized.Comment: Final version to be published in FBS (54 pgs., 11 figs., 4 tabs

    Moments of Nucleon Light Cone Quark Distributions Calculated in Full Lattice QCD

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    Moments of the quark density, helicity, and transversity distributions are calculated in unquenched lattice QCD. Calculations of proton matrix elements of operators corresponding to these moments through the operator product expansion have been performed on 163×3216^3 \times 32 lattices for Wilson fermions at β=5.6\beta = 5.6 using configurations from the SESAM collaboration and at β=5.5\beta = 5.5 using configurations from SCRI. One-loop perturbative renormalization corrections are included. At quark masses accessible in present calculations, there is no statistically significant difference between quenched and full QCD results, indicating that the contributions of quark-antiquark excitations from the Dirac Sea are small. Close agreement between calculations with cooled configurations containing essentially only instantons and the full gluon configurations indicates that quark zero modes associated with instantons play a dominant role. Naive linear extrapolation of the full QCD calculation to the physical pion mass yields results inconsistent with experiment. Extrapolation to the chiral limit including the physics of the pion cloud can resolve this discrepancy and the requirements for a definitive chiral extrapolation are described.Comment: 53 Pages Revtex, 26 Figures, 9 Tables. Added additional reference and updated referenced data in Table I

    Genetic inhibition of neurotransmission reveals role of glutamatergic input to dopamine neurons in high-effort behavior

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    Midbrain dopamine neurons are crucial for many behavioral and cognitive functions. As the major excitatory input, glutamatergic afferents are important for control of the activity and plasticity of dopamine neurons. However, the role of glutamatergic input as a whole onto dopamine neurons remains unclear. Here we developed a mouse line in which glutamatergic inputs onto dopamine neurons are specifically impaired, and utilized this genetic model to directly test the role of glutamatergic inputs in dopamine-related functions. We found that while motor coordination and reward learning were largely unchanged, these animals showed prominent deficits in effort-related behavioral tasks. These results provide genetic evidence that glutamatergic transmission onto dopaminergic neurons underlies incentive motivation, a willingness to exert high levels of effort to obtain reinforcers, and have important implications for understanding the normal function of the midbrain dopamine system.Fil: Hutchison, M. A.. National Institutes of Health; Estados UnidosFil: Gu, X.. National Institutes of Health; Estados UnidosFil: Adrover, Martín Federico. National Institutes of Health; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; ArgentinaFil: Lee, M. R.. National Institutes of Health; Estados UnidosFil: Hnasko, T. S.. University of California at San Diego; Estados UnidosFil: Alvarez, V. A.. National Institutes of Health; Estados UnidosFil: Lu, W.. National Institutes of Health; Estados Unido

    Low Energy Chiral Lagrangian in Curved Space-Time from the Spectral Quark Model

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    We analyze the recently proposed Spectral Quark Model in the light of Chiral Perturbation Theory in curved space-time. In particular, we calculate the chiral coefficients L1,...,L10L_1, ..., L_{10}, as well as the coefficients L11L_{11}, L12L_{12}, and L13L_{13}, appearing when the model is coupled to gravity. The analysis is carried for the SU(3) case. We analyze the pattern of chiral symmetry breaking as well as elaborate on the fulfillment of anomalies. Matching the model results to resonance meson exchange yields the relation between the masses of the scalar, tensor and vector mesons, Mf0=Mf2=2MV=43/NcπfπM_{f_0}=M_{f_2}=\sqrt{2} M_V= 4 \sqrt{3 /N_c} \pi f_\pi. Finally, the large-NcN_c limit suggests the dual relations in the vector and scalar channels, MV=MS=26/NcπfπM_V=M_S= 2 \sqrt{6 /N_c} \pi f_\pi and S1/2=<r2>V1/2=2Nc/fπ=0.59fm^{1/2}_S = < r^2 >^{1/2}_V = 2 \sqrt{N_c} / f_\pi = 0.59 {\rm fm} .Comment: 18 pages, no figure
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