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result(s) for
"Harris, Tim"
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Mountains and highlands
Information about the animals and plants that typically live in mountainous environments.
Book
An Effective COVID-19 Vaccine Needs to Engage T Cells
T cell reactivities in recovered patients covered multiple SARS-CoV-2 proteins and particularly targeted immunodominant epitopes in the spike (S), membrane (M), and nucleoproteins (N), indicating a benefit for including these proteins in vaccine designs rather than only S as done in several current vaccines (32,38). A third study found SARS-CoV-2 specific CD4 and CD8 T cell responses in 56% of AB-negative subjects (40). [...]as seen in SARS and MERS, T cell immunity against SARS-CoV-2 can occur in the absence of humoral immunity, might even be more prevalent in certain populations, associates with recovery, can persist longer and might serve as a more sensitive biomarker for exposure (19,48). Anecdotally, COVID-19 patients enter the hospital lymphopenic but begin to have increased respiratory difficulties as their lymphocyte counts start to recover. A third study suggests increased proportions of SARS-CoV-2 reactive cytotoxic TFH cells with dysfunctional/exhausted gene signatures and of clonally expanded cytotoxic CD4 TH cells producing myeloid cell attracting chemokines; but under-represented SARS-CoV-2 reactive suppressive Treg cells and polyfunctional TH1 and TH17 cells in severe vs. mild COVID-19 (44).
Journal Article
Lizards
Describes different types of lizards, their habitats, what they eat, and other classic questions asked by young zoologists.
Book
Frequency-splitting estimators of single-propagator traces
Single-propagator traces are the most elementary fermion Wick contractions which occur in numerical lattice QCD, and are usually computed by introducing random-noise estimators to profit from volume averaging. The additional contribution to the variance induced by the random noise is typically orders of magnitude larger than the one due to the gauge field. We propose a new family of stochastic estimators of single-propagator traces built upon a frequency splitting combined with a hopping expansion of the quark propagator, and test their efficiency in two-flavour QCD with pions as light as 190 MeV. Depending on the fermion bilinear considered, the cost of computing these diagrams is reduced by one to two orders of magnitude or more with respect to standard random-noise estimators. As two concrete examples of physics applications, we compute the disconnected contributions to correlation functions of two vector currents in the isosinglet \\[\\omega \\] channel and to the hadronic vacuum polarization relevant for the muon anomalous magnetic moment. In both cases, estimators with variances dominated by the gauge noise are computed with a modest numerical effort. Theory suggests large gains for disconnected three and higher point correlation functions as well. The frequency-splitting estimators and their split-even components are directly applicable to the newly proposed multi-level integration in the presence of fermions.
Journal Article
Non-perturbative thermal QCD at all temperatures: the case of mesonic screening masses
A
bstract
We present a strategy based on the step-scaling technique to study non-perturbatively thermal QCD up to very high temperatures. As a first concrete application, we compute the flavour non-singlet meson screening masses at 12 temperatures covering the range from
T
∼ 1 GeV up to ∼ 160 GeV in the theory with three massless quarks. The calculation is carried out by Monte Carlo simulations on the lattice by considering large spatial extensions in order to have negligible finite volume effects. For each temperature we have simulated 3 or 4 values of the lattice spacing, so as to perform the continuum limit extrapolation with confidence at a few permille accuracy. Chiral symmetry restoration manifests itself in our results through the degeneracy of the vector and the axial vector channels and of the scalar and the pseudoscalar ones. In the entire range of temperatures explored, the meson screening masses deviate from the free theory result, 2
πT
, by at most a few percent. These deviations, however, cannot be explained by the known leading term in the QCD coupling constant
g
up to the highest temperature, where other contributions are still very relevant. In particular the vector-pseudoscalar mass splitting turns out to be of
O
(
g
4
) in the entire range explored, and it remains clearly visible up to the highest temperature, where the two screening masses are still significantly different within our numerical precision. The pattern of different contributions that we have found explains why it has been difficult in the past to match non-perturbative lattice results at
T
∼ 1 GeV with the analytic behaviour at asymptotically high temperatures.
Journal Article
Vacuum correlators at short distances from lattice QCD
A
bstract
Non-perturbatively computing the hadronic vacuum polarization at large photon virtualities and making contact with perturbation theory enables a precision determination of the electromagnetic coupling at the
Z
pole, which enters global electroweak fits. In order to achieve this goal ab initio using lattice QCD, one faces the challenge that, at the short distances which dominate the observable, discretization errors are hard to control. Here we address challenges of this type with the help of static screening correlators in the high-temperature phase of QCD, yet without incurring any bias. The idea is motivated by the observations that (a) the cost of high-temperature simulations is typically much lower than their vacuum counterpart, and (b) at distances
x
3
far below the inverse temperature 1
/T
, the operator-product expansion guarantees the thermal correlator of two local currents to deviate from the vacuum correlator by a relative amount that is power-suppressed in (
x
3
T
). The method is first investigated in lattice perturbation theory, where we point out the appearance of an O(
a
2
log(1
/a
)) lattice artifact in the vacuum polarization with a prefactor that we calculate. It is then applied to non-perturbative lattice QCD data with two dynamical flavors of quarks. Our lattice spacings range down to 0.049 fm for the vacuum simulations and down to 0.033 fm for the simulations performed at a temperature of 250 MeV.
Journal Article
Fluid administration for acute circulatory dysfunction using basic monitoring: narrative review and expert panel recommendations from an ESICM task force
An international team of experts in the field of fluid resuscitation was invited by the ESICM to form a task force to systematically review the evidence concerning fluid administration using basic monitoring. The work included a particular emphasis on pre-ICU hospital settings and resource-limited settings. The work focused on four main questions: (1) What is the role of clinical assessment to guide fluid resuscitation in shock? (2) What basic monitoring is required to perform and interpret a fluid challenge? (3) What defines a fluid challenge in terms of fluid type, ranges of volume, and rate of administration? (4) What are the safety endpoints during a fluid challenge? The expert panel found insufficient evidence to provide recommendations according to the GRADE system, and was only able to make recommendations for basic interventions, based on the available evidence and expert opinion. The panel identified significant gaps in the scientific evidence on fluid administration outside the ICU (excluding the operating theater). Globally, scientific communities and health care systems should address these critical gaps in evidence through research on how basic fluid administration in resource-rich and resource-limited settings can be improved for the benefit of patients and societies worldwide.
Journal Article