Search results for "31"
showing 10 items of 4401 documents
Bioaerosols in the Amazon rain forest: temporal variations and vertical profiles of Eukarya, Bacteria, and Archaea
2021
The Amazon rain forest plays a major role in global hydrological cycling, and biogenic aerosols are likely to influence the formation of clouds and precipitation. Information about the sources and altitude profiles of primary biological aerosol particles, however, is sparse. We used fluorescence in situ hybridization (FISH), a molecular biological staining technique largely unexplored in aerosol research, to investigate the sources and spatiotemporal distribution of Amazonian bioaerosols on the domain level. We found wet season bioaerosol number concentrations in the range of 1–5 × 105 m−3 accounting for > 70 % of the coarse mode aerosol. Eukaryotic and bacterial particles predominated, …
Pollutant concentrations in placenta.
2011
Unborn children are exposed to environmental pollutants via the placenta, and there is a causal relationship between maternal intake of pollutants and fetal exposure. Placental examination is an effective way for acquiring data for estimating fetal exposure. We analyzed the concentrations of 104 congeners of persistent organic pollutants, seven organotin compounds, five heavy metals, and methylmercury in 130 randomly selected placentas. Additionally, we examined similarities between pollutant concentrations by analyzing correlations between their placental concentrations. Our results yield new information for conducting contaminant risk assessments for the prenatal period. Out of the 117 in…
Structural Validity of the Foot and Ankle Outcome Score for Orthopaedic Pathologies with Rasch Measurement Theory
2022
Publisher Copyright: © 2021 The Authors A B S T R A C T Background: The Foot and Ankle Outcome Score (FAOS) is one of the most frequently used patient reported outcome measures for foot and ankle conditions. The aim is to test the structural validity of the Finnish version of the FAOS using Rasch Measurement Theory. Methods: FAOS scores were obtained from 218 consecutive patients who received operative treatment for foot and ankle conditions. The FAOS data were fitted into the Rasch model and person separation index (PSI) calculated. Results: All the five subscales provided good coverage and targeting. Three subscales presented unidimensional structure. Thirty-eight of the 42 items had orde…
Top-pair forward-backward asymmetry beyond next-to-leading order
2011
We make use of recent results in effective theory and higher-order perturbative calculations to improve the theoretical predictions of the QCD contribution to the top-quark pair production forward-backward asymmetry at the Tevatron. In particular, we supplement the fixed-order next-to-leading order calculation with higher-order corrections from soft-gluon resummation at next-to next-to-leading order accuracy performed in two different kinematic schemes, which allows us to make improved predictions for the asymmetry in the $p\overline{p}$ and $t\overline{t}$ rest frames as a function of the rapidity and invariant mass of the $t\overline{t}$ pair. Furthermore, we provide binned results which …
Transverse-momentum resummation for vector-boson pair production at NNLL+NNLO
2015
We consider the transverse-momentum ($p_T$) distribution of $ZZ$ and $W^+W^-$ boson pairs produced in hadron collisions. At small $p_T$, the logarithmically enhanced contributions due to multiple soft-gluon emission are resummed to all orders in QCD perturbation theory. At intermediate and large values of $p_T$, we consistently combine resummation with the known fixed-order results. We exploit the most advanced perturbative information that is available at present: next-to-next-to-leading logarithmic resummation combined with the next-to-next-to-leading fixed-order calculation. After integration over $p_T$, we recover the known next-to-next-to-leading order result for the inclusive cross se…
Competition between memory-keeping and memory-erasing decoherence channels
2014
We study the competing effects of simultaneous Markovian and non-Markovian decoherence mechanisms acting on a single spin. We show the existence of a threshold in the relative strength of such mechanisms above which the spin dynamics becomes fully Markovian, as revealed by the use of several non-Markovianity measures. We identify a measure-dependent nested structure of such thresholds, hinting at a causality relationship among the various non-Markovianity witnesses used in our analysis. Our considerations are then used to argue the unavoidably non-Markovian evolution of a single-electron quantum dot exposed to both intrinsic and Markovian technical noise, the latter of arbitrary strength.
Characterization of the shape-staggering effect in mercury nuclei
2018
In rare cases, the removal of a single proton (Z) or neutron (N) from an atomic nucleus leads to a dramatic shape change. These instances are crucial for understanding the components of the nuclear interactions that drive deformation. The mercury isotopes (Z = 80) are a striking example1,2: their close neighbours, the lead isotopes (Z = 82), are spherical and steadily shrink with decreasing N. The even-mass (A = N + Z) mercury isotopes follow this trend. The odd-mass mercury isotopes 181,183,185Hg, however, exhibit noticeably larger charge radii. Due to the experimental difficulties of probing extremely neutron-deficient systems, and the computational complexity of modelling such heavy nucl…
Ultrafast critical ground state preparation via bang-bang protocols
2020
The fast and faithful preparation of the ground state of quantum systems is a challenging task but crucial for several applications in the realm of quantum-based technologies. Decoherence poses a limit to the maximum time-window allowed to an experiment to faithfully achieve such desired states. This is of particular significance in critical systems, where the vanishing energy gap challenges an adiabatic ground state preparation. We show that a bang-bang protocol, consisting of a time evolution under two different values of an externally tunable parameter, allows for a high-fidelity ground state preparation in evolution times no longer than those required by the application of standard opti…
Two-Loop Planar Corrections to Heavy-Quark Pair Production in the Quark-Antiquark Channel
2009
We evaluate the planar two-loop QCD diagrams contributing to the leading color coefficient of the heavy-quark pair production cross section, in the quark-antiquark annihilation channel. We obtain the leading color coefficient in an analytic form, in terms of one- and two-dimensional harmonic polylogarithms of maximal weight 4. The result is valid for arbitrary values of the Mandelstam invariants s and t, and of the heavy-quark mass m. Our findings agree with previous analytic results in the small-mass limit and numerical results for the exact amplitude.
Stability of multiquarks in a simple string model
2007
A simple string model inspired by the strong-coupling regime of Quantum ChromoDynamics is used as a potential for studying the spectrum of multiquark systems with two quarks and two antiquarks, with a careful treatment of the four-body problem. It is found that the ground state is stable, lying below the threshold for dissociation into two isolated mesons.