4,947 research outputs found
Signatures of four-particle correlations associated with exciton-carrier interactions in coherent spectroscopy on bulk GaAs
Transient four-wave mixing studies of bulk GaAs under conditions of broad
bandwidth excitation of primarily interband transitions have enabled
four-particle correlations tied to degenerate (exciton-exciton) and
nondegenerate (exciton-carrier) interactions to be studied. Real
two-dimensional Fourier-transform spectroscopy (2DFTS) spectra reveal a complex
response at the heavy-hole exciton emission energy that varies with the
absorption energy, ranging from dispersive on the diagonal, through absorptive
for low-energy interband transitions to dispersive with the opposite sign for
interband transitions high above band gap. Simulations using a multilevel model
augmented by many-body effects provide excellent agreement with the 2DFTS
experiments and indicate that excitation-induced dephasing (EID) and
excitation-induced shift (EIS) affect degenerate and nondegenerate interactions
equivalently, with stronger exciton-carrier coupling relative to
exciton-exciton coupling by approximately an order of magnitude. These
simulations also indicate that EID effects are three times stronger than EIS in
contributing to the coherent response of the semiconductor
Herwig++ 2.0 Release Note
A new release of the Monte Carlo program Herwig++ (version 2.0) is now
available. This is the first version of the program which can be used for
hadron-hadron physics and includes the full simulation of both initial- and
final-state QCD radiation.Comment: Source code and additional information available at
http://hepforge.cedar.ac.uk/herwig
Fine and ultrafine particle number and size measurements from industrial combustion processes : primary emissions field data
This study is to our knowledge the first to present the results of on-line measurements of residual nanoparticle numbers downstream of the flue gas treatment systems of a wide variety of medium- and large-scale industrial installations. Where available, a semi-quantitative elemental composition of the sampled particles is carried out using a Scanning Electron Microscope coupled with an Energy Dispersive Spectrometer (SEM-EDS). The semi-quantitative elemental composition as a function of the particle size is presented. EU's Best Available Technology documents (BAT) show removal efficiencies of Electrostatic Precipitator (ESP) and bag filter dedusting systems exceeding 99% when expressed in terms of weight. Their efficiency decreases slightly for particles smaller than 1 mu m but when expressed in terms of weight, still exceeds 99% for bag filters and 96% for ESP. This study reveals that in terms of particle numbers, residual nanoparticles (NP) leaving the dedusting systems dominate by several orders of magnitude. In terms of weight, all installations respect their emission limit values and the contribution of NP to weight concentrations is negligible, despite their dominance in terms of numbers. Current World Health Organisation regulations are expressed in terms of PM2.5 wt concentrations and therefore do not reflect the presence or absence of a high number of NP. This study suggests that research is needed on possible additional guidelines related to NP given their possible toxicity and high potential to easily enter the blood stream when inhaled by humans
What are the nursing competencies related to antimicrobial stewardship and how they have been assessed? Results from an integrative rapid review
Background: Antimicrobial resistance issues, and the consequent demand for antimicrobial stewardship (AMS) programs, need to be investigated urgently and clearly. Considering the large amount of time nurses spend at patients’ bedside, the aim of the present study was to examine recent literature on nursing competency in AMS. Methods: Drawing from Tricco and colleagues’ seven-stage process, a rapid review was performed. MEDLINE, CINAHL and EMBASE databased were searched from December 1st, 2019 until December 31st, 2021. Article screening and study selection were conducted independently by three reviewers. Data were analyzed narratively and categorized adopting an inductive thematic coding. Results: Sixteen studies met the inclusion criteria and were included. Publications were mainly authored in USA (n = 4), Australia and New Zealand (n = 4) and Asia (n = 4), followed by Europe (n = 2) and Africa (n = 2). Ten studies were quantitative in design, followed by qualitative (n = 4) and mixed-methods studies (n = 2). Nursing competency in AMS seems to be influenced by a two-dimensional model: on the one hand, internal factors which consisted in knowledge, attitudes and practices and, on the other hand, external aspects which are at environmental level in terms of structures and processes. Conclusion: This study provided a map of dimensions for researchers and practitioners to consider when planning clinical governance, educational activities, and research programs. Significant opportunities exist for nurses to contribute to practice, education, research, and policy efforts aimed at reducing antimicrobial resistance
The unintegrated gluon distribution from the CCFM equation
The gluon distribution f(x, k_t^2,mu^2), unintegrated over the transverse
momentum k_t of the gluon, satisfies the angular-ordered CCFM equation which
interlocks the dependence on the scale k_t with the scale \mu of the probe. We
show how, to leading logarithmic accuracy, the equation can be simplified to a
single scale problem. In particular we demonstrate how to determine the
two-scale unintegrated distribution f(x,k_t^2,mu^2) from knowledge of the
integrated gluon obtained from a unified scheme embodying both BFKL and DGLAP
evolution.Comment: 16 pages LaTeX, 3 eps figure
Weighted ensemble: Recent mathematical developments
The weighted ensemble (WE) method, an enhanced sampling approach based on
periodically replicating and pruning trajectories in a set of parallel
simulations, has grown increasingly popular for computational biochemistry
problems, due in part to improved hardware and the availability of modern
software. Algorithmic and analytical improvements have also played an important
role, and progress has accelerated in recent years. Here, we discuss and
elaborate on the WE method from a mathematical perspective, highlighting recent
results which have begun to yield greater computational efficiency. Notable
among these innovations are variance reduction approaches that optimize
trajectory management for systems of arbitrary dimensionality.Comment: 12 pages, 10 figure
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