167 research outputs found
Kinetic modelling of quantum effects in laser-beam interaction
We present the results of kinetic modelling of quantum effects in laser-beam
interaction. In the developed numerical model, electron-positron pair
production by hard photons, hard photon emission and the electromagnetic fields
generated by the created charged particles are taken into account. Interaction
of a relativistic electron beam with a strong laser pulse is analyzed. It is
shown that the quantum effects can be important even for moderately intense
laser pulses when the number of emitted photons by single electron is not
large. Electron-positron pair plasma production in extremely-intense laser
field via development of electromagnetic cascades is also studied. The
simulation results confirm the prediction of strong laser field absorption in
the self-generated electron-positron plasma. It is shown that the
self-generated electron-positron plasma can be an efficient source of energetic
gamma-quanta.Comment: Submitted to Nuclear Instruments and Methods in Physics Research
A mental number line in human newborns
Humans represent numbers on a mental number line with smaller numbers on the
left and larger numbers on the right side. A left\u2010to\u2010right oriented spatial\u2013numerical
association, (SNA), has been demonstrated in animals and infants. However, the possibility
that SNA is learnt by early exposure to caregivers\u2019 directional biases is still
open. We conducted two experiments: in Experiment 1, we tested whether SNA is
present at birth and in Experiment 2, we studied whether it depends on the relative
rather than the absolute magnitude of numerousness. Fifty\u2010five\u2010hour\u2010old newborns,
once habituated to a number (12), spontaneously associated a smaller number (4)
with the left and a larger number (36) with the right side (Experiment 1). SNA in neonates
is not absolute but relative. The same number (12) was associated with the left
side rather than the right side whenever the previously experienced number was
larger (36) rather than smaller (4) (Experiment 2). Control on continuous physical variables
showed that the effect is specific of discrete magnitudes. These results constitute
strong evidence that in our species SNA originates from pre\u2010linguistic and
biological precursors in the brain
Multimessenger astronomy with the Einstein Telescope
Gravitational waves (GWs) are expected to play a crucial role in the
development of multimessenger astrophysics. The combination of GW observations
with other astrophysical triggers, such as from gamma-ray and X-ray satellites,
optical/radio telescopes, and neutrino detectors allows us to decipher science
that would otherwise be inaccessible. In this paper, we provide a broad review
from the multimessenger perspective of the science reach offered by the third
generation interferometric GW detectors and by the Einstein Telescope (ET) in
particular. We focus on cosmic transients, and base our estimates on the
results obtained by ET's predecessors GEO, LIGO, and Virgo.Comment: 26 pages. 3 figures. Special issue of GRG on the Einstein Telescope.
Minor corrections include
Current status of turbulent dynamo theory: From large-scale to small-scale dynamos
Several recent advances in turbulent dynamo theory are reviewed. High
resolution simulations of small-scale and large-scale dynamo action in periodic
domains are compared with each other and contrasted with similar results at low
magnetic Prandtl numbers. It is argued that all the different cases show
similarities at intermediate length scales. On the other hand, in the presence
of helicity of the turbulence, power develops on large scales, which is not
present in non-helical small-scale turbulent dynamos. At small length scales,
differences occur in connection with the dissipation cutoff scales associated
with the respective value of the magnetic Prandtl number. These differences are
found to be independent of whether or not there is large-scale dynamo action.
However, large-scale dynamos in homogeneous systems are shown to suffer from
resistive slow-down even at intermediate length scales. The results from
simulations are connected to mean field theory and its applications. Recent
work on helicity fluxes to alleviate large-scale dynamo quenching, shear
dynamos, nonlocal effects and magnetic structures from strong density
stratification are highlighted. Several insights which arise from analytic
considerations of small-scale dynamos are discussed.Comment: 36 pages, 11 figures, Spa. Sci. Rev., submitted to the special issue
"Magnetism in the Universe" (ed. A. Balogh
Relativistic quantum dynamics of a charged particle in cosmic string spacetime in the presence of magnetic field and scalar potential
In this paper we analyze the relativistic quantum motion of charged spin-0
and spin-1/2 particles in the presence of a uniform magnetic field and scalar
potentials in the cosmic string spacetime. In order to develop this analysis,
we assume that the magnetic field is parallel to the string and the scalar
potentials present a cylindrical symmetry with their center on the string. Two
distinct configurations for the scalar potential, , are considered:
the potential proportional to the inverse of the polar distance, i.e.,
, and the potential proportional to this distance, i.e.,
. The energy spectra are explicitly computed for different physical
situations and presented their dependences on the magnetic field strength and
scalar coupling constants.Comment: New version with 20 pages and no figure. Some minor revisions and six
references added. Accepted for publication in EJP
Search for charginos in e+e- interactions at sqrt(s) = 189 GeV
An update of the searches for charginos and gravitinos is presented, based on
a data sample corresponding to the 158 pb^{-1} recorded by the DELPHI detector
in 1998, at a centre-of-mass energy of 189 GeV. No evidence for a signal was
found. The lower mass limits are 4-5 GeV/c^2 higher than those obtained at a
centre-of-mass energy of 183 GeV. The (\mu,M_2) MSSM domain excluded by
combining the chargino searches with neutralino searches at the Z resonance
implies a limit on the mass of the lightest neutralino which, for a heavy
sneutrino, is constrained to be above 31.0 GeV/c^2 for tan(beta) \geq 1.Comment: 22 pages, 8 figure
Search for the Xb and other hidden-beauty states in the π+π−ϒ(1S) channel at ATLAS
This Letter presents a search for a hidden-beauty counterpart of the X(3872) in the mass ranges of 10.05–10.31 GeV and 10.40–11.00 GeV, in the channel Xb→π+π−ϒ(1S)(→μ+μ−), using 16.2 fb−1 of pp collision data collected by the ATLAS detector at the LHC. No evidence for new narrow states is found, and upper limits are set on the product of the Xb cross section and branching fraction, relative to those of the ϒ(2S), at the 95% confidence level using the CLS approach. These limits range from 0.8% to 4.0%, depending on mass. For masses above 10.1 GeV, the expected upper limits from this analysis are the most restrictive to date. Searches for production of the ϒ(13DJ), , and states also reveal no significant signals
Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries
Background
Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres.
Methods
This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries.
Results
In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia.
Conclusion
This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries
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