914 research outputs found
Theory of the NO+CO surface reaction model
We derive a pair approximation (PA) for the NO+CO model with instantaneous
reactions. For both the triangular and square lattices, the PA, derived here
using a simpler approach, yields a phase diagram with an active state for
CO-fractions y in the interval y_1 < y < y_2, with a continuous (discontinuous)
phase transition to a poisoned state at y_1 (y_2). This is in qualitative
agreement with simulation for the triangular lattice, where our theory gives a
rather accurate prediction for y_2. To obtain the correct phase diagram for the
square lattice, i.e., no active state, we reformulate the PA using sublattices.
The (formerly) active regime is then replaced by a poisoned state with broken
symmetry (unequal sub- lattice coverages), as observed recently by Kortluke et
al. [Chem. Phys. Lett. 275, 85 (1997)]. In contrast with their approach, in
which the active state persists, although reduced in extent, we report here the
first qualitatively correct theory of the NO+CO model on the square lattice.
Surface diffusion of nitrogen can lead to an active state in this case. In one
dimension, the PA predicts that diffusion is required for the existence of an
active state.Comment: 15 pages, 9 figure
The Cherenkov Telescope Array Large Size Telescope
The two arrays of the Very High Energy gamma-ray observatory Cherenkov
Telescope Array (CTA) will include four Large Size Telescopes (LSTs) each with
a 23 m diameter dish and 28 m focal distance. These telescopes will enable CTA
to achieve a low-energy threshold of 20 GeV, which is critical for important
studies in astrophysics, astroparticle physics and cosmology. This work
presents the key specifications and performance of the current LST design in
the light of the CTA scientific objectives.Comment: 4 pages, 5 figures, In Proceedings of the 33rd International Cosmic
Ray Conference (ICRC2013), Rio de Janeiro (Brazil). All CTA contributions at
arXiv:1307.223
Multiwavelength Monitoring of the BL Lac Object PKS 2155-304 I. The IUE Campaign
Daily monitoring of PKS 2155-304 with the IUE satellite throughout November
1991 has revealed dramatic, large-amplitude, rapid variations in the
ultraviolet flux of this BL Lac object. Many smaller, rapid flares are
superimposed on a general doubling of the intensity. During the five-day period
when sampling was roughly continuous, the rapid flaring had an apparent
quasi-periodic nature, with peaks repeating every ~0.7 days. The short- and
long-wavelength ultraviolet light curves are well correlated with each other,
and with the optical light curve deduced from the Fine Error Sensor (FES) on
IUE. The formal lag is zero but the cross-correlation if asymmetric in the
sense that the shorter wavelength emission leads the longer. The ultraviolet
spectral shape varies a small but significant amount. The correlation between
spectral shape and intensity is complicated; an increase in intensity is
associated with spectral hardening, but lags behind the spectral change by ~1
day. The sign of the correlation is consistent with the nonthermal acceleration
processes expected in relativistic plasmas, so that the present results are
consistent with relativistic jet models, which can also account for
quasi-periodic flaring. In contrast, currently proposed accretion disk models
are stronly ruled out by the simultaneous optical and ultraviolet variability.Comment: 27 pages, plain TeX, STScI Preprint 71
Feasibility studies of time-like proton electromagnetic form factors at PANDA at FAIR
Simulation results for future measurements of electromagnetic proton form
factors at \PANDA (FAIR) within the PandaRoot software framework are reported.
The statistical precision with which the proton form factors can be determined
is estimated. The signal channel is studied on the basis
of two different but consistent procedures. The suppression of the main
background channel, , is studied.
Furthermore, the background versus signal efficiency, statistical and
systematical uncertainties on the extracted proton form factors are evaluated
using two different procedures. The results are consistent with those of a
previous simulation study using an older, simplified framework. However, a
slightly better precision is achieved in the PandaRoot study in a large range
of momentum transfer, assuming the nominal beam conditions and detector
performance
Feasibility studies of the time-like proton electromagnetic form factor measurements with PANDA at FAIR
The possibility of measuring the proton electromagnetic form factors in the
time-like region at FAIR with the \PANDA detector is discussed. Detailed
simulations on signal efficiency for the annihilation of into a
lepton pair as well as for the most important background channels have been
performed. It is shown that precision measurements of the differential cross
section of the reaction can be obtained in a wide
angular and kinematical range. The individual determination of the moduli of
the electric and magnetic proton form factors will be possible up to a value of
momentum transfer squared of (GeV/c). The total cross section will be measured up to (GeV/c).
The results obtained from simulated events are compared to the existing data.
Sensitivity to the two photons exchange mechanism is also investigated.Comment: 12 pages, 4 tables, 8 figures Revised, added details on simulations,
4 tables, 9 figure
MRI of the lung (3/3)-current applications and future perspectives
BACKGROUND: MRI of the lung is recommended in a number of clinical indications. Having a non-radiation alternative is particularly attractive in children and young subjects, or pregnant women. METHODS: Provided there is sufficient expertise, magnetic resonance imaging (MRI) may be considered as the preferential modality in specific clinical conditions such as cystic fibrosis and acute pulmonary embolism, since additional functional information on respiratory mechanics and regional lung perfusion is provided. In other cases, such as tumours and pneumonia in children, lung MRI may be considered an alternative or adjunct to other modalities with at least similar diagnostic value. RESULTS: In interstitial lung disease, the clinical utility of MRI remains to be proven, but it could provide additional information that will be beneficial in research, or at some stage in clinical practice. Customised protocols for chest imaging combine fast breath-hold acquisitions from a "buffet" of sequences. Having introduced details of imaging protocols in previous articles, the aim of this manuscript is to discuss the advantages and limitations of lung MRI in current clinical practice. CONCLUSION: New developments and future perspectives such as motion-compensated imaging with self-navigated sequences or fast Fourier decomposition MRI for non-contrast enhanced ventilation- and perfusion-weighted imaging of the lung are discussed. Main Messages • MRI evolves as a third lung imaging modality, combining morphological and functional information. • It may be considered first choice in cystic fibrosis and pulmonary embolism of young and pregnant patients. • In other cases (tumours, pneumonia in children), it is an alternative or adjunct to X-ray and CT. • In interstitial lung disease, it serves for research, but the clinical value remains to be proven. • New users are advised to make themselves familiar with the particular advantages and limitations
Aerosol delivery to ventilated newborn infants: historical challenges and new directions
There are several aerosolized drugs which have been used in the treatment of neonatal respiratory illnesses, such as bronchodilators, diuretics, and surfactants. Preclinical in vitro and in vivo studies identified a number of variables that affect aerosol efficiency, including particle size, aerosol flows, nebulizer choice, and placement. Nevertheless, an optimized aerosol drug delivery system for mechanically ventilated infants still does not exist. Increasing interest in this form of drug delivery requires more controlled and focused research of drug/device combinations appropriate for the neonatal population. In the present article, we review the research that has been conducted thus far and discuss the next steps in developing the optimal aerosol delivery system for use in mechanically ventilated neonates
European guideline (EuroGuiDerm) on atopic eczema – part II: non-systemic treatments and treatment recommendations for special AE patient populations
The evidence- and consensus-based guideline on atopic eczema was developed in accordance with the EuroGuiDerm Guideline and Consensus Statement Development Manual. Four consensus conferences were held between December 2020 and July 2021. Twenty-nine experts (including clinicians and patient representatives) from 12 European countries participated. This second part of the guideline includes recommendations and detailed information on basic therapy with emollients and moisturizers, topical anti-inflammatory treatment, antimicrobial and antipruritic treatment and UV photo- therapy. Furthermore, this part of the guideline covers techniques for avoiding provocation factors, as well as dietaryinterventions, immunotherapy, complementary medicine and educational interventions for patients with atopic eczema and deals with occupational and psychodermatological aspects of the disease. It also contains guidance on treatment for paediatric and adolescent patients and pregnant or breastfeeding women, as well as considerations for patients who want to have a child. A chapter on the patient perspective is also provided. The first part of the guideline, published sepa- rately, contains recommendations and guidance on systemic treatment with conventional immunosuppressive drugs, biologics and janus kinase (JAK) inhibitors, as well as information on the scope and purpose of the guideline, and a sec- tion on guideline methodology. Received: 17 February 2022; Accepted: 3 June 202
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