209 research outputs found
A database of aircraft measurements of carbon monoxide (CO) with high temporal and spatial resolution during 2011–2021
To understand tropospheric air pollution at regional and global scales, the
SPIRIT (SPectromètre Infra-Rouge In situ Toute
altitude) airborne instrument was developed and used on aircraft to measure volume mixing ratios
of carbon monoxide (CO), an important indicator of air pollution, during the
last decade. SPIRIT provides high-quality CO measurements with 1σ precision of 0.3 ppbv at a time resolution of 1.6 s thanks to the coupling
of a quantum cascade laser to a Robert optical multi-pass cell. It can be
operated on different aircraft such as Falcon-20 and ATR-42 from the German Aerospace Agency (DLR)
and from SAFIRE (CNRS-CNES-Météo France). With support from
various projects, measurements were taken for more than 200 flight hours
over three continents (Europe, Asia, and Africa), including two
intercontinental transects (Europe–Asia and Europe–Africa). Levels of CO
and its spatial distribution are briefly discussed and compared between
different regions/continents. CO generally decreases with altitude except in
some cases, indicating the important contribution of long-distance transport
to CO levels. A 3D trajectory mapped by CO level was plotted for each flight
and is presented in this study (which includes a Supplement). The
database is archived in the AERIS database (https://doi.org/10.25326/440), the French national center for atmospheric
observations (Catoire et al., 2023). In addition, it could help
to validate model performance and satellite measurements. For instance, the
database covers measurements at high-latitude regions (i.e., Kiruna, Sweden,
68∘ N), where satellite measurements are still challenging, and at
low-latitude regions (West Africa and Southeast Asia), where in situ data
are scarce and satellites need more validation by airborne measurements.</p
Pattern and Outcome of Chest Injuries at Bugando Medical Centre in Northwestern Tanzania.
Chest injuries constitute a continuing challenge to the trauma or general surgeon practicing in developing countries. This study was conducted to outline the etiological spectrum, injury patterns and short term outcome of these injuries in our setting. This was a prospective study involving chest injury patients admitted to Bugando Medical Centre over a six-month period from November 2009 to April 2010 inclusive. A total of 150 chest injury patients were studied. Males outnumbered females by a ratio of 3.8:1. Their ages ranged from 1 to 80 years (mean = 32.17 years). The majority of patients (72.7%) sustained blunt injuries. Road traffic crush was the most common cause of injuries affecting 50.7% of patients. Chest wall wounds, hemothorax and rib fractures were the most common type of injuries accounting for 30.0%, 21.3% and 20.7% respectively. Associated injuries were noted in 56.0% of patients and head/neck (33.3%) and musculoskeletal regions (26.7%) were commonly affected. The majority of patients (55.3%) were treated successfully with non-operative approach. Underwater seal drainage was performed in 39 patients (19.3%). One patient (0.7%) underwent thoracotomy due to hemopericardium. Thirty nine patients (26.0%) had complications of which wound sepsis (14.7%) and complications of long bone fractures (12.0%) were the most common complications. The mean LOS was 13.17 days and mortality rate was 3.3%. Using multivariate logistic regression analysis, associated injuries, the type of injury, trauma scores (ISS, RTS and PTS) were found to be significant predictors of the LOS (P < 0.001), whereas mortality was significantly associated with pre-morbid illness, associated injuries, trauma scores (ISS, RTS and PTS), the need for ICU admission and the presence of complications (P < 0.001). Chest injuries resulting from RTCs remain a major public health problem in this part of Tanzania. Urgent preventive measures targeting at reducing the occurrence of RTCs is necessary to reduce the incidence of chest injuries in this region
Reformulation of the strong-field approximation for light-matter interactions
We consider the interaction of hydrogen-like atoms with a strong laser field
and show that the strong field approximation and all its variants may be
grouped into a set of families of approximation schemes. This is done by
introducing an ansatz describing the electron wave packet as the sum of the
initial state wave function times a phase factor and a function which is the
perturbative solution in the Coulomb potential of an inhomogeneous
time-dependent Schr\"odinger equation. It is the phase factor that
characterizes a given family. In each of these families, the velocity and
length gauge version of the approximation scheme lead to the same results at
each order in the Coulomb potential. By contrast, irrespective of the gauge,
approximation schemes belonging to different families give different results.
Furthermore, this new formulation of the strong field approximations allows us
to gain deeper insight into the validity of the strong field approximation
schemes. In particular, we address two important questions: the role of the
Coulomb potential in the output channel and the convergence of the perturbative
series in the Coulomb potential. In all the physical situations we consider
here, our results are compared to those obtained by solving numerically the
time-dependent Schr\"odinger equation.Comment: 19 pages, 9 figures, submitted for publicatio
Modelling the chemistry and transport of bromoform within a sea breeze driven convective system during the SHIVA Campaign
We carry out a case study of the transport and chemistry of bromoform and its product gases (PGs) in a sea breeze driven convective episode on 19 November 2011 along the North West coast of Borneo during the "Stratospheric ozone: Halogen Impacts in a Varying Atmosphere" (SHIVA) campaign. We use ground based, ship, aircraft and balloon sonde observations made during the campaign, and a 3-D regional online transport and chemistry model capable of resolving clouds and convection explicitly that includes detailed bromine chemistry. The model simulates the temperature, wind speed, wind direction fairly well for the most part, and adequately captures the convection location, timing, and intensity. The simulated transport of bromoform from the boundary layer up to 12 km compares well to aircraft observations to support our conclusions. The model makes several predictions regarding bromine transport from the boundary layer to the level of convective detrainment (11 to 12 km). First, the majority of bromine undergoes this transport as bromoform. Second, insoluble organic bromine carbonyl species are transported to between 11 and 12 km, but only form a small proportion of the transported bromine. Third, soluble bromine species, which include bromine organic peroxides, hydrobromic acid (HBr), and hypobromous acid (HOBr), are washed out efficiently within the core of the convective column. Fourth, insoluble inorganic bromine species (principally Br2) are not washed out of the convective column, but are also not transported to the altitude of detrainment in large quantities. We expect that Br2 will make a larger relative contribution to the total vertical transport of bromine atoms in scenarios with higher CHBr3 mixing ratios in the boundary layer, which have been observed in other regions. Finally, given the highly detailed description of the chemistry, transport and washout of bromine compounds within our simulations, we make a series of recommendations about the physical and chemical processes that should be represented in 3-D chemical transport models (CTMs) and chemistry climate models (CCMs), which are the primary theoretical means of estimating the contribution made by CHBr3 and other very short-lived substances (VSLS) to the stratospheric bromine budget
Efficient and accurate modeling of electron photoemission in nanostructures with TDDFT
We derive and extend the time-dependent surface-flux method introduced in [L. Tao, A. Scrinzi, New J. Phys. 14, 013021 (2012)] within a time-dependent density-functional theory (TDDFT) formalism and use it to calculate photoelectron spectra and angular distributions of atoms and molecules when excited by laser pulses. We present other, existing computational TDDFT methods that are suitable for the calculation of electron emission in compact spatial regions, and compare their results. We illustrate the performance of the new method by simulating strong-field ionization of C60 fullerene and discuss final state effects in the orbital reconstruction of planar organic molecules
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