2,703 research outputs found
Development of a custom OMI NO2 data product for evaluating biases in a regional chemistry transport model
In this paper, we present the custom Hong Kong NO2 retrieval (HKOMI) for the Ozone Monitoring Instrument (OMI) on board the Aura satellite which was used to evaluate a high-resolution chemistry transport model (CTM) (3 km x 3 km spatial resolution). The atmospheric chemistry transport was modelled in the Pearl River Delta (PRD) region in southern China by the Models-3 Community Multiscale Air Quality (CMAQ) modelling system from October 2006 to January 2007. In the HKOMI NO2 retrieval, tropospheric air mass factors (AMFs) were recalculated using high-resolution ancillary parameters of surface reflectance, a priori NO2 and aerosol profiles, of which the latter two were taken from the CMAQ simulation. We tested the influence of the ancillary parameters on the data product using four different aerosol parametrizations. Ground-level measurements by the PRD Regional Air Quality Monitoring (RAQM) network were used as additional independent measurements. The HKOMI retrieval increases estimated tropospheric NO2 vertical column densities (VCD) by (+31 +/- 38) %,when compared to NASA's standard product (OMNO2-SP),and improves the normalized mean bias (NMB) between satellite and ground observations by 26 percentage points from -41 to -15 %. The individual influences of the parameters are (+11.4 +/- 13.4)% for NO2 profiles,(+11.0 +/- 20.9)% for surface reflectance and (+6.0 +/- 8.4)% for the best aerosol parametrization. The correlation coefficient r is low between ground and satellite observations (r = 0.35). The low r and the remaining NMB can be explained by the low model performance and the expected differences when comparing point measurements with area-averaged satellite observations. The correlation between CMAQ and the RAQM network is low (r approximate to 0.3) and the model underestimates the NO2 concentrations in the northwestern model domain (Foshan and Guangzhou). We compared the CMAQ NO2 time series of the two main plumes with our best OMI NO2 data set (HKOMI-4). The model overestimates the NO2 VCDs by about 15% in Hong Kong and Shenzhen, while the correlation coefficient is satisfactory (r = 0.56). In Foshan and Guangzhou, the correlation is low (r = 0.37) and the model underestimates the VCDs strongly (NMB = -40 %). In addition, we estimated that the OMI VCDs are also underestimated by about 10 to 20% in Foshan and Guangzhou because of the influence of the model parameters on the AMFs. In this study, we demonstrate that the HKOMI NO2 retrieval reduces the bias of the satellite observations and how the data set can be used to study the magnitude of NO2 concentrations in a regional model at high spatial resolution of 3 x 3 km(2). The low bias was achieved with recalculated AMFs using updated surface reflectance, aerosol profiles and NO2 profiles. Since unbiased concentrations are important, for example, in air pollution studies, the results of this paper can be very helpful in future model evaluation studies
Microscopic calculations of stopping and flow from 160AMeV to 160AGeV
The behavior of hadronic matter at high baryon densities is studied within
Ultrarelativistic Quantum Molecular Dynamics (URQMD). Baryonic stopping is
observed for Au+Au collisions from SIS up to SPS energies. The excitation
function of flow shows strong sensitivities to the underlying equation of state
(EOS), allowing for systematic studies of the EOS. Effects of a density
dependent pole of the -meson propagator on dilepton spectra are studied
for different systems and centralities at CERN energies.Comment: Proceedings of the Quark Matter '96 Conference, Heidelberg, German
Baryon Stopping and Charged Particle Distributions in Central Pb+Pb Collisions at 158 GeV per Nucleon
Net proton and negative hadron spectra for central \PbPb collisions at 158
GeV per nucleon at the CERN SPS were measured and compared to spectra from
lighter systems. Net baryon distributions were derived from those of net
protons, utilizing model calculations of isospin contributions as well as data
and model calculations of strange baryon distributions. Stopping (rapidity
shift with respect to the beam) and mean transverse momentum \meanpt of net
baryons increase with system size. The rapidity density of negative hadrons
scales with the number of participant nucleons for nuclear collisions, whereas
their \meanpt is independent of system size. The \meanpt dependence upon
particle mass and system size is consistent with larger transverse flow
velocity at midrapidity for \PbPb compared to \SS central collisions.Comment: This version accepted for publication in PRL. 4 pages, 3 figures.
Typos corrected, some paragraphs expanded in response to referee comments, to
better explain details of analysi
Charged Particle Production in Proton-, Deuteron-, Oxygen- and Sulphur-Nucleus Collisions at 200 GeV per Nucleon
The transverse momentum and rapidity distributions of net protons and
negatively charged hadrons have been measured for minimum bias proton-nucleus
and deuteron-gold interactions, as well as central oxygen-gold and
sulphur-nucleus collisions at 200 GeV per nucleon. The rapidity density of net
protons at midrapidity in central nucleus-nucleus collisions increases both
with target mass for sulphur projectiles and with the projectile mass for a
gold target. The shape of the rapidity distributions of net protons forward of
midrapidity for d+Au and central S+Au collisions is similar. The average
rapidity loss is larger than 2 units of rapidity for reactions with the gold
target. The transverse momentum spectra of net protons for all reactions can be
described by a thermal distribution with `temperatures' between 145 +- 11 MeV
(p+S interactions) and 244 +- 43 MeV (central S+Au collisions). The
multiplicity of negatively charged hadrons increases with the mass of the
colliding system. The shape of the transverse momentum spectra of negatively
charged hadrons changes from minimum bias p+p and p+S interactions to p+Au and
central nucleus-nucleus collisions. The mean transverse momentum is almost
constant in the vicinity of midrapidity and shows little variation with the
target and projectile masses. The average number of produced negatively charged
hadrons per participant baryon increases slightly from p+p, p+A to central
S+S,Ag collisions.Comment: 47 pages, submitted to Z. Phys.
The translation, validity and reliability of the German version of the Fremantle Back Awareness Questionnaire
Background: The Fremantle Back Awareness Questionnaire (FreBAQ) claims to assess disrupted self-perception of the back. The aim of this study was to develop a German version of the Fre-BAQ (FreBAQ-G) and assess its test-retest reliability, its known-groups validity and its convergent validity with another purported measure of back perception.
Methods: The FreBaQ-G was translated following international guidelines for the transcultural adaptation of questionnaires. Thirty-five patients with non-specific CLBP and 48 healthy participants were recruited. Assessor one administered the FreBAQ-G to each patient with CLBP on two separate days to quantify intra-observer reliability. Assessor two administered the FreBaQ-G to each patient on day 1. The scores were compared to those obtained by assessor one on day 1 to assess inter-observer reliability. Known-groups validity was quantified by comparing the FreBAQ-G score between patients and healthy controls. To assess convergent validity, patient\u27s FreBAQ-G scores were correlated to their two-point discrimination (TPD) scores.
Results: Intra- and Inter-observer reliability were both moderate with ICC3.1 = 0.88 (95%CI: 0.77 to 0.94) and 0.89 (95%CI: 0.79 to 0.94), respectively. Intra- and inter-observer limits of agreement (LoA) were 6.2 (95%CI: 5.0±8.1) and 6.0 (4.8±7.8), respectively. The adjusted mean difference between patients and controls was 5.4 (95%CI: 3.0 to 7.8, p\u3c0.01). Patient\u27s FreBAQ-G scores were not associated with TPD thresholds (Pearson\u27s r = -0.05, p = 0.79).
Conclusions: The FreBAQ-G demonstrated a degree of reliability and known-groups validity. Interpretation of patient level data should be performed with caution because the LoA were substantial. It did not demonstrate convergent validity against TPD. Floor effects of some items of the FreBAQ-G may have influenced the validity and reliability results. The clinimetric properties of the FreBAQ-G require further investigation as a simple measure of disrupted self-perception of the back before firm recommendations on its use can be made
Experimental Study of the Shortest Reset Word of Random Automata
In this paper we describe an approach to finding the shortest reset word of a
finite synchronizing automaton by using a SAT solver. We use this approach to
perform an experimental study of the length of the shortest reset word of a
finite synchronizing automaton. The largest automata we considered had 100
states. The results of the experiments allow us to formulate a hypothesis that
the length of the shortest reset word of a random finite automaton with
states and 2 input letters with high probability is sublinear with respect to
and can be estimated as $1.95 n^{0.55}.
OpenChrom: a cross-platform open source software for the mass spectrometric analysis of chromatographic data
<p>Abstract</p> <p>Background</p> <p>Today, data evaluation has become a bottleneck in chromatographic science. Analytical instruments equipped with automated samplers yield large amounts of measurement data, which needs to be verified and analyzed. Since nearly every GC/MS instrument vendor offers its own data format and software tools, the consequences are problems with data exchange and a lack of comparability between the analytical results. To challenge this situation a number of either commercial or non-profit software applications have been developed. These applications provide functionalities to import and analyze several data formats but have shortcomings in terms of the transparency of the implemented analytical algorithms and/or are restricted to a specific computer platform.</p> <p>Results</p> <p>This work describes a native approach to handle chromatographic data files. The approach can be extended in its functionality such as facilities to detect baselines, to detect, integrate and identify peaks and to compare mass spectra, as well as the ability to internationalize the application. Additionally, filters can be applied on the chromatographic data to enhance its quality, for example to remove background and noise. Extended operations like do, undo and redo are supported.</p> <p>Conclusions</p> <p>OpenChrom is a software application to edit and analyze mass spectrometric chromatographic data. It is extensible in many different ways, depending on the demands of the users or the analytical procedures and algorithms. It offers a customizable graphical user interface. The software is independent of the operating system, due to the fact that the Rich Client Platform is written in Java. OpenChrom is released under the Eclipse Public License 1.0 (EPL). There are no license constraints regarding extensions. They can be published using open source as well as proprietary licenses. OpenChrom is available free of charge at <url>http://www.openchrom.net</url>.</p
Event-by-event fluctuations of the kaon to pion ratio in central Pb+Pb collisions at 158 GeV per Nucleon
We present the first measurement of fluctuations from event to event in the
production of strange particles in collisions of heavy nuclei. The ratio of
charged kaons to charged pions is determined for individual central Pb+Pb
collisions. After accounting for the fluctuations due to detector resolution
and finite number statistics we derive an upper limit on genuine
non-statistical fluctuations, perhaps related to a first or second order QCD
phase transition. Such fluctuations are shown to be very small.Comment: 4 pages, 2 figure
Two-proton correlations from 158 AGeV Pb+Pb central collisions
The two-proton correlation function at midrapidity from Pb+Pb central
collisions at 158 AGeV has been measured by the NA49 experiment. The results
are compared to model predictions from static thermal Gaussian proton source
distributions and transport models RQMD and VENUS. An effective proton source
size is determined by minimizing CHI-square/ndf between the correlation
functions of the data and those calculated for the Gaussian sources, yielding
3.85 +-0.15(stat.) +0.60-0.25(syst.) fm. Both the RQMD and the VENUS model are
consistent with the data within the error in the correlation peak region.Comment: RevTeX style, 6 pages, 4 figures, 1 table. More discussion are added
about the structure on the tail of the correlation function. The systematic
error is revised. To appear in Phys. Lett.
Strangeness from 20 AGeV to 158 AGeV
New results from the energy scan programme of NA49, in particular kaon
production at 30 AGeV and phi production at 40 and 80 AGeV are presented. The
K+/pi+ ratio shows a pronounced maximum at 30 AGeV; the kaon slope parameters
are constant at SPS energies. Both findings support the scenario of a phase
transition at about 30 AGeV beam energy. The phi/pi ratio increases smoothly
with beam energy, showing an energy dependence similar to K-/pi-. The measured
particle yields can be reproduced by a hadron gas model, with chemical
freeze-out parameters on a smooth curve in the T-muB plane. The transverse
spectra can be understood as resulting from a rapidly expanding, locally
equilibrated source. No evidence for an earlier kinetic decoupling of heavy
hyperons is found.Comment: Contribution to the proceedings of "Strangeness in Quark Matter 2003"
(March 2003, Atlantic Beach NC, USA), to be published in Journal of Physics
G. 11 pages, 14 figure
- …