2,579 research outputs found
A multiwavelength numerical model in support of quantitative retrievals of aerosol properties from automated lidar ceilometers and test applications for AOT and PM10 estimation
Abstract. The use of automated lidar ceilometer (ALC) systems for the
aerosol vertically resolved characterization has increased in recent
years thanks to their low construction and operation costs and their
capability of providing continuous unattended measurements. At the same time
there is a need to convert the ALC signals into usable geophysical
quantities. In fact, the quantitative assessment of the aerosol properties
from ALC measurements and the relevant assimilation in meteorological
forecast models is amongst the main objectives of the EU COST Action TOPROF
("Towards operational ground-based profiling with ALCs, Doppler lidars and
microwave radiometers for improving weather forecasts"). Concurrently, the E-PROFILE program of the European
Meteorological Services Network (EUMETNET) focuses on the harmonization of
ALC measurements and data provision across Europe. Within these frameworks,
we implemented a model-assisted methodology to retrieve key aerosol
properties (extinction coefficient, surface area, and volume) from elastic
lidar and/or ALC measurements. The method is based on results from a large
set of aerosol scattering simulations (Mie theory) performed at UV, visible,
and near-IR wavelengths using a Monte Carlo approach to select the input
aerosol microphysical properties. An average "continental aerosol type"
(i.e., clean to moderately polluted continental aerosol conditions) is
addressed in this study. Based on the simulation results, we derive mean
functional relationships linking the aerosol backscatter coefficients to the
abovementioned variables. Applied in the data inversion of single-wavelength
lidars and/or ALCs, these relationships allow quantitative determination of
the vertically resolved aerosol backscatter, extinction, volume, and surface
area and, in turn, of the extinction-to-backscatter ratios (i.e., the
lidar ratios, LRs) and extinction-to-volume conversion factor
(cv) at 355, 532, and 1064ânm. These variables provide valuable
information for visibility, radiative transfer, and air quality applications.
This study also includes (1) validation of the model simulations with real
measurements and (2) test applications of the proposed model-based ALC
inversion methodology. In particular, our model simulations were compared to
backscatter and extinction coefficients independently retrieved by Raman
lidar systems operating at different continental sites within the European
Aerosol Research Lidar Network (EARLINET). This comparison shows good
modelâmeasurement agreement, with LR discrepancies below 20â%. The
model-assisted quantitative retrieval of both aerosol extinction and volume
was then tested using raw data from three different ALCs systems
(CHM 15k Nimbus), operating within the Italian Automated LIdar-CEilometer
network (ALICEnet). For this purpose, a 1-year record of the ALC-derived
aerosol optical thickness (AOT) at each site was compared to direct AOT
measurements performed by colocated sunâsky photometers. This comparison
shows an overall AOT agreement within 30â% at all sites. At one site, the
model-assisted ALC estimation of the aerosol volume and mass (i.e.,
PM10) in the lowermost levels was compared to values measured at
the surface level by colocated in situ instrumentation. Within this
exercise, the ALC-derived daily-mean mass concentration was found to
reproduce the corresponding (EU regulated) PM10 values measured by
the local air quality agency well in terms of both temporal variability and
absolute values. Although limited in space and time, the good performances of
the proposed approach suggest it could possibly
represent a valid option to extend the capabilities of ALCs to provide
quantitative information for operational air quality and meteorological
monitoring
A discrete time relativistic Toda lattice
Four integrable symplectic maps approximating two Hamiltonian flows from the
relativistic Toda hierarchy are introduced. They are demostrated to belong to
the same hierarchy and to examplify the general scheme for symplectic maps on
groups equiped with quadratic Poisson brackets. The initial value problem for
the difference equations is solved in terms of a factorization problem in a
group. Interpolating Hamiltonian flows are found for all the maps.Comment: 32 pages, LaTe
On the dimensions of secant varieties of Segre-Veronese varieties
This paper explores the dimensions of higher secant varieties to
Segre-Veronese varieties. The main goal of this paper is to introduce two
different inductive techniques. These techniques enable one to reduce the
computation of the dimension of the secant variety in a high dimensional case
to the computation of the dimensions of secant varieties in low dimensional
cases. As an application of these inductive approaches, we will prove
non-defectivity of secant varieties of certain two-factor Segre-Veronese
varieties. We also use these methods to give a complete classification of
defective s-th Segre-Veronese varieties for small s. In the final section, we
propose a conjecture about defective two-factor Segre-Veronese varieties.Comment: Revised version. To appear in Annali di Matematica Pura e Applicat
Application of COMPOCHIP Microarray to Investigate the Bacterial Communities of Different Composts
A microarray spotted with 369 different 16S rRNA gene probes specific to microorganisms involved in the degradation process of organic waste during composting was developed. The microarray was tested with pure cultures, and of the 30,258 individual probe-target hybridization reactions performed, there were only 188 false positive (0.62%) and 22 false negative signals (0.07%). Labeled target DNA was prepared by polymerase chain reaction amplification of 16S rRNA genes using a Cy5-labeled universal bacterial forward primer and a universal reverse primer. The COMPOCHIP microarray was applied to three different compost types (green compost, manure mix compost, and anaerobic digestate compost) of different maturity (2, 8, and 16 weeks), and differences in the microorganisms in the three compost types and maturity stages were observed. Multivariate analysis showed that the bacterial composition of the three composts was different at the beginning of the composting process and became more similar upon maturation. Certain probes (targeting Sphingobacterium, Actinomyces, Xylella/Xanthomonas/ Stenotrophomonas, Microbacterium, Verrucomicrobia, Planctomycetes, Low G + C and Alphaproteobacteria) were more influential in discriminating between different composts. Results from denaturing gradient gel electrophoresis supported those of microarray analysis. This study showed that the COMPOCHIP array is a suitable tool to study bacterial communities in composts
Recommendations for the detection and diagnosis of Niemann-Pick disease type C: An update.
PURPOSE OF REVIEW:
Niemann-Pick disease type C (NP-C) is a neurovisceral disorder that may be more prevalent than earlier estimates. Diagnosis of NP-C is often delayed; a key aim for clinical practice is to reduce this delay. Recently, substantial progress has been made in the field of NP-C screening and diagnosis, justifying an update to the existing recommendations for clinical practice.
RECENT FINDINGS:
New biomarker profiling and genetic analysis technologies are included as first-line diagnostic tests for NP-C. Most diagnoses can now be confirmed by combination of biomarker and genetic analyses. Filipin staining may facilitate diagnosis in uncertain cases. Recommendations are provided for psychiatrists, neuro-ophthalmologists, and radiologists, and on screening within specific at-risk patient cohorts. The NP-C diagnostic algorithm has been updated and simplified.
SUMMARY: This publication provides expert recommendations for clinicians who may see patients presenting with the signs and symptoms of NP-C, including general practitioners, pediatricians, neurologists, and psychiatrists
Mangrove microniches determine the structural and functional diversity of enriched petroleum hydrocarbon-degrading consortia
In this study, the combination of culture enrichments and molecular tools was used to identify bacterial guilds, plasmids and functional genes potentially important in the process of petroleum hydrocarbon (PH) decontamination in mangrove microniches (rhizospheres and bulk sediment). In addition, we aimed to recover PH-degrading consortia (PHDC) for future use in remediation strategies. The PHDC were enriched with petroleum from rhizosphere and bulk sediment samples taken from a mangrove chronically polluted with oil hydrocarbons. Southern blot hybridization (SBH) assays of PCR amplicons from environmental DNA before enrichments resulted in weak positive signals for the functional gene types targeted, suggesting that PH-degrading genotypes and plasmids were in low abundance in the rhizosphere and bulk sediments. However, after enrichment, these genes were detected and strong microniche-dependent differences in the abundance and composition of hydrocarbonoclastic bacterial populations, plasmids (IncP-1 alpha, IncP-1 beta, IncP-7 and IncP-9) and functional genes (naphthalene, extradiol and intradiol dioxygenases) were revealed by in-depth molecular analyses [PCR-denaturing gradient gel electrophoresis and hybridization (SBH and microarray)]. Our results suggest that, despite the low abundance of PH-degrading genes and plasmids in the environmental samples, the original bacterial composition of the mangrove microniches determined the structural and functional diversity of the PHDC enriched.Deutsche Forschungsgemeinschaft [SM59/4-1, 4-2]; FAPERJ-Brazil; European Commission [003998, 211684]; Alexander-von-Humboldt-Stiftung; CONICET (Argentina)info:eu-repo/semantics/publishedVersio
an inclusive view of saharan dust advections to italy and the central mediterranean
Abstract We address observations of physical and chemical properties of Saharan dust advections (SDA) as observed in the Central Mediterranean basin, within the framework of the LIFE+10, DIAPASON project ( www.diapason-life.eu ). DIAPASON aimed at the definition of best practices and tools to detect and evaluate the contribution of Saharan dust to ground particulate matter (PM) loads. Polarization-sensitive, automated lidar-ceilometers (PLC) are one of the tools prototyped and used in the Rome area to reach this goal. The results presented in this study focus on: 1) the effectiveness of various observational tools at detecting and characterizing atmospheric dust plumes, and 2) processes and properties of Saharan dust advections reaching the central Mediterranean region. In this respect, the combination of numerical model forecasts and time-resolved (at least hourly) PLC or chemical observations was found to constitute an efficient way to predict and confirm the presence of Saharan dust. In the period 2011â2014, Saharan dust advections were observed to reach over Rome on about 32% of the days. In some 70% of these days the dust reached the ground in dry conditions, while 30% of advection days involved wet deposition. Dry (wet) deposition was found to maximize (minimize) in summer. The northern Sahara between Algeria and Tunisia (Grand Erg Oriental), was confirmed as the most frequent region of origin of the dust mobilized towards central Italy. Secondary source regions include northern Morocco and Libya. On a statistical basis, Saharan advections to Rome were preceded by increasing atmospheric pressure and stability. These conditions were found to favor the accumulation of aerosols related to local emission sources before the SDA reached the ground. Meteorology (precipitation and turbulence in primis) resulted to be an important modulator of PM concentrations during SDAs. Magnitude and timing of these factors should be well considered to correctly evaluate the dust share in PM loads or the related health effects. Saharan advections observed during DIAPASON affected particle concentrations down to diameters of about 0.6â1âŻÎŒm, with number concentrations peaking at the 2.5âŻÎŒm diameter range. These advections were associated with a significant increase in Si-rich particles containing a non-negligible fraction of water. Rainfall was observed to preferentially remove dust particles larger than 2âŻÎŒm, causing a significant depletion in the Ca-rich fraction with respect to the Si-rich one. The increase in PLC depolarization ratios above 5%, as well as the hourly PIXE records of the Si/Ca ratio increasing above 1 were found to represent good markers for the actual presence of Saharan dust particulate matter, when Saharan advection conditions are occurring
Experimental aspects of SU(5)xU(1) supergravity
We study various aspects of supergravity as they relate to
the experimental verification or falsification of this model. We consider two
string-inspired, universal, one-parameter, no-scale soft-supersymmetry-breaking
scenarios, driven by the -terms of the moduli and dilaton fields. The model
is described in terms of the supersymmetry mass scale (\ie, the chargino mass
), , and the top-quark mass. We first determine the
combined effect on the parameter space of all presently available direct and
indirect experimental constraints, including the LEP lower bounds on sparticle
and Higgs-boson masses, the rate, the anomalous magnetic moment
of the muon, the high-precision electroweak parameters
(which imply m_t\lsim180\GeV), and the muon fluxes in underground detectors
(neutrino telescopes). For the still-allowed points in
parameter space, we re-evaluate the experimental
situation at the Tevatron, LEPII, and HERA. In the 1994 run, the Tevatron could
probe chargino masses as high as 100 GeV. At LEPII the parameter space could be
explored with probes of different resolutions: Higgs boson searches, selectron
searches, and chargino searches. Moreover, for m_t\lsim150\GeV, these
Higgs-boson searches could explore all of the allowed parameter space with
\sqrt{s}\lsim210\GeV.Comment: latex, 36 pages, 25 figures (not included). Figures are available via
anonymous ftp from hplaa02.cern.ch (/pub/lopez) as either 33 ps files
(Easpects*.ps, 8.1MB) or one uuencoded file (AllFigures.uu, 3.7MB
Direct Observation of Longitudinally Polarised W Bosons
The three different helicity states of W bosons, produced in the reaction
e+e- -> W+W- -> l nu q q~ are studied using leptonic and hadronic W decays at
sqrt{s}=183GeV and 189GeV. The W polarisation is also measured as a function of
the scattering angle between the W- and the direction of the e- beam. The
analysis demonstrates that W bosons are produced with all three helicities, the
longitudinal and the two transverse states. Combining the results from the two
center-of-mass energies and with leptonic and hadronic W decays, the fraction
of longitudinally polarised W bosons is measured to be 0.261 +/- 0.051(stat.)
+/- 0.016(syst.) in agreement with the expectation from the Standard Model
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