2,631 research outputs found
Vertex reconstruction for proton-proton collisions in ALICE
Reconstructing the interaction vertex is a challenging task in the low multiplicity environment of pp collisions at the LHC. The two innermost layers of the Inner Tracking System (ITS), made of pixels, allow to obtain a first estimate of the vertex position, which can be provided also in a quasi-online mode, since only the local reconstruction is used. The optimal vertex measurement is obtained after the full event processing, using the tracks reconstructed in the ALICE barrel detectors. We present the methods for primary vertex reconstruction in pp collisions using pixels and tracks reconstructed in the ITS+TPC or in the TPC only. We also show the performance of the vertex finder in reconstructing displaced vertices originated by short-lived particles like charmed mesons
Contrasting multi-taxa diversity patterns between abandoned and non-intensively managed forests in the southern Dolomites
The abandonment of silvicultural activities can lead to changes in species richness and composition of biological communities, when compared to those found in managed forests. The aim of this study was to compare the multi-taxonomical diversity of two mature silver fir-beech-spruce forests in the southern Dolomites (Italy), corresponding to the European Union habitat type 9130. The two sites share similar ecological and structural characteristics, but differ in their recent management histories. In the last 50 years, one site underwent non-intensive management, while the other was left unmanaged and was included in a forest reserve. The species richness and composition of eight taxa were surveyed in the two sites between 2009 and 2011. The difference in mean species richness between the two forest management types was tested through permutation tests, while differences in species composition were tested by principal coordinates analysis and the permutational multivariate analysis of variance. Mean species richness of soil macrofungi, deadwood lichens, bark beetles, and longhorn beetles were significantly higher in the abandoned than in the non-intensively managed forests. Deadwood fungi and epiphytic lichens did not differ in mean species richness between the two study sites, while mean species richness of ground beetles and birds were higher in the non-intensively managed than in the abandoned forest. Significant differences in species composition between the two sites were found for all the taxa, except for longhorn beetles. These results indicate that improving forest landscape heterogeneity through the creation of a mosaic of abandoned and extensively managed forests should better fulfill the requirements of ecologically different taxa
Measuring beauty production in Pb-Pb collisions at the LHC via single electrons in ALICE
We present the expected ALICE performance for the measurement of the
p_t-differential cross section of electrons from beauty decays in central Pb-Pb
collisions at the LHC.Comment: 4 pages, 2 figures, proceeding of poster presentation at "Quark
Matter 2005
LISA: Mars and the limits of life
We describe the results of the first tests made on LISA, a simulator of
planetary environments designed and built in Padua, dedicated to the study of
the limit of bacterial life on the planet Mars. Tests on the cryogenic circuit,
on the UV illumination and on bacterial coltures at room temperature that shall
be used as references are described.Comment: 4 pages, 3 figures. Mem. SAIt, in pres
Heavy Flavor Probes of Quark Matter
A brief survey of the role of heavy flavors as a probe of the state of matter
produced by high energy heavy ion collisions is presented. Specific examples
include energy loss, initial state gluon saturation, thermalization and flow.
The formation of quarkonium bound states from interactions in which multiple
heavy quark-antiquark pairs are initially produced is examined in general.
Results from statistical hadronization and kinetic models are summarized. New
predictions from the kinetic model for J/Psi at RHIC are presented.Comment: Based on invited plenary talk at Strange Quark Matter 2004, Cape
Town, South Africa, September 15-20, 2004, references completed, published in
J. Phys. G: Nucl. Part. Phys. 31 (2005) S641-S64
Physicochemical parameters and antibiotics residuals in Algerian honey
The aim of the present study was to evaluate the quality of 36 samples of different honey type supplied by local producers from Algeria in order to verify its compliance with the standards of Codex Alimentarius and European Union (EU). For that, five physicochemical parameters were analyzed using the HPLC method: hydroxyl-methyl furfural (HMF), sugars, diastase activity and search of antibiotic contamination with streptomycin and tetracycline. The physicochemical analyses of the Algerian honeys show that 56% of samples correspond to Codex standards and 44% not in conformity with the standards required by the Codex Alimentarius and EU, because part of the samples had one or more defects. The percentage not in conformity was due to the high rates of hydroxyl-methyl furfural, sucroseand also to the low enzyme level. Analysis performed by the laboratory to detect residues of tetracycline and streptomycin in honey have revealed insignificant traces of oxytetracycline in two samples of honey (0.03 ppb). From the present study, it is observed that the Algerian honey samples is not completely in agreement with the requirements of international honey standards which could be caused by inappropriate actions during processing and storage steps.Key words: Honey quality, sugar, diastase activity, hydroxymethylfurfural, antibiotic residues
Recent Results on Strangeness Production at RHIC
Due to its large acceptance, the STAR experiment has acquired a wealth of
data on strangeness production for a variety of collisions systems and
energies, from p+p to Au+Au. By using the yields and spectra, we address the
evolution of the bulk system, including strangeness enhancement and the flavour
dependence of radial and elliptic flow. Utilising the fact that we can identify
strange baryons and mesons, we investigate different hadronization mechanisms
in the intermediate and high p regions. The ratios of the particle
yields, measured to high p, are used to further investigate the range and
applicability of the previously reported anomalous baryon production. We also
study two-particle azimuthal correlations of identified particles in order to
investigate any flavour dependence of jet fragmentation in the available
p range. Data was presented for a number of different collision systems
and energies.Comment: Proceedings of SQM'06 Conference, LA, 2006 (submitted to J. Phys. G
Photon tagged correlations in heavy ion collisions
A detailed study of various two-particle correlation functions involving
photons and neutral pions is presented in proton-proton and lead-lead
collisions at the LHC energy. The aim is to use these correlation functions to
quantify the effect of the medium (in lead-lead collisions) on the jet decay
properties. The calculations are carried out at the leading order in QCD but
the next-to-leading order corrections are also discussed. The competition
between different production mechanisms makes the connection between the jet
energy loss spectrum and the gamma-pi correlations somewhat indirect while the
gamma-gamma correlations have a clearer relation to the jet fragmentation
properties.Comment: 32 pages, 19 figures. Minor changes, published versio
Cryotolerance of equine spermatozoa correlates with specific fatty acid pattern: A pilot study
Sperm cryopreservation represents a powerful tool for horse breeding. To improve the efficiency of artificial insemination in the horse using cryopreserved spermatozoa, an adequate understanding of the underlying biophysical properties that affect sperm cryosurvival needs to be reached yet. In this pilot study, we described isolation and analysis of the main fatty acids from sperms of stallions classified as good and poor freezers (7 GF and 5 PF, according to sperm motility and viability, before and after cryopreservation). Fatty acid profiles were only assessed in pre-thaw sperms. Eight main fatty acids were identified, using gas chromatography, and their contents were expressed as percentage of the total lipid content. We found that lauric, myristic and oleic acid (C12:0, C14:0 and C18:1n9c) turned out to be about 2-fold more abundant in the sperm cells of the GFs compared with PFs. Moreover, we described for the first time the presence of a very high amount of a trans geometrical isomer of linoleic acid, linolelaidic acid (C18:2n6t), in pre-thaw PF spermatozoa. Notably, we found in fresh sperms of PF stallions a ratio of unsaturated fatty acids to saturated fatty acids which was twice that of those of GF group, suggesting a positive effect of a high saturated-to-unsaturated fatty acid ratio for the “freezability” of equine spermatozoa. Finally, principal component analysis (PCA) confirmed the relationships between specific fatty acids and cryotolerance of equine spermatozoa, also providing a graphical classification and additional information about the dominant variables governing the classification process
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