Quitones (polyplacophora: mollusca) asociados a los arrecifes coralinos del PNN Gorgona

Los arrecifes coralinos albergan una gran diversidad de especies y la criptofauna es un componente muy importante pero poco conocido de dicha diversidad. Con esta investigación se determinó la diversidad de quitones (Mollusca: Polyplacophora) asociados a los arrecifes coralinos del PNN Gorgona en el Pacífico colombiano, área estratégica dentro del Corredor Marino del Pacífico Oriental Tropical. Para esto, se tomaron muestras de coral vivo y cascajo arrecifal (coral muerto) en dos arrecifes: La Azufrada y El Muelle. Se procesaron 160 muestras (140 de La Azufrada y 20 de El Muelle) entre sustrato vivo y muerto de corales del género Pocillopora, seleccionadas aleatoriamente. Los quitones recolectados fueron identificados hasta el menor nivel taxonómico posible. Se encontraron cuatro especies: Acanthochitona cf. Angelica, Lepidochitona aff. salvadorensis, Callistochiton cf. expressus e Ischnochiton sp. Las dos últimas especies presentaron 1 y 5 individuos respectivamente. La especie con mayor abundancia fue A. Angelica con 398 individuos, seguido por L. salvadorensis con 137 individuos. Dadas las diferencias en el tamaño de las muestras, los valores absolutos de la riqueza y la abundancia fueron superiores en La Azufrada; sin embargo, el análisis estadístico mostró que sólo el tipo de sustrato (vivo vs. muerto) afectó la densidad de quitones, con el sustrato muerto presentando mayores densidades que el coral vivo (80.3% de las veces). Se infiere que, en los arrecifes coralinos, las zonas con mayor degradación del sustrato presentan mejores condiciones para la presencia de quitones.PregradoBIOLOGO(A

Genetic diversity across the mitochondrial genome of eastern oysters (Crassostrea virginica) in the northern Gulf of Mexico

The eastern oyster, Crassostrea virginica, is divided into four populations along the western North Atlantic, however, the only published mitochondrial genome sequence was assembled using one individual in Delaware. This study aimed to 1) assemble C. virginica mitochondrial genomes from Texas with pooled restriction-site-associated DNA sequence (ezRAD), 2) evaluate the validity of the mitochondrial genome assemblies including comparison with Sanger sequencing data, and 3) evaluate genetic differentiation both between the Delaware and Texas genomes, as well as among three bays in Texas. The pooled-genome-assembled-genomes (PAGs) from Texas exhibited several characteristics indicating that they were valid, including elevated nucleotide diversity in non-coding and the third position of codons, placement as the sister haplotype of the genome from Delaware in a phylogenetic reconstruction of Crassostrea mitochondrial genomes, and a lack of genetic structure in the ND4 gene among the three Texas bays as was found with Sanger amplicons in samples from the same bays several years prior. In the comparison between the Delaware and Texas genome, 27 of 38 coding regions exhibited variability between the two populations, which were differentiated by 273 mutations, versus 1-13 mutations among the Texas samples. Using the full PAGs, there was no additional evidence for population structure among the three Texas bays. While population genetics is rapidly moving towards larger high-density datasets, studies of mitochondrial DNA (and genomes) can be particularly useful for comparing historic data prior to the modern era of genomics. As such, being able to reliably compile mitochondrial genomes from genomic data can improve the ability to compare results across studies

Multiplicity dependence of light (anti-)nuclei production in p–Pb collisions at sNN=5.02 TeV

The measurement of the deuteron and anti-deuteron production in the rapidity range −1 < y < 0 as a function of transverse momentum and event multiplicity in p–Pb collisions at √sNN = 5.02 TeV is presented. (Anti-)deuterons are identified via their specific energy loss dE/dx and via their time-of- flight. Their production in p–Pb collisions is compared to pp and Pb–Pb collisions and is discussed within the context of thermal and coalescence models. The ratio of integrated yields of deuterons to protons (d/p) shows a significant increase as a function of the charged-particle multiplicity of the event starting from values similar to those observed in pp collisions at low multiplicities and approaching those observed in Pb–Pb collisions at high multiplicities. The mean transverse particle momenta are extracted from the deuteron spectra and the values are similar to those obtained for p and particles. Thus, deuteron spectra do not follow mass ordering. This behaviour is in contrast to the trend observed for non-composite particles in p–Pb collisions. In addition, the production of the rare 3He and 3He nuclei has been studied. The spectrum corresponding to all non-single diffractive p-Pb collisions is obtained in the rapidity window −1 < y < 0 and the pT-integrated yield dN/dy is extracted. It is found that the yields of protons, deuterons, and 3He, normalised by the spin degeneracy factor, follow an exponential decrease with mass number

Measurement of prompt D0^{0}, D+^{+}, D∗+^{*+}, and DS+ {\mathrm{D}}_{\mathrm{S}}^{+} production in p–Pb collisions at sNN \sqrt{{\mathrm{s}}_{\mathrm{NN}}} = 5.02 TeV

International audienceThe measurement of the production of prompt D$^{0}$, D$^{+}$, D$^{*+}$, and ${\mathrm{D}}_{\mathrm{S}}^{+}$ mesons in proton–lead (p–Pb) collisions at the centre-of-mass energy per nucleon pair of $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV, with an integrated luminosity of 292 ± 11 μb$^{−1}$, are reported. Differential production cross sections are measured at mid-rapidity (−0.96 < y$_{cms}$< 0.04) as a function of transverse momentum (p$_{T}$) in the intervals 0 < p$_{T}$< 36 GeV/c for D$^{0}$, 1 < p$_{T}$< 36 GeV/c for D$^{+}$ and D$^{*+}$, and 2 < p$_{T}$< 24 GeV/c for D$^{+}$ mesons. For each species, the nuclear modification factor R$_{pPb}$ is calculated as a function of p$_{T}$ using a proton-proton (pp) ref- erence measured at the same collision energy. The results are compatible with unity in the whole p$_{T}$ range. The average of the non-strange D mesons R$_{pPb}$ is compared with theoretical model predictions that include initial-state effects and parton transport model predictions. The p$_{T}$ dependence of the D$^{0}$, D$^{+}$, and D$^{*+}$ nuclear modification factors is also reported in the interval 1 < p$_{T}$< 36 GeV/c as a function of the collision centrality, and the central-to-peripheral ratios are computed from the D-meson yields measured in different centrality classes. The results are further compared with charged-particle measurements and a similar trend is observed in all the centrality classes. The ratios of the p$_{T}$-differential cross sections of D$^{0}$, D$^{+}$, D$^{*+}$, and ${\mathrm{D}}_{\mathrm{S}}^{+}$ mesons are also reported. The ${\mathrm{D}}_{\mathrm{S}}^{+}$ and D$^{+}$ yields are compared as a function of the charged-particle multiplicity for several p$_{T}$ intervals. No modification in the relative abundances of the four species is observed with respect to pp collisions within the statistical and systematic uncertainties

Production of charged pions, kaons, and (anti-)protons in Pb-Pb and inelastic pppp collisions at sNN\sqrt {s_{NN}} = 5.02 TeV

International audienceMid-rapidity production of $\pi^{\pm}$, $\rm{K}^{\pm}$ and ($\bar{\rm{p}}$)p measured by the ALICE experiment at the LHC, in Pb-Pb and inelastic pp collisions at $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV, is presented. The invariant yields are measured over a wide transverse momentum ($p_{\rm{T}}$) range from hundreds of MeV/$c$ up to 20 GeV/$c$. The results in Pb-Pb collisions are presented as a function of the collision centrality, in the range 0$-$90%. The comparison of the $p_{\rm{T}}$-integrated particle ratios, i.e. proton-to-pion (p/$\pi$) and kaon-to-pion (K/$\pi$) ratios, with similar measurements in Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 2.76 TeV show no significant energy dependence. Blast-wave fits of the $p_{\rm{T}}$ spectra indicate that in the most central collisions radial flow is slightly larger at 5.02 TeV with respect to 2.76 TeV. Particle ratios (p/$\pi$, K/$\pi$) as a function of $p_{\rm{T}}$ show pronounced maxima at $p_{\rm{T}}$ $\approx$ 3 GeV/$c$ in central Pb-Pb collisions. At high $p_{\rm{T}}$, particle ratios at 5.02 TeV are similar to those measured in pp collisions at the same energy and in Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 2.76 TeV. Using the pp reference spectra measured at the same collision energy of 5.02 TeV, the nuclear modification factors for the different particle species are derived. Within uncertainties, the nuclear modification factor is particle species independent for high $p_{\rm{T}}$ and compatible with measurements at $\sqrt{s_{\rm{NN}}}$ = 2.76 TeV. The results are compared to state-of-the-art model calculations, which are found to describe the observed trends satisfactorily

Multiplicity dependence of (multi-)strange hadron production in proton-proton collisions at s\sqrt{s} = 13 TeV

The production rates and the transverse momentum distribution of strange hadrons at mid-rapidity ($\left| y\right| < 0.5$) are measured in proton-proton collisions at $\sqrt{s}$ = 13 TeV as a function of the charged particle multiplicity, using the ALICE detector at the LHC. The production rates of $\mathrm{K}^{0}_{S}$, $\Lambda$, $\Xi$, and $\Omega$ increase with the multiplicity faster than what is reported for inclusive charged particles. The increase is found to be more pronounced for hadrons with a larger strangeness content. Possible auto-correlations between the charged particles and the strange hadrons are evaluated by measuring the event-activity with charged particle multiplicity estimators covering different pseudorapidity regions. When comparing to lower energy results, the yields of strange hadrons are found to depend only on the mid-rapidity charged particle multiplicity. Several features of the data are reproduced qualitatively by general purpose QCD Monte Carlo models that take into account the effect of densely-packed QCD strings in high multiplicity collisions. However, none of the tested models reproduce the data quantitatively. This work corroborates and extends the ALICE findings on strangeness production in proton-proton collisions at 7 TeV

Λ3H^3_\Lambda\mathrm{H} and Λˉ3H‾^3_{\bar{\Lambda}}\mathrm{\overline{H}} lifetime measurement in Pb-Pb collisions at sNN=\sqrt{s_{\mathrm{NN}}} = 5.02 TeV via two-body decay

International audienceAn improved value for the lifetime of the (anti-)hypertriton has been obtained using the data sample of Pb–Pb collisions at sNN=5.02 TeV collected by the ALICE experiment at the LHC. The (anti-)hypertriton has been reconstructed via its charged two-body mesonic decay channel and the lifetime has been determined from an exponential fit to the d N /d( ct ) spectrum. The measured value, τ=242−38+34 (stat.) ± 17 (syst.) ps, is compatible with representative theoretical predictions, thus contributing to the solution of the longstanding hypertriton lifetime puzzle

Global polarization of ΛΛˉ\Lambda \bar \Lambda hyperons in Pb-Pb collisions at sNN\sqrt {s_{NN}} = 2.76 and 5.02 TeV

International audienceThe global polarization of the $\Lambda$ and $\overline\Lambda$ hyperons is measured for Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 2.76 and 5.02 TeV recorded with the ALICE at the LHC. The results are reported differentially as a function of collision centrality and hyperon's transverse momentum ($p_{\rm{T}}$) for the range of centrality 5-50%, $0.5 < p_{\rm{T}} <5$ GeV/$c$, and rapidity $|y|<0.5$. The hyperon global polarization averaged for Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 2.76 and 5.02 TeV is found to be consistent with zero, $\langle P_{\rm{H}}\rangle$ (%) $\approx$ 0.01 $\pm$ 0.06 (stat.) $\pm$ 0.03 (syst.) in the collision centrality range 15-50%, where the largest signal is expected. The results are compatible with expectations based on an extrapolation from measurements at lower collision energies at RHIC, hydrodynamical model calculations, and empirical estimates based on collision energy dependence of directed flow, all of which predict the global polarization values at LHC energies of the order of 0.01%

Global polarization of Λ and Λ hyperons in Pb-Pb collisions at √ s N N = 2.76 and 5.02 TeV

The global polarization of Λ and Λ hyperons is measured for Pb-Pb collisions at √sNN = 2.76 and 5.02 TeV recorded with the ALICE at the Large Hadron Collider (LHC). The results are reported differentially as a function of collision centrality and hyperon’s transverse momentum (pT ) for the range of centrality 5–50%, 0.5 < pT < 5 GeV/c, and rapidity |y| < 0.5. The hyperon global polarization averaged for Pb-Pb collisions at √sNN = 2.76 and 5.02 TeV is found to be consistent with zero, ⟨PH⟩(%)≈0.01±0.06(stat.)±0.03(syst.) in the collision centrality range 15–50%, where the largest signal is expected. The results are compatible with expectations based on an extrapolation from measurements at lower collision energies at the Relativistic Heavy Ion Collider, hydrodynamical model calculations, and empirical estimates based on collision energy dependence of directed flow, all of which predict the global polarization values at LHC energies of the order of 0.01%

Measurement of the inclusive isolated photon production cross section in pp collisions at s\sqrt{s} = 7 TeV

The production cross section of inclusive isolated photons has been measured by the ALICE experiment at the CERN LHC in pp collisions at a centre-of-momentum energy of $\sqrt{s}$ = 7 TeV. The measurement is performed with the electromagnetic calorimeter EMCal and the central tracking detectors, covering a range of $|\eta|$ < 0.27 in pseudorapidity and a transverse momentum range of 10<$p_{\rm T}^{\gamma}$ <60 GeV/$c$. The result extends the $p_{\rm T}$ coverage of previously published results of the ATLAS and CMS experiments at the same collision energy to smaller $p_{\rm T}$. The measurement is compared to next-to-leading order perturbative QCD calculations and to the results from the ATLAS and CMS experiments. All measurements and theory predictions are in agreement with each other.The production cross section of inclusive isolated photons has been measured by the ALICE experiment at the CERN LHC in pp collisions at a centre-of-momentum energy of $\sqrt{s}=$ 7 TeV. The measurement is performed with the electromagnetic calorimeter EMCal and the central tracking detectors, covering a range of $|\eta |<0.27$ in pseudorapidity and a transverse momentum range of $10< p_\mathrm {T}^{\gamma }< 60~\mathrm {GeV}/c$. The result extends the $p_\mathrm {T}$ coverage of previously published results of the ATLAS and CMS experiments at the same collision energy to smaller $p_\mathrm {T}$. The measurement is compared to next-to-leading order perturbative QCD calculations and to the results from the ATLAS and CMS experiments. All measurements and theory predictions are in agreement with each other.The production cross section of inclusive isolated photons has been measured by the ALICE experiment at the CERN LHC in pp collisions at a centre-of-momentum energy of $\sqrt{s}=$ 7 TeV. The measurement is performed with the electromagnetic calorimeter EMCal and the central tracking detectors, covering a range of $|\eta|<0.27$ in pseudorapidity and a transverse momentum range of $10 < p_{\rm T}^{\gamma} <$ 60 GeV/$c$. The result extends the $p_{\rm T}$ coverage of previously published results of the ATLAS and CMS experiments at the same collision energy to smaller $p_{\rm T}$. The measurement is compared to next-to-leading order perturbative QCD calculations and to the results from the ATLAS and CMS experiments. All measurements and theory predictions are in agreement with each other