Modelling the relative velocities of isolated pairs of galaxies

We study the comoving relative velocities, v12, of model isolated galaxy pairs at z=0.5. For this purpose, we use the predictions from the GALFORM semi-analytical model of galaxy formation and evolution based on a Lambda cold dark matter cosmology consistent with the results from WMAP7. In real space, we find that isolated pairs of galaxies are predicted to form an angle t with the line-of-sight that is uniformily distributed as expected if the Universe is homogeneous and isotropic. We also find that isolated pairs of galaxies separated by a comoving distance between 1 and 3 Mpc/h are predicted to have =0. For galaxies in this regime, the distribution of the angle t is predicted to change minimally from real to redshift space, with a change smaller than 5% in . However, the distances defining the comoving regime strongly depends on the applied isolation criteria.Comment: 4 pages, 4 figures, SF2A 2013 Proceedin

Amplification and cloning of cDNAS of cytochrome P4501A1 and metallothionein genes from Sparus aurata Linnaeus, 1758 and Liza aurata (Risso, 1810) by Race-PCR

The biotransformation of xenobiotics found in marine ecosystems is catalysed by inducible systems, a property that makes them useful as early-warning biomarkers of environmental pollution. We have focused our study on cytochrome P4501A1 (CYP 1A1) as a phase I response against organic aromatic xenobiotics, and metallothionein (MT), which reflects pollution by transition metals. The high homology existing between the sequences of both genes, already cloned in different fish species, enabled us to design degenerate oligos to amplify by RT-PCR specific sequences of CYP 1A1 and MT genes in two teleost fish species of the Spanish South Atlantic littoral, the gilthead seabream, Sparus aurata Linnaeus, 1758, and the grey mullet, Liza aurata (Risso 1810). To this end, the expression of both genes was previously induced by intraperitoneal injection with Aroclor 1254 (CYP 1A1) and CdCl2 (MT). The specific sequences for both genes amplified by RT-PCR with degenerate oligos were subsequently used to design new, specific oligos to obtain by Race-PCR (Rapid Amplification of cDNA Ends) the complete cDNAs coding for both genes in both fish species, which were subsequently cloned and sequenced. The coding sequences and the corresponding proteins were compared with those already obtained in other fish species. We are currently developing homologous probes for mRNA quantification using molecular biology techniques in both fish species, to be employed as molecular biomarkers of pollution in the Spanish South Atlantic littoralLa biotransformación de xenobióticos presentes en ecosistemas marinos está catalizada por varios sistemas inducibles, lo que permite su uso como biomarcadores de alerta temprana de contaminación ambiental. Este estudio se ha centrado en el citocromo P4501A1 (CYP 1A1), como respuesta de fase I contra xenobióticos orgánicos aromáticos, y la metalotioneína (MT), que refleja la contaminación por metales de transición. La alta homología existente entre las secuencias de ambos genes previamente clonados en diferentes especies de peces permitió diseñar oligos degenerados para amplificar por RT-PCR secuencias específicas de los genes CYP 1A1 y MT en dos especies de peces teleósteos del litoral suratlántico español, la dorada Sparus aurata Linnaeus, 1758 y la lisa Liza aurata (Risso, 1810). Para ello, la expresión de ambos genes se indujo por inyección intraperitoneal con Aroclor 1254 (CYP 1A1) y CdCl2 (MT). Las secuencias específicas de ambos genes, amplificadas por RT-PCR con tales oligos, se usaron posteriormente para diseñar nuevos oligos específicos; éstos se usaron para amplificar por Race-PCR (Rapid Amplification of cDNA Ends) los cDNAs completos que codifican tales genes en ambas especies de peces, que fueron posteriormente clonados y secuenciados. Las secuencias codificantes y las proteínas correspondientes se han comparado con las obtenidas en otras especies de peces. Actualmente se desarrollan sondas homólogas para cuantificar por métodos de biología molecular los mRNAs específicos en ambos peces, para su uso como biomarcadores moleculares de contaminación en el litoral suratlántico españo

Amplification and cloning of cDNAS of cytochrome P4501A1 and metallothionein genes from Sparus aurata Linnaeus, 1758 and Liza aurata (Risso, 1810) by Race-PCR

The biotransformation of xenobiotics found in marine ecosystems is catalysed by inducible systems, a property that makes them useful as early-warning biomarkers of environmental pollution. We have focused our study on cytochrome P4501A1 (CYP 1A1) as a phase I response against organic aromatic xenobiotics, and metallothionein (MT), which reflects pollution by transition metals. The high homology existing between the sequences of both genes, already cloned in different fish species, enabled us to design degenerate oligos to amplify by RT-PCR specific sequences of CYP 1A1 and MT genes in two teleost fish species of the Spanish South Atlantic littoral, the gilthead seabream, Sparus aurata Linnaeus, 1758, and the grey mullet, Liza aurata (Risso 1810). To this end, the expression of both genes was previously induced by intraperitoneal injection with Aroclor 1254 (CYP 1A1) and CdCl2 (MT). The specific sequences for both genes amplified by RT-PCR with degenerate oligos were subsequently used to design new, specific oligos to obtain by Race-PCR (Rapid Amplification of cDNA Ends) the complete cDNAs coding for both genes in both fish species, which were subsequently cloned and sequenced. The coding sequences and the corresponding proteins were compared with those already obtained in other fish species. We are currently developing homologous probes for mRNA quantification using molecular biology techniques in both fish species, to be employed as molecular biomarkers of pollution in the Spanish South Atlantic littoral.La biotransformación de xenobióticos presentes en ecosistemas marinos está catalizada por varios sistemas inducibles, lo que permite su uso como biomarcadores de alerta temprana de contaminación ambiental. Este estudio se ha centrado en el citocromo P4501A1 (CYP 1A1), como respuesta de fase I contra xenobióticos orgánicos aromáticos, y la metalotioneína (MT), que refleja la contaminación por metales de transición. La alta homología existente entre las secuencias de ambos genes previamente clonados en diferentes especies de peces permitió diseñar oligos degenerados para amplificar por RT-PCR secuencias específicas de los genes CYP 1A1 y MT en dos especies de peces teleósteos del litoral suratlántico español, la dorada Sparus aurata Linnaeus, 1758 y la lisa Liza aurata (Risso, 1810). Para ello, la expresión de ambos genes se indujo por inyección intraperitoneal con Aroclor 1254 (CYP 1A1) y CdCl2 (MT). Las secuencias específicas de ambos genes, amplificadas por RT-PCR con tales oligos, se usaron posteriormente para diseñar nuevos oligos específicos; éstos se usaron para amplificar por Race-PCR (Rapid Amplification of cDNA Ends) los cDNAs completos que codifican tales genes en ambas especies de peces, que fueron posteriormente clonados y secuenciados. Las secuencias codificantes y las proteínas correspondientes se han comparado con las obtenidas en otras especies de peces. Actualmente se desarrollan sondas homólogas para cuantificar por métodos de biología molecular los mRNAs específicos en ambos peces, para su uso como biomarcadores moleculares de contaminación en el litoral suratlántico español.Instituto Español de Oceanografí

Jackknife resampling technique on mocks: an alternative method for covariance matrix estimation

We present a fast and robust alternative method to compute covariance matrix in case of cosmology studies. Our method is based on the jackknife resampling applied on simulation mock catalogues. Using a set of 600 BOSS DR11 mock catalogues as a reference, we find that the jackknife technique gives a similar galaxy clustering covariance matrix estimate by requiring a smaller number of mocks. A comparison of convergence rates show that $\sim$7 times fewer simulations are needed to get a similar accuracy on variance. We expect this technique to be applied in any analysis where the number of available N-body simulations is low.Comment: 11 pages, 11 figures, 2 table

Measurement of the t-channel single top quark production cross section

The D0 collaboration reports direct evidence for electroweak production of single top quarks through the t-channel exchange of a virtual W boson. This is the first analysis to isolate an individual single top quark production channel. We select events containing an isolated electron or muon, missing transverse energy, and two, three or four jets from 2.3 fb^-1 of ppbar collisions at the Fermilab Tevatron Collider. One or two of the jets are identified as containing a b hadron. We combine three multivariate techniques optimized for the t-channel process to measure the t- and s-channel cross sections simultaneously. We measure cross sections of 3.14 +0.94 -0.80 pb for the t-channel and 1.05 +-0.81 pb for the s-channel. The measured t-channel result is found to have a significance of 4.8 standard deviations and is consistent with the standard model prediction.Comment: 7 pages, 6 figure

Search for new fermions ("quirks") at the Fermilab Tevatron Collider

We report results of a search for particles with anomalously high ionization in events with a high transverse energy jet and large missing transverse energy in $2.4$ fb$^{-1}$ of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron $p\bar{p}$ collider. Production of such particles (quirks) is expected in scenarios with extra QCD-like {\it SU(N)} sectors, and this study is the first dedicated search for such signatures. We find no evidence of a signal and set a lower mass limit of 107 ~GeV for the mass of a charged quirk with strong dynamics scale $\Lambda$ in the range from 10 keV to 1 MeV.Comment: submitted to Phys. Rev. Letter

Measurement of the B0_s semileptonic branching ratio to an orbitally excited D_s** state, Br(B0_s -> Ds1(2536) mu nu)

In a data sample of approximately 1.3 fb-1 collected with the D0 detector between 2002 and 2006, the orbitally excited charm state D_s1(2536) has been observed with a measured mass of 2535.7 +/- 0.6 (stat) +/- 0.5 (syst) MeV via the decay mode B0_s -> D_s1(2536) mu nu X. A first measurement is made of the branching ratio product Br(b(bar) -> D_s1(2536) mu nu X).Br(D_s1(2536)->D* K0_S). Assuming that D_s1(2536) production in semileptonic decay is entirely from B0_s, an extraction of the semileptonic branching ratio Br(B0_s -> D_s1(2536) mu nu X) is made.Comment: 7 pages, 2 figures, LaTeX, version with minor changes as accepted by Phys. Rev. Let

Measurements of differential cross sections of Z/gamma*+jets+X events in proton anti-proton collisions at sqrt{s}=1.96 TeV

We present cross section measurements for Z/gamma*+jets+X production, differential in the transverse momenta of the three leading jets. The data sample was collected with the D0 detector at the Fermilab Tevatron proton anti-proton collider at a center-of-mass energy of 1.96 TeV and corresponds to an integrated luminosity of 1 fb-1. Leading and next-to-leading order perturbative QCD predictions are compared with the measurements, and agreement is found within the theoretical and experimental uncertainties. We also make comparisons with the predictions of four event generators. Two parton-shower-based generators show significant shape and normalization differences with respect to the data. In contrast, two generators combining tree-level matrix elements with a parton shower give a reasonable description of the the shapes observed in data, but the predicted normalizations show significant differences with respect to the data, reflecting large scale uncertainties. For specific choices of scales, the normalizations for either generator can be made to agree with the measurements.Comment: Published in PLB. 11 pages, 3 figure

Simultaneous measurement of the ratio B(t->Wb)/B(t->Wq) and the top quark pair production cross section with the D0 detector at sqrt(s)=1.96 TeV

We present the first simultaneous measurement of the ratio of branching fractions, R=B(t->Wb)/B(t->Wq), with q being a d, s, or b quark, and the top quark pair production cross section sigma_ttbar in the lepton plus jets channel using 0.9 fb-1 of ppbar collision data at sqrt(s)=1.96 TeV collected with the D0 detector. We extract R and sigma_ttbar by analyzing samples of events with 0, 1 and >= 2 identified b jets. We measure R = 0.97 +0.09-0.08 (stat+syst) and sigma_ttbar = 8.18 +0.90-0.84 (stat+syst)} +/-0.50 (lumi) pb, in agreement with the standard model prediction.Comment: submitted to Phys.Rev.Letter

Measurement of the W boson mass

We present a measurement of the W boson mass in W -> ev decays using 1 fb^-1 of data collected with the D0 detector during Run II of the Fermilab Tevatron collider. With a sample of 499830 W -> ev candidate events, we measure M_W = 80.401 +- 0.043 GeV. This is the most precise measurement from a single experiment.Comment: As published in PR