277 research outputs found
Stimulation of estrogen receptor accumulation by estradiol in primary cultures of salmon hepatocytes
AbstractHepatocytes of Salmo salar in primary culture form confluent monolayers and can be maintained at 11 °C in serum-free medium for 8 days with minimal cell loss. Cultured hepatocytes from immature male salmon contain estrogen receptor both in nuclear and cytosol fractions (2000 and 2400 sites/cell, respectively). A single addition of estradiol results in an increase in the nuclear receptor to a level of 23 000 sites/cell after 24 h. This nuclear receptor concentration is similar to that in liver of estrogen-treated salmon in vivo, and is much higher than has been found for any other egg-laying vertebrate. The cultured salmon hepatocytes thus represent a highly sensitive system for the study of estrogen receptor dynamics and vitellogenesis in vitro
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Carbonate Deposits in Marine Fish Intestines: A New Source of Biomineralization
Marine teleostean fish are hypo-osmotic to seawater. As part of a multiorgan osmoregulatory strategy they drink seawater and selectively absorb water and minerals across the intestinal epithelium. Notably, divalent cations (Ca2+ and Mg2-) are left behind. We report here that in the gulf toadfish, Opsanus beta, the ionic by-products of osmoregulation in the intestine contribute to de novo formation of a carbonate mineral, tentatively identified as calcian kutnohorite. Our data suggest that intestinal mineralization is a general feature of osmoregulation in marine teleosts and that this process is an unrecognized and possibly substantial source of marine carbonate sediments
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
Observation of ZZ production in ppbar collisions at sqrt(s) = 1.96 TeV
We present an observation for ZZ -> l+l-l'+l'- (l, l' = e or mu) production
in ppbar collisions at a center-of-mass energy of sqrt(s) = 1.96 TeV. Using 1.7
fb-1 of data collected by the D0 experiment at the Fermilab Tevatron Collider,
we observe three candidate events with an expected background of 0.14 +0.03
-0.02 events. The significance of this observation is 5.3 standard deviations.
The combination of D0 results in this channel, as well as in ZZ -> l+l-nunubar,
yields a significance of 5.7 standard deviations and a combined cross section
of sigma(ZZ) = 1.60 +/- 0.63 (stat.) +0.16 -0.17 (syst.) pb.Comment: 7 pages, 1 figure, 2 tables Modified slightly following review
proces
A search for the standard model Higgs boson in the missing energy and acoplanar b-jet topology at sqrt(s) = 1.96 TeV
We report a search for the standard model Higgs boson in the missing energy
and acoplanar b-jet topology, using an integrated luminosity of 0.93 inverse
femtobarn recorded by the D0 detector at the Fermilab Tevatron Collider. The
analysis includes signal contributions from pp->ZH->nu nu b b, as well as from
WH production in which the charged lepton from the W boson decay is undetected.
Neural networks are used to separate signal from background. In the absence of
a signal, we set limits on the cross section of pp->VH times the branching
ratio of H->bb at the 95% C.L. of 2.6 - 2.3 pb, for Higgs boson masses in the
range 105 - 135 GeV, where V=W,Z. The corresponding expected limits range from
2.8 pb - 2.0 pb.Comment: Submitted to Phys. Rev. Letter
Measurement of the lifetime of the B_c meson in the semileptonic decay channel
Using approximately 1.3 fb-1 of data collected by the D0 detector between
2002 and 2006, we measure the lifetime of the B_c meson in the B_c -> J/psi mu
nu X final state. A simultaneous unbinned likelihood fit to the J/\psi+mu
invariant mass and lifetime distributions yields a signal of 881 +/- 80 (stat)
candidates and a lifetime measurement of \tau(B_c) = 0.448 +0.038 -0.036 (stat)
+/- 0.032 (syst) ps.Comment: 7 pages, 2 figures, submitted to Phys. Rev. Let
Search for Large extra spatial dimensions in the dielectron and diphoton channels in collisions at 1.96 TeV
We report on a search for large extra spatial dimensions in the dielectron
and diphoton channels using a data sample of 1.05 \invfb of \ppb collisions at
a center-of-mass energy of 1.96 TeV collected by the D0 detector at the
Fermilab Tevatron Collider. The invariant mass spectrum of the data agrees well
with the prediction of the standard model. We find 95% C.L. lower limits on the
effective Planck scale between 2.1 and 1.3 TeV for 2 to 7 extra dimensions.Comment: 7 pages, 3 figures, 3 tables, submitted to Phys. Rev. Let
Measurement of the electron charge asymmetry in ppbar->W+X->enu+X events at sqrt{s}=1.96 TeV
We present a measurement of the electron charge asymmetry in
ppbar->W+X->enu+X events at a center of mass energy of 1.96 TeV using 0.75 fb-1
of data collected with the D0 detector at the Fermilab Tevatron Collider. The
asymmetry is measured as a function of the electron transverse momentum and
pseudorapidity in the interval (-3.2, 3.2) and is compared with expectations
from next-to-leading order calculations in perturbative quantum chromodynamics.
These measurements will allow more accurate determinations of the proton parton
distribution functions.Comment: 7 pages, 3 figures, Fermilab-Pub-08/249-E, submitted to Phys. Rev.
Let
Search for resonant diphoton production with the D0 detector
We present a search for a narrow resonance in the inclusive diphoton final
state using 2.7 fb-1 of data collected with the D0 detector at the Fermilab
Tevatron ppbar Collider. We observe good agreement between the data and the
background prediction, and set the first 95% C.L. upper limits on the
production cross section times the branching ratio for decay into a pair of
photons for resonance masses between 100 and 150 GeV. This search is also
interpreted in the context of several models of electroweak symmetry breaking
with a Higgs boson decaying into two photons.Comment: 7 pages, 3 figures
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