3,330 research outputs found
Surfactant protein D modulates HIV infection of both T-cells and dendritic cells
Surfactant Protein D (SP-D) is an oligomerized C-type lectin molecule with immunomodulatory properties and involvement in lung surfactant homeostasis in the respiratory tract. SP-D binds to the enveloped viruses, influenza A virus and respiratory syncytial virus and inhibits their replication in vitro and in vivo. SP-D has been shown to bind to HIV via the HIV envelope protein gp120 and inhibit infectivity in vitro. Here we show that SP-D binds to different strains of HIV (BaL and IIIB) and the binding occurs at both pH 7.4 and 5.0 resembling physiological relevant pH values found in the body and the female urogenital tract, respectively. The binding of SP-D to HIV particles and gp120 was inhibited by the presence of several hexoses with mannose found to be the strongest inhibitor. Competition studies showed that soluble CD4 and CVN did not interfere with the interaction between SP-D and gp120. However, soluble recombinant DC-SIGN was shown to inhibit the binding between SP-D and gp120. SP-D agglutinated HIV and gp120 in a calcium dependent manner. SP-D inhibited the infectivity of HIV strains at both pH values of 7.4 and 5.0 in a concentration dependent manner. The inhibition of the infectivity was abolished by the presence of mannose. SP-D enhanced the binding of HIV to immature monocyte derived dendritic cells (iMDDCs) and was also found to enhance HIV capture and transfer to the T-cell like line PM1. These results suggest that SP-D can bind to and inhibit direct infection of T-cells by HIV but also enhance the transfer of infectious HIV particles from DCs to T-cells in vivo
Measuring the organizational impact of training: The need for greater methodological rigor
We review the methodological rigor of empirical quantitative studies that have investigated the training and organisational performance relationship. Through a content analysis of 219 studies published in quality journals, we reveal significant validity threats (internal, external construct and statistical conclusion validity) that raise questions about the methodological rigor of the field. Our findings suggest that the time is appropriate for a renewed methodological endeavour to understanding the relationship between training and organisational performance. We make specific recommendations to enhance methodological rigor and generate research finding will enhance operationalisation of theory, help researchers to make inferences about causality and inform the decision making of HRD practitioners
Observation of Hadronic W Decays in t-tbar Events with the Collider Detector at Fermilab
We observe hadronic W decays in t-tbar -> W (-> l nu) + >= 4 jet events using
a 109 pb-1 data sample of p-pbar collisions at sqrt{s} = 1.8 TeV collected with
the Collider Detector at Fermilab (CDF). A peak in the dijet invariant mass
distribution is obtained that is consistent with W decay and inconsistent with
the background prediction by 3.3 standard deviations. From this peak we measure
the W mass to be 77.2 +- 4.6 (stat+syst) GeV/c^2. This result demonstrates the
presence of two W bosons in t-tbar candidates in the W (-> l nu) + >= 4 jet
channel.Comment: 20 pages, 4 figures, submitted to PR
Production of Y(1S) Mesons from chib Decays in pp(bar) Collisions at sqrt(s)=1.8 TeV
We have reconstructed the radiative decays and in collisions
at TeV, and measured the fraction of mesons
that originate from these decays. For mesons with
GeV/, the fractions that come from and
decays are and
, respectively. We have derived the fraction of
directly produced mesons to be .Comment: 13 Pages, 2 figure
Search for Chargino-Neutralino Associated Production at the Fermilab Tevatron Collider
We have searched in collisions at = 1.8 TeV for events
with three charged leptons and missing transverse energy. In the Minimal
Supersymmetric Standard Model, we expect trilepton events from
chargino-neutralino (\chione \chitwo) pair production, with subsequent decay
into leptons. We observe no candidate , ,
or events in 106 pb integrated
luminosity. We present limits on the sum of the branching ratios times cross
section for the four channels: \sigma_{\chione\chitwo}\cdot
BR(\chione\chitwo\to 3\ell+X) 81.5 \mgev\sp and
M_\chitwo > 82.2 \mgev\sp for , ~\mgev\sp and
M_\squark= M_\gluino.Comment: 9 pages and 3 figure
Search for a Fourth-Generation Quark More Massive than the Z0 Boson in ppbar Collisions at sqrt(s) = 1.8 TeV
We present the results of a search for pair production of a fourth-generation
charge -1/3 quark (b') in sqrt(s)=1.8 TeV ppbar collisions using 88 pb^(-1) of
data obtained with the Collider Detector at Fermilab. We assume that both
quarks decay via the flavor-changing neutral current process b' -> bZ and that
the b' mass is greater than m_Z + m_b. We studied the decay mode b'b'bar -> ZZ
b bbar where one Z0 decays into e^+e^- or mu^+ mu^- and the other decays
hadronically, giving a signature of two leptons plus jets. An upper limit on
the cross section of ppbar -> b'b'bar times [BR (b' -> bZ)]^2 is established as
a function of the b' mass. We exclude at 95% confidence level a b' quark with
mass between 100 and 199 GeV/c^2 for BR(b' -> bZ) = 100%.Comment: 12 pages, 2 figures, submitted to Phys. Rev. Letters on 9/12/9
Search for charged Higgs decays of the top quark using hadronic tau decays
We present the result of a search for charged Higgs decays of the top quark,
produced in collisions at 1.8 TeV. When the charged
Higgs is heavy and decays to a tau lepton, which subsequently decays
hadronically, the resulting events have a unique signature: large missing
transverse energy and the low-charged-multiplicity tau. Data collected in the
period 1992-1993 at the Collider Detector at Fermilab, corresponding to
18.70.7~pb, exclude new regions of combined top quark and charged
Higgs mass, in extensions to the standard model with two Higgs doublets.Comment: uuencoded, gzipped tar file of LaTeX and 6 Postscript figures; 11 pp;
submitted to Phys. Rev.
Measurement of the lepton charge asymmetry in W-boson decays produced in p-pbar collisions
We describe a measurement of the charge asymmetry of leptons from W boson
decays in the rapidity range 0 enu, munu events from
110+/-7 pb^{-1}of data collected by the CDF detector during 1992-95. The
asymmetry data constrain the ratio of d and u quark momentum distributions in
the proton over the x range of 0.006 to 0.34 at Q2 \approx M_W^2. The asymmetry
predictions that use parton distribution functions obtained from previously
published CDF data in the central rapidity region (0.0<|y_l|<1.1) do not agree
with the new data in the large rapidity region (|y_l|>1.1).Comment: 13 pages, 3 tables, 1 figur
Inclusive jet cross section in collisions at TeV
The inclusive jet differential cross section has been measured for jet
transverse energies, , from 15 to 440 GeV, in the pseudorapidity region
0.10.7. The results are based on 19.5 pb of data
collected by the CDF collaboration at the Fermilab Tevatron collider. The data
are compared with QCD predictions for various sets of parton distribution
functions. The cross section for jets with GeV is significantly
higher than current predictions based on O() perturbative QCD
calculations. Various possible explanations for the high- excess are
discussed.Comment: 8 pages with 2 eps uu-encoded figures Submitted to Physical Review
Letter
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