4,379 research outputs found
Isolation of Cellular Clones of Murine Melanoma Resistants to the Photodynamic Therapy and Characterization of Some Mechanisms Involved in the Radioresistance
Effective Lagrangian description of the lepton flavor violating decays Z-->li lj
A comprehensive analysis of the lepton flavor violating (LFV) decays Z-->li
lj is presented within the effective Lagrangian approach. Both the decoupling
and nondecoupling scenarios are explored. The experimental constraints from li
--> lj lk \bar{lk} and li -->lj gamma as well as some relationships arising
from the gauge invariance of the effective Lagrangian are used to put
constraints on Z-->li lj. It is found that while current experimental data
impose very strong constraints on Z-->mu e, the channel Z --> tau mu (e)still
may be at the reach of the planned TESLA collider.Comment: References added, final version to appear in Physical Review
ÎÎČ Hinders Nuclear Targeting of AICD and Fe65 in Primary Neuronal Cultures
The intracellular domain of the Alzheimerâs amyloid precursor protein (AICD) has been described as an important player in the transactivation of specific genes. It results from proteolytic processing of the Alzheimerâs amyloid precursor protein (APP), as does the neurotoxic AÎČ peptide. Although normally produced in cells, AÎČ is typically considered to be a neurotoxic peptide, causing devastating effects. By exposing primary neuronal cultures to relatively low AÎČ concentrations, this peptide was shown to affect APP processing. Our findings indicate that APP C-terminal fragments are increased with concomitant reduction in the expression levels of APP itself. AICD nuclear immunoreactivity detected under control conditions was dramatically reduced in response to AÎČ exposure. Additionally, intracellular protein levels of Fe65 and GSK3 were also decreased in response to AÎČ. APP nuclear signaling is altered by AÎČ, affecting not only AICD production but also its nuclear translocation and complex formation with Fe65. In effect, AÎČ can trigger a physiological negative feedback mechanism that modulates its own production
Search for R-parity violating supersymmetry via the LLE couplings lambda_{121}, lambda_{122} or lambda_{133} in ppbar collisions at sqrt(s)=1.96 TeV
A search for gaugino pair production with a trilepton signature in the
framework of R-parity violating supersymmetry via the couplings lambda_121,
lambda_122, or lambda_133 is presented. The data, corresponding to an
integrated luminosity of L~360/pb, were collected from April 2002 to August
2004 with the D0 detector at the Fermilab Tevatron Collider, at a
center-of-mass energy of sqrt(s)=1.96 TeV. This analysis considers final states
with three charged leptons with the flavor combinations eel, mumul, and eetau
(l=e or mu). No evidence for supersymmetry is found and limits at the 95%
confidence level are set on the gaugino pair production cross section and lower
bounds on the masses of the lightest neutralino and chargino are derived in two
supersymmetric models.Comment: 9 pages, 4 figures (fig2 includes 3 subfigures
Search for Neutral Higgs Bosons Decaying to Tau Pairs in p-pbar Collisions at sqrt(s) = 1.96 TeV
A search for the production of neutral Higgs bosons Phi decaying into
tau^+tau^- final states in p-pbar collisions at a center-of-mass energy of 1.96
TeV is presented. The data, corresponding to an integrated luminosity of up to
348 pb^-1, were collected by the D0 experiment at the Fermilab Tevatron
Collider. Since no excess compared to the expectation from standard model
processes is found, limits on the production cross section times branching
ratio are set. The results are combined with those obtained from the D0 search
for Phi b(b) to b-bbar-b(bbar) and are interpreted in the minimal
supersymmetric standard model.Comment: Version accpeted by Phys. Rev. Lett. (minor changes
A search for W bb and W Higgs production in ppbar collisions at sqrt(s)=1.96 TeV
We present a search for W b \bar{b} production in p \bar{p} collisions at
sqrt{s}=1.96 TeV in events containing one electron, an imbalance in transverse
momentum, and two b-tagged jets. Using 174 pb-1 of integrated luminosity
accumulated by the D0 experiment at the Fermilab Tevatron collider, and the
standard-model description of such events, we set a 95% C.L. upper limit on W b
\bar{b}WH--$135
GeV.Comment: 7 pages, 4 figures, 1 table, submitted to Physical Review Letter
Search for W' boson production in the W'->tb decay channel
We present a search for the production of a new heavy gauge boson W' that
decays to a top quark and a bottom quark. We have analyzed 230 pb^{-1} of data
collected with the Dzero detector at the Fermilab Tevatron collider at a
center-of-mass energy of 1.96 TeV. No significant excess of events above the
standard model expectation is found in any region of the final state invariant
mass distribution. We set upper limits on the production cross section of W'
bosons times branching ratio to top quarks at the 95% confidence level for
several different W' boson masses. We exclude masses between 200 GeV and 610
GeV for a W' boson with standard-model-like couplings, between 200 GeV and 630
GeV for a W' boson with right-handed couplings that is allowed to decay to both
leptons and quarks, and between 200 GeV and 670 GeV for a W' boson with
right-handed couplings that is only allowed to decay to quarks.Comment: 9 pages, 6 figures, accepted by Phys. Lett.
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