15,053 research outputs found
Chirally enhanced corrections to FCNC processes in the generic MSSM
Chirally enhanced supersymmetric QCD corrections to FCNC processes are
investigated in the framework of the MSSM with generic sources of flavor
violation. These corrections arise from flavor-changing self-energy diagrams
and can be absorbed into a finite renormalization of the squark-quark-gluino
vertex. In this way enhanced two-loop and even three-loop diagrams can be
efficiently included into a leading-order (LO) calculation. Our corrections
substantially change the values of the parameters delta^{d,LL}_{23},
delta^{d,LR}_{23}, delta^{d,RL}_{23}, and delta^{d,RR}_{23} extracted from
Br[B->X_s gamma] if tan(beta) is large. We find stronger (weaker) constraints
compared to the LO result for negative (positive) values of mu. The constraints
on delta^{d,LR,RL}_{13} and delta^{d,LR,RL}_{23} from B_d mixing and B_s mixing
change drastically if the third-generation squark masses differ from those of
the first two generations. K mixing is more strongly affected by the chirally
enhanced loop diagrams and even sub-percent deviations from degenerate down and
strange squark masses lead to profoundly stronger constraints on
delta^{d,LR,RL}_{12}.Comment: 19 pages, 10 figure
Variability of surface flows on the Sun and the implications for exoplanet detection
The published Mount Wilson Doppler-shift measurements of the solar velocity
field taken in 1967--1982 are revisited with a more accurate model, which
includes two terms representing the meridional flow and three terms
corresponding to the convective limb shift. Integration of the recomputed data
over the visible hemisphere reveals significant variability of the net radial
velocity at characteristic time scales of 0.1--10 years, with a standard
deviation of 1.4 \ms. This result is supported by independent published
observations. The implications for exoplanet detection include reduced
sensitivity of the Doppler method to Earth-like planets in the habitable zone,
and an elevated probability of false detections at periods of a few to several
years.Comment: Accepted in this form for publication in Ap
Integration of a virus membrane protein into the lipid bilayer of target cells as a prerequisite for immune cytolysis
Structural requirements for membrane antigens on target cells to mediate immune cytolysis were studied in a model system with purified membrane proteins from Semliki Forest virus (SFV). These SFV spike proteins were isolated in the form of detergent- and lipid-free protein micelles (29S complexes) or, after reconstitution into lipid vesicles, in the form of virosomes. Both the 29S complexes and the virosomes were found to bind well to murine tumor cells (P815 or Eb). When these cells, however, were used as target cells in complement-dependent lysis or in antibody-dependent cell- mediated cytotoxicity assays in the presence of anti-SFV serum, they were not lysed, although they effectively bound the antibody and consumed complement. The same tumor cells infected with SFV served as positive controls in both assays.
Different results were obtained when inactivated Sendai virus was added as a fusion reagent to the cells coated with either virosomes or 29S complexes. Under these conditions the virosome-coated cells became susceptible to SFV- specific lysis, whereas the 29S complex-coated cells remained resistant. Evidence that the susceptibility to lysis ofvirosome-coated cells was dependent on active fusion and, therefore, integration of the viral antigens into the lipid bilayer of the target cells was derived from control experiments with enzyme-treated Sendai virus preparations.
The 29S complexes and the virosomes partially and selectively blocked the target cell lysis by anti-H-2 sera but not by anti-non-H-2 sera confirming our previous finding that major histocompatibility antigens serve as receptors for SFV. The general significance of these findings for mechanisms of immune cytolysis is dicussed
Projected Three-Pion Correlation Functions
We propose a new procedure for constructing projected three-pion correlation
functions which reduces undesirable artificial momentum dependences resulting
from the commonly used procedure and facilitates comparison of three-pion
correlation data with theoretical models.Comment: 6 pages revtex, incl. 1 figure. Submitted as Brief Report to Physical
Review C. Normalization error and typos correcte
Real Business Cycles of Sticky Prices? The Impact of Technology Shocks on US Manufacturing
No abstract.
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