728 research outputs found
Constraining a CP-violating WWV coupling from the W^+W^- threshold cross section at LEP2
The most general form of the and interaction contains a
-violating term which has the same threshold behaviour as the Standard
Model \ee \to \ww cross section. We calculate the cross section as a function
of the corresponding anomalous coupling, and estimate the bounds which can be
obtained from a measurement of the threshold cross section at LEP2. We show how
the effect of the coupling is most pronounced in the angular distributions of
the final-state fermions.Comment: 7 pages, LaTeX file, 5 ps figure
Very Constrained Minimal Supersymmetric Standard Models
We consider very constrained versions of the minimal supersymmetric extension
of the Standard Model (VCMSSMs) which, in addition to constraining the scalar
masses m_0 and gaugino masses m_{1/2} to be universal at some input scale,
impose relations between the trilinear and bilinear soft supersymmetry breaking
parameters A_0 and B_0. These relations may be linear, as in simple minimal
supergravity models, or nonlinear, as in the Giudice-Masiero mechanism for
generating the Higgs-mixing mu term. We discuss the application of the
electroweak vacuum conditions in VCMSSMs, which may be used to make a
prediction for tan beta as a function of m_0 and m_{1/2} that is usually
unique. We baseline the discussion of the parameter spaces allowed in VCMSSMs
by updating the parameter space allowed in the CMSSM for fixed values of tan
beta with no relation between A_0 and B_0 assumed {\it a priori}, displaying
contours of B_0 for a fixed input value of A_0, incorporating the latest CDF/D0
measurement of m_t and the latest BNL measurement of g_mu - 2. We emphasize
that phenomenological studies of the CMSSM are frequently not applicable to
specific VCMSSMs, notably those based on minimal supergravity, which require
m_0 = m_{3/2} as well as A_0 = B_0 + m_0. We then display (m_{1/2}, m_0) planes
for selected VCMSSMs, treating in a unified way the parameter regions where
either a neutralino or the gravitino is the LSP. In particular, we examine in
detail the allowed parameter space for the Giudice-Masiero model.Comment: 26 pages, 32 eps figure
Single Higgs boson production at future linear colliders including radiative corrections
The next generation of high energy e+ e- linear colliders is expected to
operate at \sqrt{s} \gtsim 500 GeV. In this energy range the WW fusion channel
dominates the Higgs boson production cross section e+ e- -> \bar\nu \nu
h^0/H^0. We calculate the one-loop corrections to this process due to fermion
and sfermion loops within the MSSM. We perform a detailed numerical analysis of
the total cross section and the distributions of the rapidity, the transverse
momentum and the production angle of the Higgs boson. The fermion-sfermion
correction is substantial being of the order of -10% and is dominated by the
fermion loops. In addition, we explore the possibility of polarized e+ / e-
beams. In the so-called "intense coupling" scenario the production of the heavy
Higgs boson H^0 is also discussed.Comment: 23 pages, 9 figures, to be published in Nucl. Phys.
Trilinear Gauge Boson Couplings in the MSSM
We study the C and P even WW\gamma and WWZ trilinear gauge boson vertices
(TGV's), in the context of the MSSM assuming that the external W's are on their
mass shell. We find that for energies less than 200 GeV squark and slepton
contributions to the aforementioned couplings are two orders of magnitude
smaller than those of the Standard Model (SM). In the same energy range the
bulk of the supersymmetric Higgs corrections to the TGV's is due to the
lightest neutral Higgs, h_0, whose contribution is like that of a Standard
Model Higgs of the same mass. The contributions of the Neutralinos and
Charginos are sensitive to the input value for the soft gaugino mass M_{1/2},
being more pronounced for values M_{1/2} < 100 GeV. In this case and in the
unphysical region, 0 < \sqrt{s} < 2 M_W , their contributions are substantially
enhanced resulting in large corrections to the static quantities of the W
boson. However, such an enhancement is not observed in the physical region. In
general for 2 M_W < \sqrt{s} < 200 GeV the MSSM predictions differ from those
of the SM but they are of the same order of magnitude. To be detectable
deviations from the SM require sensitivities reaching the per mille level and
hence unlikely to be observed at LEP200. For higher energies SM and MSSM
predictions exhibit a fast fall off behaviour, in accord with unitarity
requirements, getting smaller,in most cases, by almost an order of magnitude
already at energies \sqrt{s} 0.5 TeV.Comment: 16 pages, late
Essential role of Plasmodium perforin-like protein 4 in ookinete midgut passage.
Pore forming proteins such as those belonging to the membrane attack/perforin (MACPF) family have important functions in many organisms. Of the five MACPF proteins found in Plasmodium parasites, three have functions in cell passage and one in host cell egress. Here we report an analysis of the perforin-like protein 4, PPLP4, in the rodent parasite Plasmodium berghei. We found that the protein is expressed only in the ookinete, the invasive stage of the parasite formed in the mosquito midgut. Transcriptional analysis revealed that expression of the pplp4 gene commences during ookinete development. The protein was detected in retorts and mature ookinetes. Using two antibodies, the protein was found localized in a dotted pattern, and 3-D SIM super-resolution microcopy revealed the protein in the periphery of the cell. Analysis of a C-terminal mCherry fusion of the protein however showed mainly cytoplasmic label. A pplp4 null mutant formed motile ookinetes, but these were unable to invade and traverse the midgut epithelium resulting in severely impaired oocyst formation and no transmission to naĂŻve mice. However, when in vitro cultured ookinetes were injected into the thorax of the mosquito, thus by-passing midgut passage, sporozoites were formed and the mutant parasites were able to infect naĂŻve mice. Taken together, our data show that PPLP4 is required only for ookinete invasion of the mosquito midgut. Thus PPLP4 has a similar role to the previously studied PPLP3 and PPLP5, raising the question why three proteins with MACPF domains are needed for invasion by the ookinete of the mosquito midgut epithelium
In vitro production of bovine embryos derived from individual donors in the CorralÂź dish
Background: Since the identity of the embryo is of outmost importance during commercial in vitro embryo production, bovine oocytes and embryos have to be cultured strictly per donor. Due to the rather low yield of oocytes collected after ovum pick-up (OPU) per individual cow, oocyte maturation and embryo culture take place in small groups, which is often associated with inferior embryo development. The objective of this study was to improve embryonic development in small donor groups by using the Corral (R) dish. This commercial dish is designed for human embryo production. It contains two central wells that are divided into quadrants by a semi-permeable wall. In human embryo culture, one embryo is placed per quadrant, allowing individual follow-up while embryos are exposed to a common medium. In our study, small groups of oocytes and subsequently embryos of different bovine donors were placed in the Corral (R) dish, each donor group in a separate quadrant.
Results: In two experiments, the Corral (R) dish was evaluated during in vitro maturation (IVM) and/or in vitro culture (IVC) by grouping oocytes and embryos of individual bovine donors per quadrant. At day 7, a significantly higher blastocyst rate was noted in the Corral (R) dish used during IVM and IVC than when only used during IVM (12.9% +/- 2.10 versus 22.8% +/- 2.67) (P < 0.05). However, no significant differences in blastocyst yield were observed anymore between treatment groups at day 8 post insemination.
Conclusions: In the present study, the Corral (R) dish was used for in vitro embryo production (IVP) in cattle; allowing to allocate oocytes and/or embryos per donor. As fresh embryo transfers on day 7 have higher pregnancy outcomes, the Corral (R) dish offers an added value for commercial OPU/IVP, since a higher blastocyst development at day 7 is obtained when the Corral (R) dish is used during IVM and IVC
Phenomenological Constraints on Patterns of Supersymmetry Breaking
Specific models of supersymmetry breaking predict relations between the
trilinear and bilinear soft supersymmetry breaking parameters A_0 and B_0 at
the input scale. In such models, the value of tan beta can be calculated as a
function of the scalar masses m_0 and the gaugino masses m_{1/2}, which we
assume to be universal. The experimental constraints on sparticle and Higgs
masses, b to s gamma decay and the cold dark matter density Omega_{CDM} h^2 can
then be used to constrain tan beta in such specific models of supersymmetry
breaking. In the simplest Polonyi model with A_0 = (3 - sqrt{3})m_0 = B_0 +
m_0, we find 11 0 (mu < 0). We also
discuss other models with A_0 = B_0 + m_0, finding that only the range -1.9 <
A_0/m_0 0, and the range 1.25 < A_0/m_0 < 4.8 for mu
< 0. In these models, we find no solutions in the rapid-annihilation `funnels'
or in the `focus-point' region. We also discuss the allowed range of tan beta
in the no-scale model with A_0 = B_0 = 0. In all these models, most of the
allowed regions are in the chi - stau_1 coannihilation `tail'.Comment: 17 pages LaTeX, 9 eps figure
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Optimal tuning and assessment of inertial dampers with grounded inerter for vibration control of seismically excited base-isolated systems
In this paper, the concept of an ideal grounded linear inerter, endowing supplemental inertia to passive linear tuned mass-dampers (TMDs) through its inertance property without increasing the TMD mass, is considered to reduce lateral displacement demands in base isolated structural systems (BISs). Optimal tuned mass-damper-inerter (TMDI) design parameters are numerically determined to maximize energy dissipation by the TMDI under stationary white noise support excitation. Performance of these optimally designed TMDI-equipped BISs is assessed for stationary white and colored noise excitations as well as for four recorded earthquake acceleration ground motions (GMs) with different non-stationary frequency content. It is found that for fixed mass ratio the inclusion of the grounded inerter reduces significantly secondary mass displacement and stroke for all considered excitations while it improves appreciably BIS displacement demands except for the particular case of a near-fault accelerogram characterized by early arrival of a high-energy low-frequency pulse as captured in its wavelet spectrogram. More importantly, it leads further to reductions to BIS acceleration demands with the exception of colored noise excitation for which an insignificant increase is noted. The positive effects of the inerter saturate with increasing inertance and BIS damping ratio demonstrating that small inertance values are more effective in vibration suppression of BISs with low inherent damping. Overall, it is recommended to combine low damping isolation layers with large inertance and low secondary mass TMDIs
Smoothed particle hydrodynamics (SPH) model for coupled analysis of a damaged ship with internal sloshing in beam seas
The flooding of a damaged ship in waves is a complex process, often coupled with the internal and external liquid motion together with the ship hull motion. Paramount to the operation safety, in order to improve the prediction accuracy of ship motion during the flooding process, the strip theory is applied to study the dynamic response of the damaged ship in beam seas; a smoothed particle hydrodynamics (SPH) model is developed to consider the coupling effects of various factors including internal sloshing of intact cabins and damaged cabins and external waves. The numerical wave tank with a perfectly matched layer absorbing boundary condition is established and validated by the experimental results. The detailed sensitivity study is carried out focusing on the effects of damaged opening sizes, the relative position of opening, and the incident wave and the liquid loading conditions on the dynamic response of the damaged ship in regular beam waves. It is observed that the flooding process was slowed down and interrupted by the water exchanges at the damaged opening due to the dynamic motion. Compared with the opening facing the incident wave, the back one endangered the ship pronouncedly with large amplitude and frequency roll motion. It is also revealed that the liquid tank in the damaged ship imposes a significant influence on its rolling response. It is further demonstrated that the present SPH model is capable of handling the nonlinear phenomenon in a flooding process of a damaged ship
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