320 research outputs found
Impact of massive neutrinos on the Higgs self-coupling and electroweak vacuum stability
The presence of right-handed neutrinos in the type I seesaw mechanism may
lead to significant corrections to the RG evolution of the Higgs self-coupling.
Compared to the Standard Model case, the Higgs mass window can become narrower,
and the cutoff scale become lower. Naively, these effects decrease with
decreasing right-handed neutrino mass. However, we point out that the unknown
Dirac Yukawa matrix may impact the vacuum stability constraints even in the low
scale seesaw case not far away from the electroweak scale, hence much below the
canonical seesaw scale of 10^15 GeV. This includes situations in which
production of right-handed neutrinos at colliders is possible. We illustrate
this within a particular parametrization of the Dirac Yukawas and with explicit
low scale seesaw models. We also note the effect of massive neutrinos on the
top quark Yukawa coupling, whose high energy value can be increased with
respect to the Standard Model case.Comment: 17 pages, 7 figures, minor revisions, version to appear in JHE
Phenomenology of Higgs bosons in the Zee-Model
To generate small neutrino masses radiatively, the Zee-model introduces two
Higgs doublets and one weak-singlet charged Higgs boson to its Higgs sector.
From analyzing the renormalization group equations, we determine the
possibile range of the lightest CP-even Higgs boson () mass and the Higgs
boson self-couplings as a function of the cut-off scale beyond which either
some of the coupling constants are strong enough to invalidate the perturbative
analysis or the stability of the electroweak vacuum is no longer guaranteed.
Using the results obtained from the above analysis, we find that the singlet
charged Higgs boson can significantly modify the partial decay width of via radiative corrections, and its collider phenomenology can
also be drastically different from that of the charged Higgs bosons in the
usual two-Higgs-doublet models.Comment: Added a paragraph and a figure in Section V, corrected typos, added
references. (RevTeX, 45 pages, 16 figures included.) To appear in Physical
Review
Mass bound of the lightest neutral Higgs scalar in the extra U(1) models
The upper mass bound of the lightest neutral Higgs scalar is studied in the
problem solvable extra U(1) models by using the analysis of the
renormalization group equations. In order to restrict the parameter space we
take account of a condition of the radiative symmetry breaking and some
phenomenological constraints. We compare the bound obtained based on this
restricted parameter space with the one of the next to the minimal
supersymmetric standard model (NMSSM). Features of the scalar potential and
renormalization group equations of the Yukawa couplings among Higgs chiral
supermultiplets are rather different between them. They can reflect in this
bound.Comment: 22 pages, latex, 11 eps-figure
The Higgs Mass as the Discriminator of Electroweak Models
In the Minimal Supersymmetric Model (MSSM) and the Next to Minimal
Supersymmetric Model [(M+1)SSM], an upper bound on the lightest higgs mass can
be calculated. On the other hand, vacuum stability implies a lower limit on the
mass of the higgs boson in the Standard Model (SM). We find that a gap exists
for GeV between the SM and both the MSSM and the
(M+1)SSM bounds. Thus, if the new top quark mass measurement by CDF remains
valid, a first measurement of the higgs mass will serve to exclude either the
SM or the MSSM/(M+1)SSM higgs sectors. In addition, we discuss Supersymmetric
Grand Unified Theories, other extentions of the SM, the discovery potential of
the lightest higgs, and the assumptions on which our conclusions are based.Comment: 9 pages, 2 figures, VAND-TH-94-1
Relevance of the light signaling machinery for cellulase expression in trichoderma reesei (hypocrea jecorina)
<p>Abstract</p> <p>Background</p> <p>In nature, light is one of the most important environmental cues that fungi perceive and interpret. It is known not only to influence growth and conidiation, but also cellulase gene expression. We therefore studied the relevance of the main components of the light perception machinery of <it>Trichoderma reesei </it>(<it>Hypocrea jecorina</it>), ENV1, BLR1 and BLR2, for production of plant cell wall degrading enzymes in fermentations aimed at efficient biosynthesis of enzyme mixtures for biofuel production.</p> <p>Findings</p> <p>Our results indicate that despite cultivation in mostly dark conditions, all three components show an influence on cellulase expression. While we found the performance of the enzyme mixture secreted by a deletion mutant in <it>env1 </it>to be enhanced, the higher cellulolytic activity observed for <it>Δblr2 </it>is mainly due to an increased secretion capacity of this strain. <it>Δblr1 </it>showed enhanced biomass accumulation, but due to its obviously lower secretion capacity still was the least efficient strain in this study.</p> <p>Conclusions</p> <p>We conclude that with respect to regulation of plant cell wall degrading enzymes, the blue light regulator proteins are unlikely to act as a complex. Their regulatory influence on cellulase biosynthesis involves an alteration of protein secretion, which may be due to adjustment of transcription or posttranscriptional regulation of upstream factors. In contrast, the regulatory function of ENV1 seems to involve adjustment of enzyme proportions to environmental conditions.</p
The Antioxidant Potential of the Mediterranean Diet in Patients at High Cardiovascular Risk: An In-Depth Review of the PREDIMED
Cardiovascular disease (CVD) is the leading global cause of death. Diet is known to be important in the prevention of CVD. The PREDIMED trial tested a relatively low-fat diet versus a high-fat Mediterranean diet (MedDiet) for the primary prevention of CVD. The resulting reduction of the CV composite outcome resulted in a paradigm shift in CV nutrition. Though many dietary factors likely contributed to this effect, this review focuses on the influence of the MedDiet on endogenous antioxidant systems and the effect of dietary polyphenols. Subgroup analysis of the PREDIMED trial revealed increased endogenous antioxidant and decreased pro-oxidant activity in the MedDiet groups. Moreover, higher polyphenol intake was associated with lower incidence of the primary outcome, overall mortality, blood pressure, inflammatory biomarkers, onset of new-onset type 2 diabetes mellitus (T2DM), and obesity. This suggests that polyphenols likely contributed to the lower incidence of the primary event in the MedDiet groups. In this article, we summarize the potential benefits of polyphenols found in the MedDiet, specifically the PREDIMED cohort. We also discuss the need for further research to confirm and expand the findings of the PREDIMED in a non-Mediterranean population and to determine the exact mechanisms of action of polyphenols
Update of the direct detection of dark matter and the role of the nuclear spin
We update our exploration of the MSSM parameter space at the weak scale where
new accelerator and cosmological constraints are respected. The dependence of
WIMP-nucleon cross sections on parameters of the MSSM, uncertainties of the
nucleon structure and other theoretical assumptions like universality and
co-annihilation are considered. In particular, we find that the coannihilation
does not have a significant effect in our analysis in certain regions which are
allowed even with coannihilation. The new cosmological constraint on the relic
neutralino density used in the form does also not
significantly affect the regions of allowed neutralino-nucleon cross sections.
We notice that for nuclear targets with spin the spin-dependent interaction may
determine the lower bound for the direct detection rate when the cross section
of the scalar interaction drops below about pb.Comment: 16 pages, revtex, 6 figure
The white collar complex is essential for sexual reproduction but dispensable for conidiation and invasive growth in Fusarium verticillioides
Fvwc1 and Fvwc2, orthologues of the wc-1 and wc-2 genes encoding for proteins of the white collar complex (WCC) in Neurospora crassa were cloned from Fusarium verticillioides and lack-of-function wc mutants were obtained by targeted gene disruption. Photo-conidiation was found to be absent in F. verticillioides, on the contrary, the wild type strain produced less conidia under continuous illumination than in the dark. Inactivation of any of the wc genes led to total female sterility, without affecting male fertility or asexual conidiation. No loss in colonization capability/invasive growth of the wc mutants was observed, when assessed on tomato fruits. Both Fvwc1 and Fvwc2 showed constitutive expression in the wild type cultures incubated in the dark and exposure to light caused only negligible increases in their transcription. Both Fvwc1 and Fvwc2 were down-regulated in a ΔFvmat1-2-1 gene disruption mutant, lacking a functional mating type (mat1-2-1) gene, suggesting that the MAT1-2-1 product has a positive regulatory effect on the white collar genes
Adenylyl Cyclase Plays a Regulatory Role in Development, Stress Resistance and Secondary Metabolism in Fusarium fujikuroi
The ascomycete fungus Fusarium fujikuroi (Gibberella fujikuroi MP-C) produces secondary metabolites of biotechnological interest, such as gibberellins, bikaverin, and carotenoids. Production of these metabolites is regulated by nitrogen availability and, in a specific manner, by other environmental signals, such as light in the case of the carotenoid pathway. A complex regulatory network controlling these processes is recently emerging from the alterations of metabolite production found through the mutation of different regulatory genes. Here we show the effect of the targeted mutation of the acyA gene of F. fujikuroi, coding for adenylyl cyclase. Mutants lacking the catalytic domain of the AcyA protein showed different phenotypic alterations, including reduced growth, enhanced production of unidentified red pigments, reduced production of gibberellins and partially derepressed carotenoid biosynthesis in the dark. The phenotype differs in some aspects from that of similar mutants of the close relatives F. proliferatum and F. verticillioides: contrary to what was observed in these species, ΔacyA mutants of F. fujikuroi showed enhanced sensitivity to oxidative stress (H2O2), but no change in heavy metal resistance or in the ability to colonize tomato tissue, indicating a high versatility in the regulatory roles played by cAMP in this fungal group
- …