710 research outputs found
The sfermion mass spectrum of the MSSM at the one-loop level
The sfermion-mass spectrum of the minimal supersymmetric standard model is
investigated at the one-loop level. An on-shell scheme has been specified for
renormalization of the basic breaking parameters of the sfermionic sector.
Owing to SU(2)-invariance, the soft-breaking mass parameters of the left-chiral
scalar fermions of each isospin doublet are identical. Thus, one of the
sfermion-masses of each doublet can be expressed in terms of the other masses
and receives a mass shift at the one-loop level with respect to the
lowest-order value, which can be of GeV). Both strong and electroweak
contributions have been calculated for scalar quarks and leptons.Comment: 13 pages, 3 figures, version to appear in Eur. Phys. J.
A new cell primo-culture method for freshwater benthic diatom communities
A new cell primo-culture method was developed for the benthic diatom community isolated from biofilm sampled in rivers. The approach comprised three steps: (1) scraping biofilm from river pebbles, (2) diatom isolation
from biofilm, and (3) diatom community culture. With a view to designing a method able to stimulate the growth of diatoms, to limit the development of other microorganisms, and to maintain in culture a community similar to the original natural one, different factors were tested in step 3:
cell culture medium (Chu No 10 vs Freshwater “WC” medium modified), cell culture vessel, and time of culture. The results showed that using Chu No 10 medium in an Erlenmeyer flask for cell culture was the optimal method,
producing enough biomass for ecotoxicological tests as well as minimising development of other microorganisms. After 96 h of culture, communities differed from the original communities sampled in the two rivers studied.
Species tolerant of eutrophic or saprobic conditions were favoured during culture. This method of diatom community culture affords the opportunity to assess, in vitro, the effects of different chemicals or effluents (water samples andindustrial effluents) on diatom communities, as well as on diatom cells, from a wide range of perspectives
Supersymmetry Tests from a Combined Analysis of Chargino and Charged Higgs Boson Pair Production at a 1 TeV Linear Collider
We consider the production of chargino and charged Higgs boson pairs at
future linear colliders for c.m. energies in the one TeV range. Working in the
MSSM under the assumption of a "moderately" light SUSY scenario, we compute the
leading (double) and next-to leading (linear) supersymmetric logarithmic terms
of the so-called "Sudakov expansion" at one loop. We show that a combined
analysis of the slopes of the chargino and of the charged Higgs production
cross sections would offer a simple possibility for determining for
large () values and an allowed strip in the () plane. This
could provide a strong consistency test of the considered supersymmetric model.Comment: 4 pages, 4 Encapsulated PostScript Figure
SFOLD - a program package for calculating two-body sfermion decays at full one-loop level in the MSSM
SFOLD (Sfermion Full One Loop Decays) is a Fortran program package for
calculating all sfermion two-body decay widths and the corresponding branching
ratios at full one-loop level within the MSSM. The package adopts the SUSY
Parameter Analysis convention and supports the SUSY Les Houches Accord input
and output format. With the SFOLD package we found non-negligible electroweak
corrections in bosonic decays of sbottom, stop and stau.Comment: 17 pages, 3 figure
The effect of metals on photosynthesis processes and diatom metrics of biofilm from a metal-contaminated river: A translocation experiment
With the aim of evaluating cause-effect relationships between metal pollution and biofilm structure and function, a translocation study was performed in a metal-polluted stream (the Osor stream "la riera d'Osor", NE Spain). Biofilm responses were measured as temporal changes in chl-a fluorescence parameters, pigment composition and diatom species composition. Biofilms from a non-polluted site were translocated to four downstream sites presenting a gradient of metal pollution, corresponding to scenarios of low and moderate metal pollution. Metal effects (Zn bioaccumulation, Fe bioaccumulation and Zn in water) were distinguished from other stressors (phosphate concentration in water). Based on the results obtained, a fast bioaccumulation of Zn (after few hours of exposure) was linked to a decrease in photosynthetic efficiency and an enhancement of mechanisms of protection through the xanthophyll cycle. After longer exposure, differences in Zn and Fe bioaccumulation and Zn water concentration between sites were linked to diatom community changes; decrease in diatom cell biovolume, along with a decrease in the IPS index of diatoms. Based on our results, we recommend including Zn in the list of priority pollutant substances of the European Water Framework Directive (2000/60/EC), due to its occurrence and toxicity. In addition, our study supports the use of chl-a fluorescence parameters together with the analysis of photosynthetic pigments of biofilms as suitable functional endpoints of early toxicity. Furthermore, diatom community studies are recommended for their clear response after chronic exposure. However, new diatom indices beyond the use of the IPS are required to increase their sensitivity to metal pollution, e.g. to identify the damage caused by moderate to low metal pollution.Este estudo foi financiado polo proxecto europeo KEYBIOEFFECTS (MRTN-CT-2006-035695) e o proxecto español: FLUVIALMULTISTRESS (CTM2009-14111-CO2-01).S
Fermionic decays of sfermions: a complete discussion at one-loop order
We present a definition of an on-shell renormalization scheme for the
sfermion and chargino-neutralino sector of the Minimal Supersymmetric Standard
Model (MSSM). Then, apply this renormalization framework to the interaction
between charginos/neutralinos and sfermions. A kind of universal corrections is
identified, which allow to define effective chargino/neutralino coupling
matrices. In turn, these interactions generate (universal) non-decoupling terms
that grow as the logarithm of the heavy mass. Therefore the full MSSM spectrum
must be taken into account in the computation of radiative corrections to
observables involving these interactions. As an application we analyze the full
one-loop electroweak radiative corrections to the partial decay widths
\Gamma(\tilde{f} -> f\neut) and \Gamma(\tilde{f} -> f'\cplus) for all sfermion
flavours and generations. These are combined with the QCD corrections to
compute the corrected branching ratios of sfermions. It turns out that the
electroweak corrections can have an important impact on the partial decay
widths, as well as the branching ratios, in wide regions of the parameter
space. The precise value of the corrections is strongly dependent on the
correlation between the different particle masses.Comment: LaTeX 53 pages, 22 figures, 3 tables. Typos correcte
Influence of phosphorus on copper sensitivity of fluvial periphyton: the role of chemical, physiological and community-related factors
Sfermion Precision Measurements at a Linear Collider
At future e+- e- linear colliders, the event rates and clean signals of
scalar fermion production - in particular for the scalar leptons - allow very
precise measurements of their masses and couplings and the determination of
their quantum numbers. Various methods are proposed for extracting these
parameters from the data at the sfermion thresholds and in the continuum. At
the same time, NLO radiative corrections and non-zero width effects have been
calculated in order to match the experimental accuracy. The substantial mixing
expected for the third generation sfermions opens up additional opportunities.
Techniques are presented for determining potential CP-violating phases and for
extracting tan(beta) from the stau sector, in particular at high values. The
consequences of possible large mass differences in the stop and sbottom system
are explored in dedicated analyses.Comment: Expanded version of contributions to the proceedings of ICHEP'02
(Amsterdam) and LCWS 2002 (Jeju Island
Obstructed D-Branes in Landau-Ginzburg Orbifolds
We study deformations of Landau-Ginzburg D-branes corresponding to obstructed
rational curves on Calabi-Yau threefolds. We determine D-brane moduli spaces
and D-brane superpotentials by evaluating higher products up to homotopy in the
Landau-Ginzburg orbifold category. For concreteness we work out the details for
lines on a perturbed Fermat quintic. In this case we show that our results
reproduce the local analytic structure of the Hilbert scheme of curves on the
threefold.Comment: 44 pages; v3: typos correcte
Loss of TGFβ Signaling Destabilizes Homeostasis and Promotes Squamous Cell Carcinomas in Stratified Epithelia
SummaryAlthough TGFβ is a potent inhibitor of proliferation, epithelia lacking the essential receptor (TβRII) for TGFβ signaling display normal tissue homeostasis. By studying asymptomatic TβRII-deficient stratified epithelia, we show that tissue homeostasis is maintained by balancing hyperproliferation with elevated apoptosis. Moreover, rectal and genital epithelia, which are naturally proliferative, develop spontaneous squamous cell carcinomas with age when TβRII is absent. This progression is associated with a reduction in apoptosis and can be accelerated in phenotypically normal epidermis by oncogenic mutations in Ras. We show that TβRII deficiency leads to enhanced keratinocyte motility and integrin-FAK-Src signaling. Together, these mechanisms provide a molecular framework to account for many of the characteristics of TβRII-deficient invasive SQCCs
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