549 research outputs found
Establishment of a cell suspension culture of the halophyte Cakile maritima
Cakile maritima is a member of the Brassicaceae family also known as sea rocket. It is an annual succulent halophyte frequent in coastal dune vegetation in Mediterranean regions and Atlantic coasts from North Africa to the north of Europe. This halophyte presents a complex survival strategy at high salinity and its seeds contain up to 40% of an oil which could be suitable for biofuel production and other industrial applications. However, data concerning the cellular mechanisms allowing this plant to resist salinity are still lacking. Cell suspension cultures offer an in vitro system convenient for cell biology studies and biotechnological methods are still not developed for this putative crop. The present paper reports initiation of C. maritima cell suspension cultures from callus obtained from aerial parts of seedlings. The establishment of a suspension culture which preserves its salt resistance provides an opportunity to gain insights into C. maritima biology
The Bulk RS KK-gluon at the LHC
We study the possibility of discovering and measuring the properties of the
lightest Kaluza-Klein excitation of the gluon in a Randall-Sundrum scenario
where the Standard Model matter and gauge fields propagate in the bulk. The
KK-gluon decays primarily into top quarks. We discuss how to use the final states to discover and probe the properties of the KK-gluon.
Identification of highly energetic tops is crucial for this analysis. We show
that conventional identification methods relying on well separated decay
products will not work for heavy resonances but suggest alternative methods for
top identification for energetic tops. We find, conservatively, that resonances
with masses less than 5 TeV can be discovered if the algorithm to identify high
tops can reject the QCD background by a factor of 10. We also find that
for similar or lighter masses the spin can be determined and for lighter masses
the chirality of the coupling to can be measured. Since the energetic
top pair final state is a generic signature for a large class of new physics as
the top quark presumably couples most strongly to the electroweak symmetry
breaking sector, the methods we have outlined to study the properties of the
KK-gluon should also be important in other scenarios.Comment: 21 pages, 13 figure
Partially Supersymmetric Composite Higgs Models
We study the idea of the Higgs as a pseudo-Goldstone boson within the
framework of partial supersymmetry in Randall-Sundrum scenarios and their CFT
duals. The Higgs and third generation of the MSSM are composites arising from a
strongly coupled supersymmetric CFT with global symmetry SO(5) spontaneously
broken to SO(4), whilst the light generations and gauge fields are elementary
degrees of freedom whose couplings to the strong sector explicitly break the
global symmetry as well as supersymmetry. The presence of supersymmetry in the
strong sector may allow the compositeness scale to be raised to ~10 TeV without
fine tuning, consistent with the bounds from precision electro-weak
measurements and flavour physics. The supersymmetric flavour problem is also
solved. At low energies, this scenario reduces to the "More Minimal
Supersymmetric Standard Model" where only stops, Higgsinos and gauginos are
light and within reach of the LHC.Comment: 28 pages. v2 minor changes and Refs. adde
Effect of H2O2 pretreatment on the response of two seashore paspalum (Paspalum vaginatum Sw.) cultivars (Salam and Seaspray) to cold stress
Seashore paspalum is a warm season grass that requires few maintenance inputs. Expanded use of seashore paspalum could play a key role in making recreational sites more sustainable and environmentally. However, one key barrier to widespread Seashore paspalum use is a relative lack of winter hardiness. Under severe stress conditions, the antioxidant capacity may not be sufficient to minimize the harmful effect of oxidative injury. The search for signal molecules that mediate the stress tolerance is an important step in better understanding how plants acclimate to the adverse environment. This study aims to screen the responses of two Paspalum vaginatum cultivars (Salam and Seaspray) to local weather conditions and to study how to enhance its cold tolerance by a foliar pretreatment by hydrogen peroxide at low concentrations of 10 mM under controlled conditions. The current study provides evidence that exogenous H2O2 decreases the endogenous content of H2O2 in the first three days of exposure to cold stress in pretreated âSeasprayâ plants. in comparison to their control and pretreated âSalamâ which was in concomitant with malondialdehyde (MDA) changes. Indicating that pretreatment with 10 mM H2O2 could improve the tolerance of seashore paspalum to cold stress, especially cultivar Seaspray which showed better response to cold stress compared to âSalamâ. Exogenous H2O2 could constitute a signaling molecule that significantly increases POD relative density, and decreases MDA and H2O2 content
Chern-Simons diffusion rate in a holographic Yang-Mills theory
Using holography, we compute the Chern-Simons diffusion rate of 4d gauge
theories constructed by wrapping D4-branes on a circle. In the model with
antiperiodic boundary conditions for fermions, we find that it scales like
in the high-temperature phase. With periodic fermions, this scaling
persists at low temperatures. The scaling is reminiscent of 6d hydrodynamic
behavior even at temperatures small compared to compactification scales of the
M5-branes from which the D4-branes descend. We offer a holographic explanation
of this behavior by adding a new entry to the known map between D4 and M5
hydrodynamics, and suggest a field theory explanation based on "deconstruction"
or "fractionization".Comment: 13 pages, misstatement in published version about low temperature
phase removed, main results unaffecte
Analytical and computational indoor shelter models for infiltration of carbon dioxide into buildings : comparison with experimental data
This paper describes two indoor shelter models â an analytical model and a Computational Fluid Dynamics (CFD) model - that can be used to predict the level of infiltration of carbon dioxide (CO2) into a building following a release from an onshore CO2 pipeline. The motivation behind the development of these models was to demonstrate that the effects of shelter should be considered as part of a Quantitative Risk Assessment (QRA) for CO2 pipeline infrastructure and to provide a methodology for considering the impact of a CO2 release on building occupants.A key component in the consequence modelling of a release from a CO2 pipeline is an infiltration model for CO2 into buildings which can describe the impact on people inside buildings during a release event. This paper describes the development of an analytical shelter model and a CFD model which are capable of predicting the change in internal concentration, temperature and toxic load within a single roomed building that is totally engulfed by a transient cloud of gaseous CO2. Application of the models is demonstrated by comparison with experimental measurements of CO2 accumulation in a building placed in the path of a drifting cloud of CO2. The analytical and CFD models are shown to make good predictions of the average change in internal concentration. Furthermore, it is demonstrated that the effects of shelter should be taken into account when conducting QRA assessments on CO2 pipelines.
Document type: Articl
Dark Matter Direct Detection with Non-Maxwellian Velocity Structure
The velocity distribution function of dark matter particles is expected to
show significant departures from a Maxwell-Boltzmann distribution. This can
have profound effects on the predicted dark matter - nucleon scattering rates
in direct detection experiments, especially for dark matter models in which the
scattering is sensitive to the high velocity tail of the distribution, such as
inelastic dark matter (iDM) or light (few GeV) dark matter (LDM), and for
experiments that require high energy recoil events, such as many directionally
sensitive experiments. Here we determine the velocity distribution functions
from two of the highest resolution numerical simulations of Galactic dark
matter structure (Via Lactea II and GHALO), and study the effects for these
scenarios. For directional detection, we find that the observed departures from
Maxwell-Boltzmann increase the contrast of the signal and change the typical
direction of incoming DM particles. For iDM, the expected signals at direct
detection experiments are changed dramatically: the annual modulation can be
enhanced by more than a factor two, and the relative rates of DAMA compared to
CDMS can change by an order of magnitude, while those compared to CRESST can
change by a factor of two. The spectrum of the signal can also change
dramatically, with many features arising due to substructure. For LDM the
spectral effects are smaller, but changes do arise that improve the
compatibility with existing experiments. We find that the phase of the
modulation can depend upon energy, which would help discriminate against
background should it be found.Comment: 34 pages, 16 figures, submitted to JCAP. Tables of g(v_min), the
integral of f(v)/v from v_min to infinity, derived from our simulations, are
available for download at http://astro.berkeley.edu/~mqk/dmdd
Transplanckian axions !?
We discuss quantum gravitational effects in Einstein theory coupled to
periodic axion scalars to analyze the viability of several proposals to achieve
superplanckian axion periods (aka decay constants) and their possible
application to large field inflation models. The effects we study correspond to
the nucleation of euclidean gravitational instantons charged under the axion,
and our results are essentially compatible with (but independent of) the Weak
Gravity Conjecture, as follows: Single axion theories with superplanckian
periods contain gravitational instantons inducing sizable higher harmonics in
the axion potential, which spoil superplanckian inflaton field range. A similar
result holds for multi-axion models with lattice alignment (like the
Kim-Nilles-Peloso model). Finally, theories with axions can still achieve a
moderately superplanckian periodicity (by a factor) with no higher
harmonics in the axion potential. The Weak Gravity Conjecture fails to hold in
this case due to the absence of some instantons, which are forbidden by a
discrete gauge symmetry. Finally we discuss the realization of
these instantons as euclidean D-branes in string compactifications.Comment: 46 pages, 6 figures. Added references, clarifications, and missing
factor of 1/2 to instanton action. Conclusions unchange
Holonomy of the Ising model form factors
We study the Ising model two-point diagonal correlation function by
presenting an exponential and form factor expansion in an integral
representation which differs from the known expansion of Wu, McCoy, Tracy and
Barouch. We extend this expansion, weighting, by powers of a variable
, the -particle contributions, . The corresponding
extension of the two-point diagonal correlation function, , is shown, for arbitrary , to be a solution of the sigma
form of the Painlev{\'e} VI equation introduced by Jimbo and Miwa. Linear
differential equations for the form factors are obtained and
shown to have both a ``Russian doll'' nesting, and a decomposition of the
differential operators as a direct sum of operators equivalent to symmetric
powers of the differential operator of the elliptic integral . Each is expressed polynomially in terms of the elliptic integrals and . The scaling limit of these differential operators breaks the
direct sum structure but not the ``Russian doll'' structure. The previous -extensions, are, for singled-out values ( integers), also solutions of linear differential
equations. These solutions of Painlev\'e VI are actually algebraic functions,
being associated with modular curves.Comment: 39 page
Simplified Models for LHC New Physics Searches
This document proposes a collection of simplified models relevant to the
design of new-physics searches at the LHC and the characterization of their
results. Both ATLAS and CMS have already presented some results in terms of
simplified models, and we encourage them to continue and expand this effort,
which supplements both signature-based results and benchmark model
interpretations. A simplified model is defined by an effective Lagrangian
describing the interactions of a small number of new particles. Simplified
models can equally well be described by a small number of masses and
cross-sections. These parameters are directly related to collider physics
observables, making simplified models a particularly effective framework for
evaluating searches and a useful starting point for characterizing positive
signals of new physics. This document serves as an official summary of the
results from the "Topologies for Early LHC Searches" workshop, held at SLAC in
September of 2010, the purpose of which was to develop a set of representative
models that can be used to cover all relevant phase space in experimental
searches. Particular emphasis is placed on searches relevant for the first
~50-500 pb-1 of data and those motivated by supersymmetric models. This note
largely summarizes material posted at http://lhcnewphysics.org/, which includes
simplified model definitions, Monte Carlo material, and supporting contacts
within the theory community. We also comment on future developments that may be
useful as more data is gathered and analyzed by the experiments.Comment: 40 pages, 2 figures. This document is the official summary of results
from "Topologies for Early LHC Searches" workshop (SLAC, September 2010).
Supplementary material can be found at http://lhcnewphysics.or
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