201 research outputs found
Some Like It Hot, Some Like It Warm: Phenotyping To Explore Thermotolerance Diversity
Plants have evolved overlapping but distinct cellular responses to different aspects of high temperature stress. These responses include basal thermotolerance, short- and long-term acquired thermotolerance, and thermotolerance to moderately high temperatures. This ‘thermotolerance diversity’ means that multiple phenotypic assays are essential for fully describing the functions of genes involved in heat stress responses. A large number of genes with potential roles in heat stress responses have been identified using genetic screens and genome wide expression studies. We examine the range of phenotypic assays that have been used to characterize thermotolerance phenotypes in both Arabidopsis and crop plants. Three major variables differentiate thermotolerance assays: (1) the heat stress regime used, (2) the developmental stage of the plants being studied, and (3) the actual phenotype which is scored. Consideration of these variables will be essential for deepening our understanding of the molecular genetics of plant thermotolerance
Puzzles in physics
I discuss some puzzles observed in exclusive meson decays, concentrating
on the large difference between the direct CP asymmetries in the and modes, the large
branching ratio, and the large deviation of the mixing-induced CP asymmetries
in the penguins from those in the trees.Comment: 6 pages, 1 figure, talk presented at the 9th Workshop on High Energy
Physics Phenomenology, Bhubaneswar, Orissa, India, Jan. 3-14, 2006; reference
adde
Inflation and nonequilibrium renormalization group
We study de spectrum of primordial fluctuations and the scale dependence of
the inflaton spectral index due to self-interactions of the field. We compute
the spectrum of fluctuations by applying nonequilibrium renormalization group
techniques.Comment: 6 pages, 1 figure, submitted to J. Phys.
Nonperturbative bound on high multiplicity cross sections in phi^4_3 from lattice simulation
We have looked for evidence of large cross sections at large multiplicities
in weakly coupled scalar field theory in three dimensions. We use spectral
function sum rules to derive bounds on total cross sections where the sum can
be expresed in terms of a quantity which can be measured by Monte Carlo
simulation in Euclidean space. We find that high multiplicity cross sections
remain small for energies and multiplicities for which large effects had been
suggested.Comment: 23 pages, revtex, seven eps figures revised version: typos corrected,
some rewriting of discusion, same resul
B meson wave function from the decay
We show that the leading-power meson wave function can be extracted
reliably from the photon energy spectrum of the decay up to
and uncertainty, being the quark mass
and the strong coupling constant. The corrections from
heavy-quark expansion can be absorbed into a redefined leading-power meson
wave function. The two-parton corrections cancel exactly, and the
three-parton meson wave functions turn out to contribute at .
The constructive long-distance contribution through the
transition, being a vector meson, almost cancels the destructive
radiative correction. Using models of the leading-power meson
wave function available in the literature, we obtain the photon energy spectrum
in the perturbative QCD framework, which is then compared with those from other
approaches.Comment: 11 pages, 5 figures with minor correction
Okubo-Zweig-Iizuka-rule violation and B\to \eta^{(\prime)}K branching ratios
We show that few-percent Okubo-Zweig-Iizuka-rule violating effects in the
quark-flavor basis for the - mixing can enhance the chiral scale
associated with the meson few times. This enhancement is sufficient
for accommodating the dramatically different data of the
and branching ratios. We comment on other proposals for resolving
this problem, including flavor-singlet contributions, axial U(1) anomaly, and
nonperturbative charming penguins. Discrimination of the above proposals by
means of the and
data is suggested.Comment: 7 pages, 2 figures, discussion on B\to\eta^{(\prime)}K* added, more
references adde
Transition Form Factor up to within the Factorization Approach
In the paper, we apply the factorization approach to deal with the
transition form factor in the large recoil
regions. The B-meson wave functions and that include the
three-particle Fock states' contributions are adopted to give a consistent PQCD
analysis of the form factor up to . It has been found that
both the wave functions and can give sizable
contributions to the form factor and should be kept for a better understanding
of the meson decays. Then the contributions from different twist structures
of the kaon wavefunction are discussed, including the -breaking
effects. A sizable contribution from the twist-3 wave function is
found, whose model dependence is discussed by taking two group of parameters
that are determined by different distribution amplitude moments obtained in the
literature. It is also shown that and
, which are more
reasonable and consistent with the light-cone sum rule results in the large
recoil regions.Comment: 22 pages and 6 figure
Black Holes from Cosmic Rays: Probes of Extra Dimensions and New Limits on TeV-Scale Gravity
If extra spacetime dimensions and low-scale gravity exist, black holes will
be produced in observable collisions of elementary particles. For the next
several years, ultra-high energy cosmic rays provide the most promising window
on this phenomenon. In particular, cosmic neutrinos can produce black holes
deep in the Earth's atmosphere, leading to quasi-horizontal giant air showers.
We determine the sensitivity of cosmic ray detectors to black hole production
and compare the results to other probes of extra dimensions. With n \ge 4 extra
dimensions, current bounds on deeply penetrating showers from AGASA already
provide the most stringent bound on low-scale gravity, requiring a fundamental
Planck scale M_D > 1.3 - 1.8 TeV. The Auger Observatory will probe M_D as large
as 4 TeV and may observe on the order of a hundred black holes in 5 years. We
also consider the implications of angular momentum and possible exponentially
suppressed parton cross sections; including these effects, large black hole
rates are still possible. Finally, we demonstrate that even if only a few black
hole events are observed, a standard model interpretation may be excluded by
comparison with Earth-skimming neutrino rates.Comment: 30 pages, 18 figures; v2: discussion of gravitational infall, AGASA
and Fly's Eye comparison added; v3: Earth-skimming results modified and
strengthened, published versio
Reconstructing large running-index inflaton potentials
Recent fits of cosmological parameters by the first year Wilkinson Microwave
Anisotropy Probe (WMAP) measurement seem to favor a primordial scalar spectrum
with a large varying index from blue to red. We use the inflationary flow
equations to reconstruct large running-index inflaton potentials and comment on
current status on the inflationary flow. We find previous negligence of higher
order slow rolling contributions when using the flow equations would lead to
unprecise results.Comment: Final version to appear in Class. Quant. Grav. References adde
Developmental and heat stress-regulated expression of HsfA2 and small heat shock proteins in tomato anthers
The high sensitivity of male reproductive cells to high temperatures may be due to an inadequate heat stress response. The results of a comprehensive expression analysis of HsfA2 and Hsp17-CII, two important members of the heat stress system, in the developing anthers of a heat-tolerant tomato genotype are reported here. A transcriptional analysis at different developmental anther/pollen stages was performed using semi-quantitative and real-time PCR. The messengers were localized using in situ RNA hybridization, and protein accumulation was monitored using immunoblot analysis. Based on the analysis of the gene and protein expression profiles, HsfA2 and Hsp17-CII are finely regulated during anther development and are further induced under both short and prolonged heat stress conditions. These data suggest that HsfA2 may be directly involved in the activation of protection mechanisms in the tomato anther during heat stress and, thereby, may contribute to tomato fruit set under adverse temperatures
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