966 research outputs found
Mechanical slowing-down of cytoplasmic diffusion allows in vivo counting of proteins in individual cells.
Many key regulatory proteins in bacteria are present in too low numbers to be detected with conventional methods, which poses a particular challenge for single-cell analyses because such proteins can contribute greatly to phenotypic heterogeneity. Here we develop a microfluidics-based platform that enables single-molecule counting of low-abundance proteins by mechanically slowing-down their diffusion within the cytoplasm of live Escherichia coli (E. coli) cells. Our technique also allows for automated microscopy at high throughput with minimal perturbation to native physiology, as well as viable enrichment/retrieval. We illustrate the method by analysing the control of the master regulator of the E. coli stress response, RpoS, by its adapter protein, SprE (RssB). Quantification of SprE numbers shows that though SprE is necessary for RpoS degradation, it is expressed at levels as low as 3-4 molecules per average cell cycle, and fluctuations in SprE are approximately Poisson distributed during exponential phase with no sign of bursting
Natural Growth Promoters Replacing Traditional Growth Promoters in Diets for Light Replacement Pullets: A Systematic Approach
ABSTRACT The effect of using natural growth promoters (NGP) to replace traditional antimicrobials on performance, biometry of digestive and reproductive organs, sexual maturity and bone characteristics of replacement pullets was evaluated; and the relationship between these variables according to the diets was verified. Eight-week-old birds were randomly assigned to a completely randomized design and fed different diets: negative control (without growth promoters); positive control - conventional growth promoter; organic acids (OA); symbiotic (S); essential oil (EO); OA + S; and EO + S. The performance, relative weight of digestive and reproductive organs and length intestines, height and crest length, sternum length, bone quality and sexual maturity of birds were similar (p>0.05) between treatments. The heat map combined with cluster analysis showed a uniform static pattern with the formation of three horizontal groups formed by the treatments: 1) negative control, S and OA + S; 2) positive control and OE and 3) OA and OE + S. A null relationship between the treatments and the variables under study was observed. The principal components analysis revealed an association of variables in three components with 60.55% of variation. NGP can replace traditional promoters, as they do not interfere with performance, biometrics or sexual maturity. Height and length are predictive variables for the development of reproductive organs, especially the oviduct. A similarity was identified through multivariate techniques between symbiotic and organic + symbiotic acids; positive control and essential oils; and organic and symbiotic acids + essential oils
Symmetries of Holographic Minimal Models
It was recently proposed that a large N limit of a family of minimal model
CFTs is dual to a certain higher spin gravity theory in AdS_3, where the 't
Hooft coupling constant of the CFT is related to a deformation parameter of the
higher spin algebra. We identify the asymptotic symmetry algebra of the higher
spin theory for generic 't Hooft parameter, and show that it coincides with a
family of W-algebras previously discovered in the context of the KP hierarchy.
We furthermore demonstrate that this family of W-algebras controls the
representation theory of the minimal model CFTs in the 't Hooft limit. This
provides a non-trivial consistency check of the proposal and explains part of
the underlying mechanism.Comment: 25 pages; references added and minor corrections (published version
Numerical study of circulation on the inner Amazon Shelf
Author Posting. © Springer, 2008. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Ocean Dynamics 58 (2008): 187-198, doi:10.1007/s10236-008-0139-4.We studied the circulation on the coastal
domain of the Amazon Shelf by applying the hydrodynamic
module of the Estuarine and Coastal Ocean
Model and Sediment Transport - ECOMSED. The first
barotropic experiment aimed to explain the major bathymetric
effects on tides and those generated by anisotropy
in sediment distribution. We analyzed the continental
shelf response of barotropic tides under realistic bottom
stress parametrization (Cd), considering sediment granulometry
obtained from a faciologic map, where river
mud deposits and reworked sediments areas are well distinguished,
among others classes of sediments. Very low
Cd values were set in the fluid mud regions off the Amapa
coast (1.0 10-4 ), in contrast to values around 3:5 10-3
for coarser sediment regions off the Para coast. Three-dimensional
experiments represented the Amazon River
discharge and trade winds, combined to barotropic tide
influences and induced vertical mixing. The quasi-resonant
response of the Amazon Shelf to the M2 tide act on
the local hydrodynamics by increasing tidal admittance,
along with tidal forcing at the shelf break and extensive
fluid mud regions. Harmonic analysis of modeled
currents agreed well with analysis of the AMASSEDS
observational data set. Tidal-induced vertical shear provided
strong homogenization of threshold waters, which
are subject to a kind of hydraulic control due to the topographic
steepness. Ahead of the hydraulic jump, the
low-salinity plume is disconnected from the bottom and
acquires negative vorticity, turning southeastward. Tides
act as a generator mechanism and topography, via hydraulic
control, as a maintainer mechanism for the low-salinity
frontal zone positioning. Tidally induced southeastward
plume fate is overwhelmed by northwestward
trade winds so that, along with background circulation,
probably play the most important role on the plume fate
and variability over the Amazon Shelf
Isolation and fine mapping of Rps6: An intermediate host resistance gene in barley to wheat stripe rust
A plant may be considered a nonhost of a pathogen if all known genotypes of a plant species are resistant to all known isolates of a pathogen species. However, if a small number of genotypes are susceptible to some known isolates of a pathogen species this plant maybe considered an intermediate host. Barley (Hordeum vulgare) is an intermediate host for Puccinia striiformis f. sp. tritici (Pst), the causal agent of wheat stripe rust. We wanted to understand the genetic architecture underlying resistance to Pst and to determine whether any overlap exists with resistance to the host pathogen, Puccinia striiformis f. sp. hordei (Psh). We mapped Pst resistance to chromosome 7H and show that host and intermediate host resistance is genetically uncoupled. Therefore, we designate this resistance locus Rps6. We used phenotypic and genotypic selection on F2:3 families to isolate Rps6 and fine mapped the locus to a 0.1 cM region. Anchoring of the Rps6 locus to the barley physical map placed the region on two adjacent fingerprinted contigs. Efforts are now underway to sequence the minimal tiling path and to delimit the physical region harbouring Rps6. This will facilitate additional marker development and permit identification of candidate genes in the region
A Twist in the Dyon Partition Function
In four dimensional string theories with N=4 and N=8 supersymmetries one can
often define twisted index in a subspace of the moduli space which captures
additional information on the partition function than the ones contained in the
usual helicity trace index. We compute several such indices in type IIB string
theory on K3 x T^2 and T^6, and find that they share many properties with the
usual helicity trace index that captures the spectrum of quarter BPS states in
N=4 supersymmetric string theories. In particular the partition function is a
modular form of a subgroup of Sp(2,Z) and the jumps across the walls of
marginal stability are controlled by the residues at the poles of the partition
function. However for large charges the logarithm of this index grows as 1/n
times the entropy of a black hole carrying the same charges where n is the
order of the symmetry generator that is used to define the twisted index. We
provide a macroscopic explanation of this phenomenon using quantum entropy
function formalism. The leading saddle point corresponding to the attractor
geometry fails to contribute to the twisted index, but a Z_n orbifold of the
attractor geometry produces the desired contribution.Comment: LaTeX file, 35 pages; v2: references adde
Asymptotic W-symmetries in three-dimensional higher-spin gauge theories
We discuss how to systematically compute the asymptotic symmetry algebras of
generic three-dimensional bosonic higher-spin gauge theories in backgrounds
that are asymptotically AdS. We apply these techniques to a one-parameter
family of higher-spin gauge theories that can be considered as large N limits
of SL(N) x SL(N) Chern-Simons theories, and we provide a closed formula for the
structure constants of the resulting infinite-dimensional non-linear
W-algebras. Along the way we provide a closed formula for the structure
constants of all classical W_N algebras. In both examples the higher-spin
generators of the W-algebras are Virasoro primaries. We eventually discuss how
to relate our basis to a non-primary quadratic basis that was previously
discussed in literature.Comment: 61 page
Dense Molecular Clouds in the Crab Supernova Remnant
Abstract
Molecular emission was imaged with ALMA from numerous components near and within bright H2-emitting knots and absorbing dust globules in the Crab Nebula. These observations provide a critical test of how energetic photons and particles produced in a young supernova remnant interact with gas, cleanly differentiating between competing models. The four fields targeted show contrasting properties but within them, seventeen distinct molecular clouds are identified with CO emission; a few also show emission from HCO+, SiO, and/or SO. These observations are compared with Cloudy models of these knots. It has been suggested that the Crab filaments present an exotic environment in which H2 emission comes from a mostly neutral zone probably heated by cosmic rays produced in the supernova surrounding a cool core of molecular gas. Our model is consistent with the observed CO J = 3 − 2 line strength. These molecular line emitting knots in the Crab Nebula present a novel phase of the ISM representative of many important astrophysical environments.</jats:p
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Dense Molecular Clouds in the Crab Supernova Remnant
Abstract
Molecular emission was imaged with ALMA from numerous components near and within bright H2-emitting knots and absorbing dust globules in the Crab Nebula. These observations provide a critical test of how energetic photons and particles produced in a young supernova remnant interact with gas, cleanly differentiating between competing models. The four fields targeted show contrasting properties but within them, seventeen distinct molecular clouds are identified with CO emission; a few also show emission from HCO+, SiO, and/or SO. These observations are compared with Cloudy models of these knots. It has been suggested that the Crab filaments present an exotic environment in which H2 emission comes from a mostly neutral zone probably heated by cosmic rays produced in the supernova surrounding a cool core of molecular gas. Our model is consistent with the observed CO J = 3 − 2 line strength. These molecular line emitting knots in the Crab Nebula present a novel phase of the ISM representative of many important astrophysical environments.</jats:p
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