2,314 research outputs found
Application of scanning electron microscopy for diagnosing phytoplasmas in single and mixed (virus-phytoplasma ) infection in Papaya
Phytoplasma and some viruses, papaya ring spot (PRSV) and papaya mosaic (PapMV) have been reported in papaya, from different Mexican states. Some symptoms of yellow type diseases, such as mosaics, stunting, bunchy top and leaf chlorosis, necrosis and malformations are somewhat similar in appearance, but caused by distinct pathogens. Using a scanning electron microscopy (SEM) technique phytoplasmas were detected in the phloem tissues of field and greenhouse-indexed papaya plants from Baja California Sur (BCS). Samples from 32 local varieties, as well as cv. Maradol, showing numerous symptoms of dieback, mosaics, bunchy top, and yellow crinkle were analyzed. The pathogen was detected in stems, leafstalks, roots, axillary leaflets, leaf veins and flowers. Phytoplasma was also detected in dry and in germinated seeds within the fruit, suggesting seed transmission of the pathogen. Some ultrastructural peculiarities of phytoplasma in infected tissues were also observed. No viral infection with PRSV and PapMV was revealed neither in test-plants nor by molecular techniques. Application of SEM technique for analysis of papaya samples from Veracruz and Irapuato, both from field-grown and mechanically inoculated plants with PRSV and PapMV in various combinations also revealed phytoplasmas in the phloem of most of tested samples. In some cases, along with phytoplasmas, rod-shaped bacteria were distinguished.Keywords: Papaya, phytoplasma, papaya ringspot virus, papaya mosaic virus, scanning electron microscopy, Mexic
Spin-up of the hyperon-softened accreting neutron stars
We study the spin-up of the accreting neutron stars with a realistic
hyperon-softened equation of state. Using precise 2-D calculations we study the
evolutionary tracks of accreting neutron stars in the angular-momentum -
frequency plane. In contrast to the case of spinning-down solitary
radio-pulsars, where a strong back-bending behavior has been observed, we do
not see back-bending phenomenon in the accretion-powered spinning-up case. We
conclude that in the case of accretion-driven spin-up the back-bending is
strongly suppressed by the mass-increase effect accompanying the
angular-momentum increase.Comment: 5 pages, 5 figures, accepted by Astronomy & Astrophysic
Universal exit probabilities in the TASEP
We study the joint exit probabilities of particles in the totally asymmetric
simple exclusion process (TASEP) from space-time sets of given form. We extend
previous results on the space-time correlation functions of the TASEP, which
correspond to exits from the sets bounded by straight vertical or horizontal
lines. In particular, our approach allows us to remove ordering of time moments
used in previous studies so that only a natural space-like ordering of particle
coordinates remains. We consider sequences of general staircase-like boundaries
going from the northeast to southwest in the space-time plane. The exit
probabilities from the given sets are derived in the form of Fredholm
determinant defined on the boundaries of the sets. In the scaling limit, the
staircase-like boundaries are treated as approximations of continuous
differentiable curves. The exit probabilities with respect to points of these
curves belonging to arbitrary space-like path are shown to converge to the
universal Airy process.Comment: 46 pages, 7 figure
Cluster expansion in the canonical ensemble
We consider a system of particles confined in a box \La\subset\R^d
interacting via a tempered and stable pair potential. We prove the validity of
the cluster expansion for the canonical partition function in the high
temperature - low density regime. The convergence is uniform in the volume and
in the thermodynamic limit it reproduces Mayer's virial expansion providing an
alternative and more direct derivation which avoids the deep combinatorial
issues present in the original proof
Metagenomic recovery of two distinct comammox Nitrospira from the terrestrial subsurface
Contains fulltext :
205810pub.pdf (publisher's version ) (Open Access)Summary The recently discovered comammox process encompasses both nitrification steps, the aerobic oxidation of ammonia and nitrite, in a single organism. All known comammox bacteria are affiliated with Nitrospira sublineage II and can be grouped into two distinct clades, referred to as A and B, based on ammonia monooxygenase phylogeny. In this study, we report high-quality draft genomes of two novel comammox Nitrospira from the terrestrial subsurface, representing one clade A and one clade B comammox organism. The two metagenome-assembled genomes were compared with other representatives of Nitrospira sublineage II, including both canonical and comammox Nitrospira. Phylogenomic analyses confirmed the affiliation of the two novel Nitrospira with comammox clades A and B respectively. Based on phylogenetic distance and pairwise average nucleotide identity values, both comammox Nitrospira were classified as novel species. Genomic comparison revealed high conservation of key metabolic features in sublineage II Nitrospira, including respiratory complexes I?V and the machineries for nitrite oxidation and carbon fixation via the reductive tricarboxylic acid cycle. In addition, the presence of the enzymatic repertoire for formate and hydrogen oxidation in the Rifle clades A and B comammox genomes, respectively, suggest a broader distribution of these metabolic features than previously anticipated.11 p
Refined conformal spectra in the dimer model
Working with Lieb's transfer matrix for the dimer model, we point out that
the full set of dimer configurations may be partitioned into disjoint subsets
(sectors) closed under the action of the transfer matrix. These sectors are
labelled by an integer or half-integer quantum number we call the variation
index. In the continuum scaling limit, each sector gives rise to a
representation of the Virasoro algebra. We determine the corresponding
conformal partition functions and their finitizations, and observe an
intriguing link to the Ramond and Neveu-Schwarz sectors of the critical dense
polymer model as described by a conformal field theory with central charge
c=-2.Comment: 44 page
Frozen shuffle update for an asymmetric exclusion process on a ring
We introduce a new rule of motion for a totally asymmetric exclusion process
(TASEP) representing pedestrian traffic on a lattice. Its characteristic
feature is that the positions of the pedestrians, modeled as hard-core
particles, are updated in a fixed predefined order, determined by a phase
attached to each of them. We investigate this model analytically and by Monte
Carlo simulation on a one-dimensional lattice with periodic boundary
conditions. At a critical value of the particle density a transition occurs
from a phase with `free flow' to one with `jammed flow'. We are able to
analytically predict the current-density diagram for the infinite system and to
find the scaling function that describes the finite size rounding at the
transition point.Comment: 16 page
The critical Ising model on a torus with a defect line
The critical Ising model in two dimensions with a defect line is analyzed to
deliver the first exact solution with twisted boundary conditions. We derive
exact expressions for the eigenvalues of the transfer matrix and obtain
analytically the partition function and the asymptotic expansions of the free
energy and inverse correlation lengths for an infinitely long cylinder of
circumference . We find that finite-size corrections to scaling are of the
form for the free energy and and
for inverse correlation lengths and
, respectively, with integer values of . By exact evaluation
we find that the amplitude ratios and are universal
and verify this universal behavior using a perturbative conformal approach.Comment: 5 pages, 5 figures, added Acknowledgment
Beliefs about the Minds of Others Influence How We Process Sensory Information
Attending where others gaze is one of the most fundamental mechanisms of social cognition. The present study is the first to examine the impact of the attribution of mind to others on gaze-guided attentional orienting and its ERP correlates. Using a paradigm in which attention was guided to a location by the gaze of a centrally presented face, we manipulated participants' beliefs about the gazer: gaze behavior was believed to result either from operations of a mind or from a machine. In Experiment 1, beliefs were manipulated by cue identity (human or robot), while in Experiment 2, cue identity (robot) remained identical across conditions and beliefs were manipulated solely via instruction, which was irrelevant to the task. ERP results and behavior showed that participants' attention was guided by gaze only when gaze was believed to be controlled by a human. Specifically, the P1 was more enhanced for validly, relative to invalidly, cued targets only when participants believed the gaze behavior was the result of a mind, rather than of a machine. This shows that sensory gain control can be influenced by higher-order (task-irrelevant) beliefs about the observed scene. We propose a new interdisciplinary model of social attention, which integrates ideas from cognitive and social neuroscience, as well as philosophy in order to provide a framework for understanding a crucial aspect of how humans' beliefs about the observed scene influence sensory processing
Draft genome of a novel methanotrophic Methylobacter sp. from the volcanic soils of Pantelleria Island
The genus Methylobacter is considered an important and often dominant group of aerobic methane-oxidizing bacteria in many oxic ecosystems, where members of this genus contribute to the reduction of CH4 emissions. Metagenomic studies of the upper oxic layers of geothermal soils of the Favara Grande, Pantelleria, Italy, revealed the presence of various methane-oxidizing bacteria, and resulted in a near complete metagenome assembled genome (MAG) of an aerobic methanotroph, which was classified as a Methylobacter species. In this study, the Methylobacter sp. B2 MAG was used to investigate its metabolic potential and phylogenetic affiliation. The MAG has a size of 4,086,539 bp, consists of 134 contigs and 3955 genes were found, of which 3902 were protein coding genes. All genes for CH4 oxidation to CO2 were detected, including pmoCAB encoding particulate methane monooxygenase (pMMO) and xoxF encoding a methanol dehydrogenase. No gene encoding a formaldehyde dehydrogenase was present and the formaldehyde to formate conversion follows the tetrahydromethanopterin (H4MPT) pathway. “Ca. Methylobacter favarea” B2 uses the Ribulose-Mono-Phosphate (RuMP) pathway for carbon fixation. Analysis of the MAG indicates that Na+/H+ antiporters and the urease system might be important in the maintenance of pH homeostasis of this strain to cope with acidic conditions. So far, thermoacidophilic Methylobacter species have not been isolated, however this study indicates that members of the genus Methylobacter can be found in distinct ecosystems and their presence is not restricted to freshwater or marine sediments
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