A new grapevine yellows phytoplasma from the Buckland Valley of Victoria, Australia

A new phytoplasma detected in grapevines with grapevine yellows disease from the Buckland Valley of Victoria, Australia was characterized. Buckland Valley grapevine yellows phytoplasma (BVGYp) could not be amplified by PCR using primers specific for the stolbur (STOL, 16SrXII) group of phytoplasmas indicating that it was unlikely to be a STOL group phytoplasma. BVGYp was amplified by PCR using primers specific for both the aster yellows (AV, 16Sr I) and STOL phytoplasma groups, indicating that it may be more closely related to the AY group phytoplasmas. Sequence analysis of 16SrRNA gene sequences showed that BVGYp clustered with AY and STOL groups of phytoplasmas. Sequence similarities were determined by pairwise comparisons of the 16S rDNA sequence of BVGYp WAY and STOL group phytoplasmas and BVGYp was more closely related to the AY group phytoplasmas. Although the data indicate BVGYp may form a newAY subgroup, the similarity coefficients between BVGYp and phytoplasmas from the AY, STOL and Mexican periwinkle virescence groups, derived from putative RFLP patterns, were less than 90%, so BVGYp may actually form a new phytoplasma group.

DLCQ String Spectrum from N=2{\cal N}=2 SYM Theory

We study non planar corrections to the spectrum of operators in the ${\mathcal N}=2$ supersymmetric Yang Mills theory which are dual to string states in the maximally supersymmetric pp-wave background with a {\em compact} light-cone direction. The existence of a positive definite discrete light-cone momentum greatly simplifies the operator mixing problem. We give some examples where the contribution of all orders in non-planar diagrams can be found analytically. On the string theory side this corresponds to finding the spectrum of a string state to all orders in string loop corrections.Comment: 35 pages, no figure

Reversals in nature and the nature of reversals

The asymmetric shape of reversals of the Earth's magnetic field indicates a possible connection with relaxation oscillations as they were early discussed by van der Pol. A simple mean-field dynamo model with a spherically symmetric $\alpha$ coefficient is analysed with view on this similarity, and a comparison of the time series and the phase space trajectories with those of paleomagnetic measurements is carried out. For highly supercritical dynamos a very good agreement with the data is achieved. Deviations of numerical reversal sequences from Poisson statistics are analysed and compared with paleomagnetic data. The role of the inner core is discussed in a spectral theoretical context and arguments and numerical evidence is compiled that the growth of the inner core might be important for the long term changes of the reversal rate and the occurrence of superchrons.Comment: 24 pages, 12 figure

Bulk Filling Branes and the Baryon Density in AdS/QCD with gravity back-reaction

We consider the gravity back reaction on the metric due to the baryon density in effective ads/qcd model by reconsidering the role of the charged AdS black hole. Previously it has been known that the U(1) charge is dual to the R-charge. Here we point out that if we consider the case where $AdS_5$ is completely filled with $N_f$ flavor branes, the gravity back reaction produces charged AdS black hole where the effect of charge on the metric is proportional to $N_f/N_c$. As a consequence, phase diagram changes qualitatively if we allow $N_f/N_c$ finite: it closes at the finite density unlike the probe brane embedding approach. Another issue we discuss here is the question whether there is any chemical potential dependence in the confining phase. We consider this problem in the hard wall model with baryon charge. We conclude that there is a non-trivial dependence on the chemical potential in this case also.Comment: 17 pages 3x2 figures, v2: references added;v3 published version, title change and reference adde

Dynamical Stability of Six-Dimensional Warped Brane-Worlds

We study a generalization of the Randall-Sundrum mechanism for generating the weak/Planck hierarchy, which uses two rather than one warped extra dimension, and which requires no negative tension branes. A 4-brane with one exponentially large compact dimension plays the role of the Planck brane. We investigate the dynamical stability with respect to graviton, graviphoton and radion modes. The radion is shown to have a tachyonic instability for certain models of the 4-brane stress-energy, while it is stable in others, and massless in a special case. If stable, its mass is in the milli-eV range, for parameters of the model which solve the hierarchy problem. The radion is shown to couple to matter with gravitational strength, so that it is potentially detectable by submillimeter-range gravity experiments. The radion mass can be increased using a bulk scalar field in the manner of Goldberger and Wise, but only to order MeV, due to the effect of the large extra dimension. The model predicts a natural scale of 10^{13} GeV on the 4-brane, making it a natural setting for inflation from the ultraviolet brane.Comment: 28 pages, 7 figure

Crystal Orientation Dependent Oxidation Modes at the Buried Graphene-Cu Interface.

We combine spatially resolved scanning photoelectron spectroscopy with confocal Raman and optical microscopy to reveal how the oxidation of the buried graphene-Cu interface relates to the Cu crystallographic orientation. We analyze over 100 different graphene covered Cu (high and low index) orientations exposed to air for 2 years. Four general oxidation modes are observed that can be mapped as regions onto the polar plot of Cu surface orientations. These modes are (1) complete, (2) irregular, (3) inhibited, and (4) enhanced wrinkle interface oxidation. We present a comprehensive characterization of these modes, consider the underlying mechanisms, compare air and water mediated oxidation, and discuss this in the context of the diverse prior literature in this area. This understanding incorporates effects from across the wide parameter space of 2D material interface engineering, relevant to key challenges in their emerging applications, ranging from scalable transfer to electronic contacts, encapsulation, and corrosion protection

Bovine coronavirus in neonatal calf diarrhoea in Iran

Partial gene sequencing for the bovine coronavirus at the World Genebank is available for many countries, which are distributed unevenly in five continents, but so far, no sequencing of strains has been recorded in Iran. One hundred ninety-four stool samples from calves with diarrhoea less than one-month old were collected from five different geographical regions of country in order to detect coronavirus and characterize it if coronavirus was found. Samples were screened for the presence of BCoV by using a commercially available ELISA kit. Furthermore, RT-PCR was carried out on positive samples for confirmation of the presence of N and S specific genes. Sequencing and phylogenetic analysis was carried out following RT-PCR tests. 7.2% of samples, were positive for BCoV and all stool samples from the South-West, Northeast and West regions of Iran were negative. The results showed that all the strains of coronavirus identified in Iran were completely in independent clusters and that they did not stand in the same cluster as any of the strains identified in other parts of the world. The strains from Iran were quite different from strains in other parts of the world but from the point of similarity these viruses showed some similarities to the European strains, such as those found in France, Croatia, Denmark and Sweden

Instanton operators in five-dimensional gauge theories

This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are creditedN.L. is supported in part by STFC grant ST/J002798/1. C.P. is a Royal Society Research Fellow.N.L. is supported in part by STFC grant ST/J002798/1. C.P. is a Royal Society Research Fellow.N.L. is supported in part by STFC grant ST/J002798/1. OPen Aceess funded by SCOAP

Low-Energy Theorems from Holography

In the context of gauge/gravity duality, we verify two types of gauge theory low-energy theorems, the dilation Ward identities and the decoupling of heavy flavor. First, we provide an analytic proof of non-trivial dilation Ward identities for a theory holographically dual to a background with gluon condensate (the self-dual Liu--Tseytlin background). In this way an important class of low-energy theorems for correlators of different operators with the trace of the energy-momentum tensor is established, which so far has been studied in field theory only. Another low-energy relationship, the so-called decoupling theorem, is numerically shown to hold universally in three holographic models involving both the quark and the gluon condensate. We show this by comparing the ratio of the quark and gluon condensates in three different examples of gravity backgrounds with non-trivial dilaton flow. As a by-product of our study, we also obtain gauge field condensate contributions to meson transport coefficients.Comment: 32 pages, 4 figures, two references added, typos remove

A & B model approaches to surface operators and Toda theories

It has recently been argued by Alday et al that the inclusion of surface operators in 4d N=2 SU(2) quiver gauge theories should correspond to insertions of certain degenerate operators in the dual Liouville theory. So far only the insertion of a single surface operator has been treated (in a semi-classical limit). In this paper we study and generalise this proposal. Our approach relies on the use of topological string theory techniques. On the B-model side we show that the effects of multiple surface operator insertions in 4d N=2 gauge theories can be calculated using the B-model topological recursion method, valid beyond the semi-classical limit. On the mirror A-model side we find by explicit computations that the 5d lift of the SU(N) gauge theory partition function in the presence of (one or many) surface operators is equal to an A-model topological string partition function with the insertion of (one or many) toric branes. This is in agreement with an earlier proposal by Gukov. Our A-model results were motivated by and agree with what one obtains by combining the AGT conjecture with the dual interpretation in terms of degenerate operators. The topological string theory approach also opens up new possibilities in the study of 2d Toda field theories.Comment: 43 pages. v2: Added references, including a reference to unpublished work by S.Gukov; minor changes and clarifications