Identification of rice blast disease-suppressing bacterial strains from the rhizosphere of rice grown in Pakistan.

Sixteen bacterial strains isolated from the roots and rhizosphere of rice plants growing in saline and non-saline soils from the Shorkot area of Pakistan were tested for their ability to promote plant growth and reduce the incidence of rice blast disease. When applied to the soil, many of the isolated rhizobacterial strains increased seedling growth and/or suppressed rice blast disease in greenhouse-grown plants of the cultivars Super Basmati and Azucena, but each cultivar responded to different subsets of the bacteria. In the cv Super Basmati, increased blast resistance was correlated with the production of siderophores by the rhizobacteria. Several strains inhibited the growth of the causative agent of rice blast disease, the fungal pathogen Magnaporthe grisea, in an in vitro dual culture assay. Direct bioantagonism was correlated with disease resistance in Super Basmati, but not in Azucena, and direct antagonism as a cause for the reduced disease incidence is also unlikely since no epiphytic colonisation of leaves was detected. Rhizosphere colonisation by the bacteria in plants grown in sterile sand was correlated with disease resistance in Super Basmati, but not in Azucena. As well as the differences in strains that protected each cv against blast disease, we also found that there were differences in the ability of some strains to protect plants against blast depending on soil type. Hence, there are complex interactions between rhizobacteria and rice plants with respect to biocontrol of rice blast disease, dependent upon both rice cv and soil type. The identity of strains that promoted high levels of disease protection, including three that performed well across all plant cultivars and growth conditions, was determined by 16S rRNA gene sequencing

p-GaAs nanowire MESFETs with near-thermal limit gating

Difficulties in obtaining high-performance p-type transistors and gate insulator charge-trapping effects present two major challenges for III-V complementary metal-oxide semiconductor (CMOS) electronics. We report a p-GaAs nanowire metal-semiconductor field-effect transistor (MESFET) that eliminates the need for a gate insulator by exploiting the Schottky barrier at the metal-GaAs interface. Our device beats the best-performing p-GaSb nanowire metal-oxide-semiconductor field effect transistor (MOSFET), giving a typical sub-threshold swing of 62 mV/dec, within 4% of the thermal limit, on-off ratio $\sim 10^{5}$, on-resistance ~700 k$\Omega$, contact resistance ~30 k$\Omega$, peak transconductance 1.2 $\mu$S/$\mu$m and high-fidelity ac operation at frequencies up to 10 kHz. The device consists of a GaAs nanowire with an undoped core and heavily Be-doped shell. We carefully etch back the nanowire at the gate locations to obtain Schottky-barrier insulated gates whilst leaving the doped shell intact at the contacts to obtain low contact resistance. Our device opens a path to all-GaAs nanowire MESFET complementary circuits with simplified fabrication and improved performance

The Existence of Einstein Static Universes and their Stability in Fourth order Theories of Gravity

We investigate whether or not an Einstein Static universe is a solution to the cosmological equations in $f(R)$ gravity. It is found that only one class of $f(R)$ theories admits an Einstein Static model, and that this class is neutrally stable with respect to vector and tensor perturbations for all equations of state on all scales. Scalar perturbations are only stable on all scales if the matter fluid equation of state satisfies $c_s^2>\frac{\sqrt{5}-1}{6}\approx 0.21$. This result is remarkably similar to the GR case, where it was found that the Einstein Static model is stable for $c_s^2>{1/5}$.Comment: Minor changes, To appear in PR

Large-scale perturbations on the brane and the isotropy of the cosmological singularity

We present the complete set of propagation and constraint equations for the kinematic and non-local first order quantities which describe general linear inhomogeneous and anisotropic perturbations of a flat FRW braneworld with vanishing cosmological constant and decompose them in the standard way into their scalar, vector and tensor contributions. A detailed analysis of the perturbation dynamics is performed using dimensionless variables that are specially tailored for the different regimes of interest; namely, the low energy GR regime, the high energy regime and the dark energy regime. Tables are presented for the evolution of all the physical quantities, making it easy to do a detailed comparison of the past asymptotic behaviour of the perturbations of these models. We find results that exactly match those obtained in the analysis of the spatially inhomogeneous $G_{2}$ braneworld cosmologies presented recently; i.e., that isotropization towards the ${\cal F}_b$ model occurs for $\gamma > 4/3$.Comment: 13 pages, revtex

Modern Feedback System: A Survey

The Feedback given by the stake holders about the current state of performance of any organization is essential for its growth. It provides vital information, which can be used to improve performance. In this way it provides motivation and fuels the continual improvement process. In business, it helps to deliver the best customer experiences. It forms the backbone of success of any institution or individual. It also forms the crust of good supervision in any organization. Feedback system initially started with raising hands, saying yes or no, then it evolved into answering questions through feedback forms, suggestion boxes etc. With the evolution in internet technology, it has now changed into web based, app based feedback systems etc. This paper explains different feedback systems that are currently in use and also explains about advantages and disadvantages of these systems. DOI: 10.17762/ijritcc2321-8169.16047

SUPPRESSION OF INCIDENCE OF RHIZOCTONIA SOLANI IN RICE BY SIDEROPHORE PRODUCING RHIZOBACTERIAL STRAINS BASED ON COMPETITION FOR IRON

Rice is a major crop in much of the developing world, where disease management using agrochemicals is not economically practical, nor environmentally safe. The identification of biocontrol agents therefore presents a useful alternative. Here, we screened bacterial strains isolated from the rhizosphere of rice plants, and identified a number of these that exhibit antagonistic activity towards the fungal pathogen, Rhizoctonia solani, the causative agent of rice sheath blight disease. Correlation analysis with different metabolites produced by these bacteria revealed that antagonism was strongly correlated with the quantity of siderophores produced by individual strains, and was increased under iron-limiting conditions. Selected high-siderophore-producing strains were found to promote the growth of rice plants, possibly via the solubilisation of soil phosphates, nitrogen fixation and the production of phytohormones. These same PGPR also conferred resistance against sheath blight disease, which resulted in significant yield increases in infected plants. A consortium of the selected strains was especially effective in both growth promotion and disease suppression, and generally performed better than treatment with the fungicide, benlate. Molecular analysis indicated that the PGPR strains tested enhance plant defence gene expression, and may therefore activate induced systemic resistance in rice. Our work has identified a series of rhizobacterial strains able to promote plant growth and provide effective resistance against sheath blight disease in rice and which therefore have potential for application as biocontrol agents in agriculture

SUPPRESSION OF INCIDENCE OF RHIZOCTONIA SOLANI IN RICE BY SIDEROPHORE PRODUCING RHIZOBACTERIAL STRAINS BASED ON COMPETITION FOR IRON

Rice is a major crop in much of the developing world, where disease management using agrochemicals is not economically practical, nor environmentally safe. The identification of biocontrol agents therefore presents a useful alternative. Here, we screened bacterial strains isolated from the rhizosphere of rice plants, and identified a number of these that exhibit antagonistic activity towards the fungal pathogen, Rhizoctonia solani, the causative agent of rice sheath blight disease. Correlation analysis with different metabolites produced by these bacteria revealed that antagonism was strongly correlated with the quantity of siderophores produced by individual strains, and was increased under iron-limiting conditions. Selected high-siderophore-producing strains were found to promote the growth of rice plants, possibly via the solubilisation of soil phosphates, nitrogen fixation and the production of phytohormones. These same PGPR also conferred resistance against sheath blight disease, which resulted in significant yield increases in infected plants. A consortium of the selected strains was especially effective in both growth promotion and disease suppression, and generally performed better than treatment with the fungicide, benlate. Molecular analysis indicated that the PGPR strains tested enhance plant defence gene expression, and may therefore activate induced systemic resistance in rice. Our work has identified a series of rhizobacterial strains able to promote plant growth and provide effective resistance against sheath blight disease in rice and which therefore have potential for application as biocontrol agents in agriculture

Braneworld Dynamics of Inflationary Cosmologies with Exponential Potentials

In this work we consider Randall-Sundrum braneworld type scenarios, in which the spacetime is described by a five-dimensional manifold with matter fields confined in a domain wall or three-brane. We present the results of a systematic analysis, using dynamical systems techniques, of the qualitative behaviour of Friedmann-Lemaitre-Robertson-Walker type models, whose matter is described by a scalar field with an exponential potential. We construct the state spaces for these models and discuss how their structure changes with respect to the general-relativistic case, in particular, what new critical points appear and their nature and the occurrence of bifurcation.Comment: 15 pages, 9 figures, RevTex 4. Submitted to Physical Review

Are braneworlds born isotropic?

It has recently been suggested that an isotropic singularity may be a generic feature of brane cosmologies, even in the inhomogeneous case. Using the covariant and gauge-invariant approach we present a detailed analysis of linear perturbations of the isotropic model ${\cal F}_b$ which is a past attractor in the phase space of homogeneous Bianchi models on the brane. We find that for matter with an equation of state parameter $\gamma > 1$, the dimensionless variables representing generic anisotropic and inhomogeneous perturbations decay as $t\to 0$, showing that the model ${\cal F}_b$ is asymptotically stable in the past. We conclude that brane universes are born with isotropy naturally built-in, contrary to standard cosmology. The observed large-scale homogeneity and isotropy of the universe can therefore be explained as a consequence of the initial conditions if the brane-world paradigm represents a description of the very early universe.Comment: Changed to match published versio

The Trouble with de Sitter Space

In this paper we assume the de Sitter Space version of Black Hole Complementarity which states that a single causal patch of de Sitter space is described as an isolated finite temperature cavity bounded by a horizon which allows no loss of information. We discuss the how the symmetries of de Sitter space should be implemented. Then we prove a no go theorem for implementing the symmetries if the entropy is finite. Thus we must either give up the finiteness of the de Sitter entropy or the exact symmetry of the classical space. Each has interesting implications for the very long time behavior. We argue that the lifetime of a de Sitter phase can not exceed the Poincare recurrence time. This is supported by recent results of Kachru, Kallosh, Linde and Trivedi.Comment: 15 pages, 1 figure. v2: added fifth section with comments on long time stability of de Sitter space, in which we argue that the lifetime can not exceed the Poincare recurrence time. v3: corrected a minor error in the appendi