ON PRIME SPECTRUMS OF 2-PRIMAL RINGS

A 2−primal ring is one in which the prime radical is exactly the set of nilpotent elements. A ring is clean, provided every element is the sum of a unit and an idempotent. Keith Nicholson introduced clean rings in 1977 and proved the following: “Every clean ring is an exchange ring. Conversely, every exchange ring in which all idempotents are central, is clean. ” In this paper, we investigate some of the relationships among ring-theoretic properties and topological conditions, such as a 2-primal weakly exchange ring and its prime spectrum Spec(R). 1

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Not AvailableHeavy mortality in cage farmed cobia in the southeast coast of Tamil Nadu occurred during the summer of 2016 was investigated. About 60 per cent of the fish died following a few days of high temperature and low wind in the coastal region. The fish had an average size of 27.5 cm length and 200 g weight. The affected fish had focal erythematous lesions on the ventral distended abdomen, peritoneal serosanguinous fluid accumulation, splenomegaly and swollen kidney. Bacteriological examination of the peritoneal fluid, kidney and spleen revealed the presence of Gram negative short rods in large numbers. The bacteria grew as green colonies on thiosulphate citrate bile salt sucrose agar. The tissues were also screened for the presence of nervous necrosis nodavirus by PCR and cell culture but did not yield positive result. The bacterial strains isolated from the tissues were identified as Photobacterium damselae sub sp. damselae using API 20 E microbial identification kit. The species was confirmed by multiplex PCR for 16S rRNA and urease gene. Sequence analysis of 16S rRNA showed 99 per cent homogeneity with P. damselae subsp. damselae. One of the isolates was used for the pathogenicity study in sea bass fingerlings. The experimental infection was done by intraperitoneal administration of 50 micro liters of two dilutions of the culture at 4.2 ×10 raised to the power 5 and 4.2×103 cfu per fish. The experiment revealed that the bacteria were highly pathogenic to seabass and could induce 100 per cent mortality in 36 h. The same bacteria were re-isolated from kidney sample of moribund fish and were confirmed as Pdd with API test kits and 16S rRNA sequencing. The isolates were also screened for the presence of virulence genes.Not Availabl

Towards an Operational SAR-Based Rice Monitoring System in Asia: Examples from 13 Demonstration Sites across Asia in the RIICE Project

Rice is the most important food security crop in Asia. Information on its seasonal extent forms part of the national accounting of many Asian countries. Synthetic Aperture Radar (SAR) imagery is highly suitable for detecting lowland rice, especially in tropical and subtropical regions, where pervasive cloud cover in the rainy seasons precludes the use of optical imagery. Here, we present a simple, robust, rule-based classification for mapping rice area with regularly acquired, multi-temporal, X-band, HH-polarized SAR imagery and site-specific parameters for classification. The rules for rice detection are based on the well-studied temporal signature of rice from SAR backscatter and its relationship with crop stages. We also present a procedure for estimating the parameters based on “temporal feature descriptors” that concisely characterize the key information in the rice signatures in monitored field locations within each site. We demonstrate the robustness of the approach on a very large dataset. A total of 127 images across 13 footprints in six countries in Asia were obtained between October 2012, and April 2014, covering 4.78 m ha. More than 1900 in-season site visits were conducted across 228 monitoring locations in the footprints for classification purposes, and more than 1300 field observations were made for accuracy assessment. Some 1.6 m ha of rice were mapped with classification accuracies from 85% to 95% based on the parameters that were closely related to the observed temporal feature descriptors derived for each site. The 13 sites capture much of the diversity in water management, crop establishment and maturity in South and Southeast Asia. The study demonstrates the feasibility of rice detection at the national scale using multi-temporal SAR imagery with robust classification methods and parameters that are based on the knowledge of the temporal dynamics of the rice crop. We highlight the need for the development of an open-access library of temporal signatures, further investigation into temporal feature descriptors and better ancillary data to reduce the risk of misclassification with surfaces that have temporal backscatter dynamics similar to those of rice. We conclude with observations on the need to define appropriate SAR acquisition plans to support policies and decisions related to food security