1,043 research outputs found

    Antipathogenic Activity of Spirulina Powder

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    Spirulina is a microscopic blue-green alga in the shape of a spiral coil, living both in sea and fresh water. In this study, dried Spirulina was extracted at different solvents such as Hexane, Ethyl acetate, Ethanol, Butanol, Acetone, Methanol and chloroform. That extracts were stored in an airtight glass bottles in a refrigerator. Antimicrobial activity analysis from different pathogens and using well diffusion methods. Butanol extract of Spirulina also gave the highest antimicrobial activity of 19 mm against Staphylococcus epidermids, 18mm against Staphylococcus aureus and Aeromonas liquefaciens, 13mm against Candida glabrata, 12mm against Enterococcus feacalis, 11mm against Campylobacter coil and Vibrio cholerae and low activity against 5mm Salmonella typhi. Remaining solvents extracts antimicrobial activity low compare to butanol

    Influence of Mineralogical Nature of Aggregates on Acid Resistance of Mortar

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    Cement-based materials being alkaline in nature are often subjected to rapid deterioration on exposure to the aggressive acidic environments. Acids penetrate into the cement matrix causing calcium leaching and deterioration of phases leading to alteration in the microstructure. Currently, there are hardly any codes or standards available for evaluating the durability of materials to acid attack. Moreover, the literature addressing the material resistance is quite inconclusive. This paper aims to evaluate the influence of mineralogical nature of aggregates on the degradation kinetics of cement mortar when exposed to inorganic and organic acid solutions by performing a static accelerated leaching test. Cement mortar (1: 3) specimens of size 10 × 10 × 60 mm were prepared using Ordinary Portland Cement (OPC), using limestone (calcareous) aggregates and siliceous aggregates with a water to cement ratio of 0.40. After 28 days of initial curing in saturated lime water, the specimens were exposed to various concentrations of sulphuric (1 % and 3 %) and acetic acid solutions (0.25 M and 0.5 M) for a testing period of 4 months. The acid solution was replenished on a periodic basis to maintain the aggressiveness of the solution. The degradation kinetics was investigated by measuring mass changes, thickness changes, changes in pH of the acid solution and imaging using X-ray micro-tomography. Additionally, periodic abrasive action applied manually (using soft nylon brush) was used to accelerate the degradation process in case of sulphuric acid exposure and its effect was compared with the testing without the abrasive action. An attempt was also made to evaluate the changes in compressive strength and changes in dynamic modulus of elasticity of cylindrical mortar specimens (25 mm diameter and 50 mm height) on exposure to the acid solutions. The test results indicate that the performance of limestone aggregates is better on exposure to sulphuric acid and worse in case of acetic acid when compared to siliceous aggregates

    Studies on the growth of fishes in a brackishwater pen

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    The growth characteristics of fishes stocked in a pen of 100 sq. m. installed in the Pullavali brackishwater area were studied. The euryhaline species nf fish namely ehanos ehanos, Mugil sp., Siganus canaliculatus, Etroplus suratensis and Coranx sp. were stocked at the rate of 50 Nos. per sq. m. taking advantage of the free flow of water, rich in oxygen and plankton.

    Insertional mutagenesis in the vascular wilt pathogen Verticillium dahliae

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    Vascular wilt diseases caused by soil-borne pathogens are among the most devastating plant diseases worldwide. The ascomycete fungus Verticillium dahliae causes vascular wilt diseases in hundreds of dicotyledonous plant species, including important crops such as eggplant, lettuce, olive, spinach and tomato. The resting structures, microsclerotia, are triggered by root exudates to germinate and penetrate the roots after which the fungus grows into the xylem vessels. The fungus colonizes these vessels and interferes with the transportation of water and nutrients, resulting in the development of symptoms such as stunting, wilting, chlorosis and vascular browning. Verticillium wilt diseases are difficult to control due to the longevity of the microsclerotia, the broad host range of the pathogen, the inability of fungicides to kill the fungus once it has colonized the xylem vessels and the lack of natural resistance in many plant species. Chapter 1 is the introduction to this thesis that describes the identified pathogenicity and virulence factors of V. dahliae and strategies to identify these components. In spite of the economic importance of V. dahliae, relatively few pathogenicity genes have been identified in this species. With the availability of whole genome sequences and the development of functional genomics tools such as random mutagenesis, targeted mutagenesis, transcriptomics, RNA interference (RNAi) and comparative genomics, more strategies have become available to identify novel pathogenicity and virulence genes. Chapter 2 focuses on the identification of virulence and pathogenicity genes of V. dahliae by screening of a library of random T-DNA insertion mutants. Using Agrobacterium tumefaciens-mediated transformation, 900 T-DNA transformants with random insertions were generated and screened for altered virulence on susceptible tomato plants. This screening, followed by inverse PCR on selected transformants, resulted in the identification of 55 potential pathogenicity and virulence genes. One of the potential pathogenicity genes, VdNRS/ER, is a homolog of a nucleotide-rhamnose synthase/epimerase-reductase (NRS/ER), which is presumably involved in the biosynthesis of UDP-rhamnose. Using targeted mutagenesis, VdNRS/ER was deleted from wild-type V. dahliae and the resulting deletion mutants were characterized. VdNRS/ER deletion mutants exhibit unaltered vegetative growth and sporulation, but the deletion mutants were no longer pathogenic on tomato and N. benthamiana and showed impaired root attachment on tomato seedlings. These data suggest that UDPrhamnose is required for pathogenesis of V. dahliae. Chapter 3 describes the role of the V. dahliae homolog of Sge1, a transcriptional regulator that was shown to play a role in pathogenicity and regulate effector gene expression in Fusarium oxysporum. In this chapter it is demonstrated that V. dahliae Sge1 (VdSge1) is required for radial growth and production of asexual conidiospores. It is furthermore shown that VdSge1 deletion strains have lost pathogenicity on tomato. Since the VdSge1 deletion mutants are not able to infect and colonize tomato plants, a tomato cell suspension culture was used to the study the expression of Ave1, as well as nine other genes of which the expression is highly induced in planta. This assay revealed that VdSge1 is not required for the induction of the Ave1 effector that activates resistance mediated by Ve1 in tomato. Furthermore, the expression of one other putative effector gene was not affected by VdSge1 deletion. However, VdSge1 was shown to be required for the expression of six putative effector genes, whereas expression of the remaining two putative effectors genes was negatively regulated. Thus, the data show that VdSge1 is required for V. dahliae pathogenicity and differentially regulates effector gene expression. Chapter 4 describes the functional characterization of the gene family encoding necrosis- and ethylene-inducing-like proteins (NLPs) of V. dahliae. The cytotoxic activity of NLP family members was determined using agroinfiltration into tobacco leaves. This resulted in the identification of two out of the seven NLPs, VdNLP1 and VdNLP2, that induced plant cell death. The genes encoding these cytotoxic NLPs were found to be induced in V. dahliae upon colonization of tomato. Targeted deletion of VdNLP1 and VdNLP2 significantly reduced the virulence of V. dahliae on tomato and Arabidopsis plants. In contrast, only deletion of VdNLP1 affected virulence on N. benthamiana whereas deletion of NLP2 did not. However, subsequent transcriptional analysis revealed that VdNLP2 was not expressed in V. dahliae during colonization of N. benthamiana. Moreover, VdNLP2 also affects vegetative growth and conidiospore production. In conclusion, the expanded V. dahliae NLP family shows differential cytotoxic activity between family members and in planta induction of the cytotoxic NLP genes varies between plant hosts. In addition, VdNLP2 plays a role in vegetative growth and conidiospore production in addition to its contribution to virulence. Thus, evidence is provided for functional diversification within the V. dahliae NLP family. Finally in Chapter 5, the major findings of this thesis are discussed and placed in a broader perspective.</p

    Relating the Time Complexity of Optimization Problems in Light of the Exponential-Time Hypothesis

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    Obtaining lower bounds for NP-hard problems has for a long time been an active area of research. Recent algebraic techniques introduced by Jonsson et al. (SODA 2013) show that the time complexity of the parameterized SAT(\cdot) problem correlates to the lattice of strong partial clones. With this ordering they isolated a relation RR such that SAT(RR) can be solved at least as fast as any other NP-hard SAT(\cdot) problem. In this paper we extend this method and show that such languages also exist for the max ones problem (MaxOnes(Γ\Gamma)) and the Boolean valued constraint satisfaction problem over finite-valued constraint languages (VCSP(Δ\Delta)). With the help of these languages we relate MaxOnes and VCSP to the exponential time hypothesis in several different ways.Comment: This is an extended version of Relating the Time Complexity of Optimization Problems in Light of the Exponential-Time Hypothesis, appearing in Proceedings of the 39th International Symposium on Mathematical Foundations of Computer Science MFCS 2014 Budapest, August 25-29, 201