Atul K. Srivastava

Microbial decomposition of leaf litter as influenced by pesticides

SummaryThe application of dithane M-45, 2, 4-D and carbofuran at the rates of 1, 5 and 10 mg (active ingredients) per g air-dry litter caused insignificant variations in the microbial populations in decomposing leaf litter. The qualitative nature of mycoflora, was altered, a little, with regard to the total number of species and relative abundance of a few species. The variations in CO2 evolution was significant only in relation to the fungicidal treatment. Percent weight loss of treated and untreated litter differed insignificantly at the end except in the case of fungicidal treatment. The present study infers that the used concentrations of the test pesticides may be recommended in tropical forestry as their application does not pose any potential threat to the process of natural decomposition of the leaf litter.

Gravity modulation of thermal instability in a viscoelastic fluid saturated anisotropic porous medium

The present paper deals with a thermal instability problem in a viscoelastic fluid saturating an anisotropic porous medium under gravity modulation. To find the gravity modulation effect, the gravity field is considered in two parts: a constant part and an externally imposed time-dependent periodic part. The time-dependent part of the gravity field, which can be realized by shaking the fluid, has been represented by a sinusoidal function. Using Hill’s equation and the Floquet theory, the convective threshold has been obtained. It is found that gravity modulation can significantly affect the stability limits of the system. Further, we find that there is a competition between the synchronous and subharmonic modes of convection at the onset of instability. Effects of various parameters on the onset of instability have also been discussed.

Colony interactions and mycoparasitism betweenAcremonium furcatum andAspergillus spp.

SummaryColony interactions and mycoparasitism betweenAcremonium furcatum and ten species of Aspergillus were studied in dual cultures. It was observed thatA. furcatum overgrew the colonies of all the ten species of Aspergillus studied. During the mycoparasitic interactions frequent coiling, penetration and growth of hyphae ofA. furcatum inside the conidiophores of six species of Aspergillus were observed.

Analysis of iterative methods in PageRank computation

Abstract PageRank is one of the basic metric used in web search technology to rank the web pages. It uses power method to compute principal eigenvector of the web matrix of several billion nodes. PageRank method incorporates a parameter α called damping factor that plays a major role in PageRank computation. In this study, we have observed experimentally the efficiency of various iterative methods on hyperlink graph for different value of α. We conclude from experiment that Power method is effective and more competitive for the well condition problem i.e. small value of α. However, for α → 1 Power method becomes more complex, and other methods such as Aitken-Power, SOR, and Gauss-Seidel are more efficient than it in respect of CPU time as well as the number of iteration needed for convergence.