Persistence and Extinction of One-Prey and Two-Predators System

In this paper, a mathematical model is proposed and analysed to study the dynamics of one-prey two-predators system with ratio-dependent predators growth rate. Criteria for local stability, instability and global stability of the nonnegative equilibria are obtained. The permanent co-existence of the three species is also discussed. Finally, computer simulations are performed to investigate the dynamics of the system

Sequence-specific DNA binding by the MspI DNA methyltransferase

The MspI methyltransferase (M.MspI) recognizes the sequence CCGG and catalyzes the formation of 5-methylcytosine at the fist C-residue. We have investigated the sequence-specific DNA-binding properties of M.MspI under equilibrium conditions, using gel-mobility shift assays and DNasel footprinting. M.MspI binds to DNA in a sequence-specific manner either alone or in the presence of the normal methyl donor S-adenosyl-L-methionine as well as the analogues, sinefungin and S-adenosyl-L-homocysteine. In the presence of S-adenosyl-L-homocysteine, M.MspI shows the highest binding affinity to DNA containing a hemimethylated recognition sequence (Kd = 3.6 x 10(-7) M), but binds less well to unmethylated DNA (Kd = 8.3 x 10(-7) M). Surprisingly it shows specific, although poor, binding to fully methylated DNA (Kd = 4.2 x 10(-6) M). M.MspI binds approximately 5-fold more tightly to DNA containing its recognition sequence, CCGG, than to nonspecific sequences in the absence of cofactors. In the presence of S-adenosyl-L-methionine, S-adenosyl-L-homocysteine or sinefungin the discrimination between specific and non-specific sequences increases up to 100-fold. DNasel footprinting studies indicate that 16 base pairs of DNA are covered by M.MspI, with the recognition sequence CCGG located asymmetrically within the footprint

A hybrid evaluation approach and guidance for mHealth education applications

© Springer International Publishing AG 2018. Mobile health education applications (MHEAs) are used to support different users. However, although these applications are increasing in number, there is no effective evaluation framework to measure their usability and thus save effort and time for their many user groups. This paper outlines a useful framework for evaluating MHEAs, together with particular evaluation metrics: an efficient hybrid of selected heuristic evaluation (HE) and usability evaluation (UE) factors to enable the determination of the usefulness and usability of MHEAs. We also propose a guidance tool to help stakeholders choose the most suitable MHEA. The outcome of this framework is envisioned as meeting the requirements of different users, in addition to enhancing the development of MHEAs using software engineering approaches by creating new and more effective evaluation techniques. Finally, we present qualitative and quantitative results for the framework when used with MHEAs

Dynamics of Phytoplankton, Zooplankton and Fishery Resource Model

In this paper, a new mathematical model has been proposed and analyzed to study the interaction of phytoplankton- zooplankton-fish population in an aquatic environment with Holloing’s types II, III and IV functional responses. It is assumed that the growth rate of phytoplankton depends upon the constant level of nutrient and the fish population is harvested according to CPUE (catch per unit effort) hypothesis. Biological and bionomical equilibrium of the system has been investigated. Using Pontryagin’s Maximum Principal, the optimal harvesting policy is discussed. Chaotic nature and bifurcation analysis of the model system for a control parameter have been observed through a numerical simulation

Development of low tungsten substitute tool steels

Tunsten is a very important alloying element in high speed tool steel, hot and cold work die steel and permanent magnet alloys, but its ore deposits are limited to a few countries. Continuous development user the years to reduce tungsten content in convent- ional 18-4-1 high speed steel i.e. 18% tungsten, 1% chromium and 1% vanadium, has led to increase of molybdenum, cobalt, chromium or vanadium. These steels have a hyper eutectoid structure in the fully hardened state in which complex carbides are embedded in martensite matrix. Both of these constituents in high speed steel retain higher hardness at high temperature than their counterpart in plain carbon steel. Many such high speed steels with low amount or without tungsten have been developed. These low tung- sten steels' apart from replacing the non-available alloying elements have the additional advantage of requiring lower hardening temperature than high speed tool steel containing 18% tungsten, thus avoiding the formation of coarse grain size in steel

Tempering of Die-steels based on indigenous materials

This paper present studies on the effects of quenching temperature, tempering temperature and time on the hardness of three die steels of similar carbon contents but having increasing chromium percentages. While tempering in the range of 150°C to 400°C it was observed that hardness decreased as quenching temperature was raised. All the steels showed secondary hardening phenomenon in relation to the variables mentioned above. It was also observed that on tempering the steels above 450°C, after prior quenching from increasing temperatures, hardness gradually increased upto the quenching temperature of 1100°C, beyond which followed a decrease in hardness. This phenomenon was the decrease in hardness. This phenomenon was the same at all tempering temperatures upto 601°C, but the increase in hardness from low quenching temperatures to the maximum quenching temperature was less at 450°C than at the higher temperatures and attained a maximum at 600°C secondary hardening decreased with the increase of quenching temperatur