Dynamics of Diblock Copolymers in Dilute Solutions

We consider the dynamics of freely translating and rotating diblock (A-B), Gaussian copolymers, in dilute solutions. Using the multiple scattering technique, we have computed the diffusion and the friction coefficients D_AB and Zeta_AB, and the change Eta_AB in the viscosity of the solution as functions of x = N_A/N and t = l_B/l_A, where N_A, N are the number of segments of the A block and of the whole copolymer, respectively, and l_A, l_B are the Kuhn lengths of the A and B blocks. Specific regimes that maximize the efficiency of separation of copolymers with distinct "t" values, have been identified.Comment: 20 pages Revtex, 7 eps figures, needs epsf.tex and amssymb.sty, submitted to Macromolecule

Origin of translocation barriers for polyelectrolyte chains

For single-file translocations of a charged macromolecule through a narrow pore, the crucial step of arrival of an end at the pore suffers from free energy barriers, arising from changes in intrachain electrostatic interaction, distribution of ionic clouds and solvent molecules, and conformational entropy of the chain. All contributing factors to the barrier in the initial stage of translocation are evaluated by using the self-consistent field theory for the polyelectrolyte and the coupled Poisson-Boltzmann description for ions, without radial symmetry. The barrier is found to be essentially entropic, due to conformational changes. For moderate and high salt concentrations, the barriers for the polyelectrolyte chain are quantitatively equivalent to that of uncharged self-avoiding walks. Electrostatic effects are shown to increase the free energy barriers, but only slightly. The degree of ionization, electrostatic interaction strength, decreasing salt concentration and the solvent quality all result in increases in the barrier.Comment: J.Chem. Phys. 131, 21 (2009) - to be appeare

Polymers pushing Polymers: Polymer Mixtures in Thermodynamic Equilibrium with a Pore

We investigate polymer partitioning from polymer mixtures into nanometer size cavities by formulating an equation of state for a binary polymer mixture assuming that only one (smaller) of the two polymer components can penetrate the cavity. Deriving the partitioning equilibrium equations and solving them numerically allows us to introduce the concept of "polymers-pushing-polymers" for the action of non-penetrating polymers on the partitioning of the penetrating polymers. Polymer partitioning into a pore even within a very simple model of a binary polymer mixture is shown to depend in a complicated way on the composition of the polymer mixture and/or the pore-penetration penalty. This can lead to enhanced as well as diminished partitioning, due to two separate energy scales that we analyse in detail.Comment: 10 pages, 6 figure

DETECTION OF SPATIOTEMPORAL CHANGES IN PALAR - PORUNDALAR DAM, DINDIGUL DISTRICT, TAMIL NADU, INDIA USING GEOMATICS TECHNOLOGIES

Water is an essential natural resource which indicates the economic growth of a region along with its various sustainable development plans. However, the rapid development on demographic, economic, and technological trends results in demolishing the favorable environment condition for water availability and results it scarcity. Though, the global warming condition and the anthropogenic activities affects the climatic conditions, the natural water resources and its sustainability need to maintain for future generations. The impacts of global warming, climate change and manmade activities affects water resource availability and its quality. It is mandatory to monitor the water resources in order to manage the resource. So, it is important to detect the surface water bodies and to analyze the Spatio-temporal changes of water bodies. It helps to provide sustainable development plans in water resource management. In the recent researches, remote sensing is one of the cost effective technology which used to detect and analyze the changes of spatial features and also to monitor the natural resources present on the earth surface. The study area chosen for the analysis is the Palar- Porundalar Dam which is the largest water body present in Palani Taluk, Dindigul District, Tamil Nadu, India. The present study, strives to detect the water spread of the Palar-Porundalar Dam for the years 1997, 2009 and 2021 using multi temporal satellite images with the help of Normalized Difference Water Index (NDWI) and to identify the changes over the above said periods. The result indicates that for the year 1997 the surface water spread detected upto 4.84 sqkm, for the year 2009 the surface water spread detected upto 4.81 sqkm and in the year 2021 the surface water spread detected upto 4.88 sqkm. Finally, the validation of the result carried out using accuracy assessment method manually by using kappa coefficient formula. The validation result indicates that there is 85.08% of the match detected among the classified and the reference data. The overall accuracy is 92.59%

Continuum Theory of Polymer Crystallization

We present a kinetic model of crystal growth of polymers of finite molecular weight. Experiments help to classify polymer crystallization broadly into two kinetic regimes. One is observed in melts or in high molar mass polymer solutions and is dominated by nucleation control with $G \sim \exp(1/T \Delta T)$, where $G$ is the growth rate and $\Delta T$ is the super-cooling. The other is observed in low molar mass solutions (as well as for small molecules) and is diffusion controlled with $G \sim \Delta T$, for small $\Delta T$. Our model unifies these two regimes in a single formalism. The model accounts for the accumulation of polymer chains near the growth front and invokes an entropic barrier theory to recover both limits of nucleation and diffusion control. The basic theory applies to both melts and solutions, and we numerically calculate the growth details of a single crystal in a dilute solution. The effects of molecular weight and concentration are also determined considering conventional polymer dynamics. Our theory shows that entropic considerations, in addition to the traditional energetic arguments, can capture general trends of a vast range of phenomenology. Unifying ideas on crystallization from small molecules and from flexible polymer chains emerge from our theory.Comment: 37 double-spaced pages including 8 figures, submitted to the Journal of Chemical Physic

Assessing the in vitro efficacy of biocontrol agents and oil cakes against basal rot of onion incited by Fusarium oxysporum f.sp. cepae

Onions are an important vegetable crop, which is infected by many soils and foliar pathogens. Among them, Fusarium Basal Rot (FBR) causes yield losses of up to 50 per cent in the field and 30 to 40 per cent during post-harvest storage of bulbs.  For management of basal rot of onion, the efficacy of native antagonists such as six different Trichoderma sp. (T1-T6), five different Bacillus sp. (B1-B5) and five different oil cakes was assessed against the Fusarium oxysporum f.sp. cepae under in vitro condition. Among them, T3 collected from Kulithalai recorded maximum virulence as well as dark green sporulation with conidia length of 2.68–3.25 and breadth of 2.54-3.46µ. Among the tested isolates, In the case of  Bacillus sp., isolate B4 recorded the maximum inhibition zone (66.16%), followed by B. subtilis (B5), which recorded a (59.03%) inhibition on the mycelial growth. Among the five different oil cakes, the filtrates of neem cake showed a maximum inhibition zone against F. oxysporum f.sp. cepae of 1.29 cm @ 15% concentration, followed by groundnut cake at 1.36 cm @ 30% concentration. Hence the different control measures, Trichoderma sp. showed critically acclaimed performance under in vitro than others. The combined application of Trichoderma sp, Bacillus sp and neem oilcake significantly inhibited the growth of basal rot of onion due to the presence of the antimicrobial property.