Alok Banerjee

Bio: Alok Banerjee is an academic researcher from University of Burdwan. The author has contributed to research in topics: Irradiation & Paramagnetism. The author has an hindex of 3, co-authored 6 publications receiving 40 citations.

Influence of Captan on some microorganisms and microbial processes related to the nitrogen cycle

Abstract: Captan was applied to laboratory-incubated agricultural soil and to bacterial cultures to determine its effects on total counts of soil microorganisms, nitrification, ammonification of urea and asymbiotic dinitrogen fixation.

Paramagnetic and anti-ferromagnetic interactions in sol–gel derived Zn1−x Mn x O [50 MeV Li3+ irradiated (x=0.04) and unirradiated (x=0.02 and 0.04)] samples

Abstract: A study of Zn1−x Mn x O (x=0.02 and 0.04) pellets synthesized by sol–gel technique was performed to explore the inherent magnetic interactions. 50 MeV Li3+ ion beam irradiation was employed to a Zn0.96Mn0.04O pellet. Structural, morphological, compositional and magnetic properties of the samples were investigated. The single-phase structural nature was destroyed for a 4 at% Mn-doped sample with the formation instead of a new phase of ZnMnO3, as observed from the X-ray diffraction (XRD) pattern. The intensity of the multiphase component decreases with the ion irradiation. XRD also indicates that Mn incorporation in ZnO increased with increasing doping and, interestingly, with irradiation. The tendency of grain size is the opposite. The magnetic measurements of the samples indicate anti-ferromagnetic interactions coupled with paramagnetic counterparts. The study clearly exhibits the modification of magnetic properties with Li3+ ion beam irradiation. It has been interpreted that structural and compositional ...

Absence of Ferromagnetism in Mn Doped ZnO

Abstract: 2 and 4 at% Mn doped ZnO samples were synthesized by sol‐gel technique. The structural, compositional and magnetic properties were investigated. The 4 at% Mn doped sample contains secondary phase of ZnMnO3. The compositions of the samples are close to perfection. Crystallite size decreases with increase in doping. Both samples indicate absence of ferromagnetism. Strong presence of antiferromagnetism was found and it falls with increasing Mn doping. Simultaneously paramagnetic fraction of spin increases.

Role Of Nano Size Particle Assembly In Ferromagnetism Of Mn Doped ZnO Pellets

Abstract: 4 at% Mn doped ZnO samples were synthesized by solid‐state reaction technique. Structural and magnetic properties were explored. The sample contains a secondary phase of ZnMn2O4 that has transition temperature around 40 K. It shows room temperature (RT) ferromagnetism. The ferromagnetic (FM) part of magnetization is successfully decoupled from PM counterpart by mathematical modeling. The field and temperature dependent magnetization measurements confirm the intrinsic FM nature of the sample. Particle size distribution in nanometer length scale is responsible for typical behavior of temperature dependent magnetization curve.

The effect of swift heavy ion irradiation on critical current density in YB2Cu3O7−δ thick film with Y2O3 addition

Abstract: The effect of 200 MeV Ag ion irradiation on thick films of YBCO grown by the diffusion reaction technique has been studied. Magnetization at 40 K marks a substantial change in the critical current density (J c) of the irradiated sample when compared with unirradiated ones. The critical current density was estimated from the widths of magnetization loops using Bean's critical state model. The enhancement of J c from 1.06×105 to 2.5×105 A/cm2 with irradiation up to a fluence of 5×1011 ions/cm2 in YBCO samples is associated with an increase in the flux pinning created by the irradiation-induced columnar defects. In excess Y2O3 (10 wt%) to YBCO, the J c increases in the pristine sample to 1.33×105 A/cm2 but decreases with increasing fluence. This may be due to an excess of defects, overlapping of defected zones and weakening of the pinning barriers. Further studies using X-ray diffraction and a scanning electron microscope reveal microstructural changes in the irradiated samples.

Microbial and Faunal Interactions and Effects on Litter Nitrogen and Decomposition in Agroecosystems

Abstract: We conducted field experiments to test the general hypothesis that the com- position of decomposer communities and their trophic interactions can influence patterns of plant litter decomposition and nitrogen dynamics in ecosystems. Conventional (CT) and no-tillage (NT) agroecosystems were used to test this idea because of their structural sim- plicity and known differences in their functional properties. Biocides were applied to ex- perimentally exclude bacteria, saprophytic fungi, and microarthropods in field exclosures. Abundances of decomposer organisms (bacteria, fungi, protozoa, nematodes, microar- thropods), decomposition rates, and nitrogen fluxes were quantified in surface and buried litterbags (Secale cereale litter) placed in both NT and CT systems. Measurements of in situ soil respiration rates were made concurrently. The abundance and biomass of all microbial and faunal groups were greater on buried than surface litter. The mesofauna contributed more to the total heterotrophic C in buried litter from CT (6-22%) than in surface litter from NT (0.4-1/1%). Buried litter decay rates (1.4-1.7%/d) were -2.5 times faster than rates for surface litter (0.5-O.7%/d). Ratios of fungal to bacterial biomass and fungivore to bacterivore biomass on NT surface litter generally increased over the study period resulting in ratios that were 2.7 and 2.2 times greater, respectively, than those of CT buried litter by the end of the summer. The exclusion experiments showed that fungi had a somewhat greater influence on the decomposition of surface litter from NT while bacteria were more important in the de- composition of buried litter from CT. The fungicide and bactericide reduced decomposition rates of NT surface litter by 36 and 25% of controls, respectively, while in CT buried litter they were reduced by 21 and 35% of controls, respectively. Microarthropods were more important in mobilizing surface litter nitrogen by grazing on fungi than in contributing to litter mass loss. Where fungivorous microarthropods were experimentally excluded, there was less than a 5% reduction in mass loss from litter of both NT and CT, but fungi- fungivore interactions were important in regulating litter N dynamics in NT surface litter. As fungal densities increased following the exclusion of microarthropods on NT surface litter, there was 25% greater N retention as compared to the control after 56 d of decay. Saprophytic fungi were responsible for as much as 86% of the net N immobilized (1.81 g /m2) in surface litter by the end of the study when densities of fungivorous microarthropods were low. Although bacteria were important in regulating buried litter decomposition rates and the population dynamics of bacterivorous fauna, their influence on buried litter N dynamics remains less clear. The larger microbial biomass and greater contribution of a bacterivorous fauna on buried litter is consistent with the greater carbon losses and lower carbon assimilation in CT than NT agroecosystems. In summary, our results suggest that litter placement can strongly influence the com- position of decomposer communities and that the resulting trophic relationships are im- portant to determining the rates and timing of plant litter decomposition and N dynamics. Furthermore, cross placement studies suggest that the decomposer communities within each tillage system, while not discrete, are adapted to the native litter placements in each.

Pesticide effects on bacterial diversity in agricultural soils – a review

Abstract: According to guidelines for the approval of pesticides, side-effects on soil microorganisms should be determined by studying functional parameters such as carbon or nitrogen mineralisation. However, the microbial diversity may have been markedly changed following pesticide use despite unaltered metabolism, and such changes may affect soil fertility. This review evaluates new methods for measuring pesticide effects on bacterial diversity, and discusses how sampling should take temporal and spatial heterogeneity into account. Future research on pesticide approval protocols should establish the relationships between mineralisation assays and new and rapid bacterial diversity profiling methods, and should include the possible ecological implications of altered bacterial diversity for soil fertility.

Agricultural importance of algae

Abstract: Algae are a large and diverse group of microorganisms that can carry out photosynthesis since they capture energy from sunlight. Algae play an important role in agriculture where they are used as biofertilizer and soil stabilizers. Algae, particularly the seaweeds, are used as fertilizers, resulting in less nitrogen and phosphorous runoff than the one from the use of livestock manure. This in turn, increases the quality of water flowing into rivers and oceans. These organisms are cultivated around the world and used as human food supplements. They can produce a clean and carbon-neutral food also and can be grown on abandoned lands and arid desert lands with minimal demands for fresh water. Seaweeds are an important source of iodine. Iodine levels in milk depend on what the cow producing the milk has been fed with. Feeding milk cattle with seaweeds can increase the quantity of iodine in milk, according to Fuzhou Wonderful Biological Technology. Egg-laying rate in hen is also increased by algae feed additives. In this article, we discussed the most important aspects of algae and its agricultural uses to those who work in this area. Key words : Algae, seaweeds, agriculture, biofertilizer, soil stabilizers.

Influence of Mn doping on the magnetic and optical properties of ZnO nanocrystalline particles

Abstract: The structural, optical and magnetic properties of Mn doped ZnO nanocrystalline particles, Zn1-xMnxO, with different percentages of Mn content have been studied. XRD and XPS measurements showed that all samples with Mn doping up to x = 0.1 possess typical wurtzite structure and have no other impurity phases. The incorporation of Mn ions into the ZnO lattice was also confirmed by FTIR and UV–Vis. spectroscopy results. Both XRD and SEM results indicated a slight decrease in the grain size with increasing the Mn doping level. The XPS results indicated an increase in the oxygen vacancies concentration with increasing the Mn doping level. The magnetization measurements revealed a weak ferromagnetic behavior at room temperature and a clear ferromagnetic behavior with relatively large coercive fields at low temperature. The ferromagnetic order is improved by increasing the Mn doping. In addition, we observed an increase in the concentration of oxygen vacancies, which is also induced by increasing the Mn doping level. A ferromagnetic coupling of the local moment of Mn dopants through the sp-d exchange interaction and oxygen vacancies, in addition to different magnetic contributions due to different forms of Mn ions that coexist in the Mn doped nanoparticles were presented in order to interpret the observed magnetic behavior. We observed a clear red shift in the direct band gap and an increase in the coercive field and saturation magnetization values with increasing the Mn doping level.