Showing papers by "Jitendra Kumar published in 2010"
TL;DR: In this article, the formation and magnetic behavior of nanoparticles of various manganese oxides have been studied and it was shown that a small quantity of Mn 3 O 4 always remains in the products and can be detected by susceptibility data below 50 K only with bifurcation in χ ZFC and χ FC curves and blocking temperature in the range 30-40 K.
Abstract: The formation and magnetic behaviour of nanoparticles of various manganese oxides have been studied. For synthesis, manganese oxalate dihydrate is first produced via sol–gel process and then decomposed in oxygen, air, nitrogen, or argon ambient at different temperatures. The decomposition process leads to emergence of Mn 3 O 4 which undergoes oxidation, oxidation–reduction, or reduction process subsequently depending upon the availability of oxygen to yield Mn 2 O 3 in air/O 2 and MnO in argon/nitrogen ambient. A partial reaction causes retention of some Mn 3 O 4 alone or Mn 3 O 4 and Mn 5 O 8 together as secondary phase(s). The magnetic susceptibility ( χ ) data reveal (i) antiferro-magnetic nature for Mn 2 O 3 , Mn 5 O 8 and MnO with Neel temperature 75 K, 131 K and 115 K, respectively, (ii) orthorhombic to cubic crystallographic transition in Mn 2 O 3 at 310 K for the first time, and (iii) ferri-magnetic character for Mn 3 O 4 with Curie temperature 46 K. Further, it is demonstrated that a small quantity of Mn 3 O 4 always remains in the products and can be detected by susceptibility data below 50 K only with bifurcation in χ ZFC and χ FC curves and blocking temperature in the range 30–40 K. Also, the decomposition of manganese oxalate at 1100 °C for 4 h in air leads to formation of pure Mn 3 O 4 with saturation magnetization of 1.85 μ B per molecule and coercivity of 4750 Oe at 10 K.
52 citations
TL;DR: In this article, undoped and cesium-doped zinc oxide (ZnO) thin films have been applied to sapphire substrate (0001) using the sol-gel method.
Abstract: Undoped and cesium-doped zinc oxide (ZnO) thin films have been deposited on sapphire substrate (0001) using the sol–gel method. Films were preheated at 300 °C for 10 min and annealed at 600 and 800 °C for 1 h. The grown thin films were confirmed to be of wurtzite structure using X-ray diffraction. Surface morphology of the films was analyzed using scanning electron microscopy. The photoluminescence (PL) spectra of ZnO showed a strong ultraviolet (UV) emission band located at 3.263 eV and a very weak visible emission associated with deep-level defects. Cesium incorporation induced a blue shift of the optical band gap and quenching of the near-band-edge PL for nanocrystalline thin film at room temperatures because of the band-filling effect of free carriers. A shift of about 10–15 cm−1 is observed for the first-order longitudinal-optical (LO) phonon Raman peak of the nanocrystals when compared to the LO phonon peak of bulk ZnO. The UV resonant Raman excitation at RT shows multiphonon LO modes up to fifth order. Copyright © 2010 John Wiley & Sons, Ltd.
43 citations
TL;DR: In this paper, pure and doped zinc oxide thin films have been deposited on sapphire substrates by using the sol-gel method and spin coating technique and X-ray diffraction pattern showed that the deposited films exhibit hexagonal zinc oxide structure.
30 citations
TL;DR: A review of the impact of GM crops on contemporary agriculture across the past few decades, traces its’ history across time, highlights new achievements and breakthroughs and discusses the future implication of this powerful technology in the coming few decades.
Abstract: Post-green revolution advances made in biotechnology paved the way of cultivating the high-yielding, stress and disease resistant genetically modified (GM) varieties of wheat, rice, maize cotton and several other crops. The recent rapid commercialization of the genetically modified crops in Asia, Americas and Australia indicates the potentiality of this new technology. GM crops give higher yields and are rich in nutritional values containing vitamins and minerals and can thus can help to alleviate hunger and malnutrition of the growing population in the under developed and developing countries. It could also be possible to develop more biotic and abiotic stress resistant genotypes in these crops where it was difficult to develop due to the unavailability of genes of resistance in the crossing germplasms. However, further research and investigations are needed to popularize the cultivation of these crops in different parts of the world. This review provides an insight of the impact of GM crops on contemporary agriculture across the past few decades, traces its' history across time, highlights new achievements and breakthroughs and discusses the future implication of this powerful technology in the coming few decades.
27 citations
TL;DR: In this article, the authors studied the ferromagnetic properties of transition metal (TM) doped wurtzite GaN from first principle calculations using tight binding linear muffin-tin orbital (TBLMTO) method within the density functional theory.
16 citations
Journal Article•
TL;DR: Uptake of Nutrients was higher by rice and lowest by weeds with hand weedings and pre-emergence application of pendimethalin @ 1.0 kg ha −1 + anilophos @ 0.4 kg ha−1 over rest of the treatments.
Abstract: Three sowing dates viz.05 June, 20 June and 05 July and six weed management practices viz pendimethalin 1.5 kg ha−1(PE), pendimethalin 1.0 kg ha−1 + anilophos 0.4 kg ha−1(PE), pretilachlor 0.75 kg ha−1 (PE), fenoxapropp-ethyl 0.06 kg ha−1(15 DAS) followed by 2,4-D 0.5 kg ha−1 (30 DAS), anilophos 0.4 kg ha−1 (10 DAS) and two hand weedings (20 and 40 DAS) with weed free and weedy check treatments were evaluated in direct seeded unpuddled rice at Crop Research Centre, G.B. Pant University of Agriculture and Technology, Pantnagar during wet season of 2006 and 2007. Echinochloa colonum among grasses and Commelina benghalensis, Caesulia axillaris among non-grasses and Cyperus rotundus among sedges were the predominant weed species in the experimental plot. Highest nutrients uptake by crop (27.1, 8.1 and 68.4 kg ha−1 and 29.0, 8.1 and 69.1 kg ha−1 nitrogen, phosphorus and potassium during 2006 and 2007, respectively) was recorded from 20 June sown rice crop over rest two sowing dates (05 June and 05 July) during both the years. Use of herbicides increased nutrient uptake by rice and decreased nutrient uptake by weeds. Uptake of Nutrients was higher by rice and lowest by weeds with hand weedings and pre-emergence application of pendimethalin @ 1.0 kg ha−1 + anilophos @ 0.4 kg ha−1 over rest of the treatments. Reduction in grain yield of rice due to uncontrolled weeds in weedy plots was 70.4 per cent during 2006 and 67.4 per cent during 2007.
13 citations
TL;DR: In this paper, the effect of magnetic field and geometrical anisotropy on electronic and optical properties of self-assembled CdZnSe quantum dots is theoretically investigated.
Abstract: The effect of magnetic field and geometrical anisotropy on electronic and optical properties of self-assembled CdZnSe quantum dots is theoretically investigated. The Luttinger Hamiltonian formulation has been used in a transformed coordinate system for obtaining the energy eigenvalues and wavefunctions for the holes. The variation of energy eigenvalues with the magnetic field has been studied for anisotropic quantum dots. The degree of linear polarization is also calculated and is found to increase with magnetic field which is explained in terms of anisotropy induced valence subband mixing.
11 citations
TL;DR: Triterpenic saponins isolated from seeds of Madhuca indica and fruit pericarp from Sapindus mukorossi exhibited inhibitory effect against two phyto-parasitic nematodes.
Abstract: Triterpenic saponins isolated from seeds of Madhuca indica and fruit pericarp from Sapindus mukorossi exhibited inhibitory effect against two phyto-parasitic nematodes. Azadirachtin and salanin-nimbin-desacetylnimbin (SND) was extracted from seeds and oil of Azadirachta indica A. Juss, respectively. M. indica and S. mukorossi saponins were found to inhibit the movement of pre-adult (J4) stage of Rotylenchulus reniformis with LC50 of 168.8 and 181.9 µg/mL. Azadirachtin and SND affected the mobility of secondary juvenile stage (J2) of Meloidogyne incognita by 83.3 and 80.1% respectively, at 0.5 mg m/L. M. indica saponin (LC50 220 µg/mL) exhibited a potentiation effect in the presence of azadirachtin in a 1:3 ratio (LC50 120.1 µg/mL). A binary mixture (1:1) of azadirachtin and SND was found to show significant nematicidal activity against M. incognita (LC50 70.9 µg/mL) and R. reniformis (LC50 91.2 µg/mL).
10 citations
TL;DR: In this paper, the hydrogen bonding interactions between adenine-substituted ferrocene and a uracil-terminated organothiol monolayer were investigated on gold surfaces.
9 citations
TL;DR: In this article, a large magnetocaloric effect has been observed in Mn3O4 around its ferrimagnetic transition at TN = 42.75 K. Field-induced isothermal entropy changes (\DeltaS) were derived from both magnetic and calorimetric techniques.
Abstract: Large magnetocaloric effect has been observed in Mn3O4 around its ferrimagnetic transition at TN = 42.75 K. Field-induced isothermal entropy changes (\DeltaS) were derived from both magnetic and calorimetric techniques. The maximum |\DeltaS| and adiabatic temperature change ({\Delta}Tad) at TN are 11 J kg-1 K-1 and 1.9 K, respectively, for a magnetic field change of 20 kOe. Moreover, it is found that the complex magnetic phase transitions taking place below TN produce additional -but smaller- features on \DeltaS(T).
9 citations
Journal Article•
TL;DR: The residue of cartap hydrochloride was detected below maximum residue limit of 0.1 mg/kg in grain 72 days after its application and the bioefficacy of controlled release formulations against the rice leaf folder was studied.
Abstract: An experiment was conducted during 2005 to study the bioefficacy of controlled release formulations of cartap hydrochloride (2-dimethylaminopropane-1, 3-diol) against the rice leaf folder [Cnaphalocrocis medinalis (Guenee)]. Controlled release formulations of insecticide cartap hydrochloride were prepared using commercially available polyvinyl chloride (emulsion and suspension), carboxy methyl cellulose and carboxy methyl cellulose with clay (bentonite, kaolinite and Fullers’ earth). These released cartap hydrochloride beyond 45 days as compared to 14 days from its commercial 4G. sodium carboxy Methyl cellulose-Kaolinite-based formulation provided a superior control (3.33%) of rice leaf folder in field grown rice (Oryza sativa L.) at half the dose (375 g a i/ha) in comparison to cartap hydrochloride 4 G (5.44%) at 72 days after treatment. The residue of cartap hydrochloride was detected below maximum residue limit of 0.1 mg/kg in grain 72 days after its application.
TL;DR: In this article, high-pressure X-Ray diffraction studies on terbium oxide have been carried out up to a pressure of ∼35 GPa in a diamond anvil cell at room temperature.
TL;DR: In this article, the active layer of hybrid solar cell formed with poly(3-hexylthiophene) (P3HT) nanoparticles is optimized in terms of their mass ratio and microstructure by using absorption and scanning electron microscope (SEM).
Abstract: Hybrid solar cells have attracted considerable attention in recent years due to their high thermal and chemical stability, light weight, high carrier mobility, and low cost. The active layer of cadmium selenide (CdSe) nanoparticles- poly(3-hexylthiophene) (P3HT) is optimized in terms of their mass ratio and microstructure by using absorption and scanning electron microscope (SEM). The active layer of hybrid solar cell formed with P3HT to CdSe mass ratio as 1:9 exhibits (i) maximum absorption of solar radiation in the wavelength range of 300–850 nm, (ii) provides fine dispersion of CdSe nanocrystals (average size ∼ 15 nm). Nanocrystal-polymer blend solar cell has been fabricated by the solution spin-casting process and characterized. The fabricated solar cell device shows short circuit current (Jsc) 0.51mA/cm2 and open circuit voltage (Voc) 0.44V.
01 Oct 2010-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this article, the effect of insulating substrates on the electrical properties of structures having nano-gaps between two electrodes was investigated, and the authors compared the two configurations in light of surface conductivity of the substrate and the changes occurring due to gallium ion irradiation.
Abstract: The nano-structure based devices are normally fabricated on insulating substrates for exploitation of their electrical properties. Since the micro/nano-structures are subjected to a very high electric field even at low voltages, the substrate properties are likely to influence their behavior. We have investigated the effect of insulating substrates on the electrical properties of structures having nano-gaps between two electrodes. The electrical properties of focused ion beam fabricated metal strips in contact with the substrate and overhanging metal electrodes have been measured at a residual pressure of ∼10−6 mbar and also under clean ambient conditions. A comparative study of these two configurations has been discussed in light of surface conductivity of the substrate and the changes occurring due to gallium ion irradiation.
01 Sep 2010
TL;DR: In this article, the effect of magnetic field on the electronic structure and optical anisotropy of Zn1-xCdxSe/ZnSe quantum dots (QDs) was analyzed for varying geometrical confinement related to the in-plane asymmetry.
Abstract: The effect of magnetic field on the electronic structure and optical anisotropy of Zn1-xCdxSe/ZnSe quantum dots (QDs) has been analyzed for varying geometrical confinement related to the in-plane asymmetry. The disk-shaped QD is modeled by anisotropic parabolic potential with the magnetic field considered in Faraday geometry. The multiple band Hamiltonian in presence of magnetic field has been numerically diagonalized using appropriate basis functions and coordinate transformations for fast convergence. The eigenvalues and eigenvectors thus obtained are utilized for obtaining the dipole matrix elements. Hence, the photoluminescence spectra and the degree of linear polarization have been studied for the anisotropic QDs. The polarization degree is found to increase with magnetic field and anisotropy parameter.
26 Jul 2010
TL;DR: In this article, the I-V characteristics measured at a pressure ~10−6 mbar are shown to follow Child-Langmuir law or Fowler-Nordheim field emission depending upon the gap.
Abstract: Electrodes with nano-scale gaps have been fabricated using metallic nano-wires, derived via milling of thin films with focused ion beam (FIB) and passing current ~1012A/m2. Their I-V characteristics measured at a pressure ~10−6 mbar are shown to follow Child-Langmuir law or Fowler-Nordheim field emission depending upon the gap.
TL;DR: In this article, the effect of light exposure on the fluorescence of Alq3 sample and formation of luminescent quencher has been studied using cyclic voltammeter and 3D contour emission spectroscopy.
Abstract: Organic Tris-(8-hydroxyquinoline)aluminum (Alq3) thin films, one of the most widely used electron transport as well as emissive materials in the organic electroluminescent (EL) devices, have been deposited on glass substrates by thermal evaporation process. The deposited Alq3 thin films were exposed to light in the normal ambient. The effect of light exposure on the fluorescence of Alq3 sample and formation of luminescent quencher has been studied using cyclic voltammeter and 3D contour emission spectroscopy. It is observed that the luminescent quencher can be formed in the Alq3 during the light exposure, quenching the emission of light exposed sample. It is found that the energy of excitons in the Alq3 molecule in the light exposed Alq3 thin films can be non-radiatively transferred to its neighbouring luminescent quencher, quenching the emission of light exposed Alq3 thin films.