Blue luminescence of Au nanoclusters embedded in silica matrix

Photoluminescence study using the 325 nm He-Cd excitation is reported for the Au nanoclusters embedded in SiO2 matrix. Au clusters are grown by ion beam mixing with 100 KeV Ar+ irradiation on Au [40 nm]/SiO2 at various fluences and subsequent annealing at high temperature. The blue bands above ~3 eV match closely with reported values for colloidal Au nanoclusters and supported Au nanoislands. Radiative recombination of sp electrons above Fermi level to occupied d-band holes are assigned for observed luminescence peaks. Peaks at 3.1 eV and 3.4 eV are correlated to energy gaps at the X- and L-symmetry points, respectively, with possible involvement of relaxation mechanism. The blue shift of peak positions at 3.4 eV with decreasing cluster size is reported to be due to the compressive strain in small clusters. A first principle calculation based on density functional theory using the full potential linear augmented plane wave plus local orbitals (FP-LAPW+LO) formalism with generalized gradient approximation (GGA) for the exchange correlation energy is used to estimate the band gaps at the X- and L-symmetry points by calculating the band structures and joint density of states (JDOS) for different strain values in order to explain the blueshift of ~0.1 eV with decreasing cluster size around L-symmetry point.Comment: 13 pages, 7 Figures Only in PDF format; To be published in J. of Chem. Phys. (Tentative issue of publication 8th December 2004

Constraints in adoption of integrated management for root (wilt) disease affected coconut areas - An analysis of Alleppey district

Analysis of the constraints faced by the farming community in root (wilt) affected area was done during 2010-2011 at Alleppey district, Kerala, India. It was found that irrespective of the holding size only 50 percent of the coconut trees were in bearing stage whereas around one third were seedlings and one fifth pre bearing stage. Adoption of recommended practices were statistically significant with the area under coconut cultivation. The farmers identified 30 major constraints which were categorized as technical, input, economic, social and biophysical constraints in order of importance. Participation of the coconut farmers in meetings related to farming was only 18.9 percent and participation in training programmes was meager and only 10 percent of the sample respondents were members in any farmer groups. The results indicated need for coconut farmers' clusters/ societies for improving technology adoption in community basis

Nitrogen ion beam synthesis of InN in InP (100) at elevated temperature

InN phase is grown in crystalline InP(100) substrates by 50 keV N+ implantation at an elevated temperature of 400 deg C followed by annealing at 525 deg C in N2 ambient. Crystallographic structural and Raman scattering studies are performed for the characterization of grown phases. Temperature- and power-dependent photoluminescence studies show direct band-to-band transition peak ~1.06 eV at temperatures <=150K. Implantations at an elevated temperature with a low ion beam current and subsequent low temperature annealing step are found responsible for the growth of high-quality InN phase.Comment: 11 pages, 4 figures, Journa

Geo-spatial variability in coconut productivity in different agro - ecological units in Kerala-An analysis

Coconut plays a significant role in the agrarian economy of Kerala state. However, the state's share in the area as well as production of coconut in the country has been on the decline over the last many years. There exist huge variations in different districts and agro-ecological units of the state with regard to the productivity of coconut due to various factors including extent of adoption of crop management practices. A study was conducted covering different agro-ecological units in four selected districts of Kerala state to analyse the extent of adoption of recommended crop management practices and variability in coconut productivity in different agro-ecological units. Malappuram and Kannur districts were selected as the high productive district and the low productive district respectively in northern Kerala for the comparative study. In addition, as a representative of the root (wilt) affected southern districts, Alappuzha and Thiruvananthapuram were selected, as low and high yielders, respectively, for the study. The study involved field surveys to collect primary data on profile of coconut farmers, coconut gardens, input use, adoption of crop management practices etc. in addition to secondary information on soil and climatic variables. Each district was stratified into agro-ecological units and at least 50 gardens each with a minimum of 30 coconut palms were selected for field survey from each stratum. More than 85 % of the holdings in the surveyed districts belonged to small and marginal categories. Most of the profile characteristics of coconut growers in the state indicated limitations for them to get actively involved in farming related activities and achieve efficiency in terms of productivity and income from coconut farming. Coconut farming in the state is dominated by monocropping and homestead farming. Systematic multiple cropping and integrated farming in coconut gardens were low. Level of adoption of recommended crop management practices of coconut in different AEUs across districts was low. Low level of adoption of recommended cultivation practices of coconut clearly indicated the neglect of palms which probably is the prime factor resulting in low productivity of coconut in the state. Recommended practices like improved varieties/hybrids and integrated disease management were quite low with average adoption percentage of 8.9 and 8.8 respectively. Spacing for maintenance of optimum plant density, on farm recycling of biomass and IPM practices were adopted by less than one third of the coconut growers only. Malappuram district with an average of 59 nuts/palm/year was having the highest productivity wherein northern coastal plains (AEU 2) was the AEU with highest productivity (68 nuts/palm). Thiruvananthapuram and Alappuzha districts were having low productivity as compared to the state average at 38 and 44 nuts/palm/year, respectively. There existed significant difference in adoption of technologies between the two yield categories. Pest and disease incidence, percentage of those practised fully organic nutrients, those with neither organic nor inorganic, etc. were significantly higher in low yielders as expected. Proportion of farmers practising soil and water conservation, maintenance of optimum plant density, integrated nutrient management and IDM were significantly higher in high yielders (significant at 1% level of significance). It clearly suggests that technological interventions as per recommendation have resulted in increased yield. One of the major factors affecting crop productivity was the level of soil nutrients. Deficiency of organic carbon and potassium were more prominent in southern districts as compared to northern districts. Among the micro nutrients, boron deficiency was very prominent in all the districts. Logistic regression approach to concurrently estimate the effect of various technological and soil factors on coconut productivity validated the finding that adoption of recommended practices like soil and water conservation measures and optimum spacing contribute in yield enhancement. Based on the findings of the study, a framework for action was suggested which included institutional innovations to achieve efficiency in productivity and income from neglected gardens and to evolve AEU-wise technology packages. Major suggestions on interventions included policies and programmes to promote adoption of scientific crop management practices, and popularise multiple cropping and integrated farming; group approach to overcome the resource limitations in the fragmented holdings; farmer participatory seedling production initiatives like community coconut nurseries managed by FPOs; evolve congenial policy environment for production and marketing of customized fertilizer inputs and link trained FPOs to Agro-Service Centres. Extension interventions with emphasis on promoting water conserving irrigation methods such as drip irrigation, creating awareness about the need to restructure coconut orchards to maintain optimum palm density, increasing awareness on importance of application of liming materials, and enlightening the coconut growers about the need for shifting from individual to community based decentralised participatory approach in IPM/IDM were also suggested

Multi-phonon Raman scattering in GaN nanowires

UV Raman scattering studies show longitudinal optical (LO) mode up to 4th order in wurtzite GaN nanowire system. Frohlich interaction of electron with the long range electrostatic field of ionic bonded GaN gives rise to enhancement in LO phonon modes. Good crystalline quality, as indicated by the crystallographic as well as luminescence studies, is thought to be responsible for this significant observation. Calculated size dependence, incorporating size corrected dielectric constants, of electron-phonon interaction energy agrees well with measured values and also predict stronger interaction energy than that of the bulk for diameter below ~3 nm.Comment: 13 pages, 5 figures, Journa

Optical characterization of GaN by N+ implantation into GaAs at elevated temperature

Both hexagonal wurtzite and cubic zinc blend GaN phases were synthesized in GaAs by 50 keV N+ implantation at 400 deg C and subsequent annealing at 900 deg C for 15 min in N2 ambient. Crystallographic structural and Raman scattering studies revealed that GaN phases were grown for fluence above 2x1017 cm-2. Temperature-dependent photoluminescence study showed sharp direct band-to-band transition peak ~3.32 eV at temperature <= 200K. The intermediate bandgap value, with respect to ~3.4 eV for hexagonal and ~3.27 eV for cubic phases of GaN is an indicative for the formation of mixed hexagonal and cubic phases.Comment: 9 pages, 4 figuresn Journa

Theology of the Karaikkal Ammaiyar

Since the time man began to become intelligent, the spirit of God has been developing. Man is a man of the nature of keeping the mind sweet forever. It is the divine principle that helps people to raise. The first song of Karaikal Ammaiar, who had received the knowledge of truth, was the wonderful Thiruvanthathi. The wonderful thiruvanthathi is a novel trend. They are pleasant and simple to recite. The nature of the intellect of Knowledge is clear. He is the first to be the lord of the temple. The purpose of this article is to examine the theology of Karaikal Ammaia