Discrimination of Acacia seeds at species and subspecies levels using an image analyzer

Seeds of Acacia species and subspecies were characterized using an image analyzer and discriminated for the purpose of identification of species, using their seeds. The species considered in the study were Acacia nilotica subsp. indica, A. nilotica subsp. cupressiformis, A. nilotica subsp. tomentosa, A. tortilis subsp. raddiana, A. tortilis subsp. spirocarpa, A. raddiana, A. senegal, A. auriculiformis, A. farnesiana, A. leucophloea, A. mearnsii, A. melanoxylon, A. planifrons and A. mangium. Eight samples each consisting of 25 seeds per species were studied using the image analyzer for physical characteristics of seeds, such as 2D surface area, length, width, perimeter, roundness, aspect ratio and fullness ratio. Discriminant analysis showed that acacias can be discriminated at species and subspecies levels, with 96% accuracy. Exceptions were A. nilotica subsp. tomentosa(75.0%), A. tortilis subsp. spirocarpa(75.0%) and A. raddiana(87.5%) which had relatively low discrimination accuracy. However, discriminant analysis within selected species showed complete recognition of these species except for A. tortilis subsp. spirocarpa, that had still a large overlap with A. leucophloea. The study also revealed that both seed size and shape characteristics were responsible for species discrimination. It can be concluded that rapid analysis of seed size and shape characteristics using image analysis techniques can be used as primary and secondary keys for identification of acacias.

Ground-Based In Situ Measurements of Near-Surface Aerosol Mass Concentration over Anantapur:Heterogeneity in Source Impacts

Surface measurements of aerosol physical properties were made at Anantapur （14.62°N, 77.65°E, 331 m a.s.l）, a semiarid rural site in India, during August 2008-July 2009. Measurements included the segregated sizes of aerosolsas as well as total mass concentration and size distributions of aerosols measured at low relative humidity （RH〈75%） using a Quartz Crystal Microbalance （QCM） in the 25-0.05 um aerodynamic diameter range. The hourly average total surface aerosol mass concentration in a day varied from 15 to 70 ug m-3, with a mean value of 34.02±9.05 ug m-3 for the entire study period. A clear diurnal pattern appeared in coarse, accumulation and nucleation-mode particle concentrations, with two local maxima occurring in early morning and late evening hours. The concentration of coarse-mode particles was high during the summer season, with a maximum concentration of 11.81±0.98 ug m-3 in the month of April, whereas accumulationmode concentration was observed to be high in the winter period contributed 〉68% to the total aerosol mass concentration. Accumulation aerosol mass fraction, Af （= Ma/Mt） was highest during winter （mean value of Af -0.80） and lowest （Af - 0.64） during the monsoon season. The regression analysis shows that both Reff and Rm are dependent on coarse-mode aerosols. The relationship between the simultaneous measurements of daily mean aerosol optical depth at 500 nm （AOD500） and PM2.5 mass concentration （[PM2.5]） shows that surface-level aerosol mass concentration increases with the increase in columnar aerosol optical depth over the observation period.

Role of monovalent co-dopants on the PL emission properties of YAl_3(BO_3)_4:Ce^(3+) phosphor

The cerium （Ce3＋） doped yttrium aluminium borate （YAB） phosphor was synthesized by modified solid state reaction. The phosphor＇s phase purity and its emission properties were studied using powder X-ray diffraction pattern and photoluminescence spectroscopy. The synthesized YAB had rhomobohedral crystal structure. The phosphor had two different excitation and emission spectra. By 325 nm excitation, the phosphor had emission at 373 nm and with 363 nm excitation; the phosphor gave violet-blue emission at 418 nm. The UV emission of the phosphor originated due to Ce3＋ ions at the yttrium site and violet-blue emission owing to Ce3＋ ions at non-regular sites viz., A13＋ and interstitial sites. The emission intensity of the phosphor was enhanced when monovalent ions （K＋, Na＋, and F） were added as co-dopants. The crucial role of ionic radii of monovalent co-dopants on the emission enhancement of the YAB：Ce3＋ phosphor was reported. Thermogravimetric study showed that the YAB possessed high thermal stability at up to 900 ℃.

Photoluminescence properties of a novel orange-red emitting Ba_2CaZn_2Si_6O_(17):Sm^(3+)phosphor

Novel orange-red emitting Ba_2Ca_（1–x）Zn_2Si_6O_（17）：x Sm^（3＋）（0.02≤x≤0.08） phosphors were synthesized using conventional solid-state reaction method under air atmosphere. The phase formation of the samples was characterized by powder X-ray diffraction patterns. Scanning electron microscopy（SEM） and photoluminescence properties were also investigated. The narrow excitation and emission spectra indicated the typical 4f-4f transitions of Sm^（3＋）. The dominant excitation line was around 405 nm attributed to ~6H_（5/2）→ ~4F_（7/2） and the emission spectrum consisted of four emission peaks at 562, 600, 647, and 708 nm corresponding to the various transitions ~4G_（5/2） to ~6HJ（J=5/2, 7/2, 9/2 and 11/2） of the Sm^（3＋） ions in the same order. The strongest emission band located at 600 nm was attributed to ~4G_（5/2）→~6H_（7/2） transition of Sm^（3＋）, producing bright orange-red color emission. The optimal dopant concentration of Sm3＋ ion in Ba_2CaZn_2Si_6O_（17）：x Sm^（3＋） phosphor was around 4 mol.% and the critical transfer distance（Rc） of Sm^（3＋） was calculated to be 2.65 nm. Decay time varied with the Sm^（3＋） concentrations in Ba_2 CaZn_2Si_6O_（17） phosphors. In addition, the Commission International del＇Eclairagethe（CIE） chromaticity coordinates of Ba_2Ca_（0.96）Zn_2Si_6O_（17）：0.04Sm^（3＋） phosphor was located in the orange-red region（0.547, 0.450） and the correlated color temperature（CCT） was 2543 K. The present results indicated that Sm^（3＋） activated Ba_2CaZn_2Si_6O_（17） phosphors may be used as an orange-red emitting phosphor for near-ultraviolet（n-UV） based white light emitting diodes（WLEDs） applications.