GREEN SYNTHESIS AND CHARACTERIZATION OF SILVER NANO PARTICLES BY USING PSIDIUM GUAJAVA LEAF EXTRACT

In this study, rapid, simple approach was applied for synthesis of silver nanoparticles by using Psidium guajava aqueous leaf extract. The plant extract acts as both reducing agent and capping agent. The green synthesized silver nanoparticles were characterized by using physic-chemical techniques viz, UV-Visible spectroscopy, Fourier Transform Infrared Spectrophotometer [FTIR], Particle size analyser and Scanning electron microscopy. UV-Visible spectrophotometer showed absorbance peak in the range of 419nm.The compounds responsible for silver ions and the functional groups present in plant extract were identified and investigated by FTIR technique. The characterization data reveals that the particles were in crystalline in nature with an average size of 62nm. The silver nanoparticles (Ag NPs) were rapidly synthesized using aqueous extract of guava leaf with AgNO3 solution within 15min at room temperature, without the involvement of any hazardous chemicals. Keywords: Nano particles, green synthesis, Silver,  Psidium guajava and reducing agents

A simple methodology for the synthesis of 3,4-dihydroisocoumarins

In our studies' on the total synthesis of fredericamycin A, an antitumour antibiotic, it was desirable for us to have 1-hydroxyisochroman for building a model spiro-(4,4)-nonane system present in fredericamycin A. The most convenient approach to synthesize 1-hydroxyisochromans is by a suitable hydride reduction of the corresponding 3,4-dihydro-isocoumarins. However, most of the literature methods described for the synthesis of 3,4-dihydron L isocoumarins are quite lengthy and tedious. We describe, herein, a simple and convenient approach for the synttesis of substituted dihydroisocoumarins. This method is of general utility

Investigations of separated flow over backward facing steps in IISc hypersonic shock tunnel

Two backward facing step (2 mm and 3 mm step height) models are selected for surface heat transfer measurements. The platinum thin film gauges are deposited on the Macor inserts using both hand paint and vacuum sputtering technique. Using the Eckert reference temperature method the heating rates has been theoretically calculated along the flat plate portion of the model and the theoretical estimates are compared with experimentally determined surface heat transfer rate. Theoretical analysis of heat flux distribution down stream of the backward facing step model has been carried out using Gai’s non-dimensional analysis. Based on the measured surface heating rates on the backward facing step, the reattachment distance is estimated for 2 and 3 mm step height at nominal Mach number of 7.6. It has been found from the present study that for 2 and 3 mm step height, it approximately takes about 10 and 8 step heights downstream of the model respectively for the flow to re-attach

Measurement of Heat Transfer Rate on Backward-Facing Steps at Hypersonic Mach Number

Two backward-facing models with step heights of 2 and 3 mm are used to measure the convective surface heat transfer rates by using platinum thin-film gauges, deposited on Macor inserts. Heat transfer rates have been theoretically calculated along the flat plate portion of a model using the Eckert reference temperature method. The experimentally determined surface heat transfer rate distributions are compared with theoretical and numerical estimations. Experimental heat flux distribution over a flat plate model showed good agreement with the reference temperature method at stagnation enthalpy range of 0.8-2 MJ/kg. Theoretical analysis has been used for downstream of a backward-facing step using Gai's nondimensional analysis. It has been found from the present study that approximately 10 and 8 step heights are required for the flow to reattach for 2 and 3 mm step height backward-facing step models, respectively, at a nominal Mach number of 7.6

Prevalence and risk-factors of early childhood caries among 2–6-year-old Anganwadi children in Nellore district, Andhra Pradesh, India: A cross-sectional survey

Purpose/Objectives: The objective of this study is to study the prevalence and associated risk determinants of early childhood caries (ECC) among preschool children. Materials and Methods: A cross-sectional descriptive study was designed to assess the ECC prevalence and associated risk factors among preschool children in Anganwadi of Nellore district using a standardized questionnaire. Results: A total of 550 study participants of age 2–6 years are enrolled in this cross-sectional study. Mean age of the participants was 4.39 ± 0.89 years. Most of the study participants (38%) were in the age of 5 years. When gender wise comparison was made girls represented 62% and boys 38% of the total population. When the risk factors were assessed for their association with caries experience, socioeconomic status, mother's schooling at child's birth, duration of using bottle, and bottle feeding while sleeping and plaque scores showed significant association with caries experience. Conclusion: ECC was more prevalent among 5-year-old children as compared to other age groups and moreover demographic factors such as mother's occupation, education, socioeconomic status, developmental characteristics such as enamel hypoplasia, feeding habits like prolonged and nocturnal bottle feeding and clinical parameters like plaque scores showed significant correlation with ECC

Regiospecific synthesis of 9-ethoxy-4,5,6,8-tetramethoxy-1,3-dihydro-naphtho-(2,3-C̲)furan-1-one: a key synthon of fredericamycin A

An efficient and regiospecific synthesis of ABC ring synthon of fredericamycin A has been described