Botany, chemistry, and pharmaceutical significance of Sida cordifolia: a traditional medicinal plant

Sida cordifolia Linn. belonging to the family, Malvaceae has been widely employed in traditional medications in many parts of the world including India, Brazil, and other Asian and African countries. The plant is extensively used in the Ayurvedic medicine preparation. There are more than 200 plant species within the genus Sida, which are distributed predominantly in the tropical regions. The correct taxonomic identification is a major concern due to the fact that S. cordifolia looks morphologically similar with its related species. It possesses activity against various human ailments, including cancer, asthma, cough, diarrhea, malaria, gonorrhea, tuberculosis, obesity, ulcer, Parkinson’s disease, urinary infections, and many others. The medical importance of this plant is mainly correlated to the occurrence of diverse biologically active phytochemical compounds such as alkaloids, flavonoids, and steroids. The major compounds include β-phenylamines, 2-carboxylated tryptamines, quinazoline, quinoline, indole, ephedrine, vasicinone, 5-3-isoprenyl flavone, 5,7-dihydroxy-3-isoprenyl flavone, and 6-(isoprenyl)- 3-methoxy- 8-C-β-D-glucosyl-kaempferol 3-O-β-D-glucosyl[1–4]-α-D-glucoside. The literature survey reveals that most of the pharmacological investigations on S. cordifolia are limited to crude plant extracts and few isolated pure compounds. Therefore, there is a need to evaluate many other unexplored bioactive phytoconstituents with evidences so as to justify the traditional usages of S. cordifolia. Furthermore, detailed studies on the action of mechanisms of these isolated compounds supported by clinical research are necessary for validating their application in contemporary medicines. The aim of the present chapter is to provide a detailed information on the ethnobotanical, phytochemical, and pharmacological aspects of S. cordifolia

Synthesis and sintering of SiC under high pressure and high temperature

Starting from elemental powders, simultaneous synthesis and compaction of SiC were conducted at 3 GPa pressure and temperatures in the range 2100-2900 K. The sintered compacts were characterized by XRD, microhardness measurements, and microscopic studies. The efficiency of formation of SiC was dependent on the particle size of the silicon powder, crystallinity of the reactant carbon, molar ratio of silicon and carbon, and synthesis temperature and time. Carbon in excess of the stoichiometric amount was required to obtain compacts free from residual silicon. The SiC samples, with a Si:C molar ratio 1:1.05, prepared at 2100 K for 300 s, had a density and hardness of 3.21 g/cu cm (98.8 percent of theoretical density) and 22 GPa, respectively. The crystal structure of the SiC depended on the synthesis temperature. Pure beta-SiC in the temperature range 2100-2500 K, and a mixture of alpha- and beta-SiC above 2500 K were obtained. The beta-SiC was highly crystalline and nearly defect-free

High pressure-High temperature processing and performance of wBN-cBN composite tools

The wurtzite phase of boron nitride(wBN)is obtained in large quantities by shock loading graphitic boron nitride(gBN).The sintering of wBN powder at high pressure and temperatures leads to the conversion of wBN to the cubic boron nitride phase(cBN).Compacts with varying amounts of cBN CAN be obtained by controlling the pressure, temperature and time.The wBN-cBN composites with 45-55 % cBN have hardness in the range 30-70 GPa fracture toughness 13-16 MPa m and thermal conductivity 40-50 W m-1 K-1.The composite has a hot hardness of about 20 GPa at 1400 K. The unique combination of high hardness and fracture toughness makes the composite tool capable of machining under interupted conditions.The processing of wBN for cutting tool applications,the characterization of the tools and the performance of the composite tools in the machining of hardened steels(HRC 40-63),high nickel cast iron(BHN 120-160)and Ti-6A1-4V alloy(HV 310)are presented in this pape

A Preliminary report on the field trials and market survey of composite tools based on boron nitride

Field trials and market survey have been conducted to explore the application of composite tools (based on wurtzite boron nitride) in Indian industries. The industries covered were in and around Bangalore. The result indicates that there is a potential market for composite tools in India. A report in this regard is presented in this document

Machining Ti -6AI-4V alloy with a wBN-cBN composite tool

Titanium-based alloys are difficult-to-cut materials. The conventional tool materials (HSS and cemented carbides) fail due to the high chemical affinity of titanium and high temperatures generated while machining. An attempt has been made in this work to machine Ti-6AI-4V alloy with wurtzite boron nitride (wBN) based cutting tools. The mechanisms controlling the wear of the cutting tool have been found to be similar to those observed in poly crystalline diamond (PCD) and polycrystalline cubic boron nitride (PCBN) tools. The results indicate that the wBN-cBN composite tools can be used economically to machine titanium alloys