The complex perovskite oxide a strontium gadolinium niobate (SGN) synthesized by solid-state reaction technique has single phase with tetragonal structure. X-ray diffraction (XRD) technique and scanning electron micro...The complex perovskite oxide a strontium gadolinium niobate (SGN) synthesized by solid-state reaction technique has single phase with tetragonal structure. X-ray diffraction (XRD) technique and scanning electron microscopy (SEM) were used to study the structural and microstructural properties of the ceramics, respectively. The XRD patterns of SGN at room temperature show a tetragonal structure. Studies of the dielectric constant and dielectric loss of compound as a function of frequency (50 Hz to 1 MHz) at room temperature, and as a function of temperature (60°C to 420°C) indicate polydispersive nature of the material. The logarithmic angular frequency dependence of the loss peak is found to obey the Arrhenius law with activation energy ~0.18 eV. The small value of activation energy of the compound (~0.18 eV) can be explained by mixed ionic-polaronic conductivity mechanism. The grain size of the pellet sample was found to be 1.92 μm. The frequency-dependant electrical data are analyzed in the framework of conductivity and electric modulus formalisms. The complex plane impedance plot shows the grain boundary contribution for higher value of dielectric constant in the law frequency region.展开更多
A complex structure of barium iron niobate, Ba(Fe0.5Nb0.5)O3 (BFN) and strontium titanate SrTiO3 (ST) was fabricated by a solid-state reaction method. The phase formation of Ba(Fe0.5Nb0.5)O3-SrTiO3 was checked using X...A complex structure of barium iron niobate, Ba(Fe0.5Nb0.5)O3 (BFN) and strontium titanate SrTiO3 (ST) was fabricated by a solid-state reaction method. The phase formation of Ba(Fe0.5Nb0.5)O3-SrTiO3 was checked using X-ray diffraction (XRD) technique. The X-ray structural analysis of BFN and BFN-ST ceramics, showed the formation of single-phase compound in the monoclinic system, which is a distorted structure of an ideal cubic perovskite. Careful examination of microstructures of the individual compounds of the system was done by the scanning electron micrograph (SEM), and confirms the polycrystalline nature of the systems. Detailed studies of dielectric and electrical impedance properties of the systems in a wide range of frequency (100Hz - 5MHz) and different temperatures (30°C-285°C) showed that these properties are strongly dependent on temperature and frequency.展开更多
Tephrosia purpurea(L.) Pers. is popularly known as ‘Sarapunkha' in classical Ayurvedic texts. It is a perennial plant belonging to the family Fabaceae, and occurs throughout the Indian subcontinent. T. purpurea i...Tephrosia purpurea(L.) Pers. is popularly known as ‘Sarapunkha' in classical Ayurvedic texts. It is a perennial plant belonging to the family Fabaceae, and occurs throughout the Indian subcontinent. T. purpurea is traditionally used to treat spleenomegaly, cirrhosis, cough and cold, abdominal swelling and as an antidote in the Ayurvedic system of medicine. Phytochemical investigations indicate the presence of semiglabrin, pongamole, lanceolatins A and B, rutin, lupeol, and β-sitosterol. Flavonoids including(+)-tephrorin A and B,(+)-tephrosone, an isoflavone, 7, 4'-dihydroxy-3', 5'-dimethoxyisoflavone and a chalcone,(+)-tephropurpurin were isolated from the whole plant. Pharmacological activities of different parts of the plant reported include anti-inflammatory, antiulcer, antimicrobial, antioxidant, antiallergic, antidiabetic, hepatoprotective, antitumor and insect repellent activity. In the present review, the literature on the phytochemical and pharmacological investigations of Tephrosia purpurea(L.) Pers. are summarized to August, 2012.展开更多
Ichnocarpus frutescens R. Br. (Apocynaceae), is a woody climbing shrub, found almost in all parts of India. In India, tribes used this plant as a substitute of Indian Sarsaparilla (Hemidesmus indicus) for the treatmen...Ichnocarpus frutescens R. Br. (Apocynaceae), is a woody climbing shrub, found almost in all parts of India. In India, tribes used this plant as a substitute of Indian Sarsaparilla (Hemidesmus indicus) for the treatment of atrophy, convulsions, cough, delirium, dysentery, measles, splenomegaly, tuberculosis, tumor, diabetes as a lactogogue, antipyretic, demulcent, diaphoretic and in skin diseases. Phytochemical investigations indicate that 28 compounds reported from the plant belong to various chemical category viz. phytosterol, triterpenes, flavonoids and various other phenolic compounds. Pharmacological activities of different parts of the plant reported include antiurolithiatic, hepatoprotective, antioxidant, analgesic, antipyretic, anti-inflammatory, antidiabetic, antihyperlipi-demic and antitumor activity. In the present review the literature data on the phytochemical and biological investigations on the I. frutescens are summarized up to March 2011.展开更多
文摘The complex perovskite oxide a strontium gadolinium niobate (SGN) synthesized by solid-state reaction technique has single phase with tetragonal structure. X-ray diffraction (XRD) technique and scanning electron microscopy (SEM) were used to study the structural and microstructural properties of the ceramics, respectively. The XRD patterns of SGN at room temperature show a tetragonal structure. Studies of the dielectric constant and dielectric loss of compound as a function of frequency (50 Hz to 1 MHz) at room temperature, and as a function of temperature (60°C to 420°C) indicate polydispersive nature of the material. The logarithmic angular frequency dependence of the loss peak is found to obey the Arrhenius law with activation energy ~0.18 eV. The small value of activation energy of the compound (~0.18 eV) can be explained by mixed ionic-polaronic conductivity mechanism. The grain size of the pellet sample was found to be 1.92 μm. The frequency-dependant electrical data are analyzed in the framework of conductivity and electric modulus formalisms. The complex plane impedance plot shows the grain boundary contribution for higher value of dielectric constant in the law frequency region.
文摘A complex structure of barium iron niobate, Ba(Fe0.5Nb0.5)O3 (BFN) and strontium titanate SrTiO3 (ST) was fabricated by a solid-state reaction method. The phase formation of Ba(Fe0.5Nb0.5)O3-SrTiO3 was checked using X-ray diffraction (XRD) technique. The X-ray structural analysis of BFN and BFN-ST ceramics, showed the formation of single-phase compound in the monoclinic system, which is a distorted structure of an ideal cubic perovskite. Careful examination of microstructures of the individual compounds of the system was done by the scanning electron micrograph (SEM), and confirms the polycrystalline nature of the systems. Detailed studies of dielectric and electrical impedance properties of the systems in a wide range of frequency (100Hz - 5MHz) and different temperatures (30°C-285°C) showed that these properties are strongly dependent on temperature and frequency.
文摘Tephrosia purpurea(L.) Pers. is popularly known as ‘Sarapunkha' in classical Ayurvedic texts. It is a perennial plant belonging to the family Fabaceae, and occurs throughout the Indian subcontinent. T. purpurea is traditionally used to treat spleenomegaly, cirrhosis, cough and cold, abdominal swelling and as an antidote in the Ayurvedic system of medicine. Phytochemical investigations indicate the presence of semiglabrin, pongamole, lanceolatins A and B, rutin, lupeol, and β-sitosterol. Flavonoids including(+)-tephrorin A and B,(+)-tephrosone, an isoflavone, 7, 4'-dihydroxy-3', 5'-dimethoxyisoflavone and a chalcone,(+)-tephropurpurin were isolated from the whole plant. Pharmacological activities of different parts of the plant reported include anti-inflammatory, antiulcer, antimicrobial, antioxidant, antiallergic, antidiabetic, hepatoprotective, antitumor and insect repellent activity. In the present review, the literature on the phytochemical and pharmacological investigations of Tephrosia purpurea(L.) Pers. are summarized to August, 2012.
文摘Ichnocarpus frutescens R. Br. (Apocynaceae), is a woody climbing shrub, found almost in all parts of India. In India, tribes used this plant as a substitute of Indian Sarsaparilla (Hemidesmus indicus) for the treatment of atrophy, convulsions, cough, delirium, dysentery, measles, splenomegaly, tuberculosis, tumor, diabetes as a lactogogue, antipyretic, demulcent, diaphoretic and in skin diseases. Phytochemical investigations indicate that 28 compounds reported from the plant belong to various chemical category viz. phytosterol, triterpenes, flavonoids and various other phenolic compounds. Pharmacological activities of different parts of the plant reported include antiurolithiatic, hepatoprotective, antioxidant, analgesic, antipyretic, anti-inflammatory, antidiabetic, antihyperlipi-demic and antitumor activity. In the present review the literature data on the phytochemical and biological investigations on the I. frutescens are summarized up to March 2011.
