Search Results

You are looking at 1 - 10 of 89 items for

  • Author or Editor: P. Singh x
Clear All Modify Search

Abstract  

The thermodynamic behaviour of bulk metallic glass (BMG) forming melts have been studied by analyzing the temperature dependence of the Gibbs free energy difference (∆G), entropy difference (∆S) and enthalpy difference (∆H)between the undercooled melt and the corresponding equilibrium solid phases. The study is made by calculating∆G, ∆S and ∆H in the entire temperature range T m (melting temperature) to T g (glass transition temperature) using the expressions obtained on the basis of Taylor’s series expansion. The entire analysis is made for La-based five samples of BMGs; La55Al25Ni20, La55Al25Ni15Cu5, La55Al25Ni10Cu10, La55Al25Ni5Cu15, and La55Al25Ni5Cu10Co5 and a comparative study is also performed between present results and results obtained in the framework of expressions proposed by earlier workers. An attempt has also been made to study the glass forming ability for BMGs.

Restricted access

Abstract  

Extraction of U(VI), Zr(IV) and Th(IV) has been investigated from perchlorate media using 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC-88A) dissolved in toluene. The extraction of U(VI), Zr(IV) and Th(IV) was found to be quantitative in the pH range 1.6 to 3.2, 2.0 to 4.7 and 2.3 to 3.8, respectively, with 3.0.10-3, 5.6.10-4 and 1.0.10-2M PC-88A dissolved in toluene. U(VI) was stripped with 4.0M HCl, Zr(IV) with 2.5M NaF and Th(IV) with 8.0M HCl from the metal loaded organic phase containing PC-88A dissolved in toluene. The probable extracted species have been ascertained by plotting log D vs. log [HR] as UO2R2 .2HR, ZrR4 .2HR and ThR4 .4HR, respectively. U(VI) was separated from Zr(IV) and Th(IV) and from other associated metals. This method was proved by the determination of U(VI) in some real samples.

Restricted access

Abstract  

A number of samples of sodium phosphate glasses doped with Cd/Co or Ag chlorides were prepared and characterized by X-ray diffraction, IR spectral, ion transport and DSC studies. It was found from DSC studies that the glass transition temperature (T g) and crystallization temperature (T c) values increased with the increasing concentrations of the dopants Cd or Co chlorides. However, the T g and T c values were found to decrease when the AgCl was taken as the dopant and the following sequence is observed: T g(CoCl2)>T g(CdCl2)>T g(AgCl); T c(CoCl2)>T c(CdCl2)>T c(AgCl) These results have been discussed and explained on the basis of changes in the structure of sodium phosphate glassy matrix by the addition of different cations as dopants.

Restricted access

The role of blue green algal (BGA) biofertilizers has been limited to its relevance and utilization in rice crops, and scanty information is available on their use in conjunction with organic amendments and their influence on wheat (Triticum aestivum) . An experiment was conducted from November 2003 to April 2004 in the fields of the Indian Agricultural Research Institute (IARI), New Delhi, India to evaluate the effect of vermicompost, farmyard manure and biofertilizers (BGA and Azotobacter ) in different combinations with chemical fertilizers (N 40 P 30 K 30 ) in wheat (var. HD 2687). Selected soil biological parameters (cyanobacterial diversity/abundance, nitrogenase activity and the phototrophic biomass of soil cores) were measured. The application of vermicompost in combination with BGA biofertilizer (B+V+N 40 P 30 K 30 ) brought about a significant increase in nitrogenase activity (from 0.1 in N 80 P 30 K 30 to 2.0 nmoles mg chl −1 h −1 ), while Azotobacter + BGA (+N 40 P 30 K 30 ) treatment gave the highest values of chlorophyll (1.19 μg g −1 soil). The addition of vermicompost and farmyard manure (+N 40 P 30 K 30 ) enhanced cyanobacterial abundance, and cyanobacterial genera such as Nostoc, Anabaena, Calothrix, Oscillatoria and Phormidium were the dominant forms observed under the wheat crop. The synergistic effect of organic amendments, biofertilizers and chemical fertilizers, especially BGA inoculants, advocates their utilization in wheat crops to improve soil fertility.

Restricted access

A new lichenicolous fungus Buelliella indica colonising on the thallus of Graphis longiramea is described from the state of Nagaland, a part of the Indo-Burma biodiversity hotspot region in India. It is characterised by its brown epihymenium, much smaller ascospores with dimensions of 11.5–13.8 × 4.8–6 µm and the new host Graphis.

Restricted access

Floral anatomy of Actinomeris squarrosaand Bidens biternatahave been described. The presence of pappus is an important structural feature of the Asteraceae. It has been considered by some as phyllome and by others a trichome structure. The presence of vascular supply to the pappus scales shows that it is a phyllome structure. Once the pappus is considered as a phyllome structure, two major lines of specialization can be established in this family from a primitive type of five vascular scales. In ome line of evolution there has been increase in the number of pappus from five to twenty and finally indefinite in number and the vascular supply is totally suppressed. In another line of evolution there has been a reduction in the number of pappus scales from five to two and finally total reduction of the scales. The disc-florets of Bidens biternataare pentamerous but occasionally tetramerous florets are also observed. In Actinomeris squarrosa disc-florets are tetramerous florets are derived from pentamerous floret by complete fusion of the two anterior alternipetalous strands is discussed. In the Asteraceae, the pistillate ray florets are derived from disc florets by formation of a deep sinus in the corolla on the posterior side, followed by gradual suppression of the androecium. The neutral ray-florets are derived from ray-florets by complete reduction of an ovule, loculus and style along with its vascular supply is also discussed.

Restricted access
Authors: B. P. Mishra and D. Singh
Restricted access

This study was carried out to compare composition, density and diversity of species between dryland and irrigated agroecosystems and between agroecosystems and the marginal grassland ecosystem in dry tropics. Main management characteristics of these ecosystems are: (1) Dryland cropping, low fertilizer input, rainfed (no irrigation) and seed sown rice; (2) Irrigated cropping, high fertilizer, water (irrigation) inputs, flooded rice by transplanting; (3) Grassland, post-rainy season herbage removal and light grazing. All ecosystems showed comparable number (12-14) of species in winter, but in the rainy season higher number of species (21) were recorded in the grassland ecosystem. The species composition of the grassland was entirely different from both agroecosystems (similarity <1%). Dryland and irrigated agroecosystems showed only 25% and 38% similarity with each other during winter and rainy cropping seasons, respectively. Occurrence of few grasses (e.g., Cynodon dactylon, Dichanthium annulatum and Sporobolus diander) in the agroecosystems depends on the propagules dispersed from the marginal grassland. The change from dryland to irrigated agroecosystem involved elimination of 4-5 species during both cropping seasons and simultaneous recruitment of 2 new species in winter and 6 species in rainy season. In both agroecosystems, forbs (C_ type) dominated over graminoids (C_ type) during winter season but the dominance was reversed during the warm, rainy season. During winter some forbs were abundant in both agroecosystems due to their tolerance to widely varying moisture conditions (e.g.,Chenopodium album), others were dominant in either drier soil conditions (e.g., Anagallis arvensis in dryland) or wet conditions (e.g., Melilotus indica and Phalaris minor in irrigated). Higher species diversity occurred in the grassland relative to both agroecosystems. The seasonal trends of species diversity and species evenness were broadly similar in both agroecosystems but irrigated agroecosystem exhibited relatively higher species diversity. The changes in species composition and species diversity in agroecosystems are mainly attributed to differences in water management. The water management in irrigated agroecosystem tends to reduce weed diversity but leads to the dominance of some potentially noxious weeds (e.g., Phalaris minor).

Restricted access

A new lichenicolous fungus Melaspilea nitidochapsae colonising on the thallus of Nitidochapsa leprieurii (Mont.) Parnmen, Lücking et Lumbsch is described from India. The new species differs from other known species colonising lichen family Graphidaceae by having completely carbonised exciple, hyaline to pale brown transversely 1-septate ascospores and a different host.

Restricted access

The present report is in continuation to our earlier reports on the identification and fine mapping of three aroma QTLs in basmati rice using a bi-parental mapping population derived from a cross between Pusa 1121, a basmati rice variety, and Pusa 1342, a non-aromatic rice variety. We used a combination of genetic mapping and transcriptome profiling to narrow down the number of differentially expressed genes in rice to identify potential candidate genes for rice grain aroma. Highly aromatic and non-aromatic recombinant inbred lines (RILs) were identified through sensory analysis of mature milled grains. RILs with similar phenotypes were bulked together using bulk segregant analysis approach which drastically reduced the number of differentially expressed genes from 4016 to 1344. The transcriptome profiles generated were analyzed through Affymetrix rice genome array containing probe sets designed from all the predicted rice gene sequences. Microarray-based transcriptome profiling revealed one down-regulated gene co-located in QTL region aro3.1 on chromosome 3, eight genes co-located in the aro4.1 region on chromosome 4 and the badh2 gene on chromosome 8 to be differentially expressed in the aromatic parent and aromatic bulk. These genes are the most suitable candidates for future validation and development of new molecular functional markers to facilitate marker assisted breeding.

Restricted access