North Eastern Hill University

About: North Eastern Hill University is a education organization based out in Shillong, Meghalaya, India. It is known for research contribution in the topics: Population & Ruthenium. The organization has 2318 authors who have published 4476 publications receiving 48894 citations.

Aggregation and adsorption properties of sodium dodecyl sulfate in water-acetamide mixtures.

Abstract: The critical micelle concentration (cmc) of sodium dodecyl sulfate was determined in water + acetamide media from 0 to 70 wt% of acetamide and at temperatures in the range from 20 to 40 °C by using conductance, surface tension, and fluorescence methods. The cmc increases with increase in acetamide concentration and the reported [M.S. Akhter, Colloids Surf. A 121 (1997) 103] decrease in cmc was not observed. The limiting surface tension at the cmc does not have any dependence on the amount of acetamide added. The cmc data as a function of temperature were used to estimate the free energy, enthalpy, and entropy terms for micellization. Enthalpy–entropy compensation takes place during micellization. Counterion binding constant, surface excess, and aggregation number of SDS decrease with increasing acetamide concentration and become almost constant for weight percentages of acetamide greater or equal to 30. Pyrene appears to move from the interior of the SDS micelle to the micellar interface at about 30 wt% acetamide. The empirical relations reported by Aguiar et al. [J. Aguiar, P. Carpena, J.A. Molina-Bolivar, C. Carnero Ruiz, J. Colloid Interface Sci. 258 (2003) 116] between the parameters of a sigmoid-type expression for the ratio of fluorescence emission intensities of pyrene and surfactant properties are found to be applicable to SDS in water + acetamide medium below 20 wt% acetamide only. Standard free energy of micellization has linear correlations with reciprocal of dielectric constant and Gordon parameter of the solvent. The water + acetamide medium behaves similar to mixed solvents containing water and any polar liquid nonaqueous solvent and this study highlights the significance of solvophobicity.

Colonization of roots of rice (Oryza sativa) by symbiotic Nostoc strains

Abstract: Summary • The lack of nitrogen in agriculture, and negative environmental effects of fertilizers, have stimulated interest in creating artificial associations between N2-fixing cyanobacteria and rice (Oryza sativa). • For the first time, numerous (57) Nostoc isolates from natural symbioses were screened for their ability to associate with rice. Successful colonizers were tested for N2-fixation by acetylene reduction, and for their ability to adsorb to roots by chlorophyll a measurements. Paranodules were induced by 2,4-dichlorophenoxyacetic acid. And genetic fingerprints of the cyanobacteria were obtained for identification. Ultrastructural investigations were made by light and scanning electron microscopy. • Twenty-one symbiotic Nostoc isolates associated with rice roots, colonizing surfaces and intercellular spaces. Adsorption was high and appeared biphasic. The rates of N2 fixation by associated cyanobacteria were higher compared with those in free-living cyanobacteria. Paranodules were formed and colonized, but root growth was adversely affected. • Under laboratory conditions, artificial associations were created between one-third of the screened symbiotic cyanobacteria and rice. The agricultural potential for the association appears high since the cyanobacteria adsorb tightly and fix more N2 than when free-living.

Effect of Acetate and Propionate Co-ions on the Micellization of Sodium Dodecyl Sulfate in Water

Abstract: Electrical conductivities of sodium dodecyl sulfate (SDS) in aqueous sodium acetate (NaAc) and sodium propionate (NaPr) solutions of different concentrations were measured at 25 °C. An anomalous behavior in the form of minima in the plots of critical micelle concentration (cmc) of SDS versus concentration of NaAc and NaPr was observed, thereby indicating the effect of acetate and propionate co-ions on micellization. The conductivity data were analyzed using a conductivity equation derived on the basis of a mixed-electrolyte model for surfactant solutions wherein ion−ion interactions were accounted for by the Debye−Huckel−Onsager equation. Such an analysis provided a method to estimate the values of cmc, counterion binding constant, and aggregation number directly from conductivity data. It was observed that ionic micelles contribute to electrical conductivity but not to ionic strength of surfactant solution. The surface potentials of SDS micelles in NaAc and NaPr solutions were computed by solving the Poi...

Austro-Asiatic tribes of Northeast India provide hitherto missing genetic link between South and Southeast Asia.

Abstract: Northeast India, the only region which currently forms a land bridge between the Indian subcontinent and Southeast Asia, has been proposed as an important corridor for the initial peopling of East Asia. Given that the Austro-Asiatic linguistic family is considered to be the oldest and spoken by certain tribes in India, Northeast India and entire Southeast Asia, we expect that populations of this family from Northeast India should provide the signatures of genetic link between Indian and Southeast Asian populations. In order to test this hypothesis, we analyzed mtDNA and Y-Chromosome SNP and STR data of the eight groups of the Austro-Asiatic Khasi from Northeast India and the neighboring Garo and compared with that of other relevant Asian populations. The results suggest that the Austro-Asiatic Khasi tribes of Northeast India represent a genetic continuity between the populations of South and Southeast Asia, thereby advocating that northeast India could have been a major corridor for the movement of populations from India to East/Southeast Asia.