Pressure dependent electronic properties of MgO polymorphs: A first-principles study of Compton profiles and autocorrelation functions

The first-principles periodic linear combination of atomic orbitals method within the framework of density functional theory implemented in the CRYSTAL06 code has been applied to explore effect of pressure on the Compton profiles and autocorrelation functions of MgO. Calculations are performed for the B1, B2, B3, B4, B8_1 and h-MgO polymorphs of MgO to compute lattice constants and bulk moduli. The isothermal enthalpy calculations predict that B4 to B8_1, h-MgO to B8_1, B3 to B2, B4 to B2 and h-MgO to B2 transitions take place at 2, 9, 37, 42 and 64 GPa respectively. The high pressure transitions B8_1 to B2 and B1 to B2 are found to occur at 340 and 410 GPa respectively. The pressure dependent changes are observed largely in the valence electrons Compton profiles whereas core profiles are almost independent of the pressure in all MgO polymorphs. Increase in pressure results in broadening of the valence Compton profiles. The principal maxima in the second derivative of Compton profiles shifts towards high momentum side in all structures. Reorganization of momentum density in the B1 to B2 structural phase transition is seen in the first and second derivatives before and after the transition pressure. Features of the autocorrelation functions shift towards lower r side with increment in pressure.Comment: 19 pages, 8 figures, accepted for publication in Journal of Materials Scienc

Modulation of enhancer looping and differential gene targeting by Epstein-Barr virus transcription factors directs cellular reprogramming

Epstein-Barr virus (EBV) epigenetically reprogrammes B-lymphocytes to drive immortalization and facilitate viral persistence. Host-cell transcription is perturbed principally through the actions of EBV EBNA 2, 3A, 3B and 3C, with cellular genes deregulated by specific combinations of these EBNAs through unknown mechanisms. Comparing human genome binding by these viral transcription factors, we discovered that 25% of binding sites were shared by EBNA 2 and the EBNA 3s and were located predominantly in enhancers. Moreover, 80% of potential EBNA 3A, 3B or 3C target genes were also targeted by EBNA 2, implicating extensive interplay between EBNA 2 and 3 proteins in cellular reprogramming. Investigating shared enhancer sites neighbouring two new targets (WEE1 and CTBP2) we discovered that EBNA 3 proteins repress transcription by modulating enhancer-promoter loop formation to establish repressive chromatin hubs or prevent assembly of active hubs. Re-ChIP analysis revealed that EBNA 2 and 3 proteins do not bind simultaneously at shared sites but compete for binding thereby modulating enhancer-promoter interactions. At an EBNA 3-only intergenic enhancer site between ADAM28 and ADAMDEC1 EBNA 3C was also able to independently direct epigenetic repression of both genes through enhancer-promoter looping. Significantly, studying shared or unique EBNA 3 binding sites at WEE1, CTBP2, ITGAL (LFA-1 alpha chain), BCL2L11 (Bim) and the ADAMs, we also discovered that different sets of EBNA 3 proteins bind regulatory elements in a gene and cell-type specific manner. Binding profiles correlated with the effects of individual EBNA 3 proteins on the expression of these genes, providing a molecular basis for the targeting of different sets of cellular genes by the EBNA 3s. Our results therefore highlight the influence of the genomic and cellular context in determining the specificity of gene deregulation by EBV and provide a paradigm for host-cell reprogramming through modulation of enhancer-promoter interactions by viral transcription factors

PHOTOCATALYTICDEGRADATION OF RHODAMIN-B USING METAL COMPLEXES AND HYDROGEN PEROXIDE

ABSTRACT The photocatalytic degradation has been considered to be an efficient process for degradation of organic pollutants, which are present in the effluents released by industries. Thephotocatalytic bleaching was carried out on rhodamin-B (cationic dye) in the presence of iron (III) complex, hydrogen peroxide and was observed spectrophotometrically. The effect of various operating variables like pH, concentration of complex and dye, amount of HzOzand light intensity etc. was also observed on the efficiency of the reaction. A tentative mechanism has also been proposed for this photocatalytic degradation of rhodamin-B. Keywords: Photocatalytic degradation, rhodamin-B, metal complexes, hydrogen peroxide

Elastic properties and zone centre frequencies of Cu2O by LCAO method

918-922The elastic properties and the phonon frequencies at the Brillouin zone centre have been investigated for the cubic cuprous oxide. The calculations under the framework of density functional theory have been carried out by deploying the periodic linear combination of atomic orbitals method. After settling the crystal structure the elastic constants have been determined. The absolute values of elastic constants are well in agreement with the experimental reports. The vibrational frequencies at the centre of the Brillouin zone are classified as the Raman and Infrared active modes and compared with the available experimental data. The contribution of vibrational modes to the Gibbs free energy, entropy and heat capacity has also been found

Effect of speech coders on speech recognition performance

Speech coders with bitrates as low as 2.4 kbits/s are now being de-veloped for speech transmission in the telecommunications industry. For speech coders to work at this reduced bitrate, some speech infor-mation has to be removed and it is only natural to expect that the per-formance of speechrecognition systems will deteriorate when coded speech is applied as input to a recognition system. In this paper, the results of a study to examine the effects speech coders have on speech recogntion are presented. Six different speech coders rang-ing from 4.8 kbits/s to 40 kbits/s are used with two different speech recognition systems 1) isolated word recogntion and 2) phoneme recogntion from continuous speech. The effects on speech recog-nition performance by tandeming each of the speech coders are also presented. 1

Improved functionalization of oleic acid-coated iron oxide nanoparticles for biomedical applications

Superparamagnetic iron oxide nanoparticles can providemultiple benefits for biomedical applications in aqueous environments such asmagnetic separation or magnetic resonance imaging. To increase the colloidal stability and allow subsequent reactions, the introduction of hydrophilic functional groups onto the particles’ surface is essential. During this process, the original coating is exchanged by preferably covalently bonded ligands such as trialkoxysilanes. The duration of the silane exchange reaction, which commonly takes more than 24 h, is an important drawback for this approach. In this paper, we present a novel method, which introduces ultrasonication as an energy source to dramatically accelerate this process, resulting in high-quality waterdispersible nanoparticles around 10 nmin size. To prove the generic character, different functional groups were introduced on the surface including polyethylene glycol chains, carboxylic acid, amine, and thiol groups. Their colloidal stability in various aqueous buffer solutions as well as human plasma and serum was investigated to allow implementation in biomedical and sensing applications.status: publishe

Potential of genomics for the improvement of underutilized legumes in sub-Saharan Africa

Open Access Journal; Published online: 03 Jan 2021Underutilized, or orphan legumes, are widely distributed across farming landscapes in sub-Saharan Africa (SSA) but often have low yields and do not fulfill their potential due to very limited research, breeding, development, marketing, and awareness of their benefits. These advantages include nutritional quality and climate resilience. In this review, we focus on Bambara groundnut, African yam bean, and Kersting's groundnut. Knowledge of the challenges and rewards of exploiting them will provide opportunities for concerted approaches to their revival and contribution to future global food systems, especially in the context of climate change. This review identifies the institutional and noninstitutional challenges, the constraints, the prospects, and the rewards that can be derived from exploiting orphan legumes in SSA. The genetic resources center (GRC) of the International Institute of Tropical Agriculture (IITA) conserves a diverse collection of about 2500 accessions of these crops with the majority from Africa. In this review, we focus on the ex situ conservation of the genetic resources of these indigenous African legume crops, their characterization and evaluation, prospects for the development of improved cultivars, and the role they could play, particularly with respect to nutrition and adaptation to climate change. We emphasize progress made in recent years concerning the assembly of information required for application of genomics tools to these crops and how this will underpin the development of improved varieties

Ubv CCD Standards Near 5C1 Radio Sources at Intermediate Galactic Latitude-I

We have been doing a photometric and astrometric sample survey programme on Schmidt plates in a few selected directions in the Galaxy with an aim to study galactic stellar populations. In order to calibrate Schmidt plates photometrically, it is necessary to have a number of photometric standards which cover the entire range of magnitudes to be studied on the plates. As Schmidt plates cover a wide area of the sky, the standards should also be spread over the surface of the plate so as to minimise geometrical effects present on the plate. This paper is first in a series of papers aimed at to provide photometric standards in the selected galactic directions to be studied. In this paper we present photometric magnitudes obtained through CCD observation in the galactic direction (l=170deg, b=45deg) centered at alpha(2000) = 9h 41m 20s and delta(2000) = +49deg 54' 20'' and covering an area of 14 sq degs. B and V magnitudes have been obtained for a total of 214 stars out of which for 73 stars U magnitudes also have been obtained. The magnitude range covered is 11<V<21 and 0.18<B-V<1.85.Comment: Postscript file, 13 pages, 1 figure (figure available on request), paper accepted for publication in the Bulletin of Astronomical Society of Indi