50175 research outputs found
Sort by
Industrial applications of X-Ray Photoelectron Spectroscopy (XPS) in India
No full textThis review paper summarizes the industrial applications of XPS in India from open literature. Many industrial research and development centers in India, except for a few, do not have in-house XPS systems, and leverage either the instruments available at many government laboratories or universities across various locations in India, or their in-house instruments in other parts of the world for their research activities. While XPS is being used for a wide range of applications, based on an exhaustive literature search by the author, an understanding of the scientific basis of the technique as well as related analytical techniques such as X-ray Excited Auger Electron Spectroscopy (XAES) and depth profiling, the instrumentation, the measurement, and interpretation of the results could be improved. This could potentially avoid artifacts as well as misinterpretation of results. This paper also highlights a few key points that must be considered while measuring and interpreting XPS data
Evidence for Hidden Involvement of N3-Protonated Guanine in RNA Structure and Function
No full textCharged nucleobases have been found to occur in several known RNA molecules and are considered essential for their structure and function. The mechanism of their involvement is however not yet fully understood. Revelation of the role of N7-protonated guanine, in modulating the geometry and stability of noncanonical base pairs formed through its unprotonated edges Watson-Crick (WC) and sugar], has triggered the need to evaluate the feasibility of similar roles of other protonated nucleobases Halder et al., Phys Chem Chem Phys, 2015, 17, 26249]. In this context, N3 protonation of guanine makes an interesting case as its influence on the charge distribution of the WC edge is similar to that of N7 protonation, though its thermodynamic cost of protonation is significantly higher. In this work, we have carried out structural bioinformatics analyses and quantum mechanics-based calculations to show that N3 protonation of guanine may take place in a cellular environment, at least in the G:C W:W Trans and G:G W:H Cis base pairs. Our results provide a reasonable starting point for future investigations in order to address the larger mechanistic question
Processing-Mediated Different States of Dispersion of Multiwalled Carbon Nanotubes in PDMS Nanocomposites Influence EMI Shielding Performance
No full textAdvancement in wireless technology has increased the usage of wireless devices extensively in the past few years, which led to an increase in electromagnetic interference (EMI) in the environment. Extensive research on fabrication of EMI shielding materials has been done. However, the role of processing method of polymer composites in EMI shielding has been neglected. In this work, we investigate the role of two polymer processing methods, spin coating and compression molding, in EMI shielding application. Poly(dimethylsiloxane) (PDMS) nanocomposites with multiwalled carbon nanotube (MWCNT) were spin-coated onto glass slides and compression-molded to a similar thickness. The processing method that exhibited the best shielding was employed to fabricate multiple PDMS composites comprising different compositions of MWCNT and Fe3O4 and stacked to form a multilayered EMI shielding PDMS composite. Scanning electron micrographs revealed that MWCNT in spin-coated composites are significantly more agglomerated than in the compression-molded film. Direct current conductivity and curing temperature were higher in compression-molded films as the filler formed a well-percolated network and hindered cross-linking of polymer chains. EMI shielding results revealed that spincoated films demonstrated greater shielding effectiveness than compression-molded composites in the Ku-band (12-18 GHz). Individual agglomerates of MWCNT in spin-coated film attenuated incoming electromagnetic radiation more effectively than well-dispersed MWCNT in compression-molded films. Therefore, PDMS composites of different compositions of MWCNT and Fe3O4 nanoparticles were prepared through spin coating and stacked with a gradient of filler concentration, which resulted in maximum shielding of -28 dB, i.e., shielding more than 99% of incoming EM radiation by a 0.9 mm film
A new genus and species of natricine snake from northeast India
No full textBased on the first molecular phylogenetic analyses of samples from northeast India, specimens referred to Rhabdops from this region are more closely related to the southeast and east Asian natricine genera Opisthotropis Gunther, 1872 and Sinonatrix Rossman & Eberle, 1977 (as well as to New World and western Palearctic natricines) than to peninsular Indian (true) Rhabdops. Morphologically, these northeast Indian populations differ from other natricines by having a single ('fused' or unpaired) internasal shield and a single prefrontal shield. Given the morphological and phylogenetic distinctiveness of these northeast Indian populations, we refer them to a new genus, Smithophis gen. nov., and transfer Rhabdops bicolor (Blyth, 1854) to Smithophis bicolor comb. nov. Based on morphological and molecular variation within our northeast Indian sample, we additionally describe Smithophis atemporalis sp. nov. from the state of Mizoram
Diversity and biological activities of endophytic fungi associated with Catharanthus roseus
No full textBackground: The present study involves diversity and bioactivity of the endophytic fungal community from Catharanthus roseus inhabiting the coastal region. This study has been conducted hypothesizing that the microbial communities in the coastal regions would tolerate a range of abiotic stress such as salinity, humidity, temperature and soil composition, and it may produce new metabolites, which may possess bioactive property. Therefore in the current study, the cytotoxicity and free radical scavenging potential of the fungal organic extracts have been investigated. Moreover, the apoptotic and the antioxidant potential of the fungus that exhibited the best activity in preliminary screening has also been demonstrated. Results: Twenty endophytic fungal isolates were obtained from different parts of the plant, and identified using internal transcribed spacer region analysis. Based on the colonization frequency, the dominant genera were found to be Colletotrichum, Alternaria and Chaetomium with colonization frequency % of 8.66, 7.00 and 6.33, respectively. It was observed that the species diversity and richness was the highest in bark followed by leaf and stem regions of the plant. On screening the fungal ethyl acetate extracts for cytotoxicity against the HeLa cells, the Chaetomium nigricolor extract exhibited potent cytotoxic activity of 92.20% at 100 mu g mL(-1) concentration. Comparison between the different organic extracts (ethyl acetate, chloroform, dichloromethane and hexane) of Chaetomium nigricolor mycelial and culture filtrate, it was observed that the mycelial as well the culture filtrate ethyl acetate extracts and the culture filtrate hexane extract showed significant cytotoxic potential against the HeLa and MCF-7 cells, respectively. The apoptotic-and mitochondrial membrane depolarisation-induction potential of the Chaetomium nigricolor ethyl acetate extract has also been demonstrated in this study. Further the screening of antioxidant potential of the ethyl acetate fungal extracts using DPPH scavenging assay showed that Chaetomium nigricolor extract exhibited potential activity with a significant EC50 value of 22 mu g mL(-1). The ethyl acetate extract of Chaetomium nigricolor also exhibited superoxide radical scavenging potential. Conclusion: These results indicated that diverse endophytic fungal population inhabits Catharanthus roseus. One of the fungal isolate Chaetomium nigricolor exhibited significant cytotoxic, apoptotic and antioxidant potential
Electrical and optical properties of low-bandgap oxide Zn 2 Mo 3 O 8 for optoelectronic applications
No full textSemiconducting metal oxides are attractive for various applications since most oxides are non-toxic, stable, and easy to deposit. Wide band-gap materials have been studied more extensively, compared to low bandgap materials, which introduces limitations to the applications of oxides. Study of low band-gap semiconducting oxides can propel the usage of oxides in a wider range of applications. Here, the electronic, structural, and optical properties of Zn 2 Mo 3 O 8 (ZMO) are investigated. Stoichiometric polycrystalline films of ZMO are deposited using pulsed laser deposition system at room temperature. The unintentionally n-doped films show a hall electron mobility of 0.7 cm 2 V �1 s �1 and have a bandgap of 2.1 eV. The photoelectron spectra contain complex peak profiles which are explained to be a manifestation of final state effects. The orbital contribution to the valence band of ZMO is probed using resonant photoelectron spectroscopy, which confirms that the valence band is composed of Mo 4d levels. The conduction and valence band edges are predicted to be at 4.2 eV and 6.3 eV, so most of the conventional wide band-gap oxides can be used as hole-blocking layers with ZMO. Under A.M. 1.5 illumination, single-sided Schottky diode with Fluorine-doped tin oxide/TiO 2 /ZMO/Au structure shows no photovoltaic action, possibly due to high exciton binding energy and low carrier drift lengths. However, the Schottky device shows a higher current under illumination, which suggests that with improvement in carrier drift lengths, ZMO can find applications in low-cost optoelectronic devices on flexible substrates like plastic or Polyethylene terephthalate. © 2019 Elsevier B.V
Thermodynamics of adsorption of lysozyme on gold nanoparticles from second harmonic light scattering
No full textGold nanoparticle (GNP) interaction with hen egg white lysozyme (Lyz) has been investigated by many groups in order to understand protein mediated aggregation of GNPs and the underlying mechanism of aggregation. In this article, we have studied the interaction of citrate-capped GNPs of 16, 28, 41, and 69 nm sizes with Lyz by the non-destructive label-free second harmonic light scattering (SHLS) technique at physiological pH in phosphate buffer. The surface sensitivity of the nonlinear optical SHLS technique is very high and we have looked at the GNP-Lyz interaction at nanomolar concentrations. We have followed the increase in the SHLS intensity of GNPs as a function of the added concentration of Lyz in small aliquots. The SH intensity profile exhibits saturation behaviour and was fitted with a modified Langmuir adsorption model which yielded the binding constant (K-b), the binding stoichiometry (n(sat)) at saturation and the free energy change (G) in the adsorption process. The free energy change was further decomposed into changes in the enthalpy (H) and entropy (S) of adsorption by carrying out temperature dependent SHLS measurements in a specially designed cell. The thermodynamic quantities extracted from the measurements show that the binding is exothermic (H < 0) as well as spontaneous (S > 0). We find that the first step in the adsorption of Lyz on the GNP surface is nanoparticle protein corona (NP-PC) formation driven predominantly by electrostatic attraction. In the second step of adsorption, the adsorbed lysozymes on the surface form a bridge between two or more GNPs leading to the latter's aggregation, which is the main reason for the enhancement of the SH scattering signal. Although the interaction between the GNPs and Lyz is driven by strong electrostatic attraction, the thermodynamic quantities reported here indicate that the protein is physisorbed on the nanoparticle surface. We have also demonstrated that SHLS provides a new tool for full thermodynamic characterization of protein adsorption on metal nanoparticles at ultralow concentrations
Many-body localization due to correlated disorder in Fock space
No full textIn the presence of strong enough disorder one-dimensional systems of interacting spinless fermions at nonzero filling factor are known to be in a many-body localized phase. When represented in `Fock space,' the Hamiltonian of such a system looks like that of a single `particle' hopping on a Fock lattice in the presence of a random disordered potential. The coordination number of the Fock lattice increases linearly with the system size L in one dimension. Thus in the thermodynamic limit L ->infinity, the disordered interacting problem in one dimension maps on to an Anderson model with infinite coordination number. Despite this, this system displays localization which appears counterintuitive. A close observation of the on-site disorder potentials on the Fock lattice reveals a large degree of correlation among them as they are derived from an exponentially smaller number of on-site disorder potentials in real space. This indicates that the correlations between the on-site disorder potentials on a Fock lattice has a strong effect on the localization properties of the corresponding many-body system. This intuition is also consistent with studies of quantum random energy model where the typical mid-spectrum states are ergodic and the on-site potentials in Fock space are completely uncorrelated. In this work we perform a systematic quantitative exploration of the nature of correlations of the Fock space potential required for localization. We study different functional variations of the disorder correlation in Fock lattice by analyzing the eigenspectrum obtained through exact diagonalization. Without changing the typical strength of the on-site disorder potential in Fock lattice we show that changing the correlation strength can induce thermalization or localization in systems. From among the various forms of correlations we study, we find that only the linear variation of correlations with Hamming distance in Fock space is able to drive a thermal-MBL phase transition where the transition is driven by the correlation strength. Systems with the other forms of correlations we study are found to be ergodic
Dense 3D point cloud reconstruction using a deep pyramid network
No full textReconstructing a high-resolution 3D model of an object is a challenging task in computer vision. Designing scalable and light-weight architectures is crucial while addressing this problem. Existing point-cloud based reconstruction approaches directly predict the entire point cloud in a single stage. Although this technique can handle low-resolution point clouds, it is not a viable solution for generating dense, high-resolution outputs. In this work, we introduce DensePCR, a deep pyramidal network for point cloud reconstruction that hierarchically predicts point clouds of increasing resolution. Towards this end, we propose an architecture that first predicts a low-resolution point cloud, and then hierarchically increases the resolution by aggregating local and global point features to deform a grid. Our method generates point clouds that are accurate, uniform and dense. Through extensive quantitative and qualitative evaluation on synthetic and real datasets, we demonstrate that DensePCR outperforms the existing state-of-the-art point cloud reconstruction works, while also providing a light-weight and scalable architecture for predicting high-resolution outputs. © 2019 IEEE
A Carlitz-von Staudt type theorem for finite rings
No full textWe compute the kth power-sums (for all k > 0) over an arbitrary finite unital ring R. This unifies and extends the work of Brawley et al. (1974) 1] for matrix rings, with folklore results for finite fields and finite cyclic groups, and more general recent results of Grau and Oller-Marcen (2017) 12] for commutative rings. As an application, we resolve a conjecture by Fortuny Ayuso et al. (2017) 7] on zeta values for matrix rings over finite commutative rings. We further recast our main result via zeta values over polynomial rings, and end by classifying the translation-invariant polynomials over a large class of finite commutative rings. (C) 2018 Elsevier Inc. All rights reserved