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Probing the Crystal Structure Landscape by Doping: 4-Bromo, 4-Chloro, and 4-Methylcinnamic Acids
No full textAccessing the data points in the crystal structure landscape of a molecule is a challenging task, either experimentally or computationally. We have charted the crystal structure landscape of 4-bromocinnamic acid (4BCA) experimentally and computationally: experimental doping is achieved with 4-methylcinnamic acid (4MCA) to obtain new crystal structures; computational doping is performed with 4-chlorocinnamic acid (4CCA) as a model system, because of the difficulties associated in parameterizing the Bratom. The landscape of 4CCA is explored experimentally in turn, also by doping it with 4MCA, and is found to bear a close resemblance to the landscape of 4BCA, justifying the ready miscibility of these two halogenated cinnamic acids to form solid solutions without any change in crystal structure. In effect, 4MCA, 4CCA and 4BCA form a commutable group of crystal structures, which may be realized experimentally or computationally, and constitute the landscape. Unlike the results obtained by Kitaigorodskii, all but two of the multiple solid solutions obtained in the methyl-doping experiments take structures that are different from the hitherto observed crystal forms of the parent compounds. Even granted that the latter might be inherently polymorphic, this unusual observation provokes the suggestion that solid solution formation may be used to probe the crystal structure landscape. The influence of interactions, weak hydrogen bonds and halogen bonds in directing the formation of these new structures is also seen
Synthesis of a Block Copolymer Exhibiting Cell-Responsive Phytochemical Release for Cancer Therapy
No full textPhytochemicals constitute a promising class of therapeutics for the treatment of various diseases, but, their delivery poses significant challenges. In this work, a nanoscale polyactive emulsion was designed for smart, cell-responsive delivery of a curcumin prodrug (curcumin dicarboxylate, CDA) that was chemically conjugated to enzymatically labile oligo-peptides with polycaprolactone (PCL) as the carrier. Matrix metalloproteinase (MMP)-sensitive (PLGLYAL) or nonsensitive (GPYYPLG) peptides were used as spacers for conjugating CDA and PCL. This CDA nanoemulsion incorporating the MMP-sensitive sequence exhibited markedly higher anti-cancer activity, cell internalization, and generation of reactive oxygen species in cancer cells in vitro than the control with the nonsensitive oligopeptide. Moreover, the nanopolyactives induced minimal cytotoxicity in noncancerous cell line. This work presents a unique strategy to engineer smart nano-polyactives for efficient and targeted delivery of phytochemicals
Heat flux characteristics within and outside a forward facing cavity in a hypersonic flow
No full textA forward facing cavity effect on heat flux variations inside the cavity and over the nose surface is studied over a typical projectile geometry using the shock tunnel experiments. The flow oscillation will tend to oscillate the shock, which in turn varies the heat flux over the nose surface as well as inside the cavity. The higher length to diameter (L/D) ratio of the cavity plays an important role in nose surface heat flux reduction and investigated for L/D = 1, 2 and 3 by a uniquely designed model. The cavity flow oscillation period is determined, using the base pressure and surface heat transfer signals measured inside the cavity with reference to the picot probe steady test time and shock oscillation period. The frequency analysis for oscillations is performed using the fast Fourier transformation. Experimental results showed that, the mean nose surface heat flux reduced by approximate to 4.6% to approximate to 7%, approximate to 6% to approximate to 8% and approximate to 3% to approximate to 31.4 and the mean shock standoff distance (l) is increased by approximate to 13%, approximate to 25% and approximate to 35% for L/D = 1, 2 and 3 configurations respectively with reference to the baseline geometry (without cavity geometry). As L/D increases, the nose surface location on which the heat flux reduction is observed moves towards the cavity lip and more surface area is covered with lower heat flux. Cavity region heat flux variations are studied by incorporating the thin film sensors over the cavity surface and it is observed that, a significant approximate to 32.5% to approximate to 36%, and approximate to 28% to approximate to 58% lower mean heat flux for L/D = 2 and 3 respectively with reference to the baseline geometry stagnation point heat flux
Pt-Ru-NiTiO3 Nanoparticles Dispersed on Vulcan as High Performance Electrocatalysts for the Methanol Oxidation Reaction (MOR)
No full textWe propose a high performance electrocatalyst based on Pt-Ru-NiTiO3 nanoparticles supported on Vulcan carbon (Pt-Ru-NiTiO3/C) for the methanol oxidation reaction (MOR) in acid medium. The electrocatalyst is prepared from a two-step procedure using a wet chemical method. The morphological studies from TEM indicate that Pt-Ru-NiTiO3 nanoparticles are uniformly distributed on Vulcan carbon. The XRD shows the fcc structure of Pt nanomaterials, while the chemical composition examined using XPS indicates the presence of large fractions of Pt-0 and Ru-0 species (i.e., metallic state), OH- and O2- species are also formed on the surface of the catalyst. The Pt-Ru-NiTiO3/C electrocatalyst exhibits a higher catalytic activity compared to a PtRu/C alloy. Pt-NiTiO3/C is also more active than the alloy. Therefore, on one side, the addition of Ru enhances the MOR through the formation of oxygenated adsorbed species on Ru, which thereby promotes the oxidation of CO to CO2 at more negative potentials (i.e., the bifunctional mechanism). On the other hand, the superior electrocatalytic performance of Pt-Ru-NiTiO3/C is attributed also to the synergistic effects of NiTiO3, which promotes the reaction increasing the current density and shifting the onset potential to even more negative values, suggesting that it also participates in the bifunctional mechanism along with Ru. From the results shown here, Pt-Ru-NiTiO3/C can be a promising anode nanomaterial for direct methanol fuel cells (DMFCs)
Response of phytoplankton to heavy cloud cover and turbidity in the northern Bay of Bengal
No full textAn interesting physiological response of phytoplankton to large fluctuations in underwater photosynthetically active radiation (PAR) levels in the northern Bay of Bengal has been presented here. This study is primarily based on a 12-day time series observation in the northern Bay of Bengal during the peak Southwest Monsoon (July 2012), when the study region was recurrently exposed to alternating cloudy and sunny sky conditions. On overcast days, the PAR available underwater at the time series location (TSL) drastically decreased, with the noontime PAR at the surface water (2 m) usually being similar to 600 mu mol m(-2) s(-1) on sunny days and declining to similar to 50 mu mol m(-2) s(-1) on heavily overcast days. Closely linked with the sunny and cloudy days at TSL, chlorophyll a concentration in the water column showed noticeable features; it increased in the upper water column (surface-40 m) and decreased in the lower water column (41-80 m) on cloudy days, while the reverse was the case on sunny days. Based on in-situ and laboratory experimental data, it was observed that these temporal changes in the vertical distribution of chlorophyll a in the northern Bay of Bengal were due to the short-term physiological acclimation of phytoplankton to large changes in underwater PAR
Conformation Analysis of GalNAc-Appended Sugar Amino Acid Foldamers as Glycopeptide Mimics
No full textSugar amino acid (SAA)-based foldamers with well-defined secondary structures were appended with N-acetylgalactosamine (GalNAc) sugars to access sequence-defined, multidentate glycoconjugates with full control over number, spacing and position. Conformation analysis of these glycopeptides by extensive NMR spectroscopic studies revealed that the appended GalNAc units had a profound influence on the native conformational behaviour of the SAA foldamers. Whereas the 2,5-cis glycoconjugate showed a helical structure in water, comprising of two consecutive 16-membered hydrogen bonds, its 2,5-trans congener displayed an unprecedented 16/10-mixed turn structure not seen before in any glycopeptide foldamer
Field-of-view Constrained Polynomial Guidance Law for Interception of Moving Target using Dual-Seeker Interceptors
No full textA polynomial based guidance law dependent on range-to-go, is proposed for interception of a non-maneuvering moving target, by a dual-seeker interceptor. The guidance law is obtained by utilizing a cubic polynomial in range-to-go to arrive at the instantaneous look angle. The look angle is evolved as a function of range-to-go, so as to satisfy the field-of view constraints of the seekers. The coefficients of the polynomial are obtained by satisfying the boundary conditions on the look-angle at the launch and impact points as well as imposing the respective field-of-view constraints of the seekers during the individual phases of their operation. Simulation results show the efficacy of the guidance law. (C) 2018, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved
Lepton-specific universal seesaw model with left-right symmetry
No full textWe propose a left-right symmetric framework with a universal seesaw mechanism for the generation of masses of the Standard Model quarks and leptons. Heavy vectorlike singlet quarks and leptons are required for generation of Standard-Model-like quark and lepton masses through a seesaw mechanism. A softly broken Z(2) symmetry distinguishes the lepton sector and the quark sector of the model. This leads to the presence of some lepton-specific interactions that can produce unique collider signatures which can be explored at the current Large Hadron Collider run and also future colliders
Ionic liquids make DNA rigid
No full textPersistence length of double-stranded DNA (dsDNA) is known to decrease with an increase in ionic concentration of the solution. In contrast to this, here we show that the persistence length of dsDNA increases dramatically as a function of ionic liquid (IL) concentration. Using all atom explicit solvent molecular dynamics simulations and theoretical models, we present, for the first time, a systematic study to determine the mechanical properties of dsDNA in various hydrated ILs at different concentrations. We find that dsDNA in 50 wt% ILs have lower persistence length and stretch modulus in comparison to 80 wt% ILs. We further observe that both the persistence length and stretch modulus of dsDNA increase as we increase the concentration of ILs. The present trend of the stretch modulus and persistence length of dsDNAwith IL concentration supports the predictions of the macroscopic elastic theory, in contrast to the behavior exhibited by dsDNA in monovalent salt. Our study further suggests the preferable ILs that can be used for maintaining DNA stability during long-term storage. Published by AIP Publishing
Science and engineering research in India (1985-2016): insights from two scientometric databases
No full textWe furnish scientometric data, for science and engineering, of research organizations in India, extracted principally from the Web of Science (TM) (WoS) database via their InCites (TM) tool. We classify the data into different granularity levels and address problems in their reliable extraction from publication metadata. We accumulate scientometric measures such as the numbers of publications, citations, and the h-index for the period 1985-2016. We use them to compare research performance in science and engineering, (a) across countries, very briefly, and (b) among Indian research organizations, for which we refine the data to carry out subject-level comparisons. A brief comparison with data from Scopus (R) and SciVal(C) is also included