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Determination of Phase Composition of Cobalt Nanoparticles Using Co-59 Internal Field Nuclear Magnetic Resonance
No full textIt is well known that cobalt exhibits polymorphism, i.e., the co-existence of both the hcp and fcc phases. In particular, the method of synthesis and other thermodynamic conditions is known to play a crucial role in determining the particular phase of cobalt. In this work, we have compared the phase composition of the cobalt nanoparticles synthesized using two different solvents (water) and ethanol (Co@C). XRD measurements confirm the existence of fcc phase in commercial cobalt nanoparticles (Co@A), co-existence of fcc and hcp phases in Co@B, while the existence of the hcp phase in Co@C. We have studied these cobalt nanoparticles using Co-59 internal field nuclear magnetic resonance (IFNMR) for verification of phase composition. Our studies reveal that the Co@A has fcc as a major phase with minor quantity hcp phase. Co@B exhibits approximately equal amount of fcc and hcp phase while Co@C exhibits hcp as a major phase with minor fcc phase. Our SEM micrograph studies confirm that the cobalt particles have spherical shape in the fcc phase. The cobalt particles exhibit both spherical and dendrite morphology confirming the co-existence of fcc and hcp phases, while the sample with pure hcp phase exhibits the dendrite morphology. Our studies also throw light on understanding the effect of solvent in the phase formation of the cobalt nanoparticles
On the high temperature coarsening kinetics of gamma ` precipitates in a high strength Co37.6Ni35.4Al9.9Mo4.9Cr5.9Ta2.8Ti3.5 fcc-based high entropy alloy
No full textThe paper reports evolution of two-phase microstructure quantitatively in a high entropy alloy of composition Co37.6Ni35.4Al9.9Mo4.9Ta2.8Ti3.5. A very high-volume fraction of ordered L1(2) precipitates forms below its solvus temperature of 1156 degrees C that cannot be suppressed during quenching. The quench microstructure contains nanometric bimodal size distribution of spheroidal and irregular precipitates, both having L1(2) ordering (gamma') and a Co + Ni concentration close to 75 at. %, thus representing a stoichiometry of (Ni,Co)(3) (AI,Cr,Ta,Ti,Mo). The alloy shows hardening on aging with a peak in hardness value at 900 degrees C for 50 h of annealing. The morphology of the precipitates at this stage evolves into cuboidal shape having rounded corners with a lattice mismatch of +0.22% with the matrix. A detailed study of the coarsening behaviour of these precipitates in the matrix of complex solid solution indicates that the coarsening follows a modified LSW mechanism with estimated activation energy of 360 +/- 50 kJ/mol between 900 and 1000 degrees C. This is slightly higher than the activation energy of most of the solutes in gamma Co matrix that does not contain heavy elements like W or Re. The high-volume fraction of the precipitates together with coarsening resistance lead to an attractive high temperature strength that is higher than many of the known superalloys
Dietary CCPS from bitter gourd attenuates sodium arsenite induced female reproductive ailments cum infertility in wistar rats: anti-inflammatory and anti-apoptotic role
No full textThis investigation explored a dietary therapy of pectic polysaccharide (CCPS) (2 mg/ Kg BW) against female repro-toxicity and infertility triggered by sodium arsenite (M3+) (10 mg/ Kg BW) in Wistar rats. The isolated CCPS consists of D-galactose and D-methyl galacturonate with a molar ratio of 1: 4. FTIR spectral analysis of CCPS and CCPS- sodium arsenite (As3+) complex indicated a possible chelating property of CCPS in presence of binding sites (OH-/COOH) for As3+. Series of negatively charged galacturonate residues in CCPS provide better potential for cation chelation. CCPS significantly mitigated As3+ induced ovarian, uterine lipid peroxidation, and reactive oxygen species (ROS) generation by the restoration of superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx) activities. CCPS post-treatment enhanced ovarian steroidogenesis along with a restoration of normal tissue histoarchitecture in As3+ fed rats by regulating the estradiol receptor alpha (ER-alpha). CCPS suppressed anti-inflammatory properties effectively found since a down-regulation of NF-kappa B (NF-kappa B), pro-inflammatory tumor necrosis-alpha (TNF-alpha) and interleukin-6 (IL-6) were observed in arsenicated rats with CCPS. This study confirmed the up-regulation of uterine pro-apoptotic/ apoptotic proteins caspase-3, poly ADP ribose polymerase (PARP), proliferating cell nuclear antigen (PCNA), phospho p53 and Box, followed by downregulation of Bcl-2 and protein Kinase B (AKT) signaling pathway along with uterine tissue regeneration in As3+ exposed rats. Oral CCPS attenuated the above apoptotic expressional changes significantly and dietary CCPS ensured successful fertility with the birth of healthy pups in lieu of infertile condition in As3+ fed rats. Moreover, this study also supports that CCPS treatment attenuated the As3+ toxicity by modulating the S-adenosine methionine (SAM) pool components, B-12, folate and homocysteine
Stereochemical Assessment of (phi,psi) Outliers in Protein Structures Using Bond Geometry-Specific Ramachandran Steric-Maps
No full textRamachandran validation of protein structures is commonly performed using developments, such as MolProbity. We suggest tailoring such analyses by position-wise, geometry-specific steric-maps, which show (phi,psi) regions with steric-clash at every residue position. These maps are different from the classical steric-map because they are highly sensitive to bond length and angle values that are used, in our steric-maps, as observed in the residue positions in super-high-resolution peptide and protein structures. (phi,psi) outliers observed in such structures seldom have steric-clash. Therefore, we propose that a (phi,psi) outlier is unacceptable if it is located within the steric-clash region of a bond geometry-specific steric-map for a residue position. These steric-maps also suggest position-specific accessible (phi,psi) space. The PARAMA web resource performs in-depth position-wise analysis of protein structures using bond geometry-specific steric-maps
Emergent Magnetic State in (111)-Oriented Quasi-Two-Dimensional Spinel Oxides
No full textWe report on the emergent magnetic state of (111)-oriented CoCr2O4 ultrathin films sandwiched between Al2O3 spacer layers in a quantum confined geometry. At the two-dimensional crossover, polarized neutron reflectometry reveals an anomalous enhancement of the total magnetization compared to the bulk value. Synchrotron X-ray magnetic circular dichroism measurements demonstrate the appearance of a long-range ferromagnetic ordering of spins on both Co and Cr sublattices. Brillouin function analyses and ab-initio density functional theory calculations further corroborate that the observed phenomena are due to the strongly altered magnetic frustration invoked by quantum confinement effects, manifested by the onset of a Yafet-Kittel-type ordering as the magnetic ground state in the ultrathin limit, which is unattainable in the bulk
A nanopillar array on black titanium prepared by reactive ion etching augments cardiomyogenic commitment of stem cells
No full textA major impediment in the clinical translation of stem cell therapy has been the inability to efficiently and reproducibly direct differentiation of a large population of stem cells. Thus, we aimed to engineer a substrate for culturing stem cells to efficiently induce cardiomyogenic lineage commitment. In this work, we present a nanopillar array on the surface of titanium that was prepared by mask-less reactive ion etching. Scanning electron and atomic force microscopy revealed that the surface was covered by vertically aligned nanopillars each of approximate to 1 mu m with a diameter of approximate to 80 nm. The nanopillars supported the attachment and proliferation of human mesenchymal stem cells (hMSCs). Cardiomyogenic lineage commitment of the stem cells was more enhanced on the nanopillars than on the smooth surface. When co-cultured with neonatal rat cardiomyocytes, the cyclic pattern of calcium transport observed distinctly in cells differentiated on the arrays compared to the cells cultured on the smooth surface was the functional validation of differentiation. The use of small molecule inhibitors revealed that integrins namely, alpha(2)beta(1) and alpha(v)beta(3), are essential for cardiomyogenesis on the nanostructured surface, which is further mediated by FAK, Erk and Akt cell signaling pathways. This study demonstrates that the nanopillar array efficiently promotes the cardiomyogenic lineage commitment of stem cells via integrin-mediated signaling and can potentially serve as a platform for the ex vivo differentiation of stem cells toward cell therapy in cardiac tissue repair and regeneration
Experimental and numerical study on square anchor plate groups in geogrid reinforced sand
No full textThe paper investigates the behaviour of groups of horizontal square anchor plates in geogrid-reinforced sand using laboratory model tests. The optimum spacing for two anchor plates in unreinforced sand is 3.4 times the anchor width. The unreinforced groups of anchor plates show a clear failure at a displacement of about 5% of the anchor width, whereas this value increases to more than 45% for reinforced groups along with a two-fold increase in uplift capacity. The optimum width and length of the geogrid reinforcement for groups of two anchors is found to be 5 and 9.4 times the width of the anchor plate, respectively. The performance improvement for isolated anchor plates is found to be maximum and gradually reduces with an increase in the number of plates; however, this reduction is much less in groups of two to four. Therefore, the results obtained from the model tests for reinforced groups of two to four anchor plates can be conveniently used to extrapolate the uplift capacity of multiple anchor plate systems in a reinforced soil mass. The model test results show a reasonably good agreement with the three-dimensional (3D) numerical analysis results
Covalent binding of uracil DNA glycosylase UdgX to abasic DNA upon uracil excision
No full textUracil DNA glycosylases (UDGs) are important DNA repair enzymes that excise uracil from DNA, yielding an abasic site. Recently, UdgX, an unconventional UDG with extremely tight binding to DNA containing uracil, was discovered. The structure of UdgX from Mycobacterium smegmatis in complex with DNA shows an overall similarity to that of family 4 UDGs except for a protruding loop at the entrance of the uracil-binding pocket. Surprisingly, H109 in the loop was found to make a covalent bond to the abasic site to form a stable intermediate, while the excised uracil remained in the pocket of the active site. H109 functions as a nucleophile to attack the oxocarbenium ion, substituting for the catalytic water molecule found in other UDGs. To our knowledge, this change from a catalytic water attack to a direct nucleophilic attack by the histidine residue is unprecedented. UdgX utilizes a unique mechanism of protecting cytotoxic abasic sites from exposure to the cellular environment
Solvothermal synthesis of mesoporous NiCoP for high performance electrochemical supercapacitors
No full textMesoporous NiCoP is synthesized by a one pot solvothermal route and is studied for its morphology, structure, composition. As charge storage in electrochemical supercapacitors is a surface phenomenon, its electrochemical characterizations will be of high interest. The specific capacitance of the as prepared NiCoP is 188 C/g (418 F/g) at 8 A/g and 140 C/g (311 F/g) at a higher specific current density of 20 A/g in 3 M KOH. Interestingly, capacity retention after 5000 cycles at high current of 20 A/g is 97%. Mesoporous NiCoP is a promising electrode material, which exhibits high specific capacity and very long cycle life
Search for production of Higgs boson pairs in the four b quark final state using large-area jets in proton-proton collisions at root s 13 TeV
No full textA search is presented for pair production of the standard model Higgs boson using data from proton-proton collisions at a centre-of-mass energy of 13 TeV, collected by the CMS experiment at the CERN LHC in 2016, and corresponding to an integrated luminosity of 35.9 fb(-1). The final state consists of two b quark-antiquark pairs. The search is conducted in the region of phase space where one pair is highly Lorentz-boosted and is reconstructed as a single large-area jet, and the other pair is resolved and is reconstructed using two b-tagged jets. The results are obtained by combining this analysis with another from CMS looking for events with two large jets. Limits are set on the product of the cross sections and branching fractions for narrow bulk gravitons and radions in warped extradimensional models having a mass in the range 750-3000 GeV. The resulting observed and expected upper limits on the non-resonant Higgs boson pair production cross section correspond to 179 and 114 times the standard model value, respectively, at 95% confidence level. The existence of anomalous Higgs boson couplings is also investigated and limits are set on the non-resonant Higgs boson pair production cross sections for representative coupling values