Combinatorial effect of rolling and carbonaceous nanoparticles on the evolution of crystallographic texture and structural properties of ultra high molecular weight polyethylene

Ultra high molecular weight polyethylene (PE) is a structural polymer widely used in biomedical implants. The mechanical properties of PE can be improved either by controlled crystalline orientation (texture) or by the addition of reinforcing agents. However, the combinatorial effect has not received much attention. The objective of this study was to characterize the structure and mechanical properties of PE composites incorporating multiwall carbon nanotubes (MWCNT) and reduced graphene oxide (RGO) subjected to hot rolling. The wide angle X-ray diffraction studies revealed that mechanical deformation resulted in a mixture of orthorhombic and monoclinic crystals. Furthermore, the presence of nanoparticles resulted in lower crystallinity in PE with smaller crystallite size, more so in RGO than in MWCNT composites. Rolling strengthened the texture of both orthorhombic and the monoclinic phases in PE. Presence of RGO weakened the texture of both phases of PE after rolling whereas MWCNT only mildly weakened the texture. This resulted in a reduction in the elastic modulus of RGO composites whereas moduli of neat polymer and the MWCNT composite increased after rolling. This study provides new insight into the role of nanoparticles in texture evolution during polymer processing with implications for processing of structural polymer composites.

Effect of Groundwater Seepage on Uplift Resistance of Buried Pipelines

The uplift resistance of pipelines buried in sands, in the presence of inclined groundwater flow, considering both upward and downward flow directions, has been determined by using the lower bound finite elements limit analysis in conjunction with nonlinear optimization. A correction factor (f (gamma) ), which needs to be multiplied with the uplift factor (F (gamma) ), has been computed to account for groundwater seepage. The variation of f (gamma) has been obtained as a function of i(gamma (w) /gamma (sub) ) for different horizontal inclinations (theta) of groundwater flow; where i = absolute magnitude of hydraulic gradient along the direction of flow, gamma (w) is the unit weight of water and gamma (sub) is the submerged unit weight of soil mass. For a given magnitude of i, there exists a certain critical value of theta for which the magnitude of f (gamma) becomes the minimum. An example has also been presented to illustrate the application of the results obtained for designing pipelines in presence of groundwater seepage.

Dissociation Constants of Weak Acids from ab Initio Molecular Dynamics Using Metadynamics: Influence of the Inductive Effect and Hydrogen Bonding on pK(a) Values

The theoretical estimation of the dissociation constant, or pK(a), of weak acids continues to be a challenging field. Here, we show that ab initio CarParrinello molecular dynamics simulations in conjunction with metadynamics calculations of the free-energy profile of the dissociation reaction provide reasonable estimates of the pK(a) value. Water molecules, sufficient to complete the three hydration shells surrounding the acid molecule, were included explicitly in the computation procedure. The free-energy profiles exhibit two distinct minima corresponding to the dissociated and neutral states of the acid, and the difference in their values provides the estimate for pK(a). We show for a series of organic acids that CPMD simulations in conjunction with metadynamics can provide reasonable estimates of pK(a) values. The acids investigated were aliphatic carboxylic acids, chlorine-substituted carboxylic acids, cis- and trans-butenedioic acid, and the isomers of hydroxybenzoic acid. These systems were chosen to highlight that the procedure could correctly account for the influence of the inductive effect as well as hydrogen bonding on pK(a) values of weak organic acids. In both situations, the CPMD metadynamics procedure faithfully reproduces the experimentally observed trend and the magnitudes of the pK(a) values.

Effect of alkyl substituents in BODIPYs: a comparative DFT computational investigation

Random changes in the alkyl substitution patterns of fluorescent dyes, e.g. BODIPYs, are often accompanied by significant changes in their photophysical properties. To understand such alterations in properties in closely related molecular systems, a comparative DFT (density functional theory) computational investigation was performed in order to comprehend the effects of alkyl substitution in controlling the structural and electronic nature of BODIPY dyes. In this context, a systematic strategy was utilized, considering all possible outcomes of constitutionally-isomeric molecules to understand the alkyl groups' effects on the BODIPY molecules. Four different computational methods {i.e. B3LYP/631G(d); B3LYP/6-311++ G(d,p); wb97xd/6-311++ G(d,p) and mpw1pw91/6-311++ G(d,p)} were employed to rationalize the agreement of the trends associated with the molecular properties. In line with experimental observations, it was found that alkyl substituents in BODIPY dyes situated at 3/5-positions effectively participate in stabilization as well as planarization of such molecules. Screening of all the possible isomeric molecular systems was used to understand the individual properties and overall effects of the typical alkyl substituents in controlling several basic properties of such BODIPY molecules.

Effect of metal oxidation state on FRET: a Cu(I) silent but selectively Cu(II) responsive fluorescent reporter and its bioimaging applications

Copper(II) and copper(I) complexes of a newly designed and crystallographically characterized Schiff base (HL) derived from rhodamine hydrazide and cinnamaldehyde were isolated in pure form formulated as Cu(L)(NO3)] (L-Cu) (1) and Cu(HL)(CH3CN)(H2O)]ClO4 (HL-Cu) (2), and characterized by physicochemical and spectroscopic tools. Interestingly, complex 1 but not 2 offers red fluorescence in solution state, and eventually HL behaves as a Cu(II) ions selective FRET based fluorosensor in HEPES buffer (1 mM, acetonitrile-water: 1/5, v/v) at 25 degrees C at biological pH with almost no interference of other competitive ions. The dependency of the FRET process on the +2 oxidation state of copper has been nicely supported by exhaustive experimental studies comprising electronic, fluorimetric, NMR titration, and theoretical calculations. The sensing ability of HL has been evaluated by the LOD value towards Cu(II) ions (83.7 nM) and short responsive time (5-10 s). Even the discrimination of copper(I) and copper(II) has also been done using only UV-Vis spectroscopic study. The efficacy of this bio-friendly probe has been determined by employing HL to detect the intercellular distribution of Cu(II) ions in HeLa cells by developing image under fluorescence microscope.

Synergistic Effect of Mo plus Cu Codoping on the Photocatalytic Behavior of Metastable TiO2 Solid Solutions

Codoping with Cu and Mo is shown to have a synergistic effect on the photocatalytic activity of TiO2. The enhancement in activity is observed only if the synthesis route results in TiO2 in which (Cu, Mo) codopants are forced into the TiO2 lattice. Using X-ray photoelectron spectroscopy, Cu and Mo are shown to be present in the +2 and +6 oxidation states, respectively. A systematic study of the ternary system shows that TiO2 containing 6 mol % CuO and 1.5 mol % MoO3 is the most active ternary composition. Ab initio calculations show that codoping of TiO2 using (Mo, Cu) introduces levels above the valence band, and below the conduction band, resulting in a significant reduction in the band gap (similar to 0.8 eV). However, codoping also introduces deep defect states, which can have a deleterious impact on photoactivity. This helps rationalize the narrow compositional window over which the enhancement in photocatalytic activity is observed.

Effect of measurement noise on Granger causality

Most of the signals recorded in experiments are inevitably contaminated by measurement noise. Hence, it is important to understand the effect of such noise on estimating causal relations between such signals. A primary tool for estimating causality is Granger causality. Granger causality can be computed by modeling the signal using a bivariate autoregressive (AR) process. In this paper, we greatly extend the previous analysis of the effect of noise by considering a bivariate AR process of general order p. From this analysis, we analytically obtain the dependence of Granger causality on various noise-dependent system parameters. In particular, we show that measurement noise can lead to spurious Granger causality and can suppress true Granger causality. These results are verified numerically. Finally, we show how true causality can be recovered numerically using the Kalman expectation maximization algorithm.

Effect of radio frequency power and thickness on the electrochemical properties of Li2-x MnO3-y thin films

In the present work, Li2-x MnO3-y (LMO) thin films have been deposited by radio frequency (RF) reactive magnetron sputtering using acid-treated Li2MnO3 powder target. Systematic investigations have been carried out to study the effect of RF power on the physicochemical properties of LMO thin films deposited on platinized silicon substrates. X-ray diffraction, electron microscopy, surface chemical analysis and electrochemical studies were carried out for the LMO films after post deposition annealing treatment at 500 A degrees C for 1 h in air ambience. Galvanostatic charge discharge studies carried out using the LMO thin film electrodes, delivered a highest discharge capacity of 139 mu Ah mu m(-1) cm(-2) in the potential window 2.0-3.5 V vs. Li/Li+ at 100 W RF power and lowest discharge capacity of 80 mu Ah mu m(-1) cm(-2) at 75 W RF power. Thereafter, the physicochemical properties of LMO films deposited using optimized RF power 100 W on stainless steel substrates has been studied in the thickness range of 70 to 300 nm as a case study. From the galvanostatic charge discharge experiments, a stable discharge capacity of 68 mu Ah mu m(-1) cm(-2) was achieved in the potential window 2.0-4.2 V vs. Li/Li+ tested up to 30 cycles. As the thickness increased, the specific discharge capacity started reducing with higher magnitude of capacity fading.

Room-temperature bandlike transport and Hall effect in a high-mobility ambipolar polymer

The advent of a new class of high-mobility semiconducting polymers opens up a window to address fundamental issues in electrical transport mechanism such as transport between localized states versus extended state conduction. Here, we investigate the origin of the ultralow degree of disorder (E-a similar to 16 meV) and the ``bandlike'' negative temperature (T) coefficient of the field effect electron mobility: mu(e)(FET) (T) in a high performance (mu(e)(FET) > 2.5 cm(2) V-1 s(-1)) diketopyrrolopyrrole based semiconducting polymer. Models based on the framework of mobility edge with exponential density of states are invoked to explain the trends in transport. The temperature window over which the system demonstrates delocalized transport was tuned by a systematic introduction of disorder at the transport interface. Additionally, the Hall mobility (mu(e)(Hall)) extracted from Hall voltage measurements in these devices was found to be comparable to field effect mobility (mu(e)(FET)) in the high T bandlike regime. Comprehensive studies with different combinations of dielectrics and semiconductors demonstrate the effectiveness of rationale molecular design, which emphasizes uniform-energetic landscape and low reorganization energy.

Significant photocytotoxic effect of an iron(III) complex of a Schiff base ligand derived from vitamin B-6 and thiosemicarbazide in visible light

Iron(III)-Schiff base complexes, namely, Fe(tsc-py)(2)](NO3) (1), Fe(tsc-acpy)(2)](NO3) (2) and Fe(tsc-VB6)(2)](NO3) (3), where tsc-py, tsc-acpy and tsc-VB6 are the respective Schiff bases derived from thiosemicarbazide (tsc) and pyridine-2-aldehyde (tsc-py), 2-acetyl pyridine (tsc-acpy) and vitamin B-6 (pyridoxal, tsc-VB6), have been prepared, structurally characterized and their photocytotoxicity studied in cancer HeLa cells. The single crystal X-ray structures of the complexes 1 and 2 show a distorted octahedral geometry formed by the FeN4S2 core. The low-spin and 1 : 1 electrolytic complexes display a broad absorption band in the visible region. Complexes 1 and 2, without any VB6 moiety are not cytotoxic under light or dark conditions. Complex 3 is significantly photocytotoxic under visible light of 400-700 nm giving an IC50 value of 22.5 mu M in HeLa cells with no dark toxicity (IC50 > 100 mu M). The photo-induced cell death is attributable to apoptotic pathways involving photo-assisted generation of intracellular ROS. The observed photocytotoxicity of complex 3 could be the result of its better photosensitizing property combined with its enhanced uptake into cancer cells via a VB6 transporting membrane carrier (VTC) mediated diffusion pathway due to the presence of the VB6 moiety compared to the two non-vitamin B-6 analogues, complexes 1 and 2.

First hyperpolarizability of Ru-half-sandwich complexes: The effect of halogen atom substitution on the ancillary ligand

The first hyperpolarizability (beta) of a series of half-sandwich Ru complexes with a mercaptobenzothiazole ligand bearing a halogen atom substitution in the para-position has been investigated by hyper-Rayleigh scattering and quantum chemical calculations. The heterocyclic ligand with a bromine atom in the para position makes it a very good donor and charge flows to the Ru center enhancing the beta value of the complex by a factor of 2 compared to the complex with the ligand without the halogen substitution. The resonance (+R) and the inductive (-I) effects exerted by the halogen atom in the para position push electrons in opposing directions in the complex. For the Br and Cl atoms the resonance effect dominates which enables the ligand to donate electrons to the metal center thereby increasing the hyperpolarizability whereas for the fluorine atom, the inductive effect is dominant which reduces the charge flow to the metal and the hyperpolarizability drops even below that of the unsubstituted ligand. This unprecedented halogen atom effect on beta of metal complexes is reported. (C) 2015 Elsevier By. All rights reserved.

Effect of the nature of a transition metal dopant in BaTiO3 perovskite on the catalytic reduction of nitrobenzene

In the present study, we have synthesized Fe, Co and Ni doped BaTiO3 catalyst by a wet chemical synthesis method using oxalic acid as a chelating agent. The concentration of the metal dopant varies from 0 to 5 mol% in the catalysts. The physical and chemical properties of doped BaTiO3 catalysts were studied using various analytical methods such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), BET surface area and Transmission electron microscopy (TEM). The acidic strength of the catalysts was measured using a n-butylamine potentiometric titration method. The bulk BaTiO3 catalyst exhibits a tetragonal phase with the P4mm space group. A structural transition from tetrahedral to cubic phase was observed for Fe, Co and Ni doped BaTiO3 catalysts with an increase in doped metal concentration from 1 to 5 mol%. The particle sizes of the catalysts were calculated from TEM images and are in the range of 30-80 nm. All the catalysts were tested for the catalytic reduction of nitrobenzene to azoxybenzene. The BaTiO3 catalyst was found to be highly active and less selective compared to the doped catalysts which are active and highly selective towards azoxybenzene. The increase in selectivity towards azoxybenzene is due to an increase in acidic strength and reduction ability of the doped metal. It was also observed that the nature of the metal dopant and their content at the B-site has an impact on the catalytic reduction of nitrobenzene. The Co doped BaTiO3 catalyst showed better activity with only 0.5 mol% doping than Fe and Ni doped BaTiO3 catalysts with maximum nitrobenzene conversion of 91% with 78% selectivity to azoxybenzene. An optimum Fe loading of 2.5 mol% in BaTiO3 is required to achieve 100% conversion with 93% selectivity whereas Ni with 5 mol% showed a conversion of 93% and a azoxybenzene selectivity of 84%.

Remarkable Effect of Chalcogen Substitution on an Enzyme Mimetic for Deiodination of Thyroid Hormones

Iodothyronine deiodinases are selenoenzymes which regulate the thyroid hormone homeostasis by catalyzing the regioselective deiodination of thyroxine (T4). Synthetic deiodinase mimetics are important not only to understand the mechanism of enzyme catalysis, but also to develop therapeutic agents as abnormal thyroid hormone levels have implications in different diseases, such as hypoxia, myocardial infarction, critical illness, neuronal ischemia, tissue injury, and cancer. Described herein is that the replacement of sulfur/selenium atoms in a series of deiodinase mimetics by tellurium remarkably alters the reactivity as well as regioselectivity toward T4. The tellurium compounds reported in this paper represent the first examples of deiodinase mimetics which mediate sequential deiodination of T4 to produce all the hormone derivatives including T0 under physiologically relevant conditions.

Pt-Doped and Pt-Supported La1-xSrxCoO3: Comparative Activity of Pt4+ and Pt-0 Toward the CO Poisoning Effect in Formic Acid and Methanol Electro-oxidation

Pt-supported La1-xSrxCoO3 and Pt-doped La1-xSrxCoO3 are synthesized using chemical reduction and solution combustion method, respectively. Chemical reduction is carried out using formaldehyde as a reducing agent giving Pt-supported La1-xSrxCoO3. Solution combustion method is used to prepare Pt-doped La1-xSrxCoO3. Detailed characterization using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) surface area measurement, and transmission electron microscopy (TEM) is carried out to distinguish the Pt-supported and Pt-doped compounds in terms of their morphology and Pt oxidations states. TEM results indeed show the differences in their morphology. Further, electrochemical measurements are performed in neutral medium to differentiate their electrochemical activity. Cyclic voltammetry (CV) shows noticeable differences between Pt-supported La1-xSrxCoO3 and Pt-doped La1-xSrxCoO3. Importantly, our results show that Pt4+ in doped compound has poor to zero electrocatalytic activity toward formic acid and methanol electro-oxidation in comparison to Pt-0 in supported compound. This study shows that metallic Pt in zero oxidation state is a superior catalyst to Pt in +4 oxidation state.

Effect of catchment characteristics on the relationship between past discharge and the power law recession coefficient

This study concerns the relationship between the power law recession coefficient k (in - dQ/dt = kQ(alpha), Q being discharge at the basin outlet) and past average discharge Q(N) (where N is the temporal distance from the center of the selected time span in the past to the recession peak), which serves as a proxy for past storage state of the basin. The strength of the k-Q(N) relationship is characterized by the coefficient of determination R-N(2), which is expected to indicate the basin's ability to hold water for N days. The main objective of this study is to examine how R-N(2) value of a basin is related with its physical characteristics. For this purpose, we use streamflow data from 358 basins in the United States and selected 18 physical parameters for each basin. First, we transform the physical parameters into mutually independent principal components. Then we employ multiple linear regression method to construct a model of R-N(2) in terms of the principal components. Furthermore, we employ step-wise multiple linear regression method to identify the dominant catchment characteristics that influence R-N(2) and their directions of influence. Our results indicate that R-N(2) is appreciably related to catchment characteristics. Particularly, it is noteworthy that the coefficient of determination of the relationship between R-N(2) and the catchment characteristics is 0.643 for N = 45. We found that topographical characteristics of a basin are the most dominant factors in controlling the value of R-N(2). Our results may be suggesting that it is possible to tell about the water holding capacity of a basin by just knowing about a few of its physical characteristics. (C) 2015 Elsevier B.V. All rights reserved.