High Oxygen Storage Capacity and High Rates of CO Oxidation and NO Reduction Catalytic Properties of Ce1-xSnxO2 and Ce0.78Sn0.2Pd0.02O2-delta

Ce1-xSnxO2 (x = 0.1-0.5) solid solution and its Pd substituted analogue have been prepared by a single step solution combustion method using tin oxalate precursor. The compounds were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and H-2/temperature programmed redution (TPR) studies. The cubic fluorite structure remained intact up to 50% of Sri substitution in CeO2, and the compounds were stable up to 700 C. Oxygen storage capacity of Ce1-xSnxO2 was found to be much higher than that of Ce1-xZrxO2 due to accessible Ce4+/Ce3+ and Sn4+/Sn2+ redox couples at temperatures between 200 and 400 C. Pd 21 ions in Ce0.78Sn0.2Pd0.02O2-delta are highly ionic, and the lattice oxygen of this catalyst is highly labile, leading to low temperature CO to CO2 conversion. The rate of CO oxidation was 2 mu mol g(-1) s(-1) at 50 degrees C. NO reduction by CO with 70% N-2 selectivity was observed at similar to 200 degrees C and 100% N-2 selectivity below 260 degrees C with 1000-5000 ppm NO. Thus, Pd2+ ion substituted Ce1-xSnxO2 is a superior catalyst compared to Pd2+ ions in CeO2, Ce1-xZrxO2, and Ce1-xTixO2 for low temperature exhaust applications due to the involvement of the Sn2+/Sn4+ redox couple along with Pd2+/Pd-0 and Ce4+/Ce3+ couples.

Sonochemical synthesis of Ce1-xFexO2-delta (0 <= x <= 0.45) and Ce0.65Fe0.33Pd0.02O2-delta nanocrystallites: oxygen storage material, CO oxidation and water gas shift catalyst

Nanocrystalline Ce1-xFexO2-delta (0 <= x <= 0.45) and Ce0.65Fe0.33Pd0.02O2-delta of similar to 4 nm sizes were synthesized by a sonochemical method using diethyletriamine (DETA) as a complexing agent. Compounds were characterized by powder X-ray diffraction (XRD), X-ray photo-electron spectroscopy (XPS) and transmission electron microscopy (TEM). Ce1-xFexO2-delta (0 <= x <= 0.45) and Ce0.65Fe0.33Pd0.02O2-delta crystallize in fluorite structure where Fe is in +3, Ce is in +4 and Pd is in +2 oxidation state. Due to substitution of smaller Fe3+ ion in CeO2, lattice oxygen is activated and 33% Fe substituted CeO2 i.e. Ce0.67Fe0.33O1.835 reversibly releases 0.31O] up to 600 degrees C which is higher or comparable to the oxygen storage capacity of CeO2-ZrO2 based solid solutions (Catal. Today 2002, 74, 225-234). Due to interaction of redox potentials of Pd2+/0(0.89 V) and Fe3+/2+ (0.77 V) with Ce4+/3+ (1.61 V), Pd ion accelerates the electron transfer from Fe2+ to Ce4+ in Ce0.65Fe0.33Pd0.02O1.815, making it a high oxygen storage material as well as a highly active catalyst for CO oxidation and water gas shift reaction. The activation energy for CO oxidation with Ce0.65Fe0.33Pd0.02O1.815 is found to be as low as 38 kJ mol(-1). Ce0.67Fe0.33O1.835 and Ce0.65Fe0.33Pd0.02O1.815 have also shown high activity for the water gas shift reaction. CO conversion to CO2 is 100% H-2 specific with these catalysts and conversion rate was found to be as high 27.2 mu moles g(-1) s(-1) and the activation energy was found to be 46.4 kJ mol(-1) for Ce0.65Fe0.33Pd0.02O1.815.

Influence of Substrate Temperature and Deposition Rate on Structural and Mechanical Properties of Shape Memory NiTi Films

NiTi thin films deposited by DC magnetron sputtering of an alloy (Ni/Ti:45/55) target at different deposition rates and substrate temperatures were analyzed for their structure and mechanical properties. The crystalline structure, phase-transformation and mechanical response were characterized by X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC) and Nano-indentation techniques, respectively. The films were deposited on silicon substrates maintained at temperatures in the range 300 to 500 degrees C and post-annealed at 600 degrees C for four hours to ensure film crystallinity. Films deposited at 300 degrees C and annealed for 600 degrees C have exhibited crystalline behavior with Austenite phase as the prominent phase. Deposition onto substrates held at higher deposition temperatures (400 and 500 degrees C) resulted in the co-existence of Austenite phase along with Martensite phase. The increase in deposition rates corresponding to increase in cathode current from 250 to 350 mA has also resulted in the appearance of Martensite phase as well as improvement in crystallinity. XRD analysis revealed that the crystalline film structure is strongly influenced by process parameters such as substrate temperature and deposition rate. DSC results indicate that the film deposited at 300 degrees C had its crystallization temperature at 445 degrees C in the first thermal cycle, which is further confirmed by stress temperature response. In the second thermal cycle the Austenite and Martensite transitions were observed at 75 and 60 degrees C respectively. However, the films deposited at 500 degrees C had the Austenite and Martensite transitions at 73 and 58 degrees C, respectively. Elastic modulus and hardness values increased from 93 to 145 GPa and 7.2 to 12.6 GPa, respectively, with increase in deposition rates. These results are explained on the basis of change in film composition and crystallization. (C) 2010 Published by Elsevier Ltd

Combustion synthesis and properties of Ce1-xPrxO2-delta red ceramic pigments

Praseodymium-doped ceria red pigments, Ce1−xPrxO2−δ, x=0–0.5 have been prepared by the thermal decomposition of the redox compound Ce1−xPrx(N2H3COO)3·3H2O as well as by the combustion of aqueous solutions containing cerous nitrate, praseodymium nitrate and oxalyl dihydrazide (ODH)/ammonium acetate. Formation of the pigment has been confirmed by its characteristic red colour and reflectance spectra which shows the reflection edge not, vert, similar690 nm corresponding to charge transfer from the ligand orbitals to the localised 4f1 of Pr4+. The particulate properties of praseodymium-doped ceria pigments obtained from the combustion of redox compounds and redox mixtures are compared.

Magnetic Field Dependence of Entropy And Specific Heat of YBa2Cu3O7-delta Superconductors

The change in thermodynamic quantities (e. g., entropy, specific heat etc.) by the application of magnetic field in the case of the high-T-c superconductor YBCO system is examined phenomenological by the Ginzburg-Landau theory of anisotropic type-II superconductors. An expression for the change in the entropy (Delta S) and change in specific heat (Delta C) in a magnetic field for any general orientation of an applied magnetic field B-a with respect to the crystallographic c-axis is obtained. The observed large reduction of specific heat anomaly just below the superconducting transition and the observed variation of entropy with magnetic field are explained quantitatively.

Tectono-geomorphic and environmental set-up deduced during deposition of Mio-Pleistocene sediments in NW Himalaya, India

Detailed pedofacies characterization along-with lithofacies investigations of the Mio-Pleistocene Siwalik sediments exposed in the Ramnagar sub-basin have been studied so as to elucidate variability in time and space of fluvial processes and the role of intra- and extra-basinal controls on fluvial sedimentation during the evolution of the Himalayan foreland basin (HFB). Dominance of multiple, moderately to strongly developed palaeosol assemblages during deposition of Lower Siwalik (similar to 12-10.8 Ma) sediments suggest that the HFB was marked by Upland set-up of Thomas et al. (2002). Activity of intra-basinal faults on the uplands and deposition of terminal fans at different times caused the development of multiple soils. Further, detailed pedofacies along-with lithofacies studies indicate prevalence of stable tectonic conditions and development of meandering streams with broad floodplains. However, the Middle Siwalik (similar to 10.8-4.92 Ma) sub-group is marked by multistoried sandstones and minor mudstone and mainly weakly developed palaeosols, indicating deposition by large braided rivers in the form of megafans in a Lowland set-up of Thomas et al. (2002). Significant change in nature and size of rivers from the Lower to Middle Siwalik at similar to 10 Ma is found almost throughout of the basin from Kohat Plateau (Pakistan) to Nepal because the Himalayan orogeny witnessed its greatest tectonic upheaval at this time leading to attainment of great heights by the Himalaya, intensification of the monsoon, development of large rivers systems and a high rate of sedimentation, hereby a major change from the Upland set-up to the Lowland set-up over major parts of the HFB. An interesting geomorphic environmental set-up prevailed in the Ramnagar sub-basin during deposition of the studied Upper Siwalik (similar to 4.92 to <1.68 Ma) sediments as observed from the degree of pedogenesis and the type of palaeosols. In general, the Upper Siwalik sub-group in the Ramnagar sub-basin is subdivided from bottom to top into the Purmandal sandstone (4.92-4.49 Ma), Nagrota (4.49-1.68 Ma) and Boulder Conglomerate (<1.68 Ma) formations on the basis of sedimentological characters and change in dominant lithology. Presence of mudstone, a few thin gravel beds and dominant sandstone lithology with weakly to moderately developed palaeosols in the Purmandal sandstone Fm. indicates deposition by shallow braided fluvial streams. The deposition of mudstone dominant Nagrota Fm. with moderately to some well developed palaeosols and a zone of gleyed palaeosols with laminated mudstones and thin sandstones took place in an environment marked by numerous small lakes, water-logged regions and small streams in an environment just south of the Piedmont zone, perhaps similar to what is happening presently in the Upland region/the Upper Gangetic plain. This area is locally called the `Trai region' (Pascoe, 1964). Deposition of Boulder Conglomerate Fm. took place by gravelly braided river system close to the Himalayan Ranges. Activity along the Main Boundary Fault led to progradation of these environments distal-ward and led to development of on the whole a coarsening upward sequence. (C) 2014 Elsevier B.V. All rights reserved.

Origin of activation of Lattice Oxygen and Synergistic Interaction in Bimetal-Ionic Ce0.89Fe0.1Pd0.01O2-delta Catalyst

Flourite-type nanocrystalline Ce0.9Fe0.1O2-delta and Ce0.89Fe0.1Pd0.01O2-delta solid solutions have been synthesized by solution combustion method,'.which show higher oxygen storage/release property (OSC) compared to CeO2 and Ce0.8Zr0.2O2. Temperature programmed reduction an XPS study reveal that the presence of Pd ion in Ce0.9Fe0.1O2-delta facilitates complete reduction of Fe3+ to Fe2+ state and partial reduction of Ce4+ to Ce3+ state at.temperatures as low as 105 degrees C compared to 400 degrees C for monometal-ionic Ce0.9Fe0.1O2-delta. Fe3+ ion is reduced to Fe2+ and not to Feo due to favorable redox potential for Ce4+ + Fe2+ -> Ce3+ + Fe3+ reaction. Using first-principles density functional theory calculation we determine M-O (M = Pd, Fe, Ce) bond lengths, and find that bond lengths vary from shorter (2.16 angstrom) to longer (2.9 angstrom) bond distances compared to mean Ce-O bond distance of 2.34 angstrom. for CeO2. Using these results in bond valence analysis, we show that oxygen with bond valences as low as -1.55 are created, leading to activation of lattice oxygen in the bimetal ionic catalyst. Temperatures of CO oxidation and NO reduction by CO/H-2 are lower with the bimetalionic Ce0.89Fe0.1Pd0.01O2-delta catalyst compared to monometal-ionic Ce0.9Fe0.1O2-delta and Ce0.99Pd0.01O2-delta catalysts. From XPS studies of Pd impregnated on CeO2 and Fe2O3 oxides, we show that the synergism leading to low temperature activation of lattice oxygen in bimetal-ionic catalyst Ce0.89Fe0.1Pd0.01O2-delta is due to low-temperature reduction of Pd2+ to Pd-0, followed by Pd-0 + 2Fe(3+) -> Pd2+ + 2Fe(2+), Pd-0 + 2Ce(4+) -> Pd2+ + 2Ce(3+) redox reaction.

CD4+ alpha beta T cell and gamma delta T cell responses to Mycobacterium tuberculosis. Similarities and differences in Ag recognition, cytotoxic effector function, and cytokine production.

CD4+ and gamma delta T cells are activated readily by Mycobacterium tuberculosis. To examine their role in the human immune response to M. tuberculosis, CD4+ and gamma delta T cells from healthy tuberculin-positive donor were studied for patterns of Ag recognition, cytotoxicity, and cytokine production in response to M. tuberculosis-infected mononuclear phagocytes. Both T cell subsets responded to intact M. tuberculosis and its cytosolic Ags. However, CD4+ and gamma delta T cells differed in the range of cytosolic Ags recognized: reactivity to a wide m.w. range of Ags for CD4+ T cells, and a restricted pattern for gamma delta T cells, with dominance of Ags of 10 to 15 kDa. Both T cell subsets were equally cytotoxic for M. tuberculosis-infected monocytes. Furthermore, both CD4+ and gamma delta T cells produced large amounts of IFN-gamma: mean pg/ml of IFN-gamma in supernatants was 2458 +/- 213 for CD4+ and 2349 +/- 245 for gamma delta T cells. By filter-spot ELISA (ELISPOT), the frequency of IFN-gamma-secreting gamma delta T cells was one-half of that of CD4+ T cells in response to M. tuberculosis, suggesting that gamma delta T cells on a per cell basis were more efficient producers of IFN-gamma than CD4+ T cells. In contrast, CD4+ T cells produced more IL-2 than gamma delta T cells, which correlated with diminished T cell proliferation of gamma delta T cells compared with CD4+ T cells. These results indicate that CD4+ and gamma delta T cell subsets have similar effector functions (cytotoxicity, IFN-gamma production) in response to M. tuberculosis-infected macrophages, despite differences in the Ags recognized, IL-2 production, and efficiency of IFN-gamma production.

Metal-insulator transition and giant magnetoresistance in La1-xMnO3-delta thin films and superlattices

The first fabrication of self-doped La1-xMnO3-delta films which are unique among the other La(1-x)M(x)MnO(3) (M = Ca, Ba and Pb) thin films showing giant magnetoresistance is reported. Ag-doped La0.7MnO3-delta films were grown on LaAlO3[100] substrates. These films show ferromagnetic and metal-insulator transition at 220 K and exhibit giant magnetoresistance (GMR) with Delta R/R(o) = 85% and Delta R/R(H) > 550%. Without silver addition these self-doped films are non-magnetic, Enhancement in GMR up to 8% has been observed in superlattices having alternate magnetic and non-magnetic La1-xMnO3-delta layers.

ATP release and autocrine signaling through P2X4 receptors regulate gamma delta T cell activation

Purinergic signaling plays a key role in a variety of physiological functions, including regulation of immune responses. Conventional alpha beta T cells release ATP upon TCR cross-linking; ATP binds to purinergic receptors expressed by these cells and triggers T cell activation in an autocrine and paracrine manner. Here, we studied whether similar purinergic signaling pathways also operate in the ``unconventional'' gamma delta T lymphocytes. We observed that gamma delta T cells purified from peripheral human blood rapidly release ATP upon in vitro stimulation with anti-CD3/CD28-coated beads or IPP. Pretreatment of gamma delta T cells with (10)panx-1, CBX, or Bf A reversed the stimulation-induced increase in extracellular ATP concentration, indicating that panx-1, connexin hemichannels, and vesicular exocytosis contribute to the controlled release of cellular ATP. Blockade of ATP release with (10)panx-1 inhibited Ca2+ signaling in response to TCR stimulation. qPCR revealed that gamma delta T cells predominantly express purinergic receptor subtypes A2a, P2X1, P2X4, P2X7, and P2Y11. We found that pharmacological inhibition of P2X4 receptors with TNP-ATP inhibited transcriptional up-regulation of TNF-alpha and IFN-gamma in gamma delta T cells stimulated with anti-CD3/CD28-coated beads or IPP. Our data thus indicate that purinergic signaling via P2X4 receptors plays an important role in orchestrating the functional response of circulating human gamma delta T cells. J. Leukoc. Biol. 92: 787-794; 2012.

Diurnal and seasonal variation of mixing ratio and delta C-13 of air CO2 observed at an urban station Bangalore, India

We present here observations on diurnal and seasonal variation of mixing ratio and delta C-13 of air CO2, from an urban station-Bangalore (BLR), India, monitored between October 2008 and December 2011. On a diurnal scale, higher mixing ratio with depleted delta C-13 of air CO2 was found for the samples collected during early morning compared to the samples collected during late afternoon. On a seasonal scale, mixing ratio was found to be higher for dry summer months (April-May) and lower for southwest monsoon months (June-July). The maximum enrichment in delta C-13 of air CO2 (-8.04 +/- 0.02aEuro degrees) was seen in October, then delta C-13 started depleting and maximum depletion (-9.31 +/- 0.07aEuro degrees) was observed during dry summer months. Immediately after that an increasing trend in delta C-13 was monitored coincidental with the advancement of southwest monsoon months and maximum enrichment was seen again in October. Although a similar pattern in seasonal variation was observed for the three consecutive years, the dry summer months of 2011 captured distinctly lower amplitude in both the mixing ratio and delta C-13 of air CO2 compared to the dry summer months of 2009 and 2010. This was explained with reduced biomass burning and increased productivity associated with prominent La Nina condition. While compared with the observations from the nearest coastal and open ocean stations-Cabo de Rama (CRI) and Seychelles (SEY), BLR being located within an urban region captured higher amplitude of seasonal variation. The average delta C-13 value of the end member source CO2 was identified based on both diurnal and seasonal scale variation. The delta C-13 value of source CO2 (-24.9 +/- 3aEuro degrees) determined based on diurnal variation was found to differ drastically from the source value (-14.6 +/- 0.7aEuro degrees) identified based on seasonal scale variation. The source CO2 identified based on diurnal variation incorporated both early morning and late afternoon sample; whereas, the source CO2 identified based on seasonal variation included only afternoon samples. Thus, it is evident from the study that sampling timing is one of the important factors while characterizing the composition of end member source CO2 for a particular station. The difference in delta C-13 value of source CO2 obtained based on both diurnal and seasonal variation might be due to possible contribution from cement industry along with fossil fuel / biomass burning as predominant sources for the station along with differential meteorological conditions prevailed.

Peptide delta-Turn: Literature Survey and Recent Progress

Among the various types of a-peptide folding motifs, delta-turn, which requires a central cis-amide disposition, has been one of the least extensively investigated. In particular, this main-chain reversal topology has been studied in-depth neither in linear/cyclic peptides nor in proteins. This Minireview article assembles and critically analyzes relevant data from a literature survey on the d-turn conformation in those compounds. Unpublished results from recent conformational energy calculations and a preliminary solution-state analysis on a small model peptide, currently ongoing in our laboratories, are also briefly outlined.