Direct conversion of calcium carbonate to C-1-C-3 hydrocarbons

With the objective of investigating the direct conversion of inorganic carbonates such as CaCO3 to hydrocarbons, assisted by transition metal ions, we have carried out studies on CaCO3 in an intimate admixture with iron oxides (FeCaCO) with a wide range of Fe/Ca mole ratios (x), prepared by co-precipitation. The hydrogen reduction of FeCaCO at 673 K gives up to 23% yield of the hydrocarbons CH4, C2H4, C2H6 and C3H8, leaving solid iron residues in the form of iron metal, oxides and carbide particles. The yield of hydrocarbons increases with x and the conversion of hydrocarbons occurs through the formation of CO. While the total yield of hydrocarbons obtained by us is comparable to that in the Fischer-Tropsch synthesis, the selectivity for C-2-C-3 hydrocarbons reported here is noteworthy.

Fine scale characterization of surface/subsurface and nanosized debris particles on worn Cu-10 % Pb nanocomposites

The identification of the damage mechanisms involved in the wear process demands the finer scale characterization of the surface, as well as the subsurface region of the wear scar region, and to this end, this article discusses the results obtained with Cu-10 wt% Pb-based metallic nanocomposites using a host of characterization techniques, including transmission electron microscopy and ion milling microscopy. Apart from finer scale characterization to understand deformation and cracking during the wear process, X-ray photoelectron spectroscopy analysis of wear debris confirms the occurrence of oxidation of Pb phase to Pb3O4. In order to understand the role of oxides on friction and wear, sliding wear tests in argon were also carried out and such tests did not result in the formation of any tribo-oxides, as confirmed using electron probe microanalysis. Conclusively, oxidative wear is attributed as the dominant wear mechanism in ambient conditions for Cu-10 wt% Pb composite.

Ultrafast quasiparticle relaxation dynamics in superconducting iron pnictide Ca(Fe0.944Co0.056)(2)As-2

Nonequilibrium quasiparticle relaxation dynamics is reported in superconducting Ca(Fe0.944Co0.056)(2)As-2 single crystals by measuring transient reflectivity changes using femtosecond time-resolved pump-probe spectroscopy. Large changes in the temperature-dependent differential reflectivity values in the vicinity of the spin density wave (T-SDW) and superconducting (T-SC) transition temperatures of the sample have been inferred to have charge gap opening at those temperatures. We have estimated the zero-temperature charge gap value in the superconducting state to be similar to 1.8k(B)T(SC) and an electron-phonon coupling constant lambda of similar to 0.1 in the normal state that signifies the weak coupling in iron pnictides. From the peculiar temperature-dependence of the quasiparticle dynamics in the intermediate temperature region between T-SC and T-SDW we infer a temperature scale where the charge gap associated with the spin ordered phase is maximum and closes on either side while approaching the two phase transition temperatures.

Anomalous magnetic behavior of La0.6Sr0.4MnO3 nano-tubes constituted with 3-12 nm particles

Uniform La0.6Sr0.4MnO3 (LSMO) nanotubes of an average diameter 180 nm were synthesized by a modified sol-gel method employing nanochannel porous anodic alumina templates. The nanotubes were characterized chemically and structurally by XRD, SEM, EDX, and TEM. Postannealed (700 degrees C for 1 h hour) nanotubes were found to be polycrystalline from XRD and SAED studies. To get further insight into the nanotube structure, HRTEM studies were done, which revealed that obtained LSMO nanotubes were structurally constituted with nanoparticles of 3-12 nm size. These constituent nanoparticles were randomly aligned and self-knitted to build the nanotube wall. Investigation of magnetic properties at this structured nanoscale revealed remarkable irreversibility between the zero field cooling (ZFC) and field cooling (FC) magnetization curves accompanied with a peak in the ZFC curve indicating spin-glass-like behavior. Structural defects and compositional variations at surfaces and grain-boundaries of constituent nanoparticles might be responsible for this anomalous magnetic behavior.

Characterization and magnetic response of multiwall carbon nanotubes filled with iron nanoparticles of different aspect ratios

Three samples of multiwall carbon nanotubes (MWCNT) TF200, TF150 and TF100, where T and F stand for toluene and ferrocene respectively, and numeral denotes the amount (mg) of ferrocene] filled with iron-nanoparticles (Fe-NPs) of different aspect ratios are grown by chemical vapor deposition of toluene-ferrocene mixture. Energy dispersive X-ray analysis shows a systematic variation in the intensities of peak corresponding to Fe, indicating that Fe is present in different amounts in the three MWCNT samples. The lengths of Fe-NPs lie in the range of 200-250; 80-120; and 30-40 nm for TF200, TF150 and TF100, respectively, as estimated statistically from transmission electron microscopy micrographs. However, the diameter of the encapsulated Fe-NPs does not vary significantly for different samples and is 20-30 nm for all samples. Hysteresis loop measurements on these MWCNT samples were done at 10, 150 and 300 K up to an applied field of 1.5 T. At 10 K, values of coercivity are 2584, 2315, and 2251 Oe for TF200, TF150 and TF100 respectively. This is attributed to the strong shape anisotropy of the Fe-NPs and significant dipolar interactions between them. Further, M-H loops reveal that saturation magnetization of TF200 is almost four times that of TF100 at all temperatures.

Biotin-conjugated tumour-targeting photocytotoxic iron(III) complexes

Iron(III) complexes FeL(B)] (1-4) of a tetradentate phenolate-based ligand (H3L) and biotin-conjugated dipyridophenazine bases (B), viz. 7-aminodipyrido 3,2-a: 2',3'-c]-phenazine (dppza in 1), (N-dipyrido3,2-a: 2',3'-c]-phenazino) amidobiotin (dppzNB in 2), dipyrido 3,2-a: 2',3'-c]-phenazine-11-carboxylic acid (dppzc in 3) and 2-((2-biotinamido) ethyl) amidodipyrido 3,2-a: 2',3'-c]-phenazine (dppzCB in 4) are prepared, characterized and their interaction with streptavidin and DNA and their photocytotoxicity and cellular uptake in various cells studied. The high-spin iron(III) complexes display Fe(III)/Fe(II) redox couple near -0.7V versus saturated calomel electrode in dimethyl sulfoxide-0.1M tetrabutylammonium perchlorate. The complexes show non-specific interaction with DNA as determined from the binding studies. Complexes with appended biotin moiety show similar binding to streptavidin as that of free biotin, suggesting biotin conjugation to dppz does not cause any loss in its binding affinity to streptavidin. The photocytotoxicity of the complexes is tested in HepG2, HeLa and HEK293 cell lines. Complex 2 shows higher photocytotoxicity in HepG2 cells than in HeLa or HEK293, forming reactive oxygen species. This effect is attributed to the presence of overexpressed sodium-dependent multi-vitamin transporters in HepG2 cells. Microscopic studies in HepG2 cells show internalization of the biotin complexes 2 and 4 essentially occurring by receptor-mediated endocytosis, which is similar to that of native biotin and biotin fluorescein isothiocyanate conjugate.

Spatial memory deficits in maternal iron deficiency paradigms are associated with altered glucocorticoid levels

``The goal of this study was to examine the effect of maternal iron deficiency on the developing hippocampus in order to define a developmental window for this effect, and to see whether iron deficiency causes changes in glucocorticoid levels. The study was carried out using pre-natal, post-natal, and pre + post-natal iron deficiency paradigm. Iron deficient pregnant dams and their pups displayed elevated corticosterone which, in turn, differentially affected glucocorticoid receptor (GR) expression in the CA1 and the dentate gyrus. Brain Derived Neurotrophic Factor (BDNF) was reduced in the hippocampi of pups following elevated corticosterone levels. Reduced neurogenesis at P7 was seen in pups born to iron deficient mothers, and these pups had reduced numbers of hippocampal pyramidal and granule cells as adults. Hippocampal subdivision volumes also were altered. The structural and molecular defects in the pups were correlated with radial arm maze performance; reference memory function was especially affected. Pups from dams that were iron deficient throughout pregnancy and lactation displayed the complete spectrum of defects, while pups from dams that were iron deficient only during pregnancy or during lactation displayed subsets of defects. These findings show that maternal iron deficiency is associated with altered levels of corticosterone and GR expression, and with spatial memory deficits in their pups.'' (C) 2013 Elsevier Inc. All rights reserved.

Developments in Biotechnology for Environmentally Benign Iron Ore Beneficiation

Biomineralization and biogenesis of iron ore deposits are illustrated in relation to indigenous microorganisms inhabiting iron ore mines. Aerobic and anaerobic microorganisms indigenous to iron oxide mineralization are analyzed. Microbially-induced flotation and flocculation of iron ore minerals such as hematite, alumina, calcite and quartz are discussed with respect to use of four types of microorganisms, namely, Paenibacillus polymyxa, Bacillus subtilis, Saccharomyces cerevisiae and Desulfovibrio desulfuricans. The role of the above organisms in the removal of silica, alumina, clays and apatite from hematite is illustrated with respect to mineral-specific bioreagents, surface chemical changes and microbe-mineral interaction mechanisms. Silica and alumina removal from real iron ores through biobeneficiation is outlined. Environmental benefits of biobeneficiation are demonstrated with respect to biodegradation of toxic reagents and environmentally-safe waste disposal and processing.

Melting and solidification behavior of Pb-Sn embedded alloy nano-particles

Nano-sized bimetallic dispersoids consisting of (Pb) and beta-(Sn) phases of eutectic composition (Pb26.1Sn73.9) embedded in aluminum and Al-Cu-Fe quasicrystalline matrices have been prepared by rapid solidification processing. The two phases, face centered cubic (Pb) and body center tetragonal, beta-(Sn) solid solution co-exist in all the embedded nanoparticles at room temperature. The phases bear crystallographic orientation relationship with the matrix. In situ TEM study has been carried out for the alloy particles to study the melting and the solidification behavior. The detailed microscopic observations indicate formation of a single-phase metastable fcc (Pb) in the nano-particles prior to the melting during heating. Solidification of these particles begins with nucleation of fcc (Pb), which phase separates into fcc (Pb) and beta-(Sn) lamellae in the solid state. In situ X-ray diffraction study is carried out to obtain lattice parameter of metastable fcc (Pb) and thereby an estimate of amount of Sn dissolved in the metastable (Pb) prior to the melting. The results are discussed in terms of a metastable phase diagram between fcc Pb and fcc Sn and invoking the size effect on the metastable phase diagram. The size factor is found to play a critical role in deciding the pathway of phase transformation as well as the extension of solid solubility of Sn in fcc (Pb) in the nano-particles.

The N-terminal region containing the zinc finger domain of tobacco streak virus coat protein is essential for the formation of virus-like particles

Tobacco streak virus (TSV), a member of the genus Ilarvirus (family Bromoviridae), has a tripartite genome and forms quasi-isometric virions. All three viral capsids, encapsidating RNA 1, RNA 2 or RNA 3 and subgenomic RNA 4, are constituted of a single species of coat protein (CP). Formation of virus-like particles (VLPs) could be observed when the TSV CP gene was cloned and the recombinant CP (rCP) was expressed in E. coli. TSV VLPs were found to be stabilized by Zn2+ ions and could be disassembled in the presence of 500 mM CaCl2. Mutational analysis corroborated previous studies that showed that an N-terminal arginine-rich motif was crucial for RNA binding; however, the results presented here demonstrate that the presence of RNA is not a prerequisite for assembly of TSV VLPs. Instead, the N-terminal region containing the zinc finger domain preceding the arginine-rich motif is essential for assembly of these VLPs.

Carbohydrate-Appended Tumor Targeting Iron(III) Complexes Showing Photocytotoxicity in Red Light

Glucose-appended photocytotoxic iron(III) complexes of a tridentate Schiff base phenolate ligand Fe(bpyag) (L)] (NO3) (1-3), where bpyag is N,N-bis(2- pyridylmethyl)-2-aminoethyl-beta-D-glucopyranoside and H2L is 3-(2-hydroxyphenylimino)-1-phenylbutan-1-one (H(2)phap) in 1, 3-(2-hydroxyphenylimino)-9-anthrylbutan-1-one (H(2)anap) 2, and 3- (2-hydroxyphenylimino)-1-pyrenylbutan-1-one (H(2)pyap) in 3, were synthesized and characterized. The complex Fe(dpma)(anapn(NO3) (4), having bis-(2-pyridylmethyl)benzylamine (dpma), in which the glucose moiety of bpyag is substituted by a phenyl group, was used as a control, and the complex Fe(dpma)(anap)](PF6) (4a) was structurally characterized by X-ray crystallography. The structure shows a FeN4O2 core in a distorted octahedral geometry. The high-spin iron(III) complexes with magnetic moment value of similar to 5.9 mu(B) showed a low-energy phenolate-to-Fe(III) charge-transfer (CT) absorption band as a shoulder near 500 nm with a tail extending to 700 nm and an irreversible Fe(III)-Fe(II) redox couple near -0.6 V versus saturated calomel electrode. The complexes are avid binders to calf thymus DNA and showed photocleavage of supercoiled pUC19 DNA in red (647 nm) and green (532 nm) light. Complexes 2 and 3 displayed significant photocytotoxicity in red light, with an IC50 value of similar to 20 mu M in HeLa and HaCaT cells, and no significant toxicity in dark. The cell death is via an apoptotic pathway, by generation of reactive oxygen species. Preferential internalization of the carbohydrate-appended complexes 2 and 3 was evidenced in HeLa cells as compared to the control complex 4. A 5-fold increase in the cellular uptake was observed for the active complexes in HeLa cells. The photophysical properties of the complexes are rationalized from the density functional theory calculations.

An in situ carbon-grafted alkaline iron electrode for iron-based accumulators

An in situ carbon-grafted alkaline iron electrode prepared from the active material obtained by decomposing the alpha-FeC2O4 center dot 2H(2)O-polyvinyl alcohol (PVA) composite at 600 degrees C in a vacuum is reported. The active material comprises a mixture of a-Fe and Fe3O4 with the former as the prominent component. A specific discharge capacity in excess of 400 mA h g(-1) at a current density of 100 mA g(-1) is obtained with a faradaic efficiency of 80% for the iron electrode made from carbon-grafted active material (CGAM). The enhanced performance of the alkaline iron electrode is attributed to the increased amount of metallic iron in the active material and its concomitant in situ carbon grafting.

Influence of surface area to volume ratio of fuel particles on gasification process in a fixed bed

The paper addresses the effect of particle size on tar generation in a fixed bed gasification system. Pyrolysis, a diffusion limited process, depends on the heating rate and the surface area of the particle influencing the release of the volatile fraction leaving behind residual char. The flaming time has been estimated for different biomass samples. It is found that the flaming time for wood flakes is almost one fourth than that of coconut shells for same equivalent diameter fuel samples. The particle density of the coconut shell is more than twice that of wood spheres, and almost four times compared with wood flakes; having a significant influence on the flaming time. The ratio of the particle surface area to that of an equivalent diameter is nearly two times higher for flakes compared with wood pieces. Accounting for the density effect, on normalizing with density of the particle, the flaming rate is double in the case of wood flakes or coconut shells compared with the wood sphere for an equivalent diameter. This is due to increased surface area per unit volume of the particle. Experiments are conducted on estimation of tar content in the raw gas for wood flakes and standard wood pieces. It is observed that the tar level in the raw gas is about 80% higher in the case of wood flakes compared with wood pieces. The analysis suggests that the time for pyrolysis is lower with a higher surface area particle and is subjected to fast pyrolysis process resulting in higher tar fraction with low char yield. Increased residence time with staged air flow has a better control on residence time and lower tar in the raw gas. (C) 2014 International Energy Initiative. Published by Elsevier Inc. All rights reserved.

Iron(III) benzhydroxamates of dipicolylamines for photocytotoxicity in red light and cellular imaging

Benzhydroxamate (BHA) iron(III) complexes Fe(BHA)(L)ClICI (I, 2)], where L is (phenyl)dipicolylamine (phdpa in I) and (pyrenyl)dipicolylamine (pydpa in 2), were prepared and their photocytotoxicity in visible (400-700 nm) and red (600-720 nm) light was studied. Complex 1 was structurally characterized by X-ray crystallography. The complexes have high-spin iron(III) centers. Complex 2, with a pyrenyl fluorophore, was used for cellular imaging, showing both mitochondrial and nuclear localization in the fluorescence microscopic study. The complex exhibited photocytotoxicity in red light in HeLa cancer cells, giving IC50 value of 24.4(+/- 0.4) pM, but remained essentially non-toxic in the dark. The involvement of reactive oxygen species and an apoptotic nature of cell death were observed from the cellular studies. (C) 2014 Elsevier Ltd. All rights reserved.