Low temperature charge transport and microwave absorption of carbon coated iron nanoparticles-polymer composite films

In this paper, the low temperature electrical conductivity and microwave absorption properties of carbon coated iron nanoparticles-polyvinyl chloride composite films are investigated for different filler fractions. The filler particles are prepared by the pyrolysis of ferrocene at 980 degrees C and embedded in polyvinyl chloride matrix. The high resolution transmission electron micrographs of the filler material have shown a 5 nm thin layer graphitic carbon covering over iron particles. The room temperature electrical conductivity of the composite film changes by 10 orders of magnitude with the increase of filler concentration. A percolation threshold of 2.2 and an electromagnetic interference shielding efficiency (EMI SE) of similar to 18.6 dB in 26.5-40 GHz range are observed for 50 wt% loading. The charge transport follows three dimensional variable range hopping conduction. (C) 2012 Elsevier Ltd. All rights reserved.

Iron(III) Chloride-Catalysed Aerobic Reduction of Olefins using Aqueous Hydrazine at Ambient Temperature

A chemoselective reduction of olefins and acetylenes is demonstrated by employing catalytic amounts of ferric chloride hexahydrate (FeCl3 center dot 6H(2)O) and aqueous hydrazine (NH2NH2 center dot H2O) as hydrogen source at room temperature. The reduction is chemoselective and tolerates a variety of reducible functional groups. Unlike other metal-catalysed reduction methods, the present method employs a minimum amount of aqueous hydrazine (1.5-2 equiv.). Also, the scope of this method is demonstrated in the synthesis of ibuprofen in aqueous medium.

Cyclodextrin functionalized magnetic iron oxide nanocrystals: a host-carrier for magnetic separation of non-polar molecules and arsenic from aqueous media

A single-step magnetic separation procedure that can remove both organic pollutants and arsenic from contaminated water is clearly a desirable goal. Here we show that water dispersible magnetite nanoparticles prepared by anchoring carboxymethyl-beta-cyclodextrin (CMCD) cavities to the surface of magnetic nanoparticles are suitable host carriers for such a process. Monodisperse, 10 nm, spherical magnetite, Fe3O4, nanocrystals were prepared by the thermal decomposition of FeOOH. Trace amounts of antiferromagnet, FeO, present in the particles provides an exchange bias field that results in a high superparamagnetic blocking temperature and appreciable magnetization values that facilitate easy separation of the nanocrystals from aqueous dispersions on application of modest magnetic fields. We show here that small molecules like naphthalene and naphthol can be removed from aqueous media by forming inclusion complexes with the anchored cavities of the CMCD-Fe3O4 nanocrystals followed by separation of the nanocrystals by application of a magnetic field. The adsorption properties of the iron oxide surface towards As ions are unaffected by the CMCD capping so it too can be simultaneously removed in the separation process. The CMCD-Fe3O4 nanocrystals provide a versatile platform for magnetic separation with potential applications in water remediation.

Optimal Control of Markov Processes with Age-Dependent Transition Rates

We study optimal control of Markov processes with age-dependent transition rates. The control policy is chosen continuously over time based on the state of the process and its age. We study infinite horizon discounted cost and infinite horizon average cost problems. Our approach is via the construction of an equivalent semi-Markov decision process. We characterise the value function and optimal controls for both discounted and average cost cases.

Nuclear targeting terpyridine iron(II) complexes for cellular imaging and remarkable photocytotoxicity

Iron(II) complexes Fe(L)(2)](2+) as perchlorate (1-3) and chloride (1a-3a) salts, where L is 4'-phenyl-2,2':6',2 `'-terpyridine (phtpy in 1, 1a), 4'-(9-anthracenyl)-2,2':6',2 `'-terpyridine (antpy in 2, 2a) and 4'-(1-pyrenyl)-2,2':6',2 `'-terpyridine (pytpy in 3, 3a), were prepared and their photocytotoxicity studied. The diamagnetic complexes 1-3 having an FeN6 core showed an Fe(III)-Fe(II) redox couple near 1.0 V vs. saturated calomel electrode in MeCN-0.1 M tetrabutylammonium perchlorate. Complexes 2 and 3, in addition, displayed a quasi-reversible ligand-based redox process near 0.0 V. The redox and spectral properties are rationalized from the theoretical studies. The complexes bind to DNA in a partial intercalative mode. The pytpy complex efficiently photo-cleaves DNA in green light via superoxide and hydroxyl radical formation. The antpy and pytpy complexes exhibited a remarkable photocytotoxic effect in HeLa cancer cells (IC50, similar to 9 mu M) in visible light (400-700 nm), while remaining essentially nontoxic in dark (IC50, similar to 90 mu M). Formation of reactive oxygen species (ROS) inside the HeLa cells was evidenced from the fluorescence enhancement of dichlorofluorescein upon treatment with the pytpy complex followed by photo-exposure. The antpy and pytpy complexes were used for cellular imaging. Confocal imaging and dual staining study using propidium iodide (PI) showed nuclear localization of the complexes. (c) 2012 Elsevier Inc. All rights reserved.

Acoustic and optical phonon dynamics from femtosecond time-resolved optical spectroscopy of the superconducting iron pnictide Ca(Fe0.944Co0.056)(2)As-2

We report the temperature evolution of coherently excited acoustic and optical phonon dynamics in the superconducting iron pnictide single crystal Ca(Fe0.944Co0.056)(2)As-2 across the spin density wave transition at T-SDW similar to 85 K and the superconducting transition at T-SC similar to 20 K. The strain pulse propagation model applied to the generation of the acoustic phonons yields the temperature dependence of the optical constants, and longitudinal and transverse sound velocities in the temperature range from 3.1 K to 300 K. The frequency and dephasing times of the phonons show anomalous temperature dependence below T-SC indicating a coupling of these low-energy excitations with the Cooper-pair quasiparticles. A maximum in the amplitude of the acoustic modes at T similar to 170 is seen, attributed to spin fluctuations and strong spin-lattice coupling before T-SDW. Copyright (c) EPLA, 2012

Synthesis of zero valent iron nanoparticles and application to removal of arsenic(III) and arsenic(V) from water

Recently nano scale zero valent iron particles (nZVI) have been considered as smart adsorbent for environmental and groundwater remediation. Although several synthetic methods are available for the preparation of nZVI, air stable nZVI are not available for remediation works. Further, challenges demand synthesis of nZVI without stabilizers and capping agents. A modified methodology for the synthesis of air stable nZVI has been developed without any capping agents and characterized by powder X-Ray Diffraction (XRD), Scanning Electron Microscopy Energy-dispersive X-Ray (SEM-EDS), Transmission Electron Microscopy (TEM) and X-Ray Photoelectron Spectroscopy (XPS). The results of the present study suggest that the synthetic nZVI are air-stable over a period of one year and consists of particles of 30-40 nm in diameter. Although a layer of less than 3 am thick oxide/hydroxide is observed by TEM and XPS, it appears to be due to oxidation of outer surface during analysis. Adsorption study has shown that the synthetic nZVI are more effective adsorbent than the commercial nZVI and can remove simultaneously arsenite As-III] and arsenate As-V] from water without prior reduction of As-V to As-III. The removal process is adsorptive rather than precipitative and the removal of As-III is greater than that of As-V.

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.

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.

Modeling harvest rates and numbers from age and sex ratios: A demonstration for elephant populations

Illegal harvest rates of wildlife populations are often unknown or difficult to estimate from field data due to under-reporting or incomplete detection of carcasses. This is especially true for elephants that are killed for ivory or in conflicts with people. We describe a method to infer harvest rates from coarse field data of three population parameters, namely, adult female to male ratio, male old-adult to young-adult ratio, and proportion of adult males in the population using Jensen's (2000) 2-sex, density-dependent Leslie matrix model. The specific combination of male and female harvest rates and numbers can be determined from the history of harvest and estimate of population size. We applied this technique to two populations of elephants for which data on age structure and records of mortality were available-a forest-dwelling population of the Asian elephant (at Nagarahole, India) and an African savannah elephant population (at Samburu, Kenya) that had experienced male-biased harvest regimes over 2-3 decades. For the Nagarahole population, the recorded numbers of male and female elephants killed illegally during 1981-2000 were 64% and 88% of the values predicted by the model, respectively, implying some non-detection or incomplete reporting while for the Samburu population the recorded and modeled numbers of harvest during 1990-1999 closely matched. This technique, applicable to any animal population following logistic growth model, can be especially useful for inferring illegal harvest numbers of forest elephants in Africa and Asia.

Synthesis of pure iron magnetic nanoparticles in large quantity

Free nanoparticles of iron (Fe) and their colloids with high saturation magnetization are in demand for medical and microfluidic applications. However, the oxide layer that forms during processing has made such synthesis a formidable challenge. Lowering the synthesis temperature decreases rate of oxidation and hence provides a new way of producing pure metallic nanoparticles prone to oxidation in bulk amount (large quantity). In this paper we have proposed a methodology that is designed with the knowledge of thermodynamic imperatives of oxidation to obtain almost oxygen-free iron nanoparticles, with or without any organic capping by controlled milling at low temperatures in a specially designed high-energy ball mill with the possibility of bulk production. The particles can be ultrasonicated to produce colloids and can be bio-capped to produce transparent solution. The magnetic properties of these nanoparticles confirm their superiority for possible biomedical and other applications.

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.

A Rodinian suture in western India: New insights on India-Madagascar correlations

We report detailed evidence for a new paleo-suture zone (the Kumta suture) on the western margin of southern India. The c. 15-km-wide, westward dipping suture zone contains garnet-biotite, fuchsite-haematite, chlorite-quartz, quartz-phengite schists, biotite augen gneiss, marble and amphibolite. The isochemical phase diagram estimations and the high-Si phengite composition of quartz-phengite schist suggest a near-peak condition of c. 18 kbar at c. 550 degrees C, followed by near-isothermal decompression. The detrital SHRIMP U-Pb zircon ages from quartz-phengite schist give four age populations ranging from 3280 to 2993 Ma. Phengite from quartz-phengite schist and biotite from garnet-biotite schist have K-Ar metamorphic ages of ca. 1326 and ca. 1385 Ma respectively. Electron microprobe-CHIME ages of in situ zircons in quartz-phengite schist (ca. 3750 Ma and ca. 1697 Ma) are consistent with the above results. The Bondla ultramafic-gabbro complex in the west of the Kumta suture compositionally represents an arc with K-Ar biotite ages from gabbro in the range 1644-1536 Ma. On the eastern side of the suture are weakly deformed and unmetamorphosed shallow westward-dipping sedimentary rocks of the Sirsi shelf, which has the following upward stratigraphy: pebbly quartzite/sandstone, turbidite, magnetite iron formation, and limestone; farther east the lower lying quartzite has an unconformable contact with ca. 2571 Ma quartzo-feldspathic gneisses of the Dharwar block with a ca. 1733 Ma biotite cooling age. To the west of the suture is a c. 60-km-wide Karwar block mainly consisting of tonalite-trondhjemite-granodiorite (TTG) and amphibolite. The TTGs have U-Pb zircon magmatic ages of ca. 3200 Ma with a rare inherited core age of ca. 3601 Ma. The K-Ar biotite cooling age from the TTGs (1746 Ma and 1796 Ma) and amphibolite (ca. 1697 Ma) represents late-stage uplift. Integration of geological, structural and geochronological data from western India and eastern Madagascar suggest diachronous ocean closure during the amalgamation of Rodinia; in the north at around ca. 1380 Ma, and a progression toward the south until ca. 750 Ma. Satellite imagery based regional structural lineaments suggests that the Betsimisaraka suture continues into western India as the Kumta suture and possibly farther south toward a suture in the Coorg area, representing in total a c. 1000 km long Rodinian suture. (C) 2013 Elsevier B.V. All rights reserved.