(Table 2) Major and trace elements in black smoker particulates

We present geochemical data of black smoker particulates filtered from hydrothermal fluids with seawater-dilutions ranging from 0-99%. Results indicate the dominance of sulphide minerals (Fe, Cu, and Zn sulphides) in all samples taken at different hydrothermal sites on the Mid-Atlantic Ridge. Pronounced differences in the geochemistry of the particles between Logatchev I and 5°S hydrothermal fields could be attributed to differences in fluid chemistry. Lower metal/sulphur ratios (Me/H2S < 1) compared to Logatchev I result in a larger amount of particles precipitated per liter fluid and the occurrence of elemental sulphur at 5°S, while at Logatchev I Fe oxides occur in larger amounts. Systematic trends with dilution degree of the fluid include the precipitation of large amounts of Cu sulphides at a low dilution and a pronounced drop with increasing dilution. Moreover, Fe (sulphides or oxides) precipitation increases with dilution of the vent fluid by seawater. Geochemical reaction path modeling of hydrothermal fluid-seawater mixing and conductive cooling indicates that Cu sulphide formation at Logatchev I and 5°S mainly occurs at high temperatures and low dilution of the hydrothermal fluid by seawater. Iron precipitation is enhanced at higher fluid dilution, and the different amounts of minerals forming at 5°S and Logatchev I are thermodynamically controlled. Larger total amounts of minerals and larger amounts of sulphide precipitate during the mixing path when compared to the cooling path. Differences between model and field observations do occur and are attributable to closed system modeling, to kinetic influences and possibly to organic constituents of the hydrothermal fluids not accounted for by the model.

Geochemical composition of calcite and aragonite, and characteristics of hydrothermal fluids of ODP Leg 168 sites

During Leg 168 a transect was drilled across the eastern flank of the Juan de Fuca Ridge in an area where the volcanic basement is covered by sediments of variable thickness. Samples of basement volcanic rocks were recovered from nine locations along the transect, where the basement sediment interface is presently heated to temperatures varying from 15° to 64°C. Altered rocks with secondary calcium carbonate were common at four of the sites, where present-day temperatures range from 38° to 64°C. Fluid inclusions in aragonite suggest that the mineral precipitated from an aqueous fluid of seawater salinity at temperatures well below 100°C. The chemical compositions of secondary calcite and aragonite were determined with both an electron microprobe and a laser-ablation inductively coupled plasma-mass spectroscopy (LA-ICP-MS) microprobe. These two techniques yielded consistent analyses of the same minor elements (Mg and Sr) in the same specimens. The combined results show that secondary aragonites contain very little Mg, Mn, Fe, Co, Ni, Cu, Zn, Rb, La, Ce, Pb, or U, yet they contain significant Sr. In contrast, secondary calcites contain significant Mg, Mn, Fe, Ni, Cu, Zn, and Pb, yet very little Co, Rb, Sr, La, Ce, or U. Secondary calcium carbonates provide subseafloor reservoirs for some minor and trace elements. Replacement of aragonite by calcite should result in a release of Sr, Rb, and Zn to solution, and it provides a sink for Mg, Mn, Ni, Cu, Zn, and Pb.

(Table 1) Downcore age and bulk geochemistry of sediment core GS7202-35

The distribution of redox-sensitive metals in sediments is potentially a proxy for past ocean ventilation and productivity, but deconvolving these two major controls has proved difficult to date. Here we present a 740 kyr long record of trace element concentrations from an archived sediment core collected at ~15°S on the western flank of the East Pacific Rise (EPR) on 1.1 Myr old crust and underlying the largest known hydrothermal plume in the world ocean. The downcore trace element distribution is controlled by a variable diagenetic overprint of the inferred primary hydrothermal plume input. Two main diagenetic processes are operating at this site: redox cycling of transition metals and ferrihydrite to goethite transition during aging. The depth of oxidation in these sediments is controlled by fluctuations in the relative balance of bottom water oxygen and electron donor input (organic matter and hydrothermal sulfides). These fluctuations induce apparent variations in the accumulation of redox-sensitive species with time. Subsurface U and P peaks in glacial age sediments, in this and other published data sets along the southern EPR, indicate that basin-wide changes in deep ocean ventilation, in particular at glacial-interglacial terminations II, III, IV, and V, alter the depth of the oxidation front in the sediments. These basin-wide changes in the deep Pacific have significant implications for carbon partitioning in the ocean-atmosphere system, and the distribution of redox-sensitive metals in ridge crest sediment can be used to reconstruct past ocean conditions at abyssal depths in the absence of alternative proxy records.

Infrared spectra of trichloroacetates of copper, calcium, strontium and barium

Infrared spectra of trichloroacetates of Cu, Ca, Sr and Ba were studied in order to investigate the effect of coordination on the vibration spectra of the ligand. The shifts of the antisymmetric and symmetric COO- stretching frequencies are explained on the basis of the type of co-ordination of the COO- group to the metal ion. From the spectra it is established that the coordination of the COO- group to metal is different for trichloroacetates and monochloroacetates.

Better early osteogenesis of electroconductive hydroxyapatite-calcium titanate composites in a rabbit animal model

In view of the fact that bone healing can be enhanced due to external electric field application, it is important to assess the influence of the implant conductivity on the bone regeneration in vivo. To address this issue, this study reports the in vivo biocompatibility property of multistage spark plasma sintered hydroxyapatite (HA)-80 wt % calcium titanate (CaTiO3) composites and monolithic HA, which have widely different conductivity property (14 orders of magnitude difference). The ability of bone regeneration was assessed by implantation in cylindrical femoral bone defects of rabbit animal model for varying time period of 1, 4, and 12 weeks. The overall assessment of the histology results suggests that the progressive healing of bone defects around HA-80 wt % CaTiO3 is associated with a better efficacy with respect to (w.r.t) early stage neobone formation, which is histomorphometrically around 140% higher than monolithic HA. Overall, this study demonstrates that the in vivo biocompatibility property of HA-80 wt % CaTiO3 with respect to local effects after 12 weeks of implantation is not compromised both qualitatively and quantitatively, and a comparison with control implant (HA) points toward the critical role of electrical conductivity on better early stage bone regeneration. (c) 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 842-851, 2014.

Twinning induced enhancement of fracture toughness in ultrafine grained Hydroxyapatite-Calcium Titanate composites

Despite being highly bioactive and biocompatible, the limitations of monolithic hydroxyapatite (HA) include extremely low fracture toughness, poor electrical conductivity. While addressing these issues, the present study demonstrates how CaTiO3 (CT) addition to HA can be utilized to obtain a combination of long crack fracture toughness (1.7 MPa m(1/2) SEVNB technique) and flexural strength of 98-155 MPa (3-point bending) and a moderate tensile strength (diametral compression) of 17-36 MPa. The enhancement in fracture resistance in spark plasma sintered HA-CT composites has been explained in reference to the observed twin morphology. TEM reveals the presence of twins in CT grains due to 1800 rotation about 101]. The measured properties along with our earlier reports on biocompatibility and electrical properties make HA-CT suitable for bone tissue engineering applications. When compared with other competing HA-based biocomposites, HA-CT composites are found to have a better combination of properties useful for medium load bearing implant applications. (C) 2015 Elsevier Ltd. All rights reserved.

Copper phthalocyanine organic thin-film transistors with calcium fluoride gate insulator

We report the fabrication of organic thin-film transistors (OTFTs) with copper phthalocyanine (CuPc) as the semiconductor and calcium fluoride (CaF2) as the gate dielectric on the glass substrate. The fabricated transistors show a gate voltage dependent carrier field effect mobility that ranges from 0.001 to 0.5 cm(2) V-1 s(-1). In the devices, the CaF2 dielectric is formed by thermal evaporation; thus OTFTs with a top-gate structure can be fabricated. This provides a convenient way to produce high-performance OTFTs on a large scale and should be useful for the integration of organic displays.

Quenching of Photoactivity in Phthalocyanine Copper(II)-Titanate Nanotube Hybrid Systems

Titanate nanotubes (TiNTs) were obtained by hydrothermal treatment of anatase powder in aqueous NaOH solution and then modified with 2,9,16,23-tertracarboxyl phthalocyanine copper(H) (CuPc). This hybrid organic inorganic nanoscopic system was characterized by X-ray diffraction, microscopy, and spectroscopy. Transmission electron microscopy (TEM) images of pure and modified TiNTs revealed multiwall structures with an average outer diameter of 9 nm and a length of several hundred nanometers. The tubular morphology of the TiNTs was covered with CuPc-film. The amount of CuPc adsorbed onto the TiNTs was quantified by electron paramagnetic resonance (EPR). Using the same technique and spin-trapping methodology, the photogeneration of reactive oxygen species (ROS) from the TiNTs was systematically investigated. A drastic quenching of photoactivity was observed in the CuPc/TiNT hybrid system. Electron transfer from excited CuPc states to the TiNT conduction band followed by electron recombination may be the cause of this quenching.

Microstructural, dielectric and ferroelectric properties of calcium-modified lead titanate thin films derived by chemical processes

Ferroelectric Pb1-xCaxTiO3 (x = 0.24) thin films were formed on a Pt/Ti/SiO2/Si substrate by the polymeric precursor method using the dip-coating technique for their deposition. Characterization of the films bq X-ray diffraction showed a perovskite single phase with a tetragonal structure after annealing at 700 degreesC. Atomic force microscopy (AFM) analyses showed that the film had a smooth and crack-free surface with low surface roughness. In addition, the PCT thin film had a granular structure with an 80 nm grain size. The thickness of the films observed by the scanning electron microscopy (SEM) is 550 nm and there is a good adhesion between the film and substrate. For the electrical measurements metal-ferroelectric-metal of the type capacitors were obtained, where the thin films showed good dielectric and ferroelectric properties. The dielectric constant and dissipation factor at 1 kHz and measured at room temperature were found to be 457 and 0.03. respectively. The remanent polarization and coercive field for the: deposited films were P-r = 17 muC/cm(2) and E-c = 75 kV/cm, respectively. Moreover. The 550-nm-thick film showed a current density in the order of 10(-8) A/cm(2) at the applied voltage of 2 V. The high values of the thin film's dielectric properties are attributed to its excellent microstructural quality and the chemical homogeneity obtained by the polymeric precursor method. (C) 2001 Elsevier science Ltd. All rights reserved.