(Table 2) Trace metal concentrations in ODP Hole 169-1033B

We measured the concentrations of redox-sensitive trace metals (Mn, V, Mo, U, Cd and Re) in sediments from ODP Leg 169S Hole 1033B in Saanich Inlet, British Columbia, to determine changes in redox conditions associated with the onset of laminated sediments at ~12.5 kyr. The most striking result is a large peak in authigenic Re along with detrital levels of Mo at the glacial terrigenous clay-diatomaceous sediment transition. In contrast, the underlying glacial terrigenous clay, which extends throughout the bottom section of the core, is chemically similar to detrital concentrations, either Cowichan River particulates or average shale values. These data suggest a period of oxic bottom waters but reducing pore-waters. This could be due to the dramatic transformation of Saanich Inlet during the late deglaciation from an open bay to an inlet, which restricted circulation and slowed bottom water oxygen renewal. A peak and gradual increase in authigenic Mn in younger sediments subsequent to the Re peak suggests that increasingly oxic conditions followed the authigenic enrichment in Re. These conditions could be connected to the Younger Dryas cooling period, which was coincident with an increase in well oxygenated upwelled waters on the west coast of North America that form the bottom waters of Saanich Inlet. Metal concentrations in a gray clay bed (~11 kyr) are similar to their concentrations in the glacial terrigenous clay, implying that they have a common source. Authigenic enrichments of Re with little authigenic Mo and Cd suggest that before the deposition of this bed, bottom waters were oxic and pore-water oxygen was consumed in the top centimeter or less. Laminations above the clay layer suggest anoxic conditions, which are also indicated by higher authigenic Mo and Cd and slightly lower Re/Mo ratios in these sediments. The basin remained mostly anoxic after the gray clay was emplaced, as seen by continuous authigenic enrichment of the redox-sensitive trace metals. These results are consistent with increased stratification of the water column, brought about by an influx of fresh water to the basin by a large flood.

Total organic carbon, metal concentrations and metal and aluminium ratios in bulk sediment from the ODP sample 169-1033B-4H-4,54-74

Holocene laminated sediments in Saanich Inlet, British Columbia, are interrupted by frequent, non-laminated, massive layers. These layers may be debris flows released by earthquakes or bioturbated sediments deposited during periods of relatively high bottom water oxygen concentration and/or low surface productivity, or both. We determined the organic carbon content and the concentration of a suite of redox-sensitive metals in bulk sediments at approximately 1-cm resolution across a laminated-massive-laminated interval (ODP Leg 169S Sample 1033B-4H-4,54-74), to determine the redox conditions under which the massive layer was deposited. Our results indicate that this massive interval was deposited under anoxic bottom waters. Manganese/Al ratios are consistently low throughout the massive section, while Mo/Al, Cd/Al, Re/Al, and U/Al ratios are enriched relative to their metal/Al ratios in detrital material (represented by Cowichan River suspended sediments). The concentration of organic carbon in the lower portion of the massive layer is higher than in the upper portion, which has a concentration similar to that in the overlying and underlying laminated sediments. Well-defined peaks in Mo/Al, Cd/Al, and Re/Al and a broad peak in U/Al occur in the lower portion of the massive layer. The positions of the Cd/Al, Re/Al, and Mo/Al peaks, as well as the increase in organic carbon content with depth in the massive layer, are best explained by a process of diagenetic redistribution of metals that occurred after the massive layer was emplaced.

Effects of carbon nanotubes and metal catalysts on hydrogen storage in magnesium nanocomposites

This paper reports a study on nanostructured magnesium composites with carbon nanotubes (CNTs) and catalytic transition metals with high H-2 adsorption capacity and fast adsorption kinetics at reduced hydrogenation temperatures. Nanostructures in such a composite are shown to be responsible for improvements in both adsorption capacity and kinetics. It is found that the carbon nanotubes significantly increase the hydrogen storage capacity, and the catalytic transition metals (Fe and Ti) greatly improve the kinetics. This could be understood from the enhancement of diffusion by CNTs and decrease in energy barrier of hydrogen dissociation at the magnesium surface.

Organochlorine and heavy metal concentrations in blubber and liver tissue collected from Queensland (Australia) dugong (Dugong dugon)

Tissue samples of liver and blubber were salvaged from fifty-three dugong (Dugong dugon) carcasses stranded along the Queensland coast between 1996 and 2000. Liver tissue was analysed for a range of heavy metals and blubber samples were analysed for organochlorine compounds. Metal concentrations were similar in male and female animals and were generally highest in mature animals. Liver concentrations of arsenic, chromium, iron, lead, manganese, mercury and nickel in a number of individual animals were elevated in comparison to concentrations previously reported in Australian dugong. Dieldrin, DDT (and its breakdown products) and/or heptachlor epoxide were detected in 59% of dugong blubber samples. In general, concentrations of organochlorines were similar to those reported in dugong 20 years earlier, and were low in comparison to concentrations recorded from marine mammal tissue collected elsewhere in the world. With the exception of lead, the extent of carcass decomposition, the presence of disease or evidence of animal starvation prior to death did not significantly affect dugong tissue concentrations of metals or organochlorines. The results of the study suggest that bioaccumulation of metals and organochlorine compounds (other than dioxins) does not represent a significant risk to Great Barrier Reef dugong populations, particularly in the context of other pressures associated with coastal development and other anthropogenic activities. (c) 2004 Elsevier Ltd. All rights reserved.

Oxidation of organic compounds in molten salts

The objective of this research was to investigate the oxidation of organic compounds in molten alkali metal hydroxides containing manganates. It has been shown that controlled oxidation can be readily achieved with high specificity to give products in high yield with very short reaction times. The concurrent changes in the melt were monitored using a vibrating platinum indicator electrode with a quazi-reference electrode which was successfully developed for use in molten (Na-K)OH eutectic at 523K. Henry's Law constants for water in the molten eutectic system (Na-K)OH have been measured and used to calculate the water concentration in the melt. The electrochemistry of manganates in molten (Na-K)OH eutectic at 523K has been studied using the vibrating platinum electrode, and the existence of the species Mn(II), Mn(II!), Mn(IV), Mn(V) and Mn(VI) in such melts has been investigated at various water concentrations. The half-wave potentials of the voltammetric waves were measured versus the cathodic limit of the melt. The stability of Mn(V) or Mn(VI) in the melt was achieved by varying the water concentration. A range of organic chemicals has been passed through molten (Na-K)OH at 523K and the reactions of these chemicals with the melt have been studied. The same organics were then passed through molten (Na-K)OH containing stabilized Mn(V) or Mn{VI) without violent reaction. Methanol, allyl alcohol, propane 1, 2 diol, I-heptene and acetone were oxidized by Mn(V) and Mn(VI). Ethanol was only oxidized by Mn(VI), isopropanol and benzyl alcohol were only oxidized by Mn(V). Npropanol, butanol, 2 methyl propan-2-ol, n-hexane, n-heptane toluene and cyclohexane were unchanged by both Mn(V) and Mn(VI). Detailed experiments have been performed on the reactions of ethanol, iso-propanol and methanol in molten (Na-K)OH containing stabilized Mrt(V) or Mn(VI), and reaction mechanisms have been postulated. Ethanol and iso-propanol were oxidized to acetaldehyde and acetone respectively with a potential for useful chemical process. The oxidation of methanol could be developed as a basis for an industrial methanol disposal process.

The role of oxidation in the protection of sliding metal surfaces

This study is concerned with the mechanisms of growth and wear of protective oxide films formed under various tribological conditions. In the study three different tribological systems are examined in each of which oxidational wear is the dominant equilibrium mode. These are an unlubricated steel on steel system sliding at low and elevated temperatures, a boundary lubricated aluminium bronze on steel system and an unlubricated reciprocating sliding 9% Cr steel system operated at elevated temperature, in an atmosphere of carbon dioxide. The results of mechanical measurements of wear and friction are presented for a range of conditions of load, speed and temper.ature for the systems, together with the results of extensive examinations of the surfaces and sub­ surfaces by various physical methods of analysis. The major part of the thesis, however, is devoted to the development and application of surface models and theoretical quantative expressions in order to explain the observed oxidational wear phenomena. In this work, the mechanisms of formation of load bearing ox ide plateaux are described and are found to be dependent on system geometry and environment. The relative importance of ''in contact" and "out of contact" oxidation is identified together with growth rate constants appropriate to the two situations. Hypotheses are presented to explain the mechanisms of removal of plateaux to form wear debris. The latter hypotheses include the effects of cyclic stressing and dislocation accumulation, together with effects associated with the kinetics of growth and physical properties of the various oxides. The proposed surf ace mode1s have led to the develop­ ment of quantitative expressions for contact temperature, unlubricated wear rates, boundary lubricated wear rates and the wear of rna ter ial during the transition from severe to mild wear. In general theoretical predictions from these expressions are in very good agreement with experimental values.

Hypothesis: is Alzheimer's disease a metal-induced immune disorder?

A hypothesis that a metal-induced immune disorder may be involved in the pathogenesis of some forms of Alzheimer's disease (AD) is presented. The classical complement pathway is activated in AD and T cells and reactive microglia appear in the brain. Studies of metal induced autoimmunity and the use of compounds containing aluminium as vaccine adjuvants suggest that metals can activate complement and can be taken up by antigen presenting cells. The consequent immune response could contribute to neuronal damage, beta-amyloid deposition and cell death. The strengths and weaknesses of this hypothesis are discussed and tests of some aspects are proposed.

Observation of a 331 K (58 °C) spin transition for bis[hydrotris(1,2,4-triazol-1-yl)borate]iron(II) by variable temperature infrared spectroscopy and magnetic susceptibility measurements

Fe{HB(CHN)} is observed by variable temperature infrared and magnetic studies to have a spin transition between the low spin S = 0 and high spin S = 2 states at 331 K (58 °C) with thermal hysteresis of ~1.5 K. Changes in the triazole ligand IR absorptions demonstrate that distant non-metal-ligand vibrations are altered upon the change in electronic structure associated with the spin-crossover can be used to monitor the the spin-crossover transition.

A comparative study on the pyrolysis of metal- and ash-enriched wood and the combustion properties of the gained char

This study aims to investigate the pyrolysis behaviour of metal-contaminated wood and the combustion properties of char derived from wood pyrolysis. Seven metals (Na, Mg, Ca, Zn, Cd, Pb and Fe(III)) were introduced to willow in cation form by ion-exchange and the thermal behaviour of demineralised samples and samples with additional ash were also investigated. The results show that the char yield increased from 21% to 24-28% and levoglucosan yield in vapour phase decreased from 88% to 62-29% after the addition of inorganic compounds, even though the metal binding capacity of wood varied from one metal ion to another. While char yield seems to be effected mainly by the concentration of the metal ions, levoglucosan yield was more dependent on the ionic species especially when sodium ions were present. When combustion experiments were carried out with char made of the metal enriched wood, two consecutive steps were observed, both effected by the presence of inorganic compounds. The first step was identified as the release and combustion of volatiles, while the second peak of the burning profile is the actual combustion of the fixed carbon. The burnout temperatures, estimated ignition indices and the conversion indicate that the type and not the amount of metal ions were the determining factors during the second step of combustion. © 2012 Published by Elsevier B.V.

A new 3-D polymeric spin transition compound: [tris(1,4-bis-(tetrazol-1-yl) butane-N1,N1′)iron(II)] bis(perchlorate)

A series of novel polymeric compounds of formula [M(btzb)3][ClO4]2 (Mll = Fe, Ni or Cu) with btzb = 1,4-bis-(tetrazol-1-yl)butane have been prepared and their physical properties investigated. The btzb ligand has been prepared and its crystal structure determined, together with a tentative crystal structure of the 3-D compound [Fe(btzb)3][ClO4]2. The model of the latter shows two symmetry-related, interpenetrating Fe-btzb networks in which the iron(II) ions approach each other as close as 8.3 and 9.1 Å. This supramolecular catenane undergoes a sharp thermal spin transition around 160 K with hysteresis (20 K) along with a pronounced thermochromic effect. The spin crossover behaviour has been followed by magnetic, DSC, optical spectroscopy and 57Fe Mössbauer spectroscopy measurements. Irradiation with green light at low temperature leads to population of the metastable high-spin state for the thermally active iron(ll) ions. The nature of the spin crossover behaviour has been discussed in detail.

Asymmetric reactions of organosilicon compounds and properties of novel optically active organosilanes

Partial reduction of racemic methoxysilanes by 1:1 complexes of lithium aluminium hydride with optically active cinchona and ephedra alkaloids give optically active silanes and methoxysilanes. Optical yields depend on the groups attached to silicon and the alkaloid used but in some cases approach 50%, The method has been used to prepare novel optically active organosilanes, possessing an asymmetric silicon centre, which are either inaccessible by any of the other available routes or would require a time consuming preparation. Such compounds are of use in the study of the mechanism of substitutions at silicon. Attempts have been made to rationalize the results of the asymmetric reductions in terms of differences in sterio and electronic interactions in diastereoisomeric transition states. Circular dichroism and optical rotatory dispersion spectra have been obtained for the optically active products in an attempt to elucidate the absolute configurations of the novel asymmetric organosilanes. The results from these studies provide a useful addition to the data so far accumulated for asymmetrically perturbed aromatic chromophores. Nuclear magnetic resonanoe studies of diastereoisomaric (-)-menthoxysilanes show that these compounds possess resonances extremely useful in the determination of optical purities for asymmetric organosilanes which possess an aromatic group. The effect of variable temperature on the spectra has revealed evidence for the conformational preferences in these compounds. Other diastereoisomeric alkoxysilanes have been prepared and their n.m.r.spectra studied in the hope of establishing trends. Exploratory studies for other asymmetric reactions proceeding at silicon have proved unfruitful.

Spin transition of 1D, 2D and 3D iron(II) complex polymers - the tug-of-war between elastic interaction and a shock-absorber effect

The structures of linear chain Fe(II) spin-crossover compounds of α,β- and α,ω-bis (tetrazol-1-yl)alkane type ligands are described in relation to their magnetic properties. The first threefold interlocked 3-D catenane Fe(II) spin-transition system, [μ-tris(1,4-bis(tetrazol-1-yl)butane-N1,N1′) iron(II)] bis(perchlorate), will be discussed. An analysis is made among the structures and the cooperativity of the spin-crossover behaviour of polynuclear Fe(II) spin-transition materials.

HW Implementation of a Optimized Algorithm for the Application of Active Rules in a Transition P-system

P systems or Membrane Computing are a type of a distributed, massively parallel and non deterministic system based on biological membranes. They are inspired in the way cells process chemical compounds, energy and information. These systems perform a computation through transition between two consecutive configurations. As it is well known in membrane computing, a configuration consists in a m-tuple of multisets present at any moment in the existing m regions of the system at that moment time. Transitions between two configurations are performed by using evolution rules which are in each region of the system in a non-deterministic maximally parallel manner. This work is part of an exhaustive investigation line. The final objective is to implement a HW system that evolves as it makes a transition P-system. To achieve this objective, it has been carried out a division of this generic system in several stages, each of them with concrete matters. In this paper the stage is developed by obtaining the part of the system that is in charge of the application of the active rules. To count the number of times that the active rules is applied exist different algorithms. Here, it is presents an algorithm with improved aspects: the number of necessary iterations to reach the final values is smaller than the case of applying step to step each rule. Hence, the whole process requires a minor number of steps and, therefore, the end of the process will be reached in a shorter length of time.

Vacuum brazing of alumina ceramic to titanium for biomedical implants using pure gold as the filler metal

One of the many promising applications of metal/ceramic joining is in biomedical implantable devices. This work is focused on vacuum brazing of C.P titanium to 96% alumina ceramic using pure gold as the filler metal. A novel method of brazing is developed where resistance heating of C.P titanium is done inside a thermal evaporator using a Ta heating electrode. The design of electrode is optimized using Ansys resistive heating simulations. The materials chosen in this study are biocompatible and have prior history in implantable devices approved by FDA. This research is part of Boston Retinal implant project to make a biocompatible implantable device (www.bostonretina.org). ^ Pure gold braze has been used in the construction of single terminal feedthrough in low density hermetic packages utilizing a single platinum pin brazed to an alumina or sapphire ceramic donut (brazed to a titanium case or ferrule for many years in implantable pacemakers. Pure gold (99.99%) brazing of 96% alumina ceramic with CP titanium has been performed and evaluated in this dissertation. Brazing has been done by using electrical resistance heating. The 96% alumina ceramic disk was manufactured by high temperature cofired ceramic (HTCC) processing while the Ti ferrule and gold performs were purchased from outside. Hermetic joints having leak rate of the order of 1.6 × 10-8 atm-cc/ sec on a helium leak detector were measured. ^ Alumina ceramics made by HTCC processing were centreless grounded utilizing 800 grit diamond wheel to provide a smooth surface for sputtering of a thin film of Nb. Since pure alumina demonstrates no adhesion or wetting to gold, an adhesion layer must be used on the alumina surface. Niobium (Nb), Tantalum (Ta) and Tungsten (W) were chosen for evaluation since all are refractory (less dissolution into molten gold), all form stable oxides (necessary for adhesion to alumina) and all are readily thin film deposited as metals. Wetting studies are also performed to determine the wetting angle of pure gold to Ti, Ta, Nb and W substrates. Nano tribological scratch testing of thin film of Nb (which demonstrated the best wetting properties towards gold) on polished 96% alumina ceramic is performed to determine the adhesion strength of thin film to the substrate. The wetting studies also determined the thickness of the intermetallic compounds layers formed between Ti and gold, reaction microstructure and the dissolution of the metal into the molten gold.^

Estudo de complexos de ferro e de cobre com a base de Shiff 3-Meosalen e ligantes de relevância biológica

The goal set for this work was to synthesize and to characterize new iron and copper complexes with the Schiff base 3-MeOsalen and ligands of biological relevance, whose formulas are [Fe(3-MeOsalen)NO2], [Fe(3-MeOsalen)(etil2-dtc)], [Fe(3-MeOsalen)NO] and Na[Cu(3-MeOsalen)NO2]. The compounds were characterized by vibrational spectroscopy in the infrared region (IV) and Electronic spectroscopy in the ultraviolet and visible region (Uv-Vis). From the analysis of infrared spectra, they proved to formation of precursor complexes, as evidenced by changes in the vibrationals frequencies ν(C=N) e ν(C-O) and the emergence of vibrationals modes metal-oxygen and metal-nitrogen. For nitro complexes of iron and copper were observed ν(NO2)ass around 1300 cm-1 e ν(NO2)sim in 1271 cm-1 , indicating that the coordination is done via the nitrogen atom. The complex spectrum [Fe(3-MeOsalen)(etil2-dtc)] exhibited two bands, the ν(C-NR2) in 1508 cm-1 e ν(C-S) in 997 cm-1 , the relevant vibrational modes of coordinating ligand in the bidentate form. For the complex [Fe(3-MeOsalen)NO] was observed a new intense band in 1670 cm-1 related to the ν(NO). With the electronic spectra, the formation of complexes was evidenced by shifts of bands intraligands transitions and the emergence of new bands such as LMCT (p Cl-  d* Fe3+) in [Fe(3-MeOsalen)Cl] and the d-d in [Cu(3-MeOsalen)H2O]. As for the [Fe(3-MeOsalen)NO2] has highlighted the absence of LMCT band present in the precursor complex as for the [Cu(3-MeOsalen)NO2] found that the displacement of the band hipsocrômico d-d on 28 nm. The electronic spectrum of [Fe(3-MeOsalen)(etil2-dtc)] presented LMCT band shifts and changes in intraligantes transitions. With regard to [Fe(3-MeOsalen)NO], revealed a more energetic transitions intraligands regions from the strong character π receiver NO and MLCT band of transition dπFe(II)π*(NO).