Quarternary tephra layers in sediment cores from the Bellingshausen Sea and Scotia Sea

The Southern Ocean is a region of the world's ocean which is fundamental to the generation of cold deep ocean water which drives the global therrno-haline circulation. Previous investigations of deep-sea sediments south of the Polar Front have been significantly constrained by the lack of a suitable correlation and dating technique. In this study, deep-sea sediment cores from the Bellingshausen, Scotia and Weddell seas have been investigated for the presence of tephra layers. The major oxide and trace element composition of glass shards have been used to correlate tephra isochrons over distances in excess of 600 km. The source volcanoes for individual tephra layers have been identified. Atmospheric transport distances greater than 1500 km for >32 pm shards are reported. One megascopic tephra is identified and correlated across 7 sediment drifts on the continental rise in the Bellingshausen Sea. Its occurrence in a sedimentary unit that has been biostratigraphically dated to delta 18O substage 5e identifies it as a key regional marker horizon for that stage. An unusual bimodal megascopic ash layer erupted from Deception Island, South Shetland Islands, has been correlated between 6 sediment cores which form a 600 km NE-SW transect from the central Scotia Sea to Jane Basin. This megascopic ash layer has been 14C dated at c. 10,670 years BP. It represents the last significant input of tephra into the Scotia Sea or Jane Basin from that volcano and forms an important early Holocene marker horizon for the region. Five disseminated tephras can be correlated to varying extents across the central Scotia Sea cores. Together with the megascopic tephra they form a tephrostratigraphic framework that will greatly aid palaeoclimatic, palaeoenvironrnental and palaeoceanographic investigations in the region.

Solid-state synthesis of embedded single-crystal metal oxide and phosphate nanoparticles and in situ crystallization

A new solid state organometallic route to embedded nanoparticle-containing inorganic materials is shown, through pyrolysis of metal-containing derivatives of cyclotriphosphazenes. Pyrolysis in air and at 800 °C of new molecular precursors gives individual single-crystal nanoparticles of SiP2O7, TiO2, P4O7, WP2O7 and SiO2, depending on the precursor used. High resolution transmission electron microscopy investigations reveal, in most cases, perfect single crystals of metal oxides and the first nanostructures of negative thermal expansion metal phosphates with diameters in the range 2–6 nm for all products. While all nanoparticles are new by this method, WP2O7 and SiP2O7 nanoparticles are reported for the first time. In situ recrystallization formation of nanocrystals of SiP2O7 was also observed due to electron beam induced reactions during measurements of the nanoparticulate pyrolytic products SiO2 and P4O7. The possible mechanism for the formation of the nanoparticles at much lower temperatures than their bulk counterparts in both cases is discussed. Degrees of stabilization from the formation of P4O7 affects the nanocrystalline products: nanoparticles are observed for WP2O7, with coalescing crystallization occurring for the amorphous host in which SiP2O7 crystals form as a solid within a solid. The approach allows the simple formation of multimetallic, monometallic, metal-oxide and metal phosphate nanocrystals embedded in an amorphous dielectric. The method and can be extended to nearly any metal capable of successful coordination as an organometallic to allow embedded nanoparticle layers and features to be deposited or written on surfaces for application as high mobility pyrophosphate lithium–ion cathode materials, catalysis and nanocrystal embedded dielectric layers.

Interdigitating organic bilayers direct the short interlayer spacing in hybrid organic–inorganic layered vanadium oxide nanostructures

Layered metal oxides provide a single-step route to sheathed superlattices of atomic layers of a variety of inorganic materials, where the interlayer spacing and overall layered structure forms the most critical feature in the nanomaterials’ growth and application in electronics, health, and energy storage. We use a combination of computer simulations and experiments to describe the atomic-scale structure, dynamics and energetics of alkanethiol-intercalated layered vanadium oxide-based nanostructures. Molecular dynamics (MD) simulations identify the unusual substrate-constrained packing of the alkanethiol surfactant chains along each V2O5 (010) face that combines with extensive interdigitation between chains on opposing faces to maximize three-dimensional packing in the interlayer regions. The findings are supported by high resolution electron microscopy analyses of synthesized alkanethiol-intercalated vanadium oxide nanostructures, and the preference for this new interdigitated model is clarified using a large set of MD simulations. This dependency stresses the importance of organic–inorganic interactions in layered material systems, the control of which is central to technological applications of flexible hybrid nanomaterials.

Atomic layer structure of vanadium oxide nanotubes grown on nanourchin structures

We report the detailed characterization of high quality vanadium oxide (VOx) nanotubes (NTs) and highlight the zipping of adjacent vanadate layers in such NTs formed on remarkable nanourchin structures. These nanostructures consist of high-density spherical radial arrays of NTs. The results evidence vanadate NTs with unprecedented uniformity and evidences the first report of vanadate atomic layer zipping. The NTs are ∼2 μm in length with inner diameters of 20-30 nm. The tube walls comprise scrolled triplet-layers of vanadate intercalated with organic surfactant. Such high-volume structures might be useful as open-access electrolyte scaffolds for lithium insertion-based charge storage devices.

Miocene to Pleistocene gluconite-rich layers of the US Mid-Atlantic margin

Glauconite is generally agreed to be a reliable indicator of low sedimentation rate, but little systematic work has been done to specify the role of glauconite in a sequence-stratigraphic framework. Ocean Drilling Program Leg 174A recovered a good record of late Tertiary sediments along the shelf edge of the New Jersey US Atlantic margin, and glauconite was present in many intervals of the cores, sometimes in vertical proximity to sequence boundaries. Leg 174A glauconite was analyzed with binocular microscope, XRD and SEM to determine the percent of potassium and degree of maturity in order to relate occurrence to depositional environment. Seismic data were used to locate sequence boundaries, and percent glauconite was visually estimated. Glauconite samples from Site 1073 were found to have formed within a lowstand systems tract (LST), and as part of a distal condensed section (CS) within a transgressive systems tract (TST). These results are comparable to those from nearby Site 903 of Leg 150, which indicate a similar depositional setting for glauconite. Glauconites at shelf Sites 1071 and 1072 likely formed in the TST as well. Onshore, glauconite occurs mainly in transgressive systems tracts. The Miocene appears to be the upper limit of glauconite formation onshore. As the magnitude of sea-level change decreased, present onshore locations became too nearshore to maintain sediment-free environments, and the zone of glauconite deposition moved seaward. The same process did not occur offshore until the Plio-Pleistocene. Low subsidence-rate margins such as the US Atlantic are subject more to the variations of sea-level than to changes in sediment supply, tectonics, or other factors influencing their depositional patterns. Although glauconite occurrence is widespread in the stratigraphic record, this study demonstrates that for low subsidence-rate margins, primary deposition of glauconite is largely restricted to the TST.

Multiferroic Iron Oxide Thin Films at Room Temperature

Multiferroic behaviour at room temperature is demonstrated in ε-Fe2O3. The simple composition of this new ferromagnetic ferroelectric oxide and the discovery of a robust path for its thin film growth by using suitable seed layers may boost the exploitation of ε-Fe2O3 in novel devices.

Comparison of adhesion layers of gold on silicate glasses for SERS detection

Gold is one of the most widely used metals for building up plasmonic devices. Although slightly less efficient than silver for producing sharp resonance, its chemical properties make it one of the best choices for designing sensors. Sticking gold on a silicate glass substrate requires an adhesion layer, whose effect has to be taken into account. Traditionally, metals (Cr or Ti) or dielectric materials (TiO2 or Cr2O3 ) are deposited between the glass and the nanoparticle. Recently, indium tin oxide and (3-mercaptopropyl)trimethoxysilane (MPTMS) were used as a new adhesion layer. The aim of this work is to compare these six adhesion layers for surface- enhanced Raman scattering sensors by numerical modeling. The near-field and the far-field optical responses of gold nanocylinders on the different adhesion layers are then calculated. It is shown that MPTMS leads to the highest field enhancement, slightly larger than other dielectric materials. We attributed this effect to the lower refractive index of MPTMS compared with the others.

Use of Sludge as Ceramic Materials

Nowadays, with increase amounts of sludge derived from the treatment of domestic sewage put pressure into research on systems for the adequate use of these materials. The aim of the present work is to study the use of sludge ash, from sintering and calcinated process, as a raw material for the ceramic industry. Using the sewage sludge ashes as ceramic raw material there will be no contamination of soil and underground water. Metals and toxic compounds like Al, Fe, Ba, Cr, Cu, Mn and Zn oxides were analyzed and characterized by X-ray fluorescence (XRF), scanning electron microscopy (SEM) and plasma emission spectroscopy (ICP-OES). The leached material was chemically analyzed where the integration of oxides into the ceramic matrix of sludge ash was observed. Residual decomposition was analyzed by TG, DTG and DTA curves.

DEVELOPMENT OF LI+ AND NA+ CONDUCTING CERAMICS AND CERAMIC STRUCTURES FOR USE IN SOLID STATE BATTERIES

A solid state lithium metal battery based on a lithium garnet material was developed, constructed and tested. Specifically, a porous-dense-porous trilayer structure was fabricated by tape casting, a roll-to-roll technique conducive to high volume manufacturing. The high density and thin center layer (< 20 μm) effectively blocks dendrites even over hundreds of cycles. The microstructured porous layers, serving as electrode supports, are demonstrated to increase the interfacial surface area available to the electrodes and increase cathode loading. Reproducibility of flat, well sintered ceramics was achieved with consistent powderbed lattice parameter and ball milling of powderbed. Together, the resistance of the LLCZN trilayer was measured at an average of 7.6 ohm-cm2 in a symmetric lithium cell, significantly lower than any other reported literature results. Building on these results, a full cell with a lithium metal anode, LLCZN trilayer electrolyte, and LiCoO2 cathode was cycled 100 cycles without decay and an average ASR of 117 ohm-cm2. After cycling, the cell was held at open circuit for 24 hours without any voltage fade, demonstrating the absence of a dendrite or short-circuit of any type. Cost calculations guided the optimization of a trilayer structure predicted that resulting cells will be highly competitive in the marketplace as intrinsically safe lithium batteries with energy densities greater than 300 Wh/kg and 1000 Wh/L for under $100/kWh. Also in the pursuit of solid state batteries, an improved Na+ superionic conductor (NASICON) composition, Na3Zr2Si2PO12, was developed with a conductivity of 1.9x10-3 S/cm. New super-lithiated lithium garnet compositions, Li7.06La3Zr1.94Y0.06O12 and Li7.16La3Zr1.84Y0.16O12, were developed and studied revealing insights about the mechanisms of conductivity in lithium garnets.

Caracterização Microestrutural e Tribocorrosiva de Sistemas Metalocerâmicos Odontológicos do Tipo Ni-Cr/Porcelana E Ni-Cr/Ti/Porcelana

The partial fixed prosthodontics restoration is used to rehabilitate form and function of partial or total compromised teeth, having to remain permanently joined to remainder tooth. The most useful material on prosthodontics is the feldspar porcelain, commercialized as aluminosilicate powders. Dental porcelains are presented with limited mechanical properties to rehabilitate extensive spaces. The association with Ni-Cr metallic systems (metal-ceramic system) allows that the metallic substructure compensates the fragile porcelain nature, preserving the thermal insulation and aesthetics desirable, as well as reducing the possibility of cracking during matication efforts. Cohesive flaws by low mechanical strength connect the metallic substructure to the oral environment, characterized by a electrolytic solution (saliva), by aggressive temperature, pH cyclic changes and mechanical requests. This process results on ionic liberation that could promote allergic or inflammatory responses, and/or clinical degradation of ceramometal system. The aim of this study was to evaluate the presence of an intermediate titanium layer on the microscopic fracture behavior of porcelains on ceramometal systems. Plasma deposition of titanium films result in regular passivating oxide layers which act as barriers to protect the metallic substrate against the hazardous effects of corrosive saliva. Tribocorrosion tests were performed to simulate the oral environment and mechanical stress, making it possible the early detection of crack formation and growth on metal-ceramic systems, which estimate the adherence between the compounds of this system. Plain samples consisting of dental feldspar porcelain deposited either onto metallic substrates or titanium films were fired and characterized by scanning electron microscopy. The result showed that the titanium film improved the adherence of the system compared to conventional metal-ceramic interfaces, thus holding crack propagation

Estudo termo-mecânico de interconector metálico recoberto com filme de La0,8Ca0,2CrO3 e de interconector cerâmico de La0,8Sr0,2Cr0,92Co0,08O3 para PaCOS

Doped lanthanum chromite ( LaCrO3 ) has been the most common material used as interconnect in solid oxide fuel cells for high temperature ( SOFC-HT ) that enabling the stack of SOFCs. The reduction of the operating temperature, to around 800 º C, of solid oxide fuel cells enabled the use of metallic interconnects as an alternative to ceramic LaCrO3, From the practical point of view, to be a strong candidate for interconnect the material must have good physical and mechanical properties such as resistance to oxidizing and reducing environments, easy manufacture and appropriate thermo-mechanical properties. Thus, a study on the physic-mechanical interconnects La0,8Sr0,2Cr0,92Co0,08O3 ceramics for SOFC -AT obtained by the method of combustion , as well as thermo-mechanical properties of metallic interconnects (AISI 444) covered with La0,8Ca0,2CrO3 by deposition technique by spray-pyrolysis fuel cells for intermediate temperature (IT-SOFCs). The La0,8Sr0,2Cr0,92Co0,08O3 was characterized by X -ray diffraction(XRD) , density and porosity , Vickers hardness (HV) , the flexural strength at room temperature and 900 °C and scanning electron microscopy (SEM). The X -ray diffraction confirmed the phase formation and LaCrO3 and CoCr2O4, in order 6 GPa hardness and mechanical strength at room temperature was 62 MPa ceramic Interconnector. The coated metal interconnects La0,8Ca0,2CrO3 passed the identification by XRD after deposition of the film after the oxidation test. The oxidative behavior showed increased resistance to oxidation of the metal substrate covered by La0,8Ca0,2CrO3 In flexural strength of the coated metal substrate, it was noticed only in the increased room temperature. The a SEM analysis proved the formation of Cr2O3 and (Cr,Mn)3O4 layers on metal substrate and confirmed the stability of the ceramic La0,8 Ca0,2CrO3 film after oxidative test

Influence Of Substrate Steps On The Catalytic Properties Of Pt Layers: The Ethanol Electrooxidation Reaction.

The ethanol oxidation reaction (EOR) is investigated on Pt/Au(hkl) electrodes. The Au(hkl) single crystals used belong to the [n(111)x(110)] family of planes. Pt is deposited following the galvanic exchange of a previously deposited Cu monolayer using a Pt(2+) solution. Deposition is not epitaxial and the defects on the underlying Au(hkl) substrates are partially transferred to the Pt films. Moreover, an additional (100)-step-like defect is formed, probably as a result of the strain resulting from the Pt and Au lattice mismatch. Regarding the EOR, both vicinal Pt/Au(hkl) surfaces exhibit a behavior that differs from that expected for stepped Pt; for instance, the smaller the step density on the underlying Au substrate, the greater the ability to break the CC bond in the ethanol molecule, as determined by in situ Fourier transform infrared spectroscopy measurements. Also, we found that the acetic acid production is favored as the terrace width decreases, thus reflecting the inefficiency of the surface array to cleave the ethanol molecule.

Paired Evaluation Of Calvarial Reconstruction With Prototyped Titanium Implants With And Without Ceramic Coating.

To investigate the osseointegration properties of prototyped implants with tridimensionally interconnected pores made of the Ti6Al4V alloy and the influence of a thin calcium phosphate coating. Bilateral critical size calvarial defects were created in thirty Wistar rats and filled with coated and uncoated implants in a randomized fashion. The animals were kept for 15, 45 and 90 days. Implant mechanical integration was evaluated with a push-out test. Bone-implant interface was analyzed using scanning electron microscopy. The maximum force to produce initial displacement of the implants increased during the study period, reaching values around 100N for both types of implants. Intimate contact between bone and implant was present, with progressive bone growth into the pores. No significant differences were seen between coated and uncoated implants. Adequate osseointegration can be achieved in calvarial reconstructions using prototyped Ti6Al4V Implants with the described characteristics of surface and porosity.

S-nitrosothiols Regulate Nitric Oxide Production And Storage In Plants Through The Nitrogen Assimilation Pathway.

Nitrogen assimilation plays a vital role in plant metabolism. Assimilation of nitrate, the primary source of nitrogen in soil, is linked to the generation of the redox signal nitric oxide (NO). An important mechanism by which NO regulates plant development and stress responses is through S-nitrosylation, that is, covalent attachment of NO to cysteine residues to form S-nitrosothiols (SNO). Despite the importance of nitrogen assimilation and NO signalling, it remains largely unknown how these pathways are interconnected. Here we show that SNO signalling suppresses both nitrate uptake and reduction by transporters and reductases, respectively, to fine tune nitrate homeostasis. Moreover, NO derived from nitrate assimilation suppresses the redox enzyme S-nitrosoglutathione Reductase 1 (GSNOR1) by S-nitrosylation, preventing scavenging of S-nitrosoglutathione, a major cellular bio-reservoir of NO. Hence, our data demonstrates that (S)NO controls its own generation and scavenging by modulating nitrate assimilation and GSNOR1 activity.