Search

We performed a detailed analysis of the thermal state of the Cenozoic Roer Valley Graben, the north-western branch of the European Cenozoic Rift System, based on a new set of temperature data. We developed a numerical technique for correcting bottom hole temperatures, including an evaluation of the uncertainty of thermal parameters. Comparison with drill stem test temperatures indicated that the uncertainty in corrected bottom hole temperatures using a two-component numerical model is approximately ± 4°C, which is much more accurate than the up to 15°C errors encountered in often-used line-source or Horner correction methods. The subsurface temperatures and the derived regional heat flow estimates of 53 ± 6 to 63 ± 6mWm-2 show no significant difference between the central rift and the adjacent structural highs. The absence of an elevated heat flow is attributed to the low amount of lithospheric thinning during the Cenozoic rifting phase (β=1.06-1.15). A local thermal anomaly exceeding +10°C was found in five wells in the north-western part of the rift basin at depths of 1000-1500m, and is most likely caused by the upward flow of fluids along faults, whereas lower temperatures in the upper 1500m in the southern part of the rift basin could indicate cooling by topography-driven groundwater flow. Conflicting ideas exist on the active or passive rifting mechanisms responsible for the formation of the different rift basins of European Cenozoic Rift System. The low spatial variation in heat flow found in this study suggests that the mechanism responsible for forming the Roer Valley Graben is passive rifting. © 2010 The Authors. Basin Research © 2010 Blackwell Publishing Ltd, European Association of Geoscientists & Engineers and International Association of Sedimentologists.

In this paper an overview of the knowledge components needed for extensive documentation of small languages is given. The Language Archive is striving to offer all these tools to the linguistic community. The major tools in relation to the knowledge components are described. Followed by a discussion on what is currently lacking and possible strategies to move forward.

We present a software module, the LAT Bridge, which enables bidirectionalcommunication between the annotation and exploration tools developed at the MaxPlanck Institute for Psycholinguistics as part of our Language ArchivingTechnology (LAT) tool suite. These existing annotation and exploration toolsenable the annotation, enrichment, exploration and archive management oflinguistic resources. The user community has expressed the desire to usedifferent combinations of LAT tools in conjunction with each other. The LATBridge is designed to cater for a number of basic data interaction scenariosbetween the LAT annotation and exploration tools. These interaction scenarios(e.g. bootstrapping a wordlist, searching for annotation examples or lexicalentries) have been identified in collaboration with researchers at ourinstitute.We had to take into account that the LAT tools for annotation and explorationrepresent a heterogeneous application scenario with desktop-installed andweb-based tools. Additionally, the LAT Bridge has to work in situations wherethe Internet is not available or only in an unreliable manner (i.e. with a slowconnection or with frequent interruptions). As a result, the LAT Bridge’sarchitecture supports both online and offline communication between the LATannotation and exploration tools.

Organic-inorganic hybrid membranes of nanosized SiO2-filled polyamide composites were prepared via film casting and their transport properties were studied. Gas permeation measurements were performed at room temperature, and the membrane exhibited an increase in membrane permeability performance. In contrast to the performance of traditional dense filled polymer systems, the permeability increased with an increased number of nanosilica particles. The nanocomposites were studied using positron annihilation lifetime spectroscopy (PALS). From the ortho-positronium (o-Ps) lifetime (3), the size of the local free volume (holes) was estimated. The increase in permeability is ascribed to the additional free volume obtained. This is created by the presence of nanoparticles that alter the PA chain packing. Furthermore, wide angle X-ray diffraction (WAXD) patterns revealed that the incorporation of silica induced the structural modification of polymer chains by modifying the degree of crystallinity in comparison with the neat polymer. Polym. Eng. Sci. 44:1240-1246, 2004. © 2004 Society of Plastics Engineers

The chemical diffusion coefficient and oxygen-transfer coefficients of selected compositions in the series La1-xSrxCoO3-δ were studied using the conductivity relaxation technique. Measurements were performed in the temperature range 600-850°C and oxygen partial pressure 10-4 to 1 bar. Chemical diffusivity and oxygen surface transfer in the La1-xSrxCoO3-δ perovskites appear to be highly correlated. The general trend displayed is that both parameters decrease with decreasing pO2 below about 10-2 bar at all temperatures. This is attributed to ordering of induced vacancies at low oxygen partial pressures. The observation that the correlation between both parameters extends even to the lowest pO2 values in this study suggests a key role of the concentration of mobile oxygen vacancies, rather than of the extent of oxygen nonstoichiometry, in determining the rates of both processes. The characteristic thickness Lc, which equals the ratio of the chemical diffusion coefficient to the surface transfer coefficient, shows only a weak dependence on oxygen partial pressure and temperature. For different compositions La1-xSrxCoO3-δ, Lc is found to vary between 50 and 150 µm.

The influence of microstructure on the capacitive behavior in the dual-phase composite system platinum/cubic-yttria-stabilized zirconia (YSZ) was studied at ambient temperature. Three different synthesis methods were employed. The volume fraction of Pt metal in the composite was varied between 0 and 25 vol%. The resulting composites were characterized by scanning electron microscopy (SEM) and electrical impedance spectroscopy (EIS). The bulk capacity increased with Pt content. Depending on the synthesis method, differences in microstructural homogeneity were observed by SEM. However, for samples prepared via different routes and with similar volume fractions of metallic Pt, no significant differences in capacity were observed. A maximum increase in the capacity of approximately 12.6 compared to pure cubic yttria-stabilized zirconia was obtained for a composite containing 25 vol% platinum, prepared via the sol-gel method. The percolation threshold for the platinum phase was estimated from a fit of the experimental data to normalized percolation theory and was found to be 31.1 ± 1.5 vol%.

Ferroelectric/metal composites have been characterized for their electric field dependence of the dielectric and ferroelectric properties. The composites show an interesting change of dielectric properties with increasing metal concentration. A relatively high dielectric constant, up to four times as high as that of monolithic lead zirconate titanate (PZT), is observed in the investigated composition range. The dielectric properties are clearly electric field dependent. The tunability of the composite, defined as the difference between the dielectric constant with no applied voltage and the dielectric constant with an applied voltage, divided by the dielectric constant with no applied voltage, was found to be ∼ 17, whilst for the monolithic PZT ceramics it is about 3 only. This offers perspectives for application of these composites in lighting electronics and voltage controllers. Ferroelectric hysteresis measurements on these composites revealed a square-shaped hysteresis loop with remnant polarization comparable with single PZT ceramics, while the coercive field was much lower than that of pure PZT ceramics. This might be interesting for application of these composites as a ferroelectric memory material with decreased switching voltage.

An accurate field method that directly measures the entire range of relevant soil water potentials for periods of months to years is not yet available. The osmotic tensiometer (OT) has the potential to fulfil these demands but is still in an early stage of development. We have designed a novel OT that should overcome several drawbacks of former designs by the use of cross-linked polymeric gel grains instead of an aqueous solution of linear chain polymers inside the porous ceramic cup. For this reason, the cup can have large pores without polymer leakage. This ensures that water exchanges rapidly with the soil, resulting in a negligible pressure lag with changing temperatures, which is the most important source of a systematic measurement error of an OT. A second reason for better performance might be the inherent elasticity of the grains which should inhibit formation of a polymer cake at the filter. To study several of the key variables of the new sensor, transient and stationary experiments were performed in an aqueous solution the temperature, salt type and salt concentration of which were varied. Under similar conditions the swelling of the polymer grains was studied in more detail. The OT that we developed responds rapidly to changes in water potential, but is very susceptible to the influence of salts. To study and minimize salt influence, swelling tests of unconfined grains are proposed in combination with tests of the OT itself.

Oxygen permeation measurements were performed on dense La1-xSrxFeO3-δ (r=0.1-0.4) membranes at 1273 K. The materials were investigated in air/He and air/He,CO,CO2 gradients. The fluxes increased with increasing Sr content and were strongly enhanced by the presence of CO, up to values of 25 mmol m-2 s-1. In air/He gradients the permeation is bulk controlled and can be modelled by Wagner theory incorporating a random point defect model. Oxygen vacancy diffusion coefficients were calculated to range between 5.6-8.6-10-6 cm2 s-1. In air/CO,CO2 gradients the permeation process appeared to be totally limited by the surface reaction rate. To account for this behaviour, models are proposed in which surface oxygen vacancies act as active surface sites.

An oxygen coulometric titration cell has been designed to measure non-stoichiometry and oxygen diffusivity of mixed oxygen ion and electronic conducting, La0.8Sr0.2CoO3-δ. Chemical diffusion data, combined with oxygen non-stoichiometry data, δ, show that the oxygen vacancy diffusion coefficient is 5.25*e -(132±7 KJ/mol)RTcm2/s, and independent of the oxygen partial pressure, P01. In addition, it is found that log(δ) is linearly related to log(P01) with slope of -0.23±0.02. The entropy associated with oxygen incorporation can be modelled with the configurational entropy of the oxygen vacancies. No electronic entropy contribution is observed. The energy of oxygen incorporation decreases almost linearly with increasing oxygen stoichiometry. Both energy and entropy data agree with a model in which electrons gradually fill electron states in a broad electron band. From the data an empirical relation between vacancy-concentration, temperature and oxygen partial pressure can be formulated, which deviates from mass action behavior.

The friction and wear behaviour of two ZrO2-Al2O3 composite materials, ADZ (20 wt% Al2O3 dispersed in yttria-doped ZrO2 matrix) and ZTA (Al2O3-15 wt% ZrO2), were investigated. Sliding wear tests were carried out on these materials under dry conditions using a ball-on-plate configuration. The effects of grain size and zirconia phase transformation on friction and wear behaviour were examined. Sinter forging was applied to determine the role of grain boundaries on the wear process. It was found that for ADZ composites the wear resistance increased with decreasing grain size. Only limited grain pull-out occurs in these systems, which also explains the fact that in this case sinter forging has no positive effect on wear resistance. For ZTA composites a compressive surface caused by zirconia phase transformation has a beneficial effect on wear resistance. Here grain pull-out is the main wear mechanism which explains the positive effect of sinter forging ZTA on wear resistance.

The CPLEAR collaboration has constructed a detector at CERN for an extensive programme of CP-, T- and CPT-symmetry studies using K-0 and produced by the annihilation of in a hydrogen gas target. The K-0 and are identified by their companion products of the annihilation K(+/-)pi(-/+) which are tracked with multiwire proportional chambers, drift chambers and streamer tubes. Particle identification is carried out with a liquid Cherenkov detector for fast separation of pions and kaons and with scintillators which allow the measurement of time of flight and energy loss. Photons are measured with a lead/gas sampling electromagnetic calorimeter. The required antiproton annihilation modes are selected by fast online processors using the tracking chamber and particle identification information. All the detectors are mounted in a 0.44 T uniform field of an axial solenoid of diameter 2 m and length 3.6 m to form a magnetic spectrometer capable of full on-line reconstruction and selection of events. The design, operating parameters and performance of the subdetectors are described. Nuclear Instruments & Methods in Physics Research Section a-Accelerators Spectrometers Detectors and Associated Equipment

The equilibrium oxygen chemical potential of mixed oxygen ion and electron conducting perovskites La1-xSrxCoO3-δ was measured as a function of δ and x by high temperature oxygen coulometric titration. An almost linear decrease in the chemical potential is observed with increasing net electron concentration. The observed behavior is interpreted to reflect the corresponding change in the Fermi level upon gradually filling up states in a broad electron band with electrons induced by vacancy formation and Sr doping. Assuming a rigid band formalism, an apparent density of states at the Fermi level was calculated, the value of which is in good agreement with that obtained from XPS.

Oxygen permeation measurements were performed on dense La1−xSrxFeO3−δ (x = 0.1-0.4) membranes in large oxygen activity gradients, i.e. air/CO, CO2, in the temperature range 1173–1323 K, yielding fluxes up to 25 mmol m−2 s−1 at 1273 K. The oxygen semipermeability was linearly proportional with the CO partial pressure and the strontium content. It was concluded that the fluxes are limited by the surface exchange kinetics. Two simple models are proposed for the oxygen exchange reaction in the presence of CO. In both models oxygen vacancies at the phase boundary play a definite role in the exchange process. XPS and SEM analysis of the perovskite/CO, CO2 interfaces indicated segregation of strontium, being present at the surface mostly in the form of SrCO3 and/or SrO. The enhanced oxygen fluxes in air/He gradients as they were observed after exposure of the membrane surface to CO are probably (indirectly) related to the level of strontium segregation. Based on SEM analysis and surface profile measurements, it is suggested that the segregation process is accompanied by an enlargement of the specific surface area, which may promote the speed of the overall permeation process under exchange-controlled conditions.

The CPLEAR collaboration has constructed a detector at CERN for an extensive programme of CP-, T- and CPT-symmetry studies using K-0 and produced by the annihilation of in a hydrogen gas target. The K-0 and are identified by their companion products of the annihilation K(+/-)pi(-/+) which are tracked with multiwire proportional chambers, drift chambers and streamer tubes. Particle identification is carried out with a liquid Cherenkov detector for fast separation of pions and kaons and with scintillators which allow the measurement of time of flight and energy loss. Photons are measured with a lead/gas sampling electromagnetic calorimeter. The required antiproton annihilation modes are selected by fast online processors using the tracking chamber and particle identification information. All the detectors are mounted in a 0.44 T uniform field of an axial solenoid of diameter 2 m and length 3.6 m to form a magnetic spectrometer capable of full on-line reconstruction and selection of events. The design, operating parameters and performance of the subdetectors are described.

A zirconia-yttria gel, made by coprecipitation, was treated in six different ways to obtain a nanocrystalline Y-TZP powder: one large gel batch was split into six parts of which one was crystallized in air and the others crystallized either in water with a high pH or in methanol. The batches were subjected to several post treatments. Powder properties and densification characteristics of the six powder batches obtained in this way are described. The aircalcined powder can be sintered to a relative density of about 93% at 1070 °C/10 h, but reproducibility of the sintering characteristics is poor. Optimal hydrothermal treatment of the powder yields a reproducible sintering process, resulting in a relative density of 96% at 1070 °C/10 h and an average grain size between 120 and 130 nm.