Major and Trace Element Accumulation in Coastal Sediments along Southeastern Baja California Studied by Instrumental Neutron Activation Analysis and 210Pb Age-Dating

The vertical distribution of K, Rb, Cs, Ca, Sr, Ba, Fe, Cr, Co, Ni, Zn, Sc, Zr, Sb, Se and As was studied by means of instrumental neutron activation analysis in four sediment cores collected from the eastern shelf of tectonically active Baja California peninsula accompanied by ²¹⁰Pb age-dating. ²¹⁰Pb analysis was performed by extraction chromatography with measuring the ingrowing daughter 210Bi radioactivity by liquid-scintillation spectrometry. It was found that concentration variations of Se, As, Sb, Zr and Zn are probably controlled by the intensity and composition of the material supplied from the drainage basin constituted by volcanic and sedimentary rocks.     

Microwave assisted methodology for the determination of organic pollutants in organic municipal wastes and soils: extraction of polychlorinated biphenyls using heat transformer disks

Known benefits of microwave assisted extraction (MAE) of polychlorinated biphenyls (PCB) from solid matrices could be proven by the described approach using n-heptane as solely applied extraction solvent. Heat transfer within the extraction vessels was achieved by heat transformer disks which absorb microwave energy and transform it into heat rapidly and independently of the temperature present in the sample-solvent system. Disadvantageous co-extraction of polar substances could be ruled out and thus clean-up of the samples was simplified and sufficient for subsequent GC-MS analysis. Comparison with other extraction techniques confirmed the efficiency of this method also for aged samples.     

Performance characteristics of composite film electrolytes for intermediate-temperature solid oxide fuel cells

This paper reports on the estimated performance of a cell with a three-layer electrolyte, consisting of one gadolinia-doped ceria (GDC) layer, one yttria-stabilised zirconia (YSZ) electronblocking layer and one CGO-YSZ solid solution interlayer, the latter being used to avoid solid-state reaction and interdiffusion between YSZ and GDC, in comparison to a cell with a double-layer YSZ-CGO composite electrolyte. For a constant temperature and overall cell oxygen potential as boundary conditions, the open circuit voltage, the voltage under operating conditions and the oxygen potential profile inside the electrolyte are related to the ionic and electronic transport properties of the materials involved and are calculated as a function of the thickness of the layers involved and the relative positions of the YSZ and GDC layers. Thermodynamic stability of the electrolyte is shown to depend upon the transport properties of the materials and primarily the electronic conductivity of the air-side layers. To determine the particular ionic and electronic contributions for conduction of the materials involved, conductivity was measured as a function of the oxygen partial pressure and temperature, using the standard four point d.c. method. Based on the calculations, performed the conditions are discussed under which a functionally graded composite electrolyte YSZ-CGO can be effective for intermediate-temperature solid oxide fuel cells (SOFCs). Paper presented at the 6th Euroconference on Solid State Ionics, Cetraro, Calabria, Italy, Sept. 12–19, 1999. TMR Grant Holder     

Operator-valued Fourier multiplier theorems on Lp(X) and geometry of Banach spaces

This paper gives the optimal order l of smoothness in the Mihlin and Hörmander conditions for operator-valued Fourier multiplier theorems. This optimal order l is determined by the geometry of the underlying Banach spaces (e.g. Fourier type). This requires a new approach to such multiplier theorems, which in turn leads to rather weak assumptions formulated in terms of Besov norms.     

Synaptic Coupling Between Two Electronic Neurons

An electrical circuit is proposed to realize an unidirectional coupling between two cells, mimicking chemical synaptic coupling. Each cell represents the FitzHugh–Nagumo (FHN) model of neuron with a modified exitability (MFHN). We present experimental results on frequency doublings and on the chaotic dynamics depending on the coupling strength in a master–slave configuration. In all experiments, we stress the influence of the coupling strength on the control of the slave neuron.     

On the Initial Boundary Value Problem for the Vlasov–Poisson–Boltzmann System

We prove existence of DiPerna-Lions renormalized solutions to the Boltzmann equation and to the Vlasov-Poisson-Boltzmann system for the initial boundary value problem.     

Measuring stress intensity factors with a camera: Integrated digital image correlation (I-DIC)Mesure de facteurs d'intensité des contraintes avec une caméra : corrélation d'images numériques intégrée (CINI)

A novel ‘integrated’ approach coupling image correlation and elastic displacement field identification provides a powerful and accurate tool to evaluate mode I and II stress intensity factors. This technique is applied to silicon carbide subjected to a sandwiched three-point bend test, using digital pictures obtained in optical microscopy where the pixel physical scale is about 2 μm. A crack whose maximum opening is 500 nm can be detected and its geometry identified. The toughness is determined well within a 10%uncertainty. To cite this article: F. Hild, S. Roux, C. R. Mecanique 334 (2006).