Search results for "conductivity"
showing 10 items of 1988 documents
Generalised Maxwell-Garnett equation: application to electrical and chemical transport.
2006
In this paper we discuss the implementation of different equilibrium concentrations in each of the phases into the Maxwell-Garnett effective medium formula for diffusion in heterogeneous media. We put the derivation given by Kalnin et al., J. Phys. Chem. Solids, 2002, 63, 449, on safer grounds and extend it to non-dilute carrier concentrations. The relation to Maxwell’s mixing rule is also elaborated. It is shown that the formula can not only successfully be applied to conductivity problems but also to describe steady state chemical diffusion in heterogeneous media such as polycrystalline samples. The comparison with the brick layer model corroborates these points but also shows that—in the…
Molecular materials with conducting and magnetic properties based on ET and [ M(tdas)2]x-dithiolenes
2004
Two hybrid molecular materials showing a combination of magnetic and conducting properties, the charge-transfer (ET) 2 [Fe(tdas) 2 ] (1) and (ET)Ni(tdas) 2 (2), (ET=bis(ethylenedithio) tetrathiafulvalene; M=Fe, Ni; tdas=l,2,5-thiadiazole-3,4-dithiolate) salts, are characterized by vibrational (IR and Raman) and UV-VIS-NIR spectroscopies. These studies have proved to be effective and diagnostic tools in identifying the oxidation state (partial or integer) and the packing pattern (dimers or segregated stacks) of the ET donor only, since no v(C=C) group vibration sensitive to the charge of M(tdas) 2 complexes has been observed. This is ascribed to the extensive electron-delocalization inside t…
Short-term response to waterlogging in Quercus petraea and Quercus robur: A study of the root hydraulic responses and the transcriptional pattern of …
2015
International audience; We characterized the short-term response to waterlogging in Quercus petraea (Matt.) Liebl. and Quercus robur L. as the initial response towards their known long-term differences in tolerance to waterlogging. One-month old seedlings were subjected to hypoxic stress and leaf gas exchange, shoot water potential (Psi(s)) and root hydraulic conductivity (Lp(r)) were measured. In parallel, the expression of nine aquaporins (AQPs) along the primary root was analysed by quantitative RT-PCR. Results showed a similar reduction in net assimilation (A) and stomatal conductance (g(s)) for the two species. Notably, the response of Lpr differed temporally between the two species. Q…
Defined-size DNA triple crossover construct for molecular electronics: modification, positioning and conductance properties.
2011
We present a novel, defined-size, small and rigid DNA template, a so-called B-A-B complex, based on DNA triple crossover motifs (TX tiles), which can be utilized in molecular scale patterning for nanoelectronics, plasmonics and sensing applications. The feasibility of the designed construct is demonstrated by functionalizing the TX tiles with one biotin-triethylene glycol (TEG) and efficiently decorating them with streptavidin, and furthermore by positioning and anchoring single thiol-modified B-A-B complexes to certain locations on a chip via dielectrophoretic trapping. Finally, we characterize the conductance properties of the non-functionalized construct, first by measuring DC conductivi…
Influence of stress-level due to self-weight on the hydraulic conductivity of permeable concrete for geotechnical applications
2022
Permeable concrete is effectively used in many fields of civil and environmental engineering, including some geotechnical applications such as drainage piles, deep drainage trenches, and as a permeable backfill material for retaining walls. The principal requirements that a pervious concrete must have for geotechnical applications are those that simultaneously guarantee enough hydraulic conductivity and good filter properties against internal erosion of the soil in which the drains are realised. These requirements can be effectively achieved through special mix-designs in which a non-negligible amount of sand is added to the aggregates, unlike the permeable concretes used for example in the…
Hydraulic Characterization of a Pervious Concrete for Deep Draining Trenches
2018
Reduction in pore water pressure is an useful strategy to improve the stability of slopes. Deep draining trenches can be used for this purpose. For the realization of deep trenches, the usual conventional construction techniques are not adequate and the use of adjacent vertical panels, built by means of the methods well-established for diaphragm walls, is necessary. However, unbonded materials (i.e., gravels) cannot be used, because the excavation of a panel adjacent to one already built will cause instability. For this scope a bonded material such as pervious concrete can be used. It must have high permeability; filtering capacity, in order to prevent internal erosion of the soil in which …
Effects of reduced irradiance on hydraulic architecture and water relations of two olive clones with different growth potentials
2009
Abstract The hydraulic architecture and water relations of two olive genotypes, ‘Leccino Dwarf’ (LD) and ‘Leccino Minerva’ (LM) growing at two irradiance levels i.e. full sunlight irradiance (HI) and 50% sunlight irradiance (LI) were studied. The two clones showed similar plant hydraulic conductances (Kplant) and similar conductance of roots and leaves (Kroot and Kleaf) when growing at equal irradiance levels. However, both Kplant and Kroot were significantly lower in LI plants than in HI ones. On the contrary, Kleaf was unaffected by the light regime. One-year-old twigs of LI plants produced longer xylem conduits but lower average diameter of conduits and less conduits per unit xylem cross…
Disordered hyperuniformity in superconducting vortex lattices
2020
Particles occupying sites of a random lattice present density fluctuations at all length scales. It has been proposed that increasing interparticle interactions reduces long range density fluctuations, deviating from random behaviour. This leads to power laws in the structure factor and the number variance that can be used to characterize deviations from randomness which eventually lead to disordered hyperuniformity. It is not yet fully clear how to link density fluctuations with interactions in a disordered hyperuniform system. Interactions between superconducting vortices are very sensitive to vortex pinning, to the crystal structure of the superconductor and to the value of the magnetic …
Thermal, electric and spin transport in superconductor/ferromagnetic-insulator structures
2019
A ferromagnetic insulator (FI) attached to a conventional superconductor (S) changes drastically the properties of the latter. Specifically, the exchange field at the FI/S interface leads to a splitting of the superconducting density of states. If S is a superconducting film, thinner than the superconducting coherence length, the modification of the density of states occurs over the whole sample. The co-existence of the exchange splitting and superconducting correlations in S/FI structures leads to striking transport phenomena that are of interest for applications in thermoelectricity, superconducting spintronics and radiation sensors. Here we review the most recent progress in understandin…
Solid-State Analog of an Optical Interferometer
2004
To some extend one may treat a metal ring with two probes as a solid-state analog of an optical interferometer. One node can be considered as a beam splitter (bi-prism, for example), and the electric current at the other node as an equivalent to a light intensity of an interference pattern formed at a screen. In optics, to obtain a stationary pattern one should use a monochromatic source of radiation, as afterwards in a conventional passive media (i.e. air) the phase of the radiation is preserved. On the contrary, in solids the phase of a conducting electron wavefunction is randomly altered due to inelastic collisions (mainly phonons at high temperatures). Hence, to satisfy the condition of…