An upgrade of the Near Detector of the T2K long baseline neutrino oscillation experiment, ND280, has been proposed. This upgrade will include two new Time Projection Chambers, each equipped with 16 ...resistive Micromegas modules for gas amplification. A first prototype of resistive Micromegas has been designed, built, installed in the HARP field cage, and exposed to a beam of charged particles at CERN. The data have been used to characterize the performances of the resistive Micromegas module. A spatial resolution of 300 μm and a deposited energy resolution of 9% were observed for horizontal electrons crossing the TPCs at 30 cm from the anode. Such performances fully satisfy the requirements for the upgrade of the ND280 TPC.
A new analytical solution of the flow equation has been developed to estimate the time to reach a near‐equilibrium state in mixed aquifers, i.e., having unconfined and confined portions, following a ...large hydraulic perturbation. Near‐equilibrium is defined as the time for an initial aquifer perturbation to dissipate by an average 95% across the aquifer. The new solution has been obtained by solving the flow system of a simplified conceptual model of a mixed aquifer using Laplace transforms. The conceptual model is based on two assumptions: (1) the groundwater flow can be reduced to a horizontal 1‐D problem and (2) the transmissivity, a function of the saturated thickness, is assumed constant on the unconfined portion. This new solution depends on the storativity of the unconfined portion, the lengths of the unconfined and confined portions and the transmissivity, assumed to be constant and equal in both portions of the mixed aquifer. This solution was then tested and validated against a numerical flow model, where the variations of the saturated thickness and therefore variations of the transmissivity were either ignored, or properly modeled. The agreement between the results from the new solution and those from the numerical model is good, validating the use of this new solution to estimate the time to reach near‐equilibrium in mixed aquifers. This solution for mixed aquifers, as well as the solutions for a fully confined or fully unconfined aquifer, has been used to estimate the time to reach near‐equilibrium in 13 large aquifers in the world. For those different aquifers, the time to reach near‐equilibrium ranges between 0.7 kyr to 2.4 × 107 kyr. These results suggest that the present hydraulic heads in these aquifers are typically a mixture of responses induced from current and past hydrologic conditions and thus climate conditions. For some aquifers, the modern hydraulic heads may in fact depend upon hydrologic conditions resulting from several past climate cycles.
Key Points
New analytical solution to assess time to reach equilibrium in mixed aquifers
Current hydraulic heads may be a complex mixture of past and present climate
Some large aquifers may have never been in steady state since their formation
In this paper we describe the performance of a prototype of the High Angle Time Projection Chambers (HA-TPCs) that are being produced for the Near Detector (ND280) upgrade of the T2K experiment. The ...two HA-TPCs of ND280 will be instrumented with eight Encapsulated Resistive Anode Micromegas (ERAM) on each endplate, for a total of 32 ERAMs. This innovative technique allows the detection of the charge emitted by ionization electrons over several pads, improving the determination of the track position.
The TPC prototype has been equipped with the first ERAM module produced for T2K and with the HA-TPC readout electronics chain and it has been exposed to an electron beam at DESY in order to measure spatial and dE/dx resolution. In this paper we characterize the performances of the ERAM and, for the first time, we compare them with a newly developed simulation of the detector response.
Spatial resolution better than 800 μm and dE/dx resolution better than 10% are observed for all the incident angles and for all the drift distances of interest. All the main features of the data are correctly reproduced by the simulation and these performances fully fulfill the requirements for the HA-TPCs of T2K.
We present a methodology to determine the periodic potential of a surface from angle-resolved photoemission spectroscopy. By mapping the band structure and measuring the energy gap widths at high ...symmetry points of the surface Brillouin zone, the first Fourier components of the potential can be estimated. This method has been applied in the case of the reconstructed Ag/Cu(111) surface where controlled potassium atom doping has been used to precisely tune the band gap energies. This potential determination allows one to calculate the local density of states which is found to be in very good agreement with scanning tunneling spectroscopy data.
An integrated and theoretical approach is proposed to determine poroelastic properties of isotropic or transversely isotropic argillaceous rocks from conventional mechanical and hydraulic field ...tests. It uses values of specific storage coefficient, “undrained” elastic parameters, and porosity. No special hydromechanical test is required. In the isotropic case, a simple binomial equation is derived, whereby the poroelastic properties can be rapidly obtained. An application to deep argillaceous formations has shown that calculated poroelastic property values are in satisfactory agreement with direct experimental measurements. In the transversely isotropic case, which is more representative of sedimentary rocks, the approach is generalized from a theoretical relationship between the specific storage coefficient and the anisotropic poroelastic properties. Nevertheless, in both cases, sensitivity analyses have shown that the method is very sensitive to input data, especially the specific storage coefficient and the “undrained” mechanical parameters, which have to be measured with accuracy.
We investigate the relationship between persistent currents in multi-channel rings containing an embedded scatterer and the conductance through the same scatterer attached to leads. The case of two ...uncoupled channels corresponds to a Hubbard chain, for which the one-dimensional embedding method is readily generalized. Various tests are carried out to validate this new procedure, and the conductance of short one-dimensional Hubbard chains attached to perfect leads is computed for different system sizes and interaction strengths. In the case of two coupled channels the conductance can be obtained from a statistical analysis of the persistent current or by reducing the multi-channel scattering problem to several single-channel setups.
In plant, unusual fatty acids are produced by a limited number of species. The industrial benefits of these unusual structures have led several groups to study their production in transgenic plants. ...Their research results led to very modest accumulation in seeds which was largely due to a limited knowledge of the lipid metabolism and fatty acid transfer in plants. More specifically we need to better understand the substrate specificity and selectivity of acyltransferases which are required for the incorporation of these unusual fatty acids into storage triacylglycerols. In our studies we have compared the incorporation of
14C Oleoyl-CoA and Branched Chain Acyls-CoA into
3H LPA-C18:1 by the Lysophosphatidic acid Acyltransferase (LPAAT) from developing seeds of agronomic plants (flax (
Linum usitatissimum) and rape (
Brassica napus)) and from a plant capable of producing high amounts of hydroxy fatty acids (castor bean (
Ricinus communis)). Our assays demonstrate that LPAATs of the three studied species (1) incorporated preferentially oleyl-CoA, (2) could incorporate cyclopropane acyl-CoA when added alone as a substrate, however very weakly for rapeseed and castor bean seeds, (3) presented a low capacity to incorporate methyl branched acyl-CoA when added alone as a substrate (4) weakly incorporated cyclopropane acyl-CoA and was unable to incorporate methyl branched acyl-CoA when presented with an equimolar mix of oleyl-CoA and branched chain acyl-CoA. In all cases, the LPAAT had a low affinity for branched chain acyl-CoAs. The results show that LPAAT activity from agronomic plants constitutes a bottleneck for the incorporation of branched Chain acyl-CoA into PA.
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