Quantum properties of two-dimensional electron gas in the inversion layer of Hg1−xCdxTe bicyrstals

The electronic and magnetotransport properties of conduction electrons in the grain boundary interface of p-type Hg_1−xCd_xTe bicrystals are investigated. The results clearly demonstrate the existence of a two-dimensional degenerate n-type inversion layer in the vicinity of the grain boundary. Hydrostatic pressure up to 10³ MPa is used to characterize the properties of the two-dimensional electron gas in the inversion layer. At atmospheric pressure three series of quantum oscillations are revealled, indicating that tthree electric subbands are occupied. From quantum oscilations of the magnetoresistivity the characteristics parameters of the electric subbands (subband populations n_si, subband energies E_F−E_i, effective electron masses m^*_ci) and their pressure dependences are established. A strong decrease of the carrier concentration in the inversion layer and of the corresponding subband population is observed when pressure is applied A simple theoretical model based on the triangular-well approximation and taking into account the pressure dependence of the energy band structure of Hg_1−xCd_xTe is use to calculate the energy band diagram of the quantum well and the pressure dependence of the subband parameters.     

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Ohne Zusammenfassung     

The Effect of pH and Biogenic Ligands on the Weathering of Chrysotile Asbestos: The Pivotal Role of Tetrahedral Fe in Dissolution Kinetics and Radical Formation

Chrysotile asbestos is a soil pollutant in many countries. It is a carcinogenic mineral, partly due to its surface chemistry. In chrysotile, Fe^II and Fe^III substitute Mg octahedra (Fe[6]), and Fe^III substitutes Si tetrahedra (Fe[4]). Fe on fiber surfaces can generate hydroxyl radicals (HO^.) in Fenton reactions, which damage biomolecules. To better understand chrysotile weathering in soils, net Mg and Si dissolution rates over the pH range 3.0–11.5 were determined in the presence and absence of biogenic ligands. Also, HO^. generation and Fe bulk speciation of pristine and weathered fibers were examined by EPR and Mössbauer spectroscopy. Dissolution rates were increased by ligands and inversely related to pH with complete inhibition at cement pH (11.5). Surface-exposed Mg layers readily dissolved at low pH, but only after days at neutral pH. On longer timescales, the slow dissolution of Si layers became rate-determining. In the absence of ligands, Fe[6] precipitated as Fenton-inactive Fe phases, whereas Fe[4] (7 % of bulk Fe) remained redox-active throughout two-week experiments and at pH 7.5 generated 50±10 % of the HO^. yield of Fe[6] at pristine fiber surfaces. Ligand-promoted dissolution of Fe[4] (and potentially Al[4]) labilized exposed Si layers. This increased Si and Mg dissolution rates and lowered HO^. generation to near-background level. It is concluded that Fe[4] surface species control long-term HO^. generation and dissolution rates of chrysotile at natural soil pH.     

Comparing column dynamics in the liquid and vapor phase adsorption of biobutanol on an activated carbon monolith

Adsorption - Adsorbent monoliths are gaining increasing interest in gas phase separation processes, but have rarely been studied for liquid phase separations. In this work, we investigate an...     

The Rost nilpotence theorem for geometrically rational surfaces

We show that the Rost nilpotence theorem is true for geometrically rational surfaces over fields of characteristic zero.     

On injective modules over Azumaya algebras over locally noetherian schemes

Let be an Azumaya algebra over a locally noetherian scheme X. We describe in this work quasi-coherent -bimodules which are injective in the category of sheaves of left -modules     

Comparaison entre les solutions solides PLZT et les materiaux PZT bisubstitues

A systematic study of PLZT materials with composition close to the rhombohedral-tetragonal phase transition boundary at room temperature showed that piezoelectric properties of such materials are comparable with those exhibited by PZT with similar composition but containing two substituents. The best results were obtained with 6% lanthanum and 58% zirconium samples.     

On a question of André Verbeure

We show that a non discrete state of van Hove's Universal Receptacle in the fermion case is not unitarily equivalent to any quasi-free state.Centre National de la Recherche Scientifique.