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Relaxation of Electron Spin during High-Field Transport in GaAs Bulk
2011
A semiclassical Monte Carlo approach is adopted to study the multivalley spin depolarization of drifting electrons in a doped n-type GaAs bulk semiconductor, in a wide range of lattice temperature ($40<T_L<300$ K) and doping density ($10^{13}<n<10^{16}$cm$^{-3}$). The decay of the initial non-equilibrium spin polarization of the conduction electrons is investigated as a function of the amplitude of the driving static electric field, ranging between 0.1 and 6 kV/cm, by considering the spin dynamics of electrons in both the $\Gamma$ and the upper valleys of the semiconductor. Doping density considerably affects spin relaxation at low temperature and weak intensity of the driving electric fiel…
Organoelement derivatives of steroids: Synthesis and structural features of organosilicon, -tin and -lead derivatives of cholesterol and desoxycholic…
1987
Some organo-Main-Group-IV-element compounds of steroids of the type R3M(COL), R2Sn(COL)2 and (R3M)2(HDCA) (where R = Me or Ph; M = Si, Sn and Pb; HCOL = cholest-5-en-3β-ol; H3DCA = 3α, 12α-dihydroxy-5β-cholan-24-oic acid), have been synthesized. The structures of these compounds have been investigated by vibrational, mass, NMR (1H, 13C, 29Si, 119Sn and 207Pb) and 119Sn Mossbauer spectroscopy. For Me3Sn(COL) both in solution and in the solid state an associated structure with distorted trigonal bipyramidal geometry around tin and three-coordinated oxygen atoms is postulated. Discrete tetrahedral geometries are assigned to Ph3M(COL) complexes and to R2Sn(COL)2 complexes in solution. The latte…
Probing the non-innocent nature of an amino-functionalised β-diketiminate ligand in silylene/iminosilane systems.
2020
Electron-rich β-diketiminate ligands, featuring amino groups at the backbone β positions (“N-nacnac” ligands) have been employed in the synthesis of a range of silylene (SiII) complexes of the type (N-nacnac)SiX (where X = H, Cl, N(SiMe3)2, P(SiMe3)2 and Si(SiMe3)3). A combination of experimental and quantum chemical approaches reveals (i) that in all cases rearrangement to give an aza-butadienyl SiIV imide featuring a contracted five-membered heterocycle is thermodynamically favourable (and experimentally viable); (ii) that the kinetic lability of systems of the type (N-nacnac)SiX varies markedly as a function of X, such that compounds of this type can be isolated under ambient conditions …
Syntheses, spectroscopic and structural properties of phenoxysilyl compounds : X-ray structures, FT-IR and DFT calculations
2013
Abstract The reaction of silicon disulfide with alkylphenols yields tetraphenoxysilane, cyclodisilthiane and silanethiol. The outcome of the reaction depends on the presence of the steric hindrance in the ortho position on the reacting phenol. New products of the reaction of silicon disulfide with phenols are characterized by FT-IR, NMR, X-ray diffraction and DFT calculations. The intramolecular interactions in the compounds are mainly XH---π (X = C, S) whereas the intermolecular interactions are either very weak CH---π/CH---O contacts found in aryloxysilane or electrostatic dipole–dipole attraction in cyclodisilthiane and silanethiol. The S–H---π interactions in the obtained silanethiol ar…
RICOSTRUIRE L’IDENTITÀ Transitive-Car Design
2018
l concetto di Transitive Design si affaccia all’agone del dibattito internazionale sullo scorcio del XX secolo, nel momento in cui il disegno industriale nella sua globalità stava interrogandosi sui possibili indirizzi del gusto e sui mutamenti che stavano vivendo l’economia e la società. Il termine è stato coniato da Clino Trini Castelli per identificare quegli oggetti di produzione industriale che creano un legame sinergico tra passato e presente, riassumendo forme archetipiche e rinnovandole attraverso nuove funzioni e nuovi materiali. Rientrano nella categoria del Transitive Design tutti quei prodotti che collegano il passato e il futuro sotto il segno della continuità nel mutamento; so…
First record of Anisian deposits in the Betic External Zone of southern Spain and its paleogeographical implications
2023
In the External Zones of the Betic Cordillera (S Spain), upper Muschelkalk (Ladinian) facies have been known for decades; however, so far there is no stratigraphic record of Anisian deposits. In the present study, new biostratigraphic data from a carbonate succession in the easternmost Subbetic domain reveal a Pelsonian-Illyrian (Anisian) age. The nautiloids Germanonautilus salinarius and Germanonautilus saharonicus are documented for the first time in the Iberian Peninsula, and together with the brachiopod Tetractinella trigonella and the bivalves Neoschizodus orbicularis and Myophoria vulgaris they represent marker fossils of Anisian deposits previously described from many other basins, b…
Reactive Surface Coatings Based on Polysilsesquioxanes: Controlled Functionalization for Specific Protein Immobilization
2009
The key designing in reliable biosensors is the preparation of thin films in which biomolecular functions may be immobilized and addressed in a controlled and reproducible manner. This requires the controlled preparation of specific binding sites on planar surfaces. Poly(methylsilsesquioxane)-poly(pentafluorophenyl acrylates) (PMSSQ-PFPA) are promising materials to produce stable and adherent thin reactive coatings on various substrates. Those reactive surface coatings could be applied onto various materials, for example, gold, polycarbonate (PC), poly(tetrafluoroethylene) (PTFE), and glass. By dipping those substrates in a solution of a desired amine, specific binding sites for protein ads…
Luminescence of localized states in silicon dioxide glass. A short review
2011
Abstract The target is the description of the properties of localized states in silica glass, which relate to aspects of short-to-intermediate-range order. It has been observed that laser light interaction with localized states of silica glass leads to the creation of luminescence centers. Created luminescence centers, excited with laser light, provide intra-center luminescence of oxygen deficient centers (ODC) comprising a blue band at 2.7 eV and a UV band at 4.4 eV. Structurally, these ODCs are understood to comprise twofold-coordinated silicons that are commonly part of some larger local structure, and their luminescence bands can be suppressed by reaction with chlorine or hydrogen. Besi…
The Marine Sponge-Derived Inorganic Polymers, Biosilica and Polyphosphate, as Morphogenetically Active Matrices/Scaffolds for the Differentiation of …
2014
The two marine inorganic polymers, biosilica (BS), enzymatically synthesized from ortho-silicate, and polyphosphate (polyP), a likewise enzymatically synthesized polymer consisting of 10 to >100 phosphate residues linked by high-energy phosphoanhydride bonds, have previously been shown to display a morphogenetic effect on osteoblasts. In the present study, the effect of these polymers on the differential differentiation of human multipotent stromal cells (hMSC), mesenchymal stem cells, that had been encapsulated into beads of the biocompatible plant polymer alginate, was studied. The differentiation of the hMSCs in the alginate beads was directed either to the osteogenic cell lineage by …
High-pressure studies of topological insulators Bi2Se3, Bi2Te3, and Sb2Te3
2013
Bi2Se3, Bi2Te3, and Sb2Te3 are narrow bandgap semiconductors with tetradymite crystal structure (R-3m) which have been extensively studied along with their alloys due to their promising operation as thermoelectric materials in the temperature range between 300 and 500¿K. Studies on these layered semiconductors have increased tremendously in the last years since they have been recently predicted and demonstrated to behave as 3D topological insulators. In particular, a number of high-pressure studies have been done in the recent years in these materials. In this work we summarize the main results of the high-pressure studies performed in this family of semiconductors to date. In particular, w…