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showing 10 items of 3539 documents
Axial growth of hexactinellid spicules: Formation of cone-like structural units in the giant basal spicules of the hexactinellid Monorhaphis
2008
The glass sponge Monorhaphis chuni (Porifera: Hexactinellida) forms the largest bio-silica structures on Earth; their giant basal spicules reach sizes of up to 3 m and diameters of 8.5 mm. Previously, it had been shown that the thickness growth proceeds by appositional layering of individual lamellae; however, the mechanism for the longitudinal growth remained unstudied. Now we show, that the surface of the spicules have towards the tip serrated relief structures that are consistent in size and form with the protrusions on the surface of the spicules. These protrusions fit into the collagen net that surrounds the spicules. The widths of the individual lamellae do not show a pronounced size …
Self-organization and nanostructural control in thin film heterojunctions.
2013
In spite of more than two-decades of studies of molecular self-assembly, the achievement of low cost, easy-to-implement and multi-parameter bottom-up approaches to address the supramolecular morphology in three-dimensional (3D) systems is still missing. In the particular case of molecular thin films, the 3D nanoscale morphology and function are crucial for both fundamental and applied research. Here we show how it is possible to tune the 3D film structure (domain size, branching, etc.) of thin film heterojunctions with nanoscale accuracy together with the modulation of their optoelectronic properties by employing an easy two-step approach. At first we prepared multi-planar heterojunctions w…
Effect of structural and compositional inhomogeneities on spin-glass transition in Hg1−x−yCrxMnySe crystals
2004
Abstract We report experimental results on the growth of Hg 1 −x−y Cr x Mn y Se crystals and their magnetic susceptibility χ ( T ) in dependence on the crystal structure and composition. It was found that the crystals with the Mn composition y =0.01–0.08 exhibit the spin-glass transition temperature T g =100–110 K. An increase of y value leads to the saturation of the χ max and T g characteristics in the composition ranges of y >0.06 and y >0.02, respectively. This phenomenon is explained as a result of phase-separated magnetic behavior caused by the formation of HgCr 2 Se 4 inclusions and textures.
Research data supporting the paper "Tuning the effective spin-orbit coupling in molecular semiconductors"
2017
We here present the data underlying the paper "Tuning the effective spin-orbit coupling in molecular semiconductors" accepted at Nature Communications on 24 February 2017. For contributions of the authors to the data and experimental details, please refer to the original paper.
Nonlinear dependence on temperature and field of electron spin depolarization in GaAs semiconductors
2009
In this work the influence of temperature and drift conditions on the electron spin relaxation in lightly doped n-type GaAs bulk semiconductors is investigated. The electron transport, including the evolution of the spin polarization vector, is simulated by a Monte Carlo procedure which keeps into account all the possible scattering phenomena of the hot electrons in the medium. Electron-spin states in semiconductor structures relax by scattering with imperfections, other carriers and phonons. Spin relaxation lengths and times are computed through the D'yakonov-Perel process since this is the more relevant spin relaxation mechanism in the regime of interest (10 < T < 300 K). The decay of the…
Doping dependence of spin lifetime of drifting electrons in GaAs bulks
2010
We study the effect of the impurity density on lifetimes and relaxation lengths of electron spins in the presence of a static electric field in a n-type GaAs bulk. The transport of electrons and the spin dynamics are simulated by using a semiclassical Monte Carlo approach, which takes into account the intravalley scattering mechanisms of warm electrons in the semiconductor material. Spin relaxation is considered through the D'yakonov-Perel mechanism, which is the dominant mechanism in III-V semiconductors. The evolution of spin polarization is analyzed by computing the lifetimes and depolarization lengths as a function of the doping density in the range 10^{13} - 10^{16} cm^{-3}, for differ…
A Mesoporous 3D Hybrid Material with Dual Functionality for Hg2+Detection and Adsorption
2008
Dual-function hybrid material U1 was designed for simultaneous chromofluorogenic detection and removal of Hg(2+) in an aqueous environment. Mesoporous material UVM-7 (MCM41 type) with homogeneously distributed pores of about 2-3 nm in size, a large specific surface area exceeding 1000 m(2) g(-1), and nanoscale particles was used as an inorganic support. The mesoporous solid is decorated with thiol groups that were treated with squaraine dye III to give a 2,4-bis(4-dialkylaminophenyl)-3-hydroxy-4-alkylsulfanylcyclobut-2-enone (APC) derivative that is covalently anchored to the inorganic silica matrix. The solid was characterised by various techniques including X-ray diffraction, transmission…
Analysis of Transition Metal Oxides based Heterojunction Solar Cells with S-shaped J-V curves
2020
The use of transition metal oxides for the selective carrier contact in the crystalline silicon solar cells technology is rising to interest for the excellent optoelectrical properties of these materials whose implementation, however, can result in lousy performing cells due to an S-shaped electrical characteristic. In this paper, we fabricated solar cells showing S-shaped J-V curve and carried out an analysis of the reasons of such behavior using a model involving the series of a standard cell equivalent circuit with a Schottky junction in order to explain these atypical performances. A good matching between the experimental measurements and the adopted theoretical model was obtained. The …
A Silicone Ventricular Catheter Coated with a Combination of Rifampin and Trimethoprim for the Prevention of Catheter-related Infections
1998
So-called antiinfective catheters which are generated by incorporation of antimicrobial substances into polymers appear to be effectful devices in the prevention of catheter related infections. Such devices mainly act by prevention of bacterial colonization of the catheter surface rather than by inhibition of adherence. In a preceding study, we developed a rifampin-containing silicone catheter for the prevention of ventricular shunt infection. In the present study, this work was continued with a combination of antimicrobials incorporated in silicone ventricular catheters to reduce the risk of rifampin resistance and to expand the antimicrobial spectrum. We found that the drug release kineti…
Nonequilibrium electron spin relaxation in n-type doped GaAs sample
2019
Non-equilibrium electron spin relaxation in a n-type doped GaAs bulk semiconductor is investigated. We use a semiclassical Monte Carlo approach by considering multivalley spin dynamics of drifting electrons. Spin relaxation is considered through the D'yakonov-Perel mechanism, which is the dominant process in III-V semiconductors. An analytical expression for the inhomogeneous broadening of spin precession vector is derived by taking into account the effect of the electric field and the doping density. The inclusion of electron-electron scattering has the effect of increasing both the spin lifetime and the depolarization length. In particular, we find a non-monotonic trend with the maximum o…