627 research outputs found
A new semimagnetic compound: Cd1-xFexIn 2S4 single crystal grown by CVT
No full textSingle crystals of the Cd1-xFexIn2S 4 compounds were grown by the chemical vapour transport method using iodine as transport agent. The crystals were grown by placing the ampoule in a two zone furnace, keeping the source temperature and the deposition temperature at 850 and 800 °C respectively. The resulting crystals with nominal concentrations: x = 0.25, 0.5, 0.75 were characterized by X-ray powder diffraction, electron probe micro-analysis and magnetic measurements. Electron probe micro-analysis showed that the actual concentration of Fe was lower than the nominal one. X-ray diffractograms were taken at room temperature for each sample, revealing that the compounds form a solid solution in the whole range of compositions and crystallize with cubic symmetry in the space group Fd3m. All samples show a spinel structure with a random arrangement of cations. The magnetic behavior of the samples was investigated by low-field magnetization measurements in the range 5-300 K. The observed magnetic behavior does not show any magnetic transition in the studied temperature range. However an irreversibility has been observed between zero-field-cooled (ZFC) and field-cooled (FC) cycles. High temperature susceptibility data follow the Curie-Weiss law with a negative paramagnetic Curie temperature, indicating the predominance of antiferromagnetic interactions. The optical absorption data for sample with x = 0.75 shows a direct energy gap of 1.28 eV at RT. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Electron-microscopy study of Fe-implanted InP
No full textInP implanted with 200 keV Fe ions to a dose of 1 x 10(14) atoms/cm(2) has been investigated by Transmission Electron Microscopy (TEM). The as-implanted sample exhibits an amorphous surface region. At the annealing temperature of 650 degrees C, nearly complete solid-phase epitaxial regrowth is achieved only for annealing times greater than 1.5 h. For annealing times up to 2 h. however, the samples still contain extended defects such as stacking-fault tetrahedra of vacancy-type and dislocation loops of interstitial-type, mostly concentrated in a band which corresponds to the region of transition between amorphous top layer and crystalline substrate, as was detected in the as-implanted sample. Stacking-fault tetrahedra and loops have also been observed above and below this band, respectively. The origin of these defects is discussed
BIB-designs from circular nearrings
No full textLet (N,Φ) be a finite circular Ferrero pair. We define the disk with center b and radius a,D(a;b) , as
D(a;b)={x∈Φ(r)+c∣r≠0,b∈Φ(r)+c,|(Φ(r)+c)∩(Φ(a)+b)|=1}.
Using this definition we introduce the concept of interior part of a circle, Φ(a)+b , as the set I(Φ(a)+b)=D(a;b)∖(Φ(a)+b) . Moreover, if BD is the set of all disks, then, in some interesting cases, we show that the incidence structure (N,BD,∈) is actually a balanced incomplete block design and we are able to calculate its parameters depending on |N| and |Φ|
TiO2 thin films by a novel sol-gel processing for gas sensor applications
No full textNovel thin films of titanium dioxide dispersed in a polymeric matrix have been prepared by a chemically modified sol-gel technique. Nanostructured films of pure TiO2 in the anatase form are obtained after annealing at 500 degrees C. SEM, TEM and TG/DTA are used for the structure characterisation of TiO2 films. The role of the polymer in controlling the microstructure is confirmed. The first application of this technique in gas sensor field is presented in this work. Ethanol and methanol sensing properties are tested and reported. TiO2 sensors can detect very well concentration required for breath analysers. (C) 2000 Elsevier Science S.A. All rights reserved
Structural and Electrical-properties of N-type Bulk Gallium-arsenide Grown From Non-stoichiometric Melts
No full textNonlocal Cahn–Hilliard–Hele–Shaw Systems with Singular Potential and Degenerate Mobility
No full textWe study a Cahn–Hilliard–Hele–Shaw (or Cahn–Hilliard–Darcy) system for an incompressible mixture of two fluids. The relative concentration difference φ is governed by a convective nonlocal Cahn–Hilliard equation with degenerate mobility and logarithmic potential. The volume averaged fluid velocity u obeys a Darcy’s law depending on the so-called Korteweg force μ∇ φ, where μ is the nonlocal chemical potential. In addition, the kinematic viscosity η may depend on φ. We establish first the existence of a global weak solution which satisfies the energy identity. Then we prove the existence of a strong solution. Further regularity results on the pressure and on u are also obtained. Weak–strong uniqueness is demonstrated in the two-dimensional case. In the three-dimensional case, uniqueness of weak solutions holds if η is constant. Otherwise, weak–strong uniqueness is shown by assuming that the pressure of the strong solution is α-Hölder continuous in space for α∈ (1 / 5 , 1)
RELATIONSHIP BETWEEN MELT COMPOSITION, DISLOCATIONS, PRECIPITATES AND ELECTRON-MOBILITY IN N-TYPE LEC GAAS
No full textRegularity results for the nonlocal Cahn-Hilliard equation with singular potential and degenerate mobility
No full textWe consider the nonlocal Cahn-Hilliard equation with singular potential and degenerate mobility in a bounded domain Ω⊂R^d, d≤3. We first prove the existence of maximal strong solutions in weighted (in time) L^p spaces. Then we establish further regularity properties of the solution through maximal regularity theory. Finally, we revisit the separation property in an appendix
MPAIRMENT OF TUMOR ANGIOGENESIS AND GROWTH BY IN VIVO AQUAPORIN-1 RNA INTERFERENCE
No full textAngiogenesis has been related with the expression of a water channel protein, Aquaporin-1 (AQP1), widely expressed in vascular endothelia where it increases plasma membrane water permeability and facilitates cell migration. We here hypothesized that AQP1 knockdown (KD) by RNA interference would affect the formation of new vessels and therefore the tumor growth. In vivo experiments were performed by intratumoral injection of lipid-formulated AQP1 specific siRNAs together with scrambled siRNAs as control on a well established mouse model of melanoma. Results showed that AQP1 specific siRNAs significantly reduced the tumor growth compared with the scrambled ones. AQP1 and Factor VIII expression levels were measured by Western blot. AQP1 interference induced a 7-fold reduction of AQP1 and a parallel 2.5-fold reduction of the endothelia marker Factor VIII, indicating a reduction of the number of vessels associated with AQP1 KD. Moreover, AQP1 immunofluorescence analysis showed a weak staining in AQP1 KD melanoma vessels whose diameter and number was significantly reduced. The results indicate that i) AQP1 has an important role in tumor angiogenesis, ii) AQP1 siRNA can efficiently target and inhibit angiogenesis and tumor growth when locally delivered, iii) RNA interference can be considered a new therapeutic approach for the inhibition of tumor growth
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