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71.
Hilles H Monroy F Bonales LJ Ortega F Rubio RG 《Advances in colloid and interface science》2006,122(1-3):67-77
The linear regime (LR) of viscoelastic behavior has been found to be limited to rather small values of strain, well below the strains found in many technological processes. A Fourier-transform method is described for analyzing the surface rheology data obtained in insoluble Langmuir polymer monolayers beyond the LR. In the concentrate regime, the monolayers show a transition from elastic to plastic behavior, which is characterized by high irreversibility. A simple 2-D rubber model is presented that describes the behavior of the monolayers in the non-linear region not too far from the end of the LR. 相似文献
72.
Dilational rheology of monolayers of a miscible polymer blend: From good- to poor-solvent conditions
Rivillon S Monroy F Ortega F Rubio RG 《The European physical journal. E, Soft matter》2002,9(4):375-385
The viscoelastic moduli (elasticity and dilational viscosity) of monolayers of PVAc + P4HS has been studied over a broad frequency
range (0.1 mHz-200 kHz) using a combination of relaxation and capillary-waves techniques. The analysis of the surface pressure,
the elasticity and the viscosity on the semidilute regime show that the air-water interface is a good solvent for the monolayers
of PVAc-rich blends, and a poor (near-Θ) solvent for the monolayers of P4HS-rich blends. The solvent quality changes continuously
over a broad concentration range. The results of viscoelastic moduli show that there is a broad relaxation process in the
low-frequency range ( ω < 1 Hz). While for PVAc-rich monolayers this relaxation process follows the reptation-like behavior
described by Noskov, for P4HS-rich monolayers the model does not describe the amplitudes of the different relaxation modes.
For PVAc-rich monolayers two processes are clearly distinguished at higher frequencies: one centered at around 500 Hz and
another one at around 40 kHz. However, for P4HS-rich monolayers only one broad relaxation mode is found below 1 kHz. The crossover
from one type of behavior to the other one takes place in a very narrow blend-composition range, and is not clearly related
to the crossover from good- to poor-solvent condition.
Received 7 June 2002 and Received in final form 5 November 2002
RID="a"
ID="a"Current address: Complex Fluids Lab., Cranbury Res. Ctr., Rhodia Inc., Cranbury, NJ 08512-7500, USA.
RID="b"
ID="b"e-mail: rgrubio@quim.ucm.es 相似文献
73.
E. Sarigiannidou E. Monroy E. Bellet-Amalric H. Mariette R.M. Galera J. Cibert F. Wilhelm A. Rogalev 《Superlattices and Microstructures》2006,40(4-6):239
We report on the optimization of the growth conditions of wurtzite GaMnN grown by plasma-assisted molecular beam epitaxy in order to obtain intrinsic ferromagnetic behavior. By growing with a Ga/N ratio lower than unity and by introduction of periodic growth interruptions, we succeed in synthesizing single-phase GaMnN epilayers containing up to 6.3 at.% of Mn. The structural quality of the GaMnN epilayer and the absence of secondary phases are demonstrated by means of X-ray diffraction experiments and X-ray linear dichroism measurements performed at the Mn and Ga K-edges. The intrinsic ferromagnetism for 6.3 at.% of Mn in our GaMnN epilayer is demonstrated by means of magnetization measurements in a 5 T Quantum Design superconducting quantum interference device (SQUID) and X-ray magnetic circular dichroism investigations performed at the K-edge of Mn. The Curie temperature thus determined is equal to 8 K and a spontaneous magnetic moment of 2.4μB per Mn atom is found at 2 K. 相似文献
74.
A. Benami G. Santana B.M. Monroy A. Ortiz J.C. Alonso J. Fandio J. Aguilar-Hernndez G. Contreras-Puente 《Physica E: Low-dimensional Systems and Nanostructures》2007,38(1-2):148
The photoluminescence (PL) of silicon nanoclusters embedded in silicon nitride films grown by remote plasma-enhanced chemical vapor deposition at 200 °C, using mixtures of SiCl4/H2/Ar/NH3 is investigated. It was found that the color and the intensity of the PL of the as-grown samples depend on the H2 flow rate, and there is an optimum flow for which a maximum luminescence is obtained. A strong improvement of the PL intensity and change in color was obtained with annealing treatments in the range of 500–1000 °C. The changes in the composition, structure and optical properties of the films, as a function of H2 flow rate and thermal treatments, were studied by means of Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, ellipsometry and ultraviolet–visible transmission measurements. We conclude that the PL can be attributed to quantum confinement effect in silicon nanoclusters embedded in silicon nitride matrix, which is improved when a better passivation of the nanoclusters surface is obtained. 相似文献
75.
Influence of ammonium on the performance of a denitrifying culture under heterotrophic conditions 总被引:6,自引:0,他引:6
The effect of ammonium on a denitrifying reactor of the upflow anaerobic sludge blanket type was studied. At a constant nitrate
loading rate (2500 mg NO
3
−
-N/[L · d]), using acetate as organic electron donor and at a C/NO
3
−
-N ratio of 1.23, an increase in the N2 production rate was observed when the ammonium loading rate was increased (25, 250, and 500 mg NH
4
+
-N/[L · d]). Dissimilatory nitrate reduction to ammonium (DNRA) was not observed, and the N2 production efficiency was increased from 84 to 100% or higher. Since NH
4
+
in the output was lower than in the input, it was suggested that it was used for nitrate reduction. At constant NH
4
+
-N/NO
3
−
-N and C/NO
3
−
-N ratios of 0.2 and 1.63, respectively, the molecular nitrogen production rate was increased at 300 and 500 mg NH
4
+
-N/(L · d), whereas at 200 mg NH
4
+
-N/(L · d) DNRA took place probably owing to culture conditions of low reductive power. Molecular nitrogen production was
not observed under autotrophic conditions, and the addition of acetate to the culture recovered its high nitrogen removal
rate. Experimental results and balances indicated that the consumed ammonium was used as an additional reductive source. 相似文献