17,433 research outputs found
Computational studies on the behaviour of anionic and nonionic surfactants at the SiO (silicon dioxide)/water interface
Molecular dynamics simulations to study the behaviour of anionic (Sodium
Dodecylsulfate, SDS) and nonionic (Monooleate of Sorbitan, SPAN80) surfactants
close to a SiO (silicon dioxide) surface were carried out. Simulations
showed that a water layer was first adsorbed on the surface and then the
surfactants were attached on that layer. Moreover, it was observed that water
behaviour close to the surface influenced the surfactant adsorption since a
semi-spherical micelle was formed on the SiO surface with SDS molecules
whereas a cylindrical micelle was formed with SPAN80 molecules. Adsorption of
the micelles was conducted in terms of structural properties (density profiles
and angular distributions) and dynamical behaviour (diffusion coefficients) of
the systems. Finally, it was also shown that some water molecules moved inside
the solid surface and located at specific sites of the solid surface.Comment: 8 pages, 6 fiigure
When Do Central Bank Interventions Influence Intra-Daily and Longer-Term Exchange Rate Movements?
This paper examines dollar interventions by the G3 since 1989, and the reasons that trader reactions to these interventions might differ over time and across central banks. Market microstructure theory provides a framework for understanding the process by which sterilized central bank interventions are observed and interpreted by traders, and how this process in turn, might influence exchange rates. Using intra-daily and daily exchange-rate and intervention data, the paper analyzes the influence of interventions on exchange-rate volatility, finding evidence of both within day and daily impact effects, but little evidence that interventions influence longer term volatility.central bank intervention, exchange rate volatility, market-microstructure
Azimuthal Correlations in p-p collisions
We report the analysis of experimental azimuthal correlations measured by
STAR in p-p collisions at = 200 GeV. We conclude that for a fit
of data using Pythia event generator we need to include two values of .Comment: 4 page, 3 figures. Prepared for X Mexican Workshop on Particles and
Fields. Morelia Mich. Nov 7-12, 200
Temperature dependence of the microscopic structure and density anomaly of the SPC/E and TIP4P-Ew water models. Molecular dynamics simulation results
We have investigated temperature trends of the microscopic structure of the
SPC/E and TIP4P-Ew water models in terms of the pair distribution functions,
coordination numbers, the average number of hydrogen bonds, the distribution of
bonding states of a single molecule as well as the angular distribution of
molecules by using the constant pressure molecular dynamics simulations. The
evolution of the structure is put in correspondence with the dependence of
water density on high temperatures down to the region of temperatures where the
system becomes supercooled. It is shown that the fraction of molecules with
three and four bonds determine the maximum density for both models. Moreover,
the temperature dependence of the dielectric constant is obtained and analyzed.Comment: 11 pages, 5 figure
Intentionally disordered superlattices with high dc conductance
We study disordered quantum-well-based semiconductor superlattices where the
disorder is intentional and short-range correlated. Such systems consist of
quantum-wells of two different thicknesses randomly distributed along the
growth direction, with the additional constraint that wells of one kind always
appears in pairs. Imperfections due to interface roughness are considered by
allowing the quantum-well thicknesses to fluctuate around their {\em ideal}
values. As particular examples, we consider wide-gap
(GaAs-GaAlAs) and narrow-gap (InAs-GaSb) superlattices. We show
the existence of a band of extended states in perfect correlated disordered
superlattices, giving rise to a strong enhancement of their finite-temperature
dc conductance as compared to usual random ones whenever the Fermi level
matches this band. This feature is seen to survive even if interface roughness
is taken into account. Our predictions can be used to demonstrate
experimentally that structural correlations inhibit the localization effects of
disorder, even in the presence of imperfections. This effect might be the basis
of new, filter-like or other specific-purpose electronic devices.Comment: REVTeX 3.0, 20 pages, 7 uuencoded compressed PostScript figures as a
separate file. Submitted to IEEE J Quantum Elec
History of the special procedures: a ‘learning-by-doing’ approach to human rights implementation
The existence of UN Special Procedures is the unintended result of the competence accorded to the United Nations Commission on Human Rights and the Sub-Commission on the Prevention of Discrimination and Protection of Minorities in the 1967 Economic and Social Council Resolution 1235 (XLII). The Resolution authorised both bodies ‘to examine information relevant to gross violations of human rights and fundamental freedoms’. The lack of foresight in the creation of such mechanisms, now known as ‘special procedures’, is a fundamental factor in explaining the evolution of methods of work developed by different mandate holders. The ‘soft’ legal basis and geo-political factors surrounding the creation and renewal of mandates explains the freedom and flexibility they have enjoyed in establishing innovative monitoring activities that are more intrusive upon state sovereignty than any other UN human rights mechanism. As the significance of the Special Procedures’ work has grown, attempts to curtail their autonomy and impact have increased accordingly, facilitated precisely by what has been seen as, until recently, their major strength: the lack of a strong institutional and coherent legal framework regulating their activities. This chapter analyses this evolution and outlines the major challenges mandate holders face in maintaining their relevance
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