Search results for "Dispersion"

Chasing Weak Forces: Hierarchically Assembled Helicates as a Probe for the Evaluation of the Energetics of Weak Interactions.

2017

London dispersion forces are the weakest interactions between molecules. Because of this, their influence on chemical processes is often low, but can definitely not be ignored, and even becomes important in cases of molecules with large contact surfaces. Hierarchically assembled dinuclear titanium(IV) helicates represent a rare example in which the direct observation of London dispersion forces is possible in solution even in the presence of strong cohesive solvent effects. Hereby, the dispersion forces do not unlimitedly support the formation of the dimeric complexes. Although they have some favorable enthalpic contribution to the dimerization of the monomeric complex units, large flexible…

Development of microfluidics for sorting of carbon nanotubes

2018

Sorting of carbon nanotubes by their chirality is the current bottleneck in the way to their broad employment based on their exceptional electronic and optical properties. Despite the extensive effort, there is no known method, which would result in really pure chirality ensembles. Previously reported sorting protocols result in enrichment rather than in sorting, alter electronic structure, and suffer from low yield. This is mostly due to the statistical approach, where the nanotubes with mixed chiralities are treated as a set. In this thesis, we propose a new sorting technique based on nanotube-by-nanotube compartmelization, characterization, and sorting in a continuously running droplet-b…

Structure and dielectric breakdown strength of nano calcium carbonate/polypropylene composites

2013

Nanodielectrics, a 21st-century phenomena, is envisioned to be the answer for material challenges in progressive high-voltage technology. It is well known that the proper dispersion of nanoparticles plays a key role in improving the dielectric properties of a material, but to understand where changes in the properties of a material originate, it is also essential to reveal the multiscale structure of the material. In this study, the dielectric permittivity, breakdown strength, and structure of nano calcium carbonate (nano-CaCO3)/polypropylene composites with 1.8-8.1 wt % doping were characterized systematically. The combined results from transmission electron microscopy, Raman microscopy, a…

A one-pot method to enhance dissolution rate of low solubility drug molecules using dispersion polymerization in supercritical carbon dioxide

2009

Competition of electron-phonon mediated superconductivity and Stoner magnetism on a flat band

2018

The effective attractive interaction between electrons, mediated by electron-phonon coupling, is a well-established mechanism of conventional superconductivity. In metals exhibiting a Fermi surface, the critical temperature of superconductivity is exponentially smaller than the characteristic phonon energy. Therefore, such superconductors are found only at temperatures below a few kelvin. Systems with flat energy bands have been suggested to cure the problem and provide a route to room-temperature superconductivity, but previous studies are limited to only BCS models with an effective attractive interaction. Here we generalize Eliashberg's theory of strong-coupling superconductivity to syst…

Engineered surface waves in hyperbolic metamaterials

2013

We analyzed surface-wave propagation that takes place at the boundary between a semi-infinite dielectric and a multilayered metamaterial, the latter with indefinite permittivity and cut normally to the layers. Known hyperbolization of the dispersion curve is discussed within distinct spectral regimes, including the role of the surrounding material. Hybridization of surface waves enable tighter confinement near the interface in comparison with pure-TM surface-plasmon polaritons. We demonstrate that the effective-medium approach deviates severely in practical implementations. By using the finite-element method, we predict the existence of long-range oblique surface waves. This research was fu…

Génération de similaritons optiques à 1550 nm par amplification Raman dans une fibre NZ-DSF

2004

Nous presentons la premiere observation experimentale de similaritons optiques generes par amplification Raman a 1550 nm dans une fibre a dispersion decalee. Une caracterisation FROG des impulsions indique un profil d'intensite parabolique et un chirp lineaire conformes aux predictions theoriques.

Tube transport of water vapor with condensation and desorption

2013

Attenuation and delay of active tracers in tube transport is an important current problem, but its full explanation is still lacking. To this end a model is introduced, where part of a tracer undergoes condensation and evaporation, treated as a diffusion-type process, in addition to Taylor dispersion. Condensation of water was verified by high-speed imaging, and the model solution fitted the breakthrough curves of laboratory measurements with pulses of water vapor of varying relative humidity. The model provides a transfer function whose performance was verified against field measurements. peerReviewed

Riconfigurare i territori metroplitani. Forme di urbanizzazione e fenomeni di pressione insediativa sui sistemi di interesse naturale in Sicilia

2018

The consumption of the soil due to urbanization it is a phenomena already for many years under observations, but of which only the scientific environment has noticed the elevated environmental impact progress. From a disciplinary point of view, is possible to identify a line of research focusing on the analysis and identification of new morphologies of urbanization and on the interaction among different settlement patterns coexisting in a specific context. This reading complements with the scientific production about the forms of settlement pressure on environmental systems, producing change and deterioration on natural ecosystems and loss of biodiversity. A necessary reference for this lin…

Orientamento e inclusione: uno studio di caso nelle scuole secondarie palermitane di primo grado

2017

This paper presents the main results of the research work that promoted the design and implementation of training and guidance played in the territory of Palermo during the school years 2013/2014 and 2014/2015 in three secondary schools, with operating procedures, capable of promoting inclusive paths, based on the involvement of students, teachers and parents. The assumption from which we started is that the problems of dispersion and social marginalization can be addressed not only through direct guidance interventions with young people at risk, but also involving adults of reference because we are convinced that this will have, even at a distance of time a significant impact on students. …