Search results for "scientific method"

The Complex Process of Haemostasis and Interactions due to Hyperosmotic Fluids

2017

A slow process in confined polymer melts: layer exchange dynamics at a polymer solid interface

2010

Employing Molecular Dynamics simulations of a chemically realistic model of 1,4-polybutadiene between graphite walls we show that the mass exchange between layers close to the walls is a slow process already in the melt state. For the glass transition of confined polymers this process competes with the slowing down due to packing effects and intramolecular rotation barriers.

Multi-scale simulations of polymeric nanoparticle aggregation during rapid solvent exchange.

2018

Using a multi-scale approach which combines both molecular dynamics (MD) and kinetic Monte Carlo (KMC) simulations, we study a simple and scalable method for fabricating charge-stabilized nanoparticles through a rapid solvent exchange, i.e., Flash NanoPrecipitation (FNP). This multi-scale approach is based on microscopic information from MD simulations and uses a KMC algorithm to access macroscopic length- and time scales, which allows direct comparison with experiments and quantitative predictions. We find good agreement of our simulation results with the experiments. In addition, the model allows us to understand the aggregation mechanism on both microscopic and macroscopic levels and det…

Supercritical-fluid extraction of chlorofluoroalkanes from rigid polyurethane foams

1996

Abstract Preliminary results about a process for recovering expanding agents chlorofluoroalkanes (CFCs) both trapped in the cavities and dissolved in the polymer from rigid polyurethane foams are reported. The performances of liquid and supercritical carbon dioxide, and of CO2-propane supercritical mixtures were compared. Better results in terms of extraction time and amount of extracted CFCs were obtained with finely ground materials and supercritical propane-carbon dioxide fluids.

Photocatalytic ozonation: Maximization of the reaction rate and control of undesired by-products

2015

Abstract In the so-called photocatalytic ozonation (PO) synergistic effects between photocatalysis and ozonation enhance the rate of oxidation of organic compounds, therefore this integrated process is very promising for use in water treatment. In the present work, it is demonstrated that the improvement that can be obtained by the integrated process in comparison with the uncoupled processes depends on the relative weight between photocatalysis and ozonation. In this respect, it has been found that a relatively low rate of photocatalysis (0.3 times the rate of ozonation) is sufficient to get the highest synergy and to maximize the performances in the oxidation of formate, the adopted model…

Thermal rearrangements of 1,2-dialkoxybenzenes by flash vacuum pyrolysis

1995

Flash vacuum pyrolysis of 1,2-dialkoxybenzenes 1a-c leads to the liberation of alkanes from the interacting side chains. A rearrangement of the skeleton yields the o-hydroxy carbonyl compounds 2 and 4. The generation of phenol 3 can be rationalized by a decarbonylation. The latter reaction is the sole process which can be observed for the bicyclic starting compound 9.

Real-time observation of the charge transfer to solvent dynamics

2013

Intermolecular electron-transfer reactions have a crucial role in biology, solution chemistry and electrochemistry. The first step of such reactions is the expulsion of the electron to the solvent, whose mechanism is determined by the structure and dynamical response of the latter. Here we visualize the electron transfer to water using ultrafast fluorescence spectroscopy with polychromatic detection from the ultraviolet to the visible region, upon photo-excitation of the so-called charge transfer to solvent states of aqueous iodide. The initial emission is short lived (similar to 60 fs) and it relaxes to a broad distribution of lower-energy charge transfer to solvent states upon rearrangeme…

Offensive Transitions in High-Performance Football: Differences Between UEFA Euro 2008 and UEFA Euro 2016

2019

[Abstract] Coaches, footballers and researchers agree that offensive transitions are one of the most important moments in football today. In a sport where defense over attack dominates, with low scores on the scoreboard, the importance of these actions from the offensive point of view becomes very important. Despite this, scientific literature is still very limited on this topic. Therefore, the objectives set out in the present investigation have been two: first, by means of a proportion analysis and the application of a chisquare test, it was intended to describe the possible differences between the offensive transitions made in the UEFA Euro 2008 and UEFA Euro 2016; then, through differen…

Graphitically encapsulated cobalt nanocrystal assemblies

2010

Graphitically encapsulated cobalt nanocrystal assemblies are chemically prepared by one-pot reaction at380 degrees C followed by a reversed etching process to produce porous graphitic structure for revealing their self-assembling nature.

THE OCCURRENCE OF CHROMIUM IN RAW MATERIALS AND ITS FATE IN THE BREWING PROCESS

1987

The chromium content of raw materials, intermediate and final products in the brewing process were determined in order to evaluate the contribution of raw materials to the chromium content of beer. The contribution due to beer in the diet is considered in the light of the recommended daily intake of chromium.