1,854 research outputs found
Liquid mixtures involving fluorinated alcohols: The equation of state (p, r, T, x) of (Ethanol + Trifluoroethanol) Experimental and Simulation
Liquid mixtures involving fluorinated alcohols:
The equation of state (p, r, T, x) of (Ethanol + Trifluoroethanol)
Experimental and Simulation
Pedro Duartea, DjĂŞide Rodriguesa, Marcelo Silvaa, Pedro Morgadoa,
LuĂs Martinsa,b and Eduardo J. M. Filipea*
aCentro de QuĂmica Estrutural, Instituto Superior TĂ©cnico, 1049-001 Lisboa, Portugal
bCentro de QuĂmica de Évora, Universidade de Évora, 7000-671 Évora, Portugal
Fluorinated alcohols are substances with unique properties and high technological value in the pharmaceutical and chemical industries. Trifluoroethanol (TFE), in particular, displays a number of unusual properties as a solvent. For example, it dissolves nylon at room temperature and is effectively used as solvent in bioengineering. The presence of the three fluorines atoms gives the alcohol a high ionization constant, strong hydrogen bonding capability and stability at high temperatures.
In the pharmaceutical industry, TFE finds use as the major raw material for the production of inhalation anesthetics. Mixtures of TFE and water (known as Fluorinols®) are used as working fluids for Rankine cycle heat engines for terrestrial and space applications, as a result of a unique combination of physical and thermodynamic properties such as high thermal efficiency and excellent turbine expansion characteristics.
Environmentally, TFE is a CFC substitute with an acceptable short lifetime and with small ozone depletion potential. Additionally, TFE is known to induce conformational changes in proteins and it is used as a co-solvent to analyze structural features of partially folded states.
The (ethanol + TFE) system displays an interesting and peculiar behaviour, combining a negative azeotrope with high positive excess volumes.
In this work, liquid mixtures of (ethanol + TFE) were investigated. The densities of the mixtures were measured as a function of composition between 278K and 338K and at pressures up to 700 bar. The corresponding excess volumes as a function of temperature and pressure, the isothermal compressibilities and thermal expansivities were calculated from the experimental results. The mixtures are highly non-ideal with excess volumes ranging from 0.8 - 1.0 cm3mol-1.
Finally, molecular dynamic simulations were performed to model and interpret the experimental results. The Trappe force field was used to simulate the (TFE + ethanol) mixtures and calculate the corresponding excess volumes. The simulation results are able to reproduce the correct sign and order of magnitude of the experimental VE without fitting to the experimental data. Furthermore, the simulations suggest the presence of a particular type of hydrogen bridge between ethanol and TFE, that can help to rationalize the experimental results
Supporting the Voice of People with Disabilities in Kenya, Uganda and Jordan
Research methods need to be adapted to the cultural
context and traditions with which participants are
familiar. Limited work has been attempted to explore
ways to engage people with disabilities in low resource
settings. In this paper we present methods used in two
research projects that engage and actively support the
voice of people with disabilities living in low resource
settings. We discuss which methods have worked well
and which not, with recommendations based on our
experience and the research results
Individuality over function: the role of technology in disability identity
When designing or investigating technology use among
people with disabilities, researchers often overstate the
importance of functional aspects at the expenses of
identity. We present three case studies that showcase
how people with disabilities use, or aspire to use,
technology to advertise, reframe or hide their
identities
Thermal diffusion in solids : an overview
Thermal diffusion in liquids and gases has been the focus of a number of studies and is considered, at present, a reasonably wellknown topic. In solids though, the phenomena is far less understood namely in what regards the effects of thermal gradients upon the integrity and characteristics of
materials. Furthermore it is not clear whether or not thermal diffusion can be used as a purificating method for solids. Yet, many current techniques such as the laser, used in metal working and other
solids, induce strong thermal gradients being, therefore, potential cause for the occurrence of thermal diffusion. In this work, a survey and discussion of theoretical and experimental studies of thermal diffusion in solids is undertaken
Mini-laparoscopic hysterectomy for adenocarcinoma in situ of the uterine cervix using interchangeable 5-mm end effectors: a way to cross the line of minimally invasive surgery in gynaecologic oncology
The incidence of adenocarcinoma of the uterine cervix is increasing. It poses the affected women in risk and the definitive treatment requires hysterectomy. Here we describe a case of adenocarcinoma in situ of the uterine cervix successfully managed by minilaparoscopic hysterectomy using interchangeable 5-mm end effectors.info:eu-repo/semantics/publishedVersio
Critical scaling in standard biased random walks
The spatial coverage produced by a single discrete-time random walk, with
asymmetric jump probability and non-uniform steps, moving on an
infinite one-dimensional lattice is investigated. Analytical calculations are
complemented with Monte Carlo simulations. We show that, for appropriate step
sizes, the model displays a critical phenomenon, at . Its scaling
properties as well as the main features of the fragmented coverage occurring in
the vicinity of the critical point are shown. In particular, in the limit , the distribution of fragment lengths is scale-free, with nontrivial
exponents. Moreover, the spatial distribution of cracks (unvisited sites)
defines a fractal set over the spanned interval. Thus, from the perspective of
the covered territory, a very rich critical phenomenology is revealed in a
simple one-dimensional standard model.Comment: 4 pages, 4 figure
The role of the nature of the noise in the thermal conductance of mechanical systems
Focussing on a paradigmatic small system consisting of two coupled damped
oscillators, we survey the role of the L\'evy-It\^o nature of the noise in the
thermal conductance. For white noises, we prove that the L\'evy-It\^o
composition (Lebesgue measure) of the noise is irrelevant for the thermal
conductance of a non-equilibrium linearly coupled chain, which signals the
independence between mechanical and thermodynamical properties. On the other
hand, for the non-linearly coupled case, the two types of properties mix and
the explicit definition of the noise plays a central role.Comment: 9 pages, 2 figures. To be published in Physical Review
- …