Some universal trends of the Mie(n,m) fluid thermodynamics

By using canonical Monte Carlo simulation, the liquid-vapor phase diagram, surface tension, interface width, and pressure for the Mie(n,m) model fluids are calculated for six pairs of parameters $m$ and $n$. It is shown that after certain re-scaling of fluid density the corresponding states rule can be applied for the calculations of the thermodynamic properties of the Mie model fluids, and for some real substancesComment: 4 figure

Effect of the acrylic acid content on the permeability and water uptake of latex films

Acrylic acid (AA) is a monomer commonly employed in emulsion polymerization to provide electrostatic colloidal stability and improve specific film performance. The addition of AA not only modifies the kinetics of the polymerization, but also it takes part in the interaction between colloidal particles, which has a strong influence on their packing and consequent latex film properties. In this contribution a theoretical modeling of the latex film formation is presented and compared to experimental results: water vapor permeability and latex film capacitance are studied as a function of AA content. It has been shown that water uptake is mainly affected by film morphology which in turn is defined by intercolloidal interaction and drying rate.Comment: 16 pages, 7 figure

Monte Carlo: A versatile tool for modeling complex polymerization processes

Monte Carlo is a stochastic simulation tool which reaches the molecular level to predict both microscopic and macroscopic properties which are of profound interest to the polymer industry and science. Selection of a modeling technique in polymerization systems should be a compromise between complexity of the system, complexity of the model ,stability, the level of the output that is needed and, of course, the time of the simulation. Comparing to other techniques, Monte Carlo is usually more time consuming, but it should be kept in mind that nowadays intensive numerical calculations are cheap and fast due to the current available computational power. On the other hand, Monte Carlo simulation usually needs less simplification than other methods and very detailed information on microscopic properties of very complex systems can be obtained that is elusive (if not impossible) to obtain by deterministic models as details are too complex as to be modeled by material and population balances. This is the place where Monte Carlo enlists as a unique tool for describing complex polymerization systems. In this work we exploit the advantages of the Monte Carlo approach to analyze two complex polymerization processes. The first example analyzed is the network formation in free-radical crosslinking copolymerization. The architecture of such a system is complex and not completely understood yet i.e., presence of the multiradicals, cycles and in some cases heterogeneous density of crosslinking. A kinetic Monte Carlo (KMC) approach has been applied to study the development of polymer network formation. The proposed modelling approach is able to provide detailed information beyond the gel point that can lead to an enhanced characterization of the gel fraction. The KMC simulation intrinsically considers the primary and secondary cyclization reactions and the existence of multiradicals, avoiding the use of further assumptions. The model gave very detailed information on the microstructure of a crosslinked system after gelation like conversion evolution of the entire molecular weight distribution, the primary and secondary cyclization, the molecular weight distribution between crosslinking points and the evolution of multiradicals along the polymerization. Furthermore, 3D distributions can also be obtained like the distribution of chains with a given chain length and crosslinking density. The KMC model was used to show the detailed characterization of the gel fraction with conversion and differences observed in the distributions before and after the gel point. The second example analyzed is the synthesis of hybrid polyurethane/acrylic polymer particles by batch miniemulsion polymerization. This is a very complex system in which polyaddition of the polyurethane prepolymer with the hydroxyl group of HEMA and the free radical polymerization of the acrylic monomers occur simultaneously. Furthermore, the fact that the process is heterogeneous should be considered. A detailed kinetic Monte Carlo simulation algorithm was developed to describe this system. The simulation considers both, the polymerization in the aqueous phase and in the polymer particles, and also simultaneous polyaddition and the free radical polymerization. The model has been assessed by batch miniemulsion polymerizations carried out using an aliphatic isocyanate prepolymer, n-butyl acrylate and 2-hydroxyethyl methacrylate monomers. Detailed information on gel microstructure such as distribution of molecular weight between crosslinking points in acrylic chains, level of incorporation of PU chains (dangling or crosslinked) in the polymer network, and chain length distribution of crosslinked PU prepolymers has been derived from the model. Furthermore, fitting of the experimental kinetics and microstructure evolutions (gel fraction) suggested that the presence of the water in polymer particles cannot be ignored in the presence of isocyanate groups in the polymer particles and that the terminal pendent double bond of the HEMA in polymer chains have significantly lower reactivity than that of the HEMA free monomer

Memorias del primer Simposio Nacional de Ciencias Agronómicas

Primer simposio nacional de Ciencias Agronómicas: El renacer del espacio de discusión científica para el Agro colombiano

Memorias del primer Simposio Nacional de Ciencias Agronómicas

Primer simposio nacional de Ciencias Agronómicas: El renacer del espacio de discusión científica para el Agro colombiano

Transverse momentum spectra of charged particles in proton–proton collisions at √s=900 GeV with ALICE at the LHC

The inclusive charged particle transverse momentum distribution is measured in proton–proton collisions at s=900 GeV at the LHC using the ALICE detector. The measurement is performed in the central pseudorapidity region (|η|<0.8) over the transverse momentum range 0.15<pT<10 GeV/c. The correlation between transverse momentum and particle multiplicity is also studied. Results are presented for inelastic (INEL) and non-single-diffractive (NSD) events. The average transverse momentum for |η|<0.8 is 〈pT〉INEL=0.483±0.001 (stat.)±0.007 (syst.) GeV/c and 〈pT〉NSD=0.489±0.001 (stat.)±0.007 (syst.) GeV/c, respectively. The data exhibit a slightly larger 〈pT〉 than measurements in wider pseudorapidity intervals. The results are compared to simulations with the Monte Carlo event generators PYTHIA and PHOJET

Global economic burden of unmet surgical need for appendicitis

Background There is a substantial gap in provision of adequate surgical care in many low- and middle-income countries. This study aimed to identify the economic burden of unmet surgical need for the common condition of appendicitis. Methods Data on the incidence of appendicitis from 170 countries and two different approaches were used to estimate numbers of patients who do not receive surgery: as a fixed proportion of the total unmet surgical need per country (approach 1); and based on country income status (approach 2). Indirect costs with current levels of access and local quality, and those if quality were at the standards of high-income countries, were estimated. A human capital approach was applied, focusing on the economic burden resulting from premature death and absenteeism. Results Excess mortality was 4185 per 100 000 cases of appendicitis using approach 1 and 3448 per 100 000 using approach 2. The economic burden of continuing current levels of access and local quality was US $92 492 million using approach 1 and$73 141 million using approach 2. The economic burden of not providing surgical care to the standards of high-income countries was $95 004 million using approach 1 and$75 666 million using approach 2. The largest share of these costs resulted from premature death (97.7 per cent) and lack of access (97.0 per cent) in contrast to lack of quality. Conclusion For a comparatively non-complex emergency condition such as appendicitis, increasing access to care should be prioritized. Although improving quality of care should not be neglected, increasing provision of care at current standards could reduce societal costs substantially

Global economic burden of unmet surgical need for appendicitis

Background There is a substantial gap in provision of adequate surgical care in many low- and middle-income countries. This study aimed to identify the economic burden of unmet surgical need for the common condition of appendicitis. Methods Data on the incidence of appendicitis from 170 countries and two different approaches were used to estimate numbers of patients who do not receive surgery: as a fixed proportion of the total unmet surgical need per country (approach 1); and based on country income status (approach 2). Indirect costs with current levels of access and local quality, and those if quality were at the standards of high-income countries, were estimated. A human capital approach was applied, focusing on the economic burden resulting from premature death and absenteeism. Results Excess mortality was 4185 per 100 000 cases of appendicitis using approach 1 and 3448 per 100 000 using approach 2. The economic burden of continuing current levels of access and local quality was US $92 492 million using approach 1 and$73 141 million using approach 2. The economic burden of not providing surgical care to the standards of high-income countries was $95 004 million using approach 1 and$75 666 million using approach 2. The largest share of these costs resulted from premature death (97.7 per cent) and lack of access (97.0 per cent) in contrast to lack of quality. Conclusion For a comparatively non-complex emergency condition such as appendicitis, increasing access to care should be prioritized. Although improving quality of care should not be neglected, increasing provision of care at current standards could reduce societal costs substantially