Monte Carlo simulation of water-tetrahydrofuran mixtures

Monte Carlo simulations of water-tetrahydrofuran (THF) mixtures were performed in the isothermal-isobaric ensemble (NPT) at T = 298 K and p = 1 atm. The interaction energy was calculated using the TIP4P model for water and a five-site united atom representation for the THF molecule. The potential energy surfaces for water-THF interactions were obtained by using combining rules and the original potential functions used for pure liquids. Theoretical values obtained for the average interaction energy as a function of concentration are in good agreement with available experimental data. Results from the partitioning of the total interaction energy into water-water, water-THF and THF-THF contributions are presented. These results are useful to distinguish between the quantitative contributions of these molecular interactions to the energetic behavior of the water-THF mixing process. The radial distribution functions for HW-OTHF and OW-OTHF site-site interactions show the salient features of hydrogen-bonded liquids. Comparison of the average number of water-water complexes interacting through hydrogen bonding in water-THF and water-methanol mixtures shows an enhancement of the water-water coordination number in a THF rich environment. © 1995.

Alternate current biosusceptometry for the assessment of gastric motility after proximal gastrectomy in rats: a feasibility study

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Controlling the formation of ionic-liquid-based aqueous biphasic systems by changing the hydrogen-bonding ability of polyethylene glycol end groups

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Influência dos polimorfismos Taql e Bsml do gene do receptor de vitamina D no surgimento de infecção, tempo de internação e mortalidade em pacientes queimados

Pós-graduação em Fisiopatologia em Clínica Médica - FMB

Adsorção de cádmio e chumbo em solução aquosa por lama vermelha natural e com diferentes ativações

Pós-graduação em Engenharia Civil e Ambiental - FEB

Análise do consumo de extato hidrossolúvel de soja na qualidade do tecido ósseo de ratos jovens adultos

Pós-graduação em Ciência Animal - FMVA

Biomolecules extracted by ATPs: practical examples

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Uma experiência didática sobre viscosidade e densidade

In this work, a teaching experience is proposed in order to evaluate and differentiate, in a simple and clear way, two intrinsic properties of matter that make part of daily vocabulary, viscosity and density. To this end, three liquids for domestic use have been chosen, namely saccharose solution, biodegradable detergent and vegetal soybean oil. The results analysis evidences the lack of a proportional relationship among these properties.

Determinação do teor alcoólico de vodcas: uma abordagem multidisciplinar no ensino da física, química e matemática

In this paper, it is proposed an experimental activity to be developed with high school students, addressing the concepts of density and surface tension from a multidisciplinary approach among Physics, Chemistry and Mathematics. In this proposal, students are challenged to determine the alcohol content of vodkas from intensive physical properties of liquids. Two calibration curves were obtained, one for density and another for surface tension as a function of ethanol concentration in water. The alcohol levels obtained from these properties were very close to the values given by manufacturers, due the similarity of these beverages with ethanol-water binary mixtures.

Avaliação de um pulverizador e volume ultra baixo e de adjuvantes em caldas fitossanitárias na cultura dos citros

Pós-graduação em Agronomia (Produção Vegetal) - FCAV

Controlador de temperatura para célula de medição de propriedades de líquidos por ultrassom

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Aplicação de sensor de deslocamento angular em fibra óptica para medição de concentração de líquidos via ondas acústicas guiadas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

RB32-266 Cooling Milk on Nebraska Farms

The desire of Nebraska people to continue the improvement of living conditions and to secure more healthful foods has been responsible for many changes in methods of caring for milk. One of the important factors in keeping milk sweet and of good quality is the process of cooling and keeping it cool until used. Three of these processes are as follows: placing containers of warm milk in any quantity of still water or still air at temperatures ranging from freezing to within a few degrees of the temperature of the milk, placing the containers in such positions that air or water are circulated around them, and causing the milk to flow in such manner that a thin film comes in contact with a surface which is cooled by air or liquids varying in temperature from 10 degrees Fahrenheit to a few degrees below that of the milk. After some of the heat has been removed the milk is stored under conditions very similar to those found in cooling processes. This 1932 research bulletin discusses why milk is cooled, why milk sours, how bacteria grows, and the many ways that milk can be cooled.

Experimento para quantificar a eficiência de aspersão de líquidos: aplicação em distribuidores espinha de peixe

This paper describes a device developed on the pilot scale and a simple approach to compare liquid distributor efficiencies. The technique consists basically of analyzing the mass of the liquid collected in 21 vertical pipes measuring 52 mm in internal diameter and 800 mm in length placed in a quadratic arrangement and positioned below the distributor A 50 mm thick acrylic blanket that does not disperse liquids was placed between the distributor and the pipe bank to avoid splashes. Assays were carried out with ladder-type distributors equipped with 4 parallel pipes each for a column measuring 400 nun in diameter as an example of the application. The number (n) of orifices (95, 127, and 159 orifices/m(2)), orifice diameter (d) (2, 3, and 4 mm) and the flowrate (q) (1.2; 1.4; and 1.6 m(3)/h) were varied. The best spread efficiency, which presented the lowest standard deviation, was achieved with 159 orifices, 2 mm and 1.4 m(3)/h. The pressure (p) at the distributor inlet for this condition was only 51000 Pa (0.51 kgf/cm(2)), while the average velocity (v) was 6.3 m/s in each orifice. These results show some limitations of the practical rules used in distributor designs.

Computer simulation study of collective dynamics in the glass former Ca(NO3)(2)center dot 4H(2)O

Time correlation functions of current fluctuations were calculated by molecular dynamics (MD) simulations in order to investigate sound waves of high wavevectors in the glass-forming liquid Ca(NO3)(2)center dot 4H(2)O. Dispersion curves, omega(k), were obtained for longitudinal (LA) and transverse acoustic (TA) modes, and also for longitudinal optic (LO) modes. Spectra of LA modes calculated by MD simulations were modeled by a viscoelastic model within the memory function framework. The viscoelastic model is used to rationalize the change of slope taking place at k similar to 0.3 angstrom(-1) in the omega(k) curve of acoustic modes. For still larger wavevectors, mixing of acoustic and optic modes is observed. Partial time correlation functions of longitudinal mass currents were calculated separately for the ions and the water molecules. The wavevector dependence of excitation energies of the corresponding partial LA modes indicates the coexistence of a relatively stiff subsystem made of cations and anions, and a softer subsystem made of water molecules. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4751548]