Immiscible fluid flow through nanotubes

We have analyzed the properties that characterize the water/oil interface when flow occurs through a prismatic flexible surface of van der Waals particles at 300 K. Thermodynamics and dynamics properties of the flow as density profiles, interface width and diffusion coefficients were calculated. We have observed a complex mechanism, the back-and-forth movement of the interface when advancing through a nanotube.Facultad de Ingenierí

Path integral's formulation of the molecular solvent effects

With the formalism of the path-integral into molecular-orbital theory, we introduce the quaturn fluctuation into the molecular ground state. As a consequence, a non-linear formulation of the molecular orbitals is obtained. Then, we connect the non-linear term of the effective Hamiltonian with the solvent effects of the environment surrounding the molecular system, and explain this mechanism.Facultad de Ciencias Exacta

Orbital SCF energies in the double proton transfer of the adenine-thymine base pair

The double-minimum potential generated by the proton motion involved in the two hydrogen bonds of the adenine-thymine base pair can be accounted for through the orbital-energy spectrum. The results show that the greatest interaction between the molecular orbitals is found when the interprotonic distance of the protons is optimum,i.e. at the top of the barrier of the double-minimum potential. This raises the question of charge transfer electronic transitions as a possibility of modelling the behaviour of the double proton transfer in the excited states of this base pair.Il potenziale a doppio minimo generato dal movimento dei protoni coinvolti nei due legami a idrogeno della coppia di basi ademina-timina può essere preso in considerazione attraverso lo spettro di energia orbitale. I risultati mostrano che la maggiore interazione tra orbitali molecolari si trova quando la distanza interprotonica dei prodotti è ottimale, cioè nel punto piú alto della barriera del potenziale a doppio minimo. Ciò solleva il problema della transizioni elettroniche con trasferimento di carica come una possibilità di regolare il comportamento del doppio trasferimento di protoni negli stati eccitati di questa coppia di basi.Потенциал с двойным минимумом, образованный за счет движения протонов, участвующих в двух водородных связях пары оснований аденина и тимина, может быть объяснен с помощью спектра орбитальной энергии. Результаты показывают, что наибольшее взаимодействие между молекулярными орбиталями возникает, когда расстояние между протонами является оптимальным, т.е. на вершине барьера потенциала с двумя минимумами. При этом возникает вопрос о возможности моделирования поведения двойного переноса протонов в возбужденных состояниях этой пары оснований.Instituto de Física La Plat

Conformational properties of methyl vinyl sulfone: Ab initio geometry optimization and vibrational analysis

An ab initio conformational analysis of methyl vinyl sulfone (CH₂CHSO₂CH₃) has been carried out. Molecular geometry optimizations have been performed at the HF and MP2 levels of the theory. Relative energies of the stationary points have been determined by using different approaches, including electron correlation corrections up to the third order. The IR and Raman spectra of the liquid have been measured and a vibrational assignment is proposed. The height of the barrier to the methyl group internal rotation has been estimated. Theoretical calculations and vibrational spectra have shown that the predominant conformation of methyl vinyl sulfone has the C=C bond eclipsed with one of the S=O bonds. Similar eclipsed forms have been found in vinyl fluoro sulfone, vinyl chloro sulfone and divinyl sulfone by ab initio HF calculations.Facultad de Ciencias Exacta

Path integral's formulation of the molecular solvent effects

With the formalism of the path-integral into molecular-orbital theory, we introduce the quaturn fluctuation into the molecular ground state. As a consequence, a non-linear formulation of the molecular orbitals is obtained. Then, we connect the non-linear term of the effective Hamiltonian with the solvent effects of the environment surrounding the molecular system, and explain this mechanism.Facultad de Ciencias Exacta

Experimental dynamic stall study of an airfoil in turbulent flow

The objective of this study is to experimentally determine the fluid dynamic configuration of the dynamic stall of an airfoil in turbulent flow. Wind tunnel tests were carried out in order to characterize the airfoils behavior in static and static after a quick change in the angle of attack (“dynamic case”) using flow visualization, loads and hot-wire anemometry measurements at different Reynolds numbers and with one rate of change for the angle of attack. In all the tests, a Worthmann FX 63-137 airfoil model was used. First, with the visualizations made using a paint technique, for the different configurations, some differences in the flow pattern were found and points of interest in the airfoil were chosen. In those points, the sensors for the velocity measurements were placed. With the velocities acquired using a hot-wire system, autocorrelations, turbulence intensities, density power spectrums and wavelet maps were calculated and compared between the static and the dynamic case; different results were found and explained. Additionally, differences were traced in the turbulent intensities in the wake of the airfoil. Furthermore, a wavelets analysis was performed, and the flow scales obtained show differences for the same conditions analyzed before.Laboratorio de Capa Límite y Fluidodinámica Ambienta

Orbital SCF energies in the double proton transfer of the adenine-thymine base pair

The double-minimum potential generated by the proton motion involved in the two hydrogen bonds of the adenine-thymine base pair can be accounted for through the orbital-energy spectrum. The results show that the greatest interaction between the molecular orbitals is found when the interprotonic distance of the protons is optimum,i.e. at the top of the barrier of the double-minimum potential. This raises the question of charge transfer electronic transitions as a possibility of modelling the behaviour of the double proton transfer in the excited states of this base pair.Il potenziale a doppio minimo generato dal movimento dei protoni coinvolti nei due legami a idrogeno della coppia di basi ademina-timina può essere preso in considerazione attraverso lo spettro di energia orbitale. I risultati mostrano che la maggiore interazione tra orbitali molecolari si trova quando la distanza interprotonica dei prodotti è ottimale, cioè nel punto piú alto della barriera del potenziale a doppio minimo. Ciò solleva il problema della transizioni elettroniche con trasferimento di carica come una possibilità di regolare il comportamento del doppio trasferimento di protoni negli stati eccitati di questa coppia di basi.Потенциал с двойным минимумом, образованный за счет движения протонов, участвующих в двух водородных связях пары оснований аденина и тимина, может быть объяснен с помощью спектра орбитальной энергии. Результаты показывают, что наибольшее взаимодействие между молекулярными орбиталями возникает, когда расстояние между протонами является оптимальным, т.е. на вершине барьера потенциала с двумя минимумами. При этом возникает вопрос о возможности моделирования поведения двойного переноса протонов в возбужденных состояниях этой пары оснований.Instituto de Física La Plat

Dipolos 1,3: propiedades ópticas

En este trabajo se presentan los resultados del estudio realizado sobre el tensor de polarizabilidad y otras constantes directamente relacionadas con el índice de refracción, de un grupo seleccionado dentro de las series de compuestos que por su particular actividad química fueron agrupados bajo el nombre genérico de dipolo 1.3.Facultad de Ciencias Exacta

Conformational properties of methyl vinyl sulfone: Ab initio geometry optimization and vibrational analysis

An ab initio conformational analysis of methyl vinyl sulfone (CH₂CHSO₂CH₃) has been carried out. Molecular geometry optimizations have been performed at the HF and MP2 levels of the theory. Relative energies of the stationary points have been determined by using different approaches, including electron correlation corrections up to the third order. The IR and Raman spectra of the liquid have been measured and a vibrational assignment is proposed. The height of the barrier to the methyl group internal rotation has been estimated. Theoretical calculations and vibrational spectra have shown that the predominant conformation of methyl vinyl sulfone has the C=C bond eclipsed with one of the S=O bonds. Similar eclipsed forms have been found in vinyl fluoro sulfone, vinyl chloro sulfone and divinyl sulfone by ab initio HF calculations.Facultad de Ciencias Exacta

Dipolos 1,3: propiedades ópticas

En este trabajo se presentan los resultados del estudio realizado sobre el tensor de polarizabilidad y otras constantes directamente relacionadas con el índice de refracción, de un grupo seleccionado dentro de las series de compuestos que por su particular actividad química fueron agrupados bajo el nombre genérico de dipolo 1.3.Facultad de Ciencias Exacta