Polarization, Isopotential Maps and Tunneling in Guanine, Cytosine, and Tautomeric Forms

We have used the CNDO/2-CI method to calculate the isopotential maps for the fundamental state and the direction of the polarizations corresponding to several singlet transitions in the molecules of guanine, cytosine and tautomeric forms. We have also calculated the times for proton tunneling and equilibrium constants between both conformers corresponding to the fundamental and some excited states. The results have been compared with the available experimental data.Publicado on line en 2014.Facultad de Ciencias Exacta

The adenine and thymine molecules: some excited singlet and triplet levels of the normal and tautomeric forms

The shape of the barrier for the H transfer between the normal and tautom eric forms have been determ ined for the adenine and thymine molecules. The correlations for several singlet and triplet states has been calculated using the CNDO/2-CI method. The relative stability between both conformations and the agreement with some experimental values is also discussed.Publicado on line en 2014.Facultad de Ciencias Exacta

CPM model applied to turbulent event detections

The present work shows the application of a change-point model (CPM), based on the Cramer von Mises test for turbulent structures detection in airflow. Specifically, it models the occurrence of vortices in the wake of an airfoil having a flow control device in its trailing edge. It seeks to compare the results obtained with conventional statistical methodologies employed in this type of analysis and the application of a change-point model. The main objective is to detect the characteristic frequencies of the turbulent structures immersed in the airflow. The results show good response of the CPM methodology in the analysis of these flows, comparatively we observed the same values obtained by the methods mentioned above. This work shows a new application of change-point models for detecting changes in a time-dependent random signal which has an unknown distribution a priori.Fil: Marañon Di Leo, Julio. Universidad Nacional de La Plata. Facultad de Ingeniería. Departamento de Aeronáutica. Laboratorio de Capa Límite y Fluído Dinámica Ambiental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Calandra, Maria Valeria. Universidad Nacional de la Plata. Facultad de Ingeniería. Uidet Grupo de Ensayos Mecanicos Aplicados.; ArgentinaFil: Delnero, Juan Sebastian. Universidad Nacional de La Plata. Facultad de Ingeniería. Departamento de Aeronáutica. Laboratorio de Capa Límite y Fluído Dinámica Ambiental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentin

The tautomeric conformers for the molecules of guanine and cytosine: some remarks about their stability

In this paper we seek to determine the shape of the barrier between the normal and tautom eric conformers for some excited singlet and triplet states in the molecules of guanine and cytosine. The molecules are considered isolated and a particular movement of the H atom is analysed. The semi-empirical CNDO/2-CI has been used. The calculated results are compared with the available experimental data.Publicado on line en 2014.Facultad de Ciencias Exacta

Polarization, Barriers and Tunneling Times of Some Tautomers of Adenine and Thymine

The polarization of the radiation involved in some transitions is analysed for the normal and tautomeric forms of adenine and thymine. Tunneling times for some barriers previously reported [1] and equilibrium constants between two isomers for some excited states are also given. The calculations have been made with the CNDO/2-CI method and the results compared with the available experimental data.Publicado on line en 2014.Facultad de Ciencias Exacta

Stochastic algorithms applied to vortex detections in turbulent flow (Part I)

The need to establish the downwind fluid dynamic field of aerodynamic bodies subjected to a givenvelocity field is well known, to verify their specific aerodynamic characteristics and therefore their efficiency. In this context, different techniques allow us to establish the characteristics of the field, on the one hand, visualizations, which define the qualitative characteristics of it, but it is almost always necessary to carry out quantitative determinations to describe the field correctly, particularly when the field is made up of turbulent wakes, characteristic of aerodynamic bodies under extreme operating conditions. In this sense, in the experimental field and for the definition of the turbulent flow field, it is common to use hot-wire anemometry techniques, which have great capabilities to quantify high-frequency events. Previous work has analysed the determination of changes in hot-wire anemometry signals for the detection of events in turbulent flows with different models, based on numerical algorithms, for the determination of change points (CPM - Change PointModel). The results obtained have shown agreement with conventional methodologies used for thedetermination of turbulent flow characteristics. The present work aims to compare the results obtained previously with the application of new CPM models developed in recent years. Previously applied and evaluated measurements are used, the implementation of the new models is carried out and the results are compared. All the algorithms used can detect changes in data that do not have a known distribution, i.e. non-parametric distributions, which are typical for turbulent flow field signals. The evaluation of measurement signals based on hot-wire anemometry is performed, considering measurements of the fluctuating components of the wind tunnel velocity at a specific point. The signals used correspond to periodic detachments downstream of a flow controldevice (Gurney mini-flap) at the trailing edge of an airfoil. In this way, the determination and characterization of vortices of different types is sought, to validate the different results obtained. The results show which are the best models to use for the experimental detection of such turbulent events in the flow field. These is the first approximation to the evaluation of the complete measurement with different arrange of the mini-flaps, in this case only for the static one.Fil: Marañon Di Leo, Julio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería. Departamento de Aeronáutica. Laboratorio de Capa Límite y Fluído Dinámica Ambiental; ArgentinaFil: Calandra, Maria Valeria. Universidad Nacional de La Plata. Facultad de Ingeniería; ArgentinaFil: Delnero, Juan Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería. Departamento de Aeronáutica. Laboratorio de Capa Límite y Fluído Dinámica Ambiental; Argentin

Some Theoretical Considerations About the Excited Singlet and Triplet States of Diformamide and N-Methyl Diformamide

The molecules of diformamide and N-methyl diformamide are analysed using the CNDO-CI method. Several excited singlet and triplet states corresponding to the three possible conformers and charge distributions are discussed.Publicado on line en 2014.Facultad de Ciencias Exacta

Vortex Generation, Experimental Characterization, and Application in Turbulent Flows

This chapter is focused on vortex detection, generation, and characterization. There are many ways to generate and characterize vortex; this chapter is focused on two techniques to generate a vortex, with fixed surface, often called vortex generators (VG), and with blowing air. Vortex detection is one of the major problems in fluid dynamics and usually some characteristics of the vortex must be known in order to detect them; once, the vortex is detected, a velocity analysis is helpful to characterize it. Most characterization techniques involves the comparison of some known properties of vortex, such as velocity field, vorticity field or tensor, turbulence intensity, etc. The technique to be used to characterize a vortex is closely related to the data that one possesses. In measuring methods such as particle image velocimetry (PIV), there are algorithms that can easily detect size and vortex centers, relaying in velocity and vorticity. This chapter focuses on detection by analyzing velocity signals, via wavelet transform and statistical properties. When it is not possible to characterize a vortex because it does not have a coherent structure, another approach must be used such as defining turbulence intensities and zone of influence of the vorticose structure

Stochastic algorithms applied to vortex detections in turbulent flow (Part I)

The need to establish the downwind fluid dynamic field of aerodynamic bodies subjected to a givenvelocity field is well known, to verify their specific aerodynamic characteristics and therefore their efficiency. In this context, different techniques allow us to establish the characteristics of the field, on the one hand, visualizations, which define the qualitative characteristics of it, but it is almost always necessary to carry out quantitative determinations to describe the field correctly, particularly when the field is made up of turbulent wakes, characteristic of aerodynamic bodies under extreme operating conditions. In this sense, in the experimental field and for the definition of the turbulent flow field, it is common to use hot-wire anemometry techniques, which have great capabilities to quantify high-frequency events. Previous work has analysed the determination of changes in hot-wire anemometry signals for the detection of events in turbulent flows with different models, based on numerical algorithms, for the determination of change points (CPM - Change PointModel). The results obtained have shown agreement with conventional methodologies used for thedetermination of turbulent flow characteristics. The present work aims to compare the results obtained previously with the application of new CPM models developed in recent years. Previously applied and evaluated measurements are used, the implementation of the new models is carried out and the results are compared. All the algorithms used can detect changes in data that do not have a known distribution, i.e. non-parametric distributions, which are typical for turbulent flow field signals. The evaluation of measurement signals based on hot-wire anemometry is performed, considering measurements of the fluctuating components of the wind tunnel velocity at a specific point. The signals used correspond to periodic detachments downstream of a flow controldevice (Gurney mini-flap) at the trailing edge of an airfoil. In this way, the determination and characterization of vortices of different types is sought, to validate the different results obtained. The results show which are the best models to use for the experimental detection of such turbulent events in the flow field. These is the first approximation to the evaluation of the complete measurement with different arrange of the mini-flaps, in this case only for the static one.Fil: Marañon Di Leo, Julio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería. Departamento de Aeronáutica. Laboratorio de Capa Límite y Fluído Dinámica Ambiental; ArgentinaFil: Calandra, Maria Valeria. Universidad Nacional de La Plata. Facultad de Ingeniería; ArgentinaFil: Delnero, Juan Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería. Departamento de Aeronáutica. Laboratorio de Capa Límite y Fluído Dinámica Ambiental; Argentin

Experimental study of the effect of the wake generated by oscillating gurney flap

The study of the turbulent near wake of an airfoil provided with flow control devices shows the flow configuration in such conditions and the starting vortices mechanism, while, the far wake of-fers information about the general performance of the model. The objective of the present work is to study the develop of the fluid-dynamic structures found in the NACA 4412 airfoil wake, as well as the develop-ment of the same structures when flow control tech-niques are applied by means of a oscillating Gurney Flap place in the lower surface of the wing model, close to the trailing edge. Tests were performed at a given Reynolds numbers and the flow control system was set at different frequencies. In order to study the effect of the control mechanism on the wake, hot wire anemometry techniques were used. Two components of the velocity vector were measured - longitudinal and vertical - by means of a vertical array of three sensors acquiring simultaneously. The intention is to quantify the flow general configuration at the airfoil wake for different test conditions. The velocity vectors will be analyzed, together with the turbulence inten-sity and integral scales.Fil: Marañon Di Leo, Julio. Universidad Nacional de La Plata. Facultad de Ingeniería. Departamento de Aeronáutica. Laboratorio de Capa Límite y Fluído Dinámica Ambiental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Martinez, Mariano. Universidad Nacional de La Plata. Facultad de Ingeniería; ArgentinaFil: Delnero, Juan Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería. Departamento de Aeronáutica. Laboratorio de Capa Límite y Fluído Dinámica Ambiental; ArgentinaFil: García Saínz, Mariano Oscar. Universidad Nacional de La Plata. Facultad de Ingeniería. Departamento de Aeronáutica. Laboratorio de Capa Límite y Fluído Dinámica Ambiental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentin