Applicability of hybrid density functional theory methods to calculation of molecular hyperpolarizability

The donor/acceptor (D/A) substituted pi-conjugated organic molecules possess extremely fast nonlinear optical (NLO) response time that is purely electronic in origin. This makes them promising candidates for optoelectronic applications. In the present study, we utilized four hybrid density functionals (B3LYP, B97-2, PBE0, BMK), Hartree-Fock, and second order Moller-Plesset correlation energy correction, truncated at second-order (MP2) methods with different basis sets to estimate molecular first hyperpolarizability (beta) of D/A-substituted benzenes and stilbenes (D=OMe, OH, NMe2, NH2; A=NO2, CN). The results of density functional theory (DFT) calculations are compared to those of MP2 method and to the experimental data. We addressed the following questions: (1) the accurate techniques to compare calculated results to each other and to experiment, (2) the choice of the basis set, (3) the effect of molecular planarity, and (4) the choice of the method. Comparison of the absolute values of hyperpolarizabilities obtained computationally and experimentally is complicated by the ambiguities in conventions and reference values used by different experimental groups. A much more tangible way is to compare the ratios of beta\u27s for two (or more) given molecules of interest that were calculated at the same level of theory and measured at the same laboratory using the same conventions and reference values. Coincidentally, it is the relative hyperpolarizabilities rather than absolute ones that are of importance in the rational molecular design of effective NLO materials. This design includes prediction of the most promising candidates from particular homologous series, which are to be synthesized and used for further investigation. In order to accomplish this goal, semiquantitative level of accuracy is usually sufficient. Augmentation of the basis set with polarization and diffuse functions changes beta by 20%; however, further extension of the basis set does not have significant effect. Thus, we recommend 6-31+G(*) basis set. We also show that the use of planar geometry constraints for the molecules, which can somewhat deviate from planarity in the gas phase, leads to sufficient accuracy (with an error less than 10%) of predicted values. For all the molecules studied, MP2 values are in better agreement with experiment, while DFT hybrid methods overestimate beta values. BMK functional gives the best agreement with experiment, with systematic overestimation close to the factor of 1.4. We propose to use the scaled BMK results for prediction of molecular hyperpolarizability at semiquantitative level of accuracy

Double excitations and state-to-state transition dipoles in pi-pi* excited singlet states of linear polyenes: Time-dependent density-functional theory versus multiconfigurational methods

The effect of static and dynamic electron correlation on the nature of excited states and state-to-state transition dipole moments is studied with a multideterminant wave function approach on the example of all-trans linear polyenes (C4H6, C6H8, and C8H10). Symmetry-forbidden singlet nA(g) states were found to separate into three groups: purely single, mostly single, and mostly double excitations. The excited-state absorption spectrum is dominated by two bright transitions: 1B(u)-2A(g) and 1B(u)-mA(g), where mA(g) is the state, corresponding to two-electron excitation from the highest occupied to lowest unoccupied molecular orbital. The richness of the excited-state absorption spectra and strong mixing of the doubly excited determinants into lower-nA(g) states, reported previously at the complete active space self-consistent field level of theory, were found to be an artifact of the smaller active space, limited to pi orbitals. When dynamic sigma-pi correlation is taken into account, single- and double-excited states become relatively well separated at least at the equilibrium geometry of the ground state. This electronic structure is closely reproduced within time-dependent density-functional theory (TD DFT), where double excitations appear in a second-order coupled electronic oscillator formalism and do not mix with the single excitations obtained within the linear response. An extension of TD DFT is proposed, where the Tamm-Dancoff approximation (TDA) is invoked after the linear response equations are solved (a posteriori TDA). The numerical performance of this extension is validated against multideterminant-wave-function and quadratic-response TD DFT results. It is recommended for use with a sum-over-states approach to predict the nonlinear optical properties of conjugated molecules

All-optical delay technique for supporting multiple antennas in a hybrid optical - wireless transmission system

We introduce a novel continuously-variable optical delay technique to support beam-forming wireless communications systems using antenna arrays. We demonstrate delay with 64-QAM modulated signals at a rate of 15 Msymbol/sec with 2.5 GHz carrier frequency

Adaptation of the “Assessment of Adherence to Antiretroviral Therapy Questionnaire” (“Cuestionario de Evaluación de la Adhesión al Tratamiento antirretroviral” - CEAT-VIH) for its use in Peru

Objetivos: El objetivo de este estudio fue adaptar y validar el “Cuestionario para evaluar la adhesión al tratamiento antirretroviral” (CEAT-VIH) para su uso en el Perú, en pacientes VIH y SIDA en tratamiento antirretroviral de gran actividad (TARGA). Métodos: Se evaluó la comprensión del cuestionario así como sus propiedades psicométricas en una muestra de 41 pacientes con VIH y SIDA en tratamiento antirretroviral de gran actividad (TARGA) por más de tres meses. El periodo de estudio estuvo comprendido entre diciembre 2005 y enero 2006, el proceso de validación incluyó la aplicación del cuestionario el mismo día de la toma de muestra para el análisis de la carga viral y de los linfocitos TCD4. Se analizó la fi abilidad, la correlación de la puntuación con el recuento de linfocitos TCD4 y la carga viral. Resultados: Los resultados mostraron una adecuada fi abilidad (α = 0,706) y validez de criterio externa: respecto al recuento de linfocitos TCD4 (r = 0,439, p < 0,005), y respecto a la carga viral (r = - 0,548, p < 0, 005). Conclusiones: El CEAT-VIH ha demostrado ser una adecuada herramienta para evaluar el nivel de adherencia e identifi car los factores que infl uyen en la adherencia al tratamiento antirretroviral en una muestra de pacientes VIH y SIDA en Perú.Objective: To adapt and validate the “Assessment of Adherence to Antiretroviral Therapy Questionnary” “Cuestionario para evaluar la adhesión al tratamiento antirretroviral” (CEAT-VIH) for use in Peru, in HIV-infected patients in highly active antiretroviral therapy (HAART). Method: Understanding of the questionnaire was evaluated as well as its psychometric properties in 41 HIV-infected patients; antiretroviral therapy for at least 3 months was required. Data was obtained between December 2005 and January 2006. CEAT-VIH was carried out the day when sample for HIV viral load and CD4 cell count were taken. Reliability and validity related to two external criterions were evaluated. Results: CEAT-VIH showed appropriate reliability (α = 0,706) and adequate external criterion-related validity for CD4 cell count (r = 0,439, p < 0.005), and for HIV viral load (r = - 0,548, p < 0, 005). Conclusions: CEAT-VIH has proved to be useful to assess the level of adherence and to identify the factors affecting patient adherence to highly active antiretroviral therapy in Peru

Chemical modeling of acid-base properties of soluble biopolymers derived from municipal waste treatment materials

This work reports a study of the proton-binding capacity of biopolymers obtained from different materials supplied by a municipal biowaste treatment plant located in Northern Italy. One material was the anaerobic fermentation digestate of the urban wastes organic humid fraction. The others were the compost of home and public gardening residues and the compost of the mix of the above residues, digestate and sewage sludge. These materials were hydrolyzed under alkaline conditions to yield the biopolymers by saponification. The biopolymers were characterized by 13C NMR spectroscopy, elemental analysis and potentiometric titration. The titration data were elaborated to attain chemical models for interpretation of the proton-binding capacity of the biopolymers obtaining the acidic sites concentrations and their protonation constants. The results obtained with the models and by NMR spectroscopy were elaborated together in order to better characterize the nature of the macromolecules. The chemical nature of the biopolymers was found dependent upon the nature of the sourcing materials

Empirical multichannel power consumption model for erbium-doped fiber amplifiers

In this paper we report on the first experimental power consumption analysis and model of single and multi-stage booster erbium-doped fiber amplifiers (EDFAs) with automatic gain control (AGC), accounting for channel number dependency. Results show that the amount of channels being amplified simultaneously contributes significantly, up to 48%, to the total power consumption due to the circuitry used for controlling the EDFA. As the number of simultaneous amplified WDM channels in high capacity long and medium reach transmission links reflects closely traffic patterns generated by end-users, it is relevant to study channel number dependent power consumption for devising EDFA power efficient control and design

Efecto de la poda y el sistema de siembra sobre el rendimiento y calidad del tomato "chonto" (Lycopersicon esculentum Mill)

En el Centro Experimental Palmira del Instituto Colombiano Agropecuario ICA (Valle del Cauca), se realizó un ensayo con tomate "Chonto" en el que se compararon 2 sistemas de siembra: surco doble y surco sencillo y 4 sistemas de poda: poda a dos y 6 ramas, despunte a los 110 días luego del trasplante y libre crecimiento. En todos ellos se eliminaron los brotes nacidos bajo el primer racimo floral, excepto el inmediatamente debajo. Para ambos sistemas de siembra se utilizó la misma densidad de plantas: 26.666 plantas/Ha. Se cosechó dos veces por semana clasificando los frutos por tamaño y calidad. De los resultados obtenidos se desprende que para las densidades utilizadas, el sistema de poda más recomendable fue el despunte, por cuanto se indujo en general mayor rendimiento, mayor número de frutos grandes y menor número de frutos rajados. Los tratamientos, libre crecimiento y poda a 6 ramas, presentaron buenas producciones pero debido al excesivo crecimiento para el primero de ellos y la mayor mano de obra con el segundo deben tomarse como alternativas en condiciones especiales. El tratamiento con poda a dos ramas fue el que menores producciones indujo, lo mismo que el mayor porcentaje de frutos rajados, en comparación con los demás. No se observaron diferencias de producción entre siembra en surco sencillo y siembra en surco doble. No se observó interacción entre los sistemas de siembra y de poda, aunque el despunte fue el mejor tratamiento cuando se sembró en surco sencillo y el libre crecimiento lo fue en surco doble.At the National Experiment Center of ICA in Palmira an experiment was conducted with "Chonto" tomato in wich two planting system and four prunning systems were compared. They were: double row and single row planting with four methods of plant prunning, prunning at two branches, prunning at six branches, pinching of terminal shoots at 110 days after transplanting and free growth in all plants, Buds below the first floral inflorescence were removed with the exception of the closed bud of it. Tomatoes were harvested twice a week approximately and classified according to size and quality. It was found that for the density used, the most advisable prunning method was that of prunning at 110 days this method induced in general the greatest yield, the largest number of large fruits and the fewest cracked fruits. The systems of free growth and of prunning at 6 branches produced good results but because the management of the 1 st and the extra labor required for the 2nd, they must be considered as alternatives for use under special conditions. Prunning at two branches, induced the least production along with the most cracked fruit. There were no differences observed between double and single row planting. No relation was observed between the planting systems and the prunning systems but pinching at 110 days was the most productive at the single row and free growth at single row.Tomate-Solanum lycopersicu

Efecto de la poda y el sistema de siembra sobre el rendimiento y calidad del tomate Chonto (Lycopersicon esculentum Mill).

Se realizó un ensayo con tomate Chonto en el que se compararon 2 sistemas de siembra: surco doble y surco sencillo, y 4 sistemas de poda, poda a 2 y 6 ramas, despunte a los 110 días del trasplante y libre crecimiento. En todos ellos se eliminaron los brotes nacidos bajo el primer racimo floral, excepto el inmediatamente debajo. Para ambos sistemas de siembra se utilizó la densidad de 26666 plantas/ha. Se cosechó 2 veces por semana clasificando los frutos por tamaño y calidad. De los resultados obtenidos la poda más recomendable fué el despunte, por cuanto se indujo mayor rendimiento, mayor número de frutos grandes y menor número de frutos rajados. Los tratamientos libre crecimiento y poda a 6 ramas, presentaron buenas producciones pero debido a excesivo crecimiento para el primero de ellos y la mayor mano de obra, con el segundo deben tomarse como alternativas en condiciones especiales. El tratamiento con poda a 2 ramas fué el que menores producciones indujo lo mismo que el mayor porcentaje de frutos rajados, en comparación con los demás. No se observaron diferencias de producción entre siembra en surco sencillo y doble. No se observó interacción entre sistemas de siembra y poda, aunque el despunte fué el mejor tratamiento cuando se sembró en surco sencillo y el libre crecimiento lo fué en surco dobleTomate-Solanum lycopersicu

Free-running L-band VCSEL for 1.25 Gbps hybrid radio-fiber cloud optical interconnects

International audienceWe demonstrate a free-running directly-modulated 1580 nm VCSEL suitable for hybrid wireless/optical interconnects supporting cloud data centers. Error-free transmission at 1.25 Gbps was achieved after 6.5 GHz wireless link and 1 km bend-insensitive fiber

Adaptación del “Cuestionario de Evaluación de la Adhesión al Tratamiento antirretroviral” (CEAT-VIH) para su uso en Perú

Objective: To adapt and validate the “Assessment of Adherence to Antiretroviral Therapy Questionnary” “Cuestionariopara evaluar la adhesión al tratamiento antirretroviral” (CEAT-VIH) for use in Peru, in HIV-infected patients in highlyactive antiretroviral therapy (HAART).Method: Understanding of the questionnaire was evaluated as well as its psychometric properties in 41 HIV-infectedpatients; antiretroviral therapy for at least 3 months was required. Data was obtained between December 2005 andJanuary 2006. CEAT-VIH was carried out the day when sample for HIV viral load and CD4 cell count were taken.Reliability and validity related to two external criterions were evaluated.Results: CEAT-VIH showed appropriate reliability (α = 0,706) and adequate external criterion-related validity for CD4cell count (r = 0,439, p &lt; 0.005), and for HIV viral load (r = - 0,548, p &lt; 0, 005).Conclusions: CEAT-VIH has proved to be useful to assess the level of adherence and to identify the factors affectingpatient adherence to highly active antiretroviral therapy in Peru.Objetivos: El objetivo de este estudio fue adaptar y validar el “Cuestionario para evaluar la adhesión al tratamientoantirretroviral” (CEAT-VIH) para su uso en el Perú, en pacientes VIH y SIDA en tratamiento antirretroviral degran actividad (TARGA).Métodos: Se evaluó la comprensión del cuestionario así como sus propiedades psicométricas en una muestra de 41pacientes con VIH y SIDA en tratamiento antirretroviral de gran actividad (TARGA) por más de tres meses. Elperiodo de estudio estuvo comprendido entre diciembre 2005 y enero 2006, el proceso de validación incluyó la aplicacióndel cuestionario el mismo día de la toma de muestra para el análisis de la carga viral y de los linfocitos TCD4.Se analizó la fi abilidad, la correlación de la puntuación con el recuento de linfocitos TCD4 y la carga viral.Resultados: Los resultados mostraron una adecuada fi abilidad (α = 0,706) y validez de criterio externa: respecto alrecuento de linfocitos TCD4 (r = 0,439, p &lt; 0,005), y respecto a la carga viral (r = - 0,548, p &lt; 0, 005).Conclusiones: El CEAT-VIH ha demostrado ser una adecuada herramienta para evaluar el nivel de adherencia eidentifi car los factores que infl uyen en la adherencia al tratamiento antirretroviral en una muestra de pacientesVIH y SIDA en Perú