RESUMO
We reveal the generation of a broadband (> 1.9 THz) bi-photon quantum frequency comb (QFC) in a silicon-on-insulator (SOI) Fabry-Pérot micro-cavity and the control of its spectral correlation properties. Correlated photon pairs are generated through three spontaneous four-wave mixing (SFWM) processes by using a co-polarized bi-chromatic coherent input with power P1 and P2 on adjacent resonances of the nonlinear cavity. Adjusting the spectral power ratio r = P1/(P1 + P2) allows control over the influence of each process leading to an enhancement of the overall photon pair generation rate (PGR) µ(r) by a maximal factor of µ(r = 0.5)/µ(r = 0) ≈ 1.5, compared to the overall PGR provided by a single-pump configuration with the same power budget. We demonstrate that the efficiency aND of the non-degenerate excitation SFWM process (NDP) doubles the efficiency a1 ≈ a2 of the degenerate excitation SFWM processes (DP), showing a good agreement with the provided model.
RESUMO
We report on the generation of correlated photon pairs in AlGaAs-on-insulator (AlGaAs-OI) waveguides through nonlinear spontaneous four-wave-mixing (SFWM). Our measurements reveal an SFWM pair generation efficiency of â¼0.096×1012pairs/(sW2) at a wavelength of 1550 nm. This is one of the highest efficiencies achieved to date for integrated SFWM sources. A maximal coincidence-to-accidental ratio of â¼122 is measured. A spectral characterization of the device's pair emission at the quantum level demonstrates a broad generation bandwidth of 2.0 THz, which is important for frequency multiplexing applications. Our results indicate that AlGaAs-OI is an efficient material platform for integrated quantum photonics at telecom wavelengths.
RESUMO
A partir del gobierno de Hugo Chávez, la salud y la educación se convirtieron en derechos consagrados en la Constitución de 1999, por lo cual, las políticas públicas se aplicaron desde el principio para que no fuera letra muerta y saldar la deuda social que dejaron los gobiernos neoliberales de la IV República. Es por ello que una de las acciones, entre otras, que se ejecutaron para impulsar la inclusión a la educación universitaria (EU) fue el de crear el Sistema Nacional de Ingreso (SNI), hecho que ocurrió en el 2008 en el CNU, y posteriormente se ratificó y modificó en el 2014. Con el fin de estudiar los efectos de tales políticas, en esta primera parte del trabajo, se enfocó como ha sido la inclusión a las instituciones de educación universitaria (IEU) a nivel nacional, especialmente en el área de las Ciencias de la Salud, mediante un análisis descriptivo y comparativo de los parámetros académicos: Demanda, oferta académica y asignación de cupos por las IEU; la matrícula universitaria y el número de egresados durante los últimos 20 años; así como la inversión financiera por Estado a la EU. Los resultados obtenidos reflejan el incremento de la inclusión a la EU por las mayorías del país, logrando la formación del talento humano para el sector salud, en el cual hay muchas necesidades. A pesar de estos esfuerzos, aún existen problemas serios sobre el proceso de inclusión y la cobertura de la oferta académica.
From the Hugo Chávez government, health and education became rights enshrined in the 1999 Constitution, therefore, public policies were applied from the beginning so that it was not a dead letter and to pay the social debt left by the neoliberal governments of the IV Republic. That is why one of the actions, among others, that were carried out to promote inclusion in university education (EU) was to create the National Income System (SNI), a fact that occurred in 2008 at the CNU, and later it was ratified and modified in 2014. In order to study the effects of such policies, in this first part of the work the focus was on the inclusion of university education institutions (IEU) at the national level, especially in the area of the Health Sciences, by means of a descriptive and comparative analysis of the academic parameters: Demand, academic supply and allocation of quotas by the SNI; university enrollment and the number of graduates during the last 20 years; as well as the financial investment by State to the EU. The results obtained reflect the increase in inclusion in the EU by the majority of the country, achieving the training of human talent for the health sector, in which there are many needs. Despite these efforts, there are still serious problems regarding the inclusion process and the coverage of the academic offer
Assuntos
Humanos , Masculino , Feminino , Adolescente , Adulto , Pessoa de Meia-Idade , Adulto Jovem , Aptidão , Estudantes , Universidades , Educação em Saúde , Ciências da Saúde , Política Pública , Universidades/economia , Venezuela , Crescimento Demográfico , Investimentos em SaúdeRESUMO
En esta segunda parte del estudio sobre las políticas del gobierno para el incremento de la inclusión a la educación universitaria (EU), especialmente para el sector salud, quisimos hacer el análisis descriptivo y comparativo en las cuatro Zonas Económicas Especiales (ZEE) que ha creado el presidente Nicolás Maduro en su primera gestión, recordando que la primera parte las estudiamos a escala nacional. En esta oportunidad, realizamos el estudio con similares parámetros académicos, enfocados al área de las Ciencias de la Salud. Es decir, la demanda de cupos universitarios por parte del estudiantado, la oferta de plazas por las Instituciones de Educación Universitaria (IEU) y la asignación de cupos por el Sistema Nacional de Ingreso (SNI). Sin embargo, la matrícula y los valores de egresados de las IEU se estudiaron en tres periodos diferentes: Los tres últimos años de la presidencia de Rafael Caldera (1996-1998); los tres últimos años del presidente Hugo Chávez (2010-2012) y los cuatro primeros años de la primera gestión del presidente Nicolás Maduro (2013-2016). Finalmente, se investigó sobre los proyectos académicos aprobados por el CNU que han introducido las IEU de gestión pública de las ZEE desde 2006 hasta el 2013. Los resultados obtenidos evidencian que los primeros años de la revolución se ha logrado incrementar notablemente los valores de todos estos parámetros, indicando el aumento de la inclusión a la EU en las regiones, pero existen deficiencias notables sobre la oferta académica, algunas veces divorciadas de la realidad circundante de la ZEE, la demanda no satisfecha aún y los pocos proyectos académicos aprobados por el CNU
In this second part of the study on government policies for increasing inclusion in university education (EU), especially for the health sector, we wanted to do a descriptive and comparative analysis in the four Special Economic Zones (EEZ) that it has created President Nicolás Maduro in his first term, remembering that we studied the first part on a national scale. In this opportunity, we carried out the study with similar academic parameters, focused on the area of Health Sciences. That is, the demand for university quotas by the student body, the offer of places by the University Education Institutions (IEU) and the allocation of quotas by the National Income System (SNI). However, the enrollment and values of IEU graduates were studied in three different periods: The last three years of Rafael Caldera's presidency (1996-1998); the last three years of President Hugo Chávez (2010-2012) and the first four years of President Nicolás Maduro's first term (2013-2016). Finally, research was carried out on the academic projects approved by the CNU that have been introduced by the UIS of public management of the EEZs from 2006 to 2013. The results obtained show that the first years of the revolution have managed to significantly increase the values of all these parameters, indicating the increase of the inclusion to the EU in the regions, but there are notable deficiencies in the academic offer, sometimes divorced from the surrounding reality of the ZEE, the demand not yet satisfied and the few academic projects approved by the CNU
Assuntos
Humanos , Masculino , Feminino , Aptidão , Estudantes , Universidades , Educação em Saúde , Ciências da Saúde , Política Pública , Universidades/economia , Venezuela , Investimentos em SaúdeRESUMO
Molecular dynamic simulations were performed to study the morphology and binding energy of the most stable isomers of silver clusters with diameters of less than 2 nm. A 5-fold symmetry was found in most cases, and a novel morphology for the clusters of 39 and 116 silver atoms was identified. This morphology can be understood in terms of decahedral and icosahedral geometries, which are intercalated, as we explain in detail. These kind of structures have been observed for gold and now are predicted for small and intermediate silver nanoparticles.