Two-beam nonlinear Kerr effect to stabilize laser frequency with sub-Doppler resolution

Avoiding laser frequency drifts is a key issue in many atomic physics experiments. Several techniques have been developed to lock the laser frequency using sub-Doppler dispersive atomic lineshapes as error signals in a feedback loop. We propose here a two-beam technique that uses non-linear properties of an atomic vapor around sharp resonances to produce sub-Doppler dispersive-like lineshapes that can be used as error signals. Our simple and robust technique has the advantage of not needing either modulation or magnetic fields.Comment: 5 pages, 6 figures; http://www.opticsinfobase.org/ao/abstract.cfm?uri=ao-51-21-508

Strategies of innovation and appropriation. Sectoral analysis of Argentine manufacturing firms

Following the evolutionary and neoshumpeterian theoretical framework, this research studies how the appropriation strategy of firms is formed in different industrial sector and what factors explain the use of the mechanisms that firms use to protect their innovations. The analysis is based on evidence from Argentine manufacturing firms surveyed by the National Survey of Employment Dynamics and Innovation (ENDEI) for 2010-2012. The results of the statistical analysis allow to identify three clusters at the sectoral level with differentiated characteristics in terms of their innovation activities and business conformation. The cluster of high innovative activity shows a greater incidence of the use of secrecy and patents, while the cluster of low innovative activity presents a greater use of complementary assets and first mover. The econometric analysis (Probit models) shows different effects of the factors considered (type of effort and innovative results, capabilities, linkages, structural factors) on the mechanism used, showing that the appropriation strategy is an emerging of innovation process and differs according to the sectoral cluster considered. The type of innovative effort affects only the appropriation strategy of the high and low innovative activity clusters; while the structural factors of firms explain only the appropriation strategy of sectors of high and medium innovative activity

Hydrogen-Bonded Rosettes of Aminotriazines for Selective-Ion Recognition

Ion recognition is still an emerging topic in supramolecular chemistry and has aroused great attention in the last few years. In this work, we have examined the assemblies of selected hexameric rosettes of melamine and ammeline and their capacities to host halide and alkali ions in the gas phase and in water. Using relativistic dispersion-corrected density functional theory (DFT-D), we first studied the stability and the effect of introducing monovalent anions (Cl-, Br-, and I-) and cations (Na+, K+, and Rb+) in the center of the rosette´s cavity. Finally, we explored the interactions in two stacked rosettes with an interlayer ion. Our computations reveal that amine-substituted triazines are promising candidates for anion and cation recognition either in self-assembled monolayers or pillar array structures. The anion recognition process is governed by both the electrostatic and charge-transfer (donor-acceptor) interactions, while the cation recognition is governed by electrostatic and polarization. In addition, melamine and ammeline could constitute a potent mixture for dual-ion recognition strategies.Fil: Petelski, Andre Nicolai. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste; Argentina. Vrije Universiteit Amsterdam; Países Bajos. Universidad Tecnológica Nacional. Facultad Regional Resistencia. Departamento de Ingeniería Química. Laboratorio de Química Teórica y Experimental; ArgentinaFil: Fonseca Guerra, Célia. Vrije Universiteit Amsterdam; Países Bajo

Cluster analysis of the impact of air back-trajectories on aerosol optical properties at Hornsund, Spitsbergen

In this paper, spectra of aerosol optical thickness from the AERONET (AErosol RObotic NETwork) station at Hornsund in the southern part of Spitsbergen were employed to study the impact of air mass history on aerosol optical thickness for wavelength λ=500 nm – AOT(500) – and the Ångström exponent. Backward trajectories computed, using the NOAA HYSPLIT model, were used to trace air history. It was found that in spring, the changes in AOT values over the Hornsund station were strongly influenced by air mass trajectories 8 days or longer in duration, arriving both in the free troposphere and at an altitude of 1 km above sea level. Nevertheless, free tropospheric advection was dominant. AOT variability in summer was best explained by the local direction and speed of advection (1-day trajectories) and was dominated by the effectiveness of cleansing processes. During the ASTAR 2007 campaign, the aerosols near Hornsund displayed low AOT values ranging from 0.06 to 0.09, which is lower than the mean AOT(500) for spring seasons from 2005 to 2007 (0.110±0.007; mean ± standard deviation of mean). 9 April 2007 with AOT(500)=0.147 was exceptional. The back-trajectories belonged to clusters with low and average cluster mean AOT. Apart from the maximum AOT of 9 April 2007, the observed AOT values were close to or lower than the means for the clusters to which they belonged

Towards an atom interferometric determination of the Newtonian gravitational constant

We report on progress towards an atom interferometric determination of the Newtonian gravitational constant. Free-falling laser-cooled atoms will probe the gravitational potential of nearby source masses. To reduce systematic errors, we will perform double differential measurements between two vertically separated atom clouds and with different source mass positions

Atom interferometry gravity-gradiometer for the determination of the Newtonian gravitational constant G

We developed a gravity-gradiometer based on atom interferometry for the determination of the Newtonian gravitational constant \textit{G}. The apparatus, combining a Rb fountain, Raman interferometry and a juggling scheme for fast launch of two atomic clouds, was specifically designed to reduce possible systematic effects. We present instrument performances and show that the sensor is able to detect the gravitational field induced by source masses. A discussion of projected accuracy for \textit{G} measurement using this new scheme shows that the results of the experiment will be significant to discriminate between previous inconsistent values.Comment: 9 pages,9 figures, Submitte

EFECTOS DEL SERVICIO DE INVESTIGACIÓN SOBRE EL APRENDIZAJE Y LA AGENDA DE INVESTIGACIÓN PÚBLICOS EN ARGENTINA

Cooperation between science and industry is crucial for the economic and social development of a country and the effects it generates on public research depend on the specific collaboration scheme. This paper investigates the effects that research service can generate in public research activity, based on the contributions that industry makes and the way in which they are linked to public learning and its research agenda. For this, a qualitative methodology is used, based on the multiple case study method, which is carried out in three sectors, agrobiotechnology, biopharmaceutical and nanotechnology, of a developing country like Argentina. The main findings include the identification of four different categories within the service, the presence of benefits for the public part in terms of learning and agenda in two of them, and the possibility of a complementary relationship between this scheme and joint research.La cooperación entre ciencia e industria es crucial para el desarrollo socioeconómico de un país y los efectos que genera en la investigación pública dependen del esquema específico de colaboración. Este trabajo indaga sobre los efectos que el servicio de investigación puede generar en la actividad de investigación pública, a partir de las contribuciones que la industria realiza y del modo en que ellas se vinculan con el aprendizaje público y con su agenda de investigación. Para ello se utiliza una metodología cualitativa, basada en el método del estudio de casos múltiples, en tres sectores, agrobiotecnología, biofarmacéutica y nanotecnología, de un país en desarrollo como Argentina. Entre los principales hallazgos se destaca la identificación de cuatro categorías diferentes dentro del servicio, la presencia de beneficios en términos de aprendizaje y agenda en dos de ellos y la posibilidad de una relación de complementariedad entre este esquema y la investigación conjunta

Stable carbon and nitrogen isotope ratio in PM1 and size segregated aerosol particles over the Baltic Sea

We analysed delta C-13 of total carbon (TC) and PN of total nitrogen (TN) in submicron (PM1) and size segregated aerosol particles ( PM0.056-2.5) collected during a cruise in the Baltic Sea from 9 to 17 November 2012. PM1 were characterized by the highest delta C-13 (-26.4 parts per thousand) and lowest delta N-15 (-0.2 and 0.8 parts per thousand) values when air masses arrived from the southwest direction (Poland). The obtained delta C-13 values indicated that combined emissions of coal and diesel/gasoline combustion were the most likely sources of TC. The depleted delta N-15 values indicated that TN originated mainly from liquid fuel combustion (road traffic, shipping) during this period. The lowest PC and highest delta N-15 values were determined in PM1 samples during the western airflow when the air masses had no recent contact with land. The highest delta N-15 values were probably associated with chemical aging of nitrogenous species during long-range transport, the lowest delta C-13 values could be related to emissions from diesel/gasoline combustion, potentially from ship traffic. The delta C-13 analysis of size-segregated aerosol particles PM0.056-2.5 revealed that the lowest delta C-13 values were observed in the size range from 0.056 to 0.18 mu m and gradual C-13 enrichment occurred in the size range from 0.18 to 2.5 mu m due to different sources or formation mechanisms of the aerosols