Spot activity of the RS CVn star {\sigma} Geminorum

We model the photometry of RS CVn star $\sigma$ Geminorum to obtain new information on the changes of the surface starspot distribution, i.e., activity cycles, differential rotation and active longitudes. We use the previously published Continuous Periods Search-method (CPS) to analyse V-band differential photometry obtained between the years 1987 and 2010 with the T3 0.4 m Automated Telescope at the Fairborn Observatory. The CPS-method divides data into short subsets and then models the light curves with Fourier-models of variable orders and provides estimates of the mean magnitude, amplitude, period and light curve minima. These light curve parameters are then analysed for signs of activity cycles, differential rotation and active longitudes. We confirm the presence of two previously found stable active longitudes, synchronised with the orbital period $P_{\rm{orb}}=19.60$d and find eight events where the active longitudes are disrupted. The epochs of the primary light curve minima rotate with a shorter period $P_{\rm{min,1}}=19.47$d than the orbital motion. If the variations in the photometric rotation period were to be caused by differential rotation, this would give a differential rotation coefficient of $\alpha \ge 0.103$. The presence of two slightly different periods of active regions may indicate a superposition of two dynamo modes, one stationary in the orbital frame and the other one propagating in the azimuthal direction. Our estimate of the differential rotation is much higher than previous results. However, simulations show that this can be caused by insufficient sampling in our data.Comment: 10 pages, 6 figures. Submitted to A&

Convergencia y determinantes del crecimiento en las provincias argentinas

En el siguiente trabajo se busca determinar si existió en las provincias argentinas un fenómeno de convergencia en las tasas de crecimiento para el período 1993-2006. Además, se completa el análisis con los determinantes que contribuyeron al crecimiento de las mismas en este período. Determinar si existió o no convergencia en las provincias argentinas es un dato de suma utilidad y relevancia social, ya que permite evaluar el desempeño de las distintas políticas públicas aplicadas en los últimos años para cumplir con el objetivo de acercar los niveles de renta per cápita de las regiones más pobres a las más ricas. Comprobar que efectivamente las provincias pobres crecieron más que las ricas, implica que tuvieron éxito políticas nacionales como la promoción industrial, las transferencias fiscales o el sistema de coparticipación federal, entre otras. Conocer los determinantes del crecimiento también es relevante, sobre todo para encarar políticas, ya sea desde el sector público como del privado, para acelerar el proceso de acumulación de bienes y servicios, obviando o corrigiendo los factores que no lograron los resultados esperados y perfeccionando los que generaron efectos positivos. Se analiza los tipos de convergencia más comúnmente citados: la β- convergencia y la σ- convergencia.Fil: Bignone, Franco

Spot activity of the RS Canum Venaticorum star σ Geminorum

Aims. We model the photometry of RS CVn star σ Geminorum to obtain new information on the changes of the surface starspot distribution, that is, activity cycles, differential rotation, and active longitudes. Methods. We used the previously published continuous period search (CPS) method to analyse V-band differential photometry obtained between the years 1987 and 2010 with the T3 0.4 m Automated Telescope at the Fairborn Observatory. The CPS method divides data into short subsets and then models the light-curves with Fourier-models of variable orders and provides estimates of the mean magnitude, amplitude, period, and light-curve minima. These light-curve parameters are then analysed for signs of activity cycles, differential rotation and active longitudes. Results. We confirm the presence of two previously found stable active longitudes, synchronised with the orbital period Porb = 1960, and found eight events where the active longitudes are disrupted. The epochs of the primary light-curve minima rotate with a shorter period Pmin,1 = 1947 than the orbital motion. If the variations in the photometric rotation period were to be caused by differential rotation, this would give a differential rotation coefficient of α ≥ 0.103. Conclusions. The presence of two slightly different periods of active regions may indicate a superposition of two dynamo modes, one stationary in the orbital frame and the other one propagating in the azimuthal direction. Our estimate of the differential rotation is much higher than previous results. However, simulations show that this may be caused by insufficient sampling in our data

Spot activity of LQ Hydra from photometry between 1988 and 2011

Aims. We investigate the spot activity of the young magnetically active main sequence star LQ Hya. Our aims are to identify possible active longitudes, estimate the differential rotation, and study long and short term changes in the activity. Methods. Our analysis is based on 24 years of Johnson V-band photometry of LQ Hya obtained with the T3 0.4 m Automated Telescope at the Fairborn Observatory. We use the previously published continuous period search (CPS) method to model the evolution of the light curve of LQ Hya. The CPS fits a Fourier series model to short overlapping subsets of data. This enables us to monitor the evolution of the light curve and thus the spot configuration of the star with a higher time resolution. Results. We find seasonal variability in the mean level and amplitude of the light curve of LQ Hya. The variability of the light curve amplitude seems not to be cyclic, but the long-term variations in the mean magnitude may be indicative of an approximately 13 year cycle. However, because of the limited length of the observed time series, it is not yet possible to determine whether this structure really represents an activity cycle. Based on fluctuations of the light curve period, we estimate the differential rotation of the star to be small, and the star is potentially very close to a rigid rotator. We search for active longitudes from the inferred epochs of the light curve minima. We find that on time scales up to six months there are typically one or two relatively stable active areas on the star with limited phase migration. On the other hand, on time scales longer than one year, no stable active longitudes have been present except for the period between 2003 and 2009 and possibly also some time before 1995. Neither do we find any signs of flip-flops with a regular period. The mean time scale of change of the light curve during the observation period is determined to be of the same order of magnitude as the estimated convective turnover time for the star

Modelling job crafting behaviours: Implications for work engagement

In this study among 206 employees (103 dyads), we followed the job demands–resources approach of job crafting to investigate whether proactively changing one’s work environment influences employee’s (actor’s) own and colleague s (partner’s) work engagement. Using social cognitive theory, we hypothesized that employees would imitate each other’s job crafting behaviours, and therefore influence each other’s work engagement. Results showed that the crafting of social and structural job resources, and the crafting of challenge job demands was positively related to own work engagement, whereas decreasing hindrance job demands was unrelated to own engagement. As predicted, results showed a reciprocal relationship between dyad members’ job crafting behaviours – each of the actor’s job crafting behaviours was positively related to the partner’s job crafting behaviours. Finally, employee’s job crafting was related to colleague’s work engagement through colleague’s job crafting, suggesting a modelling process

Time series analysis of V815 Herculis photometry between 1984 and 1998

As a case study of the solar-stellar connection, we have analysed a prolonged time series of BV photometry of the chromospherically active binary V815 Her . The surface differential rotation in the rapidly rotating G5{v} primary caused changes of 4.6% in the seasonal photometric rotation periods. This would imply a differential rotation coefficient of k = 0.184, if the rotation of the starspots follows the solar law of differential rotation and the activity is confined within the same latitudinal range as in the Sun, having k = 0.189 and the spectral-type of G2{v}. Our analysis of the primary and secondary minima of the seasonal light curves indicated that the regions of stronger activity have concentrated on one active longitude, which has maintained a constant rotation period of 1.d79244 for about 14 years. No regular activity cycle was detected in the mean brightness changes of V815 Her

Development and Validation of an Instrument Measuring Determinants of Bystander Intervention to Prevent Sexual Assault: An application of the Reasoned Action Approach

Bystander Intervention (BI) is an evidence-based approach that is considered the gold standard by governmental organizations to reduce sexual assault in college. Few survey instruments are available to measure the predispositions students have towards engaging in BI. Valid and reliable instruments are greatly needed, especially those tailored to BI. The purpose of this study was to develop and validate an instrument based on the reasoned action approach with college students at two U.S. universities. An elicitation of beliefs was accomplished to inform survey items (i.e., behavioral, normative, and control beliefs). Then, an initial draft was developed and sent to an expert panel to establish validity. The final instrument was administered to undergraduate students (n = 291), and further psychometric properties (construct validity and internal consistency reliability) were evaluated. Data were fit into two separate models to evaluate fit. In the first model, a four-factor solution was evaluated (intentions, attitudes, perceived norms, and perceived behavioral control), and while results were modest, the second seven-factor solution model contained a better fit (intentions, instrumental and experiential attitudes, injunctive and descriptive norms, capacity, and autonomy). Researchers and practitioners examining BI in college can use this instrument to measure theory-based determinants of BI to reduce sexual assault