CARMENES input catalogue of M dwarfs IV. New rotation periods from photometric time series

Aims. The main goal of this work is to measure rotation periods of the M-type dwarf stars being observed by the CARMENES exoplanet survey to help distinguish radial-velocity signals produced by magnetic activity from those produced by exoplanets. Rotation periods are also fundamental for a detailed study of the relation between activity and rotation in late-type stars. Methods. We look for significant periodic signals in 622 photometric time series of 337 bright, nearby M dwarfs obtained by long-time baseline, automated surveys (MEarth, ASAS, SuperWASP, NSVS, Catalina, ASAS-SN, K2, and HATNet) and for 20 stars which we obtained with four 0.2-0.8 m telescopes at high geographical latitudes. Results. We present 142 rotation periods (73 new) from 0.12 d to 133 d and ten long-term activity cycles (six new) from 3.0 a to 11.5 a. We compare our determinations with those in the existing literature; we investigate the distribution of P rot in the CARMENES input catalogue,the amplitude of photometric variability, and their relation to vsin i and pEW(Halfa); and we identify three very active stars with new rotation periods between 0.34 d and 23.6 d.Comment: 34 pages, 43 figures, 2 appendix table

Foreign Direct Investment and Relative Wages: Evidence from Mexico's Maquiladoras

In this paper, we examine the increase in the relative wages of skilled workers in Mexico during the 1980s. We argue that rising wage inequality in Mexico is linked to capital inflows from abroad. The effect of these capital inflows, which correspond to an increase in outsourcing by multinationals from the United States and other Northern countries, is to shift production in Mexico towards relatively skill-intensive goods thereby increasing the relative demand for skilled labor. We study the impact of foreign direct investment (FDI) on the share of skilled labor in total wages in Mexico using state-level data on two-digit industries from the Industrial Census for the period 1975 to 1988. We measure the state- level growth in FDI using data on the regional activities of foreign- owned assembly plants. We find that growth in FDI is positively correlated with the relative demand for skilled labor. In the regions where FDI has been most concentrated, growth in FDI can account for over 50 percent of the increase in the skilled labor share of total wages that occurred during the late 1980s.

The Incidence of a Firm-Varying Payroll Tax: The Case of Unemployment Insurance

In this paper we theoretically and empirically examine the common, but previously unexamined, case of a firm-varying tax which is used to finance a fringe benefit. While we use data from the experience-rated unemployment insurance (UI) system, it is important to realize that differential treatment of firms (such as special considerations for small business) under mandated benefits laws leads to costs which vary across firms and are analogous to experience-rated taxes. We present a theoretical model which highlights the importance of considering this variation in taxes or costs both within and across markets. We examine annual changes in either firm average earnings and employment or individual worker earnings at the same firm. This method removes unmeasured firm and worker characteristics, and thus avoids the omitted variable bias that has plagued past work on incidence and compensating differentials. Our results suggest that most of the market level tax is borne by the worker. However, this does not imply that there are no employment effects of the tax. Rather, we find that individual firms can only pass on a small share of the within market differences in the tax they face, leading to substantial employment reallocation across firms.

Spartan Daily, October 6, 1972

Volume 60, Issue 13https://scholarworks.sjsu.edu/spartandaily/5648/thumbnail.jp

The CARMENES search for exoplanets around M dwarfs - Photospheric parameters of target stars from high-resolution spectroscopy

The new CARMENES instrument comprises two high-resolution and high-stability spectrographs that are used to search for habitable planets around M dwarfs in the visible and near-infrared regime via the Doppler technique. Characterising our target sample is important for constraining the physical properties of any planetary systems that are detected. The aim of this paper is to determine the fundamental stellar parameters of the CARMENES M-dwarf target sample from high-resolution spectra observed with CARMENES. We also include several M-dwarf spectra observed with other high-resolution spectrographs, that is CAFE, FEROS, and HRS, for completeness. We used a {chi}^2 method to derive the stellar parameters effective temperature T_eff, surface gravity log g, and metallicity [Fe/H] of the target stars by fitting the most recent version of the PHOENIX-ACES models to high-resolution spectroscopic data. These stellar atmosphere models incorporate a new equation of state to describe spectral features of low-temperature stellar atmospheres. Since T_eff, log g, and [Fe/H] show degeneracies, the surface gravity is determined independently using stellar evolutionary models. We derive the stellar parameters for a total of 300 stars. The fits achieve very good agreement between the PHOENIX models and observed spectra. We estimate that our method provides parameters with uncertainties of {sigma} T_eff = 51 K, {sigma} log g = 0.07, and {sigma} [Fe/H] = 0.16, and show that atmosphere models for low-mass stars have significantly improved in the last years. Our work also provides an independent test of the new PHOENIX-ACES models, and a comparison for other methods using low-resolution spectra. In particular, our effective temperatures agree well with literature values, while metallicities determined with our method exhibit a larger spread when compared to literature results

Changes in the Relative Structure of Wages and Employment: A Comparison of the United States, Canada, and France

Standard models suggest that adverse labor demand shocks will lead to bigger employment losses if institutional factors like minimum wages and trade unions prevent downward wage adjustments. Some economists have argued that this insight explains the contrast between the United States, where real wages fell over the 1980s and aggregate employment expanded vigorously, and Europe, where real wages were (roughly) constant and employment was stagnant. We test this hypothesis by comparing changes in wages and employment rates over the 1980s for different age and education groups in the United States, Canada, and France. We argue that the same forces that led to falling real wages for less-skilled workers in the U.S. affected similar workers in Canada and France. Consistent with the view that labor market institutions are more rigid in France, and more flexible in the U.S., we find that relative wages of less-skilled workers fell the most in the U.S., fell somewhat less in Canada, and did not fall at all in France. Contrary to expectations, however, we find little evidence that wage inflexibilities generated divergent patterns of relative employment growth across the three countries.

Needleless melt-electrospinning of polypropylene nanofibres

Polypropylene (PP) nanofibres have been electrospun from molten PP using a needleless melt-electrospinning setup containing a rotary metal disc spinneret. The influence of the disc spinneret (e.g., disc material and diameter), operating parameters (e.g., applied voltage, spinning distance), and a cationic surfactant on the fibre formation and average fibre diameter were examined. It was shown that the metal material used for making the disc spinneret had a significant effect on the fibre formation. Although the applied voltage had little effect on the fibre diameter, the spinning distance affected the fibre diameter considerably, with shorter spinning distance resulting in finer fibres. When a small amount of cationic surfactant (dodecyl trimethyl ammonium bromide) was added to the PP melt for melt-electrospinning, the fibre diameter was reduced considerably. The finest fibres produced from this system were 400±290 nm. This novel melt-electrospinning setup may provide a continuous and efficient method to produce PP nanofibres