Labor Market Segmentation and Immigrant Competition: A Quantal Response Statistical Equilibrium Analysis

Competition between and within groups of workers takes place in labor markets that are segmented along various, often unobservable dimensions. This paper proposes a measure of the intensity of competition in labor markets on the basis of limited data. The maximum entropy principle is used to make inferences about the unobserved mobility decisions of workers in US household data. The quantal response statistical equilibrium class of models can be seen to give robust microfoundations to the persistent patterns of wage inequality. An application to labor market competition between native and foreign-born workers in the United States shows that this class of models captures a substantial proportion of the informational content of observed wage distribution

El papel central de la suplementación dirigida con betacaroteno en el comportamiento endocrino y reproductivo en caprinos de las regiones áridas de México

In the Americas, Mexico leads the census and the production of goat milk; the Comarca Lagunera, located in the arid northern (26° N), is the main goat milk production region in Mexico. Two experiments (Exp1 and Exp2) were carried out to evaluate the possible effect of betacarotene (BC) supplementation at endocrine and reproductive level. In the Exp1, adult goats (n=22, 45.35 ± 1.35 kg, 3.5 years-old, 7/8 Saanen-Alpine x Criollo), during the natural breeding season (Oct-Nov) it was evaluated the serum levels of growth hormone (GH), the insulin-like growth factor type-1 and upon the total ovarian activity (AOT; antral follicles + corpus luteum). In from October to November (during the natural breeding season). The Exp2 considered young goats (n=22, anestrous, 29.17 ± 1.02 kg, 1 year-old, Alpine-Saanen-Nubian x Criollo) during the non-reproductive season (Apr-May), evaluating the pulsatility of the luteinizing hormone (LH) and the AOT. In the Exp1, the BC-group depicted an augmented AOT regarding the control groups (CONT) (8.4 vs 6.2 units), parallel to a reduction in the serum average levels of GH in the BC-group (10.0 vs 14.3 ng/mL), with no differences in the IGF-1 levels (254.6 ng/mL). In the Exp2, besides to an increased AOT in the BC-group (3.44 vs 1.87 units), it was observed a grater LH pulse amplitude (0.55 vs 0.24 ng/mL). These results demonstrate for the first time to betacarotene not only as AOT-regulating molecule but also as a modulator of the release pattern of GH in adult goats as well as LH in yearling goats with genotypes with a high degree towards highly marked seasonal reproduction. Future research should define the probable site of BC-action regarding the function of the hypothalamichypophyseal- gonadal axis in goats.En América, México es líder en inventario y nivel de producción de leche caprina; la Comarca Lagunera, situada en el norte árido (26° N), es la principal región productora de leche caprina en México. Se desarrollaron dos experimentos (Exp1 y Exp2) para evaluar el posible efecto de la suplementación de betacaroteno (BC) a nivel endocrino y reproductivo. El Exp1, consideró cabras adultas (n=22, 45.35 ± 1.35 kg., 3.5 años, Saanen- Alpino x Criollo) en la época natural de empadre (oct-nov) evaluando los niveles séricos de la hormona del crecimiento (GH), el factor de crecimiento análogo a insulina tipo 1 (IGF-1), y en la actividad ovárica total (AOT; folículos antrales + cuerpos lúteos). El Exp2 consideró cabras jóvenes (n=22, anéstricas, 29.17 ± 1.02 kg, 1 año de edad, Alpino-Saanen-Nubian x Criollo), en la época no-reproductiva (abr-mayo), evaluando la pulsatilidad de la hormona luteinizante (LH) y la AOT. En el Exp1, el grupo-BC mostró un aumento en la AOT respecto al grupo control (CONT) (8.4 vs 6.2 unidades), paralelo a una reducción en los niveles medios de GH en el grupo-BC (10.0 vs 14.3 ng/mL), sin diferencias en los niveles de IGF-1 (254.6 ng/mL). En el Exp2, además de un incremento en la AOT en el grupo-BC (3.44 vs 1.87 unidades), se observó una mayor amplitud en el pulso de LH (0.55 vs 0.24 ng/mL). Los resultados demuestran por primera vez al BC como una molécula reguladora no solo de la actividad ovárica tanto en época reproductiva como en el anestro, sino como un modulador del patrón de secreción de GH en hembras adultas y LH en primalas, en genotipos con un alto encaste hacia razas lecheras con una marcada reproducción estacional. Futuras investigaciones deberán definir el probable sitio de acción del BC en la función del eje hipotalámico-hipofisiario-gonadal caprino

Assessing the Constrained Harmonic Mean Method for Deriving the Kinematics of ICMEs with a Numerical Simulation

In this study we use a numerical simulation of an artificial coronal mass ejection (CME) to validate a method for calculating propagation directions and kinematical profiles of interplanetary CMEs (ICMEs). In this method observations from heliospheric images are constrained with in-situ plasma and field data at 1 AU. These data are used to convert measured ICME elongations into distance by applying the Harmonic Mean approach that assumes a spherical shape of the ICME front. We use synthetic white-light images, similar as observed by STEREO-A/HI, for three different separation angles between remote and in-situ spacecraft, of 30{\deg}, 60{\deg}, and 90{\deg}. To validate the results of the method they are compared to the apex speed profile of the modeled ICME, as obtained from a top view. This profile reflects the "true" apex kinematics since it is not affected by scattering or projection effects. In this way it is possible to determine the accuracy of the method for revealing ICME propagation directions and kinematics. We found that the direction obtained by the constrained Harmonic Mean method is not very sensitive to the separation angle (30{\deg} sep: \phi = W7; 60{\deg} sep: \phi = W12; 90{\deg} sep: \phi = W15; true dir.: E0/W0). For all three cases the derived kinematics are in a relatively good agreement with the real kinematics. The best consistency is obtained for the 30{\deg} case, while with growing separation angle the ICME speed at 1 AU is increasingly overestimated (30{\deg} sep: \Delta V_arr ~-50 km/s, 60{\deg} sep: \Delta V_arr ~+75 km/s, 90{\deg} sep: \Delta V_arr ~+125 km/s). Especially for future L4/L5 missions the 60{\deg} separation case is highly interesting in order to improve space weather forecasts.Comment: accepted for publication in Solar Physic

Reactive SINDy: Discovering governing reactions from concentration data

The inner workings of a biological cell or a chemical reaction can be rationalized by the network of reactions, whose structure reveals the most important functional mechanisms. For complex systems, these reaction networks are not known a priori and cannot be efficiently computed with ab initio methods, therefore an important approach goal is to estimate effective reaction networks from observations, such as time series of the main species. Reaction networks estimated with standard machine learning techniques such as least-squares regression may fit the observations, but will typically contain spurious reactions. Here we extend the sparse identification of nonlinear dynamics (SINDy) method to vector-valued ansatz functions, each describing a particular reaction process. The resulting sparse tensor regression method “reactive SINDy” is able to estimate a parsimonious reaction network. We illustrate that a gene regulation network can be correctly estimated from observed time series

Nonlinear self-collimated sound beams in sonic crystals

We report the propagation of high-intensity sound beams in a sonic crystal, under self-collimation or reduced-divergence conditions. The medium is a fluid with elastic quadratic nonlinearity, where the dominating nonlinear effect is harmonic generation. The conditions for the efficient generation of narrow, non-diverging beam of second harmonic are discussed. Numerical simulations are in agreement with the analytical predictions made, based on the linear dispersion characteristics in modulated media and the nonlinear interaction in a quadratic medium under phase matching conditions.Comment: Sent to PR

On the Approximation Quality of Markov State Models

We consider a continuous-time Markov process on a large continuous or discrete state space. The process is assumed to have strong enough ergodicity properties and to exhibit a number of metastable sets. Markov state models (MSMs) are designed to represent the effective dynamics of such a process by a Markov chain that jumps between the metastable sets with the transition rates of the original process. MSMs have been used for a number of applications, including molecular dynamics, for more than a decade. Their approximation quality, however, has not yet been fully understood. In particular, it would be desirable to have a sharp error bound for the difference in propagation of probability densities between the MSM and the original process on long timescales. Here, we provide such a bound for a rather general class of Markov processes ranging from diffusions in energy landscapes to Markov jump processes on large discrete spaces. Furthermore, we discuss how this result provides formal support or shows the limitations of algorithmic strategies that have been found to be useful for the construction of MSMs. Our findings are illustrated by numerical experiments