How Do Immigrants Spend Time?: The Process of Assimilation

Using 2004-2008 data from the American Time Use Survey, we show that sharp differences between the time use of immigrants and natives become noticeable when activities are distinguished by incidence and intensity. We develop a theory of the process of assimilation—what immigrants do with their time—based on the notion that assimilating activities entail fixed costs. The theory predicts that immigrants will be less likely than natives to undertake such activities, but conditional on undertaking them, immigrants will spend more time on them than natives. We identify several activities—purchasing, education and market work—as requiring the most interaction with the native world, and these activities more than others fit the theoretical predictions. Additional tests suggest that the costs of assimilating derive from the costs of learning English and from some immigrants’ unfamiliarity with a high-income market economy. A replication using the 1992 Australian Time Use Survey yields remarkably similar results.

Rapid grain growth in post-AGB disc systems from far-infrared and sub-millimetre photometry

The timescales on which astronomical dust grows remain poorly understood, with important consequences for our understanding of processes like circumstellar disk evolution and planet formation.A number of post-asymptotic giant branch stars are found to host optically thick, dust- and gas-rich circumstellar discs in Keplerian orbits. These discs exhibit evidence of dust evolution, similar to protoplanetary discs; however since post-AGB discs have substantially shorter lifetimes than protoplanetary discs they may provide new insights on the grain-growth process. We examine a sample of post-AGB stars with discs to determine the FIR and sub-mm spectral index by homogeneously fitting a sample of data from \textit{Herschel}, the SMA and the literature. We find that grain growth to at least hundreds of micrometres is ubiquitous in these systems, and that the distribution of spectral indices is more similar to that of protoplanetary discs than debris discs. No correlation is found with the mid-infrared colours of the discs, implying that grain growth occurs independently of the disc structure in post-AGB discs. We infer that grain growth to $\sim$mm sizes must occur on timescales $<<10^{5}$ yr, perhaps by orders of magnitude, as the lifetimes of these discs are expected to be $\lesssim10^{5}$~yr and all objects have converged to the same state. This growth timescale is short compared to the results of models for protoplanetary discs including fragmentation, and may provide new constraints on the physics of grain growth.Comment: 13 pages, 7 figures. Accepted for publication in MNRA

Defects and boundary layers in non-Euclidean plates

We investigate the behavior of non-Euclidean plates with constant negative Gaussian curvature using the F\"oppl-von K\'arm\'an reduced theory of elasticity. Motivated by recent experimental results, we focus on annuli with a periodic profile. We prove rigorous upper and lower bounds for the elastic energy that scales like the thickness squared. In particular we show that are only two types of global minimizers -- deformations that remain flat and saddle shaped deformations with isolated regions of stretching near the edge of the annulus. We also show that there exist local minimizers with a periodic profile that have additional boundary layers near their lines of inflection. These additional boundary layers are a new phenomenon in thin elastic sheets and are necessary to regularize jump discontinuities in the azimuthal curvature across lines of inflection. We rigorously derive scaling laws for the width of these boundary layers as a function of the thickness of the sheet

Hispanic Immigration to the United States

This chapter presents some of the exceptional characteristics of recent Hispanic immigration to the United States. In 2005, there were nearly 40 million Hispanic immigrants and descendants of Hispanic immigrants living in the U.S. The assimilation experience of this large cultural group does not seem to be following the path past immigrants to the U.S. followed. Most third generation Hispanics in the U.S. still find themselves with income and education levels below the U.S. averages. Most forecasts predict that about 60 million Hispanics and Hispanic-Americans will be living in the U.S. by 2030

The Non-thermal Radio Jet Toward the NGC 2264 Star Formation Region

We report sensitive VLA 3.6 cm radio observations toward the head of the Cone nebula in NGC 2264, made in 2006. The purpose of these observations was to study a non-thermal radio jet recently discovered, that appears to emanate from the head of the Cone nebula. The jet is highly polarized, with well-defined knots, and one-sided. The comparison of our images with 1995 archive data indicates no evidence of proper motions nor polarization changes. We find reliable flux density variations in only one knot, which we tentatively identify as the core of a quasar or radio galaxy. An extragalactic location seems to be the best explanation for this jet.Comment: 12 pages, 5 figure

Off-shell chromomagnetic dipole moments in the SM at and beyond the ZZ gauge boson mass scale

The off-shell anomalous chromomagnetic dipole moment of the standard model quarks ($u$, $d$, $s$, $c$ and $b$), at the $Z$ gauge boson mass scale, is computed by using the $\overline{\textrm{MS}}$ scheme. The numerical results disagree with all the previous predictions reported in the literature and show a discrepancy of up to two orders of magnitude in certain situations.Comment: 16 pages, 5 figure

Intensity-fading and other MS approaches to analyze proteases and protease in inhibitors and their interactions in biological samples

Comunicaciones a congreso

Innovation and growth in family-owned Mexican SMEs

This paper studies the relationship between innovation and the level of growth in family-owned small and medium-sized enterprises (SMEs), this is done within the context of Mexico. The conceptual framework of analysis is based on the hypothesis that innovation in products, processes and management systems contribute to the achievement of growth in family-owned SMEs. To test this hypothesis, a model of structural equation of second order was developed with data collected from 206 family-owned SMEs located in the state of Aguascalientes, Mexico. The empirical evidence provided by the analysis supports the hypothesis, showing that family-owned SMEs that increase their innovation activities will also significantly increase their opportunities for growth. This finding can be used to inform the business growth strategies formulated by the owners, or managers, of family-owned SEMs. These also indicate policy-makers that by designing effective policies and providing incentives to support innovation in family-owned SMEs, the government would not only contribute to the growth of these organisations but also to the growth of their regions and countries. Despite the importance of innovation and family-owned SMEs, evidence suggests that studies focused on investigating innovation in this type of organisations are very limited. This paper fills this gap by providing a refined understanding of the relationship between innovation and growth in family-owned SMEs