Mode competition in superradiant scattering of matter waves

Superradiant Rayleigh scattering in a Bose gas released from an optical lattice is analyzed with incident light pumping at the Bragg angle for resonant light diffraction. We show competition between superradiance scattering into the Bragg mode and into end-fire modes clearly leads to suppression of the latter at even relatively low lattice depths. A quantum light-matter interaction model is proposed for qualitatively explaining this result.Comment: 6 pages, 6 figures, accepted by PR

Human Capital Investment and the Gender Division of Labor

We use a model of human capital investment and activity choice to explain facts describing gender differentials in the levels and returns to human capital investments. These include the higher return to and level of schooling, the small effect of healthiness on wages, and the large effect of healthiness on schooling for females relative to males. The model incorporates gender differences in the level and responsiveness of brawn to nutrition in a Roy-economy setting in which activities reward skill and brawn differentially. Empirical evidence from rural Bangladesh provides support for the model and the importance of the distribution of brawn.brawn, health, schooling, gender

Abortion Legalization and Child Living Circumstances: Who is the "Marginal Child?"

We estimate the impact of changes in abortion access in the early 1970s on the average living standards of cohorts born in those years. In particular, we address the selection inherent in the abortion decision: is the marginal child who is not born when abortion access increases more or less disadvantaged than the average child? Legalization of abortion in five states around 1970, followed by legalization nationwide due to the 1973 Roe v. Wade decision, generates natural variation which can be used to estimate the effect of abortion access. We find that cohorts born after abortion was legalized experienced a significant reduction in a number of adverse outcomes. Our estimates imply that the marginal child who was not born due to legalization would have been 70% more likely to live in a single parent family, 40% more likely to live in poverty, 50% more likely to receive welfare, and 35% more likely to die as an infant. These selection effects imply that the legalization of abortion saved the government over $14 billion in welfare expenditures through 1994.

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Ingeniero (a) ElectrónicoPregrad

Virtuous Circles of Productivity: Star Bioscientists and the Institutional Transformation of Industry

The most productive (`star') bioscientists possessed intellectual human capital of extraordinary scientific and pecuniary value for some 10-15 yrs after Cohen & Boyer's 1973 founding discovery for biotechnology. This extraordinary value was due to the union of still scarce knowledge of the new research techniques and genius to apply these techniques in valuable ways. As in other sciences, star bioscientists were particularly protective of their ideas in the early years of the revolution, tending to collaborate more within their own institution which slowed diffusion to other scientists. Therefore, close, bench-level working ties between stars and firm scientists were needed to accomplish commercialization of the breakthroughs. Where and when the star scientists were actively producing academic publications is a key determinant of where and when commercial firms began to use biotechnology. The extent of collaboration by a firm's scientists with stars is a powerful predictor of its success: for each 9 articles co-authored by an academic star and firm scientists about 3 more products in development, 1 more on the market and 1550 more employees are estimated. Such collaboration with firms, or employment, also results in significantly higher rates of citation to articles written with the firm. The U.S. scientific and economic infrastructure has been quite effective in fostering and commercializing the bioscientific revolution. To provide an indication of international competitiveness, we estimate stars' distribution, commercial involvement and migration across the top 10 countries in bioscience. These results let us inside the black box to see how scientific breakthroughs become economic growth and consider the implications for policy.

The Gold Standard and the Great Depression

This paper, written primarily for historians, attempts to explain why political leaders and central bankers continued to adhere to the gold standard as the Great Depression intensified. We do not focus on the effects of the gold standard on the Depression, which we and others have documented elsewhere, but on the reasons why policy makers chose the policies they did. We argue that the mentality of the gold standard was pervasive and compelling to the leaders of the interwar economy. It was expressed and reinforced by the discourse among these leaders. It was opposed and finally defeated by mass politics, but only after the interaction of national policies had drawn the world into the Great Depression.

Spatial Distribution of Competing Ions around DNA in Solution

The competition of monovalent and divalent cations for proximity to negatively charged DNA is of biological importance and can provide strong constraints for theoretical treatments of polyelectrolytes. Resonant x-ray scattering experiments have allowed us to monitor the number and distribution of each cation in a mixed ion cloud around DNA. These measurements provide experimental evidence to support a general theoretical prediction: the normalized distribution of each ion around polyelectrolytes remains constant when ions are mixed at different ratios. In addition, the amplitudes of the scattering signals throughout the competition provide a measurement of the surface concentration parameter that predicts the competition behavior of these cations. The data suggest that ion size needs to be taken into account in applying Poisson-Boltzmann treatments to polyelectrolytes such as DNA

Search for physics beyond the standard model in events with τ leptons, jets, and large transverse momentum imbalance in pp collisions at [Formula: see text].

A search for physics beyond the standard model is performed with events having one or more hadronically decaying τ leptons, highly energetic jets, and large transverse momentum imbalance. The data sample corresponds to an integrated luminosity of 4.98 fb-1 of proton-proton collisions at [Formula: see text] collected with the CMS detector at the LHC in 2011. The number of observed events is consistent with predictions for standard model processes. Lower limits on the mass of the gluino in supersymmetric models are determined