Optical bistability in sideband output modes induced by squeezed vacuum

We consider $N$ two-level atoms in a ring cavity interacting with a broadband squeezed vacuum centered at frequency $\omega_{s}$ and an input monochromatic driving field at frequency $\omega$. We show that, besides the central mode (at \o), many other {\em sideband modes} are produced at the output, with frequencies shifted from $\omega$ by multiples of $2(\omega -\omega_{s})$. Here we analyze the optical bistability of the two nearest sideband modes, one red-shifted and the other blue-shifted.Comment: Replaced with final published versio

Dynamical aspects of Kinouchi-Copelli model: emergence of avalanches at criticality

We analyze the behavior of bursts of neural activity in the Kinouchi-Copelli model, originally conceived to explain information processing issues in sensory systems. We show that, at a critical condition, power-law behavior emerges for the size and duration of the bursts (avalanches), with exponents experimentally observed in real biological systems.Comment: Paper accepted for Brazilian Conference on Dynamics, Control and Applications (oral presentation and poster). 4 pages, 5 figure

New Approaches to the Green Revolution: Successes, Failures and New Rice for Africa

The nature of worldwide food insecurity is staggering, with thirteen percent of the world’s population currently malnourished. The situation is particularly dire in Sub- Saharan Africa, where 265 million people face hunger daily, with 30 to 50 million dying yearly. Solutions to the problem are often unsustainable, save a select few. Once such attempt, coined the Green Revolution, garnered both praise and notoriety through its relatively successful transformation of Southeast Asia in the 1960’s. Aimed at increasing food production, the project focused on small-holder farmers and their acquisition of more productive inputs such as high-yield seeds, fertilizers and pesticides. African nations remained unsuccessful in their implementation of this ‘revolution’ as poor domestic conditions rendered them unable to compete effectively. Now fifty years later, organizations like AfricaRice, Food and Agriculture Organization of the United Nations (FAO) and Alliance for a Green Revolution in Africa (AGRA) attempt to refurbish the endeavor for a new generation of self-sufficient and technologically advanced Africans. This paper is a study of the efficacy of this project and its potential to reduce and reverse the high incidences of poverty and hunger in Africa. Through a combination of interviews and an extensive literature review, this study attempts to determine the extent to which AGRA’s new interpretation of the Green Revolution is in line with the successes and failures of the previous endeavors. In conclusion, this paper in defense of the capacity of rural farmers to propel food sovereignty, and upholds bottom-up intervention and its new interpretations as an effective method of improving food production and reducing poverty and hunge

Young and embedded clusters in Cygnus-X: evidence for building up the IMF?

We provide a new view on the Cygnus-X north complex by accessing for the first time the low mass content of young stellar populations in the region. CFHT/WIRCam camera was used to perform a deep near-IR survey of this complex, sampling stellar masses down to ~0.1 M$_\odot$. Several analysis tools, including a extinction treatment developed in this work, were employed to identify and uniformly characterise a dozen unstudied young star clusters in the area. Investigation of their mass distributions in low-mass domain revealed a relatively uniform log-normal IMF with a characteristic mass of 0.32$\pm$0.08 M$_\odot$ and mass dispersion of 0.40$\pm$0.06. In the high mass regime, their derived slopes showed that while the youngest clusters (age < 4 Myr) presented slightly shallower values with respect to the Salpeter's, our older clusters (4 Myr < age < 18 Myr) showed IMF compliant values and a slightly denser stellar population. Although possibly evidencing a deviation from an 'universal' IMF, these results also supports a scenario where these gas dominated young clusters gradually 'build up' their IMF by accreting low-mass stars formed in their vicinity during their first ~3 Myr, before the gas expulsion phase, emerging at the age of ~4 Myr with a fully fledged IMF. Finally, the derived distances to these clusters confirmed the existence of at least 3 different star forming regions throughout Cygnus-X north complex, at distances of 500-900 pc, 1.4-1.7 kpc and 3.0 kpc, and revealed evidence of a possible interaction between some of these stellar populations and the Cygnus-OB2 association.Comment: 20 pages, 19 figures. Contains an appendix with 10 extra figure