Waste management in the stingless bee Melipona beecheii Bennett (Hymenoptera: Apidae)

Waste management is important in insect societies because waste can be hazardous to adults, brood and food stores. The general organization of waste management and the influence of task partitioning, division of labor and age polyethism on waste processing were studied in three colonies of the tropical American stingless bee Melipona beecheii Bennett in Yucatán, Mexico. Waste generated in the colony (feces, old brood cells, cocoons, dead adults and brood) was collected by workers throughout the nest and taken to specific waste dumps within the nest. During the day, workers based at the waste dumps formed waste pellets, which they directly transferred in 93% of cases, to other workers who subsequently removed them from the nest. This is an example of task partitioning and is hypothesized to improve nest hygiene as has been found in leafcutting ants, Atta. To investigate division of labor and age polyethism we marked a cohort of 144 emerging workers. Workers forming waste pellets were on average 31.2±6.5 days old (±SD, N= 40, range of 18-45 days). The life span of M. beecheii workers was 49.0±14.0 days (N= 144). There was no difference in the life span of workers who formed (52.2±11.6 days, N= 40) or did not form (49.9±11.5 days, N= 97) waste pellets, suggesting that waste work did not increase mortality. Although waste was probably not hazardous to adults and brood, because the dumps are located outside the brood chamber, its presence inside the nests can attract phorid flies and predators, which can harm the colony

Ensemble fluctuations of the cosmic ray energy spectrum and the intergalactic magnetic field

The origin of the most energetic cosmic ray particles is one of the most important open problems in astrophysics. Despite a big experimental effort done in the past years, the sources of these very energetic particles remain unidentified. Therefore, their distribution on the Universe and even their space density are still unknown. It has been shown that different spatial configurations of the sources lead to different energy spectra and composition profiles (in the case of sources injecting heavy nuclei) at Earth. These ensemble fluctuations are more important at the highest energies because only nearby sources, which are necessarily few, can contribute to the flux observed at Earth. This is due to the interaction of the cosmic rays with the low energy photons of the radiation field, present in the intergalactic medium, during propagation. It is believed that the intergalactic medium is permeated by a turbulent magnetic field. Although at present it is still unknown, there are several constraints for its intensity and coherence length obtained from different observational techniques. Charged cosmic rays are affected by the intergalactic magnetic field because of the bending of their trajectories during propagation through the intergalactic medium. In this work, the influence of the intergalactic magnetic field on the ensemble fluctuations is studied. Sources injecting only protons and only iron nuclei are considered. The ensemble fluctuations are studied for different values of the density of sources compatible with the constraints recently obtained from cosmic ray data. Also, the possible detection of the ensemble fluctuations in the context of the future JEM-EUSO mission is discussed.Comment: Accepted for publication in Physical Review

On the possibility of neutrino flavor identification at the highest energies

High energy astrophysical neutrinos carry relevant information about the origin and propagation of cosmic rays. They can be created as a by-product of the interactions of cosmic rays in the sources and during propagation of these high energy particles through the intergalactic medium. The determination of flavor composition in this high energy flux is important because it presents a unique chance to probe our understanding of neutrino flavor oscillations at gamma factors >10^21. In this work we develop a new statistical technique to study the flavor composition of the incident neutrino flux, which is based on the multipeak structure of the longitudinal profiles of very deep electron and tau neutrino horizontal air showers. Although these longitudinal profiles can be observed by means of fluorescence telescopes placed over the Earth's surface, orbital detectors are more suitable for neutrino observations owing to their much larger aperture. Therefore, we focus on the high energy region of the neutrino spectrum relevant for observations with orbital detectors like the planned JEM-EUSO telescope.Comment: Accepted for publication in Physical Review

Oversampling in shift-invariant spaces with a rational sampling period

8 pages, no figures.It is well known that, under appropriate hypotheses, a sampling formula allows us to recover any function in a principal shift-invariant space from its samples taken with sampling period one. Whenever the generator of the shift-invariant space satisfies the Strang-Fix conditions of order r, this formula also provides an approximation scheme of order r valid for smooth functions. In this paper we obtain sampling formulas sharing the same features by using a rational sampling period less than one. With the use of this oversampling technique, there is not one but an infinite number of sampling formulas. Whenever the generator has compact support, among these formulas it is possible to find one whose associated reconstruction functions have also compact support.This work has been supported by the Grant MTM2009-08345 from the D.G.I. of the Spanish Ministerio de Ciencia y Tecnología

Application of the war of attrition game to the analysis of intellectual property disputes

In many developing countries intellectual property infringement and the commerce of pirate goods is an entrepreneurial activity. Digital piracy is very often the only media for having access to music, cinema, books and software. At the same time, bio-prospecting and infringement of indigenous knowledge rights by international consortiums is usual in places with high biodiversity. In these arenas transnational actors interact with local communities. Accusations of piracy often go both ways. This article analyzes the case of southeast Mexico. Using a war of attrition game theory model it explains different situations of intellectual property rights piracy and protection. It analyzes different levels of interaction and institutional settings from the global to the very local. The article proposes free IP zones as a solution of IP disputes. The formation of technological local clusters through Free Intellectual Property Zones (FIPZ) would allow firms to copy and share de facto public domain content for developing new products inside the FIPZ. Enforcement of intellectual property could be pursuit outside of the FIPZ. FIPZ are envisioned as a new type of a sui generis intellectual property regime