Self-organized evolution in socio-economic environments

We propose a general scenario to analyze social and economic changes in modern environments. We illustrate the ideas with a model that incorporating the main trends is simple enough to extract analytical results and, at the same time, sufficiently complex to display a rich dynamic behavior. Our study shows that there exists a macroscopic observable that is maximized in a regime where the system is critical, in the sense that the distribution of events follow power-laws. Computer simulations show that, in addition, the system always self-organizes to achieve the optimal performance in the stationary state.Comment: 4 pages RevTeX; needs epsf.sty and rotate.sty; submitted to Phys Rev Let

Length-weight relationships of coral reef fishes from the Alacran Reef, Yucatan, Mexico

Length-weight relationships were computed for 42 species of coral reef fishes from 14 families from the Alacran Reef (Yucatan, Mexico). A total of 1 892 individuals was used for this purpose. The fish species were caught by different fishing techniques such as fishhooks, harpoons, gill and trawl nets. The sampling period was from March 1998 to January 2000

Computing the Singularities of Rational Surfaces

Given a rational projective parametrization \cP(\ttt,\sss,\vvv) of a rational projective surface \cS we present an algorithm such that, with the exception of a finite set (maybe empty) \cB of projective base points of \cP, decomposes the projective parameter plane as \projdos\setminus \cB=\cup_{k=1}^{\ell} \cSm_k such that if (\ttt_0:\sss_0:\vvv_0)\in \cSm_k then \cP(\ttt_0,\sss_0,\vvv_0) is a point of \cS of multiplicity $k$.Comment: In this new version, we only have changed the thanks. In particular, we have written: This work was developed, and partially supported, under the research project MTM2008-04699-C03-01 "Variedades param\'etricas: algoritmos y aplicaciones", Ministerio de Ciencia e Innovaci\'on, Spain and by "Fondos Europeos de Desarrollo Regional" of the European Unio

Discovery of a wide companion near the deuterium burning mass limit in the Upper Scorpius association

We present the discovery of a companion near the deuterium burning mass limit located at a very wide distance, at an angular separation of 4.6+/-0.1 arcsec (projected distance of ~ 670 AU) from UScoCTIO108, a brown dwarf of the very young Upper Scorpius association. Optical and near-infrared photometry and spectroscopy confirm the cool nature of both objects, with spectral types of M7 and M9.5, respectively, and that they are bona fide members of the association, showing low gravity and features of youth. Their masses, estimated from the comparison of their bolometric luminosities and theoretical models for the age range of the association, are 60+/-20 and 14^{+2}_{-8} MJup, respectively. The existence of this object around a brown dwarf at this wide orbit suggests that the companion is unlikely to have formed in a disk based on current planet formation models. Because this system is rather weakly bound, they did not probably form through dynamical ejection of stellar embryos.Comment: 10 pages, including 4 figures and 2 table

High Gain Amplifier with Enhanced Cascoded Compensation

A two-stage CMOS operational amplifier with both, gain-boosting and indirect current feedback frequency compensation performed by means of regulated cascode amplifiers, is presented. By using quasi-floating-gate transistors (QFGT) the supply requirements, the number of capacitors and the size of the compensation capacitors respect to other Miller schemes are reduced. A prototype was fabricated using a 0.5 μm technology, resulting, for a load of 45 pF and supply voltage of 1.65 V, in open-loop-gain of 129 dB, 23 MHz of gain-bandwidth product, 60o phase margin, 675 μW power consumption and 1% settling time of 28 ns

Comparison of Physiological Responses and Perceived Respiratory Resistance Among Mask Usage During Exercise

Since the beginning of the COVID-19 pandemic, the use of a face mask in public is recommended when social distancing cannot be maintained to decrease the spread of the virus with many fitness facilities requiring their patrons to wear a face mask during exercise. The physiological response of wearing a face mask during exercise is relatively unknown and is speculated among the media resulting in contradicting messages conveyed to the public PURPOSE: The purpose of this study was to determine if a face mask influenced performance (time to exhaustion), physiological responses (heart rate, oxyhemoglobin saturation and temperature) and subjective measurements such as dyspnea, perceived respiratory resistance, and rating of perceived exertion (RPE) during exercise. METHODS: Fifteen healthy males (n =8) and females (n=7) completed three graded exercise treadmill tests with (1) a surgical face mask, (2) a cloth face mask, and (3) no mask randomly with at least 48hrs apart. Heart rate (HR), oxyhemoglobin saturation (SpO2), temperature, RPE, dyspnea, was measured throughout exercise. Participants rated their perceived respiratory resistance for each condition at rest, beginning of exercise, and at fatigue using a 100 mm visual analog scale. RESULTS: Significant differences (p \u3c 0.05) were observed in perceived respiratory resistance between no mask and both surgical and cloth conditions at rest (1.55 ± 2.34mm; 6.33 ± 6.11mm; 9.67 ± 10.77mm respectively) and at the beginning of exercise (5.93 ± 6.64mm; 15.47 ± 12.56mm; 21.07± 15.04mm respectively). During stage 3 of the exercise test, the no mask condition had a significantly lower RPE compared to the cloth mask condition (13.22 ± 2.14;14.60 ± 2.13 respectively). Time to exhaustion was similar for all conditions (mask: 11:51 ± 2:31min; cloth: 11:16 ± 2:24min; surgical: 11:32 ± 2:23min). At all times points, there was no significant (p \u3e 0.05) difference between the conditions for HR, SpO2, temperature, and dyspnea. CONCLUSION: Wearing either a surgical or cloth face mask is safe during exercise in healthy adults and has no effect on HR, SpO2, or body temperature. It appears that wearing a face mask may have a minor influence on subjective measurements such as perceived respiratory resistance or RPE during exercise

LAGOVirtual: A Collaborative Environment for the Large Aperture GRB Observatory

We present the LAGOVirtual Project: an ongoing project to develop platform to collaborate in the Large Aperture GRB Observatory (LAGO). This continental-wide observatory is devised to detect high energy (around 100 GeV) component of Gamma Ray Bursts, by using the single particle technique in arrays of Water Cherenkov Detectors (WCD) at high mountain sites (Chacaltaya, Bolivia, 5300 m a.s.l., Pico Espejo, Venezuela, 4750 m a.s.l., Sierra Negra, Mexico, 4650 m a.s.l). This platform will allow LAGO collaboration to share data, and computer resources through its different sites. This environment has the possibility to generate synthetic data by simulating the showers through AIRES application and to store/preserve distributed data files collected by the WCD at the LAGO sites. The present article concerns the implementation of a prototype of LAGO-DR adapting DSpace, with a hierarchical structure (i.e. country, institution, followed by collections that contain the metadata and data files), for the captured/simulated data. This structure was generated by using the community, sub-community, collection, item model; available at the DSpace software. Each member institution-country of the project has the appropriate permissions on the system to publish information (descriptive metadata and associated data files). The platform can also associate multiple files to each item of data (data from the instruments, graphics, postprocessed-data, etc.).Comment: Second EELA-2 Conference Choroni, Venezuela, November 25th to 27th 200

Modular Hydraulic Propulsion: A Robot that Moves by Routing Fluid Through Itself

This paper introduces the concept of Modular Hydraulic Propulsion, in which a modular robot that operates in a fluid environment moves by routing the fluid through itself. The robot’s modules represent sections of a hydraulics network. Each module can move fluid between any of its faces. The modules (network sections) can be rearranged into arbitrary topologies. We propose a decentralized motion controller, which does not require modules to communicate, compute, nor store information during run-time. We use 3-D simulations to compare the performance of this controller to that of a centralized controller with full knowledge of the task. We also detail the design and fabrication of six 2-D prototype modules, which float in a water tank. Results of systematic experiments show that the decentralized controller, despite its simplicity, reliably steers modular robots towards a light source. Modular Hydraulic Propulsion could offer new solutions to problems requiring reconfigurable systems to move precisely in 3-D, such as inspection of pipes, vascular systems or other confined spaces