Decentralized Discrete-Time Formation Control for Multirobot Systems

Inspired from the collective behavior of biological entities for the group motion coordination, this paper analyzes the formation control of mobile robots in discrete time where each robot can sense only the position of certain team members and the group behavior is achieved through the local interactions of robots. The main contribution is an original formal proof about the global convergence to the formation pattern represented by an arbitrary Formation Graph using attractive potential functions. The analysis is addressed for the case of omnidirectional robots with numerical simulations

A memetic algorithm based on Artificial Bee Colony for optimal synthesis of mechanisms

En este documento se presenta una propuesta novedosa de un algoritmo híbrido modular, como herramienta para resolver problemas de ingeniería del mundo real. Se implementa y aplica un algoritmo memético, MemMABC, para la solución de dos casos de diseño de mecanismos, con el fin de evaluar su eficiencia y rendimiento. El algoritmo propuesto es simple y flexible debido a su modularidad; estas características lo vuelven altamente reutilizable para ser aplicado en una amplia gama de problemas de optimización. Las soluciones de los casos de estudio también son modulares, siguiendo un esquema de programación estructurada que incluye el uso de variables globales para la configuración, y de subrutinas para la función objetivo y el manejo de las restricciones. Los algoritmos meméticos son una buena opción para resolver problemas duros de optimización, debido a la sinergia derivada de la combinación de sus componentes: una metaheurística poblacional para búsqueda global y un método de refinamiento local. La calidad en los resultados de las simulaciones sugiere que el MemMABC puede aplicarse con éxito para la solución de problemas duros de diseño en ingeniería.In this paper a novel proposal of a modular hybrid algorithm as a tool for solving real-world engineering problems is presented. A memetic algorithm, MemMABC, is implemented with this approach and applied to solve two case studies of mechanism design, in order to evaluate its efficiency and performance. Because of its modularity, the proposed algorithm is simple and flexible; these features make it quite reusable to be applied on different optimization problems, with a wide scope. The solutions of the optimization problems are also modular, following a scheme of structured programming that includes the use of global variables for configuration, and subroutines for the objective function and the restrictions. Memetic algorithms are a good option to solve hard optimization problems, because of the synergy derived from the combination of their components: a global search population-based metaheuristic and a local refinement method. The quality of simulation results suggests that MemMABC can be successfully applied to solve hard problems in engineering design.Peer Reviewe

Pharmacokinetic/Pharmacodynamic Modeling of Antipyretic and Anti-Inflammatory Effects of Naproxen in the Rat

Pharmacokinetic/pharmacodynamic modeling was used to characterize the antipyretic and anti-inflammatory effects of naproxen in rats. An indirect response model was used to describe the antipyretic effects of naproxen after short intravenous infusions. The model assumes that basal temperature (T(a)) is maintained by the balance of fever mediators given by a constant (zero order) rate of synthesis (K(syn)), and a first order rate of degradation (K(out)). After an intraperitoneal injection of lipopolysaccharide, the change in T(a) was modeled assuming an increase in fever mediators described as an input rate function [IR(t)] estimated nonparametrically. An inhibitory E(max) model adequately described the inhibition of IR(t) by naproxen. A more complex model was used to describe the anti-inflammatory response of oral naproxen in the carrageenin-induced edema model. Before carrageenin injection, physiological conditions are maintained by a balance of inflammation mediators given by K(syn) and K(out) (see above). After carrageenin injection, the additional synthesis of mediators is described by IR(t) (see above). Such mediators induced an inflammatory process, which is governed by a first order rate constant (K(IN)) that can be inhibited by the presence of naproxen in plasma. The sigmoidal E(max) model also well described the inhibition of K(IN) by naproxen. Estimates for IC(50) [concentration of naproxen in plasma eliciting half of maximum inhibition of IR(t) or K(IN)] were 4.24 and 4.13 microg/ml, for the antipyretic and anti-inflammatory effects, respectively

Development of coccolithophore-based transfer functions in the western Mediterranean sea: a sea surface salinity reconstruction for the last 15.5 kyr

A new data set of 88 marine surface sediment samples and related oceanic environmental variables (temperature, salinity, chlorophyll <i>a</i>, oxygen, etc.) was studied to quantify the relationship between assemblages of coccolithophore species and modern environmental conditions in the western Mediterranean Sea and the Atlantic Ocean, west of the Strait of Gibraltar. Multivariate statistical analyses revealed that coccolithophore species were primarily related to sea surface salinity (SSS), explaining an independent and significant proportion of variance in the coccolithophore data. A quantitative coccolithophore-based transfer function to estimate SSS was developed using the modern analog technique (MAT) and weighted-averaging partial least square regression (WA-PLS). The bootstrapped regression coefficient (<i>R</i>²_boot) was 0.85_MAT and 0.80_WA-PLS, with a root-mean-square error of prediction (RMSEP) of 0.29_MAT and 0.30_WA-PLS (psu). The resulting transfer function was applied to fossil coccolithophore assemblages in the highly resolved (~ 65 years) sediment core CEUTA10PC08 from the Alboran Sea (western Mediterranean) in order to reconstruct SSS for the last 25 kyr. The reliability of the reconstruction was evaluated by assessing the degree of similarity between fossil and modern coccolithophore assemblages and by a comparison of reconstructions with fossil ordination scores. Analogs were poor for the stadials associated with Heinrich events 2 and 1 and part of the Last Glacial Maximum. Good analogs indicate a more reliable reconstruction of the SSS for the last 15.5 kyr. During this period, several millennial and centennial SSS changes were observed and associated with sea-level oscillations and variations in the Atlantic Water entering the Alboran

Secretion of biologically active interferon-gamma inducible protein-10 (IP-10) by Lactococcus lactis

<p>Abstract</p> <p>Background</p> <p>Chemokines are a large group of chemotactic cytokines that regulate and direct migration of leukocytes, activate inflammatory responses, and are involved in many other functions including regulation of tumor development. Interferon-gamma inducible-protein-10 (IP-10) is a member of the C-X-C subfamily of the chemokine family of cytokines. IP-10 specifically chemoattracts activated T lymphocytes, monocytes, and NK cells. IP-10 has been described also as a modulator of other antitumor cytokines. These properties make IP-10 a novel therapeutic molecule for the treatment of chronic and infectious diseases. Currently there are no suitable live biological systems to produce and secrete IP-10. <it>Lactococcus lactis </it>has been well-characterized over the years as a safe microorganism to produce heterologous proteins and to be used as a safe, live vaccine to deliver antigens and cytokines of interest. Here we report a recombinant strain of <it>L. lactis </it>genetically modified to produce and secrete biologically active IP-10.</p> <p>Results</p> <p>The IP-10 coding region was isolated from human cDNA and cloned into an <it>L. lactis </it>expression plasmid under the regulation of the pNis promoter. By fusion to the usp45 secretion signal, IP-10 was addressed out of the cell. Western blot analysis demonstrated that recombinant strains of <it>L. lactis </it>secrete IP-10 into the culture medium. Neither degradation nor incomplete forms of IP-10 were detected in the cell or supernatant fractions of <it>L. lactis</it>. In addition, we demonstrated that the NICE (nisin-controlled gene expression) system was able to express IP-10 "de novo" even two hours after nisin removal. This human IP-10 protein secreted by <it>L. lactis </it>was biological active as demonstrated by Chemotaxis assay over human CD3+T lymphocytes.</p> <p>Conclusion</p> <p>Expression and secretion of mature IP-10 was efficiently achieved by <it>L. lactis </it>forming an effective system to produce IP-10. This recombinant IP-10 is biologically active as demonstrated by its ability to chemoattract human CD3+ T lymphocytes. This strain of recombinant <it>L. lactis </it>represents a potentially useful tool to be used as a live vaccine <it>in vivo</it>.</p

The physical properties of star forming galaxies in the low redshift universe

(modified) We present a comprehensive study of the physical properties of \~10^5 galaxies with measurable star formation in the SDSS. By comparing physical information extracted from the emission lines with continuum properties, we build up a picture of the nature of star-forming galaxies at z<0.2. We take out essentially all aperture bias using resolved imaging, allowing an accurate estimate of the total SFRs in galaxies. We determine the SFR density to be 1.915^{+0.02}_{-0.01}(rand.)^{+0.14}_{-0.42} (sys.) h70 10^{-2} Msun/yr/Mpc^3 at z=0.1 (for a Kroupa IMF) and we study the distribution of star formation as a function of various physical parameters. The majority of the star formation in the low redshift universe takes place in moderately massive galaxies (10^10-10^11 Msun), typically in HSB disk galaxies. Roughly 15% of all star formation takes place in galaxies that show some sign of an active nucleus. About 20% occurs in starburst galaxies. We show that the present to past-average star formation rate, the Scalo b-parameter; is almost constant over almost three orders of magnitude in mass, declining only at M*>10^10 Msun. The volume averaged b parameter is 0.408^{+0.005}_{-0.002} (rand).^{+0.029}_{-0.090} (sys.) h70^{-1}. We use this value constrain the star formation history of the universe. In agreement with other work we find a correlation between $b$ and morphological type, as well as a tight correlation between the 4000AA break (D4000) and b. We discuss how D4000 can be used to estimate b parameters for high redshift galaxies.Comment: Accepted for MNRAS. Replaced with accepted version. A section on comparison with other methods of SFR estimation added and various updates have been made. The main results are almost unchange