Can Punctured Rate-1/2 Turbo Codes Achieve a Lower Error Floor than their Rate-1/3 Parent Codes?

In this paper we concentrate on rate-1/3 systematic parallel concatenated convolutional codes and their rate-1/2 punctured child codes. Assuming maximum-likelihood decoding over an additive white Gaussian channel, we demonstrate that a rate-1/2 non-systematic child code can exhibit a lower error floor than that of its rate-1/3 parent code, if a particular condition is met. However, assuming iterative decoding, convergence of the non-systematic code towards low bit-error rates is problematic. To alleviate this problem, we propose rate-1/2 partially-systematic codes that can still achieve a lower error floor than that of their rate-1/3 parent codes. Results obtained from extrinsic information transfer charts and simulations support our conclusion.Comment: 5 pages, 7 figures, Proceedings of the 2006 IEEE Information Theory Workshop, Chengdu, China, October 22-26, 200

The runaway black hole GRO J1655-40

We have used the Hubble Space Telescope to measure the motion in the sky and compute the galactocentric orbit of the black hole X-ray binary GRO J1655-40. The system moves with a runaway space velocity of $112\pm 18$ km s$^{-1}$ in a highly eccentric ($e = 0.34\pm 0.05$) orbit. The black hole was formed in the disk at a distance greater than 3 kpc from the Galactic centre and must have been shot to such an eccentric orbit by the explosion of the progenitor star. The runaway linear momentum and kinetic energy of this black hole binary are comparable to those of solitary neutron stars and millisecond pulsars. GRO J1655-40 is the first black hole for which there is evidence for a runaway motion imparted by a natal kick in a supernova explosion.Comment: Published in Astronomy and Astrophysics. 5 pages, 2 color figures. Color figure and animation can be found at http://www.iafe.uba.ar/astronomia/mirabel/mirabel.html or ftp://ftp.cea.fr/incoming/y2k01/mirabe

Milage aprender+ uma app para aprender matemática usando smartphones e tablets

O baixo desempenho dos estudantes na aprendizagem da matemática constitui problema que em alguns países se tem vindo a acentuar nos últimos anos. De acordo com um estudo realizado pelo Departamento de Educação dos EUA, em 2010, as aulas em regime de blended-learning, ou b-learning, apresentam melhores resultados do que as tradicionais aulas presenciais. Por outro lado, observa-se um número crescente de estudantes que usa smartphones e tablets nas escolas, cuja popularidade pode ser aproveitada para estimular a sua utilização em atividades educacionais para melhorar a aprendizagem. Nesta comunicação apresenta-se uma nova aplicação para dispositivos móveis, smartphones e tablets, app MILAGE, através da qual o aluno pode aceder a conteúdos pedagógicos, dentro e fora da sala de aula. De modo a estimular e apoiar a realização das várias atividades propostas, a interface incorpora características de gamificação e recursos multimédia.info:eu-repo/semantics/publishedVersio

Robustness of reserve selection procedures under temporal species turnover

Complementarity-based algorithms for the selection of reserve networks emphasize the need to represent biodiversity features efficiently, but this may not be sufficient to maintain those features in the long term. Here, we use data from the Common Birds Census in Britain as an exemplar data set to determine guidelines for the selection of reserve networks which are more robust to temporal turnover in features. The extinction patterns found over the 1981-1991 interval suggest that two such guidelines are to represent species in the best sites where they occur (higher local abundance) and to give priority to the rarer species. We tested five reserve selection strategies, one which finds the minimum representation set and others which incorporate the first or both guidelines proposed. Strategies were tested in terms of their efficiency (inversely related to the total area selected) and effectiveness (inversely related to the percentage of species lost) using data on eight pairs of ten-year intervals. The minimum set strategy was always the most efficient, but suffered higher species loss than the others, suggesting that there is a trade-off between efficiency and effectiveness. A desirable compromise can be achieved by embedding the concerns about the long-term maintenance of the biodiversity features of interest in the complementarity-based algorithms

Development of low-cost culture media for effective biosurfactant production

In this work, biosurfactant production by Pseudomonas aeruginosa and Bacillus subtillis strains was optimized using low-cost substrates. The highest biosurfactant production (3.2 g/L) by the P. aeruginosa strain was obtained using a culture medium containing corn steep liquor (CSL) (10% (v/v)) and molasses (10% (w/v)), whereas the best biosurfactant production by the B. subtillis isolate (1.3 g/L) was obtained using a culture medium consisting of 10% (v/v) of CSL. Subsequently, for the B. subtillis strain, the effect of different metals (iron, manganese and magnesium) on biosurfactant production was evaluated. When the culture medium CSL 10% was supplemented with the optimum concentration of those metals simultaneously, the biosurfactant production was increased up to 4.8 g/L. The biosurfactant produced by the P. aeruginosa strain was characterized as a mixture of eight different rhamnolipid congeners, being the most abundant the mono-rhamnolipid Rha-C10-C10, and the biosurfactant produced by the B. subtillis isolate consisted of a mixture of C13-, C14- and C15-surfactin. Both biosurfactants exhibited a good performance in oil recovery assays when compared with chemical surfactants, suggesting their potential use as an alternative to traditional chemical surfactants in enhanced oil recovery or bioremediation

Improved biosurfactant production by a Pseudomonas aeruginosa strain using agro-industrial wastes

Microbial surfactants are amphipathic molecules produced by a variety of microorganisms that exhibit pronounced surface and emulsifying activities. Biosurfactants can replace synthetic surfactants in environmental and industrial applications, such as bioremediation and microbial enhanced oil recovery. Furthermore, some biosurfactants have been reported as suitable alternatives to synthetic medicines and antimicrobial agents and may be used as effective therapeutic agents, due to their antibacterial, antifungal, antiviral and anti-adhesive activities. The main advantages of biosurfactants when compared with synthetic surfactants include their diversity, specificity, environmentally friendly nature, non-toxicity and high biodegradability, effectiveness at extreme temperatures or pH values, as well as their suitability for scale-up production. Many of the potential applications that have been considered for biosurfactants depend on whether they can be produced economically at large-scale. Several efforts have been conducted to reduce production costs, including the use of agro-industrial wastes as substrates, optimization of medium and culture conditions and efficient recovery processes. In this work, biosurfactant production by a Pseudomonas aeruginosa strain isolated from a crude oil sample was optimized using agro-industrial wastes. A culture medium containing corn step liquor (10% v/v) and molasses (10% w/v) led to the production of 5 g biosurfactant/l, which is about ten times the amount of biosurfactant produced when using LB medium. The crude biosurfactant reduced the surface tension of water to 31 mN/m and exhibited high emulsifying activity (60%), with a critical micelle concentration of 200 mg/l. Moreover, it showed antimicrobial activity against a broad range of Gram-positive and Gram-negative bacteria, as well as a high efficiency in removing oil from contaminated sand, when compared with chemical surfactants. The results obtained suggest the possibility of using this biosurfactant as an alternative to traditional chemical surfactants