Closed-loop control strategy with improved current for a flashing ratchet

We show how to switch on and off the ratchet potential of a collective Brownian motor, depending only on the position of the particles, in order to attain a current higher than or at least equal to that induced by any periodic flashing. Maximization of instant velocity turns out to be the optimal protocol for one particle but is nevertheless defeated by a periodic switching when a sufficiently large ensemble of particles is considered. The protocol presented in this article, although not the optimal one, yields approximately the same current as the optimal protocol for one particle and as the optimal periodic switching for an infinite number of them.Comment: 4 pages, 4 figure

Variability of Indoor Radon Level Accumulation: a Study in Portuguese Thermal Spas

The aim of this work was to measure the concentration of the indoor radon in 16 Portuguese thermal spas (38% of the thermal spas in Portugal) and assess its variability within each establishment as well as its contribution to the effective dose. The measurements were performed with CR-39 passive detectors placed at different workplaces within each thermal spa, for an average period of 42 days, in different seasons of the year. The indoor radon concentrations ranged from 68 to 4335 Bq/m3 with a geometric mean of 437 Bq/m3 and an arithmetic mean of 702 Bq/m3. Geological factors that can lead to such behaviour are discussed. The results showed that the EU reference level of 300 Bq/m3 (Directive 2013/59/EURATOM) was exceeded in several cases. No significant differences were observed among measurements taken during different seasons of the year, however, large differences of radon concentrations in different rooms of the same thermal establishment were noted as well as significant difference when comparing to other thermal establishments. The effective dose resulting from the inhalation of radon ranged between 2 and 32 mSv/y. In 43% of the thermal spas, the effective dose is likely to be higher than 6 mSv/y, which means that the exposure should be managed as a "planned exposure situation" according to the European Directive 2013/59/EURATOM. Also, in 19% of the cases, the annual effective dose exceeds 20 mSv/y, and in these cases, monitoring and radiological protection is required as laid down in the European Directive 2013/59/EURATOM. (c) RAD Conference Proceedings. All rights reserved

Response.

Response: Luís Lopes, MD, PhD Mário Dinis-Ribeiro, MD, PhD Carla Rolanda, MD, PhD Show more doi:10.1016/j.gie.2015.01.001 Refers To: Panagiotis Katsinelos, Georgia Lazaraki, Grigoris Chatzimavroudis, Christos Zavos, Jannis Kountouras The endoscopic morphology of major papillae influences the selected precut technique for biliary access Gastrointestinal Endoscopy, Volume 81, Issue 4, April 2015, Page 105

Optimal strategies in collective Parrondo games

We present a modification of the so-called Parrondo's paradox where one is allowed to choose in each turn the game that a large number of individuals play. It turns out that, by choosing the game which gives the highest average earnings at each step, one ends up with systematic loses, whereas a periodic or random sequence of choices yields a steadily increase of the capital. An explanation of this behavior is given by noting that the short-range maximization of the returns is "killing the goose that laid the golden eggs". A continuous model displaying similar features is analyzed using dynamic programming techniques from control theory.Comment: 4 pages, 6 figures, revised version in published for

Subcutaneous Fat Necrosis Following Induced Hypothermia

A necrose gorda do tecido celular subcutâneo do recém-nascido está associada a asfixia neonatal, aspiração de mecónio, convulsões ou hipotermia. A hipercalcemia é a complicação mais frequente, podendo em alguns casos ser grave e exigir terapêutica específica. Relata-se o caso de um recém-nascido de cesariana emergente por sofrimento fetal, tendo sido submetido a protocolo de hipotermia induzida. Foi diagnosticado com necrose gorda do recém-nascido ao 11º dia de internamento. No 23º dia identificou-se hipercalcemia, tendo iniciado terapêutica com pamidronato, com consequente diminuição gradual da calcemia. Sublinha-se a necessidade da identificação rápida de necrose gorda, possibilitando antecipar a hipercalcemia e iniciar terapêutica precoce

A CMOS signal to noise measurement circuit for infrared sectored receivers

This paper describes a circuit able to measure Signal to Noise ratios developed for Infrared applications. The Signal to Noise ratio is of major importance in IR Sectored Receivers because it provides the basis of selection or combining of signals coming from different optical sectors. This circuit estimates the ratio of the average optical signal sensed in the photo-detector and the average noise power present in the same photo-detector, with a 50dB output dynamic range.Este artigo descreve um circuito capaz de medir a Relação Sinal Ruído em sistemas de comunicação por Infravermelhos. A relação Sinal Ruído desempenha um papel fundamental em Receptores Sectorizados por IR, pois é necessária para métodos de selecção ou combinação dos sinais vindos dos diferentes sectores ópticos. O circuito aqui descrito é capaz de estimar a razão entre a potência média do sinal adquirido pelo fotodetector e a potência de ruído presente no mesmo, apresentando uma gama dinâmica de 50dB