Push & Pull: autonomous deployment of mobile sensors for a complete coverage

Mobile sensor networks are important for several strategic applications devoted to monitoring critical areas. In such hostile scenarios, sensors cannot be deployed manually and are either sent from a safe location or dropped from an aircraft. Mobile devices permit a dynamic deployment reconfiguration that improves the coverage in terms of completeness and uniformity. In this paper we propose a distributed algorithm for the autonomous deployment of mobile sensors called Push&Pull. According to our proposal, movement decisions are made by each sensor on the basis of locally available information and do not require any prior knowledge of the operating conditions or any manual tuning of key parameters. We formally prove that, when a sufficient number of sensors are available, our approach guarantees a complete and uniform coverage. Furthermore, we demonstrate that the algorithm execution always terminates preventing movement oscillations. Numerous simulations show that our algorithm reaches a complete coverage within reasonable time with moderate energy consumption, even when the target area has irregular shapes. Performance comparisons between Push&Pull and one of the most acknowledged algorithms show how the former one can efficiently reach a more uniform and complete coverage under a wide range of working scenarios.Comment: Technical Report. This paper has been published on Wireless Networks, Springer. Animations and the complete code of the proposed algorithm are available for download at the address: http://www.dsi.uniroma1.it/~novella/mobile_sensors

Pilot Tone Actuated Antenna Array Pattern Reconfiguration

A new strategy for remote reconfiguration of an antenna array far field radiation pattern is described. The scheme uses a pilot tone co-transmitted with a carrier signal from a location distant from that of a receive antenna array whose far field pattern is to be reconfigured. By mixing the co-transmitted signals locally at each antenna element in the array an IF signal is formed which defines an equivalent array spacing that can be made variable by tuning the frequency of the pilot tone with respect to the RF carrier. This makes the antenna array factor hence far field spatial characteristic reconfigurable on receive. For a 10 x 1 microstrip patch element array we show that the receive pattern can be made to vary from 35 to 10 degrees half power beam width as the difference frequency between the pilot and the carrier at 2.45 GHz varies between 10 MHz and 500 MHz carrier.</p

Dystonia: sparse synapses for D2 receptors in striatum of a DYT1 knock-out mouse model

Dystonia pathophysiology has been partly linked to downregulation and dysfunction of dopamine D2 receptors in striatum. We aimed to investigate the possible morpho-structural correlates of D2 receptor downregulation in the striatum of a DYT1 Tor1a mouse model. Adult control Tor1a+/+ and mutant Tor1a+/− mice were used. The brains were perfused and free-floating sections of basal ganglia were incubated with polyclonal anti-D2 antibody, followed by secondary immune-fluorescent antibody. Confocal microscopy was used to detect immune-fluorescent signals. The same primary antibody was used to evaluate D2 receptor expression by western blot. The D2 receptor immune-fluorescence appeared circumscribed in small disks (~0.3–0.5 μm diameter), likely representing D2 synapse aggregates, densely distributed in the striatum of Tor1a+/+ mice. In the Tor1a+/− mice the D2 aggregates were significantly smaller (μm2 2.4 ± SE 0.16, compared to μm2 6.73 ± SE 3.41 in Tor1a+/+) and sparse, with ~30% less number per microscopic field, value correspondent to the amount of reduced D2 expression in western blotting analysis. In DYT1 mutant mice the sparse and small D2 synapses in the striatum may be insufficient to “gate” the amount of presynaptic dopamine release diffusing in peri-synaptic space, and this consequently may result in a timing and spatially larger nonselective sphere of influence of dopamine action

A microscopic 2D lattice model of dimer granular compaction with friction

We study by Monte Carlo simulation the compaction dynamics of hard dimers in 2D under the action of gravity, subjected to vertical and horizontal shaking, considering also the case in which a friction force acts for horizontal displacements of the dimers. These forces are modeled by introducing effective probabilities for all kinds of moves of the particles. We analyze the dynamics for different values of the time $\tau$ during which the shaking is applied to the system and for different intensities of the forces. It turns out that the density evolution in time follows a stretched exponential behavior if $\tau$ is not very large, while a power law tail develops for larger values of $\tau$. Moreover, in the absence of friction, a critical value $\tau^*$ exists which signals the crossover between two different regimes: for $\tau < \tau^*$ the asymptotic density scales with a power law of $\tau$, while for $\tau > \tau^*$ it reaches logarithmically a maximal saturation value. Such behavior smears out when a finite friction force is present. In this situation the dynamics is slower and lower asymptotic densities are attained. In particular, for significant friction forces, the final density decreases linearly with the friction coefficient. We also compare the frictionless single tap dynamics to the sequential tapping dynamics, observing in the latter case an inverse logarithmic behavior of the density evolution, as found in the experiments.Comment: 10 pages, 15 figures, to be published in Phys. Rev.

Aborto inseguro: determinantes sociais e iniquidades em saúde em uma população vulnerável, São Paulo, Brasil

This cross-sectional population-based study in a peripheral low-income community in São Paulo, Brazil, aimed to estimate the prevalence of unsafe abortion and identify the socio-demographic characteristics associated with it and its morbidity. The article discusses the study's results, based on univariate and multiple multinomial logistic regression analyses. The final regression models included: age at first intercourse 2 sex partners in the previous year (OR = 3.63); more live born children than the woman's self-reported ideal number (OR = 3.09); acceptance of the abortion due to insufficient economic conditions (OR = 4.07); black ethnicity/color (OR = 2.67); and low schooling (OR = 2.46), all with p 2 (OR = 3,63); número de filhos nascidos vivos > ideal (OR = 3,09); aceitação do aborto por falta de condições econômicas (OR = 4,07); etnia negra/cor preta (OR = 2,67); e escolaridade baixa (OR = 2,46), todos com p < 0,05. Foi utilizada na discussão uma abordagem voltada aos determinantes sociais da saúde, segundo conceito e modelo adotados pela WHO, e às iniquidades em saúde por esses geradas na ocorrência do aborto inseguro. Verificou-se que o aborto inseguro e características sociodemográficas são influenciados pelos determinantes sociais da saúde descritos, gerando nessa população iniquidades em saúde de proporções diversas.Universidade Federal de São Paulo (UNIFESP)UNIFESPSciEL

Some homogenization and corrector results for nonlinear monotone operators

This paper deals with the limit behaviour of the solutions of quasi-linear equations of the form \ \ds -\limfunc{div}\left(a\left(x, x/{\varepsilon _h},Du_h\right)\right)=f_h on $\Omega$ with Dirichlet boundary conditions. The sequence $(\varepsilon _h)$ tends to $0$ and the map $a(x,y,\xi )$ is periodic in $y$, monotone in $\xi$ and satisfies suitable continuity conditions. It is proved that $u_h\rightarrow u$ weakly in $H_0^{1,2}(\Omega )$, where $u$ is the solution of a homogenized problem \ -\limfunc{div}(b(x,Du))=f on $\Omega$. We also prove some corrector results, i.e. we find $(P_h)$ such that $Du_h-P_h(Du)\rightarrow 0$ in $L^2(\Omega ,R^n)$

Prevalência e características sociodemográficas de mulheres com aborto provocado em uma amostra da população da cidade de São Paulo, Brasil

Objectives:This study aims at estimating the prevalence of women with induced abortion among women of childbearing age (15-49 years) who had any previous pregnancy, in the city of São Paulo, Brazil, in the last quarter of 2008, and identifying the sociodemographic characteristics (SC) associated with it. Methods:A cross-sectional survey was carried out. The dependent variable was dichotomized as: no abortion and induced abortion. The independent variables were: age, paid work/activity, familial monthly income, schooling, marital status, contraceptive use and number of live births. Statistical analysis was performed using log-binomial regression models with approximation of Poisson to estimate the prevalance ratios (PR). Results:Of all women with any previous pregnancy (n = 683), 4.5% (n = 31) reported induced abortion. The final multivariate model showed that having now between 40 and 44 years (PR = 2.76, p = 0.0043), being single (PR = 2.79, p = 0.0159), having 5 or more live births (PR = 3.97, p = 0.0013), current oral contraception or IUD use (PR = 2.70, p = 0.454) and using a non effective (or of low efficacy) contraceptive method (PR = 4.18, p = 0.0009) were sociodemographic characteristics associated with induced abortion in this population. Conclusions:Induced abortion seems to be used to limit fertility, more precisely after having reached the desired number of children. The inadequate use or non-use of effective contraceptive methods, and / or the use of contraceptivenon effective, exposed also the women to the risk of unintended pregnancies and, therefore, induced abortions. In addition, when faced with a pregnancy, single women were more likely to have an abortion than married women.Objetivos:O presente estudo busca estimar a prevalência de mulheres com aborto provocado dentre as mulheres em idade fértil (15 a 49 anos de idade) que apresentaram alguma gestação prévia, residentes na cidade de São Paulo, Brasil, no último trimestre de 2008, bem como identificar essa ocorrência em função de algumas características sociodemográficas (CSD).Métodos:Trata-se de um estudo transversal. A variável dependente aborto foi dicotomizada em: aborto provocado (AP) e nenhum aborto (NA). As variáveis independentes utilizadas foram: idade, atividade remunerada, renda mensal familiar, escolaridade, estado conjugal, uso de método(s) contraceptivo(s) e número de filhos nascidos vivos. A análise estatística foi realizada por meio de modelos de regressão log-binomial com aproximação de Poisson para avaliar as razões de prevalência (RP).Resultados:Dentre o total de mulheres com alguma gestação prévia (n = 683), 4,5% (n = 31) declararam algum AP. O modelo log-binomial final mostrou que idade atual entre 40 e 44 anos de idade (RP = 2,76; p = 0,0043), estado conjugal solteira (RP = 2,79; p = 0,0159), número de filhos nascidos vivos igual ou maior que 5 (RP = 3,97; p = 0,0013, uso de contraceptivo não eficaz ou de baixa eficácia (RP = 4,18; p = 0,0009) e uso atual de contraceptivo oral ou dispositivo intrauterino (RP = 2,70; p = 0,454) foram as características que se apresentaram mais fortemente associadas à ocorrência de AP entre as mulheres dessa população.Conclusões:O aborto provocado é utilizado para limitar a fecundidade, mais precisamente após atingir-se o número desejado de filhos. O uso inadequado, ou o não-uso, de contraceptivos eficazes e/ou a utilização de contraceptivos não eficazes, ou de baixa eficácia, também promovem a resolução pelo aborto, assim como o fato de as mulheres solteiras enfrentarem uma gestação sozinhas.Universidade Federal de São Paulo (UNIFESP) Department of Preventive MedicineCentro Universitário de GuaxupéUNIFESP, Department of Preventive MedicineSciEL

Laser Guide Stars for Extremely Large Telescopes: Efficient Shack-Hartmann Wavefront Sensor Design using Weighted center-of-gravity algorithm

Over the last few years increasing consideration has been given to the study of Laser Guide Stars (LGS) for the measurement of the disturbance introduced by the atmosphere in optical and near-infrared astronomical observations from the ground. A possible method for the generation of a LGS is the excitation of the Sodium layer in the upper atmosphere at approximately 90 km of altitude. Since the Sodium layer is approximately 10 km thick, the artificial reference source looks elongated, especially when observed from the edge of a large aperture. The spot elongation strongly limits the performance of the most common wavefront sensors. The centroiding accuracy in a Shack-Hartmann wavefront sensor, for instance, decreases proportionally to the elongation (in a photon noise dominated regime). To compensate for this effect a straightforward solution is to increase the laser power, i.e. to increase the number of detected photons per subaperture. The scope of the work presented in this paper is twofold: an analysis of the performance of the Weighted Center of Gravity algorithm for centroiding with elongated spots and the determination of the required number of photons to achieve a certain average wavefront error over the telescope aperture.Comment: 10 pages, 14 figure

Shape of the Galactic Orbits in the CNOC1 Clusters

We present an analysis of the orbital properties in 9 intermediate-redshifts cluster of the CNOC1 survey and we compare them to a control sample of 12 nearby clusters. Similar to the nearby elliptical galaxies, the bulge-dominated galaxies in clusters at redshifts ~0.1-0.4 present orbits that are more eccentric than those for disk-dominated galaxies. However, the orbital segregation is less significant than that found for elliptical and spiral galaxies in nearby cluster. When galaxies are separated by colors - red galaxies with colors in the rest frame (U-V)_o > 1.4, and blue galaxies with (U-V)_o =< 1.4 - the strongest orbital segregation is found. Therefore, the segregation we found seems to modify more efficiently the star formation activity than the internal shape of the galaxies. When we compare the orbits of early-type galaxies at intermediate-redshift with those for z=0, they seem to develop significant changes getting much more eccentric. A different behavior is observed in the late-type galaxies, which present no-significant evolution in their orbit shapes.Comment: Accepted for publication in ApJ, April 2000. Latex with aaspp4.sty, 20 pages, 4 tables, 6 eps figure