Spectral Efficiency of Spectrum Pooling Systems

In this contribution, we investigate the idea of using cognitive radio to reuse locally unused spectrum to increase the total system capacity. We consider a multiband/wideband system in which the primary and cognitive users wish to communicate to different receivers, subject to mutual interference and assume that each user knows only his channel and the unused spectrum through adequate sensing. The basic idea under the proposed scheme is based on the notion of spectrum pooling. The idea is quite simple: a cognitive radio will listen to the channel and, if sensed idle, will transmit during the voids. It turns out that, although its simplicity, the proposed scheme showed very interesting features with respect to the spectral efficiency and the maximum number of possible pairwise cognitive communications. We impose the constraint that users successively transmit over available bands through selfish water filling. For the first time, our study has quantified the asymptotic (with respect to the band) achievable gain of using spectrum pooling in terms of spectral efficiency compared to classical radio systems. We then derive the total spectral efficiency as well as the maximum number of possible pairwise communications of such a spectrum pooling system

The chronic disease management model for depression in primary care

Objective: This paper reviews the development of chronic disease management approaches, and explores the suitability and effectiveness of these ways of organizing care for depression. Method: The relevant literature including systematic reviews, service evaluations, and clinical guidelines have been appraised to provide a review of the development of health care management approaches for long term conditions and their application to depression. Results: The chronic care model originally developed in the USA has been successfully adopted in other countries, and has been applied to the management of depression in primary care. This multicomponent approach involves enhanced collaboration between primary and secondary care clinicians often by means of case managers, support for improved patient self-management, and systematic follow-up. These approaches to health care organization significantly enhance the quality of care for depression: reviews consistently show improvements in depression severity, treatment adherence, and patient satisfaction. Conclusions: There appears value in the continued use of chronic disease management approaches for depression in primary care. For depression alone and depression combined with medical conditions there is consistent evidence for beneficial effects on depression outcomes. However there remain challenges in tailoring these approaches to influence physical outcomes in patients with medical comorbidity

Disorder-induced superconductivity in ropes of carbon nanotubes

We study the interplay between disorder and superconductivity in a rope of metallic carbon nanotubes. Based on the time dependent Ginzburg Landau theory, we derive the superconducting transition temperature T$_c$ taking into account the critical superconducting fluctuations which are expected to be substantially strong in such low dimensional systems. Our results indicate that, contrary to what is expected, T$_c$ increases by increasing the amount of disorder. We argue that this behavior is due to the dynamics of the tubes which reduces the drastic effect of the local disorder on superconductivity by enhancing the intertube Josephson tunneling. We also found that T$_c$ is enhanced as the effective dimensionality of the rope increases by increasing the number N of the tubes forming the rope. However, T$_c$ tends to saturate for large values of N, expressing the establishment of a bulk three dimensional (3D) superconducting order.Comment: 9 pages, 4 figur

Detection of vibronic bands of C3_3 in a translucent cloud towards HD 169454

We report the detection of eight vibronic bands of C$_3$, seven of which have been hitherto unobserved in astrophysical objects, in the translucent cloud towards HD~169454. Four of these bands are also found towards two additional objects: HD~73882 and HD~154368. Very high signal-to-noise ratio ($\sim$1000 and higher) and high resolving power ($R=80,000$) UVES-VLT spectra (Paranal, Chile) allow for detecting novel spectral features of C$_3$, even revealing weak perturbed features in the strongest bands. The work presented here provides the most complete spectroscopic survey of the so far largest carbon chain detected in translucent interstellar clouds. High-quality laboratory spectra of C$_3$ are measured using cavity ring-down absorption spectroscopy in a supersonically expanding hydrocarbon plasma, to support the analysis of the identified bands towards HD~169454. A column density of N(C$_3$) = $(6.6 \pm 0.2) \times 10^{12}$ cm$^{-2}$ is inferred and the excitation of the molecule exhibits two temperature components; $T_{exc}= 22 \pm 1$ K for the low-$J$ states and $T_{exc}= 187 \pm 25$ K for the high-$J$ tail. The rotational excitation of C$_3$ is reasonably well explained by models involving a mechanism including inelastic collisions, formation and destruction of the molecule, and radiative pumping in the far-infrared. These models yield gas kinetic temperatures comparable to those found for $T_{exc}$. The assignment of spectral features in the UV-blue range 3793-4054 \AA\ may be of relevance for future studies aiming at unravelling spectra to identify interstellar molecules associated with the diffuse interstellar bands (DIBs).Comment: 15 pages, 13 figures, submitted to MNRA

Élimination du phénol par deux plantes aquatiques : Juncus fontanesii (Gay) et Lemna minor L.

L'élimination du phénol et de ses dérivés, substances organiques toxiques, fait appel à différents processus physico-chimiques ou biologiques. Certaines plantes aquatiques ont la capacité de déplacer des produits chimiques en les métabolisant, en les évaporant ou en les dégradant. Il faut, toutefois, rester à des concentrations inférieures aux seuils de toxicité des espèces employées.Dans le présent travail, deux plantes aquatiques: le Jonc de Desfontaines (Juncus fontanesii) de la famille des Joncacées et la Lentille d'eau (Lemna minor) de la famille des Lemnacées, ont été testées pour éliminer le phénol. Le travail a été effectué sans addition d'éléments nutritifs ni acclimatation prélable, pour des concentrations variant de 8 à 48 mg/l et pour deux densités surfaciques de la biomasse végétale fraîche : 2,8 et 5,6 kg/m2.Les deux espèces se sont révélées aptes à éliminer totalement le phénol avec des cinétiques différentes. Un phénomène de relargage, important dans le cas de l'emploi de J. fontanesii, a pu être observé. Une comparaison de ce type d'élimination à celui dû aux micro-organismes nous a permis, par utilisation des boues activées, d'aboutir à l'ordre de performance suivant : J. fontanesii > L. minor (faibles densités) > micro-organismes avec barbottage d'air > micro-organismes sous des conditions atmosphériques > témoins (sans plantes) > L. minor (fortes densités) > micro-organismes sous des conditions anaérobies.Phenols are considered as toxic organic compounds. They can be treated by different physico-chemical or biological processes. These products can be oxidized by chemicals such as H2O2, TiO2, O3, etc. The performance of the process depends on pH, temperature and phenol/oxidant ratio. Otherwise, they can be transformed biologically by enzymes, fungi, yeast or plants. Considerable work has already been done with regard to uptake of phenol by aquatic plants.In our study two aquatic plants: Juncus fontanesii, a rooted species from Joncaceae family and Lemna minor, floating species from Lemnaceae family, have been selected to study their ability to remove phenol from static phenolic solutions. The initial concentration of phenol varied from 8 to 48 mg/l. The density of biomass (wet weight) ranged from 2.8 to 5.6 kg/m2. Experiences were carried out without acclimation and without addition of nutritive elements. Controls (without plants) were prepared with the same concentrations. Under these conditions, the results of quantitative analyses show that J. fontanesii is able to remove phenol more rapidly than L. minor and can release a fraction of it to the medium particularly in the first ten hours of contact.It has been observed that phenol uptake is sensitive to the density of biomass and the initial concentration. In order to examine more closely the effect of these variables, we have carried out experiments where the initial concentration was kept constant (8 mg/l) and biomass density varied. When the density of biomass increases, the kinetic uptake of phenol by J. fontanesii increases too; however, it decreases in the presence of L. minor. In fact, at high densities, L. minor covers fully the surface of the water and causes a screen effect, such that diffusion of atmospheric oxygen into the medium is limited. In addition, L. minor has a short root system, so the amount of oxygen that enters the solution is negligible. Elimination of phenol by L. minor is rapid when the density of biomass ranges from 0.7 to 1.4 kg/m2. For both plants, we have noticed the existence of a maximum time limit of degradation and an optimal density beyond which there is no improvement in elimination.Phenol can be degraded by micro-organisms. In order to elucidate this pathway, an investigation was undertaken using activated sludges in the following situations: under atmospheric conditions, under anaerobic conditions and with bubbling air intermittently.The comparison of obtained results shows that the rate and kinetics of the elimination decrease in the following order: J. fontanesii > L. minor (low densities) > micro-organisms with air bubbling > micro-organisms under atmospheric conditions > controls (without plants) > L. minor (high densities) > micro-organisms under anaerobic conditions

Feno de capim-de-Rhodes ( Chloris gayana Kunth) e o capim elefante (Pennisetum purpureum Schum) var. Napier verde picado na alimentação de equideos em crescimento.

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Critical properties of an aperiodic model for interacting polymers

We investigate the effects of aperiodic interactions on the critical behavior of an interacting two-polymer model on hierarchical lattices (equivalent to the Migadal-Kadanoff approximation for the model on Bravais lattices), via renormalization-group and tranfer-matrix calculations. The exact renormalization-group recursion relations always present a symmetric fixed point, associated with the critical behavior of the underlying uniform model. If the aperiodic interactions, defined by s ubstitution rules, lead to relevant geometric fluctuations, this fixed point becomes fully unstable, giving rise to novel attractors of different nature. We present an explicit example in which this new attractor is a two-cycle, with critical indices different from the uniform model. In case of the four-letter Rudin-Shapiro substitution rule, we find a surprising closed curve whose points are attractors of period two, associated with a marginal operator. Nevertheless, a scaling analysis indicates that this attractor may lead to a new critical universality class. In order to provide an independent confirmation of the scaling results, we turn to a direct thermodynamic calculation of the specific-heat exponent. The thermodynamic free energy is obtained from a transfer matrix formalism, which had been previously introduced for spin systems, and is now extended to the two-polymer model with aperiodic interactions.Comment: 19 pages, 6 eps figures, to appear in J. Phys A: Math. Ge

Impact assessment of interregional government transfers in Brazil: an input-output approach

Redistributive policies carried out by the central government through interregional government transfers is a relevant feature of the Brazilian federal fiscal system. Regional shares of the central government revenues in the poorer regions have been recurrently smaller than the shares of central government expenditures in those regions. Appeal to core-periphery outcomes could be made, as São Paulo, the wealthiest state in the country, concentrated, in 2005, over 40% of total Federal tax revenue, receiving less than 35% of Federal expenditures. These figures suggest a redistribution of public funds from the spatial economic core of the economy to the peripheral areas. This paper investigates the role interregional transfers play in the redistribution of activities in the country, using an interregional input-output approach. Counterfactual simulations allow us to estimate some costs and benefits, for the core and periphery respectively, from such fiscal mechanisms.Interregional government transfers, input-output analysis, impact analysis, Brazilian economy

Cores and Peripheries: Spatial Analysis of HCV Voucher Distribution in the San Francisco

The Housing Choice Voucher (HCV) program is touted as a mechanism for providing low income households with mobility, and through that mobility, access to higher opportunity neighborhoods (HUD, 2006; McClure, 2014; Winnick, 1995). However, the success of the voucher program requires an existing supply of available housing units with landlords who are willing to participate in the program. Tight housing markets, where households are most in need of rent subsidies, are typically also the most difficult markets to find available units and willing landlords, resulting in limited choices for HCV households (Basolo and Nguyen, 2005; Khadduri, 2005). In these conditions, we can expect to find that voucher holders behave like other housing seekers and search out locations where they can maximize their housing dollars in terms of both unit characteristics and locational amenities