Long-term X-ray variability of the microquasar system LS5039/RX J1826.2-1450

We report on the results of the spectral and timing analysis of a BeppoSAX observation of the microquasar system LS 5039/RX J1826.2-1450. The source was found in a low-flux state with Fx(1-10 keV)= 4.7 x 10^{-12} erg cm^{-2} s^{-1}, which represents almost one order of magnitude lower than a previous RXTE observation 2.5 years before. The 0.1--10 keV spectrum is described by an absorbed power-law continuum with photon-number spectral index Gamma=1.8+-0.2 and hydrogen column density of NH=1.0^{+0.4}_{-0.3} x 10^{22} cm^{-2}. According to the orbital parameters of the system the BeppoSAX observation covers the time of an X-ray eclipse should one occur. However, the 1.6-10 keV light curve does not show evidence for such an event, which allows us to give an upper limit to the inclination of the system. The low X-ray flux detected during this observation is interpreted as a decrease in the mass accretion rate onto the compact object due to a decrease in the mass-loss rate from the primary.

X-ray and radio observations of RX J1826.2-1450/LS 5039

RX J1826.2-1450/LS 5039 has been recently proposed to be a radio emitting high mass X-ray binary. In this paper, we present an analysis of its X-ray timing and spectroscopic properties using different instruments on board the RXTE satellite. The timing analysis indicates the absence of pulsed or periodic emission on time scales of 0.02-2000 s and 2-200 d, respectively. The source spectrum is well represented by a power-law model, plus a Gaussian component describing a strong iron line at 6.6 keV. Significant emission is seen up to 30 keV, and no exponential cut-off at high energy is required. We also study the radio properties of the system according to the GBI-NASA Monitoring Program. RX J1826.2-1450/LS 5039 continues to display moderate radio variability with a clearly non-thermal spectral index. No strong radio outbursts have been detected after several months.

New measurements of radial velocities in clusters of galaxies

Redshifts for 100 galaxies in 10 clusters of galaxies are presented based on data obtained between March 1984 and March 1985 from Calar Alto, La Palma, and ESO, and on data from Mauna Kea. Data for individual galaxies are given, and the accuracy of the velocities of the four instruments is discussed. Comparison with published data shows the present velocities to be shifted by + 4.0 km/s on average, with a standard deviation in the difference of 89.7 km/s, consistent with the rms of redshift measurements which range from 50-100 km/s.

Photometric Bgr survey of the distant clusters of galaxies CL 1613+3104 and CL 1600+4109

We present a set of photometric data concerning two distant clusters of galaxies: Cl 1613+3104 (z=0.415) and Cl 1600+4109 (z=0.540). The photometric survey extends to a field of about 4' x 3'. It was performed in 3 filters: Johnson B, and Thuan-Gunn g and r. The sample includes 679 objects in the field of Cl 1613+3104 and 334 objects in Cl 1600+4109.

Barriers to innovation and public policy in Catalonia

The present paper analyses the link between firms’ decisions to innovate and the barriers that prevent them from being innovative. The aim is twofold. First, it analyses three groups of barriers to innovation: the cost of innovation projects, lack of knowledge and market conditions. Second, it presents the main steps taken by Catalan Government to promote the creation of new firms and to reduce barriers to innovation. The data set used is based on the 2004 official innovation survey of Catalonia which was taken from the Spanish CIS-4 sample. This sample includes individual information on 2,954 Catalan firms in manufacturing industries and knowledge-intensive services (KIS). The empirical analysis reveals pronounced differences regarding a firm’s propensity to innovate and its perception of barriers. Moreover, the results show that cost and knowledge barriers seem to be the most important and that there are substantial sectoral differences in the way that firms react to barriers. The results of this paper have important implications for the design of future public policy to promote entrepreneurship and innovation together.

Estimating the probability of leaving unemployment using uncompleted spells from repeated cross-section data

We propose a new econometric estimation method for analyzing the probabilityof leaving unemployment using uncompleted spells from repeated cross-sectiondata, which can be especially useful when panel data are not available. Theproposed method-of-moments-based estimator has two important features:(1) it estimates the exit probability at the individual level and(2) it does not rely on the stationarity assumption of the inflowcomposition. We illustrate and gauge the performance of the proposedestimator using the Spanish Labor Force Survey data, and analyze the changesin distribution of unemployment between the 1980s and 1990s during a periodof labor market reform. We find that the relative probability of leavingunemployment of the short-term unemployed versus the long-term unemployedbecomes significantly higher in the 1990s.

Two component Emden sphere

The theory of a self-gravitating gas sphere is given. The gravitational field is generated by two components, each of which is an independent isothermal gas. Various quantities of interest, such as density profiles, core radii of both components, masses, free-free luminosity, surface brightness, central surface density, and overestimate of central mass density, are given for different values of both parameters which arise naturally (ratio of central densities, ratio of rms velocities). Fundamental changes appear when comparison is made with a theory in which the second component is a 'test component'. Procedures are given for the complete analysis of real astrophysical configurations such as clusters of galaxies or globular clusters.

Factors cognitius relacionats amb el compliment d'higiene de mans. Impacte d'una campanya multimodal

La higiene de mans (HM) és la mesura preventiva més important per a la prevenció de la transmissió de les infeccions en l’entorn sanitari. No obstant això, tot i la relativa simplicitat del procediment, els estudis observacionals mostren que el compliment d’HM dels professionals de la salut és inferior al 40%. La dificultat per motivar els professionals a seguir les recomanacions respecte a l’HM i, per tant, obtenir un bon compliment suggereix que es tracta d’un comportament complex. El comportament humà és el resultat de múltiples influències com poden ser les característiques biològiques, l’entorn, l’educació i la cultura. La psicologia social intenta entendre aquestes característiques i factors individuals en el comportament. Per això, s’han desenvolupat diferents teories cognitives socials per definir la naturalesa i la relació entre els múltiples factors que afecten els diferents comportaments relacionats amb la salut. Aquestes teories identifiquen tres nivells de factors relacionats amb el comportament: 1) nivell individual o intrapersonal, 2) nivell interpersonal o d’interaccions entre els individus i 3) nivell comunitari.

Barrier for the reaction X20+ + X20+ -> X402+ in alkali-metal clusters related to electron density at the bond midpoint of the supermolecule (X20+)2

Using the extended Thomas-Fermi version of density-functional theory (DFT), calculations are presented for the barrier for the reaction Na20++Na20+¿Na402+. The deviation from the simple Coulomb barrier is shown to be proportional to the electron density at the bond midpoint of the supermolecule (Na20+)2. An extension of conventional quantum-chemical studies of homonuclear diatomic molecular ions is then effected to apply to the supermolecular ions of the alkali metals. This then allows the Na results to be utilized to make semiquantitative predictions of position and height of the maximum of the fusion barrier for other alkali clusters. These predictions are confirmed by means of similar DFT calculations for the K clusters.

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Peer-reviewed

Does bounded rationality lead to individual heterogeneity? The impact of the experimentation process and of memory constraints

In this paper we explore the effect of bounded rationality on the convergence of individual behavior toward equilibrium. In the context of a Cournot game with a unique and symmetric Nash equilibrium, firms are modeled as adaptive economic agents through a genetic algorithm. Computational experiments show that (1) there is remarkable heterogeneity across identical but boundedly rational agents; (2) such individual heterogeneity is not simply a consequence of the random elements contained in the genetic algorithm; (3) the more rational agents are in terms of memory abilities and pre-play evaluation of strategies, the less heterogeneous they are in their actions. At the limit case of full rationality, the outcome converges to the standard result of uniform individual behavior.

Individual-based modelling of bacterial cultures to study the lag ohase

Els bacteris són la forma dominant de vida del planeta: poden sobreviure en medis molt adversos, i en alguns casos poden generar substàncies que quan les ingerim ens són tòxiques. La seva presència en els aliments fa que la microbiologia predictiva sigui un camp imprescindible en la microbiologia dels aliments per garantir la seguretat alimentària. Un cultiu bacterià pot passar per quatre fases de creixement: latència, exponencial, estacionària i de mort. En aquest treball s’ha avançat en la comprensió dels fenòmens intrínsecs a la fase de latència, que és de gran interès en l’àmbit de la microbiologia predictiva. Aquest estudi, realitzat al llarg de quatre anys, s’ha abordat des de la metodologia Individual-based Modelling (IbM) amb el simulador INDISIM (INDividual DIScrete SIMulation), que ha estat millorat per poder fer-ho. INDISIM ha permès estudiar dues causes de la fase de latència de forma separada, i abordar l’estudi del comportament del cultiu des d’una perspectiva mesoscòpica. S’ha vist que la fase de latència ha de ser estudiada com un procés dinàmic, i no definida per un paràmetre. L’estudi de l’evolució de variables com la distribució de propietats individuals entre la població (per exemple, la distribució de masses) o la velocitat de creixement, han permès distingir dues etapes en la fase de latència, inicial i de transició, i aprofundir en la comprensió del que passa a nivell cel•lular. S’han observat experimentalment amb citometria de flux diversos resultats previstos per les simulacions. La coincidència entre simulacions i experiments no és trivial ni casual: el sistema estudiat és un sistema complex, i per tant la coincidència del comportament al llarg del temps de diversos paràmetres interrelacionats és un aval a la metodologia emprada en les simulacions. Es pot afirmar, doncs, que s’ha verificat experimentalment la bondat de la metodologia INDISIM.

Individual Aspirations and Satisfaction:Quantifying the Importance of Homeownership

Residential satisfaction is often used as a barometer to assess the performance of public policy and programmes designed to raise individuals' well-being. However, the fact that responses elicited from residents might be biased by subjective, non-observable factors casts doubt on whether these responses can be taken as trustable indicators of the individuals' housing situation. Emotional factors such as aspirations or expectations might affect individuals' cognitions of their true residential situation. To disentangle this puzzle, we investigated whether identical residential attributes can be perceived differently depending on tenure status. Our results indicate that tenure status is crucial not only in determining the level of housing satisfaction, but also regarding how dwellers perceive their housing characteristics. Keywords: Housing satisfaction, subjective well-being, homeownership. JEL classification: D1, R2.

Entorno de desarrollo para clusters

El presente trabajo expone los entornos de desarrollo de aplicaciones paralelas en sistemas distribuidos. Se ha dedicado especial atención a los entornos gráficos, como plataforma de acceso al cluster. Dada la cantidad de alternativas a seleccionar en este tipo de entornos, como puede ser la parametrización de las aplicaciones, especificación de la arquitectura a utilizar de los nodos, caracterización de la carga, políticas de planificación, etc, hace que este trabajo pueda servir de punto inicial de partida a usuarios que deseen iniciarse en este tipo de entornos.