VLT and NTT Observations of Two EIS Cluster Candidates. Detection of the Early-Type Galaxies Sequence at z~1

Optical data from the ESO VLT-UT1 Science Verification observations are combined with near-infrared data from SOFI at the NTT to obtain optical-infrared color-magnitude diagrams for the objects in the fields of two EIS cluster candidates. In both cases, evidence is found for a well-defined sequence of red galaxies that appear to be significantly more clustered than the background population. These results suggest that the two systems are real physical associations. The (R-Ks), (I-Ks) and (J-Ks) colors of the red sequences are used, in conjunction with similar data for spectroscopically confirmed clusters, to obtain redshift estimates of z ~ 0.9 and z ~ 1.0 for these two systems. These results make these EIS cluster candidates prime targets for follow-up spectroscopic observations to confirm their reality and to measure more accurately their redshift.Comment: 6 pages, 5 figures, to appear in Astronomy & Astrophysics (Special Letters Edition on "First Science with the VLT"

Confirming EIS Clusters. Optical and Infrared Imaging

Clusters of galaxies are important targets in observationally cosmology, as they can be used both to study the evolution of the galaxies themselves and to constrain cosmological parameters. Here we report on the first results of a major effort to build up a sample of distant galaxy clusters to form the basis for further studies within those fields. We search for simultaneous overdensities in color and space to obtain supporting evidence for the reality of the clusters. We find a confirmation rate for EIS clusters of 66%, suggesting that a total of about 80 clusters with z>=0.6 are within reach using the EIS cluster candidates.Comment: 4 pages, 2 figures, to appear in the proceedings of the IGRAP International Conference 1999 on 'Clustering at high Redshift

Persistência de dois inseticidas ao parasitoide de moscas-dasfrutas, Diachasmimorpha longicaudata (Hymenoptera: Braconidae).

O presente trabalho objetivou avaliar a persistência de dois inseticidas utilizados para o controle de Ceratitis capitata, espinosade e etofenproxi, sobre adultos de Diachasmimorpha longicaudataSICONBIOL 2013

Fractional quantization of ballistic conductance in 1D hole systems

We analyze the fractional quantization of the ballistic conductance associated with the light and heavy holes bands in Si, Ge and GaAs systems. It is shown that the formation of the localized hole state in the region of the quantum point contact connecting two quasi-1D hole leads modifies drastically the conductance pattern. Exchange interaction between localized and propagating holes results in the fractional quantization of the ballistic conductance different from those in electronic systems. The value of the conductance at the additional plateaux depends on the offset between the bands of the light and heavy holes, \Delta, and the sign of the exchange interaction constant. For \Delta=0 and ferromagnetic exchange interaction, we observe additional plateaux around the values 7e^{2}/4h, 3e^{2}/h and 15e^{2}/4h, while antiferromagnetic interaction plateaux are formed around e^{2}/4h, e^{2}/h and 9e^{2}/4h. For large \Delta, the single plateau is formed at e^2/h.Comment: 4 pages, 3 figure

ESO Imaging Survey VII. Distant Cluster Candidates over 12 square degrees

In this paper the list of candidate clusters identified from the I-band data of the ESO Imaging Survey (EIS) is completed using the images obtained over a total area of about 12 square degrees. Together with the data reported earlier the total I-band coverage of EIS is 17 square degrees, which has yielded a sample of 252 cluster candidates in the redshift range 0.2 \lsim z \lsim 1.3. This is the largest optically-selected sample currently available in the Southern Hemisphere. It is also well distributed in the sky thus providing targets for a variety of VLT programs nearly year round.Comment: 5 pages, 3 figures, submitted to Astronomy & Astrophysic

Hierarchical Spatial Organization of Geographical Networks

In this work we propose the use of a hirarchical extension of the polygonality index as a means to characterize and model geographical networks: each node is associated with the spatial position of the nodes, while the edges of the network are defined by progressive connectivity adjacencies. Through the analysis of such networks, while relating its topological and geometrical properties, it is possible to obtain important indications about the development dynamics of the networks under analysis. The potential of the methodology is illustrated with respect to synthetic geographical networks.Comment: 3 page, 3 figures. A wokring manuscript: suggestions welcome

What are the Best Hierarchical Descriptors for Complex Networks?

This work reviews several hierarchical measurements of the topology of complex networks and then applies feature selection concepts and methods in order to quantify the relative importance of each measurement with respect to the discrimination between four representative theoretical network models, namely Erd\"{o}s-R\'enyi, Barab\'asi-Albert, Watts-Strogatz as well as a geographical type of network. The obtained results confirmed that the four models can be well-separated by using a combination of measurements. In addition, the relative contribution of each considered feature for the overall discrimination of the models was quantified in terms of the respective weights in the canonical projection into two dimensions, with the traditional clustering coefficient, hierarchical clustering coefficient and neighborhood clustering coefficient resulting particularly effective. Interestingly, the average shortest path length and hierarchical node degrees contributed little for the separation of the four network models.Comment: 9 pages, 4 figure

Intermittent exploration on a scale-free network

We study an intermittent random walk on a random network of scale-free degree distribution. The walk is a combination of simple random walks of duration $t_w$ and random long-range jumps. While the time the walker needs to cover all the nodes increases with $t_w$, the corresponding time for the edges displays a non monotonic behavior with a minimum for some nontrivial value of $t_w$. This is a heterogeneity-induced effect that is not observed in homogeneous small-world networks. The optimal $t_w$ increases with the degree of assortativity in the network. Depending on the nature of degree correlations and the elapsed time the walker finds an over/under-estimate of the degree distribution exponent.Comment: 12 pages, 3 figures, 1 table, published versio