Structures in Galaxy Clusters

The analysis of the presence of substructures in 16 well-sampled clusters of galaxies suggests a stimulating hypothesis: Clusters could be classified as unimodal or bimodal, on the basis of to the sub-clump distribution in the {\em 3-D} space of positions and velocities. The dynamic study of these clusters shows that their fundamental characteristics, in particular the virial masses, are not severely biased by the presence of subclustering if the system considered is bound.Comment: (16 pages in LATEX, 4 tables in LATEX are at the end of the file, the figures not included are available upon request), REF SISSA 158/93/

Estudio de las interacciones entre el sulfatiazol y la mezcla dioxano-agua

Se ha realizado un estudio de interacciones soluto-disolvente para el sulfatiazol en dioxanp-agua a partir de medidas experimentales de solubilidad en el mencionado sistema disolvente y de la determinación de la solubilidad ideal de la sufamida mediante medidas calorimétricas. Si la sulfamida formase una disolución ideal la máxima solubilidad encontrada debería ser igual a la ideal; sin embargo, el hecho de encontrar solubilidades experimentales menores indica que se trata de una solución regular en la que el fármaco y el disolvente, o ambos, se asocian predominantemente consigo mismo por lo que las solubilidades experimentales encontradas en todos los casos son inferiores a la solubilidad ideal. Los valores del parámetro de Walker calculados, son para proporciones de mezclas tanto menores como mayores de la unidad. Se considera que en el primer caso tanto el soluto como el disolvente, o ambos, se asocian entre sí, y por lo tanto la interacción soluto-disolvente real es inferior a la ideal. Para el segundo caso. se puede interpretar esta situación como una débil solubilización del soluto

Estudio de las interacciones entre el sulfatiazol y la mezcla dioxano-agua

Se ha realizado un estudio de interacciones soluto-disolvente para el sulfatiazol en dioxanp-agua a partir de medidas experimentales de solubilidad en el mencionado sistema disolvente y de la determinación de la solubilidad ideal de la sulfamida mediante medidas calorimétricas. Si la sulfamida formase una disolución ideal la máxima solubilidad encontrada debería ser igual a la ideal; sin embargo, el hecho de encontrar solubilidades experimentales menores indica que se trata de una solución regular en la que el fármaco y el disolvente, o ambos, se asocian predominantemente consigo mismo por lo que las solubilidades experimentales encontradas en todos los casos son inferiores a la solubilidad ideal. Los valores del parámetro de Walker calculados, son para proporciones de mezclas tanto menores como mayores de la unidad. Se considera que en el primer caso tanto el soluto como el disolvente, o ambos, se asocian entre sí, y por lo tanto la interacción soluto-disolvente real es inferior a la ideal. Para el segundo caso se puede interpretar esta situación como una débil solubilización del soluto

Population stability: regulating size in the presence of an adversary

We introduce a new coordination problem in distributed computing that we call the population stability problem. A system of agents each with limited memory and communication, as well as the ability to replicate and self-destruct, is subjected to attacks by a worst-case adversary that can at a bounded rate (1) delete agents chosen arbitrarily and (2) insert additional agents with arbitrary initial state into the system. The goal is perpetually to maintain a population whose size is within a constant factor of the target size $N$. The problem is inspired by the ability of complex biological systems composed of a multitude of memory-limited individual cells to maintain a stable population size in an adverse environment. Such biological mechanisms allow organisms to heal after trauma or to recover from excessive cell proliferation caused by inflammation, disease, or normal development. We present a population stability protocol in a communication model that is a synchronous variant of the population model of Angluin et al. In each round, pairs of agents selected at random meet and exchange messages, where at least a constant fraction of agents is matched in each round. Our protocol uses three-bit messages and $\omega(\log^2 N)$ states per agent. We emphasize that our protocol can handle an adversary that can both insert and delete agents, a setting in which existing approximate counting techniques do not seem to apply. The protocol relies on a novel coloring strategy in which the population size is encoded in the variance of the distribution of colors. Individual agents can locally obtain a weak estimate of the population size by sampling from the distribution, and make individual decisions that robustly maintain a stable global population size

A 3-D wavelet analysis of substructure in the Coma cluster: statistics and morphology

Evidence for clustering within the Coma cluster is found by means of a multiscale analysis of the combined angular-redshift distribution. We have compiled a catalogue of 798 galaxy redshifts from published surveys from the region of the Coma cluster. We examine the presence of substructure and of voids at different scales ranging from $\sim 1 to \sim 16 h^{-1}$ Mpc, using subsamples of the catalogue, ranging from $cz=3000$ km/s to $cz=28000$ km/s. Our substructure detection method is based on the wavelet transform and on the segmentation analysis. The wavelet transform allows us to find out structures at different scales and the segmentation method allows us a quantitative statistical and morphological analysis of the sample. From the whole catalogue we select a subset of 320 galaxies, with redshifts between cz=5858 km/s and cz=8168 km/s that we identify as belonging to the central region of Coma and on which we have performed a deeper analysis, on scales ranging from $180 h^{-1}$ kpc to $1.44 h^{-1}$ Mpc. Our results are expressed in terms of the number of structures or voids and their sphericity for different values of the threshold detection and at all the scales investigated. According to our analysis, there is strong evidence for multiple hierarchical substructure, on scales ranging from a few hundreds of kpc to about $4 h^{-1}$ Mpc. The morphology of these substructures is rather spherical. On the scale of $720 h^{-1}$ kpc we find two main subclusters which where also found before, but our wavelet analysis shows even more substructures, whose redshift position is approximatively marked by these bright galaxies: NGC 4934 & 4840, 4889, 4898 & 4864, 4874 & 4839, 4927, 4875.Comment: 24 pages, 6 figures. ApJ (Main Journal), accepted for publication. Added one section on statistical tests and slightly modified text and abstrac

The effects of community interventions on unplanned healthcare use in patients with multimorbidity: a systematic review

OBJECTIVES: To summarise the impact of community-based interventions for multimorbid patients on unplanned healthcare use. The prevalence of multimorbidity (co-existence of multiple chronic conditions) is rapidly increasing and affects one-third of the global population. Patients with multimorbidity have complex healthcare needs and greater unplanned healthcare usage. Community-based interventions allow for continued care of patients outside hospitals, but few studies have explored the effects of these interventions on unplanned healthcare usage. DESIGN: A systematic review was conducted. MEDLINE, EMBASE, PsychINFO and Cochrane Library online databases were searched. Studies were screened and underwent risk of bias assessment. Data were synthesised using narrative synthesis. SETTING: Community-based interventions. PARTICIPANTS: Patients with multimorbidity. MAIN OUTCOME MEASURES: Unplanned healthcare usage. RESULTS: Thirteen studies, including a total of 6148 participants, were included. All included studies came from high-income settings and had elderly populations. All studies measured emergency department attendances as their primary outcome. Risk of bias was generally low. Most community interventions were multifaceted with emphasis on education, self-monitoring of symptoms and regular follow-ups. Four studies looked at improved care coordination, advance care planning and palliative care. All 13 studies found a decrease in emergency department visits post-intervention with risk reduction ranging from 0 (95% confidencec interval [CI]: -0.37 to 0.37) to 0.735 (95% CI: 0.688-0.785). CONCLUSIONS: Community-based interventions have potential to reduce emergency department visits in patients with multimorbidity. Identification of specific successful components of interventions was challenging given the overlaps between interventions. Policymakers should recognise the importance of community interventions and aim to integrate aspects of these into existing healthcare structures. Future research should investigate the impact of such interventions with broader participant characteristics

Substructure in the Coma Cluster: Giants vs Dwarfs

The processes that form and shape galaxy clusters, such as infall, mergers and dynamical relaxation, tend to generate distinguishable differences between the distributions of a cluster's giant and dwarf galaxies. Thus the dynamics of dwarf galaxies in a cluster can provide valuable insights into its dynamical history. With this in mind, we look for differences between the spatial and velocity distributions of giant (b18) galaxies in the Coma cluster. Our redshift sample contains new measurements from the 2dF and WYFFOS spectrographs, making it more complete at faint magnitudes than any previously studied sample of Coma galaxies. It includes 745 cluster members - 452 giants and 293 dwarfs. We find that the line-of-sight velocity distribution of the giants is significantly non-Gaussian, but not that for the dwarfs. A battery of statistical tests of both the spatial and localised velocity distributions of the galaxies in our sample finds no strong evidence for differences between the giant and dwarf populations. These results rule out the cluster as a whole having moved significantly towards equipartition, and they are consistent with the cluster having formed via mergers between dynamically-relaxed subclusters.Comment: 23 pages, 6 figures, to appear in Ap

Estudio comparativo de los métodos para la obtención del parámetro de solubilidad de la sulfanilamida en mezclas acetato de etilo-etanol

Este trabajo refleja un estudio comparativo de los valores hallados del parámetro de solubilidad, para la sulfanilamida, obtenidos por diferentes métodos: teórico y experimentales. El método teórico, se basa únicamente en el conocimiento de la estructura química del compuesto teniendo en cuenta la contribución aditiva de los distintos grupos químicos a la energía de vaporización del compuesto mientras que los otros métodos requieren la realización de medidas experimentales de solubilidad por lo que ya no resultan tan sencillos e inmediatos. De los resultados obtenidos se observa una notable concordancia entre los obtenidos a partir de los métodos experimentales y una ligera diferencia con el valor obtenido por el método teórico. Esto no significa que no resulte útil dicho método sino que es orientativo y puede variar en los distintos sistemas disolventes por las interacciones que se pueden producir: soluto-soluto, soluto-disolvente y disolvente-disolvente