Scale-invariance of galaxy clustering

Some years ago we proposed a new approach to the analysis of galaxy and cluster correlations based on the concepts and methods of modern statistical Physics. This led to the surprising result that galaxy correlations are fractal and not homogeneous up to the limits of the available catalogs. The usual statistical methods, which are based on the assumption of homogeneity, are therefore inconsistent for all the length scales probed so far, and a new, more general, conceptual framework is necessary to identifythe real physical properties of these structures. In the last few years the 3-d catalogs have been significatively improved and we have extended our methods to the analysis of number counts and angular catalogs. This has led to a complete analysis of all the available data that we present in this review. The result is that galaxy structures are highly irregular and self-similar: all the available data are consistent with each other and show fractal correlations (with dimension $D \simeq 2$) up to the deepest scales probed so far (1000 \hmp) and even more as indicated from the new interpretation of the number counts. The evidence for scale-invariance of galaxy clustering is very strong up to 150 \hmp due to the statistical robustness of the data but becomes progressively weaker (statistically) at larger distances due to the limited data. In These facts lead to fascinating conceptual implications about our knowledge of the universe and to a new scenario for the theoretical challenge in this field.Comment: Latex file 165 pages, 106 postscript figures. This paper is also available at http://www.phys.uniroma1.it/DOCS/PIL/pil.html To appear in Physics Report (Dec. 1997

A geographical population analysis of dental trauma in school-children aged 12 and 15 in the city of Curitiba-Brazil

<p>Abstract</p> <p>Background</p> <p>The study presents a geographical analysis of dental trauma in a population of 12 and 15 year-old school-children, in the city of Curitiba, Brazil (n = 1581), using a database obtained in the period 2005-2006. The main focus is to analyze dental trauma using a geographic information system as a tool for integrating social, environmental and epidemiological data.</p> <p>Methods</p> <p>Geostatistical analysis of the database and thematic maps were generated showing the distribution of dental trauma cases according to Curitiba's Health Districts and other variables of interest. Dental trauma spatial variation was assessed using a generalized additive model in order to identify and control the individual risk-factors and thus determine whether spatial variation is constant or not throughout the Health Districts and the place of residence of individuals. In addition, an analysis was made of the coverage of dental trauma cases taking the spatial distribution of Curitiba's primary healthcare centres.</p> <p>Results</p> <p>The overall prevalence of dental trauma was 37.1%, with 53.1% in males and 46.7% in females. The spatial analysis confirms the hypothesis that there is significant variation in the occurrence of dental trauma, considering the place of residence in the population studied (Monte Carlo test, p = 0,006). Furthermore, 28.7% of cases had no coverage by the primary healthcare centres.</p> <p>Conclusions</p> <p>The effect of the place of residence was highly significant in relation to the response variable. The delimitation of areas, as a basis for case density, enables the qualification of geographical territories where actions can be planned based on priority criteria. Promotion, control and rehabilitation actions, applied in regions of higher prevalence of dental trauma, can be more effective and efficient, thus providing healthcare refinement.</p

Finite size effects on the galaxy number counts: evidence for fractal behavior up to the deepest scale

We introduce and study two new concepts which are essential for the quantitative analysis of the statistical quality of the available galaxy samples. These are the dilution effect and the small scale fluctuations. We show that the various data that are considered as pointing to a homogenous distribution are all affected by these spurious effects and their interpretation should be completely changed. In particular, we show that finite size effects strongly affect the determination of the galaxy number counts, namely the number versus magnitude relation ($N(<m)$) as computed from the origin. When one computes $N(<m)$ averaged over all the points of a redshift survey one observes an exponent $\alpha = D/5 \approx 0.4$ compatible with the fractal dimension $D \approx 2$ derived from the full correlation analysis. Instead the observation of an exponent $\alpha \approx 0.6$ at relatively small scales, where the distribution is certainly not homogeneous, is shown to be related to finite size effects. We conclude therefore that the observed counts correspond to a fractal distribution with dimension $D \approx 2$ in the entire range 12 \ltapprox m \ltapprox 28, that is to say the largest scales ever probed for luminous matter. In addition our results permit to clarify various problems of the angular catalogs, and to show their compatibility with the fractal behavior. We consider also the distribution of Radio-galaxies, Quasars and $\gamma$ ray burst, and we show their compatibility with a fractal structure with $D \approx 1.6 \div 1.8$. Finally we have established a quantitative criterion that allows us to define and {\em predict} the statistical validity of a galaxy catalog (angular or three dimensional).Comment: 42 Latex pages. Figures and macro are avaialable under request at [email protected]

Creación de un medio comunitario a través de la red social WhatsApp en el Recinto Tres Postes

Tres Postes es un recinto en la provincia del Guayas (Ecuador), se dedica a la agricultura y venta de platos típicos en la ruta Panamericana. La información documental relacionada con su historia, creencias, tradiciones y demás factores culturales que permitan conocer su riqueza cultural y ancestral relacionada con las leyendas, rituales e historia son escasas. Además, se resalta que con la investigación realizada en el presente estudio, se logra constatar el paralelismo y contradicciones existentes entre los fundadores del recinto y aquellas generaciones jóvenes que desconocen sus raíces y relatos orales. El objetivo principal, a través del levantamiento de datos implica el desarrollo de un producto comunicativo (podcast) que difunda los saberes ancestrales, tradiciones e historia del recinto Tres Postes, a través de la creación de un medio comunitario empleando la aplicación WhatsApp para compartir el contenido desde las voces y perspectivas de sus pobladores. La metodología utilizada es cualitativa, recurriendo a las técnicas de revisión documental, observación participante, y entrevistas en profundidad a los pobladores. Los resultados obtenidos en el trabajo de campo constituyen una base para futuras investigaciones. En definitiva, con la difusión de los podcasts se pretende fomentar la memoria colectiva y sentar precedentes de una nueva forma de hacer medios comunitarios.Tres Postes is a precinct in the province of Guayas (Ecuador), dedicated to agriculture and the sale of typical dishes on the Pan-American Highway. Documentary information related to its history, beliefs, traditions and other cultural factors that allow to know its cultural and ancestral richness related to legends, rituals and history are scarce. In addition, the research conducted in this study shows the parallelism and contradictions that exist between the founders of the precinct and the younger generations who are unaware of their roots and oral stories. The main objective, through data collection, involves the development of a communicative product (podcast) that disseminates the ancestral knowledge, traditions and history of the Tres Postes precinct, through the creation of a community media using the WhatsApp application to share the content from the voices and perspectives of its inhabitants. The methodology used is qualitative, resorting to the techniques of documentary review, participant observation, and in-depth interviews with the inhabitants. The results obtained in the field work constitute a basis for future research. In short, the dissemination of the podcasts is intended to promote collective memory and set precedents for a new form of community media

Development of bean plants in soil contaminated with trifloxysulfuron-sodium after Stizolobium aterrimum and Canavalia ensiformis cultivation Desenvolvimento de plantas de feijão em solo contaminado com trifloxysulfuron-sodium, após o cultivo de Stizolobium aterrimum e Canavalia ensiformis

Phytoremediation, the use of plants to decontaminate soils and water resources from organic pollutants such as herbicides, is economically and environmentally a promising technique applied in many areas, including agriculture. The objective of this work was to evaluate the development of bean plants cultivated in the field, in soil with different levels of trifloxysulfuron-sodium contamination, following cultivation of two green manure species, as well as to evaluate the possibility of recontamination of the area by such herbicide with the straw permanence on the soil. The experiment was carried out in Coimbra, MG, Brazil, on a sandy clayey Red - Yellow Argisol from March to November 2003. Four levels of soil contamination with trifloxysulfuron-sodium (0.00; 3.75; 7.50; and 15.00 g ha-1) were used as well as the following five types of cultivation prior to bean sowing in the area after herbicide application: black velvet beans (Stizolobium aterrimum) followed by removal of straw; S. aterrimum, followed by permanence of straw; jack bean (Canavalia ensiformis), followed by removal of straw; C. ensiformis followed by permanence of straw; and without prior cultivation, weed-free (weeded control). The leguminous plants were kept in the area for 65 days, cut close to the soil, and with its aerial part left or not on the surface of the experimental plot, depending on the treatment. Fifteen days after the species were cut, bean was sown in the area. At 45 days after emergence (DAE) of the bean plants, plant height and dry mass of the aerial part were evaluated. Grain productivity was determined during harvest. Height, dry matter of the aerial part and grain productivity of the bean plants, cultivated in an area previously contaminated with trifloxysulfuron-sodium at any of the levels tested, were higher with prior cultivation of S. aterrimum or C. ensiformis. At the lowest level of herbicide contamination, prior cultivation of C. ensiformis was found to be more efficient than that of S. aterrimum in mitigating the harmful effects of trifloxysulfuron-sodium on bean grain production. The permanence of the straw of the green manure species during the bean cycle did not harm the development of the plants or caused culture productivity losses, indicating that straw permanence in the area does not promote recontamination of the area.<br>A utilização de plantas para descontaminar solos e recursos hídricos de poluentes orgânicos, como os herbicidas, denominada fitorremediação, desponta como técnica promissora tanto econômica como ambientalmente, sendo direcionada inclusive para a agricultura. O objetivo deste trabalho foi avaliar o desenvolvimento de plantas de feijão cultivadas em campo, em solo com diferentes níveis de contaminação do herbicida trifloxysulfuron-sodium, após o cultivo prévio de duas espécies de adubos verdes, bem como a possibilidade de recontaminação da área pelo herbicida com a permanência da palhada sobre o solo. O experimento foi conduzido em campo em Coimbra, MG, em um Argissolo Vermelho-Amarelo de textura argilo-arenosa. Avaliaram-se quatro níveis de contaminação do solo com trifloxysulfuron-sodium (0,00; 3,75; 7,50; e 15,00 g ha-1) e cinco tipos de cultivo prévio à semeadura do feijão na área após aplicação do herbicida: cultivo de mucuna-preta (Stizolobium aterrimum) com posterior retirada da sua palhada; cultivo de mucuna-preta seguido da permanência da palhada; cultivo de feijão-de-porco (Canavalia ensiformis) com retirada da palhada em seguida; cultivo de feijão-de-porco com posterior permanência da palhada; e sem cultivo prévio, com a área mantida no limpo (testemunha capinada). As plantas das leguminosas de cobertura foram mantidas na área por 65 dias, quando foram cortadas rente ao solo, sendo sua parte aérea deixada ou não sobre a superfície da parcela experimental, dependendo do tratamento. Quinze dias após o corte das espécies, foi semeada na área a cultura do feijão. Aos 45 dias após a emergência (DAE) das plantas de feijão, avaliaram-se a altura de plantas e a massa seca da parte aérea. A produtividade de grãos foi determinada por ocasião da colheita. A altura de plantas, a massa seca da parte aérea e a produtividade de grãos de feijão, cultivado em área com contaminação prévia do trifloxysulfuron-sodium em qualquer dos níveis testados, foram superiores quando se realizou o cultivo prévio na área com mucuna-preta ou feijão-de-porco. No menor nível de contaminação do herbicida, o cultivo prévio de feijão-de-porco se mostrou mais eficiente, em relação ao da mucuna-preta, em mitigar os efeitos deletérios do trifloxysulfuron-sodium à produção de grãos de feijão. A manutenção da palhada das espécies de adubos verdes durante o ciclo do feijão não prejudicou o desenvolvimento das plantas e não provocou perdas na produtividade da cultura, indicando que a permanência da palhada na superfície do solo não promove a recontaminação da área