Random cover times using the Poisson cylinder process

In this paper we deal with the classical problem of random cover times. We investigate the distribution of the time it takes for a Poisson process of cylinders to cover a set $A \subset \mathbb{R}^d.$ This Poisson process of cylinders is invariant under rotations, reflections and translations, and in addition we add a time component so that cylinders are "raining from the sky" at unit rate. Our main results concerns the asymptotic of this cover time as the set $A$ grows. If the set $A$ is discrete and well separated, we show convergence of the cover time to a Gumbel distribution. If instead $A$ has positive box dimension (and satisfies a weak additional assumption), we find the correct rate of convergence

Progetto di una cella a doppia curvatura in vetro ed acciaio ed analisi di un caso studio

Il progetto di tesi è finalizzato allo sviluppo di una cella a doppia curvatura in vetro e acciaio funzionale all’applicazione su superfici vetrate a forma variabile. La tesi si sviluppa su due livelli: dapprima si analizza il comportamento strutturale della cella per poi sviluppare un caso studio costituito da una copertura a doppia curvatura. Nello studio della curvatura a freddo del vetro, al fine di ottenere una superficie a doppia curvatura (paraboloide iperbolico) non è possibile prescindere da analisi non lineari, le quali consentono di cogliere notevoli incrementi dello stato tensionale rispetto al modello lineare; un fenomeno di instabilità geometrica è dimensionante per la massima deformazione che può raggiungere il pannello in vetro. Mediante analisi non lineari multistep è stato analizzata la mutua interazione tra telaio in acciaio e pannello vetrato, valutando la migliore soluzione del telaio per rendere la cella “autoportante”. Attraverso il caso studio è stato possibile valutare le possibilità di assemblaggio delle celle: unendo tra loro celle con diverso grado di deformazione è possibile discretizzare una superficie a doppia curvatura, minimizzando lo scostamento con la superficie di base. L’analisi di tale copertura ha evidenziato come la curvatura a freddo, impegnando il vetro per quasi il 60% della sua resistenza, sia fortemente limitante nelle verifiche strutturali del vetro

ON MEASURING INCOME POLARIZATION: AN APPROACH BASED ON REGRESSION TREES

This article proposes the application of regression trees for analysing income polarization. Using an approach to polarization based on the analysis of variance, we show that regression trees can uncover groups of homogeneous income receivers in a data-driven way. The regression tree can deal with nonlinear relationships between income and the characteristics of income receivers, and it can detect which characteristics and their interactions actually play a role in explaining income polarization. For these features, the regression tree is a flexible statistical tool to explore whether income receivers concentrate around local poles. An application to Italian individual income data shows an interesting partition of income receivers

Autoprotolysis constants in nonaqueous solvents and aqueous organic solvent mixtures

The recent IUPAC document on standardization of pH measurements in nonaqueous solvents and aqueous-organic solvent mixtures (P.A.C. 57 865 (1985)) underlines the importance of the autoprotolysis constant, K, which defines the normal range of pH in the relevant solvent. The recommended e.m.f. method of determination and the standard states implied by different K definitions are duly focused. This compilation is articulated in two Tables the first of which reports K data for 100% pure solvents mostly at 298.15 K and the other concerns binary aqueous-organic mixtures of different compositions and at various temperatures

Comparative Response of Different Broiler Genotypes to Dietary Nutrient Levels

ABSTRACT Three studies were conducted to evaluate how the broiler has changed over the years due to intense genetic selection. Four different broiler genotypes, one unselected since the 1950\u27s (HER) representing the old meat-type bird and three current strains (Ross 308, Ross 708, and a test product (TY)) were studied. Differences in growth, morphometry, and response in performance and processing yield to different nutrient levels were studied. Experiment 1 evaluated growth and morphometric analysis. Birds of each strain were killed weekly from day 7 to day 56, necropsied and cut up parts and organs weighed. Measurement of small intestine segments was also done. Results show that current strains have significantly increased body weight (BW) and muscle accretion, especially breast meat. Jejunum and ileum segments are longer in the current genotypes but shorter when related to body weight. Heart and gizzard relative weight has reduced and tibia breaking strength has increased as a side effect of selection. Experiment 2 evaluated performance and processing yield at four different energy levels. Results show that the HER bird is able to regulate feed intake (FI) in order to regulate energy intake. Increasing energy levels did not affect its performance. The Ross 308 bird is not able to modify FI in order to regulate energy intake. Also, Ross 308 responded to increasing levels of energy by increasing BW while Ross 708 and TY did not. Current genotypes increased caloric conversion ratio with higher levels of energy. Experiment 3 evaluated performance and processing yield at six different amino acid (AA) levels (80, 85, 90, 95, 100, and 105% of the recommended levels). Results show that HER bird response to increasing levels of AA was moderate to absent while the response of the three current genotypes was similar increasing BW, FI, and breast meat yield, reducing feed conversion ratio. In conclusion, results show that a substantial change has occurred in the broiler due to selection, modifying anatomy, and its responses to different nutrient levels. These changes need to be considered when formulating diets for the different broiler genotypes used in the US industry in order to get the best economic return

Decline and fall of the Ediacarans: late-Neoproterozoic extinctions and the rise of the modern biosphere

The end-Neoproterozoic transition marked a gradual but permanent shift between distinct configurations of Earth's biosphere. This interval witnessed the demise of the enigmatic Ediacaran Biota, ushering in the structured trophic webs and disparate animal body plans of Phanerozoic ecosystems. However, little consensus exists on the reality, drivers, and macroevolutionary implications of end-Neoproterozoic extinctions. Here we evaluate potential drivers of late-Neoproterozoic turnover by addressing recent findings on Ediacaran geochronology, the persistence of classical Ediacaran macrobionts into the Cambrian, and the existence of Ediacaran crown-group eumetazoans. Despite renewed interest in the possibility of Phanerozoic-style ‘mass extinctions’ in the latest Neoproterozoic, our synthesis of the available evidence does not support extinction models based on episodic geochemical triggers, nor does it validate simple ecological interpretations centred on direct competitive displacement. Instead, we argue that the protracted and indirect effects of early bilaterian innovations, including escalations in sediment engineering, predation, and the largely understudied impacts of reef-building, may best account for the temporal structure and possible selectivity of late-Neoproterozoic extinctions. We integrate these processes into a generalised model of early eumetazoan-dominated ecologies, charting the disruption of spatial and temporal isotropy on the Ediacaran benthos as a consequence of diversifying macrofaunal interactions. Given the nature of resource distribution in Ediacaran ecologies, the continuities among Ediacaran and Cambrian faunas, and the convergent origins of ecologically disruptive innovations among bilaterians we suggest that the rise of Phanerozoic-type biotas may have been unstoppable

Obesidad: un desafío para las políticas públicas

La obesidad es un problema médico que ha sido declarada epidemia mundial por la Organización Mundial de la Salud. El aumento de su prevalencia implica incrementos en los costos de los sistemas de salud, tanto en forma directa como indirecta, conjuntamente con un deterioro de la calidad de vida. Se vuelva un tema prioritario dentro de la agenda pública de los gobiernos. Las fallas de mercado presentes en el sector constituyen un argumento que justifica la intervención estatal. En función de ello, es que el objetivo del presente trabajo es analizar las fallas de mercado presentes en el sector y realizar una recopilación exhaustiva de las políticas públicas que han sido propuestas para el tratamiento y la prevención de la obesidad