Limits for Szegö polynomials in frequency analysis

AbstractWe characterize limits for orthogonal Szegö polynomials of fixed degree k, with respect to certain measures on the unit circle which are weakly convergent to a sum of m<k point masses. Such measures arise, for example, as a convolution of point masses with an approximate identity. It is readily seen that the underlying measures in two recently-proposed methods for estimating the m frequencies, θj, of a discrete-time trigonometric signal using Szegö polynomials are of this form. We prove existence of Szegö polynomial limits associated with a general class of weakly convergent measures, and prove that for convolution of point masses with the Poisson kernel, which underlies one of the recently-proposed methods, the limit has as a factor the Szegö polynomial with respect to a related measure, which we specify. Since m of the zeros approach the eiθj, this result uniquely characterizes the limit. A similar result is obtained for measures consisting of point masses with additive absolutely continuous part

Exploring agent-based methods for the analysis of payment systems: a crisis model for StarLogo TNG

agent-based modeling, payment systems, RTGS, liquidity, crisis simulation Abstract: This paper presents an exploratory agent-based model of a real time gross settlement (RTGS) payment system. Banks are represented as agents who exchange payment requests, which are settled according to a set of simple rules. The model features the main elements of a real-life system, including a central bank acting as liquidity provider, and a simplified money market. A simulation exercise using synthetic data of BI-REL (the Italian RTGS) predicts the macroscopic impact of a disruptive event on the flow of interbank payments. The main advantage of agent - based modeling is that we can dynamically see what happens to the major variables involved. In our reduced-scale system, three hypothetical distinct phases emerge after the disruptive event: 1) a liquidity sink effect is generated and the participants’ liquidity expectations turn out to be excessive; 2) an illusory thickening of the money market follows, along with increased payment delays; and, finally 3) defaulted obligations dramatically rise. The banks cannot staunch the losses accruing on defaults, even after they become fully aware of the critical event, and a scenario emerges in which it might be necessary for the central bank to step in as liquidity provider. The methodology presented differs from traditional payment systems simulations featuring deterministic streams of payments dealt with in a centralized manner with static behavior on the part of banks. The paper is within a recent stream of empirical research that attempts to model RTGS with agent – based techniques.

Thiosulfate-cyanide sulfurtransferase a mitochondrial essential enzyme: from cell metabolism to the biotechnological applications

Thiosulfate: cyanide sulfurtransferase (TST), also named rhodanese, is an enzyme widely distributed in both prokaryotes and eukaryotes, where it plays a relevant role in mitochondrial function. TST enzyme is involved in several biochemical processes such as: cyanide detoxification, the transport of sulfur and selenium in biologically available forms, the restoration of iron-sulfur clusters, redox system maintenance and the mitochondrial import of 5S rRNA. Recently, the relevance of TST in metabolic diseases, such as diabetes, has been highlighted, opening the way for research on important aspects of sulfur metabolism in diabetes. This review underlines the structural and functional characteristics of TST, describing the physiological role and biomedical and biotechnological applications of this essential enzyme

Mathematical methods for modeling the microcirculation

The microcirculation plays a major role in maintaining homeostasis in the body. Alterations or dysfunctions of the microcirculation can lead to several types of serious diseases. It is not surprising, then, that the microcirculation has been an object of intense theoretical and experimental study over the past few decades. Mathematical approaches offer a valuable method for quantifying the relationships between various mechanical, hemodynamic, and regulatory factors of the microcirculation and the pathophysiology of numerous diseases. This work provides an overview of several mathematical models that describe and investigate the many different aspects of the microcirculation, including geometry of the vascular bed, blood flow in the vascular networks, solute transport and delivery to the surrounding tissue, and vessel wall mechanics under passive and active stimuli. Representing relevant phenomena across multiple spatial scales remains a major challenge in modeling the microcirculation. Nevertheless, the depth and breadth of mathematical modeling with applications in the microcirculation is demonstrated in this work. A special emphasis is placed on models of the retinal circulation, including models that predict the influence of ocular hemodynamic alterations with the progression of ocular diseases such as glaucoma

Sustainable vegetable oil-based biomaterials: synthesis and biomedical applications

One of the main criteria for ecological sustainability is that the materials produced for common use are green. This can include the use of biomaterials and materials that are environmentally friendly, biodegradable and produced at low cost. The exploration of natural resources as sustainable precursors leads to the production of biopolymers that are useful for 3D printing technology. Recently, waste vegetable oils have been found to be a good alternative source for the production of biopolymers in various applications from the engineering to the biomedicine. In this review, the processes for the synthesis of vegetable oil-based biomaterials are described in detail. Moreover, the functionalization strategies to improve the mechanical properties of these materials and the cell-material interaction for their potential use as micro-structured scaffolds in regenerative medicine are discussed

Il lungo ‘Rinascimento’ e i dilemmi della modernità. T.S. Eliot, Ch. Dawson, V.A. Demant

Negli anni tra le due guerre mondiali – inserendosi nel dibattito tra classicismo e romanticismo e nella polemica contro Rousseau avviata da Irving Babbitt e soprattutto da T.E. Hulme –, T.S. Eliot, Christopher Dawson e V.A. Demant avviano un’indagine sui rapporti tra religione e politica articolata su una condivisa visione storica. Attribuendo alla fine dell’unità religiosa la valenza di una cesura tra l’epoca classica e medievale, da un lato, e quella moderna dall’altro, Dawson, Eliot e Demand elaborano la concezione di un ‘lungo Rinascimento’ le cui riverberazioni si erano prolungate fino alla tarda età moderna culminando nella crisi della tradizione occidentale e nell’esperienza dei totalitarismi.In the years between the two world wars –adding themselves in the debate between classicism and romanticism and in the polemic against Rousseau started by Irving Babbitt as well as by T.E. Hulme–, T.S. Eliot, Christopher Dawson and V.A. Demant elaborate a religious and political survey articulated on a shared historical vision. Attributing to the end of religious unity the value of a caesura between the classical and medieval era, on the one hand and the modern era, on the other, Dawson, Eliot and Demand develop the conception of a ‘long Renaissance

Human population history and genetic adaptation in the Himalayan region

The Himalayan mountain range contains the highest peaks on Earth and has provided a diversity of environments for humans, some of which have required substantial genetic adaptation. I have used a combination of SNP-chip data, genome sequences and functional studies to explore the demographic history, genetic structure and signatures of adaptation in Himalayan populations. Eight hundred and eighty three individuals from 49 different autochthonous groups from Nepal, Bhutan, North India, and the Tibetan Plateau in China were genotyped for ~600,000 genome-wide SNPs. High-coverage whole-genome sequences of 87 individuals from a subset of these populations plus three additional ones were also generated. Himalayan populations share a common genetic component derived from a single ancestral population, followed by the development of local fine structure correlating with language and geographical distribution. I find higher genetic diversification within the Himalayan populations than in the surrounding regions which correlates with the distribution of Indo-European and Tibeto-Burman speakers, suggesting that both language and geography have influenced the genetic structure of these populations. I refined Himalayan population demographic history, using both autosomal and uniparental sequences. Himalayan populations display different proportions of gene flow with neighbouring populations and diverse effective population sizes and split times. The Y-chromosome lineages identified are common in South and East Asia and Tibet, but mostly form distinct clusters in the Himalayas. High altitude adaptation seems to have originated in a single ancestral population and then spread widely in the Himalayan region in the last 5,000 years. Genetic signatures of adaptation to high altitude are observed in the Endothelial PAS Domain Protein 1 gene (EPAS1) and several other known and novel candidates. EPAS1 has previously been reported to be under selection and involved in adaptation to living at high altitudes and was suggested to result from introgression of DNA from an extinct hominin species (Denisovans) into Tibetans. However, functional studies of EPAS1 variants have not been systematically carried out and it is still unknown which variant(s) are responsible for high altitude adaptation and their mechanism of action. I used both in silico and in vitro studies to explore these topics and validate EPAS1 candidate regulatory variants. The introgressed haplotype extends for over 300 kb spanning six genes (EPAS1, TMEM247, ATP6V1E2, RHOQ, CRIPT, PIGF). I optimised a protocol to induce hypoxia in cell lines with and without the Denisovan introgressed haplotype. Preliminary results show that in cell lines without the introgressed haplotype, EPAS1 expression increases under hypoxic conditions, whereas in the cell lines with the introgressed haplotype the expression of EPAS1 remains constant. The most likely functional candidate variants fall in a ~32.7kb region within EPAS1. High altitude adaptation thus seems to be driven by EPAS1 as well as coordinated by other genes involved in the hypoxic response

Preliminari per uno studio della storia della Glottologia. Le dispense universitarie dagli anni Quaranta agli anni Sessanta.

La ricerca trae spunto da uno spoglio delle dispense universitarie che, durante alcuni decenni del Novecento, anche se in modo discontinuo, hanno attestato l'uso istituzionale della Glottologia raccontata e insegnata, generalmente dagli stessi docenti e studiosi della materia. Tale documentazione rinvia ad un modello abbastanza omogeneo nei contenuti e nella loro architettura. Il lavoro intende investigare tale composizione, secondo un criterio comparativo testuale, al fine di individuare i nuclei tematici che meglio caratterizzano i corsi propedeutici alla Glottologica. La ricerca ha anche una finalità più generale, quella, cioè, di una microstoria della tradizione della disciplina