Social Networks, Segregation and Poverty in Sao Paulo

The associations between segregation and urban poverty have been intensely scrutinized by the sociology and urban studies literatures. More recently, several studies have emphasized the importance of social networks for living conditions. Yet relatively few studies have tested the precise effects of social networks, and fewer still have focused on the joint effects of residential segregation and social networks on living conditions. This article explores the associations between networks, segregation and some of the most important dimensions of access to goods and services obtained in markets: escaping from social precariousness and obtaining monetary income. It is based on a study of the personal networks of 209 individuals living in situations of poverty in seven locales in the metropolitan area of Sao Paulo. Using network analysis and multivariate techniques, I show that relational settings strongly influence the access individuals have to markets, leading some individuals into worse living conditions and poverty. At the same time, although segregation plays an important role in poverty, its effects tend to be mediated by the networks in which individuals are embedded. Networks in this sense may enhance or mitigate the effects of isolation produced by space.

Surface Segregation in Chromium-Doped Nanocrystalline Tin Dioxide Pigments

Surface properties play an important role in understanding and controlling nanocrystalline materials. The accumulation of dopants on the surface, caused by surface segregation, can therefore significantly affect nanomaterials properties at low doping levels, offering a way to intentionally control nanoparticles features. In this work, we studied the distribution of chromium ions in SnO2 nanoparticles prepared by a liquid precursor route at moderate temperatures (500 degrees C). The powders were characterized by infrared spectroscopy, X-ray diffraction, (scanning) transmission electron microscopy, Electron Energy Loss Spectroscopy, and Mossbauer spectroscopy. We showed that this synthesis method induces a limited solid solution of chromium into SnO2 and a segregation of chromium to the surface. The s-electron density and symmetry of Sn located on the surface were significantly affected by the doping, while Sn located in the bulk remained unchanged. Chromium ions located on the surface and in the bulk showed distinct oxidation states, giving rise to the intense violet color of the nanoparticles suitable for pigment application.

Meiotic segregation and interchromosomal effect in the sperm of a double translocation carrier: a case report

Abstract Background Infertility is a natural mechanism of selection intended to prevent the delivery of a child with malformations or mental retardation. Male infertility is closely related to chromosomal abnormalities. This study was focused on the analysis of meiotic segregation involving a Robertsonian translocation, 45,XY,der(13;13) [56]/45,XY,der(13;14) [44] and the evaluation of possible interchromosomal effects. Results Hybridisation with LSI 13q14 and subtelomere 14q probes and WCP13 SpectrumGreen and WCP14 SpectrumOrange probes showed a high proportion of unbalanced gametes, corresponding to 71.2% of the spermatozoa. The disomic frequencies of the sexual chromosomes and chromosome 18 of the patient were higher (5.28% and 2.55%, respectively) than those of the control (0.6% and 0.59%, respectively). Conclusion Meiotic segregation studies in sperm are an important tool for genetic counselling of chromosomal aberrations, allowing for a prediction of the risks and consequent implications for the reproductive life. The patient with this rare translocation exhibited meiotic segregation fidelity, and a high rate of unbalanced gametes with disomic spermatozoa.

Influence of chain stiffness on structure and dynamics of polymers in the melt

Die vorliegende Arbeit beschaeftigt sich mit der Untersuchung vonPolymeren mit intrinsischer Steifigkeit. Es werden vor allem lokale statische unddynamische Eigenschaften anhand zweier verschiedener Simulationsmodellebetrachtet: Ein generisches Polymermodell, bei dem nur dieSteifigkeit als ein das spezifische Polymer charakterisierenden Parametereingeht und ein atomistisches Modell fuer trans-Polyisopren. Mit Hilfe des ersten Modells koennen Statik und Dynamik wurmartiger Kettenbeobachtet werden. Das Blob-Konzept ist eine angemessene statischeBeschreibung. Lokale Orientierungen haengen schwach von derSteifigkeit ab. Das Reptationsmodell kann die beobachtete Dynamik fuer lange Kettennicht mehr angemessen beschreiben. Lange Ketten bewegen sich, als obsie in Roehren gezwaengt waeren; jedoch ist die Bewegung starkabhaengig von der Steifigkeit. Fuer Ketten dieser Art konntequalitativ das Verhalten reproduziert werden, das in NMR-Experimentenbeobachtet wird. Eine Verhakungslaenge laesst sich fuer solche Kettenkaum mehr definieren. Dynamische Strukturfunktionen und insbesonderedie direkte Visualisierung der Ketten verdeutlichen die effektiv aufeine Roehre beschraenkte Bewegung. Das atomistische Polyisoprenmodell wurde mit verschiedenen Experimenten,verglichen. In den Simulationen bei konnten qualitativ undsemiquantitativ experimentelle Ergebnisse reproduziert werden. Zuletzt wurden die Laengen- und Zeitskalen der beiden Modelleerfolgreich aufeinander abgebildet.

Deciphering petrological signatures of reactive melt stagnation and cooling in the oceanic mantle underneath ultraslow-spreading ridges

The global mid-ocean ridge system creates oceanic crust and lithosphere that covers more than two-thirds of the Earth. Basalts are volumetrically the most important rock type sampled at mid-ocean ridges. For this reason, our present understanding of upper mantle dynamics and the chemical evolution of the earth is strongly influenced by the study of mid-ocean ridge basalts (MORB). However, MORB are aggregates of polybarically generated small melt increments that can undergo a variety of physical and chemical processes during their ascent and consequently affect their derivative geochemical composition. Therefore, MORB do not represent “direct” windows to the underlying upper mantle. Abyssal peridotites, upper mantle rocks recovered from the ocean floor, are the residual complement to MORB melting and provide essential information on melt extraction from the upper mantle. In this study, abyssal peridotites are examined to address these overarching questions posed by previous studies of MORB: How are basaltic melts formed in the mantle, how are they extracted from the mantle and what physical and chemical processes control mantle melting? The number of studies on abyssal peridotites is small compared to those on basalts, in part because seafloor exposures of abyssal peridotites are relatively rare. For this reason, abyssal peridotite characteristics need to be considered in the context of subaerially exposed peridotites associated with ophiolites, orogenic peridotite bodies and basalt-hosted xenoliths. However, orogenic peridotite bodies are mainly associated with passive continental margins, most ophiolites are formed in supra-subduction zone settings, and peridotite xenoliths are often contaminated by their host magma. Therefore, studies of abyssal peridotites are essential to understanding the primary characteristics of the oceanic upper mantle free from the influence of continental rifting, subduction and tectonic emplacement processes. Nevertheless, numerous processes such as melt stagnation and cooling-induced, inter-mineral exchange can affect residual abyssal peridotite compositions after the cessation of melting. The aim of this study is to address these post-melting modifications of abyssal peridotites from a petrological-geochemical perspective. The samples in this study were dredged along the axis of the ultraslow-spreading Gakkel Ridge in the Arctic Ocean within the “Sparsely Magmatic Zone”, a 100 km ridge section where only mantle rocks are exposed. During two expeditions (ARK XVII-2 in 2001 and ARK XX-2 in 2004), exceptionally fresh peridotites were recovered. The boulders and cobbles collected cover a range of mantle rock compositions, with most characterized as plagioclase-free spinel peridotites or plagioclase- spinel peridotites. This thesis investigates melt stagnation and cooling processes in the upper mantle and is divided into two parts. The first part focuses on processes in the stability field of spinel peridotites (>10 kb) such as melt refertilization and cooling related trace element exchange, while the second part investigates processes in the stability field of plagioclase peridotites (< 10 kb) such as reactive melt migration and melt stagnation. The dissertation chapters are organized to follow the theoretical ascent of a mantle parcel upwelling beneath the location where the samples were collected.

Zoomed simulations of Halo segregation in cosmological models with two species of coupled dark matter

La materia ordinaria copre soli pochi punti percentuali della massa-energia totale dell'Universo, che è invece largamente dominata da componenti “oscure”. Il modello standard usato per descriverle è il modello LambdaCDM. Nonostante esso sembri consistente con la maggior parte dei dati attualmente disponibili, presenta alcuni problemi fondamentali che ad oggi restano irrisolti, lasciando spazio per lo studio di modelli cosmologici alternativi. Questa Tesi mira a studiare un modello proposto recentemente, chiamato “Multi-coupled Dark Energy” (McDE), che presenta interazioni modificate rispetto al modello LambdaCDM. In particolare, la Materia Oscura è composta da due diversi tipi di particelle con accoppiamento opposto rispetto ad un campo scalare responsabile dell'Energia Oscura. L'evoluzione del background e delle perturbazioni lineari risultano essere indistinguibili da quelle del modello LambdaCDM. In questa Tesi viene presentata per la prima volta una serie di simulazioni numeriche “zoomed”. Esse presentano diverse regioni con risoluzione differente, centrate su un singolo ammasso di interesse, che permettono di studiare in dettaglio una singola struttura senza aumentare eccessivamente il tempo di calcolo necessario. Un codice chiamato ZInCo, da me appositamente sviluppato per questa Tesi, viene anch'esso presentato per la prima volta. Il codice produce condizioni iniziali adatte a simulazioni cosmologiche, con differenti regioni di risoluzione, indipendenti dal modello cosmologico scelto e che preservano tutte le caratteristiche dello spettro di potenza imposto su di esse. Il codice ZInCo è stato usato per produrre condizioni iniziali per una serie di simulazioni numeriche del modello McDE, le quali per la prima volta mostrano, grazie all'alta risoluzione raggiunta, che l'effetto di segregazione degli ammassi avviene significativamente prima di quanto stimato in precedenza. Inoltre, i profili radiale di densità ottenuti mostrano un appiattimento centrale nelle fasi iniziali della segregazione. Quest'ultimo effetto potrebbe aiutare a risolvere il problema “cusp-core” del modello LambdaCDM e porre limiti ai valori dell'accoppiamento possibili.

Mitochondrial tRNA(Leu(UUR)) mutation m.3302A > G presenting as childhood-onset severe myopathy: threshold determination through segregation study

Mitochondrial tRNA(Leu(UUR)) mutation m.3302A > G is associated with respiratory chain complex I deficiency and has been described as a rare cause of mostly adult-onset slowly progressive myopathy. Five families with 11 patients have been described so far; 5 of them died young due to cardiorespiratory failure. Here, we report on a segregation study in a family with an index patient who already presented at the age of 18 months with proximal muscular hypotonia, abnormal fatigability, and lactic acidosis. This early-onset myopathy was rapidly progressive. At 8 years, the patient is wheel-chair bound, requires nocturnal assisted ventilation, and suffers from recurrent respiratory infections. Severe complex I deficiency and nearly homoplasmy for m.3302A > G were found in muscle. We collected blood, hair, buccal swabs and muscle biopsies from asymptomatic adults in this pedigree and determined heteroplasmy levels in these tissues as well as OXPHOS activities in muscle. All participating asymptomatic adults had normal OXPHOS activities. In contrast to earlier reports, we found surprisingly little variation of heteroplasmy levels in different tissues of the same individual. Up to 45% mutation load in muscle and up to 38% mutation load in other tissues were found in non-affected adults. The phenotypic spectrum of tRNA(Leu(UUR)) m.3302A > G mutation seems to be wider than previously described. A threshold of more than 45% heteroplasmy in muscle seems to be necessary to alter complex I activity leading to clinical manifestation. The presented data may be helpful for prognostic considerations and counseling in affected families.