A study on fiber-arrangement close to the root of a sharp notch, for short fiber-reinforced thermoplastics

An approach, which aims at the morphological characterization near the sharp notch of specimens, has been developed for Short Fiber-Reinforced Thermoplastics. This work is directly related to the fa- tigue behavior of such materials, since the early stages of the cyclic damage are strictly influenced by the local microstructure at the stress concentration sites. Therefore, a comprehensive description of fi- bers\u2019 arrangement is needed in order to proceed with a modeling activity for the lifetime duration esti- mation. To this end, a semi-automatic tool has been developed, which is capable of evaluating fiber- arrangements through statistical descriptors, after submitting 2D pictures of the notch-tip area. Particu- larly, the attention was focused onto the nearest neighbor distance distribution function and onto a new formulation, which gives information about the level of the fiber-clustering phenomenon. On this basis, the repeatability of results has been evaluated with the goal of stating whether such information can be inherited by lifetime estimating models

Coherent regimes of globally coupled dynamical systems

The paper presents a method by which the mean field dynamics of a population of dynamical systems with parameter diversity and global coupling can be described in terms of a few macroscopic degrees of freedom. The method applies to populations of any size and functional form in the region of coherence. It requires linear variation or a narrow distribution for the dispersed parameter. Although being an approximation, the method allows us to quantitatively study the collective regimes that arise as a result of diversity and coupling and to interpret the transitions among these regimes as bifurcations of the effective macroscopic degrees of freedom. To illustrate, the phenomenon of oscillator death and the route to full locking are examined for chaotic oscillators with time scale mismatch.Comment: 5 pages, 3 figure

New urban frontiers: contemporary tendencies in Brazil’s urbanization

Brazil; urbanization

Low-dimensional chaos in populations of strongly-coupled noisy maps

We characterize the macroscopic attractor of infinite populations of noisy maps subjected to global and strong coupling by using an expansion in order parameters. We show that for any noise amplitude there exists a large region of strong coupling where the macroscopic dynamics exhibits low-dimensional chaos embedded in a hierarchically-organized, folded, infinite-dimensional set. Both this structure and the dynamics occuring on it are well-captured by our expansion. In particular, even low-degree approximations allow to calculate efficiently the first macroscopic Lyapunov exponents of the full system.Comment: 16 pages, 9 figures. Progress of Theoretical Physics, to appea

Necessary Optimality Conditions for Continuous-Time Optimization Problems with Equality and Inequality Constraints

The paper is devoted to obtain first and second order necessary optimality conditions for continuous-time optimization problems with equality and inequality constraints. A full rank type regularity condition along with an uniform implicit function theorem are used in order to establish such necessary conditions.Comment: 20 page

Phase transitions induced by microscopic disorder: a study based on the order parameter expansion

Based on the order parameter expansion, we present an approximate method which allows us to reduce large systems of coupled differential equations with diverse parameters to three equations: one for the global, mean field, variable and two which describe the fluctuations around this mean value. With this tool we analyze phase-transitions induced by microscopic disorder in three prototypical models of phase-transitions which have been studied previously in the presence of thermal noise. We study how macroscopic order is induced or destroyed by time independent local disorder and analyze the limits of the approximation by comparing the results with the numerical solutions of the self-consistency equation which arises from the property of self-averaging. Finally, we carry on a finite-size analysis of the numerical results and calculate the corresponding critical exponents

Time course and pathologies of in vitro maturation and fertilization of bovine oocytes

In this study, bovine oocyte maturation and early fertilization stages were systematically investigated by confocal laser scanning microscopy (CLSM) and subsequent 3-D-reconstruction. Grade I and II oocytes were isolated from 2–8 mm follicles from slaughterhouse ovaries and fixed at different time points of in vitro maturation (IVM) and in vitro fertilization (IVF). After staining the DNA, Serine 10 phosphorylated histone H3 (H3S10p), microtubules and f-actin microfilaments with four different fluorescence dyes, the oocytes were imaged in toto by serial optical sections. In the subsequent analysis, meiotic stages from the germinal vesicle to the metaphase II were morphologically characterized, and the approximate time course was determined. Using the same methodological approach, the first stages of fertilization were investigated: sperm penetration into the oocyte, completion of oocyte meiosis, the development of the maternal and paternal pronucleus, the formation of the sperm aster and the approximate time course. In parallel, the anomalies detected during in vitro oocyte maturation and fertilization were characterized and classified to subsequently determine their incidence. This study provided a large collection of three-dimensional microscopic images of bovine oocytes at different stages of presumably normal maturation and fertilization. Moreover, a spectrum of different severe anomalies was documented. In total, 1078 oocytes were fixed at 2-hour intervals from 0 to 28 hours of IVM and analyzed. Nearly all oocytes fixed before IVM were still in the germinal vesicle (GV) stage, at 10 hours virtually all oocytes had resumed meiosis and the GV had been broken down. The large number of three-dimensional snapshots of oocytes was used to reconstruct the presumably normal formation of the spindle apparatus and the chromosome alignment in meiosis I and II. Moreover, a spectrum of anomalies of meiosis I was documented: from the formation of a multipolar spindle, incorrect positioning of the spindle to chromosome segregation errors and the occurrence of chromatin bridges in anaphase I. To investigate the early steps of fertilization, in total 654 oocytes were fixed at 4, 5, 6, 7, 8, 10 and 12 hours post insemination (hpi), imaged in toto and morphologically analyzed. Thereby, we determined the time frame of sperm VII. Summary 107 penetration and oocyte activation, and the approximate time course of the development of the maternal and paternal pronucleus and the sperm aster. The formation of the two pronuclei and of the sperm aster was divided into 5 stages. Thus, we could show how the sperm nucleus shortly after penetrating into the oocyte decondenses and transiently recondenses to a small dense paternal pronucleus which decondenses again. 24.9 % of the oocytes were arrested in meiosis before metaphase II or had been already spontaneously activated and could not be fertilized. 26.9% of the penetrated and activated oocytes had severe anomalies: 11.9 % were polyspermic, 17% showed meiotic aberrations of the oocyte. The results of this study contribute to further elucidate the complex processes of oocyte maturation and fertilization in cattle and other mammals including humans and to improve the diagnostics and therapies of fertility problems.Zeitlicher Ablauf und Fehler bei der in vitro Reifung und Befruchtung boviner Eizellen In dieser Arbeit wurden systematisch die Reifung und die ersten Stadien der Befruchtung von Rinder-Eizellen mittels confocaler Laser-Scanning-Mikroskopie (CLSM) und nachfolgender 3-D-Rekonstruktion untersucht. Die Eizellen wurden aus Ovarien vom Schlachthof aus 2-8 mm Follikeln isoliert und zu unterschiedlichen Zeitpunkten der In-vitro-Maturation (IVM) und In-vitro Fertilisation (IVF) fixiert. Nach Anfärbung der DNA, Serin-10-phosphoryliertem Histon H3 (H3S10p), der Mikrotubuli und F-Actin-Filamente mit vier verschiedenen Fluoreszenzfarbstoffen wurden die Eizellen im Ganzen in optischen Serienschnitten aufgenommen. In der Auswertung wurden Stadien der Meiose vom Germinalvesikel bis zur Metaphase II morphologisch charakterisiert und der ungefähre Zeitablauf bestimmt. Mit dem gleichen methodischen Ansatz wurden die ersten Schritte der Befruchtung untersucht: das Eindringen des Spermiums und die Aktivierung der Eizelle, die Bildung des maternalen und paternalen Vorkerns, die Ausbildung des „Sperm Aster“ und der ungefähre Zeitablauf dieser Vorgänge. Parallel dazu wurden die bei der Eizellreifung und Befruchtung in vitro entdeckten Anomalien charakterisiert und klassifiziert, um anschließend ihre Häufigkeit zu bestimmen. Im Rahmen dieser Untersuchung entstand eine große Sammlung dreidimensionaler mikroskopischer Bilder, die Rinder-Eizellen in unterschiedlichen Stadien der mutmaßlich normalen Reifung und Befruchtung sowie ein Spektrum ganz unterschiedlicher schwerwiegender Anomalien erfasst. Insgesamt wurden 1078 Eizellen in 2-Stundenintervallen von 0 bis 28 Stunden IVM fixiert und analysiert. Nach unseren Beobachtungen waren nahezu alle Eizellen vor der in vitro Maturation im Germinalvesikel (GV) Stadium, nach 10 h hatten praktisch alle Eizellen die Meiose wieder aufgenommen und den GV aufgelöst. Aus der großen Zahl dreidimensionaler Momentaufnahmen wurden die mutmaßlich normale Ausbildung des Spindelapparates und die Anordnung der Chromosomen in der Meiose I und II rekonstruiert. Gleichzeitig wurde ein Spektrum von Anomalien der Meiose I dokumentiert, von der Bildung einer VI. Zusammenfassung 105 multipolaren Spindel, der falschen Positionierung der Spindel bis zu Fehlern bei der Chromosomensegregation und dem Auftreten von Chromatinbrücken in der Anaphase I. Zur Untersuchung des Befruchtungsvorgangs wurden insgesamt 654 Eizellen zu den Zeitpunkten 4, 5, 6, 7, 8, 10 und 12 Stunden nach der Besamung (hpi) im Ganzen aufgenommen und analysiert. Bei der Auswertung wurden der Zeitrahmen des Eindringens der Spermien und der Zeitablauf der Bildung des väterlichen und mütterlichen Vorkerns sowie des „Sperm Aster“ bestimmt. Die Entwicklung der beiden Vorkerne und des „Sperm Aster“ wurde jeweils in fünf Phasen unterteilt. So konnte dargestellt werden, wie der Kern des Spermiums kurz nach dem Eindringen dekondensiert, um vorübergehend wieder zu rekondensieren und einen zunächst kleinen dichten paternalen Vorkern zu bilden, der erneut expandiert. 24,9 % der Eizellen waren in der Meiose vor der Metaphase II arretiert oder waren bereits spontan aktiviert, und konnten so nicht mehr befruchtet werden. Bei 26,9 % der penetrierten und aktivierten Eizellen wurden schwerwiegende Anomalien gefunden: 11,9 % wiesen eine Polyspermie auf, 17 % Aberrationen der Meiose der Eizelle. Diese Ergebnisse dieser Untersuchungen tragen dazu bei, die komplexen Vorgänge der Eizellreifung und Befruchtung beim Rind und bei anderen Säugern einschließlich des Menschen weiter aufzuklären und die Diagnostik und Therapie von Fertilitätsstörungen zu verbessern