Simulation of the deformation behaviour of two-phase composites

Two-phase polycrystal, elasto-viscoplastic material model, heterogeneity, anisotropy, flow behaviour, crystallographic texture, strain field

Quantum phase transitions in magnetic systems: application of coupled cluster method

Magdeburg, Univ., Fak. für Naturwiss., Diss., 2009

Virtual separation of concerns : toward preprocessors 2.0 /von Christian Kästner

Software product line, variability, virtual separation, ifdef, preprocessor, cpp, annotative approaches, annotations

maintenance model for systems with phase-type distributed times to failure

Magdeburg, Univ., Fak. für Mathematik, Diss., 2010

Numerical methods for multiphase mixture conservation laws with phase transition

Magdeburg, Univ., Fak. für Mathematik, Diss., 2010

Comportamento dos cromossômios na meiose de Euryophthalmus rufipennis Laporte (Hemiptera Pyrrhocoridae)

In this paper an account is given of the principal facts observer in the meiosis of Euryophthalmus rufipennis Laporte which afford some evidence in favour of the view held by the present writer in earlier publications regarding the existence of two terminal kinetochores in Hem ip ter an chromosomes as well as the transverse division of the chromosomes. Spermatogonial mitosis - From the beginning of prophase until metaphase nothing worthy of special reference was observed. At anaphase, on the contrary, the behavior of the chromosomes deserves our best attention. Indeed, the chromoso- mes, as soon as they begin to move, they show both ends pronouncedly turned toward the poles to which they are connected by chromosomal fibres. So a premature and remarkable bending of the chromosomes not yet found in any other species of Hemiptera and even of Homoptera points strongly to terminally localized kinetochores. The explanation proposed by HUGHES-SCHRADER and RIS for Nautococcus and by RIS for Tamalia, whose chromosomes first become bent late in anaphase do not apply to chromosomes which initiate anaphase movement already turned toward the corresponding pole. In the other hand, the variety of positions assumed by the anaphase chromosomes of Euryophthalmus with regard to one another speaks conclusively against the idea of diffuse spindle attachments. First meiotic division - Corresponding to the beginning of the story of the primary spermatocytes cells are found with the nucleus entirelly filled with leptonema threads. Nuclei with thin and thick threads have been considered as being in the zygotente phase. At the pachytene stage the bivalents are formed by two parallel strands clearly separated by a narrow space. The preceding phases differ in nothing from the corresponding orthodox ones, pairing being undoubtedly of the parasynaptic type. Formation of tetrads - When the nuclei coming from the diffuse stage can be again understood the chromosomes reappear as thick threads formed by two filaments intimately united except for a short median segment. Becoming progressively shorter and thicker the bivalents sometimes unite their extremities forming ring-shaped figures. Generally, however, this does not happen and the bivalents give origin to more or less condensed characteristic Hemipteran tetrads, bent at the weak median region. The lateral duplicity of the tetrads is evident. At metaphase the tetrads are still bent and are connected with both poles by their ends. The ring-shaped diakinesis tetrads open themselves out before metaphase, showing in this way that were not chiasmata that held their ends together. Anaphase proceeds as expected. If we consider the median region of the tetrads as being terminalized chiasmata, then the chromosomes are provided with a single terminal kinetochore. But this it not the case. A critical analysis of the story of the bivalents before and after the diffuse stage points to the conclusion that they are continuous throughout their whole length. Thence the chromosomes are considered as having a kinetochore at each end. Orientation - There are some evidences that Hemipteran chromosomes are connected by chiasmata. If this is true, the orientation of the tetrads may be understood in the following manner: Chiasmata being hindered to scape by the terminal kinetochores accumulate at the ends of the tetrads, where condensation begins. Repulsion at the centric ends being prevented by chiasmata the tetrads orient themselves as if they were provided with a single kinetochore at each extremity, taking a position parallelly to the spindle axis. Anaphase separation - Anaphase separation is consequently due to a transverse division of the chromosomes. Telophase and secund meiotic division - At telophase the kinetochore repeli one another following the moving apart of the centosomes, the chiasmata slip toward the acentric extremities and the chromosomes rotate in order to arrange themselves parallelly to the axis of the new spindle. Separation is therefore throughout the pairing plane. Origin of the dicentricity of the chromosomes - Dicentricity of the chromosomes is ascribed to the division of the kinetochore of the chromosomes reaching the poles followed by separation and distension of the chromatids which remain fused at the acentric ends giving thus origin to terminally dicentric iso-chromosomes. Thence, the transverse division of the chromosomes, that is, a division through a plane perpendicular to the plane of pairing, actually corresponds to a longitudinal division realized in the preceding generation. Inactive and active kinetochores - Chromosomes carrying inactive kinetochore is not capable of orientation and active anaphasic movements. The heterochromosome of Diactor bilineatus in the division of the secondary spermatocytes is justly in this case, standing without fibrilar connection with the poles anywhere in the cell, while the autosomes are moving regularly. The heterochromosome of Euryophthalmus, on the contrary, having its kinetochores perfectly active ,is correctly oriented in the plane of the equator together with the autosomes and shows terminal chromosomal connection with both poles. Being attracted with equal strength by two opposite poles it cannot decide to the one way or the other remaining motionless in the equator until some secondary causes (as for instances a slight functional difference between the kinetochores) intervene to break the state of equilibrium. When Yiothing interferes to aide the heterochromosome in choosing its way it distends itself between the autosomal plates forming a fusiform bridge which sometimes finishes by being broken. Ordinarily, however, the bulky part of the heterochromosome passes to one pole. Spindle fibers and kinetic activity of chromosomal fragments - The kinetochore is considered as the unique part of the chromosome capable of being influenced by other kinetochore or by the poles. Under such influence the kinetochore would be stimulated or activited and would elaborate a sort of impulse which would run toward the ends. In this respect the chromosome may be compared to a neüròn, the cell being represented by the kinetochore and the axon by the body of the chromosome. Due to the action of the kinetochore the entire chromosome becomes also activated for performing its kinetic function. Nothing is known at present about the nature of this activation. We can however assume that some active chemical substance like those produced by the neuron and transferred to the effector passes from the kinetochore to the body of the chromosome runing down to the ends. And, like an axon which continues to transmit an impulse after the stimulating agent has suspended its action, so may the chromosome show some residual kinetic activity even after having lost its kinetochore. This is another explanation for the kinetic behavior of acentric chromosomal fragmehs. In the orthodox monocentric chromosomes the kinetic activity is greater at the kinetochore, that is, at the place of origin of the active substance than at any other place. In chromosomes provided with a kinetochore at each end the entire body may become active enough to produce chromosomal fibers. This is probably due to a more or less uniform distribution and concentration of the active substance coming simultaneously from both extremities of the chromosome.

Preparative chromatographic separation of ternary mixtures : analysis of fractionation times and novel concepts

Magdeburg, Univ., Fak. für Verfahrens- und Systemtechnik, Diss., 2010

Gradient injection in preparative chromatography : exploitation of sample solvents different than the mobile phase

Magdeburg, Univ., Fak. für Verfahrens- und Systemtechnik, Diss., 2010

Comportamento dos cromossômios no gênero Hypselonotus (Hemiptera -Coreidae)

The three species studied have 19 chromosomes, being one heterochromosome, one pair of microchromosomes and 8 pairs of autosomes. The microchromosomes of Hypselonotus fulvus are amongst the largest we know. During the synizesis, in Hypselonotus fulvus, we can see in several strands that scape from the chromatic knot a place in which they are widley open. As, in that phase the chromosomes have both ends converging to the same place, the openings suggest a side-to-side pairing of the chromosomal threads. The tetrads are like that studied by Piza (1945-1946). The bivalents are united side by side at their entire length. The unpaired part at the midle of the bivalents gives origin to the arms of the cross-shapede tetrads. The chromosomes have a kinetochore at each end. The bivalents sometimes unite their extremities to form ring-shaped figures, which open themselves out before metaphase. The tetrads are oriented parallelly to the spindle axis. At telophase the kinetochores repeli one another, the chiasmata, if present, slip toward the acentric extremities and the chromosomes rotate in order to arrange themselves parallelly to the axis of the new spindle. Separation is therefore through the pairing plane. In the spermatogonial anaphase of Hypselonotus subterpunctatus the chromosomes are curved to the poles, like those described by PIZA (1946) and PIZA and ZAMITH (1946). The sex chromosomes in Hypselonotus interruptus and Hypselonotus fulvus appears longitudinally divided. It is oriented with the ends in the plane of the equator and its chomatids separate by the plane of division. In the second division the sex chromosome, provided as it is with an actve klnetochore at each end, orients itself with its length parallelly to the spindle axis and passes undivided to one pole. Sometimes it is distended between the poles. This corresponds to case (a) established by PIZA (1946) for the sex chromosomes of Hemiptera In Hypselonotus subterpunctatus the sex chromosome, in the first division of the spermatocytes, orients like the tetrads and divides transversaly. In the second division, as its kinetochore becomes inactive, it remans monocentric, does not orient in the spindle, and is finally enclosed in the nearer nucleus. In the secondary telophase it recuperates its dicentricity like the autosomal chromatids. This behavior corresponds to case (c) of PIZA (1946).

Vergleich der Effektivität von CT-gesteuerter Brachytherapie gegenüber transarterieller Chemoembolisation bei Patienten mit inoperablem HCC : Interimsanalyse zur entgültigen Fallzahlplanung einer randomisierten Phase-III-Studie

Magdeburg, Univ., Med. Fak., Diss., 2011

Formation and crystallization based separation of diastereomeric salts

Magdeburg, Univ., Fak. für Verfahrens- und Systemtechnik, Diss., 2012

Postnatal maternal separation affects hippocampal longterm potentiation in adult stressed rats : molecular and hormonal mechanisms

Magdeburg, Univ., Fak. für Naturwiss., Diss., 2013

Growth of semi-polar GaN on high index silicon (11h) substrates by metal organic vapor phase epitaxy

Magdeburg, Univ., Fak. für Naturwiss., Diss., 2014

Designing crystallization based-enantiomeric separation for chiral compound-forming systems in consideration of polymorphism and solvate formation

Magdeburg, Univ., Fak. für Verfahrens- und Systemtechnik, Diss., 2014

Design of biped robot walking with double-support phase

Otto-von-Guericke-Universität Magdeburg, Fakultät für Maschinenbau, Univ., Dissertation, 2015