Emerging fractal patterns in a real 3D cerebral aneurysm

The behaviour of biological fluid flows is often investigated in medical practice to draw conclusions on the physiological or pathological conditions of the considered organs. One area where such investigations are proven to be useful is the flow-related formation and growth of different pathologic malformations of the cerebro vascular system. In this work, a detailed study is presented on the effect of a cerebral aneurysm on blood transport inside a human brain artery segment. This malformation causes strong flow instabilities that drives the flow system towards chaotic behaviour. The emerging fractal structure and some of its measurable properties have been explored using a method that makes the measurement of these properties feasible even in complicated large three dimensional data sets. We find that, from the investigated chaos parameters, the information dimension turns out to be the most reliable parameter to characterize chaotic advection in the vicinity of the aneurysm sac. We propose that properties of chaotic mixing close to aneurysms might be relevant for the condition of this pathologic malformation

Tracing back the source of contamination

From the time a contaminant is detected in an observation well, the question of where and when the contaminant was introduced in the aquifer needs an answer. Many techniques have been proposed to answer this question, but virtually all of them assume that the aquifer and its dynamics are perfectly known. This work discusses a new approach for the simultaneous identification of the contaminant source location and the spatial variability of hydraulic conductivity in an aquifer which has been validated on synthetic and laboratory experiments and which is in the process of being validated on a real aquifer

Psr1p interacts with SUN/sad1p and EB1/mal3p to establish the bipolar spindle

Regular Abstracts - Sunday Poster Presentations: no. 382During mitosis, interpolar microtubules from two spindle pole bodies (SPBs) interdigitate to create an antiparallel microtubule array for accommodating numerous regulatory proteins. Among these proteins, the kinesin-5 cut7p/Eg5 is the key player responsible for sliding apart antiparallel microtubules and thus helps in establishing the bipolar spindle. At the onset of mitosis, two SPBs are adjacent to one another with most microtubules running nearly parallel toward the nuclear envelope, creating an unfavorable microtubule configuration for the kinesin-5 kinesins. Therefore, how the cell organizes the antiparallel microtubule array in the first place at mitotic onset remains enigmatic. Here, we show that a novel protein psrp1p localizes to the SPB and plays a key role in organizing the antiparallel microtubule array. The absence of psr1+ leads to a transient monopolar spindle and massive chromosome loss. Further functional characterization demonstrates that psr1p is recruited to the SPB through interaction with the conserved SUN protein sad1p and that psr1p physically interacts with the conserved microtubule plus tip protein mal3p/EB1. These results suggest a model that psr1p serves as a linking protein between sad1p/SUN and mal3p/EB1 to allow microtubule plus ends to be coupled to the SPBs for organization of an antiparallel microtubule array. Thus, we conclude that psr1p is involved in organizing the antiparallel microtubule array in the first place at mitosis onset by interaction with SUN/sad1p and EB1/mal3p, thereby establishing the bipolar spindle.postprin

Removal of antagonistic spindle forces can rescue metaphase spindle length and reduce chromosome segregation defects

Regular Abstracts - Tuesday Poster Presentations: no. 1925Metaphase describes a phase of mitosis where chromosomes are attached and oriented on the bipolar spindle for subsequent segregation at anaphase. In diverse cell types, the metaphase spindle is maintained at a relatively constant length. Metaphase spindle length is proposed to be regulated by a balance of pushing and pulling forces generated by distinct sets of spindle microtubules and their interactions with motors and microtubule-associated proteins (MAPs). Spindle length appears important for chromosome segregation fidelity, as cells with shorter or longer than normal metaphase spindles, generated through deletion or inhibition of individual mitotic motors or MAPs, showed chromosome segregation defects. To test the force balance model of spindle length control and its effect on chromosome segregation, we applied fast microfluidic temperature-control with live-cell imaging to monitor the effect of switching off different combinations of antagonistic forces in the fission yeast metaphase spindle. We show that spindle midzone proteins kinesin-5 cut7p and microtubule bundler ase1p contribute to outward pushing forces, and spindle kinetochore proteins kinesin-8 klp5/6p and dam1p contribute to inward pulling forces. Removing these proteins individually led to aberrant metaphase spindle length and chromosome segregation defects. Removing these proteins in antagonistic combination rescued the defective spindle length and, in some combinations, also partially rescued chromosome segregation defects. Our results stress the importance of proper chromosome-to-microtubule attachment over spindle length regulation for proper chromosome segregation.postprin

Empty Your Eyes and Bite the Star: Fragments, Entropy, Confabulation, and Structure in Cut-up Methods

Cut-up method has been notably applied as an avant-garde form. It originated as a piece of anti-art and its most famous practitioner, William Burroughs, used its fragmentary aesthetic to complement his transgressive subject matter. This thesis explores cut-up method’s relationship with Surrealist painting and its application as a means to the marvellous; the method’s ability to surprise both writers and readers. It addresses the central question: how can the Cut-up method be used to disassemble text and explore how the fragments can be constructed, reconstructed, or deliberately misconstructed to create a new text? I have adopted a cognitive approach to the analytical essays, which draw upon cross-disciplinary material including art history, literary criticism, cognitive science, information theory, computing, and the neuroscience of memory. The theoretical analysis and creative practice are integrated in both process and form. Discourses from the theoretical essays are mapped and remapped onto the creative practice and back again. Associated concepts such as fragments, entropy, confabulation, structure, and entrainment are examined both in the fiction and analysis. Empty your Eyes and Bite the Star identifies how, when viewed as a way of writing, cut-up operates from the bottom up rather than top down as in conventional models of practice; and explores the resulting differences in process and structure. It demonstrates the method’s usefulness as a means of generating original text but also shows how cognition imposes certain limitations on its effectiveness. It identifies areas that may be explored by practitioners to effectively target aleatory methods within new domains of creative practice and identifies how further research into the use of cut-up is possible using a quantitative analytical approach