Arrays of coupled chemical oscillators

Oscillating chemical reactions result from complex periodic changes in the concentration of the reactants. In spatially ordered ensembles of candle flame oscillators the fluctuations in the ratio of oxygen atoms with respect to that of carbon, hydrogen and nitrogen produces an oscillation in the visible part of the flame related to the energy released per unit mass of oxygen. Thus, the products of the reaction vary in concentration as a function of time, giving rise to an oscillation in the amount of soot and radiative emission. Synchronisation of interacting dynamical sub-systems occurs as arrays of flames that act as master and slave oscillators, with groups of candles numbering greater than two, creating a synchronised motion in three-dimensions. In a ring of candles the visible parts of each flame move together, up and down and back and forth, in a manner that appears like a “worship”. Here this effect is shown for rings of flames which collectively empower a central flame to pulse to greater heights. In contrast, situations where the central flames are suppressed are also found. The phenomena leads to in-phase synchronised states emerging between periods of anti-phase synchronisation for arrays with different columnar sizes of candle and positioning

Visualization and 3D Reconstruction of Flame Cells of Taenia solium (Cestoda)

BACKGROUND: Flame cells are the terminal cells of protonephridial systems, which are part of the excretory systems of invertebrates. Although the knowledge of their biological role is incomplete, there is a consensus that these cells perform excretion/secretion activities. It has been suggested that the flame cells participate in the maintenance of the osmotic environment that the cestodes require to live inside their hosts. In live Platyhelminthes, by light microscopy, the cells appear beating their flames rapidly and, at the ultrastructural, the cells have a large body enclosing a tuft of cilia. Few studies have been performed to define the localization of the cytoskeletal proteins of these cells, and it is unclear how these proteins are involved in cell function. METHODOLOGY/PRINCIPAL FINDINGS: Parasites of two different developmental stages of T. solium were used: cysticerci recovered from naturally infected pigs and intestinal adults obtained from immunosuppressed and experimentally infected golden hamsters. Hamsters were fed viable cysticerci to recover adult parasites after one month of infection. In the present studies focusing on flame cells of cysticerci tissues was performed. Using several methods such as video, confocal and electron microscopy, in addition to computational analysis for reconstruction and modeling, we have provided a 3D visual rendition of the cytoskeletal architecture of Taenia solium flame cells. CONCLUSIONS/SIGNIFICANCE: We consider that visual representations of cells open a new way for understanding the role of these cells in the excretory systems of Platyhelminths. After reconstruction, the observation of high resolution 3D images allowed for virtual observation of the interior composition of cells. A combination of microscopic images, computational reconstructions and 3D modeling of cells appears to be useful for inferring the cellular dynamics of the flame cell cytoskeleton

Camas, Fall 2005

Hard Miles in the Dark / Janisse Ray -- Teddy’s Vision / Hank Green -- Seasons of Smoke / Cedar Brant -- Remembering Animals / Catherine Meeks -- Review / Michael Ableman -- Poetry / Kim Stafford, Becca Hall, John Noland, Kathy Conde, Craig Rigdon -- First Person / Robin Patten -- Profile: Into the Abyss / Jeff Gailu

Turbulence Transition in Shear Flows and Dynamical Systems Theory

Turbulence is allegedly “the most important unsolved problem of classical physics” (attributed to Richard Feynman). While the equations of motion are known since almost 150 years and despite the work of many physicists, in particular the transition to turbulence in linearly stable shear flows evades a satisfying description. In recent decades, the availability of more powerful computers and developments in chaos theory have provided the basis for considerable progress in our understanding of this issue. The successful work of many scientists proved dynamical systems theory to be a useful and important tool to analyze transitional turbulence in fluid mechanics, allowing to explain observed phenomena such as transition thresholds and transient lifetimes through bifurcation analyses and the identification of underlying state space structures. In this thesis we continue on that path with direct numerical simulations in plane Couette flow, the asymptotic suction boundary layer and Blasius boundary layers. We explore the state space structures and bifurcations in plane Couette flow, study the threshold dynamics in the ASBL and develop a model for the spatio-temporal dynamics in the boundary layers. The results show how the insights obtained for parallel, bounded shear flows can be transferred to spatially developing external flows

Microgravity Science and Applications. Program Tasks and Bibliography for FY 1993

An annual report published by the Microgravity Science and Applications Division (MSAD) of NASA is presented. It represents a compilation of the Division's currently-funded ground, flight and Advanced Technology Development tasks. An overview and progress report for these tasks, including progress reports by principal investigators selected from the academic, industry and government communities, are provided. The document includes a listing of new bibliographic data provided by the principal investigators to reflect the dissemination of research data during FY 1993 via publications and presentations. The document also includes division research metrics and an index of the funded investigators. The document contains three sections and three appendices: Section 1 includes an introduction and metrics data, Section 2 is a compilation of the task reports in an order representative of its ground, flight or ATD status and the science discipline it represents, and Section 3 is the bibliography. The three appendices, in the order of presentation, are: Appendix A - a microgravity science acronym list, Appendix B - a list of guest investigators associated with a biotechnology task, and Appendix C - an index of the currently funded principal investigators

Studies of the Physical Aspects of Intumescence Using Advanced Diagnostic Methods

Commercial testing of Intumescent paints can be extremely expensive. There is a need to develop lab scale systems that can cost effectively both study and test intumescent paints under conditions that are closer to commercial and real time fire tests. This research aims to present a strong case for using an impinging flame based rig to test intumescent coatings. The main feature of using flame impingement is the heterogeneous absorption of heat along the wall surface. This property is a great advantage because intumescent paints under complex fire conditions can be simulated more realistically. The heating technique is coupled with advance diagnostics methods to highlight behaviour that has not been observed before. Physical aspects of commercial coatings, under the new setup, are compared to the cone calorimeter – traditional testing setup The process of intumescence was observed through the use of diagnostic techniques such as Schlieren, thermal and digital imaging. Cross sectional area and surface textures were captured using digital images of fully intumesced char samples that revealed distinct internal structures and surface textures. Temperature of the substrate, Tb, was recorded using a thermocouple attached to the back surface of the panel under different heating conditions. Schlieren technique, based on the refraction of light phenomenon, has never been use to examine the physical aspects of intumescence. It helped highlight the interaction between the flame and paint surface. The impingement of non-reactive fuel, at low separations was clearly visible and was responsible for influencing mode shape of the resulting char. The expulsions phenomenon observed using this technique has not been visually observed before. It occurred during the pustule appearance phase offering conclusive evidence that invisible gases escape from the surface of the paint. The measurement of char expansion and its rate of growth whilst engulfed in luminous diffusion flames is a methodology developed using this technique. The results revealed that formulations tested had unique expansion behaviours and growth pattern. Furthermore, an expansion activation temperature (EAT) range with respect to substrate temperature was identified for each formulation, which was found to be consistent under a variety of experimental conditions. The distinctive yellow colour of a diffusion flames engulfs a coating during a test. Due to this, the process of intumescence has not been observed visually. Thermal imaging was used in this study because it allowed the user to bypass the flame and observe intumescence as it occurred. Using thermal imaging, the physical aspects of intumescence were studied in extensive detail and salient characteristics were identified. The appearance of surface pustules followed by majority of the expansion were characterised as the two distinct phases in the intumescence process. Analysis of the surface temperature revealed that the thermal profile of the surface was non-uniform and highly localized in nature. This was attributed to the higher temperature of the pustules relative to the paint surface. Results from thermal imaging combined well with the Schlieren technique to develop a coherent understanding of the expansion process. Diagnostic equipment, particularly thermal and digital imaging, were also used on tests conducted in a cone calorimeter. The results between cone heater and impinging flame-based tests were compared. The degree of intumescence, surface temperature profile and various characteristics were found to be different between both methods. Finally, the use of the techniques was extended to study the process of intumescence and complex char growth patterns on T-shaped panels coated with intumescent formulations. Char growth was observed to be complex and non-linear as compared to flat panel systems. A novel Image processing algorithm using the thermal imaging data from the cone calorimeter was developed marking a further advancement to the use of this technique and gain insight into the growth mechanism when examining a complicated three dimensional system such T-panels

Fifth International Microgravity Combustion Workshop

This conference proceedings document is a compilation of 120 papers presented orally or as poster displays to the Fifth International Microgravity Combustion Workshop held in Cleveland, Ohio on May 18-20, 1999. The purpose of the workshop is to present and exchange research results from theoretical and experimental work in combustion science using the reduced-gravity environment as a research tool. The results are contributed by researchers funded by NASA throughout the United States at universities, industry and government research agencies, and by researchers from at least eight international partner countries that are also participating in the microgravity combustion science research discipline. These research results are intended for use by public and private sector organizations for academic purposes, for the development of technologies needed for the Human Exploration and Development of Space, and to improve Earth-bound combustion and fire-safety related technologies

The Residue of Flight: Investigations Into the Life of Matter

This thesis is a journey that unfolds alongside the transformations of a river during springtime. Moods and movements captured by Ted Hughes in his poem Stump Pool in April inspire a series of explorations that set out to express the affective vectors of the river’s becoming through sculpture and architecture. The thesis is a manifestation of this search. Arranged as a narrative in five chapters, each offers an account of the emergence of the five works. The first three are a sculptural response to each stanza of the poem: Prometheus manifests the river’s phase-shift from ice to water, Sky Burial from water to steam and Icarus the passage of steam rising towards the sun. Prometheus’ torment, the tearing dispersal of the body during a funerary ritual and the ecstatic flight of Icarus are caught through three material and fire based experiments. Chapter four reflects on these works while investigating the conception and construction of the Bruder Klaus Chapel by the renowned Swiss architect Peter Zumthor. The fifth chapter moves the exploration from sculpture to architectural design deploying the lessons learned from the previous works. Forces of descent rather than ascent now inform the creation of a torrential void, A Lover’s Enclosure. The trajectory in each work and through the series is guided by what feels right, by the unpredictability of the material imagination, working by hand, and by forming and re-forming reoccurring themes as they reverberate and transform in a continuum of affective transformations

Molecular force measurements in desmosomes

Desmosomes are cell–cell adhesion sites especially important in heart and skin tissues. Both tissues are exposed to mechanical stress and desmosomes are essential for stable cell–cell adhesion but whether and how forces act on desmosomes was unclear. Here, a desmoplakin tension sensor was developed reporting on molecular forces experienced by desmoplakin, which is essential for the connection to the intermediate filament cytoskeleton. Tension measured with the desmoplakin tension sensor can therefore also serve as a proxy for forces transduced across desmosomes towards the intermediate filament cytoskeleton. Fluorescence lifetime imaging microscopy (FLIM)-based Förster resonance energy transfer (FRET) measurements of the desmoplakin tension sensor revealed the absence of desmoplakin forces during the formation of desmomes in keratinocytes. Forces are experienced by desmoplakin, however, on very soft substrates, where the substrate stiffness is in the range of the intermediate filament stiffness. Furthermore, desmosomes are transiently loaded in response to external mechanical stress. The stress-induced loading depends on the magnitude and orientation of the applied tissue deformation. These observations suggest that desmosomes act as stress absorbers and evolved in mammalian tissues to complement adherens junctions especially in more extreme situations. Next to the development and experiments with the desmoplakin tension sensor, the fluorescence lifetime analysis and merge software (FLAMES) was developed. The software provides an automated data analysis pipeline for FRET-based tension sensor experiments measured with FLIM. FLAMES thereby improves the estimation of lifetimes from photon count curves for the signal of interest. Moreover, FLAMES also allows the determination of the relative amount of molecules under tension, which provides a new way for the analysis of tension sensor experiments.Desmosomen sind Zellkontakte zwischen benachbarten Zellen und besonders wichtig im Herzen und in der Haut, die starker mechanischer Belastung ausgesetzt sind. Für eine stabile Zelladhäsion sind Desmosomen unerlässlich, aber es war bisher nicht bekannt ob Desmosomen direkt an der Kraftweiterleitung beteiligt sind. In dieser Arbeit wurde ein Desmoplakin-Kraftsensor entwickelt, der die Kraft über Desmoplakin ausliest. Desmoplakin ist ein essentieller Bestandteil von Desmosomen und bindet an Intermediärfilamente, welche ein wesentlicher Bestandteil des Zytoskeletts sind. Die Kraft über Desmoplakin kann daher auch als Näherung dienen für die Kraft, die über Desmosomen zum Zytoskelett weitergeitet wird. Um den Kraftsensor auszulesen, wurde die Effizienz des Förster-Resonanzenergietransfers (FRET) mit Hilfe von Fluoreszenzlebensdauermessungen (engl. FLIM) bestimmt. Diese Experimente zeigten, dass bei der Bildung von Desmosomen keine Kraft über Desmosomen ans Zytoskelett weitergeleitet wird. Wenn sich die Keratinozytenzellschicht allerdings auf einem sehr weichen Untergrund befindet, wird Kraft an Desmosomen gemessen. Im Unterschied zu den Experimenten auf festeren Untergründen ist die Umgebung in dieser Situation etwa genauso weich wie die Intermediärfilamente. Außerdem sind Desmosomen unter Kraft, wenn sie akut extern mechanisch belastet werden und zwar in Abhängigikeit von der Stärke und Orientierung der externen Belastung. Diese Beobachtungen unterstützen ein Model in dem Desmosomen in Säugetieren als weitere Zellkontakte neben Adhäsionsverbindungen entstanden sind, um zusätzliche Belastungen in extremeren Situationen abzufedern. Neben der Entwicklung und Experimenten mit dem Desmoplakin-Kraftsensor, wurde auch FLAMES (engl. fluorescence lifetime analysis and merge software) zur Analyse von Fluoreszenzlebensdauern und zum Zusammenführen von Daten entwickelt. Das Programm ermöglicht eine automatisierte Auswertung von Kraftsensorexperimenten, in denen FRET in verschiedenen Konstrukten mit Hilfe von FLIM bestimmt wird. Mit FLAMES können dabei die Fluoreszenzlebensdauern aus den Ankunftszeiten von Photonen innerhalb des spezifischen Signals bestimmt werden. Zudem kann auch der relative Anteil der Moleküle berechnet werden, die unter ausreichend Kraft stehen um den Kraftsensor zu öffnen, was einen neuen Weg darstellt die Daten eines Kraftsensorexperiments auszuwerten