WorldWideScience

Sample records for aspect pattern formation

  1. Mathematical aspects of pattern formation in biological systems

    CERN Document Server

    Wei, Juncheng

    2013-01-01

    This monograph is concerned with the mathematical analysis of patterns which are encountered in biological systems. It summarises, expands and relates results obtained in the field during the last fifteen years. It also links the results to biological applications and highlights their relevance to phenomena in nature. Of particular concern are large-amplitude patterns far from equilibrium in biologically relevant models.The approach adopted in the monograph is based on the following paradigms:• Examine the existence of spiky steady states in reaction-diffusion systems and select as observabl

  2. Pattern Formation

    Science.gov (United States)

    Hoyle, Rebecca

    2006-03-01

    From the stripes of a zebra and the spots on a leopard's back to the ripples on a sandy beach or desert dune, regular patterns arise everywhere in nature. The appearance and evolution of these phenomena has been a focus of recent research activity across several disciplines. This book provides an introduction to the range of mathematical theory and methods used to analyse and explain these often intricate and beautiful patterns. Bringing together several different approaches, from group theoretic methods to envelope equations and theory of patterns in large-aspect ratio-systems, the book also provides insight behind the selection of one pattern over another. Suitable as an upper-undergraduate textbook for mathematics students or as a fascinating, engaging, and fully illustrated resource for readers in physics and biology, Rebecca Hoyle's book, using a non-partisan approach, unifies a range of techniques used by active researchers in this growing field. Accessible description of the mathematical theory behind fascinating pattern formation in areas such as biology, physics and materials science Collects recent research for the first time in an upper level textbook Features a number of exercises - with solutions online - and worked examples

  3. High Aspect Pattern Formation by Integration of Micro Inkjetting and Electroless Plating

    CERN Document Server

    Gian, P W; Liang, Y N; Lok, B K; Lu, C W; Ooi, B L

    2008-01-01

    This paper reports on formation of high aspect micro patterns on low temperature co-fired ceramic (LTCC) substrates by integrating micro inkjetting with electroless plating. Micro inkjetting was realized by using an inkjetting printer that ejects ink droplets from a printhead. This printhead consists of a glass nozzle with a diameter of 50 micrometers and a piezoelectric transducer that is coated on the nozzle. The silver colloidal solution was inkjetted on a sintered CT800 ceramic substrate, followed by curing at 200 degrees C for 60 minutes. As a result, the silver trace with a thickness of 200 nm was obtained. The substrate, with the ejected silver thin film as the seed layer, was then immersed into a preinitiator solution to coat a layer of palladium for enhancing the deposition of nickel. Electroless nickel plating was successfully conducted at a rate of 0.39 micrometers /min, and the thickness of traces was plated up to 84 micrometers. This study demonstrates that the integration of inkjetting with plat...

  4. Pattern formations and oscillatory phenomena

    CERN Document Server

    Kinoshita, Shuichi

    2013-01-01

    Patterns and their formations appear throughout nature, and are studied to analyze different problems in science and make predictions across a wide range of disciplines including biology, physics, mathematics, chemistry, material science, and nanoscience. With the emergence of nanoscience and the ability for researchers and scientists to study living systems at the biological level, pattern formation research has become even more essential. This book is an accessible first of its kind guide for scientists, researchers, engineers, and students who require a general introduction to thi

  5. Modeling generic aspects of ideal fibril formation

    CERN Document Server

    Michel, Denis

    2016-01-01

    Many different proteins self-aggregate into insoluble fibrils growing apically by reversible addition of elementary building blocks. But beyond this common principle, the modalities of fibril formation are very disparate, with various intermediate forms which can be reshuffled by minor modifications of physico-chemical conditions or amino-acid sequences. To bypass this complexity, the multifaceted phenomenon of fibril formation is reduced here to its most elementary principles defined for a linear prototype of fibril. Selected generic features, including nucleation, elongation and conformational recruitment, are modeled using minimalist hypotheses and tools, by separating equilibrium from kinetic aspects and in vitro from in vivo conditions. These reductionist approaches allow to bring out known and new rudiments, including the kinetic and equilibrium effects of nucleation, the dual influence of elongation on nucleation, the kinetic limitations on nucleation and fibril numbers and the accumulation of complexe...

  6. Pattern formation in optical resonators

    International Nuclear Information System (INIS)

    We review pattern formation in optical resonators. The emphasis is on 'particle-like' structures such as vortices or spatial solitons. On the one hand, similarities impose themselves with other fields of physics (condensed matter, phase transitions, particle physics, fluds/super fluids). On the other hand the feedback is led by the resonator mirrors to bi- and multi-stability of the spatial field structure, which is the basic ingredient for optical information processing. The spatial dimension or the 'parallelism' is the strength of optics compared to electronics (and will have to be employed to fully use the advantages optics offers in information processing). But even in the 'serial' processing tasks of telecoms (e.g. information buffering) spatial resonator solitons can do better than the schemes proposed so far-including 'slow light'. Pattern formation in optical resonators will likely be the key to brain-like information processing like cognition, learning and association; to complement the precise but limited algorithmic capabilities of electronic processing. But even in the short term it will be useful for solving serial optical processing problems. The prospects for technical uses of pattern formation in resonators are one motivation for this research. The fundamental similarities with other fields of physics, on the other hand, inspire transfer of concepts between fields; something that has always proven fruitful for gaining deeper insights or for solving technical problems

  7. Modeling generic aspects of ideal fibril formation

    Energy Technology Data Exchange (ETDEWEB)

    Michel, D., E-mail: denis.michel@live.fr [Universite de Rennes1-IRSET, Campus de Beaulieu Bat. 13, 35042 Rennes (France)

    2016-01-21

    Many different proteins self-aggregate into insoluble fibrils growing apically by reversible addition of elementary building blocks. But beyond this common principle, the modalities of fibril formation are very disparate, with various intermediate forms which can be reshuffled by minor modifications of physico-chemical conditions or amino-acid sequences. To bypass this complexity, the multifaceted phenomenon of fibril formation is reduced here to its most elementary principles defined for a linear prototype of fibril. Selected generic features, including nucleation, elongation, and conformational recruitment, are modeled using minimalist hypotheses and tools, by separating equilibrium from kinetic aspects and in vitro from in vivo conditions. These reductionist approaches allow to bring out known and new rudiments, including the kinetic and equilibrium effects of nucleation, the dual influence of elongation on nucleation, the kinetic limitations on nucleation and fibril numbers, and the accumulation of complexes in vivo by rescue from degradation. Overlooked aspects of these processes are also pointed: the exponential distribution of fibril lengths can be recovered using various models because it is attributable to randomness only. It is also suggested that the same term “critical concentration” is used for different things, involved in either nucleation or elongation.

  8. Magnetic Assisted Colloidal Pattern Formation

    Science.gov (United States)

    Yang, Ye

    Pattern formation is a mysterious phenomenon occurring at all scales in nature. The beauty of the resulting structures and myriad of resulting properties occurring in naturally forming patterns have attracted great interest from scientists and engineers. One of the most convenient experimental models for studying pattern formation are colloidal particle suspensions, which can be used both to explore condensed matter phenomena and as a powerful fabrication technique for forming advanced materials. In my thesis, I have focused on the study of colloidal patterns, which can be conveniently tracked in an optical microscope yet can also be thermally equilibrated on experimentally relevant time scales, allowing for ground states and transitions between them to be studied with optical tracking algorithms. In particular, I have focused on systems that spontaneously organize due to particle-surface and particle-particle interactions, paying close attention to systems that can be dynamically adjusted with an externally applied magnetic or acoustic field. In the early stages of my doctoral studies, I developed a magnetic field manipulation technique to quantify the adhesion force between particles and surfaces. This manipulation technique is based on the magnetic dipolar interactions between colloidal particles and their "image dipoles" that appear within planar substrate. Since the particles interact with their own images, this system enables massively parallel surface force measurements (>100 measurements) in a single experiment, and allows statistical properties of particle-surface adhesion energies to be extracted as a function of loading rate. With this approach, I was able to probe sub-picoNewton surface interactions between colloidal particles and several substrates at the lowest force loading rates ever achieved. In the later stages of my doctoral studies, I focused on studying patterns formed from particle-particle interaction, which serve as an experimental model of

  9. Pattern Formation and Complexity Emergence

    Science.gov (United States)

    Berezin, Alexander A.

    2001-03-01

    Success of nonlinear modelling of pattern formation and self-organization encourages speculations on informational and number theoretical foundations of complexity emergence. Pythagorean "unreasonable effectiveness of integers" in natural processes is perhaps extrapolatable even to universal emergence "out-of-nothing" (Leibniz, Wheeler). Because rational numbers (R = M/N) are everywhere dense on real axis, any digital string (hence any "book" from "Library of Babel" of J.L.Borges) is "recorded" infinitely many times in arbitrary many rationals. Furthermore, within any arbitrary small interval there are infinitely many Rs for which (either or both) integers (Ms and Ns) "carry" any given string of any given length. Because any iterational process (such as generation of fractal features of Mandelbrot Set) is arbitrary closely approximatable with rational numbers, the infinite pattern of integers expresses itself in generation of complexity of the world, as well as in emergence of the world itself. This "tunnelling" from Platonic World ("Platonia" of J.Barbour) to a real (physical) world is modern recast of Leibniz's motto ("for deriving all from nothing there suffices a single principle").

  10. Pattern formation in centrosome assembly.

    Science.gov (United States)

    Mahen, Robert; Venkitaraman, Ashok R

    2012-02-01

    A striking but poorly explained feature of cell division is the ability to assemble and maintain organelles not bounded by membranes, from freely diffusing components in the cytosol. This process is driven by information transfer across biological scales such that interactions at the molecular scale allow pattern formation at the scale of the organelle. One important example of such an organelle is the centrosome, which is the main microtubule organising centre in the cell. Centrosomes consist of two centrioles surrounded by a cloud of proteins termed the pericentriolar material (PCM). Profound structural and proteomic transitions occur in the centrosome during specific cell cycle stages, underlying events such as centrosome maturation during mitosis, in which the PCM increases in size and microtubule nucleating capacity. Here we use recent insights into the spatio-temporal behaviour of key regulators of centrosomal maturation, including Polo-like kinase 1, CDK5RAP2 and Aurora-A, to propose a model for the assembly and maintenance of the PCM through the mobility and local interactions of its constituent proteins. We argue that PCM structure emerges as a pattern from decentralised self-organisation through a reaction-diffusion mechanism, with or without an underlying template, rather than being assembled from a central structural template alone. Self-organisation of this kind may have broad implications for the maintenance of mitotic structures, which, like the centrosome, exist stably as supramolecular assemblies on the micron scale, based on molecular interactions at the nanometer scale. PMID:22245706

  11. Pattern Formation by Competition: A Biological Example

    OpenAIRE

    M. Bezzi; Ciliberto, A.; A.Mengoni

    1999-01-01

    We present a simple model based on a reaction-diffusion equation to explain pattern formation in a multicellular bacterium (Streptomyces). We assume competition for resources as the basic mechanism that leads to pattern formation; in particular we are able to reproduce the spatial pattern formed by bacterial aerial mycelium in the case of growth in minimal (low resources) and maximal (large resources) culture media.

  12. Pattern formation in quantum networks

    Science.gov (United States)

    Kim, Ilki; Mahler, Günter

    1999-03-01

    We investigate the iteration of a sequence of local and pair unitary transformations (quantum gate approximation), which can be interpreted to result from a Turing-head (pseudo-spin S) rotating along a closed Turing-tape (M additional pseudo-spins). The dynamical evolution of the Bloch-vector of S, which can be decomposed into 2M primitive pure state Turing-head trajectories, gives rise to fascinating geometrical patterns reflecting the entanglement between head and tape. For specific initial states ("input"), these patterns ("output") can be easily calculated for any tape size. We thus show intuitive examples for quantum parallelism and, at the same time, means for local testing of quantum network dynamics.

  13. Separation vortices and pattern formation

    DEFF Research Database (Denmark)

    Andersen, Anders Peter; Bohr, Tomas; Schnipper, Teis

    2010-01-01

    In this paper examples are given of the importance of flow separation for fluid patterns at moderate Reynolds numbers—both in the stationary and in the time-dependent domain. In the case of circular hydraulic jumps, it has been shown recently that it is possible to generalise the Prandtl......–Kármán–Pohlhausen approach to stationary boundary layers with free surfaces going through separation, and thus obtain a quantitative theory of the simplest type of hydraulic jump, where a single separation vortex is present outside the jump. A second type of jump, where an additional roller appears at the surface, cannot...... oscillatory flow, where the separation vortices become very strong. In this case no simple theory exists for the determination of the location and strengths of separation vortices over a wavy bottom of arbitrary profile. We have, however, recently suggested an amplitude equation describing the long...

  14. Pattern Formation in Driven Systems

    Science.gov (United States)

    Klymko, Katherine

    Model colloidal particles of two types, driven in opposite directions, will in two dimensions segregate into lanes, a phenomenon studied extensively by Lowen and co-workers [Dzubiella et al. Phys. Rev. E 65, 021402 (2002)]. We have simulated mixtures of oppositely-driven particles using three numerical protocols. We find that laning results from enhanced diffusion, in the direction perpendicular to the drive, of particles surrounded by particles of the opposite type, consistent with the observation of Vissers et al. [Soft Matter 7, 6, 2352 (2011)]. By comparing protocols we find that enhanced diffusion follows from a simple geometrical constraint: oppositely-driven particles must, in the time taken to encounter each other in the direction of the drive, diffuse in the perpendicular direction by about one particle diameter. This constraint implies that the effective lateral diffusion constant grows linearly with drive speed and as the square root of the packing fraction, a prediction supported by our numerics. By invoking an analogy between hard particles with environment-dependent mobilities and mutually attractive particles we argue that there exists an equilibrium system whose pattern-forming properties are similar to those of the driven system. Katherine Klymko acknowledges support from the NSF Graduate Research Fellowship.

  15. Additional aspects of facies determination of the Souza Formation

    International Nuclear Information System (INIS)

    By means of geochemical analysis of total sample and trace elements, x-ray and DTA investigation of the clay fractions, and microfanes study, obtained by the facies determination of the Souza Formation, some additional aspects giving evidence of the sequence of events responsable by origin, deposition and formation of sediments of this middle unit of the Rio do Peixe group were established. (Author)

  16. Pattern formation in Pseudomonas aeruginosa biofilms

    DEFF Research Database (Denmark)

    Parsek, Matthew R.; Tolker-Nielsen, Tim

    2008-01-01

    Bacteria are capable of forming elaborate multicellular communities called biofilms. Pattern formation in biofilms depends on cell proliferation and cellular migration in response to the available nutrients and other external cues, as well as on self-generated intercellular signal molecules...... and the production of an extracellular matrix that serves as a structural 'scaffolding' for the biofilm cells. Pattern formation in biofilms allows cells to position themselves favorably within nutrient gradients and enables buildup and maintenance of physiologically distinct subpopulations, which facilitates...... survival of one or more subpopulations upon environmental insult, and therefore plays an important role in the innate tolerance displayed by biofilms toward adverse conditions....

  17. Transverse optical and atomic pattern formation

    CERN Document Server

    Schmittberger, Bonnie L

    2016-01-01

    The study of transverse optical pattern formation has been studied extensively in nonlinear optics, with a recent experimental interest in studying the phenomenon using cold atoms, which can undergo real-space self-organization. Here, we describe our experimental observation of pattern formation in cold atoms, which occurs using less than 1 microWatt of applied power. We show that the optical patterns and the self-organized atomic structures undergo continuous symmetry-breaking, which is characteristic of non-equilibrium phenomena in a multimode system. To theoretically describe pattern formation in cold atoms, we present a self-consistent model that allows for tight atomic bunching in the applied optical lattice. We derive the nonlinear refractive index of a gas of multi-level atoms in an optical lattice, and we derive the threshold conditions under which pattern formation occurs. We show that, by using small detunings and sub-Doppler temperatures, one achieves two orders of magnitude reduced intensity thres...

  18. Pattern formation with a conservation law

    OpenAIRE

    Winterbottom, David Mark

    2006-01-01

    The evolution of many pattern-forming systems is strongly influenced by the presence of a conserved quantity. Diverse physical phenomena such as magnetoconvection, rotating fluid convection, binary fluid convection, vibrated granular and fluid layers, filament dynamics and sandbank formation, all possess a conservation law which plays a central role in their nonlinear dynamics. In this thesis, this influence of a conserved quantity is examined through analyses of three distinct pattern-form...

  19. Pattern Formation in a Bacterial Colony Model

    Directory of Open Access Journals (Sweden)

    Xinze Lian

    2014-01-01

    Full Text Available We investigate the spatiotemporal dynamics of a bacterial colony model. Based on the stability analysis, we derive the conditions for Hopf and Turing bifurcations. Furthermore, we present novel numerical evidence of time evolution of patterns controlled by parameters in the model and find that the model dynamics exhibit a diffusion controlled formation growth to spots, holes and stripes pattern replication, which show that the bacterial colony model is useful in revealing the spatial predation dynamics in the real world.

  20. Chaotic Turing pattern formation in spatiotemporal systems

    Institute of Scientific and Technical Information of China (English)

    XIAO Jing-hua; LI Hai-hong; YANG Jun-zhong; HU Gang

    2006-01-01

    The problem of Turing pattern formation has attracted much attention in nonlinear science as well as physics,chemistry and biology.So far spatially ordered Turing patterns have been observed in stationary and oscillatory media only.In this paper we find that spatially ordered Turing patterns exist in chaotic extended systems.And chaotic Turing patterns are strikingly rich and surprisingly beautiful with their space structures.These findings are in sharp contrast with the intuition of pseudo-randomness of chaos.The richness and beauty of the chaotic Turing patterns are attributed to a large variety of symmetry properties realized by various types of self-organizations of partial chaos synchronizations.

  1. N7 logic via patterning using templated DSA: implementation aspects

    Science.gov (United States)

    Bekaert, J.; Doise, J.; Gronheid, R.; Ryckaert, J.; Vandenberghe, G.; Fenger, G.; Her, Y. J.; Cao, Y.

    2015-07-01

    In recent years, major advancements have been made in the directed self-assembly (DSA) of block copolymers (BCP). Insertion of DSA for IC fabrication is seriously considered for the 7 nm node. At this node the DSA technology could alleviate costs for multiple patterning and limit the number of masks that would be required per layer. At imec, multiple approaches for inserting DSA into the 7 nm node are considered. One of the most straightforward approaches for implementation would be for via patterning through templated DSA; a grapho-epitaxy flow using cylindrical phase BCP material resulting in contact hole multiplication within a litho-defined pre-pattern. To be implemented for 7 nm node via patterning, not only the appropriate process flow needs to be available, but also DSA-aware mask decomposition is required. In this paper, several aspects of the imec approach for implementing templated DSA will be discussed, including experimental demonstration of density effect mitigation, DSA hole pattern transfer and double DSA patterning, creation of a compact DSA model. Using an actual 7 nm node logic layout, we derive DSA-friendly design rules in a logical way from a lithographer's view point. A concrete assessment is provided on how DSA-friendly design could potentially reduce the number of Via masks for a place-and-routed N7 logic pattern.

  2. Fractals in Spatial Patterns of Vegetation Formations

    Institute of Scientific and Technical Information of China (English)

    SONG Zhiyuan; HUANG Daming; Masae Shiyomi; WANG Yusheng; Shigeo Takahashi; Hori Yoshimichi; Yasuo Yamamuru; CHEN Jun

    2006-01-01

    The spatial distribution patterns of species are always scale-dependent and spatially self-similar in ecological systems. In this work, vegetation distribution data collected from the vegetation map of the Xigazê region was analyzed using a box-counting method. The power law of the box-counting dimension (DB) across a range of scales (5-160 km) confirms the fractal patterns for most vegetation formations, while the fluctuations of the scale-specific DB among the different abundance groups indicate limitations of fractal coherence. The fractal method is shown to be a useful tool for measuring the distribution patterns of vegetation formations across scales, which provides important information for both species and habitat conservation, especially in landscape management.

  3. Taming contact line instability for pattern formation

    Science.gov (United States)

    Deblais, A.; Harich, R.; Colin, A.; Kellay, H.

    2016-08-01

    Coating surfaces with different fluids is prone to instability producing inhomogeneous films and patterns. The contact line between the coating fluid and the surface to be coated is host to different instabilities, limiting the use of a variety of coating techniques. Here we take advantage of the instability of a receding contact line towards cusp and droplet formation to produce linear patterns of variable spacings. We stabilize the instability of the cusps towards droplet formation by using polymer solutions that inhibit this secondary instability and give rise to long slender cylindrical filaments. We vary the speed of deposition to change the spacing between these filaments. The combination of the two gives rise to linear patterns into which different colloidal particles can be embedded, long DNA molecules can be stretched and particles filtered by size. The technique is therefore suitable to prepare anisotropic structures with variable properties.

  4. Pattern formation in superdiffusion Oregonator model

    Science.gov (United States)

    Feng, Fan; Yan, Jia; Liu, Fu-Cheng; He, Ya-Feng

    2016-10-01

    Pattern formations in an Oregonator model with superdiffusion are studied in two-dimensional (2D) numerical simulations. Stability analyses are performed by applying Fourier and Laplace transforms to the space fractional reaction-diffusion systems. Antispiral, stable turing patterns, and travelling patterns are observed by changing the diffusion index of the activator. Analyses of Floquet multipliers show that the limit cycle solution loses stability at the wave number of the primitive vector of the travelling hexagonal pattern. We also observed a transition between antispiral and spiral by changing the diffusion index of the inhibitor. Project supported by the National Natural Science Foundation of China (Grant Nos. 11205044 and 11405042), the Research Foundation of Education Bureau of Hebei Province, China (Grant Nos. Y2012009 and ZD2015025), the Program for Young Principal Investigators of Hebei Province, China, and the Midwest Universities Comprehensive Strength Promotion Project.

  5. Sarcomeric Pattern Formation by Actin Cluster Coalescence

    Science.gov (United States)

    Friedrich, Benjamin M.; Fischer-Friedrich, Elisabeth; Gov, Nir S.; Safran, Samuel A.

    2012-01-01

    Contractile function of striated muscle cells depends crucially on the almost crystalline order of actin and myosin filaments in myofibrils, but the physical mechanisms that lead to myofibril assembly remains ill-defined. Passive diffusive sorting of actin filaments into sarcomeric order is kinetically impossible, suggesting a pivotal role of active processes in sarcomeric pattern formation. Using a one-dimensional computational model of an initially unstriated actin bundle, we show that actin filament treadmilling in the presence of processive plus-end crosslinking provides a simple and robust mechanism for the polarity sorting of actin filaments as well as for the correct localization of myosin filaments. We propose that the coalescence of crosslinked actin clusters could be key for sarcomeric pattern formation. In our simulations, sarcomere spacing is set by filament length prompting tight length control already at early stages of pattern formation. The proposed mechanism could be generic and apply both to premyofibrils and nascent myofibrils in developing muscle cells as well as possibly to striated stress-fibers in non-muscle cells. PMID:22685394

  6. Sarcomeric pattern formation by actin cluster coalescence.

    Directory of Open Access Journals (Sweden)

    Benjamin M Friedrich

    Full Text Available Contractile function of striated muscle cells depends crucially on the almost crystalline order of actin and myosin filaments in myofibrils, but the physical mechanisms that lead to myofibril assembly remains ill-defined. Passive diffusive sorting of actin filaments into sarcomeric order is kinetically impossible, suggesting a pivotal role of active processes in sarcomeric pattern formation. Using a one-dimensional computational model of an initially unstriated actin bundle, we show that actin filament treadmilling in the presence of processive plus-end crosslinking provides a simple and robust mechanism for the polarity sorting of actin filaments as well as for the correct localization of myosin filaments. We propose that the coalescence of crosslinked actin clusters could be key for sarcomeric pattern formation. In our simulations, sarcomere spacing is set by filament length prompting tight length control already at early stages of pattern formation. The proposed mechanism could be generic and apply both to premyofibrils and nascent myofibrils in developing muscle cells as well as possibly to striated stress-fibers in non-muscle cells.

  7. Visualization of Mined Pattern and Its Human Aspects

    CERN Document Server

    Jain, Ratnesh Kumar; Kasana, Dr R S

    2009-01-01

    Researchers got success in mining the Web usage data effectively and efficiently. But representation of the mined patterns is often not in a form suitable for direct human consumption. Hence mechanisms and tools that can represent mined patterns in easily understandable format are utilized. Different techniques are used for pattern analysis, one of them is visualization. Visualization can provide valuable assistance for data analysis and decision making tasks. In the data visualization process, technical representations of web pages are replaced by user attractive text interpretations. Experiments with the real world problems showed that the visualization can significantly increase the quality and usefulness of web log mining results. However, how decision makers perceive and interact with a visual representation can strongly influence their understanding of the data as well as the usefulness of the visual presentation. Human factors therefore contribute significantly to the visualization process and should p...

  8. Femtosecond Laser Patterning of the Biopolymer Chitosan for Biofilm Formation

    Directory of Open Access Journals (Sweden)

    Regina Estevam-Alves

    2016-08-01

    Full Text Available Controlling microbial growth is crucial for many biomedical, pharmaceutical and food industry applications. In this paper, we used a femtosecond laser to microstructure the surface of chitosan, a biocompatible polymer that has been explored for applications ranging from antimicrobial action to drug delivery. The influence of energy density on the features produced on chitosan was investigated by optical and atomic force microscopies. An increase in the hydrophilic character of the chitosan surface was attained upon laser micromachining. Patterned chitosan films were used to observe Staphylococcus aureus (ATCC 25923 biofilm formation, revealing an increase in the biofilm formation in the structured regions. Our results indicate that fs-laser micromachining is an attractive option to pattern biocompatible surfaces, and to investigate basic aspects of the relationship between surface topography and bacterial adhesion.

  9. Femtosecond Laser Patterning of the Biopolymer Chitosan for Biofilm Formation

    Science.gov (United States)

    Estevam-Alves, Regina; Ferreira, Paulo Henrique Dias; Coatrini, Andrey C.; Oliveira, Osvaldo N.; Fontana, Carla Raquel; Mendonca, Cleber Renato

    2016-01-01

    Controlling microbial growth is crucial for many biomedical, pharmaceutical and food industry applications. In this paper, we used a femtosecond laser to microstructure the surface of chitosan, a biocompatible polymer that has been explored for applications ranging from antimicrobial action to drug delivery. The influence of energy density on the features produced on chitosan was investigated by optical and atomic force microscopies. An increase in the hydrophilic character of the chitosan surface was attained upon laser micromachining. Patterned chitosan films were used to observe Staphylococcus aureus (ATCC 25923) biofilm formation, revealing an increase in the biofilm formation in the structured regions. Our results indicate that fs-laser micromachining is an attractive option to pattern biocompatible surfaces, and to investigate basic aspects of the relationship between surface topography and bacterial adhesion. PMID:27548153

  10. Morphogenesis and pattern formation in biological systems experiments and models

    CERN Document Server

    Noji, Sumihare; Ueno, Naoto; Maini, Philip

    2003-01-01

    A central goal of current biology is to decode the mechanisms that underlie the processes of morphogenesis and pattern formation. Concerned with the analysis of those phenomena, this book covers a broad range of research fields, including developmental biology, molecular biology, plant morphogenesis, ecology, epidemiology, medicine, paleontology, evolutionary biology, mathematical biology, and computational biology. In Morphogenesis and Pattern Formation in Biological Systems: Experiments and Models, experimental and theoretical aspects of biology are integrated for the construction and investigation of models of complex processes. This collection of articles on the latest advances by leading researchers not only brings together work from a wide spectrum of disciplines, but also provides a stepping-stone to the creation of new areas of discovery.

  11. Femtosecond Laser Patterning of the Biopolymer Chitosan for Biofilm Formation.

    Science.gov (United States)

    Estevam-Alves, Regina; Ferreira, Paulo Henrique Dias; Coatrini, Andrey C; Oliveira, Osvaldo N; Fontana, Carla Raquel; Mendonca, Cleber Renato

    2016-01-01

    Controlling microbial growth is crucial for many biomedical, pharmaceutical and food industry applications. In this paper, we used a femtosecond laser to microstructure the surface of chitosan, a biocompatible polymer that has been explored for applications ranging from antimicrobial action to drug delivery. The influence of energy density on the features produced on chitosan was investigated by optical and atomic force microscopies. An increase in the hydrophilic character of the chitosan surface was attained upon laser micromachining. Patterned chitosan films were used to observe Staphylococcus aureus (ATCC 25923) biofilm formation, revealing an increase in the biofilm formation in the structured regions. Our results indicate that fs-laser micromachining is an attractive option to pattern biocompatible surfaces, and to investigate basic aspects of the relationship between surface topography and bacterial adhesion. PMID:27548153

  12. Pattern Formation on Networks: from Localised Activity to Turing Patterns

    Science.gov (United States)

    McCullen, Nick; Wagenknecht, Thomas

    2016-06-01

    Networks of interactions between competing species are used to model many complex systems, such as in genetics, evolutionary biology or sociology and knowledge of the patterns of activity they can exhibit is important for understanding their behaviour. The emergence of patterns on complex networks with reaction-diffusion dynamics is studied here, where node dynamics interact via diffusion via the network edges. Through the application of a generalisation of dynamical systems analysis this work reveals a fundamental connection between small-scale modes of activity on networks and localised pattern formation seen throughout science, such as solitons, breathers and localised buckling. The connection between solutions with a single and small numbers of activated nodes and the fully developed system-scale patterns are investigated computationally using numerical continuation methods. These techniques are also used to help reveal a much larger portion of of the full number of solutions that exist in the system at different parameter values. The importance of network structure is also highlighted, with a key role being played by nodes with a certain so-called optimal degree, on which the interaction between the reaction kinetics and the network structure organise the behaviour of the system.

  13. Geometry-induced protein pattern formation.

    Science.gov (United States)

    Thalmeier, Dominik; Halatek, Jacob; Frey, Erwin

    2016-01-19

    Protein patterns are known to adapt to cell shape and serve as spatial templates that choreograph downstream processes like cell polarity or cell division. However, how can pattern-forming proteins sense and respond to the geometry of a cell, and what mechanistic principles underlie pattern formation? Current models invoke mechanisms based on dynamic instabilities arising from nonlinear interactions between proteins but neglect the influence of the spatial geometry itself. Here, we show that patterns can emerge as a direct result of adaptation to cell geometry, in the absence of dynamical instability. We present a generic reaction module that allows protein densities robustly to adapt to the symmetry of the spatial geometry. The key component is an NTPase protein that cycles between nucleotide-dependent membrane-bound and cytosolic states. For elongated cells, we find that the protein dynamics generically leads to a bipolar pattern, which vanishes as the geometry becomes spherically symmetrical. We show that such a reaction module facilitates universal adaptation to cell geometry by sensing the local ratio of membrane area to cytosolic volume. This sensing mechanism is controlled by the membrane affinities of the different states. We apply the theory to explain AtMinD bipolar patterns in [Formula: see text] EcMinDE Escherichia coli. Due to its generic nature, the mechanism could also serve as a hitherto-unrecognized spatial template in many other bacterial systems. Moreover, the robustness of the mechanism enables self-organized optimization of protein patterns by evolutionary processes. Finally, the proposed module can be used to establish geometry-sensitive protein gradients in synthetic biological systems. PMID:26739566

  14. Geometry-induced protein pattern formation.

    Science.gov (United States)

    Thalmeier, Dominik; Halatek, Jacob; Frey, Erwin

    2016-01-19

    Protein patterns are known to adapt to cell shape and serve as spatial templates that choreograph downstream processes like cell polarity or cell division. However, how can pattern-forming proteins sense and respond to the geometry of a cell, and what mechanistic principles underlie pattern formation? Current models invoke mechanisms based on dynamic instabilities arising from nonlinear interactions between proteins but neglect the influence of the spatial geometry itself. Here, we show that patterns can emerge as a direct result of adaptation to cell geometry, in the absence of dynamical instability. We present a generic reaction module that allows protein densities robustly to adapt to the symmetry of the spatial geometry. The key component is an NTPase protein that cycles between nucleotide-dependent membrane-bound and cytosolic states. For elongated cells, we find that the protein dynamics generically leads to a bipolar pattern, which vanishes as the geometry becomes spherically symmetrical. We show that such a reaction module facilitates universal adaptation to cell geometry by sensing the local ratio of membrane area to cytosolic volume. This sensing mechanism is controlled by the membrane affinities of the different states. We apply the theory to explain AtMinD bipolar patterns in [Formula: see text] EcMinDE Escherichia coli. Due to its generic nature, the mechanism could also serve as a hitherto-unrecognized spatial template in many other bacterial systems. Moreover, the robustness of the mechanism enables self-organized optimization of protein patterns by evolutionary processes. Finally, the proposed module can be used to establish geometry-sensitive protein gradients in synthetic biological systems.

  15. Pattern formation in SiSb system

    OpenAIRE

    Csik, A.; Erdelyi, G.; Langer, G A; Daroczi, L.; Beke, D. L.; Nyeki, J.; Erdelyi, Z.

    2009-01-01

    Thermal annealing of Si/Si1-xSbx/Si amorphous thin film tri-layer samples (x=18 and 24 at%Sb) under 100 bar Ar pressure results in an interesting pattern formation. In pictures, taken by means of cross-sectional transmission electron microscopy (TEM), stripe-shaped contrast, with three maxima, parallel with the interfaces can be seen. Secondary neutral mass spectrometer (SNMS) measurements revealed that the regions with different contrasts correspond to Sb-rich and Sb-depleted regions. Furthe...

  16. Pattern formation, logistics, and maximum path probability

    Science.gov (United States)

    Kirkaldy, J. S.

    1985-05-01

    The concept of pattern formation, which to current researchers is a synonym for self-organization, carries the connotation of deductive logic together with the process of spontaneous inference. Defining a pattern as an equivalence relation on a set of thermodynamic objects, we establish that a large class of irreversible pattern-forming systems, evolving along idealized quasisteady paths, approaches the stable steady state as a mapping upon the formal deductive imperatives of a propositional function calculus. In the preamble the classical reversible thermodynamics of composite systems is analyzed as an externally manipulated system of space partitioning and classification based on ideal enclosures and diaphragms. The diaphragms have discrete classification capabilities which are designated in relation to conserved quantities by descriptors such as impervious, diathermal, and adiabatic. Differentiability in the continuum thermodynamic calculus is invoked as equivalent to analyticity and consistency in the underlying class or sentential calculus. The seat of inference, however, rests with the thermodynamicist. In the transition to an irreversible pattern-forming system the defined nature of the composite reservoirs remains, but a given diaphragm is replaced by a pattern-forming system which by its nature is a spontaneously evolving volume partitioner and classifier of invariants. The seat of volition or inference for the classification system is thus transferred from the experimenter or theoretician to the diaphragm, and with it the full deductive facility. The equivalence relations or partitions associated with the emerging patterns may thus be associated with theorems of the natural pattern-forming calculus. The entropy function, together with its derivatives, is the vehicle which relates the logistics of reservoirs and diaphragms to the analog logistics of the continuum. Maximum path probability or second-order differentiability of the entropy in isolation are

  17. MEDICAL STUDENTS’ FEEDBACK ABOUT FORMATIVE ASSESSMENT PATTERN

    Directory of Open Access Journals (Sweden)

    Navajothi

    2016-03-01

    Full Text Available BACKGROUND Pharmacology is the toughest subject in the II MBBS syllabus. Students have to memorise a lot about the drugs’ name and classification. We are conducting internal assessment exams after completion of each system. Number of failures will be more than 60% in the internal assessments conducted during first six months of II MBBS course. AIM To assess the formative assessment pattern followed in our institution with the students’ feedback and modify the pattern according to the students’ feedback. SETTINGS & DESIGN Prospective Observational Study conducted at Department of Pharmacology, Government Sivagangai Medical College, Sivagangai, Tamil Nadu. MATERIALS AND METHODS Questionnaire was prepared and distributed to the 300 students of Government Sivagangai Medical College and feedback was collected. Data collected was analysed in Microsoft Excel 2007 version. RESULTS Received feedback from 274 students. Most (80% of the students wanted to attend the tests in all systems. Monthly assessment test was preferred by 47% of the students. Students who preferred to finish tests before holidays was 57%. Most (56% of the students preferred tests for 1 hour. Multiple choice question (MCQ type was preferred by 43%, which is not a routine question pattern. Only 7% preferred viva. Recall type of questions was preferred by 41% of the students. CONCLUSION In our institution, internal assessment is conducted as per the students’ mind setup. As the feedback has been the generally followed one, we will add MCQs in the forthcoming tests. Application type questions will be asked for more marks than Recall type of questions.

  18. Patterning and compartment formation in the diencephalon

    Directory of Open Access Journals (Sweden)

    mallika echatterjee

    2012-05-01

    Full Text Available The diencephalon gives rise to structures that play an important role in connecting the anterior forebrain with the rest of the central nervous system. The thalamus is the major diencephalic derivative that functions as a relay station between the cortex and other lower order sensory systems. Almost two decades ago, neuromeric/prosomeric models were proposed describing the subdivision and potential segmentation of the diencephalon. Unlike the laminar structure of the cortex, the diencephalon is progressively divided into distinct functional compartments consisting principally of thalamus, epithalamus and pretectum. Neurons generated within these domains further aggregate to form clusters called nuclei, which form specific structural and functional units. We review the recent advances in understanding the genetic mechanisms that are involved in the patterning and compartment formation of the diencephalon.

  19. Effects of patterned topography on biofilm formation

    Science.gov (United States)

    Vasudevan, Ravikumar

    2011-12-01

    Bacterial biofilms are a population of bacteria attached to each other and irreversibly to a surface, enclosed in a matrix of self-secreted polymers, among others polysaccharides, proteins, DNA. Biofilms cause persisting infections associated with implanted medical devices and hospital acquired (nosocomial) infections. Catheter-associated urinary tract infections (CAUTIs) are the most common type of nosocomial infections accounting for up to 40% of all hospital acquired infections. Several different strategies, including use of antibacterial agents and genetic cues, quorum sensing, have been adopted for inhibiting biofilm formation relevant to CAUTI surfaces. Each of these methods pertains to certain types of bacteria, processes and has shortcomings. Based on eukaryotic cell topography interaction studies and Ulva linza spore studies, topographical surfaces were suggested as a benign control method for biofilm formation. However, topographies tested so far have not included a systematic variation of size across basic topography shapes. In this study patterned topography was systematically varied in size and shape according to two approaches 1) confinement and 2) wetting. For the confinement approach, using scanning electron microscopy and confocal microscopy, orienting effects of tested topography based on staphylococcus aureus (s. aureus) (SH1000) and enterobacter cloacae (e. cloacae) (ATCC 700258) bacterial models were identified on features of up to 10 times the size of the bacterium. Psuedomonas aeruginosa (p. aeruginosa) (PAO1) did not show any orientational effects, under the test conditions. Another important factor in medical biofilms is the identification and quantification of phenotypic state which has not been discussed in the literature concerning bacteria topography characterizations. This was done based on antibiotic susceptibility evaluation and also based on gene expression analysis. Although orientational effects occur, phenotypically no difference

  20. Ecological aspects of the use of lost foam patterns

    Directory of Open Access Journals (Sweden)

    Z. Żółkiewicz

    2010-07-01

    Full Text Available The paper discusses some aspects of ecology in the use of lost foam patterns for piece production of large castings poured from ferrousalloys under the conditions of Metalodlew SA. Foundry. The technological processes used in the manufacture of castings are related with numerous hazards. Numerous problems requiring prompt solution occur also during the process of foundry mould pouring, to mention only various contaminants, air pollution, noise and other factors harmful to the human health and natural environment. Varioustechnological processes cause strenuous work conditions in foundry shops. Many of the publications that have appeared so far dealing withthe problems of environmental protection and hard work conditions in foundries [1, 2, 3, 4, 5, 6, 7, 8, 9] discuss in both general anddetailed way problems related with various pollutants, noise and other factors harmful to the human health and natural environment,responsible for hazards faced by foundry workers. Studies carried out by various R&D centres are mainly focussed on the problem of howto reduce the harmful effect of technological processes on the environment through modification of the already existing or development of new ecological and energy-saving materials and technologies. This paper shows the opportunities and threats resulting from the application of the Lost Foam Process in a foundry, which up to now has been using a more traditional technology.

  1. Features of the formation of the bodily aspect of gender identity in men

    Directory of Open Access Journals (Sweden)

    Harlanova M.M.

    2015-11-01

    Full Text Available The article examines the peculiarities of the bodily aspect of gender identity in men. The urgency of this work due to the fact that currently in Russia to study the influence of the bodily aspect to the whole structure of gender identity is given little attention. At the present time the problem of studying the physicality involved in domestic psychologists: Arina G. A., V. V. Nikolaev, A. S. Kostov, A. N. Borojevic, B. T. Sokolov, V. Yu., Baskakov, who agree in opinion on the necessity to study the influence of the morpho-biological patterns of gender identity, her social and personal "add-on" – of sex-role stereotypes, perceptions, behavior, preferences. However, studies supporting their interaction was not performed [7]. In the paper the following definitions: "gender identity", "gender", "differential socialization", "the Adonis complex". Produced comprehensive analysis of foreign sources for a detailed understanding of the studied phenomenon; analysis of the structural components and characteristics of the formation of the bodily aspect of gender identity in men with the help of specifically chosen tutorials. Discovered the distinctive features of the formation of the bodily aspect of gender identity in men and their reflection in sex-role behavior. We assume that men who are not satisfied with the perception of his own body, prone to distorted perceptions of sex-role images. The data obtained can provide the basis and prospects for development of programs of prevention, diagnostics and correction.

  2. Turing pattern formation in the Brusselator system with nonlinear diffusion

    OpenAIRE

    Gambino, G.; Lombardo, M. C.; Sammartino, M.; Sciacca, V.

    2013-01-01

    In this work we investigate the effect of density dependent nonlinear diffusion on pattern formation in the Brusselator system. Through linear stability analysis of the basic solution we determine the Turing and the oscillatory instability boundaries. A comparison with the classical linear diffusion shows how nonlinear diffusion favors the occurrence of Turing pattern formation. We study the process of pattern formation both in 1D and 2D spatial domains. Through a weakly nonlinear multiple sc...

  3. Spontaneous pattern formation in an anti-ferromagnetic quantum gas

    OpenAIRE

    Kronjäger, Jochen; Becker, Christoph; Soltan-Panahi, Parvis; Bongs, Kai; Sengstock, Klaus

    2009-01-01

    Spontaneous pattern formation is a phenomenon ubiquitous in nature, examples ranging from Rayleigh-Benard convection to the emergence of complex organisms from a single cell. In physical systems, pattern formation is generally associated with the spontaneous breaking of translation symmetry and is closely related to other symmetry-breaking phenomena, of which (anti-)ferromagnetism is a prominent example. Indeed, magnetic pattern formation has been studied extensively in both solid-state mater...

  4. THEORETICAL ASPECTS OF THE FORMATION OF A LAND MARKET

    Directory of Open Access Journals (Sweden)

    Barsukova G. N.

    2016-01-01

    Full Text Available The article substantiates theoretical aspects of the formation of a land market. It is shown that there is a problem of insufficient knowledge of its formation. The article lists the features of land as part of the natural environment, a factor of production, part of the capital, a real estate object, defining features of the land market. It is shown that supply in the land market in the short term is elastically, despite the fixed supply at any given moment, and inelastically in the long term. We substantiated expediency evaluation of public and private land market in terms of turnover, which expresses the ratio of the total land area of transactions in the segmental markets to the total amount of land in some form of ownership. We proposed to evaluate the development potential of the turnover of the analyzed segment of public sector land market with the help of the methodology of growth curves. This work presents internal and external macroeconomic factors and institutions that form the infrastructure of the land market. It concludes about the need to improve the institutions of valuation of land, land banks, information base, land management and real estate cadastre. We proposed to study the land market from the standpoint of neoinstitutionalism. In accordance with the theory of Ronald Coase, this work shows the significance of transaction costs for the development of the land market. We clarified the classification of the transaction costs arising before and after the transaction O. Williamson, in relation to the land market and concluded on the need to reduce them. We substantiated the necessity of state regulation of the land market, improvement of economic land management practices

  5. Pattern formation in rotating Bénard convection

    Science.gov (United States)

    Fantz, M.; Friedrich, R.; Bestehorn, M.; Haken, H.

    1992-12-01

    Using an extension of the Swift-Hohenberg equation we study pattern formation in the Bénard experiment close to the onset of convection in the case of rotating cylindrical fluid containers. For small Taylor numbers we emphasize the existence of slowly rotating patterns and describe behaviour exhibiting defect motion. Finally, we study pattern formation close to the Küppers-Lortz instability. The instability is nucleated at defects and proceeds through front propagation into the bulk patterns.

  6. Pattern formation by a moving morphogen source

    International Nuclear Information System (INIS)

    During Drosophila melanogaster oogenesis, the follicular epithelium that envelops the germline cyst gives rise to an elaborate eggshell, which houses the future embryo and mediates its interaction with the environment. A prominent feature of the eggshell is a pair of dorsal appendages, which are needed for embryo respiration. Morphogenesis of this structure depends on broad, a zinc-finger transcription factor, regulated by the EGFR pathway. While much has been learned about the mechanisms of broad regulation by EGFR, current understanding of processes that shape the spatial pattern of broad expression is incomplete. We propose that this pattern is defined by two different phases of EGFR activation: an early, posterior-to-anterior gradient of EGFR signaling sets the posterior boundary of broad expression, while the anterior boundary is set by a later phase of EGFR signaling, distributed in a dorsoventral gradient. This model can explain the wild-type pattern of broad in D. melanogaster, predicts how this pattern responds to genetic perturbations, and provides insight into the mechanisms driving diversification of eggshell patterning. The proposed model of the broad expression pattern can be used as a starting point for the quantitative analysis of a large number of gene expression patterns in Drosophila oogenesis

  7. Sequential pattern formation governed by signaling gradients

    CERN Document Server

    Jörg, David J; Jülicher, Frank

    2016-01-01

    Rhythmic and sequential segmentation of the embryonic body plan is a vital developmental patterning process in all vertebrate species. However, a theoretical framework capturing the emergence of dynamic patterns of gene expression from the interplay of cell oscillations with tissue elongation and shortening and with signaling gradients, is still missing. Here we show that a set of coupled genetic oscillators in an elongating tissue that is regulated by diffusing and advected signaling molecules can account for segmentation as a self-organized patterning process. This system can form a finite number of segments and the dynamics of segmentation and the total number of segments formed depend strongly on kinetic parameters describing tissue elongation and signaling molecules. The model accounts for existing experimental perturbations to signaling gradients, and makes testable predictions about novel perturbations. The variety of different patterns formed in our model can account for the variability of segmentatio...

  8. Evolution of Web Applications with Aspect-Oriented Design Patterns

    DEFF Research Database (Denmark)

    Bebjak, Michal; Vranic, Valentino; Dolog, Peter

    2007-01-01

    It is more convenient to talk about changes in a domainspecific way than to formulate them at the programming construct level or-even worse-purely lexical level. Using aspect-oriented programming, changes can be modularized and made reapplicable. In this paper, selected change types in web...

  9. Pattern formations in chaotic spatio-temporal systems

    Indian Academy of Sciences (India)

    Ying Zhang; Shihong Wang; Jinhua Xiao; Hilda A Cerdeira; S Chen; Gang Hu

    2005-06-01

    Pattern formations in chaotic spatio-temporal systems modelled by coupled chaotic oscillators are investigated. We focus on various symmetry breakings and different kinds of chaos synchronization–desynchronization transitions, which lead to certain types of spontaneous spatial orderings and the emergence of some typical ordered patterns, such as rotating wave patterns with splay phase ordering (orientational symmetry breaking) and partially synchronous standing wave patterns with in-phase ordering (translational symmetry breaking). General pictures of the global behaviors of pattern formations and transitions in coupled chaotic oscillators are provided.

  10. Formation of colloidal semiconductor nanocrystals. The aspect of nucleation

    Energy Technology Data Exchange (ETDEWEB)

    Kudera, S.

    2007-08-17

    The present work describes different techniques to control some major parameters of colloidal nanocrystals. The individual techniques rely on the manipulation of the nucleation event. The sensitive control of the nanocrystals' size and shape is discussed. Furthermore the formation of hybrid nanocrystals composed of different materials is presented. The synthesis technique for the production of the different samples involves organic solvents and surfactants and reactions at elevated temperatures. The presence of magic size clusters offers a possibility to control the size of the nanocrystals even at very small dimensions. The clusters produced comprise ca. 100 atoms. In the case of CdSe, nanocrystals of this size emit a blue fluorescence and therefore extend the routinely accessible spectrum for this material over the whole visible range. Samples fluorescing in the spectral range from green to red are produced with standard recipes. In this work a reaction scheme for magic size clusters is presented and a theoretical model to explain the particular behaviour of their growth dynamics is discussed. The samples are investigated by optical spectroscopy, transmission electron microscopy, X-ray diffraction and elemental analysis. A method to form branched nanocrystals is discussed. The branching point is analysed by high resolution transmission electron microscopy and proves for the occurrence of a multiple twinned structure are strengthened by simulation of the observed patterns. Two different techniques to generate nanocrystals of this type are presented. The first relies on a seeded growth approach in which the nucleation of the second material is allowed only on de ned sites of the seeds. The second technique uses the tips of pre-formed nano-dumbbells as sacrificial domains. The material on the tips is replaced by gold. Hybrid materials are formed by a seeded-growth mechanism. Pre-formed nanocrystals provide the nucleation sites for the second material. (orig.)

  11. Geometry-induced protein pattern formation

    OpenAIRE

    Thalmeier, Dominik; Halatek, Jacob; Frey, Erwin

    2016-01-01

    Biological cells need the ability to guide intracellular processes to specific spatial locations. This requires biochemical processes to sense and adapt to the geometry of the organism. Previously suggested mechanisms either assume proteins that are able to directly sense membrane curvature or are based on nonlinear diffusion–reaction systems that can generate geometry-adapted patterns. The latter, however, requires fine-tuning of the reaction rates. Here, we show that geometry adaption alrea...

  12. Pattern formation in arrays of chemical oscillators

    Indian Academy of Sciences (India)

    Neeraj Kumar Kamal

    2012-05-01

    We describe a simple model mimicking diffusively coupled chemical micro-oscillators. We characterize the rich variety of dynamical states emerging from the model under variation of time delay in coupling, coupling strength and boundary conditions. The spatiotemporal patterns obtained include clustering, mixed dynamics, inhomogeneous steady states and amplitude death. Further, under delay in coupling, the model yields transitions from phase to antiphase oscillations, reminiscent of that observed in experiments [M Toiya et al, J. Chem. Lett. 1, 1241 (2010)].

  13. Pattern formation in quantum Turing machines

    OpenAIRE

    Kim, ILki; Mahler, Guenter

    1999-01-01

    We investigate the iteration of a sequence of local and pair unitary transformations, which can be interpreted to result from a Turing-head (pseudo-spin $S$) rotating along a closed Turing-tape ($M$ additional pseudo-spins). The dynamical evolution of the Bloch-vector of $S$, which can be decomposed into $2^{M}$ primitive pure state Turing-head trajectories, gives rise to fascinating geometrical patterns reflecting the entanglement between head and tape. These machines thus provide intuitive ...

  14. Embryogenesis, a process of pattern formation

    Institute of Scientific and Technical Information of China (English)

    Meng-Xiang SUN

    2011-01-01

    @@ Plant embryogenesis is traditionally defined as a develop-mental process from zygote to mature embryo, which has the potential to form a complete plant (Bhojwani, 1974; Hu,2005).In dicotyledonous species, the fertilized egg or zygote usually divides according to a stereotyped pattern and gives rise to an embryo that consists of an embryonic shoot,cotyledons, hypocotyls, and an embryonic root.Thus, the basic body plan of the plant is established during the embryogenesis.Interestingly, the shoot-leaf-stem structure,not including the root, is repeatedly photocopied as a basic unit throughout plant vegetative growth (Wolpert et al.,2002).

  15. Pattern formation in quantum Turing machines

    CERN Document Server

    Kim, I; Kim, Ilki; Mahler, Guenter

    1999-01-01

    We investigate the iteration of a sequence of local and pair unitary transformations, which can be interpreted to result from a Turing-head (pseudo-spin $S$) rotating along a closed Turing-tape ($M$ additional pseudo-spins). The dynamical evolution of the Bloch-vector of $S$, which can be decomposed into $2^{M}$ primitive pure state Turing-head trajectories, gives rise to fascinating geometrical patterns reflecting the entanglement between head and tape. These machines thus provide intuitive examples for quantum parallelism and, at the same time, means for local testing of quantum network dynamics.

  16. Pattern formation in quantum Turing machines

    Science.gov (United States)

    Kim, Ilki; Mahler, Günter

    1999-07-01

    We investigate the iteration of a sequence of local and pair unitary transformations, which can be interpreted to result from a Turing-head (pseudospin S) rotating along a closed Turing tape (M additional pseudospins). The dynamical evolution of the Bloch vector of S, which can be decomposed into 2M primitive pure state Turing-head trajectories, gives rise to fascinating geometrical patterns reflecting the entanglement between head and tape. These machines thus provide intuitive examples for quantum parallelism and, at the same time, means for local testing of quantum network dynamics.

  17. Lateral inhibition-induced pattern formation controlled by the size and geometry of the cell.

    Science.gov (United States)

    Seirin Lee, Sungrim

    2016-09-01

    Pattern formation in development biology is one of the fundamental processes by which cells change their functions. It is based on the communication of cells via intra- and intercellular dynamics of biochemicals. Thus, the cell is directly involved in biochemical interactions. However, many theoretical approaches describing biochemical pattern formation have usually neglected the cell's role or have simplified the subcellular process without considering cellular aspects despite the cell being the environment where biochemicals interact. On the other hand, recent experimental observations suggest that a change in the physical conditions of cell-to-cell contact can result in a change in cell fate and tissue patterning in a lateral inhibition system. Here we develop a mathematical model by which biochemical dynamics can be directly observed with explicitly expressed cell structure and geometry in higher dimensions, and reconsider pattern formation by lateral inhibition of the Notch-Delta signaling pathway. We explore how the physical characteristic of cell, such as cell geometry or size, influences the biochemical pattern formation in a multi-cellular system. Our results suggest that a property based on cell geometry can be a novel mechanism for symmetry breaking inducing cell asymmetry. We show that cell volume can critically influence cell fate determination and pattern formation at the tissue level, and the surface area of the cell-to-cell contact can directly affect the spatial range of patterning. PMID:27229622

  18. Lateral inhibition-induced pattern formation controlled by the size and geometry of the cell.

    Science.gov (United States)

    Seirin Lee, Sungrim

    2016-09-01

    Pattern formation in development biology is one of the fundamental processes by which cells change their functions. It is based on the communication of cells via intra- and intercellular dynamics of biochemicals. Thus, the cell is directly involved in biochemical interactions. However, many theoretical approaches describing biochemical pattern formation have usually neglected the cell's role or have simplified the subcellular process without considering cellular aspects despite the cell being the environment where biochemicals interact. On the other hand, recent experimental observations suggest that a change in the physical conditions of cell-to-cell contact can result in a change in cell fate and tissue patterning in a lateral inhibition system. Here we develop a mathematical model by which biochemical dynamics can be directly observed with explicitly expressed cell structure and geometry in higher dimensions, and reconsider pattern formation by lateral inhibition of the Notch-Delta signaling pathway. We explore how the physical characteristic of cell, such as cell geometry or size, influences the biochemical pattern formation in a multi-cellular system. Our results suggest that a property based on cell geometry can be a novel mechanism for symmetry breaking inducing cell asymmetry. We show that cell volume can critically influence cell fate determination and pattern formation at the tissue level, and the surface area of the cell-to-cell contact can directly affect the spatial range of patterning.

  19. Pattern formation and coarsening in crystalline membranes

    Science.gov (United States)

    Vega, Daniel A.; Pezzutti, Aldo D.

    2011-03-01

    We study through a Brazovskii-Helfrich Hamiltonian the process of defect formation, annealing and coarsening of two dimensional crystalline membranes. In good agreement with the cosmological model of Kibble and Zurek, proposed to determine the density of topological defects at the onset of a symmetry breaking phase transition, we found that the collision of orientationally uncorrelated domains produces a structure of grains with an average density of topological defects controlled by the temperature of the quench. The strain field of the dislocations and disclinations generated during the phase separation process can induce the buckling of the membrane, slowing down the Lifshitz-Safran mechanism of coarsening observed in flat systems.

  20. Gonorrhoea in men: diagnostic aspects and changing antibiotic susceptibility pattern

    Directory of Open Access Journals (Sweden)

    sandeepkumar om nanda

    2013-04-01

    Full Text Available BACKGROUND: Gonorrhea since the ancient times is causing significant morbidity. Though a number of methods are available for diagnosis in men, culture still remains the gold standard. Gonococci are delicate and fastidious bacteria but its remarkable ability to develop resistance to a variety of antibiotics makes it a major threat to public health. OBJECTIVES: - To detect the incidence in symptomatic men and in vitro antimicrobial susceptibility pattern of the gonococcal isolates. MATERIALS & METHODS: - 100 urethral swabs from men with urethritis were screened for presence of gonococci by gram stain and culture on Chocolate Agar and Modified Thayer-Martin medium. The isolated gonococci were screened for Penicillinase production and susceptibility to antibiotics was subsequently carried out by standard disc diffusion method. RESULTS: - Gonorrhoea was detected in 56 of the urethral swabs giving a incidence of 56%. The difference of detection in gram stain and culture was insignificant (P>0.05. Of all the isolated gonococci considerable resistance was seen to ciprofloxacin(46.4%, tetracycline(23.2% and Penicillin(17% with Incidence of PPNG being 12.5%. All strains were uniformly sensitive to Spectinomycin and Cephalosporins. INTERPRETATION & CONCLUSIONS: - Neisseria gonorrhoeae is main etiological agent in urethritis in sexually active men and culture though time consuming, costly and demands expertise is still better method for diagnosis as gives high isolation rate and observe changing patterns in antibiotic susceptibility to commonly used antimicrobials. [Natl J Med Res 2013; 3(2.000: 177-180

  1. Labyrinthine Instability and Pattern Formation in Ferrofluids

    CERN Document Server

    Harrison, Timothy J

    2012-01-01

    Ferrofluids suspended in liquids and constrained in quasi-two dimensional domains were exposed to transverse magnetic fields. The points of elliptical instability of nearly circular drops were measured and compared to the theoretical prediction using a fitting parameter. The data matched the predicted trend well for 3 different liquids used as suspensions; however, at extreme values of drop radius, there was a significant deviation from prediction. The angles at each node of the labyrinthine pattern, formed using high magnetic fields, were measured and compared with the prediction of 120 degrees. For the dense labyrinth the most common angles were between 135 degrees -144 degrees, suggesting interaction between arms were having a repelling effect causing angles to widen. For the less dense labyrinth the most frequent angle category decreased, supporting this hypothesis. In the experiments the area, which theoretically should be constant, was noticed to change and this encouraged an investigation into how the ...

  2. Psychoacoustic aspects of speech pattern coding for the deaf.

    Science.gov (United States)

    Faulkner, A; Fourcin, A J; Moore, B C

    1990-01-01

    The SiVo aid, which provides a sinusoidal signal indicating voice fundamental frequency and voicing information, was compared as an aid to lipreading to a conventional hearing aid having extended low-frequency output. Speech perceptual measures of consonant confusions in lipreading and the identification of a simple intonation contrast were collected from a group of 8 profoundly deaf adults. Audiometric and psychoacoustic measures were also collected. In the intonation task, 6 of the 7 patients tested performed better with the SiVo aid and the seventh scored perfectly with both aids. Four patients (out of 8) preferred to use the SiVo aid rather than the conventional aid, and 2 of these showed a significant advantage with the SiVo aid in the aided lipreading of consonants. The remaining 4 patients preferred the conventional aid, although none of these patients showed a significant advantage with the conventional aid in the lipreading of consonants. The 4 patients who preferred the SiVo aid over the conventional aid had very profound hearing loss and minimal dynamic range at 500 Hz and above, and those receiving the greatest benefit showed no measurable frequency selectivity. In the 2 patients who preferred the SiVo aid, yet showed no significant advantage for the SiVo aid in consonant lipreading, consonant confusions were also measured for aided lipreading, using a prototype aid providing both voice fundamental frequency and voiceless excitation patterns. Both patients showed additional and significant benefit from inclusion of the voiceless pattern element. PMID:2356724

  3. Pattern Formation and Quasicrystal Structure in Azobenzene Polymer Film

    Institute of Scientific and Technical Information of China (English)

    XU Ze-Da; CAI Zhi-Gang; ZHANG Ling-Zhi; LIU Yan-Fa; YANG Jie; SHE Wei-Long; ZHOU Jian-Ying

    2000-01-01

    Pattern formation in azobenzene polymer film by degenerate four-wave mixing is reported. Island arrays with specific patterns are analyzed with scanning electron microscopy and polarizing optical microscopy. It is demonstrated that the control of photo-induced nanostructure sized micropattern in the nonlinear organic film is possible by using properly polarized writing beams with the total incident power exceeding a certain threshold.

  4. The role of auxin signaling in early embryo pattern formation

    NARCIS (Netherlands)

    Smit, Margot E.; Weijers, Dolf

    2015-01-01

    Pattern formation of the early Arabidopsis embryo generates precursors to all major cell types, and is profoundly controlled by the signaling molecule auxin. Here we discuss recent milestones in our understanding of auxin-dependent embryo patterning. Auxin biosynthesis, transport and response mec

  5. Pattern formation in mutation of "Game of Life"

    Institute of Scientific and Technical Information of China (English)

    HUANG Wen-gao; PAN Zhi-geng

    2005-01-01

    This paper presents pattern formation in generalized cellular automata (GCA) by varying parameters of classic “game Experiments show the emergence of the self-organizing patterns that is analogous with life forms at the edge of chaos, which consist of certain nontrivial structure and go through periods of growth, maturity and death. We describe these experiments and discuss their potential as alternative way for creating artificial life and generative art, and as a new method for pattern genesis.

  6. Discrete Dynamical Models Showing Pattern Formation in Subaqueous Bedforms

    CERN Document Server

    Tufillaro, N B

    1993-01-01

    Abstract: A new class of ``toy models'' for subaqueous bedform formation are proposed and examined. These models all show a similar mechanism of wavelength selection via bedform unification, and they may have applications to bedform stratigraphy. The models are also useful for exploring general issues of pattern formation and complexity in stochastically driven far from equilibrium systems.

  7. Thermal recovery of bitumen from carbonate reservoirs: formation damage aspects

    Energy Technology Data Exchange (ETDEWEB)

    Thimm, H.F. [Thimm Petroleum Technologies Inc. (Canada)

    2011-07-01

    In Alberta, about a third of bitumen resources are located in carbonate reservoirs but none of it is considered as a reserve by the Alberta Energy Resources Conservation Board (ERCB). In fact no pilot has been successful in recovering bitumen from carbonate reservoirs due to formation damage problems. Carbonate rock is chemically active at the high temperatures reached in thermal recovery processes, carbon dioxide is generated and carbonate minerals are precipitated. The aim of this paper is to find methods to control the phenomenon. Kinetic and thermodynamic controls were used. Results showed that formation damage is due to aqueous carbon dioxide attacking the reservoir rock. They found that a reduction of the partial pressure of carbon dioxide could inhibit the initial dissolution of rock material by reducing the concentration of aqueous carbon dioxide. A method to overcome the formation damage problem was found and a co-injection of gas and steam process was developed to apply it.

  8. Geological pattern formation by growth and dissolution in aqueous systems

    Energy Technology Data Exchange (ETDEWEB)

    Paul Meakin

    2010-03-01

    Although many geological processes take place on time scales that are very long compared with the human experience, essentially all geological processes, fast or slow, are far from equilibrium processes. Surprisingly often, geological processes lead to the formation of quite simple and distinctive patterns, which hint at an underlying simplicity in many complex geological systems.. The ability to predict the seasons was critically important to early human society, and Halley’s prediction of the return of the comet that bears his name is still considered to be a scientific milestone. Spatial patterns have also attracted attention because of their aesthetic appeal, which depends in subtle ways on a combination of regularity and irregularity. In recent decades, rapid growth in the capabilities of digital computers has facilitated the simulation of pattern formation processes, and computer simulations have become an important tool for evaluating theoretical concepts and for scientific discovery. Computer technology in combination with other technologies such as high resolution digital cameras, scanning microprobes (atomic force microscopy AFM), confocal microscopy, and scanning tunneling microscopy (STM), for example) has facilitated the quantitative characterization of patterns over a wide range of scales and has enabled rapid advances in our ability to understand the links between large scale pattern formation and microscopic processes. The ability to quantitatively characterize patterns is important because it enables a more rigorous comparison between the predictions of computer models and real world patterns and their formation.In some cases, the idea that patterns with a high degree of regularity have simple origins appears to be justified, but in other cases, such as the formation of almost perfectly circular stone rings due to freeze-thaw cycles simple patterns appear to be the consequence of quite complex processes. In other cases, it has been shown that

  9. Neural pattern formation in networks with dendritic structure

    Science.gov (United States)

    Bressloff, P. C.; De Souza, B.

    1998-04-01

    We present a detailed analysis of a recently proposed model of neural pattern formation that is based on the combined effect of diffusion along a neuron's dendritic tree and recurrent interactions along axo-dendritic synaptic connections. For concreteness, we consider a one-dimensional array of analog neurons with the dendritic tree idealized as a one-dimensional cable. Linear stability analysis and bifurcation theory together with numerical simulations are used to establish conditions for the onset of a Turing instability leading to the formation of stable spatial patterns of network output activity. It is shown that the presence of dendritic structure can induce dynamic (time-periodic) spatial pattern formation. Moreover, correlations between the dendritic location of a synapse and the relative positions of neurons in the network are shown to result in spatially oscillating patterns of activity along the dendrites of each neuron.

  10. Pattern formation in a minimal model of continuum dislocation plasticity

    Science.gov (United States)

    Sandfeld, Stefan; Zaiser, Michael

    2015-09-01

    The spontaneous emergence of heterogeneous dislocation patterns is a conspicuous feature of plastic deformation and strain hardening of crystalline solids. Despite long-standing efforts in the materials science and physics of defect communities, there is no general consensus regarding the physical mechanism which leads to the formation of dislocation patterns. In order to establish the fundamental mechanism, we formulate an extremely simplified, minimal model to investigate the formation of patterns based on the continuum theory of fluxes of curved dislocations. We demonstrate that strain hardening as embodied in a Taylor-type dislocation density dependence of the flow stress, in conjunction with the structure of the kinematic equations that govern dislocation motion under the action of external stresses, is already sufficient for the formation of dislocation patterns that are consistent with the principle of similitude.

  11. Argon ion beam induced surface pattern formation on Si

    Energy Technology Data Exchange (ETDEWEB)

    Hofsäss, H.; Bobes, O.; Zhang, K. [2nd Institute of Physics, Faculty of Physics, University Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen (Germany)

    2016-01-21

    The development of self-organized surface patterns on Si due to noble gas ion irradiation has been studied extensively in the past. In particular, Ar ions are commonly used and the pattern formation was analyzed as function of ion incidence angle, ion fluence, and ion energies between 250 eV and 140 keV. Very few results exist for the energy regime between 1.5 keV and 10 keV and it appears that pattern formation is completely absent for these ion energies. In this work, we present experimental data on pattern formation for Ar ion irradiation between 1 keV and 10 keV and ion incidence angles between 50° and 75°. We confirm the absence of patterns at least for ion fluences up to 10{sup 18} ions/cm{sup 2}. Using the crater function formalism and Monte Carlo simulations, we calculate curvature coefficients of linear continuum models of pattern formation, taking into account contribution due to ion erosion and recoil redistribution. The calculations consider the recently introduced curvature dependence of the erosion crater function as well as the dynamic behavior of the thickness of the ion irradiated layer. Only when taking into account these additional contributions to the linear theory, our simulations clearly show that that pattern formation is strongly suppressed between about 1.5 keV and 10 keV, most pronounced at 3 keV. Furthermore, our simulations are now able to predict whether or not parallel oriented ripple patterns are formed, and in case of ripple formation the corresponding critical angles for the whole experimentally studied energies range between 250 eV and 140 keV.

  12. SOCIO-EDUCATIONAL ASPECTS OF THE WORKING MAN FORMATION.

    Directory of Open Access Journals (Sweden)

    Y. F. Zeyer

    2015-03-01

    Full Text Available The paper analyzes a new for the Russian anthropology concept of the «working man», introduced in the Urals along with the propagation of a social and political movement «For the Working Man Protection»; the semantic content of the «man» and «labor» notions being observed as well as the process and problems of the working man formation in the modern world.The author emphasizes the asymmetry of the socio-economic and vocational educational infrastructure, along with the contradictions between the labor market demands for the technical and technological profile workers and the existing educational qualification structure of vocational schools.In author's opinion, the disorganization of labor training in comprehensive school and deficiencies of vocational education hinder the process of the industrial working man formation. The professional orientation system is criticized for being unable to meet the demands of modern economy and provide the young people with the adequate concept of the working career.For overcoming the above problems affecting the working man formation, the paper recommends modernization of the labor training system in comprehensive schools, reformation of vocational training, and renovation of professional orientation system. The special emphasis is given to the continuing training of the working man. 

  13. SOCIO-EDUCATIONAL ASPECTS OF THE WORKING MAN FORMATION.

    Directory of Open Access Journals (Sweden)

    Y. F. Zeyer

    2013-01-01

    Full Text Available The paper analyzes a new for the Russian anthropology concept of the «working man», introduced in the Urals along with the propagation of a social and political movement «For the Working Man Protection»; the semantic content of the «man» and «labor» notions being observed as well as the process and problems of the working man formation in the modern world.The author emphasizes the asymmetry of the socio-economic and vocational educational infrastructure, along with the contradictions between the labor market demands for the technical and technological profile workers and the existing educational qualification structure of vocational schools.In author's opinion, the disorganization of labor training in comprehensive school and deficiencies of vocational education hinder the process of the industrial working man formation. The professional orientation system is criticized for being unable to meet the demands of modern economy and provide the young people with the adequate concept of the working career.For overcoming the above problems affecting the working man formation, the paper recommends modernization of the labor training system in comprehensive schools, reformation of vocational training, and renovation of professional orientation system. The special emphasis is given to the continuing training of the working man. 

  14. Kinetic and structural aspects of tantalum hydride formation

    Directory of Open Access Journals (Sweden)

    R. DIMITRIJEVIC

    2003-09-01

    Full Text Available Tantalum hydrides of various composition were synthesized by equilibrating tantalum with hydrogen at six different temperatures from 573 to 823 K, under a constant hydrogen pressure of 1 bar. Both the exact Ta/H mole ratios and the kinetic parameters of hydriding were determined on the basis of the dependence of the H/Ta mole ratio on time. The influence of stoichiometry on the appearance of X-ray powder diffractograms at room temperature was studied. As a consequence of hydriding, for ratios H/Ta > 0.2, the original bcc Ta-lattice undergoes distortion, manifesting itself as both a shift and a splitting of the X-ray patterns in the X-ray diffractograms. For samples with H/Ta < 0.2, the appearance of some superstructure reflections at low Bragg angles was noted, which suggests a long range ordering of hydrogen with orthorhombic symmetry.

  15. Formation of co-crystals: Kinetic and thermodynamic aspects

    Science.gov (United States)

    Gagnière, E.; Mangin, D.; Puel, F.; Rivoire, A.; Monnier, O.; Garcia, E.; Klein, J. P.

    2009-04-01

    Co-crystallisation is a recent method of great interest for the pharmaceutical industry, since pharmaceutical co-crystals represent useful materials for drug products. In this study, an active pharmaceutical ingredient (carbamazepine (CBZ)) co-crystallized with a vitamin (nicotinamide (NCT)) was chosen as a model substance. This work was focused on the construction of a phase diagram for the system CBZ/NCT, split in six domains for kinetic reasons (the different solid phases which might appear during the crystallisation) and in four domains according to thermodynamic aspects (the stable final phase obtained). Although co-crystals are not ionic compounds, the supersaturation of co-crystals can be evaluated by considering the solubility product. Batch crystallisation operations were carried out in a stirred vessel equipped with an in situ video probe. This latter device was a powerful analysis tool to monitor the CBZ/NCT co-crystals and single CBZ crystals since these two crystalline phases grown in ethanol exhibited needle and platelet habits. As concerns kinetics, the different solid phases which might appear during the experiments were observed and competed against each others. In accordance with thermodynamics, the stable solid form was obtained at the end of the operation. Finally some preliminary results indicate that the nucleation of co-crystals may be favoured by the presence of CBZ crystals. Epitaxial relationships between CBZ/NCT co-crystals and CBZ crystals were suspected.

  16. Zebrafish stripes as a model for vertebrate colour pattern formation.

    Science.gov (United States)

    Singh, Ajeet Pratap; Nüsslein-Volhard, Christiane

    2015-01-19

    Colour patterns are prominent features of many animals and have important functions in communication, such as camouflage, kin recognition and mate choice. As targets for natural as well as sexual selection, they are of high evolutionary significance. The molecular mechanisms underlying colour pattern formation in vertebrates are not well understood. Progress in transgenic tools, in vivo imaging and the availability of a large collection of mutants make the zebrafish (Danio rerio) an attractive model to study vertebrate colouration. Zebrafish display golden and blue horizontal stripes that form during metamorphosis as mosaics of yellow xanthophores, silvery or blue iridophores and black melanophores in the hypodermis. Lineage tracing revealed the origin of the adult pigment cells and their individual cellular behaviours during the formation of the striped pattern. Mutant analysis indicated that interactions between all three pigment cell types are required for the formation of the pattern, and a number of cell surface molecules and signalling systems have been identified as mediators of these interactions. The understanding of the mechanisms that underlie colour pattern formation is an important step towards deciphering the genetic basis of variation in evolution. PMID:25602311

  17. Write Pattern Format Algorithm for Reliable NAND-Based SSDs

    OpenAIRE

    Xu, Q; T. Chen; Hu, Y; Gong, P.

    2014-01-01

    This brief presents and evaluates a pre-coding algorithm to reduce power consumption and improve data retention in NAND-based solid-state drives. Compared to the state-of-the-art asymmetric coding and stripe pattern elimination algorithm, the proposed write pattern format algorithm (WPFA) achieves better data retention while consuming less power. The hardware for WPFA is simpler and requires less circuitry. The performance of WPFA is evaluated by both computer simulations and field-programmab...

  18. Dynamics of precipitation pattern formation at geothermal hot springs.

    Science.gov (United States)

    Goldenfeld, Nigel; Chan, Pak Yuen; Veysey, John

    2006-06-30

    We formulate and model the dynamics of spatial patterns arising during the precipitation of calcium carbonate from a supersaturated shallow water flow. The model describes the formation of travertine deposits at geothermal hot springs and rimstone dams of calcite in caves. We find explicit solutions for travertine domes at low flow rates, identify the linear instabilities which generate dam and pond formation on sloped substrates, and present simulations of statistical landscape evolution. PMID:16907308

  19. Spongiosa Primary Development: A Biochemical Hypothesis by Turing Patterns Formations

    Science.gov (United States)

    López-Vaca, Oscar Rodrigo; Garzón-Alvarado, Diego Alexander

    2012-01-01

    We propose a biochemical model describing the formation of primary spongiosa architecture through a bioregulatory model by metalloproteinase 13 (MMP13) and vascular endothelial growth factor (VEGF). It is assumed that MMP13 regulates cartilage degradation and the VEGF allows vascularization and advances in the ossification front through the presence of osteoblasts. The coupling of this set of molecules is represented by reaction-diffusion equations with parameters in the Turing space, creating a stable spatiotemporal pattern that leads to the formation of the trabeculae present in the spongy tissue. Experimental evidence has shown that the MMP13 regulates VEGF formation, and it is assumed that VEGF negatively regulates MMP13 formation. Thus, the patterns obtained by ossification may represent the primary spongiosa formation during endochondral ossification. Moreover, for the numerical solution, we used the finite element method with the Newton-Raphson method to approximate partial differential nonlinear equations. Ossification patterns obtained may represent the primary spongiosa formation during endochondral ossification. PMID:23193429

  20. Spongiosa Primary Development: A Biochemical Hypothesis by Turing Patterns Formations

    Directory of Open Access Journals (Sweden)

    Oscar Rodrigo López-Vaca

    2012-01-01

    Full Text Available We propose a biochemical model describing the formation of primary spongiosa architecture through a bioregulatory model by metalloproteinase 13 (MMP13 and vascular endothelial growth factor (VEGF. It is assumed that MMP13 regulates cartilage degradation and the VEGF allows vascularization and advances in the ossification front through the presence of osteoblasts. The coupling of this set of molecules is represented by reaction-diffusion equations with parameters in the Turing space, creating a stable spatiotemporal pattern that leads to the formation of the trabeculae present in the spongy tissue. Experimental evidence has shown that the MMP13 regulates VEGF formation, and it is assumed that VEGF negatively regulates MMP13 formation. Thus, the patterns obtained by ossification may represent the primary spongiosa formation during endochondral ossification. Moreover, for the numerical solution, we used the finite element method with the Newton-Raphson method to approximate partial differential nonlinear equations. Ossification patterns obtained may represent the primary spongiosa formation during endochondral ossification.

  1. Integration of IT-Security Aspects into Information Demand Analysis and Patterns

    OpenAIRE

    Sandkuhl, Kurt; Matulevicius, Raimundas; Kirikova, Marite; Ahmed, Naved

    2015-01-01

    Information logistics in general addresses demand-oriented information supply in organizations. IT-security has not received much attention in information logistics research. However, integration of security aspects into information logistics methods could be useful for application contexts with strong security requirements. As a contribution to this aspect, the paper investigates the possibility to extend information demand patterns (IDP) and information demand analysis (IDA) with security e...

  2. Temperature Controlled Lateral Pattern Formation in Confined Polymer Thin Films

    Institute of Scientific and Technical Information of China (English)

    ZHANG Hao-li; David G. Bucknall

    2004-01-01

    The thermal induced topography change in a model system consisting of a polymer film on a Si substrate capped by a thin metal layer has been studied by using AFM. Regular lateral patterns over large areas were observed on the surface when the system was heated to a sufficiently high temperature. 2D-FFT analysis to the AFM images indicates that the patterns are isotropic and have well defined periodicities. The periodicities of the characteristic patterns are found to depend strongly on the annealing temperature. The study of the kinetics of the formation reveals that such a topography forms almost instantaneously once the critical temperature is reached. It is suggested that this wave-like surface morphology is driven by the thermal expansion coefficient mismatch of the different layers. This method for generating regular wave-like patterns could be used as a general method for patterning various organic materials into micro/nanostructures.

  3. Mining Regular Patterns in Data Streams Using Vertical Format

    Directory of Open Access Journals (Sweden)

    G. Vijay Kumar

    2012-04-01

    Full Text Available The increasing prominence of data streams has been lead to the study of online mining in order to capture interesting trends, patterns and exceptions. Recently, temporal regularity in occurrence behavior of a pattern was treated as an emerging area in several online applications like network traffic, sensor networks, e-business and stock market analysis etc. A pattern is said to be regular in a data stream, if its occurrence behavior is not more than the user given regularity threshold. Although there has been some efforts done in finding regular patterns over stream data, no such method has been developed yet by using vertical data format. Therefore, in this paper we develop a new method called VDSRP-method to generate the complete set of regular patterns over a data stream at a user given regularity threshold. Our experimental results show that highly efficiency in terms of execution and memory consumption.

  4. Molecular aspect of good eating quality formation in Japonica rice.

    Directory of Open Access Journals (Sweden)

    Ming-Mao Sun

    quality, but GBSS1 decreased eating quality. The results indicated the possibility of developing high palatability cultivars through modification of key genes related to japonica rice eating quality formation in starch biosynthesis.

  5. Incremental Mining for Regular Frequent Patterns in Vertical Format

    Directory of Open Access Journals (Sweden)

    Vijay Kumar G

    2013-04-01

    Full Text Available In the real world database updates continuously in several online applications like super market, network monitoring, web administration, stock market etc. Frequent pattern mining is afundamental and essential area in data mining research. Not only occurrence frequency of a pattern but also occurrence behaviour of a pattern may be treated as important criteria to measure the interestingness of a pattern. A frequent pattern is said to be regular frequent if the occurrence behaviour is less than or equal to the user given regularity threshold. In incremental transactional databases the occurrence frequency and the occurrence behaviour of a pattern changes whenever a small set of new transactions are added to the database. It is undesirable to mine regular frequent patterns from the scratch. Thus proposes a new algorithm called RFPID (Regular Frequent Pattern Mining in Incremental Databases to mine regular frequent patterns in incremental transactional databases using vertical data format which requires only one database scan. The experimental results show our algorithm is efficient in both memory utilization and execution.

  6. Self-organized surface ripple pattern formation by ion implantation

    Science.gov (United States)

    Hofsäss, Hans; Zhang, Kun; Bobes, Omar

    2016-10-01

    Ion induced ripple pattern formation on solid surfaces has been extensively studied in the past and the theories describing curvature dependent ion erosion as well as redistribution of recoil atoms have been very successful in explaining many features of the pattern formation. Since most experimental studies use noble gas ion irradiation, the incorporation of the ions into the films is usually neglected. In this work we show that the incorporation or implantation of non-volatile ions also leads to a curvature dependent term in the equation of motion of a surface height profile. The implantation of ions can be interpreted as a negative sputter yield; and therefore, the effect of ion implantation is opposite to the one of ion erosion. For angles up to about 50°, implantation of ions stabilizes the surface, whereas above 50°, ion implantation contributes to the destabilization of the surface. We present simulations of the curvature coefficients using the crater function formalism and we compare the simulation results to the experimental data on the ion induced pattern formation using non-volatile ions. We present several model cases, where the incorporation of ions is a crucial requirement for the pattern formation.

  7. Modification of pattern formation in doubly resonant second

    DEFF Research Database (Denmark)

    Lodahl, Peter; Bache, Morten; Saffmann, M.

    2000-01-01

    We analyze pattern formation in doubly resonant intracavity second-harmonic generation in the presence of competing nondegenerate parametric downconversion. We show that for positive cavity detuning of the fundamental frequency the threshold for parametric oscillation is lower than that of...

  8. Modelling Global Pattern Formations for Collaborative Learning Environments

    DEFF Research Database (Denmark)

    Grappiolo, Corrado; Cheong, Yun-Gyung; Khaled, Rilla;

    2012-01-01

    We present our research towards the design of a computational framework capable of modelling the formation and evolution of global patterns (i.e. group structures) in a population of social individuals. The framework is intended to be used in collaborative environments, e.g. social serious games...

  9. Micron-scale pattern formation in prestressed polygonal films

    NARCIS (Netherlands)

    Annabattula, R. K.; Onck, P. R.

    2011-01-01

    In this paper we explore the spontaneous formation of micropatterns in thin prestressed polygonal films using finite element simulations. We study films with different size, thickness, and shape, including square, rectangular, pentagonal, and hexagonal films. Patterns form when the films release the

  10. NEGATIVE TRANSFER IN THE ASPECTS OF LANGUAGE, CULTURE AND THINKING PATTERN

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    While negative transfer of the native linguistic knowledge inSLA is closely studied, other aspects of the learner’s nativeknowledge have been ignored. The following is an investigationand study in this respect, revealing that negative transfer not on-ly happens in the aspect of the learner’s native linguistic knowl-edge such as that of the native grammatical rules and lexical con-ception, but also happens in aspects of cultural conventions andthinking patterns. It is also found that negative transfer of lin-guistic knowledge decreases with the learner’s progress in studywhile the other two aspects have no obvious decrease. With Level3 as a control group, this paper confirmed the effectiveness andnecessity in offering classes dealing with the other two aspects ofnegative transfer.

  11. How does tidal flow affect pattern formation in mussel beds?

    Science.gov (United States)

    Sherratt, Jonathan A; Mackenzie, Julia J

    2016-10-01

    In the Wadden Sea, mussel beds self-organise into spatial patterns consisting of bands parallel to the shore. A leading explanation for this phenomenon is that mussel aggregation reduces losses from dislodgement and predation, because of the adherence of mussels to one another. Previous mathematical modelling has shown that this can lead to spatial patterning when it is coupled to the advection from the open sea of algae-the main food source for mussels in the Wadden Sea. A complicating factor in this process is that the advection of algae will actually oscillate with the tidal flow. This has been excluded from previous modelling studies, and the present paper concerns the implications of this oscillation for pattern formation. The authors initially consider piecewise constant ("square-tooth") oscillations in advection, which enables analytical investigation of the conditions for pattern formation. They then build on this to study the more realistic case of sinusoidal oscillations. Their analysis shows that future research on the details of pattern formation in mussel beds will require an in-depth understanding of how the tides affect long-range inhibition among mussels. PMID:27343625

  12. Pattern formation in oscillatory complex networks consisting of excitable nodes

    Science.gov (United States)

    Liao, Xuhong; Xia, Qinzhi; Qian, Yu; Zhang, Lisheng; Hu, Gang; Mi, Yuanyuan

    2011-05-01

    Oscillatory dynamics of complex networks has recently attracted great attention. In this paper we study pattern formation in oscillatory complex networks consisting of excitable nodes. We find that there exist a few center nodes and small skeletons for most oscillations. Complicated and seemingly random oscillatory patterns can be viewed as well-organized target waves propagating from center nodes along the shortest paths, and the shortest loops passing through both the center nodes and their driver nodes play the role of oscillation sources. Analyzing simple skeletons we are able to understand and predict various essential properties of the oscillations and effectively modulate the oscillations. These methods and results will give insights into pattern formation in complex networks and provide suggestive ideas for studying and controlling oscillations in neural networks.

  13. Noise induced pattern formation of oscillation growth in traffic flow

    CERN Document Server

    Tian, Junfang; Treiber, Martin

    2016-01-01

    Noise is able to induce diverse patterns in physical and interdisciplinary extended systems. This Letter investigates the role of noise in pattern formation of traffic flow, which is a typical self-driven system far from equilibrium. We demonstrate that noise is necessary to correctly describe the observed spatiotemporal dynamics of growing traffic oscillation in the car following process. A heuristic analysis qualitatively explains the concave growth of the oscillation amplitude along the vehicles of a platoon. Based on this analysis, we propose a simple car-following model containing indifference regions and acceleration noise described by Brownian motion which reproduces well the experimental and empirical observations. Our study indicates that noise might also play an important role in pattern formation in other biological or socio-economic systems that are subject to stochasticity.

  14. Surface mechanics mediate pattern formation in the developing retina.

    Science.gov (United States)

    Hayashi, Takashi; Carthew, Richard W

    2004-10-01

    Pattern formation of biological structures involves organizing different types of cells into a spatial configuration. In this study, we investigate the physical basis of biological patterning of the Drosophila retina in vivo. We demonstrate that E- and N-cadherins mediate apical adhesion between retina epithelial cells. Differential expression of N-cadherin within a sub-group of retinal cells (cone cells) causes them to form an overall shape that minimizes their surface contact with surrounding cells. The cells within this group, in both normal and experimentally manipulated conditions, pack together in the same way as soap bubbles do. The shaping of the cone cell group and packing of its components precisely imitate the physical tendency for surfaces to be minimized. Thus, simple patterned expression of N-cadherin results in a complex spatial pattern of cells owing to cellular surface mechanics. PMID:15470418

  15. Mining Regular Patterns in Data Streams Using Vertical Format

    Directory of Open Access Journals (Sweden)

    G. Vijay Kumar

    2012-04-01

    Full Text Available The increasing prominence of data streams has been lead to the study of online mining in orderto capture interesting trends, patterns and exceptions. Recently, temporal regularity in occurrencebehavior of a pattern was treated as an emerging area in several online applications like networktraffic, sensor networks, e-business and stock market analysis etc. A pattern is said to be regularin a data stream, if its occurrence behavior is not more than the user given regularity threshold.Although there has been some efforts done in finding regular patterns over stream data, no suchmethod has been developed yet by using vertical data format. Therefore, in this paper wedevelop a new method called VDSRP-method to generate the complete set of regular patternsover a data stream at a user given regularity threshold. Our experimental results show that highlyefficiency in terms of execution and memory consumption.

  16. Pattern formation and self-organization in plasmas interacting with surfaces

    Science.gov (United States)

    Trelles, Juan Pablo

    2016-10-01

    Pattern formation and self-organization are fascinating phenomena commonly observed in diverse types of biological, chemical and physical systems, including plasmas. These phenomena are often responsible for the occurrence of coherent structures found in nature, such as recirculation cells and spot arrangements; and their understanding and control can have important implications in technology, e.g. from determining the uniformity of plasma surface treatments to electrode erosion rates. This review comprises theoretical, computational and experimental investigations of the formation of spatiotemporal patterns that result from self-organization events due to the interaction of low-temperature plasmas in contact with confining or intervening surfaces, particularly electrodes. The basic definitions associated to pattern formation and self-organization are provided, as well as some of the characteristics of these phenomena within natural and technological contexts, especially those specific to plasmas. Phenomenological aspects of pattern formation include the competition between production/forcing and dissipation/transport processes, as well as nonequilibrium, stability, bifurcation and nonlinear interactions. The mathematical modeling of pattern formation in plasmas has encompassed from theoretical approaches and canonical models, such as reaction-diffusion systems, to drift-diffusion and nonequilibrium fluid flow models. The computational simulation of pattern formation phenomena imposes distinct challenges to numerical methods, such as high sensitivity to numerical approximations and the occurrence of multiple solutions. Representative experimental and numerical investigations of pattern formation and self-organization in diverse types of low-temperature electrical discharges (low and high pressure glow, dielectric barrier and arc discharges, etc) in contact with solid and liquid electrodes are reviewed. Notably, plasmas in contact with liquids, found in diverse

  17. A new mechanism for dendritic pattern formation in dense systems

    Science.gov (United States)

    Oikawa, Noriko; Kurita, Rei

    2016-06-01

    Patterns are often formed when particles cluster: Since patterns reflect the connectivity of different types of material, the emergence of patterns affects the physical and chemical properties of systems and shares a close relationship to their macroscopic functions. A radial dendritic pattern (RDP) is observed in many systems such as snow crystals, polymer crystals and biological systems. Although most of these systems are considered as dense particle suspensions, the mechanism of RDP formation in dense particle systems is not yet understood. It should be noted that the diffusion limited aggregation model is not applicable to RDP formation in dense systems, but in dilute particle systems. Here, we propose a simple model that exhibits RDP formation in a dense particle system. The model potential for the inter-particle interaction is composed of two parts, a repulsive and an attractive force. The repulsive force is applied to all the particles all the time and the attractive force is exerted only among particles inside a circular domain, which expands at a certain speed as a wave front propagating from a preselected centre. It is found that an RDP is formed if the velocity of the wave front that triggers the attractive interaction is of the same order of magnitude as the time scale defined by the aggregation speed.

  18. Liesegang patterns: Complex formation of precipitate in an electric field

    Indian Academy of Sciences (India)

    István Lagzi

    2005-02-01

    Formation of 1D Liesegang patterns was studied numerically in precipitation and reversible complex formation of precipitate scenarios in an electric field. The Ostwald’s supersaturation model reported by Büki, Kárpáti-Smidróczki and Zrínyi (BKZ model) was extended further. In the presence of an electric field the position of the first and the last bands () measured from the junction point of the outer and the inner electrolytes can be described by the function = 1 $_{}^{1/2}$ + 2 + 3 , where is the time elapsed until the nth band formation, 1, 2 and 3 are constants. The variation of the total number of bands with different electric field strengths () has a maximum. For higher one can observe a moving precipitation zone that becomes wider due to precipitation and reversible complex formation.

  19. Wavenumber Locking And Pattern Formation In Spatially Forced Systems

    Energy Technology Data Exchange (ETDEWEB)

    Hagberg, Aric [Los Alamos National Laboratory; Meron, Ehud [BEN-GURION UNIV; Manor, Rotem [BEN-GURION UNIV

    2008-01-01

    We study wavenumber locking and pattern formation resulting from weak spatially periodic one-dimensional forcing of two-dimensional systems. We consider systems that support stationary or traveling stripe patterns in the absence of the forcing, and assume that the one-dimensional forcing is aligned with the direction of the stripe patterns. When the forcing wavenumber is about twice as large as the wavenumber of the unforced system we find that the forcing can either select or stabilize a resonant stripe solution at half the forcing wavenumber, or create a new resonant solution. When the wavenumber mismatch is high we find that the wave-vector component of the pattern in the direction of the forcing can stilI lock at half the forcing wavenumber, but a wave-vector component in the orthogonal direction develops to compensate for the total wavenumber. As a result stationary two-dimensional rectangular and oblique patterns form. When the unforced system supports traveling waves resonant rectangular patterns remain stationary but the oblique patterns travel in a direction orthogonal to the traveling-waves.

  20. Drying bacterial biosaline patterns capable of vital reanimation upon rehydration: novel hibernating biomineralogical life formations.

    Science.gov (United States)

    Gómez Gómez, José María; Medina, Jesús; Hochberg, David; Mateo-Martí, Eva; Martínez-Frías, Jesús; Rull, Fernando

    2014-07-01

    Water is the fundamental molecule for life on Earth. Thus, the search for hibernating life-forms in waterless environments is an important research topic for astrobiology. To date, however, the organizational patterns containing microbial life in extremely dry places, such as the deserts of Earth, the Dry Valleys of Antarctica, or Mars analog regolith, have been poorly characterized. Here, we report on the formation of bacterial biosaline self-organized drying patterns formed over plastic surfaces. These emerge during the evaporation of sessile droplets of aqueous NaCl salt 0.15 M solutions containing Escherichia coli cells. In the present study, scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS) analyses indicated that the bacterial cells and the NaCl in these biosaline formations are organized in a two-layered characteristic 3-D architectural morphology. A thin filmlike top layer formed by NaCl conjugated to, and intermingled with, "mineralized" bacterial cells covers a bottom layer constructed by the bulk of the nonmineralized bacterial cells; both layers have the same morphological pattern. In addition, optical microscopic time-lapsed movies show that the formation of these patterns is a kinetically fast process that requires the coupled interaction between the salt and the bacterial cells. Apparently, this mutual interaction drives the generative process of self-assembly that underlies the drying pattern formation. Most notably, the bacterial cells inside these drying self-assembled patterns enter into a quiescent suspended anhydrobiotic state resistant to complete desiccation and capable of vital reanimation upon rehydration. We propose that these E. coli biosaline drying patterns represent an excellent experimental model for understanding different aspects of anhydrobiosis phenomena in bacteria as well as for revealing the mechanisms of bacterially induced biomineralization, both highly relevant topics for the search of life in

  1. Pattern formation and coexistence domains for a nonlocal population dynamics

    CERN Document Server

    da Cunha, J A R; Oliveira, F A

    2011-01-01

    In this communication we propose a most general equation to study pattern formation for one-species population and their limit domains in systems of length L. To accomplish this we include non-locality in the growth and competition terms where the integral kernels are now depend on characteristic length parameters alpha and beta. Therefore, we derived a parameter space (alpha,beta) where it is possible to analyze a coexistence curve alpha*=alpha*(\\beta) which delimits domains for the existence (or not) of pattern formation in population dynamics systems. We show that this curve has an analogy with coexistence curve in classical thermodynamics and critical phenomena physics. We have successfully compared this model with experimental data for diffusion of Escherichia coli populations.

  2. On a New Mechanism of Pattern Formation in Population Dynamics

    OpenAIRE

    Génieys, Stéphane; Volpert, Vitaly; Auger, Pierre

    2005-01-01

    We study a reaction-diffusion equation with an integral term describing nonlocal consumption of resources. We show that a homogeneous equilibrium can lose its stability resulting in appearance of stationary spatial structures. It is a new mechanism of pattern formation in population dynamics that can explain emergence of biological species due to intra-specific competition and random mutations.Travelling waves connecting an unstable homogeneous equilibrium and a periodic in space stationary s...

  3. On pattern formation in the Gray-Scott model

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In the paper, we investigate an elliptic system well-known as the Gray-Scott model and present some further results for positive solutions of this model. More precisely, we give the refined a priori estimates of positive solutions, and improve some previous results for the non-existence and existence of positive non-constant solutions as the parameters are varied, which imply some certain conditions where the pattern formation occurs or not.

  4. Inherent-opening-controlled pattern formation in carbon nanotube arrays

    OpenAIRE

    Huang, Xiao; Zhou, Jijie J.; Sansom, Elijah; Gharib, Morteza; Haur, Sow Chorng

    2007-01-01

    We have introduced inherent openings into densely packed carbon nanotube arrays to study self-organized pattern formation when the arrays undergo a wetting–dewetting treatment from nanotube tips. These inherent openings, made of circular or elongated hollows in nanotube mats, serve as dewetting centres, from where liquid recedes from. As the dewetting centres initiate dry zones and the dry zones expand, surrounding nanotubes are pulled away from the dewetting centres by liquid surface tension...

  5. The role of hydrological transience in peatland pattern formation

    Science.gov (United States)

    Morris, P. J.; Baird, A. J.; Belyea, L. R.

    2013-10-01

    The sloping flanks of peatlands are commonly patterned with non-random, contour-parallel stripes of distinct micro-habitats such as hummocks, lawns and hollows. Patterning seems to be governed by feedbacks among peatland hydrological processes, plant micro-succession, plant litter production and peat decomposition. An improved understanding of peatland patterning may provide important insights into broader aspects of the long-term development of peatlands and their likely response to future climate change. We recreated a cellular simulation model from the literature, as well as three subtle variants of the model, to explore the controls on peatland patterning. Our models each consist of three submodels, which simulate: peatland water tables in a gridded landscape, micro-habitat dynamics in response to water-table depths, and changes in peat hydraulic properties. We found that the strength and nature of simulated patterning was highly dependent on the degree to which water tables had reached a steady state in response to hydrological inputs. Contrary to previous studies, we found that under a true steady state the models predict largely unpatterned landscapes that cycle rapidly between contrasting dry and wet states, dominated by hummocks and hollows, respectively. Realistic patterning only developed when simulated water tables were still transient. Literal interpretation of the degree of hydrological transience required for patterning suggests that the model should be discarded; however, the transient water tables appear to have inadvertently replicated an ecological memory effect that may be important to peatland patterning. Recently buried peat layers may remain hydrologically active despite no longer reflecting current vegetation patterns, thereby highlighting the potential importance of three-dimensional structural complexity in peatlands to understanding the two-dimensional surface-patterning phenomenon. The models were highly sensitive to the assumed values

  6. Nonlinear dynamics of pattern formation and pattern recognition in the rabbit olfactory bulb

    Science.gov (United States)

    Baird, Bill

    1986-10-01

    A mathematical model of the process of pattern recognition in the first olfactory sensory cortex of the rabbit is presented. It explains the formation and alteration of spatial patterns in neural activity observed experimentally during classical Pavlovian conditioning. On each inspiration of the animal, a surge of receptor input enters the olfactory bulb. EEG activity recorded at the surface of the bulb undergoes a transition from a low amplitude background state of temporal disorder to coherent oscillation. There is a distinctive spatial pattern of rms amplitude in this oscillation which changes reliably to a second pattern during each successful recognition by the animal of a conditioned stimulus odor. When a new odor is paired as conditioned stimulus, these patterns are replaced by new patterns that stabilize as the animal adapts to the new environment. I will argue that a unification of the theories of pattern formation and associative memory is required to account for these observations. This is achieved in a model of the bulb as a discrete excitable medium with spatially inhomogeneous coupling expressed by a connection matrix. The theory of multiple Hopf bifurcations is employed to find coupled equations for the amplitudes of competing unstable oscillatory modes. These may be created in the system by proper coupling and selectively evoked by specific classes of inputs. This allows a view of limit cycle attractors as “stored” fixed points of a gradient vector field and thereby recovers the more familiar dynamical systems picture of associative memory.

  7. Dynamics and pattern formation in a cancer network with diffusion

    Science.gov (United States)

    Zheng, Qianqian; Shen, Jianwei

    2015-10-01

    Diffusion is ubiquitous inside cells, and it is capable of inducing spontaneous pattern formation in reaction-diffusion systems on a spatially homogeneous domain. In this paper, we investigate the dynamics of a diffusive cancer network regulated by microRNA and obtain the condition that the network undergoes a Hopf bifurcation and a Turing pattern bifurcation. In addition, we also develop the amplitude equation of the network model by using Taylor series expansion, multi-scaling and further expansion in powers of a small parameter. As a result of these analyses, we obtain the explicit condition on how the dynamics of the diffusive cancer network evolve. These results reveal that this system has rich dynamics, such as spotted stripe and hexagon patterns. The bifurcation diagram helps us understand the biological mechanism in the cancer network. Finally, numerical simulations confirm our analytical results.

  8. Spontaneous Pattern Formation in an Antiferromagnetic Quantum Gas

    International Nuclear Information System (INIS)

    In this Letter we report on the spontaneous formation of surprisingly regular periodic magnetic patterns in an antiferromagnetic Bose-Einstein condensate (BEC). The structures evolve within a quasi-one-dimensional BEC of 87Rb atoms on length scales of a millimeter with typical periodicities of 20...30 μm, given by the spin healing length. We observe two sets of characteristic patterns which can be controlled by an external magnetic field. We identify these patterns as linearly unstable modes within a mean-field approach and calculate their mode structure as well as time and energy scales, which we find to be in good agreement with observations. These investigations open new prospects for controlled studies of symmetry breaking and complex quantum magnetism in bulk BEC.

  9. What drives the formation of global oil trade patterns?

    International Nuclear Information System (INIS)

    In this paper, the spatial characteristics of current global oil trade patterns are investigated by proposing a new indicator Moran-F. Meanwhile, the factors that influence the formation of oil trade patterns are identified by constructing four different kinds of spatial econometric models. The findings indicate that most oil exporters have an obvious export focus in North America and a relatively balanced export in Europe and the Asia-Pacific region. Besides supply and demand factors, technological progress and energy efficiency have also significantly influenced the oil trade. Moreover, there is a spillover effect of trade flow among different regions, but its impact is weak. In addition, oil importers in the same region have the potential to cooperate due to their similar import sources. Finally, promotion of oil importers' R&D investments can effectively reduce the demand for global oil trade. - Highlights: • A new spatial association Moran-F indicator that applies to trade flows is proposed. • Driving factors affecting the formation of oil trade patterns are identified. • Oil-exporting countries implement various export strategies in different regions. • Supply, demand and technological factors contribute to the oil trade patterns. • Spillover effect of each factor affecting oil trade flows does exist but is limited

  10. On Pattern Formation Mechanisms for Lepidopteran Wing Patterns and Mammalian Coat Markings

    Science.gov (United States)

    Murray, J. D.

    1981-10-01

    The patterns on wings of Lepidoptera can be generated with a few pattern elements, but no mechanism has been suggested for producing them. I consider two of the basic patterns, namely, central symmetry and dependent patterns. A biochemically plausible model mechanism is proposed for generating major aspects of these patterns, based on a diffusing morphogen that activates a gene or colour-specific enzyme in a threshold manner to generate a stable heterogeneous spatial pattern. The model is applied to the determination stream hypothesis of Kuhn & von Engelhardt (Wilhelm Roux Arch. Entw Mech. Org. 130, 660 (1933)), and results from the model compared with their microcautery experiments on the pupal wing of Ephestia kuhniella. In the case of dependent patterns, results are compared with patterns on specific Papilionidae. For the same mechanism and a fixed set of parameters I demonstrate the important roles of geometry and scale on the spatial patterns obtained. The results and evidence presented here suggest the existence of diffusion fields of the order of several millimetres, which are very much larger than most embryonic fields. The existence of zones of polarizing activity is also indicated. Colour patterns on animals are considered to be genetically determined, but the mechanism is not known. I have previously suggested that a single mechanism that can exhibit an infinite variety of patterns is a candidate for that mechanism, and proposed that a reaction-diffusion system that can be diffusively driven unstable could be responsible for the laying down of the spacing patterns that generates the prepattern for animal coat markings. For illustrative purposes I consider a practical reaction mechanism, which exhibits substrate inhibition, and show that the geometry and scale of the domain (part of the epidermis) play a crucial role in the structural patterns that result. Patterns are obtained for a selection of geometries, and general features are related to the coat

  11. Arch-pattern based design and aspect-oriented implementation of Readers-Writers concurrent problem

    Directory of Open Access Journals (Sweden)

    Dumitru Ciorbă

    2007-11-01

    Full Text Available The classical problems of concurrent programming start from the design problems of operating systems in the 80-s. But today there are still proposed new solutions for these problems with the help of various design and programming approaches. The present article describes a solution which was designed according to some new object-oriented principles, based on design patterns and proposes two program solutions: firstly - an object-oriented implementation in Java language, the secondly – an aspect-oriented one in AspectJ language.

  12. Formation of high aspect ratio polyamide-6 nanofibers via electrically induced double layer during electrospinning

    International Nuclear Information System (INIS)

    In the present study, the formation of high aspect ratio nanofibers in polyamide-6 was investigated as a function of applied voltage ranging from 15 to 25 kV using electrospinning technique. All other experimental parameters were kept constant. The electrospun polyamide-6 nanofibers were characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF). FE-SEM images of polyamide-6 nanofibers showed that the diameter of the electrospun fiber was decreased with increasing applied voltage. At the critical applied voltage, the polymer solution was completely ionized to form the dense high aspect ratio nanofibers in between the main nanofibers. The diameter of the polyamide-6 nanofibers was observed to be in the range of 75-110 nm, whereas the high aspect ratio structures consisted of regularly distributed very fine nanofibers with diameters of about 9-28 nm. Trends in fiber diameter and diameter distribution were discussed for the high aspect ratio nanofibers. TEM results revealed that the formation of double layers in polyamide-6 nanofibers and then split-up into ultrafine fibers. The electrically induced double layer in combination with the polyelectrolytic nature of solution is proposed as the suitable mechanisms for the formation of high aspect ratio nanofibers in polyamide-6.

  13. Structural and quantitative aspects of radical formation after heavy ion bombardment

    Energy Technology Data Exchange (ETDEWEB)

    Dusemund, B.; Hoffmann, A.K.; Weiland, B.; Huettermann, J. [Klinikum Homburg (Germany). Fachrichtung Biophysik

    1997-09-01

    In this report the authors present a summary of their recent attempts aiming at clarifying some basic structural and quantitative aspects of free radical formation in DNA constituents and in DNA as well as of product analysis from nucleotide model compounds. (orig./MG)

  14. Vortex formation and drag on low aspect ratio, normal flat plates

    Science.gov (United States)

    Ringuette, Matthew James

    Experiments were done to investigate the role of vortex formation in the drag force generation of low aspect ratio, normal flat plates starting from rest. This very simplified case is a first, fundamental step toward understanding the more complicated flow of hovering flight, which relies primarily on drag for propulsion. The relative importance of the plate's free end, or tip, with varying aspect ratio was also studied. Identifying the relationship among aspect ratio, vortex formation, and drag force can provide insight into the wing aspect ratios and kinematics found nature, with the eventual goal of designing man-made flapping wing micro air vehicles. The experiments were carried out using flat plate models in a towing tank at a moderate Reynolds number of 3000. Two aspect ratios, 6 and 2, were considered, the latter in order to have a highly tip-dominated case. A force balance measured the time-varying drag, and multiple, perpendicular sections of the flow velocity were measured quantitatively using digital particle image velocimetry. Vorticity fields were calculated from the velocity data, and features in the drag force for different aspect ratios were related to the vortex dynamics. Finally, since the flow is highly three-dimensional, dye flow visualization was done to characterize its structure and to augment the two-dimensional digital particle image velocimetry data.

  15. Flow-driven instabilities during pattern formation of Dictyostelium discoideum

    Science.gov (United States)

    Gholami, A.; Steinbock, O.; Zykov, V.; Bodenschatz, E.

    2015-06-01

    The slime mold Dictyostelium discoideum is a well known model system for the study of biological pattern formation. In the natural environment, aggregating populations of starving Dictyostelium discoideum cells may experience fluid flows that can profoundly change the underlying wave generation process. Here we study the effect of advection on the pattern formation in a colony of homogeneously distributed Dictyostelium discoideum cells described by the standard Martiel-Goldbeter model. The external flow advects the signaling molecule cyclic adenosine monophosphate (cAMP) downstream, while the chemotactic cells attached to the solid substrate are not transported with the flow. The evolution of small perturbations in cAMP concentrations is studied analytically in the linear regime and by corresponding numerical simulations. We show that flow can significantly influence the dynamics of the system and lead to a flow-driven instability that initiate downstream traveling cAMP waves. We also show that boundary conditions have a significant effect on the observed patterns and can lead to a new kind of instability.

  16. Pattern Formation by Electrostatic Self-Organization of Membrane Proteins

    Science.gov (United States)

    Boedec, G.; Jaeger, M.; Homble, F.; Leonetti, M.

    2012-07-01

    The electric activity of biological cells and organs such as heart for example is at the origin of various phenomena of pattern formation. The electric membrane potential appears as the order parameter to characterize these spatiotemporal dynamics. A kind of patterns is characterized by a stationary spatial modulation of membrane potential along the cell, breaking a symmetry of the system. They are associated to transcellular currents. A mechanism proposed in literature is based on the coupling of the electric current produced by membrane proteins and their electrophoretic mobilities. Beyond its classical linear stability analysis, the numerical and theoretical analysis of this model offers a variety of spatiotemporal dynamics. Firstly, the background in the modelization of electric phenomena is recalled. Secondly, the analysis is focused on two nonlinear dynamics.

  17. Building better oscillators using nonlinear dynamics and pattern formation

    Indian Academy of Sciences (India)

    M C Cross; Eyal Kenig; John-Mark A Allen

    2015-03-01

    Frequency and time references play an essential role in modern technology and in living systems. The precision of self-sustained oscillations is limited by the effects of noise, which becomes evermore important as the sizes of the devices become smaller. In this paper, we review our recent theoretical results on using nonlinear dynamics and pattern formation to reduce the effects of noise and improve the frequency precision of oscillators, with particular reference to ongoing experiments on oscillators based on nanomechanical resonators. We discuss using resonator nonlinearity, novel oscillator architectures and the synchronization of arrays of oscillators, to improve the frequency precision.

  18. The physics of pattern formation at liquid interfaces

    International Nuclear Information System (INIS)

    During the past year we have submitted six papers for publication, three related to the dynamics of macroscopic interfaces, and ultimately all related to solidification, and three related to the internal structure of disorderly materials, with possible applications to the processing of composite materials. In addition to completing all these projects during the past year, we have begun two new projects, one on pattern formation and one on aggregation within a composite system. A brief description is given of this research in this paper

  19. Pattern formation of frictional fingers in a gravitational potential

    CERN Document Server

    Eriksen, Jon Alm; Måløy, Knut Jørgen; Flekkøy, Eirik; Sandnes, Bjørnar

    2016-01-01

    Aligned finger structures, with a characteristic width, emerges during the slow drainage of a liquid/granular mixture in a tilted Hele-Shaw cell. A transition from vertical to horizontal alignment of the finger structures is observed as the tilting angle and the granular density are varied. An analytical model is presented, demonstrating that the alignment properties is the result of the competition between fluctuating granular stresses and the hydrostatic pressure. The dynamics is reproduced in simulations. We also show how the system explains patterns made during dyke formations.

  20. FORMATION MECHANISM AND SPATIAL PATTERN OF URBAN AGGLOMERATION IN CENTRAL JILIN OF CHINA

    Institute of Scientific and Technical Information of China (English)

    QIN Gan; ZHANG Ping-yu; JIAO Bin

    2006-01-01

    Urban agglomeration is made up of cities with different sizes to be linked by traffic network in a given area, and it is an inevitable result when urbanization reaches a certain level. Taking urban agglomerationin central Jilin(UACJ) as an example, this article analyzes the formation mechanism and spatial pattern of urban agglomeration in the less-developed area. First, the dynamics of UACJ has been analyzed from the aspects of geographical condition, economic foundation, policy background, and traffic condition. Then the development process is divided into three stages-single city, city group and city cluster. Secondly, the central cities are identified from the aspects of city centrality, and the development axes are classified based on economic communication capacity. Finally, the urban agglomeration is divided into five urban economic regions in order to establish the reasonable distribution of industries.

  1. Pattern formation mechanisms in motility mutants of Myxococcus xanthus

    CERN Document Server

    Starruss, Joern; Jakovljevic, Vladimir; Sogaard-Andersen, Lotte; Deutsch, Andreas; Baer, Markus

    2016-01-01

    Formation of spatial patterns of cells is a recurring theme in biology and often depends on regulated cell motility. Motility of M. xanthus depends on two motility machineries: the S-engine and A-engine. Moving M. xanthus cells can organize into spreading colonies or spore-filled fruiting bodies depending on their nutritional status. To understand these two pattern formation processes and the contributions by the two motility machineries, as well as cell reversal, we analyze spatial self-organization in 3 strains: i) a mutant that moves unidirectionally without reversing by the A-motility system only, ii) a unidirectional mutant that is also equipped with the S-motility system, and iii) the wild-type that, in addition to the two motility systems, reverses its direction of movement. The mutant moving by the A-engine illustrates that collective motion in the form of large moving clusters can arise in gliding bacteria due to steric interactions of the rod-shaped cells, without the need of invoking any biochemica...

  2. Pattern formation and mass transfer under stationary solutal Marangoni instability.

    Science.gov (United States)

    Schwarzenberger, Karin; Köllner, Thomas; Linde, Hartmut; Boeck, Thomas; Odenbach, Stefan; Eckert, Kerstin

    2014-04-01

    According to the seminal theory by Sternling and Scriven, solutal Marangoni convection during mass transfer of surface-active solutes may occur as either oscillatory or stationary instability. With strong support of Manuel G. Velarde, a combined initiative of experimental works, in particular to mention those of Linde, Wierschem and coworkers, and theory has enabled a classification of dominant wave types of the oscillatory mode and their interactions. In this way a rather comprehensive understanding of the nonlinear evolution of the oscillatory instability could be achieved. A comparably advanced state-of-the-art with respect to the stationary counterpart seemed to be out of reach a short time ago. Recent developments on both the numerical and experimental side, in combination with assessing an extensive number of older experiments, now allow one to draw a more unified picture. By reviewing these works, we show that three main building blocks exist during the nonlinear evolution: roll cells, relaxation oscillations and relaxation oscillations waves. What is frequently called interfacial turbulence results from the interaction between these partly coexisting basic patterns which may additionally occur in different hierarchy levels. The second focus of this review lies on the practical importance of such convection patterns concerning their influence on mass transfer characteristics. Particular attention is paid here to the interaction between Marangoni and buoyancy effects which frequently complicates the pattern formation even more. To shed more light on these dependencies, new simulations regarding the limiting case of stabilizing density stratification and vanishing buoyancy are incorporated.

  3. Nonlinear pattern formation in bone growth and architecture

    Directory of Open Access Journals (Sweden)

    Phil eSalmon

    2015-01-01

    Full Text Available The 3D morphology of bone arises through adaptation to its required engineering performance. Genetically and adaptively bone travels along a complex spatio-temporal trajectory to acquire optimal architecture. On a cellular, micro-anatomical scale, what mechanisms coordinate the activity of osteoblasts and osteoclasts to produce complex and efficient bone architectures? One mechanism is examined here – chaotic nonlinear pattern formation (NPF – which underlies in a unifying way natural structures as disparate as trabecular bone, swarms of birds flying, island formation, fluid turbulence and others. At the heart of NPF is the fact that simple rules operating between interacting elements, and Turing-like interaction between global and local signals, lead to complex and structured patterns. The study of group intelligence exhibited by swarming birds or shoaling fish has led to an embodiment of NPF called particle swarm optimization (PSO. This theoretical model could be applicable to the behavior of osteoblasts osteoclasts and osteocytes, seeing them operating socially in response simultaneously to both global and local signals (endocrine, cytokine, mechanical resulting in their clustered activity at formation and resorption sites. This represents problem-solving by social intelligence, and could potentially add further realism to in-silico simulation of bone modeling.What insights has NPF provided to bone biology? One example concerns the genetic disorder Juvenile Pagets Disease (JPD or Idiopathic Hyperphosphatasia, where the anomalous parallel trabecular architecture characteristic of this pathology is consistent with an NPF paradigm by analogy with known experimental NPF systems. Here coupling or feedback between osteoblasts and osteoclasts is the critical element.This NPF paradigm implies a profound link between bone regulation and its architecture: in bone the architecture is the regulation. The former is the emergent consequence of the

  4. Non-linear pattern formation in bone growth and architecture.

    Science.gov (United States)

    Salmon, Phil

    2014-01-01

    The three-dimensional morphology of bone arises through adaptation to its required engineering performance. Genetically and adaptively bone travels along a complex spatiotemporal trajectory to acquire optimal architecture. On a cellular, micro-anatomical scale, what mechanisms coordinate the activity of osteoblasts and osteoclasts to produce complex and efficient bone architectures? One mechanism is examined here - chaotic non-linear pattern formation (NPF) - which underlies in a unifying way natural structures as disparate as trabecular bone, swarms of birds flying, island formation, fluid turbulence, and others. At the heart of NPF is the fact that simple rules operating between interacting elements, and Turing-like interaction between global and local signals, lead to complex and structured patterns. The study of "group intelligence" exhibited by swarming birds or shoaling fish has led to an embodiment of NPF called "particle swarm optimization" (PSO). This theoretical model could be applicable to the behavior of osteoblasts, osteoclasts, and osteocytes, seeing them operating "socially" in response simultaneously to both global and local signals (endocrine, cytokine, mechanical), resulting in their clustered activity at formation and resorption sites. This represents problem-solving by social intelligence, and could potentially add further realism to in silico computer simulation of bone modeling. What insights has NPF provided to bone biology? One example concerns the genetic disorder juvenile Pagets disease or idiopathic hyperphosphatasia, where the anomalous parallel trabecular architecture characteristic of this pathology is consistent with an NPF paradigm by analogy with known experimental NPF systems. Here, coupling or "feedback" between osteoblasts and osteoclasts is the critical element. This NPF paradigm implies a profound link between bone regulation and its architecture: in bone the architecture is the regulation. The former is the emergent

  5. Hydrodynamic approach to surface pattern formation by ion beams

    Energy Technology Data Exchange (ETDEWEB)

    Castro, Mario, E-mail: marioc@upcomillas.es [Grupo Interdisciplinar de Sistemas Complejos (GISC) and Grupo de Dinamica No Lineal (DNL), Escuela Tecnica Superior de Ingenieri a - ICAI, Universidad Pontificia Comillas, E-28015 Madrid (Spain); Cuerno, Rodolfo [Departamento de Matematicas and GISC, Universidad Carlos III de Madrid, Avenida de la Universidad 30, E-28911 Leganes (Spain)

    2012-02-15

    On the proper timescale, amorphous solids can flow. Solid flow can be observed macroscopically in glaciers or lead pipes, but it can also be artificially enhanced by creating defects. Ion Beam Sputtering (IBS) is a technique in which ions with energies in the 0.110 keV range impact against a solid target inducing defect creation and dynamics, and eroding its surface leading to formation of ordered nanostructures. Despite its technological interest, a basic understanding of nanopattern formation processes occurring under IBS of amorphizable targets has not been clearly established, recent experiments on Si having largely questioned knowledge accumulated during the last two decades. A number of interfacial equations have been proposed in the past to describe these phenomena, typically by adding together different contributions coming from surface diffusion, ion sputtering or mass redistribution, etc. in a non-systematic way. Here, we exploit the general idea of solids flowing due to ion impacts in order to establish a general framework into which different mechanisms (such as viscous flow, stress, diffusion, or sputtering) can be incorporated, under generic physical conservation laws. As opposed to formulating phenomenological interfacial equations, this approach allows to assess systematically the relevance and interplay of different physical mechanisms influencing surface pattern formation by IBS.

  6. Geometrical Aspects During Formation of Compact Aggregates of Red Blood Cells

    Directory of Open Access Journals (Sweden)

    Cardoso A.V.

    2002-01-01

    Full Text Available In the past forty years considerable progress has been achieved on the knowledge of human blood as a non-Newtonian shear-thinning suspension, whose initial state, that is at rest (stasis or at very low shear rates, has a gel-like internal structure which is destroyed as shear stress increases. The main goal of this communication is to describe the role of geometrical aspects during RBC (red blood cell aggregate formation, growth and compaction on naturally aggregate (porcine blood and non-aggregate (bovine blood samples. We consider how these aspects coupled with tension equilibrium are decisive to transform red cell linear roleaux to three-dimensional aggregates or clusters. Geometrical aspects are also crucial on the compaction of red blood cell aggregates. These densely packed aggregates could precipitate out of blood- either as dangerous deposits on arterial walls, or as clots which travel in suspension until they block some crucial capillary.

  7. Spontaneous pattern formation and pinning in the visual cortex

    Science.gov (United States)

    Baker, Tanya I.

    Bifurcation theory and perturbation theory can be combined with a knowledge of the underlying circuitry of the visual cortex to produce an elegant story explaining the phenomenon of visual hallucinations. A key insight is the application of an important set of ideas concerning spontaneous pattern formation introduced by Turing in 1952. The basic mechanism is a diffusion driven linear instability favoring a particular wavelength that determines the size of the ensuing stripe or spot periodicity of the emerging spatial pattern. Competition between short range excitation and longer range inhibition in the connectivity profile of cortical neurons provides the difference in diffusion length scales necessary for the Turing mechanism to occur and has been proven by Ermentrout and Cowan to be sufficient to explain the generation of a subset of reported geometric hallucinations. Incorporating further details of the cortical circuitry, namely that neurons are also weakly connected to other neurons sharing a particular stimulus orientation or spatial frequency preference at even longer ranges and the resulting shift-twist symmetry of the neuronal connectivity, improves the story. We expand this approach in order to be able to include the tuned responses of cortical neurons to additional visual stimulus features such as motion, color and disparity. We apply a study of nonlinear dynamics similar to the analysis of wave propagation in a crystalline lattice to demonstrate how a spatial pattern formed through the Turing instability can be pinned to the geometric layout of various feature preferences. The perturbation analysis is analogous to solving the Schrodinger equation in a weak periodic potential. Competition between the local isotropic connections which produce patterns of activity via the Turing mechanism and the weaker patchy lateral connections that depend on a neuron's particular set of feature preferences create long wavelength affects analogous to commensurate

  8. Territorial pattern formation in the absence of an attractive potential.

    Science.gov (United States)

    Potts, Jonathan R; Lewis, Mark A

    2016-01-01

    Territoriality is a phenomenon exhibited throughout nature. On the individual level, it is the processes by which organisms exclude others of the same species from certain parts of space. On the population level, it is the segregation of space into separate areas, each used by subsections of the population. Proving mathematically that such individual-level processes can cause observed population-level patterns to form is necessary for linking these two levels of description in a non-speculative way. Previous mathematical analysis has relied upon assuming animals are attracted to a central area. This can either be a fixed geographical point, such as a den- or nest-site, or a region where they have previously visited. However, recent simulation-based studies suggest that this attractive potential is not necessary for territorial pattern formation. Here, we construct a partial differential equation (PDE) model of territorial interactions based on the individual-based model (IBM) from those simulation studies. The resulting PDE does not rely on attraction to spatial locations, but purely on conspecific avoidance, mediated via scent-marking. We show analytically that steady-state patterns can form, as long as (i) the scent does not decay faster than it takes the animal to traverse the terrain, and (ii) the spatial scale over which animals detect scent is incorporated into the PDE. As part of the analysis, we develop a general method for taking the PDE limit of an IBM that avoids destroying any intrinsic spatial scale in the underlying behavioral decisions. PMID:25822451

  9. Ternary eutectic dendrites: Pattern formation and scaling properties

    International Nuclear Information System (INIS)

    Extending previous work [Pusztai et al., Phys. Rev. E 87, 032401 (2013)], we have studied the formation of eutectic dendrites in a model ternary system within the framework of the phase-field theory. We have mapped out the domain in which two-phase dendritic structures grow. With increasing pulling velocity, the following sequence of growth morphologies is observed: flat front lamellae → eutectic colonies → eutectic dendrites → dendrites with target pattern → partitionless dendrites → partitionless flat front. We confirm that the two-phase and one-phase dendrites have similar forms and display a similar scaling of the dendrite tip radius with the interface free energy. It is also found that the possible eutectic patterns include the target pattern, and single- and multiarm spirals, of which the thermal fluctuations choose. The most probable number of spiral arms increases with increasing tip radius and with decreasing kinetic anisotropy. Our numerical simulations confirm that in agreement with the assumptions of a recent analysis of two-phase dendrites [Akamatsu et al., Phys. Rev. Lett. 112, 105502 (2014)], the Jackson-Hunt scaling of the eutectic wavelength with pulling velocity is obeyed in the parameter domain explored, and that the natural eutectic wavelength is proportional to the tip radius of the two-phase dendrites. Finally, we find that it is very difficult/virtually impossible to form spiraling two-phase dendrites without anisotropy, an observation that seems to contradict the expectations of Akamatsu et al. Yet, it cannot be excluded that in isotropic systems, two-phase dendrites are rare events difficult to observe in simulations

  10. Ternary eutectic dendrites: Pattern formation and scaling properties

    Energy Technology Data Exchange (ETDEWEB)

    Rátkai, László; Szállás, Attila; Pusztai, Tamás [Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, P.O. Box 49, H-1525 Budapest (Hungary); Mohri, Tetsuo [Center for Computational Materials Science, Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Gránásy, László, E-mail: granasy.laszlo@wigner.mta.hu [Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, P.O. Box 49, H-1525 Budapest (Hungary); Brunel University, Uxbridge, Middlesex UB8 3PH (United Kingdom)

    2015-04-21

    Extending previous work [Pusztai et al., Phys. Rev. E 87, 032401 (2013)], we have studied the formation of eutectic dendrites in a model ternary system within the framework of the phase-field theory. We have mapped out the domain in which two-phase dendritic structures grow. With increasing pulling velocity, the following sequence of growth morphologies is observed: flat front lamellae → eutectic colonies → eutectic dendrites → dendrites with target pattern → partitionless dendrites → partitionless flat front. We confirm that the two-phase and one-phase dendrites have similar forms and display a similar scaling of the dendrite tip radius with the interface free energy. It is also found that the possible eutectic patterns include the target pattern, and single- and multiarm spirals, of which the thermal fluctuations choose. The most probable number of spiral arms increases with increasing tip radius and with decreasing kinetic anisotropy. Our numerical simulations confirm that in agreement with the assumptions of a recent analysis of two-phase dendrites [Akamatsu et al., Phys. Rev. Lett. 112, 105502 (2014)], the Jackson-Hunt scaling of the eutectic wavelength with pulling velocity is obeyed in the parameter domain explored, and that the natural eutectic wavelength is proportional to the tip radius of the two-phase dendrites. Finally, we find that it is very difficult/virtually impossible to form spiraling two-phase dendrites without anisotropy, an observation that seems to contradict the expectations of Akamatsu et al. Yet, it cannot be excluded that in isotropic systems, two-phase dendrites are rare events difficult to observe in simulations.

  11. Tree island pattern formation in the Florida Everglades

    Science.gov (United States)

    Carr, Joel; D'Odorico, P.; Engel, Victor C.; Redwine, Jed

    2016-01-01

    The Florida Everglades freshwater landscape exhibits a distribution of islands covered by woody vegetation and bordered by marshes and wet prairies. Known as “tree islands”, these ecogeomorphic features can be found in few other low gradient, nutrient limited freshwater wetlands. In the last few decades, however, a large percentage of tree islands have either shrank or disappeared in apparent response to altered water depths and other stressors associated with human impacts on the Everglades. Because the processes determining the formation and spatial organization of tree islands remain poorly understood, it is still unclear what controls the sensitivity of these landscapes to altered conditions. We hypothesize that positive feedbacks between woody plants and soil accretion are crucial to emergence and decline of tree islands. Likewise, positive feedbacks between phosphorus (P) accumulation and trees explain the P enrichment commonly observed in tree island soils. Here, we develop a spatially-explicit model of tree island formation and evolution, which accounts for these positive feedbacks (facilitation) as well as for long range competition and fire dynamics. It is found that tree island patterns form within a range of parameter values consistent with field data. Simulated impacts of reduced water levels, increased intensity of drought, and increased frequency of dry season/soil consuming fires on these feedback mechanisms result in the decline and disappearance of tree islands on the landscape.

  12. Cleavage pattern and mesentoblast formation in Acanthochiton crinitus (Polyplacophora, Mollusca).

    Science.gov (United States)

    van den Biggelaar, J A

    1996-03-15

    In characteristic spiralian embryos the mesentoblast is the stem cell of the mesodermal bands. It is a derivative of the dorsal quadrant. At least in gastropod molluscs, the ancestral form for the specification of the dorsal quadrant out of four initially equal quadrants is by centralization of one of the four macromeres after the separation of the presumptive ecto- and entoblast cells. Then this macromere is induced by the animal micromeres to produce the mesentoblast. In this paper it is shown that in the embryo of the polyplacophoran Acanthochiton crinitus, specification of the dorsal quadrant and formation of the mesentoblast exactly follow the same pattern. After deletion of the first quartet of micromeres none of the macromeres is centralized, no mesentoblast is formed, and the embryo remains radially symmetrical. Apparently, the mechanism for the specification of the dorsal quadrant and the formation of the mesentoblast has been conserved during the evolution of the main molluscan taxa. It has been discussed whether this mechanism might be a plesiomorphous property, characteristic of less derived spiralian phyla. PMID:8631512

  13. Patterns of Glide Formation in Niger-Congo: An Optimality Account.

    Science.gov (United States)

    Casali, Roderic F.

    A study examined the pattern of formation of glides in a sample of 18 Niger-Congo languages that have substantial glide formation. It is noted first that four basic pattern dualities exist, with language-specific variations, determine by whether or not: (1) glide formation applies to both front and round first vowels or round first vowels only;…

  14. Gender aspects of formation of value potential of students’ physical training

    Directory of Open Access Journals (Sweden)

    Marchenko O. Iu.

    2014-11-01

    Full Text Available Purpose: study of gender peculiarities of formation of valuable orientations of students in physical education and sport. Material: in research students of 3 - 11 classes of secondary schools (419, with which the survey was conducted, were involved. Results : the absence of students' understanding of the necessity of motor activity to human health. Also development of adolescents values of physical culture and sports. Showing psychosocial characteristics to form a stable interest in the physical self. It was found that 15% of girls wish to play hockey on grass, athletic gymnastics, football and boxing. Conclusions: for the formation of valuable orientations of physical culture among students it is necessary to consider not only the physiological, morphological and psychological aspects, but also gender peculiarities of personality.

  15. The mechanism of pattern formation in the developing drosophila retina

    Institute of Scientific and Technical Information of China (English)

    SUN QiCheng

    2007-01-01

    The biological patterning of the drosophila retina in vivo has striking resemblance to liquid bubbles, in which the surface mechanics due to N-cadherin within a sub-group of retina cells can be mimicked by surface tension. In this work, the aggregating patterns were reasonably simplified into 2D clusters consisting of 2-6 identical bubbles confined within a shrinking boundary. By using a hybrid fluid dynamics model proposed for liquid foams, the aggregating process of 2-6 retina cells was studied. Assuming the minimal perimeter for patterning cells to be the condition of stability patterns, the stable converged patterns we simulated in this work are the same as the experimental observations. More importantly, a new pattern of 6 cells was obtained which was found physically more stable than the other two reported by Hayashi and Carthew[1]. Aggregating perimeters of cells, i.e. the surface energy, showed a good linear fit with the cell numbers.

  16. The mechanism of pattern formation in the developing drosophila retina

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The biological patterning of the drosophila retina in vivo has striking resemblance to liquid bubbles, in which the surface mechanics due to N-cadherin within a sub-group of retina cells can be mimicked by surface tension. In this work, the aggregating patterns were reasonably simplified into 2D clusters consisting of 2—6 identical bubbles confined within a shrinking boundary. By using a hybrid fluid dy-namics model proposed for liquid foams, the aggregating process of 2―6 retina cells was studied. Assuming the minimal perimeter for patterning cells to be the condition of stability patterns, the stable converged patterns we simulated in this work are the same as the experimental observations. More importantly, a new pattern of 6 cells was obtained which was found physically more stable than the other two reported by Hayashi and Carthew[1]. Aggregating perimeters of cells, i.e. the surface energy, showed a good linear fit with the cell numbers.

  17. Modeling of metal nanocluster growth on patterned substrates and surface pattern formation under ion bombardment

    Energy Technology Data Exchange (ETDEWEB)

    Numazawa, Satoshi

    2012-11-01

    This work addresses the metal nanocluster growth process on prepatterned substrates, the development of atomistic simulation method with respect to an acceleration of the atomistic transition states, and the continuum model of the ion-beam inducing semiconductor surface pattern formation mechanism. Experimentally, highly ordered Ag nanocluster structures have been grown on pre-patterned amorphous SiO{sub 2} surfaces by oblique angle physical vapor deposition at room temperature. Despite the small undulation of the rippled surface, the stripe-like Ag nanoclusters are very pronounced, reproducible and well-separated. The first topic is the investigation of this growth process with a continuum theoretical approach to the surface gas condensation as well as an atomistic cluster growth model. The atomistic simulation model is a lattice-based kinetic Monte-Carlo (KMC) method using a combination of a simplified inter-atomic potential and experimental transition barriers taken from the literature. An effective transition event classification method is introduced which allows a boost factor of several thousand compared to a traditional KMC approach, thus allowing experimental time scales to be modeled. The simulation predicts a low sticking probability for the arriving atoms, millisecond order lifetimes for single Ag monomers and {approx}1 nm square surface migration ranges of Ag monomers. The simulations give excellent reproduction of the experimentally observed nanocluster growth patterns. The second topic specifies the acceleration scheme utilized in the metallic cluster growth model. Concerning the atomistic movements, a classical harmonic transition state theory is considered and applied in discrete lattice cells with hierarchical transition levels. The model results in an effective reduction of KMC simulation steps by utilizing a classification scheme of transition levels for thermally activated atomistic diffusion processes. Thermally activated atomistic movements

  18. [A study on family pattern and psychological aspects of parent and child].

    Science.gov (United States)

    Seo, M H; Hong, M S

    1988-12-01

    This study reviews the relationship between family patterns and psychological aspects of the mother-child relationship. As the population increase in Korea will reach 50 million in 2020, population policy must deal with population quality. The data come from 118 5th and 6th grade students and their mothers. Survey results shows that the number of children and the family type are related to mothers' child rearing attitudes. Mothers in nuclear families tended to be warmer and freer towards their children than others. Family type was not related to the self-esteem of children, and the number of siblings showed a weak relationship. Children with siblings have stronger self-esteem. Birth order and younger sibling spacing had a stronger relationship with self-esteem. First borns and those who had younger siblings within a 2-year interval had the weakest self-esteem. Since families are becoming smaller, child quality is becoming more important. Not only family size but also family type, birth order, and spacing need to be considered for the psychological well-being of the population. PMID:12342280

  19. PATTERN FORMATION DURING DEVELOPMENT OF THE EMBRYONIC CEREBELLUM

    OpenAIRE

    Richard Hawkes

    2012-01-01

    The patterning of the embryonic cerebellum is vital to establish the elaborate zone and stripe architecture of the adult. This review considers early stages in cerebellar Purkinje cell patterning, from the organization of the ventricular zone to the development of Purkinje cell clusters – the precursors of the adult stripes.

  20. Stabilization and destabilization effects of the electric field on stochastic precipitate pattern formation

    NARCIS (Netherlands)

    Lagzi, István; Izsák, Ferenc

    2004-01-01

    Stabilization and destabilization effects of an applied electric field on the Liesegang pattern formation in low concentration gradient were studied with numerical model simulations. In the absence of an electric field pattern formation exhibits increasingly stochastic behaviour as the initial conce

  1. Endothelial cell motility, coordination and pattern formation during vasculogenesis.

    Science.gov (United States)

    Czirok, Andras

    2013-01-01

    How vascular networks assemble is a fundamental problem of developmental biology that also has medical importance. To explain the organizational principles behind vascular patterning, we must understand how can tissue level structures be controlled through cell behavior patterns like motility and adhesion that, in turn, are determined by biochemical signal transduction processes? We discuss the various ideas that have been proposed as mechanisms for vascular network assembly: cell motility guided by extracellular matrix alignment (contact guidance), chemotaxis guided by paracrine and autocrine morphogens, and multicellular sprouting guided by cell-cell contacts. All of these processes yield emergent patterns, thus endothelial cells can form an interconnected structure autonomously, without guidance from an external pre-pattern.

  2. Resonant matter: pattern correlates of process-in-formation

    OpenAIRE

    Báez, Manuel Antonio

    2013-01-01

    Through the aid of ever advancing technology, the analysis of complex phenomena offers us more comprehensive insights regarding the intricate inner workings of Nature’s dynamic processes. Through such digital simulations (i.e., of fluid, aero, neuro and vibratory dynamics), the operations and flow of energy are revealed as highly patterned process-structures of activity. These vivid configurations often resemble and correlate with the patterns and motifs found at different scales throughout N...

  3. Effects of growth and mutation on pattern formation in tissues.

    Directory of Open Access Journals (Sweden)

    Benedicte Mengel Pers

    Full Text Available In many developing tissues, neighboring cells enter different developmental pathways, resulting in a fine-grained pattern of different cell states. The most common mechanism that generates such patterns is lateral inhibition, for example through Delta-Notch coupling. In this work, we simulate growth of tissues consisting of a hexagonal arrangement of cells laterally inhibiting their neighbors. We find that tissue growth by cell division and cell migration tends to produce ordered patterns, whereas lateral growth leads to disordered, patchy patterns. Ordered patterns are very robust to mutations (gene silencing or activation in single cells. In contrast, mutation in a cell of a disordered tissue can produce a larger and more widespread perturbation of the pattern. In tissues where ordered and disordered patches coexist, the perturbations spread mostly at boundaries between patches. If cell division occurs on time scales faster than the degradation time, disordered patches will appear. Our work suggests that careful experimental characterization of the disorder in tissues could pinpoint where and how the tissue is susceptible to large-scale damage even from single cell mutations.

  4. Modular genetic regulatory networks increase organization during pattern formation.

    Science.gov (United States)

    Mohamadlou, Hamid; Podgorski, Gregory J; Flann, Nicholas S

    2016-08-01

    Studies have shown that genetic regulatory networks (GRNs) consist of modules that are densely connected subnetworks that function quasi-autonomously. Modules may be recognized motifs that comprise of two or three genes with particular regulatory functions and connectivity or be purely structural and identified through connection density. It is unclear what evolutionary and developmental advantages modular structure and in particular motifs provide that have led to this enrichment. This study seeks to understand how modules within developmental GRNs influence the complexity of multicellular patterns that emerge from the dynamics of the regulatory networks. We apply an algorithmic complexity to measure the organization of the patterns. A computational study was performed by creating Boolean intracellular networks within a simulated epithelial field of embryonic cells, where each cell contains the same network and communicates with adjacent cells using contact-mediated signaling. Intracellular networks with random connectivity were compared to those with modular connectivity and with motifs. Results show that modularity effects network dynamics and pattern organization significantly. In particular: (1) modular connectivity alone increases complexity in network dynamics and patterns; (2) bistable switch motifs simplify both the pattern and network dynamics; (3) all other motifs with feedback loops increase multicellular pattern complexity while simplifying the network dynamics; (4) negative feedback loops affect the dynamics complexity more significantly than positive feedback loops.

  5. Pattern Formation in Mississippi Valley-Type Deposits

    Science.gov (United States)

    Kelka, Ulrich; Koehn, Daniel

    2015-04-01

    Alternating, monomineralic dark and white bands are common features of ore hosting dolostones which are generally termed Zebra textures. These structures consist of coarse grained light and fine grained dark layers and accompany ore bodies of the Mississippi Valley-Type (MVT) worldwide. These deposits frequently develop in large hydrothermal systems, located in the flanks of foreland basins or in fold and thrust belts. The microstructural- and microchemical analysis in this study were performed on samples which were collected in the San Vicente mine. This large MVT deposit is hosted in Triassic/Jurassic Platform Carbonates located in an east-vergent fold and thrust belt of the Peruvian Andes. The thin sections were analyzed with petrographic- and scanning electron microscope. It is observed that one common striking feature is the high density of second-phase particles in the dark bands, whereas the coarser grained layers are virtually particle free. Furthermore, the particle distribution is found to be non-random. The highest particle densities in the samples occur on grain boundaries in the dark bands implying that grain boundaries can capture particles. Based on recent theories and the additional analytical findings, we developed a numerical simulation to study the pattern formation. The modelling is performed in 2D at the scale of a thin section, using a boundary-model coupled with a lattice-particle-code. During the simulation two processes are active, first a reaction takes place that replaces calcite with dolomite driven by a fluid that infiltrates the model, followed by a grain growth processes with an average grain size increase as a function of surface energy reduction. Fluid infiltration in the rock is modelled assuming Darcy Flow and an advection-diffusion equation coupled with a reaction which is a function of concentration. The reaction increases permeability of the solid and thus enhances infiltration. The reaction front in the model shifts particles

  6. CDS Simulation and Pattern Formation of Phase Separation

    Institute of Scientific and Technical Information of China (English)

    ZhangjiLIU; MenCHENG; 等

    1998-01-01

    Several properties of the generation and evolution of phase separating patterns for binary material studied by CDS model are proposed.The main conclusions are(1) for alloys spinodal decomposition,the conceptions of “macro-pattern” and “micropattern” are posed by “black-and-white graph”and “gray-scale graph” respectively.We find that though the four forms of map f that represent the self-evolution of order parameter in a cell (lattice)are similar to each other in “macro-pattern”,there are evident differences in their micro-pattern,e.g.,some different fine netted sturctures in the black domain and the white domain are found by the micro-pattern.so that distinct mechanical and physical behaviors shall be obtained.(2) If the two constituteons of block copolymers are not symmetric (i.e.r≠0.5),a pattern called “grain-strip cross pattern is discovered,is the 0.43

  7. Characteristics of pattern formation and evolution in approximations of Physarum transport networks.

    Science.gov (United States)

    Jones, Jeff

    2010-01-01

    Most studies of pattern formation place particular emphasis on its role in the development of complex multicellular body plans. In simpler organisms, however, pattern formation is intrinsic to growth and behavior. Inspired by one such organism, the true slime mold Physarum polycephalum, we present examples of complex emergent pattern formation and evolution formed by a population of simple particle-like agents. Using simple local behaviors based on chemotaxis, the mobile agent population spontaneously forms complex and dynamic transport networks. By adjusting simple model parameters, maps of characteristic patterning are obtained. Certain areas of the parameter mapping yield particularly complex long term behaviors, including the circular contraction of network lacunae and bifurcation of network paths to maintain network connectivity. We demonstrate the formation of irregular spots and labyrinthine and reticulated patterns by chemoattraction. Other Turing-like patterning schemes were obtained by using chemorepulsion behaviors, including the self-organization of regular periodic arrays of spots, and striped patterns. We show that complex pattern types can be produced without resorting to the hierarchical coupling of reaction-diffusion mechanisms. We also present network behaviors arising from simple pre-patterning cues, giving simple examples of how the emergent pattern formation processes evolve into networks with functional and quasi-physical properties including tensionlike effects, network minimization behavior, and repair to network damage. The results are interpreted in relation to classical theories of biological pattern formation in natural systems, and we suggest mechanisms by which emergent pattern formation processes may be used as a method for spatially represented unconventional computation. PMID:20067403

  8. A Broad Dynamical Model for Pattern Formation by Lateral Inhibition

    CERN Document Server

    Arcak, Murat

    2012-01-01

    Many patterning events in multi-cellular organisms rely on cell-to-cell contact signaling, such as the Notch pathway in metazoans. A particularly interesting phenomenon in this form of communication is lateral inhibition where a cell that adopts a particular fate inhibits its immediate neighbors from doing the same. Dynamical models are of great interest for understanding the circuit topologies involved in lateral inhibition and for predicting the associated patterns. Several simplified models have been employed for Notch signalling pathways in the literature. The objective of this paper is to present an abstract dynamical model that captures the essential features of lateral inhibition and to demonstrate with dynamical systems techniques that these features indeed lead to patterning.

  9. Effect of gel network on pattern formation in the ferrocyanide-iodate-sulfite reaction.

    Science.gov (United States)

    Ueno, Tomonaga; Yoshida, Ryo

    2011-06-01

    Stationary patterns have been researched experimentally since the discovery of the Turing pattern in the chlorite-iodide-malonic acid (CIMA) reaction and the self-replicating spot pattern in the ferrocyanide-iodate-sulfite (FIS) reaction. In this study, we reproduced the pattern formation in the FIS reaction by using poly(acrylamide) gels. Gels with different swelling ratios were prepared to use as a medium. The effect of the swelling ratio was compared with the effect of thickness. It was found that the swelling ratio greatly influenced pattern formation. Oscillating spot patterns appeared at high swelling ratios, and lamellar patterns appeared at a low swelling ratio. Self-replicating spot patterns appeared in between the two areas. The front velocities, which were observed in the initial stage of pattern formation, depended on the swelling ratio. Furthermore, this dependence obeys the free volume theory of diffusion. These results provide evidence that the change in front velocities is caused by a change in diffusion. Pattern formation can be controlled not only by thickness but also by swelling ratio, which may be useful for creating novel pattern templates. PMID:21557556

  10. LETTER: Self-organized pattern formation and noise-induced control based on particle computations

    Science.gov (United States)

    Rohlf, Thimo; Bornholdt, Stefan

    2005-12-01

    We propose a new non-equilibrium model for spatial pattern formation based on local information transfer. Unlike most standard models of pattern formation it is not based on the Turing instability or initially laid down morphogen gradients. Information is transmitted through the system via particle-like excitations whose collective dynamics results in pattern formation and control. Here, a simple problem of domain formation is addressed by means of this model in an implementation as stochastic cellular automata, and then generalized to a system of coupled dynamical networks. One observes stable pattern formation, even in the presence of noise and cell flow. Noise contributes through the production of quasi-particles to de novo pattern formation as well as to robust control of the domain boundary position. Pattern proportions are scale independent as regards system size. The dynamics of pattern formation is stable over large parameter ranges, with a discontinuity at vanishing noise and a second-order phase transition at increased cell flow.

  11. Pattern formation in the wake of triggered pushed fronts

    Science.gov (United States)

    Goh, Ryan; Scheel, Arnd

    2016-08-01

    Pattern-forming fronts are often controlled by an external stimulus which progresses through a stable medium at a fixed speed, rendering it unstable in its wake. By controlling the speed of excitation, such stimuli, or ‘triggers’, can mediate pattern forming fronts which freely invade an unstable equilibrium and control which pattern is selected. In this work, we analytically and numerically study when the trigger perturbs an oscillatory pushed free front. In such a situation, the resulting patterned front, which we call a pushed trigger front, exhibits a variety of phenomenon, including snaking, non-monotonic wave-number selection, and hysteresis. Assuming the existence of a generic oscillatory pushed free front, we use heteroclinic bifurcation techniques to prove the existence of trigger fronts in an abstract setting motivated by the spatial dynamics approach. We then derive a leading order expansion for the selected wave-number in terms of the trigger speed. Furthermore, we show that such a bifurcation curve is governed by the difference of certain strong-stable and weakly-stable spatial eigenvalues associated with the decay of the free pushed front. We also study prototypical examples of these phenomena in the cubic-quintic complex Ginzburg Landau equation and a modified Cahn-Hilliard equation.

  12. Spontaneous tunable Turing pattern formation for coherent high-power THz radiation

    CERN Document Server

    Huang, Shu-Wei; Yang, Shang-Hua; Yu, Mingbin; Kwong, Dim-Lee; Zelevinsky, T; Jarrahi, Mona; Wong, Chee Wei

    2016-01-01

    The spontaneous breaking of symmetry and homogeneity through dissipative pattern formation is a fundamental question in developmental biology, molecular biochemistry, mathematics and nonlinear physics. Self-organized patterns arise in nature, such as pigmentation in animals, tree branching fractals, Prigogine non-equilibrium chemical bifurcations, and are postulated by Turing to occur from diffusion-reaction driven instabilities. In spite of the spontaneous nature, these threshold-dependent patterns - when formed - can potentially be remarkably robust in the presence of noise. Here we report the spontaneous Turing pattern formation in chip-scale nonlinear oscillators, developing a precision frequency comb in the solid-state. The stationary Turing pattern is discretely tunable across 430 GHz on a THz carrier, with a sideband non-uniformity measured down to 1 part in 1.5x10^15. Local mode hybridizations in the nonlinear ring oscillator seeds the coherent pattern formation and phase matching, to obtain a record ...

  13. Nanoparticles dynamics on a surface: fractal pattern formation and fragmentation

    DEFF Research Database (Denmark)

    Dick, Veronika V.; Solov'yov, Ilia; Solov'yov, Andrey V.

    2010-01-01

    In this paper we review our recent results on the formation and the post-growth relaxation processes of nanofractals on surface. For this study we developed a method which describes the internal dynamics of particles in a fractal and accounts for their diffusion and detachment. We demonstrate tha...

  14. Fluctuation-Induced Pattern Formation in a Surface Reaction

    DEFF Research Database (Denmark)

    Starke, Jens; Reichert, Christian; Eiswirth, Markus;

    2006-01-01

    Spontaneous nucleation, pulse formation, and propagation failure have been observed experimentally in CO oxidation on Pt(110) at intermediate pressures ($\\approx 10^{-2}$mbar). This phenomenon can be reproduced with a stochastic model which includes temperature effects. Nucleation occurs randomly...

  15. Pattern formation of cortical microtubules and cellulose microfibrils

    NARCIS (Netherlands)

    Lindeboom, J.J.

    2012-01-01

    In this thesis we study the roles of microtubules at the plasma membrane and the cellulose microfibrils in the cell wall and how they are organized. This topic is introduces in chapter 1. In chapter 2 we study the formation of the transverse cortical microtubule array that is characteristic for elon

  16. The Mechanical Aspects of Formation and Application of PDMS Bilayers Rolled into a Cylindrical Structure

    Directory of Open Access Journals (Sweden)

    Dongwon Kang

    2015-01-01

    Full Text Available A polydimethylsiloxane (PDMS film with its surface being oxidized by a plasma treatment or a UV-ozone (UVO treatment, that is, a bilayer made of PDMS and its oxidized surface layer, is known to roll into a cylindrical structure upon exposure to the chloroform vapor due to the mismatch in the swelling ratio between PDMS and the oxidized layer by the chloroform vapor. Here we analyzed the formation of the rolled bilayer with the mechanical aspects: how the mismatch in the swelling ratio of the bilayer induces rolling of the bilayer, why any form of trigger that breaks the symmetry in the in-plane stress level is needed to roll the bilayer uniaxially, why the rolled bilayer does not unroll in the dry state when there is no more mismatch in the swelling ratio, and how the measured curvature of rolled bilayer matches well with the prediction by the theory. Moreover, for the use of the rolled bilayer as the channel of the microfluidic device, we examined whether the rolled bilayer deforms or unrolls by the flow of the aqueous solution that exerts the circumferential stress on the rolled bilayer.

  17. Chemistry aspects of the source term formation for a severe accident in a CANDU type reactor

    Energy Technology Data Exchange (ETDEWEB)

    Constantin, A.; Constantin, M. [Institute for Nuclear Research, Pitesti (Romania)

    2013-07-15

    The progression of a severe accident in a CANDU type reactor is slow because the core is surrounded by a large quantity of heavy and light water which acts as a heat sink to remove the decay heat. Therefore, the source term formation is a complex and long process involving fission products transport and releasing in the fuel matrix, thermal hydraulics of the transport fluid in the primary heat system and containment, deposition and transport of fission products, chemistry including the interaction with the dousing system, structural materials and paints, etc. The source term is strongly dependent on initial conditions and accident type. The paper presents chemistry aspects for a severe accident in a CANDU type reactor, in terms of the retention in the primary heat system. After releasing from the fuel elements, the fission products suffer a multitude of phenomena before they are partly transferred into the containment region. The most important species involved in the deposition were identified. At the same time, the influence of the break position in the transfer fractions from the primary heat system to the containment was investigated. (orig.)

  18. Direct numerical simulation of pattern formation in subaqueous sediment

    CERN Document Server

    Kidanemariam, Aman G

    2014-01-01

    We present results of direct numerical simulation of incompressible fluid flow over a thick bed of mobile, spherically-shaped particles. The algorithm is based upon the immersed boundary technique for fluid-solid coupling and uses a soft-sphere model for the solid-solid contact. Two parameter points in the laminar flow regime are chosen, leading to the emergence of sediment patterns classified as `small dunes', while one case under turbulent flow conditions leads to `vortex dunes' with significant flow separation on the lee side. Wavelength, amplitude and propagation speed of the patterns extracted from the spanwise-averaged fluid-bed interface are found to be consistent with available experimental data. The particle transport rates are well represented by available empirical models for flow over a plane sediment bed in both the laminar and the turbulent regimes.

  19. Dynamic array generation and pattern formation for optical tweezers

    DEFF Research Database (Denmark)

    Mogensen, P.C.; Glückstad, J.

    2000-01-01

    The generalised phase contrast approach is used for the generation of optical arrays of arbitrary beam shape, suitable for applications in optical tweezers for the manipulation of biological specimens. This approach offers numerous advantages over current techniques involving the use of computer......-generated holograms or diffractive optical elements. We demonstrate a low-loss system for generating intensity patterns suitable for the trapping and manipulation of small particles or specimens....

  20. Pattern Formation in Predator-Prey Model with Delay and Cross Diffusion

    Directory of Open Access Journals (Sweden)

    Xinze Lian

    2013-01-01

    Full Text Available We consider the effect of time delay and cross diffusion on the dynamics of a modified Leslie-Gower predator-prey model incorporating a prey refuge. Based on the stability analysis, we demonstrate that delayed feedback may generate Hopf and Turing instability under some conditions, resulting in spatial patterns. One of the most interesting findings is that the model exhibits complex pattern replication: the model dynamics exhibits a delay and diffusion controlled formation growth not only to spots, stripes, and holes, but also to spiral pattern self-replication. The results indicate that time delay and cross diffusion play important roles in pattern formation.

  1. Patterns of partnership formation among lone mothers in Russia

    OpenAIRE

    Cordula Zabel

    2008-01-01

    This study examines the determinants of partnership formation among lone mothers in Russia, using data from the Russian Generations and Gender Survey (GGS) and the Education and Employment Survey (EES). The central research question is whether difficult economic circumstances pressure lone mothers to enter new partnerships sooner than they would under other circumstances, limiting their freedom of choice of type of living arrangement. The empirical results show that while occupation influence...

  2. Influence of phase separation for surfactant driven pattern formation during ion beam erosion

    Energy Technology Data Exchange (ETDEWEB)

    Hofsaess, Hans; Zhang, Kun; Vetter, Ulrich; Bobes, Omar; Pape, Andre; Gehrke, Hans-Gregor; Broetzmann, Marc [II. Physikalisches Institut, Goettingen Univ. (Germany)

    2012-07-01

    We will present results on metal surfactant driven self-organized pattern formation on surfaces by ion beam erosion, with a focus on the role of phase separation for the initial steps of pattern formation. Si substrates were irradiated with 5 keV Xe ions at normal incidence and ion fluences up to 5.10{sup 17} Xe/cm{sup 2} under continuous deposition of surfactant atoms. In the absence of such surfactants uniform flat surfaces are obtained, while in the presence of Fe and Mo surfactants pronounced patterns like dots, combinations of dots and ripples with wavelengths around 100 nm are generated. The surfactant coverage and deposition direction determine the pattern type and the pattern orientation, respectively. A critical steady-state coverage for onset of dot formation and onset of ripple formation is in the range of 10{sup 15} and 5.10{sup 15} Xe/cm{sup 2}. The steady-state surface region consists of a thin amorphous metal silicide layer with high metal concentration in the ripple and dot regions. Pattern formation is explained by ion induced diffusion and phase separation of the initially flat amorphous silicide layer and subsequent ion beam erosion with composition dependent sputter yield. To investigate the role of initial phase separation we additionally compare the pattern formation for different other metal surfactants.

  3. Miniaturized pattern formation in elastic films cast on sinusoidally patterned substrates.

    Science.gov (United States)

    Annepu, Hemalatha; Sarkar, Jayati

    2014-10-21

    The various morphologies that are formed when van der Waals forces or electric field is induced between film cast on a sinusoidal substrate and in contact proximity with a contactor or electrode are studied. Remarkably smaller length scales are achieved (λc Waals interactions, the patterns are uniformly formed throughout the film but are not regularly ordered. When electric field is used at critical voltage, more ordered, localized patterns are formed at the zones of large local interaction strengths. When these patterns are evolved by increasing the applied voltage, coexistence of all three phases-cavities, stripes, and columns-is observed throughout the film. The localized patterns that are initially formed vary with the voltage applied and strongly dictate the phases of evolution. A patterned substrate/patterned contactor assembly can be made to operate like its unpatterned counterpart by making the interaction strength same everywhere and yet yield uniform, regularly ordered, highly miniaturized patterns. Such patterns are very useful in various applications like microfluidics; they are formed with great ease and can be morphologically tuned by tuning the externally applied electric field. PMID:25238212

  4. A mechanistic description of the formation and evolution of vegetation patterns

    Directory of Open Access Journals (Sweden)

    R. Foti

    2012-07-01

    Full Text Available Vegetation patterns are a common and well-defined characteristic of many landscapes. In this paper we explore some of the physical mechanisms responsible for the establishment of self-organized, non-random vegetation patterns that arise at the hillslope scale in many areas of the world, especially in arid and semi-arid regions. In doing so, we provide a fundamental mechanistic understanding of the dynamics of vegetation pattern formation and development. Reciprocal effects of vegetation on the hillslope thermodynamics, runoff production and run-on infiltration, root density, surface albedo and soil moisture content are analyzed. In particular, we: (1 present a physically based mechanistic description of processes leading to vegetation pattern formation; (2 quantify the relative impact of each process on pattern formation; and (3 describe the relationships between vegetation patterns and the climatic, hydraulic and topographic characteristics of the system. We validate the model by comparing simulations with observed natural patterns in the areas of Niger near Niamey and Somalia near Garoowe. Our analyses suggest that the phenomenon of pattern formation is primarily driven by run-on infiltration and mechanisms of facilitation/inhibition among adjacent vegetation groups mediated by vegetation effects on soil properties and controls on soil moisture and albedo. Nonetheless, even in presence of those mechanisms, patterns arise only when the climatic conditions, particularly annual precipitation and net radiation, are favorable.

  5. A mechanistic description of the formation and evolution of vegetation patterns

    Directory of Open Access Journals (Sweden)

    R. Foti

    2013-01-01

    Full Text Available Vegetation patterns are a common and well-defined characteristic of many landscapes. In this paper we explore some of the physical mechanisms responsible for the establishment of self-organized, non-random vegetation patterns that arise at the hillslope scale in many areas of the world, especially in arid and semi-arid regions. In doing so, we provide a fundamental mechanistic understanding of the dynamics of vegetation pattern formation and development. Reciprocal effects of vegetation on the hillslope thermodynamics, runoff production and run-on infiltration, root density, surface albedo and soil moisture content are analyzed. In particular, we: (1 present a physically based mechanistic description of processes leading to vegetation pattern formation; (2 quantify the relative impact of each process on pattern formation; and (3 describe the relationships between vegetation patterns and the climatic, hydraulic and topographic characteristics of the system. We validate the model by comparing simulations with observed natural patterns in the areas of Niger near Niamey and Somalia near Garoowe. Our analyses suggest that the phenomenon of pattern formation is primarily driven by run-on infiltration and mechanisms of facilitation/inhibition among adjacent vegetation groups, mediated by vegetation effects on soil properties and controls on soil moisture and albedo. Nonetheless, even in presence of those mechanisms, patterns arise only when the climatic conditions, particularly annual precipitation and net radiation, are favorable.

  6. The dynamics of visual experience, an EEG study of subjective pattern formation.

    Directory of Open Access Journals (Sweden)

    Mark A Elliott

    Full Text Available BACKGROUND: Since the origin of psychological science a number of studies have reported visual pattern formation in the absence of either physiological stimulation or direct visual-spatial references. Subjective patterns range from simple phosphenes to complex patterns but are highly specific and reported reliably across studies. METHODOLOGY/PRINCIPAL FINDINGS: Using independent-component analysis (ICA we report a reduction in amplitude variance consistent with subjective-pattern formation in ventral posterior areas of the electroencephalogram (EEG. The EEG exhibits significantly increased power at delta/theta and gamma-frequencies (point and circle patterns or a series of high-frequency harmonics of a delta oscillation (spiral patterns. CONCLUSIONS/SIGNIFICANCE: Subjective-pattern formation may be described in a way entirely consistent with identical pattern formation in fluids or granular flows. In this manner, we propose subjective-pattern structure to be represented within a spatio-temporal lattice of harmonic oscillations which bind topographically organized visual-neuronal assemblies by virtue of low frequency modulation.

  7. Pattern Formation and Continuation in a Trineuron Ring with Delays

    Institute of Scientific and Technical Information of China (English)

    Shang Jiang GUO; Li Hong HUANG

    2007-01-01

    In this paper, we consider a single-directional ring of three neurons with delays. First, linear stability of the model is investigated by analyzing the associated characteristic transcendental equation. Next, we studied the local Hopf bifurcations and the spatio-temporal patterns of Hopf bifurcating periodic orbits. Basing on the normal form approach and the center manifold theory, we derive the formula for determining the properties of Hopf bifurcating periodic orbit, such as the direction of Hopf bifurcation. Finally, global existence conditions for Hopf bifurcating periodic orbits are derived by using degree theory methods.

  8. Jamming and pattern formation in models of segregation

    Science.gov (United States)

    Rogers, Tim; McKane, Alan J.

    2012-04-01

    We investigate the Schelling model of social segregation, formulated as an intrinsically nonequilibrium system, in which the agents occupy districts (or patches) rather than sites on a grid. We show that this allows the equations governing the dynamical behavior of the model to be derived. Analysis of these equations reveals a jamming transition in the regime of low-vacancy density, and inclusion of a spatial dimension in the model leads to a pattern forming instability. Both of these phenomena exhibit unusual characteristics which may be studied through our approach.

  9. Pattern Formation and Growth Kinetics in Eutectic Systems

    Energy Technology Data Exchange (ETDEWEB)

    Jing Teng

    2007-12-01

    Growth patterns during liquid/solid phase transformation are governed by simultaneous effects of heat and mass transfer mechanisms, creation of new interfaces, jump of the crystallization units from liquid to solid and their rearrangement in the solid matrix. To examine how the above processes influence the scale of microstructure, two eutectic systems are chosen for the study: a polymeric system polyethylene glycol-p-dibromobenzene (PEG-DBBZ) and a simple molecular system succinonitrile (SCN)-camphor. The scaling law for SCN-camphor system is found to follow the classical Jackson-Hunt model of circular rod eutectic, where the diffusion in the liquid and the interface energy are the main physics governing the two-phase pattern. In contrast, a significantly different scaling law is observed for the polymer system. The interface kinetics of PEG phase and its solute concentration dependence thus have been critically investigated for the first time by directional solidification technique. A model is then proposed that shows that the two-phase pattern in polymers is governed by the interface diffusion and the interface kinetics. In SCN-camphor system, a new branch of eutectic, elliptical shape rodl, is found in thin samples where only one layer of camphor rods is present. It is found that the orientation of the ellipse can change from the major axis in the direction of the thickness to the direction of the width as the velocity and/or the sample thickness is decreased. A theoretical model is developed that predicts the spacing and orientation of the elliptical rods in a thin sample. The single phase growth patterns of SCN-camphor system were also examined with emphasis on the three-dimensional single cell and cell/dendrite transition. For the 3D single cell in a capillary tube, the entire cell shape ahead of the eutectic front can be described by the Saffmann-Taylor finger only at extremely low growth rate. A 3D directional solidification model is developed to

  10. Pattern formation in semiconductors: control of spatio-temporal dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Schoell, E. [Institut fuer Theoretische Physik, Technische Universitaet Berlin, Hardenbergstr. 36, 10623 Berlin (Germany)

    2004-08-01

    Semiconductors driven far from thermodynamic equilibrium by an applied dc voltage exhibit a variety of spatio-temporal electronic instabilities including complex and chaotic scenarios. We study stabilization of chaotic spatio-temporal patterns in spatially extended semiconductor models by time delayed feedback control. Different control schemes, e.g., a diagonal control matrix, or global control, or combinations of both, are compared. Specifically, we use two models of semiconductor nanostructures which are of particular current interest: (i) superlattice, (ii) double-barrier resonant-tunneling diode. (Abstract Copyright [2004], Wiley Periodicals, Inc.)

  11. Pattern Formation and Growth Kinetics in Eutectic Systems

    Energy Technology Data Exchange (ETDEWEB)

    Teng, Jing [Iowa State Univ., Ames, IA (United States)

    2007-01-01

    Growth patterns during liquid/solid phase transformation are governed by simultaneous effects of heat and mass transfer mechanisms, creation of new interfaces, jump of the crystallization units from liquid to solid and their rearrangement in the solid matrix. To examine how the above processes influence the scale of microstructure, two eutectic systems are chosen for the study: a polymeric system polyethylene glycol-p-dibromobenzene (PEG-DBBZ) and a simple molecular system succinonitrile (SCN)-camphor. The scaling law for SCN-camphor system is found to follow the classical Jackson-Hunt model of circular rod eutectic, where the diffusion in the liquid and the interface energy are the main physics governing the two-phase pattern. In contrast, a significantly different scaling law is observed for the polymer system. The interface kinetics of PEG phase and its solute concentration dependence thus have been critically investigated for the first time by directional solidification technique. A model is then proposed that shows that the two-phase pattern in polymers is governed by the interface diffusion and the interface kinetics. In SCN-camphor system, a new branch of eutectic, elliptical shape rodl, is found in thin samples where only one layer of camphor rods is present. It is found that the orientation of the ellipse can change from the major axis in the direction of the thickness to the direction of the width as the velocity and/or the sample thickness is decreased. A theoretical model is developed that predicts the spacing and orientation of the elliptical rods in a thin sample. The single phase growth patterns of SCN-camphor system were also examined with emphasis on the three-dimensional single cell and cell/dendrite transition. For the 3D single cell in a capillary tube, the entire cell shape ahead of the eutectic front can be described by the Saffmann-Taylor finger only at extremely low growth rate. A 3D directional solidification model is developed to

  12. A survey on pattern formation of autonomous mobile robots: asynchrony, obliviousness and visibility

    International Nuclear Information System (INIS)

    A robot system consists of autonomous mobile robots each of which repeats Look-Compute-Move cycles, where the robot observes the positions of other robots (Look phase), computes the track to the next location (Compute phase), and moves along the track (Move phase). In this survey, we focus on self-organization of mobile robots, especially their power of forming patterns. The formation power of a robot system is the class of patterns that the robots can form, and existing results show that the robot system's formation power is determined by their asynchrony, obliviousness, and visibility. We briefly survey existing results, with impossibilities and pattern formation algorithms. Finally, we present several open problems related to the pattern formation problem of mobile robots

  13. A survey on pattern formation of autonomous mobile robots: asynchrony, obliviousness and visibility

    Science.gov (United States)

    Yamauchi, Yukiko

    2013-12-01

    A robot system consists of autonomous mobile robots each of which repeats Look-Compute-Move cycles, where the robot observes the positions of other robots (Look phase), computes the track to the next location (Compute phase), and moves along the track (Move phase). In this survey, we focus on self-organization of mobile robots, especially their power of forming patterns. The formation power of a robot system is the class of patterns that the robots can form, and existing results show that the robot system's formation power is determined by their asynchrony, obliviousness, and visibility. We briefly survey existing results, with impossibilities and pattern formation algorithms. Finally, we present several open problems related to the pattern formation problem of mobile robots.

  14. Ternary eutectic dendrites: Pattern formation and scaling properties

    OpenAIRE

    Rátkai, László; Szállás, Attila; Pusztai, Tamás; Mohri, Tetsuo; Gránásy, László

    2015-01-01

    Extending previous work [T. Pusztai, L. R\\'atkai, A. Sz\\'all\\'as, and L. Gr\\'an\\'asy, Phys. Rev. E {\\bf 87}, 032402 (2013)], we have studied the formation of eutectic dendrites in a model ternary system within the framework of the phase-field theory. We have mapped out the domain in which two-phase dendritic structures grow. With increasing pulling velocity, the following sequence of growth morphologies is observed: flat front lamellae $\\rightarrow$ eutectic colonies $\\rightarrow$ eutectic de...

  15. Effects of exchange randomness on two-dimensional magnetic domain pattern formation

    International Nuclear Information System (INIS)

    Magnetic domain pattern formation is known to be influenced by structural disorder. We perform numerical simulations using a model of two-dimensional magnetic domain pattern formation focusing on effects of exchange randomness. The model is a scalar model with exchange and dipolar interactions, which includes disorder in the exchange interactions. Morphological change of the patterns with the increase in the disorder is observed. The distribution of the local magnetization becomes broader with the increase of the disorder. For a definite realization of the randomness, many patterns can appear. - Highlights: • Exchange randomness is introduced to the model of magnetic domain pattern formation. • Hysteretic behavior shows crossover as the randomness increases. • The crossover is observed also in the time evolution of the structure factor

  16. Pattern Formation of Bacterial Colonies by Escherichia coli

    Science.gov (United States)

    Tokita, Rie; Katoh, Takaki; Maeda, Yusuke; Wakita, Jun-ichi; Sano, Masaki; Matsuyama, Tohey; Matsushita, Mitsugu

    2009-07-01

    We have studied the morphological diversity and change in bacterial colonies, using the bacterial species Escherichia coli, as a function of both agar concentration Ca and nutrient concentration Cn. We observed various colony patterns, classified them into four types by pattern characteristics and established a morphological diagram by dividing it into four regions. They are regions A [diffusion-limited aggregation (DLA)-like], B (Eden-like), C (concentric-ring), and D (fluid-spreading). In particular, we have observed a concentric-ring colony growth for E. coli. We focused on the periodic growth in region C and obtained the following results: (i) A colony grows cyclically with the growing front repeating an advance (migration phase) and a momentary rest (consolidation phase) alternately. (ii) The growth width L and the bulge width W in one cycle decrease asymptotically to certain values, when Ca is increased. (iii) L does not depend on Cn, while W is an increasing function of Cn. Plausible mechanisms are proposed to explain the experimental results, by comparing them with those obtained for other bacterial species such as Proteus mirabilis and Bacillus subtilis.

  17. Pattern formation and firing synchronization in networks of map neurons

    Energy Technology Data Exchange (ETDEWEB)

    Wang Qingyun [State Key Laboratory for Turbulence and Complex Systems, Department of Mechanics and Aerospace Engineering, College of Engineering, Peking University, Beijing 100871 (China); Duan Zhisheng [State Key Laboratory for Turbulence and Complex Systems, Department of Mechanics and Aerospace Engineering, College of Engineering, Peking University, Beijing 100871 (China); Huang Lin [State Key Laboratory for Turbulence and Complex Systems, Department of Mechanics and Aerospace Engineering, College of Engineering, Peking University, Beijing 100871 (China); Chen Guanrong [Department of Electronic Engineering, City University of Hong Kong, Hong Kong (China); Lu Qishao [School of Science, Beijing University of Aeronautics and Astronautics, Beijing 100083 (China)

    2007-10-15

    Patterns and collective phenomena such as firing synchronization are studied in networks of nonhomogeneous oscillatory neurons and mixtures of oscillatory and excitable neurons, with dynamics of each neuron described by a two-dimensional (2D) Rulkov map neuron. It is shown that as the coupling strength is increased, typical patterns emerge spatially, which propagate through the networks in the form of beautiful target waves or parallel ones depending on the size of networks. Furthermore, we investigate the transitions of firing synchronization characterized by the rate of firing when the coupling strength is increased. It is found that there exists an intermediate coupling strength; firing synchronization is minimal simultaneously irrespective of the size of networks. For further increasing the coupling strength, synchronization is enhanced. Since noise is inevitable in real neurons, we also investigate the effects of white noise on firing synchronization for different networks. For the networks of oscillatory neurons, it is shown that firing synchronization decreases when the noise level increases. For the missed networks, firing synchronization is robust under the noise conditions considered in this paper. Results presented in this paper should prove to be valuable for understanding the properties of collective dynamics in real neuronal networks.

  18. Pattern formation in particle systems driven by color field

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The structural evolution of systems with two kinds of particles driven in opposite directions, i.e., driven by a color field, is investigated by molecular dynamics simulations. Gaussian thermostat,a common treatment to restrict the thermal velocity of the particles in the systems, has been used so as to account for the dissipation of heat and allow the system to reach a steady state. It has been found that with the increase of the strngth of driving force (F), the system undergoes an obvious structural transition from an initially random mixing state to a state characterized by separate lanes and in each lane only one kind of particles exists. The analysis shows that the reason for the formation of lane structure is not only the increase of F but also the variation of particle friction coefficient. While using Ganssian thermostat the particle friction coefficient becomes a function of F. Increasing F leads to high particle friction coefficient and inevitably results in lane formation for strong enough driving force. When lifting the effect of F on friction coefficient and choosing a constant friction coefficient,our results show that for a given F there always exists a critical value of friction coefficient higher than which the system will develop into lane structure.

  19. THEORETICAL ASPECTS OF FORMATION OF SOCIO-PROFESSIONAL SELF-DETERMINATION OF LEARNERS AT EDUCATION ESTABLISHMENTS

    Directory of Open Access Journals (Sweden)

    Alla Ya. Zhurkina

    2016-03-01

    Full Text Available Introduction: the article reveals the theoretical aspects in formation of socio-professional self-determination of learners in education institutions. The emphasis is on interdisciplinary links, integration approaches in the study of problems of self-determination. Materials and Methods: the article was written using a number of methods of theoretical pedagogical study, allowing mental penetration into the essence of the phenomenon under study teacher: analysis, synthesis, comparison, generalization method of investigating causal relationships. Results: the authors reveal the essence of the socio-professional self-determination and present grounds for separation of this concept out from the pyramid of the terms that characterise the description of the career choice process. The article substantiates the social orientation of the act of choosing a profession. It argues that career choice affects the future social position. Knowledge of theoretical bases of process of socioprofessional self-determination is very important for preparation of children for conscious career choices. Special attention is paid to the regularities, principles and f actors of this process. Discussion and Conclusions: giving a thorough account of internal and external factors of socio-professional self-determination, the authors propose to consider them solely in the system, with its inherent dynamics and the inextricable connection with the environment, suggest that changes in the social environment always entail changes in the system of factors. The article is concerned with the problem of contradictions of the process of formation of socio-professional self-determination. The authors highlight the leading role of pedagogical support in the process of socio-professional self-determination of a student’s personality, analyse modern approaches to the concept of pedagogical support. The authors characterize the educational support system as a professional educator focused

  20. HISTOLOGICAL ASPECTS OF THE MEDULLARY BONE CORRELATED TO DIFFERENT STAGES OF THE EGG FORMATION IN HENS

    Directory of Open Access Journals (Sweden)

    ALINA GHISE

    2013-12-01

    Full Text Available The experiment was carried out on a batch formed by 10 laying hens, ISA Brown hybrid, at the first laying cycles, 50 weeks old, hold single in cages and fed with granulated forage. The hens were watched for 3 weeks in order to establish the moment of the oviposition and depending on that their slaughtering was set out so that the different stages of the egg formation could be observed. The hens were divided into 4 groups – I, II, III, IV- depending on the time elapsed from the last oviposition. Femur fragments have been drawn from the central zone of the diaphises and transformed in hematoxiline-eozine and alcian-blue stained preparations, the trichromic Mallory method and the Dorfmann-Epstein method for the emphasising of the alkaline phosphatasis. At the hens of the first group the presence of the medullary bone is shown and is characterised by an intense ossification process with compact bone structure, with well formed osseus trabeculae that occupy the medullar cavity. There is also present a rich content of acid mucopolyssacharide. The hens from the second group (II have a well formed medullary bone, with visible osseus trabeculae. From the histological point of view, the medullary bone of the hens from the third group (III is rarefied with large areolae, with collagen fibres that lack osein, having thus a characteristic aspect of massive decalcification. At the hens from the fourth group (IV the medullary bone shows synthesis processes and bone matrix forming, positive, intensive FAL activity, that proves the presence of active osteoblasts, i.e. bone remodelling processes.

  1. Pattern formation in a gene network model with boundary shape dependence

    Science.gov (United States)

    Diambra, Luis; da Fontoura Costa, Luciano

    2006-03-01

    A fundamental task in developmental biology is to identify the mechanisms which drive morphogenesis. Traditionally pattern formation have been modeled mainly using Turing-type mechanisms, where complex patterns arise by symmetry breaking. However, there is a growing experimental evidence that the influence of signals derived from surrounding tissues can contribute to the patterning processes. In this paper, we show that the interplay between the shape of surrounding tissues and a hierarchically organized gene regulatory network can be able to induce stable complex patterns. The rise of these patterns depends strongly on the shape of the surrounding tissues.

  2. Pattern formation in the thiourea-iodate-sulfite system: Spatial bistability, waves, and stationary patterns

    Science.gov (United States)

    Horváth, Judit; Szalai, István; De Kepper, Patrick

    2010-06-01

    We present a detailed study of the reaction-diffusion patterns observed in the thiourea-iodate-sulfite (TuIS) reaction, operated in open one-side-fed reactors. Besides spatial bistability and spatio-temporal oscillatory dynamics, this proton autoactivated reaction shows stationary patterns, as a result of two back-to-back Turing bifurcations, in the presence of a low-mobility proton binding agent (sodium polyacrylate). This is the third aqueous solution system to produce stationary patterns and the second to do this through a Turing bifurcation. The stationary pattern forming capacities of the reaction are explored through a systematic design method, which is applicable to other bistable and oscillatory reactions. The spatio-temporal dynamics of this reaction is compared with that of the previous ferrocyanide-iodate-sulfite mixed Landolt system.

  3. Laser-based techniques for living cell pattern formation

    Science.gov (United States)

    Hopp, Béla; Smausz, Tomi; Papdi, Bence; Bor, Zsolt; Szabó, András; Kolozsvári, Lajos; Fotakis, Costas; Nógrádi, Antal

    2008-10-01

    In the production of biosensors or artificial tissues a basic step is the immobilization of living cells along the required pattern. In this paper the ability of some promising laser-based methods to influence the interaction between cells and various surfaces is presented. In the first set of experiments laser-induced patterned photochemical modification of polymer foils was used to achieve guided adherence and growth of cells to the modified areas: (a) Polytetrafluoroethylene was irradiated with ArF excimer laser ( λ=193 nm, FWHM=20 ns, F=9 mJ/cm2) in presence of triethylene tetramine liquid photoreagent; (b) a thin carbon layer was produced by KrF excimer laser ( λ=248 nm, FWHM=30 ns, F=35 mJ/cm2) irradiation on polyimide surface to influence the cell adherence. It was found that the incorporation of amine groups in the PTFE polymer chain instead of the fluorine atoms can both promote and prevent the adherence of living cells (depending on the applied cell types) on the treated surfaces, while the laser generated carbon layer on polyimide surface did not effectively improve adherence. Our attempts to influence the cell adherence by morphological modifications created by ArF laser irradiation onto polyethylene terephtalate surface showed a surface roughness dependence. This method was effective only when the Ra roughness parameter of the developed structure did not exceed the 0.1 micrometer value. Pulsed laser deposition with femtosecond KrF excimer lasers ( F=2.2 J/cm2) was effectively used to deposit structured thin films from biomaterials (endothelial cell growth supplement and collagen embedded in starch matrix) to promote the adherence and growth of cells. These results present evidence that some surface can be successfully altered to induce guided cell growth.

  4. Genetic oscillations. A Doppler effect in embryonic pattern formation.

    Science.gov (United States)

    Soroldoni, Daniele; Jörg, David J; Morelli, Luis G; Richmond, David L; Schindelin, Johannes; Jülicher, Frank; Oates, Andrew C

    2014-07-11

    During embryonic development, temporal and spatial cues are coordinated to generate a segmented body axis. In sequentially segmenting animals, the rhythm of segmentation is reported to be controlled by the time scale of genetic oscillations that periodically trigger new segment formation. However, we present real-time measurements of genetic oscillations in zebrafish embryos showing that their time scale is not sufficient to explain the temporal period of segmentation. A second time scale, the rate of tissue shortening, contributes to the period of segmentation through a Doppler effect. This contribution is modulated by a gradual change in the oscillation profile across the tissue. We conclude that the rhythm of segmentation is an emergent property controlled by the time scale of genetic oscillations, the change of oscillation profile, and tissue shortening.

  5. Genetic oscillations. A Doppler effect in embryonic pattern formation.

    Science.gov (United States)

    Soroldoni, Daniele; Jörg, David J; Morelli, Luis G; Richmond, David L; Schindelin, Johannes; Jülicher, Frank; Oates, Andrew C

    2014-07-11

    During embryonic development, temporal and spatial cues are coordinated to generate a segmented body axis. In sequentially segmenting animals, the rhythm of segmentation is reported to be controlled by the time scale of genetic oscillations that periodically trigger new segment formation. However, we present real-time measurements of genetic oscillations in zebrafish embryos showing that their time scale is not sufficient to explain the temporal period of segmentation. A second time scale, the rate of tissue shortening, contributes to the period of segmentation through a Doppler effect. This contribution is modulated by a gradual change in the oscillation profile across the tissue. We conclude that the rhythm of segmentation is an emergent property controlled by the time scale of genetic oscillations, the change of oscillation profile, and tissue shortening. PMID:25013078

  6. The formation of labyrinths, spots and stripe patterns in a biochemical approach to cardiovascular calcification

    Science.gov (United States)

    Yochelis, A.; Tintut, Y.; Demer, L. L.; Garfinkel, A.

    2008-05-01

    Calcification and mineralization are fundamental physiological processes, yet the mechanisms of calcification, in trabecular bone and in calcified lesions in atherosclerotic calcification, are unclear. Recently, it was shown in in vitro experiments that vascular-derived mesenchymal stem cells can display self-organized calcified patterns. These patterns were attributed to activator/inhibitor dynamics in the style of Turing, with bone morphogenetic protein 2 acting as an activator, and matrix GLA protein acting as an inhibitor. Motivated by this qualitative activator-inhibitor dynamics, we employ a prototype Gierer-Meinhardt model used in the context of activator-inhibitor-based biological pattern formation. Through a detailed analysis in one and two spatial dimensions, we explore the pattern formation mechanisms of steady state patterns, including their dependence on initial conditions. These patterns range from localized holes to labyrinths and localized peaks, or in other words, from dense to sparse activator distributions (respectively). We believe that an understanding of the wide spectrum of activator-inhibitor patterns discussed here is prerequisite to their biochemical control. The mechanisms of pattern formation suggest therapeutic strategies applicable to bone formation in atherosclerotic lesions in arteries (where it is pathological) and to the regeneration of trabecular bone (recapitulating normal physiological development).

  7. Formation and control of Turing patterns in a coherent quantum fluid

    Science.gov (United States)

    Ardizzone, Vincenzo; Lewandowski, Przemyslaw; Luk, M. H.; Tse, Y. C.; Kwong, N. H.; Lücke, Andreas; Abbarchi, Marco; Baudin, Emmanuel; Galopin, Elisabeth; Bloch, Jacqueline; Lemaitre, Aristide; Leung, P. T.; Roussignol, Philippe; Binder, Rolf; Tignon, Jerome; Schumacher, Stefan

    2013-10-01

    Nonequilibrium patterns in open systems are ubiquitous in nature, with examples as diverse as desert sand dunes, animal coat patterns such as zebra stripes, or geographic patterns in parasitic insect populations. A theoretical foundation that explains the basic features of a large class of patterns was given by Turing in the context of chemical reactions and the biological process of morphogenesis. Analogs of Turing patterns have also been studied in optical systems where diffusion of matter is replaced by diffraction of light. The unique features of polaritons in semiconductor microcavities allow us to go one step further and to study Turing patterns in an interacting coherent quantum fluid. We demonstrate formation and control of these patterns. We also demonstrate the promise of these quantum Turing patterns for applications, such as low-intensity ultra-fast all-optical switches.

  8. Structure Formation of Ultrathin PEO Films at Solid Interfaces—Complex Pattern Formation by Dewetting and Crystallization

    Directory of Open Access Journals (Sweden)

    Hans-Georg Braun

    2013-02-01

    Full Text Available The direct contact of ultrathin polymer films with a solid substrate may result in thin film rupture caused by dewetting. With crystallisable polymers such as polyethyleneoxide (PEO, molecular self-assembly into partial ordered lamella structures is studied as an additional source of pattern formation. Morphological features in ultrathin PEO films (thickness < 10 nm result from an interplay between dewetting patterns and diffusion limited growth pattern of ordered lamella growing within the dewetting areas. Besides structure formation of hydrophilic PEO molecules, n-alkylterminated (hydrophobic PEO oligomers are investigated with respect to self-organization in ultrathin films. Morphological features characteristic for pure PEO are not changed by the presence of the n-alkylgroups.

  9. A mechanistic description of the formation and evolution of vegetation patterns

    OpenAIRE

    R. Foti; Ramírez, J. A.

    2013-01-01

    Vegetation patterns are a common and well-defined characteristic of many landscapes. In this paper we explore some of the physical mechanisms responsible for the establishment of self-organized, non-random vegetation patterns that arise at the hillslope scale in many areas of the world, especially in arid and semi-arid regions. In doing so, we provide a fundamental mechanistic understanding of the dynamics of vegetation pattern formation and development. Reciprocal effects of vegetation on th...

  10. Pattern formation induced by cross-diffusion in a predator-prey system

    Institute of Scientific and Technical Information of China (English)

    Sun Gui-Quan; Jin Zhen; Liu Quan-Xing; Li Li

    2008-01-01

    This paper considers the Holling-Tanner model for predator-prey with self and cross-diffusion.From the Turing theory,it is believed that there is no Turing pattern formation for the equal self-diffusion coefficients.However,combined with cross-diffusion,it shows that the system will exhibit spotted pattern by both mathematical analysis and numerical simulations.Furthermore,nsynchrony of the predator and the prey in the space.The obtained results show that cross-diffusion plays an important role on the pattern formation of the predator-prey system.

  11. One-dimensional pattern of Au nanodots by ion-beam sputtering: formation and mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Kim, J-H; Ha, N-B; Kim, J-S [Department of Physics, Sook-Myung Women' s University, Seoul 140-742 (Korea, Republic of); Joe, M; Lee, K-R [Computational Science Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Cuerno, R, E-mail: jskim@sm.ac.kr [Departamento de Matematicas and Grupo Interdisciplinar de Sistemas Complejos (GISC), Universidad Carlos III de Madrid, Avenida de la Universidad 30, E-28911 Leganes (Spain)

    2011-07-15

    Highly ordered one-dimensional arrays of nanodots, or nanobeads, are fabricated by forming nanoripples and nanodots in sequence, entirely by ion-beam sputtering (IBS) of Au(001). This demonstrates the capability of IBS for the fabrication of sophisticated nanostructures via hierarchical self-assembly. The intricate nanobead pattern ideally serves to identify the governing mechanisms for the pattern formation: nonlinear effects, especially local redeposition and surface-confined transport, are essential both for the formation and the preservation of the one-dimensional order of the nanobead pattern.

  12. Spontaneous pattern formation in a thin film of bacteriorhodopsin with mixed absorptive-dispersive nonlinearity

    Science.gov (United States)

    Glückstad, J.; Saffman, M.

    1995-03-01

    We have observed the spontaneous formation of transverse spatial patterns in a thin film of bacteriorhodopsin with a feedback mirror. Bacteriorhodopsin has a mixed absorptive-dispersive nonlinearity at the wavelength used in the experiments (633 nm). Threshold values of the incident intensity for observation of pattern formation are found from a linear stability analysis of a model that describes bacteriorhodopsin as a sluggish saturable nonlinear medium with a complex Kerr coefficient. The calculated threshold intensity is in good agreement with the experimental observations, and the patterns are predicted to be frequency offset from the pump radiation.

  13. Pattern Formation and Reaction Textures during Dunite Carbonation

    Science.gov (United States)

    Lisabeth, H. P.; Zhu, W.

    2015-12-01

    Alteration of olivine-bearing rocks by fluids is one of the most pervasive geochemical processes on the surface of the Earth. Serpentinized and/or carbonated ultramafic rocks often exhibit characteristic textures on many scales, from polygonal mesh textures on the grain-scale to onion-skin or kernel patterns on the outcrop scale. Strong disequilibrium between pristine ultramafic rocks and common geological fluids such as water and carbon dioxide leads to rapid reactions and coupled mechanical and chemical feedbacks that manifest as characteristic textures. Textural evolution during metasomatic reactions can control effective reaction rates by modulating dynamic porosity and therefore reactant supply and reactive surface area. We run hydrostatic experiments on thermally cracked dunites saturated with carbon dioxide bearing brine at 15 MPa confining pressure and 150°C to explore the evolution of physical properties and reaction textures as carbon mineralization takes place in the sample. Compaction and permeability reduction are observed throughout experiments. Rates of porosity and permeability changes are sensitive to pore fluid chemistry. After reaction, samples are imaged in 3-dimension (3D) using a dual-beam FIB-SEM. Analysis of the high resolution 3D microstructure shows that permeable, highly porous domains are created by olivine dissolution at a characteristic distance from pre-existing crack surfaces while precipitation of secondary minerals such as serpentine and magnesite is limited largely to the primary void space. The porous dissolution channels provide an avenue for fluid ingress, allow reactions to continue and could lead to progressive hierarchical fracturing. Initial modeling of the system indicates that this texture is the result of coupling between dissolution-precipitation reactions and the local stress state of the sample.

  14. Ion-induced pattern formation on indium tin oxide for alignment of liquid crystals

    Energy Technology Data Exchange (ETDEWEB)

    Škereň, T., E-mail: tomas.skeren@fjfi.cvut.cz [Instituut voor Kern-en Stralingsfysica, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven Belgium (Belgium); Czech Technical University in Prague, Faculty of Nuclear Sciences and Physical Engineering, Břehová 7, 115 19 Prague 1 (Czech Republic); Doornaert, D. [Laboratory for Acoustics and Thermal Physics, Department of Physics and Astronomy, KU Leuven, B-3001 Heverlee (Belgium); Wave Propagation and Signal Processing Research Group, KU Leuven Campus Kortrijk, E. Sabbelaan 53, B-8500 Kortrijk (Belgium); Glorieux, C. [Laboratory for Acoustics and Thermal Physics, Department of Physics and Astronomy, KU Leuven, B-3001 Heverlee (Belgium); Modarresi, H. [Instituut voor Kern-en Stralingsfysica, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven Belgium (Belgium); Guan, T. [Departement Elektrotechniek ESAT-MICAS, KU Leuven, Kasteelpark Arenberg 10, B-3001 Leuven (Belgium); Temst, K. [Instituut voor Kern-en Stralingsfysica, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven Belgium (Belgium); Vandervorst, W. [Instituut voor Kern-en Stralingsfysica, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven Belgium (Belgium); IMEC, Kapeldreef 75, B-3001 Leuven (Belgium); Vantomme, A. [Instituut voor Kern-en Stralingsfysica, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven Belgium (Belgium)

    2015-08-31

    Indium tin oxide (ITO) is broadly used as a transparent conducting material for electrodes in optoelectronic devices. Irradiation of ITO with low energy ions can result in the formation of periodic surface nanopatterns which can serve as an alternative for the polymer alignment layer in liquid crystal devices. We investigated the formation of the ion-induced surface nanopatterns on ITO with focus on the influence of the crystalline structure of the material. We find that the crystallinity plays a crucial role in the pattern formation, with no pattern developing on an amorphous ITO surface. We discuss these findings in the context of the state-of-the-art theory for ion-induced patterning. We show that the ion-induced pattern plays a critical role in the liquid crystal alignment on ITO surfaces.

  15. Pattern formation in vibrated beds of dry and wet granular materials

    Science.gov (United States)

    Chuan Lim, Eldin Wee

    2014-01-01

    The Discrete Element Method was coupled with a capillary liquid bridge force model for computational studies of pattern formation in vibrated granular beds containing dry or wet granular materials. Depending on the vibration conditions applied, hexagonal, stripes, or cellular pattern was observed in the dry vibrated granular bed. In each of these cases, the same hexagonal, stripes, or cellular pattern was also observed in the spatial distribution of the magnitudes of particle-particle collision forces prior to the formation of the corresponding actual pattern in physical distributions of the particles. This seemed to suggest that the pattern formation phenomenon of vibrated granular bed systems might be the result of a two-dimensional Newton's cradle effect. In the presence of a small amount of wetness, these patterns were no longer formed in the vibrated granular beds under the same corresponding set of vibration conditions. Despite the relatively much weaker capillary forces arising from the simulated liquid bridges between particles compared with particle-particle collision forces, the spatial distributions of these collision forces, physical distributions of particles, as well as time profiles of average collision forces were altered significantly in comparison with the corresponding distributions and profiles observed for the dry vibrated granular beds. This seemed to suggest the presence of a two-dimensional Stokes' cradle effect in these wet vibrated granular bed systems which disrupted the formation of patterns in the wet granular materials that would have been observed in their dry counterparts.

  16. Synergetic aspects of gas-discharge: lateral patterns in dc systems with a high ohmic barrier

    Science.gov (United States)

    Purwins, H.-G.; Stollenwerk, L.

    2014-12-01

    The understanding of self-organized patterns in spatially extended nonlinear dissipative systems is one of the most challenging subjects in modern natural sciences. Such patterns are also referred to as dissipative structures. We review this phenomenon in planar low temperature dc gas-discharge devices with a high ohmic barrier. It is demonstrated that for these systems a deep qualitative understanding of dissipative structures can be obtained from the point of view of synergetics. At the same time, a major contribution can be made to the general understanding of dissipative structures. The discharge spaces of the experimentally investigated systems, to good approximation, have translational and rotational symmetry by contraction. Nevertheless, a given system may exhibit stable current density distributions and related patterns that break these symmetries. Among the experimentally observed fundamental patterns one finds homogeneous isotropic states, fronts, periodic patterns, labyrinth structures, rotating spirals, target patterns and localized filaments. In addition, structures are observed that have the former as elementary building blocks. Finally, defect structures as well as irregular patterns are common phenomena. Such structures have been detected in numerous other driven nonlinear dissipative systems, as there are ac gas-discharge devices, semiconductors, chemical solutions, electrical networks and biological systems. Therefore, from the experimental observations it is concluded that the patterns in planar low temperature dc gas-discharge devices exhibit universal behavior. From the theoretical point of view, dissipative structures of the aforementioned kind are also referred to as attractors. The possible sets of attractors are an important characteristic of the system. The number and/or qualitative nature of attractors may change when changing parameters. The related bifurcation behavior is a central issue of the synergetic approach chosen in the present

  17. Cortical instability drives periodic supracellular actin pattern formation in epithelial tubes.

    Science.gov (United States)

    Hannezo, Edouard; Dong, Bo; Recho, Pierre; Joanny, Jean-François; Hayashi, Shigeo

    2015-07-14

    An essential question of morphogenesis is how patterns arise without preexisting positional information, as inspired by Turing. In the past few years, cytoskeletal flows in the cell cortex have been identified as a key mechanism of molecular patterning at the subcellular level. Theoretical and in vitro studies have suggested that biological polymers such as actomyosin gels have the property to self-organize, but the applicability of this concept in an in vivo setting remains unclear. Here, we report that the regular spacing pattern of supracellular actin rings in the Drosophila tracheal tubule is governed by a self-organizing principle. We propose a simple biophysical model where pattern formation arises from the interplay of myosin contractility and actin turnover. We validate the hypotheses of the model using photobleaching experiments and report that the formation of actin rings is contractility dependent. Moreover, genetic and pharmacological perturbations of the physical properties of the actomyosin gel modify the spacing of the pattern, as the model predicted. In addition, our model posited a role of cortical friction in stabilizing the spacing pattern of actin rings. Consistently, genetic depletion of apical extracellular matrix caused strikingly dynamic movements of actin rings, mirroring our model prediction of a transition from steady to chaotic actin patterns at low cortical friction. Our results therefore demonstrate quantitatively that a hydrodynamical instability of the actin cortex can trigger regular pattern formation and drive morphogenesis in an in vivo setting.

  18. Natural patterning of templates on GaAs by formation of cracks

    Directory of Open Access Journals (Sweden)

    Yuxin Song

    2015-06-01

    Full Text Available Substrate pre-patterning is an effective way to overcome large lattice mismatch and suppress threading defects in the growth of heterostructures. In this work, a new concept was proposed to form natural patterns on commercial substrates monolithically by the formation of surface cracks. Tensile strain was intentionally brought in with a GaAs or GaNAs layer above an InGaAs layer on GaAs substrates. Surface crack patterns successfully formed during the strain relaxation. The strain in a 1 μm buffer layer atop the pattern was found effectively relaxed. Detailed residual strain distribution was simulated by the finite element method.

  19. INTEGRATION PATTERNS OF ROMANIAN IMMIGRANTS IN THE ISRAELI SOCIETY: SOCIOPOLITICAL ASPECTS

    Directory of Open Access Journals (Sweden)

    Adina BABEŞ

    2013-06-01

    Full Text Available This paper comprises parts of the theoretical and empirical research that I have conducted for my PhD studies. The theoretical structure focuses on the evaluative framework of capabilities, as it has been developed by Martha Nussbaum and the social and political aspects of Thomas Janoski’s operationalization of citizenship. The analytical framework that I came up with was further applied on the interviews that I have conducted with Romanian olim in Israel. This allowed me to come up with significant results concerning their integration within the Israeli society. These results cover aspects that belong to areas of one’s social, political, cultural life. The empirical research itself was a qualitative one with semi-structured interviews, while the results were further analyzed using the discourse analysis method.

  20. Pattern formation in the iodate-sulfite-thiosulfate reaction-diffusion system.

    Science.gov (United States)

    Liu, Haimiao; Pojman, John A; Zhao, Yuemin; Pan, Changwei; Zheng, Juhua; Yuan, Ling; Horváth, Attila K; Gao, Qingyu

    2012-01-01

    Sodium polyacrylate-induced pH pattern formation and starch-induced iodine pattern formation were investigated in the iodate-sulfite-thiosulfate (IST) reaction in a one-side fed disc gel reactor (OSFR). As binding agents of the autocatalyst of hydrogen ions or iodide ions, different content of sodium polyacrylate or starch has induced various types of pattern formation. We observed pH pulses, striped patterns, mixed spots and stripes, and hexagonal spots upon increasing the content of sodium polyacrylate and observed iodine pulses, branched patterns, and labyrinthine patterns upon increasing the starch content in the system. Coexistence of a pH front and an iodine front was also studied in a batch IST reaction-diffusion system. Both pH and iodine front instabilities were observed in the presence of sodium polyacrylate, i.e., cellular fronts and transient Turing structures resulting from the decrease in diffusion coefficients of activators. The mechanism of multiple feedback may explain the different patterns in the IST reaction-diffusion system. PMID:22068976

  1. Women in Politics: Some Historical and Cultural Aspects of Voting Patterns and Possible Influences on Education.

    Science.gov (United States)

    Smith, Peggy A.; Smith, Alan D.

    The early and formative years of women's involvement in the political structure of the United States was filled with high hopes, especially issues related to women and children. Educational reform was one of the major goals that women hoped to achieve. As demonstrated by an in-depth look at the 1920 National Convention of the Republican Party,…

  2. Finite-span rotating wings: three-dimensional vortex formation and variations with aspect ratio

    Science.gov (United States)

    Carr, Z. R.; Chen, C.; Ringuette, M. J.

    2013-02-01

    We investigate experimentally the effect of aspect ratio ( [InlineMediaObject not available: see fulltext.] ) on the time-varying, three-dimensional flow structure of flat-plate wings rotating from rest at 45° angle of attack. Plates of [InlineMediaObject not available: see fulltext.] = 2 and 4 are tested in a 50 % by mass glycerin-water mixture, with a total rotation of ϕ = 120° and a matched tip Reynolds number of 5,000. The time-varying, three-component volumetric velocity field is reconstructed using phase-locked, phase-averaged stereoscopic digital particle image velocimetry in multiple, closely-spaced chordwise planes. The vortex structure is analyzed using the {Q}-criterion, helicity density, and spanwise quantities. For both [InlineMediaObject not available: see fulltext.] s, the flow initially consists of a connected and coherent leading-edge vortex (LEV), tip vortex (TV), and trailing-edge vortex (TEV) loop; the LEV increases in size with span and tilts aft. Smaller, discrete vortices are present in the separated shear layers at the trailing and tip edges, which wrap around the primary TEV and TV. After about ϕ = 20°, the outboard-span LEV lifts off the plate and becomes arch-like. A second, smaller LEV and the formation of corner vortex structures follow. For [InlineMediaObject not available: see fulltext.] = 4, the outboard LEV moves farther aft, multiple LEVs form ahead of it, and after about ϕ = 50° a breakdown of the lifted-off LEV and the TV occurs. However, for [InlineMediaObject not available: see fulltext.] = 2, the outboard LEV lift-off is not progressive, and the overall LEV-TV flow remains more coherent and closer to the plate, with evidence of breakdown late in the motion. Inboard of about 50 % span, the [InlineMediaObject not available: see fulltext.] = 4 LEV is stable for the motion duration. Up to approximately 60 % span, the [InlineMediaObject not available: see fulltext.] = 2 LEV is distinct from the TV and is similarly stable

  3. Pattern formation in directional solidification under shear flow. I. Linear stability analysis and basic patterns.

    Science.gov (United States)

    Marietti, Y; Debierre, J M; Bock, T M; Kassner, K

    2001-06-01

    An asymptotic interface equation for directional solidification near the absolute stability limit is extended by a nonlocal term describing a shear flow parallel to the interface. In the long-wave limit considered, the flow acts destabilizing on a planar interface. Moreover, linear stability analysis suggests that the morphology diagram is modified by the flow near onset of the Mullins-Sekerka instability. Via numerical analysis, the bifurcation structure of the system is shown to change. Besides the known hexagonal cells, structures consisting of stripes arise. Due to its symmetry-breaking properties, the flow term induces a lateral drift of the whole pattern, once the instability has become active. The drift velocity is measured numerically and described analytically in the framework of a linear analysis. At large flow strength, the linear description breaks down, which is accompanied by a transition to flow-dominated morphologies which is described in the following paper. Small and intermediate flows lead to increased order in the lattice structure of the pattern, facilitating the elimination of defects. Locally oscillating structures appear closer to the instability threshold with flow than without.

  4. On the dynamics of Liesegang-type pattern formation in a gaseous system

    Science.gov (United States)

    Ramírez-Álvarez, Elizeth; Montoya, Fernando; Buhse, Thomas; Rios-Herrera, Wady; Torres-Guzmán, José; Rivera, Marco; Martínez-Mekler, Gustavo; Müller, Markus F.

    2016-01-01

    Liesegang pattern formations are widely spread in nature. In spite of a comparably simple experimental setup under laboratory conditions, a variety of spatio-temporal structures may arise. Presumably because of easier control of the experimental conditions, Liesegang pattern formation was mainly studied in gel systems during more than a century. Here we consider pattern formation in a gas phase, where beautiful but highly complex reaction-diffusion-convection dynamics are uncovered by means of a specific laser technique. A quantitative analysis reveals that two different, apparently independent processes, both highly correlated and synchronized across the extension of the reaction cloud, act on different time scales. Each of them imprints a different structure of salt precipitation at the tube walls. PMID:27025405

  5. Bifurcation and spatial pattern formation in spreading of disease with incubation period in a phytoplankton dynamics

    Directory of Open Access Journals (Sweden)

    Randhir Singh Baghel

    2012-02-01

    Full Text Available In this article, we propose a three dimensional mathematical model of phytoplankton dynamics with the help of reaction-diffusion equations that studies the bifurcation and pattern formation mechanism. We provide an analytical explanation for understanding phytoplankton dynamics with three population classes: susceptible, incubated, and infected. This model has a Holling type II response function for the population transformation from susceptible to incubated class in an aquatic ecosystem. Our main goal is to provide a qualitative analysis of Hopf bifurcation mechanisms, taking death rate of infected phytoplankton as bifurcation parameter, and to study further spatial patterns formation due to spatial diffusion. Here analytical findings are supported by the results of numerical experiments. It is observed that the coexistence of all classes of population depends on the rate of diffusion. Also we obtained the time evaluation pattern formation of the spatial system.

  6. A Theoretical Model of Jigsaw-Puzzle Pattern Formation by Plant Leaf Epidermal Cells.

    Science.gov (United States)

    Higaki, Takumi; Kutsuna, Natsumaro; Akita, Kae; Takigawa-Imamura, Hisako; Yoshimura, Kenji; Miura, Takashi

    2016-04-01

    Plant leaf epidermal cells exhibit a jigsaw puzzle-like pattern that is generated by interdigitation of the cell wall during leaf development. The contribution of two ROP GTPases, ROP2 and ROP6, to the cytoskeletal dynamics that regulate epidermal cell wall interdigitation has already been examined; however, how interactions between these molecules result in pattern formation remains to be elucidated. Here, we propose a simple interface equation model that incorporates both the cell wall remodeling activity of ROP GTPases and the diffusible signaling molecules by which they are regulated. This model successfully reproduces pattern formation observed in vivo, and explains the counterintuitive experimental results of decreased cellulose production and increased thickness. Our model also reproduces the dynamics of three-way cell wall junctions. Therefore, this model provides a possible mechanism for cell wall interdigitation formation in vivo.

  7. Pattern Formation in a Cross-Diffusive Holling-Tanner Model

    Directory of Open Access Journals (Sweden)

    Weiming Wang

    2012-01-01

    Full Text Available We present a theoretical analysis of the processes of pattern formation that involves organisms distribution and their interaction of spatially distributed population with self- as well as cross-diffusion in a Holling-Tanner predator-prey model; the sufficient conditions for the Turing instability with zero-flux boundary conditions are obtained; Hopf and Turing bifurcation in a spatial domain is presented, too. Furthermore, we present novel numerical evidence of time evolution of patterns controlled by self- as well as cross-diffusion in the model, and find that the model dynamics exhibits a cross-diffusion controlled formation growth not only to spots, but also to strips, holes, and stripes-spots replication. And the methods and results in the present paper may be useful for the research of the pattern formation in the cross-diffusive model.

  8. Performance analysis and optimal design for well patterns in anisotropic formations

    Institute of Scientific and Technical Information of China (English)

    Liu Yuetian

    2008-01-01

    The mechanism of the effects of anisotropic permeability on well patterns and reservoir development are investigated by coordinate transformation,fluid flow analysis,and reservoir development concepts.Anisotropy of permeability has reconstructive effects on well patterns.The originally designed flooding units are broken up,and new pattern units are made up of the wells that belong to different original units.The behavior possesses strong randomness,and leads to a complicated relationship among the injection and production wells,and unpredictable productivity of the formations.To prevent the break-up of well patterns,well lines should be either parallel or perpendicular to the maximum principal direction of the anisotropic permeability(i.e.the fracture direction).To optimize the development effects of anisotropic formations,the latitudinal and longitudinal well spacing of the well network are calculated from the principal values of the anisotropic permeability.

  9. Self-Assembly, Pattern Formation and Growth Phenomena in Nano-Systems

    Science.gov (United States)

    Golovin, Alexander A.; Nepomnyashchy, Alexander A.

    Nano-science and nano-technology are rapidly developing scientific and technological areas that deal with physical, chemical and biological processes that occur on nano-meter scale -- one millionth of a millimeter. Self-organization and pattern formation play crucial role on nano-scales and promise new, effective routes to control various nano-scales processes. This book contains lecture notes written by the lecturers of the NATO Advanced Study Institute "Self-Assembly, Pattern Formation and Growth Phenomena in Nano-Systems" that took place in St Etienne de Tinee, France, in the fall 2004.

  10. Topological analysis of the formation of Jet-Wake flow pattern in centrifugal impeller channel

    Institute of Scientific and Technical Information of China (English)

    ZHENG Qun; LIU Shun-long

    2004-01-01

    Topological analyses are carried out for the numerical results of internal flow field in centrifugal impeller. Topological rules of the singular point characteristics of the limiting streamline are derived and used to determine three dimensional separation patterns in centrifugal impeller and to verify the numerical results. The results reveal that the wake is saddle to nodal closed separation and the formation, its onset point and its developing process of Jet-Wake Flow pattern in centrifugal impeller are presented in this paper.

  11. Pattern Formation in a Vibrated Granular Layer on an Inclined Base

    Institute of Scientific and Technical Information of China (English)

    SHI Xiao-Dong; MIAO Guo-Qing

    2008-01-01

    We carry out the simulations of pattern formation in a two-dimensional vibrated granular layer on an inclined base by molecular dynamics.It is found that the maximum amplitude of the pattern is greater at the lower part than at the higher part of the base,and is proportional to the thickness of the layer.Meanwhile,the wavelength varies non-monotonically as the inclined angle of the base is increased.

  12. Pattern Formation in a Vibrated Granular Layer on an Inclined Base

    International Nuclear Information System (INIS)

    We carry out the simulations of pattern formation in a two-dimensional vibrated granular layer on an inclined base by molecular dynamics. It is found that the maximum amplitude of the pattern is greater at the lower part than at the higher part of the base, and is proportional to the thickness of the layer. Meanwhile, the wavelength varies non-monotonically as the inclined angle of the base is increased. (fundamental areas of phenomenology (including applications))

  13. Chirality as a physical aspect of structure formation in biological macromolecular systems

    Science.gov (United States)

    Malyshko, E. V.; Tverdislov, V. A.

    2016-08-01

    A novel regularity of hierarchical structures is found in the formation of chiral biological macromolecular systems. The formation of structures with alternating chirality (helical structures) serves as an instrument of stratification. The ability of a carbon atom to form chiral compounds is an important factor that determined the carbon basis of living systems on the Earth as well as their development through a series of chiral bifurcations. In the course of biological evolution, the helical structures became basic elements of the molecular machines in the cell. The discreteness of structural levels allowed the mechanical degrees of freedom formation in the molecular machines in the cell.

  14. Discovering local patterns of co - evolution: computational aspects and biological examples

    Directory of Open Access Journals (Sweden)

    Tuller Tamir

    2010-01-01

    Full Text Available Abstract Background Co-evolution is the process in which two (or more sets of orthologs exhibit a similar or correlative pattern of evolution. Co-evolution is a powerful way to learn about the functional interdependencies between sets of genes and cellular functions and to predict physical interactions. More generally, it can be used for answering fundamental questions about the evolution of biological systems. Orthologs that exhibit a strong signal of co-evolution in a certain part of the evolutionary tree may show a mild signal of co-evolution in other branches of the tree. The major reasons for this phenomenon are noise in the biological input, genes that gain or lose functions, and the fact that some measures of co-evolution relate to rare events such as positive selection. Previous publications in the field dealt with the problem of finding sets of genes that co-evolved along an entire underlying phylogenetic tree, without considering the fact that often co-evolution is local. Results In this work, we describe a new set of biological problems that are related to finding patterns of local co-evolution. We discuss their computational complexity and design algorithms for solving them. These algorithms outperform other bi-clustering methods as they are designed specifically for solving the set of problems mentioned above. We use our approach to trace the co-evolution of fungal, eukaryotic, and mammalian genes at high resolution across the different parts of the corresponding phylogenetic trees. Specifically, we discover regions in the fungi tree that are enriched with positive evolution. We show that metabolic genes exhibit a remarkable level of co-evolution and different patterns of co-evolution in various biological datasets. In addition, we find that protein complexes that are related to gene expression exhibit non-homogenous levels of co-evolution across different parts of the fungi evolutionary line. In the case of mammalian evolution

  15. PRACTICAL ASPECTS OF THE FORMATION OF YOUTH CIVIL POSITION IN THE PEDAGOGICAL PROCESS

    OpenAIRE

    Jurs, Pāvels; Samuseviča, Alīda

    2016-01-01

    Emphasizing the social value of the democratic state and civic society, the authors of the publication have updated the theoretical nuances of attitudes towards citizenship of young people as well as the formation of civic position and empirical findings in the field of civic engagement and promotion opportunities. The objective of publication is: basing on the theoretical understanding of the dimensions of the citizenship formation, to characterize the manifestations of civic attitudes of 9t...

  16. Chemical and rheological aspects of gel formation in the California Mastitis Test.

    Science.gov (United States)

    Whyte, David; Walmsley, Michael; Liew, Alvin; Claycomb, Rod; Mein, Graeme

    2005-02-01

    The rheological properties of the CMT gel were analysed. Data are presented to demonstrate that the gel is a non-homogenous, visco-elastic, non-Newtonian fluid with rheopectic, and rheodestructive behaviour. The fundamental chemistry of the CMT is reviewed and a modified theory of gel formation is presented. The implications of the rheological properties and modified theory of gel formation for an automatic sensor are discussed. PMID:15747739

  17. Pattern Formation in a Predator-Prey Model with Both Cross Diffusion and Time Delay

    Directory of Open Access Journals (Sweden)

    Boli Xie

    2014-01-01

    Full Text Available A predator-prey model with both cross diffusion and time delay is considered. We give the conditions for emerging Turing instability in detail. Furthermore, we illustrate the spatial patterns via numerical simulations, which show that the model dynamics exhibits a delay and diffusion controlled formation growth not only of spots and stripe-like patterns, but also of the two coexist. The obtained results show that this system has rich dynamics; these patterns show that it is useful for the diffusive predation model with a delay effect to reveal the spatial dynamics in the real model.

  18. USERS' PERCEPTION OF KOWLOON PARK, HONG KONG:VISITING PATTERNS AND SCENIC ASPECTS

    Institute of Scientific and Technical Information of China (English)

    WONG Koon-kwai; Manfred DOMROES

    2004-01-01

    Hong Kong is a hyper-dense city with 7×106 people living in an area of 1100km2.One way to improve the livability of compacted and congested cities like Hong Kong is through the provision of urban parks,an aspect that has largely been under-researched.This study focuses on how users perceive and utilize various facilities in the Kowloon Park.The findings revealed that the Kowloon Park is one of the most preferred parks in Hong Kong for both local residents and tourists.Users were quite satisfied with the park's facilities.Notably,the most important component of an urban park is its greenery.This is followed by water elements,seating places,and facilities for various recreational activities.The improvements users would like to see in urban parks include good design and management,meeting users' needs,overcoming barriers to use,and providing a high quality and varied experience for different groups in the community.The findings of this study provide a good basis to address park management issues from the users' perspective.In particular,parks should provide easy access,encourage optimum usage and enable complimentary improvements to the environment.

  19. Asymptotic Analysis in a Gas-Solid Combustion Model with Pattern Formation

    Institute of Scientific and Technical Information of China (English)

    Claude-Michel BRAUNER; Lina HU; Luca LORENZI

    2013-01-01

    The authors consider a free interface problem which stems from a gas-solid model in combustion with pattern formation.A third-order,fully nonlinear,self-consistent equation for the flame front is derived.Asymptotic methods reveal that the interface approaches a solution to the Kuramoto-Sivashinsky equation.Numerical results which illustrate the dynamics are presented.

  20. Selective formation of diamond-like carbon coating by surface catalyst patterning

    DEFF Research Database (Denmark)

    Palnichenko, A.V.; Mátéfi-Tempfli, M.; Mátéfi-Tempfli, Stefan;

    2004-01-01

    The selective formation of diamond-like carbon coating by surface catalyst patterning was studied. DLC films was deposited using plasma enhanced chemical vapor deposition, filtered vacuum arc deposition, laser ablation, magnetron sputtering and ion-beam lithography methods. The DLC coatings were...

  1. Spontaneous Transverse Pattern Formation in a Nonlinear Optical Mdium with Feedback Mirror

    Institute of Scientific and Technical Information of China (English)

    LuchuanWANG; QinliangFAN

    1998-01-01

    Spontaneous 2-D transverse pattern formation in a nonlinear optical medium with simple feedback mirror has been deduced by using nonlinear wave eguation based on slowly varying amplitude approximation.The physical mechanism and the thresholds conditions of these effects have been discussed.too.

  2. Patterned electrospun nanofiber matrices via localized dissolution: potential for guided tissue formation.

    Science.gov (United States)

    Jia, Chao; Yu, Dou; Lamarre, Marven; Leopold, Philip L; Teng, Yang D; Wang, Hongjun

    2014-12-23

    With the assistance of an ink-jet printer, solvent (the "ink") can be controllably and reproducibly printed onto electrospun nanofiber meshes (the "paper") to generate various micropatterns and subsequently guide distinct cellular organization and phenotype expression. In combination with the nanofiber-assisted layer-by-layer cell assembly, the patterned electrospun meshes will define an instructive microenvironment for guided tissue formation.

  3. Pattern formation on networks with reactions: A continuous-time random-walk approach

    Science.gov (United States)

    Angstmann, C. N.; Donnelly, I. C.; Henry, B. I.

    2013-03-01

    We derive the generalized master equation for reaction-diffusion on networks from an underlying stochastic process, the continuous time random walk (CTRW). The nontrivial incorporation of the reaction process into the CTRW is achieved by splitting the derivation into two stages. The reactions are treated as birth-death processes and the first stage of the derivation is at the single particle level, taking into account the death process, while the second stage considers an ensemble of these particles including the birth process. Using this model we have investigated different types of pattern formation across the vertices on a range of networks. Importantly, the CTRW defines the Laplacian operator on the network in a non-ad hoc manner and the pattern formation depends on the structure of this Laplacian. Here we focus attention on CTRWs with exponential waiting times for two cases: one in which the rate parameter is constant for all vertices and the other where the rate parameter is proportional to the vertex degree. This results in nonsymmetric and symmetric CTRW Laplacians, respectively. In the case of symmetric Laplacians, pattern formation follows from the Turing instability. However in nonsymmetric Laplacians, pattern formation may be possible with or without a Turing instability.

  4. Transverse Mode Structure and Pattern Formation in Oxide Confined Vertical Cavity Semiconductor Lasers

    Energy Technology Data Exchange (ETDEWEB)

    Choquette, K.D.; Geib, K.M.; Hegarty, S.P.; Hou, H.Q.; Huyet, G.; McInerney, J.G.; Porta, P.

    1999-07-06

    We analyze the transverse profiles of oxide-confined vertical cavity laser diodes as a function of aperture size. For small apertures we demonstrate that thermal lensing can be the dominant effect in determining the transverse resonator properties. We also analyze pattern formation in lasers with large apertures where we observe the appearance of tilted waves.

  5. Variation in brachial plexus formation, branching pattern and relation with major vessels

    Directory of Open Access Journals (Sweden)

    G. Anwer Khan

    2014-08-01

    Conclusion: The present study carried out on adult human cadavers revealed some rare variations in the formation, branching pattern and relations of the brachial plexus. These variations are of clinical significance for the surgeons, radiologists and the anesthesiologists. [Int J Res Med Sci 2014; 2(4.000: 1591-1594

  6. Collective motion of cells mediates segregation and pattern formation in co-cultures.

    Directory of Open Access Journals (Sweden)

    Elod Méhes

    Full Text Available Pattern formation by segregation of cell types is an important process during embryonic development. We show that an experimentally yet unexplored mechanism based on collective motility of segregating cells enhances the effects of known pattern formation mechanisms such as differential adhesion, mechanochemical interactions or cell migration directed by morphogens. To study in vitro cell segregation we use time-lapse videomicroscopy and quantitative analysis of the main features of the motion of individual cells or groups. Our observations have been extensive, typically involving the investigation of the development of patterns containing up to 200,000 cells. By either comparing keratocyte types with different collective motility characteristics or increasing cells' directional persistence by the inhibition of Rac1 GTP-ase we demonstrate that enhanced collective cell motility results in faster cell segregation leading to the formation of more extensive patterns. The growth of the characteristic scale of patterns generally follows an algebraic scaling law with exponent values up to 0.74 in the presence of collective motion, compared to significantly smaller exponents in case of diffusive motion.

  7. Temporal patterns of ant diversity across a mountain with climatically contrasting aspects in the tropics of Africa.

    Directory of Open Access Journals (Sweden)

    Thinandavha Caswell Munyai

    Full Text Available Factors that drive species richness over space and time are still poorly understood and are often context specific. Identifying these drivers for ant diversity has become particularly relevant within the context of contemporary global change events. We report on a long-term bi-annual (wet and dry seasons, standardized sampling of epigeal ants over a five year period on the mesic and arid aspects of an inselberg (Soutpansberg Mountain Range in the tropics of Africa. We detail seasonal, annual and long-term trends of species density, test the relative contribution of geometric constraints, energy, available area, climate, local environmental variables, time, and space in explaining ant species density patterns through Generalized Linear Mixed Models (GLMM where replicates were included as random factors to account for temporal pseudo-replication. Seasonal patterns were very variable and we found evidence of decreased seasonal variation in species density with increased elevation. The extent and significance of a decrease in species density with increased elevation varied with season. Annual patterns point to an increase in ant diversity over time. Ant density patterns were positively correlated with mean monthly temperature but geometric constraints dominated model performance while soil characteristics were minor correlates. These drivers and correlates accounted for all the spatio-temporal variability in the database. Ant diversity was therefore mainly determined by geometric constraints and temperature while soil characteristics (clay and carbon content accounted for smaller but significant amounts of variation. This study documents the role of season, elevation and their interaction in affecting ant species densities while highlighting the importance of neutral processes and temperature in driving these patterns.

  8. SIMULATION OF ELECTRICAL FIELD FOR THE FORMATION MECHANISM OF BIRD'S NEST PATTERNED STRUCTURES BY ELECTROSPINNING

    Institute of Scientific and Technical Information of China (English)

    Xiang-yu Ye; Yi-ning Jin; Xiao-jun Huang; Lei Luo; Zhi-kang Xu

    2013-01-01

    In our previous work,it was found that large Bird's Nest patterned nanofibrous membranes can be simply electrospun from chlorinated polypropylene solution doped with an ionic liquid,and a plausible formation mechanism of Bird's Nest patterned architectures was proposed.Here,we use Ansoft Maxwell version 12 software (3D,electrostatic solver) to simulate the electrical field distribution of the electrospirming setup,and to clarify the rationality of proposed formation mechanism.Calculation results clearly show that the introduction of charged nanofibrous bundles would produce a similar patterned electrical field distribution,which definitely confirms the important role of surface residual charges.The proposed mechanism can be well extended to other polymer systems including polystyrene,poly(acrylonitrile-co-acrylic acid) and chitosan/poly(ethvlene oxide).

  9. The effect of the signalling scheme on the robustness of pattern formation in development

    KAUST Repository

    Kang, H.-W.

    2012-03-21

    Pattern formation in development is a complex process which involves spatially distributed signals called morphogens that influence gene expression and thus the phenotypic identity of cells. Usually different cell types are spatially segregated, and the boundary between them may be determined by a threshold value of some state variable. The question arises as to how sensitive the location of such a boundary is to variations in properties, such as parameter values, that characterize the system. Here, we analyse both deterministic and stochastic reaction-diffusion models of pattern formation with a view towards understanding how the signalling scheme used for patterning affects the variability of boundary determination between cell types in a developing tissue.

  10. Block Co-Polymers for Nanolithography: Rapid Microwave Annealing for Pattern Formation on Substrates

    Directory of Open Access Journals (Sweden)

    Dipu Borah

    2015-03-01

    Full Text Available The integration of block copolymer (BCP self-assembled nanopattern formation as an alternative lithographic tool for nanoelectronic device fabrication faces a number of challenges such as defect densities, feature size, pattern transfer, etc. Key barriers are the nanopattern process times and pattern formation on current substrate stack layers such as hard masks (e.g., silicon nitride, Si3N4. We report a rapid microwave assisted solvothermal (in toluene environments self-assembly and directed self-assembly of a polystyrene-block-polydimethylsiloxane (PS-b-PDMS BCP thin films on planar and topographically patterned Si3N4 substrates. Hexagonally arranged, cylindrical structures were obtained and good pattern ordering was achieved. Factors affecting BCP self-assembly, notably anneal time and temperature, were studied and seen to have significant effects. Graphoepitaxy within the topographical structures provided long range, translational alignment of the patterns. The effect of surface topography feature size and spacing was investigated. The solvothermal microwave based technique used to provide periodic order in the BCP patterns showed significant promise and ordering was achieved in much shorter periods than more conventional thermal and solvent annealing methods. The implications of the work in terms of manufacturing technologies are discussed.

  11. Interlinked nonlinear subnetworks underlie the formation of robust cellular patterns in Arabidopsis epidermis: a dynamic spatial model

    Directory of Open Access Journals (Sweden)

    Padilla-Longoria Pablo

    2008-11-01

    Full Text Available Abstract Background Dynamical models are instrumental for exploring the way information required to generate robust developmental patterns arises from complex interactions among genetic and non-genetic factors. We address this fundamental issue of developmental biology studying the leaf and root epidermis of Arabidopsis. We propose an experimentally-grounded model of gene regulatory networks (GRNs that are coupled by protein diffusion and comprise a meta-GRN implemented on cellularised domains. Results Steady states of the meta-GRN model correspond to gene expression profiles typical of hair and non-hair epidermal cells. The simulations also render spatial patterns that match the cellular arrangements observed in root and leaf epidermis. As in actual plants, such patterns are robust in the face of diverse perturbations. We validated the model by checking that it also reproduced the patterns of reported mutants. The meta-GRN model shows that interlinked sub-networks contribute redundantly to the formation of robust hair patterns and permits to advance novel and testable predictions regarding the effect of cell shape, signalling pathways and additional gene interactions affecting spatial cell-patterning. Conclusion The spatial meta-GRN model integrates available experimental data and contributes to further understanding of the Arabidopsis epidermal system. It also provides a systems biology framework to explore the interplay among sub-networks of a GRN, cell-to-cell communication, cell shape and domain traits, which could help understanding of general aspects of patterning processes. For instance, our model suggests that the information needed for cell fate determination emerges from dynamic processes that depend upon molecular components inside and outside differentiating cells, suggesting that the classical distinction of lineage versus positional cell differentiation may be instrumental but rather artificial. It also suggests that interlinkage

  12. Biofilm formation on materials into contact with water: hygienic and technical aspects

    International Nuclear Information System (INIS)

    Biofilm formation in man-made water systems has a hygienic concern when it is considered that the continuous detachment of this structure in the water flow, condition representing a potential source of contamination of plumbing and a risk for health, allows also pathogen microorganisms to reach consumers. The trend of biofilm formation was evaluated through series of microbiological analyses performed, under controlled conditions, on pipes made of materials that come into contact with drinking water according to the Decree of Ministry of Health n. 174. The investigation showed that, respect to the other materials, the reticulated polyethylene allows to sustain higher microorganisms concentrations. This characteristic was also observed in biofilms developed in condition of water stagnation compared to biofilm risen on surfaces of pipes under water flow

  13. Thermodynamic aspects of nanostructured Ti5Si3 formation during mechanical alloying and its characterization

    Indian Academy of Sciences (India)

    S Sabooni; F Karimzadeh; M H Abbasi

    2012-06-01

    Mechanical alloying (MA) was used to produce Ti5Si3 intermetallic compound with nanocrystalline structure from elemental powders. The structural changes and characterization of powder particles during milling were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), particle size analyser (PSA) and microhardness measurements. MA resulted in gradual formation of disordered Ti5Si3 intermetallic compound with crystallite size of about 15 nm after 45 h of milling. Also a thermodynamic analysis of the process was carried out using Miedema model. The results showed that in the nominal composition of Ti5Si3 intermetallic phase (Si = 0.375), formation of an intermetallic compound has the lowest Gibbs free energy rather than solid solution or amorphous phases. So the MA product is the most stable phase in nominal composition of Ti5Si3. This intermetallic compound exhibits high microhardness value of about 1235 HV.

  14. Theoretical aspects of the formation and management of a environmentally oriented businesses portfolio in the region

    OpenAIRE

    O.V. Shkarupa; I.V. Burych

    2015-01-01

    The aim of the article. The aim of the article is to study the theoretical and methodological principles for environmentally oriented businesses formulating and portfolio management in the region. The results of the analysis. This paper studies the prospects for the formation and management of the environmentally oriented business projects business portfolio. The purpose of this is to create new clusters types which are based on the production capacity of environmental products and service...

  15. Exogenous nitric oxide donors and inhibitors of its formation (the chemical aspects)

    Science.gov (United States)

    Granik, Vladimir G.; Ryabova, Svetlana Yu; Grigoriev, Nikita B.

    1997-08-01

    The published data on the biological role of nitric oxide formed in vivo by enzymatic oxidation of L-arginine are generalised. Special attention is given to exogenous nitric oxide donors, which can release NO in vitro and in vivo in oxidation, reduction, or hydrolytic cleavage. Also considered are the data on the chemical nature of inhibitors of NO-synthase responsible for nitric oxide formation from L-arginine. The bibliography includes 161 references.

  16. Design and process aspects of laboratory scale SCF particle formation systems.

    Science.gov (United States)

    Vemavarapu, Chandra; Mollan, Matthew J; Lodaya, Mayur; Needham, Thomas E

    2005-03-23

    Consistent production of solid drug materials of desired particle and crystallographic morphologies under cGMP conditions is a frequent challenge to pharmaceutical researchers. Supercritical fluid (SCF) technology gained significant attention in pharmaceutical research by not only showing a promise in this regard but also accommodating the principles of green chemistry. Given that this technology attained commercialization in coffee decaffeination and in the extraction of hops and other essential oils, a majority of the off-the-shelf SCF instrumentation is designed for extraction purposes. Only a selective few vendors appear to be in the early stages of manufacturing equipment designed for particle formation. The scarcity of information on the design and process engineering of laboratory scale equipment is recognized as a significant shortcoming to the technological progress. The purpose of this article is therefore to provide the information and resources necessary for startup research involving particle formation using supercritical fluids. The various stages of particle formation by supercritical fluid processing can be broadly classified into delivery, reaction, pre-expansion, expansion and collection. The importance of each of these processes in tailoring the particle morphology is discussed in this article along with presenting various alternatives to perform these operations.

  17. Formation mechanism of ordered stress-relief patterns in a free sustained Cu film system

    Institute of Scientific and Technical Information of China (English)

    Chen Miao-Gen; Xie Jian-Ping; Jin Jin-Sheng; Xia A-Gen; Ye Gao-Xiang

    2008-01-01

    A nearly free sustained copper (Cu) film system has been successfully fabricated by thermal evaporation deposition of Cu atoms on silicone oil surfaces,and a characteristic ordered pattern has been systematically studied.The ordered pattern,namely,band,is composed of a large number of parallel key-formed domains with different width w but nearly uniform length L;its characteristic values of ω and L are very susceptible to the growth period,deposition rate and nominal film thickness.The formation mechanism of the ordered patterns is well explained in terms of the relaxation of the internal stress in the films,which is related to the nearly zero adhesion of the solid-liquid interface.By using a two-time deposition method,it is confirmed that the ordered patterns really form in the vacuum chamber.

  18. The role of localized recoil in the formation of Kikuchi patterns.

    Science.gov (United States)

    Winkelmann, Aimo; Vos, Maarten

    2013-02-01

    In electron scattering from crystals, diffraction spots are replaced by Kikuchi patterns at high momentum transfer. Kikuchi pattern formation is based on the concept of effective incoherent electron sources (or detectors) inside a crystal. The resulting incoherence is a consequence of energy transfer connected with the momentum transfer in large-angle scattering events. We identify atomic recoil as a key incoherent process giving rise to electron Kikuchi patterns in the scope of the "channeling-in and channeling-out" model of electron backscatter diffraction (EBSD) and electron channeling patterns (ECP) in the scanning electron microscope (SEM). Using model calculations, we explore the characteristic role of the localization of the incoherent scattering event at specific places within the unit cell. In this way, we explain why sometimes inelastic losses do cause Kikuchi-type contrast, and sometimes inelastic losses result in the disappearance of this contrast in the SEM.

  19. Modeling Elevation and Aspect Controls on Emerging Ecohydrologic Processes and Ecosystem Patterns Using the Component-based Landlab Framework

    Science.gov (United States)

    Nudurupati, S. S.; Istanbulluoglu, E.; Adams, J. M.; Hobley, D. E. J.; Gasparini, N. M.; Tucker, G. E.; Hutton, E. W. H.

    2014-12-01

    Topography plays a commanding role on the organization of ecohydrologic processes and resulting vegetation patterns. In southwestern United States, climate conditions lead to terrain aspect- and elevation-controlled ecosystems, with mesic north-facing and xeric south-facing vegetation types; and changes in biodiversity as a function of elevation from shrublands in low desert elevations, to mixed grass/shrublands in mid elevations, and forests at high elevations and ridge tops. These observed patterns have been attributed to differences in topography-mediated local soil moisture availability, micro-climatology, and life history processes of plants that control chances of plant establishment and survival. While ecohydrologic models represent local vegetation dynamics in sufficient detail up to sub-hourly time scales, plant life history and competition for space and resources has not been adequately represented in models. In this study we develop an ecohydrologic cellular automata model within the Landlab component-based modeling framework. This model couples local vegetation dynamics (biomass production, death) and plant establishment and competition processes for resources and space. This model is used to study the vegetation organization in a semiarid New Mexico catchment where elevation and hillslope aspect play a defining role on plant types. Processes that lead to observed plant types across the landscape are examined by initializing the domain with randomly assigned plant types and systematically changing model parameters that couple plant response with soil moisture dynamics. Climate perturbation experiments are conducted to examine the plant response in space and time. Understanding the inherently transient ecohydrologic systems is critical to improve predictions of climate change impacts on ecosystems.

  20. Pattern Formation in a Semi-Ratio-Dependent Predator-Prey System with Diffusion

    Directory of Open Access Journals (Sweden)

    Hunki Baek

    2013-01-01

    Full Text Available We investigate spatiotemporal dynamics of a semi-ratio-dependent predator-prey system with reaction-diffusion and zero-flux boundary. We obtain the conditions for Hopf, Turing, and wave bifurcations of the system in a spatial domain by making use of the linear stability analysis and the bifurcation analysis. In addition, for an initial condition which is a small amplitude random perturbation around the steady state, we classify spatial pattern formations of the system by using numerical simulations. The results of numerical simulations unveil that there are various spatiotemporal patterns including typical Turing patterns such as spotted, spot-stripelike mixtures and stripelike patterns thanks to the Turing instability, that an oscillatory wave pattern can be emerged due to the Hopf and wave instability, and that cooperations of Turing and Hopf instabilities can cause occurrence of spiral patterns instead of typical Turing patterns. Finally, we discuss spatiotemporal dynamics of the system for several different asymmetric initial conditions via numerical simulations.

  1. Formation and all-optical control of optical patterns in semiconductor microcavities

    Science.gov (United States)

    Binder, R.; Tsang, C. Y.; Tse, Y. C.; Luk, M. H.; Kwong, N. H.; Chan, Chris K. P.; Leung, P. T.; Lewandowski, P.; Schumacher, Stefan; Lafont, O.; Baudin, E.; Tignon, J.

    2016-05-01

    Semiconductor microcavities offer a unique way to combine transient all-optical manipulation of GaAs quantum wells with the benefits of structural advantages of microcavities. In these systems, exciton-polaritons have dispersion relations with very small effective masses. This has enabled prominent effects, for example polaritonic Bose condensation, but it can also be exploited for the design of all-optical communication devices. The latter involves non-equilibrium phase transitions in the spatial arrangement of exciton-polaritons. We consider the case of optical pumping with normal incidence, yielding a spatially homogeneous distribution of exciton-polaritons in optical cavities containing the quantum wells. Exciton-exciton interactions can trigger instabilities if certain threshold behavior requirements are met. Such instabilities can lead, for example, to the spontaneous formation of hexagonal polariton lattices (corresponding to six-spot patterns in the far field), or to rolls (corresponding to two-spot far field patterns). The competition among these patterns can be controlled to a certain degree by applying control beams. In this paper, we summarize the theory of pattern formation and election in microcavities and illustrate the switching between patterns via simulation results.

  2. The role of localized recoil in the formation of Kikuchi patterns

    Energy Technology Data Exchange (ETDEWEB)

    Winkelmann, Aimo, E-mail: winkelm@mpi-halle.mpg.de [Max-Planck-Institut für Mikrostrukturphysik, Weinberg 2, D-06120 Halle (Germany); Vos, Maarten [Research School of Physics and Engineering, Australian National University, Canberra ACT (Australia)

    2013-02-15

    In electron scattering from crystals, diffraction spots are replaced by Kikuchi patterns at high momentum transfer. Kikuchi pattern formation is based on the concept of effective incoherent electron sources (or detectors) inside a crystal. The resulting incoherence is a consequence of energy transfer connected with the momentum transfer in large-angle scattering events. We identify atomic recoil as a key incoherent process giving rise to electron Kikuchi patterns in the scope of the “channeling-in and channeling-out” model of electron backscatter diffraction (EBSD) and electron channeling patterns (ECP) in the scanning electron microscope (SEM). Using model calculations, we explore the characteristic role of the localization of the incoherent scattering event at specific places within the unit cell. In this way, we explain why sometimes inelastic losses do cause Kikuchi-type contrast, and sometimes inelastic losses result in the disappearance of this contrast in the SEM. - Highlights: ► We show the role of atomic recoil in Kikuchi pattern formation from crystals. ► The role of the localization of incoherent scattering in the unit cell is explained. ► We use dynamical diffraction simulations to reveal the mechanism of contrast loss. ► The function of recoil in the “channeling-in and channeling-out” model is clarified.

  3. EDUCATIONAL STRATEGIES OF IDENTITY FORMATION: THE NATIONAL-STATE AND ETHNO-CULTURAL ASPECTS

    Directory of Open Access Journals (Sweden)

    Nelly Anatolyevna Galaktionova

    2015-05-01

    Full Text Available Article purpose – studying of educational strategy of the Russian Federation in the conditions of the amplifying migratory streams. In article are considered distinction in treatment of the concept «national school» during the modern and Soviet period. It is claimed that during the Soviet period the concept «national school» meant school for non-russian pupils, now the concept «national school» is applied as concept of the public Russian school. The author in a new way considers the value of introduction of the unified state examination. The positive role of the unified state examination for formation of the general educational space of Russia out of an ethnic framework is no-ted. The author speaks about need of the appeal to the international experience of education and adaptation of migrants, change of a state policy concerning education of migrants that is reflected in a number of documents, in the Concept of a development of education is noted. In article the assessment of the leading role of comprehensive school in formation of ethnic and national and state identity in modern conditions is given.

  4. Structural aspects of glass-formation in Ni-Nb melts

    Energy Technology Data Exchange (ETDEWEB)

    Holland-Moritz, D.; Yang, F.; Gegner, J.; Meyer, A. [Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt (DLR), 51170 Köln (Germany); Hansen, T. [Institut Laue-Langevin (ILL), 38042 Grenoble (France); Ruiz-Martín, M. D. [Grup de Caracterització de Materials, Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya, Barcelona (Spain); Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt (DLR), 51170 Köln (Germany)

    2014-05-28

    We report on investigations of the static structure factors of glass-forming Ni{sub 59.5}Nb{sub 40.5} alloy melts by combination of the containerless processing technique of electrostatic levitation with neutron diffraction. By application of the isotopic substitution method, the full set of partial structure factors was determined. The short-range order in liquid Ni{sub 59.5}Nb{sub 40.5} is characterized by a large nearest neighbor coordination number of Z{sub NN} = 14.3 and a chemical short-range order with an affinity for the formation of heterogeneous Nb-Ni nearest neighbors. The structure factors observed here in the liquid state closely resemble those reported for amorphous Nb-Ni solids. The comparison with earlier results on the short-range structure in Zr-based glass-forming melts suggests that a large local density of packing, chemical order, and structural frustration are, amongst others, common structural properties of these metallic glass-forming systems, which favor glass-formation.

  5. Spike Train Dynamics Underlying Pattern Formation in Integrate-and-Fire Oscillator Networks

    Science.gov (United States)

    Bressloff, P. C.; Coombes, S.

    1998-09-01

    A dynamical mechanism underlying pattern formation in a spatially extended network of integrate-and-fire oscillators with synaptic interactions is identified. It is shown how in the strong coupling regime the network undergoes a discrete Turing-Hopf bifurcation of the firing times from a synchronous state to a state with periodic or quasiperiodic variations of the interspike intervals on closed orbits. The separation of these orbits in phase space results in a spatially periodic pattern of mean firing rate across the network that is modulated by deterministic fluctuations of the instantaneous firing rate.

  6. Rhythmic pattern formations in gels and Matalon–Packter law: A fresh perspective

    Indian Academy of Sciences (India)

    Jacob George; Issac Paul; P A Varughese; George Varghese

    2003-06-01

    The periodic precipitation pattern formation in gelatinous media is interpreted as a moving boundary problem. The time law, spacing law and width law are revisited on the basis of the new scenario. The explicit dependence of the geometric structure on the initial concentrations of the reactants is derived. Matalon–Packter law, which relates the spacing coefficient with the initial concentrations is reformulated removing many ambiguities and impractical parameters. Experimental results are discussed to establish the significance of moving boundary concept in the diffusion controlled pattern forming systems.

  7. Buckling patterns of gold thin films on silicon substrates: Formation of superimposed blisters

    Science.gov (United States)

    Colin, J.; Coupeau, C.; Durinck, J.; Grilhé, J.

    2009-06-01

    Buckling phenomena leading to the formation of superimposed blisters have been experimentally observed with the help of a confocal interferometric microscope onto the surface of gold thin films deposited on silicon substrates. Assuming that residual folding effects resulting from plastic deformation mechanisms take place in the film during its morphological evolution, different probable scenarios for the formation of the observed buckling patterns are elaborated in the framework of the Föppl-von Karman's theory of thin plates. Multi-step buckling with growing interface delamination is considered for the first scenario while a single or multi-step buckling at a given delamination width is assumed for the other ones.

  8. Formation of zebra pattern in low-frequency Jovian radio emission

    CERN Document Server

    Kuznetsov, A A

    2012-01-01

    We investigate the formation of zebra-like fine spectral structures (consisting of several parallel bands in the dynamic spectrum) in the Jovian broadband kilometric radiation; such radio bursts were observed by Cassini in 2000/2001. We assume that the emission is generated due to a plasma mechanism in the Io plasma torus. We have shown that the double plasma resonance effect (that was proposed earlier as a formation mechanism of the solar zebra patterns) is able to produce the observed spectral structures. The observed frequency drifts are caused, most likely, by the dynamics of the electron acceleration site. The required conditions in the emission source are discussed.

  9. The gender aspect of the formation of values of physical training of students in higher education

    Directory of Open Access Journals (Sweden)

    Marchenko O. Iu.

    2013-09-01

    Full Text Available The analysis of the place of physical education in the hierarchy of values of university students. Addresses gender characteristics of the formation of values in physical education students. The study involved students in the amount of 419 people (206 boys, 213 girls and first-year students (35 girls, 16 boys. The findings suggest that a combination of slightly traditionally masculine and feminine qualities in one person. It was found that in the study of gender differences in the choice of human traits observed distinct gender stereotypes. Among the young men identified the following personality traits: the ability to achieve goals by any means, physical strength, sociability, communication skills. Girls are the following traits: sociability, communication skills, good looks, intelligence and a wide range of interests, the ability to behave in public, optimism and prudence.

  10. Theoretical aspects of the formation and management of a environmentally oriented businesses portfolio in the region

    Directory of Open Access Journals (Sweden)

    O.V. Shkarupa

    2015-03-01

    Full Text Available The aim of the article. The aim of the article is to study the theoretical and methodological principles for environmentally oriented businesses formulating and portfolio management in the region. The results of the analysis. This paper studies the prospects for the formation and management of the environmentally oriented business projects business portfolio. The purpose of this is to create new clusters types which are based on the production capacity of environmental products and services in the region. Considering strategic direction of the Ukraine’s Regional Development the authors concluded the necessity of common instrument forming. That would help to accumulate possibilities and priorities of the various innovative structures and business in general in the region. This study considered the theoretical and methodological bases of environmentally oriented projects business portfolio formation and management in the region. Today Ukrainian government system directs the efforts for regional policy funding, development priorities coordination and calls to focus on key projects that provide improvement of innovative infrastructure for economic growth stimulation, creating conditions for private sector development and public access to services. Preference is given to the issues of financial resources concentrating on the key tasks with long term impacts on regional development and national economy as a whole. Taking in account the provisions on strategic vision formation for regional development is evident for single instruments forming that would allow regional governments to manage this process. It would help to accumulate results of activity of various innovative structures and business in general. Environmentally oriented businesses portfolio is a «collection» of strategic business groups and individual businesses (projects, especially, innovative, which are formed within the same regional development strategy (strategy of sustainable

  11. Some Aspects of Formation of Cracks in FRC with Main Reinforcement

    DEFF Research Database (Denmark)

    Brincker, Rune; Simonsen, J.; Hansen, W.

    1997-01-01

    In this paper the response of fibre reinforced concrete (FRC) with main reinforcement in pure tension is considered. Test results are presented showing three distinct regimes: a regime og linear elasticity, a regime of yielding at approximately constant stress, and finally, a regime of strain har...... behaviour of the fibre reinforced matrix. The model is compaired with experiments, and reasonable aggreement is achieved.......In this paper the response of fibre reinforced concrete (FRC) with main reinforcement in pure tension is considered. Test results are presented showing three distinct regimes: a regime og linear elasticity, a regime of yielding at approximately constant stress, and finally, a regime of strain...... hardening. a simple model is presented which takes into account the debonding between the reinforcement and the fiber reinforced matrix as well as the crack opening relation of the fiber reinforced matrix. The fracture process is described from the un-cracked state and formation of the first crack till...

  12. Mechanistic aspects of the nucleophilic substitution of pectin. On the formation of chloromethane

    DEFF Research Database (Denmark)

    Sailaukhanuly, Yerbolat; Sárossy, Zsuzsa; Carlsen, Lars;

    2014-01-01

    Chloromethane, accounting for approximately 16% of the tropospheric chlorine, is mainly coming from natural sources. However anthropogenic activities, such as combustion of biomass may contribute significantly as well. The present study focuses on the thermal solid state reaction between pectin, an...... important constituent of biomass, and chloride ions as found in alkali metal chlorides. The formation of chloromethane is evident with the amount formed being linear with respect to chloride if pectin is in great excess. Thus the reaction is explained as a pseudo first order SN2 reaction between the...... chloride ion and the methyl ester moiety in pectin. It is suggested that the polymeric nature of pectin plays an active role by an enhanced transport of halides along the carbohydrate chain. Optimal reaction temperature is around 210 °C. At higher temperatures the yield of chloromethane decreases due to a...

  13. Pattern formation in spatially extended nonlinear systems: Toward a foundation for meaning in symbolic forms

    Science.gov (United States)

    DeMaris, David

    1998-07-01

    This paper brings together observations from a variety of fields to point toward what the author believes to be the most promising computational approach to the modeling of brain-like symbol formation, unifying perceptual and linguistic domains under a common computational physics. It brings Cassirer's Gestalt era evolutionary theory of language and symbolic thought to the attention of the situated cognition community, and describes how recent observations in experimental brain dynamics and computational approaches can be brought to bear on the problem. Research by the author and others in oscillatory network models of ambiguous perception with an attentional component is emphasised as a starting point for exploring increasingly complex pattern formation processes leading to simple forms of linguistic performance. These forms occupy a space between iconic representations and grammar. The dynamic pattern network framework suggests that to separate perception, representation or models and action in a realistic biophysics of situated organisms may be problematic.

  14. Quantum properties of transverse pattern formation in second-harmonic generation

    DEFF Research Database (Denmark)

    Bache, Morten; Scotto, P.; Zambrini, R.;

    2002-01-01

    transverse wave number, which are not identified in a linearized analysis, are also described. The intensity differences between opposite points of the far fields are shown to exhibit sub-Poissonian statistics, revealing the quantum nature of the correlations. We observe twin beam correlations in both......We investigate the spatial quantum noise properties of the one-dimensional transverse pattern formation instability in intracavity second-harmonic generation. The Q representation of a quasi-probability distribution is implemented in terms of nonlinear stochastic Langevin equations. We study...... for pattern formation, beams with opposite direction of the off-axis critical wave numbers are shown to be highly correlated. This is observed for the fundamental field, for the second-harmonic field, and also for the cross-correlation between the two fields. Nonlinear correlations involving the homogeneous...

  15. On the mechanism of pattern formation in glow dielectric barrier discharge

    Energy Technology Data Exchange (ETDEWEB)

    Qiao, Yajun; Li, Ben; Ouyang, Jiting, E-mail: jtouyang@bit.edu.cn [School of Physics, Beijing Institute of Technology, Beijing 100081 (China)

    2016-01-15

    The formation mechanism of pattern in glow dielectric barrier discharge is investigated by two-dimensional fluid modeling. Experimental results are shown for comparison. The simulation results show that the non-uniform distribution of space charges makes the discharge be enhanced in the high-density region but weakened in its neighborhood, which is considered as an activation-inhibition effect. This effect shows through during a current pulse (one discharge event) but also in a certain period of time after discharge that determines a driving frequency range for the non-uniformity of space charges to be enhanced. The effects of applied voltage, surface charge, electrode boundary, and external field are also discussed. All these factors affect the formation of dielectric-barrier-discharge pattern by changing the distribution or the dynamics of space charges and hence the activation-inhibition effect of non-uniform space charges.

  16. Localized Coherent Structures and Patterns Formation in Collective Models of Beam Motion

    CERN Document Server

    Fedorova, A N; Fedorova, Antonina N.; Zeitlin, Michael G.

    2001-01-01

    We present applications of variational -- wavelet approach to three different models of nonlinear beam motions with underlying collective behaviour: Vlasov-Maxwell-Poisson systems, envelope dynamics, beam-beam model. We have the representation for dynamical variables as a multiresolution (multiscales) expansion via high-localized nonlinear eigenmodes in the base of compactly supported wavelet bases. Numerical modelling demonstrates formation of coherent structures and stable patterns.

  17. Mosaic-pattern vegetation formation and dynamics driven by the water-wind crisscross erosion

    Science.gov (United States)

    Wu, Gao-Lin; Wang, Dong; Liu, Yu; Hao, Hong-Min; Fang, Nu-Fang; Shi, Zhi-Hua

    2016-07-01

    Theoretical explanations for vegetation pattern dynamic emphasized on banded pattern-forming systems on the dynamics of the spot pattern. In this context, we explore the patch pattern forming and development in the desertification land. We hypothesized that spatial heterogeneity of microtopography and soil properties with different patch sizes would determine vegetation pattern dynamics theory. The spatial heterogeneity of microtopography and soil properties with different patch sizes were studied. Differences between the inside and outside of the canopy of soil carbon content and soil total nitrogen content were significantly increasing with patches sizes. Sampling location across vegetation patch was the main factor controlling soil properties. Soil nutrient content and saturated hydraulic conductivity were the largest, while bulk density and the coarse sand content were the lowest at the sampling location of half-way between taproot and downslope edge of the canopy. The height of the mound relative to the adjacent soil interspace between shrubs increased as patches diameter increased at the upslope of the taproot. Hydrological and aeolian processes resulted in spatial distributions of soil moisture, nutrition properties, which lead to patch migrated to downslope rather than upslope. A conceptual model was integrated hydrological and nutrient facilitation and competition effects among the plant-soil in mosaic-pattern patch formation and succession process.

  18. ARGONAUTE1 acts in Arabidopsis root radial pattern formation independently of the SHR/SCR pathway.

    Science.gov (United States)

    Miyashima, Shunsuke; Hashimoto, Takashi; Nakajima, Keiji

    2009-03-01

    The formation of radially symmetric tissue patterns is one of the most basic processes in the development of vascular plants. In Arabidopsis thaliana, plant-specific GRAS-type transcription factors, SHORT-ROOT (SHR) and SCARECROW (SCR), are required for asymmetric cell divisions that separate two ground tissue cell layers, the endodermis and cortex, as well as for endodermal cell fate specification. While loss of SHR or SCR results in a single-layered ground tissue, radially symmetric cellular patterns are still maintained, suggesting that unknown regulatory mechanisms act independently of the SHR/SCR-dependent pathway. In this study, we identified a novel root radial pattern mutant and found that it is a new argonaute1 (ago1) allele. Multiple ago1 mutant alleles contained supernumerary ground tissue cell layers lacking a concentric organization, while expression patterns of SHR and SCR were not affected, revealing a previously unreported role for AGO1 in root ground tissue patterning. Analyses of ago1 scr double mutants demonstrated that the simultaneous loss of the two pathways caused a dramatic reduction in cellular organization and ground tissue identity as compared with the single mutants. Based on these results, we propose that highly symmetric root ground tissue patterns are maintained by the actions of two independent pathways, one using post-transcriptional regulation mediated by AGO1 and the other using the SHR/SCR transcriptional regulator.

  19. Physical-geographical aspects of formation of artificial firn-ice massives

    Directory of Open Access Journals (Sweden)

    A. V. Sosnovsky

    2014-01-01

    Full Text Available The paper presents results of analysis of diurnal and potentially possible efficiency of water freezing aimed at construction of artificial infiltration (firn-ice masses on the Russia’s territory. A method of jet ice-formation (winter sprinkling developed in Institute of Geography of the Russian Academy of Sciences is used for freezing of the artificial firn-ice masses. The method applies far-reaching (long-distance sprinkler installations for spraying of water and formation of thick (more than 7 m for a day masses of artificial firn. In winter the sprinkler allows freezing of both the monolithic ice and artificial firn. A practical implementation of this method is licensed and realized for construction of ice passages, bridges, and winter automobile roads. Testing of the method demonstrated that the artificial firn can be used for desalination and purification of polluted salt waters with high efficiency. That is stipulated by both, the high productivity of the method (about 1500 tons of artificial firn for a day at the air temperature of −20°С, and low mineralization of the firn relative to initial salt water. Winter sprinkling is carried out when mean daily air temperature drops below –5 ∞С. Estimating of productivity of the artificial firn and monolithic ice under present-day climatic conditions was made over the Russia’s territory. Analysis of the climate conditions for periods 2001–2010 and 1961–2000 have shown that reduction of the firn productivity changed from 5-10% in Siberia up to 20–40% in central and southern regions of the European Russia. At the present time, a potentially possible volume of the artificial firn freezing being produced in cold seasons changes from 500 thousand tons in northern areas of Yakutia down to 10 thousand in center of European Russia. Productivity of the monolithic ice freezing by a method of thin-layer water pouring is twice lower in central areas of Yakutia than on the Arctic seashores

  20. Self-Assembly, Pattern Formation and Growth Phenomena in Nano-Systems

    CERN Document Server

    Nepomnyashchy, Alexander A

    2006-01-01

    Nano-science and nano-technology are rapidly developing scientific and technological areas that deal with physical, chemical and biological processes that occur on nano-meter scale – one millionth of a millimeter. Self-organization and pattern formation play crucial role on nano-scales and promise new, effective routes to control various nano-scales processes. This book contains lecture notes written by the lecturers of the NATO Advanced Study Institute "Self-Assembly, Pattern Formation and Growth Phenomena in Nano-Systems" that took place in St Etienne de Tinee, France, in the fall 2004. They give examples of self-organization phenomena on micro- and nano-scale as well as examples of the interplay between phenomena on nano- and macro-scales leading to complex behavior in various physical, chemical and biological systems. They discuss such fascinating nano-scale self-organization phenomena as self-assembly of quantum dots in thin solid films, pattern formation in liquid crystals caused by light, self-organi...

  1. Steady states and linear stability analysis of precipitation pattern formation at geothermal hot springs.

    Science.gov (United States)

    Chan, Pak Yuen; Goldenfeld, Nigel

    2007-10-01

    A dynamical theory of geophysical precipitation pattern formation is presented and applied to irreversible calcium carbonate (travertine) deposition. Specific systems studied here are the terraces and domes observed at geothermal hot springs, such as those at Yellowstone National Park, and speleothems, particularly stalactites and stalagmites. The theory couples the precipitation front dynamics with shallow water flow, including corrections for turbulent drag and curvature effects. In the absence of capillarity and with a laminar flow profile, the theory predicts a one-parameter family of steady state solutions to the moving boundary problem describing the precipitation front. These shapes match the measured shapes near the vent at the top of observed travertine domes well. Closer to the base of the dome, the solutions deviate from observations and circular symmetry is broken by a fluting pattern, which we show is associated with capillary forces causing thin film break-up. We relate our model to that recently proposed for stalactite growth, and calculate the linear stability spectrum of both travertine domes and stalactites. Lastly, we apply the theory to the problem of precipitation pattern formation arising from turbulent flow down an inclined plane and identify a linear instability that underlies scale-invariant travertine terrace formation at geothermal hot springs. PMID:17995057

  2. Depositional, diagenetic and stratigraphic aspects of microfacies from Riachuelo Formation, Albian, Sergipe Basin, Brazil

    Directory of Open Access Journals (Sweden)

    Caio Vinícius Gabrig Turbay

    2013-12-01

    Full Text Available The rocks of the Riachuelo Formation, Sergipe Basin, Brazil, represent an example of carbonate sedimentation related to the drift phase during the opening of the South Atlantic Ocean. The Carapeba and Brejo quarries exhibit the best onshore outcrops of the drift carbonate section along the Brazilian continental edge. Field studies and microfacies analysis of the outcropped sedimentary section showed six sedimentary deposits related to the physiography of a carbonate shelf. Proximal mixed deposits are represented by the rich-terrigenous dolostone. Levels with alternate layers of fine grained sandstones and siltstones are here related to distal facies of submarine fans deposits. Mudstones with miliolids and textularids represent a lagoonal environment in a semi-restricted middle shelf. Packstones, grainstones and occasionally wackestones with oncoids, intraclasts and peloids represent sedimentary deposits related to the back of shallow sandy bars and environments at the interface with the lagoon. Grainstones whit ooliths, oncoids, intraclasts and bioclasts, with trough cross-bedding, represent a shallower shoreface environment over the shallow carbonate back on outer shelf. Cements and other post- depositional features suggest four different diagenetic environments: a marine phreatic diagenetic environment with active water circulation; b marine phreatic diagenetic environment with stagnant water; c freshwater phreatic diagenetic environment; d burial diagenetic environment. The sedimentary succession is formed by shallowing upward cycles overlain by a possible transgressive surface, which may indicate the passage of a lowstand to a transgressive system tract.

  3. Mathematical aspects of the kinetics of formation and degradation of linear peptide or protein aggregates.

    Science.gov (United States)

    Zhdanov, Vladimir P

    2016-08-01

    In cells, peptides and proteins are sometimes prone to aggregation. In neurons, for example, amyloid β peptides form plaques related to Alzheimer's disease (AD). The corresponding kinetic models either ignore or do not pay attention to degradation of these species. Here, the author proposes a generic kinetic model describing formation and degradation of linear aggregates. The process is assumed to occur via reversible association of monomers and attachment of monomers to or detachment from terminal parts of aggregates. Degradation of monomers is described as a first-order process. Degradation of aggregates is considered to occur at their terminal and internal parts with different rates and these steps are described by first-order equations as well. Irrespective of the choice of the values of the rate constants, the model predicts that eventually the system reaches a stable steady state with the aggregate populations rapidly decreasing with increasing size at large sizes. The corresponding steady-state size distributions of aggregates are illustrated in detail. The transient kinetics are also shown. The observation of AD appears, however, to indicate that the peptide production becomes eventually unstable, i.e., the growth of the peptide population is not properly limited. This is expected to be related to the specifics of the genetic networks controlling the peptide production. Following this line, two likely general networks with, respectively, global negative and positive feedbacks in the peptide production are briefly discussed. PMID:27132946

  4. Oxidatively generated damage to the guanine moiety of DNA: Mechanistic aspects and formation in cells

    International Nuclear Information System (INIS)

    Nuclear DNA and other molecules in living systems are continuously exposed to endogenously generated oxygen species. Such species range from the unreactive superoxide radical (O2.-)-the precursor of hydrogen peroxide (H2O2)-to the highly reactive hydroxyl radical (OH.). Exogenous chemical and physical agents, such as ionizing radiation and the UVA component of solar light, can also oxidatively damage both the bases and the 2-deoxyribose moieties of cellular DNA. Over the last two decades, researchers have made major progress in understanding the oxidation degradation pathways of DNA that are most likely to occur from either oxidative metabolism or exposure to various exogenous agents. In the first part of this Account, we describe the mechanistic features of one-electron oxidation reactions of the guanine base in isolated DNA and related model compounds. These reactions illustrate the complexity of the various degradation pathways involved. Then, we briefly survey the analytical methods that can detect low amounts of oxidized bases and nucleosides in cells as they are formed. Recent data on the formation of oxidized guanine residues in cellular DNA following exposure to UVA light, ionizing radiation, and high-intensity UV pulses are also provided. We discuss these chemical reactions in the context of (OH.) radical, singlet oxygen, and two-quantum photoionization processes. (authors)

  5. Psychomotor education, an aspect of general formation of pre-school children

    Directory of Open Access Journals (Sweden)

    Ardian Shingjergji

    2013-06-01

    Full Text Available Current developments of scientific thinking in the field of education are increasingly demanding in various disciplines for young people as a matter of urgency. It is already known that child development is conditioned by ancestry, socio-cultural environment, including interaction with peers and adults. Albanian institutions (kindergarten compared to contemporary experience in more developed countries have to deal with issues such as: (1 The development of a run or optimal acceleration enrichment motor for kindergarten children, seen as an important element of the formation of the human personality and its preparation to cope with various situations of life ; (2 The role of infrastructure in the natural development of the personality of children and the educational process as a whole; (3 Parental community involvement as a fundamental prerequisite of real development of the child; (4The qualification level of the teaching staff in the elementary education system and the preparation of students teacher. I hope to add my contribution through this paper, not only by identifying the problems above, but also in presenting alternatives of a development model of kindergarten children motors skills progress, compared to contemporary experience in more developed countries. Keywords: ; ; ; ;

  6. Localization and Pattern Formation in Quantum Physics. II. Waveletons in Quantum Ensembles

    CERN Document Server

    Fedorova, A N; Fedorova, Antonina N.; Zeitlin, Michael G.

    2005-01-01

    In this second part we present a set of methods, analytical and numerical, which can describe behaviour in (non) equilibrium ensembles, both classical and quantum, especially in the complex systems, where the standard approaches cannot be applied. The key points demonstrating advantages of this approach are: (i) effects of localization of possible quantum states; (ii) effects of non-perturbative multiscales which cannot be calculated by means of perturbation approaches; (iii) effects of formation of complex/collective quantum patterns from localized modes and classification and possible control of the full zoo of quantum states, including (meta) stable localized patterns (waveletons). We demonstrate the appearance of nontrivial localized (meta) stable states/patterns in a number of collective models covered by the (quantum)/(master) hierarchy of Wigner-von Neumann-Moyal-Lindblad equations, which are the result of ``wignerization'' procedure (Weyl-Wigner-Moyal quantization) of classical BBGKY kinetic hierarchy...

  7. Localization and Pattern Formation in Quantum Physics. I. Phenomena of Localization

    CERN Document Server

    Fedorova, A N; Fedorova, Antonina N.; Zeitlin, Michael G.

    2005-01-01

    In these two related parts we present a set of methods, analytical and numerical, which can illuminate the behaviour of quantum system, especially in the complex systems. The key points demonstrating advantages of this approach are: (i) effects of localization of possible quantum states, more proper than "gaussian-like states"; (ii) effects of non-perturbative multiscales which cannot be calculated by means of perturbation approaches; (iii) effects of formation of complex quantum patterns from localized modes or classification and possible control of the full zoo of quantum states, including (meta) stable localized patterns (waveletons). We'll consider calculations of Wigner functions as the solution of Wigner-Moyal-von Neumann equation(s) corresponding to polynomial Hamiltonians. Modeling demonstrates the appearance of (meta) stable patterns generated by high-localized (coherent) structures or entangled/chaotic behaviour. We can control the type of behaviour on the level of reduced algebraical variational sy...

  8. 耦合诱导TUring斑图的形成%Turing Pattern Formation Induced by Coupling

    Institute of Scientific and Technical Information of China (English)

    雷爱中; 徐卫国

    2007-01-01

    The coupling action of the CDIMA reaction system is investigated. Our results have shown that a reaction - diffusion equation pair with parameters outside the range for Turing pattern formation can form a stable Turing pattern when it is coupled to one with parameters that produce Turing patterns.%通过数值模拟的方法研究了耦合的CDIMA反应模型.结果显示:处于不能形成图林斑图区域的系统与另一个处于图林斑图区域的系统进行耦合,两系统都能形成图林斑图.

  9. Formation of personnel corps of engineers in the Urals: sociological aspect

    Directory of Open Access Journals (Sweden)

    Boris Sergeevich Pavlov

    2012-03-01

    Full Text Available In terms of crisis economic development, one of priority goals for the technical institutes of higher education is to train engineers who are competitive on the regional labour markets. The main root of the problem of low prestige of the engineering profession in Russia, the slippage in the personnel training in technical universities lies in the depreciation of engineering work, and reduction of its social and economic attractiveness. The gap between science, education and industry leads to aging of engineering staff at the manufactures and to migration of the most talented engineers into other fields of activity. This paper analyzes current problems of engineers training organization in the Urals. The causes of sharp decline of the engineering profession social status in Russia, the fall of interest of secondary school graduates to continuation of their studies in technical institutes of higher education are reviewed. The authors show that the formation of engineering competence as a defining personal and vocational quality of a specialist involves actualization of the student's motivation, one's active and purposeful adaptation to the educational process, increasing one's responsibility for mastering the curriculum. Conclusions and suggestions of the authors are based on the results of a comprehensive sociological research conducted by them in 2011 in five high schools of the Urals (Yekaterinburg, Nizhnevartovsk and Chelyabinsk. The survey showed that during the stage of young specialists' preparation, cooperation in the «university - enterprise» system is actually shifted to the interaction, in fact, between institute of higher education and young professionals who act as the sellers of their labour. The authors believe that it makes sense to roll over (or rather - to stimulate the active engineering work of the most productive engineering professionals who have reached retirement age. Equally sharp and critical are the issues of

  10. On island landscape pattern of forests in Helan Mountain and its cause of formation

    Institute of Scientific and Technical Information of China (English)

    DENG Hongbing; WANG Yingming; ZHANG Qiaoxian; YAN Yan

    2006-01-01

    Based on the spatial information techniques such as RS, GIS, and GPS, the forest landscape patterns in the Helan Mountain, western China, were studied. The Landsat 5 TM data were used to classify the forest landscapes through RS digital cartography, and then, the landscape characteristics and landscape pattern were analyzed quantificationally. Furthermore, through spatial data collection and spatial analysis of the main disturbances in this area, the cause of landscape formation was studied. The results showed that the total 1177 forest landscape patches could be classified into 21 landscape types, and the forest landscape in the Helan Mountain was island pattern, which was encircled by deserta as matrix. The values of landscape diversity index and landscape fragmentation index were 2.61 and 0.43, respectively. In this area, the landscape pattern was clearly formed and continuously changed in response to geological processes, climate, activities of organisms, forest fire, desertification, human activities and so on. This landscape pattern had an obviously negative effect on the stability and ecosystem services of forests. So, scientific landscape planning and protection should be adopted to improve the sustainability of forest management in this area.

  11. Dynamics of fast pattern formation in porous silicon by laser interference

    Energy Technology Data Exchange (ETDEWEB)

    Peláez, Ramón J.; Kuhn, Timo; Afonso, Carmen N. [Laser Processing Group, Instituto de Óptica, CSIC, Serrano 121, 28006 Madrid (Spain); Vega, Fidel [Departament d' Òptica i Optometria, UPC, Violinista Vellsolà 37, 08222 Terrasa (Spain)

    2014-10-20

    Patterns are fabricated on 290 nm thick nanostructured porous silicon layers by phase-mask laser interference using single pulses of an excimer laser (193 nm, 20 ns pulse duration). The dynamics of pattern formation is studied by measuring in real time the intensity of the diffraction orders 0 and 1 at 633 nm. The results show that a transient pattern is formed upon melting at intensity maxima sites within a time <30 ns leading to a permanent pattern in a time <100 ns upon solidification at these sites. This fast process is compared to the longer one (>1 μs) upon melting induced by homogeneous beam exposure and related to the different scenario for releasing the heat from hot regions. The diffraction efficiency of the pattern is finally controlled by a combination of laser fluence and initial thickness of the nanostructured porous silicon layer and the present results open perspectives on heat release management upon laser exposure as well as have potential for alternative routes for switching applications.

  12. Temporal patterns and behavioral characteristics of aggregation formation and spawning in the Bermuda chub ( Kyphosus sectatrix)

    Science.gov (United States)

    Nemeth, Richard S.; Kadison, Elizabeth

    2013-12-01

    Reef fish spawning aggregations are important life history events that occur at specific times and locations and represent the primary mode of reproduction for many species. This paper provides detailed descriptions of aggregation formation and mass spawning of the Bermuda chub ( Kyphosus sectatrix). Spawning coloration and gamete release of K. sectatrix were observed and filmed at the Grammanik Bank, a deep spawning aggregation site used by many different species located on the southern edge of the Puerto Rican shelf 10 km south of St. Thomas, US Virgin Islands. Underwater visual surveys using technical Nitrox and closed circuit re-breathers were conducted from December 2002 to March 2013 and documented spatial and temporal patterns of movement and aggregation formation along 1.5 km of mesophotic reef. The largest aggregations of K. sectatrix (>200 fish) were observed on the Grammanik Bank January to March from 0 to 11 d after the full moon with peak abundance from 60 to 80 d after the winter solstice across all survey years. Aggregation formation of K. sectatrix coincided with the spawning season of Nassau ( Epinephelus striatus) and yellowfin ( Mycteroperca venenosa) groupers. These spatial and temporal patterns of aggregation formation and spawning suggest that K. sectatrix, an herbivore, may also be a transient aggregating species. On several occasions, chubs were observed both pair spawning and mass spawning. Color patterns and behaviors associated with aggregation and spawning are described and compared to spawning characteristics observed in other species, many of which are similar but others that appear unique to K. sectatrix. This represents the first report of a kyphosid species aggregating to spawn and illuminates a portion of the poorly understood life history of the Bermuda chub.

  13. On the formation mechanisms, spatial resolution and intensity of backscatter Kikuchi patterns.

    Science.gov (United States)

    Zaefferer, S

    2007-01-01

    The present paper is divided into two main sections. In the first, the formation mechanisms of backscatter Kikuchi patterns (BKP) are discussed on the basis of measurements on the sharpness of Kikuchi lines and on the spatial, that means the lateral and depth resolution of the technique. We propose that thermal diffuse scattering is the important incoherent scattering mechanism involved in pattern formation. This mechanism is not considered in the classical description of the origin of backscattered electrons in the scanning electron microscope (SEM) which is why there is in some important points no agreement between classical Monte-Carlo-type electron trajectory simulations and experimental results. We assume that the energy spectrum of the backscattered electrons shows, similar to the spectra in transmission electron microscopy, a sharp zero-loss peak. In the second section, we discuss the intensity of Kikuchi bands in BKP. It is shown that the kinematical theory gives-of course-not the correct intensities, but that these intensities are, on the other hand, not too far off the experimental ones. We subsequently introduce a simple intensity correction procedure that is based on the two-beam dynamical theory, originally proposed by Blackman for transmission electron diffraction patterns. It is shown by examples of diffraction patterns of niobium and silicon that this procedure leads to satisfying results, once two unknown variables (a universal constant and the exit depth of the electrons) have been empirically fit. It is assumed that in the future, this correction will improve the possibilities of phase identification by backscatter Kikuchi diffraction patterns.

  14. Ordered nano-scale dimple pattern formation on a titanium alloy (Ti-6Al-4V

    Directory of Open Access Journals (Sweden)

    Yue Wang

    2012-09-01

    Full Text Available Due to the many applications of nanostructured surfaces – including in biomaterials – there is a strong interest in cost- and time-efficient methods for their fabrication. Previously, our group established a simple electrochemical method generating nanoscale patterns on large areas of a number of different metal surfaces. They consist of dimples that are around 6-10 nm deep and hexagonally closed packed with a tunable periodicity of around 50 nm. Ordering requires careful tuning of the surface chemistry, which makes the translation of these findings to multi-component alloys non-obvious. Here, we demonstrate for the first time that such a pattern can also be achieved on the surface of an alloy, namely Ti-6Al-4V. This alloy is of particular interest for biomedical implants. While dimple formation on the main component metals titanium and aluminum has previously been reported (albeit under conditions that differ from each other, we now also report dimple formation on pure vanadium surfaces to occur under very different conditions. Dimple formation occurs preferentially on the (dominant α-phase grains of the alloy. The size of dimples of the alloy material is subject to the electropolishing potential, electrolyte concentration and surface chemical composition, which gives us the opportunity to control the surface features. Since a main application of this alloy are biomedical implants, this level of control will be an important tool for accommodating cell growth.

  15. NFI-C2 temporal-spatial expression and cellular localization pattern during tooth formation.

    Science.gov (United States)

    Lamani, Ejvis; Gluhak-Heinrich, Jelica; MacDougall, Mary

    2015-12-01

    Currently, little is known regarding critical signaling pathways during later stages of tooth development, especially those associated with root formation. Nfi-c null mice, lacking molar roots, have implicated the transcription factor NFI-C as having an essential role in root development. Previously, we identified three NFI-C isoforms expressed in dental tissues with NFI-C2 being the major transcript. However, the expression pattern of the NFI-C2 protein is not characterized. In this study we performed in situ hybridization and immunohistochemistry using isoform specific probes. We show the production of a NFI-C2 peptide antibody, its characterization, the temporal-spatial expression pattern of the NFI-C2 protein during odontogenesis and sub-cellular localization in dental cells. Moderate NFI-C2 staining, as early as bud stage, was detected mostly in the condensing dental ectomesenchyme. This staining intensified within the dental pulp at later stages culminating in high expression in the dentin producing odontoblasts. The dental epithelium showed slight staining until cytodifferentiation of enamel organ into ameloblasts and stratum intermedium. During root formation NFI-C2 expression was high in the Hertwig's epithelial root sheath and later was found in the fully developed root and its supporting tissues. NFI-C2 cellular staining was cytosolic, associated with the Golgi, and nuclear. These data suggest a broader role for NFI-C during tooth formation than limited to root and periodontal ligament development. PMID:26687982

  16. Molecular dynamics of single-particle impacts predicts phase diagrams for large scale pattern formation.

    Science.gov (United States)

    Norris, Scott A; Samela, Juha; Bukonte, Laura; Backman, Marie; Djurabekova, Flyura; Nordlund, Kai; Madi, Charbel S; Brenner, Michael P; Aziz, Michael J

    2011-01-01

    Energetic particle irradiation can cause surface ultra-smoothening, self-organized nanoscale pattern formation or degradation of the structural integrity of nuclear reactor components. A fundamental understanding of the mechanisms governing the selection among these outcomes has been elusive. Here we predict the mechanism governing the transition from pattern formation to flatness using only parameter-free molecular dynamics simulations of single-ion impacts as input into a multiscale analysis, obtaining good agreement with experiment. Our results overturn the paradigm attributing these phenomena to the removal of target atoms via sputter erosion: the mechanism dominating both stability and instability is the impact-induced redistribution of target atoms that are not sputtered away, with erosive effects being essentially irrelevant. We discuss the potential implications for the formation of a mysterious nanoscale topography, leading to surface degradation, of tungsten plasma-facing fusion reactor walls. Consideration of impact-induced redistribution processes may lead to a new design criterion for stability under irradiation.

  17. Tissue growth controlled by geometric boundary conditions: a simple model recapitulating aspects of callus formation and bone healing.

    Science.gov (United States)

    Fischer, F Dieter; Zickler, Gerald A; Dunlop, John W C; Fratzl, Peter

    2015-06-01

    The shape of tissues arises from a subtle interplay between biochemical driving forces, leading to cell growth, division and extracellular matrix formation, and the physical constraints of the surrounding environment, giving rise to mechanical signals for the cells. Despite the inherent complexity of such systems, much can still be learnt by treating tissues that constantly remodel as simple fluids. In this approach, remodelling relaxes all internal stresses except for the pressure which is counterbalanced by the surface stress. Our model is used to investigate how wettable substrates influence the stability of tissue nodules. It turns out for a growing tissue nodule in free space, the model predicts only two states: either the tissue shrinks and disappears, or it keeps growing indefinitely. However, as soon as the tissue wets a substrate, stable equilibrium configurations become possible. Furthermore, by investigating more complex substrate geometries, such as tissue growing at the end of a hollow cylinder, we see features reminiscent of healing processes in long bones, such as the existence of a critical gap size above which healing does not occur. Despite its simplicity, the model may be useful in describing various aspects related to tissue growth, including biofilm formation and cancer metastases. PMID:26018964

  18. Cellular pattern formation by SCRAMBLED, a leucine-rich repeat receptor-like kinase in Arabidopsis.

    Science.gov (United States)

    Kwak, Su-Hwan; Schiefelbein, John

    2008-02-01

    The appropriate specification of distinct cell types is important for generating the proper tissues and bodies of multicellular organisms. In the root epidermis of Arabidopsis, cell fate determination is accomplished by a transcriptional regulatory circuit that is influenced by positional signaling. A leucine-rich repeat receptor-like kinase, SCRAMBLED (SCM), has been shown to be responsible for the position-dependent aspect of this epidermal pattern. In a recent report, we find that SCM affects the transcriptional regulatory network by down-regulating the WEREWOLF (WER) MYB gene expression in a set of epidermal cells located in a specific position. We also find that SCM and the SCM-related SRF1 and SRF3 are not required for embryonic epidermal patterning and that SRF1 and SRF3 do not act redundantly with SCM. This suggests that distinct positional signaling mechanisms exist for embryonic and post-embryonic epidermal patterning. In this addendum, we discuss the implications of our recent findings and extend our working model for epidermal cell pattering.

  19. Disappearing scales in carps: re-visiting Kirpichnikov's model on the genetics of scale pattern formation.

    Science.gov (United States)

    Casas, Laura; Szűcs, Réka; Vij, Shubha; Goh, Chin Heng; Kathiresan, Purushothaman; Németh, Sándor; Jeney, Zsigmond; Bercsényi, Miklós; Orbán, László

    2013-01-01

    The body of most fishes is fully covered by scales that typically form tight, partially overlapping rows. While some of the genes controlling the formation and growth of fish scales have been studied, very little is known about the genetic mechanisms regulating scale pattern formation. Although the existence of two genes with two pairs of alleles (S&s and N&n) regulating scale coverage in cyprinids has been predicted by Kirpichnikov and colleagues nearly eighty years ago, their identity was unknown until recently. In 2009, the 'S' gene was found to be a paralog of fibroblast growth factor receptor 1, fgfr1a1, while the second gene called 'N' has not yet been identified. We re-visited the original model of Kirpichnikov that proposed four major scale pattern types and observed a high degree of variation within the so-called scattered phenotype due to which this group was divided into two sub-types: classical mirror and irregular. We also analyzed the survival rates of offspring groups and found a distinct difference between Asian and European crosses. Whereas nude × nude crosses involving at least one parent of Asian origin or hybrid with Asian parent(s) showed the 25% early lethality predicted by Kirpichnikov (due to the lethality of the NN genotype), those with two Hungarian nude parents did not. We further extended Kirpichnikov's work by correlating changes in phenotype (scale-pattern) to the deformations of fins and losses of pharyngeal teeth. We observed phenotypic changes which were not restricted to nudes, as described by Kirpichnikov, but were also present in mirrors (and presumably in linears as well; not analyzed in detail here). We propose that the gradation of phenotypes observed within the scattered group is caused by a gradually decreasing level of signaling (a dose-dependent effect) probably due to a concerted action of multiple pathways involved in scale formation.

  20. Disappearing scales in carps: re-visiting Kirpichnikov's model on the genetics of scale pattern formation.

    Directory of Open Access Journals (Sweden)

    Laura Casas

    Full Text Available The body of most fishes is fully covered by scales that typically form tight, partially overlapping rows. While some of the genes controlling the formation and growth of fish scales have been studied, very little is known about the genetic mechanisms regulating scale pattern formation. Although the existence of two genes with two pairs of alleles (S&s and N&n regulating scale coverage in cyprinids has been predicted by Kirpichnikov and colleagues nearly eighty years ago, their identity was unknown until recently. In 2009, the 'S' gene was found to be a paralog of fibroblast growth factor receptor 1, fgfr1a1, while the second gene called 'N' has not yet been identified. We re-visited the original model of Kirpichnikov that proposed four major scale pattern types and observed a high degree of variation within the so-called scattered phenotype due to which this group was divided into two sub-types: classical mirror and irregular. We also analyzed the survival rates of offspring groups and found a distinct difference between Asian and European crosses. Whereas nude × nude crosses involving at least one parent of Asian origin or hybrid with Asian parent(s showed the 25% early lethality predicted by Kirpichnikov (due to the lethality of the NN genotype, those with two Hungarian nude parents did not. We further extended Kirpichnikov's work by correlating changes in phenotype (scale-pattern to the deformations of fins and losses of pharyngeal teeth. We observed phenotypic changes which were not restricted to nudes, as described by Kirpichnikov, but were also present in mirrors (and presumably in linears as well; not analyzed in detail here. We propose that the gradation of phenotypes observed within the scattered group is caused by a gradually decreasing level of signaling (a dose-dependent effect probably due to a concerted action of multiple pathways involved in scale formation.

  1. Disappearing scales in carps: Re-visiting Kirpichnikov's model on the genetics of scale pattern formation

    KAUST Repository

    Casas, Laura

    2013-12-30

    The body of most fishes is fully covered by scales that typically form tight, partially overlapping rows. While some of the genes controlling the formation and growth of fish scales have been studied, very little is known about the genetic mechanisms regulating scale pattern formation. Although the existence of two genes with two pairs of alleles (S&s and N&n) regulating scale coverage in cyprinids has been predicted by Kirpichnikov and colleagues nearly eighty years ago, their identity was unknown until recently. In 2009, the \\'S\\' gene was found to be a paralog of fibroblast growth factor receptor 1, fgfr1a1, while the second gene called \\'N\\' has not yet been identified. We re-visited the original model of Kirpichnikov that proposed four major scale pattern types and observed a high degree of variation within the so-called scattered phenotype due to which this group was divided into two sub-types: classical mirror and irregular. We also analyzed the survival rates of offspring groups and found a distinct difference between Asian and European crosses. Whereas nude x nude crosses involving at least one parent of Asian origin or hybrid with Asian parent(s) showed the 25% early lethality predicted by Kirpichnikov (due to the lethality of the NN genotype), those with two Hungarian nude parents did not. We further extended Kirpichnikov\\'s work by correlating changes in phenotype (scale-pattern) to the deformations of fins and losses of pharyngeal teeth. We observed phenotypic changes which were not restricted to nudes, as described by Kirpichnikov, but were also present in mirrors (and presumably in linears as well; not analyzed in detail here). We propose that the gradation of phenotypes observed within the scattered group is caused by a gradually decreasing level of signaling (a dosedependent effect) probably due to a concerted action of multiple pathways involved in scale formation. 2013 Casas et al.

  2. Pattern formation during the evaporation of a colloidal nanoliter drop: a numerical and experimental study

    CERN Document Server

    Bhardwaj, Rajneesh; Attinger, Daniel

    2010-01-01

    An efficient way to precisely pattern particles on solid surfaces is to dispense and evaporate colloidal drops, as for bioassays. The dried deposits often exhibit complex structures exemplified by the coffee ring pattern, where most particles have accumulated at the periphery of the deposit. In this work, the formation of deposits during the drying of nanoliter colloidal drops on a flat substrate is investigated numerically and experimentally. A finite-element numerical model is developed that solves the Navier-Stokes, heat and mass transport equations in a Lagrangian framework. The diffusion of vapor in the atmosphere is solved numerically, providing an exact boundary condition for the evaporative flux at the droplet-air interface. Laplace stresses and thermal Marangoni stresses are accounted for. The particle concentration is tracked by solving a continuum advection-diffusion equation. Wetting line motion and the interaction of the free surface of the drop with the growing deposit are modeled based on crite...

  3. Pattern Formation in a Cross-Diffusive Ratio-Dependent Predator-Prey Model

    Directory of Open Access Journals (Sweden)

    Xinze Lian

    2012-01-01

    Full Text Available This paper presents a theoretical analysis of evolutionary process that involves organisms distribution and their interaction of spatial distribution of the species with self- and cross-diffusion in a Holling-III ratio-dependent predator-prey model. The diffusion instability of the positive equilibrium of the model with Neumann boundary conditions is discussed. Furthermore, we present novel numerical evidence of time evolution of patterns controlled by self- and cross-diffusion in the model and find that the model dynamics exhibits a cross-diffusion controlled formation growth to spots, stripes, and spiral wave pattern replication, which show that reaction-diffusion model is useful to reveal the spatial predation dynamics in the real world.

  4. Pattern formation in chemically interacting active rotors with self-propulsion.

    Science.gov (United States)

    Liebchen, Benno; Cates, Michael E; Marenduzzo, Davide

    2016-09-21

    We demonstrate that active rotations in chemically signalling particles, such as autochemotactic E. coli close to walls, create a route for pattern formation based on a nonlinear yet deterministic instability mechanism. For slow rotations, we find a transient persistence of the uniform state, followed by a sudden formation of clusters contingent on locking of the average propulsion direction by chemotaxis. These clusters coarsen, which results in phase separation into a dense and a dilute region. Faster rotations arrest phase separation leading to a global travelling wave of rotors with synchronized roto-translational motion. Our results elucidate the physics resulting from the competition of two generic paradigms in active matter, chemotaxis and active rotations, and show that the latter provides a tool to design programmable self-assembly of active matter, for example to control coarsening. PMID:27526180

  5. Pattern formation in polymerising actin flocks: spirals, spots and waves without nonlinear chemistry

    CERN Document Server

    Goff, Thomas Le; Marenduzzo, Davide

    2016-01-01

    We propose a model solely based on actin treadmilling and polymerisation which describes many characteristic states of actin wave formation: spots, spirals and travelling waves. In our model, as in experiments on cell recovering motility following actin depolymerisation, we choose an isotropic low density initial condition; polymerisation of actin filaments then raises the density towards the Onsager threshold where they align. We show that this alignment, in turn, destabilizes the isotropic phase and generically induces transient actin spots or spirals as part of the dynamical pathway towards a polarized phase which can either be uniform or consist of a series of actin-wave trains (flocks). Our results uncover a universal route to actin wave formation in the absence of any system specific nonlinear biochemistry, and it may help understand the mechanism underlying the observation of actin spots and waves in vivo. They also suggest a minimal setup to design similar patterns in vitro.

  6. Pattern formation in a complex Swift-Hohenberg equation with phase bistability

    CERN Document Server

    de Valcárcel, Manuel Martínez-Quesada Germán J

    2016-01-01

    We study pattern formation in a complex Swift Hohenberg equation with phase-sensitive (parametric) gain. Such an equation serves as a universal order parameter equation describing the onset of spontaneous oscillations in extended systems submitted to a kind of forcing dubbed rocking when the instability is towards long wavelengths. Applications include two-level lasers and photorefractive oscillators. Under rocking, the original continuous phase symmetry of the system is replaced by a discrete one, so that phase bistability emerges. This leads to the spontaneous formation of phase-locked spatial structures like phase domains and dark-ring (phase-) cavity solitons. Stability of the homogeneous solutions is studied and numerical simulations are made covering all the dynamical regimes of the model, which turn out to be very rich. Formal derivations of the rocked complex Swift-Hohenberg equation, using multiple scale techniques, are given for the two-level laser and the photorefractive oscillator.

  7. DSA patterning options for FinFET formation at 7nm node

    Science.gov (United States)

    Liu, Chi-Chun C.; Franke, Elliott; Lie, Fee Li; Sieg, Stuart; Tsai, Hsinyu; Lai, Kafai; Truong, Hoa; Farrell, Richard; Somervell, Mark; Sanders, Daniel; Felix, Nelson; Guillorn, Michael; Burns, Sean; Hetzer, David; Ko, Akiteru; Arnold, John; Colburn, Matthew

    2016-03-01

    Several 27nm-pitch directed self-assembly (DSA) processes targeting fin formation for FinFET device fabrication are studied in a 300mm pilot line environment, including chemoepitaxy for a conventional Fin arrays, graphoepitaxy for a customization approach and a hybrid approach for self-aligned Fin cut. The trade-off between each DSA flow is discussed in terms of placement error, Fin CD/profile uniformity, and restricted design. Challenges in pattern transfer are observed and process optimization are discussed. Finally, silicon Fins with 100nm depth and on-target CD using different DSA options with either lithographic or self-aligned customization approach are demonstrated.

  8. Influence of temporal aspects and age-correlations on the process of opinion formation based on Polish contact survey

    CERN Document Server

    Grabowski, Andrzej

    2016-01-01

    On the basis of the experimental data concerning interactions between humans the process of Ising-based model of opinion formation in a social network was investigated. In the paper the data concerning human social activity, i.e. frequency and duration time of interpersonal interactions as well as age correlations - homophily are presented in comparison to base line homogeneous, static and uniform mixing. It is known from previous studies that number of contact and average age of nearest neighbors are highly correlated with age of an individual. Such real, assortative patterns usually speed up processes (like epidemic spread) on the networks, but here it only plays a role for small social temperature values (by reducing `freezing by heating' effect). A real structure of contacts affects processes in many various studies in different way, however here it causes stronger (dynamic) and smoother (durations) susceptibility on external field. Moreover, our research shows that the cross interactions between contact ...

  9. Theoretical approaches to holistic biological features: Pattern formation, neural networks and the brain-mind relation

    Indian Academy of Sciences (India)

    Alfred Gierer

    2002-06-01

    The topic of this article is the relation between bottom-up and top-down, reductionist and ``holistic” approaches to the solution of basic biological problems. While there is no doubt that the laws of physics apply to all events in space and time, including the domains of life, understanding biology depends not only on elucidating the role of the molecules involved, but, to an increasing extent, on systems theoretical approaches in diverse fields of the life sciences. Examples discussed in this article are the generation of spatial patterns in development by the interplay of autocatalysis and lateral inhibition; the evolution of integrating capabilities of the human brain, such as cognition-based empathy; and both neurobiological and epistemological aspects of scientific theories of consciousness and the mind.

  10. Turing instability and pattern formation in a two-population neuronal network model

    Science.gov (United States)

    Wyller, John; Blomquist, Patrick; Einevoll, Gaute T.

    2007-01-01

    A two-population firing-rate model describing the dynamics of excitatory and inhibitory neural activity in one spatial dimension is investigated with respect to formation of patterns, in particular stationary periodic patterns and spatiotemporal oscillations. Conditions for existence of spatially homogeneous equilibrium states are first determined, and the stability properties of these equilibria are investigated. It is shown that the nonlocal synaptic interactions may promote a finite bandwidth instability in a way analogous to diffusion effects in the classical Turing instability for reaction-diffusion equations and modulational instability in the theory of nonlinear waves in nonlocal defocusing Kerr media. Our analysis relies on the wave-number dependent invariants of the 2×2-matrix representing the spatially Fourier-transformed linearized evolution equations. The generic picture which emerges is an instability consisting of a finite set of well-separated unstable bands in wave-number space (gain bands). The case with symmetrical, exponentially decaying connectivity functions is investigated in detail, allowing for a more comprehensive analysis of the gain-band structure, and, in particular, conditions for the excitation of a single gain band through a Turing-Hopf bifurcation with the relative inhibition time constant as control parameter. Two typical situations emerge depending on the thresholds and inclinations of the sigmoidal firing-rate functions: (i) A single gain-band is excited through a Turing-Hopf bifurcation, and the resulting state is a spatiotemporally oscillating pattern, or (ii) the instability develops into a stationary periodic pattern, i.e. a set of equidistant bumps. The dependence of instability-type on the inclinations of the firing-rate function and the time constant are comprehensively investigated, demonstrating, for example, that only stationary patterns can be generated for sufficiently small inhibitory time constants. The nonlinear

  11. Simple and non-toxic fabrication of poly(vinyl alcohol)-patterned polymer surface for the formation of cell patterns

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Negative PVA patterns were formed on NPS substrates by selective ion irradiation. • The surface of PVA patterns was more hydrophilic than that of the NPS substrate. • Well-organized cell patterns were created on the PVA-patterned NPS substrates. • It can be due to the preferential adsorption of serum proteins on PVA patterns. - Abstract: In this study, a facile and non-toxic method for the formation of cell-adhesive poly(vinyl alcohol) (PVA) patterns on the surface of a non-biological polystyrene substrate (NPS) is developed to control cellular micro-organization. PVA thin films spin-coated onto the NPS are selectively irradiated with 150 keV H+ ions through a pattern mask and developed with deionized water to form negative-type PVA patterns. Well-defined stripe patterns of PVA with a width of 100 μm are created on the NPS at a higher fluence than 5 × 1015 ions/cm2, and their surface chemical compositions are changed by ion irradiation without any significant morphological change. Based on the results of the protein adsorption test and in vitro cell culture, cancer cells are preferentially adhered and proliferated onto the more hydrophilic PVA regions of the PVA-patterned NPS, resulting in well-defined cell patterns

  12. Simple and non-toxic fabrication of poly(vinyl alcohol)-patterned polymer surface for the formation of cell patterns

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, In-Tae; Jin, Yu-Ran [Radiation Research Division for Industry and Environment, Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup-si, Jeollabuk-do 580-185 (Korea, Republic of); Oh, Min-Suk [POSCO Technical Research Laboratories, 699 Gumho-dong, Gwangyang, Jeonnam 545-090 (Korea, Republic of); Jung, Chan-Hee, E-mail: jch@kaeri.re.kr [Radiation Research Division for Industry and Environment, Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, Jeongeup-si, Jeollabuk-do 580-185 (Korea, Republic of); Choi, Jae-Hak, E-mail: jaehakchoi@cnu.ac.kr [Department of Polymer Science and Engineering, Chungnam National University, Yuseong-gu, Daejeon 305-764 (Korea, Republic of)

    2014-10-15

    Graphical abstract: - Highlights: • Negative PVA patterns were formed on NPS substrates by selective ion irradiation. • The surface of PVA patterns was more hydrophilic than that of the NPS substrate. • Well-organized cell patterns were created on the PVA-patterned NPS substrates. • It can be due to the preferential adsorption of serum proteins on PVA patterns. - Abstract: In this study, a facile and non-toxic method for the formation of cell-adhesive poly(vinyl alcohol) (PVA) patterns on the surface of a non-biological polystyrene substrate (NPS) is developed to control cellular micro-organization. PVA thin films spin-coated onto the NPS are selectively irradiated with 150 keV H{sup +} ions through a pattern mask and developed with deionized water to form negative-type PVA patterns. Well-defined stripe patterns of PVA with a width of 100 μm are created on the NPS at a higher fluence than 5 × 10{sup 15} ions/cm{sup 2}, and their surface chemical compositions are changed by ion irradiation without any significant morphological change. Based on the results of the protein adsorption test and in vitro cell culture, cancer cells are preferentially adhered and proliferated onto the more hydrophilic PVA regions of the PVA-patterned NPS, resulting in well-defined cell patterns.

  13. 13C Tracking after 13CO2 Supply Revealed Diurnal Patterns of Wood Formation in Aspen.

    Science.gov (United States)

    Mahboubi, Amir; Linden, Pernilla; Hedenström, Mattias; Moritz, Thomas; Niittylä, Totte

    2015-06-01

    Wood of trees is formed from carbon assimilated in the photosynthetic tissues. Determining the temporal dynamics of carbon assimilation, subsequent transport into developing wood, and incorporation to cell walls would further our understanding of wood formation in particular and tree growth in general. To investigate these questions, we designed a (13)CO2 labeling system to study carbon transport and incorporation to developing wood of hybrid aspen (Populus tremula × tremuloides). Tracking of (13)C incorporation to wood over a time course using nuclear magnetic resonance spectroscopy revealed diurnal patterns in wood cell wall biosynthesis. The dark period had a differential effect on (13)C incorporation to lignin and cell wall carbohydrates. No (13)C was incorporated into aromatic amino acids of cell wall proteins in the dark, suggesting that cell wall protein biosynthesis ceased during the night. The results show previously unrecognized temporal patterns in wood cell wall biosynthesis, suggest diurnal cycle as a possible cue in the regulation of carbon incorporation to wood, and establish a unique (13)C labeling method for the analysis of wood formation and secondary growth in trees.

  14. Patterned biofilm formation reveals a mechanism for structural heterogeneity in bacterial biofilms.

    Science.gov (United States)

    Gu, Huan; Hou, Shuyu; Yongyat, Chanokpon; De Tore, Suzanne; Ren, Dacheng

    2013-09-01

    Bacterial biofilms are ubiquitous and are the major cause of chronic infections in humans and persistent biofouling in industry. Despite the significance of bacterial biofilms, the mechanism of biofilm formation and associated drug tolerance is still not fully understood. A major challenge in biofilm research is the intrinsic heterogeneity in the biofilm structure, which leads to temporal and spatial variation in cell density and gene expression. To understand and control such structural heterogeneity, surfaces with patterned functional alkanthiols were used in this study to obtain Escherichia coli cell clusters with systematically varied cluster size and distance between clusters. The results from quantitative imaging analysis revealed an interesting phenomenon in which multicellular connections can be formed between cell clusters depending on the size of interacting clusters and the distance between them. In addition, significant differences in patterned biofilm formation were observed between wild-type E. coli RP437 and some of its isogenic mutants, indicating that certain cellular and genetic factors are involved in interactions among cell clusters. In particular, autoinducer-2-mediated quorum sensing was found to be important. Collectively, these results provide missing information that links cell-to-cell signaling and interaction among cell clusters to the structural organization of bacterial biofilms.

  15. The Influence of Gene Expression Time Delays on Gierer–Meinhardt Pattern Formation Systems

    KAUST Repository

    Seirin Lee, S.

    2010-03-23

    There are numerous examples of morphogen gradients controlling long range signalling in developmental and cellular systems. The prospect of two such interacting morphogens instigating long range self-organisation in biological systems via a Turing bifurcation has been explored, postulated, or implicated in the context of numerous developmental processes. However, modelling investigations of cellular systems typically neglect the influence of gene expression on such dynamics, even though transcription and translation are observed to be important in morphogenetic systems. In particular, the influence of gene expression on a large class of Turing bifurcation models, namely those with pure kinetics such as the Gierer-Meinhardt system, is unexplored. Our investigations demonstrate that the behaviour of the Gierer-Meinhardt model profoundly changes on the inclusion of gene expression dynamics and is sensitive to the sub-cellular details of gene expression. Features such as concentration blow up, morphogen oscillations and radical sensitivities to the duration of gene expression are observed and, at best, severely restrict the possible parameter spaces for feasible biological behaviour. These results also indicate that the behaviour of Turing pattern formation systems on the inclusion of gene expression time delays may provide a means of distinguishing between possible forms of interaction kinetics. Finally, this study also emphasises that sub-cellular and gene expression dynamics should not be simply neglected in models of long range biological pattern formation via morphogens. © 2010 Society for Mathematical Biology.

  16. Dynamic Pattern Formation for Wings of Pterygota in an Eclosion ---Pattern Analysis for Wings with the Imago---

    Science.gov (United States)

    Seino, M.; Kakazu, Y.

    The vein and cell patterns for the fore and hind wing of Lepidoptera, Hemiptera, Orthoptera and Odonata are analyzed and discussed. For vein patterns of them, the fractal properties are shown and the inequality between four orders is obtained. The nature of wings observed by mass distributions for fractal dimensions of the vein pattern is presented.

  17. Dynamic coupling of pattern formation and morphogenesis in the developing vertebrate retina.

    Science.gov (United States)

    Picker, Alexander; Cavodeassi, Florencia; Machate, Anja; Bernauer, Sabine; Hans, Stefan; Abe, Gembu; Kawakami, Koichi; Wilson, Stephen W; Brand, Michael

    2009-10-01

    During embryonic development, pattern formation must be tightly synchronized with tissue morphogenesis to coordinate the establishment of the spatial identities of cells with their movements. In the vertebrate retina, patterning along the dorsal-ventral and nasal-temporal (anterior-posterior) axes is required for correct spatial representation in the retinotectal map. However, it is unknown how specification of axial cell positions in the retina occurs during the complex process of early eye morphogenesis. Studying zebrafish embryos, we show that morphogenetic tissue rearrangements during eye evagination result in progenitor cells in the nasal half of the retina primordium being brought into proximity to the sources of three fibroblast growth factors, Fgf8/3/24, outside the eye. Triple-mutant analysis shows that this combined Fgf signal fully controls nasal retina identity by regulating the nasal transcription factor Foxg1. Surprisingly, nasal-temporal axis specification occurs very early along the dorsal-ventral axis of the evaginating eye. By in vivo imaging GFP-tagged retinal progenitor cells, we find that subsequent eye morphogenesis requires gradual tissue compaction in the nasal half and directed cell movements into the temporal half of the retina. Balancing these processes drives the progressive alignment of the nasal-temporal retina axis with the anterior-posterior body axis and is controlled by a feed-forward effect of Fgf signaling on Foxg1-mediated cell cohesion. Thus, the mechanistic coupling and dynamic synchronization of tissue patterning with morphogenetic cell behavior through Fgf signaling leads to the graded allocation of cell positional identity in the eye, underlying retinotectal map formation. PMID:19823566

  18. Spermidine, but not spermine, is essential for pigment pattern formation in zebrafish

    Science.gov (United States)

    Frohnhöfer, Hans Georg; Geiger-Rudolph, Silke; Pattky, Martin; Meixner, Martin; Huhn, Carolin; Maischein, Hans-Martin; Geisler, Robert; Gehring, Ines; Maderspacher, Florian; Nüsslein-Volhard, Christiane

    2016-01-01

    ABSTRACT Polyamines are small poly-cations essential for all cellular life. The main polyamines present in metazoans are putrescine, spermidine and spermine. Their exact functions are still largely unclear; however, they are involved in a wide variety of processes affecting cell growth, proliferation, apoptosis and aging. Here we identify idefix, a mutation in the zebrafish gene encoding the enzyme spermidine synthase, leading to a severe reduction in spermidine levels as shown by capillary electrophoresis-mass spectrometry. We show that spermidine, but not spermine, is essential for early development, organogenesis and colour pattern formation. Whereas in other vertebrates spermidine deficiency leads to very early embryonic lethality, maternally provided spermidine synthase in zebrafish is sufficient to rescue the early developmental defects. This allows us to uncouple them from events occurring later during colour patterning. Factors involved in the cellular interactions essential for colour patterning, likely targets for spermidine, are the gap junction components Cx41.8, Cx39.4, and Kir7.1, an inwardly rectifying potassium channel, all known to be regulated by polyamines. Thus, zebrafish provide a vertebrate model to study the in vivo effects of polyamines. PMID:27215328

  19. Mechanism Underlying the Spatial Pattern Formation of Dominant Tree Species in a Natural Secondary Forest.

    Directory of Open Access Journals (Sweden)

    Guodong Jia

    Full Text Available Studying the spatial pattern of plant species may provide significant insights into processes and mechanisms that maintain stand stability. To better understand the dynamics of naturally regenerated secondary forests, univariate and bivariate Ripley's L(r functions were employed to evaluate intra-/interspecific relationships of four dominant tree species (Populus davidiana, Betula platyphylla, Larix gmelinii and Acer mono and to distinguish the underlying mechanism of spatial distribution. The results showed that the distribution of soil, water and nutrients was not fragmented but presented clear gradients. An overall aggregated distribution existed at most distances. No correlation was found between the spatial pattern of soil conditions and that of trees. Both positive and negative intra- and interspecific relationships were found between different DBH classes at various distances. Large trees did not show systematic inhibition of the saplings. By contrast, the inhibition intensified as the height differences increased between the compared pairs. Except for Larix, universal inhibition of saplings by upper layer trees occurred among other species, and this reflected the vertical competition for light. Therefore, we believe that competition for light rather than soil nutrients underlies the mechanism driving the formation of stand spatial pattern in the rocky mountainous areas examined.

  20. Mechanism Underlying the Spatial Pattern Formation of Dominant Tree Species in a Natural Secondary Forest.

    Science.gov (United States)

    Jia, Guodong; Yu, Xinxiao; Fan, Dengxing; Jia, Jianbo

    2016-01-01

    Studying the spatial pattern of plant species may provide significant insights into processes and mechanisms that maintain stand stability. To better understand the dynamics of naturally regenerated secondary forests, univariate and bivariate Ripley's L(r) functions were employed to evaluate intra-/interspecific relationships of four dominant tree species (Populus davidiana, Betula platyphylla, Larix gmelinii and Acer mono) and to distinguish the underlying mechanism of spatial distribution. The results showed that the distribution of soil, water and nutrients was not fragmented but presented clear gradients. An overall aggregated distribution existed at most distances. No correlation was found between the spatial pattern of soil conditions and that of trees. Both positive and negative intra- and interspecific relationships were found between different DBH classes at various distances. Large trees did not show systematic inhibition of the saplings. By contrast, the inhibition intensified as the height differences increased between the compared pairs. Except for Larix, universal inhibition of saplings by upper layer trees occurred among other species, and this reflected the vertical competition for light. Therefore, we believe that competition for light rather than soil nutrients underlies the mechanism driving the formation of stand spatial pattern in the rocky mountainous areas examined. PMID:27028757

  1. Accelerated fluctuation analysis by graphic cards and complex pattern formation in financial markets

    Science.gov (United States)

    Preis, Tobias; Virnau, Peter; Paul, Wolfgang; Schneider, Johannes J.

    2009-09-01

    The compute unified device architecture is an almost conventional programming approach for managing computations on a graphics processing unit (GPU) as a data-parallel computing device. With a maximum number of 240 cores in combination with a high memory bandwidth, a recent GPU offers resources for computational physics. We apply this technology to methods of fluctuation analysis, which includes determination of the scaling behavior of a stochastic process and the equilibrium autocorrelation function. Additionally, the recently introduced pattern formation conformity (Preis T et al 2008 Europhys. Lett. 82 68005), which quantifies pattern-based complex short-time correlations of a time series, is calculated on a GPU and analyzed in detail. Results are obtained up to 84 times faster than on a current central processing unit core. When we apply this method to high-frequency time series of the German BUND future, we find significant pattern-based correlations on short time scales. Furthermore, an anti-persistent behavior can be found on short time scales. Additionally, we compare the recent GPU generation, which provides a theoretical peak performance of up to roughly 1012 floating point operations per second with the previous one. .

  2. Dynamic model based on voltage transfer curve for pattern formation in dielectric barrier glow discharge

    Science.gov (United States)

    Li, Ben; He, Feng; Duan, Xiaoxi; Ouyang, Jiting

    2015-12-01

    Simulation work is very important for understanding the formation of self-organized discharge patterns. Previous works have witnessed different models derived from other systems for simulation of discharge pattern, but most of these models are complicated and time-consuming. In this paper, we introduce a convenient phenomenological dynamic model based on the basic dynamic process of glow discharge and the voltage transfer curve (VTC) to study the dielectric barrier glow discharge (DBGD) pattern. VTC is an important characteristic of DBGD, which plots the change of wall voltage after a discharge as a function of the initial total gap voltage. In the modeling, the combined effect of the discharge conditions is included in VTC, and the activation-inhibition effect is expressed by a spatial interaction term. Besides, the model reduces the dimensionality of the system by just considering the integration effect of current flow. All these greatly facilitate the construction of this model. Numerical simulations turn out to be in good accordance with our previous fluid modeling and experimental result.

  3. Dynamic model based on voltage transfer curve for pattern formation in dielectric barrier glow discharge

    Energy Technology Data Exchange (ETDEWEB)

    Li, Ben; He, Feng; Ouyang, Jiting, E-mail: jtouyang@bit.edu.cn [School of Physics, Beijing Institute of Technology, Beijing 100081 (China); Duan, Xiaoxi [Research Center of Laser Fusion, CAEP, Mianyang 621900 (China)

    2015-12-15

    Simulation work is very important for understanding the formation of self-organized discharge patterns. Previous works have witnessed different models derived from other systems for simulation of discharge pattern, but most of these models are complicated and time-consuming. In this paper, we introduce a convenient phenomenological dynamic model based on the basic dynamic process of glow discharge and the voltage transfer curve (VTC) to study the dielectric barrier glow discharge (DBGD) pattern. VTC is an important characteristic of DBGD, which plots the change of wall voltage after a discharge as a function of the initial total gap voltage. In the modeling, the combined effect of the discharge conditions is included in VTC, and the activation-inhibition effect is expressed by a spatial interaction term. Besides, the model reduces the dimensionality of the system by just considering the integration effect of current flow. All these greatly facilitate the construction of this model. Numerical simulations turn out to be in good accordance with our previous fluid modeling and experimental result.

  4. Photo-induced self-organized pattern formation in bio-synthesized nanomaterials

    Science.gov (United States)

    Kukhtarev, Nickolai V.; Kukhtareva, Tatiana; Okafor, Florence; Johnson, Anita

    2011-09-01

    We have observed a dynamic self-organization of laser scattering from the biosynthesized nanofluids with silver and gold nanoparticles. Various procedures for nanofluid synthesis suitable for different applications are under constant investigation. In our present research the green biosynthesis process has been used for noble nanoparticles production. The aqueous solution of Magnolia Grandiflora leaves has been used as a reductant for silver and gold nanofluids.. We have applied the UV-visible spectroscopy method to control reaction process, fluorescent spectroscopy and nonlinear interferometric imaging experiments for characterization of nanofluids. From the number of laser-induced photothermal interferometric fringes it is possible to estimate the nonlinear refractive index coefficient changes. The kinetics observed in the pump-probe experiments with blue and red CW laser allowed us to estimate a timescale (~1s) of photothermal lens formation and dissipation. Moreover, we have observed the very exciting and unusual phenomena of self-organization of the laser scattering reflected from the fluid's surface. The diverse regular diffraction patterns (hexagons, rolls, squares etc), resembling diffraction of X-rays on crystal structures, were self-organized in biosynthesized solutions of nanoparticles. From the angular size of the observed hexagonal diffraction patterns it was possible to estimate the diameter of diffracting nanoclusters as 18 microns for silver and gold nanofluids and 9 microns for the Magnolia broth. The kinetics of the hexagonal scattering shows a quasiperiodic pattern, with a period of about 12 seconds with the slow build-up and sharp disappearance of scattering.

  5. In vitro biofilm formation by uropathogenic Escherichia coliand their antimicrobial susceptibility pattern

    Institute of Scientific and Technical Information of China (English)

    Poovendran Ponnusamy; Vidhya Natarajan; Murugan Sevanan

    2012-01-01

    Objective:To detect in vitro biofilm formation of uropathogenic Escherichia coli(E. coli)(UPEC) strains isolated from urine specimens and also to determine their antimicrobial susceptibility pattern using 13 commonly used antibiotics.Methods: The present study comprised of166 urine specimens collected from tertiary care hospitals in and around Coimbatore, South India. All the specimens were subjected to gram staining, bacterial culture and theE. coli strains were screened for biofilm formation using Tube Method(TM), Congo Red Agar(CRA) and Tissue Culture Plate method(TCP) respectively. Subsequently, the antimicrobial susceptibility test was performed by Kirby Bauer-disk diffusion method for the biofilm and non-biofilm producingE. colistrains.Results: Of the100 (60.2 %)E. coli strains,72 strains displayed a biofilm positive phenotype under the optimized conditions in the Tube Method and the strains were classified as highly positive(17, 23.6%), moderate positive(19, 26.3 %) and weakly positive(36, 50.0 %), similarly under the optimized conditions on Congo Red agar medium, biofilm positive phenotype strains were classified as highly positive(23, 23 %), moderate positive(37, 37 %)and weakly positive (40, 40%). While inTCP method, the biofilm positive phenotype strains were also classified as highly positive(6, 6 %), moderate positive (80, 80 %)and weakly positive(14, 14 %), it didn’t not correlate well with the tube method for detecting biofilm formation in E. coli. The rates of antibiotic resistance of biofilm producingE. coliwere found to be 100 % for chloramphenicol and amoxyclav (amoxicillin and clavulanic acid),86% for gentamicin and cefotaxime,84% for ceftazidime,83% for cotrimoxazole and piperacillin/tazobactam,75% for tetracycline and70% for amikacin.Conclusions: This study reveals the prevalence and antimicrobial susceptibility pattern of biofilm and non-biofilm producing uropathogenic E. coli strains.

  6. Formation of High Aspect Ratio TiO2 Nano tube Arrays by Anodization of Ti Foil in Organic Solution

    International Nuclear Information System (INIS)

    Titanium oxide (TiO2) nano tubes were successfully formed by anodization of pure titanium foil in a standard two-electrode bath consisting of ethylene glycol solution containing 5 wt % NH4F. The pH of the solution was ∼7 and the anodization voltage was 60 V. It was observed that such anodization condition results in ordered arrays of TiO2 nano tubes with smooth surface and a very high aspect ratio. It was observed that a minimum of 1 wt % water addition was required to form well ordered TiO2 nano tubes with length of approximately 18.5 μm. As-anodized sample, the self-organized TiO2 nano tubes have amorphous structure and annealing at 500 degree Celsius of the nano tubes promote formation of anatase and rutile phase. Photo catalytic activity of well ordered TiO2 nano tubes with two different lengths was evaluated by measuring the degradation of methyl orange (MO). The elaboration of this observation is described in detail in this paper. (author)

  7. From pattern formation to material computation multi-agent modelling of physarum polycephalum

    CERN Document Server

    Jones, Jeff

    2015-01-01

    This book addresses topics of mobile multi-agent systems, pattern formation, biological modelling, artificial life, unconventional computation, and robotics. The behaviour of a simple organism which is capable of remarkable biological and computational feats that seem to transcend its simple component parts is examined and modelled. In this book the following question is asked: How can something as simple as Physarum polycephalum - a giant amoeboid single-celled organism which does not possess any neural tissue, fixed skeleton or organised musculature - can approximate complex computational behaviour during its foraging, growth and adaptation of its amorphous body plan, and with such limited resources? To answer this question the same apparent limitations as faced by the organism are applied: using only simple components with local interactions. A synthesis approach is adopted and a mobile multi-agent system with very simple individual behaviours is employed. It is shown their interactions yield emergent beha...

  8. Dichotomous-noise-induced pattern formation in a reaction-diffusion system

    Science.gov (United States)

    Das, Debojyoti; Ray, Deb Shankar

    2013-06-01

    We consider a generic reaction-diffusion system in which one of the parameters is subjected to dichotomous noise by controlling the flow of one of the reacting species in a continuous-flow-stirred-tank reactor (CSTR) -membrane reactor. The linear stability analysis in an extended phase space is carried out by invoking Furutzu-Novikov procedure for exponentially correlated multiplicative noise to derive the instability condition in the plane of the noise parameters (correlation time and strength of the noise). We demonstrate that depending on the correlation time an optimal strength of noise governs the self-organization. Our theoretical analysis is corroborated by numerical simulations on pattern formation in a chlorine-dioxide-iodine-malonic acid reaction-diffusion system.

  9. Coherent Structures and Pattern Formation in Vlasov-Maxwell-Poisson Systems

    CERN Document Server

    Fedorova, A N; Fedorova, Antonina N.; Zeitlin, Michael G.

    2001-01-01

    We present the applications of methods from nonlinear local harmonic analysis for calculations in nonlinear collective dynamics described by different forms of Vlasov-Maxwell-Poisson equations. Our approach is based on methods provided the possibility to work with well-localized in phase space bases, which gives the most sparse representation for the general type of operators and good convergence properties. The consideration is based on a number of anzatzes, which reduce initial problems to a number of dynamical systems and on variational-wavelet approach to polynomial approximations for nonlinear dynamics. This approach allows us to construct the solutions via nonlinear high-localized eigenmodes expansions in the base of compactly supported wavelet bases and control contribution from each scale of underlying multiscales. Numerical modelling demonstrates formation of coherent structures and stable patterns.

  10. The Fokker-Planck law of diffusion and pattern formation in heterogeneous environments.

    Science.gov (United States)

    Bengfort, Michael; Malchow, Horst; Hilker, Frank M

    2016-09-01

    We analyze the influence of spatially inhomogeneous diffusion on several common ecological problems. Diffusion is modeled with Fick's law and the Fokker-Planck law of diffusion. We discuss the differences between the two formalisms and when to use either the one or the other. In doing so, we start with a pure diffusion equation, then turn to a reaction-diffusion system with one logistically growing component which invades the spatial domain. We also look at systems of two reacting components, namely a trimolecular oscillating chemical model system and an excitable predator-prey model. Contrary to Fickian diffusion, spatial inhomogeneities promote spatial and spatiotemporal pattern formation in case of Fokker-Planck diffusion. PMID:26803768

  11. The non-equilibrium charge screening effects in diffusion-driven systems with pattern formation

    Science.gov (United States)

    Kuzovkov, V. N.; Kotomin, E. A.; de la Cruz, M. Olvera

    2011-07-01

    The effects of non-equilibrium charge screening in mixtures of oppositely charged interacting molecules on surfaces are analyzed in a closed system. The dynamics of charge screening and the strong deviation from the standard Debye-Hückel theory are demonstrated via a new formalism based on computing radial distribution functions suited for analyzing both short-range and long-range spacial ordering effects. At long distances the inhomogeneous molecular distribution is limited by diffusion, whereas at short distances (of the order of several coordination spheres) by a balance of short-range (Lennard-Jones) and long-range (Coulomb) interactions. The non-equilibrium charge screening effects in transient pattern formation are further quantified. It is demonstrated that the use of screened potentials, in the spirit of the Debye-Hückel theory, leads to qualitatively incorrect results.

  12. Formation of colorimetric fingerprints on nano-patterned deterministic aperiodic surfaces.

    Science.gov (United States)

    Boriskina, Svetlana V; Lee, Sylvanus Y K; Amsden, Jason J; Omenetto, Fiorenzo G; Dal Negro, Luca

    2010-07-01

    Periodic gratings and photonic bandgap structures have been studied for decades in optical technologies. The translational invariance of periodic gratings gives rise to well-known angular and frequency filtering of the incident radiation resulting in well-defined scattered colors in response to broadband illumination. Here, we demonstrate the formation of highly complex structural color patterns, or colorimetric fingerprints, in two-dimensional (2D) deterministic aperiodic gratings using dark field scattering microscopy. The origin of colorimetric fingerprints is explained by rigorous full-wave numerical simulations based on the generalized Mie theory. We show that unlike periodic gratings, aperiodic nanopatterned surfaces feature a broadband frequency response with wide angular intensity distributions governed by the distinctive Fourier properties of the aperiodic structures. Finally, we will discuss a range of potential applications of colorimetric fingerprints for optical sensing and spectroscopy. PMID:20639942

  13. A reaction diffusion model of pattern formation in clustering of adatoms on silicon surfaces

    Directory of Open Access Journals (Sweden)

    Trilochan Bagarti

    2012-12-01

    Full Text Available We study a reaction diffusion model which describes the formation of patterns on surfaces having defects. Through this model, the primary goal is to study the growth process of Ge on Si surface. We consider a two species reaction diffusion process where the reacting species are assumed to diffuse on the two dimensional surface with first order interconversion reaction occuring at various defect sites which we call reaction centers. Two models of defects, namely a ring defect and a point defect are considered separately. As reaction centers are assumed to be strongly localized in space, the proposed reaction-diffusion model is found to be exactly solvable. We use Green's function method to study the dynamics of reaction diffusion processes. Further we explore this model through Monte Carlo (MC simulations to study the growth processes in the presence of a large number of defects. The first passage time statistics has been studied numerically.

  14. Direct observation of electric field induced pattern formation and particle aggregation in ferrofluids

    Energy Technology Data Exchange (ETDEWEB)

    Rajnak, Michal; Kopcansky, Peter; Timko, Milan [Institute of Experimental Physics SAS, Watsonova 47, 04001 Košice (Slovakia); Petrenko, Viktor I. [Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Moscow Region (Russian Federation); Kyiv Taras Shevchenko National University, Volodymyrska Street 64, Kyiv 01033 (Ukraine); Avdeev, Mikhail V. [Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Moscow Region (Russian Federation); Ivankov, Olexandr I. [Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Moscow Region (Russian Federation); Kyiv Taras Shevchenko National University, Volodymyrska Street 64, Kyiv 01033 (Ukraine); Moscow Institute of Physics and Technology, Institutskiy per. 9, Dolgoprudniy 141700 (Russian Federation); Feoktystov, Artem [Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Lichtenbergstr. 1, 85747 Garching (Germany); Dolnik, Bystrik; Kurimsky, Juraj [Faculty of Electrical Engineering and Informatics, Technical University of Košice, Letná 9, 04200 Košice (Slovakia)

    2015-08-17

    Ferrofluids typically respond to magnetic fields and can be manipulated by external magnetic fields. Here, we report on formation of visually observable patterns in a diluted low-polarity ferrofluid exposed to external electric fields. This presents a specific type of ferrofluid structure driven by a combined effect of electrohydrodynamics and electrical body forces. The free charge and permittivity variation are considered to play a key role in the observed phenomenon. The corresponding changes in the ferrofluid structure have been found at nanoscale as well. By small-angle neutron scattering (SANS), we show that the magnetic nanoparticles aggregate in direct current (dc) electric field with a strong dependence on the field intensity. The anisotropic aggregates preferably orient in the direction of the applied electric field. Conducting SANS experiments with alternating current (ac) electric fields of various frequencies, we found a critical frequency triggering the aggregation process. Our experimental study could open future applications of ferrofluids based on insulating liquids.

  15. Direct observation of electric field induced pattern formation and particle aggregation in ferrofluids

    Science.gov (United States)

    Rajnak, Michal; Petrenko, Viktor I.; Avdeev, Mikhail V.; Ivankov, Olexandr I.; Feoktystov, Artem; Dolnik, Bystrik; Kurimsky, Juraj; Kopcansky, Peter; Timko, Milan

    2015-08-01

    Ferrofluids typically respond to magnetic fields and can be manipulated by external magnetic fields. Here, we report on formation of visually observable patterns in a diluted low-polarity ferrofluid exposed to external electric fields. This presents a specific type of ferrofluid structure driven by a combined effect of electrohydrodynamics and electrical body forces. The free charge and permittivity variation are considered to play a key role in the observed phenomenon. The corresponding changes in the ferrofluid structure have been found at nanoscale as well. By small-angle neutron scattering (SANS), we show that the magnetic nanoparticles aggregate in direct current (dc) electric field with a strong dependence on the field intensity. The anisotropic aggregates preferably orient in the direction of the applied electric field. Conducting SANS experiments with alternating current (ac) electric fields of various frequencies, we found a critical frequency triggering the aggregation process. Our experimental study could open future applications of ferrofluids based on insulating liquids.

  16. Nonconstant Positive Steady States and Pattern Formation of 1D Prey-Taxis Systems

    Science.gov (United States)

    Wang, Qi; Song, Yang; Shao, Lingjie

    2016-08-01

    Prey-taxis is the process that predators move preferentially toward patches with highest density of prey. It is well known to have an important role in biological control and the maintenance of biodiversity. To model the coexistence and spatial distributions of predator and prey species, this paper concerns nonconstant positive steady states of a wide class of prey-taxis systems with general functional responses over 1D domain. Linearized stability of the positive equilibrium is analyzed to show that prey-taxis destabilizes prey-predator homogeneity when prey repulsion (e.g., due to volume-filling effect in predator species or group defense in prey species) is present, and prey-taxis stabilizes the homogeneity otherwise. Then, we investigate the existence and stability of nonconstant positive steady states to the system through rigorous bifurcation analysis. Moreover, we provide detailed and thorough calculations to determine properties such as pitchfork and turning direction of the local branches. Our stability results also provide a stable wave mode selection mechanism for thee reaction-advection-diffusion systems including prey-taxis models considered in this paper. Finally, we provide numerical studies of prey-taxis systems with Holling-Tanner kinetics to illustrate and support our theoretical findings. Our numerical simulations demonstrate that the 2× 2 prey-taxis system is able to model the formation and evolution of various striking patterns, such as spikes, periodic oscillations, and coarsening even when the domain is one-dimensional. These dynamics can model the coexistence and spatial distributions of interacting prey and predator species. We also give some insights on how system parameters influence pattern formation in these models.

  17. Delay-driven pattern formation in a reaction-diffusion predator-prey model incorporating a prey refuge

    Science.gov (United States)

    Lian, Xinze; Wang, Hailing; Wang, Weiming

    2013-04-01

    In this paper, we consider a diffusive predation model with a delay effect, which is based on a modified version of the Leslie-Gower scheme incorporating a prey refuge. We mainly investigate the effects of time delay on the stability of the homogeneous state point and the formation of spatial patterns. We give the conditions for diffusion-driven and delay-diffusion-driven instability in detail. Furthermore, we illustrate the spatial patterns via numerical simulations, which show that the model dynamics exhibits a delay and diffusion controlled formation growth not only of spots, stripes and holes, but also of self-replicating spiral patterns. The results indicate that the delay plays an important role in the pattern selection. This may enrich the pattern dynamics for a delay diffusive model.

  18. Pattern Formation by Staphylococcus epidermidis via Droplet Evaporation on Micropillars Arrays at a Surface.

    Science.gov (United States)

    Susarrey-Arce, A; Marin, A; Massey, A; Oknianska, A; Díaz-Fernandez, Y; Hernández-Sánchez, J F; Griffiths, E; Gardeniers, J G E; Snoeijer, J H; Lohse, Detlef; Raval, R

    2016-07-19

    We evaluate the effect of epoxy surface structuring on the evaporation of water droplets containing Staphylococcus epidermidis (S. epidermidis). During evaporation, droplets with S. epidermidis cells yield to complex wetting patterns such as the zipping-wetting1-3 and the coffee-stain effects. Depending on the height of the microstructure, the wetting fronts propagate circularly or in a stepwise manner, leading to the formation of octagonal or square-shaped deposition patterns.4,5 We observed that the shape of the dried droplets has considerable influence on the local spatial distribution of S. epidermidis deposited between micropillars. These changes are attributed to an unexplored interplay between the zipping-wetting1 and the coffee-stain6 effects in polygonally shaped droplets containing S. epidermidis. Induced capillary flows during evaporation of S. epidermidis are modeled with polystyrene particles. Bacterial viability measurements for S. epidermidis show high viability of planktonic cells, but low biomass deposition on the microstructured surfaces. Our findings provide insights into design criteria for the development of microstructured surfaces on which bacterial propagation could be controlled, limiting the use of biocides.

  19. Nanoscale pattern formation at surfaces under ion-beam sputtering: A perspective from continuum models

    Energy Technology Data Exchange (ETDEWEB)

    Cuerno, Rodolfo, E-mail: cuerno@math.uc3m.e [Departamento de Matematicas and Grupo Interdisciplinar de Sistemas Complejos (GISC), Universidad Carlos III de Madrid, Avenida de la Universidad 30, E-28911 Leganes, Madrid (Spain); Castro, Mario [GISC and Grupo de Dinamica No Lineal (DNL), Escuela Tecnica Superior de Ingenieria (ICAI), Universidad Pontificia Comillas, E-28015 Madrid (Spain); Munoz-Garcia, Javier [Systems Biology Ireland and GISC, University College Dublin, Belfield, Dublin 4 (Ireland); Gago, Raul; Vazquez, Luis [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, E-28049 Madrid (Spain)

    2011-05-01

    Although reports on surface nanostructuring of solid targets by low to medium energy ion irradiation date back to the 1960s, only with the advent of high resolution tools for surface/interface characterization has the high potential of this procedure been recognized as a method for efficient production of surface patterns. Such morphologies are made up of periodic arrangements of nanometric sized features, like ripples and dots, with interest for technological applications due to their electronic, magnetic, and optical properties. Thus, roughly for the last ten years large efforts have been directed towards harnessing this nanofabrication technique. However, and particularly in view of recent experimental developments, we can say that the basic mechanisms controlling these pattern formation processes remain poorly understood. The lack of nanostructuring at low angles of incidence on some pure monoelemental targets, the role of impurities in the surface dynamics and other recent observations are challenging the classic view on the phenomenon as the mere interplay between the curvature dependence of the sputtering yield and surface diffusion. We review the main attempts at a theoretical (continuum) description of these systems, with emphasis on recent developments. Strong hints already exist that the nature of the morphological instability has to be rethought as originating in the material flow that is induced by the ion beam.

  20. Frequency of Teriparatide Administration Affects the Histological Pattern of Bone Formation in Young Adult Male Mice.

    Science.gov (United States)

    Yamamoto, Tomomaya; Hasegawa, Tomoka; Sasaki, Muneteru; Hongo, Hiromi; Tsuboi, Kanako; Shimizu, Tomohiro; Ota, Masahiro; Haraguchi, Mai; Takahata, Masahiko; Oda, Kimimitsu; Luiz de Freitas, Paulo Henrique; Takakura, Aya; Takao-Kawabata, Ryoko; Isogai, Yukihiro; Amizuka, Norio

    2016-07-01

    Evidence supports that daily and once-weekly administration of teriparatide, human (h)PTH(1-34), enhance bone mass in osteoporotic patients. However, it is uncertain whether different frequencies of hPTH(1-34) administration would induce bone formation similarly in terms of quantity and quality. To investigate that issue, mice were subjected to different frequencies of PTH administration, and their bones were histologically examined. Frequencies of administration were 1 time/2 days, 1 time a day, and 2 and 4 times a day. Mice were allocated to either to control or to 3 different dosing regimens: 80 μg/kg of hPTH(1-34) per injection (80 μg/kg per dose), 80 μg/kg of hPTH(1-34) per day (80 μg/kg · d), or 20 μg/kg of hPTH(1-34) per day (20 μg/kg · d). With the regimens of 80 μg/kg per dose and 80 μg/kg · d, high-frequency hPTH(1-34) administration increased metaphyseal trabecular number. However, 4 doses per day induced the formation of thin trabeculae, whereas the daily PTH regimen resulted in thicker trabeculae. A similar pattern was observed with the lower daily hPTH(1-34) dose (20 μg/kg · d): more frequent PTH administration led to the formation of thin trabeculae, showing a thick preosteoblastic cell layer, several osteoclasts, and scalloped cement lines that indicated accelerated bone remodeling. On the other hand, low-frequency PTH administration induced new bone with mature osteoblasts lying on mildly convex surfaces representative of arrest lines, which suggests minimodeling-based bone formation. Thus, high-frequency PTH administration seems to increase bone mass rapidly by forming thin trabeculae through accelerated bone remodeling. Alternatively, low-frequency PTH administration leads to the formation of thicker trabeculae through bone remodeling and minimodeling. PMID:27227535

  1. Modeling the PbI2 formation in perovskite solar cells using XRD/XPS patterns

    Science.gov (United States)

    Sohrabpoor, Hamed; Elyasi, Majid; Aldosari, Marouf; Gorji, Nima E.

    2016-09-01

    The impact of prolonged irradiation and air humidity on the stability of perovskite solar cells is modeled using X-ray diffraction and X-ray photoelectron spectroscopy patterns reported in the literature. Light or air-moisture causes the formation of a thin PbI2 or oxide defective layers (in nanoscale) at the interface of perovskite/hole-transport-layer or at the junction with metallic back contact. This thin layer blocks the carrier transport/passivation at the interfaces and cause degradation of device parameters. Variation in thickness of defective layers, changes the XRD and XPS peaks. This allows detection and estimation of the type, crystallinity and thickness of the defective layer. A simple model is developed here to extract the thickness of such thin defective layers formed in nanometer scale at the back region of several perovskite devices. Based on this information, corrected energy band diagram of every device before and after degradation/aging is drawn and discussed in order to obtain insight into the carrier transport and charge collection at the barrier region. In addition, graphene contacted perovskite devices are investigated showing that honey-comb network of graphene contact reduces the effect of aging leading to formation of a thinner defective layer at the perovskite surface compared to perovskite devices with conventional inorganic contacts i.e. Au, Al.

  2. Determination of density pattern of fracture in Asmari Formation in Marun oilfield

    Directory of Open Access Journals (Sweden)

    Kheyrollah Noraeinezhad

    2015-05-01

    Full Text Available Marun oilfield is located in the middle part of Dezful Embayment and is situated along the Aghajari, Ahvaz and Ramin anticline. Given the important role of fracture characteristics for improving production, so the aim of this research is to investigate the density pattern of fracture in Asmari formation in Marun oilfield. For this purpose, results of image log, core data, graphic well log, methods of inscribed circle analysis and curvature changes geometry of anticline were analyzed. Asmari formation is the main reservoir rock in Marun oilfield that divided into five zones. Limestone and dolomite are the main lithology of zones 1, 2 and 3 which has a high density of fractures (especially in zones with 90% dolomite. Also there is less fracture density (micro fracture in the 4 and 5 Asmari zone due to an increase of shale and marl layers and due to less break ablity has a less distribution of fractures. The result show that there are a good conformity existed between the results of inscribed circle analysis, image log, core data, curvature and the presence of fractures in Marun anticline. The data indicate that highest density of fracture density concentrates in the southern limb in the central region of anticline and also in the north limb in the northeast region of the anticline. So, finally using these parameters, it is recommended that further development and production wells be drilled in the north eastern part of the oil filed as well as center part of southern flank of the anticline.

  3. X-ray photoemission spectromicroscopy of titanium silicide formation in patterned microstructures

    Energy Technology Data Exchange (ETDEWEB)

    Singh, S.; Solak, H.; Cerrina, F. [Univ. of Wisconsin-Madison, Stoughton, WI (United States)] [and others

    1997-04-01

    Titanium silicide has the lowest resistivity of all the refractory metal silicides and has good thermal stability as well as excellent compatibility with Al metallization. It is used as an intermediate buffer layer between W vias and the Si substrate to provide good electrical contact in ULSI technology, whose submicron patterned features form the basis of the integrated circuits of today and tomorrow, in the self aligned silicide (salicide) formation process. TiSi{sub 2} exists in two phases: a metastable C49 base-centered orthorhombic phase with specific resistivity of 60-90 {mu}{Omega}-cm that is formed at a lower temperature (formation anneal) and the stable 12-15 {mu}{Omega}-cm resistivity face-centered orthorhombic C54 phase into which C49 is transformed with a higher temperature (conversion anneal) step. C54 is clearly the target for low resistivity VLSI interconnects. However, it has been observed that when dimensions shrink below 1/mic (or when the Ti thickness drops below several hundred angstroms), the transformation of C49 into C54 is inhibited and agglomeration often occurs in fine lines at high temperatures. This results in a rise in resistivity due to incomplete transformation to C54 and because of discontinuities in the interconnect line resulting from agglomeration. Spectromicroscopy is an appropriate tool to study the evolution of the TiSi2 formation process because of its high resolution chemical imaging ability which can detect bonding changes even in the absence of changes in the relative amounts of species and because of the capability of studying thick {open_quotes}as is{close_quotes} industrial samples.

  4. A generic model of pattern formation in Mississippi Valley-Type deposits based on analytical findings

    Science.gov (United States)

    Kelka, Ulrich; Veveakis, Manolis; Beaudoin, Nicolas; Poulet, Thomas; Koehn, Daniel; Regenauer-Lieb, Klaus; Chung, Peter; Berndt, Jasper

    2016-04-01

    Rhythmically banded dolomites (zebra dolomite) are found worldwide, and are frequently associated with mineralization of the Mississippi Valley-Type (MVT). These rocks consist of dark fine grained and impurity-rich layers alternating with light coarse grained and virtually impurity-free layers. The texture of the light layers is similar to the one of tectonic syntaxial veins where crystals grow towards a median line. We present petrographic and chemical analysis of zebra dolomite samples from the San Vicente mine, Central Peru. The applied methods are petrographic microscopy, SEM, EBSD, EMP and LA-ICP-MS. The findings influence the development of a generic model of pattern formation. We found the density and the distribution of second-phase material to be one striking feature. The impurities are accumulated in the dark layers, which show an even higher density of second-phase material than the surrounding impurity-rich dolomite. With CL, it was possible to detect a luminescent structure in the center of the light bands which seems to be present independent of the thickness and spacing of the respective layers. This structure was analysed in more detail with EMP. We further found that the dolomite crystals in the dark and light layers are chemically similar but show a variation in some trace elements. Based on the analytical findings, we put forward a mathematical model of zebra dolomite formation based on Cnoidal waves. We believe that the light coarse grained layers represent hydromechanical instabilities arising during the diagenetic compaction of a fluid saturated, impurity-rich dolomite. Our approach is based on the extension of the classical compaction bands theory to a viscose, non-linear rheology. In the model, the spacing between two light coarse grained layers is linked to the compaction length during the pattern formation. With the formulation of a 1D steady-state solution we can relate the genesis of the structure to physical parameter, such as

  5. From dynamic expression patterns to boundary formation in the presomitic mesoderm.

    Directory of Open Access Journals (Sweden)

    Hendrik B Tiedemann

    Full Text Available The segmentation of the vertebrate body is laid down during early embryogenesis. The formation of signaling gradients, the periodic expression of genes of the Notch-, Fgf- and Wnt-pathways and their interplay in the unsegmented presomitic mesoderm (PSM precedes the rhythmic budding of nascent somites at its anterior end, which later develops into epithelialized structures, the somites. Although many in silico models describing partial aspects of somitogenesis already exist, simulations of a complete causal chain from gene expression in the growth zone via the interaction of multiple cells to segmentation are rare. Here, we present an enhanced gene regulatory network (GRN for mice in a simulation program that models the growing PSM by many virtual cells and integrates WNT3A and FGF8 gradient formation, periodic gene expression and Delta/Notch signaling. Assuming Hes7 as core of the somitogenesis clock and LFNG as modulator, we postulate a negative feedback of HES7 on Dll1 leading to an oscillating Dll1 expression as seen in vivo. Furthermore, we are able to simulate the experimentally observed wave of activated NOTCH (NICD as a result of the interactions in the GRN. We esteem our model as robust for a wide range of parameter values with the Hes7 mRNA and protein decays exerting a strong influence on the core oscillator. Moreover, our model predicts interference between Hes1 and HES7 oscillators when their intrinsic frequencies differ. In conclusion, we have built a comprehensive model of somitogenesis with HES7 as core oscillator that is able to reproduce many experimentally observed data in mice.

  6. ORGANIZATIONAL ASPECTS OF TYPICAL PATTERNS OF CRIME MECHANISM IN THE SPHERE OF ILLEGAL WEAPON AND AMMUNITION TURNOVER

    Directory of Open Access Journals (Sweden)

    Ragulin I. Y.

    2015-11-01

    Full Text Available This article is important today because there is not enough attention in the contemporary law publications paid to the typical patterns of crime mechanism especially in the sphere of illegal weapon and ammunition turnover. Taking into account the opinions of such well-known forensic scientists as R.S. Belkin, V.D. Zelensky, G.M. Meretukov, M.V. Golovin, V.A. Obraztsov, J.G. Korukhov, V.Y. Koldin, O.V. Chelysheva, L.Y. Drapkin, V.N. Karagodin and others, the author comes to the conclusion that it’s necessary to develop typical patterns of crime mechanism for certain types of crime. The author has worked out some typical patterns of crime mechanism in the sphere of illegal weapon and ammunition turnover based upon major informative criminalistic elements, this particular article describes seven typical patterns of crime mechanism for the illegal storage, transportation, transfer, carry, purchase and sale, manufacture, repair or alteration, theft or extortion, careless storage or improper performance of duties on protection of weapon, its basic parts and ammunition. Each pattern is accompanied with the examples of judicial and investigative practice, followed by the necessary explanations and analysis of the activities of the subject of the investigation on the preparation, followup and final stages, which leads to the conclusion about the legitimacy of the proposed patterns

  7. On the role of vegetation in the formation of river anabranching patterns

    Science.gov (United States)

    Crouzy, B.; D'Odorico, P.; Wütrich, D.; Perona, P.

    2012-04-01

    Part of studies on the couplings between the evolution of riparian vegetation and the river morphodynamics, we investigate the effect of spatial interactions between vegetation located at different positions within the channel. This work generalizes the experimental and theoretical results by Perona et al. and by Crouzy and Perona (both Advances in Water Resources, in Press) on colonization of riverbars by seedlings or large woody debris by relaxing the hypothesis made in those two works of the biomass growth and uprooting being independent on the presence of neighboring plants. While the hypothesis of independent vegetation growth and uprooting is justified for sparse vegetation cover or young seedlings, it fails as soon as the canopy significantly disturbs the flow or changes the sediment stability. Then, flow-mediated interactions between riparian vegetation located at different positions within the channel can be observed. Those interactions are either constructive or destructive. For example, a region favorable to the development of biomass appears on the lee side of a vegetated obstacle (with bleed flow) due to increased deposition of seeds and sediment (Schnauder and Moggridge, 2008) while conversely scouring can be increased laterally due to obstacle-induced flow diversion (Roulund et al., 2005; Melville and Sutherland, 1988; Zong and Nepf, 2008). We focus on the role of vegetation in the formation of the regular vegetated ridge patterns found in ephemeral rivers (see for example the work by Tooth and Nanson, 2004 on anabranching patterns) or as a succession of swales and ridges on the inside of meander bends (scroll bars). From the analysis of aerial images, we obtain the characteristic length scale of the patterns. We show how in the limit where the hydrological (interarrival time of floods) and the biological (germination and growth rates) timescales are comparable the combination between both positive and negative feedbacks between vegetation located at

  8. Charge effects and nanoparticle pattern formation in electrohydrodynamic NanoDrip printing of colloids

    Science.gov (United States)

    Richner, Patrizia; Kress, Stephan J. P.; Norris, David J.; Poulikakos, Dimos

    2016-03-01

    Advancing open atmosphere printing technologies to produce features in the nanoscale range has important and broad applications ranging from electronics to photonics, plasmonics and biology. Recently an electrohydrodynamic printing regime has been demonstrated in a rapid dripping mode (termed NanoDrip), where the ejected colloidal droplets from nozzles of diameters of O (1 μm) can controllably reach sizes an order of magnitude smaller than the nozzle and can generate planar and out-of-plane structures of similar sizes. Despite the demonstrated capabilities, our fundamental understanding of important aspects of the physics of NanoDrip printing needs further improvement. Here we address the topics of charge content and transport in NanoDrip printing. We employ quantum dot and gold nanoparticle dispersions in combination with a specially designed, auxiliary, asymmetric electric field, targeting the understanding of charge locality (particles vs. solvent) and particle distribution in the deposits as indicated by the dried nanoparticle patterns (footprints) on the substrate. We show that droplets of alternating charge can be spatially separated when applying an ac field to the nozzle. The nanoparticles within a droplet are distributed asymmetrically under the influence of the auxiliary lateral electric field, indicating that they are the main carriers. We also show that the ligand length of the nanoparticles in the colloid affects their mobility after deposition (in the sessile droplet state).Advancing open atmosphere printing technologies to produce features in the nanoscale range has important and broad applications ranging from electronics to photonics, plasmonics and biology. Recently an electrohydrodynamic printing regime has been demonstrated in a rapid dripping mode (termed NanoDrip), where the ejected colloidal droplets from nozzles of diameters of O (1 μm) can controllably reach sizes an order of magnitude smaller than the nozzle and can generate planar and

  9. Biofilm formation over surface patterned with pico-liter oil micro-drop array

    Science.gov (United States)

    Jalali, Maryam; Sheng, Jian

    2015-11-01

    It has been suggested that biodegradation by microbes is an effective process in the cleansing of oil polluted marine environments. It has also been speculated that dispersants could further enhance processes amid no direct evidence. The studies in the relevant scales are severely hampered by lack of techniques to generate uniform micro-scale drops allowing in-situ monitoring of these processes. In this paper, we present a microfabrication technique allowing patterning microfluidic surfaces with arrays of micro oil drops. The array of oil drops was printed by micro transfer molding/printing with negative PDMS stamps. The printed micro-drops have dimensions ranging from 5 μm to 50 μm. Non-circular shapes, such as square and triangle, can also be printed and maintained for weeks. Atomic force microscopy is used to characterize the topology and interfacial structures of droplets. The results reveal that although the drop with different base shapes assumes dome like profile asymptotically, donut and top-hat shapes are also observed. Time evolution measurement elucidates that in the absences of inviscid mechanisms in comparison to a micro-liter drop, subtle interplays between interfacial forces and viscosity play crucial role in the shape of pico-liter drop. With the developed surfaces, the effects of oil drop sizes and interfacial structures on biofilm formation are studied and reported.

  10. Looking at the origin of phenotypic variation from pattern formation gene networks

    Indian Academy of Sciences (India)

    Isaac Salazar-Ciudad

    2009-10-01

    This article critically reviews some widespread views about the overall functioning of development. Special attention is devoted to views in developmental genetics about the superstructure of developmental gene networks. According to these views gene networks are hierarchic and multilayered. The highest layers partition the embryo in large coarse areas and control downstream genes that subsequently subdivide the embryo into smaller and smaller areas. These views are criticized on the bases of developmental and evolutionary arguments. First, these views, although detailed at the level of gene identities, do not incorporate morphogenetic mechanisms nor do they try to explain how morphology changes during development. Often, they assume that morphogenetic mechanisms are subordinate to cell signaling events. This is in contradiction to the evidence reviewed herein. Experimental evidence on pattern formation also contradicts the view that developmental gene networks are hierarchically multilayered and that their functioning is decodable from promoter analysis. Simple evolutionary arguments suggest that, indeed, developmental gene networks tend to be non-hierarchic. Re-use leads to extensive modularity in gene networks while developmental drift blurs this modularity. Evolutionary opportunism makes developmental gene networks very dependent on epigenetic factors.

  11. Polar pattern formation in driven filament systems requires non-binary particle collisions

    Science.gov (United States)

    Suzuki, Ryo; Weber, Christoph A.; Frey, Erwin; Bausch, Andreas R.

    2015-10-01

    From the self-organization of the cytoskeleton to the synchronous motion of bird flocks, living matter has the extraordinary ability to behave in a concerted manner. The Boltzmann equation for self-propelled particles is frequently used in silico to link a system’s meso- or macroscopic behaviour to the microscopic dynamics of its constituents. But so far such studies have relied on an assumption of simplified binary collisions owing to a lack of experimental data suggesting otherwise. We report here experimentally determined binary-collision statistics by studying a recently introduced molecular system, the high-density actomyosin motility assay. We demonstrate that the alignment induced by binary collisions is too weak to account for the observed ordering transition. The transition density for polar pattern formation decreases quadratically with filament length, indicating that multi-filament collisions drive the observed ordering phenomenon and that a gas-like picture cannot explain the transition of the system to polar order. Our findings demonstrate that the unique properties of biological active-matter systems require a description that goes well beyond that developed in the framework of kinetic theories.

  12. Dynamical pattern formation in a low-concentration magnetorheological fluid under two orthogonal sinusoidal fields

    Science.gov (United States)

    Yépez, L. D.; Carrillo, J. L.; Donado, F.; Sausedo-Solorio, J. M.; Miranda-Romagnoli, P.

    2016-06-01

    The dynamical pattern formation of clusters of magnetic particles in a low-concentration magnetorheological fluid, under the influence of a superposition of two perpendicular sinusoidal fields, is studied experimentally. By varying the frequency and phase shift of the perpendicular fields, this configuration enables us to experimentally analyze a wide range of field configurations, including the case of a pure rotating field and the case of an oscillating unidirectional field. The fields are applied parallel to the horizontal plane where the fluid lies or in the vertical plane. For fields applied in the horizontal plane, we observed that, when the ratio of the frequencies increases, the average cluster size exhibits a kind of periodic resonances. When the phase shift between the fields is varied, the average chain length reaches maximal values for the cases of the rotating field and the unidirectional case. We analyze and discuss these results in terms of a weighted average of the time-dependent Mason number. In the case of a rotating field on the vertical plane, we also observe that the competition between the magnetic and the viscous forces determines the average cluster size. We show that this configuration generates a series of physically meaningful self-organization of clusters and transport phenomena.

  13. Pattern Formation in Swarming Spacecrafts using Tersoff-Brenner Potential Field

    Directory of Open Access Journals (Sweden)

    Zhifeng Zeng

    2013-05-01

    Full Text Available We present a distributed control strategy that lets a swarm of spacecrafts autonomously form a lattice in orbit around a planet. The system, based on the artificial potential field approach, proposes a novel way to divide the artificial field into two main terms: a global artificial potential field mainly based on the famous C-W equations that gathers the spacecrafts around a predefined meeting point, and a local term exploited the well-known Tersoff-Brenner potential that allows a spacecraft to place itself in the correct position relative to its closest neighbors. Moreover, in order to obtain convergence from all initial distributions of the spacecrafts, a dissipation term depended on the velocity of agent is introduced. The new methodology is demonstrated in the problem of forming a hexagon lattice, the structure unit of graphite. It is shown that a pattern formation can operate around a planet. By slightly changing the scenario our method can be easily applied to shape other configurations, such as a regular tetrahedron (with central point, the structure unit, etc.

  14. Simple and non-toxic fabrication of poly(vinyl alcohol)-patterned polymer surface for the formation of cell patterns

    Science.gov (United States)

    Hwang, In-Tae; Jin, Yu-Ran; Oh, Min-Suk; Jung, Chan-Hee; Choi, Jae-Hak

    2014-10-01

    In this study, a facile and non-toxic method for the formation of cell-adhesive poly(vinyl alcohol) (PVA) patterns on the surface of a non-biological polystyrene substrate (NPS) is developed to control cellular micro-organization. PVA thin films spin-coated onto the NPS are selectively irradiated with 150 keV H+ ions through a pattern mask and developed with deionized water to form negative-type PVA patterns. Well-defined stripe patterns of PVA with a width of 100 μm are created on the NPS at a higher fluence than 5 × 1015 ions/cm2, and their surface chemical compositions are changed by ion irradiation without any significant morphological change. Based on the results of the protein adsorption test and in vitro cell culture, cancer cells are preferentially adhered and proliferated onto the more hydrophilic PVA regions of the PVA-patterned NPS, resulting in well-defined cell patterns.

  15. Analytical solutions of jam pattern formation on a ring for a class of optimal velocity traffic models

    DEFF Research Database (Denmark)

    Gaididei, Yuri Borisovich; Berkemer, Rainer; Caputo, Jean Guy;

    2009-01-01

    A follow-the-leader model of traffic flow on a closed loop is considered in the framework of the extended optimal velocity (OV) model where the driver reacts to both the following and the preceding car. Periodic wave train solutions that describe the formation of traffic congestion patterns...

  16. Two tree-formation methods for fast pattern search using nearest-neighbour and nearest-centroid matching

    NARCIS (Netherlands)

    Schomaker, Lambertus; Mangalagiu, D.; Vuurpijl, Louis; Weinfeld, M.; Schomaker, Lambert; Vuurpijl, Louis

    2000-01-01

    This paper describes tree­based classification of character images, comparing two methods of tree formation and two methods of matching: nearest neighbor and nearest centroid. The first method, Preprocess Using Relative Distances (PURD) is a tree­based reorganization of a flat list of patterns, desi

  17. On the formation of oriented nanometer scale patterns on amorphous polymer surfaces studied by atomic force microscopy

    NARCIS (Netherlands)

    Pickering, J.P.; Vancso, G.J.

    1999-01-01

    Nanometer scale patterns were formed on the surface of several amorphous polystyrenes by a scanning probe microscope (SPM) operating in the contact mode. In order to better understand the nature of their formation, samples of several molar masses were systematically examined at room temperature in a

  18. Polychlorinated dibenzo-p-dioxin (PCDD) and dibenzofuran (PCDF) isomer patterns from municipal waste combustion: formation mechanism fingerprints.

    Science.gov (United States)

    Ryu, Jae-Yong; Choi, Kum-Chan; Mulholland, James A

    2006-11-01

    Polychlorinated dibenzo-p-dioxin (PCDD) and dibenzofuran (PCDF) byproducts can be formed in combustion systems by a variety of mechanisms. While total PCDD/F emissions and, to a lesser extent, homologue distributions from incinerators have been found to vary widely depending on combustion conditions, PCDD/F isomer distributions do not. Formation mechanisms can be grouped into two general categories: condensation of precursors, such as chlorinated phenols, and formation from particulate carbon, termed de novo synthesis. In addition to these mechanisms, chlorination and dechlorination reactions may affect isomer patterns. In this work, isomer patterns from field and laboratory municipal waste combustion samples are compared with computed thermodynamic distributions and those from the following experimental investigations: both gas-phase and metal-catalyzed condensation of chlorinated phenols, chlorination of dibenzo-p-dioxin and dibenzofuran, and dechlorination of octachlorodibenzo-p-dioxin and octachlorodibenzofuran. PCDD/F isomer patterns produced by different formation mechanisms in controlled experiments are distinct and robust, largely unaffected by combustion conditions. PCDD isomer patterns from municipal waste combustion are most similar to those produced by CuCl(2)-catalyzed phenol condensation from 10 chlorinated phenols. PCDF isomer patterns are most similar to those produced by chlorination and dechlorination.

  19. Pattern formation of reaction-diffusion system having self-determined flow in the amoeboid organism of Physarum plasmodium

    CERN Document Server

    Yamada, H; Ito, M

    1998-01-01

    The amoeboid organism, the plasmodium of Physarum polycephalum, behaves on the basis of spatio-temporal pattern formation by local contraction-oscillators. This biological system can be regarded as a reaction-diffusion system which has spatial interaction by active flow of protoplasmic sol in the cell. Paying attention to the physiological evidence that the flow is determined by contraction pattern in the plasmodium, a reaction-diffusion system having self-determined flow arises. Such a coupling of reaction-diffusion-advection is a characteristic of the biological system, and is expected to relate with control mechanism of amoeboid behaviours. Hence, we have studied effects of the self-determined flow on pattern formation of simple reaction-diffusion systems. By weakly nonlinear analysis near a trivial solution, the envelope dynamics follows the complex Ginzburg-Landau type equation just after bifurcation occurs at finite wave number. The flow term affects the nonlinear term of the equation through the critic...

  20. Swarming and complex pattern formation in Paenibacillus vortex studied by imaging and tracking cells

    Directory of Open Access Journals (Sweden)

    Jacob Eshel

    2008-02-01

    Full Text Available Abstract Background Swarming motility allows microorganisms to move rapidly over surfaces. The Gram-positive bacterium Paenibacillus vortex exhibits advanced cooperative motility on agar plates resulting in intricate colonial patterns with geometries that are highly sensitive to the environment. The cellular mechanisms that underpin the complex multicellular organization of such a simple organism are not well understood. Results Swarming by P. vortex was studied by real-time light microscopy, by in situ scanning electron microscopy and by tracking the spread of antibiotic-resistant cells within antibiotic-sensitive colonies. When swarming, P. vortex was found to be peritrichously flagellated. Swarming by the curved cells of P. vortex occurred on an extremely wide range of media and agar concentrations (0.3 to 2.2% w/v. At high agar concentrations (> 1% w/v rotating colonies formed that could be detached from the main mass of cells by withdrawal of cells into the latter. On lower percentage agars, cells moved in an extended network composed of interconnected "snakes" with short-term collision avoidance and sensitivity to extracts from swarming cells. P. vortex formed single Petri dish-wide "supercolonies" with a colony-wide exchange of motile cells. Swarming cells were coupled by rapidly forming, reversible and non-rigid connections to form a loose raft, apparently connected via flagella. Inhibitors of swarming (p-Nitrophenylglycerol and Congo Red were identified. Mitomycin C was used to trigger filamentation without inhibiting growth or swarming; this facilitated dissection of the detail of swarming. Mitomycin C treatment resulted in malcoordinated swarming and abortive side branch formation and a strong tendency by a subpopulation of the cells to form minimal rotating aggregates of only a few cells. Conclusion P. vortex creates complex macroscopic colonies within which there is considerable reflux and movement and interaction of cells. Cell

  1. Kinetic trapping through coalescence and the formation of patterned Ag-Cu nanoparticles

    Science.gov (United States)

    Grammatikopoulos, Panagiotis; Kioseoglou, Joseph; Galea, Antony; Vernieres, Jerome; Benelmekki, Maria; Diaz, Rosa E.; Sowwan, Mukhles

    2016-05-01

    In recent years, due to its inherent flexibility, magnetron-sputtering has been widely used to synthesise bi-metallic nanoparticles (NPs) via subsequent inert-gas cooling and gas-phase condensation of the sputtered atomic vapour. Utilising two separate sputter targets allows for good control over composition. Simultaneously, it involves fast kinetics and non-equilibrium processes, which can trap the nascent NPs into metastable configurations. In this study, we observed such configurations in immiscible, bi-metallic Ag-Cu NPs by scanning transmission electron microscopy (S/TEM) and electron energy-loss spectroscopy (EELS), and noticed a marked difference in the shape of NPs belonging to Ag- and Cu-rich samples. We explained the formation of Janus or Ag@Cu core/shell metastable structures on the grounds of in-flight mixed NP coalescence. We utilised molecular dynamics (MD) and Monte Carlo (MC) computer simulations to demonstrate that such configurations cannot occur as a result of nanoalloy segregation. Instead, sintering at relatively low temperatures can give rise to metastable structures, which eventually can be stabilised by subsequent quenching. Furthermore, we compared the heteroepitaxial diffusivities along various surfaces of both Ag and Cu NPs, and emphasised the differences between the sintering mechanisms of Ag- and Cu-rich NP compositions: small Cu NPs deform as coherent objects on large Ag NPs, whereas small Ag NPs dissolve into large Cu NPs, with their atoms diffusing along specific directions. Taking advantage of this observation, we propose controlled NP coalescence as a method to engineer mixed NPs of a unique, patterned core@partial-shell structure, which we refer to as a ``glass-float'' (ukidama) structure.In recent years, due to its inherent flexibility, magnetron-sputtering has been widely used to synthesise bi-metallic nanoparticles (NPs) via subsequent inert-gas cooling and gas-phase condensation of the sputtered atomic vapour. Utilising two

  2. Developer molecular size dependence of pattern formation of polymer type electron beam resists with various molecular weights

    Science.gov (United States)

    Takayama, Tomohiro; Asada, Hironori; Kishimura, Yukiko; Ochiai, Shunsuke; Hoshino, Ryoichi; Kawata, Atsushi

    2016-05-01

    The sensitivity and the resolution are affected by not only the nature of the resist such as a chemical structure and a molecular weight but also the developing process such as a developer molecular size. Exposure characteristics of positive-tone polymer resists having various molecular weights (Mw's) ranging from 60 k to 500 k are investigated using different ester solvents as a developer. The line-and-space (L/S) patterns are exposed by the electron beam writing system with an acceleration voltage of 50 kV and the samples are developed by amyl acetate, hexyl acetate and heptyl acetate. The pattern shape becomes better and the surface of the resist also becomes smoother with increasing developer molecular size, though the exposure dose required for the formation of the L/S pattern increases. The dose margin of pattern formation is also wider in all the resists having the different molecular weights. The dissolution in the unexposed portions of the 60k-Mw resist for heptyl acetate is reduced significantly compared with those for amyl acetate and hexyl acetate. The improvement of the pattern shape and the increasing of dose margin are remarkable in the low molecular weight resist. The 3σ of line width roughness tends to be smaller in the higher molecular weight resist and with the larger molecular size developer. Exposure experiment of the 35 nm pitch pattern using the 500k-Mw resist developed at the room temperature is presented.

  3. Pigment pattern formation in the guppy, Poecilia reticulata, involves the Kita and Csf1ra receptor tyrosine kinases.

    Science.gov (United States)

    Kottler, Verena A; Fadeev, Andrey; Weigel, Detlef; Dreyer, Christine

    2013-07-01

    Males of the guppy (Poecilia reticulata) vary tremendously in their ornamental patterns, which are thought to have evolved in response to a complex interplay between natural and sexual selection. Although the selection pressures acting on the color patterns of the guppy have been extensively studied, little is known about the genes that control their ontogeny. Over 50 years ago, two autosomal color loci, blue and golden, were described, both of which play a decisive role in the formation of the guppy color pattern. Orange pigmentation is absent in the skin of guppies with a lesion in blue, suggesting a defect in xanthophore development. In golden mutants, the development of the melanophore pattern during embryogenesis and after birth is affected. Here, we show that blue and golden correspond to guppy orthologs of colony-stimulating factor 1 receptor a (csf1ra; previously called fms) and kita. Most excitingly, we found that both genes are required for the development of the black ornaments of guppy males, which in the case of csf1ra might be mediated by xanthophore-melanophore interactions. Furthermore, we provide evidence that two temporally and genetically distinct melanophore populations contribute to the adult camouflage pattern expressed in both sexes: one early appearing and kita-dependent and the other late-developing and kita-independent. The identification of csf1ra and kita mutants provides the first molecular insights into pigment pattern formation in this important model species for ecological and evolutionary genetics.

  4. Cross-correlation patterns in social opinion formation with sequential data

    Science.gov (United States)

    Chakrabarti, Anindya S.

    2016-11-01

    Recent research on large-scale internet data suggests existence of patterns in the collective behavior of billions of people even though each of them may pursue own activities. In this paper, we interpret online rating activity as a process of forming social opinion about individual items, where people sequentially choose a rating based on the current information set comprising all previous ratings and own preferences. We construct an opinion index from the sequence of ratings and we show that (1) movie-specific opinion converges much slower than an independent and identically distributed (i.i.d.) sequence of ratings, (2) rating sequence for individual movies shows lesser variation compared to an i.i.d. sequence of ratings, (3) the probability density function of the asymptotic opinions has more spread than that defined over opinion arising from i.i.d. sequence of ratings, (4) opinion sequences across movies are correlated with significantly higher and lower correlation compared to opinion constructed from i.i.d. sequence of ratings, creating a bimodal cross-correlation structure. By decomposing the temporal correlation structures from panel data of movie ratings, we show that the social effects are very prominent whereas group effects cannot be differentiated from those of surrogate data and individual effects are quite small. The former explains a large part of extreme positive or negative correlations between sequences of opinions. In general, this method can be applied to any rating data to extract social or group-specific effects in correlation structures. We conclude that in this particular case, social effects are important in opinion formation process.

  5. A Review of Aspects of Oxidative Hair Dye Chemistry with Special Reference to N-Nitrosamine Formation

    OpenAIRE

    Jamie Hawkes; John Mama; David Lewis

    2013-01-01

    This review discusses a new aspect to the safety profile of oxidative hair dyes using data already in the public domain. These dyes contain secondary amines that are capable of forming potentially carcinogenic nitrosamine derivatives when exposed to atmospheric pollution. Numerous scientific articles confirm the existence of secondary amines in hair dyes (and their intermediates), the possibility of nitrosation by atmospheric NOx of secondary amines to give the N-nitrosamines, and the signifi...

  6. Pattern formation in a spatial plant-wrack model with tide effect on the wrack

    OpenAIRE

    Sun, Gui-Quan; Li, Li; Jin, Zhen; Li, Bai-Lian

    2009-01-01

    Spatial patterns are a subfield of spatial ecology, and these patterns modify the temporal dynamics and stability properties of population densities at a range of spatial scales. Localized ecological interactions can generate striking large-scale spatial patterns in ecosystems through spatial self-organization. Possible mechanisms include oscillating consumer–resource interactions, localized disturbance–recovery processes, and scale-dependent feedback. However, in this paper, our main aim is ...

  7. Multifunctional surfaces with biomimetic nanofibres and drug-eluting micro-patterns for infection control and bone tissue formation

    Directory of Open Access Journals (Sweden)

    XN Chen

    2012-09-01

    Full Text Available For long-term orthopaedic implants, the creation of a surface that is repulsive to bacteria while adhesive to tissue cells represents a promising strategy to control infection. To obtain such multifunctional surfaces, two possible approaches were explored to incorporate a model antibiotic, rifampicin (Rf, into the osteogenic polycaprolactone (PCL/chitosan (CHS biomimetic nanofibre meshes by (1 blending Rf into the electrospinning solutions and then electrospinning into nanofibres (i.e., Rf-incorporating fibres, or (2 depositing Rf-containing poly(D,L-lactic-co-glycolic acid (PLGA micro-patterns onto the PCL/chitosan nanofibre meshes via ink-jet printing (i.e., Rf-eluting micro-pattern/fibre. Rapid release of Rf from both meshes was measured even though a relatively slower release rate was obtained from the Rf-eluting micro-pattern ones. Antibacterial assay with Staphylococcus epidermidis showed that both mesh surfaces could effectively kill bacteria and prevent biofilm formation. However, only Rf-eluting micro-pattern meshes favoured the attachment, spreading and metabolic activity of preosteoblasts in the cell culture study. Furthermore, the Rf-eluting micro-pattern meshes could better support the osteogenic differentiation of preosteoblasts by up-regulating the gene expression of bone markers (type I collagen and alkaline phosphatase. Clearly, compared to Rf-incorporating nanofibre meshes, Rf-eluting micro-patterns could effectively prevent biofilm formation without sacrificing the osteogenic properties of PCL/chitosan nanofibre surfaces. This finding provides an innovative avenue to design multifunctional surfaces for enhancing bone tissue formation while controlling infection.

  8. Pattern formation in urbanism: a critical reflection on urban morphology, planning and design

    NARCIS (Netherlands)

    Çaliskan, O.

    2013-01-01

    This thesis is all about urban patterns, what we see through the windows of the plane with an admiration of their relief-like scenery covering the land surface. In a sense, the spatial pattern within our cities is the biggest collectively produced artifact of human beings. It is both the originator

  9. Pattern formation in Rayleigh-Bénard convection:Numerical simulation with a coupled-map-lattice model

    Institute of Scientific and Technical Information of China (English)

    WANG Liang; ZHANG Guanghua; FU Song

    2005-01-01

    The various patterns formed in Rayleigh-Bé- nard convection under different conditions are numerically simulated with a coupled-map-lattice model. In the case of a lower aspect ratio (L/d=5), the simulations vividly depicted the main features of the transition process from a laminar state to a soft turbulence and then to a hard turbulence. In this case, the cellular structure in a horizontal section is also reproduced. In the case of a larger aspect ratio (L/d=30), the simulations successfully reproduced the spiral-defect chaos and target chaos in the initial stage of the pattern evolution which were recently found in experiments. In this case, for a fluid of Pr=1, it is verified in simulations that both the ideal straight rolls and spiral-defect chaos are stable attractors in the same parameter regime, and that the initial condition is a decisive factor for which one of the two is formed. In the same case, for a fluid of Pr=4, the target patterns are dominant instead of the spirals, the sizes and distributions of the target are also notably dependent on the initial condition.

  10. Concurrent formation of furan-2,5-and furan-2,4-dicarboxylic acid: unexpected aspects of the Henkel reaction

    NARCIS (Netherlands)

    Thiyagarajan, S.; Pukin, A.; Haveren, van J.; Lutz, M.; Es, van D.S.

    2013-01-01

    The concurrent formation of furan-2,5- and furan-2,4-dicarboxylic acid under solvent free conditions via a disproportionation reaction is described. By reacting potassium-2-furoate at 260 degrees C in the presence of 22 mol% of (Lewis acidic) catalysts like CdI2 or ZnCl2, potassium-2-furoate is disp

  11. Formation of Polychlorinated Biphenyls on Secondary Copper Production Fly Ash: Mechanistic Aspects and Correlation to Other Persistent Organic Pollutants

    Science.gov (United States)

    Jiang, Xiaoxu; Liu, Guorui; Wang, Mei; Zheng, Minghui

    2015-09-01

    Emission of unintentionally formed polychlorinated biphenyls (PCBs) from industrial thermal processes is a global issue. Because the production and use of technical PCB mixtures has been banned, industrial thermal processes have become increasingly important sources of PCBs. Among these processes, secondary copper smelting is an important PCB source in China. In the present study, the potential for fly ash-mediated formation of PCBs in the secondary copper industry, and the mechanisms involved, were studied in laboratory thermochemical experiments. The total PCB concentrations were 37-70 times higher than the initial concentrations. Thermochemical reactions on the fly ash amplified the potential toxic equivalents of PCBs. The formation of PCBs over time and the effect of temperature were investigated. Based on analyses of PCB homologue profiles with different reaction conditions, a chlorination mechanism was proposed for forming PCBs in addition to a de novo synthesis mechanism. The chlorination pathway was supported by close correlations between each pair of adjacent homologue groups. Formation of PCBs and multiple persistent organic pollutants, including polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and polychlorinated naphthalenes, occurred during the tests, indicating that these compounds may share similar formation mechanisms.

  12. Thrombus formation patterns in the HeartMate II ventricular assist device: clinical observations can be predicted by numerical simulations.

    Science.gov (United States)

    Chiu, Wei-Che; Slepian, Marvin J; Bluestein, Danny

    2014-01-01

    Postimplant device thrombosis remains a life-threatening complication and limitation of continuous-flow ventricular assist devices (VADs). Using advanced computational fluid dynamic (CFD) simulations, we successfully depicted various flow patterns, recirculation zones, and stagnant platelet trajectories which promote thrombus formation and observed that they matched actual thrombus formation patterns observed in Thoratec HeartMate II VADs explanted from patients with pump thrombosis. Previously, these small eddies could not be captured by either digital particle image velocimetry or CFD due to insufficient resolution. Our study successfully demonstrated the potential capability of advanced CFD to be adopted for device optimization, leading to enhanced safety and efficacy of VADs for long-term destination therapy. PMID:24399065

  13. Physical mechanisms of self-organization and formation of current patterns in gas discharges of the Townsend and glow types

    Energy Technology Data Exchange (ETDEWEB)

    Raizer, Yu. P.; Mokrov, M. S. [Institute for Problems in Mechanics, Russian Academy of Sciences, Moscow 119526 (Russian Federation)

    2013-10-15

    The paper discusses current filamentation and formation of current structures (in particular, hexagonal current patterns) in discharges of the Townsend and glow types. The aim of the paper, which is in part a review, is to reveal basic reasons for formation of current patterns in different cases, namely, in dielectric barrier discharge, discharge with semiconductor cathode, and micro-discharge between metallic electrodes. Pursuing this goal, we give a very brief review of observations and discuss only those theoretical, computational, and experimental papers that shed light on the physical mechanisms involved. The mechanisms are under weak currents—the thermal expansion of the gas as a result of Joule heating; under enhanced currents—the electric field and ionization rate redistribution induced by space charge. Both mechanisms lead to instability of the homogeneous discharges. In addition, we present new results of numerical simulations of observed short-living current filaments which are chaotic in space and time.

  14. Physical mechanisms of self-organization and formation of current patterns in gas discharges of the Townsend and glow types

    International Nuclear Information System (INIS)

    The paper discusses current filamentation and formation of current structures (in particular, hexagonal current patterns) in discharges of the Townsend and glow types. The aim of the paper, which is in part a review, is to reveal basic reasons for formation of current patterns in different cases, namely, in dielectric barrier discharge, discharge with semiconductor cathode, and micro-discharge between metallic electrodes. Pursuing this goal, we give a very brief review of observations and discuss only those theoretical, computational, and experimental papers that shed light on the physical mechanisms involved. The mechanisms are under weak currents—the thermal expansion of the gas as a result of Joule heating; under enhanced currents—the electric field and ionization rate redistribution induced by space charge. Both mechanisms lead to instability of the homogeneous discharges. In addition, we present new results of numerical simulations of observed short-living current filaments which are chaotic in space and time

  15. A Review of Aspects of Oxidative Hair Dye Chemistry with Special Reference to N-Nitrosamine Formation

    Directory of Open Access Journals (Sweden)

    Jamie Hawkes

    2013-02-01

    Full Text Available This review discusses a new aspect to the safety profile of oxidative hair dyes using data already in the public domain. These dyes contain secondary amines that are capable of forming potentially carcinogenic nitrosamine derivatives when exposed to atmospheric pollution. Numerous scientific articles confirm the existence of secondary amines in hair dyes (and their intermediates, the possibility of nitrosation by atmospheric NOx of secondary amines to give the N-nitrosamines, and the significant safety risks on N-nitrosamines. It is believed that such nitrosamine derivatives should be investigated more fully in the interests of consumer safety.

  16. Formation of PCDF, PCDD, PCB, and PCN in de novo synthesis from PAH: mechanistic aspects and correlation to fluidized bed incinerators.

    Science.gov (United States)

    Weber, R; Lino, F; Imagawa, T; Takeuchi, M; Sakurai, T; Sadakata, M

    2001-09-01

    The difference of polychlorinated dibenzofurans (PCDF) isomer patterns between stoker type incinerators and some fluidized bed incinerators (FBI) is a key to understand the formation mechanisms in both types of incinerators. The total yield and the isomer patterns of PCDF, polychlorinated biphenyls (PCB), polychlorinated naphthalenes (PCN), and polychlorinated benzenes (PCBz) formed via de novo synthesis from polycyclic aromatic hydrocarbons (PAH) indicate that chlorinated aromatics in the FBI are formed as a result of PAH breakdown. The detailed analysis of the isomer patterns of PCDF, PCB and PCN gives a first insight into the transformation mechanism of the PAHs and the sequence of degradation, chlorination and oxygen insertion. The major chlorination takes part at the position of the C-C cleavage during degradation of the PAHs. Further chlorination of the hydrogen position of the former PAH takes part preferably in ortho-position to this chlorination or is directed by incorporated oxygen. A perylene structure in soot is proposed as basis for the observed PCDF pattern in the FBI. Polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated phenols (PxCP) were formed in lower concentrations from the de novo experiments indicating an additional formation pathway for these compounds in the FBI.

  17. Genetic Analysis of Two Female-Sterile Loci Affecting Eggshell Integrity and Embryonic Pattern Formation in Drosophila Melanogaster

    OpenAIRE

    Degelmann, A.; Hardy, P. A.; Mahowald, A. P.

    1990-01-01

    We have analyzed female-sterile mutations at the X-linked loci fs(1)Nas and fs(1)ph which show allele-specific effects on egg shell structure and embryonic pattern formation. The majority of mutant alleles at both loci lead to a collapsed egg phenotype. The maternal effect lethal phenotype is characterized by cuticle defects resembling those found in three autosomal mutants of the terminal class. We have analyzed the complementation behavior of various heteroallelic combinations at both loci ...

  18. Effect of clomazone herbicide on biochemical and histological aspects of silver catfish (Rhamdia quelen) and recovery pattern.

    Science.gov (United States)

    Crestani, Márcia; Menezes, Charlene; Glusczak, Lissandra; dos Santos Miron, Denise; Spanevello, Roselia; Silveira, Aron; Gonçalves, Fábio Ferreira; Zanella, Renato; Loro, Vânia Lúcia

    2007-05-01

    The effects of the herbicide, clomazone, on acetylcholinesterase (AChE), catalase and TBARS formation in teleost fish (Rhamdia quelen) were studied. The fish were exposed to 0.5 or 1.0 mg L(-1) of clomazone for 12, 24, 48, 96 and 192 h. After 192 h of exposure period, fish were transferred to clean water and kept in the same for 192 h to study the recovery response. Same parameters as that of exposure period were assayed after 96 and 192 h of recovery period. Specific AChE activity was reduced in the brain and muscle after treatments, reaching a maximum inhibition of 47% in the brain and 45% in the muscle after 12h of exposure. Fish exposed to clomazone increased TBARS production in the liver for all exposure periods. The brain presented elevated TBARS levels after 12, 24 and 48 h, but after 96 and 192 h, these levels decreased. The decrease of TBARS levels persisted in brain tissue after 96 h of recovery and returned to the control value after 192 h in clean water. Catalase activity was reduced for all periods of exposure. Histological analysis showed vacuolation in the liver after herbicide exposure. Some of the alterations observed were completely restored after recovery period.

  19. Self-assembly structure formation on patterned InP surfaces

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Self-assembly of polystyrene spheres guided by patterned n-type InP substrates has been investigated. InP surfaces were patterned using a variety of methods including wet chemical etching,sputter coating,thermal evaporation,and photo lithography. The self-assembly of polystyrene spheres depended on the appearance of patterns and was affected by the deposition techniques (sputter coating and thermal evaporation) of Au micro-squares. SEM and AFM were used to characterize the surface morphologies.

  20. Evolution of spiral wave and pattern formation in a vortical polarized electric field

    Institute of Scientific and Technical Information of China (English)

    Ma Jun; Yi Ming; Li Bing-Wei; Li Yan-Long

    2008-01-01

    In this paper, the evolution of the pattern transition induced by the vortical electric field (VEF) is investigated. Firstly, a scheme is suggested to generate the VEF by changing the spatial magnetic field. Secondly, the VEF is imposed on the whole medium, and the evolutions of the spiral wave and the spatiotemporal chaos are investigated by using the numerical simulation. The result confirms that the drift and the breakup of the spiral wave and the new net-like pattern are observed when different polarized fields are imposed on the whole medium respectively. Finally, the pattern transition induced by the polarized field is discussed theoretically.

  1. Biosilica-glass formation using enzymes from sponges [silicatein]: Basic aspects and application in biomedicine [bone reconstitution material and osteoporosis

    Science.gov (United States)

    Wang, Shun-Feng; Wang, Xiao-Hong; Gan, Lu; Wiens, Matthias; Schröder, Heinz C.; Müller, Werner E. G.

    2011-09-01

    In the last 15 years biomineralization, in particular biosilicification (i.e., the formation of biogenic silica, SiO2), has become an exciting source of inspiration for the development of novel bionic approaches, following "Nature as model". Among the silica forming organisms there are the sponges that have the unique property to catalyze their silica skeletons by a specific enzyme termed silicatein. In the present review we summarize the present state of knowledge on silicatein-mediated "biosilica" formation in marine sponges, the involvement of further molecules in silica metabolism and their potential application in biomedicine. Recent advancements in the production of bone replacement material and in the potential use as a component in the treatment of osteoporosis are highlighted.

  2. Aspects of the microvertebrate fauna of the Early Cretaceous (Barremian) Wessex Formation of the Isle of Wight, southern England

    OpenAIRE

    Sweetman, Steve

    2007-01-01

    Until this study, the microvertebrate fauna of the Early Cretaceous (Barremian) Wessex Formation of the Isle of Wight, southern England,was virtually unknown. A comprehensive survey of potentially productive horizons was undertaken using bulk screening techniques and this yielded an unexpectedly diverse microvertebrate fauna together with fragmentary but significant remains of hitherto unknown elements of the associated macro-fauna. At least forty one previously unrecorded tetrapod taxa have ...

  3. Formation of Polychlorinated Biphenyls on Secondary Copper Production Fly Ash: Mechanistic Aspects and Correlation to Other Persistent Organic Pollutants

    OpenAIRE

    Xiaoxu Jiang; Guorui Liu; Mei Wang; Minghui Zheng

    2015-01-01

    Emission of unintentionally formed polychlorinated biphenyls (PCBs) from industrial thermal processes is a global issue. Because the production and use of technical PCB mixtures has been banned, industrial thermal processes have become increasingly important sources of PCBs. Among these processes, secondary copper smelting is an important PCB source in China. In the present study, the potential for fly ash-mediated formation of PCBs in the secondary copper industry, and the mechanisms involve...

  4. Pattern formation in a cell based auxin transport model with numerical bifurcation analysis

    CERN Document Server

    Draelants, Delphine; Beemster, Gerrit T S; Vanroose, Wim

    2012-01-01

    Transport models of growth hormones can be used to reproduce the hormone accumulations that occur in plant organs. Mostly, these accumulation patterns are calculated using time step methods, even though only the resulting steady state patterns of the model are of interest. We examine the steady state solutions of the hormone transport model of Smith et al (2006) for a one-dimensional row of plant cells. We search for the steady state solutions as a function of three of the model parameters by using numerical continuation methods and bifurcation analysis. These methods are more adequate for solving steady state problems than time step methods. We discuss a trivial solution where the concentrations of hormones are equal in all cells and examine its stability region. We identify two generic bifurcation scenarios through which the trivial solution loses its stability. The trivial solution becomes either a steady state pattern with regular spaced peaks or a pattern where the concentration is periodic in time.

  5. Swarming and complex pattern formation in Paenibacillus vortex studied by imaging and tracking cells

    NARCIS (Netherlands)

    Ingham, C.J.; Jacob, Ben E.

    2008-01-01

    Background: Swarming motility allows microorganisms to move rapidly over surfaces. The Grampositive bacterium Paenibacillus vortex exhibits advanced cooperative motility on agar plates resulting in intricate colonial patterns with geometries that are highly sensitive to the environment. The cellular

  6. Measurements of pattern formation in a confocal optical parametrical oscillator with applications in quantum optics

    DEFF Research Database (Denmark)

    Lassen, Mikael Østergaard; Buchhave, Preben

    We describe simultaneous measurements of signal/idler near field and far field patterns of a 2nd order nonlinear multi-mode parametric downconverter. We also describe the use of auto- and cross correlation techniques to obtain statistical data....

  7. Kolmogorov complexity of epithelial pattern formation: the role of regulatory network configuration.

    Science.gov (United States)

    Flann, Nicholas S; Mohamadlou, Hamid; Podgorski, Gregory J

    2013-05-01

    The tissues of multicellular organisms are made of differentiated cells arranged in organized patterns. This organization emerges during development from the coupling of dynamic intra- and intercellular regulatory networks. This work applies the methods of information theory to understand how regulatory network structure both within and between cells relates to the complexity of spatial patterns that emerge as a consequence of network operation. A computational study was performed in which undifferentiated cells were arranged in a two dimensional lattice, with gene expression in each cell regulated by identical intracellular randomly generated Boolean networks. Cell-cell contact signalling between embryonic cells is modeled as coupling among intracellular networks so that gene expression in one cell can influence the expression of genes in adjacent cells. In this system, the initially identical cells differentiate and form patterns of different cell types. The complexity of network structure, temporal dynamics and spatial organization is quantified through the Kolmogorov-based measures of normalized compression distance and set complexity. Results over sets of random networks that operate in the ordered, critical and chaotic domains demonstrate that: (1) ordered and critical networks tend to create the most information-rich patterns; (2) signalling configurations in which cell-to-cell communication is non-directional mostly produce simple patterns irrespective of the internal network domain; and (3) directional signalling configurations, similar to those that function in planar cell polarity, produce the most complex patterns, but only when the intracellular networks function in non-chaotic domains.

  8. Mechanistic Aspects of Monomer,Polymer Formation,and Synthesis of PQ-Alt-Dialkyl-fluorene Conjugated Copolymer

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Suzuki coupling reaction is widely used in the construction of conjugated polymers; however, there is still no report describing the mechanism and coupling of 9,10-phenanthrenequinone(PQ) building blocks via Suzuki reaction because PQ is sensitive to bases and light. Herein is reported the efficient Suzuki coupling of PQ with 9,10-dialkylfluorene with Na2CO3 as basic species and high molecular weight PQ-Alt-Dialkyl-Fluorene conjugated copolymer obtained in an yield of 42%. Based on the characterization data and well-accepted literature, we proposed a step-by-step mechanistic explanation for the formation of the PQ containing alternating conjugated copolymer.

  9. The definition of psychological aspects in the formation of student-centered motivation of students for classes in physical education

    Directory of Open Access Journals (Sweden)

    Gruzhevsky V.A.

    2013-10-01

    Full Text Available An analysis of the publications, which demonstrates the importance of the emotional state in the formation of motivation as a psychological phenomenon. Shows the impact of physical education on the state of mental and emotional stress. Presented scientific analysis of psycho-emotional states in the 3rd year students with the region of residence and ethnicity. The study used survey results found that the circumstances are displayed on the psycho-emotional state of students. In their view, were: irritability, lack of confidence, fatigue, concern, guilt, etc. These conditions are more common in women of ethnic groups and from rural areas. It should be noted that the girls are very carefully described their emotional state and chose the answer in the questionnaire (sometimes, this response was dominant. Young men in many positions were more restrained. It is established that the formation of student-centered motivation of students to physical education should be adjusted in their emotional state. In this strategy the learning process of physical education is built on individual, ethnic differences.

  10. ORGANIZATIONAL AND METHODICAL ASPECTS OF FINANCIAL RESULTS FORMATION IN THE SYSTEM OF MANAGEMENT ACCOUNTING OF AGRICULTURAL ORGANIZATIONS

    Directory of Open Access Journals (Sweden)

    Khromova I. N.

    2015-05-01

    Full Text Available The article deals with the essence of the financial results and the need for their operational accounting in economic activities by AIC agents. The authors studied the order of profit formation in agricultural organizations′ management accounting based on industry characteristics, industrial activity specificity, operating cycle duration and management personnel functions. The study proved the need for financial responsibility centers with a view to the most effective organization of business entity management: income centers, cost centers, profit centers. Business entities profit is characterized by its forms and types diversity. As a result of research the authors determined the main classification features according to which this category is considered with better understanding of its economic essence. The accounting financial results will be more objective in the case they timely and present the necessary information for analysis and making management solutions. The authors found that the restriction of income and expenses included in the profit from ordinary activities, determines the need of the development of the alternative accounting within the system of management accounting. The each participant of accounting and analysis provision of financial results formation has particular conditions which cannot be used in traditional accounting or for modern economics analysis. As a result, the authors have carried out an assessment of financial results of accounting with use of analytical procedures

  11. The Self-Made Puzzle: Integrating Self-Assembly and Pattern Formation Under Non-Random Genetic Regulation

    Science.gov (United States)

    Doursat, René

    On the one hand, research in self-assembling systems, whether natural or artificial, has traditionally focused on pre-existing components endowed with fixed shapes. Biological development, by contrast, dynamically creates new cells that acquire selective adhesion properties through differentiation induced by their neighborhood. On the other hand, pattern formation phenomena are generally construed as orderly states of activity on top of a continuous 2-D or 3-D substrate. Yet, again, the spontaneous patterning of an organism into domains of gene expression arises within a multicellular medium in perpetual expansion and reshaping. Finally, both phenomena are often thought in terms of stochastic events, whether mixed components that randomly collide in self-assembly, or spots and stripes that occur unpredictably from instabilities in pattern formation. Here too, these notions need significant revision if they are to be extended and applied to embryogenesis. Cells are not randomly mixed but pre-positioned where cell division occurs. Genetic identity domains are not randomly distributed but highly regulated in number and position. In this work, I present a computational model of program-mable and reproducible artificial morphogenesis that integrates self-assembly and pattern formation under the control of a nonrandom gene regulatory network. The specialized properties of cells (division, adhesion, migration) are determined by the gene expression domains to which they belong, while at the same time these domains further expand and segment into subdomains due to the self-assembly of specialized cells. Through this model, I also promote a new discipline, embryomorphic engineering to solve the paradox of "meta-designing" decentralized, autonomous systems.

  12. Pattern formation in directional solidification under shear flow. II. Morphologies and their characterization.

    Science.gov (United States)

    Marietti, Y; Debierre, J M; Bock, T M; Kassner, K

    2001-06-01

    In the preceding paper, we have established an interface equation for directional solidification under the influence of a shear flow parallel to the interface. This equation is asymptotically valid near the absolute stability limit. The flow, described by a nonlocal term, induces a lateral drift of the whole pattern due to its symmetry-breaking properties. We find that at not-too-large flow strengths, the transcritical nature of the transition to hexagonal patterns shows up via a hexagonal modulation of the stripe pattern even when the linear instability threshold of the flowless case has not yet been attained. When the flow term is large, the linear description of the drift velocity breaks down and transitions to flow-dominated morphologies take place. The competition between flow-induced and diffusion-induced patterns (controlled by the temperature gradient) leads to new phenomena such as the transition to a different lattice structure in an array of hexagonal cells. Several methods to characterize the morphologies and their transitions are investigated and compared. In particular, we consider two different ways of defining topological defects useful in the description of patterns and we discuss how they are related to each other.

  13. Distinguishing Pattern Formation Phenotypes: Applying Minkowski Functionals to Cell Biology Systems

    Science.gov (United States)

    Rericha, Erin; Guven, Can; Parent, Carole; Losert, Wolfgang

    2011-03-01

    Spatial Clustering of proteins within cells or cells themselves frequently occur in cell biology systems. However quantifying the underlying order and determining the regulators of these cluster patterns have proved difficult due to the inherent high noise levels in the systems. For instance the patterns formed by wild type and cyclic-AMP regulatory mutant Dictyostelium cells are visually distinctive, yet the large error bars in measurements of the fractal number, area, Euler number, eccentricity, and wavelength making it difficult to quantitatively distinguish between the patterns. We apply a spatial analysis technique based on Minkowski functionals and develop metrics which clearly separate wild type and mutant cell lines into distinct categories. Having such a metric facilitated the development of a computational model for cellular aggregation and its regulators. Supported by NIH-NGHS Nanotechnology (R01GM085574) and the Burroughs Wellcome Fund.

  14. Linking Pattern Formation and Alternative Stable States: Ecohydrologic Thresholds and Critical Transitions in the Everglades Peatlands

    Science.gov (United States)

    Heffernan, J. B.; Ross, M. S.; Sah, J. P.; Isherwood, E.; Cohen, M. J.

    2015-12-01

    Spatial patterning occurs in a variety of ecosystems, and is important for the functional properties of landscapes; for testing spatial models of ecological processes; and as an indicator of landscape condition and resilience. Theory suggests that regular patterns arise from coupled local- and landscape-scale feedbacks that can also create multiple stable landscape states. In the Florida Everglades, hydrologic modification has degraded much of the historically-extensive ridge-slough landscape, a patterned peatland mosaic with distinct, flow-parallel patches. However, in the Everglades and in general, the hypothesis that patterned landscapes have homogeneous alternative states has little direct empirical support. Here we use microtopographic and vegetative heterogeneity, and their relation to hydrologic conditions, to infer the existence of multiple landscape equilibria and identify the hydrologic thresholds for critical transitions between these states. Dual relationships between elevation variance and water depth, and bi-modal distributions of both elevation variance and plant community distinctness, are consistent with generic predictions of multiple states, and covariation between these measures suggests that microtopography is the leading indicator of landscape degradation. Furthermore, a simple ecohydrologic multiple-state model correctly predicts the hydrologic thresholds for persistence of distinct ridges and sloughs. Predicted ridge-slough elevation differences and their relation to water depth are much greater than observed in the contemporary Everglades, but correspond closely with historical observations of pre-drainage conditions. These multiple lines of evidence represent the broadest and most direct support for the link between regular spatial pattern and landscape-scale alternative states in any ecosystem, and suggest that other patterned landscapes could undergo sudden collapse in response to changing environmental conditions. Hydrologic thresholds

  15. First union formation in Estonia, Latvia and Lithuania: patterns across countries and gender

    Directory of Open Access Journals (Sweden)

    Luule Sakkeus

    2007-11-01

    Full Text Available This article examines the transformation of first union formation in the Baltic countries between the late 1960s and early 1990s, in the context of societal and family-level gender relations. The analyses employ microdata from the European Family and Fertility Surveys program. Our results on the trends indicate that in Estonia and Latvia the shift from direct marriage to cohabitation started well before the fall of socialist regime. Event-history models provide support for a hypothesised association between union formation and gender system, with Lithuania showing more traditional features in both respect, plausibly embedded in long-standing cultural differences between the countries.

  16. Hierarchical pattern formation in thin polymer films using an electric field and vapor sorption

    NARCIS (Netherlands)

    Harkema, S; Steiner, U

    2005-01-01

    The experimental observation of electric-field-induced instabilities of polymer films exposed to toluene vapors is reported. When using a laterally structured electrode, the pattern that forms in the polymer film is governed by the interplay of the intrinsic film instability and the periodicity of t

  17. Influence of cell-to-cell variability on spatial pattern formation

    NARCIS (Netherlands)

    Greese, B.; Wester, K.; Bensch, R.; Ronneberger, O.; Timmer, J.; Huulskamp, M.; Fleck, C.

    2012-01-01

    Many spatial patterns in biology arise through differentiation of selected cells within a tissue, which is regulated by a genetic network. This is specified by its structure, parameterisation and the noise on its components and reactions. The latter, in particular, is not well examined because it is

  18. Formation of ring calcium oxalate patterns induced by domains in DPPC Langmuir-Blodgett films

    Institute of Scientific and Technical Information of China (English)

    Yi Ming Liu; Sui Ping Deng; Hui Zheng; Jian Ming Ouyang

    2007-01-01

    The ring patterns of calcium oxalate crystals were induced by domains in Langmuir-Blodgett (LB) films of dipalmitoylpho-sphatidylcholine (DPPC). The result was explained by the defects at the ring boundaries of liquid condensed (LC) and liquid expanded (LE) phases of LB film. These boundaries could provide less free energy and much more nucleating sites for COM crystals.

  19. Pattern Formation by Staphylococcus epidermidis via Droplet Evaporation on Micropillars Arrays at a Surface

    NARCIS (Netherlands)

    Susarrey-Arce, A.; Gomez Marin, A.; Massey, A.; Oknianska, A.; Diaz-Fernandez, Y.; Hernandez Sanchez, Jose Federico; Griffiths, E.; Gardeniers, J.G.E.; Snoeijer, J.H.; Lohse, D.; Raval, R.

    2016-01-01

    We evaluate the effect of epoxy surface structuring on the evaporation of water droplets containing Staphylococcus epidermidis (S. epidermidis). During evaporation, droplets with S. epidermidis cells yield to complex wetting patterns such as the zipping-wetting1−3 and the coffee-stain effects. Depen

  20. Substructure formation during pattern transposition from substrate into polymer blend film

    NARCIS (Netherlands)

    Cyganik, P; Budkowski, A; Steiner, U; Rysz, J; Bernasik, A; Walheim, S; Postawa, Z; Raczkowska, J

    2003-01-01

    A chemical pattern on a substrate is transposed into thin films of a ternary polymer blend during spin-casting from a common solvent. One of the blend components intercalates at interfaces between the other two phases to reduce their interfacial energy. As a result, an extensive substructure is form

  1. Pattern formation for a model of plankton allelopathy with cross-diffusion

    DEFF Research Database (Denmark)

    Tian, C.R.; Zhang, Lai; Lin, Z.G.

    2011-01-01

    In this paper, we develop a theoretical framework for investigating spatial patterns on plankton allelopathy with cross-diffusion. We show that under some conditions the cross-diffusion is able to induce the Turing instability, which is further confirmed by the numerical simulations. Moreover...

  2. The splicing factor SRSF1 modulates pattern formation by inhibiting transcription of tissue specific genes during embryogenesis.

    Science.gov (United States)

    Lee, Soo-Ho; Lee, Hyun-Kyung; Kim, Chowon; Kim, Yoo-Kyung; Ismail, Tayaba; Jeong, Youngeun; Park, Kyeongyeon; Park, Jeen-Woo; Kwon, Oh-Shin; Kang, Beom Sik; Lee, Dong-Seok; Park, Mae-Ja; Park, Do-Sim; Lee, Hyun-Shik

    2016-09-01

    Alternative splicing is a major mechanism regulating pattern of gene expression through the production of multiple mRNAs from a single gene transcript. Any misregulation can cause various human diseases and also have severe effects on embryogenesis. SRSF1 is one of the critical factors regulating alternative splicing at many stages of vertebrate development and any disturbance in SRSF1 leads to serious consequences. In current study, we investigated the effects of loss of the SRSF1 gene using antisense morpholino oligonucleotides (MO) in Xenopus embryogenesis. It is evident from the results of RT-PCR and whole-mount in situ hybridization that SRSF1 is a maternal gene having strong expression in head, eyes and central nervous system. Moreover, SRSF1 morphants exhibited malformed phenotypes, including miscoiled guts, heart and cartilage formation, edema in the head and heart, and small eyes. Especially, in SRSF1 morphants, bone cartilage formation was reduced in the brain and Nkx-2.5 expression was dramatically reduced in the heart of SRSF1 morphants. In addition, a dramatic reduction in functional chordin RNA in SRSF1 morphants was observed suggesting that chordin is one of the targets of SRSF1. Thus, we concluded that SRSF1 is an essential factor for pattern formation including heart, cartilage and germ layers through the regulation of specific genes. PMID:27396620

  3. Patterns and sources of variation in pollen deposition and pollen tube formation in flowers of the endemic monoecious shrub Cnidoscolus souzae (Euphorbiaceae).

    Science.gov (United States)

    Arceo-Gómez, G; Alonso, C; Abdala-Roberts, L; Parra-Tabla, V

    2016-07-01

    Pollen deposition and pollen tube formation are key components of angiosperm reproduction but intraspecific variation in these has rarely been quantified. Documenting and partitioning (populations, plants and flowers) natural variation in these two aspects of plant reproduction can help uncover spatial mosaics of reproductive success and underlying causes. In this study, we assess variation in pollen deposition and pollen tube formation for the endemic monoecious shrub Cnidoscolus souzae throughout its distribution range in Mexico, and determine how this variation is structured among populations, plants and flowers. We also infer the relative importance of pollen quantity and quality in determining pollination success in this species. While we found no evidence suggesting that pollen receipt limits C. souzae reproduction across 19 populations, we did find extensive variation in pollen load size and pollen tube number per flower. Total variation in pollen receipt and pollen tube number was mostly explained by intra-individual and among-population variance. Furthermore, pollen load size had a stronger effect on the number of pollen tubes at the base of the style than pollen germination rate, suggesting that pollen quantity may be more important than quality for pollen tube success in C. souzae. Our results suggest that both small within-plant flower differences and broad-scale differences in community attributes can play an important role in determining pollination success. We emphasise the need to evaluate patterns and sources of variation in pollen deposition and pollen tube formation as a first step in understanding the causes of variation in pollination success over broad spatial scales. PMID:26916543

  4. The influence of projectile ion induced chemistry on surface pattern formation

    Science.gov (United States)

    Karmakar, Prasanta; Satpati, Biswarup

    2016-07-01

    We report the critical role of projectile induced chemical inhomogeneity on surface nanostructure formation. Experimental inconsistency is common for low energy ion beam induced nanostructure formation in the presence of uncontrolled and complex contamination. To explore the precise role of contamination on such structure formation during low energy ion bombardment, a simple and clean experimental study is performed by selecting mono-element semiconductors as the target and chemically inert or reactive ion beams as the projectile as well as the source of controlled contamination. It is shown by Atomic Force Microscopy, Cross-sectional Transmission Electron Microscopy, and Electron Energy Loss Spectroscopy measurements that bombardment of nitrogen-like reactive ions on Silicon and Germanium surfaces forms a chemical compound at impact zones. Continuous bombardment of the same ions generates surface instability due to unequal sputtering and non-uniform re-arrangement of the elemental atom and compound. This instability leads to ripple formation during ion bombardment. For Argon-like chemically inert ion bombardment, the chemical inhomogeneity induced boost is absent; as a result, no ripples are observed in the same ion energy and fluence.

  5. Preliminary assessment of the radiological protection aspects of disposal of high-level waste in geologic formations

    International Nuclear Information System (INIS)

    The purpose of this study is to carry out a preliminary assessment of the potential radiological consequences of disposing of vitrified high-level radioactive waste in geologic formations. The events which could lead to the release of radioactivity from a geologic repository are reviewed and ingress of ground-water is identified as the principal mechanism by which radioactivity may be transported back to the biosphere. A mathematical model of radionuclide migration with ground-water is used to predict possible rates of release of radioactivity into fresh water from a hypothetical repository containing all the high-level waste which may be generated in the UK up to the year 2000. The individual and collective doses which could be received as a result of man's use of contaminated fresh water are evaluated. The numerical results of the study depend very much on the assumptions made and cannot be used to draw any detailed conclusions. The main result is the identification of areas where further studies are required in order to carry out a full evaluation of this disposal option. (author)

  6. Studying the optical second-order interference pattern formation process with classical light in the photon counting regime.

    Science.gov (United States)

    He, Yuchen; Liu, Jianbin; Zhang, Songlin; Wang, Wentao; Bai, Bin; Le, Mingnan; Xu, Zhuo

    2015-12-01

    The formation process of the second-order interference pattern is studied experimentally in the photon counting regime by superposing two independent single-mode continuous-wave lasers. Two-photon interference based on the superposition principle in Feynman's path integral theory is employed to interpret the experimental results. The second-order interference pattern of classical light can be formulated when, with high probability, there are only two photons in the interferometer at one time. The studies are helpful in understanding the second-order interference of classical light in the language of photons. The method and conclusions can be generalized to the third- and higher-order interference of light and interference of massive particles. PMID:26831397

  7. Regulation of Pattern Formation and Gene Amplification During Drosophila Oogenesis by the miR-318 microRNA

    DEFF Research Database (Denmark)

    Ge, Wanzhong; Deng, Qiannan; Guo, Ting;

    2015-01-01

    Pattern formation during epithelial development requires the coordination of multiple signaling pathways. Here, we investigate the functions of an ovary-enriched miRNA, miR-318, in epithelial development during Drosophila oogenesis. miR-318 maternal loss-of-function mutants were female sterile...... and laid eggs with abnormal morphology. Removal of miR-318 disrupted the dorsal-anterior follicle cell patterning, resulting in abnormal dorsal appendages. miR-318 mutant females also produced thin and fragile eggshells, due to impaired chorion gene amplification. We provide evidence that the ecdysone...... signaling pathway activates expression of miR-318 and that miR-318 cooperates with Tramtrack69 (Ttk69) to control the switch from endocycling to chorion gene amplification during differentiation of the follicular epithelium. The multiple functions of miR-318 in oogenesis illustrate the importance of mi...

  8. Studying the optical second-order interference pattern formation process with classical light in the photon counting regime.

    Science.gov (United States)

    He, Yuchen; Liu, Jianbin; Zhang, Songlin; Wang, Wentao; Bai, Bin; Le, Mingnan; Xu, Zhuo

    2015-12-01

    The formation process of the second-order interference pattern is studied experimentally in the photon counting regime by superposing two independent single-mode continuous-wave lasers. Two-photon interference based on the superposition principle in Feynman's path integral theory is employed to interpret the experimental results. The second-order interference pattern of classical light can be formulated when, with high probability, there are only two photons in the interferometer at one time. The studies are helpful in understanding the second-order interference of classical light in the language of photons. The method and conclusions can be generalized to the third- and higher-order interference of light and interference of massive particles.

  9. Predicting the distribution of spiral waves from cell properties in a developmental-path model of Dictyostelium pattern formation.

    Directory of Open Access Journals (Sweden)

    Daniel Geberth

    2009-07-01

    Full Text Available The slime mold Dictyostelium discoideum is one of the model systems of biological pattern formation. One of the most successful answers to the challenge of establishing a spiral wave pattern in a colony of homogeneously distributed D. discoideum cells has been the suggestion of a developmental path the cells follow (Lauzeral and coworkers. This is a well-defined change in properties each cell undergoes on a longer time scale than the typical dynamics of the cell. Here we show that this concept leads to an inhomogeneous and systematic spatial distribution of spiral waves, which can be predicted from the distribution of cells on the developmental path. We propose specific experiments for checking whether such systematics are also found in data and thus, indirectly, provide evidence of a developmental path.

  10. Pattern Formation in the Turing-Hopf Codimension-2 Phase Space in a Reaction-Diffusion System

    Institute of Scientific and Technical Information of China (English)

    YUAN Xu-Jin; SHAO Xin; LIAO Hui-Min; OUYANG Qi

    2009-01-01

    We systematically investigate the behaviour of pattern formation in a reaction-diffusion system when the system is located near the Turing-Hopf codimension-2 point in phase space. The chloride-iodide-malonic acid (CIMA) reaction is used in this study. A phase diagram is obtained using the concentration of polyvinyl alcohol (PVA) and malonic acid (MA) as control parameters. It is found that the Turing-Hopf mixed state appears only in a small vicinity near the codimension-2 point, and has the form of hexagonal pattern overlapped with anti-target wave; the boundary line separating the Thring state and the wave state is independent of the concentration of MA, only relies on the concentration of PVA. The corresponding numerical simulation using the Lengyel-Epstein (LE) model gives a similar phase diagram as the experiment; it reproduces most patterns observed in the experiment. However, the mixed state we obtain in simulation only appears in the anti-wave tip area, implying that the 3-D effect in the experiments may change the pattern forming behaviour in the codimension-2 regime.

  11. In situ formation and photo patterning of emissive quantum dots in organic small molecules

    OpenAIRE

    Bansal, Ashu K.; Sajjad, Muhammad Tariq; Antolini, Francesco; Stroea, Lenuta; Gecys, Paulius; Raciukaitis, Gediminas; Andre, Pascal; Hirzer, Andreas; Schmidt, Volker; Ortolani, Luca; Toffanin, Stefano; Allard, Sybille; Scherf, Ullrich; Samuel, Ifor

    2015-01-01

    We acknowledge financial support from FP7 LAMP project “Laser Induced Synthesis of Polymeric Nanocomposite Materials and Development of Micro-patterned Hybrid Light Emitting Diodes (LED) and Transistors (LET)” (Grant No. 247928). AKB and IDWS also acknowledge financial support from EPSRC Programme grant “Challenging the limits of photonics: Structured light” EP/J01771X/1. In addition IDWS acknowledges a Royal Society Wolfson Research Merit Award.

  12. Expression Patterns and Subcellular Localization of Carbonic Anhydrases Are Developmentally Regulated during Tooth Formation

    OpenAIRE

    Reibring, Claes-Göran; El Shahawy, Maha; Hallberg, Kristina; Kannius-Janson, Marie; Nilsson, Jeanette; Parkkila, Seppo; Sly, William S; Waheed, Abdul; Linde, Anders; Gritli-Linde, Amel

    2014-01-01

    Carbonic anhydrases (CAs) play fundamental roles in several physiological events, and emerging evidence points at their involvement in an array of disorders, including cancer. The expression of CAs in the different cells of teeth is unknown, let alone their expression patterns during odontogenesis. As a first step towards understanding the role of CAs during odontogenesis, we used immunohistochemistry, histochemistry and in situ hybridization to reveal hitherto unknown dynamic distribution pa...

  13. Efficient formation of extended line intensity patterns using matched-filtering generalized phase contrast

    DEFF Research Database (Denmark)

    Bañas, Andrew Rafael; Palima, Darwin; Aabo, Thomas;

    2013-01-01

    We demonstrate the efficient generation of line patterns using matched-filtering Generalized Phase Contrast (mGPC). So far, the main emphasis of mGPC light addressing has been on the creation of rapidly reconfigurable focused spots. This has recently been extended to encoding extended line patter...... for structured light applications and advanced microscopy. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only....

  14. Pattern formation in reaction-diffusion systems: From spiral waves to turbulence

    Science.gov (United States)

    Davidsen, Joern

    2009-05-01

    Almost all systems we encounter in nature possess some sort of form or structure. In many cases, the structures arise from an initially unstructured state without the action of an agent that predetermines the pattern. Such self-organized structures emerge from cooperative interactions among the constituents of the system and often exhibit properties that are distinct from those of their constituent elements or molecules. For example, chemical waves in reaction-diffusion systems are at the core of a huge variety of physical, chemical, and biological processes. In (quasi) two-dimensional situations, spiral wave patterns are especially prevalent and determine the characteristics of processes such as surface catalytic oxidation reactions, contraction of the heart muscle, and various signaling mechanisms in biological systems. In this talk, I will review and discuss recent theoretical and experimental results regarding the dynamics, properties and stability of spiral waves and their three-dimensional analog (scroll waves). Special emphasis will be given to synchronization defect lines which generically arise in complex-oscillatory media, and the phenomenon of defect-mediated turbulence or filament turbulence where the dynamics of a pattern is dominated by the rapid motion, nucleation, and annihilation of spirals or scroll waves, respectively. The latter is of direct relevance in the context of ventricular fibrillation - a turbulent electrical wave activity that destroys the coherent contraction of the ventricular muscle and its main pumping function leading to sudden cardiac death.

  15. Pattern formation at multiple spatial scales drives the resilience of mussel bed ecosystems.

    Science.gov (United States)

    Liu, Quan-Xing; Herman, Peter M J; Mooij, Wolf M; Huisman, Jef; Scheffer, Marten; Olff, Han; van de Koppel, Johan

    2014-01-01

    Self-organized complexity at multiple spatial scales is a distinctive characteristic of biological systems. Yet, little is known about how different self-organizing processes operating at different spatial scales interact to determine ecosystem functioning. Here we show that the interplay between self-organizing processes at individual and ecosystem level is a key determinant of the functioning and resilience of mussel beds. In mussel beds, self-organization generates spatial patterns at two characteristic spatial scales: small-scale net-shaped patterns due to behavioural aggregation of individuals, and large-scale banded patterns due to the interplay of between-mussel facilitation and resource depletion. Model analysis reveals that the interaction between these behavioural and ecosystem-level mechanisms increases mussel bed resilience, enables persistence under deteriorating conditions and makes them less prone to catastrophic collapse. Our analysis highlights that interactions between different forms of self-organization at multiple spatial scales may enhance the intrinsic ability of ecosystems to withstand both natural and human-induced disturbances.

  16. Fractal pattern formation in thermal grooving at grain boundaries in Ag films on Si(111) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Roy, A. [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India); Sundaravel, B. [Materials Science Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Batabyal, R. [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India); Dev, B.N., E-mail: msbnd@iacs.res.in [Department of Materials Science, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032 (India)

    2012-05-31

    Growth of Ag films on Br- and H-passivated Si(111) surfaces and the annealing behaviour have been investigated by Rutherford backscattering spectrometry, scanning electron microscopy and photoemission electron microscopy techniques. Upon annealing the phenomenon of thermal grooving was observed in the Ag films. Depending on the annealing temperature, at an intermediate annealing time Ag depletion (evaporation) from the grain boundaries produces fractal patterns of Ag-depleted regions. Continued annealing eventually produces a percolated network of Ag-depleted regions (thermal grooves) along the grain boundaries and isolated Ag grains appear as the depth of the grooves reaches the substrate. For the fractal structures produced by thermal grooving, the fractal dimension has been estimated to be 1.60 {+-} 0.04. Observation of a fractal pattern in thermal grooving was not hitherto reported. A thorough analysis of the experimental results has been carried out in the context of current theories. These theories are inadequate to describe the experimental results. - Highlights: Black-Right-Pointing-Pointer Thermal grooving in Ag films grown on Si(111) surfaces has been investigated. Black-Right-Pointing-Pointer At appropriate temperatures short annealing shows partly depleted grain boundaries. Black-Right-Pointing-Pointer Depleted grain boundaries reveal a fractal pattern with a fractal dimension of 1.60. Black-Right-Pointing-Pointer Long annealing produces percolated Ag-depleted regions with isolated Ag grains. Black-Right-Pointing-Pointer A thorough analysis shows that current theories are unable to explain the results.

  17. Trust, responsibility, and freedom: Focus-group research on contemporary patterns of union formation in Russia

    OpenAIRE

    Olga Isupova

    2015-01-01

    Background: While some studies directly address the issue of changes in union formation in Russia and Eastern Europe, few have focused on attitudes and norms regarding marriage and cohabitation. In Russia cohabitation has risen sharply in the last decades, but recently its level has stabilized and even decreased slightly. Objective: We intend to highlight gender and educational differences in perceptions of the advantages and disadvantages of cohabitation vs. marriage. Methods: We condu...

  18. Geochemical patterns and microbial contribution to iron plaque formation in the rice plant rhizosphere

    Science.gov (United States)

    Maisch, Markus; Murata, Chihiro; Unger, Julia; Kappler, Andreas; Schmidt, Caroline

    2015-04-01

    Rice is the major food source for more than half of the world population and 80 percent of the worldwide rice cultivation is performed on water logged paddy soils. The establishment of reducing conditions in the soil and across the soil-water interface not only stimulates the microbial production and release of the greenhouse gas methane. These settings also create optimal conditions for microbial iron(III) reduction and therefore saturate the system with reduced ferrous iron. Through the reduction and dissolution of ferric minerals that are characterized by their high surface activity, sorbed nutrients and contaminants (e.g. arsenic) will be mobilized and are thus available for uptake by plants. Rice plants have evolved a strategy to release oxygen from their roots in order to prevent iron toxification in highly ferrous environments. The release of oxygen to the reduced paddy soil causes ferric iron plaque formation on the rice roots and finally increases the sorption capacity for toxic metals. To this date the geochemical and microbiological processes that control the formation of iron plaque are not deciphered. It has been hypothesized that iron(II)-oxidizing bacteria play a potential role in the iron(III) mineral formation along the roots. However, not much is known about the actual processes, mineral products, and geochemical gradients that establish within the rhizosphere. In the present study we have developed a growth set-up that allows the co-cultivation of rice plants and iron(II)-oxidizing bacteria, as well as the visual observation and in situ measurement of geochemical parameters. Oxygen and dissolved iron(II) gradients have been measured using microelectrodes and show geochemical hot spots that offer optimal growth conditions for microaerophilic iron(II) oxidizers. First mineral identification attempts of iron plaque have been performed using Mössbauer spectroscopy and microscopy. The obtained results on mineraology and crystallinity have been

  19. Constraining the star formation histories of GRB Host Galaxies from their observed abundance patterns

    CERN Document Server

    Calura, F; Prochaska, J X; Matteucci, F

    2008-01-01

    Long-duration Gamma Ray Bursts (GRBs) are linked to the collapse of massive stars and their hosts are exclusively identified as active, star forming galaxies. Four long GRBs observed at high spectral resolution at redshift 1.5 formation history of the host galaxies of these GRBs from the study of the chemical abundances measured in their ISM. We are also able to provide constraints on the age and on the dust content of GRB hosts. Our results support the hypothesis that long duration GRBs occur preferentially in low metallicity, star forming galaxies. We compare the specific star formation rate, namely the star formation rate per unit stellar mass, predicted for the hosts of these GRBs with observational values for GRB hosts distributed across a lar...

  20. Charge Effects and Nanoparticle Pattern Formation in Electrohydrodynamic NanoDrip Printing of Colloids

    CERN Document Server

    Richner, Patrizia; Norris, David J; Poulikakos, Dimos

    2016-01-01

    Advancing open atmosphere printing technologies to produce features in the nanoscale range has important and broad applications ranging from electronics, to photonics, plasmonics and biology. Recently an electrohydrodynamic printing regime has been demonstrated in a rapid dripping mode (termed NanoDrip), where the ejected colloidal droplets from nozzles of diameters of O(1 {\\mu}m) can controllably reach sizes an order of magnitude smaller than the nozzle and can generate planar and out-of-plane structures of similar sizes. Despite demonstrated capabilities, our fundamental understanding of important aspects of the physics of NanoDrip printing needs further improvement. Here we address the topics of charge content and transport in NanoDrip printing. We employ quantum dot and gold nanoparticle dispersions in combination with a specially designed, auxiliary, asymmetric electric field, targeting the understanding of charge locality (particles vs. solvent) and particle distribution in the deposits as indicated by ...

  1. Suppression of transient enhanced diffusion in sub-micron patterned silicon template by dislocation loops formation

    Science.gov (United States)

    Hu, Kuan-Kan; Chang, Ruey-Dar; Woon, Wei Yen

    2015-10-01

    We investigate the evolution of two dimensional transient enhanced diffusion (TED) of phosphorus in sub-micron scale patterned silicon template. Samples doped with low dose phosphorus with and without high dose silicon self-implantation, were annealed for various durations. Dopant diffusion is probed with plane-view scanning capacitance microscopy. The measurement revealed two phases of TED. Significant suppression in the second phase TED is observed for samples with high dose self-implantation. Transmission electron microscopy suggests the suppressed TED is related to the evolution of end of range defect formed around ion implantation sidewalls.

  2. Suppression of transient enhanced diffusion in sub-micron patterned silicon template by dislocation loops formation

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Kuan-Kan; Woon, Wei Yen [Department of Physics, National Central University, Jungli, 32054, Taiwan (China); Chang, Ruey-Dar [Chang Gung University, Taoyuan, Taiwan 33302 (China)

    2015-10-15

    We investigate the evolution of two dimensional transient enhanced diffusion (TED) of phosphorus in sub-micron scale patterned silicon template. Samples doped with low dose phosphorus with and without high dose silicon self-implantation, were annealed for various durations. Dopant diffusion is probed with plane-view scanning capacitance microscopy. The measurement revealed two phases of TED. Significant suppression in the second phase TED is observed for samples with high dose self-implantation. Transmission electron microscopy suggests the suppressed TED is related to the evolution of end of range defect formed around ion implantation sidewalls.

  3. Suppression of transient enhanced diffusion in sub-micron patterned silicon template by dislocation loops formation

    Directory of Open Access Journals (Sweden)

    Kuan-Kan Hu

    2015-10-01

    Full Text Available We investigate the evolution of two dimensional transient enhanced diffusion (TED of phosphorus in sub-micron scale patterned silicon template. Samples doped with low dose phosphorus with and without high dose silicon self-implantation, were annealed for various durations. Dopant diffusion is probed with plane-view scanning capacitance microscopy. The measurement revealed two phases of TED. Significant suppression in the second phase TED is observed for samples with high dose self-implantation. Transmission electron microscopy suggests the suppressed TED is related to the evolution of end of range defect formed around ion implantation sidewalls.

  4. Bifurcation and pattern formation in a coupled higher autocatalator reaction diffusion system

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Spatiotemporal structures arising in two identical cells, which are governed by higher autocatalator kinetics and coupled via diffusive interchange of autocatalyst,are discussed.The stability of the unique homogeneous steady state is obtained by the linearized theory.A necessary condition for bifurcations in spatially non-uniform solutions in uncoupled and coupled systems is given.Further information about Turing pattern solutions near bifurcation points is obtained by weakly nonlinear theory.Finally, the stability of equilibrium points of the amplitude equation is discussed by weakly nonlinear theory, with the bifurcation branches of the weakly coupled system.

  5. Continuum model for pattern formation on ion-beam eroded surfaces under target rotation

    International Nuclear Information System (INIS)

    A recently proposed continuum model for the formation of nanostructures on semiconductor surfaces generated by low-energy ion-beam erosion under normal and oblique ion incidence is generalized to the case of additional target rotation. After transformation, this model takes on the form of a driven damped isotropic Kuramoto-Sivashinsky equation. Primary focus of our investigation is the theoretical analysis of the competition of flat, hexagonal and square-like surface structures as function of the external rotation rate and the sputtering time. As a major result, we find that target rotation stabilizes the occurence of flat surfaces. Comparison with recent experimental results is also given

  6. Regular pattern formation on surface of aromatic polymers and its cytocompatibility

    Science.gov (United States)

    Michaljaničová, I.; Slepička, P.; Rimpelová, S.; Slepičková Kasálková, N.; Švorčík, V.

    2016-05-01

    In this work, we describe ripple and dot nanopatterning of three different aromatic polymer substrates by KrF excimer laser treatment. The conditions for regular structures were established by laser fluence and number of pulses. Subsequently, the influence of the angle of incidence of a laser beam was investigated. We have chosen polyethersulfone (PES), polyetherimide (PEI) and polyetheretherketone (PEEK) as substrates for modification since they are thermally, chemically and mechanically resistant aromatic polymers with high absorption coefficients at excimer laser wavelength. As a tool of wettability investigation, we used contact angle measurement and for determination of the absorption edge, UV-vis spectroscopy was used. Material surface chemistry was analyzed using FTIR and the changes caused by modification were gained as differential spectra by subtraction of the spectra of non-modified material. Surface morphology was investigated by atomic force microscopy, also the roughness and surface area of modified samples were studied. The scans showed the formation of regular periodic structures, ripples and dots, after treatment by 8 and 16 mJ cm-2 and 6000 pulses. Further, initial in vitro cytocompatibility tests were performed using U-2 OS cell line growing on PES samples subjected to scanning electron microscopy analysis. The structure formation mapping contributes strongly to development of new applications using nanostructured polymers, e.g. in tissue engineering or in combination with metallization in selected electronics and metamaterials construction.

  7. Floodplain Formation and Cottonwood Colonization Patterns on the Willamette River, Oregon, USA.

    Science.gov (United States)

    Dykaar; Wigington

    2000-01-01

    / Using a series of aerial photographs taken between 1936 and 1996, we trace coevolution of floodplain and riparian forest on the Willamette River. Within-channel barforms appear to be the predominant incipient floodplain landform and habitat for primary succession. Interlinked development of bar(s) and erosion of near banks, filling of channels, and establishment and growth of cottonwoods and willows results in coalescence with older floodplain. Sizeand internal structure of riparian forest patches reflect evolution of underlying barforms or channel beds. Floodplain matures as the active channel migrates away by repetition of the bar formation and near-bank erosion process, or is progressively abandoned by infilling and/or constriction with a bar. Other parts of the floodplain are recycled as eroding banks provide the coarse sediment and large woody debris for building new bars. A multichannel planform is maintained as building bars split flow; channels lengthen as bars and islands join into larger assemblages. Avulsion appears to cut new channels only short distances. Given the central role of bars and islands in building new floodplain habitat, we identify their area as a geomorphic indicator of river-floodplain integrity. We measure an 80% decline in bar and island area between 1910 and 1988 within a 22-km section. Dams, riprap, logging, and gravel mining may all be contributing to diminished bar formation rates. Removing obstacles to natural riparian forest creation mechanisms is necessary to regenerate the river-floodplain system and realize its productive potential. PMID:10552104

  8. Coupled Particle Transport and Pattern Formation in a Nonlinear Leaky-Box Model

    Science.gov (United States)

    Barghouty, A. F.; El-Nemr, K. W.; Baird, J. K.

    2009-01-01

    Effects of particle-particle coupling on particle characteristics in nonlinear leaky-box type descriptions of the acceleration and transport of energetic particles in space plasmas are examined in the framework of a simple two-particle model based on the Fokker-Planck equation in momentum space. In this model, the two particles are assumed coupled via a common nonlinear source term. In analogy with a prototypical mathematical system of diffusion-driven instability, this work demonstrates that steady-state patterns with strong dependence on the magnetic turbulence but a rather weak one on the coupled particles attributes can emerge in solutions of a nonlinearly coupled leaky-box model. The insight gained from this simple model may be of wider use and significance to nonlinearly coupled leaky-box type descriptions in general.

  9. The Formation, Movement and Evolution Pattern of Jurassic Terrestrial Deposit Basin in Daqingshan Region

    Institute of Scientific and Technical Information of China (English)

    PENG Xiangdong; XU Zhongyuan; LIU Zhenghong

    2001-01-01

    The authors have reconstructed the original shape of Jurassic basin in Daqingshan region and discussed the movement and evolution pattern of the basin. The basin developed between Paleozoic strata sliver and metamorphic rock sliver in late stage of Early Jurassic and extended in latitude direction. The palco - terrene of the basin is higher in north and west than south and east. The boundary of basin is largest in Changhangou stage of Middle Jurassic. After middle Jurassic, the region took place Yenshan movement, and then the basin changed obviously from weakly extending environment of Early and Middle Jurassic to extruding environment of late Jurassic, and the paleoclimate of the basin changed from warmth and wetness to dry. The basin finished the evolution history in the late stage of Late Jurassic with the development of thrust.

  10. Spontaneous formation of dynamical patterns with fractal fronts in the cyclic lattice Lotka-Volterra model.

    Science.gov (United States)

    Provata, A; Tsekouras, G A

    2003-05-01

    Dynamical patterns, in the form of consecutive moving stripes or rings, are shown to develop spontaneously in the cyclic lattice Lotka-Volterra model, when realized on square lattice, at the reaction limited regime. Each stripe consists of different particles (species) and the borderlines between consecutive stripes are fractal. The interface width w between the different species scales as w(L,t) approximately L(alpha)f(t/L(z)), where L is the linear size of the interface, t is the time, and alpha and z are the static and dynamical critical exponents, respectively. The critical exponents were computed as alpha=0.49+/-0.03 and z=1.53+/-0.13 and the propagating fronts show dynamical characteristics similar to those of the Eden growth models.

  11. Quantum noise and spatio-temporal pattern formation in nonlinear optics

    DEFF Research Database (Denmark)

    Bache, Morten

    2002-01-01

    This work concerns analytical and numerical investigations of cavity enhanced x2 frequency conversion processes, specifically second-harmonic generation (SHG). We focus on how the transverse degrees of freedom affect the dynamics, where the interaction between nonlinearity and diffraction gives...... rise to spatially modulated structures, patterns. The two main parts of the thesis are the classical model and the quantum mechanical model, the latter being an extension of the former by including the inherent quantum fluctuations of light. From a theoretical point of view the classical dynamics...... a nondegenerate parametric oscillation. We find that this model may completely stabilize the instabilities normally expected in SHG, but it may also give rise to entirely new phenomena, such as oscillating cavity solitons, intensity spirals and self-pulsing solutions. Especially the self-pulsing is important...

  12. Formation of peelable rough gold patterns on an ionic liquid template.

    Science.gov (United States)

    Ohzono, Takuya; Monobe, Hirosato; Fukuda, Nobuko; Fujiwara, Masahiro; Shimizu, Yo

    2011-02-18

    The ability to control metal patterns at the micro- and nanoscales, along with the development of a simple fabrication method, is important to many applications in the fields of materials science, biological sensing, electronics, and photonics. Herein, a simple approach to fabricating gold micropatterns with controlled roughness is reported. In this approach, gold is evaporated onto a striped liquid micropattern formed on self-organized microwrinkles. Gold nanoribbons with higher roughness form on the liquid part of the substrate because the deposited gold atoms can diffuse, grow, and aggregate at the liquid-air interface, whereas flat gold films form on the solid part. The rough gold nanoribbons formed on the liquid can then be peeled off through contact with water. The extinction spectrum of the rough gold nanoribbons suggests characteristic surface-plasmon absorption. This shows the possibility of using rough gold nanoribbons with controlled shape in plasmonic technology. PMID:21246715

  13. Expression patterns and subcellular localization of carbonic anhydrases are developmentally regulated during tooth formation.

    Directory of Open Access Journals (Sweden)

    Claes-Göran Reibring

    Full Text Available Carbonic anhydrases (CAs play fundamental roles in several physiological events, and emerging evidence points at their involvement in an array of disorders, including cancer. The expression of CAs in the different cells of teeth is unknown, let alone their expression patterns during odontogenesis. As a first step towards understanding the role of CAs during odontogenesis, we used immunohistochemistry, histochemistry and in situ hybridization to reveal hitherto unknown dynamic distribution patterns of eight CAs in mice. The most salient findings include expression of CAII/Car2 not only in maturation-stage ameloblasts (MA but also in the papillary layer, dental papilla mesenchyme, odontoblasts and the epithelial rests of Malassez. We uncovered that the latter form lace-like networks around incisors; hitherto these have been known to occur only in molars. All CAs studied were produced by MA, however CAIV, CAIX and CARPXI proteins were distinctly enriched in the ruffled membrane of the ruffled MA but exhibited a homogeneous distribution in smooth-ended MA. While CAIV, CAVI/Car6, CAIX, CARPXI and CAXIV were produced by all odontoblasts, CAIII distribution displayed a striking asymmetry, in that it was virtually confined to odontoblasts in the root of molars and root analog of incisors. Remarkably, from initiation until near completion of odontogenesis and in several other tissues, CAXIII localized mainly in intracellular punctae/vesicles that we show to overlap with LAMP-1- and LAMP-2-positive vesicles, suggesting that CAXIII localizes within lysosomes. We showed that expression of CAs in developing teeth is not confined to cells involved in biomineralization, pointing at their participation in other biological events. Finally, we uncovered novel sites of CA expression, including the developing brain and eye, the olfactory epithelium, melanoblasts, tongue, notochord, nucleus pulposus and sebaceous glands. Our study provides important information for

  14. The Rim101p/PacC pathway and alkaline pH regulate pattern formation in yeast colonies.

    Science.gov (United States)

    Piccirillo, Sarah; White, Melissa G; Murphy, Jeffrey C; Law, Douglas J; Honigberg, Saul M

    2010-03-01

    Multicellular organisms utilize cell-to-cell signals to build patterns of cell types within embryos, but the ability of fungi to form organized communities has been largely unexplored. Here we report that colonies of the yeast Saccharomyces cerevisiae formed sharply divided layers of sporulating and nonsporulating cells. Sporulation initiated in the colony's interior, and this region expanded upward as the colony matured. Two key activators of sporulation, IME1 and IME2, were initially transcribed in overlapping regions of the colony, and this overlap corresponded to the initial sporulation region. The development of colony sporulation patterns depended on cell-to-cell signals, as demonstrated by chimeric colonies, which contain a mixture of two strains. One such signal is alkaline pH, mediated through the Rim101p/PacC pathway. Meiotic-arrest mutants that increased alkali production stimulated expression of an early meiotic gene in neighboring cells, whereas a mutant that decreased alkali production (cit1Delta) decreased this expression. Addition of alkali to colonies accelerated the expansion of the interior region of sporulation, whereas inactivation of the Rim101p pathway inhibited this expansion. Thus, the Rim101 pathway mediates colony patterning by responding to cell-to-cell pH signals. Cell-to-cell signals coupled with nutrient gradients may allow efficient spore formation and spore dispersal in natural environments. PMID:20038633

  15. Effect of TMAH Etching Duration on the Formation of Silicon Nano wire Transistor Patterned by AFM Nano lithography

    International Nuclear Information System (INIS)

    Atomic force microscopy (AFM) lithography was applied to produce nano scale pattern for silicon nano wire transistor fabrication. This technique takes advantage of imaging facility of AFM and the ability of probe movement controlling over the sample surface to create nano patterns. A conductive AFM tip was used to grow the silicon oxide nano patterns on silicon on insulator (SOI) wafer. The applied tip-sample voltage and writing speed were well controlled in order to form pre-designed silicon oxide nano wire transistor structures. The effect of tetra methyl ammonium hydroxide (TMAH) etching duration on the oxide covered silicon nano wire transistor structure has been investigated. A completed silicon nano wire transistor was obtained by removing the oxide layer via hydrofluoric acid etching process. The fabricated silicon nano wire transistor consists of a silicon nano wire that acts as a channel with source and drain pads. A lateral gate pad with a nano wire head was fabricated very close to the channel in the formation of transistor structures. (author)

  16. Formation mechanism and development pattern of aeolian sand landform in Yarlung Zangbo River valley

    Institute of Scientific and Technical Information of China (English)

    李森; 董光荣; 申建友; 杨萍; 刘贤万; 王跃; 靳鹤龄; 王强

    1999-01-01

    Aeolian sand landforms in the Yarlung Zangbo River valley can be divided into 4 classes and 21 types. The river valley has favourable environment conditions for the development of aeolian sand landforms. Simulation of MM4 mid-scale climate model showed that the near-surface flow field and wind vector field during the winter half year in the fiver valley are generally favourable for the aeolian sand deposition and as a whole they also affect the distribution zones and sites of aeolian sand landforms. Sand dunes and sand dune groups in the fiver valley developed mainly in three ways, namely windward retarding deposition, leeward back flow deposition and bend circumfluence deposition. Through alternating positive-reverse processes of sand dune formation under wind actions and sand dune vanishing under water actions, sand dunes developed from primary zone through main-body zone then to vanishing zone where climbing dunes and falling dunes are declining and are even disappearing.

  17. Three-dimensional pattern formation in suspensions of swimming micro-organisms

    CERN Document Server

    Saintillan, David

    2009-01-01

    Suspensions of self-propelled particles, such as swimming micro-organisms, are known to undergo complex dynamics as a result of hydrodynamic interactions. This fluid dynamics video presents a numerical simulation of such a suspension, based on a kinetic theory recently developed by Saintillan and Shelley (Physics of Fluids, 20, 123403, 2008). Starting from a nearly uniform and isotropic initial distribution, our simulations show the formation of strong density fluctuations, which merge and break up in time in a quasiperiodic fashion. These fluctuations are found to occur on the size of the simulation box, in agreement with a prediction from a linear stability analysis. In addition, the dynamics are characterized by complex chaotic flow fields, which result in efficient fluid mixing.

  18. Patterns of growth and tract formation during the early development of secondary lineages in the Drosophila larval brain.

    Science.gov (United States)

    Lovick, Jennifer K; Kong, Angel; Omoto, Jaison J; Ngo, Kathy T; Younossi-Hartenstein, Amelia; Hartenstein, Volker

    2016-04-01

    The Drosophila brain consists of a relatively small number of invariant, genetically determined lineages which provide a model to study the relationship between gene function and neuronal architecture. In following this long-term goal, we reconstruct the morphology (projection pattern and connectivity) and gene expression patterns of brain lineages throughout development. In this article, we focus on the secondary phase of lineage morphogenesis, from the reactivation of neuroblast proliferation in the first larval instar to the time when proliferation ends and secondary axon tracts have fully extended in the late third larval instar. We have reconstructed the location and projection of secondary lineages at close (4 h) intervals and produced a detailed map in the form of confocal z-projections and digital three-dimensional models of all lineages at successive larval stages. Based on these reconstructions, we could compare the spatio-temporal pattern of axon formation and morphogenetic movements of different lineages in normal brain development. In addition to wild type, we reconstructed lineage morphology in two mutant conditions. (1) Expressing the construct UAS-p35 which rescues programmed cell death we could systematically determine which lineages normally lose hemilineages to apoptosis. (2) so-Gal4-driven expression of dominant-negative EGFR ablated the optic lobe, which allowed us to conclude that the global centrifugal movement normally affecting the cell bodies of lateral lineages in the late larva is causally related to the expansion of the optic lobe, and that the central pattern of axonal projections of these lineages is independent of the presence or absence of the optic lobe. PMID:26178322

  19. Inactivation of the Huntington's disease gene (Hdh impairs anterior streak formation and early patterning of the mouse embryo

    Directory of Open Access Journals (Sweden)

    Conlon Ronald A

    2005-08-01

    Full Text Available Abstract Background Huntingtin, the HD gene encoded protein mutated by polyglutamine expansion in Huntington's disease, is required in extraembryonic tissues for proper gastrulation, implicating its activities in nutrition or patterning of the developing embryo. To test these possibilities, we have used whole mount in situ hybridization to examine embryonic patterning and morphogenesis in homozygous Hdhex4/5 huntingtin deficient embryos. Results In the absence of huntingtin, expression of nutritive genes appears normal but E7.0–7.5 embryos exhibit a unique combination of patterning defects. Notable are a shortened primitive streak, absence of a proper node and diminished production of anterior streak derivatives. Reduced Wnt3a, Tbx6 and Dll1 expression signify decreased paraxial mesoderm and reduced Otx2 expression and lack of headfolds denote a failure of head development. In addition, genes initially broadly expressed are not properly restricted to the posterior, as evidenced by the ectopic expression of Nodal, Fgf8 and Gsc in the epiblast and T (Brachyury and Evx1 in proximal mesoderm derivatives. Despite impaired posterior restriction and anterior streak deficits, overall anterior/posterior polarity is established. A single primitive streak forms and marker expression shows that the anterior epiblast and anterior visceral endoderm (AVE are specified. Conclusion Huntingtin is essential in the early patterning of the embryo for formation of the anterior region of the primitive streak, and for down-regulation of a subset of dynamic growth and transcription factor genes. These findings provide fundamental starting points for identifying the novel cellular and molecular activities of huntingtin in the extraembryonic tissues that govern normal anterior streak development. This knowledge may prove to be important for understanding the mechanism by which the dominant polyglutamine expansion in huntingtin determines the loss of neurons in

  20. Distinct patterns of notochord mineralization in zebrafish coincide with the localization of Osteocalcin isoform 1 during early vertebral centra formation

    Directory of Open Access Journals (Sweden)

    Bensimon-Brito Anabela

    2012-10-01

    Full Text Available Abstract Background In chondrichthyans, basal osteichthyans and tetrapods, vertebral bodies have cartilaginous anlagen that subsequently mineralize (chondrichthyans or ossify (osteichthyans. Chondrocytes that form the vertebral centra derive from somites. In teleost fish, vertebral centrum formation starts in the absence of cartilage, through direct mineralization of the notochord sheath. In a second step, the notochord is surrounded by somite-derived intramembranous bone. In several small teleost species, including zebrafish (Danio rerio, even haemal and neural arches form directly as intramembranous bone and only modified caudalmost arches remain cartilaginous. This study compares initial patterns of mineralization in different regions of the vertebral column in zebrafish. We ask if the absence or presence of cartilaginous arches influences the pattern of notochord sheath mineralization. Results To reveal which cells are involved in mineralization of the notochord sheath we identify proliferating cells, we trace mineralization on the histological level and we analyze cell ultrastructure by TEM. Moreover, we localize proteins and genes that are typically expressed by skeletogenic cells such as Collagen type II, Alkaline phosphatase (ALP and Osteocalcin (Oc. Mineralization of abdominal and caudal vertebrae starts with a complete ring within the notochord sheath and prior to the formation of the bony arches. In contrast, notochord mineralization of caudal fin centra starts with a broad ventral mineral deposition, associated with the bases of the modified cartilaginous arches. Similar, arch-related, patterns of mineralization occur in teleosts that maintain cartilaginous arches throughout the spine. Throughout the entire vertebral column, we were able to co-localize ALP-positive signal with chordacentrum mineralization sites, as well as Collagen II and Oc protein accumulation in the mineralizing notochord sheath. In the caudal fin region, ALP and

  1. Pattern formation in a (2 + 1)-species activator-inhibitor-immobilizer system

    Science.gov (United States)

    Pearson, John E.

    1992-09-01

    The necessary and sufficient conditions for a Turing instability in a (2 + 1)-component reaction-diffusion system are derived. The 2-component subsystem consists of an arbitrary activator-inhibitor system in which the activator and the inhibitor diffuse at identical rates. The activator reacts with an immobile substrate to form an immobile complex which does not diffuse. It is found that the critical wavenumber and the location of the instability in parameter space are independent of the initial substrate concentration. As a special case, the (2 + 1)-variable activator-inhibitor-immobilizer system can be reduced to an activator-inhibitor system in which the activator diffuses more slowly than the inhibitor. This occurs when the time scales in the system satisfy certain constraints. The general results are applied to a (2 + 1)-variable model of the chlorite-iodide-starch reaction recently proposed by Epstein and Lengyel to explain the experimental observation of Turing patterns in a related system. I find an intrinsic wavelength which is within a factor of two of the experimentally observed wavelength, but the necessary conditions for the (2 + 1)-variable system to reduce to a two-variable activator-inhibitor system with rescaled diffusion coefficients are not satisfied.

  2. Gravity is indeed the driving force for fault pattern formation and westward displacement of the lithosphere

    CERN Document Server

    Papa, A R R

    2005-01-01

    Gravity influence of the Sun and the Moon on the Earth is the cause of the fault pattern on Earth's surface we observe nowadays and also of the westward displacement of the lithosphere. A somewhat related hypotheses advanced in the past have been that tidal torque of the Moon may be significant. However, it has been argued that it is untenable essentially on the grounds that the viscosity of the Earth's mantle is far too high in comparison with the forces involved. To state this it was assumed that the Earth's relevant characteristic is that of two spherical shells separated by a viscous liquid, the external shell rotating at a constant angular velocity with respect to the inner shell. Here I show that this picture is not quite right and that a more careful look leads us to one in which both shells rotates at different mean angular velocities and with a forward-backward sequence of movements relative to each other. In this way what was supposed to be the principal factor against gravity influence becomes the ...

  3. Inherent structures of phase-separating binary mixtures: nucleation, spinodal decomposition, and pattern formation.

    Science.gov (United States)

    Sarkar, Sarmistha; Bagchi, Biman

    2011-03-01

    An energy landscape view of phase separation and nonideality in binary mixtures is developed by exploring their potential energy landscape (PEL) as functions of temperature and composition. We employ molecular dynamics simulations to study a model that promotes structure breaking in the solute-solvent parent binary liquid, at low temperatures. The PEL of the system captures the potential energy distribution of the inherent structures (IS) of the system and is obtained by removing the kinetic energy (including that of intermolecular vibrations). The broader distribution of the inherent structure energy for structure breaking liquid than that of the structure making liquid demonstrates the larger role of entropy in stabilizing the parent liquid of the structure breaking type of binary mixtures. At high temperature, although the parent structure of the structure breaking binary mixture is homogenous, the corresponding inherent structure is found to be always phase separated, with a density pattern that exhibits marked correlation with the energy of its inherent structure. Over a broad range of intermediate inherent structure energy, bicontinuous phase separation prevails with interpenetrating stripes as signatures of spinodal decomposition. At low inherent structure energy, the structure is largely phase separated with one interface where as at high inherent structure energy we find nucleation type growth. Interestingly, at low temperature, the average inherent structure energy () exhibits a drop with temperature which signals the onset of crystallization in one of the phases while the other remains in the liquid state. The nonideal composition dependence of viscosity is anticorrelated with average inherent structure energy. PMID:21517506

  4. Inherent structures of phase-separating binary mixtures: Nucleation, spinodal decomposition, and pattern formation

    Science.gov (United States)

    Sarkar, Sarmistha; Bagchi, Biman

    2011-03-01

    An energy landscape view of phase separation and nonideality in binary mixtures is developed by exploring their potential energy landscape (PEL) as functions of temperature and composition. We employ molecular dynamics simulations to study a model that promotes structure breaking in the solute-solvent parent binary liquid, at low temperatures. The PEL of the system captures the potential energy distribution of the inherent structures (IS) of the system and is obtained by removing the kinetic energy (including that of intermolecular vibrations). The broader distribution of the inherent structure energy for structure breaking liquid than that of the structure making liquid demonstrates the larger role of entropy in stabilizing the parent liquid of the structure breaking type of binary mixtures. At high temperature, although the parent structure of the structure breaking binary mixture is homogenous, the corresponding inherent structure is found to be always phase separated, with a density pattern that exhibits marked correlation with the energy of its inherent structure. Over a broad range of intermediate inherent structure energy, bicontinuous phase separation prevails with interpenetrating stripes as signatures of spinodal decomposition. At low inherent structure energy, the structure is largely phase separated with one interface where as at high inherent structure energy we find nucleation type growth. Interestingly, at low temperature, the average inherent structure energy () exhibits a drop with temperature which signals the onset of crystallization in one of the phases while the other remains in the liquid state. The nonideal composition dependence of viscosity is anticorrelated with average inherent structure energy.

  5. Dependence of crystallite formation and preferential backbone orientations on the side chain pattern in PBDTTPD polymers

    KAUST Repository

    El Labban, Abdulrahman

    2014-11-26

    (Figure Presented) Alkyl substituents appended to the π-conjugated main chain account for the solution-processability and film-forming properties of most π-conjugated polymers for organic electronic device applications, including field-effect transistors (FETs) and bulk-heterojunction (BHJ) solar cells. Beyond film-forming properties, recent work has emphasized the determining role that side-chain substituents play on polymer self-assembly and thin-film nanostructural order, and, in turn, on device performance. However, the factors that determine polymer crystallite orientation in thin-films, implying preferential backbone orientation relative to the device substrate, are a matter of some debate, and these structural changes remain difficult to anticipate. In this report, we show how systematic changes in the side-chain pattern of poly(benzo[1,2-b:4,5-b′]dithiophene-alt-thieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) polymers can (i) influence the propensity of the polymer to order in the π-stacking direction, and (ii) direct the preferential orientation of the polymer crystallites in thin films (e.g., "face-on" vs "edge-on"). Oriented crystallites, specifically crystallites that are well-ordered in the π-stacking direction, are believed to be a key contributor to improved thin-film device performance in both FETs and BHJ solar cells.

  6. Pattern formation in a growing bacterial colony facilitated by extra-cellular polymeric substances

    Science.gov (United States)

    Ghosh, Pushpita; Mondal, Jagannath; Ben-Jacob, Eshel; Levine, Herbert

    2015-03-01

    Self-organization in bacterial colony is quite pervasive and diverse phenomena. Bacteria are known to self-organize into multicellular communities, commonly known as biofilms, in which microbial cells live in close association with a solid surface and are embedded in a self-produced extracellular polymeric substances(EPS). In such dense systems mechanical interactions among the structural components can be expected to significantly contribute to the morphological properties. By a simple particle-based simulation model of nonmotile rod-shaped bacterial cells and EPS secreted in a growing colony, we investigate how the combined mechanical effects can give rise naturally spatial heterogeneity observed in a biofilm. In our individual-based simulation model all the components interact mechanically via repulsive forces by pushing each other away as bacterial cells grow and divide consuming diffusing nutrient and produce EPS. We show that mechanical interactions control the collective behavior of the system, particularly, we show that the presence of non-adsorbing EPS leads spontaneous aggregation of bacterial cells by depletion attraction and generates phase separated patterns in a nonequilibrium growing colony.

  7. Indium segregation during III–V quantum wire and quantum dot formation on patterned substrates

    Energy Technology Data Exchange (ETDEWEB)

    Moroni, Stefano T.; Dimastrodonato, Valeria; Chung, Tung-Hsun; Juska, Gediminas; Gocalinska, Agnieszka; Pelucchi, Emanuele [Tyndall National Institute, “Lee Maltings,” University College Cork, Cork (Ireland); Vvedensky, Dimitri D. [The Blackett Laboratory, Imperial College London, London SW7 2AZ (United Kingdom)

    2015-04-28

    We report a model for metalorganic vapor-phase epitaxy on non-planar substrates, specifically V-grooves and pyramidal recesses, which we apply to the growth of InGaAs nanostructures. This model—based on a set of coupled reaction-diffusion equations, one for each facet in the system—accounts for the facet-dependence of all kinetic processes (e.g., precursor decomposition, adatom diffusion, and adatom lifetimes) and has been previously applied to account for the temperature-, concentration-, and temporal-dependence of AlGaAs nanostructures on GaAs (111)B surfaces with V-grooves and pyramidal recesses. In the present study, the growth of In{sub 0.12}Ga{sub 0.88}As quantum wires at the bottom of V-grooves is used to determine a set of optimized kinetic parameters. Based on these parameters, we have modeled the growth of In{sub 0.25}Ga{sub 0.75}As nanostructures formed in pyramidal site-controlled quantum-dot systems, successfully producing a qualitative explanation for the temperature-dependence of their optical properties, which have been reported in previous studies. Finally, we present scanning electron and cross-sectional atomic force microscopy images which show previously unreported facetting at the bottom of the pyramidal recesses that allow quantum dot formation.

  8. Czech alien flora and the historical pattern of its formation: what came first to Central Europe?

    Science.gov (United States)

    Pysek, Petr; Sádlo, Jirí; Mandák, Bohumil; Jarosík, Vojtech

    2003-03-01

    Temporal patterns of immigration to the country were analysed using 668 alien species in the flora of the Czech Republic for which the dates of the first record were available (64.8% of the total number of 1031 so-called neophytes, i.e. aliens introduced after the year 1500). After a period of initial slow increase lasting to the 1840s, the accumulation of neophytes over time could be best fitted by a linear model that explained 97% of the variance. The intensity of floristic research, which varied between periods, did not significantly affect the overall increase in the number of aliens. The effect of species traits on the year of introduction was evaluated, with continent of origin, introduction type (deliberate or accidental), life history, Grime's life strategy, onset of flowering, mode of dispersal and propagule size as explanatory variables. Species of European origin and CSR strategists arrived earlier than those with other origins and strategies. Deliberately introduced species appeared earlier than accidental arrivals, and those cultivated for utilitary reasons on average arrived earlier than ornamentals. Species capable of early flowering were remarkably more prevalent among early newcomers. A separate analysis of accidentally introduced American species also identified life history as a significant predictor of immigration time, with annuals being introduced earlier than biennials and perennials. The data contribute to an understanding of a crucial stage of the invasion process that has received little attention in the literature. The model "early alien" to Central Europe is a European species with a CSR strategy deliberately brought for cultivation as a utilitary plant. Once it escaped from cultivation, its establishment in the wild was favoured by its ability to flower early and, therefore, complete the life cycle. PMID:12647111

  9. A model for oscillations and pattern formation in protoplasmic droplets of Physarum polycephalum

    Science.gov (United States)

    Radszuweit, M.; Engel, H.; Bär, M.

    2010-12-01

    A mechano-chemical model for the spatiotemporal dynamics of free calcium and the thickness in protoplasmic droplets of the true slime mold Physarum polycephalum is derived starting from a physiologically detailed description of intracellular calcium oscillations proposed by Smith and Saldana (Biopys. J. 61, 368 (1992)). First, we have modified the Smith-Saldana model for the temporal calcium dynamics in order to reproduce the experimentally observed phase relation between calcium and mechanical tension oscillations. Then, we formulate a model for spatiotemporal dynamics by adding spatial coupling in the form of calcium diffusion and advection due to calcium-dependent mechanical contraction. In another step, the resulting reaction-diffusion model with mechanical coupling is simplified to a reaction-diffusion model with global coupling that approximates the mechanical part. We perform a bifurcation analysis of the local dynamics and observe a Hopf bifurcation upon increase of a biochemical activity parameter. The corresponding reaction-diffusion model with global coupling shows regular and chaotic spatiotemporal behaviour for parameters with oscillatory dynamics. In addition, we show that the global coupling leads to a long-wavelength instability even for parameters where the local dynamics possesses a stable spatially homogeneous steady state. This instability causes standing waves with a wavelength of twice the system size in one dimension. Simulations of the model in two dimensions are found to exhibit defect-mediated turbulence as well as various types of spiral wave patterns in qualitative agreement with earlier experimental observation by Takagi and Ueda (Physica D, 237, 420 (2008)).

  10. A special recurrent pattern in small hepatocellular carcinoma after treatment: Bile duct tumor thrombus formation

    Institute of Scientific and Technical Information of China (English)

    Qing-Yu Liu; Dong-Ming Lai; Chao Liu; Lei Zhang; Wei-Dong Zhang; Hai-Gang Li; Ming Gao

    2011-01-01

    AIM: To investigate the clinicopathologic features of bile duct tumor thrombus (BDTT) occurrence after treatment of primary small hepatocellular carcinoma (sHCC).METHODS: A total of 423 patients with primary sHCC admitted to our hospital underwent surgical resection or local ablation. During follow-up, only six patients were hospitalized due to obstructive jaundice, which occurred 5-76 mo after initial treatment. The clini-copathologic features of these six patients were re-viewed.RESULTS: Six patients underwent hepatic resection (n = 5) or radio-frequency ablation (n = 1) due to prima-ry sHCC. Five cases had an R1 resection margin, and one case had an ablative margin less than 5.0 mm. No vascular infiltration, microsatellites or bile duct/cana-liculus affection was noted in the initial resected speci-mens. During the follow-up, imaging studies revealed a macroscopic BDTT extending to the common bile duct in all six patients. Four patients had a concomi-tant intrahepatic recurrent tumor. Surgical re-resection of intrahepatic recurrent tumors and removal of BDTTs (n = 4), BDTT removal through choledochotomy (n = 1), and conservative treatment (n = 1) was performed. Microscopic portal vein invasion was noted in three of the four resected specimens. All six patients died, with a mean survival of 11 mo after BDTT removal or con-servative treatment.CONCLUSION: BDTT occurrence is a rare, special re-current pattern of primary sHCC. Patients with BDTTs extending to the common bile duct usually have an un-favorable prognosis even following aggressive surgery. Insufficient resection or ablative margins against pri-mary sHCC may be a risk factor for BDTT development.

  11. WOUND HEALING AND COLLAGEN FORMATION. IV. DISTORTION OF RIBOSOMAL PATTERNS OF FIBROBLASTS IN SCURVY.

    Science.gov (United States)

    ROSS, R; BENDITT, E P

    1964-08-01

    The changes in scorbutic wounds following the administration of ascorbic acid have been investigated using the techniques of electron microscopy, histochemistry, and autoradioggraphy. Particular attention has been paid to the changes seen in the endoplasmic reticulum of the fibroblasts and to the identity of the extracellular filamentous material characteristic of scorbutic wounds. Seven-day-old wounds in scorbutic guinea pigs were examined prior to and from one to 72 hours following the administration of vitamin C. Fibroblasts from wounds of normal animals demonstrate a characteristic configuration of the ribosomes of the endoplasmic reticulum which is suggested to be analogous to polyribosomes described in cells synthesizing protein such as the reticulocyte. Tangential views of the membranes of the ergastoplasm show the ribosomes to be grouped in paired rows which take both straight and curved paths. This configuration is lost in scurvy and can be seen to begin to reappear as early as 4 hours after giving ascorbic acid. With increasing time, the morphology of the ribosomal aggregates approximates that seen in normal cells, so that by 24 hours their reorientation is complete. It is suggested that one of the disturbances in scurvy may relate to an alteration either in messenger RNA, in the ability of the ribosomes to relate to the messenger, or in the membranes of the ergastoplasm. In addition, the lack of formation of hydroxyamino acids necessary for completing collagen synthesis may be related to the architecture of the ribosomal aggregates. Extracellular collagen fibrils appear concomitant with the restoration of ribosomal and ergastoplasmic morphology as early as 12 hours after administration of ascorbic acid, with complete disappearance of the scorbutic extracellular material within 24 hours. Observations of this scorbutic material do not support the concept that it is a collagen precursor.

  12. Effects of Dynamic Changes in Ultrasound Attenuation and Blood Perfusion on Lesion Formation of Multiple focus Pattern during Ultrasound Surgery

    Institute of Scientific and Technical Information of China (English)

    ZHANG Chen-xi; BAI Jing-feng; CHEN Ya-zhu

    2007-01-01

    A nonlinear finite-element program was developed to simulate the dynamic evolution of coagulation in tissue considering temperature and thermal-dose dependence of the ultrasound attenuation and blood perfusion rate.The effects of these dynamic parameters on the lesion formation were investigated in the particular case of ultrasound hepatic ablation with bi-focus intensity pattern.The results of simulations were compared that incorporate dynamic changes of ultrasound attenuation and perfusion and results that neglect these effects.The result shows that thermal-dose-dependent ultrasound attenuation is the dominating factor in the full dynamic model.If the dynamic ultrasound attenuation is ignored, a relatively significant underestimation of the temperature rise appears in the focal plane and the region next to the focal plane, resulting in an underestimation in predicting diameter of coagulation.Higher heating intensity leads to greater underestimation.

  13. The role of phase separation for self-organized surface pattern formation by ion beam erosion and metal atom co-deposition

    Energy Technology Data Exchange (ETDEWEB)

    Hofsaess, H.; Zhang, K.; Pape, A.; Bobes, O.; Broetzmann, M. [Georg-August University Goettingen, II. Institute of Physics, Goettingen (Germany)

    2013-05-15

    We investigate the ripple pattern formation on Si surfaces at room temperature during normal incidence ion beam erosion under simultaneous deposition of different metallic co-deposited surfactant atoms. The co-deposition of small amounts of metallic atoms, in particular Fe and Mo, is known to have a tremendous impact on the evolution of nanoscale surface patterns on Si. In previous work on ion erosion of Si during co-deposition of Fe atoms, we proposed that chemical interactions between Fe and Si atoms of the steady-state mixed Fe{sub x} Si surface layer formed during ion beam erosion is a dominant driving force for self-organized pattern formation. In particular, we provided experimental evidence for the formation of amorphous iron disilicide. To confirm and generalize such chemical effects on the pattern formation, in particular the tendency for phase separation, we have now irradiated Si surfaces with normal incidence 5 keV Xe ions under simultaneous gracing incidence co-deposition of Fe, Ni, Cu, Mo, W, Pt, and Au surfactant atoms. The selected metals in the two groups (Fe, Ni, Cu) and (W, Pt, Au) are very similar regarding their collision cascade behavior, but strongly differ regarding their tendency to silicide formation. We find pronounced ripple pattern formation only for those co deposited metals (Fe, Mo, Ni, W, and Pt), which are prone to the formation of mono and disilicides. In contrast, for Cu and Au co-deposition the surface remains very flat, even after irradiation at high ion fluence. Because of the very different behavior of Cu compared to Fe, Ni and Au compared to W, Pt, phase separation toward amorphous metal silicide phases is seen as the relevant process for the pattern formation on Si in the case of Fe, Mo, Ni, W, and Pt co-deposition. (orig.)

  14. Neotectonic formation of drainage patterns and their palaeohydrological implications for the Okwa River catchment, Botswana

    Science.gov (United States)

    Hartmann, Kai; Schmidt, Mareike; Shemang, Elisha; Zhang, Shuping; Frank, Riedel

    2014-05-01

    Large inter- and intramontane endorheic basins provide long term archives of environmental change, often integrating regional to continental climate driven process dynamics of huge drainage systems. On one hand the large-scale integration can be regarded as an advantage by averaging small-scale variations of either local hydrological peculiarities or random triggered drainage behaviour (e.g. internal thresholds, tectonics, etc.) and thus just recording atmospheric circulation pattern up to hemispherical scales with millennial resolution. Otherwise, with increasing basin size the process dynamic and their response system along one or more sediment cascades often become a complexity resulting in crucial problems of sedimentological archive interpretations by e.g. signal interference, equifinality or even multiple reworking. Therefore, studies of geomorphological or hydrological response processes and ecological adaption can only be undertaken on sub-catchment scale considering process dynamics along pathways. For southern-hemispheric palaeoclimate reconstruction of land-ocean linkages, Makgadikgadi Basin - as the largest (c. 37,000 km2) and deepest depression in the middle Kalahari - provides a fluvio-lacustrine archive in high-continental position since at least 300 kyr BP. Recent studies suggest a mega-lake high-stand within the basin for the Last Glacial Maximum (LGM) For the hydrological persistence of the lake for about 6 kyrs, the since Heinrich Event 1 (17-16 ka) inactive Okwa River seems to play a key role indicating a northward-shift of the winter rainfall zone. However, beside some dating of exposed shell bearing sediments at the river mouth, a thorough investigation of the c. 129,000 km2 drainage system is missing. Our presentation aims to point out the linkages between neotectonic activity and sediment transport. The combination of adaptive DEM-filter and multispectral remote sensing data reveals obvious traps (of neotectonic origin) of small temporary

  15. Sp6 and Sp8 transcription factors control AER formation and dorsal-ventral patterning in limb development.

    Directory of Open Access Journals (Sweden)

    Endika Haro

    2014-08-01

    Full Text Available The formation and maintenance of the apical ectodermal ridge (AER is critical for the outgrowth and patterning of the vertebrate limb. The induction of the AER is a complex process that relies on integrated interactions among the Fgf, Wnt, and Bmp signaling pathways that operate within the ectoderm and between the ectoderm and the mesoderm of the early limb bud. The transcription factors Sp6 and Sp8 are expressed in the limb ectoderm and AER during limb development. Sp6 mutant mice display a mild syndactyly phenotype while Sp8 mutants exhibit severe limb truncations. Both mutants show defects in AER maturation and in dorsal-ventral patterning. To gain further insights into the role Sp6 and Sp8 play in limb development, we have produced mice lacking both Sp6 and Sp8 activity in the limb ectoderm. Remarkably, the elimination or significant reduction in Sp6;Sp8 gene dosage leads to tetra-amelia; initial budding occurs, but neither Fgf8 nor En1 are activated. Mutants bearing a single functional allele of Sp8 (Sp6-/-;Sp8+/- exhibit a split-hand/foot malformation phenotype with double dorsal digit tips probably due to an irregular and immature AER that is not maintained in the center of the bud and on the abnormal expansion of Wnt7a expression to the ventral ectoderm. Our data are compatible with Sp6 and Sp8 working together and in a dose-dependent manner as indispensable mediators of Wnt/βcatenin and Bmp signaling in the limb ectoderm. We suggest that the function of these factors links proximal-distal and dorsal-ventral patterning.

  16. Micro-pattern formation of extracellular matrix (ECM) layers by atmospheric-pressure plasmas and cell culture on the patterned ECMs

    Science.gov (United States)

    Ando, Ayumi; Asano, Toshifumi; Urisu, Tsuneo; Hamaguchi, Satoshi

    2011-12-01

    A new patterning technique for the extracellular matrix (ECM) deposited on a Si substrate was developed with the use of a low-frequency atmospheric-pressure plasma and a metal stencil mask. The development of such a patterning technique for cell arrangement is a crucial step for the development of future cell chips. In this study, optimal process conditions for ECM patterning over the size of a typical single chip (about 1 cm2) were achieved and the obtained ECM patterns were directly observed by fluorescence labelling. It was also demonstrated that HEK293 cells (human embryo kidney cells) attach to and proliferate on the ECM layer patterned by this technique, arranging themselves on the Si substrate in the mask pattern.

  17. Methodological aspects of a pattern-scaling approach to produce global fields of monthly means of daily maximum and minimum temperature

    Directory of Open Access Journals (Sweden)

    S. Kremser

    2013-09-01

    Full Text Available A Climate Pattern-Scaling Model (CPSM that simulates global patterns of climate change, for a prescribed emissions scenario, is described. A CPSM works by quantitatively establishing the statistical relationship between a climate variable at a specific location (e.g. daily maximum surface temperature, Tmax and one or more predictor time series (e.g. global mean surface temperature, Tglobal – referred to as the "training" of the CPSM. This training uses a regression model to derive fit-coefficients that describe the statistical relationship between the predictor time series and the target climate variable time series. Once that relationship has been determined, and given the predictor time series for any greenhouse gas (GHG emissions scenario, the change in the climate variable of interest can be reconstructed – referred to as the "application" of the CPSM. The advantage of using a CPSM rather than a typical atmosphere-ocean global climate model (AOGCM is that the predictor time series required by the CPSM can usually be generated quickly using a simple climate model (SCM for any prescribed GHG emissions scenario and then applied to generate global fields of the climate variable of interest. The training can be performed either on historical measurements or on output from an AOGCM. Using model output from 21st century simulations has the advantage that the climate change signal is more pronounced than in historical data and therefore a more robust statistical relationship is obtained. The disadvantage of using AOGCM output is that the CPSM training might be compromised by any AOGCM inadequacies. For the purposes of exploring the various methodological aspects of the CPSM approach, AOGCM output was used in this study to train the CPSM. These investigations of the CPSM methodology focus on monthly mean fields of daily temperature extremes (Tmax and Tmin. Key conclusions are: (1 overall, the CPSM trained on simulations based on the

  18. Facies pattern of the middle Permian Barren Measures Formation, Jharia basin, India: The sedimentary response to basin tectonics

    Indian Academy of Sciences (India)

    Prabir Dasgupta

    2005-06-01

    In the Lower Gondwana succession of the Jharia basin of eastern India, the Barren Measures Formation is characterized by the cyclic disposition of fine-grained lacustrine deposits and relatively coarse-grained fluvial deposits. The cyclic variation in the rate of coarse clastic input is attributed to the sedimentary response to basin tectonics. The sandstone–shale alternations of the Barren Measures succession can be correlated with the tectonic cyclothems developed on the hangingwall dip-slope and adjoining trough in a continental half-graben setting. Enhancement of the gradient of the hangingwall dip-slope during reactivation of the basin margin faults led to progradation of the existing fluvial system towards the half-graben trough and deposition of the coarser clastics on the fine-grained lacustrine deposits of the trough. Peneplanation of the hangingwall slope and slow increase in the lake level caused lacustrine transgression and retrogration of the fluvial system on the hangingwall block. The fluvial sediments were onlapped by the fine-grained lacustrine deposits. Episodic rejuvenation of the basin margin faults thus caused development of tectonic cyclothem on the hangingwall block. The paleocurrent pattern indicates that a persistent northward paleoslope was maintained during Barren Measures sedimentation. The inferred depositional settings were much more extensive than the present limit of the outcrop. The faults, presently defining the northern limit of the Barren Measures Formation, were possibly emplaced after Barren Measures sedimentation. The final movement along these fault planes caused preservation of the downthrown hangingwall block and the Barren Measures sediments on the footwall block were eroded during subsequent denudation. The Southern Boundary Fault came into existence after the deposition of the Barren Measures sediments.

  19. Connecting Local Environmental Sequences to Global Climate Patterns: Evidence From the Hominin-Bearing Hadar Formation, Ethiopia.

    Science.gov (United States)

    Campisano, C. J.; Feibel, C. S.

    2004-12-01

    Central to the debate surrounding global climate change and Plio-Pleistocene hominin evolution is the degree to which large-scale climate patterns influence low-latitude continental ecosystems and how these global influences can be distinguished from regional tectono-volcanic events and local environmental effects. These isolated factors must then be compared to trends or events in the hominin fossil or archaeological record. The Pliocene Hadar Formation preserves a high-resolution record of hominin paleoenvironments from roughly 3.5 to 2.3 Ma. The chronostratigraphic framework at Hadar, often divisible into sub-50,000 year intervals, provides temporal resolution relevant to evolutionary change within hominins and other taxa. Combined with a high sedimentation rate and abundant faunal remains, this tightly controlled stratigraphic framework allows Hadar to be compared to detailed climate proxies such as marine core isotope, dust, and sapropel records. Preliminary analyses from Hadar suggest that these comparisons can be used to distinguish local versus regional and global environmental change, determine the overall sensitivity of the Hadar system and its fauna to such change, and how this level of sensitively compares to other East African localities. Consistent cycling observed both between and within fluvial and lacustrine depositional environments prior to 2.9 Ma at Hadar appears to be dominantly climatic in nature. However, a significant change in depositional facies after 2.9 Ma to sequences dominated by conglomerate cut-and-fill cycles indicates a strong tectonic signature related to regional developments in the Main Ethiopian Rift (MER). While specific events seen in marine proxy records may have parallels in the Hadar environmental archive, their overall patterns of high versus low variability may be even more relevant. For example, periods of relatively high amplitude climate oscillations between 3.15 and 2.95 Ma may be linked to noted morphological

  20. Fabrication and characterization of high aspect ratio perpendicular patterned information storage media in an Al2O3/GaAs substrate

    OpenAIRE

    Wong, Joyce; Scherer, Axel; Todorovic, Mladen; Schultz, Sheldon

    1999-01-01

    In a new approach, we have fabricated 6:1 aspect ratio magnetic nanocolumns, 60–250 nm in diameter, embedded in a hard aluminum-oxide/gallium-arsenide (Al2O3/GaAs) substrate. The fabrication technique uses the highly selective etching properties of GaAs and AlAs, and highly efficient masking properties of Al2O3 to create small diameter, high aspect ratio holes. Nickel (Ni) is subsequently electroplated into the holes, followed by polishing, which creates a smooth and hard surface appropriate ...

  1. Formation and growth of fractal patterns in high energy P+-implanted silicon and N+Zn-implanted SiO2/GaAsP during thermal annealing

    Institute of Scientific and Technical Information of China (English)

    吴瑜光; 张通和

    1997-01-01

    The fractal patterns in implanted samples are observed. Possible correlation of fractal patterns with the annealing temperature and the electrical activation ratio are given. The formation and growth process of fractal patterns are compared for implanted layers both in silicon and in SiO2/GaAsP during thermal annealing. The mechanism of formation and growth process of fractal pattern is discussed.

  2. Methodological aspects of a pattern-scaling approach to produce global fields of monthly means of daily maximum and minimum temperature

    OpenAIRE

    S. Kremser; Bodeker, G. E.; Lewis, J.

    2014-01-01

    A Climate Pattern-Scaling Model (CPSM) that simulates global patterns of climate change, for a prescribed emissions scenario, is described. A CPSM works by quantitatively establishing the statistical relationship between a climate variable at a specific location (e.g. daily maximum surface temperature, Tmax) and one or more predictor time series (e.g. global mean surface temperature, Tglobal) – referred to as the "training" of the CPSM. This training uses a regression model ...

  3. Methodological aspects of a pattern-scaling approach to produce global fields of monthly means of daily maximum and minimum temperature

    OpenAIRE

    S. Kremser; Bodeker, G. E.; Lewis, J.

    2013-01-01

    A Climate Pattern-Scaling Model (CPSM) that simulates global patterns of climate change, for a prescribed emissions scenario, is described. A CPSM works by quantitatively establishing the statistical relationship between a climate variable at a specific location (e.g. daily maximum surface temperature, Tmax) and one or more predictor time series (e.g. global mean surface temperature, Tglobal) – referred to as the "training" of the CPSM. This training uses a regression model to derive fit-coef...

  4. AspectJ in action practical aspect-oriented programming

    CERN Document Server

    Laddad, Ramnivas

    2003-01-01

    A guide to aspect-oriented programming and the AspectJ language, this book provides code examples that enable quick implementation of functionality in a system. Thorough introductions to AOP and AspectJ will help developers learn or advance their knowledge of AspectJ. Examples of everyday situations in which AspectJ solutions can be applied, such as logging, policy enforcement, resource pooling, business logic, thread-safety, authentication and authorization, and transaction management are provided. In addition, design patterns and idioms are covered, as is business rule implementation. The latest technologies, such as JEES, JAAS, and log4j, are explained and connected with AspectJ.

  5. Effect of solvents on the pattern formation in a Belousov-Zhabotinsky reaction embedded into a microemulsion

    Science.gov (United States)

    Dähmlow, Patricia; Vanag, Vladimir K.; Müller, Stefan C.

    2014-01-01

    Using the ferroin- and the bathoferroin-catalyzed Belousov-Zhabotinsky (BZ) reaction embedded in the sodium-bis (2-ethylhexyl) sulfosuccinate (AOT) water-in-oil microemulsion, we observed different patterns occurring in two different solvents, hexane and octane. Turing patterns were found in both solvents with ferroin. They differ in their interaction with coexisting bulk oscillations, such that a new excitation front was formed around the evolving Turing patterns in hexane. However, in octane, the bulk oscillation merged with the evolving patterns, forming a new excitation front, which propagated into two directions: towards the existing patterns and away from them. For the bathoferroin-catalyzed BZ reaction, patterns like dash waves, jumping waves, and bubble waves were found in both solvents having different wavelengths. A curvature dependence of the splitting and merging of dashes was found.

  6. Dune field pattern formation and recent transporting winds in the Olympia Undae Dune Field, north polar region of Mars

    Science.gov (United States)

    Ewing, Ryan C.; Peyret, Aymeric-Pierre B.; Kocurek, Gary; Bourke, Mary

    2010-08-01

    High-Resolution Imaging Science Experiment (HiRISE) imagery of the central Olympia Undae Dune Field in the north polar region of Mars shows a reticulate dune pattern consisting of two sets of nearly orthogonal dune crestlines, with apparent slipfaces on the primary crests, ubiquitous wind ripples, areas of coarse-grained wind ripples, and deflated interdune areas. Geomorphic evidence and dune field pattern analysis of dune crest length, spacing, defect density, and orientation indicates that the pattern is complex, representing two constructional generations of dunes. The oldest and best-organized generation forms the primary crestlines and is transverse to circumpolar easterly winds. Gross bed form-normal analysis of the younger pattern of crestlines indicates that it emerged with both circumpolar easterly winds and NE winds and is reworking the older pattern. Mapping of secondary flow fields over the dunes indicates that the most recent transporting winds were from the NE. The younger pattern appears to represent an influx of sediment to the dune field associated with the development of the Olympia Cavi reentrant, with NE katabatic winds channeling through the reentrant. A model of the pattern reformation based upon the reconstructed primary winds and resulting secondary flow fields shows that the development of the secondary pattern is controlled by the boundary condition of the older dune topography.

  7. Pattern Formation and Chaotic Dynamics in a Cross-Flow Catalytic Converter with Kinetics of Detoxification of Exhaust Gases

    OpenAIRE

    Kohout, M.

    2012-01-01

    In this contribution, the range of patterns occurring due to interaction of transport and reactions characteristic of the three-way catalytic converter (TWC) have been explored. We examined whether and how spatiotemporal structures such as spatially nonhomogeneous steady states and travelling waves are produced. Furthermore we found that the system displays a wide variety of chaotic spatiotemporal patterns, which were examined in detail.

  8. Temperature control of pattern formation in the Ru(bpy)(3)(2+)-catalyzed BZ-AOT system.

    Science.gov (United States)

    McIlwaine, Rachel; Vanag, Vladimir K; Epstein, Irving R

    2009-03-14

    Using temperature as a control parameter, we observe a transition from stationary Turing patterns at T = 15-20 degrees C to traveling waves at T = 50 degrees C (and above) in the Ru(bpy)(3)(2+)-catalyzed Belousov-Zhabotinsky (BZ) reaction incorporated into the water nanodroplets of a water-in-oil aerosol OT (AOT) microemulsion. At constant chemical composition, molar ratio and droplet fraction, the transition takes place via a series of stable patterns, including oscillatory Turing patterns (at 35-40 degrees C) and reversed oscillatory Turing patterns (at 50 degrees C). We attribute the pattern transitions to a temperature-induced percolation transition of the BZ-AOT microemulsion, implying a change from isolated water nanodroplets to a system-spanning network of water channels. PMID:19240935

  9. Soil formation.

    NARCIS (Netherlands)

    Breemen, van N.; Buurman, P.

    1998-01-01

    Soil Formation deals with qualitative and quantitative aspects of soil formation (or pedogenesis) and the underlying chemical, biological, and physical processes. The starting point of the text is the process - and not soil classification. Effects of weathering and new formation of minerals, mobilis

  10. Laser-induced pattern formation in liquid sulfur. An indication of laser-induced phase transition to ordered polymer

    Science.gov (United States)

    Sakaguchi, Y.; Tamura, K.

    2007-04-01

    Liquid sulfur is a well-known liquid which exhibits a polymerization transition at T_p=159 °C. Recently, it was found from our experiments that such a transition can be induced below Tp through laser illumination and that an iridescent pattern appears under strong illumination with a pulsed laser of more than 60 mJ/cm2 pulse. It is proposed that the visible change in iridescence is due to a macroscopic reconstruction of laser-generated polymers and that a laser-induced phase transition takes place from a freely expanded polymer phase to an ordered polymer phase when increasing the laser illumination. To further examine this possibility, the time variation of the iridescent pattern has been fully investigated using a macro lens, a polarized microscope and an optical microscope. In an analysis of the iridescent pattern, a rapid decrease in the area was observed after an initial slow decrease, suggesting a type of phase transition. Results from the observation of a quenched sulfur sample with a polarized microscope gave evidence that the iridescent region consists of polymers. Through observation of the liquid with a microscope, a striped pattern with micrometer sized spacing was noted in the iridescent pattern. A drastic color change was observed in the pattern from its generation to its disappearance. Sample thickness dependence of the pattern was also observed. These results were well explained by assuming the self-arrangement of laser-generated colloidal polymers.

  11. Evolution-development congruence in pattern formation dynamics: Bifurcations in gene expression and regulation of networks structures.

    Science.gov (United States)

    Kohsokabe, Takahiro; Kaneko, Kunihiko

    2016-01-01

    Search for possible relationships between phylogeny and ontogeny is important in evolutionary-developmental biology. Here we uncover such relationships by numerical evolution and unveil their origin in terms of dynamical systems theory. By representing developmental dynamics of spatially located cells with gene expression dynamics with cell-to-cell interaction under external morphogen gradient, gene regulation networks are evolved under mutation and selection with the fitness to approach a prescribed spatial pattern of expressed genes. For most numerical evolution experiments, evolution of pattern over generations and development of pattern by an evolved network exhibit remarkable congruence. Both in the evolution and development pattern changes consist of several epochs where stripes are formed in a short time, while for other temporal regimes, pattern hardly changes. In evolution, these quasi-stationary regimes are generations needed to hit relevant mutations, while in development, they are due to some gene expression that varies slowly and controls the pattern change. The morphogenesis is regulated by combinations of feedback or feedforward regulations, where the upstream feedforward network reads the external morphogen gradient, and generates a pattern used as a boundary condition for the later patterns. The ordering from up to downstream is common in evolution and development, while the successive epochal changes in development and evolution are represented as common bifurcations in dynamical-systems theory, which lead to the evolution-development congruence. Mechanism of exceptional violation of the congruence is also unveiled. Our results provide a new look on developmental stages, punctuated equilibrium, developmental bottlenecks, and evolutionary acquisition of novelty in morphogenesis.

  12. Evolution-development congruence in pattern formation dynamics: Bifurcations in gene expression and regulation of networks structures.

    Science.gov (United States)

    Kohsokabe, Takahiro; Kaneko, Kunihiko

    2016-01-01

    Search for possible relationships between phylogeny and ontogeny is important in evolutionary-developmental biology. Here we uncover such relationships by numerical evolution and unveil their origin in terms of dynamical systems theory. By representing developmental dynamics of spatially located cells with gene expression dynamics with cell-to-cell interaction under external morphogen gradient, gene regulation networks are evolved under mutation and selection with the fitness to approach a prescribed spatial pattern of expressed genes. For most numerical evolution experiments, evolution of pattern over generations and development of pattern by an evolved network exhibit remarkable congruence. Both in the evolution and development pattern changes consist of several epochs where stripes are formed in a short time, while for other temporal regimes, pattern hardly changes. In evolution, these quasi-stationary regimes are generations needed to hit relevant mutations, while in development, they are due to some gene expression that varies slowly and controls the pattern change. The morphogenesis is regulated by combinations of feedback or feedforward regulations, where the upstream feedforward network reads the external morphogen gradient, and generates a pattern used as a boundary condition for the later patterns. The ordering from up to downstream is common in evolution and development, while the successive epochal changes in development and evolution are represented as common bifurcations in dynamical-systems theory, which lead to the evolution-development congruence. Mechanism of exceptional violation of the congruence is also unveiled. Our results provide a new look on developmental stages, punctuated equilibrium, developmental bottlenecks, and evolutionary acquisition of novelty in morphogenesis. PMID:26678220

  13. Formation of Nulls in Vector Beam Patterns of Monopulse Arrays of Rectangular Waveguides by Correcting Currents in Some Array Elements

    Science.gov (United States)

    Manuilov, B. D.; Bashly, P. N.; Klimukhin, D. V.

    2003-12-01

    In this paper, we consider a method for null synthesis in the vector sum and difference beam patterns of a monopulse array of rectangular waveguides. The synthesis of nulls is reached due to variation of complex currents in some elements. The proposed method eliminates shifts of the primary maximum and the nulls of the sum and difference beam patterns, respectively, of a monopulse array. Numerical studies confirming the efficiency of the proposed method are described.

  14. Evolution‐development congruence in pattern formation dynamics: Bifurcations in gene expression and regulation of networks structures

    Science.gov (United States)

    Kohsokabe, Takahiro

    2016-01-01

    ABSTRACT Search for possible relationships between phylogeny and ontogeny is important in evolutionary‐developmental biology. Here we uncover such relationships by numerical evolution and unveil their origin in terms of dynamical systems theory. By representing developmental dynamics of spatially located cells with gene expression dynamics with cell‐to‐cell interaction under external morphogen gradient, gene regulation networks are evolved under mutation and selection with the fitness to approach a prescribed spatial pattern of expressed genes. For most numerical evolution experiments, evolution of pattern over generations and development of pattern by an evolved network exhibit remarkable congruence. Both in the evolution and development pattern changes consist of several epochs where stripes are formed in a short time, while for other temporal regimes, pattern hardly changes. In evolution, these quasi‐stationary regimes are generations needed to hit relevant mutations, while in development, they are due to some gene expression that varies slowly and controls the pattern change. The morphogenesis is regulated by combinations of feedback or feedforward regulations, where the upstream feedforward network reads the external morphogen gradient, and generates a pattern used as a boundary condition for the later patterns. The ordering from up to downstream is common in evolution and development, while the successive epochal changes in development and evolution are represented as common bifurcations in dynamical‐systems theory, which lead to the evolution‐development congruence. Mechanism of exceptional violation of the congruence is also unveiled. Our results provide a new look on developmental stages, punctuated equilibrium, developmental bottlenecks, and evolutionary acquisition of novelty in morphogenesis. J. Exp. Zool. (Mol. Dev. Evol.) 326B:61–84, 2016. © 2015 The Authors. Journal of Experimental Zoology Part B: Molecular and Developmental Evolution

  15. Mechanical Model of Geometric Cell and Topological Algorithm for Cell Dynamics from Single-Cell to Formation of Monolayered Tissues with Pattern

    KAUST Repository

    Kachalo, Sëma

    2015-05-14

    Geometric and mechanical properties of individual cells and interactions among neighboring cells are the basis of formation of tissue patterns. Understanding the complex interplay of cells is essential for gaining insight into embryogenesis, tissue development, and other emerging behavior. Here we describe a cell model and an efficient geometric algorithm for studying the dynamic process of tissue formation in 2D (e.g. epithelial tissues). Our approach improves upon previous methods by incorporating properties of individual cells as well as detailed description of the dynamic growth process, with all topological changes accounted for. Cell size, shape, and division plane orientation are modeled realistically. In addition, cell birth, cell growth, cell shrinkage, cell death, cell division, cell collision, and cell rearrangements are now fully accounted for. Different models of cell-cell interactions, such as lateral inhibition during the process of growth, can be studied in detail. Cellular pattern formation for monolayered tissues from arbitrary initial conditions, including that of a single cell, can also be studied in detail. Computational efficiency is achieved through the employment of a special data structure that ensures access to neighboring cells in constant time, without additional space requirement. We have successfully generated tissues consisting of more than 20,000 cells starting from 2 cells within 1 hour. We show that our model can be used to study embryogenesis, tissue fusion, and cell apoptosis. We give detailed study of the classical developmental process of bristle formation on the epidermis of D. melanogaster and the fundamental problem of homeostatic size control in epithelial tissues. Simulation results reveal significant roles of solubility of secreted factors in both the bristle formation and the homeostatic control of tissue size. Our method can be used to study broad problems in monolayered tissue formation. Our software is publicly

  16. Phytoplankton aggregate formation: observations of patterns and mechanisms of cell sticking and the significance of exopolymeric material

    DEFF Research Database (Denmark)

    Kiørboe, Thomas; Hansen, Jorgen L. S.

    1993-01-01

    the potential for aggregate formation. In the laboratory, we examined variation in stickiness in five species of diatoms and two species of flagellates grown in batch cultures. We also investigated the production of particulate mucus by phytoplankton cells and its role in aggregate formation, and we studied...... cause other, non-sticky particles to coagulate. This emphasizes the potential importance of diatom-derived particulate mucus for particle flocculation in the ocean....

  17. Spatial pattern formation of microbes at the soil microscale affect soil C and N turnover in an individual-based microbial community model

    Science.gov (United States)

    Kaiser, Christina; Evans, Sarah; Dieckmann, Ulf; Widder, Stefanie

    2016-04-01

    At the μm-scale, soil is a highly structured and complex environment, both in physical as well as in biological terms, characterized by non-linear interactions between microbes, substrates and minerals. As known from mathematics and theoretical ecology, spatial structure significantly affects the system's behaviour by enabling synergistic dynamics, facilitating diversity, and leading to emergent phenomena such as self-organisation and self-regulation. Such phenomena, however, are rarely considered when investigating mechanisms of microbial soil organic matter turnover. Soil organic matter is the largest terrestrial reservoir for organic carbon (C) and nitrogen (N) and plays a pivotal role in global biogeochemical cycles. Still, the underlying mechanisms of microbial soil organic matter buildup and turnover remain elusive. We explored mechanisms of microbial soil organic matter turnover using an individual-based, stoichiometrically and spatially explicit computer model, which simulates the microbial de-composer system at the soil microscale (i.e. on a grid of 100 x 100 soil microsites). Soil organic matter dynamics in our model emerge as the result of interactions among individual microbes with certain functional traits (f.e. enzyme production rates, growth rates, cell stoichiometry) at the microscale. By degrading complex substrates, and releasing labile substances microbes in our model continusly shape their environment, which in turn feeds back to spatiotemporal dynamics of the microbial community. In order to test the effect of microbial functional traits and organic matter input rate on soil organic matter turnover and C and N storage, we ran the model into steady state using continuous inputs of fresh organic material. Surprisingly, certain parameter settings that induce resource limitation of microbes lead to regular spatial pattern formation (f.e. moving spiral waves) of microbes and substrate at the μm-scale at steady-state. The occurrence of these

  18. Fluorescent antibody test, quantitative polymerase chain reaction pattern and clinical aspects of rabies virus strains isolated from main reservoirs in Brazil

    Directory of Open Access Journals (Sweden)

    Camila Appolinário

    2015-10-01

    Full Text Available ABSTRACTRabies virus (RABV isolated from different mammals seems to have unique characteristics that influence the outcome of infection. RABV circulates in nature and is maintained by reservoirs that are responsible for the persistence of the disease for almost 4000 years. Considering the different pattern of pathogenicity of RABV strains in naturally and experimentally infected animals, the aim of this study was to analyze the characteristics of RABV variants isolated from the main Brazilian reservoirs, being related to a dog (variant 2,Desmodus rotundus (variant 3, crab eating fox, marmoset, and Myotis spp. Viral replication in brain tissue of experimentally infected mouse was evaluated by two laboratory techniques and the results were compared to clinical evolution from five RABV variants. The presence of the RABV was investigated in brain samples by fluorescent antibody test (FAT and real time polymerase chain reaction (qRT-PCR for quantification of rabies virus nucleoprotein gene (N gene. Virus replication is not correlated with clinical signs and evolution. The pattern of FAT is associated with RABV replication levels. Virus isolates from crab eating fox and marmoset had a longer evolution period and higher survival rate suggesting that the evolution period may contribute to the outcome. RABV virus variants had independent characteristics that determine the clinical evolution and survival of the infected mice.

  19. Fluorescent antibody test, quantitative polymerase chain reaction pattern and clinical aspects of rabies virus strains isolated from main reservoirs in Brazil.

    Science.gov (United States)

    Appolinário, Camila; Allendorf, Susan Dora; Vicente, Acácia Ferreira; Ribeiro, Bruna Devidé; Fonseca, Clóvis Reinaldo da; Antunes, João Marcelo; Peres, Marina Gea; Kotait, Ivanete; Carrieri, Maria Luiza; Megid, Jane

    2015-01-01

    Rabies virus (RABV) isolated from different mammals seems to have unique characteristics that influence the outcome of infection. RABV circulates in nature and is maintained by reservoirs that are responsible for the persistence of the disease for almost 4000 years. Considering the different pattern of pathogenicity of RABV strains in naturally and experimentally infected animals, the aim of this study was to analyze the characteristics of RABV variants isolated from the main Brazilian reservoirs, being related to a dog (variant 2), Desmodus rotundus (variant 3), crab eating fox, marmoset, and Myotis spp. Viral replication in brain tissue of experimentally infected mouse was evaluated by two laboratory techniques and the results were compared to clinical evolution from five RABV variants. The presence of the RABV was investigated in brain samples by fluorescent antibody test (FAT) and real time polymerase chain reaction (qRT-PCR) for quantification of rabies virus nucleoprotein gene (N gene). Virus replication is not correlated with clinical signs and evolution. The pattern of FAT is associated with RABV replication levels. Virus isolates from crab eating fox and marmoset had a longer evolution period and higher survival rate suggesting that the evolution period may contribute to the outcome. RABV virus variants had independent characteristics that determine the clinical evolution and survival of the infected mice.

  20. Pattern formation in a two-component reaction-diffusion system with delayed processes on a network

    Science.gov (United States)

    Petit, Julien; Asllani, Malbor; Fanelli, Duccio; Lauwens, Ben; Carletti, Timoteo

    2016-11-01

    Reaction-diffusion systems with time-delay defined on complex networks have been studied in the framework of the emergence of Turing instabilities. The use of the Lambert W-function allowed us to get explicit analytic conditions for the onset of patterns as a function of the main involved parameters, the time-delay, the network topology and the diffusion coefficients. Depending on these parameters, the analysis predicts whether the system will evolve towards a stationary Turing pattern or rather to a wave pattern associated to a Hopf bifurcation. The possible outcomes of the linear analysis overcome the respective limitations of the single-species case with delay, and that of the classical activator-inhibitor variant without delay. Numerical results gained from the Mimura-Murray model support the theoretical approach.

  1. Epidemiological aspects of bovine trypanosomosis in an endemic focus of eastern Zambia: The role of trypanosome strain variability in disease pattern

    Directory of Open Access Journals (Sweden)

    Justin Masumu

    2012-06-01

    Full Text Available Bovine trypanosomosis displays various epidemiological aspects in various areas. In some instances the disease has a high prevalence in animals with high impact on production whereas in other cases the disease has a low impact on production despite a high level of infection in animals. In addition epidemiological changes are frequently observed in various areas and are related to many factors including the vectors, the host, the parasites, the environment as well as the livestock management. However the implication of these factors in these changes is not fully elucidated. In eastern Zambia, factors predicting the establishment of severe infection in cattle are all present. However trypanosomosis occurring in cattle in this area has a low impact on livestock production. Several studies on the characterisation of trypanosome strains circulating in domestic and wild animals have been conducted in order to clarify the epidemiology of this disease in this area. These studies aimed at evaluating genetic and biological characteristics of these strains including their virulence profiles, their transmissibility by tsetse flies, their resistance to drugs and interference between different strains. In this review these findings are analysed in order to elucidate the implication of trypanosome strain variability in the distribution and the expression of this disease in the study area. The evolutionary trends of the situation occurring in this study area are also explained. Use of these findings is the context of disease control in the study area is further discussed.

  2. Spontaneous formation of spiral-like patterns with distinct periodic physical properties by confined electrodeposition of Co-In disks

    Science.gov (United States)

    Golvano-Escobal, Irati; Gonzalez-Rosillo, Juan Carlos; Domingo, Neus; Illa, Xavi; López-Barberá, José Francisco; Fornell, Jordina; Solsona, Pau; Aballe, Lucia; Foerster, Michael; Suriñach, Santiago; Baró, Maria Dolors; Puig, Teresa; Pané, Salvador; Nogués, Josep; Pellicer, Eva; Sort, Jordi

    2016-07-01

    Spatio-temporal patterns are ubiquitous in different areas of materials science and biological systems. However, typically the motifs in these types of systems present a random distribution with many possible different structures. Herein, we demonstrate that controlled spatio-temporal patterns, with reproducible spiral-like shapes, can be obtained by electrodeposition of Co-In alloys inside a confined circular geometry (i.e., in disks that are commensurate with the typical size of the spatio-temporal features). These patterns are mainly of compositional nature, i.e., with virtually no topographic features. Interestingly, the local changes in composition lead to a periodic modulation of the physical (electric, magnetic and mechanical) properties. Namely, the Co-rich areas show higher saturation magnetization and electrical conductivity and are mechanically harder than the In-rich ones. Thus, this work reveals that confined electrodeposition of this binary system constitutes an effective procedure to attain template-free magnetic, electric and mechanical surface patterning with specific and reproducible shapes.

  3. Regeneration of surgically created mixed-handed axolotl forelimbs: pattern formation in the dorsal-ventral axis.

    Science.gov (United States)

    Holder, N; Weekes, C

    1984-08-01

    The regeneration of surgically created mixed-handed limb stumps is examined in the axolotl. Operations were performed in the lower arm and upper arm regions and grafts were allowed to heal for approximately one month prior to amputation or were amputated immediately. In the lower arm group both anterior and posterior limb halves were inverted, whereas only posterior halves were inverted in the upper arm group. Almost all the limbs regenerated were normal in the anterior-posterior axis, whereas a range of limb types were found when the dorsal-ventral axis was analysed using the metacarpal muscle pattern and epidermal Leydig cell number as positional markers. The carpal and forearm muscle patterns were also analysed in order to assess whether the pattern determined from analysis at the metacarpal level reflected that seen at more proximal levels. The results are discussed in terms of the possible role of cell contribution from the stump to the blastema and the relevance of the study to models of pattern regulation.

  4. Spatial pattern formation and intraspecific competition of anabasis aphylla l. population in the diluvial fan of junggar basin, nw china

    International Nuclear Information System (INIS)

    Using conventional nearest neighbour analysis and Ripley's L-function, the goal of this study was to analyze spatial patterns of Anabasis aphylla plants in order to investigate underlying competitive processes that shape the population spatial structure from diluvial fan in Junggar Basin, NW China. We found that the spatial patterns of all growth stages were aggregated in the three study plots, and seedling and juvenile plants were more aggregated than expected by chance. Positive associations among growth stages of A. aphylla population were found at a small scale while negative associations of seedling and juvenile relative to adult plants were shown at a larger scale. The processes such as dispersal, seedling establishment, environmental heterogeneity, plant interactions and disturbance may have acted individually or in concert with other processes to produce the aggregated patterns and competitive relationship. Moreover, these findings suggested that the aggregated distribution and the competitive interaction between A. aphylla plants in the diluvial fan reflected not only in mortality, but also in decreased performance (smaller canopy) that was an important characteristic of drought-enduring plant, thus preventing a regular distribution pattern. (author)

  5. A CANDELS-3D-HST synergy: Resolved star formation patterns at 0.7 < z < 1.5

    Energy Technology Data Exchange (ETDEWEB)

    Wuyts, Stijn; Förster Schreiber, Natascha M.; Genzel, Reinhard; Lutz, Dieter; Rosario, David [Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, Giessenbachstr., D-85741 Garching (Germany); Nelson, Erica J.; Van Dokkum, Pieter G.; Momcheva, Ivelina [Astronomy Department, Yale University, New Haven, CT 06511 (United States); Brammer, Gabe [European Southern Observatory, Alonson de Córdova 3107, Casilla 19001, Vitacura, Santiago (Chile); Chang, Yu-Yen [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Faber, Sandra M. [UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Ferguson, Henry C.; Grogin, Norman A.; Koekemoer, Anton M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Franx, Marijn; Fumagalli, Mattia [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands); Kocevski, Dale D. [Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506 (United States); Lundgren, Britt [Department of Astronomy, University of Wisconsin-Madison, Madison, WI 53706 (United States); McGrath, Elizabeth J. [Department of Physics and Astronomy, Colby College, Waterville, ME 0490 (United States); Skelton, Rosalind E., E-mail: swuyts@mpe.mpg.de [South African Astronomical Observatory, Observatory Road, 7925 Cape Town (South Africa); and others

    2013-12-20

    We analyze the resolved stellar populations of 473 massive star-forming galaxies at 0.7 < z < 1.5, with multi-wavelength broadband imaging from CANDELS and Hα surface brightness profiles at the same kiloparsec resolution from 3D-HST. Together, this unique data set sheds light on how the assembled stellar mass is distributed within galaxies, and where new stars are being formed. We find the Hα morphologies to resemble more closely those observed in the ACS I band than in the WFC3 H band, especially for the larger systems. We next derive a novel prescription for Hα dust corrections, which accounts for extra extinction toward H II regions. The prescription leads to consistent star formation rate (SFR) estimates and reproduces the observed relation between the Hα/UV luminosity ratio and visual extinction, on both a pixel-by-pixel and a galaxy-integrated level. We find the surface density of star formation to correlate with the surface density of assembled stellar mass for spatially resolved regions within galaxies, akin to the so-called 'main sequence of star formation' established on a galaxy-integrated level. Deviations from this relation toward lower equivalent widths are found in the inner regions of galaxies. Clumps and spiral features, on the other hand, are associated with enhanced Hα equivalent widths, bluer colors, and higher specific SFRs compared to the underlying disk. Their Hα/UV luminosity ratio is lower than that of the underlying disk, suggesting that the ACS clump selection preferentially picks up those regions of elevated star formation activity that are the least obscured by dust. Our analysis emphasizes that monochromatic studies of galaxy structure can be severely limited by mass-to-light ratio variations due to dust and spatially inhomogeneous star formation histories.

  6. Formation of dot arrays with a pitch of 20 nm x 20 nm for patterned media using 30 keV EB drawing on thin calixarene resist

    Energy Technology Data Exchange (ETDEWEB)

    Mohamad, Zulfakri bin [Department of Nano-Material System, Graduate School of Engineering, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma 376-8515 (Japan); Shirai, Masumi [Department of Nano-Material System, Graduate School of Engineering, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma 376-8515 (Japan); Sone, Hayato [Department of Production Science and Technology, Graduate School of Engineering, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma 376-8515 (Japan); Hosaka, Sumio [Department of Production Science and Technology, Graduate School of Engineering, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma 376-8515 (Japan); Kodera, Masatoshi [Department of Electronics, Information and Communication Engineering, Osaka Institute of Technology, 5-16-1 Omiya, Asahi-ku, Osaka 535-8585 (Japan)

    2008-01-16

    We studied the possibility of achieving very fine-pitch dot arrays with a pitch of 20 nm x 20 nm using 30 keV electron beam (EB) drawing on negative calixarene resist. In order to form such patterns, we studied the dependence on resist thickness of the dot size and the packing. We propose EB drawing on an extremely thin film for very highly packed dot-array formation. Our experimental results demonstrate the possibility of forming highly packed dot-array patterns with a pitch of 20 nm x 20 nm and a resist thickness of about 13 nm, which corresponds to about 1.6 Tbits in{sup -2}.

  7. Instability and Pattern Formation in Three-Species Food Chain Model via Holling Type II Functional Response on a Circular Domain

    Science.gov (United States)

    Abid, Walid; Yafia, R.; Aziz Alaoui, M. A.; Bouhafa, H.; Abichou, A.

    2015-06-01

    This paper is devoted to the study of food chain predator-prey model. This model is given by a reaction-diffusion system defined on a circular spatial domain, which includes three-state variables namely, prey and intermediate predator and top predator and incorporates the Holling type II and a modified Leslie-Gower functional response. The aim of this paper is to investigate theoretically and numerically the asymptotic behavior of the interior equilibrium of the model. The local and global stabilities of the positive steady-state solution and the conditions that enable the occurrence of Hopf bifurcation and Turing instability in the circular spatial domain are proved. In the end, we carry out numerical simulations to illustrate how biological processes can affect spatiotemporal pattern formation in a disc spatial domain and different types of spatial patterns with respect to different time steps and diffusion coefficients are obtained.

  8. The impact of alcohol consumption on patterns of union formation in Russia 1998-2010: an assessment using longitudinal data.

    Science.gov (United States)

    Keenan, Katherine; Kenward, Michael G; Grundy, Emily; Leon, David A

    2014-01-01

    Using data from the Russian Longitudinal Monitoring Survey, 1998-2010, we investigated the extent to which patterns of alcohol consumption in Russia are associated with the subsequent likelihood of entry into cohabitation and marriage. Using discrete-time event history analysis we estimated for 16-50 year olds the extent to which the probabilities of entry into the two types of union were affected by the amount of alcohol drunk and the pattern of drinking, adjusted to allow for social and demographic factors including income, employment, and health. The results show that individuals who did not drink alcohol were less likely to embark on either cohabitation or marriage, that frequent consumption of alcohol was associated with a greater chance of entering unmarried cohabitation than of entering into a marriage, and that heavy drinkers were less likely to convert their relationship from cohabitation to marriage. PMID:25320843

  9. Pattern formation on polymer resist by solvent-assisted nanoimprinting with PDMS mold as a solvent transport medium

    International Nuclear Information System (INIS)

    Solvent-vapor-assisted imprinting lithography (SVAIL) using a 1 mm thick flexible polydimethylsiloxane (PDMS) membrane mold as a solvent transport medium in a vapor environment is demonstrated. By adjusting the solvent vapor pressure, this transport mechanism provides a sufficient amount of solvent to soften the thin polystyrene resist (<100 nm) and avoids the deformation of imprinted nanopatterns due to excess solvent that is problematic with other methods. The results show that SVAIL has potential for large-area patterning because the molding of the softened polymer can be performed without external loading. Localized molding and conformal contact with a curved surface allow multiple imprinting to be performed to obtain more complex, two-dimensional hierarchical structures using simple stripe-patterned stamps

  10. The Rim101p/PacC Pathway and Alkaline pH Regulate Pattern Formation in Yeast Colonies

    OpenAIRE

    Piccirillo, Sarah; White, Melissa G.; Murphy, Jeffrey C; Law, Douglas J.; Honigberg, Saul M.

    2010-01-01

    Multicellular organisms utilize cell-to-cell signals to build patterns of cell types within embryos, but the ability of fungi to form organized communities has been largely unexplored. Here we report that colonies of the yeast Saccharomyces cerevisiae formed sharply divided layers of sporulating and nonsporulating cells. Sporulation initiated in the colony's interior, and this region expanded upward as the colony matured. Two key activators of sporulation, IME1 and IME2, were initially transc...

  11. Discharge competence and pattern formation in peatlands: a meta-ecosystem model of the Everglades ridge-slough landscape.

    Science.gov (United States)

    Heffernan, James B; Watts, Danielle L; Cohen, Matthew J

    2013-01-01

    Regular landscape patterning arises from spatially-dependent feedbacks, and can undergo catastrophic loss in response to changing landscape drivers. The central Everglades (Florida, USA) historically exhibited regular, linear, flow-parallel orientation of high-elevation sawgrass ridges and low-elevation sloughs that has degraded due to hydrologic modification. In this study, we use a meta-ecosystem approach to model a mechanism for the establishment, persistence, and loss of this landscape. The discharge competence (or self-organizing canal) hypothesis assumes non-linear relationships between peat accretion and water depth, and describes flow-dependent feedbacks of microtopography on water depth. Closed-form model solutions demonstrate that 1) this mechanism can produce spontaneous divergence of local elevation; 2) divergent and homogenous states can exhibit global bi-stability; and 3) feedbacks that produce divergence act anisotropically. Thus, discharge competence and non-linear peat accretion dynamics may explain the establishment, persistence, and loss of landscape pattern, even in the absence of other spatial feedbacks. Our model provides specific, testable predictions that may allow discrimination between the self-organizing canal hypotheses and competing explanations. The potential for global bi-stability suggested by our model suggests that hydrologic restoration may not re-initiate spontaneous pattern establishment, particularly where distinct soil elevation modes have been lost. As a result, we recommend that management efforts should prioritize maintenance of historic hydroperiods in areas of conserved pattern over restoration of hydrologic regimes in degraded regions. This study illustrates the value of simple meta-ecosystem models for investigation of spatial processes. PMID:23671708

  12. Discharge Competence and Pattern Formation in Peatlands: A Meta-Ecosystem Model of the Everglades Ridge-Slough Landscape

    OpenAIRE

    Heffernan, James B.; Danielle L Watts; Cohen, Matthew J.

    2013-01-01

    Regular landscape patterning arises from spatially-dependent feedbacks, and can undergo catastrophic loss in response to changing landscape drivers. The central Everglades (Florida, USA) historically exhibited regular, linear, flow-parallel orientation of high-elevation sawgrass ridges and low-elevation sloughs that has degraded due to hydrologic modification. In this study, we use a meta-ecosystem approach to model a mechanism for the establishment, persistence, and loss of this landscape. T...

  13. Discharge competence and pattern formation in peatlands: a meta-ecosystem model of the Everglades ridge-slough landscape.

    Directory of Open Access Journals (Sweden)

    James B Heffernan

    Full Text Available Regular landscape patterning arises from spatially-dependent feedbacks, and can undergo catastrophic loss in response to changing landscape drivers. The central Everglades (Florida, USA historically exhibited regular, linear, flow-parallel orientation of high-elevation sawgrass ridges and low-elevation sloughs that has degraded due to hydrologic modification. In this study, we use a meta-ecosystem approach to model a mechanism for the establishment, persistence, and loss of this landscape. The discharge competence (or self-organizing canal hypothesis assumes non-linear relationships between peat accretion and water depth, and describes flow-dependent feedbacks of microtopography on water depth. Closed-form model solutions demonstrate that 1 this mechanism can produce spontaneous divergence of local elevation; 2 divergent and homogenous states can exhibit global bi-stability; and 3 feedbacks that produce divergence act anisotropically. Thus, discharge competence and non-linear peat accretion dynamics may explain the establishment, persistence, and loss of landscape pattern, even in the absence of other spatial feedbacks. Our model provides specific, testable predictions that may allow discrimination between the self-organizing canal hypotheses and competing explanations. The potential for global bi-stability suggested by our model suggests that hydrologic restoration may not re-initiate spontaneous pattern establishment, particularly where distinct soil elevation modes have been lost. As a result, we recommend that management efforts should prioritize maintenance of historic hydroperiods in areas of conserved pattern over restoration of hydrologic regimes in degraded regions. This study illustrates the value of simple meta-ecosystem models for investigation of spatial processes.

  14. The formation of various multi-soliton patterns and noise-like pulse in a fiber laser passively mode-locked by a topological insulator based saturable absorber

    International Nuclear Information System (INIS)

    We experimentally investigated the formation of various multi-soliton patterns and noise-like (NL) pulses in an erbium-doped fiber laser passively mode-locked by a new type of saturable absorber: topological insulator. With the increase of pump power, various multi-soliton operation states—ordered, chaotic and bunched multiple-soliton—were subsequently obtained. Once the pump power exceeds 401 mW, an NL pulse state emerged, with a maximum 3 dB bandwidth of about 9.3 nm. This systematic study clearly demonstrated that a topological insulator could be an effective saturable absorber for the formation of various soliton operation states in a fiber laser cavity

  15. The formation of various multi-soliton patterns and noise-like pulse in a fiber laser passively mode-locked by a topological insulator based saturable absorber

    Science.gov (United States)

    Chen, Yu; Wu, Man; Tang, Pinghua; Chen, Shuqing; Du, Juan; Jiang, Guobao; Li, Ying; Zhao, Chujun; Zhang, Han; Wen, Shuangchun

    2014-05-01

    We experimentally investigated the formation of various multi-soliton patterns and noise-like (NL) pulses in an erbium-doped fiber laser passively mode-locked by a new type of saturable absorber: topological insulator. With the increase of pump power, various multi-soliton operation states—ordered, chaotic and bunched multiple-soliton—were subsequently obtained. Once the pump power exceeds 401 mW, an NL pulse state emerged, with a maximum 3 dB bandwidth of about 9.3 nm. This systematic study clearly demonstrated that a topological insulator could be an effective saturable absorber for the formation of various soliton operation states in a fiber laser cavity.

  16. WBC27, an Adenosine Tri-phosphate-binding Cassette Protein, Controls Pollen Wall Formation and Patterning in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    Xiao-Ying Dou; Ke-Zhen Yang; Yi Zhang; Wei Wang; Xiao-Lei Liu; Li-Qun Chen; Xue-Qin Zhang; De Ye

    2011-01-01

    In flowering plants, the exine components are derived from tapetum. Despite its importance to sexual plant reproduction, little is known about the translocation of exine materials from tapetum to developing microspores. Here we report functional characterization of the arabidopsis WBC27 gene. WBC27 encodes an adenosine tri-phosphate binding cassette (ABC) transporter and is expressed preferentially in tapetum. Mutation of WBC27 disrupted the exine formation. The wbc27 mutant microspores began to degenerate once released from tetrads and most of the microspores collapsed at the uninucleate stage. Only a small number of wbc27-1 microspores could develop into tricellular pollen grains. These survival pollen grains lacked exine and germinated in the anther before anthesis. All of these results suggest that the ABC transporter, WBC27 plays important roles in the formation of arabidopsis exine, possibly by translocation of lipidic precursors of sporopollenin from tapetum to developing microspores.

  17. In-situ observation of pattern formation during the catalytic CO-oxidation on Pt{110} using Low Energy Electron Microscopy

    International Nuclear Information System (INIS)

    This study describes the spatio-temporal pattern formation in the catalytic oxidation of carbon monoxide on Pt(110) observed by Low Energy Electron Microscopy (LEEM) and Mirror Electron Microscopy (MEM). Compared to Photo Emission Electron Microscopy (PEEM), LEEM has a superior resolution and a contrast mechanism based on diffraction. This enables us to observe the properties and dynamics of the substrate like reconstruction, steps and roughening of the surface. The experimental setup has been enhanced by mounting a new electron gun, a feedback controlled gas inlet and a current controlled radiative heating device. This improved considerably the operability, the resolution, the electron intensity and the precision of the parameter settings (p(CO), p(O2), T). Thus it was possible to study the dynamic processes on the surface with a lateral resolution of 50um and a time resolution of 1/25s having a pressure of 10-5mbar. As a result of strong CO-gasphase coupling in the CO+O2/Pt{110} system the surface can undergo spatially uniform oscillations. Changes in the surface reflectivity for low energy electrons have been observed at numerous incident electron energies. These measurements have been interpreted in terms of adsorbate coverage and the degree of 1x2 reconstruction. It is then possible to arrive at a complete description of such an oscillatory cycle. Due to the mass balance in the reactor the ratio of the partialpressures p(O2) and p(CO) is changed differently in the high rate and low rate branch. Therfore gas phase coupling has a strong influence on the pattern formation, and oscillations in the CO2-rate change the pattern formation oscillatory. Taking advantage of the diffraction contrast mechanism and the superior resolution of the LEEM it is possible to investigate the fine structure of reaction diffusion fronts during propagation. The dynamics of changes in the adsorbate coverage (CO und O2) is significantly faster than that of the changes in substrate

  18. The possible role of oxides and/or elements in the transformation of PCDDs in us ball clay exhibiting. The 'Natural Formation' pattern

    Energy Technology Data Exchange (ETDEWEB)

    Gadomski, D.; Irvine, R. [Notre Dame Univ., IN (United States); Tysklind, M.; Andersson, R. [Umeaa Univ. (Sweden)

    2004-09-15

    At Dioxin 2003, we reported the 2,3,7,8-substituted PCDD/F results from the analysis of a ball clay core exhibiting the ''natural formation'' pattern from Kentucky, USA. In general, all 8 samples contained elevated levels of 2,3,7,8-PCDDs, with increasing PCDD concentrations with increasing chlorine substitution. Moreover, furans were only detected in two of the samples at extremely low concentrations. WHO-TEQs ranged from 180 to 2,500 pg WHO-TEQ/g dm, with 1,2,3,7,8- PeCDD and 1,2,3,7,8,9-HxCDD contributing most to the TEQ. The results from that study were the first to provide information on the vertical changes in both PCDD congener profile and concentrations within a clay core exhibiting this unique ''natural formation'' pattern. In addition, it confirmed the pattern found by others in ball clay and kaolin samples from different regions of the United States, Germany, and Spain. Although all samples from that study exhibit the ''natural formation'' pattern, one noticeable difference was the heptaCDD ratio. 1,2,3,4,6,7,8-HpCDD was on average 2.1 times greater than 1,2,3,4,6,7,9-HpCDD. This is in direct contrast to what others have reported for ball clay, kaolin, and even sediment samples displaying this unique PCDD/F congener profile. Ferrario et al., reported a mean 1,2,3,4,6,7,8-HpCDD/1,2,3,4,6,7,9-HpCDD ratio of 0.67.2 Prange et al., found that this ratio ranged from 0.36 to 0.83 in kaolin samples from Queensland, Australia. In this study, we report isomer specific PCDD results from the analysis of the ball clay core samples from Kentucky to determine if the dechlorination pattern observed is similar to what Gaus et al. found. Also, Principal Component Analysis (PCA) was used to evaluate the isomer specific data along with the bulk mineralogical, elemental and oxide analyses. The possible role of oxides and/or elements aiding in the dechlorination is discussed.

  19. Analysis of biofilm formation and antibiotic susceptibility pattern of uropathogens in patients admitted in a tertiary care hospital in India

    Directory of Open Access Journals (Sweden)

    Ruchi A Tayal

    2015-01-01

    Full Text Available Background: Microorganisms attach to surfaces and produce polysaccharides resulting in the formation of biofilms and providing an ideal niche for the exchange of genetic material leading to the emergence of drug-resistant pathogens. Biofilms can develop on anatomical surfaces and implants producing chronic and intractable infections. Aims: Detection of biofilm formation and comparison of antibiotic resistance between biofilm producers and nonproducers. Study Design: Prospective study in which urine specimens from adult patients with urinary tract infection (UTI during the period of the study were analyzed (1 year. Materials and Methods: Mid-stream clean catch urine from noncatheterized and urine aspirated from in-dwelling urinary catheter in catheterized patients were taken for microbiological processing. Wet mounts, Gram-staining, and urine culture were done. Biofilm formation was detected by tissue culture plate method (TCPM. Statistical Analysis: Chi-square test and mid "P" test were used to analyze the data. A value ofP<0.05 was taken as significant. Results: Gram-negative organisms predominated (89%. Biofilm production was detected in 27% isolates. Maximum biofilm production was seen in Enterococcus spp. (71%, followed by Escherichia coli (26%. Biofilm-producing isolates demonstrated higher antibiotic resistance. All the biofilm-producing Enterococcus spp. showed high-level aminoglycoside resistance. The biofilm-producing isolates of Pseudomonas aeruginosa and Klebsiella pneumoniae demonstrated multi-drug resistance. Conclusions: TCPM is an economical phenotypic method which can be used routinely to detect biofilm formation. Biofilms contribute to an increased resistance to antibiotics used for the treatment of UTIs. Therefore, detection of biofilms is recommended for all patients presenting with chronic or recurrent disease.

  20. Distinct patterns of notochord mineralization in zebrafish coincide with the localization of Osteocalcin isoform 1 during early vertebral centra formation

    OpenAIRE

    Bensimon-Brito Anabela; Cardeira João; Cancela Maria; Huysseune Ann; Witten Paul

    2012-01-01

    Abstract Background In chondrichthyans, basal osteichthyans and tetrapods, vertebral bodies have cartilaginous anlagen that subsequently mineralize (chondrichthyans) or ossify (osteichthyans). Chondrocytes that form the vertebral centra derive from somites. In teleost fish, vertebral centrum formation starts in the absence of cartilage, through direct mineralization of the notochord sheath. In a second step, the notochord is surrounded by somite-derived intramembranous bone. In several small ...

  1. SEDIMENTARY PATTERN OF PROTOTYPE BASIN IN THE DEPOSITION PERIOD OF LAIYANG FORMATION AND THE ADVANTAGEOUS AREAS FOR OIL AND GAS EXPLORATION OF JIAOLAI BASIN

    Institute of Scientific and Technical Information of China (English)

    WU Zhiping; LI Ling; LI Wei; ZHOU Yaoqi

    2004-01-01

    Laiyang formation of Jiaolai Basin is the target stratum for oil and gas exploration. By measuring several field sections, the authors find that Laiyang formation reveals the whole processes from development to death of the lake basin and its sedimentary facies differ in different structural locations.Analyses about sedimentary facies and paleocurrent orientations in association with researches about the positive tectonic units such as Dayetou horseback and Chaigou horst indicate that Laiyang sag is a relatively independent sedimentary unit that shows great water depth typical of deep lake or semideep lake and was controlled by Wulongcun fault during the deposition period of Laiyang formation. Its sediments mainly originated from Jiaobei uplift area and Dayetou horseback. Gaomi-Zhucheng sag was a fast-filled basin controlled by Wurong fault and Yishu fault zone, being high in the northeast and low in the northwest and characterized by the development of pluvial facies and fluvial facies in most areas, and with the development of lake facies being limited to local low-lying regions. Selection of advantageous hydrocarbon reservoir areas for exploration purpose mainly relies on the sedimentation pattern of prototype basin and conservation conditions. The central-west area of Laiyang sag covered by overlying Laiyang formation is the most advantageous exploration area.

  2. In vitro megakaryocyte differentiation and proplatelet formation in Ph-negative classical myeloproliferative neoplasms: distinct patterns in the different clinical phenotypes.

    Directory of Open Access Journals (Sweden)

    Alessandra Balduini

    Full Text Available BACKGROUND: Ph-negative myeloproliferative neoplasms (MPNs are clonal disorders that include primary myelofibrosis (PMF, polycythemia vera (PV and essential thrombocythemia (ET. Although the pathogenesis of MPNs is still incompletely understood, an involvement of the megakaryocyte lineage is a distinctive feature. METHODOLOGY/PRINCIPAL FINDINGS: We analyzed the in vitro megakaryocyte differentiation and proplatelet formation in 30 PMF, 8 ET, 8 PV patients, and 17 healthy controls (CTRL. Megakaryocytes were differentiated from peripheral blood CD34(+ or CD45(+ cells in the presence of thrombopoietin. Megakaryocyte output was higher in MPN patients than in CTRL with no correlation with the JAK2 V617F mutation. PMF-derived megakaryocytes displayed nuclei with a bulbous appearance, were smaller than ET- or PV-derived megakaryocytes and formed proplatelets that presented several structural alterations. In contrast, ET- and PV-derived megakaryocytes produced more proplatelets with a striking increase in bifurcations and tips compared to both control and PMF. Proplatelets formation was correlated with platelet counts in patient peripheral blood. Patients with pre-fibrotic PMF had a pattern of megakaryocyte proliferation and proplatelet formation that was similar to that of fibrotic PMF and different from that of ET. CONCLUSIONS/SIGNIFICANCE: In conclusion, MPNs are associated with high megakaryocyte proliferative potential. Profound differences in megakaryocyte morphology and proplatelet formation distinguish PMF, both fibrotic and prefibrotic, from ET and PV.

  3. Different temporal patterns in the expressions of bone morphogenetic proteins and noggin during astroglial scar formation after ischemic stroke.

    Science.gov (United States)

    Shin, Jin A; Kang, Jihee Lee; Lee, Kyung-Eun; Park, Eun-Mi

    2012-05-01

    Bone morphogenetic proteins (BMPs) and their antagonists have roles in scar formation and regeneration after central nervous system injuries. However, temporal changes in their expression during astroglial scar formation in the ischemic brain are unknown. Here, we examined protein levels of BMP2, BMP7, and their antagonist noggin in the ischemic brain up to 4 weeks after experimental stroke in mice. BMP2 and BMP7 levels were increased from 1 to 4 weeks in the ischemic brain, and their expression was associated with astrogliosis. BMP7 expression was more intense and co-localized in reactive astrocytes in the ischemic subcortex at 1 week. Noggin expression began to increase after 2 weeks and was further increased at 4 weeks only in the ischemic subcortex, but the intensity was weak compared to the intensity of BMPs. Noggin was co-localized mainly in activated microglia. These findings show that expression of BMPs and noggin differed over time, in intensity and in types of cell, and suggest that BMPs and noggin have different roles in the processes of glial scar formation and neurorestoration in the ischemic brain.

  4. interdisciplinary aspects

    OpenAIRE

    Kempf, Davorin

    2010-01-01

    Summary: Symmetry is a universal principle in nature, sciences and arts. Generally speaking symmetry means that something looks the same when observed from certain different aspects. Symmetry is almost always broken – more or less, directly (in praxis) or spontaneously (in quantum field theory). There are discrete and continuous symmetries. Various forms of discrete symmetries – like bilateral, translative or rotative – associated with the field of arts, can also be recognized in our natu...

  5. Microstructural aspects of crack formation and propagation in the austenitic steel X6CrNiNb18-10 under low cycle fatigue loading

    Energy Technology Data Exchange (ETDEWEB)

    Soppa, E.; Kohler, C.; Roos, E.; Schuler, X. [Stuttgart Univ. (Germany). MPA

    2012-07-01

    The understanding of the crack initiation mechanisms and crack growth in apparently monolithic materials like X6CrNiNb18-10 stainless steel under cyclic loading requires the explicit analysis of the phenomena underlying fatigue on both atomistic and microscopic levels. The permanent delivery of mechanical energy through cyclic loading evokes changes in the microstructure that can lead to a martensitic transformation. The transformation of a metastable cubic face centered austenite and formation of a cubic body centered α'-martensite under cyclic loading at room temperature was found, both, in the experiment and in molecular dynamics simulations. The martensite nucleates prevalently at grain boundaries, triple points and at the specimen free surface and forms small (∝ 1 μm) differently oriented grains, also in the same parent austenitic grain. By a combination of interrupted low cycle fatigue tests (LCF) and electron backscatter diffraction (EBSD) measurements the martensitic transformation and subsequent fatigue crack formation were observed at the same area in the microstructure at different stages of the specimen lifetime. The EBSD measurements showed the following crack initiation scenarios: Cracks started (a) at the phase boundary between austenite and α'-martensite, (b) inside fully martensitic areas in the matrix, (c) at broken or debonded coarse NbCs. It is obvious that formation of a hard α'-martensite in a ductile and soft austenite and forming two-phase material causes a heterogeneous stress and strain distribution on the microscopic level. α'-martensite enhances locally the stress amplitude whereas in a soft austenite the plastic strain amplitude increases. Strain concentration in the austenite along the phase boundary is connected with a stress increase along the interface and can initiate fatigue crack there. Also at the crack tip, a permanent martensitic transformation occurs, so that the growth of the fatigue cracks at room

  6. New aspects of absorption line formation in intervening turbulent clouds; 3, The inverse problem in the study of H+D profiles

    CERN Document Server

    Levshakov, S A; Takahara, F

    1997-01-01

    A new method, based on a Reverse Monte Carlo technique and aimed at the inverse problem in the analysis of interstellar (intergalactic) absorption lines is presented. We consider the process of line formation in media with a stochastic velocity field accounting for the effects of a finite correlation length (mesoturbulence). This approach generalizes the standard microturbulent approximation, which is commonly used to model the formation of absorption spectra in turbulent media. The method allows to estimate from an observed spectrum both, the physical parameters of the absorbing gas, and an appropriate structure of the velocity distribution parallel to the line of sight. The procedure is applied to a template H+D Ly-alpha profile which reproduces the Burles and Tytler [BT] spectrum of the quasar Q 1009+2956 with the DI Ly-alpha line seen at the redshift z = 2.504. The results obtained favor a low D/H ratio in this particular absorption system, although the inferred upper limit for the hydrogen isotopic ratio...

  7. Palaeoecological aspects of some invertebrate trace fossils from the mid- to Upper Permian Middleton Formation (Adelaide Subgroup, Beaufort Group, Karoo Supergroup), Eastern Cape, South Africa

    Science.gov (United States)

    Bordy, Emese M.; Linkermann, Sean; Prevec, Rose

    2011-10-01

    Ichnological and sedimentological analyses in the Eastern Cape allowed the first description of a Cochlichnus-dominated ichnofossil site from the mid- to Upper Permian Middleton Formation (Karoo Supergroup) in South Africa. The locality is within the uppermost Pristerognathus Assemblage Zone, a biostratigraphic interval characterized by a low vertebrate biodiversity at the turn of the mid- to Late Permian. Our field data indicates that the surficial bioturbation of very fine to fine-grained sand layers resulted from life activities of shallow infaunal and epifaunal invertebrates (possibly annelids, aquatic oligochaetes, nematodes, insect larvae) and fish. The morphology of the trails, their relationship to the substrate and the behaviour inferred from them indicate that the tracemakers developed a strategy that facilitated the optimization of low food resources in a permanently submerged freshwater setting. Combined ichnological and sedimentological evidence suggests a low-energy, freshwater lacustrine depositional environment, where occasional higher energy currents brought nutrients. Data also imply that colonization of these erratic event beds by opportunistic sediment-feeders was short-lived and followed by longer intervals of lower energy deposition under possibly poorly oxygenated conditions. We propose that these event beds as well as the sporadic red mudstones of the Middleton Formation may have formed during short-term, higher storm-frequency and dryer periods, signalling changes in the otherwise humid climate in this part of the main Karoo Basin during the mid- to Late Permian.

  8. Rheological and hemostasiological aspects of thrombus formation in the left atrial appendage in atrial fibrillation? A new strategy for prevention of cardioembolic stroke.

    Science.gov (United States)

    Leithäuser, Boris; Jung, Friedrich; Park, Jai-Wun

    2010-01-01

    Atrial fibrillation (AF), as the most common cardiac rhythm disturbance, gains in importance not only for the persons affected, but also for health care and social economy due to thromboembolic events, of which stroke is the most serious, disabling, and life threatening one. Cardiac embolism is due to thrombus formation mainly in the left atrial appendage (LAA). The pathophysiology leading to increased thrombogenicity is complex and requires a remodelling of the LAA structure, decreased LAA blood flow, activation of inflammatory processes, deviations of the hemostatic/fibrinolytic system, and activation/dysfunction of endothelial/endocardial cells. Altogether, a prothrombotic state proposed by Virchow more than 150 years ago. The presence of a LAA thrombus, therefore, is a result of a dynamic process of clot formation and lysis. A comprehensive understanding of this pathophysiology is helpful to optimize the management of patients at high risk of cardioembolic stroke. Especially those with contraindications for oral anticoagulation are in a need of an alternative approach that is not associated with a long-term risk of hemorrhage and other attendant circumstances. The reasonable alternative may be the exclusion of the LAA cavity from circulation by either surgical or percutaneous catheter-based procedures. PMID:20675914

  9. On Hans Marchand’s Analysis of Word- formation

    Institute of Scientific and Technical Information of China (English)

    刘莎莎

    2010-01-01

    <正>Word -formation is the branch of the science of language which studies the patterns on which a language forms new lexical units,i.e.words.Marchand’s study of word - formation involves three aspects of morphology,semantics,and grammar.He suggested that nominal compounds are derived from sentences only that the underlying sentences will take on different nominal forms, which provides a detailed analysis of word - formation.

  10. Aspects of multimetric gravity

    International Nuclear Information System (INIS)

    We present a class of gravity theories containing N ≥ 2 metric tensors and a corresponding number of standard model copies. In the Newtonian limit gravity is attractive within each standard model copy, but different standard model copies mutually repel each other. We discuss several aspects of these multimetric gravity theories, including cosmology, structure formation, the post-Newtonian limit and gravitational waves. The most interesting feature we find is an accelerating expansion of the universe that naturally becomes small at late times.

  11. Disentangling endogenous versus exogenous pattern formation in spatial ecology: a case study of the ant Azteca sericeasur in southern Mexico.

    Science.gov (United States)

    Li, Kevin; Vandermeer, John H; Perfecto, Ivette

    2016-05-01

    Spatial patterns in ecology can be described as reflective of environmental heterogeneity (exogenous), or emergent from dynamic relationships between interacting species (endogenous), but few empirical studies focus on the combination. The spatial distribution of the nests of Azteca sericeasur, a keystone tropical arboreal ant, is thought to form endogenous spatial patterns among the shade trees of a coffee plantation through self-regulating interactions with controlling agents (i.e. natural enemies). Using inhomogeneous point process models, we found evidence for both types of processes in the spatial distribution of A. sericeasur. Each year's nest distribution was determined mainly by a density-dependent relationship with the previous year's lagged nest density; but using a novel application of a Thomas cluster process to account for the effects of nest clustering, we found that nest distribution also correlated significantly with tree density in the later years of the study. This coincided with the initiation of agricultural intensification and tree felling on the coffee farm. The emergence of this significant exogenous effect, along with the changing character of the density-dependent effect of lagged nest density, provides clues to the mechanism behind a unique phenomenon observed in the plot, that of an increase in nest population despite resource limitation in nest sites. Our results have implications in coffee agroecological management, as this system provides important biocontrol ecosystem services. Further research is needed, however, to understand the effective scales at which these relationships occur. PMID:27293786

  12. Disentangling endogenous versus exogenous pattern formation in spatial ecology: a case study of the ant Azteca sericeasur in southern Mexico

    Science.gov (United States)

    Li, Kevin; Vandermeer, John H.; Perfecto, Ivette

    2016-01-01

    Spatial patterns in ecology can be described as reflective of environmental heterogeneity (exogenous), or emergent from dynamic relationships between interacting species (endogenous), but few empirical studies focus on the combination. The spatial distribution of the nests of Azteca sericeasur, a keystone tropical arboreal ant, is thought to form endogenous spatial patterns among the shade trees of a coffee plantation through self-regulating interactions with controlling agents (i.e. natural enemies). Using inhomogeneous point process models, we found evidence for both types of processes in the spatial distribution of A. sericeasur. Each year's nest distribution was determined mainly by a density-dependent relationship with the previous year's lagged nest density; but using a novel application of a Thomas cluster process to account for the effects of nest clustering, we found that nest distribution also correlated significantly with tree density in the later years of the study. This coincided with the initiation of agricultural intensification and tree felling on the coffee farm. The emergence of this significant exogenous effect, along with the changing character of the density-dependent effect of lagged nest density, provides clues to the mechanism behind a unique phenomenon observed in the plot, that of an increase in nest population despite resource limitation in nest sites. Our results have implications in coffee agroecological management, as this system provides important biocontrol ecosystem services. Further research is needed, however, to understand the effective scales at which these relationships occur. PMID:27293786

  13. Patterns of superficial fibre formation in the European pearlfish (Rutilus frisii meidingeri) provide a general template for slow muscle development in teleost fish.

    Science.gov (United States)

    Stoiber, W; Haslett, J R; Goldschmid, A; Sänger, A M

    1998-06-01

    The debate about the pattern of muscle formation in teleost fish has recently been heightened in the literature. Here we examine superficial muscle development in the pearlfish, a cyprinid endemic to a small area of Central Europe, and uninfluenced by economic interest and breeding. Using light and electron microscopy, histochemistry and immunohistochemistry techniques, we report that: (1) Superficial fibre precursors originate close to the notochord, are part of the same cell population as the so-called muscle pioneer cells, and are transferred laterally to end up at the surface of the myotome. (2) Superficial fibre maturation is exceptionally rapid. Structural and enzymatic functionality is attained at a time when prospective deep fibres have not passed beyond the early myotube state. This strong contrast weakens as the embryo develops. (3) Apart from the muscle pioneers, the superficial fibres appear to be capable of functioning before they receive any direct innervation, implying that signals are transferred to these fibres via cell-to-cell junctions. We suggest that the capability of rapid superficial fibre maturation is a rather general feature among teleosts and may aid pre-hatch survival under a variable environment. Our results indicate that muscle formation in teleost fish may follow a common basic pattern that is open to considerable ontogenetic and phylogenetic modification in response to habitat conditions. PMID:9682979

  14. Investigation of the structural aspects in the formation of optical properties of the GeO2-Eu2O3-Ag nanosystem

    Science.gov (United States)

    Belushkin, A. V.; Kichanov, S. E.; Kozlenko, D. P.; Lukin, E. V.; Savenko, B. N.; Rakhmanov, S. K.; Shevchenko, G. P.; Gurin, V. S.; Malashkevich, G. E.; Haramus, V.; Pogoreliy, D. K.; Podurets, K. M.

    2010-07-01

    The structural characteristics of the 95GeO2-5Eu2O3, 94.9GeO2-5Eu2O3-0.1Ag, and 99.9GeO2-0.1Ag xerogels annealed in air at the temperature T an = 850°C have been studied using X-ray diffraction and small-angle neutron scattering. It has been established that the significant change in the relative intensity of the 7 F 0 → 5 L 6 and 7 F 0 → 5 H 6 luminescence excitation bands of Eu3+ ions upon introduction of silver correlates with the decrease in the characteristic sizes of polydisperse clusters formed during annealing. The character of the changes in chemical bonds in the system due to the clustering and their role in the formation of optical properties have been analyzed.

  15. Formation of vanadium carbide precipitations at the surface of alloys: Thermodynamics and kinetics aspects; Bildung von Vanadiumcarbid-Ausscheidungen auf Legierungsoberflaechen: Thermodynamische und kinetische Aspekte

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, A.; Uebing, C. [Max-Planck-Institut fuer Eisenforschung GmbH, Duesseldorf (Germany)

    1998-12-31

    The paper describes the formation of vanadium carbides on the surface layers of Fe-3%V-C(100) alloys. The phase diagram calculated for this alloyed material using the ThermoCalc program package reveals a co-existence of ferritic matrix and V{sub 3}C{sub 2} at temperatures of T{<=}650 C. This carbide is instable at elevated temperatures, leading to co-existence of ferrite and the cubic VC{sub 1-x}. Experimental analyses revealed the formation of a 2D VC compound in the top layers of the surface of Fe-3%V-C(100) alloys, induced by equilibrium segregation. The paper explains the usefulness of thermodynamic and kinetic calculations for interpretation of precipitation phenomena in steels. Mathematically derived and experimental results of analyses for the case of non-equilibrium segregation showed excellent agreement in the determination of carbide thickness (nanometer scale) and time dependence of segregation under fast cooling conditions. (orig./CB) [Deutsch] In der vorliegenden Arbeit wurde die Bildung von Vanadiumcarbiden auf Fe-3%V-C(100)-Legierungsoberflaechen beschrieben. Das anhand des ThermoCalc-Programmpakets fuer diese Legierungszusammensetzung berechnete Phasendiagramm zeigt bei niedrigen Temperaturen T{<=}650 C die Koexistenz von ferritischer Matrix und V{sub 3}C{sub 2}. Bei hoeheren Temperaturen ist dieses Carbid instabil und es liegt Koexistenz von Ferrit und dem kubischen VC{sub 1-x} vor. Die experimentellen Untersuchungen zeigen die Ausbildung einer zweidimensionalen VC-Oberflaechenverbindung auf Fe-3%V-C(100)-Legierungsoberflaechen durch Gleichgewichtssegregation. Diese Arbeit zeigt, dass thermodynamische und kinetische Rechnungen bei der Deutung von Ausscheidungsphaenomenen in Staehlen sinnvoll eingesetzt werden koennen. Bei der Nichtgleichgewichtssegregation wurde bezueglich Carbiddicke (im Nanometerbereich) und Zeitabhaengigkeit der Ausscheidung bei schneller Abkuehlung eine hervorragende Uebereinstimmung zwischen Simulation und Experiment gefunden

  16. Neurofibromatosis-1 heterozygosity increases microglia in a spatially and temporally restricted pattern relevant to mouse optic glioma formation and growth.

    Science.gov (United States)

    Simmons, Grant W; Pong, Winnie W; Emnett, Ryan J; White, Crystal R; Gianino, Scott M; Rodriguez, Fausto J; Gutmann, David H

    2011-01-01

    Whereas carcinogenesis requires the acquisition of driver mutations in progenitor cells, tumor growth and progression are heavily influenced by the local microenvironment. Previous studies from our laboratory have used Neurofibromatosis-1 (NF1) genetically engineered mice to characterize the role of stromal cells and signals to optic glioma formation and growth. Previously, we have shown that Nf1+/- microglia in the tumor microenvironment are critical cellular determinants of optic glioma proliferation. To define the role of microglia in tumor formation and maintenance further, we used CD11b-TK mice, in which resident brain microglia (CD11b+, CD68+, Iba1+, CD45low cells) can be ablated at specific times after ganciclovir administration. Ganciclovir-mediated microglia reduction reduced Nf1 optic glioma proliferation during both tumor maintenance and tumor development. We identified the developmental window during which microglia are increased in the Nf1+/- optic nerve and demonstrated that this accumulation reflected delayed microglia dispersion. The increase in microglia in the Nf1+/- optic nerve was associated with reduced expression of the chemokine receptor, CX3CR1, such that reduced Cx3cr1 expression in Cx3cr1-GFP heterozygous knockout mice led to a similar increase in optic nerve microglia. These results establish a critical role for microglia in the development and maintenance of Nf1 optic glioma.

  17. Excitation and Adaptation in Bacteria–a Model Signal Transduction System that Controls Taxis and Spatial Pattern Formation

    Directory of Open Access Journals (Sweden)

    Chuan Xue

    2013-04-01

    Full Text Available The machinery for transduction of chemotactic stimuli in the bacterium E. coli is one of the most completely characterized signal transduction systems, and because of its relative simplicity, quantitative analysis of this system is possible. Here we discuss models which reproduce many of the important behaviors of the system. The important characteristics of the signal transduction system are excitation and adaptation, and the latter implies that the transduction system can function as a “derivative sensor” with respect to the ligand concentration in that the DC component of a signal is ultimately ignored if it is not too large. This temporal sensing mechanism provides the bacterium with a memory of its passage through spatially- or temporally-varying signal fields, and adaptation is essential for successful chemotaxis. We also discuss some of the spatial patterns observed in populations and indicate how cell-level behavior can be embedded in population-level descriptions.

  18. Patterns beyond Faraday waves: observation of parametric crossover from Faraday instabilities to the formation of vortex lattices in open dual fluid strata

    Science.gov (United States)

    Ohlin, Kjell; Berggren, Karl Fredrik

    2016-07-01

    Faraday first characterised the behaviour of a fluid in a container subjected to vertical periodic oscillations. His study pertaining to hydrodynamic instability, the ‘Faraday instability’, has catalysed a myriad of experimental, theoretical, and numerical studies shedding light on the mechanisms responsible for the transition of a system at rest to a new state of well-ordered vibrational patterns at fixed frequencies. Here we study dual strata in a shallow vessel containing distilled water and high-viscosity lubrication oil on top of it. At elevated driving power, beyond the Faraday instability, the top stratum is found to ‘freeze’ into a rigid pattern with maxima and minima. At the same time there is a dynamic crossover into a new state in the form of a lattice of recirculating vortices in the lower layer containing the water. Instrumentation and the physics behind are analysed in a phenomenological way together with a basic heuristic modelling of the wave field. The study, which is based on relatively low-budget equipment, stems from related art projects that have evolved over the years. The study is of value within basic research as well as in education, especially as more advanced collective project work in e.g. engineering physics, where it invites further studies of pattern formation, the emergence of vortex lattices and complexity.

  19. Structural Evolution During Formation and Filling of Self-patterned Nanoholes on GaAs (100 Surfaces

    Directory of Open Access Journals (Sweden)

    Zhou Lin

    2008-01-01

    Full Text Available Abstract Nanohole formation on an AlAs/GaAs superlattice gives insight to both the “drilling” effect of Ga droplets on AlAs as compared to GaAs and the hole-filling process. The shape and depth of the nanoholes formed on GaAs (100 substrates has been studied by the cross-section transmission electron microscopy. The Ga droplets “drill” through the AlAs layer at a much slower rate than through GaAs due to differences in activation energy. Refill of the nanohole results in elongated GaAs mounds along the [01−1] direction. As a result of capillarity-induced diffusion, GaAs favors growth inside the nanoholes, which provides the possibility to fabricate GaAs and AlAs nanostructures.

  20. Role of the temperature instabilities for formation of nano-patterns upon single femtosecond laser pulses on gold

    CERN Document Server

    Gurevich, Evgeny L; Gurevich, Svetlana V; Bulgakova, Nadezhda M

    2016-01-01

    In this paper we investigate whether the periodic structures on metal surfaces exposed to single ultrashort laser pulses can appear due to an instability induced by two-temperature heating dynamics. The results of two-temperature model (TTM) 2D simulations are presented on the irradiation of gold by a single 800 nm femtosecond laser pulse whose intensity is modulated in order to reproduce a small initial temperature perturbation, which can arise from incoming and scattered surface wave interference. The growing (unstable) modes of the temperature distribution along the surface may be responsible for the LIPSS (Laser Induced Periodic Surface Structures) formation. After the end of the laser pulse and before the complete coupling between lattice and electrons occurs, the evolution of the amplitude of the subsequent modulation in the lattice temperature reveals different tendencies depending on the spatial period of the initial modulation. This instability-like behaviour is shown to arise due to the perturbation...