402 research outputs found
In--out intermittency in PDE and ODE models
We find concrete evidence for a recently discovered form of intermittency,
referred to as in--out intermittency, in both PDE and ODE models of mean field
dynamos. This type of intermittency (introduced in Ashwin et al 1999) occurs in
systems with invariant submanifolds and, as opposed to on--off intermittency
which can also occur in skew product systems, it requires an absence of skew
product structure. By this we mean that the dynamics on the attractor
intermittent to the invariant manifold cannot be expressed simply as the
dynamics on the invariant subspace forcing the transverse dynamics; the
transverse dynamics will alter that tangential to the invariant subspace when
one is far enough away from the invariant manifold.
Since general systems with invariant submanifolds are not likely to have skew
product structure, this type of behaviour may be of physical relevance in a
variety of dynamical settings.
The models employed here to demonstrate in--out intermittency are
axisymmetric mean--field dynamo models which are often used to study the
observed large scale magnetic variability in the Sun and solar-type stars. The
occurrence of this type of intermittency in such models may be of interest in
understanding some aspects of such variabilities.Comment: To be published in Chaos, June 2001, also available at
http://www.eurico.web.co
Master-equation approach to the study of phase-change processes in data storage media
We study the dynamics of crystallization in phase-change materials using a master-equation approach in which the state of the crystallizing material is described by a cluster size distribution function. A model is developed using the thermodynamics of the processes involved and representing the clusters of size two and greater as a continuum but clusters of size one (monomers) as a separate equation. We present some partial analytical results for the isothermal case and for large cluster sizes, but principally we use numerical simulations to investigate the model. We obtain results that are in good agreement with experimental data and the model appears to be useful for the fast simulation of reading and writing processes in phase-change optical and electrical memories
Comparative secretome analysis of Colletotrichum falcatum identifies a cerato-platanin protein (EPL1) as a potential pathogen-associated molecular pattern (PAMP) inducing systemic resistance in sugarcane
Colletotrichum falcatum, an intriguing hemibiotrophic fungal pathogen causes the devastating red rot disease
of sugarcane. Repeated in vitro subculturing of C. falcatum under dark condition alters morphology and reduces
virulence of the culture. Hitherto, no information is available on this phenomenon at molecular level.
In this study, the in vitro secretome of C. falcatum cultured under light and dark conditions was analyzed
using 2-DE coupled with MALDI TOF/TOF MS. Comparative analysis identified nine differentially abundant
proteins. Among them, seven proteins were less abundant in the dark-cultured C. falcatum, wherein only
two protein species of a cerato-platanin protein called EPL1 (eliciting plant response-like protein) were found
to be highly abundant. Transcriptional expression of candidate high abundant proteins were profiled during
host-pathogen interaction using qRT-PCR. Comprehensively, this comparative secretome analysis identified
five putative effectors, two pathogenicity-related proteins and one pathogen-associated molecular pattern
(PAMP) of C. falcatum. Functional characterization of three distinct domains of the PAMP (EPL1) showed
that the major cerato-platanin domain (EPL1 Î N1â92) is exclusively essential for inducing defense and hypersensitive
response (HR) in sugarcane and tobacco, respectively. Further, priming with EPL1 Î N1â92 protein
induced systemic resistance and significantly suppressed the red rot disease severity in sugarcane.
Biological significance
Being the first secretomic investigation of C. falcatum, this study has identified five potential effectors,
two pathogenicity-related proteins and a PAMP. Although many reports have highlighted the influence of
light on pathogenicity, this study has established a direct link between light and expression of effectors, for
the first time. This study has presented the influence of a novel N-terminal domain of EPL1 in physical and
biological properties and established the functional role of major cerato-platanin domain of EPL1 as a potential
elicitor inducing systemic resistance in sugarcane. Comprehensively, the study has identified proteins that
putatively contribute to virulence of C. falcatum and for the first time, demonstrated the potential role of EPL1
in inducing PAMP-triggered immunity (PTI) in sugarcane
Volatility clustering and scaling for financial time series due to attractor bubbling
A microscopic model of financial markets is considered, consisting of many
interacting agents (spins) with global coupling and discrete-time thermal bath
dynamics, similar to random Ising systems. The interactions between agents
change randomly in time. In the thermodynamic limit the obtained time series of
price returns show chaotic bursts resulting from the emergence of attractor
bubbling or on-off intermittency, resembling the empirical financial time
series with volatility clustering. For a proper choice of the model parameters
the probability distributions of returns exhibit power-law tails with scaling
exponents close to the empirical ones.Comment: For related publications see http://www.helbing.or
Reflexivity and the construction of competing discourses of masculinity in a female-dominated profession
This paper contributes to the debates on reflexivity and change by extending our understanding of (non-)reflexivity mechanisms in the discursive constructions of gender. Specifically, I explore how and why women persistently construct contradictory discursive accounts of men and masculinity in a female-dominated profession of counselling psychology in Russia. Drawing on the concept of âinterpretative repertoiresâ I argue that female counsellors construct different kinds of masculinities based on three ârepertoiresâ: psycho-biological, structural and relational. I demonstrate how these constructions of masculinity are imbued with different meanings and are used to explain only certain contexts, which precludes women's ability to reflect on their contradictory nature. I conclude by discussing how an exploration of discursive (non-)reflexivity extends our understanding of the conditions for gender transformation
Dynamics of coupled cell networks: synchrony, heteroclinic cycles and inflation
Copyright © 2011 Springer. The final publication is available at www.springerlink.comWe consider the dynamics of small networks of coupled cells. We usually assume asymmetric inputs and no global or local symmetries in the network and consider equivalence of networks in this setting; that is, when two networks with different architectures give rise to the same set of possible dynamics. Focussing on transitive (strongly connected) networks that have only one type of cell (identical cell networks) we address three questions relating the network structure to dynamics. The first question is how the structure of the network may force the existence of invariant subspaces (synchrony subspaces). The second question is how these invariant subspaces can support robust heteroclinic attractors. Finally, we investigate how the dynamics of coupled cell networks with different structures and numbers of cells can be related; in particular we consider the sets of possible âinflationsâ of a coupled cell network that are obtained by replacing one cell by many of the same type, in such a way that the original network dynamics is still present within a synchrony subspace. We illustrate the results with a number of examples of networks of up to six cells
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Physical activity and risk of inflammatory bowel disease: prospective study from the Nursesâ Health Study cohorts
Objective: To examine the association between physical activity and risk of ulcerative colitis and Crohnâs disease. Design: Prospective cohort study. Setting: Nursesâ Health Study and Nursesâ Health Study II. Participants: 194 711 women enrolled in the Nursesâ Health Study and Nursesâ Health Study II who provided data on physical activity and other risk factors every two to four years since 1984 in the Nursesâ Health Study and 1989 in the Nursesâ Health Study II and followed up through 2010. Main outcome measure Incident ulcerative colitis and Crohnâs disease. Results: During 3 421 972 person years of follow-up, we documented 284 cases of Crohnâs disease and 363 cases of ulcerative colitis. The risk of Crohnâs disease was inversely associated with physical activity (P for trend 0.02). Compared with women in the lowest fifth of physical activity, the multivariate adjusted hazard ratio of Crohnâs disease among women in the highest fifth of physical activity was 0.64 (95% confidence interval 0.44 to 0.94). Active women with at least 27 metabolic equivalent task (MET) hours per week of physical activity had a 44% reduction (hazard ratio 0.56, 95% confidence interval 0.37 to 0.84) in risk of developing Crohnâs disease compared with sedentary women with 0.35). Conclusion: In two large prospective cohorts of US women, physical activity was inversely associated with risk of Crohnâs disease but not of ulcerative colitis
The motion of the 2D hydrodynamic Chaplygin sleigh in the presence of circulation
We consider the motion of a planar rigid body in a potential flow with
circulation and subject to a certain nonholonomic constraint. This model is
related to the design of underwater vehicles.
The equations of motion admit a reduction to a 2-dimensional nonlinear
system, which is integrated explicitly. We show that the reduced system
comprises both asymptotic and periodic dynamics separated by a critical value
of the energy, and give a complete classification of types of the motion. Then
we describe the whole variety of the trajectories of the body on the plane.Comment: 25 pages, 7 figures. This article uses some introductory material
from arXiv:1109.321
Synchronisation in Coupled Sine Circle Maps
We study the spatially synchronized and temporally periodic solutions of a
1-d lattice of coupled sine circle maps. We carry out an analytic stability
analysis of this spatially synchronized and temporally periodic case and obtain
the stability matrix in a neat block diagonal form. We find spatially
synchronized behaviour over a substantial range of parameter space. We have
also extended the analysis to higher spatial periods with similar results.
Numerical simulations for various temporal periods of the synchronized
solution, reveal that the entire structure of the Arnold tongues and the
devil's staircase seen in the case of the single circle map can also be
observed for the synchronized coupled sine circle map lattice. Our formalism
should be useful in the study of spatially periodic behaviour in other coupled
map lattices.Comment: uuencoded, 1 rextex file 14 pages, 3 postscript figure
Theta and high-frequency activity mark spontaneous recall of episodic memories.
Humans possess the remarkable ability to search their memory, allowing specific past episodes to be re-experienced spontaneously. Here, we administered a free recall test to 114 neurosurgical patients and used intracranial theta and high-frequency activity (HFA) to identify the spatiotemporal pattern of neural activity underlying spontaneous episodic retrieval. We found that retrieval evolved in three electrophysiological stages composed of: (1) early theta oscillations in the right temporal cortex, (2) increased HFA in the left hemisphere including the medial temporal lobe (MTL), left inferior frontal gyrus, as well as the ventrolateral temporal cortex, and (3) motor/language activation during vocalization of the retrieved item. Of these responses, increased HFA in the left MTL predicted recall performance. These results suggest that spontaneous recall of verbal episodic memories involves a spatiotemporal pattern of spectral changes across the brain; however, high-frequency activity in the left MTL represents a final common pathway of episodic retrieval
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