Four-phase patterns in forced oscillatory systems

We investigate pattern formation in self-oscillating systems forced by an external periodic perturbation. Experimental observations and numerical studies of reaction-diffusion systems and an analysis of an amplitude equation are presented. The oscillations in each of these systems entrain to rational multiples of the perturbation frequency for certain values of the forcing frequency and amplitude. We focus on the subharmonic resonant case where the system locks at one fourth the driving frequency, and four-phase rotating spiral patterns are observed at low forcing amplitudes. The spiral patterns are studied using an amplitude equation for periodically forced oscillating systems. The analysis predicts a bifurcation (with increasing forcing) from rotating four-phase spirals to standing two-phase patterns. This bifurcation is also found in periodically forced reaction-diffusion equations, the FitzHugh-Nagumo and Brusselator models, even far from the onset of oscillations where the amplitude equation analysis is not strictly valid. In a Belousov-Zhabotinsky chemical system periodically forced with light we also observe four-phase rotating spiral wave patterns. However, we have not observed the transition to standing two-phase patterns, possibly because with increasing light intensity the reaction kinetics become excitable rather than oscillatory.Comment: 11 page

Be vicarious: the challenge for project management in the service economy

Purpose. The paper aims to answer to the following questions: which are the critical dynamic capabilities to survive in the rubber landscape of service economy? Does it exist in service economy a dynamic capabilities provider? Methodology. The paper combines the literature review on dynamic capability perspective and that on vicariance to the Project Management professional services. Findings. Firstly, the paper identifies vicariance as an intriguing dynamic capability, crucial to survive in the rubber landscape of service economy. Secondly, the paper sheds light on Project Management (PM) as a vicarious that provides vicariance. Practical implications. For each critical organizational dimension, the paper identifies the links among the service economy challenges and the vicariance typology required to the project manager to face those challenge. Originality/value.The approach to conceive the PM as a vicarious that provides vicariance is original and leads to new insights on the professional services management. In fact, on one hand, dynamic capabilities cannot easily be bought through a market transaction; on the other hand, they must be built. This building can be achieved internally, by the organization itself (i.e. hierarchy), or through a partnership (i.e. hybrid form among hierarchy and market). PM professional services enrich organizations with additional information variety according to a hybrid (i.e. non- market) coordination model

Beyond the Object

Object orientation (OO) is regained not only in all components of integrate development media but it remarks in the rest of software world from operating system to last application domain - of course, with different intensity and success. A clear prove of OO application in all situations is the development of a wide range of industrial applications. OO technology allows drawing of relation between the geometry, topology and dimensions of data on a class hierarchy; thus, the observation of the amount of data gained by research in many scientific domains is facilitated through class libraries both for graphic primitives and for events examination. In conformity to all waiting, OO asserts in every distributive system, there are very important the applications for making open systems customer-server and dis-tributed applications in Java. Finally OO application in robot's programming and modeling needn't be omitted. However, far to be panacea, OO has also shades which will be researched so on.object orientation, adaptability, reusability component wares, mega-programming, generative programming.

The last gasps of VY CMa: Aperture synthesis and adaptive optics imagery

We present new observations of the red supergiant VY CMa at 1.25 micron, 1.65 micron, 2.26 micron, 3.08 micron and 4.8 micron. Two complementary observational techniques were utilized: non-redundant aperture masking on the 10-m Keck-I telescope yielding images of the innermost regions at unprecedented resolution, and adaptive optics imaging on the ESO 3.6-m telescope at La Silla attaining extremely high (~10^5) peak-to-noise dynamic range over a wide field. For the first time the inner dust shell has been resolved in the near-infrared to reveal a one-sided extension of circumstellar emission within 0.1" (~15 R_star) of the star. The line-of-sight optical depths of the circumstellar dust shell at 1.65 micron, 2.26 micron, and 3.08 micron have been estimated to be 1.86 +/- 0.42, 0.85 +/- 0.20, and 0.44 +/- 0.11. These new results allow the bolometric luminosity of VY~CMa to be estimated independent of the dust shell geometry, yielding L_star ~ 2x10^5 L_sun. A variety of dust condensations, including a large scattering plume and a bow-shaped dust feature, were observed in the faint, extended nebula up to 4" from the central source. While the origin of the nebulous plume remains uncertain, a geometrical model is developed assuming the plume is produced by radially-driven dust grains forming at a rotating flow insertion point with a rotational period between 1200-4200 years, which is perhaps the stellar rotational period or the orbital period of an unseen companion.Comment: 25 pages total with 1 table and 5 figures. Accepted by Astrophysical Journal (to appear in February 1999

Neural reactivations during sleep determine network credit assignment.

A fundamental goal of motor learning is to establish the neural patterns that produce a desired behavioral outcome. It remains unclear how and when the nervous system solves this 'credit assignment' problem. Using neuroprosthetic learning, in which we could control the causal relationship between neurons and behavior, we found that sleep-dependent processing was required for credit assignment and the establishment of task-related functional connectivity reflecting the casual neuron-behavior relationship. Notably, we observed a strong link between the microstructure of sleep reactivations and credit assignment, with downscaling of non-causal activity. Decoupling of spiking to slow oscillations using optogenetic methods eliminated rescaling. Thus, our results suggest that coordinated firing during sleep is essential for establishing sparse activation patterns that reflect the causal neuron-behavior relationship

Progressive Analytics: A Computation Paradigm for Exploratory Data Analysis

Exploring data requires a fast feedback loop from the analyst to the system, with a latency below about 10 seconds because of human cognitive limitations. When data becomes large or analysis becomes complex, sequential computations can no longer be completed in a few seconds and data exploration is severely hampered. This article describes a novel computation paradigm called Progressive Computation for Data Analysis or more concisely Progressive Analytics, that brings at the programming language level a low-latency guarantee by performing computations in a progressive fashion. Moving this progressive computation at the language level relieves the programmer of exploratory data analysis systems from implementing the whole analytics pipeline in a progressive way from scratch, streamlining the implementation of scalable exploratory data analysis systems. This article describes the new paradigm through a prototype implementation called ProgressiVis, and explains the requirements it implies through examples.Comment: 10 page