Numerical Study of a Lyapunov Functional for the Complex Ginzburg-Landau Equation

We numerically study in the one-dimensional case the validity of the functional calculated by Graham and coworkers as a Lyapunov potential for the Complex Ginzburg-Landau equation. In non-chaotic regions of parameter space the functional decreases monotonically in time towards the plane wave attractors, as expected for a Lyapunov functional, provided that no phase singularities are encountered. In the phase turbulence region the potential relaxes towards a value characteristic of the phase turbulent attractor, and the dynamics there approximately preserves a constant value. There are however very small but systematic deviations from the theoretical predictions, that increase when going deeper in the phase turbulence region. In more disordered chaotic regimes characterized by the presence of phase singularities the functional is ill-defined and then not a correct Lyapunov potential.Comment: 20 pages,LaTeX, Postcript version with figures included available at http://formentor.uib.es/~montagne/textos/nep

Wave-unlocking transition in resonantly coupled complex Ginzburg-Landau equations

We study the effect of spatial frequency-forcing on standing-wave solutions of coupled complex Ginzburg-Landau equations. The model considered describes several situations of nonlinear counterpropagating waves and also of the dynamics of polarized light waves. We show that forcing introduces spatial modulations on standing waves which remain frequency locked with a forcing-independent frequency. For forcing above a threshold the modulated standing waves unlock, bifurcating into a temporally periodic state. Below the threshold the system presents a kind of excitability.Comment: 4 pages, including 4 postscript figures. To appear in Physical Review Letters (1996). This paper and related material can be found at http://formentor.uib.es/Nonlinear

Synchronization of Spatiotemporal Chaos: The regime of coupled Spatiotemporal Intermittency

Synchronization of spatiotemporally chaotic extended systems is considered in the context of coupled one-dimensional Complex Ginzburg-Landau equations (CGLE). A regime of coupled spatiotemporal intermittency (STI) is identified and described in terms of the space-time synchronized chaotic motion of localized structures. A quantitative measure of synchronization as a function of coupling parameter is given through distribution functions and information measures. The coupled STI regime is shown to dissapear into regular dynamics for situations of strong coupling, hence a description in terms of a single CGLE is not appropiate.Comment: 4 pages, LaTeX 2e. Includes 3 figures made up of 8, 4 (LARGE),and 2 postscript files. Includes balanced.st

Public-private Partnerships for Government Financing, Controlling Risk, and Value-for--money: The UK Experience

Sponsored Report (for Acquisition Research Program)One of the key requirements to a successful Public-private Partnership (PPP) is the transfer of risk from the government to the private sector. This research examines the PPP experience in the United Kingdom (UK) Ministry of Defense to determine if they would be applicable to the US Department of Defense (DoD). PPP agreements have provided the UK increased capabilities. Also, this research provides an in-depth analysis of Private Financed Initiatives (PFI) that Serco Inc. has undertaken. Finally, this research evaluates the increases in value-for-money resulting from the PPP transfer of risk to the private sector. The research concludes that PPPs should be continued and expanded to provide increased real-time capability to the DoD while supporting private industry. Since the government has the lowest cost of borrowing, PPPs agreements may not appear to be cost effective as a means of procurement. However, the benefits from transferring risk to the private sector can more than offset the higher financing cost. PPPs reallocate risk and up-front capital requirements allowing the government to spread program cost over time. Without initial capital outlays, the government can acquire higher priority goods and services with its limited resources. In addition, PPPs provide the government with an increased infrastructure and technological capability than would otherwise not be available.Naval Postgraduate School Acquisition Research ProgramApproved for public release; distribution is unlimited

Scaling in the structure of directory trees in a computer cluster

We describe the topological structure and the underlying organization principles of the directories created by users of a computer cluster when storing his/her own files. We analyze degree distributions, average distance between files, distribution of communities and allometric scaling exponents of the directory trees. We find that users create trees with a broad, scale-free degree distribution. The structure of the directories is well captured by a growth model with a single parameter. The degree distribution of the different trees has a non-universal exponent associated with different values of the parameter of the model. However, the distribution of community sizes has a universal exponent analytically obtained from our model.Comment: refined data analysis and modeling, completely reorganized version, 4 pages, 2 figure

Using public-private partnerships and energy savings contracts to fund DoD mobile assets

The Department of Defense (DoD) has engaged in numerous Public-Private Partnership (PPP) ventures such as outsourcing of services and privatization of military housing. In the past, the activities considered for PPPs have been primarily administrative and support functions. This research explores the possibility of expanding the use of PPPs to enhance the DoD combat and combat-support functions. First, to better understand how PPPs function (the partnership relationships and financing arrangements), we examine Hannon Armstrong's fee for service contract solution to the lack of appropriated funds for establishing a vital fiber-optic link near the Arctic Circle. Next, we explore the history of Energy Savings Performance Contracts (ESPCs) and their potential application to re-engining the Air Force's B-52H through PPPs. Historically, this program has only been used for fixed assets, not mobile assets like engines. There is little debate over the success of ESPC contracts in reducing energy consumption, but their use in DoD mobile assets is new. Finally, we conclude that applying ESPCs to mobile assets has the potential to reduce energy consumption, save millions of dollars and increase combat efficiency.Approved for public release; distribution is unlimited

Common cellular events occur during wound healing and organ regeneration in the sea cucumber Holothuria glaberrima

<p>Abstract</p> <p>Background</p> <p>All animals possess some type of tissue repair mechanism. In some species, the capacity to repair tissues is limited to the healing of wounds. Other species, such as echinoderms, posses a striking repair capability that can include the replacement of entire organs. It has been reported that some mechanisms, namely extracellular matrix remodeling, appear to occur in most repair processes. However, it remains unclear to what extent the process of organ regeneration, particularly in animals where loss and regeneration of complex structures is a programmed natural event, is similar to wound healing. We have now used the sea cucumber <it>Holothuria glaberrima </it>to address this question.</p> <p>Results</p> <p>Animals were lesioned by making a 3–5 mm transverse incision between one of the longitudinal muscle pairs along the bodywall. Lesioned tissues included muscle, nerve, water canal and dermis. Animals were allowed to heal for up to four weeks (2, 6, 12, 20, and 28 days post-injury) before sacrificed. Tissues were sectioned in a cryostat and changes in cellular and tissue elements during repair were evaluated using classical dyes, immmuohistochemistry and phalloidin labeling. In addition, the temporal and spatial distribution of cell proliferation in the animals was assayed using BrdU incorporation. We found that cellular events associated with wound healing in <it>H. glaberrima </it>correspond to those previously shown to occur during intestinal regeneration. These include: (1) an increase in the number of spherule-containing cells, (2) remodeling of the extracellular matrix, (3) formation of spindle-like structures that signal dedifferentiation of muscle cells in the area flanking the lesion site and (4) intense cellular division occurring mainly in the coelomic epithelium after the first week of regeneration.</p> <p>Conclusion</p> <p>Our data indicate that <it>H. glaberrima </it>employs analogous cellular mechanisms during wound healing and organ regeneration. Thus, it is possible that regenerative limitations in some organisms are due either to the absence of particular mechanisms associated with repair or the inability of activating the repair process in some tissues or stages.</p