Emergence of Order in Textured Patterns

A characterization of textured patterns, referred to as the disorder function \bar\delta(\beta), is used to study properties of patterns generated in the Swift-Hohenberg equation (SHE). It is shown to be an intensive, configuration-independent measure. The evolution of random initial states under the SHE exhibits two stages of relaxation. The initial phase, where local striped domains emerge from a noisy background, is quantified by a power law decay \bar\delta(\beta) \sim t^{-{1/2} \beta}. Beyond a sharp transition a slower power law decay of \bar\delta(\beta), which corresponds to the coarsening of striped domains, is observed. The transition between the phases advances as the system is driven further from the onset of patterns, and suitable scaling of time and \bar\delta(\beta) leads to the collapse of distinct curves. The decay of $\bar\delta(\beta)$ during the initial phase remains unchanged when nonvariational terms are added to the underlying equations, suggesting the possibility of observing it in experimental systems. In contrast, the rate of relaxation during domain coarsening increases with the coefficient of the nonvariational term.Comment: 9 Pages, 8 Postscript Figures, 3 gif Figure

Potential of cultivation of Gliricidia (Gliricidia sepium) in coconut triangle for bioenergy generation

Evaluation ofleast cost and environmentally friendly energy alternatives is essential to overcome theprevailing energy crisis. Dendro thermal energy generation has been identified as one of the bestoptions due to its potential as a low cost and locally available environmentally sound energy source.However. this potential has not been exploited by the people in most of the potential areas whichhinder the further expansion of establishing bio-energy plants. With this background, a study wasundertaken to evaluate the present status and the potential of gl iricidia (Gliricidia sepium) cultivationin coconut triangle for bio-energy generation. Gliricidia sepium is a multipurpose crop used forwood, fuel wood, fodder and nitrogenous organic fertilizer. The wood is presently used for thermalenergy i.e., electricity generation for the national grid (Walapane); electricity generation for off-gridrural electrification (Kakkapalliya, Thanamalwi la);industrial heat application (Madarnpe, Kottawa etc.)and household cooking. The study further attempted to determine the factors associated with thesupply of gliricidia for bio-energy generation and attitudes of the coconut growers towards the gliricidiaintercropping. Finally, it examined the strengths and weaknesses of the supply as well as demand inorder to make sound recommendations to promote gliricidia cultivation in coconut lands for bio-energygeneration.Two field surveys were simultaneously conducted to gather the necessary data. The first survey dealtwith the existing suppliers in Anarnaduwa area, while the second survey was carried out in Kuliyapitiyaarea with the potential growers. In addition, a case study was conducted with successful growers.Logit modeling was used to analyze the data.The study found that the opportunity costs ofland and labour of the both sites of study were fairly low.Moreover, the investment on agriculture related activities in marginal coconut lands were extremelylow. Further the study revealed that even though there was a positive attitude and high demand forgl iricid ia cultivation, there is an inadequate supply to the thermal plants for bio-energy generation. Thetechnical information on growing gliricidia for bioenergy generation had not disseminated into thepeople of the area mainly due to lack of awareness programmes. The results of the logit analysisrevealed that income from coconut, total highland availability and willingness to become a contractfanner are significant variables that influence the willingness to cultivate gliricidia. The case studyrevealed that the cultivation of gliricidia appear to be economically profitable and technically feasibleoption given that its low input nature, availability of marginal coconut lands, low opportunity cost oflabour and less income opportunities avai lable in these areas, Government involvement and having areasonable price with stable market for gliricidia will encourage the public to enter into this businesswhereas effective extension service is a must for making people aware.

Predicting the optimal rotation length of Teak plantations using a simulation model

The traditional problem in Forest Economics has been mainly dealt with the estimation of optimalrotation length for sustainable management. However, given the limitation of the availability of timeseries data on growth and management in forest plantations in Sri Lanka, such estimations are notfeasible. Against this background, this study attempted to develop a simulation model and predictrotational interval of teak plantation under different management conditions.A field survey was conducted to identify the plantation related parameters in the Kurunegala District.Meantime, a simulation model was developed with Microsoft Visual Basic and Microsoft Excel usingthe equations specified in the Teak Management Plan (1997) to supplement the field data. The pastdata obtained from the Forest Department was used to parameterize the model. Using the age andthe height of a plantation at a particular time, the model was capable of predicting the plantationrelated parameters such as dbh and timber volume over the time.According to the values predicted by the simulation model, four different categories were identifiedbased on the site index, which represents the level of growth of a stand. Rotational interval wasestimated using the Faustman rotational model at different discount rates. Thereby it was estimatedthat the rotational intervals for the four categories at discount rates 10%, 15% and 20% as 19, 17 and15 years respectively. The internal rate of return obtained through the simulation was above themarket rate of 12%. Though the model yielded shorter rotational intervals than the present fieldvalues, the approach could be used in future with more reliable field data.

Universal bifurcation property of two- or higher-dimensional dissipative systems in parameter space: Why does 1D symbolic dynamics work so well?

The universal bifurcation property of the H\'enon map in parameter space is studied with symbolic dynamics. The universal-$L$ region is defined to characterize the bifurcation universality. It is found that the universal-$L$ region for relative small $L$ is not restricted to very small $b$ values. These results show that it is also a universal phenomenon that universal sequences with short period can be found in many nonlinear dissipative systems.Comment: 10 pages, figures can be obtained from the author, will appeared in J. Phys.

Using Nonlinear Response to Estimate the Strength of an Elastic Network

Disordered networks of fragile elastic elements have been proposed as a model of inner porous regions of large bones [Gunaratne et.al., cond-mat/0009221, http://xyz.lanl.gov]. It is shown that the ratio $\Gamma$ of responses of such a network to static and periodic strain can be used to estimate its ultimate (or breaking) stress. Since bone fracture in older adults results from the weakening of porous bone, we discuss the possibility of using $\Gamma$ as a non-invasive diagnostic of osteoporotic bone.Comment: 4 pages, 4 figure

Strength Reduction in Electrical and Elastic Networks

Particular aspects of problems ranging from dielectric breakdown to metal insu- lator transition can be studied using electrical o elastic networks. We present an expression for the mean breakdown strength of such networks.First, we intro- duce a method to evaluate the redistribution of current due to the removal of a finite number of elements from a hyper-cubic network of conducatances.It is used to determine the reduction of breakdown strength due to a fracture of size $\kappa$.Numerical analysis is used to show that the analogous reduction due to random removal of elements from electrical and elastic networks follow a similar form.One possible application, namely the use of bone density as a diagnostic tools for osteorosporosis,is discussed.Comment: one compressed file includes: 9 PostScrpt figures and a text fil

Variable Step Random Walks and Self-Similar Distributions

We study a scenario under which variable step random walks give anomalous statistics. We begin by analyzing the Martingale Central Limit Theorem to find a sufficient condition for the limit distribution to be non-Gaussian. We note that the theorem implies that the scaling index $\zeta$ is 1/2. For corresponding continuous time processes, it is shown that the probability density function $W(x;t)$ satisfies the Fokker-Planck equation. Possible forms for the diffusion coefficient are given, and related to $W(x,t)$. Finally, we show how a time-series can be used to distinguish between these variable diffusion processes and L\'evy dynamics.Comment: 13pages, 2 figure

A putative role for microRNA-205 in mammary epithelial cell progenitors

In an effort to understand the potential role of microRNAs (miRNAs) in mammary-gland stem or progenitor cells, miRNA microarrays were performed on subpopulations of the mouse mammary epithelial cell (MEC) line COMMA-DβGeo. This cell line contains a heterogeneous subpopulation of progenitors characterized by the expression of stem cell antigen 1 (Sca-1; encoded by Ly6a). Microarray analysis indicated that the Sca-1 subpopulations have distinct miRNA expression profiles. Functional studies were performed on miR-205, which was highly expressed in the Sca-1-positive (Sca-1+) cells. When miR-205 was overexpressed in vitro, the COMMA-DβGeo cells underwent several significant morphological and molecular changes. miR-205 overexpression led to an expansion of the progenitor-cell population, decreased cell size and increased cellular proliferation. In addition, the colony-forming potential of the two Sca-1 subpopulations was increased. Target prediction for miR-205 indicated that it might regulate the expression of the tumor-suppressor protein PTEN. Overexpression studies using reporter constructs confirmed that PTEN expression is regulated by miR-205. In addition to PTEN, several other putative and previously validated miR-205 targets were identified by microarray analysis, including the previously reported miR-205 targets ZEB1 and ZEB2. Additionally, in normal mouse MECs, high expression of miR-205 was observed in stem-cell-enriched cell populations isolated by FACS using established cell-surface markers

GASZ Is Essential for Male Meiosis and Suppression of Retrotransposon Expression in the Male Germline

Nuage are amorphous ultrastructural granules in the cytoplasm of male germ cells as divergent as Drosophila, Xenopus, and Homo sapiens. Most nuage are cytoplasmic ribonucleoprotein structures implicated in diverse RNA metabolism including the regulation of PIWI-interacting RNA (piRNA) synthesis by the PIWI family (i.e., MILI, MIWI2, and MIWI). MILI is prominent in embryonic and early post-natal germ cells in nuage also called germinal granules that are often associated with mitochondria and called intermitochondrial cement. We find that GASZ (Germ cell protein with Ankyrin repeats, Sterile alpha motif, and leucine Zipper) co-localizes with MILI in intermitochondrial cement. Knockout of Gasz in mice results in a dramatic downregulation of MILI, and phenocopies the zygotene–pachytene spermatocyte block and male sterility defect observed in MILI null mice. In Gasz null testes, we observe increased hypomethylation and expression of retrotransposons similar to MILI null testes. We also find global shifts in the small RNAome, including down-regulation of repeat-associated, known, and novel piRNAs. These studies provide the first evidence for an essential structural role for GASZ in male fertility and epigenetic and post-transcriptional silencing of retrotransposons by stabilizing MILI in nuage

Symmetry Decomposition of Chaotic Dynamics

Discrete symmetries of dynamical flows give rise to relations between periodic orbits, reduce the dynamics to a fundamental domain, and lead to factorizations of zeta functions. These factorizations in turn reduce the labor and improve the convergence of cycle expansions for classical and quantum spectra associated with the flow. In this paper the general formalism is developed, with the $N$-disk pinball model used as a concrete example and a series of physically interesting cases worked out in detail.Comment: CYCLER Paper 93mar01