Rhombic Patterns: Broken Hexagonal Symmetry

Landau-Ginzburg equations derived to conserve two-dimensional spatial symmetries lead to the prediction that rhombic arrays with characteristic angles slightly differ from 60 degrees should form in many systems. Beyond the bifurcation from the uniform state to patterns, rhombic patterns are linearly stable for a band of angles near the 60 degrees angle of regular hexagons. Experiments conducted on a reaction-diffusion system involving a chlorite-iodide-malonic acid reaction yield rhombic patterns in good accord with the theory.Energy Laboratory of the University of HoustonOffice of Naval ResearchU.S. Department of Energy Office of Basic Energy SciencesRobert A. Welch FoundationCenter for Nonlinear Dynamic

New set of measures to analyze non-equilibrium structures

We introduce a set of statistical measures that can be used to quantify non-equilibrium surface growth. They are used to deduce new information about spatiotemporal dynamics of model systems for spinodal decomposition and surface deposition. Patterns growth in the Cahn-Hilliard Equation (used to model spinodal decomposition) are shown to exhibit three distinct stages. Two models of surface growth, namely the continuous Kardar-Parisi-Zhang (KPZ) model and the discrete Restricted-Solid-On-Solid (RSOS) model are shown to have different saturation exponents

Systematic derivation of a rotationally covariant extension of the 2-dimensional Newell-Whitehead-Segel equation

An extension of the Newell-Whitehead-Segel amplitude equation covariant under abritrary rotations is derived systematically by the renormalization group method.Comment: 8 pages, to appear in Phys. Rev. Letters, March 18, 199

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

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

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.

Preliminary Study of Mineral Constituents in Selected Cultivars of Root and Tuber Crops in Sri Lanka

A study was done to determine the levels of minerals (Calcium, Magnesium, Iron,Potassium and Zinc) in three different cultivars of yams (D. alata and D. esculenta),Xanthosoma sp and four different cultivars of sweet potatoes (Ipomea batatas Lam) fromdifferent regions in Sri Lanka. Yams (Rajala, Hingurala and Kukulala), Xanthosoma sp(Kiriala) and sweet potatoes (Swp3, Swp4, Swp5 and Swp7) were prepared for analysis 2– 3 days after harvesting. Flour samples were subjected to ashing using AOAC (1980)method and mineral constituents were analysed using Atomic AbsorptionSpectrophotometer (AAS). Variation in mineral constituents on dry weight basis wereanalysed using ANOVA, Tukey‟s HSD test (p< 0.05) Minitab. All three cultivars ofyams had significant levels (p< 0.05) of Calcium and Iron and high level of Magnesiumwas observed in Kiriala (45.27± 0.31 mg 100g-1). A significantly high level of Iron andPotassium (p<0.05) was observed in Rajala and Sweet potatoes respectively. Swp5cultivar contained a comparatively high amount of Calcium and Magnesium while Swp3and Swp7 contained a high level of iron (p<0.05). Comparatively high level of Zinc waspresent in Hingurala, Swp3 and Swp7 cultivars.Key words: Dioscorea , Ipomea batatas, minerals, Xanthosoma s