Extremal dynamics on complex networks: Analytic solutions

The Bak-Sneppen model displaying punctuated equilibria in biological evolution is studied on random complex networks. By using the rate equation and the random walk approaches, we obtain the analytic solution of the fitness threshold $x_c$ to be 1/(_f+1), where _f=/ (=) in the quenched (annealed) updating case, where is the n-th moment of the degree distribution. Thus, the threshold is zero (finite) for the degree exponent \gamma 3) for the quenched case in the thermodynamic limit. The theoretical value x_c fits well to the numerical simulation data in the annealed case only. Avalanche size, defined as the duration of successive mutations below the threshold, exhibits a critical behavior as its distribution follows a power law, P_a(s) ~ s^{-3/2}.Comment: 6 pages, 2 figure

Avalanche dynamics in Bak-Sneppen evolution model observed with standard distribution width of fitness

We introduce the standard distribution width of fitness to characterize the global and individual features of a ecosystem in the Bak-Sneppen evolution model. Through tracking this quantity in evolution, a different hierarchy of avalanche dynamics, $w_{0}$ avalanche is observed. The corresponding gap equation and the self-organized threshold $w_{c}$ are obtained. The critical exponents $\tau ,$ $\gamma$and $\rho$, which describe the behavior of the avalanche size distribution, the average avalanche size and the relaxation to attractor, respectively, are calculated with numerical simulation. The exact master equation and $\gamma$ equation are derived. And the scaling relations are established among the critical exponents of this new avalanche.Comment: 14 pages, 3 figure

Mechanical basis of morphogenesis and convergent evolution of spiny seashells

Convergent evolution is a phenomenon whereby similar traits evolved independently in not closely related species, and is often interpreted in functional terms. Spines in mollusk seashells are classically interpreted as having repeatedly evolved as a defense in response to shell-crushing predators. Here we consider the morphogenetic process that shapes these structures and underlies their repeated emergence. We develop a mathematical model for spine morphogenesis based on the mechanical interaction between the secreting mantle edge and the calcified shell edge to which the mantle adheres during shell growth. It is demonstrated that a large diversity of spine structures can be accounted for through small variations in control parameters of this natural mechanical process. This physical mechanism suggests that convergent evolution of spines can be understood through a generic morphogenetic process, and provides unique perspectives in understanding the phenotypic evolution of this second largest phylum in the animal kingdom.\ud \ud Homoplasy, the appearance of similar traits in separate evolutionary lineages as a result of convergence, parallelism, or evolutionary reversals, is a major concern in phylogenetic analysis for which it is viewed as noise. However, over the past two decades, homoplasy has also become a subject of increasing interest, stimulated by the rise of evolutionary developmental biology (evo devo) and the wish to uncover the developmental basis of this phenomenon (1⇓–3). Spines constitute the most prominent ornamentation of mollusk shells and have evolved in many distantly related fossil and current mollusk species (at least 55 genera and 21 families of current gastropods; 10 genera and 8 families of current bivalves; 11 genera and 8 families of ammonoids; and 6 fossil nautiloid genera; see Fig. 1 for examples). Convergent evolution of spines in mollusks has been addressed in functional terms, these structures being interpreted as having evolved as a defense in response to shell-crushing predators (4⇓–6). This hypothesis is itself the basis of the widely cited “escalation hypothesis,” according to which long-term trends in the fossil record were caused by the evolutionary response of prey to predation pressure (7). The idea that convergent evolution of similar mollusk ornamentations might be fully explained in functional terms is based on the premise that similar characters, perceived as well designed for a presumed function, cannot conceivably have independently evolved fortuitously. Therefore, natural selection is thought to have repeatedly shaped similar functional traits out of random variations

Humble Adorations Behind Kakawin Banawa Sekar Tanakung: a Critical Discourse Analysis

This research which deals with critical discourse analysis aims (1) to find out meanings of terms and vocabularies in Kakawin Banawa Sekar Tanakung, (2) to analyze meanings of Kakawin Banawa Sekar Tanakung in religious context, and (3) to reveal ideology behind the Kakawin Banawa Sekar Tanakung. The subject of this study was Kakawin Banawa Sekar Tanakung in ancient Javanese language, while the techniques of data collections were documentation. The data was then analyzed descriptively based on theory of Critical Discourse Analysis, theory of Natural Semantic Metalanguage and theory of meaning. The results of data analysis show that (1) most meanings of terms and vocabularies in the Kakawin Banawa Sekar Tanakung were reduced and broadened due to the influence of local culture and historical events. Some words are still common in today\u27s society, especially the Balinese in which ancient Javanese literatures are kept preserved today. (2) Kakawin Banawa Sekar Tanakung has a religious and ethical meaning, that people\u27s life in the ancient Java was religiously patterned. Besides, the kakawin showed that people of the ancient Java maintained their respects and submissiveness to the royal authorities. (3) The ideology of Kakawin Banawa Sekar Tanakung is submissive adoration, seen from the way the poet selected words and presented the kakawin through humble language choices. Considering that kakawins have valuable religious, moral, and educational values, further research on ancient Javanese literature are needed. Critical analysis according to the context of the kakawin should be conducted for the raise of Indonesian research on local assets. 2 PUJIAN DENGAN KERENDAHAN HATI DALAM KAKAWIN BANAWA SEKAR TANAKUNG: SEBUAH ANALISIS WACANA KRITIS oleh Ida Bagus Arya Lawa Manuaba NIM. 1029011062 Jurusan Pendidikan Bahasa Program Pascasarjana Universitas Pendidikan Ganesha Juli 201

Improving estimation of glacier volume change: a GLIMS case study of Bering Glacier System, Alaska

International audienceThe Global Land Ice Measurements from Space (GLIMS) project has developed tools and methods that can be employed by analysts to create accurate glacier outlines and resultant measures of glacier extent. To illustrate the importance of accurate glacier outlines and the effectiveness of GLIMS standards we have conducted a case study on Bering Glacier System (BGS), Alaska. BGS is a complex glacier system aggregated from multiple drainage basins, numerous individual ice streams, and many accumulation areas. Published measurements of BGS surface area vary from 1740 to 6200 km2, depending on how the boundaries of this system have been defined. Utilizing GLIMS tools and standards we have completed a new outline and analysis of the area-altitude distribution (hypsometry) of BGS using Landsat images from 2000 and 2001. We compared this new outline (3632 km2) with three previous outlines to illustrate the errors that result from the widely varying estimates used in previous analysis of BGS area. The use of different BGS outlines results in highly variable measures of volume change and net balance (bn). Outline variability alone results in a net balance rate range of ?1.0 to ?3.2 m/yr water equivalent (W.E.), a volume change range of ?4.2 to ?8.2 km3/yr, and a near doubling in contributions to sea level equivalent (SLE), 0.0122 mm/yr to 0.0236 mm/yr. A study of three different models of BGS net balance leads us to favor estimates of bn of ?1.2 m/yr W.E. and total volume change of ?4.2 km3/yr for the period 1950?2004. These estimates result in a near doubling of contributions to sea level equivalent when compared with previous studies. While current inaccuracies in glacier outlines hinder our ability to fully understand glacier change, there is no reason why our understanding of glacier extents should not be comprehensive and accurate. Such accuracy is possible with the increasing volume of satellite imagery of glacierized regions, and recent advances in tools and standards

Exact equqations and scaling relations for f-avalanche in the Bak-Sneppen evolution model

Infinite hierarchy of exact equations are derived for the newly-observed f-avalanche in the Bak-Sneppen evolution model. By solving the first order exact equation, we found that the critical exponent which governs the divergence of the average avalanche size, is exactly 1 (for all dimensions), confirmed by the simulations. Solution of the gap equation yields another universal exponent, denoting the the relaxation to the attractor, is exactly 1. We also establish some scaling relations among the critical exponents of the new avalanche.Comment: 5 pages, 1 figur

Schumpeterian economic dynamics as a quantifiable minimum model of evolution

We propose a simple quantitative model of Schumpeterian economic dynamics. New goods and services are endogenously produced through combinations of existing goods. As soon as new goods enter the market they may compete against already existing goods, in other words new products can have destructive effects on existing goods. As a result of this competition mechanism existing goods may be driven out from the market - often causing cascades of secondary defects (Schumpeterian gales of destruction). The model leads to a generic dynamics characterized by phases of relative economic stability followed by phases of massive restructuring of markets - which could be interpreted as Schumpeterian business `cycles'. Model timeseries of product diversity and productivity reproduce several stylized facts of economics timeseries on long timescales such as GDP or business failures, including non-Gaussian fat tailed distributions, volatility clustering etc. The model is phrased in an open, non-equilibrium setup which can be understood as a self organized critical system. Its diversity dynamics can be understood by the time-varying topology of the active production networks.Comment: 21 pages, 11 figure

Self-organized criticality in deterministic systems with disorder

Using the Bak-Sneppen model of biological evolution as our paradigm, we investigate in which cases noise can be substituted with a deterministic signal without destroying Self-Organized Criticality (SOC). If the deterministic signal is chaotic the universality class is preserved; some non-universal features, such as the threshold, depend on the time correlation of the signal. We also show that, if the signal introduced is periodic, SOC is preserved but in a different universality class, as long as the spectrum of frequencies is broad enough.Comment: RevTex, 8 pages, 8 figure

Critical and Near-Critical Branching Processes

Scale-free dynamics in physical and biological systems can arise from a variety of causes. Here, we explore a branching process which leads to such dynamics. We find conditions for the appearance of power laws and study quantitatively what happens to these power laws when such conditions are violated. From a branching process model, we predict the behavior of two systems which seem to exhibit near scale-free behavior--rank-frequency distributions of number of subtaxa in biology, and abundance distributions of genotypes in an artificial life system. In the light of these, we discuss distributions of avalanche sizes in the Bak-Tang-Wiesenfeld sandpile model.Comment: 9 pages LaTex with 10 PS figures. v.1 of this paper contains results from non-critical sandpile simulations that were excised from the published versio

Microfungal community in sandy beaches located in Kedah, Pahang and Sabah, Malaysia

Microfungi are fundamental organisms help in balancing the ecosystem. The aims of this study are to identify microfungi isolated from sandy beaches based on internal transcribed spacers (ITS) sequence analysis and to determine the phylogenetic relationship among the locations of sampling areas. Fifty-seven isolates of microfungi were obtained from six beaches located in Kedah (Chenang Beach), Pahang (Balok Beach) and Sabah (Mamutik Island, Manukan Island, Sapi Island and Tanjung Aru Beach) to be used in this study. From the finding, the highest identified species were Aspergillusspecies (27 isolates) followed by Trichodermaspecies (12 isolates), Penicilliumspecies (10 isolates), Fusariumspecies (6 isolates), Bipolarisspecies (1 isolate) and Chaetomiumspecies (1 isolate). ITS fragment of all isolates was amplified in within the size range of 533–658 bp. A phylogenetic tree was constructed using maximum likelihood (ML) method; the isolates were grouped into three clades according to their classes. In conclusion, diverse microfungi isolated from sandy beach soil depicting 19 species were discovered. Future studies are highly recommended to focus on intra-and interspecies diversity based on microsatellite markers analysis, consequently the originality and distribution of the fungal isolates. The outcome of this study includesa baseline data on the occurrence and species-diversity as well as important information on the status of microfungi in Malaysia beaches located in Kedah, Melaka and Sabah. It can be used as a checklist for future studies related to fungi distributionin the tropical beaches