Three-fold way to extinction in populations of cyclically competing species

Species extinction occurs regularly and unavoidably in ecological systems. The time scales for extinction can broadly vary and inform on the ecosystem's stability. We study the spatio-temporal extinction dynamics of a paradigmatic population model where three species exhibit cyclic competition. The cyclic dynamics reflects the non-equilibrium nature of the species interactions. While previous work focusses on the coarsening process as a mechanism that drives the system to extinction, we found that unexpectedly the dynamics to extinction is much richer. We observed three different types of dynamics. In addition to coarsening, in the evolutionary relevant limit of large times, oscillating traveling waves and heteroclinic orbits play a dominant role. The weight of the different processes depends on the degree of mixing and the system size. By analytical arguments and extensive numerical simulations we provide the full characteristics of scenarios leading to extinction in one of the most surprising models of ecology

Precedence-type Test based on Progressively Censored Samples

In this paper, we introduce precedence-type tests for testing the hypothesis that two distribution functions are equal, which is an extension of the precedence life-test rst proposed by Nelson (1963), when the two samples are progressively Type-II censored. The null distributions of the test statistics are derived. Critical values for some combination of sample sizes and censoring schemes for the proposed tests are presented. Then, we present the exact power functions under the Lehmann alternative, and compare the exact power as well as simulated power (under location-shift) of the proposed precedence test based on nonparametric estimates of CDF with other precedence-type tests. We then examine the power properties of the proposed test procedures through Monte Carlo simulations. Two examples are presented to illustrate all the test procedures discussed here. Finally, we make some concluding remarks.Precedence test; Product-limit estimator; Type-II progressive censoring; Life-testing; level of significance; power; Lehmann alternative; Monte Carlo simulations

Gating of high-mobility two-dimensional electron gases in GaAs/AlGaAs heterostructures

We investigate high-mobility two-dimensional electron gases in AlGaAs heterostructures by employing Schottky-gate-dependent measurements of the samples' electron density and mobility. Surprisingly, we find that two different sample configurations can be set in situ with mobilities diering by a factor of more than two in a wide range of densities. This observation is discussed in view of charge redistributions between the doping layers and is relevant for the design of future gateable high-mobility electron gases

Optimization of laser welding of tri – metal joint via response surface methodology

 Laser welding input parameters play a major role in determining the quality of a weld joint. In the nuclear power plants, hybrid structures of nickel and steel alloys offer an advantage in comparison to conventional materials, e.g. in heat exchanger tube areas. Due to demand in the nuclear industry for new material combinations based on commercially available and qualified materials, research into thermal joining of dissimilar materials has been initiated. The use of laser for joining mild steel / nickel with 316L austenitic stainless steel filler material and structures offers some advantages compared with usual thermal joining processes. The main aim is the control of phase formation, which occurs during thermal joining of mild steel to nickel. In this research work microstructure study and optimization of laser welding of mild steel / nickel sheets with wire feeding was done using Central Composite Design(CCD) and Response Surface Methodology (RSM) are used to build the mathematical model. By means of the laser power, welding speed and pulse width on the tensile strength model was developed and tested by analysis of variance method (ANOVA), the relationship between process parameters and output response and interaction among the process parameters are analyzed and discussed in detail. The scanning electron microscopes (SEM) with energy dispersive X-ray spectroscopy (EDS) technique were used for microstructure study of the bi-metal and tri-metal joints of the weld

Encoding dynamics for multiscale community detection: Markov time sweeping for the Map equation

The detection of community structure in networks is intimately related to finding a concise description of the network in terms of its modules. This notion has been recently exploited by the Map equation formalism (M. Rosvall and C.T. Bergstrom, PNAS, 105(4), pp.1118--1123, 2008) through an information-theoretic description of the process of coding inter- and intra-community transitions of a random walker in the network at stationarity. However, a thorough study of the relationship between the full Markov dynamics and the coding mechanism is still lacking. We show here that the original Map coding scheme, which is both block-averaged and one-step, neglects the internal structure of the communities and introduces an upper scale, the `field-of-view' limit, in the communities it can detect. As a consequence, Map is well tuned to detect clique-like communities but can lead to undesirable overpartitioning when communities are far from clique-like. We show that a signature of this behavior is a large compression gap: the Map description length is far from its ideal limit. To address this issue, we propose a simple dynamic approach that introduces time explicitly into the Map coding through the analysis of the weighted adjacency matrix of the time-dependent multistep transition matrix of the Markov process. The resulting Markov time sweeping induces a dynamical zooming across scales that can reveal (potentially multiscale) community structure above the field-of-view limit, with the relevant partitions indicated by a small compression gap.Comment: 10 pages, 6 figure

AN EXPERIMENTAL INVESTIGATION OF MULTI-CYLINDER CONVENTIONAL CI ENGINE USING MADHUCA INDICA OIL AS FUEL

The present work is mainly discussed with a qualitative study of engine’s significant characteristics fuelled with mahua bio-diesel & its different types of mixtures with neat diesel. The significant technical properties of various mixtures are tabulated. A 4-S multi-cylinder (6-Cylinder) DI conventional CI engine is used for the study under different speed modes. All types of characteristics for various mixtures are estimated in running the engine. Pure diesel is indicated by B-0 and pure mahua bio-diesel is represented by B-100. From the test results, it is found that B-25 gives almost the same BTE as B-0 at maximum load, compared to all the blends. The blend B-0 and B-25 give the least SFC of 0.332 and 0.268 kg/kWh at minimum speed (1200 rpm) and maximum speed (2400 rpm) at maximum load as contrasted to all mixtures. The B-100 gave 3.01% of NOx while related to B-0 @ lower speed

Galaxy Formation with local photoionisation feedback I. Methods

We present a first study of the effect of local photoionising radiation on gas cooling in smoothed particle hydrodynamics simulations of galaxy formation. We explore the combined effect of ionising radiation from young and old stellar populations. The method computes the effect of multiple radiative sources using the same tree algorithm used for gravity, so it is computationally efficient and well resolved. The method foregoes calculating absorption and scattering in favour of a constant escape fraction for young stars to keep the calculation efficient enough to simulate the entire evolution of a galaxy in a cosmological context to the present day. This allows us to quantify the effect of the local photoionisation feedback through the whole history of a galaxy`s formation. The simulation of a Milky Way like galaxy using the local photoionisation model forms ~ 40 % less stars than a simulation that only includes a standard uniform background UV field. The local photoionisation model decreases star formation by increasing the cooling time of the gas in the halo and increasing the equilibrium temperature of dense gas in the disc. Coupling the local radiation field to gas cooling from the halo provides a preventive feedback mechanism which keeps the central disc light and produces slowly rising rotation curves without resorting to extreme feedback mechanisms. These preliminary results indicate that the effect of local photoionising sources is significant and should not be ignored in models of galaxy formation.Comment: Accepted for Publication in MNRAS, 13 pages, 13 figure

A Pairing-free Provable Secure and Efficient Identity-based Identification Scheme with Anonymity

In this paper, we propose a Blind Identity-Based Identification (Blind IBI) scheme based on the Guillou-Quisquater (GQ) scheme. Our proposed scheme combines the benefits of traditional Identity-Based Identification (IBI) schemes that can authenticate a user’s identity without rely ing on a trusted third party with the Blind Signature (BS) scheme that provides anonymity. As a result, the proposed scheme assures absolute user privacy during the authentication process. It does not rely on a third party, yet the verifier can still be assured of the user’s identity with out the user actually revealing it. In our work, we show that the proposed scheme is provably secure under the random oracle model, with the assumption that the one-more-RSA-inversion problem is difficult. Furthermore, we demonstrate that the proposed scheme is secure against passive, active, and concurrent impersonation attacks. In conclusion, the proposed scheme is able to achieve the desired blindness property without compromising the security of the GQ-IBI scheme it is based upon

Construction of genetic linkage map and QTL analysis of sinksize traits in pearl millet (Pennisetum glaucum)

A linkage map, primarily based on SSCP-SNP markers, was constructed using 188 F2:3 (F2-derived F3) mapping population progenies derived from a cross between two pearl millet inbred lines having diverse pedigrees. The parents had large differences for two sink size traits (grain size and panicle diameter), and also differed for panicle length. The skeleton linkage map covered 1019 cM and it comprised of 44 loci (detected with 24 SSCP-SNP, 10 genomic SSR, 6 EST-SSR and 4 STS primer pairs) distributed across the seven linkage groups. Average adjacent-marker intervals ranged from 14 cM on LG1 to 38 cM on LG6, with an overall mean of 23 cM. Using the F2 linkage map and phenotypic data collected from the F2 and F2:3 generations of the mapping population, a total of 18 putative QTLs were detected for the three sink-size components. Eight QTLs explained 42.7% of observed phenotypic variation for panicle length, with individual QTLs explaining 6.1 to 18.2% using the F2:3 data set. For panicle diameter, 5 QTLs explained 45.8% of observed phenotypic variation with individual QTLs accounting for 6.3 to 30.2%. Similarly for grain size, 5 QTLs explained 29.6% of phenotypic variation with individual QTLs accounting for 6.1 to 8.9%. Genomic regions associated with panicle length, panicle diameter and grain size co-mapped on LG6 between Xpsms88 and Xpsms2270, indicating the existence of a gene or gene cluster with major effects involved in the control of significant proportions of the phenotypic variation for all three sink-size traits. The QTLs for panicle length on LG2 and LG6 (LOD>3 in both F2 and F2:3 data sets), for panicle diameter on LG2 and LG3 (LOD>14 in the F2:3 data set) and for grain size on LG3 and LG6 (LOD>3 in both F2 and F2:3 data sets) were identified as promising candidates for validation prior to possible application in marker-assisted breeding

Detection of Landmine Signature using SAW-based Polymer-coated Chemical Sensor

The explosive charge within a landmine is the source for a mixture of chemical vapours that form a distinctive chemical signature indicative of a landmine. The concentrations of these compounds in the air over landmines is extremely low (parts-per-trillion or lower), well below the minimum detection limits of most field-portable chemical sensors. This paper describes a portable  surface acoustic wave-based polymer-coated sensor for the detection of hidden explosives. The sensitivity and selectivity of polymer-based sensors depend on several factors including the chemo-selective coating used, the physical properties of the vapour(s) of interest, the selected transducers, and the operating conditions. The polymer-based sensor was calibrated in the  laboratory using the explosive vapour generator. The preliminary results indicated that the carbowax 1000 could be a very good chemical interface to sense low levels of chemical signature of explosive material. Response for 50 ppb of TNT vapours was observed to be 400 Hz for an exposure of 2 min