Global Optimization by Energy Landscape Paving

We introduce a novel heuristic global optimization method, energy landscape paving (ELP), which combines core ideas from energy surface deformation and tabu search. In appropriate limits, ELP reduces to existing techniques. The approach is very general and flexible and is illustrated here on two protein folding problems. For these examples, the technique gives faster convergence to the global minimum than previous approaches.Comment: to appear in Phys. Rev. Lett. (2002

Biologically Inspired Monocular Vision Based Navigation and Mapping in GPS-Denied Environments

This paper presents an in-depth theoretical study of bio-vision inspired feature extraction and depth perception method integrated with vision-based simultaneous localization and mapping (SLAM). We incorporate the key functions of developed visual cortex in several advanced species, including humans, for depth perception and pattern recognition. Our navigation strategy assumes GPS-denied manmade environment consisting of orthogonal walls, corridors and doors. By exploiting the architectural features of the indoors, we introduce a method for gathering useful landmarks from a monocular camera for SLAM use, with absolute range information without using active ranging sensors. Experimental results show that the system is only limited by the capabilities of the camera and the availability of good corners. The proposed methods are experimentally validated by our self-contained MAV inside a conventional building

Evolution of the Caribbean Species of Columnea (Gesneriaceae) with an Emphasis on the Jamaican Species

Premise of research. Biogeography has improved understanding of evolution and diversification of organisms on both continental and island systems. One complicated island group in terms of geological history and biogeographic pattern is the Caribbean island system. A comparison across taxonomic groups does not result in overarching patterns for this group of islands. Columnea has the greatest number of species endemic to the Caribbean for any genus in Gesneriaceae that is not mostly endemic to the Caribbean with 16 species. Thirteen of these species are found on Jamaica, the remaining three each endemic to Cuba, Hispaniola, and Puerto Rico. In addition, populations of Columnea sanguinea and Columnea scandens are known from both mainland and multiple Caribbean islands. We investigate the pattern of evolution in Caribbean species of Columnea and attempt to explain the large number of species found on the island of Jamaica relative to the other islands. We explicitly test whether Caribbean species of Columnea are monophyletic and whether the 13 species endemic to Jamaica are a monophyletic group. This genus can help understand biogeographic patterns and modes of speciation in the Caribbean. Methodology. We sampled all Caribbean species of Columnea using DNA sequence data and phylogenetic methods to understand the pattern of diversity to determine whether multiple or single introductions could explain the diversity on the Caribbean islands. Pivotal results. The Caribbean species do not form a monophyletic group. The Jamaican species are monophyletic, and the endemic Cuban species, Columnea tincta, is sister to 12 of the Jamaican species, with Columnea pubescens sister to C. tincta + remaining Jamaican species. Most Jamaican species share similar corolla morphologies to section Columnea. Although never recovered as part of section Columnea, approximately unbiased tests cannot reject a sister group relationship of the Jamaican/Cuban endemic clade to section Columnea but can reject inclusion in section Columnea. Conclusions. The high diversity of Columnea in the Caribbean is due to the disproportionate number of species on Jamaica, but there is no obvious explanation for the radiation on this island, despite considering island size, topography, pollinators, and dispersers. The large number of species could be attributed to over-splitting on Jamaica, but even if a narrower concept were followed, and four of the species were combined as varieties of Columnea hirsuta as earlier taxonomy had predicted, the number of morphologically distinctive species would still be nine and much greater than that of the other islands. Our data also indicate that C. hirsutasensu lato is not monophyletic

Characteristics of predictor sets found using differential prioritization

<p>Abstract</p> <p>Background</p> <p>Feature selection plays an undeniably important role in classification problems involving high dimensional datasets such as microarray datasets. For filter-based feature selection, two well-known criteria used in forming predictor sets are relevance and redundancy. However, there is a third criterion which is at least as important as the other two in affecting the efficacy of the resulting predictor sets. This criterion is the degree of differential prioritization (DDP), which varies the emphases on relevance and redundancy depending on the value of the DDP. Previous empirical works on publicly available microarray datasets have confirmed the effectiveness of the DDP in molecular classification. We now propose to establish the fundamental strengths and merits of the DDP-based feature selection technique. This is to be done through a simulation study which involves vigorous analyses of the characteristics of predictor sets found using different values of the DDP from toy datasets designed to mimic real-life microarray datasets.</p> <p>Results</p> <p>A simulation study employing analytical measures such as the distance between classes before and after transformation using principal component analysis is implemented on toy datasets. From these analyses, the necessity of adjusting the differential prioritization based on the dataset of interest is established. This conclusion is supported by comparisons against both simplistic rank-based selection and state-of-the-art equal-priorities scoring methods, which demonstrates the superiority of the DDP-based feature selection technique. Reapplying similar analyses to real-life multiclass microarray datasets provides further confirmation of our findings and of the significance of the DDP for practical applications.</p> <p>Conclusion</p> <p>The findings have been achieved based on analytical evaluations, not empirical evaluation involving classifiers, thus providing further basis for the usefulness of the DDP and validating the need for unequal priorities on relevance and redundancy during feature selection for microarray datasets, especially highly multiclass datasets.</p

Possible new vortex matter phases in BSCCO

The vortex matter phase diagram of BSCCO crystals is analyzed by investigating vortex penetration through the surface barrier in the presence of a transport current. The strength of the effective surface barrier, its nonlinearity, and asymmetry are used to identify a possible new ordered phase above the first-order transition. This technique also allows sensitive determination of the depinning temperature. The solid phase below the first-order transition is apparently subdivided into two phases by a vertical line extending from the multicritical point.Comment: 11 pages, 3 figures, accepted for publication in PR