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Distance Measures (distance + measure)
Selected AbstractsComparing the anatomical consistency of the posterior superior iliac spine to the iliac crest as reference landmarks for the lumbopelvic spine: A retrospective radiological studyCLINICAL ANATOMY, Issue 7 2007J.M. McGaugh Abstract A palpation reference line coursing between the superior-most aspect of the iliac crests has been reported to cross the L4 spinous process or L4/L5 intervertebral space in ,80% of the population. Comparable data have not been defined for the line coursing between the posterior superior iliac spines (PSIS). The purpose of this study was to compare the anatomical consistency of the PSIS to the iliac crest as landmarks used for spinal palpation. One hundred computerized tomographic images were reviewed in a three-dimensional setting. Two horizontal lines were constructed on each image: Line 1 representing the superior-most aspect of the iliac crest and Line 2 representing the inferior margin of the PSIS. The vertical distance between each horizontal line and the inferior edge of its respective spinous process were measured. The PSIS corresponded to the S2 spinous process in 81% of subjects and the iliac crest to the L4 spinous process in 59% of subjects. Distance measures suggest that the PSIS was closer to S2 versus the iliac crest to L4 (t = 6.998; P < 0.01). The PSIS crossed S2 more frequently than the iliac crest crossed L4 (,2 = 12.719, P , 0.01). The study findings support the relationship between the PSIS, and the spinous process of S2 is more consistent when compared to the iliac crest and the spinous process of L4. The PSIS reference line may be used to find S2 as a reference standard in validity and reliability palpation studies in the lower lumbar spine. Clin. Anat. 20:819,825, 2007. © 2007 Wiley-Liss, Inc. [source] Kernel approach to possibilistic C -means clusteringINTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 3 2009Frank Chung-Hoon Rhee Kernel approaches can improve the performance of conventional clustering or classification algorithms for complex distributed data. This is achieved by using a kernel function, which is defined as the inner product of two values obtained by a transformation function. In doing so, this allows algorithms to operate in a higher dimensional space (i.e., more degrees of freedom for data to be meaningfully partitioned) without having to compute the transformation. As a result, the fuzzy kernel C -means (FKCM) algorithm, which uses a distance measure between patterns and cluster prototypes based on a kernel function, can obtain more desirable clustering results than fuzzy C -means (FCM) for not only spherical data but also nonspherical data. However, it can still be sensitive to noise as in the FCM algorithm. In this paper, to improve the drawback of FKCM, we propose a kernel possibilistic C -means (KPCM) algorithm that applies the kernel approach to the possibilistic C -means (PCM) algorithm. The method includes a variance updating method for Gaussian kernels for each clustering iteration. Several experimental results show that the proposed algorithm can outperform other algorithms for general data with additive noise. © 2009 Wiley Periodicals, Inc. [source] Novel method for analyzing proteomeINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 6 2007Bo Liao Abstract We propose a 6D representation of protein sequences consisting of 20 amino acids. Based on this 6D representation, we propose a proteome distance measure for constructing phylogenic tree. And we make use of the corresponding similarity matrix to construct phylogenic tree. The examination of phylogenic tree belong to 30 mitochondrial sequence illustrates the utility of our approach. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source] A graphical method to construct a phylogenetic treeINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 9 2006Weiping Wang Abstract A 3D graphical representation of DNA sequences, which has no circuit or degeneracy, is derived for mathematical denotation of DNA sequence. Based on this graphical representation, we propose a new sequence distance measure. We make use of the corresponding similarity matrix to construct a phylogenic tree by virtue of the fuzzy theory. The examination of phylogenic tree belong to eight species illustrates the utility of our approach. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [source] Computation of Likelihood Ratios in Fingerprint Identification for Configurations of Any Number of MinutićJOURNAL OF FORENSIC SCIENCES, Issue 1 2007Cédric Neumann M.Sc. ABSTRACT: Recent court challenges have highlighted the need for statistical research on fingerprint identification. This paper proposes a model for computing likelihood ratios (LRs) to assess the evidential value of comparisons with any number of minutić. The model considers minutiae type, direction and relative spatial relationships. It expands on previous work on three minutiae by adopting a spatial modeling using radial triangulation and a probabilistic distortion model for assessing the numerator of the LR. The model has been tested on a sample of 686 ulnar loops and 204 arches. Features vectors used for statistical analysis have been obtained following a preprocessing step based on Gabor filtering and image processing to extract minutiae data. The metric used to assess similarity between two feature vectors is based on an Euclidean distance measure. Tippett plots and rates of misleading evidence have been used as performance indicators of the model. The model has shown encouraging behavior with low rates of misleading evidence and a LR power of the model increasing significantly with the number of minutić. The LRs that it provides are highly indicative of identity of source on a significant proportion of cases, even when considering configurations with few minutić. In contrast with previous research, the model, in addition to minutia type and direction, incorporates spatial relationships of minutić without introducing probabilistic independence assumptions. The model also accounts for finger distortion. [source] Genetic similarity of polyploids: a new version of the computer program POPDIST (version 1.2.0) considers intraspecific genetic differentiationMOLECULAR ECOLOGY RESOURCES, Issue 5 2009JÜRGEN TOMIUK Abstract For evolutionary studies of polyploid species estimates of the genetic identity between species with different degrees of ploidy are particularly required because gene counting in samples of polyploid individuals often cannot be done, e.g., in triploids the phenotype AB can be genotypically either ABB or AAB. We recently suggested a genetic distance measure that is based on phenotype counting and made available the computer program POPDIST. The program provides maximum-likelihood estimates of the genetic identities and distances between polyploid populations, but this approach is not informative for populations within species that only differ in their allele frequencies. We now close this gap by applying the frequencies of shared ,bands' in both populations to Nei's identity measure. Our simulation study demonstrates the close correlation between the band-sharing identity and the genetic identity calculated on the basis of gene frequencies for any degree of ploidy. The new extended version of POPDIST (version 1.2.0) provides the option of choosing either the maximum-likelihood estimator or the band-sharing measure. [source] Crystal fingerprint space , a novel paradigm for studying crystal-structure setsACTA CRYSTALLOGRAPHICA SECTION A, Issue 5 2010Mario Valle The initial aim of the crystal fingerprint project was to solve a very specific problem: to classify and remove duplicate crystal structures from the results generated by the evolutionary crystal-structure predictor USPEX. These duplications decrease the genetic diversity of the population used by the evolutionary algorithm, potentially leading to stagnation and, after a certain time, reducing the likelihood of predicting essentially new structures. After solving the initial problem, the approach led to unexpected discoveries: unforeseen correlations, useful derived quantities and insight into the structure of the overall set of results. All of these were facilitated by the project's underlying idea: to transform the structure sets from the physical configuration space to an abstract, high-dimensional space called the fingerprint space. Here every structure is represented as a point whose coordinates (fingerprint) are computed from the crystal structure. Then the space's distance measure, interpreted as structure `closeness', enables grouping of structures into similarity classes. This model provides much flexibility and facilitates access to knowledge and algorithms from fields outside crystallography, e.g. pattern recognition and data mining. The current usage of the fingerprint-space model is revealing interesting properties that relate to chemical and crystallographic attributes of a structure set. For this reason, the mapping of structure sets to fingerprint space could become a new paradigm for studying crystal-structure ensembles and global chemical features of the energy landscape. [source] Neurofuzzy Modeling of Context,Contingent Proximity RelationsGEOGRAPHICAL ANALYSIS, Issue 2 2007Xiaobai Yao The notion of proximity is one of the foundational elements in humans' understanding and reasoning of the geographical environments. The perception and cognition of distances plays a significant role in many daily human activities. Yet, few studies have thus far provided context,contingent translation mechanisms between linguistic proximity descriptors (e.g., "near,""far") and metric distance measures. One problem with previous fuzzy logic proximity modeling studies is that they presume the form of the fuzzy membership functions of proximity relations. Another problem is that previous studies have fundamental weaknesses in considering context factors in proximity models. We argue that statistical approaches are ill suited to proximity modeling because of the inherently fuzzy nature of the relations between linguistic and metric distance measures. In this study, we propose a neurofuzzy system approach to solve this problem. The approach allows for the dynamic construction of context,contingent proximity models based on sample data. An empirical case study with human subject survey data is carried out to test the validity of the approach and to compare it with the previous statistical approach. Interpretation and prediction accuracy of the empirical study are discussed. [source] Microgeographic population structure of brook charr: a comparison of microsatellite and mark-recapture dataJOURNAL OF FISH BIOLOGY, Issue 3 2003B. K. Adams Polymorphism at five microsatellite genetic markers (genotyped n = 496) and mark-recapture tagging data (tagged n = 9813) were used to define the population structure of brook charr, Salvelinus fontinalis from the Indian Bay watershed, Newfoundland, Canada. Despite the absence of physical barriers to migration among lakes, both genetic and tagging data suggest that brook charr in each lake represent reproductively isolated populations. Exact tests comparing allele frequencies, , (global value = 0·063), Rst (global value = 0·052), individual assignment tests, and Nei's genetic distance provided congruent estimates of population subdivision in agreement with the tagging data (only 2·2% of recaptures were lake-to-lake). The genetic structure of the brook charr populations corresponded with the geographic structure of the drainage basin on a qualitative level, although linear distance over water was not significantly correlated with the tagging data or the genetic distance measures. The agreement between the tagging and the genetic data suggest that microsatellite markers can be useful tools for defining real biological units. The results also suggest that brook charr exhibit microgeographic population structure at the watershed scale, and that this is the scale at which conservation and management of this salmonid might best be implemented. [source] Intraspecific variation and population structure of the German cockroach, Blattella germanica, revealed with RFLP analysis of the non-transcribed spacer region of ribosomal DNAMEDICAL AND VETERINARY ENTOMOLOGY, Issue 2 2007D. V. MUKHA Abstract Little information is available on genetic variation within and between populations of pest cockroaches. In this study, intraspecific HindIII polymorphism was investigated in the German cockroach, Blattella germanica (Linnaeus) (Dictyoptera, Blattaria: Blattellidae), using restriction fragment length polymorphisms (RFLP) of the non-transcribed spacer (NTS) region of ribosomal DNA (rDNA). Individual male insects were collected from infestations at three different pig farms. Each population was characterized by HindIII restriction fragment frequencies and haplotype (a particular X-chromosome pattern) frequencies. The inheritance of the X-chromosome HindIII rDNA patterns over 12 generations (3 years) follows Mendelian patterns, and the stability of this polymorphic marker indicates infrequent genetic recombination of variable sites. Although pairwise genetic distance measures were uncorrelated with geographical distance, the pattern of genetic differentiation of the three cockroach populations suggests that human-mediated transport of cockroaches is an important force in shaping the population genetic structure of cockroach infestations, at least at the regional scale of 10,100 km. Sequence variation in the ribosomal NTS is a useful marker, and RFLP of rDNA is a simple, robust and reproducible technique for differentiating recently diverged cockroach populations. [source] Sea-level changes and palaeo-ranges: reconstruction of ancient shorelines and river drainages and the phylogeography of the Australian land crayfish Engaeus sericatus Clark (Decapoda: Parastacidae)MOLECULAR ECOLOGY, Issue 24 2008MARK B. SCHULTZ Abstract Historical sea levels have been influential in shaping the phylogeography of freshwater-limited taxa via palaeodrainage and palaeoshoreline connections. In this study, we demonstrate an approach to phylogeographic analysis incorporating historical sea-level information in a nested clade phylogeographic analysis (NCPA) framework, using burrowing freshwater crayfish as the model organism. Our study area focuses on the Bass Strait region of southeastern Australia, which is marine region encompassing a shallow seabed that has emerged as a land bridge during glacial cycles connecting mainland Australia and Tasmania. Bathymetric data were analysed using Geographical Information Systems (GIS) to delineate a palaeodrainage model when the palaeocoastline was 150 m below present-day sea level. Such sea levels occurred at least twice in the past 500 000 years, perhaps more often or of larger magnitude within the last 10 million years, linking Victoria and Tasmania. Inter-locality distance measures confined to the palaeodrainage network were incorporated into an NCPA of crayfish (Engaeus sericatus Clark 1936) mitochondrial 16S rDNA haplotypes. The results were then compared to NCPAs using present-day river drainages and traditional great-circle distance measures. NCPA inferences were cross-examined using frequentist and Bayesian procedures in the context of geomorphological and historical sea-level data. We found distribution of present-day genetic variation in E. sericatus to be partly explained not only by connectivity through palaeodrainages but also via present-day drainages or overland (great circle) routes. We recommend that future studies consider all three of these distance measures, especially for studies of coastally distributed species. [source] A simple method for the calculation of microsatellite genotype distances irrespective of ploidy levelMOLECULAR ECOLOGY, Issue 7 2004ICA BRUVO Abstract Microsatellites are powerful molecular markers, used commonly to estimate intraspecific genetic distances. With the exception of band sharing similarity index, available distance measures were developed specifically for diploid organisms and are unsuited for comparisons of polyploids. Here, we present a simple method for calculation of microsatellite genotype distances, which takes into account mutation processes and permits comparison of individuals with different ploidy levels. This method should provide a valuable tool for intraspecific analyses of polyploid organisms, which are widespread among plants and some animal taxa. An illustration is given using data from the planarian flatworm Schmidtea polychroa (Platyhelminthes). [source] Three social distance measures for film rankingsPROCEEDINGS OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE & TECHNOLOGY (ELECTRONIC), Issue 1 2003Gregory H. Leazer We describe the use of three alternative methods for ranking films for information retrieval (IR). A large film-person incidence matrix is generated using the principle cast, directors, producers and screenwriters for each film. These attributes are used to measure film-film distances by creating a distance matrix: two films are considered to be adjacent if there is any overlap in the people associated with each film. The distance between any two films is measured by the shortest path used to connect them through their adjacent members. The second and third methods involve the creation of a similarity matrix that expresses the amount of overlap in the people associated with any two films using Dice's coefficient. A "product distance" matrix is then derived that express the distances between any two films based on the product of the similarity weights on a path that connects those films. The highest value is chosen when alternate paths connect the two films. We also describe an "accumulative difference distance" matrix that also expresses the distances among pairs of films. The distance, product distance and accumulative difference distance matrices are used to generate rankings for a random sample of films. [source] Further analysis of the population history of ancient EgyptiansAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 2 2009Michael A. Schillaci Abstract The origins of state formation in ancient Egypt have been the focus of recent research utilizing biological data to test hypotheses regarding in situ development of local groups, or large-scale in-migration, possibly by an invading army. The primary goal of the present research is to further test these hypotheses. Our secondary goal is to compare different distance measures and assess how they might affect interpretation of population history. We analyze craniodental nonmetric data using several different measures of biological distance, as well as a method for estimating group diversity using multidimensional scaling of distance estimates. Patterns of biological variation and population relationships were interpreted in temporal and geographic contexts. The results of our analyses suggest that the formation of the ancient Egyptian state likely included a substantial in situ process, with some level of contribution by outside migrants probable. The higher level of population structure in Lower Egypt, relative to Upper Egypt, suggests that such influence and migration by outsiders may not have been widespread geographically. These findings support, but serve to refine further those obtained by the second author in a previous study. Moreover, our comparison of distance measures indicates that the choice of measure can influence identification and interpretation of the microevolutionary processes shaping population history, despite being strongly correlated with one another. Am J Phys Anthropol 2009. © 2009 Wiley-Liss, Inc. [source] | ||||||||||||||||