956 resultados para Kullback-Leibler divergence


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In certain molecular models, and related one-dimensional field theories, localized objects appear with half-integral expectation values of charge. We consider whether these states are eigenstates of charge, with half-integral eigenvalue. We find that it is indeed so for a suitably diffuse definition of the charge operator in question. This diffuse charge operator has a spectrum which approaches a continuum. The analysis is made on a lattice, to avoid divergence ambiguities, and on a finite length, which is only subsequently made large. The half-integral charge phenomenon is not tied to solitons, but can also arise as an end effect.

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The attenuation of long-wavelength phonons due to their interaction with electronic excitations in disordered systems is investigated here. Lattice strain couples to electronic stress, and thus ultrasonic attenuation measures electronic viscosity. The enhancement and critical divergence of electronic viscosity due to localization effects is calculated for the first time. Experimental consequences for the anomalous increase of ultrasonic attenuation in disordered metals close to the metal-insulator transition are discussed. In the localized regime, the appropriate model is one of electronic two-level systems (TLS’s) coupled to phonons. The TLS consists of a pair of states with one localized state occupied and the other unoccupied. The density of such low-excitation-energy TLS’s is nonzero due to long-range Coulomb interactions. The question of whether these could be significant low-energy excitations in glasses is touched upon.

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The genetic population structure of red snapper Lutjanus malabaricus and Lutjanus erythropterus in eastern Indonesia and northern Australia was investigated by allozyme electrophoresis and sequence variation in the control region of mtDNA. Samples were collected from eight sites in Indonesia and four sites in northern Australia for both species. A total of 13 allozyme loci were scored. More variable loci were observed in L. malabaricus than in L. erythropterus. Sequence variation in the control region (left domain) of the mitochondrial genome was assessed by RFLP and direct sequencing. MtDNA haplotype diversity was high (L. erythropterus, 0.95 and L. malabaricus, 0.97), as was intraspecific sequence divergence, (L. erythropterus, 0.0-12.5% and L. malabaricus, 0.0-9.5%). The pattern of mtDNA haplotype frequencies grouped both species into two broad fisheries stocks with a genetic boundary either between Kupang and Sape (L. malabaricus) or between Kupang and Australian Timor Sea (L. erythropertus). The allozyme analyses revealed similar boundaries for L. erythropterus. Seven allozymes stocks compared to two mtDNA stocks of L. malabaricus including Ambon, which was not sampled with mtDNA, however, were reported. Possible reasons for differences in discrimination between the methods include: i) increased power of multiple allozyme loci over the single mtDNA locus, ii) insufficient gene sampling in the mtDNA control region and iii) relative evolutionary dynamics of nuclear (allozyme loci) and mitochondrial DNA in these taxa. Allozyme and haplotype data did not distinguish separate stocks among the four Australian locations nor the central Indonesian (Bali and Sape locations) for both L. malabaricus and L. erythropterus.

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The leader protease (L-pro) and capsid-coding sequences (P1) constitute approximately 3 kb of the foot-and-mouth disease virus (FMDV). We studied the phylogenetic relationship of 46 FMDV serotype A isolates of Indian origin collected during the period 1968-2005 and also eight vaccine strains using the neighbour-joining tree and Bayesian tree methods. The viruses were categorized under three major groups - Asian, Euro-South American and European. The Indian isolates formed a distinct genetic group among the Asian isolates. The Indian isolates were further classified into different genetic subgroups (<5% divergence). Post-1995 isolates were divided into two subgroups while a few isolates which originated in the year 2005 from Andhra Pradesh formed a separate group. These isolates were closely related to the isolates of the 1970s. The FMDV isolates seem to undergo reverse mutation or onvergent evolution wherein sequences identical to the ancestors are present in the isolates in circulation. The eight vaccine strains included in the study were not related to each other and belonged to different genetic groups. Recombination was detected in the L-pro region in one isolate (A IND 20/82) and in the VP1 coding 1D region in another isolate (A RAJ 21/96). Positive selection was identified at aa positions 23 in the L-pro (P<0.05; 0.046*) and at aa 171 in the capsid protein VP1 (P<0.01; 0.003**).

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Population substructure and hybridization, among other factors, have the potential to cause erroneous associations in linkage disequilibrium (LD) mapping. Two closely related spotted gum eucalypts, Corymbia variegata and C. henryi (Myrtaceae) occur in sympatry in the east coast of Australia and potentially interbreed. They are morphologically similar but are distinguished as separate species based on capsule and foliage size. To determine whether they hybridize in nature and its implications for LD mapping, we investigated the level of molecular divergence between the two species at two sympatric locations separated by 300 kilometres. Very few individuals of intermediate morphology were identified, despite the two species occurring only metres apart. Analysis of genetic structure using 12 microsatellite loci showed that genetic differentiation between populations of the same species at different locations (FST = 0.07 for both species; p = 0.0001) was significantly higher than that observed between species at each location (mean FST = 0.02 and 0.04 for Cherry tree and Bunyaville respectively; p = 0.0001; all Mann-Whitney U-test p ≤ 0.01). No species-specific alleles or significant allele frequency differences were detected within a site, suggesting recurrent local gene flow between the two species. The lack of significant allele frequency differences implies no population stratification along taxonomic lines. This suggested that there is little concern for cryptic hybridization when sampling from sites of sympatry for LD mapping.

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- Purpose Communication of risk management practices are a critical component of good corporate governance. Research to date has been of little benefit in informing regulators internationally. This paper seeks to contribute to the literature by investigating how listed Australian companies in a setting where disclosures are explicitly required by the ASX corporate governance framework, disclose risk management (RM) information in the corporate governance statements within annual reports. - Design/methodology/approach To address our study’s research questions and related hypotheses, we examine the top 300 ASX-listed companies by market capitalisation at 30 June 2010. For these firms, we identify, code and categorise RM disclosures made in the annual reports according to the disclosure categories specified in Australian Stock Exchange Corporate Governance Principles and Recommendations (ASX CGPR). The derived data is then examined using a comprehensive approach comprising thematic content analysis and regression analysis. - Findings The results indicate widespread divergence in disclosure practices and low conformance with the Principle 7 of the ASX CGPR. This result suggests that companies are not disclosing all ‘material business risks’ possibly due to ignorance at the board level, or due to the intentional withholding of sensitive information from financial statement users. The findings also show mixed results across the factors expected to influence disclosure behaviour. Notably, the presence of a risk committee (RC) (in particular, a standalone RC) and technology committee (TC) are found to be associated with improved levels of disclosure. we do not find evidence that company risk measures (as proxied by equity beta and the market-to-book ratio) are significantly associated with greater levels of RM disclosure. Also, contrary to common findings in the disclosure literature, factors such as board independence and expertise, audit committee independence, and the usage of a Big-4 auditor do not seem to impact the level of RM disclosure in the Australian context. - Research limitation/implications The study is limited by the sample and study period selection as the RM disclosures of only the largest (top 300) ASX firms are examined for the fiscal year 2010. Thus, the finding may not be generalisable to smaller firms, or earlier/later years. Also, the findings may have limited applicability in other jurisdictions with different regulatory environments. - Practical implications The study’s findings suggest that insufficient attention has been applied to RM disclosures by listed companies in Australia. These results suggest that the RM disclosures practices observed in the Australian setting may not be meeting the objectives of regulators and the needs of stakeholders. - Originality/value Despite the importance of risk management communication, it is unclear whether disclosures in annual financial reports achieve this communication. The Australian setting provides an ideal environment to examine the nature and extent of risk management communication as the Australian Securities Exchange (ASX) has recommended risk management disclosures follow Principle 7 of its principle-based governance rules since 2007.

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We focus on athermal phase transitions where in discrete and dissipative avalanches are observed in physical observables as the system jumps from one metastable state to another, when driven by an external field. Using higher order statistics of time dependent avalanches, or noise, in electrical resistivity during temperature-driven martensite transformation in thin nickel-titanium films, we demonstrate evidence suggesting the existence of a singular `global instability' or divergence of the correlation length as a function of temperature at the transition. These results not only establish a mapping of non-equilibrium first order phase transition and equilibrium critical phenomena, but perhaps also call for a re-evaluation of many existing experimental claims of self-organized criticality.

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Finnish education policy, educational legislation and the entire education system changed significantly during the 1990s as part of a general restructuring of public administration. There has been a clear divergence from the former tradition of a system of regulation, founded on detailed legislation and the principle of equality. The new governance, which is based more on individual choice, efficiency and evaluation, emphasizes that the development of a high standard of education is a necessity in the light of global competition. This study explores the legislative process regarding education policy in the Finnish Parliament during the 1990s, and highlights in particular how the international discourse on education policies was restructured in the context of Finnish legislation. The research material consists of all the public parliamentary documents relating to education, including government proposals, minutes from the discussions in the chamber and archive material (final protocols, reports and statements) for the Committee for Education and Culture. The discourse on the process of drafting and passing education legislation is modelled on three interrelated policy technologies (market, management and performance), which are understood here as mechanisms connecting general political ideas to normative legislation. The changes in the regulation of education were part of a general public administration reform instigated during the mid 1980s. The research results will prove that during the left-right coalition cabinet of PM Harri Holkeri, new policy technologies affected the parliamentary discourse on education policy. This was particularly influenced by a change in the preconditions for the management of education that was created as a result of the numerous demands to deregulate and delegate decision-making authority to the local and school levels while rendering the whole education system more effective. At the turn of the decade, market-type mechanisms were more indirectly manifested in the forms of individuality and freedom of choice, which were reflected, for example, in proposals to “lower the hurdles” by separating general from vocational secondary education with a view to encouraging students to select courses from other educational establishments, in addition to relaxing the requirements for establishing private schools and abolishing a hundred-year-old strict national catchment-area system. Later, in the course of the 1990s, after the subjects, players, and methods of evaluation had been more precisely defined, evaluation based on performance would result in the active measurement of the attainment of set objectives. In the spring of 1991, from the outset of PM Esko Aho's right-centre coalition cabinet, the education budget suffered cutbacks as a result of a global recession and this influenced the legislative work of, and discourses in, parliament. Representatives of the parties in power regarded the recession solely as an external factor that was remote from the political arena. In their view, the education system should rise to the challenge by ensuring the efficient and innovative use of the resources available and by developing new forms of indicators for evaluating results. Representatives of the opposition opposed the cabinet’s standpoint as a result of the recession, criticized the measures taken by pointing out the harmful effect of constantly cutting the budget and argued that the government had made political capital out of the recession by using it as an opportunity to give more room to market, management and performance technologies within the Finnish education system. Criticism of the new education policy became even stronger during PM Paavo Lipponen's first “rainbow” coalition cabinet with critical views being expressed not only from the opposition but also from representatives within the government. Representatives from the left demanded legislative restrictions and the instigation of measures to relieve the presumed negative effects of market, management and performance in the name of educational equality. The new management by results steering method within the university sector and the introduction of commercial education services in compulsory education were fiercely criticized. The argument over “setting outer limits” including, for example, the demands for more detailed legislation and earmarked state subsidies was characteristic of Parliament’s legislative discourse in the latter part of the 1990s. Keywords: education policy, education legislation, Parliament of Finland

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Identifying species boundaries within morphologically indistinguishable cryptic species complexes is often contentious. For the whitefly Bemisia tabaci (Gennadius) (Hemiptera: Sternorrhyncha: Aleyrodoidea: Aleyrodidae), the lack of a clear understanding about the genetic limits of the numerous genetic groups and biotypes so far identified has resulted in a lack of consistency in the application of the terms, the approaches use to apply them and in our understanding of what genetic structure within B. tabaci means. Our response has been to use mitochondrial gene cytochrome oxidase one to consider how to clearly and consistently define genetic separation. Using Bayesian phylogenetic analysis and analysis of sequence pairwise divergence we found a considerably higher to number of genetic groups than had been previously determined with two breaks in the distribution, one at 11% and another at 3.5%. At >11% divergence, 11 distinct groups were resolved, whereas at >3.5% divergence 24 groups were identified. Consensus sequences for each of these groups were determined and were shown to be useful in the correct assignment of sequences of unknown origin. The 3.5% divergence bound is consistent with species level separations in other insect taxa and Suggests that B. tabaci is it cryptic species composed of at least 24 distinct species. We further show that the placement of Bemesia atriplex (Froggatt) within the B. tabaci in, group adds further weight to the argument for species level separation within B. tabaci. This new analysis, which constructs consensus sequences and uses these its a standard against which unknown sequences call be compared, provides for the first time it consistent means of identifying the genetic hounds of each species with it high degree of certainty.

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The detection of sugarcane smut disease (Ustilago scitaminea) in the Bundaberg-Childers region of eastern Australia in 2006 triggered a comprehensive and united response from BSES Limited, Queensland Government and CANEGROWERS. The response to sugarcane smut in the Bundaberg-Childers area was the first test for the Emergency Plant Pest Response Deed, an agreement between Australian governments and plant industries to facilitate a response to a plant pest incursion. As part of this response and the subsequent inquiry, economic models of the likely pattern of spread and cost of the smut epidemic were prepared. This paper reviews the predictions of those models in the light of the subsequent three years' experience. It examines reasons for divergence from the modelled outcomes, some of which were good approximations of actual experience.

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In the systematic study of amine … LiCl [amines = NH3, CH3NH2, (CH3)2NH] complexes the possibility of an ion-pair structure and the effect of methylation on the stabilization energy is investigated. ΔEis evaluated by the SCF/4-31G method and augmented by the approximate dispersion energy calculated perturbationally. The interaction energy decreases with the increasing number of methyl groups in the amine. The dispersion energy plays a negligible role in the stabilization of complexes. None of the systems studied are ion pairs; their Li bonds are of a so-called molecular type. Due to the divergence of the multipole expansion, the attempt to correct the 4-31G stabilization energies via the electrostatic energy fails. The relative order of the ΔE in the series of complexes is verified instead in the extended basis set calculation. The lithium bonds are compared with their H-bonded analogues.

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Wavenumber-frequency spectral analysis of different atmospheric variables has been carried Out using 25 years of data. The area considered is the tropical belt 25 degrees S-25 degrees N. A combined FFT wavelet analysis method has been used for this purpose. Variables considered are outgoing long wave radiation (OLR), 850 hPa divergence, zonal and meridional winds at 850, 500 and 200 hPa levels, sea level pressure and 850 hPa geopotential height. It is shown that the spectra of different variables have some common properties, but each variable also has few features diffe:rent from the rest. While Kelvin mode is prominent in OLR, and zonal winds, it is not clearly observed in pressure and geopotential height fields; the latter two have a dominant wavenumber zero mode not seen in other variables except in meridional wind at 200 hPa and 850 hPa divergences. Different dominant modes in the tropics show significant variations on sub-seasonal time scales.

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The authors examine the critical divergence of the low-frequency conductivity of the noninteracting Fermi glass and interacting electron glass models of the insulating phase of a disordered system as the metallic phase is approached. Results for the two are found to be rather different, which can be tested experimentally. In particular, for the electron glass, there exists a nonvanishing contribution to the dielectric constants from the low-frequency (hopping) conductivity even at low temperatures, which scales with the high-frequency (optical) contribution, and diverges with the same exponent at the insulator-metal transition.

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Acquiring sufficient information on the genetic variation, genetic differentiation, and the ecological and genetic relationships among individuals and populations are essential for establishing guidelines on conservation and utilization of the genetic resources of a species, and more particularly when biotic and abiotic stresses are considered. The aim of this study was to assess the extent and pattern of genetic variation in date palm (Phoenix dacttylifera L) cultivars; the genetic diversity and structure in its populations occurring over geographical ranges; the variation in economically and botanically important traits of it and the variation in its drought adaptive traits, in conservation and utilization context. In this study, the genetic diversity and relationships among selected cultivars from Sudan and Morocco were assessed using microsatellite markers. Microsatellite markers were also used to investigate the genetic diversity within and among populations collected from different geographic locations in Sudan. In a separate investigation, fruits of cultivars selected from Sudan, involved morphological and chemical characterization, and morphological and DNA polymorphism of the mother trees were also investigated. Morphological and photosynthetic adjustments to water stress were studied in the five most important date palm cultivars in Sudan, namely, Gondaila, Barakawi, Bitamoda, Khateeb and Laggai; and the mechanism enhancing photosynthetic gas exchange in date palm under water stress was also investigated. Results showed a significant (p < 0.001, t-test) differentiation between Sudan and Morocco groups of cultivars. However, the major feature of all tested cultivars was the complete lack of clustering and the absence of cultivars representing specific clones. The results indicated high genetic as well as compositional and morphological diversity among cultivars; while, compositional and morphological traits were found to be characteristic features that strongly differentiate cultivars as well as phenotypes. High genetic diversity was observed also in different populations. Slight but significant (p < 0.01, AMOVA) divergence was observed for soft and dry types; however, the genetic divergence among populations was relatively weak. The results showed a complex genetic relationships between some of the tested populations especially when isolation by distance was considered. The results of the study also revealed that date palm cultivars and phenotypes possess specific direct or interaction effects due to water availability on a range of morphological and physiological traits. Soft and dry phenotypes responded differently to different levels of water stress, while the dry phenotype was more sensitive and conservative. The results indicated that date palm has high fixation capacity to photosynthetic CO2 supply with interaction effect to water availability, which can be considered as advantageous when coping with stresses that may arise with climate change. In conclusion, although a large amount of diversity exists among date palm germplasm, the findings in this study show that the role of biological nature of the tree, isolation by distance and environmental effects on structuring date palm genome was highly influenced by human impacts. Identity of date palm cultivars as developed and manipulated by date palm growers, in the absence of scientific breeding programmes, may continue to mainly depend on tree morphology and fruit characters. The pattern of genetic differentiation may cover specific morphological and physiological traits that contribute to adaptive mechanisms in each phenotype. These traits can be considered for further studies related to drought adaptation in date palm.

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Species delineation in the spotted gum complex was revisited focusing on Corymbia maculata. This study expands the range of C. maculata analysed with microsatellite markers to include populations from the north of the species range. It supported earlier findings that it is a cohesive genetic entity, well resolved from northern spotted gum taxa, Corymbia citriodora and Corymbia henryi; and inferences that its insularity is due to early lineage divergence and historical isolation. The northern extent of C. maculata sampled, as defined by chloroplast and nuclear genomes predominantly of C. maculata character, was the location of Kiwarrak, south of the Manning River near Taree in New South Wales. Trees from a recognised intergrade zone at the Yarratt locality, around 26 km north of Kiwarrak, also possessed a uniquely C. maculata chloroplast haplotype, but their nuclear genomes were predominantly of northern taxa ancestry. Range expansion of northern taxa leading to southerly gene movement into populations formerly C. maculata, would account for this apparent instance of chloroplast capture. Two subpopulations were identified in C. maculata, a northern population of which the Ourimbah locality was the most southerly studied, and a southern population of which Wingello was the most northerly locality studied. Diminished levels of northern taxa ancestry, i.e. C. citriodora or C. henryi, in individuals from the southern, relative to the northern subpopulation of C. maculata, suggested that secondary contact with northern taxa contributes to its substructure.