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Search Results: 1 - 10 of 39101 matches for " Kendall’s tau "
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Determining the Similarities between Stations using the Haplotypes of the Species Cerastoderma glaucum (Poiret, 1789) from the Romanian Black Sea Infralittoral
Dragomir-Cosmin DAVID,?tefan I. ?IGAN
Applied Medical Informatics , 2011,
Abstract: Cerastoderma glaucum (Poiret, 1789) represents one of the marine mollusk species found on the Romanian Black Sea soft bottom infralittoral. This species had been investigated in the past by morphological methods. Some problems concerning its biological, ecological and even behavioral aspects have remained unresolved. At the moment, molecular technique studies allow the completion of these gaps. In the present article we are aiming to identify this species by molecular methods and to perform a statistical analysis of the obtained data in order to determine the distribution of this species’ haplotypes on the littoral. With the aid of the Nucleospin Tissue kits, through the PCR technique, the extraction and amplification of DNA has been performed to obtain the necessary data. The obtained sequences have been compared to the sequences from databases such as National Center for Biotechnology Information (NCBI) to establish similarities. After the identification of the similar sequences, we have interpreted their distribution in different stations using the Kendall rank correlation coefficient. A number of 12 haplotypes which belong to 32 individuals from 5 stations have been identified. Using the Kendall rank correlation coefficient the identified haplotypes show different degrees of concordance with the standard haplotypes of this species. A significant statistical similarity appears in 81.14% out of the total 493 compared haplotype pairs. Out of these, 18% present perfect similarity, 76.25% good and 5.75% acceptable. The stations are similar regarding haplotypes, with some exceptions that are commented in the paper, similarities established by calculating the Kendall rank correlation coefficient.
A Copula-based Approach to the Analysis of the Returns of Exchange Rates to EUR of the Visegrád Countries
Magda Komorníková,Jozef Komorník
Acta Polytechnica Hungarica , 2010,
Abstract: The currencies of the Visegrád countries (Poland, the Czech Republic, Hungary,and Slovakia) have been considered by the international financial community as a basket ofcurrencies which are closely related, especially in times of their depreciations. On July 1,2008 the official terminal exchange rate SKK/EUR was fixed. During the following 8months, the remaining three currencies (PLN, CZK, HUF) changed their long-termbehaviour to one of strong parallel depreciation. On the other hand, in the first selectedlong-term period (January 4, 1999 – June 30, 2008), a relatively mixed development ofHUF seemed to exhibit a rather low degree of interdependence with CZK (that had beenappreciating very intensively). The values of the Kendall’s correlation coefficientcalculated for all 3 remaining couples of returns substantially rose in the second period(indicating that similarities between the returns of these exchange rates are stronger in thetimes of crises). We have performed modeling and fitting of the dependencies of the abovementioned couples of returns of currencies in both the mentioned time periods by severalclasses of bivariate copulas, as well as by (optimized) convex combinations of theirelements.
Performance Analysis of Hybrid Forecasting Model in Stock Market Forecasting
Mahesh S. Khadka,K. M. George,N. Park
International Journal of Managing Information Technology (IJMIT) , 2012,
Abstract: This paper presents performance analysis of hybrid model comprise of concordance and Genetic Programming (GP) to forecast financial market with some existing models. This scheme can be used for in depth analysis of stock market. Different measures of concordances such as Kendall’s Tau, Gini’s Mean Difference, Spearman’s Rho, and weak interpretation of concordance are used to search for the pattern in past that look similar to present. Genetic Programming is then used to match the past trend to presenttrend as close as possible. Then Genetic Program estimates what will happen next based on what had happened next. The concept is validated using financial time series data (S&P 500 and NASDAQ indices) as sample data sets. The forecasted result is then compared with standard ARIMA model and other model to analyse its performance.
Nested Archimedean Copulas Meet R: The nacopula Package
Marius Hofert,Martin Maechler
Journal of Statistical Software , 2011,
Abstract: The package nacopula provides procedures for constructing nested Archimedean copulas in any dimensions and with any kind of nesting structure, generating vectors of random variates from the constructed objects, computing function values and probabilities of falling into hypercubes, as well as evaluation of characteristics such as Kendall's tau and the tail-dependence coefficients. As by-products, algorithms for various distributions, including exponentially tilted stable and Sibuya distributions, are implemented. Detailed examples are given.
The Structural Difference of Shanghai Stock Index before and after 2008: A Copula Based Analysis  [PDF]
Chuan Wu, Ke Huang, Xue Tian, Weikang Geng, H. J. Cai
Technology and Investment (TI) , 2012, DOI: 10.4236/ti.2012.34035
Abstract: The year 2008 witnessed the greatest joint stock reform and financial crisis in Chinese history. After these two cases, significant changes have taken place in investors’ behaviors worldwide, along with which is the occurrence of structure change in stock market. In this paper, we employ copula model to simulate the joint distribution between Shanghai Stock Index (SSE) and Chinese Shanghai Index 300 (CSI 300), to find out structure change in Chinese stock market before and after 2008. From results of empirical studies, we get conclusions that the main nature of Chinese stocks market is symmetric, in both marginal and joint distributions. Via the changes of Copula types, upper and lower tail coefficients and Kendall coefficients, we can measure the structure change in Chinese stock market, and get further conclusion about investors’ behaviors change. Before 2008, there is an equal power in quitting market and longing, while diversified investors adjusted their expectation uniformly after this year. Testing results show that the general dependence structure of CSI 300 and SSE is highly dependent and symmetric in most cases. From the distribution of upper and lower tail coefficients, we can draw the conclusion that stratified investors are mainly focused on two tasks, after this year, to close the position on stocks with high correlated stocks market and to maintain market value of stocks.
Efficient Calculation of Jackknife Confidence Intervals for Rank Statistics
Roger Newson
Journal of Statistical Software , 2005,
Abstract: An algorithm is presented for calculating concordance-discordance totals in a time of order N log N , where N is the number of observations, using a balanced binary search tree. These totals can be used to calculate jackknife estimates and confidence limits in the same time order for a very wide range of rank statistics, including Kendall’s tau, Somers’ D, Harrell’s c, the area under the receiver operating characteristic (ROC) curve, the Gini coefficient, and the parameters underlying the sign and rank-sum tests. A Stata package is introduced for calculating confidence intervals for these rank statistics using this algorithm, which has been implemented in the Mata compilable matrix programming language supplied with Stata
Leptin rescues neurons from Alzheimer’s disease-related pathways triggered by lipid burden  [PDF]
Steven J. Greco, George Perry, J. Wesson Ashford, Ashkan Hamzelou, Jane M. Johnston, Nikolaos Tezapsidis
Advances in Alzheimer's Disease (AAD) , 2013, DOI: 10.4236/aad.2013.21004
Abstract:

Adipocyte-derived leptin is a pleiotropic hormone implicated in control of lipid storage and mobilization, bone homeostasis, immune function and neuronal plasticity. Leptin has been shown to prevent accumulation of extracellular Aβ and hyperphosphorylation of tau in both cell culture and animal models. Herein an investigation was undertaken to test leptin’s ability to prevent the exacerbation/activation of AD-related pathways in neurons following their exposure to a high concentration of a variety of lipids. Specifically, cholesterol, oleic acid and/or ceramide were added to the media of cells resulting in decreased cellular viability and energy metabolism, and in increased tau phosphorylation and extracellular Aβ. Leptin increased viability, boosted cellular metabolism by activating AMP-activated protein kinase (AMPK) and the sirtuins (SIRT) and reduced tau phosphorylation and Aβ accumulation in a dose-dependent manner in response to select challenges. These findings demonstrate that leptin can attenuate the harmful effect of certain lipids that lead to exacerbation or activation of AD pathways. The study herein also provides the basis for a novel screening platform to define and identify a novel class of “metabolic” compounds addressing Alzheimer’s disease, based on a biological profile similar to leptin.

Biomarkers for Alzheimer’s Disease: Imagination or Reality-View and Review!  [PDF]
Mustafa Yassin, Zaher Armaly, Bishara Bisharat, Abdalla Bowirrat
Journal of Behavioral and Brain Science (JBBS) , 2013, DOI: 10.4236/jbbs.2013.35040
Abstract: The Alzheimers disease (AD) is the most widespread chronic, insidious neurodegenerative disease causing dementia in elderly and leading to a massive burden on AD individuals, their families, and on social and health care systems. Its diagnosis is subjective, definite AD can only be diagnosed after pathological brain specimens are examined by either biopsy or autopsy, and it covers 50%-70% of all dementia cases. It is estimated that, by 2050, the number of people aged 80 years or older will approach 370 million worldwide and that 50 percent of those aged 85 years or older will be afflicted with AD. Causes of the disease are multifactorial; where genetics and environmental risk factors work in harmony to cause the disease. Neuropathological features of AD depend on finding of extracellular deposits of β-amyloid peptides (Aβ) that lead to senile plaque formation and intracellular neurofibrillary tangles of hyperphosphory lated tau. However, increasing evidence has suggested that inflammation may play a critical role in AD pathogenesis as well. In the era of genome and sophisticated technology, AD early diagnosis still indecisive and valid biomarkers for AD to be used in routine clinical practice have met with dissatisfaction. Indeed, the relatively unchanged levels of plasma β-amyloid in AD, and a lack of analytical sensitivity for assays for the axonal damage marker have increased the effort to find an alternative ultra-
Association of Ammodramus bairdii A. 1844, and Other Species of Grassland Granivorous Birds in Winter Time in Northwestern Mexico  [PDF]
Jose Hugo Martinez-Guerrero, Martin Emilio Pereda-Solis, Christian Wehenkel
Open Journal of Ecology (OJE) , 2014, DOI: 10.4236/oje.2014.45026
Abstract:

During the winter of 2009 grassland birds were monitored in the region of Cuchillas de la Zarca to estimate the association betweenAmmodramus bairdiiAudubon 1844, focal species of grassland and bird species belonging to the trophic guild of grassland granivorous birds (n = 25 ). The study area was divided into monitoring quadrants (n = 16) where 96 transects for bird monitoring were conducted, recording 16,635 individuals of which only 32.9% were in the trophic guild of grassland granivorous birds. The association betweenA. bairdiiand other species was estimated from the nonparametric statistical index of Kendall’s coefficient of concordance (W) and the p value, through permutation analysis (n = 10,000), finding positive and significant associations (p≤0.05) of the target species for study withSturnella magna,Passerculus sandwichensisandAmmodramus savannarum, species that share habitat preferences of natural grassland in good condition, slightly grazed and with little tolerance to the shrub cover. The association W ranged from 0.072 and 0.749. These results can recognize this region as an important area for the conservation of obligate grassland birds during winter, suggesting establish training programs to better utilize this resource by means of cattle activity.

On some Formulae for Ramanujan's tau Function
GALLARDO,LUIS H.;
Revista Colombiana de Matemáticas , 2010,
Abstract: some formulae of niebur and lanphier are derived in an elementary manner from previously known formulae. a new congruence formula for τ(p) modulo p is derived as a consequence. we use this congruence to numerically investigate the order of τ(p) modulo p.
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