Fiori, Simone
2007-01-01
Bivariate statistical modeling from incomplete data is a useful statistical tool that allows to discover the model underlying two data sets when the data in the two sets do not correspond in size nor in ordering. Such situation may occur when the sizes of the two data sets do not match (i.e., there are “holes” in the data) or when the data sets have been acquired independently. Also, statistical modeling is useful when the amount of available data is enough to show relevant statistical features of the phenomenon underlying the data. We propose to tackle the problem of statistical modeling via a neural (nonlinear) system that is able to match its input-output statistic to the statistic of the available data sets. A key point of the new implementation proposed here is that it is based on look-up-table (LUT) neural systems, which guarantee a computationally advantageous way of implementing neural systems. A number of numerical experiments, performed on both synthetic and real-world data sets, illustrate the features of the proposed modeling procedure. PMID:18566641
Bivariate statistical modeling of color and range in natural scenes
NASA Astrophysics Data System (ADS)
Su, Che-Chun; Cormack, Lawrence K.; Bovik, Alan C.
2014-02-01
The statistical properties embedded in visual stimuli from the surrounding environment guide and affect the evolutionary processes of human vision systems. There are strong statistical relationships between co-located luminance/chrominance and disparity bandpass coefficients in natural scenes. However, these statistical rela- tionships have only been deeply developed to create point-wise statistical models, although there exist spatial dependencies between adjacent pixels in both 2D color images and range maps. Here we study the bivariate statistics of the joint and conditional distributions of spatially adjacent bandpass responses on both luminance/chrominance and range data of naturalistic scenes. We deploy bivariate generalized Gaussian distributions to model the underlying statistics. The analysis and modeling results show that there exist important and useful statistical properties of both joint and conditional distributions, which can be reliably described by the corresponding bivariate generalized Gaussian models. Furthermore, by utilizing these robust bivariate models, we are able to incorporate measurements of bivariate statistics between spatially adjacent luminance/chrominance and range information into various 3D image/video and computer vision applications, e.g., quality assessment, 2D-to-3D conversion, etc.
We compared the use of ternary and bivariate diagrams to distinguish the effects of atmospheric precipitation, rock weathering, and evaporation on inland surface and subsurface water chemistry. The three processes could not be statistically differentiated using bivariate models e...
NASA Astrophysics Data System (ADS)
Baran, Sándor; Möller, Annette
2016-06-01
Forecast ensembles are typically employed to account for prediction uncertainties in numerical weather prediction models. However, ensembles often exhibit biases and dispersion errors, thus they require statistical post-processing to improve their predictive performance. Two popular univariate post-processing models are the Bayesian model averaging (BMA) and the ensemble model output statistics (EMOS). In the last few years, increased interest has emerged in developing multivariate post-processing models, incorporating dependencies between weather quantities, such as for example a bivariate distribution for wind vectors or even a more general setting allowing to combine any types of weather variables. In line with a recently proposed approach to model temperature and wind speed jointly by a bivariate BMA model, this paper introduces an EMOS model for these weather quantities based on a bivariate truncated normal distribution. The bivariate EMOS model is applied to temperature and wind speed forecasts of the 8-member University of Washington mesoscale ensemble and the 11-member ALADIN-HUNEPS ensemble of the Hungarian Meteorological Service and its predictive performance is compared to the performance of the bivariate BMA model and a multivariate Gaussian copula approach, post-processing the margins with univariate EMOS. While the predictive skills of the compared methods are similar, the bivariate EMOS model requires considerably lower computation times than the bivariate BMA method.
Application of bivariate statistics to full wine bottle diamagnetic screening data.
Harley, S J; Lim, V; Augustine, M P
2012-01-30
A bivariate correlated Student distribution is applied to full wine bottle diamagnetic screening measurements. Previous work involving a limited number of rare wines indicated that like wines cluster in a plot of the first two principal component scores derived from a covariance matrix of the diamagnetic screening measurements. This study extends the approach to a much larger, statistically meaningful sixty bottle wine library where bivariate statistics are used to comment on the measured data. The full bottle diamagnetic screening of thirty-six identically labeled, sealed bottles of wine obtained from four different sources combined with principal component analysis data reduction followed by treatment with a bivariate distribution permit the effect of wine transport and storage to be observed. The usefulness and future success of the method towards the identification of counterfeit wines is mentioned. PMID:22284521
Applied Statistics: From Bivariate through Multivariate Techniques [with CD-ROM
ERIC Educational Resources Information Center
Warner, Rebecca M.
2007-01-01
This book provides a clear introduction to widely used topics in bivariate and multivariate statistics, including multiple regression, discriminant analysis, MANOVA, factor analysis, and binary logistic regression. The approach is applied and does not require formal mathematics; equations are accompanied by verbal explanations. Students are asked…
NASA Astrophysics Data System (ADS)
Jebur, M. N.; Pradhan, B.; Shafri, H. Z. M.; Yusof, Z.; Tehrany, M. S.
2014-10-01
Modeling and classification difficulties are fundamental issues in natural hazard assessment. A geographic information system (GIS) is a domain that requires users to use various tools to perform different types of spatial modeling. Bivariate statistical analysis (BSA) assists in hazard modeling. To perform this analysis, several calculations are required and the user has to transfer data from one format to another. Most researchers perform these calculations manually by using Microsoft Excel or other programs. This process is time consuming and carries a degree of uncertainty. The lack of proper tools to implement BSA in a GIS environment prompted this study. In this paper, a user-friendly tool, BSM (bivariate statistical modeler), for BSA technique is proposed. Three popular BSA techniques such as frequency ratio, weights-of-evidence, and evidential belief function models are applied in the newly proposed ArcMAP tool. This tool is programmed in Python and is created by a simple graphical user interface, which facilitates the improvement of model performance. The proposed tool implements BSA automatically, thus allowing numerous variables to be examined. To validate the capability and accuracy of this program, a pilot test area in Malaysia is selected and all three models are tested by using the proposed program. Area under curve is used to measure the success rate and prediction rate. Results demonstrate that the proposed program executes BSA with reasonable accuracy. The proposed BSA tool can be used in numerous applications, such as natural hazard, mineral potential, hydrological, and other engineering and environmental applications.
NASA Astrophysics Data System (ADS)
Jebur, M. N.; Pradhan, B.; Shafri, H. Z. M.; Yusoff, Z. M.; Tehrany, M. S.
2015-03-01
Modelling and classification difficulties are fundamental issues in natural hazard assessment. A geographic information system (GIS) is a domain that requires users to use various tools to perform different types of spatial modelling. Bivariate statistical analysis (BSA) assists in hazard modelling. To perform this analysis, several calculations are required and the user has to transfer data from one format to another. Most researchers perform these calculations manually by using Microsoft Excel or other programs. This process is time-consuming and carries a degree of uncertainty. The lack of proper tools to implement BSA in a GIS environment prompted this study. In this paper, a user-friendly tool, bivariate statistical modeler (BSM), for BSA technique is proposed. Three popular BSA techniques, such as frequency ratio, weight-of-evidence (WoE), and evidential belief function (EBF) models, are applied in the newly proposed ArcMAP tool. This tool is programmed in Python and created by a simple graphical user interface (GUI), which facilitates the improvement of model performance. The proposed tool implements BSA automatically, thus allowing numerous variables to be examined. To validate the capability and accuracy of this program, a pilot test area in Malaysia is selected and all three models are tested by using the proposed program. Area under curve (AUC) is used to measure the success rate and prediction rate. Results demonstrate that the proposed program executes BSA with reasonable accuracy. The proposed BSA tool can be used in numerous applications, such as natural hazard, mineral potential, hydrological, and other engineering and environmental applications.
Packard, Gary C
2013-09-01
The ongoing debate about methods for fitting the two-parameter allometric equation y=ax(b) to bivariate data seemed to be resolved recently when three groups of investigators independently reported that statistical models fitted by the traditional allometric method (i.e., by back-transforming a linear model fitted to log-log transformations) typically are superior to models fitted by standard nonlinear regression. However, the narrow focus for the statistical analyses in these investigations compromised the most important of the ensuing conclusions. All the investigations focused on two-parameter power functions and excluded from consideration other simple functions that might better describe pattern in the data; and all relied on Akaike's Information Criterion instead of graphical validation to identify the better statistical model. My re-analysis of data from one of the studies (BMR vs. body mass in mustelid carnivores) revealed (1) that the best descriptor for pattern in the dataset is a straight line and not a two-parameter power function; (2) that a model with additive, normal, heteroscedastic error is superior to one with multiplicative, lognormal, heteroscedastic error; and (3) that Akaike's Information Criterion is not a generally reliable metric for discriminating between models fitted to different distributions. These findings have apparent implications for interpreting the outcomes of all three of the aforementioned studies. Future investigations of allometric variation should adopt a more holistic approach to analysis and not be wedded to the traditional allometric method. PMID:23688506
Slack, James Richard; Matalas, Nicholas C.; Wallis, James R.
1976-01-01
The distribution functions for hydrologic statistics that may be used to assess the significance of differences between sample means, standard deviations, coefficients of skewness, and coefficients of variations are obtained by Monte Carlo experiments. The distributions are expressed as functions of sample size, cross correlation, and skewness. In general, the distributions are more sensitive to cross correlation than to skewness. As sample size increases, however, the distributions tend to become more sensitive to skewness. (Woodard-USGS)
Univariate description and bivariate statistical inference: the first step delving into data
2016-01-01
In observational studies, the first step is usually to explore data distribution and the baseline differences between groups. Data description includes their central tendency (e.g., mean, median, and mode) and dispersion (e.g., standard deviation, range, interquartile range). There are varieties of bivariate statistical inference methods such as Student’s t-test, Mann-Whitney U test and Chi-square test, for normal, skews and categorical data, respectively. The article shows how to perform these analyses with R codes. Furthermore, I believe that the automation of the whole workflow is of paramount importance in that (I) it allows for others to repeat your results; (II) you can easily find out how you performed analysis during revision; (III) it spares data input by hand and is less error-prone; and (IV) when you correct your original dataset, the final result can be automatically corrected by executing the codes. Therefore, the process of making a publication quality table incorporating all abovementioned statistics and P values is provided, allowing readers to customize these codes to their own needs. PMID:27047950
ERIC Educational Resources Information Center
Onwuegbuzie, Anthony J.; Daniel, Larry G.; Roberts, J. Kyle
The purpose of this paper is to illustrate how displaying disattenuated correlation coefficients along with their unadjusted counterparts will allow the reader to assess the impact of unreliability on each bivariate relationship. The paper also demonstrates how a proposed new "what if reliability" analysis can complement the conventional null…
ERIC Educational Resources Information Center
Onwuegbuzie, Anthony J.; Roberts, J. Kyle; Daniel, Larry G.
2005-01-01
In this article, the authors (a) illustrate how displaying disattenuated correlation coefficients alongside their unadjusted counterparts will allow researchers to assess the impact of unreliability on bivariate relationships and (b) demonstrate how a proposed new "what if reliability" analysis can complement null hypothesis significance tests of…
Li, Ning; Liu, Xueqin; Xie, Wei; Wu, Jidong; Zhang, Peng
2013-01-01
New features of natural disasters have been observed over the last several years. The factors that influence the disasters' formation mechanisms, regularity of occurrence and main characteristics have been revealed to be more complicated and diverse in nature than previously thought. As the uncertainty involved increases, the variables need to be examined further. This article discusses the importance and the shortage of multivariate analysis of natural disasters and presents a method to estimate the joint probability of the return periods and perform a risk analysis. Severe dust storms from 1990 to 2008 in Inner Mongolia were used as a case study to test this new methodology, as they are normal and recurring climatic phenomena on Earth. Based on the 79 investigated events and according to the dust storm definition with bivariate, the joint probability distribution of severe dust storms was established using the observed data of maximum wind speed and duration. The joint return periods of severe dust storms were calculated, and the relevant risk was analyzed according to the joint probability. The copula function is able to simulate severe dust storm disasters accurately. The joint return periods generated are closer to those observed in reality than the univariate return periods and thus have more value in severe dust storm disaster mitigation, strategy making, program design, and improvement of risk management. This research may prove useful in risk-based decision making. The exploration of multivariate analysis methods can also lay the foundation for further applications in natural disaster risk analysis. PMID:22616629
NASA Astrophysics Data System (ADS)
Tipton, J.; Hooten, M.; Pederson, N.; Tingley, M.; Bishop, D. A.
2014-12-01
The ability to reconstruct historical climate is important to understanding how climate has changed in the past. The instrumental record of temperature and precipitation only spans the most recent centuries. Thus, reconstructions of the climate features are typically based on proxy archives. The proxy archives integrate climate information through biological, geological, physical, and chemical processes. Tree ring widths provide one of the most spatially and temporally rich sources of high quality climate proxy data. However, the statistical reconstruction of paleoclimate from tree ring widths is quite challenging because the climate signal is inherently multi-dimensional while tree ring widths are a one dimensional data source. We propose a Bayesian Hierarchical model using a non-linear, scientifically motivated tree ring growth models to reconstruct multivariate climate (i.e., temperature and precipitation) in the Hudson Valley region of New York. Our proposed model extends and enhances former methods in a number of ways. We allow for species-specific responses to climate, which further constrains the many-to-one relationship between tree rings and climate. The resulting model allows for prediction of reasonable climate scenarios given tree ring widths. We explore a natural model selection framework that weighs the influence of multiple candidate growth models in terms of their predictive ability. To enable prediction backcasts, the climate variables are modeled with an underlying continuous time latent process. The continuous time process allows for added flexibility in the climate response through time at different temporal scales and enables investigation of differences in climate between the reconstruction period and the instrumental period. Validation of the model's predictive abilities is achieved through a pseudo-proxy simulation experiment where the quality of climate predictions are measured by out of sample performance based on a proper local scoring
NASA Technical Reports Server (NTRS)
Falls, L. W.; Crutcher, H. L.
1976-01-01
Transformation of statistics from a dimensional set to another dimensional set involves linear functions of the original set of statistics. Similarly, linear functions will transform statistics within a dimensional set such that the new statistics are relevant to a new set of coordinate axes. A restricted case of the latter is the rotation of axes in a coordinate system involving any two correlated random variables. A special case is the transformation for horizontal wind distributions. Wind statistics are usually provided in terms of wind speed and direction (measured clockwise from north) or in east-west and north-south components. A direct application of this technique allows the determination of appropriate wind statistics parallel and normal to any preselected flight path of a space vehicle. Among the constraints for launching space vehicles are critical values selected from the distribution of the expected winds parallel to and normal to the flight path. These procedures are applied to space vehicle launches at Cape Kennedy, Florida.
NASA Astrophysics Data System (ADS)
Akgun, Aykut; Erkan, Oguzhan
2015-04-01
In Turkey, landslide is one of the most important natural hazards. Due to landslide occurrence, several landforms and man made structures are adversely affected, and may cause many injuries and loss of life. In this context, landslide susceptibility assessment is important task to determine susceptible areas to landslide occurrence. Especially, several dam reservoir areas in Turkey are threated by landslide phenomena. For this reason, in this study, a dam reservoir area located in North Turkey was selected, and investigated in point of landslide susceptibility assessment. A landslide susceptibility assessment for the Kurtun dam reservoir area (Gumushane, North Turkey) was carried out by geographical information systems (GIS)-based statistical and deterministic models. For this purpose, frequency ratio (FR) and stability index mapping (SINMAP) methodologies were applied. In this context, eight conditioning parameters such as altitude, lithology, slope gradient, slope aspect, distance to drainage, distance to lineament, stream power index (SPI) and topographical wetness index (TWI) were considered. After assessment of these parameters by FR and SINMAP methods in a GIS environment, two landslide susceptibility maps were obtained. Then, the maps obtained were analyzed for verification purpose. For this purpose, area under curvature (AUC) approach was used. At the end of this process, the AUC values of 0.73 and 0.70 were found for FR and SINMAP methods, respectively. Additionally, the SINMAP statistical results showed that the 93.8% of the observed landslides in the area falls into the lower and upper threshold showing the stability index classes. These values indicate that the accuracies of landslide susceptibility maps are acceptable, and the maps are feasible for further natural hazard management affairs in the area.
NASA Astrophysics Data System (ADS)
Meinhardt, Markus; Fink, Manfred; Tünschel, Hannes
2015-04-01
Vietnam is regarded as a country strongly impacted by climate change. Population and economic growth result in additional pressures on the ecosystems in the region. In particular, changes in landuse and precipitation extremes lead to a higher landslide susceptibility in the study area (approx. 12,400 km2), located in central Vietnam and impacted by a tropical monsoon climate. Hence, this natural hazard is a serious problem in the study area. A probability assessment of landslides is therefore undertaken through the use of bivariate statistics. However, the landslide inventory based only on field campaigns does not cover the whole area. To avoid a systematic bias due to the limited mapping area, the investigated regions are depicted as the viewshed in the calculations. On this basis, the distribution of the landslides is evaluated in relation to the maps of 13 parameters, showing the strongest correlation to distance to roads and precipitation increase. An additional weighting of the input parameters leads to better results, since some parameters contribute more to landslides than others. The method developed in this work is based on the validation of different parameter sets used within the statistical index method. It is called "omit error" because always omitting another parameter leads to the weightings, which describe how strong every single parameter improves or reduces the objective function. Furthermore, this approach is used to find a better input parameter set by excluding some parameters. After this optimization, nine input parameters are left, and they are weighted by the omit error method, providing the best susceptibility map with a success rate of 92.9% and a prediction rate of 92.3%. This is an improvement of 4.4% and 4.2%, respectively, compared to the basic statistical index method with the 13 input parameters.
NASA Astrophysics Data System (ADS)
Hong, Haoyuan; Pourghasemi, Hamid Reza; Pourtaghi, Zohre Sadat
2016-04-01
Landslides are an important natural hazard that causes a great amount of damage around the world every year, especially during the rainy season. The Lianhua area is located in the middle of China's southern mountainous area, west of Jiangxi Province, and is known to be an area prone to landslides. The aim of this study was to evaluate and compare landslide susceptibility maps produced using the random forest (RF) data mining technique with those produced by bivariate (evidential belief function and frequency ratio) and multivariate (logistic regression) statistical models for Lianhua County, China. First, a landslide inventory map was prepared using aerial photograph interpretation, satellite images, and extensive field surveys. In total, 163 landslide events were recognized in the study area, with 114 landslides (70%) used for training and 49 landslides (30%) used for validation. Next, the landslide conditioning factors-including the slope angle, altitude, slope aspect, topographic wetness index (TWI), slope-length (LS), plan curvature, profile curvature, distance to rivers, distance to faults, distance to roads, annual precipitation, land use, normalized difference vegetation index (NDVI), and lithology-were derived from the spatial database. Finally, the landslide susceptibility maps of Lianhua County were generated in ArcGIS 10.1 based on the random forest (RF), evidential belief function (EBF), frequency ratio (FR), and logistic regression (LR) approaches and were validated using a receiver operating characteristic (ROC) curve. The ROC plot assessment results showed that for landslide susceptibility maps produced using the EBF, FR, LR, and RF models, the area under the curve (AUC) values were 0.8122, 0.8134, 0.7751, and 0.7172, respectively. Therefore, we can conclude that all four models have an AUC of more than 0.70 and can be used in landslide susceptibility mapping in the study area; meanwhile, the EBF and FR models had the best performance for Lianhua
Bivariate extreme value distributions
NASA Technical Reports Server (NTRS)
Elshamy, M.
1992-01-01
In certain engineering applications, such as those occurring in the analyses of ascent structural loads for the Space Transportation System (STS), some of the load variables have a lower bound of zero. Thus, the need for practical models of bivariate extreme value probability distribution functions with lower limits was identified. We discuss the Gumbel models and present practical forms of bivariate extreme probability distributions of Weibull and Frechet types with two parameters. Bivariate extreme value probability distribution functions can be expressed in terms of the marginal extremel distributions and a 'dependence' function subject to certain analytical conditions. Properties of such bivariate extreme distributions, sums and differences of paired extremals, as well as the corresponding forms of conditional distributions, are discussed. Practical estimation techniques are also given.
Local osmosis and isotonic transport.
Mathias, R T; Wang, H
2005-11-01
Osmotically driven water flow, u (cm/s), between two solutions of identical osmolarity, c(o) (300 mM: in mammals), has a theoretical isotonic maximum given by u = j/c(o), where j (moles/cm(2)/s) is the rate of salt transport. In many experimental studies, transport was found to be indistinguishable from isotonic. The purpose of this work is to investigate the conditions for u to approach isotonic. A necessary condition is that the membrane salt/water permeability ratio, epsilon, must be small: typical physiological values are epsilon = 10(-3) to 10(-5), so epsilon is generally small but this is not sufficient to guarantee near-isotonic transport. If we consider the simplest model of two series membranes, which secrete a tear or drop of sweat (i.e., there are no externally-imposed boundary conditions on the secretion), diffusion is negligible and the predicted osmolarities are: basal = c(o), intracellular approximately (1 + epsilon)c(o), secretion approximately (1 + 2epsilon)c(o), and u approximately (1 - 2epsilon)j/c(o). Note that this model is also appropriate when the transported solution is experimentally collected. Thus, in the absence of external boundary conditions, transport is experimentally indistinguishable from isotonic. However, if external boundary conditions set salt concentrations to c(o) on both sides of the epithelium, then fluid transport depends on distributed osmotic gradients in lateral spaces. If lateral spaces are too short and wide, diffusion dominates convection, reduces osmotic gradients and fluid flow is significantly less than isotonic. Moreover, because apical and basolateral membrane water fluxes are linked by the intracellular osmolarity, water flow is maximum when the total water permeability of basolateral membranes equals that of apical membranes. In the context of the renal proximal tubule, data suggest it is transporting at near optimal conditions. Nevertheless, typical physiological values suggest the newly filtered fluid is
Bivariate control chart with copula
NASA Astrophysics Data System (ADS)
Lestari, Tika; Syuhada, Khreshna; Mukhaiyar, Utriweni
2015-12-01
Control chart is the main and powerful tool in statistical process control in order to detect and classify data, either in control or out of control. Its concept, basically, refers to the theory of prediction interval. Accordingly, in this paper, we aim at constructing of what so called predictive bivariate control charts, both classical and Copula-based ones. We argue that appropriate joint distribution function may be well estimated by employing Copula. A numerical analysis is carried out to illustrate that a Copula-based control chart outperforms than other.
Five-Parameter Bivariate Probability Distribution
NASA Technical Reports Server (NTRS)
Tubbs, J.; Brewer, D.; Smith, O. W.
1986-01-01
NASA technical memorandum presents four papers about five-parameter bivariate gamma class of probability distributions. With some overlap of subject matter, papers address different aspects of theories of these distributions and use in forming statistical models of such phenomena as wind gusts. Provides acceptable results for defining constraints in problems designing aircraft and spacecraft to withstand large wind-gust loads.
Isotonic water transport in secretory epithelia.
Swanson, C H
1977-01-01
The model proposed by Diamond and Bossert [1] for isotonic water transport has received wide acceptance in recent years. It assumes that the local driving force for water transport is a standing osmotic gradient produced in the lateral intercellular spaces of the epithelial cell layer by active solute transport. While this model is based on work done in absorptive epithelia where the closed to open direction of the lateral space and the direction of net transport are the same, it has been proposed that the lateral spaces could also serve as the site of the local osmotic gradients for water transport in secretory epithelia, where the closed to open direction of the lateral space and net transport are opposed, by actively transporting solute out of the space rather than into it. Operation in the backward direction, however, requires a lower than ambient hydrostatic pressure within the lateral space which would seem more likely to cause the space to collapse with loss of function. On the other hand, most secretory epithelia are characterized by transport into a restricted ductal system which is similar to the lateral intercellular space in the absorptive epithelia in that its closed to open direction is the same as that of net transport. In vitro micropuncture studies on the exocrine pancreas of the rabbit indicate the presence of a small but statistically significant increase in juice osmolality, 6 mOsm/kg H(2)O, at the site of electrolyte and water secretion in the smallest extralobular ducts with secretin stimulation which suggests that the ductal system in the secretory epithelia rather than the lateral intercellular space is the site of the local osmotic gradients responsible for isotonic water transport. PMID:331693
Covariate analysis of bivariate survival data
Bennett, L.E.
1992-01-01
The methods developed are used to analyze the effects of covariates on bivariate survival data when censoring and ties are present. The proposed method provides models for bivariate survival data that include differential covariate effects and censored observations. The proposed models are based on an extension of the univariate Buckley-James estimators which replace censored data points by their expected values, conditional on the censoring time and the covariates. For the bivariate situation, it is necessary to determine the expectation of the failure times for one component conditional on the failure or censoring time of the other component. Two different methods have been developed to estimate these expectations. In the semiparametric approach these expectations are determined from a modification of Burke's estimate of the bivariate empirical survival function. In the parametric approach censored data points are also replaced by their conditional expected values where the expected values are determined from a specified parametric distribution. The model estimation will be based on the revised data set, comprised of uncensored components and expected values for the censored components. The variance-covariance matrix for the estimated covariate parameters has also been derived for both the semiparametric and parametric methods. Data from the Demographic and Health Survey was analyzed by these methods. The two outcome variables are post-partum amenorrhea and breastfeeding; education and parity were used as the covariates. Both the covariate parameter estimates and the variance-covariance estimates for the semiparametric and parametric models will be compared. In addition, a multivariate test statistic was used in the semiparametric model to examine contrasts. The significance of the statistic was determined from a bootstrap distribution of the test statistic.
Alternative geographical display strategies for bivariate relationships
Waterhouse, J.C.; Farrell, M.P.; Strand, R.H.
1981-01-01
The complexity of regional water management problems necessitates the summarization of water resource data in a form that is easily analyzed visually. Computer generated maps are well suited for displaying complex relationships since they are easy to create and modify and are relatively inexpensive compared to traditional techniques. Development of new display techniques creates questions about the most effective display of data used for generic assessments. Recent attempts at displaying bivariate data geographically have not been entirely successful due to numerous data categories and complex color patterns used in cross mapping techniques. This paper offers an alternate method of displaying bivariate data which uses the degree of differences between two variables (e.g., water supply and water demand) to create a scale in which shades of two primary colors are used for positive and negative differences while a third color is used for the null case (i.e., within the confidence limits of the statistical model.)
NASA Astrophysics Data System (ADS)
Piedade, Aldina; Alves, Tiago; Luís Zêzere, José
2016-04-01
Mass Transport Deposits (MTDs) are one of the most important process shaping passive and active margins. It is frequently happening and its characteristics, features and processes has been very well documented from diverse approaches and methodologies. In this work a methodology for evaluation of MTDs occurrence is tested in an area offshore Espírito Santo Basin, SE Brazil. MTDs inventory was made on three-dimensional (3D) seismic volume interpreting a high amplitude reflection which correspond to the top and base of the MTDs. The inventory consists of four MTDs which were integrated into a GIS database. MTDs favourability scores are computed using algorithms based on statistical/probabilistic analysis (Information Value Method) over unique condition terrain units in a raster basis. Terrain attributes derived from the Digital Terrain Model (DTM) are interpreted as proxies of driving factors of MTDs and are used as predictors in our models which are based on a set of different MTDs inventories. Three models are elaborated independently according to the area of the MTDs body (Model 1, Model 2 and Model 3). The final result is prepared by sorting all pixels according to the pixel favourability value in descending order. The robustness and accuracy of the MTDs favourability models are evaluated by the success-rate curves, which are used for the quantitative interpretation of the models expressing the goodness of fit of the MTDs. In addition, a sensitivity analysis was performed and the predisposing factors which have highest prediction performance on MTDs occurrence were identified. The obtained results allow to conclude the method is valid to apply to submarine slopes as it is demonstrated by the highest obtained goodness of fit (0.862). This work is very pioneer, the methodology used was never applied to submarine environment. It is a very promising and valid methodology within the prediction of submarine slopes regarding failing and instability to the industry. In
Collective structure of the N=40 isotones
Gaudefroy, L.; Peru, S.; Pillet, N.; Hilaire, S.; Delaroche, J.-P.; Girod, M.; Obertelli, A.
2009-12-15
The structure of even-even N=40 isotones is studied from drip line to drip line through the systematic investigation of their quadrupole modes of excitation. Calculations are performed within the Hartree-Fock-Bogoliubov approach using the Gogny D1S effective interaction. Where relevant, these calculations are extended beyond mean field within a generator-coordinate-based method. An overall good agreement with available experimental data is reported, showing that collectivity increases from the neutron to the proton drip line. Whereas {sup 60}Ca and {sup 68}Ni display a calculated spherical shape in their ground states, all other isotones show a prolate-deformed ground-state band and a quasi-{gamma} band. Coexistence features are predicted in the neutron-deficient N=40 isotones above {sup 74}Se.
Some properties of a 5-parameter bivariate probability distribution
NASA Technical Reports Server (NTRS)
Tubbs, J. D.; Brewer, D. W.; Smith, O. E.
1983-01-01
A five-parameter bivariate gamma distribution having two shape parameters, two location parameters and a correlation parameter was developed. This more general bivariate gamma distribution reduces to the known four-parameter distribution. The five-parameter distribution gives a better fit to the gust data. The statistical properties of this general bivariate gamma distribution and a hypothesis test were investigated. Although these developments have come too late in the Shuttle program to be used directly as design criteria for ascent wind gust loads, the new wind gust model has helped to explain the wind profile conditions which cause large dynamic loads. Other potential applications of the newly developed five-parameter bivariate gamma distribution are in the areas of reliability theory, signal noise, and vibration mechanics.
Bivariate Kumaraswamy distribution with an application on earthquake data
Özel, Gamze
2015-03-10
Bivariate Kumaraswamy (BK) distribution whose marginals are Kumaraswamy distributions has been recently introduced. However, its statistical properties are not studied in detail. In this study, statistical properties of the BK distribution are investigated. We suggest that the BK could provide suitable description for the earthquakes characteristics of Turkey. We support this argument using earthquakesoccurred in Turkey between 1900 and 2009. We also find that the BK distribution simulates earthquakes well.
Mechanism of isotonic water transport in glands.
Ussing, H H; Eskesen, K
1989-07-01
Since water and electrolytes pass cell membranes via separate channels, there can be no interactions in the membranes, and osmotic interactions between water and solutes can be expressed as the product of solute flux, frictional coefficient of solute, and length of pathway. It becomes clear that isotonic transport via a cell is impossible. In glands, where cation-selective junctions impede anion flux between the cells, isotonic water transport is only possible if sodium, after having passed the junction, is reabsorbed in the acinus and returned to the serosal side. Thus it can be recycled via the cation-selective junction and exert its drag on water more than once. This hypothesis was tested on frog skin glands. Skins were mounted in flux chambers with identical Ringer solutions on both sides. Na channels of the principal cells were closed with amiloride in the outside solution, and secretion stimulated with noradrenaline in the inside solution. Influx and efflux of Na, K and Br (used as tracer for Cl) were measured on paired half-skins during the constant-secretion phase. Flux ratios for both Na and K were higher than expected for electrodiffusion, indicating outgoing solvent drag. Flux ratios for K were much higher than those for Na. This is an agreement with the concept that Na is reabsorbed in the acinus and K is not. Two independent expressions for the degree of sodium recycling are developed. Under all experimental conditions these expressions give values for the recycling which are in good agreement. PMID:2473601
Chernyshev, Andrey V; Tarasov, Peter A; Semianov, Konstantin A; Nekrasov, Vyacheslav M; Hoekstra, Alfons G; Maltsev, Valeri P
2008-03-01
A mathematical model of erythrocyte lysis in isotonic solution of ammonium chloride is presented in frames of a statistical approach. The model is used to evaluate several parameters of mature erythrocytes (volume, surface area, hemoglobin concentration, number of anionic exchangers on membrane, elasticity and critical tension of membrane) through their sphering and lysis measured by a scanning flow cytometer (SFC). SFC allows measuring the light-scattering pattern (indicatrix) of an individual cell over the angular range from 10 degrees to 60 degrees . Comparison of the experimentally measured and theoretically calculated light scattering patterns allows discrimination of spherical from non-spherical erythrocytes and evaluation of volume and hemoglobin concentration for individual spherical cells. Three different processes were applied for erythrocytes sphering: (1) colloid osmotic lysis in isotonic solution of ammonium chloride, (2) isovolumetric sphering in the presence of sodium dodecyl sulphate and albumin in neutrally buffered isotonic saline, and (3) osmotic fragility test in hypotonic media. For the hemolysis in ammonium chloride, the evolution of distributions of sphered erythrocytes on volume and hemoglobin content was monitored in real-time experiments. The analysis of experimental data was performed in the context of a statistical approach, taking into account that parameters of erythrocytes vary from cell to cell. PMID:18083194
A bivariate pseudo Gamma distribution with application to acid rain data
NASA Astrophysics Data System (ADS)
Pilz, J.; Mohsin, M.; Gebhardt, A.
2012-04-01
Univariate and bivariate Gamma distributions are extensively used for statistical modeling in climatology. In this paper, a bivariate pseudo Gamma distribution is used to model the proportion of acidity and major ions in rain. The model parameters of the bivariate pseudo Gamma distribution are estimated by the maximum likelihood method. The plots of the distribution of the proportions are compared to the histograms of the observed data of the proportions of acidity and major ions in rain. The fitted pdf appears to follow the general pattern in the histograms closely.
Laberko, E L; Bogomil'sky, M R; Soldatsky, Yu L; Pogosova, I E
2016-01-01
The objective of the present study was to evaluate the influence of an isotonic saline solution containing benzalconium chloride and of a hypertonic seawater solution on the function of ciliary epithelium in the nasal cavity in vitro. To this effect, we investigated the cytological material obtained from 35 children presenting with adenoid tissue hypertrophy. The tissue samples were taken from the nasal cavity by the standard method. A cellular biopsy obtained from each patient was distributed between three tubes that contained isotonic saline solution supplemented by benzalconium chloride (0.1 mg/ml), a hypertonic seawater solution, and a standard physiological saline solution. It was shown that the number of the viable cells in both isotonic solutions was statistically comparable and significantly higher than in the hypertonic solution (p<0.05). The ciliary beat frequency of the cells embedded in the two isotonic solutions was not significantly different but considerably exceeded that in the hypertonic seawater solution (p<0.05). Thus, the present study has demonstrated the absence of the ciliotoxic influence of isotonic saline solution containing benzalconium chloride at a concentration of 0.1 mg/ml and the strong ciliotoxic effect of the hypertonic seawater solution. This finding gives reason to recommend isotonic solutions for the regular application whereas hypertonic solutions can be prescribed only during infectious and/or inflammatory ENT diseases. PMID:27213656
A new bivariate negative binomial regression model
NASA Astrophysics Data System (ADS)
Faroughi, Pouya; Ismail, Noriszura
2014-12-01
This paper introduces a new form of bivariate negative binomial (BNB-1) regression which can be fitted to bivariate and correlated count data with covariates. The BNB regression discussed in this study can be fitted to bivariate and overdispersed count data with positive, zero or negative correlations. The joint p.m.f. of the BNB1 distribution is derived from the product of two negative binomial marginals with a multiplicative factor parameter. Several testing methods were used to check overdispersion and goodness-of-fit of the model. Application of BNB-1 regression is illustrated on Malaysian motor insurance dataset. The results indicated that BNB-1 regression has better fit than bivariate Poisson and BNB-2 models with regards to Akaike information criterion.
Nonparametric Analysis of Bivariate Gap Time with Competing Risks
Huang, Chiung-Yu; Wang, Chenguang; Wang, Mei-Cheng
2016-01-01
Summary This article considers nonparametric methods for studying recurrent disease and death with competing risks. We first point out that comparisons based on the well-known cumulative incidence function can be confounded by different prevalence rates of the competing events, and that comparisons of the conditional distribution of the survival time given the failure event type are more relevant for investigating the prognosis of different patterns of recurrence disease. We then propose nonparametric estimators for the conditional cumulative incidence function as well as the conditional bivariate cumulative incidence function for the bivariate gap times, that is, the time to disease recurrence and the residual lifetime after recurrence. To quantify the association between the two gap times in the competing risks setting, a modified Kendall’s tau statistic is proposed. The proposed estimators for the conditional bivariate cumulative incidence distribution and the association measure account for the induced dependent censoring for the second gap time. Uniform consistency and weak convergence of the proposed estimators are established. Hypothesis testing procedures for two-sample comparisons are discussed. Numerical simulation studies with practical sample sizes are conducted to evaluate the performance of the proposed nonparametric estimators and tests. An application to data from a pancreatic cancer study is presented to illustrate the methods developed in this article. PMID:26990686
ERIC Educational Resources Information Center
Moses, Tim; Holland, Paul W.
2010-01-01
In this study, eight statistical strategies were evaluated for selecting the parameterizations of loglinear models for smoothing the bivariate test score distributions used in nonequivalent groups with anchor test (NEAT) equating. Four of the strategies were based on significance tests of chi-square statistics (Likelihood Ratio, Pearson,…
Mineral Composition and Nutritive Value of Isotonic and Energy Drinks.
Leśniewicz, Anna; Grzesiak, Magdalena; Żyrnicki, Wiesław; Borkowska-Burnecka, Jolanta
2016-04-01
Several very popular brands of isotonic and energy drinks consumed for fluid and electrolyte supplementation and stimulation of mental or physical alertness were chosen for investigation. Liquid beverages available in polyethylene bottles and aluminum cans as well as products in the form of tablets and powder in sachets were studied. The total concentrations of 21 elements (Ag, Al, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Na, Ni, P, Pb, Sr, Ti, V, and Zn), both essential and toxic, were simultaneously determined in preconcentrated drink samples by inductively coupled plasma-optical emission spectrometry (ICP-OES) equipped with pneumatic and ultrasonic nebulizers. Differences between the mineral compositions of isotonic and energy drinks were evaluated and discussed. The highest content of Na was found in both isotonic and energy drinks, whereas quite high concentrations of Mg were found in isotonic drinks, and the highest amount of calcium was quantified in energy drinks. The concentrations of B, Co, Cu, Ni, and P were higher in isotonic drinks, but energy drinks contained greater quantities of Ag, Cr, Zn, Mn, and Mo and toxic elements, as Cd and Pb. A comparison of element contents with micronutrient intake and tolerable levels was performed to evaluate contribution of the investigated beverages to the daily diet. The consumption of 250 cm(3) of an isotonic drink provides from 0.32 % (for Mn) up to 14.8 % (for Na) of the recommended daily intake. For the energy drinks, the maximum recommended daily intake fulfillment ranged from 0.02 % (for V) to 19.4 or 19.8 % (for Mg and Na). PMID:26286964
Proton pygmy resonances: Predictions for N = 20 isotones
NASA Astrophysics Data System (ADS)
Kim, Y.; Papakonstantinou, P.
2016-06-01
We study theoretically the low-energy electric-dipole response of N = 20 isotones. We present results from a quasiparticle random-phase approximation (QRPA) and a continuum random-phase approximation (CRPA), and we compare them with results for the mirror Z = 20 nuclei. According to our analysis, enhanced E1 strength is expected energetically well below the giant dipole resonance in the proton-rich isotones. Large amounts of E1 strength in the asymmetric N = 20 isotones are predicted, markedly unlike their equally asymmetric Z = 20 mirror nuclei, pointing unambiguously to the role of structural effects such as loose binding. A proton-skin oscillation could develop especially in 46Fe . The isoscalar response is predicted strong in all isotones. The proper description of non-localized threshold transitions and the nucleon effective mass in mean-field treatments may affect theoretical predictions. We call for systematic theoretical investigations to quantify the role of bulk-matter properties in anticipation of measurements of E1 transitions in proton-rich nuclei.
A microscopic explanation of the isotonic multiplet at N=90
Gupta, J. B.
2014-08-14
The shape phase transition from spherical to soft deformed at N=88-90 was observed long ago. After the prediction of the X(5) symmetry, for which analytical solution of the nuclear Hamiltonian is given [1], good examples of X(5) nuclei were identified in the N=90 isotones of Nd, Sm, Gd and Dy, in the recent works. The N=90 isotones have almost the similar deformed level structure, forming the isotonic multiplet in Z=50-66, N=82-104 quadrant. This is explained microscopically in terms of the Nilsson level diagram. Using the Dynamic Pairing-Plus-Quadrupole model of Kumar-Baranger, the quadrupole deformation and the occupancies of the neutrons and protons in these nuclei have been calculated, which support the formation of N=88, 90 isotonic multiplets. The existence of F-spin multiplets in Z=66-82, N=82-104 quadrant, identified in earlier works on the Interacting Boson Model, is also explained in our study.
An Annotated Bibliography of Isotonic Weight-Training Methods.
ERIC Educational Resources Information Center
Wysong, John V.
This literature study was conducted to compare and evaluate various types and techniques of weight lifting so that a weight lifting program could be selected or devised for a secondary school. Annotations of 32 research reports, journal articles, and monographs on isotonic strength training are presented. The literature in the first part of the…
Survival Analysis using Bivariate Archimedean Copulas
NASA Astrophysics Data System (ADS)
Chandra, Krishnendu
In this dissertation we solve the nonidentifiability problem of Archimedean copula models based on dependent censored data (see [Wang, 2012]). We give a set of identifiability conditions for a special class of bivariate frailty models. Our simulation results show that our proposed model is identifiable under our proposed conditions. We use EM algorithm to estimate unknown parameters and the proposed estimation approach can be applied to fit dependent censored data when the dependence is of research interest. The marginal survival functions can be estimated using the copula-graphic estimator (see [Zheng and Klein, 1995] and [Rivest and Wells, 2001]) or the estimator proposed by [Wang, 2014]. We also propose two model selection procedures for Archimedean copula models, one for uncensored data and the other one for right censored bivariate data. Our simulation results are similar to that of [Wang and Wells, 2000] and suggest that both procedures work quite well. The idea of our proposed model selection procedure originates from the model selection procedure for Archimedean copula models proposed by [Wang and Wells, 2000] for right censored bivariate data using the L2 norm corresponding to the Kendall distribution function. A suitable bootstrap procedure is yet to be suggested for our method. We further propose a new parameter estimator and a simple goodness-of-fit test for Archimedean copula models when the bivariate data is under fixed left truncation. Our simulation results suggest that our procedure needs to be improved so that it can be more powerful, reliable and efficient. In our strategy, to obtain estimates for the unknown parameters, we heavily exploit the concept of truncated tau (a measure of association established by [Manatunga and Oakes, 1996] for left truncated data). The idea of our goodness of fit test originates from the goodness-of-fit test for Archimedean copula models proposed by [Wang, 2010] for right censored bivariate data.
Bivariate flood frequency analyses using Copula function
NASA Astrophysics Data System (ADS)
Sraj, Mojca; Bezak, Nejc; Brilly, Mitja
2013-04-01
The objective of the study was (1) to perform all steps in flood frequency analyses using Copula approach, (2) to select the most appropriate Copula function and (3) to evaluate the conditional bivariate return periods for the next pairs of variables: peak-volume, volume-duration and peak-duration, respectively. Flood frequency analyses are usually made by univariate distribution functions and in most cases only peaks are considered in analyses. However, hydrological processes are multidimensional, so it is reasonable to consider more than one variable in analyses. Different marginal distributions can be used for Copula modelling. Copula function successfully models dependence between two or more depended variables and determination of marginal distributions and Copula selection are two separate processes. Hydrological station Litija on the Sava river is one of the oldest stations in Slovenia and it lies in eastern part of country. 58 years of annual maximums were used for analyses and three-points graphical method was used for base flow separation. The log-Pearson type 3 distribution was selected as marginal distribution of peaks and durations, the Pearson type 3 distribution was chosen as marginal distribution of volumes. Some frequently used Copula functions from the Archimedean (Gumbel-Hougaard, Frank, Joe, Clayton, BB1 and Ali-Mikhail-Haq), Elliptical (Student-t and Normal) and Extreme value (Galambos, Hüsler-Reiss and Tawn) families were applied to the data. Copula parameters were estimated with the method of moments based on the inversion of Kendall's tau and with the maximum likelihood method. Graphical and statistical test were applied for the comparison of different Copula functions. For the pair peak-duration the Kendall correlation coefficient was negative and only Copulas able to model negative dependence were used. The Gumbel-Hougaard, Frank and Ali-Mikhail-Haq Copulas were selected as optimal based on tests results for the pairs: peak-volume, volume
Review of some results in bivariate density estimation
NASA Technical Reports Server (NTRS)
Scott, D. W.
1982-01-01
Results are reviewed for choosing smoothing parameters for some bivariate density estimators. Experience gained in comparing the effects of smoothing parameters on probability density estimators for univariate and bivariate data is summarized.
Mitsui, Toshio; Takai, Nobukatsu; Ohshima, Hiroyuki
2011-01-01
Mitsui and Ohshima (2008) criticized the power-stroke model for muscle contraction and proposed a new model. In the new model, about 41% of the myosin heads are bound to actin filaments, and each bound head forms a complex MA3 with three actin molecules A1, A2 and A3 forming the crossbridge. The complex translates along the actin filament cooperating with each other. The new model well explained the experimental data on the steady filament sliding. As an extension of the study, the isometric tension transient and isotonic velocity transient are investigated. Statistical ensemble of crossbridges is introduced, and variation of the binding probability of myosin head to A1 is considered. When the binding probability to A1 is zero, the Hill-type force-velocity relation is resulted in. When the binding probability to A1 becomes finite, the deviation from the Hill-type force-velocity relation takes place, as observed by Edman (1988). The characteristics of the isometric tension transient observed by Ford, Huxley and Simmons (1977) and of the isotonic velocity transient observed by Civan and Podolsky (1966) are theoretically reproduced. Ratios of the extensibility are estimated as 0.22 for the crossbridge, 0.26 for the myosin filament and 0.52 for the actin filament, in consistency with the values determined by X-ray diffraction by Wakabayashi et al. (1994). PMID:21673917
Predicting Number of Zombies in a DDoS Attacks Using Isotonic Regression
NASA Astrophysics Data System (ADS)
Gupta, B. B.; Jamali, Nadeem
Anomaly based DDoS detection systems construct profile of the traffic normally seen in the network, and identify anomalies whenever traffic deviate from normal profile beyond a threshold. This deviation in traffic beyond threshold is used in the past for DDoS detection but not for finding number of zombies. This chapter presents an approach that utilizes this deviation in traffic to predict number of zombies using isotonic regression model. A relationship is established between number of zombies and observed deviation in sample entropy. Internet type topologies used for simulation are generated using Transit-Stub model of GT-ITM topology generator. NS-2 network simulator on Linux platform is used as simulation test bed for launching DDoS attacks with varied number of zombies. Various statistical performance measures are used to measure the performance of the regression model. The simulation results are promising as we are able to predict number of zombies efficiently with very less error rate using isotonic regression model.
Isotopic Ratio, Isotonic Ratio, Isobaric Ratio and Shannon Information Uncertainty
NASA Astrophysics Data System (ADS)
Ma, Chun-Wang; Wei, Hui-Ling
2014-11-01
The isoscaling and the isobaric yield ratio difference (IBD) probes, both of which are constructed by yield ratio of fragment, provide cancelation of parameters. The information entropy theory is introduced to explain the physical meaning of the isoscaling and IBD probes. The similarity between the isoscaling and IBD results is found, i.e., the information uncertainty determined by the IBD method equals to β - α determined by the isoscaling (α (β) is the parameter fitted from the isotopic (isotonic) yield ratio).
Bivariate copula in fitting rainfall data
NASA Astrophysics Data System (ADS)
Yee, Kong Ching; Suhaila, Jamaludin; Yusof, Fadhilah; Mean, Foo Hui
2014-07-01
The usage of copula to determine the joint distribution between two variables is widely used in various areas. The joint distribution of rainfall characteristic obtained using the copula model is more ideal than the standard bivariate modelling where copula is belief to have overcome some limitation. Six copula models will be applied to obtain the most suitable bivariate distribution between two rain gauge stations. The copula models are Ali-Mikhail-Haq (AMH), Clayton, Frank, Galambos, Gumbel-Hoogaurd (GH) and Plackett. The rainfall data used in the study is selected from rain gauge stations which are located in the southern part of Peninsular Malaysia, during the period from 1980 to 2011. The goodness-of-fit test in this study is based on the Akaike information criterion (AIC).
Multiple imputation methods for bivariate outcomes in cluster randomised trials.
DiazOrdaz, K; Kenward, M G; Gomes, M; Grieve, R
2016-09-10
Missing observations are common in cluster randomised trials. The problem is exacerbated when modelling bivariate outcomes jointly, as the proportion of complete cases is often considerably smaller than the proportion having either of the outcomes fully observed. Approaches taken to handling such missing data include the following: complete case analysis, single-level multiple imputation that ignores the clustering, multiple imputation with a fixed effect for each cluster and multilevel multiple imputation. We contrasted the alternative approaches to handling missing data in a cost-effectiveness analysis that uses data from a cluster randomised trial to evaluate an exercise intervention for care home residents. We then conducted a simulation study to assess the performance of these approaches on bivariate continuous outcomes, in terms of confidence interval coverage and empirical bias in the estimated treatment effects. Missing-at-random clustered data scenarios were simulated following a full-factorial design. Across all the missing data mechanisms considered, the multiple imputation methods provided estimators with negligible bias, while complete case analysis resulted in biased treatment effect estimates in scenarios where the randomised treatment arm was associated with missingness. Confidence interval coverage was generally in excess of nominal levels (up to 99.8%) following fixed-effects multiple imputation and too low following single-level multiple imputation. Multilevel multiple imputation led to coverage levels of approximately 95% throughout. © 2016 The Authors. Statistics in Medicine Published by John Wiley & Sons Ltd. PMID:26990655
Nonparametric causal inference for bivariate time series
NASA Astrophysics Data System (ADS)
McCracken, James M.; Weigel, Robert S.
2016-02-01
We introduce new quantities for exploratory causal inference between bivariate time series. The quantities, called penchants and leanings, are computationally straightforward to apply, follow directly from assumptions of probabilistic causality, do not depend on any assumed models for the time series generating process, and do not rely on any embedding procedures; these features may provide a clearer interpretation of the results than those from existing time series causality tools. The penchant and leaning are computed based on a structured method for computing probabilities.
Links to sources of cancer-related statistics, including the Surveillance, Epidemiology and End Results (SEER) Program, SEER-Medicare datasets, cancer survivor prevalence data, and the Cancer Trends Progress Report.
Quantitative texton sequences for legible bivariate maps.
Ware, Colin
2009-01-01
Representing bivariate scalar maps is a common but difficult visualization problem. One solution has been to use two dimensional color schemes, but the results are often hard to interpret and inaccurately read. An alternative is to use a color sequence for one variable and a texture sequence for another. This has been used, for example, in geology, but much less studied than the two dimensional color scheme, although theory suggests that it should lead to easier perceptual separation of information relating to the two variables. To make a texture sequence more clearly readable the concept of the quantitative texton sequence (QTonS) is introduced. A QTonS is defined a sequence of small graphical elements, called textons, where each texton represents a different numerical value and sets of textons can be densely displayed to produce visually differentiable textures. An experiment was carried out to compare two bivariate color coding schemes with two schemes using QTonS for one bivariate map component and a color sequence for the other. Two different key designs were investigated (a key being a sequence of colors or textures used in obtaining quantitative values from a map). The first design used two separate keys, one for each dimension, in order to measure how accurately subjects could independently estimate the underlying scalar variables. The second key design was two dimensional and intended to measure the overall integral accuracy that could be obtained. The results show that the accuracy is substantially higher for the QTonS/color sequence schemes. A hypothesis that texture/color sequence combinations are better for independent judgments of mapped quantities was supported. A second experiment probed the limits of spatial resolution for QTonSs. PMID:19834229
Bivariate analysis of flood peaks and volumes using copulas. An application to the Danube River
NASA Astrophysics Data System (ADS)
Papaioannou, George; Bacigal, Tomas; Jeneiova, Katarina; Kohnová, Silvia; Szolgay, Jan; Loukas, Athanasios
2014-05-01
A multivariate analysis on flood variables such as flood peaks, volumes and durations, is essential for hydrotechnical projects design. A lot of authors have suggested the use of bivariate distributions for the frequency analysis of flood peaks and volumes due to the supposition that the marginal probability distribution type is the same for these variables. The application of Copulas, which are becoming gradually widespread, can overcome this constraint. The selection of the appropriate copula type/families is not extensively treated in the literature and it remains a challenge in copula analysis. In this study a bivariate copula analysis with the use of different copula families is carried out on the basis of flood peak and the corresponding volumes along a river. This bivariate analysis of flood peaks and volumes is based on streamflow daily data of a time-series more than 100 years from several gauged stations of the Danube River. The methodology applied using annual maximum flood peaks (AMF) with the independent annual maximum volumes of fixed durations at 5, 10, 15,20,25,30 and 60 days. The discharge-volume pairs correlation are examined using Kendall's tau correlation analysis. The copulas families that selected for the bivariate modeling of the extracted pairs discharge and volumes are the Archimedean, Extreme-value and other copula families. The evaluation of the copulas performance achieved with the use of scatterplots of the observed and bootstrapped simulated pairs and formal tests of goodness of fit. Suitability of copulas was statistically compared. Archimedean (e.g. Frank and Clayton) copulas revealed to be more capable for bivariate modeling of floods than the other examined copula families at the Danube River. Results showed in general that copulas are effective tools for bivariate modeling of the two study random variables.
The role of paracellular pathways in isotonic fluid transport.
Schultz, S G
1977-01-01
Paracellular pathways across "leaky" epithelia are the major route for transepithelial ionic diffusion. The permselective properties of these pathways suggest that they offer a watery environment through which ions diffuse in their hydrated forms. There is also suggestive evidence that, at least in some tissues, paracellular pathways provide a significant route for transepithelial water flow in response to an osmotic pressure difference; however, this has not as yet been definitively established. The effect of junctional complexes that are permeable to ions and water on the predictions of the standing-osmotic gradient model for isotonic water absorption is considered. PMID:331697
The asymptotic distribution of maxima in bivariate samples
NASA Technical Reports Server (NTRS)
Campbell, J. W.; Tsokos, C. P.
1973-01-01
The joint distribution (as n tends to infinity) of the maxima of a sample of n independent observations of a bivariate random variable (X,Y) is studied. A method is developed for deriving the asymptotic distribution of the maxima, assuming that X and Y possess asymptotic extreme-value distributions and that the probability element dF(x,y) can be expanded in a canonical series. Applied both to the bivariate normal distribution and to the bivariate gamma and compound correlated bivariate Poisson distributions, the method shows that maxima from all these distributions are asymptotically uncorrelated.
The bivariate combined model for spatial data analysis.
Neyens, Thomas; Lawson, Andrew B; Kirby, Russell S; Faes, Christel
2016-08-15
To describe the spatial distribution of diseases, a number of methods have been proposed to model relative risks within areas. Most models use Bayesian hierarchical methods, in which one models both spatially structured and unstructured extra-Poisson variance present in the data. For modelling a single disease, the conditional autoregressive (CAR) convolution model has been very popular. More recently, a combined model was proposed that 'combines' ideas from the CAR convolution model and the well-known Poisson-gamma model. The combined model was shown to be a good alternative to the CAR convolution model when there was a large amount of uncorrelated extra-variance in the data. Less solutions exist for modelling two diseases simultaneously or modelling a disease in two sub-populations simultaneously. Furthermore, existing models are typically based on the CAR convolution model. In this paper, a bivariate version of the combined model is proposed in which the unstructured heterogeneity term is split up into terms that are shared and terms that are specific to the disease or subpopulation, while spatial dependency is introduced via a univariate or multivariate Markov random field. The proposed method is illustrated by analysis of disease data in Georgia (USA) and Limburg (Belgium) and in a simulation study. We conclude that the bivariate combined model constitutes an interesting model when two diseases are possibly correlated. As the choice of the preferred model differs between data sets, we suggest to use the new and existing modelling approaches together and to choose the best model via goodness-of-fit statistics. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26928309
FUNSTAT and statistical image representations
NASA Technical Reports Server (NTRS)
Parzen, E.
1983-01-01
General ideas of functional statistical inference analysis of one sample and two samples, univariate and bivariate are outlined. ONESAM program is applied to analyze the univariate probability distributions of multi-spectral image data.
Strength Development: Using Functional Isometrics in an Isotonic Strength Training Program.
ERIC Educational Resources Information Center
Jackson, Allen; And Others
1985-01-01
A study was made to determine if a combination of functional isometrics and standard isotonic training would be superior to a standard isotonic program in an instructional setting. The results provide support for functional isometrics as an enhancement where achievement of maximum strength is the goal. (Author/MT)
Statistical modeling of space shuttle environmental data
NASA Technical Reports Server (NTRS)
Tubbs, J. D.; Brewer, D. W.
1983-01-01
Statistical models which use a class of bivariate gamma distribution are examined. Topics discussed include: (1) the ratio of positively correlated gamma varieties; (2) a method to determine if unequal shape parameters are necessary in bivariate gamma distribution; (3) differential equations for modal location of a family of bivariate gamma distribution; and (4) analysis of some wind gust data using the analytical results developed for modeling application.
A precision isotonic measuring system for isolated tissues.
Mellor, P M
1984-12-01
An isotonic measuring system is described which utilizes an angular position transducer of the linear differential voltage transformer type. Resistance to corrosion, protection against the ingress of solutions, and ease of mounting and setting up were the mechanical objectives. Accuracy, linearity, and freedom from drift were essential requirements of the electrical specification. A special housing was designed to accommodate the transducer to overcome these problems. A control unit incorporating a power supply and electronic filtering components was made to serve up to four such transducers. The transducer output voltage is sufficiently high to drive directly even low sensitivity chart recorders. Constructional details and a circuit diagram are included. Fifty such transducers have been in use for up to four years in these laboratories. Examples of some of the published work done using this transducer system are referenced. PMID:6536830
Watanabe, K; Shimizu, K; Nakata, S; Watanabe, M
1991-03-01
The relationship between isotonic jaw-opening and jaw-closing muscle function was studied using a newly developed apparatus which enables load and velocity to be detected simultaneously. The following results were obtained from 17 male adults (age range 22-32 years) without any occlusal dysfunction. (i) The force-velocity relationship in jaw-opening and jaw-closing muscles was represented by a hyperbolic curve, which fitted well with Hill's equation. (ii) The theoretical maximum force obtained by extrapolation from regression was 32.55 +/- 4.98 kg for jaw opening and 35.74 +/- 4.52 kg for jaw closing. (iii) The theoretical maximum velocity obtained by extrapolation from regression was 456.70 +/- 183.27 mm s-1 for jaw opening and 372.77 +/- 141.67 mm s-1 for jaw closing. (iv) The maximum mechanical power (Pmax) calculated from the product of the force and velocity was 772.20 +/- 182.65 kg.mm s-1 for jaw opening and 708.68 +/- 128.14 kg.mm s-1 for jaw closing. (v) The Pmax exerted by individual subjects was approximately 12-34% of the maximum possible force (Fmax) calculated from the force and velocity, in both jaw opening and jaw closing. There were no statistically significant differences between jaw opening and jaw closing with regard to any isotonic muscle functions. In other words, the results of this study strongly indicated a substantial balance between isotonic jaw-opening and jaw-closing muscle function in the subjects who were investigated. PMID:2037940
Bivariate discrete beta Kernel graduation of mortality data.
Mazza, Angelo; Punzo, Antonio
2015-07-01
Various parametric/nonparametric techniques have been proposed in literature to graduate mortality data as a function of age. Nonparametric approaches, as for example kernel smoothing regression, are often preferred because they do not assume any particular mortality law. Among the existing kernel smoothing approaches, the recently proposed (univariate) discrete beta kernel smoother has been shown to provide some benefits. Bivariate graduation, over age and calendar years or durations, is common practice in demography and actuarial sciences. In this paper, we generalize the discrete beta kernel smoother to the bivariate case, and we introduce an adaptive bandwidth variant that may provide additional benefits when data on exposures to the risk of death are available; furthermore, we outline a cross-validation procedure for bandwidths selection. Using simulations studies, we compare the bivariate approach proposed here with its corresponding univariate formulation and with two popular nonparametric bivariate graduation techniques, based on Epanechnikov kernels and on P-splines. To make simulations realistic, a bivariate dataset, based on probabilities of dying recorded for the US males, is used. Simulations have confirmed the gain in performance of the new bivariate approach with respect to both the univariate and the bivariate competitors. PMID:25084764
Copula bivariate probit models: with an application to medical expenditures.
Winkelmann, Rainer
2012-12-01
The bivariate probit model is frequently used for estimating the effect of an endogenous binary regressor (the 'treatment') on a binary health outcome variable. This paper discusses simple modifications that maintain the probit assumption for the marginal distributions while introducing non-normal dependence using copulas. In an application of the copula bivariate probit model to the effect of insurance status on the absence of ambulatory health care expenditure, a model based on the Frank copula outperforms the standard bivariate probit model. PMID:22025413
Flexible marginalized models for bivariate longitudinal ordinal data
Lee, Keunbaik; Daniels, Michael J.; Joo, Yongsung
2013-01-01
Random effects models are commonly used to analyze longitudinal categorical data. Marginalized random effects models are a class of models that permit direct estimation of marginal mean parameters and characterize serial correlation for longitudinal categorical data via random effects (Heagerty, 1999). Marginally specified logistic-normal models for longitudinal binary data. Biometrics 55, 688–698; Lee and Daniels, 2008. Marginalized models for longitudinal ordinal data with application to quality of life studies. Statistics in Medicine 27, 4359–4380). In this paper, we propose a Kronecker product (KP) covariance structure to capture the correlation between processes at a given time and the correlation within a process over time (serial correlation) for bivariate longitudinal ordinal data. For the latter, we consider a more general class of models than standard (first-order) autoregressive correlation models, by re-parameterizing the correlation matrix using partial autocorrelations (Daniels and Pourahmadi, 2009). Modeling covariance matrices via partial autocorrelations. Journal of Multivariate Analysis 100, 2352–2363). We assess the reasonableness of the KP structure with a score test. A maximum marginal likelihood estimation method is proposed utilizing a quasi-Newton algorithm with quasi-Monte Carlo integration of the random effects. We examine the effects of demographic factors on metabolic syndrome and C-reactive protein using the proposed models. PMID:23365416
Decay Properties of N = 77 odd-Z Isotones
Batchelder, J. C.; Tantawy, M. N.; Danchev, M.; Hartley, D. J.; Mazzocchi, C.; Bingham, C. R.; Grzywacz, R.; Rykaczewski, K. P.; Gross, C. J.; Shapira, D.; Yu, C.-H.; Krolas, W.; Fong, D.; Hamilton, J. H.; Li, K.; Ramayya, A. V.; Ginter, T. N.; Stolz, A.; Hagino, K.; Karny, M.
2007-11-30
The systematics of the {pi}h{sub 11/2} x {nu}h{sub 11/2} and {pi}h{sub 11/2} x {nu}s{sub 1/2} isomeric configurations were studied for the odd-Z N = 77 isotones near the proton dripline. The spin and parity of I{sup {pi}} = 8{sup +} and 5{sup -} were deduced for the isomers in {sup 140}Eu and {sup 142}Tb. No evidence for the expected 1{sup +} ground-state was found in the {sup 144}Ho decay data. The proton emission from {sup 146}Tm was restudied and the spin and parity values of I{sup {pi}} = 10{sup +} and 5{sup -} were established for {sup 146m}Tm and {sup 146gs}Tm, respectively. The interpretation of the observed decay properties and structure of the proton-emitting states was made by accounting for deformation and proton and neutron coupling to the core excitations.
Mixed-symmetry octupole and hexadecapole excitations in N=52 isotones
NASA Astrophysics Data System (ADS)
Hennig, Andreas; Spieker, Mark; Werner, Volker; Ahn, Tan; Anagnostatou, Vassia; Cooper, Nathan; Derya, Vera; Elvers, Michael; Endres, Janis; Goddard, Phil; Heinz, Andreas; Hughes, Richard O.; Ilie, Gabriela; Mineva, Milena N.; Pickstone, Simon G.; Petkov, Pavel; Pietralla, Norbert; Radeck, Desirée; Ross, Tim J.; Savran, Deniz; Zilges, Andreas
2015-05-01
In addition to the well-established quadrupole mixed-symmetry states, octupole and hexadecapole excitations with mixed-symmetry character have been recently proposed for the N = 52 isotones 92Zr and 94Mo. We performed two inelastic proton-scattering experiments to study this kind of excitations in the heaviest stable N = 52 isotone 96Ru. From the combined experimental data of both experiments absolute transition strengths were extracted.
Behavior of one-quasiparticle levels in odd isotonic chains of heavy nuclei
Adamian, G. G.; Antonenko, N. V.; Kuklin, S. N.; Malov, L. A.; Lu, B. N.; Zhou, S. G.
2011-08-15
The low-lying one-quasiparticle states are studied in the isotonic chains with N=147, 149, 151, 153, and 155 within the microscopic-macroscopic and self-consistent approaches. The energies of one-quasiparticle states change rather smoothly in the isotonic chains if there is no cross of the proton subshell. The {alpha}-decay schemes of several nuclei are suggested. The isomeric states in the odd isotopes of Fm and No are discussed.
A Vehicle for Bivariate Data Analysis
ERIC Educational Resources Information Center
Roscoe, Matt B.
2016-01-01
Instead of reserving the study of probability and statistics for special fourth-year high school courses, the Common Core State Standards for Mathematics (CCSSM) takes a "statistics for all" approach. The standards recommend that students in grades 6-8 learn to summarize and describe data distributions, understand probability, draw…
Effect of an isotonic rehydration sports drink and exercise on urolithiasis in rats.
Abreu, N P; Bergamaschi, C T; di Marco, G S; Razvickas, C V; Schor, N
2005-04-01
The objective of the present study was to evaluate the role of physical exercise as well as the influence of hydration with an isotonic sports drink on renal function in male Wistar rats. Four groups were studied over a period of 42 days: 1) control (N = 9); 2) physical exercise (Exe, N = 7); 3) isotonic drink (Drink, N = 8); 4) physical exercise + isotonic drink (Exe + Drink, N = 8). Physical exercise consisted of running on a motor-driven treadmill for 1 h/day, at 20 m/min, 5 days a week. The isotonic sports drink was a commercial solution used by athletes for rehydration after physical activity, 2 ml administered by gavage twice a day. Urine cultures were performed in all animals. Twenty-four-hour urine samples were collected in metabolic cages at the beginning and at the end of the protocol period. Urinary and plasma parameters (sodium, potassium, urea, creatinine, calcium) did not differ among groups. However, an amorphous material was observed in the bladders of animals in the Exe + Drink and Drink groups. Characterization of the material by Western blot revealed the presence of Tamm-Horsfall protein and angiotensin converting enzyme. Physical exercise and the isotonic drink did not change the plasma or urinary parameters measured. However, the isotonic drink induced the formation of intravesical matrix, suggesting a potential lithogenic risk. PMID:15962183
Bilgili, D; Ryu, D; Ergönül, Ö; Ebrahimi, N
2016-03-01
Infectious diseases that can be spread directly or indirectly from one person to another are caused by pathogenic microorganisms such as bacteria, viruses, parasites, or fungi. Infectious diseases remain one of the greatest threats to human health and the analysis of infectious disease data is among the most important application of statistics. In this article, we develop Bayesian methodology using parametric bivariate accelerated lifetime model to study dependency between the colonization and infection times for Acinetobacter baumannii bacteria which is leading cause of infection among the hospital infection agents. We also study their associations with covariates such as age, gender, apache score, antibiotics use 3 months before admission and invasive mechanical ventilation use. To account for singularity, we use Singular Bivariate Extreme Value distribution to model residuals in Bivariate Accelerated lifetime model under the fully Bayesian framework. We analyze a censored data related to the colonization and infection collected in five major hospitals in Turkey using our methodology. The data analysis done in this article is for illustration of our proposed method and can be applied to any situation that our model can be used. PMID:26394029
NASA Astrophysics Data System (ADS)
Candela, Angela; Tito Aronica, Giuseppe
2014-05-01
Floods are a global problem and are considered the most frequent natural disaster world-wide. Many studies show that the severity and frequency of floods have increased in recent years and underline the difficulty to separate the effects of natural climatic changes and human influences as land management practices, urbanization etc. Flood risk analysis and assessment is required to provide information on current or future flood hazard and risks in order to accomplish flood risk mitigation, to propose, evaluate and select measures to reduce it. Both components of risk can be mapped individually and are affected by multiple uncertainties as well as the joint estimate of flood risk. Major sources of uncertainty include statistical analysis of extremes events, definition of hydrological input, channel and floodplain topography representation, the choice of effective hydraulic roughness coefficients. The classical procedure to estimate flood discharge for a chosen probability of exceedance is to deal with a rainfall-runoff model associating to risk the same return period of original rainfall, in accordance with the iso-frequency criterion. Alternatively, a flood frequency analysis to a given record of discharge data is applied, but again the same probability is associated to flood discharges and respective risk. Moreover, since flood peaks and corresponding flood volumes are variables of the same phenomenon, they should be, directly, correlated and, consequently, multivariate statistical analyses must be applied. This study presents an innovative approach to obtain flood hazard maps where hydrological input (synthetic flood design event) to a 2D hydraulic model has been defined by generating flood peak discharges and volumes from: a) a classical univariate approach, b) a bivariate statistical analysis, through the use of copulas. The univariate approach considers flood hydrographs generation by an indirect approach (rainfall-runoff transformation using input rainfall
Simultaneous estimation of parameters in the bivariate Emax model.
Magnusdottir, Bergrun T; Nyquist, Hans
2015-12-10
In this paper, we explore inference in multi-response, nonlinear models. By multi-response, we mean models with m > 1 response variables and accordingly m relations. Each parameter/explanatory variable may appear in one or more of the relations. We study a system estimation approach for simultaneous computation and inference of the model and (co)variance parameters. For illustration, we fit a bivariate Emax model to diabetes dose-response data. Further, the bivariate Emax model is used in a simulation study that compares the system estimation approach to equation-by-equation estimation. We conclude that overall, the system estimation approach performs better for the bivariate Emax model when there are dependencies among relations. The stronger the dependencies, the more we gain in precision by using system estimation rather than equation-by-equation estimation. PMID:26190048
Sodium recirculation and isotonic transport in toad small intestine.
Nedergaard, S; Larsen, E H; Ussing, H H
1999-04-01
+ fluxes, is compatible with convective flow of the two alkali metal ions through the same population of water-filled pores. With a new set of equations, the fraction of the sodium flux passing the basement membrane barrier of the lateral space that is recirculated through the cellular compartment is estimated. This fraction was, on average, 0.72 +/- 0.03 (N = 5). It is concluded that isotonicity of the transportate can be maintained by producing a hypertonic fluid emerging from the lateral space combined with reuptake of salt via the cells. PMID:10191358
NASA Astrophysics Data System (ADS)
Takeuchi, Tsutomu T.
2010-08-01
We provide an analytic method to construct a bivariate distribution function (DF) with given marginal distributions and correlation coefficient. We introduce a convenient mathematical tool, called a copula, to connect two DFs with any prescribed dependence structure. If the correlation of two variables is weak (Pearson's correlation coefficient |ρ| < 1/3), the Farlie-Gumbel-Morgenstern (FGM) copula provides an intuitive and natural way to construct such a bivariate DF. When the linear correlation is stronger, the FGM copula cannot work anymore. In this case, we propose using a Gaussian copula, which connects two given marginals and is directly related to the linear correlation coefficient between two variables. Using the copulas, we construct the bivariate luminosity function (BLF) and discuss its statistical properties. We focus especially on the far-infrared-far-ulatraviolet (FUV-FIR) BLF, since these two wavelength regions are related to star-formation (SF) activity. Though both the FUV and FIR are related to SF activity, the univariate LFs have a very different functional form: the former is well described by the Schechter function whilst the latter has a much more extended power-law-like luminous end. We construct the FUV-FIR BLFs using the FGM and Gaussian copulas with different strengths of correlation, and examine their statistical properties. We then discuss some further possible applications of the BLF: the problem of a multiband flux-limited sample selection, the construction of the star-formation rate (SFR) function, and the construction of the stellar mass of galaxies (M*)-specific SFR (SFR/M*) relation. The copulas turn out to be a very useful tool to investigate all these issues, especially for including complicated selection effects.
Fluid and electrolyte shifts during bed rest with isometric and isotonic exercise
NASA Technical Reports Server (NTRS)
Greenleaf, J. E.; Bernauer, E. M.; Young, H. L.; Morse, J. T.; Juhos, L. T.; Van Beaumont, W.; Staley, R. W.
1977-01-01
It is difficult to separate the effects of reduction in hydrostatic pressure from that of reduced energy expenditure when investigating the confinement deconditioning problem. Experiments were conducted on seven healthy young men aged 19-21 yr with the purpose of separating these two factors by using isotonic physical exercise during bed rest to provide a daily energy expenditure greater than normal ambulatory levels. Fluid and electrolyte shifts were measured during three two-week bed rest periods, each of which being separated by a three-week ambulatory recovery period. During two of the three bed rest periods they performed isometric and isotonic exercises to compare their effects on fluid and electrolyte shifts during bed rest. It is shown that during bed rest, preservation of the extracellular volume takes precedence over maintenance of the plasma volume and that this mechanism is independent of the effects of isometric or isotonic exercise.
Work capacity during 30 days of bed rest with isotonic and isokinetic exercise training
NASA Technical Reports Server (NTRS)
Greenleaf, J. E.; Bernauer, E. M.; Ertl, A. C.; Trowbridge, T. S.; Wade, C. E.
1989-01-01
Results are presented from a study to determine whether or not short-term variable intensity isotonic and intermittent high-intensity isokinetic short-duration leg exercise is effective for the maintenance of peak O2 (VO2) uptake and muscular strength and endurance, respectively, during 30 days of -6 deg head-down bed rest deconditioning. The results show no significant changes in leg peak torque, leg mean total work, arm total peak torque, or arm mean total work for members of the isotonic, isokinetic, and controls groups. Changes are observed, however, in peak VO2 levels. The results suggest that near-peak variabile intensity, isotonic leg excercise maintains peak VO2 during 30 days of bed rest, while peak intermittent, isokinetic leg excercise protocol does not.
A quantum quasi-harmonic nonlinear oscillator with an isotonic term
Rañada, Manuel F.
2014-08-01
The properties of a nonlinear oscillator with an additional term k{sub g}/x², characterizing the isotonic oscillator, are studied. The nonlinearity affects to both the kinetic term and the potential and combines two nonlinearities associated to two parameters, κ and k{sub g}, in such a way that for κ = 0 all the characteristics of the standard isotonic system are recovered. The first part is devoted to the classical system and the second part to the quantum system. This is a problem of quantization of a system with position-dependent mass of the form m(x) = 1/(1 − κx²), with a κ-dependent non-polynomial rational potential and with an additional isotonic term. The Schrödinger equation is exactly solved and the (κ, k{sub g})-dependent wave functions and bound state energies are explicitly obtained for both κ < 0 and κ > 0.
Iwase, Satoshi; Kawahara, Yuko; Nishimura, Naoki; Nishimura, Rumiko; Sugenoya, Junichi; Miwa, Chihiro; Takada, Masumi
2014-08-01
To clarify the effects of isometric and isotonic exercise during mist sauna bathing on the cardiovascular function, thermoregulatory function, and metabolism, six healthy young men (22 ± 1 years old, height 173 ± 4 cm, weight 65.0 ± 5.0 kg) were exposed to a mist sauna for 10 min at a temperature of 40 °C, and relative humidity of 100 % while performing or not performing ∼30 W of isometric or isotonic exercise. The effect of the exercise was assessed by measuring tympanic temperature, heart rate, systolic and diastolic blood pressure, chest sweat rate, chest skin blood flow, and plasma catecholamine and cortisol, glucose, lactate, and free fatty acid levels. Repeated measures ANOVA showed no significant differences in blood pressure, skin blood flow, sweat rate, and total amount of sweating. Tympanic temperature increased more during isotonic exercise, and heart rate increase was more marked during isotonic exercise. The changes in lactate indicated that fatigue was not very great during isometric exercise. The glucose level indicated greater energy expenditure during isometric exercise. The free fatty acid and catecholamine levels indicated that isometric exercise did not result in very great energy expenditure and stress, respectively. The results for isotonic exercise of a decrease in lactate level and an increase in plasma free fatty acid level indicated that fatigue and energy expenditure were rather large while the perceived stress was comparatively low. We concluded that isotonic exercise may be a more desirable form of exercise during mist sauna bathing given the changes in glucose and free fatty acid levels. PMID:23884733
NASA Astrophysics Data System (ADS)
Iwase, Satoshi; Kawahara, Yuko; Nishimura, Naoki; Nishimura, Rumiko; Sugenoya, Junichi; Miwa, Chihiro; Takada, Masumi
2014-08-01
To clarify the effects of isometric and isotonic exercise during mist sauna bathing on the cardiovascular function, thermoregulatory function, and metabolism, six healthy young men (22 ± 1 years old, height 173 ± 4 cm, weight 65.0 ± 5.0 kg) were exposed to a mist sauna for 10 min at a temperature of 40 °C, and relative humidity of 100 % while performing or not performing ˜30 W of isometric or isotonic exercise. The effect of the exercise was assessed by measuring tympanic temperature, heart rate, systolic and diastolic blood pressure, chest sweat rate, chest skin blood flow, and plasma catecholamine and cortisol, glucose, lactate, and free fatty acid levels. Repeated measures ANOVA showed no significant differences in blood pressure, skin blood flow, sweat rate, and total amount of sweating. Tympanic temperature increased more during isotonic exercise, and heart rate increase was more marked during isotonic exercise. The changes in lactate indicated that fatigue was not very great during isometric exercise. The glucose level indicated greater energy expenditure during isometric exercise. The free fatty acid and catecholamine levels indicated that isometric exercise did not result in very great energy expenditure and stress, respectively. The results for isotonic exercise of a decrease in lactate level and an increase in plasma free fatty acid level indicated that fatigue and energy expenditure were rather large while the perceived stress was comparatively low. We concluded that isotonic exercise may be a more desirable form of exercise during mist sauna bathing given the changes in glucose and free fatty acid levels.
Half-lives of N = 126 Isotones and the r-Process
Suzuki, Toshio; Yoshida, Takashi; Utsuno, Yutaka
2010-08-12
Beta decays of N = 126 isotones are studied by shell model calculations. Both the Gamow-Teller (GT) and first-forbidden (FF) transitions are taken into account to evaluate the half-lives of the isotones (Z = 64-72) with the use of shell model interactions based on G-matrix. The FF transitions are found to be important to reduce the half-lives by twice to several times of those obtained by the GT contributions only. Possible implications of the short half-lives of the waiting point nuclei on the r-process nucleosynthesis during the supernova explosions are discussed.
+Gz tolerance in man after 14-day bedrest periods with isometric and isotonic exercise conditioning
NASA Technical Reports Server (NTRS)
Greenleaf, J. E.; Haines, R. F.; Sandler, H.; Bernauer, E. M.; Morse, J. T.; Armbruster, R.; Sagan, L.; Van Beaumont, W.
1975-01-01
The effects of isometric and isotonic exercise training on post-bedrest +Gz tolerance were determined. In general, 14-day bedrest resulted in a significant loss of Gz tolerance, as previously discovered. At 2.1 Gz, neither the isometric nor the isotonic exercises regimens resulted in a significant increase in post-bedrest Gz tolerance. However, following isometric exercise, restoration of about half the tolerance decrement occurred at 3.2 Gz and 3.8 Gz. Possible reasons for this partial restoration of tolerance are put forward.
Ion secretion and isotonic transport in frog skin glands.
Ussing, H H; Lind, F; Larsen, E H
1996-07-01
The aim of this study was to clarify the mechanism of isotonic fluid transport in frog skin glands. Stationary ion secretion by the glands was studied by measuring unidirectional fluxes of 24Na+, 42K+, and carrier-free 134Cs+ in paired frog skins bathed on both sides with Ringer's solution, and with 10(-5) M noradrenaline on the inside and 10(-4) M amiloride on the outside. At transepithelial thermodynamic equilibrium conditions, the 134Cs+ flux ratio, JoutCs/JinCs, varied in seven pairs of preparations from 6 to 36. Since carrier-free 134Cs+ entering the cells is irreversibly trapped in the cellular compartment (Ussing & Lind, 1996), the transepithelial net flux of 134Cs+ indicates that a paracellular flow of water is dragging 134Cs+ in the direction from the serosal- to outside solution. From the measured flux ratios it was calculated that the force driving the secretory flux of Cs+ varied from 30 to 61 mV among preparations. In the same experiments unidirectional Na+ fluxes were measured as well, and it was found that also Na+ was subjected to secretion. The ratio of unidirectional Na+ fluxes, however, was significantly smaller than would be predicted if the two ions were both flowing along the paracellular route dragged by the flow of water. This result indicates that Na+ and Cs+ do not take the same pathway through the glands. The flux ratio of unidirectional K+ fluxes indicated active secretion of K+. The time it takes for steady-state K+ fluxes to be established was significantly longer than that of the simultaneously measured Cs+ fluxes. These results allow the conclusion that - in addition to being transported between cells - K+ is submitted to active transport along a cellular pathway. Based on the recirculation theory, we propose a new model which accounts for stationary Na+, K+, Cl- and water secretion under thermodynamic equilibrium conditions. The new features of the model, as compared to the classical Silva-model for the shark-rectal gland, are: (i
Multimodal Bivariate Thematic Maps: Auditory and Haptic Display.
ERIC Educational Resources Information Center
Jeong, Wooseob; Gluck, Myke
2002-01-01
Explores the possibility of multimodal bivariate thematic maps by utilizing auditory and haptic (sense of touch) displays. Measured completion time of tasks and the recall (retention) rate in two experiments, and findings confirmed the possibility of using auditory and haptic displays in geographic information systems (GIS). (Author/LRW)
Evaluating Univariate, Bivariate, and Multivariate Normality Using Graphical Procedures.
ERIC Educational Resources Information Center
Burdenski, Thomas K., Jr.
This paper reviews graphical and nongraphical procedures for evaluating multivariate normality by guiding the reader through univariate and bivariate procedures that are necessary, but insufficient, indications of a multivariate normal distribution. A data set using three dependent variables for two groups provided by D. George and P. Mallery…
Univariate and Bivariate Loglinear Models for Discrete Test Score Distributions.
ERIC Educational Resources Information Center
Holland, Paul W.; Thayer, Dorothy T.
2000-01-01
Applied the theory of exponential families of distributions to the problem of fitting the univariate histograms and discrete bivariate frequency distributions that often arise in the analysis of test scores. Considers efficient computation of the maximum likelihood estimates of the parameters using Newton's Method and computationally efficient…
A New Measure Of Bivariate Asymmetry And Its Evaluation
Ferreira, Flavio Henn; Kolev, Nikolai Valtchev
2008-11-06
In this paper we propose a new measure of bivariate asymmetry, based on conditional correlation coefficients. A decomposition of the Pearson correlation coefficient in terms of its conditional versions is studied and an example of application of the proposed measure is given.
ERIC Educational Resources Information Center
Tanner, Kristine; Roy, Nelson; Merrill, Ray M.; Muntz, Faye; Houtz, Daniel R.; Sauder, Cara; Elstad, Mark; Wright-Costa, Julie
2010-01-01
Purpose: To examine the effects of nebulized isotonic saline (IS) versus sterile water (SW) on self-perceived phonatory effort (PPE) and phonation threshold pressure (PTP) following a surface laryngeal dehydration challenge in classically trained sopranos. Method: In a double-blind, within-subject crossover design, 34 sopranos breathed dry air…
The Noval Properties and Construction of Multi-scale Matrix-valued Bivariate Wavelet wraps
NASA Astrophysics Data System (ADS)
Zhang, Hai-mo
In this paper, we introduce matrix-valued multi-resolution structure and matrix-valued bivariate wavelet wraps. A constructive method of semi-orthogonal matrix-valued bivari-ate wavelet wraps is presented. Their properties have been characterized by using time-frequency analysis method, unitary extension principle and operator theory. The direct decom-position relation is obtained.
Children with Heavy Prenatal Alcohol Exposure Experience Reduced Control of Isotonic Force
Nguyen, Tanya T.; Levy, Susan S.; Riley, Edward P.; Thomas, Jennifer D.; Simmons, Roger W.
2013-01-01
Background Heavy prenatal alcohol exposure can result in diverse and extensive damage to the central nervous system, including the cerebellum, basal ganglia, and cerebral cortex. Given that these brain regions are involved in the generation and maintenance of motor force, we predicted that prenatal alcohol exposure would adversely affect this parameter of motor control. We previously reported that children with gestational alcohol exposure experience significant deficits in regulating isometric (i.e., constant) force. The purpose of the present study was to determine if these children exhibit similar deficits when producing isotonic (i.e., graded) force. Methods Children with heavy prenatal alcohol exposure and typically developing children completed a series of isotonic force contractions by exerting force on a load cell to match a criterion target force displayed on a computer monitor. Two levels of target force (5% or 20% of maximum voluntary force) were investigated in combination with varying levels of visual feedback. Results Compared to controls, children with heavy prenatal alcohol exposure generated isotonic force signals that were less accurate, more variable, and less complex in the time domain compared to control children. Specifically, interactions were found between group and visual feedback for response accuracy and signal complexity, suggesting that these children have greater difficulty altering their motor output when visual feedback is low. Conclusions These data suggest that prenatal alcohol exposure produces deficits in regulating isotonic force, which presumably result from alcohol-related damage to developing brain regions involved in motor control. These children will most likely experience difficulty performing basic motor skills and daily functional skills that require coordination of finely graded force. Therapeutic strategies designed to increase feedback and, consequently, facilitate visual-motor integration could improve isotonic force
Guilhem, Gaël; Cornu, Christophe; Guével, Arnaud
2012-01-01
Context: Resistance exercise training commonly is performed against a constant external load (isotonic) or at a constant velocity (isokinetic). Researchers comparing the effectiveness of isotonic and isokinetic resistance-training protocols need to equalize the mechanical stimulus (work and velocity) applied. Objective: To examine whether the standardization protocol could be adjusted and applied to an eccentric training program. Design: Controlled laboratory study. Setting: Controlled research laboratory. Patients or Other Participants: Twenty-one sport science male students (age = 20.6 ± 1.5 years, height = 178.0 ± 4.0 cm, mass = 74.5 ± 9.1 kg). Intervention(s): Participants performed 9 weeks of isotonic (n = 11) or isokinetic (n = 10) eccentric training of knee extensors that was designed so they would perform the same amount of angular work at the same mean angular velocity. Main Outcome Measure(s): Angular work and angular velocity. Results: The isotonic and isokinetic groups performed the same total amount of work (−185.2 ± 6.5 kJ and −184.4 ± 8.6 kJ, respectively) at the same angular velocity (21 ± 1°/s and 22°/s, respectively) with the same number of repetitions (8.0 and 8.0, respectively). Bland-Altman analysis showed that work (bias = 2.4%) and angular velocity (bias = 0.2%) were equalized over 9 weeks between the modes of training. Conclusions: The procedure developed allows angular work and velocity to be standardized over 9 weeks of isotonic and isokinetic eccentric training of the knee extensors. This method could be useful in future studies in which researchers compare neuromuscular adaptations induced by each type of training mode with respect to rehabilitating patients after musculoskeletal injury. PMID:22488276
A bivariate survival model with compound Poisson frailty
Wienke, A.; Ripatti, S.; Palmgren, J.; Yashin, A.
2015-01-01
A correlated frailty model is suggested for analysis of bivariate time-to-event data. The model is an extension of the correlated power variance function (PVF) frailty model (correlated three-parameter frailty model). It is based on a bivariate extension of the compound Poisson frailty model in univariate survival analysis. It allows for a non-susceptible fraction (of zero frailty) in the population, overcoming the common assumption in survival analysis that all individuals are susceptible to the event under study. The model contains the correlated gamma frailty model and the correlated inverse Gaussian frailty model as special cases. A maximum likelihood estimation procedure for the parameters is presented and its properties are studied in a small simulation study. This model is applied to breast cancer incidence data of Swedish twins. The proportion of women susceptible to breast cancer is estimated to be 15 per cent. PMID:19856276
Bivariate cumulative probit model for the comparison of neuronal encoding hypotheses.
Hillmann, Julia; Kneib, Thomas; Koepcke, Lena; Juárez Paz, León M; Kretzberg, Jutta
2014-01-01
Understanding the way stimulus properties are encoded in the nerve cell responses of sensory organs is one of the fundamental scientific questions in neurosciences. Different neuronal coding hypotheses can be compared by use of an inverse procedure called stimulus reconstruction. Here, based on different attributes of experimentally recorded neuronal responses, the values of certain stimulus properties are estimated by statistical classification methods. Comparison of stimulus reconstruction results then allows to draw conclusions about relative importance of covariate features. Since many stimulus properties have a natural order and can therefore be considered as ordinal, we introduce a bivariate ordinal probit model to obtain classifications for the combination of light intensity and velocity of a visual dot pattern based on different covariates extracted from recorded spike trains. For parameter estimation, we develop a Bayesian Gibbs sampler and incorporate penalized splines to model nonlinear effects. We compare the classification performance of different individual cell covariates and simple features of groups of neurons and find that the combination of at least two covariates increases the classification performance significantly. Furthermore, we obtain a non-linear effect for the first spike latency. The model is compared to a naïve Bayesian stimulus estimation method where it yields comparable misclassification rates for the given dataset. Hence, the bivariate ordinal probit model is shown to be a helpful tool for stimulus reconstruction particularly thanks to its flexibility with respect to the number of covariates as well as their scale and effect type. PMID:24186131
Effect of active pre-shortening on isometric and isotonic performance of single frog muscle fibres.
Granzier, H L; Pollack, G H
1989-01-01
1. We studied the effects of shortening history on isometric force and isotonic velocity in single intact frog fibres. Fibres were isometrically tetanized. When force reached a plateau, shortening was imposed, after which the fibre was held isometric again. Isometric force after shortening could then be compared with controls in which no shortening had taken place. 2. Sarcomere length was measured simultaneously with two independent methods: a laser-diffraction method and a segment-length method that detects the distance between two markers attached to the surface of the fibre, about 800 microns apart. 3. The fibre was mounted between two servomotors. One was used to impose the load clamp while the other cancelled the translation that occurred during this load clamp. Thus, translation of the segment under investigation could be minimized. 4. Initial experiments were performed at the fibre level. We found that active preshortening reduced isometric force considerably, thereby confirming earlier work of others. Force reductions as large as 70% were observed. 5. Under conditions in which there were large effects of shortening at the fibre level, we measured sarcomere length changes in the central region of the fibre. These sarcomeres shortened much less than the fibre's average. In fact, when the load was high, these sarcomeres lengthened while the fibre as a whole shortened. Thus, while the fibre-length signal implied that sarcomeres might have shortened to some intermediate length, in reality some sarcomeres were much longer, others much shorter. 6. Experiments performed at the sarcomere level revealed that isometric force was unaffected by previous sarcomere shortening provided the shortening occurred against either a low load or over a short distance. However, if the work done during shortening was high, force after previous shortening was less than if sarcomeres had remained at the final length throughout contraction. The correlation between the force deficit and
STATISTICAL METHODOLOGY FOR EXPLORING ELEVATIONAL DIFFERENCES IN PRECIPITATION CHEMISTRY
A statistical methodology for exploring the relationships between elevation and precipitation chemistry is outlined and illustrated. he methodology utilizes maximum likelihood estimates and likelihood ratio tests with contour ellipses of assumed bivariate lognormal distributions ...
Analysis of the Bivariate Parameter Wind Differences Between Jimsphere and Windsonde
NASA Technical Reports Server (NTRS)
Susko, Michael
1987-01-01
An analysis is presented for the bivariate parameter differences between the FPS-16 Radar/Jimsphere and the Meteorological Sounding System (MSS) Windsonde. The Jimsphere is used as the standard to measure the ascent wind during the Space Shuttle launches at Kennedy Space Center, Florida, and the Windsonde is the backup system. In addition, a discussion of the terrestrial environment (below 20 km) and a description of the Jimsphere and Windsonde wind sensors are given. Computation of the wind statistics from 64 paired Jimsphere and Windsonde balloon releases in support of 14 Space Shuttle launches shows a good agreement between the two wind sensors. From the analysis of buildup and back-off data for various scales of distance and the comparison of the cumulative percent frequency (CPF) versus wind speed change, it is shown that the wind speed change for various scales of distances for the Jimsphere and Windsonde compare favorably.
Effects of isotonic fluid load on plasma water and extracellular fluid volumes in the rat.
Larsson, M; Ware, J
1983-01-01
An isotonic fluid load was given to rats by infusing 12 ml saline i.v. in 60 min. The plasma water and extracellular fluid volumes of the whole animal and selected tissues were subsequently studied with 125I human serum albumin and 51Cr EDTA. The fluid infused was equivalent to 130% of the plasma water volume. The total extracellular fluid volume increased by 17%, while the total plasma water measured with RIHSA remained unchanged. The regional extracellular fluid volumes increased in the lung (14%), the gastric fundus (15%), large intestine (21%) and skin (28%). The results illustrate the selective distribution of an isotonic fluid overload, those tissues being effected having high compliances. PMID:6617709
van Lunteren, Erik; Moyer, Michelle
2012-01-01
K(+) channel blockers like 3,4-diaminopyridine (DAP) can double isometric muscle force. Functional movements require more complex concentric and eccentric contractions, however the effects of K(+) channel blockade on these types of contractions in situ are unknown. Extensor digitorum longus (EDL) muscles were stimulated in situ with and without DAP in anesthetized rats and fatigability was addressed using a series of either concentric or eccentric contractions. During isotonic protocols (5-100% load), DAP significantly shifted shortening- and maximum shortening velocity-load curves upward and to the right and increased power and work. Maximum shortening, maximum shortening velocity, and power doubled while work increased by ∼250% during isotonic contraction at 50% load. During isotonic fatigue, DAP significantly augmented maximum shortening, work, shortening velocity, and power. During constant velocity eccentric protocols (2-12 mm/s), DAP increased muscle force during eccentric contractions at 6, 8, 10, and 12 mm/s. During eccentric contraction at a constant velocity of 6 mm/s while varying the stimulation frequency, DAP significantly increased muscle force during 20, 40, and 70 Hz. The effects of DAP on muscle contractile performance during eccentric fatigue varied with level of fatigue. DAP-induced contractile increases during isotonic contractions were similar to those produced during previously studied isometric contractions, while the DAP effect during eccentric contractions was more modest. These findings are especially important in attempting to optimize functional electrical stimulation parameters for spinal cord injury patients while also preventing rapid fatigue of those muscles. PMID:23060809
Koutras, Georgios; Letsi, Magdalini; Papadopoulos, Pericles; Gigis, Ioannis
2012-01-01
Background: Although both isotonic and isokinetic exercises are commonly used in the rehabilitation of patients after arthroscopic meniscectomy no studies have compared their effect on strength recovery and functional outcomes. Purpose: The purpose of this study was to investigate the effects of two rehabilitation programs (isotonic and isokinetic) on muscle strength and functional performance after partial knee meniscectomy. A secondary purpose was to assess the correlation between isokinetic strength deficits and hop test performance deficits. Methods: Twenty male patients who underwent arthroscopic partial meniscectomy volunteered for the study. Both isotonic and isokinetic training were performed with the same equipment thereby blinding subjects to the mode of exercise. Main outcome measures were collected on the 14th and 33rd postoperative days and included isokinetic strength of the knee extensors and flexors, functional performance (single, triple, and vertical hopping) and the Lysholm questionnaire. Multivariate and univariate analyses of variance were used to assess the effects of the independent variables on the isokinetic variables, functional tests, and Lysholm score. Pearson's correlation was used to assess the relationship between isokinetic strength deficits and functional performance deficits. Results: Isokinetic measures, functional tests, and the Lysholm score all increased between initial and final assessment (p≤0.003). However, there were no group or group*time effects on any of the outcome variables (p≥0.33). Functional tests were better predictors of isokinetic deficits in the 14th compared to the 33rd postoperative day. Conclusion: No differences were found in the outcomes of patients treated using an isokinetic and an isotonic protocol for rehabilitation after arthroscopic meniscectomy. More than half of patients did not meet the 90% criterion in the hop tests for safe return to sports five weeks after meniscectomy. There were
Internal dose assessment for 211At α-emitter in isotonic solution as radiopharmaceutical
NASA Astrophysics Data System (ADS)
Yuminov, O. A.; Fotina, O. V.; Priselkova, A. B.; Tultaev, A. V.; Platonov, S. Yu.; Eremenko, D. O.; Drozdov, V. A.
2003-12-01
The functional fitness of the α-emitter 211At for radiotherapy of the thyroid gland cancer is evaluated. Radiation doses are calculated using the MIRD method and previously obtained pharmacokinetic data for 211At in isotonic solution and for 123I as sodium iodide. Analysis of the 211At radiation dose to the thyroid gland suggests that this radiopharmaceutical may be predominantly used for the treatment of the thyroid cancer.
Isotonic contraction as a result of cooperation of sarcomeres--a model and simulation outcome.
Wünsch, Z
1996-01-01
The molecular level of the functional structure of the contractile apparatus of cross-striated muscle has been mapped out almost minutely. Most authors accept the basic principles of the theory of sliding filaments and the theory of operation of molecular generators of force which, of course, are progressively updated by integrating new knowledge. The idea of the model delineated below does not contradict these theories, for it refers to another level of the system's hierarchy. The definition of the system, hereafter referred to Ideal Sarcomere (IS), takes into account the fact that, during isotonic contraction, a large number of not wholly independently working sarcomeres and molecular generators of force is active in a synergistic way. The shortening velocity of isotonically contracting IS is determined by the relation between quantities conveying different tasks of active generators of force and the influence of the system parameters. Although IS is derived from simple axiomatic predicates, it has properties which were not premediated in defining the system and which, in spite of this, correspond to some properties of the biological original. The equations of the system allow us to calculate the shortening velocity of 'isotonic contraction' and other variables and parameters and show, inter alia, an alternative way to derive and interpret the relations stated in Hill's force-velocity equation. The simulation results indicate that the macroscopic manifestations of isotonic contraction may be also contingent on the properties of the cooperating system of the multitude of sarcomeres, which also constitutes one part of the functional structure of muscle. PMID:8924648
Microscopic investigation of structural evolution in even-even N = 60 isotones
Oudih, M. R.; Fellah, M.; Allal, N. H.; Benhamouda, N.
2012-10-20
The ground state properties of even-even N=60 isotones from the neutron-rich to the proton-rich side are investigated within the self-consistent Skyrme-Hartree-Fock-Bogoliubov theory in the triaxial landscape. Quantities such as binding energies and root-mean-square radii are investigated and compared with available experimental data. The evolution of the potential energy surfaces in the ({beta},{gamma}) deformation plane is presented and discussed.
ISOTONICITY OF LIVER AND OF KIDNEY TISSUE IN SOLUTIONS OF ELECTROLYTES
Opie, Eugene L.
1959-01-01
Solutions of a wide variety of electrolytes, isotonic with liver or with kidney tissue, have approximately the same osmotic pressure as solutions of sodium chloride isotonic with tissues of the two organs respectively; that is, with solutions approximately twice as concentrated as the sodium chloride of mammalian blood plasma. The molar concentration of various electrolytes isotonic with liver or with kidney tissue immediately after its removal from the body is determined by the molecular weight, valency, and ion-dissociation of these electrolytes in accordance with the well known conditions of osmosis. The plasma membranes of liver and of kidney cells are imperfectly semipermeable to electrolytes, and those that enter the cell, though retarded in so doing, bring about injury which increases permeability to water. The osmotic activity of cells of mammalian liver and kidney immediately after their removal from the body resembles that of plant cells, egg cells of marine invertebrates, and mammalian red blood corpuscles and presumably represents a basic property of living cells by which osmotic pressure may be adjusted to functional need. PMID:13664872
Isotonicity of liver and of kidney tissue in solutions of electrolytes.
OPIE, E L
1959-07-01
Solutions of a wide variety of electrolytes, isotonic with liver or with kidney tissue, have approximately the same osmotic pressure as solutions of sodium chloride isotonic with tissues of the two organs respectively; that is, with solutions approximately twice as concentrated as the sodium chloride of mammalian blood plasma. The molar concentration of various electrolytes isotonic with liver or with kidney tissue immediately after its removal from the body is determined by the molecular weight, valency, and ion-dissociation of these electrolytes in accordance with the well known conditions of osmosis. The plasma membranes of liver and of kidney cells are imperfectly semipermeable to electrolytes, and those that enter the cell, though retarded in so doing, bring about injury which increases permeability to water. The osmotic activity of cells of mammalian liver and kidney immediately after their removal from the body resembles that of plant cells, egg cells of marine invertebrates, and mammalian red blood corpuscles and presumably represents a basic property of living cells by which osmotic pressure may be adjusted to functional need. PMID:13664872
van Lunteren, Erik; Pollarine, Jennifer; Moyer, Michelle
2007-07-01
The hallmark of genetic CLC-1 chloride channel deficiency in myotonic humans, goats and mice is delayed muscle relaxation resulting from persistent electrical discharges. In addition to the ion channel defect, muscles from myotonic humans and mice also have major changes in fibre type and myosin isoform composition, but the extent to which this affects isometric contractions remains controversial. Many muscles, including the diaphragm, shorten considerably during normal activities, but shortening contractions have never been assessed in myotonic muscle. The present study tested the hypothesis that CLC-1 deficiency leads to an impairment of muscle isotonic contractile performance. This was tested in vitro on diaphragm muscle from SWR/J-Clcn1(adr-mto)/J myotonic mice. The CLC-1-deficient muscle demonstrated delayed relaxation, as expected. During the contractile phase, there were significant reductions in power and work across a number of stimulation frequencies and loads in CLC-1-deficient compared with normal muscle, the magnitude of which in many instances exceeded 50%. Reductions in shortening and velocity of shortening occurred, and were more pronounced when calculated as a function of absolute than relative load. However, the maximal unloaded shortening velocity calculated from Hill's equation was not altered significantly. The impaired isotonic contractile performance of CLC-1-deficient muscle persisted during fatigue-inducing stimulation. These data indicate that genetic CLC-1 chloride channel deficiency in mice not only produces myotonia but also substantially worsens the isotonic contractile performance of diaphragm muscle. PMID:17483199
Computational approach to Thornley's problem by bivariate operational calculus
NASA Astrophysics Data System (ADS)
Bazhlekova, E.; Dimovski, I.
2012-10-01
Thornley's problem is an initial-boundary value problem with a nonlocal boundary condition for linear onedimensional reaction-diffusion equation, used as a mathematical model of spiral phyllotaxis in botany. Applying a bivariate operational calculus we find explicit representation of the solution, containing two convolution products of special solutions and the arbitrary initial and boundary functions. We use a non-classical convolution with respect to the space variable, extending in this way the classical Duhamel principle. The special solutions involved are represented in the form of fast convergent series. Numerical examples are considered to show the application of the present technique and to analyze the character of the solution.
A new approach to epithelial isotonic fluid transport: an osmosensor feedback model.
Hill, A E; Shachar-Hill, B
2006-03-01
A model for control of the transport rate and osmolarity of epithelial fluid (isotonic transport) is presented by using an analogy with the control of temperature and flow rate in a shower. The model brings recent findings and theory concerning the role of aquaporins in epithelia together with measurements of epithelial paracellular flow into a single scheme. It is not based upon osmotic equilibration across the epithelium but rather on the function of aquaporins as osmotic sensors that control the tonicity of the transported fluid by mixing cellular and paracellular flows, which may be regarded individually as hyper- and hypo-tonic fluids, to achieve near-isotonicity. The system is built on a simple feedback loop and the quasi-isotonic behavior is robust to the precise values of most parameters. Although the two flows are separate, the overall fluid transport rate is governed by the rate of salt pumping through the cell. The model explains many things: how cell pumping and paracellular flow can be coupled via control of the tight junctions; how osmolarity is controlled without depending upon the precise magnitude of membrane osmotic permeability; and why many epithelia have different aquaporins at the two membranes. The model reproduces all the salient features of epithelial fluid transport seen over many years but also indicates novel behavior that may provide a subject for future research and serve to distinguish it from other schemes such as simple osmotic equilibration. Isotonic transport is freed from constraints due to limited permeability of the membranes and the precise geometry of the system. It achieves near-isotonicity in epithelia in which partial water transport by co-transporters may be present, and shows apparent electro-osmotic effects. The model has been developed with a minimum of parameters, some of which require measurement, but the model is flexible enough for the basic idea to be extended both to complex systems of water and salt transport
NASA Technical Reports Server (NTRS)
Wilson, Robert M.; Hathaway, David H.
2009-01-01
Examined are single- and bi-variate geomagnetic precursors for predicting the maximum amplitude (RM) of a sunspot cycle several years in advance. The best single-variate fit is one based on the average of the ap index 36 mo prior to cycle minimum occurrence (E(Rm)), having a coefficient of correlation (r) equal to 0.97 and a standard error of estimate (se) equal to 9.3. Presuming cycle 24 not to be a statistical outlier and its minimum in March 2008, the fit suggests cycle 24 s RM to be about 69 +/- 20 (the 90% prediction interval). The weighted mean prediction of 11 statistically important single-variate fits is 116 +/- 34. The best bi-variate fit is one based on the maximum and minimum values of the 12-mma of the ap index; i.e., APM# and APm*, where # means the value post-E(RM) for the preceding cycle and * means the value in the vicinity of cycle minimum, having r = 0.98 and se = 8.2. It predicts cycle 24 s RM to be about 92 +/- 27. The weighted mean prediction of 22 statistically important bi-variate fits is 112 32. Thus, cycle 24's RM is expected to lie somewhere within the range of about 82 to 144. Also examined are the late-cycle 23 behaviors of geomagnetic indices and solar wind velocity in comparison to the mean behaviors of cycles 2023 and the geomagnetic indices of cycle 14 (RM = 64.2), the weakest sunspot cycle of the modern era.
Modeling Bivariate Longitudinal Hormone Profiles by Hierarchical State Space Models
Liu, Ziyue; Cappola, Anne R.; Crofford, Leslie J.; Guo, Wensheng
2013-01-01
The hypothalamic-pituitary-adrenal (HPA) axis is crucial in coping with stress and maintaining homeostasis. Hormones produced by the HPA axis exhibit both complex univariate longitudinal profiles and complex relationships among different hormones. Consequently, modeling these multivariate longitudinal hormone profiles is a challenging task. In this paper, we propose a bivariate hierarchical state space model, in which each hormone profile is modeled by a hierarchical state space model, with both population-average and subject-specific components. The bivariate model is constructed by concatenating the univariate models based on the hypothesized relationship. Because of the flexible framework of state space form, the resultant models not only can handle complex individual profiles, but also can incorporate complex relationships between two hormones, including both concurrent and feedback relationship. Estimation and inference are based on marginal likelihood and posterior means and variances. Computationally efficient Kalman filtering and smoothing algorithms are used for implementation. Application of the proposed method to a study of chronic fatigue syndrome and fibromyalgia reveals that the relationships between adrenocorticotropic hormone and cortisol in the patient group are weaker than in healthy controls. PMID:24729646
Bivariate generalized Pareto distribution for extreme atmospheric particulate matter
NASA Astrophysics Data System (ADS)
Amin, Nor Azrita Mohd; Adam, Mohd Bakri; Ibrahim, Noor Akma; Aris, Ahmad Zaharin
2015-02-01
The high particulate matter (PM10) level is the prominent issue causing various impacts to human health and seriously affecting the economics. The asymptotic theory of extreme value is apply for analyzing the relation of extreme PM10 data from two nearby air quality monitoring stations. The series of daily maxima PM10 for Johor Bahru and Pasir Gudang stations are consider for year 2001 to 2010 databases. The 85% and 95% marginal quantile apply to determine the threshold values and hence construct the series of exceedances over the chosen threshold. The logistic, asymmetric logistic, negative logistic and asymmetric negative logistic models areconsidered as the dependence function to the joint distribution of a bivariate observation. Maximum likelihood estimation is employed for parameter estimations. The best fitted model is chosen based on the Akaike Information Criterion and the quantile plots. It is found that the asymmetric logistic model gives the best fitted model for bivariate extreme PM10 data and shows the weak dependence between two stations.
Household Poverty Dynamics in Malawi: A Bivariate Probit Analysis
NASA Astrophysics Data System (ADS)
Kenala Bokosi, Fanwell
The aim of this study is to identify the sources of expenditure and poverty dynamics among Malawian households between 1998 and 2002 and to model poverty transitions in Malawi using a bivariate probit model with endogenous selection to address the initial conditions' problem. The exogeneity of the initial state is strongly rejected and could result in considerable overstatement of the effects of the explanatory factors. The results of the bivariate probit model do indicate that education of the household head, per capita acreage cultivated and changes in household size are significantly related to the probability of being poor in 2002 irrespective of the poverty status in 1998. For those households who were poor in 1998, the probability of being poor in 2002 was significantly influenced by household size, value of livestock owned and mean time to services, while residence in the Northern region was a significant variable in determining the probability of being poor in 2002 for households that were not poor in 1998.
A Bayesian semiparametric model for bivariate sparse longitudinal data.
Das, Kiranmoy; Li, Runze; Sengupta, Subhajit; Wu, Rongling
2013-09-30
Mixed-effects models have recently become popular for analyzing sparse longitudinal data that arise naturally in biological, agricultural and biomedical studies. Traditional approaches assume independent residuals over time and explain the longitudinal dependence by random effects. However, when bivariate or multivariate traits are measured longitudinally, this fundamental assumption is likely to be violated because of intertrait dependence over time. We provide a more general framework where the dependence of the observations from the same subject over time is not assumed to be explained completely by the random effects of the model. We propose a novel, mixed model-based approach and estimate the error-covariance structure nonparametrically under a generalized linear model framework. We use penalized splines to model the general effect of time, and we consider a Dirichlet process mixture of normal prior for the random-effects distribution. We analyze blood pressure data from the Framingham Heart Study where body mass index, gender and time are treated as covariates. We compare our method with traditional methods including parametric modeling of the random effects and independent residual errors over time. We conduct extensive simulation studies to investigate the practical usefulness of the proposed method. The current approach is very helpful in analyzing bivariate irregular longitudinal traits. PMID:23553747
Higuchi, H; Goldman, Y E
1995-01-01
We measured isotonic sliding distance of single skinned fibers from rabbit psoas muscle when known and limited amounts of ATP were made available to the contractile apparatus. The fibers were immersed in paraffin oil at 20 degrees C, and laser pulse photolysis of caged ATP within the fiber initiated the contraction. The amount of ATP released was measured by photolyzing 3H-ATP within fibers, separating the reaction products by high-pressure liquid chromatography, and then counting the effluent peaks by liquid scintillation. The fiber stiffness was monitored to estimate the proportion of thick and thin filament sites interacting during filament sliding. The interaction distance, Di, defined as the sliding distance while a myosin head interacts with actin in the thin filament per ATP molecule hydrolyzed, was estimated from the shortening distance, the number of ATP molecules hydrolyzed by the myosin heads, and the stiffness. Di increased from 11 to 60 nm as the isotonic tension was reduced from 80% to 6% of the isometric tension. Velocity and Di increased with the concentration of ATP available. As isotonic load was increased, the interaction distance decreased linearly with decrease of the shortening velocity and extrapolated to 8 nm at zero velocity. Extrapolation of the relationship between Di and velocity to saturating ATP concentration suggests that Di reaches 100-190 nm at high shortening velocity. The interaction distance corresponds to the sliding distance while cross-bridges are producing positive (working) force plus the distance while they are dragging (producing negative forces). The results indicate that the working and drag distances increase as the velocity increases. Because Di is larger than the size of either the myosin head or the actin monomer, the results suggest that for each ATPase cycle, a myosin head interacts mechanically with several actin monomers either while working or while producing drag. PMID:8534820
The lateral intercellular space as osmotic coupling compartment in isotonic transport.
Larsen, E H; Willumsen, N J; Møbjerg, N; Sørensen, J N
2009-01-01
Solute-coupled water transport and isotonic transport are basic functions of low- and high-resistance epithelia. These functions are studied with the epithelium bathed on the two sides with physiological saline of similar composition. Hence, at transepithelial equilibrium water enters the epithelial cells from both sides, and with the reflection coefficient of tight junction being larger than that of the interspace basement membrane, all of the water leaves the epithelium through the interspace basement membrane. The common design of transporting epithelia leads to the theory that an osmotic coupling of water absorption to ion flow is energized by lateral Na(+)/K(+) pumps. We show that the theory accounts quantitatively for steady- and time dependent states of solute-coupled fluid uptake by toad skin epithelium. Our experimental results exclude definitively three alternative theories of epithelial solute-water coupling: stoichiometric coupling at the molecular level by transport proteins like SGLT1, electro-osmosis and a 'junctional fluid transfer mechanism'. Convection-diffusion out of the lateral space constitutes the fundamental problem of isotonic transport by making the emerging fluid hypertonic relative to the fluid in the lateral intercellular space. In the Na(+) recirculation theory the 'surplus of solutes' is returned to the lateral space via the cells energized by the lateral Na(+)/K(+) pumps. We show that this theory accounts quantitatively for isotonic and hypotonic transport at transepithelial osmotic equilibrium as observed in toad skin epithelium in vitro. Our conclusions are further developed for discussing their application to solute-solvent coupling in other vertebrate epithelia such as small intestine, proximal tubule of glomerular kidney and gallbladder. Evidence is discussed that the Na(+) recirculation theory is not irreconcilable with the wide range of metabolic cost of Na(+) transport observed in fluid-transporting epithelia. PMID:18983444
Spectrum-based estimators of the bivariate Hurst exponent.
Kristoufek, Ladislav
2014-12-01
We discuss two alternate spectrum-based estimators of the bivariate Hurst exponent in the power-law cross-correlations setting, the cross-periodogram and local X-Whittle estimators, as generalizations of their univariate counterparts. As the spectrum-based estimators are dependent on a part of the spectrum taken into consideration during estimation, a simulation study showing performance of the estimators under varying bandwidth parameter as well as correlation between processes and their specification is provided as well. These estimators are less biased than the already existent averaged periodogram estimator, which, however, has slightly lower variance. The spectrum-based estimators can serve as a good complement to the popular time domain estimators. PMID:25615143
Spectrum-based estimators of the bivariate Hurst exponent
NASA Astrophysics Data System (ADS)
Kristoufek, Ladislav
2014-12-01
We discuss two alternate spectrum-based estimators of the bivariate Hurst exponent in the power-law cross-correlations setting, the cross-periodogram and local X -Whittle estimators, as generalizations of their univariate counterparts. As the spectrum-based estimators are dependent on a part of the spectrum taken into consideration during estimation, a simulation study showing performance of the estimators under varying bandwidth parameter as well as correlation between processes and their specification is provided as well. These estimators are less biased than the already existent averaged periodogram estimator, which, however, has slightly lower variance. The spectrum-based estimators can serve as a good complement to the popular time domain estimators.
{alpha}-decay studies of the exotic N=125, 126, and 127 isotones
Xu Chang; Ren Zhongzhou
2007-08-15
The {alpha}-decay half-lives of the exotic N=125, 126, and 127 isotones (Po, Rn, Ra, Th, and U) are systematically studied by the density-dependent cluster model (DDCM). The influence of the neutron shell closure N=126 on the {alpha}-cluster formation and penetration probabilities is analyzed and discussed in detail. By combining the DDCM and a two-level microscopic model together, the experimental half-lives of {alpha} transitions to both the ground state and the excited state in the daughter nuclei are reproduced very well.
Bonn potential and shell-model calculations for N=126 isotones
Coraggio, L.; Covello, A.; Gargano, A.; Itaco, N.; Kuo, T. T. S.
1999-12-01
We have performed shell-model calculations for the N=126 isotones {sup 210}Po, {sup 211}At, and {sup 212}Rn using a realistic effective interaction derived from the Bonn-A nucleon-nucleon potential by means of a G-matrix folded-diagram method. The calculated binding energies, energy spectra, and electromagnetic properties show remarkably good agreement with the experimental data. The results of this paper complement those of our previous study on neutron hole Pb isotopes, confirming that realistic effective interactions are now able to reproduce with quantitative accuracy the spectroscopic properties of complex nuclei. (c) 1999 The American Physical Society.
Uemura, Tetsuji; Matsumoto, Naozumi; Tanabe, Tsuyoshi; Saitoh, Tomoichi; Matsushita, Shigeto; Mitsukawa, Nobuyuki
2005-05-01
The following report describes the combination of surgical correction with intraoperative distention using isotonic saline injection and the rotation flap method for correction of cryptotia. This technique provided extensive skin coverage of the upper portion of the auricle and was an easy and quick method of dissecting the cartilage of the posterior auricle. The main advantages of this technique include achievement of skin expansion without the need for expander material, simple design of the skin incision, and easy dissection of the cartilage. Although one patient experienced partial congestion in the upper tip of the rotation flap, no other complications occurred. Further, cryptotia did not recur. PMID:15915119
Projected quasiparticle calculations for the N =82 odd-proton isotones
Losano, L. ); Dias, H. )
1991-12-01
The structure of low-lying states in odd-mass {ital N}=82 isotones (135{le}{ital A}{le}145) is investigated in terms of a number-projected one- and three-quasiparticles Tamm-Dancoff approximation. A surface-delta interaction is taken as the residual nucleon-nucleon interaction. Excitation energies, dipole and quadrupole moments, and {ital B}({ital M}1) and {ital B}({ital E}2) values are calculated and compared with the experimental data.
Simons, Samantha; Abasolo, Daniel; Sauseng, Paul
2015-08-01
The spurious increase in coherence of electroencephalogram (EEG) signals between distant electrode points has long been understood to be due to volume conduction of the EEG signal. Reducing the volume conduction components of EEG recordings in pre-processing attenuates this. However, the effect of volume conduction on non-linear signal processing of EEG signals is yet to be fully described. This pilot study aimed to investigate the impact of volume conduction on results calculated with a distance based, bivariate form of Lempel-Ziv Complexity (dLZC) by analyzing EEG signals from Alzheimer's disease (AD) patients and healthy age-matched controls with and without pre-processing with Current Source Density (CSD) transformation. Spurious statistically significant differences between AD patients and control's EEG signals seen without CSD pre-processing were not seen with CSD volume conduction mitigation. There was, however, overlap in the region of electrodes which were seen to hold this statistically significant information. These results show that, while previously published findings are still valid, volume conduction mitigation is required to ensure non-linear signal processing methods identify changes in signals only due to the purely local signal alone. PMID:26738005
Role of the paracellular pathway in isotonic fluid movement across the renal tubule.
Boulpaep, E L; Sackin, H
1977-01-01
Evidence for a highly permeable paracellular shunt in the proximal tubule is reviewed. The paracellular pathway is described as a crucial site for the regulation of net absorption and for solute-solvent interaction. Available models for the coupling of salt and water transport are assessed with respect to the problem of isotonic water movement. Two new models are proposed taking into account that the tight junctions are permeable to salt and water and that active transport sites for sodium are distributed uniformly along the lateral cell membrane. The first model (continuous model) is a modification of Diamond and Bossert's proposal using different assumptions and boundary conditions. No appreciable standing gradients are predicted by this model. The second model (compartmental model) is an expansion of Curran's double membrane model by including additional compartments and driving forces. Both models predict a reabsorbate which is not isosmotic. For the particular case of the proximal tubule it is shown that in the presence of a leaky epithelium these deviations from isotonicity might have escaped experimental observation. PMID:331692
Fragmentation and systematics of the pygmy dipole resonance in the stable N=82 isotones
Savran, D.; Loeher, B.; Elvers, M.; Endres, J.; Zilges, A.; Fritzsche, M.; Pietralla, N.; Ponomarev, V. Yu.; Romig, C.; Schnorrenberger, L.; Sonnabend, K.
2011-08-15
The low-lying electric dipole (E1) strength in the semimagic nucleus {sup 136}Xe has been measured, which finalizes the systematic survey to investigate the so-called pygmy dipole resonance (PDR) in all stable even N=82 isotones with the method of nuclear resonance fluorescence using real photons in the entrance channel. In all cases, a fragmented resonance-like structure of E1 strength is observed in the energy region 5-8 MeV. An analysis of the fragmentation of the strength reveals that the degree of fragmentation decreases toward the proton-deficient isotones, while the total integrated strength increases, indicating a dependence of the total strength on the neutron-to-proton ratio. The experimental results are compared to microscopic calculations within the quasiparticle phonon model. The calculation includes complex configurations of up to three phonons and is able to reproduce also the fragmentation of the E1 strength, which allows us to draw conclusions on the damping of the PDR. Calculations and experimental data are in good agreement on the degree of fragmentation and also on the integrated strength if the sensitivity limit of the experiments is taken into account.
Search for the Skyrme-Hartree-Fock solutions for chiral rotation in N=75 isotones
Olbratowski, P.; Dobaczewski, J.; Dudek, J.
2006-05-15
A search for self-consistent solutions for the chiral rotational bands in the N=75 isotones {sup 130}Cs, {sup 132}La, {sup 134}Pr, and {sup 136}Pm is performed within the Skyrme-Hartree-Fock cranking approach using SKM* and SLy4 parametrizations. The dependence of the solutions on the time-odd contributions in the energy functional is studied. From among the four isotones considered, self-consistent chiral solutions are obtained only in {sup 132}La. The microscopic calculations are compared with the {sup 132}La experimental data and with results of a classical model that contains all the mechanisms underlying the chirality of the collective rotational motion. Strong similarities between the Hartree-Fock and classical model results are found. The suggestion formulated earlier by the authors that the chiral rotation cannot exist below a certain critical frequency is further illustrated and discussed, together with the microscopic origin of a transition from planar to chiral rotation in nuclei. We also formulate the separability rule by which the tilted-axis-cranking solutions can be inferred from three independent principal-axis-cranking solutions corresponding to three different axes of rotation.
Cotter, T P; Gebruers, E M; Hall, W J; O'Sullivan, M F
1986-01-01
In a group of healthy humans, plasma vasopressin (AVP) levels fell on drinking either Tyrode or mannitol solutions isosmotic with plasma. Both the timing and magnitude of the fall were appropriate to account for the transient diuresis which followed the drinking. Although plasma expansion follows drinking Tyrode solution it occurred too late to account for the fall in plasma AVP. It was also too small to inhibit AVP secretion. Even though plasma volume tended to contract on drinking isosmotic mannitol solution a fall in plasma AVP and a diuresis occurred, similar to those found after drinking Tyrode solution. These findings appear to eliminate plasma volume expansion as the stimulus for the fall in plasma AVP and the associated diuresis on drinking isotonic fluids. In a further group of human subjects, bypassing the oropharynx by intragastric infusion resulted in a slower onset of diuresis after a water load. We suggest that receptors, as yet undefined, in the upper gastrointestinal tract contribute to the early stages of a water diuresis and account for the apparently inappropriate transient diuresis which follows the drinking of isotonic fluids. PMID:3098967
Insulin and glucose responses during bed rest with isotonic and isometric exercise
NASA Technical Reports Server (NTRS)
Dolkas, C. B.; Greenleaf, J. E.
1977-01-01
The effects of daily intensive isotonic (68% maximum oxygen uptake) and isometric (21% maximum extension force) leg exercise on plasma insulin and glucose responses to an oral glucose tolerance test (OGTT) during 14-day bed-rest (BR) periods were investigated in seven young healthy men. The OGTT was given during ambulatory control and on day 10 of the no-exercise, isotonic, and isometric exercise BR periods during the 15-wk study. The subjects were placed on a controlled diet starting 10 days before each BR period. During BR, basal plasma glucose concentration remained unchanged with no exercise, but increased (P less 0.05) to 87-89 mg/100 ml with both exercise regimens on day 2, and then fell slightly below control levels on day 13. The fall in glucose content during BR was independent of the exercise regimen and was an adjustment for the loss of plasma volume. The intensity of the responses of insulin and glucose to the OGTT was inversely proportional to the total daily energy expenditure during BR. It was estimated that at least 1020 kcal/day must be provided by supplemental exercise to restore the hyperinsulinemia to control levels.
Heat-induced changes in the mechanics of a collagenous tissue: isothermal, isotonic shrinkage.
Chen, S S; Wright, N T; Humphrey, J D
1998-06-01
We present data from isothermal, isotonic-shrinkage tests wherein bovine chordae tendineae were subjected to well-defined constant temperatures (from 65 to 90 degrees C), durations of heating (from 180 to 3600 s), and isotonic uniaxial stresses during heating (from 100 to 650 kPa). Tissue response during heating and "recovery" at 37 degrees C following heating was evaluated in terms of the axial shrinkage, a gross indicator of underlying heat-induced denaturation. There were three key findings. First, scaling the heating time via temperature and load-dependent characteristic times for the denaturation process collapsed all shrinkage data to a single curve, and thereby revealed a time-temperature-load equivalency. Second, the characteristic times exhibited an Arrhenius-type behavior with temperature wherein the slopes were nearly independent of applied load--this suggested that applied loads during heating affect the activation entropy, not energy. Third, all specimens exhibited a time-dependent, partial recovery when returned to 37 degrees C following heating, but the degree of recovery decreased with increases in the load imposed during heating. These new findings on heat-induced changes in tissue behavior will aid in the design of improved clinical heating protocols and provide guidance for the requisite constitutive formulations. PMID:10412406
NASA Astrophysics Data System (ADS)
Araújo, J. P. C.; DA Silva, L. M.; Dourado, F. A. D.; Fernandes, N.
2015-12-01
Landslides are the most damaging natural hazard in the mountainous region of Rio de Janeiro State in Brazil, responsible for thousands of deaths and important financial and environmental losses. However, this region has currently few landslide susceptibility maps implemented on an adequate scale. Identification of landslide susceptibility areas is fundamental in successful land use planning and management practices to reduce risk. This paper applied the Bayes' theorem based on weight of evidence (WoE) using 8 landslide-related factors in a geographic information system (GIS) for landslide susceptibility mapping. 378 landslide locations were identified and mapped on a selected basin in the city of Nova Friburgo, triggered by the January 2011 rainfall event. The landslide scars were divided into two subsets: training and validation subsets. The 8 landslide-related factors weighted by WoE were performed using chi-square test to indicate which variables are conditionally independent of each other to be used in the final map. Finally, the maps of weighted factors were summed up to construct the landslide susceptibility map and validated by the validation landslide subset. According to the results, slope, aspect and contribution area showed the higher positive spatial correlation with landslides. In the landslide susceptibility map, 21% of the area presented very low and low susceptibilities with 3% of the validation scars, 41% presented medium susceptibility with 22% of the validation scars and 38% presented high and very high susceptibilities with 75% of the validation scars. The very high susceptibility class stands for 16% of the basin area and has 54% of the all scars. The approach used in this study can be considered very useful since 75% of the area affected by landslides was included in the high and very high susceptibility classes.
Different landslide sampling strategies in a grid-based bi-variate statistical susceptibility model
NASA Astrophysics Data System (ADS)
Hussin, Haydar Y.; Zumpano, Veronica; Reichenbach, Paola; Sterlacchini, Simone; Micu, Mihai; van Westen, Cees; Bălteanu, Dan
2016-01-01
This study had three aims. The first was to assess the performance of the weights-of-evidence (WofE) landslide susceptibility model in areas that are very different in terms of size, geoenvironmental settings, and landslide types. The second was to test the appropriate strategies to sample the mapped landslide polygon. The final aim was to evaluate the performance of the method to changes in the landslide sample size used to train the model. The method was applied to two areas: the Fella River basin (eastern Italian Alps) containing debris flows, and Buzau County (Romanian Carpathians) with shallow landslides. The three landslide sampling strategies used were: (1) the landslide scarp centroid, (2) points populating the scarp on a 50-m grid, and (3) the entire scarp polygon. The highest success rates were obtained when sampling shallow landslides as 50-m grid-points and debris flow scarps as polygons. Prediction rates were highest when using the entire scarp polygon method for both landslide types. The sample size test using the landslide centroids showed that a sample of 104 debris flow scarps was sufficient to predict the remaining 941 debris flows in the Fella River basin, while 161 shallow landslides was the minimum required number to predict the remaining 1451 scarps in Buzau County. Below these landslide sample thresholds, model performance was too low. However, using more landslides than the threshold produced a plateau effect with little to no increase in the model performance rates.
SEMG analysis of astronaut upper arm during isotonic muscle actions with normal standing posture
NASA Astrophysics Data System (ADS)
Qianxiang, Zhou; Chao, Ma; Xiaohui, Zheng
sEMG analysis of astronaut upper arm during isotonic muscle actions with normal standing posture*1 Introduction Now the research on the isotonic muscle actions by using Surface Electromyography (sEMG) is becoming a pop topic in fields of astronaut life support training and rehabilitations. And researchers paid more attention on the sEMG signal processes for reducing the influence of noise which is produced during monitoring process and the fatigue estimation of isotonic muscle actions with different force levels by using the parameters which are obtained from sEMG signals such as Condition Velocity(CV), Median Frequency(MDF), Mean Frequency(MNF) and so on. As the lucubrated research is done, more and more research on muscle fatigue issue of isotonic muscle actions are carried out with sEMG analysis and subjective estimate system of Borg scales at the same time. In this paper, the relationship between the variable for fatigue based on sEMG and the Borg scale during the course of isotonic muscle actions of the upper arm with different contraction levels are going to be investigated. Methods 13 young male subjects(23.4±2.45years, 64.7±5.43Kg, 171.7±5.41cm) with normal standing postures were introduced to do isotonic actions of the upper arm with different force levels(10% MVC, 30%MVC and 50%MVC). And the MVC which means maximal voluntary contraction was obtained firstly in the experiment. Also the sEMG would be recorded during the experiments; the Borg scales would be recorded for each contraction level. By using one-third band octave method, the fatigue variable (p) based on sEMG were set up and it was expressed as p = i g(fi ) · F (fi ). And g(fi ) is defined as the frequent factor which was 0.42+0.5 cos(π fi /f0 )+0.08 cos(2π fi /f0 ), 0 < FI fi 0, orf0 ≤> f0 . According to the equations, the p could be computed and the relationship between variable p and the Borg scale would be investigated. Results In the research, three kinds of fitted curves between
SEMG analysis of astronaut upper arm during isotonic muscle actions with normal standing posture
NASA Astrophysics Data System (ADS)
Qianxiang, Zhou; Chao, Ma; Xiaohui, Zheng
sEMG analysis of astronaut upper arm during isotonic muscle actions with normal standing posture*1 Introduction Now the research on the isotonic muscle actions by using Surface Electromyography (sEMG) is becoming a pop topic in fields of astronaut life support training and rehabilitations. And researchers paid more attention on the sEMG signal processes for reducing the influence of noise which is produced during monitoring process and the fatigue estimation of isotonic muscle actions with different force levels by using the parameters which are obtained from sEMG signals such as Condition Velocity(CV), Median Frequency(MDF), Mean Frequency(MNF) and so on. As the lucubrated research is done, more and more research on muscle fatigue issue of isotonic muscle actions are carried out with sEMG analysis and subjective estimate system of Borg scales at the same time. In this paper, the relationship between the variable for fatigue based on sEMG and the Borg scale during the course of isotonic muscle actions of the upper arm with different contraction levels are going to be investigated. Methods 13 young male subjects(23.4±2.45years, 64.7±5.43Kg, 171.7±5.41cm) with normal standing postures were introduced to do isotonic actions of the upper arm with different force levels(10% MVC, 30%MVC and 50%MVC). And the MVC which means maximal voluntary contraction was obtained firstly in the experiment. Also the sEMG would be recorded during the experiments; the Borg scales would be recorded for each contraction level. By using one-third band octave method, the fatigue variable (p) based on sEMG were set up and it was expressed as p = i g(fi ) · F (fi ). And g(fi ) is defined as the frequent factor which was 0.42+0.5 cos(π fi /f0 )+0.08 cos(2π fi /f0 ), 0 < FI fi 0, orf0 ≤> f0 . According to the equations, the p could be computed and the relationship between variable p and the Borg scale would be investigated. Results In the research, three kinds of fitted curves between
Chromosome heteromorphism quantified by high-resolution bivariate flow karyotyping.
Trask, B; van den Engh, G; Mayall, B; Gray, J W
1989-11-01
Maternal and paternal homologues of many chromosome types can be differentiated on the basis of their peak position in Hoechst 33258 versus chromomycin A3 bivariate flow karyotypes. We demonstrate here the magnitude of DNA content differences among normal chromosomes of the same type. Significant peak-position differences between homologues were observed for an average of four chromosome types in each of the karyotypes of 98 different individuals. The frequency of individuals with differences in homologue peak positions varied among chromosome types: e.g., chromosome 15, 61%; chromosome 3, 4%. Flow karyotypes of 33 unrelated individuals were compared to determine the range of peak position among normal chromosomes. Chromosomes Y, 21, 22, 15, 16, 13, 14, and 19 were most heteromorphic, and chromosomes 2-8 and X were least heteromorphic. The largest chromosome 21 was 45% larger than the smallest 21 chromosome observed. The base composition of the variable regions differed among chromosome types. DNA contents of chromosome variants determined from flow karyotypes were closely correlated to measurements of DNA content made of gallocyanin chrome alum-stained metaphase chromosomes on slides. Fluorescence in situ hybridization with chromosome-specific repetitive sequences indicated that variability in their copy number is partly responsible for peak-position variability in some chromosomes. Heteromorphic chromosomes are identified for which parental flow karyotype information will be essential if de novo rearrangements resulting in small DNA content changes are to be detected with flow karyotyping. PMID:2479266
Chromosome heteromorphism quantified by high-resolution bivariate flow karyotyping.
Trask, B; van den Engh, G; Mayall, B; Gray, J W
1989-01-01
Maternal and paternal homologues of many chromosome types can be differentiated on the basis of their peak position in Hoechst 33258 versus chromomycin A3 bivariate flow karyotypes. We demonstrate here the magnitude of DNA content differences among normal chromosomes of the same type. Significant peak-position differences between homologues were observed for an average of four chromosome types in each of the karyotypes of 98 different individuals. The frequency of individuals with differences in homologue peak positions varied among chromosome types: e.g., chromosome 15, 61%; chromosome 3, 4%. Flow karyotypes of 33 unrelated individuals were compared to determine the range of peak position among normal chromosomes. Chromosomes Y, 21, 22, 15, 16, 13, 14, and 19 were most heteromorphic, and chromosomes 2-8 and X were least heteromorphic. The largest chromosome 21 was 45% larger than the smallest 21 chromosome observed. The base composition of the variable regions differed among chromosome types. DNA contents of chromosome variants determined from flow karyotypes were closely correlated to measurements of DNA content made of gallocyanin chrome alum-stained metaphase chromosomes on slides. Fluorescence in situ hybridization with chromosome-specific repetitive sequences indicated that variability in their copy number is partly responsible for peak-position variability in some chromosomes. Heteromorphic chromosomes are identified for which parental flow karyotype information will be essential if de novo rearrangements resulting in small DNA content changes are to be detected with flow karyotyping. Images Figure 5 PMID:2479266
Joint association analysis of bivariate quantitative and qualitative traits.
Yuan, Mengdie; Diao, Guoqing
2011-01-01
Univariate genome-wide association analysis of quantitative and qualitative traits has been investigated extensively in the literature. In the presence of correlated phenotypes, it is more intuitive to analyze all phenotypes simultaneously. We describe an efficient likelihood-based approach for the joint association analysis of quantitative and qualitative traits in unrelated individuals. We assume a probit model for the qualitative trait, under which an unobserved latent variable and a prespecified threshold determine the value of the qualitative trait. To jointly model the quantitative and qualitative traits, we assume that the quantitative trait and the latent variable follow a bivariate normal distribution. The latent variable is allowed to be correlated with the quantitative phenotype. Simultaneous modeling of the quantitative and qualitative traits allows us to make more precise inference on the pleiotropic genetic effects. We derive likelihood ratio tests for the testing of genetic effects. An application to the Genetic Analysis Workshop 17 data is provided. The new method yields reasonable power and meaningful results for the joint association analysis of the quantitative trait Q1 and the qualitative trait disease status at SNPs with not too small MAF. PMID:22373162
+Gz tolerance in man after 14-day bedrest periods with isometric and isotonic exercise conditioning.
Greenleaf, J E; Bernauer, E M; Morse, J T; Sandler, H; Armbruster, R; Sagan, L; van Beaumont, W
1975-05-01
The purpose of this study was to determine the effects of isometric or isotonic exercise training on post-bedrest +Gz tolerance. Seven male volunteers, 19-22 years, underwent accelerations of +2.1 Gz (740 s), +3.2 Gz (327 s), and +3.8 Gz (312 s) in a selected, randomized order; the ramp to peak acceleration was 1.8 G/min. The centrifugation runs were terminated by loss of central vision (blackout) to a white light with a luminance of 3.15 times 10-5 log candle/cm-2 (0.092 ft-lambert). The study began with a 14-d ambulatory control period, followed by three 14-d bedrest periods (each separated by a 21-d recovery period) and then a final week of recovery. During the ambulatory periods, the subjects exercised on a bicycle ergometer at 50% of their maximal oxygen uptake (max VO2) for 1 h/d. During two of the three bedrest periods, the subjects performed in the supine position one of two routines, either isometric exercise (21% of max leg extension force for 1 min followed by 1-min rest) or isotonic exercise (68% of max VO2) for 0.5 in the morning and afternoon. During the third bedrest period, no exercise was performed. In general +Gz tolerance was reduced by 24% to 35% (p less than or equal to 0.05) after bedrest. Compared with control values, there were significant reductions in average tolerance times after bedrest with no exercise and isotonic exercise at all G levels. With isometric exercise, there was a significant decrease in tolerance at 2.1 Gz but not at 3.2 Gz or 3.8 Gz, even though the latter tolerances were reduced 15.6% and 10.0%, respectively. Both exercise regimens maintained tolerance at levels equal to or above that obtained with no exercise. Compared with control values, average tolerances were lower (p less than or equal to 0.05) after the two recovery periods between the bedrest periods (minus 24% to minus 26% at 3.2 Gz and 3.8 Gz), indicating that 3 weeks of ambulation was not sufficient time for full recovery from the deconditioning induced in
Sonka, Milan; Abramoff, Michael D.
2013-01-01
In this paper, MMSE estimator is employed for noise-free 3D OCT data recovery in 3D complex wavelet domain. Since the proposed distribution for noise-free data plays a key role in the performance of MMSE estimator, a priori distribution for the pdf of noise-free 3D complex wavelet coefficients is proposed which is able to model the main statistical properties of wavelets. We model the coefficients with a mixture of two bivariate Gaussian pdfs with local parameters which are able to capture the heavy-tailed property and inter- and intrascale dependencies of coefficients. In addition, based on the special structure of OCT images, we use an anisotropic windowing procedure for local parameters estimation that results in visual quality improvement. On this base, several OCT despeckling algorithms are obtained based on using Gaussian/two-sided Rayleigh noise distribution and homomorphic/nonhomomorphic model. In order to evaluate the performance of the proposed algorithm, we use 156 selected ROIs from 650 × 512 × 128 OCT dataset in the presence of wet AMD pathology. Our simulations show that the best MMSE estimator using local bivariate mixture prior is for the nonhomomorphic model in the presence of Gaussian noise which results in an improvement of 7.8 ± 1.7 in CNR. PMID:24222760
Uncertain Characterization of Flood Hazard Using Bivariate Analysis Based on Copulas
NASA Astrophysics Data System (ADS)
Candela, Angela; Tito Aronica, Giuseppe
2015-04-01
This study presents a methodology to derive probabilistic flood hazard map in flood prone areas taking into account uncertainties in the definition of design-hydrographs. Particularly, we present an innovative approach to obtain probabilistic inundation and flood hazard maps where hydrological input (synthetic flood design event) to a 2D hydraulic model has been defined by generating flood peak discharges and volumes from a bivariate statistical analysis, through the use of copulas. This study also aims to quantify the contribution of boundary conditions uncertainty in order to explore the impact of this uncertainty on probabilistic flood hazard mapping. The uncertainty of extreme flood events is considered in terms of different possible combinations of peak discharge and flood volume given by the copula. Further, we analyzed the role of a multivariate probability hydrological analysis on inundation and flood hazard maps highlighting the differences between deterministic and probabilistic approaches. The methodology has been applied to a study area located in Sicily that was subject to several flooding events in the past.
A semiparametric bivariate probit model for joint modeling of outcomes in STEMI patients.
Ieva, Francesca; Marra, Giampiero; Paganoni, Anna Maria; Radice, Rosalba
2014-01-01
In this work we analyse the relationship among in-hospital mortality and a treatment effectiveness outcome in patients affected by ST-Elevation myocardial infarction. The main idea is to carry out a joint modeling of the two outcomes applying a Semiparametric Bivariate Probit Model to data arising from a clinical registry called STEMI Archive. A realistic quantification of the relationship between outcomes can be problematic for several reasons. First, latent factors associated with hospitals organization can affect the treatment efficacy and/or interact with patient's condition at admission time. Moreover, they can also directly influence the mortality outcome. Such factors can be hardly measurable. Thus, the use of classical estimation methods will clearly result in inconsistent or biased parameter estimates. Secondly, covariate-outcomes relationships can exhibit nonlinear patterns. Provided that proper statistical methods for model fitting in such framework are available, it is possible to employ a simultaneous estimation approach to account for unobservable confounders. Such a framework can also provide flexible covariate structures and model the whole conditional distribution of the response. PMID:24799953
Wen, Yalu; Schaid, Daniel J; Lu, Qing
2013-04-01
Although comorbidity among complex diseases (e.g., drug dependence syndromes) is well documented, genetic variants contributing to the comorbidity are still largely unknown. The discovery of genetic variants and their interactions contributing to comorbidity will likely shed light on underlying pathophysiological and etiological processes, and promote effective treatments for comorbid conditions. For this reason, studies to discover genetic variants that foster the development of comorbidity represent high-priority research projects, as manifested in the behavioral genetics studies now underway. The yield from these studies can be enhanced by adopting novel statistical approaches, with the capacity of considering multiple genetic variants and possible interactions. For this purpose, we propose a bivariate Mann-Whitney (BMW) approach to unravel genetic variants and interactions contributing to comorbidity, as well as those unique to each comorbid condition. Through simulations, we found BMW outperformed two commonly adopted approaches in a variety of underlying disease and comorbidity models. We further applied BMW to datasets from the Study of Addiction: Genetics and Environment, investigating the contribution of 184 known nicotine dependence (ND) and alcohol dependence (AD) single nucleotide polymorphisms (SNPs) to the comorbidity of ND and AD. The analysis revealed a candidate SNP from CHRNA5, rs16969968, associated with both ND and AD, and replicated the findings in an independent dataset with a P-value of 1.06 × 10(-03) . PMID:23334941
Segmentation of 3D holographic images using bivariate jointly distributed region snake
NASA Astrophysics Data System (ADS)
Daneshpanah, Mehdi; Javidi, Bahram
2006-06-01
In this paper, we describe the bivariate jointly distributed region snake method in segmentation of microorganisms in Single Exposure On- Line (SEOL) holographic microscopy images. 3D images of the microorganisms are digitally reconstructed and numerically focused from any arbitrary depth from a single recorded digital hologram without mechanical scanning. Living organisms are non-rigid and they vary in shape and size. Moreover, they often do not exhibit clear edges in digitally reconstructed SEOL holographic images. Thus, conventional segmentation techniques based on the edge map may fail to segment these images. However, SEOL holographic microscopy provides both magnitude and phase information of the sample specimen, which could be helpful in the segmentation process. In this paper, we present a statistical framework based on the joint probability distribution of magnitude and phase information of SEOL holographic microscopy images and maximum likelihood estimation of image probability density function parameters. An optimization criterion is computed by maximizing the likelihood function of the target support hypothesis. In addition, a simple stochastic algorithm has been adapted for carrying out the optimization, while several boosting techniques have been employed to enhance its performance. Finally, the proposed method is applied for segmentation of biological microorganisms in SEOL holographic images and the experimental results are presented.
A relativistic continuum Hartree-Bogoliubov theory description of N = 3 isotones
NASA Astrophysics Data System (ADS)
Han, Rui; Ji, Juan-Xia; Li, Jia-Xing
2011-09-01
The ground-state properties of N = 3 isotones and mirror nuclei have been investigated in the Rrelativistic Continuum Hartree-Bogoliubov theory with the NLSH effective interaction. Pairing correlations are taken into account by a density-dependent δ-force. The calculations show that the proton density distributions of 8B and 9C have a long tail, the core has an increasing tendency of 9C and the paired off valence protons make the halo distribution shrink. The cross sections for the 8B(9C)+12C reaction which are consistent with the experimental data are calculated using the Glauber model. On the whole, we think that 8B is a one-proton halo nucleus and 9C is a two-proton halo nucleus.
Study of oxygen isotopes and N=8 isotones with an extended cluster-orbital shell model
NASA Astrophysics Data System (ADS)
Masui, H.; Katō, K.; Ikeda, K.
2006-03-01
We attempt to obtain a unified description of the bound and unbound states of multivalence nucleons of a core system in the framework of the cluster-orbital shell model (COSM). In this framework, the interaction between the core and a valence nucleon (the core-N interaction) is treated microscopically, and the changes in both the core structure and the core-N interaction are discussed on the same basis. Furthermore, the center-of-mass motion of every nucleon is completely eliminated, and higher shell configurations, including unbound continuum components, are appropriately taken into account by applying a stochastic variational approach. To examine the reliability of this approach and to discuss how the dynamics of the core reflects to the total system, we study oxygen isotopes and N=8 isotones, which are described by O16 + Xn and O16 + Xp models, respectively.
Kuriyama, H; Oshima, K; Sakamoto, Y
1971-08-01
The membrane properties of the longitudinal smooth muscle of the guinea-pig portal vein were investigated under various experimental conditions.1. In isotonic Krebs solution, the membrane potential (-48.7 mV), the maximum rates of rise and fall of the spike (4.6 and 2.3 V/sec respectively), the space constant (0.61 mm), the conduction velocity of excitation (0.97 cm/sec) and the time constant of the foot of the propagated spike (18.4 msec) were measured.2. The various parameters of the muscle membrane in the isotonic solution were compared with those in the hypertonic solution prepared by the addition of solid sucrose (twice the normal tonicity).3. When the muscles were perfused with hypertonic solution, marked depolarization of the membrane and increased membrane resistance occurred. These were probably due to reduction of the K permeability, increased internal resistance of the muscle and shrinkage of the muscle fibre.4. The membrane potential in isotonic and hypertonic solutions was analysed into two components, i.e. the metabolic (electrogenic Na-pump) and the ionic (electrical diffusion potential) component in the various environmental conditions.(a) In isotonic and hypertonic solutions, the membrane was depolarized by lowering the temperature or by removal of K ion from the solutions. When the tissues were rewarmed or on readdition of K ion, the membrane was markedly hyperpolarized. These hyperpolarizations of the membrane were suppressed by treatment with ouabain (10(-5) g/ml.), by warming to only 20 degrees C and by K-free solution.(b) The relationships between the membrane potential and the [K](o) in isotonic Krebs, in the hypertonic (sucrose) Krebs, in the Na-free (Tris) Krebs and in the Cl-deficient (C(6)H(5)SO(3)) Krebs were observed. The maximum slopes of the membrane depolarization against tenfold changes of [K](o) were much lower than that expected if it behaved like a K electrode.(c) In Na-free (Tris) solution, the membrane was not depolarized in
Nucleon-pair states of even-even N =82 isotones
NASA Astrophysics Data System (ADS)
Cheng, Y. Y.; Zhao, Y. M.; Arima, A.
2016-08-01
In this paper we study low-lying states of five N =82 isotones, 134Te, 136Xe, 138Ba, 140Ce and 142Nd, within the framework of the nucleon-pair approximation (NPA). For the low-lying yrast states of 136Xe and 138Ba, we calculate the overlaps between the wave functions obtained in the full shell-model (SM) space and those obtained in the truncated NPA space, and find that most of these overlaps are very close to 1. Very interestingly and surprisingly, for most of these yrast states, the SM wave functions are found to be well approximated by one-dimensional, optimized pair basis states, which indicates a simple picture of "nucleon-pair states". The positive-parity yrast states with spin J >6 in these nuclei, as well as the 82+ state, are found to be well described by breaking one or two S pair(s) of the 61+ or 62+ state (low-lying, seniority-two, spin-maximum, and positive-parity); similarly, negative-parity yrast states with spin J >9 are well represented by breaking one or two S pair(s) of the 91- state (low-lying, seniority-two, spin-maximum, and negative-parity). It is shown that the low-lying negative-parity yrast states of 136Xe and 138Ba are reasonably described to be one-octupole-phonon excited states. The evolution of the 61+ and 62+ states for the five isotones are also systematically investigated.
Asymptotics of bivariate generating functions with algebraic singularities
NASA Astrophysics Data System (ADS)
Greenwood, Torin
Flajolet and Odlyzko (1990) derived asymptotic formulae the coefficients of a class of uni- variate generating functions with algebraic singularities. Gao and Richmond (1992) and Hwang (1996, 1998) extended these results to classes of multivariate generating functions, in both cases by reducing to the univariate case. Pemantle and Wilson (2013) outlined new multivariate ana- lytic techniques and used them to analyze the coefficients of rational generating functions. After overviewing these methods, we use them to find asymptotic formulae for the coefficients of a broad class of bivariate generating functions with algebraic singularities. Beginning with the Cauchy integral formula, we explicity deform the contour of integration so that it hugs a set of critical points. The asymptotic contribution to the integral comes from analyzing the integrand near these points, leading to explicit asymptotic formulae. Next, we use this formula to analyze an example from current research. In the following chapter, we apply multivariate analytic techniques to quan- tum walks. Bressler and Pemantle (2007) found a (d + 1)-dimensional rational generating function whose coefficients described the amplitude of a particle at a position in the integer lattice after n steps. Here, the minimal critical points form a curve on the (d + 1)-dimensional unit torus. We find asymptotic formulae for the amplitude of a particle in a given position, normalized by the number of steps n, as n approaches infinity. Each critical point contributes to the asymptotics for a specific normalized position. Using Groebner bases in Maple again, we compute the explicit locations of peak amplitudes. In a scaling window of size the square root of n near the peaks, each amplitude is asymptotic to an Airy function.
Causal networks clarify productivity-richness interrelations, bivariate plots do not
Grace, James B.; Adler, Peter B.; Harpole, W. Stanley; Borer, Elizabeth T.; Seabloom, Eric W.
2014-01-01
We urge ecologists to consider productivity–richness relationships through the lens of causal networks to advance our understanding beyond bivariate analysis. Further, we emphasize that models based on a causal network conceptualization can also provide more meaningful guidance for conservation management than can a bivariate perspective. Measuring only two variables does not permit the evaluation of complex ideas nor resolve debates about underlying mechanisms.
Description of the evolution of mixed-symmetry states in the N = 78 isotonic chain with IBM2
NASA Astrophysics Data System (ADS)
Zhang, Da-Li; Yuan, Shu-Qing; Ding, Bin-Gang
2015-07-01
The characteristics of the lowest mixed-symmetry states 2+ms and 1+ms for 132Xe, 134Ba and 136Ce in the even-even N = 78 isotones are investigated within the framework of the IBM2 model. The lowest mixed-symmetry state 2+ms levels for both a single isolated state in 132Xe and 136Ce and a fragmented state in 134Ba are reproduced by the predictions. The agreement between the IBM2 calculation and the experimental values is good for the B(E2) and B(M1) transition probabilities both quantitatively and qualitatively. The predicted summed B(M1) strength follows the experimental data, remaining nearly constant as a function of proton number along the chain of the N = 78 isotones. Supported by National Natural Science Foundation of China (11475062) and Natural Science Foundation of Zhejiang Province, China (KY6100135)
Experimental study of β and β -n decay of the neutron-rich N =54 isotone 87As
NASA Astrophysics Data System (ADS)
Korgul, A.; Rykaczewski, K. P.; Grzywacz, R.; Bingham, C. R.; Brewer, N. T.; Ciemny, A. A.; Gross, C. J.; Jost, C.; Karny, M.; Madurga, M.; Mazzocchi, C.; Mendez, A. J.; Miernik, K.; Miller, D.; Padgett, S.; Paulauskas, S. V.; Stracener, D. W.; Wolińska-Cichocka, M.
2015-11-01
The β -decay properties of neutron-rich 87As produced in the proton-induced fission of 238U were studied at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. The low-energy excited states in N =53 87Se and N =52 86Se were identified through β -γ and β -delayed neutron-γ decay of 87As, respectively. The experimental systematics of low-energy levels of N =53 isotones, Z =34 Se87, and Z =32 85Ge, and along with an analysis of shell-model calculations, allow us to discuss the main features of excited states expected for the next N =53 isotone, 83Zn.
Gironés-Vilaplana, Amadeo; Villaño, Débora; Moreno, Diego A; García-Viguera, Cristina
2013-11-01
The aim of the study was to design new isotonic drinks with lemon juice and berries: maqui [Aristotelia chilensis (Molina) Stuntz], açaí (Euterpe oleracea Mart.) and blackthorn (Prunus spinosa L.), following on from previous research. Quality parameters - including colour (CIELab parameters), minerals, phytochemical identification and quantification by high-performance liquid chromatography with diode array detector, total phenolic content by the Folin-Ciocalteu reagent, the antioxidant capacity (ABTS(+), DPPH• and [Formula: see text] assays) and biological activities (in vitro alpha-glucosidase and lipase inhibitory effects) - were tested in the samples and compared to commercially available isotonic drinks. The new isotonic blends with lemon and anthocyanins-rich berries showed an attractive colour, especially in maqui samples, which is essential for consumer acceptance. Significantly higher antioxidant and biological effects were determined in the new blends, in comparison with the commercial isotonic beverages. PMID:23815554
A rank test for bivariate time-to-event outcomes when one event is a surrogate.
Shaw, Pamela A; Fay, Michael P
2016-08-30
In many clinical settings, improving patient survival is of interest but a practical surrogate, such as time to disease progression, is instead used as a clinical trial's primary endpoint. A time-to-first endpoint (e.g., death or disease progression) is commonly analyzed but may not be adequate to summarize patient outcomes if a subsequent event contains important additional information. We consider a surrogate outcome very generally as one correlated with the true endpoint of interest. Settings of interest include those where the surrogate indicates a beneficial outcome so that the usual time-to-first endpoint of death or surrogate event is nonsensical. We present a new two-sample test for bivariate, interval-censored time-to-event data, where one endpoint is a surrogate for the second, less frequently observed endpoint of true interest. This test examines whether patient groups have equal clinical severity. If the true endpoint rarely occurs, the proposed test acts like a weighted logrank test on the surrogate; if it occurs for most individuals, then our test acts like a weighted logrank test on the true endpoint. If the surrogate is a useful statistical surrogate, our test can have better power than tests based on the surrogate that naively handles the true endpoint. In settings where the surrogate is not valid (treatment affects the surrogate but not the true endpoint), our test incorporates the information regarding the lack of treatment effect from the observed true endpoints and hence is expected to have a dampened treatment effect compared with tests based on the surrogate alone. Published 2016. This article is a U.S. Government work and is in the public domain in the USA. PMID:27059817
Hasstedt, Sandra J; Hanis, Craig L; Elbein, Steven C
2010-01-01
Summary Dyslipidemia frequently co-occurs with type 2 diabetes (T2D) and with obesity. To investigate whether the co-occurrence is due to pleiotropic genes, we performed univariate linkage analysis of lipid levels and bivariate linkage analysis of pairs of lipid levels and of lipid levels paired with T2D, body mass index (BMI), and waist-hip ratio (WHR) in the African American subset of the Genetics of NIDDM (GENNID) sample. We obtained significant evidence for a pleiotropic low density lipoprotein cholesterol (LDL-C)–T2D locus on chromosome 1 at 16–19 megabases (MB) (bivariate lod = 4.41), as well as a non-pleiotropic triglyceride (TG) locus on chromosome 20 at 28–34 MB (univariate lod = 3.57). In addition, near-significant evidence supported TG–T2D loci on chromosome 2 at 81–101 MB (bivariate lod = 4.23) and 232–239 MB (bivariate lod = 4.27) and on chromosome 7 at 147–151 MB (univariate lod = 3.08 for TG with P = 0.041 supporting pleiotropy with T2D), as well as an LDL-C–BMI locus on chromosome 3 at 137–147 MB (bivariate lod score = 4.25). These finding provide evidence that at least some of the co-occurrence of dyslipidemia with T2D and obesity is due to common underlying genes. PMID:20597901
A Model of Peritubular Capillary Control of Isotonic Fluid Reabsorption by the Renal Proximal Tubule
Deen, W. M.; Robertson, C. R.; Brenner, B. M.
1973-01-01
A mathematical model of peritubular transcapillary fluid exchange has been developed to investigate the role of the peritubular environment in the regulation of net isotonic fluid transport across the mammalian renal proximal tubule. The model, derived from conservation of mass and the Starling transcapillary driving forces, has been used to examine the quantitative effects on proximal reabsorption of changes in efferent arteriolar protein concentration and plasma flow rate. Under normal physiological conditions, relatively small perturbations in protein concentration are predicted to influence reabsorption more than even large variations in plasma flow, a prediction in close accord with recent experimental observations in the rat and dog. Changes either in protein concentration or plasma flow have their most pronounced effects when the opposing transcapillary hydrostatic and osmotic pressure differences are closest to equilibrium. Comparison of these theoretical results with variations in reabsorption observed in micropuncture studies makes it possible to place upper and lower bounds on the difference between interstitial oncotic and hydrostatic pressures in the renal cortex of the rat. PMID:4696761
Nomura, Toshiyuki; Tani, Shuji; Yamamoto, Makoto; Nakagawa, Takumi; Toyoda, Shunsuke; Fujisawa, Eri; Yasui, Akiko; Konishi, Yasuhiro
2016-04-01
The effects of surface physicochemical properties of functionalized polystyrene latex (PSL) nanoparticles (NPs) and model filamentous fungi Aspergillus oryzae and Aspergillus nidulans cultivated in different environment (aqueous and atmospheric environment) on the colloidal behavior and cytotoxicity were investigated in different isotonic solutions (154 mM NaCl and 292 mM sucrose). When the liquid cultivated fungal cells were exposed to positively charged PSL NPs in 154 mM NaCl solution, the NPs were taken into A. oryzae, but not A. nidulans. Atomic force microscopy revealed that the uptake of NPs was more readily through the cell wall of A. oryzae because of its relatively softer cell wall compared with A. nidulans. In contrast, the positively charged PSL NPs entirely covered the liquid cultivated fungal cell surfaces and induced cell death in 292 mM sucrose solution because of the stronger electrostatic attractive force between the cells and NPs compared with in 154 mM NaCl. When the agar cultivated fungal cells were exposed to the positively charged PSL NPs, both fungal cells did not take the NPs inside the cells. Contact angle measurement revealed that the hydrophobin on the agar cultivated cell surfaces inhibited the uptake of NPs because of its relatively more hydrophobic cell surface compared with the liquid cultivated cells. PMID:26855210
A Review of Classification Techniques of EMG Signals during Isotonic and Isometric Contractions.
Nazmi, Nurhazimah; Abdul Rahman, Mohd Azizi; Yamamoto, Shin-Ichiroh; Ahmad, Siti Anom; Zamzuri, Hairi; Mazlan, Saiful Amri
2016-01-01
In recent years, there has been major interest in the exposure to physical therapy during rehabilitation. Several publications have demonstrated its usefulness in clinical/medical and human machine interface (HMI) applications. An automated system will guide the user to perform the training during rehabilitation independently. Advances in engineering have extended electromyography (EMG) beyond the traditional diagnostic applications to also include applications in diverse areas such as movement analysis. This paper gives an overview of the numerous methods available to recognize motion patterns of EMG signals for both isotonic and isometric contractions. Various signal analysis methods are compared by illustrating their applicability in real-time settings. This paper will be of interest to researchers who would like to select the most appropriate methodology in classifying motion patterns, especially during different types of contractions. For feature extraction, the probability density function (PDF) of EMG signals will be the main interest of this study. Following that, a brief explanation of the different methods for pre-processing, feature extraction and classifying EMG signals will be compared in terms of their performance. The crux of this paper is to review the most recent developments and research studies related to the issues mentioned above. PMID:27548165
Charge density distributions and charge form factors of the N=82 and N=126 isotonic nuclei
Wang Zaijun; Fan Ying; Ren Zhongzhou
2006-01-15
Charge form factors for N=82 and N=126 isotonic nuclei are calculated with the relativistic eikonal approximation, in which the charge density distributions are from the relativistic mean-field theory. The variations of charge form factors with proton number are discussed in detail. It is found that the most sensitive parts of the charge form factors are those around the minimums and maximums. For an increasing proton number, the charge form factors near the extrema have an upward shift. As the protons increase and occupy a new shell, the minimums and maximums of the charge form factors could also have a significant inward shift. The results can be useful for the study of behaviors of valence-proton wave functions for such nuclei as can be considered as a core plus proton(s), and thus the proton-halo phenomenon. In addition, the results can also be useful for future electron-unstable nucleus scattering experiments and provide tests of the reliability of the relativistic mean-field theory for the unstable nuclei.
Role of atrial natriuretic peptide in systemic responses to acute isotonic volume expansion
NASA Technical Reports Server (NTRS)
Watenpaugh, Donald E.; Yancy, Clyde W.; Buckey, Jay C.; Lane, Lynda D.; Hargens, Alan R.; Blomqvist, C. G.
1992-01-01
A hypothesis is proposed that a temporal relationship exists between increases in cardiac filling pressure and plasma artrial natriuretic peptide (ANP) concentration and also between ANP elevation and vasodilation, fluid movement from plasma to interstitium, and increased urine volume (UV). To test the hypothesis, 30 ml/kg isotonic saline were infused in supine male subjects over 24 min and responses were monitored for 3 h postinfusion. Results show that at end infusion, mean arterial pressure (RAP), heart rate and plasma volume exhibited peak increases of 146, 23, and 27 percent, respectively. Mean plasma ANP and UV peaked (45 and 390 percent, respectively) at 30 min postinfusion. Most cardiovascular variables had returned toward control levels by 1 h postinfusion, and net reabsorption of extravascular fluid ensued. It is concluded that since ANP was not significantly increased until 30 min postinfusion, factors other than ANP initiate responses to intravascular fluid loading. These factors include increased vascular pressures, baroreceptor-mediated vasolidation, and hemodilution of plasma proteins. ANP is suggested to mediate, in part, the renal response to saline infusion.
Del Prete, Zaccaria; Musarò, Antonio; Rizzuto, Emanuele
2008-07-01
Contractile properties of fast-twitch (EDL) and slow-twitch (soleus) skeletal muscles were measured in MLC/mIgf-1 transgenic and wild-type mice. MLC/mIgf-1 mice express the local factor mIgf-1 under the transcriptional control of MLC promoter, selectively activated in fast-twitch muscle fibers. Isolated muscles were studied in vitro in both isometric and isotonic conditions. We used a rapid "ad hoc" testing protocol that measured, in a single procedure, contraction time, tetanic force, Hill's (F-v) curve, power curve and isotonic muscle fatigue. Transgenic soleus muscles did not differ from wild-type with regard to any measured variable. In contrast, transgenic EDL muscles displayed a hypertrophic phenotype, with a mass increase of 29.2% compared to wild-type. Absolute tetanic force increased by 21.5% and absolute maximum power by 34.1%. However, when normalized to muscle cross-sectional area and mass, specific force and normalized power were the same in transgenic and wild-type EDL muscles, revealing that mIgf-1 expression induces a functional hypertrophy without altering fibrotic tissue accumulation. Isotonic fatigue behavior did not differ between transgenic and wild-type muscles, suggesting that the ability of mIgf-1 transgenic muscle to generate a considerable higher absolute power did not affect its resistance to fatigue. PMID:18415017
Hahn, R G; Isacson, M Nyberg; Fagerström, T; Rosvall, J; Nyman, C R
2016-02-01
Isotonic saline is a widely-used infusion fluid, although the associated chloride load may cause metabolic acidosis and impair kidney function in young, healthy volunteers. We wished to examine whether these effects also occurred in the elderly, and conducted a crossover study in 13 men with a mean age of 73 years (range 66-84), who each received intravenous infusions of 1.5 l of Ringer's acetate and of isotonic saline. Isotonic saline induced mild changes in plasma sodium (mean +1.5 mmol.l(-1) ), plasma chloride (+3 mmol.l(-1) ) and standard bicarbonate (-2 mmol.l(-1) ). Three hours after starting the infusions, 68% of the Ringer's acetate and 30% of the infused saline had been excreted (p < 0.01). The glomerular filtration rate increased in response to both fluids, but more after the Ringer's acetate (p < 0.03). Pre-infusion fluid retention, as evidenced by high urinary osmolality (> 700 mOsmol.kg(-1) ) and/or creatinine (> 7 mmol.l(-1) ), was a strong factor governing the responses to both fluid loads. PMID:26669730
Interpreting Bivariate Regression Coefficients: Going beyond the Average
ERIC Educational Resources Information Center
Halcoussis, Dennis; Phillips, G. Michael
2010-01-01
Statistics, econometrics, investment analysis, and data analysis classes often review the calculation of several types of averages, including the arithmetic mean, geometric mean, harmonic mean, and various weighted averages. This note shows how each of these can be computed using a basic regression framework. By recognizing when a regression model…
Investigating NARCCAP Precipitation Extremes via Bivariate Extreme Value Theory (Invited)
NASA Astrophysics Data System (ADS)
Weller, G. B.; Cooley, D. S.; Sain, S. R.; Bukovsky, M. S.; Mearns, L. O.
2013-12-01
We introduce methodology from statistical extreme value theory to examine the ability of reanalysis-drive regional climate models to simulate past daily precipitation extremes. Going beyond a comparison of summary statistics such as 20-year return values, we study whether the most extreme precipitation events produced by climate model simulations exhibit correspondence to the most extreme events seen in observational records. The extent of this correspondence is formulated via the statistical concept of tail dependence. We examine several case studies of extreme precipitation events simulated by the six models of the North American Regional Climate Change Assessment Program (NARCCAP) driven by NCEP reanalysis. It is found that the NARCCAP models generally reproduce daily winter precipitation extremes along the Pacific coast quite well; in contrast, simulation of past daily summer precipitation extremes in a central US region is poor. Some differences in the strength of extremal correspondence are seen in the central region between models which employ spectral nudging and those which do not. We demonstrate how these techniques may be used to draw a link between extreme precipitation events and large-scale atmospheric drivers, as well as to downscale extreme precipitation simulated by a future run of a regional climate model. Specifically, we examine potential future changes in the nature of extreme precipitation along the Pacific coast produced by the pineapple express (PE) phenomenon. A link between extreme precipitation events and a "PE Index" derived from North Pacific sea-surface pressure fields is found. This link is used to study PE-influenced extreme precipitation produced by a future-scenario climate model run.
Contributions to the Underlying Bivariate Normal Method for Factor Analyzing Ordinal Data
ERIC Educational Resources Information Center
Xi, Nuo; Browne, Michael W.
2014-01-01
A promising "underlying bivariate normal" approach was proposed by Jöreskog and Moustaki for use in the factor analysis of ordinal data. This was a limited information approach that involved the maximization of a composite likelihood function. Its advantage over full-information maximum likelihood was that very much less computation was…
BIVARIATE MODELLING OF CLUSTERED CONTINUOUS AND ORDERED CATEGORICAL OUTCOMES. (R824757)
Simultaneous observation of continuous and ordered categorical outcomes for each subject is common in biomedical research but multivariate analysis of the data is complicated by the multiple data types. Here we construct a model for the joint distribution of bivariate continuous ...
Bivariate normal, conditional and rectangular probabilities: A computer program with applications
NASA Technical Reports Server (NTRS)
Swaroop, R.; Brownlow, J. D.; Ashwworth, G. R.; Winter, W. R.
1980-01-01
Some results for the bivariate normal distribution analysis are presented. Computer programs for conditional normal probabilities, marginal probabilities, as well as joint probabilities for rectangular regions are given: routines for computing fractile points and distribution functions are also presented. Some examples from a closed circuit television experiment are included.
NASA Technical Reports Server (NTRS)
Smith, O. E.; Adelfang, S. I.
1981-01-01
A model of the largest gust amplitude and gust length is presented which uses the properties of the bivariate gamma distribution. The gust amplitude and length are strongly dependent on the filter function; the amplitude increases with altitude and is larger in winter than in summer.
A Method for Determining If Unequal Shape Parameters are Necessary in a Bivariate Gamma Distribution
NASA Technical Reports Server (NTRS)
Tubbs, J. D.
1983-01-01
A procedure to aid in the deciding between four and five parameters in a Jensen's type bivariate gamma distribution is presented. It is based upon the CDF of the ratio of correlated gamma distributed variates. The criteria are posed in a test of hypothesis setting and results are presented.
Eskelinen, S; Mela, M
1984-12-01
The osmotic behaviour of erythrocytes under the influence of lysophosphatidylcholine (LPC) was investigated at temperatures of +4 degrees C and 20 degrees C by allowing them either to swell rapidly in hypotonic media in the presence of LPC or to swell gradually at first and then interact with LPC. Prelytic potassium release, the degree of hemolysis and the cell volume under various osmotic conditions were measured, together with the 'returning volumes', i.e. the volumes in an isotonic solution to which the cells returned from that in the hypotonic solution. LPC had a hemolyzing effect on erythrocytes in an isotonic medium and in slightly hypotonic media under all the osmotic conditions investigated, and the degree of hemolysis increased with increasing concentrations of LPC or decreasing temperatures, being greater during gradual than during rapid swelling. LPC also produced a prelytic leakage of potassium connected with the decrease in cell volume in an isotonic medium and in 'returning volumes' in all the media and under all the osmotic conditions investigated. The semipermeability of the membrane was preserved in all these cases, however, for osmotic swelling of the erythrocytes was observed, although to a lesser extent than without LPC. During rapid swelling both the curves for the prelytic potassium leakage and the degree of hemolysis were shifted towards more dilute solutions. Since the critical hemolytic volume was not increased, the shift in potassium leakage and hemolysis caused by LPC may be due to increased rigidity in the cell membrane. The curves for both potassium leakage and hemolysis shifted towards more concentrated solutions during gradual swelling, perhaps due to increased membrane fragmentation. PMID:6524395
NASA Technical Reports Server (NTRS)
Bernauer, E. M.; Walby, W. F.; Ertl, A. C.; Dempster, P. T.; Bond, M.; Greenleaf, J. E.
1994-01-01
To determine if daily isotonic exercise or isokinetic exercise training coupled with daily leg proprioceptive training, would influence leg proprioceptive tracking responses during bed rest (BR), 19 men (36 +/- SD 4 years, 178 +/- 7 cm, 76.8 +/- 7.8 kg) were allocated into a no-exercise (NOE) training control group (n = 5), and isotonic exercise (ITE, n = 7) and isokinetic exercise (IKE, n = 7) training groups. Exercise training was conducted during BR for two 30-min periods.d-1, 5 d.week-1. Only the IKE group performed proprioceptive training using a new isokinetic procedure with each lower extremity for 2.5 min before and after the daily exercise training sessions; proprioceptive testing occurred weekly for all groups. There were no significant differences in proprioceptive tracking scores, expressed as a percentage of the perfect score of 100, in the pre-BR ambulatory control period between the three groups. Knee extension and flexion tracking responses were unchanged with NOE during BR, but were significantly greater (*p < 0.05) at the end of BR in both exercise groups when compared with NOE responses (extension: NOE 80.7 +/- 0.7%, ITE 82.9* +/- 0.6%, IKE 86.5* +/- 0.7%; flexion: NOE 77.6 +/- 1.5%, ITE 80.0 +/- 0.8% (NS), IKE 83.6* +/- 0.8%). Although proprioceptive tracking was unchanged during BR with NOE, both isotonic exercise training (without additional proprioceptive training) and especially isokinetic exercise training when combined with daily proprioceptive training, significantly improved knee proprioceptive tracking responses after 30 d of BR.
Uvelius, B
1976-03-01
Isometric and isotonic length-tension relations of longitudinal smooth muscle from rabbit urinary bladder were studied together with muscle cell length and tissue structure as revealed histologically. In vivo strip length at a bladder volume of 10 m1 is referred to as L10. The smooth muscle was relaxed by Ca2+-free solution and contracted by K+-high solution with different Ca2+-concentrations. Maximal active force, 12.5+/-0.4 N/cm2 (S.E., n =11), for wholestrips was attained at a length of 206+/-4% (S.E., n=5) of L10. Passive tension at this length was about 15% of total tension. After correction for amount of connective tissue, maximal active tension of pure muscle bundles was 19 N/cm2. Up to about 165% of L10 isometric and isotonic length-tension relations were identical; if the muscle was stretched beyond this, it failed to shorten isotonically to the same length as when contracting from a shorter starting length. This decreased shortening capacity was reversible if the muscle was shortened passively. The extent of shortening against zero load was dependent on degree of activation suggesting an internal resistance to shortening. A linear relationship was found between bladder radius and muscle cell length, indicating that no slippage occurs between the cells when the bladder is filled. Mean cell diameter in the nuclear regionat L10 was 7.2+/-0.2 mum (S.D.,n=10). Mean macimal active tension per cell was calculated to be 2.3-10(-6) N and occurred at a cell length of 655 mum. PMID:818878
High-spin states in the semimagic nucleus 89Y and neutron-core excitations in the N =50 isotones
NASA Astrophysics Data System (ADS)
Li, Z. Q.; Wang, S. Y.; Niu, C. Y.; Qi, B.; Wang, S.; Sun, D. P.; Liu, C.; Xu, C. J.; Liu, L.; Zhang, P.; Wu, X. G.; Li, G. S.; He, C. Y.; Zheng, Y.; Li, C. B.; Yu, B. B.; Hu, S. P.; Yao, S. H.; Cao, X. P.; Wang, J. L.
2016-07-01
The semimagic nucleus 89Y 89 has been investigated using the 82Se(11>B,4 n ) reaction at beam energies of 48 and 52 MeV. More than 24 new transitions have been identified, leading to a considerable extension of the level structures of 89Y. The experimental results are compared with the large-basis shell model calculations. They show that cross-shell neutron excitations play a pivotal role in high-spin level structures of 89Y. The systematic features of neutron-core excitations in the N =50 isotones are also discussed.
Morales, A. I.; Benlliure, J.; Alvarez-Pol, H.; Casarejos, E.; Dragosavac, D.; Perez-Loureiro, D.; Verma, S.; Agramunt, J.; Molina, F.; Rubio, B.; Algora, A.; Alkhomashi, N.; Farrelly, G.; Gelletly, W.; Pietri, S.; Podolyak, Z.; Regan, P. H.; Steer, S. J.; Boutachkov, P.; Caceres, L. S.
2011-07-15
The production cross sections of four N=127 isotones ({sup 207}Hg, {sup 206}Au, {sup 205}Pt, and {sup 204}Ir) have been measured using (p,n) charge-exchange reactions, induced in collisions of a {sup 208}Pb primary beam at 1 A GeV with a Be target. These data allow one to investigate the use of a reaction mechanism to extend the limits of the chart of nuclides toward the important r-process nuclei in the region of the third peak of elemental abundance distribution.
A new spreadsheet method for the analysis of bivariate flow cytometric data
Tzircotis, George; Thorne, Rick F; Isacke, Clare M
2004-01-01
Background A useful application of flow cytometry is the investigation of cell receptor-ligand interactions. However such analyses are often compromised due to problems interpreting changes in ligand binding where the receptor expression is not constant. Commonly, problems are encountered due to cell treatments resulting in altered receptor expression levels, or when cell lines expressing a transfected receptor with variable expression are being compared. To overcome this limitation we have developed a Microsoft Excel spreadsheet that aims to automatically and effectively simplify flow cytometric data and perform statistical tests in order to provide a clearer graphical representation of results. Results To demonstrate the use and advantages of this new spreadsheet method we have investigated the binding of the transmembrane adhesion receptor CD44 to its ligand hyaluronan. In the first example, phorbol ester treatment of cells results in both increased CD44 expression and increased hyaluronan binding. By applying the spreadsheet method we effectively demonstrate that this increased ligand binding results from receptor activation. In the second example we have compared AKR1 cells transfected either with wild type CD44 (WT CD44) or a mutant with a truncated cytoplasmic domain (CD44-T). These two populations do not have equivalent receptor expression levels but by using the spreadsheet method hyaluronan binding could be compared without the need to generate single cell clones or FACS sorting the cells for matching CD44 expression. By this method it was demonstrated that hyaluronan binding requires a threshold expression of CD44 and that this threshold is higher for CD44-T. However, at high CD44-T expression, binding was equivalent to WT CD44 indicating that the cytoplasmic domain has a role in presenting the receptor at the cell surface in a form required for efficient hyaluronan binding rather than modulating receptor activity. Conclusion Using the attached
Systematics of isomeric configurations in N=77 odd-Z isotones near the proton drip line
Tantawy, M.N.; Danchev, M.; Hartley, D.J.; Mazzocchi, C.; Bingham, C.R.; Grzywacz, R.; Rykaczewski, K.P.; Gross, C.J.; Shapira, D.; Yu, C.-H.; Batchelder, J.C.; Krolas, W.; Fong, D.; Hamilton, J. H.; Li, K.; Ramayya, A. V.; Ginter, T.N.; Stolz, A.; Hagino, K.; Karny, M.
2006-02-15
The systematics of the {pi}h{sub 11/2}x{nu}h{sub 11/2} and {pi}h{sub 11/2}x{nu}s{sub 1/2} isomeric configurations was studied for the odd-Z N=77 isotones near the proton drip line. The isomeric decays in {sup 140}Eu, {sup 142}Tb, {sup 144}Ho, and {sup 146}Tm were measured by means of x-ray, {gamma}-ray, and charged particle spectroscopy at the Recoil Mass Spectrometer at the Holifield Radioactive Ion Beam Facility (ORNL). The spin and parity of I{sup {pi}}=8{sup +} and 5{sup -} were deduced for the isomers in {sup 140}Eu and {sup 142}Tb. New decay schemes were established, and the half-lives of the 8{sup +} isomers were measured to be 302(4) ns for {sup 140m2}Eu and 25(1) {mu}s for {sup 142m2}Tb. No evidence for the expected 1{sup +} ground-state was found in the {sup 144}Ho decay data. The proton-emission from {sup 146}Tm was restudied. Five proton transitions were assigned to two proton-emitting states. The half-lives of 198(3) ms and 68(3) ms and the spin and parity values of I{sup {pi}}=10{sup +} and 5{sup -} were established for {sup 146m}Tm and {sup 146gs}Tm, respectively. For the first time for an odd-odd nucleus, the interpretation of the observed decay properties and structure of the proton-emitting states was made by accounting for deformation and proton and neutron coupling to the core excitations. A complex wave-function structure was obtained, with dominating components of {pi}h{sub 11/2}x{nu}h{sub 11/2} for the 10{sup +} isomer and {pi}h{sub 11/2}x{nu}s{sub 1/2} for the 5{sup -} ground state.
[General pharmacological study of iodixanol, a new non-ionic isotonic contrast medium].
Takasuna, K; Kasai, Y; Kitano, Y; Mori, K; Kobayashi, R; Makino, M; Hagiwara, T; Hirohashi, M; Nomura, M; Algate, D R
1995-10-01
The general pharmacological study of iodixanol, a non-ionic isotonic contrast medium, was conducted. 1) Iodixanol administered intravenously over a dose range of 320 to 3,200 mgI/kg had little or no effect on the general behavior, spontaneous locomotor activity, hexobarbital sleeping time, pain response, electroshock- or pentylenetetrazol-induced convulsion (mouse), EEG or body temperature (rabbit), gastrointestinal propulsion (mouse) or skeletal muscle contraction (rabbit). Iodixanol had no specific interaction with acetylcholine, histamine, serotonin, nicotin, BaCl2 (ileum), methacholine (trachea), isoprenaline (atrium) or oxytocin (pregnant uterus), nor had any effect on spontaneous contractility (atrium and uterus), or transmural electrostimulation-induced contractility (vas deferens) at concentrations of < or = 3.2 x 10(-3) gI/ml in vitro. Iodixanol had no effect on the cardiovascular system of dog, except that it increased femoral blood flow and respiratory rate at doses of > or = 1,000 mgI/kg. Iodixanol at 3,200 mgI/kg i.v. reduced urine output with a decrease in Na+ and Cl- excretion, whereas at 320 mgI/kg i.v., it slightly increased urine output (rat). 2) Injections of iodixanol into the cerebroventricular (0.96, 9.6 mgI/mouse and 3.2, 32 mgI/rat), left ventricular (1,920, 6,400 mgI/dog) or coronary artery (640, 1,920 mgI/dog) had no conspicuous effect on the central nervous system or the cardiovascular system, respectively. There was no marked difference among iodixanol, iohexol and iopamidol in this respect. Vascular pain during injection into the femoral artery (300-320 mgI/guinea pig) appeared to be less intense with iodixanol, compared with the other contrast media iohexol and iopamidol. These results suggest that intravenous injection of iodixanol is relatively free from pharmacological activity, and effects of iodixanol on the central nervous system (intracerebroventricular injection) and cardiovascular system (intra-left ventricular and -coronary
Statistical analysis of multivariate atmospheric variables. [cloud cover
NASA Technical Reports Server (NTRS)
Tubbs, J. D.
1979-01-01
Topics covered include: (1) estimation in discrete multivariate distributions; (2) a procedure to predict cloud cover frequencies in the bivariate case; (3) a program to compute conditional bivariate normal parameters; (4) the transformation of nonnormal multivariate to near-normal; (5) test of fit for the extreme value distribution based upon the generalized minimum chi-square; (6) test of fit for continuous distributions based upon the generalized minimum chi-square; (7) effect of correlated observations on confidence sets based upon chi-square statistics; and (8) generation of random variates from specified distributions.
Vink, Margaretha A; Berkhof, Johannes; van de Kassteele, Jan; van Boven, Michiel; Bogaards, Johannes A
2016-01-01
Post-vaccine monitoring programs for human papillomavirus (HPV) have been introduced in many countries, but HPV serology is still an underutilized tool, partly owing to the weak antibody response to HPV infection. Changes in antibody levels among non-vaccinated individuals could be employed to monitor herd effects of immunization against HPV vaccine types 16 and 18, but inference requires an appropriate statistical model. The authors developed a four-component bivariate mixture model for jointly estimating vaccine-type seroprevalence from correlated antibody responses against HPV16 and -18 infections. This model takes account of the correlation between HPV16 and -18 antibody concentrations within subjects, caused e.g. by heterogeneity in exposure level and immune response. The model was fitted to HPV16 and -18 antibody concentrations as measured by a multiplex immunoassay in a large serological survey (3,875 females) carried out in the Netherlands in 2006/2007, before the introduction of mass immunization. Parameters were estimated by Bayesian analysis. We used the deviance information criterion for model selection; performance of the preferred model was assessed through simulation. Our analysis uncovered elevated antibody concentrations in doubly as compared to singly seropositive individuals, and a strong clustering of HPV16 and -18 seropositivity, particularly around the age of sexual debut. The bivariate model resulted in a more reliable classification of singly and doubly seropositive individuals than achieved by a combination of two univariate models, and suggested a higher pre-vaccine HPV16 seroprevalence than previously estimated. The bivariate mixture model provides valuable baseline estimates of vaccine-type seroprevalence and may prove useful in seroepidemiologic assessment of the herd effects of HPV vaccination. PMID:27537200
Vink, Margaretha A.; Berkhof, Johannes; van de Kassteele, Jan; van Boven, Michiel; Bogaards, Johannes A.
2016-01-01
Post-vaccine monitoring programs for human papillomavirus (HPV) have been introduced in many countries, but HPV serology is still an underutilized tool, partly owing to the weak antibody response to HPV infection. Changes in antibody levels among non-vaccinated individuals could be employed to monitor herd effects of immunization against HPV vaccine types 16 and 18, but inference requires an appropriate statistical model. The authors developed a four-component bivariate mixture model for jointly estimating vaccine-type seroprevalence from correlated antibody responses against HPV16 and -18 infections. This model takes account of the correlation between HPV16 and -18 antibody concentrations within subjects, caused e.g. by heterogeneity in exposure level and immune response. The model was fitted to HPV16 and -18 antibody concentrations as measured by a multiplex immunoassay in a large serological survey (3,875 females) carried out in the Netherlands in 2006/2007, before the introduction of mass immunization. Parameters were estimated by Bayesian analysis. We used the deviance information criterion for model selection; performance of the preferred model was assessed through simulation. Our analysis uncovered elevated antibody concentrations in doubly as compared to singly seropositive individuals, and a strong clustering of HPV16 and -18 seropositivity, particularly around the age of sexual debut. The bivariate model resulted in a more reliable classification of singly and doubly seropositive individuals than achieved by a combination of two univariate models, and suggested a higher pre-vaccine HPV16 seroprevalence than previously estimated. The bivariate mixture model provides valuable baseline estimates of vaccine-type seroprevalence and may prove useful in seroepidemiologic assessment of the herd effects of HPV vaccination. PMID:27537200
Exploratory Causal Analysis in Bivariate Time Series Data
NASA Astrophysics Data System (ADS)
McCracken, James M.
Many scientific disciplines rely on observational data of systems for which it is difficult (or impossible) to implement controlled experiments and data analysis techniques are required for identifying causal information and relationships directly from observational data. This need has lead to the development of many different time series causality approaches and tools including transfer entropy, convergent cross-mapping (CCM), and Granger causality statistics. In this thesis, the existing time series causality method of CCM is extended by introducing a new method called pairwise asymmetric inference (PAI). It is found that CCM may provide counter-intuitive causal inferences for simple dynamics with strong intuitive notions of causality, and the CCM causal inference can be a function of physical parameters that are seemingly unrelated to the existence of a driving relationship in the system. For example, a CCM causal inference might alternate between ''voltage drives current'' and ''current drives voltage'' as the frequency of the voltage signal is changed in a series circuit with a single resistor and inductor. PAI is introduced to address both of these limitations. Many of the current approaches in the times series causality literature are not computationally straightforward to apply, do not follow directly from assumptions of probabilistic causality, depend on assumed models for the time series generating process, or rely on embedding procedures. A new approach, called causal leaning, is introduced in this work to avoid these issues. The leaning is found to provide causal inferences that agree with intuition for both simple systems and more complicated empirical examples, including space weather data sets. The leaning may provide a clearer interpretation of the results than those from existing time series causality tools. A practicing analyst can explore the literature to find many proposals for identifying drivers and causal connections in times series data
Volcano clustering determination: Bivariate Gauss vs. Fisher kernels
NASA Astrophysics Data System (ADS)
Cañón-Tapia, Edgardo
2013-05-01
Underlying many studies of volcano clustering is the implicit assumption that vent distribution can be studied by using kernels originally devised for distribution in plane surfaces. Nevertheless, an important change in topology in the volcanic context is related to the distortion that is introduced when attempting to represent features found on the surface of a sphere that are being projected into a plane. This work explores the extent to which different topologies of the kernel used to study the spatial distribution of vents can introduce significant changes in the obtained density functions. To this end, a planar (Gauss) and a spherical (Fisher) kernels are mutually compared. The role of the smoothing factor in these two kernels is also explored with some detail. The results indicate that the topology of the kernel is not extremely influential, and that either type of kernel can be used to characterize a plane or a spherical distribution with exactly the same detail (provided that a suitable smoothing factor is selected in each case). It is also shown that there is a limitation on the resolution of the Fisher kernel relative to the typical separation between data that can be accurately described, because data sets with separations lower than 500 km are considered as a single cluster using this method. In contrast, the Gauss kernel can provide adequate resolutions for vent distributions at a wider range of separations. In addition, this study also shows that the numerical value of the smoothing factor (or bandwidth) of both the Gauss and Fisher kernels has no unique nor direct relationship with the relevant separation among data. In order to establish the relevant distance, it is necessary to take into consideration the value of the respective smoothing factor together with a level of statistical significance at which the contributions to the probability density function will be analyzed. Based on such reference level, it is possible to create a hierarchy of
Chen, Zhengjia; Wang, Zhibo; Wang, Haibin; Owonikoko, Taofeek K; Kowalski, Jeanne; Khuri, Fadlo R
2013-01-01
Isotonic Design using Normalized Equivalent Toxicity Score (ID-NETS) is a novel Phase I design that integrates the novel toxicity scoring system originally proposed by Chen et al. [1] and the original Isotonic Design proposed by Leung et al. [2]. ID-NETS has substantially improved the accuracy of maximum tolerated dose (MTD) estimation and trial efficiency in the Phase I clinical trial setting by fully utilizing all toxicities experienced by each patient and treating toxicity response as a quasi-continuous variable instead of a binary indicator of dose limiting toxicity (DLT). To facilitate the incorporation of the ID-NETS method into the design and conduct of Phase I clinical trials, we have designed and developed a user-friendly software, ID-NETS(©TM), which has two functions: 1) Calculating the recommended dose for the subsequent patient cohort using available completed data; and 2) Performing simulations to obtain the operating characteristics of a trial designed with ID-NETS. Currently, ID-NETS(©TM)v1.0 is available for free download at http://winshipbbisr.emory.edu/IDNETS.html. PMID:23847695
NASA Technical Reports Server (NTRS)
Ellis, S.; Kirby, L. C.; Greenleaf, J. E.
1993-01-01
Muscle thickness was measured in 19 Bed-Rested (BR) men (32-42 year) subjected to IsoTonic (ITE, cycle orgometer) and IsoKi- netic (IKE, torque orgometer) lower extremity exercise training, and NO Exercise (NOE) training. Thickness was measured with ultrasonography in anterior thigh-Rectus Femoris (RF) and Vastus Intermadius (VI), and combined posterior log-soleus, flexor ballucis longus, and tibialis posterior (S + FHL +TP) - muscles. Compared with ambulatory control values, thickness of the (S + FHL + TP) decreased by 90%-12% (p less than 0.05) In all three test groups. The (RF) thickness was unchanged in the two exercise groups, but decreased by 10% (p less than 0.05) in the NOE. The (VI) thickness was unchanged In the ITE group, but decreased by 12%-l6% (p less than 0.05) in the IKE and NOE groups. Thus, intensive, alternating, isotonic cycle ergometer exercise training is as effective as intensive, intermittent, isokinetic exercise training for maintaining thicknesses of rectus femoris and vastus lntermedius anterior thigh muscles, but not posterior log muscles, during prolonged BR deconditioning.
Neelon, Brian; Anthopolos, Rebecca; Miranda, Marie Lynn
2014-04-01
Motivated by a study examining geographic variation in birth outcomes, we develop a spatial bivariate probit model for the joint analysis of preterm birth and low birth weight. The model uses a hierarchical structure to incorporate individual and areal-level information, as well as spatially dependent random effects for each spatial unit. Because rates of preterm birth and low birth weight are likely to be correlated within geographic regions, we model the spatial random effects via a bivariate conditionally autoregressive prior, which induces regional dependence between the outcomes and provides spatial smoothing and sharing of information across neighboring areas. Under this general framework, one can obtain region-specific joint, conditional, and marginal inferences of interest. We adopt a Bayesian modeling approach and develop a practical Markov chain Monte Carlo computational algorithm that relies primarily on easily sampled Gibbs steps. We illustrate the model using data from the 2007-2008 North Carolina Detailed Birth Record. PMID:22599322
Modeling two-vehicle crash severity by a bivariate generalized ordered probit approach.
Chiou, Yu-Chiun; Hwang, Cherng-Chwan; Chang, Chih-Chin; Fu, Chiang
2013-03-01
This study simultaneously models crash severity of both parties in two-vehicle accidents at signalized intersections in Taipei City, Taiwan, using a novel bivariate generalized ordered probit (BGOP) model. Estimation results show that the BGOP model performs better than the conventional bivariate ordered probit (BOP) model in terms of goodness-of-fit indices and prediction accuracy and provides a better approach to identify the factors contributing to different severity levels. According to estimated parameters in latent propensity functions and elasticity effects, several key risk factors are identified-driver type (age>65), vehicle type (motorcycle), violation type (alcohol use), intersection type (three-leg and multiple-leg), collision type (rear ended), and lighting conditions (night and night without illumination). Corresponding countermeasures for these risk factors are proposed. PMID:23246710
Reprint of "Modeling two-vehicle crash severity by a bivariate generalized ordered probit approach".
Chiou, Yu-Chiun; Hwang, Cherng-Chwan; Chang, Chih-Chin; Fu, Chiang
2013-12-01
This study simultaneously models crash severity of both parties in two-vehicle accidents at signalized intersections in Taipei City, Taiwan, using a novel bivariate generalized ordered probit (BGOP) model. Estimation results show that the BGOP model performs better than the conventional bivariate ordered probit (BOP) model in terms of goodness-of-fit indices and prediction accuracy and provides a better approach to identify the factors contributing to different severity levels. According to estimated parameters in latent propensity functions and elasticity effects, several key risk factors are identified-driver type (age>65), vehicle type (motorcycle), violation type (alcohol use), intersection type (three-leg and multiple-leg), collision type (rear ended), and lighting conditions (night and night without illumination). Corresponding countermeasures for these risk factors are proposed. PMID:23915470
Ramdani, Sofiane; Bonnet, Vincent; Tallon, Guillaume; Lagarde, Julien; Bernard, Pierre Louis; Blain, Hubert
2016-08-01
Entropy measures are often used to quantify the regularity of postural sway time series. Recent methodological developments provided both multivariate and multiscale approaches allowing the extraction of complexity features from physiological signals; see "Dynamical complexity of human responses: A multivariate data-adaptive framework," in Bulletin of Polish Academy of Science and Technology, vol. 60, p. 433, 2012. The resulting entropy measures are good candidates for the analysis of bivariate postural sway signals exhibiting nonstationarity and multiscale properties. These methods are dependant on several input parameters such as embedding parameters. Using two data sets collected from institutionalized frail older adults, we numerically investigate the behavior of a recent multivariate and multiscale entropy estimator; see "Multivariate multiscale entropy: A tool for complexity analysis of multichannel data," Physics Review E, vol. 84, p. 061918, 2011. We propose criteria for the selection of the input parameters. Using these optimal parameters, we statistically compare the multivariate and multiscale entropy values of postural sway data of non-faller subjects to those of fallers. These two groups are discriminated by the resulting measures over multiple time scales. We also demonstrate that the typical parameter settings proposed in the literature lead to entropy measures that do not distinguish the two groups. This last result confirms the importance of the selection of appropriate input parameters. PMID:26372426
NASA Astrophysics Data System (ADS)
Huang, Xuan; An, Haizhong; Gao, Xiangyun; Hao, Xiaoqing; Liu, Pengpeng
2015-06-01
This study introduces an approach to study the multiscale transmission characteristics of the correlation modes between bivariate time series. The correlation between the bivariate time series fluctuates over time. The transmission among the correlation modes exhibits a multiscale phenomenon, which provides richer information. To investigate the multiscale transmission of the correlation modes, this paper describes a hybrid model integrating wavelet analysis and complex network theory to decompose and reconstruct the original bivariate time series into sequences in a joint time-frequency domain and defined the correlation modes at each time-frequency domain. We chose the crude oil spot and futures prices as the sample data. The empirical results indicate that the main duration of volatility (32-64 days) for the strongly positive correlation between the crude oil spot price and the futures price provides more useful information for investors. Moreover, the weighted degree, weighted indegree and weighted outdegree of the correlation modes follow power-law distributions. The correlation fluctuation strengthens the extent of persistence over the long term, whereas persistence weakens over the short and medium term. The primary correlation modes dominating the transmission process and the major intermediary modes in the transmission process are clustered both in the short and long term.
NASA Astrophysics Data System (ADS)
Metwally, Fadia H.
2008-02-01
The quantitative predictive abilities of the new and simple bivariate spectrophotometric method are compared with the results obtained by the use of multivariate calibration methods [the classical least squares (CLS), principle component regression (PCR) and partial least squares (PLS)], using the information contained in the absorption spectra of the appropriate solutions. Mixtures of the two drugs Nifuroxazide (NIF) and Drotaverine hydrochloride (DRO) were resolved by application of the bivariate method. The different chemometric approaches were applied also with previous optimization of the calibration matrix, as they are useful in simultaneous inclusion of many spectral wavelengths. The results found by application of the bivariate, CLS, PCR and PLS methods for the simultaneous determinations of mixtures of both components containing 2-12 μg ml -1 of NIF and 2-8 μg ml -1 of DRO are reported. Both approaches were satisfactorily applied to the simultaneous determination of NIF and DRO in pure form and in pharmaceutical formulation. The results were in accordance with those given by the EVA Pharma reference spectrophotometric method.
Metwally, Fadia H
2008-02-01
The quantitative predictive abilities of the new and simple bivariate spectrophotometric method are compared with the results obtained by the use of multivariate calibration methods [the classical least squares (CLS), principle component regression (PCR) and partial least squares (PLS)], using the information contained in the absorption spectra of the appropriate solutions. Mixtures of the two drugs Nifuroxazide (NIF) and Drotaverine hydrochloride (DRO) were resolved by application of the bivariate method. The different chemometric approaches were applied also with previous optimization of the calibration matrix, as they are useful in simultaneous inclusion of many spectral wavelengths. The results found by application of the bivariate, CLS, PCR and PLS methods for the simultaneous determinations of mixtures of both components containing 2-12microgml(-1) of NIF and 2-8microgml(-1) of DRO are reported. Both approaches were satisfactorily applied to the simultaneous determination of NIF and DRO in pure form and in pharmaceutical formulation. The results were in accordance with those given by the EVA Pharma reference spectrophotometric method. PMID:17631041
A Statistical Analysis of Cotton Fiber Properties
NASA Astrophysics Data System (ADS)
Ghosh, Anindya; Das, Subhasis; Majumder, Asha
2016-04-01
This paper reports a statistical analysis of different cotton fiber properties, such as strength, breaking elongation, upper half mean length, length uniformity index, short fiber index, micronaire, reflectance and yellowness measured from 1200 cotton bales. The uni-variate, bi-variate and multi-variate statistical analysis have been invoked to elicit interrelationship between above-mentioned properties taking them up singularly, pairwise and multiple way, respectively. In multi-variate analysis all cotton fiber properties are simultaneously considered for multi-dimensional techniques of principal factor analysis.
Naftalin, R J; Tripathi, S
1986-01-01
Water movements have been studied in sheets of isolated rabbit ileum using a method which measures net volume flows across the mucosal and serosal surfaces of the tissue continuously with high resolution. At 35 degrees C, with the tissues incubated in isotonic Ringer solution containing D-glucose (25 mM) on both sides, there is a steady net inflow of fluid at the rate of 24 +/- 2 microliter cm-2 h-1 across the mucosal surface (Jm) and an outflow of 8 +/- 1 microliter cm-2 h-1 across the serosal surface (Js) (n = 16). The stable transepithelial p.d. across these tissues is 2.7 +/- 0.2 mV, serosa positive. Jm can be reversibly inhibited by anoxia. Ouabain (0.1 mM) added to the serosal solution inhibits inflow across the mucosal and serosal surfaces by 75% (n = 7) within 30 min. If phlorizin (0.1 mM) is added to the mucosal Ringer solution containing glucose (20 mM) within 30 min of the commencement of in vitro absorption, Jm is reduced from 37 +/- 3 to 28 +/- 2 microliter cm-2 h-1 (n = 3). Dilution of the mucosal Ringer solution by 50 mosmol kg-1 (with the serosal solution kept isosmolar) results in a rapid transient increase in mucosal inflow. An increase of 50 mosmol kg-1 in the mucosal Ringer solution with NaCl, sucrose or mannitol causes a transient reversal of mucosal flow, followed by a return of inflow at a reduced level. Rabbit ileum can transport water against gradients of approximately 75 mosmol kg-1 of sucrose, NaCl, or mannitol. Addition of polyethylene glycol (mol. wt. 20000; 3 mosmol kg-1) causes a sustained reversal of mucosal inflow; inflow can be restored only by removing polyethylene glycol from the mucosal Ringer solution. The tissue can absorb water against an osmotic gradient of 200 mM-glycerol. The above data have been incorporated into a new model to explain isotonic flow of fluid by this epithelium. The main features are that the hydraulic conductivity (Lp) of the mucosal boundary of the lateral intercellular space is approximately 1 X 10
Yamano, Hiro-o; Matsushita, Hiro-o; Yoshikawa, Kenjiro; Takagi, Ryo; Harada, Eiji; Tanaka, Yoshihito; Nakaoka, Michiko; Himori, Ryogo; Yoshida, Yuko; Satou, Kentarou; Imai, Yasushi
2016-01-01
Objectives Bowel cleansing is necessary before colonoscopy, but is a burden to patients because of the long cleansing time and large dose volume. A low-volume (2 L) hypertonic polyethylene glycol-ascorbic acid solution (PEG-Asc) has been introduced, but its possible dehydration effects have not been quantitatively studied. We compared the efficacy and safety including the dehydration risk between hypertonic PEG-Asc and isotonic PEG regimens. Design This was an observer-blinded randomised study. Participants (n=310) were allocated to receive 1 of 3 regimens on the day of colonoscopy: PEG-Asc (1.5 L) and water (0.75 L) dosed with 1 split (PEG-Asc-S) or 4 splits (PEG-Asc-M), or PEG-electrolyte solution (PEG-ES; 2.25 L) dosed with no split. Dehydration was analysed by measuring haematocrit (Ht). Results The cleansing time using the hypertonic PEG-Asc-S (3.33±0.48 hours) was significantly longer than that with isotonic PEG-ES (3.05±0.56 hours; p<0.001). PEG-Asc-M (3.00±0.53 hours) did not have this same disadvantage. Successful cleansing was achieved in more than 94% of participants using each of the 3 regimens. The percentage changes in Ht from baseline (before dosing) to the end of dosing with PEG-Asc-S (3.53±3.32%) and PEG-Asc-M (4.11±3.07%) were significantly greater than that with PEG-ES (1.31±3.01%). Conclusions These 3 lower volume regimens were efficacious and had no serious adverse effects. Even patients cleansed with isotonic PEG-ES showed significant physiological dehydration at the end of dosing. The four-split PEG-Asc-M regimen is recommended because of its shorter cleansing time without causing serious nausea. Trial registration number UMIN000013103; Results. PMID:27547443
Majumdar, Anandamayee; Gries, Corinna
2010-01-01
Lately, bivariate zero-inflated (BZI) regression models have been used in many instances in the medical sciences to model excess zeros. Examples include the BZI Poisson (BZIP), BZI negative binomial (BZINB) models, etc. Such formulations vary in the basic modeling aspect and use the EM algorithm (Dempster, Laird and Rubin, 1977) for parameter estimation. A different modeling formulation in the Bayesian context is given by Dagne (2004). We extend the modeling to a more general setting for multivariate ZIP models for count data with excess zeros as proposed by Li, Lu, Park, Kim, Brinkley and Peterson (1999), focusing on a particular bivariate regression formulation. For the basic formulation in the case of bivariate data, we assume that Xi are (latent) independent Poisson random variables with parameters λ i, i = 0, 1, 2. A bi-variate count vector (Y1, Y2) response follows a mixture of four distributions; p0 stands for the mixing probability of a point mass distribution at (0, 0); p1, the mixing probability that Y2 = 0, while Y1 = X0 + X1; p2, the mixing probability that Y1 = 0 while Y2 = X0 + X2; and finally (1 - p0 - p1 - p2), the mixing probability that Yi = Xi + X0, i = 1, 2. The choice of the parameters {pi, λ i, i = 0, 1, 2} ensures that the marginal distributions of Yi are zero inflated Poisson (λ 0 + λ i). All the parameters thus introduced are allowed to depend on co-variates through canonical link generalized linear models (McCullagh and Nelder, 1989). This flexibility allows for a range of real-life applications, especially in the medical and biological fields, where the counts are bivariate in nature (with strong association between the processes) and where there are excess of zeros in one or both processes. Our contribution in this paper is to employ a fully Bayesian approach consolidating the work of Dagne (2004) and Li et al. (1999) generalizing the modeling and sampling-based methods described by Ghosh, Mukhopadhyay and Lu (2006) to estimate the
NASA Astrophysics Data System (ADS)
Sohn, Soo-Jin; Tam, Chi-Yung
2016-05-01
Capturing climatic variations in boreal winter to spring (December-May) is essential for properly predicting droughts in South Korea. This study investigates the variability and predictability of the South Korean climate during this extended season, based on observations from 60 station locations and multi-model ensemble (MME) hindcast experiments (1983/1984-2005/2006) archived at the APEC Climate Center (APCC). Multivariate empirical orthogonal function (EOF) analysis results based on observations show that the first two leading modes of winter-to-spring precipitation and temperature variability, which together account for ~80 % of the total variance, are characterized by regional-scale anomalies covering the whole South Korean territory. These modes were also closely related to some of the recurrent large-scale circulation changes in the northern hemisphere during the same season. Consistent with the above, examination of the standardized precipitation evapotranspiration index (SPEI) indicates that drought conditions in South Korea tend to be accompanied by regional-to-continental-scale circulation anomalies over East Asia to the western north Pacific. Motivated by the aforementioned findings on the spatial-temporal coherence among station-scale precipitation and temperature anomalies, a new bivariate and pattern-based downscaling method was developed. The novelty of this method is that precipitation and temperature data were first filtered using multivariate EOFs to enhance their spatial-temporal coherence, before being linked to large-scale circulation variables using canonical correlation analysis (CCA). To test its applicability and to investigate its related potential predictability, a perfect empirical model was first constructed with observed datasets as predictors. Next, a model output statistics (MOS)-type hybrid dynamical-statistical model was developed, using products from nine one-tier climate models as inputs. It was found that, with model sea
NASA Astrophysics Data System (ADS)
Sohn, Soo-Jin; Tam, Chi-Yung
2015-07-01
Capturing climatic variations in boreal winter to spring (December-May) is essential for properly predicting droughts in South Korea. This study investigates the variability and predictability of the South Korean climate during this extended season, based on observations from 60 station locations and multi-model ensemble (MME) hindcast experiments (1983/1984-2005/2006) archived at the APEC Climate Center (APCC). Multivariate empirical orthogonal function (EOF) analysis results based on observations show that the first two leading modes of winter-to-spring precipitation and temperature variability, which together account for ~80 % of the total variance, are characterized by regional-scale anomalies covering the whole South Korean territory. These modes were also closely related to some of the recurrent large-scale circulation changes in the northern hemisphere during the same season. Consistent with the above, examination of the standardized precipitation evapotranspiration index (SPEI) indicates that drought conditions in South Korea tend to be accompanied by regional-to-continental-scale circulation anomalies over East Asia to the western north Pacific. Motivated by the aforementioned findings on the spatial-temporal coherence among station-scale precipitation and temperature anomalies, a new bivariate and pattern-based downscaling method was developed. The novelty of this method is that precipitation and temperature data were first filtered using multivariate EOFs to enhance their spatial-temporal coherence, before being linked to large-scale circulation variables using canonical correlation analysis (CCA). To test its applicability and to investigate its related potential predictability, a perfect empirical model was first constructed with observed datasets as predictors. Next, a model output statistics (MOS)-type hybrid dynamical-statistical model was developed, using products from nine one-tier climate models as inputs. It was found that, with model sea
Gils, H.J.; Rebel, H.; Friedman, E.
1984-04-01
The elastic scattering of 104 MeV ..cap alpha.. particles by /sup 40,42,43,44,48/Ca, /sup 50/Ti, /sup 51/V, and /sup 52/Cr has been analyzed by phenomenological and semimicroscopic optical potentials in order to get information on isotopic and isotonic differences of the ..cap alpha.. particle optical potentials and of nuclear matter densities. The phenomenological optical potentials based on a Fourier-Bessel description of the real part reveal different behavior in size and shape for the isotonic chain as compared to the isotopic chain. Odd-even effects are also indicated to be different for isotones and isotopes. The semimicroscopic analyses use a single-folding model with a density-dependent effective ..cap alpha..N interaction including a realistic local density approximation. The calculated potentials are fully consistent with the phenomenological ones. Isotopic and isotonic differences of the nuclear matter densities obtained from the folding model in general show a similar behavior as the optical potential differences. The results on matter densities are compared to other investigations.
Wang, Lin; Wang, Xiaohan; Li, Xiaozhou
2014-07-20
Hydrosoluble emodin-borate (EmB) nanoparticles (NPs) were fabricated by a simple solvent exchange method to address emodin's poor water solubility. As the result, negative charges were introduced in the surface of EmB NPs. In addition, layer-by-layer assembled multilayer films containing cation-rich polymeric microgels (named PAHD) and sodium carboxymethyl cellulose (NaCMC) were employed as drug carrier. Anionic EmB can be loaded into the PAHD/CMC multilayer films. The influences of various experimental parameters on cargo capacity of the PAHD/CMC film were studied in detail. The loaded EmB can be released in the form of emodin molecule in presence of isotonic sodium bicarbonate (ISB) solution. Gratifyingly, EmB did not almost release in presence of water, PBS buffer solution, 0.9% normal saline, and 5% glucose solution. PMID:24755249
NASA Astrophysics Data System (ADS)
Roshanzamir-Nikou, M.; Goudarzi, H.
2016-02-01
A strong magnetic field significantly affects the intrinsic magnetic moment of fermions. In quantum electrodynamics, it was shown that the anomalous magnetic moment of an electron arises kinematically, while it results from a dynamical interaction with an external magnetic field for hadrons (proton). Taking the anomalous magnetic moment of a fermion into account, we find an exact expression for the boundstate energy and the corresponding eigenfunctions of a two-dimensional nonrelativistic spin-1/2 harmonic oscillator with a centripetal barrier (known as the isotonic oscillator) including an Aharonov-Bohm term in the presence of a strong magnetic field. We use the Laplace transform method in the calculations. We find that the singular solution contributes to the phase of the wave function at the origin and the phase depends on the spin and magnetic flux.
NASA Technical Reports Server (NTRS)
Fitts, R. H.; Romatowski, J. G.; Blaser, C.; De La Cruz, L.; Gettelman, G. J.; Widrick, J. J.
2000-01-01
Experiments from both Cosmos and Space Shuttle missions have shown weightlessness to result in a rapid decline in the mass and force of rat hindlimb extensor muscles. Additionally, despite an increased maximal shortening velocity, peak power was reduced in rat soleus muscle post-flight. In humans, declines in voluntary peak isometric ankle extensor torque ranging from 15-40% have been reported following long- and short-term spaceflight and prolonged bed rest. Complete understanding of the cellular events responsible for the fiber atrophy and the decline in force, as well as the development of effective countermeasures, will require detailed knowledge of how the physiological and biochemical processes of muscle function are altered by spaceflight. The specific purpose of this investigation was to determine the extent to which the isotonic contractile properties of the slow- and fast-twitch fiber types of the soleus and gastrocnemius muscles of rhesus monkeys (Macaca mulatta) were altered by a 14-day spaceflight.
NASA Astrophysics Data System (ADS)
Dung, N. V.; Merz, B.; Bárdossy, A.; Apel, H.
2013-02-01
In this paper we present a novel approach for flood hazard analysis of the whole Mekong Delta with a particular focus on the Vietnamese part. Based on previous studies identifying the flood regime in the Mekong delta as non-stationary (Delgado et al., 2010), we develop a non-stationary approach for flood hazard analysis. Moreover, the approach is also bi-variate, as the flood severity in the Mekong Delta is determined by both maximum discharge and flood volume, which determines the flood duration. Probabilities of occurrences of peak discharge and flood volume are estimated by a copula. The flood discharges and volumes are used to derive synthetic hydrographs, which in turn constitute the upper boundary condition for a large-scale hydrodynamic model covering the whole Mekong Delta. The hydrodynamic model transforms the hydrographs into hazard maps. In addition, we extrapolate the observed trends in flood peak and volume and their associated non-stationary extreme value distributions to the year 2030 in order to give a flood hazard estimate for the near future. The uncertainty of extreme flood events in terms of different possible combinations of peak discharge and flood volume given by the copula is considered. Also, the uncertainty in flood hydrograph shape is combined with parameter uncertainty of the hydrodynamic model in a Monte Carlo framework yielding uncertainty estimates in terms of quantile flood maps. The proposed methodology sets the frame for the development of probabilistic flood hazard maps for the entire Mekong Delta. The combination of bi-variate, non-stationary extreme value statistics with large-scale flood inundation modeling and uncertainty quantification is novel in itself. Moreover, it is in particular novel for the Mekong Delta: a region where not even a standard hazard analysis based on a univariate, stationary extreme value statistic exists.
Investigation of the Non-Symmetrical Dependence of Precipitation using Empirical Bivariate Copulas
NASA Astrophysics Data System (ADS)
Suroso, Suroso; Bárdossy, András
2015-04-01
Precipitation plays important role in hydrological analysis. Some common precipitation models are developed based on the assumption of the symmetrical Gaussian dependence structure. This study tries to examine the asymmetrical spatial dependence of precipitation using empirical bivariate copulas. Empirical bivariate copulas are constructed from all possible pairwise combination of the rain gauge data at different locations located in Singapore and Germany. In addition, concept of regionalized variables in spatial random process is also applied with given separating distance. For any selected time interval, precipitation over the region of interest is assumed to be a realization of spatially stationary random process. In order to take into account temporal characteristics, precipitation with different time scales (hourly, 2-hours, 3-hours, 4-hours, 6-hours, 12-hours, daily, 5-days, 10-days, 15-days, monthly, quarterly) and different seasons are analyzed. The behavior of correlation functions are elaborated considering zero precipitation treated as censored values. Asymmetrical spatial dependence is measured by calculating integration from empirical bivariate copula density in the upper right and the lower left parts for given some thresholds, and then by their comparisons. Similarly, zero precipitation is handled as latent variables, and the thresholds are therefore taken percentiles bigger than probability of zeroes. Gaussian simulation based testing is adopted for counting its degree of uncertainty. Empirical evidences prove that precipitation correlation decrease along with the length of distance interval and increases with the length of time interval. There is an interesting systematic pattern relating to the domination of positive non-symmetrical spatial dependence in comparison to negative and symmetrical dependence in terms of distance and time interval. Number of pairs of rain gauge stations which has positive dependence is clearly seen the biggest for cases
Bivariate Genome-Wide Association Analysis of the Growth and Intake Components of Feed Efficiency
Beever, Jonathan E.; Bollero, Germán A.; Southey, Bruce R.; Faulkner, Daniel B.; Rodriguez-Zas, Sandra L.
2013-01-01
Single nucleotide polymorphisms (SNPs) associated with average daily gain (ADG) and dry matter intake (DMI), two major components of feed efficiency in cattle, were identified in a genome-wide association study (GWAS). Uni- and multi-SNP models were used to describe feed efficiency in a training data set and the results were confirmed in a validation data set. Results from the univariate and bivariate analyses of ADG and DMI, adjusted by the feedlot beef steer maintenance requirements, were compared. The bivariate uni-SNP analysis identified (P-value <0.0001) 11 SNPs, meanwhile the univariate analyses of ADG and DMI identified 8 and 9 SNPs, respectively. Among the six SNPs confirmed in the validation data set, five SNPs were mapped to KDELC2, PHOX2A, and TMEM40. Findings from the uni-SNP models were used to develop highly accurate predictive multi-SNP models in the training data set. Despite the substantially smaller size of the validation data set, the training multi-SNP models had slightly lower predictive ability when applied to the validation data set. Six Gene Ontology molecular functions related to ion transport activity were enriched (P-value <0.001) among the genes associated with the detected SNPs. The findings from this study demonstrate the complementary value of the uni- and multi-SNP models, and univariate and bivariate GWAS analyses. The identified SNPs can be used for genome-enabled improvement of feed efficiency in feedlot beef cattle, and can aid in the design of empirical studies to further confirm the associations. PMID:24205251
PCR Diagnosis of Pneumocystis Pneumonia: a Bivariate Meta-Analysis ▿
Lu, Yuan; Ling, Guoya; Qiang, Chenyi; Ming, Qinshou; Wu, Cong; Wang, Ke; Ying, Zouxiao
2011-01-01
We undertook a bivariate meta-analysis to assess the overall accuracy of respiratory specimen PCR assays for diagnosing Pneumocystis pneumonia. The summary sensitivity and specificity were 0.99 (95% confidence interval, 0.96 to 1.00) and 0.90 (0.87 to 0.93). Subgroup analyses showed that quantitative PCR analysis and the major surface glycoprotein gene target had the highest specificity value (0.93). Respiratory specimen PCR results are sufficient to confirm or exclude the disease for at-risk patients suspected of having Pneumocystis pneumonia. PMID:22012008
An efficient algorithm for generating random number pairs drawn from a bivariate normal distribution
NASA Technical Reports Server (NTRS)
Campbell, C. W.
1983-01-01
An efficient algorithm for generating random number pairs from a bivariate normal distribution was developed. Any desired value of the two means, two standard deviations, and correlation coefficient can be selected. Theoretically the technique is exact and in practice its accuracy is limited only by the quality of the uniform distribution random number generator, inaccuracies in computer function evaluation, and arithmetic. A FORTRAN routine was written to check the algorithm and good accuracy was obtained. Some small errors in the correlation coefficient were observed to vary in a surprisingly regular manner. A simple model was developed which explained the qualities aspects of the errors.
Dogu, Beril; Sirzai, Hulya; Yilmaz, Figen; Polat, Basak; Kuran, Banu
2013-10-01
The primary objective of our study was to evaluate the effect of 6-week-long isotonic and isometric hand exercises on pain, hand functions, dexterity and quality of life in women diagnosed as rheumatoid arthritis (RA). Our secondary objective was to assess the changes in handgrip strength and disease activity. This randomized, parallel, single-blinded 6-week intervention study enrolled 52 female patients between 40 and 70 years of age, who were diagnosed with RA according to American College of Rheumatology criteria, had disease duration of at least 1 year and had a stage 1-3 disease according to Steinbrocker's functional evaluation scale. Patients were randomized into isotonics and isometrics groups. Exercises were performed on sixth week. All patients were applied wax therapy in the first 2 weeks. Their pain was assessed with visual analog scale (VAS), their hand functions with Duruöz Hand Index (DHI), dexterity with nine hole peg test (NHPT) and quality of life with Rheumatoid Arthritis Quality of Life questionnaire (RAQoL). Dominant and non-dominant handgrip strengths (HS) were measured. Disease activity was determined by disease activity score (DAS 28). We evaluated the difference in the above parameters between baseline and 6 weeks by Wilcoxon paired t test. The study was completed with 47 patients (isotonics n = 23; isometrics n = 24). VAS, DHI, NHPT, and RAQoL scores significantly improved in both groups by the end of 6th week compared to the baseline scores of the study (for isotonics p = 0.036, p = 0.002; p = 0.0001, p = 0.003; for isometrics p = 0.021, p = 0.002, p = 0.005, p = 0.01, respectively). DAS 28 scores decreased in both exercise groups (p = 0.002; p = 0.0001, respectively), while isometrics showed a significant increase in dominant HS (p = 0.029), and isotonics showed a significant increase in non-dominant HS (p = 0.013). This study showed that isometric and isotonic hand exercises decrease pain and disease activity and improve hand functions
Application of a Bivariate Gamma Distribution for a Chemically Reacting Plume in the Atmosphere
NASA Astrophysics Data System (ADS)
Ferrero, Enrico; Mortarini, Luca; Alessandrini, Stefano; Lacagnina, Carlo
2013-04-01
The joint concentration probability density function of two reactive chemical species is modelled using a bivariate Gamma distribution coupled with a three-dimensional fluctuating plume model able to simulate the diffusion and mixing of turbulent plumes. A wind-tunnel experiment (Brown and Bilger, J Fluid Mech 312:373-407, 1996), carried out in homogeneous unbounded turbulence, in which nitrogen oxide is released from a point source in an ozone doped background and the chemical reactions take place in non-equilibrium conditions, is considered as a test case. The model is based on a stochastic Langevin equation reproducing the barycentre position distribution through a proper low-pass filter for the turbulence length scales. While the meandering large-scale motion of the plume is directly simulated, the internal mixing relative to the centroid is reproduced using a bivariate Gamma density function. The effect of turbulence on the chemical reaction (segregation), which in this case has not yet attained equilibrium, is directly evaluated through the covariance of the tracer concentration fields. The computed mean concentrations and the O3-NO concentration covariance are also compared with those obtained by the Alessandrini and Ferrero Lagrangian single particle model (Alessandrini and Ferrero, Physica A 388:1375-1387, 2009) that entails an ad hoc parametrization for the segregation coefficient.
Kipnis, Victor; Freedman, Laurence S.; Carroll, Raymond J.; Midthune, Douglas
2015-01-01
SUMMARY Semicontinuous data in the form of a mixture of a large portion of zero values and continuously distributed positive values frequently arise in many areas of biostatistics. This study is motivated by the analysis of relationships between disease outcomes and intakes of episodically consumed dietary components. An important aspect of studies in nutritional epidemiology is that true diet is unobservable and commonly evaluated by food frequency questionnaires with substantial measurement error. Following the regression calibration approach for measurement error correction, unknown individual intakes in the risk model are replaced by their conditional expectations given mismeasured intakes and other model covariates. Those regression calibration predictors are estimated using short-term unbiased reference measurements in a calibration substudy. Since dietary intakes are often “energy-adjusted”, e.g., by using ratios of the intake of interest to total energy intake, the correct estimation of the regression calibration predictor for each energy-adjusted episodically consumed dietary component requires modeling short-term reference measurements of the component (a semicontinuous variable) and energy (a continuous variable) simultaneously in a bivariate model. In this paper, we develop such a bivariate model, together with its application to regression calibration. We illustrate the new methodology using data from the NIH-AARP Diet and Health Study (Schatzkin et al., 2001, American Journal of Epidemiology 154, 1119–1125), and also evaluate its performance in a simulation study. PMID:26332011
Das, Kiranmoy; Daniels, Michael J
2014-03-01
Estimation of the covariance structure for irregular sparse longitudinal data has been studied by many authors in recent years but typically using fully parametric specifications. In addition, when data are collected from several groups over time, it is known that assuming the same or completely different covariance matrices over groups can lead to loss of efficiency and/or bias. Nonparametric approaches have been proposed for estimating the covariance matrix for regular univariate longitudinal data by sharing information across the groups under study. For the irregular case, with longitudinal measurements that are bivariate or multivariate, modeling becomes more difficult. In this article, to model bivariate sparse longitudinal data from several groups, we propose a flexible covariance structure via a novel matrix stick-breaking process for the residual covariance structure and a Dirichlet process mixture of normals for the random effects. Simulation studies are performed to investigate the effectiveness of the proposed approach over more traditional approaches. We also analyze a subset of Framingham Heart Study data to examine how the blood pressure trajectories and covariance structures differ for the patients from different BMI groups (high, medium, and low) at baseline. PMID:24400941
McCabe, E.R.B.; Towbin, J.A. ); Engh, G. van den; Trask, B.J. )
1992-12-01
Bivariate flow karyotyping was used to estimate the deletion sizes for a series of patients with Xp21 contiguous gene syndromes. The deletion estimates were used to develop an approximate scale for the genomic map in Xp21. The bivariate flow karyotype results were compared with clinical and molecular genetic information on the extent of the patients' deletions, and these various types of data were consistent. The resulting map spans >15 Mb, from the telomeric interval between DXS41 (99-6) and DXS68 (1-4) to a position centromeric to the ornithine transcarbamylase locus. The deletion sizing was considered to be accurate to [plus minus]1 Mb. The map provides information on the relative localization of genes and markers within this region. For example, the map suggests that the adrenal hypoplasia congenita and glycerol kinase genes are physically close to each other, are within 1-2 Mb of the telomeric end of the Duchenne muscular dystrophy (DMD) gene, and are nearer to the DMD locus than to the more distal marker DXS28 (C7). Information of this type is useful in developing genomic strategies for positional cloning in Xp21. These investigations demonstrate that the DNA from patients with Xp21 contiguous gene syndromes can be valuable reagents, not only for ordering loci and markers but also for providing an approximate scale to the map of the Xp21 region surrounding DMD. 44 refs., 3 figs.
Bützler, Jennifer; Vetter, Sebastian; Jochems, Nicole; Schlick, Christopher M
2012-01-01
On the basis of three empirical studies Fitts' Law was refined for bivariate pointing tasks on large touch screens. In the first study different target width parameters were investigated. The second study considered the effect of the motion angle. Based on the results of the two studies a refined model for movement time in human-computer interaction was formulated. A third study, which is described here in detail, concerns the validation of the refined model. For the validation study 20 subjects had to execute a bivariate pointing task on a large touch screen. In the experimental task 250 rectangular target objects were displayed at a randomly chosen position on the screen covering a broad range of ID values (ID= [1.01; 4.88]). Compared to existing refinements of Fitts' Law, the new model shows highest predictive validity. A promising field of application of the model is the ergonomic design and evaluation of project management software. By using the refined model, software designers can calculate a priori the appropriate angular position and the size of buttons, menus or icons. PMID:22317256
Pamidimukkala, Jaya; Jandhyala, Bhagavan S
2004-01-01
Obese Zucker rats (OZR) are hyperinsulenemic, hyperglycemic and dyslipidemic and develop salt dependent hypertension. Since salt sensitivity is considered to be due to impaired handling of renal sodium excretion, these studies were conducted in the obese and lean Zucker rats (LZR) anesthetized with Inactin to evaluate renal function under basal conditions and during acute isotonic fluid volume expansion (VE). Mean Arterial blood pressure (MBP), heart rate (HR), renal blood flow(RBF) and glomerular filtration rate (GFR) were not significantly different between the lean Zucker rats fed normal diet or that fed salt rich diet(8% NaCI). However, basal UV and UNaV were significantly greater in the LZR fed high salt. During VE essentially identical increases occurred in GFR, UV and UNaV in both the lean groups. In the OZR fed salt rich diet also, there were no significant changes in the heart rate, RBF and GFR. However, arterial blood pressure of the OZR fed salt rich diet was significantly greater than that of the OZR on the normal diet as well as that of both the lean groups. Also, as in the LZR, basal UV and UNaV were significantly greater in the salt fed obese rats. During volume expansion there were no impairments in the ability of the obese groups fed normal or salt rich diet to eliminate sodium and water during volume load. In fact, the net sodium and water excretions during and 60 min after VE in both the obese groups were significantly greater than that of corresponding lean groups. Furthermore, these values in the OZR fed salt rich diet were significantly greater than that of the obese rats on normal salt diet perhaps due to the contribution of pressure natriuretic mechanisms'. These data demonstrate that although OZR are salt sensitive, the renal mechanisms that would collectively respond to acute isotonic VE were fully functional. An unexpected and a novel finding in these studies is that the salt rich diet, in addition to increasing arterial blood pressure
Cosmic statistics of statistics
NASA Astrophysics Data System (ADS)
Szapudi, István; Colombi, Stéphane; Bernardeau, Francis
1999-12-01
The errors on statistics measured in finite galaxy catalogues are exhaustively investigated. The theory of errors on factorial moments by Szapudi & Colombi is applied to cumulants via a series expansion method. All results are subsequently extended to the weakly non-linear regime. Together with previous investigations this yields an analytic theory of the errors for moments and connected moments of counts in cells from highly non-linear to weakly non-linear scales. For non-linear functions of unbiased estimators, such as the cumulants, the phenomenon of cosmic bias is identified and computed. Since it is subdued by the cosmic errors in the range of applicability of the theory, correction for it is inconsequential. In addition, the method of Colombi, Szapudi & Szalay concerning sampling effects is generalized, adapting the theory for inhomogeneous galaxy catalogues. While previous work focused on the variance only, the present article calculates the cross-correlations between moments and connected moments as well for a statistically complete description. The final analytic formulae representing the full theory are explicit but somewhat complicated. Therefore we have made available a fortran program capable of calculating the described quantities numerically (for further details e-mail SC at colombi@iap.fr). An important special case is the evaluation of the errors on the two-point correlation function, for which this should be more accurate than any method put forward previously. This tool will be immensely useful in the future for assessing the precision of measurements from existing catalogues, as well as aiding the design of new galaxy surveys. To illustrate the applicability of the results and to explore the numerical aspects of the theory qualitatively and quantitatively, the errors and cross-correlations are predicted under a wide range of assumptions for the future Sloan Digital Sky Survey. The principal results concerning the cumulants ξ, Q3 and Q4 is that
NASA Astrophysics Data System (ADS)
Speich, Matthias J. R.; Bernhard, Luzi; Teuling, Adriaan J.; Zappa, Massimiliano
2015-04-01
Hydrological classification schemes are important tools for assessing the impacts of a changing climate on the hydrology of a region. In this paper, we present bivariate mapping as a simple means of classifying hydrological data for a quantitative and qualitative assessment of temporal change. Bivariate mapping consists of classifying map objects into discrete classes based on the values of two variables. We demonstrate the application of bivariate mapping to distributed hydro-climatic model outputs for the whole of Switzerland with a cell size of 200 m and compared the resulting bivariate maps with an existing classification of Swiss river regimes. The effects of scale were investigated by comparing these raster maps with a map showing the same variables aggregated to sub-basins with a mean area of 40 km2. Finally, maps of the current state were compared with predictions for future periods based on various model chains and greenhouse gas emission scenarios. For the map comparisons, four measures of association and two measures of agreement were used. Of all the variable pairs tested, a bivariate map combining runoff and snowmelt contribution to runoff obtained the highest similarity scores with the map of river regimes, which suggests a strong link between the combination of these variables and intra-annual streamflow variations. Also, this classification offers new insights, as it includes absolute values of runoff, which are often ignored in classification schemes. Comparing current-state maps with future predictions indicated that the magnitude of change is reflected in the patterns of bivariate maps, with lower agreement scores for predictions further away in time or when higher greenhouse gas emissions are assumed. Furthermore, a visualization of the spatial distribution of agreement scores allows a qualitative assessment of the magnitude of change for different regions, and an analysis of the differences in spatial patterns of predictions based on different
Reinking, Mark F.; Rauh, Mitchell J.
2012-01-01
Purpose: The purpose of this study was to examine the relationships between isotonic ankle plantar flexor endurance (PFE), foot pronation as measured by navicular drop, and exercise-related leg pain (ERLP). Background: Exercise-related leg pain is a common occurrence in competitive and recreational runners. The identification of factors contributing to the development of ERLP may help guide methods for the prevention and management of overuse injuries. Methods: Seventy-seven (44 males, 33 females) competitive runners from five collegiate cross-country (XC) teams consented to participate in the study. Isotonic ankle PFE and foot pronation were measured using the standing heel-rise and navicular drop (ND) tests, respectively. Demographic information, anthropometric measurements, and ERLP history were also recorded. Subjects were then prospectively tracked for occurrence of ERLP during the 2009 intercollegiate cross-country season. Multivariate logistic regression analysis was used to examine the relationships between isotonic ankle joint PFE and ND and the occurrence of ERLP. Results: While no significant differences were identified for isotonic ankle PFE between groups of collegiate XC runners with and without ERLP, runners with a ND >10 mm were almost 7 times (OR=6.6, 95% CI=1.2–38.0) more likely to incur medial ERLP than runners with ND <10 mm. Runners with a history of ERLP in the month previous to the start of the XC season were 12 times (OR=12.3, 95% CI=3.1–48.9) more likely to develop an in-season occurrence of ERLP. Conclusion: While PFE did not appear to be a risk factor in the development of ERLP in this group of collegiate XC runners, those with a ND greater than 10 mm may be at greater odds of incurring medial ERLP. Level of Evidence: 2b. PMID:22666641
Bayesian neural networks for bivariate binary data: an application to prostate cancer study.
Chakraborty, Sounak; Ghosh, Malay; Maiti, Tapabrata; Tewari, Ashutosh
2005-12-15
Prostate cancer is one of the most common cancers in American men. The cancer could either be locally confined, or it could spread outside the organ. When locally confined, there are several options for treating and curing this disease. Otherwise, surgery is the only option, and in extreme cases of outside spread, it could very easily recur within a short time even after surgery and subsequent radiation therapy. Hence, it is important to know, based on pre-surgery biopsy results how likely the cancer is organ-confined or not. The paper considers a hierarchical Bayesian neural network approach for posterior prediction probabilities of certain features indicative of non-organ confined prostate cancer. In particular, we find such probabilities for margin positivity (MP) and seminal vesicle (SV) positivity jointly. The available training set consists of bivariate binary outcomes indicating the presence or absence of the two. In addition, we have certain covariates such as prostate specific antigen (PSA), gleason score and the indicator for the cancer to be unilateral or bilateral (i.e. spread on one or both sides) in one data set and gene expression microarrays in another data set. We take a hierarchical Bayesian neural network approach to find the posterior prediction probabilities for a test and validation set, and compare these with the actual outcomes for the first data set. In case of the microarray data we use leave one out cross-validation to access the accuracy of our method. We also demonstrate the superiority of our method to the other competing methods through a simulation study. The Bayesian procedure is implemented by an application of the Markov chain Monte Carlo numerical integration technique. For the problem at hand, our Bayesian bivariate neural network procedure is shown to be superior to the classical neural network, Radford Neal's Bayesian neural network as well as bivariate logistic models to predict jointly the MP and SV in a patient in both the
NASA Technical Reports Server (NTRS)
Greenleaf, J. E.; Bernauer, E. M.; Ertl, A. C.; Bulbulian, R.; Bond, M.
1994-01-01
The purpose of our study was to determine if an intensive, intermittent, isokinetic, lower extremity exercise training program would attenuate or eliminate the decrease of muscular strength and endurance during prolonged bed rest (BR). The 19 male subjects (36 +/- 1 yr, 178 +/- 2 cm, 76.5 +/- 1.7 kg) were allocated into a no exercise (NOE) training group (N = 5), an isotonic (lower extremity cycle ergometer) exercise (ITE) training group (N = 7), and an isokinetic (isokinetic knee flexion-extension) exercise (IKE) training group (N = 7). Peak knee (flexion and extension) and shoulder (abduction-adduction) functions were measured weekly in all groups with one 5-repetition set. After BR, average knee extension total work decreased by 16% with NOE, increased by 27% with IKE, and was unchanged with ITE. Average knee flexion total work and peak torque (strength) responses were unchanged in all groups. Force production increased by 20% with IKE and was unchanged with NOE and ITE. Shoulder total work was unchanged in all groups, while gross average peak torque increased by 27% with ITE and by 22% with IKE, and was unchanged with NOE. Thus, while ITE training can maintain some isokinetic functions during BR, maximal intermittent IKE training can increase other functions above pre-BR control levels.
NASA Technical Reports Server (NTRS)
Greenleaf, J. E.; Bernauer, E. M.; Ertl, A. C.; Bond, M.; Bulbulian, R.
1994-01-01
The purpose of our study was to determine if an intensive, intermittent, isokinetic, lower extremity exercise training program would attenuate or eliminate the decrease of muscular strength and endurance during prolonged bed rest (BR). The 19 male subjects (36 +/- 1 yr, 178 +/- 2 cm, 76.5 +/- 1.7 kg) were allocated into a no exercise (NOE) training group (N = 5), an isotonic (lower extremity cycle orgometer) exercise (ITE) training group (N = 7), and an isokinetic (isokinetic knee flexion-extension) exercise (IKE) training group (N = 7). Peak knee (flexion and extension) and shoulder (abduction-adduction) functions were measured weekly in all groups with one 5-repetition set. After BR, average knee extension total work decreased by 16% with NOE, increased by 27% with IKE, and was unchanged with ITE. Average knee flexion total work and peak torque (strength) responses were unchanged in all groups. Force production increased by 20% with IKE and was unchanged with NOE and ITE. Shoulder total work was unchanged in all groups, while gross average peak torque increased by 27% with ITE and by 22% with IKE, and was unchanged with NOE. Thus, while ITE training can maintain some isokinetic functions during BR, maximal intermittent IKE training can increase other functions above pre-BR control levels.
NASA Technical Reports Server (NTRS)
Greenleaf, J. E.; Starr, J. C.; Van Beaumont, W.; Convertino, V. A.
1983-01-01
Measurements of maximal grip strength and endurance at 40 percent max strength were obtained for 7 men 19-21 years of age, 1-2 days before and on the first recovery day during three 2-week bedrest (BR) periods, each separated by a 3-week ambulatory recovery period. The subjects performed isometric exercise (IME) for 1 hr/day, isotonic exercise (ITE) for 1 hr/day, and no exercise (NOE) in the three BR periods. It was found that the mean maximal grip strength was unchanged after all three BR periods. Mean grip endurance was found to be unchanged after IME and ITE training, but was significantly reduced after NOE. These results indicate that IME and ITE training during BR do not increase or decrease maximal grip strength, alghough they prevent loss of grip endurance, while the maximal strength of all other major muscle groups decreases in proportion to the length of BR to 70 days. The maximal strength reduction of the large muscle groups was found to be about twice that of the small muscle groups during BR. In addition, it is shown that changes in maximal strength after spaceflight, BR, or water immersion deconditioning cannot be predicted from changes in submaximal or maximal oxygen uptake values.
Oh, Won Sup; Chon, Sung-Bin
2016-05-01
Fluid resuscitation, hemostasis, and transfusion is essential in care of hemorrhagic shock. Although estimation of the residual blood volume is crucial, the standard measuring methods are impractical or unsafe. Vital signs, central venous or pulmonary artery pressures are inaccurate. We hypothesized that the residual blood volume for acute, non-ongoing hemorrhage was calculable using serial hematocrit measurements and the volume of isotonic solution infused. Blood volume is the sum of volumes of red blood cells and plasma. For acute, non-ongoing hemorrhage, red blood cell volume would not change. A certain portion of the isotonic fluid would increase plasma volume. Mathematically, we suggest that the residual blood volume after acute, non-ongoing hemorrhage might be calculated as 0·25N/[(Hct1/Hct2)-1], where Hct1 and Hct2 are the initial and subsequent hematocrits, respectively, and N is the volume of isotonic solution infused. In vivo validation and modification is needed before clinical application of this model. PMID:27134507
NASA Astrophysics Data System (ADS)
Yang, Qiong; Wang, Hua-Lei; Chai, Qing-Zhen; Liu, Min-Liang
2015-09-01
Total Routhian surface (TRS) calculations for even-even N = 76 isotones with 54 ≤ Z ≤ 68 have been performed in three-dimensional (β2, γ, β4) deformation space. Calculated results of the equilibrium deformations are presented and compared with other theoretical predictions and available experimental data. The behavior of collective angular momentum shows the neutron rotation-alignment is preferred in the lighter N = 76 isotones, while for the heavier ones the proton alignment is favored. Moreover, multi-pair nucleon alignments and their competition (e.g., in 144Er) are predicted. It is pointed out that these nuclei in the N = 76 isotonic chain exhibit triaxiality or γ softness in high-spin states as well as ground states. Based on deformation-energy curves with respect to axial and non-axial quadrupole deformations, the shape instabilities are evaluated in detail and predicted, particularly in γ direction. Such instabilities are also supported by the odd- and even-spin level staggering of the observed γ bands, which is usually used to distinguish between γ-rigid and γ7-soft asymmetry. Supported by National Natural Science Foundation of China (10805040, 11175217), Foundation and Advanced Technology Research Program of Henan Province(132300410125), S & T Research Key Program of Henan Province Education Department (13A140667)
2016-01-01
Fluid resuscitation, hemostasis, and transfusion is essential in care of hemorrhagic shock. Although estimation of the residual blood volume is crucial, the standard measuring methods are impractical or unsafe. Vital signs, central venous or pulmonary artery pressures are inaccurate. We hypothesized that the residual blood volume for acute, non-ongoing hemorrhage was calculable using serial hematocrit measurements and the volume of isotonic solution infused. Blood volume is the sum of volumes of red blood cells and plasma. For acute, non-ongoing hemorrhage, red blood cell volume would not change. A certain portion of the isotonic fluid would increase plasma volume. Mathematically, we suggest that the residual blood volume after acute, non-ongoing hemorrhage might be calculated as 0·25N/[(Hct1/Hct2)–1], where Hct1 and Hct2 are the initial and subsequent hematocrits, respectively, and N is the volume of isotonic solution infused. In vivo validation and modification is needed before clinical application of this model. PMID:27134507
Nomogram for Obtaining Z-Test Statistic from Kendall's S and Sample Size 10 to 50.
ERIC Educational Resources Information Center
Graney, Marshall J.
1979-01-01
Kendall's S is often used for measuring magnitude of bivariate association in social and behavioral research. This nomogram permits a research analyst to make rapid and accurate evaluation of the statistical significance of S without recourse to formulae or computations in all except borderline cases. (Author/CTM)
Modeling the Growth of Students' Covariational Reasoning during an Introductory Statistics Course
ERIC Educational Resources Information Center
Zieffler, Andrew S.; Garfield, Joan B.
2009-01-01
This study examined students' development of reasoning about quantitative bivariate data during a one-semester university-level introductory statistics course. There were three research questions of interest: (1) What is the nature, or pattern of change in students' development in reasoning throughout the course?; (2) Is the sequencing of…
Akdur, Hülya; Yigit, Zerrin; Arabaci, Umit; Polat, Mine Gülden; Gürses, Hülya Nilgün; Güzelsoy, Deniz
2002-11-01
The aim of the present study was to evaluate the tolerance to various exercises by determining the cardiovascular response to static and dynamic exercises in patients with nonvalvular atrial fibrillation. Fifty patients (mean age: 63.6 +/- 10.3 years; male: 25, female: 25) with chronic (more than one year) nonvalvular atrial fibrillation were included in the study. All patients underwent exercise tests, adjusted appropriately according to their symptoms, as dynamic exercise on a Marquette Case 15 device according to a modified Bruce protocol. Heart rate, and systolic and diastolic arterial pressures were measured at rest and at all stages of the exercise; and the heart rate-pressure products were evaluated. A handgrip test was also conducted as static exercise. The measurements were made before, at the 1st, 2nd and 3rd minutes, and in the recovery periods of the exercise. The percent values of the changes of the 1st, 2nd and 3rd minute measurements in relation to the initial values for both exercises were compared. In addition, the maximal responses to the exercise tests and the post exercise values were also compared. For statistical evaluations, the paired Student-t test was used. Heart rate and pressure-heart rate product values obtained at 1, 2, and 3 minutes during the treadmill exercise test were significantly high compared to the handgrip values (P < 0.0001). The arterial systolic and diastolic pressure values in the 1st minute were also significantly higher during the handgrip test (P = 0.0100 and P = 0.0320, respectively). The values of diastolic arterial pressure at the 2nd minute during the handgrip test, and systolic arterial pressure at the 3rd minute during the treadmill test were found to be statistically significant (P = 0.0240, P = 0.0340, respectively). The mean exercise time and MET value during the treadmill exercise test were 7.18 +/- 2.65 minutes and 5.32 +/- 1.38 mL.kg(-1) x dk(-1). respectively. During the recovery period, the 5th minute
Estimating the Correlation in Bivariate Normal Data with Known Variances and Small Sample Sizes1
Fosdick, Bailey K.; Raftery, Adrian E.
2013-01-01
We consider the problem of estimating the correlation in bivariate normal data when the means and variances are assumed known, with emphasis on the small sample case. We consider eight different estimators, several of them considered here for the first time in the literature. In a simulation study, we found that Bayesian estimators using the uniform and arc-sine priors outperformed several empirical and exact or approximate maximum likelihood estimators in small samples. The arc-sine prior did better for large values of the correlation. For testing whether the correlation is zero, we found that Bayesian hypothesis tests outperformed significance tests based on the empirical and exact or approximate maximum likelihood estimators considered in small samples, but that all tests performed similarly for sample size 50. These results lead us to suggest using the posterior mean with the arc-sine prior to estimate the correlation in small samples when the variances are assumed known. PMID:23378667
Tavlarides, Lawrence L.; Bae, Jae-Heum
1991-01-01
A laser capillary spectrophotometric technique measures real time or near real time bivariate drop size and concentration distribution for a reactive liquid-liquid dispersion system. The dispersion is drawn into a precision-bore glass capillary and an appropriate light source is used to distinguish the aqueous phase from slugs of the organic phase at two points along the capillary whose separation is precisely known. The suction velocity is measured, as is the length of each slug from which the drop free diameter is calculated. For each drop, the absorptivity at a given wavelength is related to the molar concentration of a solute of interest, and the concentration of given drops of the organic phase is derived from pulse heights of the detected light. This technique permits on-line monitoring and control of liquid-liquid dispersion processes.
Tavlarides, L.L.; Bae, J.H.
1991-12-24
A laser capillary spectrophotometric technique measures real time or near real time bivariate drop size and concentration distribution for a reactive liquid-liquid dispersion system. The dispersion is drawn into a precision-bore glass capillary and an appropriate light source is used to distinguish the aqueous phase from slugs of the organic phase at two points along the capillary whose separation is precisely known. The suction velocity is measured, as is the length of each slug from which the drop free diameter is calculated. For each drop, the absorptivity at a given wavelength is related to the molar concentration of a solute of interest, and the concentration of given drops of the organic phase is derived from pulse heights of the detected light. This technique permits on-line monitoring and control of liquid-liquid dispersion processes. 17 figures.
Motsa, S S; Magagula, V M; Sibanda, P
2014-01-01
This paper presents a new method for solving higher order nonlinear evolution partial differential equations (NPDEs). The method combines quasilinearisation, the Chebyshev spectral collocation method, and bivariate Lagrange interpolation. In this paper, we use the method to solve several nonlinear evolution equations, such as the modified KdV-Burgers equation, highly nonlinear modified KdV equation, Fisher's equation, Burgers-Fisher equation, Burgers-Huxley equation, and the Fitzhugh-Nagumo equation. The results are compared with known exact analytical solutions from literature to confirm accuracy, convergence, and effectiveness of the method. There is congruence between the numerical results and the exact solutions to a high order of accuracy. Tables were generated to present the order of accuracy of the method; convergence graphs to verify convergence of the method and error graphs are presented to show the excellent agreement between the results from this study and the known results from literature. PMID:25254252
Motsa, S. S.; Magagula, V. M.; Sibanda, P.
2014-01-01
This paper presents a new method for solving higher order nonlinear evolution partial differential equations (NPDEs). The method combines quasilinearisation, the Chebyshev spectral collocation method, and bivariate Lagrange interpolation. In this paper, we use the method to solve several nonlinear evolution equations, such as the modified KdV-Burgers equation, highly nonlinear modified KdV equation, Fisher's equation, Burgers-Fisher equation, Burgers-Huxley equation, and the Fitzhugh-Nagumo equation. The results are compared with known exact analytical solutions from literature to confirm accuracy, convergence, and effectiveness of the method. There is congruence between the numerical results and the exact solutions to a high order of accuracy. Tables were generated to present the order of accuracy of the method; convergence graphs to verify convergence of the method and error graphs are presented to show the excellent agreement between the results from this study and the known results from literature. PMID:25254252
A composite likelihood method for bivariate meta-analysis in diagnostic systematic reviews
Liu, Yulun; Ning, Jing; Nie, Lei; Zhu, Hongjian; Chu, Haitao
2014-01-01
Diagnostic systematic review is a vital step in the evaluation of diagnostic technologies. In many applications, it involves pooling pairs of sensitivity and specificity of a dichotomized diagnostic test from multiple studies. We propose a composite likelihood method for bivariate meta-analysis in diagnostic systematic reviews. This method provides an alternative way to make inference on diagnostic measures such as sensitivity, specificity, likelihood ratios and diagnostic odds ratio. Its main advantages over the standard likelihood method are the avoidance of the non-convergence problem, which is non-trivial when the number of studies are relatively small, the computational simplicity and some robustness to model mis-specifications. Simulation studies show that the composite likelihood method maintains high relative efficiency compared to that of the standard likelihood method. We illustrate our method in a diagnostic review of the performance of contemporary diagnostic imaging technologies for detecting metastases in patients with melanoma. PMID:25512146
Bayesian bivariate generalized Lindley model for survival data with a cure fraction.
Martinez, Edson Z; Achcar, Jorge A
2014-11-01
The cure fraction models have been widely used to analyze survival data in which a proportion of the individuals is not susceptible to the event of interest. In this article, we introduce a bivariate model for survival data with a cure fraction based on the three-parameter generalized Lindley distribution. The joint distribution of the survival times is obtained by using copula functions. We consider three types of copula function models, the Farlie-Gumbel-Morgenstern (FGM), Clayton and Gumbel-Barnett copulas. The model is implemented under a Bayesian framework, where the parameter estimation is based on Markov Chain Monte Carlo (MCMC) techniques. To illustrate the utility of the model, we consider an application to a real data set related to an invasive cervical cancer study. PMID:25123102
On the joint spectral density of bivariate random sequences. Thesis Technical Report No. 21
NASA Technical Reports Server (NTRS)
Aalfs, David D.
1995-01-01
For univariate random sequences, the power spectral density acts like a probability density function of the frequencies present in the sequence. This dissertation extends that concept to bivariate random sequences. For this purpose, a function called the joint spectral density is defined that represents a joint probability weighing of the frequency content of pairs of random sequences. Given a pair of random sequences, the joint spectral density is not uniquely determined in the absence of any constraints. Two approaches to constraining the sequences are suggested: (1) assume the sequences are the margins of some stationary random field, (2) assume the sequences conform to a particular model that is linked to the joint spectral density. For both approaches, the properties of the resulting sequences are investigated in some detail, and simulation is used to corroborate theoretical results. It is concluded that under either of these two constraints, the joint spectral density can be computed from the non-stationary cross-correlation.
NASA Astrophysics Data System (ADS)
Requena, Ana; Prosdocimi, Ilaria; Kjeldsen, Thomas R.; Mediero, Luis
2014-05-01
Flood frequency analyses based on stationary assumptions are usually employed for estimating design floods. However, more complex non-stationarity approaches are trying to be incorporated with the aim of improving such estimates. In this study, the effect of changing urbanisation on maximum flood peak (Q) and volume (V) series is analysed. The potential changes in an urbanised catchment and in a nearby hydrologically similar rural catchment in northwest England are investigated. The urbanised catchment is characterised by a noticeable increase of the urbanisation level in time, while the rural catchment has not been altered by anthropogenic actions. Winter, summer and annual maximum flood events are studied. With the aim of analysing changes in time, two non-superimposed time-windows are defined covering the periods 1976-1992 and 1993-2008, respectively. A preliminary analysis of temporal trends in Q, V and Kendall's tau is visually done, being formal tested by a resampling procedure. Differences were found among winter, summer and annual maximum flood events. As annual maximum flood events are commonly used for designing purposes, the corresponding bivariate distribution (margins and copula) was obtained for the different time-windows. Trends regarding both time-windows were analysed by comparing bivariate return period curves in the Q-V space. Different behaviours were found depending on the catchment. As a result, the application of the proposed methodology provides useful information in describing changes in flood events, regarding different flood variables and their relationship. In addition, the methodology can inform practitioners on the potential changes connected with urbanisation for appropriate design flood estimation.
Knowles, Emma E. M.; McKay, D. Reese; Kent, Jack W.; Sprooten, Emma; Carless, Melanie A.; Curran, Joanne E.; de Almeida, Marcio A. A.; Dyer, Thomas D.; Göring, Harald H. H.; Olvera, Rene; Duggirala, Ravi; Fox, Peter; Almasy, Laura; Blangero, John; Glahn, David. C.
2014-01-01
The role of the amygdala in emotion recognition is well established and separately each trait has been shown to be highly heritable, but the potential role of common genetic influences on both traits has not been explored. Here we present an investigation of the pleiotropic influences of amygdala and emotion recognition in a sample of randomly selected, extended pedigrees (N = 858). Using a combination of univariate and bivariate linkage we found a pleiotropic region for amygdala and emotion recognition on 4q26 (LOD = 4.34). Association analysis conducted in the region underlying the bivariate linkage peak revealed a variant meeting the corrected significance level (pBonferroni = 5.01×10−05) within an intron of PDE5A (rs2622497, Χ2 =16.67, p = 4.4×10−05) as being jointly influential on both traits. PDE5A has been implicated previously in recognition-memory deficits and is expressed in subcortical structures that are thought to underlie memory ability including the amygdala. The present paper extends our understanding of the shared etiology between amygdala and emotion recognition by showing that the overlap between the two traits is due, at least in part, to common genetic influences. Moreover, the present paper identifies a pleiotropic locus for the two traits and an associated variant, which localizes the genetic signal even more precisely. These results, when taken in the context of previous research, highlight the potential utility of PDE5-inhibitors for ameliorating emotion-recognition deficits in populations including, but not exclusively, those individuals suffering from mental or neurodegenerative illness. PMID:25322361
A bivariate mixture model analysis of body weight and ascites traits in broilers.
Zerehdaran, S; van Grevehof, E M; van der Waaij, E H; Bovenhuis, H
2006-01-01
The objective of the present study was to use bivariate mixture models to study the relationships between body weight (BW) and ascites indicator traits. Existing data were used from an experiment in which birds were housed in 2 groups under different climate conditions. In the first group, BW, the ratio of right ventricular weight to total ventricular weight (RV:TV), and hematocrit value (HCT) were measured in 4,202 broilers under cold conditions; in the second group, the same traits were measured in 795 birds under normal temperature conditions. Cold-stress conditions were applied to identify individuals that were susceptible to ascites. The RV:TV and HCT were approximately normally distributed under normal temperature conditions, whereas the distributions of these traits were skewed under cold temperature conditions, suggesting different underlying distributions. Fitting a bivariate mixture model to the observations showed that there was only one homogeneous population for ascites traits under normal temperature conditions, whereas there was a mixture of (2) distributions under cold conditions. One distribution contained nonascitic birds and the other distribution contained ascitic birds. In the distribution of nonascitic birds, the inferred phenotypic correlations (phenotypic correlations with 2 distinguishing underlying distributions) of BW with RV:TV and HCT were close to zero (0.10 and -0.07, respectively), whereas in the distribution of ascitic birds, the inferred phenotypic correlations of BW with RV:TV and HCT were negative (-0.39 and -0.4, respectively). The negative inferred correlations of BW with RV:TV and HCT in the distribution of ascitic birds resulted in negative overall correlations (correlations without 2 distinguishing distributions) of BW with RV:TV (-0.30) and HCT (-0.37) under cold conditions. The present results indicate that the overall correlations between BW and ascites traits are dependent on the relative frequency of ascitic and
Shi, Runhua; McLarty, Jerry W
2009-10-01
In this article, we introduced basic concepts of statistics, type of distributions, and descriptive statistics. A few examples were also provided. The basic concepts presented herein are only a fraction of the concepts related to descriptive statistics. Also, there are many commonly used distributions not presented herein, such as Poisson distributions for rare events and exponential distributions, F distributions, and logistic distributions. More information can be found in many statistics books and publications. PMID:19891281
ERIC Educational Resources Information Center
Petocz, Peter; Sowey, Eric
2008-01-01
As a branch of knowledge, Statistics is ubiquitous and its applications can be found in (almost) every field of human endeavour. In this article, the authors track down the possible source of the link between the "Siren song" and applications of Statistics. Answers to their previous five questions and five new questions on Statistics are presented.
ERIC Educational Resources Information Center
Callamaras, Peter
1983-01-01
This buyer's guide to seven major types of statistics software packages for microcomputers reviews Edu-Ware Statistics 3.0; Financial Planning; Speed Stat; Statistics with DAISY; Human Systems Dynamics package of Stats Plus, ANOVA II, and REGRESS II; Maxistat; and Moore-Barnes' MBC Test Construction and MBC Correlation. (MBR)
ERIC Educational Resources Information Center
Meyer, Donald L.
Bayesian statistical methodology and its possible uses in the behavioral sciences are discussed in relation to the solution of problems in both the use and teaching of fundamental statistical methods, including confidence intervals, significance tests, and sampling. The Bayesian model explains these statistical methods and offers a consistent…
NASA Technical Reports Server (NTRS)
Bernauer, E. M.; Walby, W. F.; Ertl, A. C.; Dempster, P. T.; Bond, M.; Greenleaf, J. E.
1994-01-01
To determine if daily isotonic exercise or isokinetic exercise training coupled with daily log proprioceptive training, would influence log proprioceptive tracking responses during Bed Rest (BR), 19 men (36 +/- SD 4 years, 178 +/- 7 cm, 76.8 +/- 7.8 kg) were allocated into a NO-Exercise (NOE) training control group (n = 5), and IsoTanic Exercise (ITE, n = 7) and IsoKinetic Exercise (IKE, n = 7) training groups. Exercise training was conducted during BR for two 30-min period / d, 5 d /week. Only the IKE group performed proprioceptive training using a now isokinetic procedure with each lower extremity for 2.5 min before and after the daily exercise training sessions; proprioceptive testing occurred weekly for all groups. There were no significant differences in proprioceptive tracking scores, expressed as a percentage of the perfect score of 100, in the pro-BR ambulatory control period between the three groups. Knee extension and flexion tracking responses were unchanged with NOE during BR, but were significantly greater (*p less than 0.05) at the end of BR in both exercise groups when compared with NOE responses (extension: NOE 80.7 +/- 0.7%, ITE 82.9 +/- 0.6%, IKE 86.5* +/- 0.7%; flexion: NOE 77.6 +/- 1.50, ITE 80.0 +/- 0.8% (NS), IKE 83.6* +/- 0.8%). Although proprioceptive tracking was unchanged during BR with NOE, both lsotonic exercise training (without additional propriaceptive training) and especially isokinetic exercise training when combined with daily proprioceptive training, significantly improved knee proprioceptive tracking responses after 30 d of BR.
NASA Technical Reports Server (NTRS)
Greenleaf, J. E.; Lee, P. L.; Ellis, S.; Selzer, R. H.; Ortendahl, D. A.
1994-01-01
Magnetic resonance imaging (MRI) was used to compare the effect of two modes of lower-extremity exercise training on the mass (volume) of posterior leg group (PLG) muscles (soleus, flexor hallucis longus, tibialis posterior, lateral and medial gastrocnemius, and flexor digitorum longus) on 19 men (ages 32-42 years) subjected to intense dynamic-isotonic (ITE, cycle ergometer, number of subjects (N) = 7), isokinetic (IKE, torque egrometer, N = 7), and no exercise (NOE, N = 5) training for 60 min/day during head-down bed rest (HDBR). Total volume of the PLG muscles decreased (p less than 0.05) similarly: ITE = 4.3 +/- SE 1.6%, IKE = 7.7 +/- 1.6%, and NOE = 6.3 +/- 0.8%; combined volume (N = 19) loss was 6.1 +/- 0.9%. Ranges of volume changes were 2.6% to -9.0% (ITE), -2.1% to -14.9% (IKE), and -3.4% to -8/1% (NOE). Correlation coefficients (r) of muscle volume versus thickness measured with ultrasonography were: ITE r + 0.79 (p less than 0.05), IKE r = 0.27 (not significant (NS)), and NOE r = 0.63 (NS). Leg-muscle volume and thickness were highly correlated (r = 0.79) when plasma volume was maintained during HDBR with ITE. Thus, neither intensive lower extremity ITE nor IKE training influence the normal non-exercised posterior leg muscle atrophy during HDBR. The relationship of muscle volume and thickness may depend on the mode of exercise training associated with the maintenance of plasma volume.
NASA Technical Reports Server (NTRS)
Fitts, R. H.; Hurst, J. E.; Norenberg, K. M.; Widrick, J. J.; Riley, D. A.; Bain, J. L. W.; Trappe, S. W.; Trappe, T. A.; Costill, D. L.
1999-01-01
Exposure to microgravity or models designed to mimic the unloaded condition, such as bed rest in humans and hindlimb unloading (HU) in rats leads to skeletal muscle atrophy, a loss in peak force and power, and an increased susceptibility to fatigue. The posterior compartment muscles of the lower leg (calf muscle group) appear to be particularly susceptible. Following only 1 wk in space or HU, rat soleus muscle showed a 30 to 40% loss in wet weight. After 3 wk of HU, almost all of the atrophied soleus fibers showed a significant increase in maximal shortening velocity (V(sub 0)), while only 25 to 30 % actually transitioned to fast fibers. The increased V(sub 0), was protective in that it reduced the decline in peak power associated with the reduced peak force. When the soleus is stimulated in situ following HU or zero-g one observes an increased rate and extent of fatigue, and in the former the increased fatigue is associated with a more rapid depletion of muscle glycogen and lactate production. Our working hypothesis is that following HU or spaceflight in rats and bed rest or spaceflight in humans limb skeletal muscles during contractile activity depend more on carbohydrates and less on fatty acids for their substrate supply. Baldwin et al. found 9 days of spaceflight to reduce by 37% the ability of both the high and low oxidative regions of the vastus muscle to oxidize long-chain fatty acids. This decline was not associated with any change in the enzymes of the tricarboxylic acid cycle or oxidation pathway. The purpose of the current research was to establish the extent of functional change in the slow type I and fast type H fibers of the human calf muscle following 17 days of spaceflight, and determine the cellular mechanisms of the observed changes. A second goal was to study the effectiveness of high resistance isotonic and isometric exercise in preventing the deleterious functional changes associated with unloading.
Petrovic, Igor; Hip, Ivan; Fredlund, Murray D
2016-09-01
The variability of untreated municipal solid waste (MSW) shear strength parameters, namely cohesion and shear friction angle, with respect to waste stability problems, is of primary concern due to the strong heterogeneity of MSW. A large number of municipal solid waste (MSW) shear strength parameters (friction angle and cohesion) were collected from published literature and analyzed. The basic statistical analysis has shown that the central tendency of both shear strength parameters fits reasonably well within the ranges of recommended values proposed by different authors. In addition, it was established that the correlation between shear friction angle and cohesion is not strong but it still remained significant. Through use of a distribution fitting method it was found that the shear friction angle could be adjusted to a normal probability density function while cohesion follows the log-normal density function. The continuous normal-lognormal bivariate density function was therefore selected as an adequate model to ascertain rational boundary values ("confidence interval") for MSW shear strength parameters. It was concluded that a curve with a 70% confidence level generates a "confidence interval" within the reasonable limits. With respect to the decomposition stage of the waste material, three different ranges of appropriate shear strength parameters were indicated. Defined parameters were then used as input parameters for an Alternative Point Estimated Method (APEM) stability analysis on a real case scenario of the Jakusevec landfill. The Jakusevec landfill is the disposal site of the capital of Croatia - Zagreb. The analysis shows that in the case of a dry landfill the most significant factor influencing the safety factor was the shear friction angle of old, decomposed waste material, while in the case of a landfill with significant leachate level the most significant factor influencing the safety factor was the cohesion of old, decomposed waste material. The
NASA Astrophysics Data System (ADS)
Subramaniyam, Narayan Puthanmadam; Hyttinen, Jari
2015-02-01
Recently Andrezejak et al. combined the randomness and nonlinear independence test with iterative amplitude adjusted Fourier transform (iAAFT) surrogates to distinguish between the dynamics of seizure-free intracranial electroencephalographic (EEG) signals recorded from epileptogenic (focal) and nonepileptogenic (nonfocal) brain areas of epileptic patients. However, stationarity is a part of the null hypothesis for iAAFT surrogates and thus nonstationarity can violate the null hypothesis. In this work we first propose the application of the randomness and nonlinear independence test based on recurrence network measures to distinguish between the dynamics of focal and nonfocal EEG signals. Furthermore, we combine these tests with both iAAFT and truncated Fourier transform (TFT) surrogate methods, which also preserves the nonstationarity of the original data in the surrogates along with its linear structure. Our results indicate that focal EEG signals exhibit an increased degree of structural complexity and interdependency compared to nonfocal EEG signals. In general, we find higher rejections for randomness and nonlinear independence tests for focal EEG signals compared to nonfocal EEG signals. In particular, the univariate recurrence network measures, the average clustering coefficient C and assortativity R , and the bivariate recurrence network measure, the average cross-clustering coefficient Ccross, can successfully distinguish between the focal and nonfocal EEG signals, even when the analysis is restricted to nonstationary signals, irrespective of the type of surrogates used. On the other hand, we find that the univariate recurrence network measures, the average path length L , and the average betweenness centrality BC fail to distinguish between the focal and nonfocal EEG signals when iAAFT surrogates are used. However, these two measures can distinguish between focal and nonfocal EEG signals when TFT surrogates are used for nonstationary signals. We also
NASA Astrophysics Data System (ADS)
Masud, M. B.; Khaliq, M. N.; Wheater, H. S.
2015-03-01
This study is focused on the Saskatchewan River Basin (SRB) that spans southern parts of Alberta, Saskatchewan and Manitoba, the three Prairie Provinces of Canada, where most of the country's agricultural activities are concentrated. The SRB is confronted with immense water-related challenges and is now one of the ten GEWEX (Global Energy and Water Exchanges) Regional Hydroclimate Projects in the world. In the past, various multi-year droughts have been observed in this part of Canada that impacted agriculture, energy and socio-economic sectors. Therefore, proper understanding of the spatial and temporal characteristics of historical droughts is important for many water resources planning and management related activities across the basin. In the study, observed gridded data of daily precipitation and temperature and conventional univariate and copula-based bivariate frequency analyses are used to characterize drought events in terms of drought severity and duration on the basis of two drought indices, the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI). Within the framework of univariate and bivariate analyses, drought risk indicators are developed and mapped across the SRB to delineate the most vulnerable parts of the basin. Based on the results obtained, southern parts of the SRB (i.e., western part of the South Saskatchewan River, Seven Persons Creek and Bigstick Lake watersheds) are associated with a higher drought risk, while moderate risk is noted for the North Saskatchewan River (except its eastern parts), Red Deer River, Oldman River, Bow River, Sounding Creek, Carrot River and Battle River watersheds. Lower drought risk is found for the areas surrounding the Saskatchewan-Manitoba border (particularly, the Saskatchewan River watershed). It is also found that the areas characterized with higher drought severity are also associated with higher drought duration. A comparison of SPI- and SPEI
Omouessi, S T; Lemamy, G J; Kiki-Mvouaka, S; Fernette, B; Falconetti, C; Ndeboko, B; Mouecoucou, J; Thornton, S N
2016-02-01
In the course of exposure to fluid deprivation and heated environment, mammals regulate their hydromineral balance and body temperature by a number of mechanisms including sweating, water and salt intakes. Here we challenged obese Zucker rats, known to have a predisposition to hypertension, with 0.9%NaCl alone or with 2%NaCl solution + water to drink under fluid deprivation and heated conditions. Food and fluid intakes, body weight, diuresis and natriuresis were measured daily throughout. Serum aldosterone levels and Na(+) concentration were also analyzed. Data showed that obese and lean rats presented similar baseline measurements of food, 0.9%NaCl and fluid intakes, diuresis and fluid balance; whereas hypertonic 2%NaCl consumption was almost absent. Before and during fluid deprivation animals increased isotonic but not hypertonic NaCl intake; the obese showed significant increases in diuresis and Na(+) excretion, whereas, total fluid intake was similar between groups. Heat increased isotonic NaCl intake and doubled natriuresis in obese which were wet on their fur and displayed a paradoxical increase of fluid gain. Fluid deprivation plus heat produced similar negative fluid balance in all groups. Body weight losses, food intake and diuresis reductions were amplified under the combined conditions. Animals exposed to 2%NaCl showed higher circulating levels of aldosterone and obese were lower than leans. In animals which drank 0.9%NaCl, obese showed higher serum levels of Na(+) than leans. We conclude that in spite of their higher sensitivity to high salt and heat obese Zucker rats can control hydromineral balance in response to fluid deprivation and heat by adjusting isotonic NaCl preference with sodium balance and circulating levels of aldosterone. This suggests a key hormonal role in the mechanisms underlying thermoregulation, body fluid homeostasis and sodium intake. PMID:26621332
Kogalovskii, M.R.
1995-03-01
This paper presents a review of problems related to statistical database systems, which are wide-spread in various fields of activity. Statistical databases (SDB) are referred to as databases that consist of data and are used for statistical analysis. Topics under consideration are: SDB peculiarities, properties of data models adequate for SDB requirements, metadata functions, null-value problems, SDB compromise protection problems, stored data compression techniques, and statistical data representation means. Also examined is whether the present Database Management Systems (DBMS) satisfy the SDB requirements. Some actual research directions in SDB systems are considered.
Smith, Alwyn
1969-01-01
This paper is based on an analysis of questionnaires sent to the health ministries of Member States of WHO asking for information about the extent, nature, and scope of morbidity statistical information. It is clear that most countries collect some statistics of morbidity and many countries collect extensive data. However, few countries relate their collection to the needs of health administrators for information, and many countries collect statistics principally for publication in annual volumes which may appear anything up to 3 years after the year to which they refer. The desiderata of morbidity statistics may be summarized as reliability, representativeness, and relevance to current health problems. PMID:5306722
A Basic Bivariate Structure of Personality Attributes Evident Across Nine Languages.
Saucier, Gerard; Thalmayer, Amber Gayle; Payne, Doris L; Carlson, Robert; Sanogo, Lamine; Ole-Kotikash, Leonard; Church, A Timothy; Katigbak, Marcia S; Somer, Oya; Szarota, Piotr; Szirmák, Zsofia; Zhou, Xinyue
2013-01-01
Here, two studies seek to characterize a parsimonious common-denominator personality structure with optimal cross-cultural replicability. Personality differences are observed in all human populations and cultures, but lexicons for personality attributes contain so many distinctions that parsimony is lacking. Models stipulating the most important attributes have been formulated by experts or by empirical studies drawing on experience in a very limited range of cultures. Factor analyses of personality lexicons of nine languages of diverse provenance (Chinese, Korean, Filipino, Turkish, Greek, Polish, Hungarian, Maasai, and Senoufo) were examined, and their common structure was compared to that of several prominent models in psychology. A parsimonious bivariate model showed evidence of substantial convergence and ubiquity across cultures. Analyses involving key markers of these dimensions in English indicate that they are broad dimensions involving the overlapping content of the interpersonal circumplex, models of communion and agency, and morality/warmth and competence. These "Big Two" dimensions-Social Self-Regulation and Dynamism-provide a common-denominator model involving the two most crucial axes of personality variation, ubiquitous across cultures. The Big Two might serve as an umbrella model serving to link diverse theoretical models and associated research literatures. PMID:23301793
IDF relationships using bivariate copula for storm events in Peninsular Malaysia
NASA Astrophysics Data System (ADS)
Ariff, N. M.; Jemain, A. A.; Ibrahim, K.; Wan Zin, W. Z.
2012-11-01
SummaryIntensity-duration-frequency (IDF) curves are used in many hydrologic designs for the purpose of water managements and flood preventions. The IDF curves available in Malaysia are those obtained from univariate analysis approach which only considers the intensity of rainfalls at fixed time intervals. As several rainfall variables are correlated with each other such as intensity and duration, this paper aims to derive IDF points for storm events in Peninsular Malaysia by means of bivariate frequency analysis. This is achieved through utilizing the relationship between storm intensities and durations using the copula method. Four types of copulas; namely the Ali-Mikhail-Haq (AMH), Frank, Gaussian and Farlie-Gumbel-Morgenstern (FGM) copulas are considered because the correlation between storm intensity, I, and duration, D, are negative and these copulas are appropriate when the relationship between the variables are negative. The correlations are attained by means of Kendall's τ estimation. The analysis was performed on twenty rainfall stations with hourly data across Peninsular Malaysia. Using Akaike's Information Criteria (AIC) for testing goodness-of-fit, both Frank and Gaussian copulas are found to be suitable to represent the relationship between I and D. The IDF points found by the copula method are compared to the IDF curves yielded based on the typical IDF empirical formula of the univariate approach. This study indicates that storm intensities obtained from both methods are in agreement with each other for any given storm duration and for various return periods.
Ayuso, Mercedes; Bermúdez, Lluís; Santolino, Miguel
2016-04-01
The analysis of factors influencing the severity of the personal injuries suffered by victims of motor accidents is an issue of major interest. Yet, most of the extant literature has tended to address this question by focusing on either the severity of temporary disability or the severity of permanent injury. In this paper, a bivariate copula-based regression model for temporary disability and permanent injury severities is introduced for the joint analysis of the relationship with the set of factors that might influence both categories of injury. Using a motor insurance database with 21,361 observations, the copula-based regression model is shown to give a better performance than that of a model based on the assumption of independence. The inclusion of the dependence structure in the analysis has a higher impact on the variance estimates of the injury severities than it does on the point estimates. By taking into account the dependence between temporary and permanent severities a more extensive factor analysis can be conducted. We illustrate that the conditional distribution functions of injury severities may be estimated, thus, providing decision makers with valuable information. PMID:26871615
Arab, Ali; Holan, Scott H.; Wikle, Christopher K.; Wildhaber, Mark L.
2012-01-01
Ecological studies involving counts of abundance, presence–absence or occupancy rates often produce data having a substantial proportion of zeros. Furthermore, these types of processes are typically multivariate and only adequately described by complex nonlinear relationships involving externally measured covariates. Ignoring these aspects of the data and implementing standard approaches can lead to models that fail to provide adequate scientific understanding of the underlying ecological processes, possibly resulting in a loss of inferential power. One method of dealing with data having excess zeros is to consider the class of univariate zero-inflated generalized linear models. However, this class of models fails to address the multivariate and nonlinear aspects associated with the data usually encountered in practice. Therefore, we propose a semiparametric bivariate zero-inflated Poisson model that takes into account both of these data attributes. The general modeling framework is hierarchical Bayes and is suitable for a broad range of applications. We demonstrate the effectiveness of our model through a motivating example on modeling catch per unit area for multiple species using data from the Missouri River Benthic Fishes Study, implemented by the United States Geological Survey.
Cheng, Xiaoya; Shaw, Stephen B; Marjerison, Rebecca D; Yearick, Christopher D; DeGloria, Stephen D; Walter, M Todd
2014-05-01
Predicting runoff producing areas and their corresponding risks of generating storm runoff is important for developing watershed management strategies to mitigate non-point source pollution. However, few methods for making these predictions have been proposed, especially operational approaches that would be useful in areas where variable source area (VSA) hydrology dominates storm runoff. The objective of this study is to develop a simple approach to estimate spatially-distributed risks of runoff production. By considering the development of overland flow as a bivariate process, we incorporated both rainfall and antecedent soil moisture conditions into a method for predicting VSAs based on the Natural Resource Conservation Service-Curve Number equation. We used base-flow immediately preceding storm events as an index of antecedent soil wetness status. Using nine sub-basins of the Upper Susquehanna River Basin, we demonstrated that our estimated runoff volumes and extent of VSAs agreed with observations. We further demonstrated a method for mapping these areas in a Geographic Information System using a Soil Topographic Index. The proposed methodology provides a new tool for watershed planners for quantifying runoff risks across watersheds, which can be used to target water quality protection strategies. PMID:24632403