A method of statistical analysis in the field of sports science when assumptions of parametric tests are not violated

Directory of Open Access Journals (Sweden)

Elżbieta Sandurska

2016-12-01

Full Text Available Introduction: Application of statistical software typically does not require extensive statistical knowledge, allowing to easily perform even complex analyses. Consequently, test selection criteria and important assumptions may be easily overlooked or given insufficient consideration. In such cases, the results may likely lead to wrong conclusions. Aim: To discuss issues related to assumption violations in the case of Student's t-test and one-way ANOVA, two parametric tests frequently used in the field of sports science, and to recommend solutions. Description of the state of knowledge: Student's t-test and ANOVA are parametric tests, and therefore some of the assumptions that need to be satisfied include normal distribution of the data and homogeneity of variances in groups. If the assumptions are violated, the original design of the test is impaired, and the test may then be compromised giving spurious results. A simple method to normalize the data and to stabilize the variance is to use transformations. If such approach fails, a good alternative to consider is a nonparametric test, such as Mann-Whitney, the Kruskal-Wallis or Wilcoxon signed-rank tests. Summary: Thorough verification of the parametric tests assumptions allows for correct selection of statistical tools, which is the basis of well-grounded statistical analysis. With a few simple rules, testing patterns in the data characteristic for the study of sports science comes down to a straightforward procedure.

Statistical trend analysis methods for temporal phenomena

Energy Technology Data Exchange (ETDEWEB)

Lehtinen, E.; Pulkkinen, U. [VTT Automation, (Finland); Poern, K. [Poern Consulting, Nykoeping (Sweden)

1997-04-01

We consider point events occurring in a random way in time. In many applications the pattern of occurrence is of intrinsic interest as indicating a trend or some other systematic feature in the rate of occurrence. The purpose of this report is to survey briefly different statistical trend analysis methods and illustrate their applicability to temporal phenomena in particular. The trend testing of point events is usually seen as the testing of the hypotheses concerning the intensity of the occurrence of events. When the intensity function is parametrized, the testing of trend is a typical parametric testing problem. In industrial applications the operational experience generally does not suggest any specified model and method in advance. Therefore, and particularly, if the Poisson process assumption is very questionable, it is desirable to apply tests that are valid for a wide variety of possible processes. The alternative approach for trend testing is to use some non-parametric procedure. In this report we have presented four non-parametric tests: The Cox-Stuart test, the Wilcoxon signed ranks test, the Mann test, and the exponential ordered scores test. In addition to the classical parametric and non-parametric approaches we have also considered the Bayesian trend analysis. First we discuss a Bayesian model, which is based on a power law intensity model. The Bayesian statistical inferences are based on the analysis of the posterior distribution of the trend parameters, and the probability of trend is immediately seen from these distributions. We applied some of the methods discussed in an example case. It should be noted, that this report is a feasibility study rather than a scientific evaluation of statistical methods, and the examples can only be seen as demonstrations of the methods. 14 refs, 10 figs.

Statistical trend analysis methods for temporal phenomena

International Nuclear Information System (INIS)

Lehtinen, E.; Pulkkinen, U.; Poern, K.

1997-04-01

We consider point events occurring in a random way in time. In many applications the pattern of occurrence is of intrinsic interest as indicating a trend or some other systematic feature in the rate of occurrence. The purpose of this report is to survey briefly different statistical trend analysis methods and illustrate their applicability to temporal phenomena in particular. The trend testing of point events is usually seen as the testing of the hypotheses concerning the intensity of the occurrence of events. When the intensity function is parametrized, the testing of trend is a typical parametric testing problem. In industrial applications the operational experience generally does not suggest any specified model and method in advance. Therefore, and particularly, if the Poisson process assumption is very questionable, it is desirable to apply tests that are valid for a wide variety of possible processes. The alternative approach for trend testing is to use some non-parametric procedure. In this report we have presented four non-parametric tests: The Cox-Stuart test, the Wilcoxon signed ranks test, the Mann test, and the exponential ordered scores test. In addition to the classical parametric and non-parametric approaches we have also considered the Bayesian trend analysis. First we discuss a Bayesian model, which is based on a power law intensity model. The Bayesian statistical inferences are based on the analysis of the posterior distribution of the trend parameters, and the probability of trend is immediately seen from these distributions. We applied some of the methods discussed in an example case. It should be noted, that this report is a feasibility study rather than a scientific evaluation of statistical methods, and the examples can only be seen as demonstrations of the methods

Numerical investigations of non-collinear optical parametric chirped pulse amplification for Laguerre-Gaussian vortex beam

Science.gov (United States)

Xu, Lu; Yu, Lianghong; Liang, Xiaoyan

2016-04-01

We present for the first time a scheme to amplify a Laguerre-Gaussian vortex beam based on non-collinear optical parametric chirped pulse amplification (OPCPA). In addition, a three-dimensional numerical model of non-collinear optical parametric amplification was deduced in the frequency domain, in which the effects of non-collinear configuration, temporal and spatial walk-off, group-velocity dispersion and diffraction were also taken into account, to trace the dynamics of the Laguerre-Gaussian vortex beam and investigate its critical parameters in the non-collinear OPCPA process. Based on the numerical simulation results, the scheme shows promise for implementation in a relativistic twisted laser pulse system, which will diversify the light-matter interaction field.

Monitoring coastal marshes biomass with CASI: a comparison of parametric and non-parametric models

Science.gov (United States)

Mo, Y.; Kearney, M.

2017-12-01

Coastal marshes are important carbon sinks that face multiple natural and anthropogenic stresses. Optical remote sensing is a powerful tool for closely monitoring the biomass of coastal marshes. However, application of hyperspectral sensors on assessing the biomass of diverse coastal marsh ecosystems is limited. This study samples spectral and biophysical data from coastal freshwater, intermediate, brackish, and saline marshes in Louisiana, and develops parametric and non-parametric models for using the Compact Airborne Spectrographic Imager (CASI) to retrieve the marshes' biomass. Linear models and random forest models are developed from simulated CASI data (48 bands, 380-1050 nm, bandwidth 14 nm). Linear models are also developed using narrowband vegetation indices computed from all possible band combinations from the blue, red, and near infrared wavelengths. It is found that the linear models derived from the optimal narrowband vegetation indices provide strong predictions for the marshes' Leaf Area Index (LAI; R2 > 0.74 for ARVI), but not for their Aboveground Green Biomass (AGB; R2 > 0.25). The linear models derived from the simulated CASI data strongly predict the marshes' LAI (R2 = 0.93) and AGB (R2 = 0.71) and have 27 and 30 bands/variables in the final models through stepwise regression, respectively. The random forest models derived from the simulated CASI data also strongly predict the marshes' LAI and AGB (R2 = 0.91 and 0.84, respectively), where the most important variables for predicting LAI are near infrared bands at 784 and 756 nm and for predicting ABG are red bands at 684 and 670 nm. In sum, the random forest model is preferable for assessing coastal marsh biomass using CASI data as it offers high R2 for both LAI and AGB. The superior performance of the random forest model is likely to due to that it fully utilizes the full-spectrum data and makes no assumption of the approximate normality of the sampling population. This study offers solutions

A non-parametric hierarchical model to discover behavior dynamics from tracks

NARCIS (Netherlands)

Kooij, J.F.P.; Englebienne, G.; Gavrila, D.M.

2012-01-01

We present a novel non-parametric Bayesian model to jointly discover the dynamics of low-level actions and high-level behaviors of tracked people in open environments. Our model represents behaviors as Markov chains of actions which capture high-level temporal dynamics. Actions may be shared by

How characterization and clearance process is planned to be optimized by combining MARSSIM methods with parametric statistics in decommissioning of Karolinska University Hospital in Stockholm

International Nuclear Information System (INIS)

Jiselmark, J.

2017-01-01

There are different standards for the characterization and clearance process used globally in the radiological industry. All of them have advantages and disadvantages. This paper is describing a decommissioning project which is combining two methods in order to use the advantages of both and minimizing the disadvantages. In Sweden there have been a standard since several years to use a method based on parametric Bayesian statistics for the characterization and clearance process. This method has great advantages close to the clearance limits due to few measurements per m"2, an ability to add extra measurements if needed and an ability to reshape area units without restarting the clearance process. Since the method is based on units with a normal or LOG-normal distribution of the contamination there can be several units far from the clearance limits. The American MARSSIM method use non parametric statistics instead of parametric. In comparison to the Bayesian methods this results in the disadvantage of less accuracy close to the clearance limits but also in the great advantage with few units far from the clearance limits. In the characterizing and clearance process of old radiological facilities at the Karolinska University Hospital in Stockholm the MARSSIM method is combined with the Bayesian statistics method to minimize the amount of measurements and by that the cost for clearance. By using Bayesian statistics close to the clearance limits, more areas will be approved for clearance and the risk of having to redo the survey is minimized. By using MARSSIM methods in the area with an assumed contamination below 25 % of the clearance limits, the areas are not needed to be divided into units with normal or LOG-normal distributed activity. Bigger areas can be handled as units which result in fewer measurements and a faster process. (authors)

Automated detection of acute haemorrhagic stroke in non-contrasted CT images

International Nuclear Information System (INIS)

Meetz, K.; Buelow, T.

2007-01-01

An efficient treatment of stroke patients implies a profound differential diagnosis that includes the detection of acute haematoma. The proposed approach provides an automated detection of acute haematoma, assisting the non-stroke expert in interpreting non-contrasted CT images. It consists of two steps: First, haematoma candidates are detected applying multilevel region growing approach based on a typical grey value characteristic. Second, true haematomas are differentiated from partial volume artefacts, relying on spatial features derived from distance-based histograms. This approach achieves a specificity of 77% and a sensitivity of 89.7% in detecting acute haematoma in non-contrasted CT images when applied to a set of 25 non-contrasted CT images. (orig.)

Hadron Energy Reconstruction for ATLAS Barrel Combined Calorimeter Using Non-Parametrical Method

CERN Document Server

Kulchitskii, Yu A

2000-01-01

Hadron energy reconstruction for the ATLAS barrel prototype combined calorimeter in the framework of the non-parametrical method is discussed. The non-parametrical method utilizes only the known e/h ratios and the electron calibration constants and does not require the determination of any parameters by a minimization technique. Thus, this technique lends itself to fast energy reconstruction in a first level trigger. The reconstructed mean values of the hadron energies are within \\pm1% of the true values and the fractional energy resolution is [(58\\pm 3)%{\\sqrt{GeV}}/\\sqrt{E}+(2.5\\pm0.3)%]\\bigoplus(1.7\\pm0.2) GeV/E. The value of the e/h ratio obtained for the electromagnetic compartment of the combined calorimeter is 1.74\\pm0.04. Results of a study of the longitudinal hadronic shower development are also presented.

Statistical parametric mapping of Tc-99m HMPAO SPECT cerebral perfusion in the normal elderly

International Nuclear Information System (INIS)

Turlakow, A.; Scott, A.M.; Berlangieri, S.U.; Sonkila, C.; Wardill, T.D.; Crowley, K.; Abbott, D.; Egan, G.F.; McKay, W.J.; Hughes, A.

1998-01-01

Full text: The clinical value of Tc-99m HMPAO SPECT cerebral blood flow studies in cognitive and neuropsychiatric disorders has been well described. Currently, interpretation of these studies relies on qualitative or semi- quantitative techniques. The aim of our study is to generate statistical measures of regional cerebral perfusion in the normal elderly using statistical parametric mapping (Friston et al, Wellcome Department of Cognitive Neurology, London, UK) in order to facilitate the objective analysis of cerebral blood flow studies in patient groups. A cohort of 20 healthy, elderly volunteers, aged 68 to 81 years, was prospectively selected on the basis of normal physical examination and neuropsychological testing. Subjects with risk factors, or a history of cognitive impairment were excluded from our study group. All volunteers underwent SPECT cerebral blood flow imaging, 30 minutes following the administration of 370 MBq Tc-99m HMPAO, on a Trionix Triad XLT triple-headed scanner (Trionix Research Laboratory Twinsburg, OH) using high resolution, fan-beam collimators resulting in a system resolution of 10 mm full width at half-maximum (FWHM). The SPECT cerebral blood flow studies were analysed using statistical parametric mapping (SPM) software specifically developed for the routine statistical analysis of functional neuroimaging data. The SPECT images were coregistered with each individual's T1-weighted MR volume brain scan and spatially normalized to standardised Talairach space. Using SPM, these data were analyzed for differences in interhemispheric regional cerebral blood flow. Significant asymmetry of cerebral perfusion was detected in the pre-central gyrus at the 95th percentile. In conclusion, the interpretation of cerebral blood flow studies in the elderly should take into account the statistically significant asymmetry in interhemispheric pre-central cortical blood flow. In the future, clinical studies will be compared to statistical data sets in age

Statistical parametric mapping of Tc-99m HMPAO SPECT cerebral perfusion in the normal elderly

Energy Technology Data Exchange (ETDEWEB)

Turlakow, A.; Scott, A.M.; Berlangieri, S.U.; Sonkila, C.; Wardill, T.D.; Crowley, K.; Abbott, D.; Egan, G.F.; McKay, W.J.; Hughes, A. [Austin and Repatriation Medical Centre, Heidelberg, VIC (Australia). Departments of Nuclear Medicine and Centre for PET Neurology and Clinical Neuropsychology

1998-06-01

Full text: The clinical value of Tc-99m HMPAO SPECT cerebral blood flow studies in cognitive and neuropsychiatric disorders has been well described. Currently, interpretation of these studies relies on qualitative or semi- quantitative techniques. The aim of our study is to generate statistical measures of regional cerebral perfusion in the normal elderly using statistical parametric mapping (Friston et al, Wellcome Department of Cognitive Neurology, London, UK) in order to facilitate the objective analysis of cerebral blood flow studies in patient groups. A cohort of 20 healthy, elderly volunteers, aged 68 to 81 years, was prospectively selected on the basis of normal physical examination and neuropsychological testing. Subjects with risk factors, or a history of cognitive impairment were excluded from our study group. All volunteers underwent SPECT cerebral blood flow imaging, 30 minutes following the administration of 370 MBq Tc-99m HMPAO, on a Trionix Triad XLT triple-headed scanner (Trionix Research Laboratory Twinsburg, OH) using high resolution, fan-beam collimators resulting in a system resolution of 10 mm full width at half-maximum (FWHM). The SPECT cerebral blood flow studies were analysed using statistical parametric mapping (SPM) software specifically developed for the routine statistical analysis of functional neuroimaging data. The SPECT images were coregistered with each individual`s T1-weighted MR volume brain scan and spatially normalized to standardised Talairach space. Using SPM, these data were analyzed for differences in interhemispheric regional cerebral blood flow. Significant asymmetry of cerebral perfusion was detected in the pre-central gyrus at the 95th percentile. In conclusion, the interpretation of cerebral blood flow studies in the elderly should take into account the statistically significant asymmetry in interhemispheric pre-central cortical blood flow. In the future, clinical studies will be compared to statistical data sets in age

Non-Intrusive Solution of Stochastic and Parametric Equations

KAUST Repository

Matthies, Hermann

2015-01-07

Many problems depend on parameters, which may be a finite set of numerical values, or mathematically more complicated objects like for example processes or fields. We address the situation where we have an equation which depends on parameters; stochastic equations are a special case of such parametric problems where the parameters are elements from a probability space. One common way to represent this dependability on parameters is by evaluating the state (or solution) of the system under investigation for different values of the parameters. But often one wants to evaluate the solution quickly for a new set of parameters where it has not been sampled. In this situation it may be advantageous to express the parameter dependent solution with an approximation which allows for rapid evaluation of the solution. Such approximations are also called proxy or surrogate models, response functions, or emulators. All these methods may be seen as functional approximations—representations of the solution by an “easily computable” function of the parameters, as opposed to pure samples. The most obvious methods of approximation used are based on interpolation, in this context often labelled as collocation. In the frequent situation where one has a “solver” for the equation for a given parameter value, i.e. a software component or a program, it is evident that this can be used to independently—if desired in parallel—solve for all the parameter values which subsequently may be used either for the interpolation or in the quadrature for the projection. Such methods are therefore uncoupled for each parameter value, and they additionally often carry the label “non-intrusive”. Without much argument all other methods— which produce a coupled system of equations–are almost always labelled as “intrusive”, meaning that one cannot use the original solver. We want to show here that this not necessarily the case. Another approach is to choose some other projection onto

Non-Intrusive Solution of Stochastic and Parametric Equations

KAUST Repository

Matthies, Hermann

2015-01-01

Many problems depend on parameters, which may be a finite set of numerical values, or mathematically more complicated objects like for example processes or fields. We address the situation where we have an equation which depends on parameters; stochastic equations are a special case of such parametric problems where the parameters are elements from a probability space. One common way to represent this dependability on parameters is by evaluating the state (or solution) of the system under investigation for different values of the parameters. But often one wants to evaluate the solution quickly for a new set of parameters where it has not been sampled. In this situation it may be advantageous to express the parameter dependent solution with an approximation which allows for rapid evaluation of the solution. Such approximations are also called proxy or surrogate models, response functions, or emulators. All these methods may be seen as functional approximations—representations of the solution by an “easily computable” function of the parameters, as opposed to pure samples. The most obvious methods of approximation used are based on interpolation, in this context often labelled as collocation. In the frequent situation where one has a “solver” for the equation for a given parameter value, i.e. a software component or a program, it is evident that this can be used to independently—if desired in parallel—solve for all the parameter values which subsequently may be used either for the interpolation or in the quadrature for the projection. Such methods are therefore uncoupled for each parameter value, and they additionally often carry the label “non-intrusive”. Without much argument all other methods— which produce a coupled system of equations–are almost always labelled as “intrusive”, meaning that one cannot use the original solver. We want to show here that this not necessarily the case. Another approach is to choose some other projection onto

Post traumatic brain perfusion SPECT analysis using reconstructed ROI maps of radioactive microsphere derived cerebral blood flow and statistical parametric mapping.

Science.gov (United States)

McGoron, Anthony J; Capille, Michael; Georgiou, Michael F; Sanchez, Pablo; Solano, Juan; Gonzalez-Brito, Manuel; Kuluz, John W

2008-02-29

Assessment of cerebral blood flow (CBF) by SPECT could be important in the management of patients with severe traumatic brain injury (TBI) because changes in regional CBF can affect outcome by promoting edema formation and intracranial pressure elevation (with cerebral hyperemia), or by causing secondary ischemic injury including post-traumatic stroke. The purpose of this study was to establish an improved method for evaluating regional CBF changes after TBI in piglets. The focal effects of moderate traumatic brain injury (TBI) on cerebral blood flow (CBF) by SPECT cerebral blood perfusion (CBP) imaging in an animal model were investigated by parallelized statistical techniques. Regional CBF was measured by radioactive microspheres and by SPECT 2 hours after injury in sham-operated piglets versus those receiving severe TBI by fluid-percussion injury to the left parietal lobe. Qualitative SPECT CBP accuracy was assessed against reference radioactive microsphere regional CBF measurements by map reconstruction, registration and smoothing. Cerebral hypoperfusion in the test group was identified at the voxel level using statistical parametric mapping (SPM). A significant area of hypoperfusion (P TBI. Statistical mapping of the reference microsphere CBF data confirms a focal decrease found with SPECT and SPM. The suitability of SPM for application to the experimental model and ability to provide insight into CBF changes in response to traumatic injury was validated by the SPECT SPM result of a decrease in CBP at the left parietal region injury area of the test group. Further study and correlation of this characteristic lesion with long-term outcomes and auxiliary diagnostic modalities is critical to developing more effective critical care treatment guidelines and automated medical imaging processing techniques.

A method of statistical analysis in the field of sports science when assumptions of parametric tests are not violated

OpenAIRE

Sandurska, Elżbieta; Szulc, Aleksandra

2016-01-01

Sandurska Elżbieta, Szulc Aleksandra. A method of statistical analysis in the field of sports science when assumptions of parametric tests are not violated. Journal of Education Health and Sport. 2016;6(13):275-287. eISSN 2391-8306. DOI http://dx.doi.org/10.5281/zenodo.293762 http://ojs.ukw.edu.pl/index.php/johs/article/view/4278 The journal has had 7 points in Ministry of Science and Higher Education parametric evaluation. Part B item 754 (09.12.2016). 754 Journal...

Validation of statistical models for creep rupture by parametric analysis

Energy Technology Data Exchange (ETDEWEB)

Bolton, J., E-mail: john.bolton@uwclub.net [65, Fisher Ave., Rugby, Warks CV22 5HW (United Kingdom)

2012-01-15

Statistical analysis is an efficient method for the optimisation of any candidate mathematical model of creep rupture data, and for the comparative ranking of competing models. However, when a series of candidate models has been examined and the best of the series has been identified, there is no statistical criterion to determine whether a yet more accurate model might be devised. Hence there remains some uncertainty that the best of any series examined is sufficiently accurate to be considered reliable as a basis for extrapolation. This paper proposes that models should be validated primarily by parametric graphical comparison to rupture data and rupture gradient data. It proposes that no mathematical model should be considered reliable for extrapolation unless the visible divergence between model and data is so small as to leave no apparent scope for further reduction. This study is based on the data for a 12% Cr alloy steel used in BS PD6605:1998 to exemplify its recommended statistical analysis procedure. The models considered in this paper include a) a relatively simple model, b) the PD6605 recommended model and c) a more accurate model of somewhat greater complexity. - Highlights: Black-Right-Pointing-Pointer The paper discusses the validation of creep rupture models derived from statistical analysis. Black-Right-Pointing-Pointer It demonstrates that models can be satisfactorily validated by a visual-graphic comparison of models to data. Black-Right-Pointing-Pointer The method proposed utilises test data both as conventional rupture stress and as rupture stress gradient. Black-Right-Pointing-Pointer The approach is shown to be more reliable than a well-established and widely used method (BS PD6605).

Functional brain mapping using H215O positron emission tomography (I): statistical parametric mapping method

International Nuclear Information System (INIS)

Lee, Dong Soo; Lee, Jae Sung; Kim, Kyeong Min; Chung, June Key; Lee, Myung Chul

1998-01-01

We investigated the statistical methods to compose the functional brain map of human working memory and the principal factors that have an effect on the methods for localization. Repeated PET scans with successive four tasks, which consist of one control and three different activation tasks, were performed on six right-handed normal volunteers for 2 minutes after bolus injections of 925 MBq H 2 15 O at the intervals of 30 minutes. Image data were analyzed using SPM96 (Statistical Parametric Mapping) implemented with Matlab (Mathworks Inc., U.S.A.). Images from the same subject were spatially registered and were normalized using linear and nonlinear transformation methods. Significant difference between control and each activation state was estimated at every voxel based on the general linear model. Differences of global counts were removed using analysis of covariance (ANCOVA) with global activity as covariate. Using the mean and variance for each condition which was adjusted using ANCOVA, t-statistics was performed on every voxel. To interpret the results more easily, t-values were transformed to the standard Gaussian distribution (Z-score). All the subjects carried out the activation and control tests successfully. Average rate of correct answers was 95%. The numbers of activated blobs were 4 for verbal memory I, 9 for verbal memory II, 9 for visual memory, and 6 for conjunctive activation of these three tasks. The verbal working memory activates predominantly left-sided structures, and the visual memory activates the right hemisphere. We conclude that rCBF PET imaging and statistical parametric mapping method were useful in the localization of the brain regions for verbal and visual working memory

Different uptake of {sup 99m}Tc-ECD and {sup 99m}Tc-HMPAO in the same brains: analysis by statistical parametric mapping

Energy Technology Data Exchange (ETDEWEB)

Hyun, I.Y. [Dept. of Nuclear Medicine, Inha University College of Medicine, Incheon (Korea); Lee, J.S.; Lee, D.S. [Dept. of Nuclear Medicine, Seoul National University College of Medicine, Seoul (Korea); Rha, J.H.; Lee, I.K.; Ha, C.K. [Dept. of Neurology, Inha University College of Medicine, Incheon (Korea)

2001-02-01

The purpose of this study was to investigate the differences between technetium-99m ethyl cysteinate dimer ({sup 99m}Tc-ECD) and technetium-99m hexamethylpropylene amine oxime ({sup 99m}Tc-HMPAO) uptake in the same brains by means of statistical parametric mapping (SPM) analysis. We examined 20 patients (9 male, 11 female, mean age 62{+-}12 years) using {sup 99m}Tc-ECD and {sup 99m}Tc-HMPAO single-photon emission tomography (SPET) and magnetic resonance imaging (MRI) of the brain less than 7 days after onset of stroke. MRI showed no cortical infarctions. Infarctions in the pons (6 patients) and medulla (1), ischaemic periventricular white matter lesions (13) and lacunar infarction (7) were found on MRI. Split-dose and sequential SPET techniques were used for {sup 99m}Tc-ECD and {sup 99m}Tc-HMPAO brain SPET, without repositioning of the patient. All of the SPET images were spatially transformed to standard space, smoothed and globally normalized. The differences between the {sup 99m}Tc-ECD and {sup 99m}Tc-HMPAO SPET images were statistically analysed using statistical parametric mapping (SPM) 96 software. The difference between two groups was considered significant at a threshold of uncorrected P values less than 0.01. Visual analysis showed no hypoperfused areas on either {sup 99m}Tc-ECD or {sup 99m}Tc-HMPAO SPET images. SPM analysis revealed significantly different uptake of {sup 99m}Tc-ECD and {sup 99m}Tc-HMPAO in the same brains. On the {sup 99m}Tc-ECD SPET images, relatively higher uptake was observed in the frontal, parietal and occipital lobes, in the left superior temporal lobe and in the superior region of the cerebellum. On the {sup 99m}Tc-HMPAO SPET images, relatively higher uptake was observed in the medial temporal lobes, thalami, periventricular white matter and brain stem. These differences in uptake of the two tracers in the same brains on SPM analysis suggest that interpretation of cerebral perfusion is possible using SPET with {sup 99m}Tc-ECD and

Using multinomial and imprecise probability for non-parametric modelling of rainfall in Manizales (Colombia

Directory of Open Access Journals (Sweden)

Ibsen Chivatá Cárdenas

2008-05-01

Full Text Available This article presents a rainfall model constructed by applying non-parametric modelling and imprecise probabilities; these tools were used because there was not enough homogeneous information in the study area. The area’s hydro-logical information regarding rainfall was scarce and existing hydrological time series were not uniform. A distributed extended rainfall model was constructed from so-called probability boxes (p-boxes, multinomial probability distribu-tion and confidence intervals (a friendly algorithm was constructed for non-parametric modelling by combining the last two tools. This model confirmed the high level of uncertainty involved in local rainfall modelling. Uncertainty en-compassed the whole range (domain of probability values thereby showing the severe limitations on information, leading to the conclusion that a detailed estimation of probability would lead to significant error. Nevertheless, rele-vant information was extracted; it was estimated that maximum daily rainfall threshold (70 mm would be surpassed at least once every three years and the magnitude of uncertainty affecting hydrological parameter estimation. This paper’s conclusions may be of interest to non-parametric modellers and decisions-makers as such modelling and imprecise probability represents an alternative for hydrological variable assessment and maybe an obligatory proce-dure in the future. Its potential lies in treating scarce information and represents a robust modelling strategy for non-seasonal stochastic modelling conditions

A non-parametric Bayesian approach to decompounding from high frequency data

NARCIS (Netherlands)

Gugushvili, Shota; van der Meulen, F.H.; Spreij, Peter

2016-01-01

Given a sample from a discretely observed compound Poisson process, we consider non-parametric estimation of the density f0 of its jump sizes, as well as of its intensity λ0. We take a Bayesian approach to the problem and specify the prior on f0 as the Dirichlet location mixture of normal densities.

Variance in parametric images: direct estimation from parametric projections

International Nuclear Information System (INIS)

Maguire, R.P.; Leenders, K.L.; Spyrou, N.M.

2000-01-01

Recent work has shown that it is possible to apply linear kinetic models to dynamic projection data in PET in order to calculate parameter projections. These can subsequently be back-projected to form parametric images - maps of parameters of physiological interest. Critical to the application of these maps, to test for significant changes between normal and pathophysiology, is an assessment of the statistical uncertainty. In this context, parametric images also include simple integral images from, e.g., [O-15]-water used to calculate statistical parametric maps (SPMs). This paper revisits the concept of parameter projections and presents a more general formulation of the parameter projection derivation as well as a method to estimate parameter variance in projection space, showing which analysis methods (models) can be used. Using simulated pharmacokinetic image data we show that a method based on an analysis in projection space inherently calculates the mathematically rigorous pixel variance. This results in an estimation which is as accurate as either estimating variance in image space during model fitting, or estimation by comparison across sets of parametric images - as might be done between individuals in a group pharmacokinetic PET study. The method based on projections has, however, a higher computational efficiency, and is also shown to be more precise, as reflected in smooth variance distribution images when compared to the other methods. (author)

Generalized Correlation Coefficient for Non-Parametric Analysis of Microarray Time-Course Data.

Science.gov (United States)

Tan, Qihua; Thomassen, Mads; Burton, Mark; Mose, Kristian Fredløv; Andersen, Klaus Ejner; Hjelmborg, Jacob; Kruse, Torben

2017-06-06

Modeling complex time-course patterns is a challenging issue in microarray study due to complex gene expression patterns in response to the time-course experiment. We introduce the generalized correlation coefficient and propose a combinatory approach for detecting, testing and clustering the heterogeneous time-course gene expression patterns. Application of the method identified nonlinear time-course patterns in high agreement with parametric analysis. We conclude that the non-parametric nature in the generalized correlation analysis could be an useful and efficient tool for analyzing microarray time-course data and for exploring the complex relationships in the omics data for studying their association with disease and health.

Parametric methods for spatial point processes

DEFF Research Database (Denmark)

Møller, Jesper

is studied in Section 4, and Bayesian inference in Section 5. On one hand, as the development in computer technology and computational statistics continues,computationally-intensive simulation-based methods for likelihood inference probably will play a increasing role for statistical analysis of spatial...... inference procedures for parametric spatial point process models. The widespread use of sensible but ad hoc methods based on summary statistics of the kind studied in Chapter 4.3 have through the last two decades been supplied by likelihood based methods for parametric spatial point process models......(This text is submitted for the volume ‘A Handbook of Spatial Statistics' edited by A.E. Gelfand, P. Diggle, M. Fuentes, and P. Guttorp, to be published by Chapmand and Hall/CRC Press, and planned to appear as Chapter 4.4 with the title ‘Parametric methods'.) 1 Introduction This chapter considers...

Inferential, non-parametric statistics to assess the quality of probabilistic forecast systems

NARCIS (Netherlands)

Maia, A.H.N.; Meinke, H.B.; Lennox, S.; Stone, R.C.

2007-01-01

Many statistical forecast systems are available to interested users. To be useful for decision making, these systems must be based on evidence of underlying mechanisms. Once causal connections between the mechanism and its statistical manifestation have been firmly established, the forecasts must

Statistical reliability analyses of two wood plastic composite extrusion processes

International Nuclear Information System (INIS)

Crookston, Kevin A.; Mark Young, Timothy; Harper, David; Guess, Frank M.

2011-01-01

Estimates of the reliability of wood plastic composites (WPC) are explored for two industrial extrusion lines. The goal of the paper is to use parametric and non-parametric analyses to examine potential differences in the WPC metrics of reliability for the two extrusion lines that may be helpful for use by the practitioner. A parametric analysis of the extrusion lines reveals some similarities and disparities in the best models; however, a non-parametric analysis reveals unique and insightful differences between Kaplan-Meier survival curves for the modulus of elasticity (MOE) and modulus of rupture (MOR) of the WPC industrial data. The distinctive non-parametric comparisons indicate the source of the differences in strength between the 10.2% and 48.0% fractiles [3,183-3,517 MPa] for MOE and for MOR between the 2.0% and 95.1% fractiles [18.9-25.7 MPa]. Distribution fitting as related to selection of the proper statistical methods is discussed with relevance to estimating the reliability of WPC. The ability to detect statistical differences in the product reliability of WPC between extrusion processes may benefit WPC producers in improving product reliability and safety of this widely used house-decking product. The approach can be applied to many other safety and complex system lifetime comparisons.

Statistical analysis plan for the family-led rehabilitation after stroke in India (ATTEND) trial: A multicenter randomized controlled trial of a new model of stroke rehabilitation compared to usual care.

Science.gov (United States)

Billot, Laurent; Lindley, Richard I; Harvey, Lisa A; Maulik, Pallab K; Hackett, Maree L; Murthy, Gudlavalleti Vs; Anderson, Craig S; Shamanna, Bindiganavale R; Jan, Stephen; Walker, Marion; Forster, Anne; Langhorne, Peter; Verma, Shweta J; Felix, Cynthia; Alim, Mohammed; Gandhi, Dorcas Bc; Pandian, Jeyaraj Durai

2017-02-01

Background In low- and middle-income countries, few patients receive organized rehabilitation after stroke, yet the burden of chronic diseases such as stroke is increasing in these countries. Affordable models of effective rehabilitation could have a major impact. The ATTEND trial is evaluating a family-led caregiver delivered rehabilitation program after stroke. Objective To publish the detailed statistical analysis plan for the ATTEND trial prior to trial unblinding. Methods Based upon the published registration and protocol, the blinded steering committee and management team, led by the trial statistician, have developed a statistical analysis plan. The plan has been informed by the chosen outcome measures, the data collection forms and knowledge of key baseline data. Results The resulting statistical analysis plan is consistent with best practice and will allow open and transparent reporting. Conclusions Publication of the trial statistical analysis plan reduces potential bias in trial reporting, and clearly outlines pre-specified analyses. Clinical Trial Registrations India CTRI/2013/04/003557; Australian New Zealand Clinical Trials Registry ACTRN1261000078752; Universal Trial Number U1111-1138-6707.

Some statistical issues important to future developments in human radiation research

International Nuclear Information System (INIS)

Vaeth, Michael

1991-01-01

Using his two years experience at the Radiation Effects Research Foundation at Hiroshima, the author tries to outline some of the areas of statistics where methodologies relevant to the future developments in human radiation research are likely to be found. Problems related to statistical analysis of existing data are discussed, together with methodological developments in non-parametric and semi-parametric regression modelling, and interpretation and presentation of results. (Author)

Mathematical statistics and stochastic processes

CERN Document Server

Bosq, Denis

2013-01-01

Generally, books on mathematical statistics are restricted to the case of independent identically distributed random variables. In this book however, both this case AND the case of dependent variables, i.e. statistics for discrete and continuous time processes, are studied. This second case is very important for today's practitioners.Mathematical Statistics and Stochastic Processes is based on decision theory and asymptotic statistics and contains up-to-date information on the relevant topics of theory of probability, estimation, confidence intervals, non-parametric statistics and rob

Perception of stroke symptoms and utilization of emergency medical services

Directory of Open Access Journals (Sweden)

Maximiliano A. Hawkes

Full Text Available ABSTRACT Lack of stroke awareness and slow activation of emergency medical services (EMS are frequently reported reasons for delayed arrival to the hospital. We evaluated these variables in our population. Methods Review of hospital records and structured telephone interviews of 100 consecutive stroke patients. Forward stepwise logistic regression was used for the statistical analysis. Results Seventy patients (75% arrived at the hospital 4.5 hours after stroke symptoms onset. The use of EMS did not improve arrival times. Most patients who recognized their symptoms did not use EMS (p < 0.02. Nineteen patients (20% were initially misdiagnosed. Eighteen of them were first assessed by non-neurologist physicians (p < 0.001. Conclusions Our population showed a low level of stroke awareness. The use of EMS did not improve arrival times at the hospital and the non-utilization of the EMS was associated with the recognition of stroke symptoms. There was a concerning rate of misdiagnosis, mostly by non-neurologist medical providers.

MR diffusion tensor analysis of schizophrenic brain using statistical parametric mapping

International Nuclear Information System (INIS)

Yamada, Haruyasu; Abe, Osamu; Kasai, Kiyoto

2005-01-01

The purpose of this study is to investigate diffusion anisotropy in the schizophrenic brain by voxel-based analysis of diffusion tensor imaging (DTI), using statistical parametric mapping (SPM). We studied 33 patients with schizophrenia diagnosed by diagnostic and statistical manual of mental disorders (DSM)-IV criteria and 42 matched controls. The data was obtained with a 1.5 T MRI system. We used single-shot spin-echo planar sequences (repetition time/echo time (TR/TE)=5000/102 ms, 5 mm slice thickness and 1.5 mm gap, field of view (FOV)=21 x 21 cm 2 , number of excitation (NEX)=4, 128 x 128 pixel matrix) for diffusion tensor acquisition. Diffusion gradients (b-value of 500 or 1000 s/mm 2 ) were applied on two axes simultaneously. Diffusion properties were measured along 6 non-linear directions. The structural distortion induced by the large diffusion gradients was corrected, based on each T 2 -weighted echo-planar image (b=0 s/mm 2 ). The fractional anisotropy (FA) maps were generated on a voxel-by-voxel basis. T 2 -weighted echo-planar images were then segmented into gray matter, white matter, and cerebrospinal fluid, using SPM (Wellcome Department of Imaging, University College London, UK). All apparent diffusion coefficient (ADC) and FA maps in native space were transformed to the stereotactic space by registering each of the images to the same template image. The normalized data was smoothed and analyzed using SPM. The significant FA decrease in the patient group was found in the uncinate fasciculus, parahippocampal white matter, anterior cingulum and other areas (corrected p<0.05). No significant increased region was noted. Our results may reflect reduced diffusion anisotropy of the white matter pathway of the limbic system as shown by the decreased FA. Manual region-of-interest analysis is usually more sensitive than voxel-based analysis, but it is subjective and difficult to set with anatomical reproducibility. Voxel-based analysis of the diffusion tensor

A multi-instrument non-parametric reconstruction of the electron pressure profile in the galaxy cluster CLJ1226.9+3332

Science.gov (United States)

Romero, C.; McWilliam, M.; Macías-Pérez, J.-F.; Adam, R.; Ade, P.; André, P.; Aussel, H.; Beelen, A.; Benoît, A.; Bideaud, A.; Billot, N.; Bourrion, O.; Calvo, M.; Catalano, A.; Coiffard, G.; Comis, B.; de Petris, M.; Désert, F.-X.; Doyle, S.; Goupy, J.; Kramer, C.; Lagache, G.; Leclercq, S.; Lestrade, J.-F.; Mauskopf, P.; Mayet, F.; Monfardini, A.; Pascale, E.; Perotto, L.; Pisano, G.; Ponthieu, N.; Revéret, V.; Ritacco, A.; Roussel, H.; Ruppin, F.; Schuster, K.; Sievers, A.; Triqueneaux, S.; Tucker, C.; Zylka, R.

2018-04-01

Context. In the past decade, sensitive, resolved Sunyaev-Zel'dovich (SZ) studies of galaxy clusters have become common. Whereas many previous SZ studies have parameterized the pressure profiles of galaxy clusters, non-parametric reconstructions will provide insights into the thermodynamic state of the intracluster medium. Aim. We seek to recover the non-parametric pressure profiles of the high redshift (z = 0.89) galaxy cluster CLJ 1226.9+3332 as inferred from SZ data from the MUSTANG, NIKA, Bolocam, and Planck instruments, which all probe different angular scales. Methods: Our non-parametric algorithm makes use of logarithmic interpolation, which under the assumption of ellipsoidal symmetry is analytically integrable. For MUSTANG, NIKA, and Bolocam we derive a non-parametric pressure profile independently and find good agreement among the instruments. In particular, we find that the non-parametric profiles are consistent with a fitted generalized Navaro-Frenk-White (gNFW) profile. Given the ability of Planck to constrain the total signal, we include a prior on the integrated Compton Y parameter as determined by Planck. Results: For a given instrument, constraints on the pressure profile diminish rapidly beyond the field of view. The overlap in spatial scales probed by these four datasets is therefore critical in checking for consistency between instruments. By using multiple instruments, our analysis of CLJ 1226.9+3332 covers a large radial range, from the central regions to the cluster outskirts: 0.05 R500 generation of SZ instruments such as NIKA2 and MUSTANG2.

A nonparametric spatial scan statistic for continuous data.

Science.gov (United States)

Jung, Inkyung; Cho, Ho Jin

2015-10-20

Spatial scan statistics are widely used for spatial cluster detection, and several parametric models exist. For continuous data, a normal-based scan statistic can be used. However, the performance of the model has not been fully evaluated for non-normal data. We propose a nonparametric spatial scan statistic based on the Wilcoxon rank-sum test statistic and compared the performance of the method with parametric models via a simulation study under various scenarios. The nonparametric method outperforms the normal-based scan statistic in terms of power and accuracy in almost all cases under consideration in the simulation study. The proposed nonparametric spatial scan statistic is therefore an excellent alternative to the normal model for continuous data and is especially useful for data following skewed or heavy-tailed distributions.

Post traumatic brain perfusion SPECT analysis using reconstructed ROI maps of radioactive microsphere derived cerebral blood flow and statistical parametric mapping

Directory of Open Access Journals (Sweden)

Gonzalez-Brito Manuel

2008-02-01

Full Text Available Abstract Background Assessment of cerebral blood flow (CBF by SPECT could be important in the management of patients with severe traumatic brain injury (TBI because changes in regional CBF can affect outcome by promoting edema formation and intracranial pressure elevation (with cerebral hyperemia, or by causing secondary ischemic injury including post-traumatic stroke. The purpose of this study was to establish an improved method for evaluating regional CBF changes after TBI in piglets. Methods The focal effects of moderate traumatic brain injury (TBI on cerebral blood flow (CBF by SPECT cerebral blood perfusion (CBP imaging in an animal model were investigated by parallelized statistical techniques. Regional CBF was measured by radioactive microspheres and by SPECT 2 hours after injury in sham-operated piglets versus those receiving severe TBI by fluid-percussion injury to the left parietal lobe. Qualitative SPECT CBP accuracy was assessed against reference radioactive microsphere regional CBF measurements by map reconstruction, registration and smoothing. Cerebral hypoperfusion in the test group was identified at the voxel level using statistical parametric mapping (SPM. Results A significant area of hypoperfusion (P Conclusion The suitability of SPM for application to the experimental model and ability to provide insight into CBF changes in response to traumatic injury was validated by the SPECT SPM result of a decrease in CBP at the left parietal region injury area of the test group. Further study and correlation of this characteristic lesion with long-term outcomes and auxiliary diagnostic modalities is critical to developing more effective critical care treatment guidelines and automated medical imaging processing techniques.

Post traumatic brain perfusion SPECT analysis using reconstructed ROI maps of radioactive microsphere derived cerebral blood flow and statistical parametric mapping

International Nuclear Information System (INIS)

McGoron, Anthony J; Capille, Michael; Georgiou, Michael F; Sanchez, Pablo; Solano, Juan; Gonzalez-Brito, Manuel; Kuluz, John W

2008-01-01

Assessment of cerebral blood flow (CBF) by SPECT could be important in the management of patients with severe traumatic brain injury (TBI) because changes in regional CBF can affect outcome by promoting edema formation and intracranial pressure elevation (with cerebral hyperemia), or by causing secondary ischemic injury including post-traumatic stroke. The purpose of this study was to establish an improved method for evaluating regional CBF changes after TBI in piglets. The focal effects of moderate traumatic brain injury (TBI) on cerebral blood flow (CBF) by SPECT cerebral blood perfusion (CBP) imaging in an animal model were investigated by parallelized statistical techniques. Regional CBF was measured by radioactive microspheres and by SPECT 2 hours after injury in sham-operated piglets versus those receiving severe TBI by fluid-percussion injury to the left parietal lobe. Qualitative SPECT CBP accuracy was assessed against reference radioactive microsphere regional CBF measurements by map reconstruction, registration and smoothing. Cerebral hypoperfusion in the test group was identified at the voxel level using statistical parametric mapping (SPM). A significant area of hypoperfusion (P < 0.01) was found as a response to the TBI. Statistical mapping of the reference microsphere CBF data confirms a focal decrease found with SPECT and SPM. The suitability of SPM for application to the experimental model and ability to provide insight into CBF changes in response to traumatic injury was validated by the SPECT SPM result of a decrease in CBP at the left parietal region injury area of the test group. Further study and correlation of this characteristic lesion with long-term outcomes and auxiliary diagnostic modalities is critical to developing more effective critical care treatment guidelines and automated medical imaging processing techniques

Statistical concepts a second course

CERN Document Server

Lomax, Richard G

2012-01-01

Statistical Concepts consists of the last 9 chapters of An Introduction to Statistical Concepts, 3rd ed. Designed for the second course in statistics, it is one of the few texts that focuses just on intermediate statistics. The book highlights how statistics work and what they mean to better prepare students to analyze their own data and interpret SPSS and research results. As such it offers more coverage of non-parametric procedures used when standard assumptions are violated since these methods are more frequently encountered when working with real data. Determining appropriate sample sizes

Diagnosis of regional cerebral blood flow abnormalities using SPECT: agreement between individualized statistical parametric maps and visual inspection by nuclear medicine physicians with different levels of expertise in nuclear neurology

Energy Technology Data Exchange (ETDEWEB)

Rocha, Euclides Timoteo da, E-mail: euclidestimoteo@uol.com.b [Fundacao Pio XII, Barretos, SP (Brazil). Hospital de Cancer. Dept. de Medicina Nuclear; Buchpiguel, Carlos Alberto [Hospital do Coracao, Sao Paulo, SP (Brazil). Dept. de Medicina Nuclear; Nitrini, Ricardo [Universidade de Sao Paulo (USP), SP (Brazil). Faculdade de Medicina. Dept. de Neurologia; Tazima, Sergio [Hospital Alemao Oswaldo Cruz (HAOC), Sao Paulo, SP (Brazil). Dept. de Medicina Nuclear; Peres, Stela Verzinhase [Fundacao Pio XII, Barretos, SP (Brazil). Hospital de Cancer; Busatto Filho, Geraldo [Universidade de Sao Paulo (USP), SP (Brazil). Faculdade de Medicina. Div. de Medicina Nuclear

2009-07-01

Introduction: visual analysis is widely used to interpret regional cerebral blood flow (rCBF) SPECT images in clinical practice despite its limitations. Automated methods are employed to investigate between-group rCBF differences in research studies but have rarely been explored in individual analyses. Objectives: to compare visual inspection by nuclear physicians with the automated statistical parametric mapping program using a SPECT dataset of patients with neurological disorders and normal control images. Methods: using statistical parametric mapping, 14 SPECT images from patients with various neurological disorders were compared individually with a databank of 32 normal images using a statistical threshold of p<0.05 (corrected for multiple comparisons at the level of individual voxels or clusters). Statistical parametric mapping results were compared with visual analyses by a nuclear physician highly experienced in neurology (A) as well as a nuclear physician with a general background of experience (B) who independently classified images as normal or altered, and determined the location of changes and the severity. Results: of the 32 images of the normal databank, 4 generated maps showing rCBF abnormalities (p<0.05, corrected). Among the 14 images from patients with neurological disorders, 13 showed rCBF alterations. Statistical parametric mapping and physician A completely agreed on 84.37% and 64.28% of cases from the normal databank and neurological disorders, respectively. The agreement between statistical parametric mapping and ratings of physician B were lower (71.18% and 35.71%, respectively). Conclusion: statistical parametric mapping replicated the findings described by the more experienced nuclear physician. This finding suggests that automated methods for individually analyzing rCBF SPECT images may be a valuable resource to complement visual inspection in clinical practice. (author)

A simple non-parametric goodness-of-fit test for elliptical copulas

Directory of Open Access Journals (Sweden)

Jaser Miriam

2017-12-01

Full Text Available In this paper, we propose a simple non-parametric goodness-of-fit test for elliptical copulas of any dimension. It is based on the equality of Kendall’s tau and Blomqvist’s beta for all bivariate margins. Nominal level and power of the proposed test are investigated in a Monte Carlo study. An empirical application illustrates our goodness-of-fit test at work.

Basic statistical tools in research and data analysis

Directory of Open Access Journals (Sweden)

Zulfiqar Ali

2016-01-01

Full Text Available Statistical methods involved in carrying out a study include planning, designing, collecting data, analysing, drawing meaningful interpretation and reporting of the research findings. The statistical analysis gives meaning to the meaningless numbers, thereby breathing life into a lifeless data. The results and inferences are precise only if proper statistical tests are used. This article will try to acquaint the reader with the basic research tools that are utilised while conducting various studies. The article covers a brief outline of the variables, an understanding of quantitative and qualitative variables and the measures of central tendency. An idea of the sample size estimation, power analysis and the statistical errors is given. Finally, there is a summary of parametric and non-parametric tests used for data analysis.

Soliton Coupling Driven by Phase Fluctuations in Auto-Parametric Resonance

CERN Document Server

Binder, B

2002-01-01

In this paper the interaction of sine-Gordon solitons and mediating linear waves is modelled by a special case of auto-parametric resonance, the Rayleigh-type self-excited non-linear autonomous system driven by a statistical phase gradient related to the soliton energy. Spherical symmetry can stimulate "whispering gallery modes" (WGM) with integral coupling number M=137.

A multitemporal and non-parametric approach for assessing the impacts of drought on vegetation greenness

DEFF Research Database (Denmark)

Carrao, Hugo; Sepulcre, Guadalupe; Horion, Stéphanie Marie Anne F

2013-01-01

This study evaluates the relationship between the frequency and duration of meteorological droughts and the subsequent temporal changes on the quantity of actively photosynthesizing biomass (greenness) estimated from satellite imagery on rainfed croplands in Latin America. An innovative non-parametric...... and non-supervised approach, based on the Fisher-Jenks optimal classification algorithm, is used to identify multi-scale meteorological droughts on the basis of empirical cumulative distributions of 1, 3, 6, and 12-monthly precipitation totals. As input data for the classifier, we use the gridded GPCC...... for the period between 1998 and 2010. The time-series analysis of vegetation greenness is performed during the growing season with a non-parametric method, namely the seasonal Relative Greenness (RG) of spatially accumulated fAPAR. The Global Land Cover map of 2000 and the GlobCover maps of 2005/2006 and 2009...

A non-parametric framework for estimating threshold limit values

Directory of Open Access Journals (Sweden)

Ulm Kurt

2005-11-01

Full Text Available Abstract Background To estimate a threshold limit value for a compound known to have harmful health effects, an 'elbow' threshold model is usually applied. We are interested on non-parametric flexible alternatives. Methods We describe how a step function model fitted by isotonic regression can be used to estimate threshold limit values. This method returns a set of candidate locations, and we discuss two algorithms to select the threshold among them: the reduced isotonic regression and an algorithm considering the closed family of hypotheses. We assess the performance of these two alternative approaches under different scenarios in a simulation study. We illustrate the framework by analysing the data from a study conducted by the German Research Foundation aiming to set a threshold limit value in the exposure to total dust at workplace, as a causal agent for developing chronic bronchitis. Results In the paper we demonstrate the use and the properties of the proposed methodology along with the results from an application. The method appears to detect the threshold with satisfactory success. However, its performance can be compromised by the low power to reject the constant risk assumption when the true dose-response relationship is weak. Conclusion The estimation of thresholds based on isotonic framework is conceptually simple and sufficiently powerful. Given that in threshold value estimation context there is not a gold standard method, the proposed model provides a useful non-parametric alternative to the standard approaches and can corroborate or challenge their findings.

Robot Training With Vector Fields Based on Stroke Survivors' Individual Movement Statistics.

Science.gov (United States)

Wright, Zachary A; Lazzaro, Emily; Thielbar, Kelly O; Patton, James L; Huang, Felix C

2018-02-01

The wide variation in upper extremity motor impairments among stroke survivors necessitates more intelligent methods of customized therapy. However, current strategies for characterizing individual motor impairments are limited by the use of traditional clinical assessments (e.g., Fugl-Meyer) and simple engineering metrics (e.g., goal-directed performance). Our overall approach is to statistically identify the range of volitional movement capabilities, and then apply a robot-applied force vector field intervention that encourages under-expressed movements. We investigated whether explorative training with such customized force fields would improve stroke survivors' (n = 11) movement patterns in comparison to a control group that trained without forces (n = 11). Force and control groups increased Fugl-Meyer UE scores (average of 1.0 and 1.1, respectively), which is not considered clinically meaningful. Interestingly, participants from both groups demonstrated dramatic increases in their range of velocity during exploration following only six days of training (average increase of 166.4% and 153.7% for the Force and Control group, respectively). While both groups showed evidence of improvement, we also found evidence that customized forces affected learning in a systematic way. When customized forces were active, we observed broader distributions of velocity that were not present in the controls. Second, we found that these changes led to specific changes in unassisted motion. In addition, while the shape of movement distributions changed significantly for both groups, detailed analysis of the velocity distributions revealed that customized forces promoted a greater proportion of favorable changes. Taken together, these results provide encouraging evidence that patient-specific force fields based on individuals' movement statistics can be used to create new movement patterns and shape them in a customized manner. To the best of our knowledge, this paper is the first

Robust non-parametric one-sample tests for the analysis of recurrent events.

Science.gov (United States)

Rebora, Paola; Galimberti, Stefania; Valsecchi, Maria Grazia

2010-12-30

One-sample non-parametric tests are proposed here for inference on recurring events. The focus is on the marginal mean function of events and the basis for inference is the standardized distance between the observed and the expected number of events under a specified reference rate. Different weights are considered in order to account for various types of alternative hypotheses on the mean function of the recurrent events process. A robust version and a stratified version of the test are also proposed. The performance of these tests was investigated through simulation studies under various underlying event generation processes, such as homogeneous and nonhomogeneous Poisson processes, autoregressive and renewal processes, with and without frailty effects. The robust versions of the test have been shown to be suitable in a wide variety of event generating processes. The motivating context is a study on gene therapy in a very rare immunodeficiency in children, where a major end-point is the recurrence of severe infections. Robust non-parametric one-sample tests for recurrent events can be useful to assess efficacy and especially safety in non-randomized studies or in epidemiological studies for comparison with a standard population. Copyright © 2010 John Wiley & Sons, Ltd.

Non-parametric model selection for subject-specific topological organization of resting-state functional connectivity.

Science.gov (United States)

Ferrarini, Luca; Veer, Ilya M; van Lew, Baldur; Oei, Nicole Y L; van Buchem, Mark A; Reiber, Johan H C; Rombouts, Serge A R B; Milles, J

2011-06-01

In recent years, graph theory has been successfully applied to study functional and anatomical connectivity networks in the human brain. Most of these networks have shown small-world topological characteristics: high efficiency in long distance communication between nodes, combined with highly interconnected local clusters of nodes. Moreover, functional studies performed at high resolutions have presented convincing evidence that resting-state functional connectivity networks exhibits (exponentially truncated) scale-free behavior. Such evidence, however, was mostly presented qualitatively, in terms of linear regressions of the degree distributions on log-log plots. Even when quantitative measures were given, these were usually limited to the r(2) correlation coefficient. However, the r(2) statistic is not an optimal estimator of explained variance, when dealing with (truncated) power-law models. Recent developments in statistics have introduced new non-parametric approaches, based on the Kolmogorov-Smirnov test, for the problem of model selection. In this work, we have built on this idea to statistically tackle the issue of model selection for the degree distribution of functional connectivity at rest. The analysis, performed at voxel level and in a subject-specific fashion, confirmed the superiority of a truncated power-law model, showing high consistency across subjects. Moreover, the most highly connected voxels were found to be consistently part of the default mode network. Our results provide statistically sound support to the evidence previously presented in literature for a truncated power-law model of resting-state functional connectivity. Copyright © 2010 Elsevier Inc. All rights reserved.

Latest astronomical constraints on some non-linear parametric dark energy models

Science.gov (United States)

Yang, Weiqiang; Pan, Supriya; Paliathanasis, Andronikos

2018-04-01

We consider non-linear redshift-dependent equation of state parameters as dark energy models in a spatially flat Friedmann-Lemaître-Robertson-Walker universe. To depict the expansion history of the universe in such cosmological scenarios, we take into account the large-scale behaviour of such parametric models and fit them using a set of latest observational data with distinct origin that includes cosmic microwave background radiation, Supernove Type Ia, baryon acoustic oscillations, redshift space distortion, weak gravitational lensing, Hubble parameter measurements from cosmic chronometers, and finally the local Hubble constant from Hubble space telescope. The fitting technique avails the publicly available code Cosmological Monte Carlo (COSMOMC), to extract the cosmological information out of these parametric dark energy models. From our analysis, it follows that those models could describe the late time accelerating phase of the universe, while they are distinguished from the Λ-cosmology.

Appraisal of within- and between-laboratory reproducibility of non-radioisotopic local lymph node assay using flow cytometry, LLNA:BrdU-FCM: comparison of OECD TG429 performance standard and statistical evaluation.

Science.gov (United States)

Yang, Hyeri; Na, Jihye; Jang, Won-Hee; Jung, Mi-Sook; Jeon, Jun-Young; Heo, Yong; Yeo, Kyung-Wook; Jo, Ji-Hoon; Lim, Kyung-Min; Bae, SeungJin

2015-05-05

Mouse local lymph node assay (LLNA, OECD TG429) is an alternative test replacing conventional guinea pig tests (OECD TG406) for the skin sensitization test but the use of a radioisotopic agent, (3)H-thymidine, deters its active dissemination. New non-radioisotopic LLNA, LLNA:BrdU-FCM employs a non-radioisotopic analog, 5-bromo-2'-deoxyuridine (BrdU) and flow cytometry. For an analogous method, OECD TG429 performance standard (PS) advises that two reference compounds be tested repeatedly and ECt(threshold) values obtained must fall within acceptable ranges to prove within- and between-laboratory reproducibility. However, this criteria is somewhat arbitrary and sample size of ECt is less than 5, raising concerns about insufficient reliability. Here, we explored various statistical methods to evaluate the reproducibility of LLNA:BrdU-FCM with stimulation index (SI), the raw data for ECt calculation, produced from 3 laboratories. Descriptive statistics along with graphical representation of SI was presented. For inferential statistics, parametric and non-parametric methods were applied to test the reproducibility of SI of a concurrent positive control and the robustness of results were investigated. Descriptive statistics and graphical representation of SI alone could illustrate the within- and between-laboratory reproducibility. Inferential statistics employing parametric and nonparametric methods drew similar conclusion. While all labs passed within- and between-laboratory reproducibility criteria given by OECD TG429 PS based on ECt values, statistical evaluation based on SI values showed that only two labs succeeded in achieving within-laboratory reproducibility. For those two labs that satisfied the within-lab reproducibility, between-laboratory reproducibility could be also attained based on inferential as well as descriptive statistics. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

The Support Reduction Algorithm for Computing Non-Parametric Function Estimates in Mixture Models

OpenAIRE

GROENEBOOM, PIET; JONGBLOED, GEURT; WELLNER, JON A.

2008-01-01

In this paper, we study an algorithm (which we call the support reduction algorithm) that can be used to compute non-parametric M-estimators in mixture models. The algorithm is compared with natural competitors in the context of convex regression and the ‘Aspect problem’ in quantum physics.

Statistical parametric mapping for effects of verapamil on olfactory connections of rat brain in vivo using manganese-enhanced MR imaging

International Nuclear Information System (INIS)

Soma, Tsutomu; Kurakawa, Masami; Koto, Daichi

2011-01-01

We investigated the effect of verapamil on the transport of manganese in the olfactory connections of rat brains in vivo using statistical parametric mapping and manganese-enhanced magnetic resonance (MR) imaging. We divided 12 7-week-old male Sprague-Dawley rats into 2 groups of six and injected 10 μL of saline into the right nasal cavities of the first group and 10 μL of verapamil (2.5 mg/mL) into the other group. Twenty minutes after the initial injection, we injected 10 μL of MnCl 2 (1 mol/L) into the right nasal cavities of both groups. We obtained serial T 1 -weighted MR images before administering the verapamil or saline and at 0.5, one, 24, 48, and 72 hours and 7 days after administering the MnCl 2 , spatially normalized the MR images on the rat brain atlas, and analyzed the data using voxel-based statistical comparison. Statistical parametric maps demonstrated the transport of manganese. Manganese ions created significant enhancement (t-score=36.6) 24 hours after MnCl 2 administration in the group administered saline but not at the same time point in the group receiving verapamil. The extent of significantly enhanced regions peaked at 72 hours in both groups and both sides of the brain. The peak of extent in the right side brain in the group injected with saline was 70.2 mm 3 and in the group with verapamil, 92.4 mm 3 . The extents in the left side were 64.0 mm 3 for the group with saline and 53.2 mm 3 for the group with verapamil. We applied statistical parametric mapping using manganese-enhanced MR imaging to demonstrate in vivo the transport of manganese in the olfactory connections of rat brains with and without verapamil and found that verapamil did affect this transport. (author)

Statistical dynamics of parametrically perturbed sine-square map

Indian Academy of Sciences (India)

Abstract. We discuss the emergence and destruction of complex, critical and completely chaotic attractors in a nonlinear system when subjected to a small parametric perturba- tion in trigonometric, hyperbolic or noise function forms. For this purpose, a hybrid optical bistable system, which is a nonlinear physical system, has ...

Measuring energy performance with sectoral heterogeneity: A non-parametric frontier approach

International Nuclear Information System (INIS)

Wang, H.; Ang, B.W.; Wang, Q.W.; Zhou, P.

2017-01-01

Evaluating economy-wide energy performance is an integral part of assessing the effectiveness of a country's energy efficiency policy. Non-parametric frontier approach has been widely used by researchers for such a purpose. This paper proposes an extended non-parametric frontier approach to studying economy-wide energy efficiency and productivity performances by accounting for sectoral heterogeneity. Relevant techniques in index number theory are incorporated to quantify the driving forces behind changes in the economy-wide energy productivity index. The proposed approach facilitates flexible modelling of different sectors' production processes, and helps to examine sectors' impact on the aggregate energy performance. A case study of China's economy-wide energy efficiency and productivity performances in its 11th five-year plan period (2006–2010) is presented. It is found that sectoral heterogeneities in terms of energy performance are significant in China. Meanwhile, China's economy-wide energy productivity increased slightly during the study period, mainly driven by the technical efficiency improvement. A number of other findings have also been reported. - Highlights: • We model economy-wide energy performance by considering sectoral heterogeneity. • The proposed approach can identify sectors' impact on the aggregate energy performance. • Obvious sectoral heterogeneities are identified in evaluating China's energy performance.

A non-parametric peak calling algorithm for DamID-Seq.

Directory of Open Access Journals (Sweden)

Renhua Li

Full Text Available Protein-DNA interactions play a significant role in gene regulation and expression. In order to identify transcription factor binding sites (TFBS of double sex (DSX-an important transcription factor in sex determination, we applied the DNA adenine methylation identification (DamID technology to the fat body tissue of Drosophila, followed by deep sequencing (DamID-Seq. One feature of DamID-Seq data is that induced adenine methylation signals are not assured to be symmetrically distributed at TFBS, which renders the existing peak calling algorithms for ChIP-Seq, including SPP and MACS, inappropriate for DamID-Seq data. This challenged us to develop a new algorithm for peak calling. A challenge in peaking calling based on sequence data is estimating the averaged behavior of background signals. We applied a bootstrap resampling method to short sequence reads in the control (Dam only. After data quality check and mapping reads to a reference genome, the peaking calling procedure compromises the following steps: 1 reads resampling; 2 reads scaling (normalization and computing signal-to-noise fold changes; 3 filtering; 4 Calling peaks based on a statistically significant threshold. This is a non-parametric method for peak calling (NPPC. We also used irreproducible discovery rate (IDR analysis, as well as ChIP-Seq data to compare the peaks called by the NPPC. We identified approximately 6,000 peaks for DSX, which point to 1,225 genes related to the fat body tissue difference between female and male Drosophila. Statistical evidence from IDR analysis indicated that these peaks are reproducible across biological replicates. In addition, these peaks are comparable to those identified by use of ChIP-Seq on S2 cells, in terms of peak number, location, and peaks width.

A non-parametric peak calling algorithm for DamID-Seq.

Science.gov (United States)

Li, Renhua; Hempel, Leonie U; Jiang, Tingbo

2015-01-01

Protein-DNA interactions play a significant role in gene regulation and expression. In order to identify transcription factor binding sites (TFBS) of double sex (DSX)-an important transcription factor in sex determination, we applied the DNA adenine methylation identification (DamID) technology to the fat body tissue of Drosophila, followed by deep sequencing (DamID-Seq). One feature of DamID-Seq data is that induced adenine methylation signals are not assured to be symmetrically distributed at TFBS, which renders the existing peak calling algorithms for ChIP-Seq, including SPP and MACS, inappropriate for DamID-Seq data. This challenged us to develop a new algorithm for peak calling. A challenge in peaking calling based on sequence data is estimating the averaged behavior of background signals. We applied a bootstrap resampling method to short sequence reads in the control (Dam only). After data quality check and mapping reads to a reference genome, the peaking calling procedure compromises the following steps: 1) reads resampling; 2) reads scaling (normalization) and computing signal-to-noise fold changes; 3) filtering; 4) Calling peaks based on a statistically significant threshold. This is a non-parametric method for peak calling (NPPC). We also used irreproducible discovery rate (IDR) analysis, as well as ChIP-Seq data to compare the peaks called by the NPPC. We identified approximately 6,000 peaks for DSX, which point to 1,225 genes related to the fat body tissue difference between female and male Drosophila. Statistical evidence from IDR analysis indicated that these peaks are reproducible across biological replicates. In addition, these peaks are comparable to those identified by use of ChIP-Seq on S2 cells, in terms of peak number, location, and peaks width.

Multi-Directional Non-Parametric Analysis of Agricultural Efficiency

DEFF Research Database (Denmark)

Balezentis, Tomas

This thesis seeks to develop methodologies for assessment of agricultural efficiency and employ them to Lithuanian family farms. In particular, we focus on three particular objectives throughout the research: (i) to perform a fully non-parametric analysis of efficiency effects, (ii) to extend...... to the Multi-Directional Efficiency Analysis approach when the proposed models were employed to analyse empirical data of Lithuanian family farm performance, we saw substantial differences in efficiencies associated with different inputs. In particular, assets appeared to be the least efficiently used input...... relative to labour, intermediate consumption and land (in some cases land was not treated as a discretionary input). These findings call for further research on relationships among financial structure, investment decisions, and efficiency in Lithuanian family farms. Application of different techniques...

Recurrent Stroke: The Value of the CHA2DS2VASc Score and the Essen Stroke Risk Score in a Nationwide Stroke Cohort.

Science.gov (United States)

Andersen, Søren Due; Gorst-Rasmussen, Anders; Lip, Gregory Y H; Bach, Flemming W; Larsen, Torben Bjerregaard

2015-09-01

The CHA2DS2VASc score and the Essen Stroke Risk Score are respectively used for risk stratification in patients with atrial fibrillation and in patients with cerebrovascular incidents. We aimed to test the ability of the 2 scores to predict stroke recurrence, death, and cardiovascular events (stroke, transient ischemic attack, myocardial infarction, or arterial thromboembolism) in a nationwide Danish cohort study, among patients with incident ischemic stroke and no atrial fibrillation. We conducted a registry-based study in patients with incident ischemic stroke and no atrial fibrillation. Patients were stratified according to the CHA2DS2VASc score and the Essen Stroke Risk Score and were followed up until stroke recurrence or death. We estimated stratified incidence rates and hazard ratios and calculated the cumulative risks. 42 182 patients with incident ischemic stroke with median age 70.1 years were included. The overall 1-year incidence rates of recurrent stroke, death, and cardiovascular events were 3.6%, 10.5%, and 6.7%, respectively. The incidence rates, the hazard ratios, and the cumulative risk of all outcomes increased with increasing risk scores. C-statistics for both risk scores were around 0.55 for 1-year stroke recurrence and cardiovascular events and correspondingly for death around 0.67 for both scores. In this cohort of non-atrial fibrillation patients with incident ischemic stroke, increasing CHA2DS2VASc score and Essen Stroke Risk Score was associated with increasing risk of recurrent stroke, death, and cardiovascular events. Their discriminatory performance was modest and further refinements are required for clinical application. © 2015 American Heart Association, Inc.

Debt and growth: A non-parametric approach

Science.gov (United States)

Brida, Juan Gabriel; Gómez, David Matesanz; Seijas, Maria Nela

2017-11-01

In this study, we explore the dynamic relationship between public debt and economic growth by using a non-parametric approach based on data symbolization and clustering methods. The study uses annual data of general government consolidated gross debt-to-GDP ratio and gross domestic product for sixteen countries between 1977 and 2015. Using symbolic sequences, we introduce a notion of distance between the dynamical paths of different countries. Then, a Minimal Spanning Tree and a Hierarchical Tree are constructed from time series to help detecting the existence of groups of countries sharing similar economic performance. The main finding of the study appears for the period 2008-2016 when several countries surpassed the 90% debt-to-GDP threshold. During this period, three groups (clubs) of countries are obtained: high, mid and low indebted countries, suggesting that the employed debt-to-GDP threshold drives economic dynamics for the selected countries.

Stroke mimic diagnoses presenting to a hyperacute stroke unit.

Science.gov (United States)

Dawson, Ang; Cloud, Geoffrey C; Pereira, Anthony C; Moynihan, Barry J

2016-10-01

Stroke services have been centralised in several countries in recent years. Diagnosing acute stroke is challenging and a high proportion of patients admitted to stroke units are diagnosed as a non-stroke condition (stroke mimics). This study aims to describe the stroke mimic patient group, including their impact on stroke services. We analysed routine clinical data from 2,305 consecutive admissions to a stroke unit at St George's Hospital, London. Mimic groupings were derived from 335 individual codes into 17 groupings. From 2,305 admissions, 555 stroke mimic diagnoses were identified (24.2%) and 72% of stroke mimics had at least one stroke risk factor. Common mimic diagnoses were headache, seizure and syncope. Medically unexplained symptoms and decompensation of underlying conditions were also common. Median length of stay was 1 day; a diagnosis of dementia (p=0.028) or needing MRI (p=0.006) was associated with a longer stay. Despite emergency department assessment by specialist clinicians and computed tomography brain, one in four suspected stroke patients admitted to hospital had a non-stroke diagnosis. Stroke mimics represent a heterogeneous patient group with significant impacts on stroke services. Co-location of stroke and acute neurology services may offer advantages where service reorganisation is being considered. © Royal College of Physicians 2016. All rights reserved.

Application of statistical parametric mapping to SPET in the assessment of intractable childhood epilepsy

International Nuclear Information System (INIS)

Bruggemann, Jason M.; Lawson, John A.; Cunningham, Anne M.; Som, Seu S.; Haindl, Walter; Bye, Ann M.E.

2004-01-01

Statistical parametric mapping (SPM) quantification and analysis has been successfully applied to functional imaging studies of partial epilepsy syndromes in adults. The present study evaluated whether localisation of the epileptogenic zone (determined by SPM) improves upon visually examined single-photon emission tomography (SPET) imaging in presurgical assessment of children with temporal lobe epilepsy (TLE) and frontal lobe epilepsy (FLE). The patient sample consisted of 24 children (15 males) aged 2.1-17.8 years (9.8±4.3 years; mean±SD) with intractable TLE or FLE. SPET imaging was acquired routinely in presurgical evaluation. All patient images were transformed into the standard stereotactic space of the adult SPM SPET template prior to SPM statistical analysis. Individual patient images were contrasted with an adult control group of 22 healthy adult females. Resultant statistical parametric maps were rendered over the SPM canonical magnetic resonance imaging (MRI). Two corresponding sets of ictal and interictal SPM and SPET images were then generated for each patient. Experienced clinicians independently reviewed the image sets, blinded to clinical details. Concordance of the reports between SPM and SPET images, syndrome classification and MRI abnormality was studied. A fair level of inter-rater reliability (kappa=0.73) was evident for SPM localisation. SPM was concordant with SPET in 71% of all patients, the majority of the discordance being from the FLE group. SPM and SPET localisation were concordant with epilepsy syndrome in 80% of the TLE cases. Concordant localisation to syndrome was worse for both SPM (33%) and SPET (44%) in the FLE group. Data from a small sample of patients with varied focal structural pathologies suggested that SPM performed poorly relative to SPET in these cases. Concordance of SPM and SPET with syndrome was lower in patients younger than 6 years than in those aged 6 years and above. SPM is effective in localising the potential

Application of statistical parametric mapping to SPET in the assessment of intractable childhood epilepsy

Energy Technology Data Exchange (ETDEWEB)

Bruggemann, Jason M.; Lawson, John A.; Cunningham, Anne M. [Department of Neurology, Sydney Children' s Hospital and School of Women' s and Children' s Health, Faculty of Medicine, University of New South Wales, Randwick, New South Wales (Australia); Som, Seu S.; Haindl, Walter [Department of Nuclear Medicine, Prince of Wales Hospital, Randwick, New South Wales (Australia); Bye, Ann M.E. [Department of Neurology, Sydney Children' s Hospital and School of Women' s and Children' s Health, Faculty of Medicine, University of New South Wales, Randwick, New South Wales (Australia); Department of Neurology, Sydney Children' s Hospital, High Street, 2031, Randwick, NSW (Australia)

2004-03-01

Statistical parametric mapping (SPM) quantification and analysis has been successfully applied to functional imaging studies of partial epilepsy syndromes in adults. The present study evaluated whether localisation of the epileptogenic zone (determined by SPM) improves upon visually examined single-photon emission tomography (SPET) imaging in presurgical assessment of children with temporal lobe epilepsy (TLE) and frontal lobe epilepsy (FLE). The patient sample consisted of 24 children (15 males) aged 2.1-17.8 years (9.8{+-}4.3 years; mean{+-}SD) with intractable TLE or FLE. SPET imaging was acquired routinely in presurgical evaluation. All patient images were transformed into the standard stereotactic space of the adult SPM SPET template prior to SPM statistical analysis. Individual patient images were contrasted with an adult control group of 22 healthy adult females. Resultant statistical parametric maps were rendered over the SPM canonical magnetic resonance imaging (MRI). Two corresponding sets of ictal and interictal SPM and SPET images were then generated for each patient. Experienced clinicians independently reviewed the image sets, blinded to clinical details. Concordance of the reports between SPM and SPET images, syndrome classification and MRI abnormality was studied. A fair level of inter-rater reliability (kappa=0.73) was evident for SPM localisation. SPM was concordant with SPET in 71% of all patients, the majority of the discordance being from the FLE group. SPM and SPET localisation were concordant with epilepsy syndrome in 80% of the TLE cases. Concordant localisation to syndrome was worse for both SPM (33%) and SPET (44%) in the FLE group. Data from a small sample of patients with varied focal structural pathologies suggested that SPM performed poorly relative to SPET in these cases. Concordance of SPM and SPET with syndrome was lower in patients younger than 6 years than in those aged 6 years and above. SPM is effective in localising the

Non-obstructive carotid atherosclerosis and patent foramen ovale in young adults with cryptogenic stroke.

Science.gov (United States)

Jaffre, A; Guidolin, B; Ruidavets, J-B; Nasr, N; Larrue, V

2017-05-01

Up to 50% of ischaemic strokes in young adults are classified as cryptogenic despite extensive work-up. We sought to evaluate the prevalence of non-obstructive carotid atherosclerosis (NOCA) and its association with patent foramen ovale (PFO) in young adults with cryptogenic stroke (CS). Patients aged 18-54 years, consecutively treated for first-ever CS in an academic stroke service, were included. NOCA was assessed using carotid ultrasound examination and was defined as carotid plaque with young adults with CS. NOCA is negatively associated with PFO. Detecting NOCA is an important component of stroke investigation in young adults. © 2017 EAN.

Comparison of statistical and clinical predictions of functional outcome after ischemic stroke.

Directory of Open Access Journals (Sweden)

Douglas D Thompson

Full Text Available To determine whether the predictions of functional outcome after ischemic stroke made at the bedside using a doctor's clinical experience were more or less accurate than the predictions made by clinical prediction models (CPMs.A prospective cohort study of nine hundred and thirty one ischemic stroke patients recruited consecutively at the outpatient, inpatient and emergency departments of the Western General Hospital, Edinburgh between 2002 and 2005. Doctors made informal predictions of six month functional outcome on the Oxford Handicap Scale (OHS. Patients were followed up at six months with a validated postal questionnaire. For each patient we calculated the absolute predicted risk of death or dependence (OHS≥3 using five previously described CPMs. The specificity of a doctor's informal predictions of OHS≥3 at six months was good 0.96 (95% CI: 0.94 to 0.97 and similar to CPMs (range 0.94 to 0.96; however the sensitivity of both informal clinical predictions 0.44 (95% CI: 0.39 to 0.49 and clinical prediction models (range 0.38 to 0.45 was poor. The prediction of the level of disability after stroke was similar for informal clinical predictions (ordinal c-statistic 0.74 with 95% CI 0.72 to 0.76 and CPMs (range 0.69 to 0.75. No patient or clinician characteristic affected the accuracy of informal predictions, though predictions were more accurate in outpatients.CPMs are at least as good as informal clinical predictions in discriminating between good and bad functional outcome after ischemic stroke. The place of these models in clinical practice has yet to be determined.

Non-parametric transformation for data correlation and integration: From theory to practice

Energy Technology Data Exchange (ETDEWEB)

Datta-Gupta, A.; Xue, Guoping; Lee, Sang Heon [Texas A& M Univ., College Station, TX (United States)

1997-08-01

The purpose of this paper is two-fold. First, we introduce the use of non-parametric transformations for correlating petrophysical data during reservoir characterization. Such transformations are completely data driven and do not require a priori functional relationship between response and predictor variables which is the case with traditional multiple regression. The transformations are very general, computationally efficient and can easily handle mixed data types for example, continuous variables such as porosity, permeability and categorical variables such as rock type, lithofacies. The power of the non-parametric transformation techniques for data correlation has been illustrated through synthetic and field examples. Second, we utilize these transformations to propose a two-stage approach for data integration during heterogeneity characterization. The principal advantages of our approach over traditional cokriging or cosimulation methods are: (1) it does not require a linear relationship between primary and secondary data, (2) it exploits the secondary information to its fullest potential by maximizing the correlation between the primary and secondary data, (3) it can be easily applied to cases where several types of secondary or soft data are involved, and (4) it significantly reduces variance function calculations and thus, greatly facilitates non-Gaussian cosimulation. We demonstrate the data integration procedure using synthetic and field examples. The field example involves estimation of pore-footage distribution using well data and multiple seismic attributes.

SECONDARY PREVENTION OF STROKE IN PATIENTS WITH NON-VALVULAR ATRIAL FIBRILLATION: THE CLINICIANS’ VIEWPOINT

Directory of Open Access Journals (Sweden)

E. A. Drozdova

2015-09-01

Full Text Available Atrial fibrillation is one of the main risk factor of ischemic stroke. Current problems of the management of patients with stroke due to non-valvular atrial fibrillation and secondary stroke prevention in these patients are considered. Data of own author’s observation for patients of this type during 6 months after discharge from the hospital are presented. The problems which patients faced with are analyzed. Comparative assessment of warfarin and dabigatran therapies is given.

Causes of Death Data in the Global Burden of Disease Estimates for Ischemic and Hemorrhagic Stroke.

Science.gov (United States)

Truelsen, Thomas; Krarup, Lars-Henrik; Iversen, Helle K; Mensah, George A; Feigin, Valery L; Sposato, Luciano A; Naghavi, Mohsen

2015-01-01

Stroke mortality estimates in the Global Burden of Disease (GBD) study are based on routine mortality statistics and redistribution of ill-defined codes that cannot be a cause of death, the so-called 'garbage codes' (GCs). This study describes the contribution of these codes to stroke mortality estimates. All available mortality data were compiled and non-specific cause codes were redistributed based on literature review and statistical methods. Ill-defined codes were redistributed to their specific cause of disease by age, sex, country and year. The reassignment was done based on the International Classification of Diseases and the pathology behind each code by checking multiple causes of death and literature review. Unspecified stroke and primary and secondary hypertension are leading contributing 'GCs' to stroke mortality estimates for hemorrhagic stroke (HS) and ischemic stroke (IS). There were marked differences in the fraction of death assigned to IS and HS for unspecified stroke and hypertension between GBD regions and between age groups. A large proportion of stroke fatalities are derived from the redistribution of 'unspecified stroke' and 'hypertension' with marked regional differences. Future advancements in stroke certification, data collections and statistical analyses may improve the estimation of the global stroke burden. © 2015 S. Karger AG, Basel.

MEASURING DARK MATTER PROFILES NON-PARAMETRICALLY IN DWARF SPHEROIDALS: AN APPLICATION TO DRACO

International Nuclear Information System (INIS)

Jardel, John R.; Gebhardt, Karl; Fabricius, Maximilian H.; Williams, Michael J.; Drory, Niv

2013-01-01

We introduce a novel implementation of orbit-based (or Schwarzschild) modeling that allows dark matter density profiles to be calculated non-parametrically in nearby galaxies. Our models require no assumptions to be made about velocity anisotropy or the dark matter profile. The technique can be applied to any dispersion-supported stellar system, and we demonstrate its use by studying the Local Group dwarf spheroidal galaxy (dSph) Draco. We use existing kinematic data at larger radii and also present 12 new radial velocities within the central 13 pc obtained with the VIRUS-W integral field spectrograph on the 2.7 m telescope at McDonald Observatory. Our non-parametric Schwarzschild models find strong evidence that the dark matter profile in Draco is cuspy for 20 ≤ r ≤ 700 pc. The profile for r ≥ 20 pc is well fit by a power law with slope α = –1.0 ± 0.2, consistent with predictions from cold dark matter simulations. Our models confirm that, despite its low baryon content relative to other dSphs, Draco lives in a massive halo.

Non-fluent speech following stroke is caused by impaired efference copy.

Science.gov (United States)

Feenaughty, Lynda; Basilakos, Alexandra; Bonilha, Leonardo; den Ouden, Dirk-Bart; Rorden, Chris; Stark, Brielle; Fridriksson, Julius

2017-09-01

Efference copy is a cognitive mechanism argued to be critical for initiating and monitoring speech: however, the extent to which breakdown of efference copy mechanisms impact speech production is unclear. This study examined the best mechanistic predictors of non-fluent speech among 88 stroke survivors. Objective speech fluency measures were subjected to a principal component analysis (PCA). The primary PCA factor was then entered into a multiple stepwise linear regression analysis as the dependent variable, with a set of independent mechanistic variables. Participants' ability to mimic audio-visual speech ("speech entrainment response") was the best independent predictor of non-fluent speech. We suggest that this "speech entrainment" factor reflects integrity of internal monitoring (i.e., efference copy) of speech production, which affects speech initiation and maintenance. Results support models of normal speech production and suggest that therapy focused on speech initiation and maintenance may improve speech fluency for individuals with chronic non-fluent aphasia post stroke.

Technical issues relating to the statistical parametric mapping of brain SPECT studies

International Nuclear Information System (INIS)

Hatton, R.L.; Cordato, N.; Hutton, B.F.; Lau, Y.H.; Evans, S.G.

2000-01-01

Full text: Statistical Parametric Mapping (SPM) is a software tool designed for the statistical analysis of functional neuro images, specifically Positron Emission Tomography and functional Magnetic Resonance Imaging, and more recently SPECT. This review examines some problems associated with the analysis of SPECT. A comparison of a patient group with normal studies revealed factors that could influence results, some that commonly occur, others that require further exploration. To optimise the differences between two groups of subjects, both spatial variability and differences in global activity must be minimised. The choice and effectiveness of co registration method and approach to normalisation of activity concentration can affect the optimisation. A small number of subject scans were identified as possessing truncated data resulting in edge effects that could adversely influence the analysis. Other problems included unusual areas of significance possibly related to reconstruction methods and the geometry associated with nonparallel collimators. Areas of extra cerebral significance are a point of concern - and may result from scatter effects, or mis registration. Difficulties in patient positioning, due to postural limitations, can lead to resolution differences. SPM has been used to assess areas of statistical significance arising from these technical factors, as opposed to areas of true clinical significance when comparing subject groups. This contributes to a better understanding of the effects of technical factors so that these may be eliminated, minimised, or incorporated in the study design. Copyright (2000) The Australian and New Zealand Society of Nuclear Medicine Inc

Markovian Dynamics of Josephson Parametric Amplification

Directory of Open Access Journals (Sweden)

W. Kaiser

2017-09-01

Full Text Available In this work, we derive the dynamics of the lossy DC pumped non-degenerate Josephson parametric amplifier (DCPJPA. The main element in a DCPJPA is the superconducting Josephson junction. The DC bias generates the AC Josephson current varying the nonlinear inductance of the junction. By this way the Josephson junction acts as the pump oscillator as well as the time varying reactance of the parametric amplifier. In quantum-limited amplification, losses and noise have an increased impact on the characteristics of an amplifier. We outline the classical model of the lossy DCPJPA and derive the available noise power spectral densities. A classical treatment is not capable of including properties like spontaneous emission which is mandatory in case of amplification at the quantum limit. Thus, we derive a quantum mechanical model of the lossy DCPJPA. Thermal losses are modeled by the quantum Langevin approach, by coupling the quantized system to a photon heat bath in thermodynamic equilibrium. The mode occupation in the bath follows the Bose-Einstein statistics. Based on the second quantization formalism, we derive the Heisenberg equations of motion of both resonator modes. We assume the dynamics of the system to follow the Markovian approximation, i.e. the system only depends on its actual state and is memory-free. We explicitly compute the time evolution of the contributions to the signal mode energy and give numeric examples based on different damping and coupling constants. Our analytic results show, that this model is capable of including thermal noise into the description of the DC pumped non-degenerate Josephson parametric amplifier.

Markovian Dynamics of Josephson Parametric Amplification

Science.gov (United States)

Kaiser, Waldemar; Haider, Michael; Russer, Johannes A.; Russer, Peter; Jirauschek, Christian

2017-09-01

In this work, we derive the dynamics of the lossy DC pumped non-degenerate Josephson parametric amplifier (DCPJPA). The main element in a DCPJPA is the superconducting Josephson junction. The DC bias generates the AC Josephson current varying the nonlinear inductance of the junction. By this way the Josephson junction acts as the pump oscillator as well as the time varying reactance of the parametric amplifier. In quantum-limited amplification, losses and noise have an increased impact on the characteristics of an amplifier. We outline the classical model of the lossy DCPJPA and derive the available noise power spectral densities. A classical treatment is not capable of including properties like spontaneous emission which is mandatory in case of amplification at the quantum limit. Thus, we derive a quantum mechanical model of the lossy DCPJPA. Thermal losses are modeled by the quantum Langevin approach, by coupling the quantized system to a photon heat bath in thermodynamic equilibrium. The mode occupation in the bath follows the Bose-Einstein statistics. Based on the second quantization formalism, we derive the Heisenberg equations of motion of both resonator modes. We assume the dynamics of the system to follow the Markovian approximation, i.e. the system only depends on its actual state and is memory-free. We explicitly compute the time evolution of the contributions to the signal mode energy and give numeric examples based on different damping and coupling constants. Our analytic results show, that this model is capable of including thermal noise into the description of the DC pumped non-degenerate Josephson parametric amplifier.

SPM analysis of parametric (R)-[11C]PK11195 binding images: plasma input versus reference tissue parametric methods.

Science.gov (United States)

Schuitemaker, Alie; van Berckel, Bart N M; Kropholler, Marc A; Veltman, Dick J; Scheltens, Philip; Jonker, Cees; Lammertsma, Adriaan A; Boellaard, Ronald

2007-05-01

(R)-[11C]PK11195 has been used for quantifying cerebral microglial activation in vivo. In previous studies, both plasma input and reference tissue methods have been used, usually in combination with a region of interest (ROI) approach. Definition of ROIs, however, can be labourious and prone to interobserver variation. In addition, results are only obtained for predefined areas and (unexpected) signals in undefined areas may be missed. On the other hand, standard pharmacokinetic models are too sensitive to noise to calculate (R)-[11C]PK11195 binding on a voxel-by-voxel basis. Linearised versions of both plasma input and reference tissue models have been described, and these are more suitable for parametric imaging. The purpose of this study was to compare the performance of these plasma input and reference tissue parametric methods on the outcome of statistical parametric mapping (SPM) analysis of (R)-[11C]PK11195 binding. Dynamic (R)-[11C]PK11195 PET scans with arterial blood sampling were performed in 7 younger and 11 elderly healthy subjects. Parametric images of volume of distribution (Vd) and binding potential (BP) were generated using linearised versions of plasma input (Logan) and reference tissue (Reference Parametric Mapping) models. Images were compared at the group level using SPM with a two-sample t-test per voxel, both with and without proportional scaling. Parametric BP images without scaling provided the most sensitive framework for determining differences in (R)-[11C]PK11195 binding between younger and elderly subjects. Vd images could only demonstrate differences in (R)-[11C]PK11195 binding when analysed with proportional scaling due to intersubject variation in K1/k2 (blood-brain barrier transport and non-specific binding).

Thrombolysis for acute ischaemic stroke with alteplase in an Asian population: results of the multicenter, multinational Safe Implementation of Thrombolysis in Stroke-Non-European Union World (SITS-NEW).

Science.gov (United States)

Rha, Joung-Ho; Shrivastava, Vasantha Padma; Wang, Yongjun; Lee, Kim En; Ahmed, Niaz; Bluhmki, Erich; Hermansson, Karin; Wahlgren, Nils

2014-10-01

Safe Implementation of Thrombolysis in Stroke-Non-European Union World was a multinational, prospective, open, monitored, observational study of intravenous alteplase as thrombolytic therapy in clinical practice. Safe Implementation of Thrombolysis in Stroke-Non-European Union World was required to assess the safety of alteplase in an Asian population by comparison with results from the European Safe Implementation of Thrombolysis in Stroke-Monitoring Study and pooled results from randomized controlled trials. To evaluate the efficacy and safety of intravenous alteplase (0·9 mg/kg) as thrombolytic therapy within three-hours of onset of acute ischaemic stroke in an Asian population. The 591 patients included were treated at 48 centers in four countries (South Korea, China, India, and Singapore) between 2006 and 2008. Primary outcomes were symptomatic (deterioration in National Institutes of Health Stroke Scale score ≥4 or death within the first 24 h) intracerebral haemorrhage type 2 22-36 h after the thrombolysis and mortality at three-month follow-up. The secondary outcome was functional independence (modified Rankin Scale score 0-2) at three-months. Results were compared with those from Safe Implementation of Thrombolysis in Stroke-Monitoring Study (n = 6483) and pooled results of patients (n = 415) who received intravenous alteplase (0·9 mg/kg) zero- to three-hours from onset of stroke symptoms in four randomized controlled trials (National Institute of Neurological Disorders and Stroke A and B, Altephase Thrombolysis for Acute Noninterventional Therapy in Ischaemic Stroke, and European Cooperative Acute Stroke Study II). Results are presented as Safe Implementation of Thrombolysis in Stroke-Non-European Union World vs. Safe Implementation of Thrombolysis in Stroke-Monitoring Study vs. pooled randomized controlled trials. Median age was 64 vs. 68 vs. 70 years, National Institutes of Health Stroke Scale score at baseline was 12 vs. 12 vs. 13

rSeqNP: a non-parametric approach for detecting differential expression and splicing from RNA-Seq data.

Science.gov (United States)

Shi, Yang; Chinnaiyan, Arul M; Jiang, Hui

2015-07-01

High-throughput sequencing of transcriptomes (RNA-Seq) has become a powerful tool to study gene expression. Here we present an R package, rSeqNP, which implements a non-parametric approach to test for differential expression and splicing from RNA-Seq data. rSeqNP uses permutation tests to access statistical significance and can be applied to a variety of experimental designs. By combining information across isoforms, rSeqNP is able to detect more differentially expressed or spliced genes from RNA-Seq data. The R package with its source code and documentation are freely available at http://www-personal.umich.edu/∼jianghui/rseqnp/. jianghui@umich.edu Supplementary data are available at Bioinformatics online. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Functional brain mapping using H{sub 2}{sup 15}O positron emission tomography (I): statistical parametric mapping method

Energy Technology Data Exchange (ETDEWEB)

Lee, Dong Soo; Lee, Jae Sung; Kim, Kyeong Min; Chung, June Key; Lee, Myung Chul [College of Medicine, Seoul National Univ., Seoul (Korea, Republic of)

1998-08-01

We investigated the statistical methods to compose the functional brain map of human working memory and the principal factors that have an effect on the methods for localization. Repeated PET scans with successive four tasks, which consist of one control and three different activation tasks, were performed on six right-handed normal volunteers for 2 minutes after bolus injections of 925 MBq H{sub 2}{sup 15}O at the intervals of 30 minutes. Image data were analyzed using SPM96 (Statistical Parametric Mapping) implemented with Matlab (Mathworks Inc., U.S.A.). Images from the same subject were spatially registered and were normalized using linear and nonlinear transformation methods. Significant difference between control and each activation state was estimated at every voxel based on the general linear model. Differences of global counts were removed using analysis of covariance (ANCOVA) with global activity as covariate. Using the mean and variance for each condition which was adjusted using ANCOVA, t-statistics was performed on every voxel. To interpret the results more easily, t-values were transformed to the standard Gaussian distribution (Z-score). All the subjects carried out the activation and control tests successfully. Average rate of correct answers was 95%. The numbers of activated blobs were 4 for verbal memory I, 9 for verbal memory II, 9 for visual memory, and 6 for conjunctive activation of these three tasks. The verbal working memory activates predominantly left-sided structures, and the visual memory activates the right hemisphere. We conclude that rCBF PET imaging and statistical parametric mapping method were useful in the localization of the brain regions for verbal and visual working memory.

Induction of neuroplasticity and recovery in post-stroke aphasia by non-invasive brain stimulation.

Science.gov (United States)

Shah, Priyanka P; Szaflarski, Jerzy P; Allendorfer, Jane; Hamilton, Roy H

2013-12-24

Stroke victims tend to prioritize speaking, writing, and walking as the three most important rehabilitation goals. Of note is that two of these goals involve communication. This underscores the significance of developing successful approaches to aphasia treatment for the several hundred thousand new aphasia patients each year and over 1 million stroke survivors with chronic aphasia in the U.S. alone. After several years of growth as a research tool, non-invasive brain stimulation (NBS) is gradually entering the arena of clinical aphasiology. In this review, we first examine the current state of knowledge of post-stroke language recovery including the contributions from the dominant and non-dominant hemispheres. Next, we briefly discuss the methods and the physiologic basis of the use of inhibitory and excitatory repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) as research tools in patients who experience post-stroke aphasia. Finally, we provide a critical review of the most influential evidence behind the potential use of these two brain stimulation methods as clinical rehabilitative tools.

A statistical approach to bioclimatic trend detection in the airborne pollen records of Catalonia (NE Spain)

Science.gov (United States)

Fernández-Llamazares, Álvaro; Belmonte, Jordina; Delgado, Rosario; De Linares, Concepción

2014-04-01

Airborne pollen records are a suitable indicator for the study of climate change. The present work focuses on the role of annual pollen indices for the detection of bioclimatic trends through the analysis of the aerobiological spectra of 11 taxa of great biogeographical relevance in Catalonia over an 18-year period (1994-2011), by means of different parametric and non-parametric statistical methods. Among others, two non-parametric rank-based statistical tests were performed for detecting monotonic trends in time series data of the selected airborne pollen types and we have observed that they have similar power in detecting trends. Except for those cases in which the pollen data can be well-modeled by a normal distribution, it is better to apply non-parametric statistical methods to aerobiological studies. Our results provide a reliable representation of the pollen trends in the region and suggest that greater pollen quantities are being liberated to the atmosphere in the last years, specially by Mediterranean taxa such as Pinus, Total Quercus and Evergreen Quercus, although the trends may differ geographically. Longer aerobiological monitoring periods are required to corroborate these results and survey the increasing levels of certain pollen types that could exert an impact in terms of public health.

Comparison of the Chinese ischemic stroke subclassification and Trial of Org 10172 in acute stroke treatment systems in minor stroke.

Science.gov (United States)

Tan, Sha; Zhang, Lei; Chen, Xiaoyu; Wang, Yanqiang; Lin, Yinyao; Cai, Wei; Shan, Yilong; Qiu, Wei; Hu, Xueqiang; Lu, Zhengqi

2016-09-06

The underlying causes of minor stroke are difficult to assess. Here, we evaluate the reliability of the Chinese Ischemic Stroke Subclassification (CISS) system in patients with minor stroke, and compare it to the Trial of Org 10172 in Acute Stroke Treatment (TOAST) system. A total of 320 patients with minor stroke were retrospectively registered and categorized into different subgroups of the CISS and TOAST by two neurologists. Inter- and intra-rater agreement with the two systems were assessed with kappa statistics. The percentage of undetermined etiology (UE) cases in the CISS system was 77.3 % less than that in the TOAST system, which was statistically significant (P < 0.001). The percentage of large artery atherosclerosis (LAA) in the CISS system was 79.7 % more than that in the TOAST system, which was also statistically significant (P < 0.001). The kappa values for inter-examiner agreement were 0.898 (P = 0.031) and 0.732 (P = 0.022) for the CISS and TOAST systems, respectively. The intra-observer reliability indexes were moderate (0.569 for neurologist A, and 0.487 for neurologist B). The CISS and TOAST systems are both reliable in classifying patients with minor stroke. CISS classified more patients into known etiologic categories without sacrificing reliability.

Statistics for non-statisticians

CERN Document Server

Madsen, Birger Stjernholm

2016-01-01

This book was written for those who need to know how to collect, analyze and present data. It is meant to be a first course for practitioners, a book for private study or brush-up on statistics, and supplementary reading for general statistics classes. The book is untraditional, both with respect to the choice of topics and the presentation: Topics were determined by what is most useful for practical statistical work, and the presentation is as non-mathematical as possible. The book contains many examples using statistical functions in spreadsheets. In this second edition, new topics have been included e.g. within the area of statistical quality control, in order to make the book even more useful for practitioners working in industry. .

Comparison of short term mortality in ischemic stroke patients with or without stress hyperglycemia

International Nuclear Information System (INIS)

Raja, W; Zaidi, S.B.H.; Waheed, S.; Khan, M.

2016-01-01

Objective: To compare short term mortality in non-diabetic ischemic stroke patients with or without stress hyperglycemia. Study Design: Cohort study. Place and Duration of Study: This study was carried out at Neurology Department of Military Hospital, Rawalpindi from Jan 2010 to Jul 2012 for a total duration of six months. Material and Methods: Non-diabetic ischemic stroke patients were included in the study and they were divided in two groups. Each group had 75 patients. Group 'I' (Normoglycemic or control group) had normal blood glucose level while group 'II' (Hyperglycaemic or cohort) had hyperglycaemia on presentation or over next 72 hours. Prognosis in terms of patient either being dead or alive was determined within or at 4 weeks of admission in both groups. Data were entered and analysed using Statistical Package for Social Sciences SPSS version 10. Descriptive statistics were calculated for both qualitative and quantitative variables. For comparison of short term mortality in hyperglycaemic and normoglycemic stroke patients, chi-square test was applied. p-value <0.05 was considered statistically significant. Results: Short term mortality was higher in cohort (hyperglycemic) group as compared to control (normoglycemic) group (34.7 percent vs. 14.7 percent). Relative risk was 2.36. The groups had a statistically significant difference in the short term mortality within four weeks with a Chi-Square 'p' value of 0.004 (p=0.004). Conclusion: Short term mortality in non-diabetic ischemic stroke patients with stress hyperglycemia is higher than those patients who do not have stress hyperglycemia. (author)

A NON-PARAMETRIC APPROACH TO CONSTRAIN THE TRANSFER FUNCTION IN REVERBERATION MAPPING

Energy Technology Data Exchange (ETDEWEB)

Li, Yan-Rong; Wang, Jian-Min [Key Laboratory for Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, 19B Yuquan Road, Beijing 100049 (China); Bai, Jin-Ming, E-mail: liyanrong@mail.ihep.ac.cn [Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China)

2016-11-10

Broad emission lines of active galactic nuclei stem from a spatially extended region (broad-line region, BLR) that is composed of discrete clouds and photoionized by the central ionizing continuum. The temporal behaviors of these emission lines are blurred echoes of continuum variations (i.e., reverberation mapping, RM) and directly reflect the structures and kinematic information of BLRs through the so-called transfer function (also known as the velocity-delay map). Based on the previous works of Rybicki and Press and Zu et al., we develop an extended, non-parametric approach to determine the transfer function for RM data, in which the transfer function is expressed as a sum of a family of relatively displaced Gaussian response functions. Therefore, arbitrary shapes of transfer functions associated with complicated BLR geometry can be seamlessly included, enabling us to relax the presumption of a specified transfer function frequently adopted in previous studies and to let it be determined by observation data. We formulate our approach in a previously well-established framework that incorporates the statistical modeling of continuum variations as a damped random walk process and takes into account long-term secular variations which are irrelevant to RM signals. The application to RM data shows the fidelity of our approach.

A NON-PARAMETRIC APPROACH TO CONSTRAIN THE TRANSFER FUNCTION IN REVERBERATION MAPPING

International Nuclear Information System (INIS)

Li, Yan-Rong; Wang, Jian-Min; Bai, Jin-Ming

2016-01-01

Broad emission lines of active galactic nuclei stem from a spatially extended region (broad-line region, BLR) that is composed of discrete clouds and photoionized by the central ionizing continuum. The temporal behaviors of these emission lines are blurred echoes of continuum variations (i.e., reverberation mapping, RM) and directly reflect the structures and kinematic information of BLRs through the so-called transfer function (also known as the velocity-delay map). Based on the previous works of Rybicki and Press and Zu et al., we develop an extended, non-parametric approach to determine the transfer function for RM data, in which the transfer function is expressed as a sum of a family of relatively displaced Gaussian response functions. Therefore, arbitrary shapes of transfer functions associated with complicated BLR geometry can be seamlessly included, enabling us to relax the presumption of a specified transfer function frequently adopted in previous studies and to let it be determined by observation data. We formulate our approach in a previously well-established framework that incorporates the statistical modeling of continuum variations as a damped random walk process and takes into account long-term secular variations which are irrelevant to RM signals. The application to RM data shows the fidelity of our approach.

Non-parametric causality detection: An application to social media and financial data

Science.gov (United States)

Tsapeli, Fani; Musolesi, Mirco; Tino, Peter

2017-10-01

According to behavioral finance, stock market returns are influenced by emotional, social and psychological factors. Several recent works support this theory by providing evidence of correlation between stock market prices and collective sentiment indexes measured using social media data. However, a pure correlation analysis is not sufficient to prove that stock market returns are influenced by such emotional factors since both stock market prices and collective sentiment may be driven by a third unmeasured factor. Controlling for factors that could influence the study by applying multivariate regression models is challenging given the complexity of stock market data. False assumptions about the linearity or non-linearity of the model and inaccuracies on model specification may result in misleading conclusions. In this work, we propose a novel framework for causal inference that does not require any assumption about a particular parametric form of the model expressing statistical relationships among the variables of the study and can effectively control a large number of observed factors. We apply our method in order to estimate the causal impact that information posted in social media may have on stock market returns of four big companies. Our results indicate that social media data not only correlate with stock market returns but also influence them.

Piracetam for acute ischaemic stroke.

Science.gov (United States)

Ricci, Stefano; Celani, Maria Grazia; Cantisani, Teresa Anna; Righetti, Enrico

2012-09-12

Piracetam has neuroprotective and antithrombotic effects that may help to reduce death and disability in people with acute stroke. This is an update of a Cochrane Review first published in 1999, and previously updated in 2006 and 2009. To assess the effects of piracetam in acute, presumed ischaemic stroke. We searched the Cochrane Stroke Group Trials Register (last searched 15 May 2011), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 2), MEDLINE (1966 to May 2011), EMBASE (1980 to May 2011), and ISI Science Citation Index (1981 to May 2011). We also contacted the manufacturer of piracetam to identify further published and unpublished studies. Randomised trials comparing piracetam with control, with at least mortality reported and entry to the trial within three days of stroke onset. Two review authors extracted data and assessed trial quality and this was checked by the other two review authors. We contacted study authors for missing information. We included three trials involving 1002 patients, with one trial contributing 93% of the data. Participants' ages ranged from 40 to 85 years, and both sexes were equally represented. Piracetam was associated with a statistically non-significant increase in death at one month (approximately 31% increase, 95% confidence interval 81% increase to 5% reduction). This trend was no longer apparent in the large trial after correction for imbalance in stroke severity. Limited data showed no difference between the treatment and control groups for functional outcome, dependence or proportion of patients dead or dependent. Adverse effects were not reported. There is some suggestion (but no statistically significant result) of an unfavourable effect of piracetam on early death, but this may have been caused by baseline differences in stroke severity in the trials. There is not enough evidence to assess the effect of piracetam on dependence.

Using non-parametric methods in econometric production analysis

DEFF Research Database (Denmark)

Czekaj, Tomasz Gerard; Henningsen, Arne

Econometric estimation of production functions is one of the most common methods in applied economic production analysis. These studies usually apply parametric estimation techniques, which obligate the researcher to specify the functional form of the production function. Most often, the Cobb...... results—including measures that are of interest of applied economists, such as elasticities. Therefore, we propose to use nonparametric econometric methods. First, they can be applied to verify the functional form used in parametric estimations of production functions. Second, they can be directly used...

Non-breathing-related sleep disorders following stroke.

Science.gov (United States)

Marquez-Romero, J M; Morales-Ramírez, M; Arauz, A

2014-01-01

It has been shown that sleep-related breathing disorders, especially sleep apnea, are very common in patients who have had a stroke, and that they also reduce the potential for neurological recovery. Nevertheless, other sleep disorders caused by stroke (excessive daytime sleepiness, insomnia, sleep related movement disorders) can also cause or increase stroke-related disability, and this fact is less commonly known. Studies with polysomnography have shown many abnormalities in sleep architecture during the acute phase of stroke; these abnormalities have a negative impact on the patient's quality of life although they tend to improve with time. This also happens with other sleep disorders occurring as the result of a stroke (insomnia, narcolepsy, restless legs syndrome, periodic limb movement disorder and REM sleep behavior disorder), which are nevertheless potentially treatable. In this article, we briefly review the physiopathology and epidemiology of the disorders listed above in order to raise awareness about the importance of these disorders and the effects they elicit in stroke patients. Sleep disorders that are not breathing-related have scarcely been studied in stroke patients despite the fact that almost all such disorders may present as a result of a cerebrovascular event. Copyright © 2012 Sociedad Española de Neurología. Published by Elsevier Espana. All rights reserved.

Non-Parametric Bayesian Updating within the Assessment of Reliability for Offshore Wind Turbine Support Structures

DEFF Research Database (Denmark)

Ramirez, José Rangel; Sørensen, John Dalsgaard

2011-01-01

This work illustrates the updating and incorporation of information in the assessment of fatigue reliability for offshore wind turbine. The new information, coming from external and condition monitoring can be used to direct updating of the stochastic variables through a non-parametric Bayesian u...

SOCR Analyses - an Instructional Java Web-based Statistical Analysis Toolkit.

Science.gov (United States)

Chu, Annie; Cui, Jenny; Dinov, Ivo D

2009-03-01

The Statistical Online Computational Resource (SOCR) designs web-based tools for educational use in a variety of undergraduate courses (Dinov 2006). Several studies have demonstrated that these resources significantly improve students' motivation and learning experiences (Dinov et al. 2008). SOCR Analyses is a new component that concentrates on data modeling and analysis using parametric and non-parametric techniques supported with graphical model diagnostics. Currently implemented analyses include commonly used models in undergraduate statistics courses like linear models (Simple Linear Regression, Multiple Linear Regression, One-Way and Two-Way ANOVA). In addition, we implemented tests for sample comparisons, such as t-test in the parametric category; and Wilcoxon rank sum test, Kruskal-Wallis test, Friedman's test, in the non-parametric category. SOCR Analyses also include several hypothesis test models, such as Contingency tables, Friedman's test and Fisher's exact test.The code itself is open source (http://socr.googlecode.com/), hoping to contribute to the efforts of the statistical computing community. The code includes functionality for each specific analysis model and it has general utilities that can be applied in various statistical computing tasks. For example, concrete methods with API (Application Programming Interface) have been implemented in statistical summary, least square solutions of general linear models, rank calculations, etc. HTML interfaces, tutorials, source code, activities, and data are freely available via the web (www.SOCR.ucla.edu). Code examples for developers and demos for educators are provided on the SOCR Wiki website.In this article, the pedagogical utilization of the SOCR Analyses is discussed, as well as the underlying design framework. As the SOCR project is on-going and more functions and tools are being added to it, these resources are constantly improved. The reader is strongly encouraged to check the SOCR site for most

Detection of Parametric Roll on Ships

DEFF Research Database (Denmark)

Galeazzi, Roberto; Blanke, Mogens; Poulsen, Niels Kjølstad

2012-01-01

phenomenon could make the navigator change ship’s speed and heading, and these remedial actions could make the vessel escape the bifurcation. This chapter proposes non-parametric methods to detect the onset of parametric roll resonance. Theoretical conditions for parametric resonance are re...... on experimental data from towing tank tests and data from a container ship passing an Atlantic storm....

SOCR Analyses: Implementation and Demonstration of a New Graphical Statistics Educational Toolkit

Directory of Open Access Journals (Sweden)

Annie Chu

2009-04-01

Full Text Available The web-based, Java-written SOCR (Statistical Online Computational Resource toolshave been utilized in many undergraduate and graduate level statistics courses for sevenyears now (Dinov 2006; Dinov et al. 2008b. It has been proven that these resourcescan successfully improve students' learning (Dinov et al. 2008b. Being rst publishedonline in 2005, SOCR Analyses is a somewhat new component and it concentrate on datamodeling for both parametric and non-parametric data analyses with graphical modeldiagnostics. One of the main purposes of SOCR Analyses is to facilitate statistical learn-ing for high school and undergraduate students. As we have already implemented SOCRDistributions and Experiments, SOCR Analyses and Charts fulll the rest of a standardstatistics curricula. Currently, there are four core components of SOCR Analyses. Linearmodels included in SOCR Analyses are simple linear regression, multiple linear regression,one-way and two-way ANOVA. Tests for sample comparisons include t-test in the para-metric category. Some examples of SOCR Analyses' in the non-parametric category areWilcoxon rank sum test, Kruskal-Wallis test, Friedman's test, Kolmogorov-Smirno testand Fligner-Killeen test. Hypothesis testing models include contingency table, Friedman'stest and Fisher's exact test. The last component of Analyses is a utility for computingsample sizes for normal distribution. In this article, we present the design framework,computational implementation and the utilization of SOCR Analyses.

On the Optimal Location of Sensors for Parametric Identification of Linear Structural Systems

DEFF Research Database (Denmark)

Kirkegaard, Poul Henning; Brincker, Rune

A survey of the field of optimal location of sensors for parametric identification of linear structural systems is presented. The survey shows that few papers are devoted to the case of optimal location sensors in which the measurements are modelled by a random field with non-trivial covariance...... function. Most often it is assumed that the results of the measurements are statistically independent variables. In an example the importance of considering the measurements as statistically dependent random variables is shown. The example is concerned with optimal location of sensors for parametric...... identification of modal parameters for a vibrating beam under random loading. The covariance of the modal parameters expected to be obtained is investigated to variations of number and location of sensors. Further, the influence of the noise on the optimal location of the sensors is investigated....

Bootstrapping the economy -- a non-parametric method of generating consistent future scenarios

OpenAIRE

Müller, Ulrich A; Bürgi, Roland; Dacorogna, Michel M

2004-01-01

The fortune and the risk of a business venture depends on the future course of the economy. There is a strong demand for economic forecasts and scenarios that can be applied to planning and modeling. While there is an ongoing debate on modeling economic scenarios, the bootstrapping (or resampling) approach presented here has several advantages. As a non-parametric method, it directly relies on past market behaviors rather than debatable assumptions on models and parameters. Simultaneous dep...

Non-invasive brain stimulation for fine motor improvement after stroke: a meta-analysis.

Science.gov (United States)

O'Brien, A T; Bertolucci, F; Torrealba-Acosta, G; Huerta, R; Fregni, F; Thibaut, A

2018-05-09

The aim of this study was to determine whether non-invasive brain stimulation (NIBS) techniques improve fine motor performance in stroke. We searched PubMed, EMBASE, Web of Science, SciELO and OpenGrey for randomized clinical trials on NIBS for fine motor performance in stroke patients and healthy participants. We computed Hedges' g for active and sham groups, pooled data as random-effects models and performed sensitivity analysis on chronicity, montage, frequency of stimulation and risk of bias. Twenty-nine studies (351 patients and 152 healthy subjects) were reviewed. Effect sizes in stroke populations for transcranial direct current stimulation and repeated transcranial magnetic stimulation were 0.31 [95% confidence interval (CI), 0.08-0.55; P = 0.010; Tau 2 , 0.09; I 2 , 34%; Q, 18.23; P = 0.110] and 0.46 (95% CI, 0.00-0.92; P = 0.05; Tau 2 , 0.38; I 2 , 67%; Q, 30.45; P = 0.007). The effect size of non-dominant healthy hemisphere transcranial direct current stimulation on non-dominant hand function was 1.25 (95% CI, 0.09-2.41; P = 0.04; Tau 2 , 1.26; I 2 , 93%; Q, 40.27; P < 0.001). Our results show that NIBS is associated with gains in fine motor performance in chronic stroke patients and healthy subjects. This supports the effects of NIBS on motor learning and encourages investigation to optimize their effects in clinical and research settings. © 2018 EAN.

ASTRAL-R score predicts non-recanalisation after intravenous thrombolysis in acute ischaemic stroke.

Science.gov (United States)

Vanacker, Peter; Heldner, Mirjam R; Seiffge, David; Mueller, Hubertus; Eskandari, Ashraf; Traenka, Christopher; Ntaios, George; Mosimann, Pascal J; Sztajzel, Roman; Mendes Pereira, Vitor; Cras, Patrick; Engelter, Stefan; Lyrer, Philippe; Fischer, Urs; Lambrou, Dimitris; Arnold, Marcel; Michel, Patrik

2015-05-01

Intravenous thrombolysis (IVT) as treatment in acute ischaemic strokes may be insufficient to achieve recanalisation in certain patients. Predicting probability of non-recanalisation after IVT may have the potential to influence patient selection to more aggressive management strategies. We aimed at deriving and internally validating a predictive score for post-thrombolytic non-recanalisation, using clinical and radiological variables. In thrombolysis registries from four Swiss academic stroke centres (Lausanne, Bern, Basel and Geneva), patients were selected with large arterial occlusion on acute imaging and with repeated arterial assessment at 24 hours. Based on a logistic regression analysis, an integer-based score for each covariate of the fitted multivariate model was generated. Performance of integer-based predictive model was assessed by bootstrapping available data and cross validation (delete-d method). In 599 thrombolysed strokes, five variables were identified as independent predictors of absence of recanalisation: Acute glucose > 7 mmol/l (A), significant extracranial vessel STenosis (ST), decreased Range of visual fields (R), large Arterial occlusion (A) and decreased Level of consciousness (L). All variables were weighted 1, except for (L) which obtained 2 points based on β-coefficients on the logistic scale. ASTRAL-R scores 0, 3 and 6 corresponded to non-recanalisation probabilities of 18, 44 and 74 % respectively. Predictive ability showed AUC of 0.66 (95 %CI, 0.61-0.70) when using bootstrap and 0.66 (0.63-0.68) when using delete-d cross validation. In conclusion, the 5-item ASTRAL-R score moderately predicts non-recanalisation at 24 hours in thrombolysed ischaemic strokes. If its performance can be confirmed by external validation and its clinical usefulness can be proven, the score may influence patient selection for more aggressive revascularisation strategies in routine clinical practice.

Statistical Parametric Mapping to Identify Differences between Consensus-Based Joint Patterns during Gait in Children with Cerebral Palsy.

Science.gov (United States)

Nieuwenhuys, Angela; Papageorgiou, Eirini; Desloovere, Kaat; Molenaers, Guy; De Laet, Tinne

2017-01-01

Experts recently identified 49 joint motion patterns in children with cerebral palsy during a Delphi consensus study. Pattern definitions were therefore the result of subjective expert opinion. The present study aims to provide objective, quantitative data supporting the identification of these consensus-based patterns. To do so, statistical parametric mapping was used to compare the mean kinematic waveforms of 154 trials of typically developing children (n = 56) to the mean kinematic waveforms of 1719 trials of children with cerebral palsy (n = 356), which were classified following the classification rules of the Delphi study. Three hypotheses stated that: (a) joint motion patterns with 'no or minor gait deviations' (n = 11 patterns) do not differ significantly from the gait pattern of typically developing children; (b) all other pathological joint motion patterns (n = 38 patterns) differ from typically developing gait and the locations of difference within the gait cycle, highlighted by statistical parametric mapping, concur with the consensus-based classification rules. (c) all joint motion patterns at the level of each joint (n = 49 patterns) differ from each other during at least one phase of the gait cycle. Results showed that: (a) ten patterns with 'no or minor gait deviations' differed somewhat unexpectedly from typically developing gait, but these differences were generally small (≤3°); (b) all other joint motion patterns (n = 38) differed from typically developing gait and the significant locations within the gait cycle that were indicated by the statistical analyses, coincided well with the classification rules; (c) joint motion patterns at the level of each joint significantly differed from each other, apart from two sagittal plane pelvic patterns. In addition to these results, for several joints, statistical analyses indicated other significant areas during the gait cycle that were not included in the pattern definitions of the consensus study

Effects of non-paretic arm exercises using a tubing band on abdominal muscle activity in stroke patients.

Science.gov (United States)

Lee, Dong-Kyu; Kang, Min-Hyeok; Kim, Ji-Won; Kim, Yang-Gon; Park, Ji-Hyuk; Oh, Jae-Seop

2013-01-01

Abdominal strengthening exercises are important for stroke patients; however, there is a lack of research on therapeutic exercises for increasing abdominal muscle activity in stroke patients. We investigated the effects of non-paretic arm exercises using a tubing band on abdominal muscle activity in stroke patients. In total, 18 hemiplegic subjects (13 males, 5 females) were recruited. All subjects performed non-paretic arm exercises involving three different shoulder movements (extension, flexion, and horizontal abduction) using an elastic tubing band. Surface electromyography (EMG) signals were recorded from the rectus abdominis (RA), external oblique (EO), and internal oblique (IO) muscles bilaterally during non-paretic arm exercises. EMG activities of abdominal muscles during non-paretic arm extension and horizontal abduction were increased significantly versus shoulder flexion when subjects performed the arm exercise in a seated position. Muscle activity of the EO was significantly greater in the paretic than the non-paretic side during non-paretic arm extension and horizontal abduction. We suggest that non-paretic arm extension and horizontal abduction exercises using an elastic tubing band may be effective in increasing abdominal muscle activity.

30-Day Mortality and Readmission after Hemorrhagic Stroke among Medicare Beneficiaries in Joint Commission Primary Stroke Center Certified and Non-Certified Hospitals

Science.gov (United States)

Lichtman, Judith H.; Jones, Sara B.; Leifheit-Limson, Erica C.; Wang, Yun; Goldstein, Larry B.

2012-01-01

Background and Purpose Ischemic stroke patients treated at Joint Commission Primary Stroke Center (JC-PSC) certified hospitals have better outcomes. Data reflecting the impact of JC-PSC status on outcomes after hemorrhagic stroke are limited. We determined whether 30-day mortality and readmission rates after hemorrhagic stroke differed for patients treated at JC-PSC certified versus non-certified hospitals. Methods The study included all fee-for-service Medicare beneficiaries ≥65 years old with a primary discharge diagnosis of subarachnoid hemorrhage (SAH) or intracerebral hemorrhage (ICH) in 2006. Covariate-adjusted logistic and Cox proportional hazards regression assessed the effect of care at a JC-PSC certified hospital on 30-day mortality and readmission. Results There were 2,305 SAH and 8,708 ICH discharges from JC-PSC certified hospitals and 3,892 SAH and 22,564 ICH discharges from non-certified hospitals. Unadjusted in-hospital mortality (SAH: 27.5% vs. 33.2%, pmortality (SAH: 35.1% vs. 44.0%, pmortality was 34% lower (OR 0.66, 95% CI 0.58–0.76) after SAH and 14% lower (OR 0.86, 95% CI 0.80–0.92) after ICH for patients discharged from JC-PSC certified hospitals. There was no difference in 30-day risk-adjusted readmission rates for SAH or ICH based on JC-PSC status. Conclusions Patients treated at JC-PSC certified hospitals had lower risk-adjusted mortality rates for both SAH and ICH but similar 30-day readmission rates as compared with non-certified hospitals. PMID:22033986

A local non-parametric model for trade sign inference

Science.gov (United States)

Blazejewski, Adam; Coggins, Richard

2005-03-01

We investigate a regularity in market order submission strategies for 12 stocks with large market capitalization on the Australian Stock Exchange. The regularity is evidenced by a predictable relationship between the trade sign (trade initiator), size of the trade, and the contents of the limit order book before the trade. We demonstrate this predictability by developing an empirical inference model to classify trades into buyer-initiated and seller-initiated. The model employs a local non-parametric method, k-nearest neighbor, which in the past was used successfully for chaotic time series prediction. The k-nearest neighbor with three predictor variables achieves an average out-of-sample classification accuracy of 71.40%, compared to 63.32% for the linear logistic regression with seven predictor variables. The result suggests that a non-linear approach may produce a more parsimonious trade sign inference model with a higher out-of-sample classification accuracy. Furthermore, for most of our stocks the observed regularity in market order submissions seems to have a memory of at least 30 trading days.

Statistical significance of trends in monthly heavy precipitation over the US

KAUST Repository

Mahajan, Salil

2011-05-11

Trends in monthly heavy precipitation, defined by a return period of one year, are assessed for statistical significance in observations and Global Climate Model (GCM) simulations over the contiguous United States using Monte Carlo non-parametric and parametric bootstrapping techniques. The results from the two Monte Carlo approaches are found to be similar to each other, and also to the traditional non-parametric Kendall\\'s τ test, implying the robustness of the approach. Two different observational data-sets are employed to test for trends in monthly heavy precipitation and are found to exhibit consistent results. Both data-sets demonstrate upward trends, one of which is found to be statistically significant at the 95% confidence level. Upward trends similar to observations are observed in some climate model simulations of the twentieth century, but their statistical significance is marginal. For projections of the twenty-first century, a statistically significant upwards trend is observed in most of the climate models analyzed. The change in the simulated precipitation variance appears to be more important in the twenty-first century projections than changes in the mean precipitation. Stochastic fluctuations of the climate-system are found to be dominate monthly heavy precipitation as some GCM simulations show a downwards trend even in the twenty-first century projections when the greenhouse gas forcings are strong. © 2011 Springer-Verlag.

On the Optimal Location of Sensors for Parametric Identification of Linear Systems

DEFF Research Database (Denmark)

Kirkegaard, Poul Henning; Brincker, Rune

1994-01-01

. It is assumed most often that the results of the measurements are statistically independent random variables. In an example the importance of considering the measurements as statistically dependent random variables is shown. The covariance of the model parameters expected to be obtained is investigated......An outline of the field of optimal location of sensors for parametric identification of linear structural systems is presented. There are few papers devoted to the case of optimal location of sensors in which the measurements are modeled by a random field with non-trivial covariance function...

Statistical analysis applied to safety culture self-assessment

International Nuclear Information System (INIS)

Macedo Soares, P.P.

2002-01-01

Interviews and opinion surveys are instruments used to assess the safety culture in an organization as part of the Safety Culture Enhancement Programme. Specific statistical tools are used to analyse the survey results. This paper presents an example of an opinion survey with the corresponding application of the statistical analysis and the conclusions obtained. Survey validation, Frequency statistics, Kolmogorov-Smirnov non-parametric test, Student (T-test) and ANOVA means comparison tests and LSD post-hoc multiple comparison test, are discussed. (author)

Hyperbolic and semi-parametric models in finance

Science.gov (United States)

Bingham, N. H.; Kiesel, Rüdiger

2001-02-01

The benchmark Black-Scholes-Merton model of mathematical finance is parametric, based on the normal/Gaussian distribution. Its principal parametric competitor, the hyperbolic model of Barndorff-Nielsen, Eberlein and others, is briefly discussed. Our main theme is the use of semi-parametric models, incorporating the mean vector and covariance matrix as in the Markowitz approach, plus a non-parametric part, a scalar function incorporating features such as tail-decay. Implementation is also briefly discussed.

Epidemiology of non-fatal cerebrovascular stroke and transient ischemic attacks in Al Quseir, Egypt

Directory of Open Access Journals (Sweden)

El-Tallawy HN

2013-11-01

Full Text Available Hamdy N El-Tallawy,1 Wafaa MA Farghaly,1 Ghaydaa A Shehata,1 Nabil M Abdel-Hakeem,2 Tarek A Rageh,1 Reda Badry,1 Mahmoud R Kandil1 1Department of Neurology and Psychiatry, Faculty of Medicine, Assiut University Hospital, 2Department of Neurology, Faculty of Medicine, Al-Azhar University, Assiut branch, Assuit, Egypt Background and purpose: Stroke is a medical emergency that can cause permanent neurological damage, complications, and disability. We aim to determine the epidemiology of non-fatal cerebrovascular stroke (CVS and transient ischemic attacks (TIAs in Al Quseir City, Red Sea, Egypt. Methods: The total population (n=33,285 was screened through a door to door study by three specialists of neurology and 15 female social workers (for demographic data collection. All suspected stroke patients were subjected to a full clinical examination, computerized tomography (CT and/or magnetic resonance imaging (MRI of their brain, blood sugar, lipogram, serum uric acid, complete blood cells, blood urea, and serum creatinine, as well as evaluated by Barthel Index and Scandinavian Stroke Scale. Carotid doppler, echocardiography, and thyroid functions were done for selected cases. Results: CVS was recorded among 130 patients out of 19,848 subjects aged 20 years and more, yielding a total prevalence of 6.55/1,000 population. From June 1, 2010 to May 31, 2011, 36 patients were recorded to have stroke within 1-year, yielding an incidence rate of 1.81/1,000. Prevalence and incidence rates were higher among males than females, and both indices increased steadily with advancing age to reach the highest prevalence (37.02/1,000 and incidence rate (9.5/1,000 among aged persons 60 years and more. Conclusion: The prevalence of non-fatal stroke in Al Quseir city (6.55/1,000 was at the lower range of that recorded in developing countries (5–10/1,000 and slightly higher than that recorded in industrialized countries (5/1,000 population. Ischemic stroke is the most

Examining a participation-focused stroke self-management intervention in a day rehabilitation setting: a quasi-experimental pilot study.

Science.gov (United States)

Lee, Danbi; Fischer, Heidi; Zera, Sarah; Robertson, Rosetta; Hammel, Joy

2017-12-01

Background People with stroke often find discharge from rehabilitation distressing because they do not feel prepared to participate in life roles as they want. A self-management approach can facilitate improvement in confidence and ability to manage post-stroke community living and participation after transitioning into the community. Objective To evaluate the feasibility and effectiveness of the Improving Participation After Stroke Self-management program - Rehab version (IPASS-R) in a day rehabilitation setting. Methods We used a mixed-method non-randomized quasi-experimental design. The IPASS-R program is a six-session group-based intervention led by a trained occupational therapist and lay person with stroke. The program uses an efficacy building approach to support aging adults to maintain active participation in home and community activities post-stroke. Primary outcome measures were the Reintegration to Normal Living Index (RNLI), Stroke Impact Scale (SIS), and Participation Strategies Self-Efficacy Scale. Qualitative feedback was collected post-treatment. Results Seventeen participants with stroke (intervention n = 9; control n = 8) were enrolled across two sites. Non-parametric effect sizes calculated using the Wilcoxon Signed-Rank test revealed larger effects on RNLI and SIS outcomes in the intervention group. The Mann-Whitney U test showed significant differences between the two groups' changes in scores on perceived recovery and strength. Conclusions The result shows that IPASS-R has the potential to be integrated into a day rehabilitation setting with a positive impact on community integration and perceived recovery outcomes. Future study is needed to investigate the IPASS-R with a larger sample size and more rigorous study design.

Outcome of Secondary Stroke Prevention in Patients Taking Non-Vitamin K Antagonist Oral Anticoagulants.

Science.gov (United States)

Nakase, Taizen; Moroi, Junta; Ishikawa, Tatsuya

2018-05-01

Since non-vitamin K antagonist oral anticoagulants (NOACs) were released for clinical use, many studies have investigated its effectiveness in stroke prevention. In this study, to determine whether or not there is a difference in outcome in secondary stroke prevention between warfarin and NOACs, patients with embolic stroke with newly prescribed anticoagulants were prospectively analyzed. Patients with acute ischemic stroke, who newly started anticoagulant therapy, were consecutively asked to participate in this study. Enrolled patients (76.3 ± 11.0 years old) were classified into warfarin (n = 48), dabigatran (n = 73), rivaroxaban (n = 49), and apixaban (n = 65). The outcome in 1 year was prospectively investigated at outpatient clinic or telephone interview. Recurrence of stroke and death was considered as the critical incidence. The prevalence of risk factors was not different among all medicines. Patients with dabigatran showed significantly younger onset age (P incident rates were 7.1%, 15.3%, 19.0%, and 29.7% for dabigatran, apixaban, rivaroxaban, and warfarin, respectively. Dabigatran showed relatively better outcome compared with warfarin (P = .069) and rivaroxaban (P = .055). All patients on NOACs presented lower cumulative stroke recurrence compared with warfarin. Even in the situation of secondary stroke prevention, noninferiority of NOACs to warfarin might be demonstrated. Copyright © 2018 National Stroke Association. Published by Elsevier Inc. All rights reserved.

Identification of stroke mimics among clinically diagnosed acute strokes.

Science.gov (United States)

Tuntiyatorn, Lojana; Saksornchai, Pichaya; Tunlayadechanont, Supoch

2013-09-01

Stroke is a clinically syndrome of a sudden onset of neurological deficit in a vascular cause. Stroke mimics is the non-vascular disorders with stroke-like clinical symptoms. It is important to distinguish true stroke from mimics since treatment plan may differ To determine the incidence of the stroke mimics and identify their etiologies. All non-contrast head CT of the patients with clinically diagnosed stroke who immediately received imaging upon arrival at the emergency department of the university hospital were retrospectively reviewed in 12-month period between January 1 and December 31, 2008. Medical records, laboratory results, MRI, and 6-month clinical follow-up records were reviewed for final diagnosis. Seven hundred four patients were included in this study, including 363 (51.5%) men and 341 (48.5%) women with range in age from 24 to 108 years. Amongst those, 417 (59.2%) were ischemic stroke, 80 (11.40%) were hemorrhagic stroke, 186 (26.4%) were stroke-mimics, and 21 (3%) were inconclusive. The etiologies among stroke-mimics were metabolic/intoxication (35, 18.8%), sepsis (28, 15.0%), seizure (21, 11.3%), syncope (20, 10.8%), subdural hemorrhage (14, 7.5%), vertigo (11, 6.0%), brain tumor (10, 5.30%), central nervous system infection (5, 2.7%), others (26, 14.0%), and unspecified (16, 8.6%). Incidence rates and etiologies of the stroke mimics were similar to the western reports. However the frequency of each mimic was not.

Statistical Survey of Non-Formal Education

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Ondřej Nývlt

2012-12-01

Full Text Available focused on a programme within a regular education system. Labour market flexibility and new requirements on employees create a new domain of education called non-formal education. Is there a reliable statistical source with a good methodological definition for the Czech Republic? Labour Force Survey (LFS has been the basic statistical source for time comparison of non-formal education for the last ten years. Furthermore, a special Adult Education Survey (AES in 2011 was focused on individual components of non-formal education in a detailed way. In general, the goal of the EU is to use data from both internationally comparable surveys for analyses of the particular fields of lifelong learning in the way, that annual LFS data could be enlarged by detailed information from AES in five years periods. This article describes reliability of statistical data aboutnon-formal education. This analysis is usually connected with sampling and non-sampling errors.

Spurious Seasonality Detection: A Non-Parametric Test Proposal

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Aurelio F. Bariviera

2018-01-01

Full Text Available This paper offers a general and comprehensive definition of the day-of-the-week effect. Using symbolic dynamics, we develop a unique test based on ordinal patterns in order to detect it. This test uncovers the fact that the so-called “day-of-the-week” effect is partly an artifact of the hidden correlation structure of the data. We present simulations based on artificial time series as well. While time series generated with long memory are prone to exhibit daily seasonality, pure white noise signals exhibit no pattern preference. Since ours is a non-parametric test, it requires no assumptions about the distribution of returns, so that it could be a practical alternative to conventional econometric tests. We also made an exhaustive application of the here-proposed technique to 83 stock indexes around the world. Finally, the paper highlights the relevance of symbolic analysis in economic time series studies.

A Non-Parametric Surrogate-based Test of Significance for T-Wave Alternans Detection

Science.gov (United States)

Nemati, Shamim; Abdala, Omar; Bazán, Violeta; Yim-Yeh, Susie; Malhotra, Atul; Clifford, Gari

2010-01-01

We present a non-parametric adaptive surrogate test that allows for the differentiation of statistically significant T-Wave Alternans (TWA) from alternating patterns that can be solely explained by the statistics of noise. The proposed test is based on estimating the distribution of noise induced alternating patterns in a beat sequence from a set of surrogate data derived from repeated reshuffling of the original beat sequence. Thus, in assessing the significance of the observed alternating patterns in the data no assumptions are made about the underlying noise distribution. In addition, since the distribution of noise-induced alternans magnitudes is calculated separately for each sequence of beats within the analysis window, the method is robust to data non-stationarities in both noise and TWA. The proposed surrogate method for rejecting noise was compared to the standard noise rejection methods used with the Spectral Method (SM) and the Modified Moving Average (MMA) techniques. Using a previously described realistic multi-lead model of TWA, and real physiological noise, we demonstrate the proposed approach reduces false TWA detections, while maintaining a lower missed TWA detection compared with all the other methods tested. A simple averaging-based TWA estimation algorithm was coupled with the surrogate significance testing and was evaluated on three public databases; the Normal Sinus Rhythm Database (NRSDB), the Chronic Heart Failure Database (CHFDB) and the Sudden Cardiac Death Database (SCDDB). Differences in TWA amplitudes between each database were evaluated at matched heart rate (HR) intervals from 40 to 120 beats per minute (BPM). Using the two-sample Kolmogorov-Smirnov test, we found that significant differences in TWA levels exist between each patient group at all decades of heart rates. The most marked difference was generally found at higher heart rates, and the new technique resulted in a larger margin of separability between patient populations than

An introduction to inferential statistics: A review and practical guide

International Nuclear Information System (INIS)

Marshall, Gill; Jonker, Leon

2011-01-01

Building on the first part of this series regarding descriptive statistics, this paper demonstrates why it is advantageous for radiographers to understand the role of inferential statistics in deducing conclusions from a sample and their application to a wider population. This is necessary so radiographers can understand the work of others, can undertake their own research and evidence base their practice. This article explains p values and confidence intervals. It introduces the common statistical tests that comprise inferential statistics, and explains the use of parametric and non-parametric statistics. To do this, the paper reviews relevant literature, and provides a checklist of points to consider before and after applying statistical tests to a data set. The paper provides a glossary of relevant terms and the reader is advised to refer to this when any unfamiliar terms are used in the text. Together with the information provided on descriptive statistics in an earlier article, it can be used as a starting point for applying statistics in radiography practice and research.

An introduction to inferential statistics: A review and practical guide

Energy Technology Data Exchange (ETDEWEB)

Marshall, Gill, E-mail: gill.marshall@cumbria.ac.u [Faculty of Health, Medical Sciences and Social Care, University of Cumbria, Lancaster LA1 3JD (United Kingdom); Jonker, Leon [Faculty of Health, Medical Sciences and Social Care, University of Cumbria, Lancaster LA1 3JD (United Kingdom)

2011-02-15

Building on the first part of this series regarding descriptive statistics, this paper demonstrates why it is advantageous for radiographers to understand the role of inferential statistics in deducing conclusions from a sample and their application to a wider population. This is necessary so radiographers can understand the work of others, can undertake their own research and evidence base their practice. This article explains p values and confidence intervals. It introduces the common statistical tests that comprise inferential statistics, and explains the use of parametric and non-parametric statistics. To do this, the paper reviews relevant literature, and provides a checklist of points to consider before and after applying statistical tests to a data set. The paper provides a glossary of relevant terms and the reader is advised to refer to this when any unfamiliar terms are used in the text. Together with the information provided on descriptive statistics in an earlier article, it can be used as a starting point for applying statistics in radiography practice and research.

Non-linear statistical downscaling of present and LGM precipitation and temperatures over Europe

Directory of Open Access Journals (Sweden)

M. Vrac

2007-12-01

Full Text Available Local-scale climate information is increasingly needed for the study of past, present and future climate changes. In this study we develop a non-linear statistical downscaling method to generate local temperatures and precipitation values from large-scale variables of a Earth System Model of Intermediate Complexity (here CLIMBER. Our statistical downscaling scheme is based on the concept of Generalized Additive Models (GAMs, capturing non-linearities via non-parametric techniques. Our GAMs are calibrated on the present Western Europe climate. For this region, annual GAMs (i.e. models based on 12 monthly values per location are fitted by combining two types of large-scale explanatory variables: geographical (e.g. topographical information and physical (i.e. entirely simulated by the CLIMBER model.

To evaluate the adequacy of the non-linear transfer functions fitted on the present Western European climate, they are applied to different spatial and temporal large-scale conditions. Local projections for present North America and Northern Europe climates are obtained and compared to local observations. This partially addresses the issue of spatial robustness of our transfer functions by answering the question "does our statistical model remain valid when applied to large-scale climate conditions from a region different from the one used for calibration?". To asses their temporal performances, local projections for the Last Glacial Maximum period are derived and compared to local reconstructions and General Circulation Model outputs.

Our downscaling methodology performs adequately for the Western Europe climate. Concerning the spatial and temporal evaluations, it does not behave as well for Northern America and Northern Europe climates because the calibration domain may be too different from the targeted regions. The physical explanatory variables alone are not capable of downscaling realistic values. However, the inclusion of

Ischaemic and haemorrhagic stroke associated with non-vitamin K antagonist oral anticoagulants and warfarin use in patients with atrial fibrillation

DEFF Research Database (Denmark)

Staerk, Laila; Fosbøl, Emil Loldrup; Lip, Gregory Y. H.

2017-01-01

BACKGROUND: Non-vitamin K antagonist (VKA) oral anticoagulants (NOACs) are widely used as stroke prophylaxis in non-valvular atrial fibrillation (AF), but comparative data are sparse. PURPOSE: To compare dabigatran, rivaroxaban, and apixaban vs. VKA and the risk of stroke/thromboembolism (TE) and...

Fritzsch-type mass matrices and the Wolfenstein parametrization of quark mixing

International Nuclear Information System (INIS)

Kang, K.; Hadjitheodoridis, S.; Brown Univ., Providence, RI

1987-01-01

We give approximate and analytic expressions of polynomial type in small parameters defined in terms of quark mass ratios for the elements of the flavor-mixing matrix predicted from the Fritzsch-type mass matrices of quarks. The results are successfully tested against experiments as represented by the Wolfenstein parametrization of quark mixing. From the reality of the CP phases we get an allowed range for m s , which in turn implies that m t can be as large as 80.8 GeV. In addition we find that the two CP phases α and β are very close, i.e., vertical strokeα-βvertical stroke ≅ O(λ). (orig.)

An Uncommon Cause of Stroke: Non-bacterial Thrombotic Endocarditis.

Science.gov (United States)

Gundersen, Hilde; Moynihan, Barry

2016-10-01

Our objective is to present the case of an uncommon but probably under-recognized cause of stroke: Non-bacterial thrombotic endocarditis (NBTE). A 59-year-old man presented to our hospital with multiple bihemispheric infarcts despite taking rivaroxaban for pulmonary emboli diagnosed 2 weeks earlier. The patient's symptoms progressed quickly and he died within a week of his initial presentation despite attempts at neuroradiologically guided clot retrieval and early recognition and treatment of disseminated intravascular coagulation. On postmortem examination it was discovered that he had an undiagnosed squamous cell adenocarcinoma of the lung and NBTE. NBTE is difficult to diagnose and difficult to treat. It is associated with a mortality rate and is often not diagnosed until autopsy. However there are case reports in the literature where NBTE has been successfully treated. Early recognition and prompt treatment of the underlying disease process is the essential first step. Copyright © 2016 National Stroke Association. Published by Elsevier Inc. All rights reserved.

Non-invasive brain stimulation: an interventional tool for enhancing behavioral training after stroke

Directory of Open Access Journals (Sweden)

Maximilian Jonas Wessel

2015-05-01

Full Text Available Stroke is the leading cause of disability among adults. Motor deficit is the most common impairment after stroke. Especially, deficits in fine motor skills impair numerous activities of daily life. Re-acquisition of motor skills resulting in improved or more accurate motor performance is paramount to regain function, and is the basis of behavioral motor therapy after stroke. Within the past years, there has been a rapid technological and methodological development in neuroimaging leading to a significant progress in the understanding of the neural substrates that underlie motor skill acquisition and functional recovery in stroke patients. Based on this and the development of novel non-invasive brain stimulation techniques, new adjuvant interventional approaches that augment the response to behavioral training have been proposed. Transcranial direct current (tDCS, transcranial magnetic (TMS and paired associative (PAS stimulation are noninvasive brain stimulation techniques that can modulate cortical excitability, neuronal plasticity and interact with learning and memory in both healthy individuals and stroke patients. These techniques can enhance the effect of practice and facilitate the retention of tasks that mimic daily life activities. The purpose of the present review is to provide a comprehensive overview of neuroplastic phenomena in the motor system during learning of a motor skill, recovery after brain injury, and of interventional strategies to enhance the beneficial effects of customarily used neurorehabilitation after stroke.

Non-invasive brain stimulation: an interventional tool for enhancing behavioral training after stroke.

Science.gov (United States)

Wessel, Maximilian J; Zimerman, Máximo; Hummel, Friedhelm C

2015-01-01

Stroke is the leading cause of disability among adults. Motor deficit is the most common impairment after stroke. Especially, deficits in fine motor skills impair numerous activities of daily life. Re-acquisition of motor skills resulting in improved or more accurate motor performance is paramount to regain function, and is the basis of behavioral motor therapy after stroke. Within the past years, there has been a rapid technological and methodological development in neuroimaging leading to a significant progress in the understanding of the neural substrates that underlie motor skill acquisition and functional recovery in stroke patients. Based on this and the development of novel non-invasive brain stimulation (NIBS) techniques, new adjuvant interventional approaches that augment the response to behavioral training have been proposed. Transcranial direct current, transcranial magnetic, and paired associative (PAS) stimulation are NIBS techniques that can modulate cortical excitability, neuronal plasticity and interact with learning and memory in both healthy individuals and stroke patients. These techniques can enhance the effect of practice and facilitate the retention of tasks that mimic daily life activities. The purpose of the present review is to provide a comprehensive overview of neuroplastic phenomena in the motor system during learning of a motor skill, recovery after brain injury, and of interventional strategies to enhance the beneficial effects of customarily used neurorehabilitation after stroke.

Theory of Mind and Executive Functioning Following Stroke.

Science.gov (United States)

Hamilton, Jackie; Radlak, Bogna; Morris, Paul G; Phillips, Louise H

2017-08-01

Cognitive deficits following stroke are well documented, but less is known about problems with social skills such as understanding others' thoughts and feelings. This study investigated the effect of stroke on a visual-affective measure of social understanding: the Reading the Mind in the Eyes test (RMET). The aims were to investigate whether right hemisphere stroke was particularly detrimental to this aspect of Theory of Mind (ToM), and investigate the relationship between ToM ability and executive function following stroke. Performance of stroke patients (right hemisphere stroke, n = 15; left hemisphere stroke, n = 15) was compared to that of controls (n = 40) matched for age, years of education, and IQ on tasks measuring ToM and executive functioning. Right hemisphere stroke was associated with impaired ToM ability, but left hemisphere stroke was not. There was no effect of stroke on a matched non-ToM control task. High correlations were found between performance on the RMET and some measures of executive functioning in participants with right hemisphere stroke only. Further analyses suggested that deficits in executive functioning could not statistically explain all of the difficulties shown by stroke participants on the RMET. A reduction in the ability to attribute mental states to others following right hemisphere stroke may adversely affect psychosocial functioning, disrupt interpersonal relationships, and lead to reduced quality of life. The clinical importance of these findings, implications for clinical practice and future research are discussed. © The Author 2017. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Parametric Methods for Order Tracking Analysis

DEFF Research Database (Denmark)

Nielsen, Jesper Kjær; Jensen, Tobias Lindstrøm

2017-01-01

Order tracking analysis is often used to find the critical speeds at which structural resonances are excited by a rotating machine. Typically, order tracking analysis is performed via non-parametric methods. In this report, however, we demonstrate some of the advantages of using a parametric method...

Hyponatremia in stroke

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Sheikh Saleem

2014-01-01

Full Text Available Introduction: Hyponatremia is a common electrolyte disorder encountered in patients of neurological disorders which is usually either due to inappropriate secretion of Antidiuretic hormone (SIADH or cerebral salt wasting syndrome (CSWS. We conducted this study in a tertiary care hospital to determine the incidence and etiology of hyponatremia in patients of stroke admitted in the hospital. Materials and Methods: It was a prospective study done over a period of two years that included established cases of stroke diagnosed on the basis of clinical history, examination and neuroimaging. 1000 stoke patients were evaluated for hyponatremia (serum sodium <130 meq/l. The data was analysed using Chi-square test using SPSS (Statistical package for social science software. Results: Out of 1000 patients, 353 patients had hyponatremia. Out of this 353 patients, 238 (67% had SIADH and 115 (33% had CSWS. SIADH was seen in 83 patients who had ischemic stroke and 155 patients of hemorrhagic stroke. CSWS was found in 38 patients with ischemic stroke and 77 patients with hemorrhagic stroke. Statistical analysis revealed that hyponatremia significantly affects the outcome of stroke especially when it is due to CSWS rather than SIADH. Conclusion: Incidence of hyponatremia in our study population was 35%. In patients of hyponatremia 67% were having SIADH and 33% were having CSWS. Overall hyponatremia affected the outcome of stroke especially when caused by CSWS. Therefore close monitoring of serum sodium must be done in all patients who are admitted with stroke and efforts must be made to determine the cause of hyponatremia, in order to properly manage such patients thereby decreasing the mortality rate.

[Impact to Z-score Mapping of Hyperacute Stroke Images by Computed Tomography in Adaptive Statistical Iterative Reconstruction].

Science.gov (United States)

Watanabe, Shota; Sakaguchi, Kenta; Hosono, Makoto; Ishii, Kazunari; Murakami, Takamichi; Ichikawa, Katsuhiro

The purpose of this study was to evaluate the effect of a hybrid-type iterative reconstruction method on Z-score mapping of hyperacute stroke in unenhanced computed tomography (CT) images. We used a hybrid-type iterative reconstruction [adaptive statistical iterative reconstruction (ASiR)] implemented in a CT system (Optima CT660 Pro advance, GE Healthcare). With 15 normal brain cases, we reconstructed CT images with a filtered back projection (FBP) and ASiR with a blending factor of 100% (ASiR100%). Two standardized normal brain data were created from normal databases of FBP images (FBP-NDB) and ASiR100% images (ASiR-NDB), and standard deviation (SD) values in basal ganglia were measured. The Z-score mapping was performed for 12 hyperacute stroke cases by using FBP-NDB and ASiR-NDB, and compared Z-score value on hyperacute stroke area and normal area between FBP-NDB and ASiR-NDB. By using ASiR-NDB, the SD value of standardized brain was decreased by 16%. The Z-score value of ASiR-NDB on hyperacute stroke area was significantly higher than FBP-NDB (pASiR100% for Z-score mapping had potential to improve the accuracy of Z-score mapping.

Radiation parametric generation in non-linear crystals

International Nuclear Information System (INIS)

Pacheco, M.T.; Pereira, M.A.C.Q.

1983-01-01

A short historical development review is presented on the optical parametric oscillators. Analysis on behaviour of the simple resonant oscillators (SRO), double resonant oscillators (DRO) and ring resonant oscillators (RRO), in the plane wave pumping approximation is shown. Comparision between the three oscillators types is given. (Author) [pt

Association of inflammatory gene polymorphisms with ischemic stroke in a Chinese Han population.

Science.gov (United States)

Zhao, Nan; Liu, Xin; Wang, Yongqin; Liu, Xiaoqiu; Li, Jiana; Yu, Litian; Ma, Liyuan; Wang, Shuyu; Zhang, Hongye; Liu, Lisheng; Zhao, Jingbo; Wang, Xingyu

2012-07-06

Inflammatory mechanisms are important in stroke risk, and genetic variations in components of the inflammatory response have been implicated as risk factors for stroke. We tested the inflammatory gene polymorphisms and their association with ischemic stroke in a Chinese Han population. A total of 1,124 ischemic stroke cases and 1,163 controls were genotyped with inflammatory panel strips containing 51 selected inflammatory gene polymorphisms from 35 candidate genes. We tested the genotype-stroke association with logistic regression model. We found two single nucleotide polymorphisms (SNPs) in CCL11 were associated with ischemic stroke. After adjusting for multiple testing using false discovery rate (FDR) with a 0.20 cut-off point, CCL11 rs4795895 remained statistically significant. We further stratified the study population by their hypertension status. In the hypertensive group, CCR2 rs1799864, CCR5 rs1799987 and CCL11 rs4795895 were nominally associated with increased risk of stroke. In the non-hypertensive group, CCL11 rs3744508, LTC4S rs730012, FCER1B rs569108, TGFB1 rs1800469, LTA rs909253 and CCL11 rs4795895 were associated with ischemic stroke. After correction for multiple testing, CCR2 rs1799864 and CCR5 rs1799987 remained significant in the hypertensive group, and CCL11 rs3744508, LTC4S rs730012, FCER1B rs569108, TGFB1 rs1800469, LTA rs909253 remained significant in the non-hypertensive group. Our results indicate that inflammatory genetic variants are associated with increased risk of ischemic stroke in a Chinese Han population, particularly in non-hypertensive individuals.

Interprofessional stroke rehabilitation for stroke survivors using home care.

Science.gov (United States)

Markle-Reid, Maureen; Orridge, Camille; Weir, Robin; Browne, Gina; Gafni, Amiram; Lewis, Mary; Walsh, Marian; Levy, Charissa; Daub, Stacey; Brien, Heather; Roberts, Jacqueline; Thabane, Lehana

2011-03-01

To compare a specialized interprofessional team approach to community-based stroke rehabilitation with usual home care for stroke survivors using home care services. Randomized controlled trial of 101 community-living stroke survivors (stroke) using home care services. Subjects were randomized to intervention (n=52) or control (n=49) groups. The intervention was a 12-month specialized, evidence-based rehabilitation strategy involving an interprofessional team. The primary outcome was change in health-related quality of life and functioning (SF-36) from baseline to 12 months. Secondary outcomes were number of strokes during the 12-month follow-up, and changes in community reintegration (RNLI), perceived social support (PRQ85-Part 2), anxiety and depressive symptoms (Kessler-10), cognitive function (SPMSQ), and costs of use of health services from baseline to 12 months. A total of 82 subjects completed the 12-month follow-up. Compared with the usual care group, stroke survivors in the intervention group showed clinically important (although not statistically significant) greater improvements from baseline in mean SF-36 physical functioning score (5.87, 95% CI -3.98 to 15.7; p=0.24) and social functioning score (9.03, CI-7.50 to 25.6; p=0.28). The groups did not differ for any of the secondary effectiveness outcomes. There was a higher total per-person costs of use of health services in the intervention group compared to usual home care although the difference was not statistically significant (p=0.76). A 12-month specialized, interprofessional team is a feasible and acceptable approach to community-based stroke rehabilitation that produced greater improvements in quality of life compared to usual home care. Clinicaltrials.gov identifier: NCT00463229.

The Relationship between Metabolically Obese Non-Obese Weight and Stroke: The Korea National Health and Nutrition Examination Survey.

Directory of Open Access Journals (Sweden)

Young-Gyun Seo

Full Text Available Both metabolic syndrome (MetS and obesity increase the risk of stroke. However, few studies have compared the risks of stroke associated with metabolically obese non-obese weight (MONW and metabolically healthy obesity (MHO. This study aimed to compare the prevalence of stroke in MONW and MHO individuals.A total of 25,744 subjects aged ≥40 years were selected from the 2007-2014 Korean National Health and Nutrition Examination Survey. MetS was defined using 2001 National Cholesterol Education Program/Adult Treatment Panel III and 2005 American Heart Association/National Heart, Lung, and Blood Institute criteria. Non-obese weight and obesity were defined as a body mass index (BMI <25 kg/m2 and ≥25 kg/m2, respectively. MONW was defined as meeting the MetS criteria with a BMI <25 kg/m2 and MHO was defined as not meeting the MetS criteria with a BMI ≥25 kg/m2.Women with MONW had a higher prevalence of stroke than those with MHO (odds ratio [OR] = 2.27, 95% confidence interval [CI]: 1.45-3.57. The prevalence of stroke increased as the number of MetS components increased. The ORs for MONW with 3, 4, and 5 MetS components were 1.95 (95% CI: 1.19-3.21, 2.49 (95% CI: 1.46-4.24 and 2.74 (95% CI: 1.39-5.40, respectively.Our study findings may better emphasize the risk of stroke among more lean but unhealthy individuals, who appear healthy but may be suffering from MetS. These findings also highlight the need for stroke risk factor assessment in non-obese weight individuals.

Greater stroke severity predominates over all other factors for the worse outcome of cardioembolic stroke.

Science.gov (United States)

Hong, Keun-Sik; Lee, Juneyoung; Bae, Hee-Joon; Lee, Ji Sung; Kang, Dong-Wha; Yu, Kyung-Ho; Han, Moon-Ku; Cho, Yong-Jin; Song, Pamela; Park, Jong-Moo; Oh, Mi-Sun; Koo, Jaseong; Lee, Byung-Chul

2013-11-01

Cardioembolic (CE) strokes are more disabling and more fatal than non-CE strokes. Multiple prognostic factors have been recognized, but the magnitude of their relative contributions has not been well explored. Using a prospective stroke outcome database, we compared the 3-month outcomes of CE and non-CE strokes. We assessed the relative contribution of each prognostic factor of initial stroke severity, poststroke complications, and baseline characteristics with multivariable analyses and model fitness improvement using -2 log-likelihood and Nagelkerke R2. This study included 1233 patients with acute ischemic stroke: 193 CE strokes and 1040 non-CE strokes. Compared with the non-CE group, CE group had less modified Rankin Scale (mRS) 0-2 outcomes (47.2% versus 68.5%; odds ratio [95% confidence interval], .41 [.30-.56]), less mRS 0-1 outcomes (33.7% versus 53.5%; .44 [.32-.61]), more mRS 5-6 outcomes (32.1% versus 10.9%; 3.88 [2.71-5.56]), and higher mortality (19.2% versus 5.2%; 4.33 [2.76-6.80]) at 3 months. When adjusting either baseline characteristics or poststroke complications, the outcome differences between the 2 groups remained significant. However, adjusting initial National Institute of Health Stroke Scale (NIHSS) score alone abolished all outcome differences except for mortality. For mRS 0-2 outcomes, the decrement of -2 log-likelihood and the Nagelkerke R2 of the model adjusting initial NIHSS score alone approached 70.2% and 76.7% of the fully adjusting model. Greater stroke severity predominates over all other factors for the worse outcome of CE stroke. Primary prevention and more efficient acute therapy for stroke victims should be given top priorities to reduce the burden of CE strokes. Copyright © 2013 National Stroke Association. Published by Elsevier Inc. All rights reserved.

Differences in clinical features and computed tomographic findings between embolic and non-embolic acute ischemic stroke. A quantitative differential diagnosis

International Nuclear Information System (INIS)

Takano, Kentaro; Yamaguchi, Takenori; Minematsu, Kazuo; Sawada, Tohru; Omae, Teruo

1998-01-01

A diagnosis based on the presumed mechanism of stroke onset is useful for management strategies in acute ischemic stroke. Ninety-two patients with embolic (cardiac or artery-to-artery) and 107 with non-embolic (thrombotic or hemodynamic) stroke were diagnosed on strict cerebral angiographic criteria alone. To clearly discriminate between these two groups, the neurological and computed tomographic (CT) findings were then compared. Rapidity of onset, vomiting, urinary incontinence, level of consciousness, cervical bruit, anisocoria, tongue deviation, sensory disturbance, and CT findings (location of hypodense area, findings of brain edema and hemorrhagic transformation) were discriminatory factors between the two groups (p<0.01). According to these 11 items, we prepared a numerical table for quantitative differential diagnosis. A diagnostic accuracy of 98.9% for embolic and 87.9% for non-embolic stroke in internal verification, and 90.0% and 82.9%, respectively, in external verification was observed. The differences in clinical features and CT findings between embolic and non-embolic stroke may reflect the pathophysiological mechanisms of the occlusive process of cerebral artery as well as the extent and severity of ischemia. (author)

Differences in clinical features and computed tomographic findings between embolic and non-embolic acute ischemic stroke. A quantitative differential diagnosis

Energy Technology Data Exchange (ETDEWEB)

Takano, Kentaro; Yamaguchi, Takenori; Minematsu, Kazuo; Sawada, Tohru; Omae, Teruo [National Cardiovascular Center, Suita, Osaka (Japan)

1998-02-01

A diagnosis based on the presumed mechanism of stroke onset is useful for management strategies in acute ischemic stroke. Ninety-two patients with embolic (cardiac or artery-to-artery) and 107 with non-embolic (thrombotic or hemodynamic) stroke were diagnosed on strict cerebral angiographic criteria alone. To clearly discriminate between these two groups, the neurological and computed tomographic (CT) findings were then compared. Rapidity of onset, vomiting, urinary incontinence, level of consciousness, cervical bruit, anisocoria, tongue deviation, sensory disturbance, and CT findings (location of hypodense area, findings of brain edema and hemorrhagic transformation) were discriminatory factors between the two groups (p<0.01). According to these 11 items, we prepared a numerical table for quantitative differential diagnosis. A diagnostic accuracy of 98.9% for embolic and 87.9% for non-embolic stroke in internal verification, and 90.0% and 82.9%, respectively, in external verification was observed. The differences in clinical features and CT findings between embolic and non-embolic stroke may reflect the pathophysiological mechanisms of the occlusive process of cerebral artery as well as the extent and severity of ischemia. (author)

On Rigorous Drought Assessment Using Daily Time Scale: Non-Stationary Frequency Analyses, Revisited Concepts, and a New Method to Yield Non-Parametric Indices

Directory of Open Access Journals (Sweden)

Charles Onyutha

2017-10-01

Full Text Available Some of the problems in drought assessments are that: analyses tend to focus on coarse temporal scales, many of the methods yield skewed indices, a few terminologies are ambiguously used, and analyses comprise an implicit assumption that the observations come from a stationary process. To solve these problems, this paper introduces non-stationary frequency analyses of quantiles. How to use non-parametric rescaling to obtain robust indices that are not (or minimally skewed is also introduced. To avoid ambiguity, some concepts on, e.g., incidence, extremity, etc., were revisited through shift from monthly to daily time scale. Demonstrations on the introduced methods were made using daily flow and precipitation insufficiency (precipitation minus potential evapotranspiration from the Blue Nile basin in Africa. Results show that, when a significant trend exists in extreme events, stationarity-based quantiles can be far different from those when non-stationarity is considered. The introduced non-parametric indices were found to closely agree with the well-known standardized precipitation evapotranspiration indices in many aspects but skewness. Apart from revisiting some concepts, the advantages of the use of fine instead of coarse time scales in drought assessment were given. The links for obtaining freely downloadable tools on how to implement the introduced methods were provided.

Update of the Preventive Antibiotics in Stroke Study (PASS): Statistical analysis plan

NARCIS (Netherlands)

W.F. Westendorp (Willeke); J.-D. Vermeij (Jan-Dirk); D.W.J. Dippel (Diederik); M.G.W. Dijkgraaf (Marcel); T. van der Poll (Tom); J.M. Prins (Jan); F.H. Vermeij (Frederique); Y.B.W.E.M. Roos (Yvo); M.C. Brouwer (Matthijs C.); A.H. Zwinderman (Ailko); D. van de Beek (Diederik); P.J. Nederkoorn (Paul)

2014-01-01

textabstractBackground: Infections occur in 30% of stroke patients and are associated with unfavorable outcomes. Preventive antibiotic therapy lowers the infection rate after stroke, but the effect of preventive antibiotic treatment on functional outcome in patients with stroke is unknown. The PASS

Update of the Preventive Antibiotics in Stroke Study (PASS): statistical analysis plan

NARCIS (Netherlands)

Westendorp, Willeke F.; Vermeij, Jan-Dirk; Dippel, Diederik W. J.; Dijkgraaf, Marcel G. W.; van der Poll, Tom; Prins, Jan M.; Vermeij, Frederique H.; Roos, Yvo B. W. E. M.; Brouwer, Matthijs C.; Zwinderman, Aeilko H.; van de Beek, Diederik; Nederkoorn, Paul J.

2014-01-01

Infections occur in 30% of stroke patients and are associated with unfavorable outcomes. Preventive antibiotic therapy lowers the infection rate after stroke, but the effect of preventive antibiotic treatment on functional outcome in patients with stroke is unknown. The PASS is a multicenter,

Planar Parametrization in Isogeometric Analysis

DEFF Research Database (Denmark)

Gravesen, Jens; Evgrafov, Anton; Nguyen, Dang-Manh

2012-01-01

Before isogeometric analysis can be applied to solving a partial differential equation posed over some physical domain, one needs to construct a valid parametrization of the geometry. The accuracy of the analysis is affected by the quality of the parametrization. The challenge of computing...... and maintaining a valid geometry parametrization is particularly relevant in applications of isogemetric analysis to shape optimization, where the geometry varies from one optimization iteration to another. We propose a general framework for handling the geometry parametrization in isogeometric analysis and shape...... are suitable for our framework. The non-linear methods we consider are based on solving a constrained optimization problem numerically, and are divided into two classes, geometry-oriented methods and analysis-oriented methods. Their performance is illustrated through a few numerical examples....

Voxel-based lesion-symptom mapping of stroke lesions underlying somatosensory deficits

Directory of Open Access Journals (Sweden)

Sarah Meyer

2016-01-01

Full Text Available The aim of this study was to investigate the relationship between stroke lesion location and the resulting somatosensory deficit. We studied exteroceptive and proprioceptive somatosensory symptoms and stroke lesions in 38 patients with first-ever acute stroke. The Erasmus modified Nottingham Sensory Assessment was used to clinically evaluate somatosensory functioning in the arm and hand within the first week after stroke onset. Additionally, more objective measures such as the perceptual threshold of touch and somatosensory evoked potentials were recorded. Non-parametric voxel-based lesion-symptom mapping was performed to investigate lesion contribution to different somatosensory deficits in the upper limb. Additionally, structural connectivity of brain areas that demonstrated the strongest association with somatosensory symptoms was determined, using probabilistic fiber tracking based on diffusion tensor imaging data from a healthy age-matched sample. Voxels with a significant association to somatosensory deficits were clustered in two core brain regions: the central parietal white matter, also referred to as the sensory component of the superior thalamic radiation, and the parietal operculum close to the insular cortex, representing the secondary somatosensory cortex. Our objective recordings confirmed findings from clinical assessments. Probabilistic tracking connected the first region to thalamus, internal capsule, brain stem, postcentral gyrus, cerebellum, and frontal pathways, while the second region demonstrated structural connections to thalamus, insular and primary somatosensory cortex. This study reveals that stroke lesions in the sensory fibers of the superior thalamocortical radiation and the parietal operculum are significantly associated with multiple exteroceptive and proprioceptive deficits in the arm and hand.

Voxel-based lesion-symptom mapping of stroke lesions underlying somatosensory deficits.

Science.gov (United States)

Meyer, Sarah; Kessner, Simon S; Cheng, Bastian; Bönstrup, Marlene; Schulz, Robert; Hummel, Friedhelm C; De Bruyn, Nele; Peeters, Andre; Van Pesch, Vincent; Duprez, Thierry; Sunaert, Stefan; Schrooten, Maarten; Feys, Hilde; Gerloff, Christian; Thomalla, Götz; Thijs, Vincent; Verheyden, Geert

2016-01-01

The aim of this study was to investigate the relationship between stroke lesion location and the resulting somatosensory deficit. We studied exteroceptive and proprioceptive somatosensory symptoms and stroke lesions in 38 patients with first-ever acute stroke. The Erasmus modified Nottingham Sensory Assessment was used to clinically evaluate somatosensory functioning in the arm and hand within the first week after stroke onset. Additionally, more objective measures such as the perceptual threshold of touch and somatosensory evoked potentials were recorded. Non-parametric voxel-based lesion-symptom mapping was performed to investigate lesion contribution to different somatosensory deficits in the upper limb. Additionally, structural connectivity of brain areas that demonstrated the strongest association with somatosensory symptoms was determined, using probabilistic fiber tracking based on diffusion tensor imaging data from a healthy age-matched sample. Voxels with a significant association to somatosensory deficits were clustered in two core brain regions: the central parietal white matter, also referred to as the sensory component of the superior thalamic radiation, and the parietal operculum close to the insular cortex, representing the secondary somatosensory cortex. Our objective recordings confirmed findings from clinical assessments. Probabilistic tracking connected the first region to thalamus, internal capsule, brain stem, postcentral gyrus, cerebellum, and frontal pathways, while the second region demonstrated structural connections to thalamus, insular and primary somatosensory cortex. This study reveals that stroke lesions in the sensory fibers of the superior thalamocortical radiation and the parietal operculum are significantly associated with multiple exteroceptive and proprioceptive deficits in the arm and hand.

Performance of non-parametric algorithms for spatial mapping of tropical forest structure

Directory of Open Access Journals (Sweden)

Liang Xu

2016-08-01

Full Text Available Abstract Background Mapping tropical forest structure is a critical requirement for accurate estimation of emissions and removals from land use activities. With the availability of a wide range of remote sensing imagery of vegetation characteristics from space, development of finer resolution and more accurate maps has advanced in recent years. However, the mapping accuracy relies heavily on the quality of input layers, the algorithm chosen, and the size and quality of inventory samples for calibration and validation. Results By using airborne lidar data as the “truth” and focusing on the mean canopy height (MCH as a key structural parameter, we test two commonly-used non-parametric techniques of maximum entropy (ME and random forest (RF for developing maps over a study site in Central Gabon. Results of mapping show that both approaches have improved accuracy with more input layers in mapping canopy height at 100 m (1-ha pixels. The bias-corrected spatial models further improve estimates for small and large trees across the tails of height distributions with a trade-off in increasing overall mean squared error that can be readily compensated by increasing the sample size. Conclusions A significant improvement in tropical forest mapping can be achieved by weighting the number of inventory samples against the choice of image layers and the non-parametric algorithms. Without future satellite observations with better sensitivity to forest biomass, the maps based on existing data will remain slightly biased towards the mean of the distribution and under and over estimating the upper and lower tails of the distribution.

Cardiorespiratory fitness, cognition and brain structure after TIA or minor ischemic stroke.

Science.gov (United States)

Boss, H Myrthe; Van Schaik, Sander M; Witkamp, Theo D; Geerlings, Mirjam I; Weinstein, Henry C; Van den Berg-Vos, Renske M

2017-10-01

Background It is not known whether cardiorespiratory fitness is associated with better cognitive performance and brain structure in patients with a TIA or minor ischemic stroke. Aims To examine the association between cardiorespiratory fitness, cognition and brain structure in patients with a TIA and minor stroke. Methods The study population consisted of patients with a TIA or minor stroke with a baseline measurement of the peak oxygen consumption, a MRI scan of brain and neuropsychological assessment. Composite z-scores were calculated for the cognitive domains attention, memory and executive functioning. White matter hyperintensities, microbleeds and lacunes were rated visually. The mean apparent diffusion coefficient was measured in regions of interest in frontal and occipital white matter and in the centrum semiovale as a marker of white matter structure. Normalized brain volumes were estimated by use of Statistical Parametric Mapping. Results In 84 included patients, linear regression analysis adjusted for age, sex and education showed that a higher peak oxygen consumption was associated with higher cognitive z-scores, a larger grey matter volume (B = 0.15 (95% CI 0.05; 0.26)) and a lower mean apparent diffusion coefficient (B = -.004 (95% CI -.007; -.001)). We found no association between the peak oxygen consumption and severe white matter hyperintensities, microbleeds, lacunes and total brain volume. Conclusions These data suggest that cardiorespiratory fitness is associated with better cognitive performance, greater grey matter volume and greater integrity of the white matter in patients with a TIA or minor ischemic stroke. Further prospective trials are necessary to define the effect of cardiorespiratory fitness on cognition and brain structure in patients with TIA or minor stroke.

Association of inflammatory gene polymorphisms with ischemic stroke in a Chinese Han population

Directory of Open Access Journals (Sweden)

Zhao Nan

2012-07-01

Full Text Available Abstract Background Inflammatory mechanisms are important in stroke risk, and genetic variations in components of the inflammatory response have been implicated as risk factors for stroke. We tested the inflammatory gene polymorphisms and their association with ischemic stroke in a Chinese Han population. Methods A total of 1,124 ischemic stroke cases and 1,163 controls were genotyped with inflammatory panel strips containing 51 selected inflammatory gene polymorphisms from 35 candidate genes. We tested the genotype-stroke association with logistic regression model. Results We found two single nucleotide polymorphisms (SNPs in CCL11 were associated with ischemic stroke. After adjusting for multiple testing using false discovery rate (FDR with a 0.20 cut-off point, CCL11 rs4795895 remained statistically significant. We further stratified the study population by their hypertension status. In the hypertensive group, CCR2 rs1799864, CCR5 rs1799987 and CCL11 rs4795895 were nominally associated with increased risk of stroke. In the non-hypertensive group, CCL11 rs3744508, LTC4S rs730012, FCER1B rs569108, TGFB1 rs1800469, LTA rs909253 and CCL11 rs4795895 were associated with ischemic stroke. After correction for multiple testing, CCR2 rs1799864 and CCR5 rs1799987 remained significant in the hypertensive group, and CCL11 rs3744508, LTC4S rs730012, FCER1B rs569108, TGFB1 rs1800469, LTA rs909253 remained significant in the non-hypertensive group. Conclusions Our results indicate that inflammatory genetic variants are associated with increased risk of ischemic stroke in a Chinese Han population, particularly in non-hypertensive individuals.

Parametric form of QCD travelling waves

OpenAIRE

Peschanski, R.

2005-01-01

We derive parametric travelling-wave solutions of non-linear QCD equations. They describe the evolution towards saturation in the geometric scaling region. The method, based on an expansion in the inverse of the wave velocity, leads to a solvable hierarchy of differential equations. A universal parametric form of travelling waves emerges from the first two orders of the expansion.

Measurement of vertical stroke Vub vertical stroke using b hadron semileptonic decay

International Nuclear Information System (INIS)

Abbiendi, G.; Aakesson, P.F.

2001-01-01

The magnitude of the CKM matrix element vertical stroke V ub vertical stroke is determined by measuring the inclusive charmless semileptonic branching fraction of beauty hadrons at OPAL based on b → X u lν event topology and kinematics. This analysis uses OPAL data collected between 1991 and 1995, which correspond to about four million hadronic Z decays. We measure Br(b → X u lν) to be (1.63 ±0.53 +0.55 -0.62 ) x 10 -3 . The first uncertainty is the statistical error and the second is the systematic error. From this analysis, vertical stroke V ub vertical stroke is determined to be: vertical stroke V ub vertical stroke =(4.00±0.65(stat) +0.67 -0.76 (sys)±0.19(HQE)) x 10 -3 . The last error represents the theoretical uncertainties related to the extraction of vertical stroke V ub vertical stroke from Br(b→X u l ν) using the Heavy Quark Expansion. (orig.)

The problem of low variance voxels in statistical parametric mapping; a new hat avoids a 'haircut'.

Science.gov (United States)

Ridgway, Gerard R; Litvak, Vladimir; Flandin, Guillaume; Friston, Karl J; Penny, Will D

2012-02-01

Statistical parametric mapping (SPM) locates significant clusters based on a ratio of signal to noise (a 'contrast' of the parameters divided by its standard error) meaning that very low noise regions, for example outside the brain, can attain artefactually high statistical values. Similarly, the commonly applied preprocessing step of Gaussian spatial smoothing can shift the peak statistical significance away from the peak of the contrast and towards regions of lower variance. These problems have previously been identified in positron emission tomography (PET) (Reimold et al., 2006) and voxel-based morphometry (VBM) (Acosta-Cabronero et al., 2008), but can also appear in functional magnetic resonance imaging (fMRI) studies. Additionally, for source-reconstructed magneto- and electro-encephalography (M/EEG), the problems are particularly severe because sparsity-favouring priors constrain meaningfully large signal and variance to a small set of compactly supported regions within the brain. (Acosta-Cabronero et al., 2008) suggested adding noise to background voxels (the 'haircut'), effectively increasing their noise variance, but at the cost of contaminating neighbouring regions with the added noise once smoothed. Following theory and simulations, we propose to modify--directly and solely--the noise variance estimate, and investigate this solution on real imaging data from a range of modalities. Copyright © 2011 Elsevier Inc. All rights reserved.

Statistical Analysis of Data for Timber Strengths

DEFF Research Database (Denmark)

Sørensen, John Dalsgaard

2003-01-01

Statistical analyses are performed for material strength parameters from a large number of specimens of structural timber. Non-parametric statistical analysis and fits have been investigated for the following distribution types: Normal, Lognormal, 2 parameter Weibull and 3-parameter Weibull...... fits to the data available, especially if tail fits are used whereas the Log Normal distribution generally gives a poor fit and larger coefficients of variation, especially if tail fits are used. The implications on the reliability level of typical structural elements and on partial safety factors...... for timber are investigated....

Stroke survivors' endorsement of a "stress belief model" of stroke prevention predicts control of risk factors for recurrent stroke.

Science.gov (United States)

Phillips, L Alison; Tuhrim, Stanley; Kronish, Ian M; Horowitz, Carol R

2014-01-01

Perceptions that stress causes and stress-reduction controls hypertension have been associated with poorer blood pressure (BP) control in hypertension populations. The current study investigated these "stress-model perceptions" in stroke survivors regarding prevention of recurrent stroke and the influence of these perceptions on patients' stroke risk factor control. Stroke and transient ischemic attack survivors (N=600) participated in an in-person interview in which they were asked about their beliefs regarding control of future stroke; BP and cholesterol were measured directly after the interview. Counter to expectations, patients who endorsed a "stress-model" but not a "medication-model" of stroke prevention were in better control of their stroke risk factors (BP and cholesterol) than those who endorsed a medication-model but not a stress-model of stroke prevention (OR for poor control=.54, Wald statistic=6.07, p=.01). This result was not explained by between group differences in patients' reported medication adherence. The results have implications for theory and practice, regarding the role of stress belief models and acute cardiac events, compared to chronic hypertension.

Prevention Of Stroke

Directory of Open Access Journals (Sweden)

Nagaraja D

2005-01-01

Full Text Available Stroke is an important cause for neurological morbidity and mortality. Prevention of ischemic stroke involves identification and prevention of risk factors and optimal use of pharmacotherapy. Risk factors have been classified as modifiable and non-modifiable; control of modifiable factors should prevent stroke occurrence. Stroke prevention has been described at three levels: primary, secondary and tertiary. Prolonged hypertension increases an individual′s risk for developing fatal or nonfatal stroke by three times and its control has been shown to prevent stroke. Diabetes mellitus is an important cause for microangiopathy and predisposes to stroke. Statin trials have shown significant reduction in stroke in those who were treated with statins. Stroke risk can be reduced by avoiding tobacco use, control of obesity and avoiding sedentary life style. Anti platelet medications are effective for secondary prevention of stroke. Educating society regarding modifiable risk factors and optimal use of pharmacotherapy form the cornerstone for the prevention of stroke.

Lacunar strokes: a single institutional experience

Directory of Open Access Journals (Sweden)

Osama Shukir Muhammed Amin

2013-08-01

Full Text Available Abstract: Objective: Lacunar ischemic strokes comprise approximately 25% of all ischemic strokes. We compared the risk factors and clinical pattern of this type of stroke between males and females. Methods: This observational study involved 50 consecutive patients with their first-ever lacunar stroke and was conducted at the department of neurology of Sulaimaniya general teaching hospital, Iraq from December 1, 2010 to March 1, 2013. Patients’ risk factors, clinical presentation, and strokes’ patterns were noted and a comparison was made between males and females. Results: Males (64% outnumbered females (36% with a male to female ration of 1.7. The mean age of males was 63 years while it was 61 years in females. Although hypertension was more common in females than in males, diabetes and smoking were more common in the latter group; however, there were no statistically significant differences between the 2 genders in terms of hypertension (P-value <0.3 and diabetes (P-value < 0.07 while smoking was strongly associated with male gender (P-value<0.0001. Pure motor hemiparesis, ataxic hemiparesis, pure sensory stroke, and dysarthria-clumsy hand syndrome were more common in males; only senori-motor stroke revealed a statistically significant difference in favor males (P-value<0.0001; 95% CI -1.7 to 19.2. There was no statistically significant difference in terms of which side of the brain was infarcted between males and females (P-value<0.4. Conclusion: Males around the age of 63 years were the main target for these lacunar strokes. Cigarette smoking and sensorimotor strokes were significantly associated with male gender. [Cukurova Med J 2013; 38(4.000: 659-666

An appraisal of statistical procedures used in derivation of reference intervals.

Science.gov (United States)

Ichihara, Kiyoshi; Boyd, James C

2010-11-01

When conducting studies to derive reference intervals (RIs), various statistical procedures are commonly applied at each step, from the planning stages to final computation of RIs. Determination of the necessary sample size is an important consideration, and evaluation of at least 400 individuals in each subgroup has been recommended to establish reliable common RIs in multicenter studies. Multiple regression analysis allows identification of the most important factors contributing to variation in test results, while accounting for possible confounding relationships among these factors. Of the various approaches proposed for judging the necessity of partitioning reference values, nested analysis of variance (ANOVA) is the likely method of choice owing to its ability to handle multiple groups and being able to adjust for multiple factors. Box-Cox power transformation often has been used to transform data to a Gaussian distribution for parametric computation of RIs. However, this transformation occasionally fails. Therefore, the non-parametric method based on determination of the 2.5 and 97.5 percentiles following sorting of the data, has been recommended for general use. The performance of the Box-Cox transformation can be improved by introducing an additional parameter representing the origin of transformation. In simulations, the confidence intervals (CIs) of reference limits (RLs) calculated by the parametric method were narrower than those calculated by the non-parametric approach. However, the margin of difference was rather small owing to additional variability in parametrically-determined RLs introduced by estimation of parameters for the Box-Cox transformation. The parametric calculation method may have an advantage over the non-parametric method in allowing identification and exclusion of extreme values during RI computation.

The SU(1, 1) Perelomov number coherent states and the non-degenerate parametric amplifier

Energy Technology Data Exchange (ETDEWEB)

Ojeda-Guillén, D., E-mail: dojedag@ipn.mx; Granados, V. D. [Escuela Superior de Física y Matemáticas, Instituto Politécnico Nacional, Ed. 9, Unidad Profesional Adolfo López Mateos, C.P. 07738 México D. F. (Mexico); Mota, R. D. [Escuela Superior de Ingeniería Mecánica y Eléctrica, Unidad Culhuacán, Instituto Politécnico Nacional, Av. Santa Ana No. 1000, Col. San Francisco Culhuacán, Delegación Coyoacán, C.P. 04430, México D. F. (Mexico)

2014-04-15

We construct the Perelomov number coherent states for an arbitrary su(1, 1) group operation and study some of their properties. We introduce three operators which act on Perelomov number coherent states and close the su(1, 1) Lie algebra. By using the tilting transformation we apply our results to obtain the energy spectrum and eigenfunctions of the non-degenerate parametric amplifier. We show that these eigenfunctions are the Perelomov number coherent states of the two-dimensional harmonic oscillator.

Induction of neuroplasticity and recovery in post-stroke aphasia by non-invasive brain stimulation

Directory of Open Access Journals (Sweden)

Priyanka eShah

2013-12-01

Full Text Available Stroke victims tend to prioritize speaking, writing and walking as the three most important rehabilitation goals. Of note is that two of these goals involve communication. This underscores the significance of developing successful approaches to aphasia treatment for the several hundred thousand new aphasia patients each year and over 1 million stroke survivors with chronic aphasia in the U.S. alone. After several years of growth as a research tool, noninvasive brain stimulation (NBS is gradually entering the arena of clinical aphasiology. In this review, we first examine the current state of knowledge of post-stroke language recovery including the contributions from the dominant and non-dominant hemispheres. Next, we briefly discuss the methods and the physiologic basis of the use of inhibitory and excitatory repetitive transcranial magnetic stimulation (rTMS and transcranial direct current stimulation (tDCS as research tools in patients who experience post-stroke aphasia. Finally, we provide a critical review of the most influential evidence behind the potential use of these two brain stimulation methods as clinical rehabilitative tools.

Statistical modelling approach to derive quantitative nanowastes classification index; estimation of nanomaterials exposure

CSIR Research Space (South Africa)

Ntaka, L

2013-08-01

Full Text Available . In this work, statistical inference approach specifically the non-parametric bootstrapping and linear model were applied. Data used to develop the model were sourced from the literature. 104 data points with information on aggregation, natural organic matter...

Brain SPECT analysis using statistical parametric mapping in patients with posttraumatic stress disorder

Energy Technology Data Exchange (ETDEWEB)

Kim, Euy Neyng; Sohn, Hyung Sun; Kim, Sung Hoon; Chung, Soo Kyo; Yang, Dong Won [College of Medicine, The Catholic Univ. of Korea, Seoul (Korea, Republic of)

2001-07-01

This study investigated alterations in regional cerebral blood flow (rCBF) in patients with posttraumatic stress disorder (PTSD) using statistical parametric mapping (SPM99). Noninvasive rCBF measurements using {sup 99m}Tc-ethyl cysteinate dimer (ECD) SPECT were performed on 23 patients with PTSD and 21 age matched normal controls without re-exposure to accident-related stimuli. The relative rCBF maps in patients with PTSD and controls were compared. In patients with PTSD, significant increased rCBF was found along the limbic system in the brain. There were a few foci of decreased rCBF in the superior frontal gyrus, parietal and temporal region. PTSD is associated with increased rCBF in limbic areas compared with age-matched normal controls. These findings implicate regions of the limbic brain, which may mediate the response to aversive stimuli in healthy individuals, play on important role in patients suffering from PTSD and suggest that ongoing hyperfunction of 'overlearned survival response' or flashbacks response in these regions after painful, life threatening, or horrifying events without re-exposure to same traumatic stimulus.

Brain SPECT analysis using statistical parametric mapping in patients with posttraumatic stress disorder

International Nuclear Information System (INIS)

Kim, Euy Neyng; Sohn, Hyung Sun; Kim, Sung Hoon; Chung, Soo Kyo; Yang, Dong Won

2001-01-01

This study investigated alterations in regional cerebral blood flow (rCBF) in patients with posttraumatic stress disorder (PTSD) using statistical parametric mapping (SPM99). Noninvasive rCBF measurements using 99m Tc-ethyl cysteinate dimer (ECD) SPECT were performed on 23 patients with PTSD and 21 age matched normal controls without re-exposure to accident-related stimuli. The relative rCBF maps in patients with PTSD and controls were compared. In patients with PTSD, significant increased rCBF was found along the limbic system in the brain. There were a few foci of decreased rCBF in the superior frontal gyrus, parietal and temporal region. PTSD is associated with increased rCBF in limbic areas compared with age-matched normal controls. These findings implicate regions of the limbic brain, which may mediate the response to aversive stimuli in healthy individuals, play on important role in patients suffering from PTSD and suggest that ongoing hyperfunction of 'overlearned survival response' or flashbacks response in these regions after painful, life threatening, or horrifying events without re-exposure to same traumatic stimulus

Influence of image reconstruction methods on statistical parametric mapping of brain PET images

International Nuclear Information System (INIS)

Yin Dayi; Chen Yingmao; Yao Shulin; Shao Mingzhe; Yin Ling; Tian Jiahe; Cui Hongyan

2007-01-01

Objective: Statistic parametric mapping (SPM) was widely recognized as an useful tool in brain function study. The aim of this study was to investigate if imaging reconstruction algorithm of PET images could influence SPM of brain. Methods: PET imaging of whole brain was performed in six normal volunteers. Each volunteer had two scans with true and false acupuncturing. The PET scans were reconstructed using ordered subsets expectation maximization (OSEM) and filtered back projection (FBP) with 3 varied parameters respectively. The images were realigned, normalized and smoothed using SPM program. The difference between true and false acupuncture scans was tested using a matched pair t test at every voxel. Results: (1) SPM corrected multiple comparison (P corrected uncorrected <0.001): SPM derived from the images with different reconstruction method were different. The largest difference, in number and position of the activated voxels, was noticed between FBP and OSEM re- construction algorithm. Conclusions: The method of PET image reconstruction could influence the results of SPM uncorrected multiple comparison. Attention should be paid when the conclusion was drawn using SPM uncorrected multiple comparison. (authors)

Nonparametric statistics for social and behavioral sciences

CERN Document Server

Kraska-MIller, M

2013-01-01

Introduction to Research in Social and Behavioral SciencesBasic Principles of ResearchPlanning for ResearchTypes of Research Designs Sampling ProceduresValidity and Reliability of Measurement InstrumentsSteps of the Research Process Introduction to Nonparametric StatisticsData AnalysisOverview of Nonparametric Statistics and Parametric Statistics Overview of Parametric Statistics Overview of Nonparametric StatisticsImportance of Nonparametric MethodsMeasurement InstrumentsAnalysis of Data to Determine Association and Agreement Pearson Chi-Square Test of Association and IndependenceContingency

Hormone replacement therapy and risk of non-fatal stroke

DEFF Research Database (Denmark)

Pedersen, A T; Lidegaard, O; Kreiner, S

1997-01-01

haemorrhage, 846 thromboembolic infarction, 321 transient ischaemic attack) and 3171 controls. FINDINGS: After adjustment for confounding variables and correction for the trend in sales of HRT preparations, no significant associations were detected between current use of unopposed oestrogen replacement...... influence on the risk of subarachnoid haemorrhage (1.22 [0.79-1.89]), intracerebral haemorrhage (1.17 [0.64-2.13]), or thromboembolic infarction (1.17 [0.92-1.47]). A significantly increased incidence of transient ischaemic attacks among former users of HRT and among current users of unopposed oestrogen may...... to some extent be explained by selection--HRT users being more aware of symptoms than non-users. INTERPRETATION: Unopposed oestrogen and combined oestrogen-progestagen replacement therapy have no influence on the risk of non-fatal thromboembolic or haemorrhagic stroke in women aged 45-64 years....

Stroke subtypes and factors associated with ischemic stroke in ...

African Journals Online (AJOL)

Stroke subtypes assessed four OCSP (Oxfordshire Communi-. African Health Sciences Vol 15 Issue 1, March 2015. 68. 69 ty Stroke Project Classification) subtypes classification. 13 was used with lacunar circulation infarct (LACI) and total anterior (TACI), partial anterior (PACI), posterior. (POCI) circulation infarcts as non ...

Stroke-attributable death among older persons during the great recession.

Science.gov (United States)

Falconi, April; Gemmill, Alison; Karasek, Deborah; Goodman, Julia; Anderson, Beth; Lee, Murray; Bellows, Benjamin; Catalano, Ralph

2016-05-01

Epidemiological evidence indicates an elevated risk for stroke among stressed persons, in general, and among individuals who have lost their job, in particular. We, therefore, tested the hypothesis that stroke accounted for a larger fraction of deaths during the Great Recession than expected from other deaths and from trends, cycles, and other forms of autocorrelation. Based on vital statistics death data from California spanning 132 months from January 2000 through December 2010, we found support for the hypothesis. These findings appear attributable to non-Hispanic white men, who experienced a 5% increase in their monthly odds of stroke-attributable death. Total mortality in this group, however, did not increase. Findings suggest that 879 deaths among older white men shifted from other causes to stroke during the 36 months following the start of the Great Recession. We infer the Great Recession may have affected social, biologic, and behavioral risk factors that altered the life histories of older white men in ways that shifted mortality risk toward stroke. Copyright © 2015 Elsevier B.V. All rights reserved.

Breast-Lesion Characterization using Textural Features of Quantitative Ultrasound Parametric Maps.

Science.gov (United States)

Sadeghi-Naini, Ali; Suraweera, Harini; Tran, William Tyler; Hadizad, Farnoosh; Bruni, Giancarlo; Rastegar, Rashin Fallah; Curpen, Belinda; Czarnota, Gregory J

2017-10-20

This study evaluated, for the first time, the efficacy of quantitative ultrasound (QUS) spectral parametric maps in conjunction with texture-analysis techniques to differentiate non-invasively benign versus malignant breast lesions. Ultrasound B-mode images and radiofrequency data were acquired from 78 patients with suspicious breast lesions. QUS spectral-analysis techniques were performed on radiofrequency data to generate parametric maps of mid-band fit, spectral slope, spectral intercept, spacing among scatterers, average scatterer diameter, and average acoustic concentration. Texture-analysis techniques were applied to determine imaging biomarkers consisting of mean, contrast, correlation, energy and homogeneity features of parametric maps. These biomarkers were utilized to classify benign versus malignant lesions with leave-one-patient-out cross-validation. Results were compared to histopathology findings from biopsy specimens and radiology reports on MR images to evaluate the accuracy of technique. Among the biomarkers investigated, one mean-value parameter and 14 textural features demonstrated statistically significant differences (p feature selection method could classify the legions with a sensitivity of 96%, a specificity of 84%, and an AUC of 0.97. Findings from this study pave the way towards adapting novel QUS-based frameworks for breast cancer screening and rapid diagnosis in clinic.

Prediabetes is associated with post-stroke cognitive impairment in ischaemic stroke patients.

Science.gov (United States)

Wang, Qiongzhang; Zhao, Kai; Cai, Yan; Tu, Xinjie; Liu, Yuntao; He, Jincai

2018-05-15

Diabetes mellitus is associated with post-stroke cognitive impairment. To the best of our knowledge, no study has explored the relationship between prediabetes and post-stroke cognitive impairment. The purpose of this study is to explore the association between prediabetes and cognitive impairment in ischaemic stroke patients at 1 month. Two hundred one acute ischaemic stroke patients were consecutively recruited within the first 24 h after admission and were followed up for 1 month. Patients were divided into a diabetes mellitus group, prediabetes group and non-diabetes mellitus group by fasting glucose levels, 2-h postprandial blood glucose levels and glycosylated haemoglobin levels at admission. Cognitive function was evaluated by the Mini-Mental State Examination at 1 month after stroke. The prediabetes group had a higher risk of post-stroke cognitive impairment than the non-diabetes group (35.7% vs. 18.1%, χ 2  = 4.252, P = .039). In logistical analyses, prediabetes was associated with post-stroke cognitive impairment after adjusting for potential confounding factors (odds ratio 3.062, 95% confidence interval 1.130-8.299, P = .028). Our findings show that prediabetes is associated with post-stroke cognitive impairment and may predict its development at 1 month post-stroke. Copyright © 2018 Elsevier B.V. All rights reserved.

Applications of quantum entropy to statistics

International Nuclear Information System (INIS)

Silver, R.N.; Martz, H.F.

1994-01-01

This paper develops two generalizations of the maximum entropy (ME) principle. First, Shannon classical entropy is replaced by von Neumann quantum entropy to yield a broader class of information divergences (or penalty functions) for statistics applications. Negative relative quantum entropy enforces convexity, positivity, non-local extensivity and prior correlations such as smoothness. This enables the extension of ME methods from their traditional domain of ill-posed in-verse problems to new applications such as non-parametric density estimation. Second, given a choice of information divergence, a combination of ME and Bayes rule is used to assign both prior and posterior probabilities. Hyperparameters are interpreted as Lagrange multipliers enforcing constraints. Conservation principles are proposed to act statistical regularization and other hyperparameters, such as conservation of information and smoothness. ME provides an alternative to heirarchical Bayes methods

Non-stenotic intracranial arteries have atherosclerotic changes in acute ischemic stroke patients: a 3T MRI study

Energy Technology Data Exchange (ETDEWEB)

Lee, Woo Jin; Choi, Hyun Seok; Jang, Jinhee; Sung, Jinkyeong; Jung, So-Lyung; Ahn, Kook-Jin; Kim, Bum-soo [The Catholic University of Korea, Department of Radiology, Seoul St. Mary' s Hospital, College of Medicine, Seoul (Korea, Republic of); Kim, Tae-Won; Koo, Jaseong [The Catholic University of Korea, Department of Neurology, College of Medicine, Seoul (Korea, Republic of); Shin, Yong Sam [The Catholic University of Korea, Department of Neurosurgery, College of Medicine, Seoul (Korea, Republic of)

2015-10-15

The aim of this study is to evaluate the degree of atherosclerotic changes in intracranial arteries by assessing arterial wall thickness using T1-weighted 3D-turbo spin echo (3D-TSE) and time-of-flight MR angiography (TOF-MRA) in patients with acute ischemic stroke as compared with unaffected controls. Thirty-three patients with acute ischemic stroke and 36 control patients were analyzed. Acute ischemic stroke patients were divided according to TOAST classification. At both distal internal carotid arteries and basilar artery without stenosis, TOF-MRA was used to select non-stenotic portion of assessed arteries. 3D-TSE was used to measure the area including the lumen and wall (Area{sub Outer}) and luminal area (Area{sub Inner}). The area of the vessel wall (Area{sub VW}) of assessed intracranial arteries and the ratio index (RI) of each patient were determined. Area{sub Inner}, Area{sub Outer}, Area{sub VW}, and RI showed good inter-observer reliability and excellent intra-observer reliability. Area{sub Inner} did not significantly differ between stroke patients and controls (P = 0.619). However, Area{sub Outer}, Area{sub VW}, and RI were significantly larger in stroke patients (P < 0.001). The correlation coefficient between Area{sub Inner} and Area{sub Outer} was higher in the controls (r = 0.918) than in large vessel disease patients (r = 0.778). RI of large vessel disease patients was significantly higher than that of normal control, small vessel disease, and cardioembolic groups. In patients with acute ischemic stroke, wall thickening and positive remodeling are evident in non-stenotic intracranial arteries. This change is more definite in stroke subtype that is related to atherosclerosis than that in other subtypes which are not. (orig.)

Alcohol intake in relation to non-fatal and fatal coronary heart disease and stroke

DEFF Research Database (Denmark)

Ricci, Cristian; Wood, Angela; Muller, David

2018-01-01

OBJECTIVE: To investigate the association between alcohol consumption (at baseline and over lifetime) and non-fatal and fatal coronary heart disease (CHD) and stroke. DESIGN: Multicentre case-cohort study. SETTING: A study of cardiovascular disease (CVD) determinants within the European Prospecti...

Association between β-cell function estimated by HOMA-β and prognosis of non-diabetic patients with ischaemic stroke.

Science.gov (United States)

Zhou, M; Pan, Y; Jing, J; Wang, Y; Zhao, X; Liu, L; Li, H; Wang, Y

2018-03-01

Studies showed that β-cell dysfunction is associated with increased risk of cardiovascular disease and subclinical carotid atherosclerosis. This study aimed to investigate the association between β-cell function and prognosis of non-diabetic patients with ischaemic stroke. Ischaemic stroke patients without diabetes in the Abnormal Glucose Regulation in Patients with Acute Stroke across China registry were included in this analysis. Homeostasis assessment of β-cell function (HOMA-β) was performed and classified into four groups according to quartiles. The outcomes included stroke recurrence, poor functional outcome and all-cause mortality. In a total of 1244 patients, the average age was 62.3 years; 63.1% patients were male. At 1 year, the first quartile of HOMA-β (HOMA-β (≥166.3) after adjustment for insulin resistance and other potential covariates. The second and third quartiles of HOMA-β were significantly associated with an increased risk of poor functional outcome. Multivariable regression analysis with restricted cubic splines showed an L-shaped association between HOMA-β and outcomes at 1 year. Our study shows that lower HOMA-β level is associated with poor outcomes at 1 year in non-diabetic patients with ischaemic stroke. © 2017 EAN.

Comparing parametric and nonparametric regression methods for panel data

DEFF Research Database (Denmark)

Czekaj, Tomasz Gerard; Henningsen, Arne

We investigate and compare the suitability of parametric and non-parametric stochastic regression methods for analysing production technologies and the optimal firm size. Our theoretical analysis shows that the most commonly used functional forms in empirical production analysis, Cobb......-Douglas and Translog, are unsuitable for analysing the optimal firm size. We show that the Translog functional form implies an implausible linear relationship between the (logarithmic) firm size and the elasticity of scale, where the slope is artificially related to the substitutability between the inputs....... The practical applicability of the parametric and non-parametric regression methods is scrutinised and compared by an empirical example: we analyse the production technology and investigate the optimal size of Polish crop farms based on a firm-level balanced panel data set. A nonparametric specification test...

Efficacy of Aquatic Treadmill Training on Gait Symmetry and Balance in Subacute Stroke Patients.

Science.gov (United States)

Lee, Mi Eun; Jo, Geun Yeol; Do, Hwan Kwon; Choi, Hee Eun; Kim, Woo Jin

2017-06-01

To determine the efficacy of aquatic treadmill training (ATT) as a new modality for stroke rehabilitation, by assessing changes in gait symmetry, balance function, and subjective balance confidence for the paretic and non-paretic leg in stroke patients. Twenty-one subacute stroke patients participated in 15 intervention sessions of aquatic treadmill training. The Comfortable 10-Meter Walk Test (CWT), spatiotemporal gait parameters, Berg Balance Scale (BBS), and Activities-specific Balance Confidence scale (ABC) were assessed pre- and post-interventions. From pre- to post-intervention, statistically significant improvements were observed in the CWT (0.471±0.21 to 0.558±0.23, pstroke therapy, with other modalities.

Analysis on risk factors for post-stroke emotional incontinence

Directory of Open Access Journals (Sweden)

Xiao-chun ZHANG

2018-01-01

Full Text Available Objective To investigate the occurrence rate and related risk factors for post-stroke emotional incontinence (PSEI. Methods The clinical data [sex, age, body mass index (BMI, education, marital status, medical history (hypertension, heart disease, diabetes, hyperlipemia, smoking and drinking and family history of stroke] of 162 stroke patients were recorded. Serum homocysteine (Hcy level was examined. Head CT and/or MRI were used to indicate stroke subtype, site of lesion and number of lesion. Diagnostic and Statistical Manual of Mental Disorders Fifth Edition (DSM-Ⅴ Chinese version and Hamilton Depression Rating Scale-17 Items (HAMD-17 were used to evaluate the degree of depression. House diagnostic standard was used to diagnose PSEI. Univariate and multivariate backward Logistic regression analysis was used to screen related risk factor for PSEI. Spearman rank correlation analysis was used to discuss the correlation between PSEI and post-stroke depression (PSD. Results Among 162 stroke patients, 12 cases were diagnosed as PSEI (7.41% . The ratio of age < 60 years in PSEI group was significantly higher than non-PSEI group (P = 0.045. The ratio of smoking in PSEI group was significantly lower than non-PSEI group (P = 0.036. Univariate and multivariate backward Logistic regression analysis showed age < 60 years was independent risk factor for PSEI (OR = 4.000, 95%CI: 1.149-13.924; P = 0.029. Ten cases were combined with PSD in 12 PSEI patients, and the co-morbidity rate of PSEI and PSD was83.33%. Spearman rank correlation analysis showed PSEI was positively related to PSD (rs = 0.305, P = 0.000. Conclusions PSEI is common affective disorder in stroke patients, which easily happens in patients under 60 years of age. DOI: 10.3969/j.issn.1672-6731.2017.12.010

Statistical Analysis of Data with Non-Detectable Values

Energy Technology Data Exchange (ETDEWEB)

Frome, E.L.

2004-08-26

Environmental exposure measurements are, in general, positive and may be subject to left censoring, i.e. the measured value is less than a ''limit of detection''. In occupational monitoring, strategies for assessing workplace exposures typically focus on the mean exposure level or the probability that any measurement exceeds a limit. A basic problem of interest in environmental risk assessment is to determine if the mean concentration of an analyte is less than a prescribed action level. Parametric methods, used to determine acceptable levels of exposure, are often based on a two parameter lognormal distribution. The mean exposure level and/or an upper percentile (e.g. the 95th percentile) are used to characterize exposure levels, and upper confidence limits are needed to describe the uncertainty in these estimates. In certain situations it is of interest to estimate the probability of observing a future (or ''missed'') value of a lognormal variable. Statistical methods for random samples (without non-detects) from the lognormal distribution are well known for each of these situations. In this report, methods for estimating these quantities based on the maximum likelihood method for randomly left censored lognormal data are described and graphical methods are used to evaluate the lognormal assumption. If the lognormal model is in doubt and an alternative distribution for the exposure profile of a similar exposure group is not available, then nonparametric methods for left censored data are used. The mean exposure level, along with the upper confidence limit, is obtained using the product limit estimate, and the upper confidence limit on the 95th percentile (i.e. the upper tolerance limit) is obtained using a nonparametric approach. All of these methods are well known but computational complexity has limited their use in routine data analysis with left censored data. The recent development of the R environment for statistical

EXTRACRANIAL NON-ATHEROSCLEROTIC PATHOLOGY OF THE CAROTID ARTERY IN THE CAUSES OF ACUTE ISCHEMIC STROKE

Directory of Open Access Journals (Sweden)

I. P. Dudanov

2017-01-01

Full Text Available Purpose. We present the experience of treatment of patients with cerebral vascular accident by the ischemic type, the cause of which was non-atherosclerotic lesion of brachiocephalic arteries.Materials and methods. During 2011–2015 years 4118 patients with acute ischemic stroke were observed. Of these, 589 patients (14.3% were operated in the acute period of stroke in the period from 4–6 hours to 14 days. The cause of the stroke was various types of pathology of the extracranial divisions of the brachiocephalic arteries (EDBA. Of this number, with atherosclerotic carotid artery stenoses, 336 patients (57.1% were operated on, with non-atherosclerotic pathology of carotid arteries — 253 patients (42.9%. Of these 253 patients, dissection of the intima of the carotid arteries was detected in 10 (3.9% patients, aneurysms in the extracranial segment of the ECA and ICA were detected in 14 (5.5%, and 229 (90.6% revealed various types of tortuosity and kinks carotid arteries and fibrous dysplasia. All patients are operated on. Various types of reconstructions of carotid arteries with a good clinical effect have been performed. There were no lethal outcomes.Concusions. The data obtained in the study confirm the opinion that not only atherosclerotic lesions of the ICA are an indication for surgical treatment at an early date. This stage is an important part of the comprehensive rehabilitation of patients with acute ischemic stroke.

Acute management of stroke patients taking non-vitamin K antagonist oral anticoagulants Addressing Real-world Anticoagulant Management Issues in Stroke (ARAMIS) Registry: Design and rationale.

Science.gov (United States)

Xian, Ying; Hernandez, Adrian F; Harding, Tina; Fonarow, Gregg C; Bhatt, Deepak L; Suter, Robert E; Khan, Yosef; Schwamm, Lee H; Peterson, Eric D

2016-12-01

Non-vitamin K antagonist oral anticoagulants (NOACs, dabigatran, rivaroxaban, apixaban, and edoxaban) have been increasingly used as alternatives to warfarin for stroke prophylaxis in patients with atrial fibrillation. Yet there is substantial lack of information on how patients on NOACs are currently treated when they have an acute ischemic stroke and the best strategies for treating intracerebral hemorrhage for those on chronic anticoagulation with warfarin or a NOAC. These are critical unmet needs for real world clinical decision making in these emergent patients. The ARAMIS Registry is a multicenter cohort study of acute stroke patients who were taking chronic anticoagulation therapy prior to admission and are admitted with either an acute ischemic stroke or intracerebral hemorrhage. Built upon the existing infrastructure of American Heart Association/American Stroke Association Get With the Guidelines Stroke, the ARAMIS Registry will enroll a total of approximately 10,000 patients (5000 with acute ischemic stroke who are taking a NOAC and 5000 with anticoagulation-related intracerebral hemorrhage who are on warfarin or a NOAC). The primary goals of the ARAMIS Registry are to provide a comprehensive picture of current treatment patterns and outcomes of acute ischemic stroke patients on NOACs, as well as anticoagulation-related intracerebral hemorrhage in patients on either warfarin or NOACs. Beyond characterizing the index hospitalization, up to 2500 patients (1250 ischemic stroke and 1250 intracerebral hemorrhage) who survive to discharge will be enrolled in an optional follow-up sub-study and interviewed at 3 and 6 months after discharge to assess longitudinal medication use, downstream care, functional status, and patient-reported outcomes. The ARAMIS Registry will document the current state of management of NOAC treated patients with acute ischemic stroke as well as contemporary care and outcome of anticoagulation-related intracerebral hemorrhage. These

MEAN PLATELET VOLUME AND RISK OF THROMBOTIC STROKE

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Prasantha Kumar Thankappan

2017-07-01

Full Text Available BACKGROUND Stroke is a major cause of long term morbidity and mortality. Several factors are known to increase the liability to stroke. Platelets play a crucial role in the pathogenesis of atherosclerotic complications, contributing to thrombus formation. Platelet size (mean platelet volume, MPV is a marker and possible determinant of platelet function, large platelets being potentially more reactive. Hence an attempt has-been made to study the association if any between mean platelet volume and thrombotic stroke. The aim of this study was to determine whether an association exists between Mean Platelet Volume (MPV and thrombotic stroke. MATERIALS AND METHODS The study is a case control study and data was collected at Government Medical College Hospital, Kottayam, Kerala a tertiary care referral centre. The study was carried out among fifty patients diagnosed with thrombotic stroke and presenting to the hospital within forty eight hours of onset of symptoms. Fifty age group and sex matched controls were also recruited. Mean platelet volume was obtained using a SYSMEX automated analyser. RESULTS This study has shown a statistically significant relation between mean platelet volume and risk of thrombotic stroke but no statistically significant correlation between clinical severity of stroke and mean platelet volume. CONCLUSION This study has shown an elevation of MPV in acute phase of thrombotic stroke. Platelet mass was found to be more or less a constant. This study did not find a statistically significant correlation between clinical severity of stroke and mean platelet volume.

Convergence in energy consumption per capita across the US states, 1970–2013: An exploration through selected parametric and non-parametric methods

International Nuclear Information System (INIS)

Mohammadi, Hassan; Ram, Rati

2017-01-01

Noting the paucity of studies of convergence in energy consumption across the US states, and the usefulness of a study that shares the spirit of the enormous research on convergence in energy-related variables in cross-country contexts, this paper explores convergence in per-capita energy consumption across the US states over the 44-year period 1970–2013. Several well-known parametric and non-parametric approaches are explored partly to shed light on the substantive question and partly to provide a comparative methodological perspective on these approaches. Several statements summarize the outcome of our explorations. First, the widely-used Barro-type regressions do not indicate beta-convergence during the entire period or any of several sub-periods. Second, lack of sigma-convergence is also noted in terms of standard deviation of logarithms and coefficient of variation which do not show a decline between 1970 and 2013, but show slight upward trends. Third, kernel density function plots indicate some flattening of the distribution which is consistent with the results from sigma-convergence scenario. Fourth, intra-distribution mobility (“gamma convergence”) in terms of an index of rank concordance suggests a slow decline in the index. Fifth, the general impression from several types of panel and time-series unit-root tests is that of non-stationarity of the series and thus the lack of stochastic convergence during the period. Sixth, therefore, the overall impression seems to be that of the lack of convergence across states in per-capita energy consumption. The present interstate inequality in per-capita energy consumption may, therefore, reflect variations in structural factors and might not be expected to diminish.

Log-concave Probability Distributions: Theory and Statistical Testing

DEFF Research Database (Denmark)

An, Mark Yuing

1996-01-01

This paper studies the broad class of log-concave probability distributions that arise in economics of uncertainty and information. For univariate, continuous, and log-concave random variables we prove useful properties without imposing the differentiability of density functions. Discrete...... and multivariate distributions are also discussed. We propose simple non-parametric testing procedures for log-concavity. The test statistics are constructed to test one of the two implicati ons of log-concavity: increasing hazard rates and new-is-better-than-used (NBU) property. The test for increasing hazard...... rates are based on normalized spacing of the sample order statistics. The tests for NBU property fall into the category of Hoeffding's U-statistics...

Seizure development after stroke.

Science.gov (United States)

Misirli, H; Ozge, A; Somay, G; Erdoğan, N; Erkal, H; Erenoğlu, N Y

2006-12-01

Although there have been many studies on seizures following stroke, there is still much we do not know about them. In this study, we evaluated the characteristics of seizures in stroke patients. There were 2267 patients with a first-ever stroke, and after excluding 387 patients, 1880 were available for analysis. Of these 1880 patients, we evaluated 200 patients with seizures and 400 patients without seizures. We investigated the seizures according to age, gender, stroke type, the aetiology of ischaemic stroke and the localisation of the lesion. The seizures were classified as early onset and late onset and the seizure type as partial, generalised or secondarily generalised. Seizures occurred in 200 (10.6%) of 1880 strokes. The number of patients with seizures were 138 (10.6%) in ischaemic stroke group and 62 (10.7%) in haemorrhagic stroke group. Patients with ischaemic strokes had 41 embolic (29.7%) and 97 thrombotic (70.3%) origin, and these were not statistically significant in comparison with controls. Cortical involvement for the development of seizures was the most important risk factor (odds ratios = 4.25, p < 0.01). It was concluded that embolic strokes, being younger than 65 years old, and cortical localisation of stroke were important risks for developing seizures.

Parametric Method Performance for Dynamic 3'-Deoxy-3'-18F-Fluorothymidine PET/CT in Epidermal Growth Factor Receptor-Mutated Non-Small Cell Lung Carcinoma Patients Before and During Therapy.

Science.gov (United States)

Kramer, Gerbrand Maria; Frings, Virginie; Heijtel, Dennis; Smit, E F; Hoekstra, Otto S; Boellaard, Ronald

2017-06-01

The objective of this study was to validate several parametric methods for quantification of 3'-deoxy-3'- 18 F-fluorothymidine ( 18 F-FLT) PET in advanced-stage non-small cell lung carcinoma (NSCLC) patients with an activating epidermal growth factor receptor mutation who were treated with gefitinib or erlotinib. Furthermore, we evaluated the impact of noise on accuracy and precision of the parametric analyses of dynamic 18 F-FLT PET/CT to assess the robustness of these methods. Methods : Ten NSCLC patients underwent dynamic 18 F-FLT PET/CT at baseline and 7 and 28 d after the start of treatment. Parametric images were generated using plasma input Logan graphic analysis and 2 basis functions-based methods: a 2-tissue-compartment basis function model (BFM) and spectral analysis (SA). Whole-tumor-averaged parametric pharmacokinetic parameters were compared with those obtained by nonlinear regression of the tumor time-activity curve using a reversible 2-tissue-compartment model with blood volume fraction. In addition, 2 statistically equivalent datasets were generated by countwise splitting the original list-mode data, each containing 50% of the total counts. Both new datasets were reconstructed, and parametric pharmacokinetic parameters were compared between the 2 replicates and the original data. Results: After the settings of each parametric method were optimized, distribution volumes (V T ) obtained with Logan graphic analysis, BFM, and SA all correlated well with those derived using nonlinear regression at baseline and during therapy ( R 2 ≥ 0.94; intraclass correlation coefficient > 0.97). SA-based V T images were most robust to increased noise on a voxel-level (repeatability coefficient, 16% vs. >26%). Yet BFM generated the most accurate K 1 values ( R 2 = 0.94; intraclass correlation coefficient, 0.96). Parametric K 1 data showed a larger variability in general; however, no differences were found in robustness between methods (repeatability coefficient, 80

Association of the Single Nucleotide Polymorphisms in microRNAs 130b, 200b, and 495 with Ischemic Stroke Susceptibility and Post-Stroke Mortality.

Directory of Open Access Journals (Sweden)

Jinkwon Kim

Full Text Available The microRNA (miRNA is a small non-coding RNA molecule that modulates gene expression at the posttranscriptional level. Platelets have a crucial role in both hemostasis and thrombosis, a condition that can occlude a cerebral artery and cause ischemic stroke. miR-130b, miR-200b, and miR-495 are potential genetic modulators involving platelet production and activation. We hypothesized that single nucleotide polymorphisms (SNPs in these miRNAs might potentially contribute to the susceptibility to ischemic stroke and post-stroke mortality. This study included 523 ischemic stroke patients and 400 control subjects. We investigated the association of three miRNA SNPs (miR-130bT>C, miR-200bT>C, and miR-495A>C with ischemic stroke prevalence and post-stroke mortality. In the multivariate logistic regression, there was no statistically significant difference in the distribution of miR-130bT>C, miR-200bT>C, or miR-495A>C between the ischemic stroke and control groups. In the subgroup analysis based on ischemic stroke subtype, the miR-200b CC genotype was less frequently found in the large-artery atherosclerosis stroke subtype compared with controls (TT+CT vs CC; adjusted odds ratio for CC, 0.506; 95% confidence interval, 0.265-0.965. During a mean follow-up period of 4.80 ± 2.11 years after stroke onset, there were 106 all-cause deaths among the 523 stroke patients. Multivariate Cox regression analysis did not find a significant association between post-stroke mortality and three miRNA SNPs. Our findings suggest that the functional SNP of miR-200b might be responsible for the susceptibility to large-artery atherosclerotic stroke.

The multilevel four-stroke swap engine and its environment

Science.gov (United States)

Uzdin, Raam; Kosloff, Ronnie

2014-09-01

A multilevel four-stroke engine where the thermalization strokes are generated by unitary collisions with thermal bath particles is analyzed. Our model is solvable even when the engine operates far from thermal equilibrium and in the strong system-bath coupling. Necessary operation conditions for the heat machine to perform as an engine or a refrigerator are derived. We relate the work and efficiency of the device to local and non-local statistical properties of the baths (purity, index of coincidence, etc) and put upper bounds on these quantities. Finally, in the ultra-hot regime, we analytically optimize the work and find a striking similarity to results obtained for efficiency at maximal power of classical engines. The complete swap limit of our results holds for any four-stroke quantum Otto engine that is coupled to the baths for periods that are significantly longer than the thermal relaxation time.

The multilevel four-stroke swap engine and its environment

International Nuclear Information System (INIS)

Uzdin, Raam; Kosloff, Ronnie

2014-01-01

A multilevel four-stroke engine where the thermalization strokes are generated by unitary collisions with thermal bath particles is analyzed. Our model is solvable even when the engine operates far from thermal equilibrium and in the strong system–bath coupling. Necessary operation conditions for the heat machine to perform as an engine or a refrigerator are derived. We relate the work and efficiency of the device to local and non-local statistical properties of the baths (purity, index of coincidence, etc) and put upper bounds on these quantities. Finally, in the ultra-hot regime, we analytically optimize the work and find a striking similarity to results obtained for efficiency at maximal power of classical engines. The complete swap limit of our results holds for any four-stroke quantum Otto engine that is coupled to the baths for periods that are significantly longer than the thermal relaxation time. (paper)

Statistical downscaling of rainfall: a non-stationary and multi-resolution approach

Science.gov (United States)

Rashid, Md. Mamunur; Beecham, Simon; Chowdhury, Rezaul Kabir

2016-05-01

A novel downscaling technique is proposed in this study whereby the original rainfall and reanalysis variables are first decomposed by wavelet transforms and rainfall is modelled using the semi-parametric additive model formulation of Generalized Additive Model in Location, Scale and Shape (GAMLSS). The flexibility of the GAMLSS model makes it feasible as a framework for non-stationary modelling. Decomposition of a rainfall series into different components is useful to separate the scale-dependent properties of the rainfall as this varies both temporally and spatially. The study was conducted at the Onkaparinga river catchment in South Australia. The model was calibrated over the period 1960 to 1990 and validated over the period 1991 to 2010. The model reproduced the monthly variability and statistics of the observed rainfall well with Nash-Sutcliffe efficiency (NSE) values of 0.66 and 0.65 for the calibration and validation periods, respectively. It also reproduced well the seasonal rainfall over the calibration (NSE = 0.37) and validation (NSE = 0.69) periods for all seasons. The proposed model was better than the tradition modelling approach (application of GAMLSS to the original rainfall series without decomposition) at reproducing the time-frequency properties of the observed rainfall, and yet it still preserved the statistics produced by the traditional modelling approach. When downscaling models were developed with general circulation model (GCM) historical output datasets, the proposed wavelet-based downscaling model outperformed the traditional downscaling model in terms of reproducing monthly rainfall for both the calibration and validation periods.

Parametric roll resonance monitoring using signal-based detection

DEFF Research Database (Denmark)

Galeazzi, Roberto; Blanke, Mogens; Falkenberg, Thomas

2015-01-01

Extreme roll motion of ships can be caused by several phenomena, one of which is parametric roll resonance. Several incidents occurred unexpectedly around the millennium and caused vast fiscal losses on large container vessels. The phenomenon is now well understood and some consider parametric roll...... algorithms in real conditions, and to evaluate the frequency of parametric roll events on the selected vessels. Detection performance is scrutinised through the validation of the detected events using owners’ standard methods, and supported by available wave radar data. Further, a bivariate statistical...... analysis of the outcome of the signal-based detectors is performed to assess the real life false alarm probability. It is shown that detection robustness and very low false warning rates are obtained. The study concludes that small parametric roll events are occurring, and that the proposed signal...

Theoretical remarks on the statistics of three discriminants in Piety's automated signature analysis of PSD [Power Spectral Density] data

International Nuclear Information System (INIS)

Behringer, K.; Spiekerman, G.

1984-01-01

Piety (1977) proposed an automated signature analysis of power spectral density data. Eight statistical decision discriminants are introduced. For nearly all the discriminants, improved confidence statements can be made. The statistical characteristics of the last three discriminants, which are applications of non-parametric tests, are considered. (author)

Optimal parametric modelling of measured short waves

Digital Repository Service at National Institute of Oceanography (India)

Mandal, S.

the importance of selecting a suitable sampling interval for better estimates of parametric modelling and also for better statistical representation. Implementation of the above algorithms in a structural monitoring system has the potential advantage of storing...

Visuospatial asymmetry and non-spatial attention in subacute stroke patients with and without neglect

NARCIS (Netherlands)

Van Kessel, M.E.; Van Nes, I.J.W.; Brouwer, W.H.; Geurts, A.C.H.; Fasotti, L

Asymmetry in performance and an association with non-lateralized attention are often mentioned as two important aspects of the clinical manifestation of visuospatial neglect. Both these aspects were investigated in 21 left (LH) and 24 right hemisphere (RH) stroke patients and in 20 healthy subjects.

Choosing a particular oral anticoagulant and dose for stroke prevention in individual patients with non-valvular atrial fibrillation: part 1

NARCIS (Netherlands)

Diener, H.C.; Aisenberg, J.; Ansell, J.; Atar, D.; Breithardt, G.; Eikelboom, J.; Ezekowitz, M.D.; Granger, C.B.; Halperin, J.L.; Hohnloser, S.H.; Hylek, E.M.; Kirchhof, P.; Lane, D.A.; Verheugt, F.W.A.; Veltkamp, R.; Lip, G.Y.

2017-01-01

Patients with atrial fibrillation (AF) have a high risk of stroke and mortality, which can be considerably reduced by oral anticoagulants (OAC). Recently, four non-vitamin-K oral anticoagulants (NOACs) were compared with warfarin in large randomized trials for the prevention of stroke and systemic

Minority race and male sex as risk factors for non-beneficial gastrostomy tube placements after stroke.

Science.gov (United States)

Faigle, Roland; Carrese, Joseph A; Cooper, Lisa A; Urrutia, Victor C; Gottesman, Rebecca F

2018-01-01

Percutaneous endoscopic gastrostomy (PEG) tubes are widely used for enteral feeding after stroke; however, PEG tubes placed in patients in whom death is imminent are considered non-beneficial. We sought to determine whether placement of non-beneficial PEG tubes differs by race and sex. In this retrospective cohort study, inpatient admissions for stroke patients who underwent palliative/withdrawal of care, were discharged to hospice, or died during the hospitalization, were identified from the Nationwide Inpatient Sample between 2007 and 2011. Logistic regression was used to evaluate the association between race and sex with PEG placement. Of 36,109 stroke admissions who underwent palliative/withdrawal of care, were discharge to hospice, or experienced in-hospital death, a PEG was placed in 2,258 (6.3%). Among PEG recipients 41.1% were of a race other than white, while only 22.0% of patients without PEG were of a minority race (prace was associated with PEG placement compared to whites (OR 1.75, 95% CI 1.57-1.96), and men had 1.27 times higher odds of PEG compared to women (95% CI 1.16-1.40). Racial differences were most pronounced among women: ethnic/racial minority women had over 2-fold higher odds of a PEG compared to their white counterparts (OR 2.09, 95% CI 1.81-2.41), while male ethnic/racial minority patients had 1.44 increased odds of a PEG when compared to white men (95% CI 1.24-1.67, p-value for interaction race and male sex are risk factors for non-beneficial PEG tube placements after stroke.

Brain SPECT analysis using statistical parametric mapping in patients with transient global amnesia

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Kim, E. N.; Sohn, H. S.; Kim, S. H; Chung, S. K.; Yang, D. W. [College of Medicine, The Catholic Univ. of Korea, Seoul (Korea, Republic of)

2001-07-01

This study investigated alterations in regional cerebral blood flow (rCBF) in patients with transient global amnesia (TGA) using statistical parametric mapping 99 (SPM99). Noninvasive rCBF measurements using 99mTc-ethyl cysteinate dimer (ECD) SPECT were performed on 8 patients with TGA and 17 age matched controls. The relative rCBF maps in patients with TGA and controls were compared. In patients with TGA, significantly decreased rCBF was found along the left superior temporal extending to left parietal region of the brain and left thalamus. There were areas of increased rCBF in the right temporal, right frontal region and right thalamus. We could demonstrate decreased perfusion in left cerebral hemisphere and increased perfusion in right cerebral hemisphere in patients with TGA using SPM99. The reciprocal change of rCBF between right and left cerebral hemisphere in patients with TGA might suggest that imbalanced neuronal activity between the bilateral hemispheres may be important role in the pathogenesis of the TGA. For quantitative SPECT analysis in TGA patients, we recommend SPM99 rather than the ROI method because of its definitive advantages.

Brain SPECT analysis using statistical parametric mapping in patients with transient global amnesia

International Nuclear Information System (INIS)

Kim, E. N.; Sohn, H. S.; Kim, S. H; Chung, S. K.; Yang, D. W.

2001-01-01

This study investigated alterations in regional cerebral blood flow (rCBF) in patients with transient global amnesia (TGA) using statistical parametric mapping 99 (SPM99). Noninvasive rCBF measurements using 99mTc-ethyl cysteinate dimer (ECD) SPECT were performed on 8 patients with TGA and 17 age matched controls. The relative rCBF maps in patients with TGA and controls were compared. In patients with TGA, significantly decreased rCBF was found along the left superior temporal extending to left parietal region of the brain and left thalamus. There were areas of increased rCBF in the right temporal, right frontal region and right thalamus. We could demonstrate decreased perfusion in left cerebral hemisphere and increased perfusion in right cerebral hemisphere in patients with TGA using SPM99. The reciprocal change of rCBF between right and left cerebral hemisphere in patients with TGA might suggest that imbalanced neuronal activity between the bilateral hemispheres may be important role in the pathogenesis of the TGA. For quantitative SPECT analysis in TGA patients, we recommend SPM99 rather than the ROI method because of its definitive advantages

[Embolic stroke by thrombotic non bacterial endocarditis in an Antiphospholipid Syndrome patient].

Science.gov (United States)

Graña, D; Ponce, C; Goñi, M; Danza, A

2016-01-01

The antiphospholipid syndrome (APS) is an acquired thrombophilia, considered a systemic autoimmune disorder. We report a patient with APS who presented multiple cerebral infarcts (stroke) as a complication of a thrombotic non bacterial endocarditis. We review the literature focused on the physiological mechanism that produce this disease and its complications. Clinical features and their prognostic value and the different therapeutic options were also studied.

Therapeutic Potential of Non-Psychotropic Cannabidiol in Ischemic Stroke

Directory of Open Access Journals (Sweden)

Michihiro Fujiwara

2010-07-01

Full Text Available Cannabis contains the psychoactive component delta9-tetrahydrocannabinol (delta9-THC, and the non-psychoactive components cannabidiol (CBD, cannabinol, and cannabigerol. It is well-known that delta9-THC and other cannabinoid CB1 receptor agonists are neuroprotective during global and focal ischemic injury. Additionally, delta9-THC also mediates psychological effects through the activation of the CB1 receptor in the central nervous system. In addition to the CB1 receptor agonists, cannabis also contains therapeutically active components which are CB1 receptor independent. Of the CB1 receptor-independent cannabis, the most important is CBD. In the past five years, an increasing number of publications have focused on the discovery of the anti-inflammatory, anti-oxidant, and neuroprotective effects of CBD. In particular, CBD exerts positive pharmacological effects in ischemic stroke and other chronic diseases, including Parkinson’s disease, Alzheimer’s disease, and rheumatoid arthritis. The cerebroprotective action of CBD is CB1 receptor-independent, long-lasting, and has potent anti-oxidant activity. Importantly, CBD use does not lead to tolerance. In this review, we will discuss the therapeutic possibility of CBD as a cerebroprotective agent, highlighting recent pharmacological advances, novel mechanisms, and therapeutic time window of CBD in ischemic stroke.

DrawFromDrawings: 2D Drawing Assistance via Stroke Interpolation with a Sketch Database.

Science.gov (United States)

Matsui, Yusuke; Shiratori, Takaaki; Aizawa, Kiyoharu

2017-07-01

We present DrawFromDrawings, an interactive drawing system that provides users with visual feedback for assistance in 2D drawing using a database of sketch images. Following the traditional imitation and emulation training from art education, DrawFromDrawings enables users to retrieve and refer to a sketch image stored in a database and provides them with various novel strokes as suggestive or deformation feedback. Given regions of interest (ROIs) in the user and reference sketches, DrawFromDrawings detects as-long-as-possible (ALAP) stroke segments and the correspondences between user and reference sketches that are the key to computing seamless interpolations. The stroke-level interpolations are parametrized with the user strokes, the reference strokes, and new strokes created by warping the reference strokes based on the user and reference ROI shapes, and the user study indicated that the interpolation could produce various reasonable strokes varying in shapes and complexity. DrawFromDrawings allows users to either replace their strokes with interpolated strokes (deformation feedback) or overlays interpolated strokes onto their strokes (suggestive feedback). The other user studies on the feedback modes indicated that the suggestive feedback enabled drawers to develop and render their ideas using their own stroke style, whereas the deformation feedback enabled them to finish the sketch composition quickly.

[The research protocol VI: How to choose the appropriate statistical test. Inferential statistics].

Science.gov (United States)

Flores-Ruiz, Eric; Miranda-Novales, María Guadalupe; Villasís-Keever, Miguel Ángel

2017-01-01

The statistical analysis can be divided in two main components: descriptive analysis and inferential analysis. An inference is to elaborate conclusions from the tests performed with the data obtained from a sample of a population. Statistical tests are used in order to establish the probability that a conclusion obtained from a sample is applicable to the population from which it was obtained. However, choosing the appropriate statistical test in general poses a challenge for novice researchers. To choose the statistical test it is necessary to take into account three aspects: the research design, the number of measurements and the scale of measurement of the variables. Statistical tests are divided into two sets, parametric and nonparametric. Parametric tests can only be used if the data show a normal distribution. Choosing the right statistical test will make it easier for readers to understand and apply the results.

The research protocol VI: How to choose the appropriate statistical test. Inferential statistics

Directory of Open Access Journals (Sweden)

Eric Flores-Ruiz

2017-10-01

Full Text Available The statistical analysis can be divided in two main components: descriptive analysis and inferential analysis. An inference is to elaborate conclusions from the tests performed with the data obtained from a sample of a population. Statistical tests are used in order to establish the probability that a conclusion obtained from a sample is applicable to the population from which it was obtained. However, choosing the appropriate statistical test in general poses a challenge for novice researchers. To choose the statistical test it is necessary to take into account three aspects: the research design, the number of measurements and the scale of measurement of the variables. Statistical tests are divided into two sets, parametric and nonparametric. Parametric tests can only be used if the data show a normal distribution. Choosing the right statistical test will make it easier for readers to understand and apply the results.

Stroke risk perception among participants of a stroke awareness campaign

Science.gov (United States)

Kraywinkel, Klaus; Heidrich, Jan; Heuschmann, Peter U; Wagner, Markus; Berger, Klaus

2007-01-01

Background Subjective risk factor perception is an important component of the motivation to change unhealthy life styles. While prior studies assessed cardiovascular risk factor knowledge, little is known about determinants of the individual perception of stroke risk. Methods Survey by mailed questionnaire among 1483 participants of a prior public stroke campaign in Germany. Participants had been informed about their individual stroke risk based on the Framingham stroke risk score. Stroke risk factor knowledge, perception of lifetime stroke risk and risk factor status were included in the questionnaire, and the determinants of good risk factor knowledge and high stroke risk perception were identified using logistic regression models. Results Overall stroke risk factor knowledge was good with 67–96% of the participants recognizing established risk factors. The two exceptions were diabetes (recognized by 49%) and myocardial infarction (57%). Knowledge of a specific factor was superior among those affected by it. 13% of all participants considered themselves of having a high stroke risk, 55% indicated a moderate risk. All major risk factors contributed significantly to the perception of being at high stroke risk, but the effects of age, sex and education were non-significant. Poor self-rated health was additionally associated with high individual stroke risk perception. Conclusion Stroke risk factor knowledge was high in this study. The self perception of an increased stroke risk was associated with established risk factors as well as low perception of general health. PMID:17371603

Hospital heterogeneity: what drives the quality of health care.

Science.gov (United States)

Ali, Manhal; Salehnejad, Reza; Mansur, Mohaimen

2018-04-01

A major feature of health care systems is substantial variation in health care quality across hospitals. The quality of stroke care widely varies across NHS hospitals. We investigate factors that may explain variations in health care quality using measures of quality of stroke care. We combine NHS trust data from the National Sentinel Stroke Audit with other data sets from the Office for National Statistics, NHS and census data to capture hospitals' human and physical assets and organisational characteristics. We employ a class of non-parametric methods to explore the complex structure of the data and a set of correlated random effects models to identify key determinants of the quality of stroke care. The organisational quality of the process of stroke care appears as a fundamental driver of clinical quality of stroke care. There are rich complementarities amongst drivers of quality of stroke care. The findings strengthen previous research on managerial and organisational determinants of health care quality.

Peripheral glucose levels and cognitive outcome after ischemic stroke : Results from the Munich Stroke Cohort

NARCIS (Netherlands)

Zietemann, Vera; Wollenweber, Frank Arne; Bayer-Karpinska, Anna; Biessels, Geert Jan; Dichgans, Martin

2016-01-01

Introduction: The relationship between glucose metabolism and stroke outcome is likely to be complex. We examined whether there is a linear or non-linear relationship between glucose measures in the acute phase of stroke and post-stroke cognition, and whether altered glucose metabolism at different

International Conference on Robust Statistics 2015

CERN Document Server

Basu, Ayanendranath; Filzmoser, Peter; Mukherjee, Diganta

2016-01-01

This book offers a collection of recent contributions and emerging ideas in the areas of robust statistics presented at the International Conference on Robust Statistics 2015 (ICORS 2015) held in Kolkata during 12–16 January, 2015. The book explores the applicability of robust methods in other non-traditional areas which includes the use of new techniques such as skew and mixture of skew distributions, scaled Bregman divergences, and multilevel functional data methods; application areas being circular data models and prediction of mortality and life expectancy. The contributions are of both theoretical as well as applied in nature. Robust statistics is a relatively young branch of statistical sciences that is rapidly emerging as the bedrock of statistical analysis in the 21st century due to its flexible nature and wide scope. Robust statistics supports the application of parametric and other inference techniques over a broader domain than the strictly interpreted model scenarios employed in classical statis...

Parametric resonance in the early Universe—a fitting analysis

Energy Technology Data Exchange (ETDEWEB)

Figueroa, Daniel G. [Theoretical Physics Department, CERN, Geneva (Switzerland); Torrentí, Francisco, E-mail: daniel.figueroa@cern.ch, E-mail: f.torrenti@csic.es [Instituto de Física Teórica IFT-UAM/CSIC, Universidad Autónoma de Madrid, Cantoblanco 28049, Madrid (Spain)

2017-02-01

Particle production via parametric resonance in the early Universe, is a non-perturbative, non-linear and out-of-equilibrium phenomenon. Although it is a well studied topic, whenever a new scenario exhibits parametric resonance, a full re-analysis is normally required. To avoid this tedious task, many works present often only a simplified linear treatment of the problem. In order to surpass this circumstance in the future, we provide a fitting analysis of parametric resonance through all its relevant stages: initial linear growth, non-linear evolution, and relaxation towards equilibrium. Using lattice simulations in an expanding grid in 3+1 dimensions, we parametrize the dynamics' outcome scanning over the relevant ingredients: role of the oscillatory field, particle coupling strength, initial conditions, and background expansion rate. We emphasize the inaccuracy of the linear calculation of the decay time of the oscillatory field, and propose a more appropriate definition of this scale based on the subsequent non-linear dynamics. We provide simple fits to the relevant time scales and particle energy fractions at each stage. Our fits can be applied to post-inflationary preheating scenarios, where the oscillatory field is the inflaton, or to spectator-field scenarios, where the oscillatory field can be e.g. a curvaton, or the Standard Model Higgs.

Parametric resonance in the early Universe—a fitting analysis

International Nuclear Information System (INIS)

Figueroa, Daniel G.; Torrentí, Francisco

2017-01-01

Particle production via parametric resonance in the early Universe, is a non-perturbative, non-linear and out-of-equilibrium phenomenon. Although it is a well studied topic, whenever a new scenario exhibits parametric resonance, a full re-analysis is normally required. To avoid this tedious task, many works present often only a simplified linear treatment of the problem. In order to surpass this circumstance in the future, we provide a fitting analysis of parametric resonance through all its relevant stages: initial linear growth, non-linear evolution, and relaxation towards equilibrium. Using lattice simulations in an expanding grid in 3+1 dimensions, we parametrize the dynamics' outcome scanning over the relevant ingredients: role of the oscillatory field, particle coupling strength, initial conditions, and background expansion rate. We emphasize the inaccuracy of the linear calculation of the decay time of the oscillatory field, and propose a more appropriate definition of this scale based on the subsequent non-linear dynamics. We provide simple fits to the relevant time scales and particle energy fractions at each stage. Our fits can be applied to post-inflationary preheating scenarios, where the oscillatory field is the inflaton, or to spectator-field scenarios, where the oscillatory field can be e.g. a curvaton, or the Standard Model Higgs.

Predictors for Stroke and Death in Non-Anticoagulated Asian Patients with Atrial Fibrillation: The Fushimi AF Registry.

Science.gov (United States)

Hamatani, Yasuhiro; Yamashita, Yugo; Esato, Masahiro; Chun, Yeong-Hwa; Tsuji, Hikari; Wada, Hiromichi; Hasegawa, Koji; Abe, Mitsuru; Lip, Gregory Y H; Akao, Masaharu

2015-01-01

Atrial fibrillation (AF) increases the risk of stroke and death. Data on the predictors for stroke and death in 'real-world' AF patients are limited, especially from large prospective Asian cohorts. The Fushimi AF Registry is a community-based prospective survey designed to enroll all AF patients who visited the participating medical institutions in Fushimi-ku, Kyoto, Japan. Follow-up data were available for 3,304 patients (median follow-up period 741 days). We explored the predictors for 'death, stroke, and systemic embolism (SE)' during follow-up in 1,541 patients not receiving oral anticoagulants (OAC) at baseline. The mean age was 73.1 ± 12.5 years, and 673 (44%) patients were female. The mean CHADS2 and CHA2DS2-VASc scores were 1.76 and 3.08, respectively. Cumulative events were as follows: stroke/SE in 61 (4%) and death in 230 (15%), respectively. On multivariate analysis, advanced age (hazard ratio (HR): 1.68, 95% confidence interval (CI): 1.24-2.29), underweight (body mass index death/stroke/SE. Cumulative numbers of these 6 risk predictors could stratify the incidence of death/stroke/SE in patients without OAC, as well as those with OAC in our registry. Advanced age, underweight, previous stroke/SE/transient ischemic attack, heart failure, chronic kidney disease, and anemia were independently associated with the risk of death/stroke/SE in non-anticoagulated Japanese AF patients.

Aortic Aneurysm Statistics

Science.gov (United States)

... Summary Coverdell Program 2012-2015 State Summaries Data & Statistics Fact Sheets Heart Disease and Stroke Fact Sheets ... Roadmap for State Planning Other Data Resources Other Statistic Resources Grantee Information Cross-Program Information Online Tools ...

Airplane stroke syndrome.

Science.gov (United States)

Humaidan, Hani; Yassi, Nawaf; Weir, Louise; Davis, Stephen M; Meretoja, Atte

2016-07-01

Only 37 cases of stroke during or soon after long-haul flights have been published to our knowledge. In this retrospective observational study, we searched the Royal Melbourne Hospital prospective stroke database and all discharge summaries from 1 September 2003 to 30 September 2014 for flight-related strokes, defined as patients presenting with stroke within 14days of air travel. We hypothesised that a patent foramen ovale (PFO) is an important, but not the only mechanism, of flight-related stroke. We describe the patient, stroke, and flight characteristics. Over the study period, 131 million passengers arrived at Melbourne airport. Our centre admitted 5727 stroke patients, of whom 42 (0.73%) had flight-related strokes. Flight-related stroke patients were younger (median age 65 versus 73, p<0.001), had similar stroke severity, and received intravenous thrombolysis more often than non-flight-related stroke patients. Seven patients had flight-related intracerebral haemorrhage. The aetiology of the ischaemic strokes was cardioembolic in 14/35 (40%), including seven patients with confirmed PFO, one with atrial septal defect, four with atrial fibrillation, one with endocarditis, and one with aortic arch atheroma. Paradoxical embolism was confirmed in six patients. Stroke related to air travel is a rare occurrence, less than one in a million. Although 20% of patients had a PFO, distribution of stroke aetiologies was diverse and was not limited to PFO and paradoxical embolism. Copyright © 2016 Elsevier Ltd. All rights reserved.

Nuclear modification factor using Tsallis non-extensive statistics

Energy Technology Data Exchange (ETDEWEB)

Tripathy, Sushanta; Garg, Prakhar; Kumar, Prateek; Sahoo, Raghunath [Indian Institute of Technology Indore, Discipline of Physics, School of Basic Sciences, Simrol (India); Bhattacharyya, Trambak; Cleymans, Jean [University of Cape Town, UCT-CERN Research Centre and Department of Physics, Rondebosch (South Africa)

2016-09-15

The nuclear modification factor is derived using Tsallis non-extensive statistics in relaxation time approximation. The variation of the nuclear modification factor with transverse momentum for different values of the non-extensive parameter, q, is also observed. The experimental data from RHIC and LHC are analysed in the framework of Tsallis non-extensive statistics in a relaxation time approximation. It is shown that the proposed approach explains the R{sub AA} of all particles over a wide range of transverse momentum but does not seem to describe the rise in R{sub AA} at very high transverse momenta. (orig.)

Plasma lipoprotein(a levels: a comparison between diabetic and non-diabetic patients with acute ischemic stroke

Directory of Open Access Journals (Sweden)

Holanda Maurus Marques de Almeida

2004-01-01

Full Text Available OBJECTIVE: The aim of this study was to evaluate lipoprotein(a (Lp(a, total cholesterol, high density lipoprotein cholesterol (HDL, low density lipoprotein cholesterol (LDL, very low density lipoprotein cholesterol (VLDL , triglycerides , apolipoprotein A (apo A and B100 (apo B100, uric acid, glycaemic and insulin plasmatic concentrations in patients affected by acute stroke. In this group of patients, we have compared the variables between type 2 diabetic patients and non-diabetic patients. METHOD: We evaluate a total of 34 non-diabetic patients (22 males and 12 females; mean age 66.71 ± 10.83 years and a group of 26 type 2 diabetic patients (15 males and 11 females; mean age 66.35 ± 9.92 years in a cross-sectional study. RESULTS: Mean Lp(a concentration did not significantly differ between type 2 diabetic patients and non-diabetic subjects (29.49 ± 23.09 vs 44.81 ± 44.34 mg/dl. The distribution of Lp(alevels was highly skewed towards the higher levels in both groups, being over 30 mg/dl in 50%. Lp(a concentration was positively correlated with abdominal adiposity, using waist-hip ratio(WHR(p< 0.05. No association was found between Lp(a and others risk factors like sex, age, other lipidic parameters and the presence of stroke. CONCLUSIONS: Our results showed that there were no significant differences between diabetic and non-diabetic patients' serum Lp(a levels, which indicates that elevated Lp(a levels were associated with ischemic stroke, irrespective of the presence of type 2 diabetes mellitus (type 2 DM.

Knowledge of stroke risk factors amongst black diabetic, hypertensive and stroke patients

Directory of Open Access Journals (Sweden)

G. Bogoshi

2003-01-01

knowledge of black patients diagnosed with hypertension, diabetes and stroke about the risk factors for stroke.  Four groups made up of 33 subjects (hypertensive, diabetic, stroke and control group were interviewed using open-ended questions and a structured questionnaire. Qualitative coding, frequencies and proportions were used to determine their knowledge.  Groups were compared with respect to percentage knowledge using the chi-square statistic at a 0.05 level of significance.  Stress was mentioned as the most important risk factor in all groups.  Although identification of stroke risk factors was  inadequate, the diabetic group was found to be significantly better in  identifying some of the risk factors (salt - p =0,05; sugar - p = 0,001; fat - p = 0,004; moderate smoking - p = 0,05; weight - p = 0,002

Disentangling the contribution of the paretic and non-paretic leg to balance control in stroke.

NARCIS (Netherlands)

van Asseldonk, Edwin H.F.; Buurke, Jaap; Bloem, Bastiaan R.; van der Helm, F.C.T.; Renzenbrink, Gerbert J.; van der Kooij, Herman; Nene, A.V.

2005-01-01

During stroke recovery, restoration of the paretic ankle and compensation in the non-paretic ankle may contribute to improved balance maintenance. We examine a new approach to disentangle these recovery mechanisms by objectively quantifying the contribution of each ankle to balance maintenance.

Old and new oral anticoagulants for secondary stroke prevention in atrial fibrillation

Directory of Open Access Journals (Sweden)

Tommaso Sacquegna

2015-12-01

Full Text Available Vitamin K antagonists, such as warfarin, used in oral anticoagulation therapy currently represent the standard drugs for the primary and secondary prevention of stroke in non-valvular atrial fibrillation (AF, with a relative risk reduction close to 70%. Newer oral anticoagulants, such as direct thrombin inhibitors (i.e., dabigatran and direct factor Xa inhibitors (i.e., apixaban and rivaroxaban have been recently compared with warfarin in large randomized trials for stroke prevention in AF. The new oral anticoagulants showed, compared with warfarin, no statistically significant difference in the rate of stroke or systemic embolism in secondary prevention (patients with previous transient ischemic attack or stroke subgroups. With regard to safety, the risk of intracranial bleeding was reduced with new anticoagulants compared with warfarin. Indirect treatment comparisons of clinical trials on secondary prevention cohorts showed no significant difference in efficacy among apixaban, rivaroxaban, and dabigatran; but dabigatran 110 mg was associated with less intracranial bleedings than rivaroxaban.

The association between race/ethnicity and the prevalence of stroke among United States adults in 2015: a secondary analysis study using Behavioural Risk Factor Surveillance System (BRFSS).

Science.gov (United States)

Aldayel, Abdulrahman Yousef; Alharbi, Muteb Mousa; Shadid, Asem Mustafa; Zevallos, Juan Carlos

2017-12-01

Worldwide, stroke is considered the second leading cause of death, accounting for 11.8% of all deaths in 2013. In the Unites States (US), approximately 795,000 people have a stroke every year. Stroke has many different risk factors that vary by race/ethnicity. There is limited contemporary published literature about the prevalence of stroke among racial/ethnic groups in the US adult population. This study aimed to determine the association between race/ethnicity and the prevalence of stroke among US adults in 2015. This study was an observational, non-concurrent prospective of the Behavioural Risk Factor Surveillance System (BRFSS) in 2015 to assess the association between race/ethnicity and the prevalence of stroke. The final study sample was 432,814 US adults ≥ 18 years old. Variables were excluded from the model if there were missing, refused, or did not know responses to the variables of interest. A binary logistic regression analysis was used to obtain odds ratios (OR) and 95% confidence intervals (CI) for the association between race/ethnicity and stroke. The Chi-square test was used to study bivariate associations between categorical variables. The collinearity was assessed. A p-value of <0.05 was considered statistically significant. Statistical analysis was completed using STATA version 14 (Stata Corp, College Station, TX). The highest proportion of participants (43%) were ≥ 44 years old with a balanced distribution of males and females. The highest proportion of stroke was found among Hispanics (4.2%) and non-Hispanic Blacks (4.1%) as compared to 3.2% among non-Hispanic Whites (p<0.001). Furthermore, Hispanics and Blacks were significantly more likely to develop stroke (OR=1.57, 95% CI=1.28-1.91; and OR=1.30, 95% CI=1.16-1.45, respectively) after adjusting for confounding variables. Hispanics and Blacks had a higher prevalence of stroke in comparison with non-Hispanic Whites. Further studies are needed to verify these findings and to determine which

Statistical Analysis for High-Dimensional Data : The Abel Symposium 2014

CERN Document Server

Bühlmann, Peter; Glad, Ingrid; Langaas, Mette; Richardson, Sylvia; Vannucci, Marina

2016-01-01

This book features research contributions from The Abel Symposium on Statistical Analysis for High Dimensional Data, held in Nyvågar, Lofoten, Norway, in May 2014. The focus of the symposium was on statistical and machine learning methodologies specifically developed for inference in “big data” situations, with particular reference to genomic applications. The contributors, who are among the most prominent researchers on the theory of statistics for high dimensional inference, present new theories and methods, as well as challenging applications and computational solutions. Specific themes include, among others, variable selection and screening, penalised regression, sparsity, thresholding, low dimensional structures, computational challenges, non-convex situations, learning graphical models, sparse covariance and precision matrices, semi- and non-parametric formulations, multiple testing, classification, factor models, clustering, and preselection. Highlighting cutting-edge research and casting light on...

Discrete non-parametric kernel estimation for global sensitivity analysis

International Nuclear Information System (INIS)

Senga Kiessé, Tristan; Ventura, Anne

2016-01-01

This work investigates the discrete kernel approach for evaluating the contribution of the variance of discrete input variables to the variance of model output, via analysis of variance (ANOVA) decomposition. Until recently only the continuous kernel approach has been applied as a metamodeling approach within sensitivity analysis framework, for both discrete and continuous input variables. Now the discrete kernel estimation is known to be suitable for smoothing discrete functions. We present a discrete non-parametric kernel estimator of ANOVA decomposition of a given model. An estimator of sensitivity indices is also presented with its asymtotic convergence rate. Some simulations on a test function analysis and a real case study from agricultural have shown that the discrete kernel approach outperforms the continuous kernel one for evaluating the contribution of moderate or most influential discrete parameters to the model output. - Highlights: • We study a discrete kernel estimation for sensitivity analysis of a model. • A discrete kernel estimator of ANOVA decomposition of the model is presented. • Sensitivity indices are calculated for discrete input parameters. • An estimator of sensitivity indices is also presented with its convergence rate. • An application is realized for improving the reliability of environmental models.

Effect of pre-stroke use of ACE inhibitors on ischemic stroke severity

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Caplan Louis

2005-06-01

Full Text Available Abstract Background Recent trials suggest that angiotensin-converting enzyme inhibitors (ACEI are effective in prevention of ischemic stroke, as measured by reduced stroke incidence. We aimed to compare stroke severity between stroke patients who were taking ACEI before their stroke onset and those who were not, to examine the effects of pretreatment with ACEI on ischemic stroke severity. Methods We retrospectively studied 126 consecutive patients presenting within 24 hours of ischemic stroke onset, as confirmed by diffusion-weighted magnetic resonance imaging (DWI. We calculated the NIHSS score at presentation, as the primary measure of clinical stroke severity, and categorized stroke severity as mild (NIHSS [less than or equal to] 7, moderate (NIHSS 8–13 or severe (NIHSS [greater than or equal to] 14. We analyzed demographic data, risk-factor profile, blood pressure (BP and medications on admissions, and determined stroke mechanism according to TOAST criteria. We also measured the volumes of admission diffusion- and perfusion-weighted (DWI /PWI magnetic resonance imaging lesions, as a secondary measure of ischemic tissue volume. We compared these variables among patients on ACEI and those who were not. Results Thirty- three patients (26% were on ACE-inhibitors. The overall median baseline NIHSS score was 5.5 (range 2–21 among ACEI-treated patients vs. 9 (range 1–36 in non-ACEI patients (p = 0.036. Patients on ACEI prior to their stroke had more mild and less severe strokes, and smaller DWI and PWI lesion volumes compared to non-ACEI treated patients. However, none of these differences were significant. Predictably, a higher percentage of patients on ACEI had a history of heart failure (p = 0.03. Age, time-to-imaging or neurological evaluation, risk-factor profile, concomitant therapy with lipid lowering, other antihypertensives or antithrombotic agents, or admission BP were comparable between the two groups. Conclusion Our results

Measurement of the CKM matrix element vertical stroke Vts vertical stroke 2

International Nuclear Information System (INIS)

Unverdorben, Christopher Gerhard

2015-03-01

This is the first direct measurement of the CKM matrix element vertical stroke V ts vertical stroke, using data collected by the ATLAS detector in 2012 at √(s)= 8 TeV pp-collisions with a total integrated luminosity of 20.3 fb -1 . The analysis is based on 112 171 reconstructed t anti t candidate events in the lepton+jets channel, having a purity of 90.0 %. 183 t anti t→W + W - b anti s decays are expected (charge conjugation implied), which are available for the extraction of the CKM matrix element vertical stroke V ts vertical stroke 2 . To identify these rare decays, several observables are examined, such as the properties of jets, tracks and of b-quark identification algorithms. Furthermore, the s-quark hadrons K 0 s are considered, reconstructed by a kinematic fit. The best observables are combined in a multivariate analysis, called ''boosted decision trees''. The responses from Monte Carlo simulations are used as templates for a fit to data events yielding a significance value of 0.7σ for t→s+W decays. An upper limit of vertical stroke V ts vertical stroke 2 <1.74 % at 95 % confidence level is set, including all systematic and statistical uncertainties. So this analysis, using a direct measurement of the CKM matrix element vertical stroke V ts vertical stroke 2 , provides the best direct limit on vertical stroke V ts vertical stroke 2 up to now.

Burden of stroke in Bangladesh.

Science.gov (United States)

Islam, Md Nazmul; Moniruzzaman, Mohammed; Khalil, Md Ibrahim; Basri, Rehana; Alam, Mohammad Khursheed; Loo, Keat Wei; Gan, Siew Hua

2013-04-01

Stroke is the third leading cause of death in Bangladesh. The World Health Organization ranks Bangladesh's mortality rate due to stroke as number 84 in the world. The reported prevalence of stroke in Bangladesh is 0.3%, although no data on stroke incidence have been recorded. Hospital-based studies conducted in past decades have indicated that hypertension is the main cause of ischaemic and haemorrhagic stroke in Bangladesh. The high number of disability-adjusted life-years lost due to stroke (485 per 10,000 people) show that stroke severely impacts Bangladesh's economy. Although two non-governmental organizations, BRAC and the Centre for the Rehabilitation of the Paralysed, are actively involved in primary stroke prevention strategies, the Bangladeshi government needs to emphasize healthcare development to cope with the increasing population density and to reduce stroke occurrence. © 2012 The Authors. International Journal of Stroke © 2012 World Stroke Organization.

Coherent states for oscillators of non-conventional statistics

International Nuclear Information System (INIS)

Dao Vong Duc; Nguyen Ba An

1998-12-01

In this work we consider systematically the concept of coherent states for oscillators of non-conventional statistics - parabose oscillator, infinite statistics oscillator and generalised q-deformed oscillator. The expressions for the quadrature variances and particle number distribution are derived and displayed graphically. The obtained results show drastic changes when going from one statistics to another. (author)

Parametric Portfolio Selection: Evaluating and Comparing to Markowitz Portfolios

Directory of Open Access Journals (Sweden)

Marcelo C. Medeiros

2014-10-01

Full Text Available In this paper we exploit the parametric portfolio optimization in the Brazilian market. Our data consists of monthly returns of 306 Brazilian stocks in the period between 2001 and 2013. We tested the model both in and out of sample and compared the results with the value and equal weighted portfolios and with a Markowitz based portfolio. We performed statistical inference in the parametric optimization using bootstrap techniques in order to build the parameters empirical distributions. Our results showed that the parametric optimization is a very efficient technique out of sample. It consistently showed superior results when compared with the VW, EW and Markowitz portfolios even when transaction costs were included. Finally, we consider the parametric approach to be very flexible to the inclusion of constraints in weights, transaction costs and listing and delisting of stocks.

Implementation of a stroke registry is associated with an improvement in stroke performance measures in a tertiary hospital in Mexico.

Science.gov (United States)

Herrera, Ana Lucia; Góngora-Rivera, Fernando; Muruet, Walter; Villarreal, Héctor Jorge; Gutiérrez-Herrera, Mildred; Huerta, Lena; Carrasco, Diana; Soto-García, Anally; Espinosa-Ortega, Meztli

2015-04-01

Stroke registries provide a simple way for improving patient care, and its use has been associated with a better adherence to the published guidelines. Few Latin American countries had established stroke registries. Our study is the first in Mexico to report the effects of implementing a stroke registry. To determine if the implementation of a systematized registry is associated with an improved adherence to the performance measures. We compared prospective data (August 2008-November 2010) against historical controls (February 2005-July 2008). Our stroke registry (i-Registro Neurovascular) consists of a standardized clinical form that includes demographic and clinical variables (risk factors, medications, neuroimaging, etiology, acute and outpatient treatments, and neurologic scores [National Institutes of Health Stroke Scale and modified Rankin Scale]). We evaluated 9 performance measures suggested by the American Heart Association and the Joint Commission. We analyzed the data from 574 patients, 260 from the prospective phase and 314 from historical controls. No significant statistical differences in demographic characteristics or stroke risk factors were found. The implementation of the stroke registry was associated with a statistically significant (P cost and readily achievable and a viable option for encouraging an increased report of guidelines adherence of other hospitals in Latin America. Copyright © 2015 National Stroke Association. Published by Elsevier Inc. All rights reserved.

Non-extensive statistical effects in nuclear many-body problems

International Nuclear Information System (INIS)

Lavagno, A.; Quarati, P.

2007-01-01

Density and temperature conditions in many stellar core and in the first stage of relativistic heavy-ion collisions imply the presence of non-ideal plasma effects with memory and long-range interactions between particles. Recent progress in statistical mechanics indicates that Tsallis non-extensive thermostatistics could be the natural generalization of the standard classical and quantum statistics, when memory effects and long range forces are not negligible. In this framework, we show that in weakly non-ideal plasma non-extensive effects should be taken into account to derive the equilibrium distribution functions, the quantum fluctuations and correlations between the particles. The strong influence of these effects is discussed in the context of the solar plasma physics and in the high-energy nuclear-nuclear collision experiments. Although the deviation from Boltzmann-Gibbs statistics, in both cases, is very small, the stellar plasma and the hadronic gas are strongly influenced by the non-extensive feature and the discrepancies between experimental data and theoretical previsions are sensibly reduced. (authors)

Single photon emission computed tomography and statistical parametric mapping analysis in cirrhotic patients with and without minimal hepatic encephalopathy

International Nuclear Information System (INIS)

Nakagawa, Yuri; Matsumura, Kaname; Iwasa, Motoh; Kaito, Masahiko; Adachi, Yukihiko; Takeda, Kan

2004-01-01

The early diagnosis and treatment of cognitive impairment in cirrhotic patients is needed to improve the patients' daily living. In this study, alterations of regional cerebral blood flow (rCBF) were evaluated in cirrhotic patients using statistical parametric mapping (SPM). The relationships between rCBF and neuropsychological test, severity of disease and biochemical data were also assessed. 99m Tc-ethyl cysteinate dimer single photon emission computed tomography was performed in 20 patients with non-alcoholic liver cirrhosis without overt hepatic encephalopathy (HE) and in 20 age-matched healthy subjects. Neuropsychological tests were performed in 16 patients; of these 7 had minimal HE. Regional CBF images were also analyzed in these groups using SPM. On SPM analysis, cirrhotic patients showed regions of significant hypoperfusion in the superior and middle frontal gyri, and inferior parietal lobules compared with the control group. These areas included parts of the premotor and parietal associated areas of the cortex. Among the cirrhotic patients, those with minimal HE had regions of significant hypoperfusion in the cingulate gyri bilaterally as compared with those without minimal HE. Abnormal function in the above regions may account for the relatively selective neuropsychological deficits in the cognitive status of patients with cirrhosis. These findings may be important in the identification and management of cirrhotic patients with minimal HE. (author)

Predictive capacity of a non-radioisotopic local lymph node assay using flow cytometry, LLNA:BrdU-FCM: Comparison of a cutoff approach and inferential statistics.

Science.gov (United States)

Kim, Da-Eun; Yang, Hyeri; Jang, Won-Hee; Jung, Kyoung-Mi; Park, Miyoung; Choi, Jin Kyu; Jung, Mi-Sook; Jeon, Eun-Young; Heo, Yong; Yeo, Kyung-Wook; Jo, Ji-Hoon; Park, Jung Eun; Sohn, Soo Jung; Kim, Tae Sung; Ahn, Il Young; Jeong, Tae-Cheon; Lim, Kyung-Min; Bae, SeungJin

2016-01-01

In order for a novel test method to be applied for regulatory purposes, its reliability and relevance, i.e., reproducibility and predictive capacity, must be demonstrated. Here, we examine the predictive capacity of a novel non-radioisotopic local lymph node assay, LLNA:BrdU-FCM (5-bromo-2'-deoxyuridine-flow cytometry), with a cutoff approach and inferential statistics as a prediction model. 22 reference substances in OECD TG429 were tested with a concurrent positive control, hexylcinnamaldehyde 25%(PC), and the stimulation index (SI) representing the fold increase in lymph node cells over the vehicle control was obtained. The optimal cutoff SI (2.7≤cutoff <3.5), with respect to predictive capacity, was obtained by a receiver operating characteristic curve, which produced 90.9% accuracy for the 22 substances. To address the inter-test variability in responsiveness, SI values standardized with PC were employed to obtain the optimal percentage cutoff (42.6≤cutoff <57.3% of PC), which produced 86.4% accuracy. A test substance may be diagnosed as a sensitizer if a statistically significant increase in SI is elicited. The parametric one-sided t-test and non-parametric Wilcoxon rank-sum test produced 77.3% accuracy. Similarly, a test substance could be defined as a sensitizer if the SI means of the vehicle control, and of the low, middle, and high concentrations were statistically significantly different, which was tested using ANOVA or Kruskal-Wallis, with post hoc analysis, Dunnett, or DSCF (Dwass-Steel-Critchlow-Fligner), respectively, depending on the equal variance test, producing 81.8% accuracy. The absolute SI-based cutoff approach produced the best predictive capacity, however the discordant decisions between prediction models need to be examined further. Copyright © 2015 Elsevier Inc. All rights reserved.

Limiting processes in non-equilibrium classical statistical mechanics

International Nuclear Information System (INIS)

Jancel, R.

1983-01-01

After a recall of the basic principles of the statistical mechanics, the results of ergodic theory, the transient at the thermodynamic limit and his link with the transport theory near the equilibrium are analyzed. The fundamental problems put by the description of non-equilibrium macroscopic systems are investigated and the kinetic methods are stated. The problems of the non-equilibrium statistical mechanics are analyzed: irreversibility and coarse-graining, macroscopic variables and kinetic description, autonomous reduced descriptions, limit processes, BBGKY hierarchy, limit theorems [fr

A determination of the CKM-matrix element ratio vertical stroke Vtsvertical stroke /vertical stroke Vcbvertical stroke from the rare B-decays B →K*+γ and B →Xs + γ

International Nuclear Information System (INIS)

Ali, A.; Greub, C.

1993-05-01

Implication of the recent CLEO observation of the rare decay mode B→K * +γhaving a combined branching ratio BR(B→K * +γ)=(4.5±1.5±0.9)x10 -5 and an improved upper limit on the inclusive branching ratio BR(B→X s +γ) -4 (95% C.L.) are discussed in the context of the Standard Model (SM). Unsing the unitarity of the CKM-matrix and taking into account QCD radiative corrections in the decay rate and the inclusive photon energy spectrum we obtain an improved upper limit on the inclusive branching ratio BR(B→X s +γ) -4 (95% C.L.). This can be used to constrain possible non-SM contributions to the inclusive branching ratio, giving BR(B→X s +γ)(non-SM) -4 for m t ≥108 GeV. Within the SM, we show that the resulting experimental upper limit can be interpreted as a corresponding limit on the CKM-matrix element ratio yielding vertical stroke V ts vertical stroke /vertical stroke V cb vertical stroke * /X s )≡Γ(B→K * +γ)/Γ(B→X s +γ), based on the inclusive hadronic invariant mass distribution in B→X s +γ. Estimating the K * -contribution from this distribution in the threshold region (m K +m π)≤ m X s ≤0.97 GeV and using experimental measurements from the semileptonic D-decays D→K+π+lν l in the same mass interval, we obtain R(K * /X s )=0.13±0.03. This enables us to put a lower bound on the ratio vertical stroke V ts vertical stroke /vertical stroke V cb vertical stroke from the 95% C.L. lower limit on the branching rato BR(B→K * +γ)>1.6x10 -5 . Combining the exclusive and inclusive decay rates, we determine 0.50≤vertical stroke V ts vertical stroke /vertical stroke V cb vertical stroke ≤1.67 (at 95% C.L.). (orig.). 7 figs

A parametric FE modeling of brake for non-linear analysis

Energy Technology Data Exchange (ETDEWEB)

Ahmed,Ibrahim; Fatouh, Yasser [Automotive and Tractors Technology Department, Faculty of Industrial Education, Helwan University, Cairo (Egypt); Aly, Wael [Refrigeration and Air-Conditioning Technology Department, Faculty of Industrial Education, Helwan University, Cairo (Egypt)

2013-07-01

A parametric modeling of a drum brake based on 3-D Finite Element Methods (FEM) for non-contact analysis is presented. Many parameters are examined during this study such as the effect of drum-lining interface stiffness, coefficient of friction, and line pressure on the interface contact. Firstly, the modal analysis of the drum brake is also studied to get the natural frequency and instability of the drum to facilitate transforming the modal elements to non-contact elements. It is shown that the Unsymmetric solver of the modal analysis is efficient enough to solve this linear problem after transforming the non-linear behavior of the contact between the drum and the lining to a linear behavior. A SOLID45 which is a linear element is used in the modal analysis and then transferred to non-linear elements which are Targe170 and Conta173 that represent the drum and lining for contact analysis study. The contact analysis problems are highly non-linear and require significant computer resources to solve it, however, the contact problem give two significant difficulties. Firstly, the region of contact is not known based on the boundary conditions such as line pressure, and drum and friction material specs. Secondly, these contact problems need to take the friction into consideration. Finally, it showed a good distribution of the nodal reaction forces on the slotted lining contact surface and existing of the slot in the middle of the lining can help in wear removal due to the friction between the lining and the drum. Accurate contact stiffness can give a good representation for the pressure distribution between the lining and the drum. However, a full contact of the front part of the slotted lining could occur in case of 20, 40, 60 and 80 bar of piston pressure and a partially contact between the drum and lining can occur in the rear part of the slotted lining.

On the problem of neutron spectroscopy of parametrically non-equilibrium quasiparticles in solids

International Nuclear Information System (INIS)

Vo Khong An'.

1981-01-01

A suitable for numerical estimations formula for coherent neutron inelastic scattering cross sections on the plasmon-phonon mixed modes of electron-phonon systems in the parametric resonance conditions is obtained from the analytical one presented in the previous work using some relations of the general parametric excitation theory. The cross sections of neutron scattering on the high-frequency plasmon-like and the low-frequency longitudinal optical phonon-like modes in InSb crystals are calculated as functions of the driving laser field intensity, which show an increase in values by about two orders of magnitude as the field intensity approaches the parametric excitation threshold

Likert scales, levels of measurement and the "laws" of statistics.

Science.gov (United States)

Norman, Geoff

2010-12-01

Reviewers of research reports frequently criticize the choice of statistical methods. While some of these criticisms are well-founded, frequently the use of various parametric methods such as analysis of variance, regression, correlation are faulted because: (a) the sample size is too small, (b) the data may not be normally distributed, or (c) The data are from Likert scales, which are ordinal, so parametric statistics cannot be used. In this paper, I dissect these arguments, and show that many studies, dating back to the 1930s consistently show that parametric statistics are robust with respect to violations of these assumptions. Hence, challenges like those above are unfounded, and parametric methods can be utilized without concern for "getting the wrong answer".

Design Automation Using Script Languages. High-Level CAD Templates in Non-Parametric Programs

Science.gov (United States)

Moreno, R.; Bazán, A. M.

2017-10-01

The main purpose of this work is to study the advantages offered by the application of traditional techniques of technical drawing in processes for automation of the design, with non-parametric CAD programs, provided with scripting languages. Given that an example drawing can be solved with traditional step-by-step detailed procedures, is possible to do the same with CAD applications and to generalize it later, incorporating references. In today’s modern CAD applications, there are striking absences of solutions for building engineering: oblique projections (military and cavalier), 3D modelling of complex stairs, roofs, furniture, and so on. The use of geometric references (using variables in script languages) and their incorporation into high-level CAD templates allows the automation of processes. Instead of repeatedly creating similar designs or modifying their data, users should be able to use these templates to generate future variations of the same design. This paper presents the automation process of several complex drawing examples based on CAD script files aided with parametric geometry calculation tools. The proposed method allows us to solve complex geometry designs not currently incorporated in the current CAD applications and to subsequently create other new derivatives without user intervention. Automation in the generation of complex designs not only saves time but also increases the quality of the presentations and reduces the possibility of human errors.

Bootstrap Prediction Intervals in Non-Parametric Regression with Applications to Anomaly Detection

Science.gov (United States)

Kumar, Sricharan; Srivistava, Ashok N.

2012-01-01

Prediction intervals provide a measure of the probable interval in which the outputs of a regression model can be expected to occur. Subsequently, these prediction intervals can be used to determine if the observed output is anomalous or not, conditioned on the input. In this paper, a procedure for determining prediction intervals for outputs of nonparametric regression models using bootstrap methods is proposed. Bootstrap methods allow for a non-parametric approach to computing prediction intervals with no specific assumptions about the sampling distribution of the noise or the data. The asymptotic fidelity of the proposed prediction intervals is theoretically proved. Subsequently, the validity of the bootstrap based prediction intervals is illustrated via simulations. Finally, the bootstrap prediction intervals are applied to the problem of anomaly detection on aviation data.

Relationship of nocturnal concentrations of melatonin, gamma-aminobutyric acid and total antioxidants in peripheral blood with insomnia after stroke: study protocol for a prospective non-randomized controlled trial

Institute of Scientific and Technical Information of China (English)

Wei Zhang; Fang Li; Tong Zhang

2017-01-01

Melatonin and gamma-aminobutyric acid (GABA) have been shown to regulate sleep. The nocturnal concentrations of melatonin, GABA and total antioxidants may relate to insomnia in stroke patients. In this prospective single-center non-randomized controlled clinical trial performed in the China Rehabilitation Research Center, we analyzed the relationship of nocturnal concentrations of melatonin, GABA and total antioxidants with insomnia after stroke. Patients during rehabilitation of stroke were recruited and assigned to the insomnia group or non-insomnia group. Simultaneously, persons without stroke or insomnia served as normal controls. Each group contained 25 cases. The primary outcome was nocturnal concentrations of melatonin, GABA and total antioxidants in peripheral blood. The secondary outcomes were Pittsburgh Sleep Quality Index, Insomnia Severity Index, Epworth Sleepiness Scale, Fatigue Severity Scale, Morningness-Eveningness Questionnaire (Chinese version), and National Institute of Health Stroke Scale. The relationship of nocturnal concentrations of melatonin, GABA and total antioxidants with insomnia after stroke was analyzed and showed that they were lower in the insomnia group than in the non-insomnia group. The severity of stroke was higher in the insomnia group than in the non-insomnia group. Correlation analysis demonstrated that the nocturnal concentrations of melatonin and GABA were associated with insomnia after stroke. This trial was regis-tered at ClinicalTrials.gov, identifier: NCT03202121.

Parametric Resonance in the Early Universe - A Fitting Analysis

CERN Document Server

Figueroa, Daniel G.

2017-02-01

Particle production via parametric resonance in the early Universe, is a non-perturbative, non-linear and out-of-equilibrium phenomenon. Although it is a well studied topic, whenever a new scenario exhibits parametric resonance, a full re-analysis is normally required. To avoid this tedious task, many works present often only a simplified linear treatment of the problem. In order to surpass this circumstance in the future, we provide a fitting analysis of parametric resonance through all its relevant stages: initial linear growth, non-linear evolution, and relaxation towards equilibrium. Using lattice simulations in an expanding grid in $3+1$ dimensions, we parametrise the dynamics' outcome scanning over the relevant ingredients: role of the oscillatory field, particle coupling strength, initial conditions, and background expansion rate. We emphasise the inaccuracy of the linear calculation of the decay time of the oscillatory field, and propose a more appropriate definition of this scale based on the subsequ...

Confronting Passive and Active Sensors with Non-Gaussian Statistics

Directory of Open Access Journals (Sweden)

Pablo Rodríguez-Gonzálvez

2014-07-01

Full Text Available This paper has two motivations: firstly, to compare the Digital Surface Models (DSM derived by passive (digital camera and by active (terrestrial laser scanner remote sensing systems when applied to specific architectural objects, and secondly, to test how well the Gaussian classic statistics, with its Least Squares principle, adapts to data sets where asymmetrical gross errors may appear and whether this approach should be changed for a non-parametric one. The field of geomatic technology automation is immersed in a high demanding competition in which any innovation by one of the contenders immediately challenges the opponents to propose a better improvement. Nowadays, we seem to be witnessing an improvement of terrestrial photogrammetry and its integration with computer vision to overcome the performance limitations of laser scanning methods. Through this contribution some of the issues of this “technological race” are examined from the point of view of photogrammetry. A new software is introduced and an experimental test is designed, performed and assessed to try to cast some light on this thrilling match. For the case considered in this study, the results show good agreement between both sensors, despite considerable asymmetry. This asymmetry suggests that the standard Normal parameters are not adequate to assess this type of data, especially when accuracy is of importance. In this case, standard deviation fails to provide a good estimation of the results, whereas the results obtained for the Median Absolute Deviation and for the Biweight Midvariance are more appropriate measures.

Genetic determinants and stroke in children with sickle cell disease,

Directory of Open Access Journals (Sweden)

Daniela O.W. Rodrigues

Full Text Available Abstract Objective: To verify genetic determinants associated with stroke in children with sickle cell disease (SCD. Methods: Prospective cohort with 110 children submitted to neonatal screening by the Neonatal Screening Program, between 1998 and 2007, with SCD diagnosis, followed at a regional reference public service for hemoglobinopathies. The analyzed variables were type of hemoglobinopathy, gender, coexistence with alpha thalassemia (α-thal, haplotypes of the beta globin chain cluster, and stroke. The final analysis was conducted with 66 children with sickle cell anemia (SCA, using the chi-squared test in the program SPSS® version 14.0. Results: Among children with SCD, 60% had SCA. The prevalence of coexistence with α-thal was 30.3% and the Bantu haplotype (CAR was identified in 89.2%. The incidence of stroke was significantly higher in those with SCA (27.3% vs. 2.3%; p = 0.001 and males (24.1% vs. 9.6%; p = 0.044. The presence of α-thal (p = 0.196, the CAR haplotype (p = 0.543, and socioeconomic factors were not statistically significant in association with the occurrence of stroke. Conclusion: There is a high incidence of stroke in male children and in children with SCA. Coexistence with α-thal and haplotypes of the beta globin chain cluster did not show any significant association with stroke. The heterogeneity between previously evaluated populations, the non-reproducibility between studies, and the need to identify factors associated with stroke in patients with SCA indicate the necessity of conducting further research to demonstrate the relevance of genetic factors in stroke related to SCD.

Pregnancy and puerperium-related strokes in Asian women.

Science.gov (United States)

Khan, Maria; Wasay, Mohammad; Menon, Bindu; Saadatnia, Mohammad; Venketasubramanian, Narayanaswamy; Gunaratne, Padma; Mehndiratta, M M; Dai, Alper; Kaul, Subhash

2013-11-01

Despite an increased risk of stroke in pregnancy and puerperium, the overall incidence of the condition in this population is low. Therefore, there is limited data pertaining to these patients particularly from Asian countries. Our objective was to describe the risk factors and outcomes of 110 pregnancy-related ischemic strokes from 5 Asian countries. Data were collected by retrospective chart review in most cases and prospectively in the rest. Inclusion criteria for this subanalysis were women, pregnant or within 1-month postpartum, presenting to the study center with acute ischemic stroke (arterial or venous) confirmed by neuroimaging. Intracranial hemorrhages other than the ones associated with cerebral venous thrombosis or hemorrhagic infarct were excluded. Risk factors were diagnosed based on already published criteria. Outcomes were measured using modified Rankin score. Statistical analysis was done using Statistical Package for Social Sciences version 19.0. In all, 110 women with mean age of 27.94 years presented with pregnancy-related ischemic strokes; 58.2% of the strokes occurred postpartum and 49.1% were secondary to cerebral venous thrombosis. Venous strokes were significantly more likely to occur postpartum compared with arterial strokes (P=.01), to have abnormal "hypercoagulable panel result on admission" (PAsian women. Both traditional and pregnancy-specific risk factors should be addressed to control ischemic stroke risk in these women. Copyright © 2013 National Stroke Association. Published by Elsevier Inc. All rights reserved.

Bilirubin and Stroke Risk Using a Mendelian Randomization Design.

Science.gov (United States)

Lee, Sun Ju; Jee, Yon Ho; Jung, Keum Ji; Hong, Seri; Shin, Eun Soon; Jee, Sun Ha

2017-05-01

Circulating bilirubin, a natural antioxidant, is associated with decreased risk of stroke. However, the nature of the relationship between the two remains unknown. We used a Mendelian randomization analysis to assess the causal effect of serum bilirubin on stroke risk in Koreans. The 14 single-nucleotide polymorphisms (SNPs) (bilirubin level in the KCPS-II (Korean Cancer Prevention Study-II) Biobank subcohort consisting of 4793 healthy Korean and 806 stroke cases. Weighted genetic risk score was calculated using 14 SNPs selected from the top SNPs. Both rs6742078 (F statistics=138) and weighted genetic risk score with 14 SNPs (F statistics=187) were strongly associated with bilirubin levels. Simultaneously, serum bilirubin level was associated with decreased risk of stroke in an ordinary least-squares analysis. However, in 2-stage least-squares Mendelian randomization analysis, no causal relationship between serum bilirubin and stroke risk was found. There is no evidence that bilirubin level is causally associated with risk of stroke in Koreans. Therefore, bilirubin level is not a risk determinant of stroke. © 2017 American Heart Association, Inc.

Statistical parametric mapping in the detection of rCBF changes in mild Alzheimer's disease

International Nuclear Information System (INIS)

Rowe, C.; Barnden, L.; Boundy, K.; McKinnon, J.; Liptak, M.

1998-01-01

Full text: Reduction in temporoparietal regional cerebral blood flow (rCBF) is proportional to the degree of cognitive deficit in patients with Alzheimer's Disease (AD). The characteristic pattern is readily apparent in advanced disease but is often subtle in early stage AD, reducing the clinical value of SPECT in the management of this condition. We have previously reported that Statistical Parametric Mapping (SPM95) revealed significant temporoparietal hypoperfusion when 10 patients with mild AD (classified by the Clinical Dementia Rating Scale) were compared to 10 age matched normals. We have now begun to evaluate the sensitivity and specificity of SPM95 in individuals with mild AD by comparison to our bank of 39 normals (30 female, 9 male, age range 26 to 74, mean age 52). Preliminary results reveal low sensitivity (<40%) when the standard reference region for normalization (i.e. global brain counts) is used. Better results are expected from normalizing to the cerebellum or basal ganglia and this is under investigation. An objective method to improve the accuracy of rCBF imaging for the diagnosis of early AD would be very useful in clinical practice. This study will demonstrate whether SPM can fulfill this role

Statistical analysis of non-homogeneous Poisson processes. Statistical processing of a particle multidetector

International Nuclear Information System (INIS)

Lacombe, J.P.

1985-12-01

Statistic study of Poisson non-homogeneous and spatial processes is the first part of this thesis. A Neyman-Pearson type test is defined concerning the intensity measurement of these processes. Conditions are given for which consistency of the test is assured, and others giving the asymptotic normality of the test statistics. Then some techniques of statistic processing of Poisson fields and their applications to a particle multidetector study are given. Quality tests of the device are proposed togetherwith signal extraction methods [fr

Two-Sample Statistics for Testing the Equality of Survival Functions Against Improper Semi-parametric Accelerated Failure Time Alternatives: An Application to the Analysis of a Breast Cancer Clinical Trial

Science.gov (United States)

BROËT, PHILIPPE; TSODIKOV, ALEXANDER; DE RYCKE, YANN; MOREAU, THIERRY

2010-01-01

This paper presents two-sample statistics suited for testing equality of survival functions against improper semi-parametric accelerated failure time alternatives. These tests are designed for comparing either the short- or the long-term effect of a prognostic factor, or both. These statistics are obtained as partial likelihood score statistics from a time-dependent Cox model. As a consequence, the proposed tests can be very easily implemented using widely available software. A breast cancer clinical trial is presented as an example to demonstrate the utility of the proposed tests. PMID:15293627

Two-sample statistics for testing the equality of survival functions against improper semi-parametric accelerated failure time alternatives: an application to the analysis of a breast cancer clinical trial.

Science.gov (United States)

Broët, Philippe; Tsodikov, Alexander; De Rycke, Yann; Moreau, Thierry

2004-06-01

This paper presents two-sample statistics suited for testing equality of survival functions against improper semi-parametric accelerated failure time alternatives. These tests are designed for comparing either the short- or the long-term effect of a prognostic factor, or both. These statistics are obtained as partial likelihood score statistics from a time-dependent Cox model. As a consequence, the proposed tests can be very easily implemented using widely available software. A breast cancer clinical trial is presented as an example to demonstrate the utility of the proposed tests.

The ARTICO study: identification of patients at high risk of vascular recurrence after a first non-cardioembolic stroke.

Science.gov (United States)

Serena, Joaquín; Segura, Tomás; Roquer, Jaume; García-Gil, María; Castillo, José

2015-03-11

About 20% of patients with a first ischaemic stroke will experience a new vascular event within the first year. The atherosclerotic burden, an indicator of the extension of atherosclerosis in a patient, has been associated with the risk of new cardiovascular events in the general population. However, no predictive models reliably identify groups at a high risk of recurrence. The ARTICO study prospectively analysed the predictive value for the risk of recurrence of specific atherosclerotic markers. The multicentre ARTICO study included 620 consecutive independent patients older than 60 years suffering from a first non-cardioembolic stroke. We analysed classical stroke risk factors; duplex study of supraaortic trunk including intima-media thickness (IMT) measurement; quantification of internal carotid (ICA) stenosis; number, morphology and surface characteristics of carotid plaques; ankle brachial index (ABI); and the presence of microalbuminuria. Patients were followed up at 6 and 12 months after inclusion. The primary end-point was death or major cardiovascular events. Any vascular event or death at 12 months occurred in 78 (13.8%) patients. In 40 (7.1%) of these the vascular event was a stroke recurrence. Weight, history of diabetes mellitus, history of symptomatic PAD, ABI 50%) were associated with a higher risk of vascular events on follow-up in the bivariate analysis. In the final Cox regression analysis, body mass index (BMI), systolic blood pressure, history of diabetes mellitus, symptomatic PAD (HR, 2.76; 95% CI, 1.10-6.95; p=0.03), and particularly patients with both ICA stenosis >50% and PAD (HR 4.52; 95% CI, 2.14-9.53; p50% nor isolated abnormal ABI remained associated with an increased risk of recurrence in comparison with the whole population. Symptomatic PAD identifies a high risk group of vascular recurrence after a first non-cardioembolic stroke. The associated increased risk was particularly high in patients with both ICA stenosis and either

Conjugate pair of non-extensive statistics in quantum scattering

International Nuclear Information System (INIS)

Ion, D.B.; Ion, M.L.D.

1999-01-01

In this paper, by defining the Fourier transform of the scattering amplitudes as a bounded linear mapping from the space L 2p to the space L 2q when 1/(2p)+1/(2q)=1, we introduced a new concept in quantum physics in terms of Tsallis-like entropies S J (p) and S θ (q), namely, that of conjugate pair of non-extensive statistics. This new concept is experimentally illustrated by using 88 + 49 sets of pion-nucleon and pion-nucleus phase shifts. From the experimental determination of the (p,q) - non-extensivity indices by choosing the pairs for which the [χ L 2 (p) + χ θ 2 (q min )] - optimal - test function is minimum we get the conjugate pair of [(p min ,J),(q min , θ)]- non-extensive statistics with 0.50 ≤ p min ≤ 0.60. This new non-extensive statistical effect is experimentally evidenced with high degree of accuracy (CL≥ 99%). Moreover, it is worth to mention that the modification of the statistics has been more efficient than the modification of the PMD-SQS-optimum principle in obtaining the best overall fitting to the experimental data. (authors)

Knowledge of heart attack and stroke symptomology: a cross-sectional comparison of rural and non-rural US adults

Directory of Open Access Journals (Sweden)

Swanoski Michael T

2012-06-01

Full Text Available Abstract Background Understanding the signs and symptoms of heart attacks and strokes are important not only in saving lives, but also in preserving quality of life. Findings from recent research have yielded that the prevalence of cardiovascular disease risk factors are higher in rural populations, suggesting that adults living in rural locales may be at higher risk for heart attack and/or stroke. Knowledge of heart attack and stroke symptomology as well as calling 911 for a suspected heart attack or stroke are essential first steps in seeking care. This study sought to examine the knowledge of heart attack and stroke symptoms among rural adults in comparison to non-rural adults living in the U.S. Methods Using multivariate techniques, a cross-sectional analysis of an amalgamated multi-year Behavioral Risk Factor Surveillance Survey (BRFSS database was performed. The dependent variable for this analysis was low heart attack and stroke knowledge score. The covariates for the analysis were: age, sex, race/ethnicity, annual household income, attained education, health insurance status, having a health care provider (HCP, timing of last routine medical check-up, medical care deferment because of cost, self-defined health status and geographic locale. Results The weighted n for this study overall was 103,262,115 U.S. adults > =18 years of age. Approximately 22.0% of these respondents were U.S. adults living in rural locales. Logistic regression analysis revealed that those U.S. adults who had low composite heart attack and stroke knowledge scores were more likely to be rural (OR = 1.218 95%CI 1.216-1.219 rather than non-rural residents. Furthermore, those with low scores were more likely to be: male (OR = 1.353 95%CI 1.352-1.354, >65 years of age (OR = 1.369 95%CI 1.368-1.371, African American (OR = 1.892 95%CI 1.889-1.894, not educated beyond high school (OR = 1.400 955CI 1.399-1.402, uninsured (OR = 1.308 95%CI 1

Theory of fluctuations and parametric noise in a point nuclear reactor model

International Nuclear Information System (INIS)

Rodriguez, M.A.; San Miguel, M.; Sancho, J.M.

1984-01-01

We present a joint description of internal fluctuations and parametric noise in a point nuclear reactor model in which delayed neutrons and a detector are considered. We obtain kinetic equations for the first moments and define effective kinetic parameters which take into account the effect of parametric Gaussian white noise. We comment on the validity of Langevin approximations for this problem. We propose a general method to deal with weak but otherwise arbitrary non-white parametric noise. Exact kinetic equations are derived for Gaussian non-white noise. (author)

Parametric Linear Dynamic Logic

Directory of Open Access Journals (Sweden)

Peter Faymonville

2014-08-01

Full Text Available We introduce Parametric Linear Dynamic Logic (PLDL, which extends Linear Dynamic Logic (LDL by temporal operators equipped with parameters that bound their scope. LDL was proposed as an extension of Linear Temporal Logic (LTL that is able to express all ω-regular specifications while still maintaining many of LTL's desirable properties like an intuitive syntax and a translation into non-deterministic Büchi automata of exponential size. But LDL lacks capabilities to express timing constraints. By adding parameterized operators to LDL, we obtain a logic that is able to express all ω-regular properties and that subsumes parameterized extensions of LTL like Parametric LTL and PROMPT-LTL. Our main technical contribution is a translation of PLDL formulas into non-deterministic Büchi word automata of exponential size via alternating automata. This yields a PSPACE model checking algorithm and a realizability algorithm with doubly-exponential running time. Furthermore, we give tight upper and lower bounds on optimal parameter values for both problems. These results show that PLDL model checking and realizability are not harder than LTL model checking and realizability.

Heritability of young- and old-onset ischaemic stroke.

Science.gov (United States)

Bluher, A; Devan, W J; Holliday, E G; Nalls, M; Parolo, S; Bione, S; Giese, A K; Boncoraglio, G B; Maguire, J M; Müller-Nurasyid, M; Gieger, C; Meschia, J F; Rosand, J; Rolfs, A; Kittner, S J; Mitchell, B D; O'Connell, J R; Cheng, Y C

2015-11-01

Although the genetic contribution to stroke risk is well known, it remains unclear if young-onset stroke has a stronger genetic contribution than old-onset stroke. This study aims to compare the heritability of ischaemic stroke risk between young and old, using common genetic variants from whole-genome array data in population-based samples. This analysis included 4050 ischaemic stroke cases and 5765 controls from six study populations of European ancestry; 47% of cases were young-onset stroke (age stroke risk in these unrelated individuals, the pairwise genetic relatedness was estimated between individuals based on their whole-genome array data using a mixed linear model. Heritability was estimated separately for young-onset stroke and old-onset stroke (age ≥ 55 years). Heritabilities for young-onset stroke and old-onset stroke were estimated at 42% (±8%, P genetic contribution to the risk of stroke may be higher in young-onset ischaemic stroke, although the difference was not statistically significant. © 2015 EAN.

On the SU(2 vertical stroke 1) WZNW model and its statistical mechanics applications

Energy Technology Data Exchange (ETDEWEB)

Saleur, H [CEA Centre d' Etudes de Saclay, 91 - Gif-sur-Yvette (France). Service de Physique Theorique; [University of Southern California, Los Angeles, CA (United States). Dept. of Physics; Schomerus, V [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)

2006-11-15

Motivated by a careful analysis of the Laplacian on the supergroup SU(2 vertical stroke 1) we formulate a proposal for the state space of the SU(2 vertical stroke 1) WZNW model. We then use properties of sl(2 vertical stroke 1) characters to compute the partition function of the theory. In the special case of level k=1 the latter is found to agree with the properly regularized partition function for the continuum limit of the integrable sl(2 vertical stroke 1)3- anti 3 super-spin chain. Some general conclusions applicable to other WZNW models (in particular the case k=-1/2) are also drawn. (orig.)

Ischemic stroke risk, smoking, and the genetics of inflammation in a biracial population: the stroke prevention in young women study

Directory of Open Access Journals (Sweden)

Sorkin John D

2008-08-01

Full Text Available Abstract Background Although cigarette smoking is a well-established risk factor for vascular disease, the genetic mechanisms that link cigarette smoking to an increased incidence of stroke are not well understood. Genetic variations within the genes of the inflammatory pathways are thought to partially mediate this risk. Here we evaluate the association of several inflammatory gene single nucleotide polymorphisms (SNPs with ischemic stroke risk among young women, further stratified by current cigarette smoking status. Methods A population-based case-control study of stroke among women aged 15–49 identified 224 cases of first ischemic stroke (47.3% African-American and 211 age-comparable control subjects (43.1% African-American. Several inflammatory candidate gene SNPs chosen through literature review were genotyped in the study population and assessed for association with stroke and interaction with smoking status. Results Of the 8 SNPs (across 6 genes analyzed, only IL6 SNP rs2069832 (allele C, African-American frequency = 92%, Caucasian frequency = 55% was found to be significantly associated with stroke using an additive model, and this was only among African-Americans (age-adjusted: OR = 2.2, 95% CI = 1.0–5.0, p = 0.049; risk factor adjusted: OR = 2.5, 95% CI = 1.0–6.5, p = 0.05. When stratified by smoking status, two SNPs demonstrated statistically significant gene-environment interactions. First, the T allele (frequency = 5% of IL6 SNP rs2069830 was found to be protective among non-smokers (OR = 0.30, 95% CI = 0.11–.082, p = 0.02, but not among smokers (OR = 1.63, 95% CI = 0.48–5.58, p = 0.43; genotype by smoking interaction (p = 0.036. Second, the C allele (frequency = 39% of CD14 SNP rs2569190 was found to increase risk among smokers (OR = 2.05, 95% CI = 1.09–3.86, p = 0.03, but not among non-smokers (OR = 0.93, 95% CI = 0.62–1.39, p = 0.72; genotype by smoking interaction (p = 0.039. Conclusion This study demonstrates

Effect of an external alternating electric field non-monochromaticity on parametric excitation of surface ion cyclotron X-modes

International Nuclear Information System (INIS)

Girka, V O; Puzyrkov, S Yu; Shpagina, V O; Shpagina, L O

2012-01-01

The application of an external alternating electric field in the range of ion cyclotron frequencies is a well-known method for the excitation of surface electromagnetic waves. The present paper is devoted to the development of a kinetic theory of parametric excitation of these eigenwaves propagating across an external steady magnetic field along the plasma boundary at the second harmonic of the ion cyclotron frequency. Unlike previous papers on this subject, parametric excitation of surface ion cyclotron X-modes is studied here under the condition of non-monochromaticity of an external alternating electric field. Non-monochromaticity of the external alternating electric field is modeled by the superposition of two uniform and monochromatic electric fields with different amplitudes and frequencies. The nonlinear boundary condition is formulated for a tangential magnetic field of the studied surface waves. An infinite set of equations for the harmonics of a tangential electric field is solved using the approximation of the wave packet consisting of the main harmonic and two nearest satellite harmonics. Two different regimes of instability have been considered. If one of the applied generators has an operation frequency that is close to the ion cyclotron frequency, then changing the amplitude of the second generator allows one to enhance the growth rate of the parametric instability or to diminish it. But if the operation frequencies of the both generators are not close to the ion cyclotron frequency, then changing the amplitudes of their fields allows one to decrease the growth rate of the instability and even to suppress its development. The problem is studied both analytically and numerically.

EFFECTS OF PARAMETRIC VARIATIONS ON SEISMIC ANALYSIS METHODS FOR NON-CLASSICALLY DAMPED COUPLED SYSTEMS

International Nuclear Information System (INIS)

XU, J.; DEGRASSI, G.

2000-01-01

A comprehensive benchmark program was developed by Brookhaven National Laboratory (BNL) to perform an evaluation of state-of-the-art methods and computer programs for performing seismic analyses of coupled systems with non-classical damping. The program, which was sponsored by the US Nuclear Regulatory Commission (NRC), was designed to address various aspects of application and limitations of these state-of-the-art analysis methods to typical coupled nuclear power plant (NPP) structures with non-classical damping, and was carried out through analyses of a set of representative benchmark problems. One objective was to examine the applicability of various analysis methods to problems with different dynamic characteristics unique to coupled systems. The examination was performed using parametric variations for three simple benchmark models. This paper presents the comparisons and evaluation of the program participants' results to the BNL exact solutions for the applicable ranges of modeling dynamic characteristic parameters

Fast, Sequence Adaptive Parcellation of Brain MR Using Parametric Models

DEFF Research Database (Denmark)

Puonti, Oula; Iglesias, Juan Eugenio; Van Leemput, Koen

2013-01-01

In this paper we propose a method for whole brain parcellation using the type of generative parametric models typically used in tissue classification. Compared to the non-parametric, multi-atlas segmentation techniques that have become popular in recent years, our method obtains state-of-the-art ...

Modelación de episodios críticos de contaminación por material particulado (PM10 en Santiago de Chile: Comparación de la eficiencia predictiva de los modelos paramétricos y no paramétricos Modeling critical episodes of air pollution by PM10 in Santiago, Chile: Comparison of the predictive efficiency of parametric and non-parametric statistical models

Directory of Open Access Journals (Sweden)

Sergio A. Alvarado

2010-12-01

Full Text Available Objetivo: Evaluar la eficiencia predictiva de modelos estadísticos paramétricos y no paramétricos para predecir episodios críticos de contaminación por material particulado PM10 del día siguiente, que superen en Santiago de Chile la norma de calidad diaria. Una predicción adecuada de tales episodios permite a la autoridad decretar medidas restrictivas que aminoren la gravedad del episodio, y consecuentemente proteger la salud de la comunidad. Método: Se trabajó con las concentraciones de material particulado PM10 registradas en una estación asociada a la red de monitorización de la calidad del aire MACAM-2, considerando 152 observaciones diarias de 14 variables, y con información meteorológica registrada durante los años 2001 a 2004. Se ajustaron modelos estadísticos paramétricos Gamma usando el paquete estadístico STATA v11, y no paramétricos usando una demo del software estadístico MARS v 2.0 distribuida por Salford-Systems. Resultados: Ambos métodos de modelación presentan una alta correlación entre los valores observados y los predichos. Los modelos Gamma presentan mejores aciertos que MARS para las concentraciones de PM10 con valores Objective: To evaluate the predictive efficiency of two statistical models (one parametric and the other non-parametric to predict critical episodes of air pollution exceeding daily air quality standards in Santiago, Chile by using the next day PM10 maximum 24h value. Accurate prediction of such episodes would allow restrictive measures to be applied by health authorities to reduce their seriousness and protect the community´s health. Methods: We used the PM10 concentrations registered by a station of the Air Quality Monitoring Network (152 daily observations of 14 variables and meteorological information gathered from 2001 to 2004. To construct predictive models, we fitted a parametric Gamma model using STATA v11 software and a non-parametric MARS model by using a demo version of Salford

Disentangling the contribution of the paretic and non-paretic ankle to balance control in stroke patients.

NARCIS (Netherlands)

Asseldonk, E.H.F. van; Buurke, J.H.; Bloem, B.R.; Renzenbrink, G.J.; Nene, A.V.; Helm, F.C.T. van der; Kooij, H. van der

2006-01-01

During stroke recovery, restoration of the paretic ankle and compensation in the non-paretic ankle may contribute to improved balance maintenance. We examine a new approach to disentangle these recovery mechanisms by objectively quantifying the contribution of each ankle to balance maintenance.

Ground reaction force analysed with correlation coefficient matrix in group of stroke patients.

Science.gov (United States)

Szczerbik, Ewa; Krawczyk, Maciej; Syczewska, Małgorzata

2014-01-01

Stroke is the third cause of death in contemporary society and causes many disorders. Clinical scales, ground reaction force (GRF) and objective gait analysis are used for assessment of patient's rehabilitation progress during treatment. The goal of this paper is to assess whether signal correlation coefficient matrix applied to GRF can be used for evaluation of the status of post-stroke patients. A group of patients underwent clinical assessment and instrumented gait analysis simultaneously three times. The difference between components of patient's GRF (vertical, fore/aft, med/lat) and normal ones (reference GRF of healthy subjects) was calculated as correlation coefficient. Patients were divided into two groups ("worse" and "better") based on the clinical functional scale tests done at the beginning of rehabilitation process. The results obtained by these two groups were compared using statistical analysis. An increase of median value of correlation coefficient is observed in all components of GRF, but only in non-paretic leg. Analysis of GRF signal can be helpful in assessment of post-stroke patients during rehabilitation. Improvement in stroke patients was observed in non-paretic leg of the "worse" group. GRF analysis should not be the only tool for objective validation of patient's improvement, but could be used as additional source of information.

Relational Processing Following Stroke

Science.gov (United States)

Andrews, Glenda; Halford, Graeme S.; Shum, David; Maujean, Annick; Chappell, Mark; Birney, Damian

2013-01-01

The research examined relational processing following stroke. Stroke patients (14 with frontal, 30 with non-frontal lesions) and 41 matched controls completed four relational processing tasks: sentence comprehension, Latin square matrix completion, modified Dimensional Change Card Sorting, and n-back. Each task included items at two or three…

PHYSICS OF NON-GAUSSIAN FIELDS AND THE COSMOLOGICAL GENUS STATISTIC

International Nuclear Information System (INIS)

James, J. Berian

2012-01-01

We report a technique to calculate the impact of distinct physical processes inducing non-Gaussianity on the cosmological density field. A natural decomposition of the cosmic genus statistic into an orthogonal polynomial sequence allows complete expression of the scale-dependent evolution of the topology of large-scale structure, in which effects including galaxy bias, nonlinear gravitational evolution, and primordial non-Gaussianity may be delineated. The relationship of this decomposition to previous methods for analyzing the genus statistic is briefly considered and the following applications are made: (1) the expression of certain systematics affecting topological measurements, (2) the quantification of broad deformations from Gaussianity that appear in the genus statistic as measured in the Horizon Run simulation, and (3) the study of the evolution of the genus curve for simulations with primordial non-Gaussianity. These advances improve the treatment of flux-limited galaxy catalogs for use with this measurement and further the use of the genus statistic as a tool for exploring non-Gaussianity.

The Importance of Integrating Clinical Relevance and Statistical Significance in the Assessment of Quality of Care--Illustrated Using the Swedish Stroke Register.

Directory of Open Access Journals (Sweden)

Anita Lindmark

Full Text Available When profiling hospital performance, quality inicators are commonly evaluated through hospital-specific adjusted means with confidence intervals. When identifying deviations from a norm, large hospitals can have statistically significant results even for clinically irrelevant deviations while important deviations in small hospitals can remain undiscovered. We have used data from the Swedish Stroke Register (Riksstroke to illustrate the properties of a benchmarking method that integrates considerations of both clinical relevance and level of statistical significance.The performance measure used was case-mix adjusted risk of death or dependency in activities of daily living within 3 months after stroke. A hospital was labeled as having outlying performance if its case-mix adjusted risk exceeded a benchmark value with a specified statistical confidence level. The benchmark was expressed relative to the population risk and should reflect the clinically relevant deviation that is to be detected. A simulation study based on Riksstroke patient data from 2008-2009 was performed to investigate the effect of the choice of the statistical confidence level and benchmark value on the diagnostic properties of the method.Simulations were based on 18,309 patients in 76 hospitals. The widely used setting, comparing 95% confidence intervals to the national average, resulted in low sensitivity (0.252 and high specificity (0.991. There were large variations in sensitivity and specificity for different requirements of statistical confidence. Lowering statistical confidence improved sensitivity with a relatively smaller loss of specificity. Variations due to different benchmark values were smaller, especially for sensitivity. This allows the choice of a clinically relevant benchmark to be driven by clinical factors without major concerns about sufficiently reliable evidence.The study emphasizes the importance of combining clinical relevance and level of statistical

The Importance of Integrating Clinical Relevance and Statistical Significance in the Assessment of Quality of Care--Illustrated Using the Swedish Stroke Register.

Science.gov (United States)

Lindmark, Anita; van Rompaye, Bart; Goetghebeur, Els; Glader, Eva-Lotta; Eriksson, Marie

2016-01-01

When profiling hospital performance, quality inicators are commonly evaluated through hospital-specific adjusted means with confidence intervals. When identifying deviations from a norm, large hospitals can have statistically significant results even for clinically irrelevant deviations while important deviations in small hospitals can remain undiscovered. We have used data from the Swedish Stroke Register (Riksstroke) to illustrate the properties of a benchmarking method that integrates considerations of both clinical relevance and level of statistical significance. The performance measure used was case-mix adjusted risk of death or dependency in activities of daily living within 3 months after stroke. A hospital was labeled as having outlying performance if its case-mix adjusted risk exceeded a benchmark value with a specified statistical confidence level. The benchmark was expressed relative to the population risk and should reflect the clinically relevant deviation that is to be detected. A simulation study based on Riksstroke patient data from 2008-2009 was performed to investigate the effect of the choice of the statistical confidence level and benchmark value on the diagnostic properties of the method. Simulations were based on 18,309 patients in 76 hospitals. The widely used setting, comparing 95% confidence intervals to the national average, resulted in low sensitivity (0.252) and high specificity (0.991). There were large variations in sensitivity and specificity for different requirements of statistical confidence. Lowering statistical confidence improved sensitivity with a relatively smaller loss of specificity. Variations due to different benchmark values were smaller, especially for sensitivity. This allows the choice of a clinically relevant benchmark to be driven by clinical factors without major concerns about sufficiently reliable evidence. The study emphasizes the importance of combining clinical relevance and level of statistical confidence when

Phase locking and quantum statistics in a parametrically driven nonlinear resonator

OpenAIRE

Hovsepyan, G. H.; Shahinyan, A. R.; Chew, Lock Yue; Kryuchkyan, G. Yu.

2016-01-01

We discuss phase-locking phenomena at low-level of quanta for parametrically driven nonlinear Kerr resonator (PDNR) in strong quantum regime. Oscillatory mode of PDNR is created in the process of a degenerate down-conversion of photons under interaction with a train of external Gaussian pulses. We calculate the Wigner functions of cavity mode showing two-fold symmetry in phase space and analyse formation of phase-locked states in the regular as well as the quantum chaotic regime.

TRANSIT TIMING OBSERVATIONS FROM KEPLER. II. CONFIRMATION OF TWO MULTIPLANET SYSTEMS VIA A NON-PARAMETRIC CORRELATION ANALYSIS

International Nuclear Information System (INIS)

Ford, Eric B.; Moorhead, Althea V.; Morehead, Robert C.; Fabrycky, Daniel C.; Steffen, Jason H.; Carter, Joshua A.; Fressin, Francois; Holman, Matthew J.; Ragozzine, Darin; Charbonneau, David; Lissauer, Jack J.; Rowe, Jason F.; Borucki, William J.; Bryson, Stephen T.; Burke, Christopher J.; Caldwell, Douglas A.; Welsh, William F.; Allen, Christopher; Batalha, Natalie M.; Buchhave, Lars A.

2012-01-01

We present a new method for confirming transiting planets based on the combination of transit timing variations (TTVs) and dynamical stability. Correlated TTVs provide evidence that the pair of bodies is in the same physical system. Orbital stability provides upper limits for the masses of the transiting companions that are in the planetary regime. This paper describes a non-parametric technique for quantifying the statistical significance of TTVs based on the correlation of two TTV data sets. We apply this method to an analysis of the TTVs of two stars with multiple transiting planet candidates identified by Kepler. We confirm four transiting planets in two multiple-planet systems based on their TTVs and the constraints imposed by dynamical stability. An additional three candidates in these same systems are not confirmed as planets, but are likely to be validated as real planets once further observations and analyses are possible. If all were confirmed, these systems would be near 4:6:9 and 2:4:6:9 period commensurabilities. Our results demonstrate that TTVs provide a powerful tool for confirming transiting planets, including low-mass planets and planets around faint stars for which Doppler follow-up is not practical with existing facilities. Continued Kepler observations will dramatically improve the constraints on the planet masses and orbits and provide sensitivity for detecting additional non-transiting planets. If Kepler observations were extended to eight years, then a similar analysis could likely confirm systems with multiple closely spaced, small transiting planets in or near the habitable zone of solar-type stars.

TRANSIT TIMING OBSERVATIONS FROM KEPLER. II. CONFIRMATION OF TWO MULTIPLANET SYSTEMS VIA A NON-PARAMETRIC CORRELATION ANALYSIS

Energy Technology Data Exchange (ETDEWEB)

Ford, Eric B.; Moorhead, Althea V.; Morehead, Robert C. [Astronomy Department, University of Florida, 211 Bryant Space Sciences Center, Gainesville, FL 32611 (United States); Fabrycky, Daniel C. [UCO/Lick Observatory, University of California, Santa Cruz, CA 95064 (United States); Steffen, Jason H. [Fermilab Center for Particle Astrophysics, P.O. Box 500, MS 127, Batavia, IL 60510 (United States); Carter, Joshua A.; Fressin, Francois; Holman, Matthew J.; Ragozzine, Darin; Charbonneau, David [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Lissauer, Jack J.; Rowe, Jason F.; Borucki, William J.; Bryson, Stephen T.; Burke, Christopher J.; Caldwell, Douglas A. [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Welsh, William F. [Astronomy Department, San Diego State University, San Diego, CA 92182-1221 (United States); Allen, Christopher [Orbital Sciences Corporation/NASA Ames Research Center, Moffett Field, CA 94035 (United States); Batalha, Natalie M. [Department of Physics and Astronomy, San Jose State University, San Jose, CA 95192 (United States); Buchhave, Lars A., E-mail: eford@astro.ufl.edu [Niels Bohr Institute, Copenhagen University, DK-2100 Copenhagen (Denmark); Collaboration: Kepler Science Team; and others

2012-05-10

We present a new method for confirming transiting planets based on the combination of transit timing variations (TTVs) and dynamical stability. Correlated TTVs provide evidence that the pair of bodies is in the same physical system. Orbital stability provides upper limits for the masses of the transiting companions that are in the planetary regime. This paper describes a non-parametric technique for quantifying the statistical significance of TTVs based on the correlation of two TTV data sets. We apply this method to an analysis of the TTVs of two stars with multiple transiting planet candidates identified by Kepler. We confirm four transiting planets in two multiple-planet systems based on their TTVs and the constraints imposed by dynamical stability. An additional three candidates in these same systems are not confirmed as planets, but are likely to be validated as real planets once further observations and analyses are possible. If all were confirmed, these systems would be near 4:6:9 and 2:4:6:9 period commensurabilities. Our results demonstrate that TTVs provide a powerful tool for confirming transiting planets, including low-mass planets and planets around faint stars for which Doppler follow-up is not practical with existing facilities. Continued Kepler observations will dramatically improve the constraints on the planet masses and orbits and provide sensitivity for detecting additional non-transiting planets. If Kepler observations were extended to eight years, then a similar analysis could likely confirm systems with multiple closely spaced, small transiting planets in or near the habitable zone of solar-type stars.

Transit Timing Observations from Kepler: II. Confirmation of Two Multiplanet Systems via a Non-parametric Correlation Analysis

Energy Technology Data Exchange (ETDEWEB)

Ford, Eric B.; /Florida U.; Fabrycky, Daniel C.; /Lick Observ.; Steffen, Jason H.; /Fermilab; Carter, Joshua A.; /Harvard-Smithsonian Ctr. Astrophys.; Fressin, Francois; /Harvard-Smithsonian Ctr. Astrophys.; Holman, Matthew J.; /Harvard-Smithsonian Ctr. Astrophys.; Lissauer, Jack J.; /NASA, Ames; Moorhead, Althea V.; /Florida U.; Morehead, Robert C.; /Florida U.; Ragozzine, Darin; /Harvard-Smithsonian Ctr. Astrophys.; Rowe, Jason F.; /NASA, Ames /SETI Inst., Mtn. View /San Diego State U., Astron. Dept.

2012-01-01

We present a new method for confirming transiting planets based on the combination of transit timing variations (TTVs) and dynamical stability. Correlated TTVs provide evidence that the pair of bodies are in the same physical system. Orbital stability provides upper limits for the masses of the transiting companions that are in the planetary regime. This paper describes a non-parametric technique for quantifying the statistical significance of TTVs based on the correlation of two TTV data sets. We apply this method to an analysis of the transit timing variations of two stars with multiple transiting planet candidates identified by Kepler. We confirm four transiting planets in two multiple planet systems based on their TTVs and the constraints imposed by dynamical stability. An additional three candidates in these same systems are not confirmed as planets, but are likely to be validated as real planets once further observations and analyses are possible. If all were confirmed, these systems would be near 4:6:9 and 2:4:6:9 period commensurabilities. Our results demonstrate that TTVs provide a powerful tool for confirming transiting planets, including low-mass planets and planets around faint stars for which Doppler follow-up is not practical with existing facilities. Continued Kepler observations will dramatically improve the constraints on the planet masses and orbits and provide sensitivity for detecting additional non-transiting planets. If Kepler observations were extended to eight years, then a similar analysis could likely confirm systems with multiple closely spaced, small transiting planets in or near the habitable zone of solar-type stars.

An augmented reality system for upper-limb post-stroke motor rehabilitation: a feasibility study.

Science.gov (United States)

Assis, Gilda Aparecida de; Corrêa, Ana Grasielle Dionísio; Martins, Maria Bernardete Rodrigues; Pedrozo, Wendel Goes; Lopes, Roseli de Deus

2016-08-01

To determine the clinical feasibility of a system based on augmented reality for upper-limb (UL) motor rehabilitation of stroke participants. A physiotherapist instructed the participants to accomplish tasks in augmented reality environment, where they could see themselves and their surroundings, as in a mirror. Two case studies were conducted. Participants were evaluated pre- and post-intervention. The first study evaluated the UL motor function using Fugl-Meyer scale. Data were compared using non-parametric sign tests and effect size. The second study used the gain of motion range of shoulder flexion and abduction assessed by computerized biophotogrammetry. At a significance level of 5%, Fugl-Meyer scores suggested a trend for greater UL motor improvement in the augmented reality group than in the other. Moreover, effect size value 0.86 suggested high practical significance for UL motor rehabilitation using the augmented reality system. System provided promising results for UL motor rehabilitation, since enhancements have been observed in the shoulder range of motion and speed. Implications for Rehabilitation Gain of range of motion of flexion and abduction of the shoulder of post-stroke patients can be achieved through an augmented reality system containing exercises to promote the mental practice. NeuroR system provides a mental practice method combined with visual feedback for motor rehabilitation of chronic stroke patients, giving the illusion of injured upper-limb (UL) movements while the affected UL is resting. Its application is feasible and safe. This system can be used to improve UL rehabilitation, an additional treatment past the traditional period of the stroke patient hospitalization and rehabilitation.

INFLAMMATORY MARKERS IN ACUTE ISCHAEMIC STROKE IN RELATION TO CLINICAL SEVERITY AND EARLY OUTCOME

Directory of Open Access Journals (Sweden)

S. Gopi

2018-01-01

Full Text Available BACKGROUND Biochemical markers of inflammation could be useful to predict severity of stroke in acute phase. Stroke is the third cause of mortality and the first cause of disability. Recent literature have demonstrated that inflammation contributes to all phases of atherosclerosis. The results of researchers suggest that atherosclerosis is an inflammatory disease. The aim of the study is to assess the1. Level of peripheral inflammatory markers in acute ischaemic stroke and their relation to severity of acute stroke. 2. Value of inflammatory markers in predicting the short-term outcome and disability at the end of six months. MATERIALS AND METHODS This is a prospective case control study for 6 months done from September 2014 to August 2016 in 100 patients of acute ischaemic stroke within first 5 days of symptom onset in comparison >18 years of age with 50 age and sex matched controls. Blood samples for all cases and controls were sent for erythrocyte sedimentation rate, Neutrophil-to-Lymphocyte Ratio (NLR, hs-C-reactive protein, mean platelet volume, serum ferritin, serum albumin and S. gamma-glutamyl transferase at admission. RESULTS The mean values of ESR, NLR, hs-CRP in all the cases are higher when compared to the controls and are statistically significant, whereas the mean values of MPV, S. ferritin, S. albumin and GGT in cases are lower when compared to controls, but are within normal range and difference is statistically significant except ferritin. ESR, hs-CRP has significant correlation with severity of acute ischaemic stroke. The mean values of these markers increased with increase in severity. Serum albumin has significant correlation with severity of acute ischaemic stroke with mean values of these markers decreasing with increase in severity of stroke. There is no significant correlation of the inflammatory markers in present study with the short-term outcome. CONCLUSION Inflammation plays an important role in the pathogenesis of non

Parametric statistical inference for discretely observed diffusion processes

DEFF Research Database (Denmark)

Pedersen, Asger Roer

Part 1: Theoretical results Part 2: Statistical applications of Gaussian diffusion processes in freshwater ecology......Part 1: Theoretical results Part 2: Statistical applications of Gaussian diffusion processes in freshwater ecology...

Ethnic differences in ischemic stroke subtypes in young-onset stroke: the Stroke Prevention in Young Adults Study.

Science.gov (United States)

Trivedi, Megh M; Ryan, Kathleen A; Cole, John W

2015-10-29

Prior studies indicate that young African-Americans (AA) have a greater frequency of ischemic stroke than similarly aged European-Americans (EA). We hypothesized that differences in stroke subtype frequency mediated through sex and differing risk factor profiles may play a role in ethnicity-specific stroke. Utilizing our biracial young-onset stroke population, we explored these relationships. Fifty nine hospitals in the Baltimore-Washington area participated in a population-based study of young-onset stroke in men (218-AA, 291-EA) and women (219-AA, 222-EA) aged 16-49. Data on age, sex, ethnicity and stroke risk factors (hypertension (HTN) and smoking) were gathered through standardized interview. A pair of vascular neurologists adjudicated each case to determine TOAST subtype. Logistic regression analyses evaluating for differences in stroke risk factors by TOAST subtype were performed. Analyses controlling for age and sex demonstrated that AA were more likely to have a lacunar stroke than EA (OR = 1.61; 95% CI = 1.12-2.32; p = 0.011) when utilizing the other TOAST subtypes as the reference group. This effect was mediated by HTN, which increases the risk of lacunar stroke (OR = 2.03; 95% CI = 1.38-2.98; p = 0.0003) and large artery stroke (OR = 1.70; 95% CI = 1.01-2.88; p = 0.048) when controlling for sex, ethnicity, and age. Cases below age 40 were more likely to have a cardioembolic stroke than those above age 40 (OR = 1.62; 95% CI = 1.15-2.27; p = 0.006), controlling for sex and ethnicity. Lastly, current smokers were more likely to have a large artery stroke than non-smokers (OR = 1.79; 95% CI = 1.08-2.98; p = 0.024). Our population-based data demonstrate ethnic differences in ischemic stroke subtypes. These findings may help clarify mechanisms of stroke in young adults which may in part be driven by ethnic-specific differences in early-onset traditional risk factors, thereby indicating differing emphasis on workup and prevention.

A validation study using a modified version of Postural Assessment Scale for Stroke Patients: Postural Stroke Study in Gothenburg (POSTGOT

Directory of Open Access Journals (Sweden)

Danielsson Anna

2011-10-01

Full Text Available Abstract Background A modified version of Postural Assessment Scale for Stroke Patients (PASS was created with some changes in the description of the items and clarifications in the manual (e.g. much help was defined as support from 2 persons. The aim of this validation study was to assess intrarater and interrater reliability using this modified version of PASS, at a stroke unit, for patients in the acute phase after their first event of stroke. Methods In the intrarater reliability study 114 patients and in the interrater reliability study 15 patients were examined twice with the test within one to 24 hours in the first week after stroke. Spearman's rank correlation, Kappa coefficients, Percentage Agreement and the newer rank-invariant methods; Relative Position, Relative Concentration and Relative rank Variance were used for the statistical analysis. Results For the intrarater reliability Spearman's rank correlations were 0.88-0.98 and k were 0.70-0.93 for the individual items. Small, statistically significant, differences were found for two items regarding Relative Position and for one item regarding Relative Concentration. There was no Relative rank Variance for any single item. For the interrater reliability, Spearman's rank correlations were 0.77-0.99 for individual items. For some items there was a possible, even if not proved, reliability problem regarding Relative Position and Relative Concentration. There was no Relative rank Variance for the single items, except for a small Relative rank Variance for one item. Conclusions The high intrarater and interrater reliability shown for the modified Postural Assessment Scale for Stroke Patients, the Swedish version of Postural Assessment Scale for Stroke Patients, with traditional and newer statistical analyses, particularly for assessments performed by the same rater, support the use of the Swedish version of Postural Assessment Scale for Stroke Patients, in the acute stage after stroke both

Estimated probability of stroke among medical outpatients in Enugu ...

African Journals Online (AJOL)

Risk factors for stroke were evaluated using a series of laboratory tests, medical history and physical examinations. The 10‑year probability of stroke was determined by applying the Framingham stroke risk equation. Statistical analysis was performed with the use of the SPSS 17.0 software package (SPSS Inc., Chicago, IL, ...

Cerebral Blood Flow Changes after Shunt in Hydrocephalus after Aneurysmal Subarachnoid Hemorrhage: Analysis by statistical Parametric Mapping

International Nuclear Information System (INIS)

Hyun, I. Y.; Choi, W. S.; Pak, H. S.

2003-01-01

The purpose of this study was to evaluate the changes of regional cerebral blood flow (rCBF) after shunt operation in patients with hydrocephalus after aneurysmal subarachnoid hemorrhage ba statistical parametric mapping (SPM). Seven patients (4 male, mean age 54 years) with hydrocephalus after aneurysmal subarachnoid hemorrhage underwent a shunt operation. Tc-99m HMPAO SPECT was performed within I week before, and 2 weeks after the shunt operation. All of the SPECT images were spatially transformed to standard space, smoothed, and globally normalized. After spatial and count normalization, rCBF of pre- and post- shunting Tc- 99m HMPAO SPECT was estimated at every voxel using t statistics. The voxels with a P value of less than 0.001 were considered to be significantly different. The shunt operation was effective in all patients. Pre-shunting Tc-99m HMPAO SPECT showed hypoperfusion, predominantly in the periventricular area. After shunt operation, periventricular low perfusion was disappeared. The results of this study show that periventricular CBF is impaired in hydrocephalus after aneurysmal subarachnoid hemorrhage. Significant increase of periventricular CBF after shunt operation suggests the evaluation of periventricular CBF by SPM might be of value for the prediction of shunt effectiveness in hydrocephalus

Cerebral Blood Flow Changes after Shunt in Hydrocephalus after Aneurysmal Subarachnoid Hemorrhage: Analysis by statistical Parametric Mapping

Energy Technology Data Exchange (ETDEWEB)

Hyun, I. Y.; Choi, W. S.; Pak, H. S. [College of Medicine, Univ. of Inhwa, Incheon (Korea, Republic of)

2003-07-01

The purpose of this study was to evaluate the changes of regional cerebral blood flow (rCBF) after shunt operation in patients with hydrocephalus after aneurysmal subarachnoid hemorrhage ba statistical parametric mapping (SPM). Seven patients (4 male, mean age 54 years) with hydrocephalus after aneurysmal subarachnoid hemorrhage underwent a shunt operation. Tc-99m HMPAO SPECT was performed within I week before, and 2 weeks after the shunt operation. All of the SPECT images were spatially transformed to standard space, smoothed, and globally normalized. After spatial and count normalization, rCBF of pre- and post- shunting Tc- 99m HMPAO SPECT was estimated at every voxel using t statistics. The voxels with a P value of less than 0.001 were considered to be significantly different. The shunt operation was effective in all patients. Pre-shunting Tc-99m HMPAO SPECT showed hypoperfusion, predominantly in the periventricular area. After shunt operation, periventricular low perfusion was disappeared. The results of this study show that periventricular CBF is impaired in hydrocephalus after aneurysmal subarachnoid hemorrhage. Significant increase of periventricular CBF after shunt operation suggests the evaluation of periventricular CBF by SPM might be of value for the prediction of shunt effectiveness in hydrocephalus.

Does cognitive impairment impact adherence? A systematic review and meta-analysis of the association between cognitive impairment and medication non-adherence in stroke.

LENUS (Irish Health Repository)

Rohde, Daniela

2017-12-08

While medication adherence is essential for the secondary prevention of stroke, it is often sub-optimal, and can be compromised by cognitive impairment. This study aimed to systematically review and meta-analyse the association between cognitive impairment and medication non-adherence in stroke.

The geometry of distributional preferences and a non-parametric identification approach: The Equality Equivalence Test.

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Kerschbamer, Rudolf

2015-05-01

This paper proposes a geometric delineation of distributional preference types and a non-parametric approach for their identification in a two-person context. It starts with a small set of assumptions on preferences and shows that this set (i) naturally results in a taxonomy of distributional archetypes that nests all empirically relevant types considered in previous work; and (ii) gives rise to a clean experimental identification procedure - the Equality Equivalence Test - that discriminates between archetypes according to core features of preferences rather than properties of specific modeling variants. As a by-product the test yields a two-dimensional index of preference intensity.

Statistical Analysis of Environmental Tritium around Wolsong Site

Energy Technology Data Exchange (ETDEWEB)

Kim, Ju Youl [FNC Technology Co., Yongin (Korea, Republic of)

2010-04-15

To find the relationship among airborne tritium, tritium in rainwater, TFWT (Tissue Free Water Tritium) and TBT (Tissue Bound Tritium), statistical analysis is conducted based on tritium data measured at KHNP employees' house around Wolsong nuclear power plants during 10 years from 1999 to 2008. The results show that tritium in such media exhibits a strong seasonal and annual periodicity. Tritium concentration in rainwater is observed to be highly correlated with TFWT and directly transmitted to TFWT without delay. The response of environmental radioactivity of tritium around Wolsong site is analyzed using time-series technique and non-parametric trend analysis. Tritium in the atmosphere and rainwater is strongly auto-correlated by seasonal and annual periodicity. TFWT concentration in pine needle is proven to be more sensitive to rainfall phenomenon than other weather variables. Non-parametric trend analysis of TFWT concentration within pine needle shows a increasing slope in terms of confidence level of 95%. This study demonstrates a usefulness of time-series and trend analysis for the interpretation of environmental radioactivity relationship with various environmental media.

Effects of body-weight supported treadmill training on kinetic symmetry in persons with chronic stroke.

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Combs, Stephanie A; Dugan, Eric L; Ozimek, Elicia N; Curtis, Amy B

2012-11-01

The purpose was to examine changes in kinetic symmetry in persons with chronic stroke immediately and 6-months after body-weight supported treadmill training. Fifteen participants at least six-months post stroke and able to ambulate between 0.4 and 0.8m/s and 20 participants without neurological conditions completed all phases of the study and were included in the analysis. The non-disabled group served as a comparison for describing changes in kinetic symmetry. The stroke group completed 24 sessions of body-weight supported treadmill training over 8-weeks with 20 minutes of total walking per session. Bilateral 3-dimensional motion analysis and gait speed were assessed 1-week before training (pre-test), 1-week after training (post-test) and 6-months after training (retention) in a repeated measures design. Relative propulsion of the paretic leg and relative positive work of the hip, knee and ankle joints of both legs were calculated to evaluate symmetry of kinetic forces. Statistically significant differences in relative propulsion and positive joint work within the paretic and non-paretic legs were not found over time. The stroke group significantly improved gait speed from pre- to post-test (p=.001) and pre-test to retention (p=.008). In comparison to the non-disabled group, forces produced by the stroke group were asymmetrical demonstrating compensatory adaptation. Although the participants with chronic stroke walked faster after body-weight supported treadmill training, the relative percentages of propulsion and positive work remained unchanged. These findings suggest that the increase in speed was likely due to strengthening existing compensatory strategies rather than through recovery of normal kinetic symmetry. Copyright © 2012 Elsevier Ltd. All rights reserved.

Genetic determinants and stroke in children with sickle cell disease.

Science.gov (United States)

Rodrigues, Daniela O W; Ribeiro, Luiz C; Sudário, Lysla C; Teixeira, Maria T B; Martins, Marina L; Pittella, Anuska M O L; Junior, Irtis de O Fernandes

To verify genetic determinants associated with stroke in children with sickle cell disease (SCD). Prospective cohort with 110 children submitted to neonatal screening by the Neonatal Screening Program, between 1998 and 2007, with SCD diagnosis, followed at a regional reference public service for hemoglobinopathies. The analyzed variables were type of hemoglobinopathy, gender, coexistence with alpha thalassemia (α-thal), haplotypes of the beta globin chain cluster, and stroke. The final analysis was conducted with 66 children with sickle cell anemia (SCA), using the chi-squared test in the program SPSS ® version 14.0. Among children with SCD, 60% had SCA. The prevalence of coexistence with α-thal was 30.3% and the Bantu haplotype (CAR) was identified in 89.2%. The incidence of stroke was significantly higher in those with SCA (27.3% vs. 2.3%; p=0.001) and males (24.1% vs. 9.6%; p=0.044). The presence of α-thal (p=0.196), the CAR haplotype (p=0.543), and socioeconomic factors were not statistically significant in association with the occurrence of stroke. There is a high incidence of stroke in male children and in children with SCA. Coexistence with α-thal and haplotypes of the beta globin chain cluster did not show any significant association with stroke. The heterogeneity between previously evaluated populations, the non-reproducibility between studies, and the need to identify factors associated with stroke in patients with SCA indicate the necessity of conducting further research to demonstrate the relevance of genetic factors in stroke related to SCD. Copyright © 2016 Sociedade Brasileira de Pediatria. Published by Elsevier Editora Ltda. All rights reserved.

Using Spline Regression in Semi-Parametric Stochastic Frontier Analysis: An Application to Polish Dairy Farms

DEFF Research Database (Denmark)

Czekaj, Tomasz Gerard; Henningsen, Arne

of specifying an unsuitable functional form and thus, model misspecification and biased parameter estimates. Given these problems of the DEA and the SFA, Fan, Li and Weersink (1996) proposed a semi-parametric stochastic frontier model that estimates the production function (frontier) by non......), Kumbhakar et al. (2007), and Henningsen and Kumbhakar (2009). The aim of this paper and its main contribution to the existing literature is the estimation semi-parametric stochastic frontier models using a different non-parametric estimation technique: spline regression (Ma et al. 2011). We apply...... efficiency of Polish dairy farms contributes to the insight into this dynamic process. Furthermore, we compare and evaluate the results of this spline-based semi-parametric stochastic frontier model with results of other semi-parametric stochastic frontier models and of traditional parametric stochastic...

Acceleration of the direct reconstruction of linear parametric images using nested algorithms

International Nuclear Information System (INIS)

Wang Guobao; Qi Jinyi

2010-01-01

Parametric imaging using dynamic positron emission tomography (PET) provides important information for biological research and clinical diagnosis. Indirect and direct methods have been developed for reconstructing linear parametric images from dynamic PET data. Indirect methods are relatively simple and easy to implement because the image reconstruction and kinetic modeling are performed in two separate steps. Direct methods estimate parametric images directly from raw PET data and are statistically more efficient. However, the convergence rate of direct algorithms can be slow due to the coupling between the reconstruction and kinetic modeling. Here we present two fast gradient-type algorithms for direct reconstruction of linear parametric images. The new algorithms decouple the reconstruction and linear parametric modeling at each iteration by employing the principle of optimization transfer. Convergence speed is accelerated by running more sub-iterations of linear parametric estimation because the computation cost of the linear parametric modeling is much less than that of the image reconstruction. Computer simulation studies demonstrated that the new algorithms converge much faster than the traditional expectation maximization (EM) and the preconditioned conjugate gradient algorithms for dynamic PET.

2015 International Symposium in Statistics

CERN Document Server

2016-01-01

This proceedings volume contains eight selected papers that were presented in the International Symposium in Statistics (ISS) 2015 On Advances in Parametric and Semi-parametric Analysis of Multivariate, Time Series, Spatial-temporal, and Familial-longitudinal Data, held in St. John’s, Canada from July 6 to 8, 2015. The main objective of the ISS-2015 was the discussion on advances and challenges in parametric and semi-parametric analysis for correlated data in both continuous and discrete setups. Thus, as a reflection of the theme of the symposium, the eight papers of this proceedings volume are presented in four parts. Part I is comprised of papers examining Elliptical t Distribution Theory. In Part II, the papers cover spatial and temporal data analysis. Part III is focused on longitudinal multinomial models in parametric and semi-parametric setups. Finally Part IV concludes with a paper on the inferences for longitudinal data subject to a challenge of important covariates selection from a set of large num...

Optimized statistical parametric mapping procedure for NIRS data contaminated by motion artifacts : Neurometric analysis of body schema extension.

Science.gov (United States)

Suzuki, Satoshi

2017-09-01

This study investigated the spatial distribution of brain activity on body schema (BS) modification induced by natural body motion using two versions of a hand-tracing task. In Task 1, participants traced Japanese Hiragana characters using the right forefinger, requiring no BS expansion. In Task 2, participants performed the tracing task with a long stick, requiring BS expansion. Spatial distribution was analyzed using general linear model (GLM)-based statistical parametric mapping of near-infrared spectroscopy data contaminated with motion artifacts caused by the hand-tracing task. Three methods were utilized in series to counter the artifacts, and optimal conditions and modifications were investigated: a model-free method (Step 1), a convolution matrix method (Step 2), and a boxcar-function-based Gaussian convolution method (Step 3). The results revealed four methodological findings: (1) Deoxyhemoglobin was suitable for the GLM because both Akaike information criterion and the variance against the averaged hemodynamic response function were smaller than for other signals, (2) a high-pass filter with a cutoff frequency of .014 Hz was effective, (3) the hemodynamic response function computed from a Gaussian kernel function and its first- and second-derivative terms should be included in the GLM model, and (4) correction of non-autocorrelation and use of effective degrees of freedom were critical. Investigating z-maps computed according to these guidelines revealed that contiguous areas of BA7-BA40-BA21 in the right hemisphere became significantly activated ([Formula: see text], [Formula: see text], and [Formula: see text], respectively) during BS modification while performing the hand-tracing task.

Interventions for dysarthria due to stroke and other adult-acquired, non-progressive brain injury.

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Mitchell, Claire; Bowen, Audrey; Tyson, Sarah; Butterfint, Zoe; Conroy, Paul

2017-01-25

Dysarthria is an acquired speech disorder following neurological injury that reduces intelligibility of speech due to weak, imprecise, slow and/or unco-ordinated muscle control. The impact of dysarthria goes beyond communication and affects psychosocial functioning. This is an update of a review previously published in 2005. The scope has been broadened to include additional interventions, and the title amended accordingly. To assess the effects of interventions to improve dysarthric speech following stroke and other non-progressive adult-acquired brain injury such as trauma, infection, tumour and surgery. We searched the Cochrane Stroke Group Trials Register (May 2016), CENTRAL (Cochrane Library 2016, Issue 4), MEDLINE, Embase, and CINAHL on 6 May 2016. We also searched Linguistics and Language Behavioral Abstracts (LLBA) (1976 to November 2016) and PsycINFO (1800 to September 2016). To identify further published, unpublished and ongoing trials, we searched major trials registers: WHO ICTRP, the ISRCTN registry, and ClinicalTrials.gov. We also handsearched the reference lists of relevant articles and contacted academic institutions and other researchers regarding other published, unpublished or ongoing trials. We did not impose any language restrictions. We selected randomised controlled trials (RCTs) comparing dysarthria interventions with 1) no intervention, 2) another intervention for dysarthria (this intervention may differ in methodology, timing of delivery, duration, frequency or theory), or 3) an attention control. Three review authors selected trials for inclusion, extracted data, and assessed risk of bias. We attempted to contact study authors for clarification and missing data as required. We calculated standardised mean difference (SMD) and 95% confidence interval (CI), using a random-effects model, and performed sensitivity analyses to assess the influence of methodological quality. We planned to conduct subgroup analyses for underlying clinical

A non-parametric consistency test of the ΛCDM model with Planck CMB data

Energy Technology Data Exchange (ETDEWEB)

Aghamousa, Amir; Shafieloo, Arman [Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of); Hamann, Jan, E-mail: amir@aghamousa.com, E-mail: jan.hamann@unsw.edu.au, E-mail: shafieloo@kasi.re.kr [School of Physics, The University of New South Wales, Sydney NSW 2052 (Australia)

2017-09-01

Non-parametric reconstruction methods, such as Gaussian process (GP) regression, provide a model-independent way of estimating an underlying function and its uncertainty from noisy data. We demonstrate how GP-reconstruction can be used as a consistency test between a given data set and a specific model by looking for structures in the residuals of the data with respect to the model's best-fit. Applying this formalism to the Planck temperature and polarisation power spectrum measurements, we test their global consistency with the predictions of the base ΛCDM model. Our results do not show any serious inconsistencies, lending further support to the interpretation of the base ΛCDM model as cosmology's gold standard.

Statistical time series methods for damage diagnosis in a scale aircraft skeleton structure: loosened bolts damage scenarios

International Nuclear Information System (INIS)

Kopsaftopoulos, Fotis P; Fassois, Spilios D

2011-01-01

A comparative assessment of several vibration based statistical time series methods for Structural Health Monitoring (SHM) is presented via their application to a scale aircraft skeleton laboratory structure. A brief overview of the methods, which are either scalar or vector type, non-parametric or parametric, and pertain to either the response-only or excitation-response cases, is provided. Damage diagnosis, including both the detection and identification subproblems, is tackled via scalar or vector vibration signals. The methods' effectiveness is assessed via repeated experiments under various damage scenarios, with each scenario corresponding to the loosening of one or more selected bolts. The results of the study confirm the 'global' damage detection capability and effectiveness of statistical time series methods for SHM.

Comparison of normal adult and children brain SPECT imaging using statistical parametric mapping(SPM)

Energy Technology Data Exchange (ETDEWEB)

Lee, Myoung Hoon; Yoon, Seok Nam; Joh, Chul Woo; Lee, Dong Soo [Ajou University School of Medicine, Suwon (Korea, Republic of); Lee, Jae Sung [Seoul national University College of Medicine, Seoul (Korea, Republic of)

2002-07-01

This study compared rCBF pattern in normal adult and normal children using statistical parametric mapping (SPM). The purpose of this study was to determine distribution pattern not seen visual analysis in both groups. Tc-99m ECD brain SPECT was performed in 12 normal adults (M:F=11:1, average age 35 year old) and 6 normal control children (M:F=4:2, 10.5{+-}3.1y) who visited psychiatry clinic to evaluate ADHD. Their brain SPECT revealed normal rCBF pattern in visual analysis and they were diagnosed clinically normal. Using SPM method, we compared normal adult group's SPECT images with those of 6 normal children subjects and measured the extent of the area with significant hypoperfusion and hyperperfusion (p<0.001, extent threshold=16). The areas of both angnlar gyrus, both postcentral gyrus, both superior frontal gyrus, and both superior parietal lobe showed significant hyperperfusion in normal adult group compared with normal children group. The areas of left amygdala gyrus, brain stem, both cerebellum, left globus pallidus, both hippocampal formations, both parahippocampal gyrus, both thalamus, both uncus, both lateral and medial occipitotemporal gyrus revealed significantly hyperperfusion in the children. These results demonstrated that SPM can say more precise anatomical area difference not seen visual analysis.

Comparison of normal adult and children brain SPECT imaging using statistical parametric mapping(SPM)

International Nuclear Information System (INIS)

Lee, Myoung Hoon; Yoon, Seok Nam; Joh, Chul Woo; Lee, Dong Soo; Lee, Jae Sung

2002-01-01

This study compared rCBF pattern in normal adult and normal children using statistical parametric mapping (SPM). The purpose of this study was to determine distribution pattern not seen visual analysis in both groups. Tc-99m ECD brain SPECT was performed in 12 normal adults (M:F=11:1, average age 35 year old) and 6 normal control children (M:F=4:2, 10.5±3.1y) who visited psychiatry clinic to evaluate ADHD. Their brain SPECT revealed normal rCBF pattern in visual analysis and they were diagnosed clinically normal. Using SPM method, we compared normal adult group's SPECT images with those of 6 normal children subjects and measured the extent of the area with significant hypoperfusion and hyperperfusion (p<0.001, extent threshold=16). The areas of both angnlar gyrus, both postcentral gyrus, both superior frontal gyrus, and both superior parietal lobe showed significant hyperperfusion in normal adult group compared with normal children group. The areas of left amygdala gyrus, brain stem, both cerebellum, left globus pallidus, both hippocampal formations, both parahippocampal gyrus, both thalamus, both uncus, both lateral and medial occipitotemporal gyrus revealed significantly hyperperfusion in the children. These results demonstrated that SPM can say more precise anatomical area difference not seen visual analysis

Interobserver agreement in ABCD scoring between non-stroke specialists and vascular neurologists following suspected TIA is only fair.

LENUS (Irish Health Repository)

Kinsella, Justin A

2012-02-01

The appropriateness of use and accuracy of age, blood pressure, clinical features and duration of symptoms (ABCD) scoring by non-stroke specialists while risk-stratifying patients with suspected transient ischaemic attack (TIA) are unknown. We reviewed all available ABCD data from referrals to a specialist neurovascular clinic. ABCD scoring was defined as \\'appropriate\\' in this study if an experienced vascular neurologist subsequently confirmed a clinical diagnosis of possible, probable or definite TIA, and \\'inappropriate\\' if the patient had an alternative diagnosis or stroke. Interobserver agreement between the referring physician and the neurologist was calculated. One hundred and four patients had completed ABCD referral proformas available for analysis. Forty-five (43%) were deemed appropriate, and 59 (57%) inappropriate. In the entire dataset, the neurologist agreed with the referring physician\\'s total ABCD score in only 42% of cases [kappa = 0.28]. The two most unreliable components of the scoring system were clinical features [kappa = 0.51], and duration of symptoms [kappa = 0.48]. ABCD scoring by non-stroke specialists is frequently inappropriate and inaccurate in routine clinical practice, emphasising the importance of urgent specialist assessment of suspected TIA patients.

Statistical limitations in functional neuroimaging. I. Non-inferential methods and statistical models.

Science.gov (United States)

Petersson, K M; Nichols, T E; Poline, J B; Holmes, A P

1999-01-01

Functional neuroimaging (FNI) provides experimental access to the intact living brain making it possible to study higher cognitive functions in humans. In this review and in a companion paper in this issue, we discuss some common methods used to analyse FNI data. The emphasis in both papers is on assumptions and limitations of the methods reviewed. There are several methods available to analyse FNI data indicating that none is optimal for all purposes. In order to make optimal use of the methods available it is important to know the limits of applicability. For the interpretation of FNI results it is also important to take into account the assumptions, approximations and inherent limitations of the methods used. This paper gives a brief overview over some non-inferential descriptive methods and common statistical models used in FNI. Issues relating to the complex problem of model selection are discussed. In general, proper model selection is a necessary prerequisite for the validity of the subsequent statistical inference. The non-inferential section describes methods that, combined with inspection of parameter estimates and other simple measures, can aid in the process of model selection and verification of assumptions. The section on statistical models covers approaches to global normalization and some aspects of univariate, multivariate, and Bayesian models. Finally, approaches to functional connectivity and effective connectivity are discussed. In the companion paper we review issues related to signal detection and statistical inference. PMID:10466149

Critical statistics for non-Hermitian matrices

International Nuclear Information System (INIS)

Garcia-Garcia, A.M.; Verbaarschot, J.J.M.; Nishigaki, S.M.

2002-01-01

We introduce a generalized ensemble of non-Hermitian matrices interpolating between the Gaussian Unitary Ensemble, the Ginibre ensemble, and the Poisson ensemble. The joint eigenvalue distribution of this model is obtained by means of an extension of the Itzykson-Zuber formula to general complex matrices. Its correlation functions are studied both in the case of weak non-Hermiticity and in the case of strong non-Hermiticity. In the weak non-Hermiticity limit we show that the spectral correlations in the bulk of the spectrum display critical statistics: the asymptotic linear behavior of the number variance is already approached for energy differences of the order of the eigenvalue spacing. To lowest order, its slope does not depend on the degree of non-Hermiticity. Close the edge, the spectral correlations are similar to the Hermitian case. In the strong non-Hermiticity limit the crossover behavior from the Ginibre ensemble to the Poisson ensemble first appears close to the surface of the spectrum. Our model may be relevant for the description of the spectral correlations of an open disordered system close to an Anderson transition

Burden of stroke in Cambodia.

Science.gov (United States)

Loo, Keat Wei; Gan, Siew Hua

2013-08-01

In Cambodia, stroke is not ranked among the top 10 leading causes of death, but infectious disease are among the top three leading causes of death. This finding could be attributed to a lack of awareness among Cambodians of the signs and symptoms of stroke or to poor reporting, incomplete data, lack of neurologists and neurosurgeons, or low accessibility to the hospitals. The only study of stroke in Cambodia is the Prevalence of Non-Communicable Disease Risk Factors in Cambodia survey, which identified several stroke-related risk factors in the population. Tobacco chewing or smoking is the main risk factor for stroke in Cambodia. Traditional therapies, such as oyt pleung (moxibustion) and jup (cupping), are widely practiced for stroke rehabilitation. In Cambodia, there are few neurologists and few important equipment, such as magnetic resonance imaging machines and computed tomography scanners. The Cambodian government should cooperate with the World Health Organization and the United Nations Children's Fund to attract foreign expertise and technologies to treat stroke patients. © 2012 The Authors. International Journal of Stroke © 2012 World Stroke Organization.

Non-Invasive Brain Stimulation to Enhance Post-Stroke Recovery.

Science.gov (United States)

Kubis, Nathalie

2016-01-01

Brain plasticity after stroke remains poorly understood. Patients may improve spontaneously within the first 3 months and then more slowly in the coming year. The first day, decreased edema and reperfusion of the ischemic penumbra may possibly account for these phenomena, but the improvement during the next weeks suggests plasticity phenomena and cortical reorganization of the brain ischemic areas and of more remote areas. Indeed, the injured ischemic motor cortex has a reduced cortical excitability at the acute phase and a suspension of the topographic representation of affected muscles, whereas the contralateral motor cortex has an increased excitability and an enlarged somatomotor representation; furthermore, contralateral cortex exerts a transcallosal interhemispheric inhibition on the ischemic cortex. This results from the imbalance of the physiological reciprocal interhemispheric inhibition of each hemisphere on the other, contributing to worsening of neurological deficit. Cortical excitability is measurable through transcranial magnetic stimulation (TMS) and prognosis has been established according to the presence of motor evoked potentials (MEP) at the acute phase of stroke, which is predictive of better recovery. Conversely, the lack of response to early stimulation is associated with a poor functional outcome. Non-invasive stimulation techniques such as repetitive TMS (rTMS) or transcranial direct current stimulation (tDCS) have the potential to modulate brain cortical excitability with long lasting effects. In the setting of cerebrovascular disease, around 1000 stroke subjects have been included in placebo-controlled trials so far, most often with an objective of promoting motor recovery of the upper limb. High frequency repetitive stimulation (>3 Hz) rTMS, aiming to increase excitability of the ischemic cortex, or low frequency repetitive stimulation (≤1 Hz), aiming to reduce excitability of the contralateral homonymous cortex, or combined therapies

Non invasive brain stimulation to enhance post-stroke recovery

Directory of Open Access Journals (Sweden)

Nathalie Kubis

2016-07-01

Full Text Available Brain plasticity after stroke remains poorly understood. Patients may improve spontaneously within the first 3 months and then more slowly in the coming year. The first days, decreased edema and reperfusion of the ischemic penumbra may possibly account for these phenomena, but the improvement during the next weeks suggests plasticity phenomena and cortical reorganization of the brain ischemic areas and of more remote areas. Indeed, the injured ischemic motor cortex has a reduced cortical excitability at the acute phase and a suspension of the topographic representation of affected muscles, whereas the contralateral motor cortex has an increased excitability and an enlarged somatomotor representation; furthermore, contralateral cortex exerts a transcallosal interhemispheric inhibition on the ischemic cortex. This results from the imbalance of the physiological reciprocal interhemispheric inhibition of each hemisphere on the other, contributing to worsening of neurological deficit. Cortical excitability is measurable through transcranial magnetic stimulation (TMS and prognosis has been established according to the presence of motor evoked potentials (MEP at the acute phase of stroke, which is predictive of better recovery. Conversely, the lack of response to early stimulation is associated with a poor functional outcome. Non-invasive stimulation techniques such as repetitive TMS (rTMS or transcranial direct current stimulation (tDCS have the potential to modulate brain cortical excitability with long lasting effects. In the setting of cerebrovascular disease, around 1000 stroke subjects have been included in placebo-controlled trials so far, most often with an objective of promoting motor recovery of the upper limb. High frequency repetitive stimulation (> 3 Hz rTMS, aiming to increase excitability of the ischemic cortex, or low frequency repetitive stimulation (≤ 1 Hz, aiming to reduce excitability of the contralateral homonymous cortex, or

Returning to paid employment after stroke: the Psychosocial Outcomes In StrokE (POISE cohort study.

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Maree L Hackett

Full Text Available OBJECTIVES: To determine which early modifiable factors are associated with younger stroke survivors' ability to return to paid work in a cohort study with 12-months of follow-up conducted in 20 stroke units in the Stroke Services NSW clinical network. PARTICIPANTS: Were aged >17 and <65 years, recent (within 28 days stroke, able to speak English sufficiently to respond to study questions, and able to provide written informed consent. Participants with language or cognitive impairment were eligible to participate if their proxy provided consent and completed assessments on the participants' behalf. The main outcome measure was return to paid work during the 12 months following stroke. RESULTS: Of 441 consented participants (average age 52 years, 68% male, 83% with ischemic stroke, 218 were in paid full-time and 53 in paid part-time work immediately before their stroke, of whom 202 (75% returned to paid part- or full-time work within 12 months. Being male, female without a prior activity restricting illness, younger, independent in activities of daily living (ADL at 28 days after stroke, and having private health insurance was associated with return to paid work, following adjustment for other illnesses and a history of depression before stroke (C statistic 0·81. Work stress and post stroke depression showed no such independent association. CONCLUSIONS: Given that independence in ADL is the strongest predictor of return to paid work within 12 months of stroke, these data reinforce the importance of reducing stroke-related disability and increasing independence for younger stroke survivors. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry ANZCTRN 12608000459325.

Long-Term Effect of Participation in an Early Exercise and Education Program on Clinical Outcomes and Cost Implications, in Patients with TIA and Minor, Non-Disabling Stroke.

Science.gov (United States)

Faulkner, James; Stoner, Lee; Lanford, Jeremy; Jolliffe, Evan; Mitchelmore, Andrew; Lambrick, Danielle

2017-06-01

Participation in exercise and education programs following transient ischemic attack (TIA) or minor stroke may decrease cardiovascular disease risk. The purpose of this study was to assess the long-term effect (3.5 years) of an exercise and education program administered soon after TIA or minor stroke diagnosis on clinical outcome measures (stroke classification and number, patient deaths, hospital/emergency department admission) and cost implications obtained from standard hospital records. Hospital records were screened for 60 adults (male, n = 31; 71 ± 10 years), diagnosed with TIA or non-disabling stroke, who had previously been randomised and completed either an 8-week exercise and education program, or usual care control. Follow-up clinical outcomes and cost implications were obtained 3.5 ± 0.3 years post-exercise. Participants randomised to the exercise and education program had significantly fewer recurrent stroke/TIAs (n = 3 vs. n = 13, Cohen's d = 0.79) than the control group (P ≤ 0.003). Similar finding were reported for patient deaths (n = 0 vs. n = 4, d = 0.53), and hospital admissions (n = 48 vs. n = 102, d = 0.54), although these findings were only approaching statistical significance. The relative risk (mean; 95%CI) of death, stroke/TIAs and hospital admissions were 0.11 (0.01 to 1.98), 0.23 (0.07 to 0.72) and 0.79 (0.57 to 1.09), respectively. Hospital admission costs were significantly lower for the exercise group ($9041 ± 15,080 NZD [~$6000 ± 10,000 USD]) than the control group ($21,750 ± 22,973 NZD [~$14,000 ± 15,000 USD]) during the follow-up period (P TIA and minor stroke. URL: http://www.anzctr.org.au/ ; Trial Registration Number: ACTRN12611000630910.

A Statistical Analysis of Cryptocurrencies

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Stephen Chan

2017-05-01

Full Text Available We analyze statistical properties of the largest cryptocurrencies (determined by market capitalization, of which Bitcoin is the most prominent example. We characterize their exchange rates versus the U.S. Dollar by fitting parametric distributions to them. It is shown that returns are clearly non-normal, however, no single distribution fits well jointly to all the cryptocurrencies analysed. We find that for the most popular currencies, such as Bitcoin and Litecoin, the generalized hyperbolic distribution gives the best fit, while for the smaller cryptocurrencies the normal inverse Gaussian distribution, generalized t distribution, and Laplace distribution give good fits. The results are important for investment and risk management purposes.

Altered glucose metabolism in juvenile myoclonic epilepsy: a PET study with statistical parametric mapping

International Nuclear Information System (INIS)

Lim, G. C.; Kim, J. H.; Kang, J. G.; Kim, J. S.; Yeo, J. S.; Lee, S. A.; Moon, D. H

2004-01-01

Juvenile myoclonic epilepsy (JME) is a hereditary, age-dependent epilepsy syndrome, characterized by myoclonic jerks on awakening and generalized tonic-clonic seizures. Although there have been considerable studies on the mechanism to elucidate pathogenesis of JME, the accurate pathogenesis of JME remains obscure. The aim of this study was to investigate alterations of cerebral glucose metabolism in patients with JME. We studied 16 JME patients (Mean age: 22 yrs, M/F: 9/7) with brain FDG-PET and simultaneous EEG recording. On the basis of the number of generalized spike-and-wave (GSW) discharges on the 30 min EEG recording after the injection of FDG (370MBq), we classified patients into two groups (patients in group A had 10 or more GSW and group B. 9 or less). We applied the automated and objective technique of statistical parametric mapping (SPM) to the analysis of FDG-PET to determine the significant hyper- and hypometabolic regions compared with those of 19 age matched normal control subjects. We found significant hypermetabolic regions in bilateral thalamus and central portion of upper brainstem in 16 patients with JME at a statistical threshold of uncorrected P < 0.05. These changes were also shown in group A (n=8), but not in group B (n=8). Additionally, we found significant hypometabolism in bilateral, widespread cortical regions in 16 patients with JME at a threshold of uncorrected P < 0.01. Similar hypometabolic patterns were also observed in both group A and group B, being more prominent in group A. This study provides evidence for the key role of the thalamus and brainstem reticular activating system in generating spontaneous GSW discharge, which is considered as a fundamental pathogenesis underlying JME. This study also suggests that patients with JME might suffer from subtle abnormalities of cognitive and executive cortical functions

Altered glucose metabolism in juvenile myoclonic epilepsy: a PET study with statistical parametric mapping

Energy Technology Data Exchange (ETDEWEB)

Lim, G. C.; Kim, J. H.; Kang, J. G.; Kim, J. S.; Yeo, J. S.; Lee, S. A.; Moon, D. H [Asan Medical Center, Seoul (Korea, Republic of)

2004-07-01

Juvenile myoclonic epilepsy (JME) is a hereditary, age-dependent epilepsy syndrome, characterized by myoclonic jerks on awakening and generalized tonic-clonic seizures. Although there have been considerable studies on the mechanism to elucidate pathogenesis of JME, the accurate pathogenesis of JME remains obscure. The aim of this study was to investigate alterations of cerebral glucose metabolism in patients with JME. We studied 16 JME patients (Mean age: 22 yrs, M/F: 9/7) with brain FDG-PET and simultaneous EEG recording. On the basis of the number of generalized spike-and-wave (GSW) discharges on the 30 min EEG recording after the injection of FDG (370MBq), we classified patients into two groups (patients in group A had 10 or more GSW and group B. 9 or less). We applied the automated and objective technique of statistical parametric mapping (SPM) to the analysis of FDG-PET to determine the significant hyper- and hypometabolic regions compared with those of 19 age matched normal control subjects. We found significant hypermetabolic regions in bilateral thalamus and central portion of upper brainstem in 16 patients with JME at a statistical threshold of uncorrected P < 0.05. These changes were also shown in group A (n=8), but not in group B (n=8). Additionally, we found significant hypometabolism in bilateral, widespread cortical regions in 16 patients with JME at a threshold of uncorrected P < 0.01. Similar hypometabolic patterns were also observed in both group A and group B, being more prominent in group A. This study provides evidence for the key role of the thalamus and brainstem reticular activating system in generating spontaneous GSW discharge, which is considered as a fundamental pathogenesis underlying JME. This study also suggests that patients with JME might suffer from subtle abnormalities of cognitive and executive cortical functions.

The Stroke Assessment of Fall Risk (SAFR): predictive validity in inpatient stroke rehabilitation

Science.gov (United States)

Breisinger, Terry P; Skidmore, Elizabeth R; Niyonkuru, Christian; Terhorst, Lauren; Campbell, Grace B

2014-01-01

Objective To evaluate relative accuracy of a newly developed Stroke Assessment of Fall Risk (SAFR) for classifying fallers and non-fallers, compared with a health system fall risk screening tool, the Fall Harm Risk Screen. Design and setting Prospective quality improvement study conducted at an inpatient stroke rehabilitation unit at a large urban university hospital. Participants Patients admitted for inpatient stroke rehabilitation (N = 419) with imaging or clinical evidence of ischemic or hemorrhagic stroke, between 1 August 2009 and 31 July 2010. Interventions Not applicable. Main outcome measure(s) Sensitivity, specificity, and area under the curve for Receiver Operating Characteristic Curves of both scales’ classifications, based on fall risk score completed upon admission to inpatient stroke rehabilitation. Results A total of 68 (16%) participants fell at least once. The SAFR was significantly more accurate than the Fall Harm Risk Screen (p stroke rehabilitation patients. While the SAFR improves upon the accuracy of a general assessment tool, additional refinement may be warranted. PMID:24849795

Socioeconomic Status and Stroke Prevalence in Morocco: Results from the Rabat-Casablanca Study

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Engels, Thomas; Baglione, Quentin; Audibert, Martine; Viallefont, Anne; Mourji, Fouzi; El Alaoui Faris, Mustapha

2014-01-01

Background Stroke is a growing public health concern in low- and middle- income countries. Improved knowledge about the association between socioeconomic status and stroke in these countries would enable the development of effective stroke prevention and management strategies. This study presents the association between socioeconomic status and the prevalence of stroke in Morocco, a lower middle-income country. Methods Data on the prevalence of stroke and stroke-related risk factors were collected during a large population-based survey. The diagnosis of stroke in surviving patients was confirmed by neurologists while health, demographic, and socioeconomic characteristics of households were collected using structured questionnaires. We used Multiple Correspondence Analysis to develop a wealth index based on characteristics of the household dwelling as well as ownership of selected assets. We used logistic regressions controlling for multiple variables to assess the statistical association between socioeconomic status and stroke. Findings Our results showed a significant association between household socioeconomic status and the prevalence of stroke. This relationship was non-linear, with individuals from both the poorest (mainly rural) and richest (mainly urban) households having a lower prevalence of stroke as compared to individuals with medium wealth level. The latter belonged mainly to urban households with a lower socioeconomic status. When taking into account the urban population only, we observed that a third of poorest households experienced a significantly higher prevalence of stroke compared to the richest third (OR = 2.06; CI 95%: 1.09; 3.89). Conclusion We conclude that individuals from the most deprived urban households bear a higher risk of stroke than the rest of the population in Morocco. This result can be explained to a certain extent by the higher presence of behavioral risk factors in this specific category of the population, which leads in

Socioeconomic status and stroke prevalence in Morocco: results from the Rabat-Casablanca study.

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Thomas Engels

Full Text Available BACKGROUND: Stroke is a growing public health concern in low- and middle- income countries. Improved knowledge about the association between socioeconomic status and stroke in these countries would enable the development of effective stroke prevention and management strategies. This study presents the association between socioeconomic status and the prevalence of stroke in Morocco, a lower middle-income country. METHODS: Data on the prevalence of stroke and stroke-related risk factors were collected during a large population-based survey. The diagnosis of stroke in surviving patients was confirmed by neurologists while health, demographic, and socioeconomic characteristics of households were collected using structured questionnaires. We used Multiple Correspondence Analysis to develop a wealth index based on characteristics of the household dwelling as well as ownership of selected assets. We used logistic regressions controlling for multiple variables to assess the statistical association between socioeconomic status and stroke. FINDINGS: Our results showed a significant association between household socioeconomic status and the prevalence of stroke. This relationship was non-linear, with individuals from both the poorest (mainly rural and richest (mainly urban households having a lower prevalence of stroke as compared to individuals with medium wealth level. The latter belonged mainly to urban households with a lower socioeconomic status. When taking into account the urban population only, we observed that a third of poorest households experienced a significantly higher prevalence of stroke compared to the richest third (OR = 2.06; CI 95%: 1.09; 3.89. CONCLUSION: We conclude that individuals from the most deprived urban households bear a higher risk of stroke than the rest of the population in Morocco. This result can be explained to a certain extent by the higher presence of behavioral risk factors in this specific category of the population

Does novel oral anticoagulant improve anticoagulation for non-valvular atrial fibrillation associated stroke: An inpatient registration study in Shanghai

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Feng-Di Liu

2015-12-01

Full Text Available Abstracts: Objective: To summarize the use rate, safety, efficacy of antithrombotics in stroke/transient ischemic attack (TIA prevention, and reasons for not using dabigatran etexilate (DE in Shanghai, China. Methods: Non-valvular atrial fibrillation (NVAF-associated stroke patients were prospectively registered as an electronic database. Use rate of antithrombotics and reasons for not using DE were extracted during follow-up. Patients' baseline characteristics, recurrent ischemic stroke/TIA events and bleeding complications were analyzed. Patients: From April 2012 to August 2014, 110 inpatients with NVAF-associated stroke were studied in our hospital. NVAF was diagnosed by 12-lead electrocardiogram, 24 h Holter and echocardiography. Results: Before introduction of DE (April 2013, use rates of warfarin and antiplatelets were 28.9% (11/38 and 60.5% (23/38 respectively; after that, use rates of warfarin, DE, and antiplatelets were 20.8% (15/72, 12.5% (9/72, and 43.1% (31/72. The DE did not improve use of anticoagulants (P = 0.639. There were 19 (17.3% recurrent ischemic stroke events up to October 2015; two (9.5% in the non-user group, 10 (18.5% in the antiplatelet group, and seven (20.0% in the anticoagulants group (P = 0.570. Furthermore, recurrence rates were similar between the DE group (20.0% and the Warfarin group (20.0%, P = 1.000. The most common reason for not using DE was financial concerns (61.0%, followed by inconvenience to purchase (14.0% and hemorrhage concerns (11.0%. Two patients using warfarin found fecal occult blood so they stopped warfarin and began to use antiplatelet drugs. No bleeding event occurred in the other groups. Only one patient had side effects (dyspepsia and gastroesophageal reflux from DE. Conclusion: The use rate of either DE or warfarin in Shanghai was low; DE had not improved anticoagulation therapy for NVAF patients in Shanghai mainly because DE had not been covered by health insurance. Keywords

Stroke rehabilitation: recent advances and future therapies.

LENUS (Irish Health Repository)

Brewer, L

2012-09-27

Despite advances in the acute management of stroke, a large proportion of stroke patients are left with significant impairments. Over the coming decades the prevalence of stroke-related disability is expected to increase worldwide and this will impact greatly on families, healthcare systems and economies. Effective neuro-rehabilitation is a key factor in reducing disability after stroke. In this review, we discuss the effects of stroke, principles of stroke rehabilitative care and predictors of recovery. We also discuss novel therapies in stroke rehabilitation, including non-invasive brain stimulation, robotics and pharmacological augmentation. Many trials are currently underway, which, in time, may impact on future rehabilitative practice.

Pre-operative Carotid Plaque Echolucency Assessment has no Predictive Value for Long-Term Risk of Stroke or Cardiovascular Death in Patients Undergoing Carotid Endarterectomy.

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de Waard, D; de Borst, G J; Bulbulia, R; Pan, H; Halliday, A

2017-08-01

In patients with carotid stenosis receiving medical treatment, carotid plaque echolucency has been thought to predict risk of future stroke and of other cardiovascular events. This study evaluated the prognostic value of pre-operative plaque echolucency for future stroke and cardiovascular death in patients undergoing carotid endarterectomy in the first Asymptomatic Carotid Surgery Trial (ACST-1). In ACST-1, 1832/3120 patients underwent carotid endarterectomy (CEA), of whom 894 had visual echolucency assessment according to the Gray-Weale classification. During follow-up patients were monitored both for peri-procedural (i.e. within 30 days) death, stroke, or MI, and for long-term risk of stroke or cardiovascular death. Unconditional maximum likelihood estimation was used to calculate odds ratios of peri-procedural risk and Kaplan-Meier statistics with log-rank test were used to compare cumulative long-term risks. Of 894 operated patients in whom echolucency was assessed, 458 plaques (51%) were rated as echolucent and peri-procedural risk of death/stroke/MI in these patients was non-significantly higher when compared with patients with non-echolucent plaques (OR 1.48 [95% CI 0.76-2.88], p = .241). No differences were found in the 10 year risk of any stroke (30/447 [11.6%] vs. 29/433 [11.0%], p = .900) or cardiovascular (non-stroke) death (85/447 [27.9%] vs. 93/433 [32.1%], p = .301). In ACST-1, carotid plaque echolucency assessment in patients undergoing CEA offered no predictive value with regard to peri-operative or long-term stroke risk or of cardiovascular (non-stroke) death. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

SPECT image analysis using statistical parametric mapping in patients with temporal lobe epilepsy associated with hippocampal sclerosis

International Nuclear Information System (INIS)

Shiraki, Junko

2004-01-01

The author examined interictal 123 I-IMP SPECT images using statistical parametric mapping (SPM) in 19 temporal lobe epilepsy patients who revealed hippocampal sclerosis with MRI. Decreased regional cerebral blood flow (rCBF) were shown for eight patients in the medial temporal lobe, six patients in the lateral temporal lobe and five patients in the both medial and lateral temporal lobe. These patients were classified into two types; medial type and lateral type, the former decreased rCBF only in medial and the latter decreased rCBF in the other temporal area. Correlation of rCBF and clinical parameters in the lateral type, age at seizure onset was significantly older (p=0.0098, t-test) than those of patients in the medial type. SPM analysis for interictal SPECT of temporal lobe epilepsy clarified location of decreased rCBF and find correlations with clinical characteristics. In addition, SPM analysis of SPECT was useful to understand pathophysiology of the epilepsy. (author)

Data and Statistics: Heart Failure

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... Summary Coverdell Program 2012-2015 State Summaries Data & Statistics Fact Sheets Heart Disease and Stroke Fact Sheets ... Roadmap for State Planning Other Data Resources Other Statistic Resources Grantee Information Cross-Program Information Online Tools ...

Lifetime health effects and medical costs of integrated stroke services - a non-randomized controlled cluster-trial based life table approach

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Dirks Maaike

2010-11-01

Full Text Available Abstract Background Economic evaluation of stroke services indicates that such services may lead to improved quality of life at affordable cost. The present study assesses lifetime health impact and cost consequences of stroke in an integrated service setting. Methods The EDISSE study is a prospective non-randomized controlled cluster trial that compared stroke services (n = 151 patients to usual care (n = 187 patients. Health status and cost trial-data were entered in multi-dimensional stroke life-tables. The tables distinguish four levels of disability which are defined by the modified Rankin scale. Quality-of-life scores (EuroQoL-5D, transition and survival probabilities are based on concurrent Dutch follow-up studies. Outcomes are quality-adjusted life years lived and lifetime medical cost by disability category. An economic analysis compares outcomes from a successful stroke service to usual care, by bootstrapping individual costs and effects data from patients in each arm. Results Lifetime costs and QALYs after stroke depend on age-of-onset of first-ever stroke. Lifetime QALYs after stroke are 2.42 (90% CI - 0.49 - 2.75 for male patients in usual care and 2.75 (-0.61; 6.26 for females. Lifetime costs for men in the usual care setting are €39,335 (15,951; 79,837 and €42,944 (14,081; 95,944 for women. A comparison with the stroke service results in an ICER of €11,685 saved per QALY gained (€14,211 and €7,745 for men and women respectively. This stroke service is with 90% certainty cost-effective. Conclusions Our analysis shows the potential of large health benefits and cost savings of stroke services, taking a lifetime perspective, also in other European settings.

The Association Between Chlamydia pneumoniae Infection and Ischemic Stroke

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Eini

2014-10-01

Full Text Available Background Chlamydia pneumoniae has been linked with increased risk of cardiovascular diseases; however, data on stroke and cerebrovascular accidents are sparse. Objectives The aim of this study was to determine the association between C. pneumoniae infection and ischemic stroke. Patients and Methods In a case-control study, 141 patients, admitted with ischemic stroke, were compared with gender and age-matched control subjects (n = 141. Using an enzyme-linked immunosorbent assay kit, the presence of C. pneumoniae IgG and IgA in the patients’ sera was determined. The data were analyzed by SPSS software (version 15 and were compared between the two groups using T-test and chi square test. Results The mean ages of the case and control groups were 68.97 ± 12.29 and 66.95 ± 6.68 years old, respectively. The difference between these two groups was not statistically significant (P = 0.102. The seroprevalence of C. pneumoniae-specific IgG were 78.7% in the patients with stroke and 52.5% in the control group. The difference between the two groups was statistically significant (P = 0.0001. The seroprevalence of C. pneumoniae-specific IgA were 41.1% in the stroke and 15.6% in the control group. The difference between the two groups was statistically significant (P = 0.0001. Conclusions The results supported the hypothesis that serological evidence of C. pneumoniae infection may be associated with an increased risk of ischemic stroke and cerebrovascular accident.

Acute ischaemic stroke prediction from physiological time series patterns

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Qing Zhang,

2013-05-01

Full Text Available BackgroundStroke is one of the major diseases with human mortality. Recent clinical research has indicated that early changes in common physiological variables represent a potential therapeutic target, thus the manipulation of these variables may eventually yield an effective way to optimise stroke recovery.AimsWe examined correlations between physiological parameters of patients during the first 48 hours after a stroke, and their stroke outcomes after 3 months. We wanted to discover physiological determinants that could be used to improve health outcomes by supporting the medical decisions that need to be made early on a patient’s stroke experience.Method We applied regression-based machine learning techniques to build a prediction algorithm that can forecast 3-month outcomes from initial physiological time series data during the first 48 hours after stroke. In our method, not only did we use statistical characteristics as traditional prediction features, but also we adopted trend patterns of time series data as new key features.ResultsWe tested our prediction method on a real physiological data set of stroke patients. The experiment results revealed an average high precision rate: 90%. We also tested prediction methods only considering statistical characteristics of physiological data, and concluded an average precision rate: 71%.ConclusionWe demonstrated that using trend pattern features in prediction methods improved the accuracy of stroke outcome prediction. Therefore, trend patterns of physiological time series data have an important role in the early treatment of patients with acute ischaemic stroke.

On two methods of statistical image analysis

NARCIS (Netherlands)

Missimer, J; Knorr, U; Maguire, RP; Herzog, H; Seitz, RJ; Tellman, L; Leenders, K.L.

1999-01-01

The computerized brain atlas (CBA) and statistical parametric mapping (SPM) are two procedures for voxel-based statistical evaluation of PET activation studies. Each includes spatial standardization of image volumes, computation of a statistic, and evaluation of its significance. In addition,

Portuguese Observational Study of Ischaemic Stroke in Patients Medicated with Non-Vitamin K Antagonist Oral Anticoagulants.

Science.gov (United States)

Beato-Coelho, José; Marto, João Pedro; Alves, José Nuno; Marques-Matos, Cláudia; Calado, Sofia; Araújo, José; Cunha, Luís; Pinho, João; Azevedo, Elsa; Viana-Baptista, Miguel; Sargento-Freitas, João

2018-01-01

Clinical trials and subsequent meta-analyses showed advantages of non-vitamin K antagonists oral anticoagulants (NOACs) over vitamin K antagonists (VKAs) in patients with non-valvular atrial fibrillation. The impact of preadmission anticoagulation in acute ischaemic stroke (AIS) has not been established. To compare functional outcome of patients with AIS with preadmission NOACs vs. VKAs. A retrospective analysis was conducted on consecutive AIS patients under oral anticoagulation (VKAs or NOACs) admitted in 4 Portuguese hospitals within a period of 30 months. Two primary outcomes were defined and compared between VKA and NOAC groups: symptomatic intracerebral hemorrhage transformation (sICH) and modified Rankin Scale (mRS) at 3 months. Four hundred sixty-nine patients were included, of whom 332 (70.8%) were treated with VKA and 137 (29.2%) with NOAC. Patients' median age was 78.0 and 234 (49.9%) were male. NOAC-treated patients had a higher median CHA2DS2-VASc score than those under VKA (5.0 vs. 4.0, p = 0.023). The two primary outcomes showed no statistical differences between the VKAs' group and the NOACs' group (sICH: 5.4 vs. 5.4% [p = 0.911]; mRS at 3 months: 3.0 vs. 3.0 [p = 0.646], respectively). Preadmission anticoagulation with NOACs in AIS has a functional impact similar to that of VKAs. © 2018 S. Karger AG, Basel.

Parametric statistical change point analysis

CERN Document Server

Chen, Jie

2000-01-01

This work is an in-depth study of the change point problem from a general point of view and a further examination of change point analysis of the most commonly used statistical models Change point problems are encountered in such disciplines as economics, finance, medicine, psychology, signal processing, and geology, to mention only several The exposition is clear and systematic, with a great deal of introductory material included Different models are presented in each chapter, including gamma and exponential models, rarely examined thus far in the literature Other models covered in detail are the multivariate normal, univariate normal, regression, and discrete models Extensive examples throughout the text emphasize key concepts and different methodologies are used, namely the likelihood ratio criterion, and the Bayesian and information criterion approaches A comprehensive bibliography and two indices complete the study

Comparing a diffusion tensor and non-tensor approach to white matter fiber tractography in chronic stroke.

Science.gov (United States)

Auriat, A M; Borich, M R; Snow, N J; Wadden, K P; Boyd, L A

2015-01-01

not DTI. CSD identified ipsilesional CST pathways in 9 stroke participants who did not have tracts identified with DTI. Additionally, CSD differentiated between stroke ipsilesional and healthy control non-dominant CST for several measures (number of tracts, tract volume, FA, ADC, and RD) whereas DTI only detected group differences for number of tracts. In the stroke group, motor behavior correlated with fewer diffusion metrics derived from the DTI as compared to CSD-reconstructed ipsilesional CST and CC. CSD is superior to DTI-based tractography in detecting differences in diffusion characteristics between the nondominant healthy control and ipsilesional CST. CSD measures of microstructure tissue properties related to more motor outcomes than DTI measures did. Our results suggest the potential utility and functional relevance of characterizing complex fiber organization using tensor-free diffusion modeling approaches to investigate white matter pathways in the brain after stroke.

Comparing a diffusion tensor and non-tensor approach to white matter fiber tractography in chronic stroke

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A.M. Auriat

2015-01-01

using CSD but not DTI. CSD identified ipsilesional CST pathways in 9 stroke participants who did not have tracts identified with DTI. Additionally, CSD differentiated between stroke ipsilesional and healthy control non-dominant CST for several measures (number of tracts, tract volume, FA, ADC, and RD whereas DTI only detected group differences for number of tracts. In the stroke group, motor behavior correlated with fewer diffusion metrics derived from the DTI as compared to CSD-reconstructed ipsilesional CST and CC. CSD is superior to DTI-based tractography in detecting differences in diffusion characteristics between the nondominant healthy control and ipsilesional CST. CSD measures of microstructure tissue properties related to more motor outcomes than DTI measures did. Our results suggest the potential utility and functional relevance of characterizing complex fiber organization using tensor-free diffusion modeling approaches to investigate white matter pathways in the brain after stroke.

Stroke due to non-bacterial thrombotic endocarditis as initial presentation of breast invasive ductal carcinoma.

Science.gov (United States)

Detremerie, Celine; Timmermans, Frank; De Pauw, Michel; Gheeraert, Peter; Hemelsoet, Dimitri; Toeback, Jonas; Bové, Thierry; Vandecasteele, Els

2017-08-01

We present a case of a 71-year-old woman with recurrent stroke episodes due to non-bacterial thrombotic endocarditis (NBTE) leading to the diagnosis of an early-stage breast carcinoma. NBTE is associated with a variety of inflammatory states, including malignancy. NBTE presents itself with systemic embolization, mostly stroke. Treatment consists of treating the underlying condition and start of systemic anticoagulation therapy. Cardiac surgery is restricted to highly selected cases, since prognosis usually is limited by the neoplasm, which usually is in an advanced stage at time of diagnosis of NBTE. The malignancy usually is diagnosed prior to NBTE. Cases presenting with NBTE leading to the diagnosis of malignancy, however, are rarely reported. To our knowledge, we present the first case leading to the diagnosis of an early-stage breast carcinoma.

A Novel Parametric Model For The Human Respiratory System

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Clara Mihaela IONESCU

2003-12-01

Full Text Available The purpose of this work is to present some recent results in an ongoing research project between Ghent University and Chess Medical Technology Company Belgium. The overall aim of the project is to provide a fast method for identification of the human respiratory system in order to allow for an instantaneously diagnosis of the patient by the medical staff. A novel parametric model of the human respiratory system as well as the obtained experimental results is presented in this paper. A prototype apparatus developed by the company, based on the forced oscillation technique is used to record experimental data from 4 patients in this paper. Signal processing is based on spectral analysis and is followed by the parametric identification of a non-linear mechanistic model. The parametric model is equivalent to the structure of a simple electrical RLC-circuit, containing a non-linear capacitor. These parameters have a useful and easy-to-interpret physical meaning for the medical staff members.

Cognitive performance after ischaemic stroke

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Maria Gabriela R. Ferreira

Full Text Available Cognitive impairment after stroke affects the patient recovery process. Therefore, the identification of factors associated with cognitive outcomes is important since it allows risk profiles of stroke survivors to be determined. OBJECTIVE: To assess cognitive outcome of stroke outpatients and investigate associations among clinical and demographic variables, vascular risk factors, depression symptoms and functional ability; and to describe the neuropsychological profile of these patients. METHODS: A cross-sectional design study was conducted. Subjects who suffered a first-ever ischaemic stroke 6 to 10 months prior to data collection underwent neuropsychological assessment and screening for depressive symptoms and functional ability. The outcome "cognitive performance" was analyzed considering two groups: "cognitive impairment" and "no cognitive impairment". RESULTS: There was a statistically significant association between cognitive impairment and female gender, age, stroke severity and functional ability. Regarding neuropsychological profile, the cognitive impairment group exhibited more generalized deficits in attention, visuospatial organization, verbal functions and verbal memory domains compared to the community control group. CONCLUSION: The occurrence of cognitive impairment among patients was high, especially in women, older participants, individuals with more severe stroke, and greater impairment in functional ability. Multiple cognitive domains are affected and this may hamper recovery and negatively impact independence and quality of life after stroke.

Influenza vaccination and risk of stroke: Self-controlled case-series study.

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Asghar, Zahid; Coupland, Carol; Siriwardena, Niroshan

2015-10-05

Stroke may be triggered by respiratory infections, including influenza. Influenza vaccination could therefore reduce risk of stroke. Previous studies of this association have shown conflicting results. We aimed to investigate whether influenza vaccination was associated with reduced risk of stroke. We used a self-controlled case series design. The General Practice Research Database (GPRD) was used to extract records of patients aged 18 years or over recorded with stroke (fatal or non-fatal) from September 2001 to May 2009. Statistical modelling with conditional Poisson regression was employed to compute incidence rate ratios (IRR). The incidence rate of stroke in fixed time periods after influenza vaccination was compared with the incidence rate during a baseline period. There were 17,853 eligible individuals who received one or more influenza vaccinations and experienced a stroke during the observation period. The incidence of stroke was significantly reduced in the first 59 days following influenza vaccination compared with the baseline period. We found reductions of 55% (IRR 0.45; 95% CI 0.36-0.57) in the first 1-3 days after vaccination, 36% (0.64; 0.53-0.76) at 4-7 days, 30% (0.70; 0.61-0.79) at 8-14 days, 24% (0.76; 0.70-0.84) at 15-28 days and 17% (0.83; 0.77-0.89) at 29-59 days after vaccination. Early vaccination between 1 September and 15 November showed a greater reduction in IRR compared to later vaccination given after mid-November. Influenza vaccination is associated with a reduction in incidence of stroke. This study supports previous studies which have shown a beneficial association of influenza vaccination for stroke prevention. Copyright © 2015 Elsevier Ltd. All rights reserved.

A Non-Parametric Delphi Approach to Foster Innovation Policy Debate in Spain

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Juan Carlos Salazar-Elena

2016-05-01

Full Text Available The aim of this paper is to identify some changes needed in Spain’s innovation policy to fill the gap between its innovation results and those of other European countries in lieu of sustainable leadership. To do this we apply the Delphi methodology to experts from academia, business, and government. To overcome the shortcomings of traditional descriptive methods, we develop an inferential analysis by following a non-parametric bootstrap method which enables us to identify important changes that should be implemented. Particularly interesting is the support found for improving the interconnections among the relevant agents of the innovation system (instead of focusing exclusively in the provision of knowledge and technological inputs through R and D activities, or the support found for “soft” policy instruments aimed at providing a homogeneous framework to assess the innovation capabilities of firms (e.g., for funding purposes. Attention to potential innovators among small and medium enterprises (SMEs and traditional industries is particularly encouraged by experts.

Non-parametric adaptive importance sampling for the probability estimation of a launcher impact position

International Nuclear Information System (INIS)

Morio, Jerome

2011-01-01

Importance sampling (IS) is a useful simulation technique to estimate critical probability with a better accuracy than Monte Carlo methods. It consists in generating random weighted samples from an auxiliary distribution rather than the distribution of interest. The crucial part of this algorithm is the choice of an efficient auxiliary PDF that has to be able to simulate more rare random events. The optimisation of this auxiliary distribution is often in practice very difficult. In this article, we propose to approach the IS optimal auxiliary density with non-parametric adaptive importance sampling (NAIS). We apply this technique for the probability estimation of spatial launcher impact position since it has currently become a more and more important issue in the field of aeronautics.

Investigation of olfactory function in normal volunteers by Tc-99m ECD Brain SPECT: Analysis using statistical parametric mapping

International Nuclear Information System (INIS)

Chung, Y.A.; Kim, S.H.; Park, Y.H.; Lee, S.Y.; Sohn, H.S.; Chung, S.K.

2002-01-01

The purpose of this study was to investigate olfactory function according to Tc-99m ECD uptake pattern in brain perfusion SPET of normal volunteer by means of statistical parametric mapping (SPM) analysis. The study population was 8 healthy volunteer subjects (M:F = 6:2, age range: 22-54 years, mean 34 years). We performed baseline brain perfusion SPET using 555 MBq of Tc-99m ECD in a silent dark room. Two hours later, we obtained brain perfusion SPET using 1110 MBq of Tc-99m ECD after 3% butanol solution under the same condition. All SPET images were spatially transformed to standard space smoothed and globally normalized. The differences between the baseline and odor-identification SPET images were statistically analyzed using SPM-99 software. The difference between two sets of brain perfusion SPET was considered significant at a threshold of uncorrected p values less than 0.01. SPM analysis revealed significant hyper-perfusion in both cingulated gyri, right middle temporal gyrus, right superior and inferior frontal gyri, right lingual gyrus and right fusiform gyrus on odor-identification SPET. This study shows that brain perfusion SPET can securely support other diagnostic techniques in the evaluation of olfactory function

Short-term monitoring of benzene air concentration in an urban area: a preliminary study of application of Kruskal-Wallis non-parametric test to assess pollutant impact on global environment and indoor.

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Mura, Maria Chiara; De Felice, Marco; Morlino, Roberta; Fuselli, Sergio

2010-01-01

In step with the need to develop statistical procedures to manage small-size environmental samples, in this work we have used concentration values of benzene (C6H6), concurrently detected by seven outdoor and indoor monitoring stations over 12 000 minutes, in order to assess the representativeness of collected data and the impact of the pollutant on indoor environment. Clearly, the former issue is strictly connected to sampling-site geometry, which proves critical to correctly retrieving information from analysis of pollutants of sanitary interest. Therefore, according to current criteria for network-planning, single stations have been interpreted as nodes of a set of adjoining triangles; then, a) node pairs have been taken into account in order to estimate pollutant stationarity on triangle sides, as well as b) node triplets, to statistically associate data from air-monitoring with the corresponding territory area, and c) node sextuplets, to assess the impact probability of the outdoor pollutant on indoor environment for each area. Distributions from the various node combinations are all non-Gaussian, in the consequently, Kruskal-Wallis (KW) non-parametric statistics has been exploited to test variability on continuous density function from each pair, triplet and sextuplet. Results from the above-mentioned statistical analysis have shown randomness of site selection, which has not allowed a reliable generalization of monitoring data to the entire selected territory, except for a single "forced" case (70%); most important, they suggest a possible procedure to optimize network design.

Short-term monitoring of benzene air concentration in an urban area: a preliminary study of application of Kruskal-Wallis non-parametric test to assess pollutant impact on global environment and indoor

Directory of Open Access Journals (Sweden)

Maria Chiara Mura

2010-12-01

Full Text Available In step with the need to develop statistical procedures to manage small-size environmental samples, in this work we have used concentration values of benzene (C6H6, concurrently detected by seven outdoor and indoor monitoring stations over 12 000 minutes, in order to assess the representativeness of collected data and the impact of the pollutant on indoor environment. Clearly, the former issue is strictly connected to sampling-site geometry, which proves critical to correctly retrieving information from analysis of pollutants of sanitary interest. Therefore, according to current criteria for network-planning, single stations have been interpreted as nodes of a set of adjoining triangles; then, a node pairs have been taken into account in order to estimate pollutant stationarity on triangle sides, as well as b node triplets, to statistically associate data from air-monitoring with the corresponding territory area, and c node sextuplets, to assess the impact probability of the outdoor pollutant on indoor environment for each area. Distributions from the various node combinations are all non-Gaussian, in the consequently, Kruskal-Wallis (KW non-parametric statistics has been exploited to test variability on continuous density function from each pair, triplet and sextuplet. Results from the above-mentioned statistical analysis have shown randomness of site selection, which has not allowed a reliable generalization of monitoring data to the entire selected territory, except for a single "forced" case (70%; most important, they suggest a possible procedure to optimize network design.

Non-vitamin K oral anticoagulants are non-inferior for stroke prevention but cause fewer major bleedings than well-managed warfarin: A retrospective register study.

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Vilhelm Sjögren

Full Text Available For patients with atrial fibrillation, non-vitamin K oral anticoagulants, or NOACs (dabigatran, rivaroxaban, edoxaban, and apixaban have been proven non-inferior or superior to warfarin in preventing stroke and systemic embolism, and in risk of haemorrhage. In the pivotal NOAC studies, quality of warfarin treatment was poor with mean time in therapeutic range (TTR 55-65%, compared with ≥70% in Swedish clinical practice.We compared NOACs (as a group to warfarin in non-valvular atrial fibrillation, studying all 12,694 patients starting NOAC treatment within the Swedish clinical register and dosing system Auricula, from July 1, 2011 to December 31, 2014, and matching them to 36,317 patients starting warfarin using propensity scoring. Endpoints were thromboembolic events and major bleedings that were fatal or required hospital care. Outcome data were collected from validated Swedish hospital administrative and clinical registers.Mean age was 72.2 vs 72.3 years, proportion of males 58.2% vs 57.0%, and mean follow-up time 299 vs 283 days for NOACs and warfarin. Distribution of NOACs was: dabigatran 40.3%, rivaroxaban 31.2%, and apixaban 28.5%. Mean TTR was 70%. There were no significant differences in rates of thromboembolic/thrombotic events or gastrointestinal bleeding. NOAC treated patients had lower rates of major bleeding overall, hazard ratio 0.78 (95% confidence interval 0.67-0.92, intracranial bleeding 0.59 (0.40-0.87, haemorrhagic stroke 0.49 (0.28-0.86, and other major bleeding 0.71 (0.57-0.89.For patients with atrial fibrillation, NOACs are as effective for stroke prevention as well-managed warfarin but cause fewer major bleedings.

Parametric statistical techniques for the comparative analysis of censored reliability data: a review

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Bohoris, George A.

1995-01-01

This paper summarizes part of the work carried out to date on seeking analytical solutions to the two-sample problem with censored data in the context of reliability and maintenance optimization applications. For this purpose, parametric two-sample tests for failure and censored reliability data are introduced and their applicability/effectiveness in common engineering problems is reviewed

PARAMETRIC DISTRIBUTION FAMILIES USEFUL FOR MODELLING NON - LIFE INSURANCE PAYMENTS DATA. TAIL BEHAVIOUR

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Sandra Teodorescu

2013-11-01

Full Text Available The present paper describes a series of parametric distributions used for modeling non-life insurance payments data.Of those listed, special attention is paid to the transformed Beta distribution family.This distribution as well as those which are obtained from it(special cases of four-parameter transformed Beta distribution are used in the modeling of high costs, or even extreme ones.In the literature it follows the tail behaviour of distributions depending on the parameters, because the insurance payments data are tipically highly positively skewed and distributed with large upper tails.In the paper is described the tail behavior of the distribution in the left and right side respectively, and deduced from it, a general case.There are also some graphs of probability density function for one of the transformed Beta family members, which comes to reinforce the comments made.

Stroke subtype classification by geometrical descriptors of lesion shape.

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Bastian Cheng

Full Text Available Inference of etiology from lesion pattern in acute magnetic resonance imaging is valuable for management and prognosis of acute stroke patients. This study aims to assess the value of three-dimensional geometrical lesion-shape descriptors for stroke-subtype classification, specifically regarding stroke of cardioembolic origin.Stroke Etiology was classified according to ASCOD in retrospectively selected patients with acute stroke. Lesions were segmented on diffusion-weighed datasets, and descriptors of lesion shape quantified: surface area, sphericity, bounding box volume, and ratio between bounding box and lesion volume. Morphological measures were compared between stroke subtypes classified by ASCOD and between patients with embolic stroke of cardiac and non-cardiac source.150 patients (mean age 77 years; 95% CI, 65-80 years; median NIHSS 6, range 0-22 were included. Group comparison of lesion shape measures demonstrated that lesions caused by small-vessel disease were smaller and more spherical compared to other stroke subtypes. No significant differences of morphological measures were detected between patients with cardioembolic and non-cardioembolic stroke.Stroke lesions caused by small vessel disease can be distinguished from other stroke lesions based on distinctive morphological properties. However, within the group of embolic strokes, etiology could not be inferred from the morphology measures studied in our analysis.

Motor recovery in post-stroke patients with aphasia: the role of specific linguistic abilities.

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Ginex, Valeria; Veronelli, Laura; Vanacore, Nicola; Lacorte, Eleonora; Monti, Alessia; Corbo, Massimo

2017-09-01

Aphasia is a serious consequence of stroke but aphasics patients have been routinely excluded from participation in some areas of stroke research. To assess the role of specific linguistic and non-verbal cognitive abilities on the short-term motor recovery of patients with aphasia due to first-ever stroke to the left hemisphere after an intensive rehabilitation treatment. 48 post-acute aphasic patients, who underwent physiotherapy and speech language therapy, were enrolled for this retrospective cohort-study. Four types of possible predictive factors were taken into account: clinical variables, functional status, language and non-verbal cognitive abilities. The motor FIM at discharge was used as the main dependent variable. Patients were classified as follows: 6 amnestic, 9 Broca's, 7 Wernicke's, and 26 global aphasics. Motor FIM at admission (p = 0.003) and at discharge (p = 0.042), all linguistic subtests of Aachener AphasieTest (p = 0.001), and non-verbal reasoning abilities (Raven's CPM, p = 0.006) resulted significantly different across different types of aphasia. Post-hoc analyses showed differences only between global aphasia and the other groups. A Multiple Linear Regression shows that admission motor FIM (p = 0.001) and Token test (p = 0.040), adjusted for clinical, language, and non-verbal reasoning variables, resulted as independent predictors of motor FIM scores at discharge, while Raven's CPM resulted close to statistical significance. Motor function at admission resulted as the variable that most affects the motor recovery of post-stroke patients with aphasia after rehabilitation. A linguistic test requiring also non-linguistic abilities, including attention and working memory (i.e. Token test) is an independent predictor as well.

The social and economic burden of stroke survivors in Italy: a prospective, incidence-based, multi-centre cost of illness study

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Fattore Giovanni

2012-11-01

Full Text Available Abstract Background The aim of this study was to estimate the one-year societal costs due to a stroke event in Italy and to investigate variables associated with costs in different phases following hospital admission. Methods The patients were enrolled in 44 hospitals across the country and data on socio-demographic, clinical variables and resource consumption were prospectively surveyed for 411 stroke survivors at admission, discharge and 3, 6 and 12 months post the event. We adopted a micro-costing procedure to identify cost generating components and the attribution of appropriate unit costs for three cost categories: direct healthcare, direct non-healthcare (including informal care costs and productivity losses. The relation between costs of stroke management and socio-demographic and clinical characteristics as well as disability levels was evaluated in a series of bivariate analyses using non parametric tests (Mann Whitney and Kruskal-Wallis. Multiple linear regression analyses were performed to determine predictors of costs incurred by stroke patients during the acute phase and follow-up of 1 year. Results On average, one-year healthcare and societal costs amounted to €11,747 and € 19,953 per stroke survivor, respectively. The major cost component of societal costs was informal care accounting for € 6,656 (33.4% of total, followed by the initial hospitalisation, (€ 5,573; 27.9% of total, rehabilitation during follow up (€ 4,112; 20.6 %, readmissions (€ 439 and specialist and general practioner visits (€ 326. Mean drug costs per patient over the follow-up period was about € 50 per month. Costs associated to the provision of paid and informal care followed different pattern and were persistent over time (ranging from € 639 to € 597 per month in the first and the second part of the year, respectively. Clinical variables (presence of diabetes mellitus and hemorrhagic stroke were significant predictors of total healthcare