The Estimation of Tree Posterior Probabilities Using Conditional Clade Probability Distributions
Larget, Bret
2013-01-01
In this article I introduce the idea of conditional independence of separated subtrees as a principle by which to estimate the posterior probability of trees using conditional clade probability distributions rather than simple sample relative frequencies. I describe an algorithm for these calculations and software which implements these ideas. I show that these alternative calculations are very similar to simple sample relative frequencies for high probability trees but are substantially more accurate for relatively low probability trees. The method allows the posterior probability of unsampled trees to be calculated when these trees contain only clades that are in other sampled trees. Furthermore, the method can be used to estimate the total probability of the set of sampled trees which provides a measure of the thoroughness of a posterior sample. [Bayesian phylogenetics; conditional clade distributions; improved accuracy; posterior probabilities of trees.] PMID:23479066
Posterior Probabilities for a Consensus Ordering.
ERIC Educational Resources Information Center
Fligner, Michael A.; Verducci, Joseph S.
1990-01-01
The concept of consensus ordering is defined, and formulas for exact and approximate posterior probabilities for consensus ordering are developed under the assumption of a generalized Mallows' model with a diffuse conjugate prior. These methods are applied to a data set concerning 98 college students. (SLD)
Posterior Probability Matching and Human Perceptual Decision Making
Murray, Richard F.; Patel, Khushbu; Yee, Alan
2015-01-01
Probability matching is a classic theory of decision making that was first developed in models of cognition. Posterior probability matching, a variant in which observers match their response probabilities to the posterior probability of each response being correct, is being used increasingly often in models of perception. However, little is known about whether posterior probability matching is consistent with the vast literature on vision and hearing that has developed within signal detection theory. Here we test posterior probability matching models using two tools from detection theory. First, we examine the models’ performance in a two-pass experiment, where each block of trials is presented twice, and we measure the proportion of times that the model gives the same response twice to repeated stimuli. We show that at low performance levels, posterior probability matching models give highly inconsistent responses across repeated presentations of identical trials. We find that practised human observers are more consistent across repeated trials than these models predict, and we find some evidence that less practised observers more consistent as well. Second, we compare the performance of posterior probability matching models on a discrimination task to the performance of a theoretical ideal observer that achieves the best possible performance. We find that posterior probability matching is very inefficient at low-to-moderate performance levels, and that human observers can be more efficient than is ever possible according to posterior probability matching models. These findings support classic signal detection models, and rule out a broad class of posterior probability matching models for expert performance on perceptual tasks that range in complexity from contrast discrimination to symmetry detection. However, our findings leave open the possibility that inexperienced observers may show posterior probability matching behaviour, and our methods provide new tools
Learning about Posterior Probability: Do Diagrams and Elaborative Interrogation Help?
ERIC Educational Resources Information Center
Clinton, Virginia; Alibali, Martha W.; Nathan, Mitchell J.
2016-01-01
To learn from a text, students must make meaningful connections among related ideas in that text. This study examined the effectiveness of two methods of improving connections--elaborative interrogation and diagrams--in written lessons about posterior probability. Undergraduate students (N = 198) read a lesson in one of three questioning…
Predicting accurate probabilities with a ranking loss
Menon, Aditya Krishna; Jiang, Xiaoqian J; Vembu, Shankar; Elkan, Charles; Ohno-Machado, Lucila
2013-01-01
In many real-world applications of machine learning classifiers, it is essential to predict the probability of an example belonging to a particular class. This paper proposes a simple technique for predicting probabilities based on optimizing a ranking loss, followed by isotonic regression. This semi-parametric technique offers both good ranking and regression performance, and models a richer set of probability distributions than statistical workhorses such as logistic regression. We provide experimental results that show the effectiveness of this technique on real-world applications of probability prediction. PMID:25285328
Mapping genes with longitudinal phenotypes via Bayesian posterior probabilities.
Musolf, Anthony; Nato, Alejandro Q; Londono, Douglas; Zhou, Lisheng; Matise, Tara C; Gordon, Derek
2014-01-01
Most association studies focus on disease risk, with less attention paid to disease progression or severity. These phenotypes require longitudinal data. This paper presents a new method for analyzing longitudinal data to map genes in both population-based and family-based studies. Using simulated systolic blood pressure measurements obtained from Genetic Analysis Workshop 18, we cluster the phenotype data into trajectory subgroups. We then use the Bayesian posterior probability of being in the high subgroup as a quantitative trait in an association analysis with genotype data. This method maintains high power (>80%) in locating genes known to affect the simulated phenotype for most specified significance levels (α). We believe that this method can be useful to aid in the discovery of genes that affect severity or progression of disease. PMID:25519410
Estimating the posterior probability that genome-wide association findings are true or false
Bukszár, József; McClay, Joseph L.; van den Oord, Edwin J. C. G.
2009-01-01
Motivation: A limitation of current methods used to declare significance in genome-wide association studies (GWAS) is that they do not provide clear information about the probability that GWAS findings are true of false. This lack of information increases the chance of false discoveries and may result in real effects being missed. Results: We propose a method to estimate the posterior probability that a marker has (no) effect given its test statistic value, also called the local false discovery rate (FDR), in the GWAS. A critical step involves the estimation the parameters of the distribution of the true alternative tests. For this, we derived and implemented the real maximum likelihood function, which turned out to provide us with significantly more accurate estimates than the widely used mixture model likelihood. Actual GWAS data are used to illustrate properties of the posterior probability estimates empirically. In addition to evaluating individual markers, a variety of applications are conceivable. For instance, posterior probability estimates can be used to control the FDR more precisely than Benjamini–Hochberg procedure. Availability: The codes are freely downloadable from the web site http://www.people.vcu.edu/∼jbukszar. Contact: jbukszar@vcu.edu Supplementary information: Supplementary data are available at Bioinformatics online. PMID:19420056
Generalizing Swendsen-Wang to sampling arbitrary posterior probabilities.
Barbu, Adrian; Zhu, Song-Chun
2005-08-01
Many vision tasks can be formulated as graph partition problems that minimize energy functions. For such problems, the Gibbs sampler provides a general solution but is very slow, while other methods, such as Ncut and graph cuts are computationally effective but only work for specific energy forms and are not generally applicable. In this paper, we present a new inference algorithm that generalizes the Swendsen-Wang method to arbitrary probabilities defined on graph partitions. We begin by computing graph edge weights, based on local image features. Then, the algorithm iterates two steps. 1) Graph clustering: It forms connected components by cutting the edges probabilistically based on their weights. 2) Graph relabeling: It selects one connected component and flips probabilistically, the coloring of all vertices in the component simultaneously. Thus, it realizes the split, merge, and regrouping of a "chunk" of the graph, in contrast to Gibbs sampler that flips a single vertex. We prove that this algorithm simulates ergodic and reversible Markov chain jumps in the space of graph partitions and is applicable to arbitrary posterior probabilities or energy functions defined on graphs. We demonstrate the algorithm on two typical problems in computer vision--image segmentation and stereo vision. Experimentally, we show that it is 100-400 times faster in CPU time than the classical Gibbs sampler and 20-40 times faster then the DDMCMC segmentation algorithm. For stereo, we compare performance with graph cuts and belief propagation. We also show that our algorithm can automatically infer generative models and obtain satisfactory results (better than the graphic cuts or belief propagation) in the same amount of time. PMID:16119263
Inference of posterior inclusion probability of QTLs in Bayesian shrinkage analysis.
Yang, Deguang; Han, Shanshan; Jiang, Dan; Yang, Runqing; Fang, Ming
2015-01-01
Bayesian shrinkage analysis estimates all QTLs effects simultaneously, which shrinks the effect of "insignificant" QTLs close to zero so that it does not need special model selection. Bayesian shrinkage estimation usually has an excellent performance on multiple QTLs mapping, but it could not give a probabilistic explanation of how often a QTLs is included in the model, also called posterior inclusion probability, which is important to assess the importance of a QTL. In this research, two methods, FitMix and SimMix, are proposed to approximate the posterior probabilities. Under the assumption of mixture distribution of the estimated QTL effect, FitMix and SimMix mathematically and intuitively fit mixture distribution, respectively. The simulation results showed that both methods gave very reasonable estimates for posterior probabilities. We also applied the two methods to map QTLs for the North American Barley Genome Mapping Project data. PMID:25857576
Tentori, Katya; Chater, Nick; Crupi, Vincenzo
2016-04-01
Inductive reasoning requires exploiting links between evidence and hypotheses. This can be done focusing either on the posterior probability of the hypothesis when updated on the new evidence or on the impact of the new evidence on the credibility of the hypothesis. But are these two cognitive representations equally reliable? This study investigates this question by comparing probability and impact judgments on the same experimental materials. The results indicate that impact judgments are more consistent in time and more accurate than probability judgments. Impact judgments also predict the direction of errors in probability judgments. These findings suggest that human inductive reasoning relies more on estimating evidential impact than on posterior probability. PMID:26100936
Serang, Oliver; MacCoss, Michael J.; Noble, William Stafford
2010-01-01
The problem of identifying proteins from a shotgun proteomics experiment has not been definitively solved. Identifying the proteins in a sample requires ranking them, ideally with interpretable scores. In particular, “degenerate” peptides, which map to multiple proteins, have made such a ranking difficult to compute. The problem of computing posterior probabilities for the proteins, which can be interpreted as confidence in a protein’s presence, has been especially daunting. Previous approaches have either ignored the peptide degeneracy problem completely, addressed it by computing a heuristic set of proteins or heuristic posterior probabilities, or by estimating the posterior probabilities with sampling methods. We present a probabilistic model for protein identification in tandem mass spectrometry that recognizes peptide degeneracy. We then introduce graph-transforming algorithms that facilitate efficient computation of protein probabilities, even for large data sets. We evaluate our identification procedure on five different well-characterized data sets and demonstrate our ability to efficiently compute high-quality protein posteriors. PMID:20712337
Performance of the Rayleigh task based on the posterior probability of tomographic reconstructions
Hanson, K.M.
1991-01-01
We seek the best possible performance of the Rayleigh task in which one must decide whether a perceived object is a pair of Gaussian-blurred points or a blurred line. Two Bayesian reconstruction algorithms are used, the first based on a Gaussian prior-probability distribution with a nonnegativity constraint and the second based on an entropic prior. In both cases, the reconstructions are found that maximize the posterior probability. We compare the performance of the Rayleigh task obtained with two decision variables, the logarithm of the posterior probability ratio and the change in the mean-squared deviation from the reconstruction. The method of evaluation is based on the results of a numerical testing procedure in which the stated discrimination task is carried out on reconstructions of a randomly generated sequence of images. The ability to perform the Rayleigh task is summarized in terms of a discrimination index that is derived from the area under the receiver-operating characteristic (ROC) curve. We find that the use of the posterior probability does not result in better performance of the Rayleigh task than the mean-squared deviation from the reconstruction. 10 refs., 6 figs.
A modified approach for change detection using change vector analysis in posterior probability space
NASA Astrophysics Data System (ADS)
Azzouzi, S. A.; Vidal, A.; Bentounes, H. A.
2015-04-01
The multispectral and multitemporal data coming from satellites allow us to extract valuable spatiotemporal change. Consequently, Earth surface change detection analysis has been used in the past to monitor land cover changes caused by different reasons. Several techniques have been used for that purpose and change vector analysis (CVA) has been frequently employed to carry out automatic spatiotemporal information extraction. This work describes a modified methodology based on Supervised Change Vector Analysis in Posterior probability Space (SCVAPS) with the final aim of obtaining a change detection map in Blida, Algeria. The proposed technique is a Modified version of Supervised Change Vector Analysis Posterior probability Space (MSCVAPS) and it is applied at the same region that the original technique studied in the literature. The classical Maximum Likelihood classifier is the selected method for supervised classification since it provides good properties in the posterior probability map. An improved method for threshold determination based on Double Flexible Pace Search (DFPS) is proposed in this work and it is employed to obtain the most adequate threshold value. Then, the MSCVAPS approach is evaluated by two cases study of the land cover change detection in the region of Blida, Algeria, and in the region of Shunyi District, Beijing, China, using a pair of Landsat Thematic Mapper images and pair of Landsat Enhanced Thematic Mapper images, respectively. The final evaluation is given by the overall accuracy of changed and unchanged pixels and the kappa coefficient. The results show that the modified approach gives excellent results using the same area of study that was selected in the literature.
Lindhiem, Oliver; Kolko, David J.; Yu, Lan
2013-01-01
Using traditional Diagnostic and Statistical Manual of Mental Disorders (DSM; American Psychiatric Association, 2000) diagnostic criteria, clinicians are forced to make categorical decisions (diagnosis versus no diagnosis). This forced choice implies that mental and behavioral health disorders are categorical and does not fully characterize varying degrees of uncertainty associated with a particular diagnosis. Using an IRT (latent trait model) framework, we describe the development of the Posterior Probability of Diagnosis (PPOD) Index which answers the question, “What is the likelihood that a patient meets or exceeds the latent trait threshold for a diagnosis.” The PPOD Index is based on the posterior distribution of θ (latent trait score) for each patient’s profile of symptoms. The PPOD Index allows clinicians to quantify and communicate the degree of uncertainty associated with each diagnosis in probabilistic terms. We illustrate the advantages of the PPOD Index in a clinical sample (N = 321) of children and adolescents with Oppositional Defiant Disorder (ODD). PMID:23356682
Posterior brain white matter abnormalities in older adults with probable mild cognitive impairment
Cooley, Sarah A.; Cabeen, Ryan P.; Laidlaw, David H.; Conturo, Thomas E.; Lane, Elizabeth M.; Heaps, Jodi M.; Bolzenius, Jacob D.; Baker, Laurie M.; Salminen, Lauren E.; Scott, Staci E.; Paul, Robert H.
2014-01-01
Objective Much of the mild cognitive impairment (MCI) neuroimaging literature has exclusively focused on regions associated with Alzheimer’s disease. Little research has examined white matter abnormalities of other brain regions, including those associated with visual processing, despite evidence that other brain abnormalities appear in these regions in early disease stages. Method Diffusion tensor imaging (DTI) was utilized to examine participants (n = 44) that completed baseline imaging as part of a longitudinal healthy aging study. Participants were divided into two groups based on scores from the Montreal Cognitive Assessment (MoCA), a brief screening tool for MCI. Participants who scored < 26 were defined as “probable MCI” while those who scored ≥ 26 were labled cognitively healthy. Two DTI indices were analyzed including fractional anisotropy (FA) and mean diffusivity (MD). DTI values for white matter in the lingual gyrus, cuneus, pericalcarine, fusiform gyrus and all four lobes were compared using MANOVA. Regression analyses examined the relationship between DTI indices and total MoCA score. Results Results revealed significantly lower FA in the probable MCI group in the cuneus, fusiform, pericalcarine and occipital lobe, and significantly higher MD in the temporal lobe. Fusiform FA and temporal lobe MD were significantly related to total MoCA score after accounting for age and education. Conclusions Results indicate that there are posterior white matter microstructural changes in individuals with probable MCI. These differences demonstrate that white matter abnormalities are evident among individuals with probable MCI in regions beyond those commonly associated with Alzheimer’s disease and anterior brain aging patterns. PMID:25523313
NASA Astrophysics Data System (ADS)
Du, Zhanwei; Yang, Yongjian; Bai, Yuan; Wang, Lijun; Su, Le; Chen, Yong; Li, Xianchang; Zhou, Xiaodong; Jia, Jun; Shen, Aiguo; Hu, Jiming
2013-03-01
The existing methods for early and differential diagnosis of oral cancer are limited due to the unapparent early symptoms and the imperfect imaging examination methods. In this paper, the classification models of oral adenocarcinoma, carcinoma tissues and a control group with just four features are established by utilizing the hybrid Gaussian process (HGP) classification algorithm, with the introduction of the mechanisms of noise reduction and posterior probability. HGP shows much better performance in the experimental results. During the experimental process, oral tissues were divided into three groups, adenocarcinoma (n = 87), carcinoma (n = 100) and the control group (n = 134). The spectral data for these groups were collected. The prospective application of the proposed HGP classification method improved the diagnostic sensitivity to 56.35% and the specificity to about 70.00%, and resulted in a Matthews correlation coefficient (MCC) of 0.36. It is proved that the utilization of HGP in LRS detection analysis for the diagnosis of oral cancer gives accurate results. The prospect of application is also satisfactory.
ERIC Educational Resources Information Center
Dardick, William R.; Mislevy, Robert J.
2016-01-01
A new variant of the iterative "data = fit + residual" data-analytical approach described by Mosteller and Tukey is proposed and implemented in the context of item response theory psychometric models. Posterior probabilities from a Bayesian mixture model of a Rasch item response theory model and an unscalable latent class are expressed…
Meek, Garrett A; Levine, Benjamin G
2014-07-01
Spikes in the time-derivative coupling (TDC) near surface crossings make the accurate integration of the time-dependent Schrödinger equation in nonadiabatic molecular dynamics simulations a challenge. To address this issue, we present an approximation to the TDC based on a norm-preserving interpolation (NPI) of the adiabatic electronic wave functions within each time step. We apply NPI and two other schemes for computing the TDC in numerical simulations of the Landau-Zener model, comparing the simulated transfer probabilities to the exact solution. Though NPI does not require the analytical calculation of nonadiabatic coupling matrix elements, it consistently yields unsigned population transfer probability errors of ∼0.001, whereas analytical calculation of the TDC yields errors of 0.0-1.0 depending on the time step, the offset of the maximum in the TDC from the beginning of the time step, and the coupling strength. The approximation of Hammes-Schiffer and Tully yields errors intermediate between NPI and the analytical scheme. PMID:26279558
Musella, Vincenzo; Rinaldi, Laura; Lagazio, Corrado; Cringoli, Giuseppe; Biggeri, Annibale; Catelan, Dolores
2014-09-15
Model-based geostatistics and Bayesian approaches are appropriate in the context of Veterinary Epidemiology when point data have been collected by valid study designs. The aim is to predict a continuous infection risk surface. Little work has been done on the use of predictive infection probabilities at farm unit level. In this paper we show how to use predictive infection probability and related uncertainty from a Bayesian kriging model to draw a informative samples from the 8794 geo-referenced sheep farms of the Campania region (southern Italy). Parasitological data come from a first cross-sectional survey carried out to study the spatial distribution of selected helminths in sheep farms. A grid sampling was performed to select the farms for coprological examinations. Faecal samples were collected for 121 sheep farms and the presence of 21 different helminths were investigated using the FLOTAC technique. The 21 responses are very different in terms of geographical distribution and prevalence of infection. The observed prevalence range is from 0.83% to 96.69%. The distributions of the posterior predictive probabilities for all the 21 parasites are very heterogeneous. We show how the results of the Bayesian kriging model can be used to plan a second wave survey. Several alternatives can be chosen depending on the purposes of the second survey: weight by posterior predictive probabilities, their uncertainty or combining both information. The proposed Bayesian kriging model is simple, and the proposed samping strategy represents a useful tool to address targeted infection control treatments and surbveillance campaigns. It is easily extendable to other fields of research. PMID:25131190
Taylor, J. F.; Abbitt, B.; Walter, J. P.; Davis, S. K.; Jaques, J. T.; Ochoa, R. F.
1993-01-01
β-Mannosidosis is a lethal lysosomal storage disease inherited as an autosomal recessive in man, cattle and goats. Laboratory assay data of plasma β-mannosidase activity represent a mixture of homozygous normal and carrier genotype distributions in a proportion determined by genotype frequency. A maximum likelihood approach employing data transformations for each genotype distribution and assuming a diallelic model of inheritance is described. Estimates of the transformation and genotype distribution parameters, gene frequency, genotype fitness and carrier probability were obtained simultaneously from a sample of 2,812 observations on U.S. purebred Salers cattle with enzyme activity, age, gender, month of pregnancy, month of testing, and parents identified. Transformations to normality were not required, estimated gene and carrier genotype frequencies of 0.074 and 0.148 were high, and the estimated relative fitness of heterozygotes was 1.36. The apparent overdominance in fitness may be due to a nonrandom sampling of progeny genotypes within families. The mean of plasma enzyme activity was higher for males than females, higher in winter months, lower in summer months and decreased with increased age. Estimates of carrier probabilities indicate that the test is most effective when animals are sampled as calves, although effectiveness of the plasma assay was less for males than females. Test effectiveness was enhanced through averaging repeated assays of enzyme activity on each animal. Our approach contributes to medical diagnostics in several ways. Rather than assume underlying normality for the distributions comprising the mixture, we estimate transformations to normality for each genotype distribution simultaneously with all other model parameters. This process also excludes potential biases due to data preadjustment for systematic effects. We also provide a method for partitioning phenotypic variation within each genotypic distribution which allows an assessment
Lindhiem, Oliver; Yu, Lan; Grasso, Damion J; Kolko, David J; Youngstrom, Eric A
2015-04-01
This study adapts the Posterior Probability of Diagnosis (PPOD) Index for use with screening data. The original PPOD Index, designed for use in the context of comprehensive diagnostic assessments, is overconfident when applied to screening data. To correct for this overconfidence, we describe a simple method for adjusting the PPOD Index to improve its calibration when used for screening. Specifically, we compare the adjusted PPOD Index to the original index and naïve Bayes probability estimates on two dimensions of accuracy, discrimination and calibration, using a clinical sample of children and adolescents (N = 321) whose caregivers completed the Vanderbilt Assessment Scale to screen for attention-deficit/hyperactivity disorder and who subsequently completed a comprehensive diagnostic assessment. Results indicated that the adjusted PPOD Index, original PPOD Index, and naïve Bayes probability estimates are comparable using traditional measures of accuracy (sensitivity, specificity, and area under the curve), but the adjusted PPOD Index showed superior calibration. We discuss the importance of calibration for screening and diagnostic support tools when applied to individual patients. PMID:25000935
van de Merwe, J P
1984-01-01
A program is presented for the Hewlett-Packard HP- 41C programmable hand-held calculator that calculates the posterior probability and relative risk of an event (e.g. a disease) on the basis of prior probability (prevalence) and sensitivity, specificity and result of the test. PMID:6370577
Atutov, S. N. Plekhanov, A. I.
2015-01-15
We present the results of a systematic study of Knudsen’s flow of Rb atoms in cylindrical capillary cells coated with a polydimethylsiloxane (PDMS) compound. The purpose of the investigation is to determine the characterization of the coating in terms of the sticking probability and sticking time of Rb on the two types of coating of high and medium viscosities. We report the measurement of the sticking probability of a Rb atom to the coating equal to 4.3 × 10{sup −5}, which corresponds to the number of bounces 2.3 × 10{sup 4} at room temperature. These parameters are the same for the two kinds of PDMS used. We find that at room temperature, the respective sticking times for high-viscosity and medium-viscosity PDMS are 22 ± 3 μs and 49 ± 6 μs. These sticking times are about million times larger than the sticking time derived from the surface Rb atom adsorption energy and temperature of the coating. A tentative explanation of this surprising result is proposed based on the bulk diffusion of the atoms that collide with the surface and penetrate inside the coating. The results can be important in many resonance cell experiments, such as the efficient magnetooptical trapping of rare elements or radioactive isotopes and in experiments on the light-induced drift effect.
Accurate Estimation of the Entropy of Rotation-Translation Probability Distributions.
Fogolari, Federico; Dongmo Foumthuim, Cedrix Jurgal; Fortuna, Sara; Soler, Miguel Angel; Corazza, Alessandra; Esposito, Gennaro
2016-01-12
The estimation of rotational and translational entropies in the context of ligand binding has been the subject of long-time investigations. The high dimensionality (six) of the problem and the limited amount of sampling often prevent the required resolution to provide accurate estimates by the histogram method. Recently, the nearest-neighbor distance method has been applied to the problem, but the solutions provided either address rotation and translation separately, therefore lacking correlations, or use a heuristic approach. Here we address rotational-translational entropy estimation in the context of nearest-neighbor-based entropy estimation, solve the problem numerically, and provide an exact and an approximate method to estimate the full rotational-translational entropy. PMID:26605696
Fast and accurate probability density estimation in large high dimensional astronomical datasets
NASA Astrophysics Data System (ADS)
Gupta, Pramod; Connolly, Andrew J.; Gardner, Jeffrey P.
2015-01-01
Astronomical surveys will generate measurements of hundreds of attributes (e.g. color, size, shape) on hundreds of millions of sources. Analyzing these large, high dimensional data sets will require efficient algorithms for data analysis. An example of this is probability density estimation that is at the heart of many classification problems such as the separation of stars and quasars based on their colors. Popular density estimation techniques use binning or kernel density estimation. Kernel density estimation has a small memory footprint but often requires large computational resources. Binning has small computational requirements but usually binning is implemented with multi-dimensional arrays which leads to memory requirements which scale exponentially with the number of dimensions. Hence both techniques do not scale well to large data sets in high dimensions. We present an alternative approach of binning implemented with hash tables (BASH tables). This approach uses the sparseness of data in the high dimensional space to ensure that the memory requirements are small. However hashing requires some extra computation so a priori it is not clear if the reduction in memory requirements will lead to increased computational requirements. Through an implementation of BASH tables in C++ we show that the additional computational requirements of hashing are negligible. Hence this approach has small memory and computational requirements. We apply our density estimation technique to photometric selection of quasars using non-parametric Bayesian classification and show that the accuracy of the classification is same as the accuracy of earlier approaches. Since the BASH table approach is one to three orders of magnitude faster than the earlier approaches it may be useful in various other applications of density estimation in astrostatistics.
NASA Astrophysics Data System (ADS)
Sun, J.; Shen, Z.; Burgmann, R.; Liang, F.
2012-12-01
We develop a three-step Maximum-A-Posterior probability (MAP) method for coseismic rupture inversion, which aims at maximizing the a posterior probability density function (PDF) of elastic solutions of earthquake rupture. The method originates from the Fully Bayesian Inversion (FBI) and the Mixed linear-nonlinear Bayesian inversion (MBI) methods , shares the same a posterior PDF with them and keeps most of their merits, while overcoming its convergence difficulty when large numbers of low quality data are used and improving the convergence rate greatly using optimization procedures. A highly efficient global optimization algorithm, Adaptive Simulated Annealing (ASA), is used to search for the maximum posterior probability in the first step. The non-slip parameters are determined by the global optimization method, and the slip parameters are inverted for using the least squares method without positivity constraint initially, and then damped to physically reasonable range. This step MAP inversion brings the inversion close to 'true' solution quickly and jumps over local maximum regions in high-dimensional parameter space. The second step inversion approaches the 'true' solution further with positivity constraints subsequently applied on slip parameters using the Monte Carlo Inversion (MCI) technique, with all parameters obtained from step one as the initial solution. Then the slip artifacts are eliminated from slip models in the third step MAP inversion with fault geometry parameters fixed. We first used a designed model with 45 degree dipping angle and oblique slip, and corresponding synthetic InSAR data sets to validate the efficiency and accuracy of method. We then applied the method on four recent large earthquakes in Asia, namely the 2010 Yushu, China earthquake, the 2011 Burma earthquake, the 2011 New Zealand earthquake and the 2008 Qinghai, China earthquake, and compared our results with those results from other groups. Our results show the effectiveness of
NASA Astrophysics Data System (ADS)
Wang, Kang-Ning; Sun, Zan-Dong; Dong, Ning
2015-12-01
Economic shale gas production requires hydraulic fracture stimulation to increase the formation permeability. Hydraulic fracturing strongly depends on geomechanical parameters such as Young's modulus and Poisson's ratio. Fracture-prone sweet spots can be predicted by prestack inversion, which is an ill-posed problem; thus, regularization is needed to obtain unique and stable solutions. To characterize gas-bearing shale sedimentary bodies, elastic parameter variations are regarded as an anisotropic Markov random field. Bayesian statistics are adopted for transforming prestack inversion to the maximum posterior probability. Two energy functions for the lateral and vertical directions are used to describe the distribution, and the expectation-maximization algorithm is used to estimate the hyperparameters of the prior probability of elastic parameters. Finally, the inversion yields clear geological boundaries, high vertical resolution, and reasonable lateral continuity using the conjugate gradient method to minimize the objective function. Antinoise and imaging ability of the method were tested using synthetic and real data.
Lindhiem, Oliver; Yu, Lan; Grasso, Damion J.; Kolko, David J.; Youngstrom, Eric A.
2014-01-01
This study adapts the Posterior Probability of Diagnosis (PPOD) Index for use with screening data. The original PPOD Index, designed for use in the context of comprehensive diagnostic assessments, is overconfident when applied to screening data. To correct for this overconfidence, we describe a simple method for adjusting the PPOD Index to improve its calibration when used for screening. Specifically, we compare the adjusted PPOD Index to the original index and Naïve Bayes probability estimates on two dimensions of accuracy, discrimination and calibration, using a clinical sample of children and adolescents (N = 321) whose caregivers completed the Vanderbilt Assessment Scale to screen for Attention-Deficit/Hyperactivity Disorder (ADHD) and who subsequently completed a comprehensive diagnostic assessment. Results indicated that the adjusted PPOD Index, original PPOD Index, and Naïve Bayes probability estimates are comparable using traditional measures of accuracy (sensitivity, specificity, AUC) but the adjusted PPOD Index showed superior calibration. We discuss the importance of calibration for screening and diagnostic support tools when applied to individual patients. PMID:25000935
ERIC Educational Resources Information Center
Sueiro, Manuel J.; Abad, Francisco J.
2011-01-01
The distance between nonparametric and parametric item characteristic curves has been proposed as an index of goodness of fit in item response theory in the form of a root integrated squared error index. This article proposes to use the posterior distribution of the latent trait as the nonparametric model and compares the performance of an index…
A Posteriori Transit Probabilities
NASA Astrophysics Data System (ADS)
Stevens, Daniel J.; Gaudi, B. Scott
2013-08-01
Given the radial velocity (RV) detection of an unseen companion, it is often of interest to estimate the probability that the companion also transits the primary star. Typically, one assumes a uniform distribution for the cosine of the inclination angle i of the companion's orbit. This yields the familiar estimate for the prior transit probability of ~Rlowast/a, given the primary radius Rlowast and orbital semimajor axis a, and assuming small companions and a circular orbit. However, the posterior transit probability depends not only on the prior probability distribution of i but also on the prior probability distribution of the companion mass Mc, given a measurement of the product of the two (the minimum mass Mc sin i) from an RV signal. In general, the posterior can be larger or smaller than the prior transit probability. We derive analytic expressions for the posterior transit probability assuming a power-law form for the distribution of true masses, dΓ/dMcvpropMcα, for integer values -3 <= α <= 3. We show that for low transit probabilities, these probabilities reduce to a constant multiplicative factor fα of the corresponding prior transit probability, where fα in general depends on α and an assumed upper limit on the true mass. The prior and posterior probabilities are equal for α = -1. The posterior transit probability is ~1.5 times larger than the prior for α = -3 and is ~4/π times larger for α = -2, but is less than the prior for α>=0, and can be arbitrarily small for α > 1. We also calculate the posterior transit probability in different mass regimes for two physically-motivated mass distributions of companions around Sun-like stars. We find that for Jupiter-mass planets, the posterior transit probability is roughly equal to the prior probability, whereas the posterior is likely higher for Super-Earths and Neptunes (10 M⊕ - 30 M⊕) and Super-Jupiters (3 MJup - 10 MJup), owing to the predicted steep rise in the mass function toward smaller
Daly, Megan E.; Luxton, Gary; Choi, Clara Y.H.; Gibbs, Iris C.; Chang, Steven D.; Adler, John R.; Soltys, Scott G.
2012-04-01
Purpose: To determine whether normal tissue complication probability (NTCP) analyses of the human spinal cord by use of the Lyman-Kutcher-Burman (LKB) model, supplemented by linear-quadratic modeling to account for the effect of fractionation, predict the risk of myelopathy from stereotactic radiosurgery (SRS). Methods and Materials: From November 2001 to July 2008, 24 spinal hemangioblastomas in 17 patients were treated with SRS. Of the tumors, 17 received 1 fraction with a median dose of 20 Gy (range, 18-30 Gy) and 7 received 20 to 25 Gy in 2 or 3 sessions, with cord maximum doses of 22.7 Gy (range, 17.8-30.9 Gy) and 22.0 Gy (range, 20.2-26.6 Gy), respectively. By use of conventional values for {alpha}/{beta}, volume parameter n, 50% complication probability dose TD{sub 50}, and inverse slope parameter m, a computationally simplified implementation of the LKB model was used to calculate the biologically equivalent uniform dose and NTCP for each treatment. Exploratory calculations were performed with alternate values of {alpha}/{beta} and n. Results: In this study 1 case (4%) of myelopathy occurred. The LKB model using radiobiological parameters from Emami and the logistic model with parameters from Schultheiss overestimated complication rates, predicting 13 complications (54%) and 18 complications (75%), respectively. An increase in the volume parameter (n), to assume greater parallel organization, improved the predictive value of the models. Maximum-likelihood LKB fitting of {alpha}/{beta} and n yielded better predictions (0.7 complications), with n = 0.023 and {alpha}/{beta} = 17.8 Gy. Conclusions: The spinal cord tolerance to the dosimetry of SRS is higher than predicted by the LKB model using any set of accepted parameters. Only a high {alpha}/{beta} value in the LKB model and only a large volume effect in the logistic model with Schultheiss data could explain the low number of complications observed. This finding emphasizes that radiobiological models
Congenital basis of posterior fossa anomalies
Cotes, Claudia; Bonfante, Eliana; Lazor, Jillian; Jadhav, Siddharth; Caldas, Maria; Swischuk, Leonard
2015-01-01
The classification of posterior fossa congenital anomalies has been a controversial topic. Advances in genetics and imaging have allowed a better understanding of the embryologic development of these abnormalities. A new classification schema correlates the embryologic, morphologic, and genetic bases of these anomalies in order to better distinguish and describe them. Although they provide a better understanding of the clinical aspects and genetics of these disorders, it is crucial for the radiologist to be able to diagnose the congenital posterior fossa anomalies based on their morphology, since neuroimaging is usually the initial step when these disorders are suspected. We divide the most common posterior fossa congenital anomalies into two groups: 1) hindbrain malformations, including diseases with cerebellar or vermian agenesis, aplasia or hypoplasia and cystic posterior fossa anomalies; and 2) cranial vault malformations. In addition, we will review the embryologic development of the posterior fossa and, from the perspective of embryonic development, will describe the imaging appearance of congenital posterior fossa anomalies. Knowledge of the developmental bases of these malformations facilitates detection of the morphological changes identified on imaging, allowing accurate differentiation and diagnosis of congenital posterior fossa anomalies. PMID:26246090
NASA Astrophysics Data System (ADS)
Ni, Yan-Chun; Zhang, Feng-Liang; Lam, Heung-Fai; Au, Siu-Kui
2016-03-01
A Bayesian statistical framework has been developed for modal identification using free vibration data in the companion paper (Zhang et al., Mech. Syst. Sig. Process. (2015)). Efficient strategies have been developed for evaluating the most probable value (MPV) of the modal parameters in both well-separated mode and general multiple mode cases. This paper investigates the posterior uncertainty of the modal parameters in terms of their posterior covariance matrix, which is mathematically equal to the inverse of the Hessian of the negative log-likelihood function (NLLF) evaluated at the MPVs. Computational issues associated with the determination of the posterior covariance matrix are discussed. Analytical expressions are derived for the Hessian so that it can be evaluated accurately and efficiently without resorting to finite difference method. The proposed methods are verified with synthetic data and then applied to field vibration test data.
Evaluation of posterior fossa lesions by computer assisted tomography (CAT).
Lott, T; El Gammal, T; Volcan, I
1977-07-01
Valuable neuroradiologic information can be obtained with routine examination of the posterior fossa by computer assisted tomography (CAT). The diagnosis can be difficult in the posterior fossa due to the relatively small size of the compartment and its proximities to large bony masses and air in the mastoid cells. However, many lesions can be accurately diagnosed when close attention is given to anatomic detail and the frequent use of contrast enhancement. We introduced a new CAT classification of posterior fossa neoplasms. PMID:877637
[Posterior capsule opacification].
Milazzo, S; Grenot, M; Benzerroug, M
2014-12-01
Posterior capsule opacification (PCO) is the most common complication after cataract surgery, with an incidence of 30%. It tends to be considered a normal event in the natural history of cataract surgery. Better understanding of its pathophysiology and advancement of intraocular lens material and design along with the improvement of phacoemulsification technique have contributed to decrease the incidence of PCO. Although treatment by Nd: YAG laser posterior capsulotomy is quick and non-invasive, the opening of the posterior capsule may be associated with numerous complications. Prevention remains the best measure for controlling this pathology. PMID:25455552
ERIC Educational Resources Information Center
Weatherly, Myra S.
1984-01-01
Instruction in mathematical probability to enhance higher levels of critical and creative thinking with gifted students is described. Among thinking skills developed by such an approach are analysis, synthesis, evaluation, fluency, and complexity. (CL)
... of the posterior fossa, it can block the flow of spinal fluid and cause increased pressure on the brain and ... the cancer early. A total blockage in the flow of spinal fluid can be life threatening. If tumors are found ...
Posterior Tibial Tendon Dysfunction
... when the posterior tibial tendon becomes inﬂamed or torn. As a result, the tendon may not be ... repetitive use. Once the tendon becomes inﬂamed or torn, the arch will slowly fall (collapse) over time. ...
Posterior ankle impingement syndrome.
Maquirriain, Javier
2005-10-01
Posterior ankle impingement syndrome is a clinical disorder characterized by posterior ankle pain that occurs in forced plantar flexion. The pain may be acute as a result of trauma or chronic from repetitive stress. Pathology of the os trigonum-talar process is the most common cause of this syndrome, but it also may result from flexor hallucis longus tenosynovitis, ankle osteochondritis, subtalar joint disease, and fracture. Patients usually report chronic or recurrent posterior ankle pain caused or exacerbated by forced plantar flexion or push-off maneuvers, such as may occur during dancing, kicking, or downhill running. Diagnosis of posterior ankle impingement syndrome is based primarily on clinical history and physical examination. Radiography, scintigraphy, computed tomography, and magnetic resonance imaging depict associated bone and soft-tissue abnormalities. Symptoms typically improve with nonsurgical management, but surgery may be required in refractory cases. PMID:16224109
Lawler, J. E.; Guzman, A.; Wood, M. P.; Sneden, C.; Cowan, J. J. E-mail: adrianaguzman2014@u.northwestern.edu E-mail: chris@verdi.as.utexas.edu
2013-04-01
New atomic transition probability measurements for 948 lines of Ti I are reported. Branching fractions from Fourier transform spectra and from spectra recorded using a 3 m echelle spectrometer are combined with published radiative lifetimes from laser-induced fluorescence measurements to determine these transition probabilities. Generally good agreement is found in comparisons to the NIST Atomic Spectra Database. The new Ti I data are applied to re-determine the Ti abundance in the photospheres of the Sun and metal-poor star HD 84937 using many lines covering a range of wavelength and excitation potential to explore possible non-local thermal equilibrium effects. The variation of relative Ti/Fe abundance with metallicity in metal-poor stars observed in earlier studies is supported in this study.
Bayesian inference of a lake water quality model by emulating its posterior density
NASA Astrophysics Data System (ADS)
Dietzel, A.; Reichert, P.
2014-10-01
We use a Gaussian stochastic process emulator to interpolate the posterior probability density of a computationally demanding application of the biogeochemical-ecological lake model BELAMO to accelerate statistical inference of deterministic model and error model parameters. The deterministic model consists of a mechanistic description of key processes influencing the mass balance of nutrients, dissolved oxygen, organic particles, and phytoplankton and zooplankton in the lake. This model is complemented by a Gaussian stochastic process to describe the remaining model bias and by Normal, independent observation errors. A small subsample of the Markov chain representing the posterior of the model parameters is propagated through the full model to get model predictions and uncertainty estimates. We expect this approximation to be more accurate at only slightly higher computational costs compared to using a Normal approximation to the posterior probability density and linear error propagation to the results as we did in an earlier paper. The performance of the two techniques is compared for a didactical example as well as for the lake model. As expected, for the didactical example, the use of the emulator led to posterior marginals of the model parameters that are closer to those calculated by Markov chain simulation using the full model than those based on the Normal approximation. For the lake model, the new technique proved applicable without an excessive increase in computational requirements, but we faced challenges in the choice of the design data set for emulator calibration. As the posterior is a scalar function of the parameters, the suggested technique is an alternative to the emulation of a potentially more complex, structured output of the simulation model that allows for the use of a less case-specific emulator. This is at the cost that still the full model has to be used for prediction (which can be done with a smaller, approximately independent subsample
Bilateral posterior sternoclavicular dislocation.
Baumann, Matthias; Vogel, Tobias; Weise, Kuno; Muratore, Tim; Trobisch, Per
2010-07-01
Posterior sternoclavicular dislocations are a rare injury, representing <5% of all sternoclavicular dislocations and 1 in 1600 shoulder girdle injuries. Proper imaging with computed tomography and prompt diagnosis are essential steps in preventing potentially lethal complications observed in approximately 3% of all posterior sternoclavicular dislocations. Surgical treatment is necessary if closed reduction fails. With the medial clavicular epiphysis being the last to close (between ages 22 and 25), children and adolescents typically present with epiphyseal fractures rather than joint dislocations. If closed reduction fails, open reduction and internal fixation (ORIF) should be considered in fractures, whereas complex reconstructions with tendon graft procedures have been recommended for joint dislocations. This article presents a case of a traumatic bilateral posterior sternoclavicular dislocation due to an epiphyseal fracture in a 15-year-old boy. To our knowledge, this is the first reported case of a bilateral posterior sternoclavicular dislocation. Attempted closed reduction failed with redislocation after 2 days. The patient subsequently required ORIF. This article describes our technique with anterior retraction of the medial clavicle, closure of the posterior periosteum, and ORIF using nonabsorbable sutures. Postoperative shoulder mobilization was started on day 1. At final follow-up, the patient was completely asymptomatic. PMID:20608625
Huge interparietal posterior fontanel meningohydroencephalocele
Dos Santos, Manuel Filipe Dias; de Santa Barbara, Rita de Cassia
2015-01-01
Congenital encephalocele is a neural tube defect characterized by a sac-like protrusion of the brain, meninges, and other intracranial structures through the skull, which is caused by an embryonic development abnormality. The most common location is at the occipital bone, and its incidence varies according to different world regions. We report a case of an 1-month and 7-day-old male child with a huge interparietal-posterior fontanel meningohydroencephalocele, a rare occurrence. Physical examination and volumetric computed tomography were diagnostic. The encephalocele was surgically resected. Intradural and extradural approaches were performed; the bone defect was not primarily closed. Two days after surgery, the patient developed hydrocephaly requiring ventriculoperitoneal shunting. The surgical treatment of the meningohydroencephalocele of the interparietal-posterior fontanel may be accompanied by technical challenges and followed by complications due to the presence of large blood vessels under the overlying skin. In these cases, huge sacs herniate through large bone defects including meninges, brain, and blood vessels. The latter present communication with the superior sagittal sinus and ventricular system. A favorable surgical outcome generally follows an accurate strategy taking into account individual features of the lesion. PMID:26484324
Tibialis Posterior Tendon Entrapment Within Posterior Malleolar Fracture Fragment.
Fantry, Amanda; Lareau, Craig; Vopat, Bryan; Blankenhorn, Brad
2016-01-01
Management of posterior malleolus fractures continues to be controversial, with respect to both need for fixation and fixation methods. Fixation methods include an open posterior approach to the ankle as well as percutaneous reduction and fixation with or without arthroscopy for visualization of the articular surface. Plain radiographs are unreliable in identifying fracture pattern and intraoperative reduction, making arthroscopy a valuable adjunct to posterior malleolus fracture management. In this article, we report a case of tibialis posterior tendon entrapment within a posterior malleolus fracture, as identified by arthroscopy and managed with open reduction. Tibialis posterior tendon entrapment within a posterior malleolus has not been previously reported. Ankle arthroscopy for posterior malleolus fractures provides an opportunity to identify soft-tissue or tendinous entrapment, articular surface reduction, and articular cartilage injuries unlikely to be identified with fluoroscopy alone and should be considered in reduction and fixation of posterior malleolus fractures. PMID:26991573
Role of posterior hypothalamus in hypobaric hypoxia induced pulmonary edema.
Sharma, R K; Choudhary, R C; Reddy, M K; Ray, A; Ravi, K
2015-01-01
To investigate the role of posterior hypothalamus and central neurotransmitters in the pulmonary edema due to hypobaric hypoxia, rats were placed in a high altitude simulation chamber (barometric pressure-294.4 mmHg) for 24 h. Exposure to hypobaric hypoxia resulted in increases in mean arterial blood pressure, renal sympathetic nerve activity, right ventricular systolic pressure, lung wet to dry weight ratio and Evans blue dye leakage. There was a significant attenuation in these responses to hypobaric hypoxia (a) after lesioning posterior hypothalamus and (b) after chronic infusion of GABAA receptor agonist muscimol into posterior hypothalamus. No such attenuation was evident with the chronic infusion of the nitric oxide donor SNAP into the posterior hypothalamus. It is concluded that in hypobaric hypoxia, there is over-activity of posterior hypothalamic neurons probably due to a local decrease in GABA-ergic inhibition which increases the sympathetic drive causing pulmonary hypertension and edema. PMID:25448396
Posterior Tibial Tendon Transfer.
Shane, Amber M; Reeves, Christopher L; Cameron, Jordan D; Vazales, Ryan
2016-01-01
When performed correctly with the right patient population, a tibialis posterior muscle/tendon transfer is an effective procedure. Many different methods have been established for fixating the tendon, each of which has its' own indications. Passing through the interosseous membrane is the preferred and recommended method and should be used unless this is not possible. Good surgical planning based on patient needs and expectations, along with excellent postoperative care including early range of motion and physical therapy minimizes risk of complications and allows for the optimal outcome to be achieved. PMID:26590722
Gelman, Joel; Wisenbaugh, Eric S.
2015-01-01
Pelvic fracture urethral injuries are typically partial and more often complete disruptions of the most proximal bulbar and distal membranous urethra. Emergency management includes suprapubic tube placement. Subsequent primary realignment to place a urethral catheter remains a controversial topic, but what is not controversial is that when there is the development of a stricture (which is usually obliterative with a distraction defect) after suprapubic tube placement or urethral catheter removal, the standard of care is delayed urethral reconstruction with excision and primary anastomosis. This paper reviews the management of patients who suffer pelvic fracture urethral injuries and the techniques of preoperative urethral imaging and subsequent posterior urethroplasty. PMID:26691883
Posterior Urethral Strictures.
Gelman, Joel; Wisenbaugh, Eric S
2015-01-01
Pelvic fracture urethral injuries are typically partial and more often complete disruptions of the most proximal bulbar and distal membranous urethra. Emergency management includes suprapubic tube placement. Subsequent primary realignment to place a urethral catheter remains a controversial topic, but what is not controversial is that when there is the development of a stricture (which is usually obliterative with a distraction defect) after suprapubic tube placement or urethral catheter removal, the standard of care is delayed urethral reconstruction with excision and primary anastomosis. This paper reviews the management of patients who suffer pelvic fracture urethral injuries and the techniques of preoperative urethral imaging and subsequent posterior urethroplasty. PMID:26691883
Crutch, Sebastian J; Lehmann, Manja; Schott, Jonathan M; Rabinovici, Gil D; Rossor, Martin N; Fox, Nick C
2013-01-01
Posterior cortical atrophy (PCA) is a neurodegenerative syndrome that is characterized by a progressive decline in visuospatial, visuoperceptual, literacy and praxic skills. The progressive neurodegeneration affecting parietal, occipital and occipito-temporal cortices which underlies PCA is attributable to Alzheimer's disease (AD) in the majority of patients. However, alternative underlying aetiologies including Dementia with Lewy Bodies (DLB), corticobasal degeneration (CBD) and prion disease have also been identified, and not all PCA patients have atrophy on clinical imaging. This heterogeneity has led to diagnostic and terminological inconsistencies, caused difficulty comparing studies from different centres, and limited the generalizability of clinical trials and investigations of factors driving phenotypic variability. Significant challenges remain in identifying the factors associated with both the selective vulnerability of posterior cortical regions and the young age of onset seen in PCA. Greater awareness of the syndrome and agreement over the correspondence between syndrome-and disease-level classifications are required in order to improve diagnostic accuracy, research study design and clinical management. PMID:22265212
Pig Data and Bayesian Inference on Multinomial Probabilities
ERIC Educational Resources Information Center
Kern, John C.
2006-01-01
Bayesian inference on multinomial probabilities is conducted based on data collected from the game Pass the Pigs[R]. Prior information on these probabilities is readily available from the instruction manual, and is easily incorporated in a Dirichlet prior. Posterior analysis of the scoring probabilities quantifies the discrepancy between empirical…
Multiple model cardinalized probability hypothesis density filter
NASA Astrophysics Data System (ADS)
Georgescu, Ramona; Willett, Peter
2011-09-01
The Probability Hypothesis Density (PHD) filter propagates the first-moment approximation to the multi-target Bayesian posterior distribution while the Cardinalized PHD (CPHD) filter propagates both the posterior likelihood of (an unlabeled) target state and the posterior probability mass function of the number of targets. Extensions of the PHD filter to the multiple model (MM) framework have been published and were implemented either with a Sequential Monte Carlo or a Gaussian Mixture approach. In this work, we introduce the multiple model version of the more elaborate CPHD filter. We present the derivation of the prediction and update steps of the MMCPHD particularized for the case of two target motion models and proceed to show that in the case of a single model, the new MMCPHD equations reduce to the original CPHD equations.
Novel posterior fixation keratoprosthesis
NASA Astrophysics Data System (ADS)
Lacombe, Emmanuel
1992-08-01
The keratoprosthesis is the last solution for corneally blind patients that cannot benefit from corneal transplants. Keratoprostheses that have been designed to be affixed anteriorly usually necessitate multi-step surgical procedures and are continuously subjected to the extrusion forces generated by the positive intraocular pressure; therefore, clinical results in patients prove inconsistent. We proposed a novel keratoprosthesis concept that utilizes posterior corneal fixation which `a priori' minimizes the risk of aqueous leakage and expulsion. This prosthesis is implanted in a single procedure thereby reducing the number of surgical complications normally associated with anterior fixation devices. In addition, its novel design makes this keratoprosthesis implantable in phakic eyes. With an average follow-up of 13 months (range 3 to 25 months), our results on 21 cases are encouraging. Half of the keratoprostheses were implanted in severe burn cases, with the remainder in cases of pseudo- pemphigus. Good visual results and cosmetic appearance were obtained in 14 of 21 eyes.
A SNP discovery method to assess variant allele probability from next-generation resequencing data
Shen, Yufeng; Wan, Zhengzheng; Coarfa, Cristian; Drabek, Rafal; Chen, Lei; Ostrowski, Elizabeth A.; Liu, Yue; Weinstock, George M.; Wheeler, David A.; Gibbs, Richard A.; Yu, Fuli
2010-01-01
Accurate identification of genetic variants from next-generation sequencing (NGS) data is essential for immediate large-scale genomic endeavors such as the 1000 Genomes Project, and is crucial for further genetic analysis based on the discoveries. The key challenge in single nucleotide polymorphism (SNP) discovery is to distinguish true individual variants (occurring at a low frequency) from sequencing errors (often occurring at frequencies orders of magnitude higher). Therefore, knowledge of the error probabilities of base calls is essential. We have developed Atlas-SNP2, a computational tool that detects and accounts for systematic sequencing errors caused by context-related variables in a logistic regression model learned from training data sets. Subsequently, it estimates the posterior error probability for each substitution through a Bayesian formula that integrates prior knowledge of the overall sequencing error probability and the estimated SNP rate with the results from the logistic regression model for the given substitutions. The estimated posterior SNP probability can be used to distinguish true SNPs from sequencing errors. Validation results show that Atlas-SNP2 achieves a false-positive rate of lower than 10%, with an ∼5% or lower false-negative rate. PMID:20019143
Gossypiboma mimicking posterior urethral stricture
Kumar, Bindey; Kumar, Prem; Sinha, Sanjay Kumar; Sinha, Neelam; Hasan, Zaheer; Thakur, Vinit Kumar; Anand, Utpal; Priyadarshi, Rajiv Nayan; Mandal, Manish
2013-01-01
INTRODUCTION Foreign bodies in the urogenital tract are not uncommon. Hairpins, glass rods, umbilical tapes, ball point pen are described in lower urogenital tract. Retained gauze piece (gossypiboma) in posterior urethra may cause diagnostic dilemma. Symptoms and investigations may mimic stricture of posterior urethra. PRESENTATION OF CASE Two cases of retained gauze pieces in the urethra are described here. The micturating cystourethrogram was suggestive of posterior urethral stricture. DISCUSSION Two cases described here had retained gauze piece as a cause of filling defect and abnormal appearance in the micturating cystourethrogram. Gossypiboma may be a possibility where posterior urethral stricture are seen after previous surgery in paediatric age group. CONCLUSION In the setting of previous urogenital surgery gossypiboma should be kept in the differential diagnosis where posterior urethral stricture are seen in the paediatric age group. PMID:23500749
[Posterior reversible encephalopathy syndrome].
Fischer, M; Schmutzhard, E
2016-06-01
Posterior reversible encephalopathy syndrome refers to a neurological disorder characterized by headache, disorders of consciousness, visual disturbances, epileptic seizures, and subcortical vasogenic edema. About two thirds of patients develop neurological symptoms, which are associated with blood pressure fluctuations. One hypothesis is that hypertensive episodes cause autoregulatory failure, and values above the upper limit of cerebral autoregulation result in a breakthrough followed by hyperperfusion and blood-brain barrier dysfunction. In another hypothesis, endothelial dysfunction triggered by numerous factors including preeclampsia, immunosuppressive agents, chemotherapeutics, sepsis, or autoimmune disorders is thought to be the key pathomechanism. Endo- or exogenic toxic agents including pharmacological substances, cytokines, or bacterial toxins are supposed to trigger endothelial activation and dysfunction resulting in the release of vasoconstrictors, pro-inflammatory mediators, and vascular leakage. Diagnosis is usually based on clinical and neuroimaging findings that frequently show a bilateral, symmetric, and parietooccipital pattern. However, the diagnosis can often only be confirmed during the course of disease after excluding important differential diagnoses. Currently, there is no specific treatment available. Lowering of arterial blood pressure and eliminating the underlying cause usually leads to an improvement of clinical and neuroradiological findings. Admission to a critical care unit is required in about 40 % of patients due to complicating conditions including status epilepticus, cerebral vasoconstriction, ischemia, or intracerebral hemorrhage. Prognosis is favorable; in the majority of patients neurological deficits and imaging findings resolve completely. PMID:27272329
Probability mapping of contaminants
Rautman, C.A.; Kaplan, P.G.; McGraw, M.A.; Istok, J.D.; Sigda, J.M.
1994-04-01
Exhaustive characterization of a contaminated site is a physical and practical impossibility. Descriptions of the nature, extent, and level of contamination, as well as decisions regarding proposed remediation activities, must be made in a state of uncertainty based upon limited physical sampling. The probability mapping approach illustrated in this paper appears to offer site operators a reasonable, quantitative methodology for many environmental remediation decisions and allows evaluation of the risk associated with those decisions. For example, output from this approach can be used in quantitative, cost-based decision models for evaluating possible site characterization and/or remediation plans, resulting in selection of the risk-adjusted, least-cost alternative. The methodology is completely general, and the techniques are applicable to a wide variety of environmental restoration projects. The probability-mapping approach is illustrated by application to a contaminated site at the former DOE Feed Materials Production Center near Fernald, Ohio. Soil geochemical data, collected as part of the Uranium-in-Soils Integrated Demonstration Project, have been used to construct a number of geostatistical simulations of potential contamination for parcels approximately the size of a selective remediation unit (the 3-m width of a bulldozer blade). Each such simulation accurately reflects the actual measured sample values, and reproduces the univariate statistics and spatial character of the extant data. Post-processing of a large number of these equally likely statistically similar images produces maps directly showing the probability of exceeding specified levels of contamination (potential clean-up or personnel-hazard thresholds).
An improved probability mapping approach to assess genome mosaicism
Zhaxybayeva, Olga; Gogarten, J Peter
2003-01-01
Background Maximum likelihood and posterior probability mapping are useful visualization techniques that are used to ascertain the mosaic nature of prokaryotic genomes. However, posterior probabilities, especially when calculated for four-taxon cases, tend to overestimate the support for tree topologies. Furthermore, because of poor taxon sampling four-taxon analyses suffer from sensitivity to the long branch attraction artifact. Here we extend the probability mapping approach by improving taxon sampling of the analyzed datasets, and by using bootstrap support values, a more conservative tool to assess reliability. Results Quartets of orthologous proteins were complemented with homologs from selected reference genomes. The mapping of bootstrap support values from these extended datasets gives results similar to the original maximum likelihood and posterior probability mapping. The more conservative nature of the plotted support values allows to focus further analyses on those protein families that strongly disagree with the majority or plurality of genes present in the analyzed genomes. Conclusion Posterior probability is a non-conservative measure for support, and posterior probability mapping only provides a quick estimation of phylogenetic information content of four genomes. This approach can be utilized as a pre-screen to select genes that might have been horizontally transferred. Better taxon sampling combined with subtree analyses prevents the inconsistencies associated with four-taxon analyses, but retains the power of visual representation. Nevertheless, a case-by-case inspection of individual multi-taxon phylogenies remains necessary to differentiate unrecognized paralogy and shared phylogenetic reconstruction artifacts from horizontal gene transfer events. PMID:12974984
Multinomial mixture model with heterogeneous classification probabilities
Holland, M.D.; Gray, B.R.
2011-01-01
Royle and Link (Ecology 86(9):2505-2512, 2005) proposed an analytical method that allowed estimation of multinomial distribution parameters and classification probabilities from categorical data measured with error. While useful, we demonstrate algebraically and by simulations that this method yields biased multinomial parameter estimates when the probabilities of correct category classifications vary among sampling units. We address this shortcoming by treating these probabilities as logit-normal random variables within a Bayesian framework. We use Markov chain Monte Carlo to compute Bayes estimates from a simulated sample from the posterior distribution. Based on simulations, this elaborated Royle-Link model yields nearly unbiased estimates of multinomial and correct classification probability estimates when classification probabilities are allowed to vary according to the normal distribution on the logit scale or according to the Beta distribution. The method is illustrated using categorical submersed aquatic vegetation data. ?? 2010 Springer Science+Business Media, LLC.
Superior labrum anterior to posterior tears in throwing athletes.
Lintner, David M
2013-01-01
Superior labrum anterior to posterior (SLAP) tears and partial undersurface tears of the rotator cuff are common in experienced throwers, may be adaptive, and are only occasionally symptomatic. Pain in the shoulder of a throwing athlete with an MRI-documented SLAP tear or partial undersurface tear of the rotator cuff can be managed nonsurgically, with attention to posterior capsular contracture, scapular dyskinesia, and rotator cuff strength. The results of the surgical repair of SLAP lesions in the throwing athlete, with or without rotator cuff repair, are inferior to those of nonsurgical treatment. The cause of pain in the throwing athlete must be accurately diagnosed without reliance on MRI findings. PMID:23395053
Probability tree algorithm for general diffusion processes
NASA Astrophysics Data System (ADS)
Ingber, Lester; Chen, Colleen; Mondescu, Radu Paul; Muzzall, David; Renedo, Marco
2001-11-01
Motivated by path-integral numerical solutions of diffusion processes, PATHINT, we present a tree algorithm, PATHTREE, which permits extremely fast accurate computation of probability distributions of a large class of general nonlinear diffusion processes.
ERIC Educational Resources Information Center
Koo, Reginald; Jones, Martin L.
2011-01-01
Quite a number of interesting problems in probability feature an event with probability equal to 1/e. This article discusses three such problems and attempts to explain why this probability occurs with such frequency.
Isolated Posterior Fossa Involvement in Posterior Reversible Encephalopathy Syndrome
Shimizu, Yukie; Tha, Khin Khin; Iguchi, Akihiro; Cho, Yuko; Yoshida, Atsushi; Fujima, Noriyuki; Tsukahara, Akiko; Shirato, Hiroki; Terae, Satoshi
2013-01-01
Summary Posterior reversible encephalopathy syndrome (PRES) is characterized by reversible vasogenic edema affecting the subcortical white matter of bilateral occipital and parietal lobes. We describe a case of isolated posterior fossa involvement of PRES which occurred during remission induction chemotherapy for T-cell acute lymphoblastic leukemia. Both the brainstem and cerebellum were extensively involved, but the supratentorial structures were completely spared. The follow-up magnetic resonance images revealed reversibility of most lesions. The knowledge of atypical radiological features of PRES is essential for prompt diagnosis. PMID:24199811
Posterior polar cataract: A review
Kalantan, Hatem
2011-01-01
Posterior polar cataract is a rare form of congenital cataract. It is usually inherited as an autosomal dominant disease, yet it can be sporadic. Five genes have been attributed to the formation of this disease. It is highly associated with complications during surgery, such as posterior capsule rupture and nucleus drop. The reason for this high complication rate is the strong adherence of the opacity to the weak posterior capsule. Different surgical strategies were described for the handling of this challenging entity, most of which emphasized the need for gentle maneuvering in dealing with these cases. It has a unique clinical appearance that should not be missed in order to anticipate, avoid, and minimize the impact of the complications associated with it. PMID:23960967
Rethinking "posterior" tongue-tie.
Douglas, Pamela Sylvia
2013-12-01
Currently, many clinicians who help with breastfeeding problems are diagnosing "posterior" tongue-tie in infants and performing or referring for frenotomy. In this "Speaking Out" article, I argue that the diagnosis of "posterior" tongue-tie has successfully raised awareness of the importance of impaired tongue function in breastfeeding difficulty. However, the diagnosis of "posterior" tongue-tie also applies a reductionist, medicalized theoretical frame to the complex problem of impaired tongue function, risking unintended outcomes. Impaired tongue function arises out of multiple interacting and co-evolving factors, including the interplay between social behaviors concerning breastfeeding and mother-infant biology. Consideration of theoretical frames is vital if we are to build an evidence base through efficient use of the scarce resources available for clinical breastfeeding research and minimize unintended outcomes. PMID:24143939
The neuropsychiatric profile of posterior cortical atrophy.
Isella, Valeria; Villa, Giulia; Mapelli, Cristina; Ferri, Francesca; Appollonio, Ildebrando Marco; Ferrarese, Carlo
2015-06-01
We analyzed scores obtained at the Neuropsychiatric Inventory (NPI) by 20 patients with posterior cortical atrophy (PCA) and contrasted it with 20 patients having Alzheimer disease (AD). Patients with hallucinations and delusions were not included due to the high probability of a diagnosis of Lewy body disease. Prevalence of behavioral and psychological symptoms (BPSD) was 95% in the PCA group, the most frequent being apathy and anxiety. Cluster analysis on NPI subscales highlighted a behavioral subsyndrome characterized by agitated temper and irritability. Depression, anxiety, and apathy did not cluster with any other BPSD nor with each other. The PCA group showed a significantly higher proportion of anxious patients and worse anxiety score than patients with AD. No correlation was found between NPI data and demographic, clinical, or neuropsychological features nor were there significant differences for the same variables between anxious and nonanxious cases with PCA. In agreement with anecdotal reports, anxiety seems particularly relevant in PCA. PMID:25330926
NASA Astrophysics Data System (ADS)
Frič, Roman; Papčo, Martin
2015-12-01
Domains of generalized probability have been introduced in order to provide a general construction of random events, observables and states. It is based on the notion of a cogenerator and the properties of product. We continue our previous study and show how some other quantum structures fit our categorical approach. We discuss how various epireflections implicitly used in the classical probability theory are related to the transition to fuzzy probability theory and describe the latter probability theory as a genuine categorical extension of the former. We show that the IF-probability can be studied via the fuzzy probability theory. We outline a "tensor modification" of the fuzzy probability theory.
Neural representation of probabilities for Bayesian inference.
Rich, Dylan; Cazettes, Fanny; Wang, Yunyan; Peña, José Luis; Fischer, Brian J
2015-04-01
Bayesian models are often successful in describing perception and behavior, but the neural representation of probabilities remains in question. There are several distinct proposals for the neural representation of probabilities, but they have not been directly compared in an example system. Here we consider three models: a non-uniform population code where the stimulus-driven activity and distribution of preferred stimuli in the population represent a likelihood function and a prior, respectively; the sampling hypothesis which proposes that the stimulus-driven activity over time represents a posterior probability and that the spontaneous activity represents a prior; and the class of models which propose that a population of neurons represents a posterior probability in a distributed code. It has been shown that the non-uniform population code model matches the representation of auditory space generated in the owl's external nucleus of the inferior colliculus (ICx). However, the alternative models have not been tested, nor have the three models been directly compared in any system. Here we tested the three models in the owl's ICx. We found that spontaneous firing rate and the average stimulus-driven response of these neurons were not consistent with predictions of the sampling hypothesis. We also found that neural activity in ICx under varying levels of sensory noise did not reflect a posterior probability. On the other hand, the responses of ICx neurons were consistent with the non-uniform population code model. We further show that Bayesian inference can be implemented in the non-uniform population code model using one spike per neuron when the population is large and is thus able to support the rapid inference that is necessary for sound localization. PMID:25561333
Posterior Tibial Tendon Dysfunction (PTTD)
... ACFAS | Información en Español Advanced Search Home » Foot & Ankle Conditions » Posterior Tibial Tendon Dysfunction (PTTD) Text Size ... the arch, and an inward rolling of the ankle. As the condition progresses, the symptoms will change. ...
Stereolithography for Posterior Fossa Cranioplasty
Agner, Celso; Dujovny, Manuel; Evenhouse, Raymond; Charbel, Fady T.; Sadler, Lewis
1998-01-01
Posterior fossa cranioplasty has been suggested for improvement of neurological symptoms following craniectomy. However, there is no particular recommendation in the literature about techniques for prosthesis manufacture and implantation. We report our experience using rapid prototyping technology and stereolithography for pre-surgical implant design and production of cranioplasties. ImagesFigure 1Figure 2Figure 3Figure 4Figure 5 PMID:17171056
Probability and Relative Frequency
NASA Astrophysics Data System (ADS)
Drieschner, Michael
2016-01-01
The concept of probability seems to have been inexplicable since its invention in the seventeenth century. In its use in science, probability is closely related with relative frequency. So the task seems to be interpreting that relation. In this paper, we start with predicted relative frequency and show that its structure is the same as that of probability. I propose to call that the `prediction interpretation' of probability. The consequences of that definition are discussed. The "ladder"-structure of the probability calculus is analyzed. The expectation of the relative frequency is shown to be equal to the predicted relative frequency. Probability is shown to be the most general empirically testable prediction.
ERIC Educational Resources Information Center
Bailey, David H.
2000-01-01
Some of the most impressive-sounding criticisms of the conventional theory of biological evolution involve probability. Presents a few examples of how probability should and should not be used in discussing evolution. (ASK)
BIODEGRADATION PROBABILITY PROGRAM (BIODEG)
The Biodegradation Probability Program (BIODEG) calculates the probability that a chemical under aerobic conditions with mixed cultures of microorganisms will biodegrade rapidly or slowly. It uses fragment constants developed using multiple linear and non-linear regressions and d...
ERIC Educational Resources Information Center
Ewbank, William A.; Ginther, John L.
2002-01-01
Describes how to use common dice numbered 1-6 for simple mathematical situations including probability. Presents a lesson using regular dice and specially marked dice to explore some of the concepts of probability. (KHR)
ERIC Educational Resources Information Center
Edwards, William F.; Shiflett, Ray C.; Shultz, Harris
2008-01-01
The mathematical model used to describe independence between two events in probability has a non-intuitive consequence called dependent spaces. The paper begins with a very brief history of the development of probability, then defines dependent spaces, and reviews what is known about finite spaces with uniform probability. The study of finite…
Palay, A.J.
1985-01-01
This book examines how probability distributions can be used as a knowledge representation technique. It presents a mechanism that can be used to guide a selective search algorithm to solve a variety of tactical chess problems. Topics covered include probabilities and searching the B algorithm and chess probabilities - in practice, examples, results, and future work.
Arthroscopic Management of Anterior, Posterior, and Multidirectional Shoulder Instabilities.
Field, Larry D; Ryu, Richard K N; Abrams, Jeffrey S; Provencher, Matthew
2016-01-01
Arthroscopic shoulder stabilization offers several potential advantages compared with open surgery, including the opportunity to more accurately evaluate the glenohumeral joint at the time of diagnostic assessment; comprehensively address multiple pathologic lesions that may be identified; and avoid potential complications unique to open stabilization, such as postoperative subscapularis failure. A thorough understanding of normal shoulder anatomy and biomechanics, along with the pathoanatomy responsible for anterior, posterior, and multidirectional shoulder instability patterns, is very important in the management of patients who have shoulder instability. The treating physician also must be familiar with diagnostic imaging and physical examination maneuvers that are required to accurately diagnose shoulder instability. PMID:27049209
Posterior cruciate ligament of the knee (image)
The posterior cruciate ligament (PCL) is a powerful ligament extending from the top-rear surface of the tibia to the bottom-front surface of the femur. The ligament prevents the knee joint from posterior instability.
Bilateral posterior cerebral artery infarction.
Ryan, Davinia; Murphy, Sinead M; Hennessey, Michael J
2010-01-01
We report the case of a 70-year-old man who presented with short-term memory impairment and a homonymous left inferior quadrantanopia secondary to simultaneous bilateral posterior cerebral artery (PCA) territory infarction. As in more than a quarter of cases of PCA infarction, no aetiological cause was identified. Unlike the transient nature of symptoms in some cases following unilateral infarction, his deficits persisted on 2-month follow-up. PMID:22798298
Spinal hemianesthesia: Unilateral and posterior
Imbelloni, Luiz Eduardo
2014-01-01
The injection of a non-isobaric local anesthetic should induce a unilateral spinal anesthesia in patients in a lateral decubitus position. The posterior spinal hemianesthesia only be obtained with hypobaric solutions injected in the jackknife position. The most important factors to be considered when performing a spinal hemianesthesia are: type and gauge of the needle, density of the local anesthetic relative to the CSF, position of the patient, speed of administration of the solution, time of stay in position, and dose/concentration/volume of the anesthetic solution. The distance between the spinal roots on the right-left sides and anterior-posterior is, approximately, 10-15 mm. This distance allows performing unilateral spinal anesthesia or posterior spinal anesthesia. The great advantage of obtaining spinal hemianesthesia is the reduction of cardiovascular changes. Likewise, both the dorsal and unilateral sensory block predominates in relation to the motor block. Because of the numerous advantages of producing spinal hemianesthesia, anesthesiologists should apply this technique more often. This review considers the factors which are relevant, plausible and proven to obtain spinal hemianesthesia. PMID:25886320
In All Probability, Probability is not All
ERIC Educational Resources Information Center
Helman, Danny
2004-01-01
The national lottery is often portrayed as a game of pure chance with no room for strategy. This misperception seems to stem from the application of probability instead of expectancy considerations, and can be utilized to introduce the statistical concept of expectation.
Bladder neck incompetence at posterior urethroplasty
Koraitim, Mamdouh M.
2015-01-01
The finding of an incompetent bladder neck (BN) at the time of posterior urethroplasty will necessarily exacerbate the already difficult situation. In such cases the aim of the treatment is not only to restore urethral continuity by end-to-end urethral anastomosis, but also to restore the function of the BN to maintain urinary continence. Fortunately, the incidence of incompetence of the BN at posterior urethroplasty is uncommon, usually ≈4.5%. It seems that pelvic fracture-related BN injuries, in contrast to urethral injuries which result from a shearing force, are due to direct injury by the sharp edge of the fractured and displaced pubic bone. The risk of injuries to the BN is greater in children, in patients with a fracture involving both superior and inferior pubic rami on the same side, and in those managed initially by primary realignment. An incompetent BN is suspected by finding an open rectangular BN on cystography, and a fixedly open BN on suprapubic cystoscopy. An incompetent BN can be treated either subsequent to or concomitant with the urethral repair, according to whether a perineal or a perineo-abdominal urethroplasty is used, respectively. Several options have been reported to treat pelvic fracture-related BN incompetence, including reconstructing the BN, forming a new sphincter by tubularisation of a rectangular flap of the anterior bladder wall, and mechanical occlusion by an artificial sphincter or collagen injection. Reconstruction of the BN by the Young-Dees-Leadbetter∗∗ procedure probably provides the most successful results. PMID:26019982
Flood hazard probability mapping method
NASA Astrophysics Data System (ADS)
Kalantari, Zahra; Lyon, Steve; Folkeson, Lennart
2015-04-01
In Sweden, spatially explicit approaches have been applied in various disciplines such as landslide modelling based on soil type data and flood risk modelling for large rivers. Regarding flood mapping, most previous studies have focused on complex hydrological modelling on a small scale whereas just a few studies have used a robust GIS-based approach integrating most physical catchment descriptor (PCD) aspects on a larger scale. The aim of the present study was to develop methodology for predicting the spatial probability of flooding on a general large scale. Factors such as topography, land use, soil data and other PCDs were analysed in terms of their relative importance for flood generation. The specific objective was to test the methodology using statistical methods to identify factors having a significant role on controlling flooding. A second objective was to generate an index quantifying flood probability value for each cell, based on different weighted factors, in order to provide a more accurate analysis of potential high flood hazards than can be obtained using just a single variable. The ability of indicator covariance to capture flooding probability was determined for different watersheds in central Sweden. Using data from this initial investigation, a method to subtract spatial data for multiple catchments and to produce soft data for statistical analysis was developed. It allowed flood probability to be predicted from spatially sparse data without compromising the significant hydrological features on the landscape. By using PCD data, realistic representations of high probability flood regions was made, despite the magnitude of rain events. This in turn allowed objective quantification of the probability of floods at the field scale for future model development and watershed management.
Silverman, C.L.; Simpson, J.R.
1982-11-01
Fifty patients with biopsy-proven cerebellar medulloblastoma were retrospectively analyzed for prognostic factors, survival and patterns of failure. Five- and ten-year actuarial survivals for the entire group were 51% and 42%. Survival and local control were significantly better for the 21 patients who received doses greater than 5000 rad to the posterior fossa (85% and 80% respectively) than for the remaining patients (38% and 38%, respectively). Significant prognostic factors included achievement of local control in the posterior fossa (p = .0001) and dose to the posterior fossa (p = .0005). Sex, age, duration of symptoms, extent of surgery and initial T-stage of disease were not significant. Posterior fossa was the predominant site of failure (71% of failures), but 10% of patients failed in the cerebrum and 12% outside the CNS. This experience confirms that survival rates of 70-80% are achievable with current treatment policies but accurate and consistent dose delivery to the posterior fossa is essential.
Silverman, C.L.; Simpson, J.R.
1982-11-01
Fifty patients with biopsy-proven cerebellar medulloblastoma were retrospectively analyzed for prognostic factors, survival and patterns of failure. Five- and ten-year actuarial survivals for the entire group were 51% and 42%. Survival and local control were significantly better for the 21 patients who received doses greater that 5000 rad to the posterior fossa (85% and 80% respectively) than for the remaining patients (38% and 38%, respectively). Significant prognostic factors included achievement of local control in the posterior fossa (p = .0001) and dose to the posterior fossa (p = .0005). Sex, age, duration of symptoms, extent of surgery and initial T-stage of disease were not significant. Posterior fossa was the predominant site of failure (71% of failures), but 10% of patients failed in the cerebrum and 12% outside the CNS. This experience confirms that survival rates of 70-80% are achievable with current treatment policies but accurate and consistent dose delivery to the posterior fossa is essential.
FEMORAL INSERTION OF THE POSTERIOR CRUCIATE LIGAMENT: AN ANATOMICAL STUDY
de Paula Leite Cury, Ricardo; Severino, Nilson Roberto; Camargo, Osmar Pedro Arbix; Aihara, Tatsuo; Neto, Leopoldo Viana Batista; Goarayeb, Dedley Nelson
2015-01-01
Objective: To identify objective parameters to guide correct location of the posterior cruciate ligament (PCL) in the femur. Methods: The PCLs of 20 human cadavers were resected. The following portions were measured: distance from the most distal portion of the PCL, close to the roof, to the most anterior edge of the cartilage (AB); distance from the most proximal portion of the PCL, close to the roof, to the most anterior cartilage (AC); distance between the two parts of the ligament close to the roof (BC); distance from the distal edge in its posterior portion, to the more posterior joint edge (DE); distance from the distal edge of the ligament in its posterior portion, to the intercondylar roof (DF); and finally, the format of the ligament insertion and area of coverage on the femoral condyle. Results: The PCL has the shape of a quarter ellipse, with an average area of 153.5mm2. The mean distances found were: AB of 2.1mm, AC of 10.7mm, BC of 8.6mm DE of 12.4mm and DF of 16.8mm. Conclusions: The edge close to the roof of the anterolateral bundle is closer to the joint cartilage (2.1mm) than the posteromedial bundle is, which is 12.4mm from the edge proximal to the cartilage. These references should assist in better and more accurate positioning of femoral tunnels in PCL reconstruction. PMID:27027059
Bilateral posterior shoulder dislocation after electrical shock: A case report
Ketenci, Ismail Emre; Duymus, Tahir Mutlu; Ulusoy, Ayhan; Yanik, Hakan Serhat; Mutlu, Serhat; Durakbasa, Mehmet Oguz
2015-01-01
Introduction Posterior dislocation of the shoulder is a rare and commonly missed injury. Unilateral dislocations occur mostly due to trauma. Bilateral posterior shoulder dislocations are even more rare and result mainly from epileptic seizures. Electrical injury is a rare cause of posterior shoulder dislocation. Injury mechanism in electrical injury is similar to epileptic seizures, where the shoulder is forced to internal rotation, flexion and adduction. Presentation of case This report presents a case of bilateral posterior shoulder dislocation after electrical shock. We were able to find a few individual case reports describing this condition. The case was acute and humeral head impression defects were minor. Our treatment in this case consisted of closed reduction under general anesthesia and applying of orthoses which kept the shoulders in abduction and external rotation. A rehabilitation program was begun after 3 weeks of immobilization. After 6 months of injury the patient has returned to work. 20 months postoperatively, at final follow-up, he was painless and capable of performing all of his daily activities. Discussion The amount of bilateral shoulder dislocations after electrical injury is not reported but is known to be very rare. The aim of this case presentation is to report an example for this rare entity, highlight the difficulties in diagnosis and review the treatment options. Conclusion Physical examination and radiographic evaluation are important for quick and accurate diagnosis. PMID:26904192
Isolated posterior cruciate ligament calcification.
Koukoulias, Nikolaos E; Papastergiou, Stergios G
2011-01-01
The authors present a case of calcified posterior cruciate ligament (PCL). A 61-year-old female presented in our department reporting 12 months history of knee pain that was getting worse during the night. The patient was under medication for epileptic seizure, osteoporosis and hyperthyroidism. X-rays demonstrated calcification of the PCL. CT and MRI excluded any other intra-articular and extra-articular pathology. Arthroscopic debridement of the calcium deposits was performed and the symptoms resolved immediately, while the postoperative x-rays were normal. Histological examination confirmed the calcium nature of the lesion. Two years postoperatively the patient remains asymptomatic. PMID:22669889
Isolated posterior cruciate ligament calcification
Koukoulias, Nikolaos E; Papastergiou, Stergios G
2011-01-01
The authors present a case of calcified posterior cruciate ligament (PCL). A 61-year-old female presented in our department reporting 12 months history of knee pain that was getting worse during the night. The patient was under medication for epileptic seizure, osteoporosis and hyperthyroidism. X-rays demonstrated calcification of the PCL. CT and MRI excluded any other intra-articular and extra-articular pathology. Arthroscopic debridement of the calcium deposits was performed and the symptoms resolved immediately, while the postoperative x-rays were normal. Histological examination confirmed the calcium nature of the lesion. Two years postoperatively the patient remains asymptomatic. PMID:22669889
Posterior ankyloglossia: a case report.
Chu, Michael W; Bloom, David C
2009-06-01
Ankyloglossia, or tongue-tie, refers to an abnormally short lingual frenulum. Ankyloglossia is a recognized but poorly defined condition and has been reported to cause feeding difficulties, dysarthria, dyspnea, and social or mechanical problems. In infants, the most concerning symptoms are feeding difficulties and inability to breastfeed. While a recent trend toward breastfeeding has brought frenulectomy back into favor, the literature regarding treatment remains inconclusive. We report a case of posterior ankyloglossia with anterior mucosal hooding and a simple, safe, and effective way to treat it to improve breastfeeding. PMID:19303646
Longevity of Posterior Composite Restorations
Opdam, N.J.M.; van de Sande, F.H.; Bronkhorst, E.; Cenci, M.S.; Bottenberg, P.; Pallesen, U.; Gaengler, P.; Lindberg, A.; Huysmans, M.C.D.N.J.M.; van Dijken, J.W.
2014-01-01
The aim of this meta-analysis, based on individual participant data from several studies, was to investigate the influence of patient-, materials-, and tooth-related variables on the survival of posterior resin composite restorations. Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we conducted a search resulting in 12 longitudinal studies of direct posterior resin composite restorations with at least 5 years’ follow-up. Original datasets were still available, including placement/failure/censoring of restorations, restored surfaces, materials used, reasons for clinical failure, and caries-risk status. A database including all restorations was constructed, and a multivariate Cox regression method was used to analyze variables of interest [patient (age; gender; caries-risk status), jaw (upper; lower), number of restored surfaces, resin composite and adhesive materials, and use of glass-ionomer cement as base/liner (present or absent)]. The hazard ratios with respective 95% confidence intervals were determined, and annual failure rates were calculated for subgroups. Of all restorations, 2,816 (2,585 Class II and 231 Class I) were included in the analysis, of which 569 failed during the observation period. Main reasons for failure were caries and fracture. The regression analyses showed a significantly higher risk of failure for restorations in high-caries-risk individuals and those with a higher number of restored surfaces. PMID:25048250
ERIC Educational Resources Information Center
Rom, Mark Carl
2011-01-01
Grades matter. College grading systems, however, are often ad hoc and prone to mistakes. This essay focuses on one factor that contributes to high-quality grading systems: grading accuracy (or "efficiency"). I proceed in several steps. First, I discuss the elements of "efficient" (i.e., accurate) grading. Next, I present analytical results…
NASA Astrophysics Data System (ADS)
Miller, David
1991-12-01
The propensity interpretation of probability, bred by Popper in 1957 (K. R. Popper, in Observation and Interpretation in the Philosophy of Physics, S. Körner, ed. (Butterworth, London, 1957, and Dover, New York, 1962), p. 65; reprinted in Popper Selections, D. W. Miller, ed. (Princeton University Press, Princeton, 1985), p. 199) from pure frequency stock, is the only extant objectivist account that provides any proper understanding of single-case probabilities as well as of probabilities in ensembles and in the long run. In Sec. 1 of this paper I recall salient points of the frequency interpretations of von Mises and of Popper himself, and in Sec. 2 I filter out from Popper's numerous expositions of the propensity interpretation its most interesting and fertile strain. I then go on to assess it. First I defend it, in Sec. 3, against recent criticisms (P. Humphreys, Philos. Rev. 94, 557 (1985); P. Milne, Erkenntnis 25, 129 (1986)) to the effect that conditional [or relative] probabilities, unlike absolute probabilities, can only rarely be made sense of as propensities. I then challenge its predominance, in Sec. 4, by outlining a rival theory: an irreproachably objectivist theory of probability, fully applicable to the single case, that interprets physical probabilities as instantaneous frequencies.
Decoding Trajectories from Posterior Parietal Cortex Ensembles
Mulliken, Grant H.; Musallam, Sam; Andersen, Richard A.
2009-01-01
High-level cognitive signals in the posterior parietal cortex (PPC) have previously been used to decode the intended endpoint of a reach, providing the first evidence that PPC can be used for direct control of a neural prosthesis (Musallam et al., 2004). Here we expand on this work by showing that PPC neural activity can be harnessed to estimate not only the endpoint but also to continuously control the trajectory of an end effector. Specifically, we trained two monkeys to use a joystick to guide a cursor on a computer screen to peripheral target locations while maintaining central ocular fixation. We found that we could accurately reconstruct the trajectory of the cursor using a relatively small ensemble of simultaneously recorded PPC neurons. Using a goal-based Kalman filter that incorporates target information into the state-space, we showed that the decoded estimate of cursor position could be significantly improved. Finally, we tested whether we could decode trajectories during closed-loop brain control sessions, in which the real-time position of the cursor was determined solely by a monkey’s neural activity in PPC. The monkey learned to perform brain control trajectories at 80% success rate(for 8 targets) after just 4–5 sessions. This improvement in behavioral performance was accompanied by a corresponding enhancement in neural tuning properties (i.e., increased tuning depth and coverage of encoding parameter space) as well as an increase in off-line decoding performance of the PPC ensemble. PMID:19036985
ERIC Educational Resources Information Center
Marshall, Jennings B.
2007-01-01
This article describes how roulette can be used to teach basic concepts of probability. Various bets are used to illustrate the computation of expected value. A betting system shows variations in patterns that often appear in random events.
Minimally invasive posterior hamstring harvest.
Wilson, Trent J; Lubowitz, James H
2013-01-01
Autogenous hamstring harvesting for knee ligament reconstruction is a well-established standard. Minimally invasive posterior hamstring harvest is a simple, efficient, reproducible technique for harvest of the semitendinosus or gracilis tendon or both medial hamstring tendons. A 2- to 3-cm longitudinal incision from the popliteal crease proximally, in line with the semitendinosus tendon, is sufficient. The deep fascia is bluntly penetrated, and the tendon or tendons are identified. Adhesions are dissected. Then, an open tendon stripper is used to release the tendon or tendons proximally; a closed, sharp tendon stripper is used to release the tendon or tendons from the pes. Layered, absorbable skin closure is performed, and the skin is covered with a skin sealant, bolster dressing, and plastic adhesive bandage for 2 weeks. PMID:24266003
Primary Burkitt lymphoma in the posterior mediastinum.
Chaari, Zied; Charfi, Slim; Hentati, Abdessalem; Ayadi, Ines; Abid, Hanene; Frikha, Imed
2015-11-01
A 13-year-old boy was admitted to our hospital with complaints of posterior chest pain and dyspnea. Computed tomography and magnetic resonance imaging of the chest revealed a mass in the posterior mediastinum, extending from T8 to T11 with intraspinal involvement. A percutaneous core needle biopsy confirmed the diagnosis of Burkitt lymphoma. He was treated according to the Lymphoma Malignancy B protocol 2001 arm C3, but he presented with liver and brain relapses and died 7.5 months after admission. Although lymphoma is rarely localized in the posterior mediastinum, it should be considered in the differential diagnosis of posterior mediastinal masses in children. PMID:26038605
NASA Technical Reports Server (NTRS)
Bollenbacher, Gary; Guptill, James D.
1999-01-01
This report analyzes the probability of a launch vehicle colliding with one of the nearly 10,000 tracked objects orbiting the Earth, given that an object on a near-collision course with the launch vehicle has been identified. Knowledge of the probability of collision throughout the launch window can be used to avoid launching at times when the probability of collision is unacceptably high. The analysis in this report assumes that the positions of the orbiting objects and the launch vehicle can be predicted as a function of time and therefore that any tracked object which comes close to the launch vehicle can be identified. The analysis further assumes that the position uncertainty of the launch vehicle and the approaching space object can be described with position covariance matrices. With these and some additional simplifying assumptions, a closed-form solution is developed using two approaches. The solution shows that the probability of collision is a function of position uncertainties, the size of the two potentially colliding objects, and the nominal separation distance at the point of closest approach. ne impact of the simplifying assumptions on the accuracy of the final result is assessed and the application of the results to the Cassini mission, launched in October 1997, is described. Other factors that affect the probability of collision are also discussed. Finally, the report offers alternative approaches that can be used to evaluate the probability of collision.
Homonymous Hemianopsia Associated with Probable Alzheimer's Disease.
Ishiwata, Akiko; Kimura, Kazumi
2016-01-01
Posterior cortical atrophy (PCA) is a rare neurodegenerative disorder that has cerebral atrophy in the parietal, occipital, or occipitotemporal cortices and is characterized by visuospatial and visuoperceptual impairments. The most cases are pathologically compatible with Alzheimer's disease (AD). We describe a case of PCA in which a combination of imaging methods, in conjunction with symptoms and neurological and neuropsychological examinations, led to its being diagnosed and to AD being identified as its probable cause. Treatment with donepezil for 6 months mildly improved alexia symptoms, but other symptoms remained unchanged. A 59-year-old Japanese woman with progressive alexia, visual deficit, and mild memory loss was referred to our neurologic clinic for the evaluation of right homonymous hemianopsia. Our neurological examination showed alexia, constructional apraxia, mild disorientation, short-term memory loss, and right homonymous hemianopsia. These findings resulted in a score of 23 (of 30) points on the Mini-Mental State Examination. Occipital atrophy was identified, with magnetic resonance imaging (MRI) showing left-side dominance. The MRI data were quantified with voxel-based morphometry, and PCA was diagnosed on the basis of these findings. Single photon emission computed tomography with (123)I-N-isopropyl-p-iodoamphetamine showed hypoperfusion in the corresponding voxel-based morphometry occipital lobes. Additionally, the finding of hypoperfusion in the posterior associate cortex, posterior cingulate gyrus, and precuneus was consistent with AD. Therefore, the PCA was considered to be a result of AD. We considered Lewy body dementia as a differential diagnosis because of the presence of hypoperfusion in the occipital lobes. However, the patient did not meet the criteria for Lewy body dementia during the course of the disease. We therefore consider including PCA in the differential diagnoses to be important for patients with visual deficit, cognitive
Estimating the Probability of Negative Events
ERIC Educational Resources Information Center
Harris, Adam J. L.; Corner, Adam; Hahn, Ulrike
2009-01-01
How well we are attuned to the statistics of our environment is a fundamental question in understanding human behaviour. It seems particularly important to be able to provide accurate assessments of the probability with which negative events occur so as to guide rational choice of preventative actions. One question that arises here is whether or…
Accurate monotone cubic interpolation
NASA Technical Reports Server (NTRS)
Huynh, Hung T.
1991-01-01
Monotone piecewise cubic interpolants are simple and effective. They are generally third-order accurate, except near strict local extrema where accuracy degenerates to second-order due to the monotonicity constraint. Algorithms for piecewise cubic interpolants, which preserve monotonicity as well as uniform third and fourth-order accuracy are presented. The gain of accuracy is obtained by relaxing the monotonicity constraint in a geometric framework in which the median function plays a crucial role.
Accurate Finite Difference Algorithms
NASA Technical Reports Server (NTRS)
Goodrich, John W.
1996-01-01
Two families of finite difference algorithms for computational aeroacoustics are presented and compared. All of the algorithms are single step explicit methods, they have the same order of accuracy in both space and time, with examples up to eleventh order, and they have multidimensional extensions. One of the algorithm families has spectral like high resolution. Propagation with high order and high resolution algorithms can produce accurate results after O(10(exp 6)) periods of propagation with eight grid points per wavelength.
Experimental Probability in Elementary School
ERIC Educational Resources Information Center
Andrew, Lane
2009-01-01
Concepts in probability can be more readily understood if students are first exposed to probability via experiment. Performing probability experiments encourages students to develop understandings of probability grounded in real events, as opposed to merely computing answers based on formulae.
Gaussianization for fast and accurate inference from cosmological data
NASA Astrophysics Data System (ADS)
Schuhmann, Robert L.; Joachimi, Benjamin; Peiris, Hiranya V.
2016-06-01
We present a method to transform multivariate unimodal non-Gaussian posterior probability densities into approximately Gaussian ones via non-linear mappings, such as Box-Cox transformations and generalizations thereof. This permits an analytical reconstruction of the posterior from a point sample, like a Markov chain, and simplifies the subsequent joint analysis with other experiments. This way, a multivariate posterior density can be reported efficiently, by compressing the information contained in Markov Chain Monte Carlo samples. Further, the model evidence integral (i.e. the marginal likelihood) can be computed analytically. This method is analogous to the search for normal parameters in the cosmic microwave background, but is more general. The search for the optimally Gaussianizing transformation is performed computationally through a maximum-likelihood formalism; its quality can be judged by how well the credible regions of the posterior are reproduced. We demonstrate that our method outperforms kernel density estimates in this objective. Further, we select marginal posterior samples from Planck data with several distinct strongly non-Gaussian features, and verify the reproduction of the marginal contours. To demonstrate evidence computation, we Gaussianize the joint distribution of data from weak lensing and baryon acoustic oscillations, for different cosmological models, and find a preference for flat Λcold dark matter. Comparing to values computed with the Savage-Dickey density ratio, and Population Monte Carlo, we find good agreement of our method within the spread of the other two.
A highly accurate interatomic potential for argon
NASA Astrophysics Data System (ADS)
Aziz, Ronald A.
1993-09-01
A modified potential based on the individually damped model of Douketis, Scoles, Marchetti, Zen, and Thakkar [J. Chem. Phys. 76, 3057 (1982)] is presented which fits, within experimental error, the accurate ultraviolet (UV) vibration-rotation spectrum of argon determined by UV laser absorption spectroscopy by Herman, LaRocque, and Stoicheff [J. Chem. Phys. 89, 4535 (1988)]. Other literature potentials fail to do so. The potential also is shown to predict a large number of other properties and is probably the most accurate characterization of the argon interaction constructed to date.
Pseudoaneurysm of the Posterior Tibial Artery After Posterior Tibial Tendon Transfer.
Elabdi, Monsef; Roukhsi, Redouane; Tijani, Youssef; Chtata, Hassan; Jaafar, Abdeloihab
2016-01-01
Pseudoaneurysm of the posterior tibial artery is an uncommon condition that, left untreated, can lead to hemorrhage, thrombosis, or emboli. We present the case of a 54-year-old male who developed pseudoaneurysm of the posterior tibial artery 4 months after undergoing tibialis posterior tendon transfer for management of peroneal nerve palsy, which had developed as a complication of hip arthroplasty. PMID:26972754
Acceptance, values, and probability.
Steel, Daniel
2015-10-01
This essay makes a case for regarding personal probabilities used in Bayesian analyses of confirmation as objects of acceptance and rejection. That in turn entails that personal probabilities are subject to the argument from inductive risk, which aims to show non-epistemic values can legitimately influence scientific decisions about which hypotheses to accept. In a Bayesian context, the argument from inductive risk suggests that value judgments can influence decisions about which probability models to accept for likelihoods and priors. As a consequence, if the argument from inductive risk is sound, then non-epistemic values can affect not only the level of evidence deemed necessary to accept a hypothesis but also degrees of confirmation themselves. PMID:26386533
Posterior Cervical Foraminotomy: Indications, Technique, and Outcomes.
Dodwad, Shah-Jahan M; Dodwad, Shah-Nawaz M; Prasarn, Mark L; Savage, Jason W; Patel, Alpesh A; Hsu, Wellington K
2016-06-01
Cervical radiculopathy presents with upper extremity pain, decreased sensation, and decreased strength caused by irritation of specific nerve root(s). After failure of conservative management, surgical options include anterior cervical decompression and fusion, disk arthroplasty, and posterior cervical foraminotomy. In this review, we discuss indications, techniques, and outcomes of posterior cervical laminoforaminotomy. PMID:27187617
Consistently inconsistent, the posterior vaginal wall.
Hale, Douglass S; Fenner, Dee
2016-03-01
Posterior vaginal wall prolapse is one of the most common prolapses encountered by gynecological surgeons. What appears to be a straightforward condition to diagnose and treat surgically for physicians has proven to be frustratingly unpredictable with regard to symptom relief for patients. Functional disorders such as dyssynergic defecation and constipation are often attributed to posterior vaginal wall prolapse. Little scientific evidence supports this assumption, emphasizing that structure and function are not synonymous when treating posterior vaginal wall prolapse. Rectoceles, enteroceles, sigmoidoceles, peritoneoceles, rectal and intraanal intussusception, rectal prolapse, and descending perineal syndrome are all conditions that have an impact on the posterior vaginal wall. All too often these different anatomic conditions are treated with the same surgical approach, addressing a posterior vaginal wall bulge with a traditional posterior colporrhaphy. Studies that examine the correlation between stage of posterior wall prolapse and patient symptoms have failed to reliably do so. Surgical outcomes measured by prolapse staging appear successful, yet patient expectations are often not met. As increasing attention is being placed on patient satisfaction outcomes concerning surgical treatments, this fact will need to be addressed. Surgeons will have to clearly communicate what can and what cannot be expected with surgical repair of posterior vaginal wall prolapse. PMID:26348375
Posterior shoulder pain and anterior instability: a preliminary clinical study.
Castagna, Alessandro; Conti, Marco; Borroni, Mario; Massazza, Giuseppe; Vinci, Enzo; Franceschi, Giorgio; Garofalo, Raffaele
2008-02-01
. It can also be related to eccentric work of posterior stabilising muscles of scapula during the altered biomechanics observed in case of anterior shoulder instability. This pain responds positively to surgical intervention showing that re-centring the humeral head probably also re-establishes the periscapular muscle-firing pattern with a mechanism mediated by the proprioceptive system. PMID:18320378
Approximating Integrals Using Probability
ERIC Educational Resources Information Center
Maruszewski, Richard F., Jr.; Caudle, Kyle A.
2005-01-01
As part of a discussion on Monte Carlo methods, which outlines how to use probability expectations to approximate the value of a definite integral. The purpose of this paper is to elaborate on this technique and then to show several examples using visual basic as a programming tool. It is an interesting method because it combines two branches of…
ERIC Educational Resources Information Center
Varga, Tamas
This booklet resulted from a 1980 visit by the author, a Hungarian mathematics educator, to the Teachers' Center Project at Southern Illinois University at Edwardsville. Included are activities and problems that make probablility concepts accessible to young children. The topics considered are: two probability games; choosing two beads; matching…
Application of Quantum Probability
NASA Astrophysics Data System (ADS)
Bohdalová, Mária; Kalina, Martin; Nánásiová, Ol'ga
2009-03-01
This is the first attempt to smooth time series using estimators with applying quantum probability with causality (non-commutative s-maps on an othomodular lattice). In this context it means that we use non-symmetric covariance matrix to construction of our estimator.
Univariate Probability Distributions
ERIC Educational Resources Information Center
Leemis, Lawrence M.; Luckett, Daniel J.; Powell, Austin G.; Vermeer, Peter E.
2012-01-01
We describe a web-based interactive graphic that can be used as a resource in introductory classes in mathematical statistics. This interactive graphic presents 76 common univariate distributions and gives details on (a) various features of the distribution such as the functional form of the probability density function and cumulative distribution…
Bilateral posterior circulation stroke secondary to a crotalid envenomation: case report.
Vale, Thiago Cardoso; Leite, Alysson Ferreira; Hora, Priscila Ribeiro da; Coury, Marayra Inês França; Silva, Ricardo Cipriano da; Teixeira, Antônio Lúcio
2013-01-01
Snake bite envenoming is a disease with potential serious neurological complications. We report a case of an adolescent who was bitten by a rattlesnake and developed bilateral posterior circulation stroke. The rattlesnake was later identified as being Crotalus durissus terrificus. Stroke was probably due to toxic vasculitis or toxin-induced vascular spasm and endothelial damage. PMID:23740059
NASA Astrophysics Data System (ADS)
Itano, Wayne M.; Ramsey, Norman F.
1993-07-01
The paper discusses current methods for accurate measurements of time by conventional atomic clocks, with particular attention given to the principles of operation of atomic-beam frequency standards, atomic hydrogen masers, and atomic fountain and to the potential use of strings of trapped mercury ions as a time device more stable than conventional atomic clocks. The areas of application of the ultraprecise and ultrastable time-measuring devices that tax the capacity of modern atomic clocks include radio astronomy and tests of relativity. The paper also discusses practical applications of ultraprecise clocks, such as navigation of space vehicles and pinpointing the exact position of ships and other objects on earth using the GPS.
Accurate quantum chemical calculations
NASA Technical Reports Server (NTRS)
Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Taylor, Peter R.
1989-01-01
An important goal of quantum chemical calculations is to provide an understanding of chemical bonding and molecular electronic structure. A second goal, the prediction of energy differences to chemical accuracy, has been much harder to attain. First, the computational resources required to achieve such accuracy are very large, and second, it is not straightforward to demonstrate that an apparently accurate result, in terms of agreement with experiment, does not result from a cancellation of errors. Recent advances in electronic structure methodology, coupled with the power of vector supercomputers, have made it possible to solve a number of electronic structure problems exactly using the full configuration interaction (FCI) method within a subspace of the complete Hilbert space. These exact results can be used to benchmark approximate techniques that are applicable to a wider range of chemical and physical problems. The methodology of many-electron quantum chemistry is reviewed. Methods are considered in detail for performing FCI calculations. The application of FCI methods to several three-electron problems in molecular physics are discussed. A number of benchmark applications of FCI wave functions are described. Atomic basis sets and the development of improved methods for handling very large basis sets are discussed: these are then applied to a number of chemical and spectroscopic problems; to transition metals; and to problems involving potential energy surfaces. Although the experiences described give considerable grounds for optimism about the general ability to perform accurate calculations, there are several problems that have proved less tractable, at least with current computer resources, and these and possible solutions are discussed.
Adaptive approximation of higher order posterior statistics
Lee, Wonjung
2014-02-01
Filtering is an approach for incorporating observed data into time-evolving systems. Instead of a family of Dirac delta masses that is widely used in Monte Carlo methods, we here use the Wiener chaos expansion for the parametrization of the conditioned probability distribution to solve the nonlinear filtering problem. The Wiener chaos expansion is not the best method for uncertainty propagation without observations. Nevertheless, the projection of the system variables in a fixed polynomial basis spanning the probability space might be a competitive representation in the presence of relatively frequent observations because the Wiener chaos approach not only leads to an accurate and efficient prediction for short time uncertainty quantification, but it also allows to apply several data assimilation methods that can be used to yield a better approximate filtering solution. The aim of the present paper is to investigate this hypothesis. We answer in the affirmative for the (stochastic) Lorenz-63 system based on numerical simulations in which the uncertainty quantification method and the data assimilation method are adaptively selected by whether the dynamics is driven by Brownian motion and the near-Gaussianity of the measure to be updated, respectively.
Waste Package Misload Probability
J.K. Knudsen
2001-11-20
The objective of this calculation is to calculate the probability of occurrence for fuel assembly (FA) misloads (i.e., Fa placed in the wrong location) and FA damage during FA movements. The scope of this calculation is provided by the information obtained from the Framatome ANP 2001a report. The first step in this calculation is to categorize each fuel-handling events that occurred at nuclear power plants. The different categories are based on FAs being damaged or misloaded. The next step is to determine the total number of FAs involved in the event. Using the information, a probability of occurrence will be calculated for FA misload and FA damage events. This calculation is an expansion of preliminary work performed by Framatome ANP 2001a.
Sickle cell disease and posterior reversible leukoencephalopathy.
Geevasinga, Nimeshan; Cole, Catherine; Herkes, Geoffrey K; Barnett, Yael; Lin, Jamie; Needham, Merrilee
2014-08-01
Sickle cell disease can present with neurological manifestations. One such presentation is with posterior reversible leukoencephalopathy also known as reversible posterior leukoencephalopathy. The condition is classically described as reversible over time; it commonly presents with oedematous changes involving the white matter of the occipital and parietal regions. Only a few patients with the association between sickle cell disease and posterior reversible leukoencephalopathy have been described in the adult literature. We present two patients from our institutions to emphasise the association between the two conditions and summarise the published cases in the literature. PMID:24656986
Computing posterior probabilities for score-based alignments using ppALIGN.
Wolfsheimer, Stefan; Hartmann, Alexander; Rabus, Ralf; Nuel, Gregory
2012-01-01
Score-based pairwise alignments are widely used in bioinformatics in particular with molecular database search tools, such as the BLAST family. Due to sophisticated heuristics, such algorithms are usually fast but the underlying scoring model unfortunately lacks a statistical description of the reliability of the reported alignments. In particular, close to gaps, in low-score or low-complexity regions, a huge number of alternative alignments arise which results in a decrease of the certainty of the alignment. ppALIGN is a software package that uses hidden Markov Model techniques to compute position-wise reliability of score-based pairwise alignments of DNA or protein sequences. The design of the model allows for a direct connection between the scoring function and the parameters of the probabilistic model. For this reason it is suitable to analyze the outcomes of popular score based aligners and search tools without having to choose a complicated set of parameters. By contrast, our program only requires the classical score parameters (the scoring function and gap costs). The package comes along with a library written in C++, a standalone program for user defined alignments (ppALIGN) and another program (ppBLAST) which can process a complete result set of BLAST. The main algorithms essentially exhibit a linear time complexity (in the alignment lengths), and they are hence suitable for on-line computations. We have also included alternative decoding algorithms to provide alternative alignments. ppALIGN is a fast program/library that helps detect and quantify questionable regions in pairwise alignments. Due to its structure, the input/output interface it can to be connected to other post-processing tools. Empirically, we illustrate its usefulness in terms of correctly predicted reliable regions for sequences generated using the ROSE model for sequence evolution, and identify sensor-specific regions in the denitrifying betaproteobacterium Aromatoleum aromaticum. PMID:22628350
Namba, Robert; Graves, Stephen; Robertsson, Otto; Furnes, Ove; Stea, Susanna; Puig-Verdié, Lluis; Hoeffel, Daniel; Cafri, Guy; Paxton, Elizabeth; Sedrakyan, Art
2014-01-01
Background: Mobile-bearing total knee prostheses were designed to reduce wear and improve implant survivorship following total knee arthroplasty. However, the benefit of mobile-bearing total knee arthroplasty remains unproven. Both mobile-bearing and fixed-bearing total knee arthroplasty implants are available in posterior-stabilized and non-posterior-stabilized designs. With the latter, the implant does not recreate the function of the posterior cruciate ligament (PCL) with a posterior-stabilizing cam mechanism. The purpose of the present study was to compare mobile-bearing, non-posterior-stabilized devices with fixed-bearing, non-posterior-stabilized devices used in total knee arthroplasty through a novel multinational study design. Methods: Through the use of a distributed health data network, primary total knee arthroplasties performed for osteoarthritis from 2001 to 2010 were identified from six national and regional total joint arthroplasty registries. Multivariate meta-analysis was performed with use of linear mixed models, with the primary outcome of interest being revision for any reason. Survival probabilities and their standard errors were extracted from each registry for each unique combination of the covariates. Results: A total of 319,616 patients (60% female) underwent non-posterior-stabilized total knee arthroplasty. A fixed-bearing, non-posterior-stabilized design was used in 258,190 (81%) of the knees and a mobile-bearing, non-posterior-stabilized design in 61,426 (19%) of the knees. Sixty-nine percent of the patients who received a fixed-bearing implant were over sixty-five years of age, compared with 63% of those who received a mobile-bearing implant. Mobile-bearing designs had a higher risk of revision, with a hazard ratio of 1.43 (95% confidence interval, 1.36 to 1.51; p < 0.001). Conclusions: Previous comparisons of mobile-bearing and fixed-bearing total knee arthroplasty outcomes have been inconclusive. The current study utilized an advanced
Posterior Reversible Encephalopathy Syndrome in ALL.
Millichap, J Gordon
2015-07-01
Investigators from Soochow University, Suzhou, China, studied the possible pathogenetic mechanisms and treatment of posterior reversible encephalopathy syndrome (PRES) observed in 11 cases of pediatric acute lymphoblastic leukemia (ALL) after induction chemotherapy. PMID:26933594
Posterior cruciate ligament (PCL) injury - aftercare
... posterior cruciate ligament (PCL) is located inside your knee joint and connects the bones of your upper and ... such as a knee dislocation , you will need knee surgery to repair the joint. For milder injuries, you may not need surgery. ...
Cryptorchidism in boys with posterior urethral valves.
Krueger, R P; Hardy, B E; Churchill, B M
1980-07-01
A review of 207 male children with poterior urethral valves revealed an over-all incidence of cryptorchidism of 12 per cent. This association of cryptorchidism in boys with posterior urethral valves has not been described previously. PMID:6106069
Posterior Hip Pain in an Athletic Population
Frank, Rachel M.; Slabaugh, Mark A.; Grumet, Robert C.; Virkus, Walter W.; Bush-Joseph, Charles A.; Nho, Shane J.
2010-01-01
Context: Posterior hip pain is a relatively uncommon but increasingly recognized complaint in the orthopaedic community. Patient complaints and presentations are often vague or nonspecific, making diagnosis and subsequent treatment decisions difficult. The purposes of this article are to review the anatomy and pathophysiology related to posterior hip pain in the athletic patient population. Evidence Acquisition: Data were collected through a thorough review of the literature via a MEDLINE search of all relevant articles between 1980 and 2010. Results: Many patients who complain of posterior hip pain actually have pain referred from another part of the body—notably, the lumbar spine or sacroiliac joint. Treatment options for posterior hip pain are typically nonoperative; however, surgery is warranted in some cases. Conclusions: Recent advancements in the understanding of hip anatomy, pathophysiology, and treatment options have enabled physicians to better diagnosis athletic hip injuries and select patients for appropriate treatment. PMID:23015944
Katsuki, Fumi; Saito, Mizuki; Constantinidis, Christos
2014-09-01
The dorsolateral prefrontal and the posterior parietal cortex have both been implicated in the guidance of visual attention. Traditionally, posterior parietal cortex has been thought to guide visual bottom-up attention and prefrontal cortex to bias attention through top-down information. More recent studies suggest a parallel time course of activation of the two areas in bottom-up attention tasks, suggesting a common involvement, though these results do not necessarily imply identical roles. To address the specific roles of the two areas, we examined the influence of neuronal activity recorded from the prefrontal and parietal cortex of monkeys as they performed attention tasks based on choice probability and on correlation between reaction time and neuronal activity. The results revealed that posterior parietal but not dorsolateral prefrontal activity correlated with behavioral choice during the fixation period, prior to the appearance of the stimulus, resembling a bias factor. This preferential influence of posterior parietal activity on behavior was transient, so that dorsolateral prefrontal activity predicted choice after the appearance of the stimulus. Additionally, reaction time was better predicted by posterior parietal activity. These findings confirm the involvement of both dorsolateral prefrontal and posterior parietal cortex in the bottom-up guidance of visual attention, but indicate different roles of the two areas in the guidance of attention and a dynamic time course of their effects, influencing behavior at different stages of the task. PMID:24964224
Measurement Uncertainty and Probability
NASA Astrophysics Data System (ADS)
Willink, Robin
2013-02-01
Part I. Principles: 1. Introduction; 2. Foundational ideas in measurement; 3. Components of error or uncertainty; 4. Foundational ideas in probability and statistics; 5. The randomization of systematic errors; 6. Beyond the standard confidence interval; Part II. Evaluation of Uncertainty: 7. Final preparation; 8. Evaluation using the linear approximation; 9. Evaluation without the linear approximations; 10. Uncertainty information fit for purpose; Part III. Related Topics: 11. Measurement of vectors and functions; 12. Why take part in a measurement comparison?; 13. Other philosophies; 14. An assessment of objective Bayesian methods; 15. A guide to the expression of uncertainty in measurement; 16. Measurement near a limit - an insoluble problem?; References; Index.
Poster error probability in the Mu-11 Sequential Ranging System
NASA Technical Reports Server (NTRS)
Coyle, C. W.
1981-01-01
An expression is derived for the posterior error probability in the Mu-2 Sequential Ranging System. An algorithm is developed which closely bounds the exact answer and can be implemented in the machine software. A computer simulation is provided to illustrate the improved level of confidence in a ranging acquisition using this figure of merit as compared to that using only the prior probabilities. In a simulation of 20,000 acquisitions with an experimentally determined threshold setting, the algorithm detected 90% of the actual errors and made false indication of errors on 0.2% of the acquisitions.
Singh, Kiranjit; Mittal, Vikas; Kaur, Harmit
2011-07-01
We describe use of an oval capsulorhexis rather than the conventional circular capsulorhexis for phacoemulsification in posterior polar cataract with preexisting posterior capsule rupture. An oval capsulorhexis minimizes the turbulence in the capsular bag by increasing the area available for efflux of fluid. It also enables end-to-end nuclear sculpting, removal of the nuclear fragment from the bag, intraocular lens (IOL) implantation, and vitrectomy without stretching the capsular bag. The smaller axis of the oval capsulorhexis facilitates optic capture of a sulcus-fixated IOL. The oval capsulorhexis can be used safely for phacoemulsification of all grades of nuclear sclerosis in posterior polar cataract with preexisting posterior capsule rupture. PMID:21700098
Downs, J. Crawford; Burgoyne, Claude F.; Suh, J-K. Francis
2009-01-01
Background The sclera is the white outer shell and principal load-bearing tissue of the eye as it sustains the intraocular pressure. We have hypothesized that the mechanical properties of the posterior sclera play a significant role in, and are altered by the development of glaucoma – an ocular disease manifested by structural damage to the optic nerve head. Method of Approach An anisotropic hyperelastic constitutive model is presented to simulate the mechanical behavior of the posterior sclera under acute elevations of intraocular pressure. The constitutive model is derived from fiber-reinforced composite theory, and incorporates stretch-induced stiffening of the reinforcing collagen fibers. Collagen fiber alignment was assumed to be multi-directional at local material points, confined within the plane tangent to the scleral surface, and described by the semi-circular von-Mises distribution. The introduction of a model parameter, namely the fiber concentration factor, was used to control collagen fiber alignment along a preferred fiber orientation. To investigate the effects of scleral collagen fiber alignment on the overall behaviors of the posterior sclera and optic nerve head, finite element simulations of an idealized eye were performed. The four output quantities analyzed were the scleral canal expansion, the scleral canal twist, the posterior scleral canal deformation and the posterior laminar deformation. Results A circumferential fiber organization in the sclera restrained scleral canal expansion but created posterior laminar deformation, whereas the opposite was observed with a meridional fiber organization. Additionally, the fiber concentration factor acted as an amplifying parameter on the considered outputs. Conclusions The present model simulation suggests that the posterior sclera has a large impact on the overall behavior of the optic nerve head. It is therefore primordial to provide accurate mechanical properties for this tissue. In a companion
Characterization of Posterior Glenoid Bone Loss
Yanke, Adam Blair; Frank, Rachel M.; Shin, Jason J.; Van Thiel, Geoffrey S.; Verma, Nikhil N.; Cole, Brian J.; Romeo, Anthony A.; Provencher, Matthew T.
2016-01-01
Objectives: The purpose of this study was to characterize the morphology and location of posterior glenoid bone loss in pat ients with posterior instability instability utilizing computed tomography (CT). Methods: Clinical data was selected for patients with posterior shoulder instability that had undergone posterior stabilization (open or arthroscopic) or posterior osseous augmentation (distal tibia or iliac crest). Three fellowship-trained surgeons from two institutions contributed patients. Pre-operative CT data was collected for all patients. The axial cuts were segmented and reformatted in three-dimensions for glenoid analysis using Osirix. From this three-dimensional model, the following was calculated: percent bone loss (Nobuhara), total arc of the defect (degrees), and a clock-face description (start point, stop point, and average or direction). Pearson correlation coefficients were performed using significance of p<0.05. Results: Fifty shoulders from 50 patients were reviewed. Fourteen patients (average age 30 years; 93% male) had evidence of posterior glenoid bone loss and were included for evaluation. Defects on average involved 13.7±8.6% of the glenoid (range, 2-35%). The average start time (assuming all right shoulders) on the clock face was 10 o’clock ± 40 minutes and stopped at 6:30 ± 25 minutes. The average direction of the defect pointed toward 8:15 ± 25 minutes. The percent bone loss correlated with the total arc of the defect (Pearson: 0.93, p<0.05, R2: 0.86) and the direction of the bone loss (Pearson: 0.64, p<0.05, R2: 0.40). The direction of bone loss significantly moved more posterosuperior the larger the defect became (Pearson: 0.63, p<0.05, R2: 0.40). Conclusion: Posterior bone loss associated with posterior glenohumeral instability is typically directed posteriorly at 8:15 on the clock. As defect get bigger, this direction moves more posterosuperior. This information will help guide clinicians in understanding the typical location of
Emptiness Formation Probability
NASA Astrophysics Data System (ADS)
Crawford, Nicholas; Ng, Stephen; Starr, Shannon
2016-08-01
We present rigorous upper and lower bounds on the emptiness formation probability for the ground state of a spin-1/2 Heisenberg XXZ quantum spin system. For a d-dimensional system we find a rate of decay of the order {exp(-c L^{d+1})} where L is the sidelength of the box in which we ask for the emptiness formation event to occur. In the {d=1} case this confirms previous predictions made in the integrable systems community, though our bounds do not achieve the precision predicted by Bethe ansatz calculations. On the other hand, our bounds in the case {d ≥ 2} are new. The main tools we use are reflection positivity and a rigorous path integral expansion, which is a variation on those previously introduced by Toth, Aizenman-Nachtergaele and Ueltschi.
Direct probability mapping of contaminants
Rautman, C.A.
1993-09-17
Exhaustive characterization of a contaminated site is a physical and practical impossibility. Descriptions of the nature, extent, and level of contamination, as well as decisions regarding proposed remediation activities, must be made in a state of uncertainty based upon limited physical sampling. Geostatistical simulation provides powerful tools for investigating contaminant levels, and in particular, for identifying and using the spatial interrelationships among a set of isolated sample values. This additional information can be used to assess the likelihood of encountering contamination at unsampled locations and to evaluate the risk associated with decisions to remediate or not to remediate specific regions within a site. Past operation of the DOE Feed Materials Production Center has contaminated a site near Fernald, Ohio, with natural uranium. Soil geochemical data have been collected as part of the Uranium-in-Soils Integrated Demonstration Project. These data have been used to construct a number of stochastic images of potential contamination for parcels approximately the size of a selective remediation unit. Each such image accurately reflects the actual measured sample values, and reproduces the univariate statistics and spatial character of the extant data. Post-processing of a large number of these equally likely, statistically similar images produces maps directly showing the probability of exceeding specified levels of contamination. Evaluation of the geostatistical simulations can yield maps representing the expected magnitude of the contamination for various regions and other information that may be important in determining a suitable remediation process or in sizing equipment to accomplish the restoration.
Posterior dental size reduction in hominids: the Atapuerca evidence.
Bermúdez de Castro, J M; Nicolas, M E
1995-04-01
In order to reassess previous hypotheses concerning dental size reduction of the posterior teeth during Pleistocene human evolution, current fossil dental evidence is examined. This evidence includes the large sample of hominid teeth found in recent excavations (1984-1993) in the Sima de los Huesos Middle Pleistocene cave site of the Sierra de Atapuerca (Burgos, Spain). The lower fourth premolars and molars of the Atapuerca hominids, probably older than 300 Kyr, have dimensions similar to those of modern humans. Further, these hominids share the derived state of other features of the posterior teeth with modern humans, such as a similar relative molar size and frequent absence of the hypoconulid, thus suggesting a possible case of parallelism. We believe that dietary changes allowed size reduction of the posterior teeth during the Middle Pleistocene, and the present evidence suggests that the selective pressures that operated on the size variability of these teeth were less restrictive than what is assumed by previous models of dental reduction. Thus, the causal relationship between tooth size decrease and changes in food-preparation techniques during the Pleistocene should be reconsidered. Moreover, the present evidence indicates that the differential reduction of the molars cannot be explained in terms of restriction of available growth space. The molar crown area measurements of a modern human sample were also investigated. The results of this study, as well as previous similar analyses, suggest that a decrease of the rate of cell proliferation, which affected the later-forming crown regions to a greater extent, may be the biological process responsible for the general and differential dental size reduction that occurred during human evolution. PMID:7604890
Posterior Predictive Bayesian Phylogenetic Model Selection
Lewis, Paul O.; Xie, Wangang; Chen, Ming-Hui; Fan, Yu; Kuo, Lynn
2014-01-01
We present two distinctly different posterior predictive approaches to Bayesian phylogenetic model selection and illustrate these methods using examples from green algal protein-coding cpDNA sequences and flowering plant rDNA sequences. The Gelfand–Ghosh (GG) approach allows dissection of an overall measure of model fit into components due to posterior predictive variance (GGp) and goodness-of-fit (GGg), which distinguishes this method from the posterior predictive P-value approach. The conditional predictive ordinate (CPO) method provides a site-specific measure of model fit useful for exploratory analyses and can be combined over sites yielding the log pseudomarginal likelihood (LPML) which is useful as an overall measure of model fit. CPO provides a useful cross-validation approach that is computationally efficient, requiring only a sample from the posterior distribution (no additional simulation is required). Both GG and CPO add new perspectives to Bayesian phylogenetic model selection based on the predictive abilities of models and complement the perspective provided by the marginal likelihood (including Bayes Factor comparisons) based solely on the fit of competing models to observed data. [Bayesian; conditional predictive ordinate; CPO; L-measure; LPML; model selection; phylogenetics; posterior predictive.] PMID:24193892
Approximation of Failure Probability Using Conditional Sampling
NASA Technical Reports Server (NTRS)
Giesy. Daniel P.; Crespo, Luis G.; Kenney, Sean P.
2008-01-01
In analyzing systems which depend on uncertain parameters, one technique is to partition the uncertain parameter domain into a failure set and its complement, and judge the quality of the system by estimating the probability of failure. If this is done by a sampling technique such as Monte Carlo and the probability of failure is small, accurate approximation can require so many sample points that the computational expense is prohibitive. Previous work of the authors has shown how to bound the failure event by sets of such simple geometry that their probabilities can be calculated analytically. In this paper, it is shown how to make use of these failure bounding sets and conditional sampling within them to substantially reduce the computational burden of approximating failure probability. It is also shown how the use of these sampling techniques improves the confidence intervals for the failure probability estimate for a given number of sample points and how they reduce the number of sample point analyses needed to achieve a given level of confidence.
Posterior osseous bridging of C1.
Simsek, Serkan; Yigitkanli, Kazim; Comert, Ayhan; Acar, Halil I; Seckin, Hakan; Er, Uygur; Belen, Deniz; Tekdemir, Ibrahim; Elhan, Alaittin
2008-06-01
The sulcus of the vertebral artery is located behind the lateral mass of the atlas and in some cases is converted into a foramen by anomalous ossification known as the posterior ponticulus (osseous bridge). This study involved anatomical observations of 158 isolated anatomical specimens of dry C1 vertebrae. The incidence and types of posterior osseous bridging were identified for the 158 dry samples of atlas vertebrae. In nine (5.6%) dry C1 vertebrae, partial osseous bridging was detected (bilaterally in eight vertebrae and unilaterally on the left in one). Complete osseous bridging (arcuate foramen) was observed in six (3.8%) dry C1 vertebrae (bilaterally in one vertebra, unilaterally on the left in three, and on the right in two). Awareness of the types of posterior osseous bridging of C1 in craniocervical junction surgery is essential, and may be helpful in surgical interventions in this region. PMID:18378457
Posterior predictive checking of multiple imputation models.
Nguyen, Cattram D; Lee, Katherine J; Carlin, John B
2015-07-01
Multiple imputation is gaining popularity as a strategy for handling missing data, but there is a scarcity of tools for checking imputation models, a critical step in model fitting. Posterior predictive checking (PPC) has been recommended as an imputation diagnostic. PPC involves simulating "replicated" data from the posterior predictive distribution of the model under scrutiny. Model fit is assessed by examining whether the analysis from the observed data appears typical of results obtained from the replicates produced by the model. A proposed diagnostic measure is the posterior predictive "p-value", an extreme value of which (i.e., a value close to 0 or 1) suggests a misfit between the model and the data. The aim of this study was to evaluate the performance of the posterior predictive p-value as an imputation diagnostic. Using simulation methods, we deliberately misspecified imputation models to determine whether posterior predictive p-values were effective in identifying these problems. When estimating the regression parameter of interest, we found that more extreme p-values were associated with poorer imputation model performance, although the results highlighted that traditional thresholds for classical p-values do not apply in this context. A shortcoming of the PPC method was its reduced ability to detect misspecified models with increasing amounts of missing data. Despite the limitations of posterior predictive p-values, they appear to have a valuable place in the imputer's toolkit. In addition to automated checking using p-values, we recommend imputers perform graphical checks and examine other summaries of the test quantity distribution. PMID:25939490
Popliteal pseudoaneurysm after arthroscopic posterior cruciate ligament reconstruction.
van Dorp, Karin B; Breugem, Stefan J M; Driessen, Marcel J M
2014-09-01
This report presents the case of a 30-year-old motocross (BMX) cyclist with a third-degree posterior cruciate ligament rupture. The technique used for reconstruction was the transtibial single-bundle autologous hamstring technique. Unfortunately, the procedure was complicated by a popliteal pseudoaneurysm, which was located in line with the tibial canal. The pseudoaneurysm was treated with an end-to-end anastomosis and the patient recovered without further complaints. In this case, the popliteal artery was damaged most probably by the edge of the reamer or the guide wire during removal. Vascular complications can be limb- and life-threatening. This case report aims to increase the awareness of this serious complication with a review of the literature. PMID:25229050
Posterior encephalopathy subsequent to cyclosporin A presenting as irreversible abulia.
Nishie, Makoto; Kurahashi, Kozo; Ogawa, Masaya; Yoshida, Yasuji; Midorikawa, Hiroshi
2003-08-01
A case of cyclosporin A (Cys A)-induced posterior encephalopathy developed into persistent abulia despite rapid and marked improvement of abnormal T2- and FLAIR MRI hyperintense regions. Diffusion-weighted MRI signal intensity was also high at the onset. This change is atypical in Cys A-induced encephalopathy and was thought to predict poor recovery from the encephalopathy. Persistent abulia was probably due to marked hypoperfusion in the whole cortex including bilateral frontal lobes and basal ganglia as detected by SPECT. Apart from the breakdown of the blood-brain barrier, direct toxicity of Cys A to the brain may play a role in the pathogenesis of chronic, irreversible encephalopathy. PMID:12924507
Imaging the posterior mediastinum: a multimodality approach
Occhipinti, Mariaelena; Heidinger, Benedikt H.; Franquet, Elisa; Eisenberg, Ronald L.; Bankier, Alexander A.
2015-01-01
The posterior mediastinum contains several structures that can produce a wide variety of pathologic conditions. Descending thoracic aorta, esophagus, azygos and hemiazygos veins, thoracic duct, lymph nodes, adipose tissue, and nerves are all located in this anatomical region and can produce diverse abnormalities. Although chest radiography may detect many of these pathologic conditions, computed tomography and magnetic resonance are the imaging modalities of choice for further defining the relationship of posterior mediastinal lesions to neighboring structures and showing specific imaging features that narrow the differential diagnosis. This review emphasizes modality-related answers to morphologic questions, which provide precise diagnostic information. PMID:25993732
Imaging the posterior mediastinum: a multimodality approach.
Occhipinti, Mariaelena; Heidinger, Benedikt H; Franquet, Elisa; Eisenberg, Ronald L; Bankier, Alexander A
2015-01-01
The posterior mediastinum contains several structures that can produce a wide variety of pathologic conditions. Descending thoracic aorta, esophagus, azygos and hemiazygos veins, thoracic duct, lymph nodes, adipose tissue, and nerves are all located in this anatomical region and can produce diverse abnormalities. Although chest radiography may detect many of these pathologic conditions, computed tomography and magnetic resonance are the imaging modalities of choice for further defining the relationship of posterior mediastinal lesions to neighboring structures and showing specific imaging features that narrow the differential diagnosis. This review emphasizes modality-related answers to morphologic questions, which provide precise diagnostic information. PMID:25993732
Arthroscopic Approach to Posterior Ankle Impingement.
Theodoulou, Michael H; Bohman, Laura
2016-10-01
Posterior ankle pain can occur for many reasons. If it is produced by forced plantarflexion of the foot, it is often a result of impingement from an enlarged posterior talar process or an os trigonum. This condition may present in an acute or chronic state. Management is initially nonoperative, but surgical treatments are available. This condition is often seen in athletes, so procedures that limit surgical trauma and allow early return to activity are ideal. An arthroscopic approach for this disorder produces good outcomes with limited complications. Understanding the indications, local anatomy, and surgical technique, allows good, reproducible outcomes. PMID:27599438
Fusion probability in heavy nuclei
NASA Astrophysics Data System (ADS)
Banerjee, Tathagata; Nath, S.; Pal, Santanu
2015-03-01
Background: Fusion between two massive nuclei is a very complex process and is characterized by three stages: (a) capture inside the potential barrier, (b) formation of an equilibrated compound nucleus (CN), and (c) statistical decay of the CN leading to a cold evaporation residue (ER) or fission. The second stage is the least understood of the three and is the most crucial in predicting yield of superheavy elements (SHE) formed in complete fusion reactions. Purpose: A systematic study of average fusion probability,
NASA Astrophysics Data System (ADS)
Zhao, Xiao-mei; Xie, Dong-fan; Li, Qi
2015-02-01
With the development of intelligent transport system, advanced information feedback strategies have been developed to reduce traffic congestion and enhance the capacity. However, previous strategies provide accurate information to travelers and our simulation results show that accurate information brings negative effects, especially in delay case. Because travelers prefer to the best condition route with accurate information, and delayed information cannot reflect current traffic condition but past. Then travelers make wrong routing decisions, causing the decrease of the capacity and the increase of oscillations and the system deviating from the equilibrium. To avoid the negative effect, bounded rationality is taken into account by introducing a boundedly rational threshold BR. When difference between two routes is less than the BR, routes have equal probability to be chosen. The bounded rationality is helpful to improve the efficiency in terms of capacity, oscillation and the gap deviating from the system equilibrium.
ERIC Educational Resources Information Center
Falk, Ruma; Kendig, Keith
2013-01-01
Two contestants debate the notorious probability problem of the sex of the second child. The conclusions boil down to explication of the underlying scenarios and assumptions. Basic principles of probability theory are highlighted.
Validation of Bayesian posterior distributions using a multidimensional Kolmogorov-Smirnov test
NASA Astrophysics Data System (ADS)
Harrison, Diana; Sutton, David; Carvalho, Pedro; Hobson, Michael
2015-08-01
We extend the Kolmogorov-Smirnov (K-S) test to multiple dimensions by suggesting a R^n ⇒ [0,1] mapping based on the probability content of the highest probability density region of the reference distribution under consideration; this mapping reduces the problem back to the one-dimensional case to which the standard K-S test may be applied. The universal character of this mapping also allows us to introduce a simple, yet general, method for the validation of Bayesian posterior distributions of any dimensionality. This new approach goes beyond validating software implementations; it provides a sensitive test for all assumptions, explicit or implicit, that underlie the inference. In particular, the method assesses whether the inferred posterior distribution is a truthful representation of the actual constraints on the model parameters. We illustrate our multidimensional K-S test by applying it to a simple two-dimensional Gaussian toy problem, and demonstrate our method for posterior validation in the real-world astrophysical application of estimating the physical parameters of galaxy clusters parameters from their Sunyaev-Zel'dovich effect in microwave background data. In the latter example, we show that the method can validate the entire Bayesian inference process across a varied population of objects for which the derived posteriors are different in each case.
The Probability of Causal Conditionals
ERIC Educational Resources Information Center
Over, David E.; Hadjichristidis, Constantinos; Evans, Jonathan St. B. T.; Handley, Simon J.; Sloman, Steven A.
2007-01-01
Conditionals in natural language are central to reasoning and decision making. A theoretical proposal called the Ramsey test implies the conditional probability hypothesis: that the subjective probability of a natural language conditional, P(if p then q), is the conditional subjective probability, P(q [such that] p). We report three experiments on…
Equal prior probabilities: can one do any better?
Biedermann, A; Taroni, F; Garbolino, P
2007-10-25
This paper discusses recommendations concerning the use of prior probabilities that underlie recent, but in no way novel, proposals of presenting scientific evidence in terms of posterior probabilities, in the context sometimes referred to as the 'full Bayes' approach'. A chief issue of this procedure is a proposal that--given the unavailability of case-specific circumstantial information--scientists should consider the prior probabilities of the propositions under which scientific evidence is evaluated as equal. The discussion presented here draws the reader's attention to the fact that the philosophical foundations of such a recommendation (in particular, attempted justifications through the Principle of Maximum Entropy (PME)) are far more controversial than what is actually admitted by the advocates for their use in the theory and practice of forensic science. Invoking only basic assumptions and the mathematical rules of probability calculus, the authors of this paper propose an argument that shows that there can be other more feasible and defensible strategies for eliciting reasonable prior probabilities. It is solely demanded that the reasoner is willing to make up his mind seriously on certain standard issues of fairly general criminal cases, such as evidential relevance or the probability of a suspect's guilt. However, because these issues intimately pertain to the responsibility of the trier of the fact, it is argued here that scientists' attempts to define appropriate prior probabilities should continue to be considered as untenable for the need. PMID:17267153
[Therapy of posterior and posterolateral knee instability].
Jakob, R P; Rüegsegger, M
1993-11-01
The natural course after posterior cruciate ligament (PCL) tear is a slow process of degeneration starting in the medial compartment. Functional disability is mainly present in those instabilities that are combined with posterolateral insufficiency. The surgical treatment at present mainly addresses these combined types of posterior-posterolateral instability. It is generally agreed that suture of the torn PCL alone is insufficient and augmentation with autologous structures, such as the patellar ligament, are mandatory. Synthetic augmentation to facilitate after treatment is another adjunct. Because of the difficulty of precise tibial tunnel placement a two-stage procedure is advocated, an anterior approach with the patient supine being used for femoral graft placement. If a posterior approach with the patient prone is used, a straight posterior incision is made between the two heads of the gastrocnemius and the neuromuscular bundle. With this approach the tibial bone block is placed in a trough. The accuracy of graft placement and the immediate functional aftertreatment facilitated by the use of osseous fixation of a synthetic augmentation device at both ends have made better results of surgical reconstruction of the PCL possible. PMID:8309701
Subspecialization in the human posterior medial cortex
Bzdok, Danilo; Heeger, Adrian; Langner, Robert; Laird, Angela R.; Fox, Peter T.; Palomero-Gallagher, Nicola; Vogt, Brent A.; Zilles, Karl; Eickhoff, Simon B.
2014-01-01
The posterior medial cortex (PMC) is particularly poorly understood. Its neural activity changes have been related to highly disparate mental processes. We therefore investigated PMC properties with a data-driven exploratory approach. First, we subdivided the PMC by whole-brain coactivation profiles. Second, functional connectivity of the ensuing PMC regions was compared by task-constrained meta-analytic coactivation mapping (MACM) and task-unconstrained resting-state correlations (RSFC). Third, PMC regions were functionally described by forward/reverse functional inference. A precuneal cluster was mostly connected to the intraparietal sulcus, frontal eye fields, and right temporo-parietal junction; associated with attention and motor tasks. A ventral posterior cingulate cortex (PCC) cluster was mostly connected to the ventromedial prefrontal cortex and middle left inferior parietal cortex (IPC); associated with facial appraisal and language tasks. A dorsal PCC cluster was mostly connected to the dorsomedial prefrontal cortex, anterior/posterior IPC, posterior midcingulate cortex, and left dorsolateral prefrontal cortex; associated with delay discounting. A cluster in the retrosplenial cortex was mostly connected to the anterior thalamus and hippocampus. Furthermore, all PMC clusters were congruently coupled with the default mode network according to task-constrained but not task-unconstrained connectivity. We thus identified distinct regions in the PMC and characterized their neural networks and functional implications. PMID:25462801
Posterior instability caused by batter's shoulder.
Kang, Richard W; Mahony, Gregory T; Harris, Thomas C; Dines, Joshua S
2013-10-01
In summary, batter’s shoulder is a rare and only recently recognized entity. This condition is posterior shoulder instability caused by a missed attempt at hitting a pitch, especially with an outside pitch. The lack of counterforce from hitting a ball produces increased forces imparted on the posterior capsulolabral complex of the lead shoulder during batting. If the player fails conservative management, she or he can undergo an arthroscopic posterior labral repair instead of debridement. After treatment, the player can expect to return to play after approximately 6 to 7 months. Initial results from a small, retrospective series demonstrate greater than 90% excellent results. These findings are similar to current literature for arthroscopic treatment of posterior instability, which reports success rates that range from 75% to 91%. Longer-term follow-up will be needed to determine the natural history and prognosis or batter’s shoulder. Based on initial results, the authors predict good to excellent results for most players with batter’s shoulder who undergo proper treatment. Additionally, with the exception of switch hitters, the nonthrowing arm is affected. This can also improve the athlete’s return to play. PMID:24079435
Quantum probability and many worlds
NASA Astrophysics Data System (ADS)
Hemmo, Meir; Pitowsky, Itamar
We discuss the meaning of probabilities in the many worlds interpretation of quantum mechanics. We start by presenting very briefly the many worlds theory, how the problem of probability arises, and some unsuccessful attempts to solve it in the past. Then we criticize a recent attempt by Deutsch to derive the quantum mechanical probabilities from the non-probabilistic parts of quantum mechanics and classical decision theory. We further argue that the Born probability does not make sense even as an additional probability rule in the many worlds theory. Our conclusion is that the many worlds theory fails to account for the probabilistic statements of standard (collapse) quantum mechanics.
Probability workshop to be better in probability topic
NASA Astrophysics Data System (ADS)
Asmat, Aszila; Ujang, Suriyati; Wahid, Sharifah Norhuda Syed
2015-02-01
The purpose of the present study was to examine whether statistics anxiety and attitudes towards probability topic among students in higher education level have an effect on their performance. 62 fourth semester science students were given statistics anxiety questionnaires about their perception towards probability topic. Result indicated that students' performance in probability topic is not related to anxiety level, which means that the higher level in statistics anxiety will not cause lower score in probability topic performance. The study also revealed that motivated students gained from probability workshop ensure that their performance in probability topic shows a positive improvement compared before the workshop. In addition there exists a significance difference in students' performance between genders with better achievement among female students compared to male students. Thus, more initiatives in learning programs with different teaching approaches is needed to provide useful information in improving student learning outcome in higher learning institution.
An Unusual Cause of Posterior Elbow Impingement: Detachment of a Hypertrophied Posterior Fat Pad.
Hamada, Daisuke; Matsuura, Tetsuya; Sugiura, Kosuke; Higuchi, Tadahiro; Suzue, Naoto; Goto, Tomohiro; Tsutsui, Takahiko; Wada, Keizo; Fukuta, Shoji; Sairyo, Koichi
2015-01-01
We report a case of a 47-year-old woman who developed posterior impingement of the elbow due to detachment of a hypertrophied posterior fat pad. She reported acute left elbow pain after leaning back onto a hard object with her hand and subsequently experienced a "catching" sensation. Comparison with the magnetic resonance images of a normal elbow revealed a hypertrophied posterior fat pad interposed between the olecranon and olecranon fossa in both elbows, with the fat pad in the left elbow located more inferiorly than that in the right elbow. Elbow arthroscopy showed the olecranon fossa covered by the fat pad, a portion of which was detached from the rest of the pad. Debridement of the detached portion was performed until no impingement was evident. Postoperatively, full extension of the elbow did not elicit pain. Clinicians should include this pathology among the differential diagnoses for posterior elbow pain. PMID:26613057
Posterior cruciate-retaining versus posterior-stabilized total knee arthroplasty: a meta-analysis.
Bercik, Michael J; Joshi, Ashish; Parvizi, Javad
2013-03-01
The objective of this meta-analysis was to compare outcomes of posterior cruciate-retaining and posterior stabilized prostheses. A computerized literature search was conducted to identify randomized controlled trials comparing the clinical outcomes of cruciate-retaining and posterior-stabilized designs. The table of contents of four major Orthopaedic journals and the references section of two arthroplasty text books were reviewed to identify other relevant studies. Ultimately, 1114 patients (1265 knees) were compared. Statistical analysis revealed a significant difference in flexion and range of motion in favor of posterior-stabilized knees, but no difference in complication rates. The clinical importance of this remains unknown. The decision to use one design versus the other should rest with the surgeon's preference and comfort with a particular design. PMID:23433255
An Unusual Cause of Posterior Elbow Impingement: Detachment of a Hypertrophied Posterior Fat Pad
Hamada, Daisuke; Matsuura, Tetsuya; Sugiura, Kosuke; Higuchi, Tadahiro; Suzue, Naoto; Goto, Tomohiro; Tsutsui, Takahiko; Wada, Keizo; Fukuta, Shoji; Sairyo, Koichi
2015-01-01
We report a case of a 47-year-old woman who developed posterior impingement of the elbow due to detachment of a hypertrophied posterior fat pad. She reported acute left elbow pain after leaning back onto a hard object with her hand and subsequently experienced a “catching” sensation. Comparison with the magnetic resonance images of a normal elbow revealed a hypertrophied posterior fat pad interposed between the olecranon and olecranon fossa in both elbows, with the fat pad in the left elbow located more inferiorly than that in the right elbow. Elbow arthroscopy showed the olecranon fossa covered by the fat pad, a portion of which was detached from the rest of the pad. Debridement of the detached portion was performed until no impingement was evident. Postoperatively, full extension of the elbow did not elicit pain. Clinicians should include this pathology among the differential diagnoses for posterior elbow pain. PMID:26613057
Propensity, Probability, and Quantum Theory
NASA Astrophysics Data System (ADS)
Ballentine, Leslie E.
2016-08-01
Quantum mechanics and probability theory share one peculiarity. Both have well established mathematical formalisms, yet both are subject to controversy about the meaning and interpretation of their basic concepts. Since probability plays a fundamental role in QM, the conceptual problems of one theory can affect the other. We first classify the interpretations of probability into three major classes: (a) inferential probability, (b) ensemble probability, and (c) propensity. Class (a) is the basis of inductive logic; (b) deals with the frequencies of events in repeatable experiments; (c) describes a form of causality that is weaker than determinism. An important, but neglected, paper by P. Humphreys demonstrated that propensity must differ mathematically, as well as conceptually, from probability, but he did not develop a theory of propensity. Such a theory is developed in this paper. Propensity theory shares many, but not all, of the axioms of probability theory. As a consequence, propensity supports the Law of Large Numbers from probability theory, but does not support Bayes theorem. Although there are particular problems within QM to which any of the classes of probability may be applied, it is argued that the intrinsic quantum probabilities (calculated from a state vector or density matrix) are most naturally interpreted as quantum propensities. This does not alter the familiar statistical interpretation of QM. But the interpretation of quantum states as representing knowledge is untenable. Examples show that a density matrix fails to represent knowledge.
NNLOPS accurate associated HW production
NASA Astrophysics Data System (ADS)
Astill, William; Bizon, Wojciech; Re, Emanuele; Zanderighi, Giulia
2016-06-01
We present a next-to-next-to-leading order accurate description of associated HW production consistently matched to a parton shower. The method is based on reweighting events obtained with the HW plus one jet NLO accurate calculation implemented in POWHEG, extended with the MiNLO procedure, to reproduce NNLO accurate Born distributions. Since the Born kinematics is more complex than the cases treated before, we use a parametrization of the Collins-Soper angles to reduce the number of variables required for the reweighting. We present phenomenological results at 13 TeV, with cuts suggested by the Higgs Cross section Working Group.
Saha, Anubha; Mandal, Shyamash
2015-01-01
Introduction: Various studies have been done regarding variations of circle of Willis, but few literatures are available about the detail configurations on Indian population. Posterior communicating artery is the main collateral channel between the vertebrobasilar and carotid system. It may act as a main source of blood flow via posterior cerebral artery if fetal configuration is present. Aim of the study is to see the bilateral configurations to compare the blood supply of both cerebral hemispheres via posterior cerebral artery in human cadavers. Materials and Methods: Fifty six formalin fixed brains were used for study. The specimens were classified into 3 types and 21 subtypes according to the configuration of the vessel of both hemispheres. As hemodynamic balance is dependent on the calibre of the vessel, the diameter of the arteries were also taken into consideration. Pearson’s correlation had been done. Result: In present study type I is 57.2%, type II is 37.5% and type III is 5.4%. Incidence of unilateral fetal type posterior cerebral artery is in high percentage (33.9%). Greatest diameter of posterior communicating artery is 3.8mm on right and 3.6mm on left side. Significant correlations also have been found between arterial segments of different types. Conclusion: It is expected that the study will help to enrich the knowledge about the arterial predominance of origin of posterior cerebral artery of both cerebral hemispheres in normal or variant cases and its effect on perfusion images. PMID:25954608
Posterior Wnts Have Distinct Roles in Specification and Patterning of the Planarian Posterior Region
Sureda-Gómez, Miquel; Pascual-Carreras, Eudald; Adell, Teresa
2015-01-01
The wnt signaling pathway is an intercellular communication mechanism essential in cell-fate specification, tissue patterning and regional-identity specification. A βcatenin-dependent signal specifies the AP (Anteroposterior) axis of planarians, both during regeneration of new tissues and during normal homeostasis. Accordingly, four wnts (posterior wnts) are expressed in a nested manner in central and posterior regions of planarians. We have analyzed the specific role of each posterior wnt and the possible cooperation between them in specifying and patterning planarian central and posterior regions. We show that each posterior wnt exerts a distinct role during re-specification and maintenance of the central and posterior planarian regions, and that the integration of the different wnt signals (βcatenin dependent and independent) underlies the patterning of the AP axis from the central region to the tip of the tail. Based on these findings and data from the literature, we propose a model for patterning the planarian AP axis. PMID:26556349
Arthroscopic approach to the posterior compartment of the knee using a posterior transseptal portal
Ohishi, Tsuyoshi; Takahashi, Masaaki; Suzuki, Daisuke; Matsuyama, Yukihiro
2015-01-01
Arthroscopic surgery of the posterior compartment of the knee is difficult when only two anterior portals are used for access because of the inaccessibility of the back of the knee. Since its introduction, the posterior transseptal portal has been widely employed to access lesions in the posterior compartment. However, special care should be taken to avoid neurovascular injuries around the posteromedial, posterolateral, and transseptal portals. Most importantly, popliteal vessel injury should be avoided when creating and using the transseptal portal during surgery. Purpose of the present study is to describe how to avoid the neurovascular injuries during establishing the posterior three portals and to introduce our safer technique to create the transseptal portal. To date, we have performed arthroscopic surgeries via the transseptal portal in the posterior compartments of 161 knees and have not encountered nerve or vascular injury. In our procedure, the posterior septum is perforated with a 1.5-3.0-mm Kirschner wire that is protected by a sheath inserted from the posterolateral portal and monitored from the posteromedial portal to avoid popliteal vessel injury. PMID:26301179
Sureda-Gómez, Miquel; Pascual-Carreras, Eudald; Adell, Teresa
2015-01-01
The wnt signaling pathway is an intercellular communication mechanism essential in cell-fate specification, tissue patterning and regional-identity specification. A βcatenin-dependent signal specifies the AP (Anteroposterior) axis of planarians, both during regeneration of new tissues and during normal homeostasis. Accordingly, four wnts (posterior wnts) are expressed in a nested manner in central and posterior regions of planarians. We have analyzed the specific role of each posterior wnt and the possible cooperation between them in specifying and patterning planarian central and posterior regions. We show that each posterior wnt exerts a distinct role during re-specification and maintenance of the central and posterior planarian regions, and that the integration of the different wnt signals (βcatenin dependent and independent) underlies the patterning of the AP axis from the central region to the tip of the tail. Based on these findings and data from the literature, we propose a model for patterning the planarian AP axis. PMID:26556349
NASA Astrophysics Data System (ADS)
Fernandes, Stenio; Kamienski, Carlos; Sadok, Djamel
2003-08-01
Synthetic self-similar traffic in computer networks simulation is of imperative significance for the capturing and reproducing of actual Internet data traffic behavior. A universally used procedure for generating self-similar traffic is achieved by aggregating On/Off sources where the active (On) and idle (Off) periods exhibit heavy tailed distributions. This work analyzes the balance between accuracy and computational efficiency in generating self-similar traffic and presents important results that can be useful to parameterize existing heavy tailed distributions such as Pareto, Weibull and Lognormal in a simulation analysis. Our results were obtained through the simulation of various scenarios and were evaluated by estimating the Hurst (H) parameter, which measures the self-similarity level, using several methods.
How to accurately bypass damage
Broyde, Suse; Patel, Dinshaw J.
2016-01-01
Ultraviolet radiation can cause cancer through DNA damage — specifically, by linking adjacent thymine bases. Crystal structures show how the enzyme DNA polymerase η accurately bypasses such lesions, offering protection. PMID:20577203
Accurate Evaluation of Quantum Integrals
NASA Technical Reports Server (NTRS)
Galant, David C.; Goorvitch, D.
1994-01-01
Combining an appropriate finite difference method with Richardson's extrapolation results in a simple, highly accurate numerical method for solving a Schr\\"{o}dinger's equation. Important results are that error estimates are provided, and that one can extrapolate expectation values rather than the wavefunctions to obtain highly accurate expectation values. We discuss the eigenvalues, the error growth in repeated Richardson's extrapolation, and show that the expectation values calculated on a crude mesh can be extrapolated to obtain expectation values of high accuracy.
PROBABILITY SURVEYS, CONDITIONAL PROBABILITIES, AND ECOLOGICAL RISK ASSESSMENT
We show that probability-based environmental resource monitoring programs, such as U.S. Environmental Protection Agency's (U.S. EPA) Environmental Monitoring and Asscssment Program EMAP) can be analyzed with a conditional probability analysis (CPA) to conduct quantitative probabi...
Probability Surveys, Conditional Probability, and Ecological Risk Assessment
We show that probability-based environmental resource monitoring programs, such as the U.S. Environmental Protection Agency’s (U.S. EPA) Environmental Monitoring and Assessment Program, and conditional probability analysis can serve as a basis for estimating ecological risk over ...
Girard, Michaël J A; Downs, J Crawford; Burgoyne, Claude F; Suh, J-K Francis
2009-05-01
The sclera is the white outer shell and principal load-bearing tissue of the eye as it sustains the intraocular pressure. We have hypothesized that the mechanical properties of the posterior sclera play a significant role in and are altered by the development of glaucoma-an ocular disease manifested by structural damage to the optic nerve head. An anisotropic hyperelastic constitutive model is presented to simulate the mechanical behavior of the posterior sclera under acute elevations of intraocular pressure. The constitutive model is derived from fiber-reinforced composite theory, and incorporates stretch-induced stiffening of the reinforcing collagen fibers. Collagen fiber alignment was assumed to be multidirectional at local material points, confined within the plane tangent to the scleral surface, and described by the semicircular von Mises distribution. The introduction of a model parameter, namely, the fiber concentration factor, was used to control collagen fiber alignment along a preferred fiber orientation. To investigate the effects of scleral collagen fiber alignment on the overall behaviors of the posterior sclera and optic nerve head, finite element simulations of an idealized eye were performed. The four output quantities analyzed were the scleral canal expansion, the scleral canal twist, the posterior scleral canal deformation, and the posterior laminar deformation. A circumferential fiber organization in the sclera restrained scleral canal expansion but created posterior laminar deformation, whereas the opposite was observed with a meridional fiber organization. Additionally, the fiber concentration factor acted as an amplifying parameter on the considered outputs. The present model simulation suggests that the posterior sclera has a large impact on the overall behavior of the optic nerve head. It is therefore primordial to provide accurate mechanical properties for this tissue. In a companion paper (Girard, Downs, Bottlang, Burgoyne, and Suh, 2009
Posterior fossa lesions associated with neuropsychiatric symptomatology.
Pollak, L; Klein, C; Rabey, J M; Schiffer, J
1996-11-01
We reviewed 7 cases with posterior fossa structural abnormalities (3 tumors, 2 megacisterna magna and 2 Dandy-Walker syndrome) presenting with neuropsychiatric symptomatology. Derangement in the balance of dopamine, serotonin and noradrenergic networks has been implicated in the pathogenesis of schizophrenia, affective and even personality disorders. Disruption of the cerebellar output to mesial dopaminergic areas, locus coeruleus and raphe nuclei, or deafferentation of the thalamolimbic circuits by a cerebellar lesion may lead to behavioral changes. Seven patients (pts) (comprising 4 men and 3 women with mean age 22 years) were diagnosed as suffering from psychosis (2 pts), major depression (1 pt), personality disorders (2 pts) and somatoform disorders (2 pts) (DSM-IV criteria). Brain CT scan (7 pts) and MRI (4 pts) revealed tumors of the posterior fossa (2 pts), megacisterna magna (2 pts) and Dandy-Walker variant (2 pts). In one patient a IVth ventricle tumor was removed in childhood. PMID:9003973
Fractures of posterior teeth in adults.
Eakle, W S; Maxwell, E H; Braly, B V
1986-02-01
Examined in this study were 191 patients with 206 complete or incomplete fractures of posterior teeth. The patients ranged in age from 14 to 76 years, with 66.5% younger than 40 years. The number of fractures occurring in each arch was almost equal. The mandibular first molar was the most frequently fractured posterior tooth. The lingual cusps of mandibular molars fractured more often than did the buccal cusps of mandibular molars by a ratio of 2 to 1. In maxillary molars, buccal and lingual cusps fractured with almost equal frequency, but, in maxillary premolars, the lingual cusps fractured slightly more often than buccal cusps. Data gathered on the widths of the isthmuses of restorations in 109 teeth showed that fewer fractures occurred in teeth with more conservative restorations, with widths of isthmuses a quarter of the inter-cusp distance, and intact marginal ridges. PMID:3456380
The relationship between species detection probability and local extinction probability
Alpizar-Jara, R.; Nichols, J.D.; Hines, J.E.; Sauer, J.R.; Pollock, K.H.; Rosenberry, C.S.
2004-01-01
In community-level ecological studies, generally not all species present in sampled areas are detected. Many authors have proposed the use of estimation methods that allow detection probabilities that are <1 and that are heterogeneous among species. These methods can also be used to estimate community-dynamic parameters such as species local extinction probability and turnover rates (Nichols et al. Ecol Appl 8:1213-1225; Conserv Biol 12:1390-1398). Here, we present an ad hoc approach to estimating community-level vital rates in the presence of joint heterogeneity of detection probabilities and vital rates. The method consists of partitioning the number of species into two groups using the detection frequencies and then estimating vital rates (e.g., local extinction probabilities) for each group. Estimators from each group are combined in a weighted estimator of vital rates that accounts for the effect of heterogeneity. Using data from the North American Breeding Bird Survey, we computed such estimates and tested the hypothesis that detection probabilities and local extinction probabilities were negatively related. Our analyses support the hypothesis that species detection probability covaries negatively with local probability of extinction and turnover rates. A simulation study was conducted to assess the performance of vital parameter estimators as well as other estimators relevant to questions about heterogeneity, such as coefficient of variation of detection probabilities and proportion of species in each group. Both the weighted estimator suggested in this paper and the original unweighted estimator for local extinction probability performed fairly well and provided no basis for preferring one to the other.
Ciprofloxacin-associated posterior reversible encephalopathy
Al Bu Ali, Waleed Hammad
2013-01-01
Posterior reversible encephalopathy syndrome (PRES) is a clinico-neuroradiological syndrome characterised by numerous symptoms and of no specific aetiology. Headache, confusion, seizures, cortical visual disturbances or blindness are the key symptoms. As this syndrome is reversible and readily treated by interrupting or discontinuing the aetiology, it should sharply be acknowledged. Ciprofloxacin was associated with PRES in an adolescent male treated from chest infection. It was managed in a hospital intensive care unit and was observed until disappearance. PMID:23585504
The mechanism of continence after posterior urethroplasty
Bagga, Herman S.; Angermeier, Kenneth W.
2015-01-01
The standard of care after a pelvic fracture urethral injury is a repair via a one-stage anastomotic posterior urethroplasty using a step-wise perineal approach. The initial injury, immediate postoperative management, and surgical repair can all affect urinary continence in these patients. Proximal continence mechanisms, particularly the bladder neck, are particularly important in maintaining urinary continence in these patients. Patients with bladder neck dysfunction should be counselled about the greater risk of urinary incontinence. PMID:26019981
Cervical disc hernia operations through posterior laminoforaminotomy
Yolas, Coskun; Ozdemir, Nuriye Guzin; Okay, Hilmi Onder; Kanat, Ayhan; Senol, Mehmet; Atci, Ibrahim Burak; Yilmaz, Hakan; Coban, Mustafa Kemal; Yuksel, Mehmet Onur; Kahraman, Umit
2016-01-01
Objective: The most common used technique for posterolateral cervical disc herniations is anterior approach. However, posterior cervical laminotoforaminomy can provide excellent results in appropriately selected patients with foraminal stenosis in either soft disc prolapse or cervical spondylosis. The purpose of this study was to present the clinical outcomes following posterior laminoforaminotomy in patients with radiculopathy. Materials and Methods: We retrospectively evaluated 35 patients diagnosed with posterolateral cervical disc herniation and cervical spondylosis with foraminal stenosis causing radiculopathy operated by the posterior cervical keyhole laminoforaminotomy between the years 2010 and 2015. Results: The file records and the radiographic images of the 35 patients were assessed retrospectively. The mean age was 46.4 years (range: 34-66 years). Of the patients, 19 were males and 16 were females. In all of the patients, the neurologic deficit observed was radiculopathy. The posterolaterally localized disc herniations and the osteophytic structures were on the left side in 18 cases and on the right in 17 cases. In 10 of the patients, the disc level was at C5-6, in 18 at C6-7, in 2 at C3-4, in 2 at C4-5, in 1 at C7-T1, in 1 patient at both C5-6 and C6-7, and in 1 at both C4-5 and C5-6. In 14 of these 35 patients, both osteophytic structures and protruded disc herniation were present. Intervertebral foramen stenosis was present in all of the patients with osteophytes. Postoperatively, in 31 patients the complaints were relieved completely and four patients had complaints of neck pain and paresthesia radiating to the arm (the success of operation was 88.5%). On control examinations, there was no finding of instability or cervical kyphosis. Conclusion: Posterior cervical laminoforaminotomy is an alternative appropriate choice in both cervical soft disc herniations and cervical stenosis. PMID:27217655
The diagnostic dilemma of the posterior mediastinal thymus: CT manifestations
Cohen, M.D.; Weber, T.R.; Sequeira, F.W.; Vane, D.W.; King, H.
1983-03-01
Extension of the normal thymus into the posterior mediastinum is rare. The CT appearance of this anomaly in an infant is presented. A mass of soft-tissue density extended from the anterior mediastinum to the posterior chest wall. The absence of any tissue-cleavage plane in the lesion and a smooth continuous lateral margin are signs of posterior extension of the thymus, and they help to distinguish this from a normal anterior thymus being present with a posterior tumor.
Indocyanine green angiography in posterior uveitis
Agrawal, Rupesh V; Biswas, Jyotirmay; Gunasekaran, Dinesh
2013-01-01
Literature review for indocyanine green angiography and evaluate the role of indocyanine green angiogram (ICGA) in patients with posterior uveitis seen at a tertiary referral eye care centre. Detailed review of the literature on ICGA was performed. Retrospective review of medical records of patients with posterior uveitis and dual fundus and ICGA was done after institutional board approval. Eighteen patients (26 eyes) had serpiginous choroiditis out of which 12 patients had active choroiditis and six patients had healed choroiditis, six patients (12 eyes) had ampiginous choroiditis, six patients (12 eyes) had acute multifocal posterior placoid pigment epitheliopathy, eight patients (10 eyes) had multifocal choroiditis, four patients (eight eyes) had presumed ocular histoplasmosis syndrome, four patients (eight eyes) had presumed tuberculous choroiditis, two patients (four eyes) had multiple evanescent white dot syndrome and two patients (four eyes) had Vogt Koyanagi Harada (VKH) syndrome. The most characteristic feature noted on ICGA was the presence of different patterns of hypofluorescent dark spots, which were present at different stages of the angiogram. ICGA provides the clinician with a powerful adjunctive tool in choroidal inflammatory disorders. It is not meant to replace already proven modalities such as the fluorescein angiography, but it can provide additional information that is useful in establishing a more definitive diagnosis in inflammatory chorioretinal diseases associated with multiple spots. It still needs to be determined if ICGA can prove to be a follow up parameter to evaluate disease progression. PMID:23685486
Girard, Michaël J A; Downs, J Crawford; Bottlang, Michael; Burgoyne, Claude F; Suh, J-K Francis
2009-05-01
The posterior sclera likely plays an important role in the development of glaucoma, and accurate characterization of its mechanical properties is needed to understand its impact on the more delicate optic nerve head--the primary site of damage in the disease. The posterior scleral shells from both eyes of one rhesus monkey were individually mounted on a custom-built pressurization apparatus. Intraocular pressure was incrementally increased from 5 mm Hg to 45 mm Hg, and the 3D displacements were measured using electronic speckle pattern interferometry. Finite element meshes of each posterior scleral shell were reconstructed from data generated by a 3D digitizer arm (shape) and a 20 MHz ultrasound transducer (thickness). An anisotropic hyperelastic constitutive model described in a companion paper (Girard, Downs, Burgoyne, and Suh, 2009, "Peripapillary and Posterior Scleral Mechanics--Part I: Development of an Anisotropic Hyperelastic Constitutive Model," ASME J. Biomech. Eng., 131, p. 051011), which includes stretch-induced stiffening and multidirectional alignment of the collagen fibers, was applied to each reconstructed mesh. Surface node displacements of each model were fitted to the experimental displacements using an inverse finite element method, which estimated a unique set of 13 model parameters. The predictions of the proposed constitutive model matched the 3D experimental displacements well. In both eyes, the tangent modulus increased dramatically with IOP, which indicates that the sclera is mechanically nonlinear. The sclera adjacent to the optic nerve head, known as the peripapillary sclera, was thickest and exhibited the lowest tangent modulus, which might have contributed to the uniform distribution of the structural stiffness for each entire scleral shell. Posterior scleral deformation following acute IOP elevations appears to be nonlinear and governed by the underlying scleral collagen microstructure as predicted by finite element modeling. The
Rich, M.W.; Imburgia, M.; King, T.R.; Fischer, K.C.; Kovach, K.L. )
1989-09-01
The accuracy of four electrocardiographic criteria for diagnosing remote posterior myocardial infarction was assessed prospectively in 369 patients undergoing exercise treadmill testing with thallium scintigraphy. Criteria included the following: (1) R-wave width greater than or equal to 0.04 s and R-wave greater than or equal to S-wave in V1; (2) R-wave greater than or equal to S-wave in V2; (3) T-wave voltage in V2 minus V6 greater than or equal to 0.38 mV (T-wave index); (4) Q-wave greater than or equal to 0.04 s in left paraspinal lead V9. Twenty-seven patients (7.3 percent) met thallium criteria for posterior myocardial infarction, defined as a persistent perfusion defect in the posterobase of the left ventricle. Sensitivities for the four criteria ranged from 4 to 56 percent, and specificities ranged from 64 to 99 percent. Posterior paraspinal lead V9 provided the best overall predictive accuracy (94 percent), positive predictive value (58 percent), and ability to differentiate patients with and without posterior myocardial infarction of any single criterion (p less than .0001). Combining the T-wave index with lead V9 further enhanced the diagnostic yield: the sensitivity for detecting posterior infarction by at least one of these criteria was 78 percent, and when both criteria were positive, specificity was 98.5 percent. It is concluded that a single, unipolar posterior lead in the V9 position is superior to standard 12-lead electrocardiographic criteria in diagnosing remote posterior myocardial infarction, and that combining V9 with the T-wave index maximizes the diagnostic yield.
Repetition probability effects for inverted faces.
Grotheer, Mareike; Hermann, Petra; Vidnyánszky, Zoltán; Kovács, Gyula
2014-11-15
It has been shown, that the repetition related reduction of the blood-oxygen level dependent (BOLD) signal is modulated by the probability of repetitions (P(rep)) for faces (Summerfield et al., 2008), providing support for the predictive coding (PC) model of visual perception (Rao and Ballard, 1999). However, the stage of face processing where repetition suppression (RS) is modulated by P(rep) is still unclear. Face inversion is known to interrupt higher level configural/holistic face processing steps and if modulation of RS by P(rep) takes place at these stages of face processing, P(rep) effects are expected to be reduced for inverted when compared to upright faces. Therefore, here we aimed at investigating whether P(rep) effects on RS observed for face stimuli originate at the higher-level configural/holistic stages of face processing by comparing these effects for upright and inverted faces. Similarly to previous studies, we manipulated P(rep) for pairs of stimuli in individual blocks of fMRI recordings. This manipulation significantly influenced repetition suppression in the posterior FFA, the OFA and the LO, independently of stimulus orientation. Our results thus reveal that RS in the ventral visual stream is modulated by P(rep) even in the case of face inversion and hence strongly compromised configural/holistic face processing. An additional whole-brain analysis could not identify any areas where the modulatory effect of probability was orientation specific either. These findings imply that P(rep) effects on RS might originate from the earlier stages of face processing. PMID:25123974
The Probabilities of Conditionals Revisited
ERIC Educational Resources Information Center
Douven, Igor; Verbrugge, Sara
2013-01-01
According to what is now commonly referred to as "the Equation" in the literature on indicative conditionals, the probability of any indicative conditional equals the probability of its consequent of the conditional given the antecedent of the conditional. Philosophers widely agree in their assessment that the triviality arguments of…
Minimizing the probable maximum flood
Woodbury, M.S.; Pansic, N. ); Eberlein, D.T. )
1994-06-01
This article examines Wisconsin Electric Power Company's efforts to determine an economical way to comply with Federal Energy Regulatory Commission requirements at two hydroelectric developments on the Michigamme River. Their efforts included refinement of the area's probable maximum flood model based, in part, on a newly developed probable maximum precipitation estimate.
Decision analysis with approximate probabilities
NASA Technical Reports Server (NTRS)
Whalen, Thomas
1992-01-01
This paper concerns decisions under uncertainty in which the probabilities of the states of nature are only approximately known. Decision problems involving three states of nature are studied. This is due to the fact that some key issues do not arise in two-state problems, while probability spaces with more than three states of nature are essentially impossible to graph. The primary focus is on two levels of probabilistic information. In one level, the three probabilities are separately rounded to the nearest tenth. This can lead to sets of rounded probabilities which add up to 0.9, 1.0, or 1.1. In the other level, probabilities are rounded to the nearest tenth in such a way that the rounded probabilities are forced to sum to 1.0. For comparison, six additional levels of probabilistic information, previously analyzed, were also included in the present analysis. A simulation experiment compared four criteria for decisionmaking using linearly constrained probabilities (Maximin, Midpoint, Standard Laplace, and Extended Laplace) under the eight different levels of information about probability. The Extended Laplace criterion, which uses a second order maximum entropy principle, performed best overall.
Titus, J.G.; Narayanan, V.K.
1995-10-01
The report develops probability-based projections that can be added to local tide-gage trends to estimate future sea level at particular locations. It uses the same models employed by previous assessments of sea level rise. The key coefficients in those models are based on subjective probability distributions supplied by a cross-section of climatologists, oceanographers, and glaciologists.
Computation of Most Probable Numbers
Russek, Estelle; Colwell, Rita R.
1983-01-01
A rapid computational method for maximum likelihood estimation of most-probable-number values, incorporating a modified Newton-Raphson method, is presented. The method offers a much greater reliability for the most-probable-number estimate of total viable bacteria, i.e., those capable of growth in laboratory media. PMID:6870242
Predicting most probable conformations of a given peptide sequence in the random coil state.
Bayrak, Cigdem Sevim; Erman, Burak
2012-11-01
In this work, we present a computational scheme for finding high probability conformations of peptides. The scheme calculates the probability of a given conformation of the given peptide sequence using the probability distribution of torsion states. Dependence of the states of a residue on the states of its first neighbors along the chain is considered. Prior probabilities of torsion states are obtained from a coil library. Posterior probabilities are calculated by the matrix multiplication Rotational Isomeric States Model of polymer theory. The conformation of a peptide with highest probability is determined by using a hidden Markov model Viterbi algorithm. First, the probability distribution of the torsion states of the residues is obtained. Using the highest probability torsion state, one can generate, step by step, states with lower probabilities. To validate the method, the highest probability state of residues in a given sequence is calculated and compared with probabilities obtained from the Coil Databank. Predictions based on the method are 32% better than predictions based on the most probable states of residues. The ensemble of "n" high probability conformations of a given protein is also determined using the Viterbi algorithm with multistep backtracking. PMID:22955874
Yu, Hai Ming; Malhotra, Karan; Butler, Joseph S; Wu, Shi Qiang
2015-01-01
Posterior atlantoaxial dislocation (PAAD) without fracture of the odontoid process is a rare injury. Authors have variously reported closed or open reduction, followed by either anterior or posterior fixation, but there is no consensus on best treatment. We present a particularly unstable case of PAAD. Open reduction through a retropharyngeal approach with odontoidectomy was required for reduction. Anterior fixation with transarticular lag screws was required prior to posterior fixation with pedicle screws. Despite non-compliance with postoperative immobilisation, imaging at 20-month follow-up confirmed solid fusion. The patient is pain-free with a good range of movement of the neck and has returned to a manual job. Our case had a greater degree of instability than was previously reported, which necessitated 360° fixation. This is the first reported case of this treatment strategy, which provided a very stable fixation allowing fusion despite early movement and without causing undue stiffness. PMID:26516249
Aqel, Raed A; Hage, Fadi G; Ellipeddi, Pavani; Blackmon, Linda; McElderry, Hugh T; Kay, G Neal; Plumb, Vance; Iskandrian, Ami E
2009-01-15
A significant proportion of patients with myocardial infarction are missed upon initial presentation to the emergency department. The 12-lead electrocardiogram (ECG) has a low sensitivity for the detection of acute myocardial infarction, especially if the culprit lesion is in the left circumflex artery (LCA). This study was designed to evaluate the benefit of adding 3 posterior chest leads on top of the 12-lead ECG to detect ischemia resulting from LC disease, using a model of temporary balloon occlusion to produce ischemia. We studied 53 consecutive patients who underwent clinically indicated coronary interventions. At the time of coronary angiography, the balloon was inflated to produce complete occlusion of the proximal LCA. We recorded and analyzed the changes noted on the 15-lead ECG, which included 3 posterior leads in addition to the standard 12 leads. In response to acute occlusion of the LCA, the posterior chest leads showed more ST elevation than the other leads, and more patients had ST elevation in the posterior leads than in any other lead. The 15-lead ECG was able to detect>or=0.5 mm (74% vs 38%, p<0.0001) and >or=1 mm (62% vs 34%, p<0.0001) ST elevation in any 2 contiguous leads more frequently than the 12-lead ECG. In conclusion, the 15-lead ECG identified more patients with posterior myocardial wall ischemia because of temporary balloon occlusion of the LC than the 12-lead ECG. This information may enhance the detection of posterior MI in the emergency department and potentially facilitate early institution of reperfusion therapy. PMID:19121429
Borja, David; Siedlecki, Damian; de Castro, Alberto; Uhlhorn, Stephen; Ortiz, Sergio; Arrieta, Esdras; Parel, Jean-Marie; Marcos, Susana; Manns, Fabrice
2010-01-01
We quantify the posterior surface distortions in optical coherence tomography (OCT) images of isolated crystalline lenses. The posterior radius of curvature and asphericity obtained from OCT images acquired with the beam incident first on the anterior, and then the posterior, surface were compared. The results were compared with predictions of a ray-tracing model which includes the index gradient. The results show that the error in the radius of curvature is within the measurement reproducibility and that it can be corrected by assuming a uniform refractive index. However, accurate asphericity values require a correction algorithm that takes into account the gradient. PMID:21258553
Surgical options for posterior tibial plateau fracture
Chen, Hongwei; Wu, Lijun
2015-01-01
Objective: To investigate surgical methods and clinical effectiveness of posteromedial and posterolateral approaches for the posterior tibial plateau fracture. Method: 21 cases who received surgery through posterior approaches for the treatment of posterior tibial plateau fractures (PTPFs) were included. Results: 21 cases were subject to follow-up for 12-24 months (an average of 16.2 months). No cases developed incision inflammation, neurovascular injury, internal fixation loosening and breakage. All fractures were healed. No cases developed knee varus and valgus deformity and fracture dislocation. After surgery, Rasmussen score for knee joint functions was 13-30 points (a mean of 24.2). The results were excellent in 12 cases, good in 7 cases and fair in 2 cases. The percentage of excellent and good results was 90.5%. Rasmussen radiology score was 10-18 points (a mean of 15.6 points). The results were excellent in 13 cases, good in 7 cases and fair in 1 cases. The percentage of excellent and good results was 95.2%. 1 case had significant limited range of knee flexion and extension, which was improved after phase II release under arthroscopy combined with function exercise. 2 cases developed traumatic arthritis, which was relieved after intra-articular injection with sodium hyaluronate and oral nonsteroidal anti-inflammatory drug. Conclusion: The posteromedial and posterolateral approaches for PTPF is good for reduction and fixation of PTPF. The approaches have benefits such as clear exposure, convenient placement of internal fixation, less trauma and good clinical outcome. PMID:26885086
Complications when augmenting the posterior maxilla.
Fugazzotto, Paul; Melnick, Philip R; Al-Sabbagh, Mohanad
2015-01-01
The maxillary posterior edentulous region presents a challenge when planning for restoring missing teeth with a dental implant. The available bone in such cases is often not dense and not adequate for the placement of a properly sized implant because of maxillary sinus pneumatization and alveolar bone loss. Maxillary sinus lift is a predictable procedure to provide adequate bone height for the purpose of implant placement. However, complications are encountered during or after the execution of the sinus lift procedure. In this article, the prevention and management of maxillary sinus complications are discussed. PMID:25434561
Trigeminal neuralgia secondary to posterior fossa tumor.
Agrawal, Mamta; Agrawal, Vikrant; Agrawal, Rajiv; Pramod, D S R
2010-01-01
Trigeminal neuralgia (TN) is by no means an uncommon entity presenting as typical or atypical pain syndrome with a standard treatment protocol consisting of medical and surgical therapies. The diagnosis of TN is mainly dependent on the characteristics of symptoms conveyed by the patient and the clinical presentation. Careful history taking, proper interpretation of the signs and symptoms and cranial nerve assessment are necessary for proper diagnosis. Here, we report a case of TN, treated for dental problems and then for neuralgia with only short-term relief. Subsequently, the patient underwent neuroimaging and was found to be having an uncommon space-occupying lesion in the posterior cranial fossa. PMID:22442556
The probabilities of unique events.
Khemlani, Sangeet S; Lotstein, Max; Johnson-Laird, Phil
2012-01-01
Many theorists argue that the probabilities of unique events, even real possibilities such as President Obama's re-election, are meaningless. As a consequence, psychologists have seldom investigated them. We propose a new theory (implemented in a computer program) in which such estimates depend on an intuitive non-numerical system capable only of simple procedures, and a deliberative system that maps intuitions into numbers. The theory predicts that estimates of the probabilities of conjunctions should often tend to split the difference between the probabilities of the two conjuncts. We report two experiments showing that individuals commit such violations of the probability calculus, and corroborating other predictions of the theory, e.g., individuals err in the same way even when they make non-numerical verbal estimates, such as that an event is highly improbable. PMID:23056224
Transition probabilities of Br II
NASA Technical Reports Server (NTRS)
Bengtson, R. D.; Miller, M. H.
1976-01-01
Absolute transition probabilities of the three most prominent visible Br II lines are measured in emission. Results compare well with Coulomb approximations and with line strengths extrapolated from trends in homologous atoms.
The Probabilities of Unique Events
Khemlani, Sangeet S.; Lotstein, Max; Johnson-Laird, Phil
2012-01-01
Many theorists argue that the probabilities of unique events, even real possibilities such as President Obama's re-election, are meaningless. As a consequence, psychologists have seldom investigated them. We propose a new theory (implemented in a computer program) in which such estimates depend on an intuitive non-numerical system capable only of simple procedures, and a deliberative system that maps intuitions into numbers. The theory predicts that estimates of the probabilities of conjunctions should often tend to split the difference between the probabilities of the two conjuncts. We report two experiments showing that individuals commit such violations of the probability calculus, and corroborating other predictions of the theory, e.g., individuals err in the same way even when they make non-numerical verbal estimates, such as that an event is highly improbable. PMID:23056224
VESPA: False positive probabilities calculator
NASA Astrophysics Data System (ADS)
Morton, Timothy D.
2015-03-01
Validation of Exoplanet Signals using a Probabilistic Algorithm (VESPA) calculates false positive probabilities and statistically validates transiting exoplanets. Written in Python, it uses isochrones [ascl:1503.010] and the package simpledist.
Dinosaurs, Dinosaur Eggs, and Probability.
ERIC Educational Resources Information Center
Teppo, Anne R.; Hodgson, Ted
2001-01-01
Outlines several recommendations for teaching probability in the secondary school. Offers an activity that employs simulation by hand and using a programmable calculator in which geometry, analytical geometry, and discrete mathematics are explored. (KHR)
Crouch, Dustin L.; Plate, Johannes F.; Li, Zhongyu; Saul, Katherine R.
2013-01-01
Purpose To determine if transfer to only the anterior branch of the axillary nerve will restore useful function following axillary nerve injury with persistent posterior deltoid and teres minor paralysis. Methods We used a computational musculoskeletal model of the upper limb to determine the relative contributions of posterior deltoid and teres minor to maximum joint moment generated during a simulated static strength assessment and to joint moments during 3 sub-maximal shoulder movements. Movement simulations were performed with and without simulated posterior deltoid and teres minor paralysis to identify muscles which may compensate for their paralysis. Results In the unimpaired limb model, teres minor and posterior deltoid accounted for 16% and 14% of the total isometric shoulder extension and external rotation joint moments, respectively. During the 3 movement simulations, posterior deltoid produced as much as 20% of the mean shoulder extension moment, while teres minor accounted for less than 5% of the mean joint moment in all directions of movement. When posterior deltoid and teres minor were paralyzed, the mean extension moments generated by the supraspinatus, long head of triceps, latissimus dorsi, and middle deltoid increased to compensate. Compensatory muscles were not fully activated during movement simulations when posterior deltoid and teres minor were paralyzed. Conclusions Reconstruction of the anterior branch of the axillary nerve only is an appropriate technique for restoring shoulder abduction strength following isolated axillary nerve injury. When shoulder extension strength is compromised by extensive neuromuscular shoulder injury, reconstruction of both the anterior and posterior branches of the axillary nerve should be considered. Clinical Relevance By quantifying the biomechanical role of muscles during sub-maximal movement, in addition to quantifying muscle contributions to maximal shoulder strength, we can inform pre-operative planning and
Joint probabilities and quantum cognition
Acacio de Barros, J.
2012-12-18
In this paper we discuss the existence of joint probability distributions for quantumlike response computations in the brain. We do so by focusing on a contextual neural-oscillator model shown to reproduce the main features of behavioral stimulus-response theory. We then exhibit a simple example of contextual random variables not having a joint probability distribution, and describe how such variables can be obtained from neural oscillators, but not from a quantum observable algebra.
Joint probabilities and quantum cognition
NASA Astrophysics Data System (ADS)
de Barros, J. Acacio
2012-12-01
In this paper we discuss the existence of joint probability distributions for quantumlike response computations in the brain. We do so by focusing on a contextual neural-oscillator model shown to reproduce the main features of behavioral stimulus-response theory. We then exhibit a simple example of contextual random variables not having a joint probability distribution, and describe how such variables can be obtained from neural oscillators, but not from a quantum observable algebra.
Evaluation of microbial release probabilities
NASA Technical Reports Server (NTRS)
1972-01-01
Work undertaken to improve the estimation of the probability of release of microorganisms from unmanned Martian landing spacecraft is summarized. An analytical model is described for the development of numerical values for release parameters and release mechanisms applicable to flight missions are defined. Laboratory test data are used to evolve parameter values for use by flight projects in estimating numerical values for release probabilities. The analysis treats microbial burden located on spacecraft surfaces, between mated surfaces, and encapsulated within materials.
Joint probability distributions for projection probabilities of random orthonormal states
NASA Astrophysics Data System (ADS)
Alonso, L.; Gorin, T.
2016-04-01
The quantum chaos conjecture applied to a finite dimensional quantum system implies that such a system has eigenstates that show similar statistical properties as the column vectors of random orthogonal or unitary matrices. Here, we consider the different probabilities for obtaining a specific outcome in a projective measurement, provided the system is in one of its eigenstates. We then give analytic expressions for the joint probability density for these probabilities, with respect to the ensemble of random matrices. In the case of the unitary group, our results can be applied, also, to the phenomenon of universal conductance fluctuations, where the same mathematical quantities describe partial conductances in a two-terminal mesoscopic scattering problem with a finite number of modes in each terminal.
Hydatidosis of the liver and posterior mediastinum
Quail, Jacob F; Gramins, Daniel L; Dutton, William D
2014-01-01
Introduction Cystic echinococcus (CE) is an endemic zoonosis secondary to infection by the larval form of the cestode Echinococcus granulosus. An intermediate host, humans enter the organism’s life cycle by exposure to infected canid feces. The liver is the most common location of CE while mediastinal hydatid cysts are rarely reported. Presentation of case We report a case of synchronous CE of the liver and posterior mediastinum treated sequentially using chemotherapy, percutaneous aspiration with injection of a scolicidal agent and re-aspiration (PAIR) and then staged minimally-invasive surgeries. Discussion Synchronous CE involving the liver and posterior mediastinum is rare. The treatment of hydatid liver and mediastinal disease is multimodal including chemotherapy, percutaneous and laparoscopic or open surgical interventions. One option for controlled puncture of hepatic and mediastinal CE includes PAIR followed by surgery. Conclusion The sequential use of chemotherapy and PAIR followed by surgery provides another treatment strategy for management of CE. We believe this strategy may be used safely in locations without endemic CE, including most regions of the United States. PMID:25562598
Traumatic posterior dislocation of hip in children.
Kutty, S; Thornes, B; Curtin, W A; Gilmore, M F
2001-02-01
Traumatic posterior dislocation of the hip joint in children is an uncommon injury. It constitutes a true orthopedic emergency. It makes up over 80% of pediatric hip dislocations. In children, it can occur as a result of minimal trauma, which is attributed to a soft pliable acetabulum and ligamentous laxity. In skeletally mature adolescents, a greater force is required to dislocate the hip joint. Delay in reduction is associated with long-term complications such as avascular necrosis and degenerative arthritis. Avascular necrosis is related to the duration of dislocation. A poorer prognosis is associated with delay in reduction beyond 6 hours, advanced skeletal maturity, or multiple traumas. Prompt reduction minimizes complications. We report two cases of traumatic posterior dislocation of hip in children aged 3 and 14 years. Both were reduced within 6 hours of dislocation, and review at 6 months revealed normal examination and no evidence of any post-traumatic changes. Post-reduction treatment remains without a consensus. This review highlights the clinical presentation, management, and time-sensitive complications of the injury. PMID:11265904
The posterior calf fascial free flap.
Walton, R L; Matory, W E; Petry, J J
1985-12-01
Six posterior calf fascial free flaps were employed to reconstruct defects of the upper and lower extremities. One flap failed due to a constricting dressing. Two flaps sustained partial loss secondary to bleeding and hematoma formation. One flap dehisced at the distal suture line due to mobility of an underlying fracture. All surviving flaps eventually healed and resulted in stable, thin coverage. Donor-site morbidity has been minimal. Shortcomings of this flap model have been defined in the peculiarities of its thinness, diffuse vascular oozing, the extent of the vascular territory, and in postoperative monitoring. These problems are analyzed and recommendations for their resolution are presented. Fascia represents a unique tissue which offers an exciting new dimension in the reconstruction of certain defects--particularly those in which thinness is a desirable option. In the posterior calf model, the inclusion of fat represents an alternative modification that allows the surgeon to tailor the design to a variety of problems where fascia alone is too thin and a cutaneous flap is too thick. This concept may find its greatest application in wounds involving the hand or foot. We believe that this and other fascial flap prototypes may offer an ideal solution for reconstruction of major wounds of the extremities. PMID:3906718
Mycophenolate-Induced Posterior Reversible Encephalopathy Syndrome.
Khajuria, Bhavik; Khajuria, Mansi; Agrawal, Yashwant
2016-01-01
A 29-year-old woman presented with diffuse anasarca and shortness of breath. Workup revealed a creatinine of 3.3 and a glomerular filtration rate of 17. The patient was also found to be pancytopenic with evidence of hemolytic anemia. A renal biopsy showed evidence of stage IV lupus nephritis with rapidly progressive glomerulonephritis. Her lupus was further classified as ANA negative and anti-dsDNA positive. Mycophenolate and triweekly hemodialysis were started along with a steroid burst of methylprednisolone 1 g for 3 days followed by prednisone 60 mg daily. Four days after discharge, the patient represented with a witnessed 3-minute seizure involving bowel incontinence, altered mental status, and tongue biting. She was given 2 mg intravenous lorazepam and loaded with 1000 mg levetiracetam for seizure prophylaxis. Magnetic resonance imaging of the head revealed bilateral posterior hemispheric subcortical edema, and the diagnosis of posterior reversible encephalopathy syndrome was made. Mycophenolate was immediately discontinued and replaced with cyclophosphamide. Strict blood pressure control below 140/90 mm Hg was maintained initially with intravenous nicardipine drip and then transitioned to oral nifedipine, clonidine, losartan, and minoxidil. A repeat head magnetic resonance imaging 8 days later showed resolved subcortical edema consistent with the patient's improved mental status. No permanent neurologic sequelae were recorded as a result of this hospital episode. PMID:25933141
Management of an Uncomplicated Posterior Elbow Dislocation
Blackard, Douglas; Sampson, Jo-Ann
1997-01-01
Objective: To present a case of an uncomplicated posterior elbow dislocation in a US World Cup athlete and discuss her rehabilitation. Background: Traditional protocol for management of this injury has been splint immobilization for several weeks, but research suggests a shortened duration of immobilization and early active motion. Differential Diagnosis: Elbow dislocation with possible fracture. Treatment: The dislocation was reduced and a compression bandage and sling were applied. The sports medicine staff and athlete determined that rehabilitation would involve limited immobilization with a posterior splint. Also, active range-of- motion exercises were to be incorporated early in the range-of- motion program to decrease pain at the articulation. Uniqueness: The athlete was not immobilized and her aggressive five-phase rehabilitation program progressed according to decrease in inflammation and increase in range of motion and strength. Conclusions: Shortened immobilization and return to World Championship competition 6 weeks postinjury had no longterm adverse effects on the athlete. ImagesFig 1.Fig 2.Fig 3.Fig 4.Fig. 5. PMID:16558436
ERIC Educational Resources Information Center
Frak, Victor; Paulignan, Yves; Jeannerod, Marc; Michel, Francois; Cohen, Henri
2006-01-01
Prehension movements of the right hand were recorded in a right-handed man (AC), with an injury to the left posterior parietal cortex (PPC) and with a section of the left half of the splenium. The kinematic analysis of AC's grasping movements in direct and perturbed conditions was compared to that of five control subjects. A novel effect in…
Calculation of the Isotope Cluster for Polypeptides by Probability Grouping
Olson, Matthew T.; Yergey, Alfred L.
2014-01-01
This paper presents a novel theoretical basis for accurately calculating the isotope cluster of polypeptides. In contrast to previous approaches to this problem, which consider exhaustive or near exhaustive combinations of isotopic species, the program, Neutron Cluster, groups probabilities to yield highly accurate information without elucidating any fine structure within a nominal mass unit. This is a fundamental difference from any previously described algorithm for calculating the isotope cluster. As a result of this difference, the accurate isotope clusters for high molecular weight polypeptides can be calculated rapidly without any pruning. When applied to isotope enriched polypeptides, the algorithm introduces “grouping error”, which is described, quantified, and avoided by using probability partitioning. PMID:19026561
Calculation of the isotope cluster for polypeptides by probability grouping.
Olson, Matthew T; Yergey, Alfred L
2009-02-01
This paper presents a novel theoretical basis for accurately calculating the isotope cluster of polypeptides. In contrast to previous approaches to this problem, which consider exhaustive or near exhaustive combinations of isotopic species, the program, Neutron Cluster, groups probabilities to yield highly accurate information without elucidating any fine structure within a nominal mass unit. This is a fundamental difference from any previously described algorithm for calculating the isotope cluster. As a result of this difference, the accurate isotope clusters for high molecular weight polypeptides can be calculated rapidly without any pruning. When applied to isotope enriched polypeptides, the algorithm introduces "grouping error", which is described, quantified, and avoided by using probability partitioning. PMID:19026561
Potential acuity meter for predicting visual acuity after Nd:YAG posterior capsulotomy
Smiddy, W.E.; Radulovic, D.; Yeo, J.H.; Stark, W.J.; Maumenee, A.E.
1986-03-01
We studied 30 patients with opacifications of the posterior capsule to determine if the potential acuity meter (PAM) could accurately predict final visual outcome after Nd:YAG discussion. The final visual acuity was within one line of the PAM prediction in 22 of 30 patients (73%), better by two or more lines in seven patients (23%), and worse in one patient (4%) by two lines. Although in thicker capsules the final acuity was occasionally better than the PAM prediction, the rates of false negative and false positive predictions were very low. Mild cystoid macular edema (3 patients), age-related macular degeneration (3 patients), intraocular lens status, and level of initial acuity did not diminish PAM accuracy. The PAM effectively predicts final visual acuity after YAG posterior capsulotomy, when used in a patient, unhurried manner.
MARKOV CHAIN MONTE CARLO POSTERIOR SAMPLING WITH THE HAMILTONIAN METHOD
K. HANSON
2001-02-01
The Markov Chain Monte Carlo technique provides a means for drawing random samples from a target probability density function (pdf). MCMC allows one to assess the uncertainties in a Bayesian analysis described by a numerically calculated posterior distribution. This paper describes the Hamiltonian MCMC technique in which a momentum variable is introduced for each parameter of the target pdf. In analogy to a physical system, a Hamiltonian H is defined as a kinetic energy involving the momenta plus a potential energy {var_phi}, where {var_phi} is minus the logarithm of the target pdf. Hamiltonian dynamics allows one to move along trajectories of constant H, taking large jumps in the parameter space with relatively few evaluations of {var_phi} and its gradient. The Hamiltonian algorithm alternates between picking a new momentum vector and following such trajectories. The efficiency of the Hamiltonian method for multidimensional isotropic Gaussian pdfs is shown to remain constant at around 7% for up to several hundred dimensions. The Hamiltonian method handles correlations among the variables much better than the standard Metropolis algorithm. A new test, based on the gradient of {var_phi}, is proposed to measure the convergence of the MCMC sequence.
Advances in the Measurement of Atomic Transition Probabilities
NASA Astrophysics Data System (ADS)
O'Brian, Thomas Raymond
The technology for measuring absolute atomic transition probabilities is extended. Radiative lifetimes are measured by time-resolved laser-induced fluorescence on a slow atomic beam generated by a versatile hollow cathode discharge source. The radiative lifetimes are free from systematic error at the five percent level. Combined with branching fractions measured with emission or absorption sources, the lifetimes result in absolute transition probabilities usually accurate to 5-10 %. Three new developments in the lifetime and branching fraction technique are reported. Radiative lifetimes for 186 levels in neutral iron are measured, with the energy of the upper levels densely spanning the entire excitation range of neutral iron. Combined with branching fractions measured in emission with Fourier transform spectrophotometry, the level lifetimes directly yield absolute transition probabilities for 1174 transitions. An additional 640 transition probabilities are determined by interpolating level populations in an emission source. The dense energy spacing of the levels with directly measured lifetimes permits accurate population interpolation despite departures from local thermodynamic equilibrium. This technique has the potential to permit accurate absolute transition probability measurements for essentially every classified line in a spectrum. Radiative lifetime measurements are extended into the vacuum ultraviolet with a continuously tunable vacuum ultraviolet laser based on stimulated anti-Stokes Raman scattering. When used with the hollow cathode atomic beam source, accurate lifetimes are measured for 47 levels in neutral silicon and 8 levels in neutral boron, primarily in the vacuum ultraviolet spectral region. Transition probabilities are reported for many lines connected to these upper levels, using previously measured or calculated branching fractions. The hollow cathode beam source is developed for use with refractory non-metals. Intense atomic beams of boron
Imprecise probabilities in engineering analyses
NASA Astrophysics Data System (ADS)
Beer, Michael; Ferson, Scott; Kreinovich, Vladik
2013-05-01
Probabilistic uncertainty and imprecision in structural parameters and in environmental conditions and loads are challenging phenomena in engineering analyses. They require appropriate mathematical modeling and quantification to obtain realistic results when predicting the behavior and reliability of engineering structures and systems. But the modeling and quantification is complicated by the characteristics of the available information, which involves, for example, sparse data, poor measurements and subjective information. This raises the question whether the available information is sufficient for probabilistic modeling or rather suggests a set-theoretical approach. The framework of imprecise probabilities provides a mathematical basis to deal with these problems which involve both probabilistic and non-probabilistic information. A common feature of the various concepts of imprecise probabilities is the consideration of an entire set of probabilistic models in one analysis. The theoretical differences between the concepts mainly concern the mathematical description of the set of probabilistic models and the connection to the probabilistic models involved. This paper provides an overview on developments which involve imprecise probabilities for the solution of engineering problems. Evidence theory, probability bounds analysis with p-boxes, and fuzzy probabilities are discussed with emphasis on their key features and on their relationships to one another. This paper was especially prepared for this special issue and reflects, in various ways, the thinking and presentation preferences of the authors, who are also the guest editors for this special issue.
Measure and probability in cosmology
NASA Astrophysics Data System (ADS)
Schiffrin, Joshua S.; Wald, Robert M.
2012-07-01
General relativity has a Hamiltonian formulation, which formally provides a canonical (Liouville) measure on the space of solutions. In ordinary statistical physics, the Liouville measure is used to compute probabilities of macrostates, and it would seem natural to use the similar measure arising in general relativity to compute probabilities in cosmology, such as the probability that the Universe underwent an era of inflation. Indeed, a number of authors have used the restriction of this measure to the space of homogeneous and isotropic universes with scalar field matter (minisuperspace)—namely, the Gibbons-Hawking-Stewart measure—to make arguments about the likelihood of inflation. We argue here that there are at least four major difficulties with using the measure of general relativity to make probability arguments in cosmology: (1) Equilibration does not occur on cosmological length scales. (2) Even in the minisuperspace case, the measure of phase space is infinite and the computation of probabilities depends very strongly on how the infinity is regulated. (3) The inhomogeneous degrees of freedom must be taken into account (we illustrate how) even if one is interested only in universes that are very nearly homogeneous. The measure depends upon how the infinite number of degrees of freedom are truncated, and how one defines “nearly homogeneous.” (4) In a Universe where the second law of thermodynamics holds, one cannot make use of our knowledge of the present state of the Universe to retrodict the likelihood of past conditions.
Model estimates hurricane wind speed probabilities
NASA Astrophysics Data System (ADS)
Mumane, Richard J.; Barton, Chris; Collins, Eric; Donnelly, Jeffrey; Eisner, James; Emanuel, Kerry; Ginis, Isaac; Howard, Susan; Landsea, Chris; Liu, Kam-biu; Malmquist, David; McKay, Megan; Michaels, Anthony; Nelson, Norm; O Brien, James; Scott, David; Webb, Thompson, III
In the United States, intense hurricanes (category 3, 4, and 5 on the Saffir/Simpson scale) with winds greater than 50 m s -1 have caused more damage than any other natural disaster [Pielke and Pielke, 1997]. Accurate estimates of wind speed exceedance probabilities (WSEP) due to intense hurricanes are therefore of great interest to (re)insurers, emergency planners, government officials, and populations in vulnerable coastal areas.The historical record of U.S. hurricane landfall is relatively complete only from about 1900, and most model estimates of WSEP are derived from this record. During the 1899-1998 period, only two category-5 and 16 category-4 hurricanes made landfall in the United States. The historical record therefore provides only a limited sample of the most intense hurricanes.
Khuyagbaatar, Batbayar; Kim, Kyungsoo; Park, Won Man; Kim, Yoon Hyuk
2016-06-01
Ossification of the posterior longitudinal ligament is a common cause of the cervical myelopathy due to compression of the spinal cord. Patients with ossification of the posterior longitudinal ligament usually require the decompression surgery, and there is a need to better understand the optimal surgical extent with which sufficient decompression without excessive posterior shifting can be achieved. However, few quantitative studies have clarified this optimal extent for decompression of cervical ossification of the posterior longitudinal ligament. We used finite element modeling of the cervical spine and spinal cord to investigate the effect of posterior decompression extent for continuous-type cervical ossification of the posterior longitudinal ligament on changes in stress, strain, and posterior shifting that occur with three different surgical methods (laminectomy, laminoplasty, and hemilaminectomy). As posterior decompression extended, stress and strain in the spinal cord decreased and posterior shifting of the cord increased. The location of the decompression extent also influenced shifting. Laminectomy and laminoplasty were very similar in terms of decompression results, and both were superior to hemilaminectomy in all parameters tested. Decompression to the extents of C3-C6 and C3-C7 of laminectomy and laminoplasty could be considered sufficient with respect to decompression itself. Our findings provide fundamental information regarding the treatment of cervical ossification of the posterior longitudinal ligament and can be applied to patient-specific surgical planning. PMID:26951839
Facilitating normative judgments of conditional probability: frequency or nested sets?
Yamagishi, Kimihiko
2003-01-01
Recent probability judgment research contrasts two opposing views. Some theorists have emphasized the role of frequency representations in facilitating probabilistic correctness; opponents have noted that visualizing the probabilistic structure of the task sufficiently facilitates normative reasoning. In the current experiment, the following conditional probability task, an isomorph of the "Problem of Three Prisoners" was tested. "A factory manufactures artificial gemstones. Each gemstone has a 1/3 chance of being blurred, a 1/3 chance of being cracked, and a 1/3 chance of being clear. An inspection machine removes all cracked gemstones, and retains all clear gemstones. However, the machine removes 1/2 of the blurred gemstones. What is the chance that a gemstone is blurred after the inspection?" A 2 x 2 design was administered. The first variable was the use of frequency instruction. The second manipulation was the use of a roulette-wheel diagram that illustrated a "nested-sets" relationship between the prior and the posterior probabilities. Results from two experiments showed that frequency alone had modest effects, while the nested-sets instruction achieved a superior facilitation of normative reasoning. The third experiment compared the roulette-wheel diagram to tree diagrams that also showed the nested-sets relationship. The roulette-wheel diagram outperformed the tree diagrams in facilitation of probabilistic reasoning. Implications for understanding the nature of intuitive probability judgments are discussed. PMID:12693194
Interference of probabilities in dynamics
Zak, Michail
2014-08-15
A new class of dynamical systems with a preset type of interference of probabilities is introduced. It is obtained from the extension of the Madelung equation by replacing the quantum potential with a specially selected feedback from the Liouville equation. It has been proved that these systems are different from both Newtonian and quantum systems, but they can be useful for modeling spontaneous collective novelty phenomena when emerging outputs are qualitatively different from the weighted sum of individual inputs. Formation of language and fast decision-making process as potential applications of the probability interference is discussed.
Probability as a Physical Motive
NASA Astrophysics Data System (ADS)
Martin, Peter
2007-06-01
Recent theoretical progress in nonequilibrium thermodynamics, linking thephysical principle of Maximum Entropy Production (“MEP”) to the information-theoretical“MaxEnt” principle of scientific inference, together with conjectures from theoreticalphysics that there may be no fundamental causal laws but only probabilities for physicalprocesses, and from evolutionary theory that biological systems expand “the adjacentpossible” as rapidly as possible, all lend credence to the proposition that probability shouldbe recognized as a fundamental physical motive. It is further proposed that spatial order andtemporal order are two aspects of the same thing, and that this is the essence of the secondlaw of thermodynamics.
Knowledge typology for imprecise probabilities.
Wilson, G. D.; Zucker, L. J.
2002-01-01
When characterizing the reliability of a complex system there are often gaps in the data available for specific subsystems or other factors influencing total system reliability. At Los Alamos National Laboratory we employ ethnographic methods to elicit expert knowledge when traditional data is scarce. Typically, we elicit expert knowledge in probabilistic terms. This paper will explore how we might approach elicitation if methods other than probability (i.e., Dempster-Shafer, or fuzzy sets) prove more useful for quantifying certain types of expert knowledge. Specifically, we will consider if experts have different types of knowledge that may be better characterized in ways other than standard probability theory.
Achieving target voriconazole concentrations more accurately in children and adolescents.
Neely, Michael; Margol, Ashley; Fu, Xiaowei; van Guilder, Michael; Bayard, David; Schumitzky, Alan; Orbach, Regina; Liu, Siyu; Louie, Stan; Hope, William
2015-01-01
Despite the documented benefit of voriconazole therapeutic drug monitoring, nonlinear pharmacokinetics make the timing of steady-state trough sampling and appropriate dose adjustments unpredictable by conventional methods. We developed a nonparametric population model with data from 141 previously richly sampled children and adults. We then used it in our multiple-model Bayesian adaptive control algorithm to predict measured concentrations and doses in a separate cohort of 33 pediatric patients aged 8 months to 17 years who were receiving voriconazole and enrolled in a pharmacokinetic study. Using all available samples to estimate the individual Bayesian posterior parameter values, the median percent prediction bias relative to a measured target trough concentration in the patients was 1.1% (interquartile range, -17.1 to 10%). Compared to the actual dose that resulted in the target concentration, the percent bias of the predicted dose was -0.7% (interquartile range, -7 to 20%). Using only trough concentrations to generate the Bayesian posterior parameter values, the target bias was 6.4% (interquartile range, -1.4 to 14.7%; P = 0.16 versus the full posterior parameter value) and the dose bias was -6.7% (interquartile range, -18.7 to 2.4%; P = 0.15). Use of a sample collected at an optimal time of 4 h after a dose, in addition to the trough concentration, resulted in a nonsignificantly improved target bias of 3.8% (interquartile range, -13.1 to 18%; P = 0.32) and a dose bias of -3.5% (interquartile range, -18 to 14%; P = 0.33). With the nonparametric population model and trough concentrations, our control algorithm can accurately manage voriconazole therapy in children independently of steady-state conditions, and it is generalizable to any drug with a nonparametric pharmacokinetic model. (This study has been registered at ClinicalTrials.gov under registration no. NCT01976078.). PMID:25779580
Achieving Target Voriconazole Concentrations More Accurately in Children and Adolescents
Margol, Ashley; Fu, Xiaowei; van Guilder, Michael; Bayard, David; Schumitzky, Alan; Orbach, Regina; Liu, Siyu; Louie, Stan; Hope, William
2015-01-01
Despite the documented benefit of voriconazole therapeutic drug monitoring, nonlinear pharmacokinetics make the timing of steady-state trough sampling and appropriate dose adjustments unpredictable by conventional methods. We developed a nonparametric population model with data from 141 previously richly sampled children and adults. We then used it in our multiple-model Bayesian adaptive control algorithm to predict measured concentrations and doses in a separate cohort of 33 pediatric patients aged 8 months to 17 years who were receiving voriconazole and enrolled in a pharmacokinetic study. Using all available samples to estimate the individual Bayesian posterior parameter values, the median percent prediction bias relative to a measured target trough concentration in the patients was 1.1% (interquartile range, −17.1 to 10%). Compared to the actual dose that resulted in the target concentration, the percent bias of the predicted dose was −0.7% (interquartile range, −7 to 20%). Using only trough concentrations to generate the Bayesian posterior parameter values, the target bias was 6.4% (interquartile range, −1.4 to 14.7%; P = 0.16 versus the full posterior parameter value) and the dose bias was −6.7% (interquartile range, −18.7 to 2.4%; P = 0.15). Use of a sample collected at an optimal time of 4 h after a dose, in addition to the trough concentration, resulted in a nonsignificantly improved target bias of 3.8% (interquartile range, −13.1 to 18%; P = 0.32) and a dose bias of −3.5% (interquartile range, −18 to 14%; P = 0.33). With the nonparametric population model and trough concentrations, our control algorithm can accurately manage voriconazole therapy in children independently of steady-state conditions, and it is generalizable to any drug with a nonparametric pharmacokinetic model. (This study has been registered at ClinicalTrials.gov under registration no. NCT01976078.) PMID:25779580
Posterior Cruciate Ligament: Focus on Conflicting Issues
Lee, Yong Seuk
2013-01-01
There is little consensus on how to optimally reconstruct the posterior cruciate ligament (PCL) and the natural history of injured PCL is also unclear. The graft material (autograft vs. allograft), the type of tibial fixation (tibial inlay vs. transtibial tunnel), the femoral tunnel position within the femoral footprint (isometric, central, or eccentric), and the number of bundles in the reconstruction (1 bundle vs. 2 bundles) are among the many decisions that a surgeon must make in a PCL reconstruction. In addition, there is a paucity of information on rehabilitation after reconstruction of the PCL and posterolateral structures. This article focused on the conflicting issues regarding the PCL, and the scientific rationales behind some critical points are discussed. PMID:24340144
Arthroscopic Reverse Remplissage for Posterior Instability.
Lavender, Chad D; Hanzlik, Shane R; Pearson, Sara E; Caldwell, Paul E
2016-02-01
Posterior shoulder dislocation is an unusual injury often associated with electrical shock or seizure. As with anterior instability, patients frequently present with an impaction injury to the anterior aspect of the humeral head known as a "reverse Hill-Sachs lesion." The treatment of this bony defect is controversial, and multiple surgical procedures to fill the defect in an effort to decrease recurrence have been described. Most of the reports have focused on an open approach using variations of lesser tuberosity and subscapularis transfers, bone allograft, and even arthroplasty to assist with persistent instability. We advocate an arthroscopic technique that involves a suture anchor-based distal tenodesis of the subscapularis tendon or a reverse remplissage procedure. PMID:27073776
[Posterior cortical atrophy with progressive visual agnosia].
Zarranz, J J; Lasa, A; Fernández, M; Lezcano, E; Pérez Bas, M; Varona, L; Ruiz, J; Beristain, X
1995-03-01
Interest in progressive focal cerebral syndromes associated with classical degenerative diseases has increased in recent years. Descriptions of posterior cortical atrophy with progressive visual agnosia are relatively rare. We present 5 patients (2 women) ranging in age between 57 and 72 years old. In all cases symptoms began and progressed with no known etiology. All cases were sporadic. The main clinical signs are difficulty in recognizing objects, colors, persons or places; topographical disorientation and visual memory alterations; alexia, simultagnosia, loss of ocular fixing and optic ataxia. Some patients presented other disturbances of praxis or memory and 2 progressed to global dementia. Language function was preserved and behavioral disturbances did not develop. The amplitude of the P100 visual evoked potential was low but latency was normal in 4 patients and prolonged in 1. Brain images showed atrophy and hypoperfusion in the parieto-occipital area. The neuropathology status of these patients is unknown. PMID:7756009
Iodine-125 radiation of posterior uveal melanoma
Packer, S.
1987-12-01
Twenty-eight cases of posterior choroidal melanoma were treated with iodine-125 in gold eye plaques. Eleven cases were located within 3.0 mm of the optic nerve (group A), nine were within 3.0 mm of the fovea (group B), and eight were within 3.0 mm of the optic nerve and fovea (group C). The mean follow-up of group A was 46.3 months; group B, 25.5 months; and group C, 42.7 months. Complications included macular edema, cataract and tumor growth. Visual acuity remained within two lines of that tested preoperatively for 4 of 11 patients in group A, 4 of 9 in group B, and 5 of 8 in group C. These results with iodine-125 suggest it as an appropriate treatment for patients with choroidal melanoma located near optic nerve and/or macula.
Rapid Maxillary Expansion without Posterior Anchorage.
Oliveira, Adauê; Amaral, Cássia
2016-01-01
This work aimed to evaluate an alternative form of maxillary expansion anchored with mini-implants. A patient 12 years, class III in permanent canine teeth, with multiple agenesis of upper posterior teeth was treated with the aid of four mini-implants in the palate and Haas modified type appliance. During the period of expansion, an interincisal diastema was observed as the first clinical sign of disjunction of the sutures. After correction of cross bite, the expansion of the palate was confirmed by upper occlusal radiographs. Thus, the evaluations showed that the technique was effective and that new scientific studies should be conducted to further develop this subject. Keywords: Appliances; Biomechanics; Implants; Malocclusions PMID:27319047
Ectomesenchymal chondromyxoid tumour of the posterior tongue.
Cardin, Marie-Josée; Fiset, Pierre Olivier; Zeitouni, Anthony G; Caglar, Derin
2014-01-01
Ectomesenchymal chondromyxoid tumor (ECMT) is a rare benign neoplasm arising in the tongue. With only 45 cases reported in the literature, there are several unique features defining this lesion. Firstly, almost all patients present with an asymptomatic slow growing mass on the anterior dorsum of the tongue. At the microscopic level, it is recognizable as a well-circumscribed unencapsulated proliferation of uniform round to fusiform cells embedded in a chondromyxoid matrix. Lastly, the immunohistochemistry profile is characterised by positivity for glial fibrillary acidic protein and frequent positivity for S-100 and cytokeratins. We report a case of a mass located on the posterior dorsum of the tongue and meeting the aforementioned morphological and immunohistochemical criteria of ECMT. PMID:24288100
Tibial Tuberosity-Posterior Cruciate Ligament Distance.
Daynes, Jake; Hinckel, Betina Bremer; Farr, Jack
2016-08-01
When trochlear dysplasia is present, it is difficult to measure the tibial tuberosity to trochlear groove (TT-TG) distance. A new measurement to assess tuberosity position was recently described by Seitlinger et al, which avoids the difficulty of identifying the TG as it references the posterior cruciate ligament (PCL). To evaluate the reproducibility of the Seitlinger et al findings, 42 knees in 41 patients with a documented history of recurrent patellar instability and 84 knees in patients with no history of patellar instability or patellofemoral symptoms were evaluated with magnetic resonance imaging. The TT-PCL distance was increased in the instability group (mean, 21.6 mm) compared with the control group (mean, 19.0 mm). The TT-PCL distance is an independent risk factor for patients with recurrent patellar instability. Its role in surgical planning remains to be determined. PMID:26509659
Arthroscopic Reverse Remplissage for Posterior Instability
Lavender, Chad D.; Hanzlik, Shane R.; Pearson, Sara E.; Caldwell, Paul E.
2016-01-01
Posterior shoulder dislocation is an unusual injury often associated with electrical shock or seizure. As with anterior instability, patients frequently present with an impaction injury to the anterior aspect of the humeral head known as a “reverse Hill-Sachs lesion.” The treatment of this bony defect is controversial, and multiple surgical procedures to fill the defect in an effort to decrease recurrence have been described. Most of the reports have focused on an open approach using variations of lesser tuberosity and subscapularis transfers, bone allograft, and even arthroplasty to assist with persistent instability. We advocate an arthroscopic technique that involves a suture anchor–based distal tenodesis of the subscapularis tendon or a reverse remplissage procedure. PMID:27073776
NASA Astrophysics Data System (ADS)
Kasaragod, Deepa; Sugiyama, Satoshi; Ikuno, Yasushi; Alonso-Caneiro, David; Yamanari, Masahiro; Fukuda, Shinichi; Oshika, Tetsuro; Hong, Young-Joo; Li, En; Makita, Shuichi; Miura, Masahiro; Yasuno, Yoshiaki
2016-03-01
Polarization sensitive optical coherence tomography (PS-OCT) is a functional extension of OCT that contrasts the polarization properties of tissues. It has been applied to ophthalmology, cardiology, etc. Proper quantitative imaging is required for a widespread clinical utility. However, the conventional method of averaging to improve the signal to noise ratio (SNR) and the contrast of the phase retardation (or birefringence) images introduce a noise bias offset from the true value. This bias reduces the effectiveness of birefringence contrast for a quantitative study. Although coherent averaging of Jones matrix tomography has been widely utilized and has improved the image quality, the fundamental limitation of nonlinear dependency of phase retardation and birefringence to the SNR was not overcome. So the birefringence obtained by PS-OCT was still not accurate for a quantitative imaging. The nonlinear effect of SNR to phase retardation and birefringence measurement was previously formulated in detail for a Jones matrix OCT (JM-OCT) [1]. Based on this, we had developed a maximum a-posteriori (MAP) estimator and quantitative birefringence imaging was demonstrated [2]. However, this first version of estimator had a theoretical shortcoming. It did not take into account the stochastic nature of SNR of OCT signal. In this paper, we present an improved version of the MAP estimator which takes into account the stochastic property of SNR. This estimator uses a probability distribution function (PDF) of true local retardation, which is proportional to birefringence, under a specific set of measurements of the birefringence and SNR. The PDF was pre-computed by a Monte-Carlo (MC) simulation based on the mathematical model of JM-OCT before the measurement. A comparison between this new MAP estimator, our previous MAP estimator [2], and the standard mean estimator is presented. The comparisons are performed both by numerical simulation and in vivo measurements of anterior and
Is Posterior Leaflet Extension and Associated Commissurotomy
Omeroglu, Suat Nail; Kirali, Kaan; Mansuroglu, Denyan; Goksedef, Deniz; Balkanay, Mehmet; Ipek, Gokhan; Isik, Omer; Yakut, Cevat
2004-01-01
In this prospective study, the long-term effect of posterior leaflet extension with glutaraldehyde-preserved autologous pericardium and associated mitral valve commissurotomy was investigated in patients with mixed mitral valve disease of rheumatic origin. Mitral commissurotomy and posterior leaflet extension using a pericardial patch were performed in 25 patients from 1 January 1994 through 31 December 1995 for mixed mitral valve disease. Preoperatively, no patient had chordal rupture or papillary muscle dysfunction. Four patients had left atrial thrombosis. The mean age was 35.7 ± 15.4 years. Associated procedures were tricuspid annuloplasty in 4 patients, aortic annuloplasty in 3, aortic and tricuspid annuloplasty in 1, and aortic homograft replacement in 1. There were no early deaths. One patient died 2 years after surgery due to noncardiac causes. Mitral valve area increased from 1.53 ± 0.63 cm2 to 2 ± 0.33 cm2 (P = 0.09), and left atrial diameter decreased from 5.8 ± 1 cm to 4.86 ± 1.27 cm (P = 0.07) after 6.1 ± 0.7 years (range, 5.5 to 7.1 years). Mitral insufficiency was reduced significantly, from grade 2.65 ± 0.9 to grade 1.2 ± 0.9 (P = 0.007). Functional capacity improved in all patients (New York Heart Association functional class, 3 ± 0.58 preoperatively vs 1.44 ± 0.82 postoperatively; P = 0.001). Three patients required reoperation and valve replacement. This type of reconstruction may be a good alternative for patients who are not able to use anticoagulant therapy. Long-term results of this technique are acceptable; however, the risk of reoperation is an important disadvantage in these young patients. PMID:15562843
Diagnostics for insufficiencies of posterior calculations in Bayesian signal inference.
Dorn, Sebastian; Oppermann, Niels; Ensslin, Torsten A
2013-11-01
We present an error-diagnostic validation method for posterior distributions in Bayesian signal inference, an advancement of a previous work. It transfers deviations from the correct posterior into characteristic deviations from a uniform distribution of a quantity constructed for this purpose. We show that this method is able to reveal and discriminate several kinds of numerical and approximation errors, as well as their impact on the posterior distribution. For this we present four typical analytical examples of posteriors with incorrect variance, skewness, position of the maximum, or normalization. We show further how this test can be applied to multidimensional signals. PMID:24329375
Simultaneous correction of functional posterior cross bite and midline shift
Arvinth, R.; Rana, Shailendra Singh; Duggal, Ritu; Kharbanda, Om Prakash
2016-01-01
The most frequent cause of functional posterior crossbite is the reduction in width of the maxillary dental arch. This posterior crossbite is associated with anterior crowding which is presented as an infrapositioned canine or a palatally positioned lateral incisor on one side; this leads to an upper midline shift toward the crowded side. The present case report shows the management of posterior crossbite with functional shift and upper midline shift simultaneously without adverse side effects. In this case, rapid maxillary expansion along with fixed appliance is used to correct posterior crossbite with the upper dental midline shift using reciprocal action of elastic transseptal fibers.
Stretching Probability Explorations with Geoboards
ERIC Educational Resources Information Center
Wheeler, Ann; Champion, Joe
2016-01-01
Students are faced with many transitions in their middle school mathematics classes. To build knowledge, skills, and confidence in the key areas of algebra and geometry, students often need to practice using numbers and polygons in a variety of contexts. Teachers also want students to explore ideas from probability and statistics. Teachers know…
ESTIMATION OF AGE TRANSITION PROBABILITIES.
ERIC Educational Resources Information Center
ZINTER, JUDITH R.
THIS NOTE DESCRIBES THE PROCEDURES USED IN DETERMINING DYNAMOD II AGE TRANSITION MATRICES. A SEPARATE MATRIX FOR EACH SEX-RACE GROUP IS DEVELOPED. THESE MATRICES WILL BE USED AS AN AID IN ESTIMATING THE TRANSITION PROBABILITIES IN THE LARGER DYNAMOD II MATRIX RELATING AGE TO OCCUPATIONAL CATEGORIES. THREE STEPS WERE USED IN THE PROCEDURE--(1)…
Probability Simulation in Middle School.
ERIC Educational Resources Information Center
Lappan, Glenda; Winter, M. J.
1980-01-01
Two simulations designed to teach probability to middle-school age pupils are presented. The first simulates the one-on-one foul shot simulation in basketball; the second deals with collecting a set of six cereal box prizes by buying boxes containing one toy each. (MP)
Some Surprising Probabilities from Bingo.
ERIC Educational Resources Information Center
Mercer, Joseph O.
1993-01-01
Investigates the probability of winning the largest prize at Bingo through a series of five simpler problems. Investigations are conducted with the aid of either BASIC computer programs, spreadsheets, or a computer algebra system such as Mathematica. Provides sample data tables to illustrate findings. (MDH)
GPS: Geometry, Probability, and Statistics
ERIC Educational Resources Information Center
Field, Mike
2012-01-01
It might be said that for most occupations there is now less of a need for mathematics than there was say fifty years ago. But, the author argues, geometry, probability, and statistics constitute essential knowledge for everyone. Maybe not the geometry of Euclid, but certainly geometrical ways of thinking that might enable us to describe the world…
Conditional Independence in Applied Probability.
ERIC Educational Resources Information Center
Pfeiffer, Paul E.
This material assumes the user has the background provided by a good undergraduate course in applied probability. It is felt that introductory courses in calculus, linear algebra, and perhaps some differential equations should provide the requisite experience and proficiency with mathematical concepts, notation, and argument. The document is…
Dynamic SEP event probability forecasts
NASA Astrophysics Data System (ADS)
Kahler, S. W.; Ling, A.
2015-10-01
The forecasting of solar energetic particle (SEP) event probabilities at Earth has been based primarily on the estimates of magnetic free energy in active regions and on the observations of peak fluxes and fluences of large (≥ M2) solar X-ray flares. These forecasts are typically issued for the next 24 h or with no definite expiration time, which can be deficient for time-critical operations when no SEP event appears following a large X-ray flare. It is therefore important to decrease the event probability forecast with time as a SEP event fails to appear. We use the NOAA listing of major (≥10 pfu) SEP events from 1976 to 2014 to plot the delay times from X-ray peaks to SEP threshold onsets as a function of solar source longitude. An algorithm is derived to decrease the SEP event probabilities with time when no event is observed to reach the 10 pfu threshold. In addition, we use known SEP event size distributions to modify probability forecasts when SEP intensity increases occur below the 10 pfu event threshold. An algorithm to provide a dynamic SEP event forecast, Pd, for both situations of SEP intensities following a large flare is derived.
Maximum Probability Reaction Sequences in Stochastic Chemical Kinetic Systems
Salehi, Maryam; Perkins, Theodore J.
2010-01-01
The detailed behavior of many molecular processes in the cell, such as protein folding, protein complex assembly, and gene regulation, transcription and translation, can often be accurately captured by stochastic chemical kinetic models. We investigate a novel computational problem involving these models – that of finding the most-probable sequence of reactions that connects two or more states of the system observed at different times. We describe an efficient method for computing the probability of a given reaction sequence, but argue that computing most-probable reaction sequences is EXPSPACE-hard. We develop exact (exhaustive) and approximate algorithms for finding most-probable reaction sequences. We evaluate these methods on test problems relating to a recently-proposed stochastic model of folding of the Trp-cage peptide. Our results provide new computational tools for analyzing stochastic chemical models, and demonstrate their utility in illuminating the behavior of real-world systems. PMID:21629860
Fast and accurate database searches with MS-GF+Percolator.
Granholm, Viktor; Kim, Sangtae; Navarro, José C F; Sjölund, Erik; Smith, Richard D; Käll, Lukas
2014-02-01
One can interpret fragmentation spectra stemming from peptides in mass-spectrometry-based proteomics experiments using so-called database search engines. Frequently, one also runs post-processors such as Percolator to assess the confidence, infer unique peptides, and increase the number of identifications. A recent search engine, MS-GF+, has shown promising results, due to a new and efficient scoring algorithm. However, MS-GF+ provides few statistical estimates about the peptide-spectrum matches, hence limiting the biological interpretation. Here, we enabled Percolator processing for MS-GF+ output and observed an increased number of identified peptides for a wide variety of data sets. In addition, Percolator directly reports p values and false discovery rate estimates, such as q values and posterior error probabilities, for peptide-spectrum matches, peptides, and proteins, functions that are useful for the whole proteomics community. PMID:24344789
Fast and accurate database searches with MS-GF+Percolator
Granholm, Viktor; Kim, Sangtae; Navarro, Jose' C.; Sjolund, Erik; Smith, Richard D.; Kall, Lukas
2014-02-28
To identify peptides and proteins from the large number of fragmentation spectra in mass spectrometrybased proteomics, researches commonly employ so called database search engines. Additionally, postprocessors like Percolator have been used on the results from such search engines, to assess confidence, infer peptides and generally increase the number of identifications. A recent search engine, MS-GF+, has previously been showed to out-perform these classical search engines in terms of the number of identified spectra. However, MS-GF+ generates only limited statistical estimates of the results, hence hampering the biological interpretation. Here, we enabled Percolator-processing for MS-GF+ output, and observed an increased number of identified peptides for a wide variety of datasets. In addition, Percolator directly reports false discovery rate estimates, such as q values and posterior error probabilities, as well as p values, for peptide-spectrum matches, peptides and proteins, functions useful for the whole proteomics community.
Neville, Christopher; Flemister, Adolph S.; Houck, Jeff R.
2010-01-01
Background Tibialis posterior muscle weakness has been documented in subjects with Stage II posterior tibial tendon dysfunction (PTTD) but the effect of weakness on foot structure remains unclear. The association between strength and flatfoot kinematics may guide treatment such as the use of strengthening programs targeting the tibialis posterior muscle. Materials and Methods Thirty Stage II PTTD subjects (age; 58.1 ± 10.5 years, BMI 30.6 ± 5.4) and 15 matched controls (age; 56.5 ± 7.7 years, BMI 30.6 ± 3.6) volunteered for this study. Deep Posterior Compartment strength was measured from both legs of each subject and the strength ratio was used to compare each subject’s involved side to their uninvolved side. A 20% deficit was defined, a priori, to define two groups of subjects with PTTD. The strength ratio for each group averaged; 1.06 ± 0.1 (range 0.87 to 1.36) for controls, 1.06 ± 0.1 (range, 0.89 to 1.25), for the PTTD strong group, and 0.64 ± 0.2 (range 0.42 to 0.76) for the PTTD weak group. Across four phases of stance, kinematic measures of flatfoot were compared between the three groups using a two-way mixed effect ANOVA model repeated for each kinematic variable. Results Subjects with PTTD regardless of group demonstrated significantly greater hindfoot eversion compared to controls. Subjects with PTTD who were weak demonstrated greater hindfoot eversion compared to subjects with PTTD who were strong. For forefoot abduction and MLA angles the differences between groups depended on the phase of stance with significant differences between each group observed at the pre-swing phase of stance. Conclusion Strength was associated with the degree of flatfoot deformity observed during walking, however, flatfoot deformity may also occur without strength deficits. PMID:20371019
Costello syndrome: Analysis of the posterior cranial fossa in children with posterior fossa crowding
D’Apolito, Gabriella; Panfili, Marco; Zampino, Giuseppe; Tartaglione, Tommaso; Colosimo, Cesare
2015-01-01
This study aimed to assess changes in the posterior cranial fossa (PCF) to shed light on the mechanism of cerebellar herniation in children with Costello syndrome (CS) and posterior fossa crowding. We performed a morphovolumetric PCF analysis on brain magnetic resonance imaging (MRI) in seven children with CS (mean age 31 ± 16 months) comparing the MRI scans with those of seven age-matched healthy subjects. PCF volume (PCFV), PCF brain volume (PCFBV) and cerebellar volume (CeV) were assessed on axial T2-weighted MRI. Morphometric parameters (diameters of the foramen magnum, tentorial angle, basiocciput, supraocciput, basisphenoid and exocciput lengths) were measured on sagittal T1-weighted MRI. The volume of the cerebrospinal fluid (CSF) spaces was calculated as PCFV minus PCFBV. Five out of seven CS children showed tonsillar herniation in the upper cervical canal; no child had hydrocephalus but three out of seven children showed ventriculomegaly. In addition, the PCFV/PCFBV ratio, PCFV, CSF spaces volume, basiocciput, basisphenoid and exocciput lengths and latero-lateral and antero-posterior diameters of the foramen magnum were significantly reduced, whereas no significant changes were found in supraocciput length, PCFBV, CeV or hindbrain volume The volumetric reduction of the PCF due to bony posterior fossa hypoplasia is a predisposing factor for developing cerebellar tonsillar herniation through the foramen magnum in children with CS. The altered anatomy of the foramen magnum and upward expansion of the PCF secondary to an increased tentorial slope serves to explain the possible mechanism of cerebellar herniation in patients with CS. PMID:26246091
Predict amine solution properties accurately
Cheng, S.; Meisen, A.; Chakma, A.
1996-02-01
Improved process design begins with using accurate physical property data. Especially in the preliminary design stage, physical property data such as density viscosity, thermal conductivity and specific heat can affect the overall performance of absorbers, heat exchangers, reboilers and pump. These properties can also influence temperature profiles in heat transfer equipment and thus control or affect the rate of amine breakdown. Aqueous-amine solution physical property data are available in graphical form. However, it is not convenient to use with computer-based calculations. Developed equations allow improved correlations of derived physical property estimates with published data. Expressions are given which can be used to estimate physical properties of methyldiethanolamine (MDEA), monoethanolamine (MEA) and diglycolamine (DGA) solutions.
Accurate thickness measurement of graphene
NASA Astrophysics Data System (ADS)
Shearer, Cameron J.; Slattery, Ashley D.; Stapleton, Andrew J.; Shapter, Joseph G.; Gibson, Christopher T.
2016-03-01
Graphene has emerged as a material with a vast variety of applications. The electronic, optical and mechanical properties of graphene are strongly influenced by the number of layers present in a sample. As a result, the dimensional characterization of graphene films is crucial, especially with the continued development of new synthesis methods and applications. A number of techniques exist to determine the thickness of graphene films including optical contrast, Raman scattering and scanning probe microscopy techniques. Atomic force microscopy (AFM), in particular, is used extensively since it provides three-dimensional images that enable the measurement of the lateral dimensions of graphene films as well as the thickness, and by extension the number of layers present. However, in the literature AFM has proven to be inaccurate with a wide range of measured values for single layer graphene thickness reported (between 0.4 and 1.7 nm). This discrepancy has been attributed to tip-surface interactions, image feedback settings and surface chemistry. In this work, we use standard and carbon nanotube modified AFM probes and a relatively new AFM imaging mode known as PeakForce tapping mode to establish a protocol that will allow users to accurately determine the thickness of graphene films. In particular, the error in measuring the first layer is reduced from 0.1-1.3 nm to 0.1-0.3 nm. Furthermore, in the process we establish that the graphene-substrate adsorbate layer and imaging force, in particular the pressure the tip exerts on the surface, are crucial components in the accurate measurement of graphene using AFM. These findings can be applied to other 2D materials.
Electrofishing capture probability of smallmouth bass in streams
Dauwalter, D.C.; Fisher, W.L.
2007-01-01
Abundance estimation is an integral part of understanding the ecology and advancing the management of fish populations and communities. Mark-recapture and removal methods are commonly used to estimate the abundance of stream fishes. Alternatively, abundance can be estimated by dividing the number of individuals sampled by the probability of capture. We conducted a mark-recapture study and used multiple repeated-measures logistic regression to determine the influence of fish size, sampling procedures, and stream habitat variables on the cumulative capture probability for smallmouth bass Micropterus dolomieu in two eastern Oklahoma streams. The predicted capture probability was used to adjust the number of individuals sampled to obtain abundance estimates. The observed capture probabilities were higher for larger fish and decreased with successive electrofishing passes for larger fish only. Model selection suggested that the number of electrofishing passes, fish length, and mean thalweg depth affected capture probabilities the most; there was little evidence for any effect of electrofishing power density and woody debris density on capture probability. Leave-one-out cross validation showed that the cumulative capture probability model predicts smallmouth abundance accurately. ?? Copyright by the American Fisheries Society 2007.