Beam, Craig A.; Conant, Emily F.; Krupinski, Elizabeth A.; Kundel, Harold L.; Sickles, Edward A.
2005-04-01
We introduce an interesting interpretation of the ROC Curve that, subsequently, opens a new research paradigm. We define the "Diagnostician Operating Choice" (DOC) Curve to be the set of all (True Positive Probability/True Negative Probability) or ("skill in diseased population"/"skill in non-diseased population" when considered from the diagnostician's perspective) options made available to a particular radiologist when interpreting a particular diagnostic technology. The DOC Curve is, thus, the choice set presented to the diagnostician by their interaction with the technology. This new paradigm calls for tools that can measure the particular choice set of any particular individual radiologist interpreting a particular technology when applied in a particular clinical setting. Fundamental requirements for this paradigm are for the DOC Curve to be unique to individuals and constant across similar experimental conditions. To investigate constancy, we analyzed data from a reading study of 10 radiologists. Each radiologist interpreted the same set of 148 screening mammograms twice using a modified version of BI-RADS. ROC Curves for each radiologist were computed and compared between the two reading occasions with the CORROC2 program. None of the areas were statistically significantly different (p<0.05), providing confirmation (but not proof) of constancy across the two reading conditions. The DOC Curve paradigm suggests new areas of research focusing on the behavior in individuals interacting with technology. A clear need is for more efficient estimation of individual DOC Curves based on limited case sets. Paradoxically, the answer to this last problem might lie in using large population-based ("MRMC") studies to develop highly efficient and externally validated standardized testing tools for assessment of the individual.
ARC Code TI: ROC Curve Code Augmentation
National Aeronautics and Space Administration — ROC (Receiver Operating Characteristic) curve Code Augmentation was written by Rodney Martin and John Stutz at NASA Ames Research Center and is a modification of ROC...
The ROC Curves of Fused Independent Classification Systems
2008-09-01
spectral settings arises in many fields of study; in medicine, the detection of a cancer; in marketing , the detection of the best customer base; in the...p ≤ 0.4 p/3 + 2/3, 0.4 ≤ p ≤ 1.0 fB(p) = tanh( 4p ) fC(p) = p1/3 The following plots will show how these ROC curves combine, and how the optimal
Statistical comparison of ROC curves from multiple readers
Swaving, M; VanHouwelingen, H; Ottes, FP; Steerneman, T
1996-01-01
Receiver operating characteristic (ROC) analysis is the commonly accepted method for comparing diagnostic imaging systems. In general, ROC studies are designed in such a way that multiple readers read the same images and each image is presented by means of two different imaging systems. Statistical
Evaluation of biomarker using two parameter bi-exponential ROC curve
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Sudesh Pundir
2015-12-01
Full Text Available Receiver Operating Characteristic (ROC Curve is used for assessing the ability of a biomarker/screening test to discriminate between non-diseased and diseased subject. In this paper, the parametric ROC curve is studied by assuming two-parameter exponential distribution to the biomarker values. The ROC model developed under this assumption is called bi-exponential ROC (EROC model. Here, the research interest is to know how far the biomarker will make a distinction between diseased and non-diseased subjects when the gold standard is available using parametric EROC curve and its Area Under the EROC Curve (AUC. Here, the standard error is used as an estimate of the precision of the accuracy measure AUC. The properties of EROC curve that explains the behavior of the EROC curve are also discussed. The AUC along with its asymptotic variance and confidence interval are derived.
Pesce, Lorenzo L; Metz, Charles E
2007-07-01
Estimation of ROC curves and their associated indices from experimental data can be problematic, especially in multireader, multicase (MRMC) observer studies. Wilcoxon estimates of area under the curve (AUC) can be strongly biased with categorical data, whereas the conventional binormal ROC curve-fitting model may produce unrealistic fits. The "proper" binormal model (PBM) was introduced by Metz and Pan to provide acceptable fits for both sturdy and problematic datasets, but other investigators found that its first software implementation was numerically unstable in some situations. Therefore, we created an entirely new algorithm to implement the PBM. This paper describes in detail the new PBM curve-fitting algorithm, which was designed to perform successfully in all problematic situations encountered previously. Extensive testing was conducted also on a broad variety of simulated and real datasets. Windows, Linux, and Apple Macintosh OS X versions of the algorithm are available online at http://xray.bsd.uchicago.edu/krl/. Plots of fitted curves as well as summaries of AUC estimates and their standard errors are reported. The new algorithm never failed to converge and produced good fits for all of the several million datasets on which it was tested. For all but the most problematic datasets, the algorithm also produced very good estimates of AUC standard error. The AUC estimates compared well with Wilcoxon estimates for continuously distributed data and are expected to be superior for categorical data. This implementation of the PBM is reliable in a wide variety of ROC curve-fitting tasks.
ROC curve analyses of eyewitness identification decisions: An analysis of the recent debate.
Rotello, Caren M; Chen, Tina
2016-01-01
How should the accuracy of eyewitness identification decisions be measured, so that best practices for identification can be determined? This fundamental question is under intense debate. One side advocates for continued use of a traditional measure of identification accuracy, known as the diagnosticity ratio , whereas the other side argues that receiver operating characteristic curves (ROCs) should be used instead because diagnosticity is confounded with response bias. Diagnosticity proponents have offered several criticisms of ROCs, which we show are either false or irrelevant to the assessment of eyewitness accuracy. We also show that, like diagnosticity, Bayesian measures of identification accuracy confound response bias with witnesses' ability to discriminate guilty from innocent suspects. ROCs are an essential tool for distinguishing memory-based processes from decisional aspects of a response; simulations of different possible identification tasks and response strategies show that they offer important constraints on theory development.
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Heidi L. Weiss
2004-01-01
Full Text Available The role of biomarkers in disease prognosis continues to be an important investigation in many cancer studies. In order for these biomarkers to have practical application in clinical decision making regarding patient treatment and follow-up, it is common to dichotomize patients into those with low vs. high expression levels. In this study, receiver operating characteristic (ROC curves, area under the curve (AUC of the ROC, sensitivity, specificity, as well as likelihood ratios were calculated to determine levels of growth factor biomarkers that best differentiate lung cancer cases versus control subjects. Selected cut-off points for p185erbB-2 and EGFR membrane appear to have good discriminating power to differentiate control tissues versus uninvolved tissues from patients with lung cancer (AUC = 89% and 90%, respectively; while AUC increased to at least 90% for selected cut-off points for p185erbB-2 membrane, EGFR membrane, and FASE when comparing between control versus carcinoma tissues from lung cancer cases. Using data from control subjects compared to patients with lung cancer, we presented a simple and intuitive approach to determine dichotomized levels of biomarkers and validated the value of these biomarkers as surrogate endpoints for cancer outcome.
Weiss, Heidi L.; Niwas, Santosh; Grizzle, William E.; Piyathilake, Chandrika
2004-01-01
The role of biomarkers in disease prognosis continues to be an important investigation in many cancer studies. In order for these biomarkers to have practical application in clinical decision making regarding patient treatment and follow-up, it is common to dichotomize patients into those with low vs. high expression levels. In this study, receiver operating characteristic (ROC) curves, area under the curve (AUC) of the ROC, sensitivity, specificity, as well as likelihood ratios were calculat...
Ding, Feng; Shi, Qing-ping; Jiang, Xiao-dong; Liu, Yan; Sang, Ran; Zhu, Jin-xiu; Wei, Sheng-tong; Xin, Zhi-ming; Song, Ru
2015-04-01
To study relevant risk factors of Shenmai injection induced adverse reactions by using Logistic model and ROC curve, and made the prediction for the occurrence of relevant adverse reactions/events. Case data of patients treated with Shenmai injection were collected by using the prospective, multi-center, large-sample, nested-case control method, in order to analyze the risk factors of Shenmai injection-induced adverse reactions/events, establish the logistic model and draw the receiver operating characteristic (ROC) curve for risk factors. During the study, 7632 patients (including 3 477 males and 4 155 females) were included, and eight of them suffered adverse reactions/events. Based on a multi-factor Logistic model analysis, the age (> or = 50 years) (OR = 5.061, 95% CI: 2.197-7.924; P = 0.001), the total number of medication days (OR = -1.020, 95% CI: -l.652 - 0.388; P = 0.002) and the single dose (OR = 0.245, 95% CI: 0.127-0.364; P = 0.000) were significant independent risk factors for Shenmai injection-induced adverse reactions/events. According to the results, ROC curves were drawn with age (> or = 50 years), the total number of days of inedication and single dose; The area under ROC curves the joint predictor (0.9753, 95% CI: 0.9443-1.000, P adverse reactions/events included the age (> or = 50 years), the total number of days of medication and single dose. In clinical practice, the age (> or = 50 years), the total number of days of medication and the medication dose can be substituted in the joint predictor calculation formula (P = 1 / [1 + e(-(-21.58 + 5.061 x Xage - 1.020 x Xd + 0.245 x X(mL)] to predict the potential adverse reactions of patients and adjust the dosage regimen.
Reliable and computationally efficient maximum-likelihood estimation of “proper” binormal ROC curves
Pesce, Lorenzo L.; Metz, Charles E.
2009-01-01
Rationale and Objectives Estimation of ROC curves and their associated indices from experimental data can be problematic, especially in multi-reader, multi-case (MRMC) observer studies. Wilcoxon estimates of area under the curve (AUC) can be strongly biased with categorical data, whereas the conventional binormal ROC curve-fitting model may produce unrealistic fits. The “proper” binormal model (PBM) was introduced by Metz and Pan (1) to provide acceptable fits for both sturdy and problematic datasets, but other investigators found that its first software implementation was numerically unstable in some situations (2). Therefore, we created an entirely new algorithm to implement the PBM. Materials and Methods This paper describes in detail the new PBM curve-fitting algorithm, which was designed to perform successfully in all problematic situations encountered previously. Extensive testing was conducted also on a broad variety of simulated and real datasets. Windows, Linux, and Apple Macintosh OS X versions of the algorithm are available online at http://xray.bsd.uchicago.edu/krl/. Results Plots of fitted curves as well as summaries of AUC estimates and their standard errors are reported. The new algorithm never failed to converge and produced good fits for all of the several million datasets on which it was tested. For all but the most problematic datasets, the algorithm also produced very good estimates of AUC standard error. The AUC estimates compared well with Wilcoxon estimates for continuously -distributed data and are expected to be superior for categorical data. Conclusion This implementation of the PBM is reliable in a wide variety of ROC curve-fitting tasks. PMID:17574132
Diagnostic accuracy of quantitative 99mTc-MIBI scintimammography according to ROC curve analysis
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Kim, J. H.; Lee, H. K.; Seo, J. W.; Cho, N. S.; Cha, K. H.; Lee, T. H. [Gachon Medical College, Gil Medical Center, Inchon (Korea, Republic of)
1998-07-01
99mTc-sestamibi scintimammography (SMM) has been shown to be a useful diagnostic test in the detection of breast cancer and the receiver operating characteristic (ROC) curve analysis provides detailed information of a diagnostic test. The purpose of this study was to evaluate the feasibility and efficacy of quantitative indices of SMM in the detection of malignant breast lesions according to ROC analysis. Prone anterior, lateral planar and supine SPECT imagings were performed on 75 female patients (mean age=43.4 yr) with breast mass (size{>=}0.8cm) after intravenous injection of 20-30 mCi 99mTc-sestamibi. 45 Malignant (Invasive ductal ca(36), Inv lobular ca(5), Inv duc + lob (1), Inv tubular ca (3)) and 30 benign (fibroadenoma (13), fib cyst(12), Fat necrosis(3), papilloma(1), paraffinoma (1)) lesions were histologically proven. Data were analyzed by creating three regions of interest (ROIs) over designated areas: lesion, normal breast and right chest wall. Lesion to normal (L/NL) and lesion to chest wall (L/CW) ratios were calculated for each patient both on the planar and SPECT. The area under the ROC curve (AUC) was calculated and compared among four semiquantitative indices and an average scintimammographic index (SMM(mean)) from arithmatic mean. ROC curve analysis revealed planar L/N, SPECT L/N and L/CW ratios provide comparable better diagnostic accuracies for detection of breast cancer than planar L/CW ratio (p<0.05), respectively. For quantitative SMM of 75 lesions, malignancy rate was 60%, and Sensitivity, Specificity, Positive Predictive Value, Negative Predictive Value and Accuracy were 0.78, 0.77, 0.84, 0.72 and 0.77, respectively. Quantitative SMM is an useful objective method for differentiating malignant from benign breast lesions.
Anthropometry, CT, and DXA as predictors of GH deficiency in premenopausal women: ROC curve analysis
Bredella, Miriam A.; Utz, Andrea L.; Torriani, Martin; Thomas, Bijoy; Schoenfeld, David A.; Miller, Karen K.
2009-01-01
Visceral adiposity is a strong determinant of growth hormone (GH) secretion, and states of GH deficiency are associated with increased visceral adiposity and decreased lean body mass. The purpose of our study was to determine the sensitivity and specificity of different methods of assessing body composition [anthropometry, dual-energy X-ray absorptiometry (DXA), and computed tomography (CT)] to predict GH deficiency in premenopausal women and threshold values for each technique to predict GH deficiency, using receiver operator characteristic (ROC) curve analysis. We studied a group of 45 healthy lean, overweight, and obese premenopausal women who underwent anthropometric measurements (body mass index, waist and hip circumferences, skin fold thickness), DXA, CT, and a GH-releasing hormone-arginine stimulation test. ROC curve analysis was used to determine cutoff values for each method to identify GH deficiency. Visceral adiposity measured by CT showed the highest sensitivity and specificity for identifying subjects with GH deficiency with a cutoff of >9,962 mm2 [area under the curve (AUC), 0.95; sensitivity, 100%; specificity, 77.8%; P = 0.0001]. Largest waist circumference showed high sensitivity and specificity with a cutoff of >101.7 cm (AUC, 0.89; sensitivity, 88.9%; specificity, 75%; P = 0.0001). When the ROC curves of visceral fat measured by CT and largest waist circumference were compared, the difference between the two methods was not statistically significant (P = 0.36). Our study showed that the largest waist circumference predicts the presence of GH deficiency in healthy premenopausal women with high sensitivity and specificity and nearly as well as CT measurement of visceral adiposity. It can be used to identify women in whom GH deficiency is likely and therefore in whom formal GH stimulation testing might be indicated. PMID:19095751
Time dependent ROC curves for the estimation of true prognostic capacity of microarray data.
Foucher, Yohann; Danger, Richard
2012-11-22
Microarray data can be used to identify prognostic signatures based on time-to-event data. The analysis of microarrays is often associated with overfitting and many papers have dealt with this issue. However, little attention has been paid to incomplete time-to-event data (truncated and censored follow-up). We have adapted the 0.632+ bootstrap estimator for the evaluation of time-dependent ROC curves. The interpretation of ROC-based results is well-established among the scientific and medical community. Moreover, the results do not depend on the incidence of the event, as opposed to many other prognostic statistics. Here, we have tested this methodology by simulations. We have illustrated its utility by analyzing a data set of diffuse large-B-cell lymphoma patients. Our results demonstrate the well-adapted properties of the 0.632+ ROC-based approach to evaluate the true prognostic capacity of a microarray-based signature. This method has been implemented in an R package ROCt632.
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Mimy Young
2013-12-01
Full Text Available Reported for the first time are receiver operating characteristic (ROC curves constructed to describe the performance of a sorbent-coated disk, planar solid phase microextraction (PSPME unit for non-contact sampling of a variety of volatiles. The PSPME is coupled to ion mobility spectrometers (IMSs for the detection of volatile chemical markers associated with the presence of smokeless powders, model systems of explosives containing diphenylamine (DPA, 2,4-dinitrotoluene (2,4-DNT and nitroglycerin (NG as the target analytes. The performance of the PSPME-IMS was compared with the widely accepted solid-phase microextraction (SPME, coupled to a GC-MS. A set of optimized sampling conditions for different volume containers (1–45 L with various sample amounts of explosives, were studied in replicates (n = 30 to determine the true positive rates (TPR and false positive detection rates (FPR for the different scenarios. These studies were obtained in order to construct the ROC curves for two IMS instruments (a bench-top and field-portable system and a bench top GC-MS system in low and high clutter environments. Both static and dynamic PSPME sampling were studied in which 10–500 mg quantities of smokeless powders were detected within 10 min of static sampling and 1 min of dynamic sampling.
ROC curve of the Pediatric Voice Related Quality-of-Life Survey (P-VRQOL).
Krohling, Lívia Lima; Paula, Kely Maria Pereira de; Behlau, Mara
2016-05-31
To verify the efficiency and to determine the cutoff values that discriminate children/adolescents with and without vocal complaints, as well as the measures of sensibility, specificity and efficiency of the Brazilian Pediatric Voice-Related Quality-of-Life Survey (P-VRQOL). The participants included 230 parents of children/adolescents of both genders, aged between 2 years and 18 years, with and without vocal complaints that responded the validated Brazilian version of P-VRQOL. The three scores (total, physical and social-emotional) were analyzed by the Receiver Operating Characteristic Curve (ROC curve). The cutoff values, ROC curve and the measures of specificity, sensibility and efficiency varied as the score investigated - total, physical or social-emotional. The total score demonstrated excellent discrimination (efficiency=0.936; specificity=0.991; and sensibility=0.881); the social-emotional score was a reasonable indicator (efficiency=0.794; specificity=0.604; and sensibility=0.983) and the physical score was an excellent sorter (efficiency=0.918; specificity=0.946; and sensibility=0.890). The cutoff values and area under curve were: total score- cutoff=96.25 and AUC=0.98; physical score- cutoff=91.68 and AUC=0.97; social-emotional score cutoff=96.87 and AUC=0.79. The P-VRQOL is an excellent sorter to discriminate children/adolescents with and without vocal complaints. The perception of parents about the presence of vocal problem allows the judge of lower quality of life in 98% of the cases, especially, in P-VRQOL physical domain.
International Nuclear Information System (INIS)
Ping, G.
2007-01-01
Full text: Objective: To assess the diagnostic value of CEA CA199 and CA50 for colorectal neoplasm by logistic regression and ROC curve. Methods: The subjects include 75 patients of colorectal cancer, 35 patients of benign intestinal disease and 49 health controls. CEA CA199 and CA50 are measured by CLIA ECLIA and IRMA respectively. The area under the curve (AUC) of CEA CA 199 CA50 and logistic regression results are compared. [Result] In the cancer-benign group, the AUC of CA50 is larger than the AUC of CA199 Compared with the AUC of combination of CEA CA199 and CA50 (0.604),the AUC of combination of CEA and CA50 (0.875) is larger and it is also larger than any other AUC of CEA CA199 or CA50 alone. In the cancerhealth group, the AUC of combination of CEA CA199 and CA50 is larger than any other AUC of CEA CA199 or CA50 alone. No matter in the cancer-benign group or cancerhealth group. The AUC of CEA is larger than the AUC of CA199 or CA50. Conclusion: CEA is useful in the diagnosis of colorectal cancer. In the process of differential diagnosis, the combination of CEA and CA50 can give more information, while the combination of three tumor markers does not perform well. Furthermore, as a statistical method, logistic regression can improve the diagnostic sensitivity and specificity. (author)
Optimizing area under the ROC curve using semi-supervised learning.
Wang, Shijun; Li, Diana; Petrick, Nicholas; Sahiner, Berkman; Linguraru, Marius George; Summers, Ronald M
2015-01-01
Receiver operating characteristic (ROC) analysis is a standard methodology to evaluate the performance of a binary classification system. The area under the ROC curve (AUC) is a performance metric that summarizes how well a classifier separates two classes. Traditional AUC optimization techniques are supervised learning methods that utilize only labeled data (i.e., the true class is known for all data) to train the classifiers. In this work, inspired by semi-supervised and transductive learning, we propose two new AUC optimization algorithms hereby referred to as semi-supervised learning receiver operating characteristic (SSLROC) algorithms, which utilize unlabeled test samples in classifier training to maximize AUC. Unlabeled samples are incorporated into the AUC optimization process, and their ranking relationships to labeled positive and negative training samples are considered as optimization constraints. The introduced test samples will cause the learned decision boundary in a multidimensional feature space to adapt not only to the distribution of labeled training data, but also to the distribution of unlabeled test data. We formulate the semi-supervised AUC optimization problem as a semi-definite programming problem based on the margin maximization theory. The proposed methods SSLROC1 (1-norm) and SSLROC2 (2-norm) were evaluated using 34 (determined by power analysis) randomly selected datasets from the University of California, Irvine machine learning repository. Wilcoxon signed rank tests showed that the proposed methods achieved significant improvement compared with state-of-the-art methods. The proposed methods were also applied to a CT colonography dataset for colonic polyp classification and showed promising results.
Optimizing area under the ROC curve using semi-supervised learning
Wang, Shijun; Li, Diana; Petrick, Nicholas; Sahiner, Berkman; Linguraru, Marius George; Summers, Ronald M.
2014-01-01
Receiver operating characteristic (ROC) analysis is a standard methodology to evaluate the performance of a binary classification system. The area under the ROC curve (AUC) is a performance metric that summarizes how well a classifier separates two classes. Traditional AUC optimization techniques are supervised learning methods that utilize only labeled data (i.e., the true class is known for all data) to train the classifiers. In this work, inspired by semi-supervised and transductive learning, we propose two new AUC optimization algorithms hereby referred to as semi-supervised learning receiver operating characteristic (SSLROC) algorithms, which utilize unlabeled test samples in classifier training to maximize AUC. Unlabeled samples are incorporated into the AUC optimization process, and their ranking relationships to labeled positive and negative training samples are considered as optimization constraints. The introduced test samples will cause the learned decision boundary in a multidimensional feature space to adapt not only to the distribution of labeled training data, but also to the distribution of unlabeled test data. We formulate the semi-supervised AUC optimization problem as a semi-definite programming problem based on the margin maximization theory. The proposed methods SSLROC1 (1-norm) and SSLROC2 (2-norm) were evaluated using 34 (determined by power analysis) randomly selected datasets from the University of California, Irvine machine learning repository. Wilcoxon signed rank tests showed that the proposed methods achieved significant improvement compared with state-of-the-art methods. The proposed methods were also applied to a CT colonography dataset for colonic polyp classification and showed promising results.1 PMID:25395692
A boosting method for maximizing the partial area under the ROC curve
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Eguchi Shinto
2010-06-01
Full Text Available Abstract Background The receiver operating characteristic (ROC curve is a fundamental tool to assess the discriminant performance for not only a single marker but also a score function combining multiple markers. The area under the ROC curve (AUC for a score function measures the intrinsic ability for the score function to discriminate between the controls and cases. Recently, the partial AUC (pAUC has been paid more attention than the AUC, because a suitable range of the false positive rate can be focused according to various clinical situations. However, existing pAUC-based methods only handle a few markers and do not take nonlinear combination of markers into consideration. Results We have developed a new statistical method that focuses on the pAUC based on a boosting technique. The markers are combined componentially for maximizing the pAUC in the boosting algorithm using natural cubic splines or decision stumps (single-level decision trees, according to the values of markers (continuous or discrete. We show that the resulting score plots are useful for understanding how each marker is associated with the outcome variable. We compare the performance of the proposed boosting method with those of other existing methods, and demonstrate the utility using real data sets. As a result, we have much better discrimination performances in the sense of the pAUC in both simulation studies and real data analysis. Conclusions The proposed method addresses how to combine the markers after a pAUC-based filtering procedure in high dimensional setting. Hence, it provides a consistent way of analyzing data based on the pAUC from maker selection to marker combination for discrimination problems. The method can capture not only linear but also nonlinear association between the outcome variable and the markers, about which the nonlinearity is known to be necessary in general for the maximization of the pAUC. The method also puts importance on the accuracy of
Zhang, Xiaodong; Zhao, Yinxia; Hu, Shaoyong; Hao, Shuai; Yan, Jiewen; Zhang, Lingyan; Zhao, Jing; Li, Shaolin
2015-09-01
To investigate the correlation between the lumbar vertebra bone mineral density (BMD) and age, gender, height, weight, body mass index, waistline, hipline, bone marrow and abdomen fat, and to explore the key factor affecting the BMD. A total of 72 cases were randomly recruited. All the subjects underwent a spectroscopic examination of the third lumber vertebra with single-voxel method in 1.5T MR. Lipid fractions (FF%) were measured. Quantitative CT were also performed to get the BMD of L3 and the corresponding abdomen subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT). The statistical analysis were performed by SPSS 19.0. Multiple linear regression showed except the age and FF% showed significant difference (P0.05). The correlation of age and FF% with BMD was statistically negatively significant (r=-0.830, -0.521, P<0.05). The ROC curve analysis showed that the sensitivety and specificity of predicting osteoporosis were 81.8% and 86.9%, with a threshold of 58.5 years old. And it showed that the sensitivety and specificity of predicting osteoporosis were 90.9% and 55.7%, with a threshold of 52.8% for FF%. The lumbar vertebra BMD was significantly and negatively correlated with age and bone marrow FF%, but it was not significantly correlated with gender, height, weight, BMI, waistline, hipline, SAT and VAT. And age was the critical factor.
Rational points on elliptic curves
Silverman, Joseph H
2015-01-01
The theory of elliptic curves involves a pleasing blend of algebra, geometry, analysis, and number theory. This book stresses this interplay as it develops the basic theory, thereby providing an opportunity for advanced undergraduates to appreciate the unity of modern mathematics. At the same time, every effort has been made to use only methods and results commonly included in the undergraduate curriculum. This accessibility, the informal writing style, and a wealth of exercises make Rational Points on Elliptic Curves an ideal introduction for students at all levels who are interested in learning about Diophantine equations and arithmetic geometry. Most concretely, an elliptic curve is the set of zeroes of a cubic polynomial in two variables. If the polynomial has rational coefficients, then one can ask for a description of those zeroes whose coordinates are either integers or rational numbers. It is this number theoretic question that is the main subject of this book. Topics covered include the geometry and ...
Obuchowski, Nancy A.; Bullen, Jennifer A.
2018-04-01
Receiver operating characteristic (ROC) analysis is a tool used to describe the discrimination accuracy of a diagnostic test or prediction model. While sensitivity and specificity are the basic metrics of accuracy, they have many limitations when characterizing test accuracy, particularly when comparing the accuracies of competing tests. In this article we review the basic study design features of ROC studies, illustrate sample size calculations, present statistical methods for measuring and comparing accuracy, and highlight commonly used ROC software. We include descriptions of multi-reader ROC study design and analysis, address frequently seen problems of verification and location bias, discuss clustered data, and provide strategies for testing endpoints in ROC studies. The methods are illustrated with a study of transmission ultrasound for diagnosing breast lesions.
International Nuclear Information System (INIS)
Zanca, Federica; Hillis, Stephen L.; Claus, Filip; Van Ongeval, Chantal; Celis, Valerie; Provoost, Veerle; Yoon, Hong-Jun; Bosmans, Hilde
2012-01-01
Purpose: From independently conducted free-response receiver operating characteristic (FROC) and receiver operating characteristic (ROC) experiments, to study fixed-reader associations between three estimators: the area under the alternative FROC (AFROC) curve computed from FROC data, the area under the ROC curve computed from FROC highest rating data, and the area under the ROC curve computed from confidence-of-disease ratings. Methods: Two hundred mammograms, 100 of which were abnormal, were processed by two image-processing algorithms and interpreted by four radiologists under the FROC paradigm. From the FROC data, inferred-ROC data were derived, using the highest rating assumption. Eighteen months afterwards, the images were interpreted by the same radiologists under the conventional ROC paradigm; conventional-ROC data (in contrast to inferred-ROC data) were obtained. FROC and ROC (inferred, conventional) data were analyzed using the nonparametric area-under-the-curve (AUC), (AFROC and ROC curve, respectively). Pearson correlation was used to quantify the degree of association between the modality-specific AUC indices and standard errors were computed using the bootstrap-after-bootstrap method. The magnitude of the correlations was assessed by comparison with computed Obuchowski-Rockette fixed reader correlations. Results: Average Pearson correlations (with 95% confidence intervals in square brackets) were: Corr(FROC, inferred ROC) = 0.76[0.64, 0.84] > Corr(inferred ROC, conventional ROC) = 0.40[0.18, 0.58] > Corr (FROC, conventional ROC) = 0.32[0.16, 0.46]. Conclusions: Correlation between FROC and inferred-ROC data AUC estimates was high. Correlation between inferred- and conventional-ROC AUC was similar to the correlation between two modalities for a single reader using one estimation method, suggesting that the highest rating assumption might be questionable.
Mohammadi, Hassanreza R; Azimi, Parisa; Benzel, Edward C; Shahzadi, Sohrab; Azhari, Shirzad
2016-09-01
The aim of this study was to elucidate independent factors that predict surgical satisfaction in lumbar spinal canal stenosis (LSCS) patients. Patients who underwent surgery were grouped based on the age, gender, duration of symptoms, walking distance, Neurogenic Claudication Outcome Score (NCOS) and the stenosis ratio (SR) described by Lurencin. We recorded on 2-year patient satisfaction using standardized measure. The optimal cut-off points in SR, NCOS and walking distance for predicting surgical satisfaction were estimated from sensitivity and specificity calculations and receiver operator characteristic (ROC) curves. One hundred fifty consecutive patients (51 male, 99 female, mean age 62.4±10.9 years) were followed up for 34±13 months (range 24-49). One, two, three and four level stenosis was observed in 10.7%, 39.3%, 36.0 % and 14.0% of patients, respectively. Post-surgical satisfaction was 78.5% at the 2 years follow up. In ROC curve analysis, the asymptotic significance is less than 0.05 in SR and the optimal cut-off value of SR to predict worsening surgical satisfaction was measured as more than 0.52, with 85.4% sensitivity and 77.4% specificity (AUC 0.798, 95% CI 0.73-0.90; Ppatients with degenerative lumbar stenosis considered for surgical treatment. Using a ROC curve analysis, a radiological feature, the SR, demonstrated superiority in predicting patient satisfaction, compared to functional and clinical characteristics such as walking distance and NCOS.
Bantis, Leonidas E; Tsimikas, John V; Georgiou, Stelios D
2013-09-01
The use of ROC curves in evaluating a continuous or ordinal biomarker for the discrimination of two populations is commonplace. However, in many settings, marker measurements above or below a certain value cannot be obtained. In this paper, we study the construction of a smooth ROC curve (or surface in the case of three populations) when there is a lower or upper limit of detection. We propose the use of spline models that incorporate monotonicity constraints for the cumulative hazard function of the marker distribution. The proposed technique is computationally stable and simulation results showed a satisfactory performance. Other observed covariates can be also accommodated by this spline-based approach. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Diagnostic accuracy of the MMPI-2 with the Mexican criminal personality: The ROC curve analysis
Ampudia Rueda, Amada; Sánchez Crespo, Guadalupe; Jiménez Gómez, Fernando
2016-01-01
The objective of this study is to assess the diagnostic accuracy of the personality of the Mexican criminal with the Minnesota Multiphasic Personality Inventory-2 (MMPI-2). The inventory was administered to 1,740 Mexican participants of which 870 (728 male and 142 female) are prison inmates, processed and/or sentenced for various crimes from various prisons in Mexico City, and the other 870 participants (728 male and 142 female) are not prison inmates. The ROC (Receiver Operating Characterist...
Directory of Open Access Journals (Sweden)
Ping Wan
2016-08-01
Full Text Available Driving anger, called “road rage”, has become increasingly common nowadays, affecting road safety. A few researches focused on how to identify driving anger, however, there is still a gap in driving anger grading, especially in real traffic environment, which is beneficial to take corresponding intervening measures according to different anger intensity. This study proposes a method for discriminating driving anger states with different intensity based on Electroencephalogram (EEG spectral features. First, thirty drivers were recruited to conduct on-road experiments on a busy route in Wuhan, China where anger could be inducted by various road events, e.g., vehicles weaving/cutting in line, jaywalking/cyclist crossing, traffic congestion and waiting red light if they want to complete the experiments ahead of basic time for extra paid. Subsequently, significance analysis was used to select relative energy spectrum of β band (β% and relative energy spectrum of θ band (θ% for discriminating the different driving anger states. Finally, according to receiver operating characteristic (ROC curve analysis, the optimal thresholds (best cut-off points of β% and θ% for identifying none anger state (i.e., neutral were determined to be 0.2183 ≤ θ% < 1, 0 < β% < 0.2586; low anger state is 0.1539 ≤ θ% < 0.2183, 0.2586 ≤ β% < 0.3269; moderate anger state is 0.1216 ≤ θ% < 0.1539, 0.3269 ≤ β% < 0.3674; high anger state is 0 < θ% < 0.1216, 0.3674 ≤ β% < 1. Moreover, the discrimination performances of verification indicate that, the overall accuracy (Acc of the optimal thresholds of β% for discriminating the four driving anger states is 80.21%, while 75.20% for that of θ%. The results can provide theoretical foundation for developing driving anger detection or warning devices based on the relevant optimal thresholds.
Zur, Richard M; Pesce, Lorenzo L; Jiang, Yulei
2015-05-01
To evaluate stratified random sampling (SRS) of screening mammograms by (1) Breast Imaging Reporting and Data System (BI-RADS) assessment categories, and (2) the presence of breast cancer in mammograms, for estimation of screening-mammography receiver operating characteristic (ROC) curves in retrospective observer studies. We compared observer study case sets constructed by (1) random sampling (RS); (2) SRS with proportional allocation (SRS-P) with BI-RADS 1 and 2 noncancer cases accounting for 90.6% of all noncancer cases; (3) SRS with disproportional allocation (SRS-D) with BI-RADS 1 and 2 noncancer cases accounting for 10%-80%; and (4) SRS-D and multiple imputation (SRS-D + MI) with missing BI-RADS 1 and 2 noncancer cases imputed to recover the 90.6% proportion. Monte Carlo simulated case sets were drawn from a large case population modeled after published Digital Mammography Imaging Screening Trial data. We compared the bias, root-mean-square error, and coverage of 95% confidence intervals of area under the ROC curve (AUC) estimates from the sampling methods (200-2000 cases, of which 25% were cancer cases) versus from the large case population. AUC estimates were unbiased from RS, SRS-P, and SRS-D + MI, but biased from SRS-D. AUC estimates from SRS-P and SRS-D + MI had 10% smaller root-mean-square error than RS. Both SRS-P and SRS-D + MI can be used to obtain unbiased and 10% more efficient estimate of screening-mammography ROC curves. Copyright © 2015 AUR. Published by Elsevier Inc. All rights reserved.
Directory of Open Access Journals (Sweden)
Pistoia Vito
2008-10-01
Full Text Available Abstract Background Most microarray experiments are carried out with the purpose of identifying genes whose expression varies in relation with specific conditions or in response to environmental stimuli. In such studies, genes showing similar mean expression values between two or more groups are considered as not differentially expressed, even if hidden subclasses with different expression values may exist. In this paper we propose a new method for identifying differentially expressed genes, based on the area between the ROC curve and the rising diagonal (ABCR. ABCR represents a more general approach than the standard area under the ROC curve (AUC, because it can identify both proper (i.e., concave and not proper ROC curves (NPRC. In particular, NPRC may correspond to those genes that tend to escape standard selection methods. Results We assessed the performance of our method using data from a publicly available database of 4026 genes, including 14 normal B cell samples (NBC and 20 heterogeneous lymphomas (namely: 9 follicular lymphomas and 11 chronic lymphocytic leukemias. Moreover, NBC also included two sub-classes, i.e., 6 heavily stimulated and 8 slightly or not stimulated samples. We identified 1607 differentially expressed genes with an estimated False Discovery Rate of 15%. Among them, 16 corresponded to NPRC and all escaped standard selection procedures based on AUC and t statistics. Moreover, a simple inspection to the shape of such plots allowed to identify the two subclasses in either one class in 13 cases (81%. Conclusion NPRC represent a new useful tool for the analysis of microarray data.
Comparing risk of failure models in water supply networks using ROC curves
International Nuclear Information System (INIS)
Debon, A.; Carrion, A.; Cabrera, E.; Solano, H.
2010-01-01
The problem of predicting the failure of water mains has been considered from different perspectives and using several methodologies in engineering literature. Nowadays, it is important to be able to accurately calculate the failure probabilities of pipes over time, since water company profits and service quality for citizens depend on pipe survival; forecasting pipe failures could have important economic and social implications. Quantitative tools (such as managerial or statistical indicators and reliable databases) are required in order to assess the current and future state of networks. Companies managing these networks are trying to establish models for evaluating the risk of failure in order to develop a proactive approach to the renewal process, instead of using traditional reactive pipe substitution schemes. The main objective of this paper is to compare models for evaluating the risk of failure in water supply networks. Using real data from a water supply company, this study has identified which network characteristics affect the risk of failure and which models better fit data to predict service breakdown. The comparison using the receiver operating characteristics (ROC) graph leads us to the conclusion that the best model is a generalized linear model. Also, we propose a procedure that can be applied to a pipe failure database, allowing the most appropriate decision rule to be chosen.
Comparing risk of failure models in water supply networks using ROC curves
Energy Technology Data Exchange (ETDEWEB)
Debon, A., E-mail: andeau@eio.upv.e [Centro de Gestion de la Calidad y del Cambio, Dpt. Estadistica e Investigacion Operativa Aplicadas y Calidad, Universidad Politecnica de Valencia, E-46022 Valencia (Spain); Carrion, A. [Centro de Gestion de la Calidad y del Cambio, Dpt. Estadistica e Investigacion Operativa Aplicadas y Calidad, Universidad Politecnica de Valencia, E-46022 Valencia (Spain); Cabrera, E. [Dpto. De Ingenieria Hidraulica Y Medio Ambiente, Instituto Tecnologico del Agua, Universidad Politecnica de Valencia, E-46022 Valencia (Spain); Solano, H. [Universidad Diego Portales, Santiago (Chile)
2010-01-15
The problem of predicting the failure of water mains has been considered from different perspectives and using several methodologies in engineering literature. Nowadays, it is important to be able to accurately calculate the failure probabilities of pipes over time, since water company profits and service quality for citizens depend on pipe survival; forecasting pipe failures could have important economic and social implications. Quantitative tools (such as managerial or statistical indicators and reliable databases) are required in order to assess the current and future state of networks. Companies managing these networks are trying to establish models for evaluating the risk of failure in order to develop a proactive approach to the renewal process, instead of using traditional reactive pipe substitution schemes. The main objective of this paper is to compare models for evaluating the risk of failure in water supply networks. Using real data from a water supply company, this study has identified which network characteristics affect the risk of failure and which models better fit data to predict service breakdown. The comparison using the receiver operating characteristics (ROC) graph leads us to the conclusion that the best model is a generalized linear model. Also, we propose a procedure that can be applied to a pipe failure database, allowing the most appropriate decision rule to be chosen.
Receiver operating characteristic (ROC) curve for classification of {sup 18}F-NaF uptake on PET/CT
Energy Technology Data Exchange (ETDEWEB)
Valadares, Agnes Araujo, E-mail: agnesvaladares@me.com [Universidade de Sao Paulo (HC/FM/USP), SP (Brazil). Hospital das Clinicas. Fac. de Mediciana; Duarte, Paulo Schiavom; Ono, Carla Rachel; Coura-Filho, George Barberio; Sado, Heitor Naoki; Carvalho, Giovanna [Instituto do Cancer do Estado de Sao Paulo Octavio Frias de Oliveira (ICESP), Sao Paulo, SP (Brazil). Servico de Medicina Nuclear; Sapienza, Marcelo Tatit; Buchpiguel, Carlos Alberto [Universidade de Sao Paulo (FM/USP), Sao Paulo, SP (Brazil). Fac. de Medicina. Dept. de Radiologia e Oncologia
2016-01-15
Objective: To assess the cutoff values established by ROC curves to classify {sup 18}F-NaF uptake as normal or malignant. Materials and Methods: PET/CT images were acquired 1 hour after administration of 185 MBq of {sup 18}F-NaF. Volumes of interest (VOIs) were drawn on three regions of the skeleton as follows: proximal right humerus diaphysis (HD), proximal right femoral diaphysis (FD) and first vertebral body (VB1), in a total of 254 patients, totalling 762 VOIs. The uptake in the VOIs was classified as normal or malignant on the basis of the radiopharmaceutical distribution pattern and of the CT images. A total of 675 volumes were classified as normal and 52 were classified as malignant. Thirty-five VOIs classified as indeterminate or nonmalignant lesions were excluded from analysis. The standardized uptake value (SUV) measured on the VOIs were plotted on an ROC curve for each one of the three regions. The area under the ROC (AUC) as well as the best cutoff SUVs to classify the VOIs were calculated. The best cutoff values were established as the ones with higher result of the sum of sensitivity and specificity. Results: The AUCs were 0.933, 0.889 and 0.975 for UD, FD and VB1, respectively. The best SUV cutoffs were 9.0 (sensitivity: 73%; specificity: 99%), 8.4 (sensitivity: 79%; specificity: 94%) and 21.0 (sensitivity: 93%; specificity: 95%) for UD, FD and VB1, respectively. Conclusion: The best cutoff value varies according to bone region of analysis and it is not possible to establish one value for the whole body. (author)
Froud, Robert; Abel, Gary
2014-01-01
Receiver Operator Characteristic (ROC) curves are being used to identify Minimally Important Change (MIC) thresholds on scales that measure a change in health status. In quasi-continuous patient reported outcome measures, such as those that measure changes in chronic diseases with variable clinical trajectories, sensitivity and specificity are often valued equally. Notwithstanding methodologists agreeing that these should be valued equally, different approaches have been taken to estimating MIC thresholds using ROC curves. We aimed to compare the different approaches used with a new approach, exploring the extent to which the methods choose different thresholds, and considering the effect of differences on conclusions in responder analyses. Using graphical methods, hypothetical data, and data from a large randomised controlled trial of manual therapy for low back pain, we compared two existing approaches with a new approach that is based on the addition of the sums of squares of 1-sensitivity and 1-specificity. There can be divergence in the thresholds chosen by different estimators. The cut-point selected by different estimators is dependent on the relationship between the cut-points in ROC space and the different contours described by the estimators. In particular, asymmetry and the number of possible cut-points affects threshold selection. Choice of MIC estimator is important. Different methods for choosing cut-points can lead to materially different MIC thresholds and thus affect results of responder analyses and trial conclusions. An estimator based on the smallest sum of squares of 1-sensitivity and 1-specificity is preferable when sensitivity and specificity are valued equally. Unlike other methods currently in use, the cut-point chosen by the sum of squares method always and efficiently chooses the cut-point closest to the top-left corner of ROC space, regardless of the shape of the ROC curve.
Twisted vector bundles on pointed nodal curves
Indian Academy of Sciences (India)
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
is an element different from the identity and u is a geometric point of U fixed by γ, then the automorphism of the fiber ηu induced by γ is not trivial. 3. An essential action of a finite group on (η,U) is called tame, if the action of on. (U → S, i) is tame. DEFINITION 2.3. Let S be a k-scheme. Let C → S be an n-pointed nodal curve ...
Some genus 3 curves with many points
Auer, R; Top, J; Fieker, C; Kohel, DR
2002-01-01
We explain a naive approach towards the problem of finding genus 3 curves C over any given finite field F-q of odd characteristic, with a number of rational points close to the Hasse-Weil-Serre upper bound q+1+3[2rootq]. The method turns out to be successful at least in characteristic 3.
A modified Wald interval for the area under the ROC curve (AUC) in diagnostic case-control studies.
Kottas, Martina; Kuss, Oliver; Zapf, Antonia
2014-02-19
The area under the receiver operating characteristic (ROC) curve, referred to as the AUC, is an appropriate measure for describing the overall accuracy of a diagnostic test or a biomarker in early phase trials without having to choose a threshold. There are many approaches for estimating the confidence interval for the AUC. However, all are relatively complicated to implement. Furthermore, many approaches perform poorly for large AUC values or small sample sizes. The AUC is actually a probability. So we propose a modified Wald interval for a single proportion, which can be calculated on a pocket calculator. We performed a simulation study to compare this modified Wald interval (without and with continuity correction) with other intervals regarding coverage probability and statistical power. The main result is that the proposed modified Wald intervals maintain and exploit the type I error much better than the intervals of Agresti-Coull, Wilson, and Clopper-Pearson. The interval suggested by Bamber, the Mann-Whitney interval without transformation and also the interval of the binormal AUC are very liberal. For small sample sizes the Wald interval with continuity has a comparable coverage probability as the LT interval and higher power. For large sample sizes the results of the LT interval and of the Wald interval without continuity correction are comparable. If individual patient data is not available, but only the estimated AUC and the total sample size, the modified Wald intervals can be recommended as confidence intervals for the AUC. For small sample sizes the continuity correction should be used.
Point- and curve-based geometric conflation
López-Vázquez, C.
2013-01-01
Geometric conflation is the process undertaken to modify the coordinates of features in dataset A in order to match corresponding ones in dataset B. The overwhelming majority of the literature considers the use of points as features to define the transformation. In this article we present a procedure to consider one-dimensional curves also, which are commonly available as Global Navigation Satellite System (GNSS) tracks, routes, coastlines, and so on, in order to define the estimate of the displacements to be applied to each object in A. The procedure involves three steps, including the partial matching of corresponding curves, the computation of some analytical expression, and the addition of a correction term in order to satisfy basic cartographic rules. A numerical example is presented. © 2013 Copyright Taylor and Francis Group, LLC.
Detecting corner points from digital curves
International Nuclear Information System (INIS)
Sarfraz, M.
2011-01-01
Corners in digital images give important clues for shape representation, recognition, and analysis. Since dominant information regarding shape is usually available at the corners, they provide important features for various real life applications in the disciplines like computer vision, pattern recognition, computer graphics. Corners are the robust features in the sense that they provide important information regarding objects under translation, rotation and scale change. They are also important from the view point of understanding human perception of objects. They play crucial role in decomposing or describing the digital curves. They are also used in scale space theory, image representation, stereo vision, motion tracking, image matching, building mosaics and font designing systems. If the corner points are identified properly, a shape can be represented in an efficient and compact way with sufficient accuracy. Corner detection schemes, based on their applications, can be broadly divided into two categories: binary (suitable for binary images) and gray level (suitable for gray level images). Corner detection approaches for binary images usually involve segmenting the image into regions and extracting boundaries from those regions that contain them. The techniques for gray level images can be categorized into two classes: (a) Template based and (b) gradient based. The template based techniques utilize correlation between a sub-image and a template of a given angle. A corner point is selected by finding the maximum of the correlation output. Gradient based techniques require computing curvature of an edge that passes through a neighborhood in a gray level image. Many corner detection algorithms have been proposed in the literature which can be broadly divided into two parts. One is to detect corner points from grayscale images and other relates to boundary based corner detection. This contribution mainly deals with techniques adopted for later approach
Directory of Open Access Journals (Sweden)
Salvador Sánchez-Carrillo
2011-07-01
Full Text Available In remote sensing, traditional methodologies for image classification consider the spectral values of a pixel in different image bands. More recently, classification methods have used neighboring pixels to provide more information. In the present study, we used these more advanced techniques to discriminate between mangrove and non‑mangrove regions in the Gulf of California of northwestern Mexico. A maximum likelihood algorithm was used to obtain a spectral distance map of the vegetation signature characteristic of mangrove areas. Receiver operating characteristic (ROC curve analysis was applied to this map to improve classification. Two classification thresholds were set to determine mangrove and non-mangrove areas, and two performance statistics (sensitivity and specificity were calculated to express the uncertainty (errors of omission and commission associated with the two maps. The surface area of the mangrove category obtained by maximum likelihood classification was slightly higher than that obtained from the land cover map generated by the ROC curve, but with the difference of these areas to have a high level of accuracy in the prediction of the model. This suggests a considerable degree of uncertainty in the spectral signatures of pixels that distinguish mangrove forest from other land cover categories.
International Nuclear Information System (INIS)
Gu Ping; Huang Gang; Han Yuan
2007-01-01
Objective: To assess the diagnostic value of CEA, CA199 and CA50 for colorectal neoplasm by logistic regression and ROC curve. Methods: Serum CEA (with CLIA), CA199 (with ECLIA) and CA50 (with IRMA) levels were measured in 75 patients with colorectal cancer, 35 patients with benign colorectal disorders and 49 controls. The area under the ROC curve (AUC)s of CEA, CA199, CA50 from logistic regression results were compared. Results: In the cancer-benign disorder group, the AUC of CA50 was larger than the AUC of CA199. AUC of combined CEA, CA50 was largest: not only larger than any AUC of CEA, CA50, CA199 alone but also larger than the AUC of the combined three markers (0.875 vs 0.604). In cancer-control group, the AUC of combination of CEA, CA199 and CA50 was larger than any AUC of CEA, CA199 or CA50 alone. Both in the cancer-benign disorder group or cancer-control group, the AUC of CEA was larger than the AUC of CA199 or CA50. Conclusion: CEA is of definite value in the diagnosis of colorectal cancer. For differential diagnosis, the combination of CEA and CA50 can give more information, while the combination of three tumor markers is less helpful. As an advanced statistical method, logistic regression can improve the diagnostic sensitivity and specificity. (authors)
Twisted vector bundles on pointed nodal curves
Indian Academy of Sciences (India)
Abstract. Motivated by the quest for a good compactification of the moduli space of -bundles on a nodal curve we establish a striking relationship between Abramovich's and Vistoli's twisted bundles and Gieseker vector bundles.
Twisted Vector Bundles on Pointed Nodal Curves
Indian Academy of Sciences (India)
Abstract. Motivated by the quest for a good compactification of the moduli space of -bundles on a nodal curve we establish a striking relationship between Abramovich's and Vistoli's twisted bundles and Gieseker vector bundles.
Abbey, Craig K; Gallas, Brandon D; Boone, John M; Niklason, Loren T; Hadjiiski, Lubomir M; Sahiner, Berkman; Samuelson, Frank W
2014-01-01
Rationale and Objectives Our objective is to determine whether expected utility (EU) and the area under the ROC (AUC) are consistent with one another as endpoints of observer performance studies in mammography. These two measures characterize ROC performance somewhat differently. We compare these two study endpoints at the level of individual reader effects, statistical inference, and components of variance across readers and cases. Materials and Methods We reanalyze three previously published laboratory observer performance studies that investigate various x-ray breast imaging modalities using EU and AUC. The EU measure is based on recent estimates of relative utility for screening mammography. Results The AUC and EU measures are correlated across readers for individual modalities (r = 0.93) and differences in modalities (r = 0.94 to 0.98). Statistical inference for modality effects based on multi-reader multi-case analysis is very similar, with significant results (p < 0.05) in exactly the same conditions. Power analyses show mixed results across studies, with a small increase in power on average for EU that corresponds to approximately a 7% reduction in the number of readers. Despite a large number of crossing ROC curves (59% of readers), modality effects only rarely have opposite signs for EU and AUC (6%). Conclusions We do not find any evidence of systematic differences between EU and AUC in screening mammography observer studies. Thus, when utility approaches are viable (i.e. an appropriate value of relative utility exists), practical effects such as statistical efficiency may be used to choose study endpoints. PMID:24594418
Distance of Sample Measurement Points to Prototype Catalog Curve
DEFF Research Database (Denmark)
Hjorth, Poul G.; Karamehmedovic, Mirza; Perram, John
2006-01-01
We discuss strategies for comparing discrete data points to a catalog (reference) curve by means of the Euclidean distance from each point to the curve in a pump's head H vs. flow Qdiagram. In particular we find that a method currently in use is inaccurate. We propose several alternatives that ar...
Using BIRADS categories in ROC experiments
Kallergi, Maria; Hersh, Marla R.; Thomas, Jerry A.
2002-04-01
This paper investigated the use of the Breast Imaging Reporting And Data System (BIRADS) Lexicon in ROC mammography experiments. Analysis was based on data from parallel ROC experiments performed at two Institutions with different readers and databases to compare film to digitized mammography. Seven readers participated in the studies and read approximately 200 cases each in two formats: film and digital or softcopy. Reporting was done using BIRADS categories 1 through 5. Training was done with a separate set of cases and included detailed review of the relationship between BIRADS and a standard ROC discrete 5-point rating scale. The results from both sites showed equivalency between film and softcopy mammography. Decisions using the BIRADS categories showed no unsampled ROC regions and no degenerate data. Fits yielded smooth ROC curves that correlated to clinical practice. In a qualitative evaluation, all observers indicated preference in using the BIRADS classes instead of a discrete or continuous rating scheme. Familiarity with the rating process seems to relieve some of the bias associated with the interpretation of digitized mammograms from computer monitors (softcopy reading). Our results suggested that BIRADS categories can be used in comparative ROC studies because they represent a scale familiar to the reader that can be followed consistently and they provide a rating approach that accounts for both positive and negative cases to be evaluated and categorized.
Constructing "proper" ROCs from ordinal response data using weighted power functions.
Mossman, Douglas; Peng, Hongying
2014-05-01
Receiver operating characteristic (ROC) analysis is the standard method for describing the accuracy of diagnostic systems where the decision task involves distinguishing between 2 mutually exclusive possibilities. The popular binormal curve-fitting model usually produces ROCs that are improper in that they do not have the ever-decreasing slope required by signal detection theory. Not infrequently, binormal ROCs have visible hooks that falsely imply worse-than-chance diagnostic differentiation where the curve lies below the no-information diagonal. In this article, we present and evaluate a 2-parameter, weighted power function (WPF) model that always results in a proper ROC curve with a positive, monotonically decreasing slope. We used a computer simulation study to compare results from binormal and WPF models. The WPF model produces ROC curves that are less biased and closer to the true values than are curves obtained using the binormal model. The better performance of the WPF model follows from its design constraint as a necessarily proper ROC. The WPF model fits a broader variety of data sets than previously published power function models while maintaining straightforward relationships among the original decision variable, specific operating points, ROC curve contours, and model parameters. Compared with other proper ROC models, the WPF model is distinctive in its simplicity, and it avoids the flaws of the conventional binormal ROC model.
PLOTTAB, Curve and Point Plotting with Error Bars
International Nuclear Information System (INIS)
1999-01-01
1 - Description of program or function: PLOTTAB is designed to plot any combination of continuous curves and/or discrete points (with associated error bars) using user supplied titles and X and Y axis labels and units. If curves are plotted, the first curve may be used as a standard; the data and the ratio of the data to the standard will be plotted. 2 - Method of solution: PLOTTAB: The program has no idea of what data is being plotted and yet by supplying titles, X and Y axis labels and units the user can produce any number of plots with each plot containing almost any combination of curves and points with each plot properly identified. In order to define a continuous curve between tabulated points, this program must know how to interpolate between points. By input the user may specify either the default option of linear x versus linear y interpolation or alternatively log x and/or log Y interpolation. In all cases, regardless of the interpolation specified, the program will always interpolate the data to the plane of the plot (linear or log x and y plane) in order to present the true variation of the data between tabulated points, based on the user specified interpolation law. Tabulated points should be tabulated at a sufficient number of x values to insure that the difference between the specified interpolation and the 'true' variation of a curve between tabulated values is relatively small. 3 - Restrictions on the complexity of the problem: A combination of up to 30 curves and sets of discrete points may appear on each plot. If the user wishes to use this program to compare different sets of data, all of the data must be in the same units
International Nuclear Information System (INIS)
Kong, Eun Jung; Cho, Ihn Ho; Chun, Kyung Ah; Won, Kyu Chang; Lee, Hyung Woo; Choi, Jun Heok; Shin, Duk Seop
2007-01-01
We evaluated the standard uptake value (SUV) of F-18 FDG at PET/CT for differentiation of benign from malignant tumor in primary musculoskeletal tumors. Forty-six tumors (11 benign and 12 malignant soft tissue tumors, 9 benign and 14 malignant bone tumors) were examined with F-18 FDG PET/CT (Discovery ST, GE) prior to tissue diagnosis. The maxSUV(maximum value of SUV) were calculated and compared between benign and malignant lesions. The lesion analysis was based on the transverse whole body image. The maxSUV with cutoff of 4.1 was used in distinguishing benign from malignant soft tissue tumor and 3.05 was used in bone tumor by ROC curve. There was a statistically significant difference in maxSUV between benign (n = 11; maxSUV 3.4 ± 3.2) and malignant (n = 12; maxSUV 14.8 ± 12.2) lesion in soft tissue tumor (ρ = 0.001). Between benign bone tumor (n = 9; maxSUV 5.4 ± 4.0) and malignant bone tumor (n = 14; maxSUV 7.3 ± 3.2), there was not a significant difference in maxSUV. The sensitivity and specificity for differentiating malignant from benign soft tissue tumor was 83% and 91%, respectively. There were four false positive malignant bone tumor cases to include fibrous dysplasia, Langerhans-cell histiocytosis (n = 2) and osteoid osteoma. Also, one false positive case of malignant soft tissue tumor was nodular fasciitis. The maxSUV was useful for differentiation of benign from malignant lesion in primary soft tissue tumors. In bone tumor, the low maxSUV correlated well with benign lesions but high maxSUV did not always mean malignancy
Distribution of some sequences of points on elliptic curves
DEFF Research Database (Denmark)
Lange, Tanja; Shparlinski, Igor
2007-01-01
We estimate character sums over points on elliptic curves over a finite field of q elements. Pseudorandom sequences can be constructed by taking linear combinations with small coefficients (for example, from the set {−1, 0, 1}) of a fixed vector of points, which forms the seed of the generator. We...
Feature curve extraction from point clouds via developable strip intersection
Directory of Open Access Journals (Sweden)
Kai Wah Lee
2016-04-01
Full Text Available In this paper, we study the problem of computing smooth feature curves from CAD type point clouds models. The proposed method reconstructs feature curves from the intersections of developable strip pairs which approximate the regions along both sides of the features. The generation of developable surfaces is based on a linear approximation of the given point cloud through a variational shape approximation approach. A line segment sequencing algorithm is proposed for collecting feature line segments into different feature sequences as well as sequential groups of data points. A developable surface approximation procedure is employed to refine incident approximation planes of data points into developable strips. Some experimental results are included to demonstrate the performance of the proposed method.
Directory of Open Access Journals (Sweden)
José Kawazoe Lazzoli
2002-04-01
ível de segmento S-T em cinco ou mais derivações e presença de transição precordial rápida. DISCUSSÃO E CONCLUSÃO: O desempenho dos critérios eletrocardiográficos em termos de VPP, VPN e AC foi muito limitado, com a exceção da duração do intervalo R-R. A combinação de outros critérios como amplitude da onda T em V5 e V6, amplitude da onda R em V4 e presença de supradesnível de ponto J e do segmento S-T em várias derivações pode auxiliar na predição de vagotonia.OBJECTIVE: To determine sensitivity (Sens, specificity (Spec, positive (PPV and negative (NPV predictive value, and accuracy of different electrocardiographic criteria for vagotonia. METHODS: Seventy-four Olympic athletes (51 male and 23 female; age = 24 ± 5 years underwent an evaluation consisting of a 12-lead resting electrocardiogram (ECG, and an assessment of cardiac vagal tone (CVT by the 4-second cycling exercise testing (4-sET, with the B/C index utilized as the gold standard. The 4-sET is a well-standardized and valid protocol for CVT assessment based on the mechanism of exercise-onset tachycardia regardless of the sympathetic component. Using ROC (receiver operating characteristic curves, the authors selected the cut-point with the best sensitivity (Sens/specificity (Spec ratio for each ECG variable, and calculated the positive (PPV and negative predictive values (NPV, and accuracy (AC. The authors also correlated B/C index with ECG variables. RESULTS: B/C index showed a poor association with ECG variables, with the exception of R-R interval (r = 0.353; P = 0.004, that also presented a significant ROC curve (chi2= 0.863; P = 0.002, whereas the R-R interval > or = 990 ms criterion showed the following results: Sens - 100%; Spec - 73%; VPP 20%; VPN 100%; AC 75%. The ECG variables that presented cut-points with accuracy > 80% were: T-wave amplitude in lead V5 > or = 8.0 mm; T-wave amplitude in lead V6 > or = 7.0 mm; Q-wave amplitude in V5 > or = 7.0 mm; R-wave amplitude in V4 > or
Rational points, rational curves, and entire holomorphic curves on projective varieties
Gasbarri, Carlo; Roth, Mike; Tschinkel, Yuri
2015-01-01
This volume contains papers from the Short Thematic Program on Rational Points, Rational Curves, and Entire Holomorphic Curves and Algebraic Varieties, held from June 3-28, 2013, at the Centre de Recherches Mathématiques, Université de Montréal, Québec, Canada. The program was dedicated to the study of subtle interconnections between geometric and arithmetic properties of higher-dimensional algebraic varieties. The main areas of the program were, among others, proving density of rational points in Zariski or analytic topology on special varieties, understanding global geometric properties of rationally connected varieties, as well as connections between geometry and algebraic dynamics exploring new geometric techniques in Diophantine approximation.
Point splitting in a curved space-time background
International Nuclear Information System (INIS)
Liggatt, P.A.J.; Macfarlane, A.J.
1979-01-01
A prescription is given for point splitting in a curved space-time background which is a natural generalization of that familiar in quantum electrodynamics and Yang-Mills theory. It is applied (to establish its validity) to the verification of the gravitational anomaly in the divergence of a fermion axial current. Notable features of the prescription are that it defines a point-split current that can be differentiated straightforwardly, and that it involves a natural way of averaging (four-dimensionally) over the directions of point splitting. The method can extend directly from the spin-1/2 fermion case treated to other cases, e.g., to spin-3/2 Rarita-Schwinger fermions. (author)
Growth Curve Analysis and Change-Points Detection in Extremes
Meng, Rui
2016-05-15
The thesis consists of two coherent projects. The first project presents the results of evaluating salinity tolerance in barley using growth curve analysis where different growth trajectories are observed within barley families. The study of salinity tolerance in plants is crucial to understanding plant growth and productivity. Because fully-automated smarthouses with conveyor systems allow non-destructive and high-throughput phenotyping of large number of plants, it is now possible to apply advanced statistical tools to analyze daily measurements and to study salinity tolerance. To compare different growth patterns of barley variates, we use functional data analysis techniques to analyze the daily projected shoot areas. In particular, we apply the curve registration method to align all the curves from the same barley family in order to summarize the family-wise features. We also illustrate how to use statistical modeling to account for spatial variation in microclimate in smarthouses and for temporal variation across runs, which is crucial for identifying traits of the barley variates. In our analysis, we show that the concentrations of sodium and potassium in leaves are negatively correlated, and their interactions are associated with the degree of salinity tolerance. The second project studies change-points detection methods in extremes when multiple time series data are available. Motived by the scientific question of whether the chances to experience extreme weather are different in different seasons of a year, we develop a change-points detection model to study changes in extremes or in the tail of a distribution. Most of existing models identify seasons from multiple yearly time series assuming a season or a change-point location remains exactly the same across years. In this work, we propose a random effect model that allows the change-point to vary from year to year, following a given distribution. Both parametric and nonparametric methods are developed
The Motion of Point Particles in Curved Spacetime
Directory of Open Access Journals (Sweden)
Eric Poisson
2011-09-01
Full Text Available This review is concerned with the motion of a point scalar charge, a point electric charge, and a point mass in a specified background spacetime. In each of the three cases the particle produces a field that behaves as outgoing radiation in the wave zone, and therefore removes energy from the particle. In the near zone the field acts on the particle and gives rise to a self-force that prevents the particle from moving on a geodesic of the background spacetime. The self-force contains both conservative and dissipative terms, and the latter are responsible for the radiation reaction. The work done by the self-force matches the energy radiated away by the particle. The field's action on the particle is difficult to calculate because of its singular nature: the field diverges at the position of the particle. But it is possible to isolate the field's singular part and show that it exerts no force on the particle -- its only effect is to contribute to the particle's inertia. What remains after subtraction is a regular field that is fully responsible for the self-force. Because this field satisfies a homogeneous wave equation, it can be thought of as a free field that interacts with the particle; it is this interaction that gives rise to the self-force. The mathematical tools required to derive the equations of motion of a point scalar charge, a point electric charge, and a point mass in a specified background spacetime are developed here from scratch. The review begins with a discussion of the basic theory of bitensors (Part I. It then applies the theory to the construction of convenient coordinate systems to chart a neighbourhood of the particle's word line (Part II. It continues with a thorough discussion of Green's functions in curved spacetime (Part III. The review presents a detailed derivation of each of the three equations of motion (Part IV. Because the notion of a point mass is problematic in general relativity, the review concludes (Part V
Applications of ROC analysis in diagnostic image evaluation
International Nuclear Information System (INIS)
Metz, C.E.
1979-01-01
The need for Receiver Operating Characteristic (ROC) analysis is indicated by a discussion of the limitations of accuracy and of sensitivity and specificity as indices of diagnostic detection or discrmination performance. The concept of a variable decision threshold is shown to lead in a natural way to the ROC curve as a means for specifying diagnostic performance. Practical techniques for measuring ROC curves are described, and directions for possible generalizations of conventional ROC analysis are indicated
The rotation curve of a point particle in stringy gravity
Energy Technology Data Exchange (ETDEWEB)
Ko, Sung Moon; Park, Jeong-Hyuck; Suh, Minwoo, E-mail: sinsmk2003@sogang.ac.kr, E-mail: park@sogang.ac.kr, E-mail: minsuh@usc.edu [Department of Physics, Sogang University, 35 Baekbeom-ro, Mapo-gu, Seoul, 04107 (Korea, Republic of)
2017-06-01
Double Field Theory suggests to view the whole massless sector of closed strings as the gravitational unity. The fundamental symmetries therein, including the O( D , D ) covariance, can determine unambiguously how the Standard Model as well as a relativistic point particle should couple to the closed string massless sector. The theory also refines the notion of singularity. We consider the most general, spherically symmetric, asymptotically flat, static vacuum solution to D =4 Double Field Theory, which contains three free parameters and consequently generalizes the Schwarzschild geometry. Analyzing the circular geodesic of a point particle in string frame, we obtain the orbital velocity as a function of R /( M {sub ∞} G ) which is the dimensionless radial variable normalized by mass. The rotation curve generically features a maximum and thus non-Keplerian over a finite range, while becoming asymptotically Keplerian at infinity, R /( M {sub ∞} G )→ ∞. The adoption of the string frame rather than Einstein frame is the consequence of the fundamental symmetry principle. Our result opens up a new scheme to solve the dark matter/energy problems by modifying General Relativity at 'short' range of R /( M {sub ∞} G ).
On group orders of retional points of elliptic curves | Weng ...
African Journals Online (AJOL)
We consider elliptic curves without complex multiplication defined over the rationals or with complex multiplication defined over the Hilbert class field of the endomorphism ring. We examine the distribution of almost prime group orders of these curves when reduced modulo a prime ideal. Mathematics Subject Classification ...
Current-voltage curves of gold quantum point contacts revisited
DEFF Research Database (Denmark)
Hansen, K.; Nielsen, S K.; Brandbyge, Mads
2000-01-01
clean ultra-high-vacuum conditions at room temperature. The I - V curves are found to he almost linear in contrast to previous reports. Tight-binding calculations of I - V curves for one- and two-atom contacts are in excellent agreement with our measurements. On the other hand, clearly nonlinear I - V...
Matsumoto, Toru; Fukuda, Nobuo; Furukawa, Akira; Suwa, Koji; Wada, Shinichi; Matsumoto, Mitsuomi; Sone, Shusuke
2006-03-01
When physicians inspect an image, they make up a certain degree of confidence that the image are abnormal; p(t), or normal; n(t)[n(t)=1-p(t)]. After infinite time of the inspection, they reach the equilibrium levels of the confidence of p*=p(∞) and n*=n(∞). There are psychological conflicts between the decisions of normal and abnormal. We assume that the decision of "normal" is distracted by the decision of "abnormal" by a factor of k(1 + ap), and in an inverse direction by a factor of k(1 + bn), where k ( > 0) is a parameter that relates with image quality and skill of the physicians, and a and b are unknown constants. After the infinite time of inspection, the conflict reaches the equilibrium, which satisfies the equation, k(1 + ap*)n* = k(1 + bn*)p*. Here we define a parameter C, which is 2p*/[p*(1 - p*)]. After the infinite time of inspection, the conflict reaches the equilibrium, which satisfies t that changes in the confidence level with the time (dp/dt) is proportional to [k(1+ap)n - k(1+bn)p], i.e. k[-cp2 + (c - 2)p + 1]. Solving the differential equation, we derived the equation; t(p) and p(t) depending with the parameters; k, c, S. S (0-1) is the value arbitrary selected and related with probability of "abnormal" before the image inspection (S = p(0)). Image reading studies were executed for CT images. ROC curves were generated both by the traditional 4-step score-based method and by the confidence level; p estimated from the equation t(p) of the DDC model using observed judgment time. It was concluded that ROC curves could be generated by measuring time for dichotomous judgment without the subjective scores of diagnostic confidence and applying the DDC model.
Degree of a isolated real point or a singular complex point on a plane curve defined over Q
DEFF Research Database (Denmark)
Hansen, Johan Peder
2010-01-01
Let $X$ be a curve in the affine plane defined by a reduced polynomial of degree $d$ with rational coefficients. Assume that $P$ is an isolated real point or a singular complex point on the curve $X$. The coordinates of $P$ are algebraic numbers over the rationals of degree at most $d^2$. The res......Let $X$ be a curve in the affine plane defined by a reduced polynomial of degree $d$ with rational coefficients. Assume that $P$ is an isolated real point or a singular complex point on the curve $X$. The coordinates of $P$ are algebraic numbers over the rationals of degree at most $d^2...
Critical points in logistic growth curves and treatment comparisons
Directory of Open Access Journals (Sweden)
José Raimundo de Souza Passos
2012-10-01
Full Text Available Several biological phenomena have a behavior over time mathematically characterized by a strong increasing function in the early stages of development, then by a less pronounced growth, sometimes showing stability. The separation between these phases is very important to the researcher, since the maintenance of a less productive phase results in uneconomical activity. In this report we present methods of determining critical points in logistic functions that separate the early stages of growth from the asymptotic phase, with the aim of establishing a stopping critical point in the growth and on this basis determine differences in treatments. The logistic growth model is fitted to experimental data of imbibition of araribá seeds (Centrolobium tomentosum. To determine stopping critical points the following methods were used: i accelerating growth function, ii tangent at the inflection point, iii segmented regression; iv modified segmented regression; v non-significant difference; and vi non-significant difference by simulation. The analysis of variance of the abscissas and ordinates of the breakpoints was performed with the objective of comparing treatments and methods used to determine the critical points. The methods of segmented regression and of the tangent at the inflection point lead to early stopping points, in comparison with other methods, with proportions ordinate/asymptote lower than 0.90. The non-significant difference method by simulation had higher values of abscissas for stopping point, with an average proportion ordinate/asymptote equal to 0.986. An intermediate proportion of 0.908 was observed for the acceleration function method.
Directory of Open Access Journals (Sweden)
Miriam Raquel Diniz Zanetti
Full Text Available CONTEXT AND OBJECTIVE: Several risk factors are involved in perineal lacerations during vaginal delivery. However, little is known about the influence of perineal distensibility as a protective factor. The aim here was to determine a cutoff value for pelvic floor distensibility measured using the Epi-no balloon, which could be used as a predictive factor for perineal integrity in vaginal delivery. DESIGN AND SETTING: Prospective observational single cohort study conducted in a maternity hospital. METHODS: A convenience sample of 227 consecutive at-term parturients was used. All women had a single fetus in the vertex presentation, with up to 9.0 cm of dilation. The maximum dilation of the Epi-no balloon was measured using a tape measure after it had been inflated inside the vagina up to the parturients' maximum tolerance. The receiver operating characteristic (ROC curve was used to obtain the Epi-no circumference measurement with best sensitivity and specificity. RESULTS: Among the 161 patients who were included in the study, 50.9% underwent episiotomy, 21.8% presented lacerations and 27.3% retained an intact perineum. Age > 25.9 years; number of pregnancies > 3.4; number of deliveries > 2.2 and circumference measured by Epi-no > 21.4 cm were all directly correlated with an intact perineum. Circumference measurements using the Epi-no balloon that were greater than 20.8 cm showed sensitivity and specificity of 70.5% and 66.7% (area under curve = 0.713, respectively, as a predictive factor for an intact perineum in vaginal delivery. CONCLUSION: Circumferences greater than 20.8 cm achieved using the Epi-no balloon are a predictive factor for perineal integrity in parturients.
Variable Selection in ROC Regression
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Binhuan Wang
2013-01-01
Full Text Available Regression models are introduced into the receiver operating characteristic (ROC analysis to accommodate effects of covariates, such as genes. If many covariates are available, the variable selection issue arises. The traditional induced methodology separately models outcomes of diseased and nondiseased groups; thus, separate application of variable selections to two models will bring barriers in interpretation, due to differences in selected models. Furthermore, in the ROC regression, the accuracy of area under the curve (AUC should be the focus instead of aiming at the consistency of model selection or the good prediction performance. In this paper, we obtain one single objective function with the group SCAD to select grouped variables, which adapts to popular criteria of model selection, and propose a two-stage framework to apply the focused information criterion (FIC. Some asymptotic properties of the proposed methods are derived. Simulation studies show that the grouped variable selection is superior to separate model selections. Furthermore, the FIC improves the accuracy of the estimated AUC compared with other criteria.
Migración M.O.S.S. 2007 a SharePoint 2010 de Hospital Universitario Virgen del Rocío
Castro Palomo, Esteban
2013-01-01
En el presente trabajo se ha descrito el análisis y diseño que motiva el proyecto de migración de Microsoft SharePoint Server 2007 a la versión SharePoint Server 2010 que desarrolla la intranet de uno de los mayores complejos hospitalarios de nuestro país. En el present treball s'ha descrit l'anàlisi i disseny que motiva el projecte de migració de Microsoft SharePoint Server 2007 a la versió SharePoint Server 2010 que desenvolupa la intranet d'un dels majors complexos hospitalaris del nost...
Feature Extraction from 3D Point Cloud Data Based on Discrete Curves
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Yi An
2013-01-01
Full Text Available Reliable feature extraction from 3D point cloud data is an important problem in many application domains, such as reverse engineering, object recognition, industrial inspection, and autonomous navigation. In this paper, a novel method is proposed for extracting the geometric features from 3D point cloud data based on discrete curves. We extract the discrete curves from 3D point cloud data and research the behaviors of chord lengths, angle variations, and principal curvatures at the geometric features in the discrete curves. Then, the corresponding similarity indicators are defined. Based on the similarity indicators, the geometric features can be extracted from the discrete curves, which are also the geometric features of 3D point cloud data. The threshold values of the similarity indicators are taken from [0,1], which characterize the relative relationship and make the threshold setting easier and more reasonable. The experimental results demonstrate that the proposed method is efficient and reliable.
Elliptic Curve Integral Points on y2 = x3 + 3x ‑ 14
Zhao, Jianhong
2018-03-01
The positive integer points and integral points of elliptic curves are very important in the theory of number and arithmetic algebra, it has a wide range of applications in cryptography and other fields. There are some results of positive integer points of elliptic curve y 2 = x 3 + ax + b, a, b ∈ Z In 1987, D. Zagier submit the question of the integer points on y 2 = x 3 ‑ 27x + 62, it count a great deal to the study of the arithmetic properties of elliptic curves. In 2009, Zhu H L and Chen J H solved the problem of the integer points on y 2 = x 3 ‑ 27x + 62 by using algebraic number theory and P-adic analysis method. In 2010, By using the elementary method, Wu H M obtain all the integral points of elliptic curves y 2 = x 3 ‑ 27x ‑ 62. In 2015, Li Y Z and Cui B J solved the problem of the integer points on y 2 = x 3 ‑ 21x ‑ 90 By using the elementary method. In 2016, Guo J solved the problem of the integer points on y 2 = x 3 + 27x + 62 by using the elementary method. In 2017, Guo J proved that y 2 = x 3 ‑ 21x + 90 has no integer points by using the elementary method. Up to now, there is no relevant conclusions on the integral points of elliptic curves y 2 = x 3 + 3x ‑ 14, which is the subject of this paper. By using congruence and Legendre Symbol, it can be proved that elliptic curve y 2 = x 3 + 3x ‑ 14 has only one integer point: (x, y) = (2, 0).
IMAGE-PLANE ANALYSIS OF n-POINT-MASS LENS CRITICAL CURVES AND CAUSTICS
International Nuclear Information System (INIS)
Danek, Kamil; Heyrovský, David
2015-01-01
The interpretation of gravitational microlensing events caused by planetary systems or multiple stars is based on the n-point-mass lens model. The first planets detected by microlensing were well described by the two-point-mass model of a star with one planet. By the end of 2014, four events involving three-point-mass lenses had been announced. Two of the lenses were stars with two planetary companions each; two were binary stars with a planet orbiting one component. While the two-point-mass model is well understood, the same cannot be said for lenses with three or more components. Even the range of possible critical-curve topologies and caustic geometries of the three-point-mass lens remains unknown. In this paper we provide new tools for mapping the critical-curve topology and caustic cusp number in the parameter space of n-point-mass lenses. We perform our analysis in the image plane of the lens. We show that all contours of the Jacobian are critical curves of re-scaled versions of the lens configuration. Utilizing this property further, we introduce the cusp curve to identify cusp-image positions on all contours simultaneously. In order to track cusp-number changes in caustic metamorphoses, we define the morph curve, which pinpoints the positions of metamorphosis-point images along the cusp curve. We demonstrate the usage of both curves on simple two- and three-point-mass lens examples. For the three simplest caustic metamorphoses we illustrate the local structure of the image and source planes
Learning vector quantization classifiers for ROC-optimization
Villmann, T.; Kaden, M.; Hermann, W.; Biehl, M.
2016-01-01
This paper proposes a variant of the generalized learning vector quantizer (GLVQ) optimizing explicitly the area under the receiver operating characteristics (ROC) curve for binary classification problems instead of the classification accuracy, which is frequently not appropriate for classifier
Collisions in Fast Generation of Ideal Classes and Points on Hyperelliptic and Elliptic Curves
DEFF Research Database (Denmark)
Lange, Tanja; Shparlinski, Igor
2005-01-01
Koblitz curves have been proposed to quickly generate random ideal classes and points on hyperelliptic and elliptic curves. To obtain a further speed-up a different way of generating these random elements has recently been proposed. In this paper we give an upper bound on the number of collisions...... for this alternative approach. For elliptic Koblitz curves we additionally use the same methods to derive a bound for a modified algorithm. These bounds are tight for cyclic subgroups of prime order, which is the case of most practical interest for cryptography....
Overestimation of test performance by ROC analysis: Effect of small sample size
International Nuclear Information System (INIS)
Seeley, G.W.; Borgstrom, M.C.; Patton, D.D.; Myers, K.J.; Barrett, H.H.
1984-01-01
New imaging systems are often observer-rated by ROC techniques. For practical reasons the number of different images, or sample size (SS), is kept small. Any systematic bias due to small SS would bias system evaluation. The authors set about to determine whether the area under the ROC curve (AUC) would be systematically biased by small SS. Monte Carlo techniques were used to simulate observer performance in distinguishing signal (SN) from noise (N) on a 6-point scale; P(SN) = P(N) = .5. Four sample sizes (15, 25, 50 and 100 each of SN and N), three ROC slopes (0.8, 1.0 and 1.25), and three intercepts (0.8, 1.0 and 1.25) were considered. In each of the 36 combinations of SS, slope and intercept, 2000 runs were simulated. Results showed a systematic bias: the observed AUC exceeded the expected AUC in every one of the 36 combinations for all sample sizes, with the smallest sample sizes having the largest bias. This suggests that evaluations of imaging systems using ROC curves based on small sample size systematically overestimate system performance. The effect is consistent but subtle (maximum 10% of AUC standard deviation), and is probably masked by the s.d. in most practical settings. Although there is a statistically significant effect (F = 33.34, P<0.0001) due to sample size, none was found for either the ROC curve slope or intercept. Overestimation of test performance by small SS seems to be an inherent characteristic of the ROC technique that has not previously been described
Tautological rings of spaces of pointed genus two curves of compact type
DEFF Research Database (Denmark)
Petersen, Dan Erik
2016-01-01
We prove that the tautological ring of , the moduli space of -pointed genus two curves of compact type, does not have Poincaré duality for any. This result is obtained via a more general study of the cohomology groups of. We explain how the cohomology can be decomposed into pieces corresponding t...
Integration Over Curves and Surfaces Defined by the Closest Point Mapping
2015-04-01
3 Numerical simulations In this section we investigate the convergence of our numerical integration using simple Riemann sum over uniform Cartesian...be considered integration of functions defined on suitable hypercubes, periodically extended. In such settings, simple Riemann sums on Cartesian grids... Integration over curves and surfaces defined by the closest point mapping Catherine Kublik∗ and Richard Tsai† Abstract We propose a new formulation
Coenegracht, P.M.J.; Duisenberg, A.J.M.
The systematic titration error which is introduced by the intersection of tangents to hyperbolic titration curves is discussed. The effects of the apparent (conditional) formation constant, of the concentration of the unknown component and of the ranges used for the end-point construction are
Hu, Shuangwei; Lundgren, Martin; Niemi, Antti J.
2011-06-01
We develop a transfer matrix formalism to visualize the framing of discrete piecewise linear curves in three-dimensional space. Our approach is based on the concept of an intrinsically discrete curve. This enables us to more effectively describe curves that in the limit where the length of line segments vanishes approach fractal structures in lieu of continuous curves. We verify that in the case of differentiable curves the continuum limit of our discrete equation reproduces the generalized Frenet equation. In particular, we draw attention to the conceptual similarity between inflection points where the curvature vanishes and topologically stable solitons. As an application we consider folded proteins, their Hausdorff dimension is known to be fractal. We explain how to employ the orientation of Cβ carbons of amino acids along a protein backbone to introduce a preferred framing along the backbone. By analyzing the experimentally resolved fold geometries in the Protein Data Bank we observe that this Cβ framing relates intimately to the discrete Frenet framing. We also explain how inflection points (a.k.a. soliton centers) can be located in the loops and clarify their distinctive rôle in determining the loop structure of folded proteins.
Study on characteristic points of boiling curve by using wavelet analysis and genetic algorithm
International Nuclear Information System (INIS)
Wei Huiming; Su Guanghui; Qiu Suizheng; Yang Xingbo
2009-01-01
Based on the wavelet analysis theory of signal singularity detection,the critical heat flux (CHF) and minimum film boiling starting point (q min ) of boiling curves can be detected and analyzed by using the wavelet multi-resolution analysis. To predict the CHF in engineering, empirical relations were obtained based on genetic algorithm. The results of wavelet detection and genetic algorithm prediction are consistent with experimental data very well. (authors)
ROC analysis of acid demineralized artificial caries
Energy Technology Data Exchange (ETDEWEB)
Kang, Byung Cheol [Dept. of Oral and Maxillofacial Radiology, College of Dentistry, Chonnam National University, Kwangju (Korea, Republic of)
1997-08-15
This study is designed to determine the artificial incipient proximal caries lesion detectability by dentists on Ektaspeed Plus film using ROC analysis. Sixteen premolars and 30 molars, which have 52 proximal caries-like demineralized lesions using acid-gel technique were added to 20 sound premolars and 30 sound molars to make 24 plaster blocks. Each block with 4 teeth and 6 contacting proximal surfaces was placed in an optical bench to take 12 bitewing radiographs with Ektaspeed Plus film. Thirty-six dentists acted as observers to evaluated the proximal lesions using five rating scales for ROC analysis. They were also asked to determine the presence or absence of the proximal caries. The true status of the proximal caries was established by the consensus of three oral and maxillofacila radiologists. For evaluation of intra-observer agreement, 9 dentist reread the radiographs at an interval of 1 month. The Pearson correlation coefficient for the intra-observer agreement was 0.746 (good agreement). Ten observer's data set were degenerated. The mean area under ROC curve from 26 observers was 0.806 and standard deviation was 0.061. The sensitivity and the specificity of the binary response were 0.17 (SD=0.11) and 0.78 (SD=0.17) respectively. The binary response only reveal a single values of sensitivity and the specificity. The ROC analysis to assess the diagnostic accuracy in caries detection, which producing estimates of sensitivities for all specifities, yield more comprehensive measures of diagnostic performance than single values for sensitivity and specificity.
Bounds for the integral points on elliptic curves over function fields
Sedunova, Alisa
2017-01-01
In this paper we give an upper bound for the number of integral points on an elliptic curve E over F_q[T] in terms of its conductor N and q. We proceed by applying the lower bounds for the canonical height that are analogous to those given by Silverman and extend the technique developed by Helfgott-Venkatesh to express the number of integral points on E in terms of its algebraic rank. We also use the sphere packing results to optimize the size of an implied constant. In the end we use partial...
Comparison of Optimization and Two-point Methods in Estimation of Soil Water Retention Curve
Ghanbarian-Alavijeh, B.; Liaghat, A. M.; Huang, G.
2009-04-01
Soil water retention curve (SWRC) is one of the soil hydraulic properties in which its direct measurement is time consuming and expensive. Since, its measurement is unavoidable in study of environmental sciences i.e. investigation of unsaturated hydraulic conductivity and solute transport, in this study the attempt is to predict soil water retention curve from two measured points. By using Cresswell and Paydar (1996) method (two-point method) and an optimization method developed in this study on the basis of two points of SWRC, parameters of Tyler and Wheatcraft (1990) model (fractal dimension and air entry value) were estimated and then water content at different matric potentials were estimated and compared with their measured values (n=180). For each method, we used both 3 and 1500 kPa (case 1) and 33 and 1500 kPa (case 2) as two points of SWRC. The calculated RMSE values showed that in the Creswell and Paydar (1996) method, there exists no significant difference between case 1 and case 2. However, the calculated RMSE value in case 2 (2.35) was slightly less than case 1 (2.37). The results also showed that the developed optimization method in this study had significantly less RMSE values for cases 1 (1.63) and 2 (1.33) rather than Cresswell and Paydar (1996) method.
Directory of Open Access Journals (Sweden)
Lynne M Boddy
Full Text Available OBJECTIVES: 1. to investigate whether 20 m multi-stage shuttle run performance (20mSRT, an indirect measure of aerobic fitness, could discriminate between healthy and overweight status in 9-10.9 yr old schoolchildren using Receiver Operating Characteristic (ROC analysis; 2. Investigate if cardiometabolic risk differed by aerobic fitness group by applying the ROC cut point to a second, cross-sectional cohort. DESIGN: Analysis of cross-sectional data. PARTICIPANTS: 16,619 9-10.9 year old participants from SportsLinx project and 300 11-13.9 year old participants from the Welsh Schools Health and Fitness Study. OUTCOME MEASURES: SportsLinx; 20mSRT, body mass index (BMI, waist circumference, subscapular and superilliac skinfold thicknesses. Welsh Schools Health and Fitness Study; 20mSRT performance, waist circumference, and clustered cardiometabolic risk. ANALYSES: Three ROC curve analyses were completed, each using 20mSRT performance with ROC curve 1 related to BMI, curve 2 was related to waist circumference and 3 was related to skinfolds (estimated % body fat. These were repeated for both girls and boys. The mean of the three aerobic fitness thresholds was retained for analysis. The thresholds were subsequently applied to clustered cardiometabolic risk data from the Welsh Schools study to assess whether risk differed by aerobic fitness group. RESULTS: The diagnostic accuracy of the ROC generated thresholds was higher than would be expected by chance (all models AUC >0.7. The mean thresholds were 33 and 25 shuttles for boys and girls respectively. Participants classified as 'fit' had significantly lower cardiometabolic risk scores in comparison to those classed as unfit (p<0.001. CONCLUSION: The use of the ROC generated cut points by health professionals, teachers and coaches may provide the opportunity to apply population level 'risk identification and stratification' processes and plan for "at-risk" children to be referred onto intervention
International Nuclear Information System (INIS)
Claisse, A.; Després, B.; Labourasse, E.; Ledoux, F.
2012-01-01
The aim of this paper is the numerical simulation of compressible hydrodynamic strong implosions, which take place for instance in Inertial Confinement Fusion. It focuses in particular on two crucial issues, for such calculations: very low CFL number at the implosion center and approximation error on the initial geometry. Thus, we propose an exceptional points method, which is translation invariant and suitable to curved meshes. This method is designed for cell-centered Lagrangian schemes (GLACE, EUCCLHYD). Several numerical examples on significant test cases are presented to show the relevance of our approach.
Spline Trajectory Algorithm Development: Bezier Curve Control Point Generation for UAVs
Howell, Lauren R.; Allen, B. Danette
2016-01-01
A greater need for sophisticated autonomous piloting systems has risen in direct correlation with the ubiquity of Unmanned Aerial Vehicle (UAV) technology. Whether surveying unknown or unexplored areas of the world, collecting scientific data from regions in which humans are typically incapable of entering, locating lost or wanted persons, or delivering emergency supplies, an unmanned vehicle moving in close proximity to people and other vehicles, should fly smoothly and predictably. The mathematical application of spline interpolation can play an important role in autopilots' on-board trajectory planning. Spline interpolation allows for the connection of Three-Dimensional Euclidean Space coordinates through a continuous set of smooth curves. This paper explores the motivation, application, and methodology used to compute the spline control points, which shape the curves in such a way that the autopilot trajectory is able to meet vehicle-dynamics limitations. The spline algorithms developed used to generate these curves supply autopilots with the information necessary to compute vehicle paths through a set of coordinate waypoints.
Computing fixed points of nonexpansive mappings by $\\alpha$-dense curves
Directory of Open Access Journals (Sweden)
G. García
2017-08-01
Full Text Available Given a multivalued nonexpansive mapping defined on a convex and compact set of a Banach space, with values in the class of convex and compact subsets of its domain, we present an iteration scheme which (under suitable conditions converges to a fixed point of such mapping. This new iteration provides us another method to approximate the fixed points of a singlevalued nonexpansive mapping, defined on a compact and convex set into itself. Moreover, the conditions for the singlevalued case are less restrictive than for the multivalued case. Our main tool will be the so called $\\alpha$-dense curves, which will allow us to construct such iterations. Some numerical examples are provided to illustrate our results.
Solving eigenvalue problems on curved surfaces using the Closest Point Method
Macdonald, Colin B.
2011-06-01
Eigenvalue problems are fundamental to mathematics and science. We present a simple algorithm for determining eigenvalues and eigenfunctions of the Laplace-Beltrami operator on rather general curved surfaces. Our algorithm, which is based on the Closest Point Method, relies on an embedding of the surface in a higher-dimensional space, where standard Cartesian finite difference and interpolation schemes can be easily applied. We show that there is a one-to-one correspondence between a problem defined in the embedding space and the original surface problem. For open surfaces, we present a simple way to impose Dirichlet and Neumann boundary conditions while maintaining second-order accuracy. Convergence studies and a series of examples demonstrate the effectiveness and generality of our approach. © 2011 Elsevier Inc.
Etingof, P.; Henriques, A.G.; Kamnitzer, J.; Rains, E.M.
2010-01-01
We compute the Poincaré polynomial and the cohomology algebra with rational coefficients of the manifold Mn of real points of the moduli space of algebraic curves of genus 0 with n labeled points. This cohomology is a quadratic algebra, and we conjecture that it is Koszul. We also compute the
Self-organizing adaptive map: autonomous learning of curves and surfaces from point samples.
Piastra, Marco
2013-05-01
Competitive Hebbian Learning (CHL) (Martinetz, 1993) is a simple and elegant method for estimating the topology of a manifold from point samples. The method has been adopted in a number of self-organizing networks described in the literature and has given rise to related studies in the fields of geometry and computational topology. Recent results from these fields have shown that a faithful reconstruction can be obtained using the CHL method only for curves and surfaces. Within these limitations, these findings constitute a basis for defining a CHL-based, growing self-organizing network that produces a faithful reconstruction of an input manifold. The SOAM (Self-Organizing Adaptive Map) algorithm adapts its local structure autonomously in such a way that it can match the features of the manifold being learned. The adaptation process is driven by the defects arising when the network structure is inadequate, which cause a growth in the density of units. Regions of the network undergo a phase transition and change their behavior whenever a simple, local condition of topological regularity is met. The phase transition is eventually completed across the entire structure and the adaptation process terminates. In specific conditions, the structure thus obtained is homeomorphic to the input manifold. During the adaptation process, the network also has the capability to focus on the acquisition of input point samples in critical regions, with a substantial increase in efficiency. The behavior of the network has been assessed experimentally with typical data sets for surface reconstruction, including suboptimal conditions, e.g. with undersampling and noise. Copyright © 2012 Elsevier Ltd. All rights reserved.
Rostami, Kamran; Marsh, Michael N; Johnson, Matt W; Mohaghegh, Hamid; Heal, Calvin; Holmes, Geoffrey; Ensari, Arzu; Aldulaimi, David; Bancel, Brigitte; Bassotti, Gabrio; Bateman, Adrian; Becheanu, Gabriel; Bozzola, Anna; Carroccio, Antonio; Catassi, Carlo; Ciacci, Carolina; Ciobanu, Alexandra; Danciu, Mihai; Derakhshan, Mohammad H; Elli, Luca; Ferrero, Stefano; Fiorentino, Michelangelo; Fiorino, Marilena; Ganji, Azita; Ghaffarzadehgan, Kamran; Going, James J; Ishaq, Sauid; Mandolesi, Alessandra; Mathews, Sherly; Maxim, Roxana; Mulder, Chris J; Neefjes-Borst, Andra; Robert, Marie; Russo, Ilaria; Rostami-Nejad, Mohammad; Sidoni, Angelo; Sotoudeh, Masoud; Villanacci, Vincenzo; Volta, Umberto; Zali, Mohammad R; Srivastava, Amitabh
2017-01-01
Objectives Counting intraepithelial lymphocytes (IEL) is central to the histological diagnosis of coeliac disease (CD), but no definitive ‘normal’ IEL range has ever been published. In this multicentre study, receiver operating characteristic (ROC) curve analysis was used to determine the optimal cut-off between normal and CD (Marsh III lesion) duodenal mucosa, based on IEL counts on >400 mucosal biopsy specimens. Design The study was designed at the International Meeting on Digestive Pathology, Bucharest 2015. Investigators from 19 centres, eight countries of three continents, recruited 198 patients with Marsh III histology and 203 controls and used one agreed protocol to count IEL/100 enterocytes in well-oriented duodenal biopsies. Demographic and serological data were also collected. Results The mean ages of CD and control groups were 45.5 (neonate to 82) and 38.3 (2–88) years. Mean IEL count was 54±18/100 enterocytes in CD and 13±8 in normal controls (p=0.0001). ROC analysis indicated an optimal cut-off point of 25 IEL/100 enterocytes, with 99% sensitivity, 92% specificity and 99.5% area under the curve. Other cut-offs between 20 and 40 IEL were less discriminatory. Additionally, there was a sufficiently high number of biopsies to explore IEL counts across the subclassification of the Marsh III lesion. Conclusion Our ROC curve analyses demonstrate that for Marsh III lesions, a cut-off of 25 IEL/100 enterocytes optimises discrimination between normal control and CD biopsies. No differences in IEL counts were found between Marsh III a, b and c lesions. There was an indication of a continuously graded dose–response by IEL to environmental (gluten) antigenic influence. PMID:28893865
International Nuclear Information System (INIS)
Metz, C.E.; Starr, S.J.; Lusted, L.B.
1976-01-01
An ROC curve provides an empirical description of the trade-offs which are possible among the various types of correct and incorrect decisions as the human decision-maker varies one or more confidence thresholds. Conventional ROC curves measured in simple decision-making situations can, in some cases, be used to predict human decision performance in more complex situations. By considering both the consequences of the various types of diagnostic decisions and the overhead cost of a diagnostic study, one can use the ROC curve to evaluate the diagnostic usefulness of a study in any particular clinical context. Since the ROC curve describes the possible relationships among the probabilities of the various types of correct and incorrect decisions, it plays a central role in optimizing diagnostic strategies using the general techniques of decision analysis. Applications in radiographic image evaluation are described
Directory of Open Access Journals (Sweden)
Francesca Vetro
2002-11-01
Full Text Available Let Y be an elliptic curve, p a prime number and WH_{p,n}(Y the Hurwitz space that parametrizes equivalence classes of p-sheeted branched coverings of Y , with n branch points, n − 1 of which are points of simple ramification and one of total ramification.In this paper, we prove that WH_{p,n}(Y is irreducible if n − 1≥ 2 p.
Directory of Open Access Journals (Sweden)
A. Narayan
2013-01-01
Full Text Available The oblateness and the photogravitational effects of both the primaries on the location and the stability of the triangular equilibrium points in the elliptical restricted three-body problem have been discussed. The stability of the triangular points under the photogravitational and oblateness effects of both the primaries around the binary systems Achird, Lyeten, Alpha Cen-AB, Kruger 60, and Xi-Bootis, has been studied using simulation techniques by drawing different curves of zero velocity.
Bounding the number of points on a curve using a generalization of Weierstrass semigroups
DEFF Research Database (Denmark)
Beelen, Peter; Ruano, Diego
2013-01-01
In this article we use techniques from coding theory to derive upper bounds for the number of rational places of the function field of an algebraic curve defined over a finite field. The used techniques yield upper bounds if the (generalized) Weierstrass semigroup (J Pure Appl Algebra 207(2), 243......–260, 2006) for an n-tuple of places is known, even if the exact defining equation of the curve is not known. As shown in examples, this sometimes enables one to get an upper bound for the number of rational places for families of function fields. Our results extend results in (J Pure Appl Algebra 213...
Torsion points on elliptic curves over number fields of small degree
Derickx, M.
2016-01-01
Barry Mazur famously classified the finitely many groups that can occur as a torsion subgroup of an elliptic curve over the rationals. This thesis deals with generalizations of this to higher degree number fields. Merel proved that for all integers d one has that the number of isomorphsim classes of
THE ROLE AND PLACE OF LOGISTIC REGRESSION AND ROC ANALYSIS IN SOLVING MEDICAL DIAGNOSTIC TASK
Directory of Open Access Journals (Sweden)
S. G. Grigoryev
2016-01-01
Full Text Available Diagnostics, equally with prevention and treatment, is a basis of medical science and practice. For its history the medicine has accumulated a great variety of diagnostic methods for different diseases and pathologic conditions. Nevertheless, new tests, methods and tools are being developed and recommended to application nowadays. Such indicators as sensitivity and specificity which are defined on the basis of fourfold contingency tables construction or ROC-analysis method with ROC – curve modelling (Receiver operating characteristic are used as the methods to estimate the diagnostic capability. Fourfold table is used with the purpose to estimate the method which confirms or denies the diagnosis, i.e. a quality indicator. ROC-curve, being a graph, allows making the estimation of model quality by subdivision of two classes on the basis of identifying the point of cutting off a continuous or discrete quantitative attribute.The method of logistic regression technique is introduced as a tool to develop some mathematical-statistical forecasting model of probability of the event the researcher is interested in if there are two possible variants of the outcome. The method of ROC-analysis is chosen and described in detail as a tool to estimate the model quality. The capabilities of the named methods are demonstrated by a real example of creation and efficiency estimation (sensitivity and specificity of a forecasting model of probability of complication development in the form of pyodermatitis in children with atopic dermatitis.
Accrual of ROCs LECs and REGOs
Energy Technology Data Exchange (ETDEWEB)
NONE
2005-07-01
This report summarises the findings of a project to identify the technical and administrative difficulties experienced by microgenerators in accessing the benefits of Renewables Obligation Certificates (ROCs), Levy Exemption Certificates (LECs) and Renewable Electricity Guarantees of Origin (REGO). These include cost, administrative complexity and financial risk. Changes allowing bulk processing, meter data provision, sell and buyback contracts, and alignment of ROCs, LECs and REGOs are discussed as well as making the schemes more customer friendly. The background to the project is traced, and an overview of the processes associated with gaining ROCs, LECs and REGOs is presented.
Regularized binormal ROC method in disease classification using microarray data
Directory of Open Access Journals (Sweden)
Huang Jian
2006-05-01
Full Text Available Abstract Background An important application of microarrays is to discover genomic biomarkers, among tens of thousands of genes assayed, for disease diagnosis and prognosis. Thus it is of interest to develop efficient statistical methods that can simultaneously identify important biomarkers from such high-throughput genomic data and construct appropriate classification rules. It is also of interest to develop methods for evaluation of classification performance and ranking of identified biomarkers. Results The ROC (receiver operating characteristic technique has been widely used in disease classification with low dimensional biomarkers. Compared with the empirical ROC approach, the binormal ROC is computationally more affordable and robust in small sample size cases. We propose using the binormal AUC (area under the ROC curve as the objective function for two-sample classification, and the scaled threshold gradient directed regularization method for regularized estimation and biomarker selection. Tuning parameter selection is based on V-fold cross validation. We develop Monte Carlo based methods for evaluating the stability of individual biomarkers and overall prediction performance. Extensive simulation studies show that the proposed approach can generate parsimonious models with excellent classification and prediction performance, under most simulated scenarios including model mis-specification. Application of the method to two cancer studies shows that the identified genes are reasonably stable with satisfactory prediction performance and biologically sound implications. The overall classification performance is satisfactory, with small classification errors and large AUCs. Conclusion In comparison to existing methods, the proposed approach is computationally more affordable without losing the optimality possessed by the standard ROC method.
Singularity structure of the two-point function in quantum field theory in curved spacetime, II
International Nuclear Information System (INIS)
Fulling, S.A.; Narcowich, F.J.; Wald, R.M.
1981-01-01
We prove that, for a massive, scalar, quantum field in a wide class of static spacetimes, the two-point function has singularity structure of the Hadamard form. In particular, this implies that the point-splitting renormalization prescription is well defined in these spacetimes. As a corollary of this result and a previous result of Fulling, Sweeny, and Wald, we show that in an arbitrary globally hyperbolic spacetime there always exists a large class of states for which the singular part of the two-point function has the Hadamard form. In addition, we prove that, for a closed universe which is both initially and finally static, the S-matrix exists
A coexistence curve equation for refrigerant-F-113 within the vicinity of the critical point
International Nuclear Information System (INIS)
Al'okhyin, O.D.; Bezruchko, Yi.V.; Bulavyin, L.A.
2003-01-01
The experimental data on the dependence of the density on temperature have been presented for refrigerant F-113 along the coexistence curve within the wide temperature range including the close vicinity of the critical temperature. The extended equation of state for freon-113 along this direction has been proposed on the base of the van der Waals model of a fluctuation gas. Parameters of the equation is determined by the interaction of molecules inside density fluctuations at the distances r>R c and by the interaction between fluctuations at the distances r>R c (R c is the correlation radius of the system)
International Nuclear Information System (INIS)
Liggatt, P.A.J.; Macfarlane, A.J.
1978-01-01
A prescription is given for point-splitting in a curved space-time background which is a natural generalization of that familiar in quantum electrodynamics and Yang-Mills theory. It is applied (to establish its validity) to the verification of the gravitational anomaly in the divergence of a fermion axial current. Notable features of the prescription are that it defines a point-split current which can be differentiated straightforwardly, and that it involves a natural way of averaging (four dimensionally) over the directions of point splitting. The method can extend directly from the spin-1/2 fermion case treated to other cases, e.g. to spin -3/2 Rarita-Schwinger fermions. (author)
Three-way ROC analysis using SAS Software
Directory of Open Access Journals (Sweden)
Juraj Kapasný
2013-01-01
Full Text Available The most commonly used measure of model accuracy in medicine with three categories of target variable is the volume under ROC surface (VUS, which is the extension of the area under curve (AUC for binary models (Le and Lili, 2013. This paper deals primarily with usage of the multinomial logistic regression and the three–way ROC analysis in the financial sector, especially in the credit risk management. Moreover, SAS system is very often used software in the financial sector. Therefore this paper is focused on ways of doing three–way ROC analysis in this statistical software, in particular on estimating the VUS.We propose an estimate of the VUS based on the confusion matrix, which is compared to estimates based on Mann-Whitney statistic and on empirical distribution functions. We developed three SAS macros based on these approaches for computing the VUS. Further- more, we developed some logistic models for three-value target variable based on the Loss Given Default (LGD. This was done on real financial data. Results obtained by the SAS macros on these models are presented a discussed in the paper.
Merzlikin, Boris S.; Shapiro, Ilya L.; Wipf, Andreas; Zanusso, Omar
2017-12-01
Using covariant methods, we construct and explore the Wetterich equation for a nonminimal coupling F (ϕ )R of a quantized scalar field to the Ricci scalar of a prescribed curved space. This includes the often considered nonminimal coupling ξ ϕ2R as a special case. We consider the truncations without and with scale- and field-dependent wave-function renormalization in dimensions between four and two. Thereby the main emphasis is on analytic and numerical solutions of the fixed point equations and the behavior in the vicinity of the corresponding fixed points. We determine the nonminimal coupling in the symmetric and spontaneously broken phases with vanishing and nonvanishing average fields, respectively. Using functional perturbative renormalization group methods, we discuss the leading universal contributions to the RG flow below the upper critical dimension d =4 .
International Nuclear Information System (INIS)
Mosqueira, J.; Torron, C.; Veira, J.A.; Vidal, F.
1998-01-01
The crossing point of the magnetization vs. temperature curves that appears below T c in highly anisotropic superconducting cuprates was measured in different compounds, with a different number, N, of superconducting CuO 2 layers per periodicity length, s, and also with different values of s. By correcting the measurements from different extrinsic inhomogeneity effects through the Meissner fraction, it is demonstrated experimentally for the first time that in the high-magnetic-field limit the intrinsic crossing point may be explained at a quantitative level in terms of the Tesanovic and coworkers approach based on thermal fluctuations of quasi-2D vortices (pancakes), with an effective periodicity length equal to s, independently of N. (orig.)
International Nuclear Information System (INIS)
Christensen, S.M.
1976-01-01
A method known as covariant geodesic point separation is developed to calculate the vacuum expectation value of the stress tensor for a massive scalar field in an arbitrary gravitational field. The vacuum expectation value will diverge because the stress-tensor operator is constructed from products of field operators evaluated at the same space-time point. To remedy this problem, one of the field operators is taken to a nearby point. The resultant vacuum expectation value is finite and may be expressed in terms of the Hadamard elementary function. This function is calculated using a curved-space generalization of Schwinger's proper-time method for calculating the Feynman Green's function. The expression for the Hadamard function is written in terms of the biscalar of geodetic interval which gives a measure of the square of the geodesic distance between the separated points. Next, using a covariant expansion in terms of the tangent to the geodesic, the stress tensor may be expanded in powers of the length of the geodesic. Covariant expressions for each divergent term and for certain terms in the finite portion of the vacuum expectation value of the stress tensor are found. The properties, uses, and limitations of the results are discussed
Receiver operator characteristic (ROC) analysis without truth
International Nuclear Information System (INIS)
Henkelman, R.M.; Kay, I.; Bronskill, M.J.
1990-01-01
Receiver operator characteristic (ROC) analysis, the preferred method of evaluating diagnostic imaging tests, requires an independent assessment of the true state of disease, which can be difficult to obtain and is often of questionable accuracy. A new method of analysis is described which does not require independent truth data and which can be used when several accurate tests are being compared. This method uses correlative information to estimate the underlying model of multivariate normal distributions of disease-positive and disease-negative patients. The method is shown to give results equivalent to conventional ROC analysis in a comparison of computed tomography, radionuclide scintigraphy, and magnetic resonance imaging for liver metastasis. When independent truth is available, the method can be extended to incorporate truth data or to evaluate the consistency of the truth data with the imaging data
Separating Mnemonic Process From Participant and Item Effects in the Assessment of ROC Asymmetries
Pratte, Michael S.; Rouder, Jeffrey N.; Morey, Richard D.
One of the most influential findings in the study of recognition memory is that receiver operating characteristic (ROC) curves are asymmetric about the negative diagonal. This result has led to the rejection of the equal-variance signal detection model of recognition memory and has provided
Separating Mnemonic Process from Participant and Item Effects in the Assessment of ROC Asymmetries
Pratte, Michael S.; Rouder, Jeffrey N.; Morey, Richard D.
2010-01-01
One of the most influential findings in the study of recognition memory is that receiver operating characteristic (ROC) curves are asymmetric about the negative diagonal. This result has led to the rejection of the equal-variance signal detection model of recognition memory and has provided motivation for more complex models, such as the…
The Use of Continuous Confidence Judgments in ROC of Digital Radiography
Energy Technology Data Exchange (ETDEWEB)
Kim, Hark Sung; Lee, In Ja [Dept. of Radiologic Technology, Dongnam Health College, Suwon (Korea, Republic of); Kim, Sung Chul [Dept. of Radiological Science, Gachon University of Medicine and Science, Inchon (Korea, Republic of)
2009-06-15
In general, the discrete confidence judgments that use five-step assessment method have been used to assess the medical images by ROC. TPF or FPF can be computed easily with this independent reading test. However, during experiments, it happens frequently that adequate distribution for observers is required to smoothly estimate the ROC curve. In addition, data becomes invalid for distribution of the created categories. To solve such problems or to apply the ROC interpretation to data that is not obtained from the experimental observation, the continuous confidence judgements (CCJ) has been proposed, which implements ROC interpretation using continuously-distributed experimental results without category classification has been used. As the use of CCJ to assess medical images was barely reported in Korea, we applied it to the assessment of chest digital images in this study. The results showed that a smooth ROC curve was obtained conveniently by the commercialized program and the characteristic value was measured easily. Therefore, it is recommended that this method can be applied to the assessment of digital medical images.
Ikemoto, Yukio; Demura, Shinichi; Yamaji, Shunsuke
2004-04-01
Individual differences in muscle contractile speed during static explosive muscle contraction are reflected in the developmental phase of the force-time curve. The purposes of this study were to clarify the properties and reliability of the inflection point of force-time, statistically dividing speed during static explosive grip into two phases and to assess the relations between that inflection point and others. Static explosive grip data were measured two times with a 5-min. rest (sampling frequency; 100 Hz). 32 healthy, young men (age: 15.5 +/- 0.8 yr., height: 173.9 +/- 7.3 cm, body mass: 71.5 +/- 11.2 kg) participated. 8 static explosive grip parameters were selected: time of reaching, integrated area, and quotient values of the integrated areas up to 0.25, 0.5, and 1.0 sec. divided by maximal grip force. The inflection point was calculated statistically from two regression lines fitted to a developmental phase and the almost steady-state phase of reaching maximal grip force by applying a two-phase regression model. The reliabilities of maximal grip force, time of reaching 90% of maximal grip force, and the integrated area until 0.5 sec. and 1.0 sec. after the onset of grip were good (ICC=.77 to .93). The time of reaching an inflection force value appeared at 0.3 sec. after the onset of grip, corresponding to 80% of maximal grip force, and the reliabilities of the parameters regarding inflection point were good (ICC=.77 to .95). The time determined by boundary data between the former and the latter regression data set and the regression coefficient during the developmental phase correlated significantly with the time of reaching 90% of maximal grip force, the integrated area, and the quotient values of the integrated areas up to 0.25, 0.5, and 1.0 sec. divided by maximal grip force (rs=-.78 to -.96 and -.75 to 0.88, respectively, pforce. A force during the developmental phase and maximal grip force can depend on different physiological factors. The time
Statistical evaluation of diagnostic performance topics in ROC analysis
Zou, Kelly H; Bandos, Andriy I; Ohno-Machado, Lucila; Rockette, Howard E
2016-01-01
Statistical evaluation of diagnostic performance in general and Receiver Operating Characteristic (ROC) analysis in particular are important for assessing the performance of medical tests and statistical classifiers, as well as for evaluating predictive models or algorithms. This book presents innovative approaches in ROC analysis, which are relevant to a wide variety of applications, including medical imaging, cancer research, epidemiology, and bioinformatics. Statistical Evaluation of Diagnostic Performance: Topics in ROC Analysis covers areas including monotone-transformation techniques in parametric ROC analysis, ROC methods for combined and pooled biomarkers, Bayesian hierarchical transformation models, sequential designs and inferences in the ROC setting, predictive modeling, multireader ROC analysis, and free-response ROC (FROC) methodology. The book is suitable for graduate-level students and researchers in statistics, biostatistics, epidemiology, public health, biomedical engineering, radiology, medi...
Validation of Nonparametric Two-Sample Bootstrap in ROC Analysis on Large Datasets.
Wu, Jin Chu; Martin, Alvin F; Kacker, Raghu N
The nonparametric two-sample bootstrap is applied to computing uncertainties of measures in ROC analysis on large datasets in areas such as biometrics, speaker recognition, etc., when the analytical method cannot be used. Its validation was studied by computing the SE of the area under ROC curve using the well-established analytical Mann-Whitney-statistic method and also using the bootstrap. The analytical result is unique. The bootstrap results are expressed as a probability distribution due to its stochastic nature. The comparisons were carried out using relative errors and hypothesis testing. They match very well. This validation provides a sound foundation for such computations.
International Nuclear Information System (INIS)
Liang, Fusheng; Zhao, Ji; Ji, Shijun; Zhang, Bing; Fan, Cheng
2017-01-01
The B-spline curve has been widely used in the reconstruction of measurement data. The error-bounded sampling points reconstruction can be achieved by the knot addition method (KAM) based B-spline curve fitting. In KAM, the selection pattern of initial knot vector has been associated with the ultimate necessary number of knots. This paper provides a novel initial knots selection method to condense the knot vector required for the error-bounded B-spline curve fitting. The initial knots are determined by the distribution of features which include the chord length (arc length) and bending degree (curvature) contained in the discrete sampling points. Firstly, the sampling points are fitted into an approximate B-spline curve Gs with intensively uniform knot vector to substitute the description of the feature of the sampling points. The feature integral of Gs is built as a monotone increasing function in an analytic form. Then, the initial knots are selected according to the constant increment of the feature integral. After that, an iterative knot insertion (IKI) process starting from the initial knots is introduced to improve the fitting precision, and the ultimate knot vector for the error-bounded B-spline curve fitting is achieved. Lastly, two simulations and the measurement experiment are provided, and the results indicate that the proposed knot selection method can reduce the number of ultimate knots available. (paper)
Aukenthaler, Manuel; Brinkgreve, R.B.J.; Haxaire, A
2016-01-01
Knowing that extensive field tests and laboratory tests are time-consuming and expensive, this paper describes a practical approach to obtain crucial properties of frozen soil such as the soil freezing characteristic curve (SFCC), the freezing/melting point of a soil-water system and its hydraulic
DEFF Research Database (Denmark)
Medford, Andrew James; Lilliedal, Mathilde Raad
2010-01-01
Inflection point behaviour is often observed in the current-voltage (IV) curve of polymer and organic solar cells. This phenomenon is examined in the context of flexible roll-to-roll (R2R) processed polymer solar cells in a large series of devices with a layer structure of: PET-ITO-ZnO-P3HT...
DEFF Research Database (Denmark)
Lilliedal, Mathilde Raad; Medford, Andrew James; Vesterager Madsen, Morten
2010-01-01
Inflection point behaviour is often observed in the current–voltage (IV) curve of polymer solar cells. This phenomenon is examined in the context of flexible roll-to-roll (R2R) processed polymer solar cells in a large series of devices with a layer structure of: PET–ITO–ZnO–P3HT:PCBM–PEDOT:PSS–Ag...
DEFF Research Database (Denmark)
Srinivas, Nuggehally R; Syed, Muzeeb
2016-01-01
concentration–time curve (AUC) and minimum plasma drug concentration (Cmin) versus AUC relationship was established by linear regression models. The predictions of the AUC values were performed using published mean/median Cmax or Cmin data and appropriate regression lines. The quotient of observed and predicted...
Geisinger high-risk osteoporosis clinic (HiROC): 2013-2015 FLS performance analysis.
Dunn, P; Webb, D; Olenginski, T P
2018-02-01
Geisinger Health System (GHS) high-risk osteoporosis clinic (HiROC), which treats patients with low-trauma, fragility fractures, reports their 2013-2015 performance measures in secondary fracture prevention. This fracture liaison service (FLS) pathway treats 75% of high-risk, drug eligible patients, compared to 13.8% in GHS primary care. This performance points to the need for more FLS programs throughout the world. The purpose of this study is to analyze and report ongoing performance measures in outpatient and inpatient high-risk osteoporosis clinic (HiROC) program designed for patients with low-trauma, fragility fractures. Retrospective chart review of outpatient HiROC (511 patients) and inpatient HiROC (1279 patients) performance from 2013 to 2015 is reported within Geisinger Health System (GHS). Similar to a prior report, we document that Geisinger's branded outpatient and inpatient HiROC pathways continue to function as an all-fracture FLS. Importantly, this analysis emphasizes the importance of FLS care that HiROC's treatment rate of 75% was markedly superior to GHS-PCP care of 13.8%. However, a large percentage of patients (37.8%) were lost to follow-up care. This led to the identification of multiple care gaps/barriers to ideal best practice. FLS programs use case finding strategies and address secondary fracture prevention. GHS HiROC's performance and initiation of drug therapy in this fracture patient population contrasts with GHS-PCP care's much lower rate of treatment, documenting the need for ongoing FLS care. Importantly, the results of this analysis have prompted the beginnings of GHS programmatic changes, designed to narrow the reported care gaps in this mature FLS.
International Nuclear Information System (INIS)
Cullen, D.E.
1987-06-01
This program is designed to be a general application independent plotting program to plot any combination of continuous curves and/or discrete points (with associated error bars) using user supplied titles and x and y axis labels and units. Using this method the program has no idea what data is being plotted and yet the user can produce any number of plots with each plot properly identified. This program is available upon request costfree from the IAEA Nuclear Data Section. (author)
Quantum motion of a point particle in the presence of the Aharonov–Bohm potential in curved space
Energy Technology Data Exchange (ETDEWEB)
Silva, Edilberto O., E-mail: edilbertoo@gmail.com [Departamento de Física, Universidade Federal do Maranhão, Campus Universitário do Bacanga, 65085-580 São Luís, Maranhão (Brazil); Ulhoa, Sérgio C., E-mail: sc.ulhoa@gmail.com [Instituto de Física, Universidade de Brasília, 70910-900, Brasília, Distrito Federal (Brazil); Andrade, Fabiano M., E-mail: f.andrade@ucl.ac.uk [Department of Computer Science, University College London, WC1E 6BT London (United Kingdom); Departamento de Matemática e Estatística, Universidade Estadual de Ponta Grossa, 84030-900 Ponta Grossa, Paraná (Brazil); Filgueiras, Cleverson, E-mail: cleversonfilgueiras@yahoo.com.br [Departamento de Física, Universidade Federal de Campina Grande, Caixa Postal 10071, 58109-970, Campina Grande, Paraíba (Brazil); Departamento de Física (DFI), Universidade Federal de Lavras (UFLA), Caixa Postal 3037, 37200-000, Lavras, Minas Gerais (Brazil); Amorim, R.G.G., E-mail: ronniamorim@gmail.com [Instituto de Física, Universidade de Brasília, 70910-900, Brasília, Distrito Federal (Brazil); Faculdade Gama, Universidade de Brasília, Setor Leste (Gama), 72444-240, Brasília, Distrito Federal (Brazil)
2015-11-15
The nonrelativistic quantum dynamics of a spinless charged particle in the presence of the Aharonov–Bohm potential in curved space is considered. We chose the surface as being a cone defined by a line element in polar coordinates. The geometry of this line element establishes that the motion of the particle can occur on the surface of a cone or an anti-cone. As a consequence of the nontrivial topology of the cone and also because of two-dimensional confinement, the geometric potential should be taken into account. At first, we establish the conditions for the particle describing a circular path in such a context. Because of the presence of the geometric potential, which contains a singular term, we use the self-adjoint extension method in order to describe the dynamics in all space including the singularity. Expressions are obtained for the bound state energies and wave functions. -- Highlights: •Motion of particle under the influence of magnetic field in curved space. •Bound state for Aharonov–Bohm problem. •Particle describing a circular path. •Determination of the self-adjoint extension parameter.
Directory of Open Access Journals (Sweden)
Luciane Stallivieri
2015-11-01
Full Text Available Students from around the world are increasingly interested in learning new languages and be inserted in different cultures, increasing the numbers of international mobility. However, when traveling to another country, cultural differences are strongly perceived, even if in different ways, influencing the adaptation process. Given the importance and growth of the international academic mobility, this study analyzes the process of cultural adaptation of students in mobility, considering the assumptions of the theory of curves "U" and "W". As for the methodology, it is a descriptive research with quantitative approach. Data collection was conducted through closed questionnaires sent to international students from different countries who have studied or are still studying in a Brazilian Institution of Higher Education. The results showed that after the stage of culture shock, students feel more connected to local culture, make more friends and feel more confident. It was confirmed also that almost all international students managed to adapt well to local customs.
Lagrangian Curves on Spectral Curves of Monopoles
International Nuclear Information System (INIS)
Guilfoyle, Brendan; Khalid, Madeeha; Ramon Mari, Jose J.
2010-01-01
We study Lagrangian points on smooth holomorphic curves in TP 1 equipped with a natural neutral Kaehler structure, and prove that they must form real curves. By virtue of the identification of TP 1 with the space LE 3 of oriented affine lines in Euclidean 3-space, these Lagrangian curves give rise to ruled surfaces in E 3 , which we prove have zero Gauss curvature. Each ruled surface is shown to be the tangent lines to a curve in E 3 , called the edge of regression of the ruled surface. We give an alternative characterization of these curves as the points in E 3 where the number of oriented lines in the complex curve Σ that pass through the point is less than the degree of Σ. We then apply these results to the spectral curves of certain monopoles and construct the ruled surfaces and edges of regression generated by the Lagrangian curves.
Tafiadis, Dionysios; Chronopoulos, Spyridon K; Kosma, Evangelia I; Voniati, Louiza; Raptis, Vasilis; Siafaka, Vasiliki; Ziavra, Nausica
2017-07-11
Voice performance is an inextricable key factor of everyday life. Obviously, the deterioration of voice quality can cause various problems to human communication and can therefore reduce the performance of social skills (relevant to voice). The deterioration could be originated from changes inside the system of the vocal tract and larynx. Various prognostic methods exist, and among them is the Voice Handicap Index (VHI). This tool includes self-reported questionnaires, used for determining the cutoff points of total score and of its three domains relevant to young male Greek smokers. The interpretation of the calculated cutoff points can serve as a strong indicator of imminent or future evaluation by a clinician. Consistent with previous calculation, the VHI can also act as a feedback for smokers' voice condition and as monitoring procedure toward smoking cessation. Specifically, the sample consisted of 130 male nondysphonic smokers (aged 18-33 years) who all participated in the VHI test procedure. The test results (through receiver operating characteristic analysis) concluded to a total cutoff point score of 19.50 (sensitivity: 0.838, 1-specificity: 0). Also, in terms of constructs, the Functional domain was equal to 7.50 (sensitivity: 0.676, 1-specificity: 0.032), the Physical domain was equal to 7.50 (sensitivity: 0.706, 1-specificity: 0.032), and the Emotional domain was equal to 6.50 (sensitivity: 0.809, 1-specificity: 0.048). Copyright © 2017 The Voice Foundation. Published by Elsevier Inc. All rights reserved.
Rudi, Katharina; Ho, Franz Y; Gilsbach, Bernd K; Pots, Henderikus; Wittinghofer, Alfred; Kortholt, Arjan; Klare, Johann P
2015-08-26
Ras of complex proteins (Roc) is a Ras-like GTP-binding domain that always occurs in tandem with the C-terminal of Roc (COR) domain and is found in bacteria, plants and animals. Recently, it has been shown that Roco proteins belong to the family of G-proteins activated by nucleotide (nt)-dependent dimerization (GADs). We investigated the RocCOR tandem from the bacteria Chlorobium tepidum with site-directed spin labelling and pulse EPR distance measurements to follow conformational changes during the Roco G-protein cycle. Our results confirm that the COR domains are a stable dimerization device serving as a scaffold for the Roc domains that, in contrast, are structurally heterogeneous and dynamic entities. Contrary to other GAD proteins, we observed only minor structural alterations upon binding and hydrolysis of GTP, indicating significant mechanistic variations within this protein class. Mutations in the most prominent member of the Roco family of proteins, leucine-rich repeat (LRR) kinase 2 (LRRK2), are the most frequent cause of late-onset Parkinson's disease (PD). Using a stable recombinant LRRK2 Roc-COR-kinase fragment we obtained detailed kinetic data for the G-protein cycle. Our data confirmed that dimerization is essential for efficient GTP hydrolysis and PD mutations in the Roc domain result in decreased GTPase activity. Previous data have shown that these LRRK2 PD-mutations are located in the interface between Roc and COR. Importantly, analogous mutations in the conserved C. tepidum Roc/COR interface significantly influence the structure and nt-induced conformational changes of the Roc domains. © 2015 Authors.
DEFF Research Database (Denmark)
Kuntsche, Judith; Herre, Angela; Fahr, Alfred
2013-01-01
and SC lipid organization. Cultivation for 21days resulted in further minor changes in the structural organization of ROC SC. The SAXS patterns of ROC SC had overall large similarities with that of human SC and point to the presence of a long periodicity phase with a repeat distance of about 122Å, e...... barrier similar to that of human stratum corneum is, however, a prerequisite. In this study, the stratum corneum lipid organization in an epidermal cell culture model based on rat epidermal keratinocytes (REK organotypic culture, ROC) was investigated by small-angle X-ray scattering (SAXS) in dependence...... of ROC SC obtained at different cultivation times (7, 14 and 21days at the air-liquid interface) was connected with an increase in structural order of the SC lipids in SAXS measurements: Already cultivation for 14days at the air-liquid interface resulted overall in a competent SC permeability barrier...
1SXPS: A DEEP SWIFT X-RAY TELESCOPE POINT SOURCE CATALOG WITH LIGHT CURVES AND SPECTRA
International Nuclear Information System (INIS)
Evans, P. A.; Osborne, J. P.; Beardmore, A. P.; Page, K. L.; Willingale, R.; Mountford, C. J.; Pagani, C.; Burrows, D. N.; Kennea, J. A.; Perri, M.; Tagliaferri, G.; Gehrels, N.
2014-01-01
We present the 1SXPS (Swift-XRT point source) catalog of 151,524 X-ray point sources detected by the Swift-XRT in 8 yr of operation. The catalog covers 1905 deg 2 distributed approximately uniformly on the sky. We analyze the data in two ways. First we consider all observations individually, for which we have a typical sensitivity of ∼3 × 10 –13 erg cm –2 s –1 (0.3-10 keV). Then we co-add all data covering the same location on the sky: these images have a typical sensitivity of ∼9 × 10 –14 erg cm –2 s –1 (0.3-10 keV). Our sky coverage is nearly 2.5 times that of 3XMM-DR4, although the catalog is a factor of ∼1.5 less sensitive. The median position error is 5.''5 (90% confidence), including systematics. Our source detection method improves on that used in previous X-ray Telescope (XRT) catalogs and we report >68, 000 new X-ray sources. The goals and observing strategy of the Swift satellite allow us to probe source variability on multiple timescales, and we find ∼30, 000 variable objects in our catalog. For every source we give positions, fluxes, time series (in four energy bands and two hardness ratios), estimates of the spectral properties, spectra and spectral fits for the brightest sources, and variability probabilities in multiple energy bands and timescales
Schulze, Ralf K W; Grimm, Stefanie; Schulze, Dirk; Voss, Kai; Keller, Hans-Peter; Wedel, Matthias
2011-08-01
To investigate the diagnostic quality of different quality, individually calibrated ink-jet printers for the very challenging dental radiographic task of approximal carious lesion detection. A test-pattern evaluating resolution, contrast and homogeneity of the ink-jet prints was developed. 50 standardized dental radiographs each showing two neighbouring teeth in natural contact were printed on glossy paper with calibrated, randomly selected ink-jet printers (Canon S520 and iP4500, Epson Stylus Photo R2400). Printing size equalled the viewing size on a 17″ cathode-ray-tube monitor daily quality-tested according to German regulations. The true caries status was determined from serial sectioning and microscopic evaluation. 16 experienced observers evaluated the radiographs on a five-point confidence scale on all prints plus the viewing monitor with respect to the visibility of a carious lesion. A non-parametric Receiver-Operating Characteristics (ROC-) analysis was performed explicitly designed for the evaluation of readings stemming from identical samples but different modality. Significant differences are expressed by a critical ratio z exceeding ±2. Diagnostic accuracy was determined by the area (Az) underneath the ROC-curves. Average Az-values ranged between 0.62 (S520 and R2400) and 0.64 (monitor, iP4500), with no significant difference between modalities (P=0.172). Neither significant (range mean z: -0.40 (S520) and -0.11 (iP4500)) nor clinically relevant differences were found between printers and viewing monitor. Our results for a challenging task in dental radiography indicate that calibrated, off-the-shelf ink-jet printers are able to reproduce (dental) radiographs at quality levels sufficient for radiographic diagnosis in a typical dental working environment. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.
International Nuclear Information System (INIS)
Schulze, Ralf K.W.; Grimm, Stefanie; Schulze, Dirk; Voss, Kai; Keller, Hans-Peter; Wedel, Matthias
2011-01-01
Aims: To investigate the diagnostic quality of different quality, individually calibrated ink-jet printers for the very challenging dental radiographic task of approximal carious lesion detection. Materials and methods: A test-pattern evaluating resolution, contrast and homogeneity of the ink-jet prints was developed. 50 standardized dental radiographs each showing two neighbouring teeth in natural contact were printed on glossy paper with calibrated, randomly selected ink-jet printers (Canon S520 and iP4500, Epson Stylus Photo R2400). Printing size equalled the viewing size on a 17'' cathode-ray-tube monitor daily quality-tested according to German regulations. The true caries status was determined from serial sectioning and microscopic evaluation. 16 experienced observers evaluated the radiographs on a five-point confidence scale on all prints plus the viewing monitor with respect to the visibility of a carious lesion. A non-parametric Receiver-Operating Characteristics (ROC-) analysis was performed explicitly designed for the evaluation of readings stemming from identical samples but different modality. Significant differences are expressed by a critical ratio z exceeding ±2. Diagnostic accuracy was determined by the area (Az) underneath the ROC-curves. Results: Average Az-values ranged between 0.62 (S520 and R2400) and 0.64 (monitor, iP4500), with no significant difference between modalities (P = 0.172). Neither significant (range mean z: -0.40 (S520) and -0.11 (iP4500)) nor clinically relevant differences were found between printers and viewing monitor. Conclusions: Our results for a challenging task in dental radiography indicate that calibrated, off-the-shelf ink-jet printers are able to reproduce (dental) radiographs at quality levels sufficient for radiographic diagnosis in a typical dental working environment.
Energy Technology Data Exchange (ETDEWEB)
Schulze, Ralf K.W., E-mail: rschulze@mail.uni-mainz.de [Poliklinik fuer Zahnaerztliche Chirurgie, University Medical Center of the Johannes Gutenberg-University, Augustusplatz 2, D-55131 Mainz (Germany); Grimm, Stefanie, E-mail: StefanieGrimm@gmx.de [Poliklinik fuer Zahnaerztliche Chirurgie, University Medical Center of the Johannes Gutenberg-University, Augustusplatz 2, D-55131 Mainz (Germany); Schulze, Dirk, E-mail: dirk.schulze@uniklinik-freiburg.de [Klinik fuer Mund,- Kiefer- und Gesichtschirurgie, Sektion Roentgen, Universitaetsklinikum Freiburg, Hugstetterstr. 55, D-79106 Freiburg (Germany); Voss, Kai, E-mail: zahnarzt@drvoss.eu [Zahnaerztekammer Schleswig-Holstein, Vorstand fuer Praxisfuehrung, Westring 496, D- 24106 Kiel (Germany); Keller, Hans-Peter, E-mail: hans-peter.keller@din.de [NA Dental (NADENT) im DIN, Alexander-Wellendorff-Str. 2, D-75172 Pforzheim (Germany); Wedel, Matthias, E-mail: matthias.wedel@siemens.com [Siemens AG, Medical Solutions, Postfach 32 60, D-91050 Erlangen (Germany)
2011-08-15
Aims: To investigate the diagnostic quality of different quality, individually calibrated ink-jet printers for the very challenging dental radiographic task of approximal carious lesion detection. Materials and methods: A test-pattern evaluating resolution, contrast and homogeneity of the ink-jet prints was developed. 50 standardized dental radiographs each showing two neighbouring teeth in natural contact were printed on glossy paper with calibrated, randomly selected ink-jet printers (Canon S520 and iP4500, Epson Stylus Photo R2400). Printing size equalled the viewing size on a 17'' cathode-ray-tube monitor daily quality-tested according to German regulations. The true caries status was determined from serial sectioning and microscopic evaluation. 16 experienced observers evaluated the radiographs on a five-point confidence scale on all prints plus the viewing monitor with respect to the visibility of a carious lesion. A non-parametric Receiver-Operating Characteristics (ROC-) analysis was performed explicitly designed for the evaluation of readings stemming from identical samples but different modality. Significant differences are expressed by a critical ratio z exceeding {+-}2. Diagnostic accuracy was determined by the area (Az) underneath the ROC-curves. Results: Average Az-values ranged between 0.62 (S520 and R2400) and 0.64 (monitor, iP4500), with no significant difference between modalities (P = 0.172). Neither significant (range mean z: -0.40 (S520) and -0.11 (iP4500)) nor clinically relevant differences were found between printers and viewing monitor. Conclusions: Our results for a challenging task in dental radiography indicate that calibrated, off-the-shelf ink-jet printers are able to reproduce (dental) radiographs at quality levels sufficient for radiographic diagnosis in a typical dental working environment.
Directory of Open Access Journals (Sweden)
Y. Yang
2017-12-01
Full Text Available We model the outage probability and bit-error rate (BER for an intensity-modulation/direct detection optical wireless communication (OWC systems for the ground-to-train of the curved track in rainy weather. By adopting the inverse Gaussian models of the raining turbulence, we derive the outage probability and average BER expression for the channel with pointing errors. The numerical analysis reveals that the rainfall can disrupt the stability and accuracy of the system, especially the rainstorm weather. The improving of the shockproof performance of the tracks and using long wavelength of the signal source will improve the communication performance of OWC links. The atmospheric turbulence has greater impact on the OWC link than the cover track length. The pointing errors caused by beam wander or train vibration are the dominant factors decreasing the performance of OWC link for the train along the curved track. We can choose the size of communication transmitting and receiving apertures to optimize the performance of the OWC link.
Energy Technology Data Exchange (ETDEWEB)
Marques, Maria de Lourdes S.P.; Mendes, Luana de Jesus [Fundacao Gorceix, Ouro Preto, MG (Brazil); Medina, Lilian Carmen [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil)
2008-07-01
PETROBRAS and others petroleum companies adopt the ASTM norms as reference method for oil distillation, ASTM D2892 (2005) that uses columns with 14 to 18 theoretical plates and the ASTM D 5236 (2003) , that distills mixture of heavy hydrocarbons with boiling point over 150 deg C. The result of these two distillations is the TBP (True Boiling Point) curve that is the main tool to define the yield of oil derivatives, the 'royalties' payment, the oil price for commercialization and the logistic support of oil location or in new plants projects of distillation and optimization studies. This procedure has some limitations as the volume sample, at least 1L, and the time of distillation, 2 to 4 days. The objective of this work is to propose a new alternative to attain de PEV curve, developing a new methodology using micro scale distillation that uses a more efficient column than the conventional method. Graphics of both methods were created and the results between the conventional and the micro distillation received statistical treatment to prove the equivalence between them. (author)
Chenkin, Jordan; McCartney, Colin J L; Jelic, Tomislav; Romano, Michael; Heslop, Claire; Bandiera, Glen
2015-12-01
Unrecognized esophageal intubations are associated with significant patient morbidity and mortality. No single confirmatory device has been shown to be 100 % accurate at ruling out esophageal intubations in the emergency department. Recent studies have demonstrated that point-of-care ultrasound (POCUS) may be a useful adjunct for confirming endotracheal tube placement; however, the amount of practice required to become proficient at this technique is unclear. The purpose of this study is to determine the amount of practice required by emergency physicians to become proficient at interpreting ultrasound video clips of esophageal and endotracheal intubations. Emergency physicians and emergency medicine residents completed a baseline interpretation test followed by a 10 min online tutorial. They then interpreted POCUS clips of esophageal and endotracheal intubations in a randomly selected order. If an incorrect response was provided, the participant completed another practice session with feedback. This process continued until they correctly interpreted ten consecutive ultrasound clips. Descriptive statistics were used to summarize the data. Of the 87 eligible physicians, 66 (75.9 %) completed the study. The mean score on the baseline test was 42.9 % (SD 32.7 %). After the tutorial, 90.9 % (60/66) of the participants achieved proficiency after one practice attempt and 100 % achieved proficiency after two practice attempts. Six intubation ultrasound clips were misinterpreted, for a total error rate of 0.9 % (6/684). Overall, the participants had a sensitivity of 98.3 % (95 % CI 96.3-99.4 %) and specificity of 100 % (95 % CI 98.9-100 %) for detecting correct tube location. Scans were interpreted within an average of 4 s (SD 2.9 s) of the intubation. After a brief online tutorial and only two practice attempts, emergency physicians were able to quickly and accurately interpret ultrasound intubation clips of esophageal and endotracheal intubations.
Analysis of ROC on chest direct digital radiography (DR) after image processing in diagnosis of SARS
Lv, Guozheng; Lan, Rihui; Zeng, Qingsi; Zheng, Zhong
2004-05-01
The Severe Acute Respiratory Syndrome (SARS, also called Infectious Atypical Pneumonia), which initially broke out in late 2002, has threatened the public"s health seriously. How to confirm the patients contracting SARS becomes an urgent issue in diagnosis. This paper intends to evaluate the importance of Image Processing in the diagnosis on SARS at the early stage. Receiver Operating Characteristics (ROC) analysis has been employed in this study to compare the value of DR images in the diagnosis of SARS patients before and after image processing by Symphony Software supplied by E-Com Technology Ltd., and DR image study of 72 confirmed or suspected SARS patients were reviewed respectively. All the images taken from the studied patients were processed by Symphony. Both the original and processed images were taken into ROC analysis, based on which the ROC graph for each group of images has been produced as described below: For processed images: a = 1.9745, b = 1.4275, SA = 0.8714; For original images: a = 0.9066, b = 0.8310, SA = 0.7572; (a - intercept, b - slop, SA - Area below the curve). The result shows significant difference between the original images and processed images (P<0.01). In summary, the images processed by Symphony are superior to the original ones in detecting the opacity lesion, and increases the accuracy of SARS diagnosis.
Maximum likelihood fitting of FROC curves under an initial-detection-and-candidate-analysis model
International Nuclear Information System (INIS)
Edwards, Darrin C.; Kupinski, Matthew A.; Metz, Charles E.; Nishikawa, Robert M.
2002-01-01
We have developed a model for FROC curve fitting that relates the observer's FROC performance not to the ROC performance that would be obtained if the observer's responses were scored on a per image basis, but rather to a hypothesized ROC performance that the observer would obtain in the task of classifying a set of 'candidate detections' as positive or negative. We adopt the assumptions of the Bunch FROC model, namely that the observer's detections are all mutually independent, as well as assumptions qualitatively similar to, but different in nature from, those made by Chakraborty in his AFROC scoring methodology. Under the assumptions of our model, we show that the observer's FROC performance is a linearly scaled version of the candidate analysis ROC curve, where the scaling factors are just given by the FROC operating point coordinates for detecting initial candidates. Further, we show that the likelihood function of the model parameters given observational data takes on a simple form, and we develop a maximum likelihood method for fitting a FROC curve to this data. FROC and AFROC curves are produced for computer vision observer datasets and compared with the results of the AFROC scoring method. Although developed primarily with computer vision schemes in mind, we hope that the methodology presented here will prove worthy of further study in other applications as well
International Nuclear Information System (INIS)
Gearhart, C.A. Jr.; Zimmermann, W. Jr.
1979-01-01
Values of the concentration susceptibility (partial x/partial Δ)/sub T/,P of liquid 3 He/ 4 He mixtures have been determined near the lambda curve and tricritical point from measurements of the differential osmotic pressure as a function of temperature T at four values of the 3 He mole fraction, x = 0.594, x = 0.644, x = 0.680, and x = 0.706. Here Δ = μ 3 - μ 4 is the difference between molar chemical potentials and P is the pressure. Our results for the two values of x less than the tricritical value x/sub t/ = 0.675 show pronounced peaks at the lambda transition. For 3 x 10 -4 -2 , where t equals [T - T/sub lambda/(x)]/T/sub lambda/(x), these peaks may be characterized both above and below the transition by the form (A/sub plus-or-minus//α/sub plus-or-minus/) (vertical-bart vertical-bar/sup -alpha/ +- - 1) + B/sub plus-or-minus/, with exponents α/sub plus-or-minus/ lying in the range from approx. 0.0 to approx. 0.2. Except perhaps for x -1 [T-T/sub t//T/sub t/)/vertical-barx-x/sub t//x/sub t/vertical-bar], where f and Ψ are functions determined by experiment and T/sub t/ = 0.867 K is the tricritical value of T. With the aid of this scaling relationship, the behavior of (partialx/partialΔ)/sub T/,P along curves of constant Δ near the lambda curve has been constucted from our data at constant x
Serrano, O K; Bangdiwala, A S; Vock, D M; Berglund, D; Dunn, T B; Finger, E B; Pruett, T L; Matas, A J; Kandaswamy, R
2017-07-01
The United Network for Organ Sharing recommends that fellowship-trained surgeons participate in 15 laparoscopic donor nephrectomy (LDN) procedures to be considered proficient. The American Society of Transplant Surgeons (ASTS) mandates 12 LDNs during an abdominal transplant surgery fellowship. We performed a retrospective intraoperative case analysis to create a risk-adjusted cumulative summation (RACUSUM) model to assess the learning curve of novice transplant surgery fellows (TSFs). Between January 2000 and December 2014, 30 novice TSFs participated in the organ procurement rotation of our ASTS-approved abdominal transplant surgery fellowship. Measures of surgical performance included intraoperative time, estimated blood loss, and incidence of intraoperative complications. The performance of senior TSFs was used to benchmark novice TSF performance. Scores were tabulated in a learning curve model, adjusting for case complexity and prior TSF case volume. Rates of adverse surgical events were significantly higher for novice TSFs than for senior TSFs. In univariable analysis, multiple renal arteries, high BMI, prior abdominal surgery, male donor, and nephrolithiasis were correlated with higher incidence of adverse surgical events. Based on the RACUSUM model, high intraoperative time is mitigated after 28 procedures, incidence of intraoperative complications tends to diminish after 24 procedures, and improvement in estimated blood loss did not remain consistent. TSFs exhibit a tipping point in LDN performance by 24-28 cases and proficiency by 35-38 cases. © 2016 The American Society of Transplantation and the American Society of Transplant Surgeons.
Susan L. King
2003-01-01
The performance of two classifiers, logistic regression and neural networks, are compared for modeling noncatastrophic individual tree mortality for 21 species of trees in West Virginia. The output of the classifier is usually a continuous number between 0 and 1. A threshold is selected between 0 and 1 and all of the trees below the threshold are classified as...
Performance quantification of clustering algorithms for false positive removal in fMRI by ROC curves
Directory of Open Access Journals (Sweden)
André Salles Cunha Peres
Full Text Available Abstract Introduction Functional magnetic resonance imaging (fMRI is a non-invasive technique that allows the detection of specific cerebral functions in humans based on hemodynamic changes. The contrast changes are about 5%, making visual inspection impossible. Thus, statistic strategies are applied to infer which brain region is engaged in a task. However, the traditional methods like general linear model and cross-correlation utilize voxel-wise calculation, introducing a lot of false-positive data. So, in this work we tested post-processing cluster algorithms to diminish the false-positives. Methods In this study, three clustering algorithms (the hierarchical cluster, k-means and self-organizing maps were tested and compared for false-positive removal in the post-processing of cross-correlation analyses. Results Our results showed that the hierarchical cluster presented the best performance to remove the false positives in fMRI, being 2.3 times more accurate than k-means, and 1.9 times more accurate than self-organizing maps. Conclusion The hierarchical cluster presented the best performance in false-positive removal because it uses the inconsistency coefficient threshold, while k-means and self-organizing maps utilize a priori cluster number (centroids and neurons number; thus, the hierarchical cluster avoids clustering scattered voxels, as the inconsistency coefficient threshold allows only the voxels to be clustered that are at a minimum distance to some cluster.
GEOMETRIC PROGRESSIONS ON ELLIPTIC CURVES.
Ciss, Abdoul Aziz; Moody, Dustin
2017-01-01
In this paper, we look at long geometric progressions on different model of elliptic curves, namely Weierstrass curves, Edwards and twisted Edwards curves, Huff curves and general quartics curves. By a geometric progression on an elliptic curve, we mean the existence of rational points on the curve whose x -coordinate (or y -coordinate) are in geometric progression. We find infinite families of twisted Edwards curves and Huff curves with geometric progressions of length 5, an infinite family of Weierstrass curves with 8 term progressions, as well as infinite families of quartic curves containing 10-term geometric progressions.
Wallner, Sandra Johanna; Horejsi, Renate; Zweiker, Robert; Watzinger, Norbert; Möller, Reinhard; Schnedl, Wolfgang Johann; Schauenstein, Konrad; Tafeit, Erwin
2008-06-01
The aim of this study was to investigate whether subcutaneous adipose tissue topography (SAT-Top) is different in female CHD patients (n=26) and healthy controls (n=36) matched to age, body size, weight, and BMI. The thicknesses of SAT layers were measured by LIPOMETER at 15 specified body sites. To calculate the power of the different body sites to discriminate between CHD women and healthy controls, receiver operating characteristic (ROC) curve analysis was performed. For each parameter, sensitivity and specificity were calculated at different cutoff points. CHD women showed a significant decrease to 78.36% (p=0.012) at body site 11-front thigh, 73.10% (p=0.012) at 12-lateral thigh, 72.20% (p=0.009) at 13-rear thigh, 66.43% (pSAT thickness at each measured body site is able to discriminate between the two subject groups. The good discrimination results obtained for the present dataset are encouraging enough to recommend applying LIPOMETER SAT-Top measurements in further studies to investigate individual risks for CHD.
Dendumrongsup, Thaworn; Plumb, Andrew A; Halligan, Steve; Fanshawe, Thomas R; Altman, Douglas G; Mallett, Susan
2014-01-01
We examined the design, analysis and reporting in multi-reader multi-case (MRMC) research studies using the area under the receiver-operating curve (ROC AUC) as a measure of diagnostic performance. We performed a systematic literature review from 2005 to 2013 inclusive to identify a minimum 50 studies. Articles of diagnostic test accuracy in humans were identified via their citation of key methodological articles dealing with MRMC ROC AUC. Two researchers in consensus then extracted information from primary articles relating to study characteristics and design, methods for reporting study outcomes, model fitting, model assumptions, presentation of results, and interpretation of findings. Results were summarized and presented with a descriptive analysis. Sixty-four full papers were retrieved from 475 identified citations and ultimately 49 articles describing 51 studies were reviewed and extracted. Radiological imaging was the index test in all. Most studies focused on lesion detection vs. characterization and used less than 10 readers. Only 6 (12%) studies trained readers in advance to use the confidence scale used to build the ROC curve. Overall, description of confidence scores, the ROC curve and its analysis was often incomplete. For example, 21 (41%) studies presented no ROC curve and only 3 (6%) described the distribution of confidence scores. Of 30 studies presenting curves, only 4 (13%) presented the data points underlying the curve, thereby allowing assessment of extrapolation. The mean change in AUC was 0.05 (-0.05 to 0.28). Non-significant change in AUC was attributed to underpowering rather than the diagnostic test failing to improve diagnostic accuracy. Data reporting in MRMC studies using ROC AUC as an outcome measure is frequently incomplete, hampering understanding of methods and the reliability of results and study conclusions. Authors using this analysis should be encouraged to provide a full description of their methods and results.
Directory of Open Access Journals (Sweden)
Thaworn Dendumrongsup
Full Text Available We examined the design, analysis and reporting in multi-reader multi-case (MRMC research studies using the area under the receiver-operating curve (ROC AUC as a measure of diagnostic performance.We performed a systematic literature review from 2005 to 2013 inclusive to identify a minimum 50 studies. Articles of diagnostic test accuracy in humans were identified via their citation of key methodological articles dealing with MRMC ROC AUC. Two researchers in consensus then extracted information from primary articles relating to study characteristics and design, methods for reporting study outcomes, model fitting, model assumptions, presentation of results, and interpretation of findings. Results were summarized and presented with a descriptive analysis.Sixty-four full papers were retrieved from 475 identified citations and ultimately 49 articles describing 51 studies were reviewed and extracted. Radiological imaging was the index test in all. Most studies focused on lesion detection vs. characterization and used less than 10 readers. Only 6 (12% studies trained readers in advance to use the confidence scale used to build the ROC curve. Overall, description of confidence scores, the ROC curve and its analysis was often incomplete. For example, 21 (41% studies presented no ROC curve and only 3 (6% described the distribution of confidence scores. Of 30 studies presenting curves, only 4 (13% presented the data points underlying the curve, thereby allowing assessment of extrapolation. The mean change in AUC was 0.05 (-0.05 to 0.28. Non-significant change in AUC was attributed to underpowering rather than the diagnostic test failing to improve diagnostic accuracy.Data reporting in MRMC studies using ROC AUC as an outcome measure is frequently incomplete, hampering understanding of methods and the reliability of results and study conclusions. Authors using this analysis should be encouraged to provide a full description of their methods and results.
Indian Academy of Sciences (India)
In this article some Peano curves are exhibited and some of their recent applications are dis- cussed. A C++ program to draw the Hilbert curve approximately is given. 1. Introduction. A 'continuous curve' in the plane is usually defined as the path traced by a moving point (x (t), Y (t)) as t runs over an interval of the real line, ...
Duncan, Michael J; Vale, Susana; Santos, Maria Paula; Ribeiro, José Carlos; Mota, Jorge
2013-01-01
To examine the efficacy of aerobic fitness thresholds in predicting weight status and cardiovascular disease risk (CVD) in young people. A cross-sectional school-based study was conducted on 414 Portuguese young people (235 girls and 179 boys) aged 10-16 years (Mean age ± SD = 13.6 ± 1. 8 years). Height and mass were assessed to determine body mass index (BMI). The 20 m multistage shuttle-fitness test (MSFT) was used as an estimate of aerobic fitness. Capillary blood sampling was used to determine: total cholesterol, triglycerides, high-, and low-density lipoprotein. These were combined with measures of systolic blood pressure as z-scores and summed to create a CVD risk score. Analysis of covariance, controlling for sexual maturation, indicated a significant main effect for BMI as a result of fitness category (P = 0.0001). When applied to CVD risk data, there was no difference between "fit" and "unfit" groups (P = 0.136). Subsequent receiver operating curve (ROC) analysis indicated significant diagnostic accuracy of 20 mMSFT performance for boys and girls (both P = 0.0001) with subsequent cut-offs of estimated VO2 peak of 49.5 ml kg(-1) min(-1) for girls and 47.7 ml kg(-1) min(-1) for boys. When applied to BMI and CVD risk data, there was a significant main effect as a result of fitness category for BMI (P = 0.0001) and CVD risk score (P = 0.0001). Recently established cut-points proposed by Boddy et al. (Boddy et al. [2012]: PLoS One 7(9): e45755) show validity in distinguishing between weight status but not CVD risk in Portuguese young people. Alternative ROC generated cut points significantly predicted BMI and CVD risk in this sample. Copyright © 2013 Wiley Periodicals, Inc.
ROC analyses of the signal detection on CRT-displayed radiographs after digitalization
International Nuclear Information System (INIS)
Yamashita, Kazuya; Inamoto, Kazuo; Morikawa, Kaoru
1986-01-01
In the present paper, we have described experimental evaluation studies using the ROC analysis on displayed images of the radiographs converted after digitization. Two types of images were used in these studies : one was signal images composed of 2 mm diameter beads disseminated (absorbed images) and another was 2 mm diameter cavities (penetrated images). The psychophysical experiment was carried out using the rating experiment of obtaining the ROC curve based on the signal detection theory. The detectability was evaluated by the maximum transmitted information. The results were summarized as follows: (1) The detectabilities of the images on the CRT were significantly lower than those of the original ones. The decreasing rate of information was 67.8 % in the bead signal images and 65.6 % in the cavity signal images. (2) However, the detectability of the cavity signal images was two times better than that of the bead. (3) Detectabilities could be improved to 98.9 % by double gradient processing and 70.1 % by quadruple gradient processing in the studies of the bead images. (author)
MODELING URBAN DYNAMICS USING RANDOM FOREST: IMPLEMENTING ROC AND TOC FOR MODEL EVALUATION
Directory of Open Access Journals (Sweden)
M. Ahmadlou
2016-06-01
Full Text Available The importance of spatial accuracy of land use/cover change maps necessitates the use of high performance models. To reach this goal, calibrating machine learning (ML approaches to model land use/cover conversions have received increasing interest among the scholars. This originates from the strength of these techniques as they powerfully account for the complex relationships underlying urban dynamics. Compared to other ML techniques, random forest has rarely been used for modeling urban growth. This paper, drawing on information from the multi-temporal Landsat satellite images of 1985, 2000 and 2015, calibrates a random forest regression (RFR model to quantify the variable importance and simulation of urban change spatial patterns. The results and performance of RFR model were evaluated using two complementary tools, relative operating characteristics (ROC and total operating characteristics (TOC, by overlaying the map of observed change and the modeled suitability map for land use change (error map. The suitability map produced by RFR model showed 82.48% area under curve for the ROC model which indicates a very good performance and highlights its appropriateness for simulating urban growth.
DEFF Research Database (Denmark)
Bernstein, Daniel J.; Birkner, Peter; Lange, Tanja
2013-01-01
This paper introduces EECM-MPFQ, a fast implementation of the elliptic-curve method of factoring integers. EECM-MPFQ uses fewer modular multiplications than the well-known GMP-ECM software, takes less time than GMP-ECM, and finds more primes than GMP-ECM. The main improvements above the modular......-arithmetic level are as follows: (1) use Edwards curves instead of Montgomery curves; (2) use extended Edwards coordinates; (3) use signed-sliding-window addition-subtraction chains; (4) batch primes to increase the window size; (5) choose curves with small parameters and base points; (6) choose curves with large...
Medical decision making tools: Bayesian analysis and ROC analysis
International Nuclear Information System (INIS)
Lee, Byung Do
2006-01-01
During the diagnostic process of the various oral and maxillofacial lesions, we should consider the following: 'When should we order diagnostic tests? What tests should be ordered? How should we interpret the results clinically? And how should we use this frequently imperfect information to make optimal medical decision?' For the clinicians to make proper judgement, several decision making tools are suggested. This article discusses the concept of the diagnostic accuracy (sensitivity and specificity values) with several decision making tools such as decision matrix, ROC analysis and Bayesian analysis. The article also explain the introductory concept of ORAD program
Yuan, Guoqiang; Niu, Liang; Zhang, Yinian; Wang, Xiaoqing; Ma, Kejun; Yin, Hang; Dai, Junqiang; Zhou, Wangning; Pan, Yawen
2017-05-01
Resistance to temozolomide (TMZ) chemotherapy poses a significant challenge in the treatment of glioblastoma (GBM). Hypermethylation in O 6 -methylguanine-DNA methyltransferase (MGMT) promoter is thought to play a critical role in this resistance. Pyrosequencing (PSQ) has been shown to be accurate and robust for MGMT promoter methylation testing. The unresolved issue is the determination of a cut-off value for dichotomization of quantitative MGMT PSQ results into "MGMT methylated" and "MGMT unmethylated" patient subgroups as a basis for further treatment decisions. In this study, receiver operating characteristic (ROC) curve analysis was used to identify an optimal cutoff of MGMT promoter methylation by testing mean percentage of methylation of 4 CpG islands (76-79) within MGMT exon 1. The area under the ROC (AUC) as well as the best cutoff to classify the methylation were calculated. Positive likelihood ratio (LR+) was chosen as a diagnostic parameter for defining an optimal cut-off. Meanwhile, we also analyzed whether mean percentage of methylation at the investigated CpG islands could be regarded as a marker for evaluating prognostication. ROC analysis showed that the optimal threshold was 12.5% (sensitivity: 60.87%; specificity: 76%) in response to the largest LR+ 2.54. 12.5% was established to distinguish MGMT promoter methylation, which was confirmed using validation set. According to the cutoff value, the MGMT promoter methylation was found in 58.3% of GBM. Mean methylation level of the investigated CpG sites strong correlated with overall survival (OS), which means GBM patients with a high level of methylation survived longer than those with low level of methylation(log-rank test, P = 0.017). In conclusion, ROC curve analysis enables the best cutoff for discriminating MGMT promoter methylation status. LR+ can be used as a key factor that evaluates cutoff. The promoter methylation level of MGMT by PSQ in GBM patients had prognostic value.
Directory of Open Access Journals (Sweden)
S.O. Moraes
1993-12-01
normalidade para estas tensões, indicando que se deve sempre dar preferência à curva completa de retenção de água no solo e não apenas a dois ou três pontos de interesse imediato, como é feito usualmente. As umidades às várias tensões utilizadas apresentaram baixo coeficiente de variação (In an area of "Terra Roxa Estruturada Latossólica" (Rhodic Kanhapludalf, in Piracicaba, SP, Brazil (20° 42' 30" S, 47° 38' 00" W, 576 m, 250 undisturbed soil samples were collected at 25 cm soil depth, according to a regular grid of spacing of 5 m, resulting a network of 25 Unes and 10 columns. These samples were used to determine 250 soil water retention curves each one with eigth experimental points, using Haines funnels (tensions of 5xl0², 1x10³, 6x10³ and 1x10(4 Pa and Richards pressure chambers (pressures of 3x10(4, 8x10(4,3x10(5 and 1x10(6 Pa, totalizing two thousand values. Position measurements (mode, median and arithmetic mean, variability (total amplitude, interquartil amplitude, standard deviation, coefficient of variation, assimetry, kurtosis and confident limits around the mean and number of samples to estimate the mean of the soil water content at a specific probability level, were used with the following objectives: a to verify how close to the normal distribution are the values of soil water content for the different considered tensions and hence, to investigate what is the best position measurement; b to quantify the variability in each considered tension, identifying the most problematic in the study of soil-water retention and also to analyse the measurement sensibility through the calculation of the necessary number of samples to estimate the mean (assuming a spatial independence of the samples. From the analysis of the obtained results, it could be concluded that the soil-water content values corresponding to tensions of 5x10² and 1x10³ Pa showed very skewed distributions, so that care should be taken in using the arithmetic mean as a position
Energy Technology Data Exchange (ETDEWEB)
Rocha, Rodrigo S.; Batistella, Cesar B.; Maciel, Maria Regina W.; Maciel Filho, Rubens [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Faculdade de Engenharia Quimica; Medina, Lilian C. [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil). Centro de Pesquisas (CENPES)
2008-07-01
For the determination of the TBP (True Boiling Point) Curve, which defines the yield of petroleum products, the ASTM D2892 method for petroleum distillation and ASTM D5236 method for vacuum distillation of heavy hydrocarbons were applied. Furthermore, from these distillations, cuts that are submitted to several analyses to determine its physical-chemical properties are obtained, and all this information generates the evaluation of petroleum. For heavy petroleum, these conventional methods have been limited, since the total distilled percentage determined for temperatures up to 565 deg C (maximum reached with ASTM D5236 method) is lower for these oils, reducing the points of the curve, limiting its information. To improve this data set for heavy oils, a methodology for the extension of TBP curve through molecular distillation was established. It was possible to reach values up to 700 deg C, representing a considerable progress for the extension of TBP curve. The objective of this work is to present the results of Extended TBP curve for a heavy petroleum and characterization carried out through the cuts and residues obtained in molecular distillation of the residue 'Zeta' 400 deg C+ (fancy name), made by ASTM D2892 method. (author)
Integrated Radio and Optical Communication (iROC)
Raible, Daniel; Romanofsky, Robert; Pease, Gary; Kacpura, Thomas
2016-01-01
This is an overview of the Integrated Radio and Optical Communication (iROC) Project for Space Communication and Navigation Industry Days. The Goal is to develop and demonstrate new, high payoff space technologies that will promote mission utilization of optical communications, thereby expanding the capabilities of NASA's exploration, science, and discovery missions. This is an overview that combines the paramount features of select deep space RF and optical communications elements into an integrated system, scalable from deep space to near earth. It will realize Ka-band RF and 1550 nanometer optical capability. The approach is to prototype and demonstrate performance of key components to increase to TRL-5, leading to integrated hybrid communications system demonstration to increase to TRL-5, leading to integrated hybrid communications system demonstration.
Linden, Ariel
2006-04-01
Diagnostic or predictive accuracy concerns are common in all phases of a disease management (DM) programme, and ultimately play an influential role in the assessment of programme effectiveness. Areas, such as the identification of diseased patients, predictive modelling of future health status and costs and risk stratification, are just a few of the domains in which assessment of accuracy is beneficial, if not critical. The most commonly used analytical model for this purpose is the standard 2 x 2 table method in which sensitivity and specificity are calculated. However, there are several limitations to this approach, including the reliance on a single defined criterion or cut-off for determining a true-positive result, use of non-standardized measurement instruments and sensitivity to outcome prevalence. This paper introduces the receiver operator characteristic (ROC) analysis as a more appropriate and useful technique for assessing diagnostic and predictive accuracy in DM. Its advantages include; testing accuracy across the entire range of scores and thereby not requiring a predetermined cut-off point, easily examined visual and statistical comparisons across tests or scores, and independence from outcome prevalence. Therefore the implementation of ROC as an evaluation tool should be strongly considered in the various phases of a DM programme.
DEFF Research Database (Denmark)
Gottschall, Julia; Courtney, Michael
2015-01-01
In this paper, we review a dynamical power curve concept that was introduced in earlier publications and shown to provide results for a wind turbine’s power characteristic with several benefits compared with the IEC 61400-12-1 standard procedure. After summarizing the theoretical concept based on...... performance data, but with some technical difficulties that demand a careful consideration in order to obtain reproducible and representative results. Copyright © 2014 John Wiley & Sons, Ltd....
Barry, J. H.; Muttalib, K. A.; Tanaka, T.
2008-01-01
We consider a two-dimensional (d=2) kagomé lattice gas model with attractive three-particle interactions around each triangular face of the kagomé lattice. Exact solutions are obtained for multiparticle correlations along the liquid and vapor branches of the coexistence curve and at criticality. The correlation solutions are also determined along the continuation of the curvilinear diameter of the coexistence region into the disordered fluid region. The method generates a linear algebraic system of correlation identities with coefficients dependent only upon the interaction parameter. Using a priori knowledge of pertinent solutions for the density and elementary triplet correlation, one finds a closed and linearly independent set of correlation identities defined upon a spatially compact nine-site cluster of the kagomé lattice. Resulting exact solution curves of the correlations are plotted and discussed as functions of the temperature and are compared with corresponding results in a traditional kagomé lattice gas having nearest-neighbor pair interactions. An example of application for the multiparticle correlations is demonstrated in cavitation theory.
Souza, Wayner Vieira de; Araújo, Thalia Velho Barreto de; Albuquerque, Maria de Fátima P Militão; Braga, Maria Cynthia; Ximenes, Ricardo Arraes de Alencar; Miranda-Filho, Demócrito de Barros; Bezerra, Luciana Caroline Albuquerque; Dimech, George Santiago; Carvalho, Patrícia Ismael de; Assunção, Romildo Siqueira de; Santos, Roselene Hans; Oliveira, Wanderson Kleber de; Rodrigues, Laura Cunha; Martelli, Celina Maria Turchi
2016-01-01
The increase in the number of reported cases of microcephaly in Pernambuco State, and Northeast Brazil, characterized an epidemic that led the Brazilian Ministry of Health to declare a national public health emergency. The Brazilian Ministry of Health initially defined suspected cases as newborns with gestational age (GA) ≥ 37 weeks and head circumference (HC) ≤ 33cm, but in December 2015 this cutoff was lowered to 32cm. The current study aimed to estimate the accuracy, sensitivity, and specificity of different cutoff points for HC, using ROC curves, with the Fenton and Intergrowth (2014) curves as the gold standard. The study described cases reported in Pernambuco from August 8 to November 28, 2015, according to sex and GA categories. The Fenton and Intergrowth methods provide HC growth curves according to GA and sex, and microcephaly is defined as a newborn with HC below the 3rd percentile in these distributions. Of the 684 reported cases, 599 were term or post-term neonates. For these, the analyses with ROC curves show that according to the Fenton criterion the cutoff point with the largest area under the ROC curve, with sensitivity greater than specificity, is 32cm for both sexes. Using the Intergrowth method and following the same criteria, the cutoff points are 32cm and 31.5cm for males and females, respectively. The cutoff point identified by the Fenton method (32cm) coincided with the Brazilian Ministry of Health recommendation. Adopting Intergrowth as the standard, the choice would be 32cm for males and 31.5cm for females. The study identified the need to conduct critical and on-going analyses to evaluate cutoff points, including other characteristics for microcephaly case definition.
Exploring Polypharmacology Using a ROCS-Based Target Fishing Approach
2012-01-01
will interact with the target. Abbreviations: DB number, Drug Bank number; ATC, anatomical therapeutic chemical classification; AMPC, AmpC β- lactamase ...receptor 2; ALR2, aldose reductase 2; AmpC, AmpC β- lactamase ; AUC, area under the curve. Journal of Chemical Information and Modeling Article dx.doi.org...Fluanisone, and (C) Fluoxetine. Abbreviations: ALPHA, α adrenergic receptor; D, dopamine receptor; BETA , β adrenergic receptor; H1, histamine H1 receptor
A Novel Volume CT With X-Ray on a Trough-Like Surface and Point Detectors on Circle-Plus-Arc Curve
National Research Council Canada - National Science Library
Xu, H
2001-01-01
A novel imaging mode of cone-beam volume CT is proposed in this paper. It adopts a raster scanning x-ray source on a trough-like surface, and a group of point detectors distributing on a large circle plus an orthogonal arc...
A ROC-based feature selection method for computer-aided detection and diagnosis
Wang, Songyuan; Zhang, Guopeng; Liao, Qimei; Zhang, Junying; Jiao, Chun; Lu, Hongbing
2014-03-01
Image-based computer-aided detection and diagnosis (CAD) has been a very active research topic aiming to assist physicians to detect lesions and distinguish them from benign to malignant. However, the datasets fed into a classifier usually suffer from small number of samples, as well as significantly less samples available in one class (have a disease) than the other, resulting in the classifier's suboptimal performance. How to identifying the most characterizing features of the observed data for lesion detection is critical to improve the sensitivity and minimize false positives of a CAD system. In this study, we propose a novel feature selection method mR-FAST that combines the minimal-redundancymaximal relevance (mRMR) framework with a selection metric FAST (feature assessment by sliding thresholds) based on the area under a ROC curve (AUC) generated on optimal simple linear discriminants. With three feature datasets extracted from CAD systems for colon polyps and bladder cancer, we show that the space of candidate features selected by mR-FAST is more characterizing for lesion detection with higher AUC, enabling to find a compact subset of superior features at low cost.
Tafiadis, Dionysios; Kosma, Evangelia I; Chronopoulos, Spyridon K; Papadopoulos, Aggelos; Drosos, Konstantinos; Siafaka, Vassiliki; Toki, Eugenia I; Ziavra, Nausica
2018-01-01
The relationship between smoking and alterations of the vocal tract and larynx is well known. This pathology leads to the degradation of voice performance in daily living. Multiple assessment methods of vocal tract and larynx have been developed, and in recent years they were enriched with self-reported questionnaires such as Voice Handicap Index (VHI). This study determined the cutoff points of VHI's total score and its three domains for young female smokers in Greece. These estimated cutoff points could be used by voice specialists as an indicator for further clinical evaluation (foreseeing a potential risk of developing a vocal symptom because of smoking habits). A sample of 120 female nondysphonic smokers (aged 18-31) was recruited. Participants filled out the VHI and Voice Evaluation Form. VHI's cutoff point of total score was calculated at the value of 19.50 (sensitivity: 0.780, 1-specificity: 0.133). Specifically, the construct domain of functional was 7.50 (sensitivity: 0.900, 1-specificity: 0.217), for physical it was 8.50 (sensitivity: 0.867, 1-specificity: 0.483), and for emotional it was 7.50 (sensitivity: 0.833, 1-specificity: 0.200) through the use of receiver operating characteristic. Furthermore, VHI could be used as a monitoring tool for smokers and as a feedback for smoking cessation. Copyright © 2018 The Voice Foundation. Published by Elsevier Inc. All rights reserved.
Algebraic curves and cryptography
Murty, V Kumar
2010-01-01
It is by now a well-known paradigm that public-key cryptosystems can be built using finite Abelian groups and that algebraic geometry provides a supply of such groups through Abelian varieties over finite fields. Of special interest are the Abelian varieties that are Jacobians of algebraic curves. All of the articles in this volume are centered on the theme of point counting and explicit arithmetic on the Jacobians of curves over finite fields. The topics covered include Schoof's \\ell-adic point counting algorithm, the p-adic algorithms of Kedlaya and Denef-Vercauteren, explicit arithmetic on
Skinfold reference curves and their use in predicting metabolic syndrome risk in children.
Andaki, Alynne C R; Quadros, Teresa M B de; Gordia, Alex P; Mota, Jorge; Tinôco, Adelson L A; Mendes, Edmar L
To draw skinfold (SF) reference curves (subscapular, suprailiac, biceps, triceps) and to determine SF cutoff points for predicting the risk of metabolic syndrome (MetS) in children aged 6-10 years old. This was a cross-sectional study with a random sample of 1480 children aged 6-10 years old, 52.2% females, from public and private schools located in the urban and rural areas of the municipality of Uberaba (MG). Anthropometry, blood pressure, and fasting blood samples were taken at school, following specific protocols. The LMS method was used to draw the reference curves and ROC curve analysis to determine the accuracy and cutoff points for the evaluated skinfolds. The four SF evaluated (subscapular, suprailiac, biceps, and triceps) and their sum (∑4SF) were accurate in predicting MetS for both girls and boys. Additionally, cutoffs have been proposed and percentile curves (p5, p10, p25, p50, p75, p90, and p95) were outlined for the four SF and ∑4SF, for both genders. SF measurements were accurate in predicting metabolic syndrome in children aged 6-10 years old. Age- and gender-specific smoothed percentiles curves of SF provide a reference for the detection of risk for MetS in children. Copyright © 2017. Published by Elsevier Editora Ltda.
Lederman, Dror; Zheng, Bin; Wang, Xingwei; Wang, Xiao Hui; Gur, David
2011-03-01
We have developed a multi-probe resonance-frequency electrical impedance spectroscope (REIS) system to detect breast abnormalities. Based on assessing asymmetry in REIS signals acquired between left and right breasts, we developed several machine learning classifiers to classify younger women (i.e., under 50YO) into two groups of having high and low risk for developing breast cancer. In this study, we investigated a new method to optimize performance based on the area under a selected partial receiver operating characteristic (ROC) curve when optimizing an artificial neural network (ANN), and tested whether it could improve classification performance. From an ongoing prospective study, we selected a dataset of 174 cases for whom we have both REIS signals and diagnostic status verification. The dataset includes 66 "positive" cases recommended for biopsy due to detection of highly suspicious breast lesions and 108 "negative" cases determined by imaging based examinations. A set of REIS-based feature differences, extracted from the two breasts using a mirror-matched approach, was computed and constituted an initial feature pool. Using a leave-one-case-out cross-validation method, we applied a genetic algorithm (GA) to train the ANN with an optimal subset of features. Two optimization criteria were separately used in GA optimization, namely the area under the entire ROC curve (AUC) and the partial area under the ROC curve, up to a predetermined threshold (i.e., 90% specificity). The results showed that although the ANN optimized using the entire AUC yielded higher overall performance (AUC = 0.83 versus 0.76), the ANN optimized using the partial ROC area criterion achieved substantially higher operational performance (i.e., increasing sensitivity level from 28% to 48% at 95% specificity and/ or from 48% to 58% at 90% specificity).
Interpolation and Polynomial Curve Fitting
Yang, Yajun; Gordon, Sheldon P.
2014-01-01
Two points determine a line. Three noncollinear points determine a quadratic function. Four points that do not lie on a lower-degree polynomial curve determine a cubic function. In general, n + 1 points uniquely determine a polynomial of degree n, presuming that they do not fall onto a polynomial of lower degree. The process of finding such a…
Lee, Subum; Seo, Junghan; Lee, Moon Kyu; Jeon, Sang Ryong; Roh, Sung Woo; Rhim, Seung Chul; Park, Jin Hoon
2017-08-01
OBJECTIVE The small diameter of cervical pedicles and a large transverse cervical pedicle angle are challenges that have led spinal surgeons to investigate how they could achieve a wider safety trajectory and reduce the insertion angle during cervical pedicle screw (CPS) placement. In this paper, the authors detail the advantages of using a curved pedicle probe and a laterally located entry point for overcoming these challenges. METHODS From March 2012 to May 2016, the authors performed posterior cervical fusions using CPSs on 119 consecutive patients. The lateral mass screw conversion and the CPS breach rate were analyzed. Using preoperative CT, it was determined that θ lat is similar to the anatomical pedicle angle, and θ med is the minimally acceptable medial angle. The actual insertion medial angle (θ ins ) was determined by postoperative CT. To identify how much of the medial angle on θ ins could be reduced from the anatomical pedicle angle (θ lat ), and how much closer to θ med , (θ ins -θ med ) / (θ lat -θ med ) was calculated. To verify shifting of the entry point and widening of the trajectory, the mean df/Df (i.e., shifted facet point/planned facet point) values were analyzed. RESULTS The total number of planed CPSs was 759, the conversion rate was 4.61% (35/759), and the accuracy rate was 95.9% (694/724). The authors could calculate that θ ins could be expected near the 90%, 80%, 80%, 80%, and 110% value of θ lat on C-3, C-4, C-5, C-6, and C-7 levels, respectively, with the (θ ins -θ med ) / (θ lat -θ med ) equation. The mean df/Df values were 0.64, 0.62, 0.63, 0.63, and 1.24 on the C3-7 levels, respectively. CONCLUSIONS Through the use of a curved pedicle probe and a laterally located starting point, the planned and laterally located entry point medial shift was made during CPS placement. The entry point shift yielded a wider, safe trajectory and reduced the burden of making a large medial angle, similar to an anatomical cervical pedicle
Directory of Open Access Journals (Sweden)
Valmore Bermúdez
2015-01-01
Full Text Available Introduction. The purpose of this study was to analyze the influence of metabolic phenotypes during the construction of ROC curves for waist circumference (WC cutpoint selection. Materials and Methods. A total of 1,902 subjects of both genders were selected from the Maracaibo City Metabolic Syndrome Prevalence Study database. Two-Step Cluster Analysis (TSCA was applied to select metabolically healthy and sick men and women. ROC curves were constructed to determine WC cutoff points by gender. Results. Through TSCA, metabolic phenotype predictive variables were selected: HOMA2-IR and HOMA2-βcell for women and HOMA2-IR, HOMA2-βcell, and TAG for men. Subjects were classified as healthy normal weight, metabolically obese normal weight, healthy and metabolically disturbed overweight, and healthy and metabolically disturbed obese. Final WC cutpoints were 91.50 cm for women (93.4% sensitivity, 93.7% specificity and 98.15 cm for men (96% sensitivity, 99.5% specificity. Conclusions. TSCA in the selection of the groups used in ROC curves construction proved to be an important tool, aiding in the detection of MOWN and MHO which cannot be identified with WC alone. The resulting WC cutpoints were <91.00 cm for women and <98.00 cm for men. Furthermore, anthropometry is insufficient to determine healthiness, and, biochemical analysis is needed to properly filter subjects during classification.
Directory of Open Access Journals (Sweden)
K S Mwitondi
2013-05-01
Full Text Available Differences in modelling techniques and model performance assessments typically impinge on the quality of knowledge extraction from data. We propose an algorithm for determining optimal patterns in data by separately training and testing three decision tree models in the Pima Indians Diabetes and the Bupa Liver Disorders datasets. Model performance is assessed using ROC curves and the Youden Index. Moving differences between sequential fitted parameters are then extracted, and their respective probability density estimations are used to track their variability using an iterative graphical data visualisation technique developed for this purpose. Our results show that the proposed strategy separates the groups more robustly than the plain ROC/Youden approach, eliminates obscurity, and minimizes over-fitting. Further, the algorithm can easily be understood by non-specialists and demonstrates multi-disciplinary compliance.
Complementary curves of descent
Mungan, Carl E.; Lipscombe, Trevor C.
2013-01-01
The shapes of two wires in a vertical plane with the same starting and ending points are described as complementary curves of descent if beads frictionlessly slide down both of them in the same time, starting from rest. Every analytic curve has a unique complement, except for a cycloid (solution of the brachistochrone problem), which is self complementary. A striking example is a straight wire whose complement is a lemniscate of Bernoulli. Alternatively, the wires can be tracks down which round objects undergo a rolling race. The level of presentation is appropriate for an intermediate undergraduate course in classical mechanics.
Proposing a tentative cut point for the Compulsive Sexual Behavior Inventory.
Storholm, Erik David; Fisher, Dennis G; Napper, Lucy E; Reynolds, Grace L; Halkitis, Perry N
2011-12-01
Bivariate analyses were utilized in order to identify the relations between scores on the Compulsive Sexual Behavior Inventory (CSBI) and self-report of risky sexual behavior and drug abuse among 482 racially and ethnically diverse men and women. CSBI scores were associated with both risky sexual behavior and drug abuse among a diverse non-clinical sample, thereby providing evidence of criterion-related validity. The variables that demonstrated a high association with the CSBI were subsequently entered into a multiple regression model. Four variables (number of sexual partners in the last 30 days, self-report of trading drugs for sex, having paid for sex, and perceived chance of acquiring HIV) were retained as variables with good model fit. Receiver operating characteristic (ROC) curve analyses were conducted in order to determine the optimal tentative cut point for the CSBI. The four variables retained in the multiple regression model were utilized as exploratory gold standards in order to construct ROC curves. The ROC curves were then compared to one another in order to determine the point that maximized both sensitivity and specificity in the identification of compulsive sexual behavior with the CSBI scale. The current findings suggest that a tentative cut point of 40 may prove clinically useful in discriminating between persons who exhibit compulsive sexual behavior and those who do not. Because of the association between compulsive sexual behavior and HIV, STIs, and drug abuse, it is paramount that a psychometrically sound measure of compulsive sexual behavior is made available to all healthcare professionals working in disease prevention and other areas.
Cubic spline functions for curve fitting
Young, J. D.
1972-01-01
FORTRAN cubic spline routine mathematically fits curve through given ordered set of points so that fitted curve nearly approximates curve generated by passing infinite thin spline through set of points. Generalized formulation includes trigonometric, hyperbolic, and damped cubic spline fits of third order.
Twisted vector bundles on pointed nodal curves
Indian Academy of Sciences (India)
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
other hand, as shown in [6], the notion of Gieseker vector bundles leads to the construction of the stack of stable maps into ..... residue field R/m = k. Let be a cyclic group of order e prime to the characteristic of k and let γ ∈ be a generator. Assume that acts on R such that the induced action on k is trivial. Let M be a trivial ...
Bantis, Leonidas E; Nakas, Christos T; Reiser, Benjamin; Myall, Daniel; Dalrymple-Alford, John C
2017-06-01
The three-class approach is used for progressive disorders when clinicians and researchers want to diagnose or classify subjects as members of one of three ordered categories based on a continuous diagnostic marker. The decision thresholds or optimal cut-off points required for this classification are often chosen to maximize the generalized Youden index (Nakas et al., Stat Med 2013; 32: 995-1003). The effectiveness of these chosen cut-off points can be evaluated by estimating their corresponding true class fractions and their associated confidence regions. Recently, in the two-class case, parametric and non-parametric methods were investigated for the construction of confidence regions for the pair of the Youden-index-based optimal sensitivity and specificity fractions that can take into account the correlation introduced between sensitivity and specificity when the optimal cut-off point is estimated from the data (Bantis et al., Biomet 2014; 70: 212-223). A parametric approach based on the Box-Cox transformation to normality often works well while for markers having more complex distributions a non-parametric procedure using logspline density estimation can be used instead. The true class fractions that correspond to the optimal cut-off points estimated by the generalized Youden index are correlated similarly to the two-class case. In this article, we generalize these methods to the three- and to the general k-class case which involves the classification of subjects into three or more ordered categories, where ROC surface or ROC manifold methodology, respectively, is typically employed for the evaluation of the discriminatory capacity of a diagnostic marker. We obtain three- and multi-dimensional joint confidence regions for the optimal true class fractions. We illustrate this with an application to the Trail Making Test Part A that has been used to characterize cognitive impairment in patients with Parkinson's disease.
International Nuclear Information System (INIS)
Hansson, Jonny; Maansson, Lars Gunnar; Baath, Magnus
2016-01-01
The purpose of the present work was to investigate the validity of using single-reader-adapted receiver operating characteristics (ROC) software for analysis of visual grading characteristics (VGC) data. VGC data from four published VGC studies on optimisation of X-ray examinations, previously analysed using ROCFIT, were reanalysed using a recently developed software dedicated to VGC analysis (VGC Analyzer), and the outcomes [the mean and 95 % confidence interval (CI) of the area under the VGC curve (AUC VGC ) and the p-value] were compared. The studies included both paired and non-paired data and were reanalysed both for the fixed-reader and the random-reader situations. The results showed good agreement between the softwares for the mean AUC VGC . For non-paired data, wider CIs were obtained with VGC Analyzer than previously reported, whereas for paired data, the previously reported CIs were similar or even broader. Similar observations were made for the p-values. The results indicate that the use of single-reader-adapted ROC software such as ROCFIT for analysing non-paired VGC data may lead to an increased risk of committing Type I errors, especially in the random-reader situation. On the other hand, the use of ROC software for analysis of paired VGC data may lead to an increased risk of committing Type II errors, especially in the fixed-reader situation. (authors)
Meyer, Carolina; Barbosa, Diego Grasel; Junior, Geraldo Jose Ferrari; Andrade, Rubian Diego; Silva, Diego Augusto Santos; Pelegrini, Andreia; Gomes Felden, Érico Pereira
2018-03-01
The objective of the present study was to propose cutoff points for the Pediatric Daytime Sleepiness Scale (PDSS) through sensitivity and specificity analyses in order to identify excessive daytime sleepiness, considering parameters such as duration and quality of sleep, health perception, stress control and depressive moods (feelings of sadness) in adolescents. A total of 1,132 adolescents, aged 14-19 years old, of both sexes, from the public high school of São José - SC, answered the questionnaire with information on age, daytime sleepiness, sleep duration, health perception, stress management, depressive moods (feelings of sadness) and quality of sleep. The Receiver Operating Characteristic (ROC) curve was used to estimate cutoff points considering the sensitivity and specificity values that best identify adolescents with excessive daytime sleepiness, using independent variables as a reference. The majority of the sample was female (54.2%), aged 14-16 years. The girls presented worse quality of sleep (66.4%), and the boys had a more positive perception of health (74.8%), better stress control (64.8%) and lower depressive moods (feelings of sadness) (63.3%). The largest area in the ROC curve was the one that considered sleep quality as a parameter in both sexes (area of the curve = 0.709 and 0.659, respectively, for boys and girls, p sleep quality as a reference, the cutoff point for excessive daytime sleepiness was 15 points. The other parameters used were also significant (p sleep quality was the parameter most strongly related to daytime sleepiness, and a cutoff of 15 points for the PDSS for both sexes should be used in the definition of excessive daytime sleepiness. For the other parameters, stress management, depressive mood (feelings of sadness) and health perception, different cutoff points are suggested for boys and girls.
Bhamidipati, Ravi Kanth; Syed, Muzeeb; Mullangi, Ramesh; Srinivas, Nuggehally
2018-02-01
1. Dalbavancin, a lipoglycopeptide, is approved for treating gram-positive bacterial infections. Area under plasma concentration versus time curve (AUC inf ) of dalbavancin is a key parameter and AUC inf /MIC ratio is a critical pharmacodynamic marker. 2. Using end of intravenous infusion concentration (i.e. C max ) C max versus AUC inf relationship for dalbavancin was established by regression analyses (i.e. linear, log-log, log-linear and power models) using 21 pairs of subject data. 3. The predictions of the AUC inf were performed using published C max data by application of regression equations. The quotient of observed/predicted values rendered fold difference. The mean absolute error (MAE)/root mean square error (RMSE) and correlation coefficient (r) were used in the assessment. 4. MAE and RMSE values for the various models were comparable. The C max versus AUC inf exhibited excellent correlation (r > 0.9488). The internal data evaluation showed narrow confinement (0.84-1.14-fold difference) with a RMSE regression models, a single time point strategy of using C max (i.e. end of 30-min infusion) is amenable as a prospective tool for predicting AUC inf of dalbavancin in patients.
Traudt, Elizabeth M.; Ranville, James F.; Smith, Samantha A.; Meyer, Joseph S.
2018-01-01
Mixtures of metals are often present in surface waters, leading to toxicity that is difficult to predict. To provide data for development of multimetal toxicity models, Daphnia magna neonates were exposed to individual metals (Cd, Cu, Ni, Zn) and to binary combinations of those metals in standard 48-h lethality tests conducted in US Environmental Protection Agency moderately hard reconstituted water with 3 mg dissolved organic carbon (DOC)/L added as Suwannee River fulvic acid. Toxicity tests were performed with mixtures of Ni and 1) Cd, which is considerably more toxic than Ni; 2) Cu, which is less toxic than Cd but more toxic than Ni; and 3) Zn, which has a toxicity threshold similar to Ni. For each combination of metals in the binary mixtures, the concentration of 1 metal was held constant while the second metal was varied through a series that ranged from nonlethal to lethal concentrations; then the roles of the metals were reversed. Inflection points of the concentration–response curves were compared to test for additivity of toxicity. Sublethal concentrations of Ni caused less-than-additive toxicity with Cd, slightly less-than-additive toxicity with Zn, and greater-than-additive toxicity with Cu. One explanation of these results might be competition among the metals for binding to biological ligands and/or dissolved organic matter. Therefore, models might have to incorporate sometimes competing chemical interactions to accurately predict metal-mixture toxicity. PMID:26681657
Comparison of rat epidermal keratinocyte organotypic culture (ROC) with intact human skin
DEFF Research Database (Denmark)
Pappinen, Sari; Hermansson, Martin; Kuntsche, Judith
2008-01-01
study was to compare the stratum corneum lipid content of ROC with the corresponding material from human skin. The lipid composition was determined by thin-layer chromatography (TLC) and mass-spectrometry, and the thermal phase transitions of stratum corneum were studied by differential scanning...
Item Strength Influences Source Confidence and Alters Source Memory zROC Slopes
Starns, Jeffrey J.; Ksander, John C.
2016-01-01
Increasing the number of study trials creates a crossover pattern in source memory zROC slopes; that is, the slope is either below or above 1 depending on which source receives stronger learning. This pattern can be produced if additional learning affects memory processes such as the relative contribution of recollection and familiarity to source…
Legendre Elliptic Curves over Finite Fields
Auer, Roland; Top, Jakob
2002-01-01
We show that every elliptic curve over a finite field of odd characteristic whose number of rational points is divisible by 4 is isogenous to an elliptic curve in Legendre form, with the sole exception of a minimal respectively maximal elliptic curve. We also collect some results concerning the
Curves from Motion, Motion from Curves
2000-01-01
tautochrone and brachistochrone properties. To Descartes, however, the rectification of curves such as the spiral (3) and the cycloid (4) was suspect - they...UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADP012017 TITLE: Curves from Motion, Motion from Curves DISTRIBUTION...Approved for public release, distribution unlimited This paper is part of the following report: TITLE: International Conference on Curves and Surfaces [4th
Twists of genus three curves and their Jacobians
Meagher, Stephen
2008-01-01
An algebraic curve is a curve defined over by polynomial equations with coefficients in a given field. This thesis treats problems which arise from genus three curves over finite fields. An important tool for treating such curves is the Jacobian variety of the curve. One problem is how many points
Cano Megías, Marta; González Albarrán, Olga; Guisado Vasco, Pablo; Lamas Ferreiro, Adelaida; Máiz Carro, Luis
2015-02-01
diabetes has become a co-morbidity with a negative impact on nutritional status, lung function and survival in cystic fibrosis. To identify any changes in intermediate points after a 2-hour oral glucose tolerance test (OGTT), pancreatic β-cell dysfunction, and insulin resistance in cystic fibrosis-related diabetes. It was carried out a retrospective analysis in a cohort of 64 patients affected of cystic fibrosis, older than 14 years, using the first pathological OGTT. Peripheral insulin resistance was measured using the homeostasis model assessment for insulin resistance (HOMA- IR), and pancreatic β-cell function was calculated according to Wareham. Time to maximum plasma insulin and glucose levels and area under the curve (AUC0-120) were also measured. Twenty-eight women and 36 men with a mean age of 26.8 years were enrolled, of whom 26.7% had normal glucose tolerance (NGT), 18.3% cystic fibrosis-related diabetes without fasting hyperglycemia (CFRD w/o FPG), 10% indeterminate (INDET), and 45% impaired glucose tolerance (IGT). HOMA-IR values were not significantly different between the diagnostic categories. Patients with any pathological change had worse β cell function, with a significant delay in insulin secretion, although there were no differences in total insulin production (AUC0-120). Time to maximum glucose levels was significantly shorter in NGT patients as compared to other categories, with glucose AUC0-120 being higher in the different diagnostic categories as compared to NGT. In over half the cases, peak blood glucose levels during a standard OGTT are reached in the intermediate time points, rather than at the usual time of 120minutes. Patients with cystic fibrosis and impaired glucose metabolism have a delayed insulin secretion during the standard OGTT due to loss of first-phase insulin secretion, with no differences in total insulin production. Absence of significant changes in HOMA-IR suggests that β-cell dysfunction is the main pathogenetic
GTP binding to the ROC domain of DAP-kinase regulates its function through intramolecular signalling
Carlessi, Rodrigo; Levin-Salomon, Vered; Ciprut, Sara; Bialik, Shani; Berissi, Hanna; Albeck, Shira; Peleg, Yoav; Kimchi, Adi
2011-01-01
Death-associated protein kinase (DAPk) was recently suggested by sequence homology to be a member of the ROCO family of proteins. Here, we show that DAPk has a functional ROC (Ras of complex proteins) domain that mediates homo-oligomerization and GTP binding through a defined P-loop motif. Upon binding to GTP, the ROC domain negatively regulates the catalytic activity of DAPk and its cellular effects. Mechanistically, GTP binding enhances an inhibitory autophosphorylation at a distal site that suppresses kinase activity. This study presents a new mechanism of intramolecular signal transduction, by which GTP binding operates in cis to affect the catalytic activity of a distal domain in the protein. PMID:21738225
Energy Technology Data Exchange (ETDEWEB)
Baltzer, Pascal A.T., E-mail: patbaltzer@gmail.com [Department of Biomedical Imaging and Imge-guided Therapy, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna (Austria); Kaiser, Werner Alois [Department of Diagnostic and Interventional Radiology, University Hospital Jena, Erlanger Allee 101, 07740 Jena (Germany); Dietzel, Matthias, E-mail: dietzelmatthias2@hotmail.com [Department of Neuroradiology, University Hospital Erlangen, Schwabachanlage 6, 91054 Erlangen (Germany)
2015-01-15
Highlights: • The main findings of our study are, that reader experience and lesion type (i.e., mass versus non-mass enhancement) are independent predictors of the diagnostic accuracy of breast MRI. • Specifically, benign and malignant non-mass lesions cannot be differentiated with sufficient accuracy, especially if readers are not experienced. • We conclude that future research in breast MRI should focus on non-mass lesions, as these are the problem makers in modern breast MRI. - Abstract: Purpose: To evaluate the influence of lesion type (mass versus non-mass) and reader experience on the diagnostic performance of breast MRI (BMRI) in a non-screening setting. Materials and methods: Consecutive patients (mean age, 55 ± 12 years) with breast lesions that were verified by biopsy or surgery, and who had had BMRI as part of their diagnostic workup, were eligible for this retrospective single-center study. Cancers diagnosed by biopsy before BMRI were excluded to eliminate biological and interpretation bias due to biopsy or chemotherapy effects (n = 103). Six blinded readers (experience level, high (HE, n = 2); intermediate (IE, n = 2); and low (LE, n = 2)) evaluated all examinations and assigned independent MRI BI-RADS ratings. Lesion type (mass, non-mass, focal) was noted. Receiver operating characteristics (ROC) and logistic regression analysis was performed to compare diagnostic accuracies. Results: There were 259 histologically verified lesions (123 malignant, 136 benign) investigated. There were 169 mass (103 malignant, 66 benign) and 48 non-mass lesions (19 malignant, 29 benign). Another 42 lesions that met the inclusion criteria were biopsied due to conventional findings (i.e., microcalcifications, architectural distortions), but did not enhance on MRI (41 benign, one DCIS). ROC analysis revealed a total area under the curve (AUC) between 0.834 (LE) and 0.935 (HI). Logistic regression identified a significant effect of non-mass lesions (P < 0.0001) and
iROCS: Integrated accident management framework for coping with beyond-design-basis external events
International Nuclear Information System (INIS)
Kim, Jaewhan; Park, Soo-Yong; Ahn, Kwang-Il; Yang, Joon-Eon
2016-01-01
Highlights: • An integrated mitigating strategy to cope with extreme external events, iROCS, is proposed. • The strategy aims to preserve the integrity of the reactor vessel as well as core cooling. • A case study for an extreme damage state is performed to assess the effectiveness and feasibility of candidate mitigation strategies under an extreme event. - Abstract: The Fukushima Daiichi accident induced by the Great East Japan earthquake and tsunami on March 11, 2011, poses a new challenge to the nuclear society, especially from an accident management viewpoint. This paper presents a new accident management framework called an integrated, RObust Coping Strategy (iROCS) to cope with beyond-design-basis external events (BDBEEs). The iROCS approach is characterized by classification of various plant damage conditions (PDCs) that might be impacted by BDBEEs and corresponding integrated coping strategies for each of PDCs, aiming to maintain and restore core cooling (i.e., to prevent core damage) and to maintain the integrity of the reactor pressure vessel if it is judged that core damage may not be preventable in view of plant conditions. From a case study for an extreme damage condition, it showed that candidate accident management strategies should be evaluated from the viewpoint of effectiveness and feasibility against accident scenarios and extreme damage conditions of the site, especially when employing mobile or portable equipment under BDBEEs within the limited time available to achieve desired goals such as prevention of core damage as well as a reactor vessel failure.
iROCS: Integrated accident management framework for coping with beyond-design-basis external events
Energy Technology Data Exchange (ETDEWEB)
Kim, Jaewhan; Park, Soo-Yong; Ahn, Kwang-Il, E-mail: kiahn@kaeri.re.kr; Yang, Joon-Eon
2016-03-15
Highlights: • An integrated mitigating strategy to cope with extreme external events, iROCS, is proposed. • The strategy aims to preserve the integrity of the reactor vessel as well as core cooling. • A case study for an extreme damage state is performed to assess the effectiveness and feasibility of candidate mitigation strategies under an extreme event. - Abstract: The Fukushima Daiichi accident induced by the Great East Japan earthquake and tsunami on March 11, 2011, poses a new challenge to the nuclear society, especially from an accident management viewpoint. This paper presents a new accident management framework called an integrated, RObust Coping Strategy (iROCS) to cope with beyond-design-basis external events (BDBEEs). The iROCS approach is characterized by classification of various plant damage conditions (PDCs) that might be impacted by BDBEEs and corresponding integrated coping strategies for each of PDCs, aiming to maintain and restore core cooling (i.e., to prevent core damage) and to maintain the integrity of the reactor pressure vessel if it is judged that core damage may not be preventable in view of plant conditions. From a case study for an extreme damage condition, it showed that candidate accident management strategies should be evaluated from the viewpoint of effectiveness and feasibility against accident scenarios and extreme damage conditions of the site, especially when employing mobile or portable equipment under BDBEEs within the limited time available to achieve desired goals such as prevention of core damage as well as a reactor vessel failure.
Optimization of restricted ROC surfaces in three-class classification tasks.
Edwards, Darrin C; Metz, Charles E
2007-10-01
We have shown previously that an N-class ideal observer achieves the optimal receiver operating characteristic (ROC) hypersurface in a Neyman-Pearson sense. Due to the inherent complexity of evaluating observer performance even in a three-class classification task, some researchers have suggested a generally incomplete but more tractable evaluation in terms of a surface, plotting only the three "sensitivities." More generally, one can evaluate observer performance with a single sensitivity or misclassification probability as a function of two linear combinations of sensitivities or misclassification probabilities. We analyzed four such formulations including the "sensitivity" surface. In each case, we applied the Neyman-Pearson criterion to find the observer which achieves optimal performance with respect to each given set of "performance description variables" under consideration. In the unrestricted case, optimization with respect to the Neyman-Pearson criterion yields the ideal observer, as does maximization of the observer's expected utility. Moreover, during our consideration of the restricted cases, we found that the two optimization methods do not merely yield the same observer, but are in fact completely equivalent in a mathematical sense. Thus, for a wide variety of observers which maximize performance with respect to a restricted ROC surface in the Neyman-Pearson sense, that ROC surface can also be shown to provide a complete description of the observer's performance in an expected utility sense.
DEFF Research Database (Denmark)
Conway, Paul Maurice; Høgh (Hogh), Annie; Nabe-Nielsen, Kirsten
2018-01-01
, the present study aimed to: (i) identify optimal cut-off points, reflecting a possible subjectively experienced exposure to occasional and frequent workplace bullying, for the 9-item Short Negative Act Questionnaire (S-NAQ), and (ii) examine the criterion validity of these cut-off points in relation...... and frequent workplace bullying. We employed receiver operating characteristic (ROC) curve analyses to derive the cut-off points for the S-NAQ. Based on these cut-off points, we created a new S-NAQ variable with three levels of exposure (i.e. ‘not exposed’, ‘first threshold’, and ‘second threshold’) and tested...... its criterion validity in relation to depressive symptoms (N = 4071) and diagnosis of depression (N = 4844). Results The S-NAQ cut-off points obtained were ≥12 and ≥16 when using occasional and frequent bullying as reference standards, respectively. Both cut-off points showed high classification...
Considerations for reference pump curves
International Nuclear Information System (INIS)
Stockton, N.B.
1992-01-01
This paper examines problems associated with inservice testing (IST) of pumps to assess their hydraulic performance using reference pump curves to establish acceptance criteria. Safety-related pumps at nuclear power plants are tested under the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (the Code), Section 11. The Code requires testing pumps at specific reference points of differential pressure or flow rate that can be readily duplicated during subsequent tests. There are many cases where test conditions cannot be duplicated. For some pumps, such as service water or component cooling pumps, the flow rate at any time depends on plant conditions and the arrangement of multiple independent and constantly changing loads. System conditions cannot be controlled to duplicate a specific reference value. In these cases, utilities frequently request to use pump curves for comparison of test data for acceptance. There is no prescribed method for developing a pump reference curve. The methods vary and may yield substantially different results. Some results are conservative when compared to the Code requirements; some are not. The errors associated with different curve testing techniques should be understood and controlled within reasonable bounds. Manufacturer's pump curves, in general, are not sufficiently accurate to use as reference pump curves for IST. Testing using reference curves generated with polynomial least squares fits over limited ranges of pump operation, cubic spline interpolation, or cubic spline least squares fits can provide a measure of pump hydraulic performance that is at least as accurate as the Code required method. Regardless of the test method, error can be reduced by using more accurate instruments, by correcting for systematic errors, by increasing the number of data points, and by taking repetitive measurements at each data point
Multiphasic growth curve analysis.
Koops, W.J.
1986-01-01
Application of a multiphasic growth curve is demonstrated with 4 data sets, adopted from literature. The growth curve used is a summation of n logistic growth functions. Human height growth curves of this type are known as "double logistic" (n = 2) and "triple logistic" (n = 3) growth curves (Bock
Retrograde curves of solidus and solubility
International Nuclear Information System (INIS)
Vasil'ev, M.V.
1979-01-01
The investigation was concerned with the constitutional diagrams of the eutectic type with ''retrograde solidus'' and ''retrograde solubility curve'' which must be considered as diagrams with degenerate monotectic transformation. The solidus and the solubility curves form a retrograde curve with a common retrograde point representing the solubility maximum. The two branches of the Aetrograde curve can be described with the aid of two similar equations. Presented are corresponding equations for the Cd-Zn system and shown is the possibility of predicting the run of the solubility curve
Cut-off point of body mass index for malnutrition screening in end stage lung disease
Directory of Open Access Journals (Sweden)
R. Sadegh
2015-10-01
Full Text Available Background: Malnutrition is one of the serious complications in end stage lung disease that affects quality of life, mortality rate and lung transplantation outcome. Objective: The aim of this was to determine the cut-off point of body mass index (BMI for malnutrition screening in end stage lung disease. Methods: This cross-sectional study was conducted in 86 patients referred to the lung transplant clinic of Masih Daneshvari Hospital from July 2012 to February 2013. Nutritional status was evaluated using anthropometric measurements including Mid-Arm Muscle Circumference (MAMC, Triceps Skinfold (TSF, BMI, and Fat-Free Mass Index (FFMI. With ROC curve analysis, the cut-off point of BMI for diagnosis of patients with MAMC and SFT<25% and FFMI<5% of normal range was determined. Data were analyzed using Chi-square test and T-test. Findings: Mean age was 36.7±13.73. Mean BMI was 21.1±5.12 kg/m2, mean TSF was 11.76±7.79 mm, mean MAMC was 21.41±3.93 cm2, and mean FFMI was 16.69±2.35 kg/m2. Twenty eight patients (32.6% had FFMI<5% and MAMC and SFT<25% of normal range. In ROC curve analysis, the cut-off point of BMI for malnutrition was 19.4 kg/m2 with sensitivity of 0.844, specificity of 0.842, Youden Index of 0.686 and Shortest distance from the point (0, 1 of 0.0493. Conclusion: With regards to the results, it seems that the cut-off point of BMI for malnutrition screening is 19.4 kg/m2 in patients with end stage lung disease.
Directory of Open Access Journals (Sweden)
tayebeh Rezaie nasab
2013-02-01
Results: In this study, cut-off point was calculated as 6.5%, sensitivity as 55.8%, characteristic as 81.2%, and the area under the Roc curve as 0.69. Moreover, positive predictive value, negative predictive value and efficiency were 95.08%, 22.03%, and 59.17%, respectively. Conclusion: Results of this study revealed that Bender Gestalt Test is relatively weak in diagnosis of mild TBI. Hence, its characteristic is high and it was successful in diagnosing healthy individuals.
Rudi, Katharina; Ho, Franz Y.; Gilsbach, Bernd K.; Pots, Henderikus; Wittinghofer, Alfred; Kortholt, Arjan; Klare, Johann P.
2015-01-01
Ras of complex proteins (Roc) is a Ras-like GTP-binding domain that always occurs in tandem with the C-terminal of Roc (COR) domain and is found in bacteria, plants and animals. Recently, it has been shown that Roco proteins belong to the family of G-proteins activated by nucleotide (nt)-dependent dimerization (GADs). We investigated the RocCOR tandem from the bacteria Chlorobium tepidum with site-directed spin labelling and pulse EPR distance measurements to follow conformational changes during the Roco G-protein cycle. Our results confirm that the COR domains are a stable dimerization device serving as a scaffold for the Roc domains that, in contrast, are structurally heterogeneous and dynamic entities. Contrary to other GAD proteins, we observed only minor structural alterations upon binding and hydrolysis of GTP, indicating significant mechanistic variations within this protein class. Mutations in the most prominent member of the Roco family of proteins, leucine-rich repeat (LRR) kinase 2 (LRRK2), are the most frequent cause of late-onset Parkinson's disease (PD). Using a stable recombinant LRRK2 Roc-COR-kinase fragment we obtained detailed kinetic data for the G-protein cycle. Our data confirmed that dimerization is essential for efficient GTP hydrolysis and PD mutations in the Roc domain result in decreased GTPase activity. Previous data have shown that these LRRK2 PD-mutations are located in the interface between Roc and COR. Importantly, analogous mutations in the conserved C. tepidum Roc/COR interface significantly influence the structure and nt-induced conformational changes of the Roc domains. PMID:26310572
ROCS: a Reproducibility Index and Confidence Score for Interaction Proteomics Studies
Directory of Open Access Journals (Sweden)
Dazard Jean-Eudes
2012-06-01
Full Text Available Abstract Background Affinity-Purification Mass-Spectrometry (AP-MS provides a powerful means of identifying protein complexes and interactions. Several important challenges exist in interpreting the results of AP-MS experiments. First, the reproducibility of AP-MS experimental replicates can be low, due both to technical variability and the dynamic nature of protein interactions in the cell. Second, the identification of true protein-protein interactions in AP-MS experiments is subject to inaccuracy due to high false negative and false positive rates. Several experimental approaches can be used to mitigate these drawbacks, including the use of replicated and control experiments and relative quantification to sensitively distinguish true interacting proteins from false ones. Methods To address the issues of reproducibility and accuracy of protein-protein interactions, we introduce a two-step method, called ROCS, which makes use of Indicator Prey Proteins to select reproducible AP-MS experiments, and of Confidence Scores to select specific protein-protein interactions. The Indicator Prey Proteins account for measures of protein identifiability as well as protein reproducibility, effectively allowing removal of outlier experiments that contribute noise and affect downstream inferences. The filtered set of experiments is then used in the Protein-Protein Interaction (PPI scoring step. Prey protein scoring is done by computing a Confidence Score, which accounts for the probability of occurrence of prey proteins in the bait experiments relative to the control experiment, where the significance cutoff parameter is estimated by simultaneously controlling false positives and false negatives against metrics of false discovery rate and biological coherence respectively. In summary, the ROCS method relies on automatic objective criterions for parameter estimation and error-controlled procedures. Results We illustrate the performance of our method by applying
Method of construction spatial transition curve
Directory of Open Access Journals (Sweden)
S.V. Didanov
2013-04-01
Full Text Available Purpose. The movement of rail transport (speed rolling stock, traffic safety, etc. is largely dependent on the quality of the track. In this case, a special role is the transition curve, which ensures smooth insertion of the transition from linear to circular section of road. The article deals with modeling of spatial transition curve based on the parabolic distribution of the curvature and torsion. This is a continuation of research conducted by the authors regarding the spatial modeling of curved contours. Methodology. Construction of the spatial transition curve is numerical methods for solving nonlinear integral equations, where the initial data are taken coordinate the starting and ending points of the curve of the future, and the inclination of the tangent and the deviation of the curve from the tangent plane at these points. System solutions for the numerical method are the partial derivatives of the equations of the unknown parameters of the law of change of torsion and length of the transition curve. Findings. The parametric equations of the spatial transition curve are calculated by finding the unknown coefficients of the parabolic distribution of the curvature and torsion, as well as the spatial length of the transition curve. Originality. A method for constructing the spatial transition curve is devised, and based on this software geometric modeling spatial transition curves of railway track with specified deviations of the curve from the tangent plane. Practical value. The resulting curve can be applied in any sector of the economy, where it is necessary to ensure a smooth transition from linear to circular section of the curved space bypass. An example is the transition curve in the construction of the railway line, road, pipe, profile, flat section of the working blades of the turbine and compressor, the ship, plane, car, etc.
DEFF Research Database (Denmark)
Brücker, Herbert; Jahn, Elke J.
Based on a wage curve approach we examine the labor market effects of migration in Germany. The wage curve relies on the assumption that wages respond to a change in the unemployment rate, albeit imperfectly. This allows one to derive the wage and employment effects of migration simultaneously...... with a vocational degree. The wage and employment effects of migration are moderate: a 1 percent increase in the German labor force through immigration increases the aggregate unemployment rate by less than 0.1 percentage points and reduces average wages by less 0.1 percent. While native workers benefit from...... increased wages and lower unemployment, foreign workers are adversely affected....
Morse theory on timelike and causal curves
International Nuclear Information System (INIS)
Everson, J.; Talbot, C.J.
1976-01-01
It is shown that the set of timelike curves in a globally hyperbolic space-time manifold can be given the structure of a Hilbert manifold under a suitable definition of 'timelike.' The causal curves are the topological closure of this manifold. The Lorentzian energy (corresponding to Milnor's energy, except that the Lorentzian inner product is used) is shown to be a Morse function for the space of causal curves. A fixed end point index theorem is obtained in which a lower bound for the index of the Hessian of the Lorentzian energy is given in terms of the sum of the orders of the conjugate points between the end points. (author)
Evaluation of the water retention curve of Abidjan Quaternary aquifer ...
African Journals Online (AJOL)
Methods and Results: The water retention curve is difficult to measure in situ on large sites like this aquifer. Kovac's modified model to predict the water retention curve is tested. Predicted curves are compared with in situ measurements points. The results show that, overall, the model predicts well the water retention curves.
Item strength influences source confidence and alters source memory zROC slopes.
Starns, Jeffrey J; Ksander, John C
2016-03-01
Increasing the number of study trials creates a crossover pattern in source memory zROC slopes; that is, the slope is either below or above 1 depending on which source receives stronger learning. This pattern can be produced if additional learning affects memory processes such as the relative contribution of recollection and familiarity to source performance. However, the pattern can also be produced by decision processes if participants are more willing to make high-confidence source judgments when they are more confident that the test item was studied. We explored the role of memory and decision processes by comparing performance across 3 conditions: (a) words seen once with a male or female face (no repetition), (b) words seen once with a face after being presented twice with a picture of either a bird or a fish (different-source repetition), and (c) words seen 3 times with the same face (same-source repetition). zROC functions for the male-female decision showed that different-source repetition produced the same crossover effect as same-source repetition. This pattern was predicted by the decision process account, because it assumes that increasing item memory affects source confidence ratings even if source memory is not improved. Also supporting this account, we found a strong positive relationship between recognition confidence and source confidence even when analyses were limited to items that were attributed to the incorrect source or items that were not studied in either source. (c) 2016 APA, all rights reserved).
Youngstrom, Eric A
2014-03-01
To offer a practical demonstration of receiver operating characteristic (ROC) analyses, diagnostic efficiency statistics, and their application to clinical decision making using a popular parent checklist to assess for potential mood disorder. Secondary analyses of data from 589 families seeking outpatient mental health services, completing the Child Behavior Checklist and semi-structured diagnostic interviews. Internalizing Problems raw scores discriminated mood disorders significantly better than did age- and gender-normed T scores, or an Affective Problems score. Internalizing scores 30 had a diagnostic likelihood ratio of 7.4. This study illustrates a series of steps in defining a clinical problem, operationalizing it, selecting a valid study design, and using ROC analyses to generate statistics that support clinical decisions. The ROC framework offers important advantages for clinical interpretation. Appendices include sample scripts using SPSS and R to check assumptions and conduct ROC analyses.
A Mean Value Formula for Elliptic Curves
Directory of Open Access Journals (Sweden)
Rongquan Feng
2014-01-01
Full Text Available It is proved in this paper that, for any point on an elliptic curve, the mean value of x-coordinates of its n-division points is the same as its x-coordinate and that of y-coordinates of its n-division points is n times that of its y-coordinate.
Directory of Open Access Journals (Sweden)
Janusz Charatonik
1991-11-01
Full Text Available Results concerning contractibility of curves (equivalently: of dendroids are collected and discussed in the paper. Interrelations tetween various conditions which are either sufficient or necessary for a curve to be contractible are studied.
Indian Academy of Sciences (India)
Institute, Calcutta. Apart from mathematics, he likes painting and reading. Unlike most others he dislikes computers. Ritabrata Munshi. Introduction. In this two-part article we will consider one of the classi- cal theorems of mathematics, the Jordan curve theorem. It states that a simple closed curve (i.e., a closed curve which.
Automorphisms of double coverings of curves
International Nuclear Information System (INIS)
Torres, F.
1994-11-01
We study automorphisms of curves that commute with each other. We prove that the order and the number of fixed points of one of them satisfy certain relations involving those of the other. Then, we specialize our results to the case of double coverings of curves. For instance, if the genus of the curve is at least 4γ + 2 and γ >= 1 (γ = the genus of the covered curve) we prove that the order of an automorphism is bounded above by 2γ + 1 (resp. 4γ + 2) provided it is prime (resp. it has at least five fixed points). We also improve Farkas' bound on the number of fixed points namely 4γ + 4 by showing that it involves the order of the automorphism except in the case of even order when such an improvement is obtained provided the automorphism and the γ-involution has at least one common fixed point. (author). 15 refs
Curves along which plane waves can interfere
Energy Technology Data Exchange (ETDEWEB)
Karp, S.N.; Machover, M.
1977-07-01
Partial results are given on a conjecture in inverse scattering theory concerning the interference of two-dimensional plane waves. The conjecture states that an odd number of plane waves of the same frequency can only cancel each other at isolated points and not along a simple continuous curve. It is partially confirmed here for curves which are nearly flat at some point. An analysis is also made for various possible nodes for an even number of plane waves.
MICA: Multiple interval-based curve alignment
Mann, Martin; Kahle, Hans-Peter; Beck, Matthias; Bender, Bela Johannes; Spiecker, Heinrich; Backofen, Rolf
2018-01-01
MICA enables the automatic synchronization of discrete data curves. To this end, characteristic points of the curves' shapes are identified. These landmarks are used within a heuristic curve registration approach to align profile pairs by mapping similar characteristics onto each other. In combination with a progressive alignment scheme, this enables the computation of multiple curve alignments. Multiple curve alignments are needed to derive meaningful representative consensus data of measured time or data series. MICA was already successfully applied to generate representative profiles of tree growth data based on intra-annual wood density profiles or cell formation data. The MICA package provides a command-line and graphical user interface. The R interface enables the direct embedding of multiple curve alignment computation into larger analyses pipelines. Source code, binaries and documentation are freely available at https://github.com/BackofenLab/MICA
Sun, Yuhang; Wang, Bo; Shu, Shi; Zhang, Hongyou; Xu, Chuang; Wu, Ling; Xia, Cheng
2015-01-01
Fatty liver syndrome and ketosis are important metabolic disorders in high-producing cows during early lactation with fatty liver usually preceding ketosis. To date, parameters for early prediction of the risk of ketosis have not been investigated in China. To determine the predictive value of some parameters on the risk of ketosis in China. In a descriptive study, 48 control and 32 ketotic Holstein Friesian cows were randomly selected from one farm with a serum β-hydroxybutyrate (BHBA) concentration of 1.20 mmol/L as cutoff point. The risk prediction thresholds for ketosis were determined by receiver operating characteristic (ROC) analysis. In line with a high BHBA concentration, blood glucose concentration was significantly lower in ketotic cows compared to control animals (2.77 ± 0.24 versus 3.34 ± 0.03 mmol/L; P = 0.02). Thresholds were more than 0.76 mmol/L for nonesterified fatty acids (NEFA, with 65% sensitivity and 92% specificity), more than 104 U/L for aspartate aminotransferase (AST, 74% and 85%, respectively), less than 140 U/L for cholinesterase (CHE, 75% and 59%, respectively), and more than 3.3 µmol/L for total bilirubin (TBIL, 58% and 83%, respectively). There were significant correlations between BHBA and glucose (R = -4.74), or CHE (R = -0.262), BHBA and NEFA (R = 0.520), or AST (R = 0.525), or TBIL (R = 0.278), or direct bilirubin (DBIL, R = 0.348). AST, CHE, TBIL and NEFA may be useful parameters for risk prediction of ketosis. This study might be of value in addressing novel directions for future research on the connection between ketosis and liver dysfunction.
Directory of Open Access Journals (Sweden)
Farheen Fatima
Full Text Available ABSTRACT Introduction: Differential diagnosis of skeletal and dental relationships is crucial for planning orthodontic treatment. Overbite depth indicator (ODI and anteroposterior dysplasia indicator (APDI had been introduced in the past for assessment of vertical and sagittal jaw relationships, respectively. Objective: The objectives of this study were to evaluate the reliability of ODI and APDI in overbite and Angle malocclusions, as well as assess their diagnostic reliability among males and females of different age groups. Material and Methods: This study was conducted using pretreatment dental casts and lateral cephalograms of 90 subjects. For ODI, subjects were divided into three groups based on overbite (normal overbite, open bite and deep bite. Likewise, the same subjects were divided for APDI into three groups, based on Angle's malocclusion classification (dental Class I, II and III malocclusions. Mann-Whitney U test was applied for comparison of study parameters regarding sex and different age groups. The mean values of ODI and APDI were compared among study groups by means of Kruskal-Wallis and post-hoc Dunnet T3 tests. The receiver operating characteristic (ROC curve was applied to test diagnostic reliability. Results: Insignificant differences were found for ODI and APDI angles, particularly in regards to sex and age. Significant intergroup differences were found in different overbite groups and Angle's classification for ODI and APDI, respectively (p < 0.001. ROC showed 91% and 88% constancy with dental pattern in ODI and APDI, respectively. Conclusions: ODI can reliably differentiate deep bite versus normal overbite and deep bite versus open bite. APDI can reliably differentiate dental Class I, II and III malocclusions.
DEFF Research Database (Denmark)
Gardner, Ian A.; Greiner, Matthias
2006-01-01
Receiver-operating characteristic (ROC) curves provide a cutoff-independent method for the evaluation of continuous or ordinal tests used in clinical pathology laboratories. The area under the curve is a useful overall measure of test accuracy and can be used to compare different tests (or differ...
Chan, Heang-Ping; Goodsitt, Mitch M.; Helvie, Mark A.; Hadjiiski, Lubomir M.; Lydick, Justin T.; Roubidoux, Marilyn A.; Bailey, Janet E.; Nees, Alexis; Blane, Caroline E.; Shen, Joseph; Foster, Michelle; Sahiner, Berkman
2004-05-01
An ROC study was conducted to evaluate the usefulness of assessing breast lesion characteristics with stereomammography. Stereoscopic image pairs of 158 breast biopsy tissue specimens were acquired with a GE digital mammography system. Two stereo image pairs were taken at 1.8X magnification geometry and at approximately orthogonal orientations for each specimen. Display software was developed for a high resolution MegaScan CRT monitor driven by a DOME stereo display board. The specimens contained either a mass, microcalcifications, both, or normal tissue. About 40% of the specimens were found to contain malignancy by pathological analysis. Five MQSA radiologists participated in the observer performance experiment. The two views of each specimen were read independently and were separated by a large number of other specimen images to reduce any effects of memorization. Each observer read 316 specimen images in a systematically randomized order. The observer first read the monoscopic image and entered his/her assessment in terms of the confidence ratings on the presence of microcalcifications and/or masses, margin clearance, BI-RADS assessment, and the likelihood of malignancy. The corresponding stereoscopic images were then displayed on the same monitor and were viewed through stereoscopic LCD glasses. The observer was free to change the ratings in every category after stereoscopic reading. The ratings of the observers were analyzed by ROC methodology. For the 5 MQSA radiologists, the average Az value for estimation of the likelihood of malignancy of the lesions improved from 0.70 for monoscopic viewing to 0.72 (p<0.05) after stereoscopic viewing, and the average Az value for the presence of microcalcifications improved from 0.94 to 0.95 (p<0.05). The Az value for the presence of masses improved from 0.80 to 0.82 after stereoscopic viewing, but the difference fell short of statistical significance (p=0.08). The visual assessment of margin clearance was found to have
Indian Academy of Sciences (India)
mathematics and computer applications for the last 20 years. He has been a National Science. Talent awardee of. NCERT in mathematics. GENERAL I ARTICLE. Space-filling Curves. ReMittal. In this article some Peano curves are exhibited and some of their recent applications are dis- cussed. A C++ program to draw the ...
Simulating Supernova Light Curves
Energy Technology Data Exchange (ETDEWEB)
Even, Wesley Paul [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dolence, Joshua C. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2016-05-05
This report discusses supernova light simulations. A brief review of supernovae, basics of supernova light curves, simulation tools used at LANL, and supernova results are included. Further, it happens that many of the same methods used to generate simulated supernova light curves can also be used to model the emission from fireballs generated by explosions in the earth’s atmosphere.
Tempo curves considered harmful
Desain, P.; Honing, H.
1993-01-01
In the literature of musicology, computer music research and the psychology of music, timing or tempo measurements are mostly presented in the form of continuous curves. The notion of these tempo curves is dangerous, despite its widespread use, because it lulls its users into the false impression
DEFF Research Database (Denmark)
Federici, Paolo; Georgieva Yankova, Ginka
The report describes power curve measurements carried out on a given wind turbine. The measurements are carried out in accordance to a draft of IEC 61400-12-1 Ed.2.......The report describes power curve measurements carried out on a given wind turbine. The measurements are carried out in accordance to a draft of IEC 61400-12-1 Ed.2....
Invariance for Single Curved Manifold
Castro, Pedro Machado Manhaes de
2012-08-01
Recently, it has been shown that, for Lambert illumination model, solely scenes composed by developable objects with a very particular albedo distribution produce an (2D) image with isolines that are (almost) invariant to light direction change. In this work, we provide and investigate a more general framework, and we show that, in general, the requirement for such in variances is quite strong, and is related to the differential geometry of the objects. More precisely, it is proved that single curved manifolds, i.e., manifolds such that at each point there is at most one principal curvature direction, produce invariant is surfaces for a certain relevant family of energy functions. In the three-dimensional case, the associated energy function corresponds to the classical Lambert illumination model with albedo. This result is also extended for finite-dimensional scenes composed by single curved objects. © 2012 IEEE.
ROC-based determination of the number of clusters for fMRI activation detection
Jahanian, Hesamoddin; Soltanian-Zadeh, Hamid; Hossein-Zadeh, Gholam A.; Siadat, Mohammad-Reza
2004-05-01
Fuzzy C-means (FCM), in spite of its potent advantages in exploratory analyze of functional magnetic resonance imaging (fMRI), suffers from limitations such as a priori determination of number of clusters, unknown statistical significance for the results, and instability of the results when it is applied on raw fMRI time series. Choosing different number of clusters, or thresholding the membership degree at different levels, lead to considerably different activation maps. However, research work for finding a standard index to determine the number of clusters has not yet succeeded. Using randomization, we developed a method to control false positive rate in FCM, which gives a meaningful statistical significance to the results. Making use of this novel method and an ROC-based cluster validity measure, we determined the optimal number of clusters. In this study, we applied the FCM on a feature space that takes the variability of hemodynamic response function into account (HRF-based feature space). The proposed method found the accurate number of clusters in simulated fMRI data. In addition, the proposed method generated excellent results for experimental fMRI data and showed a good reproducibility for determining the number of clusters.
An ROC study detecting ability of idiopathic pulmonary fibrosis using digital radiography
International Nuclear Information System (INIS)
Chung, Eun Chul; Im, Jung Gi; Han, Man Chung; Kim, Jong Hyo
1991-01-01
One potential advantage of the digital radiography system is its ability to enhance image quality by various types of processing. Digital unsharp masking is one of the simplest and most useful forms of enhancing processes. The efficacy of unsharp masking in radiological diagnosis has not been investigated thoroughly. To evaluate the effects of unsharp masking in film-digital chest images, 3 observers were shown 150 test radiographs. These test radiographs consisted of 50 unprocessed images (25 normals and 25 patients with idiopathic pulmonary fibrosis with honey combing) and their 100 processed images by using 450 and 15-sized masks respectively. An ROC analysis of these data suggests that unsharp masking is more effective in detecting idiopathic pulmonary fibrosis than unprocessed image (ρ < 0.05), and so it may improve diagnostic accuracy for interstitial fibrosis. In addition, the smaller mask size (15) is more effective than the larger one (mask size 45) (ρ < 0.05). By using this analytic approach, an optimal parameter in digital chest radiography may be investigated in many other forms of pulmonary disease such as pulmonary nodule or mediastinal mass
International Nuclear Information System (INIS)
Lee, Kyung Han; Choi, Yoon Ho; Lee, Bum Woo; Moon, Dae Hyuk; Chung, June Key; Lee, Myung Chul; Koh, Chang Soon; Koong, Sung Soo
1989-01-01
Visual assessment of regional wall motion abnormality (RWMA) by gated blood pol scan (GBPS) serves as an useful parameter in thc diagnosis, functional evaluation, and follow up in various clinical settings, but are still subject to some inherent limitations. On important problem may be the interobserver as well as intraobsever variation that may well be present due to the subjective nature of the interpretations. This study was carried out to determine the reliability and reproducibility of visual assessments made in GBPSs, and to observe the degree to which the results would be influenced by observer variation. Fifty two patients with coronary heart disease had resting GBPS and contrast ventriculography within 4 days apart. Contrast ventriculography showed normal wall motion in 6 patients and the remaining 46 had RWMA in one or more segments. The anterior and left anterolateral views of all 52 GBPSs were analyzed by three independent observers, who selected from 5 scales, their level of confidence that there was RWMA in that segment. Receiver operating characteristic (ROC) curves for each analysis was plotted and the area under the curve (θ) was used as a parameter representing each observer's performance in his interpretations. The findings of contract ventriculographies were used as the standard for RWMA. The apical and inferoapical segments showed the best correlation with contrast ventriculography (θ=0.90-.094, 0.81-0.94, respectively), and the inferior wall showed the poorest correlation (θ=0.70-0.74). The interpretations of the inferior, septal, apical and posteroinferior, segments showed no difference between the observers, but there was significantly better performance in assessment by observer A compared to that by B or C for the anterolateral segments (θ=0.87, 0.78, 0.76, respectively, p<0.01 for A vs B, p<0,05 for A vs C), as well as when all segments were considered altogether (θ=0,88, 0.83, 0.82, respectively, both p<0 05). This was also true for
Energy Technology Data Exchange (ETDEWEB)
Halligan, Steve [University College London, Centre for Medical Imaging, University College Hospital, London (United Kingdom); Altman, Douglas G. [University of Oxford, Centre for Statistics in Medicine, Oxford (United Kingdom); Mallett, Susan [University of Oxford, Department of Primary Care Health Sciences, Oxford (United Kingdom)
2015-04-01
The objectives are to describe the disadvantages of the area under the receiver operating characteristic curve (ROC AUC) to measure diagnostic test performance and to propose an alternative based on net benefit. We use a narrative review supplemented by data from a study of computer-assisted detection for CT colonography. We identified problems with ROC AUC. Confidence scoring by readers was highly non-normal, and score distribution was bimodal. Consequently, ROC curves were highly extrapolated with AUC mostly dependent on areas without patient data. AUC depended on the method used for curve fitting. ROC AUC does not account for prevalence or different misclassification costs arising from false-negative and false-positive diagnoses. Change in ROC AUC has little direct clinical meaning for clinicians. An alternative analysis based on net benefit is proposed, based on the change in sensitivity and specificity at clinically relevant thresholds. Net benefit incorporates estimates of prevalence and misclassification costs, and it is clinically interpretable since it reflects changes in correct and incorrect diagnoses when a new diagnostic test is introduced. ROC AUC is most useful in the early stages of test assessment whereas methods based on net benefit are more useful to assess radiological tests where the clinical context is known. Net benefit is more useful for assessing clinical impact. (orig.)
Directory of Open Access Journals (Sweden)
Fátima Higuera-de la Tijera
2014-10-01
Conclusions: The development of HE is the main factor associated to early mortality. Coexistence of cirrhosis is a factor that worsen the prognosis. Lille score is the most accurate for predict early mortality.
On the Quaternionic Focal Curves
Directory of Open Access Journals (Sweden)
Nurten (BAYRAK GÜRSES
2017-06-01
Full Text Available In this study, a brief summary about quaternions and quaternionic curves are firstly presented. Also, the definition of focal curve is given. The focal curve of a smooth curve consists of the centers of its osculating hypersphere. By using this definition and the quaternionic osculating hyperspheres of these curves, the quaternionic focal curves in the spaces $\\Q$ and $\\Q_\
Wrist Acceleration Cut Points for Moderate-to-Vigorous Physical Activity in Youth.
Okely, Anthony D; Batterham, Marijka J; Hinkley, Trina; Ekelund, Ulf; Brage, Søren; Reilly, John J; Trost, Stewart G; Jones, Rachel A; Janssen, Xanne; Cliff, Dylan P; VAN Loo, Christiana Maria Theodora
2018-03-01
This study aimed to examine the validity of wrist acceleration cut points for classifying moderate (MPA), vigorous (VPA), and moderate-to-vigorous (MVPA) physical activity. Fifty-seven children (5-12 yr) completed 15 semistructured activities. Three sets of wrist cut points (>192 mg, >250 mg, and >314 mg), previously developed using Euclidian norm minus one (ENMO192+), GENEActiv software (GENEA250+), and band-pass filter followed by Euclidian norm (BFEN314+), were evaluated against indirect calorimetry. Analyses included classification accuracy, equivalence testing, and Bland-Altman procedures. All cut points classified MPA, VPA, and MVPA with substantial accuracy (ENMO192+: κ = 0.72 [95% confidence interval = 0.72-0.73], MVPA: area under the receiver operating characteristic curve (ROC-AUC) = 0.85 [0.85-0.86]; GENEA250+: κ = 0.75 [0.74-0.76], MVPA: ROC-AUC = 0.85 [0.85-0.86]; BFEN314+: κ = 0.73 [0.72-0.74], MVPA: ROC-AUC = 0.86 [0.86-0.87]). BFEN314+ misclassified 19.7% non-MVPA epochs as MPA, whereas ENMO192+ and GENEA250+ misclassified 32.6% and 26.5% of MPA epochs as non-MVPA, respectively. Group estimates of MPA time were equivalent (P < 0.01) to indirect calorimetry for the BFEN314+ MPA cut point (mean bias = -1.5%, limits of agreement [LoA] = -57.5% to 60.6%), whereas estimates of MVPA time were equivalent (P < 0.01) to indirect calorimetry for the ENMO192+ (mean bias = -1.1%, LoA = -53.7% to 55.9%) and GENEA250+ (mean bias = 2.2%, LoA = -56.5% to 52.2%) cut points. Individual variability (LoA) was large for MPA (min: BFEN314+, -60.6% to 57.5%; max: GENEA250+, -42.0% to 104.1%), VPA (min: BFEN314+, -238.9% to 54.6%; max: ENMO192+, -244.5% to 127.4%), and MVPA (min: ENMO192+, -53.7% to 55.0%; max: BFEN314+, -83.9% to 25.3%). Wrist acceleration cut points misclassified a considerable proportion of non-MVPA and MVPA. Group-level estimates of MVPA were acceptable; however, error for individual-level prediction was larger.
Directory of Open Access Journals (Sweden)
Paulo Prochno
2004-07-01
Full Text Available Learning curves have been studied for a long time. These studies provided strong support to the hypothesis that, as organizations produce more of a product, unit costs of production decrease at a decreasing rate (see Argote, 1999 for a comprehensive review of learning curve studies. But the organizational mechanisms that lead to these results are still underexplored. We know some drivers of learning curves (ADLER; CLARK, 1991; LAPRE et al., 2000, but we still lack a more detailed view of the organizational processes behind those curves. Through an ethnographic study, I bring a comprehensive account of the first year of operations of a new automotive plant, describing what was taking place on in the assembly area during the most relevant shifts of the learning curve. The emphasis is then on how learning occurs in that setting. My analysis suggests that the overall learning curve is in fact the result of an integration process that puts together several individual ongoing learning curves in different areas throughout the organization. In the end, I propose a model to understand the evolution of these learning processes and their supporting organizational mechanisms.
Deformation Based Curved Shape Representation.
Demisse, Girum G; Aouada, Djamila; Ottersten, Bjorn
2017-06-02
In this paper, we introduce a deformation based representation space for curved shapes in Rn. Given an ordered set of points sampled from a curved shape, the proposed method represents the set as an element of a finite dimensional matrix Lie group. Variation due to scale and location are filtered in a preprocessing stage, while shapes that vary only in rotation are identified by an equivalence relationship. The use of a finite dimensional matrix Lie group leads to a similarity metric with an explicit geodesic solution. Subsequently, we discuss some of the properties of the metric and its relationship with a deformation by least action. Furthermore, invariance to reparametrization or estimation of point correspondence between shapes is formulated as an estimation of sampling function. Thereafter, two possible approaches are presented to solve the point correspondence estimation problem. Finally, we propose an adaptation of k-means clustering for shape analysis in the proposed representation space. Experimental results show that the proposed representation is robust to uninformative cues, e.g. local shape perturbation and displacement. In comparison to state of the art methods, it achieves a high precision on the Swedish and the Flavia leaf datasets and a comparable result on MPEG-7, Kimia99 and Kimia216 datasets.
Quaternion orders, quadratic forms, and Shimura curves
Alsina, Montserrat
2004-01-01
Shimura curves are a far-reaching generalization of the classical modular curves. They lie at the crossroads of many areas, including complex analysis, hyperbolic geometry, algebraic geometry, algebra, and arithmetic. The text provides an introduction to the subject from a theoretic and algorithmic perspective. The main topics covered in it are Shimura curves defined over the rational number field, the construction of their fundamental domains, and the determination of their complex multiplication points. The study of complex multiplication points in Shimura curves leads to the study of families of binary quadratic forms with algebraic coefficients and to their classification by arithmetic Fuchsian groups. In this regard, the authors develop a theory full of new possibilities which parallels Gauss' theory on the classification of binary quadratic forms with integral coefficients by the action of the modular group. Each topic covered in the book begins with a theoretical discussion followed by carefully worked...
Deyaert, Egon; Kortholt, Arjan; Versées, Wim
2017-09-01
Roco proteins are characterized by the presence of a Roc-COR supradomain harbouring GTPase activity, which is often preceded by an LRR domain. The most notorious member of the Roco protein family is the Parkinson's disease-associated LRRK2. The Roco protein from the bacterium Chlorobium tepidum has been used as a model system to investigate the structure and mechanism of this class of enzymes. Here, the crystallization and crystallographic analysis of the LRR-Roc-COR construct of the C. tepidum Roco protein is reported. The LRR-Roc-COR crystals belonged to space group P2 1 2 1 2 1 , with unit-cell parameters a = 95.6, b = 129.8, c = 179.5 Å, α = β = γ = 90°, and diffracted to a resolution of 3.3 Å. Based on the calculated Matthews coefficient, Patterson map analysis and an initial molecular-replacement analysis, one protein dimer is present in the asymmetric unit. The crystal structure of this protein will provide valuable insights into the interaction between the Roc-COR and LRR domains within Roco proteins.
Terluin, B.; Eekhout, I.; Terwee, C.B.; de Vet, H.C.W.
2015-01-01
Objectives To present a new method to estimate a "minimal important change" (MIC) of health-related quality of life (HRQOL) scales, based on predictive modeling, and to compare its performance with the MIC based on receiver operating characteristic (ROC) analysis. To illustrate how the new method
Verified Indifferentiable Hashing into Elliptic Curves
Barthe, Gilles; Grégoire, Benjamin; Heraud, Sylvain; Olmedo, Federico; Zanella-Béguelin, Santiago
2012-01-01
International audience; Many cryptographic systems based on elliptic curves are proven secure in the Random Oracle Model, assuming there exist probabilistic functions that map elements in some domain (e.g. bitstrings) onto uniformly and independently distributed points in a curve. When implementing such systems, and in order for the proof to carry over to the implementation, those mappings must be instantiated with concrete constructions whose behavior does not deviate significantly from rand...
Lightlike contractions in curved spacetime
International Nuclear Information System (INIS)
Aichelburg, P.C.; Embacher, F.
1984-01-01
The technique of lightlike contractions in flat and curved space is described. The method consists in boosting a classical field configuration to the velocity of light by an appropriate generalized Lorentz transformation. Within this framework the gravitational field of a massless neutral particle is a meaningful concept. For electrically charged particles, however, the field equations seem to prevent an analogous procedure. We thus conjecture that general relativity forbids the existance of charged point particles moving with the velocity of light. Further examples for lightlike contractions of a self-dual electromagnetic field and of a linearized Rarita-Schwinger (spin-3/2) field are given. (Author)
U.S. Environmental Protection Agency — an UV calibration curve for SRHA quantitation. This dataset is associated with the following publication: Chang, X., and D. Bouchard. Surfactant-Wrapped Multiwalled...
Directory of Open Access Journals (Sweden)
Kožul Nataša
2014-01-01
Full Text Available In the broadest sense, yield curve indicates the market's view of the evolution of interest rates over time. However, given that cost of borrowing it closely linked to creditworthiness (ability to repay, different yield curves will apply to different currencies, market sectors, or even individual issuers. As government borrowing is indicative of interest rate levels available to other market players in a particular country, and considering that bond issuance still remains the dominant form of sovereign debt, this paper describes yield curve construction using bonds. The relationship between zero-coupon yield, par yield and yield to maturity is given and their usage in determining curve discount factors is described. Their usage in deriving forward rates and pricing related derivative instruments is also discussed.
Replication and Analysis of Ebbinghaus' Forgetting Curve.
Murre, Jaap M J; Dros, Joeri
2015-01-01
We present a successful replication of Ebbinghaus' classic forgetting curve from 1880 based on the method of savings. One subject spent 70 hours learning lists and relearning them after 20 min, 1 hour, 9 hours, 1 day, 2 days, or 31 days. The results are similar to Ebbinghaus' original data. We analyze the effects of serial position on forgetting and investigate what mathematical equations present a good fit to the Ebbinghaus forgetting curve and its replications. We conclude that the Ebbinghaus forgetting curve has indeed been replicated and that it is not completely smooth but most probably shows a jump upwards starting at the 24 hour data point.
Replication and Analysis of Ebbinghaus’ Forgetting Curve
Murre, Jaap M. J.; Dros, Joeri
2015-01-01
We present a successful replication of Ebbinghaus’ classic forgetting curve from 1880 based on the method of savings. One subject spent 70 hours learning lists and relearning them after 20 min, 1 hour, 9 hours, 1 day, 2 days, or 31 days. The results are similar to Ebbinghaus' original data. We analyze the effects of serial position on forgetting and investigate what mathematical equations present a good fit to the Ebbinghaus forgetting curve and its replications. We conclude that the Ebbinghaus forgetting curve has indeed been replicated and that it is not completely smooth but most probably shows a jump upwards starting at the 24 hour data point. PMID:26148023
Replication and Analysis of Ebbinghaus' Forgetting Curve.
Directory of Open Access Journals (Sweden)
Jaap M J Murre
Full Text Available We present a successful replication of Ebbinghaus' classic forgetting curve from 1880 based on the method of savings. One subject spent 70 hours learning lists and relearning them after 20 min, 1 hour, 9 hours, 1 day, 2 days, or 31 days. The results are similar to Ebbinghaus' original data. We analyze the effects of serial position on forgetting and investigate what mathematical equations present a good fit to the Ebbinghaus forgetting curve and its replications. We conclude that the Ebbinghaus forgetting curve has indeed been replicated and that it is not completely smooth but most probably shows a jump upwards starting at the 24 hour data point.
Indian Academy of Sciences (India)
We had defined when an arc is said to cross a circle. We broaden the definition of crossing as follows: Definition: Suppose f is a piece-wise circular simple closed curve and, is a piece-wise circular arc. Suppose ..... curve formed by p' pp", q' qq", part of r between p' and q' and part of r between pI! and q", as shown (Figures 6 ...
DEFF Research Database (Denmark)
Georgieva Yankova, Ginka; Federici, Paolo
This report describes power curve measurements carried out on a given turbine in a chosen period. The measurements are carried out in accordance to IEC 61400-12-1 Ed. 1 and FGW Teil 2.......This report describes power curve measurements carried out on a given turbine in a chosen period. The measurements are carried out in accordance to IEC 61400-12-1 Ed. 1 and FGW Teil 2....
Effects of the continuous and discrete confidence rating scales in ROC observer studies
Hadjiiski, Lubomir M.; Chan, Heang-Ping; Sahiner, Berkman; Helvie, Mark A.; Roubidoux, Marilyn A.
2005-04-01
We previously conducted an observer study evaluating radiologists' performance for characterization of mammographic masses on serial mammograms with and without CAD. 253 temporal image pairs (138 malignant and 115 benign) from 96 patients containing masses on serial mammograms were used. The interval change characteristics of the masses on each temporal pair were analyzed by our CAD program to differentiate malignant and benign masses. The classifier achieved a test Az value of 0.87 for the data set. Eight MQSA radiologists and 2 fellows assessed the temporal masses and provided estimates of the likelihood of malignancy (LM) and BI-RADS assessment without and then with CAD. The LM estimates were provided on a quasi-continuous confidence-rating scale (CRS) of 1 to 100. In the current study we investigated the effects of using discrete CRS with fewer categories on ROC analysis. We simulated three discrete CRSs containing 5, 10, and 20 categories by binning the radiologists" LM quasi-continuous ratings. For the ten radiologists, without CAD, the average Az in estimating the LM for the 5, 10, 20 and 100 category CRSs were 0.788, 0.786, 0.785, and 0.787, respectively. With CAD, the observers' Az improved to 0.845, 0.843, 0.844, and 0.843, respectively. The improvement was statistically significant (p<0.011) for each CRS. The partial area index for the four CRSs without CAD was 0.198, 0.204, 0.200, and 0.206, respectively. With CAD the partial area index was also significantly improved to 0.369, 0.365, 0.369, and 0.366, respectively (p<0.006 for all CRSs). The use of continuous and discrete confidence-rating scales in this study had minimal effect on the analysis of observer performance.
Polar representation of centrifugal pump homologous curves
International Nuclear Information System (INIS)
Veloso, Marcelo Antonio; Mattos, Joao Roberto Loureiro de
2008-01-01
Essential for any mathematical model designed to simulate flow transient events caused by pump operations is the pump performance data. The performance of a centrifugal pump is characterized by four basic parameters: the rotational speed, the volumetric flow rate, the dynamic head, and the hydraulic torque. Any one of these quantities can be expressed as a function of any two others. The curves showing the relationships between these four variables are called the pump characteristic curves, also referred to as four-quadrant curves. The characteristic curves are empirically developed by the pump manufacturer and uniquely describe head and torque as functions of volumetric flow rate and rotation speed. Because of comprising a large amount of points, the four-quadrant configuration is not suitable for computational purposes. However, it can be converted to a simpler form by the development of the homologous curves, in which dynamic head and hydraulic torque ratios are expressed as functions of volumetric flow and rotation speed ratios. The numerical use of the complete set of homologous curves requires specification of sixteen partial curves, being eight for the dynamic head and eight for the hydraulic torque. As a consequence, the handling of homologous curves is still somewhat complicated. In solving flow transient problems that require the pump characteristic data for all the operation zones, the polar form appears as the simplest way to represent the homologous curves. In the polar method, the complete characteristics of a pump can be described by only two closed curves, one for the dynamic head and other for the hydraulic torque, both in function of a single angular coordinate defined adequately in terms of the quotient between volumetric flow ratio and rotation speed ratio. The usefulness and advantages of this alternative method are demonstrated through a practical example in which the homologous curves for a pump of the type used in the main coolant loops of a
High rank elliptic curves with torsion ℤ/4ℤ.
Khoshnam, Foad; Moody, Dustin
2016-01-01
Working over the field ℚ( t ), Kihara constructed an elliptic curve with torsion group ℤ/4ℤ and five independent rational points, showing the rank is at least five. Following his approach, we give a new infinite family of elliptic curves with torsion group ℤ/4ℤ and rank at least five. This matches the current record for such curves. In addition, we give specific examples of these curves with high ranks 10 and 11.
Predicting the outcome of oral food challenges with hen's egg through skin test end-point titration.
Tripodi, S; Businco, A Di Rienzo; Alessandri, C; Panetta, V; Restani, P; Matricardi, P M
2009-08-01
Oral food challenge (OFC) is the diagnostic 'gold standard' of food allergies but it is laborious and time consuming. Attempts to predict a positive OFC through specific IgE assays or conventional skin tests so far gave suboptimal results. To test whether skin test with titration curves predict with enough confidence the outcome of an oral food challenge. Children (n=47; mean age 6.2 +/- 4.2 years) with suspected and diagnosed allergic reactions to hen's egg (HE) were examined through clinical history, physical examination, oral food challenge, conventional and end-point titrated skin tests with HE white extract and determination of serum specific IgE against HE white. Predictive decision points for a positive outcome of food challenges were calculated through receiver operating characteristic (ROC) analysis for HE white using IgE concentration, weal size and end-point titration (EPT). OFC was positive (Sampson's score >or=3) in 20/47 children (42.5%). The area under the ROC curve obtained with the EPT method was significantly bigger than the one obtained by measuring IgE-specific antibodies (0.99 vs. 0.83, P<0.05) and weal size (0.99 vs. 0.88, P<0.05). The extract's dilution that successfully discriminated a positive from a negative OFC (sensitivity 95%, specificity 100%) was 1 : 256, corresponding to a concentration of 5.9 microg/mL of ovotransferrin, 22.2 microg/mL of ovalbumin, and 1.4 microg/mL of lysozyme. EPT is a promising approach to optimize the use of skin prick tests and to predict the outcome of OFC with HE in children. Further studies are needed to test whether this encouraging finding can be extended to other populations and food allergens.
Fatima, Farheen; Fida, Mubassar; Shaikh, Attiya
2016-01-01
Differential diagnosis of skeletal and dental relationships is crucial for planning orthodontic treatment. Overbite depth indicator (ODI) and anteroposterior dysplasia indicator (APDI) had been introduced in the past for assessment of vertical and sagittal jaw relationships, respectively. The objectives of this study were to evaluate the reliability of ODI and APDI in overbite and Angle malocclusions, as well as assess their diagnostic reliability among males and females of different age groups. This study was conducted using pretreatment dental casts and lateral cephalograms of 90 subjects. For ODI, subjects were divided into three groups based on overbite (normal overbite, open bite and deep bite). Likewise, the same subjects were divided for APDI into three groups, based on Angle's malocclusion classification (dental Class I, II and III malocclusions). Mann-Whitney U test was applied for comparison of study parameters regarding sex and different age groups. The mean values of ODI and APDI were compared among study groups by means of Kruskal-Wallis and post-hoc Dunnet T3 tests. The receiver operating characteristic (ROC) curve was applied to test diagnostic reliability. Insignificant differences were found for ODI and APDI angles, particularly in regards to sex and age. Significant intergroup differences were found in different overbite groups and Angle's classification for ODI and APDI, respectively (p overbite and deep bite versus open bite. APDI can reliably differentiate dental Class I, II and III malocclusions.
Boiling curve in high quality flow boiling
International Nuclear Information System (INIS)
Shiralkar, B.S.; Hein, R.A.; Yadigaroglu, G.
1980-01-01
The post dry-out heat transfer regime of the flow boiling curve was investigated experimentally for high pressure water at high qualities. The test section was a short round tube located downstream of a hot patch created by a temperature controlled segment of tubing. Results from the experiment showed that the distance from the dryout point has a significant effect on the downstream temperatures and there was no unique boiling curve. The heat transfer coefficients measured sufficiently downstream of the dryout point could be correlated using the Heineman correlation for superheated steam, indicating that the droplet deposition effects could be neglected in this region
DEFF Research Database (Denmark)
Gómez Arranz, Paula; Vesth, Allan
This report describes the power curve measurements carried out on a given wind turbine in a chosen period. The measurements were carried out following the measurement procedure in the draft of IEC 61400-12-1 Ed.2 [1], with some deviations mostly regarding uncertainty calculation. Here, the refere......This report describes the power curve measurements carried out on a given wind turbine in a chosen period. The measurements were carried out following the measurement procedure in the draft of IEC 61400-12-1 Ed.2 [1], with some deviations mostly regarding uncertainty calculation. Here......, the reference wind speed used in the power curve is the equivalent wind speed obtained from lidar measurements at several heights between lower and upper blade tip, in combination with a hub height meteorological mast. The measurements have been performed using DTU’s measurement equipment, the analysis...
Parametric representation of centrifugal pump homologous curves
International Nuclear Information System (INIS)
Veloso, Marcelo A.; Mattos, Joao R.L. de
2015-01-01
Essential for any mathematical model designed to simulate flow transient events caused by pump operations is the pump performance data. The performance of a centrifugal pump is characterized by four basic quantities: the rotational speed, the volumetric flow rate, the dynamic head, and the hydraulic torque. The curves showing the relationships between these four variables are called the pump characteristic curves. The characteristic curves are empirically developed by the pump manufacturer and uniquely describe head and torque as functions of volumetric flow rate and rotation speed. Because of comprising a large amount of points, this configuration is not suitable for computational purposes. However, it can be converted to a simpler form by the development of the homologous curves, in which dynamic head and hydraulic torque ratios are expressed as functions of volumetric flow and rotation speed ratios. The numerical use of the complete set of homologous curves requires specification of sixteen partial curves, being eight for the dynamic head and eight for the hydraulic torque. As a consequence, the handling of homologous curves is still somewhat complicated. In solving flow transient problems that require the pump characteristic data for all the operation zones, the parametric form appears as the simplest way to deal with the homologous curves. In this approach, the complete characteristics of a pump can be described by only two closed curves, one for the dynamic head and other for the hydraulic torque, both in function of a single angular coordinate defined adequately in terms of the quotient between volumetric flow ratio and rotation speed ratio. The usefulness and advantages of this alternative method are demonstrated through a practical example in which the homologous curves for a pump of the type used in the main coolant loops of a pressurized water reactor (PWR) are transformed to the parametric form. (author)
Parametric representation of centrifugal pump homologous curves
Energy Technology Data Exchange (ETDEWEB)
Veloso, Marcelo A.; Mattos, Joao R.L. de, E-mail: velosom@cdtn.br, E-mail: jrmattos@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)
2015-07-01
Essential for any mathematical model designed to simulate flow transient events caused by pump operations is the pump performance data. The performance of a centrifugal pump is characterized by four basic quantities: the rotational speed, the volumetric flow rate, the dynamic head, and the hydraulic torque. The curves showing the relationships between these four variables are called the pump characteristic curves. The characteristic curves are empirically developed by the pump manufacturer and uniquely describe head and torque as functions of volumetric flow rate and rotation speed. Because of comprising a large amount of points, this configuration is not suitable for computational purposes. However, it can be converted to a simpler form by the development of the homologous curves, in which dynamic head and hydraulic torque ratios are expressed as functions of volumetric flow and rotation speed ratios. The numerical use of the complete set of homologous curves requires specification of sixteen partial curves, being eight for the dynamic head and eight for the hydraulic torque. As a consequence, the handling of homologous curves is still somewhat complicated. In solving flow transient problems that require the pump characteristic data for all the operation zones, the parametric form appears as the simplest way to deal with the homologous curves. In this approach, the complete characteristics of a pump can be described by only two closed curves, one for the dynamic head and other for the hydraulic torque, both in function of a single angular coordinate defined adequately in terms of the quotient between volumetric flow ratio and rotation speed ratio. The usefulness and advantages of this alternative method are demonstrated through a practical example in which the homologous curves for a pump of the type used in the main coolant loops of a pressurized water reactor (PWR) are transformed to the parametric form. (author)
Piecewise power laws in individual learning curves.
Donner, Yoni; Hardy, Joseph L
2015-10-01
The notion that human learning follows a smooth power law (PL) of diminishing gains is well-established in psychology. This characteristic is observed when multiple curves are averaged, potentially masking more complex dynamics underpinning the curves of individual learners. Here, we analyzed 25,280 individual learning curves, each comprising 500 measurements of cognitive performance taken from four cognitive tasks. A piecewise PL (PPL) model explained the individual learning curves significantly better than a single PL, controlling for model complexity. The PPL model allows for multiple PLs connected at different points in the learning process. We also explored the transition dynamics between PL curve component pieces. Performance in later pieces typically surpassed that in earlier pieces, after a brief drop in performance at the transition point. The transition rate was negatively associated with age, even after controlling for overall performance. Our results suggest at least two processes at work in individual learning curves: locally, a gradual, smooth improvement, with diminishing gains within a specific strategy, which is modeled well as a PL; and globally, a discrete sequence of strategy shifts, in which each strategy is better in the long term than the ones preceding it. The piecewise extension of the classic PL of practice has implications for both individual skill acquisition and theories of learning.
Physical Activity Questionnaire for children and adolescents: English norms and cut-off points.
Voss, Christine; Ogunleye, Ayodele A; Sandercock, Gavin R H
2013-08-01
The Physical Activity Questionnaire for Children and Adolescents (PAQ-C/-A) provides general estimates of physical activity levels. Following recent expert recommendations for using the PAQ for population surveillance, the aim of this paper was twofold: first, to describe normative PAQ data for English youth; and second, to determine a criterion-referenced PAQ-score cut-off point. Participants (n = 7226, 53% boys, 10-15 years) completed an anglicized version of the PAQ. Peak oxygen uptake (VO2peak ) was predicted from PACER lap count according to latest FITNESSGRAM standards and categorized into "at-risk" and "no-risk" for metabolic syndrome. ROC curves were drawn for each age-sex group to identify PAQ scores, which categorized youth into "sufficiently active" versus "low-active" groups, using cardiorespiratory fitness as the criterion-referenced standard. PAQ scores were higher in boys than in girls and declined with age. Mean PAQ score was a significant, albeit relatively weak (area under the curve PAQ scores of ≥2.9 for boys and ≥2.7 for girls were identified as cut-off points, although it may be more appropriate to use lower, age-specific PAQ scores for girls of 13, 14 and 15 years (2.6, 2.4, 2.3, respectively). The normative and criterion-referenced PAQ values may be used to standardize and categorize PAQ scores in future youth population studies. © 2013 The Authors. Pediatrics International © 2013 Japan Pediatric Society.
Groot, L.F.M.|info:eu-repo/dai/nl/073642398
2008-01-01
The purpose of this paper is twofold. First, it exhibits that standard tools in the measurement of income inequality, such as the Lorenz curve and the Gini-index, can successfully be applied to the issues of inequality measurement of carbon emissions and the equity of abatement policies across
Paulton, Richard J. L.
1991-01-01
A procedure that allows students to view an entire bacterial growth curve during a two- to three-hour student laboratory period is described. Observations of the lag phase, logarithmic phase, maximum stationary phase, and phase of decline are possible. A nonpathogenic, marine bacterium is used in the investigation. (KR)
African Journals Online (AJOL)
Adele
Introduction. Both the Unique™ LMA, and lately the Cobra™ PLA, is available in most of the larger state hospitals in South Africa. This study's objective is to evaluate and compare the learning curves for insertion of these two single-use airway devices. This is to ascertain which of these two devices is easier and safer to ...
DEFF Research Database (Denmark)
Kock, Carsten Weber; Vesth, Allan
The report describes power curve measurements carried out on a given wind turbine. The measurements are carried out in accordance to Ref. [1]. A site calibration has been carried out; see Ref. [2], and the measured flow correction factors for different wind directions are used in the present...... analyze of power performance of the turbine....
DEFF Research Database (Denmark)
Federici, Paolo; Kock, Carsten Weber
This report describes the power curve measurements performed with a nacelle LIDAR on a given wind turbine in a wind farm and during a chosen measurement period. The measurements and analysis are carried out in accordance to the guidelines in the procedure “DTU Wind Energy-E-0019” [1]. The reporting...
DEFF Research Database (Denmark)
Gómez Arranz, Paula; Villanueva, Héctor
The report describes power curve measurements carried out on a given wind turbine. The measurements are carried out in accordance to Ref. [1]. A site calibration has been carried out; see Ref. [2], and the measured flow correction factors for different wind directions are used in the present...... analyze of power performance of the turbine...
DEFF Research Database (Denmark)
Gómez Arranz, Paula; Kock, Carsten Weber
The report describes power curve measurements carried out on a given wind turbine. The measurements are carried out in accordance to Ref. [1]. A site calibration has been carried out; see Ref. [2], and the measured flow correction factors for different wind directions are used in the present...... analyze of power performance of the turbine....
DEFF Research Database (Denmark)
Georgieva Yankova, Ginka; Villanueva, Héctor
The report describes power curve measurements carried out on a given wind turbine. The measurements are carried out in accordance to Ref. [1]. A site calibration has been carried out; see Ref. [2], and the measured flow correction factors for different wind directions are used in the present anal...
DEFF Research Database (Denmark)
Villanueva, Héctor; Vesth, Allan
This report describes the power curve measurements carried out on a given wind turbine in a chosen period. The measurements were carried out following the measurement procedure in the draft of IEC 61400-12-1 Ed.2 [1], with some deviations mostly regarding uncertainty calculation. Here, the refere...
DEFF Research Database (Denmark)
Gómez Arranz, Paula; Villanueva, Héctor
The report describes power curve measurements carried out on a given wind turbine. The measurements are carried out in accordance to Ref. [1]. A site calibration has been carried out; see Ref. [2], and the measured flow correction factors for different wind directions are used in the present anal...
Textbook Factor Demand Curves.
Davis, Joe C.
1994-01-01
Maintains that teachers and textbook graphics follow the same basic pattern in illustrating changes in demand curves when product prices increase. Asserts that the use of computer graphics will enable teachers to be more precise in their graphic presentation of price elasticity. (CFR)
DEFF Research Database (Denmark)
Vesth, Allan; Kock, Carsten Weber
The report describes power curve measurements carried out on a given wind turbine. The measurements are carried out in accordance to Ref. [1]. A site calibration has been carried out; see Ref. [2], and the measured flow correction factors for different wind directions are used in the present...... analyze of power performance of the turbine....
DEFF Research Database (Denmark)
Villanueva, Héctor; Gómez Arranz, Paula
, the reference wind speed used in the power curve is the equivalent wind speed obtained from lidar measurements at several heights between lower and upper blade tip, in combination with a hub height meteorological mast. The measurements have been performed using DTU’s measurement equipment, the analysis...
Power Curve Measurements, REWS
DEFF Research Database (Denmark)
Villanueva, Héctor; Gómez Arranz, Paula
, the reference wind speed used in the power curve is the equivalent wind speed obtained from lidar measurements at several heights between lower and upper blade tip, in combination with a hub height meteorological mast. The measurements have been performed using DTU’s measurement equipment, the analysis...
DEFF Research Database (Denmark)
Federici, Paolo; Kock, Carsten Weber
The report describes power curve measurements carried out on a given wind turbine. The measurements are carried out in accordance to Ref. [1]. A site calibration has been carried out; see Ref. [2], and the measured flow correction factors for different wind directions are used in the present...... analyze of power performance of the turbine...
DEFF Research Database (Denmark)
Gómez Arranz, Paula; Wagner, Rozenn
This report describes the power curve measurements performed with a nacelle LIDAR on a given wind turbine in a wind farm and during a chosen measurement period. The measurements and analysis are carried out in accordance to the guidelines in the procedure “DTU Wind Energy-E-0019” [1]. The reporting...
Directory of Open Access Journals (Sweden)
Maysa M. Khadra
2016-06-01
Full Text Available Objective: To assess the clinical value of a single early human chorionic gonadotropin (HCG assay (day 14 post embryo transfer in assisted reproductive technology (ART pregnancies. Design: Retrospective study. Settings: The Assisted Reproductive Unit at Jordan University Hospital, Amman, Jordan. Patients: During 2009–2011, a total of 248 embryo transfer cycles resulting in pregnancy, defined as serum HCG concentration of ⩾10 IU/l, were included. Interventions: None. Materials and methods: Pregnancies were classified as viable (live fetus at 24 weeks gestation or non-viable (biochemical pregnancy, miscarriage, ectopic pregnancy. Receiver operating characteristic (ROC curve analysis was used to evaluate the cutoff value of HCG with maximal sensitivity and specificity to differentiate between viable and non-viable pregnancies. Results: The median HCG concentration was 264 IU/l in viable pregnancies and 120 IU/l in non-viable pregnancies (p < 0.001. The median HCG concentration was 222 IU/l in singleton pregnancies, 389 IU/l in twin pregnancies and 809 IU/l in triplet pregnancies (p < 0.001. An HCG value of 145 IU/l emerged as the most suitable cutoff point to predict viable pregnancy. Conclusion: HCG cutoff values determined by a ROC curve analysis are useful but not absolute for discriminating between viable and non-viable pregnancy outcomes on day 14 after embryo transfer. So it is important to continue routine monitoring of ART pregnancy outcomes.
Surface growth kinematics via local curve evolution
Moulton, Derek E.
2012-11-18
A mathematical framework is developed to model the kinematics of surface growth for objects that can be generated by evolving a curve in space, such as seashells and horns. Growth is dictated by a growth velocity vector field defined at every point on a generating curve. A local orthonormal basis is attached to each point of the generating curve and the velocity field is given in terms of the local coordinate directions, leading to a fully local and elegant mathematical structure. Several examples of increasing complexity are provided, and we demonstrate how biologically relevant structures such as logarithmic shells and horns emerge as analytical solutions of the kinematics equations with a small number of parameters that can be linked to the underlying growth process. Direct access to cell tracks and local orientation enables for connections to be made to the underlying growth process. © 2012 Springer-Verlag Berlin Heidelberg.
Bezier Curve Modeling for Neutrosophic Data Problem
Directory of Open Access Journals (Sweden)
Ferhat Tas
2017-02-01
Full Text Available Neutrosophic set concept is defined with membership, non-membership and indeterminacy degrees. This concept is the solution and representation of the problems with various fields. In this paper, a geometric model is introduced for Neutrosophic data problem for the first time. This model is based on neutrosophic sets and neutrosophic relations. Neutrosophic control points are defined according to these points, resulting in neutrosophic Bezier curves.
NLINEAR - NONLINEAR CURVE FITTING PROGRAM
Everhart, J. L.
1994-01-01
A common method for fitting data is a least-squares fit. In the least-squares method, a user-specified fitting function is utilized in such a way as to minimize the sum of the squares of distances between the data points and the fitting curve. The Nonlinear Curve Fitting Program, NLINEAR, is an interactive curve fitting routine based on a description of the quadratic expansion of the chi-squared statistic. NLINEAR utilizes a nonlinear optimization algorithm that calculates the best statistically weighted values of the parameters of the fitting function and the chi-square that is to be minimized. The inputs to the program are the mathematical form of the fitting function and the initial values of the parameters to be estimated. This approach provides the user with statistical information such as goodness of fit and estimated values of parameters that produce the highest degree of correlation between the experimental data and the mathematical model. In the mathematical formulation of the algorithm, the Taylor expansion of chi-square is first introduced, and justification for retaining only the first term are presented. From the expansion, a set of n simultaneous linear equations are derived, which are solved by matrix algebra. To achieve convergence, the algorithm requires meaningful initial estimates for the parameters of the fitting function. NLINEAR is written in Fortran 77 for execution on a CDC Cyber 750 under NOS 2.3. It has a central memory requirement of 5K 60 bit words. Optionally, graphical output of the fitting function can be plotted. Tektronix PLOT-10 routines are required for graphics. NLINEAR was developed in 1987.
TBI-ROC Part Seven: Traumatic Brain Injury--Technologies to Support Memory and Cognition
Scherer, Marcia; Elias, Eileen; Weider, Katie
2010-01-01
This article is the seventh of a multi-part series on traumatic brain injury (TBI). The six earlier articles in this series have discussed the individualized nature of TBI and its consequences, the rehabilitation continuum, and interventions at various points along the continuum. As noted throughout the articles, many individuals with TBI…
Approximation by planar elastic curves
DEFF Research Database (Denmark)
Brander, David; Gravesen, Jens; Nørbjerg, Toke Bjerge
2016-01-01
We give an algorithm for approximating a given plane curve segment by a planar elastic curve. The method depends on an analytic representation of the space of elastic curve segments, together with a geometric method for obtaining a good initial guess for the approximating curve. A gradient-driven...
Energy Technology Data Exchange (ETDEWEB)
Groot, L. [Utrecht University, Utrecht School of Economics, Janskerkhof 12, 3512 BL Utrecht (Netherlands)
2008-11-15
The purpose of this paper is twofold. First, it exhibits that standard tools in the measurement of income inequality, such as the Lorenz curve and the Gini-index, can successfully be applied to the issues of inequality measurement of carbon emissions and the equity of abatement policies across countries. These tools allow policy-makers and the general public to grasp at a single glance the impact of conventional distribution rules such as equal caps or grandfathering, or more sophisticated ones, on the distribution of greenhouse gas emissions. Second, using the Samuelson rule for the optimal provision of a public good, the Pareto-optimal distribution of carbon emissions is compared with the distribution that follows if countries follow Nash-Cournot abatement strategies. It is shown that the Pareto-optimal distribution under the Samuelson rule can be approximated by the equal cap division, represented by the diagonal in the Lorenz curve diagram.
DEFF Research Database (Denmark)
Villanueva, Héctor; Gómez Arranz, Paula
This report describes the analysis carried out with data from a given turbine in a wind farm and a chosen period. The purpose of the analysis is to correlate the power output of the wind turbine to the wind speed measured by a nacelle-mounted anemometer. The measurements and analysis are not perf......This report describes the analysis carried out with data from a given turbine in a wind farm and a chosen period. The purpose of the analysis is to correlate the power output of the wind turbine to the wind speed measured by a nacelle-mounted anemometer. The measurements and analysis...... are not performed according to IEC 61400-12-1 [1]. Therefore, the results presented in this report cannot be considered a power curve according to the reference standard, and are referred to as “power curve investigation” instead. The measurements have been performed by a customer and the data analysis has been...
Directory of Open Access Journals (Sweden)
Iram Ansari
2012-01-01
Full Text Available Dilaceration is the result of a developmental anomaly in which there has been an abrupt change in the axial inclination between the crown and the root of a tooth. Dilaceration can be seen in both the permanent and deciduous dentitions, and is more commonly found in posterior teeth and in maxilla. Periapical radiographs are the most appropriate way to diagnose the presence of root dilacerations. The controlled regularly tapered preparation of the curved canals is the ultimate challenge in endodontics. Careful and meticulous technique will yield a safe and sufficient enlargement of the curved canals. This article gives a review of the literature and three interesting case reports of root dilacerations.
Kronberg, Max; Soomro, Muhammad Afzal; Top, Jaap
2017-10-01
In this note we extend the theory of twists of elliptic curves as presented in various standard texts for characteristic not equal to two or three to the remaining characteristics. For this, we make explicit use of the correspondence between the twists and the Galois cohomology set H^1\\big({G}_{\\overline{K}/K}, \\operatorname{Aut}_{\\overline{K}}(E)\\big). The results are illustrated by examples.
Transvaginal cholecystectomy learning curve.
Wood, Stephanie G; Dai, Feng; Dabu-Bondoc, Susan; Mikhael, Hosni; Vadivelu, Nalini; Duffy, Andrew; Roberts, Kurt E
2015-07-01
There are few surgeons in the United States, within private practice and academic centers, currently performing transvaginal cholecystectomies (TVC). The lack of exposure to TVC during residency or fellowship training, coupled with a poorly defined learning curve, further limits interested surgeons who want to apply this technique to their practice. This study describes the learning curve encountered during the introduction of TVC to our academic facility. This study is an analysis of consecutive TVCs performed between August 14, 2009 and August 3, 2012 at an academic center. The TVC patients were divided into sequential quartiles (n = 15/16). The learning curve outcome was measured as the operative time of TVC patients and compared to the operative time of female laparoscopic cholecystectomy (LC) patients performed during the same time period. Sixty-one patients underwent a TVC with a mean age of 38 ± 12 years and mean BMI was 29 ± 6 kg/m(2). Sixty-seven female patients who underwent a LC with average age 41 ± 15 years and average BMI 33 ± 12 kg/m(2). The average operative time of LC patients and TVC patients was 48 ± 20 and 60 ± 17 min, respectively. Significant improvement in TVC operative times was seen between the first (n = 15 TVCs) and second quartiles (p = 0.04) and stayed relatively constant for third quartile, during which there was no statistically significant difference between the mean LC operative time for the second and third TVC quartiles The learning curve of a fellowship-trained surgeon introducing TVC to their surgical repertoire, as measured by improved operative times, can be achieved with approximately 15 cases.
Pelce, Pierre
1989-01-01
In recent years, much progress has been made in the understanding of interface dynamics of various systems: hydrodynamics, crystal growth, chemical reactions, and combustion. Dynamics of Curved Fronts is an important contribution to this field and will be an indispensable reference work for researchers and graduate students in physics, applied mathematics, and chemical engineering. The book consist of a 100 page introduction by the editor and 33 seminal articles from various disciplines.
Vo, Martin
2017-08-01
Light Curves Classifier uses data mining and machine learning to obtain and classify desired objects. This task can be accomplished by attributes of light curves or any time series, including shapes, histograms, or variograms, or by other available information about the inspected objects, such as color indices, temperatures, and abundances. After specifying features which describe the objects to be searched, the software trains on a given training sample, and can then be used for unsupervised clustering for visualizing the natural separation of the sample. The package can be also used for automatic tuning parameters of used methods (for example, number of hidden neurons or binning ratio). Trained classifiers can be used for filtering outputs from astronomical databases or data stored locally. The Light Curve Classifier can also be used for simple downloading of light curves and all available information of queried stars. It natively can connect to OgleII, OgleIII, ASAS, CoRoT, Kepler, Catalina and MACHO, and new connectors or descriptors can be implemented. In addition to direct usage of the package and command line UI, the program can be used through a web interface. Users can create jobs for ”training” methods on given objects, querying databases and filtering outputs by trained filters. Preimplemented descriptors, classifier and connectors can be picked by simple clicks and their parameters can be tuned by giving ranges of these values. All combinations are then calculated and the best one is used for creating the filter. Natural separation of the data can be visualized by unsupervised clustering.
Liquefaction Probability Curves for Surficial Geologic Units
Holzer, T. L.; Noce, T. E.; Bennett, M. J.
2009-12-01
Liquefaction probability curves that predict the probability of surface manifestations of earthquake-induced liquefaction are developed for 14 different surficial geologic deposits. The geologic units include alluvial fan, beach ridge, river delta, eolian dune, point bar, floodbasin, natural river levee, abandoned river channel, deep-water lake, lagoonal, sandy artificial fill, and valley train deposits. Probability is conditioned on earthquake magnitude and peak ground acceleration. Curves are developed for water table depths of 1.5 and 5.0 m. Probabilities were derived from complementary cumulative frequency distributions of the liquefaction potential index (LPI) that were computed from 935 cone penetration tests. Most of the curves can be fit with a 3-parameter logistic function, which facilitates computations of probability. For natural deposits with a water table at 1.5 m depth and subjected to an M7.5 earthquake with a PGA = 0.25 g, probabilities range from 0.5 for fluvial point bar, barrier island beach ridge, and deltaic deposits. Retrospective predictions of liquefaction during historical earthquakes based on the curves compare favorably to post-earthquake observations. We also have used the curves to assign ranges of liquefaction probabilities to the susceptibility categories proposed by Youd and Perkins (1978) for different geologic deposits. For the earthquake loading and conditions described above, probabilities range from 0-0.08 for low, 0.09-0.30 for moderate, 0.31-0.62 for high, to 0.63-1.00 for very high susceptibility. Liquefaction probability curves have two primary practical applications. First, the curves can be combined with seismic source characterizations to transform surficial geologic maps into probabilistic liquefaction hazard maps. Geographic specific curves are clearly desirable, but in the absence of such information, generic liquefaction probability curves provide a first approximation of liquefaction hazard. Such maps are useful both
Hammer, A
2017-11-01
It was 140 years ago that George von Meyer presented his anatomical diagrams of human bones to a meeting in Zurich. There he was told by Prof. Karl Culmann that the trabecular lines shown within the diagram of the upper femur closely resembled those lines of force which Culmann had determined with Graphic Statics to be passing through a curved, loaded Fairbairn crane. This drew the attention of Julius Wolff, who used this as the basis for his 'Trajectorial theory' which was widely accepted and, to date, has been the underlying basis for all biomechanical investigations of this region. Following Wolff and Culmann, the upper femur is considered to be a curved structure and is investigated as such. Unfortunately, this concept is wrong. The upper femur is not curved but is angular. It is formed by the junction of two straight bones, the femoral neck and the femoral shaft, as may be simply seen as the neck/shaft angle constructed on the antero-posterior radiograph of any normal femur. The internal trabecular bone forms only part of the load bearing structure of the femoral neck. The configuration of this trabecular substance in this region suggests that it is related specifically to the force present during flexion and extension movements of the hip joint. This being so, combined with the delayed timing of the appearance of the trabecular columns, it must be questioned as to whether the remodelling of the upper femur is in response to one or to two distinct forces.
Euler characteristics and elliptic curves.
Coates, J; Howson, S
1997-10-14
Let E be a modular elliptic curve over [symbol, see text], without complex multiplication; let p be a prime number where E has good ordinary reduction; and let Finfinity be the field obtained by adjoining [symbol, see text] to all p-power division points on E. Write Ginfinity for the Galois group of Finfinity over [symbol, see text]. Assume that the complex L-series of E over [symbol, see text] does not vanish at s = 1. If p >/= 5, we make a precise conjecture about the value of the Ginfinity-Euler characteristic of the Selmer group of E over Finfinity. If one makes a standard conjecture about the behavior of this Selmer group as a module over the Iwasawa algebra, we are able to prove our conjecture. The crucial local calculations in the proof depend on recent joint work of the first author with R. Greenberg.
Faceting of curved surfaces using the curvature coordinate system
DEFF Research Database (Denmark)
Almegaard, Henrik
2008-01-01
In many situations, a curved surface has to be approximated by a facetted surface, i.e., as a network with planar meshes. Most often this is done by triangulation of the surface. Points are chosen on the surface and the points are connected by straight lines so that these lines make a network...... this is by tangent faceting. Tangent points are chosen on the surface and the tangent planes at these points are connected along lines of intersection so that these lines make a network with planar meshes and so that no normal to the curved surface intersect more than one facet. The result is a faceted surface...... of triangular meshes and so that no normal to the curved surface intersect more than one mesh/facet. The result is a faceted surface, with vertices, edges and triangular facets. But faceting a curved surface can also be done using planes as the basic geometrical element instead of points. One way of doing...
Light extraction block with curved surface
Levermore, Peter; Krall, Emory; Silvernail, Jeffrey; Rajan, Kamala; Brown, Julia J.
2016-03-22
Light extraction blocks, and OLED lighting panels using light extraction blocks, are described, in which the light extraction blocks include various curved shapes that provide improved light extraction properties compared to parallel emissive surface, and a thinner form factor and better light extraction than a hemisphere. Lighting systems described herein may include a light source with an OLED panel. A light extraction block with a three-dimensional light emitting surface may be optically coupled to the light source. The three-dimensional light emitting surface of the block may includes a substantially curved surface, with further characteristics related to the curvature of the surface at given points. A first radius of curvature corresponding to a maximum principal curvature k.sub.1 at a point p on the substantially curved surface may be greater than a maximum height of the light extraction block. A maximum height of the light extraction block may be less than 50% of a maximum width of the light extraction block. Surfaces with cross sections made up of line segments and inflection points may also be fit to approximated curves for calculating the radius of curvature.
Localized qubits in curved spacetimes
Palmer, Matthew C.; Takahashi, Maki; Westman, Hans F.
2012-04-01
We provide a systematic and self-contained exposition of the subject of localized qubits in curved spacetimes. This research was motivated by a simple experimental question: if we move a spatially localized qubit, initially in a state |ψ1>, along some spacetime path Γ from a spacetime point x1 to another point x2, what will the final quantum state |ψ2> be at point x2? This paper addresses this question for two physical realizations of the qubit: spin of a massive fermion and polarization of a photon. Our starting point is the Dirac and Maxwell equations that describe respectively the one-particle states of localized massive fermions and photons. In the WKB limit we show how one can isolate a two-dimensional quantum state which evolves unitarily along Γ. The quantum states for these two realizations are represented by a left-handed 2-spinor in the case of massive fermions and a four-component complex polarization vector in the case of photons. In addition we show how to obtain from this WKB approach a fully general relativistic description of gravitationally induced phases. We use this formalism to describe the gravitational shift in the Colella-Overhauser-Werner 1975 experiment. In the non-relativistic weak field limit our result reduces to the standard formula in the original paper. We provide a concrete physical model for a Stern-Gerlach measurement of spin and obtain a unique spin operator which can be determined given the orientation and velocity of the Stern-Gerlach device and velocity of the massive fermion. Finally, we consider multipartite states and generalize the formalism to incorporate basic elements from quantum information theory such as quantum entanglement, quantum teleportation, and identical particles. The resulting formalism provides a basis for exploring precision quantum measurements of the gravitational field using techniques from quantum information theory.
Migration and the Wage-Settings Curve
DEFF Research Database (Denmark)
Brücker, Herbert; Jahn, Elke
Germany on basis of a wage-setting curve. The wage-setting curve relies on the assumption that wages respond to a hange in the unemployment rate, albeit imperfectly. This allows one to derive the wage and employment effects of migration simultaneously in a general equilibrium framework. Using...... in the German labor force through immigration increases the aggregate unemployment rate by less than 0.1 percentage points and reduces average wages by 0.1 percent in the short run. While native workers benefit from increased wages and lower unemployment, foreign workers are adversely affected....
Basic concepts and development of an all-purpose computer interface for ROC/FROC observer study.
Shiraishi, Junji; Fukuoka, Daisuke; Hara, Takeshi; Abe, Hiroyuki
2013-01-01
In this study, we initially investigated various aspects of requirements for a computer interface employed in receiver operating characteristic (ROC) and free-response ROC (FROC) observer studies which involve digital images and ratings obtained by observers (radiologists). Secondly, by taking into account these aspects, an all-purpose computer interface utilized for these observer performance studies was developed. Basically, the observer studies can be classified into three paradigms, such as one rating for one case without an identification of a signal location, one rating for one case with an identification of a signal location, and multiple ratings for one case with identification of signal locations. For these paradigms, display modes on the computer interface can be used for single/multiple views of a static image, continuous viewing with cascade images (i.e., CT, MRI), and dynamic viewing of movies (i.e., DSA, ultrasound). Various functions on these display modes, which include windowing (contrast/level), magnifications, and annotations, are needed to be selected by an experimenter corresponding to the purpose of the research. In addition, the rules of judgment for distinguishing between true positives and false positives are an important factor for estimating diagnostic accuracy in an observer study. We developed a computer interface which runs on a Windows operating system by taking into account all aspects required for various observer studies. This computer interface requires experimenters to have sufficient knowledge about ROC/FROC observer studies, but allows its use for any purpose of the observer studies. This computer interface will be distributed publicly in the near future.
Learning curves in health professions education.
Pusic, Martin V; Boutis, Kathy; Hatala, Rose; Cook, David A
2015-08-01
Learning curves, which graphically show the relationship between learning effort and achievement, are common in published education research but are not often used in day-to-day educational activities. The purpose of this article is to describe the generation and analysis of learning curves and their applicability to health professions education. The authors argue that the time is right for a closer look at using learning curves-given their desirable properties-to inform both self-directed instruction by individuals and education management by instructors.A typical learning curve is made up of a measure of learning (y-axis), a measure of effort (x-axis), and a mathematical linking function. At the individual level, learning curves make manifest a single person's progress towards competence including his/her rate of learning, the inflection point where learning becomes more effortful, and the remaining distance to mastery attainment. At the group level, overlaid learning curves show the full variation of a group of learners' paths through a given learning domain. Specifically, they make overt the difference between time-based and competency-based approaches to instruction. Additionally, instructors can use learning curve information to more accurately target educational resources to those who most require them.The learning curve approach requires a fine-grained collection of data that will not be possible in all educational settings; however, the increased use of an assessment paradigm that explicitly includes effort and its link to individual achievement could result in increased learner engagement and more effective instructional design.
Sadek, Mohammad
2012-01-01
In this paper we consider genus one equations of degree $n$, namely a (generalised) binary quartic when $n=2$, a ternary cubic when $n=3$, and a pair of quaternary quadrics when $n=4$. A new definition for the minimality of genus one equations of degree $n$ over local fields is introduced. The advantage of this definition is that it does not depend on invariant theory of genus one curves. We prove that this definition coincides with the classical definition of minimality for all $n\\le4$. As a...
Learning from uncertain curves
DEFF Research Database (Denmark)
Mallasto, Anton; Feragen, Aasa
2017-01-01
We introduce a novel framework for statistical analysis of populations of nondegenerate Gaussian processes (GPs), which are natural representations of uncertain curves. This allows inherent variation or uncertainty in function-valued data to be properly incorporated in the population analysis....... Using the 2-Wasserstein metric we geometrize the space of GPs with L2 mean and covariance functions over compact index spaces. We prove uniqueness of the barycenter of a population of GPs, as well as convergence of the metric and the barycenter of their finite-dimensional counterparts. This justifies...
Indian Academy of Sciences (India)
such that '[q,p) lies inside of G and '(p,rj lies outside of G. Now suppose, is a polygonal arc and G is a circle, such that. , crosses G at least once and the end points, a and b, of, lie. 'outside' C. If we start 'moving' from a towards b along " let a be the first crossing and b the last. At every point p in. C - {a, b} we attach a direction ...
Real parabolic vector bundles over a real curve
Indian Academy of Sciences (India)
Abstract. We define real parabolic structures on real vector bundles over a real curve. Let (X,σX ) be a real curve, and let S ⊂ X be a non-empty finite subset of X such that σX (S) = S. Let N ≥ 2 be an integer. We construct an N-fold cyclic cover p : Y → X in the category of real curves, ramified precisely over each point of S, ...
Interpretation of photometric observations of R Coronae Borealis. Light curves
International Nuclear Information System (INIS)
Pugach, A.F.
1990-01-01
The calculations confirm the 'reptive hypothesis' of light variations of R CrB. The central point of the hypothesis is an assertion of infinite expansion of an elementary dust cloud. The calculations for different masses of the dust cloud provide a set of elementary light curves. Superposition of the curves yields a complex light curve. The comparison with the observed minima of 1972 has been performed
Differential geometry of curves and surfaces
Banchoff, Thomas F
2010-01-01
Students and professors of an undergraduate course in differential geometry will appreciate the clear exposition and comprehensive exercises in this book that focuses on the geometric properties of curves and surfaces, one- and two-dimensional objects in Euclidean space. The problems generally relate to questions of local properties (the properties observed at a point on the curve or surface) or global properties (the properties of the object as a whole). Some of the more interesting theorems explore relationships between local and global properties. A special feature is the availability of accompanying online interactive java applets coordinated with each section. The applets allow students to investigate and manipulate curves and surfaces to develop intuition and to help analyze geometric phenomena.
Body mass index cutoff point estimation as obesity diagnostic criteria in Down syndrome adolescents.
Samur San-Matín, Juan Eduardo; Gonçalves, Ezequiel Moreira; Bertapelli, Fabio; Mendes, Roberto Teixeira; Guerra-Júnior, Gil
2016-09-20
Adolescents with Down syndrome (DS) show high rate of overweight and tend to accumulate high amount of fat compared to the same people without the syndrome. To estimate the cutoff point of the Body Mass Index (BMI) for the diagnosis of obesity in adolescents with DS according to different references for BMI in relation to the percentage of body fat (%BF) measured by dual-energy X-ray absorptiometry (DXA). The sample was composed of 34 adolescents with DS (aged: 10 to 17 years old). BMI was evaluated according to the references of the International Obesity Task Force (IOTF), the World Health Organization (WHO) for the general population, and Myrelid et al. and Styles et al. for people with DS. The %BF was assessed by whole body DXA and classified according to National Health And Nutrition Examination Survey (NHANES, 2011). The boys were significantly taller than the girls and this %BF higher than boys. All references who have used BMI to assess obesity was positively associated with %BF measured by DXA in the diagnosis of obesity. Using the ROC curve in relation to %BF by DXA, all references showed high sensitivity, but the z-score of BMI by WHO showed better specificity, with the value of the accuracy of 0.82 for the cutoff point above 2.14. All the references used for the diagnosis of obesity were associated with %BF measured by DXA, and the cutoff point of z-scores above 2.14 by WHO showed better specificity.
Sund, T; Olsen, J B
2006-09-01
To investigate whether sliding window adaptive histogram equalization (SWAHE) of digital mammograms improves the detection of simulated calcifications, as compared to images normalized by global histogram equalization (GHE). Direct digital mammograms were obtained from mammary tissue phantoms superimposed with different frames. Each frame was divided into forty squares by a wire mesh, and contained granular calcifications randomly positioned in about 50% of the squares. Three radiologists read the mammograms on a display monitor. They classified their confidence in the presence of microcalcifications in each square on a scale of 1 to 5. Images processed with GHE were first read and used as a reference. In a later session, the same images processed with SWAHE were read. The results were compared using ROC methodology. When the total areas AZ were compared, the results were completely equivocal. When comparing the high-specificity partial ROC area AZ,0.2 below false-positive fraction (FPF) 0.20, two of the three observers performed best with the images processed with SWAHE. The difference was not statistically significant. When the reader's confidence threshold in malignancy is set at a high level, increasing the contrast of mammograms with SWAHE may enhance the visibility of microcalcifications without adversely affecting the false-positive rate. When the reader's confidence threshold is set at a low level, the effect of SWAHE is an increase of false positives. Further investigation is needed to confirm the validity of the conclusions.
Stuck between a ROC and a hard place? Barriers to the take up of green energy in the UK
International Nuclear Information System (INIS)
Diaz-Rainey, Ivan; Ashton, John K.
2008-01-01
This paper examines the UK mechanisms for ensuring future investment in renewable energy through consumer adoption of green energy tariffs and the Renewable Obligation Certificate (ROC) system. Using a national survey and focus groups the stated willingness by UK customers to pay a premium for renewable or green energy and actual take up of such tariffs is assessed. Substantial differences between willingness to pay for and the adoption of green energy tariffs are reported. This disparity is linked to a range of factors including consumer confusion, lack of supply, complexities of constructing 'green source' tariffs under the ROC system and a lack of customer trust. It is concluded that the re-definition of the green energy market in favour of 'green source' tariffs, greater direct compliance with the Renewable Obligation by addressing supply constraints, and efforts in providing clearer information and choices for consumers via a compulsory green energy accreditation scheme are required if willing consumers' are to contribute to investment in renewable energy
The Characteristic Curves of Water
Neumaier, Arnold; Deiters, Ulrich K.
2016-09-01
In 1960, E. H. Brown defined a set of characteristic curves (also known as ideal curves) of pure fluids, along which some thermodynamic properties match those of an ideal gas. These curves are used for testing the extrapolation behaviour of equations of state. This work is revisited, and an elegant representation of the first-order characteristic curves as level curves of a master function is proposed. It is shown that Brown's postulate—that these curves are unique and dome-shaped in a double-logarithmic p, T representation—may fail for fluids exhibiting a density anomaly. A careful study of the Amagat curve (Joule inversion curve) generated from the IAPWS-95 reference equation of state for water reveals the existence of an additional branch.
Torsionfree sheaves over a nodal curve of arithmetic genus one
Indian Academy of Sciences (India)
We classify all isomorphism classes of stable torsionfree sheaves on an irreducible nodal curve of arithmetic genus one defined over C C . Let be a nodal curve of arithmetic genus one defined over R R , with exactly one node, such that does not have any real points apart from the node. We classify all isomorphism ...
Galois representations of elliptic curves and abelian entanglements
Brau Avila, Julio
2015-01-01
This thesis deals primarily with the study of Galois representations attached to torsion points on elliptic curves. In the first chapter we consider the problem of determining the image of the Galois representation flE attached to a non-CM elliptic curve over the rational number field Q. We give a
Univolatility curves in ternary mixtures: geometry and numerical computation
DEFF Research Database (Denmark)
Shcherbakova, Nataliya; Rodriguez-Donis, Ivonne; Abildskov, Jens
2017-01-01
We propose a new non-iterative numerical algorithm allowing computation of all univolatility curves in homogeneous ternary mixtures independently of the presence of the azeotropes. The key point is the concept of generalized univolatility curves in the 3D state space, which allows the main...... computational part to be reduced to a simple integration of a system of ordinary differential equations....
Twists of genus three curves over finite fields
Meagher, Stephen; Top, Jakob
In this article we recall how to describe the twists of a curve over a finite field and we show how to compute the number of rational points on such a twist by methods of linear algebra We illustrate this in the case of plane quartic curves with at least 16 automorphisms In particular we treat the
AKLSQF - LEAST SQUARES CURVE FITTING
Kantak, A. V.
1994-01-01
The Least Squares Curve Fitting program, AKLSQF, computes the polynomial which will least square fit uniformly spaced data easily and efficiently. The program allows the user to specify the tolerable least squares error in the fitting or allows the user to specify the polynomial degree. In both cases AKLSQF returns the polynomial and the actual least squares fit error incurred in the operation. The data may be supplied to the routine either by direct keyboard entry or via a file. AKLSQF produces the least squares polynomial in two steps. First, the data points are least squares fitted using the orthogonal factorial polynomials. The result is then reduced to a regular polynomial using Sterling numbers of the first kind. If an error tolerance is specified, the program starts with a polynomial of degree 1 and computes the least squares fit error. The degree of the polynomial used for fitting is then increased successively until the error criterion specified by the user is met. At every step the polynomial as well as the least squares fitting error is printed to the screen. In general, the program can produce a curve fitting up to a 100 degree polynomial. All computations in the program are carried out under Double Precision format for real numbers and under long integer format for integers to provide the maximum accuracy possible. AKLSQF was written for an IBM PC X/AT or compatible using Microsoft's Quick Basic compiler. It has been implemented under DOS 3.2.1 using 23K of RAM. AKLSQF was developed in 1989.
Development of the curve of Spee.
Marshall, Steven D; Caspersen, Matthew; Hardinger, Rachel R; Franciscus, Robert G; Aquilino, Steven A; Southard, Thomas E
2008-09-01
Ferdinand Graf von Spee is credited with characterizing human occlusal curvature viewed in the sagittal plane. This naturally occurring phenomenon has clinical importance in orthodontics and restorative dentistry, yet we have little understanding of when, how, or why it develops. The purpose of this study was to expand our understanding by examining the development of the curve of Spee longitudinally in a sample of untreated subjects with normal occlusion from the deciduous dentition to adulthood. Records of 16 male and 17 female subjects from the Iowa Facial Growth Study were selected and examined. The depth of the curve of Spee was measured on their study models at 7 time points from ages 4 (deciduous dentition) to 26 (adult dentition) years. The Wilcoxon signed rank test was used to compare changes in the curve of Spee depth between time points. For each subject, the relative eruption of the mandibular teeth was measured from corresponding cephalometric radiographs, and its contribution to the developing curve of Spee was ascertained. In the deciduous dentition, the curve of Spee is minimal. At mean ages of 4.05 and 5.27 years, the average curve of Spee depths are 0.24 and 0.25 mm, respectively. With change to the transitional dentition, corresponding to the eruption of the mandibular permanent first molars and central incisors (mean age, 6.91 years), the curve of Spee depth increases significantly (P < 0.0001) to a mean maximum depth of 1.32 mm. The curve of Spee then remains essentially unchanged until eruption of the second molars (mean age, 12.38 years), when the depth increases (P < 0.0001) to a mean maximum depth of 2.17 mm. In the adolescent dentition (mean age, 16.21 years), the depth decreases slightly (P = 0.0009) to a mean maximum depth of 1.98 mm, and, in the adult dentition (mean age 26.98 years), the curve remains unchanged (P = 0.66), with a mean maximum depth of 2.02 mm. No significant differences in curve of Spee development were found between
Directory of Open Access Journals (Sweden)
Je Hyun Baekt
2000-01-01
Full Text Available A numerical study is conducted on the fully-developed laminar flow of an incompressible viscous fluid in a square duct rotating about a perpendicular axis to the axial direction of the duct. At the straight duct, the rotation produces vortices due to the Coriolis force. Generally two vortex cells are formed and the axial velocity distribution is distorted by the effect of this Coriolis force. When a convective force is weak, two counter-rotating vortices are shown with a quasi-parabolic axial velocity profile for weak rotation rates. As the rotation rate increases, the axial velocity on the vertical centreline of the duct begins to flatten and the location of vorticity center is moved near to wall by the effect of the Coriolis force. When the convective inertia force is strong, a double-vortex secondary flow appears in the transverse planes of the duct for weak rotation rates but as the speed of rotation increases the secondary flow is shown to split into an asymmetric configuration of four counter-rotating vortices. If the rotation rates are increased further, the secondary flow restabilizes to a slightly asymmetric double-vortex configuration. Also, a numerical study is conducted on the laminar flow of an incompressible viscous fluid in a 90°-bend square duct that rotates about axis parallel to the axial direction of the inlet. At a 90°-bend square duct, the feature of flow by the effect of a Coriolis force and a centrifugal force, namely a secondary flow by the centrifugal force in the curved region and the Coriolis force in the downstream region, is shown since the centrifugal force in curved region and the Coriolis force in downstream region are dominant respectively.
Magnetism in curved geometries
Streubel, Robert
Deterministically bending and twisting two-dimensional structures in the three-dimensional (3D) space provide means to modify conventional or to launch novel functionalities by tailoring curvature and 3D shape. The recent developments of 3D curved magnetic geometries, ranging from theoretical predictions over fabrication to characterization using integral means as well as advanced magnetic tomography, will be reviewed. Theoretical works predict a curvature-induced effective anisotropy and effective Dzyaloshinskii-Moriya interaction resulting in a vast of novel effects including magnetochiral effects (chirality symmetry breaking) and topologically induced magnetization patterning. The remarkable development of nanotechnology, e.g. preparation of high-quality extended thin films, nanowires and frameworks via chemical and physical deposition as well as 3D nano printing, has granted first insights into the fundamental properties of 3D shaped magnetic objects. Optimizing magnetic and structural properties of these novel 3D architectures demands new investigation methods, particularly those based on vector tomographic imaging. Magnetic neutron tomography and electron-based 3D imaging, such as electron holography and vector field electron tomography, are well-established techniques to investigate macroscopic and nanoscopic samples, respectively. At the mesoscale, the curved objects can be investigated using the novel method of magnetic X-ray tomography. In spite of experimental challenges to address the appealing theoretical predictions of curvature-induced effects, those 3D magnetic architectures have already proven their application potential for life sciences, targeted delivery, realization of 3D spin-wave filters, and magneto-encephalography devices, to name just a few. DOE BES MSED (DE-AC02-05-CH11231).
Titration Curves: Fact and Fiction.
Chamberlain, John
1997-01-01
Discusses ways in which datalogging equipment can enable titration curves to be measured accurately and how computing power can be used to predict the shape of curves. Highlights include sources of error, use of spreadsheets to generate titration curves, titration of a weak acid with a strong alkali, dibasic acids, weak acid and weak base, and…
Moduli spaces of curves and enumerative geometry via topological recursion
Lewański, D.
2017-01-01
The thesis considers several enumerative geometric problems concerning the topology of the moduli space of curves and their combinatorics. These enumerative geometric problems are analysed from different intertwined points of view and using different mathematical tools, including Hurwitz theory,
Brachistochrone curve of a fluid filled cylinder
Sarma, Srikanth; Raja, Sharan; Mahapatra, Pallab Sinha; Panchangnula, Mahesh
2017-11-01
The brachistochrone curve for a non-dissipative particle tries to maximize inertia of the particle but for a fluid filled cylinder, increasing inertia would amount to high dissipative losses. Hence the trade off between inertia and dissipation plays a vital role in the dynamics of a fluid filled cylinder. This trade off manifests itself in the form of an integro-differential equation governing the angular acceleration of the cylinder. Here, we compute the brachistochrone curve using optimal control principles and investigate the effect of the fore mentioned trade off on the deviation of the brachistochrone curve from that of a non-dissipative particle. Also, we investigate the effects of the non-dimensional parameters of the problem on the shape of the brachistochrone curve. We analyze the dissipation rate during the cylinder's motion and show that energy based arguments don't hold good for a fluid filled cylinder. We then analyze the stability of the time varying fluid flow in the cylinder and find an admissible region for the terminal point which would ensure the stability of the fluid flow as the cylinder rolls over the brachistochrone curve.
Critical Factors for Inducing Curved Somatosensory Saccades
Directory of Open Access Journals (Sweden)
Tamami Nakano
2011-10-01
Full Text Available We are able to make a saccade toward a tactile stimuli to one hand, but trajectories of many saccades curved markedly when the arms were crossed (Groh & Sparks, 2006. However, it remains unknown why some curved and others did not. We therefore examined critical factors for inducing the curved somatosensory saccades. Participants made a saccade as soon as possible from a central fixation point toward a tactile stimulus delivered to one of the two hands, and switched between arms-crossed and arms-uncrossed postures every 6 trials. Trajectories were generally straight when the arms were uncrossed, but all participants made curved saccades when the arms were crossed (12–64%. We found that the probability of curved saccades depended critically on the onset latency: the probability was less than 5% when the latency was larger than 250 ms, but the probability increased up to 70–80% when the onset latency was 160 ms. This relationship was shared across participants. The results suggest that a touch in the arms-crossed posture was always mapped to the wrong hand in the initial phase up to 160 ms, and then remapped to the correct hand during the next 100 ms by some fundamental neural mechanisms shared across participants.
Paulmichl, Katharina; Hatunic, Mensud; Højlund, Kurt; Jotic, Aleksandra; Krebs, Michael; Mitrakou, Asimina; Porcellati, Francesca; Tura, Andrea; Bergsten, Peter; Forslund, Anders; Manell, Hannes; Widhalm, Kurt; Weghuber, Daniel; Anderwald, Christian-Heinz
2016-09-01
The triglyceride-to-HDL cholesterol (TG/HDL-C) ratio was introduced as a tool to estimate insulin resistance, because circulating lipid measurements are available in routine settings. Insulin, C-peptide, and free fatty acids are components of other insulin-sensitivity indices but their measurement is expensive. Easier and more affordable tools are of interest for both pediatric and adult patients. Study participants from the Relationship Between Insulin Sensitivity and Cardiovascular Disease [43.9 (8.3) years, n = 1260] as well as the Beta-Cell Function in Juvenile Diabetes and Obesity study cohorts [15 (1.9) years, n = 29] underwent oral-glucose-tolerance tests and euglycemic clamp tests for estimation of whole-body insulin sensitivity and calculation of insulin sensitivity indices. To refine the TG/HDL ratio, mathematical modeling was applied including body mass index (BMI), fasting TG, and HDL cholesterol and compared to the clamp-derived M-value as an estimate of insulin sensitivity. Each modeling result was scored by identifying insulin resistance and correlation coefficient. The Single Point Insulin Sensitivity Estimator (SPISE) was compared to traditional insulin sensitivity indices using area under the ROC curve (aROC) analysis and χ(2) test. The novel formula for SPISE was computed as follows: SPISE = 600 × HDL-C(0.185)/(TG(0.2) × BMI(1.338)), with fasting HDL-C (mg/dL), fasting TG concentrations (mg/dL), and BMI (kg/m(2)). A cutoff value of 6.61 corresponds to an M-value smaller than 4.7 mg · kg(-1) · min(-1) (aROC, M:0.797). SPISE showed a significantly better aROC than the TG/HDL-C ratio. SPISE aROC was comparable to the Matsuda ISI (insulin sensitivity index) and equal to the QUICKI (quantitative insulin sensitivity check index) and HOMA-IR (homeostasis model assessment-insulin resistance) when calculated with M-values. The SPISE seems well suited to surrogate whole-body insulin sensitivity from inexpensive fasting single-point blood draw and BMI
1990-01-01
M.Milanese Dipartimento di Automatica e Informatica Politecnico di Torino Many different problems such as linear and nonlinear regressions, parameter and...OF A GIVEN SET OF POINTS Leonardo Traversoni Dominguez Division de Ciencias Basicas e Ingenieria Universidad Autonoma Metropolitana (Iztapalapa) ap
Directory of Open Access Journals (Sweden)
Sergey A. Cherkis
2007-03-01
Full Text Available A typical solution of an integrable system is described in terms of a holomorphic curve and a line bundle over it. The curve provides the action variables while the time evolution is a linear flow on the curve's Jacobian. Even though the system of Nahm equations is closely related to the Hitchin system, the curves appearing in these two cases have very different nature. The former can be described in terms of some classical scattering problem while the latter provides a solution to some Seiberg-Witten gauge theory. This note identifies the setup in which one can formulate the question of relating the two curves.
Full Text Available ... en español Blog About OnSafety CPSC Stands for Safety The Tipping Point Home > 60 Seconds of Safety (Videos) > The Tipping Point The Tipping Point by ... danger death electrical fall furniture head injury product safety television tipover tv Watch the video in Adobe ...
Xu, Lili; Luo, Shuqian
2010-01-01
Microaneurysms (MAs) are the first manifestations of the diabetic retinopathy (DR) as well as an indicator for its progression. Their automatic detection plays a key role for both mass screening and monitoring and is therefore in the core of any system for computer-assisted diagnosis of DR. The algorithm basically comprises the following stages: candidate detection aiming at extracting the patterns possibly corresponding to MAs based on mathematical morphological black top hat, feature extraction to characterize these candidates, and classification based on support vector machine (SVM), to validate MAs. Feature vector and kernel function of SVM selection is very important to the algorithm. We use the receiver operating characteristic (ROC) curve to evaluate the distinguishing performance of different feature vectors and different kernel functions of SVM. The ROC analysis indicates the quadratic polynomial SVM with a combination of features as the input shows the best discriminating performance.
Johnson, L. E.; Kim, J.; Cifelli, R.; Chandra, C. V.
2016-12-01
Potential water retention, S, is one of parameters commonly used in hydrologic modeling for soil moisture accounting. Physically, S indicates total amount of water which can be stored in soil and is expressed in units of depth. S can be represented as a change of soil moisture content and in this context is commonly used to estimate direct runoff, especially in the Soil Conservation Service (SCS) curve number (CN) method. Generally, the lumped and the distributed hydrologic models can easily use the SCS-CN method to estimate direct runoff. Changes in potential water retention have been used in previous SCS-CN studies; however, these studies have focused on long-term hydrologic simulations where S is allowed to vary at the daily time scale. While useful for hydrologic events that span multiple days, the resolution is too coarse for short-term applications such as flash flood events where S may not recover its full potential. In this study, a new method for estimating a time-variable potential water retention at hourly time-scales is presented. The methodology is applied for the Napa River basin, California. The streamflow gage at St Helena, located in the upper reaches of the basin, is used as the control gage site to evaluate the model performance as it is has minimal influences by reservoirs and diversions. Rainfall events from 2011 to 2012 are used for estimating the event-based SCS CN to transfer to S. As a result, we have derived the potential water retention curve and it is classified into three sections depending on the relative change in S. The first is a negative slope section arising from the difference in the rate of moving water through the soil column, the second is a zero change section representing the initial recovery the potential water retention, and the third is a positive change section representing the full recovery of the potential water retention. Also, we found that the soil water moving has traffic jam within 24 hours after finished first
Identification and "reverse engineering" of Pythagorean-hodograph curves
Farouki, RT; Giannelli, C; Sestini, A
2015-01-01
© 2015 Elsevier B.V. All rights reserved. Methods are developed to identify whether or not a given polynomial curve, specified by Bézier control points, is a Pythagorean-hodograph (PH) curve - and, if so, to reconstruct the internal algebraic structure that allows one to exploit the advantageous properties of PH curves. Two approaches to identification of PH curves are proposed. The first is based on the satisfaction of a system of algebraic constraints by the control-polygon legs, and the se...
International Nuclear Information System (INIS)
Moura, A.M.S.; Campos, J.C.F. de; Scaff, L.A.M.; Val Kopacek, A.B. do
1985-01-01
Information about the beam profile of 4 MV X-rays through irradiation of radiographic films is presented. The films were irradiated in parallel to the central axis, within tissue-like phantom and in conditions of clinical application. The conclusion is that the method does not supply absolute values of percentage depth dose over points outside of beam bounds, but throughout the corrections it may be of great utility in radiation dosimetry. (Author) [pt
Analysis and research on curved surface's prototyping error based on FDM process
Gong, Y. D.; Zhang, Y. C.; Yang, T. B.; Wang, W. S.
2008-12-01
Analysis and research methods on curved surface's prototyping error with FDM (Fused Deposition Modeling) process are introduced in this paper, then the experiment result of curved surface's prototyping error is analyzed, and the integrity of point cloud information and the fitting method of curved surface prototyping are discussed as well as the influence on curved surface's prototyping error with different software. Finally, the qualitative and quantitative conclusions on curved surface's prototyping error are acquired in this paper.
Anzolin, Caroline Cristina; Silva, Diego Augusto Santos; Zanuto, Edner Fernando; Cayres, Suziane Ungari; Codogno, Jamile Sanches; Costa Junior, Paulo; Machado, Dalmo Roberto Lopes; Christofaro, Diego Giulliano Destro
To evaluate the sensitivity and specificity of different cutoff points of body mass index for predicting overweight/obesity according to body fat values estimated by DEXA among Brazilian adolescents. Cross-sectional study including 229 male adolescents aged 10-15 years, in which body adiposity and anthropometric measures were assessed. Nutritional status was classified by BMI according to cutoff points described in scientific literature. Moderate agreements were observed between body fat estimated by DEXA and cutoffs proposed by Cole et al. (K=0.61), Conde and Monteiro (K=0.65), Must et al. (K=0.61) and WHO (K=0.63). The BMI in continuous form showed good agreement with the Dexa (ICC=0.72). The highest sensitivity was observed for cutoff by Conde and Monteiro (0.74 [0.62, 0.84]) and the highest specificity by Cole et al. (0.98 [0.94, 0.99]). For the areas under the ROC curve of cutoff points analyzed, significant difference comparing the cutoff points by Cole et al. and Conde and Monteiro (0.0449 [0.00294, 0.0927]) was observed. The cutoff proposed by Conde and Monteiro was more sensitive in identifying overweight and obesity when compared to the reference method, and the cutoff proposed by Cole et al. presented the highest specificity for such outcomes. Copyright © 2016 Sociedade Brasileira de Pediatria. Published by Elsevier Editora Ltda. All rights reserved.
Directory of Open Access Journals (Sweden)
Gustavo José Mora-García
2014-03-01
Full Text Available Objective. To estimate anthropometric parameters’ (APs cut-off points and association for metabolic syndrome (MetS. Materials and methods. A cross-sectional study was carried out with a total of 434 adult women from Cartagena de Indias, Colombia, in 2012. APs measured were waist circumference (WC, body mass index (BMI, body adiposity index (BAI, waist-hip ratio (WHR and waist-height ratio (WHtR. Cut-off points were estimated by a receiver operating characteristic curve (ROC. Logistic regression was applied to estimate possible associations. Results. Cut-off points for WC, BMI, BAI, WHR and WHtR were 85 cm, 28 kg/m2, 39%, 0.80 and 56, respectively. Only WHtR was associated to MetS (OR=1.11, CI95% [1.07-1.15]. Conclusion. WC cut-off point was higher than those proposed for Latin-American women by the Joint Interim Statement (JIS. WHtR had a low predictive value for MetS.
Tian, Guangming; Wang, Qin; Wei, Xuetuan; Ma, Xin; Chen, Shouwen
2017-04-01
Poly-γ-glutamic acid (γ-PGA), a natural biopolymer, is widely used in cosmetics, medicine, food, water treatment, and agriculture owing to its features of moisture sequestration, cation chelation, non-toxicity and biodegradability. Intracellular glutamic acid, the substrate of γ-PGA, is a limiting factor for high yield in γ-PGA production. Bacillus subtilis and Bacillus licheniformis are both important γ-PGA producing strains, and B. subtilis synthesizes glutamic acid in vivo using the unique GOGAT/GS pathway. However, little is known about the glutamate synthesis pathway in B. licheniformis. The aim of this work was to characterize the glutamate dehydrogenase (RocG) in glutamic acid synthesis from B. licheniformis with both in vivo and in vitro experiments. By re-directing the carbon flux distribution, the rocG gene deletion mutant WX-02ΔrocG produced intracellular glutamic acid with a concentration of 90ng/log(CFU), which was only 23.7% that of the wild-type WX-02 (380ng/log(CFU)). Furthermore, the γ-PGA yield of mutant WX-02ΔrocG was 5.37g/L, a decrease of 45.3% compared to the wild type (9.82g/L). In vitro enzymatic assays of RocG showed that RocG has higher affinity for 2-oxoglutarate than glutamate, and the glutamate synthesis rate was far above degradation. This is probably the first study to reveal the glutamic acid synthesis pathway and the specific functions of RocG in B. licheniformis. The results indicate that γ-PGA production can be enhanced through improving intracellular glutamic acid synthesis. Copyright © 2017 Elsevier Inc. All rights reserved.
DeBari, Vincent A
2009-01-01
It has been demonstrated that decision levels (DL) and their confidence intervals (CI) can be estimated from the second derivative, f '' (P), of the logistic regression probability curve (LRPC). Although this method generally provides smooth curves from which DL and CI can be obtained, there are datasets that generate "noisy" curves making these measurements difficult. The purpose of this study was to develop a procedure to obviate this noise, thus allowing the more facile estimation of DL and CI. Data from two clinical studies were examined. Logistic regression analysis was performed and the first derivatives, f ' (P), were fitted to Gaussian models. The derivatives of these surrogate f ' (P) were generated to provide f '' (P) and were compared with data from receiver operating characteristic (ROC) curves. For both sets of data, the surrogate curves demonstrated strong fits to the natural f ' (P) with r(2) = 0.986 for one study and 0.832 for the second. The f '' (P) generated from the surrogate curves demonstrated single maxima (M) and minima (m), compared with the f '' (P) generated from the natural f ' (P) in which multiple M and m were observed. Easily discernible DL and CI were observed for both datasets with differences from ROC-estimated DL of 1.7% for the first study and 4.8% for the second. The use of a surrogate Gaussian simulation of f ' (P) may be a useful alternative to natural f ' (P) when using the f '' (P) of the LRPC to determine DL and CI.
CUTOFF POINT OF THE PHASE ANGLE IN PRE-RADIOTHERAPY CANCER PATIENTS.
Souza Thompson Motta, Rachel; Alves Castanho, Ivany; Guillermo Coca Velarde, Luis
2015-11-01
malnutrition is a common complication for cancer patients. The phase angle (PA), direct measurement of bioelectrical impedance analysis (BIA), has been considered a predictor of body cell mass and prognostic indicator. Cutoff points for phase angle (PA) associated with nutritional risk in cancer patients have not been determined yet. assess the possibility of determining the cutoff point for PA to identify nutritional risk in pre-radiotherapy cancer patients. sample group: Patients from both genders diagnosed with cancer and sent for ambulatory radiotherapy. body mass index (BMI), percentage of weight loss (% WL), mid-arm circumference (MAC), triceps skinfold thickness (TST), mid-arm muscle circumference (MAMC), mid-arm muscle area (MAMA), score and categorical assessment obtained using the Patient-Generated Subjective Global Assessment (PG-SGA) form, PA and standardized phase angle (SPA). Kappa coefficient was used to test the degree of agreement between the diagnoses of nutritional risk obtained from several different methods of nutritional assessment. Cutoff points for the PA through anthropometric indicators and PG-SGA were determined by using Receiver Operating Characteristic (ROC) curves, and patient survival was analyzed with the Cox regression method. the cutoff points with the greatest discriminatory power were those obtained from BMI (5.2) and the categorical assessment of PG-SGA (5.4). The diagnosis obtained using these cutoff points showed a significant association with risk of death for the patients in the sample group. we recommend using the cutoff point 5.2 for the PA as a criterion for identifying nutritional risk in pre-radiotherapy cancer patients. Copyright AULA MEDICA EDICIONES 2014. Published by AULA MEDICA. All rights reserved.
Rapid point-of-care breath test for biomarkers of breast cancer and abnormal mammograms.
Directory of Open Access Journals (Sweden)
Michael Phillips
Full Text Available BACKGROUND: Previous studies have reported volatile organic compounds (VOCs in breath as biomarkers of breast cancer and abnormal mammograms, apparently resulting from increased oxidative stress and cytochrome p450 induction. We evaluated a six-minute point-of-care breath test for VOC biomarkers in women screened for breast cancer at centers in the USA and the Netherlands. METHODS: 244 women had a screening mammogram (93/37 normal/abnormal or a breast biopsy (cancer/no cancer 35/79. A mobile point-of-care system collected and concentrated breath and air VOCs for analysis with gas chromatography and surface acoustic wave detection. Chromatograms were segmented into a time series of alveolar gradients (breath minus room air. Segmental alveolar gradients were ranked as candidate biomarkers by C-statistic value (area under curve [AUC] of receiver operating characteristic [ROC] curve. Multivariate predictive algorithms were constructed employing significant biomarkers identified with multiple Monte Carlo simulations and cross validated with a leave-one-out (LOO procedure. RESULTS: Performance of breath biomarker algorithms was determined in three groups: breast cancer on biopsy versus normal screening mammograms (81.8% sensitivity, 70.0% specificity, accuracy 79% (73% on LOO [C-statistic value], negative predictive value 99.9%; normal versus abnormal screening mammograms (86.5% sensitivity, 66.7% specificity, accuracy 83%, 62% on LOO; and cancer versus no cancer on breast biopsy (75.8% sensitivity, 74.0% specificity, accuracy 78%, 67% on LOO. CONCLUSIONS: A pilot study of a six-minute point-of-care breath test for volatile biomarkers accurately identified women with breast cancer and with abnormal mammograms. Breath testing could potentially reduce the number of needless mammograms without loss of diagnostic sensitivity.
Intersection numbers of spectral curves
Eynard, B
2011-01-01
We compute the symplectic invariants of an arbitrary spectral curve with only 1 branchpoint in terms of integrals of characteristic classes in the moduli space of curves. Our formula associates to any spectral curve, a characteristic class, which is determined by the laplace transform of the spectral curve. This is a hint to the key role of Laplace transform in mirror symmetry. When the spectral curve is y=\\sqrt{x}, the formula gives Kontsevich--Witten intersection numbers, when the spectral curve is chosen to be the Lambert function \\exp{x}=y\\exp{-y}, the formula gives the ELSV formula for Hurwitz numbers, and when one chooses the mirror of C^3 with framing f, i.e. \\exp{-x}=\\exp{-yf}(1-\\exp{-y}), the formula gives the topological vertex formula, i.e. the generating function of Gromov-Witten invariants of C^3. In some sense this formula generalizes ELSV formula, and Mumford formula.
Optimization on Spaces of Curves
DEFF Research Database (Denmark)
Møller-Andersen, Jakob
This thesis is concerned with computational and theoretical aspects of Riemannian metrics on spaces of regular curves, and their applications. It was recently proved that second order constant coefficient Sobolev metrics on curves are geodesically complete. We extend this result to the case...... of Sobolev metrics with coefficient functions depending on the length of the curve. We show how to apply this result to analyse a wide range of metrics on the submanifold of unit and constant speed curves. We present a numerical discretization of second order Sobolev metrics on the space of regular curves...... of cardiac deformations. Finally we investigate a new application of Riemannian shape analysis in shape optimization. We setup a simple elliptic model problem, and describe how to apply shape calculus to obtain directional derivatives in the manifold of planar curves. We present an implementation based...
Reflection of curved shock waves
Mölder, S.
2017-09-01
Shock curvatures are related to pressure gradients, streamline curvatures and vorticity in flows with planar and axial symmetry. Explicit expressions, in an influence coefficient format, are used to relate post-shock pressure gradient, streamline curvature and vorticity to pre-shock gradients and shock curvature in steady flow. Using higher order, von Neumann-type, compatibility conditions, curved shock theory is applied to calculate the flow near singly and doubly curved shocks on curved surfaces, in regular shock reflection and in Mach reflection. Theoretical curved shock shapes are in good agreement with computational fluid dynamics calculations and experiment.
Goncalves, Elton C; Koh, Jin; Zhu, Ning; Yoo, Mi-Jeong; Chen, Sixue; Matsuo, Takuya; Johnson, Jodie V; Rathinasabapathi, Bala
2016-03-01
Microalgal triacylglycerol (TAG), a promising source of biofuel, is induced upon nitrogen starvation (-N), but the proteins and genes involved in this process are poorly known. We performed isobaric tagging for relative and absolute quantification (iTRAQ)-based quantitative proteomics to identify Chlorella proteins with modulated expression under short-term -N. Out of 1736 soluble proteins and 2187 membrane-associated proteins identified, 288 and 56, respectively, were differentially expressed under -N. Gene expression analysis on select genes confirmed the same direction of mRNA modulation for most proteins. The MYB-related transcription factor ROC40 was the most induced protein, with a 9.6-fold increase upon -N. In a previously generated Chlamydomonas mutant, gravimetric measurements of crude total lipids revealed that roc40 was impaired in its ability to increase the accumulation of TAG upon -N, and this phenotype was complemented when wild-type Roc40 was expressed. Results from radiotracer experiments were consistent with the roc40 mutant being comparable to the wild type in recycling membrane lipids to TAG but being impaired in additional de novo synthesis of TAG during -N stress. In this study we provide evidence to support the hypothesis that transcription factor ROC40 has a role in -N-induced lipid accumulation, and uncover multiple previously unknown proteins modulated by short-term -N in green algae. © 2016 The Authors The Plant Journal © 2016 John Wiley & Sons Ltd.
Bayat, Hossein; Sedaghat, Azadeh; Safari Sinegani, Ali Akbar; Gregory, Andrew S.
2015-03-01
This study was conducted to estimate the soil unsaturated hydraulic conductivity through the van Genuchten model using easy to measure soil properties by regression and artificial neural networks methods. In this study, 148 soil samples were taken from five provinces of Iran. Basic soil properties (clay, silt/sand and bulk density) and other soil properties were measured. Soil water retention curve was measured to obtain the unsaturated hydraulic conductivity curve using the van Genuchten-Mualem model. Confined compression curve was measured and the modified model of van Genuchten was fitted on its data. Two-thirds and one-third of the data were used for the training and testing steps, respectively. Confined compression curve parameters and other soil properties were used as predictors to estimate unsaturated hydraulic conductivity curve. Pedotransfer functions (PTFs) were developed in two separate parts: in 5 and 6 PTFs basic soil properties were or were not used as predictors, respectively. The artificial neural networks (ANNs) performed better than the regression methods. Among the ANN-developed PTFs which have not used basic soil properties as predictors, PTFa3, with the inputs of the parameters of confined compression curve (n∗, α∗ and e0), performed better than the others. Also, among the ANN-developed PTFs that used basic soil properties as predictors along with the other input variables, PTFb5 that used the σmc (stress at the maximum curvature) and σi (stress at the inflection point) as inputs along with basic soil properties, performed better than the other PTFs. The results showed a successful prediction of the hydraulic conductivity curve using confined compression curve.
Directory of Open Access Journals (Sweden)
Rita Maria da Silva
2009-12-01
Full Text Available OBJETIVO: Analisar a acurácia do diagnóstico de dois protocolos de imunofluorescência indireta para leishmaniose visceral canina. MÉTODOS: Cães provenientes de inquérito soroepidemiológico realizado em área endêmica nos municípios de Araçatuba e de Andradina, na região noroeste do estado de São Paulo, em 2003, e área não endêmica da região metropolitana de São Paulo, foram utilizados para avaliar comparativamente dois protocolos da reação de imunofluorescência indireta (RIFI para leishmaniose: um utilizando antígeno heterólogo Leishmania major (RIFI-BM e outro utilizando antígeno homólogo Leishmania chagasi (RIFI-CH. Para estimar acurácia utilizou-se a análise two-graph receiver operating characteristic (TG-ROC. A análise TG-ROC comparou as leituras da diluição 1:20 do antígeno homólogo (RIFI-CH, consideradas como teste referência, com as diluições da RIFI-BM (antígeno heterólogo. RESULTADOS: A diluição 1:20 do teste RIFI-CH apresentou o melhor coeficiente de contingência (0,755 e a maior força de associação entre as duas variáveis estudadas (qui-quadrado=124,3, sendo considerada a diluição-referência do teste nas comparações com as diferentes diluições do teste RIFI-BM. Os melhores resultados do RIFI-BM foram obtidos na diluição 1:40, com melhor coeficiente de contingência (0,680 e maior força de associação (qui-quadrado=80,8. Com a mudança do ponto de corte sugerido nesta análise para a diluição 1:40 da RIFI-BM, o valor do parâmetro especificidade aumentou de 57,5% para 97,7%, embora a diluição 1:80 tivesse apresentado a melhor estimativa para sensibilidade (80,2% com o novo ponto de corte. CONCLUSÕES: A análise TG-ROC pode fornecer importantes informações sobre os testes de diagnósticos, além de apresentar sugestões sobre pontos de cortes que podem melhorar as estimativas de sensibilidade e especificidade do teste, e avaliá-los a luz do melhor custo
Full Text Available ... OnSafety CPSC Stands for Safety The Tipping Point Home > 60 Seconds of Safety (Videos) > The Tipping Point ... 24 hours a day. For young children whose home is a playground, it’s the best way to ...
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 5; Issue 5. Fixed Points - From Russia with Love - A Primer of Fixed Point Theory. A K Vijaykumar. Book Review Volume 5 Issue 5 May 2000 pp 101-102. Fulltext. Click here to view fulltext PDF. Permanent link:
Parameter Deduction and Accuracy Analysis of Track Beam Curves in Straddle-type Monorail Systems
Directory of Open Access Journals (Sweden)
Xiaobo Zhao
2015-12-01
Full Text Available The accuracy of the bottom curve of a PC track beam is strongly related to the production quality of the entire beam. Many factors may affect the parameters of the bottom curve, such as the superelevation of the curve and the deformation of a PC track beam. At present, no effective method has been developed to determine the bottom curve of a PC track beam; therefore, a new technique is presented in this paper to deduce the parameters of such a curve and to control the accuracy of the computation results. First, the domain of the bottom curve of a PC track beam is assumed to be a spindle plane. Then, the corresponding supposed top curve domain is determined based on a geometrical relationship that is the opposite of that identified by the conventional method. Second, several optimal points are selected from the supposed top curve domain according to the dichotomy algorithm; the supposed top curve is thus generated by connecting these points. Finally, one rigorous criterion is established in the fractal dimension to assess the accuracy of the assumed top curve deduced in the previous step. If this supposed curve coincides completely with the known top curve, then the assumed bottom curve corresponding to the assumed top curve is considered to be the real bottom curve. This technique of determining the bottom curve of a PC track beam is thus proven to be efficient and accurate.
Batic, D.; Nelson, S.; Nowakowski, M.
2015-05-01
We consider the motion of light on different spacetime manifolds by calculating the deflection angle, lensing properties and by probing into the possibility of bound states. The metrics in which we examine the light motion include, among other items, a general relativistic dark matter metric, a dirty black hole, and a worm hole metric, the last two inspired by noncommutative geometry. The lensing in a holographic screen metric is discussed in detail. We study also the bending of light around naked singularities like, e.g., the Janis-Newman-Winicour metric and include other cases. A generic property of light behavior in these exotic metrics is pointed out. For the standard metric like the Schwarzschild and Schwarzschild-de Sitter cases, we improve the accuracy of the lensing results for the weak and strong regimes.
Coexistence Curve of Perfluoromethylcyclohexane-Isopropyl Alcohol
Jacobs, D. T.; Kuhl, D. E.; Selby, C. E.
1996-01-01
The coexistence curve of the binary fluid mixture perfluoromethylcyclohexane-isopropyl alcohol was determined by precisely measuring the refractive index both above and below its upper critical consolute point. Sixty-seven two-phase data points were obtained over a wide range of reduced temperatures, 10(exp -5) less than t less than 2.5 x 10(exp -1), to determine the location of the critical point: critical temperature=89.901 C, and critical composition = 62.2% by volume perfluoromethylcyclohexane. These data were analyzed to determine the critical exponent 8 close to the critical point, the amplitude B, and the anomaly in the diameter. The volume-fraction coexistence curve is found to be as symmetric as any composition like variable. Correction to scaling is investigated as well as the need for a crossover theory. A model is proposed that describes the asymptotic approach to zero of the effective exponent Beta, which allows an estimation of the temperature regime free of crossover effects.
Use of tidal breathing curves for evaluating expiratory airway obstruction in infants.
Hevroni, Avigdor; Goldman, Aliza; Blank-Brachfeld, Miriam; Abu Ahmad, Wiessam; Ben-Dov, Lior; Springer, Chaim
2018-01-15
To evaluate tidal breathing (TB) flow-volume and flow-time curves for identification of expiratory airway obstruction in infants. Pulmonary function tests were analyzed retrospectively in 156 infants aged 3-24 months with persistent or recurrent respiratory complaints. Parameters derived from TB curves were compared to maximal expiratory flow at functional residual capacity ([Formula: see text]maxFRC) measured by rapid thoracoabdominal compression technique. Analyzed parameters were: inspiratory time (t I ), expiratory time (t E ), tidal volume, peak tidal expiratory flow (PTEF), time to peak tidal expiratory flow (t PTEF ), expiratory flow when 50% and 25% of tidal volume remains in the lungs (FEF 50 , FEF 25 , respectively), and the ratios t PTEF /t E , t I /t E , FEF 50 /PTEF, and FEF 25 /PTEF. Statistical comparisons between flow indices and TB parameters were performed using mean squared error and Pearson's sample correlation coefficient. The study population was also divided into two groups based on severity of expiratory obstruction (above or below z-score for [Formula: see text]maxFRC of -2) to generate receiver operating characteristic (ROC) curves and calculate discriminatory values between the groups. TB parameters that were best correlated to [Formula: see text]maxFRC were: t PTEF /t E , FEF 50 /PTEF, and FEF 25 /PTEF, with r = 0.61, 0.67, 0.65, respectively (p < 0.0001 for all). ROC curves for FEF 50 /PTEF, FEF 25 /PTEF and t PTEF /t E showed areas under the curve of 0.813, 0.797, and 0.796, respectively. Cutoff value z-scores of -0.35, -0.34, and -0.43 for these three parameters, respectively, showed an 86% negative predictive value for severe airway obstructions. TB curves can assist in ruling out severe expiratory airway obstruction in infants.
Regular homotopy of Hurwitz curves
International Nuclear Information System (INIS)
Auroux, D; Kulikov, Vik S; Shevchishin, V V
2004-01-01
We prove that any two irreducible cuspidal Hurwitz curves C 0 adn C 1 (or, more generally, two curves with A-type singularities) in the Hirzebruch surface F N with the same homology classes and sets of singularities are regular homotopic. Moreover, they are symplectically regular homotopic if C 0 and C 1 are symplectic with respect to a compatible symplectic form
Space curves, anholonomy and nonlinearity
Indian Academy of Sciences (India)
Walker parallel transport [14] of any vector P moved ... of Fermi–Walker parallel transport to the case of a moving space curve. 4. General curve evolution equations .... ear term of the Lamb equation (eq. (34)) is just the time derivative of the total.
potentiometric titration curves of aluminium salt solutions and its
African Journals Online (AJOL)
a
species, which set up a base to study on the hydrolysis-polymerization of Al3+. At the same time, significant effects of total aluminum concentration, temperature, halide ion, silicate radical, and organic acid radical on the titration curves and its critical points were observed. Given the three critical points which demarcating the ...
Potentiometric titration curves of aluminium salt solutions and its ...
African Journals Online (AJOL)
At the same time, significant effects of total aluminum concentration, temperature, halide ion, silicate radical, and organic acid radical on the titration curves and its critical points were observed. Given the three critical points which demarcating the aluminum forms, we carry out a through investigation into the fundamental ...
Gunka, Katrin; Newman, Joseph A; Commichau, Fabian M; Herzberg, Christina; Rodrigues, Cecilia; Hewitt, Lorraine; Lewis, Richard J; Stülke, Jörg
2010-07-23
Any signal transduction requires communication between a sensory component and an effector. Some enzymes engage in signal perception and transduction, as well as in catalysis, and these proteins are known as "trigger" enzymes. In this report, we detail the trigger properties of RocG, the glutamate dehydrogenase of Bacillus subtilis. RocG not only deaminates the key metabolite glutamate to form alpha-ketoglutarate but also interacts directly with GltC, a LysR-type transcription factor that regulates glutamate biosynthesis from alpha-ketoglutarate, thus linking the two metabolic pathways. We have isolated mutants of RocG that separate the two functions. Several mutations resulted in permanent inactivation of GltC as long as a source of glutamate was present. These RocG proteins have lost their ability to catabolize glutamate due to a strongly reduced affinity for glutamate. The second class of mutants is exemplified by the replacement of aspartate residue 122 by asparagine. This mutant protein has retained enzymatic activity but has lost the ability to control the activity of GltC. Crystal structures of glutamate dehydrogenases that permit a molecular explanation of the properties of the various mutants are presented. Specifically, we may propose that D122N replacement affects the surface of RocG. Our data provide evidence for a correlation between the enzymatic activity of RocG and its ability to inactivate GltC, and thus give insights into the mechanism that couples the enzymatic activity of a trigger enzyme to its regulatory function. Copyright (c) 2010 Elsevier Ltd. All rights reserved.
Directory of Open Access Journals (Sweden)
Mingjia Tan
2006-12-01
Full Text Available Skp1-cullin-F-box protein (SCF is a multicomponent E3 ubiquitin (Ub ligase that ubiquitinates a number of important biologic molecules such as p27, β-catenin, and lκB for proteasomal degradation, thus regulating cell proliferation and survival. One SCF component, SAG/ROC2/Rbx2/Hrt2, a RING finger protein, was first identified as a redox-inducible protein, which, when overexpressed, inhibited apoptosis both in vitro and in vivo. We report here that sensitive to apoptosis gene (SAG, as well as its family member ROC1/Rbxi, bound to the proinactive form of caspase-3 (pro-caspase-3. Binding was likely mediated through F-box protein, β-transducin repeat-containing protein (β-TrCP, which binds to the first 38 amino acids of pro-caspase-3. Importantly, β-TrCP1 expression significantly shortened the protein half-life of pro-caspase-3, whereas expression of a dominant-negative β-TrCP1 mutant with the F-box domain deleted extended it. An in vitro ubiquitination assay showed that SAG/ROC-SCF -Trcp promoted ubiquitination of pro-caspase-3. Furthermore, endogenous levels of pro-caspase-3 were decreased by overexpression of SAG/ROC-SCFβ-TrCP E3 Ub ligases, but increased on siRNA silencing of SAG, regulator of cullin-1 (ROC1, or β-TrCPs, leading to increased apoptosis by etoposide and TNF-related apoptosis-inducing ligand through increased activation of caspase-3. Thus, pro-caspase-3 appears to be a substrate of SAG/ROC-SCFβ-TrCP E3 Ub ligase, which protects cells from apoptosis through increased apoptosis threshold by reducing the basal level of pro-caspase-3.
Full Text Available ... Point by CPSC Blogger September 22, 2009 appliance child Childproofing CPSC danger death electrical fall furniture head ... see news reports about horrible accidents involving young children and furniture, appliance and tv tip-overs. The ...
Sacco, Chiara; Perna, Serena; Vicari, Donatella; Alfò, Marco; Bauer, Carl-Peter; Hoffman, Ute; Forster, Johannes; Zepp, Fred; Schuster, Antje; Wahn, Ulrich; Keil, Thomas; Lau, Susanne; Matricardi, Paolo Maria
2017-09-01
Previous studies of serum total IgE (t-IgE) were not able to discriminate well-enough atopic from non-atopic subjects, that is, with or without serum-specific IgE antibodies to allergens. To model growth curves of the total IgE levels in children without atopic sensitization (hereafter defined as "normal" t-IgE levels) and to test their usefulness in predicting atopic sensitization. The German Multicentre Allergy Study (MAS), a birth cohort with 1314 recruited newborns, began in 1990 and examined the participants until age 20 years. Total and specific IgE (t-IgE, s-IgE) were analyzed with a fluorescent enzyme immunoassay ImmunoCAP (TFS, Sweden) at ages 1, 2, 3, 5, 6, 7, 10, 13, and 20 years. Participants were classified as "never atopic" if all their available serum samples had negative response (cutoff: IgE to the nine common foodborne and airborne allergenic extracts (milk, egg, soy, wheat, house dust mite, cat, dog, birch, and grass) tested in the MAS birth cohort. By contrast, participants were defined as atopic if they had, for at least at one available serum sample, s-IgE≥0.35 kU A /L to at least one allergenic extract tested. The evolution of t-IgE levels in the "never atopic" children was described by growth curves, estimated by exploiting a quantile regression model. A "reference" percentile, based on the t-IgE value measured at age 5 years, was assigned to each child with no IgE sensitization at that age. Upward deviations from the own "reference" quantile of t-IgE in atopic and "never atopic" children were calculated and a ROC analysis was used to identify the best cutoff point for predicting atopic sensitization. Overall, 1113 of 1314 children were included in this analysis. Of these, 469 were "never atopic" and 644 atopic. Quantile trajectories of t-IgE levels in "never atopic" subjects were stable from 5 years of age, increased to a plateau at age 10-13 years, and decreased slightly afterward. The onset of atopic s-IgE responses was
Computational aspects of algebraic curves
Shaska, Tanush
2005-01-01
The development of new computational techniques and better computing power has made it possible to attack some classical problems of algebraic geometry. The main goal of this book is to highlight such computational techniques related to algebraic curves. The area of research in algebraic curves is receiving more interest not only from the mathematics community, but also from engineers and computer scientists, because of the importance of algebraic curves in applications including cryptography, coding theory, error-correcting codes, digital imaging, computer vision, and many more.This book cove
CYCLING CURVES AND THEIR APPLICATIONS
Directory of Open Access Journals (Sweden)
RAICU Lucian
2015-06-01
Full Text Available This paper proposes an analysis of the cyclic curves that can be considered as some of the most important regarding their applications in science, technique, design, architecture and art. These curves include the following: cycloid, epicycloid, hypocycloid, spherical cycloid and special cases thereof. In the first part of the paper the main curves of cycloids family are presented with their methods of generating and setting parametric equations. In the last part some of cycloid applications are highlighted in different areas of science, technology and art.
Equations for arithmetic pointed tori
Sijsling, J.R.
2010-01-01
In 1983, Kisao Takeuchi enumerated all 71 arithmetic (1;e)-groups. This is a special set of discrete subgroups of SL(2,R) of finite covolume and signature (1;e). The corresponding quotients of the upper half plane (called (1;e)-curves) have genus equal to 1 and a single elliptic point of order e.
A generative Bezier curve model for surf-zone tracking in coastal image sequences
CSIR Research Space (South Africa)
Burke, Michael G
2017-09-01
Full Text Available This work introduces a generative Bezier curve model suitable for surf-zone curve tracking in coastal image sequences. The model combines an adaptive curve parametrised by control points governed by local random walks with a global sinusoidal motion...
Elliptic Curves and Number Theory
Indian Academy of Sciences (India)
R. Sujatha, School of Mathematics, Tata Institute of Fundamental Research, Mumbai, INDIA
1. Aim: To explain the connection between a simple ancient problem in number theory and a deep sophisticated conjecture about Elliptic Curves. ('arithmetic Geometry'). Notation: N : set of natural numbers (1,2,3,...) ...
51Cr - erythrocyte survival curves
International Nuclear Information System (INIS)
Paiva Costa, J. de.
1982-07-01
Sixteen patients were studied, being fifteen patients in hemolytic state, and a normal individual as a witness. The aim was to obtain better techniques for the analysis of the erythrocytes, survival curves, according to the recommendations of the International Committee of Hematology. It was used the radiochromatic method as a tracer. Previously a revisional study of the International Literature was made in its aspects inherent to the work in execution, rendering possible to establish comparisons and clarify phonomena observed in cur investigation. Several parameters were considered in this study, hindering both the exponential and the linear curves. The analysis of the survival curves of the erythrocytes in the studied group, revealed that the elution factor did not present a homogeneous answer quantitatively to all, though, the result of the analysis of these curves have been established, through listed programs in the electronic calculator. (Author) [pt
Management of the learning curve
DEFF Research Database (Denmark)
Pedersen, Peter-Christian; Slepniov, Dmitrij
2016-01-01
Purpose – This paper focuses on the management of the learning curve in overseas capacity expansions. The purpose of this paper is to unravel the direct as well as indirect influences on the learning curve and to advance the understanding of how these affect its management. Design/methodology...... the dimensions of the learning process involved in a capacity expansion project and identified the direct and indirect labour influences on the production learning curve. On this basis, the study proposes solutions to managing learning curves in overseas capacity expansions. Furthermore, the paper concludes...... employs qualitative methodology and draws on a longitudinal, factory-level analysis of an in-depth case study of a Danish wind turbine manufacturer. Findings – This study goes beyond a simplistic treatment of the lead time and learning required to establish a new capacity. The authors examined...
Nonlinear mechanics of rigidifying curves.
Al Mosleh, Salem; Santangelo, Christian
2017-07-01
Thin shells are characterized by a high cost of stretching compared to bending. As a result isometries of the midsurface of a shell play a crucial role in their mechanics. In turn, curves on the midsurface with zero normal curvature play a critical role in determining the number and behavior of isometries. In this paper, we show how the presence of these curves results in a decrease in the number of linear isometries. Paradoxically, shells are also known to continuously fold more easily across these rigidifying curves than other curves on the surface. We show how including nonlinearities in the strain can explain these phenomena and demonstrate folding isometries with explicit solutions to the nonlinear isometry equations. In addition to explicit solutions, exact geometric arguments are given to validate and guide our analysis in a coordinate-free way.
Zhu, Luchang; Olsen, Randall J; Horstmann, Nicola; Shelburne, Samuel A; Fan, Jia; Hu, Ye; Musser, James M
2016-07-01
Variable-number tandem-repeat (VNTR) polymorphisms are ubiquitous in bacteria. However, only a small fraction of them has been functionally studied. Here, we report an intergenic VNTR polymorphism that confers an altered level of toxin production and increased virulence in Streptococcus pyogenes The nature of the polymorphism is a one-unit deletion in a three-tandem-repeat locus upstream of the rocA gene encoding a sensor kinase. S. pyogenes strains with this type of polymorphism cause human infection and produce significantly larger amounts of the secreted cytotoxins S. pyogenes NADase (SPN) and streptolysin O (SLO). Using isogenic mutant strains, we demonstrate that deleting one or more units of the tandem repeats abolished RocA production, reduced CovR phosphorylation, derepressed multiple CovR-regulated virulence factors (such as SPN and SLO), and increased virulence in a mouse model of necrotizing fasciitis. The phenotypic effect of the VNTR polymorphism was nearly the same as that of inactivating the rocA gene. In summary, we identified and characterized an intergenic VNTR polymorphism in S. pyogenes that affects toxin production and virulence. These new findings enhance understanding of rocA biology and the function of VNTR polymorphisms in S. pyogenes. Copyright © 2016, American Society for Microbiology. All Rights Reserved.
Bezier-curve Navigation Guidance for Impact Time and Angle Control
Directory of Open Access Journals (Sweden)
Gun-Hee MOON
2018-03-01
Full Text Available This paper addresses a novel impact time and angle control guidance law using a Bézier curve. The 2nd order Bézier curve consists of one control point and two boundary points; initial point P0, middle point P1 and end point P2. The curve is tangent to the line P0-P1 and the line P1-P2, respectively, and always exists in the convex hull of the control points. Proposed Bézier curve navigation guidance, makes the missile follow the Bézier curve with the feedback form of guidance command so that the missile hits the target on the desired time in the desired direction. We conducted numerical simulations on several terminal conditions to demonstrate the performance of proposed method.
International Nuclear Information System (INIS)
Haverkamp, U.; Wiezorek, C.; Poetter, R.
1990-01-01
Lyoluminescence dosimetry is based upon light emission during dissolution of previously irradiated dosimetric materials. The lyoluminescence signal is expressed in the dissolution glow curve. These curves begin, depending on the dissolution system, with a high peak followed by an exponentially decreasing intensity. System parameters that influence the graph of the dissolution glow curve, are, for example, injection speed, temperature and pH value of the solution and the design of the dissolution cell. The initial peak does not significantly correlate with the absorbed dose, it is mainly an effect of the injection. The decay of the curve consists of two exponential components: one fast and one slow. The components depend on the absorbed dose and the dosimetric materials used. In particular, the slow component correlates with the absorbed dose. In contrast to the fast component the argument of the exponential function of the slow component is independent of the dosimetric materials investigated: trehalose, glucose and mannitol. The maximum value, following the peak of the curve, and the integral light output are a measure of the absorbed dose. The reason for the different light outputs of various dosimetric materials after irradiation with the same dose is the differing solubility. The character of the dissolution glow curves is the same following irradiation with photons, electrons or neutrons. (author)
International Nuclear Information System (INIS)
Choi, Chang Woon; Lee, Dong Soo; Kim, Sang Eun; Chung, June Key; Lee, Myung Chul; Park, Young Bae; Seo, Jung Don; Lee, Young Woo; Koh, Chang Soon
1992-01-01
Gated blood pool scan is frequently used for evaluating the change in cardiac function in various cardiac diseases. But resting gated blood pool scan using only LVEF as a cardiac index has been consistently shown to have a low sensitivity, which is about 50%, in detecting coronary artery disease. So it is recommended to compare exercise gated blood pool scan to resting gated blood pool scan. Exercise tests, however, are not always possible, especially in patients with musculoskeletal diseases, recent myocardial infarction and in elderly persons. We studied the usefulness of resting gated blood pool scan using multiple indices in evaluating the patients with coronary artery disease. Studied cases were 185 patients with coronary artery disease (angina pectoris 31, myocardial infarction 154) and 25 normals with low likelihood of coronary artery disease. We used 99m Tc-labeled RBC, 740 MBq labeled by in vivo method. The data were evaluated by Micro DELTA computer program. The results were as following: 1) The ejection rates (PER, AER) and filling rates (PFR, AFR) were different in normals and patients with angina pectoris or myocardial infarction. 2) Mean phase angle, ejection rates and filling rates could separate normals from coronary artery disease patients with normal LVEF. 3) Regional ejection fraction was decreased at the site of the infarct in patients with myocardial infarction. 4) Peak filling rate was the most detectable index in evaluation of cardiac function in patients with coronary artery disease. 5) The threshold at 1.5 standard deviation of normal range was considered as the most reliable cut-off value from ROC analysis. These data suggest that the resting gated blood pool scan has an important role in the evaluation of cardiac functional changes using various cardiac indices in patients with coronary artery disease.
Study and program implementation of transient curves' piecewise linearization
International Nuclear Information System (INIS)
Shi Yang; Zu Hongbiao
2014-01-01
Background: Transient curves are essential for the stress analysis of related equipment in nuclear power plant (NPP). The actually operating data or the design transient data of a NPP usually consist of a large number of data points with very short time intervals. To simplify the analysis, transient curves are generally piecewise linearized in advance. Up to now, the piecewise linearization of transient curves is accomplished manually, Purpose: The aim is to develop a method for the piecewise linearization of transient curves, and to implement it by programming. Methods: First of all, the fitting line of a number of data points was obtained by the least square method. The segment of the fitting line is set while the accumulation error of linearization exceeds the preset limit with the increasing number of points. Then the linearization of subsequent data points was begun from the last point of the preceding curve segment to get the next segment in the same way, and continue until the final data point involved. Finally, averaging of junction points is taken for the segment connection. Results: A computer program named PLTC (Piecewise Linearization for Transient Curves) was implemented and verified by the linearization of the standard sine curve and typical transient curves of a NPP. Conclusion: The method and the PLTC program can be well used to the piecewise linearization of transient curves, with improving efficiency and precision. (authors)
The estimation of I–V curves of PV panel using manufacturers’ I–V curves and evolutionary strategy
International Nuclear Information System (INIS)
Barukčić, M.; Hederić, Ž.; Špoljarić, Ž.
2014-01-01
Highlights: • The approximation of a I–V curve by two linear and a sigmoid functions is proposed. • The sigmoid function is used to estimate the knee of the I–V curve. • Dependence on irradiance and temperature of sigmoid function parameters is proposed. • The sigmoid function is used to estimate maximum power point (MPP). - Abstract: The method for estimation of I–V curves of photovoltaic (PV) panel by analytic expression is presented in the paper. The problem is defined in the form of an optimization problem. The optimization problem objective is based on data from I–V curves obtained by manufacturers’ or measured I–V curves. In order to estimate PV panel parameters, the optimization problem is solved by using an evolutionary strategy. The proposed method is tested for different PV panel technologies using data sheets. In this method the I–V curve approximation with two linear and a sigmoid function is proposed. The method for estimating the knee of the I–V curve and maximum power point at any irradiance and temperature is proposed
ESTIMATING TORSION OF DIGITAL CURVES USING 3D IMAGE ANALYSIS
Directory of Open Access Journals (Sweden)
Christoph Blankenburg
2016-04-01
Full Text Available Curvature and torsion of three-dimensional curves are important quantities in fields like material science or biomedical engineering. Torsion has an exact definition in the continuous domain. However, in the discrete case most of the existing torsion evaluation methods lead to inaccurate values, especially for low resolution data. In this contribution we use the discrete points of space curves to determine the Fourier series coefficients which allow for representing the underlying continuous curve with Cesàro’s mean. This representation of the curve suits for the estimation of curvature and torsion values with their classical continuous definition. In comparison with the literature, one major advantage of this approach is that no a priori knowledge about the shape of the cyclic curve parts approximating the discrete curves is required. Synthetic data, i.e. curves with known curvature and torsion, are used to quantify the inherent algorithm accuracy for torsion and curvature estimation. The algorithm is also tested on tomographic data of fiber structures and open foams, where discrete curves are extracted from the pore spaces.
Analyzing Exoplanet Phase Curve Information Content: Toward Optimized Observing Strategies
Placek, Ben; Angerhausen, Daniel; Knuth, Kevin H.
2017-10-01
Secondary eclipses and phase curves reveal information about the reflectivity and heat distribution in exoplanet atmospheres. The phase curve is composed of a combination of reflected and thermally emitted light from the planet, and for circular orbits the phase curve peaks during the secondary eclipse or at an orbital phase of 0.5. Physical mechanisms have been discovered that shift the phase curve maximum of tidally locked close-in planets to the right, or left, of the secondary eclipse. These mechanisms include cloud formations and atmospheric superrotation, both of which serve to shift the thermally bright hot-spot or highly reflective bright spot of the atmosphere away from the sub-stellar point. Here, we present a methodology for optimizing observing strategies for both secondary eclipses and phase curves with the goal of maximizing the information gained about the planetary atmosphere while minimizing the (assumed) continuous observation time. We show that we can increase the duty cycle of observations aimed at the measurements of phase curve characteristics (amplitude, phase offset) by up to 50% for future platforms such as CHaracterising ExOPlanets Satellite (CHEOPS) and JWST. We apply this methodology to the test cases of the Spitzer phase curve of 55-Cancri-e, which displays an eastward shift in its phase curve maximum as well as model-generated observations of an ultra-short period planet observed with CHEOPS.
Directory of Open Access Journals (Sweden)
Roberto Añez
2015-04-01
Full Text Available Insulin Resistance (IR is an important finding in several diseases including diabetes and metabolic syndrome, and its diagnosis seems pertinent during the evaluation of insulin sensitivity, though mathematical models like HOMA (Homeostasis Model Assessment. The purpose of the present study was to determine an appropriate cutpoint for HOMA-IR in adult individuals from the Maracaibo municipality, Zulia state, Venezuela. Two-thousand and twenty-six individuals from both sexes and beyond 18 years of age were selected from the Maracaibo city Metabolic Syndrome Prevalence Study, a descriptive cross-sectional study with multietapic sampling. HOMA-IR was calculated using the formula [Fasting Insulin (µU/L x Fasting Glycemia (mmol/L/22,5]. To estimate the cutpoint, 602 healthy individuals were selected and a percentile distribution was calculates, alongside ROC Curve in order to identify the best cutoff point according to sensitivity and specificity. Overall, the average HOMA-IR was 3,71±3,01, with 3,65±2,96 for women and 3,76±3,06 for men (p=0,397. Using the reference population, the resulting arithmetic value was 2,64±1,67. When distributing per percentile, p75 was 3,02. When selecting a cutpoint using ROC Curve, the chosen cutoff point was 3.03 with an Area Under the Curve of 0.814 (75,2% sensitivity and 75,6% specificity. The obtained results are good enough to propose a cutpoint of 3,00 for HOMA-IR, which can be use in the clinical evaluation of IR in adults from our population
Curved version of Radon’s inversion formula on the plane
Gindikin, Simon
2018-01-01
We extend Radon’s inversion formula for lines on the plane up to a closed differential 1-form on the set of plane curves, which expresses a function at a point through the integrals along the curves of some differential operators of this function. We consider characteristic families of curves for which functions can be reconstructed through integrals along curves of the family using our inversion formula. We verify that the families of affine lines and of hyperbolic horocycles are characteristic.
Liu, Si-jun; Huang, Zhao-sheng; Wu, Qing-guang; Huang, Zhang-jie; Wu, Li-rong; Yan, Wen-li; Wang, Qi; Wang, Zong-wei; Chang, David Lungpao; Yang, Zheng
2016-04-01
To establish the diagnostic quantitative criteria for fire-heat syndrome (FHS) of Chinese medicine (CM) based on the receiver operating characteristic (ROC) curve and principal component analysis (PCA). The symptoms and signs of FHS cases and healthy subjects from Guangzhou, Henan and Hunan of China were collected through questionnaire, and the diagnostic quantitative score tables were established for the three regions, respectively, with the method of maximum likelihood analysis. The homogeneity test was then performed on the diagnostic score tables for the three regions with ROC curve, and the diagnostic efficiency of diagnostic score tables for the three regions was compared with the prospective test and retrospective test. The method of PCA was adopted to obtain the analysis matrix for classifying the tapes of FHS. Twenty-seven elements of FHS were confirmed through Chi-square test, and the diagnostic score tables for the three regions were established with the method of maximum likelihood analysis on the basis of the collected case data. According to the ROC curve test, the areas under ROC curve of Guangzhou diagnostic score table assessment with candidates in Guangzhou, Henan and Hunan were 0.998, 0.961 and 0.956, respectively. It showed that the diagnostic efficiency of Guangzhou diagnostic score tables was the highest one. With the prospective test, the area under ROC of Guangzhou diagnostic score table was 0.949, and more than any other diagnostic score table. By PCA, FHS was classified into excess fire and deficiency fire, and then classified into syndrome of flaring up of Heart (Xin) fire, syndrome of Lung (Fei)-Stomach (Wei) excess fire, syndrome of deficiency of Liver (Gan)-yin and Kidney (Shen)-yin, and syndrome of deficiency of Lung-yin from the view of viscera. In the retrospective test, the consistency with clinicians' diagnosis was 69.4%, and in the prospective test, it was 70.1%. The Guangzhou diagnostic score table could be used as the
Curve Digitizer – A software for multiple curves digitizing
Directory of Open Access Journals (Sweden)
Florentin ŞPERLEA
2010-06-01
Full Text Available The Curve Digitizer is software that extracts data from an image file representing a graphicand returns them as pairs of numbers which can then be used for further analysis and applications.Numbers can be read on a computer screen stored in files or copied on paper. The final result is adata set that can be used with other tools such as MSEXCEL. Curve Digitizer provides a useful toolfor any researcher or engineer interested in quantifying the data displayed graphically. The image filecan be obtained by scanning a document
Four-dimensional hilbert curves for R-trees
DEFF Research Database (Denmark)
Haverkort, Herman; Walderveen, Freek van
2011-01-01
Two-dimensional R-trees are a class of spatial index structures in which objects are arranged to enable fast window queries: report all objects that intersect a given query window. One of the most successful methods of arranging the objects in the index structure is based on sorting the objects...... according to the positions of their centers along a two-dimensional Hilbert space-filling curve. Alternatively, one may use the coordinates of the objects' bounding boxes to represent each object by a four-dimensional point, and sort these points along a four-dimensional Hilbert-type curve. In experiments...
Graphical interpretation of confidence curves in rankit plots
DEFF Research Database (Denmark)
Hyltoft Petersen, Per; Blaabjerg, Ole; Andersen, Marianne
2004-01-01
A well-known transformation from the bell-shaped Gaussian (normal) curve to a straight line in the rankit plot is investigated, and a tool for evaluation of the distribution of reference groups is presented. It is based on the confidence intervals for percentiles of the calculated Gaussian...... will fit to the straight line describing the calculated In-Gaussian distribution. The quality of the fit is evaluated by adding confidence intervals (CI) to each point on the line and calculating the percentage of points outside the hyperbola-like CI-curves. The assumption was that the 95% confidence...
Calibration curves for biological dosimetry
International Nuclear Information System (INIS)
Guerrero C, C.; Brena V, M. . E-mail cgc@nuclear.inin.mx
2004-01-01
The generated information by the investigations in different laboratories of the world, included the ININ, in which settles down that certain class of chromosomal leisure it increases in function of the dose and radiation type, has given by result the obtaining of calibrated curves that are applied in the well-known technique as biological dosimetry. In this work is presented a summary of the work made in the laboratory that includes the calibrated curves for gamma radiation of 60 Cobalt and X rays of 250 k Vp, examples of presumed exposure to ionizing radiation, resolved by means of aberration analysis and the corresponding dose estimate through the equations of the respective curves and finally a comparison among the dose calculations in those people affected by the accident of Ciudad Juarez, carried out by the group of Oak Ridge, USA and those obtained in this laboratory. (Author)
Laffer Curves and Home Production
Directory of Open Access Journals (Sweden)
Kotamäki Mauri
2017-06-01
Full Text Available In the earlier related literature, consumption tax rate Laffer curve is found to be strictly increasing (see Trabandt and Uhlig (2011. In this paper, a general equilibrium macro model is augmented by introducing a substitute for private consumption in the form of home production. The introduction of home production brings about an additional margin of adjustment – an increase in consumption tax rate not only decreases labor supply and reduces the consumption tax base but also allows a substitution of market goods with home-produced goods. The main objective of this paper is to show that, after the introduction of home production, the consumption tax Laffer curve exhibits an inverse U-shape. Also the income tax Laffer curves are significantly altered. The result shown in this paper casts doubt on some of the earlier results in the literature.
The New Keynesian Phillips Curve
DEFF Research Database (Denmark)
Ólafsson, Tjörvi
This paper provides a survey on the recent literature on the new Keynesian Phillips curve: the controversies surrounding its microfoundation and estimation, the approaches that have been tried to improve its empirical fit and the challenges it faces adapting to the open-economy framework. The new...... Keynesian Phillips curve has been severely criticized for poor empirical dynamics. Suggested improvements involve making some adjustments to the standard sticky price framework, e.g. introducing backwardness and real rigidities, or abandoning the sticky price model and relying on models of inattentiveness......, learning or state-dependant pricing. The introduction of openeconomy factors into the new Keynesian Phillips curve complicate matters further as it must capture the nexus between price setting, inflation and the exchange rate. This is nevertheless a crucial feature for any model to be used for inflation...
Chu, Fu-Ling; Hsu, Chung-Huei; Jeng, Chii
2015-01-01
In previous study, we found that in order to prevent MS in women aged obesity indicators should be lowered. To investigate whether our proposed cutoff points of obesity indicators predict the occurrence of hypertension (HT), diabetes mellitus (DM), and hyperlipidemia in premenopausal women with greater sensitivity and specificity compared to reference cutoff points of obesity that are currently being used. Using the database of the "2002 Survey on the Prevalence of Hypertension, Hyperglycemia and Hyperlipidemia in Taiwan" provided by the Bureau of Health Promotion, Taiwan as research material, data from 2270 premenopausal women aged 20-65 years were used for the analyses. The receiver-operating characteristic curves (ROC) of the body-mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR), and waist-to-height ratio (WHtR) were used to predict HT, DM, and hyperlipidemia. Obesity is not a good predictor of the occurrence of hyperlipidemia in premenopausal women aged obesity indicators should be reduced. The proposed values are as follows: a WHR of 0.79; a WC of 74.7 cm; a WHtR of 0.49; and a BMI of 22.3 kg/m(2). Copyright © 2014 Asian Oceanian Association for the Study of Obesity. Published by Elsevier Ltd. All rights reserved.
Receiver operating characteristic curve evaluation on computed radiography: an experimental study
International Nuclear Information System (INIS)
Yu Zixi; Wang Changyuan; Xu Yue; Xie Jindong; Zhang Menglong; Wang Jian
2003-01-01
Objective: To get the maximum information from computed radiography (CR) output images by changing post-processing parameters. Methods: Six experimental photos of polypropylene balls of 2.0 mm in diameter were taken by means of one time X-ray exposing on an imaging plate (IP) with different post-processing parameters including rotation amount (GA), gray gradation type (GT), rotation center (GC), shifting amount (GS), frequency rank (RN), frequency type (RT), and degree of enhancement (RE). 6 photos were viewed by three students and one radiologist on a 6000 lx illuminance viewbox. Receiver operating characteristic (ROC) curves were made by means of 5-value-differentiation method. Results: The largest mean area value (Az) below ROC curves of a low contrast experimental photo with post-processing parameters GA=1.0, GT=A, GC=1.6, GS=0.3, RN=4.0, RT=R and RE=3.0 was 0.96, and the maximum information was obtained. The smallest mean area value (Az) was 0.78 with changed post-processing parameters GA=0.8, GS=-0.2 and RE=0.5 while other parameters were not changed. The minimum information was obtained from this photo. Conclusion: In order to get the maximum information from a CR output image, the post-processing parameters should be suitably selected
Electro-Mechanical Resonance Curves
Greenslade, Thomas B.
2018-03-01
Recently I have been investigating the frequency response of galvanometers. These are direct-current devices used to measure small currents. By using a low-frequency function generator to supply the alternating-current signal and a stopwatch smartphone app to measure the period, I was able to take data to allow a resonance curve to be drawn. This is the sort of project that should provide a fascinating research experience for the introductory physics student. In this article I will discuss the galvanometers that I used in this work, and will show a resonance curve for one of them.
Shock detachment from curved wedges
Mölder, S.
2017-09-01
Curved shock theory is used to show that the flow behind attached shocks on doubly curved wedges can have either positive or negative post-shock pressure gradients depending on the freestream Mach number, the wedge angle and the two wedge curvatures. Given enough wedge length, the flow near the leading edge can choke to force the shock to detach from the wedge. This local choking can preempt both the maximum deflection and the sonic criteria for shock detachment. Analytical predictions for detachment by local choking are supported by CFD results.
Directory of Open Access Journals (Sweden)
Jose M. Martínez-Sánchez
2009-12-01
specificity according to sex, age, smoking status (daily and occasional, and exposure to second-hand smoke at home. ROC curves and the area under the curve were calculated. Results: The prevalence of smokers (daily and occasional was 27.8% (95% CI: 25.2-30.4%. The optimal cut-point to discriminate smoking status was 9.2ng/ml (sensitivity=88.7% and specificity=89.0%. The area under the ROC curve was 0.952. The optimal cut-point was 12.2ng/ml in men and 7.6ng/ml in women. The optimal cut-point was higher at ages with a greater prevalence of smoking. Daily smokers had a higher cut-point than occasional smokers. Conclusions: The optimal cut-point to discriminate smoking status in the adult population is 9.2ng/ml, with sensitivities and specificities around 90%. The cut-point was higher in men and in younger people. The cut-point increases with higher prevalence of daily smokers.
Vallipakorn, Sakda Arj-Ong; Vallipakorn, Orawin; Sophonsritsuk, Areepan; Jirapinyo, Mayuree; Sritara, Chanika
2016-03-01
To determine the optimal cut-off point of quantitative ultrasound (QUS) of the calcaneus, and optimized position for QUS of the calcaneus, between non-weight (sitting) and weight (standing) position, to screen osteoporosis in postmenopausal women. A cross-sectional study of postmenopausal women aged 65 years or older who came for bone mineral density (BMD) evaluation at the menopause unit, Department of Obstetrics and Gynecology, Ramathibodi Hospital between April 2013 and October 2015. Bone tissue was measured by using QUS of the calcaneus in the standard sitting (non-weight position) and in standing (weight position) consecutively of non-dominant calcaneus to compared with BMD that measured by dual energy X-ray absorptiometry (DXA) of lumbar spine and hip within the same visit of QUS measurement. The area under Receiver Operating Characteristic (ROC) curve and optimal of diagnostic properties to diagnosed osteoporosis were analyzed by sensitivity, specificity, positive and negative likelihood ratio (LR +/-). One hundred sixty one postmenopausal women were enrolled, median age was 70 (65, 94) years old, median time since menopause was 22 (10, 55) years. Ten point five percent of subjects had history of osteoporotic fracture at wrist. The prevalence of osteoporosis was 23% at lumbar spine and 30% at femoral neck respectively. Area under ROC curve for diagnosed osteoporosis was 0.73 in the non-weight QUS of the calcaneus and correlated well with using DXA at neck of femur (gold standard). However the weight or standing position did not improve the diagnostic power of QUS of the calcaneus. The optimal cut-point value of QUS of the calcaneus to screen osteoporosis at stiffness index was determined by T-score of ≤ -2.6 with 81.42%, 45.83%, 1.5, and 0.41 for the sensitivity, specificity, LR +/- respectively. QUS of the calcaneus was acceptable and promising to be alternative tool for screening osteoporosis in postmenopausal woman age older than 65 years by the optimal
Energy Technology Data Exchange (ETDEWEB)
Lee, Sinae; Park, Taegyu; Park, Soyeon; Pahk, Kisoo; Rhee, Seunghong; Cho, Jaehyuk; Jeong, Eugene; Kim, Sungeun; Choe, Jae Gol [Korea Univ., Seoul (Korea, Republic of)
2014-06-15
Thyroid incidentalomas are common findings during imaging studies including {sup 18}F-fluorodeoxyglucose ({sup 18}F-FDG) positron emission tomography/computed tomography (PET/CT) for cancer evaluation. Although the overall incidence of incidental thyroid uptake detected on PET imaging is low, clinical attention should be warranted owing to the high incidence of harboring primary thyroid malignancy.We retrospectively reviewed 2,368 dual-time-point {sup 18}F-FDG PET/CT cases that were undertaken for cancer evaluation from November 2007 to February 2009, to determine the clinical impact of dual-time-point imaging in the differential diagnosis of thyroid incidentalomas. Focal thyroid uptake was identified in 64 PET cases and final diagnosis was clarified with cytology/histology in a total of 27 patients with {sup 18}F-FDG-avid incidental thyroid lesion. The maximum standardized uptake value (SUVmax) of the initial image (SUV1) and SUVmax of the delayed image (SUV2) were determined, and the retention index (RI) was calculated by dividing the difference between SUV2 and SUV1 by SUV1 (i. e., RI=[SUV2-SUV1]/SUV1Χ100). These indices were compared between patient groups that were proven to have pathologically benign or malignant thyroid lesions. There was no statistically significant difference in SUV1 between benign and malignant lesions. SUV2 and RI of the malignant lesions were significantly higher than the benign lesions. The areas under the ROC curves showed that SUV2 and RI have the ability to discriminate between benign and malignant thyroid lesions. The predictability of dual-time-point PET parameters for thyroid malignancy was assessed by ROC curve analyses. When SUV2 of 3.9 was used as cut-off threshold, malignancy on the pathology could be predicted with a sensitivity of 87.5 % and specificity of 75 %. A thyroid lesion that shows RI greater than 12.5 % could be expected to be malignant (sensitivity 88.9 %, specificity 66.3 %). All malignant lesions showed an
Dual Smarandache Curves of a Timelike Curve lying on Unit dual Lorentzian Sphere
Kahraman, Tanju; Hüseyin Ugurlu, Hasan
2016-01-01
In this paper, we give Darboux approximation for dual Smarandache curves of time like curve on unit dual Lorentzian sphere. Firstly, we define the four types of dual Smarandache curves of a timelike curve lying on dual Lorentzian sphere.
Archaeomagnetic SV curve for Belgium
Ech-chakrouni, Souad; Hus, Jozef
2017-04-01
Archaeomagnetic secular variation curves have been established for different countries in Europe, especially when different archeological sites are more or less uniformly distributed in time are available. The disadvantage in that case is that data had to be relocated to a single reference site. The proximity of the reference locality Paris to Belgium makes that we used the French archaeomagnetic SV curve for the last three millennia up to the present for archaeomagnetic dating undated baked structures. In total, 85 baked structures have been examined, unearthed in 24 archaeological sites of the territory of Belgium. The ChRM of each sample was obtained by principal component analysis for at least three demagnetisation steps (Kirschvink 1980). Except for some outliers, the ChRM directions are very coherent with a high confidence factor (α95archaeomagnetism. At present, only six baked structures were dated radiometrically and may be considered as reference data for a limited area about 30500 km2 in Western Europe. The ultimate aim is to construct an archaeomagnetic SV curve for Belgium with Uccle as reference locality, where the first measurement of the geomagnetic field was done in 1895. This curve would include all the available reference data in a radius of about 500 km around Uccle. Keywords: secular variation, archaeomagnetic dating, Belgium.
The aeolian dust accumulation curve
Goossens, D.
2001-01-01
This article presents a simple physical concept of aeolian dust accumulation, based on the behaviour of the subprocesses of dust deposition and dust erosion. The concept is tested in an aeolian dust wind tunnel. The agreement between the accumulation curve predicted by the model and the accumulation
Indian Academy of Sciences (India)
The cause-effect relationship for a wide variety of biologi- cal processes from molecular to ecosystem levels can be described by a curvilinear function called the rectangular hyperbola. Although a simple algebraic equation adequately describes this curve, biological models have generated different equations incorporating ...
Survival curves for irradiated cells
International Nuclear Information System (INIS)
Gibson, D.K.
1975-01-01
The subject of the lecture is the probability of survival of biological cells which have been subjected to ionising radiation. The basic mathematical theories of cell survival as a function of radiation dose are developed. A brief comparison with observed survival curves is made. (author)
2013-01-01
This software can be used to assist with the assessment of margin of safety for a horizontal curve. It is intended for use by engineers and technicians responsible for safety analysis or management of rural highway pavement or traffic control devices...
Ultrasonic Fetal Cephalometry: Percentiles Curve
Flamme, P.
1972-01-01
Measurements by ultrasound of the biparietal diameter of the fetal head during pregnancy are a reliable guide to fetal growth. As a ready means of comparison with the normal we constructed from 4,170 measurements in 1,394 cases a curve showing the percentiles distribution of biparietal diameters for each week of gestation. PMID:5070162
Research of Cubic Bezier Curve NC Interpolation Signal Generator
Directory of Open Access Journals (Sweden)
Shijun Ji
2014-08-01
Full Text Available Interpolation technology is the core of the computer numerical control (CNC system, and the precision and stability of the interpolation algorithm directly affect the machining precision and speed of CNC system. Most of the existing numerical control interpolation technology can only achieve circular arc interpolation, linear interpolation or parabola interpolation, but for the numerical control (NC machining of parts with complicated surface, it needs to establish the mathematical model and generate the curved line and curved surface outline of parts and then discrete the generated parts outline into a large amount of straight line or arc to carry on the processing, which creates the complex program and a large amount of code, so it inevitably introduce into the approximation error. All these factors affect the machining accuracy, surface roughness and machining efficiency. The stepless interpolation of cubic Bezier curve controlled by analog signal is studied in this paper, the tool motion trajectory of Bezier curve can be directly planned out in CNC system by adjusting control points, and then these data were put into the control motor which can complete the precise feeding of Bezier curve. This method realized the improvement of CNC trajectory controlled ability from the simple linear and circular arc to the complex project curve, and it provides a new way for economy realizing the curve surface parts with high quality and high efficiency machining.
A NURBS approximation of experimental stress-strain curves
International Nuclear Information System (INIS)
Fedorov, Timofey V.; Morrev, Pavel G.
2016-01-01
A compact universal representation of monotonic experimental stress-strain curves of metals and alloys is proposed. It is based on the nonuniform rational Bezier splines (NURBS) of second order and may be used in a computer library of materials. Only six parameters per curve are needed; this is equivalent to a specification of only three points in a stress-strain plane. NURBS-functions of higher order prove to be surplus. Explicit expressions for both yield stress and hardening modulus are given. Two types of curves are considered: at a finite interval of strain and at infinite one. A broad class of metals and alloys of various chemical compositions subjected to various types of preliminary thermo-mechanical working is selected from a comprehensive data base in order to test the methodology proposed. The results demonstrate excellent correspondence to the experimental data. Keywords: work hardening, stress-strain curve, spline approximation, nonuniform rational B-spline, NURBS.
International Nuclear Information System (INIS)
Jang, S.; Jaszczak, R.J.; Duke Univ. Medical Center, Durham, NC; Gilland, D.R.; Turkington, T.G.; Coleman, R.E.; Tsui, B.M.W.; Metz, C.E.
1998-01-01
The purpose of this work was to evaluate lesion detectability with and without nonuniform attenuation compensation (AC) in myocardial perfusion SPECT imaging in women using an anthropomorphic phantom and receiver operating characteristics (ROC) methodology. Breast attenuation causes artifacts in reconstructed images and may increase the difficulty of diagnosis of myocardial perfusion imaging in women. The null hypothesis tested using the ROC study was that nonuniform AC does not change the lesion detectability in myocardial perfusion SPECT imaging in women. The authors used a filtered backprojection (FBP) reconstruction algorithm and Chang's single iteration method for AC. In conclusion, with the proposed myocardial defect model nuclear medicine physicians demonstrated no significant difference for the detection of the anterior wall defect; however, a greater accuracy for the detection of the inferior wall defect was observed without nonuniform AC than with it. Medical physicists did not demonstrate any statistically significant difference in defect detection accuracy with or without nonuniform AC in the female phantom
He, Xin; Song, Xiyun; Frey, Eric C
2008-11-01
The diagnosis of cardiac disease using dual-isotope myocardial perfusion SPECT (MPS) is based on the defect status in both stress and rest images, and can be modeled as a three-class task of classifying patients as having no, reversible, or fixed perfusion defects. Simultaneous acquisition protocols for dual-isotope MPS imaging have gained much interest due to their advantages including perfect registration of the (201)Tl and (99m)Tc images in space and time, increased patient comfort, and higher clinical throughput. As a result of simultaneous acquisition, however, crosstalk contamination, where photons emitted by one isotope contribute to the image of the other isotope, degrades image quality. Minimizing the crosstalk is important in obtaining the best possible image quality. One way to minimize the crosstalk is to optimize the injected activity of the two isotopes by considering the three-class nature of the diagnostic problem. To effectively do so, we have previously developed a three-class receiver operating characteristic (ROC) analysis methodology that extends and unifies the decision theoretic, linear discriminant analysis, and psychophysical foundations of binary ROC analysis in a three-class paradigm. In this work, we applied the proposed three-class ROC methodology to the assessment of the image quality of simultaneous dual-isotope MPS imaging techniques and the determination of the optimal injected activity combination. In addition to this application, the rapid development of diagnostic imaging techniques has produced an increasing number of clinical diagnostic tasks that involve not only disease detection, but also disease characterization and are thus multiclass tasks. This paper provides a practical example of the application of the proposed three-class ROC analysis methodology to medical problems.
Starns, Jeffrey J.; Ratcliff, Roger; McKoon, Gail
2011-01-01
We tested two explanations for why the slope of the z-transformed receiver operating characteristic (zROC) is less than 1 in recognition memory: the unequal-variance account (target evidence is more variable than lure evidence) or the dual-process account (responding reflects both a continuous familiarity process and a threshold recollection process). These accounts are typically implemented in signal detection models that do not make predictions for response time (RT) data. We tested them us...
A Universal Genus-Two Curve from Siegel Modular Forms
Malmendier, Andreas; Shaska, Tony
2017-11-01
Let p be any point in the moduli space of genus-two curves M_2 and K its field of moduli. We provide a universal equation of a genus-two curve C_{&alpha,; β} defined over K(α, β), corresponding to p, where α and β satisfy a quadratic α^2+ b β^2= c such that b and c are given in terms of ratios of Siegel modular forms. The curve C_{α, β} is defined over the field of moduli K if and only if the quadratic has a K-rational point (α, β). We discover some interesting symmetries of the Weierstrass equation of C_{α, β}. This extends previous work of Mestre and others.
Modern cryptography and elliptic curves a beginner's guide
Shemanske, Thomas R
2017-01-01
This book offers the beginning undergraduate student some of the vista of modern mathematics by developing and presenting the tools needed to gain an understanding of the arithmetic of elliptic curves over finite fields and their applications to modern cryptography. This gradual introduction also makes a significant effort to teach students how to produce or discover a proof by presenting mathematics as an exploration, and at the same time, it provides the necessary mathematical underpinnings to investigate the practical and implementation side of elliptic curve cryptography (ECC). Elements of abstract algebra, number theory, and affine and projective geometry are introduced and developed, and their interplay is exploited. Algebra and geometry combine to characterize congruent numbers via rational points on the unit circle, and group law for the set of points on an elliptic curve arises from geometric intuition provided by Bézout's theorem as well as the construction of projective space. The structure of the...
On the behavior of certain ink aging curves.
Cantú, Antonio A
2017-09-01
This work treats writing inks, particularly ballpoint pen inks. It reviews those ink aging methods that are based on the analysis (measurement) of ink solvents (e.g., 2-phenoxyethanol, which is the most common among ballpoint pen inks). Each method involves measurements that are components of an ink aging parameter associated with the method. Only mass independent parameters are considered. An ink solvent from an ink that is on an air-exposed substrate will evaporate at a decreasing rate and is never constant as the ink ages. An ink aging parameter should reflect this behavior. That is, the graph of a parameter's experimentally-determined values plotted against ink age (which yields the ink aging curve) should show this behavior. However, some experimentally-determined aging curves contain outlying points that are below or above where they should be or points corresponding to different ages that have the same ordinate (parameter value). Such curves, unfortunately, are useless since such curves show that an ink can appear older or younger than what it should be in one or more of its points or have the same age in two or more of its points. This work explains that one cause of this unexpected behavior is that the parameter values were improperly determined such as when a measurement is made of an ink solvent that is not completely extracted (removed) from an ink sample with a chosen extractor such as dry heat or a solvent. Copyright © 2017 Elsevier B.V. All rights reserved.
Quantifying and Reducing Curve-Fitting Uncertainty in Isc
Energy Technology Data Exchange (ETDEWEB)
Campanelli, Mark; Duck, Benjamin; Emery, Keith
2015-06-14
Current-voltage (I-V) curve measurements of photovoltaic (PV) devices are used to determine performance parameters and to establish traceable calibration chains. Measurement standards specify localized curve fitting methods, e.g., straight-line interpolation/extrapolation of the I-V curve points near short-circuit current, Isc. By considering such fits as statistical linear regressions, uncertainties in the performance parameters are readily quantified. However, the legitimacy of such a computed uncertainty requires that the model be a valid (local) representation of the I-V curve and that the noise be sufficiently well characterized. Using more data points often has the advantage of lowering the uncertainty. However, more data points can make the uncertainty in the fit arbitrarily small, and this fit uncertainty misses the dominant residual uncertainty due to so-called model discrepancy. Using objective Bayesian linear regression for straight-line fits for Isc, we investigate an evidence-based method to automatically choose data windows of I-V points with reduced model discrepancy. We also investigate noise effects. Uncertainties, aligned with the Guide to the Expression of Uncertainty in Measurement (GUM), are quantified throughout.
Quantifying and Reducing Curve-Fitting Uncertainty in Isc: Preprint
Energy Technology Data Exchange (ETDEWEB)
Campanelli, Mark; Duck, Benjamin; Emery, Keith
2015-09-28
Current-voltage (I-V) curve measurements of photovoltaic (PV) devices are used to determine performance parameters and to establish traceable calibration chains. Measurement standards specify localized curve fitting methods, e.g., straight-line interpolation/extrapolation of the I-V curve points near short-circuit current, Isc. By considering such fits as statistical linear regressions, uncertainties in the performance parameters are readily quantified. However, the legitimacy of such a computed uncertainty requires that the model be a valid (local) representation of the I-V curve and that the noise be sufficiently well characterized. Using more data points often has the advantage of lowering the uncertainty. However, more data points can make the uncertainty in the fit arbitrarily small, and this fit uncertainty misses the dominant residual uncertainty due to so-called model discrepancy. Using objective Bayesian linear regression for straight-line fits for Isc, we investigate an evidence-based method to automatically choose data windows of I-V points with reduced model discrepancy. We also investigate noise effects. Uncertainties, aligned with the Guide to the Expression of Uncertainty in Measurement (GUM), are quantified throughout.
Learning curves for strabismus surgery in two ophthalmologists
Directory of Open Access Journals (Sweden)
Yonguk Kim
2015-01-01
Full Text Available Purpose: To identify the average turning point by comparing the learning curves of two surgeons learning to perform strabismus surgery. Materials and Methods: Patients who underwent procedures to correct exotropia between January 2010 and December 2014 followed for at least 3 months were retrospectively assessed. The first 70 patients on whom each of two ophthalmologists (A and B performed surgery to treat strabismus were divided into 7 cohorts comprising 10 patients each based on the chronological order of the surgery. Factors, including patient age, preoperative angle of deviation, operative time, and success or failure of the operation, were compared between the two surgeons. Learning curves were calculated based on changes in operative time and operation success rate. Operation success was determined by measuring the angle of deviation at a distance of 5 m 3 months after the operation. Results: A turning point was observed after 40 cases for Surgeon A and 50 cases for Surgeon B based on the operative time learning curve. No turning point was observed in the operation success rate learning curve based on the absence of a specific trend. Success rate by cohort was not significantly different between the two surgeons (P > 0.05. Surgeon B had a significantly longer mean operative time than Surgeon A (P = 0.045. Conclusions: Approximately 50 cases are required for an ophthalmologist to reach a turning point in strabismus surgery. This outcome can be used as a guideline when training surgeons to perform strabismus surgery.
Quantum cohomology of moduli spaces of genus zero stable curves
Fontanari, Claudio
2007-01-01
We investigate the (small) quantum cohomology ring of the moduli spaces of stable n-pointed curves of genus 0. In particular, we determine an explicit presentation in the case n=5 and we outline a computational approach to the case n=6.
On the topology of real algebraic plane curves
DEFF Research Database (Denmark)
Cheng, Jinsan; Lazard, Sylvain; Peñaranda, Luis
2010-01-01
We revisit the problem of computing the topology and geometry of a real algebraic plane curve. The topology is of prime interest but geometric information, such as the position of singular and critical points, is also relevant. A challenge is to compute efficiently this information for the given ...
An Update on the Depth-Dose Curve of Antiprotons
DEFF Research Database (Denmark)
Taasti, Vicki Trier; Holzscheiter, Michael H.; Knudsen, Helge
Purpose: The CERN AD-4/ACE project aims to measure the relative biological effectiveness of antiprotons. We have revisited previously published data for the antiproton depth-dose curve [1], where the relative dose deposition normalized to a point in the plateau region was plotted. In this revisio...
Strong asymptotics for Lp extremal polynomials off a complex curve
Directory of Open Access Journals (Sweden)
Rabah Khaldi
2004-01-01
Full Text Available We study the asymptotic behavior of Lp(σ extremal polynomials with respect to a measure of the form σ=α+γ, where α is a measure concentrated on a rectifiable Jordan curve in the complex plane and γ is a discrete measure concentrated on an infinite number of mass points.
Liu, Zhenqiu; Tan, Ming
2008-12-01
In medical diagnosis, the diseased and nondiseased classes are usually unbalanced and one class may be more important than the other depending on the diagnosis purpose. Most standard classification methods, however, are designed to maximize the overall accuracy and cannot incorporate different costs to different classes explicitly. In this article, we propose a novel nonparametric method to directly maximize the weighted specificity and sensitivity of the receiver operating characteristic curve. Combining advances in machine learning, optimization theory, and statistics, the proposed method has excellent generalization property and assigns different error costs to different classes explicitly. We present experiments that compare the proposed algorithms with support vector machines and regularized logistic regression using data from a study on HIV-1 protease as well as six public available datasets. Our main conclusion is that the performance of proposed algorithm is significantly better in most cases than the other classifiers tested. Software package in MATLAB is available upon request.
Rational quadratic trigonometric Bézier curve based on new basis with exponential functions
Directory of Open Access Journals (Sweden)
Wu Beibei
2017-06-01
Full Text Available We construct a rational quadratic trigonometric Bézier curve with four shape parameters by introducing two exponential functions into the trigonometric basis functions in this paper. It has the similar properties as the rational quadratic Bézier curve. For given control points, the shape of the curve can be flexibly adjusted by changing the shape parameters and the weight. Some conics can be exactly represented when the control points, the shape parameters and the weight are chosen appropriately. The C0, C1 and C2 continuous conditions for joining two constructed curves are discussed. Some examples are given.
A catalog of special plane curves
Lawrence, J Dennis
2014-01-01
Among the largest, finest collections available-illustrated not only once for each curve, but also for various values of any parameters present. Covers general properties of curves and types of derived curves. Curves illustrated by a CalComp digital incremental plotter. 12 illustrations.
Computation of undulator tuning curves
International Nuclear Information System (INIS)
Dejus, Roger J.
1997-01-01
Computer codes for fast computation of on-axis brilliance tuning curves and flux tuning curves have been developed. They are valid for an ideal device (regular planar device or a helical device) using the Bessel function formalism. The effects of the particle beam emittance and the beam energy spread on the spectrum are taken into account. The applicability of the codes and the importance of magnetic field errors of real insertion devices are addressed. The validity of the codes has been experimentally verified at the APS and observed discrepancies are in agreement with predicted reduction of intensities due to magnetic field errors. The codes are distributed as part of the graphical user interface XOP (X-ray OPtics utilities), which simplifies execution and viewing of the results
A curved resonant flexoelectric actuator
Zhang, Shuwen; Liu, Kaiyuan; Xu, Minglong; Shen, Shengping
2017-08-01
Flexoelectricity is an electro-mechanical coupling effect that exists in all dielectrics and has the potential to replace piezoelectric actuating on the microscale. In this letter, a curved flexoelectric actuator with non-polarized polyvinylidene fluoride is presented and shown to exhibit good electro-mechanical properties. This provides experimental support for a body of theoretical research into converse flexoelectricity in polymeric materials. In addition, this work demonstrates the feasibility of lead-free microscale actuating without piezoelectricity.
Active Particles on Curved Surfaces
Fily, Yaouen; Baskaran, Aparna; Hagan, Michael F.
2016-01-01
Recent studies have highlighted the sensitivity of active matter to boundaries and their geometries. Here we develop a general theory for the dynamics and statistics of active particles on curved surfaces and illustrate it on two examples. We first show that active particles moving on a surface with no ability to probe its curvature only exhibit steady-state inhomogeneities in the presence of orientational order. We then consider a strongly confined 3D ideal active gas and compute its steady-...
Growth curves for Laron syndrome.
Laron, Z; Lilos, P; Klinger, B
1993-06-01
Growth curves for children with Laron syndrome were constructed on the basis of repeated measurements made throughout infancy, childhood, and puberty in 24 (10 boys, 14 girls) of the 41 patients with this syndrome investigated in our clinic. Growth retardation was already noted at birth, the birth length ranging from 42 to 46 cm in the 12/20 available measurements. The postnatal growth curves deviated sharply from the normal from infancy on. Both sexes showed no clear pubertal spurt. Girls completed their growth between the age of 16-19 years to a final mean (SD) height of 119 (8.5) cm whereas the boys continued growing beyond the age of 20 years, achieving a final height of 124 (8.5) cm. At all ages the upper to lower body segment ratio was more than 2 SD above the normal mean. These growth curves constitute a model not only for primary, hereditary insulin-like growth factor-I (IGF-I) deficiency (Laron syndrome) but also for untreated secondary IGF-I deficiencies such as growth hormone gene deletion and idiopathic congenital isolated growth hormone deficiency. They should also be useful in the follow up of children with Laron syndrome treated with biosynthetic recombinant IGF-I.
Projection-based curve clustering
International Nuclear Information System (INIS)
Auder, Benjamin; Fischer, Aurelie
2012-01-01
This paper focuses on unsupervised curve classification in the context of nuclear industry. At the Commissariat a l'Energie Atomique (CEA), Cadarache (France), the thermal-hydraulic computer code CATHARE is used to study the reliability of reactor vessels. The code inputs are physical parameters and the outputs are time evolution curves of a few other physical quantities. As the CATHARE code is quite complex and CPU time-consuming, it has to be approximated by a regression model. This regression process involves a clustering step. In the present paper, the CATHARE output curves are clustered using a k-means scheme, with a projection onto a lower dimensional space. We study the properties of the empirically optimal cluster centres found by the clustering method based on projections, compared with the 'true' ones. The choice of the projection basis is discussed, and an algorithm is implemented to select the best projection basis among a library of orthonormal bases. The approach is illustrated on a simulated example and then applied to the industrial problem. (authors)
Dual Smarandache Curves and Smarandache Ruled Surfaces
Tanju KAHRAMAN; Mehmet ÖNDER; H. Hüseyin UGURLU
2013-01-01
In this paper, by considering dual geodesic trihedron (dual Darboux frame) we define dual Smarandache curves lying fully on dual unit sphere S^2 and corresponding to ruled surfaces. We obtain the relationships between the elements of curvature of dual spherical curve (ruled surface) x(s) and its dual Smarandache curve (Smarandache ruled surface) x1(s) and we give an example for dual Smarandache curves of a dual spherical curve.
Parametrizations of elliptic curves by Shimura curves and by classical modular curves.
Ribet, K A; Takahashi, S
1997-10-14
Fix an isogeny class of semistable elliptic curves over Q. The elements A of have a common conductor N, which is a square-free positive integer. Let D be a divisor of N which is the product of an even number of primes--i.e., the discriminant of an indefinite quaternion algebra over Q. To D we associate a certain Shimura curve X(0)D(N/D), whose Jacobian is isogenous to an abelian subvariety of J0(N). There is a unique A [symbol; see text] A in for which one has a nonconstant map piD : X(0)D(N/D) --> A whose pullback A --> Pic0(X(0)D(N/D)) is injective. The degree of piD is an integer deltaD which depends only on D (and the fixed isogeny class A). We investigate the behavior of deltaD as D varies.
Direct Analysis of JV-Curves Applied to an Outdoor-Degrading CdTe Module (Presentation)
Energy Technology Data Exchange (ETDEWEB)
Jordan, D; Kurtz, S.; Ulbrich, C.; Gerber, A.; Rau, U.
2014-03-01
We present the application of a phenomenological four parameter equation to fit and analyze regularly measured current density-voltage JV curves of a CdTe module during 2.5 years of outdoor operation. The parameters are physically meaningful, i.e. the short circuit current density Jsc, open circuit voltage Voc and differential resistances Rsc, and Roc. For the chosen module, the fill factor FF degradation overweighs the degradation of Jsc and Voc. Interestingly, with outdoor exposure, not only the conductance at short circuit, Gsc, increases but also the Gsc(Jsc)-dependence. This is well explained with an increase in voltage dependent charge carrier collection in CdTe.
The evolution of space curves by curvature and torsion
International Nuclear Information System (INIS)
Richardson, G; King, J R
2002-01-01
We apply Lie group based similarity methods to the study of a new, and widely relevant, class of objects, namely motions of a space curve. In particular, we consider the motion of a curve evolving with a curvature κ and torsion τ dependent velocity law. We systematically derive the Lie point symmetries of all such laws of motion and use these to catalogue all their possible similarity reductions. This calculation reveals special classes of law with high degrees of symmetry (and a correspondingly large number of similarity reductions). Of particular note is one class which is invariant under general linear transformations in space. This has potential applications in pattern and signal recognition
Extended HI Rotation Curve and Mass Distribution of M31
Carignan, Claude; Chemin, Laurent; Huchtmeier, Walter K.; Lockman, Felix J.
2006-01-01
New HI observations of Messier 31 (M31) obtained with the Effelsberg and Green Bank 100-m telescopes make it possible to measure the rotation curve of that galaxy out to ~35 kpc. Between 20 and 35 kpc, the rotation curve is nearly flat at a velocity of ~226 km/s. A model of the mass distribution shows that at the last observed velocity point, the minimum dark-to-luminous mass ratio is \\~0.5 for a total mass of 3.4 10^11 Msol at R < 35 kpc. This can be compared to the estimated MW mass of 4.9 ...
Optimization on shape curves with application to specular stereo
Balzer, Jonathan
2010-01-01
We state that a one-dimensional manifold of shapes in 3-space can be modeled by a level set function. Finding a minimizer of an independent functional among all points on such a shape curve has interesting applications in computer vision. It is shown how to replace the commonly encountered practice of gradient projection by a projection onto the curve itself. The outcome is an algorithm for constrained optimization, which, as we demonstrate theoretically and numerically, provides some important benefits in stereo reconstruction of specular surfaces. © 2010 Springer-Verlag.
A note on families of fragility curves
International Nuclear Information System (INIS)
Kaplan, S.; Bier, V.M.; Bley, D.C.
1989-01-01
In the quantitative assessment of seismic risk, uncertainty in the fragility of a structural component is usually expressed by putting forth a family of fragility curves, with probability serving as the parameter of the family. Commonly, a lognormal shape is used both for the individual curves and for the expression of uncertainty over the family. A so-called composite single curve can also be drawn and used for purposes of approximation. This composite curve is often regarded as equivalent to the mean curve of the family. The equality seems intuitively reasonable, but according to the authors has never been proven. The paper presented proves this equivalence hypothesis mathematically. Moreover, the authors show that this equivalence hypothesis between fragility curves is itself equivalent to an identity property of the standard normal probability curve. Thus, in the course of proving the fragility curve hypothesis, the authors have also proved a rather obscure, but interesting and perhaps previously unrecognized, property of the standard normal curve
Differential geometry curves, surfaces, manifolds
Kühnel, Wolfgang
2015-01-01
This carefully written book is an introduction to the beautiful ideas and results of differential geometry. The first half covers the geometry of curves and surfaces, which provide much of the motivation and intuition for the general theory. The second part studies the geometry of general manifolds, with particular emphasis on connections and curvature. The text is illustrated with many figures and examples. The prerequisites are undergraduate analysis and linear algebra. This new edition provides many advancements, including more figures and exercises, and-as a new feature-a good number of so
LINS Curve in Romanian Economy
Directory of Open Access Journals (Sweden)
Emilian Dobrescu
2016-02-01
Full Text Available The paper presents theoretical considerations and empirical evidence to test the validity of the Laffer in Narrower Sense (LINS curve as a parabola with a maximum. Attention is focused on the so-called legal-effective tax gap (letg. The econometric application is based on statistical data (1990-2013 for Romania as an emerging European economy. Three cointegrating regressions (fully modified least squares, canonical cointegrating regression and dynamic least squares and three algorithms, which are based on instrumental variables (two-stage least squares, generalized method of moments, and limited information maximum likelihood, are involved.
Principal Curves on Riemannian Manifolds
DEFF Research Database (Denmark)
Hauberg, Søren
2015-01-01
Euclidean statistics are often generalized to Riemannian manifolds by replacing straight-line interpolations with geodesic ones. While these Riemannian models are familiar-looking, they are restricted by the inflexibility of geodesics, and they rely on constructions which are optimal only...... in Euclidean domains. We consider extensions of Principal Component Analysis (PCA) to Riemannian manifolds. Classic Riemannian approaches seek a geodesic curve passing through the mean that optimize a criteria of interest. The requirements that the solution both is geodesic and must pass through the mean tend...
Using the minimum spanning tree to recognize dotted and dashed curves
Zahn, C T
1974-01-01
An important problem in pattern recognition is the organization into two and three-dimensional space curves of data given as points ('dots') or short line segments ('dashes'). This paper describes a general method for recognizing such dotted or dashed space curves employing the Minimum Spanning Tree (MST). The use of the MST is motivated by its successful use in grouping two-dimensional point sets in a fashion closely resembling human visual perception. The extension of the method to handle 'dashed' curves requires only the definition of a closeness measure between dashes which reflects the directional information as well as positional. It is possible to use the method in a layered hierarchy where the MST of dots is used to detect dashes, the MST of dashes to detect short curves without inflexions, and an MST constructed from these curves is used to detect larger curves with possible inflexions. (8 refs).
Establishing meaningful cut points for online user ratings.
Hirschfeld, Gerrit; Thielsch, Meinald T
2015-01-01
Subjective perceptions of websites can be reliably measured with questionnaires. But it is unclear how such scores should be interpreted in practice, e.g. is an aesthetics score of 4 points on a seven-point-scale satisfactory? The current paper introduces a receiver-operating characteristic (ROC)-based methodology to establish meaningful cut points for the VisAWI (visual aesthetics of websites inventory) and its short form the VisAWI-S. In two studies we use users' global ratings (UGRs) and website rankings as anchors. A total of 972 participants took part in the studies which yielded similar results. First, one-item UGRs correlate highly with the VisAWI. Second, cut points on the VisAWI reliably differentiate between sites that are perceived as attractive versus unattractive. Third, these cut points are variable, but only within a certain range. Together the research presented here establishes a score of 4.5 on the VisAWI which is a reasonable goal for website designers and highlights the utility of the ROC methodology to derive relevant scores for rating scales.
Jong, Trynke R de; Menon, Rohit; Bludau, Anna; Grund, Thomas; Biermeier, Verena; Klampfl, Stefanie M; Jurek, Benjamin; Bosch, Oliver J; Hellhammer, Juliane; Neumann, Inga D
2015-12-01
Intranasal oxytocin (OXT) application is emerging as a potential treatment for socio-emotional disorders associated with abnormalities in OXT system (re-) activity. The crucial identification of patients with such abnormalities could be streamlined by the assessment of basal and stimulus-induced OXT concentrations in saliva, using a simple, stress-free sampling procedure (i.e. an OXT challenge test). We therefore established the Regensburg Oxytocin Challenge (ROC) test to further validate salivary OXT concentrations as a practical, reliable and sensitive biomarker. OXT concentrations were quantified by radioimmunoassay in samples collected at home by healthy adult male and female volunteers before and after running ("Run") or sexual self-stimulation ("Sex"). In lactating women, salivary OXT concentrations were quantified before, during and after breastfeeding. Salivary OXT along with salivary cortisol and heart rate were monitored in healthy adult participants undergoing the Trier Social Stress Test (TSST). The home-based "Run" and "Sex" challenges as well as the laboratory-based TSST caused quantifiable, rapid, and consistent increases in salivary OXT (approximately 2.5-fold after 10-15min), which were similar for men and women. Breastfeeding did not result in measurably increased salivary OXT levels, probably because the short pulses of OXT release characteristic for lactation were missed. Taken together, ROC tests reliably assess the responsiveness of the OXT system (i.e., the increase in salivary OXT concentrations as compared to basal levels) to challenges such as "Run" and "Sex" at home or psychosocial stress (TSST) in the laboratory. Further studies with larger sample numbers are essentially needed in order to reveal individual differences in ROC test outcomes depending on, for example, genetic or environmental factors. Copyright © 2015 Elsevier Ltd. All rights reserved.
Differential geometry and topology of curves
Animov, Yu
2001-01-01
Differential geometry is an actively developing area of modern mathematics. This volume presents a classical approach to the general topics of the geometry of curves, including the theory of curves in n-dimensional Euclidean space. The author investigates problems for special classes of curves and gives the working method used to obtain the conditions for closed polygonal curves. The proof of the Bakel-Werner theorem in conditions of boundedness for curves with periodic curvature and torsion is also presented. This volume also highlights the contributions made by great geometers. past and present, to differential geometry and the topology of curves.
Directory of Open Access Journals (Sweden)
Keiko Nanishi
Full Text Available Breastfeeding self-efficacy can be measured with the Breastfeeding Self-Efficacy Scale-Short Form (BSES-SF. Mothers with low BSES-SF scores stop exclusive breastfeeding prematurely, but specific interventions can prevent that undesirable outcome. Because those interventions can be expensive, often one must decide which mothers will receive them. For that purpose, a cut-off BSES-SF score would be useful, but none is available. Therefore, we aimed to assess the overall accuracy of BSES-SF scores as predictors of not practicing post-discharge exclusive breastfeeding, and to choose an appropriate cut-off score for making that prediction.This is a secondary data analysis of an intervention study. Data from 378 women in two non-Baby-Friendly Hospitals were analyzed. Participants were women in their third trimester who were 16 years of age or older, were able to read and write Japanese, were expected to have a singleton birth, and had completed the BSES-SF before discharge. BSES-SF scores were measured before discharge. Breastfeeding status was assessed 4 weeks and 12 weeks postpartum. Receiver Operating Characteristic (ROC curves were used to assess the predictive ability of the BSES-SF and to inform the choice of a cut-off point.For both of the ROC curves (4 and 12 weeks postpartum the area under the curve was 0.74. To obtain a high sensitivity, a cut-off score of 50 was chosen. With that cut-off score the sensitivity was 79% and the specificity was 52% 4 weeks postpartum, and they were 77% and 52%, respectively, 12 weeks postpartum.In conclusion, the BSES-SF has moderate overall accuracy to distinguish women who will not practice exclusive breastfeeding after discharge from those who will. At non-Baby-Friendly hospitals in Japan, interventions to support exclusive breastfeeding might be considered for new mothers who have BSES-SF scores that are less than or equal to 50.
International Nuclear Information System (INIS)
Wang Dongqing; Zhang Jian; Li Baosheng; Sun Hongfu
2012-01-01
Objective: To assess the accuracy (ACC), sensitivity (SEN), and specificity (SPE) of dose-volume histogram (DVH) parameters in predicting the radiation pneumonitis (RP) using receiver operating characteristic (ROC) curve. Methods: Complete clinical data of 118 non-small cell lung cancer patients treated with three-dimensional conformal and intensity-modulated radiotherapy plus chemotherapy were included. Chi-square and logistic regression were retrospectively applied to analyze the correlations between DVH parameters [relative lung volume received ≥ 5 Gy (V 5 ), 10 Gy (V 10 ), 13 Gy (V 13 ), 20 Gy (V 20 ) and 30 Gy (V 30 ) and mean lung dose (MLD)] and grade 2 (and above) RP defined by the National Cancer Institute Common Terminology Criteria for Adverse Events, version 3.0. ROC curve was adopted to investigate the predictive ACC, SEN and SPE of potential DVH parameters associated with RP. Results: Total lungs V 5 , V 10 , V 13 , V 20 and MLD were all correlated to the development of RP (χ 2 =4.786, 5.771, 6.366, 7.367 and 6.945, P<0.05) according to univariate analysis. However, total lungs V 30 , patient characteristics (age, sex, KPS, tumor location, pathology) and treatment factors (prescription dose, radiotherapy technique, chemotherapy method and timing) were not contributors to RP. Logistic regression showed that V 20 of both lungs remains tight by associated with RP (χ 2 =10.96, OR=4.16, 95% CI 1.40 ∼ 12.36, P<0.05), although significant colinearity was found between V 20 and other DVH parameters (r=0.767-0.902, P<0.05). ROC curve confirmed that V 20 of both lungs could act as a predictor for RP (Z=2.038, P<0.05). The predictive ACC, SEN, and SPE were 0.645 (95% CI 0.498-0.793), 0.650 (95% CI 0.408-0.864), and 0.674 (95% CI 0.571-0.765), respectively. However, the positive predictive value was only 28.9%. Conclusions: V 20 of both lungs was correlated to the development of RP. It could act as a predictor for RP though the predictability is limited
Flow characteristics of curved ducts
Directory of Open Access Journals (Sweden)
Rudolf P.
2007-10-01
Full Text Available Curved channels are very often present in real hydraulic systems, e.g. curved diffusers of hydraulic turbines, S-shaped bulb turbines, fittings, etc. Curvature brings change of velocity profile, generation of vortices and production of hydraulic losses. Flow simulation using CFD techniques were performed to understand these phenomena. Cases ranging from single elbow to coupled elbows in shapes of U, S and spatial right angle position with circular cross-section were modeled for Re = 60000. Spatial development of the flow was studied and consequently it was deduced that minor losses are connected with the transformation of pressure energy into kinetic energy and vice versa. This transformation is a dissipative process and is reflected in the amount of the energy irreversibly lost. Least loss coefficient is connected with flow in U-shape elbows, biggest one with flow in Sshape elbows. Finally, the extent of the flow domain influenced by presence of curvature was examined. This isimportant for proper placement of mano- and flowmeters during experimental tests. Simulations were verified with experimental results presented in literature.
Classical optics and curved spaces
International Nuclear Information System (INIS)
Bailyn, M.; Ragusa, S.
1976-01-01
In the eikonal approximation of classical optics, the unit polarization 3-vector of light satisfies an equation that depends only on the index, n, of refraction. It is known that if the original 3-space line element is d sigma 2 , then this polarization direction propagates parallely in the fictitious space n 2 d sigma 2 . Since the equation depends only on n, it is possible to invent a fictitious curved 4-space in which the light performs a null geodesic, and the polarization 3-vector behaves as the 'shadow' of a parallely propagated 4-vector. The inverse, namely, the reduction of Maxwell's equation, on a curve 'dielectric free) space, to a classical space with dielectric constant n=(-g 00 ) -1 / 2 is well known, but in the latter the dielectric constant epsilon and permeability μ must also equal (-g 00 ) -1 / 2 . The rotation of polarization as light bends around the sun by utilizing the reduction to the classical space, is calculated. This (non-) rotation may then be interpreted as parallel transport in the 3-space n 2 d sigma 2 [pt
E. Martínez-Valle; A. Lagares-Borrego; P. Gacto-Sánchez; A. Lorite-Álvaro; F. Lobo-Bailón; I. Gómez-Contreras; F. Barrera-Pulido; D. Sicilia-Castro; T. Gómez-Cía
2013-01-01
Las amputaciones de pulgar son indicación de reimplante en todos los casos, ya que el papel de este dedo es crucial para que una mano sea funcional. El objetivo de nuestro estudio es revisar la casuística de reimplantes de pulgar de los últimos 6 años en el Hospital Universitario Virgen del Rocío de Sevilla, España. Revisamos el mecanismo de lesión, el nivel de amputación, el uso de injerto venoso y el tipo de osteosíntesis realizado. La tasa de supervivencia lograda fue del 74,19%. Creemos q...
Optimizing the diagnostic power with gastric emptying scintigraphy at multiple time points
Directory of Open Access Journals (Sweden)
Gajewski Byron J
2011-05-01
Full Text Available Abstract Background Gastric Emptying Scintigraphy (GES at intervals over 4 hours after a standardized radio-labeled meal is commonly regarded as the gold standard for diagnosing gastroparesis. The objectives of this study were: 1 to investigate the best time point and the best combination of multiple time points for diagnosing gastroparesis with repeated GES measures, and 2 to contrast and cross-validate Fisher's Linear Discriminant Analysis (LDA, a rank based Distribution Free (DF approach, and the Classification And Regression Tree (CART model. Methods A total of 320 patients with GES measures at 1, 2, 3, and 4 hour (h after a standard meal using a standardized method were retrospectively collected. Area under the Receiver Operating Characteristic (ROC curve and the rate of false classification through jackknife cross-validation were used for model comparison. Results Due to strong correlation and an abnormality in data distribution, no substantial improvement in diagnostic power was found with the best linear combination by LDA approach even with data transformation. With DF method, the linear combination of 4-h and 3-h increased the Area Under the Curve (AUC and decreased the number of false classifications (0.87; 15.0% over individual time points (0.83, 0.82; 15.6%, 25.3%, for 4-h and 3-h, respectively at a higher sensitivity level (sensitivity = 0.9. The CART model using 4 hourly GES measurements along with patient's age was the most accurate diagnostic tool (AUC = 0.88, false classification = 13.8%. Patients having a 4-h gastric retention value >10% were 5 times more likely to have gastroparesis (179/207 = 86.5% than those with ≤10% (18/113 = 15.9%. Conclusions With a mixed group of patients either referred with suspected gastroparesis or investigated for other reasons, the CART model is more robust than the LDA and DF approaches, capable of accommodating covariate effects and can be generalized for cross institutional applications, but
Statistical re-evaluation of the ASME K{sub IC} and K{sub IR} fracture toughness reference curves
Energy Technology Data Exchange (ETDEWEB)
Wallin, K.; Rintamaa, R. [Valtion Teknillinen Tutkimuskeskus, Espoo (Finland)
1998-11-01
Historically the ASME reference curves have been treated as representing absolute deterministic lower bound curves of fracture toughness. In reality, this is not the case. They represent only deterministic lower bound curves to a specific set of data, which represent a certain probability range. A recently developed statistical lower bound estimation method called the `Master curve`, has been proposed as a candidate for a new lower bound reference curve concept. From a regulatory point of view, the Master curve is somewhat problematic in that it does not claim to be an absolute deterministic lower bound, but corresponds to a specific theoretical failure probability that can be chosen freely based on application. In order to be able to substitute the old ASME reference curves with lower bound curves based on the master curve concept, the inherent statistical nature (and confidence level) of the ASME reference curves must be revealed. In order to estimate the true inherent level of safety, represented by the reference curves, the original data base was re-evaluated with statistical methods and compared to an analysis based on the master curve concept. The analysis reveals that the 5% lower bound Master curve has the same inherent degree of safety as originally intended for the K{sub IC}-reference curve. Similarly, the 1% lower bound Master curve corresponds to the K{sub IR}-reference curve. (orig.)
Smarandache Curves In Terms of Sabban Frame of Fixed Pole Curve
Directory of Open Access Journals (Sweden)
Süleyman Şenyurt
2016-06-01
Full Text Available In this paper, we study the special Smarandache curve interms of Sabban frame of Fixed Pole curve and we give some characterization of Smarandache curves. Besides, we illustrate examples of our results.
Submaximal Riemann-Roch expected curves and symplectic packing.
Directory of Open Access Journals (Sweden)
Wioletta Syzdek
2007-06-01
Full Text Available We study Riemann-Roch expected curves on $mathbb{P}^1 imes mathbb{P}^1$ in the context of the Nagata-Biran conjecture. This conjecture predicts that for sufficiently large number of points multiple points Seshadri constants of an ample line bundle on algebraic surface are maximal. Biran gives an effective lower bound $N_0$. We construct examples verifying to the effect that the assertions of the Nagata-Biran conjecture can not hold for small number of points. We discuss cases where our construction fails. We observe also that there exists a strong relation between Riemann-Roch expected curves on $mathbb{P}^1 imes mathbb{P}^1$ and the symplectic packing problem. Biran relates the packing problem to the existence of solutions of certain Diophantine equations. We construct such solutions for any ample line bundle on $mathbb{P}^1 imes mathbb{P}^1$ and a relatively smallnumber of points. The solutions geometrically correspond to Riemann-Roch expected curves. Finally we discuss in how far the Biran number $N_0$ is optimal in the case of mathbb{P}^1 imes mathbb{P}^1. In fact we conjecture that it can be replaced by a lower number and we provide evidence justifying this conjecture.
Power curve of the AWEC-60 wind turbine
International Nuclear Information System (INIS)
Avia, F.
1992-01-01
The experimental wind turbine AWEC-60 was developed to evaluate the possibilities of the Large Wind turbines, from the technical and economical point of view. The project was developed by a spanish-german group, integrated by Union Fenosa, Asinel, M.A.N. Neue Technologie and the Instituto de Energias Renovables from CIEMAT, starting the operation during the year 1990. In this paper, the obtention of the wind turbine's power curve is presented, which has been obtained in agreement with the 'Recommended Practices for Wind Turbine Testing and Evaluation' from the Executive Committee for the Research and Development on Wind Energy, of the International Energy Agency (AIE). Using the functioning data of the wind turbine corresponding to the first quarter of the year 1991, the power curves have been obtained, and the results have been compared with the curves measured in other similar large windturbines. (author)
Power Curve of the AWEC-60 wind turbine
International Nuclear Information System (INIS)
Avia, F.
1992-01-01
The experimental wind turbine AWEC-60 was developed to evaluate the possibilities of the Large Wind turbines, from the technical and economical point of view. The project was developed by a spanish-german group, integrated by Union Fenosa, Asinel, M.A.N. Neue Technologie and the Instituto de Energias Renovables from CIEMAT, starting the operation during the year 1990. In this paper, the obtention of the wind turbine power curve is presented, which has been obtained in agreement with the Recommended Practices for Wind Turbine Testing and Evaluation from the Executive Committee for the Research and Development on Wind Energy, of the International Energy Agency (AIE). Using the functioning data of the wind turbine correspondig to the first quarter of the year 1991, the power curves have been obtained, and the results have been compared with the curves measured in other similar Large wind turbines. (Author) 7 refs
Transition curves for highway geometric design
Kobryń, Andrzej
2017-01-01
This book provides concise descriptions of the various solutions of transition curves, which can be used in geometric design of roads and highways. It presents mathematical methods and curvature functions for defining transition curves. .
2002-01-01
The Atlas of Stress-Strain Curves, Second Edition is substantially bigger in page dimensions, number of pages, and total number of curves than the previous edition. It contains over 1,400 curves, almost three times as many as in the 1987 edition. The curves are normalized in appearance to aid making comparisons among materials. All diagrams include metric (SI) units, and many also include U.S. customary units. All curves are captioned in a consistent format with valuable information including (as available) standard designation, the primary source of the curve, mechanical properties (including hardening exponent and strength coefficient), condition of sample, strain rate, test temperature, and alloy composition. Curve types include monotonic and cyclic stress-strain, isochronous stress-strain, and tangent modulus. Curves are logically arranged and indexed for fast retrieval of information. The book also includes an introduction that provides background information on methods of stress-strain determination, on...
Integration over Tropical Plane Curves and Ultradiscretization
Iwao, Shinsuke
2008-01-01
In this article we study holomorphic integrals on tropical plane curves in view of ultradiscretization. We prove that the lattice integrals over tropical curves can be obtained as a certain limit of complex integrals over Riemannian surfaces.
Directory of Open Access Journals (Sweden)
Suhan Lin
2017-01-01
Full Text Available Background and Aims. This study evaluated the prognostic accuracy of BUN for severe acute pancreatitis (SAP and in-hospital mortality (IHM in terms of the best timing for BUN measurement and the optimal BUN cutoff points. Methods. BUN determinants at the time of admission and 24 hrs after hospital admission were recorded and analyzed statistically. The ability of BUN in predicting the SAP and the occurrence of IHM were assessed using the area under the receiver-operating characteristic (ROC curve. Results. For SAP, AUC of BUN at admission and 24 hrs after hospital admission was 0.75 and 0.80, respectively. For IHM in acute pancreatitis, it was 0.86 at admission and 0.84 after 24 hrs of hospital admission, respectively. The optimal cutoff point of BUN 24 hrs after hospital admission for SAP and at admission for IHM was 8.3 mmol/L and 13.3 mmol/L, respectively. Conclusion. BUN determination after 24 hrs of hospital admission has high accuracy for prediction of SAP while BUN at initial admission has high accuracy for prediction of IHM.
Vo, San C.; Biegel, Bryan (Technical Monitor)
2001-01-01
Scalar multiplication is an essential operation in elliptic curve cryptosystems because its implementation determines the speed and the memory storage requirements. This paper discusses some improvements on two popular signed window algorithms for implementing scalar multiplications of an elliptic curve point - Morain-Olivos's algorithm and Koyarna-Tsuruoka's algorithm.
Ko, William L.; Fleischer, Van Tran
2011-01-01
The Ko displacement theory originally developed for shape predictions of straight beams is extended to shape predictions of curved beams. The surface strains needed for shape predictions were analytically generated from finite-element nodal stress outputs. With the aid of finite-element displacement outputs, mathematical functional forms for curvature-effect correction terms are established and incorporated into straight-beam deflection equations for shape predictions of both cantilever and two-point supported curved beams. The newly established deflection equations for cantilever curved beams could provide quite accurate shape predictions for different cantilever curved beams, including the quarter-circle cantilever beam. Furthermore, the newly formulated deflection equations for two-point supported curved beams could provide accurate shape predictions for a range of two-point supported curved beams, including the full-circular ring. Accuracy of the newly developed curved-beam deflection equations is validated through shape prediction analysis of curved beams embedded in the windward shallow spherical shell of a generic crew exploration vehicle. A single-point collocation method for optimization of shape predictions is discussed in detail
Estimation method of the fracture resistance curve
Energy Technology Data Exchange (ETDEWEB)
Cho, Sung Keun; Lee, Kwang Hyeon; Koo, Jae Mean; Seok, Chang Sung [Sungkyunkwan Univ., Suwon (Korea, Republic of); Park, Jae Sil [Samsung Electric Company, Suwon (Korea, Republic of)
2008-07-01
Fracture resistance curves for concerned materials are required in order to perform elastic-plastic fracture mechanical analysis. Fracture resistance curve is built with J-integral values and crack extension values. The objective of this paper is to propose the estimation method of the fracture resistance curve. The estimation method of the fracture resistance curve for the pipe specimen was proposed by the load ratio method from load - displacement data for the standard specimen.
M-curves and symmetric products
Indian Academy of Sciences (India)
Indranil Biswas
2017-08-03
Aug 3, 2017 ... Since M-curves play a special role in the topology of real algebraic varieties, it is useful to have a criterion for M-curves. It was proved earlier that a curve defined over R is an. M-curve if and only if its Jacobian is an M-variety [5]. We use this result of [5] and the. Picard bundle to prove that the n-th symmetric ...
Allyn, Jérôme; Allou, Nicolas; Augustin, Pascal; Philip, Ivan; Martinet, Olivier; Belghiti, Myriem; Provenchere, Sophie; Montravers, Philippe; Ferdynus, Cyril
2017-01-01
The benefits of cardiac surgery are sometimes difficult to predict and the decision to operate on a given individual is complex. Machine Learning and Decision Curve Analysis (DCA) are recent methods developed to create and evaluate prediction models. We conducted a retrospective cohort study using a prospective collected database from December 2005 to December 2012, from a cardiac surgical center at University Hospital. The different models of prediction of mortality in-hospital after elective cardiac surgery, including EuroSCORE II, a logistic regression model and a machine learning model, were compared by ROC and DCA. Of the 6,520 patients having elective cardiac surgery with cardiopulmonary bypass, 6.3% died. Mean age was 63.4 years old (standard deviation 14.4), and mean EuroSCORE II was 3.7 (4.8) %. The area under ROC curve (IC95%) for the machine learning model (0.795 (0.755-0.834)) was significantly higher than EuroSCORE II or the logistic regression model (respectively, 0.737 (0.691-0.783) and 0.742 (0.698-0.785), p machine learning model, in this monocentric study, has a greater benefit whatever the probability threshold. According to ROC and DCA, machine learning model is more accurate in predicting mortality after elective cardiac surgery than EuroSCORE II. These results confirm the use of machine learning methods in the field of medical prediction.
Aurrekoetxea, Juan J; Murcia, Mario; Rebagliato, Marisa; López, María José; Castilla, Ane Miren; Santa-Marina, Loreto; Guxens, Mónica; Fernández-Somoano, Ana; Espada, Mercedes; Lertxundi, Aitana; Tardón, Adonina; Ballester, Ferran
2013-01-24
To estimate the prevalence and factors associated with smoking and misclassification in pregnant women from INMA (INfancia y Medio Ambiente, Environment and Childhood) project, Spain, and to assess the optimal cut-offs for urinary cotinine (UC) that best distinguish daily and occasional smokers with varying levels of second-hand smoke (SHS) exposure. We used logistic regression models to study the relationship between sociodemographic variables and self-reported smoking and misclassification (self-reported non-smokers with UC >50 ng/ml). Receiver operating characteristic (ROC) curves were used to calculate the optimal cut-off point for discriminating smokers. The cut-offs were also calculated after stratification among non-smokers by the number of sources of SHS exposure. The cut-off points used to discriminate smoking status were the level of UC given by Youden's index and for 50 and 100 ng/ml for daily smokers, or 25 and 50 ng/ml for occasional smokers. At the third trimester of pregnancy, 2263 pregnant women of the INMA Project were interviewed between 2004 and 2008 and a urine sample was collected. Prevalence of self-reported smokers at the third trimester of pregnancy was 18.5%, and another 3.9% misreported their smoking status. Variables associated with self-reported smoking and misreporting were similar, including born in Europe, educational level and exposure to SHS. The optimal cut-off was 82 ng/ml (95% CI 42 to 133), sensitivity 95.2% and specificity 96.6%. The area under the ROC curve was 0.986 (95% CI 0.982 to 0.990). The cut-offs varied according to the SHS exposure level being 42 (95% CI 27 to 57), 82 (95% CI 46 to 136) and 106 ng/ml (95% CI 58 to 227) for not being SHS exposed, exposed to one, and to two or more sources of SHS, respectively. The optimal cut-off for discriminating occasional smokers from non-smokers was 27 ng/ml (95% CI 11 to 43). Prevalence of smoking during pregnancy in Spain remains high. UC is a reliable biomarker for classifying
Modeling fertility curves in Africa
Directory of Open Access Journals (Sweden)
Ezra Gayawan
2010-02-01
Full Text Available The modeling of fertility patterns is an essential method researchers use to understand world-wide population patterns. Various types of fertility models have been reported in the literature to capture the patterns specific to developed countries. While much effort has been put into reducing fertility rates in Africa, models which describe the fertility patterns have not been adequately described. This article presents a flexible parametric model that can adequately capture the varying patterns of the age-specific fertility curves of African countries. The model has parameters that are interpretable in terms of demographic indices. The performance of this model was compared with other commonly used models and Akaike's Information Criterion was used for selecting the model with best fit. The presented model was able to reproduce the empirical fertility data of 11 out of 15 countries better than the other models considered.
Ait-Haddou, Rachid
2013-02-01
We show that the generalized Bernstein bases in Müntz spaces defined by Hirschman and Widder (1949) and extended by Gelfond (1950) can be obtained as pointwise limits of the Chebyshev–Bernstein bases in Müntz spaces with respect to an interval [a,1][a,1] as the positive real number a converges to zero. Such a realization allows for concepts of curve design such as de Casteljau algorithm, blossom, dimension elevation to be transferred from the general theory of Chebyshev blossoms in Müntz spaces to these generalized Bernstein bases that we termed here as Gelfond–Bernstein bases. The advantage of working with Gelfond–Bernstein bases lies in the simplicity of the obtained concepts and algorithms as compared to their Chebyshev–Bernstein bases counterparts.
Separation control on curved boundaries
Kamal Kumar, R.; Mathur, Manikandan
2017-11-01
Flow separation and its characteristics are an important consideration in the field of bluff body aerodynamics. Specifically, the location and slope of the separation, and the size of the re-circulation bubble that forms downstream of the bluff body significantly affect the resulting aerodynamic forces. Recent theories based on dynamical systems (Haller, 2004) have established criteria based on wall-based quantities that identify the location and slope of separation in unsteady flows. In this work, we adapt the closed-loop separation control algorithm proposed by Alam, Liu & Haller (2006) to curved boundaries, and demonstrate the effectiveness of the same via numerical simulations on the flow past a cylinder in the vortex-shedding regime. Using appropriately placed wall-based actuators that use inputs from shear stress sensors placed between the actuators, we demonstrate that the separation characteristics including the re-circulation bubble length, can be desirably modified.
Bacterial streamers in curved microchannels
Rusconi, Roberto; Lecuyer, Sigolene; Guglielmini, Laura; Stone, Howard
2009-11-01
Biofilms, generally identified as microbial communities embedded in a self-produced matrix of extracellular polymeric substances, are involved in a wide variety of health-related problems ranging from implant-associated infections to disease transmissions and dental plaque. The usual picture of these bacterial films is that they grow and develop on surfaces. However, suspended biofilm structures, or streamers, have been found in natural environments (e.g., rivers, acid mines, hydrothermal hot springs) and are always suggested to stem from a turbulent flow. We report the formation of bacterial streamers in curved microfluidic channels. By using confocal laser microscopy we are able to directly image and characterize the spatial and temporal evolution of these filamentous structures. Such streamers, which always connect the inner corners of opposite sides of the channel, are always located in the middle plane. Numerical simulations of the flow provide evidences for an underlying hydrodynamic mechanism behind the formation of the streamers.
Sibling curves of quadratic polynomials | Wiggins | Quaestiones ...
African Journals Online (AJOL)
Sibling curves were demonstrated in [1, 2] as a novel way to visualize the zeroes of real valued functions. In [3] it was shown that a polynomial of degree n has n sibling curves. This paper focuses on the algebraic and geometric properites of the sibling curves of real and complex quadratic polynomials. Key words: Quadratic ...
Trigonometric Characterization of Some Plane Curves
Indian Academy of Sciences (India)
IAS Admin
(Figure 1). A relation between tan θ and tanψ gives the trigonometric equation of the family of curves. In this article, trigonometric equations of some known plane curves are deduced and it is shown that these equations reveal some geometric characteristics of the families of the curves under consideration. In Section 2,.
Holomorphic curves in exploded manifolds: Kuranishi structure
Parker, Brett
2013-01-01
This paper constructs a Kuranishi structure for the moduli stack of holomorphic curves in exploded manifolds. To avoid some technicalities of abstract Kuranishi structures, we embed our Kuranishi structure inside a moduli stack of curves. The construction also works for the moduli stack of holomorphic curves in any compact symplectic manifold.
Automated Blazar Light Curves Using Machine Learning
Energy Technology Data Exchange (ETDEWEB)
Johnson, Spencer James [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2017-07-27
This presentation describes a problem and methodology pertaining to automated blazar light curves. Namely, optical variability patterns for blazars require the construction of light curves and in order to generate the light curves, data must be filtered before processing to ensure quality.
A Conjectural Generating Function for Numbers of Curves on Surfaces
Göttsche, Lothar
I give a conjectural generating function for the numbers of δ-nodal curves in a linear system of dimension δ on an algebraic surface. It reproduces the results of Vainsencher [V] for the case δ &\\le 6 and Kleiman-Piene [K-P] for the case δ &\\le 8. The numbers of curves are expressed in terms of five universal power series, three of which I give explicitly as quasimodular forms. This gives in particular the numbers of curves of arbitrary genus on a K3 surface and an abelian surface in terms of quasimodular forms, generalizing the formula of Yau-Zaslow for rational curves on K3 surfaces. The coefficients of the other two power series can be determined by comparing with the recursive formulas of Caporaso-Harris for the Severi degrees in 2. We verify the conjecture for genus 2 curves on an abelian surface. We also discuss a link of this problem with Hilbert schemes of points.
Power forward curves: a managerial perspective
International Nuclear Information System (INIS)
Nagarajan, Shankar
1999-01-01
This chapter concentrates on managerial application of power forward curves, and examines the determinants of electricity prices such as transmission constraints, its inability to be stored in a conventional way, its seasonality and weather dependence, the generation stack, and the swing risk. The electricity forward curve, classical arbitrage, constructing a forward curve, volatilities, and electricity forward curve models such as the jump-diffusion model, the mean-reverting heteroscedastic volatility model, and an econometric model of forward prices are examined. A managerial perspective of the applications of the forward curve is presented covering plant valuation, capital budgeting, performance measurement, product pricing and structuring, asset optimisation, valuation of transmission options, and risk management
International Nuclear Information System (INIS)
McNeil, B.J.; Hanley, J.A.; Funkenstein, H.H.; Wallman, J.
1983-01-01
The use of a statistical technique for paired comparisons using receiver operating characteristic (ROC) curves is illustrated by studying the extent to which clinical history altered the interpretation of computed tomographic (CT) examinations of the head. Eighty-nine CT examinations of the head were presented in random order to four readers, first with minimum history (age and sex) and then several weeks later with complete neutrological history as of the time the CT examination had been obtained. Using a paired ROC analysis, a small but significant (p < .05) improvement was detected for the interpretations in the presence of complete history; for readings without history the average area was 94.4% and for readings with history it was 97.7%
The consistent histories interpretation of quantum fields in curved spacetime
International Nuclear Information System (INIS)
Blencowe, M.
1991-01-01
As an initial attempt to address some of the foundation problems of quantum mechanics, the author formulates the consistent histories interpretation of quantum field theory on a globally hyperbolic curved space time. He then constructs quasiclassical histories for a free, massive scalar field. In the final part, he points out the shortcomings of the theory and conjecture that one must take into account the fact that gravity is quantized in order to overcome them
Luminous Intensity Distribution Curve Effect on Luminaire Placement
Bayer, Rudolf; Brejcha, Michal
2015-01-01
The paper discusses a way to deploy a given number of point light sources in the interior to provide required illuminance levels and uniformity of the working plane by using a genetic algorithm. Furthermore a genetic algorithm has been used to generate a proper luminous intensity distribution curve of multiple luminaires to meet the given criteria for the reference plane of the model room for predefined luminaire positions.
Torsionfree sheaves over a nodal curve of arithmetic genus one
Indian Academy of Sciences (India)
(n, d) is empty. Let X be a geometrically irreducible nodal curve of arithmetic genus one defined over R. We assume that X does not have any other real points apart from the node. Let UX(n, d) denote the moduli space of semistable torsionfree sheaves of rank n and degree d on X, and let U. X. (n, d) ⊂ UX(n, d) be the open ...
Beaconless Pointing for Deep-Space Optical Communication
Swank, Aaron J.; Aretskin-Hariton, Eliot; Le, Dzu K.; Sands, Obed S.; Wroblewski, Adam
2016-01-01
Free space optical communication is of interest to NASA as a complement to existing radio frequency communication methods. The potential for an increase in science data return capability over current radio-frequency communications is the primary objective. Deep space optical communication requires laser beam pointing accuracy on the order of a few microradians. The laser beam pointing approach discussed here operates without the aid of a terrestrial uplink beacon. Precision pointing is obtained from an on-board star tracker in combination with inertial rate sensors and an outgoing beam reference vector. The beaconless optical pointing system presented in this work is the current approach for the Integrated Radio and Optical Communication (iROC) project.
Families of Smooth Rational Curves of Small Degree on the Fano Variety of Degree 5 of Main Series
Directory of Open Access Journals (Sweden)
M. S. Omelkova
2013-01-01
Full Text Available In this paper we consider some families of smooth rational curves of degree 2, 3 and 4 on a smooth Fano threefold X which is a linear section of the Grassmanian G(1, 4 under the Pl¨ucker embedding. We prove that these families are irreducible. The proof of the irreducibility of the families of curves of degree d is based on the study of degeneration of a rational curve of degree d into a curve which decomposes into an irreducible rational curve of degree d−1 and a projective line intersecting transversally at a point. We prove that the Hilbert scheme of curves of degree d on X is smooth at the point corresponding to such a reducible curve. Then calculations in the framework of deformation theory show that such a curve varies into a smooth rational curve of degree d. Thus, the set of reducible curves of degree d of the above type lies in the closure of a unique component of the Hilbert scheme of smooth rational curves of degree d on X. From this fact and the irreducibility of the Hilbert scheme of smooth rational curves of degree d on the Grassmannian G(1, 4 one deduces the irreducibility of the Hilbert scheme of smooth rational curves of degree d on a general Fano threefold X.
Directory of Open Access Journals (Sweden)
L. Romero-Marrero
2018-01-01
Full Text Available The current research presents a methodology to select pump working as turbines (PAT in recovery system in water distribution networks using their pump characteristic curve. The methodology is based on the review of the empirical methods that are currently proposed and enables the empiric estimation the operating point of the energy converter. The methodology determines the analysis of the operation point (flow, recovered head and efficiency both constant and variable flows over time. When the flow changes, the methodology uses experiments curves that are based on characteristic parameters (discharge and head number. This proposal was applied on case study that is located in Callosa d’en Sarrià (Alicante. In the analyzed case, the recovered energy was 76884.71 kWh/year, representing 74.2% of the current energy that is dissipated by the pressure reduction valve.
Page curves for tripartite systems
International Nuclear Information System (INIS)
Hwang, Junha; Lee, Deok Sang; Nho, Dongju; Oh, Jeonghun; Park, Hyosub; Zoe, Heeseung; Yeom, Dong-han
2017-01-01
We investigate information flow and Page curves for tripartite systems. We prepare a tripartite system (say, A , B , and C ) of a given number of states and calculate information and entropy contents by assuming random states. Initially, every particle was in A (this means a black hole), and as time goes on, particles move to either B (this means Hawking radiation) or C (this means a broadly defined remnant, including a non-local transport of information, the last burst, an interior large volume, or a bubble universe, etc). If the final number of states of the remnant is smaller than that of Hawking radiation, then information will be stored by both the radiation and the mutual information between the radiation and the remnant, while the remnant itself does not contain information. On the other hand, if the final number of states of the remnant is greater than that of Hawking radiation, then the radiation contains negligible information, while the remnant and the mutual information between the radiation and the remnant contain information. Unless the number of states of the remnant is large enough compared to the entropy of the black hole, Hawking radiation must contain information; and we meet the menace of black hole complementarity again. Therefore, this contrasts the tension between various assumptions and candidates of the resolution of the information loss problem. (paper)
Schulze, R K W; Richter, A; d'Hoedt, B
2008-01-01
The study compared diagnostic performances of 2 different image compression methods: JPEG (discrete cosine transform; Joint Photographic Experts Group compression standard) versus JPEG2000 (discrete wavelet transform), both at a compression ratio of 12:1, from the original uncompressed TIFF radiograph with respect to the detection of non-cavitated carious lesions. Therefore, 100 approximal surfaces of 50 tooth pairs were evaluated on the radiographs by 10 experienced observers using a 5-point confidence scale. Observations were carried out on a standardized viewing monitor under subdued light conditions. The proportion of diseased surfaces was balanced to approximately 50% to avoid bias. True caries status was assessed by serial ground sectioning and microscopic evaluation. A non-parametric receiver operating characteristic analysis revealed non-significant differences between the 3 image modalities, as computed from the critical ratios z not exceeding +/-2 (JPEG/JPEG2000, z = -0.0339; TIFF/JPEG2000, z = 0.251;TIFF/JPEG, z = 0.914). The mean area beneath the curve was highest for TIFF (0.604) followed by JPEG2000 (0.593) and JPEG (0.591). Both intra-rater and inter-rater agreement were significantly higher for TIFF (kappa(intra) = 0.52; kappa(inter) = 0.40) and JPEG2000 images (kappa(intra) = 0.49; kappa(inter) = 0.38) than for JPEG images (kappa(intra) = 0.33; kappa(inter) = 0.35). Our results indicate that image compression with typical compression algorithms at rates yielding storage sizes of around 50 kB is sufficient even for the challenging task of radiographic detection of non-cavitated carious approximal lesions. Copyright 2008 S. Karger AG, Basel.
A glow curve analyzer (GCA) for routine analysis of personnel thermoluminescent dosemeter results
International Nuclear Information System (INIS)
Chase, W.J.; Bezaire, M.D.; Vanderzwet, F.P.; Taylor, C.E.
2008-01-01
A glow curve analyzer (GCA) spreadsheet has been developed using Microsoft Excel to perform glow curve analysis on thermoluminescent dosimeter (TLD) data from a personnel dosimetry system. The TLD data come from cards with four LiF:Mg,Ti chips that have been annealed and therefore have a simple glow peak structure. GCA removes spikes in the glow curve data, and then smoothes it. After select start and end points for the glow peak, it fits a Boltzmann function to represent the glow curve signal background under the glow peak. The Boltzmann function is subtracted and two Weibull curves are fit to the remaining net signal between the start and end points. The first Weibull curve is fit to peak 5, and the second one to any small remaining contribution from peaks 3 and 4 or from contaminants. The sum of the two Weibull curves is the glow curve signal result. GCA provides rapid review and correction of all glow curves, improving the quality of the results and reducing the time required for complete processing of official dose results
Large Nc from Seiberg–Witten curve and localization
Directory of Open Access Journals (Sweden)
Jorge G. Russo
2015-09-01
Full Text Available When N=2 gauge theories are compactified on S4, the large Nc limit then selects a unique vacuum of the theory determined by saddle-point equations, which remains determined even in the flat-theory limit. We show that exactly the same equations can be reproduced purely from Seiberg–Witten theory, describing a vacuum where magnetically charged particles become massless, and corresponding to a specific degenerating limit of the Seiberg–Witten spectral curve where 2Nc−2 branch points join pairwise giving aDn=0, n=1,…,Nc−1. We consider the specific case of N=2 SU(Nc SQCD coupled with 2Nf massive fundamental flavors. We show that the theory exhibits a quantum phase transition where the critical point describes a particular Argyres–Douglas point of the Riemann surface.
Environmental Kuznets Curve Hypothesis. A Survey
International Nuclear Information System (INIS)
Dinda, Soumyananda
2004-01-01
The Environmental Kuznets Curve (EKC) hypothesis postulates an inverted-U-shaped relationship between different pollutants and per capita income, i.e., environmental pressure increases up to a certain level as income goes up; after that, it decreases. An EKC actually reveals how a technically specified measurement of environmental quality changes as the fortunes of a country change. A sizeable literature on EKC has grown in recent period. The common point of all the studies is the assertion that the environmental quality deteriorates at the early stages of economic development/growth and subsequently improves at the later stages. In other words, environmental pressure increases faster than income at early stages of development and slows down relative to GDP growth at higher income levels. This paper reviews some theoretical developments and empirical studies dealing with EKC phenomenon. Possible explanations for this EKC are seen in (1) the progress of economic development, from clean agrarian economy to polluting industrial economy to clean service economy; (2) tendency of people with higher income having higher preference for environmental quality, etc. Evidence of the existence of the EKC has been questioned from several corners. Only some air quality indicators, especially local pollutants, show the evidence of an EKC. However, an EKC is empirically observed, till there is no agreement in the literature on the income level at which environmental degradation starts declining. This paper provides an overview of the EKC literature, background history, conceptual insights, policy and the conceptual and methodological critique
Directory of Open Access Journals (Sweden)
E. Martínez-Valle
2013-09-01
Full Text Available Las amputaciones de pulgar son indicación de reimplante en todos los casos, ya que el papel de este dedo es crucial para que una mano sea funcional. El objetivo de nuestro estudio es revisar la casuística de reimplantes de pulgar de los últimos 6 años en el Hospital Universitario Virgen del Rocío de Sevilla, España. Revisamos el mecanismo de lesión, el nivel de amputación, el uso de injerto venoso y el tipo de osteosíntesis realizado. La tasa de supervivencia lograda fue del 74,19%. Creemos que es una tasa de supervivencia elevada, que asocia los mejores resultados a las amputaciones sin componente de aplastamiento. El uso de injerto venoso se asocia igualmente a mejores resultados de la cirugía en casos de aplastamiento o arrancamiento como mecanismo de lesión.
Development of a Charpy master curve-based embrittlement trend curve
International Nuclear Information System (INIS)
Erikson, M.
2011-01-01
Under the current U.S. surveillance programs, the Charpy V-notch energy (CVE), yield strength, and tensile strength are measured (all as a function of test temperature) at various times during the operational life of the reactor vessel. Conventionally, the CVE vs. temperature data are fit using a hyperbolic tangent (tanh) function to determine the temperature at which the mean CVE is equal to 30 ft-lbs (41J). This index temperature, which is designated T30 or T41J, is used to track irradiation damage. Recently an alternative strategy for fitting the CVE vs. temperature data was proposed in which a single CVE vs. temperature relationship appears to well represent the behavior of a very wide variety of ferritic steels for temperatures at and below fracture mode transition. It was demonstrated that when upper shelf data are excluded from a fit of Charpy V-notch energy (CVE) vs. temperature a single exponential function is found that well represents the transition temperature behavior of ferritic steels. The findings suggest that a reanalysis of already tested Charpy surveillance specimens can provide the basis for development of an embrittlement trend curve that is less influenced by the biases that arise from the tanh curve fitting method. Recently, a program was initiated with a goal of using the Charpy MC transition data fit to define a reference temperature, to use instead of the traditionally defined tanh-based T30/T41J reference temperature, in development of an embrittlement trend curve. The existing USLWR database was mined for datasets with sufficient data points within the transition temperature region for use in defining a TCVE reference temperature. These values were then used to define ΔTCVE data with irradiation. This data, along with chemistry, temperature, flux and fluence information, was used to develop the embrittlement trend curve presented herein. Predictions of embrittlement behavior made using this ETC were then compared to predictions made
Directory of Open Access Journals (Sweden)
Tatiana Chagoyen Barroso
Full Text Available Introducción: En los últimos años se ha incrementado la violencia laboral, y un sector de los más afectados es el sanitario. En la actualidad, está cobrando importancia la violencia laboral en el personal de urgencias. Las agresiones suelen ser por parte de los usuarios y, en ocasiones de sus familiares, a los profesionales de la Salud. Objetivos: Conocer si los trabajadores de Urgencias Generales del Hospital Universitario Virgen del Rocío (HUVR saben de la existencia de un plan de prevención y atención de agresiones para los profesionales del sistema público de Andalucía. Conocer agresiones no registradas hacia el personal de urgencias en HUVR. Material y métodos: Se trata de un estudio observacional, descriptivo con 221 trabajadores (68 varones y 153 mujeres, a los que se les entrega un cuestionario sobre la Violencia Laboral Externa (VLE percibida durante los 2 últimos años; se realiza un estudio descriptivo con análisis de frecuencias. Y posteriormente, se realizará test de Chi Cuadrado o prueba exacta de Fisher para ver si existe relación entre variables categóricas. Resultados: De 221 trabajadores que realizaron la encuesta, solo 26 conocen el plan de agresiones de HUVR. De 127 agresiones en los 2 últimos años, solo se registraron 13 (no existe significación estadística con sexo, edad o categoría profesional. Conclusiones: Existe infradeclaración de agresiones y un claro desconocimiento del plan de agresiones en el Hospital Universitario Virgen del Rocío.
Hodgkins, Jamie; Marean, Curtis W; Turq, Alain; Sandgathe, Dennis; McPherron, Shannon J P; Dibble, Harold
2016-07-01
Neandertals disappeared from Europe just after 40,000 years ago. Some hypotheses ascribe this to numerous population crashes associated with glacial cycles in the late Pleistocene. The goal of this paper is to test the hypothesis that glacial periods stressed Neandertal populations. If cold climates stressed Neandertals, their subsistence behaviors may have changed-requiring intensified use of prey through more extensive nutrient extraction from faunal carcasses. To test this, an analysis of Neandertal butchering was conducted on medium sized bovid/cervid remains composed of predominately red deer (Cervus elaphus), reindeer (Rangifer tarandus), and roe deer (Capreolus caprelous) deposited during global warm and cold phases from two French sites: Pech de l'Azé IV (Pech IV, Bordes' excavation) and Roc de Marsal (RDM). Analysis of surface modification on high survival long bones and proximal and middle phalanges demonstrates that skeletal elements excavated from the cold levels (RDM Level 4, Pech IV Level I2) at each cave have more cut marks and percussion marks than elements from the warm levels (RDM Level 9, Pech IV Level Y-Z) after controlling for fragment size. At both sites, epiphyseal fragments are rare, and although this pattern can result from carnivore consumption, carnivore tooth marks are almost nonexistent (climate, but may have been a general Neandertal behavioral characteristic, suggesting that these hominids were regularly on the edge of sufficient nutrient availability even during interglacials. Overall, the faunal assemblages from Roc de Marsal and Pech IV provide some support for the hypothesis that Neandertals were processing faunal remains more heavily during glacial periods, suggesting a response to increased nutritional stress during colder time periods. Copyright © 2016 Elsevier Ltd. All rights reserved.
Construction of calibration curve for accountancy tank
International Nuclear Information System (INIS)
Kato, Takayuki; Goto, Yoshiki; Nidaira, Kazuo
2009-01-01
Tanks are equipped in a reprocessing plant for accounting solution of nuclear material. The careful measurement of volume in tanks is very important to implement rigorous accounting of nuclear material. The calibration curve relating the volume and level of solution needs to be constructed, where the level is determined by differential pressure of dip tubes. Several calibration curves are usually employed, but it's not explicitly decided how many segment are used, where to select segment, or what should be the degree of polynomial curve. These parameters, i.e., segment and degree of polynomial curve are mutually interrelated to give the better performance of calibration curve. Here we present the construction technique of giving optimum calibration curves and their characteristics. (author)
Address Points - Allegheny County Address Points 201601
NSGIC Education | GIS Inventory — This dataset contains Address Points in Allegheny County. The Address Points were created by GDR for the Allegheny County CAD project, October 2008. Data is updated...
Soil Water Thermodynamic to Unify Water Retention Curve by Pressure Plates and Tensiometer
Directory of Open Access Journals (Sweden)
Erik eBraudeau
2014-10-01
Full Text Available The pressure plate method is a standard method for measuring the pF curves, also called soil water retention curves, in a large soil moisture range from saturation to a dry state corresponding to a tension pressure of near 1500 kPa. However, the pressure plate can only provide discrete water retention curves represented by a dozen measured points. In contrast, the measurement of the soil water retention curves by tensiometer is direct and continuous, but limited to the range of the tensiometer reading: from saturation to near 70-80 kPa. The two methods stem from two very different concepts of measurement and the compatibility of both methods has never been demonstrated. The recently established thermodynamic formulation of the pedostructure water retention curve, will allow the compatibility of the two curves to be studied, both theoretically and experimentally. This constitutes the object of the present article. We found that the pressure plate method provides accurate measurement points of the pedostructure water retention curve h(W, conceptually the same as that accurately measured by the tensiometer. However, contrarily to what is usually thought, h is not equal to the applied air pressure on the sample, but rather, is proportional to its logarithm, in agreement with the thermodynamic theory developed in the article. The pF curve and soil water retention curve, as well as their methods of measurement are unified in a same physical theory. It is the theory of the soil medium organization (pedostructure and its interaction with water. We show also how the hydrostructural parameters of the theoretical curve equation can be estimated from any measured curve, whatever the method of measurement. An application example using published pF curves is given.
Regional Marginal Abatement Cost Curves for NOx
U.S. Environmental Protection Agency — Data underlying the figures included in the manuscript "Marginal abatement cost curve for NOx incorporating controls, renewable electricity, energy efficiency and...
Water Retention Curves of Opalinus Clay
Energy Technology Data Exchange (ETDEWEB)
Villar, M. V.; Romero, F. J.
2012-11-01
The water retention curve of Opalinus clay samples was determined under different conditions: total and matric suction, stress or no-stress conditions, wetting and drying paths. Through the fitting of these results to the van Genuchten expression the P parameter, related to the air entry value (AEV), was obtained. The AEV is the suction value above which air is able to enter the pores of the sample, and consequently, above which 2-phase flow can take place in the soil pore structure. The samples used in this research came from two different boreholes, BHT-1 and BHG-D1, but the behaviour of them did not depend on their location, what was probably due to the fact that both were drilled in the shay facies of the Opalinus clay. There was not a distinct difference between the results obtained under total or matric suctions. In the drying paths, both the water contents and the degrees of saturation tended to be higher when total suction was applied, however the reverse trend was observed for the water contents reached in wetting paths. As well, no clear difference was observed in the water retention curves obtained in odometers under matric and total suctions, what points to the osmotic component of suction in Opalinus clay not being significant. Overall, the water contents were lower and the degrees of saturation higher when suction was applied under vertical stress, what would indicate that the water retention capacity was lower under 8 MPa vertical stress than under free volume conditions. This vertical stress value is slightly higher than the maximum in situ stress. Also, the samples showed hysteresis according to the expected behaviour, i.e. the water contents for a given suction were higher during a drying path than during a wetting path. The P values obtained were between 6 and 34 MPa, and tended to be higher for the samples tested under stress, in drying paths and when total suction was used. The air entry value calculated from the mercury intrusion porosimetry
Energy Technology Data Exchange (ETDEWEB)
McGreevy, John Austen; /Stanford U., Phys. Dept.
2005-07-06
This thesis is a study of D-branes in string compactifications. In this context, D-branes are relevant as an important component of the nonperturbative spectrum, as an incisive probe of these backgrounds, and as a natural stringy tool for localizing gauge interactions. In the first part of the thesis, we discuss half-BPS D-branes in compactifications of type II string theory on Calabi-Yau threefolds. The results we describe for these objects are pertinent both in their role as stringy brane-worlds, and in their role as solitonic objects. In particular, we determine couplings of these branes to the moduli determining the closed-string geometry, both perturbatively and non-perturbatively in the worldsheet expansion. We provide a local model for transitions in moduli space where the BPS spectrum jumps, and discuss the extension of mirror symmetry between Calabi-Yau manifolds to the case when D-branes are present. The next section is an interlude which provides some applications of D-branes to other curved backgrounds of string theory. In particular, we discuss a surprising phenomenon in which fundamental strings moving through background Ramond-Ramond fields dissolve into large spherical D3-branes. This mechanism is used to explain a previously-mysterious fact discovered via the AdS-CFT correspondence. Next, we make a connection between type IIA string vacua of the type discussed in the first section and M-theory compactifications on manifolds of G{sub 2} holonomy. Finally we discuss constructions of string vacua which do not have large radius limits. In the final part of the thesis, we develop techniques for studying the worldsheets of open strings ending on the curved D-branes studied in the first section. More precisely, we formulate a large class of massive two-dimensional gauge theories coupled to boundary matter, which flow in the infrared to the relevant boundary conformal field theories. Along with many other applications, these techniques are used to describe
Directory of Open Access Journals (Sweden)
Alireza Shahab Jahanlou
2016-07-01
Full Text Available Background Two popular indicators for detecting obesity are body mass index (BMI and waist-to-hip ratio (WHR. Objectives The primary purpose of this study was to examine the agreement between the BMI and WHR classifications in diagnosing obesity among adult Iranians by using cutoff points of world health organization (WHO gold standards. The secondary purpose was to estimate suitable cutoff points for BMI and WHR for various sex and age-groups. Methods The study was cross-sectional. The data were obtained from 13,691 females and 5,675 males between 2009 and 2014. Body composition indices were measured by bioelectrical impedance method (BIA. Percentage of body fat (PBF, total fat (TF, BMI, and WHR were determined. Data analysis included t-test, chi-square test, receiver-operating characteristic (ROC curves, Fisher’s r-to-z transformation, linear regression, and Hanely formula. Results In the WHR classification, nearly 78% of obese subjects had been wrongly classified as non-obese, but only 15.8% of obese females were wrongly classified as non-obese. The WHR was ineffective in detecting obesity among males between 20 and 39 years old. By the BMI classification, 42.5% of obese males had been wrongly classified as non-obese, but it was effective in detecting obesity in females between the ages of 20 and 39 years. Conclusions The suitable BMI cutoff points for detecting obesity for adult Iranians are 27.7 in all subjects, 27.7 in females, and 27.3 in males, which are all less than the BMI of 30 recommended by the WHO. On the basis of the WHR, they are 0.88 and 0.83 for males and females, respectively, which are less than the recommended cutoff points for Europeans but similar to those Eastern Asians.
Hong Shen
2011-01-01
The concepts of curve profile, curve intercept, curve intercept density, curve profile area density, intersection density in containing intersection (or intersection density relied on intersection reference), curve profile intersection density in surface (or curve intercept intersection density relied on intersection of containing curve), and curve profile area density in surface (AS) were defined. AS expressed the amount of curve profile area of Y phase in the unit containing surface area, S...
Directory of Open Access Journals (Sweden)
A.S. Jahanlou
2015-07-01
Full Text Available Introduction & Objective: Proportion of Waist-to-Hip Ratio (WHR is an indicator of abdominal obesity, which is supported by some studies but rejected by others. The aim of this study was to examine the accuracy of the WHR and obtain suitable cut- off points for detecting obesity among adult Iranians. Materials & Methods: In this cross-sectional-descriptive study the sample consisted of 19366 adults. The data collection took place from 2009 to 2014, using Bioelectrical Impedance Analysis (BIA. The following data were obtained: WHR, Percentile of Body Fat (PBF, To-tal Fat (TF, and Soft Lean Mass (SLM. Sensitivity and specificity, based on World Health Organization’s Gold Standards were calculated for both sexes at three age groups. The data analysis included t-test, chi-square, ROC curve, and linear regression. Results: All study variables were correlated with each other. Age was only correlated with the WHR. Percentages of sensitivity and Negative Predictive Value (NPV were 84.2% and 85.6% in women; 21% and 50.7% in men. Increase in age was associated with increase in sensitivity in men and women, and NPV in men. The suitable cut-off points for men and women were found to be 87.5% and 83.5%, respectively. Conclusion: Waist-to-Hip ration is a suitable indictor of obesity for Iranian women but not men, especially among those who are under 59 years old. (Sci J Hamadan Univ Med Sci 2015; 22 (2: 144-151
DEFF Research Database (Denmark)
Tatu, Aditya Jayant
tracking interfaces, active contour based segmentation methods and others. It can also be used to study shape spaces, as deforming a shape can be thought of as evolving its boundary curve. During curve evolution a curve traces out a path in the infinite dimensional space of curves. Due to application...... defined subspace, the N-links bicycle chain space, i.e. the space of curves with equidistant neighboring landmark points. This in itself is a useful shape space for medical image analysis applications. The Histogram of Gradient orientation based features are many in number and are widely used...
Particles and Dirac-type operators on curved spaces
International Nuclear Information System (INIS)
Visinescu, Mihai
2003-01-01
We review the geodesic motion of pseudo-classical particles in curved spaces. Investigating the generalized Killing equations for spinning spaces, we express the constants of motion in terms of Killing-Yano tensors. Passing from the spinning spaces to the Dirac equation in curved backgrounds we point out the role of the Killing-Yano tensors in the construction of the Dirac-type operators. The general results are applied to the case of the four-dimensional Euclidean Taub-Newman-Unti-Tamburino space. From the covariantly constant Killing-Yano tensors of this space we construct three new Dirac-type operators which are equivalent with the standard Dirac operator. Finally the Runge-Lenz operator for the Dirac equation in this background is expressed in terms of the fourth Killing-Yano tensor which is not covariantly constant. As a rule the covariantly constant Killing-Yano tensors realize certain square roots of the metric tensor. Such a Killing-Yano tensor produces simultaneously a Dirac-type operator and the generator of a one-parameter Lie group connecting this operator with the standard Dirac one. On the other hand, the not covariantly constant Killing-Yano tensors are important in generating hidden symmetries. The presence of not covariantly constant Killing-Yano tensors implies the existence of non-standard supersymmetries in point particle theories on curved background. (author)
Limiting Accuracy of Segregated Solution Methods for Nonsymmetric Saddle Point Problems
Czech Academy of Sciences Publication Activity Database
Jiránek, P.; Rozložník, Miroslav
Roc. 215, c. 1 (2008), s. 28-37 ISSN 0377-0427 R&D Projects: GA MŠk 1M0554; GA AV ČR 1ET400300415 Institutional research plan: CEZ:AV0Z10300504 Keywords : saddle point problems * Schur complement reduction method * null-space projection method * rounding error analysis Subject RIV: BA - General Mathematics Impact factor: 1.048, year: 2008
Comparison and evaluation of mathematical lactation curve ...
African Journals Online (AJOL)
p2492989
and on the log of 305-d divided by day in lactation (linear and quadratic) were better than the Gamma function. A study of lactation curves in dairy cattle on farms in central Mexico showed that the Dijkstra function was superior to the Wood, Wilmink and Rook functions for describing the lactation curve (Val-. Arreola et al.
Spectral Curves of Operators with Elliptic Coefficients
Directory of Open Access Journals (Sweden)
J. Chris Eilbeck
2007-03-01
Full Text Available A computer-algebra aided method is carried out, for determining geometric objects associated to differential operators that satisfy the elliptic ansatz. This results in examples of Lamé curves with double reduction and in the explicit reduction of the theta function of a Halphen curve.
Inverse Problem for a Curved Quantum Guide
Directory of Open Access Journals (Sweden)
Laure Cardoulis
2012-01-01
Full Text Available We consider the Dirichlet Laplacian operator −Δ on a curved quantum guide in ℝ n(n=2,3 with an asymptotically straight reference curve. We give uniqueness results for the inverse problem associated to the reconstruction of the curvature by using either observations of spectral data or a boot-strapping method.
Deep-learnt classification of light curves
DEFF Research Database (Denmark)
Mahabal, Ashish; Gieseke, Fabian; Pai, Akshay Sadananda Uppinakudru
2017-01-01
Astronomy light curves are sparse, gappy, and heteroscedastic. As a result standard time series methods regularly used for financial and similar datasets are of little help and astronomers are usually left to their own instruments and techniques to classify light curves. A common approach is to d...
Learning curves in energy planning models
Energy Technology Data Exchange (ETDEWEB)
Barreto, L.; Kypreos, S. [Paul Scherrer Inst. (PSI), Villigen (Switzerland)
1999-08-01
This study describes the endogenous representation of investment cost learning curves into the MARKAL energy planning model. A piece-wise representation of the learning curves is implemented using Mixed Integer Programming. The approach is briefly described and some results are presented. (author) 3 figs., 5 refs.
The Koch curve as a smooth manifold
International Nuclear Information System (INIS)
Epstein, Marcelo; Sniatycki, Jedrzej
2008-01-01
We show that there exists a homeomorphism between the closed interval [0,1] is contained in R and the Koch curve endowed with the subset topology of R 2 . We use this homeomorphism to endow the Koch curve with the structure of a smooth manifold with boundary
Trigonometric Characterization of Some Plane Curves
Indian Academy of Sciences (India)
IAS Admin
There is a way to describe a family of plane curves different from that using Cartesian or po- lar co-ordinates. This is a trigonometric equation involving two angles. In this article, we highlight the fact that trigonometric equations are conve- nient to describe certain one-parameter families of plane curves. In some cases, the ...
Heterozygote PCR product melting curve prediction.
Dwight, Zachary L; Palais, Robert; Kent, Jana; Wittwer, Carl T
2014-03-01
Melting curve prediction of PCR products is limited to perfectly complementary strands. Multiple domains are calculated by recursive nearest neighbor thermodynamics. However, the melting curve of an amplicon containing a heterozygous single-nucleotide variant (SNV) after PCR is the composite of four duplexes: two matched homoduplexes and two mismatched heteroduplexes. To better predict the shape of composite heterozygote melting curves, 52 experimental curves were compared with brute force in silico predictions varying two parameters simultaneously: the relative contribution of heteroduplex products and an ionic scaling factor for mismatched tetrads. Heteroduplex products contributed 25.7 ± 6.7% to the composite melting curve, varying from 23%-28% for different SNV classes. The effect of ions on mismatch tetrads scaled to 76%-96% of normal (depending on SNV class) and averaged 88 ± 16.4%. Based on uMelt (www.dna.utah.edu/umelt/umelt.html) with an expanded nearest neighbor thermodynamic set that includes mismatched base pairs, uMelt HETS calculates helicity as a function of temperature for homoduplex and heteroduplex products, as well as the composite curve expected from heterozygotes. It is an interactive Web tool for efficient genotyping design, heterozygote melting curve prediction, and quality control of melting curve experiments. The application was developed in Actionscript and can be found online at http://www.dna.utah.edu/hets/. © 2013 WILEY PERIODICALS, INC.
A minicourse on moduli of curves
International Nuclear Information System (INIS)
Looijenga, E.
2000-01-01
These are notes that accompany a short course given at the School on Algebraic Geometry 1999 at the ICTP, Trieste. A major goal is to outline various approaches to moduli spaces of curves. In the last part I discuss the algebraic classes that naturally live on these spaces; these can be thought of as the characteristic classes for bundles of curves. (author)
Sibling curves of polynomials | Wiggins | Quaestiones Mathematicae
African Journals Online (AJOL)
Sibling curves were demonstrated in papers [2, 3] as a novel way to visualize the zeros of complex valued functions. In this paper, we continue the work done in those papers by focusing solely on polynomials. We proceed to prove that the number of sibling curves of a polynomial is the degree of the polynomial. Keywords: ...
Measuring Model Rocket Engine Thrust Curves
Penn, Kim; Slaton, William V.
2010-01-01
This paper describes a method and setup to quickly and easily measure a model rocket engine's thrust curve using a computer data logger and force probe. Horst describes using Vernier's LabPro and force probe to measure the rocket engine's thrust curve; however, the method of attaching the rocket to the force probe is not discussed. We show how a…
Curve Matching with Applications in Medical Imaging
DEFF Research Database (Denmark)
Bauer, Martin; Bruveris, Martins; Harms, Philipp
2015-01-01
In the recent years, Riemannian shape analysis of curves and surfaces has found several applications in medical image analysis. In this paper we present a numerical discretization of second order Sobolev metrics on the space of regular curves in Euclidean space. This class of metrics has several...
Single curved fiber sedimentation under gravity
Xiaoying Rong; Dewei Qi; Junyong Zhu
2005-01-01
Dynamics of single curved fiber sedimentation under the gravity are simulated by using lattice Boltzmann method. The results of migration and rotation of the curved fiber at different Reynolds numbers are reported. The results show that the rotation and migration processes are sensitive to the curvature of the fiber.
Wind Turbine Power Curves Incorporating Turbulence Intensity
DEFF Research Database (Denmark)
Sørensen, Emil Hedevang Lohse
2014-01-01
The performance of a wind turbine in terms of power production (the power curve) is important to the wind energy industry. The current IEC-61400-12-1 standard for power curve evaluation recognizes only the mean wind speed at hub height and the air density as relevant to the power production...
Directory of Open Access Journals (Sweden)
V. V. Lahuta
2008-01-01
Full Text Available The numerical method of solution of a differential equation of railway shifts is presented allowing to calculate the quantity of shifts in any point of a railway curve during its straightening. Shifts calculated between the points of measurement of bend arrows can be used as control ones.
Computation of the locus crossing point location of MC circuit
International Nuclear Information System (INIS)
Liu Hai-Jun; Li Zhi-Wei; Bu Kai; Sun Zhao-Lin; Nie Hong-Shan
2014-01-01
In this paper, the crossing point property of the i–v hysteresis curve in a memristor–capacitor (MC) circuit is analyzed. First, the ideal passive memristor on the crossing point property of i–v hysteresis curve is studied. Based on the analysis, the analytical derivation with respect to the crossing point location of MC circuit is given. Then the example of MC with linear memristance-versus-charge state map is demonstrated to discuss the drift property of cross-point location, caused by the frequency and capacitance value. (interdisciplinary physics and related areas of science and technology)
Generators for the em>l>-torsion subgroup of Jacobians of Genus Two Curves
DEFF Research Database (Denmark)
Ravnshøj, Christian Robenhagen
2008-01-01
We give an explicit description of the matrix representation of the Frobenius endomorphism on the Jacobian of a genus two curve on the subgroup of l-torsion points. By using this description, we can describe the matrix representation of the Weil-pairing on the subgroup of l-torsion points explici...... explicitly. Finally, the explicit description of the Weil-pairing provides us with an efficient, probabilistic algorithm to find generators of the subgroup of l-torsion points on the Jacobian of a genus two curve....
Quantum curves and conformal field theory
Manabe, Masahide; Sułkowski, Piotr
2017-06-01
To a given algebraic curve we assign an infinite family of quantum curves (Schrödinger equations), which are in one-to-one correspondence with, and have the structure of, Virasoro singular vectors. For a spectral curve of a matrix model we build such quantum curves out of an appropriate representation of the Virasoro algebra, encoded in the structure of the α /β -deformed matrix integral and its loop equation. We generalize this construction to a large class of algebraic curves by means of a refined topological recursion. We also specialize this construction to various specific matrix models with polynomial and logarithmic potentials, and among other results, show that various ingredients familiar in the study of conformal field theory (Ward identities, correlation functions and a representation of Virasoro operators acting thereon, Belavin-Polyakov-Zamolodchikov equations) arise upon specialization of our formalism to the multi-Penner matrix model.
Curved and conformal high-pressure vessel
Croteau, Paul F.; Kuczek, Andrzej E.; Zhao, Wenping
2016-10-25
A high-pressure vessel is provided. The high-pressure vessel may comprise a first chamber defined at least partially by a first wall, and a second chamber defined at least partially by the first wall. The first chamber and the second chamber may form a curved contour of the high-pressure vessel. A modular tank assembly is also provided, and may comprise a first mid tube having a convex geometry. The first mid tube may be defined by a first inner wall, a curved wall extending from the first inner wall, and a second inner wall extending from the curved wall. The first inner wall may be disposed at an angle relative to the second inner wall. The first mid tube may further be defined by a short curved wall opposite the curved wall and extending from the second inner wall to the first inner wall.
Graphical interpretation of confidence curves in rankit plots
DEFF Research Database (Denmark)
Hyltoft Petersen, Per; Blaabjerg, Ole; Andersen, Marianne
2004-01-01
distribution and the percentage of cumulative points exceeding these limits. The process is to rank the reference values and plot the cumulative frequency points in a rankit plot with a logarithmic (In=log(e)) transformed abscissa. If the distribution is close to In-Gaussian the cumulative frequency points......-Gaussian distributions of subgroups of reference values from healthy individuals is presented. In addition, distributions of values from well-defined diseased individuals may show up as In-Gaussian. It is evident from the examples that the rankit transformation and simple graphical evaluation for non......A well-known transformation from the bell-shaped Gaussian (normal) curve to a straight line in the rankit plot is investigated, and a tool for evaluation of the distribution of reference groups is presented. It is based on the confidence intervals for percentiles of the calculated Gaussian...
Curve fitting methods for solar radiation data modeling
Energy Technology Data Exchange (ETDEWEB)
Karim, Samsul Ariffin Abdul, E-mail: samsul-ariffin@petronas.com.my, E-mail: balbir@petronas.com.my; Singh, Balbir Singh Mahinder, E-mail: samsul-ariffin@petronas.com.my, E-mail: balbir@petronas.com.my [Department of Fundamental and Applied Sciences, Faculty of Sciences and Information Technology, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak Darul Ridzuan (Malaysia)
2014-10-24
This paper studies the use of several type of curve fitting method to smooth the global solar radiation data. After the data have been fitted by using curve fitting method, the mathematical model of global solar radiation will be developed. The error measurement was calculated by using goodness-fit statistics such as root mean square error (RMSE) and the value of R{sup 2}. The best fitting methods will be used as a starting point for the construction of mathematical modeling of solar radiation received in Universiti Teknologi PETRONAS (UTP) Malaysia. Numerical results indicated that Gaussian fitting and sine fitting (both with two terms) gives better results as compare with the other fitting methods.
Curve fitting methods for solar radiation data modeling
Karim, Samsul Ariffin Abdul; Singh, Balbir Singh Mahinder
2014-10-01
This paper studies the use of several type of curve fitting method to smooth the global solar radiation data. After the data have been fitted by using curve fitting method, the mathematical model of global solar radiation will be developed. The error measurement was calculated by using goodness-fit statistics such as root mean square error (RMSE) and the value of R2. The best fitting methods will be used as a starting point for the construction of mathematical modeling of solar radiation received in Universiti Teknologi PETRONAS (UTP) Malaysia. Numerical results indicated that Gaussian fitting and sine fitting (both with two terms) gives better results as compare with the other fitting methods.
Normal Type-2 Fuzzy Geometric Curve Modeling: A Literature Review
Adesah, R. S.; Zakaria, R.
2017-09-01
Type-2 Fuzzy Set Theory (T2FST) is widely used for defining uncertainty data points rather than the traditional fuzzy set theory (type-1) since 2001. Recently, T2FST is used in many fields due to its ability to handle complex uncertainty data. In this paper, a review of normal type-2 fuzzy geometric curve modeling methods and techniques is presented. In particular, there have been recent applications of Normal Type-2 Fuzzy Set Theory (NT2FST) in geometric modeling, where it has helped improving results over type-1 fuzzy sets. In this paper, a concise and representative review of the processes in normal type-2 fuzzy geometrical curve modeling such as the fuzzification is presented.
Fermion on Curved Spaces, Symmetries, and Quantum Anomalies
Directory of Open Access Journals (Sweden)
Mihai Visinescu
2006-11-01
Full Text Available We review the geodesic motion of pseudo-classical spinning particles in curved spaces. Investigating the generalized Killing equations for spinning spaces, we express the constants of motion in terms of Killing-Yano tensors. Passing from the spinning spaces to the Dirac equation in curved backgrounds we point out the role of the Killing-Yano tensors in the construction of the Dirac-type operators. The general results are applied to the case of the four-dimensional Euclidean Taub-Newman-Unti-Tamburino space. The gravitational and axial anomalies are studied for generalized Euclidean Taub-NUT metrics which admit hidden symmetries analogous to the Runge-Lenz vector of the Kepler-type problem. Using the Atiyah-Patodi-Singer index theorem for manifolds with boundaries, it is shown that the these metrics make no contribution to the axial anomaly.