353 research outputs found
Star clusters in the triangulum galaxy: star cluster catalog and mass function fitting
No full texthonors thesisCollege of SciencePhysics & AstronomyAnil SethWe construct a catalog of star clusters in the Triangulum Galaxy (M33). The catalog is the result of the Local Group Cluster Search (LGCS) citizen science project through Zooniverse, where users classify images from the Hubble Space Telescope (HST). We base our star cluster catalog on the fraction of the 60 users that viewed each image who identified each object as a star cluster. We derive the completeness of the catalog from analyzing 1700 synthetic clusters to determine detection limits, as well as comparing our results to previous catalogs in the literature. By weighting Zooniverse users based on how many objects they classified as star clusters that were in fact star clusters, we improve catalog completeness. The catalog improves upon previous ground based catalogs extending the catalog by approximately 1300 clusters, providing base data for further research into star formation in M33. Using the star cluster catalog, we measure the cluster mass function for 290 young star clusters in M33 whose ages and masses were derived through integrated light spectral energy distribution fitting. Our mass function fitting uses a probabilistic Markov chain Monte Carlo technique. Although fits to integrated light observations lead to larger uncertainties than from other methods, a majority of extragalactic star cluster samples rely on integrated light fitting. We compare integrated light mass function fitting results in M31 to the mass function results for the exact same clusters whose ages and masses were derived through color magnitude diagram fitting previously published. We find the truncation mass log(Mc / M!) is 0.4 dex higher than the previously published CMD value, suggesting that uncertainties on the mass estimates of individual clusters can bias the upper mass truncation parameter of the cluster mass function to significantly higher values. We then run experiments using M51, M83 and NGC628 incorporating individual cluster mass errors into a simulated mass function fit. We find that the high errors of the integrated light method of deriving ages and masses systematically biases the truncation mass towards higher masses
HIGH RESOLUTION SPECTROSCOPY OF VIBRATIONALLY EXCITED FLUOROFORM-D BY HETERODYNE FREQUENCY MEASUREMENT OF SMMW LASER EMISSION
No full textAuthor Institution: U. S. Army Electronics Research and Development Command, Harry Diamond LaboratoriesSubmillimeter wave laser action has been previously in deuterated fluoroform which is optically pumped by a laser. In this paper, accurate heterodyne measurements are reported for the frequencies of 21 of these laser emissions. Nineteen of these lines can be assigned to the degenerate vibrational state. The data were fit with a theoretical expression for the frequencies containing terms up to sixth order in J and K and also containing all important -doubling effects. The quality of the fit was excellent, yielding accurate values for many of the molecular constants of the state. M. S. Tobin and R. D. Felock, Opt. Lett. 5, 430 (1980)
Retinal Image Quality Analysis For Automatic Diabetic Retinopathy Detection
No full textSufficient image quality is a necessary prerequisite for reliable automatic detection systems in several healthcare environments. Specifically for Diabetic Retinopathy (DR) detection, poor quality fund us makes more difficult the analysis of discontinuities that characterize lesions, as well as to generate evidence that can incorrectly diagnose the presence of anomalies. Several methods have been applied for classification of image quality and recently, have shown satisfactory results. However, most of the authors have focused only on the visibility of blood vessels through detection of blurring. Furthermore, these studies frequently only used fund us images from specific cameras which are not validated on datasets obtained from different retinographers. In this paper, we propose an approach to verify essential requirements of retinal image quality for DR screening: field definition and blur detection. The methods were developed and validated on two large, representative datasets collected by different cameras. The first dataset comprises 5,776 images and the second, 920 images. For field definition, the method yields a performance close to optimal with an area under the Receiver Operating Characteristic curve (ROC) of 96.0%. For blur detection, the method achieves an area under the ROC curve of 95.5%. © 2012 IEEE.229236Saaddine, J., Honeycutt, A., Narayan, K., Zhang, X., Klein, R., Boyle, J., Projection of diabetic retinopathy and other major eye diseases among people with diabetes mellitus: United states, 2005-2050 (2008) Arch Ophthalmol., 126 (12), pp. 1740-1747Spurling, G., Askew, D., Hansar, N.H.N., Cooney, A., Jackson, C., Retinal photography for diabetic retinopathy screening in indigenous primary health care: The inala experience (2010) Australian and New Zealand Journal of Public Health, 34, pp. S30-S33Pettitt, D.J., Wollitzer, A.O., Jovanovic, L., He, G., Ipp, E., Decreasing the risk of diabetic retinopathy in a study of case management: The California medi-cal type 2 diabetes study (2005) Diabetes Care, 28 (12), pp. 2819-2822. , http://care.diabetesjournals.org/cgi/reprint/28/12/2819, DOI 10.2337/diacare.28.12.2819Bragge, P., Gruen, R., Chau, M., Forbes, A., Taylor, H., Screening for presence or absence of diabetic retinopathy: A meta-analysis (2011) Arch Ophthalmol., 129 (4), pp. 435-444Maberley, D., Morris, A., Hay, D., Chang, A., Hall, L., Mandava, N., A comparison of digital retinal image quality among photographers with different levels of training using a non-mydriatic fundus camera (2004) Ophthalmic Epidemiology, 11 (3), pp. 191-197. , DOI 10.1080/09286580490514496Philip, S., Fleming, A.D., Goatman, K.A., Fonseca, S., Mcnamee, P., Scotland, G.S., Prescott, G.J., Olson, J.A., The efficacy of automated "disease/no disease" grading for diabetic retinopathy in a systematic screening programme (2007) British Journal of Ophthalmology, 91 (11), pp. 1512-1517. , DOI 10.1136/bjo.2007.119453Jelinek, H., Cree, M., (2010) Automated Image Detection of Retinal Pathology, , Boca Raton: CRC PressDavis, H., Russell, S., Barriga, E., Abramoff, M., Soliz, P., Visionbased, real-time retinal image quality assessment (2009) IEEE CMBS, pp. 1-6Giancardo, L., Meriaudeau, F., Karnowski, T., Chaum, E., Tobin, K., (2010) New Developments in Biomedical Engineering, pp. 201-224. , InTech, ch. Quality Assessment of Retinal Fundus Images using Elliptical Local Vessel DensityLalonde, M., Gagnon, L., Boucher, M.-C., Automatic visual quality assessment in optical fundus images (2001) Vision Interface, pp. 259-264Niemeijer, M., Abramoff, M.D., Van Ginneken, B., Image structure clustering for image quality verification of color retina images in diabetic retinopathy screening (2006) Medical Image Analysis, 10 (6), pp. 888-898. , DOI 10.1016/j.media.2006.09.006, PII S1361841506000739Patton, N., Aslam, T.M., MacGillivray, T., Deary, I.J., Dhillon, B., Eikelboom, R.H., Yogesan, K., Constable, I.J., Retinal image analysis: Concepts, applications and potential (2006) Progress in Retinal and Eye Research, 25 (1), pp. 99-127. , DOI 10.1016/j.preteyeres.2005.07.001, PII S1350946205000406Jelinek, H., Rocha, A., Carvalho, T., Goldenstein, S., Wainer, J., Machine learning and pattern classification in identification of indigenous retinal pathology (2011) IEEE EMBSFacey, K., (2002) Health Tech. Assessment: Organisation of Services for Diabetic Retinopathy Screening, , Health Tech. Board for ScotlandFleming, A.D., Philip, S., Goatman, K.A., Olson, J.A., Sharp, P.F., Automated assessment of diabetic retinal image quality based on clarity and field definition (2006) Investigative Ophthalmology and Visual Science, 47 (3), pp. 1120-1125. , DOI 10.1167/iovs.05-1155Winn, J., Criminisi, A., Minka, T., Object categorization by learned universal visual dictionary (2005) Proceedings of the IEEE International Conference on Computer Vision, 2, pp. 1800-1807. , DOI 10.1109/ICCV.2005.171, 1544935, Proceedings - 10th IEEE International Conference on Computer Vision, ICCV 2005Herbert, J., Pires, R., Padilha, R., Goldenstein, S., Wainer, J., Bossomaier, T., Rocha, A., Data fusion for multi-lesion diabetic retinopathy detection IEEE EMBS, 2012Wang, Z., Bovik, A., Sheikh, H., Simoncelli, E., Image quality assessment: From error visibility to structural similarity (2004) IEEE Trans. on Image Processing, 13 (4), pp. 600-612Pizer Stephen, M., Amburn, E.P., Austin John, D., Cromartie, R., Geselowitz, A., Greer, T., Ter Haar Romeny, B., Zuiderveld, K., Adaptive histogram equalization and its variations (1987) Computer vision, graphics, and image processing, 39 (3), pp. 355-368Chang, C.-C., Lin, C.-J., LIBSVM: A library for support vector machines (2011) ACM Trans. on Intelligent Systems and Tech., 2, pp. 2701-2727Gonzalez, R., Woods, R., (2006) Digital Image Processing, , (3rd Ed.). Upper Saddle River, NJ, USA: Prentice-Hall, IncBay, H., Tuytelaars, T., Van Gool, L., SURF: Speeded up robust features (2006) Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 3951, pp. 404-417. , DOI 10.1007/11744023-32, Computer Vision - ECCV 2006, 9th European Conference on Computer Vision, ProceedingsSivic, J., Zisserman, A., Video google: A text retrieval approach to object matching in videos (2003) IEEE ICCV, pp. 1470-1477Do Valle Jr., E.A., (2008) Local-descriptor Matching for Image Identification Systems, , Ph.D. dissertation, Université de Cergy-Pontoise École Doctorale Sciences et Ingénierie, Cergy-Pontoise, France, JuneRocha, A., Papa, J., Meira, L., How far do we get using machine learning black-boxes? Intl. Journal of Pattern Recognition and Artificial Intelligence, 2012, pp. 1-
The spectral characteristics of wind-farm power output
No full textOver time-scales short enough that wind is relatively steady (.10 minutes), wind-power variability is due to atmospheric turbulence. Power fluctuations at time scales such as these are important for maintaining frequency regulation on the power grid. This thesis presents a holistic, physics-based approach to modeling the spatio-temporal structures of the atmospheric boundary layer, and the ways in which these structures impart themselves in wind-power variability. The following primary findings are presented. Field and laboratory experiments were performed to unravel the structure of the power output fluctuations of horizontal-axis wind turbines based on incoming flow turbulence. The study considers the power data of three wind turbines of rotor sizes 0.12 m, 3.2 m and 96 m, with rated power spanning 6 decades from the order of 100 to 106 W. The 0.12 m wind turbine was tested in a wind tunnel while the 3.2 and 96 m wind turbines were operated in open fields under approximately neutrally-stratified thermal conditions. Incoming flow turbulence was characterized by hotwire and sonic anemometers for the wind tunnel and field setups. While previous works have observed a filtering behavior in wind turbine power output, this exact behavior has not, to date, been properly characterized. Based on the spectral structure of the incoming flow turbulence at hub height, and the mechanical and structural properties of the turbines, a physical basis for the behavior of temporal power fluctuations and their spectral structure is found with potential applications in turbine control and numerical simulations. Consistent results are observed across the geometrical scales of the wind turbines investigated, suggesting no Reynolds number dependence in the tested range. The structure of the turbulence-driven power fluctuations in a wind farm is fundamentally described from basic concepts. A derived tuning-free model, supported with experiments, reveals the underlying spectral content of the power fluctuations of a wind farm. It contains two power-law trends and oscillations in the relatively low- and high-frequency ranges. The former is mostly due to the turbulent interaction between the flow and the turbine properties; whereas the latter is due to the advection between turbine pairs. The spectral wind-farm scale power fluctuations ΦP exhibits a power-law decay proportional to f−5/3−2 in the region corresponding to the turbulence inertial subrange and at relatively large scales, ΦP ∼ f−2. Due to the advection and turbulent diffusion of large-scale structures, a spectral oscillation exists with the product of a sinusoidal behavior and an exponential decay in the frequency domain. Simultaneous power measurements from a model wind farm are presented to investigate the spectral correlation of their power output. Application of a random-sweeping hypothesis to the turbulent flow in a wind farm uncovers distinctive correlations, characterized by advection and turbulent diffusion of coherent motions. This correlation is most evident in the cross-spectra of power output between turbine pairs, which contributes to peaks and troughs in the power spectra of the combined signals. These peaks and troughs occur at frequencies corresponding to the advection time between turbines, and diminish in magnitude at high frequencies due to turbulent decoherence. Experimental results support the results from the random-sweeping hypothesis in predicting characteristic advection and decoherence frequencies. The presence of turbine wakes leads to coherence magnitudes smaller than expected. This difference appears to be a function of the flow approaching the first turbine in a pair. The impact of lateral displacement is unclear from the data. Wind-farm large-eddy simulations are used to uncover the dependence of temporal correlations in the power output of turbine pairs on atmospheric stability. For this purpose, a range of five distinct stability regimes are investigated with the same aligned wind-farm layout used among simulations. The coherence spectrum between turbine pairs in each simulation is compared to theoretical predictions. We found that higher levels of atmospheric instability lead to higher coherence between turbines. This is attributed to higher dominance of atmospheric motions over wakes in highly unstable flows. An empirical model for wake-added turbulence is shown to adequately predict the variation of coherence with ambient turbulence intensity. The modulation of boundary-layer turbulence across scales by passage through the rotor of a model wind turbine is assessed experimentally using synchronous upwind and downwind hotwire anemometers. Consistent with literature, results show that the rotor simultaneously eliminates large-scale motions, and introduces comparatively small-scale flow structures. The synchronous data allows for the distinct quantification of added and dampened turbulence by considering the temporal correlation between upwind and downwind time series. The destroyed turbulence is of a larger characteristic length scale than the created turbulence, but both scales increase with downwind distance. The intensity of the destroyed turbulence does not change substantially with downwind distance, suggesting that the turbine has a much stronger effect on turbulence destruction than simple natural evolution. The cross spectra between upwind and downwind velocity measurements suggest a dispersion relation for different time scales. In the near wake, lower-frequency components appear to be advected at velocity lower than the local wake velocity, and this advection velocity asymptotically approaches the local velocity at high frequency. This trend diminishes in magnitude with downwind distance.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2020-12-01The student, Nicolas Tobin, accepted the attached license on 2018-12-02 at 21:47.The student, Nicolas Tobin, submitted this Dissertation for approval on 2018-12-02 at 21:51.This Dissertation was approved for publication on 2018-12-03 at 16:35.DSpace SAF Submission Ingestion Package generated from Vireo submission #13167 on 2019-02-08 at 11:40:43Made available in DSpace on 2019-02-08T18:43:48Z (GMT). No. of bitstreams: 2
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Advancing Bag-of-Visual-Words Representations for Lesion Classification in Retinal Images
No full textDiabetic Retinopathy (DR) is a complication of diabetes that can lead to blindness if not readily discovered. Automated screening algorithms have the potential to improve identification of patients who need further medical attention. However, the identification of lesions must be accurate to be useful for clinical application. The bag-of-visual-words (BoVW) algorithm employs a maximum-margin classifier in a flexible framework that is able to detect the most common DR-related lesions such as microaneurysms, cotton-wool spots and hard exudates. BoVW allows to bypass the need for pre- and post-processing of the retinographic images, as well as the need of specific ad hoc techniques for identification of each type of lesion. An extensive evaluation of the BoVW model, using three large retinograph datasets (DR1, DR2 and Messidor) with different resolution and collected by different healthcare personnel, was performed. The results demonstrate that the BoVW classification approach can identify different lesions within an image without having to utilize different algorithms for each lesion reducing processing time and providing a more flexible diagnostic system. Our BoVW scheme is based on sparse low-level feature detection with a Speeded-Up Robust Features (SURF) local descriptor, and mid-level features based on semisoft coding with max pooling. The best BoVW representation for retinal image classification was an area under the receiver operating characteristic curve (AUC-ROC) of 97.8% (exudates) and 93.5% (red lesions), applying a cross-dataset validation protocol. To assess the accuracy for detecting cases that require referral within one year, the sparse extraction technique associated with semi-soft coding and max pooling obtained an AUC of 94.2±2.0%, outperforming current methods. Those results indicate that, for retinal image classification tasks in clinical practice, BoVW is equal and, in some instances, surpasses results obtained using dense detection (widely believed to be the best choice in many vision problems) for the low-level descriptors. © 2014 Pires et al.96Sinthanayothin, C., Boyce, J.F., Williamson, T.H., Cook, H.L., Mensah, E., Lal, S., Usher, D., Automated detection of diabetic retinopathy on digital fundus images (2002) Diabetic Medicine, 19 (2), pp. 105-112. , DOI 10.1046/j.1464-5491.2002.00613.xJelinek, H.F., Cree, M.J., Worsley, D., Luckie, A.P., Nixon, P., An automated microaneurysm detector as a tool for identification of diabetic retinopathy in rural optometric practice (2006) Clinical and Experimental Optometry, 89, pp. 299-305Fleming, A.D., Philip, S., Goatman, K.A., Olson, J.A., Sharp, P.F., Automated microaneurysm detection using local contrast normalization and local vessel detection (2006) IEEE Transactions on Medical Imaging, 25 (9), pp. 1223-1232. , DOI 10.1109/TMI.2006.879953, 1677728Niemeijer, M., Van Ginneken, B., Russell, S.R., Suttorp-Schulten, M.S.A., Abramoff, M.D., Automated detection and differentiation of drusen, exudates, and cotton-wool spots in digital color fundus photographs for diabetic retinopathy diagnosis (2007) Investigative Ophthalmology and Visual Science, 48 (5), pp. 2260-2267. , DOI 10.1167/iovs.06-0996Giancardo, L., Mériaudeau, F., Karnowski, T.P., Tobin, K.W., Li, Y., Microaneurysms Detection with the Radon Cliff Operator in Retinal Fundus Images (2010) SPIE Medical Imaging, pp. 76230U-76230U. , International Society for Optics and PhotonicsAntal, B., Hajdu, A., An Ensemble-based System for Microaneurysm Detection and Diabetic Retinopathy Grading (2012) IEEE Transactions on Biomedical Engineering, 59 (6), pp. 1720-1726Lazar, I., Hajdu, A., Retinal Microaneurysm Detection Through Local Rotating Cross-section Profile Analysis (2013) IEEE Transactions on Medical Imaging, 32 (2), pp. 400-407Zhang, B., Wu, X., You, J., Li, Q., Karray, F., Hierarchical Detection of Red Lesions in Retinal Images by Multiscale Correlation Filtering (2009) SPIE Medical Imaging, pp. 72601L-72601L. , International Society for Optics and PhotonicsSánchez, C.I., Hornero, R., Mayo, A., García, M., Mixture model-based clustering and logistic regression for automatic detection of microaneurysms in retinal images (2009) SPIE Medical Imaging, pp. 72601M-72601M. , International Society for Optics and PhotonicsSánchez, C.I., García, M., Mayo, A., López, M.I., Hornero, R., Retinal image analysis based on mixture models to detect hard exudates (2009) Medical Image Analysis, 13 (4), pp. 650-658Giancardo, L., Meriaudeau, F., Karnowski, T.P., Li, Y., Garg, S., Tobin, K.W., Chaum, E., Exudate-based diabetic macular edema detection in fundus images using publicly available datasets (2012) Medical Image Analysis, 16 (1), pp. 216-226Fleming, A.D., Philip, S., Goatman, K.A., Williams, G.J., Olson, J.A., Sharp, P.F., Automated detection of exudates for diabetic retinopathy screening (2007) Physics in Medicine and Biology, 52 (24), pp. 7385-7396. , DOI 10.1088/0031-9155/52/24/012, PII S0031915507570430Sopharak, A., Uyyanonvara, B., Barman, S., Williamson, T.H., Automatic detection of diabetic retinopathy exudates from non-dilated retinal images using mathematical morphology methods (2008) Computerized Medical Imaging and Graphics, 32, p. 8Welfer, D., Scharcanski, J., Marinho, D.R., A coarse-to-fine strategy for automatically detecting exudates in color eye fundus images (2010) Computerized Medical Imaging and Graphics, 34, pp. 228-235Boureau, Y., Bach, F., LeCun, Y., Ponce, J., Learning mid-level features for recognition (2010) IEEE Intl. Conference on Computer Vision and Pattern RecognitionRocha, A., Carvalho, T., Jelinek, H.F., Goldenstein, S., Wainer, J., Points of interest and visual dictionaries for automatic retinal lesion detection (2012) IEEE Transactions on Biomedical Engineering, 59, pp. 2244-2253Jelinek, H.F., Rocha, A., Carvalho, T., Goldenstein, S., Wainer, J., Machine learning and pattern classification in identification of indigenous retinal pathology (2011) Intl. Conference of the IEEE Engineering in Medicine and Biology Society, pp. 5951-5954Jelinek, H.F., Pires, R., Padilha, R., Goldenstein, S., Wainer, J., Data fusion for multi-lesion diabetic retinopathy detection (2012) IEEE Intl. Computer-Based Medical Systems, pp. 1-4Phillips, P.J., Visible manifestations of diabetic retinopathy (2012) Medicine Today, 5, p. 83(2013) Diabetes Programme. Online, , http://www.who.int/diabetes/en, World Health Organization Available: Accessed 6 May 2014Giancardo, L., Meriaudeau, F., Karnowski, T.P., Li, Y., Tobin, K., Microaneurysm detection with radon transform-based classification on retina images (2011) Intl. Conference of the IEEE Engineering in Medicine and Biology Society, pp. 5939-5942Li, Y., Karnowski, T.P., Tobin, K.W., Giancardo, L., Morris, S., A health insurance portability and accountability act-compliant ocular telehealth network for the remote diagnosis and management of diabetic retinopathy (2011) Telemedicine and E-Health, 17, pp. 627-634Cree, M.J., Gamble, E., Cornforth, D.J., Colour normalisation to reduce interpatient and intrapatient variability in microaneurysm detection in colour retinal images (2005) Workshop on Digital Image Computing, pp. 163-168Soares, J.V.B., Leandro, J.J.G., Cesar Jr., R.M., Jelinek, H.F., Cree, M.J., Retinal vessel segmentation using the 2-D Gabor wavelet and supervised classification (2006) IEEE Transactions on Medical Imaging, 25 (9), pp. 1214-1222. , DOI 10.1109/TMI.2006.879967, 1677727Acharya, U.R., Lim, C.M., Ng, E.Y.K., Chee, C., Tamura, T., Computer-based detection of diabetes retinopathy stages using digital fundus images (2009) Journal of Engineering in Medicine, 223, pp. 545-553Gonzalez, R.C., Woods, R.E., (2006) Digital Image Processing, , Upper Saddle River, NJ, USA: PrenticeHall, Inc., 2nd editionNayak, J., Bhat, P.S., Acharya, U.R., Lim, C.M., Kagathi, M., Automated identification of diabetic retinopathy stages using digital fundus images (2008) Journal of Medical Systems, 32, pp. 107-115Jelinek, H.F., Al-Saedi, K., Backlund, L.B., Computer assisted 'top-down' assessment of diabetic retinopathy (2009) World Congress on Medical Physics and Biomedical Engineering, pp. 127-130Yun, W.L., Rajendra, A.U., Venkatesh, Y.V., Chee, C., Min, L.C., Ng, E.Y.K., Identification of different stages of diabetic retinopathy using retinal optical images (2008) Information Sciences, 178 (1), pp. 106-121. , DOI 10.1016/j.ins.2007.07.020, PII S0020025507003635Sivic, J., Zisserman, A., Video Google: A Text Retrieval Approach to Object Matching in Videos (2003) IEEE Intl. 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Conference on Machine Learning, pp. 111-118Cortes, C., Vapnik, V., Support-vector networks (1995) Machine Learning, 20, pp. 273-297Chang, C.C., Lin, C.J., (2001) LIBSVM: A Library for Support Vector Machines, , http://www.csie.ntu.edu.tw/~cjlin/libsvm, Available: Accessed: 6 May 2014Pires, R., Jelinek, H.F., Wainer, J., Rocha, A., Retinal image quality analysis for automatic diabetic retinopathy detection (2012) Intl. Conference on Graphics, Patterns and ImagesBay, H., Ess, A., Tuytelaars, T., Gool, L.V., Speeded-up robust features (SURF) (2008) Computer Vision and Image Understanding, 110, pp. 346-359Lowe, D.G., Distinctive image features from scale-invariant keypoints (2004) Intl Journal of Computer Vision, 60, pp. 91-110Decencière, E., Cazuguel, G., Zhang, X., Thibault, G., Klein, J.C., (2013) TeleOphta: Machine Learning and Image Processing Methods for Teleophthalmology, , Ingénierie et Recherche BiomédicaleBarriga, E.S., Murray, V., Agurto, C., Pattichis, M., Bauman, W., Automatic System for Diabetic Retinopathy Screening Based on AM-FM, Partial Least Squares, and Support Vector Machines (2010) IEEE Intl. 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ETDRS Report Number 10 (1991) Ophthalmology, 98, pp. 786-806. , ETDRS Research GroupMitchell, P., Foran, S., Wong, T.Y., Chua, B., Patel, I., (2008) Guidelines for the Management of Diabetic Retinopathy, , http://www.nhmrc.gov.au/_files_nhmrc/file/publications/synopses/di15.pdf, Available: Accessed: 6 May 2014Chew, E.Y., A simplified diabetic retinopathy scale (2003) Ophthalmology, 110 (9), pp. 1675-1676. , SepAbramoff, M.D., Niemeijer, M., Suttorp-Schulten, M.S.A., Viergever, M.A., Russell, S.R., Van Ginneken, B., Evaluation of a system for automatic detection of diabetic retinopathy from color fundus photographs in a large population of patients with diabetes (2008) Diabetes Care, 31 (2), pp. 193-198. , http://care.diabetesjournals.org/cgi/reprint/31/2/193, DOI 10.2337/dc07-1312Fleming, A.D., Goatman, K.A., Philip, S., Williams, G.J., Prescott, G.J., The role of haemorrhage and exudate detection in automated grading of diabetic retinopathy (2010) British Journal of Ophthalmology, 94 (6), pp. 706-711Abramoff, M.D., Folk, J.C., Han, D.P., Walker, J.D., Williams, D.F., Automated analysis of retinal images for detection of referable diabetic retinopathy (2013) JAMA Ophthalmol, 131 (3), pp. 351-357Ahmed, J., Ward, T.P., Bursell, S.-E., Aiello, L.M., Cavallerano, J.D., Vigersky, R.A., The sensitivity and specificity of nonmydriatic digital stereoscopic retinal imaging in detecting diabetic retinopathy (2006) Diabetes Care, 29 (10), pp. 2205-2209. , http://care.diabetesjournals.org/cgi/reprint/29/10/2205.pdf, DOI 10.2337/dc06-0295Chatfield, K., Lempitsky, V., Vedaldi, A., Zisserman, A., The devil is in the details: An evaluation of recent feature encoding methods (2011) British Machine Vision Conference (BMVC), pp. 1-12Perronnin, F., Akata, Z., Harchaoui, Z., Schmid, C., Towards good practice in large-scale learning for image classification (2012) Intl. Conference on Computer Vision and Pattern Recognition (CVPR), pp. 1-
Rotación de presidentes ejecutivos y directores en Venezuela
No full text(Disponible en idioma inglés únicamente) El propósito de este estudio es propiciar una mejor comprensión de las estructuras y los mecanismos de conducción empresarial fuera de Estados Unidos, observando una economía emergente específica: Venezuela. Primero formulamos un índice de prácticas de conducción empresarial de las compañías inscritas en bolsa, cuyos resultados generales indican que Venezuela exhibe puntajes de gestión empresarial relativamente bajos. Descubrimos, empleando esta muestra limitada, que existe una relación positiva entre este índice de conducción empresarial y sus subcomponentes y mediciones alternativas de valor (coeficiente de Tobin, relación precio/valor contable y pago de dividendos). En este entorno, caracterizado por un mercado financiero subdesarrollado, un sistema jurídico débil, una aplicación precaria de la normativa legal y una elevada concentración de la propiedad, abordamos la cuestión de si el sistema de conducción empresarial funciona en lo absoluto en Venezuela. Nos interesa especialmente estudiar las siguientes dos cuestiones, las cuales constituyen condiciones necesarias para el buen funcionamiento de cualquier sistema de conducción empresarial. En primer lugar, ¿es más probable que presidentes ejecutivos de desempeño deslucido pierdan su cargo que sus colegas de mejor desempeño? En segundo lugar, ¿le corresponde a la junta directiva la tarea de vigilar al presidente ejecutivo o simplemente cumplir una labor de asesoría? A tal fin, recabamos información detallada de 51 compañías venezolanas durante el período de 1984 a 2002. Una vez controladas características relacionadas con el presidente ejecutivo, la junta directiva, la propiedad, las empresas y los períodos abarcados, hallamos que el desempeño financiero precario hace aumentar considerablemente la probabilidad de la rotación de presidentes ejecutivos y directores. Los elementos de juicio empíricos también se corresponden con la idea de que, en Venezuela, los directores desempeñan principalmente una función de asesoría y no de vigilancia de la labor del presidente ejecutivo.
Genome-wide association study identifies a variant in HDAC9 associated with large vessel ischemic stroke
No full textGenetic factors have been implicated in stroke risk, but few replicated associations have been reported. We conducted a genome-wide association study (GWAS) for ischemic stroke and its subtypes in 3,548 affected individuals and 5,972 controls, all of European ancestry. Replication of potential signals was performed in 5,859 affected individuals and 6,281 controls. We replicated previous associations for cardioembolic stroke near PITX2 and ZFHX3 and for large vessel stroke at a 9p21 locus. We identified a new association for large vessel stroke within HDAC9 (encoding histone deacetylase 9) on chromosome 7p21.1 (including further replication in an additional 735 affected individuals and 28,583 controls) (rs11984041; combined P = 1.87 × 10<sup>−11</sup>; odds ratio (OR) = 1.42, 95% confidence interval (CI) = 1.28–1.57). All four loci exhibited evidence for heterogeneity of effect across the stroke subtypes, with some and possibly all affecting risk for only one subtype. This suggests distinct genetic architectures for different stroke subtypes
Characterization of Water Vapor and Carbon Dioxide Spectral Line Parameters in the Two micron Region
No full text1. R. M. Sova, M. E. Thomas, D. Tobin, D. Byrum and L. L. Strow, ""Characterization of Candidate DLAL Lidar Water Vapor and Carbon Dioxide Absorption Lines in the Two Micron Region,'' SPIE Proccedings - Optical Instrumentation for Regional and Global Atmospheric Studies 2365, Nov., 1994.Author Institution: Applied Physics Laboratory, Laurel, Maryland 20723.; University of Maryland Baltimore County, Baltimore Marviand 21228.DIAL lidar for water vapor and temperature remote sensing in the eye safe atmospheric window regions has been receiving much interest. Such systems rely on accurate spectral line characterization. Typically the HITRAN data base on atmospheric spectral lines is used. However, the database is incomplete and not sufficiently accurate. A series of transmittance measurements are made on water vapor and carbon dioxide to verify and improve the HITRAN data base in spectral . A 3 meter base path White cell attached to a BOMEM DA3.02 is used for the transmittance measurements. The White cell is set to a path length of 216 meters for all experiments. Measurements on pure at various pressures, broadened and broadened are collected at room temperature. Also, measurements on pure at various pressures and broadened are collected at room temperature. Data analysis is performed on lines that are accessible by lasers. The measured spectrum is converted to the absorption coefficient and is fitted to a synthetic spectrum to determine the spectral line parameters. This includes the pressure shift, halfwidth and line strength. Water vapor exhibits a strong pressure shift effect. Oxygen broadening is observed to be significantly less than that due to nitrogen. Some lines show good agreement (within a few percent) with the HITRAN database, other lines disagree by more than . Thus care must be exercised in applying the HITRAN data based to DLAL lidar applications. The pressure shift, self-halfwidth and oxygen-broadened halfwidth are not available on the HITRAN database
\u3cem\u3eWedlocked\u3c/em\u3e: The Perils of Marriage Equality – The Author Meets Her Readers
No full textYou write a book and you wonder: “will anyone read it?” This Boston University Law Review Annex Symposium on Wedlocked answers my question. Not only did “someone” read the book, but those “someones” are some of the scholars I admire most, and they took the time and thought to engage Wedlocked’s arguments in this symposium. Thank you to each of the scholars who participated in this symposium, thank you to Professor Linda McClain for inviting their participation, and thank you to James Tobin, the Online Editor for the BU Law Review, for providing a home for this conversation about the virtues and perils of marriage equality
Voucher privatization with investment funds : an institutional analysis
No full textCommon wisdom among post-socialist reformers has beento use voucher investment funds to provide the corporate governance needed to restructure newly privatized enterprises after mass privatization efforts. The idea has been that mass privatization would spread the ownership too wide and make corporate governance difficult. The author examines the likely institutional behavior of voucher funds and the possible effects of their development on a transition economy. Since most policy advice has been in favor of voucher privatization with investment funds, the author can be seen as playing the devil's advocate, but his argument is institutional, not statistical. Policymaking requires insight and foresight into how institutions will tend to function. He concludes that voucher funds will introduce a bias in the economy away from the real industrial sector toward an ersatz"financial sector"that will have little if any positive financial role but will be well-protected by friendly regulators. One long-term consequence of voucher privatization with investment funds, according to this view, is a de facto"industrial policy"of real sector decapitalization in favor of short-term rent-seeking by fund managers through board sinecures and lucrative side deals with portfolio companies and through financial market manipulation and paper entrepreneurship in the"financial sector."Without strong corporate governance from the funds and without stable ownership of their own, many enterprise managers will exploit the post-socialist version of the"separation of ownership and control"to grab what they can in the form of salaries, bonuses, perquisites, and side deals. The most likely results of the strategy of voucher privatization with investment funds may be a two-sided grab fest by fund managers and enterprise managers -- together with the accompanying drift, stagnation, and decapitalization of the privatized industrial sector.Economic Adjustment and Lending,Payment Systems&Infrastructure,International Terrorism&Counterterrorism,Economic Theory&Research,Banks&Banking Reform,International Terrorism&Counterterrorism,Banks&Banking Reform,Economic Adjustment and Lending,Environmental Economics&Policies,Economic Theory&Research
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