Sample records for age optic disc

  1. Effect of optic disc size or age on evaluation of optic disc variables

    Microsoft Academic Search

    Changwon Kee; Hyungjin Koo; Yonghoon Ji; Seonwoo Kim

    1997-01-01

    AIMS\\/BACKGROUNDIt has been reported that the number of optic nerve fibres decrease with age, and the cup\\/disc (C\\/D) ratio increases as the optic disc size increases. Consequently, the normal value of the optic disc variables measured by an optic disc analyser may change according to the optic disc size or age. The effect of individual variations in optic disc size

  2. Age Effect on Retina and Optic Disc Normal Values

    Microsoft Academic Search

    Aljoscha S. Neubauer; Christos Chryssafis; Martin Thiel; Ioannis Tsinopoulos; Christoph Hirneiss; Anselm Kampik

    2005-01-01

    Purpose: To investigate retinal thickness and optic disc parameters by the Retinal Thickness Analyzer (RTA) glaucoma program in older normal subjects and to determine any age effect. Methods: Subjects over 40 years of age without any prior history of eye diseases were recruited. Only subjects completely normal on clinical ophthalmologic examination and on visual field testing by Humphrey Field Analyzer

  3. Imaging of the optic disc and retinal nerve fiber layer: the effects of age, optic disc area, refractive error, and gender

    Microsoft Academic Search

    Christopher Bowd; Linda M. Zangwill; Eytan Z. Blumenthal; Cristiana Vasile; Andreas G. Boehm; Parag A. Gokhale; Kourosh Mohammadi; Payam Amini; Timothy M. Sankary; Robert N. Weinreb

    2002-01-01

    We cross-sectionally examined the relationship between age, optic disc area, refraction, and gender and optic disc topography and retinal nerve fiber layer (RNFL) measurements, using optical imaging techniques. One eye from each of 155 Caucasian subjects (age range 23.0-80.8 y) without ocular pathology was included. Measurements were obtained by using the Heidelberg Retina Tomography (HRT), the GDx Nerve Fiber Analyzer,

  4. Optic disc shape in glaucoma

    Microsoft Academic Search

    Jost B. Jonas; Konstantinos I. Papastathopoulos

    1996-01-01

    • Background: This study was performed to evaluate the shape of the optic disc in glaucoma. • Methods: We examined morphometrically\\u000a color stereo optic disc photographs of patients with primary open-angle glaucoma (n=804), secondary open-angle glaucoma (n=130), normal-pressure glaucoma (n=75), and high myopia combined with open-angle glaucoma (n=33), visually normal subjects (n=421), and nonglaucomatous subjects with high myopia (n=36). The

  5. The Chemistry of Optical Discs

    NASA Astrophysics Data System (ADS)

    Birkett, David

    2002-09-01

    The rapid rise of optical data storage is clearly a triumph for physics, engineering, and information technology, but a great deal of chemical innovation has also been necessary to make this revolution possible. This article explores the polymer and material science that has gone into the development of CDs and DVDs in prerecorded, write-once, and erasable formats, and magneto-optical (MO) discs and the related minidiscs. Prerecorded CDs and DVDs, where the data is stored as a series of pits physically stamped into a plastic disc, have required new optically-clear grades of the base plastic, technically sophisticated UV acrylic adhesives and lacquers, and a detailed understanding of the surface energy and the optical and electrochemical properties of metals in very thin layers. The different recordable formats have all needed new chemistry for the recording layer: cyanine and phthalocyanine dyes for write-once discs, low-melting alloys with a glassy state for erasable discs, and magnetic materials with closely defined Curie temperatures and hysteresis for MO and minidiscs. Even newer optical storage formats, including multilayer fluorescent or holographic discs are under development, and these are already demanding critical inputs by chemists.

  6. Location of Optical Disc in Retinal Image

    Microsoft Academic Search

    D. Santhi; D. Manimegalai

    2007-01-01

    This paper proposes a method to automatically locate the optic disc in a retinal image. Our method of finding the optic disc is based on the properties of the optic disc using simple image processing algorithms which include multilevel thresholding, Morphological process detection of object roundness and circle detection by circle fitting method. The proposed method is able to recognize

  7. Locating the Optic Disc in Retinal Images

    Microsoft Academic Search

    Mira Park; Jesse S. Jin; Suhuai Luo

    2006-01-01

    We present a method to automatically outline the optic disc in a retinal image. Our method for finding the optic disc is based on the properties of the optic disc using simple image processing algorithms which include thresholding, detection of object roundness and circle detection by Hough transformation. Our method is able to recognize the retinal images with general properties

  8. Optical Disc Applications in Libraries.

    ERIC Educational Resources Information Center

    Andre, Pamela Q. J.

    1989-01-01

    Discusses a variety of library applications of optical disc storage technology, including CD-ROM, digital videodisc, and WORM. Research and development projects at the Library of Congress, National Library of Medicine, and National Agricultural Library are described, products offered by library networks are reviewed, and activities in academic and…

  9. Optical Discs: New Storage Media for Education.

    ERIC Educational Resources Information Center

    Helgerson, Linda W.

    1987-01-01

    Discusses three new advances in the use of optical disc technology in education. Describes the storage formats and capabilities of the videodisc, the compact disc, and the optical write-once disc. Contrasts the three technologies in terms of their production requirements, the hardware involved, and some projected applications in education. (TW)

  10. Computer animation via optical video disc

    E-print Network

    Bender, Walter

    1981-01-01

    This paper explores the notion of marrying two technologies: raster-scan computer animation and optical video discs. Animated sequences, generated at non real-time rates, then transfered to video disc, can be recalled under ...

  11. The Optical Disc Roundup.

    ERIC Educational Resources Information Center

    Galbreath, Jeremy

    1993-01-01

    Provides an update on optical disk technology as a means of digital media storage and explains why it may become a standard storage technology for telemedia technology. Topics discussed include read-only formats; write-once formats, including WORM and CD-WORM; rewritable formats; videodiscs; and future possibilities. (LRW)

  12. OPTIC DISC CHARACTERISTICS ASSESSED BY EVALUATION OF CLINICAL OPTIC DISC PHOTOGRAPHS IN GLAUCOMA PATIENTS

    Microsoft Academic Search

    Ikuyo Ohguro; Hiroshi Ohguro; Hiroshi Ohkuro; Mitsuru Nakazawa

    Purpose: To describe optic disc characteristics assessed by evaluation of clinical optic disc photographs and to utilize these findings to differentiate glaucoma patients and normal subjects. Patients and Methods: A total of 329 eyes of 329 glaucoma patients and 220 eyes of 220 normal subjects were included The disc diameter to disc-to-macula distance ratio (DD\\/DM ratio), cup-to-disc diameter ratio (C\\/D

  13. The automatic detection of the optic disc location in retinal images using optic disc location regression

    Microsoft Academic Search

    M. D. Abramoff; M. Niemeijer

    2006-01-01

    The automatic detection of the position of the optic disc is an important step in the automatic analysis of retinal images. A method to detect the approximate position of the optic disc using kNN regression is presented. The method starts by building a regression model of the optic disc position. Using a prior vessel segmentation all vessel pixels are searched

  14. Optic Disc Segmentation in Retinal Images

    Microsoft Academic Search

    Radim Chrástek; Matthias Wolf; Klaus Donath; Georg Michelson; Heinrich Niemann

    2002-01-01

    Abstract: Retinal images give unique diagnostic information not onlyabout eye disease but about other organs as well [1]. To give the physiciansa tool for objective quantitative assessment of the retina, automatedmethods have been developed. In this paper an automated methodfor the optic disc segmentation is presented. The method consists of 4steps: localization of the optic disc, nonlinearltering, Canny edge detectorand

  15. Optic disc morphology--rethinking shape.

    PubMed

    Sanfilippo, Paul G; Cardini, Andrea; Hewitt, Alex W; Crowston, Jonathan G; Mackey, David A

    2009-07-01

    Morphometrics, a branch of morphology, represents the study of size and shape components of biological form and their variation in the population. Assessment of optic disc morphology is essential in the diagnosis and management of many ophthalmic disorders. Much work has been performed to characterize size-related parameters of the optic disc; however, limited information is available on shape variation in the general population. In contrast to optic disc or cup sizes, which are conceptually meaningful variables with a defined unit of measurement, there are few metric constructs by which to quantify, visualize and interpret variation in optic disc or cup shape. This has significance in ophthalmic diseases with a genetic basis as recent evidence has suggested that optic disc shape may be heritable. Conventional optic disc shape measures of 'ovality' and 'form-factor' reduce a complex structure to a single number and eliminate information of potential diagnostic relevance from further analyses. The recent advent of 'geometric morphometrics', a branch of statistics that incorporates tools from geometry, biometrics and computer graphics in the quantitative analysis of biological forms, has enabled spatial relationships in shape data to be retained during analysis. The analytical methods employed in geometric morphometrics can be separated into two distinct groups: landmark-based (e.g. Procrustes analysis, thin-plate splines) and boundary outline techniques (e.g. Fourier analysis). In this review, we summarize current approaches to the study of optic disc morphology, discuss the underlying theory of geometric morphometrics within the context of analytical techniques and then explore the contemporary relevance of the subject matter to several biological fields. Finally we illustrate the potential application of geometric morphometrics to the specific problem of optic disc shape and glaucoma assessment. PMID:19520180

  16. Optic disc morphology in juvenile primary open-angle glaucoma

    Microsoft Academic Search

    Jost B. Jonas; Anselm Griindler

    1996-01-01

    • Background: The aim of the study was to evaluate whether, in primary open-angle glaucoma (POAG), patients younger than 40 years differ in optic disc morphology from patients older than 40 years. • Methods: Out of a total group of 419 patients with POAG, we formed and compared two subgroups, one consisting of 37 patients with an age of less

  17. Optic disc anomalies and frontonasal dysplasia

    PubMed Central

    Hodgkins, P; Lees, M; Lawson, J; Reardon, W; Leitch, J; Thorogood, P; Winter, R; Taylor, D

    1998-01-01

    AIMS—To document the optic disc abnormalities in patients with frontonasal dysplasia in association with basal encephalocele.?METHODS—Names and hospital numbers of patients with midline clefts were obtained from the ophthalmology and genetics database. Six patients were identified who had the following common findings: midline facial cleft with midline cleft lip and palate; hypertelorism; absent corpus callosum; basal (sphenoethmoidal) encephalocele; and pituitary deficiency (five out of six cases). Ophthalmic examination was performed with fundal photography where possible.?RESULTS—Two patients had unilateral and one a bilateral peripapillary staphyloma. Two patients had bilateral optic disc hypoplasia and one appeared to have a peripapillary staphyloma in one eye and a morning glory disc in the other.?CONCLUSION—Optic disc abnormalities were found in all patients with this constellation of clinical findings. This association appears to represent a distinct subgroup within the spectrum of frontonasal dysplasia. The presence of midline facial anomalies and any dysplastic disc should alert the physician as to the presence of an encephalocele.?? Keywords: frontonasal dysplasia; optic disc; encephalocele PMID:9602627

  18. The automatic detection of the optic disc location in retinal images using optic disc location regression.

    PubMed

    Abràmoff, Michael D; Niemeijer, Meindert

    2006-01-01

    The automatic detection of the position of the optic disc is an important step in the automatic analysis of retinal images. A method to detect the approximate position of the optic disc using kNN regression is presented. The method starts by building a regression model of the optic disc position. Using a prior vessel segmentation all vessel pixels are searched for those which are inside the optic disc according to the regression model. The regression output is blurred to handle noise. The point which is closest to the middle of the optic disc is chosen. The method was tested on 1000 screening images and was able to find the correct position in 99.9% of all cases. PMID:17947087

  19. Electron beam recording of optical disc

    Microsoft Academic Search

    Giles Cartwright; Gerald Reynolds; Chris Baylis; Adrian Pearce; Colin Dix; Nick Ogilvie

    2002-01-01

    The Nimbus Technology & Engineering e?Beam Mastering System was developed to gain a large improvement in optical disc and structured hard disc recording capacity, significantly more than is possible from deep UV and SIL mastering. The current electron beam recorder is essentially a production machine capable of making full-length exposures at capacities of up to 50GB with a simple low-cost

  20. Correlation between optic disc atrophy and aetiology: anterior ischaemic optic neuropathy vs optic neuritis

    Microsoft Academic Search

    E Z Rath; U Rehany; S Linn; S Rumelt

    2003-01-01

    Background The morphologic features of swollen disc in the acute stage of optic neuritis and anterior ischaemic optic neuropathy (AION) have been extensively investigated in contrast to the morphologic features of optic disc atrophy after these events.Objective: A prospective study to evaluate the morphologic features of optic disc atrophy 6 months or more after optic neuritis and nonarteritic AION.Patients and

  1. Automatic Optic Disc Boundary Extraction from Color Fundus Images

    Microsoft Academic Search

    Thresiamma Devasia; Paulose Jacob; Tessamma Thomas

    2014-01-01

    Efficient optic disc segmentation is an important task in automated retinal screening. For the same reason optic disc detection is fundamental for medical references and is important for the retinal image analysis application. The most difficult problem of optic disc extraction is to locate the region of interest. More over it is a time consuming task. This paper tries to

  2. Optic disc morphology in pigmentary glaucoma

    Microsoft Academic Search

    Jost B Jonas; Albert Dichtl; Wido M Budde; Peter Lang

    1998-01-01

    AIMTo evaluate the morphology of the optic nerve head in eyes with pigmentary glaucoma.METHODSColour stereo optic disc photographs of 62 patients with pigmentary glaucoma and 566 patients with primary open angle glaucoma were morphometrically evaluated. By prestudy selection, mean visual field defect and neuroretinal rim area were not significantly different between the two groups (p=0.89 and p=0.45).RESULTSThe pigmentary glaucoma group

  3. Robust Optic Disc Location via Combination of Weak Detectors

    Microsoft Academic Search

    Adria Perez-Rovira; Emanuele Trucco

    2008-01-01

    This paper presents a new robust approach for the automatic location of the optic disc. We detect several candi- dates independently for optic disc, macula and the main blood vessels (arcades). Candidates are sorted by reliability. The space of all possible triplets disc-macula-arcades is searched using a- priori anatomical knowledge, selecting the triplet formed by the most reliable candidates satisfying

  4. Automatic optic disc segmentation with peripapillary atrophy elimination

    Microsoft Academic Search

    Jun Cheng; Jiang Liu; Damon Wing Kee Wong; Fengshou Yin; Carol Cheung; Mani Baskaran; Tin Aung; Tien Yin Wong

    2011-01-01

    Optic disc segmentation from retinal fundus image is a fundamental but important step for automatic glaucoma diagnosis. In this paper, an optic disc segmentation method is proposed based on peripapillary atrophy elimination. The elimination is done through edge filtering, constraint elliptical Hough transform and peripapillary atrophy detection. With the elimination, edges that are likely from non-disc structures especially peripapillary atrophy

  5. Detection of optic disc center and macula using spatial information of optic cup

    Microsoft Academic Search

    Azin Poshtyar; Jamshid Shanbehzadeh; Zeinab Ghassabi

    2011-01-01

    The Optic Disc is a circular and bright region in retinal fundus images. Macula is a yellow portion of the posterior retina, lateral to the optic nerve, with a depression in its center. This paper presents an approach to detect optic disc center and macula using spatial information of optic cup. Optic Cup is a region in optic disc with

  6. Optic disc size and optic nerve damage in normal pressure glaucoma

    Microsoft Academic Search

    J B Jonas; J Stürmer; K I Papastathopoulos; F Meier-Gibbons; A Dichtl

    1995-01-01

    BACKGROUND--Recent reports indicate that eyes with normal pressure glaucoma have larger optic discs than eyes with primary open angle glaucoma or normal eyes. This study was performed to find whether, in normal pressure glaucoma, a large disc is associated with more optic nerve damage than a small disc. METHODS--Colour optic disc photographs of 74 patients with normal pressure glaucoma were

  7. Agreement in assessing optic discs with a digital stereoscopic optic disc camera (Discam) and Heidelberg retina tomograph

    Microsoft Academic Search

    Velota C T Sung; Anna Bhan; Stephen A Vernon

    2002-01-01

    Aims: To assess the intraobserver agreement, interobserver agreement, and the agreement between a digital stereo optic disc camera (Discam) and Heidelberg retina tomograph (HRT) in measuring area cup-disc ratio (ACDR) and radial cup-disc ratio (RCDR) by two observers.Methods: The optic discs of 78 eyes of 39 people (17 cases of primary open angle glaucoma, eight normal tension glaucoma, two ocular

  8. Optic nerve head drusen associated with abnormally small optic discs

    Microsoft Academic Search

    Jost B. Jonas; Gabriele Ch. Gusek; Irene Guggenmoos-Holzmann; Gottfried O. H. Naumann

    1987-01-01

    Using Littmann's method for correcting the magnification of central fundus photographs we evaluated the absolute optic disc size in 26 eyes with visible optic nerve head drusen. The optic nerve head area in these eyes (1.79 + -0.50mm2) was significantly smaller (p<0.001) than normal standard values previously determined (2.89 + -0.76 mm2). The drusen were most commonly located and most

  9. Reappraisal of the ratio of disc to macula\\/disc diameter in optic nerve hypoplasia

    Microsoft Academic Search

    S M Zeki; J Dudgeon; G N Dutton

    1991-01-01

    The ratio of disc to macula\\/disc diameter is characteristically increased in eyes with optic nerve hypoplasia. We present the largest reported series of patients with a definitive diagnosis of optic nerve hypoplasia for whom this ratio has been determined. All measurements were made by an independent masked observer. Our results are in accordance with previous reports. A ratio of 2.94

  10. Interactive Optical Disc Systems: Part 1: Analog Storage.

    ERIC Educational Resources Information Center

    Hessler, David W.

    1984-01-01

    Details distinction between digital and analog data, advantages of analog storage, and optical disc use to store analog data. Configuration and potential of three levels of laser disc systems are explained. Selection of display devices for use with laser disc systems and accessing audio data are addressed. (Continued in next issue.) (EJS)

  11. Simple and Robust Optic Disc Localisation Using Colour Decorrelated Templates

    Microsoft Academic Search

    Tomi Kauppi; Heikki Kälviäinen

    2008-01-01

    Automatic analysis of digital fundus images, where optic disc extraction is an essential part, is an active research topic\\u000a in retinal image analysis. A simple, fast and robust optic disc localisation method using colour decorrelated templates is\\u000a proposed which results an accurate location of the optic disc in colour fundus images. In the training stage, PCA is performed\\u000a on the

  12. Clinical measurement and categorization of optic disc in glaucoma patients

    PubMed Central

    Rao, Harsha B L; Sekhar, G C; Babu, Ganesh J; Parikh, Rajul S

    2009-01-01

    Background: Assessment of optic disc size is an important component of optic nerve head examination. Agreement between different methods of disc size measurements is not very good. Purpose: To assess the agreement between the disc size assessed by Heidelberg retina tomograph (HRT) and stereobiomicroscopy with a 90 diopter (D) lens. To report the clinical (measured by biomicroscopy) disc diameters of small, average and large optic discs categorized by HRT disc areas. Setting and Design: Observational study of subjects examined in the glaucoma clinic of a tertiary eye institute. Materials and Methods: Seventy-five eyes of 75 glaucoma subjects were studied. Disc diameter was measured using stereobiomicroscopy and HRT. The agreement between the two sets of measurements was assessed by intraclass correlation coefficient (ICC). Discs were classified into small (<1.6 mm2), average (1.6-2.6 mm2) and large (>2.6 mm2) depending on cutoffs provided by the manufacturers of HRT. The means (95% CI) of the corresponding vertical disc diameter in these groups were assessed. Statistical Analysis: ICC, Bland and Altman plots. Results: ICC for measurements of clinical and HRT horizontal disc diameter was 0.518 and for vertical disc diameter measurement was 0.487. The mean difference between the clinical and HRT measurements as analyzed by the Bland and Altman plot was 0.17 (95% CI, 0.13- 0.47) for horizontal and 0.22 (95% CI, 0.11- 0.54) for vertical disc diameter. Of the 75 eyes, 3 eyes had small discs, 54 average and 18 large discs. The mean clinical vertical disc diameter for small discs was 1.55 mm (95% CI, 1.2-1.7), for average discs was 1.91 mm (95% CI, 1.87-1.96) and for large discs was 2.15 mm (95% CI, 2.03–2.27). Conclusion: The agreement between clinical and HRT disc diameter measurements is moderate. Disc diameter measurement on stereobiomicroscopy can be used to categorize discs into small, average and large discs. PMID:19700874

  13. Optic disc oedema: a diagnostic dilemma

    PubMed Central

    Agarwal, Prakash Chand; Gupta, Saroj; Thakur, Arunendu; Biswas, Rakesh

    2011-01-01

    The authors describe a patient who presented with bilateral disc oedema and left eye visual loss. The patient was evaluated for intracranial space occupying lesion, however, a CT and cerebrospinal tap was normal. No definitive diagnosis could be established and patient developed left eye optic atrophy which was thought to be post papilloedema atrophy. Six months later, the patient had similar visual loss in right eye and he was diagnosed as anterior ischemic optic atrophy (AION) by the ophthalmologist. The inferior altitudinal visual field loss, delayed visual evoked response and clinical picture supported the diagnosis. The patient was diagnosed with hypertension and type 2 diabetes and managed accordingly. All the symptoms, clinical findings, investigations supported the diagnosis of AION which occurred in left eye followed by right eye 6 months later. Appropriate treatment was started and patient regained vision in right eye. PMID:22679155

  14. Localization of optic disc in fluorescein angiography images

    Microsoft Academic Search

    Rubiel Vargas Canas; Panos Liatsis

    2011-01-01

    Optic disc detection is an important task in retinal imaging due to its significance in both clinical and image understanding aspects. In the clinical setting, the optic disc represents the entrance and exit sites of vascular and nervous structures, and its size and shape could be used in diagnostics and treatment of diseases, such as glaucoma. In terms of automated

  15. An improved gradient vector flow algorithm for optic disc segmentation

    Microsoft Academic Search

    Huiyu Zhou; Gerald Schaefer; Tangwei Liu; Faquan Lin

    2010-01-01

    The optic disc provides important cues for accurate diagnosis of various retinopathic diseases. Accurate segmentation of the optic disc is therefore an important step in the analysis of retinal images. Gradient vector flow (GVF) based segmentation algorithms have been used successfully on a variety of medical imagery, however, due to the compromise of internal and external energy forces, it can

  16. Automated Detection of Optic Disc Location in Retinal Images

    Microsoft Academic Search

    Carmen Alina Lupascu; Domenico Tegolo; Luigi Di Rosa

    2008-01-01

    This contribution presents an automated method to locate the optic disc in color fundus images. The method uses texture descriptors and a regression based method in order to determine the best circle that fits the optic disc. The best circle is chosen from a set of circles determined with an innovative method, not using the Hough transform as past approaches.

  17. Pharmacological enhancement of disc diffusion and differentiation of healthy, ageing and degenerated discs

    Microsoft Academic Search

    S. Rajasekaran; K. Venkatadass; J. Naresh Babu; K. Ganesh; Ajoy P. Shetty

    2008-01-01

    Degenerative disc disease (DDD) is still a poorly understood phenomenon because of the lack of availability of precise definition\\u000a of healthy, ageing and degenerated discs. Decreased nutrition is the final common pathway for DDD and the status of the endplate\\u000a (EP) plays a crucial role in controlling the extent of diffusion, which is the only source of nutrition. The vascular

  18. Optic Disc Change during Childhood Myopic Shift: Comparison between Eyes with an Enlarged Cup-To-Disc Ratio and Childhood Glaucoma Compared to Normal Myopic Eyes

    PubMed Central

    Park, Hae-Young Lopilly; Kim, Sung Eum; Park, Chan Kee

    2015-01-01

    Background Progressive disc tilting and the development or enlargement of peripapillary atrophy (PPA) are observed during a myopic shift in children. This could be related to the changes around the optic nerve head during eyeball elongation. If the biomechanical properties at or around the optic nerve head are changed after exposure to elevated intraocular pressure (IOP) in glaucoma eyes, different response of the disc tilting and PPA changes could take place during eyeball elongation by myopic shift. On the basis of this background, the aim of this study was to compare the morphological changes in the optic disc induced by a myopic shift during childhood between normal control eyes, eyes from disc suspects with an enlarged cup-to-disc ratio (CDR), and eyes with childhood glaucoma. Methods Total of 82 eyes from 82 subjects younger than 14 years of age were included in the study. Serial disc photographs were classified into one of two groups: eyes with an optic nerve head (ONH) or peripapillary atrophy (PPA) change or without an ONH/PPA change. Using ImageJ software, the outlines of the optic disc and PPA were plotted, and the vertical disc diameter (VDD), horizontal disc diameter (HDD), and maximum PPA width (PPW) were measured. The changes in the ratios of these parameters and the relationships between the degree of myopic shift or the ONH/PPA change were analyzed. Results Twenty-five eyes with normal optic disc appearance, 36 eyes with enlarged cup-to-disc ratio, and 21 eyes of glaucoma patients were analyzed. The initial intraocular pressure (IOP) at diagnosis was significantly different among the groups (P<0.001). The degree of myopic shift during follow-up period was not significantly different among the groups (P=0.612). However, the changes in the HDD/VDD and PPW/VDD ratios were significantly greater in the disc suspect group and significantly smaller in the glaucoma group. Among the 42 eyes with an ONH/PPA change, 16 (38.1%) were from the normal control group, 24 (57.1%) were from the disc suspect group, and 2 (4.8%) were from the glaucoma group (P < 0.001). Conclusions and Relevance The optic disc change during childhood myopic shift was different in eyes with various conditions. Eyes of childhood glaucoma showed less change in the disc morphology during myopic shift compared to eyes with normal disc or enlarged cup-to-disc ratio. PMID:26147983

  19. Three dimensional optic disc visualisation from stereo images via dual registration and ocular media optical correction

    Microsoft Academic Search

    J Xu; O Chutatape; C Zheng; P C T Kuan

    2006-01-01

    Background\\/aims: The three dimensional (3-D) visualisation of the optic disc in true colour will give essential meaning in clinical application. It is not only useful for clinicians in the evaluation of the condition of the optic disc, but it also simplifies the pathological diagnosis and disease progression monitoring. This paper describes a complete 3-D optic disc reconstruction method from a

  20. Ranking of Optic Disc Variables for Detection of Glaucomatous Optic Nerve Damage

    Microsoft Academic Search

    Jost B. Jonas; Antonio Bergua; Paul Schmitz-Valckenberg; Konstantinos I. Papastathopoulos; Wido M. Budde

    2000-01-01

    PURPOSE. To describe optic disc variables assessed by evaluation of clinical optic disc photographs and to compare sensitivity and specificity of these optic disc parameters in identifying patients with ocular hypertension who have nerve fiber layer defects and normal visual fields and patients with visual field defects. METHODS. The study included 500 normal subjects, 132 patients with ocular hypertension with

  1. Multilayer optical disc system using homodyne detection

    NASA Astrophysics Data System (ADS)

    Kurokawa, Takahiro; Ide, Tatsuro; Tanaka, Yukinobu; Watanabe, Koichi

    2014-09-01

    A write/read system using high-productivity multilayer optical discs was developed. The recording medium used in the system consists of planar recording layers and a separated guide layer, and is fabricated by web coating and lamination process. The recording layers in the medium are made of one-photon-absorption material, on which data can be recorded with a normal laser diode. The developed system is capable of focusing and tracking on the medium and amplifying readout signals by using phase-diversity homodyne detection. A highly layer-selective focusing method using homodyne detection was also proposed. This method obtains stable focus-error signals with clearly separated S-shaped curves even when layer spacing is quite narrow, causing large interlayer crosstalk. Writing on the medium and reading with the signal amplification effect of homodyne detection was demonstrated. In addition, the effectiveness of the method was experimentally evaluated.

  2. Product and process for manufacturing an optical disc master

    SciTech Connect

    Dobbin, R.B.; Loeppky, D.G.; Norton, J.R.; Del Mar, B.E.

    1994-01-11

    The invention discloses a simplified four step process for making an optical disc master or alternatively a WORM disc by first making or obtaining a transparent polymer disc with a tracking groove of desired geometry molded therein, then spin coating an optically active lamina on the grooved side of the disc, then recording data on said polymer disc with groove controlled and tracked laser means by ablating active lamina, forming pits, the shape of which is determined by the groove geometry and finally depositing a conductive and reflective lamina over the pitted active lamina. To change the OD master to an OD WORM, a protective cover is added to the electrically conductive and optically reflective lamina. 12 figs.

  3. Screening of Diabetic Retinopathy - Automatic Segmentation of Optic Disc in Colour Fundus Images

    Microsoft Academic Search

    S. S. Lee; M. Rajeswari; D. Ramachandram; B. Shaharuddin

    2006-01-01

    In this paper, a novel approach to automatically segment the optic disc contour using the center point of an optic disc candidate is proposed. The optic disc segmentation algorithm consists of 2 stages. The first stage involves the removal of blood vessels that obscure the optic disc. The blood vessel structures are detected using morphological operations. These detected structures are

  4. Automatic optic disc segmentation with peripapillary atrophy elimination.

    PubMed

    Cheng, Jun; Liu, Jiang; Wong, Damon Wing Kee; Yin, Fengshou; Cheung, Carol; Baskaran, Mani; Aung, Tin; Wong, Tien Yin

    2011-01-01

    Optic disc segmentation from retinal fundus image is a fundamental but important step for automatic glaucoma diagnosis. In this paper, an optic disc segmentation method is proposed based on peripapillary atrophy elimination. The elimination is done through edge filtering, constraint elliptical Hough transform and peripapillary atrophy detection. With the elimination, edges that are likely from non-disc structures especially peripapillary atrophy are excluded to make the segmentation more accurate. The proposed method has been tested in a database of 650 images with disc boundaries marked by trained professionals manually. The experimental results by the proposed method show average m(1), m(2) and m(VD) of 10.0%, 7.4% and 4.9% respectively. It can be used to compute cup to disc ratio as well as other features for application in automatic glaucoma diagnosis systems. PMID:22255761

  5. Optic disc changes following trabeculectomy: longitudinal and localisation of change

    Microsoft Academic Search

    Aachal Kotecha; Dilani Siriwardena; Frederick W Fitzke; Roger A Hitchings; Peng T Khaw

    2001-01-01

    AIMSTo determine whether there were any changes in the optic disc at 2 years after trabeculectomy. To determine the factors that most influenced change and whether change was localised to any region of the optic disc.METHODS95 patients undergoing routine trabeculectomy as part of the ongoing Moorfields\\/MRC 5-fluorouracil trial were recruited into the study. Eyes were imaged preoperatively (4 (SD 3)

  6. A Genome-Wide Association Study of Optic Disc Parameters

    Microsoft Academic Search

    Wishal D. Ramdas; Leonieke M. E. van Koolwijk; M. Kamran Ikram; Nomdo M. Jansonius; Arthur A. B. Bergen; Aaron Isaacs; Najaf Amin; Yurii S. Aulchenko; Roger C. W. Wolfs; Albert Hofman; Fernando Rivadeneira; Ben A. Oostra; Andre G. Uitterlinden; Pirro Hysi; Christopher J. Hammond; Hans G. Lemij; Johannes R. Vingerling; Caroline C. W. Klaver; Cornelia M. van Duijn

    2010-01-01

    The optic nerve head is involved in many ophthalmic disorders, including common diseases such as myopia and open-angle glaucoma. Two of the most important parameters are the size of the optic disc area and the vertical cup-disc ratio (VCDR). Both are highly heritable but genetically largely undetermined. We performed a meta-analysis of genome-wide association (GWA) data to identify genetic variants

  7. Measurement of a novel optic disc topographic parameter, ”spikiness”, in glaucoma

    Microsoft Academic Search

    Justin Morgan-Davies; Anthony J. King; Peter Aspinall; Colm J. O’Brien

    2000-01-01

    Background: Structural changes in the lamina cribrosa have been implicated in the pathogenesis of glaucomatous optic atrophy, but not\\u000a observed. This paper presents a novel parameter of topographic variability within the optic disc, termed ”spikiness”, which\\u000a may reflect glaucoma-related changes in the lamina. Methods: Four age-matched groups of normal patients (n=12, mean age 64.8 years) and patients with ocular hypertension

  8. Measuring Hemoglobin Levels in the Optic Disc of Parkinson's Disease Patients Using New Colorimetric Analysis Software

    PubMed Central

    Bambo, Maria Pilar; Garcia-Martin, Elena; Satue, Maria; Perez-Olivan, Susana; Alayon, Silvia; Gonzalez-Hernandez, Marta; Polo, Vicente; Larrosa, Jose Manuel; Gonzalez-De la Rosa, Manuel

    2014-01-01

    Objective. To evaluate a new method of measuring hemoglobin (Hb) levels and quantifying the color changes in the optic nerve head of Parkinson's disease (PD) patients. We also compared differences in retinal nerve fiber layer (RNFL) thicknesses obtained using spectral domain optical coherence tomography (OCT) device between PD group and healthy group. Methods. One hundred and fifty-five PD patients and 91 sex- and age-matched healthy subjects were included in this cross-sectional study. OCT examinations and one photograph of the optic disc were performed. The Laguna ONhE (“optic nerve hemoglobin”; Insoft SL, Tenerife, Spain) software was used to analyze the Hb level on the acquired optic disc photographs. Results. PD patients exhibited significantly reduced mean optic disc Hb percentages (57.56% in PD, 67.63% in healthy subjects; P = 0.001) as well as reduced Hb in almost all analyzed sectors, with the largest differences detected in the inferior and nasal sectors. RNFL parameters were significantly reduced in PD patients compared with healthy subjects, especially in the inferior quadrant. Conclusions. Measurements of optic disc Hb levels obtained with the Laguna ONhE software had good ability to detect optic nerve color changes (more papillary paleness and consequently this could suggest optic atrophy and axonal loss) in PD patients. PMID:25587487

  9. An unusual case of congenital unilateral Coats's disease associated with morning glory optic disc anomaly.

    PubMed Central

    Kremer, I; Cohen, S; Izhak, R B; Ben-Sira, I

    1985-01-01

    We present the case of a 13-year-old girl with a right congenital esotropia who at the age of 6 months presented an anomaly of the optic disc and retinal vessels in the same eye. In the following year she developed Coats's disease, rubeosis iridis, and neovascular glaucoma that led to enucleation. Pathological examination confirmed the clinical diagnosis. Images PMID:3965027

  10. Plaque Radiotherapy for Juxtapapillary Choroidal Melanoma Overhanging the Optic Disc in 141 Consecutive Patients

    Microsoft Academic Search

    Mandeep S. Sagoo; Carol L. Shields; Arman Mashayekhi; Jorge Freire; Jacqueline Emrich; Jay Reiff; Lydia Komarnicky; Jerry A. Shields

    2008-01-01

    Objective: To evaluate tumor control with plaque ra- diotherapy for juxtapapillary choroidal melanoma that overhangs the optic disc. Methods: Retrospective medical record review of 141 consecutivepatientswithdataoncomplicationsoftreat- ment, final visual acuity, visual loss, enucleation, tumor recurrence, metastasis, and death. Results: The median patient age was 61 years. Present- ing symptoms included reduced visual acuity in 72 eyes (51%), photopsia in 14

  11. High-resolution optical coherence tomography demonstration of membranes spanning optic disc pits and colobomas

    Microsoft Academic Search

    E Doyle; D Trivedi; P Good; R A Scott; G R Kirkby

    2009-01-01

    Objectives:To demonstrate the features of optic disc pits and colobomas revealed by high-resolution optical coherence tomography (OCT) and their association with the development of maculopathy.Methods:Subjects with disc pits or colobomas and no other ocular history underwent full ophthalmic examinations including logMAR visual acuity and contrast sensitivity. Fundus photographs and high-resolution OCT images were obtained.Results:Seven patients were identified with optic disc

  12. Segmentation of the Optic Disc in 3-D OCT Scans of the Optic Nerve Head

    Microsoft Academic Search

    Kyungmoo Lee; Meindert Niemeijer; Mona Kathryn Garvin; Young H. Kwon; Milan Sonka; Michael D. Abràmoff

    2010-01-01

    Glaucoma is the second leading ocular disease causing blindness due to gradual damage to the optic nerve and resultant visual field loss. Segmentations of the optic disc cup and neuroretinal rim can provide important parameters for detecting and tracking this disease. The purpose of this study is to describe and evaluate a method that can automatically segment the optic disc

  13. Automatic optic disc segmentation based on image brightness and contrast

    Microsoft Academic Search

    Shijian Lu; Jiang Liu; Joo Hwee Lim; Zhuo Zhang; Ngan Meng Tan; Wing Kee Wong; Huiqi Li; Tien Yin Wong

    2010-01-01

    Untreated glaucoma leads to permanent damage of the optic nerve and resultant visual field loss, which can progress to blindness. As glaucoma often produces additional pathological cupping of the optic disc (OD), cupdisc- ratio is one measure that is widely used for glaucoma diagnosis. This paper presents an OD localization method that automatically segments the OD and so can be

  14. Optic disc morphometry in chronic primary open-angle glaucoma

    Microsoft Academic Search

    Jost B. Jonas; Gabriele C. Gusek; Gottfried O. H. Naumann

    1988-01-01

    Four hundred twenty-seven optic discs of 233 unselected patients suffering from chronic primary open-angle glaucoma were morphometrically evaluated and compared with the optic nerve heads of 253 unselected normal subjects. Only one randomly chosen eye per patient was taken into consideration. We found that glaucoma leads to a change in the characteristic configuration of the neuroretinal rim that in normal

  15. Optic disc detection and boundary extraction in retinal images.

    PubMed

    Basit, A; Fraz, Muhammad Moazam

    2015-04-10

    With the development of digital image processing, analysis and modeling techniques, automatic retinal image analysis is emerging as an important screening tool for early detection of ophthalmologic disorders such as diabetic retinopathy and glaucoma. In this paper, a robust method for optic disc detection and extraction of the optic disc boundary is proposed to help in the development of computer-assisted diagnosis and treatment of such ophthalmic disease. The proposed method is based on morphological operations, smoothing filters, and the marker controlled watershed transform. Internal and external markers are used to first modify the gradient magnitude image and then the watershed transformation is applied on this modified gradient magnitude image for boundary extraction. This method has shown significant improvement over existing methods in terms of detection and boundary extraction of the optic disc. The proposed method has optic disc detection success rate of 100%, 100%, 100% and 98.9% for the DRIVE, Shifa, CHASE_DB1, and DIARETDB1 databases, respectively. The optic disc boundary detection achieved an average spatial overlap of 61.88%, 70.96%, 45.61%, and 54.69% for these databases, respectively, which are higher than currents methods. PMID:25967336

  16. An improved gradient vector flow algorithm for optic disc segmentation.

    PubMed

    Zhou, Huiyu; Schaefer, Gerald; Liu, Tangwei; Lin, Faquan

    2010-01-01

    The optic disc provides important cues for accurate diagnosis of various retinopathic diseases. Accurate segmentation of the optic disc is therefore an important step in the analysis of retinal images. Gradient vector flow (GVF) based segmentation algorithms have been used successfully on a variety of medical imagery, however, due to the compromise of internal and external energy forces, it can lead to less accurate segmentation in certain cases. In this paper, we show, that through incorporation of a mean shift term into the GVF framework, improved segmentation accuracy can be achieved. Experimental results on a large dataset of retinal images demonstrate that the presented method reliably detects the border of the optic disc. PMID:21097291

  17. Direct stimulation of optic nerve by electrodes implanted in optic disc of rabbit eyes

    Microsoft Academic Search

    Xiaoyun Fang; Hirokazu Sakaguchi; Takashi Fujikado; Makoto Osanai; Hiroyuki Kanda; Yasushi Ikuno; Motohiro Kamei; Masahito Ohji; Dekang Gan; Junsub Choi; Tetsuya Yagi; Yasuo Tano

    2005-01-01

    Purpose To determine whether wire microelectrodes implanted in the optic disc can be used to elicit cortical potentials. Methods Two or four platinum wire electrodes of two types, viz., the cut-end type and the exposed-tip type, were inserted through the vitreous and fixed in the optic disc of 16 rabbit eyes. Electrically evoked potentials (EEPs) were recorded after bipolar electrical

  18. Optic Disc Hemorrhage Is Related to Various Hemodynamic Findings by Disc Angiography

    PubMed Central

    Park, Hae Young Lopilly; Jeong, Hyun Jin; Kim, Yoon Hee; Park, Chan Kee

    2015-01-01

    Background To investigate the hemodynamic characteristics of glaucoma eyes with disc hemorrhage (DH) by disc fluorescein angiography, and its relationship with glaucomatous changes of the optic disc and surrounding retinal nerve fiber layer (RNFL). Methods This study included 35 glaucoma eyes with DH who were followed up at least 5 years and had DH at presentation. Eyes were classified as eyes with DH at the border of localized RNFL defects and eyes with DH not related to localized RNFL defects. Prevalence of DH and location of the proximal border were recorded from disc photographs. Fluorescein angiography was performed 3 months after detecting the DH. Arm-retina time, arteriovenous transit time, disc filling time, choroidal filling time, and venous filling time were measured as retinal circulation parameters. The presence of disc filling defects and disc leaks were evaluated. Results There were 19 (54.3%) eyes with DH accompanying localized RNFL defects. The arm-retina time was prolonged in eyes with DH not related to RNFL defects (P = 0.044) and the arteriovenous transit time was prolonged in eyes with DH accompanying RNFL defects (P = 0.029). Among eyes with DH accompanying RNFL defects, 11 (57.9%) had vessel filling defects or delayed filling indicating blood flow stasis at the cup margin proximal to where DH occurred. Eyes with DH not related to RNFL defects did not show vessel filling defects or delayed filling. Conclusions and Relevance Eyes with DH related to RNFL defects showed prolonged arteriovenous transit time and had frequent vessel filling defects or delayed filling indicating blood flow stasis and thrombus formation at the site DH occurred. These findings suggest that vascular and hemodynamic changes due to glaucomatous structural changes cause DH in relation to localized RNFL defects. PMID:25879852

  19. TeOx thin films for an optical disc memory

    NASA Astrophysics Data System (ADS)

    Takenaga, Mutsuo; Yamada, Noboru; Nishiuchi, Kenichi; Akahira, Nobuo; Ohta, Takeo; Nakamura, Suguru; Yamashita, Tadaoki

    1983-09-01

    Tellurium suboxide thin films TeOx were found to change in refractive index and extinction coefficient on thermal or optical heating, with accompanying changes in the reflectivity and transmission. The preparation method and thermal or optical properties of the TeOx thin films were investigated to obtain a stable and highly sensitive optical disc memory. A two-source evaporation method using Te and TeO2 provided uniform and any desired composition. The properties of the film depended on the x value; increasing x to as large as x=1.2, which represents a Te-poor composition, produced an excellent humidity and heat stability, and decreasing x to 0.8 made the film more sensitive to a laser diode, but susceptible to humidity. The TeO1.1 thin film was found to sufficiently satisfy all requirements for practical disc applications. A reflective optical disc was prepared using the TeO1.1 thin film deposited on a polymethylmethacrylate substrate with grooves for optical tracking. This disc is capable of recording video signals at real time by laser diodes. It showed no reflectivity changes on recorded or unrecorded areas and no sensitivity change to laser light after long term storage in high humidity and temperature.

  20. Superpixel classification based optic disc and optic cup segmentation for glaucoma screening.

    PubMed

    Cheng, Jun; Liu, Jiang; Xu, Yanwu; Yin, Fengshou; Wong, Damon Wing Kee; Tan, Ngan-Meng; Tao, Dacheng; Cheng, Ching-Yu; Aung, Tin; Wong, Tien Yin

    2013-06-01

    Glaucoma is a chronic eye disease that leads to vision loss. As it cannot be cured, detecting the disease in time is important. Current tests using intraocular pressure (IOP) are not sensitive enough for population based glaucoma screening. Optic nerve head assessment in retinal fundus images is both more promising and superior. This paper proposes optic disc and optic cup segmentation using superpixel classification for glaucoma screening. In optic disc segmentation, histograms, and center surround statistics are used to classify each superpixel as disc or non-disc. A self-assessment reliability score is computed to evaluate the quality of the automated optic disc segmentation. For optic cup segmentation, in addition to the histograms and center surround statistics, the location information is also included into the feature space to boost the performance. The proposed segmentation methods have been evaluated in a database of 650 images with optic disc and optic cup boundaries manually marked by trained professionals. Experimental results show an average overlapping error of 9.5% and 24.1% in optic disc and optic cup segmentation, respectively. The results also show an increase in overlapping error as the reliability score is reduced, which justifies the effectiveness of the self-assessment. The segmented optic disc and optic cup are then used to compute the cup to disc ratio for glaucoma screening. Our proposed method achieves areas under curve of 0.800 and 0.822 in two data sets, which is higher than other methods. The methods can be used for segmentation and glaucoma screening. The self-assessment will be used as an indicator of cases with large errors and enhance the clinical deployment of the automatic segmentation and screening. PMID:23434609

  1. Edge Detection of the Optic Disc in Retinal Images Based on Identification of a Round Shape

    Microsoft Academic Search

    Thanapong Chaichana; Sarat Yoowattana; Zhonghua Sun; Supan Tangjitkusolmun; Supot Sookpotharom; Manas Sangworasil

    2008-01-01

    This paper presents a novel method for identification of the position of the optic disc in retinal images. The method is based on the preliminary detection of the main edge detection of retinal image. The segmentation optic disc is estimated as a circular area. We searched for areas of optic disc using Hough transform which detected several straight lines and

  2. Automatic optic disc detection using retinal background and retinal blood vessels

    Microsoft Academic Search

    Shijian Lu

    2010-01-01

    This paper presents an automatic optic disc detection technique that locates the optic disc through retinal background surface estimation and retinal blood vessel analysis. In the proposed technique, a retinal background surface is first estimated through an iterative Savitzky-Golay smoothing procedure. Multiple optic disc candidates are then detected from the difference between the retinal image under study and the estimated

  3. Fractal-based Automatic Localization and Segmentation of Optic Disc in Retinal Images

    Microsoft Academic Search

    Huajun Ying; Ming Zhang; Jyh-Charn Liu

    2007-01-01

    In this paper, we proposed a novel algorithm to detect optic disc location in retinal images. Optic disc is a bright disk area and all major blood vessels and nerves originate from it. With its high fractal dimension of blood vessel, optic disc can be easily differentiated from other bright regions such as hard exudates and artifacts. Compared with existing

  4. Localisation of optic disc in fundus images by using clustering and histogram techniques

    Microsoft Academic Search

    G. Brenie Sekar; P. Nagarajan

    2012-01-01

    Optic Disc (OD) is considered as one of the main features of a retinal fundus image. Segmenting the OD can be used for automatic extraction of anatomical structures. The change in the shape, color or depth of optic disc is an indicator of various ophthalmic pathologies. Before segmenting the optic disc, the position of OD has to be found. This

  5. Fast localization of optic disc and fovea in retinal images for eye disease screening

    Microsoft Academic Search

    H. Yu; S. Barriga; C. Agurto; S. Echegaray; M. Pattichis; G. Zamora; W. Bauman; P. Soliz

    2011-01-01

    Optic disc (OD) and fovea locations are two important anatomical landmarks in automated analysis of retinal disease in color fundus photographs. This paper presents a new, fast, fully automatic optic disc and fovea localization algorithm developed for diabetic retinopathy (DR) screening. The optic disc localization methodology comprises of two steps. First, the OD location is identified using template matching and

  6. Automated localization of the optic disc and the fovea

    Microsoft Academic Search

    M. Niemeijer; M. D. Abramoff; B. van Ginneken

    2008-01-01

    The detection of the position of the normal anatomy in color fundus photographs is an important step in the automated analysis of retinal images. An automatic system for the detection of the position of the optic disc and the fovea is presented. The method integrates the use of local vessel geometry and image intensity features to find the correct positions

  7. Automatic detection of optic disc and exudates in retinal images

    Microsoft Academic Search

    D. Kavitha; S. Shenbaga Devi

    2005-01-01

    A fast, reliable and efficient method for detecting the optic disc and exudates in retinal fundus images is presented in this work. The algorithm proceeds through three main steps: 1. Segmentation of blood vessels using median filtering and morphological operations and detection of the convergent point by fitting the blood vessels data using least square polynomial curve fitting algorithm. 2.

  8. Superpixel classification for initialization in model based optic disc segmentation.

    PubMed

    Cheng, Jun; Liu, Jiang; Xu, Yanwu; Yin, Fengshou; Wong, Damon Wing Kee; Lee, Beng-Hai; Cheung, Carol; Aung, Tin; Wong, Tien Yin

    2012-01-01

    Optic disc segmentation in retinal fundus image is important in ocular image analysis and computer aided diagnosis. Because of the presence of peripapillary atrophy which affects the deformation, it is important to have a good initialization in deformable model based optic disc segmentation. In this paper, a superpixel classification based method is proposed for the initialization. It uses histogram of superpixels from the contrast enhanced image as features. In the training, bootstrapping is adopted to handle the unbalanced cluster issue due to the presence of peripapillary atrophy. A self-assessment reliability score is computed to evaluate the quality of the initialization and the segmentation. The proposed method has been tested in a database of 650 images with optic disc boundaries marked by trained professionals manually. The experimental results show an mean overlapping error of 10.0% and standard deviation of 7.5% in the best scenario. The results also show an increase in overlapping error as the reliability score reduces, which justifies the effectiveness of the self-assessment. The method can be used for optic disc boundary initialization and segmentation in computer aided diagnosis system and the self-assessment can be used as an indicator of cases with large errors and thus enhance the usage of the automatic segmentation. PMID:23366174

  9. Assessment of optic disc topography with scanning laser ophthalmoscope

    Microsoft Academic Search

    Etsuo Chihara; Fusano Takahashi; Keiko Chihara

    1993-01-01

    Evaluation of the topography of the optic disc is of clinical importance to assess the degree of nerve damage. We conducted a study in 17 glaucomatous and 20 control subjects with a scanning laser ophthalmoscope (SLO; Rodenstock) and compared the results with those in conventional photographs. A tomographic image of the cup area in control subjects and the neuroretinal rim

  10. A genome-wide association study of optic disc parameters.

    PubMed

    Ramdas, Wishal D; van Koolwijk, Leonieke M E; Ikram, M Kamran; Jansonius, Nomdo M; de Jong, Paulus T V M; Bergen, Arthur A B; Isaacs, Aaron; Amin, Najaf; Aulchenko, Yurii S; Wolfs, Roger C W; Hofman, Albert; Rivadeneira, Fernando; Oostra, Ben A; Uitterlinden, Andre G; Hysi, Pirro; Hammond, Christopher J; Lemij, Hans G; Vingerling, Johannes R; Klaver, Caroline C W; van Duijn, Cornelia M

    2010-06-01

    The optic nerve head is involved in many ophthalmic disorders, including common diseases such as myopia and open-angle glaucoma. Two of the most important parameters are the size of the optic disc area and the vertical cup-disc ratio (VCDR). Both are highly heritable but genetically largely undetermined. We performed a meta-analysis of genome-wide association (GWA) data to identify genetic variants associated with optic disc area and VCDR. The gene discovery included 7,360 unrelated individuals from the population-based Rotterdam Study I and Rotterdam Study II cohorts. These cohorts revealed two genome-wide significant loci for optic disc area, rs1192415 on chromosome 1p22 (p = 6.72x10(-19)) within 117 kb of the CDC7 gene and rs1900004 on chromosome 10q21.3-q22.1 (p = 2.67x10(-33)) within 10 kb of the ATOH7 gene. They revealed two genome-wide significant loci for VCDR, rs1063192 on chromosome 9p21 (p = 6.15x10(-11)) in the CDKN2B gene and rs10483727 on chromosome 14q22.3-q23 (p = 2.93x10(-10)) within 40 kbp of the SIX1 gene. Findings were replicated in two independent Dutch cohorts (Rotterdam Study III and Erasmus Rucphen Family study; N = 3,612), and the TwinsUK cohort (N = 843). Meta-analysis with the replication cohorts confirmed the four loci and revealed a third locus at 16q12.1 associated with optic disc area, and four other loci at 11q13, 13q13, 17q23 (borderline significant), and 22q12.1 for VCDR. ATOH7 was also associated with VCDR independent of optic disc area. Three of the loci were marginally associated with open-angle glaucoma. The protein pathways in which the loci of optic disc area are involved overlap with those identified for VCDR, suggesting a common genetic origin. PMID:20548946

  11. Dibenzotetraaza [14] annulene materials for recordable blue laser optical disc

    NASA Astrophysics Data System (ADS)

    Bin, Yuejing; Zhao, Fuqun; Huang, Lei; Li, Zhongyu; Zhang, Fushi

    2008-03-01

    Phthalocyanine materials have successfully been applied in infrared ray optical disc systems. Seeking for the phthalocyanine-analogous materials with great conjugate macrocyclic ? bond system is the key for new materials research of super high density blue laser optical storage. Dibenzotetraaza [14] annulene have the similar macrocyclic structure. It was used as a building block for the preparation of multi-component materials matched the requirement of recordable blue laser optical disc. Ester substituents have been generated with oxalyl dichloride (or phosgene) and appropriate HO-function-containing substrates. A range of new complexes equipped with ester groups derived from various alcohols and phenols have been prepared. The new products have been characterized by UV-Vis spectrometer, TGA, refractive index of the organic films. These kinds of materials have suitable light and thermal sensitivity, and it is a valuable material for blue laser optical storage.

  12. Lamina Cribrosa Defects and Optic Disc Morphology in Primary Open Angle Glaucoma with High Myopia

    PubMed Central

    Kimura, Yugo; Akagi, Tadamichi; Hangai, Masanori; Takayama, Kohei; Hasegawa, Tomoko; Suda, Kenji; Yoshikawa, Munemitsu; Yamada, Hiroshi; Nakanishi, Hideo; Unoki, Noriyuki; Ikeda, Hanako Ohashi; Yoshimura, Nagahisa

    2014-01-01

    Purpose To investigate whether lamina cribrosa (LC) defects are associated with optic disc morphology in primary open angle glaucoma (POAG) eyes with high myopia. Methods A total of 129 POAG patients and 55 age-matched control subjects with high myopia were evaluated. Three-dimensional scan images obtained by swept source optical coherence tomography were used to detect LC defects. Radial B-scans and infrared images obtained by spectral domain optical coherence tomography were used to measure ?-peripapillary atrophy (PPA) lengths with and without Bruch's membrane (BM) (temporal, nasal, superior, and inferior), tilt angle (vertical and horizontal), and disc diameter (transverse and longitudinal). Peripapillary intrachoroidal cavitations (PICCs), disc area, ovality index, and cyclotorsion of the optic disc were analyzed as well. Results LC defects were found in 70 of 129 (54.2%) POAG eyes and 1 of 55 (1.8%) control eyes (P<0.001). Age, sex, spherical equivalent, axial length, intraocular pressure, and central corneal thickness were not significantly different among POAG eyes with LC defects, POAG eyes without LC defects, and control eyes. Temporal PPA lengths without BM in all three groups correlated significantly with vertical and horizontal tilt angles, although no PPA length with BM correlated significantly with any tilt angle. PICCs were detected more frequently in POAG eyes with LC defects than those without LC defects (P?=?0.01) and control eyes (P?=?0.02). POAG eyes with LC defects showed a smaller ovality index (P?=?0.004), longer temporal PPA without BM (P<0.001), and larger vertical/horizontal tilt angles (vertical, P<0.001; horizontal, P?=?0.01), and transverse diameter (P?=?0.01). In multivariate analysis for the presence of LC defects, presence of POAG (P<0.001) and vertical tilt angle (P<0.001) were identified as significant. Conclusions The presence of LC defects was associated with myopic optic disc morphology in POAG eyes with high myopia. PMID:25531656

  13. Performance Enhancement of Optic Disc Boundary Detection using Active Contours via Improved Homogenization of Optic Disc Region

    Microsoft Academic Search

    G. Vijaya Saradhi; S. Balasubramanian; V. Chandrasekaran

    2006-01-01

    Accurate segmentation of optic disc (OD) in retinal images is of critical importance in diagnosis of diabetic retinopathy (DR). The accuracy of OD boundary detection using active contours is based on homogeneity of OD region. In this work we improve upon active contour model segmentation of OD from morphologically preprocessed fundus image in the Lab color space. The key contribution

  14. Ultracool white dwarfs and the age of the Galactic disc

    NASA Astrophysics Data System (ADS)

    Gianninas, A.; Curd, B.; Thorstensen, John R.; Kilic, Mukremin; Bergeron, P.; Andrews, Jeff J.; Canton, Paul; Agüeros, M. A.

    2015-06-01

    We present parallax observations and a detailed model atmosphere analysis of 54 cool and ultracool (Teff < 4000 K) white dwarfs (WDs) in the solar neighbourhood. For the first time, a large number of cool and ultracool WDs have distance and tangential velocities measurements available. Our targets have distances ranging from 21 pc to >100 pc, and include five stars within 30 pc. Contrary to expectations, all but two of them have tangential velocities smaller than 150 km s-1 thus suggesting Galactic disc membership. The oldest WDs in this sample have WD cooling ages of 10 Gyr, providing a firm lower limit to the age of the thick disc population. Many of our targets have uncharacteristically large radii, indicating that they are low-mass WDs. It appears that we have detected the brighter population of cool and ultracool WDs near the Sun. The fainter population of ultracool CO-core WDs remain to be discovered in large numbers. The Large Synoptic Survey Telescope should find these elusive, more massive ultracool WDs in the solar neighbourhood.

  15. Fundus optic disc localization and segmentation method based on phase congruency.

    PubMed

    Geng, Lei; Shao, Yi-Ting; Xiao, Zhi-Tao; Zhang, Fang; Wu, Jun; Li, Min; Shan, Chun-Yan

    2014-01-01

    It has been demonstrated that shape, area and depth of the optic disc are relevant indices of diabetic retinopathy. In this paper, we present a new fundus optic disc localization and segmentation method based on phase congruency (PC). Firstly, in order to highlight the optic disc, channel images with the highest contrast between optic disc and background are selected in LAB, YUV, YIQ and HSV spaces respectively. Secondly, with the use of PC, features of four selected channel images can be extracted. Multiplication operation is then used to enhance PC detection results. Thirdly, window scanning and gray accumulating are utilized to locate the optic disc. Finally, iterative OTSU automatic threshold segmentation and Hough transform are performed on location images, before the final optic disc segmentation result can be obtained. The experimental results showed that the proposed method can effectively and accurately perform optic disc location and segmentation. PMID:25227031

  16. Comparison between laser scanning tomography and computerised image analysis of the optic disc

    Microsoft Academic Search

    Augusto Azuara-Blanco; George L Spaeth; Jamie Nicholl; Ines M Lanzl; James J Augsburger

    1999-01-01

    AIMSTo study the interchangeability of the measurements of the optic disc topography obtained by one computerised image analyser and one confocal laser tomographic scanner.METHODSOne eye of 28 patients with glaucoma or glaucoma suspects was studied. All cases had simultaneous stereoscopic disc photographs taken with the fundus camera Topcon TRC-SS and optic disc examination with the Heidelberg retina tomograph (HRT) during

  17. A study on optical pickup actuator for small form-factor optical disc drives

    Microsoft Academic Search

    Kyung Taek Lee; Sam-Nyol Hong

    2009-01-01

    Optical disc drives (ODDs) such as CD, DVD and HD-DVD are cheaper and more distributable than solid-state memories and hard disc drives (HDDs). In the era of mobile environment, ultra-slim ODDs have been studied and developed to show the feasibility of mobile application. This paper is a study on miniaturization of an optical pickup actuator, one of key components for

  18. Unilateral swollen optic disc: do not forget neurosyphilis

    PubMed Central

    Porto, Lénea; Capelo, Joana; Carragoso, Adelino

    2013-01-01

    A 51-year-old man presented with a 3?month history of progressive right visual loss. On examination, the only abnormal findings were a right visual acuity of 4/10 and a swollen right optic disc. The patient had previously undergone MRI that had been reported as being normal and a trial of corticosteroids under the care of the referring ophthalmologist. An extensive battery of blood tests was normal apart from a rapid plasmatic reagin titre of 1:64. ELISA revealed elevated levels of total and immunoglobulin M antibodies against Treponema pallidum. Cerebrospinal fluid analysis revealed a mild leucocytosis and mildly elevated protein content. The patient was treated with a 5?week course of penicillin. Three months after starting treatment, his right visual acuity had improved to 8/10 and his right optic disc swelling had resolved. PMID:23843402

  19. Automated Optic Disc Localization and Contour Detection Using Ellipse Fitting and Wavelet Transform

    Microsoft Academic Search

    P. M. D. S. Pallawala; Wynne Hsu; Mong-li Lee; Kah-guan Au Eong

    2004-01-01

    \\u000a Optic disc detection is important in the computer-aided analysis of retinal images. It is crucial for the precise identification\\u000a of the macula to enable successful grading of macular pathology such as diabetic maculopathy. However, the extreme variation\\u000a of intensity features within the optic disc and intensity variations close to the optic disc boundary presents a major obstacle\\u000a in automated optic

  20. Chondroadherin fragmentation mediated by the protease HTRA1 distinguishes human intervertebral disc degeneration from normal aging.

    PubMed

    Akhatib, Bashar; Onnerfjord, Patrik; Gawri, Rahul; Ouellet, Jean; Jarzem, Peter; Heinegård, Dick; Mort, John; Roughley, Peter; Haglund, Lisbet

    2013-06-28

    Chondroadherin, a member of the leucine-rich repeat family, has previously been demonstrated to be fragmented in some juveniles with idiopathic scoliosis. This observation led us to investigate adults with disc degeneration. Immunoblotting analysis demonstrated that non-degenerate discs from three different age groups show no chondroadherin fragmentation. Furthermore, the chondroadherin fragments in adult degenerate disc and the juvenile scoliotic disc were compared via immunoblot analysis and appeared to have a similar size. We then investigated whether or not chondroadherin fragmentation increases with the severity of disc degeneration. Three different samples with different severities were chosen from the same disc, and chondroadherin fragmentation was found to be more abundant with increasing severity of degeneration. This observation led us to the creation of a neoepitope antibody to the cleavage site observed. We then observed that the cleavage site in adult degenerate discs and juvenile scoliotic discs was identical as confirmed by the neoepitope antibody. Consequently, investigation of the protease capable of cleaving chondroadherin at this site was necessary. In vitro digests of disc tissue demonstrated that ADAMTS-4 and -5; cathepsins K, B, and L; and MMP-3, -7, -12, and -13 were incapable of cleavage of chondroadherin at this site and that HTRA1 was indeed the only protease capable. Furthermore, increased protein levels of the processed form of HTRA1 were demonstrated in degenerate disc tissues via immunoblotting. The results suggest that chondroadherin fragmentation can be used as a biomarker to distinguish the processes of disc degeneration from normal aging. PMID:23673665

  1. Automated segmentation of the optic disc margin in 3-D optical coherence tomography images using a graph-theoretic approach

    Microsoft Academic Search

    Zhihong Hu; Meindert Niemeijer; Kyungmoo Lee; Michael D. Abràmoff; Milan Sonka; Mona K. Garvin

    2009-01-01

    The optic disc margin is of interest due to its use for detecting and managing glaucoma. We developed a method for segmenting the optic disc margin of the optic nerve head (ONH) in spectral-domain optical coherence tomography (OCT) images using a graph-theoretic approach. A small number of slices surrounding the Bruch's membrane opening (BMO) plane was taken and used for

  2. Emerging Digital Optical Disc Technologies: An Opportunity and a Challenge for Educational Researchers.

    ERIC Educational Resources Information Center

    Harvey, Francis A.

    1987-01-01

    Description of new applications of digital optical disc storage technologies focuses on CD-ROM (Compact Disc--Read Only Memory); CD-I (Compact Disc--Interactive); and DV-I (Digital Video--Interactive). Features of each technology are described in the context of instructional design and educational technology, and the role of educational research…

  3. Fractal-based automatic localization and segmentation of optic disc in retinal images.

    PubMed

    Ying, Huajun; Zhang, Ming; Liu, Jyh-Charn

    2007-01-01

    In this paper, we proposed a novel algorithm to detect optic disc location in retinal images. Optic disc is a bright disk area and all major blood vessels and nerves originate from it. With its high fractal dimension of blood vessel, optic disc can be easily differentiated from other bright regions such as hard exudates and artifacts. Compared with existing algorithms, ours has much lower computational cost and is more robust. With its location known, segmentation of optic disc can be done with simple local histogram analysis. The algorithm can be valuable for automated processing for early stage retinal disease. PMID:18002913

  4. Optic disc detection in color fundus images using ant colony optimization.

    PubMed

    Pereira, Carla; Gonçalves, Luís; Ferreira, Manuel

    2013-03-01

    Diabetic retinopathy has been revealed as the most common cause of blindness among people of working age in developed countries. However, loss of vision could be prevented by an early detection of the disease and, therefore, by a regular screening program to detect retinopathy. Due to its characteristics, the digital color fundus photographs have been the easiest way to analyze the eye fundus. An important prerequisite for automation is the segmentation of the main anatomical features in the image, particularly the optic disc. Currently, there are many works reported in the literature with the purpose of detecting and segmenting this anatomical structure. Though, none of them performs as needed, especially when dealing with images presenting pathologies and a great variability. Ant colony optimization (ACO) is an optimization algorithm inspired by the foraging behavior of some ant species that has been applied in image processing with different purposes. In this paper, this algorithm preceded by anisotropic diffusion is used for optic disc detection in color fundus images. Experimental results demonstrate the good performance of the proposed approach as the optic disc was detected in most of all the images used, even in the images with great variability. PMID:23160896

  5. Optic nerve axons and acquired alterations in the appearance of the optic disc.

    PubMed Central

    Wirtschafter, J D

    1983-01-01

    The pathophysiologic events in optic nerve axons have recently been recognized as crucial to an understanding of clinically significant acquired alterations in the ophthalmoscopic appearance of the optic disc. Stasis and related abnormalities of axonal transport appear to explain most aspects of optic nerve head swelling, including optic disc drusen and retinal cottonwool spots. Loss of axoplasm and axonal death can be invoked to interpret optic disc pallor, thinning and narrowing of rim tissue, changes in the size and outline of the optic cup, laminar dots, atrophy of the retinal nerve fiber layer, and acquired demyelination and myelination of the retinal nerve fiber layer. It is speculated that the axons may also play a role in the mechanical support of the lamina cribrosa in resisting the pressure gradient across the pars scleralis of the optic nerve head. Axons and their associated glial cells may be involved in those cases where "reversibility" of cupping of the optic disc has been reported. The structure, physiology, and experimental pathologic findings of the optic nerve head have been reviewed. Many aspects concerning the final anatomic appearance of the optic nerve head have been explained. However, many questions remain concerning the intermediate mechanisms by which increased intracranial pressure retards the various components of axonal transport in papilledema and by which increased IOP causes axonal loss in glaucoma. Investigation of the molecular biology of axonal constituents and their responses to abnormalities in their physical and chemical milieu could extend our understanding of the events that result from mechanical compression and local ischemia. Moreover, we have identified a need to further explore the role of axons in the pathophysiology of optic disc cupping. Images FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 FIGURE 7 FIGURE 8 FIGURE 11 FIGURE 12 FIGURE 13 PMID:6203209

  6. Optical Coherence Tomography Before and After Vitrectomy with Internal Limiting Membrane Removal in a Child with Optic Disc Pit Maculopathy

    Microsoft Academic Search

    Kohei Ishikawa; Hiroko Terasaki; Masako Mori; Kimiko Sugita; Yozo Miyake

    2005-01-01

    Background: The pathogenesis of optic disc pit maculopathy is still unknown, although recent optical coherence tomographic (OCT) analyses have made a great contribution to clarifying its morphological appearance. The best treatment for this disease is also controversial. Case: We report on a 7-year-old girl with optic disc pit maculopathy associated with a separation of the internal limiting membrane (ILM) near

  7. Optic Disc and Visual Field Changes in a Prospective Longitudinal Study of Patients With Glaucoma Comparison of Scanning Laser Tomography With Conventional Perimetry and Optic Disc Photography

    Microsoft Academic Search

    Balwantray C. Chauhan; Terry A. McCormick; Marcelo T. Nicolela; Raymond P. LeBlanc

    Objective: To investigate the relationship between op- tic disc changes measured with scanning laser tomogra- phy and those measured with conventional perimetry and optic disc photography. Methods: In a prospective longitudinal study, we fol- lowed up 77 patients with early glaucomatous visual field damage. Scanning laser tomography (using the Heidelberg Retina Tomograph) and conventional perimetry (using the Humphrey Field Analyzer)

  8. Automatic optic disc detection in OCT slices via low-rank reconstruction.

    PubMed

    Fu, Huazhu; Xu, Dong; Lin, Stephen; Wong, Damon Wing Kee; Liu, Jiang

    2015-04-01

    Optic disc measurements provide useful diagnostic information as they have correlations with certain eye diseases. In this paper, we provide an automatic method for detecting the optic disc in a single OCT slice. Our method is developed from the observation that the retinal pigment epithelium (RPE) which bounds the optic disc has a low-rank appearance structure that differs from areas within the disc. To detect the disc, our method acquires from the OCT image an RPE appearance model that is specific to the individual and imaging conditions, by learning a low-rank dictionary from image areas known to be part of the RPE according to priors on ocular anatomy. The edge of the RPE, where the optic disc is located, is then found by traversing the retinal layer containing the RPE, reconstructing local appearance with the low-rank model, and detecting the point at which appearance starts to deviate (i.e., increased reconstruction error). To aid in this detection, we also introduce a geometrical constraint called the distance bias that accounts for the smooth shape of the RPE. Experiments demonstrate that our method outperforms other OCT techniques in localizing the optic disc and estimating disc width. Moreover, we also show the potential usage of our method on optic disc area detection in 3-D OCT volumes. PMID:25438300

  9. Towards Vessel Characterisation in the Vicinity of the Optic Disc in Digital Retinal Images

    Microsoft Academic Search

    H. F. Jelinek; C. Depardieu; C. Lucas; D. J. Cornforth; W. Huang; M. J. Cree

    Automated image processing has the potential to assist in the early detection of diabetes, by detecting changes in blood vessel patterns in the retina. This paper describes progress towards the development of an integrated automated analyser of the retinal blood vessels in the vicinity of the optic disc using digital colour retinal images. First the optic disc was detected using

  10. Fast localization of optic disc and fovea in retinal images for eye disease screening

    NASA Astrophysics Data System (ADS)

    Yu, H.; Barriga, S.; Agurto, C.; Echegaray, S.; Pattichis, M.; Zamora, G.; Bauman, W.; Soliz, P.

    2011-03-01

    Optic disc (OD) and fovea locations are two important anatomical landmarks in automated analysis of retinal disease in color fundus photographs. This paper presents a new, fast, fully automatic optic disc and fovea localization algorithm developed for diabetic retinopathy (DR) screening. The optic disc localization methodology comprises of two steps. First, the OD location is identified using template matching and directional matched filter. To reduce false positives due to bright areas of pathology, we exploit vessel characteristics inside the optic disc. The location of the fovea is estimated as the point of lowest matched filter response within a search area determined by the optic disc location. Second, optic disc segmentation is performed. Based on the detected optic disc location, a fast hybrid level-set algorithm which combines the region information and edge gradient to drive the curve evolution is used to segment the optic disc boundary. Extensive evaluation was performed on 1200 images (Messidor) composed of 540 images of healthy retinas, 431 images with DR but no risk of macular edema (ME), and 229 images with DR and risk of ME. The OD location methodology obtained 98.3% success rate, while fovea location achieved 95% success rate. The average mean absolute distance (MAD) between the OD segmentation algorithm and "gold standard" is 10.5% of estimated OD radius. Qualitatively, 97% of the images achieved Excellent to Fair performance for OD segmentation. The segmentation algorithm performs well even on blurred images.

  11. Optic Disc Detection in Retinal Images using Tensor Voting and Adaptive Mean-Shift

    Microsoft Academic Search

    Jonghyun Park; Nguyen Trung Kien; Gueesang Lee

    2007-01-01

    In this paper, we present a new approach to identify the position of an optic disc in retinal fundus images. The proposed algorithm is based on a tensor voting to analyze vessel structures, and the position of the optic disc is identified by mean-shift based mode detection. The core technique consists of three preprocessing stages that enhance local contrasts through

  12. Basal Meningoencephalocele, Anomaly of Optic Disc and Panhypopituitarism in Association with Moyamoya Disease

    Microsoft Academic Search

    Masaki Komiyama; Toshihiro Yasui; Hiroaki Sakamoto; Keinosuke Fujita; Toshihiko Sato; Mariko Ota; Masahiko Sugita

    2000-01-01

    Basal meningoencephalocele is frequently associated with midfacial anomaly, optic disc anomaly, brain anomaly, cerebrospinal fluid rhinorrhea, chiasma syndrome, and endocrinologic disturbance. The combination of basal meningoencephalocele and moyamoya disease is extremely rare. A 29-year-old man had basal meningoencephalocele (transsphenoidal type), anomaly of the optic disc (morning glory syndrome), panhypopituitarism and moyamoya disease. The patient was treated by hormone replacement, but

  13. Effects of short term increase of intraocular pressure on optic disc cupping

    Microsoft Academic Search

    Augusto Azuara-Blanco; Alon Harris; Louis B Cantor; Marcio M Abreu; Monika Weinland

    1998-01-01

    AIMSTo evaluate the effect of acute elevation of intraocular pressure (IOP) on optic disc cupping.METHODS10 emmetropic and 10 myopic volunteers were included in this study. The cup area (CA) and cup volume (CV) of the optic disc were determined with the Heidelberg retina tomograph (HRT). After baseline determinations, a suction cup was used to increase the intraocular pressure (IOP) to

  14. Segmentation of the Optic Disc, Macula and Vascular Arch in Fundus Photographs

    Microsoft Academic Search

    Meindert Niemeijer; Michael D. Abràmoff; Bram Van Ginneken

    2007-01-01

    An automatic system is presented to find the location of the major anatomical structures in color fundus photographs; the optic disc, the macula, and the vascular arch. These structures are found by fitting a single point-distribution-model to the image, that contains points on each structure. The method can handle optic disc and macula centered images of both the left and

  15. Automatic initialization of level set segmentation for application to optic disc margin identification

    Microsoft Academic Search

    Sebastian Echegaray; Peter Soliz; Wenbin Luo

    2009-01-01

    This paper presents a methodology for automatic initialization of a level-set segmentation algorithm to find the margin of the optic disc in fundus images as an indicator for glaucoma. Accurate segmentation of the optic disc is fundamental to the diagnosis and treatment of glaucoma. Our algorithm improves on previous applications by automatically finding the initialization points for ideal segmentation and

  16. Automated Analysis of Heidelberg Retina Tomograph Optic Disc Images by Glaucoma Probability Score

    Microsoft Academic Search

    Annemiek Coops; David Barry Henson; Anna J. Kwartz; Paul Habib Artes

    2006-01-01

    RESULTS. In 8 (7%) patients with glaucoma and 10 (11%) control subjects, the GPS failed to provide a complete global and sectoral optic disc classification. Although we could not iden- tify a single distinct cause of this failure in the glaucoma group, failures in the control subjects occurred most often (7\\/10) with small and crowded optic discs. In subjects who

  17. Dysversion of the optic disc and axial length measurements in a presumed amblyopic population

    Microsoft Academic Search

    Philip Lempert; Lynn Porter

    1998-01-01

    Purpose: Our purpose was to evaluate anatomic variations of eyes presumed to be amblyopic. Method: Computer imaging and photography of the optic discs of 205 amblyopic subjects were performed and the axial lengths of 183 of the subjects were measured. The paired optic nerve images were evaluated for symmetry of disc contours and orientation of central blood vessels to detect

  18. Parapapillary atrophy and optic disc region assessment (PANDORA): retinal imaging tool for assessment of the optic disc and parapapillary atrophy

    NASA Astrophysics Data System (ADS)

    Lu, Cheng-Kai; Tang, Tong Boon; Laude, Augustinus; Dhillon, Baljean; Murray, Alan F.

    2012-10-01

    We describe a computer-aided measuring tool, named parapapillary atrophy and optic disc region assessment (PANDORA), for automated detection and quantification of both the parapapillary atrophy (PPA) and the optic disc (OD) regions in two-dimensional color retinal fundus images. The OD region is segmented using a combination of edge detection and ellipse fitting methods. The PPA region is identified by the presence of bright pixels in the temporal zone of the OD, and it is segmented using a sequence of techniques, including a modified Chan-Vese approach, thresholding, scanning filter, and multiseed region growing. PANDORA has been tested with 133 color retinal images (82 with PPA; 51 without PPA) drawn randomly from the Lothian Birth Cohort (LBC) database, together with a "ground truth" estimate from an ophthalmologist. The PPA detection rate is 89.47% with a sensitivity of 0.83 and a specificity of 1. The mean accuracy in defining the OD region is 81.31% (SD=10.45) when PPA is present and 95.32% (SD=4.36) when PPA is absent. The mean accuracy in defining the PPA region is 73.57% (SD=11.62). PANDORA demonstrates for the first time how to quantify the OD and PPA regions using two-dimensional fundus images, enabling ophthalmologists to study ocular diseases related to PPA using a standard fundus camera.

  19. The aging mouse partially models the aging human spine: lumbar and coccygeal disc height, composition, mechanical properties, and Wnt signaling in young and old mice

    PubMed Central

    Aguilar, Rhiannon; Harland, Robin A.; Bomar, Bradley A.; Silva, Matthew J.

    2014-01-01

    Murine lumbar and coccygeal (tail) regions of spines are commonly used to study cellular signaling of age-related disc diseases, but the tissue-level changes of aging intervertebral discs and vertebrae of each spinal region remain unclear. Furthermore, the impact of aging lumbar and coccygeal discs on Wnt/?-catenin signaling, which is putatively involved in the catabolism of intervertebral discs, is also unclear. We compared disc/vertebrae morphology and mechanics and biochemical composition of intervertebral discs from lumbar and coccygeal regions between young (4–5 mo) and old (20–22 mo) female C57BL/6 mice. Center intervertebral disc height from both regions was greater in old discs than young discs. Compared with young, old lumbar discs had a lower early viscous coefficient (a measure of stiffness) by 40%, while conversely old coccygeal discs were stiffer by 53%. Biochemically, old mice had double the collagen content in lumbar and coccygeal discs of young discs, greater glycosaminoglycan in lumbar discs by 37%, but less glycosaminoglycan in coccygeal discs by 32%. Next, we compared Wnt activity of lumbar and coccygeal discs of 4- to 5-mo and 12- to 14-mo TOPGAL mice. Despite the disc-specific changes, aging decreased Wnt signaling in the nucleus pulposus from both spinal regions by ?64%. Compared with young, trabecular bone volume/tissue volume and ultimate force were less in old lumbar vertebrae, but greater in old coccygeal vertebrae. Thus intervertebral discs and vertebrae age in a spinal region-dependent manner, but these differential age-related changes may be uncoupled from Wnt signaling. Overall, lumbar and coccygeal regions are not interchangeable in modeling human aging. PMID:24790018

  20. Optical coherence tomography of pneumatic displacement of optic disc pit maculopathy

    Microsoft Academic Search

    Harvey Lincoff; Ingrid Kreissig

    1998-01-01

    BACKGROUNDThe authors have previously concluded that fluid from an optic disc pit creates an inner layer separation (ILS) of the retina. An outer layer detachment (OLD) centred on the macula is a secondary phenomenon that causes a dense central scotoma. Pneumatic displacement of the OLD effects an improvement in central vision. Pathology to confirm these conclusions is lacking. Intraretinal images

  1. Optic disc changes following trabeculectomy: longitudinal and localisation of change

    PubMed Central

    Kotecha, A.; Siriwardena, D.; Fitzke, F.; Hitchings, R.; Khaw, P.

    2001-01-01

    AIMS—To determine whether there were any changes in the optic disc at 2 years after trabeculectomy. To determine the factors that most influenced change and whether change was localised to any region of the optic disc.?METHODS—95 patients undergoing routine trabeculectomy as part of the ongoing Moorfields/MRC 5-fluorouracil trial were recruited into the study. Eyes were imaged preoperatively (4 (SD 3) weeks) with the Heidelberg retina tomograph (HRT, Heidelberg Engineering), and at 3 months (SD 2 weeks), 1 year (SD 1 month), and 2 years (SD 1 month) after surgery. Parameters investigated for change were rim area, rim volume, and maximum cup depth. The predefined segment analysis available on the HRT analysis software was used to determine segmental change.?RESULTS—The images of 70 patients were analysed. Intraocular pressure reduced from 22.25 (SD 3.76) mm Hg, at the time of preoperative imaging to 15.27 (SD 4.96) mm Hg at 3 months, 14.38 (SD 3.89) mm Hg at 1 year, and 13.80 (SD 3.54) mm Hg at 2 years after trabeculectomy. An increase in rim area and rim volume was present at all time points after surgery, but was only found to be statistically significant at 2 years after surgery. Maximum depth of cup reduced by month 3 and month 12, but showed a slight increase at 2 years after surgery, although this was still lower than the preoperative measure. Segmental analysis found a significant change in rim volume in the nasal, inferonasal, superonasal, and superotemporal regions at 2 years after surgery. No significant regional localisation for change was found at any other time point or in any other parameter investigated.?CONCLUSIONS—Reversal of disc cupping is present at 2 years after trabeculectomy. The factor most influencing change is reduction of intraocular pressure. Segmental analysis showed that change in rim volume was greatest in the nasal, inferonasal, superonasal and superotemporal regions at 2 years.?? PMID:11466255

  2. Topographic optic disc analysis by Heidelberg retinal tomography in ocular Behçet's disease

    PubMed Central

    Berker, Nilufer; Elgin, Ufuk; Ozdal, Pinar; Batman, Aygen; Soykan, Emel; Ozkan, Seyhan S

    2007-01-01

    Aim To compare the topographic characteristics of the optic discs in patients with severe and mild ocular Behçet's disease by using Heidelberg retinal tomographaphy (HRT). Methods This prospective study included 47 eyes of 47 patients with ocular BD who were being followed?up at the Uveitis Clinic of the Ankara Ulucanlar Eye Research Hospital, Ankara, Turkey. The patients were divided into two groups. Group 1 consisted of 21 eyes with mild uveitis, and group 2 consisted of 26 eyes with severe uveitis. All patients underwent topographic optic disc analysis by HRT II, and the quantitative optic disc parameters of both groups were compared by non?parametric Mann?Whitney U test. Results The mean cup volume, rim volume, cup area, disc area and cup depth in group 1 were found to be statistically significantly greater than those in group 2 (p<0.0001, p?=?0.03, p?=?0.021, p?=?0.01 and p?=?0.017, respectively), while the difference between the mean cup?to?disc ratios in group 1 and group 2 were found to be statistically insignificant (p?=?0.148). Conclusion A relationship was found between the severity of ocular BD and optic disc topography determined by HRT. In eyes with smaller optic discs, uveitis was observed to have a more severe course with more frequent relapses than those with larger discs. PMID:17475703

  3. Preperimetric glaucoma diagnosis by confocal scanning laser tomography of the optic disc

    PubMed Central

    Mardin, C.; Horn, F.; Jonas, J.; Budde, W.

    1999-01-01

    AIM—To evaluate the ability of confocal scanning laser tomography of the optic nerve head to detect glaucomatous optic nerve damage in ocular hypertensive eyes without visual field defects.?METHODS—The study included 50 normal subjects, 61 glaucoma patients with glaucomatous changes in the optic disc and visual field, and 102 "preperimetric" patients with increased intraocular pressure, normal visual fields, and glaucomatous appearance of the optic disc as evaluated on colour stereo optic disc photographs. For all individuals, confocal scanning laser tomographs of the optic nerve head were taken using the Heidelberg retina tomograph (HRT; software 2.01).?RESULTS—Almost all investigated HRT variables varied significantly (p<0.05) between the normal eyes and preperimetric glaucoma eyes with pronounced overlap between the two study groups. Corresponding to the overlap, sensitivity and specificity values were relatively low when HRT variables were taken to differentiate between normal and preperimetric glaucoma eyes. At a given specificity of 95% highest sensitivities were found for the variables "rim area in the superior disc sector" (24.8%), "nerve fibre layer thickness in the inferior disc sector" (26.5%), and "rim volume in the superior disc sector" (25.5%). A multivariate approach increased sensitivity to 42.2% at a given specificity of 95%. For the glaucoma group highest sensitivity values were reached by rim volume in the superior disc sector (73.8%) and rim area (72.1%); the multivariate approach reached 83.6%.?CONCLUSIONS—Owing to pronounced overlapping between the groups, confocal scanning laser tomography of the optic nerve head has relatively low diagnostic power to differentiate between normal eyes and preperimetric glaucoma eyes. One of the reasons may be the biological interindividual variability of quantitative optic disc variables.?? Keywords: glaucoma; confocal scanning laser tomography; optic disc PMID:10365037

  4. Mitochondrial-derived reactive oxygen species (ROS) play a causal role in aging-related intervertebral disc degeneration

    PubMed Central

    Nasto, Luigi A.; Robinson, Andria R.; Ngo, Kevin; Clauson, Cheryl L.; Dong, Qing; St. Croix, Claudette; Sowa, Gwendolyn; Pola, Enrico; Robbins, Paul D.; Kang, James; Niedernhofer, Laura J.; Wipf, Peter; Vo, Nam V.

    2013-01-01

    Oxidative damage is a well-established driver of aging. Evidence of oxidative stress exists in aged and degenerated discs, but it is unclear how it affects disc metabolism. In this study, we first determined whether oxidative stress negatively impacts disc matrix metabolism using disc organotypic and cell cultures. Mouse disc organotypic culture grown at atmospheric oxygen (20% O2) exhibited perturbed disc matrix homeostasis, including reduced proteoglycan synthesis and enhanced expression of matrix metalloproteinases, compared to discs grown at low oxygen levels (5% O2). Human disc cells grown at 20% O2 showed increased levels of mitochondrial-derived superoxide anions and perturbed matrix homeostasis. Treatment of disc cells with the mitochondria-targeted reactive oxygen species (ROS) scavenger XJB-5-131 blunted the adverse effects caused by 20% O2. Importantly, we demonstrated that treatment of accelerated aging Ercc1?/?mice, previously established to be a useful in vivo model to study age-related intervertebral disc degeneration (IDD), also resulted in improved disc total glycosaminoglycan content and proteoglycan synthesis. This demonstrates that mitochondrial-derived ROS contributes to age-associated IDD in Ercc1?/?mice. Collectively, these data provide strong experimental evidence that mitochondrial-derived ROS play a causal role in driving changes linked to aging-related IDD and a potentially important role for radical scavengers in preventing IDD. PMID:23389888

  5. Biostereometrics in Ophthalmology: Topographic Analysis of the Optic Disc Cup in Glaucoma

    NASA Astrophysics Data System (ADS)

    Takamoto, Takenori; Schwartz, Bernard

    1986-07-01

    Glaucoma is a disease characterized by increased ocular pressure with optic nerve atrophy and loss of visual field, or side vision, which eventually leads to blindness. The optic disc becomes more cupped with increasing progress of the disease. We have devised a system for the use of the Donaldson simultaneous stereophotographic fundus camera to obtain optimal reproducibility and sensitivity of measurements from optic disc stereophotographs. Stereomodel deformations caused by eye-to-camera optical variables (photographic magnification, working distance, relative orientation between the camera optical axis and the optic disc, and position of the optic disc image in the film frame) were evaluated. We developed an analytical correction method for stereomodel deformations and evaluated the impact on measurement of optic disc cupping. We have evaluated the reproducibility of new techniques for measurement of cup parameters such as volume, depth, and area of the cup relative to the disc area; slope of the cup floor, wall, and rim; and cup shape using volume profiles in which contour areas were plotted of the cup depth from the top to the bottom.

  6. Biostereometrics In Ophthalmology For Measurement Of The Optic Disc Cup In Glaucoma

    NASA Astrophysics Data System (ADS)

    Schwartz, Bernard; Takamoto, Takenori

    1980-07-01

    Glaucoma is a disease characterized by increased ocular pressure with optic nerve atrophy and loss of visual field or side vision which eventually leads to blindness. The surface of the portion of the optic nerve within the eye, the optic disc, becomes depressed and its contours are altered. The optic disc becomes more cupped with increasing progress of the disease. For measurement of the cup, retinal cameras can provide simultaneous stereo photographs of the optic disc taken through the pupil. However, the photographs have to be obtained at a narrow angle due to the limit of the size of the dilated pupil. Our studies of the geometry of the stereo photographs show a greater error in depth compared to horizontal dimensions because of this biological limit. Similarly, data for the optimal conditions for photography of the optic disc, including aperture size and magnification have been obtained. Since the changes in the optic disc can progress with increase of the desease, photogrammetric techniques for measuring relative changes in the dimensions of the cup have been developed. Both subsequent and initial photographs are measured after being similarly oriented in space. The photogrammetric measurement of changes in the optic disc cup in glaucoma has potential as a useful technique which can have wide clinical application.

  7. Relationship of Cholesterol Content to Spatial Distribution and Age of Disc Membranes in Retinal Rod Outer Segments*

    PubMed Central

    Boesze-Battaglia, Kathleen; Fliesler, Steven J.; Albert, Arlene D.

    2015-01-01

    The initial events of visual transduction occur on disc membranes which are sequestered within the photoreceptor outer segment. In rod cells, the discs are stacked in the outer segment. Discs are formed at the base of the rod outer segment (ROS) from evaginations of the plasma membrane. As new discs form, older discs move toward the apical tip of the rod, from which they are eventually shed and subsequently phagocytosed by the adjacent pigment epithelium. Thus, disc membranes within a given rod cell are not of uniform age. We have recently shown that disc membranes are not homogeneous with respect to cholesterol content (Boesze-Battaglia, K., Hennessey, T., and Albert, A. D. (1989) J. Biol. Chem. 264, 8151–8155). In the present study, freshly isolated bovine retinas were incubated with [3H]leucine for 4 h in order to allow sufficient time for the radiolabeled proteins to become incorporated into the basal-most (newest) discs. Osmotically intact discs were then isolated. After the addition of digitonin, the discs were fractionated based on cholesterol content, and radioactivity (indicative of newly synthesized protein) was measured. Discs which exhibited high cholesterol content also exhibited high radioactivity. These results demonstrate that the cholesterol heterogeneity of ROS disc membranes is related to the age, and thus the position, of the discs in the ROS. PMID:2229047

  8. Retinal imaging tool for assessment of the parapapillary atrophy and the optic disc 

    E-print Network

    Lu, Cheng-Kai

    2012-11-29

    Ophthalmic diseases such as glaucoma are associated with progressive changes in the structure of the optic disc (OD) and parapapillary atrophy (PPA). These structural changes may therefore have relevance to other systemic ...

  9. Intraobserver and interobserver reproducibility in the evaluation of optic disc stereometric parameters by Heidelberg retina tomograph

    Microsoft Academic Search

    Stefano Miglior; Elena Albé; Magda Guareschi; Luca Rossetti; Nicola Orzalesi

    2002-01-01

    Purpose: To assess intraobserver and interobserver reproducibility of the measurement of stereometric parameters of the optic disc by means of the Heidelberg Retina Tomograph I (HRT).Study design: Observational study, with interobserver variability.Participants: Fifty-five volunteers (healthy subjects and patients with glaucoma).Methods: HRT examination of the optic disc was repeated on 3 consecutive days on 1 eye of each of the 55

  10. Morphologic Predictive Factors for Development of Optic Disc Hemorrhages in Glaucoma

    Microsoft Academic Search

    Jost B. Jonas; Peter Martus; Wido M. Budde; Jochen Hayler

    PURPOSE. To evaluate which optic disc parameters are predic- tive factors for the development of disc hemorrhages in chronic open-angle glaucoma. METHODS. The prospective comparative clinical observational study included 432 eyes of 281 white patients with chronic open-angle glaucoma. Mean follow-up time was 38.8 months (median, 31.5). Eyes in the whole study group were divided into those with an optic

  11. Influence of optic disc size on the sensitivity of the Heidelberg Retina Tomograph

    Microsoft Academic Search

    Christian Yahya Mardin; Folkert Kurt Horn

    1998-01-01

    · Purpose: The aim of this study was to evaluate the influence of optic disc size on the ability of variables generated by\\u000a the Heidelberg Retina Tomograph, software version 1.11, to distinguish glaucoma patients from normals in a cross-sectional\\u000a study.?· Patients and methods: For evaluation of the optic disc with the Heidelberg Retina Tomograph, eyes of 87 normals and\\u000a 61

  12. Influence of optic disc size on parameters of retinal nerve fiber analysis with laser scanning polarimetry

    Microsoft Academic Search

    Robert Laemmer; Folkert K. Horn; Arne Viestenz; Anselm G. Juenemann; Christian Y. Mardin

    2006-01-01

    Purpose  The aim of the study was to evaluate the influence of optic disc size on the variables of laser scanning polarimetry (GDx).Patients and methods  One hundred and nineteen healthy controls and 161 patients with ocular hypertension (OHT) received detailed ophthalmologic investigation with respect to glaucoma including retinal nerve fiber analysis with GDx (Version 3.0.05×1; Laser Diagnostic Technologies Europe). Optic disc size

  13. A study on central corneal thickness and optic disc size in patients with primary open angle glaucoma.

    PubMed

    Bandyopadhyay, Arun Kumar; Bhattacharya, Apala; Dan, Amit Kumar; Banerjee, Bhakti; Biswas, Indranil; Das, Sibes Kumar; Bhaduri, Gautam

    2011-07-01

    The aim of the study was to evaluate a possible relationship between central corneal thickness (CCT) and optic disc area in patients with primary open angle glaucoma (POAG). Patients with POAG and age matched control group underwent routine ocular examination along with optic nerve head evaluation by Stratus optical coherence tomography (OCT) and CCT measurement by ultrasound pachymetry. Pearson's coefficient was calculated in both groups to find out correlation between these two parameters. In this series 90 eyes of 45 control subjects and 94 eyes of 47 POAG patients were studied. In the control group 40% were female, 60% male and among the POAG patients 34% female, 66% male. Mean CCT in control subjects was 566.98 micron (SD = 19.36, n = 90) and in POAG patients was 526.61 micron (SD = 29.93, n = 94). There was a significant difference in two groups (p = 0.0002). Disc area in control group had mean of 2.32mm(2) (SD = 0.305, n = 90) and in POAG group 2.982mm(2) (SD = 0.566, n = 94). Statistically significant difference was found among the two groups (p = 0.0). CCT was inversely correlated with optic disc size. In control subjects, r = -0.141, but it was not statistically significant (p = 0.092). In POAG group, r = -0.256 and the correlation was statistically significant (p = 0.0063). CCT was significantly less in POAG patients compared to control subjects. Mean disc area was significantly higher among the POAG group compared to control subjects. CCT was inversely correlated with disc area in both groups, but was statistically significant in POAG patients. PMID:22315836

  14. Diffractive read-out of optical discs Joseph Braat

    E-print Network

    the CD (Compact Disc) , the DVD (Digital Versatile Disc) and the blue light DVR system. After a short in the DVD-system and the compatibility aspects between the DVD- and CD-system. Throughout this chapter we or less unchanged since the start some thirty years ago. An interesting feature of the DVD-system is its

  15. Influence of disc area on retinal nerve fiber layer thickness measurement by spectral domain optical coherence tomography.

    PubMed

    Mansoori, Tarannum; Balakrishna, Nagalla; Viswanath, Kalluri

    2013-11-11

    Background: To examine the effect of optic disc area on peripapillary RNFLT (retinal nerve fiber layer thickness) measurement at circle diameter of 3.4 mm around optic nerve head using spectral OCT/SLO (Optical coherence tomography/scanning laser ophthalmoscope). Materials and Methods : In this prospective, cross sectional study, one hundred and two eyes of 102 normal subjects underwent RNFLT and disc area measurement using spectral OCT/SLO. Based on disc area, subjects were divided into three groups i.e., <3 mm2 (32 eyes), 3-4 mm2 (36 eyes) and >4 mm2 (34 eyes). The effect of disc area on RNFLT parameters was analyzed using linear regression analysis. Results: The mean and quadrant RNFLT did not show significant correlation with disc area in subjects with disc area of <4 mm2, however in eyes with disc area >4 mm2, average RNFLT, superior and temporal quadrant RNFLT showed negative correlation with disc area, which was statistically significant (P = 0.004, P = 0.005 and P = 0.002, respectively) Conclusion: In healthy eyes of disc area <4 mm2, disc size does not appear to affect peripapillary RNFLT measurement by spectral OCT/SLO. Average, superior and temporal quadrant RNFLT measurements were inversely proportional to disc area in eyes with disc area >4 mm2. Hence, RNFLT measurement by OCT in eyes with optic disc area of >4 mm2 should be interpreted carefully. PMID:24212211

  16. Bilateral macular colobomata: Temporal dragging of optic disc

    PubMed Central

    Mathew, David J

    2015-01-01

    A 13-year-old male presented with decreased vision and squint from childhood. He had bilateral large colobomata at the macula in each eye, the one on the right being larger than the left. The disc was dragged temporally with straightening of the temporal retinal vessels. This is a case report of bilateral large macular coloboma and serves to report its association with a temporally dragged disc and straightened temporal retinal vessels. A dragged disc if present with a colobomatous defect at the macula may strengthen the case for diagnosis of macular coloboma and help exclude other differentials. PMID:26044479

  17. Obvious optic disc swelling in a patient with cryopyrin-associated periodic syndrome

    PubMed Central

    Kawai, Mariko; Yoshikawa, Tadanobu; Nishikomori, Ryuta; Heike, Toshio; Takahashi, Kanji

    2013-01-01

    Cryopyrin-associated periodic syndrome (CAPS) is a group of rare hereditary autoinflammatory diseases caused by mutations of the NLRP3 gene, and leads to excessive production of the proinflammatory cytokine, interleukin-l?. A 35-year-old male presented with recurrent symptoms of urticarial-like rash, periodic fever, arthralgia, headache, and eye redness. His best-corrected visual acuity was 1.0 OD and 0.9 OS. Slit-lamp examination showed conjunctival and episcleral injection in both eyes. Ophthalmoscopy revealed obvious bilateral optic disc swelling and retinal vascular sheathing around the optic discs. Spectral domain optical coherence tomography also showed obvious optic disc swelling. Steroid and nonsteroidal anti-inflammatory drugs did not improve these symptoms. Genetic testing detected a heterozygous mutation of c.907G>A. Thus, the patient was genetically confirmed with CAPS. Visual acuity did not decrease for 3 years, although the optic discs became white in color. CAPS should therefore be distinguished from other disorders when examining optic disc swelling and/or uveitis patients with urticarial-like rash and periodic fever. PMID:23966762

  18. Sensitivity and specificity of optic disc variables and analysis of a new variable (MP\\/D) for glaucoma diagnosis with the Glaucoma-Scope

    Microsoft Academic Search

    Yves Lachkar; Howard Cohn

    1997-01-01

    AIMIn an attempt to use the quantitative optic disc measurements of the Glaucoma-Scope (OIS Sacramento, CA, USA) to distinguish glaucomatous from normal optic discs, a new variable was investigated, the mean disc corrected for the disc size by dividing by the disc area: MP\\/D.METHODSGlaucoma-Scope disc evaluation was performed on 81 eyes of 51 patients split into the following groups based

  19. Application of intuitionistic fuzzy histon segmentation for the automated detection of optic disc in digital fundus images

    Microsoft Academic Search

    Muthu Rama Krishnan M; U Rajendra Acharya; Chua Kuang Chua; Lim Choo Min; E Y K Ng; Milind M. Mushrif; Augustinus Laude

    2012-01-01

    Human eye is the most sophisticated organ, with perfectly interrelated subsystems such as retina, pupil, iris cornea, lens and optic nerve. Uncontrolled diabetes retinopathy (DR) and glaucoma may lead to blindness. Optic disc helps to identify the different stages of DR, and glaucoma. In this paper, a novel automated, reliable and efficient optic disc localization and segmentation method using digital

  20. Optic disc and cup segmentation from color fundus photograph using graph cut with priors.

    PubMed

    Zheng, Yuanjie; Stambolian, Dwight; O'Brien, Joan; Gee, James C

    2013-01-01

    For automatic segmentation of optic disc and cup from color fundus photograph, we describe a fairly general energy function that can naturally fit into a global optimization framework with graph cut. Distinguished from most previous work, our energy function includes priors on the shape & location of disc & cup, the rim thickness and the geometric interaction of "disc contains cup". These priors together with the effective optimization of graph cut enable our algorithm to generate reliable and robust solutions. Our approach is able to outperform several state-of-the-art segmentation methods, as shown by a set of experimental comparisons with manual delineations and a series of results of correlations with the assessments of a merchant-provided software from Optical Coherence Tomography (OCT) regarding several cup and disc parameters. PMID:24579126

  1. Agreement of glaucoma specialists and experienced optometrists in gonioscopy and optic disc evaluation

    PubMed Central

    Kumar, Addepalli U.; Jonnadula, Ganesh B.; Garudadri, Chandrasekhar; Rao, Harsha L.; Senthil, Sirisha; Papas, Eric B.; Sankaridurg, Padmaja; Khanna, Rohit C.

    2013-01-01

    Purpose To compare the diagnostic performance of glaucoma specialists and experienced optometrists in gonioscopy and optic disc assessment. Methods This study was done to validate the diagnostic performance of two experienced optometrists for using their skills of detecting glaucoma using gonioscopy and optic disc assessment in a major epidemiological study, the L V Prasad Eye Institute Glaucoma Epidemiology and Molecular Genetics Study (LVPEI-GLEAMS). Gonioscopic findings for 150 eyes were categorized as 0, 1 and 2 for open angle, primary angle closure suspect (PACS) and primary angle closure (PAC) respectively. Optic disc findings for 200 eyes were categorized as 0, 1 and 2 for normal, suspects and glaucomatous respectively. Weighted kappa (?) and diagnostic accuracy parameters were calculated. Two optometrists (#1 and #2) participated in the study. Results Agreement between glaucoma specialists and optometrist for interpretation of gonioscopy to discriminate PACS and PAC from open angles and for interpretation of optic disc to discriminate glaucomatous and suspicious discs from normal, the kappa (?) was 0.92 and 0.84 and 0.90 and 0.89 for optometrists #1 and #2 respectively. Sensitivities and specificities were above 90% for gonioscopy. Optic disc evaluation had specificities greater than 95% to discriminate normal from glaucomatous discs while the sensitivities were 83% and 93% for optometrists #1 and #2 respectively. Conclusion Agreement between optometrists and glaucoma specialists, in diagnostic performance of gonioscopy and optic assessment was excellent with high sensitivity and specificity. Hence, we conclude that the experienced optometrists can detect glaucoma accurately in the LVPEI-GLEAMS.

  2. Fast detection of the optic disc and fovea in color fundus photographs.

    PubMed

    Niemeijer, Meindert; Abràmoff, Michael D; van Ginneken, Bram

    2009-12-01

    A fully automated, fast method to detect the fovea and the optic disc in digital color photographs of the retina is presented. The method makes few assumptions about the location of both structures in the image. We define the problem of localizing structures in a retinal image as a regression problem. A kNN regressor is utilized to predict the distance in pixels in the image to the object of interest at any given location in the image based on a set of features measured at that location. The method combines cues measured directly in the image with cues derived from a segmentation of the retinal vasculature. A distance prediction is made for a limited number of image locations and the point with the lowest predicted distance to the optic disc is selected as the optic disc center. Based on this location the search area for the fovea is defined. The location with the lowest predicted distance to the fovea within the foveal search area is selected as the fovea location. The method is trained with 500 images for which the optic disc and fovea locations are known. An extensive evaluation was done on 500 images from a diabetic retinopathy screening program and 100 specially selected images containing gross abnormalities. The method found the optic disc in 99.4% and the fovea in 96.8% of regular screening images and for the images with abnormalities these numbers were 93.0% and 89.0% respectively. PMID:19782633

  3. Exhaustion of nucleus pulposus progenitor cells with ageing and degeneration of the intervertebral disc

    PubMed Central

    Sakai, Daisuke; Nakamura, Yoshihiko; Nakai, Tomoko; Mishima, Taishi; Kato, Shunichi; Grad, Sibylle; Alini, Mauro; Risbud, Makarand V.; Chan, Danny; Cheah, Kathryn S.E.; Yamamura, Ken-ichi; Masuda, Koichi; Okano, Hideyuki; Ando, Kiyoshi; Mochida, Joji

    2012-01-01

    Despite the high prevalence of intervertebral disc disease, little is known about changes in intervertebral disc cells and their regenerative potential with ageing and intervertebral disc degeneration. Here we identify populations of progenitor cells that are Tie2 positive (Tie2+) and disialoganglioside 2 positive (GD2+), in the nucleus pulposus from mice and humans. These cells form spheroid colonies that express type II collagen and aggrecan. They are clonally multipotent and differentiated into mesenchymal lineages and induced reorganization of nucleus pulposus tissue when transplanted into non-obese diabetic/severe combined immunodeficient mice. The frequency of Tie2+ cells in tissues from patients decreases markedly with age and degeneration of the intervertebral disc, suggesting exhaustion of their capacity for regeneration. However, progenitor cells (Tie2+GD2+) can be induced from their precursor cells (Tie2+GD2?) under simple culture conditions. Moreover, angiopoietin-1, a ligand of Tie2, is crucial for the survival of nucleus pulposus cells. Our results offer insights for regenerative therapy and a new diagnostic standard. PMID:23232394

  4. Intervertebral disc cell response to dynamic compression is age and frequency dependent.

    PubMed

    Korecki, Casey L; Kuo, Catherine K; Tuan, Rocky S; Iatridis, James C

    2009-06-01

    The maintenance of the intervertebral disc extracellular matrix is regulated by mechanical loading, nutrition, and the accumulation of matrix proteins and cytokines that are affected by both aging and degeneration. Evidence suggests that cellular aging may lead to alterations in the quantity and quality of extracellular matrix produced. The aims of this study were to examine the role of loading and maturation (a subset of aging), and the interaction between these two factors in intervertebral disc cell gene expression and biosynthesis in a controlled 3D culture environment. Cells were isolated from young (4-6 months) and mature (18-24 months) bovine caudal annulus fibrosus and nucleus pulposus tissue. Isolated cells were seeded into alginate and dynamically compressed for 7 days at either 0.1, 1, or 3 Hz or maintained as a free-swelling control. After 7 days, DNA and sulfated glycosaminoglycan contents were analyzed along with real time, quantitative reverse transcription-polymerase chain reaction analysis for collagen types I and II, aggrecan, and matrix metalloproteinase-3 gene expression. Results suggest that maturation plays an important role in intervertebral disc homeostasis and influences the cell response to mechanical loading. While isolated intervertebral disc cells responded to mechanical compression in 3D culture, the effect of loading frequency was minimal. Altered cellular phenotype and biosynthesis rates appear to be an attribute of the cell maturation process, potentially independent of changes in cellular microenvironment associated with lost nutrition and disc degeneration. Mature cells may have a decreased capacity to create or retain extracellular matrix components in response to mechanical loading compared to young cells. PMID:19058142

  5. Retinal image registration based on multiscale products and optic disc detection.

    PubMed

    Koukounis, Dimitris; Nicholson, Lindsay; Bull, David R; Achim, Alin

    2011-01-01

    This paper presents a new approach to segmentation-driven retinal image registration. The proposed algorithm aims to help physicians to detect changes that occur in the blood vasculature due to various diseases. The proposed approach uses multiscale products, which augment the difference between blood vessels and the rest of the retina. The result of scale multiplication is then iteratively thresholded in order to obtain a binary map of vessels inside the retina. For the registration part, the centre of the optic disc is detected and used as control point. Having determined both the position of the blood vessels and the centre of the optic disc, translational and rotational differences between the images can be eliminated and registration can be achieved. The centroid of the optic disc is used as the center of rotation. The final registration is then achieved by searching the best match between the two images using a XOR operation. PMID:22255765

  6. Topographic changes in the optic disc in eyes with cotton-wool spots and primary open-angle glaucoma

    Microsoft Academic Search

    Etsuo Chihara; Yoshihito Honda

    1991-01-01

    Changes in the topography of the optic disc in 26 eyes with cotton-wool spots displaying defects in the retinal nerve-fiber layer and in 31 eyes with early primary open-angle glaucoma showing a similar degree of such defects were studied by computer-assisted optic disc analyzer and then compared with 27 controls. Changes in the cup-to-disc ratio, cup volume, and ratio of

  7. Vertical cup\\/disc ratio in relation to optic disc size: its value in the assessment of the glaucoma suspect

    Microsoft Academic Search

    David F Garway-Heath; Simon T Ruben; Ananth Viswanathan; Roger A Hitchings

    1998-01-01

    AIMSThe vertical cup\\/disc ratio (CDR) has long been used in the assessment of the glaucoma suspect, though the wide range of CDR values in the normal population limits its use. Cup size is related physiologically to disc size and pathologically to glaucomatous damage. Disc size can be measured at the slit lamp as the vertical disc diameter (DD). The ability

  8. Influence of Clinically Invisible, but Optical Coherence Tomography Detected, Optic Disc Margin Anatomy on Neuroretinal Rim Evaluation

    PubMed Central

    Reis, Alexandre S. C.; O'Leary, Neil; Yang, Hongli; Sharpe, Glen P.; Nicolela, Marcelo T.; Burgoyne, Claude F.; Chauhan, Balwantray C.

    2012-01-01

    Purpose. We previously demonstrated that most eyes have regionally variable extensions of Bruch's membrane (BM) inside the clinically identified disc margin (DM) that are clinically and photographically invisible. We studied the impact of these findings on DM- and BM opening (BMO)-derived neuroretinal rim parameters. Methods. Disc stereo-photography and spectral domain optical coherence tomography (SD-OCT, 24 radial B-scans centered on the optic nerve head) were performed on 30 glaucoma patients and 10 age-matched controls. Photographs were colocalized to SD-OCT data such that the DM and BMO could be visualized in each B-scan. Three parameters were computed: (1) DM-horizontal rim width (HRW), the distance between the DM and internal limiting membrane (ILM) along the DM reference plane; (2) BMO-HRW, the distance between BMO and ILM along the BMO reference plane; and (3) BMO-minimum rim width (MRW), the minimum distance between BMO and ILM. Rank-order correlations of sectors ranked by rim width and spatial concordance measured as angular distances between equivalently ranked sectors were derived. Results. The average DM position was external to BMO in all quadrants, except inferotemporally. There were significant sectoral differences among all three rim parameters. DM-HRW and BMO-HRW sector ranks were better correlated (median ? = 0.84) than DM-HRW and BMO-MRW (median ? = 0.55), or BMO-HRW and BMO-MRW (median ? = 0.60) ranks. Sectors with the narrowest BMO-MRW were infrequently the same as those with the narrowest DM-HRW or BMO-HRW. Conclusions. BMO-MRW quantifies the neuroretinal rim from a true anatomical outer border and accounts for its variable trajectory at the point of measurement. PMID:22410561

  9. Automatic localization of the optic disc by combining vascular and intensity information.

    PubMed

    Mendonça, Ana Maria; Sousa, António; Mendonça, Luís; Campilho, Aurélio

    2013-01-01

    This paper describes a new methodology for automatic location of the optic disc in retinal images, based on the combination of information taken from the blood vessel network with intensity data. The distribution of vessel orientations around an image point is quantified using the new concept of entropy of vascular directions. The robustness of the method for OD localization is improved by constraining the search for maximal values of entropy to image areas with high intensities. The method was able to obtain a valid location for the optic disc in 1357 out of the 1361 images of the four datasets. PMID:23726437

  10. A multiscale decomposition approach to detect abnormal vasculature in the optic disc.

    PubMed

    Agurto, Carla; Yu, Honggang; Murray, Victor; Pattichis, Marios S; Nemeth, Sheila; Barriga, Simon; Soliz, Peter

    2015-07-01

    This paper presents a multiscale method to detect neovascularization in the optic disc (NVD) using fundus images. Our method is applied to a manually selected region of interest (ROI) containing the optic disc. All the vessels in the ROI are segmented by adaptively combining contrast enhancement methods with a vessel segmentation technique. Textural features extracted using multiscale amplitude-modulation frequency-modulation, morphological granulometry, and fractal dimension are used. A linear SVM is used to perform the classification, which is tested by means of 10-fold cross-validation. The performance is evaluated using 300 images achieving an AUC of 0.93 with maximum accuracy of 88%. PMID:25698545

  11. Learning-based approach for the automatic detection of the optic disc in digital retinal fundus photographs

    Microsoft Academic Search

    D. W. K. Wong; J. Liu; N. M. Tan; F. Yin; B. H. Lee; T. Y. Wong

    2010-01-01

    The optic disc is an important feature in the retina. We propose a method for the detection of the optic disc based on a supervised learning scheme. The method employs pixel and local neighbourhood features extracted from the ROI of a digital retinal fundus photograph. A support vector machine based classification mechanism is used to classify each image point as

  12. Superior segmental optic nerve hypoplasia: The topless disc syndrome

    Microsoft Academic Search

    Joseph Sowka; Lori Vollmer; Sherrol Reynolds

    2008-01-01

    BackgroundOptic nerve hypoplasia is a well-known congenital maldevelopment presenting with an abnormally small optic nerve head occupying the central aspect of a normally sized chorioscleral canal. Characteristically, the optic nerve head is surrounded by scleral anlage with a “double ring sign.” Less commonly appreciated, however, is the fact that optic nerve hypoplasia may be sectorial rather than total and involving

  13. Influence of age and gender on thoracic vertebral body shape and disc degeneration: an MR investigation of 169 cases

    PubMed Central

    GOH, S.; TAN, C.; PRICE, R. I.; EDMONDSTON, S. J.; SONG, S.; DAVIS, S.; SINGER, K. P.

    2000-01-01

    There are limited data detailing the pattern of age and gender-related changes to the thoracic vertebral bodies and intervertebral discs. A retrospective MR investigation, involving T1-weighted midsagittal images from 169 cases, was undertaken to examine age influences on the anterior wedge (anteroposterior height ratio or Ha/Hp), biconcavity (midposterior height ratio or Hm/Hp), and compression indices (posterior height/anteroposterior diameter or Hp/D) of the thoracic vertebral bodies. Disc degenerative changes in the annulus, nucleus, end-plate and disc margin were noted on T2-weighted sagittal images for the 169 cases, based on a 3-level grading system. A linear age-related decline in the Ha/Hp and Hm/Hp indices was noted. The Hp/D index increased during the first few decades of life, then decreased gradually thereafter. The prevalence of abnormal findings in the annuli, nuclei and disc margins increased with increasing age, particularly in the mid and lower thoracic discs. Greater disc degenerative changes were observed in males. These findings provide further insight into the nature of thoracic vertebral shape changes across the lifespan, and the typical patterns of degeneration of the thoracic intervertebral discs. PMID:11197538

  14. Promising Rapid Access High-Capacity Mass Storage Technique For Diagnostic Information Utilizing Optical Disc

    NASA Astrophysics Data System (ADS)

    Colby, R. L.; Bartuska, A. J.; Herzog, D. G.

    1982-01-01

    The optical disc has become a new technique for mass digital data storage of X-ray images from examinations and films in todays hospitals. Up to 36,000 X-ray images can be stored on one side of a 12-inch disc by melting holes 0.015 mils in size in an ablative material such as tellerium with a laser beam. This unique characteristic makes the disc suitable for storage and retrieval of X-rays in a record and playback system in either a single disc or multiple disc "jukebox" configuration. Doctors, nurses, technicians and other hospital personnel can call up a particular X-ray in less than 0.6 of a second in an on-line single disc system and up to less than 6 seconds in an on-line "jukebox" system. The jukebox is configured to hold up to 100 discs, thus storing 3,600,000 X-rays in hospitals with a bed size of greater than 500. The estimated exposed films on file in those hospitals is 327,400,000 and the estimated annual X-ray exams are 44,300. Thus, a single disc system could be used for an all electronic X-ray scanning system for annual X-ray exams. The jukebox configuration, which has expansion capability for servicing multiple simultaneous user request, can be applied to large archival mass storage. These systems could store the existing exposed films in hospitals with bed size greater than 500 at record and playback data rates of 50 Mb/s with access times of less than 15 seconds.

  15. Accurate and reliable segmentation of the optic disc in digital fundus images.

    PubMed

    Giachetti, Andrea; Ballerini, Lucia; Trucco, Emanuele

    2014-07-01

    We describe a complete pipeline for the detection and accurate automatic segmentation of the optic disc in digital fundus images. This procedure provides separation of vascular information and accurate inpainting of vessel-removed images, symmetry-based optic disc localization, and fitting of incrementally complex contour models at increasing resolutions using information related to inpainted images and vessel masks. Validation experiments, performed on a large dataset of images of healthy and pathological eyes, annotated by experts and partially graded with a quality label, demonstrate the good performances of the proposed approach. The method is able to detect the optic disc and trace its contours better than the other systems presented in the literature and tested on the same data. The average error in the obtained contour masks is reasonably close to the interoperator errors and suitable for practical applications. The optic disc segmentation pipeline is currently integrated in a complete software suite for the semiautomatic quantification of retinal vessel properties from fundus camera images (VAMPIRE). PMID:26158034

  16. Accurate and Efficient Optic Disc Detection and Segmentation by a Circular Transformation

    Microsoft Academic Search

    Shijian Lu

    2011-01-01

    Under the framework of computer-aided diagnosis, this paper presents an accurate and efficient optic disc (OD) de- tection and segmentation technique. A circular transformation is designed to capture both the circular shape of the OD and the image variation across the OD boundary simultaneously. For each retinal image pixel, it evaluates the image variation along multiple evenly-oriented radial line segments

  17. Optic Disc Detection From Normalized Digital Fundus Images by Means of a Vessels' Direction Matched Filter

    Microsoft Academic Search

    Aliaa Abdel-Haleim Abdel-Razik Youssif; Atef Zaki Ghalwash; Amr Ahmed Sabry Abdel-rahman Ghoneim

    2008-01-01

    Optic disc (OD) detection is a main step while developing automated screening systems for diabetic retinopathy. We present in this paper a method to automatically detect the position of the OD in digital retinal fundus images. The method starts by normalizing luminosity and contrast through out the image using illumination equalization and adaptive histogram equalization methods respectively. The OD detection

  18. Graph based detection of optic disc and fovea in retinal images

    Microsoft Academic Search

    Laszlo Kovacs; Rashid Jalal Qureshi; Brigitta Nagy; Balazs Harangi; Andras Hajdu

    2010-01-01

    Diabetic retinopathy (DR) is the damage to the eye's retina that occurs with long-term diabetes, which can eventually lead to blindness. Screening programs for DR are being introduced, however, an important prerequisite for automation is the accurate localization of the main anatomical features in the image, notably the optic disc (OD) and the macula. A series of interesting algorithms have

  19. Detection of New Vessels on the Optic Disc Using Retinal Photographs

    Microsoft Academic Search

    Keith A. Goatman; Alan D. Fleming; Sam Philip; Graeme J. Williams; John A. Olson; Peter F. Sharp

    2011-01-01

    Proliferative diabetic retinopathy is a rare condition likely to lead to severe visual impairment. It is characterized by the development of abnormal new retinal vessels. We describe a method for automatically detecting new vessels on the optic disc using retinal photography. Vessel-like candidate segments are first detected using a method based on watershed lines and ridge strength measurement. Fifteen feature

  20. Detection of optic disc in retinal images by means of a geometrical model of vessel structure

    Microsoft Academic Search

    Marco Foracchia; Enrico Grisan; Alfredo Ruggeri

    2004-01-01

    We present here a new method to identify the position of the optic disc (OD) in retinal fundus images. The method is based on the preliminary detection of the main retinal vessels. All retinal vessels originate from the OD and their path follows a similar directional pattern (parabolic course) in all images. To describe the general direction of retinal vessels

  1. Detection of the optic disc in images of the retina using the Hough transform

    Microsoft Academic Search

    Xiaolu Zhu; Rangaraj M. Rangayyan

    2008-01-01

    We propose a method to locate automatically the optic disc (OD) in fundus images of the retina. Based on the properties of the OD, our proposed method includes edge detection using the Sobel or the Canny method, and detection of circles using the Hough transform. The Hough transform assists in the detection of the center and radius of a circle

  2. Localisation of the optic disc by means of GA-optimised Topological Active Nets

    Microsoft Academic Search

    J. Novo; Manuel G. Penedo; José Santos

    2009-01-01

    In this paper we propose a new approach to the optic disc localisation process in digital retinal images by means of Topological Active Nets (TAN). This is a deformable model used for image segmentation that integrates features of region-based and edge-based segmentation techniques, being able to fit the edges of the objects and model their inner topology. In this paper

  3. Enhancement of optic cup to disc ratio detection in glaucoma diagnosis

    Microsoft Academic Search

    A. Murthi; M. Madheswaran

    2012-01-01

    Glaucoma is a major global cause of blindness. An approach to automatically extract the main features in color fundus images is proposed in this paper. The optic cup-to-disc ratio (CDR) in retinal fundus images is one of the principle physiological characteristics in the diagnosis of glaucoma. The least square fitting algorithm aims to improve the accuracy of the boundary estimation.

  4. Optic disc segmentation using a matching filter and a deformable model

    Microsoft Academic Search

    C. MARI; N. BARREIRA; M. G. PENEDO; M. HORTAS; A. P ´ EREZ-URRIA; J. L. DONCEL

    This paper presents an algorithm for automatic extraction of the optic disc in re tinal digital images. The developed system consists of two main parts. Firstly, a clustering algorithm is u sed to select the regions which contain the pixels with the highest gray levels. A correlation filter is applied to the se regions to compute the approximate center of

  5. Extraction of the Contours of Optic Disc and Exudates Based on Marker-Controlled Watershed Segmentation

    Microsoft Academic Search

    C. Eswaran; Ahmed Wasif Reza; Subhas Hati

    2008-01-01

    The optic disc (OD) and exudates form the main features of fundus images for diagnosing eye disease such as diabetic retinopathy and glaucoma. In this paper, an algorithm for the extraction of OD and exudates from fundus images based on marker controlled watershed segmentation is presented. The proposed algorithm makes use of average filtering and contrast adjustment as preprocessing steps

  6. Fast detection of the optic disc and fovea in color fundus photographs

    Microsoft Academic Search

    Meindert Niemeijer; Michael D. Abràmoff; Bram van Ginneken

    2009-01-01

    A fully automated, fast method to detect the fovea and the optic disc in digital color photographs of the retina is presented. The method makes few assumptions about the location of both structures in the image. We define the problem of localizing structures in a retinal image as a regression problem. A kNN regressor is utilized to predict the distance

  7. Accurate and reliable segmentation of the optic disc in digital fundus images

    PubMed Central

    Giachetti, Andrea; Ballerini, Lucia; Trucco, Emanuele

    2014-01-01

    Abstract. We describe a complete pipeline for the detection and accurate automatic segmentation of the optic disc in digital fundus images. This procedure provides separation of vascular information and accurate inpainting of vessel-removed images, symmetry-based optic disc localization, and fitting of incrementally complex contour models at increasing resolutions using information related to inpainted images and vessel masks. Validation experiments, performed on a large dataset of images of healthy and pathological eyes, annotated by experts and partially graded with a quality label, demonstrate the good performances of the proposed approach. The method is able to detect the optic disc and trace its contours better than the other systems presented in the literature and tested on the same data. The average error in the obtained contour masks is reasonably close to the interoperator errors and suitable for practical applications. The optic disc segmentation pipeline is currently integrated in a complete software suite for the semiautomatic quantification of retinal vessel properties from fundus camera images (VAMPIRE).

  8. Design and fabrication of polymer microfluidic substrates using the optical disc process

    Microsoft Academic Search

    Chun-Han Wu; Chun-Hwa Chen; Kuo-Wei Fan; Wen-Syang Hsu; Yu-Cheng Lin

    2007-01-01

    This paper presents a new method for manufacturing a microfluidic structure on a polymer-based substrate. The method uses a new optical disc process to prevent damage on the mirror plate of the mold. In addition, the cycle time of the injection molding can be reduced several ten-folds compared to the conventional methods by means of a new cooling system. The

  9. Correlation between Disc Damage Likelihood Scale and Optical Coherence Tomography in the Diagnosis of Glaucoma

    Microsoft Academic Search

    Aman Shah B. Abdul Majid; Jee Hyun Kwag; Sang Hoon Jung; Hye Bin Yim; Yeon Deok Kim; Kui Dong Kang

    2010-01-01

    Purpose: To investigate the relationship between the Disc Damage Likelihood Scale (DDLS), visual field and various optical coherence tomography (OCT) parameters for glaucoma diagnosis. Methods: The study comprised 149 eyes from 149 patients. The patients were categorized as normal, glaucoma suspect or with glaucoma. They were clinically examined and graded according to the DDLS system. OCT was performed to acquire

  10. Relation between size of optic disc and thickness of retinal nerve fibre layer in normal subjects

    Microsoft Academic Search

    Shigeo Funaki; Motohiro Shirakashi; Haruki Abe

    1998-01-01

    AIMSTo evaluate the relation between the optic disc size and the thickness of the peripapillary retinal nerve fibre layer (RNFL) in normal Japanese subjects by means of scanning laser polarimetry.METHODSScanning laser polarimetry was performed in 60 normal subjects. One eye of each subject was randomly selected for study. Using a scanning laser polarimeter, the integral of RNFL thickness was measured

  11. Nerve fiber analysis and optic disc parameters with the glaucoma-scope

    Microsoft Academic Search

    Yves Lachkar; Howard Cohn

    1996-01-01

    Purpose: We evaluated the ability of optic disc parameters and nerve fiber analysis with the Glaucoma-scope to distinguish glaucoma from normal or hypertensive eyes. Methods: Glaucoma-scope examination was performed on 68 eyes of 44 patients split into following groups based on Humphrey 24-2 visual field and clinical criteria of glaucoma: normal eyes (n = 17), ocular hypertension (n = 19),

  12. MEMS focus control and spherical aberration correction for multilayer optical discs

    NASA Astrophysics Data System (ADS)

    Lukes, Sarah J.; Dickensheets, David L.

    2012-03-01

    We present the use of a large-stroke deformable membrane mirror at 45° incidence to achieve a very compact optical system capable of fast multi-layer focusing in an optical disc unit. The MEMS mirror replaces a lens translation mechanism and liquid crystal compensator, resulting in a single optical element to control both focus depth and compensation of attendant focus-dependent spherical aberration. We outline the membrane optical requirements in terms of stroke and aberration compensation required for multi-layer focusing for current DVD and BD standards. We demonstrate an adjustable range of at least 1.6 ?m peak wavefront spherical aberration correction at a membrane displacement of 7 ?m, which should be sufficient capability for quadruple layer BDXL™ discs.

  13. Retinal ganglion cell layer and visual function in a patient with optic disc drusen

    Microsoft Academic Search

    Marcus-Matthias Gellrich; Stephan Neumaier; Claudia Auw-Hädrich; Nils-Claudius Gellrich; Lutz Lothar Hansen

    1998-01-01

    · Background: To correlate the retinal ganglion cell pattern to visual acuity and visual field data in a patient with bilateral\\u000a optic disc drusen, a quantitative clinicopathological study was carried out. · Methods: Both retinae of a patient with optic\\u000a drusen were whole-mounted. Retinal ganglion cell counts were made using a sampling scheme covering the whole retina and compared\\u000a to

  14. Correlation of Blue-on-Yellow Visual Fields With Scanning Confocal Laser Optic Disc Measurements

    Microsoft Academic Search

    Pait Teesalu; Kyosti Vihanninjoki; P. Juhani Airaksinen; Anja Tuulonen

    Purpose. Visual field defects and changes in the optic nerve head are signs of glaucoma. It has been shown that blue-on-yellow (B-Y) perimetry can reveal visual field defects earlier and shows them larger than does white-on-white (W-W) perimetry. The Heidelberg retina tomograph (HRT) can produce three-dimensional images of the optic disc. The aim of this study was to find out

  15. Analysis of the Correlation Among Age, Disc Morphology, Positive Discography and Prognosis in Patients With Chronic Low Back Pain

    PubMed Central

    Kim, Seung-Min; Lee, Bo-Ram; Hwang, Jeong-Won

    2015-01-01

    Objective To investigate the correlation among age, disc morphology, positive discography, and prognosis in patients with chronic low back pain. Methods A total of 183 intervertebral discs in 72 patients with chronic low back pain were studied. Discography was performed using a pressure-controlled manometric technique. The pain reaction during discography at each level was recorded as follows: no pain, dissimilar pain, similar pain, or concordant pain. Discs with similar or concordant pain were classified as positive. All the examined discs were assessed morphologically using axial computed tomography imaging. The grade of general degeneration and annular disruption of the discs were assessed according to the Dallas discogram description (DDD). Intradiscal injection of steroid was tried for patients with symptomatic disc identified during provocative discography and who did not consent to surgical operation. Results There was a higher correlation between general degeneration and age, as compared with annular disruption and age. Higher general degeneration and annular disruption grades had higher positive rates of discography. However, annular disruption alone was independently associated with positive discography. Age and grade of general degeneration did not affect the prognosis. Conclusion The grade of general degeneration was associated with age, but it was not correlated with positive discography and prognosis. In addition, high grade of annular disruption correlated with positive discography. PMID:26161339

  16. Mechanical properties of human lumbar spine motion segments. Influence of age, sex, disc level, and degeneration.

    PubMed

    Nachemson, A L; Schultz, A B; Berkson, M H

    1979-01-01

    The influences of age, sex, disc level, and degree of degenration on the mechanical behavior of 42 fresh cadaver lumbar motion segments are reported. The motions and intradiscal pressure changes that result from the application of flexion, extension, lateral bending, and torsional moments; compression; and anterior, posterior, and lateral shears are described. The authors find that the mean behaviors of the different segment classes sometimes differ, but these differences are seldom pronounced. Scatter in the behavior of individual motion segments is pronounced, and very often overshadows any class differences. PMID:432710

  17. Bilateral acute anterior uveitis and optic disc edema following a snake bite.

    PubMed

    Kumar, Praveen K; Ahuja, Shashi; Kumar, Praveen S

    2014-04-01

    The authors wish to report a case of bilateral acute anterior uveitis and optic disc edema following a hemotoxic snake bite, in order to highlight the concomitant occurrence of these conditions and the potential adverse effects of anti-snake venom (ASV). A 35-year-old male was bitten by a viper at seventeen thirty hours, and was started on ASV. Two days following treatment he experienced sudden onset redness and painful diminution of vision in both eyes (OU). On examination, the patient's visual acuity (VA) in OU was 20/200. Examination revealed fresh keratic precipitates, cells, and flare in the anterior chamber (AC), posterior synechiae, sluggish and ill-sustained pupillary reaction, and hyperemic, edematous disc with blurred margins in OU. He was started on topical steroids, cycloplegics and intravenous methylprednisolone. Following treatment, the patient showed improvement and was continued on topical medications and oral prednisolone tapered over 3 weeks, after which VA OU improved, the AC showed no cells and flare and disc edema resolved. Uveitis and optic disc edema in snake bite can either be due to the direct toxic effects of the venom or the effect of ASV. Steroids have a beneficial role in the management of these symptoms. PMID:24688264

  18. The impact of accretion disc winds on the optical spectra of cataclysmic variables

    NASA Astrophysics Data System (ADS)

    Matthews, J. H.; Knigge, C.; Long, K. S.; Sim, S. A.; Higginbottom, N.

    2015-07-01

    Many high-state non-magnetic cataclysmic variables (CVs) exhibit blueshifted absorption or P-Cygni profiles associated with ultraviolet (UV) resonance lines. These features imply the existence of powerful accretion disc winds in CVs. Here, we use our Monte Carlo ionization and radiative transfer code to investigate whether disc wind models that produce realistic UV line profiles are also likely to generate observationally significant recombination line and continuum emission in the optical waveband. We also test whether outflows may be responsible for the single-peaked emission line profiles often seen in high-state CVs and for the weakness of the Balmer absorption edge (relative to simple models of optically thick accretion discs). We find that a standard disc wind model that is successful in reproducing the UV spectra of CVs also leaves a noticeable imprint on the optical spectrum, particularly for systems viewed at high inclination. The strongest optical wind-formed recombination lines are H ? and He II ?4686. We demonstrate that a higher density outflow model produces all the expected H and He lines and produces a recombination continuum that can fill in the Balmer jump at high inclinations. This model displays reasonable verisimilitude with the optical spectrum of RW Trianguli. No single-peaked emission is seen, although we observe a narrowing of the double-peaked emission lines from the base of the wind. Finally, we show that even denser models can produce a single-peaked H ? line. On the basis of our results, we suggest that winds can modify, and perhaps even dominate, the line and continuum emission from CVs.

  19. Application of vascular bundle displacement in the optic disc for glaucoma detection using fundus images.

    PubMed

    Fuente-Arriaga, José Abel de la; Felipe-Riverón, Edgardo M; Garduño-Calderón, Eduardo

    2014-04-01

    This paper presents a methodology for glaucoma detection based on measuring displacements of blood vessels within the optic disc (vascular bundle) in human retinal images. The method consists of segmenting the region of the vascular bundle in an optic disc to set a reference point in the temporal side of the cup, determining the position of the centroids of the superior, inferior, and nasal vascular bundle segmented zones located within the segmented region, and calculating the displacement from normal position using the chessboard distance metric. The method was successful in 62 images out of 67, achieving 93.02% sensitivity, 91.66% specificity, and 91.34% global accuracy in pre-diagnosis. PMID:24530536

  20. Method and system for assigning a confidence metric for automated determination of optic disc location

    DOEpatents

    Karnowski, Thomas P. (Knoxville, TN); Tobin, Jr., Kenneth W. (Harriman, TN); Muthusamy Govindasamy, Vijaya Priya (Knoxville, TN); Chaum, Edward (Memphis, TN)

    2012-07-10

    A method for assigning a confidence metric for automated determination of optic disc location that includes analyzing a retinal image and determining at least two sets of coordinates locating an optic disc in the retinal image. The sets of coordinates can be determined using first and second image analysis techniques that are different from one another. An accuracy parameter can be calculated and compared to a primary risk cut-off value. A high confidence level can be assigned to the retinal image if the accuracy parameter is less than the primary risk cut-off value and a low confidence level can be assigned to the retinal image if the accuracy parameter is greater than the primary risk cut-off value. The primary risk cut-off value being selected to represent an acceptable risk of misdiagnosis of a disease having retinal manifestations by the automated technique.

  1. Optical Disc Technology and the Cooperative Television Library.

    ERIC Educational Resources Information Center

    Kranch, Douglas

    1989-01-01

    Discusses the feasibility of individual television film libraries combining film holdings onto optical disks and developing networks that would allow online searching of, access to, and transmission of video images. It is concluded that recent advances in technology would support fast and cost effective image retrieval with no loss in video…

  2. Optical Pickup for Compact Disc Player Using Computer-Generated Hologram and Reflection-Type Grating

    Microsoft Academic Search

    Chul Woo Lee; Chong Sam Chung

    1993-01-01

    A functional prototype of an optical pickup using a Computer-generated hologram (CGH) has been developed for compact disc player (CDP). A 780 nm-wavelength laser diode, a finite conjugated objective lens, and a reflection-type grating are used in the pickup. The fringe pattern of the CGH functions as cylindrical and negative power lenses, and produces astigmatism for focusing signal to the

  3. An Approach to Identify Optic Disc in Human Retinal Images Using Ant Colony Optimization Method

    Microsoft Academic Search

    Ganesan Kavitha; Swaminathan Ramakrishnan

    2010-01-01

    In this work, an attempt has been made to identify optic disc in retinal images using digital image processing and optimization\\u000a based edge detection algorithm. The edge detection was carried out using Ant Colony Optimization (ACO) technique with and\\u000a without pre-processing and was correlated with morphological operations based method. The performance of the pre-processed\\u000a ACO algorithm was analysed based on

  4. Ultrafast Localization of the Optic Disc Using Dimensionality Reduction of the Search Space

    Microsoft Academic Search

    Ahmed Essam Mahfouz; Ahmed S. Fahmy

    2009-01-01

    Optic Disc (OD) localization is an important pre-processing step that significantly simplifies subsequent segmentation of\\u000a the OD and other retinal structures. Current OD localization techniques suffer from impractically-high computation times (few minutes\\/image). In this work, we present an ultrafast technique that requiresless than a second to localize the OD. The technique is based on reducing the dimensionality of the search

  5. Optic Disc Segmentation by Means of GA-Optimized Topological Active Nets

    Microsoft Academic Search

    J. Novo; Manuel G. Penedo; José Santos

    2008-01-01

    In this paper we propose a new approach to the optic disc segmentation process in digital retinal images by means of Topological\\u000a Active Nets (TAN). This is a deformable model used for image segmentation that integrates features of region-based and edge-based\\u000a segmentation techniques, being able to fit the edges of the objects and model their inner topology. The optimization of

  6. Automatic Tracing of Optic Disc and Exudates from Color Fundus Images Using Fixed and Variable Thresholds

    Microsoft Academic Search

    Ahmed Wasif Reza; Chantra Eswaran; Subhas Hati

    2009-01-01

    The detection of bright objects such as optic disc (OD) and exudates in color fundus images is an important step in the diagnosis\\u000a of eye diseases such as diabetic retinopathy and glaucoma. In this paper, a novel approach to automatically segment the OD\\u000a and exudates is proposed. The proposed algorithm makes use of the green component of the image and

  7. Automatic detection of optic disc based on PCA and mathematical morphology.

    PubMed

    Morales, Sandra; Naranjo, Valery; Angulo, Us; Alcaniz, Mariano

    2013-04-01

    The algorithm proposed in this paper allows to automatically segment the optic disc from a fundus image. The goal is to facilitate the early detection of certain pathologies and to fully automate the process so as to avoid specialist intervention. The method proposed for the extraction of the optic disc contour is mainly based on mathematical morphology along with principal component analysis (PCA). It makes use of different operations such as generalized distance function (GDF), a variant of the watershed transformation, the stochastic watershed, and geodesic transformations. The input of the segmentation method is obtained through PCA. The purpose of using PCA is to achieve the grey-scale image that better represents the original RGB image. The implemented algorithm has been validated on five public databases obtaining promising results. The average values obtained (a Jaccard's and Dice's coefficients of 0.8200 and 0.8932, respectively, an accuracy of 0.9947, and a true positive and false positive fractions of 0.9275 and 0.0036) demonstrate that this method is a robust tool for the automatic segmentation of the optic disc. Moreover, it is fairly reliable since it works properly on databases with a large degree of variability and improves the results of other state-of-the-art methods. PMID:23314772

  8. Lens-scanning Raman microspectroscopy system using compact disc optical pickup technology.

    PubMed

    Kim, Jaeyoun; Liu, Gang; Lee, Luke

    2005-06-13

    We propose and demonstrate the adoption of the compact disc optical pickup technology for Raman microspectroscopy. We utilize both the focusing and the 2-dimensional lateral scanning capabilities of the optical pickup for implementing a miniaturized microspectroscopy system. The resolution of this pickup-based system is characterized by scanning polystyrene microspheres. We test the completed microspectroscopy system by obtaining Raman images of Adenine microstructures. This system will be particularly useful for table-top biological analyzers and other remote medicine applications. PMID:19495396

  9. From the channel model of an InSb-based superresolution optical disc system to impulse response and resolution limits.

    PubMed

    Hepper, Dietmar

    2011-06-10

    The signal model of a superresolution optical channel can be an efficient tool for developing components of an associated high-density optical disc system. While the behavior of the laser diode, aperture, lens, and detector are properly described, a general mathematical model of the superresolution disc itself has not yet been available until recently. Different approaches have been made to describe the properties of a mask layer, mainly based on temperature- or power-dependent nonlinear effects. A complete signal-based or phenomenological optical channel model--from non-return-to-zero inverted input to disc readout signal--has recently been developed including the reflectivity of a superresolution disc with InSb used for the mask layer. In this contribution, the model is now extended and applied to a moving disc including a land-and-pit structure, and results are compared with data read from real superresolution discs. Both impulse response and resolution limits are derived and discussed. Thus the model provides a bridge from physical to readout signal properties, which count after all. The presented approach allows judging of the suitability of a mask layer material for storage density enhancement already based on static experiments, i.e., even before developing an associated disc drive. PMID:21673750

  10. Are the broad optical Balmer lines in PG 1613+658 from the central accretion disc?

    NASA Astrophysics Data System (ADS)

    Zhang, Xue-Guang

    2015-02-01

    In this letter, we report on the positive correlations between the broad-line width and broad-line flux for the broad Balmer lines of the active galactic nucleus (AGN) PG 1613+658, which has been observed for a long time. Rather than the expected negative correlations that come with the widely accepted virialization assumption for AGN broad emission-line regions (BLRs), the positive correlations indicate very different BLR structures of PG 1613+658 from the commonly considered BLR structures that are dominated by the equilibrium between radiation pressure and gas pressure. Therefore, it is preferable to assume that the observed broad single-peaked optical Balmer lines of PG 1613+658 originate from the accretion disc, because the mainly gravity-dominated disc-like BLRs with radial structures have few effects from radiation pressure.

  11. Computation models simulating notochordal cell extinction during early ageing of an intervertebral disc.

    PubMed

    Louman-Gardiner, K M; Coombe, D; Hunter, C J

    2011-12-01

    Lower back pain due to intervertebral disc (IVD) degeneration is a prevalent problem which drastically affects the quality of life of millions of sufferers. Healthy IVDs begin with high populations of notochordal cells in the nucleus pulposus, while by the second stage of degeneration, these cells will be replaced by chondrocyte-like cells. Because the IVD is avascular, these cells rely on passive diffusion of nutrients to survive. It is thought that this transition in cell phenotype causes the shift of the IVD's physical properties, which impede the flow of nutrients. Our computational model of the IVD illustrates its ability to simulate the evolving chemical and mechanical environments occurring during the early ageing process. We demonstrate that, due to the insufficient nutrient supply and accompanying changes in physical properties of the IVD, there was a resultant exponential decay in the number of notochordal cells over time. PMID:21424951

  12. Segmentation of Color Fundus Images of the Human Retina: Detection of the Optic Disc and the Vascular Tree Using Morphological Techniques

    Microsoft Academic Search

    Thomas Walter; Jean-claude Klein

    2001-01-01

    This paper presents new algorithms based on mathematical morphology for the detection of the optic disc and the vascular tree\\u000a in noisy low contrast color fundus photographs. Both features - vessels and optic disc - deliver landmarks for image registration\\u000a and are indispensable to the understanding of retinal fundus images. For the detection of the optic disc, we first find

  13. Influence of optic-disc size on parameters of retinal nerve fibre analysis as measured using GDx VCC and ECC in healthy subjects

    Microsoft Academic Search

    Hemma Resch; Gabor Deak; Clemens Vass

    2010-01-01

    BackgroundTo date, there is no knowledge on the impact of optic-disc size on the retinal nerve fibre layer (RNFL) as measured with GDx VCC or GDx ECC. Since the size of the optic disc is not taken into account for the analyses carried out by the GDx, it might affect sensitivity in large optic discs and specificity in small ones.MethodsTopographic

  14. Behaviour of disc oedema during and after amiodarone optic neuropathy: case report.

    PubMed

    Martínez-LóPez-Portillo, Med Alejandro; Martínez-Gamero, Bertha O; Mohamed-Noriega, Jibran; Cavazos-Adame, Med Humberto; Mohamed-Hamsho, Med Jesús

    2014-04-01

    A 73-year-old woman with atrial fibrillation treated with Amiodarone presented with Optic Disc oedema in right eye (OD). Using Optical Coherence Tomography (OCT) we describe the impact of this neuropathy on Retinal Nerve Fibre Layer (RNFL). At diagnosis RNFL average was of 188 ?m OD and 77 ?m in the left eye (OS), six months after discontinuation of the drug decreased to 40 ?m in OD and 76 ?m in OS. The RNFL average of OD presented a transient increase during the acute oedema that returned to normal levels during the first month after discontinuation of the drug and fell dramatically to 44 ?m at the second month and 40 ?m at the sixth month. We show there is axonal loss after amiodarone-associated optic neuropathy measured with OCT. The OCT may be used in these patients to document changes in RNFL in the follow-up. PMID:24959500

  15. Genome-wide association identifies ATOH7 as a major gene determining human optic disc size.

    PubMed

    Macgregor, Stuart; Hewitt, Alex W; Hysi, Pirro G; Ruddle, Jonathan B; Medland, Sarah E; Henders, Anjali K; Gordon, Scott D; Andrew, Toby; McEvoy, Brian; Sanfilippo, Paul G; Carbonaro, Francis; Tah, Vikas; Li, Yi Ju; Bennett, Sonya L; Craig, Jamie E; Montgomery, Grant W; Tran-Viet, Khanh-Nhat; Brown, Nadean L; Spector, Timothy D; Martin, Nicholas G; Young, Terri L; Hammond, Christopher J; Mackey, David A

    2010-07-01

    Optic nerve assessment is important for many blinding diseases, with cup-to-disc ratio (CDR) assessments commonly used in both diagnosis and progression monitoring of glaucoma patients. Optic disc, cup, rim area and CDR measurements all show substantial variation between human populations and high heritability estimates within populations. To identify loci underlying these quantitative traits, we performed a genome-wide association study in two Australian twin cohorts and identified rs3858145, P=6.2x10(-10), near the ATOH7 gene as associated with the mean disc area. ATOH7 is known from studies in model organisms to play a key role in retinal ganglion cell formation. The association with rs3858145 was replicated in a cohort of UK twins, with a meta-analysis of the combined data yielding P=3.4x10(-10). Imputation further increased the evidence for association for several SNPs in and around ATOH7 (P=1.3x10(-10) to 4.3x10(-11), top SNP rs1900004). The meta-analysis also provided suggestive evidence for association for the cup area at rs690037, P=1.5x10(-7), in the gene RFTN1. Direct sequencing of ATOH7 in 12 patients with optic nerve hypoplasia, one of the leading causes of blindness in children, revealed two novel non-synonymous mutations (Arg65Gly, Ala47Thr) which were not found in 90 unrelated controls (combined Fisher's exact P=0.0136). Furthermore, the Arg65Gly variant was found to have very low frequency (0.00066) in an additional set of 672 controls. PMID:20395239

  16. Segmentation of the optic disc, macula and vascular arch in fundus photographs.

    PubMed

    Niemeijer, Meindert; Abràmoff, Michael D; van Ginneken, Bram

    2007-01-01

    An automatic system is presented to find the location of the major anatomical structures in color fundus photographs; the optic disc, the macula, and the vascular arch. These structures are found by fitting a single point-distribution-model to the image, that contains points on each structure. The method can handle optic disc and macula centered images of both the left and the right eye. The system uses a cost function, which is based on a combination of both global and local cues, to find the correct position of the model points. The global terms in the cost function are based on the orientation and width of the vascular pattern in the image. The local term is derived from the image structure around the points of the model. To optimize the fit of the point-distribution-model to an image, a sophisticated combination of optimization processes is proposed which combines optimization in the parameter space of the model and in the image space, where points are moved directly. Experimental results are presented demonstrating that our specific choices for the cost function components and optimization scheme are needed to obtain good results. The system was developed and trained on a set of 500 screening images, and tested on a completely independent set of 500 screening images. In addition to this the system was also tested on a separate set of 100 pathological images. In the screening set it was able to find the vascular arch in 93.2%, the macula in 94.4%, the optic disc location in 98.4% and whether it is dealing with a left or right eye in 100% of all tested cases. For the pathological images test set, this was 77.0%, 92.0%, 94.0%, and 100% respectively. PMID:17243590

  17. Automated identification of exudates and optic disc based on inverse surface thresholding.

    PubMed

    Yazid, Haniza; Arof, Hamzah; Isa, Hazlita Mohd

    2012-06-01

    This paper presents a new approach to detect exudates and optic disc from color fundus images based on inverse surface thresholding. The strategy involves the applications of fuzzy c-means clustering, edge detection, otsu thresholding and inverse surface thresholding. The main advantage of the proposed approach is that it does not depend on manually selected parameters that are normally chosen to suit the tested databases. When applied to two sets of databases the proposed method outperforms a method based on watershed segmentation. PMID:21318328

  18. Optical Spectroscopic Monitoring of Parachute Yarn Aging

    SciTech Connect

    Tallant, D.R.; Garcia, M.J.; Simpson, R.L.; Behr, V.L.; Whinery, L.D.; Peng, L.W.

    1999-04-01

    Optical spectroscopic techniques were evaluated as nondestructive monitors of the aging of parachutes in nuclear weapons. We analyzed thermally aged samples of nylon and Kevlar webbing by photoluminescence spectroscopy and reflection spectroscopy. Infrared analysis was also performed to help understand the degradation mechanisms of the polymer materials in the webbing. The photoluminescence and reflection spectra were analyzed by chemometric data treatment techniques to see if aged-induced changes in the spectra correlated to changes in measured tensile strength. A correlation was found between the shapes of the photoluminescent bands and the measured tensile strengths. Photoluminescent spectra can be used to predict the tensile strengths of nylon and Kevlar webbing with sufficient accuracy to categorize the webbing sample as above rated tensile strength, marginal or below rated tensile strength. The instrumentation required to perform the optical spectroscopic measurement can be made rugged, compact and portable. Thus, optical spectroscopic techniques offer a means for nondestructive field monitoring of parachutes in the enduring stockpile/

  19. Detection of optic disc change with the Heidelberg retina tomograph before confirmed visual field change in ocular hypertensives converting to early glaucoma

    Microsoft Academic Search

    D S Kamal; A C Viswanathan; D F Garway-Heath; R A Hitchings; D Poinoosawmy; C Bunce

    1999-01-01

    AIMTo determine whether analysis of sequential optic disc images obtained with the Heidelberg retina tomograph (HRT) is able to demonstrate optic disc change before the development of reproducible field defects in a group of ocular hypertensive (OHT) patients converting to early glaucoma.METHODSTwo groups were analysed: (1) 13 eyes of 13 OHT patients who subsequently developed reproducible field defects (converters); and

  20. Detection of neovascularization in the optic disc using an AM-FM representation, granulometry, and vessel segmentation.

    PubMed

    Agurto, Carla; Yu, Honggang; Murray, Victor; Pattichis, Marios S; Barriga, Simon; Bauman, Wendall; Soliz, Peter

    2012-01-01

    Neovascularization, defined as abnormal formation of blood vessels in the retina, is a sight-threatening condition indicative of late-stage diabetic retinopathy (DR). Ischemia due to leakage of blood vessels causes the body to produce new and weak vessels that can lead to complications such as vitreous hemorrhages. Neovascularization on the disc (NVD) is diagnosed when new vessels are located within one disc-diameter of the optic disc. Accurately detecting NVD is important in preventing vision loss due to DR. This paper presents a method for detecting NVD in digital fundus images. First, a region of interest (ROI) containing the optic disc is manually selected from the image. By adaptively combining contrast enhancement methods with a vessel segmentation technique, the ROI is reduced to the regions indicated by the segmented vessels. Textural features extracted by using amplitude-modulation frequency-modulation (AM-FM) techniques and granulometry are used to differentiate NVD from a normal optic disc. Partial least squares is used to perform the final classification. Leave-one-out cross-validation was used to evaluate the performance of the system with 27 NVD and 30 normal cases. We obtained an area under the receiver operator characteristic curve (AUC) of 0.85 by using all features, increasing to 0.94 with feature selection. PMID:23367037

  1. Propriospinal Myoclonus Induced by a Herniated Lumbar Intervertebral Disc at a Young Age: A Case Report

    PubMed Central

    Song, Kwan Su; Kim, Chang Hyun; Lee, Ho Kook

    2011-01-01

    The cause of propriospinal myoclonus (PSM) is idiopathic. Cervical trauma, ischemic myelopathy secondary to a spinal dural arteriovenous fistula, syringomyelia, Lyme neuroborreliosis, human immunodeficiency virus central nervous system infection, and cervical disc herniation can be the cause of PSM, but lumbar herniated intervertebral disc (HIVD) induced PSM has not been reported. We describe a patient who presented with PSM induced by HIVD and was treated with an epidural steroid injection using a transforaminal approach.

  2. The effect of cell age on chloroplast structure and chlorophyll in cultured spinach leaf discs

    Microsoft Academic Search

    D. G. Cran; J. V. Possingham

    1974-01-01

    Summary Discs from young spinach leaves show a 50-fold increase in fresh weight and a 10-fold increase in chlorophyll over 7 days when cultured in high intensity white light (6.5 mWcm?2). In darkness the increase in fresh weight is 10-fold while chlorophyll decreases. Discs from mature spinach leaves show only a 2-fold increase in fresh weight and a marked decrease

  3. Automated Optic Disc Detection in Retinal Images of Patients with Diabetic Retinopathy and Risk of Macular Edema

    Microsoft Academic Search

    Arturo Aquino; Manuel Emilio Geg; Diego Mar ´ in

    In this paper, a new automated methodology to detect the optic disc (OD) automatically in retinal images from patients with risk of being affected by Diabetic Retinopathy (DR) and Macular Edema (ME) is presented. The detection procedure comprises two independent methodologies. On one hand, a location methodology obtains a pixel that belongs to the OD using image contrast analysis and

  4. Automatic detection of the optic disc, fovea and vascular arch in digital color photographs of the retina

    Microsoft Academic Search

    Meindert Niemeijer; Bram van Ginneken

    We present a novel method that determines whether a macula centered retinal image is from the left or right eye and automatically detects the optic disc, the fovea and the vascular arch by inferring the location of a set of landmarks placed on these structures. The algorithm relies on a specific energy function that combines global and local cues. The

  5. Comparing Neural Networks and Linear Discriminant Functions for Glaucoma Detection Using Confocal Scanning Laser Ophthalmoscopy of the Optic Disc

    Microsoft Academic Search

    Christopher Bowd; Kwokleung Chan; Linda M. Zangwill; Michael H. Goldbaum; Te-Won Lee; Terrence J. Sejnowski; Robert N. Weinreb

    2002-01-01

    PURPOSE. To determine whether neural network techniques can improve differentiation between glaucomatous and non- glaucomatous eyes, using the optic disc topography parame- ters of the Heidelberg Retina Tomograph (HRT; Heidelberg Engineering, Heidelberg, Germany) . METHODS. With the HRT, one eye was imaged from each of 108 patients with glaucoma (defined as having repeatable visual field defects with standard automated perimetry)

  6. The chemical morphology of age-related changes in human intervertebral disc glycosaminoglycans from cervical, thoracic and lumbar nucleus pulposus and annulus fibrosus.

    PubMed Central

    Scott, J E; Bosworth, T R; Cribb, A M; Taylor, J R

    1994-01-01

    Hyaluronan (HA), chondroitin and keratan sulphates (CS, KS), collagen and dry weights were measured in the annulus fibrosus and nucleus pulposus of human cervical, thoracic and lumbar intervertebral discs aged 36-79 y. Alcian blue-critical electrolyte concentration (CEC) staining of sections extended the results. The collagen, total polyanion, HA, CS and KS contents of the nucleus pulposus and annulus fibrosus were plotted for all 3 regions against age. Regional differences and age-related trends were found. For regional differences, the collagen content of the nucleus pulposus was highest in cervical discs and lowest in lumbar discs. In contrast, the total polyanion content of the nucleus pulposus was highest in lumbar discs and lowest in cervical discs. These differences were seen in fetal and adult discs. With respect to age-related trends, the collagen content of the annulus fibrosus was higher in adults and children than in neonates and infants. The collagen content of the nucleus pulposus increased with age in thoracic and lumbar discs, but it was consistently high in cervical discs. There was generally a downward trend of total polyanion and CS with increase in age. This was quite consistent for the annulus fibrosus in all regions and there were dramatic decreases in the lumbar nucleus pulposus in all adults compared with infants and children. These trends were least evident in the cervical nucleus pulposus where infant values were low. CS changes correlated with water content. HA and KS increased in all discs with increasing maturity. Oversulphated KS, absent from fetal discs, reached mature levels by 10 y. Many of the changes occurred before maturity. Glycosaminoglycan (GAG) levels correlated with increasing compressive loads. Higher collagen levels in the cervical nucleus pulposus correlated with greater ranges of torsional and shearing strains in cervical discs. High GAG levels in cervical annulus fibrosus probably facilitate lamellar movements during torsional and flexional movements by lubrication and increase of tissue compressibility. Increased KS/CS ratios before maturity correlated with decreased disc blood supply. Ambient O2 tensions may determine KS/CS balance, the former consuming little O2 during biosynthesis. Images Fig. 7 PMID:8157495

  7. Optical methods for diagnostics and feedback control in laser-induced regeneration of spine disc and joint cartilages

    NASA Astrophysics Data System (ADS)

    Sobol, Emil; Sviridov, Alexander; Omeltchenko, Alexander; Baum, Olga; Baskov, Andrey; Borchshenko, Igor; Golubev, Vladimir; Baskov, Vladimir

    2011-03-01

    In 1999 we have introduced a new approach for treatment of spine diseases based on the mechanical effect of nondestructive laser radiation on the nucleus pulposus of the intervertebral disc. Laser reconstruction of spine discs (LRD) involves puncture of the disc and non-destructive laser irradiation of the nucleus pulposus to activate reparative processes in the disc tissues. In vivo animal study has shown that LRD allows activate the growth of hyaline type cartilage in laser affected zone. The paper considers physical processes and mechanisms of laser regeneration, presents results of investigations aimed to optimize laser settings and to develop feedback control system for laser reparation in cartilages of spine and joints. The results of laser reconstruction of intervertebral discs for 510 patients have shown substantial relief of back pain for 90% of patients. Laser technology has been experimentally tested for reparation of traumatic and degenerative diseases in joint cartilage of 20 minipigs. It is shown that laser regeneration of cartilage allows feeling large (more than 5 mm) defects which usually never repair on one's own. Optical techniques have been used to promote safety and efficacy of the laser procedures.

  8. Inter and intraobserver variation in the analysis of optic disc images: comparison of the Heidelberg retina tomograph and computer assisted planimetry

    Microsoft Academic Search

    D F Garway-Heath; D Poinoosawmy; G Wollstein; A Viswanathan; D Kamal; L Fontana; R A Hitchings

    1999-01-01

    AIMSThe development of imaging and measurement techniques has brought the prospect of greater objectivity in the measurement of optic disc features, and therefore better agreement between observers. The purpose of this study was to quantify and compare the variation between observers using two measurement devices.METHODSOptic disc photographs and images from the Heidelberg retina tomograph (HRT) of 30 eyes of 30

  9. Automated segmentation of optic disc region on retinal fundus photographs: Comparison of contour modeling and pixel classification methods.

    PubMed

    Muramatsu, Chisako; Nakagawa, Toshiaki; Sawada, Akira; Hatanaka, Yuji; Hara, Takeshi; Yamamoto, Tetsuya; Fujita, Hiroshi

    2011-01-01

    The automatic determination of the optic disc area in retinal fundus images can be useful for calculation of the cup-to-disc (CD) ratio in the glaucoma screening. We compared three different methods that employed active contour model (ACM), fuzzy c-mean (FCM) clustering, and artificial neural network (ANN) for the segmentation of the optic disc regions. The results of these methods were evaluated using new databases that included the images captured by different camera systems. The average measures of overlap between the disc regions determined by an ophthalmologist and by using the ACM (0.88 and 0.87 for two test datasets) and ANN (0.88 and 0.89) methods were slightly higher than that by using FCM (0.86 and 0.86) method. These results on the unknown datasets were comparable with those of the resubstitution test; this indicates the generalizability of these methods. The differences in the vertical diameters, which are often used for CD ratio calculation, determined by the proposed methods and based on the ophthalmologist's outlines were even smaller than those in the case of the measure of overlap. The proposed methods can be useful for automatic determination of CD ratios. PMID:20546966

  10. Age related reduction of T1rho and T2 magnetic resonance relaxation times of lumbar intervertebral disc.

    PubMed

    Wang, Yi-Xiang J; Griffith, James F; Leung, Jason C S; Yuan, Jing

    2014-08-01

    This report aims to study the age related T1rho and T2 relaxation time changes in lumbar intervertebral disc. Lumbar sagittal magnetic resonance imaging (MRI) was performed with a 3 Tesla scanner in 52 subjects. With a spin-lock frequency of 500 Hz, T1rho was measured using a rotary echo spin-lock pulse embedded in a 3D balanced fast field echo sequence. A multi-echo turbo spin echo sequence was used for T2 mapping. Regions-of-interest were drawn over the T1rho and T2 maps, including nucleus pulposus and annulus fibrosus. For L1/2-L4/5 discs, results showed the age associated reduction of T1rho of nucleus pulposus had a of slope of -1.06, the reduction of T2 of nucleus pulposus had a slope of -1.47, the reduction of T1rho of annulus fibrosus had a slope of -0.25, and the reduction of T2 of annulus fibrosus had a slope of -0.18, with all the slopes significantly non-zero. In nucleus pulposus the slope of T2 was slightly steeper than that of T1rho (P=0.085), while in annulus fibrosus the slope of T1rho was slightly steeper than that of T2 (P=0.31). We conclude that significant age related reduction of T1rho and T2 magnetic resonance relaxation times of lumbar intervertebral disc was observed, however, the relative performances of T1rho vs. T2 were broadly similar. PMID:25202661

  11. Age related reduction of T1rho and T2 magnetic resonance relaxation times of lumbar intervertebral disc

    PubMed Central

    Griffith, James F.; Leung, Jason C. S.; Yuan, Jing

    2014-01-01

    This report aims to study the age related T1rho and T2 relaxation time changes in lumbar intervertebral disc. Lumbar sagittal magnetic resonance imaging (MRI) was performed with a 3 Tesla scanner in 52 subjects. With a spin-lock frequency of 500 Hz, T1rho was measured using a rotary echo spin-lock pulse embedded in a 3D balanced fast field echo sequence. A multi-echo turbo spin echo sequence was used for T2 mapping. Regions-of-interest were drawn over the T1rho and T2 maps, including nucleus pulposus and annulus fibrosus. For L1/2-L4/5 discs, results showed the age associated reduction of T1rho of nucleus pulposus had a of slope of –1.06, the reduction of T2 of nucleus pulposus had a slope of –1.47, the reduction of T1rho of annulus fibrosus had a slope of –0.25, and the reduction of T2 of annulus fibrosus had a slope of –0.18, with all the slopes significantly non-zero. In nucleus pulposus the slope of T2 was slightly steeper than that of T1rho (P=0.085), while in annulus fibrosus the slope of T1rho was slightly steeper than that of T2 (P=0.31). We conclude that significant age related reduction of T1rho and T2 magnetic resonance relaxation times of lumbar intervertebral disc was observed, however, the relative performances of T1rho vs. T2 were broadly similar. PMID:25202661

  12. Learning-based approach for the automatic detection of the optic disc in digital retinal fundus photographs.

    PubMed

    Wong, D K; Liu, J; Tan, N M; Yin, F; Lee, B H; Wong, T Y

    2010-01-01

    The optic disc is an important feature in the retina. We propose a method for the detection of the optic disc based on a supervised learning scheme. The method employs pixel and local neighbourhood features extracted from the ROI of a digital retinal fundus photograph. A support vector machine based classification mechanism is used to classify each image point as belonging to the cup and retina. The proposed method is evaluated on a sample image set of 68 retinal fundus images. The results show a high correlation (r>0.9) with the ground truth segmentation, with an overlap error of 6.02%, and found to be comparable to the inter-observer variability based on an independent second observer segmentation of the same data set. PMID:21096259

  13. Diagnosis of Diabetic Retinopathy: Automatic Extraction of Optic Disc and Exudates from Retinal Images using Marker-controlled Watershed Transformation

    Microsoft Academic Search

    Ahmed Wasif Reza; C. Eswaran; Kaharudin Dimyati

    Due to increasing number of diabetic retinopathy cases, ophthalmologists are experiencing serious problem to automatically\\u000a extract the features from the retinal images. Optic disc (OD), exudates, and cotton wool spots are the main features of fundus\\u000a images which are used for diagnosing eye diseases, such as diabetic retinopathy and glaucoma. In this paper, a new algorithm\\u000a for the extraction of

  14. Size of the optic nerve scleral canal and comparison with intravital determination of optic disc dimensions

    Microsoft Academic Search

    Jost B. Jonas; Gabriele C. Gusek; Irene Guggenmoos-Holzmann; Gottfried O. H. Naumann

    1988-01-01

    Diameters, area, and form of the optic nerve scleral canal were measured in 107 freshly enucleated, unfixed, human donor eyes. Macrophotographs of the sectioned posterior fundus pole were provided with a millimeter scale and evaluated planimetrically. They revealed a surprising variation: area: 2.59 ± 0.72 mm2 (minimum 0.68 mm2, maximum 4.42 mm2); minimal diameter: 1.67 ± 0.72 mm; maximal diameter:

  15. Accurate and efficient optic disc detection and segmentation by a circular transformation.

    PubMed

    Lu, Shijian

    2011-12-01

    Under the framework of computer-aided diagnosis, this paper presents an accurate and efficient optic disc (OD) detection and segmentation technique. A circular transformation is designed to capture both the circular shape of the OD and the image variation across the OD boundary simultaneously. For each retinal image pixel, it evaluates the image variation along multiple evenly-oriented radial line segments of specific length. The pixels with the maximum variation along all radial line segments are determined, which can be further exploited to locate both the OD center and the OD boundary accurately. Experiments show that OD detection accuracies of 99.75%, 97.5%, and 98.77% are obtained for the STARE dataset, the ARIA dataset, and the MESSIDOR dataset, respectively, and the OD center error lies around six pixels for the STARE dataset and the ARIA dataset which is much smaller than that of state-of-the-art methods ranging 14-29 pixels. In addition, the OD segmentation accuracies of 93.4% and 91.7% are obtained for STARE dataset and ARIA dataset, respectively, that consists of many severely degraded images of pathological retinas that state-of-the-art methods cannot segment properly. Furthermore, the algorithm runs in 5 s, which is substantially faster than many of the state-of-the-art methods. PMID:21843983

  16. Fast localization of the optic disc using projection of image features.

    PubMed

    Mahfouz, Ahmed E; Fahmy, Ahmed S

    2010-12-01

    Optic Disc (OD) localization is an important pre-processing step that significantly simplifies subsequent segmentation of the OD and other retinal structures. Current OD localization techniques suffer from impractically-high computation times (few minutes per image). In this work, we present a fast technique that requires less than a second to localize the OD. The technique is based upon obtaining two projections of certain image features that encode the x- and y- coordinates of the OD. The resulting 1-D projections are then searched to determine the location of the OD. This avoids searching the 2-D image space and, thus, enhances the speed of the OD localization process. Image features such as retinal vessels orientation and the OD brightness are used in the current method. Four publicly-available databases, including STARE and DRIVE, are used to evaluate the proposed technique. The OD was successfully located in 330 images out of 340 images (97%) with an average computation time of 0.65 s. PMID:20550999

  17. Ultrafast localization of the optic disc using dimensionality reduction of the search space.

    PubMed

    Mahfouz, Ahmed Essam; Fahmy, Ahmed S

    2009-01-01

    Optic Disc (OD) localization is an important pre-processing step that significantly simplifies subsequent segmentation of the OD and other retinal structures. Current OD localization techniques suffer from impractically-high computation times (few minutes/image). In this work, we present an ultrafast technique that requires less than a second to localize the OD. The technique is based on reducing the dimensionality of the search space by projecting the 2D image feature space onto two orthogonal (x- and y-) axes. This results in two 1D signals that can be used to determine the x- and y- coordinates of the OD. Image features such as retinal vessels orientation and the OD brightness and shape are used in the current method. Four publicly-available databases, including STARE and DRIVE, were used to evaluate the proposed technique. The OD was successfully located in 330 images out of 340 images (97%) with an average computation time of 0.65 seconds. PMID:20426207

  18. Circumpapillary Course of Retinal Pigment Epithelium Can Be Fit to Sine Wave and Amplitude of Sine Wave Is Significantly Correlated with Ovality Ratio of Optic Disc

    PubMed Central

    Yoshihara, Naoya; Terasaki, Hiroto; Kii, Yuya; Tanaka, Minoru; Nakao, Kumiko

    2015-01-01

    The purpose of this study was to develop a method of quantifying the degree of optic disc tilt in normal eyes. This was a prospective, observational cross sectional study of 126 right eyes of 126 healthy volunteers. The optic disc tilt was determined from the circular peripapillary optical coherence tomographic (OCT) scan images. The course of the retinal pigment epithelium (RPE) layer in the peripapillary cross sectional scan images was fit to a sine wave curve, and the amplitude of the sine curve was used to reflect the degree of the optic disc tilt in the optical axis. The repeatability of the amplitude determinations was calculated. The correlation between the amplitude and the ovality ratio of the optic disc was determined. The correlation between the amplitude and the body height was also calculated. The mean amplitudewas 36.6 ± 17.5 pixels, which was significantly and inversely correlated with the ovality ratio of the optic disc (R = -0.59, P<0.001). The intra-rater and inter-rater correlation coefficients of the amplitude were significant high (P<0.001, both). The amplitude was significantly and inversely correlated with the body height (R = -0.38, P<0.001), but not with the axial length. In conclusion, a sine wave function can be used to describe the course of the RPE in the circumpapillary OCT images. The results indicate that the amplitude of the sine wave can be used to represent the degree of optic disc tilt. Thus, the sine wave analyses can be used as a quantifiable and repeatable method to determine the optic disc tilt. PMID:25848777

  19. Obtaining optic disc center and pixel region by automatic thresholding methods on morphologically processed fundus images.

    PubMed

    Marin, Diego; Gegundez-Arias, Manuel E; Suero, Angel; Bravo, Jose M

    2015-02-01

    Development of automatic retinal disease diagnosis systems based on retinal image computer analysis can provide remarkably quicker screening programs for early detection. Such systems are mainly focused on the detection of the earliest ophthalmic signs of illness and require previous identification of fundal landmark features such as optic disc (OD), fovea or blood vessels. A methodology for accurate center-position location and OD retinal region segmentation on digital fundus images is presented in this paper. The methodology performs a set of iterative opening-closing morphological operations on the original retinography intensity channel to produce a bright region-enhanced image. Taking blood vessel confluence at the OD into account, a 2-step automatic thresholding procedure is then applied to obtain a reduced region of interest, where the center and the OD pixel region are finally obtained by performing the circular Hough transform on a set of OD boundary candidates generated through the application of the Prewitt edge detector. The methodology was evaluated on 1200 and 1748 fundus images from the publicly available MESSIDOR and MESSIDOR-2 databases, acquired from diabetic patients and thus being clinical cases of interest within the framework of automated diagnosis of retinal diseases associated to diabetes mellitus. This methodology proved highly accurate in OD-center location: average Euclidean distance between the methodology-provided and actual OD-center position was 6.08, 9.22 and 9.72 pixels for retinas of 910, 1380 and 1455 pixels in size, respectively. On the other hand, OD segmentation evaluation was performed in terms of Jaccard and Dice coefficients, as well as the mean average distance between estimated and actual OD boundaries. Comparison with the results reported by other reviewed OD segmentation methodologies shows our proposal renders better overall performance. Its effectiveness and robustness make this proposed automated OD location and segmentation method a suitable tool to be integrated into a complete prescreening system for early diagnosis of retinal diseases. PMID:25433912

  20. Comparison of optical and electrical investigations of meat ageing

    NASA Astrophysics Data System (ADS)

    Prokopyeva, Elena; Tománek, Pavel; Kocová, Lucie; Palai-Dany, Tomáš; Balík, Zden?k.; Škarvada, Pavel; Grmela, Lubomír.

    2013-05-01

    Different ultrasonic, electromagnetic, electrical and optical methods are used for meat ageing detection. Muscles are turbid anisotropic media, they exhibit changes in electrical and optical properties according to the direction of the electrical and optical fields in the sample. The work assesses the feasibility of impedance measurements for meat ageing detection and their comparison with optical measurement of scattered light. The pork chop slices were used for their relative homogeneity. An investigation was carried out for the detection of the ageing of unpacked slices exposed directly to the air, and other packed in polyethylene bags. The electrical method is a promising method due to the possibility of getting much information and realizing cheap and fast enough measurement systems. The optical method allows measure the rotation of polarization plane in the range of 95 degrees within considered period. Nevertheless, further work has to be provided to determine closer relationships between optical scattering characteristics, electrical anisotropy in ageing-related tissue structural properties.

  1. Thermal Aging Reliability of Package-Level Polymer Optical Waveguides

    Microsoft Academic Search

    Shashikant G. Hegde; Suresh K. Sitaraman

    2008-01-01

    Polymer optical waveguides are viewed as a potential interconnect solution in board-level optoelectronic systems. In this paper, the optical loss changes in siloxane polymer waveguides during thermal aging conditions are studied for the wavelengths of 850 and 1310 nm. The optical loss in waveguides during intended operation and temperature exposure can increase due to factors such as oxidation of waveguides,

  2. Age-related decline of human optic nerve axon populations

    Microsoft Academic Search

    Betty M. Johnson; Michael Miao; Alfredo A. Sadun

    1987-01-01

    Human intracranial optic nerves were morphometrically examined to determine whether retinal ganglion cell axon populations\\u000a vary with age. A high-contrast lipid stain, paraphenylene-diamine (PPD), and a video image measurement system were employed\\u000a to sufficiently resolve the optic nerve fiber image for measurement at 5600X magnification. Total axon population decreased\\u000a with increasing age; mean axon diameter and optic nerve area did

  3. Genome-wide association studies in Asians confirm the involvement of ATOH7 and TGFBR3, and further identify CARD10 as a novel locus influencing optic disc area.

    PubMed

    Khor, Chiea Chuen; Ramdas, Wishal D; Vithana, Eranga N; Cornes, Belinda K; Sim, Xueling; Tay, Wan-Ting; Saw, Seang-Mei; Zheng, Yingfeng; Lavanya, Raghavan; Wu, Renyi; Wang, Jie Jin; Mitchell, Paul; Uitterlinden, André G; Rivadeneira, Fernando; Teo, Yik-Ying; Chia, Kee-Seng; Seielstad, Mark; Hibberd, Martin; Vingerling, Johannes R; Klaver, Caroline C W; Jansonius, Nomdo M; Tai, E-Shyong; Wong, Tien-Yin; van Duijn, Cornelia M; Aung, Tin

    2011-05-01

    Damage to the optic nerve (e.g. from glaucoma) has an adverse and often irreversible impact on vision. Earlier studies have suggested that the size of the optic nerve head could be governed by hereditary factors. We conducted a genome-wide association study (GWAS) on 4445 Singaporean individuals (n = 2132 of Indian and n = 2313 of Malay ancestry, respectively), with replication in Rotterdam, the Netherlands (n = 9326 individuals of Caucasian ancestry) using the most widely reported parameter for optic disc traits, the optic disc area. We identified a novel locus on chromosome 22q13.1, CARD10, which strongly associates with optic disc area in both Singaporean cohorts as well as in the Rotterdam Study (RS; rs9607469, per-allele change in optic disc area = 0.051 mm(2); P(meta) = 2.73×10(-12)) and confirmed the association between CDC7/TGFBR3 (lead single nucleotide polymorphism (SNP) rs1192415, P(meta) = 7.57×10(-17)) and ATOH7 (lead SNP rs7916697, P(meta) = 2.00 × 10(-15)) and optic disc area in Asians. This is the first Asian-based GWAS on optic disc area, identifying a novel locus for the optic disc area, but also confirming the results found in Caucasian persons suggesting that there are general genetic determinants applicable to the size of the optic disc across different ethnicities. PMID:21307088

  4. Lumbar Disc Herniation in Adolescence

    Microsoft Academic Search

    Serdar Ozgen; Deniz Konya; O. Zafer Toktas; Adnan Dagcinar; M. Memet Ozek

    2007-01-01

    Lumbar disc herniation very rarely occurs in adolescence. The aim of this study was to assess the radiological, clinical and surgical features and case outcomes for adolescents with lumbar disc herniation, and to compare with adult cases. The cases of 17 adolescents (7 girls and 10 boys, age range 13–17 years) who were surgically treated for lumbar disc herniation in

  5. Raman optical activity comes of age

    Microsoft Academic Search

    Laurence D. Barron; Lutz Hecht; Iain H. McColl; Ewan W. Blanch

    2004-01-01

    The theory and applications of Raman optical activity (ROA), which measures vibrational optical activity by means of a small difference in the intensity of Raman scattering from chiral molecules in right- and left-circularly polarized incident light or, equivalently, a small circularly polarized component in the scattered light, are briefly reviewed. Thanks to new developments in instrumentation, ROA may be applied

  6. A search for eclipsing binaries that host discs

    NASA Astrophysics Data System (ADS)

    Meng, Zeyang; Quillen, Alice C.; Bell, Cameron P. M.; Mamajek, Eric E.; Scott, Erin L.; Zhou, Ji-Lin

    2014-07-01

    We search for systems hosting eclipsing discs using a complete sample of eclipsing binaries (EBs); those previously identified in the third phase of the Optical Gravitational Lensing Experiment (OGLE-III). Within a subsample of 2823 high-cadence, high-photometric precision and large eclipsing depth detached EBs previously identified in the Large Magellanic Cloud (LMC), we find that the skewness and kurtosis of the light-curve magnitude distribution within the primary eclipse can distinguish EBs with a complex-shaped eclipse from those without. Two systems with previously identified eclipsing discs (OGLE-LMC-ECL-11893 and OGLE-LMC-ECL-17782) are identified with near zero skewness (|S| < 0.5) and positive kurtosis. No additional eclipsing disc systems were found in the OGLE-III LMC, Small Magellanic Cloud or Galactic Disc EB light curves. We estimate that the fraction of detached early-type LMC EBs (which have a primary with an I-band magnitude brighter than ?19 mag) that exhibit atypical eclipses and so could host a disc is approximately 1/1000. As circumstellar disc lifetimes are short, we expected to primarily find eclipsing discs around young stars. In addition, as there is more room for a disc in a widely separated binary and because a disc close to a luminous star would be above the dust sublimation temperature, we expected to primarily find eclipsing discs in long-period binaries. However, OGLE-LMC-ECL-17782 is a 13.3 d period B star system with a transient and hot (˜6000 K, ˜0.1 au radius) disc and Scott et al. estimate an age of 150 Myr for OGLE-LMC-ECL-11893. Both discs are unexpected in the EB sample and impel explanation.

  7. The Palenque Optical Disc Prototype: Design of Multimedia Experiences for Education and Entertainment in a Nontraditional Learning Context. Technical Report No. 44.

    ERIC Educational Resources Information Center

    Wilson, Kathleen S.

    This report describes Palenque, an interactive, multimedia, optical disc research prototype developed for home use by 8- to 14-year-old children and their families. The report begins by providing an overview of the project, which is followed by a discussion of the target audience and context for use of the videodisc. A discussion of learning…

  8. Use of sequential Heidelberg retina tomograph images to identify changes at the optic disc in ocular hypertensive patients at risk of developing glaucoma

    Microsoft Academic Search

    D S Kamal; D F Garway-Heath; R A Hitchings; F W Fitzke

    2000-01-01

    AIMTo determine if global and segmental changes in optic disc parameters of sequential Heidelberg retina tomograph (HRT) images develop in individual ocular hypertensive (OHT) patients without white on white visual field defects.METHODSPatients and normal controls were recruited from a prospective ocular hypertension treatment trial. The subject groups consisted of 21 OHT patients who had converted to early glaucoma on the

  9. Design, Installation and Post-Implementation Assessment of an Optical Disc Based Storage and Retrieval System for Images of Engineering Contract Documents.

    ERIC Educational Resources Information Center

    Ashford, J. H.; Masters, A. M.

    1992-01-01

    Describes an image storage system for contract documentation in the Engineering Directorate of Thames Water Utilities (England) which uses optical disc storage and a relational database for indexing and retrieval of nearly 500,000 pages in compressed image format, and provides end user access through 7 workstations. Requirements, feasibility…

  10. Diagnosis of diabetic retinopathy: automatic extraction of optic disc and exudates from retinal images using marker-controlled watershed transformation.

    PubMed

    Reza, Ahmed Wasif; Eswaran, C; Dimyati, Kaharudin

    2011-12-01

    Due to increasing number of diabetic retinopathy cases, ophthalmologists are experiencing serious problem to automatically extract the features from the retinal images. Optic disc (OD), exudates, and cotton wool spots are the main features of fundus images which are used for diagnosing eye diseases, such as diabetic retinopathy and glaucoma. In this paper, a new algorithm for the extraction of these bright objects from fundus images based on marker-controlled watershed segmentation is presented. The proposed algorithm makes use of average filtering and contrast adjustment as preprocessing steps. The concept of the markers is used to modify the gradient before the watershed transformation is applied. The performance of the proposed algorithm is evaluated using the test images of STARE and DRIVE databases. It is shown that the proposed method can yield an average sensitivity value of about 95%, which is comparable to those obtained by the known methods. PMID:20703768

  11. Aging behavior of optical fibers in aqueous environments

    NASA Astrophysics Data System (ADS)

    Lindholm, Eric A.; Li, Jie; Hokansson, Adam; Slyman, Brian; Burgess, David

    2004-09-01

    Silica optical fibers drawn from a common preform and coated with specialty coatings were exposed to zero-stress aging in various aqueous environments for approximately ten months. The strength of the fiber samples was tracked with two-point bend testing. The onset of an aging "knee" was observed for some fiber samples while other coatings offered enhanced protection from the effects of moisture-induced strength degradation.

  12. The Coming of Age of Adaptive Optics

    NASA Astrophysics Data System (ADS)

    1995-10-01

    How Ground-Based Astronomers Beat the Atmosphere Adaptive Optics (AO) is the new ``wonder-weapon'' in ground-based astronomy. By means of advanced electro-optical devices at their telescopes, astronomers are now able to ``neutralize'' the image-smearing turbulence of the terrestrial atmosphere (seen by the unaided eye as the twinkling of stars) so that much sharper images can be obtained than before. In practice, this is done with computer-controlled, flexible mirrors which refocus the blurred images up to 100 times per second, i.e. at a rate that is faster than the changes in the atmospheric turbulence. This means that finer details in astronomical objects can be studied and also - because of the improved concentration of light in the telescope's focal plane - that fainter objects can be observed. At the moment, Adaptive Optics work best in the infrared part of spectrum, but at some later time it may also significantly improve observations at the shorter wavelengths of visible light. The many-sided aspects of this new technology and its impact on astronomical instrumentation was the subject of a recent AO conference [1] with over 150 participants from about 30 countries, presenting a total of more than 100 papers. The Introduction of AO Techniques into Astronomy The scope of this meeting was the design, fabrication and testing of AO systems, characterisation of the sources of atmospheric disturbance, modelling of compensation systems, individual components, astronomical AO results, non-astronomical applications, laser guide star systems, non-linear optical phase conjugation, performance evaluation, and other areas of this wide and complex field, in which front-line science and high technology come together in a new and powerful symbiosis. One of the specific goals of the meeting was to develop contacts between AO scientists and engineers in the western world and their colleagues in Russia and Asia. For the first time at a conference of this type, nine Russian scientists were invited to give presentations; this was made possible by a grant from the European Office of Aerospace Research and Development (EOARD) Following the declassification of much AO technology and the introduction of AO into regular astronomical research several years ago, first at ESO with the ``Come-On'' system at La Silla [2], the fundamental importance of AO to ground-based astronomy has now become widely recognised. Since the last AO meeting that was held in Garching in August 1993, many groups in different countries have been developing such systems and have begun to use them. As Fritz Merkle (Carl Zeiss, Jena) emphasized during a review talk, there has also been an interesting opening of new commercial and industrial AO applications, such as for high power lasers and for laser communications systems. However, the chief field of AO development and application remains astronomy and the vast majority of papers presented at the conference were concerned, directly or indirectly, with this science. Towards Scientific and Technological Maturity According to Martin Cullum (ESO), the organiser of this conference, it is apparent that a certain technological maturity has been reached during the past two years. However, it is also much more widely realised that it is not straightforward to produce good science, even with a high-performance AO system. A detailed characterization of the atmosphere, painstaking system calibrations and a lot of hard work during the astronomical observations and especially at the time of the reduction and interpretation of the voluminous datasets are necessary to obtain reliable results of high quality. Many of the presentations reflected this fact. From the technical standpoint, highlights of the meeting included the significant progress that was reported in the development of adaptive secondary mirrors for the upgrade of the Multi-Mirror-Telescope (MMT) in Arizona, the initial tests of the laser guide-star AO system installed on the Lick 3-metre telescope in California, as well as the development of an advanced visible-light AO

  13. Topographic Differences in the Age-Related Changes in the Retinal Nerve Fiber Layer of Normal Eyes Measured by Stratus™ Optical Coherence Tomography

    PubMed Central

    Feuer, William J.; Budenz, Donald L.; Anderson, Douglas R.; Cantor, Louis; Greenfield, David S.; Savell, Jonathan; Schuman, Joel S.; Varma, Rohit

    2010-01-01

    Purpose To determine whether there are regional differences in the age-related changes in peripapillary retinal nerve fiber layer thickness as measured by time-domain optical coherence tomography (OCT). Methods Fast peripapillary RNFL scans obtained with the Stratus™ time-domain OCT with nominal diameter of 3.46 mm centered on the optic disc were performed on 425 normal subjects over a wide age range. One eye was randomly selected for scanning or analysis. Average RNFL-, clock hour-, and quadrant-specific rates of RNFL thickness change were calculated and compared. Results The 425 study participants ranged in age from 18 to 85 years with mean (±SD) of 46 (±15) years. The mean (±SD) average measured RNFL thickness was 104.7 (±10.8) micrometers (?m). The decline in the average RNFL thickness was 2.4 ?m per decade of age. Changes in RNFL thickness per decade of age ranged from -5.4 (p<0.001) at clock hour 12 to -0.9 (p=0.28) at clock hour 6. Similarly, the rate of thickness change per decade of age in the superior quadrant was -4.3 (p<0.001) versus -1.5 (p=0.006) in the inferior quadrant. The slopes of thinning superiorly and inferiorly were highly significantly different (p=0.001). Conclusions The age-related decline in normal RNFL measurements does not occur at equal rates around the disc and occurs mainly superiorly. PMID:20577113

  14. The sensitivity and specificity of direct ophthalmoscopic optic disc assessment in screening for glaucoma: a multivariate analysis

    Microsoft Academic Search

    Robert Harper; Barnaby Reeves

    2000-01-01

    Background: Previous studies have shown that the cup:disc (C\\/D) ratio has limited sensitivity and specificity. Improved sensitivity and\\u000a specificity has been found with combinations of disc parameters using stereophotography or disc imaging, but the extent to\\u000a which these studies reflect what can be achieved by direct assessment is unclear. The purpose of this paper is to report the\\u000a sensitivities and

  15. Inter- and intraobserver variation in the analysis of optic disc images: comparison of the Heidelberg retina tomograph and computer assisted planimetry

    PubMed Central

    Garway-Heath, D; Poinoosawmy, D; Wollstein, G; Viswanathan, A; Kamal, D; Fontana, L; Hitchings, R

    1999-01-01

    AIMS—The development of imaging and measurement techniques has brought the prospect of greater objectivity in the measurement of optic disc features, and therefore better agreement between observers. The purpose of this study was to quantify and compare the variation between observers using two measurement devices.?METHODS—Optic disc photographs and images from the Heidelberg retina tomograph (HRT) of 30 eyes of 30 subjects were presented to six observers for analysis, and to one observer on five separate occasions. Agreement between observers was studied by comparing the analysis of each observer with the median result of the other five, and expressed as the mean difference and standard deviation of differences between the observer and the median. Inter- and intraobserver variation was calculated as a coefficient of variation (mean SD/mean × 100).?RESULTS—For planimetry, agreement between observers was dependent on observer experience, for the HRT it was independent. Agreement between observers (SD of differences as a percentage of the median) for optic disc area was 4.0% to 7.2% (planimetry) and 3.3% to 6.0% (HRT), for neuroretinal rim area it was 10.8% to 21.0% (planimetry) and 5.2% to 9.6% (HRT). The mean interobserver coefficient of variation for optic disc area was 8.1% (planimetry) and 4.4% (HRT), for neuroretinal rim area it was 16.3% (planimetry) and 8.1% (HRT), and (HRT only) for rim volume was 16.3%, and reference height 9.1%. HRT variability was greater for the software version 1.11 reference plane than for version 1.10. The intraobserver coefficient of variation for optic disc area was 1.5% (planimetry) and 2.4% (HRT), for neuroretinal rim area it was 4.0% (planimetry) and 4.5% (HRT).?CONCLUSIONS—Variation between observers is greatly reduced by the HRT when compared with planimetry. However, levels of variation, which may be clinically significant, remain for variables that depend on the subjective drawing of the disc margin.?? PMID:10340972

  16. Indium Phosphide Planar Integrated Optics Comes of Age Jens Noeckel

    E-print Network

    Nöckelm, Jens

    Indium Phosphide Planar Integrated Optics Comes of Age Jens Noeckel Tom Pierson Jane Zucker exceeds supply. Indium Phosphide: Adapting Form to Function PLCs can serve many roles in fiberoptic of the spectrum, the current material of choice is indium phosphide. When compared with the sophistication

  17. Photogrammetry of the optic disc in glaucoma and ocular hypertension with simultaneous stereo photography

    Microsoft Academic Search

    Chris A. Johnson; John L. Keltner; Marijane A. Krohn; Gerald L. Portney

    Stereophotogrammetric evaluations of the optic cup were performed for normal, ocular hy- pertensive, and glaucomatous eyes. Average volume, area, and depth measurements were progressively larger from normal to ocular hypertensive to glaucomatous eyes, although the distributions of individual values exhibited considerable overlap among the three groups. Similar results were obtained for volume, area, and depth asymmetry between each pair of

  18. The Use of WORM Optical Disc Storage for Newspaper Cuttings in a Public Library.

    ERIC Educational Resources Information Center

    Fulton, Alan R.

    1990-01-01

    Describes the collection of the Local History Department of the Central Library in Aberdeen (which includes 2,300 volumes of locally produced newspapers and 101,000 sheets of press cuttings) and the use of an optical disk system to help solve the problems of storage and access to these materials. (CLB)

  19. AUTOMATIC EXTRACTION OF THE OPTIC DISC BOUNDARY FOR DETECTING RETINAL DISEASES

    E-print Network

    Li, Baihua

    Boundary extraction, fundus image, Automatic Feature Detection, Glaucoma, Active Shape Model 1 Introduction or geometrical, can be used to determine the occurrence of retinal diseases such as Glaucoma. Glaucoma is one.7% of the cases being affected by it [19]. Glaucoma leads to irreversible structural changes in the Optic Nerve

  20. Detecting the optic disc boundary in digital fundus images using morphological, edge detection, and feature extraction techniques.

    PubMed

    Aquino, Arturo; Gegundez-Arias, Manuel Emilio; Marin, Diego

    2010-11-01

    Optic disc (OD) detection is an important step in developing systems for automated diagnosis of various serious ophthalmic pathologies. This paper presents a new template-based methodology for segmenting the OD from digital retinal images. This methodology uses morphological and edge detection techniques followed by the Circular Hough Transform to obtain a circular OD boundary approximation. It requires a pixel located within the OD as initial information. For this purpose, a location methodology based on a voting-type algorithm is also proposed. The algorithms were evaluated on the 1200 images of the publicly available MESSIDOR database. The location procedure succeeded in 99% of cases, taking an average computational time of 1.67 s. with a standard deviation of 0.14 s. On the other hand, the segmentation algorithm rendered an average common area overlapping between automated segmentations and true OD regions of 86%. The average computational time was 5.69 s with a standard deviation of 0.54 s. Moreover, a discussion on advantages and disadvantages of the models more generally used for OD segmentation is also presented in this paper. PMID:20562037

  1. Optical coherence tomography as approach for the minimal invasive localization of the germinal disc in ovo before chicken sexing

    NASA Astrophysics Data System (ADS)

    Burkhardt, Anke; Geissler, Stefan; Koch, Edmund

    2010-04-01

    In most industrial states a huge amount of newly hatched male layer chickens are usually killed immediately after hatching by maceration or gassing. The reason for killing most of the male chickens of egg producing races is their slow growth rate compared to races specialized on meat production. When the egg has been laid, the egg contains already a small disc of cells on the surface of the yolk known as the blastoderm. This region is about 4 - 5 mm in diameter and contains the information whether the chick becomes male or female and hence allows sexing of the chicks by spectroscopy and other methods in the unincubated state. Different imaging methods like sonography, 3D-X-ray micro computed tomography and magnetic resonance imaging were used for localization of the blastoderm until now, but found to be impractical for different reasons. Optical coherence tomography (OCT) enables micrometer-scale, subsurface imaging of biological tissue and could therefore be a suitable technique for an accurate localization. The intention of this study is to prove if OCT can be an appropriate approach for the precise in ovo localization.

  2. Accretion discs

    NASA Astrophysics Data System (ADS)

    Abramowicz, Marek A.; Straub, Odele

    2014-08-01

    Accretion discs are flattened astronomical objects made of rapidly rotating gas which slowly spirals onto a central gravitating body. The gravitational energy of infalling matter extracted in accretion discs powers stellar binaries, active galactic nuclei, proto-planetary discs and some gamma-ray bursts. The black hole accretion in quasars is the most powerful and efficient stationary engine known in the universe. In accretion discs the high angular momentum of rotating matter is gradually transported outwards by stresses (related to turbulence, viscosity, shear and magnetic fields). This gradual loss of angular momentum allows matter to progressively move inwards, towards the centre of gravity. The gravitational energy of the gaseous matter is thereby converted to heat. A fraction of the heat is converted into radiation, which partially escapes and cools down the accretion disc. Accretion disc physics is thus governed by a non-linear combination of many processes, includ! ing gravity, hydrodynamics, viscosity, radiation and magnetic fields.

  3. A trifurcated fiber-optic-probe-based optical system designed for AGEs measurement

    NASA Astrophysics Data System (ADS)

    Wang, Yikun; Zhang, Long; Zhu, Ling; Liu, Yong; Zhang, Gong; Wang, An

    2012-03-01

    Advanced Glycation End-products (AGEs) are biochemical end-products of non-enzymatic glycation and are formed irreversibly in human serum and skin tissue. AGEs are thought to play an important role in the pathogenesis of diabetes and corresponding complications. All conventional methods for measuring AGEs must take sampling and measure in vitro. These methods are invasive and have the problem of relatively time-consuming. AGEs have fluorescent characteristics. Skin AGEs can be assessed noninvasively by collecting the fluorescence emitted from skin tissue when excited with proper light. However, skin tissue has absorption and scattering effects on fluorescence of AGEs, it is not reliable to evaluate the accumulation of AGEs according the emitted fluorescence but not considering optical properties of skin tissue. In this study, a portable system for detecting AGEs fluorescence and skin reflectance spectrum simultaneously has been developed. The system mainly consists of an ultraviolet light source, a broadband light source, a trifurcated fiber-optic probe, and a compact charge coupled device (CCD) spectrometer. The fiber-optic probe consists of 36 optical fibers which are connected to the ultraviolet light source, 6 optical fibers connected to the broadband light source, and a core fiber connected to the CCD spectrometer. Demonstrative test measurements with the system on skin tissue of 40 healthy subjects have been performed. Using parameters that are calculated from skin reflectance spectrum, the distortion effects caused by skin absorption and scattering can be eliminated, and the integral intensity of corrected fluorescence has a strong correlation with the accumulation of AGEs. The system looks very promising for both laboratory and clinical applications to monitor AGEs related diseases, especially for chronic diabetes and complications.

  4. A trifurcated fiber-optic-probe-based optical system designed for AGEs measurement

    NASA Astrophysics Data System (ADS)

    Wang, Yikun; Zhang, Long; Zhu, Ling; Liu, Yong; Zhang, Gong; Wang, An

    2011-11-01

    Advanced Glycation End-products (AGEs) are biochemical end-products of non-enzymatic glycation and are formed irreversibly in human serum and skin tissue. AGEs are thought to play an important role in the pathogenesis of diabetes and corresponding complications. All conventional methods for measuring AGEs must take sampling and measure in vitro. These methods are invasive and have the problem of relatively time-consuming. AGEs have fluorescent characteristics. Skin AGEs can be assessed noninvasively by collecting the fluorescence emitted from skin tissue when excited with proper light. However, skin tissue has absorption and scattering effects on fluorescence of AGEs, it is not reliable to evaluate the accumulation of AGEs according the emitted fluorescence but not considering optical properties of skin tissue. In this study, a portable system for detecting AGEs fluorescence and skin reflectance spectrum simultaneously has been developed. The system mainly consists of an ultraviolet light source, a broadband light source, a trifurcated fiber-optic probe, and a compact charge coupled device (CCD) spectrometer. The fiber-optic probe consists of 36 optical fibers which are connected to the ultraviolet light source, 6 optical fibers connected to the broadband light source, and a core fiber connected to the CCD spectrometer. Demonstrative test measurements with the system on skin tissue of 40 healthy subjects have been performed. Using parameters that are calculated from skin reflectance spectrum, the distortion effects caused by skin absorption and scattering can be eliminated, and the integral intensity of corrected fluorescence has a strong correlation with the accumulation of AGEs. The system looks very promising for both laboratory and clinical applications to monitor AGEs related diseases, especially for chronic diabetes and complications.

  5. Segmentation of optic disc in retinal images using an improved gradient vector flow algorithm

    Microsoft Academic Search

    Huiyu Zhou; Gerald Schaefer; Tangwei Liu; Faquan Lin

    2010-01-01

    Image segmentation plays an important role in the analysis of retinal images as the extraction of the optic disk provides\\u000a important cues for accurate diagnosis of various retinopathic diseases. In recent years, gradient vector flow (GVF) based\\u000a algorithms have been used successfully to successfully segment a variety of medical imagery. However, due to the compromise\\u000a of internal and external energy

  6. Measurement of optic disc size: equivalence of methods to correct for ocular magnification

    Microsoft Academic Search

    D F Garway-Heath; A R Rudnicka; T Lowe; P J Foster; F W Fitzke; R A Hitchings

    1998-01-01

    AIMSTo compare methods available to correct the magnification of images that result from the optics of the eye and identify errors, and source of error, of the methods.METHODS11 methods were applied to ocular biometry data from three independent cohorts. Each method was compared with the method of Bennett, which uses most biometric data. The difference between each method and Bennett’s

  7. Design of swing arm actuator for small and slim optical disc drives

    Microsoft Academic Search

    Dong-Ju Lee; Je-Seung Oh; Sa-Ung Kim; Jeong-Hoon Yoo; No-Cheol Park; Young-Pil Park; Takeshi Shimano; Shigeo Nakamura

    2007-01-01

    Recent advancements in mobile devices have fueled a requirement for information storage systems with characteristics such\\u000a as subminiature size, low cost, and minimum power consumption. Small optical disk drives could provide a good solution, because\\u000a their storage media is cheaper than those of hard disk drives or flash memories. In this paper, we proposed the miniaturized\\u000a swing arm type actuator

  8. Herniated lumbar disc

    PubMed Central

    2009-01-01

    Introduction Herniated lumbar disc is a displacement of disc material (nucleus pulposus or annulus fibrosis) beyond the intervertebral disc space. The highest prevalence is among people aged 30-50 years, with a male to female ratio of 2:1. There is little evidence to suggest that drug treatments are effective in treating herniated disc. Methods and outcomes We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of drug treatments, non-drug treatments, and surgery for herniated lumbar disc? We searched: Medline, Embase, The Cochrane Library, and other important databases up to July 2008 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA). Results We found 49 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions. Conclusions In this systematic review, we present information relating to the effectiveness and safety of the following interventions: acupuncture, advice to stay active, analgesics, antidepressants, bed rest, corticosteroids (epidural injections), cytokine inhibitors (infliximab), discectomy (automated percutaneous, laser, microdisectomy, standard), exercise therapy, heat, ice, massage, muscle relaxants, non-steroidal anti-inflammatory drugs (NSAIDs), percutaneous disc decompression, spinal manipulation, and traction. PMID:19445754

  9. MRI Evaluation of Lumbar Disc Degenerative Disease

    PubMed Central

    Patel, Rupal; Mehta, Chetan; Patel, Narrotam

    2015-01-01

    Introduction: Lower back pain secondary to degenerative disc disease is a condition that affects young to middle-aged persons with peak incidence at approximately 40 y. MRI is the standard imaging modality for detecting disc pathology due to its advantage of lack of radiation, multiplanar imaging capability, excellent spinal soft-tissue contrast and precise localization of intervertebral discs changes. Aims and Objective: To evaluate the characterization, extent, and changes associated with the degenerative lumbar disc disease by Magnetic Resonance Imaging. Study Design: Cross-sectional and observational study. Materials and Methods: A total 109 patients of the lumbar disc degeneration with age group between 17 to 80 y were diagnosed & studied on 1.5 Tesla Magnetic Resonance Imaging machine. MRI findings like lumbar lordosis, Schmorl’s nodes, decreased disc height, disc annular tear, disc herniation, disc bulge, disc protrusion and disc extrusion were observed. Narrowing of the spinal canal, lateral recess and neural foramen with compression of nerve roots observed. Ligamentum flavum thickening and facetal arthropathy was observed. Result: Males were more commonly affected in Degenerative Spinal Disease & most of the patients show loss of lumbar lordosis. Decreased disc height was common at L5-S1 level. More than one disc involvement was seen per person. L4 – L5 disc was the most commonly involved. Annular disc tear, disc herniation, disc extrusion, narrowing of spinal canal, narrowing of lateral recess, compression of neural foramen, ligamentum flavum thickening and facetal arthropathy was common at the L4 –L5 disc level. Disc buldge was common at L3 – L4 & L4 – L5 disc level. Posterior osteophytes are common at L3 - L4 & L5 –S1 disc level. L1- L2 disc involvement and spondylolisthesis are less common. Conclusion: Lumbar disc degeneration is the most common cause of low back pain. Plain radiograph can be helpful in visualizing gross anatomic changes in the intervertebral disc. But, MRI is the standard imaging modality for detecting disc pathology due to its advantage of lack of radiation, multiplanar imaging capability, excellent spinal soft-tissue contrast and precise localization of intervertebral discs changes. PMID:26023617

  10. Homozygous FOXE3 mutations cause non-syndromic, bilateral, total sclerocornea, aphakia, microphthalmia and optic disc coloboma

    PubMed Central

    Buentello-Volante, Beatriz; McKibbin, Martin; Rocha-Medina, J. Alberto; Fernandez-Fuentes, Narcis; Koga-Nakamura, Wilson; Ashiq, Aruna; Khan, Kamron; Booth, Adam P.; Williams, Grange; Raashid, Yasmin; Jafri, Hussain; Rice, Aine; Inglehearn, Chris F.; Zenteno, Juan Carlos

    2010-01-01

    Purpose To investigate the genetic basis of recessively-inherited congenital, non syndromic, bilateral, total sclerocornea in two consanguineous pedigrees, one from the Punjab province of Pakistan and the other from the Tlaxcala province of Mexico. Methods Ophthalmic examinations were conducted on each family member to confirm their diagnosis and magnetic resonance imaging (MRI) or ultrasonography of the eyes was performed on some family members. Genomic DNA was analyzed by homozygosity mapping using the Affymetrix 6.0 SNP array and linkage was confirmed with polymorphic microsatellite markers. Candidate genes were sequenced. Results A diagnosis of autosomal recessive sclerocornea was established for 7 members of the Pakistani and 8 members of the Mexican pedigrees. In the Pakistani family we established linkage to a region on chromosome 1p that contained Forkhead Box E3 (FOXE3), a strong candidate gene since FOXE3 mutations had previously been associated with various anterior segment abnormalities. Sequencing FOXE3 identified the previously reported nonsense mutation, c.720C>A, p.C240X, in the Pakistani pedigree and a novel missense mutation which disrupts an evolutionarily conserved residue in the forkhead domain, c.292T>C, p.Y98H, in the Mexican pedigree. Individuals with heterozygous mutations had no ocular abnormalities. MRI or ultrasonography confirmed that the patients with sclerocornea were also aphakic, had microphthalmia and some had optic disc coloboma. Conclusions This is the fourth report detailing homozygous FOXE3 mutations causing anterior segment abnormalities in human patients. Previous papers have emphasized aphakia and microphthalmia as the primary phenotype, but we find that the initial diagnosis – and perhaps the only one possible in a rural setting – is one of non-syndromic, bilateral, total sclerocornea. Dominantly inherited anterior segment defects have also been noted in association with heterozygous FOXE3 mutations. However the absence of any abnormalities in the FOXE3 heterozygotes described suggests that genetic background and environmental factors plays a role in the penetrance of the mutant allele. PMID:20664696

  11. Lens Thickness with Age and Accommodation by Optical Coherence Tomography

    PubMed Central

    Richdale, Kathryn; Bullimore, Mark A.; Zadnik, Karla

    2010-01-01

    Purpose To utilize time-domain optical coherence tomography (OCT) to measure changes in the crystalline lens with age and accommodation. Methods A cross-sectional study of pre-presbyopic and presbyopic subjects was conducted. Amplitude of accommodation was measured with the push-up test. Objective accommodation was measured with the Grand Seiko auto-refractor and a Badal lens system. Lens thickness was measured with the Zeiss Visante OCT and an internal optometer. The data were analyzed using correlation coefficients, linear regression, and by calculating the average change in lens thickness per diopter change in objective accommodation. Results Twenty-two subjects between the ages of 36 and 50 years completed the study. Subjective amplitude of accommodation ranged from 2.17 to 6.38 D. Objective accommodation ranged from 0.22 to 4.56 D. The mean lens thickness was 4.05 ± 0.20 mm. The mean change in lens thickness for up to a 5-D accommodative stimulus ranged from 0.01 to 0.26 mm. The correlation coefficients were: age and subjective accommodation, r = ?0.74; age and objective accommodation, r = ?0.84; change in lens thickness and age, r = ?0.65; change in lens thickness and subjective accommodation, r = 0.74; change in lens thickness and objective accommodation, r = 0.64; objective and subjective accommodation, r = 0.82; (all p < 0.01). An increase in lens thickness of 21 ?m per year of age was determined by linear regression. For the subjects who showed at least 1 D of accommodative response on the Grand Seiko auto-refractor, there was an increase of 51 ± 19 ?m per diopter of accommodation. Conclusions OCT is a non-invasive technique that can be used to quantify changes in the thickness of the crystalline lens. Subjective and objective measurements of accommodation, as well as age, were robustly correlated with the measured changes in lens thickness. Lens thickness changes with age and accommodation as measured with the Visante OCT compare well with previous findings using Scheimpflug photography and ultrasound. PMID:18761481

  12. Optical characters and texture maps of skin and the aging mechanism by use of multiphoton microscopy and optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Wu, Shulian; Li, Hui; Zhang, Xiaoman; Huang, Yudian; Xu, Xiaohui

    2012-03-01

    Cutaneous aging is a complicated biological process affecting different constituents of skin, which can be divided into two types: the chronological aging and the photo-aging. The two cutaneous aging processes often co-exist accompanying with each other. The effects are often overlapped including changes in epithelium and dermis. The degeneration of collagen is a major factor in dermal alteration with aging. In this study, multiphoton microscopy (MPM) with its high resolution imaging and optical coherence tomography (OCT) with its depth resolved imaging were used to study the anti-aging dermatology in vivo. It was attempted to make the optical parameter and texture feature to evaluate the process of aging skin using mathematical image processing. The links among optical parameter, spectrum and texture feature in collagen with aging process were established to uncover mechanism of aging skin.

  13. Structural and optical properties of CuO layered hexagonal discs synthesized by a low-temperature hydrothermal process

    NASA Astrophysics Data System (ADS)

    Abaker, M.; Umar, Ahmad; Baskoutas, S.; Kim, S. H.; Hwang, S. W.

    2011-04-01

    Layered hexagonal discs of CuO were synthesized on a large scale via low-temperature hydrothermal growth process at 130 °C using copper nitrate, hexamethylenediamine and NH4OH. The detailed morphological investigations by field emission scanning electron microscopy and transmission electron microscopy (TEM) clearly revealed that the synthesized CuO structures are made by the well layer-by-layer accumulation of several sheets which arranged themselves in such a special manner that they exhibit the hexagonal discs of CuO. The detailed structural characterizations of the hexagonal CuO discs were done by high-resolution TEM and x-ray diffraction which confirmed that the synthesized structures possessing well nanocrystalline nature and monoclinic structure. The purity and composition of the synthesized products were examined using energy dispersive spectroscopy, elemental mapping and Fourier transform infrared spectroscopy. Using UV-Vis spectroscopy at room temperature we obtained indirect and direct band gap values slightly blue shifted to the bulk values. Finally, a plausible growth mechanism has been proposed for the formation of CuO layered hexagonal discs.

  14. Herniated Lumbar Disc and Lumbar Radiculopathy

    Microsoft Academic Search

    Parviz Kambin

    The satisfactory outcome of arthroscopically and endoscopically assisted management of herniated lumbar discs hinges on accurate\\u000a diagnosis of the symptom-producing site. Although the mean age of onset of symptoms of disc herniation is around 35 yr, disc\\u000a herniations are occasionally observed in populations older than 60 or younger than 20 yr of age. In younger children, combined\\u000a slippage of the

  15. Slope analysis of the optic disc in eyes with ocular hypertension and early normal tension glaucoma by confocal scanning laser ophthalmoscope

    Microsoft Academic Search

    J Dong; E Chihara

    2001-01-01

    AIMSTo determine whether quantitative differences in sector based slope can differentiate between eyes with ocular hypertension with and without glaucomatous disc changes and eyes with normal tension glaucoma with glaucomatous disc changes.METHODSSeventy six eyes with ocular hypertension or early glaucomatous disc changes were consecutively categorised into three groups: 22 eyes with ocular hypertension and no glaucomatous disc changes (OHND); 35

  16. On the reliability of protostellar disc mass measurements and the existence of fragmenting discs

    NASA Astrophysics Data System (ADS)

    Dunham, Michael M.; Vorobyov, Eduard I.; Arce, Héctor G.

    2014-10-01

    We couple non-magnetic, hydrodynamical simulations of collapsing protostellar cores with radiative transfer evolutionary models to generate synthetic observations. We then use these synthetic observations to investigate the extent to which a simple method for measuring protostellar disc masses used in the literature recovers the intrinsic masses of the discs formed in the simulations. We evaluate the effects of contamination from the surrounding core, partially resolving out the disc, optical depth, fixed assumed dust temperatures, inclination, and the dust opacity law. We show that the combination of these effects can lead to disc mass underestimates by up to factors of 2-3 at millimetre wavelengths and up to an order of magnitude or larger at submillimetre wavelengths. The optically thin portions of protostellar discs are generally cooler in the Class I stage than the Class 0 stage since Class I discs are typically larger and more optically thick, and thus more shielded. The observed disc mass distribution closely resembles the intrinsic distribution if this effect is taken into account, especially at millimetre wavelengths where optical depth effects are minimized. Approximately 50-70 per cent of protostellar discs observed to date with this method are consistent with the masses of the gravitationally unstable discs formed in the simulations, suggesting that at least some protostellar discs are likely sufficiently massive to fragment. We emphasize key future work needed to confirm these results, including assembling larger, less biased samples, and using molecular line observations to distinguish between rotationally supported, Keplerian discs and magnetically supported pseudodiscs.

  17. Chemical and optical aging of forest fire plumes

    NASA Astrophysics Data System (ADS)

    Howell, S. G.; Clarke, A. D.; Freitag, S.; Kapustin, V. N.; McNaughton, C. S.; Shank, L.

    2010-12-01

    During recent aircraft-based projects, we have penetrated fresh fire plumes, followed them for tens of kilometers, and sampled them thousands of kms from their sources. Chemical analysis with an Aerosol Mass Spectrometer (AMS) for non-refractory composition and a Single Particle Soot Photometer (SP2) alongside nephelometers and a Particle Soot Absorption Spectrometer (PSAP) for optical properties of the aerosol show consistent changes in particle properties as they age. We use BC to normalize for dilution and scavenging, as it is unlikely to be created outside of the fire. Chemical changes are rapid within the first 50 minutes as the organic matter becomes more oxygenated. Single Scatter Albedo rises concurrently which reflects increasing non-absorbing aerosol mass. Somewhat unexpectedly, the absorption ?ngstrom exponent (between 470 and 660 nm) also rises, indicating that the complex aromatic organic material, sometimes referred to as Brown Carbon, either takes some time to condense or has its absorption amplified as other material condenses upon it. At long range from the source, biomass burning plumes can be significant sources of CCN to remote areas even when diluted and scavenged to such an extent that direct optical effects are inconsequential.

  18. X-ray - UV/optical lag measurement in the very low mass AGN NGC4395 using the OM in sub-second readout mode: Implications for disc models

    NASA Astrophysics Data System (ADS)

    McHardy, I.; Connolly, S.; Gandhi, P.; Peterson, B.; Bieryla, A.; Chand, H.; Kaspi, S.; Uemura, M.; Emmanoulopoulos, D.

    2015-07-01

    The lag between the X-ray and UV/optical variations in AGN is a strong diagnostic of the emission processes in those bands; eg an X-ray lag means that seed photon variations drive X-ray variability but an X-ray lead means that the UV/optical variations result from reprocessing of X-rays by a surrounding accretion disc. Previous RXTE-based observations suggest that the UV/optical usually lags, although with large uncertainty. Recent Swift observations of NGC5548 (McHardy et al 2014; Edelson et al 2015), mass 4e7 solar, confirm a definite UV/optical lag, but the lag is larger than expected from a standard Shakura-Sunyaev disc model. To properly test our understanding of disc models it is vital to make similar lag observations of an AGN of very different mass. Here we report XMM-Newton observations of the low mass (3e5 solar) AGN, NGC4395. Using the OM in sub-second readout mode, we find that UVW1 lags the X-rays (EPIC) by ˜ 450 s. We consider the implications of this result and of parallel ground based g-band observations, together with our previous Swift observations, for our understanding of accretion discs. To the best of our knowledge, these observations represent the first successful use of the OM fast-readout mode for AGN lag measurements.

  19. Herniated Lumbar Disc

    MedlinePLUS

    ... effective as a cushion. This may cause a displacement of the disc’s center (called a herniated or ruptured disc) through a crack in the outer layer. Most disc herniations occur in the bottom two discs of the lumbar spine, at and just below the waist. A herniated ...

  20. Impacts of the induced current on the aging of the ADSS fiber optic cables

    Microsoft Academic Search

    Essam Al-Ammar; George G. Karady; Monty W. Tuominen

    2006-01-01

    An environmental chamber has been built at Arizona State University (ASU) for purpose of establishing a long-term aging test of all dielectric self supporting (ADSS) fiber optic cable. This paper presents an experimental analysis of the effect of the induced current on the aging of two of the cables in the aging chamber. Both cables have polyethylene outer jackets and

  1. Experimental studies of the aging characteristics of the ADSS fiber optic cables

    Microsoft Academic Search

    E. Al-Ammar; G. G. Karady; M. W. Tuominen; D. J. Vermeers

    2007-01-01

    An environmental chamber has been built at Arizona State University (ASU) for purpose of establishing a long-term aging test of All Dielectric Self Supporting (ADSS) fiber optic cable. Six ADSS cables are subjected to UV radiation, salt fog, clean rain and mechanical tension in the aging chamber. This paper briefly compares aging characteristics of six ADSS cables subject to various

  2. Congenital disorders of the optic nerve: excavations and hypoplasia

    Microsoft Academic Search

    G N Dutton

    2004-01-01

    The principal congenital abnormalities of the optic disc that can significantly impair visual function are excavation of the optic disc and optic nerve hypoplasia. The excavated optic disc abnormalities comprise optic disc coloboma, morning glory syndrome, and peripapillary staphyloma. Optic nerve hypoplasia manifests as a small optic nerve, which may or may not be accompanied by a peripapillary ring (the

  3. Effects of scattering and dust grain size on the temperature structure of protoplanetary discs: a three-layer approach

    Microsoft Academic Search

    Akio K. Inoue; Akinori Oka; Taishi Nakamoto

    2009-01-01

    The temperature in the optically thick interior of protoplanetary discs is essential for the interpretation of millimetre observations of the discs, for the vertical structure of the discs, for models of the disc evolution and the planet formation, and for the chemistry in the discs. Since large icy grains have a large albedo even in the infrared, the effect of

  4. Fast and automatic algorithm for optic disc extraction in retinal images using principle-component-analysis-based preprocessing and curvelet transform.

    PubMed

    Shahbeig, Saleh; Pourghassem, Hossein

    2013-01-01

    Optic disc or optic nerve (ON) head extraction in retinal images has widespread applications in retinal disease diagnosis and human identification in biometric systems. This paper introduces a fast and automatic algorithm for detecting and extracting the ON region accurately from the retinal images without the use of the blood-vessel information. In this algorithm, to compensate for the destructive changes of the illumination and also enhance the contrast of the retinal images, we estimate the illumination of background and apply an adaptive correction function on the curvelet transform coefficients of retinal images. In other words, we eliminate the fault factors and pave the way to extract the ON region exactly. Then, we detect the ON region from retinal images using the morphology operators based on geodesic conversions, by applying a proper adaptive correction function on the reconstructed image's curvelet transform coefficients and a novel powerful criterion. Finally, using a local thresholding on the detected area of the retinal images, we extract the ON region. The proposed algorithm is evaluated on available images of DRIVE and STARE databases. The experimental results indicate that the proposed algorithm obtains an accuracy rate of 100% and 97.53% for the ON extractions on DRIVE and STARE databases, respectively. PMID:23455998

  5. Compact Disc Recordable with Substrate of Biomass Plastic Material

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Atsushi; Kodama, Yasuhiro; Matsuo, Hiroto; Ohno, Minoru; Osugi, Satomi; Maeno, Yoshiaki; Higuchi, Masahiro

    2006-08-01

    Polylactic acid (PLA) is a biomass material made of starch. Compact disc recordable (CD-R) discs with a PLA substrate were prepared and their properties were measured. Although the glass transition point of PLA is lower than that of polycarbonate (PC), the PLA substrate is usable for CD-R discs. It was confirmed that the substrate is usable for recordable optical discs at temperatures under 50 °C.

  6. Percutaneous diode laser disc nucleoplasty

    NASA Astrophysics Data System (ADS)

    Menchetti, P. P.; Longo, Leonardo

    2004-09-01

    The treatment of herniated disc disease (HNP) over the years involved different miniinvasive surgical options. The classical microsurgical approach has been substituted over the years both by endoscopic approach in which is possible to practice via endoscopy a laser thermo-discoplasty, both by percutaneous laser disc nucleoplasty. In the last ten years, the percutaneous laser disc nucleoplasty have been done worldwide in more than 40000 cases of HNP. Because water is the major component of the intervertebral disc, and in HNP pain is caused by the disc protrusion pressing against the nerve root, a 980 nm Diode laser introduced via a 22G needle under X-ray guidance and local anesthesia, vaporizes a small amount of nucleous polposus with a disc shrinkage and a relief of pressure on nerve root. Most patients get off the table pain free and are back to work in 5 to 7 days. Material and method: to date, 130 patients (155 cases) suffering for relevant symptoms therapy-resistant 6 months on average before consulting our department, have been treated. Eightyfour (72%) males and 46 (28%) females had a percutaneous laser disc nucleoplasty. The average age of patients operated was 48 years (22 - 69). The level of disc removal was L3/L4 in 12 cases, L4/L5 in 87 cases and L5/S1 in 56 cases. Two different levels were treated at the same time in 25 patients. Results: the success rate at a minimum follow-up of 6 months was 88% with a complication rate of 0.5%.

  7. Clinical Analysis of Disc Battery Ingestion in Children

    Microsoft Academic Search

    Yi-Jung Chang; Hsun-Chin Chao; Man-Shan Kong; Ming-Wei Lai

    Background: The purpose of this study was to evaluate the characteristics, management, and outcomes of disc battery ingestion in children. Methods: We reviewed the medical records of children aged between 1 and 15 years old admitted to Chang Gung Children's Hospital due to disc battery ingestion from September 1997 through July 2003). The diagnosis of disc battery ingestion was based

  8. Intervertebral disc degeneration: evidence for two distinct phenotypes

    PubMed Central

    Adams, Michael A; Dolan, Patricia

    2012-01-01

    We review the evidence that there are two types of disc degeneration. ‘Endplate-driven’ disc degeneration involves endplate defects and inwards collapse of the annulus, has a high heritability, mostly affects discs in the upper lumbar and thoracic spine, often starts to develop before age 30 years, usually leads to moderate back pain, and is associated with compressive injuries such as a fall on the buttocks. ‘Annulus-driven’ disc degeneration involves a radial fissure and/or a disc prolapse, has a low heritability, mostly affects discs in the lower lumbar spine, develops progressively after age 30 years, usually leads to severe back pain and sciatica, and is associated with repetitive bending and lifting. The structural defects which initiate the two processes both act to decompress the disc nucleus, making it less likely that the other defect could occur subsequently, and in this sense the two disc degeneration phenotypes can be viewed as distinct. PMID:22881295

  9. Heidelberg Retina Tomograph Disc Area: Correlation with Glaucoma Severity, Using the Disc Damage Likelihood Scale

    Microsoft Academic Search

    Paul Harasymowycz; Gang Xu; Jonathan Myers; William Steinmann; George L. Spaeth

    Purpose: To determine the correlation of Heidelberg Retina Tomograph disc area (HRT DA) to glaucoma severity, and how the severity of glaucoma may influence this relationship. Definition: The Disc Damage Likelihood Scale (DDLS) is a method of estimating the amount of optic nerve damage based on the width of the neuroretinal rim or the circum- ferential extent of rim absence.

  10. Intra- and inter-observer variation of optic nerve head measurements in glaucoma suspects using disc-data

    Microsoft Academic Search

    Jörg Stürmer; Darmalingam Poinoosawmy; David C. Broadway; Roger A. Hitchings

    1992-01-01

    The aim of this study was to determine the intra- and inter-observer variation in the use of a system designed for exact measurements from standard optic nerve head photographs. The commercially available system consisted of a colour CCD Videocamera, a dedicated frame grabber and customised software run on a IBM AT compatible computer. Masked measurements were made 3 times by

  11. Baseline Topographic Optic Disc Measurements Are Associated With the Development of Primary Open-Angle Glaucoma: The Confocal Scanning Laser Ophthalmoscopy Ancillary Study to the Ocular Hypertension Treatment Study

    Microsoft Academic Search

    Linda M. Zangwill; Robert N. Weinreb; Julia A. Beiser; Charles C. Berry; George A. Cioffi; Anne L. Coleman; Gary Trick; Jeffrey M. Liebmann; James D. Brandt; Jody R. Piltz-Seymour; Keri A. Dirkes; Suzanne Vega; Michael A. Kass; Mae O. Gordon

    2005-01-01

    Objective:Todeterminewhetherbaselineconfocalscan- ning laser ophthalmoscopy (CSLO) optic disc topo- graphic measurements are associated with the develop- ment of primary open-angle glaucoma (POAG) in individuals with ocular hypertension. Methods: Eight hundred sixty-five eyes from 438 par- ticipants in the CSLO Ancillary Study to the Ocular Hy- pertension Treatment Study with good-quality baseline CSLO images were included in this study. Each baseline CSLO

  12. DSC Study of Collagen in Disc Disease.

    PubMed

    Skrzy?ski, S; Sionkowska, A; Marciniak, A

    2009-01-01

    Differential scanning calorimetry (DSC) has been used to estimate the effect of disc disease on the collagen helix-coil transition and morphology for tissue extracted from patients during surgical operation. Forty discs were obtained from patients with degenerative disc disease undergoing surgery for low back pain. The patients were in the age between 20 and 70 years old. The specimens were kept wet during DSC experiment. The data allow the comparison between thermal stability of collagen tissue from healthy patients and from patients suffering from disc disease. In the paper the comparison between thermal helix-coil transition for collagen fibers from patients suffering from disc disease and collagen fibers from healthy organisms has been discussed. The heating rate has an influence on the position on denaturation temperatures of collagen in disc tissues. Higher helix-coil transition temperature of collagen in degenerated disc suggests that additional intermolecular cross linking of collagen fibers occurs. Denaturation temperatures of collagen in degenerated male disc possess smaller values than in female ones. Disc disease induces changes in collagen structure and leads to formation of additional crosslinks between collagen fibers. PMID:20169086

  13. Does Posterior Capsule Opacification Affect the Results of Diagnostic Technologies to Evaluate the Retina and the Optic Disc?

    PubMed Central

    Garcia-Medina, Jose Javier; del Rio-Vellosillo, Monica; Zanon-Moreno, Vicente; Santos-Bueso, Enrique; Gallego-Pinazo, Roberto; Ferreras, Antonio; Pinazo-Duran, Maria Dolores

    2015-01-01

    The visual outcome obtained after cataract removal may progressively decline because of posterior capsular opacification (PCO). This condition can be treated by creating an opening in the posterior lens capsule by Nd:YAG laser capsulotomy. PCO optical imperfections cause several light reflection, refraction, and diffraction phenomena, which may interfere with the functional and structural tests performed in different ocular locations for the diagnosis and follow-up of ocular disease, like macular and optic nerve diseases. Some parameters measured by visual field examinations, scanning laser polarimetry, and optical coherence tomography (OCT) have changed after PCO removal. Imaging quality also changes following capsulotomy. Consequently, the results of ancillary tests in pseudophakic eyes for studying ocular diseases like glaucoma or maculopathies should be correlated with other clinical examinations, for example, slit-lamp biomicroscopy or funduscopy. If PCO is clinically significant, a new baseline should be set for future comparisons following capsulotomy when using automated perimetry and scanning laser polarimetry. To perform OCT in the presence of PCO, reliable examinations (considering signal strength) apparently guarantee that measurements are not influenced by PCO.

  14. [Correlation of clinico-neurological peculiarities and morphological signs of small hernias (protrusion) of the lumbar intervertebral discs in formation of discogenic pain syndromes in patients of different age].

    PubMed

    Khizhniak, M V; Makeeva, T I; Pri?mak, I V

    2014-01-01

    Morphological signs of small hernias (protrusion) of intervertebral discs (IVD), the results of a neurovisualizing methods of investigation and clinico-neurological features of osteochondrosis as well, were summarized. In young and middle age patients morphological chatacteristics of small hernias (protrusion) of IVD, data of neurovisualizing methods of investigation have had correlated with clinico-neurological features of the disease and were the key determinants while performance of the puncture laser microdiscectomy. In a middle age and elderly patients a weak correlation was noted between the IVD protrusion dimensions and intensity of a lumbar and radicular pain syndromes, functional activity (Osvestry index), what have had permitted to apply a pathogenetically substantiated method of a durable epidural pharmacotherapy. The investigation results witness the necessity of differentiated application of the puncture methods of treatment for the pain discogenic syndromes in patients of different age. PMID:24923150

  15. Stability of a hot two-temperature accretion disc with advection

    E-print Network

    Xue-Bing Wu

    1997-08-01

    The effects of radial advection and thermal diffusion were considered in investigating the linear stability of an optically thin, two-temperature accretion disc. If the disc has only very little advection, we proved that the thermal instability exists when the disc is geometrically thin. But it dispears in a geometrically slim disc if the thermal diffusion was considered. Moreover, if the disc is advection dominated, the thermal instability does not exist. In addition, we found that the instabilities of inertial-acoustic modes exist only in a geometrically thin disc or an advection-dominated disc with low Mach number, whereas the Lightman & Eardley viscous instability always dispears in a two-temperature disc. A simple comparison also showed that an optically thin, bremsstrahlung cooling dominated disc is generally more thermally unstable than a two-temperature disc if it is not advection-dominated.

  16. Chemical and optical aging of forest fire plumes

    Microsoft Academic Search

    S. G. Howell; A. D. Clarke; S. Freitag; V. N. Kapustin; C. S. McNaughton; L. Shank

    2010-01-01

    During recent aircraft-based projects, we have penetrated fresh fire plumes, followed them for tens of kilometers, and sampled them thousands of kms from their sources. Chemical analysis with an Aerosol Mass Spectrometer (AMS) for non-refractory composition and a Single Particle Soot Photometer (SP2) alongside nephelometers and a Particle Soot Absorption Spectrometer (PSAP) for optical properties of the aerosol show consistent

  17. Effects of age on nerve fibers in the rhesus monkey optic nerve.

    PubMed

    Sandell, J H; Peters, A

    2001-01-22

    During normal aging there is a reduction in white matter volume in the cerebral hemispheres and structural abnormalities in myelin in some parts of the central nervous system, but whether nerve fibers are lost with age and whether the myelin changes are ubiquitous is not known. Studying the optic nerve, which is a circumscribed bundle of nerve fibers, offers an opportunity to gain further insight into the effects of normal aging on white matter. The present study examined the optic nerves from young (4-10 years) and old (27-33 years) rhesus monkeys using light and electron microscopy. These nerves had been perfused transcardially to obtain optimal preservation of the tissue. Varying degrees of degeneration were encountered in all the optic nerves from the old monkeys. The changes included myelin abnormalities, similar to those reported in other parts of the central nervous system; the presence of degenerating axons and their sheaths; changes in neuroglial cells; and thickening of the trabeculae of connective tissue in the nerve. The total number of nerve fibers was reduced from an average of 1.6 x 10(6) in the young optic nerves to as few as 4 x 10(5) in one old monkey, and with one exception in all of the old optic nerves the packing density of nerve fibers was less than in any of the young optic nerves. The degenerative changes were most marked in those optic nerves that contained the fewest nerve fibers. PMID:11135234

  18. Counterrotating stars in simulated galaxy discs

    NASA Astrophysics Data System (ADS)

    Algorry, David G.; Navarro, Julio F.; Abadi, Mario G.; Sales, Laura V.; Steinmetz, Matthias; Piontek, Franziska

    2014-02-01

    Counterrotating stars in disc galaxies are a puzzling dynamical feature whose origin has been ascribed to either satellite accretion events or to disc instabilities triggered by deviations from axisymmetry. We use a cosmological simulation of the formation of a disc galaxy to show that counterrotating stellar disc components may arise naturally in hierarchically clustering scenarios even in the absence of merging. The simulated disc galaxy consists of two coplanar, overlapping stellar components with opposite spins: an inner counterrotating bar-like structure made up mostly of old stars surrounded by an extended, rotationally supported disc of younger stars. The opposite-spin components originate from material accreted from two distinct filamentary structures which at turn around, when their net spin is acquired, intersect delineating a `V'-like structure. Each filament torques the other in opposite directions; the filament that first drains into the galaxy forms the inner counterrotating bar, while material accreted from the other filament forms the outer disc. Mergers do not play a substantial role and most stars in the galaxy are formed in situ; only 9 per cent of all stars are contributed by accretion events. The formation scenario we describe here implies a significant age difference between the co- and counterrotating components, which may be used to discriminate between competing scenarios for the origin of counterrotating stars in disc galaxies.

  19. A revised burial dose estimation procedure for optical dating of youngand modern-age sediments

    USGS Publications Warehouse

    Arnold, L.J.; Roberts, R.G.; Galbraith, R.F.; DeLong, S.B.

    2009-01-01

    The presence of genuinely zero-age or near-zero-age grains in modern-age and very young samples poses a problem for many existing burial dose estimation procedures used in optical (optically stimulated luminescence, OSL) dating. This difficulty currently necessitates consideration of relatively simplistic and statistically inferior age models. In this study, we investigate the potential for using modified versions of the statistical age models of Galbraith et??al. [Galbraith, R.F., Roberts, R.G., Laslett, G.M., Yoshida, H., Olley, J.M., 1999. Optical dating of single and multiple grains of quartz from Jinmium rock shelter, northern Australia: Part I, experimental design and statistical models. Archaeometry 41, 339-364.] to provide reliable equivalent dose (De) estimates for young and modern-age samples that display negative, zero or near-zero De estimates. For this purpose, we have revised the original versions of the central and minimum age models, which are based on log-transformed De values, so that they can be applied to un-logged De estimates and their associated absolute standard errors. The suitability of these 'un-logged' age models is tested using a series of known-age fluvial samples deposited within two arroyo systems from the American Southwest. The un-logged age models provide accurate burial doses and final OSL ages for roughly three-quarters of the total number of samples considered in this study. Sensitivity tests reveal that the un-logged versions of the central and minimum age models are capable of producing accurate burial dose estimates for modern-age and very young (<350??yr) fluvial samples that contain (i) more than 20% of well-bleached grains in their De distributions, or (ii) smaller sub-populations of well-bleached grains for which the De values are known with high precision. Our results indicate that the original (log-transformed) versions of the central and minimum age models are still preferable for most routine dating applications, since these age models are better suited to the statistical properties of typical single-grain and multi-grain single-aliquot De datasets. However, the unique error properties of modern-age samples, combined with the problems of calculating natural logarithms of negative or zero-Gy De values, mean that the un-logged versions of the central and minimum age models currently offer the most suitable means of deriving accurate burial dose estimates for very young and modern-age samples. ?? 2009 Elsevier Ltd. All rights reserved.

  20. Automotive disc brake squeal

    Microsoft Academic Search

    N. M. Kinkaid; O. M. O'Reilly; P. Papadopoulos

    2003-01-01

    Disc brake squeal remains an elusive problem in the automotive industry. Since the early 20th century, many investigators have examined the problem with experimental, analytical, and computational techniques, but there is as yet no method to completely suppress disc brake squeal. This paper provides a comprehensive review and bibliography of works on disc brake squeal. In an effort to make

  1. Turbine disc sealing assembly

    DOEpatents

    Diakunchak, Ihor S.

    2013-03-05

    A disc seal assembly for use in a turbine engine. The disc seal assembly includes a plurality of outwardly extending sealing flange members that define a plurality of fluid pockets. The sealing flange members define a labyrinth flow path therebetween to limit leakage between a hot gas path and a disc cavity in the turbine engine.

  2. Effects of age on the glial cells in the rhesus monkey optic nerve.

    PubMed

    Sandell, Julie H; Peters, Alan

    2002-03-25

    The optic nerve is a circumscribed white matter tract consisting of myelinated nerve fibers and neuroglial cells. Previous work has shown that during normal aging in the rhesus monkey, many optic nerves lose some of their nerve fibers, and in all old optic nerves there are both myelin abnormalities and degenerating nerve fibers. The present study assesses how the neuroglial cell population of the optic nerve is affected by age. To address this question, optic nerves from young (4-10 years) and old (27-33 years) rhesus monkeys were examined by using both light and electron microscopy. It was found that with age the astrocytes, oligodendrocytes, and microglia all develop characteristic cytoplasmic inclusions. The astrocytes hypertrophy and fill space vacated by degenerated nerve fibers, and they often develop abundant glial filaments in their processes. Oligodendrocytes and microglial cells both become more numerous with age, and microglial cells often become engorged with phagocytosed debris. Some of the debris can be recognized as degenerating myelin, and in general, the greater the loss of nerve fibers, the more active the microglial cells become. PMID:11891651

  3. Optical properties of neonatal skin measured in vivo as a function of age and skin pigmentation

    NASA Astrophysics Data System (ADS)

    Bosschaart, Nienke; Mentink, Rosaline; Kok, Joke H.; van Leeuwen, Ton G.; Aalders, Maurice C. G.

    2011-09-01

    Knowledge of the optical properties of neonatal skin is invaluable when developing new, or improving existing optical techniques for use at the neonatal intensive care. In this article, we present in vivo measurements of the absorption ?a and reduced scattering coefficient ?s' of neonatal skin between 450 and 600 nm and assess the influence of age and skin pigmentation on the optical properties. The optical properties were measured using a spatially resolved, steady state diffuse reflectance spectroscopy setup, combined with a modified spatially resolved diffusion model. The method was validated on phantoms with known values for the absorption and reduced scattering coefficient. Values of ?a and ?s' were obtained from the skin at four different body locations (forehead, sternum, hand, and foot) of 60 neonates with varying gestational age, postnatal age, and skin pigmentation. We found that ?a ranged from 0.02 to 1.25 mm-1 and ?s' was in the range of 1 to 2.8 mm-1 (5th to 95th percentile of the patient population), independent of body location. In contrast to previous studies, no to very weak correlation was observed between the optical properties and gestational maturity, but a strong dependency of the absorption coefficient on postnatal age was found for dark skinned patients.

  4. Percutaneous Treatment of Intervertebral Disc Herniation

    Microsoft Academic Search

    Xavier Buy; Afshin Gangi; Stéphane Guth; Ali Guermazi

    \\u000a Disc herniation is defined as rupture of the fibrocartilagenous annulus fibrosus that surrounds the intervertebral disc, associated\\u000a with the release of the central gelatinous nucleus pulposus. Most herniations take place in the lumbar area of the spine.\\u000a They occur more frequently in middle aged and older men, especially those involved in strenuous physical activity. They cause\\u000a physical disability with significant

  5. Lumbar Disc Degenerative Disease: Disc Degeneration Symptoms and Magnetic Resonance Image Findings

    PubMed Central

    Saleem, Shafaq; Rehmani, Muhammad Asim Khan; Raees, Aisha; Alvi, Arsalan Ahmad; Ashraf, Junaid

    2013-01-01

    Study Design Cross sectional and observational. Purpose To evaluate the different aspects of lumbar disc degenerative disc disease and relate them with magnetic resonance image (MRI) findings and symptoms. Overview of Literature Lumbar disc degenerative disease has now been proven as the most common cause of low back pain throughout the world. It may present as disc herniation, lumbar spinal stenosis, facet joint arthropathy or any combination. Presenting symptoms of lumbar disc degeneration are lower back pain and sciatica which may be aggravated by standing, walking, bending, straining and coughing. Methods This study was conducted from January 2012 to June 2012. Study was conducted on the diagnosed patients of lumbar disc degeneration. Diagnostic criteria were based upon abnormal findings in MRI. Patients with prior back surgery, spine fractures, sacroiliac arthritis, metabolic bone disease, spinal infection, rheumatoid arthritis, active malignancy, and pregnancy were excluded. Results During the targeted months, 163 patients of lumbar disc degeneration with mean age of 43.92±11.76 years, came into Neurosurgery department. Disc degeneration was most commonly present at the level of L4/L5 105 (64.4%).Commonest types of disc degeneration were disc herniation 109 (66.9%) and lumbar spinal stenosis 37 (22.7%). Spondylolisthesis was commonly present at L5/S1 10 (6.1%) and associated mostly with lumbar spinal stenosis 7 (18.9%). Conclusions Results reported the frequent occurrence of lumbar disc degenerative disease in advance age. Research efforts should endeavor to reduce risk factors and improve the quality of life. PMID:24353850

  6. Annulo-nucleoplasty using Disc-FX in the management of lumbar disc pathology: Early results

    PubMed Central

    Kumar, Aravind; Siddharth M, Shah; Sambhav P, Shah; Tan, Justin

    2014-01-01

    Background Back pain due to Lumbar Disc Disease is a major clinical problem. The treatment options range from physiotherapy to fusion surgery. A number of minimally invasive procedures have also been developed in the recent past for its management. Disc-FX is a new minimally invasive technique that combines percutaneous discectomy, nuclear ablation and annular modification. Literature on its role in the management of lumbar disc pathology is scarce. Methods We included 24 consecutive patients who underwent the Disc-FX for back pain due to lumbar disc pathology non-responsive to non-operative treatment for a period of at least 6 months. Based on Magnetic Resonance Imaging (MRI) these patients fell into 2 groups – those with degenerative disc disease (DDD) (n = 12) and those with a contained lumbar disc herniation (CLDH)(n = 12). They were evaluated using the Visual analogue scale (VAS), Oswestry Disability Index (ODI) and Short Form-36 (SF-36) scores preoperatively and postoperatively. Results The mean age was 37.9 years (21-53 years). There were 17 males and 7 females. One patient in each subgroup was excluded from the final evaluation. Significant improvement was seen in all outcome measures. The overall rate of reintervention for persistent symptoms was 18.18% (4/22); in the CLDH subgroup, it was 36.36% (4/11). Conclusions and level of evidence Early results after the Disc-FX procedure suggest that it s a reasonable treatment option for patients with back pain due to lumbar disc disease, especially for those with DDD who fail conservative treatment. It could be an alternative to procedures like fusion or disc replacement. This study presents Level IV evidence. Clinical relevance We feel that our study establishes Disc-FX as a modality of treating symptomatic lumbar disc disease due to DDD. However, longer term prospective studies are needed to prove this and to evaluate its role in the treatment of patients with CLDH. PMID:25694914

  7. Cone photopigment in older subjects: decreased optical density in early age-related macular degeneration

    NASA Astrophysics Data System (ADS)

    Elsner, Ann E.; Burns, Stephen A.; Weiter, John J.

    2002-01-01

    We measured changes to cone photoreceptors in patients with early age-related macular degeneration. The data of 53 patients were compared with normative data for color matching measurements of long- and middle-wavelength-sensitive cones in the central macula. A four-parameter model quantified cone photopigment optical density and kinetics. Cone photopigment optical density was on average less for the patients than for normal subjects and was uncorrelated with visual acuity. More light was needed to reduce the photopigment density by 50% in the steady state for patients. These results imply that cone photopigment optical density is reduced by factors other than slowed kinetics.

  8. Gradual disc prolapse.

    PubMed

    Adams, M A; Hutton, W C

    1985-01-01

    Fifty-two cadaveric lumbar motion segments were subjected to fatigue loading in compression and bending to determine if the intervertebral discs could prolapse in a gradual manner. Prior to testing, the nucleus pulposus of each disc was stained with a small quantity of blue dye and radiopaque solution. This enabled the progress of any gradual prolapse to be monitored by direct observation and by discogram. Six discs developed a gradual prolapse during the testing period. The injury starts with the lamellae of the annulus being distorted to form radial fissures and then nuclear pulp is extruded from the disc and leaks into the spinal canal. Discs most commonly affected were from the lower lumbar spine of young cadavers. Tests on ten older discs with pre-existing ruptures showed that such discs are stable and do not leak nuclear pulp. PMID:4081867

  9. Age-Related Fiber Order in the Ferret's Optic Nerve and Optic Chiasm

    Microsoft Academic Search

    C. Walsh

    rangement of fibers between the nerve and the tract. The goal of this study was to determine where this age-related sorting occurs. In the ferret, a close relative of the cat, the older retinofugal fibers in the tract have been labeled directly. These older fibers lie deep in the tract, with newer fibers nearer the pial surface, and this age-related

  10. Kinetics of degradation during fatigue and aging of fused silica optical fiber M. John Matthewson

    E-print Network

    Matthewson, M. John

    Fiber Optic Materials Research Program Department of Ceramics Rutgers University, Piscataway, NJ 08855, the phenomenon is associated with the glass since is occurs even in the absence of a coating. Krause3 observed of surface roughness of fiber that had been coated with gold after aging to make the surface conducting. 204

  11. Aging changes of the optic nerve head in relation to open angle glaucoma

    Microsoft Academic Search

    D F Garway-Heath; G Wollstein; R A Hitchings

    1997-01-01

    AIMSTo determine the age related changes in optic nerve head structure in a group of normal subjects and assess the significance of any changes in relation to those found in open angle glaucoma.METHODSA group of 88 white volunteers and friends and spouses of patients with a normal visual field and normal intraocular pressure was studied. Two different imaging and measurement

  12. Average Optical Performance of the Human Eye as a Function of Age in a Normal Population

    Microsoft Academic Search

    Antonio Guirao; Manuel Redondo; Edward Geraghty; Sverker Norrby

    1999-01-01

    PURPOSE. TO determine the average optical performance of the human eye, in terms of the modulation transfer function (MTF). as a function of age. METHODS. An apparatus was constructed to measure the ocular MTF, based on the recording of images of a green, 543-nm laser-point source after reflection in the retina and double pass through the ocular media. MTFs were

  13. Experimental investigation of aging effects of dry-band arcing on ADSS fiber-optic cables

    Microsoft Academic Search

    G. G. Karady; Y. Lei; Devarajan Srinivasan; M. Tuominen; B. G. Risch

    2003-01-01

    A testing method for evaluating the quality of ADSS fiber optic cable is presented. Aging effect due to arcing under different voltage and pollution levels (heavy and light) is described. Measurement of area and depth of damaged cable is conducted to analyze the damage severity. Experiments show that 2 mA and 7 kV are threshold current and voltage which might

  14. Aging Studies of LiF Coated Optics for use in the Far Ultraviolet

    E-print Network

    diffraction gratings. Two mirrors and two gratings are coated with silicon carbide (SiC) and have a bandpassF) over aluminum (Al) providing about twice the reflectivity of the SiC at wavelengths larger than 105Aging Studies of LiF Coated Optics for use in the Far Ultraviolet Cristina M. Oliveira, Kurt

  15. Aging Studies of LiF Coated Optics for use in the Far Ultraviolet

    E-print Network

    raction gratings. Two mirrors and two gratings are coated with silicon carbide SiC and have a bandpass aluminum Al providing about twice the re ectivity of the SiC at wavelengths larger than 105.0 nm but veryAging Studies of LiF Coated Optics for use in the Far Ultraviolet Cristina M. Oliveira, Kurt

  16. Assessment of fiber optic sensors for aging monitoring of industrial liquid coolants

    NASA Astrophysics Data System (ADS)

    Riziotis, Christos; El Sachat, Alexandros; Markos, Christos; Velanas, Pantelis; Meristoudi, Anastasia; Papadopoulos, Aggelos

    2015-03-01

    Lately the demand for in situ and real time monitoring of industrial assets and processes has been dramatically increased. Although numerous sensing techniques have been proposed, only a small fraction can operate efficiently under harsh industrial environments. In this work the operational properties of a proposed photonic based chemical sensing scheme, capable to monitor the ageing process and the quality characteristics of coolants and lubricants in industrial heavy machinery for metal finishing processes is presented. The full spectroscopic characterization of different coolant liquids revealed that the ageing process is connected closely to the acidity/ pH value of coolants, despite the fact that the ageing process is quite complicated, affected by a number of environmental parameters such as the temperature, humidity and development of hazardous biological content as for example fungi. Efficient and low cost optical fiber sensors based on pH sensitive thin overlayers, are proposed and employed for the ageing monitoring. Active sol-gel based materials produced with various pH indicators like cresol red, bromophenol blue and chorophenol red in tetraethylorthosilicate (TEOS), were used for the production of those thin film sensitive layers deposited on polymer's and silica's large core and highly multimoded optical fibers. The optical characteristics, sensing performance and environmental robustness of those optical sensors are presented, extracting useful conclusions towards their use in industrial applications.

  17. The avian intervertebral disc arises from rostral sclerotome and lacks a nucleus pulposus: Implications for evolution of the vertebrate disc

    PubMed Central

    Bruggeman, Bradley J.; Maier, Jennifer A.; Mohiuddin, Yasmin S.; Powers, Rae; Lo, YinTing; Guimarães-Camboa, Nuno; Evans, Sylvia M.; Harfe, Brian D.

    2012-01-01

    Deterioration of the intervertebral discs is an unfortunate consequence of aging. The intervertebral disc in mammals is composed of three parts: a jelly-like center called the nucleus pulposus, the cartilaginous annulus fibrosus and anterior and posterior endplates that attach the discs to vertebrae. In order to understand the origin of the disc, we have investigated the intervertebral region of chickens. Surprisingly, our comparison of mouse and chicken discs revealed that chicken discs lack nuclei pulposi. In addition, the notochord, which in mice forms nuclei pulposi, was found to persist as a rod-like structure and express Shh throughout chicken embryogenesis. Our fate mapping data indicates that cells originating from the rostral half of each somite are responsible for forming the avian disc while cells in the caudal region of each somite form vertebrae. A histological analysis of mammalian and non-mammalian organisms suggests that nuclei pulposi are only present in mammals. PMID:22354863

  18. Rotating discs and non-kinematic double peaks

    NASA Astrophysics Data System (ADS)

    Elitzur, Moshe; Asensio Ramos, Andrés.; Ceccarelli, Cecilia

    2012-05-01

    Double-peaked line profiles are commonly considered a hallmark of rotating discs, with the distance between the peaks a measure of the rotation velocity. However, double-peaks can arise also from radiative transfer effects in optically thick non-rotating sources. Utilizing exact solutions of the line transfer problem we present a detailed study of line emission from geometrically thin Keplerian discs. We derive the conditions for emergence of kinematic double peaks in optically thin and thick discs, and find that it is generally impossible to disentangle the effects of kinematics and line opacity in observed double-peaked profiles. Unless supplemented by additional information, a double-peaked profile alone is not a reliable indicator of a rotating disc. In certain circumstances, triple and quadruple profiles might be better indicators of rotation in optically thick discs.

  19. Radially truncated galactic discs

    E-print Network

    Richard de Grijs; Michiel Kregel; Karen H. Wesson

    2001-02-02

    We present the first results of a systematic analysis of radially truncated exponential discs for four galaxies of a complete sample of disc-dominated edge-on spiral galaxies. The discs of our sample galaxies are truncated at similar radii on either side of their centres. With possible the exception of the disc of ESO 416-G25, it appears that the truncations in our sample galaxies are closely symmetric, in terms of both their sharpness and the truncation length. However, the truncations occur over a larger region and not as abruptly as found in previous studies. We show that the truncated luminosity distributions of our sample galaxies, if also present in the mass distributions, comfortably meet the requirements for longevity. The formation and maintenance of disc truncations are likely closely related to stability requirements for galactic discs.

  20. Childhood intervertebral disc calcification

    Microsoft Academic Search

    B. Theo Mellion; John P. Laurent; William C. Watters

    1993-01-01

    Two cases of intervertebral disc calcification in children are reported. A 13-year-old boy presented with right subscapular pain radiating into the axilla with radiographic demonstration of multiple calcified intervertebral discs and a herniated fragment of calcified nucleus pulposus at T2–3. His condition improved with conservative therapy, and follow-up radiographic evaluation revealed resolution of the herniated calcified disc material. A second

  1. Zero stress aging and the static fatigue transition in optical glass fibers

    NASA Astrophysics Data System (ADS)

    Cuellar, Enrique; Kennedy, Michael T.; Roberts, Daniel R.; Ritter, John E., Jr.

    1993-02-01

    Optical glass fibers can exhibit, under severe environmental conditions, an accelerated static fatigue behavior at long times under moderate stresses. This behavior is manifested by a transition, or 'knee', in the plot of ln (time to failure) versus ln (applied stress). This accelerated fatigue effect depends on several variables, including temperature, relative humidity, and pH, as well as on the composition of the cladding and polymeric coating. Similarly, optical fibers can exhibit a pronounced strength degradation due to zero stress aging. It was found that the onset of significant strength loss during zero stress aging occurred at about the same time as the static fatigue transition. Also, the spread in the distributions of time to failure at a given applied stress narrows after the transition. These results suggest that zero stress aging represents a second mechanism of crack growth which takes place on a longer time scale and is superimposed on the crack growth of stress corrosion. Finally, a model was used to predict this accelerated fatigue behavior in optical glass fibers by assuming the combined influence of zero stress aging and stress corrosion on crack growth.

  2. Effect of diffusion rates in optical fiber polymer coatings on aging

    NASA Astrophysics Data System (ADS)

    Armstrong, Janet L.; Matthewson, M. John; Juarez, Mayra G.; Chou, Catherine Y.

    1999-12-01

    Optical fibers have been found to exhibit an accelerated rate of strength reduction during static fatigue and zero stress aging for long times in aggressive environments. This phenomenon has been commonly referred to as the fatigue and aging `knee'. The onset of the knee has been found to be highly variable and is sensitive to the polymer buffer coating. In past work we have shown that moisture vapor penetrates most polymer coatings on the time scale of minutes, which implies that the diffusion rate of small molecules is not the rate-determining step for aging. On the other hand, the diffusion of large molecules through the polymer coatings can take anywhere from weeks to years to reach the polymer/glass interface. The implication of this result is that large molecule diffusion might be the rate- determining step in aging. In the work presented here the diffusion of moisture and pH buffer solutions through various optical fiber coatings will be discussed. These results are correlated with the zero stress aging behavior of the same fibers.

  3. Optic nerve head measurements: The optic nerve head analyzer — its advantages and its limitations

    Microsoft Academic Search

    E. Gramer; M. Siebert

    1989-01-01

    Summary The Optic Nerve Head Analyzer (ONHA) calculates by means of computer-assisted analysis of stereo images different parameters of the optic disc: disc diameter, disc size, cup\\/disc ratio (CDR), neuroretinal rim area, and excavation volume for the disc quadrants and for the total disc. To obtain first indications of the clinical value of ONHA measurements for diagnosis and follow-up in

  4. Age-Associated Changes in the Retinal Nerve Fiber Layer and Optic Nerve Head

    PubMed Central

    Patel, Nimesh B.; Lim, Mimi; Gajjar, Avni; Evans, Kelsey B.; Harwerth, Ronald S.

    2014-01-01

    Purpose. Optical coherence tomography (OCT) measures of the retinal nerve fiber layer (RNFL) thickness and neuroretinal rim (NRR) parameters are often used as a surrogate for retinal ganglion cell content. The purpose of this study was to investigate the relationship between these morphological measures and the aging effects on these structures. Methods. One hundred thirteen healthy individuals, aged 19 to 76 years, with no prior history of retinal of optic nerve head pathology were recruited. A circumpapillary and radial OCT scan centered on the optic nerve head (ONH) was used for data analysis. Transverse scaling was calculated for each subject using measures from optical biometry. Custom algorithms were used for morphological analysis of the ONH NRR and RNFL that included quantification of major retinal vascular contribution. Results. There was a significant age-related loss of RNFL thickness (?0.23 ?m/y, R2 = 0.24, P < 0.01), major retinal vascular contribution (?0.03 ?m/y, R2 = 0.07, P = 0.01, neural rim volume (NRV, ?0.004 mm3/y, R2 = 0.15, P < 0.01), and minimum rim width (MRW, ?1.77 ?m/y, R2 = 0.23, P < 0.01) before, and after, incorporating the Bruch's membrane opening size (sMRW, ?1.86 ?m/y, R2 = 0.22, P < 0.01). When normalized, the rates of change for ONH NRR parameters (NRV, 0.69%/y and sMRW, 0.50%/y) exceeded that of RNFL thickness (0.19%/y, P < 0.01). Conclusions. Although both RNFL and ONH NRR parameters contain axons of retinal ganglion cells, there are differences in age-related changes in these measures that should be considered in clinical application. PMID:25052998

  5. Reconstructing the star formation history of the Milky Way disc(s) from chemical abundances

    NASA Astrophysics Data System (ADS)

    Snaith, O.; Haywood, M.; Di Matteo, P.; Lehnert, M. D.; Combes, F.; Katz, D.; Gómez, A.

    2015-06-01

    We develop a chemical evolution model to study the star formation history of the Milky Way. Our model assumes that the Milky Way has formed from a closed-box-like system in the inner regions, while the outer parts of the disc have experienced some accretion. Unlike the usual procedure, we do not fix the star formation prescription (e.g. Kennicutt law) to reproduce the chemical abundance trends. Instead, we fit the abundance trends with age to recover the star formation history of the Galaxy. Our method enables us to recover the star formation history of the Milky Way in the first Gyrs with unprecedented accuracy in the inner (R < 7-8 kpc) and outer (R > 9-10 kpc) discs, as sampled in the solar vicinity. We show that half the stellar mass formed during the thick-disc phase in the inner galaxy during the first 4-5 Gyr. This phase was followed by a significant dip in star formation activity (at 8-9 Gyr) and a period of roughly constant lower-level star formation for the remaining 8 Gyr. The thick-disc phase has produced as many metals in 4 Gyr as the thin-disc phase in the remaining 8 Gyr. Our results suggest that a closed-box model is able to fit all the available constraints in the inner disc. A closed-box system is qualitatively equivalent to a regime where the accretion rate maintains a high gas fraction in the inner disc at high redshift. In these conditions the SFR is mainly governed by the high turbulence of the interstellar medium. By z ~ 1 it is possible that most of the accretion takes place in the outer disc, while the star formation activity in the inner disc is mostly sustained by the gas that is not consumed during the thick-disc phase and the continuous ejecta from earlier generations of stars. The outer disc follows a star formation history very similar to that of the inner disc, although initiated at z ~ 2, about 2 Gyr before the onset of the thin-disc formation in the inner disc.

  6. Spiral density waves in the outer galactic gaseous discs

    E-print Network

    Khoperskov, S A

    2015-01-01

    Deep HI observations of the outer parts of disc galaxies demonstrate the frequent presence of extended, well-developed spiral arms far beyond the optical radius. To understand the nature and the origin of such outer spiral structure, we investigate the propagation in the outer gaseous disc of large-scale spiral waves excited in the bright optical disc. Using hydrodynamical simulations, we show that non-axisymmetric density waves, penetrating in the gas through the outer Lindblad resonance, can exhibit relatively regular spiral structures outside the bright optical stellar disc. For low-amplitude structures, the results of numerical simulations match the predictions of a simple WKB linear theory. The amplitude of spiral structure increases rapidly with radius. Beyond $\\approx 2$ optical radii, spirals become nonlinear (the linear theory becomes quantitatively and qualitatively inadequate) and unstable to Kelvin-Helmholtz instability. In numerical simulations, in models for which gas is available very far out, ...

  7. Demographics of transition discs in Ophiuchus and Taurus

    NASA Astrophysics Data System (ADS)

    Najita, Joan R.; Andrews, Sean M.; Muzerolle, James

    2015-07-01

    Transition disc systems are young stars that appear to be on the verge of dispersing their protoplanetary discs. We explore the nature of these systems by comparing the stellar accretion rates dot{M}_* and disc masses Md of transition discs and normal T Tauri stars in Taurus and Ophiuchus. After controlling for the known dependences of dot{M}_* and Md on age, dot{M}_* on stellar mass and Md on the presence of stellar or substellar companions, we find that the normal T Tauri stars show a trend of dot{M}_* increasing with Md. The transition discs tend to have higher average disc masses than normal T Tauri stars as well as lower accretion rates than normal T Tauri stars of the same disc mass. These results are most consistent with the interpretation that the transition discs have formed objects massive enough to alter the accretion flow, i.e. single or multiple giant planets. Several Ophiuchus T Tauri stars that are not known transition disc systems also have very low accretion rates for their disc masses. We speculate on the possible nature of these sources.

  8. Older observers' tolerance of optical blur: age differences in the identification of defocused text signs.

    PubMed

    Kline, D W; Buck, K; Sell, Y; Bolan, T L; Dewar, R E

    1999-09-01

    To determine if visual aging affects the ability to identify blurred text signs in daytime or nighttime viewing conditions, the photopic and mesopic legibility thresholds of young and old adult observers were compared at three levels of optically induced acuity (Experiment 1). For both age groups, legibility was reduced by nighttime luminance and degraded acuity. Surprisingly, older observers were better than younger ones in identifying defocused (optically blurred) text in both daytime and nighttime conditions. In Experiment 2, older observers were also superior to younger ones in identifying defocused standard and spatially matched novel text signs. These findings indicate that older observers' tolerance of optical blur is a generic ability, rather than one explained by familiarity with the low-pass optical profile of specific signs. Consistent with the notion that factors beyond acuity contribute more importantly to text legibility for older than for younger observers, acuity was a stronger predictor of legibility thresholds in the younger group. Actual or potential applications of this research include the need to consider functional acuity in visual screening protocols and the design of text displays, as well as the utilization of compensatory letter-recognition training for older observers or others with diminished acuity. PMID:10665204

  9. Cauda equina compression syndrome in a child due to lumbar disc herniation

    Microsoft Academic Search

    Kadir Kotil; Mustafa Akçetin; Turgay Bilge

    2004-01-01

    IntroductionCauda equina syndrome with sphincter dysfunction is an uncommon and feared complication of lumbar disc herniation.Case reportLumbar disc disease in the pediatric age has been reported infrequently, but to the best of our knowledge, this is the first pediatric case of acute lumber disc herniation presenting with caudal compression.

  10. An optical age chronology of late Quaternary extreme fluvial events recorded in Ugandan dambo soils

    USGS Publications Warehouse

    Mahan, S.A.; Brown, D.J.

    2007-01-01

    There is little geochonological data on sedimentation in dambos (seasonally saturated, channel-less valley floors) found throughout Central and Southern Africa. Radiocarbon dating is problematic for dambos due to (i) oxidation of organic materials during dry seasons; and (ii) the potential for contemporary biological contamination of near-surface sediments. However, for luminescence dating the equatorial site and semi-arid climate facilitate grain bleaching, while the gentle terrain ensures shallow water columns, low turbidity, and relatively long surface exposures for transported grains prior to deposition and burial. For this study, we focused on dating sandy strata (indicative of high-energy fluvial events) at various positions and depths within a second-order dambo in central Uganda. Blue-light quartz optically stimulated luminescences (OSL) ages were compared with infrared stimulated luminescence (IRSL) and thermoluminescence (TL) ages from finer grains in the same sample. A total of 8 samples were dated, with 6 intervals obtained at ???35, 33, 16, 10.4, 8.4, and 5.9 ka. In general, luminescence ages were stratigraphically, geomorphically and ordinally consistent and most blue-light OSL ages could be correlated with well-dated climatic events registered either in Greenland ice cores or Lake Victoria sediments. Based upon OSL age correlations, we theorize that extreme fluvial dambo events occur primarily during relatively wet periods, often preceding humid-to-arid transitions. The optical ages reported in this study provide the first detailed chronology of dambo sedimentation, and we anticipate that further dambo work could provide a wealth of information on the paleohydrology of Central and Southern Africa. ?? 2006 Elsevier Ltd. All rights reserved.

  11. Association of age and macular pigment optical density using dual-wavelength autofluorescence imaging

    PubMed Central

    Lima, Verônica Castro; Rosen, Richard B; Prata, Tiago Santos; Dorairaj, Syril; Spielberg, Leigh; Maia, Mauricio; Sallum, Juliana M

    2013-01-01

    Background Several lines of evidence suggest that macular pigment may play a protective role against age-related macular degeneration, but the influence of age on macular pigment density levels remains unclear. This study was designed to investigate the relationship between age and the normal distribution of macular pigment optical density (MPOD) values surrounding the fovea. Methods Consecutive healthy subjects with no evidence of ocular disease were enrolled in this study. After inclusion, MPOD values were measured at specific eccentricities (0.5, 1, and 2 degrees) from the foveal center using a dual-wavelength autofluorescence method employing a modified confocal scanning laser ophthalmoscope. Whenever both eyes were eligible, one was randomly selected for analysis. The correlation between age and MPOD values was investigated using regression analysis. Results Thirty subjects (30 eyes) were included (mean age 48.6 ± 16.4 [range 23–77] years). Significant differences were found between MPOD values measured at 0.5, 1, and 2 degrees from the center of the fovea (0.49 ± 0.12 density units, 0.37 ± 0.11 density units, and 0.13 ± 0.05 density units, respectively, P < 0.05). Significant correlations between age and MPOD values at 0.5 and 1 degree were found (P ? 0.02). Values measured at 2 degrees did not correlate significantly with age (P = 0.06). Conclusion In healthy subjects, MPOD values were highest near the foveal center. These values appeared to increase during adulthood (peak at 45–50 years), followed by a gradual reduction after 60 years of age. PMID:23589675

  12. Age-related changes in optical and biometric characteristics of emmetropic eyes.

    PubMed

    Atchison, David A; Markwell, Emma L; Kasthurirangan, Sanjeev; Pope, James M; Smith, George; Swann, Peter G

    2008-01-01

    We measured optical and biometric parameters of emmetropic eyes as a function of age. There were approximately 20 subjects each in age groups 18-29, 30-39, 40-49, 50-59, and 60-69 years with similar male and female numbers. One eye was tested for each subject, having spherical equivalent in the range -0.88 D to +0.75 D and age changes: anterior chamber depth decreased 0.011 mm/year, lens central thickness increased 0.024 mm/year, anterior segment depth increased 0.013 mm/year, eye length increased 0.011 mm/year, anterior lens radius of curvature decreased 0.044 mm/year, and lens equivalent refractive index decreased 0.0003/year. Males had higher anterior corneal radii of curvature (0.16 mm), lower lens equivalent refractive index (0.006), longer vitreous lengths (0.51 mm), and longer axial lengths (0.62 mm) than females. Superficially, the results suggest that eyes get bigger as they age. However, results can be related to refraction patterns in which refraction is stable in 20s to 40s and then moves in the hypermetropic direction. It is likely that several young subjects will become hypermetropic as they age, and it is possible that some of the older subjects were myopic when younger. PMID:18484868

  13. Evolution of Black Carbon Optical Properties during Atmospheric Aging: Comparison Between Theoretical Calculations and Laboratory Experiments

    NASA Astrophysics Data System (ADS)

    He, C.; Liou, K. N.; Takano, Y.; Li, Q.; Yang, P.; Zhang, R.

    2014-12-01

    The optical properties of black carbon (BC) are significantly affected by its aging process in the atmosphere. We have built a conceptual model defining three BC aging stages, including freshly emitted BC aggregates, coating by soluble material and hygroscopic growth. We apply an improved geometric-optics surface-wave approach (Liou et al., 2011; Takano et al., 2013) to calculate the absorption and scattering properties of BC at each stage and compare the theoretical results with those obtained from laboratory experiments (Zhang et al., 2008; Khalizov et al., 2009). Preliminary results show a general agreement between calculated and measured BC absorption cross sections (bias < 10%) and scattering cross sections (bias < 30%) for BC aerosols with mobility diameters of 155, 245 and 320 nm at Stages 1 and 2, where BC is coated by sulfuric acid and its water solution, respectively. We find that the calculated scattering and absorption cross sections for fresh BC aggregates (Stage 0) with different sizes are invariably larger than experimental results partly because of the uncertainty in theoretical calculations for BC with size parameters less than 1. It appears that the uncertainty in the experiment could also contribute to the discrepancy, considering that the measuring instrument missed some scattering in certain angles (0-7° and 170-180°). Finally, we will apply the conceptual model and the single-scattering results to assess the effects of BC aging processes on direct radiative forcing using observed BC vertical profiles.

  14. Radiation magnetohydrodynamics in global simulations of protoplanetary discs

    NASA Astrophysics Data System (ADS)

    Flock, M.; Fromang, S.; González, M.; Commerçon, B.

    2013-12-01

    Aims: Our aim is to study the thermal and dynamical evolution of protoplanetary discs in global simulations, including the physics of radiation transfer and magneto-hydrodynamic turbulence caused by the magneto-rotational instability. Methods: We have developed a radiative transfer method based on the flux-limited diffusion approximation that includes frequency dependent irradiation by the central star. This hybrid scheme is implemented in the PLUTO code. The focus of our implementation is on the performance of the radiative transfer method. Using an optimized Jacobi preconditioned BiCGSTAB solver, the radiative module is three times faster than the magneto-hydrodynamic step for the disc set-up we consider. We obtain weak scaling efficiencies of 70% up to 1024 cores. Results: We present the first global 3D radiation magneto-hydrodynamic simulations of a stratified protoplanetary disc. The disc model parameters were chosen to approximate those of the system AS 209 in the star-forming region Ophiuchus. Starting the simulation from a disc in radiative and hydrostatic equilibrium, the magneto-rotational instability quickly causes magneto-hydrodynamic turbulence and heating in the disc. We find that the turbulent properties are similar to that of recent locally isothermal global simulations of protoplanetary discs. For example, the rate of angular momentum transport ? is a few times 10-3. For the disc parameters we use, turbulent dissipation heats the disc midplane and raises the temperature by about 15% compared to passive disc models. The vertical temperature profile shows no temperature peak at the midplane as in classical viscous disc models. A roughly flat vertical temperature profile establishes in the optically thick region of the disc close to the midplane. We reproduce the vertical temperature profile with viscous disc models for which the stress tensor vertical profile is flat in the bulk of the disc and vanishes in the disc corona. Conclusions: The present paper demonstrates for the first time that global radiation magneto-hydrodynamic simulations of turbulent protoplanetary discs are feasible with current computational facilities. This opens up the window to a wide range of studies of the dynamics of the inner parts of protoplanetary discs, for which there are significant observational constraints.

  15. Mechanical concepts for disc regeneration

    Microsoft Academic Search

    Klaus John Schnake; Michael Putzier; Norbert P. Haas; Frank Kandziora

    2006-01-01

    Different strategies exist to treat intervertebral disc degeneration. Biological attempts to regenerate the disc are promising.\\u000a However, degeneration of the disc is always accompanied by alterations of disc height, intradiscal pressure, load distribution,\\u000a and motion patterns, respectively. Since those preconditions are independent factors for disc degeneration, it is unlikely\\u000a that regeneration may occur without firstly restoring the physiological status of

  16. Bryan total disc arthroplasty: a replacement disc for cervical disc disease

    PubMed Central

    Wenger, Markus; Markwalder, Thomas-Marc

    2010-01-01

    Total disc arthroplasty is a new option in the treatment of cervical degenerative disc disease. Several types of cervical disc prostheses currently challenge the gold-standard discectomy and fusion procedures. This review describes the Bryan Cervical Disc System and presents the Bryan prosthesis, its indications, surgical technique, complications, and outcomes, as given in the literature. PMID:22915917

  17. Kinetics of degradation during fatigue and aging of fused silica optical fiber

    NASA Astrophysics Data System (ADS)

    Matthewson, M. John; Yuce, Hakan H.

    1994-09-01

    Fused silica optical fiber tested in aggressive environments can exhibit a 'knee' in both the zero-stress aging and the fatigue under stress; degradation proceeds at an accelerated rate beyond the knee. This behavior leads to shorter lifetimes than predicted from short term data and to strength degradation even in the absence of an applied stress which can result in handleability problems. While the first observation of this behavior was for a humid environment, later work only reported the knee in liquid aqueous environments. This paper reports the observation of a pronounced fatigue and aging knee for a fiber tested in 85 degree(s)C, 85% relative humidity, clearly indicting this phenomenon can occur in more benign environments. Surface roughness measurements using atomic force microscopy also show an abrupt increase in roughness indicting that, for this fiber at least, the development of surface roughness before the knee can not be used as a precursor for predicting the position of the knee.

  18. Classification of wet aged related macular degeneration using optical coherence tomographic images

    NASA Astrophysics Data System (ADS)

    Haq, Anam; Mir, Fouwad Jamil; Yasin, Ubaid Ullah; Khan, Shoab A.

    2013-12-01

    Wet Age related macular degeneration (AMD) is a type of age related macular degeneration. In order to detect Wet AMD we look for Pigment Epithelium detachment (PED) and fluid filled region caused by choroidal neovascularization (CNV). This form of AMD can cause vision loss if not treated in time. In this article we have proposed an automated system for detection of Wet AMD in Optical coherence tomographic (OCT) images. The proposed system extracts PED and CNV from OCT images using segmentation and morphological operations and then detailed feature set are extracted. These features are then passed on to the classifier for classification. Finally performance measures like accuracy, sensitivity and specificity are calculated and the classifier delivering the maximum performance is selected as a comparison measure. Our system gives higher performance using SVM as compared to other methods.

  19. Age-related changes in the optic nerve of Sprague-Dawley rats: an ultrastructural and immunohistochemical study.

    PubMed

    Yassa, Hanan Dawood

    2014-07-01

    The optic nerve is a unique part of the central nervous system. It lacks neuronal cell bodies and consists of axons of the retinal ganglion cells together with the supporting neuroglial cells. In the present study, aging of the optic nerve was studied in female Sprague-Dawley rats aged 3, 12, 24 and 30 months old, ultrastructurally, immunohistochemically and morphometrically trying to answer the question why aging is a common risk factor for many ocular diseases especially glaucoma. Additionally, studying the optic nerve aging offered a good opportunity to gain further insight into the effects of aging on white matter. Both nerve fibers and neuroglial cells demonstrated several age related changes which were more profound in 30 months old rats. Optic nerve axons displayed watery degeneration and dark degeneration. Myelin disturbances including widening, whorls, splitting and vacuolations of the myelin lamellae were also observed. Neuroglial cells appeared to be more frequent than in younger rats especially microglia cells and developed dense cytoplasmic inclusions. GFAP-positive astrocytes delineated age-related progressive increase in number, size as well as length and thickness of their processes. CD68 immunohistochemical staining revealed age-related changes in the morphology, location and number of CD68 positive microglia cells. PMID:24958340

  20. Optical coherence tomography: age estimation of Calliphora vicina pupae in vivo?

    PubMed

    Brown, Katherine; Harvey, Michelle

    2014-09-01

    Necrophagous blowfly pupae are valuable contributors to the estimation of post-mortem interval, should an accurate age estimate be obtained. At present, this is reliant on a combination of rearing and destructive methods conducted on preserved samples, including morphological observation and gene expression analyses. This study demonstrates the use of optical coherence tomography (OCT) as a tool for in vivo morphological observation and pupal age estimation. Using a Michelson OCT microscope, alive and preserved four and ten-day old Calliphora vicina pupae were scanned in different orientations. Two and three-dimensional images were created. Morphological characteristics such as the brain, mouthparts and legs were identifiable in both living and preserved samples, with distinct differences noted between the two ages. Absorption of light by the puparium results in a vertical resolution of 1-2 mm, preventing observation of deeper tissues. The use of contrast agents or a longer wavelength laser would improve the images obtainable. At present, the data suggests OCT provides a primary view of external and internal morphology, which can be used to distinguish younger and older pupae for further analysis of age and PMI estimation. PMID:25064575

  1. Optically stimulated luminescence dating of sand-dune formed within the Little Ice Age

    NASA Astrophysics Data System (ADS)

    Du, Jin-Hua; Wang, Xu-Long

    2014-09-01

    Optically Stimulated Luminescence (OSL) dating has been intensively used to date the late Quaternary deposits. The Single-Aliquot Regenerative-dose (SAR) protocol was applied to measure coarse quartz grains extracted from Dali sand dunes, central China. It was found that this popular method could not accurately date sand dunes activities that recently happened. This is due to the low OSL sensitivity of quartz grains, leading to a failure in OSL dating that has also been met in other sediments before. To overcome this limitation, quartz grains were heated to 500 °C to increase the OSL output for one magnitude. Sensitivity changes could also be corrected by the following test dose OSL responses and has no influence on OSL ages. Thus it is suggested to carry out the SAR protocol for dim and young quartz OSL samples with additional annealing step (e.g. 500 °C) after the measurements of natural cycle. The resultant OSL ages proved that the last sand-dune activities happened during the Little Ice Age (?400 years ago), which was further supported by independent age control (?1600 AD) from historical documents.

  2. Hyperhomocysteinaemia in young patients with non-arteritic anterior ischaemic optic neuropathy

    Microsoft Academic Search

    Aki Kawasaki; Valerie A Purvin; Richard A Burgett

    1999-01-01

    BACKGROUND\\/AIMElevated plasma homocysteine is a newly identified vascular risk factor among patients under age 55 years with cerebrovascular, cardiovascular, or peripheral vascular disease. This study sought to evaluate retrospectively the plasma homocysteine status among healthy younger patients with ischaemic optic disc disease.METHODS12 non-diabetic patients who had been diagnosed with non-arteritic anterior ischaemic optic neuropathy (NAION) before the age of 50

  3. Optical absorption as a sensitive monitor of tensile strength loss in thermally aged nylon 6,6

    SciTech Connect

    Renschler, C.L.

    1985-01-01

    Chemical changes which take place in polymers during thermal aging often adversely affect the bulk physical properties of the material. Aging rates under ambient conditions are usually so slow as to require extremely long aging cycles to achieve measurable losses in such properties as tensile strength. Therefore, accelerated aging under more stressful conditions (e.g., higher temperatures) with Arrhenius-plot extrapolations to ambient conditions is often employed. Since this scheme requires that there is no change in the predominate aging mechanism at higher temperatures, one would prefer to increase the sensitivity of aging detection so one could measure aging at lower temperatures on a reasonable time scale. We describe here the use of optical absorption spectrophotometry as a sensitive monitor of thermal aging in nylon 6,6 which correlates with tensile strength loss. 8 refs., 3 figs.

  4. Probing the Galactic Bulge with deep Adaptive Optics imaging: the age of NGC 6440

    E-print Network

    L. Origlia; S. Lena; E. Diolaiti; F. R. Ferraro; E. Valenti; S. Fabbri; G. Beccari

    2008-09-23

    We present first results of a pilot project aimed at exploiting the potentiality of ground based adaptive optics imaging in the near infrared to determine the age of stellar clusters in the Galactic Bulge. We have used a combination of high resolution adaptive optics (ESO-VLT NAOS-CONICA) and wide-field (ESO-NTT-SOFI) photometry of the metal rich globular cluster NGC 6440 located towards the inner Bulge, to compute a deep color magnitude diagram from the tip of the Red Giant Branch down to J~22$, two magnitudes below the Main Sequence Turn Off (TO). The magnitude difference between the TO level and the red Horizontal Branch has been used as an age indicator. It is the first time that such a measurement for a bulge globular cluster has been obtained with a ground based telescope. From a direct comparison with 47 Tuc and with a set of theoretical isochrones, we concluded that NGC 6440 is old and likely coeval to 47 Tuc. This result adds a new evidence that the Galactic Bulge is ~2 Gyr younger at most than the pristine, metal poor population of the Galactic Halo.

  5. Constraining the age and formation of stone runs in the Falkland Islands using Optically Stimulated Luminescence

    NASA Astrophysics Data System (ADS)

    Hansom, James D.; Evans, David J. A.; Sanderson, David C. W.; Bingham, Robert G.; Bentley, Michael J.

    2008-02-01

    The stone runs of the Falkland Islands are thought to be periglacial blockfields but their age and detailed origin remain enigmatic. We examine the fine sediments that underlie two stone runs in order to establish whether Optically Stimulated Luminescence (OSL) dating is an appropriate technique to constrain the date of emplacement of the fine sediments and, hence, the stone runs. Six samples were collected from two accessible sections during the Scotia Centenary Antarctic expedition in 2003. All samples were used to explore the main luminescence characteristics of the sediment, followed by quartz SAR dating procedures on four of the samples. Age estimates range from in excess of 54 ka to 16 ka, suggesting that the overlying stone runs remained active until 16 ka or later. Saturation of luminescence from quartz limits age estimates for the oldest samples in the sequences, however these are not critical to define the upper limit to the emplacement age for the overlying stone runs. The sediments also contain feldspars and initial results suggest that these may be useful in extending the timescale further, but require further samples to be obtained from other parts of the sequence. Extending the method to other stone runs in the Port Stanley Formation may allow estimates of the age of stabilisation of the stone runs to be extended into the 1-250 ka timescale. Luminescence dating of the underlying sediments, used in conjunction with cosmogenic isotope dating of the surface boulders from a range of locations along the stone runs, appears to offer a useful route towards decoding the depositional history of these impressive deposits.

  6. Resolved DEBRIS Discs

    NASA Astrophysics Data System (ADS)

    Booth, Mark; DEBRIS Team

    2011-09-01

    The Herschel DEBRIS survey is a volume-limited survey of 446 of the closest stars at wavelengths of 100 and 160 microns. Excesses at these wavelengths imply the presence of debris discs. Many of these discs were previously imaged with Spitzer but the superior angular resolution of Herschel has allowed us to resolve more than 20 of the largest of these discs. Although similar to the Kuiper belt in our own Solar System, these discs are much more massive and extend much further from their host stars. I will present images for a selection of these systems and discuss what extra information the resolved data can provide about these systems. For instance, the radii measured from the resolved images are shown to be different from that predicted by a black-body fit to the SEDs. This information allows us to infer properties about the size and composition of the dust. Resolved images can also tell us about the planetary system as a whole as the inner edges of these discs are likely to be the result of sculpting by planets. This research is funded through a Space Science Enhancement Program grant from the Canadian Space Agency.

  7. Enhanced fatigue and aging resistance using reactive powders in the optical fiber buffer coating

    NASA Astrophysics Data System (ADS)

    Rondinella, Vincenzo V.; Matthewson, M. John; Foy, Paul R.; Schmid, Steven R.; Krongayz, Vadim V.

    1994-03-01

    We have shown in previous work that the addition of small quantities of colloidal silica to the UV- curable polymer coating of fused silica optical fiber causes a dramatic improvement in the fatigue and aging resistance both in aqueous and in constant humidity environments. The presence of silica in the coating inhibits the mechanisms responsible for the surface roughening that causes the fatigue knee and strength degradation during zero-stress aging. This work presents results which show the effect of higher concentrations of the silica additive (6 wt%) and of an adhesion promoting agent on both the rheological properties of the polymer coating and the fatigue and zero-stress aging behavior of the fiber. Viscosity measurements show thixotropic behavior which indicates that the silica particles tend to form a network structure in the prepolymer. Filtration of the prepolymer to remove large particles is hampered by this phenomenon. The fiber coated with the silica-containing polymer exhibits substantial improvement in the long term mechanical reliability compared to a reference fiber without additive in the coating.

  8. Accelerated aging studies and the prediction of the archival lifetime of optical disk media

    NASA Astrophysics Data System (ADS)

    Nikles, David E.; Wiest, John M.

    1999-11-01

    Data archivists expect information storage media to have a lifetime greater than ten years. Furthermore they desire the ability to predict when the media will fail in order to plan for its replacement. Archival lifetime predictions are based on accelerated aging studies, where the media are subjected to conditions of high temperature and high humidity. The rate of failure is measured and the data extrapolated to obtain rates of failure under ambient conditions. This extrapolation is reasonable provided the degradation process is activated and the Arrhenius relationship holds. However this may not be the case for the complicated materials packages in optical data storage media. A primary concern for the polymeric materials is any phase transition, such a glass transition or a beta relaxation, that may occur at temperatures between ambient and the accelerated aging conditions. It is not clear how one extrapolates through those transitions. These phase transitions can give rise to large changes in the rates of diffusion for water, oxygen and other agents of degradation. Furthermore, for polymers, such as polycarbonate, the mode of failure is often hydrolysis and the degradation products can catalyze further hydrolysis, an autocatalytic degradation. The polymer degradation will change the phase transition temperatures. The degradation products may also plasticize the polymer, causing further changes in diffusion rates. We provide here a simple analysis of accelerated aging techniques and discuss other factors that may be involved.

  9. Appearance of Keplerian discs orbiting Kerr superspinars

    NASA Astrophysics Data System (ADS)

    Stuchlík, Zden?k; Schee, Jan

    2010-11-01

    We study optical phenomena related to the appearance of Keplerian accretion discs orbiting Kerr superspinars predicted by string theory. The superspinar exterior is described by standard Kerr naked singularity geometry breaking the black hole limit on the internal angular momentum (spin). We construct local photon escape cones for a variety of orbiting sources that enable us to determine the superspinars silhouette in the case of distant observers. We show that the superspinar silhouette depends strongly on the assumed edge where the external Kerr spacetime is joined to the internal spacetime governed by string theory and significantly differs from the black hole silhouette. The appearance of the accretion disc is strongly dependent on the value of the superspinar spin in both their shape and frequency shift profile. Apparent extension of the disc grows significantly with the growing spin, while the frequency shift grows with the descending spin. This behaviour differs substantially from the appearance of discs orbiting black holes enabling thus, at least in principle, to distinguish clearly the Kerr superspinars and black holes. In vicinity of a Kerr superspinar the non-escaped photons have to be separated to those captured by the superspinar and those being trapped in its strong gravitational field leading to self-illumination of the disc that could even influence its structure and cause self-reflection effect of radiation of the disc. The amount of trapped photons grows with descending superspinar spin. We thus can expect significant self-illumination effects in the field of Kerr superspinars with near-extreme spin a ~ 1.

  10. Why do some intervertebral discs degenerate, when others (in the same spine) do not?

    PubMed

    Adams, Michael A; Lama, Polly; Zehra, Uruj; Dolan, Patricia

    2015-03-01

    This review suggests why some discs degenerate rather than age normally. Intervertebral discs are avascular pads of fibrocartilage that allow movement between vertebral bodies. Human discs have a low cell density and a limited ability to adapt to mechanical demands. With increasing age, the matrix becomes yellowed, fibrous, and brittle, but if disc structure remains intact, there is little impairment in function, and minimal ingrowth of blood vessels or nerves. Approximately half of old lumbar discs degenerate in the sense of becoming physically disrupted. The posterior annulus and lower lumbar discs are most affected, presumably because they are most heavily loaded. Age and genetic inheritance can weaken discs to such an extent that they are physically disrupted during everyday activities. Damage to the endplate or annulus typically decompresses the nucleus, concentrates stress within the annulus, and allows ingrowth of nerves and blood vessels. Matrix disruption progresses by mechanical and biological means. The site of initial damage leads to two disc degeneration "phenotypes": endplate-driven degeneration is common in the upper lumbar and thoracic spine, and annulus-driven degeneration is common at L4-S1. Discogenic back pain can be initiated by tissue disruption, and amplified by inflammation and infection. Healing is possible in the outer annulus only, where cell density is highest. We conclude that some discs degenerate because they are disrupted by excessive mechanical loading. This can occur without trauma if tissues are weakened by age and genetic inheritance. Moderate mechanical loading, in contrast, strengthens all spinal tissues, including discs. PMID:24753325

  11. Modeling the Compact Disc Read System in Lab

    ERIC Educational Resources Information Center

    Hinaus, Brad; Veum, Mick

    2009-01-01

    One of the great, engaging aspects of physics is its application to everyday technology. The compact disc player is an example of one such technology that applies fundamental principles from optics in order to efficiently store and quickly retrieve information. We have created a lab in which students use simple optical components to assemble a…

  12. Electrostatic rotation of glass disc

    Microsoft Academic Search

    Roland Moser; Toshiro Higuchi

    2002-01-01

    This paper reports the successful electrostatic rotation of a glass disc of 65mm diameter. The realized electrostatic glass disc drive features high compactness and simplicity. The goal of the presented experimental work is to verify that the concept of the electrostatic glass motor can be applied to data storage devices, especially for disc drives with diameters <1in. The basic principle

  13. Revival of the Jumping Disc

    ERIC Educational Resources Information Center

    Ucke, C.; Schlichting, H-J.

    2009-01-01

    Snap discs made of bimetal have many technical applications as thermostats. Jumping discs are a toy version of such snap discs. Besides giving technical information, we describe physical investigations. We show especially how, through simple measurements and calculations, you can determine the initial speed ([approximately equal to]3.5 m…

  14. The DISC Quotient

    NASA Astrophysics Data System (ADS)

    Elliott, John R.; Baxter, Stephen

    2012-09-01

    D.I.S.C: Decipherment Impact of a Signal's Content. The authors present a numerical method to characterise the significance of the receipt of a complex and potentially decipherable signal from extraterrestrial intelligence (ETI). The purpose of the scale is to facilitate the public communication of work on any such claimed signal, as such work proceeds, and to assist in its discussion and interpretation. Building on a "position" paper rationale, this paper looks at the DISC quotient proposed and develops the algorithmic steps and comprising measures that form this post detection strategy for information dissemination, based on prior work on message detection, decipherment. As argued, we require a robust and incremental strategy, to disseminate timely, accurate and meaningful information, to the scientific community and the general public, in the event we receive an "alien" signal that displays decipherable information. This post-detection strategy is to serve as a stepwise algorithm for a logical approach to information extraction and a vehicle for sequential information dissemination, to manage societal impact. The "DISC Quotient", which is based on signal analysis processing stages, includes factors based on the signal's data quantity, structure, affinity to known human languages, and likely decipherment times. Comparisons with human and other phenomena are included as a guide to assessing likely societal impact. It is submitted that the development, refinement and implementation of DISC as an integral strategy, during the complex processes involved in post detection and decipherment, is essential if we wish to minimize disruption and optimize dissemination.

  15. Infrared Variability from Circumbinary Disc Temperature Modulations

    E-print Network

    Bodman, Eva

    2015-01-01

    The temperature of a circumbinary disc edge should undulate due to variations in illumination as a function of binary orbital phase. We explore circumbinary disc temperature variations as a source of broad-band infrared light curve variability. Approximating the wall of a circumbinary disc edge as a wide optically thick cylinder with surface temperature dependent on its illumination, we find that a binary comprised of 1 M$_\\odot$ and 0.5 M$_\\odot$ pre-main sequence stars in a $\\sim$15.5 day period, would exhibit the largest amplitude variations of $\\sim$9% at 3.77 and 4.68 {\\mu}m as seen by a distant observer. The amplitude of variations and shape of the light curve is sensitive to the luminosity and mass ratios of the stars in the binary, the radius of the circumbinary disc clearing, the binary separation, and the orbital inclination. The light curve variations are smooth and very red with a non-sinusoidal shape for most of the parameter space explored. Possible morphologies include a single peak with a flat...

  16. Surgical treatment of thoracic disc herniations via tailored posterior approaches

    Microsoft Academic Search

    Wolfgang Börm; U. Bäzner; R. W. König; T. Kretschmer; G. Antoniadis; J. Kandenwein

    We present clinical findings, radiological characteristics and surgical modalities of various posterior approaches to thoracic\\u000a disc herniations and report the clinical results in 27 consecutive patients. Within an 8-year period 27 consecutive patients\\u000a (17 female, 10 male) aged 30–83 years (mean 53 years.) were surgically treated for 28 symptomatic herniated thoracic discs\\u000a in our department. Six of these lesions (21%) were calcified.

  17. Electrical, structural and optical properties of fluorine-doped zinc oxide thin films: Effect of the solution aging time

    Microsoft Academic Search

    S. M. Rozati; S. Moradi; S. Golshahi; R. Martins; E. Fortunato

    2009-01-01

    In this paper ageing effects of the solution used to prepare fluorine-doped ZnO films by the spray pyrolysis technique were investigated, concerning its role on the structure, the electrical and optical properties of films produced. The data reveal that the sheet resistance of the ZnO:F thin film decreases with the age of the solution used, reaching a minimum of 24 ?\\/?,

  18. Characterization of Choroidal Layers in Normal Aging Eyes Using Enface Swept-Source Optical Coherence Tomography

    PubMed Central

    Mullins, Robert F.; Baumal, Caroline R.; Mohler, Kathrin J.; Kraus, Martin F.; Liu, Jonathan; Badaro, Emmerson; Alasil, Tarek; Hornegger, Joachim; Fujimoto, James G.; Duker, Jay S.; Waheed, Nadia K.

    2015-01-01

    Purpose To characterize qualitative and quantitative features of the choroid in normal eyes using enface swept-source optical coherence tomography (SS-OCT). Methods Fifty-two eyes of 26 consecutive normal subjects were prospectively recruited to obtain multiple three-dimensional 12x12mm volumetric scans using a long-wavelength high-speed SS-OCT prototype. A motion-correction algorithm merged multiple SS-OCT volumes to improve signal. Retinal pigment epithelium (RPE) was segmented as the reference and enface images were extracted at varying depths every 4.13?m intervals. Systematic analysis of the choroid at different depths was performed to qualitatively assess the morphology of the choroid and quantify the absolute thicknesses as well as the relative thicknesses of the choroidal vascular layers including the choroidal microvasculature (choriocapillaris, terminal arterioles and venules; CC) and choroidal vessels (CV) with respect to the subfoveal total choroidal thickness (TC). Subjects were divided into two age groups: younger (<40 years) and older (?40 years). Results Mean age of subjects was 41.92 (24-66) years. Enface images at the level of the RPE, CC, CV, and choroidal-scleral interface were used to assess specific qualitative features. In the younger age group, the mean absolute thicknesses were: TC 379.4?m (SD±75.7?m), CC 81.3?m (SD±21.2?m) and CV 298.1?m (SD±63.7?m). In the older group, the mean absolute thicknesses were: TC 305.0?m (SD±50.9?m), CC 56.4?m (SD±12.1?m) and CV 248.6?m (SD±49.7?m). In the younger group, the relative thicknesses of the individual choroidal layers were: CC 21.5% (SD±4.0%) and CV 78.4% (SD±4.0%). In the older group, the relative thicknesses were: CC 18.9% (SD±4.5%) and CV 81.1% (SD±4.5%). The absolute thicknesses were smaller in the older age group for all choroidal layers (TC p=0.006, CC p=0.0003, CV p=0.03) while the relative thickness was smaller only for the CC (p=0.04). Conclusions Enface SS-OCT at 1050nm enables a precise qualitative and quantitative characterization of the individual choroidal layers in normal eyes. Only the CC is relatively thinner in the older eyes. In-vivo evaluation of the choroid at variable depths may be potentially valuable in understanding the natural history of age-related posterior segment disease. PMID:26172550

  19. Stationary Population III accretion discs

    E-print Network

    Michael Mayer; Wolfgang J. Duschl

    2004-09-02

    We present stationary models of protostellar population III (Pop III, for short) accretion discs, compare them to Pop I discs, and investigate the influence of the different chemical compositions on the occurence of gravitational, thermal and thermal-viscous instabilities in the discs. In particular in the cooler regions, we find major differences between Pop III and Pop I discs, both in the structure and stability behaviour. This is mainly due to the absence of most molecules and dust in Pop III, which are very efficient absorbers in Pop I discs.

  20. Warp propagation in astrophysical discs

    E-print Network

    Nixon, Chris

    2015-01-01

    Astrophysical discs are often warped, that is, their orbital planes change with radius. This occurs whenever there is a non-axisymmetric force acting on the disc, for example the Lense-Thirring precession induced by a misaligned spinning black hole, or the gravitational pull of a misaligned companion. Such misalignments appear to be generic in astrophysics. The wide range of systems that can harbour warped discs - protostars, X-ray binaries, tidal disruption events, quasars and others - allows for a rich variety in the disc's response. Here we review the basic physics of warped discs and its implications.

  1. Response of a galactic disc to vertical perturbations: strong dependence on density distribution

    NASA Astrophysics Data System (ADS)

    Pranav, Pratyush; Jog, Chanda J.

    2010-07-01

    We study the self-consistent, linear response of a galactic disc to non-axisymmetric perturbations in the vertical direction as due to a tidal encounter, and show that the density distribution near the disc mid-plane has a strong impact on the radius beyond which distortions like warps develop. The self-gravity of the disc resists distortion in the inner parts. Applying this approach to a galactic disc with an exponential vertical profile, Saha & Jog showed that warps develop beyond 4-6 disc scalelengths, which could hence be only seen in HI. The real galactic discs, however, have less steep vertical density distributions that lie between a sech and an exponential profile. Here we calculate the disc response for such a general sec h2/n density distribution, and show that the warps develop from a smaller radius of 2-4 disc scalelengths. This naturally explains why most galaxies show stellar warps that start within the optical radius. Thus, a qualitatively different picture of ubiquitous optical warps emerges for the observed less steep density profiles. The surprisingly strong dependence on the density profile is due to the fact that the disc self-gravity depends crucially on its mass distribution close to the mid-plane. General results for the radius of onset of warps, obtained as a function of the disc scalelength and the vertical scaleheight, are presented as contour plots which can be applied to any galaxy.

  2. Biometric, optical and physical changes in the isolated human crystalline lens with age in relation to presbyopia

    Microsoft Academic Search

    Adrian Glasser; Melanie C. W. Campbell

    1999-01-01

    The biometric, optical and physical properties of 19 pairs of isolated human eye-bank lenses ranging in age from 5 to 96 years were compared. Lens focal length and spherical aberration were measured using a scanning laser apparatus, lens thickness and the lens surface curvatures were measured by digitizing the lens profiles and equivalent refractive indices were calculated for each lens

  3. A multi-stress environmental chamber for the aging of all-dielectric self-support fiber optic cables

    Microsoft Academic Search

    George G. Karady; Baozhuang Shi; Qi Huang; M. W. Tuominem

    2003-01-01

    This paper presents an environmental chamber built at Arizona State University for the long-term aging test of ADSS fiber optic cables. Five 14-foot long cable samples can be tested in the chamber under a series of stresses, including UV radiation, salt fog, clean rain, and mechanical tension. The voltage and leakage current can be recorded continuously for the analysis of

  4. Disc resonator gyroscope fabrication process requiring no bonding alignment

    NASA Technical Reports Server (NTRS)

    Shcheglov, Kirill V. (Inventor)

    2010-01-01

    A method of fabricating a resonant vibratory sensor, such as a disc resonator gyro. A silicon baseplate wafer for a disc resonator gyro is provided with one or more locating marks. The disc resonator gyro is fabricated by bonding a blank resonator wafer, such as an SOI wafer, to the fabricated baseplate, and fabricating the resonator structure according to a pattern based at least in part upon the location of the at least one locating mark of the fabricated baseplate. MEMS-based processing is used for the fabrication processing. In some embodiments, the locating mark is visualized using optical and/or infrared viewing methods. A disc resonator gyroscope manufactured according to these methods is described.

  5. A disc in the heart of the Ant nebula

    E-print Network

    Foteini Lykou; Olivier Chesneau; Eric Lagadec; Albert Zijlstra

    2007-10-03

    We present the discovery of a silicate disc at the centre of the planetary nebula Mz3 (the Ant). The nebula was observed with MIDI on the Very Large Telescope Interferometer (VLTI). The visibilities obtained at different orientations clearly indicate the presence of a dusty, nearly edge-on disc in the heart of the nebula. An amorphous silicate absorption feature is clearly seen in our mid-IR spectrum and visibility curves. We used radiative transfer Monte Carlo simulations to constrain the geometrical and physical parameters of the disc. We derive an inner radius of 9 AU (~6mas assuming D=1.4kpc). This disc is perpendicular to, but a factor of 10^{3} smaller than the optical bipolar outflow.

  6. First results of the SONS survey: submillimetre detections of debris discs

    NASA Astrophysics Data System (ADS)

    Pani?, O.; Holland, W. S.; Wyatt, M. C.; Kennedy, G. M.; Matthews, B. C.; Lestrade, J. F.; Sibthorpe, B.; Greaves, J. S.; Marshall, J. P.; Phillips, N. M.; Tottle, J.

    2013-10-01

    New detections of debris discs at submillimetre wavelengths present highly valuable complementary information to prior observations of these sources at shorter wavelengths. Characterization of discs through spectral energy distribution modelling including the submillimetre fluxes is essential for our basic understanding of disc mass and temperature, and presents a starting point for further studies using millimetre interferometric observations. In the framework of the ongoing SCUBA-2 Observations of Nearby Stars, the instrument SCUBA-2 on the James Clerk Maxwell Telescope was used to provide measurements of 450 and 850 ?m fluxes towards a large sample of nearby main-sequence stars with debris discs detected previously at shorter wavelengths. We present the first results from the ongoing survey, concerning 850 ?m detections and 450 ?m upper limits towards 10 stars, the majority of which are detected at submillimetre wavelengths for the first time. One, or possibly two, of these new detections is likely a background source. We fit the spectral energy distributions of the star+disc systems with a blackbody emission approach and derive characteristic disc temperatures. We use these temperatures to convert the observed fluxes to disc masses. We obtain a range of disc masses from 0.001 to 0.1 M?, values similar to the prior dust mass measurements towards debris discs. There is no evidence for evolution in dust mass with age on the main sequence, and indeed the upper envelope remains relatively flat at ?0.5 M? at all ages. The inferred disc masses are lower than those from disc detections around pre-main-sequence stars, which may indicate a depletion of solid mass. This may also be due to a change in disc opacity, though limited sensitivity means that it is not yet known what fraction of pre-main-sequence stars have discs with dust masses similar to debris disc levels. New, high-sensitivity detections are a path towards investigating the trends in dust mass evolution.

  7. Mechanotransduction in intervertebral discs

    PubMed Central

    Tsai, Tsung-Ting; Cheng, Chao-Min; Chen, Chien-Fu; Lai, Po-Liang

    2014-01-01

    Mechanotransduction plays a critical role in intracellular functioning—it allows cells to translate external physical forces into internal biochemical activities, thereby affecting processes ranging from proliferation and apoptosis to gene expression and protein synthesis in a complex web of interactions and reactions. Accordingly, aberrant mechanotransduction can either lead to, or be a result of, a variety of diseases or degenerative states. In this review, we provide an overview of mechanotransduction in the context of intervertebral discs, with a focus on the latest methods of investigating mechanotransduction and the most recent findings regarding the means and effects of mechanotransduction in healthy and degenerative discs. We also provide some discussion of potential directions for future research and treatments. PMID:25267492

  8. Biomechanics of Disc Degeneration

    PubMed Central

    Palepu, V.; Kodigudla, M.; Goel, V. K.

    2012-01-01

    Disc degeneration and associated disorders are among the most debated topics in the orthopedic literature over the past few decades. These may be attributed to interrelated mechanical, biochemical, and environmental factors. The treatment options vary from conservative approaches to surgery, depending on the severity of degeneration and response to conservative therapies. Spinal fusion is considered to be the “gold standard” in surgical methods till date. However, the association of adjacent level degeneration has led to the evolution of motion preservation technologies like spinal arthroplasty and posterior dynamic stabilization systems. These new technologies are aimed to address pain and preserve motion while maintaining a proper load sharing among various spinal elements. This paper provides an elaborative biomechanical review of the technologies aimed to address the disc degeneration and reiterates the point that biomechanical efficacy followed by long-term clinical success will allow these nonfusion technologies as alternatives to fusion, at least in certain patient population. PMID:22745914

  9. Counter-rotating accretion discs

    NASA Astrophysics Data System (ADS)

    Dyda, S.; Lovelace, R. V. E.; Ustyugova, G. V.; Romanova, M. M.; Koldoba, A. V.

    2015-01-01

    Counter-rotating discs can arise from the accretion of a counter-rotating gas cloud on to the surface of an existing corotating disc or from the counter-rotating gas moving radially inwards to the outer edge of an existing disc. At the interface, the two components mix to produce gas or plasma with zero net angular momentum which tends to free-fall towards the disc centre. We discuss high-resolution axisymmetric hydrodynamic simulations of viscous counter-rotating discs for the cases where the two components are vertically separated and radially separated. The viscosity is described by an isotropic ?-viscosity including all terms in the viscous stress tensor. For the vertically separated components, a shear layer forms between them and the middle part of this layer free-falls to the disc centre. The accretion rates are increased by factors of ˜102-104 over that for a conventional disc rotating in one direction with the same viscosity. The vertical width of the shear layer and the accretion rate are strongly dependent on the viscosity and the mass fraction of the counter-rotating gas. In the case of radially separated components where the inner disc corotates and the outer disc rotates in the opposite direction, a gap between the two components opens and closes quasi-periodically. The accretion rates are ?25 times larger than those for a disc rotating in one direction with the same viscosity.

  10. Probabilistic diffusion tractography of the optic radiations and visual function in preterm infants at term equivalent age.

    PubMed

    Bassi, Laura; Ricci, Daniela; Volzone, Anna; Allsop, Joanna M; Srinivasan, Latha; Pai, Aakash; Ribes, Carmen; Ramenghi, Luca A; Mercuri, Eugenio; Mosca, Fabio; Edwards, A David; Cowan, Frances M; Rutherford, Mary A; Counsell, Serena J

    2008-02-01

    Children born prematurely have a high incidence of visual disorders which cannot always be explained by focal retinal or brain lesions. The aim of this study was to test the hypothesis that visual function in preterm infants is related to the microstructural development of white matter in the optic radiations. We used diffusion tensor imaging (DTI) with probabilistic diffusion tractography to delineate the optic radiations at term equivalent age and compared the fractional anisotropy (FA) to a contemporaneous evaluation of visual function. Thirty-seven preterm infants (19 male) born at median (range) 28(+4) (24(+1)-32(+3)) weeks gestational age, were examined at a post-menstrual age of 42 (39(+6)-43) weeks. MRI and DTI were acquired on a 3 Tesla MR system with DTI obtained in 15 non-collinear directions with a b value of 750 s/mm(2). Tracts were generated from a seed mask placed in the white matter lateral to the lateral geniculate nucleus and mean FA values of these tracts were determined. Visual assessment was performed using a battery of nine items assessing different aspects of visual abilities. Ten infants had evidence of cerebral lesions on conventional MRI. Multiple regression analysis demonstrated that the visual assessment score was independently correlated with FA values, but not gestational age at birth, post-menstrual age at scan or the presence of lesions on conventional MRI. The occurrence of mild retinopathy of prematurity did not affect the FA measures or visual scores. We then performed a secondary analysis using tract-based spatial statistics to determine whether global brain white matter development was related to visual function and found that only FA in the optic radiations was correlated with visual assessment score. Our results suggest that in preterm infants at term equivalent age visual function is directly related to the development of white matter in the optic radiations. PMID:18222994

  11. Enclosed rotary disc air pulser

    DOEpatents

    Olson, A. L. (Idaho Falls, ID); Batcheller, Tom A. (Idaho Falls, ID); Rindfleisch, J. A. (Arco, ID); Morgan, John M. (Arco, ID)

    1989-01-01

    An enclosed rotary disc air pulser for use with a solvent extraction pulse olumn includes a housing having inlet, exhaust and pulse leg ports, a shaft mounted in the housing and adapted for axial rotation therein, first and second disc members secured to the shaft within the housing in spaced relation to each other to define a chamber therebetween, the chamber being in communication with the pulse leg port, the first disc member located adjacent the inlet port, the second disc member being located adjacent the exhaust port, each disc member having a milled out portion, the disc members positioned on the shaft so that as the shaft rotates, the milled out portions permit alternative cyclical communication between the inlet port and the chamber and the exhaust port and the chamber.

  12. Inflammation in intervertebral disc degeneration and regeneration

    PubMed Central

    Molinos, Maria; Almeida, Catarina R.; Caldeira, Joana; Cunha, Carla; Gonçalves, Raquel M.; Barbosa, Mário A.

    2015-01-01

    Intervertebral disc (IVD) degeneration is one of the major causes of low back pain, a problem with a heavy economic burden, which has been increasing in prevalence as populations age. Deeper knowledge of the complex spatial and temporal orchestration of cellular interactions and extracellular matrix remodelling is critical to improve current IVD therapies, which have so far proved unsatisfactory. Inflammation has been correlated with degenerative disc disease but its role in discogenic pain and hernia regression remains controversial. The inflammatory response may be involved in the onset of disease, but it is also crucial in maintaining tissue homeostasis. Furthermore, if properly balanced it may contribute to tissue repair/regeneration as has already been demonstrated in other tissues. In this review, we focus on how inflammation has been associated with IVD degeneration by describing observational and in vitro studies as well as in vivo animal models. Finally, we provide an overview of IVD regenerative therapies that target key inflammatory players. PMID:25673296

  13. Radicular interdural lumbar disc herniation

    Microsoft Academic Search

    Ali Akhaddar; Omar Boulahroud; Abad Elasri; Brahim Elmostarchid; Mohammed Boucetta

    2010-01-01

    Intraradicular lumbar disc herniation is a rare complication of disc disease that is generally diagnosed only during surgery.\\u000a The mechanism for herniated disc penetration into the intradural space is not known with certainty, but adhesion between the\\u000a radicular dura and the posterior longitudinal ligament was suggested as the most important condition. The authors report the\\u000a first case of an intraradicular

  14. Dynamics of warped accretion discs

    NASA Astrophysics Data System (ADS)

    Tremaine, Scott; Davis, Shane W.

    2014-06-01

    Accretion discs are present around both stellar-mass black holes in X-ray binaries and supermassive black holes in active galactic nuclei. A wide variety of circumstantial evidence implies that many of these discs are warped. The standard Bardeen-Petterson model attributes the shape of the warp to the competition between Lense-Thirring torque from the central black hole and viscous angular-momentum transport within the disc. We show that this description is incomplete in many accretion discs, and that torques from the companion star (for X-ray binaries) or the self-gravity of the disc (for active galactic nuclei) can play a major role in determining the properties of the warped disc. Including these effects leads to a rich set of new phenomena. For example, (i) when a companion star is present and the warp arises from a misalignment between the companion's orbital axis and the black hole's spin axis, there is no steady-state solution of the Pringle-Ogilvie equations for a warped disc when the viscosity falls below a critical value, which typically requires a disc aspect ratio ?10-3 in X-ray binaries; (ii) in AGN accretion discs, the warp can excite short-wavelength bending waves governed by the self-gravity of the disc, which propagate inwards with growing amplitude until they are damped by the disc viscosity. We show that both phenomena can occur for plausible values of the black hole and disc parameters, and briefly discuss their observational implications.

  15. Age- and subcaste-related patterns of serotonergic immunoreactivity in the optic lobes of the ant Pheidole dentata.

    PubMed

    Seid, Marc A; Goode, Katarzyna; Li, Christine; Traniello, James F A

    2008-09-15

    Serotonin, a biogenic amine known to be a neuromodulator of insect behavior, has recently been associated with age-related patterns of task performance in the ant Pheidole dentata. We identified worker age- and subcaste-related patterns of serotonergic activity within the optic lobes of the P. dentata brain to further examine its relationship to polyethism. We found strong immunoreactivity in the optic lobes of the brains of both minor and major workers. Serotonergic cell bodies in the optic lobes increased significantly in number as major and minor workers matured. Old major workers had greater numbers of serotonergic cell bodies than minors of a similar age. This age-related increase in serotonergic immunoreactivity, as well as the presence of diffuse serotonin networks in the mushroom bodies, antennal lobes, and central complex, occurs concomitantly with an increase in the size of worker task repertoires. Our results suggest that serotonin is associated with the development of the visual system, enabling the detection of task-related stimuli outside the nest, thus playing a significant role in worker behavioral development and colony-wide division of labor. PMID:18666203

  16. Twin disc gear tooth simulator

    NASA Astrophysics Data System (ADS)

    Eusepi, Martin W.; Dill, James F.

    1994-05-01

    This report describes the results of an effort to develop a disc on disc test rig for evaluating lubricant load capacity. The goal of the program has been to develop a reliable disc on disc (or Twin Disc) test rig capable of providing more reliable and lower cost evaluation of lubricant load capacity than the Ryder gear test which is currently used. Disc rigs have been evaluated for this application in the past, but have failed to provide scuffing results which are comparable to those found in gear tests. The unique feature of the rig designed and evaluated under this program is a drive system design which varies the disc to disc sliding and rolling speeds in a fixed manner to simulate the combined rolling and sliding motion found in a gear tooth contact. Other features include a drive system design which insures that the same points on each disc always contact each other as they rotate, and material selection and heating system design for operation with experimental lubricants at temperatures up to 700 deg F.

  17. Disc-corona energetics in the very high state of Galactic black holes

    NASA Astrophysics Data System (ADS)

    Done, Chris; Kubota, Aya

    2006-09-01

    The X-ray spectra of Galactic binary systems dominated by a quasi-thermal component (disc dominated or high/soft state) are well described by a standard Shakura-Sunyaev disc structure down to the last stable orbit around the black hole. This is not the case in the very high (or steep power-law) state, where the X-ray spectra show both a strong disc component and strong, steep tail to higher energies. We use two such spectra from the black hole transient XTE J1550-564 as specific examples of this state, where the power emitted in the tail is more than 50 per cent of the bolometric luminosity. The simultaneous ASCA and RXTE data show that these have disc spectra which are significantly lower in temperature than those seen from the same source at the same luminosity in the high/soft state. If these give a true picture of the disc, then either the disc emissivity has reduced, and/or the disc truncates above the last stable orbit. However, it is often assumed that the tail is produced by Compton scattering, in which case its shape in these spectra requires that the Comptonizing region is marginally optically thick (? ~ 2-3), and covers a large fraction of the inner disc. This will distort our view of the disc, especially of the hottest-temperature material. We build a theoretical model of a Comptonizing corona over an inner disc, and fit this to the data, but find that it still requires a large increase in inner disc radius for a standard disc emissivity. Instead, it seems more probable that the disc emissivity changes in the presence of the corona. We implement the specific inner disc-corona coupling model of Svensson & Zdziarski, in which some fraction f of the accretion power is dissipated in the corona, leaving only a fraction 1 - f to be dissipated in the optically thick disc. We show that this can explain the low-temperature/high-luminosity disc emission seen in the very high state with only a small increase in radius of the disc. While this inferred disc truncation is probably not significant, given the model uncertainties, it is consistent with the low-frequency quasi-periodic oscillation and gives continuity of properties with the low/hard-state spectra.

  18. Preparation of ormetoprim sulfadimethoxine medicated discs for disc diffusion assay

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Romet (a blend of ormetoprim and sulfadimethoxine) is a typeA medicated article for the manufacture of medicated feed in the catfish industry. Recently, the commercial manufacture of ormetoprim–sulfadimethoxine susceptibility discs was discontinued. Ormetoprim–sulfadimethoxine discs were prepared at...

  19. Sizes of protoplanetary discs after star-disc encounters

    NASA Astrophysics Data System (ADS)

    Breslau, Andreas; Steinhausen, Manuel; Vincke, Kirsten; Pfalzner, Susanne

    2014-05-01

    Most stars do not form in isolation, but as part of a star cluster or association. These young stars are initially surrounded by protoplanetary discs. In these cluster environments tidal interactions with other cluster members can alter the disc properties. Besides the disc frequency, its mass, angular momentum, and energy, the disc's size is particularly prone to being changed by a passing star. So far the change in disc size has only been investigated for a small number of very specific encounters. Several studies investigated the effect of the cluster environment on the sizes of planetary systems like our own solar system, based on a generalisation of information from this limited sample. We performed numerical simulations covering the wide parameter space typical of young star clusters, to test the validity of this approach. Here the sizes of discs after encounters are presented, based on a size definition that is comparable to the one used in observational studies. We find that, except for encounters between equal-mass stars, the usually applied estimates are insufficient. They tend to severely overestimate the remaining disc size. We show that the disc size after an encounter can be described by a relatively simple dependence on the periastron distance and the mass ratio of the encounter partners. This knowledge allows us, for example, to pin down the types of encounter possibly responsible for the structure of today's solar system. Appendix A is available in electronic form at http://www.aanda.org

  20. Dust filtration at gap edges: Implications for the spectral energy distributions of discs with embedded planets

    E-print Network

    W. K. M. Rice; Philip J. Armitage; Kenneth Wood; Giuseppe Lodato

    2006-09-29

    The spectral energy distributions (SEDs) of some T Tauri stars display a deficit of near-IR flux that could be a consequence of an embedded Jupiter-mass planet partially clearing an inner hole in the circumstellar disc. Here, we use two-dimensional numerical simulations of the planet-disc interaction, in concert with simple models for the dust dynamics, to quantify how a planet influences the dust at different radii within the disc. We show that pressure gradients at the outer edge of the gap cleared by the planet act as a filter - letting particles smaller than a critical size through to the inner disc while holding back larger particles in the outer disc. The critical particle size depends upon the disc properties, but is typically of the order of 10 microns. This filtration process will lead to discontinuous grain populations across the planet's orbital radius, with small grains in the inner disc and an outer population of larger grains. We show that this type of dust population is qualitatively consistent with SED modelling of systems that have optically thin inner holes in their circumstellar discs. This process can also produce a very large gas-to-dust ratio in the inner disc, potentially explaining those systems with optically thin inner cavities that still have relatively high accretion rates.

  1. SPOTTED DISC AND SPHERE GRAPHS URSULA HAMENSTADT

    E-print Network

    Hamenstädt, Ursula

    SPOTTED DISC AND SPHERE GRAPHS URSULA HAMENST¨ADT Abstract. The disc graph of a handlebody H;2 URSULA HAMENST¨ADT (1) For m = 1 the disc graph of H contains quasi-isometrically embedded copies of R2

  2. Outwards migration for planets in stellar irradiated 3D discs

    E-print Network

    Lega, E; Bitsch, B; Crida, A; Szulagyi, J

    2015-01-01

    For the very first time we present 3D simulations of planets embedded in stellar irradiated discs. It is well known that thermal effects could reverse the direction of planetary migration from inwards to outwards, potentially saving planets in the inner, optically thick parts of the protoplanetary disc. When considering stellar irradiation in addition to viscous friction as a source of heating, the outer disc changes from a shadowed to a flared structure. Using a suited analytical formula it has been shown that in the flared part of the disc the migration is inwards; planets can migrate outwards only in shadowed regions of the disc, { because the radial gradient of entropy is stronger there}. In order to confirm this result numerically, we have computed the total torque acting on planets held on fixed orbits embedded in stellar irradiated 3D discs using the hydrodynamical code FARGOCA. We find qualitatively good agreement between the total torque obtained with numerical simulations and the one predicted by th...

  3. Galaxy Zoo: CANDELS barred discs and bar fractions

    NASA Astrophysics Data System (ADS)

    Simmons, B. D.; Melvin, Thomas; Lintott, Chris; Masters, Karen L.; Willett, Kyle W.; Keel, William C.; Smethurst, R. J.; Cheung, Edmond; Nichol, Robert C.; Schawinski, Kevin; Rutkowski, Michael; Kartaltepe, Jeyhan S.; Bell, Eric F.; Casteels, Kevin R. V.; Conselice, Christopher J.; Almaini, Omar; Ferguson, Henry C.; Fortson, Lucy; Hartley, William; Kocevski, Dale; Koekemoer, Anton M.; McIntosh, Daniel H.; Mortlock, Alice; Newman, Jeffrey A.; Ownsworth, Jamie; Bamford, Steven; Dahlen, Tomas; Faber, Sandra M.; Finkelstein, Steven L.; Fontana, Adriano; Galametz, Audrey; Grogin, N. A.; Grützbauch, Ruth; Guo, Yicheng; Häußler, Boris; Jek, Kian J.; Kaviraj, Sugata; Lucas, Ray A.; Peth, Michael; Salvato, Mara; Wiklind, Tommy; Wuyts, Stijn

    2014-12-01

    The formation of bars in disc galaxies is a tracer of the dynamical maturity of the population. Previous studies have found that the incidence of bars in discs decreases from the local Universe to z ˜ 1, and by z > 1 simulations predict that bar features in dynamically mature discs should be extremely rare. Here, we report the discovery of strong barred structures in massive disc galaxies at z ˜ 1.5 in deep rest-frame optical images from the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey. From within a sample of 876 disc galaxies identified by visual classification in Galaxy Zoo, we identify 123 barred galaxies. Selecting a subsample within the same region of the evolving galaxy luminosity function (brighter than L*), we find that the bar fraction across the redshift range 0.5 ? z ? 2 ( f_{bar} = 10.7^{+6.3}_{-3.5} per cent after correcting for incompleteness) does not significantly evolve. We discuss the implications of this discovery in the context of existing simulations and our current understanding of the way disc galaxies have evolved over the last 11 billion years.

  4. Optical Disks.

    ERIC Educational Resources Information Center

    Gale, John C.; And Others

    1985-01-01

    This four-article section focuses on information storage capacity of the optical disk covering the information workstation (uses microcomputer, optical disk, compact disc to provide reference information, information content, work product support); use of laser videodisc technology for dissemination of agricultural information; encoding databases…

  5. Image Learning: Higher Education and Interactive Video Disc.

    ERIC Educational Resources Information Center

    Davis, Ben

    1988-01-01

    New optical information storage technologies such as the interactive video disc make possible change in how students will learn in classrooms of the future. Similar historical developments whose influences were wide ranging are discussed. Ongoing studies of interactive video applications at Massachusetts Institute of Technology are described. (JL)

  6. New ages for Middle and Later Stone Age deposits at Mumba rockshelter, Tanzania: optically stimulated luminescence dating of quartz and feldspar grains.

    PubMed

    Gliganic, Luke A; Jacobs, Zenobia; Roberts, Richard G; Domínguez-Rodrigo, Manuel; Mabulla, Audax Z P

    2012-04-01

    The archaeological deposits at Mumba rockshelter, northern Tanzania, have been excavated for more than 70 years, starting with Margit and Ludwig Köhl-Larsen in the 1930s. The assemblages of Middle Stone Age (MSA) and Later Stone Age (LSA) artefacts collected from this site constitute the type sequences for these cultural phases in East Africa. Despite its archaeological importance, however, the chronology of the site is poorly constrained, despite the application since the 1980s of several dating methods (radiocarbon, uranium-series and amino acid racemisation) to a variety of materials recovered from the deposits. Here, we review these previous chronologies for Mumba and report new ages obtained from optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL) measurements on single grains of quartz and multi-grain aliquots of potassium (K) feldspar from the MSA and LSA deposits. Measurements of single grains of quartz allowed the rejection of unrepresentative grains and the application of appropriate statistical models to obtain the most reliable age estimates, while measurements of K-feldspars allowed the chronology to be extended to older deposits. The seven quartz ages and four K-feldspar ages provide improved temporal constraints on the archaeological sequence at Mumba. The deposits associated with the latest Kisele Industry (Bed VI-A) and the earliest Mumba Industry (Bed V) are dated to 63.4 ± 5.7 and 56.9 ± 4.8 ka (thousands of years ago), respectively, thus constraining the time of transition between these two archaeological phases to ~60 ka. An age of 49.1 ± 4.3 ka has been obtained for the latest deposits associated with the Mumba Industry, which show no evidence for post-depositional mixing and contain ostrich eggshell (OES) beads and abundant microlithics. The Nasera Industry deposits (Bed III) contain large quantities of OES beads and date to 36.8 ± 3.4 ka. We compare the luminescence ages with the previous chronologies for Mumba, and briefly discuss how the revised chronology fits in the context of existing archaeological records and palaeoclimatic reconstructions for East Africa. PMID:22425240

  7. Arrhythmogenic cardiomyopathy: a disease of intercalated discs.

    PubMed

    Calore, Martina; Lorenzon, Alessandra; De Bortoli, Marzia; Poloni, Giulia; Rampazzo, Alessandra

    2015-06-01

    Arrhythmogenic cardiomyopathy (ACM) is an acquired progressive disease having an age-related penetrance and showing clinical manifestations usually during adolescence and young adulthood. It is characterized clinically by a high incidence of severe ventricular tachyarrhythmias and sudden cardiac death and pathologically by degeneration of ventricular cardiomyocytes with replacement by fibro-fatty tissue. Whereas, in the past, the disease was considered to involve only the right ventricle, more recent clinical studies have established that the left ventricle is frequently involved. ACM is an inherited disease in up to 50 % of cases, with predominantly an autosomal dominant pattern of transmission, although recessive inheritance has also been described. Since most of the pathogenic mutations have been identified in genes encoding desmosomal proteins, ACM is currently defined as a disease of desmosomes. However, on the basis of the most recent description of the intercalated disc organization and of the identification of a novel ACM gene encoding for an area composita protein, ACM can be considered as a disease of the intercalated disc, rather than only as a desmosomal disease. Despite increasing knowledge of the genetic basis of ACM, we are just beginning to understand early molecular events leading to cardiomyocyte degeneration, fibrosis and fibro-fatty substitution. This review summarizes recent advances in our comprehension of the link between the molecular genetics and pathogenesis of ACM and of the novel role of cardiac intercalated discs. PMID:25344329

  8. A SCUBA-2 850-?m survey of protoplanetary discs in the ? Orionis cluster

    NASA Astrophysics Data System (ADS)

    Williams, Jonathan P.; Cieza, Lucas A.; Andrews, Sean M.; Coulson, Iain M.; Barger, Amy J.; Casey, Caitlin M.; Chen, Chian-Chou; Cowie, Lennox L.; Koss, Michael; Lee, Nicholas; Sanders, David B.

    2013-10-01

    We present the results from a large 850-?m survey of the ? Orionis cluster using the SCUBA-2 camera on the James Clerk Maxwell Telescope. The 0.5° diameter circular region we surveyed contains 297 young stellar objects with an age estimated at about 3 Myr. We detect nine of these objects, eight of which have infrared excesses from an inner disc. We also serendipitously detect three non-stellar sources at >5? that are likely background submillimetre galaxies. The nine detected stars have inferred disc masses ranging from 5 to about 17 MJup, assuming similar dust properties as Taurus discs and an interstellar medium gas-to-dust ratio of 100. There is a net positive signal towards the positions of the individually undetected infrared excess sources indicating a mean disc mass of 0.5 MJup. Stacking the emission towards those stars without infrared excesses constrains their mean disc mass to less than 0.3 MJup, or an equivalent Earth mass in dust. The submillimetre luminosity distribution is significantly different from that in the younger Taurus region, indicating disc mass evolution as star-forming regions age and the infrared excess fraction decreases. Submillimetre Array observations reveal CO emission towards four sources demonstrating that some, but probably not much, molecular gas remains in these relatively evolved discs. These observations provide new constraints on the dust and gas mass of protoplanetary discs during the giant planet building phase and provide a reference level for future studies of disc evolution.

  9. Congenital fibrosis of the extraocular muscles type 1, distinctive conjunctival changes and intrapapillary disc colobomata.

    PubMed

    Flaherty, Maree P; Balachandran, Chandra; Jamieson, Robyn; Engle, Elizabeth C

    2009-06-01

    A 6-month-old boy presented with a congenital eye movement disorder consistent with congenital fibrosis of the extraocular muscles type 1 (CFEOM1). Mutational analysis confirmed the most common mutation in the CFEOM1 gene KIF21A. In addition to the typical findings in CFEOM1, distinctive conjunctival changes and small bilateral optic disc colobomata were also noted. It is suggested that optic disc colobomata represent a new association of CFEOM1. PMID:19373680

  10. RETNADAKYAA BALI MAKULA DEJENERASYONUNUN (YBMD), ?STATSTKSEL VE BÖLGE BÜYÜTME YÖNTEMLER ? ?LE BÖLÜTLEME SONUÇLARININ KARILATIRILMASI COMPARING THE RESULTS OF STATISTICS AND REGION GROWING SEGMENTATION METHODS FOR AGE-RELATED MACULA DEGENERATION IN RETINA

    Microsoft Academic Search

    Hidayet Erdöl; Zafer Yavuz

    Age-Related Macular Degeneration (ARMD) is one of the most common eye diseases causing the vision lost over 65 years old. In this study, a method is proposed to determine the drusens or ARMDs which occur as yellow-white small accumulation on the macula in the beginning of the disease. In the application, the optic disc is first detected in order to

  11. Cervical Total Disc Arthroplasty

    PubMed Central

    Basho, Rahul; Hood, Kenneth A.

    2012-01-01

    Symptomatic adjacent segment degeneration of the cervical spine remains problematic for patients and surgeons alike. Despite advances in surgical techniques and instrumentation, the solution remains elusive. Spurred by the success of total joint arthroplasty in hips and knees, surgeons and industry have turned to motion preservation devices in the cervical spine. By preserving motion at the diseased level, the hope is that adjacent segment degeneration can be prevented. Multiple cervical disc arthroplasty devices have come onto the market and completed Food and Drug Administration Investigational Device Exemption trials. Though some of the early results demonstrate equivalency of arthroplasty to fusion, compelling evidence of benefits in terms of symptomatic adjacent segment degeneration are lacking. In addition, non-industry-sponsored studies indicate that these devices are equivalent to fusion in terms of adjacent segment degeneration. Longer-term studies will eventually provide the definitive answer. PMID:24353955

  12. New test method for evaluation of corona-caused aging in fiber-optic cables

    Microsoft Academic Search

    George G. Karady; M. Torgerson; D. Torgerson; J. Wild; M. Tuominen

    1999-01-01

    Fiber-optic communication cables installed on high voltage transmission line structures are subject to high electric fields, which may cause corona discharge near the grounded cable support. This corona discharge, in the long term, deteriorates the cable jacket, which may result in puncture and failure. This paper proposes a new test method to evaluate the corona resistance of fiber-optic cable jackets.

  13. Effect of Intravitreous Anti–Vascular Endothelial Growth Factor Therapy on Choroidal Thickness in Neovascular Age-Related Macular Degeneration Using Spectral-Domain Optical Coherence Tomography

    E-print Network

    Branchini, Lauren

    A critical method of monitoring patients with neovascular age-related macular degeneration (AMD) being treated with anti–vascular endothelial growth factor (anti-VEGF) is optical coherence tomography (OCT), which uses ...

  14. Dust trapping by spiral arms in gravitationally unstable protostellar discs

    E-print Network

    Dipierro, Giovanni; Lodato, Giuseppe; Testi, Leonardo

    2015-01-01

    In this paper we discuss the influence of gravitational instabilities in massive protostellar discs on the dynamics of dust grains. Starting from a Smoothed Particle Hydrodynamics (SPH) simulation, we have computed the evolution of the dust in a quasi-static gas density structure typical of self-gravitating disc. For different grain size distributions we have investigated the capability of spiral arms to trap particles. We have run 3D radiative transfer simulations in order to construct maps of the expected emission at (sub-)millimetre and near-infrared wavelengths. Finally, we have simulated realistic observations of our disc models at (sub-)millimetre and near-infrared wavelengths as they may appear with the Atacama Large Millimetre/sub-millimetre Array (ALMA) and the High-Contrast Coronographic Imager for Adaptive Optics (HiCIAO) in order to investigate whether there are observational signatures of the spiral structure. We find that the pressure inhomogeites induced by gravitational instabilities produce a...

  15. Planet signatures in collisionally active debris discs: scattered light images

    NASA Astrophysics Data System (ADS)

    Thebault, P.; Kral, Q.; Ertel, S.

    2012-11-01

    Context. Planet perturbations have been often invoked as a potential explanation for many spatial structures that have been imaged in debris discs. So far this issue has been mostly investigated with pure N-body numerical models, which neglect the crucial effect collisions within the disc can have on the disc's response to dynamical perturbations. Aims: We numerically investigate how the coupled effect of collisions and radiation pressure can affect the formation and survival of radial and azimutal structures in a disc perturbed by a planet. We consider two different set-ups: a planet embedded within an extended disc and a planet exterior to an inner debris ring. One important issue we want to address is under which conditions a planet's signature can be observable in a collisionally active disc. Methods: We use our DyCoSS code, which is designed to investigate the structure of perturbed debris discs at dynamical and collisional steady-state, and derive synthetic images of the system in scattered light. The planet's mass and orbit, as well as the disc's collisional activity (parameterized by its average vertical optical depth ?0) are explored as free parameters. Results: We find that collisions always significantly damp planet-induced spatial structures. For the case of an embedded planet, the planet's signature, mostly a density gap around its radial position, should remain detectable in head-on images if Mplanet ? MSaturn. If the system is seen edge-on, however, inferring the presence of the planet is much more difficult, as only weak asymmetries remain in a collisionally active disc, although some planet-induced signatures might be observable under very favourable conditions. For the case of an inner ring and an external planet, planetary perturbations cannot prevent collision-produced small fragments from populating the regions beyond the ring. The radial luminosity profile exterior to the ring is in most cases close to the one it should have in the absence of the external planet. The most significant signature left by a Jovian planet on a circular orbit are precessing azimutal structures that can be used to indirectly infer its presence. For a planet on an eccentric orbit, we show that the ring becomes elliptic and that the well known pericentre glow effect is visible despite of collisions and radiation pressure, but that detecting such features in observed discs is not an unambiguous indicator of the presence of an outer planet. Movies are available in electronic form at http://www.aanda.org

  16. Tissue engineering: A live disc

    NASA Astrophysics Data System (ADS)

    Hukins, David W. L.

    2005-12-01

    A material-cell hybrid device that mimics the anatomic shape of the intervertebral disc has been made and successfully implanted into mice to show that tissue engineering may, in the future, benefit sufferers from back pain.

  17. Damage accumulation location under cyclic loading in the lumbar disc shifts from inner annulus lamellae to peripheral annulus with increasing disc degeneration.

    PubMed

    Qasim, Muhammad; Natarajan, Raghu N; An, Howard S; Andersson, Gunnar B J

    2014-01-01

    It is difficult to study the breakdown of lumbar disc tissue over several years of exposure to bending and lifting by experimental methods. In our earlier published study we have shown how a finite element model of a healthy lumbar motion segment was used to predict the damage accumulation location and number of cyclic to failure under different loading conditions. The aim of the current study was to extend the continuum damage mechanics formulation to the degenerated discs and investigate the initiation and progression of mechanical damage. Healthy disc model was modified to represent degenerative discs (Thompson grade III and IV) by incorporating both geometrical and biochemical changes due to degeneration. Analyses predicted decrease in the number of cycles to failure with increasing severity of disc degeneration. The study showed that the damage initiated at the posterior inner annulus adjacent to the endplates and propagated outwards towards its periphery in healthy and grade III degenerated discs. The damage accumulated preferentially in the posterior region of the annulus. However in grade IV degenerated disc damage initiated at the posterior outer periphery of the annulus and propagated circumferentially. The finite element model predictions were consistent with the infrequent occurrence of rim lesions at early age but a much higher incidence in severely degenerated discs. PMID:24231247

  18. Compact Disc Interactive.

    ERIC Educational Resources Information Center

    Valk, Anton

    1987-01-01

    This overview of a digital optical storage medium with a multimedia capability includes a global description of specifications, current status, and elements required to make a CD-I (compact disk interactive) launch possible. (Author/CLB)

  19. A geometrically thin accretion disc around a Maclaurin spheroid

    NASA Astrophysics Data System (ADS)

    Mishra, B.; Vaidya, B.

    2015-02-01

    We investigated a semi-analytic and numerical model to study a geometrically thin and optically thick accretion disc around a Maclaurin spheroid (MS). The main interest is in the inner region of the so-called ?-disc, ? being the viscosity parameter. Analytical calculations are done assuming radiation pressure and gas pressure dominated for close to the Eddington mass accretion rate and dot{M} ? 0.1dot{M}_Edd, respectively. We found that the change in the eccentricity of the MS causes a change at the high-frequency region in the emitted spectra. We found that disc parameters are dependent on the eccentricity of the MS. Our semi-analytic results show that qualitatively an increase in the eccentricity of the MS has the same behaviour as a decrease in the mass accretion rate. Numerical work has been carried out to see the viscous time evolution of the accretion disc around an MS. In a numerical model, we showed that if the eccentricity of an object is high, the matter will diffuse slowly during its viscous evolution. This gives a clue how spin-up or spin-down can change the time evolution of the accretion disc using a simple Newtonian approach. The change in spectra can be used to determine the eccentricity and thus the period of the MS.

  20. Precision manufacture of optical disc master stampers

    E-print Network

    , reduced hazardous waste, and lower production costs. All critical process steps have proved feasible process steps that produce toxic and hazardous wastes. The process is suitable for production of CD layer of nickel is grown on top of the photoresist to form a stamper. After peeling it from the glass

  1. Are large optic nerve heads susceptible to glaucomatous damage at normal intraocular pressure?

    Microsoft Academic Search

    Reinhard O. W. Burk; Klaus Rohrschneidern; Herbert Noack; Hans Eberhard Völcker

    1992-01-01

    To evaluate the effects of the presence of glaucomatous visual field defects and of intraocular pressure elevations on optic nerve head topography, we analyzed 148 left optic nerve heads of 148 patients using laser scanning tomography. The optic discs are classified according to computerized static perimetry and documented IOP readings: 101 discs show normal visual fields (36 normal discs, 22

  2. Witelo--Polish vision scientist of the middle ages: father of physiological optics.

    PubMed

    Fryczkowski, A W; Bieganowski, L; Nye, C N

    1996-01-01

    Unknown to the Western hemisphere, a Polish scientist, naturalist, anatomist, physiologist, philosopher and optician, Witelo, wrote an important ten volume manuscript, Peri-Optikes, usually cited in the literature as Perspectiva. This classic textbook was first published in 1535 in Nuremberg under the title: Vitellionis mathematici doctissimi ... vulgo Perspectivam vocant libri X, which is translated to English as Perspectiva. It was a vital source of information for such scientists as Leonardo da Vinci, Keppler and others in the next few centuries. Although many of his ideas were similar to Alhazan's, who earlier had written a significant optical manuscript De aspectibus, Witelo developed his own interpretation of many optical issues. He was one of the first scientists to discover spherical aberration of concave lenses and concave mirrors. He was also first to point out "that deflection of the light ray increases with the angle in which they approach two different optical substances and each increase is smaller than the previous one." Until recently, Witelo's achievements and contributions to the understanding of optical and anatomical aspects of the eye and visual function have remained unknown in western literature. Undoubtedly, Witelo should be recognized as the father of physiological optics. PMID:8970240

  3. Reoperations Following Cervical Disc Replacement

    PubMed Central

    Skovrlj, Branko; Lee, Dong-Ho; Caridi, John Michael

    2015-01-01

    Cervical disc replacement (CDR) has emerged as an alternative surgical option to cervical arthrodesis. With increasing numbers of patients and longer follow-ups, complications related to the device and/or aging spine are growing, leaving us with a new challenge in the management and surgical revision of CDR. The purpose of this study is to review the current literature regarding reoperations following CDR and to discuss about the approaches and solutions for the current and future potential complications associated with CDR. The published rates of reoperation (mean, 1.0%; range, 0%-3.1%), revision (mean, 0.2%; range, 0%-0.5%), and removal (mean, 1.2%; range, 0%-1.9%) following CDR are low and comparable to the published rates of reoperation (mean, 1.7%; range; 0%-3.4%), revision (mean, 1.5%; range, 0%-4.7%), and removal (mean, 2.0%; range, 0%-3.4%) following cervical arthrodesis. The surgical interventions following CDR range from the repositioning to explantation followed by fusion or the reimplantation to posterior foraminotomy or fusion. Strict patient selection, careful preoperative radiographic review and surgical planning, as well as surgical technique may reduce adverse events and the need for future intervention. Minimal literature and no guidelines exist for the approaches and techniques in revision and for the removal of implants following CDR. Adherence to strict indications and precise surgical technique may reduce the number of reoperations, revisions, and removals following CDR. Long-term follow-up studies are needed, assessing the implant survivorship and its effect on the revision and removal rates.

  4. Optically stimulated luminescence age controls on late Pleistocene and Holocene coastal lithosomes, North Carolina, USA

    USGS Publications Warehouse

    Mallinson, D.; Burdette, K.; Mahan, S.; Brook, G.

    2008-01-01

    Luminescence ages from a variety of coastal features on the North Carolina Coastal Plain provide age control for shoreline formation and relative sea-level position during the late Pleistocene. A series of paleoshoreline ridges, dating to Marine Isotope Stage (MIS) 5a and MIS 3 have been defined. The Kitty Hawk beach ridges, on the modern Outer Banks, yield ages of 3 to 2??ka. Oxygen-isotope data are used to place these deposits in the context of global climate and sea-level change. The occurrence of MIS 5a and MIS 3 shorelines suggests that glacio-isostatic adjustment (GIA) of the study area is large (ca. 22 to 26??m), as suggested and modeled by other workers, and/or MIS 3 sea level was briefly higher than suggested by some coral reef studies. Correcting the shoreline elevations for GIA brings their elevation in line with other sea-level indicators. The age of the Kitty Hawk beach ridges places the Holocene shoreline well west of its present location at ca. 3 to 2??ka. The age of shoreline progradation is consistent with the ages of other beach ridge complexes in the southeast USA, suggesting some regionally contemporaneous forcing mechanism. ?? 2007 University of Washington.

  5. Optically stimulated luminescence age controls on late Pleistocene and Holocene coastal lithosomes, North Carolina, USA

    NASA Astrophysics Data System (ADS)

    Mallinson, David; Burdette, Kevin; Mahan, Shannon; Brook, George

    2008-01-01

    Luminescence ages from a variety of coastal features on the North Carolina Coastal Plain provide age control for shoreline formation and relative sea-level position during the late Pleistocene. A series of paleoshoreline ridges, dating to Marine Isotope Stage (MIS) 5a and MIS 3 have been defined. The Kitty Hawk beach ridges, on the modern Outer Banks, yield ages of 3 to 2 ka. Oxygen-isotope data are used to place these deposits in the context of global climate and sea-level change. The occurrence of MIS 5a and MIS 3 shorelines suggests that glacio-isostatic adjustment (GIA) of the study area is large (ca. 22 to 26 m), as suggested and modeled by other workers, and/or MIS 3 sea level was briefly higher than suggested by some coral reef studies. Correcting the shoreline elevations for GIA brings their elevation in line with other sea-level indicators. The age of the Kitty Hawk beach ridges places the Holocene shoreline well west of its present location at ca. 3 to 2 ka. The age of shoreline progradation is consistent with the ages of other beach ridge complexes in the southeast USA, suggesting some regionally contemporaneous forcing mechanism.

  6. Effects of age and blood pressure on the retinal arterial wall, analyzed using adaptive optics scanning laser ophthalmoscopy

    PubMed Central

    Arichika, Shigeta; Uji, Akihito; Ooto, Sotaro; Muraoka, Yuki; Yoshimura, Nagahisa

    2015-01-01

    The wall-to-lumen ratio (WLR) of the vasculature is a promising early marker of retinal microvascular changes. Recently, adaptive optics scanning laser ophthalmoscopy (AOSLO) enabled direct and noninvasive visualization of the arterial wall. Using AOSLO, we analyzed the correlation between age and WLR in 51 normal subjects. In addition, correlations between blood pressure and WLR were analyzed in 73 subjects (51 normal subjects and 22 hypertensive patients). WLR showed a strong correlation with age (r?=?0.68, P?age in the normal group (r?=?0.13, P?=?0.36 and r?=??0.12, P?=?0.41, respectively). In the normal and hypertensive groups, WLR showed a strong correlation with systolic and diastolic blood pressure (r?=?0.60, P?age and blood pressure. PMID:26192115

  7. Signs of a faint disc population at polluted white dwarfs

    E-print Network

    Bergfors, Carolina; Dufour, Patrick; Rocchetto, Marco

    2014-01-01

    Observations of atmospheric metals and dust discs around white dwarfs provide important clues to the fate of terrestrial planetary systems around intermediate mass stars. We present Spitzer IRAC observations of 15 metal polluted white dwarfs to investigate the occurrence and physical properties of circumstellar dust created by the disruption of planetary bodies. We find subtle infrared excess emission consistent with warm dust around KUV 15519+1730 and HS 2132+0941, and weaker excess around the DZ white dwarf G245-58, which, if real, makes it the coolest white dwarf known to exhibit a 3.6 micron excess and the first DZ star with a bright disc. All together our data corroborate a picture where 1) discs at metal-enriched white dwarfs are commonplace and most escape detection in the infrared (possibly as narrow rings), 2) the discs are long lived, having lifetimes on the order of 10^6 yr or longer, and 3) the frequency of bright, infrared detectable discs decreases with age, on a timescale of roughly 500 Myr, su...

  8. The effect of aging on smoke optical properties and scavenging characteristics

    SciTech Connect

    Penner, J.E.

    1986-11-01

    Aging of smoke in dense smoke plumes is known to alter its size distribution and scavenging characteristics. In this paper, I review data pertaining to these processes and compare them to model simulations of the coagulation of smoke. Model simulations of the degree of smoke coagulation in the first few days after a nuclear war are summarized. The predicted size of smoke particles after several days of coagulation is found to be larger than that of any data pertaining to the absorption properties of smoke. Thus, it is suggested that more relevant data on the absorption properties of smoke is needed. I also review aging experiments pertaining to the number of cloud condensation nuclei in a smoke sample. I show that the fraction of smoke particles which act as CCN after aging depends on the number of particles initially present in the aging chamber. Smoke from an acetylene flame can quickly coagulate to sizes wherein nearly all of the particles act as CCN. On the other hand, only 10% of the smoke particles from an outdoor fire of gasoline and diesel fuel became CCN after 30 hours of aging. The development of CCN concentrations in this experiment may have been quenched by low initial concentrations in the aging chamber. Both experiments are consistent with particles as small as 0.08 micron in radius (and perhaps even smaller) acting as CCN. Model simulations of the coagulation of smoke particles above a large, intense fire show that coagulation would allow approximately 50% of the particles to become larger than 0.08 micron before the plume reaches cloud base. Furthermore, aging over several days time would transform nearly all the particles into the scavengable size range.

  9. Morphological evolution in situ: disc-dominated cluster red sequences at z ˜ 1.25

    NASA Astrophysics Data System (ADS)

    Propris, Roberto De; Bremer, Malcolm N.; Phillipps, Steven

    2015-06-01

    We have carried out a joint photometric and structural analysis of red sequence galaxies in four clusters at a mean redshift of ˜ 1.25 using optical and near-infrared Hubble Space Telescope imaging reaching to at least three magnitudes fainter than M*. As expected, the photometry and overall galaxy sizes imply purely passive evolution of stellar populations in red sequence cluster galaxies. However, the morphologies of red sequence cluster galaxies at these redshifts show significant differences to those of local counterparts. Apart from the most massive galaxies, the high-redshift red sequence galaxies are significantly discier than their low-redshift analogues. These galaxies also show significant colour gradients, again not present in their low-redshift equivalents, most straightforwardly explained by radial age gradients. A clear implication of these findings is that red sequence cluster galaxies originally arrive on the sequence as disc-dominated galaxies whose discs subsequently fade or evolve secularly to end up as high Sérsic index early-type galaxies (classical S0s or possibly ellipticals) at lower redshift. The apparent lack of growth seen in a comparison of high- and low-redshift red sequence galaxies implies that any evolution is internal and is unlikely to involve significant mergers. While significant star formation may have ended at high redshift, the cluster red sequence population continues to evolve (morphologically) for several gigayears thereafter.

  10. Aging of savanna biomass burning aerosols: Consequences on their optical properties

    Microsoft Academic Search

    C. Liousse; C. Devaux; F. Dulac; H. Cachier

    1995-01-01

    During the FOS-DECAFE experiment at Lamto, Ivory Coast, in January 1991, various ground studies were undertaken simultaneously in order to investigate the physical and chemical characteristics of smoke emitted by savanna biomass burning. Here we present sunphotometer ground-based results which allow the measurements of the spectral optical depth between 450 and 850 nm, the atmospheric water vapour content and the

  11. Intervertebral disc magnetic resonance image: correlation with gross morphology and biochemical composition

    PubMed Central

    Bishop, Paul B

    1993-01-01

    The magnetic resonance image, gross morphology, and biochemical composition of the intervertebral disc nucleus pulposus (NP), anulus fibrosus (AF) and cartilaginous endplates (CEP) from two groups of three human lumbar spines were compared. Group I consisted of all healthy discs from young donors (Grade I) and group II was comprised of discs that had undergone degeneration and age-related changes (average Grade 4). The gross morphological changes in the individual disc tissues associated with ageing/degeneration were consistent with specific changes in the characteristics of the magnetic resonance image. In particular, the mid-nuclear band of decreased magnetic resonance signal intensity seen in Grade 4 discs was associated with the appearance of clefts and fissures as well as a region of mucinous infiltration. The results of the biochemical analysis suggest that the changes in signal intensity are not due merely to changes in water content, but are also associated with changes in proteoglycan content. The changes associated with ageing/degeneration in the magnetic resonance image of the disc were related to a decrease in the proteoglycan content of the AF and NP. The water content of the NP also decreased. There was no clear association between the biochemical composition of the CEP and the magnetic resonance image. These results demonstrate that magnetic resonance imaging is an effective technique for evaluating subtle morphological changes in the intervertebral disc tissues and may be a sensitive indicator of the proteoglycan content of the AF and NP. ImagesFigure 1Figure 2

  12. Can intervertebral disc prolapse be predicted by disc mechanics?

    PubMed

    McNally, D S; Adams, M A; Goodship, A E

    1993-09-01

    The hypothesis was tested that stress concentrations in the posterior anulus of an intervertebral disc predispose it to prolapse under high compressive loads and anterolateral bending. The distribution of compressive stress inside the intervertebral discs of 22 cadaveric lumbar motion segments was measured with the specimens loaded in pure compression and in compression combined with anterolateral bending. Each motion segment was then loaded to failure in combined compression and anterolateral bending. Failure occurred in the vertebral body (n = 12) or posterolateral anulus (n = 10); the latter group showed a significantly greater incidence of stress concentrations (P < 0.001) in the posterior anulus, when loaded in compression and bending. It was concluded that some discs are predisposed to prolapse because of damaging, localized concentrations of stress in the posterior anulus in combined anterolateral bending and compression. PMID:8235825

  13. Extending the upper age limit for luminescence dating using the thermally transferred optically stimulated luminescence signal from quartz

    NASA Astrophysics Data System (ADS)

    Duller, Geoff A. T.; Wintle, Ann G.

    2010-05-01

    The optically stimulated luminescence (OSL) signal from quartz has been exploited for the last 20 years to date heated and unheated materials. While methods based on this signal have been extremely successful and are now widely adopted in laboratories around the world, growth of the signal with dose is affected by saturation and this commonly limits application to samples with equivalent doses of ~100 to 300 Gy. In most environments this limits application of the method to the last 100-150 ka. Studies of OSL from quartz in the late 1980's showed that if the OSL signal from a sample was reduced to background level by measurement, and the sample then heated, further optical stimulation gave a significant signal. This recuperated OSL was viewed as a problem to be avoided, particularly for young samples. Three years ago papers were published showing that this recuperated signal has the potential to be valuable in dosimetry, and in particular that the signal continues to grow to doses in excess of 10,000 Gy offering the possibility of extending the age range over which quartz can be used to as much as 1 Ma. The first work on this signal was undertaken on fine grain quartz extracted from Chinese loess, and ages back to the Brunhes-Matuyama boundary were obtained. The signal is now commonly referred to as thermally transferred optically stimulated luminescence (TT-OSL). Intense research on the signal has focussed on a number of areas, including, (a) understanding the origin of the charge measured in TT-OSL, (b) improving methods for measuring the TT-OSL signal, and (c) developing protocols for using TT-OSL in dose estimation, and these are reviewed in this presentation.

  14. Accelerated aging studies and the prediction of the archival lifetime of optical disk media

    Microsoft Academic Search

    David E. Nikles; John M. Wiest

    1999-01-01

    Data archivists expect information storage media to have a lifetime greater than ten years. Furthermore they desire the ability to predict when the media will fail in order to plan for its replacement. Archival lifetime predictions are based on accelerated aging studies, where the media are subjected to conditions of high temperature and high humidity. The rate of failure is

  15. Accelerated Aging Studies and the Prediction of the Archival Lifetime of Optical Disk Media

    Microsoft Academic Search

    David E. Nikles; John M. Wiest

    2000-01-01

    Data archivists expect information storage media to have a lifetime greater than ten years. Furthermore they desire the ability to predict when the media will fail in order to plan for its replacement. Archival lifetime predictions are based on accelerated aging studies, where the media are subjected to conditions of high temperature and high humidity. The rate of failure is

  16. Astigmatism and biometric optic components of diode laser-treated threshold retinopathy of prematurity at 9 years of age

    PubMed Central

    Yang, C-S; Wang, A-G; Shih, Y-F; Hsu, W-M

    2013-01-01

    Purpose To assess the prevalence of astigmatism and its relationship with biometric optic components in preterm school children with diode laser-treated threshold retinopathy of prematurity (ROP). Methods A prospective, cross-sectional study in which cycloplegic keratometry, refraction, and ultrasound biometric measurement of optic components were performed on 24 consecutive preterm children with diode laser-treated threshold ROP at the age of 9 years. The study results were compared with data on 1021 age-matched full-term control children from a national survey. Results The laser-treated eyes had a mean astigmatism of 3.47?D, with a mean spherical equivalent of ?4.49?D. Of the 46 eyes studied, 98% of eyes showed astigmatism ?0.5?D and 50% had high astigmatism (>3.0?D). Most astigmatic eyes (97.7%) showed with-the-rule astigmatism, with the mean plus cylinder axis at 89.30o. Further correlation analysis showed the astigmatism in refraction was highly correlated with the corneal astigmatism (r=0.921, P<0.001) and the vertical corneal curvature (r=0.405, P=0.005). There was significantly steeper vertical corneal curvature (P=0.003) and flatter horizontal corneal curvature (P=0.031) in eyes with laser-treated ROP when compared with age-matched full-term controls. The eyes with laser-treated ROP also show significantly thicker lens (3.93?mm) and shallower anterior chamber depth (ACD; 2.92?mm) than full-term controls (P<0.001). Conclusions There is significantly higher prevalence and greater magnitude of astigmatism in eyes with laser-treated threshold ROP compared with full-term controls. The steeper vertical corneal curvature component contributes to the increased astigmatism in eyes with laser-treated ROP. PMID:23222565

  17. Potential regenerative treatment strategies for intervertebral disc degeneration in dogs

    PubMed Central

    2014-01-01

    Pain due to spontaneous intervertebral disc (IVD) disease is common in dogs. In chondrodystrophic (CD) dogs, IVD disease typically develops in the cervical or thoracolumbar spine at about 3–7 years of age, whereas in non-chondrodystrophic (NCD) dogs, it usually develops in the caudal cervical or lumbosacral spine at about 6–8 years of age. IVD degeneration is characterized by changes in the biochemical composition and mechanical integrity of the IVD. In the degenerated IVD, the content of glycosaminoglycan (GAG, a proteoglycan side chain) decreases and that of denatured collagen increases. Dehydration leads to tearing of the annulus fibrosus (AF) and/or disc herniation, which is clinically characterized by pain and/or neurological signs. Current treatments (physiotherapy, anti-inflammatory/analgesic medication, surgery) for IVD disease may resolve neurological deficits and reduce pain (although in many cases insufficient), but do not lead to repair of the degenerated disc. For this reason, there is interest in new regenerative therapies that can repair the degenerated disc matrix, resulting in restoration of the biomechanical function of the IVD. CD dogs are considered a suitable animal model for human IVD degeneration because of their spontaneous IVD degeneration, and therefore studies investigating cell-, growth factor-, and/or gene therapy-based regenerative therapies with this model provide information relevant to both human and canine patients. The aim of this article is to review potential regenerative treatment strategies for canine IVD degeneration, with specific emphasis on cell-based strategies. PMID:24387033

  18. The Environment of M85 Optical Transient 2006-1: Constraints on the Progenitor Age and Mass

    NASA Astrophysics Data System (ADS)

    Ofek, E. O.; Kulkarni, S. R.; Rau, A.; Cenko, S. B.; Peng, E. W.; Blakeslee, J. P.; Côté, P.; Ferrarese, L.; Jordán, A.; Mei, S.; Puzia, T.; Bradley, L. D.; Magee, D.; Bouwens, R.

    2008-02-01

    M85 Optical Transient 2006-1 (M85 OT 2006-1) is the most luminous member of the small family of V838 Mon-like objects, whose nature is still a mystery. This event took place in the Virgo Cluster of galaxies and peaked at an absolute magnitude of MI~-13. Here we present Hubble Space Telescope images of M85 OT 2006-1 and its environment, taken before and after the eruption, along with a spectrum of the host galaxy at the transient location. We find that the progenitor of M85 OT 2006-1 was not associated with any star-forming region. The g- and z-band absolute magnitudes of the progenitor were fainter than about -4 and -6 mag, respectively. Therefore, we can set a lower limit of ~50 Myr on the age of the youngest stars at the location of the progenitor that corresponds to a mass of <7 Msolar. Previously published line indices suggest that M85 has a mean stellar age of 1.6+/-0.3 Gyr. If this mean age is representative of the progenitor of M85 OT 2006-1, then we can further constrain its mass to be less than 2 Msolar. We compare the energetics and mass limit derived for the M85 OT 2006-1 progenitor with those expected from a simple model of violent stellar mergers. Combined with further modeling, these new clues may ultimately reveal the true nature of these puzzling events.

  19. Laser microbeams for DNA damage induction, optical tweezers for the search on blood pressure relaxing drugs: contributions to ageing research

    NASA Astrophysics Data System (ADS)

    Grigaravicius, P.; Monajembashi, S.; Hoffmann, M.; Altenberg, B.; Greulich, K. O.

    2009-08-01

    One essential cause of human ageing is the accumulation of DNA damages during lifetime. Experimental studies require quantitative induction of damages and techniques to visualize the subsequent DNA repair. A new technique, the "immuno fluorescent comet assay", is used to directly visualize DNA damages in the microscope. Using DNA repair proteins fluorescently labeled with green fluorescent protein, it could be shown that the repair of the most dangerous DNA double strand breaks starts with the inaccurate "non homologous end joining" pathway and only after 1 - 1 ½ minutes may switch to the more accurate "homologous recombination repair". One might suggest investigating whether centenarians use "homologous recombination repair" differently from those ageing at earlier years and speculate whether it is possible, for example by nutrition, to shift DNA repair to a better use of the error free pathway and thus promote healthy ageing. As a complementary technique optical tweezers, and particularly its variant "erythrocyte mediated force application", is used to simulate the effects of blood pressure on HUVEC cells representing the inner lining of human blood vessels. Stimulating one cell induces in the whole neighbourhood waves of calcium and nitric oxide, known to relax blood vessels. NIFEDIPINE and AMLODIPINE, both used as drugs in the therapy of high blood pressure, primarily a disease of the elderly, prolong the availability of nitric oxide. This partially explains their mode of action. In contrast, VERAPAMILE, also a blood pressure reducing drug, does not show this effect, indicating that obviously an alternative mechanism must be responsible for vessel relaxation.

  20. On the absolute age of the metal-rich globular M71 (NGC 6838): I. optical photometry

    E-print Network

    Di Cecco, Alessandra; Moroni, Pier Giorgio Prada; Tognelli, Emanuele; Allard, France; Stetson, Peter B; Buonanno, Roberto; Ferraro, Ivan; Iannicola, Giacinto; Monelli, Matteo; Nonino, Mario; Pulone, Luigi

    2015-01-01

    We investigated the absolute age of the Galactic globular cluster M71 (NGC 6838) by using optical ground-based images (u',g',r',i',z') collected with the MegaCam camera at the Canada-France-Hawaii-Telescope (CFHT). We performed a robust selection of field and cluster stars by applying a new method based on the 3D (r',u'-g',g'-r') Color-Color-Magnitude-Diagram. The comparison between the Color-Magnitude-Diagram of the candidate cluster stars and a new set of isochrones, at the locus of the Main Sequence Turn Off (MSTO), suggests an absolute age of 12+/-2 Gyr. The absolute age was also estimated using the difference in magnitude between the MSTO and the so-called main sequence knee, a well defined bending occurring in the lower main sequence. This feature was originally detected in the near-infrared (NIR) bands and explained as a consequence of an opacity mechanism (collisionally induced absorption of molecular hydrogen) in the atmosphere of cool low-mass stars (Bono et al. 2010). The same feature was also dete...

  1. Debris disc formation induced by planetary growth

    NASA Astrophysics Data System (ADS)

    Kobayashi, H.; Löhne, T.

    2014-08-01

    Several hundred stars older than 10 million years have been observed to have infrared excesses. These observations are explained by dust grains formed by the collisional fragmentation of hidden planetesimals. Such dusty planetesimal discs are known as debris discs. In a dynamically cold planetesimal disc, collisional coagulation of planetesimals produces planetary embryos which then stir the surrounding leftover planetesimals. Thus, the collisional fragmentation of planetesimals that results from planet formation forms a debris disc. We aim to determine the properties of the underlying planetesimals in debris discs by numerically modelling the coagulation and fragmentation of planetesimal populations. The brightness and temporal evolution of debris discs depend on the radial distribution of planetesimal discs, the location of their inner and outer edges, their total mass, and the size of planetesimals in the disc. We find that a radially narrow planetesimal disc is most likely to result in a debris disc that can explain the trend of observed infrared excesses of debris discsvvv around G-type stars, for which planet formation occurs only before 100 million years. Early debris disc formation is induced by planet formation, while the later evolution is explained by the collisional decay of leftover planetesimals around planets that have already formed. Planetesimal discs with underlying planetesimals of radii ˜100 km at ?30 au most readily explain the Spitzer Space Telescope 24 and 70 ?m fluxes from debris discs around G-type stars.

  2. Keplerian discs around post-AGB stars: a common phenomenon?

    E-print Network

    S. De Ruyter; H. Van Winckel; T. Maas; T. Lloyd Evans; L. B. F. M. Waters; H. Dejonghe

    2006-01-25

    Aims: We aim at showing that the broad-band SED characteristics of our sample of post-AGB stars are best interpreted, assuming the circumstellar dust is stored in Keplerian rotating passive discs. Methods: We present a homogeneous and systematic study of the Spectral Energy Distributions (SEDs) of a sample of 51 post-AGB objects. The selection criteria to define the whole sample were tuned to cover the broad-band characteristics of known binary post-AGB stars. The whole sample includes 20 dusty RV Tauri stars from the General Catalogue of Variable Stars (GCVS). We supplemented our own Geneva optical photometry with literature data to cover a broad range of fluxes from the UV to the far-IR. Results: All the SEDs display very similar characteristics: a large IR excess with a dust excess starting near the sublimation temperature, irrespective of the effective temperature of the central star. Moreover, when available, the long wavelength fluxes show a black-body slope indicative of the presence of a component of large mm sized grains. Conclusions: We argue that in all systems, gravitationally bound dusty discs are present. The discs must be puffed-up to cover a large opening angle for the central star and we argue that the discs have some similarity with the passive discs detected around young stellar objects. We interpret the presence of a disc to be a signature for binarity of the central object, but this will need confirmation by long-term monitoring of the radial velocities. We argue that dusty RV Tauri stars are those binaries which happen to be in the Population II instability strip.

  3. Dust trapping by spiral arms in gravitationally unstable protostellar discs

    NASA Astrophysics Data System (ADS)

    Dipierro, Giovanni; Pinilla, Paola; Lodato, Giuseppe; Testi, Leonardo

    2015-07-01

    In this paper, we discuss the influence of gravitational instabilities in massive protostellar discs on the dynamics of dust grains. Starting from a smoothed particle hydrodynamics simulation, we have computed the evolution of the dust in a quasi-static gas density structure typical of self-gravitating disc. For different grain size distributions, we have investigated the capability of spiral arms to trap particles. We have run 3D radiative transfer simulations in order to construct maps of the expected emission at (sub-)millimetre and near-infrared wavelengths. Finally, we have simulated realistic observations of our disc models at (sub-)millimetre and near-infrared wavelengths as they may appear with the Atacama Large Millimetre/submillimetre Array (ALMA) and the High-Contrast Coronographic Imager for Adaptive Optics (HiCIAO) in order to investigate whether there are observational signatures of the spiral structure. We find that the pressure inhomogeneities induced by gravitational instabilities produce a non-negligible dynamical effect on centimetre-sized particles leading to significant overdensities in spiral arms. We also find that the spiral structure is readily detectable by ALMA over a wide range of (sub-)millimetre wavelengths and by HiCIAO in near-infrared scattered light for non-face-on discs located in the Ophiuchus star-forming region. In addition, we find clear spatial spectral index variations across the disc, revealing that the dust trapping produces a migration of large grains that can be potentially investigated through multiwavelength observations in the (sub-)millimetric. Therefore, the spiral arms observed to date in protoplanetary disc might be interpreted as density waves induced by the development of gravitational instabilities.

  4. A case of subretinal tubercular abscess presenting as disc edema

    PubMed Central

    Shetty, Sachin Bermu; Bawtag, Mohammad Abdullah; Biswas, Jyotirmay

    2015-01-01

    We report a case of ocular tuberculosis (TB) which initially presented with disc edema and was mistaken for optic neuritis. With no definite pathology being identified, the patient was treated on the lines of optic neuritis with intravenous (IV) steroid with beneficial effect. Ocular TB was suspected when he presented later with a subretinal abscess. Based on positive Mantoux, QuantiFERON TB gold results and radiographic findings, a diagnosis of subretinal abscess of presumed tubercular etiology was made. The patient was successfully treated with anti-tubercular therapy. To the best of our knowledge, this is the first case report of ocular TB presenting as disc edema followed by subretinal abscess. PMID:25827550

  5. Photon Bubbles in Accretion Discs

    E-print Network

    Charles F. Gammie

    1998-02-17

    We show that radiation dominated accretion discs are likely to suffer from a ``photon bubble'' instability similar to that described by Arons in the context of accretion onto neutron star polar caps. The instability requires a magnetic field for its existence. In an asymptotic regime appropriate to accretion discs, we find that the overstable modes obey the remarkably simple dispersion relation \\omega^2 = -i g k F(B,k). Here g is the vertical gravitational acceleration, B the magnetic field, and F is a geometric factor of order unity that depends on the relative orientation of the magnetic field and the wavevector. In the nonlinear outcome it seems likely that the instability will enhance vertical energy transport and thereby change the structure of the innermost parts of relativistic accretion discs.

  6. Bio-Sensing with Compact Discs and Nanofibers

    Microsoft Academic Search

    M. Tabuchi; K. Kobayashi; Y. Baba

    2006-01-01

    This paper describes a novel, high-sensitive detection system for biomolecules such as DNAs and proteins utilizing optical compact discs (CDs) and unique bio-nanofibers; bacterial cellulose (BC). The new method comprises a microchannel containing CD grating that confines fragments of three-dimensional structure of BC, which has nanometer scale fibrils and holes. A maximum of six times higher light-amplification to detect DNA

  7. Physics and chemistry of gas in discs 

    E-print Network

    Tilling, Ian

    2013-11-28

    Protoplanetary discs set the initial conditions for planet formation. By combining observations with detailed modelling, it is possible to constrain the physics and chemistry in such discs. I have used the detailed ...

  8. [Stimulation of degenerative changes in the intervertebral disc through axial compression. Radiologic, histologic and biomechanical research in an animal model].

    PubMed

    Unglaub, F; Lorenz, H; Nerlich, A; Richter, W; Kroeber, M W

    2003-01-01

    Degeneration of the intervertebral disc is a common disease in the adults, especially at advanced age. A causal therapy is not known, but the progress in new therapeutic strategies, for example in tissue engineering, shows new possibilities. The goal of our study was to develop a new animal model that stimulates a load induced degeneration of the disc. We used the New Zealand rabbit, because morphology is similar to the human intervertebral disc. The degeneration was induced by axial compression of the disc L4 - L5 with an external fixateur. After different loading intervals, the animals were sacrified and the discs examined by radiology, histology, apoptosis and biomechanical testing. Radiography showed a significant decrease of the disc thickness in all loaded groups. Morphologically the intervertebral discs of loaded rabbits showed degenerative changes which were comparable to those in humans. A significantly increased number of dead cells in the annulus occurred after 14 and 28 days loading compared to the controls. The bending stress measured as the load to failure was not significantly different between the unloaded discs and the 28 days loaded discs. The results show that our animal modell can create degeneration. Four weeks compression leads to significant degeneration. Degeneration of the discs persisted in animals that were allowed a recovery time of 28 days after 28 days of loading. PMID:12928998

  9. Migrated herniated disc mimicking a neoplasm

    Microsoft Academic Search

    Benjamin Hoch; George Hermann

    2010-01-01

    Disc sequestration is defined as migration of a herniated disc fragment into the epidural space such that it is completely\\u000a separated from the parent disc. We report a case of a migrated herniated disc that was initially pathologically diagnosed\\u000a as a cartilage neoplasm. In addition to confounding morphological features, this interpretation may have been influenced by\\u000a an initial radiological interpretation

  10. Calcification in the ovine intervertebral disc: a model of hydroxyapatite deposition disease

    PubMed Central

    Burkhardt, D.; Taylor, T. K. F.; Dillon, C. T.; Read, R.; Cake, M.; Little, C. B.

    2009-01-01

    The study design included a multidisciplinary examination of the mineral phase of ovine intervertebral disc calcifications. The objective of the study was to investigate the mineral phase and its mechanisms of formation/association with degeneration in a naturally occurring animal model of disc calcification. The aetiology of dystrophic disc calcification in adult humans is unknown, but occurs as a well-described clinical disorder with hydroxyapatite as the single mineral phase. Comparable but age-related pathology in the sheep could serve as a model for the human disorder. Lumbar intervertebral discs (n = 134) of adult sheep of age 6 years (n = 4), 8 years (n = 12) and 11 years (n = 2) were evaluated using radiography, morphology, scanning and transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray powder diffraction, histology, immunohistology and proteoglycan analysis. Half of the 6-year, 84% of the 8-year and 86% of the 11-year-old discs had calcific deposits. These were not well delineated by plain radiography. They were either: (a) punctate deposits in the outer annulus, (b) diffuse deposits in the transitional zone or inner annulus fibrosus with occasional deposits in the nucleus, or (c) large deposits in the transitional zone extending variably into the nucleus. Their maximal incidence was in the lower lumbar discs (L4/5–L6/7) with no calcification seen in the lumbosacral or lower thoracic discs. All deposits were hydroxyapatite with large crystallite sizes (800–1,300 Å) compared to cortical bone (300–600 Å). No type X-collagen, osteopontin or osteonectin were detected in calcific deposits, although positive staining for bone sialoprotein was evident. Calcified discs had less proteoglycan of smaller hydrodynamic size than non-calcified discs. Disc calcification in ageing sheep is due to hydroxyapatite deposition. The variable, but large, crystal size and lack of protein markers indicate that this does not occur by an endochondral ossification-like process. The decrease in disc proteoglycan content and size suggests that calcification may precede or predispose to disc degeneration in ageing sheep. PMID:19165512

  11. Requirements and specifications for cartographic video discs

    Microsoft Academic Search

    D. J. Costanzo

    1984-01-01

    Video discs can store large quantities of analog (paper, film, and video tape) and digital cartographic products on a compact, nonvolatile medium. These discs can be interfaced with microcomputers to provide compact and portable systems for accessing this cartographic information. Such interactive video disc systems could be used for terrain analysis, navigation, map use training, and command and control. Video

  12. Segmentation and quantification of retinal lesions in age-related macular degeneration using polarization-sensitive optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Baumann, Bernhard; Götzinger, Erich; Pircher, Michael; Sattmann, Harald; Schütze, Christopher; Schlanitz, Ferdinand; Ahlers, Christian; Schmidt-Erfurth, Ursula; Hitzenberger, Christoph K.

    2010-11-01

    We present polarization-sensitive optical coherence tomography (PS-OCT) for quantitative assessment of retinal pathologies in age-related macular degeneration (AMD). On the basis of the polarization scrambling characteristics of the retinal pigment epithelium, novel segmentation algorithms were developed that allow one to segment pathologic features such as drusen and atrophic zones in dry AMD as well as to determine their dimensions. Results from measurements in the eyes of AMD patients prove the ability of PS-OCT for quantitative imaging based on the retinal features polarizing properties. Repeatability measurements were performed in retinas diagnosed with drusen and geographic atrophy in order to evaluate the performance of the described methods. PS-OCT appears as a promising imaging modality for three-dimensional retinal imaging and ranging with additional contrast based on the structures' tissue-inherent polarization properties.

  13. Stem Cell Therapy for Degenerative Disc Disease

    PubMed Central

    Drazin, Doniel; Rosner, Jack; Avalos, Pablo; Acosta, Frank

    2012-01-01

    Low back pain is widely recognized as one of the most prevalent pathologies in the developed world. In the United States, low back pain is the most common health problem for adults under the age of 50, resulting in significant societal and personal costs. While the causes of low back pain are myriad, it has been significantly associated with intervertebral disc (IVD) degeneration. Current first-line therapies for IVD degeneration such as physical therapy and spinal fusion address symptoms, but do not treat the underlying degeneration. The use of tissue engineering to treat IVD degeneration provides an opportunity to correct the pathological process. Novel techniques are currently being investigated and have shown mixed results. One major avenue of investigation has been stem cell injections. Mesenchymal stem cells (MSCs) have shown promise in small animal models, but results in larger vertebrates have been mixed. PMID:22593830

  14. Methodologic evaluation of the lumbar disc syndrome.

    PubMed Central

    Robinson, J. S.

    1981-01-01

    Though the lumbar disc syndrome is a costly and ubiquitous affliction, effective evaluation of the disease process has been confounded by major unaddressed methodological short falls. Prominent difficulties include: inattention to the clinical boundaries of the syndrome, neglected co-morbid disease processes, comparison of unequal treatment groups and premature clinical data extrapolation, inadequate diagnostic validation, variability in surgical observation, and reliance upon follow-up techniques faulted by unaddressed distorting factors. Proposals for improvement include: formulation of suitable stratification subgroups emphasizing age and sign-symptom intensity and duration, techniques for improved diagnostic return from surgical exploration, suggestions toward improved quantitation of clinical testing procedures, and implantation of a quality of life scale. PMID:6454306

  15. Intramural Sports Ultimate Disc "Hat"

    E-print Network

    Escher, Christine

    Intramural Sports Ultimate Disc "Hat" Tournament Summer 2014 Intramural Sports Calendar of Events on the day of the tournament, teams will be drawn out of a hat and mixed for play. Sports and Special or Faculty/Staff/Affiliates with a Recreational Sports Membership are eligible to participate. http://oregonstate.edu/recsports/intramural-sports

  16. Electromagnetic Levitation of a Disc

    ERIC Educational Resources Information Center

    Valle, R.; Neves, F.; de Andrade, R., Jr.; Stephan, R. M.

    2012-01-01

    This paper presents a teaching experiment that explores the levitation of a disc of ferromagnetic material in the presence of the magnetic field produced by a single electromagnet. In comparison to the classical experiment of the levitation of a sphere, the main advantage of the proposed laboratory bench is that the uniform magnetic field…

  17. Failure of the Intervertebral Disc

    Microsoft Academic Search

    Famke Kraaijeveld; Jacques M. Huyghe; Joris J. C. Remmers; Rene de Borst; Frank P. T. Baaijens

    2008-01-01

    In ionized porous media, such as shales, clays and biological tissues, localization or even crack forma- tion during swelling or shrinking can take place. This can lead to for example earthquakes, borehole instability and intervertebral disc (IVD) herniation. The goal is to study the effect of swelling on the failure mechanism. Currently, there is no numerical framework which includes osmotic

  18. Evolution of linear warps in accretion discs and applications to protoplanetary discs in binaries

    NASA Astrophysics Data System (ADS)

    Foucart, Francois; Lai, Dong

    2014-12-01

    Warped accretion discs are expected in many protostellar binary systems. In this paper, we study the long-term evolution of disc warp and precession for discs with dimensionless thickness H/r larger than their viscosity parameter ?, such that bending waves can propagate and dominate the warp evolution. For small warps, these discs undergo approximately rigid-body precession. We derive analytical expressions for the warp/twist profiles of the disc and the alignment time-scale for a variety of models. Applying our results to circumbinary discs, we find that these discs align with the orbital plane of the binary on a time-scale comparable to the global precession time of the disc, and typically much smaller than its viscous time-scale. We discuss the implications of our finding for the observations of misaligned circumbinary discs (such as KH 15D) and circumbinary planetary systems (such as Kepler-413); these observed misalignments provide useful constraints on the uncertain aspects of the disc warp theory. On the other hand, we find that circumstellar discs can maintain large misalignments with respect to the plane of the binary companion over their entire lifetime. We estimate that inclination angles larger than ˜20° can be maintained for typical disc parameters. Overall, our results suggest that while highly misaligned circumstellar discs in binaries are expected to be common, such misalignments should be rare for circumbinary discs. These expectations are consistent with current observations of protoplanetary discs and exoplanets in binaries, and can be tested with future observations.

  19. Note: Light ageing with simultaneous colorimetry via fibre optics reflection spectrometry

    NASA Astrophysics Data System (ADS)

    ?ojewski, Tomasz; Thomas, Jacob; Go?ab, Roman; Kawa?ko, Jakub; ?ojewska, Joanna

    2011-07-01

    In this article, the design and characteristics of a micro-fadeometer is presented. The technique allows for a non-(micro-) destructive evaluation of the light fastness of colorants on various materials and can be used to directly assess valuable materials, such as heritage objects, and develop safer display strategies to promote their preservation. The presented instrument has several benefits over standard light ageing methods - low operating cost, non-damaging, real time measurement of induced changes for kinetics studies, and automated high throughput screening of materials. A selection of data is presented to demonstrate the flexibility of the presented instrument and illustrate how it can be used to evaluate museum lighting and oxygen-free display of heritage objects.

  20. Note: Light ageing with simultaneous colorimetry via fibre optics reflection spectrometry.

    PubMed

    ?ojewski, Tomasz; Thomas, Jacob; Go??b, Roman; Kawa?ko, Jakub; ?ojewska, Joanna

    2011-07-01

    In this article, the design and characteristics of a micro-fadeometer is presented. The technique allows for a non-(micro-) destructive evaluation of the light fastness of colorants on various materials and can be used to directly assess valuable materials, such as heritage objects, and develop safer display strategies to promote their preservation. The presented instrument has several benefits over standard light ageing methods--low operating cost, non-damaging, real time measurement of induced changes for kinetics studies, and automated high throughput screening of materials. A selection of data is presented to demonstrate the flexibility of the presented instrument and illustrate how it can be used to evaluate museum lighting and oxygen-free display of heritage objects. PMID:21806236

  1. Percutaneous cervical nucleoplasty in the treatment of cervical disc herniation.

    PubMed

    Li, Jian; Yan, Deng-lu; Zhang, Zai-Heng

    2008-12-01

    Percutaneous disc decompression procedures have been performed in the past. Various percutaneous techniques such as percutaneous discectomy, laser discectomy, and nucleoplasty have been successful. Our prospective study was directly to evaluate the results of percutaneous cervical nucleoplasty (PCN) surgery for cervical disc herniation, and illustrate the effectiveness of PCN in symptomatic patients who had cervical herniated discs. From July of 2002 to June of 2005, 126 consecutive patients with contained cervical disc herniations have presented at the authors' clinic and treated by PCN. The patients' gender distribution for PCN was 65 male, 61 female. The age of patients ranged from 34 to 66 years (mean 51.9 +/- 10.2 years). The levels of involvement were 21 cases at C3-4, 30 cases at C4-5, 40 cases at C5-6, and 35 cases at C6-7. The clinical outcomes, pain reduction and the segment stability were all recorded during this study. A clinical outcome was quantified by the Macnab standard and using VAS. The angular displacement (AD) > or =11 degrees or horizontal displacement (HD) > or =3 mm was considered to be radiographically unstable. In the results of this study, puncture of the needle into the disc space was accurately performed under X-ray guidance in all cases. There was one case where the Perc-D Spine Wand had broken in the disc space during the procedure. The partial Perc-D Spine Wand, which had broken in the disc space could not be removed by the percutaneous cervical discectomy and thus remained there. There were no recurrent cases or complications in our series. Macnab standard results were excellent in 62 cases, good in 41 cases and fair in 23 cases. The rate of excellent and good was 83.73%. The VAS scores demonstrated statistically significant improvement in PCN at the 2-week, 1, 3, 6, and 12-month follow-up visits when compared to preoperational values (P < 0.01). There were no cases of instability following the PCN procedure. There was no significant difference in stability either preoperatively or postoperatively (P > 0.05). Our findings confirm that PCN for the treatment of cervical disc herniation results in a good outcome without any tampering of the stability of the cervical spine. Hence, PCN as a procedure is safe, minimally invasive, less traumatic, requiring less time with an excellent clinical outcome. PCN should be performed for those patients who fail conservative medical management including medication, physical therapy, behavioral management, psychotherapy, and who are unwilling to undergo a more invasive technique such as spinal surgery. PMID:18830638

  2. Experimental Correlation of the Aging Process of the ADSS Fiber-Optic Cables in ASU's Environmental Chamber to Field Tests in Bandon, OR

    Microsoft Academic Search

    Essam Al-Ammar; George G. Karady; Monty W. Tuominen; Danna J. Vermeers

    2008-01-01

    An environmental chamber has been constructed at Arizona State University to establish a long-term aging test of all-dielectric self-supporting (ADSS) fiber-optic cable. A polymer-jacketed ADSS (track resistant) cable is subjected to UV radiation, salt fog, clean rain, and mechanical tension in the aging chamber. Installed by the Bonneville Power Administration (BPA), a similar track resistant ADSS has been in operation

  3. Association between apparent diffusion coefficient and intervertebral disc degeneration in patients with ankylosing spondylitis

    PubMed Central

    Resorlu, Mustafa; Gokmen, Ferhat; Resorlu, Hatice; Adam, Gurhan; Akbal, Ayla; Cevizci, Sibel; Sariyildirim, Abdullah; Savas, Yilmaz; Guven, Mustafa; Aras, Adem Bozkurt

    2015-01-01

    Purpose: To assess the relation between ankylosing spondylitis (AS) and degenerative disc disease emerging in association with various intrinsic and extrinsic factors and to evaluate the correlation between degree of degeneration in intervertebral discs and apparent diffusion coefficient (ADC) values. Methods: Thirty-five patients with AS and a control group of 35 patients were included in the study. Three hundred fifty intervertebral discs were assessed in terms of degeneration by analyzing signal intensities and morphologies on T2 weighted series of a 1.5 Tesla magnetic resonance scanner. ADC values were determined in diffusion weighted images (DWI) using a “b value of 500 s/mm2”. Patients in the AS and control groups were compared in terms of intervertebral disc degeneration, and association between degree of degeneration and ADC values was analyzed. Results: The mean of total degeneration degrees for five lumbar intervertebral discs was significantly higher in the patients with AS compared to the control group (16.77±4.67 vs 13.00±4.08, respectively; P=0.001). When intervertebral discs were analyzed separately, disc degeneration was again significantly higher in patients with AS compared to the control group, with the exception of L5-S1. Age, cholesterol level, triglyceride level, duration of disease and BASFI index were significantly associated with degree of degeneration in patients with AS. A negative correlation was determined between disc degeneration and ADC value. Conclusion: AS is a risk factor for degenerative disc disease due to its systemic effects, the fact it leads to posture impairment and its inflammatory effects on the vertebrae. A decrease in ADC values is observed as degeneration worsens in degenerative disc disease. PMID:25785119

  4. A young hierarchical triple system harbouring a candidate debris disc

    NASA Astrophysics Data System (ADS)

    Deacon, N. R.; Schlieder, J. E.; Olofsson, J.; Johnston, K. G.; Henning, Th.

    2013-09-01

    We report the detection of a wide young hierarchical triple system where the primary has a candidate debris disc. The primary, TYC 5241-986-1 A, is a known Tycho star which we classify as a late-K star with emission in the X-ray, near- and far-ultraviolet (UV) and H? suggestive of youth. Its proper motion, photometric distance (65-105 pc) and radial velocity lead us to associate the system with the broadly defined Local Association of young stars but not specifically with any young moving group. The presence of weak lithium absorption and X-ray and calcium H and K emission support an age in the 20 to ˜125 Myr range. The secondary is a pair of M4.5 ± 0.5 dwarfs with near- and far-UV and H? emission separated by approximately 1 arcsec (˜65-105 au projected separation) which lie of 145 arcsec (9200-15200 au) from the primary. The primary has a Wide-field Infrared Survey Explorer (WISE) 22 ?m excess and follow-up Herschel observations also detect an excess at 70 ?m. The excess emissions are indicative of a 100-175 K debris disc. We also explore the possibility that this excess could be due to a coincident background galaxy and conclude that this is unlikely. Debris discs are extremely rare around stars older than 15 Myr, hence if the excess is caused by a disc this is an extremely novel system.

  5. Searching for signatures of planet formation in stars with circumstellar debris discs

    NASA Astrophysics Data System (ADS)

    Maldonado, J.; Eiroa, C.; Villaver, E.; Montesinos, B.; Mora, A.

    2015-07-01

    Context. Tentative correlations between the presence of dusty circumstellar debris discs and low-mass planets have recently been presented. In parallel, detailed chemical abundance studies have reported different trends between samples of planet and non-planet hosts. Whether these chemical differences are indeed related to the presence of planets is still strongly debated. Aims: We aim to test whether solar-type stars with debris discs show any chemical peculiarity that could be related to the planet formation process. Methods: We determine in a homogeneous way the metallicity, [Fe/H], and abundances of individual elements of a sample of 251 stars including stars with known debris discs, stars harbouring simultaneously debris discs and planets, stars hosting exclusively planets, and a comparison sample of stars without known discs or planets. High-resolution échelle spectra (R ~ 57 000) from 2-3 m class telescopes are used. Our methodology includes the calculation of the fundamental stellar parameters (Teff, log g, microturbulent velocity, and metallicity) by applying the iron ionisation and equilibrium conditions to several isolated Fe i and Fe ii lines, as well as individual abundances of C, O, Na, Mg, Al, Si, S, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Cu, and Zn. Results: No significant differences have been found in metallicity, individual abundances or abundance-condensation temperature trends between stars with debris discs and stars with neither debris nor planets. Stars with debris discs and planets have the same metallicity behaviour as stars hosting planets, and they also show a similar ?[ X/Fe ] ? - TC trend. Different behaviour in the ?[ X/Fe ] ? - TC trends is found between the samples of stars without planets and the samples of planet hosts. In particular, when considering only refractory elements, negative slopes are shown in cool giant planet hosts, whilst positive ones are shown in stars hosting low-mass planets. The statistical significance of the derived slopes is low, however, probably because of the wide range of stellar parameters of our samples. Stars hosting exclusively close-in giant planets behave in a different way, showing higher metallicities and positive ?[ X/Fe ] ? - TC slope. A search for correlations between the ?[ X/Fe ] ? - TC slopes and the stellar properties reveals a moderate but significant correlation with the stellar radius and a weak correlation with the stellar age, which remain even if Galactic chemical evolution effects are considered. No correlation between the ?[ X/Fe ] ? - TC slopes and the disc/planet properties are found. Conclusions: The fact that stars with debris discs and stars with low-mass planets do not show either metal enhancement or a different ?[ X/Fe ] ? - TC trend might indicate a correlation between the presence of debris discs and the presence of low-mass planets. We extend results from previous works based mainly on solar analogues with reported differences in the ?[ X/Fe ] ? - TC trends between planet hosts and non-hosts to a wider range of parameters. However, these differences tend to be present only when the star hosts a cool distant planet and not in stars hosting exclusively low-mass planets. The interpretation of these differences as a signature of planetary formation should be considered with caution since moderate correlations between the TC-slopes with the stellar radius and the stellar age are found, suggesting that an evolutionary effect might be at work. Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto, operated jointly by the Max-Planck Institut für Astronomie and the Instituto de Astrofísica de Andalucía (CSIC); observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundación Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica); observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del R

  6. The lumbar disc and low back pain.

    PubMed

    Bogduk, N

    1991-10-01

    The lumbar disc serves to sustain compression loads and is subject to tension and shear in forward bending and rotation. Its outer third is innervated and can be a source of pain. The annulus fibrosus may be injured in rotation and flexion of the lumbar spine and may become symptomatic as a ligamentous injury. Compression injuries of the disc are initially asymptomatic but may set in train a degradative process that, in time, leads to internal disc disruption, which becomes symptomatic as a result of chemical or mechanical irritation of nociceptors in the annulus fibrosus. Disc prolapse is but one possible end stage of internal disc disruption and represents the culmination of a series of destructive processes affecting the disc. This condition can be symptomatic while the external appearance of the disc remains normal and before nerve roots are affected in any way. PMID:1821758

  7. Intermediate-mass black holes in AGN discs - II. Model predictions and observational constraints

    NASA Astrophysics Data System (ADS)

    McKernan, B.; Ford, K. E. S.; Kocsis, B.; Lyra, W.; Winter, L. M.

    2014-06-01

    If intermediate-mass black holes (IMBHs) grow efficiently in gas discs around supermassive black holes, their host active galactic nucleus (AGN) discs should exhibit myriad observational signatures. Gap-opening IMBHs in AGN discs can exhibit spectral features and variability analogous to gapped protoplanetary discs. A gap-opening IMBH in the innermost disc imprints ripples and oscillations on the broad Fe K? line which may be detectable with future X-ray missions. A non-gap-opening IMBH will accrete and produce a soft X-ray excess relative to continuum emission. An IMBH on a retrograde orbit in an AGN disc will not open a gap and will generate soft X-rays from a bow-shock `headwind'. Accreting IMBH in a large cavity can generate ULX-like X-ray luminosities and LINER-like optical line ratios from local ionized gas. We propose that many LINERs house a weakly accreting MBH binary in a large central disc cavity and will be luminous sources of gravitational waves (GW). IMBHs in galactic nuclei may also be detected via intermittent observational signatures including: UV/X-ray flares due to tidal disruption events, asymmetric X-ray intensity distributions as revealed by AGN transits, quasi-periodic oscillations and underluminous Type Ia supernovae. GW emitted during IMBH inspiral and collisions may be detected with eLISA and LIGO, particularly from LINERs. We summarize observational signatures and compare to current data where possible or suggest future observations.

  8. The discovery of a debris disc around the DAV white dwarf PG 1541+651

    NASA Astrophysics Data System (ADS)

    Kilic, Mukremin; Patterson, Adam J.; Barber, Sara; Leggett, S. K.; Dufour, P.

    2012-01-01

    To search for circumstellar discs around evolved stars, we targeted roughly 100 DA white dwarfs from the Palomar Green survey with the Peters Automated Infrared Imaging Telescope (PAIRITEL). Here we report the discovery of a debris disc around one of these targets, the pulsating white dwarf PG 1541+651 (KX Draconis, hereafter PG1541). We detect a significant flux excess around PG1541 in the K band. Follow-up near-infrared spectroscopic observations obtained at the NASA Infrared Telescope Facility and photometric observations with the warm Spitzer Space Telescope confirm the presence of a warm debris disc within 0.13-0.36 R? (11-32 × the stellar radius) at an inclination angle of 60°. At Teff= 11 880 K, PG1541 is almost a twin of the DAV white dwarf G29-38, which also hosts a debris disc. All previously known dusty white dwarfs are of the DAZ/DBZ spectral type due to accretion of metals from the disc. High-resolution optical spectroscopy is needed to search for metal absorption lines in PG1541 and to constrain the accretion rate from the disc. PG1541 is only 55 pc away from the Sun and the discovery of its disc in our survey demonstrates that our knowledge of the nearby dusty white dwarf population is far from complete.

  9. Dynamics of stress wave propagation in a chain of photoelastic discs impacted by a planar shock wave; Part I, experimental investigation

    Microsoft Academic Search

    B. Glam; O. Igra; A. Britan; G. Ben-Dor

    2007-01-01

    The propagation of stress waves through a chain of discs has been studied experimentally. Optically transparent 20-mm diameter\\u000a discs, made of epoxy, were loaded dynamically by head-on collision with an incident planar shock wave. The loading was done\\u000a in a vertical shock tube. The head-on collision between the punch-plate, placed on top of the chain of discs, and the incident

  10. Multiwavelength studies of the gas and dust disc of IRAS 04158+2805

    E-print Network

    A. M. Glauser; F. Ménard; C. Pinte; G. Duchêne; M. Güdel; J. -L. Monin; D. L. Padgett

    2008-04-22

    We present a study of the circumstellar environment of IRAS 04158+2805 based on multi-wavelength observations and models. Images in the optical and near-infrared, a polarisation map in the optical, and mid-infrared spectra were obtained with VLT-FORS1, CFHT-IR, and Spitzer-IRS. Additionally we used an X-ray spectrum observed with Chandra. We interpret the observations in terms of a central star surrounded by an axisymmetric circumstellar disc, but without an envelope, to test the validity of this simple geometry. We estimate the structural properties of the disc and its gas and dust content. We modelled the dust disc with a 3D continuum radiative transfer code, MCFOST, based on a Monte-Carlo method that provides synthetic scattered light images and polarisation maps, as well as spectral energy distributions. We find that the disc images and spectral energy distribution narrowly constrain many of the disc model parameters, such as a total dust mass of 1.0-1.75x10^-4 sollar masses and an inclination of 62-63 degrees. The maximum grain size required to fit all available data is of the order of 1.6-2.8 microns although the upper end of this range is loosely constrained. The observed optical polarisation map is reproduced well by the same disc model, suggesting that the geometry we find is adequate and the optical properties are representative of the visible dust content. We compare the inferred dust column density to the gas column density derived from the X-ray spectrum and find a gas-to-dust ratio along the line of sight that is consistent with the ISM value. To our knowledge, this measurement is the first to directly compare dust and gas column densities in a protoplanetary disc.

  11. Mixture model-based approach for optic cup segmentation.

    PubMed

    Tan, N M; Liu, J; Wong, D K; Yin, F; Lim, J H; Wong, T Y

    2010-01-01

    Glaucoma is a leading cause of blindness with permanent damage to optic nerve head. ARGALI is an automated computer-aided diagnosis system designed for glaucoma detection via optic cup-to-disc ratio assessment. It employs several methods to determine the optic cup and disc from retinal images. PMID:21097297

  12. Near-Field Optical Data Storage Proefschrift

    E-print Network

    #12;#12;Near-Field Optical Data Storage Proefschrift ter verkrijging van de graad van doctor aan de schematically depicts the light-path of the near-field optical recording set-up that is described in this thesis, coding and bit detection 8 2.2 Read-out of optical discs 10 2.3 Key parameters of consumer optical disc

  13. Ptolemy relations for punctured discs

    E-print Network

    Baur, Karin

    2007-01-01

    We construct frieze patterns of type D_N with entries which are numbers of matchings between vertices and triangles of corresponding triangulations of a punctured disc. For triangulations corresponding to orientations of the Dynkin diagram of type D_N, we show that the numbers in the pattern can be interpreted as specialisations of cluster variables in the corresponding Fomin-Zelevinsky cluster algebra.

  14. Hydrodynamic instability in eccentric astrophysical discs

    NASA Astrophysics Data System (ADS)

    Barker, A. J.; Ogilvie, G. I.

    2014-12-01

    Eccentric Keplerian discs are believed to be unstable to three-dimensional hydrodynamical instabilities driven by the time-dependence of fluid properties around an orbit. These instabilities could lead to small-scale turbulence, and ultimately modify the global disc properties. We use a local model of an eccentric disc, derived in a companion paper, to compute the non-linear vertical (`breathing mode') oscillations of the disc. We then analyse their linear stability to locally axisymmetric disturbances for any disc eccentricity and eccentricity gradient using a numerical Floquet method. In the limit of small departures from a circular reference orbit, the instability of an isothermal disc is explained analytically. We also study analytically the small-scale instability of an eccentric neutrally stratified polytropic disc with any polytropic index using a Wentzel-Kramers-Brillouin (WKB) approximation. We find that eccentric discs are generically unstable to the parametric excitation of small-scale inertial waves. The non-linear evolution of these instabilities should be studied in numerical simulations, where we expect them to lead to a decay of the disc eccentricity and eccentricity gradient as well as to induce additional transport and mixing. Our results highlight that it is essential to consider the three-dimensional structure of eccentric discs, and their resulting vertical oscillatory flows, in order to correctly capture their evolution.

  15. Accretion Discs with Strong Toroidal Magnetic Fields

    E-print Network

    M. C. Begelman; J. E. Pringle

    2006-12-12

    Simulations and analytic arguments suggest that the turbulence driven by magnetorotational instability (MRI) in accretion discs can amplify the toroidal (azimuthal) component of the magnetic field to a point at which magnetic pressure exceeds the combined gas + radiation pressure in the disc. Arguing from the recent analysis by Pessah and Psaltis, and other MRI results in the literature, we conjecture that the limiting field strength for a thin disc is such that the Alfven speed roughly equals the geometric mean of the Keplerian speed and the gas sound speed. We examine the properties of such magnetically-dominated discs, and show that they resolve a number of outstanding problems in accretion disc theory. The discs would be thicker than standard (Shakura-Sunyaev) discs at the same radius and accretion rate, and would tend to have higher colour temperatures. If they transport angular momentum according to an alpha-prescription, they would be stable against the thermal and viscous instabilities that are found in standard disc models. In discs fuelling active galactic nuclei, magnetic pressure support could also alleviate the restriction on accretion rate imposed by disc self-gravity.

  16. Cloning and Characterization of Disc1, the Mouse Ortholog of DISC1 (Disrupted-in-Schizophrenia 1)

    Microsoft Academic Search

    Lei Ma; Yuan Liu; Betty Ky; Paul J. Shughrue; Christopher P. Austin; Jill A. Morris

    2002-01-01

    We cloned the mouse ortholog of DISC1 (Disrupted-in-Schizophrenia 1), a candidate gene for schizophrenia. Disc1 is 3163 nucleotides long and has 60% identity with the human DISC1. Disc1 encodes 851 amino acids and has 56% identity with the human protein. Disc1 maps to the DISC1 syntenic region in the mouse, and genomic structure is conserved. A Disc1 splice variant deletes

  17. Proto-planetary disc evolution and dispersal

    NASA Astrophysics Data System (ADS)

    Rosotti, Giovanni Pietro

    2015-05-01

    Planets form from gas and dust discs in orbit around young stars. The timescale for planet formation is constrained by the lifetime of these discs. The properties of the formed planetary systems depend thus on the evolution and final dispersal of the discs, which is the main topic of this thesis. Observations reveal the existence of a class of discs called "transitional", which lack dust in their inner regions. They are thought to be the last stage before the complete disc dispersal, and hence they may provide the key to understanding the mechanisms behind disc evolution. X-ray photoevaporation and planet formation have been studied as possible physical mechanisms responsible for the final dispersal of discs. However up to now, these two phenomena have been studied separately, neglecting any possible feedback or interaction. In this thesis we have investigated what is the interplay between these two processes. We show that the presence of a giant planet in a photo-evaporating disc can significantly shorten its lifetime, by cutting the inner regions from the mass reservoir in the exterior of the disc. This mechanism produces transition discs that for a given mass accretion rate have larger holes than in models considering only X-ray photo-evaporation, constituting a possible route to the formation of accreting transition discs with large holes. These discs are found in observations and still constitute a puzzle for the theory. Inclusion of the phenomenon called "thermal sweeping", a violent instability that can destroy a whole disc in as little as 10 4 years, shows that the outer disc left can be very short-lived (depending on the X-ray luminosity of the star), possibly explaining why very few non accreting transition discs are observed. However the mechanism does not seem to be efficient enough to reconcile with observations. In this thesis we also show that X-ray photo-evaporation naturally explains the observed correlation between stellar masses and accretion rates and is therefore the ideal candidate for driving disc evolution. Another process that can influence discs is a close encounter with another star. In this thesis we develop a model to study the effect of stellar dynamics in the natal stellar cluster on the discs, following for the first time at the same time the stellar dynamics together with the evolution of the discs. We find that, although close encounters with stars are unlikely to change significantly the mass of a disc, they can change substantially its size, hence imposing an upper limit on the observed disc radii. Finally, we investigated in this thesis whether discs can be reformed after their dispersal. If a star happens to be in a region that is currently forming stars, it can accrete material from the interstellar medium. This mechanism may result in the production of "second generation" discs such that in a given star forming region a few percent of stars may still possess a disc, in tentative agreement with observations of so called "old accretors", which are difficult to explain within the current paradigm of disc evolution and dispersal.

  18. SCUBA observations of dust around Lindroos stars: evidence for a substantial submillimetre disc population

    NASA Astrophysics Data System (ADS)

    Wyatt, M. C.; Dent, W. R. F.; Greaves, J. S.

    2003-07-01

    We have observed 22 young stars from the Lindroos sample at 850 ?m with SCUBA on the James Clerk Maxwell Telescope to search for evidence of dust discs. Stars in this sample are the less massive companions of B-type primaries and have well-defined ages that are 10- 170 Myr; i.e. they are about to, or have recently arrived on the main sequence. Dust was detected around three of these stars (HD 112412, 74067 and 99803B). The emission around HD 74067 is centrally peaked and is approximately symmetrically distributed out to ~70 arcsec from the star. This emission arises from either a two-component disc, one circumstellar and the other circumbinary with dust masses of 0.3 and <27 M?, respectively, or an unrelated background object. The other two detections we attribute to circumsecondary discs with masses of 0.04 and 0.3 M?. We were also able to show that a circumprimary disc is present around HD 112413 with a similar mass to that around the companion HD 112412. Cross-correlation of our sample with the IRAS catalogues only showed evidence for dust emission at 25 and 60 ?m toward one star (HD 1438); none of the submillimetre detections were evident in the far-infrared data implying that these discs are cold (>40 K assuming ?= 1). Our submillimetre detections are some of the first of dust discs surrounding evolved stars that were not detected by IRAS or ISO and imply that 9-14 per cent of stars could harbour previously undetected dust discs that await discovery in unbiased sub-mm surveys. If these discs are protoplanetary remnants, rather than secondary debris discs, dust lifetime arguments show that they must be devoid of small <0.1 mm grains. Thus it may be possible to determine the origin of these discs from their spectral energy distributions. The low inferred dust masses for this sample support the picture that protoplanetary dust discs are depleted to the levels of the brightest debris discs (~1 M?) within 10 Myr, although if the extended emission of HD 74067 is associated with the star, this would indicate that >10 M? of circumbinary material can persist until ~60 Myr and would also support the theory that T Tauri discs in binary systems are replenished by circumbinary envelopes.

  19. Prevalence of Disc Degeneration in Asymptomatic Korean Subjects. Part 1 : Lumbar Spine

    PubMed Central

    Lee, Tae Hoon; Lim, Soo Mee

    2013-01-01

    Objective Asymptomatic patients show high degeneration prevalence at lumbar disc in previous literatures. Unfortunately, there are few Korean data, so the authors attempted to analyze the prevalence of disc degeneration in highly selective asymptomatic Korean subjects using MRI. Methods We performed 3 T MRI sagittal scans from T12 to S1 on 102 asymptomatic subjects (50 men and 52 women) who visited our hospital between the ages of 14 and 82 years (mean age 46.3 years). All images were read independently by three observers (two neurosurgeons and one neuroradiologist) who were not given any information about the subjects. We classified grading for lumbar disc herniation (HN), annular fissure (AF), and nucleus degeneration (ND), using disc degeneration classification. Results The prevalence of HN, AF, and ND were 81.4%, 76.1%, and 75.8% respectively. Almost all levels showed an age-related proportional tendency with some exceptions. Conclusion In asymptomatic Korean subjects, the abnormal findings showed high prevalence of AF, ND, and extrusion. Especially in young ages, the authors found that bulging, protrusion, and AF showed high prevalence at L4/5 and L5/S1. And ND showed high prevalence at L5/S1. So, all lumbar disc degenerations are not pathologic, especially in children and adolescents. PMID:23440899

  20. Optical ages indicate the southwestern margin of the Green Bay Lobe in Wisconsin, USA, was at its maximum extent until about 18,500 years ago

    NASA Astrophysics Data System (ADS)

    Attig, J. W.; Hanson, P. R.; Rawling, J. E., III; Young, A. R.; Carson, E. C.

    2011-07-01

    Samples for optical dating were collected to estimate the time of sediment deposition in small ice-marginal lakes in the Baraboo Hills of Wisconsin. These lakes formed high in the Baraboo Hills when drainage was blocked by the Green Bay Lobe when it was at or very near its maximum extent. Therefore, these optical ages provide control for the timing of the thinning and recession of the Green Bay Lobe from its maximum position. Sediment that accumulated in four small ice-marginal lakes was sampled and dated. Difficulties with field sampling and estimating dose rates made the interpretation of optical ages derived from samples from two of the lake basins problematic. Samples from the other two lake basins-South Bluff and Feltz basins-responded well during laboratory analysis and showed reasonably good agreement between the multiple ages produced at each site. These ages averaged 18.2 ka (n = 6) and 18.6 ka (n = 6), respectively. The optical ages from these two lake basins where we could carefully select sediment samples provide firm evidence that the Green Bay Lobe stood at or very near its maximum extent until about 18.5 ka. The persistence of ice-marginal lakes in these basins high in the Baraboo Hills indicates that the ice of the Green Bay Lobe had not experienced significant thinning near its margin prior to about 18.5 ka. These ages are the first to directly constrain the timing of the maximum extent of the Green Bay Lobe and the onset of deglaciation in the area for which the Wisconsin Glaciation was named.

  1. Optical ages indicate the southwestern margin of the Green Bay Lobe in Wisconsin, USA, was at its maximum extent until about 18,500 years ago

    USGS Publications Warehouse

    Attig, J.W.; Hanson, P.R.; Rawling, J.E.; Young, A.R.; Carson, E.C.

    2011-01-01

    Samples for optical dating were collected to estimate the time of sediment deposition in small ice-marginal lakes in the Baraboo Hills of Wisconsin. These lakes formed high in the Baraboo Hills when drainage was blocked by the Green Bay Lobe when it was at or very near its maximum extent. Therefore, these optical ages provide control for the timing of the thinning and recession of the Green Bay Lobe from its maximum position. Sediment that accumulated in four small ice-marginal lakes was sampled and dated. Difficulties with field sampling and estimating dose rates made the interpretation of optical ages derived from samples from two of the lake basins problematic. Samples from the other two lake basins-South Bluff and Feltz basins-responded well during laboratory analysis and showed reasonably good agreement between the multiple ages produced at each site. These ages averaged 18.2. ka (n= 6) and 18.6. ka (n= 6), respectively. The optical ages from these two lake basins where we could carefully select sediment samples provide firm evidence that the Green Bay Lobe stood at or very near its maximum extent until about 18.5. ka.The persistence of ice-marginal lakes in these basins high in the Baraboo Hills indicates that the ice of the Green Bay Lobe had not experienced significant thinning near its margin prior to about 18.5. ka. These ages are the first to directly constrain the timing of the maximum extent of the Green Bay Lobe and the onset of deglaciation in the area for which the Wisconsin Glaciation was named. ?? 2011 Elsevier B.V.

  2. Optical dating of quartz sediments and accelerator mass spectrometry C dating of bone gelatin and moa eggshell: A comparison of age estimates for non?archaeological deposits in New Zealand

    Microsoft Academic Search

    Richard N. Holdaway; Richard G. Roberts; Jon M. Olley; Trevor H. Worthy

    2002-01-01

    A consensus has not been reached on the validity of “old” (pre?Polynesian settlement) C ages for Pacific rat bones from New Zealand. As an independent test of their validity, we have applied optical dating techniques to fossiliferous sediments at three non?archaeological sites in the North and South Islands. In this paper, we report the optical ages obtained from quartz grains

  3. Lumbar disc herniation in three patients with cystic fibrosis: a case series

    PubMed Central

    2011-01-01

    Introduction To date, lumbar disc herniation has not been reported in the context of cystic fibrosis even though back pain and musculoskeletal problems are very common in patients with cystic fibrosis. Case presentation We report on three patients with cystic fibrosis who experienced lumbar disc herniation in the course of their disease at ages 19 to 21 years (a 22-year-old Caucasian man, a 23-year-old Caucasian man, and a 21-year-old Caucasian woman). Our third patient eventually died because of her deteriorated pulmonary situation, which was influenced by the lumbar disc herniation as it was not possible for her to perform pulmonary drainage techniques properly because of the pain. Conclusions Lumbar disc herniation can lead to a vicious cycle for patients with cystic fibrosis as it may promote pulmonary infections. This report highlights the need to investigate patients correctly. PMID:21896180

  4. In Vivo Measurement of Age-Related Stiffening in the Crystalline Lens by Brillouin Optical Microscopy

    PubMed Central

    Scarcelli, Giuliano; Kim, Pilhan; Yun, Seok Hyun

    2011-01-01

    Abtract The biophysical and biomechanical properties of the crystalline lens (e.g., viscoelasticity) have long been implicated in accommodation and vision problems, such as presbyopia and cataracts. However, it has been difficult to measure such parameters noninvasively. Here, we used in vivo Brillouin optical microscopy to characterize material acoustic properties at GHz frequency and measure the longitudinal elastic moduli of lenses. We obtained three-dimensional elasticity maps of the lenses in live mice, which showed biomechanical heterogeneity in the cortex and nucleus of the lens with high spatial resolution. An in vivo longitudinal study of mice over a period of 2 months revealed a marked age-related stiffening of the lens nucleus. We found remarkably good correlation (log-log linear) between the Brillouin elastic modulus and the Young's modulus measured by conventional mechanical techniques at low frequencies (?1 Hz). Our results suggest that Brillouin microscopy is potentially useful for basic and animal research and clinical ophthalmology. PMID:21943436

  5. On the theory of disc photoevaporation

    E-print Network

    Owen, James E; Ercolano, Barbara

    2011-01-01

    We discuss a hydrodynamical model for the dispersal of protoplanetary discs around young, low mass (100) luminosity ratios, the FUV constricts the X-ray flow and may dominate the mass-loss. Simulations of low mass discs with inner holes demonstrate a further stage of disc clearing, which we call `thermal sweeping'. This process occurs when the mid-plane pressure drops to sufficiently low values. At this stage a bound, warm, X-ray heated region becomes sufficiently large and unstable, such that the remaining disc material is cleared on approximately dynamical time-scales. This process significantly reduces the time taken to clear the outer regions of the disc, resulting in an expected transition disc population that will be dominated by accreting objects, as indicated by recent observations.

  6. Immunolocalization of Delta-Giardin within the Ventral Disc in of Trophozoites and in cysts of Giardia duodenalis using the Multiplex Laser Scanning Confocal Microscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Immunolocalization of alpha2-, beta- and delta-giardin in Giardia showed that in the trophozoites and cysts delta-giardin it strictly associated with the ventral disc. Optical sectioning of the ventral discs, together with quantitative colocalization of the immunoreactivity for delta- and beta-giard...

  7. Stirring in massive, young debris discs from spatially resolved Herschel images

    NASA Astrophysics Data System (ADS)

    Moór, A.; Kóspál, Á.; Ábrahám, P.; Apai, D.; Balog, Z.; Grady, C.; Henning, Th.; Juhász, A.; Kiss, Cs.; Krivov, A. V.; Pawellek, N.; Szabó, Gy. M.

    2015-02-01

    A significant fraction of main-sequence stars are encircled by dusty debris discs, where the short-lived dust particles are replenished through collisions between planetesimals. Most destructive collisions occur when the orbits of smaller bodies are dynamically stirred up, either by the gravitational effect of locally formed Pluto-sized planetesimals (self-stirring scenario), or via secular perturbation caused by an inner giant planet (planetary stirring). The relative importance of these scenarios in debris systems is unknown. Here, we present new Herschel Space Observatory imagery of 11 discs selected from the most massive and extended known debris systems. All discs were found to be extended at far-infrared wavelengths, five of them being resolved for the first time. We evaluated the feasibility of the self-stirring scenario by comparing the measured disc sizes with the predictions of the model calculated for the ages of our targets. We concluded that the self-stirring explanation works for seven discs. However, in four cases, the predicted pace of outward propagation of the stirring front, assuming reasonable initial disc masses, was far too low to explain the radial extent of the cold dust. Therefore, for HD 9672, HD 16743, HD 21997, and HD 95086, another explanation is needed. We performed a similar analysis for ? Pic and HR 8799, reaching the same conclusion. We argue that planetary stirring is a promising possibility to explain the disc properties in these systems. In HR 8799 and HD 95086, we may already know the potential perturber, since their known outer giant planets could be responsible for the stirring process. Interestingly, the discs around HD 9672, HD 21997, and ? Pic are also unique in harbouring detectable amount of molecular CO gas. Our study demonstrates that among the largest and most massive debris discs self-stirring may not be the only active scenario, and potentially planetary stirring is responsible for destructive collisions and debris dust production in a number of systems.

  8. OFTALMOSKOPSKA OCENA IZGLEDA PAPILE VIDNEGA ŽIVCA PRI GLAVKOMSKI NEVROPATIJI OPHTHALMOSCOPIC EVALUATION OF THE OPTIC NERVE HEAD

    Microsoft Academic Search

    Marija Zupan; Kristina Mikek; Smiljana Gruden

    Background. Optic nerve diseases, such as glauco- mas, lead to changes in the intrapapillary and parapapillary region of the optic nerve head. Conclusions. These changes can be described by the following variables: size and shape of the optic disc; size, shape, and pallor of the neuroretinal rim; size of the optic cup in relation to the area of the disc;

  9. Maelstrom -Dynamic Aging System Submitted to

    E-print Network

    Wood, Stephen L.

    of Dynamic Testing A. Drum Test B. Shallow submergence C. Poseidon Test V. Dynamic Aging Tank A. Concept B. Prototype 1. Water Pump Jet Analysis/Calculations 2. Disc Flow analysis C. Final Design ­ "Maelstrom" 1

  10. 8 Areas of Age-Related Change

    MedlinePLUS

    ... please turn Javascript on. Photo: PhotoDisc 1. Brain: Memory and Alzheimer's Disease (AD) As adults age, many ... Researchers from 12 institutions, including the NIH's National Human Genome Research Institute (NHGRI), recently announced the results ...

  11. Close-packing of growing discs

    SciTech Connect

    Bursill, L.A.; Xudong, F. (Melbourne Univ., Parkville (Australia). School of Physics)

    1988-12-01

    Spiral lattices are derived by allowing growing discs to aggregate under a close-packing rule. Both Fibonacci and Lucas numbers of visible spirals arise naturally, dependent only on the choice of growth centre. Both the rate of convergence towards an ideal spiral, and chirality, are determined by the initial placement of the first few discs (initial conditions). Thus the appearance of spiral packings is no more or less mysterious than the appearance of hexagonal packed arrays of equal discs.

  12. Stellar capture by an accretion disc

    E-print Network

    D. Vokrouhlicky; V. Karas

    1997-10-15

    Long-term evolution of a stellar orbit captured by a massive galactic center via successive interactions with an accretion disc has been examined. An analytical solution describing evolution of the stellar orbital parameters during the initial stage of the capture was found. Our results are applicable to thin Keplerian discs with an arbitrary radial distribution of density and rather general prescription for the star-disc interaction. Temporal evolution is given in the form of quadrature which can be carried out numerically.

  13. Endoscopic Discectomy for Extraforaminal Lumbar Disc Herniation

    Microsoft Academic Search

    Yuichi Takano; Nobuhiro Yuasa

    The microendoscopic discectomy (MED) technique has been one of the promising surgeries for lumbar disc herniation in the last few years. The purpose of this study is to report the feasibility of a minimally invasive technique for extraforaminal lumbar disc herniation. Ten patients with extraforaminal lumbar disc herniation (one at L3-4, four at L4-5, and five at L5-S1) underwent MED

  14. Kinematics and excitation of the molecular hydrogen accretion disc in NGC 1275

    NASA Astrophysics Data System (ADS)

    Scharwächter, J.; McGregor, P. J.; Dopita, M. A.; Beck, T. L.

    2013-03-01

    We report the results of high spatial and spectral resolution integral-field spectroscopy of the central ˜3 × 3 arcsec2 of the active galaxy NGC 1275 (Perseus A), based on observations with the Near-infrared Integral Field Spectrograph (NIFS) and the ALTitude conjugate Adaptive optics for the InfraRed (ALTAIR) adaptive-optics system on the Gemini North telescope. The circum-nuclear disc in the inner R ˜ 50 pc of NGC 1275 is seen in both the H2 and [Fe II] lines. The disc is interpreted as the outer part of a collisionally excited turbulent accretion disc. The kinematic major axis of the disc at a position angle of 68° is oriented perpendicular to the radio jet. A streamer-like feature to the south-west of the disc, detected in H2 but not in [Fe II], is discussed as one of possibly several molecular streamers, presumably falling into the nuclear region. Indications of an ionization structure within the disc are deduced from the He I and Br? emission lines, which may partially originate from the inner portions of the accretion disc. The kinematics of these two lines agrees with the signature of the circum-nuclear disc, but both lines display a larger central velocity dispersion than the H2 line. The ro-vibrational H2 transitions from the core of NGC 1275 are indicative of thermal excitation caused by shocks and agree with excitation temperatures of ˜1360 and ˜4290 K for the lower and higher energy H2 transitions, respectively. The data suggest X-ray heating as the dominant excitation mechanism of [Fe II] emission in the core, while fast shocks are a possible alternative. The [Fe II] lines indicate an electron density of ˜4000 cm-3. The H2 disc is modelled using simulated NIFS data cubes of H2 emission from inclined discs in Keplerian rotation around a central mass. Assuming a disc inclination of 45° ± 10°, the best-fitting models imply a central mass of (8 + 7 - 2) × 108 M?. Taken as a black hole mass estimate, this value is larger than previous estimates for the black hole mass in NGC 1275, but is in agreement with the M-? relation within the rms scatter. However, the molecular gas mass in the core region is tentatively estimated to be non-negligible, which suggests that the central mass may rather represent an upper limit for the black hole mass. In comparison to other H2-luminous radio galaxies, we discuss the relative role of jet feedback and accretion in driving shocks and turbulence in the molecular gas component.

  15. EFFECT OF DISC HEIGHT AND DISC WEDGE ANGLE ON LUMBAR SPINE UNDER AXIAL COMPRESSIVE FORCE

    Microsoft Academic Search

    YUAN LI ZHOU; QING HANG ZHANG; EE CHON TEO

    Three-dimensional L4-L5 finite element (FE) models of three disc heights (9.5mm, 11.5mm, and 13.5mm) and three disc wedge angles (5º, 8 º, and 10 º) were developed to investigate their effect on L4-L5 lumbar motion segment under pure axial compressive loading. The FE predictions indicated that the axial disc displacement and the posterior disc bulge increased greatly with an increase

  16. On the evolution of the protolunar disc.

    PubMed

    Ward, William R

    2014-09-13

    The structure and viscous evolution of a post-impact, protolunar disc is examined. The equations for a silicate disc in two-phase (vapour-liquid) equilibrium are employed to derive an analytical solution to vertical structure. Both a vertically mixed phase disc and a stratified disc, where a magma layer exists in the mid-plane surrounded by a vapour reservoir, are considered. The former largely reproduces the low gas mass fraction, x?1, profiles of the disc described in earlier literature that proposed that the disc would hover on the brink of gravitational instability. In the latter, the vapour layer has x?1 and is generally gravitationally stable, while the magma layer is vigorously unstable. The viscous evolution of the stratified model is then explored. Initially, the disc quickly settles to a quasi-steady state with a vapour reservoir containing the majority of the disc mass. The magma layer viscously spreads on a time scale of approximately 3-4 years, during which vapour continuously condenses into droplets that settle to the mid-plane, maintaining the magma surface density in spite of disc spreading. Material flowing inwards is accreted by the Earth; material flowing outwards past the Roche boundary can become incorporated into accreting moonlets. This evolution persists until the vapour reservoir is depleted in approximately 50-100 years, depending on its initial mass. PMID:25114314

  17. Misaligned angular momentum in hydrodynamic cosmological simulations: warps, outer discs and thick discs

    NASA Astrophysics Data System (ADS)

    Roškar, Rok; Debattista, Victor P.; Brooks, Alyson M.; Quinn, Thomas R.; Brook, Chris B.; Governato, Fabio; Dalcanton, Julianne J.; Wadsley, James

    2010-10-01

    We present a detailed analysis of a disc galaxy forming in a high-resolution fully cosmological simulation to investigate the nature of the outer regions of discs and their relevance for the disc formation process. Specifically, we focus on the phenomenon of misaligned disc components and find that the outer disc warp is a consequence of the misalignment between the inner disc and the surrounding hot gaseous halo. As the infalling cold gas sinks towards the centre of the galaxy, it is strongly torqued by the hot gas halo. By the time the fresh gas reaches the central disc-forming region, its angular momentum is completely aligned with the spin of the hot gas halo. If the spin of the hot gas halo, in turn, is not aligned with that of the inner disc, a misaligned outer disc forms, comprised of newly accreted material. The inner and outer components are misaligned with each other because they respond differently to infalling substructure and accretion. The warped disc feeds the main gas disc due to viscous angular momentum losses, but small amounts of star formation in the warp itself form a low-metallicity thick disc. We show that observations of resolved stellar populations in warped galaxies in the local Universe could provide evidence for the presence of these processes and therefore indirectly reveal ongoing gas accretion and the existence of hot gas haloes.

  18. Optical absorption as a sensitive monitor of tensile strength loss in thermally aged nylon 6,6

    Microsoft Academic Search

    1985-01-01

    Chemical changes which take place in polymers during thermal aging often adversely affect the bulk physical properties of the material. Aging rates under ambient conditions are usually so slow as to require extremely long aging cycles to achieve measurable losses in such properties as tensile strength. Therefore, accelerated aging under more stressful conditions (e.g., higher temperatures) with Arrhenius-plot extrapolations to

  19. 21 cm absorption by compact hydrogen discs around black holes in radio-loud nuclei of galaxies

    SciTech Connect

    Loeb, Abraham, E-mail: aloeb@cfa.harvard.edu [Astronomy Department, Harvard University, 60 Garden Street, Cambridge, MA 02138 (United States)] [Astronomy Department, Harvard University, 60 Garden Street, Cambridge, MA 02138 (United States)

    2008-05-15

    The clumpy maser discs observed in some galactic nuclei mark the outskirts of the accretion disc that fuels the central black hole and provide a potential site of nuclear star formation. Unfortunately, most of the gas in maser discs is currently not being probed; large maser gains favor paths that are characterized by a small velocity gradient and require rare edge-on orientations of the disc. Here we propose a method for mapping the atomic hydrogen distribution in nuclear discs through its 21 cm absorption against the radio continuum glow around the central black hole. In NGC 4258, the 21 cm optical depth may approach unity for high angular resolution (VLBI) imaging of coherent clumps which are dominated by thermal broadening and have the column density inferred from x-ray absorption data, {approx}10{sup 23} cm{sup -2}. Spreading the 21 cm absorption over the full rotation velocity width of the material in front of the narrow radio jets gives a mean optical depth of {approx}0.1. Spectroscopic searches for the 21 cm absorption feature in other galaxies can be used to identify the large population of inclined gaseous discs which are not masing in our direction. Follow-up imaging of 21 cm silhouettes of accelerating clumps within these discs can in turn be used to measure cosmological distances.

  20. Theory of Black Hole Accretion Discs

    NASA Astrophysics Data System (ADS)

    Abramowicz, Marek A.; Björnsson, Gunnlaugur; Pringle, James E.

    2010-08-01

    Part I. Observations of Black Holes: 1. Black holes in our Galaxy: observations P. Charles; 2. Black holes in Active Galactic Nuclei: observations G. M. Madejski; Part II. Physics Close to a Black Hole: 3. Physics of black holes I. D. Novikov; 4. Physics of black hole accretion M. A. Abramowicz; Part III. Turbulence, Viscosity: 5. Disc turbulence and viscosity A. Brandenburg; Part IV. Radiative Processes: 6. The role of electron-positron pairs in accretion flows G. Björnsson; 7. Accretion disc-corona models and X/Y-ray spectra of accreting black holes J. Poutanen; 8. Emission lines: signatures of relativistic rotation A. C. Fabian; Part V. Accretion Discs: 9. Spectral tests of models for accretion disks around black holes J. H. Krolik; 10. Advection-dominated accretion around black holes R. Narayan, R. Mahadevan and E. Quataert; 11. Accretion disc instabilities and advection dominated accretion flows J.-P. Lasota; 12. Magnetic field and multi-phase gas in AGN A. Celotti and M. J. Rees; Part V. Discs in Binary Black Holes: 13. Supermassive binary black holes in galaxies P. Artymowicz; Part VI. Stability of Accretion Discs: 14. Large scale perturbation of an accretion disc by a black hole binary companion J. C. B. Papaloizou, C. Terquem and D. N. C. Lin; 15. Stable oscillations of black hole accretion discs M. Nowak and D. Lehr; Part VI. Coherant Structures: 16. Spotted discs A. Bracco, A. Provenzale, E. A. Spiegel and P. Yecko; Self-organized critically in accretion discs P. Wiita and Y. Xiong; Summary: old and new advances in black hole accretion disc theory R. Svensson.

  1. Theory of Black Hole Accretion Discs

    NASA Astrophysics Data System (ADS)

    Abramowicz, Marek A.; Björnsson, Gunnlaugur; Pringle, James E.

    1999-03-01

    Part I. Observations of Black Holes: 1. Black holes in our Galaxy: observations P. Charles; 2. Black holes in Active Galactic Nuclei: observations G. M. Madejski; Part II. Physics Close to a Black Hole: 3. Physics of black holes I. D. Novikov; 4. Physics of black hole accretion M. A. Abramowicz; Part III. Turbulence, Viscosity: 5. Disc turbulence and viscosity A. Brandenburg; Part IV. Radiative Processes: 6. The role of electron-positron pairs in accretion flows G. Björnsson; 7. Accretion disc-corona models and X/Y-ray spectra of accreting black holes J. Poutanen; 8. Emission lines: signatures of relativistic rotation A. C. Fabian; Part V. Accretion Discs: 9. Spectral tests of models for accretion disks around black holes J. H. Krolik; 10. Advection-dominated accretion around black holes R. Narayan, R. Mahadevan and E. Quataert; 11. Accretion disc instabilities and advection dominated accretion flows J.-P. Lasota; 12. Magnetic field and multi-phase gas in AGN A. Celotti and M. J. Rees; Part V. Discs in Binary Black Holes: 13. Supermassive binary black holes in galaxies P. Artymowicz; Part VI. Stability of Accretion Discs: 14. Large scale perturbation of an accretion disc by a black hole binary companion J. C. B. Papaloizou, C. Terquem and D. N. C. Lin; 15. Stable oscillations of black hole accretion discs M. Nowak and D. Lehr; Part VI. Coherant Structures: 16. Spotted discs A. Bracco, A. Provenzale, E. A. Spiegel and P. Yecko; Self-organized critically in accretion discs P. Wiita and Y. Xiong; Summary: old and new advances in black hole accretion disc theory R. Svensson.

  2. Quantitative Classification of Eyes with and without Intermediate Age-related Macular Degeneration Using Optical Coherence Tomography

    PubMed Central

    Farsiu, Sina; Chiu, Stephanie J.; O'Connell, Rachelle V.; Folgar, Francisco A.; Yuan, Eric; Izatt, Joseph A.; Toth, Cynthia A.

    2013-01-01

    Objective To define quantitative indicators for the presence of intermediate age-related macular degeneration (AMD) via spectral-domain optical coherence tomography (SD-OCT) imaging of older adults. Design Evaluation of diagnostic test and technology. Participants and Controls One eye from 115 elderly subjects without AMD and 269 subjects with intermediate AMD from the Age-Related Eye Disease Study 2 (AREDS2) Ancillary SD-OCT Study. Methods We semiautomatically delineated the retinal pigment epithelium (RPE) and RPE drusen complex (RPEDC, the axial distance from the apex of the drusen and RPE layer to Bruch's membrane) and total retina (TR, the axial distance between the inner limiting and Bruch's membranes) boundaries. We registered and averaged the thickness maps from control subjects to generate a map of “normal” non-AMD thickness. We considered RPEDC thicknesses larger or smaller than 3 standard deviations from the mean as abnormal, indicating drusen or geographic atrophy (GA), respectively. We measured TR volumes, RPEDC volumes, and abnormal RPEDC thickening and thinning volumes for each subject. By using different combinations of these 4 disease indicators, we designed 5 automated classifiers for the presence of AMD on the basis of the generalized linear model regression framework. We trained and evaluated the performance of these classifiers using the leave-one-out method. Main Outcome Measures The range and topographic distribution of the RPEDC and TR thicknesses in a 5-mm diameter cylinder centered at the fovea. Results The most efficient method for separating AMD and control eyes required all 4 disease indicators. The area under the curve (AUC) of the receiver operating characteristic (ROC) for this classifier was >0.99. Overall neurosensory retinal thickening in eyes with AMD versus control eyes in our study contrasts with previous smaller studies. Conclusions We identified and validated efficient biometrics to distinguish AMD from normal eyes by analyzing the topographic distribution of normal and abnormal RPEDC thicknesses across a large atlas of eyes. We created an online atlas to share the 38 400 SD-OCT images in this study, their corresponding segmentations, and quantitative measurements. Financial Disclosure(s) Proprietary or commercial disclosure may be found after the references. PMID:23993787

  3. The properties of discs around planets and brown dwarfs as evidence for disc fragmentation

    NASA Astrophysics Data System (ADS)

    Stamatellos, Dimitris; Herczeg, Gregory J.

    2015-06-01

    Direct imaging searches have revealed many very low mass objects, including a small number of planetary-mass objects, as wide-orbit companions to young stars. The formation mechanism of these objects remains uncertain. In this paper, we present the predictions of the disc fragmentation model regarding the properties of the discs around such low-mass objects. We find that the discs around objects that have formed by fragmentation in discs hosted by Sun-like stars (referred to as parent discs and parent stars) are more massive than expected from the Mdisc-M* relation (which is derived for stars with masses M* > 0.2 M?). Accordingly, the accretion rates on to these objects are also higher than expected from the dot{M}_*-M_* relation. Moreover, there is no significant correlation between the mass of the brown dwarf or planet with the mass of its disc nor with the accretion rate from the disc on to it. The discs around objects that form by disc fragmentation have larger than expected masses as they accrete gas from the disc of their parent star during the first few kyr after they form. The amount of gas that they accrete and therefore their mass depend on how they move in their parent disc and how they interact with it. Observations of disc masses and accretion rates on to very low mass objects are consistent with the predictions of the disc fragmentation model. Future observations (e.g. by Atacama Large Millimeter/submillimeter Array) of disc masses and accretion rates on to substellar objects that have even lower masses (young planets and young, low-mass brown dwarfs), where the scaling relations predicted by the disc fragmentation model diverge significantly from the corresponding relations established for higher mass stars, will test the predictions of this model.

  4. Lifestyle factors and lumbar disc disease: results of a German multi-center case-control study (EPILIFT)

    PubMed Central

    2010-01-01

    Introduction In the large-scale case-control study EPILIFT, we investigated the dose-response relationship between lifestyle factors (weight, smoking amount, cumulative duration of different sports activities) and lumbar disc disease. Methods In four German study regions (Frankfurt am Main, Freiburg, Halle/Saale, Regensburg), 564 male and female patients with lumbar disc herniation and 351 patients with lumbar disc narrowing (chondrosis) aged 25 to 70 years were prospectively recruited. From the regional population registers, 901 population control subjects were randomly selected. In a structured personal interview, we enquired as to body weight at different ages, body height, cumulative smoking amount and cumulative duration of different sports activities. Confounders were selected according to biological plausibility and to the change-in-estimate criterion. Adjusted, gender-stratified odds ratios with 95% confidence intervals were calculated using unconditional logistic regression analysis. Results The results of this case-control study reveal a positive association between weight and lumbar disc herniation as well as lumbar disc narrowing among men and women. A medium amount of pack-years was associated with lumbar disc herniation and narrowing in men and women. A non-significantly lowered risk of lumbar disc disease was found in men with high levels of cumulative body building and strength training. Conclusions According to our multi-center case-control study, body weight might be related to lumbar disc herniation as well as to lumbar disc narrowing. Further research should clarify the potential protective role of body building or strength training on lumbar disc disease. PMID:20955546

  5. Gas in the protoplanetary disc of HD 169142: Herschel's view

    E-print Network

    Meeus, G; Woitke, P; Montesinos, B; Mendigutía, I; Riviere-Marichalar, P; Eiroa, C; Mathews, G S; Vandenbussche, B; Howard, C D; Roberge, A; Sandell, G; Duchêne, G; Ménard, F; Grady, C A; Dent, W R F; Kamp, I; Augereau, J C; Thi, W F; Tilling, I; Alacid, J M; Andrews, S; Ardila, D R; Aresu, G; Barrado, D; Brittain, S; Ciardi, D R; Danchi, W; Fedele, D; de Gregorio-Monsalvo, I; Heras, A; Huelamo, N; Krivov, A; Lebreton, J; Liseau, R; Martin-Zaidi, C; Mora, A; Morales-Calderon, M; Nomura, H; Pantin, E; Pascucci, I; Phillips, N; Podio, L; Poelman, D R; Ramsay, S; Riaz, B; Rice, K; Solano, E; Walker, H; White, G J; Williams, J P; Wright, G

    2010-01-01

    In an effort to simultaneously study the gas and dust components of the disc surrounding the young Herbig Ae star HD 169142, we present far-IR observations obtained with the PACS instrument onboard the Herschel Space Observatory. This work is part of the Open Time Key Project GASPS, which is aimed at studying the evolution of protoplanetary discs. To constrain the gas properties in the outer disc, we observed the star at several key gas-lines, including [OI] 63.2 and 145.5 micron, [CII] 157.7 micron, CO 72.8 and 90.2 micron, and o-H2O 78.7 and 179.5 micron. We only detect the [OI] 63.2 micron line in our spectra, and derive upper limits for the other lines. We complement our data set with PACS photometry and 12/13CO data obtained with the Submillimeter Array. Furthermore, we derive accurate stellar parameters from optical spectra and UV to mm photometry. We model the dust continuum with the 3D radiative transfer code MCFOST and use this model as an input to analyse the gas lines with the thermo-chemical code ...

  6. Cervical arthroplasty using ProDisc-C Case Report

    PubMed Central

    Nica, DA; Copaciu, R

    2013-01-01

    Cervical disc replacement is an emerging motion-preserving technology in the surgical treatment of the cervical degenerative disc disorders used as an alternative to the classic interbody fusion. We present a case report of a patient diagnosed with C6-7 right disc herniation who underwent anterior discectomy and received a total disc replacement using ProDisc C artificial disc prosthesis. PMID:23599830

  7. Cervical arthroplasty using ProDisc-C case report.

    PubMed

    Nica, D A; Copaciu, R

    2013-03-15

    Cervical disc replacement is an emerging motion-preserving technology in the surgical treatment of the cervical degenerative disc disorders used as an alternative to the classic interbody fusion. We present a case report of a patient diagnosed with C6-7 right disc herniation who underwent anterior discectomy and received a total disc replacement using ProDisc C artificial disc prosthesis. PMID:23599830

  8. Galaxies that shine: radiation-hydrodynamical simulations of disc galaxies

    NASA Astrophysics Data System (ADS)

    Rosdahl, Joakim; Schaye, Joop; Teyssier, Romain; Agertz, Oscar

    2015-07-01

    Radiation feedback is typically implemented using subgrid recipes in hydrodynamical simulations of galaxies. Very little work has so far been performed using radiation-hydrodynamics (RHD), and there is no consensus on the importance of radiation feedback in galaxy evolution. We present RHD simulations of isolated galaxy discs of different masses with a resolution of 18 pc. Besides accounting for supernova feedback, our simulations are the first galaxy-scale simulations to include RHD treatments of photoionization heating and radiation pressure, from both direct optical/UV radiation and multiscattered, re-processed infrared (IR) radiation. Photoheating smooths and thickens the discs and suppresses star formation about as much as the inclusion of (`thermal dump') supernova feedback does. These effects decrease with galaxy mass and are mainly due to the prevention of the formation of dense clouds, as opposed to their destruction. Radiation pressure, whether from direct or IR radiation, has little effect, but for the IR radiation we show that its impact is limited by our inability to resolve the high optical depths for which multiscattering becomes important. While artificially boosting the IR optical depths does reduce the star formation, it does so by smoothing the gas rather than by generating stronger outflows. We conclude that although higher resolution simulations, and potentially also different supernova implementations, are needed for confirmation, our findings suggest that radiation feedback is more gentle and less effective than is often assumed in subgrid prescriptions.

  9. Reprocessing of X-rays in the outer accretion disc of the black hole binary XTE J1817--330

    E-print Network

    Marek Gierlinski; Chris Done; Kim Page

    2008-11-06

    We build a simple model of the optical/UV emission from irradiation of the outer disc by the inner disc and coronal emission in black hole binaries. We apply this to the broadband Swift data from the outburst of the black hole binary XTE J1817--330 to confirm previous results that the optical/UV emission in the soft state is consistent with a reprocessing a constant fraction of the bolometric X-ray luminosity. However, this is very surprising as the disc temperature drops by more than a factor 3 in the soft state, which should produce a marked change in the reprocessing efficiency. The easiest way to match the observed constant reprocessed fraction is for the disc skin to be highly ionized (as suggested 30 years ago by van Paradijs), so that the bulk of the disc flux is reflected and only the hardest X-rays heat the disc. The constant reprocessed fraction also favours direct illumination of the disc over a scattering origin as the optical depth/solid angle of any scattering material (wind/corona) over the disc should decrease as the source luminosity declines. By contrast, the reprocessed fraction increases very significantly (by a factor ~6) as the source enters the hard state. This dramatic change is not evident from X-ray/UV flux correlations as it is masked by bandpass effects. However, it does not necessarily signal a change in emission e.g. the emergence of the jet dominating the optical/UV flux as the reflection albedo must change with the dramatic change in spectral shape.

  10. A debris disc under the influence of a wide planetary-mass companion: the system of HD 106906

    NASA Astrophysics Data System (ADS)

    Jílková, Lucie; Zwart, Simon Portegies

    2015-07-01

    The 13-Myr old star HD 106906 is orbited by a debris disc of at least 0.067 MMoon with inner and outer radii of 20 and 120 au, respectively, and by a planet at a distance of 650 au. We use this curious combination of a close low-mass disc and a wide planet to motivate our simulations of this system. We study the parameter space of the initial conditions to quantify the mass loss from the debris disc and its lifetime under the influence of the planet. We find that when the planet orbits closer to the star than about 50 au and with low inclination relative to the disc (less than about 10°), more disc material is perturbed outside than inside the region constrained by observations on time-scales shorter than 1 Myr. Considering the age of the system, such a short lifetime of the disc is incompatible with the time-scale for planet-planet scattering, which is one of the scenarios suggested to explain the wide separation of the planet. For some configurations, when the planet orbit is inclined with respect to the disc, the latter will start to wobble. We argue that this wobbling is caused by a mechanism similar to Kozai-Lidov oscillations. We also observe various resonant structures (such as rings and spiral arms) induced in the disc by the planet.

  11. D-Zero Cryostat Supplemental Rupture Disc

    SciTech Connect

    Mulholland, G.T.; /Fermilab

    1987-08-03

    The common relief and rupture disc vent line requires a double disc assembly with vented interspace for accurate disc burst pressures. The first disc must take pump and purge vacuum loading, but be set to operate at 110% of the MAWP, 18.3 psig (ASME code). The available solution is 18.3 psig with a burst tolerance of +/- psig. The interspace should be locally vented by a flow limiting vent valve to decouple the vent line backpressure from the vessel rupture disc. The second disc must take the worst case vent line backpressure, the steady state value found in D-Zero engineering note 3740.000-EN-63 with all three cryostats simultaneously venting at the fire condition into the 4-inch x 6-inch and 6-inch x 8-inch sections. This value is less than 2 psid. The maximum rupture value for the second disc must be less than the minimum rupture value for the first disc less 2 psid i.e. < 16.3.

  12. Spiral waves in accretion discs - theory

    E-print Network

    Henri M. J. Boffin

    2001-10-09

    Spirals shocks have been widely studied in the context of galactic dynamics and protostellar discs. They may however also play an important role in some classes of close binary stars, and more particularly in cataclysmic variables. In this paper, we review the physics of spirals waves in accretion discs, present the results of numerical simulations and consider whether theory can be reconcilied with observations.

  13. Interactive Visualization of a Thin Disc around a Schwarzschild Black Hole

    ERIC Educational Resources Information Center

    Muller, Thomas; Frauendiener, Jorg

    2012-01-01

    In a first course in general relativity, the Schwarzschild spacetime is the most discussed analytic solution to Einstein's field equations. Unfortunately, there is rarely enough time to study the optical consequences of the bending of light for some advanced examples. In this paper, we present how the visual appearance of a thin disc around a…

  14. High speed recording on MnBi thin films deposited on discs

    Microsoft Academic Search

    REGIS LANGLET; BERNARD CARRE; JEAN-PAUL PIVOT

    1973-01-01

    In the case of a rotating disc memory system with optical access, the effects of the rotating speed and of the depth of focus are investigated. It is shown that for high speeds and short pulse durations, the written bits are shifted with respect to their static position. A \\

  15. DC drift activation energy of LiNbO3 optical modulators based on thousands of hours of active accelerated aging tests

    Microsoft Academic Search

    Hirotoshi Nagata; Yagang Li; Ian Croston; David R. Maack; Andy Appleyard

    2002-01-01

    Activation energy Ea in the drift of a separate dc bias port of x-cut LiNbO3 (LN) optical modulators has been estimated based on thousands of hours of accelerated aging test data. The obtained drift curves show peaking and suggest an absence of catastrophically increasing bias voltages in these x-cut LN modulators. The Ea values calculated from the first positive drift

  16. Magnetic resonance imaging of luxury perfusion of the optic nerve head in anterior ischemic optic neuropathy.

    PubMed

    Yovel, Oren S; Katz, Miriam; Leiba, Hana

    2012-09-01

    A 49-year-old woman with painless reduction in visual acuity in her left eye was found to have nonarteritic anterior ischemic optic neuropathy (NAION). Fluorescein angiography revealed optic disc capillary leakage consistent with "luxury perfusion." Contrast-enhanced FLAIR magnetic resonance imaging (MRI) showed marked enhancement of the left optic disc. Resolution of the optic disc edema and the MRI abnormalities followed a similar time course. This report appears unique in documenting the MRI findings of luxury perfusion in NAION. PMID:22573229

  17. Multiwavelength studies of the gas and dust disc of IRAS 04158+2805

    E-print Network

    Glauser, A M; Pinte, C; Duchêne, G; Güdel, M; Monin, J -L; Padgett, D L

    2008-01-01

    We present a study of the circumstellar environment of IRAS 04158+2805 based on multi-wavelength observations and models. Images in the optical and near-infrared, a polarisation map in the optical, and mid-infrared spectra were obtained with VLT-FORS1, CFHT-IR, and Spitzer-IRS. Additionally we used an X-ray spectrum observed with Chandra. We interpret the observations in terms of a central star surrounded by an axisymmetric circumstellar disc, but without an envelope, to test the validity of this simple geometry. We estimate the structural properties of the disc and its gas and dust content. We modelled the dust disc with a 3D continuum radiative transfer code, MCFOST, based on a Monte-Carlo method that provides synthetic scattered light images and polarisation maps, as well as spectral energy distributions. We find that the disc images and spectral energy distribution narrowly constrain many of the disc model parameters, such as a total dust mass of 1.0-1.75x10^-4 sollar masses and an inclination of 62-63 de...

  18. Expression of the two pore domain potassium channel TREK-1 in human intervertebral disc cells.

    PubMed

    Sharma, Pankaj; Hughes, Stephen; El Haj, Alicia; Maffulli, Nicola

    2012-07-01

    Potassium channels play a major role in intracellular homeostasis and regulation of cell volume. Intervertebral disc cells respond to mechanical loading in a complex manner. Mechanical loading may play a role in disc degeneration. Lumbar intervertebral disc samples from 5 patients (average age: 47 years, range: 25-64 years) were used for this study, investigating cells from the nucleus pulposus and the annulus fibrosus duplicate samples to determine RNA expression and protein expression. Analysis of mRNA expression by RT-PCR demonstrated that TREK 1 was expressed by nucleus pulposus (n=5) and annulus fibrosus (n=5) cells. Currently, TREK-1 is the only potassium channel known to be activated by intracellular acidosis, and responds to mechanical and chemical stimuli. Whilst the precise role of potassium channels in cellular homeostasis remains to be determined, TREK-1 may be important to protect disc cells against ischaemic damage, and subsequent disc degeneration, and may also play a role in effecting mechanotransduction. Further research is required to fully elucidate the role of the TREK-1 ion channel in intervertebral disc cells. PMID:22563662

  19. Bending Instabilities in Magnetized Accretion Discs

    E-print Network

    Vasso Agapitou; John C. B. Papaloizou; Caroline Terquem

    1997-07-29

    We study the global bending modes of a thin annular disc subject to both an internally generated magnetic field and a magnetic field due to a dipole embedded in the central star with axis aligned with the disc rotation axis. When there is a significant inner region of the disc corotating with the star, we find spectra of unstable bending modes. These may lead to elevation of the disc above the original symmetry plane facilitating accretion along the magnetospheric field lines. The resulting non-axisymmetric disc configuration may result in the creation of hot spots on the stellar surface and the periodic photometric variations observed in many classical T Tauri stars (CTTS). Time-dependent behaviour may occur including the shadowing of the central source in magnetic accretors even when the dipole and rotation axes are aligned.

  20. Distinction between the extracellular matrix of the nucleus pulposus and hyaline cartilage: a requisite for tissue engineering of intervertebral disc.

    PubMed

    Mwale, F; Roughley, P; Antoniou, J

    2004-01-01

    Tissue engineering of intervertebral discs (IVD) using mesenchymal stem cells (MSCs) induced to differentiate into a disc-cell phenotype has been considered as an alternative treatment for disc degeneration. However, since there is no unique marker characteristic of discs and since hyaline cartilage and immature nucleus pulposus (NP) possess similar macromolecules in their extracellular matrix, it is currently difficult to recognize MSC conversion to a disc cell. This study was performed to compare the proteoglycan to collagen ratio (measured as GAG to hydroxyproline ratio) in the NP of normal disc to that of the hyaline cartilage of the endplate within the same group of individuals and test the hypothesis that this ratio can be used for in vivo studies to distinguish between a normal NP and hyaline cartilage phenotype. Whole human lumbar spine specimens from fresh cadavers, ranging in age from 12 weeks to 79 years, were used to harvest the IVDs and adjacent endplates. The GAG to hydroxyproline ratio within the NP of young adults is approximately 27:1, whereas the ratio within the hyaline cartilage endplate of the same aged individuals is about 2:1. The production of an extracellular matrix with a high proteoglycan to collagen ratio can be used in vivo to distinguish NP cells from chondrocytes, and could help in identifying a NP-like phenotype in vivo as opposed to a chondrocyte when MSCs are induced to differentiate for tissue engineering of a disc. PMID:15602703

  1. Outcome of symptomatic upper lumbar disc herniation.

    PubMed

    Awwal, M A; Ahsan, M K; Sakeb, N

    2014-10-01

    "Upper" lumbar disc herniations (LDH) are different from the "lower" and possess increased chance of neural compromise and cauda equina syndrome that necessitates operative management despite of contradictory surgical outcome. We underwent the study to assess the clinical and functional outcome of symptomatic upper LDH surgery from July 2003 to June 2012 in BSMMU, Dhaka, Bangladesh. The records of 123 patients (age range, 30-69 years), 56 men and 67 women (mean 52 years) having upper lumbar discectomy were reviewed. The surgical time, intra-operative blood loss, self evaluated back pain and thigh and/or groin pain status [using Visual Analogue Score (VAS)] and the disability status [using Oswestry disability (ODI) questionnaire] was analyzed. Radiological stability (using Posner's criteria), functional outcome [using Japanese Orthopaedic Association (JOA) Score] and overall outcome (using MacNab`s criteria), was calculated. Chi-squared test and z-test using SPSS revealed mean operative time and mean blood loss had no significant (p>0.05) difference. Pain, sensory, motor and reflex status as well as VAS, ODI and all the components of JOA questionnaire had significant (p<0.05) improvement. In spite of intra-operative complications in 20.32% cases, overall satisfactory outcome was achieved in 83.74% cases. The postoperative complications (08.13%) could be managed conservatively. However, carefully decided surgical alternatives resulted in satisfactory clinical and functional outcome in upper LDH surgery. PMID:25481595

  2. Quantitative evaluation of the optic nerve head in early glaucoma

    Microsoft Academic Search

    D F Garway-Heath; R A Hitchings

    1998-01-01

    AIMSProgressive loss of neuroretinal rim tissue is known to occur early in glaucoma and measurement of the neuroretinal rim area is possible by magnification corrected analysis of optic disc photographs (planimetry). This study was performed to determine whether the facility to distinguish between glaucomatous and normal optic discs could be improved upon by: (a) taking into account the known relation

  3. Kilonova light curves from the disc wind outflows of compact object mergers

    NASA Astrophysics Data System (ADS)

    Kasen, Daniel; Fernández, Rodrigo; Metzger, Brian D.

    2015-06-01

    We study the radioactively powered transients produced by accretion disc winds following a compact object merger. Based on the outflows found in two-dimensional hydrodynamical disc models, we use wavelength-dependent radiative transfer calculations to generate synthetic light curves and spectra. We show that resulting kilonova transients generally produce both optical and infrared emission, with the brightness and colour carrying information about the merger physics. In those regions of the wind subject to high neutrino irradiation, r-process nucleosynthesis may halt before producing high-opacity, complex ions (the lanthanides). The kilonova light curves thus typically has two distinct components: a brief (˜2 d) blue optical transient produced in the outer lanthanide-free ejecta, and a longer (˜10 d) infrared transient produced in the inner, lanthanide line-blanketed region. Mergers producing a longer lived neutron star, or a more rapidly spinning black hole, have stronger neutrino irradiation, generate more lanthanide-free ejecta and are optically brighter and bluer. At least some optical emission is produced in all disc wind models, which should enhance the detectability of electromagnetic counterparts to gravitational wave sources. However, the presence of even a small amount (10-4 M?) of overlying, neutron-rich dynamical ejecta will act as a `lanthanide-curtain', obscuring the optical wind emission from certain viewing angles. Because the disc outflows have moderate velocities (˜10 000 km s-1), numerous resolved line features are discernible in the spectra, distinguishing disc winds from fast-moving dynamical ejecta, and offering a potential diagnostic of the detailed composition of freshly produced r-process material.

  4. Spectral Domain Optical Coherence Tomography Imaging of Drusen in Non-Exudative Age-Related Macular Degeneration

    PubMed Central

    Gregori, Giovanni; Wang, Fenghua; Rosenfeld, Philip J.; Yehoshua, Zohar; Gregori, Ninel Z; Lujan, Brandon J.; Puliafito, Carmen A.; Feuer, William J.

    2010-01-01

    Purpose To measure drusen area and volume in eyes with non-exudative age-related macular degeneration (AMD) using spectral domain optical coherence tomography imaging (SDOCT). Design Evaluation of diagnostic technology Participants One hundred three eyes from 74 patients with drusen Methods Patients with drusen secondary to non-exudative AMD were enrolled in this study. Five separate SDOCT scans, each consisting of 40000 uniformly spaced A-scans organized as 200 A-scans in each B-scan and 200 horizontal B-scans, were performed on each eye. Each scan covered a retinal area of 6×6 mm centered on the fovea. A novel algorithm was used to quantitatively assess drusen area and volume. Measurements from the entire scans, as well as in regions contained within 3 mm and 5 mm circles centered on the fovea, were analyzed. Test-retest standard deviations of drusen area and volume measurements were calculated for each eye. Main Outcome Measure Drusen area and volume Results The algorithm created drusen maps that permitted both qualitative and quantitative assessment of drusen area and volume. Both the qualitative appearance and the quantitative measurements of drusen area and volume were highly reproducible over the 5 different datasets. The intraclass correlation coefficient (ICC) was above 0.99 for both area and volume measurements on the entire dataset as well as the 3 mm and 5 mm circles. The correlation between lesion size and the test-retest standard deviations can be eliminated by performing a square-root transformation of the area measurements and a cube-root transformation of the volume measurements. These transformed data allowed for the inclusion of all drusen sizes in the calculation of an estimated single pooled test-retest standard deviation which will be useful for longitudinal studies of drusen natural history. Conclusions A novel algorithm for the qualitative and quantitative assessment of drusen imaged using SDOCT was shown to be highly reproducible. The ability to assess drusen volume reliably represents a new quantitative parameter to measure in AMD and may be useful when assessing disease progression, particularly in trials for treatments of non-exudative AMD. PMID:21388687

  5. Ischemic Optic Neuropathies

    Microsoft Academic Search

    Anthony C. Arnold

    ? Ischemic optic neuropathy is classified by location as anterior or posterior and by etiology as arteritic or nonarteritic.\\u000a \\u000a \\u000a ? Anterior ischemic optic neuropathy (AION) presents with rapid, usually painless, monocular visual field loss in the presence\\u000a of optic disc edema. \\u000a \\u000a \\u000a \\u000a ? Arteritic AION is typically more severe and more frequently bilateral than nonarteritic AION, and is associated with severe

  6. Tidal Warping of Be Star Decretion Discs

    E-print Network

    Martin, Rebecca G; Tout, Christopher A; Lubow, Stephen H

    2011-01-01

    Rapidly rotating Be stars are observed as shell stars when the decretion disc is viewed edge on. Transitions between the two implies that the discs may be warped and precessing. Type II X-ray outbursts are thought to occur when the warped disc interacts with the fast stellar wind. We suggest that tides from a misaligned companion neutron star can cause the observed effects. We make numerical models of a Be star decretion disc in which the spin of the Be star is misaligned with the orbital axis of a neutron star companion. Tidal torques from the neutron star truncate the disc at a radius small enough that the neutron star orbit does not intersect the disc unless the eccentricity or misalignment is very large. A magnetic torque from the Be star that is largest at the equator, where the rotation is fastest, is approximated by an inner boundary condition. There are large oscillations in the mass and inclination of the disc as it moves towards a steady state. These large variations may explain the observed changes...

  7. Lumbar spinal surgery for sciatica due to intervertebral disc disease in the elderly

    Microsoft Academic Search

    Alpaslan Kulali; Klaus von Wild

    1996-01-01

    This report reviews 36 patients aged 71 to 93 years who had lumbar spinal surgey for sciatica pain some with motor and or sensory disturbances and with no motor and sensory disturbances. Even though we found soft disc herniations, these patients should have a thorough circumferential decompression because of bony osteophytes and facet hypertrophy. Special attention is drawn to the

  8. Outer edges of debris discs: how sharp is sharp?

    E-print Network

    Philippe Thebault; Yanqin Wu

    2008-02-04

    Ring-like features have been observed in several debris discs. Outside the main ring, while some systems exhibit smooth surface brightness profiles (SB) that fall off roughly as r**-3.5, others display large luminosity drops at the ring's outer edge and steeper radial SB profiles. We seek to understand this diversity of outer edge profiles under the ``natural'' collisional evolution of the system, without invoking external agents such as planets or gas. We use a statistical code to follow the evolution of a collisional population, ranging from dust grains (submitted to radiation pressure) to planetesimals and initially confined within a belt (the 'birth ring'). The system typically evolves toward a "standard" steady state, with no sharp edge and SB \\propto r**-3.5 outside the birth ring. Deviations from this standard profile, in the form of a sharp outer edge and a steeper fall-off, occur only when two parameters take their extreme values: 1) When the birth ring is so massive that it becomes radially optically thick for the smallest grains. However, the required disc mass is here probably too high to be realistic. 2) When the dynamical excitation of the dust-producing planetesimals is so low ( <0.01) that the smallest grains, which otherwise dominate the total optical depth, are preferentially depleted. This low-excitation case, although possibly not generic, cannot be ruled out by observations. Our "standard" profile provides a satisfactory explanation for a large group of debris discs with outer edges and SB falling as r**-3.5. Systems with sharper outer edges, barring other confining agents, could still be explained by ``natural'' collisional evolution if their dynamical excitation is very low. We show that such a dynamically-cold case provides a satisfactory fit for HR4796A

  9. Optics

    NSDL National Science Digital Library

    Wolfgang Christian

    This page allows users to simulate standard optic elements (lens, mirror, dielectrics, sources, apertures) and observe how light rays propagate through these elements. Element properties, such as position and focal length, can be adjusted using and a click and drag metaphor.

  10. DISC1 genetics, biology and psychiatric illness

    PubMed Central

    THOMSON, Pippa A.; MALAVASI, Elise L.V.; GRÜNEWALD, Ellen; SOARES, Dinesh C.; BORKOWSKA, Malgorzata; MILLAR, J. Kirsty

    2012-01-01

    Psychiatric disorders are highly heritable, and in many individuals likely arise from the combined effects of genes and the environment. A substantial body of evidence points towards DISC1 being one of the genes that influence risk of schizophrenia, bipolar disorder and depression, and functional studies of DISC1 consequently have the potential to reveal much about the pathways that lead to major mental illness. Here, we review the evidence that DISC1 influences disease risk through effects upon multiple critical pathways in the developing and adult brain. PMID:23550053

  11. New strategies for disc repair: novel preclinical trials

    Microsoft Academic Search

    Joji Mochida

    2005-01-01

    Degeneration of lumbar intervertebral discs is a major cause of low back complaints, an irreversible occurrence with no currently available treatment. Furthermore, various surgical procedures can accelerate disc degeneration. On the other hand, recent experimental studies on disc cells have demonstrated an important role for the nucleus pulposus in preserving overall disc structure. The author’s group has already found that

  12. 21 CFR 866.1620 - Antimicrobial susceptibility test disc.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...antimicrobic-impregnated paper discs used to measure by a disc-agar diffusion technique or a disc-broth elution technique the in vitro...bacterial pathogens to antimicrobial agents. In the disc-agar diffusion technique, bacterial susceptibility is...

  13. 21 CFR 866.1620 - Antimicrobial susceptibility test disc.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...antimicrobic-impregnated paper discs used to measure by a disc-agar diffusion technique or a disc-broth elution technique the in vitro...bacterial pathogens to antimicrobial agents. In the disc-agar diffusion technique, bacterial susceptibility is...

  14. 21 CFR 866.1620 - Antimicrobial susceptibility test disc.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...antimicrobic-impregnated paper discs used to measure by a disc-agar diffusion technique or a disc-broth elution technique the in vitro...bacterial pathogens to antimicrobial agents. In the disc-agar diffusion technique, bacterial susceptibility is...

  15. Cervical intervertebral disc injury during simulated frontal impact

    Microsoft Academic Search

    S. Ito; P. C. Ivancic; A. M. Pearson; Y. Tominaga; S. E. Gimenez; W. Rubin; Manohar M. Panjabi

    2005-01-01

    Cervical disc injury due to frontal impact has been observed in both clinical and biomechanical investigations; however, there is a lack of data that elucidate the mechanisms of disc injury during these collisions. The goals of the current study were to determine the peak dynamic disc annular tissue strain and disc shear strain during simulated frontal impact of the whole

  16. Total disc replacement surgery for symptomatic degenerative lumbar disc disease: a systematic review of the literature

    Microsoft Academic Search

    Karin D. van den Eerenbeemt; Raymond W. Ostelo; Barend J. van Royen; Wilco C. Peul; Maurits W. van Tulder

    2010-01-01

    The objective of this study is to evaluate the effectiveness and safety of total disc replacement surgery compared with spinal\\u000a fusion in patients with symptomatic lumbar disc degeneration. Low back pain (LBP), a major health problem in Western countries,\\u000a can be caused by a variety of pathologies, one of which is degenerative disc disease (DDD). When conservative treatment fails,\\u000a surgery

  17. Study of a thermal lens in thin laser-ceramics discs

    SciTech Connect

    Snetkov, I L; Soloviev, A A; Khazanov, Efim A [Institute of Applied Physics, Russian Academy of Sciences, Nizhnii Novgorod (Russian Federation)

    2009-04-30

    Thermal distortions of the radiation phase are studied theoretically in laser ceramics. Special attention is paid to the small-scale phase modulation inherent in ceramics, which is caused by the arbitrary orientation of its single-crystal grains. Expressions are derived which describe the average phase distortion and its dispersion in disc elements in approximations of a thin disc cooled through optical surfaces and of weak heat exchange. The numerical calculation has confirmed the high accuracy of these expressions. The proposed approximate solutions of the heat conduction and elasticity equations are of their own importance. In particular, the obtained solutions can be used to describe phase and polarisation distortions of radiation in an arbitrarily oriented single-crystal disc. (active media)

  18. Stellar population gradients in galaxy discs from the CALIFA survey. The influence of bars

    NASA Astrophysics Data System (ADS)

    Sánchez-Blázquez, P.; Rosales-Ortega, F. F.; Méndez-Abreu, J.; Pérez, I.; Sánchez, S. F.; Zibetti, S.; Aguerri, J. A. L.; Bland-Hawthorn, J.; Catalán-Torrecilla, C.; Cid Fernandes, R.; de Amorim, A.; de Lorenzo-Caceres, A.; Falcón-Barroso, J.; Galazzi, A.; García Benito, R.; Gil de Paz, A.; González Delgado, R.; Husemann, B.; Iglesias-Páramo, Jorge; Jungwiert, B.; Marino, R. A.; Márquez, I.; Mast, D.; Mendoza, M. A.; Mollá, M.; Papaderos, P.; Ruiz-Lara, T.; van de Ven, G.; Walcher, C. J.; Wisotzki, L.

    2014-10-01

    While studies of gas-phase metallicity gradients in disc galaxies are common, very little has been done towards the acquisition of stellar abundance gradients in the same regions. We present here a comparative study of the stellar metallicity and age distributions in a sample of 62 nearly face-on, spiral galaxies with and without bars, using data from the CALIFA survey. We measure the slopes of the gradients and study their relation with other properties of the galaxies. We find that the mean stellar age and metallicity gradients in the disc are shallow and negative. Furthermore, when normalized to the effective radius of the disc, the slope of the stellar population gradients does not correlate with the mass or with the morphological type of the galaxies. In contrast to this, the values of both age and metallicity at ~2.5 scale lengths correlate with the central velocity dispersion in a similar manner to the central values of the bulges, although bulges show, on average, older ages and higher metallicities than the discs. One of the goals of the present paper is to test the theoretical prediction that non-linear coupling between the bar and the spiral arms is an efficient mechanism for producing radial migrations across significant distances within discs. The process of radial migration should flatten the stellar metallicity gradient with time and, therefore, we would expect flatter stellar metallicity gradients in barred galaxies. However, we do not find any difference in the metallicity or age gradients between galaxies with and without bars. We discuss possible scenarios that can lead to this lack of difference. Tables 1-3 and Appendices are available in electronic form at http://www.aanda.org

  19. HST spatially-resolved spectra of the accretion disc and gas stream of the nova-like variable UX Ursae Majoris

    E-print Network

    R. Baptista; K. Horne; R. A. Wade; I. Hubeny; K. S. Long; R. G. M. Rutten

    1998-04-07

    Time-resolved eclipse spectroscopy of the nova-like variable UX UMa obtained with the HST/FOS on 1994 August and November is analyzed with eclipse mapping techniques to produce spatially resolved spectra of its accretion disc and gas stream as a function of distance from disc centre. The inner accretion disc is characterized by a blue continuum filled with absorption bands and lines which cross over to emission with increasing disc radius, similar to that reported by Rutten et al (1994) at optical wavelengths. The comparison of spatially resolved spectra at different azimuths reveals a significant asymmetry in the disc emission at UV wavelengths, with the disc side closest to the secondary star showing pronounced absorption by an `iron curtain' and a Balmer jump in absorption. These results suggest the existence of an absorbing ring of cold gas whose density and/or vertical scale increase with disc radius. The spectrum of the infalling gas stream is noticeably different from the disc spectrum at the same radius suggesting that gas overflows through the impact point at disc rim and continues along the stream trajectory, producing distinct emission down to 0.1 RL1. The radial temperature profiles of the continuum maps are well described by a steady-state disc model in the inner and intermediate disc regions. There is evidence of an increase in the mass accretion rate from August to November (from Mdot= 10^{-8.3 +/- 0.1} to 10^{-8.1 +/- 0.1} Msun/yr), in accordance with the observed increase in brightness. Since the UX UMa disc seems to be in a high mass accretion, high-viscosity regime in both epochs, this result suggests that the mass transfer rate of UX UMa varies substantially (~ 50 per cent) on time scales of a few months.

  20. Growth Factors and Anticatabolic Substances for Prevention and Management of Intervertebral Disc Degeneration

    PubMed Central

    Longo, Umile Giuseppe; Petrillo, Stefano; Franceschetti, Edoardo; Maffulli, Nicola; Denaro, Vincenzo

    2012-01-01

    Intervertebral disc (IVD) degeneration is frequent, appearing from the second decade of life and progressing with age. Conservative management often fails, and patients with IVD degeneration may need surgical intervention. Several treatment strategies have been proposed, although only surgical discectomy and arthrodesis have been proved to be predictably effective. Biological strategies aim to prevent and manage IVD degeneration, improving the function and anabolic and reparative capabilities of the nucleus pulposus and annulus fibrosus cells and inhibiting matrix degradation. At present, clinical applications are still in their infancy. Further studies are required to clarify the role of growth factors and anticatabolic substances for prevention and management of intervertebral disc degeneration. PMID:25098367

  1. Planet formation in self-gravitating discs 

    E-print Network

    Gibbons, Peter George

    2013-11-28

    The work performed here studies particle dynamics in local two-dimensional simulations of self-gravitating accretion discs with a simple cooling law. It is well known that the structure which arises in the gaseous component ...

  2. Contemporary management of symptomatic lumbar disc herniations.

    PubMed

    Jegede, Kolawole A; Ndu, Anthony; Grauer, Jonathan N

    2010-04-01

    Lumbar disc herniations are common clinical entities that may cause lumbar-related symptoms. The spectrum of treatment options is geared toward a patient's clinical presentation and ranges from nothing to surgical intervention. Many lumbar disc herniations cause no significant symptoms. In studies of asymptomatic individuals who have never experienced lumbar-related symptoms, 30% have been reported to have major abnormality on magnetic resonance imaging. The mainstay of treatment of patients with symptomatic disc herniations is accepted to be nonoperative (as long as there are no acute or progressive neurologic deficits); this includes medications, physical therapy, and potentially lumbar injection. For patients with symptomatic disc herniations who fail to respond appropriately to conservative measures, surgical intervention may be considered. For this population, lumbar discectomy is considered to be a good option. PMID:20399360

  3. Disc valve for sampling erosive process streams

    DOEpatents

    Mrochek, John E. (Oak Ridge, TN); Dinsmore, Stanley R. (Norris, TN); Chandler, Edward W. (Knoxville, TN)

    1986-01-01

    A four-port disc valve for sampling erosive, high temperature process streams. A rotatable disc defining opposed first and second sampling cavities rotates between fired faceplates defining flow passageways positioned to be alternatively in axial alignment with the first and second cavities. Silicon carbide inserts and liners composed of .alpha. silicon carbide are provided in the faceplates and in the sampling cavities to limit erosion while providing lubricity for a smooth and precise operation when used under harsh process conditions.

  4. Investigation of cryogenic rupture disc design

    NASA Technical Reports Server (NTRS)

    Keough, J. B.; Oldland, A. H.

    1973-01-01

    Rupture disc designs of both the active (command actuated) and passive (pressure ruptured) types were evaluated for performance characteristics at cryogenic temperatures and for capability to operate in a variety of cryogens, including gaseous and liquid fluorine. The test results, coupled with information from literature and industry searches, were used to establish a statement of design criteria and recommended practices for application of rupture discs to cryogenic rocket propellant feed and vent systems.

  5. Cranial Neuropathy due to Intradural Disc Herniation

    PubMed Central

    Rapoport, Benjamin I.; Hartl, Roger; Schwartz, Theodore H.

    2014-01-01

    Background and Importance Herniated intervertebral disc fragments rarely penetrate the thecal sac, and intracranial hypotension attributable to such penetrating fragments is even more unusual. We describe the first reported case of a cranial neuropathy due to intradural herniation of a disc fragment, in which intracranial hypotension from a resulting cerebrospinal fluid leak caused bilateral abducens palsies. Clinical Presentation A 45-year-old man presented with a positional headache after having experienced a “popping” sensation in his back while lifting a heavy object. He also complained of blurred vision and was noted to have lateral gaze palsies bilaterally. Magnetic resonance imaging (MRI) of the brain revealed bilateral subdural collections, abnormal pachymeningeal enhancement, and cerebellar tonsillar herniation, suggesting intracranial hypotension. T2-weighted MRI of the spine revealed extrusion of the T12-L1 disc and suggested the presence of a disc fragment in the intradural space, displacing the caudal nerve roots. A myelogram demonstrated a filling defect extending into the subarachnoid space adjacent to the disc herniation, consistent with a free disc fragment in the intradural space. A diagnosis of intracranial hypotension due to a cerebrospinal fluid leak resulting from an intradural herniated disc was made. The diagnosis was confirmed intraoperatively. Conclusion Surgical removal of the herniated disc fragment and repair of the dural defect resulted in complete resolution of the cranial neuropathy. This rare etiology of a cranial neuropathy, arising from pathology in the thoracolumbar spine, illustrates the clinical teaching that the sixth cranial nerves are highly sensitive to deformation induced by intracranial hypotension. PMID:24535263

  6. Kinematic structures in galactic disc simulations

    NASA Astrophysics Data System (ADS)

    Roca-Fàbrega, S.; Romero-Gómez, M.; Figueras, F.; Antoja, T.; Valenzuela, O.

    2011-10-01

    N-body and test particle simulations have been used to characterize the stellar streams in the galactic discs of Milky Way type galaxies. Tools such as the second and third order moments of the velocity ellipsoid and clustering methods -EM-WEKA and FoF- allow characterizing these kinematic structures and linking them to the stellar overdensities and to the resonant regions all through the disc.

  7. Mach disc formation in cylindrical recovery systems

    SciTech Connect

    Morris, C.E.; McQueen, R.G.; Marsh, S.P.

    1983-01-01

    Cylindrical recovery systems have been used to shock-load polymers to pressures exceeding 50 GPa. In order to determine the pressures generated in these recovery systems the formation of the Mach disc on axis and its approach to steady state was monitored. The relation of the Mach disc diameter to the lateral dimension of the high explosive used to compress the polymer samples was also investigated.

  8. Herniation of the upper lumbar discs

    Microsoft Academic Search

    E. Pásztor; I. Szarvas

    1981-01-01

    Summary On the basis of investigations involving 134 patients operated on at the National Institute of Neurosurgery, Budapest, the authors point out that herniations of the intervertebral discs at L 1\\/2, L 2\\/3, L 3\\/4 levels are characterized by more severe neurological changes. Paresis and autonomic disorders occur much more frequently than in lower lumbar disc herniations: paresis was found

  9. Particle Acceleration in (by) Accretion Discs

    E-print Network

    J. I. Katz

    1992-05-04

    I present a model for acceleration of protons by the second-order Fermi process acting on randomly scrambled magnetic flux arches above an accretion disc. The accelerated protons collide with thermal protons in the disc, producing degraded energetic protons, charged and neutral pions, and neutrons. The pions produce gamma-rays by spontaneous decay of $\\pi^0$ and by bremsstrahlung and Compton processes following the decay of $\\pi^\\pm$ to $e^\\pm$.

  10. Theory of Disc-Like Crystal Growth

    Microsoft Academic Search

    Jian-Jun Xu; Junichiro Shimizu

    2004-01-01

    The present paper is concerned with disc-like crystal growth from a pure undercooled melt. We assume that the growth of the top\\/bottom interface of the disc is very slow, dominated by the kinetic effect, while the growth of its side-interface is much faster, dominated by heat diffusion mechanism. We obtained the uniformly valid asymptotic solution for the basic state in

  11. Turbulent drag reduction through oscillating discs

    E-print Network

    Wise, Daniel J

    2014-01-01

    The changes of a turbulent channel flow subjected to oscillations of wall flush-mounted rigid discs are studied by means of direct numerical simulations. The Reynolds number is $R_\\tau$=$180$, based on the friction velocity of the stationary-wall case and the half channel height. The primary effect of the wall forcing is the sustained reduction of wall-shear stress, which reaches a maximum of 20%. A parametric study on the disc diameter, maximum tip velocity, and oscillation period is presented, with the aim to identify the optimal parameters which guarantee maximum drag reduction and maximum net energy saving, computed by taking into account the power spent to actuate the discs. This may be positive and reaches 6%. The Rosenblat viscous pump flow is used to predict the power spent for disc motion in the turbulent channel flow and to estimate localized and transient regions over the disc surface subjected to the turbulent regenerative braking effect, for which the wall turbulence exerts work on the discs. The...

  12. Prognostic factors for return to work after low-back disc herniation surgery.

    PubMed

    Seyedmehdi, Mohammad; Attarchi, Mirsaeed; Ghaffari, Mostafa; Mohammadi, Saber; Darnahal, Maryam; Sadeghi, Zargham

    2015-03-01

    Return to work (RTW) is an important outcome following disc herniation surgery. The present study aimed at determining factors that may affect early RTW after disc herniation surgery. Data were collected from 603 patients who underwent disc herniation surgery in an educational hospital via phone interviews during a 4-year period (2005-2009). Delayed RTW and failed RTW were associated with female gender, lower educational levels, longer hospitalization periods, greater BMI, biological age exceeding 40 years, employment in manual labor, lack of encouragement by the physician to RTW, being in pain at the time of the phone interview, having negative expectations about the outcome of surgery preoperatively, and low job satisfaction (P < .05). Psychological and occupational factors have direct effects on RTW. Important factors include positive expectations about the outcome of surgery, encouragement by the physician to RTW, job characteristics, and job satisfaction. RTW can be accelerated by appropriate strategies and team work. PMID:23293315

  13. Gradient of mineral contents of vertebral column with special reference to intervertebral discs.

    PubMed

    Tohno, Y; Tohno, S; Nishiwaki, F; Utsumi, M; Yamada, M; Minami, T; Ichii, M; Okazaki, Y

    1994-12-01

    To study quantitatively the mineral elements in the vertebral column, we examined the vertebrae and intervertebral discs resected from three normal cadavers which died at middle age, by inductively coupled plasma atomic emission spectrometry. The relative contents of calcium, phosphorus, and sodium in vertebrae were high in the order from cervical to lumbar vertebrae. The ratios of calcium per phosphorus were 1.80 +/- 0.25 in cervical vertebrae, 1.59 +/- 0.22 in thoracic vertebrae, and 1.23 +/- 0.24 in lumbar vertebrae. The ratio of cervical vertebrae was the highest among them. In regard to intervertebral discs, both the relative contents of calcium and phosphorus were very much higher in the intervertebral discs between the 4th and 8th thoracic vertebrae than the others. PMID:7887122

  14. Monitoring transformer oil insulation using optical absorption properties

    NASA Astrophysics Data System (ADS)

    Rose, Benjamin P.

    As the electrical power distribution system ages, new methods of determining the quality of electrical transformer units are needed. Due to the relatively high expense of loss of service and safety hazards, a relatively cheap sensor to track the age of the insulation would aide in the progress of an intelligent power grid. The degradation of solid insulating paper releases some of the age indicating organic compounds into the oil. At present, the only available method to determine the concentration of those compounds is to perform high performance liquid chromatography (HPLC) testing in a laboratory. This is an expensive and time consuming activity that also requires transformer to be taken offline. Currently there are no sensors that can directly (on-line) measure the chemical integrity of the material. This research was focused upon one of the well known organic compounds released by paper into the transformer oil - 2-furfuraldehyde (2FAL). Previous methods of 2FAL detection were explored and expounded upon. A device was constructed to utilize light emitting diodes to optically interrogate solid discs made out of chemically active material in multiple tests. A 10 kVA distribution transformer was fitted with a special device allowing a continuous oil circulation and the optical setup. The transformer was tested while being loaded under accelerated ageing conditions. A premature failure of the distribution transformer did not allow any correlation between concentration of 2FAL and the optical signals. Previously sampled oils for a current transformer (CT) were also tested for chemical analysis in the laboratory and optical signals from the newly developed optical device were obtained. A 95% linear correlation was found between the age of the CT oil and the output of the optical device. Although the technique was validated and does seem to have merit, more tests are needed before the optical device can be recommended for use in the field.

  15. Evaluation of the Magic Island: Relaxation for Kids, compact disc.

    PubMed

    Huth, Myra Martz; Daraiseh, Nancy M; Henson, Melissa A; McLeod, Sharon M

    2009-01-01

    Managing post-operative pain continues to elude health care professionals despite children's reports of severe pain. Although research has demonstrated that guided imagery is a beneficial complementary treatment for pain, clinicians rarely incorporate it into their practice. This study evaluated the effectiveness of a guided imagery audio compact disc (CD) in reducing post-operative pain, increasing relaxation, and stimulating imagery in children by child life specialists in the clinical setting. This cross sectional study compared pain and relaxation scores before and after the use of the CD. Sixteen children (7 to 12 years of age) reported pain on a 0 to 10 scale and relaxation on a 1 to 5 scale, and answered questions about what they imagined. Pain scores were significantly decreased, with no significant differences in relaxation scores. Findings support that school-age children are capable of using guided imagery, and relaxation may not be necessary to achieve pain reduction. PMID:19916345

  16. Stirring in massive, young debris discs from spatially resolved Herschel images

    E-print Network

    Moór, A; Ábrahám, P; Apai, D; Balog, Z; Grady, C; Henning, Th; Juhász, A; Kiss, Cs; Krivov, A V; Pawellek, N; Szabó, Gy M

    2014-01-01

    A significant fraction of main-sequence stars are encircled by dusty debris discs, where the short-lived dust particles are replenished through collisions between planetesimals. Most destructive collisions occur when the orbits of smaller bodies are dynamically stirred up, either by the gravitational effect of locally formed Pluto-sized planetesimals (self-stirring scenario), or via secular perturbation caused by an inner giant planet (planetary stirring). The relative importance of these scenarios in debris systems is unknown. Here we present new Herschel Space Observatory imagery of 11 discs selected from the most massive and extended known debris systems. All discs were found to be extended at far-infrared wavelengths, five of them being resolved for the first time. We evaluated the feasibility of the self-stirring scenario by comparing the measured disc sizes with the predictions of the model calculated for the ages of our targets. We concluded that the self-stirring explanation works for seven discs. How...

  17. Mechanical Vibrations Reduce the Intervertebral Disc Swelling and Muscle Atrophy from Bed Rest

    NASA Technical Reports Server (NTRS)

    Holguin, Nilsson; Muir, Jesse; Evans, Harlan J.; Qin, Yi-Xian; Rubin, Clinton; Wagshul, Mark; Judex, Stefan

    2007-01-01

    Loss of functional weight bearing, such as experienced during space flight or bed rest (BR), distorts intervertebral disc (IVD) and muscle morphology. IVDs are avascular structures consisting of cells that may derive their nutrition and waste removal from the load induced fluid flow into and out of the disc. A diurnal cycle is produced by forces related to weight bearing and muscular activity, and comprised of a supine and erect posture over a 24 hr period. A diurnal cycle will include a disc volume change of approx. 10-13%. However, in space there are little or no diurnal changes because of the microgravity, which removes the gravitational load and compressive forces to the back muscles. The BR model and the etiology of the disc swelling and muscle atrophy could provide insight into those subjects confined to bed for chronic disease/injury and aging. We hypothesize that extremely low-magnitude, high frequency mechanical vibrations will abate the disc degeneration and muscle loss associated with long-term BR.

  18. An Unappreciated Correlation : Surgical Treatment of Lumbosacral Disc Disease and Erectile Dysfunction

    PubMed Central

    Kulaksizoglu, Haluk

    2010-01-01

    Objective The aim of the present study was to assess the effect of lumbar disc herniation surgery for low back pain on the erectile functioning. Methods Thirty-eight patients, with age ranging from 22 to 56 years, who had presented with pain due to herniated lumbar discs were included in the study. International Index of Erectile Function (IIEF) Short Form questionnaire was used to evaluate the erectile functioning. Patient visits on the 1st week,1st month and 3rd month postoperatively were analyzed. Pain scores were also noted together with side effects and the complications of the surgery. Results Of the 38 patients, 18 patients had reported erectile dysfunction; 10 patients mild and 8 patients moderate erectile dysfunction. Twenty patients did not report erectile problems. The herniation levels mostly were L5-S1 in 12 (31.6%). Overall, erectile dysfunction rates have improved in 31.7% of those previously with erectile dysfunction in a 3 month period after the surgery. Best results were obtained in those patients with mild erectile dysfunction preoperatively. Conclusion Mild erectile dysfunction together with radiculopathy tends to improve after lumbosacral disc surgery. Moderate and severe erectile dysfunction may be related to a more severe nerve injury or to vascular and/or psychiatric factors. An evaluation of erectile functioning should routinely be performed in patients with lumbosacral disc disease both for data accumulation and for medico legal causes since the documentation of the correlation between erectile dysfunction and lumbosacral disc disease is still lacking. PMID:20461169

  19. Long-lived disc accretion in the ? Chamaeleontis pre-main sequence star cluster

    NASA Astrophysics Data System (ADS)

    Lawson, Warrick A.; Lyo, A.-Ran; Muzerolle, James

    2004-06-01

    High-resolution spectroscopic study of late-type members of the ~9-Myr-old ? Chamaeleontis star cluster shows that four stars, RECX 5, 9, 11 and ECHA J0843.3-7905, have broad H? profiles indicative of ballistic accretion of material from circumstellar discs first identified by virtue of their infrared (IR) excess emission. Quantitative analysis of the profiles finds accretion in ? Cha stars at rates comparable to that derived by Muzerolle et al. for members of the similarly aged TW Hydrae Association (TWA); rates 1-3 orders of magnitude lower than in younger classical T Tauri (CTT) stars. Together these studies indicate that the fraction of long-lived inner discs can be significantly higher than that inferred from study of younger pre-main sequence (PMS) populations, which suggest a disc lifetime of <6 Myr. The detection of long-lived discs may have implications for the formation of planetary systems. If slow accretion processes are the dominant formation mechanism for Jovian planets then long-lived discs may be ideal sites to search for evidence for protoplanets.

  20. Lumbar Disc Herniation in a Patient With Congenital Vertebral Body Anomaly: A Case Report

    PubMed Central

    Atabey, Cem; Topuz, Ali Kivanc; Velio?lu, Murat; Demircan, Mehmet Nusret

    2014-01-01

    Lumbar disc herniation is characterized with low back and leg pain resulting from the degenerated lumbar disc compressing the spinal nerve root. The etiology of degenerative spine is related to age, smoking, microtrauma, obesity, disorders of familial collagen structure, occupational and sports-related physical activity. However, disc herniations induced by congenital lumbar vertebral anomalies are rarely seen. Vertebral fusion defect is one of the causes of congenital anomalies. The pathogenesis of embryological corpus vertebral fusion anomaly is not fully known. In this paper, a 30-year-old patient who had the complaints of low back and right leg pain after falling from a height is presented. She had right L5-S1 disc herniation that had developed on the basis of S1 vertebra corpus fusion anomaly in Lumbar computed tomography. This case has been discussed in the light of literature based on evaluations of Lumbar Computed Tomography (CT) and Magnetic Resonance Imaging (MRI). This case is unique in that it is the first case with development of lumbar disc herniation associated with S1 vertebral corpus fusion anomaly. Congenital malformations with unusual clinical presentation after trauma should be evaluated through advanced radiological imaging techniques. PMID:25620987