Note: This page contains sample records for the topic age optic disc from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
1

Age Effect on Retina and Optic Disc Normal Values  

Microsoft Academic Search

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

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

2005-01-01

2

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

NASA Astrophysics Data System (ADS)

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, and the Optical Coherence Tomograph (OCT). The effects of age were small (R2<17%) and were limited to specific HRT, GDx, and OCT parameters. Disc area was significantly associated with most HRT parameters and isolated GDx and OCT parameters. Refraction and gender were not significantly associated with any optic disc or RNFL parameters. Although effects of age on the optic disc and RNFL are small, they should be considered in monitoring ocular disease. Optic disc area should be considered when cross-sectionally evaluating disc topography and, to a lesser extent, RNFL thickness.

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

2002-01-01

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

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,

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

4

On the age and metallicity estimation of disc galaxies using optical and near-infrared photometry  

NASA Astrophysics Data System (ADS)

We have investigated the robustness of stellar population models in order to address the age and metallicity estimation of disc galaxies. We note that the scatter among simple stellar population models by different groups is surprisingly large at ages t<2 Gyr. The dominant uncertainties in stellar population models arise from convective core overshoot assumptions and the treatment of the thermally pulsing asymptotic giant branch phase and helium abundance may play a significant role at higher metallicities. It is also emphasized that the current composite stellar population models need some implementation of chemical enrichment histories for the proper analysis of the observational data.

Lee, Hyun-chul

5

Optic disc vasculitis  

Microsoft Academic Search

Background: Our studies had indicated that optic disc vasculitis (ODV) is a distinct clinical entity. We investigated the presentation\\u000a and clinical characteristics of ODV and determined the efficacy of systemic corticosteroids in its management. Methods: From 1973 to 1997, we investigated 32 patients (34 eyes) with ODV. The information was obtained by complete medical and ophthalmic\\u000a history taking and a

K. T. Oh; D. M. Oh; S. S. Hayreh

2000-01-01

6

The Chemistry of Optical Discs.  

ERIC Educational Resources Information Center

Explains the chemistry used in compact discs (CD), digital versatile discs (DVD), and magneto-optical (MO) discs focusing on the steps of initial creation of the mold, the molding of the polycarbonate, the deposition of the reflective layers, the lacquering of the CDs, and the bonding of DVDs. (Contains 15 references.) (YDS)

Birkett, David

2002-01-01

7

A new digital optic disc stereo camera: intraobserver and interobserver repeatability of optic disc measurements  

PubMed Central

AIMS—To investigate the intraobserver and interobserver repeatability of optic disc measurement using a new digital optic disc stereo camera.?METHODS—112 consecutive new patients presenting to a glaucoma service had dilated optic disc photography performed using a new digital stereo camera (Discam, Marcher Enterprises Ltd, Hereford). The images were analysed by two masked observers using a stereo viewer and computer simulated stereopsis. Vertical and horizontal cup:disc ratios (CDR), cup area:disc area, and cup circumference:disc circumference were computed. Intraobserver and interobserver repeatability analyses were performed. Intraclass correlation coefficients (ICC) and 95% tolerance for change (TC) were computed.?RESULTS—220 optic discs were photographed, of which 196 were suitable for analysis (10 were of poor image quality and 14 had anomalous discs). Mean age of patients was 65 years, 60 were male and 48 female. For intraobserver measurements of: horizontal CDR, ICC = 0.94, TC = 0.11 (15% of range); vertical CDR, ICC = 0.92, TC = 0.14 (16% of range); cup area:disc area, ICC = 0.95, TC = 0.10 (13% of range), and cup circumference:disc circumference, ICC = 0.95, TC = 0.09 (14% of range). For interobserver measurements of: horizontal CDR, ICC = 0.89, TC = 0.14 (19% of range); vertical CDR, ICC = 0.90, TC = 0.14 (16% of range); cup area:disc area, ICC = 0.92, TC = 0.13 (16% of range), and cup circumference:disc circumference, ICC = 0.90, TC = 0.12 (17% of range). Systematic bias between observers was within acceptable limits.?CONCLUSIONS—Digital stereo disc photography and analysis provide repeatable measures of optic disc variables. The results compare favourably with ophthalmoscopic and stereophotographic methods of assessment of the optic disc.??

Shuttleworth, G; Khong, C; Diamond, J

2000-01-01

8

Medical Information on Optical Disc*  

PubMed Central

Optical discs may permit a revolutionary change in the distribution and use of medical information. A single compact disc, similar in size to that used for digital audio recording, can contain over 500 million characters of information that is accessible by a Personal Computer. These discs can be manufactured at a cost lower than that of print on paper, at reasonable volumes. Software can provide the health care professional with nearly instantaneous access to the information. Thus, for the first time, the opportunity exists to have large local medical information collections. This paper describes an application of this technology in the field of Oncology.

Schipma, Peter B.; Cichocki, Edward M.; Ziemer, Susan M.

1987-01-01

9

Papilloedema and the optic disc.  

PubMed

The anatomy and blood supply of the optic nerve head are reviewed along with the variations in normal appearance and the aetiology of so-called pseudo-papilloedema. The clinical features and causes of papilloedema due to increased intra-cranial pressure are discussed along with optic disc oedema from other causes. The conditions of optic neuritis, neuropathy and the ischaemic optic neuropathies are also evaluated. PMID:2751237

Cullen, J F

1989-03-01

10

[Pseudopapilledema--optic disc drusen].  

PubMed

Optic disc drusen (ODD) are benign calcified deposits, which are located at the head of the optic disc. Most ODD patients are asymptomatic. Ocular complications, related to ODD, are considered rare. Optic disc drusen, especially if it is bilateral, may mimic the clinical presentation of papilledema. The clinical discrimination between ODD and papilledema may be a challenging task, and in many cases, especially in the pediatric population, an ocular ultrasound examination is needed. A fundus examination, in order to rule out papilledema, is a common daily task for the ophthalmologist and is considered perhaps the most common interface between pediatricians, neurologists, internal physicians and ophthalmologists. In this review, we focused on the pathogenesis, epidemiology, diagnosis and clinical implications of ODD. PMID:23713375

Kinori, Michael; Moroz, Iris; Zolf, Ricky; Fabian, Ido Didi

2013-03-01

11

Membrane tissue on the optic disc may cause macular schisis associated with a glaucomatous optic disc without optic disc pits  

PubMed Central

This article reports a case of possible involvement of membrane tissue on the optic disc with macular schisis formation associated with glaucomatous optic disc without optic disc pits. A 78-year-old man presented with loss of central visual acuity of the left eye. He had a medical history of primary open-angle glaucoma. Visual acuity was 0.6 in his left eye, and funduscopy revealed macular schisis and a glaucomatous optic disc without optic disc pits. Optical coherence tomography (OCT) revealed membrane tissue on the optic disc and a tunnel-like hyporeflective lesion connecting the schisis cavity and a site near the tissue, but no obvious optic disc pit. He underwent pars plana vitrectomy during which the membrane tissue on the disc and internal limiting membrane were removed. Posterior vitreous detachment was observed intraoperatively. Thereafter, the tunnel-like lesion observed on OCT was rapidly obscured and the macular schisis gradually reduced. Eighteen months after surgery, his visual acuity had improved to 0.9 with almost complete regression of the macular schisis. No optic disc pit was visualized after surgery. The changes in OCT findings described here suggest an etiology for macular schisis without optic disc pits in an eye with a glaucomatous optic disc with posterior vitreous detachment. A connection between the schisis cavity and the vitreous cavity may have appeared via the tunnel-like structure due to the membrane tissue exerting traction on the optic disc.

Takashina, Saori; Saito, Wataru; Noda, Kousuke; Katai, Maki; Ishida, Susumu

2013-01-01

12

Membrane tissue on the optic disc may cause macular schisis associated with a glaucomatous optic disc without optic disc pits.  

PubMed

This article reports a case of possible involvement of membrane tissue on the optic disc with macular schisis formation associated with glaucomatous optic disc without optic disc pits. A 78-year-old man presented with loss of central visual acuity of the left eye. He had a medical history of primary open-angle glaucoma. Visual acuity was 0.6 in his left eye, and funduscopy revealed macular schisis and a glaucomatous optic disc without optic disc pits. Optical coherence tomography (OCT) revealed membrane tissue on the optic disc and a tunnel-like hyporeflective lesion connecting the schisis cavity and a site near the tissue, but no obvious optic disc pit. He underwent pars plana vitrectomy during which the membrane tissue on the disc and internal limiting membrane were removed. Posterior vitreous detachment was observed intraoperatively. Thereafter, the tunnel-like lesion observed on OCT was rapidly obscured and the macular schisis gradually reduced. Eighteen months after surgery, his visual acuity had improved to 0.9 with almost complete regression of the macular schisis. No optic disc pit was visualized after surgery. The changes in OCT findings described here suggest an etiology for macular schisis without optic disc pits in an eye with a glaucomatous optic disc with posterior vitreous detachment. A connection between the schisis cavity and the vitreous cavity may have appeared via the tunnel-like structure due to the membrane tissue exerting traction on the optic disc. PMID:23690678

Takashina, Saori; Saito, Wataru; Noda, Kousuke; Katai, Maki; Ishida, Susumu

2013-01-01

13

Locating the Optic Disc in Retinal Images  

Microsoft Academic Search

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

Mira Park; Jesse S. Jin; Suhuai Luo

2006-01-01

14

Location of Optical Disc in Retinal Image  

Microsoft Academic Search

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

D. Santhi; D. Manimegalai

2007-01-01

15

The Optical Disc Roundup.  

ERIC Educational Resources Information Center

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)

Galbreath, Jeremy

1993-01-01

16

Optic disc dysplasia in poland syndrome.  

PubMed

Abstract Purpose: To report optic disc dysplasia in a case of Poland syndrome. Design: Non-interventional case report. Methods: A 2-year-old boy with Poland syndrome was referred for ophthalmic evaluation after abnormal optic discs were found on exam. Results: Physical exam at birth revealed right-sided aplasia of the pectoralis major muscle, symbrachydactyly, hypoplastic scapula, and an abnormal third rib. On dilated examination the optic nerve heads were dysplastic. The findings included multiple cilioretinal vessels, situs inversus, inferotemporal excavation, and surrounding pigmentary disturbances. Conclusion: Only one case of optic disc anomaly has been reported in Poland syndrome and was described as morning glory syndrome. The optic discs in our patient do not fit well with other optic disc excavation syndromes but are most reminiscent of those in papillorenal syndrome. As both Poland syndrome and papillorenal syndrome share vascular dysfunction as a possible etiology, this case adds to the literature of vascular dysgenesis in Poland syndrome. PMID:23647425

Maxfield, Steven D; Strominger, Mitchell B

2014-06-01

17

Optic Disc Segmentation in Retinal Images  

Microsoft Academic Search

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

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

2002-01-01

18

Optic Disc Vasculitis, Report of 42 Cases.  

National Technical Information Service (NTIS)

Optic disc vasculitis may be of 2 different types, hence the fundus may show either marked edema of the optic disc or signs of central retinal vein obstruction without other ocular or systemic abnormality. 42 cases of this disease (51 eyes) are presented ...

C. Qingkui Z. Qi

1980-01-01

19

Optic disc edema associated with spinocerebellar degeneration.  

PubMed

A 58-year-old man presented with optic disc edema as a rare association with spinocerebellar degeneration (SCD). The patient also had chronic idiopathic intestinal pseudo-obstruction with hypoalbuminemia. No elevation of intraspinal pressure and no intracranial lesion was observed. The hypoalbuminemia reacted promptly to treatment, whereas the optic disc edema regressed gradually. An association between SCD and optic atrophy has often been described, but to our knowledge this is the first report of SCD in association with optic disc edema. PMID:9672220

Nakazawa, T; Abe, T; Hasegawa, T; Tamai, M

1998-01-01

20

Acute visual loss in a patient with optic disc drusen.  

PubMed

Here we report a case of sudden, unilateral, painless visual loss in a middle-aged patient. A 45-year-old gentleman with no known past medical history presented with acute painless left visual impairment. Clinically, he was found to have a left optic neuropathy associated with a swollen and hyperemic left optic disc. The right optic disc was noted to be small and crowded, and both optic discs were noted to have irregular margins. Humphrey perimetry revealed a constricted visual field in the left eye. Fundus autofluorescence imaging revealed autofluorescence, and B-scan ultrasonography showed hyperreflectivity within both nerve heads. Blood investigations for underlying ischemic and inflammatory markers revealed evidence of hyperlipidemia but were otherwise normal. A diagnosis of left nonarteritic anterior ischemic optic neuropathy (NAAION) was made, with associated optic disc drusen and hyperlipidemia. NAAION typically occurs in eyes with small, structurally crowded optic discs. The coexistence of optic disc drusen and vascular risk factors may further augment the risk of developing NAAION. PMID:23658477

Tan, Deborah Kl; Tow, Sharon Lc

2013-01-01

21

Acute visual loss in a patient with optic disc drusen  

PubMed Central

Here we report a case of sudden, unilateral, painless visual loss in a middle-aged patient. A 45-year-old gentleman with no known past medical history presented with acute painless left visual impairment. Clinically, he was found to have a left optic neuropathy associated with a swollen and hyperemic left optic disc. The right optic disc was noted to be small and crowded, and both optic discs were noted to have irregular margins. Humphrey perimetry revealed a constricted visual field in the left eye. Fundus autofluorescence imaging revealed autofluorescence, and B-scan ultrasonography showed hyperreflectivity within both nerve heads. Blood investigations for underlying ischemic and inflammatory markers revealed evidence of hyperlipidemia but were otherwise normal. A diagnosis of left nonarteritic anterior ischemic optic neuropathy (NAAION) was made, with associated optic disc drusen and hyperlipidemia. NAAION typically occurs in eyes with small, structurally crowded optic discs. The coexistence of optic disc drusen and vascular risk factors may further augment the risk of developing NAAION.

Tan, Deborah KL; Tow, Sharon LC

2013-01-01

22

Automatic detection of the optic disc using majority voting in a collection of optic disc detectors  

Microsoft Academic Search

This paper proposes an efficient method for locating the optic disc in retinal images automatically using majority voting scheme and data fusion. We show that instead of inventing a new algorithm which ends up being a minor variation on an old idea, the fusion of different optic disc (OD) detectors can enhance the overall performance of the detection system. The

Balazs Harangi; Rashid Jalal Qureshi; Adrienne Csutak; Tünde Petö; András Hajdu

2010-01-01

23

Electron beam recording of optical disc  

NASA Astrophysics Data System (ADS)

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 50 GB with a simple low-cost upgrade path to disc capacities of several hundred gigabytes and beyond and hard disk drives (HDD) with capacities of up to 1 tera bit per square inch.

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

2002-09-01

24

Optical Disc Systems in Libraries: Problems and Issues.  

ERIC Educational Resources Information Center

Discusses optical disc (CD-ROM and videodisc) reference sources in terms of: (1) databases; (2) system characteristics; (3) end-user searching; (4) education and training requirements; (5) staffing; (6) costs; and (7) funding. Areas for further research are identified and new roles suggested for the librarian in the electronic age. (34 references)…

Harter, Stephen P.; Jackson, Susan M.

1988-01-01

25

Retinal complications of optic disc drusen.  

PubMed Central

Following reports by Sanders et al. and Wise et al. of optic disc drusen associated with retinal bleeding, an additional 19 cases were studied and followed up for 1 to 10 years (average 5 years). Four of them showed haemorrhages at the optic disc and its borders only, but 15 showed extensive retinopathy with macular involvement. In 3 cases retinopathy was serous and not haemorrhagic. Apart from cases in which bleeding was limited to the disc and its immediate vicinity the main clinical features of the syndrome were as follows: (1) the presence of optic disc drusen; (2) extensive retinal haemorrhage; (3) intraretinal extravasation of serum with or without the presence of blood; (4) elevated mounds lifting the retina and causing striae radiating from the mounds towards the macula and beyond; (5) pigmentary disturbance of the macula or a wider area of papillo-macular bundle after the resolution of acute stages which, while often clinically severe, is compatible with recovery of normal or near normal vision. It is proposed that the syndrome be designated the 'optic disc drusen retinopathy.' Images

Rubinstein, K; Ali, M

1982-01-01

26

Optic Disc Cupping in Arteritic Anterior Ischemic Optic Neuropathy  

Microsoft Academic Search

Patients with anterior ischemic optic neuropathy due to giant cell arteritis are thought to develop optic disc cupping, resembling that seen in glaucomatous eyes, while such cupping does not seem to occur in nonarteritic anterior ischemic optic neuropathy. However, this remains controversial. We describe a patient with arteritic anterior ischemic optic neuropathy (the clinical diagnosis was confirmed with a biopsy

S. Orgül; A. Gass; J. Flammer

1994-01-01

27

Optical Disc Technology for Information Management.  

ERIC Educational Resources Information Center

This summary of the literature on document image processing from 1988-90 focuses on WORM (write once read many) technology and on rewritable (i.e., erasable) optical discs, and excludes CD-ROM. Highlights include vendors and products, standards, comparisons of storage media, software, legal issues, records management, indexing, and computer…

Brumm, Eugenia K.

1991-01-01

28

[Optic disc drusen - current diagnostic possibilities].  

PubMed

Authors present the findings of two patients with optic nerve drusen, and an overview of current examination techniques in the diagnostics of optic nerve drusen including ultrasound examination, fundus photography, florescein angiography, computerized perimetry, auto-florescence fundus examination, examination of the nerve fibre layer using optical coherence tomography (OCT) or nerve fibres layer analyzer (GDx). In the first case, the patient was recommended to be supervised without any therapy. The second patient with regard to perimeter finding, loss of nerve fibre layer and increase of the intraocular pressure was prescribed local anti-glaucoma therapy. Key words: drusae papillae nervi optici, optic disc drusen. PMID:24862373

Ziak, P; Jarabáková, K; Koyšová, M

2014-01-01

29

Basics of videodisc and optical disc technology  

SciTech Connect

The optical videodisc is now being used for archival storage of photographs and for records management. The spacedisc project, co-sponsored by nasa and drew university's center for aerospace education, is a prime example of using a videodisc to store individual photographs, slides, and motion sequences with an accompanying paper index. These discs are also used in schools in an interactive individualized learning carrel under microcomputer control. Museums also are using discs as complements to exhibits as well as in cataloging and in classification, information storage and retrieval systems. Ongoing imaginative applications of the optical videodisc include surrogate travel, job performance aids, simulators, electronic malls, and travelogues. Eventually, one will see the videodisc and computer technology with artificial intelligence programs used by the medical community and others. Optical disc and videodisc technology have opened up new horizons for information processing, storage and retrieval, education and training. Regardless of whether a mass consumer market materializes, optical recording technology will play a major role in the future design and development of information systems in the late 1980s and beyond.

Paris, J.

1983-11-01

30

Superresolution technology applied to optical discs  

NASA Astrophysics Data System (ADS)

Smaller focal points are essential for the development of the next-generation optical disc. The size of focal point depends on the diffraction effect that is dependant on the numerical aperture of a lens and the wavelength of light. However, increase of the numerical aperture and decrease of the light wavelength will be ultimately limited due to the technical difficulty of fabricating a too-high NA lens and the too-short wavelength laser. In this paper, we report another approach of using the superresolution technology to compress the size of the so-called Airy spot for the next-generation optical disc, which is independent on the wavelength of laser. The superresolution phase plates are designed and fabricated with a microoptics technique. When such a phase plate is inserted into the optical system, the central spot at the focal plane of a lens is decreased to be 0.8 times of the Airy pattern, implying the possibility of reading higher storage density of optical discs. The most attractive feature is that the phase plate can be mass-produced at a very low cost, compared with the high cost of the high-numerical lens and/or the short wavelength laser. The disadvantages are that the inserted phase plate will induce the slight circular sidelobes around the central sport, so that it consumes a little more laser energy. The shortcoming could be overcome with suitable amendment. We have fabricated the phase plates with the surface-relief profile on a normal glass for phase modulation. Experimental results of superresolution effect with a low numerical aperture (NA=0.1) and a high-numerical lens (NA=0.8) are reported, which are in good agreement with the theoretical prediction. Superresolution technique should be highly interesting as a novel technique of the next-generation pickup head for reading the high storage of the optical discs.

Zhou, Changhe; Luo, Hongxin

2005-09-01

31

Automatic optic disc segmentation with peripapillary atrophy elimination  

Microsoft Academic Search

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

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

2011-01-01

32

Robust Optic Disc Location via Combination of Weak Detectors  

Microsoft Academic Search

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

Adria Perez-Rovira; Emanuele Trucco

2008-01-01

33

Dependence of optic disc parameters on disc area according to Heidelberg Retina Tomograph: Part II.  

NASA Astrophysics Data System (ADS)

With the help of Heidelberg Retina Tomograph (HRT-II) optic disc parameters in 211 eyes of 115 healthy patients with refraction Em +/- 3,0 D and 96 eyes of 72 patients with myopia 3,5-14,0 D without any signs of glaucoma were studied. Analysis of optic disc parameters were carried out in 5 groups of patients according to disc area: less than 1,5 mm2, 1,5- 2,5 mm2, 2,5-3,0 mm2, 3,0-3,5 mm2 and more than 3,5 mm2. An accurate depending on disc area was revealed for all optic disc parameters in all sectors, which was manifested by increasing cup disc and rim disc (area and volume) and other parameters. We consider it is necessary to use the proper tables for right interpretation of received data for early diagnosis of glaucoma.

Machekhin, V.; Manaenkova, G.; Bondarenko, O.

2007-06-01

34

Simple and Robust Optic Disc Localisation Using Colour Decorrelated Templates  

Microsoft Academic Search

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

Tomi Kauppi; Heikki Kälviäinen

2008-01-01

35

Optic Disc Margin Anatomy in Glaucoma Patients and Normal Controls with Spectral Domain Optical Coherence Tomography  

PubMed Central

Objective To characterize optic nerve head (ONH) anatomy related to the clinical optic disc margin with spectral domain optical coherence tomography (SD-OCT). Design Cross-sectional study. Participants Open-angle glaucoma patients with focal, diffuse and sclerotic optic disc damage, and age-matched normal controls. Methods High-resolution radial SD-OCT B-scans centered on the ONH were analyzed at each clock hour. For each scan, the border tissue of Elschnig was classified for obliqueness (internally oblique, externally oblique, or non-oblique), and presence of Bruch’s membrane overhang over border tissue. Optic disc stereo-photographs were co-localized to SD-OCT data with customized software. The frequency with which the disc margin identified in stereo-photographs coincided with (1) Bruch’s membrane opening, defined as the innermost edge of Bruch’s membrane; (2) Bruch’s membrane/border tissue, defined as any aspect of either, outside Bruch’s membrane opening or border tissue; or (3) border tissue, defined as any aspect of border tissue alone, in the B-scans was computed at each clock hour. Main Outcome Measures SD-OCT structures coinciding with the disc margin in stereo-photographs. Results There were 30 patients (10 with each type of disc damage) and 10 controls, with median (range) age 68.1 (42–86) and 63.5 (42–77) years respectively. Although 28 (93%) patients had 2 or more border tissue configurations, the most predominant one was internally oblique, primarily superiorly and nasally, frequently with Bruch’s membrane overhang. Externally oblique border tissue was less frequent, observed mostly inferiorly and temporally. In controls, there was predominantly internally oblique configuration around the disc. While the configurations were not statistically different between patients and controls, they were among the 3 glaucoma groups. At most locations the SD-OCT structure most frequently identified as the disc margin was some aspect of Bruch’s membrane and border tissue, outside Bruch’s membrane opening. Bruch’s membrane overhang was regionally present in the majority of glaucoma patients and controls, however, in most cases not visible as the disc margin. Conclusions The clinically perceived disc margin is most likely not the SD-OCT detected innermost edge of Bruch’s membrane. These findings have important implications for the automated detection of the disc margin and estimates of the neuroretinal rim.

Reis, Alexandre S C; Sharpe, Glen P; Yang, Hongli; Nicolela, Marcelo T; Burgoyne, Claude F; Chauhan, Balwantray C

2011-01-01

36

The optic disc is minimal in children with idiopathic intracranial hypertension.  

PubMed

This study sought to characterize the optic disc morphology, particularly the cup-to-disc ratio of the optic nerve head in children with idiopathic intracranial hypertension. The medical charts and digital optic disc photos of children with confirmed diagnosis of idiopathic intracranial hypertension were reviewed retrospectively. The optic disc area, cup area, and cup-to-disc ratio were measured digitally using VISUPAC software, and the mean values of those parameters were compared to the published norms. Of children with idiopathic intracranial hypertension, 83% had absence of the physiological cup of the optic disc, compared to 10% of children in the general population of the same age. The median disc area was 2.2 mm(2), and median cup area was 0.0mm(2), compared to the published norms of 2.69 mm(2) and 0.44 mm(2), respectively. There is very significantly high prevalence of small optic disc cups in children with idiopathic intracranial hypertension, with the cup being absent on majority of cases in our patient cohort. This may signal an underlying systemic predisposition to the development of intracranial hypertension. PMID:23034982

Dai, Shuan; Trimboli, Carmelina; Buncic, J Raymond

2013-10-01

37

Automated Detection of Optic Disc Location in Retinal Images  

Microsoft Academic Search

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.

Carmen Alina Lupascu; Domenico Tegolo; Luigi Di Rosa

2008-01-01

38

An improved gradient vector flow algorithm for optic disc segmentation  

Microsoft Academic Search

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

Huiyu Zhou; Gerald Schaefer; Tangwei Liu; Faquan Lin

2010-01-01

39

Optical measurements upon compact discs in education in optoelectronics  

Microsoft Academic Search

The aims of this article are connected with application of optical measurement methods in education in electronics. They are used for evaluation of some of peculiarities of different types of compact discs used as optical storage memories. A semiconductor laser diode is used as light beam source during measurements. The compact disc irradiated by laser beam at certain conditions operates

T. Pencheva; B. Gyoch; P. Mashkov

2010-01-01

40

78 FR 55292 - Certain Optical Disc Drives, Components Thereof, and Products Containing the Same; Notice of...  

Federal Register 2010, 2011, 2012, 2013

...COMMISSION [Docket No. 2977] Certain Optical Disc Drives, Components Thereof, and Products...received a complaint entitled Certain Optical Disc Drives, Components Thereof, and Products...States after importation of certain optical disc drives, components thereof, and...

2013-09-10

41

Optic disc detection using ant colony optimization  

NASA Astrophysics Data System (ADS)

The retinal fundus images are used in the treatment and diagnosis of several eye diseases, such as diabetic retinopathy and glaucoma. This paper proposes a new method to detect the optic disc (OD) automatically, due to the fact that the knowledge of the OD location is essential to the automatic analysis of retinal images. Ant Colony Optimization (ACO) is an optimization algorithm inspired by the foraging behaviour of some ant species that has been applied in image processing for edge detection. Recently, the ACO was used in fundus images to detect edges, and therefore, to segment the OD and other anatomical retinal structures. We present an algorithm for the detection of OD in the retina which takes advantage of the Gabor wavelet transform, entropy and ACO algorithm. Forty images of the retina from DRIVE database were used to evaluate the performance of our method.

Dias, Marcy A.; Monteiro, Fernando C.

2012-09-01

42

Optical coherence tomography findings and retinal changes after vitrectomy for optic disc pit maculopathy  

PubMed Central

Purpose: To study the optical coherence tomography (OCT) patterns in optic disc pit maculopathy and retinal changes after vitreous surgery. Materials and Methods: Retrospective review of consecutive cases with optic disc pit maculopathy seen at two tertiary eye institutes from January 2005 to June 2009. Results: Twenty-four eyes of 23 patients are included. The presenting visual acuity ranged from 20/400 to 20/20 (median:20/80). The median age at presentation was 24 years (range, 6-57 years). Optical coherence tomography demonstrated a combination of retinoschisis and outer layer detachment (OLD) in 19 (79.17%) eyes, OLD only in 3 (12.5%) eyes and retinoschisis only in 2 (8.33%) eyes. An obvious communication (outer layer hole) between the schisis and OLD was seen in 14 (73.68%) of the 19 eyes with both features. Of the 21 eyes with retinoschisis, schisis was present in multiple layers in 15 (71.43%) and single layer in 6 (28.57%) eyes. Eleven eyes underwent pars plana vitrectomy including creation of posterior vitreous detachment (PVD), fluid-air exchange, low intensity laser photocoagulation at the temporal edge of the optic disc pit and non-expansile perfluoropropane gas (14%) injection. Five (45.45%) of 11 eyes undergoing vitrectomy had complete resolution and 4 (36.36%) eyes had partial resolution of maculopathy. Visual acuity improved in 8 (72.72%) of 11 eyes. Conclusion: Optical coherence tomography demonstrates multiple layer schisis and outer layer detachment as main features of optic disc pit maculopathy. Vitrectomy with PVD induction, laser photocoagulation and gas tamponade results in anatomical and visual improvement in most cases with optic disc pit maculopathy.

Sanghi, Gaurav; Padhi, Tapas R; Warkad, Vivekanand U; Vazirani, Jayesh; Gupta, Vishali; Dogra, Mangat R; Gupta, Amod; Das, Taraprasad

2014-01-01

43

Prediction of Functional Loss in Glaucoma From Progressive Optic Disc Damage  

PubMed Central

Objective To evaluate the ability of progressive optic disc damage detected by assessment of longitudinal stereophotographs to predict future development of functional loss in those with suspected glaucoma. Methods The study included 639 eyes of 407 patients with suspected glaucoma followed up for an average of 8.0 years with annual standard automated perimetry visual field and optic disc stereophotographs. All patients had normal and reliable standard automated perimetry results at baseline. Conversion to glaucoma was defined as development of 3 consecutive abnormal visual fields during follow-up. Presence of progressive optic disc damage was evaluated by grading longitudinally acquired simultaneous stereophotographs. Other predictive factors included age, intraocular pressure, central corneal thickness, pattern standard deviation, and baseline stereophotograph grading. Hazard ratios for predicting visual field loss were obtained by extended Cox models, with optic disc progression as a time-dependent covariate. Predictive accuracy was evaluated using a modified R2 index. Results Progressive optic disc damage had a hazard ratio of 25.8 (95% confidence interval, 16.0-41.7) and was the most important risk factor for development of visual field loss with an R2 of 79%. The R2s for other predictive factors ranged from 6% to 26%. Conclusions Presence of progressive optic disc damage on stereophotographs was a highly predictive factor for future development of functional loss in glaucoma. These findings suggest the importance of careful monitoring of the optic disc appearance and a potential role for longitudinal assessment of the optic disc as an end point in clinical trials and as a reference for evaluation of diagnostic tests in glaucoma.

Medeiros, Felipe A.; Alencar, Luciana M.; Zangwill, Linda M.; Bowd, Christopher; Sample, Pamela A.; Weinreb, Robert N.

2010-01-01

44

Automatic optic disc segmentation with peripapillary atrophy elimination.  

PubMed

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

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

2011-01-01

45

Preliminary optical coherence tomography investigation of the temporo-mandibular joint disc  

NASA Astrophysics Data System (ADS)

Aim and objectives. The morphology and position of the temporo-mandibular disc are key issues in the diagnosis and treatment of arthrogenous temporo-mandibular disorders. Magnetic resonance imaging and arthroscopy are used today to identify: flattening of the pars posterior of the disc, perforation and/or adhesions in the pars intermedia of the disc and disc displacements. The present study proposes the investigation of the temporo-mandibular joint disc by optical coherence tomography (OCT). Material and methods. 8 human temporo-mandibular joint discs were harvested from dead subjects, under 40 year of age, and conserved in formalin. They had a normal morphology, with a thicker pars posterior (2,6 mm on the average) and a thinner pars intermedia (1mm on the average). We investigated the disc samples using two different OCT systems: an en-face OCT (time domain (TD)-OCT) system, working at 1300 nm (C-scan and B-scan mode) and a spectral OCT system (a Fourier domain (FD)-OCT) system , working at 840 nm (B-scan mode). Results. The OCT investigation of the temporo-mandibular joint discs revealed a homogeneous microstructure. The longer wavelength of the TD-OCT offers a higher penetration depth (2,5 mm in air), which is important for the analysis of the pars posterior, while the FD-OCT is much faster. Conclusions: OCT is a promising imaging method for the microstructural characterization of the temporo-mandibular disc.

M?rc?uteanu, Corina; Demjan, Enikö; Sinescu, Cosmin; Negrutiu, Meda; Motoc, Adrian; Lighezan, Rodica; Vasile, Liliana; Hughes, Mike; Bradu, Adrian; Dobre, George; Podoleanu, Adrian G.

2010-02-01

46

Qualitative changes with age of proteoglycans of human lumbar discs  

Microsoft Academic Search

A detailed study of the biochemistry of each of the lower lumbar intervertebral discs from 3 spines aged 8, 16, and 44 years has shown progressive changes down the spine in a number of biochemical parameters. These were most apparent in the 44-year-old spine. The chemical composition of proteoglycans of the nucleus pulposus and of its constituent proteoglycans differed from

P Adams; H Muir

1976-01-01

47

Application of Optical Disc Databases and Related Technology to Public Access Settings.  

National Technical Information Service (NTIS)

Recently developed optical disc technology offers economical, convenient, and durable storage of large quantities of data. Advanced data retrieval software allows rapid search optical discs. A number of commercial and government publishers produce optical...

D. F. DeFord

1992-01-01

48

Optic disc measurement with the Zeiss four mirror contact lens.  

PubMed

A knowledge of the optic disc size may be of value when assessing the glaucoma suspect. The vertical diameter of the optic disc was measured using a Zeiss four mirror gonioscope and a 900 Haag-Streit slit-lamp in one eye of 39 patients, 32 with refractive errors within 3 dioptres of emmetropia. The disc was measured by projecting a slit beam of known height onto the image of the disc. A magnification factor for the contact lens was calculated from first principles and disc height recalculated. These measurements were compared with those obtained by photographic methods using the corrections suggested by Bengtsson and Krakau. In the analysis on the 32 eyes within 3 dioptres of emmetropia the best correlation with clinical measurements was obtained with correction 3 using spectacle refraction and keratometry (r = 0.8614). The contact lens measurement was within plus or minus 0.1 mm of the photographic measurement in 67% of cases and plus or minus 0.2 mm in all cases. This simple method is advocated for the routine assessment of optic disc size. PMID:7803355

Spencer, A F; Vernon, S A

1994-10-01

49

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

Microsoft Academic Search

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

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

2008-01-01

50

Characteristics of patients with a localized retinal nerve fiber layer defect and normal optic disc appearance  

PubMed Central

Purpose To investigate the characteristics of patients with a localized retinal nerve fiber layer (RNFL) defect and normal optic disc appearance compared with normal tension glaucoma (NTG) patients. Methods A total of 40 patients with an unchanged RNFL defect for more than 5 years and normal optic disc appearance, who were presumed as non-glaucomatous patients, were enrolled (group A). We recruited 40 age-matched patients with NTG (group B). On the RNFL photographs, we evaluated angles of RNFL defects. Angle ? and ? were the angles made by the line ‘L' from the center of the fovea to the disc center and the lines ‘A' and ‘B' from the disc center to the disc margin where the proximal and the distal border of the defect met, respectively. Angle ? was the angular width of the defect. Angle ? was the angle made by lines ‘L' and ‘R', which divides angle ? into a 2?:?1 ratio from line ‘A' to line ‘B'. We compared systemic diseases, baseline IOP, and location and angles of the RNFL defects between the two groups. Results Systemic diseases and superotemporal RNFL defects in group A were significantly greater than those in group B (P<0.001). Angle ? was greater in group A, but angle ?, ?, and ? were smaller in group A (P<0.05). Conclusion If the patients with a superotemporal RNFL defect and normal optic disc appearance had systemic diseases and distal borders of the defects are closer to the macula, glaucoma is less likely.

Lee, J; Kim, J; Kee, C

2012-01-01

51

Optic Disc and Nerve Fiber Layer Imaging To Detect Glaucoma  

PubMed Central

Purpose To compare optic disc and retinal nerve fiber layer (RNFL) imaging methods to discriminate eyes with early glaucoma from normal eyes. Design Retrospective, cross-sectional study. Methods Setting: Tertiary care academic glaucoma center. Ninety-two eyes of 92 subjects (46 with early perimetric open-angle glaucoma and 46 controls) were studied. Diagnostic performance of optical coherence tomography (StratusOCT), scanning laser polarimetry (GDx-VCC), confocal laser ophthalmoscopy (Heidelberg Retinal Tomograph III), and qualitative assessment of stereoscopic optic disc photographs were compared. Outcome measures were areas under receiver operator characteristic curves (AUC) and sensitivities at fixed specificities. Classification and Regression Trees (CART) analysis was used to evaluate combinations of quantitative parameters. Results The average (±SD) visual field mean deviation for glaucomatous eyes was ?4.0±2.5 dB. Parameters with largest AUCs (±SE) were: average RNFL thickness for StratusOCT (0.96±0.02), nerve fiber indicator for GDx-VCC (0.92±0.03), FSM discriminant function for HRT III (0.91±0.03), and 0.97±0.02 for disc photograph evaluation. At 95% specificity, sensitivity of disc photograph evaluation (90%) was greater than GDx-VCC (p=0.05) and HRT III (p=0.002), but not significantly different than that of StratusOCT (p>0.05). Combination of StratusOCT average RNFL thickness and HRT III cup/disc area with CART produced a sensitivity of 91% and specificity of 96% Conclusions StratusOCT, GDx-VCC, and HRT III performed as well as, but not better than, qualitative evaluation of optic disc stereophotographs for detection of early perimetric glaucoma. The combination of StratusOCT average RNFL thickness and HRT III cup/disc area ratio provided a high diagnostic precision.

Badala, Federico; Nouri-Mahdavi, Kouros; Raoof, Duna A.; Leeprechanon, Narakorn; Law, Simon K.; Caprioli, Joseph

2007-01-01

52

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

Microsoft Academic Search

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

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

2008-01-01

53

Thermal Recording for High-Density Optical Disc Mastering  

NASA Astrophysics Data System (ADS)

Thermal recording using a dielectric as a recording material was examined to make a high-density optical disc master. We confirmed that a pit of 53 nm length was able to be recorded with a laser of 405 nm wavelength. As a result we could make a master with a 200 gigabyte (GB) data capacity with a conventional laser beam recorder (LBR). A 100 GB disc made by the same method was able to be read with a tester equipped with a solid immersion lens (SIL) and the measured jitter value was 9.9%.

Yamaoka, Nobuki; Murakami, Shigenori; Sugawara, Yukihiro; Ohshima, Seiro; Takishita, Toshihiko; Yokogawa, Fumihiko

2010-08-01

54

Bilateral optic disc swelling; is a CT scan necessary?  

PubMed

A 47 year old man sustained a head injury after tripping. He presented to the accident and emergency department next morning where head x ray revealed no fractures. However, the casualty doctor found bilateral blurred optic disc margins on ophthalmoscopy. Although his head injury was classed as non-serious, an urgent computed tomography scan was ordered and an ophthalmic opinion sought. After detailed retinal examination, the ophthalmologist made a diagnosis of bilateral optic nerve head drusen (ONHD), which was confirmed by a B-scan ultrasound. The patient was advised not to drive (due to constricted visual fields associated with ONHD) and to inform his siblings of his condition so they could also be assessed. In cases of apparent optic disc swellings, it is essential to distinguish between true and pseudo-papillo-oedema to avoid subjecting patients to unnecessary neuroimaging procedures and associated exposure to radiation. PMID:16244354

Bhatt, U K

2005-11-01

55

Optic disc topography of normal tension glaucoma patients in Malaysia.  

PubMed

There are limited data in the literature on the optic disc topography in normal tension glaucoma (NTG) patients in Asian countries, especially in Southeast Asia. This study is aimed at comparing optic disc topography in NTG patients and a control group in Malaysia, and we discuss the literature on NTG studies in other Asian populations. A comparative cross-sectional study was conducted in two hospitals with glaucoma services in Malaysia from November 2010 to February 2012. A total of 109 eyes of 109 Malay patients were included in this study: 32 NTG patients and 77 subjects in the control group. All participants underwent a thorough ocular examination, including visual acuity, subjective refraction, anterior segment and fundus examinations, Humphrey visual field 24-2, intraocular pressure measurement, gonioscopy examination and fundus photography. Optic disc topography was assessed using the Heidelberg Retinal Tomograph III by an identified masked investigator in each hospital. NTG patients had a notably larger disc area (2.65 (0.41) vs 2.19 (0.43) mm(2), respectively), larger cupping (1.54 (0.43) vs 0.63 (0.40) mm(2), respectively), smaller retinal rim areas (1.12 (0.41) vs 1.56 (0.33) mm(2), respectively), higher cup volume (0.47 (0.28) vs 0.11 (0.19) mm(3), respectively), reduced rim volume (0.23 (0.13) vs 0.41 (0.16) mm(3), respectively), higher cup to disc area ratio (0.58 (0.14) vs 0.27 (0.15), respectively), higher linear cup to disc ratio (0.76 (0.09) vs 0.49 (0.17) mm(2), respectively), higher mean cup depth (0.37 (0.09) vs 0.22 (0.09) mm, respectively), higher maximum cup depth (0.77 (0.16) vs 0.59 (0.20) mm, respectively), higher mean of cup shape measure (-0.04 (0.06) vs -0.16 (0.07), respectively), and thinner mean retinal nerve fibre layer thickness (0.15 (0.15) vs 0.24 (0.07) mm, respectively) compared to the control group (p<0.05). In conclusion, most of the optic disc parameters were significantly different in NTG patients compared to healthy individuals in Malaysia. Our findings are comparable to those reported in NTG studies in other Asian countries. PMID:24145263

Adlina, Abdul Rahim; Shatriah, Ismail; Liza Sharmini, Ahmad Tajudin; Ahmad, Mt Saad

2013-08-01

56

Unilateral swollen optic disc: do not forget neurosyphilis.  

PubMed

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

Porto, Lénea; Capelo, Joana; Carragoso, Adelino

2013-01-01

57

A user's view of optical disc applications  

NASA Technical Reports Server (NTRS)

An overall space information system is considered. It is found that data storage is required in all elements of the system with the possible exception of the wideband communication link. The data capture facility is the first ground facility to handle space-acquired data. A typical nine-day Spacelab mission is expected to generate up to 10 to the 13th bits of data. The current storage medium for this data is approximately 4000 magnetic tapes. It is pointed out that optical disk storage provides an attractive alternative to magnetic disk and tape storage. Options to install an optical disk storage system in the GSFC data capture facility in the 1986 time frame are evaluated by NASA. Attention is given to data capture and data base applications, onboard data storage applications, and numerical computation applications.

Holcomb, L. B.

1983-01-01

58

VECPs and optic disc damage in diabetes.  

PubMed

Abnormal VECP latencies can be found in type 1 diabetic patients without retinopathy or neuropathy. The pathogenesis of this finding is still unclear. The authors report the clinical history of a diabetic patient showing normal fundus, normal oscillatory potentials, and pathological VECP latency on first examination. The clinical follow-up of this patient showed rapid evolution toward proliferative retinopathy. This finding is suggestive of a peripheral (optic nerve or retina) origin of the VECP impairment. PMID:3428087

Anastasi, M; Lodato, G; Cillino, S

1987-08-01

59

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

Microsoft Academic Search

\\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

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

2004-01-01

60

High-density optical discs for audio, video, and image applications  

NASA Astrophysics Data System (ADS)

Great progress in optical storage has taken place in the last decade. The development of optical discs is always towards higher and higher storage density and data transfer rate in order to meet the ever-increasing requirements of applications in audio, video and image areas. It has been proved a logical and effective approach to employ laser light of shorter wavelength and lenses of higher numerical aperture for increasing storage density, as is shown by the evolution of optical disc from CD family to DVD family. At present, research and development of high density DVD (HD-DVD), blu-ray disc and advanced storage magneto-optical (AS-MO) disc are carried out very extensively. Meanwhile, miniaturization of disc size and use of multiplication techniques to increase the storage density and capacity have already given rise to new formats such as iD Photo disc and Data Play disc as well as multi-layer discs. Digital holographic storage (DHS) disc is also one of the research and development subjects of many companies and research institutions. Some new concept optical storage such as fluorescent multiplayer disc (FMD) is also under intensive development. All these have greatly promoted applications of optical discs in audio, video and image devices.

Gan, Fuxi; Hou, Lisong

2003-04-01

61

Localization and Extraction of the Optic Disc Using the Fuzzy Circular Hough Transform  

Microsoft Academic Search

\\u000a This paper presents an algorithm for automatic extraction of the optic disc in retinal images. The developed system consists\\u000a of two main parts. Firstly, the localization of the region containing the optic disc is performed by means of a clustering\\u000a algorithm. Then, in order to extract the optic disc, the fuzzy circular Hough transform is applied to the edges of

Marianne Blanco; Manuel G. Penedo; Noelia Barreira; Marta Penas; María J. Carreira

2006-01-01

62

Cup-To-Disc Ratio Of The Optic Disc By Image Analysis To Assist Diagnosis Of Glaucoma Risk And Evolution  

NASA Astrophysics Data System (ADS)

This work builds an image analysis algorithm to give assistance in the cup to disc ratio estimation of glaucomatous eyes. Often the contours of both the optic cup and disc are faint and intersected by entangled veins that make it difficult to draw their silhouettes. The algorithm, which takes into account the viewing conditions of the specialist, is based on the information of color, the color differences between neighbor pixels and the geometry of the areas involved.

Valencia, Edison; Millán, María S.; Kotynski, Rafal

2006-10-01

63

Chondroadherin Fragmentation Mediated by the Protease HTRA1 Distinguishes Human Intervertebral Disc Degeneration from Normal Aging*  

PubMed Central

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.

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

2013-01-01

64

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

PubMed Central

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

Wirtschafter, J D

1983-01-01

65

4.7 GB Phase Change Optical Disc with In-Groove Recording  

Microsoft Academic Search

We developed a rewritable optical disc with 4.7 GB\\/side capacity as an extension of the digital versatile disc recordable (DVD-R) system.The disc is readily playable on a read-only DVD player or a DVD-ROM drive with a small firmware modification.As far as the fundamental characteristics of the disc which adopts an in-groove recording are concerned, the reflectivity is 18% or more,

Masataka Yamaguchi; Takahiro Togashi; Satoshi Jinno; Hideo Kudo; Eiji Muramatsu; Shoji Taniguchi; Akiyoshi Inoue

1999-01-01

66

Unilateral Optic Disc Edema in a Paediatric Patient: Diagnostic Dilemmas and Management  

PubMed Central

Introduction. We report a case of unilateral optic disc edema in a paediatric patient and discuss the concerns involved in diagnosis and management of similar cases. Materials and Methods. Female aged 10 years was referred to our clinic due to progressive visual loss of the LE over a few days. Her visual acuities (VA) were RE 10/10, LE 3/10, and she had a relative afferent pupillary defect and decreased colour vision in her LE and normal and painless eye movements. Fundoscopy showed a remarkably swollen disc of the LE, and visual field (VF) examination revealed enlargement of the blind spot and presence of horizontal inferior papillomacular scotoma. Neurological examination, CT of brain and orbits and blood tests were normal. Visual evoked potentials revealed an obstacle in the myelin substance before the optic chiasma of the LE. Results. The patient was treated with intravenous methylprednoslone for 3 days and with oral methylprednizole for 15 days in progressively diminished daily doses. This led to gradual improvement of VA, colour vision, and visual field and resolution of optic disc oedema. Discussion. Concerns that have to be taken into account regarding diagnosis and management of similar cases are related to lumbar puncture indications, treatment with corticosteroids, and appropriate followup.

Kanonidou, Evgenia; Chatziralli, Irini; Kanonidou, Christina; Parava, Maria; Ziakas, Nikolas

2010-01-01

67

Unilateral optic disc edema in a paediatric patient: diagnostic dilemmas and management.  

PubMed

Introduction. We report a case of unilateral optic disc edema in a paediatric patient and discuss the concerns involved in diagnosis and management of similar cases. Materials and Methods. Female aged 10 years was referred to our clinic due to progressive visual loss of the LE over a few days. Her visual acuities (VA) were RE 10/10, LE 3/10, and she had a relative afferent pupillary defect and decreased colour vision in her LE and normal and painless eye movements. Fundoscopy showed a remarkably swollen disc of the LE, and visual field (VF) examination revealed enlargement of the blind spot and presence of horizontal inferior papillomacular scotoma. Neurological examination, CT of brain and orbits and blood tests were normal. Visual evoked potentials revealed an obstacle in the myelin substance before the optic chiasma of the LE. Results. The patient was treated with intravenous methylprednoslone for 3 days and with oral methylprednizole for 15 days in progressively diminished daily doses. This led to gradual improvement of VA, colour vision, and visual field and resolution of optic disc oedema. Discussion. Concerns that have to be taken into account regarding diagnosis and management of similar cases are related to lumbar puncture indications, treatment with corticosteroids, and appropriate followup. PMID:21209745

Kanonidou, Evgenia; Chatziralli, Irini; Kanonidou, Christina; Parava, Maria; Ziakas, Nikolas

2010-01-01

68

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

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)

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

69

Automatic optic disc segmentation based on image brightness and contrast  

NASA Astrophysics Data System (ADS)

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 applied for the cup-disc-ratio based glaucoma diagnosis. The proposed OD segmentation method is based on the observations that the OD is normally much brighter and at the same time have a smoother texture characteristics compared with other regions within retinal images. Given a retinal image we first capture the ODs smooth texture characteristic by a contrast image that is constructed based on the local maximum and minimum pixel lightness within a small neighborhood window. The centre of the OD can then be determined according to the density of the candidate OD pixels that are detected by retinal image pixels of the lowest contrast. After that, an OD region is approximately determined by a pair of morphological operations and the OD boundary is finally determined by an ellipse that is fitted by the convex hull of the detected OD region. Experiments over 71 retinal images of different qualities show that the OD region overlapping reaches up to 90.37% according to the OD boundary ellipses determined by our proposed method and the one manually plotted by an ophthalmologist.

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

2010-03-01

70

Double-Vitrectomy for Optic Disc Pit Maculopathy  

PubMed Central

Background The origin of the fluid and precise pathophysiology of optic pit maculopathy remain unclear. It has been suggested that submacular fluid originates either from vitreous or cerebrospinal fluid. We report a case of optic pit maculopathy which was unsuccessfully treated with vitrectomy and internal limiting membrane (ILM) peeling, and subsequently resolved with revision of vitrectomy and gas tamponade. Methods We report a case of optic disc pit maculopathy, well documented by spectral- domain optical coherence tomography, before and after pars plana vitrectomy with ILM peeling, and its revision with gas tamponade. Results After ILM peeling, there was no improvement either in visual acuity or in the tomographic aspect of the retina. A revision of the surgery was then needed and gas tamponade was performed, which resulted in a complete resolution of the optic pit maculopathy. Conclusion The absence of improvement after ILM peeling during the first surgical procedure, accompanied by resolution of the clinical picture with gas tamponade during the second surgical procedure, sustained the hypothesis of a subarachnoidal origin of the fluid.

Pichi, Francesco; Morara, Mariachiara; Veronese, Chiara; Lembo, Andrea; Vitale, Lucia; Ciardella, Antonio P.; Nucci, Paolo

2012-01-01

71

Cup to disc ratio by optical coherence tomography is abnormal in Multiple Sclerosis  

PubMed Central

Objective To identify and characterize cup to disc ratio (CDR) and related optic nerve head abnormalities in multiple sclerosis (MS) using spectral domain optical coherence tomography (OCT). Background While CDR is routinely assessed by ophthalmologists in the evaluation of glaucoma, CDR and related optic nerve head metrics remain largely unexplored in MS. Design/Methods Cirrus-HD (high density) OCT was used to evaluate average CDR, vertical CDR, optic disc area, optic cup volume and neuro-retinal rim area in 105 MS patients and 88 age-matched healthy individuals. High-contrast (100%) visual acuity, 2.5% low-contrast letter acuity and 1.25% low-contrast letter acuity were assessed in 77 MS patients. Two-sample t-tests were used in the analysis of OCT-derived optic nerve head measures between healthy controls and MS patients. Multivariate regression (accounting for age and gender) was used to assess relationships between optic nerve head measures and visual function. Results Average CDR (p=0.007) and vertical CDR (p=0.005) was greater in MS patients compared to healthy controls, while neuro-retinal rim area was decreased in MS patients (p=0.001). CDR increased with retinal nerve fiber layer (RNFL) thinning (r=?0.29, p=0.001). 2.5% low-contrast (p=0.005) and 1.25% low-contrast letter acuity (p=0.03) were lower in MS patients with higher vertical CDR. Conclusions/Relevance CDR (as determined by spectral domain OCT), is abnormal in MS and correlates with visual function. OCT derived CDR and related optic nerve head metrics may represent an objective measure by which to monitor disease progression, and potentially neuroprotection, in therapeutic MS trials.

Syc, S.B.; Warner, C.V.; Saidha, S.; Farrell, S.K.; Conger, A.; Bisker, E.R.; Wilson, J.; Frohman, E.M.; Balcer, L.J.; Calabresi, P.A.

2010-01-01

72

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)

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.

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

2012-10-01

73

Accelerated aging of intervertebral discs in a mouse model of progeria.  

PubMed

Intervertebral disc degeneration (IDD) is a common and debilitating disorder that results in reduced flexibility of the spine, pain, and reduced mobility. Risk factors for IDD include age, genetic predisposition, injury, and other environmental factors such as smoking. Loss of proteoglycans (PGs) contributes to IDD with advancing age. Currently there is a lack of a model for rapid investigation of disc aging and evaluation of therapeutic interventions. Here we examined progression of disc aging in a murine model of a human progeroid syndrome caused by deficiency of the DNA repair endonuclease, ERCC1-XPF (Ercc1(-/?) mice). The ERCC1-deficient mice showed loss of disc height and degenerative structural changes in their vertebral bodies similar to those reported for old rodents. Compared to their wild-type littermates, Ercc1(-/?) mice also exhibit other age-related IDD characteristics, including premature loss of disc PG, reduced matrix PG synthesis, and enhanced apoptosis and cell senescence. Finally, the onset of age-associated disc pathologies was further accelerated in Ercc1(-/?) mice following chronic treatment with the chemotherapeutic agent mechlorethamine. These results demonstrate that Ercc1(-/?) mice represent an accurate and rapid model of disc aging and provide novel evidence that DNA damage negatively impacts PG synthesis. PMID:20973062

Vo, Nam; Seo, Hyoung-Yeon; Robinson, Andria; Sowa, Gwendolyn; Bentley, Douglas; Taylor, Lauren; Studer, Rebecca; Usas, Arvydas; Huard, Johnny; Alber, Sean; Watkins, Simon C; Lee, Joon; Coehlo, Paulo; Wang, Dong; Loppini, Mattia; Robbins, Paul D; Niedernhofer, Laura J; Kang, James

2010-12-01

74

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

NASA Astrophysics Data System (ADS)

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.

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

2011-03-01

75

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

Microsoft Academic Search

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

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

2000-01-01

76

Optic Disc Hemorrhage after Phacoemulsification in Patients with Glaucoma  

PubMed Central

Background. Optic disk hemorrhage is known to be a risk factor for glaucoma progression. Cataract surgery by phacoemulsification results in large intraocular pressure fluctuations. We aim to investigate whether phacoemulsification is associated with optic disc hemorrhage in patients with glaucoma. Methods. This is a retrospective review of consecutive university clinic based glaucoma patients undergoing phacoemulsification alone, with at least 3 visits in the year before and at least 5 visits in the year following phacoemulsification. The presence of optic disk hemorrhage was evaluated with slit lamp biomicroscopy at each clinic visit prior to and following phacoemulsification. Results. We evaluated 158 eyes of 158 subjects; 15 (9.5%) had ODH noted at least once during the 2-year study period. Four eyes had ODH identified on postoperative day 1, for a cross-sectional prevalence of 2.5%. Fourteen ODH episodes were noted preoperatively versus 12 episodes postoperatively (P = 0.68). Aspirin use was associated with ODH (P = 0.015). Conclusions. Our cross-sectional study found a prevalence of ODH immediately after CE that was similar to other published rates, and our longitudinal study did not find an increase in ODH in the year after phacoemulsification when compared to the year prior to surgery.

Bojikian, Karine D.; Moore, Daniel B.; Chen, Philip P.; Slabaugh, Mark A.

2014-01-01

77

A study of the causes of bilateral optic disc swelling in Japanese patients  

PubMed Central

Purpose To investigate the etiology of bilateral disc swelling in Japanese. Methods Using Kitasato University’s Department of Neuro-Ophthalmology medical records and fundus photographs of the period December 1977 through November 2010, we retrospectively identified 121 outpatients who had been initially confirmed with bilateral disc swelling. Results The most common cause of the bilateral disc swelling was increased intracranial pressure (ICP) (59%); followed by pseudopapillitis (16%); uveitis (8%); hypertensive retinopathy (5%); bilateral optic neuritis, acute disseminated encephalomyelitis (ADEM) and optic disc drusen (all at 2% each); and leukemia (1%). Unknown etiology accounted for 6% of the cases. Conclusion Although increased ICP is the most common etiology for bilateral disc swelling, it can also be triggered by a variety of other causes. Pseudopapillitis is the most important progenitor of bilateral disc swelling in Japanese.

Iijima, Kei; Shimizu, Kimiya; Ichibe, Yoshiaki

2014-01-01

78

Topographic optic disc analysis by Heidelberg retinal tomography in ocular Beh?et's disease  

PubMed Central

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.

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

2007-01-01

79

Correlation of peripheral displacement thresholds and optic disc parameters in ocular hypertension.  

PubMed Central

Both peripheral displacement thresholds and measurement of optic disc parameters have been advocated in the early diagnosis of glaucoma at the stage before scotomata are detected on conventional visual field assessment. The peripheral movement displacement thresholds were measured in 50 eyes of 50 patients with ocular hypertension and a significant correlation was found with neuroretinal rim areas measured using a computerised image system. There was also a significant correlation with optic disc diameter but no correlation with cup-disc ratio. The results support the proposition that measurement of peripheral movement displacement thresholds may be a useful tool in the detection of early glaucomatous optic nerve damage.

Ruben, S; Fitzke, F

1994-01-01

80

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

PubMed Central

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 cup and rim in spectral-domain 3-D OCT (SD-OCT) volumes. Four intraretinal surfaces were segmented using a fast multiscale 3-D graph search algorithm. After surface segmentation, the retina in each 3-D OCT scan was flattened to ensure a consistent optic nerve head shape. A set of 15 features, derived from the segmented intraretinal surfaces and voxel intensities in the SD-OCT volume, were used to train a classifier that can determine which A-scans in the OCT volume belong to the background, optic disc cup and rim. Finally, prior knowledge about the shapes of the cup and rim was incorporated into the system using a convex hull-based approach. Two glaucoma experts annotated the cup and rim area using planimetry, and the annotations of the first expert were used as the reference standard. A leave-one-subject-out experiment on 27 optic nerve head-centered OCT volumes (14 right eye scans and 13 left eye scans from 14 patients) was performed. Two different types of classification methods were compared, and experimental results showed that the best performing method had an unsigned error for the optic disc cup of 2.52±0.87 pixels (0.076±0.026 mm) and for the neuroretinal rim of 2.04 ± 0.86 pixels (0.061 ± 0.026 mm). The interobserver variability as indicated by the unsigned border positioning difference between the second expert observer and the reference standard was 2.54 ± 1.03 pixels (0.076 ± 0.031 mm for the optic disc cup and 2.14 ± 0.80 pixels (0.064 ± 0.024 mm for the neuroretinal rim. The unsigned error of the best performing method was not significantly different (p > 0.2) from the interobserver variability.

Niemeijer, Meindert; Garvin, Mona K.; Kwon, Young H.; Sonka, Milan; Abramoff, Michael D.

2010-01-01

81

Segmentation of the optic disc in 3-D OCT scans of the optic nerve head.  

PubMed

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 cup and rim in spectral-domain 3-D OCT (SD-OCT) volumes. Four intraretinal surfaces were segmented using a fast multiscale 3-D graph search algorithm. After surface segmentation, the retina in each 3-D OCT scan was flattened to ensure a consistent optic nerve head shape. A set of 15 features, derived from the segmented intraretinal surfaces and voxel intensities in the SD-OCT volume, were used to train a classifier that can determine which A-scans in the OCT volume belong to the background, optic disc cup and rim. Finally, prior knowledge about the shapes of the cup and rim was incorporated into the system using a convex hull-based approach. Two glaucoma experts annotated the cup and rim area using planimetry, and the annotations of the first expert were used as the reference standard. A leave-one-subject-out experiment on 27 optic nerve head-centered OCT volumes (14 right eye scans and 13 left eye scans from 14 patients) was performed. Two different types of classification methods were compared, and experimental results showed that the best performing method had an unsigned error for the optic disc cup of 2.52+/-0.87 pixels (0.076+/-0.026 mm) and for the neuroretinal rim of 2.04+/-0.86 pixels (0.061+/-0.026 mm). The interobserver variability as indicated by the unsigned border positioning difference between the second expert observer and the reference standard was 2.54+/-1.03 pixels (0.076+/-0.031 mm for the optic disc cup and 2.14+/-0.80 pixels (0.064+/-0.024 mm for the neuroretinal rim. The unsigned error of the best performing method was not significantly different (p > 0.2) from the interobserver variability. PMID:19758857

Lee, Kyungmoo; Niemeijer, Meindert; Garvin, Mona K; Kwon, Young H; Sonka, Milan; Abramoff, Michael D

2010-01-01

82

Detecting Optic Disc on Asians by Multiscale Gaussian Filtering  

PubMed Central

The optic disc (OD) is an important anatomical feature in retinal images, and its detection is vital for developing automated screening programs. Currently, there is no algorithm designed to automatically detect the OD in fundus images captured from Asians which are larger and have thicker vessels compared to Caucasians. In this paper, we propose such a method to complement current algorithms using two steps: OD vessel candidate detection and OD vessel candidate matching. The first step is achieved with multiscale Gaussian filtering, scale production, and double thresholding to initially extract the vessels' directional map of various thicknesses. The map is then thinned before another threshold is applied to remove pixels with low intensities. This result forms the OD vessel candidates. In the second step, a Vessels' Directional Matched Filter (VDMF) of various dimensions is applied to the candidates to be matched, and the pixel with the smallest difference designated the OD center. We tested the proposed method on a new database consisting of 402 images from a diabetic retinopathy (DR) screening programme consisting of Asians. The OD center was successfully detected with an accuracy of 99.25% (399/402).

Zhang, Bob; You, Jane; Karray, Fakhri

2012-01-01

83

Perimetrist's Guide for Optic Disc Visual Field Screening: The Armaly-Drance Method.  

National Technical Information Service (NTIS)

Disc-related defects constitute over 90% of field defects found in typical outpatient clinical population--e.g., ischemic neuropathy, optic neuritis, glaucoma. This handout is designed for anyone who uses a Goldman Visual Field Perimeter. It describes an ...

D. W. Carlson L. Tychsen

1988-01-01

84

Retinoschisis and macular detachment associated with acquired enlarged optic disc cup  

PubMed Central

We describe a case of maculopathy consisting of macular retinoschisis and serous macular detachment occurring in a patient with an acquired enlarged optic disc cup, similar to the maculopathy observed in congenital optic nerve abnormalities, mainly optic nerve pits and colobomas, without vitreomacular traction nor angiographic leak. Pars plana vitrectomy with argon laser endophotocoagulation and gas tamponade was found to be useful. Traction from membranes covering deep optic disc cups may create small retinal dehiscences, as described in congenital optic nerve abnormalities, which will enable the liquefied vitreous to pass, leading to retinoschisis with or without associated neurosensory detachment. Vitrectomy, photocoagulation, and gas tamponade may be a useful therapy for this entity.

Moreno-Lopez, Maria; Gonzalez-Lopez, Julio Jose; Jarrin, Elena; Bertrand, Josefina

2012-01-01

85

Detection of optic disc glaucoma damages using image analysis and artificial neural net  

NASA Astrophysics Data System (ADS)

A new method of the optic disc glaucomatous damage detection and the diagnosis determination is presented in this paper. This method is based on the measurement of the relative size of the representative pallor area on the color digital optic disc image and its evaluation using a statistical method and computer-simulated artificial neural net. Finally, the dependence of the relative pallor area size of the glaucomatous eye and glaucomatous visual field changes is studied.

Pluhá?ek, František; Pospíšil, Jaroslav; Kub?na, Tomáš; Marešová, Klára

2003-10-01

86

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

PubMed Central

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.

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

87

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

PubMed

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% O(2)) exhibited perturbed disc matrix homeostasis, including reduced proteoglycan synthesis and enhanced expression of matrix metalloproteinases, compared to discs grown at low oxygen levels (5% O(2)). Human disc cells grown at 20% O(2) 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% O(2). 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

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

2013-07-01

88

Inverted autologous internal limiting membrane for management of optic disc pit with macular detachment.  

PubMed

Macular detachment causes visual deterioration in 25-75% of patients with congenital optic disc pit. A number of treatment options have been reported to manage the macular detachment in optic pit. An optic disc pit represents a defect in the lamina cribrosa; theoretically, an ideal procedure to treat optic pit associated macular detachment would be one that prevents the flow of fluid across the pit by creating an additional barrier. We present a new surgical technique that employs an autologous internal limiting membrane (ILM) to create this barrier. The technique involves standard vitrectomy along-with ILM peeling. Subsequently, the peeled ILM was inverted and transplanted onto the optic disc pit to close the optic nerve pit. This technique showed satisfactory anatomic result with good functional improvement in visual acuity. PMID:24339690

Mohammed, Osman Abdelzaher; Pai, Anant

2013-01-01

89

Inverted Autologous Internal Limiting Membrane for Management of Optic Disc Pit with Macular Detachment  

PubMed Central

Macular detachment causes visual deterioration in 25-75% of patients with congenital optic disc pit. A number of treatment options have been reported to manage the macular detachment in optic pit. An optic disc pit represents a defect in the lamina cribrosa; theoretically, an ideal procedure to treat optic pit associated macular detachment would be one that prevents the flow of fluid across the pit by creating an additional barrier. We present a new surgical technique that employs an autologous internal limiting membrane (ILM) to create this barrier. The technique involves standard vitrectomy along-with ILM peeling. Subsequently, the peeled ILM was inverted and transplanted onto the optic disc pit to close the optic nerve pit. This technique showed satisfactory anatomic result with good functional improvement in visual acuity.

Mohammed, Osman Abdelzaher; Pai, Anant

2013-01-01

90

New Efficient Run-Length Limited Code for Multilevel Read-Only Optical Disc  

NASA Astrophysics Data System (ADS)

Multilevel recording with run-length limited (RLL) modulation is a novel way to significantly increase the recording density without changing the optical or mechanical units of current optical disc systems. In this paper, a new efficient 4-ary RLL(2,13) code with special constraint is designed for four-level RLL modulation on read-only digital versatile disc (DVD-ROM). This code can result in alternate multilevel pits and lands on the disc, and reduce the difficulty of multilevel disc replication. Further more, simulation results show the symbol error rate (SER) performance can be improved about 3 dB when the proposed code is used for optical recording channel with partial-response maximum-likelihood (PRML) detection.

Hu, Hua; Pan, Longfa; Xiong, Jianping; Ni, Yi

2007-06-01

91

Automated Assessment of the Optic Nerve Head on Stereo Disc Photographs  

PubMed Central

Purpose To develop automated software for optic nerve head (ONH) quantitative assessment from stereoscopic disc photographs and to evaluate its performance in comparison with human expert assessment. Methods A fully automated system, including three-dimensional ONH modeling, disc margin detection, cup margin detection, and calculation of stereometric ONH parameters, was developed and tested. One eye each from 54 subjects (23 healthy, 17 suspected glaucoma, and 14 glaucoma) was enrolled. The majority opinion of three experts defined disc and cup margins on the disc photographs was used for comparison. Seven ONH parameters, disc area, rim area, rim volume, cup area, cup volume, cup-to-disc (C/D) area ratio, and vertical C/D ratio, were computed based on both machine- and expert-defined margins and compared between the methods. Results All automated ONH measurements showed good correlation with the expert defined margins (Pearson r = 0.90, disc area; 0.56, rim area; 0.78, rim volume; 0.88, cup area; 0.93, cup volume; 0.69, C/D area ratio; and 0.67, vertical C/D ratio; all P ? 0.0001). No statistically significant difference was found in the glaucoma-discriminating ability of all seven ONH parameters (P ? 0.21). The mean or median of automatically defined disc and cup areas was significantly higher than the subjective assessment (disc area P = 0.0001, t-test; cup area P = 0.036, Wilcoxon signed ranks test), although they had high correlation coefficients. The software failed to detect the disc margin for all the disc photographs with peripapillary atrophy. Conclusions The automated ONH analysis method provides an objective and quantitative ONH evaluation using widely available stereo disc photographs.

Xu, Juan; Ishikawa, Hiroshi; Wollstein, Gadi; Bilonick, Richard A.; Sung, Kyung R.; Kagemann, Larry; Townsend, Kelly A.; Schuman, Joel S.

2010-01-01

92

Dissecting simulated disc galaxies - I. The structure of mono-age populations  

NASA Astrophysics Data System (ADS)

We study seven simulated disc galaxies, three with a quiescent merger history, and four with mergers in their last 9 Gyr of evolution. We compare their structure at z = 0 by decomposing them into `mono-age populations' (MAPs) of stars within 500 Myr age bins. All studied galaxies undergo a phase of merging activity at high redshift, so that stars older than 9 Gyr are found in a centrally concentrated component, while younger stars are mostly found in discs. We find that most MAPs have simple exponential radial and vertical density profiles, with a scaleheight that typically increases with age. Because a large range of merger histories can create populations with simple structures, this suggests that the simplicity of the structure of mono-abundance populations observed in the Milky Way by Bovy et al. is not necessarily a direct indicator of a quiescent history for the Milky Way. Similarly, the anticorrelation between scalelength and scaleheight does not necessarily imply a merger-free history. However, mergers produce discontinuities between thin and thick disc components, and jumps in the age-velocity relation. The absence of a structural discontinuity between thin and thick disc observed in the Milky Way would seem to be a good indicator that no merger with a mass ratio larger than 1:15-1:10 occurred in the last 9 Gyr. Mergers at higher redshift might nevertheless be necessary to produce the thickest, hottest components of the Milky Way's disc.

Martig, Marie; Minchev, Ivan; Flynn, Chris

2014-08-01

93

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

PubMed Central

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.

Mansoori, Tarannum; Balakrishna, Nagalla; Viswanath, Kalluri

2014-01-01

94

Genotoxic stress accelerates age-associated degenerative changes in intervertebral discs  

PubMed Central

Intervertebral disc degeneration (IDD) is the leading cause of debilitating spinal disorders such as chronic lower back pain. Aging is the greatest risk factor for IDD. Previously, we demonstrated IDD in a murine model of a progeroid syndrome caused by reduced expression of a key DNA repair enzyme. This led us to hypothesize that DNA damage promotes IDD. To test our hypothesis, we chronically exposed adult wild-type (Wt) and DNA repair-deficient Ercc1?/? mice to the cancer therapeutic agent mechlorethamine (MEC) or ionization radiation (IR) to induce DNA damage and measured the impact on disc structure. Proteoglycan, a major structural matrix constituent of the disc, was reduced 3-5x in the discs of MEC- and IR-exposed animals compared to untreated controls. Expression of the protease ADAMTS4 and aggrecan proteolytic fragments were significantly increased. Additionally, new PG synthesis was reduced 2-3x in MEC- and IR-treated discs compared to untreated controls. Both cellular senescence and apoptosis were increased in discs of treated animals. The effects were more severe in the DNA repair-deficient Ercc1?/? mice than in Wt littermates. Local irradiation of the vertebra in Wt mice elicited a similar reduction in PG. These data demonstrate that genotoxic stress drives degenerative changes associated with IDD.

Nasto, Luigi A.; Wang, Dong; Robinson, Andria R.; Clauson, Cheryl L.; Ngo, Kevin; Dong, Qing; Roughley, Peter; Epperly, Michael; Huq, Saiful M.; Pola, Enrico; Sowa, Gwendolyn; Robbins, Paul D.; Kang, James; Niedernhofer, Laura J.; Vo, Nam V.

2013-01-01

95

The inner diameter of the optic disc pit decreases with pars plana vitrectomy.  

PubMed

To report a patient with optic disc pit who showed decreased inner diameter of the optic disc pit along with resolution of recurrent macular detachment after pars plana vitrectomy. Pneumatic retinopexy and peripapillary laser photocoagulation was performed in a 28-year-old female with optic disc pit and serous macular detachment. Two months after the initial therapy, serous macular detachment recurred. Then, pars plana vitrectomy with removal of the posterior hyaloid was performed, and intraocular perfluoro-octane (C3F8) tamponade was used. Fundus photography and ocular coherence tomography were obtained at each visit. The patient was followed up for 1 year. Visual acuity was 20/400 (Snellen) at first presentation, improved to 20/40 at 2 weeks after pneumatic retinopexy and peripapillary laser treatment. Then, 2 months later visual acuity decreased to 20/200, improved to 20/40 at 2 weeks after the vitreoretinal surgery, and stayed stable during the 1-year follow-up. It was also noticed on clinical examinations as well as fundus photographs that the inner diameter of the optic disc pit had decreased significantly. Vitreous traction plays an important role in the formation of serous macular detachments with optic disc pits. In these patients, pars plana vitrectomy and posterior hyaloid removal may be an effective treatment for reduction of the inner diameter of the optic pit and resolution of the serous macular detachments. PMID:23111570

Pinarci, Eylem Yaman; Karacal, Humeyra; Oncel, Banu; Bayar, Sezin Akca; Karakaya, Muharrem

2013-04-01

96

Playback Signal Processing System Using Improved Waveform Correction for High Density Optical Disc  

NASA Astrophysics Data System (ADS)

A new playback signal processing system capable of large-capacity optical disc playback of over 25GB in the same optical format as the Blu-ray Disc has been developed. Generally, as optical disc capacity increases, the read-out signal of minimum pits is markedly degraded due to inter-symbol interference (ISI) from adjacent pits, asymmetries caused by pit-form distortion, and the frequency characteristics of optical transfer function (OTF). Partial Response Maximum Likelihood (PRML) is known to effectively improve ISI and asymmetries by compensating for these factors electrically. However, in high-density optical discs greater than 25GB, bit errors frequently occur even when PRML is applied. This proposed system consists of a PRML circuit and Improved Waveform Correction circuit that control only read-out signals of minimum pits more surely. Bit error rate (BER) measurements of the playback of a 30GB optical disc showed better BER performance. The system can be realized without major changes to the current PRML system.

Sugiyama, Kazuhiro; Michihata, Satoshi; Fujiyama, Naoyuki; Yoshida, Hideo

97

Changes in the molecular phenotype of nucleus pulposus cells with intervertebral disc aging.  

PubMed

Intervertebral disc (IVD) disorder and age-related degeneration are believed to contribute to low back pain. Cell-based therapies represent a promising strategy to treat disc degeneration; however, the cellular and molecular characteristics of disc cells during IVD maturation and aging still remain poorly defined. This study investigated novel molecular markers and their age-related changes in the rat IVD. Affymetrix cDNA microarray analysis was conducted to identify a new set of genes characterizing immature nucleus pulposus (NP) cells. Among these markers, select neuronal-related proteins (Basp1, Ncdn and Nrp-1), transcriptional factor (Brachyury T), and cell surface receptors (CD24, CD90, CD155 and CD221) were confirmed by real-time PCR and immunohistochemical (IHC) staining for differential expression between IVD tissue regions and among various ages (1, 12 and 21 months). NP cells generally possessed higher levels of mRNA or protein expression for all aforementioned markers, with the exception of CD90 in anulus fibrosus (AF) cells. In addition, CD protein (CD24 and CD90) and Brachyury (T) expression in immature disc cells were also confirmed via flow cytometry. Similar to IHC staining, results revealed a higher percentage of immature NP cells expressing CD24 and Brachyury, while higher percentage of immature AF cells was stained positively for CD90. Altogether, this study identifies that tissue-specific gene expression and age-related differential expression of the above markers do exist in immature and aged disc cells. These age-related phenotype changes provide a new insight for a molecular profile that may be used to characterize NP cells for developing cell-based regenerative therapy for IVD regeneration. PMID:23284858

Tang, Xinyan; Jing, Liufang; Chen, Jun

2012-01-01

98

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

PubMed Central

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.

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

2013-01-01

99

A New and Efficient Method for Automatic Optic Disc Detection Using Geometrical Features  

Microsoft Academic Search

\\u000a Automatic optic disc (OD) detection is a key processing step in algorithms aiming for automatic extraction of retinal vascular\\u000a abnormalities for diagnosing cardiovascular diseases and cup-to-disc ratio assessment for diagnosing glaucoma. In this paper,\\u000a we propose a new method for automatic OD segmentation and center computation. The proposed method automatically determines\\u000a the threshold intensity value by utilizing OD area information

Alauddin Bhuiyan; Ryo Kawasaki; Tien Yin Wong; Rao Kotagiri

100

Deep-UV liquid immersion mastering of high-density optical discs  

Microsoft Academic Search

A water immersion technique has been developed to increase the numerical aperture (NA) of a 257 nm optical disc mastering system from 0.9 to 1.2. The developed system is capable of performing point exposures on a rotating disc at scanning velocities of more than 5 m\\/s. Gas inclusion in the immersion liquid, either from the photo-resist or through the dynamic

Helmar van Santen; Jaap H. M. Neijzen

2003-01-01

101

Drusen of the Optic Disc with Visual Field Defect and Marcus Gunn Pupillary Phenomenon.  

National Technical Information Service (NTIS)

Optic disc drusen (colloid or hyaline bodies) are an important clinical finding in flight personnel. This paper presents a highly experienced, 41-year-old pilot who was found to have a quadrantic uniocular visual field defect secondary to extensive optic ...

T. J. Tredici W. E. Barry

1972-01-01

102

Fast Detection of the Optic Disc and Fovea in Color Fundus Photographs  

PubMed Central

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.

Niemeijer, Meindert; Abramoff, Michael D.; van Ginnekena, Bram

2009-01-01

103

Influence of age on symptoms and signs in lumbar disc herniation  

Microsoft Academic Search

In a prospective and consecutive study we evaluated the prevalence of pain-related symptoms, the results of the strainght leg raising (SLR) test and neurological disturbances by age group in a total of 150 patients operated on due to lumbar disc herniation. On admission, all patients were interviewed, and pain at rest, at night and on coughing was recorded. Walking capacity

B. Jönsson; B. Strömqvist

1995-01-01

104

The Palenque Project: A Process of Design and Development as Research in the Evolution of an Optical Disc Prototype for Children. Technical Report No. 47.  

ERIC Educational Resources Information Center

This report describes the Palenque Project, a highly interactive, multimedia, optical disc research prototype which was developed for home use and tested by observing 25 children in the 9 to 14 year age range and their families and 8 12-year-olds in pairs. It is noted that the project was intended to create a rich, multimedia database environment…

Wilson, Kathleen S.; Tally, William J.

105

Automated Quantification of Volumetric Optic Disc Swelling in Papilledema Using Spectral-Domain Optical Coherence Tomography  

PubMed Central

Purpose. To develop an automated method for the quantification of volumetric optic disc swelling in papilledema subjects using spectral-domain optical coherence tomography (SD-OCT) and to determine the extent that such volumetric measurements correlate with Frisén scale grades (from fundus photographs) and two-dimensional (2-D) peripapillary retinal nerve fiber layer (RNFL) and total retinal (TR) thickness measurements from SD-OCT. Methods. A custom image-analysis algorithm was developed to obtain peripapillary circular RNFL thickness, TR thickness, and TR volume measurements from SD-OCT volumes of subjects with papilledema. In addition, peripapillary RNFL thickness measures from the commercially available Zeiss SD-OCT machine were obtained. Expert Frisén scale grades were independently obtained from corresponding fundus photographs. Results. In 71 SD-OCT scans, the mean (± standard deviation) resulting TR volumes for Frisén scale 0 to scale 4 were 11.36 ± 0.56, 12.53 ± 1.21, 14.42 ± 2.11, 17.48 ± 2.63, and 21.81 ± 3.16 mm3, respectively. The Spearman's rank correlation coefficient was 0.737. Using 55 eyes with valid Zeiss RNFL measurements, Pearson's correlation coefficient (r) between the TR volume and the custom algorithm's TR thickness, the custom algorithm's RNFL thickness, and Zeiss' RNFL thickness was 0.980, 0.929, and 0.946, respectively. Between Zeiss' RNFL and the custom algorithm's RNFL, and the study's TR thickness, r was 0.901 and 0.961, respectively. Conclusions. Volumetric measurements of the degree of disc swelling in subjects with papilledema can be obtained from SD-OCT volumes, with the mean volume appearing to be roughly linearly related to the Frisén scale grade. Using such an approach can provide a more continuous, objective, and robust means for assessing the degree of disc swelling compared with presently available approaches.

Wang, Jui-Kai; Kardon, Randy H.; Kupersmith, Mark J.; Garvin, Mona K.

2012-01-01

106

High-Track-Density Optical Disc by Radial Direction Partial Response  

NASA Astrophysics Data System (ADS)

We propose a new recording method, the radial direction partial response (RPR), with which we are able to use a narrow track pitch. This method can be used only for optical read-only-memory discs. We present experimental results of this method combined with the multilevel recording technique called “single carrier independent pit edge recording” (SCIPER). (The combined method is called SCIPER-RPR). When a track pitch of 0.45 ?m and 0.28 ?m/bit in linear recording density is read out by a digital versatile disc (DVD) equivalent optical pickup, we confirmed a bit error rate of 1.5× 10-4.

Kobayashi, Seiji; Horigome, Toshihiro; Yamatsu, Hisayuki

2001-04-01

107

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

PubMed Central

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.

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

108

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

Microsoft Academic Search

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

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

2010-01-01

109

Teaching of optics in the optics age  

NASA Astrophysics Data System (ADS)

The present Optics Age of science had not been foreseen by curriculum- makers in many countries. The result is that during the last 25 years when activity in science, engineering, technology and industry related to optics and lasers was exploding in the advanced countries optics was being de-emphasized in curricula in these countries. The consequence is that these countries including India have not played good enough a role. It is shown that the changes needed are more in attitude, pedagogic tools, terminology, and teaching methodology than in curricular contents. Examples: (1) The sequence of topics be changed, (2) The concept of coherence be introduced by considering thought experiments with different light sources; it is shown that the Michelson interferometer along with an HeNe laser can be used to introduce spatial as well as temporal coherence, (3) Modern terminology be used, (4) Crystal optics which is difficult be divorced from the concept of polarization which is simple; greater attention be paid to polarization helix than to polarization ellipse so that the confusion in 'handedness' is eliminated, (5) Group velocity be introduced as related to stationary phase approximation, (6) Modern terms like irradiance, temporal, spatial, frequency spectrum, spatial frequency, etc be used extensively, and so on.

Parasnis, A. S.

1995-10-01

110

Deep-UV liquid immersion mastering of high-density optical discs  

NASA Astrophysics Data System (ADS)

A water immersion technique has been developed to increase the numerical aperture (NA) of a 257 nm optical disc mastering system from 0.9 to 1.2. The developed system is capable of performing point exposures on a rotating disc at scanning velocities of more than 5 m/s. Gas inclusion in the immersion liquid, either from the photo-resist or through the dynamic movement of the substrate could be avoided. Furthermore, unwanted mechanical disturbances were sufficiently suppressed. Contamination of the photo-resist was avoided through careful handling of the water that was applied as immersion liquid. The resulting resolution enhancement was demonstrated in grooves. In 25 nm Novolac type resist, 70 nm wide grooves were written with liquid immersion, compared to 100 nm wide grooves at NA = 0.9. Liquid immersion was also successfully applied to write the master substrate from which a ROM disc can be made through injection molding. ROM discs for the recently launched Blu-ray Disc system have been successfully written with a density corresponding to 25 GB in a single layer of a 12 cm disc.

van Santen, Helmar; Neijzen, Jaap H. M.

2003-06-01

111

Comparison of Apparent Diffusion Coefficient and T2 Relaxation Time Variation Patterns in Assessment of Age and Disc Level Related Intervertebral Disc Changes  

PubMed Central

Purpose To compare the variation patterns of ADC and T2 values in different age and intervertebral disc (IVD) levels, thus to identify their sensitivities in assessing age and disc level related IVDs changes. Materials and Methods The T2 and ADC values were recorded from 345 IVDs of 69 volunteers. Kendall's correlation analysis was used to identify the relationship between age and T2/ADC mean values respectively. The one-way analysis of variance (ANOVA) with post hoc analysis was then applied to test the differences of T2 and ADC values among different IVD levels and age groups, followed by linear regression analysis between age (<45 and >45 years) and T2/ADC mean values. This study was approved by the Ethics Committee of the Chinese Academy of Medical Sciences and the Peking Union Medical College Hospital. Results Significant negative correlation was observed between age and T2/ADC mean values. The T2 and ADC values showed significant differences among IVD levels and among age groups except for T2 values in age group 1 (25–34 years) and group 2 (35–44 years), and for ADC values at L1–2 level. Both T2 and ADC values showed significant differences between young (age<45 years) and elderly group (age>45 years) at each IVD level. A linear relationship was observed between age and T2/ADC mean values in the elderly group as well as in the young group for the ADC mean values, while no such tendency was identified in the young group for the T2 mean values. Conclusions ADC values may be a more sensitive parameter than T2 in assessing age and disc level related intervertebral disc changes.

Zhao, Luo; Zuo, Wei; Ming, Yue; Liu, Sen; Liu, Jiaqi; Su, Xinlin; Gao, Baoxiang; Tang, Zhiquan; Qiu, Guixing; Ma, Guolin; Wu, Zhihong

2013-01-01

112

Involution of endophytic optic disc hemangioma with a single session of photodynamic treatment.  

PubMed

We report a 58-year-old otherwise healthy woman with unilateral endophytic optic disc hemangioma and associated serous retinal detachment and exudation. A standard verteporfin dose was given and a photodynamic treatment (PDT) protocol was followed. A moderate vitreous hemorrhage occurred four days after PDT. The hemangioma regressed markedly 6 weeks after the procedure and serous retinal detachment showed marked resolution. PMID:17914208

Yaman, Aylin; Saatci, Ali Osman; Arikan, Gul; Gunduz, Kaan

2007-01-01

113

Channel model for InSb-based superresolution optical disc system.  

PubMed

A signal model of a superresolution optical channel would 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 is properly described, a general mathematical model of the superresolution disc itself is not yet available. However, different approaches have been made to describe the properties of a mask layer, mainly based on temperature- or power-dependent nonlinear effects. The main problem of the modeling is that temperature-dependent material properties, such as thermal conductivity and refractive indices, are not known or not accurate enough to allow quantitative predictions. Therefore, it could be useful to define a signal-based or phenomenological model that can be calibrated with experimental data. In this contribution, we developed a complete optical channel model--from non-return-to-zero inverted (NRZI) input to disc readout signal--including the reflectivity of a superresolution disc with InSb used for the mask layer. Model parameters are derived from data measured using a static tester. The model is finally applied to a configuration appropriate for a dynamic superresolution optical drive by moving the focused spot relative to the material. PMID:20357878

Hepper, Dietmar; Knappmann, Stephan

2010-04-01

114

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

Microsoft Academic Search

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

C. Eswaran; Ahmed Wasif Reza; Subhas Hati

2008-01-01

115

Graph based detection of optic disc and fovea in retinal images  

Microsoft Academic Search

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

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

2010-01-01

116

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

Microsoft Academic Search

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

Shijian Lu

2011-01-01

117

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

Microsoft Academic Search

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

Xiaolu Zhu; Rangaraj M. Rangayyan

2008-01-01

118

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

Microsoft Academic Search

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

Marco Foracchia; Enrico Grisan; Alfredo Ruggeri

2004-01-01

119

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

Microsoft Academic Search

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

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

2008-01-01

120

Fast Localization of the Optic Disc Using Projection of Image Features  

Microsoft Academic Search

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

Ahmed Essam Mahfouz; Ahmed S. Fahmy

2010-01-01

121

Optical Discs for Storage and Access in ARL Libraries. SPEC KIT 133.  

ERIC Educational Resources Information Center

This SPEC (Systems and Procedures Exchange Center) kit provides a sample of excerpts from technical and planning documents contributed by 40 Association of Research Libraries (ARL) member libraries that are planning to install or have already implemented optical disc technology. Selected to represent a variety of media and applications, the…

Holibaugh, Ralph

122

Vitrectomy for optic disc pit-associated maculopathy with or without preoperative posterior vitreous detachment  

PubMed Central

Background The purpose of this study was to evaluate the efficacy of pars plana vitrectomy for the treatment of optic disc pit-associated maculopathy with or without preoperative posterior vitreous detachment. Methods We reviewed the clinical records of four consecutive patients who underwent pars plana vitrectomy in one eye for the treatment of optic disc pit-associated maculopathy, with an emphasis on the preoperative condition of the posterior hyaloid membrane. Results Two of four eyes were confirmed to have an attached posterior hyaloid membrane, which was subsequently removed during surgery. Following vitrectomy, these two eyes experienced an improvement in visual acuity with complete retinal attachment of the macula. However, the other two eyes, which already had a posterior vitreous detachment at the time of surgery, showed a decrease in visual acuity with persistent maculopathy postoperatively. Conclusion Pars plana vitrectomy for optic disc pit-associated maculopathy was beneficial for improving visual acuity in two eyes without preoperative posterior vitreous detachment but not in two eyes with preoperative posterior vitreous detachment. Our study suggests that preoperative assessment of a posterior hyaloid membrane is clinically important in predicting the surgical outcome of optic disc pit-associated maculopathy.

Haruta, Masatoshi; Kamada, Rika; Umeno, Yumi; Yamakawa, Ryoji

2012-01-01

123

Retinal detachment associated with optic disc colobomas and morning glory syndrome  

PubMed Central

We report the diagnosis and treatment of patients with retinal detachment and/or retinoschisis associated with optic nerve coloboma or morning glory syndrome. A retrospective review of patients with optic nerve coloboma or morning glory syndrome with associated retinal detachment or retinoschisis was conducted. For five patients (six eyes), we report the clinical findings, spectral domain optical coherence tomography (OCT) imaging, intraoperative findings, and treatment outcomes. OCT scans demonstrate a bilaminar structure of maculopathy, consisting of inner schisis-like changes and outer layer retinal detachment. In most cases, a retinal break was demonstrated within the optic disc defect with three-dimensional OCT imaging. Glial tissue was sometimes observed within the anomalous defect. Vitrectomy and resection of the tractional tissue in these cases produced good anatomical and visual outcomes. Retinal detachment spontaneously resolved in cases where traction was not present. Traction may contribute to the pathogenesis of retinal detachment associated with colobomatous optic disc anomalies, either directly or by creating a secondary retinal break. OCT imaging assists with understanding the contributing factors to retinal detachment in individual cases of colobomatous optic disc anomalies and can thereby assist with determining the most effective approach to management.

Chang, S; Gregory-Roberts, E; Chen, R

2012-01-01

124

Retinal detachment associated with optic disc colobomas and morning glory syndrome.  

PubMed

We report the diagnosis and treatment of patients with retinal detachment and/or retinoschisis associated with optic nerve coloboma or morning glory syndrome. A retrospective review of patients with optic nerve coloboma or morning glory syndrome with associated retinal detachment or retinoschisis was conducted. For five patients (six eyes), we report the clinical findings, spectral domain optical coherence tomography (OCT) imaging, intraoperative findings, and treatment outcomes. OCT scans demonstrate a bilaminar structure of maculopathy, consisting of inner schisis-like changes and outer layer retinal detachment. In most cases, a retinal break was demonstrated within the optic disc defect with three-dimensional OCT imaging. Glial tissue was sometimes observed within the anomalous defect. Vitrectomy and resection of the tractional tissue in these cases produced good anatomical and visual outcomes. Retinal detachment spontaneously resolved in cases where traction was not present. Traction may contribute to the pathogenesis of retinal detachment associated with colobomatous optic disc anomalies, either directly or by creating a secondary retinal break. OCT imaging assists with understanding the contributing factors to retinal detachment in individual cases of colobomatous optic disc anomalies and can thereby assist with determining the most effective approach to management. PMID:22241012

Chang, S; Gregory-Roberts, E; Chen, R

2012-04-01

125

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

PubMed Central

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.

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

2000-01-01

126

Optic Disc Pit with Peripapillary Retinoschisis Presenting as a Localized Retinal Nerve Fiber Layer Defect  

PubMed Central

A 59-year-old woman was referred to our clinic for a glaucoma evaluation. The visual acuity and intraocular pressure were normal in both eyes. However, red-free fundus photography in the left eye showed a superotemporal wedge-shaped retinal nerve fiber layer defect, and visual field testing showed a corresponding partial arcuate scotoma. In an optical coherence tomography examination, the macula was flat, but an arcuate-shaped peripapillary retinoschisis was found. Further, the retinoschisis seemed to be connected with a superotemporal optic pit shown in a disc photograph. After 3 months of a topical prostaglandin analogue medication, the intraocular pressure in the retinoschisis eye was lowered from 14 to 10 mmHg and the peripapillary retinoschisis was almost resolved. We report a rare case of an optic disc pit with peripapillary retinoschisis presenting as a localized retinal nerve fiber layer defect.

Song, In Seok; Shin, Joong Won; Shin, Yong Woon

2011-01-01

127

Point-of-Care Ultrasonography for the Identification of 2 Children With Optic Disc Drusen Mimicking Papilledema.  

PubMed

We present 2 cases of asymptomatic patients who were found to have raised and blurred optic discs on physical examination, suggestive of papilledema. Evaluation in the emergency department revealed 2 well-appearing children with normal vital signs and neurologic evaluation results, without symptoms of increased intracranial pressure. Point-of-care ocular ultrasonography was performed on both children, demonstrating calcification at the optic nerve, which is diagnostic of optic disc drusen. Optic disc drusen is caused by the deposition of calcified axonal debris and is often buried within the optic disc in pediatric patients. It can cause some changes in visual acuity and visual fields, but patients who are otherwise asymptomatic can be easily diagnosed through point-of-care ultrasound, thereby sparing patients an aggressive workup if their clinical picture is otherwise reassuring. PMID:24987997

Braun, Alanna; Doniger, Stephanie J

2014-07-01

128

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

PubMed

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

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

2014-04-01

129

Modulation Code and Signal Characteristics for Signal Waveform Modulation Optical Disc  

NASA Astrophysics Data System (ADS)

A high-efficient and novel varying-level multilevel run-length-limited modulation code is proposed for signal waveform modulation (SWM) optical discs. The proposed code is composed of a maximum transition run (MTR) code and a level modulation process. The MTR code is employed to realize high code rate and satisfy the requirements of channels. Level modulation is used to eliminate inappropriate codewords for SWM channels and determine the level numbers for different runs. The rate of the presented code is 7/8 bits/symbols, and the recording density parameter RBPF (recording bits per 400 nm) is 2.26, which is 50.7% more than that of a digital versatile disc (DVD). The realization of the proposed code in SWM discs and the corresponding signal characteristics are also shown. With the run-length detection and level detection solution, the bit error rate (BER) is less than 2× 10-4, which is feasible for SWM multilevel optical discs.

Liu, Hailong; Pei, Jing; Pan, Longfa; Ni, Yi

2010-08-01

130

Expression and regulation of metalloproteinases and their inhibitors in intervertebral disc aging and degeneration  

PubMed Central

BACKGROUND CONTEXT Destruction of extracellular matrix (ECM) leads to intervertebral disc degeneration (IDD), which underlies many spine-related disorders. Matrix metalloproteinases (MMPs), and disintegrins and metalloproteinases with thrombospondin motifs (ADAMTSs) are believed to be the major proteolytic enzymes responsible for ECM degradation in the intervertebral disc (IVD). PURPOSE To summarize the current literature on gene expression and regulation of MMPs, ADAMTSs, and tissue inhibitors of metalloproteinases (TIMPs) in IVD aging and IDD. METHODS A comprehensive literature review of gene expression of MMP, ADAMTS, and TIMP in human IDD and reported studies on regulatory factors controlling their expressions and activities in both human and animal model systems. RESULTS Upregulation of specific MMPs (MMP-1, -2, -3, -7, -8, -10, and -13) and ADAMTS (ADAMTS-1, -4, and -15) were reported in human degenerated IVDs. However, it is still unclear from conflicting published studies whether the expression of ADAMTS-5, the predominant aggrecanase, is increased with IDD. Tissue inhibitors of metalloproteinase-3 is downregulated, whereas TIMP-1 is upregulated in human degenerated IVDs relative to nondegenerated IVDs. Numerous studies indicate that the expression levels of MMP and ADAMTS are modulated by a combination of many factors, including mechanical, inflammatory, and oxidative stress, some of which are mediated in part through the p38 mitogen-activated protein kinase pathway. Genetic predisposition also plays an important role in determining gene expression of MMP-1, -2, -3, and -9. CONCLUSIONS Upregulation of MMP and ADAMTS expression and enzymatic activity is implicated in disc ECM destruction, leading to the development of IDD. Future IDD therapeutics depends on identifying specific MMPs and ADAMTSs whose dysregulation result in pathological proteolysis of disc ECM.

Vo, Nam V.; Hartman, Robert A.; Yurube, Takashi; Jacobs, Lloydine J.; Sowa, Gwendolyn A.; Kang, James D.

2013-01-01

131

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

DOEpatents

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.

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

2012-07-10

132

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

PubMed

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

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

2014-04-01

133

Unilateral morning glory optic disc anomaly in a case with Down syndrome  

PubMed Central

Background This case is unique because it is the first reported case of Down syndrome with morning glory optic disc anomaly in literature. Case presentation A 15-year-old girl with features of Down syndrome presented to the Clinic of Ophthalmology for a regular ophthalmologic examination. Her best corrected visual acuity was 20/50 in the right eye and 20/20 in the left eye. The fundus examination revealed findings compatible with unilateral morning glory optic disc anomaly in the right eye. The patient underwent a complete ophthalmologic and systemic evaluation to explore possible associated findings. Conclusion This case report emphasizes the importance of ophthalmic screening-examinations in Down children to rule out any vision relevant pathology.

2014-01-01

134

Thin Optical Head with Flip-Chip Bonded Module for Compact Disc Read Only Memory Drives  

Microsoft Academic Search

A thin optical head for compact disc read only memory drives, whose thickness is 6.9 mm including the objective lens working distance, has been developed. It features a flip-chip bonded module, in which a laser diode chip, a micromirror and a preamplifier chip are integrated on a photodiode chip. The module size is 6 mm(W)× 6 mm(D)× 1.64 mm(H), and

Tsuyoshi Nagano; Eiichi Ueda; Shuichi Onayama; Ryuichi Katayama; Hiroshi Hamada; Yuzo Ono

1993-01-01

135

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

Microsoft Academic Search

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

Ganesan Kavitha; Swaminathan Ramakrishnan

2010-01-01

136

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

Microsoft Academic Search

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

J. Novo; Manuel G. Penedo; José Santos

2008-01-01

137

Automated Identification of Exudates and Optic Disc Based on Inverse Surface Thresholding  

Microsoft Academic Search

This paper presents a new approach to detect exudates and optic disc from color fundus images based on inverse surface thresholding.\\u000a The strategy involves the applications of fuzzy c-means clustering, edge detection, otsu thresholding and inverse surface\\u000a thresholding. The main advantage of the proposed approach is that it does not depend on manually selected parameters that\\u000a are normally chosen to

Haniza Yazid; Hamzah Arof; Hazlita Mohd Isa

138

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

Microsoft Academic Search

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

Ahmed Wasif Reza; Chantra Eswaran; Subhas Hati

2009-01-01

139

Multimodal segmentation of optic disc and cup from stereo fundus and SD-OCT images  

NASA Astrophysics Data System (ADS)

Glaucoma is one of the major causes of blindness worldwide. One important structural parameter for the diagnosis and management of glaucoma is the cup-to-disc ratio (CDR), which tends to become larger as glaucoma progresses. While approaches exist for segmenting the optic disc and cup within fundus photographs, and more recently, within spectral-domain optical coherence tomography (SD-OCT) volumes, no approaches have been reported for the simultaneous segmentation of these structures within both modalities combined. In this work, a multimodal pixel-classification approach for the segmentation of the optic disc and cup within fundus photographs and SD-OCT volumes is presented. In particular, after segmentation of other important structures (such as the retinal layers and retinal blood vessels) and fundus-to-SD-OCT image registration, features are extracted from both modalities and a k-nearest-neighbor classification approach is used to classify each pixel as cup, rim, or background. The approach is evaluated on 70 multimodal image pairs from 35 subjects in a leave-10%-out fashion (by subject). A significant improvement in classification accuracy is obtained using the multimodal approach over that obtained from the corresponding unimodal approach (97.8% versus 95.2%; p < 0:05; paired t-test).

Miri, Mohammad Saleh; Lee, Kyungmoo; Niemeijer, Meindert; Abràmoff, Michael D.; Kwon, Young H.; Garvin, Mona K.

2013-03-01

140

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

PubMed

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

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

2013-04-01

141

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

NASA Astrophysics Data System (ADS)

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 creating planar 2-D projection images. An edge-based cost function - more specifically, a signed edge-based term favoring a dark-to-bright transition in the vertical direction of polar projection images (corresponding to the radial direction in Cartesian coordinates) - was obtained. Information from the segmented vessels was used to suppress the vasculature influence by modifying the polar cost function and remedy the segmentation difficulty due to the presence of large vessels. The graph search was performed in the modified edge-based cost images. The algorithm was tested on 22 volumetric OCT scans. The segmentation results were compared with expert segmentations on corresponding stereo fundus disc photographs. We found a signed mean difference of 0.0058 +/- 0.0706 mm and an unsigned mean difference of 0.1083 +/- 0.0350 mm between the automatic and expert segmentations.

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

2009-02-01

142

A comparison of optic disc topographic parameters in patients with primary open angle glaucoma, normal tension glaucoma, and ocular hypertension  

Microsoft Academic Search

BackgroundHeidelberg Retina Tomograph (HRT) findings have been employed to quantitatively assess the topography of optic discs. We measured topographic parameters of optic discs in patients with primary open-angle glaucoma (POAG), normal-tension glaucoma (NTG), and ocular hypertension (OH) using an HRT in order to determine whether HRT topographic parameters can be used to differentiate those conditions.MethodsSeventeen eyes in 17 patients with

Naoko Kiriyama; Akira Ando; Chieko Fukui; Hiroyuki Nambu; Maki Nishikawa; Hiroo Terauchi; Atsuko Kuwahara; Miyo Matsumura

2003-01-01

143

The correlation between rat retinal nerve fiber layer thickness around optic disc by using optical coherence tomography and histological measurements  

PubMed Central

AIM To explore the correlation between the retinal nerve fiber layer (RNFL) thickness by using optical coherence tomography (OCT) and by histological measurements in normal adult rats and optic nerve transected rats. METHODS The RNFL thickness of 36 rats was scanned in a circle 3.46mm far from the optic disc by OCT. The two experimental groups were the normal group (n=20 rats) and the optic nerve transected group (n=16 rats). The latter group included 4 groups (n=4/group) surviving for 1 day, 3, 5 and 7 days. Then the RNFL thickness of the same retina area was also measured by NF-200 immunohistochemical staining method. Linear regression was used to analyze the correlation between the data obtained from these two methods. RESULTS The RNFL thickness of normal right eyes around optic disc by OCT was 72.35±5.71µm and that of the left eyes was 72.65±5.88µm (P=0.074). The RNFL thickness of the corresponding histological section by immunohistochemistry was 37.54±4.05µm (right eyes) and 37.38±4.23µm (left eyes) (P=0.059). There was a good correlation between the RNFL thickness measured by OCT and that measured by histology (R2=0.8131). After optic nerve transection, the trend of the RNFL thickness was thinner with the prolonged survival time. The correlation of the thickness detected by the above two methods was approximately (R2=0.8265). Value of the RNFL thickness in rats around optic disc measured by OCT was obviously higher than that measured by common histological measurement in normal adult rats and optic nerve transected rats. CONCLUSION The RNFL thickness measured by OCT has a strong correlation with that measured by histological method. Through OCT scanning, we found that the thickness of RNFL gradually becomes thinner in a time-dependent manner.

Huang, Ju-Fang; Yu, Hui-Min; Shang, Lei; Ma, Ruo-Fei; Cynthia, Ngobe Akume; Cao, Yan-Qun; Luo, Jia; Zeng, Le-Ping; Chen, Dan; Xiong, Kun

2013-01-01

144

Digital stereo-optic disc image analyzer for monitoring progression of glaucoma  

NASA Astrophysics Data System (ADS)

This paper describes an automated 3-D surface recovery algorithm for consistent and quantitative evaluation of the deformation in the ONH (optic nerve head). Additional measures, such as the changes in the volume of the cup and the disc as an improvement to the traditional cup to disc ratios, can thus be developed for longitudinal follow-up study of a patient. We propose an automated computerized technique for stereo pair registration and surface visualization of the ONH. Power cepstrum and zero mean cross correlation are embedded in the registration and a 3-D surface recovery technique is proposed. Preprocessing, as well as an overall registration, is performed upon stereo pairs. Then a coarse to fine feature matching strategy is used to reduce the ambiguity in finding the conjugate pair of the same point within the constraints of the epipolar plane. A cubic B-spline interpolation smooths the representation of the ONH obtained, while superimposition of features such as blood vessels is added. Studies show high correlation between traditional cup/disc measures derived from manual segmentation by ophthalmologists and computer generated cup/disc volume ratio. Such longitudinal studies over a large population of glaucoma patients are currently in progress for validation of the surface recovery algorithm.

Corona, Enrique; Mitra, Sunanda; Wilson, Mark P.; Soliz, Peter

2002-05-01

145

ISSLS PRIZE WINNER: INHIBITION OF NF-?B ACTIVITY AMELIORATES AGE-ASSOCIATED DISC DEGENERATION IN A MOUSE MODEL OF ACCELERATED AGING  

PubMed Central

Study Design NF-?B activity was pharmacologically and genetically blocked in an accelerated aging mouse model to mitigate age-related disc degenerative changes. Objective To study the mediatory role of NF-?B signaling pathway in age-dependent intervertebral disc degeneration. Summary of Background Data Aging is a major contributor to intervertebral disc degeneration (IDD), but the molecular mechanism behind this process is poorly understood. NF-?B is a family of transcription factors which play a central role in mediating cellular response to damage, stress, and inflammation. Growing evidence implicates chronic NF-?B activation as a culprit in many aging-related diseases, but its role in aging-related IDD has not been adequately explored. We studied the effects of NF-?B inhibition on IDD using a DNA repair-deficient mouse model of accelerated aging (Ercc1-/? mice) previously been reported to exhibit age-related IDD. Methods Systemic inhibition of NF-?B activation was achieved either genetically by deletion of one allele of the NF-?B subunit p65 (Ercc1-/?p65+/- mice) or pharmacologically by chronic intra-peritoneal administration of the Nemo Binding Domain (8K-NBD) peptide to block the formation of the upstream activator of NF-?B, I?B Inducible Kinase (IKK), in Ercc1-/? mice. Disc cellularity, total proteoglycan content and proteoglycan synthesis of treated mice and untreated controls were assessed. Results Decreased disc matrix proteoglycan content, a hallmark feature of IDD, and elevated disc NF-?B activity were observed in discs of progeroid Ercc1-/? mice and naturally aged wild-type compared to young WT mice. Systemic inhibition of NF-?B by the 8K-NBD peptide in Ercc1-/? mice increased disc proteoglycan synthesis and ameriolated loss disc cellularity and matrix proteoglycan. These results were confirmed genetically by using the p65 haploinsufficient Ercc1-/?p65+/- mice. Conclusion These findings demonstrate that the IKK/NF-?B signaling pathway is a key mediator of age-dependent IDD and represents a therapeutic target for mitigating disc degenerative diseases associated with aging.

Nasto, Luigi A.; Seo, Hyoung-Yeon; Robinson, Andria R.; Tilstra, Jeremy S.; Clauson, Cheryl L.; Sowa, Gwendolyn A.; Ngo, Kevin; Dong, Qing; Pola, Enrico; Lee, Joon Y.; Niedernhofer, Laura J.; Kang, James D.; Robbins, Paul D.; Vo, Nam V.

2012-01-01

146

Disc Jockey.  

ERIC Educational Resources Information Center

"Disc Jockey" is described as a classroom activity for junior high students with moderate/severe disabilities. The disc jockey of the day chooses music and operates a classroom tape recorder. The activity encourages students to learn days of the week, communication skills, age-appropriate behavior, and motor skills, and to develop feelings of…

Sparber, Sandra R.

1996-01-01

147

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

PubMed

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

Hepper, Dietmar

2011-06-10

148

Surgical Management of Optic Disc Pit Maculopathy with Outer Retinal Hole  

PubMed Central

Objective To report the successful outcome of a rare optic pit-associated maculopathy with an outer retinal hole following 23 G vitrectomy, internal limiting membrane (ILM) peeling and fluid-gas exchange without additional endolaser. Method Interventional case report. Results This case report documents a 56-year-old male patient with complaints of progressive diminution of vision in the right eye more than in the left eye due to an optic disc pit with an outer retinal hole and a cataract. Optical coherence tomography confirmed the presence of an outer retinal hole. The case report shows the successful outcome of a rare optic pit-associated maculopathy with an outer retinal hole and a cataract following phacoemulsification with 23 G vitrectomy, ILM peeling and fluid-gas exchange without additional endolaser.

Kelkar, Aditya Shreekant; Kelkar, Jai Aditya; Bhanushali, Devanshi Ramji; Kelkar, Shreekant Bhaskar

2012-01-01

149

Characterization of the age-dependent intervertebral disc changes in rabbit by correlation between MRI, histology and gene expression  

PubMed Central

Background The present study was conducted to address whether the intervertebral disc of rabbit could be considered (i) as a valuable model to provide new insights into the tissue and cellular changes of Nucleus pulposus aging and (ii) as an appropriate tool to investigate the efficacy of Nucleus pulposus cell-based biotherapies. Methods Lumbar intervertebral disc from rabbits with increasing ages (1, 6 and 30 month-old) were compared by MRI and histological observation using Pfirrmann's grading and Boos' scoring respectively. The expression of transcripts (COL2A1, AGC1, COL1A1, MMP13, BMP2, MGP and p21) in Nucleus pulposus cells were analysed by quantitative real-time PCR. Results MRI analysis indicated an early age-dependent increase in the Pfirrmann's grading. Histological Boos' scoring was also increased. The analysis of transcript expression levels showed that COL2A1 and AGC1 were down-regulated as a function of age. Conversely, COL1A1, MMP-13, BMP-2, MGP and p21 were significantly up-regulated in the Nucleus pulposus cells of aged rabbit intervertebral disc. Conclusions Our study describes the consistency of the rabbit as a model of intervertebral disc changes as a function of age by correlating tissue alteration with cellular modification measured.

2011-01-01

150

Behaviour of Disc Oedema During and After Amiodarone Optic Neuropathy: Case Report  

PubMed Central

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.

Martinez-Gamero, Bertha O.; Mohamed-Noriega, Jibran; Cavazos-Adame, Med. Humberto; Mohamed-Hamsho, Med. Jesus

2014-01-01

151

Papilledema and optic disc pit: The association of two pathologies in one patient  

PubMed Central

Histologically, optic disc pit (ODP) is described as a small congenital defect in the cribriform plate where a herniation of the dysplastic retina extends to the subarachnoid space in the optic nerve, which is surrounded by a layer of collagen-rich tissue. Approximately 25–75% of cases are complicated by optic disc pit maculopathy (ODPM). The pathogenesis of maculopathies associated with ODP has not been fully elucidated. We present an unusual case of a patient with a history of papilledema secondary to a fronto-temporal meningioma. The patient underwent a successful surgical intervention with resolution of the papilledema 15 years before the detection of an ODP that was associated with retinal detachment in the macular region. Several studies have reported on the importance of intracranial pressure in the development of maculopathies associated with ODP. During the period of intracranial hypertension and papilledema in our patient, the hernia sac that was associated with ODP may have been small, which would have decreased the chances of developing a maculopathy that was associated with OPD.

Galvez-Ruiz, Alberto; Ghazi, Nicola; Ruhaily, Yasir

2012-01-01

152

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

PubMed

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

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

2012-06-01

153

Post-traumatic macular break associated to congenital optic disc pit and pre-existing sensory macular detachment  

Microsoft Academic Search

Background. Optic disc pits represent a rare congenital abnormality frequently associated with macular detachment. Several theories on the pathogenesis of the detachment have been proposed, but the issue still remains unclear. Treatment remains speculative as well; advocated treatments include eye-patching, bed rest, steroids, laser photocoagulation, pars plana vitrectomy with fluid-air exchange and optic nerve sheath decompression. Methods. The Authors report

Bernardo Billi; Guido Lesnoni; Mario Giuliano; Tommaso Rossi; Mario Stirpe

1996-01-01

154

Video Discs in Education.  

ERIC Educational Resources Information Center

This discussion of the use of images in learning processes focuses on recent developments in optical storage disc technology, particularly compact disc read-only (CD-ROM) and optical video discs. Interactive video systems and user interfaces are described, and applications in education and industry in the United Kingdom are reviewed. (Author/LRW)

Barker, Philip

1986-01-01

155

Correlation between Optic Nerve Parameters Obtained Using 3D Nonmydriatic Retinal Camera and Optical Coherence Tomography: Interobserver Agreement on the Disc Damage Likelihood Scale  

PubMed Central

Purpose. To compare stereometric parameters obtained by three-dimensional (3D) optic disc photography and optical coherence tomography (OCT) and assess interobserver agreement on the disc damage likelihood scale (DDLS). Methods. This retrospective study included 190 eyes from 190 patients classified as normal, glaucoma suspect, or glaucomatous. Residents at different levels of training completed the DDLS for each patient before and after attending a training module. 3D optic disc photography and OCT were performed on each eye, and correlations between the DDLS and various parameters obtained by each device were calculated. Results. We found moderate agreement (weighted kappa value, 0.59?±?0.03) between DDLS scores obtained by 3D optic disc photography and the glaucoma specialist. The weighted kappa values for agreement and interobserver concordance increased among residents after the training module. Interobserver concordance was the poorest at DDLS stages 5 and 6. The DDLS scored by the glaucoma specialist had the highest predictability value (0.941). Conclusions. The DDLS obtained by 3D optic disc photography is a useful diagnostic tool for glaucoma. A supervised teaching program increased trainee interobserver agreement on the DDLS. DDLS stages 5 and 6 showed the poorest interobserver agreement, suggesting that caution is required when recording these stages.

Han, Jae Wook; Cho, Soon Young; Kang, Kui Dong

2014-01-01

156

Detection of new vessels on the optic disc using retinal photographs.  

PubMed

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 parameters, associated with shape, position, orientation, brightness, contrast and line density are calculated for each candidate segment. Based on these features, each segment is categorized as normal or abnormal using a support vector machine (SVM) classifier. The system was trained and tested by cross-validation using 38 images with new vessels and 71 normal images from two diabetic retinal screening centers and one hospital eye clinic. The discrimination performance of the fifteen features was tested against a clinical reference standard. Fourteen features were found to be effective and used in the final test. The area under the receiver operator characteristic curve was 0.911 for detecting images with new vessels on the disc. This accuracy may be sufficient for it to play a useful clinical role in an automated retinopathy analysis system. PMID:21156389

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

2011-04-01

157

Automatic tracing of optic disc and exudates from color fundus images using fixed and variable thresholds.  

PubMed

The detection of bright objects such as optic disc (OD) and exudates in color fundus images is an important step in the diagnosis of eye diseases such as diabetic retinopathy and glaucoma. In this paper, a novel approach to automatically segment the OD and exudates is proposed. The proposed algorithm makes use of the green component of the image and preprocessing steps such as average filtering, contrast adjustment, and thresholding. The other processing techniques used are morphological opening, extended maxima operator, minima imposition, and watershed transformation. The proposed algorithm is evaluated using the test images of STARE and DRIVE databases with fixed and variable thresholds. The images drawn by human expert are taken as the reference images. The proposed method yields sensitivity values as high as 96.7%, which are better than the results reported in the literature. PMID:19238899

Reza, Ahmed Wasif; Eswaran, C; Hati, Subhas

2009-02-01

158

Automatic Detection of Optic Disc from Fundus Images of ROP Infant Using 2D Circular Hough Transform  

Microsoft Academic Search

In this paper, a method of automatic detection of an Optic Disc (OD) in low-contrast infant's digital fundus images based on circular Hough transform is proposed. Number of dimensions of normal circular Hough Transforms histogram is reduced from 3 to 2 dimensions based on an approximation of OD radius. First few circles are approximated by using maximum points from Hough

Viranee Thongnuch; Bunyarit Uyyanonvara

159

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

Microsoft Academic Search

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

Arturo Aquino; Manuel Emilio Geg; Diego Mar ´ in

160

Detecting the Optic Disc Boundary in Digital Fundus Images Using Morphological, Edge Detection, and Feature Extraction Techniques  

Microsoft Academic Search

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

Arturo Aquino; Manuel Emilio Gegúndez-Arias; Diego Marin

2010-01-01

161

Optic disc and fovea detection via multi-scale matched filters and a vessels' directional matched filter  

Microsoft Academic Search

The optic disc (OD) and fovea are important anatomical features in retinal images. Its detections are crucial for developing an automated screening program. This paper proposes a method to automatically detect the OD and fovea in fundus images in three stages: OD vessel candidate detection, OD vessel candidate matching, and fovea detection. The first stage is achieved with multi-scale Gaussian

Bob Zhang; Fakhreddine Karray

2010-01-01

162

Agreement in identification of glaucomatous progression between the optic disc photography and Heidelberg retina tomography in young glaucomatous patients  

PubMed Central

AIM To evaluate concordance between the clinical assessment of glaucomatous progression of the optic disc photography and progression identified by Heidelberg Retina Tomograph (HRT) in patients with suspected primary juvenile open angle glaucoma (JOAG). METHODS Optic disc photographs and corresponding HRT II series were reviewed. Optic disc changes between first and final photographs were noted as well as progression identified by HRT topographic change analysis (TCA) and rim area regression line (RARL) Agreement between progression indentified by photography and HRT methods was assessed. Progression, determined from optic disc photographs by consensus assessment was used as the reference standard. RESULTS A total of 31 patients (59 eyes) with suspected JOAG were studied. Agreement for progression/no progression between TCA and photography was obtained in 4 progressing eyes and 38 stable eyes (71.19%, k=0.11). Agreement for progression/no progression between RARL and photography was detected in 5 progressing eyes and in 34 stable eyes (66.10%, k=0.15). The number of HRT per patient was statistically higher in the progressing group (P=0.034). CONCLUSION Agreement for detection of longitudinal changes between photography and HRT analysis was poor. One way to improve the chance of discovery of the progression could be increasing the number of HRT examinations.

Hentova-Sencanic, Paraskeva; Sencanic, Ivan; Trajkovic, Goran; Bozic, Marija; Bjelovic, Nevena

2014-01-01

163

Genetic Contributions to Glaucoma: Heritability of Intraocular Pressure, Retinal Nerve Fiber Layer Thickness, and Optic Disc Morphology  

Microsoft Academic Search

PURPOSE. The genetic etiology of primary open-angle glaucoma (POAG) is still largely unknown, because of its complexity and disparities in its classification. This study was undertaken to determine the genetic contribution to various early, continu- ous markers of POAG by assessing the heritability of intraocular pressure (IOP), retinal nerve fiber layer (RNFL) thickness, and neuroretinal rim and optic disc parameters

Leonieke M. E. van Koolwijk; Dominiek D. G. Despriet; Cornelia M. van Duijn; Luba M. Pardo Cortes; Johannes R. Vingerling; Yurii S. Aulchenko; Ben A. Oostra; Caroline C. W. Klaver; Hans G. Lemij

2007-01-01

164

4.7 GB PhaseChange Optical Disk for an Authoring System of Digital Versatile Disc  

Microsoft Academic Search

A phase-change optical disk that has an optical phase-shift signal reproducing structure and the same physical specifications as the 4.7 GB read-only digital versatile disc (DVD) was developed. A minimum jitter of 9% and a wide tilt tolerance for the jitter were obtained under DVD reproducing conditions of lambda=650 nm and NA=0.60. This new medium can be used as an

Ken'ichi Nagata; Tetsuo Saimi; Shigeaki Furukawa; Ken'ichi Nishiuchi; Noboru Yamada; Nobuo Akahira

1998-01-01

165

Laser-Induced Forward Transfer-printing of focused ion beam pre-machined crystalline magneto-optic yttrium iron garnet micro-discs.  

PubMed

We present femtosecond laser-induced forward transfer of focused ion beam pre-machined discs of crystalline magneto-optic yttrium iron garnet (YIG) films. Debris-free circular micro-discs with smooth edges and surface uniformity have been successfully printed. The crystalline nature of the printed micro-discs has not been altered by the LIFT printing process, as was confirmed via micro-Raman measurements. PMID:22772215

Sones, C L; Feinaeugle, M; Sposito, A; Gholipour, B; Eason, R W

2012-07-01

166

Dynamics of Astrophysical Discs  

NASA Astrophysics Data System (ADS)

Preface; Names and addresses of participants; Conference photograph; 1. Spiral waves in Saturn's rings; 2. Structure of the Uranian rings; 3. Planetary rings: theory; 4. Simulations of light scattering in planetary rings; 5. Accretion discs around young stellar objects and the proto-Sun; 6. The ß Pictoris disc: a planetary rather than a protoplanetary one; 7. Optical polarimetry and thermal imaging of the disc axound ß Pictoris; 8. Observations of discs around protostars and young stars; 9. VLA observations of ammonia towaxd moleculax outflow sources; 10. Derivation of the physical properties of molecular discs by an MEM method; 11. Masers associated with discs around young stars; 12. The nature of polarisation discs axound young stars; 13. The correlation between the main parameters of the interstellar gas (including Salpeter's spectrum of masses) as a result of the development of turbulent Rossby waves; 14. Discs in cataclysmic variables and X-ray binaries; 15. A disc instability model for soft X-ray transients containing black holes; 16. X-ray variability from the accretion disc of NGC 5548; 17. Viscously heated coronae and winds around accretion discs; 18. Optical emission line profiles of symbiotic stars; 19. The effect of formation of Fell in winds confined to discs for luminous stars; 20. Observational evidence for accretion discs in active galactic nuclei; 21. The fuelling of active galactic nuclei by non-axisynlinetric instabilities; 22. The circum-nuclear disc in the Galactic centre; 23. Non-axisymmetric instabilities in thin self-gravitating differentially rotating gaseous discs; 24. Non-linear evolution of non-axisymmetric perturbations in thin self-gravitating gaseous discs; 25. Eccentric gravitational instabilities in nearly Keplerian discs; 26. Gravity mode instabilities in accretion tori; 27. The stability of viscous supersonic shear flows - critical Reynolds numbers and their implications for accretion discs; 28. Asymptotic analysis of overstable convective modes of uniformly rotating stars; 29. Polytropic models in very rapid rotation; 30. Distribution and kinematics of gas in galaxy discs; 31. Are the smallest galaxies optically invisible?; 32. Can we understand the constancy of rotation curves?; 33. How well do we know the surface density of the Galactic disc?; 34. On the heating of the Galactic disc; 35. The bulge-disc interaction in galactic centres; 36. Dynamics of the large-scale disc in NGC 1068; 37. The flow of gas in barred galaxies; 38. The warped dust lane in A1029-459; 39. Structure and evolution of dissipative non-planar galactic discs; 40. Non-axisymmetric magnetic fields in turbulent gas discs; 41. Non-axisymmetric disturbances in galactic discs; 42. Spiral instabilities in N-body simulations; 43. Long-lived spiral waves in N-body simulations; 44. Overstable modes in stellar disc systems; 45. Galactic seismological approach to the spiral galaxy NGC 3198; 46. Characteristics of bars from 3-1) simulations; 47. Spirals and bars in linear theory; 48. Stellar hydrodynamical solutions for Eddington discs; 49. Theory of gradient instabilities of the gaseous Galactic disc and rotating shallow water; 50. Stability criteria for gravitating discs; 51. Stability of two-component galactic discs; 52. The smoothed particle hydrodynamics of galactic discs; 53. Tidal triggering of active disc galaxies by rich clusters; 54. The formation of spiral arms in early stages of galaxy interaction; 55. Formation of leading spiral arms in retrograde galaxy encounters; 56. The influence of galaxy interactions on stellar bars; 57. Disc galaxies - work in progress in Gothenburg; 58. Motion of a satellite in a disc potential; 59. Observer's summary; 60. Common processes and problems in disc dynamics; Citation index; Index of authors; Subject index.

Sellwood, J. A.

2004-01-01

167

Optical Recording Properties of Styryl Derivatives for Digital Versatile Disc-Recordable (DVD-R)  

Microsoft Academic Search

New styryl dyes for the recording layer of digital versatile disc-recordable (DVD-R) were synthesized and analyzed by UV-vis spectroscopy and thermal analyzer. Using these dyes, we prepared two-type DVD-R discs, with\\/without metallic thin film between substrate and organic buffer layer. The metal-polymer deformation 4.7 GB DVD-R discs were recorded by high-power 658nm-wavelength laser diode and their recording characteristics were evaluated

Ki Hong Park; Chul Joo Lee; Donghyun Song; Jaepil Kim; Young Jae Huh; Kyung Sun Min

2001-01-01

168

Spontaneous Resolution of Long-Standing Macular Detachment due to Optic Disc Pit with Significant Visual Improvement  

PubMed Central

Purpose To report a case of spontaneous resolution of a long-standing serous macular detachment associated with an optic disc pit, leading to significant visual improvement. Case Presentation A 63-year-old female presented with a 6-month history of blurred vision and micropsia in her left eye. Her best-corrected visual acuity was 6/24 in the left eye, and fundoscopy revealed serous macular detachment associated with optic disc pit, which was confirmed by optical coherence tomography (OCT). The patient was offered vitrectomy as a treatment alternative, but she preferred to be reviewed conservatively. Three years after initial presentation, neither macular detachment nor subretinal fluid was evident in OCT, while the inner segment/outer segment (IS/OS) junction line was intact. Her visual acuity was improved from 6/24 to 6/12 in her left eye, remaining stable at the 6-month follow-up after resolution. Conclusion We present a case of spontaneous resolution of a long-standing macular detachment associated with an optic disc pit with significant visual improvement, postulating that the integrity of the IS/OS junction line may be a prognostic factor for final visual acuity and suggesting OCT as an indicator of visual prognosis and the probable necessity of a surgical management.

Parikakis, Efstratios A.; Chatziralli, Irini P.; Peponis, Vasileios G.; Karagiannis, Dimitrios; Stratos, Aimilianos; Tsiotra, Vasileia A.; Mitropoulos, Panagiotis G.

2014-01-01

169

Microstructure-based fiber optic pressure sensor for measurements in lumbar intervertebral discs  

NASA Astrophysics Data System (ADS)

A fiberoptic system with a microstructure sensor element was used for measuring lumbar intervertebral disc pressure in a porcine model. The fiberoptic pressure sensor was inserted in the disc using a guiding needle. A reference sensor was also introduced into the same area of an adjacent disc. The fiberoptic sensor detected pressures from 0.7-8 bar in the disc. Dynamic measurements were carried out at frequencies between 2 and 10 Hz. No phase lag was observed between the applied force and the measured pressures. Sensitivity, dynamic response and available pressure range are all important design characteristics for which this fiberoptic sensor has a competitive edge.

Hoejer, Svante; Krantz, Martin; Ekstroem, Lars; Kaigle, Allison; Holm, Sten

1999-01-01

170

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

PubMed

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

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

2010-01-01

171

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

Microsoft Academic Search

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

Ahmed Wasif Reza; C. Eswaran; Kaharudin Dimyati

172

Optic Disc Detection by Multi-scale Gaussian Filtering with Scale Production and a Vessels' Directional Matched Filter  

Microsoft Academic Search

\\u000a The optic disc (OD) is an important anatomical feature in retinal images, and its detection is vital for developing automated\\u000a screening programs. In this paper we propose a method to automatically detect the OD in fundus images using two steps: OD\\u000a vessel candidate detection and OD vessel candidate matching. The first step is achieved with multi-scale Gaussian filtering,\\u000a scale production,

Bob Zhang; Fakhri Karray

2010-01-01

173

The mass distribution in early-type disc galaxies: declining rotation curves and correlations with optical properties  

Microsoft Academic Search

We present rotation curves for 19 early-type disc galaxies (S0-Sab). The galaxies span a B-band absolute magnitude range from -17.5 to -22, but the majority have a high luminosity with MB < -20. Rotation velocities are measured from a combination of HI velocity fields and long-slit optical emission line spectra along the major axis; the resulting rotation curves probe the

E. Noordermeer; J. M. van der Hulst; R. Sancisi; R. S. Swaters; T. S. van Albada

2007-01-01

174

Scattered depressions with temporal preponderance in visual field test coexisting with optic disc temporal atrophy in cerebral arteriovenous malformation  

PubMed Central

In this article, the unusual association of optic disc temporal atrophy associated with scattered depressions with temporal preponderance in visual field test resembling incomplete bitemporal hemianopsia is reported. A 22-year-old man with cerebral arteriovenous malformation (AVM), which was located adjacent to the inferomedial portion of the posterior limb of the right internal capsule at the level of lateral ventricle, revealed interesting and unexpected ophthalmological findings. Possible mechanisms including anatomical variant, previously larger AVM, and retrograde optic neuropathy were mentioned. This case also highlighted that the usual complaint of visual disturbance might associate with unusual visual field defect in cerebral AVMs.

Gokce, Gokcen; Oren, Nisa Cem; Ceylan, Osman Melih; Mumcuoglu, Tarkan; Hurmeric, Volkan

2013-01-01

175

Optic disc neovascularisation in diabetic retinopathy: II. Natural history and results of photocoagulation treatment.  

PubMed Central

A follow-up study on 67 diabetic patients with new proliferation on the nerve head (neovascularisation of the disc and fibrous proliferation of the disc) was carried out for 4 years. The patients were randomly assigned for treatment with argon laser and xenon photocoagulation in only one eye, with the other eye serving as a control. The disc condition was periodically evaluated for NVD, FPD, and for the relations between them according to a grading taxonomy which was previously established. It was found that there were significant differences in NVD and FPD evolution between treated and untreated eyes. The various parameters concerned with these differences were observed, analysed, and correlated.

Yassur, Y; Pickle, L W; Fine, S L; Singerman, L; Orth, D H; Patz, A

1980-01-01

176

Is the Transport of a Gadolinium-Based Contrast Agent Decreased in a Degenerated or Aged Disc? A Post Contrast MRI Study  

PubMed Central

A post contrast magnetic resonance imaging study has been performed in a wide population of low back pain patients to investigate which radiological and phenotypic characteristics influence the penetration of the contrast agent in lumbar discs in vivo. 37 patients affected by different pathologies (disc herniation, spondylolisthesis, foraminal stenosis, central canal stenosis) were enrolled in the study. The selected population included 26 male and 11 female subjects, with a mean age of 42.4±9.3 years (range 18–60). Magnetic resonance images of the lumbar spine were obtained with a 1.5 T scanner (Avanto, Siemens, Erlangen, Germany) with a phased-array back coil. A paramagnetic non–ionic contrast agent was injected with a dose of 0.4 ml/kg. T1-weighted magnetic resonance images were subsequently acquired at 5 time points, 5 and 10 minutes, 2, 4 and 6 hours after injection. Endplates presented clear enhancement already 5 minutes after injection, and showed an increase in the next 2 hours followed by a decrease. At 5 and 10 minutes, virtually no contrast medium was present inside the intervertebral disc; afterwards, enhancement significantly increased. Highly degenerated discs showed higher enhancement in comparison with low and medium degenerated discs. Discs classified as Pfirrmann 5 showed a statistically significant higher enhancement than Pfirrmann 1, 2 and 3 at all time points but the first one, possibly due to vascularization. Disc height collapse and Modic changes significantly increased enhancement. Presence of endplate defects did not show any significant influence on post contrast enhancement, but the lack of a clear classification of endplate defects as seen on magnetic resonance scans may be shadowing some effects. In conclusion, disc height, high level of degeneration and presence of Modic changes are factors which increase post contrast enhancement in the intervertebral disc. The effect of age could not be demonstrated.

Tibiletti, Marta; Galbusera, Fabio; Ciavarro, Cristina; Brayda-Bruno, Marco

2013-01-01

177

Minimal invasive localization of the germinal disc in ovo for subsequent chicken sexing using optical coherence tomography  

NASA Astrophysics Data System (ADS)

Reason for using optical coherence tomography (OCT) to locate the germinal disc is the questionable and ethically alarming killing of male layer chickens because for the layer line only the females are necessary. To avoid this and to protect the animal rights, the sex of the fertilized chicken egg has to be determined as early as possible in the unincubated state. Because the information whether the chick becomes male or female can be found in the germinal disc an accurate localization for sexing is essential. The germinal disc is located somewhere on top of the yolk and has a diameter of approximately 4 - 5 mm. Different imaging methods like ultrasonography, 3D-X-ray micro computed tomography and magnetic resonance imaging were used for localization until now, but found to be impractical. The goal of this study is to prove if OCT can be a moderate approach for the precise in ovo localization. Because the eggshell is an impenetrable barrier for OCT and to minimize the penetration of germs a very small hole is placed in the eggshell and a fan-shaped optical scanning pattern is used.

Burkhardt, Anke; Geissler, Stefan; Cimalla, Peter; Walther, Julia; Koch, Edmund

2010-02-01

178

The Advanced Glaucoma Intervention Study (AGIS): 10. Variability among academic glaucoma subspecialists in assessing optic disc notching.  

PubMed Central

PURPOSE: An analysis of data from the Advanced Glaucoma Intervention Study (AGIS) has found eyes reported to have partial optic disc rim notching (not to the edge) at baseline to have less risk of subsequent visual field loss than eyes with no notching. Because this is counterintuitive and because classification of notching had not been defined in the AGIS protocol, we have assessed AGIS ophthalmologists interobserver and intraobserver agreement on notching. METHODS: Fourteen glaucoma subspecialists classified notching in 26 pairs of stereoscopic disc photographs of eyes with mild to severe glaucomatous optic neuropathy. They classified images as showing either no notching, notching not to the edge, or notching to the edge. Several hours later, 10 of them classified the same images a second time. RESULTS: In an analysis of interobserver agreement, of 26 stereoscopic images, a plurality of ophthalmologists classified notching as absent in 9 (35%), as present but not to the edge in 7 (27%), and as present and not to the edge in 10 (38%). All 14 ophthalmologists (100%) agreed on the classification of 7 (27%) of the images, and 13 of the 14 ophthalmologists (93%) agreed on the classification of 4 additional images (15%). Of these 11 images with at least 93% agreement, notching was reported as absent in 3 (27%) and to the edge in 8 (73%). In the remaining 15 images, there was substantial disagreement about whether notching was present and, if so, whether it was to the edge. In an analysis of intraobserver agreement, none of the 10 ophthalmologists who completed the viewing a second time classified all eyes exactly the same as the first time, though 5 ophthalmologists made 4 or fewer reclassifications. Overall, 80% of the original classifications were reproduced on second reading. Of the initial classifications that were not reproduced, slightly more than half were first classified as having notching not to the edge. CONCLUSION: Without definitions or examples of optic disc rim notching, the glaucoma subspecialists had relatively high intraobserver agreement but were likely to disagree with each other in characterizing the degree of disc rim notching. We recommend development of a standard photographic classification of disc rim notching. The classification should be tested for inter- and intra-observer agreement.

Gaasterland, D E; Blackwell, B; Dally, L G; Caprioli, J; Katz, L J; Ederer, F

2001-01-01

179

Characterization of the optic disc in retinal imagery using a probabilistic approach  

NASA Astrophysics Data System (ADS)

The application of computer based image analysis to the diagnosis of retinal disease is rapidly becoming a reality due to the broad-based acceptance of electronic imaging devices throughout the medical community and through the collection and accumulation of large patient histories in picture archiving and communications systems. Advances in the imaging of ocular anatomy and pathology can now provide data to diagnose and quantify specific diseases such as diabetic retinopathy (DR). Visual disability and blindness have a profound socioeconomic impact upon the diabetic population and DR is the leading cause of new blindness in working-age adults in the industrialized world. To reduce the impact of diabetes on vision loss, robust automation is required to achieve productive computer-based screening of large at-risk populations at lower cost. Through this research we are developing automation methods for locating and characterizing important structures in the human retina such as the vascular arcades, optic nerve, macula, and lesions. In this paper we present results for the automatic detection of the optic nerve using digital red-free fundus photography. Our method relies on the accurate segmentation of the vasculature of the retina along with spatial probability distributions describing the luminance across the retina and the density, average thickness, and average orientation of the vasculature in relation to the position of the optic nerve. With these features and other prior knowledge, we predict the location of the optic nerve in the retina using a two-class, Bayesian classifier. We report 81% detection performance on a broad range of red-free fundus images representing a population of over 345 patients with 19 different pathologies associated with DR.

Tobin, Kenneth W., Jr.; Chaum, Edward; Govindasamy, V. P.; Karnowski, Thomas P.; Sezer, Omer

2006-03-01

180

Adaptive phase locked loop to improve the readability of optical disc drive  

Microsoft Academic Search

An adaptive PLL is proposed to improve the readability of ODD. The proposed PLL is designed by using Kalman filter and implemented in a commercial ODD. Contrary to the conventional fixed PLL, the adaptive PLL can meet flexibly various situations such as eccentricity, deflection, and defect of rotating discs. The experimental results show that the proposed adaptive PLL is superior

D. H. Yeom

2009-01-01

181

Function and morphology in macular retinoschisis associated with optic disc pit in a child before and after its spontaneous resolution.  

PubMed

Optic disc pit (ODP) is a rare congenital defect within the optic nerve head. Macula elevation associated with ODP develops in 75-93% of the adult patients. Macular involvement in children with optic disc pit is rare, and only a few cases have been published to date. In the present case, we have observed morphology and function of the central retina in a child with ODP-associated macular detachment and following its spontaneous resolution. An 8-year-old white boy diagnosed with a macular detachment in an eye with an ODP. Optical coherent tomography (OCT) and multifocal electroretinography (mfERG), as well as visual acuity and visual field, were performed in the follow-up of the unilateral schisis-like retinal detachment. A large retinoschisis associated with ODP in a child showed a tendency to spontaneously resolve at 3 months, which was confirmed on OCT. At this time, an mfERG revealed markedly reduced responses. Despite morphologic reattachment at follow-up and improvement in visual acuity, increased mfERG responses were still not the same as in the fellow healthy eye. In contrast to the OCT which is very helpful to assess the extent of the neurosensory detachment, the mfERG offers an additional tool for follow-up of retinal function in this disorder. The good visual outcome in our patient shows that in the presence of residual retinal function on mfERG and in the absence of further lesions on OCT, follow-up is a valid option in children with an ODP-associated macular detachment. PMID:22322392

Polunina, Anna A; Todorova, Margarita G; Palmowski-Wolfe, Anja M

2012-04-01

182

Lumbar Disc Herniation in Adolescence  

Microsoft Academic Search

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

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

2007-01-01

183

Mechanism enabling the observation of the formally optically-forbidden 2Ag- and 1Bu- states in resonance-Raman excitation profiles of spheroidene in KBr disc  

NASA Astrophysics Data System (ADS)

An expression for the Albrecht A-term resonance-Raman excitation profiles (RREP) of a pigment dispersed in a KBr disc, in such a way that the pigment molecules aggregate in a microcrystal and the microcrystals are dispersed in the KBr disc, is formulated by taking into account the self-absorption of incident and scattered light and the distribution of microcrystals properly. Based on the resultant formula, simulations for the RREPs of spheroidene dispersed in KBr disc were carried out in the spectral region from 12,000 to 24,000 cm -1. Fairly good agreement between the simulations and the observed RREPs was obtained for different concentrations of spheroidene. Mechanisms have been investigated which enable the observation of the formally optically-forbidden (very weakly allowed) 2Ag- and 1Bu- states of spheroidne in RREPs free from the contribution of the optically-allowed 1Bu+ state, and a two-step self-absorption mechanism is proposed.

Nagae, Hiroyoshi; Koyama, Yasushi

2010-07-01

184

Determination of cup-to-disc ratio of optical nerve head for diagnosis of glaucoma on stereo retinal fundus image pairs  

NASA Astrophysics Data System (ADS)

A large cup-to-disc (C/D) ratio, which is the ratio of the diameter of the depression (cup) to that of the optical nerve head (ONH, disc), can be one of the important signs for diagnosis of glaucoma. Eighty eyes, including 25 eyes with the signs of glaucoma, were imaged by a stereo retinal fundus camera. An ophthalmologist provided the outlines of cup and disc on a regular monitor and on the stereo display. The depth image of the ONH was created by determining the corresponding pixels in a pair of images based on the correlation coefficient in localized regions. The areas of the disc and cup were determined by use of the red component in one of the color images and by use of the depth image, respectively. The C/D ratio was determined based on the largest vertical lengths in the cup and disc areas, which was then compared with that by the ophthalmologist. The disc areas determined by the computerized method agreed relatively well with those determined by the ophthalmologist, whereas the agreement for the cup areas was somewhat lower. When C/D ratios were employed for distinction between the glaucomatous and non-glaucomatous eyes, the area under the receiver operating characteristic curve (AUC) was 0.83. The computerized analysis of ONH can be useful for diagnosis of glaucoma.

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

2009-02-01

185

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

PubMed

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

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

2011-12-01

186

A search for eclipsing binaries that host discs  

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

187

Optics in the Age of Euler  

NASA Astrophysics Data System (ADS)

This book studies the eighteenth-century origins and early phase of a fundamental debate in optics: whether light is a particle or wave. Specifically, it is the first in-depth study of the contents and reception of Leonhard Euler's wave theory of light. The author shows that contrary to what has been assumed, the debate did not start in 1672 with Newton's particle theory of light. Rather, it only really got under way after Euler published his wave theory in 1746. He also corrects the misapprehension that Newton's theory was prevalently held in Germany in the early years of the debate, but really only became dominant around 1795. In his discussion, Professor Hakfoort demonstrates in dramatic fashion the relevance of chemical experiments on physical optics. Finally, in the epilogue, the author reflects on the mathematical, experimental, and metaphysical aspects of physical optics that shaped early modern science.

Hakfoort, Casper

1995-01-01

188

Fast and Robust Optic Disc Detection using Pyramidal Decomposition and Hausdorff-based Template Matching  

Microsoft Academic Search

Reports on the design and test of an image processing algorithm for the localization of the optic disk (OD) in low-resolution (about 20 \\\\?\\/pixel) color fundus images. The design relies on the combination of two procedures: 1) a Hausdorff-based template matching technique on edge map, guided by 2) a pyramidal decomposition for large scale object tracking. The two approaches are

Marc Lalonde; Mario Beaulieu; Langis Gagnon

2001-01-01

189

Correlation of Blue Chromatic Macular Sensitivity with Optic Disc Change in Early Glaucoma Patients  

Microsoft Academic Search

Purpose: To investigate the relationship between morphological changes of the optic nerve head (ONH) and macular sensitivity determined with blue on yellow (B on Y) and white on white (W on W) perimetry in normal subjects and patients with glaucoma.Methods: One randomly chosen eye was evaluated in each of 28 healthy subjects, 23 patients with ocular hypertension (OH), and 23

Yoshio Yamazaki; Kenji Mizuki; Fukuko Hayamizu; Chizuru Tanaka

2002-01-01

190

Free space optical communications: coming of age  

NASA Astrophysics Data System (ADS)

Information superiority, where for the military or business, is the decisive advantage of the 21st Century. While business enjoys the information advantage of robust, high-bandwidth fiber optic connectivity that heavily leverages installed commercial infrastructure and service providers, mobile military forces need the wireless equivalent to leverage that advantage. In other words, an ability to deploy anywhere on the globe and maintain a robust, reliable communications and connectivity infrastructure, equivalent to that enjoyed by a CONUS commercial user, will provide US forces with information superiority. Assured high-data-rate connectivity to the tactical user is the biggest gap in developing and truly exploiting the potential of the information superiority weapon. Though information superiority is much discussed and its potential is well understood, a robust communications network available to the lowest military echelons is not yet an integral part of the force structure, although high data rate RF communications relays, e.g., Tactical Common Data Link, and low data SATCOM, e.g, Ku Spread Spectrum, are deployed and used by the military. This may change with recent advances in laser communications technologies created by the fiber optic communications revolution. This paper will provide a high level overview of the various laser communications programs conducted over the last 30 plus years, and proposed efforts to get these systems finally deployed.

Stotts, Larry B.; Stadler, Brian; Lee, Gary

2008-05-01

191

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

Microsoft Academic Search

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

Huiyu Zhou; Gerald Schaefer; Tangwei Liu; Faquan Lin

2010-01-01

192

Macular Pigment Optical Density in an Ageing Irish Population: The Irish Longitudinal Study on Ageing  

Microsoft Academic Search

Purpose: The 3 carotenoids lutein, zeaxanthin, and meso-zeaxanthin, which account for the ‘yellow spot’ at the macula and which are referred to as macular pigment (MP), are believed to play a role in visual function and protect against age-related macular degeneration (AMD) via their optical and antioxidant properties. This study was undertaken to compare MP optical density (MPOD) in a

John M. Nolan; Roseanne Kenny; Claire O’Regan; Hilary Cronin; James Loughman; Eithne E. Connolly; Patricia Kearney; Edward Loane; Stephen Beatty

2010-01-01

193

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

PubMed

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

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

2010-11-01

194

Optic disc swelling and vision loss in a patient with cystic fibrosis and diabetes.  

PubMed

Advances in cystic fibrosis management have significantly improved life expectancy in these patients. However, we are now faced with a growing number of long-term extrapulmonary consequences of this disease, including ophthalmic complications of diabetes in cystic fibrosis patients. We present a unique report that documents a case of diabetic papillopathy progressing to nonarteritic anterior ischemic optic neuropathy resulting in vision loss in a patient with CF and diabetes. It highlights the potentially devastating consequences of longstanding diabetes in CF patients. PMID:24024047

Iosfina, Ioulia; Chuo, Jean Y; Godinho, Derek V; Wilcox, Pearce G; Kreisman, Stuart H; Quon, Bradley S

2013-01-01

195

The Coming of Age of Adaptive Optics  

NASA Astrophysics Data System (ADS)

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

1995-10-01

196

Aging and drug-induced optic nerve side effects.  

PubMed

In this review the authors attempt to explain how aging can determine optic nerve neuropathy and modify the pharmacodynamics and pharmacokinetics of a drug. The major causes of increased drug toxicity in the elderly are discussed. The most frequently used drugs that can cause optic nerve side effects are reported. The authors stress problems related to drug administration in the elderly and push towards the study of this aspect of geriatric ophthalmology. PMID:2671587

Dorigo, M T; Altafini, R

1989-01-01

197

Optical polarimetry and thermal imaging of the disc around Beta Pictoris  

NASA Technical Reports Server (NTRS)

The dust disk around the main-sequence A5 star Beta Pic is characterized on the basis of recently obtained data. Optical polarimetry indicates that the disk has polarization of about 15 percent and polarization vectors normal to the scattering plane, indicating that the features observed are indeed a dust disk made visible by scattering. Thermal images of the central 13-arcsec-diameter region, obtained at 10 and 20 microns by Telesco et al. (1988) using the NASA Marshall 20-pixel bolometer array, suggest that the dust grains in the disk have a mean diameter of 1 micron or smaller. Also discussed are (1) unsuccessful searches for other nearby stars with disks and (2) the potential value of Hubble Space Telescope images for understanding the structure of Beta Pic.

Wolstencroft, R. D.; Scarrott, S. M.; Warren-Smith, R. F.; Telesco, C. M.; Decher, R.

1989-01-01

198

Bilateral ischemic optic neuropathy after transurethral prostatic resection: a case report  

Microsoft Academic Search

BACKGROUND: Nonarteritic ischemic optic neuropathy affects the anterior portion of the optic nerve and is characterized by sudden, painless visual loss. The affected eye has a relative afferent pupillary defect. The typical funduscopic appearance includes optic disc edema, with associated nerve fiber layer hemorrhage. Risk factors include advanced age, systemic hypertension, nocturnal hypotension, diabetes mellitus, and a small cup-to-disc ratio.

Luis M Sadaba; Alfredo Garcia-Layana; Miguel J Maldonado; Jose M Berian

2006-01-01

199

Progress towards automated detection and characterization of the optic disc in glaucoma and diabetic retinopathy.  

PubMed

The shape and appearance of the optic nerve head region are sensitive to changes associated with glaucoma and diabetes that may be otherwise asymptomatic. The changes can be diagnostic of the diseases, and tracking of the changes in sequential images can be used to assess treatment and the progress of the illness. At present, change detection and tracking are performed manually, which can be a cause of poor repeatability. We are concerned with developing automated techniques of generating quantitative descriptions of the retinal images that might be used in diagnosis and assessment. In this paper, we investigate the use of images that have been collected and stored remotely, as this will replicate capture and automated processing by outreach clinics. Normal and abnormal images were collected from a range of sources, to simulate the mass screening process. The images were processed using simple signal-processing methods and divided into two groups. Using a chi-squared test, the separation of normal and abnormal images using this test was found to be highly significant (p < 0.05, n = 60). PMID:17365641

Abdel-Ghafar, R A; Morris, T

2007-03-01

200

Density impact of doped ZnO discs on the structural, electrical and optical properties in the ohmic region  

NASA Astrophysics Data System (ADS)

The influence of different densities of doped ZnO discs on their structural, electrical and optical properties has been studied in this work by measuring the average grain size, resistivity, critical frequency, critical capacitance and energy band gap as functions of density. The microstructure of ZnO material has been investigated by a combination of X-ray diffractometry (XRD) and analytical electron microscopy (SEM, EDX). Doped ZnO has a large number of grains and grain boundaries, which are observed to be very disordered. Every sample has a different densities depending on the different grain size, which had a major effect on the properties of ZnO. There are also a considerable number of pores which depend on the size and the shape of grains. The voltage (V) against the current (I) curves, revealed a high linear (ohmic) relationship, mainly in sample B4, which represented the highest density value (5.486 g/cm3), highest resistivity value (0.46 G?.cm), and maximum capacitive critical frequency (48.23 MHz). However, the critical capacitance value (1.21 nF) decreased at a higher density, which could be due to the high traps. The photoluminescent measurements showed that the doped ZnO had a strong ultraviolet emission at around 381nm and a weak red emission around 650 nm. The results from PL spectroscopy revealed the band gap energy of ZnO (ranged from 3.25 eV to 3.29 eV), which increased gradually with density, depending on the grain boundaries barrier.

Sendi, Rabab Khalid; Mahmud, Shahrom

2012-09-01

201

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

PubMed Central

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.

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

202

Lumbar disc syndrome in Finland  

Microsoft Academic Search

The prevalence of lumbar disc syndrome (herniated disc or typical sciatica) and its consequences in terms of disability, handicap, and need for medical care were studied as part of the Mini-Finland Health Survey. A sample of 8000 persons representative of the Finnish population aged 30 or over was asked to come for examination, and 7217 (90%) participated. A diagnosis of

M Heliövaara; O Impivaara; K Sievers; T Melkas; P Knekt; J Korpi; A Aromaa

1987-01-01

203

Pathophysiology of Degenerative Disc Disease  

PubMed Central

The intervertebral disc is characterized by a tension-resisting annulus fibrosus and a compression-resisting nucleus pulposus composed largely of proteoglycan. The most important function of the annulus and nucleus is to provide mechanical stability to the disc. Degenerative disc disease in the lumbar spine is a serious health problem. Although the three joint complex model of the degenerative process is widely accepted, the etiological basis of this degeneration is poorly understood. With the recent progress in molecular biology and modern biological techniques, there has been dramatic improvement in the understanding of aging and degenerative changes of the disc. Knowledge of the pathophysiology of the disc degeneration can help in the appropriate choice of treatment and to develop tissue engineering for biological restoration of degenerated discs.

2009-01-01

204

Combined Anti-Inflammatory and Anti-AGE Drug Treatments Have a Protective Effect on Intervertebral Discs in Mice with Diabetes  

PubMed Central

Objective Diabetes and low back pain are debilitating diseases and modern epidemics. Diabetes and obesity are also highly correlated with intervertebral disc (IVD) degeneration and back pain. Advanced-glycation-end-products (AGEs) increase reactive-oxygen-species (ROS) and inflammation, and are one cause for early development of diabetes mellitus. We hypothesize that diabetes results in accumulation of AGEs in spines and associated spinal pathology via increased catabolism. We present a mouse model showing that: 1) diabetes induces pathological changes to structure and composition of IVDs and vertebrae; 2) diabetes is associated with accumulation of AGEs, TNF?, and increased catabolism spinal structures; and 3) oral-treatments with a combination of anti-inflammatory and anti-AGE drugs mitigate these diabetes-induced degenerative changes to the spine. Methods Three age-matched groups of ROP-Os mice were compared: non-diabetic, diabetic (streptozotocin (STZ)-induced), or diabetic mice treated with pentosan-polysulfate (anti-inflammatory) and pyridoxamine (AGE-inhibitor). Mice were euthanized and vertebra-IVD segments were analyzed by ?CT, histology and Immunohistochemistry. Results Diabetic mice exhibited several pathological changes including loss in IVD height, decreased vertebral bone mass, decreased glycosaminoglycan content and morphologically altered IVDs with focal deposition of tissues highly expressing TNF?, MMP-13 and ADAMTS-5. Accumulation of larger amounts of methylglyoxal suggested that AGE accumulation was associated with these diabetic degenerative changes. However, treatment prevented or reduced these pathological effects on vertebrae and IVD. Conclusion This is the first study to demonstrate specific degenerative changes to nucleus pulposus (NP) morphology and their association with AGE accumulation in a diabetic mouse model. Furthermore, this is the first study to demonstrate that oral-treatments can inhibit AGE-induced ROS and inflammation in spinal structures and provide a potential treatment to slow progression of degenerative spine changes in diabetes. Since diabetes, IVD degeneration, and accumulation of AGEs are frequent consequences of aging, early treatments to reduce AGE-induced ROS and Inflammation may have broad public-health implications.

Illien-Junger, Svenja; Grosjean, Fabrizio; Laudier, Damien M.; Vlassara, Helen; Striker, Gary E.; Iatridis, James C.

2013-01-01

205

Absence of age-related optic disk changes in young children with optic nerve hypoplasia.  

PubMed

PurposeTo determine whether the ratio of optic disk diameter to disk-to-macula distance (DD/DM) in children with optic nerve hypoplasia (ONH) changes over time.Patients and methodsFifteen subjects (29 eyes) enrolled in a prospective registry study on ONH had fundus photography performed under the age of 24 months and again at 60 months. Using the ratio of the DD/DM method, the relative size of the optic disk was assessed twice for each photo by one masked expert examiner to determine whether any change in relative disk size occurred over time.ResultsThere was no change in relative optic disk size between initial and final fundus photographs. The average (±SD) age at the time of initial and final fundus photography was, respectively, 11.6±5.2 months and 60.6±1.3 months. Strong concordance was noted between the average DD/DM of the initial and the final photographs (?=0.939; 95% CI: 0.893, 0.981). There was negligible difference between the individual time point measurements (-0.011±0.03) (95% LOA: -0.07, 0.04).ConclusionThere were no clinically significant changes in relative optic disk size over time in children with ONH; thus, DD/DM measurements need not be adjusted by age beyond 1 year in children with this disorder. PMID:24556885

Sutedja, J; Garcia-Filion, P; Fink, C; Borchert, M

2014-05-01

206

Chemical and optical aging of forest fire plumes  

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

207

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

PubMed

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

Shahbeig, Saleh; Pourghassem, Hossein

2013-01-01

208

Disc Hemorrhages in Patients with both Normal Tension Glaucoma and Branch Retinal Vein Occlusion in Different Eyes  

PubMed Central

Purpose To document the clinical features of disc hemorrhage in patients with branch retinal vein occlusion (BRVO) and normal tension glaucoma (NTG), and to evaluate the relationship between BRVO and NTG with disc hemorrhages. Methods From July 2001 to May 2006, sixteen patients with both NTG and BRVO in different eyes were successively collected from outpatient population of Seoul National University Hospital in this observational case series. The frequency and location of disc hemorrhages, history of associated systemic diseases, and the order of the time of diagnosis between NTG and BRVO were studied. Results All patients had unilateral BRVO, and their mean age was 63.3±10.6 years. Disc hemorrhages were detected in eight patients (50%) during the mean follow-up of 26.8 months (range, 3-96 months). Six patients (75%) had disc hemorrhages in the non-BRVO eyes and two patients (25%) in BRVO eyes. Five hemorrhages (62.5%) were located at inferior-temporal quadrant of the optic disc. History of systemic hypertension was identified in 12 patients (75.0%). In 11 patients (68.8%), NTG was diagnosed at the same time as BRVO. Conclusions A higher frequency of disc hemorrhages was identified in patients with both BRVO and NTG. Therefore, some cases of NTG, especially with disc hemorrhages, may share a common vascular pathophysiology with BRVO.

Yoo, Young Cheol

2007-01-01

209

Percutaneous diode laser disc nucleoplasty  

NASA Astrophysics Data System (ADS)

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%.

Menchetti, P. P.; Longo, Leonardo

2004-09-01

210

Compact Disc Recordable with Substrate of Biomass Plastic Material  

NASA Astrophysics Data System (ADS)

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.

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

2006-08-01

211

Radiation fields in star-forming galaxies: the disc, thin disc and bulge  

NASA Astrophysics Data System (ADS)

We provide and describe a library of diffuse stellar radiation fields in spiral galaxies derived using calculations of the transfer of stellar radiation from the main morphological components - discs, thin discs and bulges - through the dusty interstellar medium. These radiation fields are self-consistent with the solutions for the integrated panchromatic spectral energy distributions (SEDs) previously presented using the same model. Because of this, observables calculated from the radiation fields, such as gamma-ray or radio emission, can be self-consistently combined with the solutions for the ultraviolet/optical/submillimetre SEDs, thus expanding the range of applicability of the radiation transfer model to a broader range of wavelengths and physical quantities. We also give analytic solutions for radiation fields in optically thin stellar discs, in stellar discs with one dust disc and in stellar discs with two dust discs. The analytic solutions for the direct light are exact and can be used as benchmarks. The analytic solutions with scattering are only approximate, becoming exact only in the extreme optically thick limit. We find strongly contrasting solutions for the spatial distribution of the radiation fields for discs, thin discs and bulges. For bulges, we find a strong dependence of the radiation fields on the Sérsic index.

Popescu, Cristina C.; Tuffs, Richard J.

2013-12-01

212

Disc-planet interactions in subkeplerian discs  

NASA Astrophysics Data System (ADS)

Context: One class of protoplanetary disc models, the X-wind model, predicts strongly subkeplerian orbital gas velocities, a configuration that can be sustained by magnetic tension. Aims: We investigate disc-planet interactions in these subkeplerian discs, focusing on orbital migration for low-mass planets and gap formation for high-mass planets. Methods: We use linear calculations and nonlinear hydrodynamical simulations to measure the torque and look at gap formation. In both cases, the subkeplerian nature of the disc is treated as a fixed external constraint. Results: We show that, depending on the degree to which the disc is subkeplerian, the torque on low-mass planets varies between the usual type I torque and the one-sided outer Lindblad torque, which is also negative but an order of magnitude stronger. In strongly subkeplerian discs, corotation effects can be ignored, making migration fast and inward. Gap formation near the planet's orbit is more difficult in such discs, since there are no resonances close to the planet accommodating angular momentum transport. The location of the gap is shifted inwards with respect to the planet, leaving the planet on the outside of a surface density depression. Conclusions: Depending on the degree to which a protoplanetary disc is subkeplerian, disc-planet interactions can be very different from the usual Keplerian picture, making these discs in general more hazardous for young planets.

Paardekooper, S.-J.

2009-11-01

213

Rapid evolution of the innermost dust disc of protoplanetary discs surrounding intermediate-mass stars  

NASA Astrophysics Data System (ADS)

We derived the intermediate-mass (?1.5-7 M?) disc fraction (IMDF) in the near-infrared JHK photometric bands as well as in the mid-infrared (MIR) bands for young clusters in the age range of 0 to ˜10 Myr. From the JHK IMDF, the lifetime of the innermost dust disc (˜0.3 au; hereafter the K disc) is estimated to be ˜3 Myr, suggesting a stellar mass (M*) dependence of K-disc lifetime (?1.5-7 M?). However, from the MIR IMDF, the lifetime of the inner disc (˜5 au; hereafter the MIR disc) is estimated to be ˜6.5 Myr, suggesting a very weak stellar mass dependence (M*). The much shorter K-disc lifetime compared to the MIR-disc lifetime for intermediate-mass (IM) stars suggests that IM stars with transition discs, which have only MIR excess emission but no K-band excess emission, are more common than classical Herbig Ae/Be stars, which exhibit both. We suggest that this prominent early disappearance of the K disc for IM stars is due to dust settling/growth in the protoplanetary disc, and it could be one of the major reasons for the paucity of close-in planets around IM stars.

Yasui, Chikako; Kobayashi, Naoto; Tokunaga, Alan T.; Saito, Masao

2014-08-01

214

Degeneration of the intervertebral disc  

PubMed Central

The intervertebral disc is a cartilaginous structure that resembles articular cartilage in its biochemistry, but morphologically it is clearly different. It shows degenerative and ageing changes earlier than does any other connective tissue in the body. It is believed to be important clinically because there is an association of disc degeneration with back pain. Current treatments are predominantly conservative or, less commonly, surgical; in many cases there is no clear diagnosis and therapy is considered inadequate. New developments, such as genetic and biological approaches, may allow better diagnosis and treatments in the future.

Urban, Jill PG; Roberts, Sally

2003-01-01

215

Adaptive optics-assisted optical coherence tomography for imaging of patients with age related macular degeneration  

NASA Astrophysics Data System (ADS)

We developed an optical coherence tomography (OCT) prototype with a sample arm that uses a 3.4 mm beam, which is considerably larger than the 1.2 to 1.5 mm beam that is used in commercialized OCT systems. The system is equipped with adaptive optics (AO), and to distinguish it from traditional AO-OCT systems with a larger 6 mm beam we have coined this concept AO-assisted OCT. Compared to commercialized OCT systems, the 3.4 mm aperture combined with AO improves light collection efficiency and imaging lateral resolution. In this paper, the performance of the AOa-OCT system was compared to a standard OCT system and demonstrated for imaging of age-related macular degeneration (AMD). Measurements were performed on the retinas of three human volunteers with healthy eyes and on one eye of a patient diagnosed with AMD. The AO-assisted OCT system imaged retinal structures of healthy human eyes and a patient eye affected by AMD with higher lateral resolution and a 9° by 9° field of view. This combination of a large isoplanatic patch and high lateral resolution can be expected to fill a gap between standard OCT with a 1.2 mm beam and conventional AO-OCT with a 6 mm beam and a 1.5° by 1.5° isoplanatic patch.

Sudo, Kenta; Cense, Barry

2013-03-01

216

In vivo evaluation of optic nerve aging in adult rhesus monkey by diffusion tensor imaging  

PubMed Central

Aging of the optic nerve can result in reduced visual sensitivity or vision loss. Normal optic nerve aging has been investigated previously in tissue specimens but poorly explored in vivo. In the present study, the normal aging of optic nerve was evaluated by diffusion tensor imaging (DTI) in non-human primates. Adult female rhesus monkeys at the ages of 9 to 13 years old (young group, n=8) and 21 to 27 years old (old group, n=7) were studied using parallel-imaging-based DTI on a clinical 3T scanner. Compared to young adults, the old monkeys showed 26% lower fractional anisotropy (P<0.01), and 44% greater radial diffusivity, although the latter difference was of marginal statistical significance (P=0.058). These MRI findings are largely consistent with published results of light and electron microscopic studies of optic nerve aging in macaque monkeys, which indicate a loss of fibers and degenerative changes in myelin sheaths.

Yan, Yumei; Li, Longchuan; Preuss, Todd M.; Hu, Xiaoping; Herndon, James G.

2014-01-01

217

Study of the shape of an optical window in a super-resolution state by electromagnetic-thermal coupled simulation: Effects of melting of an active layer in an optical disc  

NASA Astrophysics Data System (ADS)

We performed a multi-physics simulation for the propagation of electromagnetic waves and heat conduction in a super-resolution optical disc that includes an active layer of InSb. Because the change in the optical constant of InSb due to the phase transition is taken into account, the melting of the active layer can be realistically simulated in our calculation. It was found that in the case of an incident light power (P) of 2 mW, a profile of the electric field intensity transmitted through the InSb layer has an asymmetric shape with a narrow peak. This beam-narrowing was suggested to be an essential mechanism of the super-resolution, because a narrower light beam allows the detection of a smaller pit structure than the optical diffraction limit. This beam-narrowing was found to be originating from a small molten region produced in the InSb layer, which works as a mask for light exposure.

Sano, Haruyuki; Shima, Takayuki; Kuwahara, Masashi; Fujita, Yoshiya; Uchiyama, Munehisa; Aono, Yoshiyuki

2014-04-01

218

Automotive disc brake squeal  

NASA Astrophysics Data System (ADS)

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 this review accessible to a large audience, background sections on vibrations, contact and disc brake systems are also included.

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

2003-10-01

219

Quantitative evaluation of the optic nerve head in early glaucoma  

PubMed Central

AIMS—Progressive 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 between optic disc size and neuroretinal rim area, and (b) measuring rim area in a number of segments, in order to detect focal changes.?METHODS—Planimetric examination of the optic disc photographs of 88 control subjects and 51 patients with early visual field defects was performed. In the control group, multiple linear regression analysis was performed between neuroretinal rim area and optic disc area, age, sex, eye side, refraction, and keratometry. This was repeated for the whole disc and for each of twelve 30 degree segments. Normal ranges were defined by the 98% prediction intervals of the regression analysis and the sensitivity and specificity for correct identification of optic discs in the two groups determined.?RESULTS—Multiple linear regression demonstrated significant associations between the neuroretinal rim area and optic disc area and age in normal subjects. Sensitivity and specificity for glaucoma diagnosis, using the cut off derived from the 98% prediction intervals, was 37.7% and 98.9% respectively when total neuroretinal rim area alone was considered, and 88.7% and 94.3% respectively when the 30 degree segments were included. The most frequent pattern of neuroretinal rim loss was diffuse, followed by thinning in more than one sector and then by thinning in the inferotemporal sector alone.?CONCLUSIONS—This method of optic disc analysis enables the examiner to identify glaucomatous optic discs at the stage of early perimetric loss with a high degree of precision. Optic disc photography is simple, and fundus cameras are widely available. This method for glaucoma case identification may therefore be suitable for the primary care setting as well as hospital practice.?? Keywords: optic disc; glaucoma; case finding; imaging

Garway-Heath, D; Hitchings, R

1998-01-01

220

Evaluation of Carbon Nanotube Thin Films for Optically Transparent Microwave Applications Using On-Wafer Probing of Corbino Disc Test Structures.  

National Technical Information Service (NTIS)

We present a generalized technique, involving the on-wafer probing of Corbino disc test structures, for conveniently evaluating conducting films of arbitrary thickness in terms of complex conductivity and related physical parameters. Using this method, we...

E. H. Ngo J. B. Doggett M. P. Ivill R. C. Toonen S. G. Hirsch

2013-01-01

221

Liquid crystals of disc-like molecules  

Microsoft Academic Search

Thermotropic mesomorphism has been observed in pure compounds consisting of simple disc-like molecules, viz., benzene-hexa-n-alkanoates. Thermodynamic, optical and x-ray studies indicate that the mesophase is a highly ordered lamellar type of liquid\\u000a crystal. Based on the x-ray data, a structure is proposed in which the discs are stacked one on top of the other in columns\\u000a that constitute a hexagonal

S. Chandrasekhar; B K Sadashiva; K A Suresh

1977-01-01

222

Turbine disc sealing assembly  

DOEpatents

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.

Diakunchak, Ihor S.

2013-03-05

223

A study of axonal degeneration in the optic nerves of aging mice  

NASA Technical Reports Server (NTRS)

The optic nerves of C57BL/6J mice ranging from 3 to 30 months were examined by electron microscopy. At all ages investigated, optic nerve axons contained enlarged mitochondria with abnormal cristae. With increasing age, a large number of necrotic axons were observed and were in the process of being phagocytized. The abnormal mitochondria may represent preliminary changes that eventually lead to necrosis of the axon.

Johnson, J. E., Jr.; Philpott, D. E.; Miquel, J.

1978-01-01

224

Counterrotating stars in simulated galaxy discs  

NASA Astrophysics Data System (ADS)

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.

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

2014-02-01

225

Artificial Discs for Lumbar and Cervical Degenerative Disc Disease -Update  

PubMed Central

Executive Summary Objective To assess the safety and efficacy of artificial disc replacement (ADR) technology for degenerative disc disease (DDD). Clinical Need Degenerative disc disease is the term used to describe the deterioration of 1 or more intervertebral discs of the spine. The prevalence of DDD is roughly described in proportion to age such that 40% of people aged 40 years have DDD, increasing to 80% among those aged 80 years or older. Low back pain is a common symptom of lumbar DDD; neck and arm pain are common symptoms of cervical DDD. Nonsurgical treatments can be used to relieve pain and minimize disability associated with DDD. However, it is estimated that about 10% to 20% of people with lumbar DDD and up to 30% with cervical DDD will be unresponsive to nonsurgical treatments. In these cases, surgical treatment is considered. Spinal fusion (arthrodesis) is the process of fusing or joining 2 bones and is considered the surgical gold standard for DDD. Artificial disc replacement is the replacement of the degenerated intervertebral disc with an artificial disc in people with DDD of the lumbar or cervical spine that has been unresponsive to nonsurgical treatments for at least 6 months. Unlike spinal fusion, ADR preserves movement of the spine, which is thought to reduce or prevent the development of adjacent segment degeneration. Additionally, a bone graft is not required for ADR, and this alleviates complications, including bone graft donor site pain and pseudoarthrosis. It is estimated that about 5% of patients who require surgery for DDD will be candidates for ADR. Review Strategy The Medical Advisory Secretariat conducted a computerized search of the literature published between 2003 and September 2005 to answer the following questions: What is the effectiveness of ADR in people with DDD of the lumbar or cervical regions of the spine compared with spinal fusion surgery? Does an artificial disc reduce the incidence of adjacent segment degeneration (ASD) compared with spinal fusion? What is the rate of major complications (device failure, reoperation) with artificial discs compared with surgical spinal fusion? One reviewer evaluated the internal validity of the primary studies using the criteria outlined in the Cochrane Musculoskeletal Injuries Group Quality Assessment Tool. The quality of concealment allocation was rated as: A, clearly yes; B, unclear; or C, clearly no. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) system was used to evaluate the overall quality of the body of evidence (defined as 1 or more studies) supporting the research questions explored in this systematic review. A random effects model meta-analysis was conducted when data were available from 2 or more randomized controlled trials (RCTs) and when there was no statistical and or clinical heterogeneity among studies. Bayesian analyses were undertaken to do the following: Examine the influence of missing data on clinical success rates; Compute the probability that artificial discs were superior to spinal fusion (on the basis of clinical success rates); Examine whether the results were sensitive to the choice of noninferiority margin. Summary of Findings The literature search yielded 140 citations. Of these, 1 Cochrane systematic review, 1 RCT, and 10 case series were included in this review. Unpublished data from an RCT reported in the grey literature were obtained from the manufacturer of the device. The search also yielded 8 health technology assessments evaluating ADR that are also included in this review. Six of the 8 health technology assessments concluded that there is insufficient evidence to support the use of either lumbar or cervical ADR. The results of the remaining 2 assessments (one each for lumbar and cervical ADR) led to a National Institute for Clinical Excellence guidance document supporting the safety and effectiveness of lumbar and cervical ADR with the proviso that an ongoing audit of all clinical outcomes be undertaken owing to a lack of long-term outcome data from clinical trials. Regard

2006-01-01

226

Autonomous Optical Sensor System for the Monitoring of Nitrogen Dioxide from Aging Rocket Propellant  

Microsoft Academic Search

An optical sensor system has been developed for the autonomous monitoring of NOâ evolution in energetic material aging studies. The system is minimally invasive, requiring only the presence of a small sensor film within the aging chamber. The sensor material is a perylene\\/PMMA film that is excited by a blue LED light source and the fluorescence detected with a CCD

TRISHA D. COX; SEEMA SINGH; JOHN A. HUNTER; GARY D. JONES; MICHAEL B. SINCLAIR; LAUREN E. S. ROHWER; PHILLIP I. POHL; WILLIAM ANDRZEJEWSKI; DARRYL Y. SASAKI

2001-01-01

227

Presbyopia and the optical changes in the human crystalline lens with age  

Microsoft Academic Search

Lenses from 27 human eyes ranging in age from 10 to 87 years were used to determine how accommodation and age affect the optical properties of the lens. A scanning laser technique was used to measure focal length and spherical aberration of the lenses, while the lenses were subjected to stretching forces applied through the ciliary body\\/zonular complex. The focal

Adrian Glasser; Melanie C. W. Campbell

1998-01-01

228

[Optical hallucinations in the aged with diseases of the eye].  

PubMed

Two cases of Charles Bonnet Syndrome (CBS) showing an unusual history are reported. In a 67-year-old man visual hallucinations developed 38 years after bilateral optic nerve damage due to methyl alcohol poisoning. A 78-year-old woman suffering from bilateral advanced cataract experienced visual hallucinations which ceased after improvement of vision resulting from cataract extraction. Sensory deprivation and--possibly--central neurophysiological disturbance are to be regarded as important pathogenetic factors. Signs of cerebral dysfunction which could be relevant to the pathogenesis of CBS were revealed by the EEG. PMID:3660920

Olbrich, H M; Lodemann, E; Engelmeier, M P

1987-01-01

229

Spectroscopic Parameters of Lumbar Intervertebral Disc Material  

NASA Astrophysics Data System (ADS)

There are numerous methods of investigating intervertebral disc. Visualization methods are widely used in clinical practice. Histological, imunohistochemical and biochemical methods are more used in scientific research. We propose that a new spectroscopic investigation would be useful in determining intervertebral disc material, especially when no histological specimens are available. Purpose: to determine spectroscopic parameters of intervertebral disc material; to determine emission spectra common for all intervertebral discs; to create a background for further spectroscopic investigation where no histological specimen will be available. Material and Methods: 20 patients, 68 frozen sections of 20 ?m thickness from operatively removed intervertebral disc hernia were excited by Nd:YAG microlaser STA-01-TH third harmonic 355 nm light throw 0, 1 mm fiber. Spectrophotometer OceanOptics USB2000 was used for spectra collection. Mathematical analysis of spectra was performed by ORIGIN multiple Gaussian peaks analysis. Results: In each specimen of disc hernia were found distinct maximal spectral peaks of 4 types supporting the histological evaluation of mixture content of the hernia. Fluorescence in the spectral regions 370-700 nm was detected in the disc hernias. The main spectral component was at 494 nm and the contribution of the components with the peak wavelength values at 388 nm, 412 nm and 435+/-5 nm were varying in the different groups of samples. In comparison to average spectrum of all cases, there are 4 groups of different spectral signatures in the region 400-500 nm in the patient groups, supporting a clinical data on different clinical features of the patients. Discussion and Conclusion: besides the classical open discectomy, new minimally invasive techniques of treating intervertebral disc emerge (PLDD). Intervertebral disc in these techniques is assessed by needle, no histological specimen is taken. Spectroscopic investigation via fiber optics through the needle can give additional information of needle position, assuring the needle tip is directed into intervertebral disc material. Spectroscopic analysis of intervertebral disc removed during open surgery, creates background for further investigation on intervertebral disc degeneration spectral classification.

Terbetas, G.; Kozlovskaja, A.; Varanius, D.; Graziene, V.; Vaitkus, J.; Vaitkuviene, A.

2009-06-01

230

Childhood intervertebral disc calcification  

Microsoft Academic Search

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

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

1993-01-01

231

Twin Disc Gear Tooth Simulator.  

National Technical Information Service (NTIS)

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 lo...

M. W. Eusepi J. F. Dill

1994-01-01

232

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

PubMed Central

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.

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

2012-01-01

233

Multi-month thermal aging of electro-optic polymer waveguides: Synthesis, fabrication, and relaxation modeling  

Microsoft Academic Search

The preparation of polyimides containing side-chain chromophores and the long-term aging performance of poled films are described. These materials were compared to guest–host polycarbonate films. Mach–Zehnder optical interferometers were fabricated from these polymers that contained CLD- and FTC-type chromophores. Changes in optical properties were monitored for months at four temperatures ranging from ambient to 110°C. The isothermal relaxation data were

Geoffrey A. Lindsay; Andrew J. Guenthner; Michael E. Wright; Mohan Sanghadasa; Paul R. Ashley

2007-01-01

234

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

NASA Astrophysics Data System (ADS)

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.

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

2011-09-01

235

Changes in diffusion path length with old age in diffuse optical tomography  

NASA Astrophysics Data System (ADS)

Diffuse, optical near infrared imaging is increasingly being used in various neurocognitive contexts where changes in optical signals are interpreted through activation maps. Statistical population comparison of different age or clinical groups rely on the relative homogeneous distribution of measurements across subjects in order to infer changes in brain function. In the context of an increasing use of diffuse optical imaging with older adult populations, changes in tissue properties and anatomy with age adds additional confounds. Few studies investigated these changes with age. Duncan et al. measured the so-called diffusion path length factor (DPF) in a large population but did not explore beyond the age of 51 after which physiological and anatomical changes are expected to occur [Pediatr. Res. 39(5), 889-894 (1996)]. With increasing interest in studying the geriatric population with optical imaging, we studied changes in tissue properties in young and old subjects using both magnetic resonance imaging (MRI)-guided Monte-Carlo simulations and time-domain diffuse optical imaging. Our results, measured in the frontal cortex, show changes in DPF that are smaller than previously measured by Duncan et al. in a younger population. The origin of these changes are studied using simulations and experimental measures.

Bonnéry, Clément; Leclerc, Paul-Olivier; Desjardins, Michèle; Hoge, Rick; Bherer, Louis; Pouliot, Philippe; Lesage, Frédéric

2012-05-01

236

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

NASA Astrophysics Data System (ADS)

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.

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

2002-01-01

237

The effectiveness of percutaneous laser disc decompression for the prolapsed lumbar intervertebral disc  

NASA Astrophysics Data System (ADS)

Objective: to investigate the role of associated factors in the effectiveness of laser treatment for prolapsed lumber intervertebral disc. Method: 302 prolapsed lumber intervertebral discs in 212 patients were treated with percutaneous laser disc decompression (PLDD). Patients were followed up by 12month, the associated factors which affecting the effectiveness of treatment, ie age, duration of illness were analyzed. Results: Punctual Success rate was 100%. After 12 month's follow up, 86% successful outcomes were obtained, in which 93% successful outcomes were obtained in patients less than 50 years old, 92% successful outcomes was obtained in the patients whose duration of illness less than 1 year.

Mu, Ming Wei; Liu, Wei; Feng, Wei; Ma, Nan

2009-07-01

238

Angles in fuzzy disc and angular noncommutative solitons  

NASA Astrophysics Data System (ADS)

The fuzzy disc, introduced by the authors of [1], is a disc-shaped region in a noncommutative plane, and is a fuzzy approximation of a commutative disc. In this paper we show that one can introduce a concept of angles to the fuzzy disc, by using the phase operator and phase states known in quantum optics. We gave a description of the fuzzy disc in terms of operators and their commutation relations, and studied properties of angular projection operators. A similar construction for the fuzzy annulus is also given. As an application, we constructed fan-shaped soliton solutions of a scalar field theory on the fuzzy disc. We also applied this concept to the theory of noncommutative gravity we proposed in [2]. In addition, possible connections to some systems in physics are suggested.

Kobayashi, Shinpei; Asakawa, Tsuguhiko

2013-04-01

239

New Laser Labeling Technology for Recordable Digital Versatile Disc  

NASA Astrophysics Data System (ADS)

A new labeling technology, i.e., “LabelflashTM”, is reported. This technology uses the digital versatile disc (DVD) drive data recording head to burn high-quality images directly into a specialized dye layer on the label side of DVD discs. The basic structure of the disc is similar to a conventional double-sided recordable digital versatile disc (DVD-R). Consequently, a Labelflash disc shows various features as follows: non consumable, no special optical path or drive control system, the same working distance as that for data recording, manufactured using conventional equipment for double-sided DVD-R, fast drawing speed, high durability, and professional appearance. Moreover, four color variation types and mat-type discs were developped. The graphic quality performance index for Labelflash was newly proposed. The values were closely matched by the subjective evaluations of contrast.

Kubo, Hiroshi; Shibata, Michihiro; Yamada, Seiya; Itoga, Hisanori; Fushiki, Tatsuo

2007-06-01

240

Optic Pathway Hypothalamic Gliomas in Children under Three Years of Age: The Role of Chemotherapy  

Microsoft Academic Search

Objectives: Optic pathway\\/hypothalamic gliomas (OPHGs) tend to occur in young children. Treatment options consist of surgical resection, radiation therapy (RT) and chemotherapy. Due to complications induced by surgery and RT, chemotherapy has gained significant recognition for the treatment of OPHG in young children. Chemosensitivity of OPHG in very young children under 3 years of age has not been well documented.

Michele Madeira Silva; Stewart Goldman; Gesina Keating; Mary Anne Marymont; John Kalapurakal; Tadanori Tomita

2000-01-01

241

Pseudopapilledema and congenital disc anomalies in growth hormone deficiency.  

PubMed

Optic nerve hypoplasia is a congenital disc anomaly associated with growth hormone deficiency (GHD). Pseudotumor cerebri is an adverse event associated with growth hormone treatment (hGH) and manifested by increased intracranial pressure and papilledema. Pseudopapilledema is a generic ophthalmologic term encompassing several conditions, including congenital disc anomalies. It is benign and can be distinguished from papilledema by physical examination. The objective of this report is to document that congenital disc abnormalities, which can be confused with papilledema, occur in children with GHD. Three patients with GHD had fundoscopic examinations suggestive of papilledema and possibly pseudotumor cerebri. The abnormal optic nerves were characteristic of pseudo-papilledema, and appear to be a variant of optic nerve hypoplasia. The finding of optic disc abnormality during hGH may reflect pseudo-papilledema and not pseudotumor cerebri. Of equal importance, the reported patients indicate that the finding of pseudopapilledema in short children should suggest the possibility of GHD. PMID:9642641

Collett-Solberg, P F; Liu, G T; Satin-Smith, M; Katz, L L; Moshang, T

1998-01-01

242

Gas Modelling in the Disc of HD 163296.  

National Technical Information Service (NTIS)

We present detailed model fits to observations of the disc around the Herbig Ae star HD 163296. This well-studied object has an age of approx. 4Myr, with evidence of a circumstellar disc extending out to approx. 540AU. We use the radiation thermo-chemical...

A. Isella A. Mora A. Roberge B. Montesinos C. Eiroa C. Martin-Zaidi C. Pinte F. Menard G. Aresu G. Duchene G. Meeus G. Sandell I. Kamp I. Mendigutia I. Tilling M. Spaans P. Riviere-Marichalar P. Woitke R. Meijerink W. D. Vacca W. F. Thi W. R. F. Dent

2011-01-01

243

Modeling the strengthening response to aging process of heat-treatable aluminum alloys containing plate\\/disc- or rod\\/needle-shaped precipitates  

Microsoft Academic Search

For the heat-treatable aluminum alloys containing plate or rod\\/needle-shaped precipitates, a previous model was modified to present quantitative relationships between the yield strengths of the alloys and the sizes, volume percentages of precipitates, related to aging temperature and aging time as well as alloy compositions, while the strengthening of the precipitates was coupled with the whole evolution process, i.e. nucleation,

G. Liu; G. J. Zhang; X. D. Ding; J. Sun; K. H. Chen

2003-01-01

244

Spontaneous regression of intervertebral disc calcifications in a child.  

PubMed

This article presents the case of a boy who complained of cervical and thoracic spine pain for the first time at the age of nine. Plain films of cervical and thoracic spine showed calcifications of intervertebral disc C4-C5, C5-C6, C6-C7 and D3-D4. The symptoms disappeared after conservative therapy. Plain films taken 16 months later showed spontaneous disappearance of all disc calcifications. This spontaneous regression of intervertebral disc calcifications in childhood has also been described in other cases reported in the medical literature. Except for the rare cases when disc calcifications are associated with disc herniation, the discovery of disc calcifications on a plain X-ray of a child corresponds to a benign abnormality. PMID:2065515

Ginalski, J M; Schnyder, P; Gerster, J C

1991-03-01

245

Herniated Cervical Disc  

MedlinePLUS

... are sometimes prescribed for more severe arm and neck pain because of their very powerful anti-inflammatory effect. ... caused by a herniated cervical disc. However, some neck pain may persist. Most patients respond well to discectomy; ...

246

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

PubMed Central

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.

Wenger, Markus; Markwalder, Thomas-Marc

2010-01-01

247

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

PubMed

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

Wenger, Markus; Markwalder, Thomas-Marc

2010-01-01

248

Optic disc boundary segmentation from diffeomorphic demons registration of monocular fundus image sequences versus 3D visualization of stereo fundus image pairs for automated early stage glaucoma assessment  

NASA Astrophysics Data System (ADS)

Despite the current availability in resource-rich regions of advanced technologies in scanning and 3-D imaging in current ophthalmology practice, world-wide screening tests for early detection and progression of glaucoma still consist of a variety of simple tools, including fundus image-based parameters such as CDR (cup to disc diameter ratio) and CAR (cup to disc area ratio), especially in resource -poor regions. Reliable automated computation of the relevant parameters from fundus image sequences requires robust non-rigid registration and segmentation techniques. Recent research work demonstrated that proper non-rigid registration of multi-view monocular fundus image sequences could result in acceptable segmentation of cup boundaries for automated computation of CAR and CDR. This research work introduces a composite diffeomorphic demons registration algorithm for segmentation of cup boundaries from a sequence of monocular images and compares the resulting CAR and CDR values with those computed manually by experts and from 3-D visualization of stereo pairs. Our preliminary results show that the automated computation of CDR and CAR from composite diffeomorphic segmentation of monocular image sequences yield values comparable with those from the other two techniques and thus may provide global healthcare with a cost-effective yet accurate tool for management of glaucoma in its early stage.

Gatti, Vijay; Hill, Jason; Mitra, Sunanda; Nutter, Brian

2014-03-01

249

Autonomous Optical Sensor System for the Monitoring of Nitrogen Dioxide from Aging Rocket Propellant  

SciTech Connect

An optical sensor system has been developed for the autonomous monitoring of NO{sub 2} evolution in energetic material aging studies. The system is minimally invasive, requiring only the presence of a small sensor film within the aging chamber. The sensor material is a perylene/PMMA film that is excited by a blue LED light source and the fluorescence detected with a CCD spectrometer. Detection of NO{sub 2} gas is done remotely through the glass window of the aging chamber. Irreversible reaction of NO{sub 2} with perylene, producing the non-fluorescent nitroperylene, provides the optical sensing scheme. The rate of fluorescence intensity loss over time can be modeled using a numerical solution to the coupled diffusion and a nonlinear chemical reaction problem to evaluate NO{sub 2} concentration levels. The light source, spectrometer, spectral acquisition, and data processing were controlled through a Labivew program run by a laptop PC. Due to the long times involved with materials aging studies the system was designed to turn on, warm up, acquire data, power itself off, then recycle at a specific time interval. This allowed the monitoring of aging HE material over the period of several weeks with minimal power consumption and stable LED light output. Despite inherent problems with gas leakage of the aging chamber they were able to test the sensor system in the field under an accelerated aging study of rocket propellant. They found that the propellant evolved NO{sub 2} at a rate that yielded a concentration of between 10 and 100 ppm. The sensor system further revealed that the propellant, over an aging period of 25 days, evolves NO{sub 2} with cyclic behavior between active and dormant periods.

COX, TRISHA D.; SINGH, SEEMA; HUNTER, JOHN A.; JONES, GARY D.; SINCLAIR, MICHAEL B.; ROHWER, LAUREN E. S.; POHL, PHILLIP I.; ANDRZEJEWSKI, WILLIAM; SASAKI, DARRYL Y.

2001-09-01

250

Radiation magnetohydrodynamics in global simulations of protoplanetary discs  

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

251

Magneto-optic\\/eddy current imaging of aging aircraft: A new NDI technique  

Microsoft Academic Search

An eddy current instrument called a magneto-optic\\/eddy current imager (MOI) has been developed for the purpose of nondestructive inspection (NDI) of aging aircraft. The MOI produces realistic, real-time, eddy current images of both surface-breaking fatigue cracks and hidden multilayer cracking or corrosion. While it also works on steel and titanium, the MOI was designed to yield optimum results on aluminum

G. L. Fitzpatrick; D. K. Thome; R. L. Skaugset; E. Y. C. Shih; W. C. L. Shih

1993-01-01

252

Far-infrared and sub-millimetre surveys of circumstellar discs  

NASA Astrophysics Data System (ADS)

Stars of all ages and evolutionary stages are seen to be surrounded by discs of material. During the formation of a stellar system the stars are orbited by a massive protoplanetary disc composed of interstellar gas and dust, in which planet formation occurs. Between 1 and 10 Myr the protoplanetary disc disperses, leaving behind the newly formed system of planets and smaller bodies. The remaining material which has not formed into planets is referred to as a debris disc. Even though the interstellar dust grains from the protoplanetary disc have long been removed from the system, debris discs can contain large quantities of dust due to collisions between larger bodies and cometary activity. Such dust can be detected by its thermal emission. This thesis focuses on observational studies at far-infrared and sub-millimetre wavelengths of debris discs and the late stages of protoplanetary disc evolution. An overview of surveys for debris discs performed to date is presented, highlighting the limitations and statistical biases. The motivation, design and sample selection for two large surveys for debris discs around nearby stars, with the Herschel space observatory and the SCUBA-2 sub-millimetre camera on the James Clerk Maxwell Telescope, are described. The combination of a uniform observational strategy, longer wavelengths than previous surveys, and a large, clearly chosen sample - unbiased by stellar properties - will allow robust statistical conclusions of how the incidence and properties of debris discs depend on system parameters such as stellar mass, age, metallicity, binarity, and the presence of planets. As a precursor to the Herschel and SCUBA-2 surveys, a volume-limited sample of 130 A type star systems was surveyed using observations at 24 and 70 ?m from the Spitzer space telescope. Stellar photosphere fluxes at 24 and 70 ?m, which were required to determine the presence of emission from dust, were predicted by fitting model flux distributions to optical and near-infrared photometry. Debris discs were detected around 46 systems, 12 of which - including the system with the largest dust mass - are new discoveries. This survey adds to the results of previous studies which show that debris disc incidence is not correlated with host star metallicity, despite the well known giant planet - metallicity correlation. This is in accordance with what is predicted from the core accretion theory of planet formation. The most significant result from this survey is that, contrary to results reported in a previous work, debris discs are overall less common around binary stars. Further investigation shows that systems with separations of ˜3-150 AU are especially deficient of debris, whilst closer binaries and the primaries of wider binaries show debris detection rates consistent with those for single stars. A sample of circumstellar discs around 29 young stellar systems with ages of 5-30 Myr were observed with the LABOCA sub-millimetre instrument on the APEX telescope at 870 ?m, to provide disc masses or mass upper limits in support of a large Herschel programme. These targets included the ? Chamaeleontis cluster and four bright Herbig Ae/Be stars which have not previously been observed at this wavelength. All but the Herbig Ae/Be stars were not detected, and 3? dust mass upper limits of ˜0.1-3M_? are determined, with corresponding total disc masses of ˜0.03-1M_{Jup}. These mass limits indicate that there is insufficient remaining material in these discs to form gas giant planets, and add to the prevailing view that protoplanetary discs typically disperse within 10 Myr and that gas giant planet formation must be completed before this time. A search for cold dust emission from two of the Solar System's nearest neighbours - ? Centauri AB and ? Indi - was also performed with LABOCA. In both cases no debris disc emission was detected. A bright resolved feature was detected near ? Centauri AB, however, follow-up observations at a second epoch, two years after the initial observations, showed that the feature is not co-moving w

Phillips, N. M.

2011-06-01

253

Radiographic evaluation of the lumbosacral disc height  

Microsoft Academic Search

Objective. To establish criteria for the radiographic evaluation of narrowing of the L5–S1 disc height, which varies widely with transition\\u000a of the L5 vertebra.\\u000a \\u000a \\u000a Design and patients. Nondegenerated disc heights of L3–4 to L5–S1 and the thickness and length of the L5 transverse process were measured on plain\\u000a radiographs of the lumbar spine in 166 outpatients, aged 18–35 years (mean

H. Inoue; K. Ohmori; K. Miyasaka; H. Hosoe

1999-01-01

254

Optical Coherence Tomography Reveals Regional Differences in Macular Thickness with Age  

PubMed Central

Purpose In order to assist identification of macular thickness abnormalities by optical coherence tomography (OCT), we use techniques that improve spatial localization across the retina to establish any age-related retinal thickness changes in healthy eyes. Methods Retinal thickness was measured in 30 eyes of 30 healthy subjects aged 13–69 years. Using Stratus OCT™ 3, twelve radial scans centered at the foveola were acquired and points between scans were interpolated to create a topographic map of the central 20°. The thickness map was divided into 37 hexagonal regions. A mean retinal thickness for each hexagon was computed. Retinal thickness versus age was evaluated for the entire scanned area, 5 anatomical regions, and within individual hexagons. The retinal nerve fiber layer (RNFL) contribution to total retinal thinning was analyzed in the papillomacular region. Results There was a small but significant thinning of the overall macular area with increasing age (2.7 ?m/decade; P = 0.027). Comparing the 10 youngest subjects (age 13–27) to the 10 oldest (age 51–68), retinal thicknesses in the temporal, superior, inferior and foveal regions were not significantly different. However, the two age groups differed significantly in retinal thickness in the nasal region (P < 0.008). Across all subjects retinal thickness in this region was linearly correlated with age, decreasing by 4.1?m/decade (P < 0.002). Approximately 43% of the retinal thinning in the nasal region was attributed to RNFL loss. Conclusions The method of OCT acquisition and analysis used in this study allows for greater spatial localization of change in retinal thickness due to age or pathological processes. Based on the results of this study, the macula thins with increasing age, but does so non-uniformly. The greatest amount of thinning occurs nasal to the fovea. RNFL loss accounts for much, but not all of, the thinning in this area.

Neuville, Jessica M.; Bronson-Castain, Kevin; Bearse, Marcus A.; Ng, Jason S.; Harrison, Wendy W.; Schneck, Marilyn E.; Adams, Anthony J.

2009-01-01

255

High Speed Rewritable Digital Versatile Disc Recording  

NASA Astrophysics Data System (ADS)

High speed rewritable digital versatile discs (DVD+RW) can be written well in a speed range from 3.3× to 8×. Special attention points for recording this type of discs are in the area of byte error rate (BER) and archival-overwrite. Archival-overwrite means that the disc is written with data, archived for some time and subsequently overwritten once. The cause of the high BER is unwanted nucleation near the trailing edge of the amorphous marks. This nucleation can be avoided by choosing proper cooling gap lengths in the write strategy. The raised jitter after archival-overwrite is caused by changes of the crystalline phase during aging. These changes might also endanger the reliability of the results of the optimum power control (OPC), which is performed prior to recording. By applying measures from both the drive side and the media side, a good archival-overwrite and a robust OPC-result is ensured.

van der Vleuten, M.; Spruit, H.; Elfrink, R.; Adelerhof, D. J.; van Dorst, P.; Wei, Gongming

2006-02-01

256

Inheritance of disc calcification in the dachshund.  

PubMed

The occurrence of intervertebral disc calcification was investigated by conventional spinal radiography in eight families of wirehaired dachshunds, with each family comprising one sire, two dams and one litter from each dam. Each offspring was examined radiographically once at 24-35 months of age. The occurrence of disc calcification was rated according to four different scales. A strong correlation was found in the occurrence of disc calcification between offspring and mean parent (P < 0.001) and between offspring and dams (P < 0.005) on an either/or scale. Statistically significant estimates of heritability of 0.60 and 0.87 were found based on the offspring-sire relationship using the total score and three-class scale, respectively. Higher correlation estimates were found based on the dam-offspring relationship than based on the sire-offspring relationship, suggesting an effect of maternal environmental factors. PMID:11008442

Jensen, V F; Christensen, K A

2000-08-01

257

Progression of Geographic Atrophy in Age-Related Macular Degeneration Imaged with Spectral Domain Optical Coherence Tomography  

PubMed Central

Purpose To determine the area and enlargement rate (ER) of geographic atrophy (GA) in patients with age-related macular degeneration (AMD) using the spectral-domain optical coherence tomography (SDOCT) fundus image. Design Prospective longitudinal natural history study Participants Eighty-six eyes of 64 patients with at least 6 months follow-up. Methods Patients with GA secondary to AMD were enrolled in this study. Macular scans were performed using the Cirrus SDOCT (Carl Zeiss Meditec, Dublin CA). The areas of GA identified on the SDOCT fundus images were quantified using a digitizing tablet. Reproducibility of these measurements was assessed and the ER of GA was calculated. The usefulness of performing square root transformations of the lesion area measurements was explored. Main Outcome Measure Enlargement rate of GA Results At baseline, 27% of eyes had a single area of GA. The mean total area at baseline was 4.59mm2 (1.8 disc areas (DA)). The mean follow up time was 1.24 years. Reproducibility, as assessed with the intraclass correlation coefficient (ICC), was excellent on both the original area scale (ICC = 0.995) and the square-root scale (ICC=0.996). Inter-grader differences were not an important source of variability in lesion size measurement (ICC=0.999, 0.997). On average, the ER of GA per year was 1.2 mm2 (0.47 DA; range [0.01 - 3.61 mm2/year]. The ER correlated with the initial area of GA (r=0.45, p<0.001), but there were variable growth rates for any given baseline area. When the square root transformation of the lesion area measurements was used as a measure of lesion size, the enlargement rate (0.28 mm/yr) was not correlated with baseline size (r=-0.09,p=0.40). In this cohort of lesions, no correlation was found between ER and length of follow-up. Square root transformation of the data helped facilitate sample size estimates for controlled clinical trials involving GA. Conclusions The SDOCT fundus image can be used to visualize and quantify GA. Advantages of this approach include the convenience and assurance of using a single imaging technique that permits simultaneous visualization of GA along with the loss of photoreceptors and the retinal pigment epithelium which should correlate with the loss of visual function.

Yehoshua, Zohar; Rosenfeld, Philip J.; Gregori, Giovanni; Feuer, William J.; Falcao, Manuel; Lujan, Brandon J.; Puliafito, Carmen

2010-01-01

258

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

USGS Publications Warehouse

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.

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

2007-01-01

259

Changes in quantitative 3D shape features of the optic nerve head associated with age  

NASA Astrophysics Data System (ADS)

Optic nerve head (ONH) structure is an important biological feature of the eye used by clinicians to diagnose and monitor progression of diseases such as glaucoma. ONH structure is commonly examined using stereo fundus imaging or optical coherence tomography. Stereo fundus imaging provides stereo views of the ONH that retain 3D information useful for characterizing structure. In order to quantify 3D ONH structure, we applied a stereo correspondence algorithm to a set of stereo fundus images. Using these quantitative 3D ONH structure measurements, eigen structures were derived using principal component analysis from stereo images of 565 subjects from the Ocular Hypertension Treatment Study (OHTS). To evaluate the usefulness of the eigen structures, we explored associations with the demographic variables age, gender, and race. Using regression analysis, the eigen structures were found to have significant (p < 0.05) associations with both age and race after Bonferroni correction. In addition, classifiers were constructed to predict the demographic variables based solely on the eigen structures. These classifiers achieved an area under receiver operating characteristic curve of 0.62 in predicting a binary age variable, 0.52 in predicting gender, and 0.67 in predicting race. The use of objective, quantitative features or eigen structures can reveal hidden relationships between ONH structure and demographics. The use of these features could similarly allow specific aspects of ONH structure to be isolated and associated with the diagnosis of glaucoma, disease progression and outcomes, and genetic factors.

Christopher, Mark; Tang, Li; Fingert, John H.; Scheetz, Todd E.; Abramoff, Michael D.

2013-02-01

260

Monoamine oxidase enzymes and oxidative stress in the rat optic nerve: age-related changes  

PubMed Central

In this study, age-related changes in the monoamine oxidases (MAO) were studied in the optic nerve (ON) of both young and aged male rats. The aim of the study was to assess the role of MAO in age-related changes in the rat ON and explain the mechanisms of neuroprotection mediated by MAO-B-specific inhibitors. Fifteen three month old and fifteen 26 month old Sprague–Dawley rats were used. The animals were killed by terminal anaesthesia. Staining of MAO, quantitative analysis of images, biochemical assays and statistical analysis of data were carried out. Samples of the ON were washed in water, fixed in Bowen fluid, dehydrated and embedded in Entellan. Histological sections were stained for MAO-enzymatic activities. The specificity of the reaction was evaluated by incubating control sections in a medium either without substrate or without dye. The quantitative analysis of images was carried out at the same magnification and the same lighting using a Zeiss photomicroscope. The histochemical findings were compared with the biochemical results. After enzymatic staining, MAO could be demonstrated in the ON fibres of both young and aged animals; however, MAO were increased in the nerve fibres of the elderly rats. These morphological findings were confirmed biochemically. The possibility that age-related changes in MAO levels may be attributed to impaired energy production mechanisms and/or represent the consequence of reduced energy needs is discussed.

Nebbioso, Marcella; Pascarella, Antonia; Cavallotti, Carlo; Pescosolido, Nicola

2012-01-01

261

Handmade compact disc spectroscope  

NASA Astrophysics Data System (ADS)

Astronomy data center held some programs for the open house day of 2005, and a program of handmade compact disc spectroscope in craft corner received a favorable review. We report a summary of the program and the product in this article.

Kawanomoto, Satoshi

2006-10-01

262

The Teddy Bears' Disc.  

ERIC Educational Resources Information Center

Reports an evaluation of the Teddy Bear disc, an interactive videodisc developed at the Open University for a second-level course in metallurgy and materials technology. Findings from observation of students utilizing the videodisc are reviewed; successful design features and design problems are considered; and development costs are outlined. (MBR)

Laurillard, Diana

1985-01-01

263

Head Disc Interface Design.  

National Technical Information Service (NTIS)

A recording medium for heat assisted magnetic recording includes a magnetic disc having a data zone portion and a non-data zone portion. A liquid lubricant is disposed on the non-data zone portion, and a solid lubricant disposed on the data zone portion. ...

C. L. Platt L. Li Y. T. Hsia

2004-01-01

264

Vortices in Astrophysical Discs  

Microsoft Academic Search

Dynamical theory of astrophysical discs predicts two different kinds of vortices: ``linear'' and ``nonlinear.'' If galactic spiral arms are density waves, linear vortices in the velocity field are predicted at infinitesimal amplitude, and both spirals and vortices grow together at equal rate. The centres of linear vortices lie in the neighborhood of the corotation circle and between spiral arms for

A. M. Fridman; O. V. Khoruzhii

1999-01-01

265

Probing dust grain evolution in IM Lupi's circumstellar disc. Multi-wavelength observations and modelling of the dust disc  

NASA Astrophysics Data System (ADS)

Aims: We present a panchromatic study, involving a multiple technique approach, of the circumstellar disc surrounding the T Tauri star IM Lupi (Sz 82). Methods: We have undertaken a comprehensive observational study of IM Lupi using photometry, spectroscopy, millimetre interferometry and multi-wavelength imaging. For the first time, the disc is resolved from optical and near-infrared wavelengths in scattered light, to the millimetre regime in thermal emission. Our data-set, in conjunction with existing photometric data, provides an extensive coverage of the spectral energy distribution, including a detailed spectrum of the silicate emission bands. We have performed a simultaneous modelling of the various observations, using the radiative transfer code MCFOST, and analysed a grid of models over a large fraction of the parameter space via Bayesian inference. Results: We have constructed a model that can reproduce all of the observations of the disc. Our analysis illustrates the importance of combining a wide range of observations in order to fully constrain the disc model, with each observation providing a strong constraint only on some aspects of the disc structure and dust content. Quantitative evidence of dust evolution in the disc is obtained: grain growth up to millimetre-sized particles, vertical stratification of dust grains with micrometric grains close to the disc surface and larger grains which have settled towards the disc midplane, and possibly the formation of fluffy aggregates and/or ice mantles around grains.

Pinte, C.; Padgett, D. L.; Ménard, F.; Stapelfeldt, K. R.; Schneider, G.; Olofsson, J.; Pani?, O.; Augereau, J. C.; Duchêne, G.; Krist, J.; Pontoppidan, K.; Perrin, M. D.; Grady, C. A.; Kessler-Silacci, J.; van Dishoeck, E. F.; Lommen, D.; Silverstone, M.; Hines, D. C.; Wolf, S.; Blake, G. A.; Henning, T.; Stecklum, B.

2008-10-01

266

Revival of the Jumping Disc  

ERIC Educational Resources Information Center

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…

Ucke, C.; Schlichting, H-J.

2009-01-01

267

Toshiba Review, Vol. 43, No. 10, 1988. Special Issue: Compact Disc-Read Only Memory/Transportation Technology.  

National Technical Information Service (NTIS)

Compact Disc-Read Only Memory and Transportation Technology contains: Compact Disc-Read Only Memory (Preface to Special Issue on CD-ROM; Half-Height CD-ROM Drive, XM-3000 Series; Optical Disc Head TOPH8340 for CD-ROM Drive; CD-ROM Pre-Mastering System; Ap...

1988-01-01

268

Scalelength of disc galaxies  

NASA Astrophysics Data System (ADS)

We have derived disc scalelengths for 30374 non-interacting disc galaxies in all five Sloan Digital Sky Survey (SDSS) bands. Virtual Observatory methods and tools were used to define, retrieve and analyse the images for this unprecedentedly large sample classified as disc/spiral galaxies in the LEDA catalogue. Cross-correlation of the SDSS sample with the LEDA catalogue allowed us to investigate the variation of the scalelengths for different types of disc/spiral galaxies. We further investigate asymmetry, concentration and central velocity dispersion as indicators of morphological type, and are able to assess how the scalelength varies with respect to galaxy type. We note, however, that the concentration and asymmetry parameters have to be used with caution when investigating type dependence of structural parameters in galaxies. Here, we present the scalelength derivation method and numerous tests that we have carried out to investigate the reliability of our results. The average r-band disc scalelength is 3.79kpc, with an rms dispersion of 2.05kpc, and this is a typical value irrespective of passband and galaxy morphology, concentration and asymmetry. The derived scalelengths presented here are representative for a typical galaxy mass of 1010.8+/-0.54Msolar, and the rms dispersion is larger for more massive galaxies. Separating the derived scalelengths for different galaxy masses, the r-band scalelength is 1.52 +/- 0.65kpc for galaxies with total stellar mass 109-1010Msolar and 5.73 +/- 1.94kpc for galaxies with total stellar mass between 1011 and 1012Msolar. Distributions and typical trends of scalelengths have also been derived in all the other SDSS bands with linear relations that indicate the relation that connect scalelengths in one passband to another. Such transformations could be used to test the results of forthcoming cosmological simulations of galaxy formation and evolution of the Hubble sequence.

Fathi, Kambiz; Allen, Mark; Boch, Thomas; Hatziminaoglou, Evanthia; Peletier, Reynier F.

2010-08-01

269

Optical Sensing of Polarization States Changes in Meat due to the Ageing  

NASA Astrophysics Data System (ADS)

Food materials or biological materials display large compositional variations, inhomogeneities, and anisotropic structures. The biological tissues consist of cells which dimensions are bigger than a wavelength of visible light, therefore Mie scattering of transmitted and reflected light occurs and different polarization states arise. The meat industry needs reliable meat quality information throughout the production process in order to guarantee high-quality meat products for consumers. The minor importance is still given to the food quality control and inspection during processing operations or storing conditions. The paper presents a quite simple optical method allowing measure the freshness or ageing of products. The principle is to study temporal characteristics of polarization states of forward or backward scattered laser light in the samples in function of meat ageing.

Tománek, Pavel; Mikláš, Jan; Abubaker, Hamed Mohamed; Grmela, Lubomír

2010-11-01

270

Disc degeneration in Scheuermann disease.  

PubMed

Comparison of the radiographic signs of Scheuermann disease and the corresponding disc degeneration on thoracolumbar magnetic resonance (MR) images was made in 21 young patients. Marginal sclerosis, Schmorl nodes and narrowed disc spaces, but not irregular or wedge-shaped end-plates, were significantly associated with disc degeneration. Fifty-five percent of the discs in the patients with Scheuermann disease were abnormal on MRI, compared with 10% in asymptomatic controls. Our study confirms that thoracolumbar disc degeneration is enhanced in 20-year-old patients with low back pain who have radiological evidence of Scheuermann disease. PMID:2588031

Paajanen, H; Alanen, A; Erkintalo, M; Salminen, J J; Katevuo, K

1989-01-01

271

Automatic detection of age-related macular degeneration pathologies in retinal fundus images  

Microsoft Academic Search

Advanced techniques in image processing and analysis are being extensively studied to assist clinical diagnoses. Digital colour retinal fundus images are widely utilised to investigate various eye diseases. In this paper, we describe the detection of optic disc (OD), macula and age-related macular degeneration (ARMD) pathologies of the macular regions in colour fundus images. ARMD causes the loss of central

Ay?egül Güven

2012-01-01

272

Central retinal vein occlusion in people aged 40 years or less: a review of 17 patients  

Microsoft Academic Search

Seventeen patients with central retinal vein occlusion aged 40 or under were reviewed. Ocular involvement was characteristically unilateral, with moderate degrees of retinal haemorrhage, little retinal ischaemia, and a tendency to optic disc swelling. Visual prognosis was good. Follow-up showed that most patients have good general health and no involvement of the fellow eye. There was little evidence to support

R F Walters; D J Spalton

1990-01-01

273

Maximum Age Predictions for Optical Dating on Mars Based on Dose\\/Depth Models and Martian Meteorite Compositions  

Microsoft Academic Search

A fundamental need in the Mars exploration portfolio is in-situ absolute dating. Optical dating has been proposed for determining the age of Mars surface features and landforms as well as the rates of martian surface processes. On Earth, the method is employed for Quaternary studies because the technique currently has a terrestrial maximum age limit of approximately 350 ka. This

R. T. Franklund; K. Lepper

2004-01-01

274

Probing the Galactic Bulge with Deep Adaptive Optics Imaging: The Age of NGC 6440  

NASA Astrophysics Data System (ADS)

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 toward the inner bulge, to compute a deep color-magnitude diagram from the tip of the red giant branch down to J~22, 2 magnitudes below the main-sequence turnoff (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. Based on observations collected at the European Southern Observatory (programs 075.D-0359(A) and 077.D-0316(A)), at the VLT, Paranal, and through program 081.D-0371(A) at NTT, La Silla, Chile.

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

2008-11-01

275

Near-field optical-beam-induced current spectroscopy as a tool for analyzing aging processes in diode lasers  

NASA Astrophysics Data System (ADS)

We present a near-field optical beam induced current study of aged high power laser diode arrays (LDA). A near-field scanning optical microscope was used as a light source for creating a photocurrent or a photovoltage in the LDA. Mechanisms generating the signal as well as methodical aspects such as resolution limits and application fields of the technique are discussed. The method is demonstrated to provide insight into the microscopic aging properties of LDAs. Both monitoring of the aging status as well as the localization of defects becomes possible.

Tomm, Jens W.; Richter, A.; Lienau, Ch.; Elsaesser, Thomas; Luft, J.

1997-05-01

276

Risk Factors for Recurrent Lumbar Disc Herniations  

PubMed Central

The most common complication after lumbar discectomy is reherniation. As the first step in reducing the rate of recurrence, many studies have been conducted to find out the factors that may increase the reherniation risk. Some reported factors are age, sex, the type of lumbar disc herniation, the amount of fragments removed, smoking, alcohol consumption and the length of restricted activities. In this review, the factors studied thus far are summarized, excepting factors which cannot be chosen or changed, such as age or sex. Apart from the factors shown here, many other risk factors such as diabetes, family history, history of external injury, duration of illness and body mass index are considered. Few are agreed upon by all. The reason for the diverse opinions may be that many clinical and biomechanical variables are involved in the prognosis following operation. For the investigation of risk factors in recurrent lumbar disc herniation, large-scale multicenter prospective studies will be required in the future.

2014-01-01

277

Biomechanics of Disc Degeneration  

PubMed Central

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.

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

2012-01-01

278

Total disc replacement.  

PubMed

Total disc replacement (TDR) (partial disc replacement will not be described) has been used in the lumbar spine since the 1980s, and more recently in the cervical spine. Although the biomechanical concepts are the same and both are inserted through an anterior approach, lumbar TDR is conventionally indicated for chronic low back pain, whereas cervical TDR is used for soft discal hernia resulting in cervicobrachial neuralgia. The insertion technique must be rigorous, with precise centering in the disc space, taking account of vascular anatomy, which is more complex in the lumbar region, particularly proximally to L5-S1. All of the numerous studies, including prospective randomized comparative trials, have demonstrated non-inferiority to fusion, or even short-term superiority regarding speed of improvement. The main implant-related complication is bridging heterotopic ossification with resulting loss of range of motion and increased rates of adjacent segment degeneration, although with an incidence lower than after arthrodesis. A sufficiently long follow-up, which has not yet been reached, will be necessary to establish definitively an advantage for TDR, particularly in the cervical spine. PMID:24412045

Vital, J-M; Boissière, L

2014-02-01

279

Gas Modelling in the Disc of HD 163296  

NASA Technical Reports Server (NTRS)

We present detailed model fits to observations of the disc around the Herbig Ae star HD 163296. This well-studied object has an age of approx. 4Myr, with evidence of a circumstellar disc extending out to approx. 540AU. We use the radiation thermo-chemical disc code ProDiMo to model the gas and dust in the circumstellar disc of HD 163296, and attempt to determine the disc properties by fitting to observational line and continuum data. These include new Herschel/PACS observations obtained as part of the open-time key program GASPS (Gas in Protoplanetary Systems), consisting of a detection of the [Oi] 63 m line and upper limits for several other far infrared lines. We complement this with continuum data and ground-based observations of the CO-12 3-2, 2-1 and CO-13 J=1-0 line transitions, as well as the H2 S(1) transition. We explore the effects of stellar ultraviolet variability and dust settling on the line emission, and on the derived disc properties. Our fitting efforts lead to derived gas/dust ratios in the range 9-100, depending on the assumptions made. We note that the line fluxes are sensitive in general to the degree of dust settling in the disc, with an increase in line flux for settled models. This is most pronounced in lines which are formed in the warm gas in the inner disc, but the low excitation molecular lines are also affected. This has serious implications for attempts to derive the disc gas mass from line observations. We derive fractional PAH abundances between 0.007 and 0.04 relative to ISM levels. Using a stellar and UV excess input spectrum based on a detailed analysis of observations, we find that the all observations are consistent with the previously assumed disc geometry

Tilling, I.; Woitke, P.; Meeus, G.; Mora, A.; Montesinos, B.; Riviere-Marichalar, P.; Eiroa, C.; Thi, W. -F.; Isella, A.; Roberge, A.; Martin-Zaidi, C.; Kamp, I.; Pinte, C.; Sandell, G.; Vacca, W. D.; Menard, F.; Mendigutia, I.; Duchene, G.; Dent, W. R. F.; Aresu, G.; Meijerink, R.; Spaans, M.

2011-01-01

280

Gas modelling in the disc of HD 163296  

NASA Astrophysics Data System (ADS)

We present detailed model fits to observations of the disc around the Herbig Ae star HD 163296. This well-studied object has an age of ~4 Myr, with evidence of a circumstellar disc extending out to ~540 AU. We use the radiation thermo-chemical disc code ProDiMo to model the gas and dust in the circumstellar disc of HD 163296, and attempt to determine the disc properties by fitting to observational line and continuum data. These include new Herschel/PACS observations obtained as part of the open-time key program GASPS (GAS in Protoplanetary Systems), consisting of a detection of the [Oi] 63 ?m line and upper limits for several other far infrared lines. We complement this with continuum data and ground-based observations of the 12CO 3-2, 2-1 and 13CO J = 1-0 line transitions, as well as an upper limit for the H2 0-0 S(1) transition. We explore the effects of stellar ultraviolet variability and dust settling on the line emission, and on the derived disc properties. Our fitting efforts lead to derived gas/dust ratios in the range 9-100, depending on the assumptions made. We note that the line fluxes are sensitive in general to the degree of dust settling in the disc, with an increase in line flux for settled models. This is most pronounced in lines which are formed in the warm gas in the inner disc, but the low excitation molecular lines are also affected. This has serious implications for attempts to derive the disc gas mass from line observations. We derive fractional PAH abundances between 0.007 and 0.04 relative to ISM levels. Using a stellar and UV excess input spectrum based on a detailed analysis of observations, we find that the all observations are consistent with the previously assumed disc geometry.

Tilling, I.; Woitke, P.; Meeus, G.; Mora, A.; Montesinos, B.; Riviere-Marichalar, P.; Eiroa, C.; Thi, W.-F.; Isella, A.; Roberge, A.; Martin-Zaidi, C.; Kamp, I.; Pinte, C.; Sandell, G.; Vacca, W. D.; Ménard, F.; Mendigutía, I.; Duchêne, G.; Dent, W. R. F.; Aresu, G.; Meijerink, R.; Spaans, M.

2012-02-01

281

Neurovascular coupling in normal aging: a combined optical, ERP and fMRI study.  

PubMed

Brain aging is characterized by changes in both hemodynamic and neuronal responses, which may be influenced by the cardiorespiratory fitness of the individual. To investigate the relationship between neuronal and hemodynamic changes, we studied the brain activity elicited by visual stimulation (checkerboard reversals at different frequencies) in younger adults and in older adults varying in physical fitness. Four functional brain measures were used to compare neuronal and hemodynamic responses obtained from BA17: two reflecting neuronal activity (the event-related optical signal, EROS, and the C1 response of the ERP), and two reflecting functional hemodynamic changes (functional magnetic resonance imaging, fMRI, and near-infrared spectroscopy, NIRS). The results indicated that both younger and older adults exhibited a quadratic relationship between neuronal and hemodynamic effects, with reduced increases of the hemodynamic response at high levels of neuronal activity. Although older adults showed reduced activation, similar neurovascular coupling functions were observed in the two age groups when fMRI and deoxy-hemoglobin measures were used. However, the coupling between oxy- and deoxy-hemoglobin changes decreased with age and increased with increasing fitness. These data indicate that departures from linearity in neurovascular coupling may be present when using hemodynamic measures to study neuronal function. PMID:23664952

Fabiani, Monica; Gordon, Brian A; Maclin, Edward L; Pearson, Melanie A; Brumback-Peltz, Carrie R; Low, Kathy A; McAuley, Edward; Sutton, Bradley P; Kramer, Arthur F; Gratton, Gabriele

2014-01-15

282

Disc-mass distribution in star-disc encounters  

NASA Astrophysics Data System (ADS)

Aims: Investigations of stellar encounters in cluster environments have demonstrated their potential influence on the mass and angular momentum of protoplanetary discs around young stars. We investigated how far the initial surface density in the disc surrounding a young star influences the outcome of an encounter. Methods: The numerical method applied here allows us to determine the mass and angular momentum losses in an encounter for any initial disc-mass distribution. On the basis of a power-law ansatz for the surface density, ?(r) ? r - p, we perform a parameter study of star-disc encounters with different initial disc-mass distributions using N-body simulations. Results: We demonstrate that the shape of the disc-mass distribution has a significant impact on the quantity of the disc-mass and angular momentum losses in star-disc encounters. In particular, the results are most sensitive to how the outer parts of the disc are perturbed by high-mass stars. In contrast, disc-penetrating encounters lead more or less independently of the disc-mass distribution always to large losses. However, maximum losses are generally obtained for initially flat distributed disc material. Based on a parameter study, a fit formula is derived, describing how the relative mass and angular momentum loss depend on the initial disc-mass distribution index p. Encounters generally lead to a steepening of the density profile of the disc. The resulting profiles can have a r-2-dependence or an even steeper one that is independent of the initial distribution of the disc material. Conclusions: From observations, the initial density distribution in discs remains unconstrained, hence the strong dependence on the initial density distribution that we find here might require a revision of the effect of encounters in young stellar clusters. The steep surface density distributions induced by some encounters might be a prerequisite to the formation of planetary systems similar to our own Solar System. Appendices A and B are available in electronic form at http://www.aanda.org

Steinhausen, M.; Olczak, C.; Pfalzner, S.

2012-02-01

283

Aging.  

PubMed

Aging is initiated based on genetic and environmental factors that operate from the time of birth of organisms. Aging induces physiological phenomena such as reduction of cell counts, deterioration of tissue proteins, tissue atrophy, a decrease of the metabolic rate, reduction of body fluids, and calcium metabolism abnormalities, with final progression onto pathological aging. Despite the efforts from many researchers, the progression and the mechanisms of aging are not clearly understood yet. Therefore, the authors would like to introduce several theories which have gained attentions among the published theories up to date; genetic program theory, wear-and-tear theory, telomere theory, endocrine theory, DNA damage hypothesis, error catastrophe theory, the rate of living theory, mitochondrial theory, and free radical theory. Although there have been many studies that have tried to prevent aging and prolong life, here we introduce a couple of theories which have been proven more or less; food, exercise, and diet restriction. PMID:24653904

Park, Dong Choon; Yeo, Seung Geun

2013-09-01

284

Development of fluorescent multilayer disc structure  

NASA Astrophysics Data System (ADS)

The fluorescent multilayer disc (FMD) consists of a substrate and the sandwich-structure of information and intermediate layers. While all the structure of the disc is transparent and homogeneous the parasitic signal will be caused mostly by photoluminescence (PL) and absorption of pits areas where laser light is unfocused. At large number of layers (10 or more) the noise level will get significant value, so it was suggested to derive readout signal as a variable one. Also it was proposed to record information only by the lands, to decrease the absorbance level and thus uncontrolled changing of the noise level. Furthermore in the FMD information layer there are inner and outside peripheral areas which hold a stable level of parasitic signal during readout from the edges of the disc. While the PL readout signal is spatially isotropic the optical head of the FMD drive receives just a part of the probing beam energy. PL quantum yield, absorption factor, receiver systems exposure loss coefficients are other reasons of the low PL signal. Thus the problem of the low SNR in this case is a major one and the only way of its solving is synthesis of the dye with a high PL quantum yield. The PL relaxation time on the other hand is a main feature of the data reading rate and therefore selection of the appropriate recording material will allow to bring this parameter in accordance to parameters of modern optical discs. To achieve this goal the composite organic pyrazoline dyes where synthesized and investigated as effective medium with a PL quantum yield up to 60-70%, relaxation time less than 100 ns, PL wide spectrum and opportunity of two-photon absorption. These parameters were further improved by a method based on the performance of organic dye molecules in the zeolite matrix.

Beliak, Ievgen; Butenko, Larisa

2011-08-01

285

Enclosed rotary disc air pulser  

DOEpatents

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.

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

1989-01-01

286

In vivo measurement of age-related stiffening in the crystalline lens by Brillouin optical microscopy.  

PubMed

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

Scarcelli, Giuliano; Kim, Pilhan; Yun, Seok Hyun

2011-09-21

287

Dynamics of warped accretion discs  

NASA Astrophysics Data System (ADS)

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.

Tremaine, Scott; Davis, Shane W.

2014-06-01

288

Use of Prescribed Optical Devices in Age-Related Macular Degeneration  

PubMed Central

Purpose To evaluate prescribed optical device use in terms of frequency and perceived usefulness among people with age-related macular degeneration (AMD). We also sought to determine the tasks for which they were using their prescribed low vision device. Methods 199 patients with AMD presenting for the first time to the low vision service were recruited from a university-based clinic. Prior to the low vision evaluation and device prescription, they completed the NEI-VFQ 25, Center for Epidemiological Studies Depression Scale, Short Portable Mental Status Questionnaire and a general health questionnaire. The low vision evaluation included best-corrected ETDRS visual acuity, MNRead testing, microperimetry, prescription and dispensing of optical low vision devices. Telephone follow-up interviews were conducted about device usage 1-week, 1-month and 3-months post-intervention. Results 181 participants were prescribed low vision devices. 93% completed all 3 follow-up interviews. Intensive users (? 1hour/day) of devices were similar in demographic and visual characteristics to non-intensive users (<1 hour/day) except for habitual reading acuity and speed as well as contrast sensitivity. Overall, device use increased slightly over 3 months of follow-up. Magnifiers were reported to be moderately to extremely useful by greater than 80% of participants at all time points except the 1 month follow-up for hand magnifiers (75%). High plus spectacles were the least frequently prescribed device and rated as moderately to extremely useful by 70%, 74% and 59% at 1 week, 1 month and 3 months, respectively. Most participants used their devices for leisure reading, followed by managing bills. Very few devices (n=3, <1%)were not used at any time point. Conclusions Patients with AMD who are provided with prescribed optical low vision devices do use them and perceive them as useful, especially for leisure reading activities. High rates of usage were maintained over 3 months.

DeCarlo, Dawn K.; McGwin, Gerald; Searcey, Karen; Gao, Liyan; Snow, Marsha; Stevens, Lynne; Owsley, Cynthia

2012-01-01

289

Twin disc gear tooth simulator  

NASA Astrophysics Data System (ADS)

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.

Eusepi, Martin W.; Dill, James F.

1994-05-01

290

Numbered nasal discs for waterfowl  

USGS Publications Warehouse

Numbered nasal discs were successfully used in studies requiring large numbers of individually marked waterfowl. The procedure for constructing these discs is outlined. Blue-winged teal (Anas discors) with 5/8-inch discs, and canvasback (Aythya valisineria) and redhead (A. americana) with 3/4-inch discs can be individually identified up to 50 and 80 yards, respectively, with a gunstock-mounted, 20-power spotting scope. The particular value of these markers is their durability, the number of combinations possible, and the apparent absence of behavioral or mortality influence among such species as the blue-winged teal.

Bartonek, J. C.; Dane, C. W.

1964-01-01

291

Sizes of protoplanetary discs after star-disc encounters  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

292

Disc degeneration after disc herniation: are we accelerating the process?  

PubMed

Study design: ?Systematic review. Study rationale: ?Disc degeneration is a common process starting early in life. Often disc herniation is an early step in disc degeneration, which may cause pain or stenosis. How quickly this subsequent disc degeneration occurs following a disc herniation and subsequent surgical treatment and whether certain spinal procedures increase the rate of degeneration remain unclear. Objectives: ?To investigate the risk of subsequent radiographic disc degeneration following discectomy, discography, and conservative care in patients with a first-time diagnosed herniated nucleus pulpous (HNP) and to ascertain whether this risk in these defined groups changes over time. Methods: ?A systematic review of pertinent articles published up to June 2012. Key articles were searched to identify studies evaluating the risk of subsequent radiographic disc degeneration following treatment for HNP. Studies that included patients undergoing secondary surgery for disc herniation or that did not use a validated classification system to measure the severity of disc degeneration were excluded. Two independent reviewers assessed the strength of evidence using the GRADE criteria and disagreements were resolved by consensus. Results: ?From a total of 147 possible citations, three cohort studies (class of evidence III) met our inclusion criteria and form the basis for this report. The risk of subsequent lumbar disc degeneration following standard discectomy was significantly greater compared with both microdiscectomy (48.7% vs 9.1%) and asymptomatic controls (90% vs 68%) in two studies with mean follow-ups of 5.5 and 25.3 years, respectively. Following conservative care for first-time HNP in the third study, the risk of progression of lumbar disc degeneration was 47.6% over the first 2 years of follow-up and 95.2% over the next 6 years of follow-up. In the same study, the risk of lumbar disc degeneration was shown to increase incrementally over the course of the 8-year follow-up, with all patients showing signs of degeneration at final examination. Conclusion: ?Standard discectomy in first-time lumbar HNP may increase the risk of subsequent same-level lumbar disc degeneration compared with microdiscectomy as seen in one low-quality study. However, disc degeneration is likely a natural, temporal consequence following HNP, as demonstrated in a second low-quality study. The overall strength of evidence for the conclusions is very low. PMID:23526910

Schroeder, Josh E; Dettori, Joseph R; Brodt, Erika D; Kaplan, Leon

2012-11-01

293

Disc degeneration after disc herniation: are we accelerating the process?  

PubMed Central

Study design:?Systematic review. Study rationale:?Disc degeneration is a common process starting early in life. Often disc herniation is an early step in disc degeneration, which may cause pain or stenosis. How quickly this subsequent disc degeneration occurs following a disc herniation and subsequent surgical treatment and whether certain spinal procedures increase the rate of degeneration remain unclear. Objectives:?To investigate the risk of subsequent radiographic disc degeneration following discectomy, discography, and conservative care in patients with a first-time diagnosed herniated nucleus pulpous (HNP) and to ascertain whether this risk in these defined groups changes over time. Methods:?A systematic review of pertinent articles published up to June 2012. Key articles were searched to identify studies evaluating the risk of subsequent radiographic disc degeneration following treatment for HNP. Studies that included patients undergoing secondary surgery for disc herniation or that did not use a validated classification system to measure the severity of disc degeneration were excluded. Two independent reviewers assessed the strength of evidence using the GRADE criteria and disagreements were resolved by consensus. Results:?From a total of 147 possible citations, three cohort studies (class of evidence III) met our inclusion criteria and form the basis for this report. The risk of subsequent lumbar disc degeneration following standard discectomy was significantly greater compared with both microdiscectomy (48.7% vs 9.1%) and asymptomatic controls (90% vs 68%) in two studies with mean follow-ups of 5.5 and 25.3 years, respectively. Following conservative care for first-time HNP in the third study, the risk of progression of lumbar disc degeneration was 47.6% over the first 2 years of follow-up and 95.2% over the next 6 years of follow-up. In the same study, the risk of lumbar disc degeneration was shown to increase incrementally over the course of the 8-year follow-up, with all patients showing signs of degeneration at final examination. Conclusion:?Standard discectomy in first-time lumbar HNP may increase the risk of subsequent same-level lumbar disc degeneration compared with microdiscectomy as seen in one low-quality study. However, disc degeneration is likely a natural, temporal consequence following HNP, as demonstrated in a second low-quality study. The overall strength of evidence for the conclusions is very low.

Schroeder, Josh E.; Dettori, Joseph R.; Brodt, Erika D.; Kaplan, Leon

2012-01-01

294

Thermal fatigue cracks of fire fighting vehicles gray iron brake discs  

Microsoft Academic Search

A considerable number of brake discs of fire fighting vehicles used in supporting to the aeronautical activities were found cracked during NDT. Macrofractography of the discs, manufactured in gray iron, showed several cracks running along the radius of the friction surfaces having length approximately in the range 1–7.5cm. Further cracks examination by using optical microscope and field emission scanning electron

F. Bagnoli; F. Dolce; M. Bernabei

2009-01-01

295

Vertical cup-to-disc ratio measurement for diagnosis of glaucoma on fundus images  

NASA Astrophysics Data System (ADS)

Glaucoma is a leading cause of permanent blindness. Retinal fundus image examination is useful for early detection of glaucoma. In order to evaluate the presence of glaucoma, the ophthalmologists determine the cup and disc areas and they diagnose glaucoma using a vertical cup-to-disc ratio. However, determination of the cup area is very difficult, thus we propose a method to measure the cup-to-disc ratio using a vertical profile on the optic disc. First, the blood vessels were erased from the image and then the edge of optic disc was then detected by use of a canny edge detection filter. Twenty profiles were then obtained around the center of the optic disc in the vertical direction on blue channel of the color image, and the profile was smoothed by averaging these profiles. After that, the edge of the cup area on the vertical profile was determined by thresholding technique. Lastly, the vertical cup-to-disc ratio was calculated. Using seventy nine images, including twenty five glaucoma images, the sensitivity of 80% and a specificity of 85% were achieved with this method. These results indicated that this method can be useful for the analysis of the optic disc in glaucoma examinations.

Hatanaka, Yuji; Noudo, Atsushi; Muramatsu, Chisako; Sawada, Akira; Hara, Takeshi; Yamamoto, Tetsuya; Fujita, Hiroshi

2010-03-01

296

Dead discs, unstable discs and the stars they surround  

NASA Astrophysics Data System (ADS)

Strong stellar magnetic fields significantly alter the behaviour of surrounding accretion discs. Recent work has demonstrated that at low accretion rates a large amount of mass can remain confined in the disc, contrary to the standard assumption that the magnetic field will expel the disc in an outflow (the "propeller regime"). These "dead discs" often become unstable, causing cycles of accretion onto the central star. Here I present the main predictions of this model, and argue that it provides a good explanation for the peculiar behaviour seen in several accreting sources with strong magnetic fields. I will focus in particular on three accreting millisecond X-ray pulsars: SAX J1808.4-3658, NGC 6440 X-2 and IGR J00291+5934. These sources all show low-frequency quasi-periodic oscillations consistent with a variable accretion rate, as well as unusual outburst patterns that suggest gas is confined in the inner disc regions during quiescence.

D'Angelo, Caroline

2014-01-01

297

Genome-wide association study in Dachshund: identification of a major locus affecting intervertebral disc calcification.  

PubMed

Intervertebral disc calcification and herniation commonly affects Dachshund where the predisposition is caused by an early onset degenerative process resulting in disc calcification. A continuous spectrum of disc degeneration is seen within and among dog breeds, suggesting a multifactorial etiology. The number of calcified discs at 2 years of age determined by a radiographic evaluation is a good indicator of the severity of disc degeneration and thus serves as a measure for the risk of developing intervertebral disc herniation. The aim of the study was to identify genetic variants associated with intervertebral disc calcification in Dachshund through a genome-wide association (GWA) study. Based on thorough radiographic examinations, 48 cases with ? 6 disc calcifications or surgically treated for disc herniation and 46 controls with 0-1 disc calcifications were identified. GWA using the Illumina CanineHD BeadChip identified a locus on chromosome 12 from 36.8 to 38.6 Mb with 36 markers reaching genome-wide significance (P(genome) = 0.00001-0.026). This study suggests that a major locus on chromosome 12 harbors genetic variations affecting the development of intervertebral disc calcification in Dachshund. PMID:21846751

Mogensen, Mette Sloth; Karlskov-Mortensen, Peter; Proschowsky, Helle Friis; Lingaas, Frode; Lappalainen, Anu; Lohi, Hannes; Jensen, Vibeke Frøkjær; Fredholm, Merete

2011-01-01

298

Tandem coupled cavity lasers with separate current control and high parasitic resistance between them for bistability and negative resistance characteristics and use thereof for optical disc readout  

SciTech Connect

A two-segment contact buried heterostructure (BH) laser is pumped by a current applied to its absorber contact from a source of high impedance on the order of 100K..cap omega.. or more. The parasitic resistance between the absorber contact and the gain contact is high on the order of 10K..cap omega... For a given absorber (bias) current the laser exhibits a relatively wide hysteresis on the order of 1 mA or more in the light vs. gain contact current. Such a laser is highly useful as a bistable optical element. The laser is also bistable with selected pump gain and absorber currents to exhibit a wide hysteresis of voltage across the absorber contact vs. relative amounts of light which is reflected back to the laser as feedback. The laser serve both as a light source and as a detector for reading out binary information stored as light reflective spots on a medium, e.g. a video disk.

Yariv, A.; Harder, C.; Lau, K. L.

1985-12-31

299

Fantastic Disc Activities for Fitness  

ERIC Educational Resources Information Center

Disc activities are an excellent elementary content area for both skill and fitness enhancement. They may occur through progressive skill and drill practice, small sided-game examples, modifications of traditional disc activities appropriate to large groups, and with adjustments designed to increase activity and fitness levels. For games in this…

Griffin, Michael R.; Johnson, Romona; Thomas, Jessica; Spell, Melissa; Popham, John; Croft, Brent; Umpleby, Albert; Verbel, Eric

2005-01-01

300

Intervertebral Disc Adaptation to Wedging  

Microsoft Academic Search

Although scoliosis includes wedge deformities of both vertebrae and discs, little is known about the causes of the discal changes, and whether they result from mechanical influences on growth and\\/or remodelling. Methods and Materials: An external apparatus attached to transvertebral pins applied compression and 15 degrees of angulation to each of two adjacent young rat caudal intervertebral discs for 5

Ian A. F. STOKES; David D. ARONSSON; Katherine C. CLARK; Maria L. ROEMHILDT

301

Radicular interdural lumbar disc herniation.  

PubMed

Intraradicular lumbar disc herniation is a rare complication of disc disease that is generally diagnosed only during surgery. The mechanism for herniated disc penetration into the intradural space is not known with certainty, but adhesion between the radicular dura and the posterior longitudinal ligament was suggested as the most important condition. The authors report the first case of an intraradicular lumbar disc herniation without subdural penetration; the disc hernia was lodged between the two radicular dura layers. The patient, a 34-year-old soldier, was admitted with a 12-month history of low back pain and episodic left sciatica. Neurologic examination showed a positive straight leg raising test on the left side without sensory, motor or sphincter disturbances. Spinal CT scan and MRI exploration revealed a left posterolateral osteophyte formation at the L5-S1 level with an irregular large disc herniation, which migrated superiorly. An intradural extension was suspected. A left L5 hemilaminectomy and S1 foraminotomy were performed. The exploration revealed a large fragment of disc material located between the inner and outer layers of the left S1 radicular dura. The mass was extirpated without cerebrospinal fluid outflow. The postoperative course was uneventful. Radicular interdural lumbar disc herniation should be suspected when a swollen, hard and immobile nerve root is present intraoperatively. PMID:19888608

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

2010-07-01

302

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

NASA Astrophysics Data System (ADS)

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.

Done, Chris; Kubota, Aya

2006-09-01

303

Variability and stellar populations with deep optical-IR images of the Milky Way disc: matching VVV with VLT/VIMOS data  

NASA Astrophysics Data System (ADS)

Aims: We have used deep V-band and JHKs-band observations to investigate variability and stellar populations near the Galactic plane in Centaurus, and compared the observations with the Galactic model of Besançon. Methods: By applying image subtraction technique to a series of over 580 V-band frames taken with the ESO VLT/VIMOS instrument during two contiguous nights in April 2005, we have detected 333 variables among 84 734 stars in the brightness range 12.7 < V < 26.0 mag. Infrared data collected in March 2010 with the new ESO VISTA telescope allowed us to construct deep combined optical-IR colour-magnitude and colour-colour diagrams. Results: All detected variables but four transit candidates are reported for the first time. The majority of the variables are eclipsing/ellipsoidal binaries and ? Scuti-type pulsators. The occurrence rate of eclipsing/ellipsoidal variables reached ~0.28% of all stars. This is very close to the highest fraction of binary systems detected using ground-based data so far (0.30%), but still about four times less than the average occurrence rate recently obtained from the Kepler space mission after 44 days of operation. Comparison of the observed Ks vs. V - Ks diagram with a diagram based on the Besançon model shows significant effects of both distance and reddening in the investigated direction of the sky. We demonstrate that the best model indicates the presence of absorbing clouds at distances 11-13 kpc from the Sun in the minor Carina-Sagittarius arm. Based on observations collected with the VLT and VISTA telescopes at Paranal Observatory (ESO Programmes 075.C-0427(A) and 179.B-2002(B), respectively).Photometry and data table on detected variables are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/537/A116

Pietrukowicz, P.; Minniti, D.; Alonso-García, J.; Hempel, M.

2012-01-01

304

Using Integrated Optical Feedback to Counter Pixel Aging and Stabilize Light Output of Organic LED Display Technology  

Microsoft Academic Search

We define a metric of useful operating lifetime of an organic light-emitting device (OLED) display and relate it to the commonly measured half-life of constituent OLED pixels. We enumerate sources of OLED operational instability and propose an optical feedback solution in a novel integrated configuration to counter pixel aging and maintain stable light output across all of the pixels of

Jennifer Yu; Jonathan R. Tischler; Charles G. Sodini; Vladimir Bulovic

2008-01-01

305

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

Microsoft Academic Search

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

Adrian Glasser; Melanie C. W. Campbell

1999-01-01

306

AGING AIRCRAFT RIVET SITE INSPECTION USING MAGNETO-OPTIC IMAGING: AUTOMATION AND REAL-TIME IMAGE PROCESSING  

Microsoft Academic Search

Magneto-optic imaging (MOI) technique, developed in the last two decades, is becoming increasingly popular for aging aircraft inspection. In recent years, it is widely used in detecting surface and subsurface cracks and corrosion in aircraft skins. The merits of MOI that make it attractive include rapid and large-area inspection, insensitivity to liftoff variations, easy interpretation and low false call rate.

Yuan Fan; Yiming Deng; Zhiwei Zeng; Lalita Udpa; William Shih; Gerald Fitzpatrick

307

Spectral-Domain Optical Coherence Tomography Characteristics of Intermediate Age-Related Macular Degeneration  

PubMed Central

Purpose Describe qualitative spectral-domain optical coherence tomography (SD-OCT) characteristics of eyes classified as intermediate age-related macular degeneration (nonadvanced AMD) from Age-Related Eye Disease Study 2 (AREDS2) color fundus photography (CFP) grading. Design Prospective cross-sectional study. Participants We included 345 AREDS2 participants from 4 study centers and 122 control participants who lack CFP features of intermediate AMD. Methods Both eyes were imaged with SD-OCT and CFP. The SD-OCT macular volume scans were graded for the presence of 5 retinal, 5 subretinal, and 4 drusen characteristics. In all, 314 AREDS2 participants with ?1 category-3 AMD eye and all controls each had 1 eye entered into SD-OCT analysis, with 63 eyes regraded to test reproducibility. Main Outcome Measures We assessed SD-OCT characteristics at baseline. Results In 98% of AMD eyes, SD-OCT grading of all characteristics was successful, detecting drusen in 99.7%, retinal pigment epithelium (RPE) atrophy/absence in 22.9%, subfoveal geographic atrophy in 2.5%, and fluid in or under the retina in 25.5%. Twenty-eight percent of AMD eyes had characteristics of possible advanced AMD on SD-OCT. Two percent of control eyes had drusen on SD-OCT. Vision loss was not correlated with foveal drusen alone, but with foveal drusen that were associated with other foveal pathology and with overlying focal hyperreflectivity. Focal hyperreflectivity over drusen, drusen cores, and hyper- or hyporeflectivity of drusen were also associated with RPE atrophy. Conclusions Macular pathologies in AMD can be qualitatively and reproducibly evaluated with SD-OCT, identifying pathologic features that are associated with vision loss, RPE atrophy, and even possibly the presence of advanced AMD not apparent on CFP. Qualitative and detailed SD-OCT analysis can contribute to the anatomic characterization of AMD in clinical studies of vision loss and disease progression.

Leuschen, Jessica N.; Schuman, Stefanie G.; Winter, Katrina P.; McCall, Michelle N.; Wong, Wai T.; Chew, Emily Y.; Hwang, Thomas; Srivastava, Sunil; Sarin, Neeru; Clemons, Traci; Harrington, Molly; Toth, Cynthia A.

2012-01-01

308

Cervical Total Disc Arthroplasty  

PubMed Central

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.

Basho, Rahul; Hood, Kenneth A.

2012-01-01

309

Clumpy disc and bulge formation  

NASA Astrophysics Data System (ADS)

We present a set of hydrodynamical/N-body controlled simulations of isolated gas-rich galaxies that self-consistently include supernova (SN) feedback and a detailed chemical evolution model, both tested in cosmological simulations. The initial conditions are motivated by the observed star-forming galaxies at z ˜ 2-3. We find that the presence of a multiphase interstellar media in our models promotes the growth of disc instability favouring the formation of clumps which, in general, are not easily disrupted on time-scales compared to the migration time. We show that stellar clumps migrate towards the central region and contribute to form a classical-like bulge with a Sérsic index, n > 2. Our physically motivated SN feedback has a mild influence on clump survival and evolution, partially limiting the mass growth of clumps as the energy released per SN event is increased, with the consequent flattening of the bulge profile. This regulation does not prevent the building of a classical-like bulge even for the most energetic feedback tested. Our SN feedback model is able to establish self-regulated star formation, producing mass-loaded outflows and stellar age spreads comparable to observations. We find that the bulge formation by clumps may coexist with other channels of bulge assembly such as bars and mergers. Our results suggest that galactic bulges could be interpreted as composite systems with structural components and stellar populations storing archaeological information of the dynamical history of their galaxy.

Perez, Josefa; Valenzuela, Octavio; Tissera, Patricia B.; Michel-Dansac, Leo

2013-11-01

310

Magneto-optic/eddy current imaging of aging aircraft: A new NDI technique  

SciTech Connect

An eddy current instrument called a magneto-optic/eddy current imager (MOI) has been developed for the purpose of nondestructive inspection (NDI) of aging aircraft. The MOI produces realistic, real-time, eddy current images of both surface-breaking fatigue cracks and hidden multilayer cracking or corrosion. While it also works on steel and titanium, the MOI was designed to yield optimum results on aluminum aircraft skins and structural components. At eddy current frequencies of 25.6--102.4 kHz, most surface-breaking fatigue cracks in aluminum are easily imaged; while at lower frequencies hidden multilayer cracks, corrosion, and aircraft substructure may be imaged. The advantages of the MOI are its speed (5 to 10 times faster than conventional eddy current NDI), its easily interpreted image information, the near elimination of false calls, the elimination of the need for paint or decal removal, the reduction of operator fatigue, and the easy documentation of results via video tape or 35 mm film. MOI images for both fatigue cracks and corrosion are illustrated. Recent improvements in the technology, including rotating or multidirectional (by nonmechanical means) eddy current excitation are illustrated. Finally, the application of the MOI to specially tagged composite materials is illustrated.

Fitzpatrick, G.L.; Thome, D.K.; Skaugset, R.L.; Shih, E.Y.C. (Physical Research, Inc., Kirkland, WA (United States)); Shih, W.C.L. (PRI Instrumentation, Inc., Torrance, CA (United States))

1993-12-01

311

Forming disc galaxies in ?CDM simulations  

NASA Astrophysics Data System (ADS)

We used fully cosmological, high-resolution N-body + smooth particle hydrodynamic (SPH) simulations to follow the formation of disc galaxies with rotational velocities between 135 and 270kms-1 in a ? cold dark matter (CDM) universe. The simulations include gas cooling, star formation, the effects of a uniform ultraviolet (UV) background and a physically motivated description of feedback from supernovae (SNe). The host dark matter haloes have a spin and last major merger redshift typical of galaxy-sized haloes as measured in recent large-scale N-body simulations. The simulated galaxies form rotationally supported discs with realistic exponential scalelengths and fall on both the I band and baryonic Tully-Fisher relations. An extended stellar disc forms inside the Milky Way (MW)-sized halo immediately after the last major merger. The combination of UV background and SN feedback drastically reduces the number of visible satellites orbiting inside a MW-sized halo, bringing it in fair agreement with observations. Our simulations predict that the average age of a primary galaxy's stellar population decreases with mass, because feedback delays star formation in less massive galaxies. Galaxies have stellar masses and current star formation rates as a function of total mass that are in good agreement with observational data. We discuss how both high mass and force resolution and a realistic description of star formation and feedback are important ingredients to match the observed properties of galaxies.

Governato, F.; Willman, B.; Mayer, L.; Brooks, A.; Stinson, G.; Valenzuela, O.; Wadsley, J.; Quinn, T.

2007-02-01

312

Imaging findings in dogs with caudal intervertebral disc herniation.  

PubMed

The radiographic and magnetic resonance imaging (MRI) findings for four dogs with herniation of the Cd1-Cd2 intervertebral disc are described. All dogs were 7 years of age at the time of presentation, with one neutered male and three neutered females. Breeds included one Beagle, one Bassett hound, and two large, mixed breed dogs. All dogs had tail pain on manipulation, two had pain during defecation, and two maintained an abnormal tail position. Three dogs had radiographs in which mineralization within the disc space was apparent. Two of these dogs also had mineralization within the vertebral canal. Three dogs underwent MRI, which was characterized by varying degrees of disc herniation and nerve root compression at Cd1-Cd2. Mobility may be a factor predisposing to disc herniation in the cranial aspect of the caudal spine. We documented that caudal disc herniation does occur occasionally in dogs and that radiography and MRI may be used to identify this disease. Caudal intervertebral disc herniation should be considered as a differential for dogs with caudal vertebral pain, pain with tail manipulation, pain during defecation, or abnormal tail carriage. PMID:21689201

Lawson, Caitlin M; Reichle, Jean K; McKlveen, Tori; Smith, Mary O

2011-01-01

313

Maximum Age Predictions for Optical Dating on Mars Based on Dose/Depth Models and Martian Meteorite Compositions  

NASA Astrophysics Data System (ADS)

A fundamental need in the Mars exploration portfolio is in-situ absolute dating. Optical dating has been proposed for determining the age of Mars surface features and landforms as well as the rates of martian surface processes. On Earth, the method is employed for Quaternary studies because the technique currently has a terrestrial maximum age limit of approximately 350 ka. This maximum age limit is a function of the saturation dose of the dosimeter material (silicate sediments) and the local ionizing radiation dose rate. The sources of ionizing radiation germane to optical dating are K, Rb, U, Th in the sediment/soil environment and cosmic rays. On Mars the near surface dose rate will be dominated by cosmic rays, however, at depth the decay of radioisotopes will be the principle contributor of ionizing radiation. In this work we present an evaluation of the maximum age limits for OSL dating on Mars as a function of depth. At this time we have considered only static burial. Our calculations are based on published models of and data for: (i) Mars surface cosmic dose rate and its attenuation by martian regolith, (ii) elemental analyses of Mars meteorites, (iii) an experimental evaluation of the saturation dose for the martian soil simulant JSC Mars-1. Our analysis confirms earlier inferences that optical dating should have a greater effective age range on Mars than on Earth. At depths easily accessible by penetrators or moles (1-3 m), maximum optical ages greater than 600 ka are possible. Geochronology on this scale would include at least two stadial/interstadial cycles within Mars' last "Glacial Epoch" (synchronized insolation variations between the poles). A wide range of landforms and surface processes associated with climate variability -- e.g. outwash and lacustrine deposition, large-scale eolian activation -- could potentially be optically dated. At greater depths, that could be reached by mobile drilling rigs or cryobots (10-30m), optical age maximums of 4.5 to greater than 35 Ma appear to be possible.

Franklund, R. T.; Lepper, K.

2004-12-01

314

Measurements of brake disc surface temperature and emissivity by two-color pyrometry  

Microsoft Academic Search

A fiber optic two-color pyrometer was developed for brake disc surface temperature and emissivity measurements. The two-color pyrometer consists of a fluoride glass optical fiber, two HgCdTe detectors equipped with bandwidth filters and a data conditioning and acquisition device. The two-color pyrometer measures the brake disc temperature in the 200–800°C range with a time resolution of 8?s. The calibration formula

Jean Thevenet; Monica Siroux; Bernard Desmet

2010-01-01

315

Model-based optic nerve head segmentation on retinal fundus images  

Microsoft Academic Search

The optic nerve head (optic disc) plays an important role in the diagnosis of retinal diseases. Automatic localization and segmentation of the optic disc is critical towards a good computer-aided diagnosis (CAD) system. In this paper, we propose a method that combines edge detection, the Circular Hough Transform and a statistical deformable model to detect the optic disc from retinal

Fengshou Yin; Jiang Liu; Sim Heng Ong; Ying Sun; Damon W. K. Wong; Ngan Meng Tan; Carol Cheung; Mani Baskaran; Tin Aung; Tien Yin Wong

2011-01-01

316

OPTICAL COHERENCE TOMOGRAPHY-BASED CORRELATION BETWEEN CHOROIDAL THICKNESS AND DRUSEN LOAD IN DRY AGE-RELATED MACULAR DEGENERATION  

PubMed Central

Purpose Spectral domain optical coherence tomography can be used to measure both choroidal thickness and drusen load. The authors conducted an exploratory study using spectral domain optical coherence tomography to determine if a correlation between choroidal thickness and drusen load exists in patients with dry age-related macular degeneration. Methods Forty-four patients with dry age-related macular degeneration were recruited. The drusen area and volume were determined using the automated software algorithm of the spectral domain optical coherence tomography device, and choroidal thickness was measured using enhanced depth imaging. Correlations were determined using multivariable and univariable analyses. Results The authors found an inverse correlation between choroidal thickness and drusen load (r = ?0.35, P = 0.04). Drusen load was also correlated with visual acuity (r = 0.32, P = 0.04). A correlation between choroidal thickness and visual acuity was suggested (r = ?0.22, P = 0.21). Conclusion Spectral domain optical coherence tomography can be used to assess the correlation between drusen load and choroidal thickness, both of which show a relationship with visual acuity. The measurement of these outcomes may serve as important outcome parameters in routine clinical care and in clinical trials for patients with dry age-related macular degeneration.

KO, ASHLEY; CAO, SIJIA; PAKZAD-VAEZI, KAIVON; BRASHER, PENELOPE M.; MERKUR, ANDREW B.; ALBIANI, DAVID A.; KIRKER, ANDREW W.; CUI, JING; MATSUBARA, JOANNE; FOROOGHIAN, FARZIN

2014-01-01

317

Ageing  

NASA Astrophysics Data System (ADS)

By 2020, the number of the world’s older population is expected to exceed one billion, and maintaining a high quality of life for these people has become an important issue throughout the world. The Web has been shown to have a positive experience on the quality of life and well-being of older persons, by assisting them to maintain an independent living. However, many older people seem to shy away from the Web due to various problems they experience when interacting with the Web. To understand the nature of these problems, this chapter presents the functional impairments and the attitudes that might contribute to older persons’ hesitation of utilising the Web. This chapter discusses the changes that happen with age, their effects on Web interaction and how they can be mediated through the accessible Web.

Kurniawan, Sri H.

318

Enlivening Physics, a Local Video Disc Project.  

ERIC Educational Resources Information Center

Describes how to make and use an inexpensive video disc of physics demonstrations. Discusses the background, production of the disc, subject of the disc including angular momentum, "monkey and the hunter" experiment, Doppler shift, pressure of a constant volume of gas thermometer, and wave effects, and using the disc in classroom. (YP)

McInerney, M.

1989-01-01

319

Disc pack cleaning table saves computer time  

NASA Technical Reports Server (NTRS)

Disc pack holding table is support frame upon which computer disc pack is loaded and protective cover released. This combination permits manual off-line cleaning of disc pack storage units at any time without shutting down the computer, and eliminates on-line disc drive unit to hold pack during cleaning.

Guy, J. T., Sr.

1970-01-01

320

Clinical Evaluation of Disc Battery Ingestion in Children  

PubMed Central

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 admitted to Mofid Children’s Hospital due to disc battery ingestion from January 2006 to January 2010. Clear history, clinical symptoms and results of imaging studies revealed diagnosis of disc battery ingestion in suspected patients. The clinical data reviewed included age, gender, clinical manifestation, radiologic findings, location of disc battery, duration of ingestion, endoscopic results and surgical treatment. RESULTS We found 22 cases (11 males and 11 females) of disc battery ingestion with a mean age of 4.3 years (range: 9 months to 12 years). Common symptoms were vomiting, cough, dysphagia, and dyspnea. The mean duration of ingestion was 2.7 days (4 hours to 1.5 months). A total of 19 patients had histories of disc battery ingestion, but three cases referred with the above symptoms, and the batteries were accidentally found by x-ray. Only three cases had batteries impacted in the esophagus. Twelve batteries were removed endoscopically, 6 batteries spontaneously passed through the gastrointestinal (GI) tract within 5 to 7 days, and 4 patients underwent surgery due to complications: 3 due to tracheo-esophageal fistula (TEF) and 1 due to intestinal perforation. There was no mortality in our study. CONCLUSION Most cases of disc battery ingestion run uneventful courses, but some may be complicated. If the battery lodges in the esophagus, emergency endoscopic management is necessary. However, once in the stomach, it will usually pass through the GI tract.

Mirshemirani, AliReza; Khaleghnejad-tabari, Ahmad; Kouranloo, Jaefar; Sadeghian, Naser; Rouzrokh, Mohsen; Roshanzamir, Fatolah; Razavi, Sajad; Sayary, Ali Akbar; Imanzadeh, Farid

2012-01-01

321

Planet formation in evolving protoplanetary discs  

NASA Astrophysics Data System (ADS)

I attempt to summarize our knowledge of planet formation in evolving protoplanetary discs. I first review the physics of disc evolution and dispersal. For most of the disc lifetime evolution is driven by accretion and photoevaporation, and I discuss how the interplay between these processes shapes protoplanetary discs. I also discuss the observations that we use to test these models, and the major uncertainties that remain. I will then move on to consider planet formation and migration in evolving discs, and discuss how observations of both discs and planets can be used to inform our understanding of protoplanetary disc evolution.

Alexander, Richard

2014-01-01

322

Asymptomatic radiographic disappearance of calcified intervertebral disc material in the Dachshund.  

PubMed

The occurrence of asymptomatic disappearance of intervertebral disc calcification was evaluated in a radiographic prospective longitudinal study of 40 Dachshunds followed from 6 or 12 months of age to 2 years of age. Radiographic follow-up was performed at 3 to 4 years of age in 12 dogs. Disappearance of calcified disc material was observed in 9 thoracic and 1 lumbar intervertebral discs. The crude incidence rate tended to increase with age from 1 year of age. The features of the disappearing calcifications involved indicate that the phenomenon is part of the progressive degenerative process. A possible pathogenesis includes tearing of the annulus fibrosus due to the severe degeneration of the disc, followed by an inflammatory response to nuclear material and phagocytic resorption of calcified material. PMID:11327362

Jensen, V F

2001-01-01

323

Molecular basis of intervertebral disc degeneration.  

PubMed

This review will acquaint the reader with normal development, structure, and function of the intervertebral disc. The disc is composed of the vertebral endplate, nucleus pulposus, and annulus fibrosus. These three functional components all serve important purposes for health and function of the disc. Nutrition and biomechanics are also discussed. The molecular basis of disc degeneration is reviewed so that biologic approaches to the reversal and or treatment of disc degeneration may be better understood. PMID:15541661

Walker, Matthew H; Anderson, D Greg

2004-01-01

324

High-efficiency high-power semiconductor disc laser  

NASA Astrophysics Data System (ADS)

High efficiency, high power and excellent beam quality has been achieved in optically-pumped semiconductor disc lasers (OPS-disc laser) emitting at 1000nm. Minimizing the thermal resistance between active region and heat-sink, more than 5.5W of continuous wave (cw) output has been obtained at room-temperature. Even more remarkable, the laser characteristics corresponding to this power display differential efficiencies of better than 50% and optical conversion efficiencies of better than 40%. This combination of high power and high efficiency represents the best reported values so far. As such, a highly efficient beam converter has been realized, transforming low-brightness optical pump power into high-brightness laser emission.

Brick, Peter; Lutgen, Stephan; Albrecht, Tony; Luft, Johann; Späth, Werner

2003-06-01

325

Clinical Outcomes of Percutaneous Plasma Disc Coagulation Therapy for Lumbar Herniated Disc Diseases  

PubMed Central

Objective This is prospective study of clinical outcomes of percutaneous plasma disc coagulation Therapy (PDCT) in patients with herniated lumbar disc disease (HLD) to evaluate the safety and efficacy in its clinical application and usefulness as a reliable alternative to microscopic discectomy. Methods Forty-six patients were enrolled in this study from April 2006 to June 2010. All patients had one-level HLD. Disc degeneration was graded on routine T2-weighted magnetic resonance Image (MRI) using the Pfirrmann's grading system and all index levels were grade 3 and grade 4. Indications for surgery were radiculopathy caused by disc protrusion with soft consistency. MRI was done at one month after the procedure in all patients to check post-PDCT change. The clinical outcomes were evaluated using Visual Analog Scales (VAS) score and MacNab's criteria. Results This study was approved by the Institutional Review Board of our institution. The age of the study population ranged from 16 to 59 years with a mean age of 37.2 years. There were 29 males and 17 females in this study. The mean period of clinical follow-up was 21 months. The average preoperative VAS score for radiculopathy was 7.4±1.4, while the final follow-up VAS score was 1.4±0.7 (p<0.001). In MacNab's criteria, 41 patients (89.1%) had achieved favorable improvement (excellent and good) until later follow-up. There were one patient from infection and two patients who needed to convert to open discectomy. Conclusion PDCT is a safe and efficient treatment modality in a selective patient with HLD.

Kim, Sung Chul; Cho, Ki Hong

2012-01-01

326

Imbalanced Protein Expression Patterns of Anabolic, Catabolic, Anti-Catabolic and Inflammatory Cytokines in Degenerative Cervical Disc Cells: New Indications for Gene Therapeutic Treatments of Cervical Disc Diseases  

PubMed Central

Degenerative disc disease (DDD) of the cervical spine is common after middle age and can cause loss of disc height with painful nerve impingement, bone and joint inflammation. Despite the clinical importance of these problems, in current publications the pathology of cervical disc degeneration has been studied merely from a morphologic view point using magnetic resonance imaging (MRI), without addressing the issue of biological treatment approaches. So far a wide range of endogenously expressed bioactive factors in degenerative cervical disc cells has not yet been investigated, despite its importance for gene therapeutic approaches. Although degenerative lumbar disc cells have been targeted by different biological treatment approaches, the quantities of disc cells and the concentrations of gene therapeutic factors used in animal models differ extremely. These indicate lack of experimentally acquired data regarding disc cell proliferation and levels of target proteins. Therefore, we analysed proliferation and endogenous expression levels of anabolic, catabolic, ant-catabolic, inflammatory cytokines and matrix proteins of degenerative cervical disc cells in three-dimensional cultures. Preoperative MRI grading of cervical discs was used, then grade III and IV nucleus pulposus (NP) tissues were isolated from 15 patients, operated due to cervical disc herniation. NP cells were cultured for four weeks with low-glucose in collagen I scaffold. Their proliferation rates were analysed using 3-(4, 5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide. Their protein expression levels of 28 therapeutic targets were analysed using enzyme-linked immunosorbent assay. During progressive grades of degeneration NP cell proliferation rates were similar. Significantly decreased aggrecan and collagen II expressions (P<0.0001) were accompanied by accumulations of selective catabolic and inflammatory cytokines (disintegrin and metalloproteinase with thrombospondin motifs 4 and 5, matrix metalloproteinase 3, interleukin-1?, interleukin-1 receptor) combined with low expression of anti-catabolic factor (metalloproteinase inhibitor 3) (P<0.0001). This study might contribute to inhibit inflammatory catabolism of cervical discs.

Mern, Demissew S.; Beierfu?, Anja; Fontana, Johann; Thome, Claudius; Hegewald, Aldemar A.

2014-01-01

327

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

PubMed

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 using this data. The second lens from each donor was used to measure resistance to physical deformation by providing a compressive force to the lens. The lens capsule was then removed from each lens and each measurement was repeated to ascertain what role the capsule plays in determining these optical and physical characteristics. Age dependent changes in lens focal length, lens surface curvatures and lens resistance to physical deformation are described. Isolated lens focal length was found to be significantly linearly correlated with both the anterior and posterior surface curvatures. No age dependent change in equivalent refractive index of the isolated lens was found. Although decapsulating human lenses causes similar changes in focal length to that which we have shown to occur when human lenses are mechanically stretched into an unaccommodated state, the effects are due to nonsystematic changes in lens curvatures. These studies reinforce the conclusion that lens hardening must be considered as an important factor in the development of presbyopia, that age changes in the human lens are not limited to the loss of accommodation that characterizes presbyopia but that the lens optical and physical properties change substantially with age in a complex manner. PMID:10343784

Glasser, A; Campbell, M C

1999-06-01

328

Risk factors for recurrent lumbar disc herniations.  

PubMed

The most common complication after lumbar discectomy is reherniation. As the first step in reducing the rate of recurrence, many studies have been conducted to find out the factors that may increase the reherniation risk. Some reported factors are age, sex, the type of lumbar disc herniation, the amount of fragments removed, smoking, alcohol consumption and the length of restricted activities. In this review, the factors studied thus far are summarized, excepting factors which cannot be chosen or changed, such as age or sex. Apart from the factors shown here, many other risk factors such as diabetes, family history, history of external injury, duration of illness and body mass index are considered. Few are agreed upon by all. The reason for the diverse opinions may be that many clinical and biomechanical variables are involved in the prognosis following operation. For the investigation of risk factors in recurrent lumbar disc herniation, large-scale multicenter prospective studies will be required in the future. PMID:24761206

Shin, Byung-Joon

2014-04-01

329

New ages for Middle and Later Stone Age deposits at Mumba rockshelter, Tanzania: optically stimulated luminescence dating of quartz and feldspar grains.  

PubMed

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

Gliganic, Luke A; Jacobs, Zenobia; Roberts, Richard G; Domínguez-Rodrigo, Manuel; Mabulla, Audax Z P

2012-04-01

330

Nonlinear Optics and Coherent Optical Control of Single Electron Systems.  

National Technical Information Service (NTIS)

Work on this program was aimed at developing and understanding nano- optical structures with emphasis on developing quantum optical based devices. Specific work focused on semiconductor quantum dots. During this research period, a number of important disc...

D. G. Steel

2008-01-01

331

Hydrogel discs for digital microfluidics  

PubMed Central

Hydrogels are networks of hydrophilic polymer chains that are swollen with water, and they are useful for a wide range of applications because they provide stable niches for immobilizing proteins and cells. We report here the marriage of hydrogels with digital microfluidic devices. Until recently, digital microfluidics, a fluid handling technique in which discrete droplets are manipulated electromechanically on the surface of an array of electrodes, has been used only for homogeneous systems involving liquid reagents. Here, we demonstrate for the first time that the cylindrical hydrogel discs can be incorporated into digital microfluidic systems and that these discs can be systematically addressed by droplets of reagents. Droplet movement is observed to be unimpeded by interaction with the gel discs, and gel discs remain stationary when droplets pass through them. Analyte transport into gel discs is observed to be identical to diffusion in cases in which droplets are incubated with gels passively, but transport is enhanced when droplets are continually actuated through the gels. The system is useful for generating integrated enzymatic microreactors and for three-dimensional cell culture. This paper demonstrates a new combination of techniques for lab-on-a-chip systems which we propose will be useful for a wide range of applications.

Fiddes, Lindsey K.; Luk, Vivienne N.; Au, Sam H.; Ng, Alphonsus H. C.; Luk, Victoria; Kumacheva, Eugenia; Wheeler, Aaron R.

2012-01-01

332

Ruptured disc after arthroscopic repositioning in the temporomandibular joint: a retrospective magnetic resonance imaging study.  

PubMed

Our aim was to explore the incidence of rupture after arthroscopic repositioning of the disc of the temporomandibular joint (TMJ) by reviewing magnetic resonance images (MRI) of the TMJ taken before and after operation, and to investigate correlations retrospectively. We studied 247 patients with anterior disc displacement of the TMJ, and categorised them into 3 groups based on the postoperative MRI. The first group comprised those whose disc ruptured after repositioning, the second those who had a possible rupture of the disc after repositioning, and the third had no rupture of the disc after repositioning. Age, sex, duration of symptoms, maximum incisal mouth opening, whether the anterior disc displacement was unilateral or bilateral, and the Wilkes stage, were included in the analysis. The incidence of rupture (5/247) was 2%. Weak points at the intermediate zone of the disc were found in 4 of the 5 joints. The patients whose discs ruptured were significantly younger than the other 2 groups (p=0.001). There was no statistically significant difference in preoperative duration of symptoms and mouth opening among the groups. The proportions of unilateral and bilateral disc displacement (p=0.047) and Wilkes stage (p=0.027) differed among the 3 groups. The Wilkes stages was significantly more advanced in the ruptured group than in the other 2 groups (p=0.027) with 4/5 being bilateral. The weak point in the intermediate zone of the disc on MRI could be a sign of rupture. Teenagers and young adults with anterior disc displacement without reduction, particularly those in whom it is bilateral, are at a higher risk of a rupture after repositioning of the disc by arthroscopy. PMID:24736122

Li, Hui; Cai, Xieyi; Yang, Chi; Wang, Shaoyi; Huang, Linjian

2014-07-01

333

SHEDDING NEW LIGHT ON THE AGE OF THE PALOUSE LOESS, SOUTHEASTERN WASHINGTON, USING OPTICALLY STIMULATED LUMINESCENCE DATING OF QUARTZ  

NASA Astrophysics Data System (ADS)

A single-aliquot regenerative-dose (SAR) protocol was applied to fine-silt (4-11 micron), coarse-silt (35-50 micron), and sand-sized (90-125 micron) quartz grains extracted from loess from the Palouse, southeastern Washington. Since its introduction in 2000, this optically stimulated luminescence (OSL) dating method has been applied to a wide variety of sediments, and has been shown to be robust and reliable. A clearly defined set of quality control checks has been developed to assess the suitability of samples to which this method is applied; if a sample passes these quality checks, then the ages are considered to be reliable. For the Palouse loess samples in this study, the luminescence characteristics of the various size fractions differed, and not all quartz fractions proved to be suitable for OSL dating. The coarse-grain quartz samples appear to be contaminated with feldspar, probably as inclusions within the quartz grains. OSL ages were determined using the 35-50 micron quartz fraction; the OSL signals from both this and the 4-11 micron quartz fraction passed all of the quality control checks associated with determining an accurate and precise quartz SAR OSL age. On the basis on the luminescence characteristics, therefore, the quartz OSL ages generated are believed to be robust and reliable. At some sites within the Palouse Loess region, the quartz OSL ages generated were in agreement with independent age control provided by chemical identification of tephra layers associated with known eruptions. However, at a number of sites the quartz OSL ages and the tephra evidence did not agree. The cause of this discrepancy was unknown, but given the anticipated reliability of the quartz OSL ages, attention turned to re-evaluation and re-analysis of the tephra layers which had originally been sampled and analysed more than 15 years prior to collection of the samples for quartz OSL dating. The chronology at the site was further complicated by two much earlier studies which applied IRSL and TL dating methods to polymineral fine-grains, generating ages which were acknowledged by the authors to potentially underestimate the true age of the loess units, whilst other ages appeared to agree broadly with the ages of the tephra units identified. Both the previously published luminescence ages and tephrochronologic data, and the newly generated OSL and tephra data are evaluated; the implications for stratigraphic interpretation at these and other loess sites is discussed.

Roberts, H. M.; Gaylord, D.; Foit, F. F.; Sweeney, M.; Busacca, A. J.

2009-12-01

334

Debris disc formation induced by planetary growth  

NASA Astrophysics Data System (ADS)

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.

Kobayashi, H.; Löhne, T.

2014-08-01

335

Cone Structure Imaged With Adaptive Optics Scanning Laser Ophthalmoscopy in Eyes With Nonneovascular Age-Related Macular Degeneration  

PubMed Central

Purpose. To evaluate cone spacing using adaptive optics scanning laser ophthalmoscopy (AOSLO) in eyes with nonneovascular AMD, and to correlate progression of AOSLO-derived cone measures with standard measures of macular structure. Methods. Adaptive optics scanning laser ophthalmoscopy images were obtained over 12 to 21 months from seven patients with AMD including four eyes with geographic atrophy (GA) and four eyes with drusen. Adaptive optics scanning laser ophthalmoscopy images were overlaid with color, infrared, and autofluorescence fundus photographs and spectral domain optical coherence tomography (SD-OCT) images to allow direct correlation of cone parameters with macular structure. Cone spacing was measured for each visit in selected regions including areas over drusen (n = 29), at GA margins (n = 14), and regions without drusen or GA (n = 13) and compared with normal, age-similar values. Results. Adaptive optics scanning laser ophthalmoscopy imaging revealed continuous cone mosaics up to the GA edge and overlying drusen, although reduced cone reflectivity often resulted in hyporeflective AOSLO signals at these locations. Baseline cone spacing measures were normal in 13/13 unaffected regions, 26/28 drusen regions, and 12/14 GA margin regions. Although standard clinical measures showed progression of GA in all study eyes, cone spacing remained within normal ranges in most drusen regions and all GA margin regions. Conclusions. Adaptive optics scanning laser ophthalmoscopy provides adequate resolution for quantitative measurement of cone spacing at the margin of GA and over drusen in eyes with AMD. Although cone spacing was often normal at baseline and remained normal over time, these regions showed focal areas of decreased cone reflectivity. These findings may provide insight into the pathophysiology of AMD progression. (ClinicalTrials.gov number, NCT00254605.)

Zayit-Soudry, Shiri; Duncan, Jacque L.; Syed, Reema; Menghini, Moreno; Roorda, Austin J.

2013-01-01

336

High-resolution optical signatures of fresh and aged explosives in the 420nm to 620nm illumination range  

NASA Astrophysics Data System (ADS)

Optical signatures of fresh and aged explosives are measured and compared to determine whether there exist differences in the signatures that can be exploited for detection. The explosives examined are RDX, TNT, and HMX, which have been heated for two weeks at 75 degrees centigrade or irradiated for two weeks with a 15-Watt ultraviolet lamp (254nm). The optical signatures are obtained by illuminating the samples with a sequence of laser wavelengths between 420nm and 620nm in 10 nm steps and measuring the spectra of light scattered from the sample at each laser wavelength. The measurements are performed on the Naval Research Laboratory's SWOrRD instrument. SWOrRD is capable of illuminating a sample with laser wavelength between 210nm and 2000nm, in steps of 0.1nm, and measuring the spectrum of light scattered from the sample at each wavelength. SWOrRD's broad tuning range, high average power (1- 300mW), narrow line width (< 4cm-1), and rapid wavelength tunability enable these measurements. Results, based on more than 80 measurements - each at 21 sequential laser wavelengths, indicate that the variation in spectral line amplitude observed when altering laser illumination wavelength differs between fresh and aged explosives. Thus, an instrument for rapid and reagent-less differentiation between aged and fresh explosives, based on illumination with a few appropriately chosen laser wavelengths appears feasible.

Lunsford, Robert; Grun, Jacob; Gump, Jared

2012-05-01

337

Correlation of Choroidal Thickness and Volume Measurements with Axial Length and Age Using Swept Source Optical Coherence Tomography and Optical Low-Coherence Reflectometry  

PubMed Central

Purpose. To report choroidal thickness and volume in healthy eyes using swept source optical coherence tomography (SS-OCT). Methods. A prospective observational study of 122 patients examined with swept source OCT (DRI-OCT, Topcon, Japan). In each eye, we performed 256 horizontal scans, 12?mm in length and centered on the fovea. We calculated choroidal thickness manually with a built-in caliper and automatically using DRI-OCT mapping software. Choroidal volume was also automatically calculated. We measured axial length with optical low-coherence reflectometry (Lenstar LS 900, Haag-Streit, Switzerland). Results. The choroid has focally increased thickness under the fovea. Choroid was thinnest in the outer nasal quadrant. In stepwise regression analysis, age was estimated as the most significant factor correlating with decreased choroidal thickness (F = 23.146, P < 0.001) followed by axial length (F = 4.902, P = 0.03). Refractive error was not statistically significant (F = 1.16, P = 0.28). Conclusions. SS-OCT is the first commercially available system that can automatically create choroidal thickness and volume maps. Choroidal thickness is increased at the fovea and is thinnest nasally. Age and axial length are critical for the estimation of choroidal thickness and volume. Choroidal measurements derived from SS-OCT images have potential value for objectively documenting disease-related choroidal thickness abnormalities and monitoring progressive changes over time.

Michalewski, Janusz; Nawrocka, Zofia; Bednarski, Maciej; Nawrocki, Jerzy

2014-01-01

338

Requirements and Specifications for Cartographic Video Discs.  

National Technical Information Service (NTIS)

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 ...

D. J. Costanzo

1984-01-01

339

The Age of Enlightenment: Evolving Opportunities in Brain Research Through Optical Manipulation of Neuronal Activity  

PubMed Central

Optical manipulation of neuronal activity has rapidly developed into the most powerful and widely used approach to study mechanisms related to neuronal connectivity over a range of scales. Since the early use of single site uncaging to map network connectivity, rapid technological development of light modulation techniques has added important new options, such as fast scanning photostimulation, massively parallel control of light stimuli, holographic uncaging, and two-photon stimulation techniques. Exciting new developments in optogenetics complement neurotransmitter uncaging techniques by providing cell-type specificity and in vivo usability, providing optical access to the neural substrates of behavior. Here we review the rapid evolution of methods for the optical manipulation of neuronal activity, emphasizing crucial recent developments.

Jerome, Jason; Heck, Detlef H.

2011-01-01

340

Measuring system of transient temperature distribution on the brake disc rotor  

SciTech Connect

A system to measure transient temperature distribution on the brake disc rotor at high speed braking has been developed and its measuring principle and configuration are discussed in this paper. This system consists of two revolution sensors and two sets of optical fiber array, photoelectric elements, and microprocessor, which fiber array is so arranged that it faces the brake disc rotor. This new system has the following features: Measuring is made using a visible radiation wavelength range for red hot temperatures higher than 550/sup 0/C. The optical plastic fibers allow non-contact measuring in a narrow space. Ever-changing temperature distribution patterns on the disc rotor surface during high speed braking can be measured for each revolution while the disc is revolving.

Idogaki, T.; Kawai, H.; Harada, H.; Inoue, H.

1987-01-01

341

Error Rate Reduction of Super-Resolution Near-Field Structure Disc  

NASA Astrophysics Data System (ADS)

We report the error rate improvement of super-resolution near-field structure (super-RENS) write-once read-many (WORM) and read-only-memory (ROM) discs in a blue laser optical system [laser wavelength (?), 405 nm; numerical aperture (NA), 0.85]. We prepared samples of higher carrier level WORM discs and wider pit width ROM discs. Using controlled equalization (EQ) characteristics and an adaptive write strategy and an advanced adaptive partial response maximum likelihood (PRML) technique, we obtained a bit error rate (bER) of 10-4 level. This result shows the high feasibility of super-RENS technology for practical use.

Kim, Jooho; Bae, Jaecheol; Hwang, Inoh; Lee, Jinkyung; Park, Hyunsoo; Chung, Chongsam; Kim, Hyunki; Park, Insik; Tominaga, Junji

2007-06-01

342

26 CFR 1.246-4 - Dividends from a DISC or former DISC.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 2009-04-01 false Dividends from a DISC or former DISC. 1.246-4 Section 1.246-4 Internal Revenue...for Corporations § 1.246-4 Dividends from a DISC or former DISC. The deduction provided...

2009-04-01

343

26 CFR 1.246-4 - Dividends from a DISC or former DISC.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Dividends from a DISC or former DISC. 1.246-4 Section 1.246-4 Internal Revenue...for Corporations § 1.246-4 Dividends from a DISC or former DISC. The deduction provided...

2013-04-01

344

Potential regenerative treatment strategies for intervertebral disc degeneration in dogs.  

PubMed

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

Bach, Frances C; Willems, Nicole; Penning, Louis C; Ito, Keita; Meij, Björn P; Tryfonidou, Marianna A

2014-01-01

345

Stellar discs in massive galaxies  

NASA Astrophysics Data System (ADS)

Excluding those unsettled systems undergoing mergers, bright galaxies come in two flavours: with and without discs. In this work we look for photometric evidence for presence of discs and compare it with kinematic results of the ATLAS3D survey (Cappellari et al. 2011). We fit a Sérsic (1968) function to azimuthally averaged light profiles of ATLAS3D galaxies to derive single component fits and, subsequently, we fit a combination of the Sérsic function (free index n) and an exponential function (n=1) with the purpose of decomposing the light profiles into ``bulge'' and ``disc'' components (B+D model) of all non-barred sample galaxies. We compare the residuals of the B+D models with those of the single Sérsic fits and select the B+D model as preferred only when the improvement is substantial and there are no correlations within residuals. We find that the high angular momentum objects (fast rotators) are disc dominated systems with bulges of typically low n (when their light profiles can be decomposed) or are best represented with a single Sérsic function with a low Sérsic index (n<3). Single component systems with large Sérsic indices are characteristic of low angular momentum objects (slow rotators).

Krajnovi?, D.; Alatalo, K.; Blitz, L.; Bois, M.; Bournaud, F.; Bureau, M.; Cappellari, M.; Davies, R. L.; Davis, T. A.; de Zeeuw, P. T.; Emsellem, E.; Khochfar, S.; Kuntschner, H.; McDermid, R. M.; Morganti, R.; Naab, T.; Sarzi, M.; Scott, N.; Serra, P.; Weijmans, A.; Young, L. M.

2013-07-01

346

Intervertebral disc degeneration in dogs  

Microsoft Academic Search

Back pain is common in both dogs and humans, and is often associated with intervertebral disc (IVD) degeneration. The IVDs are essential structures of the spine and degeneration can ultimately result in diseases such as IVD herniation or spinal instability. In order to design new treatments halting or even preventing IVD degeneration, more basic knowledge of the disease process is

N. Bergknut

2011-01-01

347

Tank Car Frangible Disc Test.  

National Technical Information Service (NTIS)

Tests were performed at the Transportation Test Center to evaluate the performance of various frangible disc designs, with respect to AAR Specification A5.03. Tests were also performed to determine the range of burst pressures and effect of temperature, c...

D. A. DiBrito B. R. Rajkumar

1990-01-01

348

Electromagnetic Levitation of a Disc  

ERIC Educational Resources Information Center

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…

Valle, R.; Neves, F.; de Andrade, R., Jr.; Stephan, R. M.

2012-01-01

349

Circumstellar discs around A stars  

NASA Astrophysics Data System (ADS)

Since the IRAS mission it is known that a couple of nearby young stars are surrounded by dust disks (Aumann 1995); two prominent examples are Vega and \\beta Pictoris. CO radio observations of these stars, carried out to trace the gas component of these disks, revealed a strong depletion of CO (Dent et al. 1995). This has been interpreted as a general gas depletion, and models for the formation of gas-giant planets have been called in question. Detailed disc models concentrating on the discs' gas component show that CO has been selectively depleted in the dusty and gaseous discs by photodissociation and freezing out of CO on the cold dust grain surfaces (Rentzsch-Holm, Holweger & Bertoldi (1998), Kamp & Bertoldi 1998). We will now compare our models with the observation to fix the remaining free parameters. The disc mass, the main free parameter, can be inferred from modeling the infrared excess using dust models with various grain sizes and chemical composition. References: Aumann, H.H. 1985. PASP 97, 885 Dent, W.R.F., et al. 1995. MNRAS 277, L25 Rentzsch-Holm, I., Holweger, H., Bertoldi, F. 1998. ASP Conference Series 132, 275 Kamp, I., Bertoldi, F. 1998. in preparation

Kamp, I.; Holweger, H.; Bertoldi, I.

350

Disc detector assembly  

SciTech Connect

A miniature, nonevacuated, detector refrigerator assembly for use in infrared imaging systems is described. The assembly incorporates a miniature Joule-Thomson laminar refrigerator which serves as the substrate for the detector subassembly, electrical leads, as well as the primary structural element of the assembly. The detector subassembly is positioned on the cold region of the refrigerator, surrounded by insulating material and capped by an optical window or filter as required. As a result, the detector is cooled while the contact pads used for connection to external devices are at the ambient temperature. A piece of high thermally conductive material may be placed in the vicinity of the detector subassembly so that during operation gases in the chamber surrounding the detector assembly will preferentially condense thereon rather than on the detector subassembly.

Jungkman, D.L.; Coda, R.C.; Nicholson, P.N.

1984-12-18

351

Human lumbar apophyseal joint damage and intervertebral disc degeneration.  

PubMed Central

OBJECTIVES--To record the extent and location of lumbar apophyseal cartilage damage, and to ascertain if the extent of damage is correlated with the grade of disc degeneration, age, or both. METHODS--The extent and location of fibrillated areas of the apophyseal cartilage of the joint surfaces of 29 lumbar motion segments were examined using computer aided image processing of Indian ink stained areas, and degeneration of the associated intervertebral discs graded using the method of Nachemson. RESULTS--It was found that these joints showed a greater extent and prevalence of cartilage fibrillation than the knee, hip or ankle, with significant damage in specimens younger than 30 years. Damage was predominantly located peripherally, superiorly, and posteriorly in the concave superior apophyseal surfaces, and was predominantly peripheral and posterior in the inferior surfaces, with a tendency to be located inferiorly. There was a weak correlation between apophyseal joint damage and the intervertebral disc degenerative grade, but this was inconclusive, as both increased with age. CONCLUSIONS--The pattern of damage exhibited by superior joint surfaces is most probably caused by tension on collagenous joint capsule fibres which insert into the surfaces posteriorly, so producing an area of fibrocartilage unsuited to loadbearing. Tension on such fibres would be greatest during spinal flexion. The pattern of damage of the inferior surfaces lends some support to the hypothesis that their apices impact the laminae of the lumbar vertebra inferior to them, consequent upon the degeneration and narrowing of the associated intervertebral disc. The predominantly peripheral location of fibrillation of both superior and inferior surfaces may be associated with inadequate mechanical conditioning of marginal joint areas. Disc degeneration cannot be the initial cause of apophyseal fibrillation in most specimens. The study indicates a need for regular spinal exercise, starting at a young age.

Swanepoel, M W; Adams, L M; Smeathers, J E

1995-01-01

352

Age-related compaction of lens fibers affects the structure and optical properties of rabbit lenses  

Microsoft Academic Search

BACKGROUND: The goal of this investigation was to correlate particular age-related structural changes (compaction) to the amount of scatter in rabbit lenses and to determine if significant fiber compaction occurred in the nuclear and inner cortical regions. METHODS: New Zealand White rabbits at 16–20 months old (adult; n = 10) and at 3.5–4 years old (aged; n = 10) were

Samer Al-khudari; Sean T Donohue; Walid M Al-Ghoul; Kristin J Al-Ghoul

2007-01-01

353

46 CFR 64.61 - Rupture disc.  

Code of Federal Regulations, 2013 CFR

... 2013-10-01 2013-10-01 false Rupture disc. 64.61 Section 64.61 Shipping COAST...Vacuum Relief Devices for MPTs § 64.61 Rupture disc. If a rupture disc is the only pressure relief device on the tank,...

2013-10-01

354

Occupational risk factors for symptomatic lumbar disc herniation; a case-control study  

PubMed Central

Background: Previous studies mostly did not separate between symptomatic disc herniation combined with osteochondrosis/spondylosis of the lumbar spine and symptomatic disc herniation in radiographically normal intervertebral spaces. This may at least in part explain the differences in the observed risk patterns. Aims: To investigate the possible aetiological relevance of physical and psychosocial workload to lumbar disc herniation with and without concomitant osteochondrosis/spondylosis. Methods: A total of 267 cases with acute lumbar disc herniation (in two practices and four clinics) and 197 control subjects were studied. Data were gathered in a structured personal interview and analysed using logistic regression to control for age, region, nationality, and diseases affecting the lumbar spine. Cases without knowledge about osteochondrosis/spondylosis (n=42) were excluded from analysis. Risk factors were examined separately for those cases with (n=131) and without (n=94) radiographically diagnosed concomitant osteochondrosis or spondylosis. Results: There was a statistically significant positive association between extreme forward bending and lumbar disc herniation with, as well as without concomitant osteochondrosis/spondylosis. There was a statistically significant relation between cumulative exposure to weight lifting or carrying and lumbar disc herniation with, but not without, concomitant osteochondrosis/spondylosis. Cases with disc herniation reported time pressure at work as well as psychic strain through contact with clients more frequently than control subjects. Conclusions: Further larger studies are needed to verify the concept of distinct aetiologies of lumbar disc herniation in relatively younger persons with otherwise normal discs and of disc herniation in relatively older persons with structurally damaged discs.

Seidler, A; Bolm-Audorff, U; Siol, T; Henkel, N; Fuchs, C; Schug, H; Leheta, F; Marquardt, G; Schmitt, E; Ulrich, P; Beck, W; Missalla, A; Elsner, G

2003-01-01

355

Age-related compaction of lens fibers affects the structure and optical properties of rabbit lenses  

PubMed Central

Background The goal of this investigation was to correlate particular age-related structural changes (compaction) to the amount of scatter in rabbit lenses and to determine if significant fiber compaction occurred in the nuclear and inner cortical regions. Methods New Zealand White rabbits at 16–20 months old (adult; n = 10) and at 3.5–4 years old (aged; n = 10) were utilized for this study. Immediately after euthanising, scatter was assessed in fresh lenses by low power helium-neon laser scan analysis. Scatter data was analyzed both for whole lenses and regionally, to facilitate correlation with morphometric data. After functional analysis, lenses were fixed and processed for scanning electron microcopy (SEM; right eyes) and light microscopy (LM; left eyes). Morphometric analysis of SEM images was utilized to evaluate compaction of nuclear fibers. Similarly, measurements from LM images were used to assess compaction of inner cortical fibers. Results Scatter was significantly greater in aged lenses as compared to adult lenses in all regions analyzed, however the difference in the mean was slightly more pronounced in the inner cortical region. The anterior and posterior elliptical angles at 1 mm (inner fetal nucleus) were significantly decreased in aged vs. adult lenses (anterior, p = 0.040; posterior, p = 0.036). However, the average elliptical angles at 2.5 mm (outer fetal nucleus) were not significantly different in adult and aged lenses since all lenses examined had comparable angles to inner fetal fibers of aged lenses, i.e. they were all compacted. In cortical fibers, measures of average cross-sectional fiber area were significantly different at diameters of both 6 and 7 mm as a function of age (p = 0.011 and p = 0.005, respectively). Accordingly, the estimated fiber volume was significantly decreased in aged as compared to adult lenses at both 6 mm diameter (p = 0.016) and 7 mm diameter (p = 0.010). Conclusion Morphometric data indicates that inner cortical fibers undergo a greater degree of age-related compaction than nuclear fibers. Increased scatter appears to be only tentatively correlated with regions of fiber compaction, suggesting that it is simply one of an array of factors that contribute to the overall decreased transparency in aged rabbit lenses.

Al-khudari, Samer; Donohue, Sean T; Al-Ghoul, Walid M; Al-Ghoul, Kristin J

2007-01-01

356

Cervical arthroplasty using ProDisc-C Case Report  

PubMed Central

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.

Nica, DA; Copaciu, R

2013-01-01

357

Comparison of Lasnex Calculations with Experimental Results of Parylene Disc Irradiations at 1.06 mu M.  

National Technical Information Service (NTIS)

Calculations are discussed using the 2D Lagrangian code LASNEX to simulate irradiation of Parylene discs. Using a representation of the experimental beam profile, geometric optics propagation, and an absorption model based on plasma simulations, the scatt...

W. C. Mead W. L. Kruer J. D. Lindl H. D. Shay

1975-01-01

358

Intraradicular disc herniations in the lumbar spine and a new classification of intradural disc herniations  

Microsoft Academic Search

Study design: A case report of intraradicular disc herniation. Intraradicular disc herniation is a special type of intradural disc hernations. In this report, we present the tenth case of intraradicular lumbar disc herniation and suggest a new classification for intradural disc herniations.Case Report: A 32-year-old male was admitted to hospital having experienced pain in the lower back and right leg

M Mut; M Berker; S Palao?lu

2001-01-01

359

Dust grain sizes in Herschel-resolved debris discs  

NASA Astrophysics Data System (ADS)

Collisional models of debris discs robustly predict that the effective minimum size of their dust grains, smin, should be set by stellar radiation pressure. Under reasonable assumptions for the composition and density of dust, the blowout radius sblow -\\ the radius of the smallest grains that can stay in bound orbits around the star against radiation pressure -\\ is expected to vary from several tenths of a micron for G-type stars to several microns for A-type stars. For most of the discs, smin is predicted to be a few times sblow, and the size distribution index q to lie approximately between 3 and 4. As a result, the grains with s0=smin*sqrt((1-q)/(3-q)) should dominate the cross section of material and thus contribute the most into the observed emission at mid- to far-infrared wavelengths. The exact smin/sblow ratio depends on several factors, such as the optical depth of the disc or the degree of dynamical excitation of dust-producing planetesimals. At a first glance, this seems to be supported by observations. Typical grain sizes inferred from thermal emission and scattered light images of many individual discs lie at a few microns. However, the expected correlation between s0 (or smin) and sblow across a broad luminosity range have not been checked in depth. Here we use a uniform sample of 22 discs well resolved in several Herschel programmes to re-address the question. Setting the disc radii rdisc to the values inferred from the resolved images, we perform the SED modelling to find best-fit smin and q. We confirm that rdisc does not correlate with the stellar type, as found before. We also confirm that the ratio of the dust temperature to the blackbody temperature at the dust location goes from 2 - 2.5 for G-type stars to about unity for the most luminous A-type stars, as pointed out by Booth et al. (2013). However, we find that the data are more consistent with a constant s0 ( 7 microns) or smin ( 3 microns) across the luminosity range, rather than with a constant smin/sblow. This finding needs further verification with a larger sample of discs. If confirmed, it might indicate systematic differences in disc properties with the stellar type, such as those in the chemical composition of dust, degree of stirring or width of the underlying planetesimal belts.

Pawellek, Nicole; Krivov, Alexander; Marshall, Jonathan; Montesinos, Benjamin; Eiroa, Carlos

2013-07-01

360

Microimmunoanalysis on standard compact discs to determine low abundant compounds.  

PubMed

High-density competitive indirect microimmunoassays were performed in both sides of compact discs by direct absorption of immunoreagents on polycarbonate surface, using gold- or enzyme-labeled immunoglobulins as tracers for displaying the immunoreaction. The operational principle is based on the use of a low-reflectivity compact disc as analytical platform that allows the reflection/transmission (30/70%) of the CD reader laser beam (lambda 780 nm). The reflected light is used to scan the disc track keeping it in movement. The transmitted light is detected by a planar photodiode integrated on the CD drive. The variation of the optical transmission of the light caused by the immunoreaction products is related to the sample concentration. As a proof of concept, low abundant compounds, commonly used as pesticides, were detected in a 60-min total assay time, with a limit of detection ranging from 0.02 to 0.62 microg/L for 2,4,5-TP, chlorpyriphos, and metolachlor. The obtained results show the enormous prospective of compact discs in combination with CD players for multiresidue and drug discovery applications. PMID:17854157

Morais, Sergi; Carrascosa, Javier; Mira, David; Puchades, Rosa; Maquieira, Angel

2007-10-15

361

Sudden blindness caused by anterior ischemic optic neuropathy in 5 children on continuous peritoneal dialysis 1 1 Published partially (case 3) in abstract form in Arch Ped 7:437, 2000, and in Pediatr Nephrol 16:C4, 2001  

Microsoft Academic Search

The authors report the occurrence of sudden blindness in 5 children (mean age, 32 months; range, 11 to 60) during continuous peritoneal dialysis regimen. All children presented with loss of light perception, visual fixation and ocular pursuit, and bilateral mydriasis unreactive to bright light. Fundoscopic examination found signs of anterior ischemic optic neuropathy with disc swelling, edema, and hemorrhages. Whereas

Anne-Laure Lapeyraque; Elie Haddad; Jean-Luc André; Dominique Brémond-Gignac; C. Mark Taylor; Pornpimol Rianthavorn; Isidro B Salusky; Chantal Loirat

2003-01-01

362

Sealing arrangement with annular flexible disc  

DOEpatents

Fluid sealing arrangements including an annular shaped flexible disc having enlarged edges disposed within channel-shaped annular receptacles which are spaced from one another. The receptacles form an annular region for contacting and containing the enlarged edges of the disc, and the disc is preloaded to a conical configuration. The disc is flexibly and movably supported within the receptacles so that unevenly distributed relative motion between the components containing the receptacles is accommodated without loss of sealing contact between the edges of the disc and the walls of the receptacles.

Pennell, William E. (Greensburg, PA) [Greensburg, PA; Honigsberg, Charles A. (Monroeville, PA) [Monroeville, PA

1983-01-01

363

Methodologic evaluation of the lumbar disc syndrome.  

PubMed Central

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.

Robinson, J. S.

1981-01-01

364

Optical-Ultraviolet Spectrum and Proper Motion of the Middle-aged Pulsar B1055-52  

NASA Astrophysics Data System (ADS)

PSR B1055-52 is a middle-aged (? = 535 kyr) radio, X-ray, and ?-ray pulsar showing X-ray thermal emission from the neutron star (NS) surface. A candidate optical counterpart to PSR B1055-52 was proposed by Mignani and coworkers based on Hubble Space Telescope (HST) observations performed in 1996, in one spectral band only. We report on HST observations of this field carried out in 2008, in four spectral bands. The astrometric and photometric analyses of these data confirm the identification of the proposed candidate as the pulsar's optical counterpart. Similar to other middle-aged pulsars, its optical-UV spectrum can be described by the sum of a power-law (PLO) component (F_{?} ? ?^{-?_O}), presumably emitted from the pulsar magnetosphere, and a Rayleigh-Jeans (RJ) component emitted from the NS surface. The spectral index of the PLO component, ?O = 1.05 ± 0.34, is larger than for other pulsars with optical counterparts. The RJ component, with a brightness temperature T O = (0.66 ± 0.10) d 2 350 R -2 O,13 MK (where d 350 and R O,13 are the distance to the pulsar in units of 350 pc and the radius of the emitting area in units of 13 km, respectively), shows a factor of 4 excess with respect to the extrapolation of the X-ray thermal component into the UV-optical. This hints that the RJ component is emitted from a larger, colder area, and suggests that the distance to the pulsar is smaller than previously thought. From absolute astrometry of the HST images, we measured the pulsar coordinates with a position accuracy of 0farcs15. From comparison with previous observations, we measured the pulsar proper motion, ? = 42 ± 5 mas yr-1, which corresponds to a transverse velocity Vt = (70 ± 8) d 350 km s-1. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under contract No. NAS 5-26555. Based on observations collected at the European Southern Observatory (ESO), La Silla, and Paranal, Chile under program ID 68.D-0407(A).

Mignani, R. P.; Pavlov, G. G.; Kargaltsev, O.

2010-09-01

365

Shear Mechanics of the TMJ Disc  

PubMed Central

The temporomandibular joint (TMJ) is a complex hinge and gliding joint that induces significant shear loads onto the fibrocartilage TMJ disc during jaw motion. The purpose of this study was to assess regional variation in the disc’s shear loading characteristics under physiologically relevant loads and to associate those mechanical findings with common clinical observations of disc fatigue and damage. Porcine TMJ discs were compressed between an axially translating bottom platen and a 2.5-cm-diameter indenter within a hydrated testing chamber. Discs were cyclically sheared at 0.5, 1, or 5 Hz to 1, 3, or 5% shear strain. Within the anterior and intermediate regions of the disc when sheared in the anteroposterior direction, both shear and compressive moduli experienced a significant decrease from instantaneous to steady state, while the posterior region’s compressive modulus decreased approximately 5%, and no significant loss of shear modulus was noted. All regions retained their shear modulus within 0.5% of instantaneous values when shear was applied in the mediolateral direction. The results of the disc’s regional shear mechanics suggest an observable and predictable link with the common clinical observation that the posterior region of the disc is most often the zone in which fatigue occurs, which may lead to disc damage and perforation.

Juran, C.M.; Dolwick, M.F.; McFetridge, P.S.

2013-01-01

366

Modelling spikes in quasar accretion disc temperature  

NASA Astrophysics Data System (ADS)

Microlensing observations indicate that quasar accretion discs have half-light radii larger than standard theories predict. The observations of Blackburne and colleagues suggest that these half-light radii may have a weak wavelength dependence. We consider disc temperature profiles that might match these observations. Nixon and colleagues have suggested that misaligned discs around spinning black holes can have annuli torn off them at radii where the Lense-Thirring torque overcomes the disc's viscosity. These annuli precess, spread radially, and intersect with the remaining disc, heating the disc at potentially large radii. However, unless the intersections occur at an angle of <1°, highly supersonic collisions will shock heat intersecting gas to T ˜ 107 K. Discs with such shock-heated regions have significantly larger half-light radii, but are overluminous in X-rays. If instead heating occurs through intermittent weak shocks, the X-ray luminosities are consistent with observations but the half-light radii are not significantly larger. We also study two phenomenological disc temperature profiles. Discs with a temperature spike at relatively large radii and lowered temperatures at radii inside the spike yield improved and acceptable fits to microlensing sizes in most cases. Such temperature profiles could in principle occur in sub-Keplerian discs partially supported by magnetic pressure. However, such discs overpredict the fluxes from quasars studied with microlensing except in the limit of negligible continuum emission from radii inside the temperature spike.

Hall, P. B.; Noordeh, E. S.; Chajet, L. S.; Weiss, E.; Nixon, C. J.

2014-08-01

367

Accelerated Aging Studies and the Prediction of the Archival Lifetime of Optical Disk Media  

Microsoft Academic Search

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

David E. Nikles; John M. Wiest

2000-01-01

368

Kilovoltage stereotactic radiosurgery for age-related macular degeneration: assessment of optic nerve dose and patient effective dose.  

PubMed

Age-related macular degeneration (AMD) is a leading cause for vision loss for people over the age of 65 in the United States and a major health problem worldwide. Research for new treatments of the wet form of the disease using kilovoltage stereotactic radiosurgery is currently underway at Oraya Therapeutics, Inc. In the present study, the authors extend their previous computational stylized model of a single treated eye [Med. Phys. 35, 5151-5160 (2008)] to include full NURBS-based reference head phantoms of the adult male and female using anatomical data from ICRP Publication 89. The treatment was subsequently modeled in MCNPX 2.5 using a 1 x 1 x 1 mm3 voxelized version of the NURBS models. These models incorporated several organs of interest including the brain, thyroid, salivary glands, cranium, mandible, and cervical vertebrae. A higher resolution eye section at 0.5 x 0.5 x 0.5 mm3 voxel resolution was extracted from the head phantoms to model smaller eye structures including the macula target, cornea, lens, vitreous humor, sclera/retina layer, and optic nerve. Due to lack of literature data on optic nerve pathways, a CT imaging study was undertaken to quantify the anatomical position of the optic nerve. The average absorbed doses to the organs of interest were below generally accepted thresholds for radiation safety. The estimated effective dose was 0.28 mSv which is comparable to diagnostic procedures such as a head radiograph and a factor of 10 lower than a head CT scan. PMID:19746800

Hanlon, Justin; Lee, Choonsik; Chell, Erik; Gertner, Michael; Hansen, Steven; Howell, Roger W; Bolch, Wesley E

2009-08-01

369

Extending the upper age limit for luminescence dating using the thermally transferred optically stimulated luminescence signal from quartz  

NASA Astrophysics Data System (ADS)

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.

Duller, Geoff A. T.; Wintle, Ann G.

2010-05-01

370

Percutaneous cervical nucleoplasty in the treatment of cervical disc herniation  

PubMed Central

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) ?11° or horizontal displacement (HD) ?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.

Li, Jian; Zhang, Zai-Heng

2008-01-01

371

Wnt Signaling Activates Shh Signaling in Early Postnatal Intervertebral Discs, and Re-Activates Shh Signaling in Old Discs in the Mouse  

PubMed Central

Intervertebral discs (IVDs) are strong fibrocartilaginous joints that connect adjacent vertebrae of the spine. As discs age they become prone to failure, with neurological consequences that are often severe. Surgical repair of discs treats the result of the disease, which affects as many as one in seven people, rather than its cause. An ideal solution would be to repair degenerating discs using the mechanisms of their normal differentiation. However, these mechanisms are poorly understood. Using the mouse as a model, we previously showed that Shh signaling produced by nucleus pulposus cells activates the expression of differentiation markers, and cell proliferation, in the postnatal IVD. In the present study, we show that canonical Wnt signaling is required for the expression of Shh signaling targets in the IVD. We also show that Shh and canonical Wnt signaling pathways are down-regulated in adult IVDs. Furthermore, this down-regulation is reversible, since re-activation of the Wnt or Shh pathways in older discs can re-activate molecular markers of the IVD that are lost with age. These data suggest that biological treatments targeting Wnt and Shh signaling pathways may be feasible as a therapeutic for degenerative disc disease.

Sinner, Debora; Wylie, Christopher C.; Dahia, Chitra Lekha

2014-01-01

372

Calcification in the ovine intervertebral disc: a model of hydroxyapatite deposition disease.  

PubMed

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 A) compared to cortical bone (300-600 A). 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

Melrose, James; Burkhardt, D; Taylor, T K F; Dillon, C T; Read, R; Cake, M; Little, C B

2009-04-01

373

Calcification in the ovine intervertebral disc: a model of hydroxyapatite deposition disease  

PubMed Central

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.

Burkhardt, D.; Taylor, T. K. F.; Dillon, C. T.; Read, R.; Cake, M.; Little, C. B.

2009-01-01

374

Astigmatism and biometric optic components of diode laser-treated threshold retinopathy of prematurity at 9 years of age  

PubMed Central

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.

Yang, C-S; Wang, A-G; Shih, Y-F; Hsu, W-M

2013-01-01

375

Spontaneous cervical intradural disc herniation.  

PubMed

Cervical intradural disc herniation (IDH) is a rare condition with very few case reports in the literature. We report a 64-year-old man who presented with sudden onset neck pain and rapidly progressing weakness in the left upper and lower limb. There was no history of trauma. MRI of the cervical spine showed a C6-C7 disc prolapse, for which he underwent a C6-C7 discectomy and fusion with bone graft through an anterior cervical approach. To our knowledge, all patients with a cervical IDH reported in the literature have a traumatic etiology. To the best of our knowledge, we report the first patient with a spontaneous cervical IDH. PMID:24210799

Warade, Abhijit G; Misra, Basant K

2014-05-01

376

Star-disc-binary interactions in protoplanetary disc systems and primordial spin-orbit misalignments  

NASA Astrophysics Data System (ADS)

We study the interactions between a protostar and circumstellar disc under the influence of a binary companion to determine the evolution of the mutual misalignment between the stellar spin and disc angular momentum axes. Significant misalignments can be generated as the star-disc system evolves in time such that the frequency of disc precession (driven by the binary companion) and that of stellar precession (driven by the disc) cross each other. This resonance behaviour can be understood in a geometric way from the precession dynamics of spin and disc angular momenta. We show that such resonance crossing can occur under reasonable protostar-disc-binary conditions. The star-disc inclination is also affected by mass accretion and by magnetic star-disc interaction torques, which can either promote or reduce star-disc misalignment. In general, a variety of star-disc misalignment angles are produced within the lifetimes of protoplanetary discs. We discuss the implications of our results for stellar spin orientations in binaries, for the alignments/misalignments of protostellar and debris discs, and for the stellar obliquities in exoplanetary systems. In particular, even for systems where the Kozai effect is absent or suppressed, misaligned planets and hot Jupiters may still be produced during the protoplanetary disc phase.

Lai, Dong

2014-06-01

377

The Environment of M85 Optical Transient 2006-1: Constraints on the Progenitor Age and Mass  

NASA Astrophysics Data System (ADS)

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.

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

378

Relationship between physical work load and lumbar disc herniation.  

PubMed

Lumbar disc herniation (LDH) is a disabling problem. This retrospective case control study was done to evaluate the possible relevance of physical work load with Lumbar Disc Herniation. We have performed this study in the Spinal Surgery Unit of Department of Orthopaedic Surgery at BSMMU, Dhaka from July 2007 to June 2010 where 200 cases with Lumbar Disc Herniation and 200 control subjects matched by age, gender and area of residence were taken and analyzed. Chi-square test was computed for sex, area of residence, type of physical work and effort at work, whereas Odds ratio was computed for physical work load, stress at work and daily working period. The highest odds ratio (OR) was with the physical work load (OR: 03.48, CI: 01.84-06.59), hard work (OR: 03.14, CI: 01.74-05.65) and working period of >8 hours (OR: 01.34, CI: 0.75-02.38). Odds ratio for heavy load carrying at work was 03.48 and less job satisfaction or stress at work was 02.45. There was a statistically significant positive association between cumulative exposure of physical work load and lumbar disc herniation indicating an increased occurrence of herniation in heavy physical work load and occupation requiring harder efforts. PMID:23982545

Ahsan, M K; Matin, T; Ali, M I; Ali, M Y; Awwal, M A; Sakeb, N

2013-07-01

379

Intermediate-mass black holes in AGN discs - II. Model predictions and observational constraints  

NASA Astrophysics Data System (ADS)

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.

McKernan, B.; Ford, K. E. S.; Kocsis, B.; Lyra, W.; Winter, L. M.

2014-06-01

380

The Effect of Age on Optic Nerve Axon Counts, SDOCT Scan Quality, and Peripapillary Retinal Nerve Fiber Layer Thickness Measurements in Rhesus Monkeys  

PubMed Central

Purpose To evaluate the effect of age on optic nerve axon counts, spectral-domain optical coherence tomography (SDOCT) scan quality, and peripapillary retinal nerve fiber layer thickness (RNFLT) measurements in healthy monkey eyes. Methods In total, 83 healthy rhesus monkeys were included in this study (age range: 1.2–26.7 years). Peripapillary RNFLT was measured by SDOCT. An automated algorithm was used to count 100% of the axons and measure their cross-sectional area in postmortem optic nerve tissue samples (N = 46). Simulation experiments were done to determine the effects of optical changes on measurements of RNFLT. An objective, fully-automated method was used to measure the diameter of the major blood vessel profiles within each SDOCT B-scan. Results Peripapillary RNFLT was negatively correlated with age in cross-sectional analysis (P < 0.01). The best-fitting linear model was RNFLT(?m) = ?0.40 × age(years) + 104.5 ?m (R2 = 0.1, P < 0.01). Age had very little influence on optic nerve axon count; the result of the best-fit linear model was axon count = ?1364 × Age(years) + 1,210,284 (R2 < 0.01, P = 0.74). Older eyes lost the smallest diameter axons and/or axons had an increased diameter in the optic nerve of older animals. There was an inverse correlation between age and SDOCT scan quality (R = ?0.65, P < 0.0001). Simulation experiments revealed that approximately 17% of the apparent cross-sectional rate of RNFLT loss is due to reduced scan quality associated with optical changes of the aging eye. Another 12% was due to thinning of the major blood vessels. Conclusions RNFLT declines by 4 ?m per decade in healthy rhesus monkey eyes. This rate is approximately three times faster than loss of optic nerve axons. Approximately one-half of this difference is explained by optical degradation of the aging eye reducing SDOCT scan quality and thinning of the major blood vessels. Translational Relevance Current models used to predict retinal ganglion cell losses should be reconsidered.

Fortune, Brad; Reynaud, Juan; Cull, Grant; Burgoyne, Claude F.; Wang, Lin

2014-01-01

381

A miniature fiber optic pressure sensor for intradiscal pressure measurements of rodents  

NASA Astrophysics Data System (ADS)

Lower back pain continues to be a leading cause of disability in people of all ages, and has been associated with degenerative disc disease. It is well accepted that mechanical stress, among other factors, can play a role in the development of disc degeneration. Pressures generated in the intervertebral disc have been measured both in vivo and in vitro for humans and animals. However, thus far it has been difficult to measure pressure experimentally in rodent discs due to their small size. With the prevalent use of rodent tail disc models in mechanobiology, it is important to characterize the intradiscal pressures generated with externally applied stresses. In this paper, a miniature fiber optic Fabry-Perot interferometric pressure sensor with an outer diameter of 360 ?m was developed to measure intradiscal pressures in rat caudal discs. A low coherence interferometer based optical system was used, which includes a broadband light source, a high-speed spectrometer, and a Fabry-Perot sensor. The sensor employs a capillary tube, a flexible, polymer diaphragm coated with titanium as a partial mirror, and a fiber tip as another mirror. The pressure induced deformation of the diaphragm results in a cavity length change of the Fabry-Perot interferometer which can be calculated from the wavelength shift of interference fringes. The sensor exhibited good linearity with small applied pressures. Our validation experiments show that owing to the small size, inserting the sensor does not disrupt the annulus fibrosus and will not alter intradiscal pressures generated. Measurements also demonstrate the feasibility of using this sensor to quantify external load intradiscal pressure relationships in small animal discs.

Nesson, Silas; Yu, Miao; Hsieh, Adam H.

2007-04-01

382

Congenital disorders of the optic nerve: excavations and hypoplasia.  

PubMed

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 double ring sign). In addition, the optic disc cupping, which occurs as a sequel to some cases of periventricular leucomalacia, can arguably be classified as a type of optic nerve hypoplasia. All of these conditions can be unilateral or bilateral and can impair visual function mildly or severely. It is essential that children with poor vision due to any of these conditions are managed by treating refractive errors, giving occlusion therapy in selected cases, and optimising the conditions at home and at school in an attempt to ensure that impaired vision does not impede development or education. PMID:15534588

Dutton, G N

2004-11-01

383

The Aerodynamics of a Flying Sports Disc  

NASA Astrophysics Data System (ADS)

The flying sports disc is a spin-stabilised axi-symmetric wing of quite remarkable design. A typical disc has an approximate elliptical cross-section and hollowed out under-side cavity, such as the Frisbee(TM) disc. An experimental study of flying disc aerodynamics, including both spinning and non-spinning tests, has been carried out in the wind tunnel. Load measurements, pressure data and flow visualisation techniques have enabled an explanation of the flow physics and provided data for free-flight simulations. A computer simulation that predicts free-flight trajectories from a given set of initial conditions was used to investigate the dynamics of a flying disc. This includes a six-degree of freedom mathematical model of disc flight mechanics, with aerodynamic coefficients derived from experimental data. A flying sports disc generates lift through forward velocity just like a conventional wing. The lift contributed by spin is insignificant and does not provide nearly enough down force to support hover. Without spin, the disc tumbles ground-ward under the influence of an unstable aerodynamic pitching moment. From a backhand throw however, spin is naturally given to the disc. The unchanged pitching moment now results in roll, due to gyroscopic precession, stabilising the disc in free-flight.

Potts, Jonathan R.; Crowther, William J.

2001-11-01

384

[Analysis of LCD aging with polarized optical texture and transmission spectrum].  

PubMed

Light radiation experiment was done to a group of liquid crystal display devices, and the influence of light radiation on the display quality of liquid crystal display devices was studied. The changes in their polarized textures after light radiation were observed with a polarized optical microscope. Parallel stripe texture and black holes, which lost extinction function, appeared in liquid crystal texture. With the increase of light radiation time, more and more black holes result, and the area of black holes gets bigger and bigger. The authors tested the transmission spectrum with computer-controlled ultraviolet/visible light spectrometer, finding that the transmission rate declines with the increase of light radiation time. The results show that the appearance of stripe texture and black holes resulted from the changes in liquid crystal molecular structure after ultraviolet radiation, and the occurrence of black holes, which lost extinction function, is the main reason for the continuous decline of transmission rate. PMID:17058936

Huang, Chong; Zhou, Xue-Ping; Liu, Ji; Ouyang, Yan-Dong

2006-08-01

385

The Combined Use of a Posterior Dynamic Transpedicular Stabilization System and a Prosthetic Disc Nucleus Device in Treating Lumbar Degenerative Disc Disease With Disc Herniations  

Microsoft Academic Search

BackgroundProsthetic replacement of spinal discs is emerging as a treatment option for degenerative disc disease. Posterior dynamic transpedicular stabilization (PDTS) and prosthetic disc nucleus (PDN) devices have been used sporadically in spinal surgery.

Mehdi Sasani; Ahmet Levent Aydin; Tunc Oktenoglu; Murat Cosar; Yaprak Ataker; Tuncay Kaner; Ali Fahir Ozer

2008-01-01

386

MaGICC thick disc - I. Comparing a simulated disc formed with stellar feedback to the Milky Way  

NASA Astrophysics Data System (ADS)

We analyse the structure and chemical enrichment of a Milky Way-like galaxy with a stellar mass of 2 × 1010 M?, formed in a cosmological hydrodynamical simulation. It is disc dominated with a flat rotation curve, and has a disc scalelength similar to the Milky Way's, but a velocity dispersion that is ˜50 per cent higher. Examining stars in narrow [Fe/H] and [?/Fe] abundance ranges, we find remarkable qualitative agreement between this simulation and observations. (a) The old stars lie in a thickened distribution with a short scalelength, while the young stars form a thinner disc, with scalelengths decreasing, as [Fe/H] increases. (b) Consequently, there is a distinct outward metallicity gradient. (c) Mono-abundance populations exist with a continuous distribution of scaleheights (from thin to thick). However, the simulated galaxy has a distinct and substantive very thick disc (hz ˜ 1.5 kpc), not seen in the Milky Way. The broad agreement between simulations and observations allows us to test the validity of observational proxies used in the literature: we find in the simulation that mono-abundance populations are good proxies for single age populations (<1 Gyr) for most abundances.

Stinson, G. S.; Bovy, J.; Rix, H.-W.; Brook, C.; Roškar, R.; Dalcanton, J. J.; Macciò, A. V.; Wadsley, J.; Couchman, H. M. P.; Quinn, T. R.

2013-11-01

387

Effect of phlorizin on sugar uptake by broadbean leaf discs. [Vica faba L  

SciTech Connect

Phlorizin is a competitive inhibitor of Na/sup +//glucose symport in animal cells and of H/sup +//3-O-methylglucose (3-O-MeG) symport in liverworts. The effects of this compound on the uptake of (U-/sup 14/C) sucrose and of (/sup 14/C) 3-O-MeG by broadbean (Vicia faba L.) leaf discs were studied. Leaf discs without lower epidermis were preincubated in the dark for 30 min (fresh discs) or for 12 h (aged discs) on a medium buffered at pH 5.0 containing mannitol as an osmoticum. They were then incubated for 30 min in the light on a similar solution added with 1 mM (/sup 14/C) sucrose or (/sup 14/C) 3-O-MeG and 5 mM phlorizin. Phlorizin inhibited uptake of 3-O-MeG by 37 and 50% respectively in fresh and aged discs. Sucrose uptake was more sensitive to the inhibitor than 3-O-MeG uptake and was also more inhibited in aged than in fresh discs (76% inhibition vs 54%). Kinetic studies showed that the inhibition exerted by phlorizin in fresh material is of competitive type both for sucrose and for 3-O-MeG uptake. Electrophysiological measurements indicated that the inhibitor did not affect the transmembrane potential difference of parenchyma cells within 30 min. The data suggest that phlorizin can be recognized by the hexose and by the sucrose carrier of leaf cells.

Lemoine, R.; Delrot, S.

1986-04-01

388

Segmentation and quantification of retinal lesions in age-related macular degeneration using polarization-sensitive optical coherence tomography  

NASA Astrophysics Data System (ADS)

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.

Baumann, Bernhard; Götzinger, Erich; Pircher, Michael; Sattmann, Harald; Schütze, Christopher; Schlanitz, Ferdinand; Ahlers, Christian; Schmidt-Erfurth, Ursula; Hitzenberger, Christoph K.

2010-11-01

389

Segmentation and quantification of retinal lesions in age-related macular degeneration using polarization-sensitive optical coherence tomography  

PubMed Central

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.

Baumann, Bernhard; Gotzinger, Erich; Pircher, Michael; Sattmann, Harald; Schutze, Christopher; Schlanitz, Ferdinand; Ahlers, Christian; Schmidt-Erfurth, Ursula; Hitzenberger, Christoph K.

2011-01-01

390

Three-dimensional spectral domain optical coherence tomography in X linked foveal retinoschisis.  

PubMed

Spectral domain optical coherence tomography (SD-OCT) was performed in two cases of bilateral X linked foveal retinoschisis of different age groups. On fundus examination spoke wheel and honeycomb pattern of cysts were observed along with retinal nerve fibre layer (RNFL) defects. On SD-OCT, schisis was observed in the outer plexiform layer. External limiting membrane disruption was observed in the subfoveal area, along with disruption of outer nuclear layer (ONL) and inner-outer segment junction. Elevation of ONL due to tractional pull of central palisade was a novel observation. Retinoschisis extended beyond the optic disc up to the nasal region. Extracted RNFL tomogram presented an unprecedented visualisation of schisis along 360° of the optic disc. Tractional elevation in the foveal area and schisis involving nasal region, not observed upon clinical examination, was highlighted on SD-OCT. This investigative modality is an important adjunct in the assessment of foveal retinoschisis. PMID:23563673

Saxena, Sandeep; Manisha; Meyer, Carsten H

2013-01-01

391

Rossby wave instability in astrophysical discs  

NASA Astrophysics Data System (ADS)

A brief review is given of the Rossby wave instability in astrophysical discs. In non-self-gravitating discs, around for example a newly forming stars, the instability can be triggered by an axisymmetric bump at some radius r0 in the disc surface mass-density. It gives rise to exponentially growing non-axisymmetric perturbation (\\propto \\exp \\,({ { i}}m\\phi ) , m = 1,2,…) in the vicinity of r0 consisting of anticyclonic vortices. These vortices are regions of high pressure and consequently act to trap dust particles which in turn can facilitate planetesimal growth in proto-planetary discs. The Rossby vortices in the discs around stars and black holes may cause the observed quasi-periodic modulations of the disc's thermal emission.

Lovelace, R. V. E.; Romanova, M. M.

2014-08-01

392

Note: Light ageing with simultaneous colorimetry via fibre optics reflection spectrometry.  

PubMed

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

?ojewski, Tomasz; Thomas, Jacob; Go??b, Roman; Kawa?ko, Jakub; ?ojewska, Joanna

2011-07-01

393

A disc inside the bipolar planetary nebula M2-9  

NASA Astrophysics Data System (ADS)

Aims: Bipolarity in proto-planetary and planetary nebulae is associated with events occurring in or around their cores. Past infrared observations have revealed the presence of dusty structures around the cores, many in the form of discs. Characterising those dusty discs provides invaluable constraints on the physical processes that govern the final mass expulsion of intermediate mass stars. We focus this study on the famous M2-9 bipolar nebula, where the moving lighthouse beam pattern indicates the presence of a wide binary. The compact and dense dusty core in the centre of the nebula can be studied by means of optical interferometry. Methods: M2-9 was observed with VLTI/MIDI at 39-47 m baselines with the UT2-UT3 and UT3-UT4 baseline configurations. These observations are interpreted using a dust radiative transfer Monte Carlo code. Results: A disc-like structure is detected perpendicular to the lobes, and a good fit is found with a stratified disc model composed of amorphous silicates. The disc is compact, 25 × 35 mas at 8 ?m and 37 × 46 mas at 13 ?m. For the adopted distance of 1.2 kpc, the inner rim of the disc is ~15 AU. The mass represents a few percent of the mass found in the lobes. The compactness of the disc puts strong constraints on the binary content of the system, given an estimated orbital period 90-120 yr. We derive masses of the binary components between 0.6-1.0 M? for a white dwarf and 0.6-1.4 M? for an evolved star. We present different scenarios on the geometric structure of the disc accounting for the interactions of the binary system, which includes an accretion disc as well. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile, ESO N: 079.D-146.

Lykou, F.; Chesneau, O.; Zijlstra, A. A.; Castro-Carrizo, A.; Lagadec, E.; Balick, B.; Smith, N.

2011-03-01

394

Turbulent drag reduction through oscillating discs  

NASA Astrophysics Data System (ADS)

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 FIK identity is employed to show that the wall-friction reduction is due to two distinguished effects. One effect is linked to the direct shearing action of the near-wall oscillating disc boundary layer on the wall turbulence, which causes the attenuation of the turbulent Reynolds stresses. The other effect is due the additional disc-flow Reynolds stresses produced by the inter-disc structures. The contribution to drag reduction due to turbulent Reynolds stress attenuation depends on the penetration thickness of the disc-flow boundary layer, while the contribution due to the elongated structures scales linearly with a simple function of the maximum tip velocity and oscillation period for the largest disc diameter tested, a result suggested by the Rosenblat flow solution. A brief discussion on the future applicability of the oscillating-disc technique is also presented.

Wise, Daniel J.; Ricco, Pierre

2014-05-01

395

DISC: the dynamic instruction set computer  

Microsoft Academic Search

A dynamic instruction set computer (DISC) has been developed to support demand-driven instruction set modification. Using partial reconfiguration, DISC pages instruction modules in and out of an FPGA as demanded by the executing program. Instructions occupy FPGA resources only when needed and FPGA resources can be reused to implement an arbitrary number of performance-enhancing application-specific instructions. DISC further enhances the

Michael J. Wirthlin; Brad L. Hutchings

1995-01-01

396

Accretion in giant planet circumplanetary discs  

NASA Astrophysics Data System (ADS)

During the final growth phase of giant planets, accretion is thought to be controlled by a surrounding circumplanetary disc. Current astrophysical accretion disc models rely on hydromagnetic turbulence or gravitoturbulence as the source of effective viscosity within the disc. However, the magnetically coupled accreting region in these models is so limited that the disc may not support inflow at all radii, or at the required rate. Here, we examine the conditions needed for self-consistent accretion, in which the disc is susceptible to accretion driven by magnetic fields or gravitational instability. We model the disc as a Shakura-Sunyaev ? disc and calculate the level of ionization, the strength of coupling between the field and disc using Ohmic, Hall and Ambipolar diffusevities for both a magnetorotational instability (MRI) field and vertical field, and the strength of gravitational instability. We find that the standard constant-? disc is only coupled to the field by thermal ionization within 30 RJ with strong magnetic diffusivity prohibiting accretion through the bulk of the mid-plane. In light of the failure of the constant-? disc to produce accretion consistent with its viscosity, we drop the assumption of constant-? and present an alternate model in which ? varies radially according to the level magnetic turbulence or gravitoturbulence. We find that a vertical field may drive accretion across the entire disc, whereas MRI can drive accretion out to ˜ 200 RJ, beyond which Toomre's Q = 1 and gravitoturbulence dominates. The discs are relatively hot (T ? 800 K), and consequently massive (Mdisc ˜ 0.5 MJ).

Keith, Sarah L.; Wardle, Mark

2014-05-01

397

Disentangling the stellar populations in the counter-rotating disc galaxy NGC 4550  

NASA Astrophysics Data System (ADS)

In order to try and understand its origins, we present high-quality long-slit spectral observations of the counter-rotating stellar discs in the strange S0 galaxy NGC 4550. We kinematically decompose the spectra into two counter-rotating stellar components (plus a gaseous component), in order to study both their kinematics and their populations. The derived kinematics largely confirm what was known previously about the stellar discs, but trace them to larger radii with smaller errors; the fitted gaseous component allows us to trace the hydrogen emission lines for the first time, which are found to follow the same rather strange kinematics previously seen in the [O iii] line. Analysis of the populations of the two separate stellar components shows that the secondary disc has a significantly younger mean age than the primary disc, consistent with later star formation from the associated gaseous material. In addition, the secondary disc is somewhat brighter, also consistent with such additional star formation. However, these measurements cannot be self-consistently modelled by a scenario in which extra stars have been added to initially identical counter-rotating stellar discs, which rules out the Evans & Collett's elegant `separatrix-crossing' model for the formation of such massive counter-rotating discs from a single galaxy, leaving some form of unusual gas accretion history as the most likely formation mechanism.

Johnston, Evelyn J.; Merrifield, Michael R.; Aragón-Salamanca, Alfonso; Cappellari, Michele

2013-01-01

398

Accretion Discs Show Their True Colours  

NASA Astrophysics Data System (ADS)

Quasars are the brilliant cores of remote galaxies, at the hearts of which lie supermassive black holes that can generate enough power to outshine the Sun a trillion times. These mighty power sources are fuelled by interstellar gas, thought to be sucked into the hole from a surrounding 'accretion disc'. A paper in this week's issue of the journal Nature, partly based on observations collected with ESO's Very Large Telescope, verifies a long-standing prediction about the intensely luminous radiation emitted by these accretion discs. Uncovering the disc ESO PR Photo 21/08 Uncovering the inner disc "Astronomers were puzzled by the fact that the best models of these discs couldn't quite be reconciled with some of the observations, in particular, with the fact that these discs did not appear as blue as they should be," explains lead-author Makoto Kishimoto. Such a discrepancy could be the signal that there was something very wrong with the models. With his colleagues, he investigated this discrepancy by studying the polarised light from six quasars. This enabled them to demonstrate that the disc spectrum is as blue as predicted. "The crucial observational difficulty here has been that the disc is surrounded by a much larger torus containing hot dust, whose light partly outshines that of the disc," says Kishimoto. "Because the light coming from the disc is scattered in the disc vicinity and thus polarised, by observing only polarised light from the quasars, one can uncover the buried light from the disc." In a similar way that a fisherman would wear polarised sunglasses to help get rid of the glare from the water surface and allow him to see more clearly under the water, the filter on the telescope allowed the astronomers to see beyond surrounding clouds of dust and gas to the blue colour of the disc in infrared light. The observations were done with the FORS and ISAAC instruments on one of the 8.2-m Unit Telescopes of ESO's Very Large Telescope, located in the Atacama Desert, in Chile, as well as several other telescopes, including STFC's UKIRT. The standard picture of the accretion disc is therefore vindicated. The authors believe that further measurements could eventually provide valuable insight into how and where the disc ends, and how material is being supplied to the disc.

2008-07-01

399

Automated optic disk localization and detection in colored retinal images  

Microsoft Academic Search

Automated localization and detection of the optic disc (OD) is an essential step in the analysis of digital diabetic retinopathy systems. Accurate localization and detection of optic disc boundary is very useful in proliferative diabetic retinopathy where fragile vessels develop in the retina. In this paper, we propose an automated system for optic disk localization and detection. Our method localizes

M. Usman Akram; Anam Tariq

2009-01-01

400

Linear eigenvalue analysis of the disc-brake squeal problem  

Microsoft Academic Search

SUMMARY This paper presents a numerical method to calculate the unstable frequencies of a car disc brake and suggests a suitable analysis procedure. The stationary components of the disc brake are modelled using finite elements and the disc as a thin plate. The separate treatments of the stationary components and the rotating disc facilitate the modelling of the disc brake

Q. Cao; H. Ouyang; M. I. Friswell; J. E. Mottershead

2004-01-01

401

Use of adipose stem cells and polylactide discs for tissue engineering of the temporomandibular joint disc  

PubMed Central

There is currently no suitable replacement for damaged temporomandibular joint (TMJ) discs after discectomy. In the present study, we fabricated bilayer biodegradable polylactide (PLA) discs comprising a non-woven mat of poly(L/D)lactide (P(L/D)LA) 96/4 and a P(L/DL)LA 70/30 membrane plate. The PLA disc was examined in combination with adipose stem cells (ASCs) for tissue engineering of the fibrocartilaginous TMJ disc in vitro. ASCs were cultured in parallel in control and chondr