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1

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

2

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

3

Holographic optical disc  

NASA Astrophysics Data System (ADS)

The holographic disc is a high capacity, disk-based data storage device that can provide the performance for next generation mass data storage needs. With a projected capacity approaching 1 terabit on a single 12 cm platter, the holographic disc has the potential to become a highly efficient storage hardware for data warehousing applications. The high readout rate of holographic disc makes it especially suitable for generating multiple, high bandwidth data streams such as required for network server computers. Multimedia applications such as interactive video and HDTV can also potentially benefit from the high capacity and fast data access of holographic memory.

Zhou, Gan; An, Xin; Pu, Allen; Psaltis, Demetri; Mok, Fai H.

1999-11-01

4

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

2013-05-13

5

Optical Disc Applications in Libraries.  

ERIC Educational Resources Information Center

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

Andre, Pamela Q. J.

1989-01-01

6

Integrated-optic disc pickups  

NASA Astrophysics Data System (ADS)

The present status of waveguide-type integrated-optic disc pickups are reviewed. The authors have proposed and fabricated several types, and have demonstrated their fundamental functions. For the ROM pickup, they successfully reduced the focused spot to a diameter that is slightly larger than the diffraction-limited value, and confirmed capability of the focusing/tracking error signal detection. The pickup was extended to that for magneto-optical (MO) disc system, and the MO pickup was found experimentally to detect a polarization rotation as small as one contained in the signal beam reflected from MO medium. The pickup for parallel-data cards was also fabricated with photodiode array, and seven-track parallel readout was demonstrated. It was found by theoretical analysis that the waveguide-FGC combined type pickup has the possibility of super-resolution readout.

Nishihara, Hiroshi; Suhara, Toshiaki; Ura, Shogo

1992-08-01

7

Toxocariasis of the optic disc.  

PubMed

A healthy 46-year-old man presented with decreased vision in the right eye after ingestion of raw meat. On funduscopic examination, a cystic lesion was found on an edematous right optic disc with adjacent serous retinal detachment. Optical coherence tomography confirmed a peripapillary serous retinal detachment and a well-demarcated cystic lesion (200 × 200 × 500 ?m) in the right eye. The patient had moderate eosinophilia and was seropositive for anti-Toxocara IgG antibody. Diagnosed with ocular toxocariasis, he was treated with systemic corticosteroids and albendazole with improvement in vision and fundus appearance. PMID:23535570

Kim, Yong Joon; Moon, Chan Hee; Chang, Jee Ho

2013-06-01

8

RetCam image analysis of the optic disc in premature infants.  

PubMed

PurposeTo evaluate the correlation between optic disc parameters and birth weight or gestational age in premature infants.MethodsRetCam fundal images were taken of 97 premature infants who needed screening for retinopathy of prematurity and who had no ischemic brain injury. The images were taken at a postmenstrual age of 36 weeks and analyzed. The optic disc cup to disc ratio, optic disc area, rim area, and cup to disc area ratio were calculated using image analysis. We evaluated the relationship between these optic disc parameters and gestational age or birth weight.ResultsThe optic cup to disc ratio was less than 0.15 in 139 eyes (71.6%) and 0.5 or more in six eyes (3.1%). The optic cup disc area ratio was less than 0.05 in 146 eyes (75.3%) and 0.3 or more in four eyes (2.1%). On evaluating the association between optic disc parameters and gestational age or birth weight, optic disc cup to disc ratio, optic disc area, rim area, and cup to disc area ratio did not show significant relationships.ConclusionThe optic disc parameters of premature infants had no correlation with birth weight and gestational age. PMID:23846380

Park, J W; Park, S W; Heo, H

2013-07-12

9

512 GB recording on 16-layer optical disc with Blu-ray Disc based optics  

NASA Astrophysics Data System (ADS)

We confirmed the feasibility of a 16-layer write once disc based on Blu-ray Disc optics that was fabricated with inorganic recording material Bi-Ge-O. The total capacity of the disc achieved 400 GB and 512 GB per single disc side with BD 1x recording speed utilizing conventional BD technique.

Inoue, Motohiro; Kosuda, Atsuko; Mishima, Koji; Ushida, Tomoki; Kikukawa, Takashi

2010-06-01

10

Optic disc morphology in south India: the Vellore Eye Study  

PubMed Central

Aim: To evaluate the morphology of the optic nerve head in an unselected population group in south India. Methods: The study included 70 subjects forming a population based sample, selected in a random manner. Mean age was 47.5 (SD 8.7) years, mean refractive error measured ?0.07 (1.11) dioptres (range ?4.50 to +2.50 dioptres). Optic disc slides were morphometrically analysed. Results: Mean optic disc area measured 2.58 (0.65) mm2. It was statistically independent of age and refractive error. Optic disc shape was slightly vertically oval. Mean neuroretinal rim area was 1.60 (0.37) mm2. It was significantly and positively correlated with optic disc size and optic cup size. It was independent of age, sex, refractive error, and axial length. In all subjects included in the study, the rim was smallest in the temporal horizontal optic disc sector. Mean horizontal cup/disc diameter ratio (0.66 (0.07)) was significantly (p<0.001) higher than the mean vertical cup/disc diameter ratio (0.56 (0.08)). Both ratios were highly significantly (p <0.001) and positively correlated with optic disc size. The ? zone of parapapillary atrophy (0.84 (0.29) mm2), and ? zone (0.13 (0.38) mm2), respectively, occurred in 69 (98.6%) subjects and in eight (11.4%) subjects, respectively. They were significantly larger in the temporal horizontal sector. The ? zone was significantly (p<0.001) larger and occurred significantly more often than ? zone. Retinal arterioles and venules were wider, and in spatial correlation, the visibility of the retinal nerve fibre layer was significantly better, in the temporal inferior disc arcade and the temporal superior arcade than in the nasal superior arcade and the nasal inferior vessel arcade. Except for the absolute size measurements these optic nerve head parameters did not differ markedly (p >0.05) from the values found in white people. Conclusions: South Indians and white people do not show marked differences in the morphology of the optic nerve head as measured by morphometric optic disc parameters, with the possible exception of the absolute optic disc dimensions.

Jonas, J B; Thomas, R; George, R; Berenshtein, E; Muliyil, J

2003-01-01

11

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

12

Optic disc morphology--rethinking shape.  

PubMed

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

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

2009-06-10

13

Ethnic variation in optic disc size by fundus photography.  

PubMed

Abstract Purpose: To compare optic disc size among Caucasian, Chinese, African, Filipino and Hispanic subjects recruited from a university-based general ophthalmology clinic. Methods: In this retrospective cross-sectional study, optic disc size was calculated from fundus photographs. Differences in age, sex and spherical equivalent among the ethnic groups were examined with either Kruskal--Wallis test or Chi-square test. Ethnic differences in optic disc size were evaluated with linear mixed-effects regression models that adjusted for age, sex, spherical equivalent, glaucoma status, lens status and use of both eyes in the same subject. Results: Five hundred and seventy-four eyes of 305 subjects were analyzed. The mean and standard deviation of the optic disc size were 2.16?±?0.41?mm(2) for Caucasian, 2.30?±?0.56?mm(2) for Chinese, 2.31?±?0.41?mm(2) for Filipino, 2.38?±?0.40?mm(2) for African and 2.40?±?0.38?mm(2) for Hispanic subjects. Age and spherical equivalent differed among the ethnic groups by Kruskal--Wallis test (p?optic disc size were not observed among African, Hispanic, Filipino and Chinese subjects in linear mixed-effects regression analyses (p?>?0.05). However, Caucasian differed from the other ethnicities in linear mixed-effects regression analyses (p?Optic disc size was significantly smaller in Caucasian compared to the other ethnic groups. Optic disc size differences among non-Caucasian ethnic groups were not significant. PMID:23841871

Lee, Roland Y; Kao, Andrew A; Kasuga, Toshimitsu; Vo, Baotran N; Cui, Qi N; Chiu, Cynthia S; Weinreb, Robert N; Lin, Shan C

2013-07-10

14

Optic Disc Pit with Sectorial Retinitis Pigmentosa  

PubMed Central

Sectorial retinitis pigmentosa (RP) and optic disc pit (ODP) are rare clinical conditions. We present a 40-year-old woman with a history of mild night blindness and decreased vision in the right eye for about 5 years. Fundus examination revealed retinal pigmentary changes in the superior and inferotemporal sectors covering the macula and reduced arterial calibre and ODP at the temporal edge of the optic disc. In addition, fundus autofluorescence, spectral-domain optical coherence tomography, fluorescein angiography, and multifocal electroretinogram scans confirmed these clinical findings. Visual acuity was decreased due to an atrophic-appearing foveal lesion. No intervention was suggested because of the poor visual potential. To the best of our knowledge, the present study is the first to describe coexistent optic disc pit and sectorial RP in the superior and inferotemporal sectors covering the macula in the same eye with figures.

Taskapili, Muhittin; Yilmaz, Tolga; Teke, Mehmet Yasin

2013-01-01

15

Optic disc topographic analysis in diabetic patients.  

PubMed

The aim of our study was to evaluate the optic disc (OD) topographic parameters by using Heidelberg Retina Tomograph II (HRT II) in patients with type 2 diabetes mellitus (DM). The study group consisted of 78 patients with type 2 DM (patient group) and age-sex matched 50 healthy subjects (control group). All patients and controls underwent a detailed ophthalmological examination, automated perimetry, central corneal thickness (CCT) measurement and OD topography by using HRT II. Glycosylated haemoglobin (HbA1c) levels of the diabetic patients were also noted. Age, gender, intraocular pressure and CCT measurements were similar in patients with diabetes and control group. Mean retinal nerve fiber layer thickness (MRNFLT) and retinal nerve fiber layer cross-sectional area (RNFLcsA) parameters were found significantly lower in diabetic patients compared to those of the controls (p = 0.030, p = 0.038). In the patient group, MRNFLT value was found significantly lower in patients with DM duration ?120 months (p = 0.020) and HbA1c level ?7 % (p = 0.029). Rim volume, MRNFLT and RNFLcsA values were significantly lower in proliferative diabetic retinopathy group (p = 0.004, p = 0.003, p = 0.001 respectively) and laser treated patients (p = 0.003, p = 0.002, p = 0.004 respectively). In conclusion, poor metabolic control of diabetes, severe DR and received laser therapies cause RNFL damage. Heidelberg Retina Tomograph may help us to detect and follow-up the changes in optic disc and RNFL in diabetic patients. PMID:22825888

Toprak, Ibrahim; Yildirim, Cem; Yaylali, Volkan

2012-07-24

16

Variability in digital analysis of optic disc topography  

Microsoft Academic Search

We determined the magnitude of variability in optic disc topographical parameters on digital analysis of the optic disc using the IS 2000. The variability introduced by the system, the observer, the observer and patient, and by clinically different types of discs was assessed in the measurement of the vertical cup-to-disc ratio, horizontal cup-to-disc ratio, cup area-to-disc area, cup volume, neuroretinal

Rohit Varma; William C. Steinmann; George L. Spaeth; Richard P. Wilson

1988-01-01

17

Optic disc size in a population based study in northern China: the Beijing Eye Study  

PubMed Central

Aim To determine the optic disc size in the adult Chinese population in an urban and a rural region of Beijing. Methods The population based, cross sectional cohort study included 4439 subjects out of 5324 subjects invited to participate (response rate 83.4%). It was divided into a rural part (1973 (44.4%) subjects) and an urban part (2466 (55.6%) subjects). Mean age was 56.2 (SD 10.6) years (range 40–101?years). Colour optic disc photographs were morphometrically examined. Main outcome measure was optic disc area. Results Optic disc photographs were available for 4027 (90.7%) subjects. Mean optic disc area measured 2.65 (0.57) mm2 (range 1.03?mm2–7.75?mm2). Optic disc area was significantly (p<0.001) correlated with myopic refractive error, with a steep decrease in optic disc area from high myopia to the mid?range of refractive error, a slightly horizontal course in the refractive error range between ?8?dioptres and +4?dioptres, and a further decrease in optic disc area towards higher hyperopia. Optic disc area was not related to age (p?=?0.14) or sex (p?=?0.93) (optic disc area, males: 2.65 (0.56) mm2 versus females: 2.65 (0.57) mm2). “Microdiscs” may be defined as smaller than 1.51?mm2, and “macrodiscs” as larger than 3.79?mm2. Conclusions Compared with data of preceding studies, mean optic disc size is larger in Chinese people than in white people. In Chinese people highly hyperopic eyes have significantly smaller optic discs, and highly myopic eyes have significantly larger optic discs than emmetropic eyes.

Wang, Y; Xu, L; Zhang, L; Yang, H; Ma, Y; Jonas, J B

2006-01-01

18

The optic disc in glaucoma. I: Classification  

Microsoft Academic Search

Five different descriptive types of glaucomatous optic discs are described, based on the examination of X2 magnification stereophotographs of 252 patients from the files of the Glaucoma Service at Wills Eye Hospital. The method of analysis is described in detail. These types include: overpass cupping, cupping without pallor of the neuroretinal rim, cupping with pallor of the neuroretinal rim, focal

R A Hitchings; G L Spaeth

1976-01-01

19

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

20

Optic disc findings in normal tension glaucoma  

Microsoft Academic Search

One hundred thirty stereo photographs of optic discs in patients with normal tension glaucoma (NTG) were reviewed in order to identify characteristics of the three following types of NTG: focal ischemic, senile sclerotic, and generalized cup enlargement. Twenty patients in each group were selected. Focal ischemic patients were more frequently women, had a higher incidence of migraine, a relatively smaller

Yoshio Yamazaki; Fukuko Hayamizu; Satoshi Miyamoto; Takako Nakagami; Chizuru Tanaka; Shigeri Inui

1997-01-01

21

Optic disc morphology in pigmentary glaucoma  

Microsoft Academic Search

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

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

1998-01-01

22

Optic disc findings in normal tension glaucoma.  

PubMed

One hundred thirty stereo photographs of optic discs in patients with normal tension glaucoma (NTG) were reviewed in order to identify characteristics of the three following types of NTG: focal ischemic, senile sclerotic, and generalized cup enlargement. Twenty patients in each group were selected. Focal ischemic patients were more frequently women, had a higher incidence of migraine, a relatively smaller disc size, and localized superior scotoma that often threatened fixation. Senile sclerotic patients were generally elderly, had a higher incidence of surgery under general anesthesia, had more ischemic heart disease or systemic hypertension, had a small rim area, and also had extensive peripapillary atrophy as well as combined diffuse and localized visual field defects. Generalized cup enlargement patients were younger, had a relatively larger disc size and a greater incidence of purely diffuse visual field loss. Results of our study suggest that the different characteristics of the groups are related to pathogenic mechanisms specific to each group. PMID:9304442

Yamazaki, Y; Hayamizu, F; Miyamoto, S; Nakagami, T; Tanaka, C; Inui, S

23

[Specifity of Optic Disc Evaluation in Healthy Subjects with Large Optic Discs and Physiologic Cupping Using Confocal Scanning Laser Ophthalmoscopy.  

PubMed

Purpose: Imaging methods of the optic nerve head appear to have an increasing impact in glaucoma diagnosis. The aim of this study is to evaluate the specifity of the Heidelberg Retina Tomograph (software version 1.7 and 3.0) in subjects with physiological cupping and large optic discs.Patients and Methods: 27 eyes of 27 subjects (mean age 41.3 ± 15.8 years) with bilateral physiological cupping and large optic discs (vertical cup-to-disc-ratio > 0.3, optic disc area 2.48 ± 0.45 mm2, max. 3.54 mm2) were included in a clinical study. All subjects had an intraocular pressure < 22 mmHg, physiological cupping by funduscopy and no nerve fibre layer defects (Scanning Laser Ophthalmoscope, Rodenstock, Germany). Standard achromatic perimetry (Humphrey Field Analyzer, Humphrey-Zeiss, 24/2 SITA or full threshold), short-wavelength automated perimetry (Humphrey Field Analyzer, Humphrey-Zeiss), and frequency doubling technology (FDT, Humphrey-Zeiss) revealed no visual field defects. Optic disc imaging was performed in all subjects using the Heidelberg Retina Tomograph II (HRT). Optic disc images were transferred to the software-update of the HRT 3 (Version 3.0, Heidelberg Engineering). Specifity was calculated using the Moorfields regression analysis (MRA, software version 1.7 and 3.0) and the glaucoma probability score (GPS analysis) using all disc sectors and omitting the nasal and 3 nasal sectors.Results: Specifity of the MRA (software version 1.7) was 66.6 % (most specific criteria), and 22.2 % (least specific criteria). Specifity of the MRA (software version 3.0) was 33.3 % (most specific criteria), and 14.8 % (least specific criteria), whereas specifity of the GPS analysis was 37.0 % (most specific criteria), and 11.1 % (least specific criteria). When the nasal sectors were omitted for analysis, specifity increased for the MRA analysis, but not for the GPS analysis.Conclusions: Specifity of the MRA was unsatisfactory using the software version 1.7 and 3.0 in subjects with large optic discs and physiological cupping when the nasal sectors were included in the analysis. The observer-independent GPS analysis did not improve the results in these subjects. PMID:23775290

Plange, N; Hirsch, T; Bienert, M; Remky, A

2013-06-17

24

The relationship between accretion disc age and stellar age and its consequences for protostellar discs  

NASA Astrophysics Data System (ADS)

We show that for young stars which are still accreting and for which measurements of stellar age t*, disc mass Mdisc and accretion rate ? are available, nominal disc age ? is approximately equal to the stellar age t*, at least within the considerable observational scatter. We then consider theoretical models of protostellar discs through analytic and numerical models. A variety of viscosity prescriptions including empirical power laws, magnetohydrodynamic turbulence and gravitational instability were considered within models describing the disc phenomena of dead zones, photoevaporation and planet formation. These models are generally poor fits to the observational data, showing values of tdisc which are too high by factors of 3-10. We then ask whether a systematic error in the measurement of one of the observational quantities might provide a reasonable explanation for this discrepancy. We show that for the observed systems only disc mass shows a systematic dependence on the value of tdisc/t*, and we note that a systematic underestimate of the value of disc mass by a factor of around 3-5 would account for the discrepancy between theory and observations.

Jones, Michael G.; Pringle, J. E.; Alexander, R. D.

2012-01-01

25

Study of optical destruction techniques for optical discs  

NASA Astrophysics Data System (ADS)

The topic of this dissertation is on the investigation of optical techniques for completely destroying data stored in optical discs. Complete and secure destruction of data is important when disposal of an optical disc containing sensitive and possibly classified information is concerned, since some information can be retrieved even from a fragment of a disc. After several candidate techniques and related systems are examined and fundamental system components are identified, an optical data destruction (ODD) system using a focused high power laser beam is devised, and a prototype system is designed and constructed. The ODD system uses a high power laser diode (HPLD) to expose data marks on optical discs and maintains the focused laser beam on a data layer by a focus servo using a diffractive optical element (DOE). The optical characteristics of the beam emitted from an HPLD are thoroughly investigated, and a few methods of modeling an HPLD beam in an optical system are studied. With the understanding of the HPLD beam properties, a limited-divergence raytracing (LDRT) model is developed to predict the propagation behavior of the HPLD beam in an optical system and shows good agreement with the real HPLD beam. This LDRT method is used to model the HPLD beam in the ODD system and simulate the resultant focus error signal with and without fabrication errors. The DOE focus sensor overcomes the problems in conventional focus sensors associated with the use of an intense line beam. The DOE comprising two angled gratings is designed to use only two weak 3rd order beams for focus sensing and fabricated on a chrome-coated glass substrate using a maskless lithography tool. The constructed ODD system is then used to perform destruction tests on various optical discs, which are examined using static and dynamic methods of data observation and retrieval. The observations show that data marks are optical invisible or completely covered with numerous micro-bubbles. These test results demonstrate that secure and complete destruction of data on optical discs is achieved using an ODD system. Successful destruction, however, depends greatly on exposure conditions and the type of optical media.

Choi, Taeyoung

26

The average optical depth of disc galaxies  

NASA Astrophysics Data System (ADS)

The average optical depth of disc galaxies is calculated assuming that their infrared output originates from the dust reprocessing of stellar light. Essentially, the luminosity functions at both optical (B-band) and FIR (IRAS) wavelengths are integrated to give a local luminosity density in the optical and FIR. This method was first proposed by Saunders et al., who found a B-band optical depth of tau_B=0.26. In this paper we reconsider the method and employ more realistic models. We conclude that on average a B-band photon originates from a region with an optical depth of tau_B~0.9, a value that indicates that galaxies have high rather than low optical depths. Adjusting the FIR luminosity for flux at wavelengths longer than those detected by IRAS could increase this value further (to tau_B>1). Interpreting this, a galaxy with the dust distributed in a similar manner to the stars would have a central face-on optical depth of tau_B>2.5, and this `typical' galaxy would become optically thin at ~1 scalelength from the centre.

Trewhella, M.; Davies, J. I.; Disney, M. J.; Jones, H. G. W.

1997-06-01

27

Optic disc and visual test findings in patients with migraine.  

PubMed

This study was conducted to determine whether the optic disc appearance and the visual field parameters of patients with migraine vary from those of age-matched controls. Twenty-two patients with migraine and 20 control participants were enrolled in the study. The automated visual field tests by Humphrey Field Analyzer® and optic disc images by Topcon® fundus camera were obtained from each participant. Horizontal and vertical cup-to-disc ratios were calculated by a manual, planimetric technique performed by two independent observers. The visual field indices including mean deviation (MD) and pattern standard deviations (PSD) were documented. No difference was found in the average cup-to-disc ratio between patients with migraine and control participants. However, MD and PSD of the groups were different. The average MD in the migraine group was -0.86+1.21, and in the control group was 0.10+1.03 (p=0.009). The average PSD in the migraine group was 2.11+0.68 and in the control group was 1.68+0.44 (p=0.024). In conclusion, this study demonstrated that patients with migraine had decreased sensitivity in their visual fields compared to the control participants. PMID:23014074

Dersu, Inci I; Thostenson, Jeff; Durcan, F Jane; Hamilton, Sarah M; Digre, Kathleen B

2012-09-24

28

A comparison of stereoscopic and monoscopic evaluation of optic disc topography using a digital optic disc stereo camera  

PubMed Central

AIMS—To compare stereophotographic and monophotographic optic disc assessments made using a digital optic disc stereo camera.?METHODS—Stereo digital optic disc photographs of 150 selected patients who had presented to a glaucoma clinic were assessed by two masked observers on separate occasions using (1) the stereophotographs and a stereoviewer, (2) a single image from the same stereopair. Results were analysed for both right and left eyes separately. 95% tolerance limits for change (TC) and intraclass correlation coefficients (ICC) were calculated and a multivariate analysis using a general linear model for repeated measures was performed.?RESULTS—A total of 201 optic disc images of 150 patients (84 females, 108 left eyes) were analysed. Mean age of patients was 64 years. The results for right eyes are as follows (similar results were obtained for left eyes). Intraobserver (stereoscopic compared to monoscopic) measurements of: horizontal cup:disc ratios (CDR), ICC = 0.5995 and 0.7269, TC = 34% and 27%; vertical CDR, ICC = 0.8298 and 0.817, TC = 25% and 27%; area CDR, ICC = 0.7757 and 0.8259, TC = 28% and 25%; circumference CDR, ICC = 0.7618 and 0.8103, TC = 28% and 25%. Interobserver measurements of: horizontal CDR, ICC stereoscopic (SS) = 0.7287; monoscopic (MS) = 0.5030; TC SS = 30%; MS = 32%; vertical CDR, ICC SS = 0.8439; MS = 0.7106; TC SS = 25%; MS = 31%; area CDR, ICC SS = 0.8392; MS = 0.6276; TC SS = 26%; MS = 32%; circumference CDR, ICC SS = 0.8433; MS = 0.6438, TC SS = 26%; MS = 31%. Systematic bias between observers and between methods was within acceptable limits.?CONCLUSIONS—This study using a digital stereo camera indicates that there may be little benefit of stereoscopic imaging over monoscopic imaging despite demonstrating small but inconsistent differences between both observers and methods.??

Parkin, B.; Shuttleworth, G.; Costen, M.; Davison, C.

2001-01-01

29

Ultrasound assessment of optic disc edema in patients with headache.  

PubMed

Point-of-care ocular ultrasonography is emerging as a powerful tool to evaluate emergency department (ED) patients at risk for ophthalmologic and intracranial pathology.We present cases of 3 patients in whom optic disc swelling was identified using ocular ultrasound. Causes for optic disc swelling in our patients included idiopathic intracranial hypertension, secondary syphilis, and malignant hypertension with associated hypertensive retinopathy. Because direct visualization of the optic disc may be challenging in an ED setting, ultrasound examination of the optic disc may represent an important adjunct to fundoscopy when assessing patients with headache or visual complaints. PMID:22030203

Daulaire, Siri; Fine, Lauren; Salmon, Margaret; Cummings, Catherine; Liebmann, Otto; Shah, Sachita; Teismann, Nathan

2011-10-24

30

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

31

Optic disc oedema: a diagnostic dilemma  

PubMed Central

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

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

2011-01-01

32

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

2012-10-03

33

Prevalence of Optic Disc Hemorrhages in Rural Central India. The Central India Eye and Medical Study  

PubMed Central

Purpose To determine the frequency of optic disc hemorrhages in a rural Indian population. Methods The population-based Central Indian Eye and Medical Study included 4711 subjects. Mean age was 48.5±12.9 years (range: 30-100 years). Color optic disc photographs were examined. Results Optic disc photographs were available for 4570 (97.0%) subjects. Prevalence of disc hemorrhages was 17/8869 (0.19%; 95%CI:0.10,0.28) per eye and 16/4570 (0.35±0.09%; 95%CI:0.18,0.52) per subject. Prevalence of disc hemorrhages increased from 0.05% (95%CI:0.00,0.13) in the age group of 30-39 years to 0.25% (95CI:0.00,0.49) in the age group of 60-69 years and to 0.91% (95%CI:0.24,1.58) in the age group of 70+ years. After adjusting for older age, higher systolic blood pressure, diabetes mellitus, myopic refractive error, smaller neuroretinal rim area and thinner retinal nerve fiber layer, occurrence of disc hemorrhages was associated only with glaucomatous optic nerve damage (P<0.001; Odds ratio: 87; 95%CI:32,239). Eleven of the 17 (65%; 95%CI:39,90) disc hemorrhages were found in glaucomatous eyes. Out of 193 glaucomatous eyes, 11 eyes (5.7%; 95%CI:2.4,9.0) showed a disc hemorrhage. Out of the 8676 non-glaucomatous eyes, 6 eyes (0.07%; 95%CI:0.01,0.12) had an optic disc hemorrhage. Conclusions Prevalence of disc hemorrhages (0.2% per eye; 0.4% per subject) in Indians aged 30+ years was strongly associated with glaucoma after adjustment for age, blood pressure and diabetes mellitus. A disc hemorrhage suggested glaucomatous optic nerve damage with a positive predictive value of 65%. About 6% of glaucomatous eyes showed a disc hemorrhage at the time of clinical examination highlighting the importance of optic disc hemorrhages for the diagnosis of glaucoma.

Khare, Anshu; Kulkarni, Maithili; Matin, Arshia; Sinha, Ajit; Bhojwani, Krishna; Nangia, Prabhat; Panda-Jonas, Songhomitra

2013-01-01

34

Changes in retinal nerve fiber layer and optic disc algorithms by optical coherence tomography in glaucomatous Arab subjects  

PubMed Central

Purpose To assess the difference in retinal nerve fiber layer (RNFL) and optic disc algorithms between glaucomatous and normal Arab subjects using optical coherence tomography (OCT). Methods RNFL thickness and optic disc parameters were obtained in 65 patients aged 50.1 ± 7.7 years. Percentage differences in all parameters were calculated and analyzed between groups. Results The mean RNFL thickness around the disc and at all quadrants was significantly thinner in glaucomatous eyes than in normal eyes (P < 0.01). The greatest decrease in RNFL thickness was observed at the inferior (39.5%) and superior (39.3%) quadrants and at 1 o’clock (43%) and 5 o’clock (40%) hour sectors. Significant differences were observed between glaucomatous and control eyes in all disc parameters (P < 0.005) assessed. The disc area, cup area, mean cup/disc ratio, and vertical and horizontal cup/disc ratios were significantly larger (P < 0.01), whereas the vertical integrated rim area, horizontal integrated rim width, and rim area were significantly smaller (P < 0.001) in glaucomatous eyes than in normal eyes. Conclusion Stratus OCT is still a valuable tool in the diagnosis of early glaucoma changes and, as such, its use should be encouraged in glaucoma clinics in Saudi Arabia. The best OCT parameters for detecting early glaucoma change were RNFL thickness in the inferior, superior, and 1 o’clock hour sector; the cup area; and the vertical integrated rim area of the optic disc.

Zeried, Ferial M; Osuagwu, Uchechukwu L

2013-01-01

35

Product and process for manufacturing an optical disc master  

SciTech Connect

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

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

1994-01-11

36

Utility of Digital Stereo Images for Optic Disc Evaluation  

PubMed Central

Purpose. To assess the suitability of digital stereo images for optic disc evaluations in glaucoma. Methods. Stereo color optic disc images in both digital and 35-mm slide film formats were acquired contemporaneously from 29 subjects with various cup-to-disc ratios (range, 0.26–0.76; median, 0.475). Using a grading scale designed to assess image quality, the ease of visualizing optic disc features important for glaucoma diagnosis, and the comparative diameters of the optic disc cup, experienced observers separately compared the primary digital stereo images to each subject's 35-mm slides, to scanned images of the same 35-mm slides, and to grayscale conversions of the digital images. Statistical analysis accounted for multiple gradings and comparisons and also assessed image formats under monoscopic viewing. Results. Overall, the quality of primary digital color images was judged superior to that of 35-mm slides (P < 0.001), including improved stereo (P < 0.001), but the primary digital color images were mostly equivalent to the scanned digitized images of the same slides. Color seemingly added little to grayscale optic disc images, except that peripapillary atrophy was best seen in color (P < 0.0001); both the nerve fiber layer (P < 0.0001) and the paths of blood vessels on the optic disc (P < 0.0001) were best seen in grayscale. The preference for digital over film images was maintained under monoscopic viewing conditions. Conclusions. Digital stereo optic disc images are useful for evaluating the optic disc in glaucoma and allow the application of advanced image processing applications. Grayscale images, by providing luminance distinct from color, may be informative for assessing certain features.

Ying, Gui-shuang; Pearson, Denise J.; Bansal, Mayank; Puri, Manika; Miller, Eydie; Alexander, Judith; Piltz-Seymour, Jody; Nyberg, William; Maguire, Maureen G.; Eledath, Jayan; Sawhney, Harpreet

2010-01-01

37

Heterotopic Adipose Tissue and Smooth Muscle in the Optic Disc.  

National Technical Information Service (NTIS)

The clinical and histopathologic features of a poorly recognized malformation of the optic disc are described. Typically, the otherwise asymptomatic patient has a blind eye requiring enucleation either because of pain from secondary glaucoma or for cosmet...

B. Crawford L. E. Zimmerman R. O'Grady R. Willis R. S. Smith

1971-01-01

38

Optical Coherence Tomography Study of Peripapillary Retinal Nerve Fiber Layer and Choroidal Thickness in Eyes With Tilted Optic Disc.  

PubMed

PURPOSE:: The tilted optic disc is associated with peripapillary choroidal and retinal nerve fiber layer (RNFL) changes as well as visual field defects, often leading to diagnostic difficulties due to similarities with glaucomatous discs. We studied the peripapillary RNFL of the tilted optic disc by comparing values obtained with spectral-domain (SD) and time-domain (TD) optical coherence tomography (OCT) in order to identify characteristic RNFL patterns verified by both OCT devices, and also to determine whether SD-OCT offers any diagnostic advantage over TD-OCT. METHODS:: Prospective case-control study of 16 individuals with tilted optic discs (27 eyes) and an age-matched control group (10 individuals, 20 eyes). Each case was subjected to ophthalmological examination and automated perimetry. Tilt orientation was classified based on observation of optic disc photographs, and angle of disc torsion was calculated with image processing software. RNFL measurements were obtained with TD-OCT and SD-OCT. Peripapillary choroid thickness was measured with SD-OCT. The findings were related with optic disc morphology and automated perimetry results. RESULTS:: Stratus OCT results showed significantly lower superior RNFL (P<0.001) on the tilted group, whereas Spectralis indicated significantly lower superotemporal (P<0.001), superonasal (P=0.001), temporal (P=0.01), and global (P=0.01) RNFL on the tilted disc group. A significant correspondence was found between elevated disc rim and location of RNFL defect on the Spectralis (P=0.004). On the tilted group, peripapillary choroidal thickness was significantly thicker adjacent to the elevated rim (P<0.001). No correspondence was found between tilt orientation, peripapillary RNFL, or choroidal thickness and location of perimetric defects. CONCLUSIONS:: Our results provide a clinical characterization of the main tilted disc morphologies and are valuable for correctly differentiating a tilted disc from a myopic glaucomatous disc. RNFL assessment by Spectralis OCT seems to be more susceptible to altered disc morphologies. The peripapillary RNFL changes found on titled disc cases could not predict the location of visual field defects. PMID:23429636

Brito, Pedro N; Vieira, Marco P; Falcão, Manuel S; Faria, Olinda S; Falcão-Reis, Fernando

2013-02-19

39

Fluorescein angiographic defects of the optic disc in glaucoma.  

PubMed

An improved technique for high-contast, high-resolution fluorescein angiography of the optic disc has been developed that almost eliminates pseudofluorescence. Fluorescein angiography of the optic disc was performed on normal, ocular hypertensive, and glaucomatous patients. Rapid-sequence angiograms in the early arterial phases have demonstrated localized areas of hypofluorescence or filling defects of the optic disc. Two types of fluorescein filling defects were observed-absolute and relative. The number of absolute filling defects, which increased with degree of visual field loss, was greater in glaucomatous than in ocular hypertensive or normal eyes. Similarly, ocular hypertensive eyes showed a larger number of discs with filling defects than normal eyes. It is postulated that relative defects progress to absolute filling defects, which may be an indication of impending loss of visual field. PMID:921573

Schwartz, B; Rieser, J C; Fishbein, S L

1977-11-01

40

Characteristics of Optic Disc Melanocytomas Presenting with Visual Dysfunction  

PubMed Central

Objective and Design: A retrospective review study was designed to describe five cases of optic disc melanocytomas with tumor-related visual impairment. Participants: Five patients with optic disc melanocytoma presented with visual complaints to a tertiary eye hospital in Saudi Arabia. Materials and Methods: Demographic and clinical data were analyzed, including the results of ocular examination, lesion laterality, best-corrected Snellen visual acuity, pupillary reflex, visual field testing, color fundus photography, fundus fluorescein angiography, and ophthalmic ultrasound. Results: Visual dysfunction secondary to optic disc melanocytoma was identified. Case 1 had macular star edema with mild tumor enlargement, Case 2 had optic atrophy, Case 3 had juxtapapillary choroidal neovascular membrane with macular involvement, Case 4 had optic disc swelling with an enlarged blind spot, and Case 5 had a large altitudinal visual field defect. Conclusion: Although melanocytomas of the optic disc tend to have a benign behavior with slow evolution and stable vision, they may adversely affect visual function through a variety of mechanisms.

Al-Rashaed, Saba; Abboud, Emad B.; Nowilaty, Sawsan R.

2010-01-01

41

Amaurosis and optic disc blanching during upgaze in graves ophthalmopathy.  

PubMed

A 60-year-old man with worsening Graves ophthalmopathy complained of complete loss of vision in the left eye on upgaze ("gaze-evoked amaurosis" [GEA]). Examination disclosed congestive orbital signs bilaterally. Upon upgaze, intraocular rose from 18 to 35 mm Hg in the left eye and visual acuity fell in that eye from 20/25 to no light perception. Evidence of optic nerve dysfunction and a swollen optic disc were present in the affected eye, and CT showed enlarged extraocular muscles with apical orbital compression of the optic nerve. Fundus photography performed during GEA disclosed blanching of the optic disc surface vessels in the affected eye. Surgical orbital decompression alleviated the congestive features and optic neuropathy and eliminated the GEA. This is the second case of GEA to be reported in Graves ophthalmopathy and the first to document blanching of optic disc vessels. The presumed mechanism of GEA in this patient is optic nerve ischemia, perhaps provoked by an elevation in intraocular pressure in a congested optic disc. PMID:19726945

Seery, Loren S; Zaldívar, Renzo A; Garrity, James A

2009-09-01

42

Features of intervertebral disc degeneration in rat's aging process*  

PubMed Central

Objective: The age-related change is important part of degenerative disc disease. However, no appropriate animal model or objective evaluation index is available. This study aimed to investigate the features of intervertebral disc degeneration in aging process of rats. Methods: 22-month-old Sprague-Dawley (SD) rats were used as spontaneously occurring intervertebral disc degeneration models and 6-month-old rats as young controls. Expression of collagen types II and X was measured by immunohistochemistry. Degenerations of intervertebral discs were scored according to Miyamoto’s method. Numbers and areas of afferent vascular buds were measured. The thicknesses of non-calcified and calcified layers were measured and statistically analyzed. Results: There were less collagen type II expression and more collagen type X expression in the calcified layer of the cartilage endplates and nucleus pulposus in the rats of the aged group than in the young control. There were fewer and smaller afferent vascular buds in the rats of the aged group than in the young control group. The ratio of the non-calcified to the calcified layers in the rats of the aged group significantly decreased, compared with that of the young control group (P<0.01). Conclusion: Rats can spontaneously establish intervertebral disc age-related degeneration. The expression of collagen types II and X, numbers and areas of afferent vascular buds, the ratio of the non-calcified to the calcified layers, and water and glycosaminoglycan contents in the nucleus pulposus are sensitive indexes of intervertebral disc degeneration.

Zhang, Yin-gang; Sun, Zheng-ming; Liu, Jiang-tao; Wang, Shi-jie; Ren, Feng-ling; Guo, Xiong

2009-01-01

43

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

NASA Astrophysics Data System (ADS)

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

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

2008-03-01

44

A Genome-Wide Association Study of Optic Disc Parameters  

PubMed Central

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

Jansonius, Nomdo M.; de Jong, Paulus T. V. M.; Bergen, Arthur A. B.; Isaacs, Aaron; Amin, Najaf; Aulchenko, Yurii S.; Wolfs, Roger C. W.; Hofman, Albert; Rivadeneira, Fernando; Oostra, Ben A.; Uitterlinden, Andre G.; Hysi, Pirro; Hammond, Christopher J.; Lemij, Hans G.; Vingerling, Johannes R.

2010-01-01

45

The optic disc in glaucoma II: correlation of the appearance of the optic disc with the visual field  

Microsoft Academic Search

Examination of stereoscopic optic disc photographs allowed accurate prediction of glaucomatous and normal fields to be made in 82 and 95% of eyes respectively and for visual field loss to be correctly located in upper and lower half in 83 and 91% of cases respectively. Despite this high correlation the existence of false positive and fale negative predictions means that

R A Hitchings; G L Spaeth

1977-01-01

46

An unusual cause for an optic disc haemorrhage  

PubMed Central

A 51-year-old male on chemotherapy for myeloma presented initially with a unilateral optic disc haemorrhage and signs of optic neuropathy. This rapidly progressed to affect both eyes and within a few days he developed retinal features suggestive of progressive outer retinal necrosis. He was treated with intravenous acyclovir that was subsequently changed to ganciclovir when serological tests for cytomegalovirus were found to be positive for immunoglobulin M antibodies. His visual loss continued to deteriorate despite treatment, and he subsequently developed a retinal detachment in one eye. The causes of optic neuropathy in immunocompromised patients and the importance of eliminating an infective cause are discussed.

Baxter, Julia; Kailasanathan, Anusha; Chen, Hean

2011-01-01

47

Teaching optical fiber communications and optical data storage techniques using a compact disc player  

NASA Astrophysics Data System (ADS)

The principles of optical fiber communication and optical data storage have evolved over the past decade into industry standards for transmission, distribution, storage, and archival of digital audio, multimedia, and computer data. The fundamentals of these sophisticated systems are traditionally taught in the lecture hall, and laboratory exposure to the hardware is at the device rather than the system level. In our educational approach, after the student has been introduced to the device basics, the compact disc audio player is used as a tool to teach the fundamentals of optical communication and storage. The ubiquitous compact disc audio system, from analog input, through optical storage and distribution, to audio reproduction, provides an excellent model of a complete real world optical transmission and storage system. The laboratory time is divided into three segments: Introduction to Electro- Optic Devices, Optical Storage, and Optical Communication. During the introduction, students learn the basics of emitters, detectors, and optical fiber. The optical data storage and retrieval function of the compact disc player is investigated in the second segment. Students are introduced to optical information storage techniques, information density limits, the optical pick-up, laser diodes, photodiode arrays, eye patterns, and the tracking and focusing sub-systems. In the third segment, the compact disc system is used as a model of an entire optical communication system. Students are introduced to sampling and quantization, channel encoding techniques, modulation, high-speed transmitters and receivers, demodulation, decoding, error correction, digital signal processing, and digital-to-analog conversion.

Lane, Pierre M.; van Dommelen, Ronnie F.; Cada, Michael

1997-12-01

48

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

Microsoft Academic Search

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

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

1999-01-01

49

Effect of aging on optic nerve appearance: a longitudinal study  

PubMed Central

AIM—To determine whether aging causes detectable changes in the appearance of the optic disc.?METHODS—A retrospective longitudinal study was performed with quantitative and qualitative evaluations of digitised stereoscopic optic disc photographs of 224 eyes of 224 subjects. There were three groups: 100 normal subjects from the Framingham Eye Study, 68 glaucomatous patients followed longitudinally, and 56 normal subjects and glaucoma patients who had separate sets of disc photos taken on the same day. A disc was considered qualitatively worse if two of three experienced observers agreed that it was worse. Quantitative progression was defined as a >10% decrease in rim/disc area ratio measured with computer assisted planimetry.?RESULTS—With quantitative evaluation, normal eyes (mean follow up 13 years) and same day eyes displayed no statistically significant difference in change of rim/disc area ratios (p=0.095), nor in the number of discs that progressed—five of 100 (5%) v two of 56 (4%) respectively. Glaucomatous eyes (mean follow up 9 years) showed a quantitative loss of disc rim in 24 of 68 (35%), and differed significantly from the normal eyes both in the change of rim/disc area ratio (p<0.0005) and number of discs that progressed (p<0.0005). With qualitative evaluation, the number of progressive discs in the glaucomatous eyes (31%) differed significantly (p<0.0005) from the normal eyes (3%) and the same day eyes (0%).?CONCLUSIONS—Over a period of follow up appropriate for long term outcome studies in glaucoma, there was no quantitatively or qualitatively detectable neuroretinal rim loss in normal aging optic nerves with stereoscopic optic disc photographs.??

Moya, F.; Brigatti, L.; Caprioli, J.

1999-01-01

50

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

PubMed Central

Aims: To assess the intraobserver agreement, interobserver agreement, and the agreement between a digital stereo optic disc camera (Discam) and Heidelberg retina tomograph (HRT) in measuring area cup-disc ratio (ACDR) and radial cup-disc ratio (RCDR) by two observers. Methods: The optic discs of 78 eyes of 39 people (17 cases of primary open angle glaucoma, eight normal tension glaucoma, two ocular hypertension, and 12 normal subjects) were imaged with Discam and HRT. Two observers independently drew the disc margins on the HRT mean topography images and the disc and cup margins on the Discam images. ACDR and the RCDR at various angles were measured with the two systems. Intraobserver agreement, interobserver agreement, and the agreement between the two systems were assessed by 95% tolerance limit of changes (TC) and intraclass correlation coefficient (ICC). Results: Eight eyes were excluded due to poor image quality (six Discam and two HRT). 70 eyes were analysed. The intraobserver ACDR agreement was almost perfect in both systems (ICCs = 0.97 and 0.92, and TCs = 11.0% and 15.1% in HRT and Discam respectively). The interobserver ACDR agreement was almost perfect in HRT (ICC = 0.97) and substantial in Discam (ICC = 0.79), (TCs = 10.5% and 24.5% respectively). The ACDR agreement between the two systems was substantial in observer A (ICC = 0.67) and moderate in observer B (ICC = 0.53), (TCs = 24.8% and 46.7% respectively). The HRT measured the ACDR significantly larger than the Discam (p <0.001), and the differences were significantly larger in the glaucomatous group (p <0.001). RCDR agreement between the two systems was fair to substantial in observer A (ICC = 0.36 to 0.74) and slight to moderate in observer B (ICC = 0.12 to 0.45). Both observers achieved the best RCDR agreement between the two systems at the inferior optic disc position. Conclusion: There is almost perfect intraobserver agreement in each system. The interobserver agreement was better with the HRT than the Discam. There was substantial variation in ACDR and RCDR agreement between the two systems measured by the two observers. The variation in ACDR and RCDR measurements between the two systems may be too large for interchangeable use in a clinical setting.

Sung, Velota C T; Bhan, Anna; Vernon, Stephen A

2002-01-01

51

The effect of age on intervertebral disc compression during running.  

PubMed

Previous studies have shown that intervertebral discs compress under axial loading, yet few studies have examined the relationship between disc age and compressibility. The purpose of this study was to determine if the amount of vertebral column height (VCH) loss induced by running was significantly different between two age groups, 17 males ages 20-27 years and 14 males ages 50-57 years, who could comfortably run 6 miles. The subjects had no previous or current back pathologies. Within 1.5 hours of rising in the morning, each subject's VCH was measured from spinous processes C7 to S2. Immediately following the measurement, each subject ran a predetermined, paved, 6-mile course at a comfortable pace. Within minutes after completing the run, each subject was again measured for VCH. Paired t tests revealed significant decreases in VCH after the run in both groups. An independent t test showed no significant differences between the respective age groups in terms of postrun VCH decreases. Although no significant differences were noted between groups, this study has demonstrated that both age groups experienced significant decreases in VCH after a 6-mile run. These findings have implications for physical therapy for younger and older male patients who may have back pathologies and require an exercise program. Patients may be advised to limit running due to possible exacerbation of back symptoms. PMID:8081404

Ahrens, S F

1994-07-01

52

Bilateral optic disc oedema and associated optic neuropathy in the setting of FOLFOX chemotherapy  

PubMed Central

Background To report a case of bilateral optic disc oedema and associated optic neuropathy in the setting of FOLFOX chemotherapy. Case presentation A case of a 57-year-old male being treated with FOLFOX chemotherapy for stage 3B colorectal cancer, who developed bilateral optic disc oedema and associated left sided optic neuropathy is described. The patient presented following cycles 7, 8 and 9 of chemotherapy with a history of bilateral simultaneous intermittent inferior altitudinal field defects. These episodes progressed to bilateral optic nerve oedema and a subsequent left sided optic neuropathy. The patient’s symptoms and oedema regressed with discontinuation of chemotherapy. Conclusion This is the first report suggesting a vasospastic role of 5-fluoruracil in 5-FU associated optic neuropathy. It highlights that 5-FU may have the potential to cause arterial vasospasm outside the cardiac vasculature, resulting in end-organ optic nerve ischaemia.

2013-01-01

53

A case of bilateral uveitis and optic disc swelling with Chiari I malformation  

PubMed Central

We report a case of bilateral uveitis and optic disc swelling with Chiari I malformation. A 16-year-old girl was admitted to our clinic due to conjunctival hyperaemia and blurred vision in her right eye. Ophthalmologic and systemic examinations were performed. Visual acuity was 0.7 (OD) and 1.0 (OS). Bilateral optic disc swelling was observed. Fluorescein angiography demonstrated bilateral retinal vasculitis as well as optic disc hyperflourescence due to leakage. Laboratory examinations were within normal limits. Cranial magnetic resonance venography imaging revealed neither cranial mass nor cerebral venous thrombosis but a Chiari I malformation. The patient was started oral cetazolamid, topical and oral corticosteroids. After six months follow-up, bilateral optic disc swelling was resolved completely and visual acuity was 1.0 in both eyes. Optic disc swelling may be associated with intraocular inflammation; however, patients with bilateral optic disc swelling should be suspected of having an accompanying intracranial pathology.

Eken, Volkan; Nilufer Yalc?ndag, F.; Bat?oglu, Figen; Is?kay, Canan Togay

2012-01-01

54

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

55

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

ERIC Educational Resources Information Center

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

Harvey, Francis A.

1987-01-01

56

Morphometric changes in the heights and anteroposterior diameters of the lumbar intervertebral discs with age.  

PubMed Central

Changes in the heights and anteroposterior diameters of human lumbar intervertebral discs have been studied by means of measurements from radiographs. The results confirm previous reports that there is overall increase in the various dimensions of the disc with age. Growth of the discs apparently does not follow a linear pattern. There are alternating periods of overgrowth and thinning. After the 5th decade of life there is an appreciable decline of disc height. The significance of the findings is discussed.

Amonoo-Kuofi, H S

1991-01-01

57

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

PubMed

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

Pereira, Carla; Gonçalves, Luís; Ferreira, Manuel

2012-11-19

58

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

59

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

60

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

61

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

PubMed Central

AIMS—To evaluate the relation between the optic disc size and the thickness of the peripapillary retinal nerve fibre layer (RNFL) in normal Japanese subjects by means of scanning laser polarimetry.?METHODS—Scanning laser polarimetry was performed in 60 normal subjects. One eye of each subject was randomly selected for study. Using a scanning laser polarimeter, the integral of RNFL thickness was measured totally and regionally within a circular band located 1.75 disc diameters from the centre of the optic disc. The correlation between the optic disc size and the integral of RNFL thickness was examined.?RESULTS—The optic disc size showed a significant correlation with the integral of RNFL thickness (R = 0.497, p <0.001). A significant negative correlation was observed between the optic disc size and the ratio of inferior integral to total integral of RNFL thickness (R = ?0.274, p = 0.034).?CONCLUSIONS—The cross sectional area occupied by the RNF, measured by scanning laser polarimetry increased significantly with an increase in optic disc size while the ratio of inferior to total cross sectional area decreased significantly. These facts should be considered when one evaluates the RNFL thickness in patients with progressive optic neuropathies such as glaucoma.?? Keywords: scanning laser polarimeter; normal subjects; optic disc; retinal nerve fibre layer

Funaki, S.; Shirakashi, M.; Abe, H.

1998-01-01

62

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

63

Comparison of Colour Spaces for Optic Disc Localisation in Retinal Images  

Microsoft Academic Search

The location of the optic disc is of critical importance in retinal image analysis. In this work we improve on an approach introduced in (3) who localised an optic disc region through greylevel morphology followed by snake fitting. We propose and implement both the automatic initialisation of the snake and the application of morphol- ogy in colour space. We examine

Alireza Osareh I; Majid Mirmehdi; Barry T. Thomas; Richard Markham

2002-01-01

64

Correlation of Asymmetry of Visual Field Loss With Optic Disc Topography in Normal-Tension Glaucoma  

Microsoft Academic Search

Results: The correlation coefficients between the in- terocular differences in mean defect and those of the area under the optic disc profile in the superior to temporal sections ranged from\\\\m=-\\\\.71to \\\\m=-\\\\.61(.007optic disc profile in

Kristina Nyman; Goji Tomita; Christina Raitt; Mitsuya Kawamura

65

Optic disc excavation in the atrophic stage of Leber's hereditary optic neuropathy: comparison with normal tension glaucoma  

Microsoft Academic Search

Background. Abnormal optic disc excavations are reportedly seen in patients with Leber's hereditary optic neuropathy (LHON), a mitochondrial dysfunction disease. We examined the disc morphology in the eyes of patients with LHON at the atrophic stage and compared it to that in eyes with normal-tension glaucoma (NTG). Methods. We studied 15 LHON patients with the 11778 mutation, 15 patients with

Yukihiko Mashima; Itaru Kimura; Yusuke Yamamoto; Hisao Ohde; Yuichirou Ohtake; Tomihiko Tanino; Goji Tomita; Yoshihisa Oguchi

2003-01-01

66

Optic disc edema in non-arteritic anterior ischemic optic neuropathy  

Microsoft Academic Search

We investigated the clinical characteristics, time to resolution and the factors that influence it, and evolutionary pattern\\u000a of optic disc edema (ODE) in non-arteritic anterior ischemic optic neuropathy (NA-AION). Our study was conducted in 591 consecutive\\u000a patients (749 eyes) with NA-AION who fulfilled our inclusion criteria. On their first visit to our clinic, all patients had\\u000a a detailed ophthalmic and

Sohan Singh Hayreh; M. Bridget Zimmerman

2007-01-01

67

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

PubMed

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

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

2013-05-14

68

Optic disc changes following trabeculectomy: longitudinal and localisation of change  

PubMed Central

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

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

2001-01-01

69

Assessment of stereoscopic optic disc images using an autostereoscopic screen - experimental study  

PubMed Central

Background Stereoscopic assessment of the optic disc morphology is an important part of the care of patients with glaucoma. The aim of this study was to assess stereoviewing of stereoscopic optic disc images using an example of the new technology of autostereoscopic screens compared to the liquid shutter goggles. Methods Independent assessment of glaucomatous disc characteristics and measurement of optic disc and cup parameters whilst using either an autostereoscopic screen or liquid crystal shutter goggles synchronized with a view switching display. The main outcome measures were inter-modality agreements between the two used modalities as evaluated by the weighted kappa test and Bland Altman plots. Results Inter-modality agreement for measuring optic disc parameters was good [Average kappa coefficient for vertical Cup/Disc ratio was 0.78 (95% CI 0.62–0.91) and 0.81 (95% CI 0.6–0.92) for observer 1 and 2 respectively]. Agreement between modalities for assessing optic disc characteristics for glaucoma on a five-point scale was very good with a kappa value of 0.97. Conclusion This study compared two different methods of stereo viewing. The results of assessment of the different optic disc and cup parameters were comparable using an example of the newly developing autostereoscopic display technologies as compared to the shutter goggles system used. The Inter-modality agreement was high. This new technology carries potential clinical usability benefits in different areas of ophthalmic practice.

Habib, Maged S; Lowell, James A; Holliman, Nick S; Hunter, Andrew; Vaideanu, Daniella; Hildreth, Anthony; Steel, David HW

2008-01-01

70

Interocular asymmetry of optic disc size and its relevance to visual field loss in normal-tension glaucoma  

Microsoft Academic Search

We evaluated the relevance of interocular asymmetry of optic disc size to the level of intraocular pressure and the extent of optic disc and visual field changes in normal-tension glaucoma (NTG). Fifty-two eyes of 26 patients with NTG were measured for optic disc topography using a computerized image analysis system (IMAGEnet, Topcon), diurnal intraocular pressure (IOP), and Octopus automated visual

Goji Tomita; Kristina Nyman; Christina Raitta; Mitsuya Kawamura

1994-01-01

71

Immunolocalization of type X collagen in human lumbar intervertebral discs during ageing and degeneration  

Microsoft Academic Search

Type X collagen has so far not been reported to occur in human intervertebral discs. The objective of this study was therefore\\u000a to investigate the occurrence of type X collagen in human lumbar intervertebral discs during ageing and degeneration. Ninety\\u000a intervertebral discs with adjacent endplates were excised in toto from individuals (0–86 years) without known spinal disease\\u000a and were processed

N. Boos; Andreas G. Nerlich; Irmgard Wiest; Klaus von der Mark; Max Aebi

1997-01-01

72

Infiltration of the Optic Chiasm, Nerve, and Disc by Gliomatosis Cerebri.  

PubMed

ABSTRACT:: An 18-year-old man with gliomatosis cerebri (GC) developed tumor infiltration of the optic chiasm and right optic nerve including the optic disc. Although papilledema often is seen with GC, tumor invasion of the optic nerve head is observed. PMID:23287703

Traynis, Ilana; Singer, Samuel; Winterkorn, Jacqueline; Rosenblum, Marc; Dinkin, Marc

2013-01-01

73

Optic disc analysis with Heidelberg Retina Tomography III in glaucoma with unilateral visual field defects  

Microsoft Academic Search

Purpose  To find the optic disc features of asymmetric primary open-angle glaucoma.\\u000a \\u000a \\u000a \\u000a Methods  In this observational case-control study, 52 consecutive open-angle glaucoma patients with unilateral visual field defects\\u000a participated. In each patient, an optic disc analysis using Heidelberg Retina Tomography III (HRT-III) was performed. Optic\\u000a disc parameters of HRT-III of eyes with abnormal visual fields were compared with their fellow eyes with

Ge-Ge Xiao; Ling-Ling Wu

2010-01-01

74

Identification of glaucomatous visual field defects from examination of monocular photographs of the optic disc  

Microsoft Academic Search

A study was carried out of monocular disc photographs from 33 eyes for which the visual fields on both static profile and kinetic perimetry has been performed. Physical signs looked for at the optic disc included thinning of the neuroretinal rim, angulation of retinal vessels, extension of laminar dots, undercutting of the neuroretinal rim, and absence and pallor of the

R. A. Hitchings; S. Anderton

1983-01-01

75

Optic Disc Morphology in Open-Angle Glaucoma Compared with Anterior Ischemic Optic Neuropathies  

PubMed Central

Purpose. To compare optic disc topography performed by confocal laser ophthalmoscopy in eyes with nonarteritic anterior ischemic optic neuropathy (NAION), arteritic anterior ischemic optic neuropathy (AAION), and open-angle glaucoma (OAG), adjusting for the amount of retinal ganglion cell (RGC) loss, as measured by nerve fiber layer (NFL) thickness and average visual field loss. Methods. At four referral centers, patients who met specific diagnostic criteria for OAG (103 persons, 152 eyes), NAION (53 persons, 57 eyes), or AAION (18 persons, 20 eyes) underwent Heidelberg Retinal Tomography (HRT; Heidelberg Engineering, Heidelberg, Germany), Stratus Optical Coherence Tomography (OCT; Carl Zeiss Meditec, Inc., Dublin, CA), and Humphrey visual field testing (HFA; Carl Zeiss Meditec, Inc.). HRT parameters were compared in univariate and multivariate models, accounting for degree of RGC loss by either OCT NFL thickness or visual field mean deviation (MD). Acute AION occurred at least 6 weeks before testing. Results. After adjustment for degree of injury according to either MD or mean NFL thickness, all HRT parameters were significantly different between OAG and both NAION and AAION. With similar damage, OAG eyes had larger, deeper cups; smaller rims; more cup volume; and less rim volume (all P ? 0.001). There were differences in disc topography between NAION and AAION, but they were not consistent for both measures of damage. Disc area and MD were also significantly associated with many HRT parameters. NFL thickness was greater at the same MD for both AAION and NAION compared with OAG. Conclusions. NAION and AAION cause loss of RGCs, but have significantly different disc topography compared with OAG at a given level of RGC loss.

Boland, Michael V.; Savino, Peter J.; Miller, Neil R.; Subramanian, Prem S.; Girkin, Christopher A.; Quigley, Harry A.

2010-01-01

76

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

77

Detecting optic disc on asians by multiscale gaussian filtering.  

PubMed

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). PMID:22844267

Zhang, Bob; You, Jane; Karray, Fakhri

2012-06-26

78

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

79

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

80

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

Microsoft Academic Search

AIMTo evaluate the ability of confocal scanning laser tomography of the optic nerve head to detect glaucomatous optic nerve damage in ocular hypertensive eyes without visual field defects.METHODSThe study included 50 normal subjects, 61 glaucoma patients with glaucomatous changes in the optic disc and visual field, and 102 “preperimetric” patients with increased intraocular pressure, normal visual fields, and glaucomatous appearance

Christian Y Mardin; Folkert K Horn; Jost B Jonas; Wido M Budde

1999-01-01

81

The comparison of manual vs automated disc margin delineation using spectral-domain optical coherence tomography.  

PubMed

AimsTo examine the impact of manual vs automated disc margin delineation on optic nerve head (ONH) and retinal nerve fiber layer (RNFL) parameters using spectral-domain optical coherence tomography (SDOCT).MethodsA prospective cohort study consisting of normal, glaucoma suspect (GS) and glaucoma patients who underwent ONH and RNFL measurements using SDOCT technology (RTVue; Optovue Inc.). The retinal pigment epithelium/Bruch's membrane (RPE/BM) complex end points were automatically determined first, and were manually redefined subsequently. Analysis of variance, coefficient of variation (COV), concordance correlation coefficient (CCC), and Bland-Altman plots were used for the analyses.ResultsNinety-nine eyes of 50 subjects (age 68±10 years) consisting of 36 glaucoma, 56 GS, and 7 normal eyes were included. The RNFL thickness measurements were similar (P>0.05) between the two methods of demarcation, except for the inferior-nasal sector (P=0.04). For the ONH measurements, the cup-to-disc (C/D) ratio and rim area showed significant differences between the two methods (P<0.001). COV/CCC values for the ONH parameters were as follows: cup area 17.6%/0.88; cup volume 7.4%/0.91; average C/D ratio 18.1%/0.78; rim area 25.3%/0.69; and rim volume 42.6%/0.71, respectively. CCC/COV values for the RNFL parameters were as follows: average 2.1%/0.98; inferior-temporal quadrant 8.1%/0.79; inferior-nasal quadrant INQ quadrant 12.6%/0.67; SNQ quadrant 7.8%/0.83; and STQ quadrant 7.8%/0.88, respectively.ConclusionAn overall high agreement and moderate-substantial concordance was observed between the demarcation methods. Automated disc margin delineation of SDOCT can be used reliably in clinical practice. PMID:23907624

Iverson, S M; Sehi, M

2013-08-02

82

On how optical depth tunes the effects of the interstellar medium on debris discs  

NASA Astrophysics Data System (ADS)

The flux of neutral atoms of the interstellar medium (ISM) surrounding stars and their environment affects the motion of dust particles in debris discs, causing a significant dynamical evolution. Large values of eccentricity and inclination can be excited, and strong correlations settle in among the orbital angles. This dynamical behaviour, in particular for bound dust grains, can potentially cause significant asymmetries in dusty discs around solar-type stars, which might be detected by observations. However, the amount of orbital change as a result of this non-gravitational perturbation is strongly limited by the collisional lifetime of dust particles. We show that, for large values of the disc's optical depth, the influence of the ISM flow on the disc shape is almost negligible. This is because the grains are collisionally destroyed before they can accumulate enough orbital changes as a result of the ISM perturbations. However, for values smaller than 10-3, peculiar asymmetric patterns appear in the density profile of the disc when we consider grains of 1-10 ?m grains, just above the blow-out threshold. The extent and relevance of these asymmetries grow for lower values of the optical depth. An additional sink mechanism, which might prevent the formation of large clumps and warping in the discs, is related to the fast inward migration as a result of the drag component of the forces. When a significant eccentricity is enlarged by the ISM perturbations, the drag forces (Poynting-Robertson drag and, in particular, ISM drag) drive the disc particles on fast migrating tracks, leading them into the star on a short time-scale. It is then expected that discs with small optical depth expand inside the parent body ring all the way towards the star, while discs with large optical depth would not significantly extend inside.

Marzari, F.; Thébault, P.

2011-09-01

83

Familial cavitary optic disc anomalies: Identification of a novel genetic locus  

PubMed Central

PURPOSE To identify the chromosomal location of the gene involved in the pathogenesis of cavitary optic disc anomalies in a large pedigree with autosomal dominant inheritance of disease. DESIGN Linkage analysis of a pedigree affected with cavitary optic disc anomalies. METHODS Optic disc photographs were examined for the presence of cavitary optic disc anomalies. Sixteen affected family members and one obligate carrier were identified and studied with linkage analysis using both microarrays of single nucleotide polymorphisms (SNPs) and short tandem repeat polymorphism (STRP) markers. RESULTS Multipoint linkage analysis of SNP genotypes yielded a maximum nonparametric LOD score of 21.7 with markers located on chromosome 12q. Linkage was confirmed with 16 STRP markers in the 12q region. A maximum two point LOD score of 4.06 (?=0) was obtained with marker D12S1700. The disease interval defined by observed recombinants is 9.1 cM, which corresponds to 13.5 Mbp. Three candidate genes (GDF-11, NEUROD4, and WIF1) in the chromosome 12q locus were evaluated as possible disease-causing genes. No mutations were detected in the coding sequence of these genes. DISCUSSION The discovery of the chromosomal location of a gene responsible for cavitary optic disc anomalies is a key step in identifying the genetic basis of this condition and may ultimately provide important insight into the pathogenesis of more common optic nerve diseases such as normal tension glaucoma and primary open angle glaucoma.

Fingert, John H.; Honkanen, Robert A.; Shankar, Suma P.; Affatigato, Louisa M.; Ehlinger, Mary A.; Moore, Michael D.; Jampol, Lee M.; Sheffield, Val C.; Stone, Edwin M.; Alward, Wallace L.M.

2007-01-01

84

Donor disc attachment assessment with intraoperative spectral optical coherence tomography during descemet stripping automated endothelial keratoplasty.  

PubMed

Optical coherence tomography has already been proven to be useful for pre- and post-surgical anterior eye segment assessment, especially in lamellar keratoplasty procedures. There is no evidence for intraoperative usefulness of optical coherence tomography (OCT). We present a case report of the intraoperative donor disc attachment assessment with spectral-domain optical coherence tomography in case of Descemet stripping automated endothelial keratoplasty (DSAEK) surgery combined with corneal incisions. The effectiveness of the performed corneal stab incisions was visualized directly by OCT scan analysis. OCT assisted DSAEK allows the assessment of the accuracy of the Descemet stripping and donor disc attachment. PMID:24104711

Wylegala, Edward; Nowinska, Anna K; Wroblewska-Czajka, Ewa; Janiszewska, Dominika

2013-09-01

85

Development of Recording Stacks for a Rewritable Dual-Layer Optical Disc  

NASA Astrophysics Data System (ADS)

In this paper results are presented on the development of recording layers for a rewritable dual-layer phase-change optical disc. The disc is based on the digital video recording (DVR) system utilising a blue laser and a high numerical-aperture objective lens. With such a disc the capacity of the DVR system could be increased to about 45 GB. Various stack designs, write strategies and recording characteristics of the media are discussed. For each recording layer a design with a fairly good performance is found.

Mijiritskii, Andrei; Hellmig, Jochen; Borg, Herman; Meinders, Erwin

2002-03-01

86

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

87

Effect of Disease Severity and Optic Disc Size on Diagnostic Accuracy of RTVue Spectral Domain Optical Coherence Tomograph in Glaucoma  

PubMed Central

Purpose. To evaluate the effect of disease severity and optic disc size on the diagnostic accuracies of optic nerve head (ONH), retinal nerve fiber layer (RNFL), and macular parameters with RTVue (Optovue, Fremont, CA) spectral domain optical coherence tomography (SDOCT) in glaucoma. Methods. 110 eyes of 62 normal subjects and 193 eyes of 136 glaucoma patients from the Diagnostic Innovations in Glaucoma Study underwent ONH, RNFL, and macular imaging with RTVue. Severity of glaucoma was based on visual field index (VFI) values from standard automated perimetry. Optic disc size was based on disc area measurement using the Heidelberg Retina Tomograph II (Heidelberg Engineering, Dossenheim, Germany). Influence of disease severity and disc size on the diagnostic accuracy of RTVue was evaluated by receiver operating characteristic (ROC) and logistic regression models. Results. Areas under ROC curve (AUC) of all scanning areas increased (P < 0.05) as disease severity increased. For a VFI value of 99%, indicating early damage, AUCs for rim area, average RNFL thickness, and ganglion cell complex–root mean square were 0.693, 0.799, and 0.779, respectively. For a VFI of 70%, indicating severe damage, corresponding AUCs were 0.828, 0.985, and 0.992, respectively. Optic disc size did not influence the AUCs of any of the SDOCT scanning protocols of RTVue (P > 0.05). Sensitivity of the rim area increased and specificity decreased in large optic discs. Conclusions. Diagnostic accuracies of RTVue scanning protocols for glaucoma were significantly influenced by disease severity. Sensitivity of the rim area increased in large optic discs at the expense of specificity.

Rao, Harsha L.; Leite, Mauro T.; Weinreb, Robert N.; Zangwill, Linda M.; Alencar, Luciana M.; Sample, Pamela A.

2011-01-01

88

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

89

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

2013-02-06

90

The Spectrum of Optic Disc Ischemia in Patients Younger than 50 Years (An Amercian Ophthalmological Society Thesis)  

PubMed Central

Purpose: To identify the spectrum of clinical and fluorescein angiographic features of optic disc ischemia in patients younger than 50 years. Methods: This retrospective comparative case series from a university consultative neuro-ophthalmology practice consisted of two phases. The first compared 108 cases of nonarteritic anterior ischemic optic neuropathy in patients younger than 50 years (NAIONy) to a cohort of 108 cases in patients 50 years or older (NAIONo). Predisposing risk factors, fluorescein angiographic features, and clinical course were compared. In the second phase, 12 cases of diabetic papillopathy under age 50 were assessed by fluorescein angiographic criteria for evidence of optic disc ischemia and compared to patients with NAIONy. Results: NAIONy comprised 108 (12.7%) of 848 NAION cases reviewed. Chronic renal failure with dialysis and migraine were more common in NAIONy. Fellow eye involvement rate was significantly higher for NAIONy patients (46/108, 42.6%) than for NAIONo patients (32/108, 29.6%). Fluorescein angiographic features of ischemia were documented in 44 (81.5%) of 54 eyes studied. In one case, these features were documented in pre-NAION edema. Diabetic papillopathy demonstrated delayed filling consistent with ischemia in 7 of 10 (70.0%), without significant visual field loss. Conclusions: Ischemic optic neuropathy in patients younger than 50 years is not rare. Fellow eye involvement is more frequent in younger patients. Fluorescein angiography confirmation of impaired perfusion in multiple syndromes of optic neuropathy corroborates a spectrum of optic disc ischemia ranging from perfusion delay without visual loss to severely impaired perfusion and visual loss and incorporates optic neuropathies previously considered nonischemic.

Arnold, Anthony C.; Costa, Roberta M. S.; Dumitrascu, Oana M.

2013-01-01

91

Scleral edge, not optic disc or retina, is the primary site of injury in chronic glaucoma.  

PubMed

In chronic glaucoma, there is a gradual painless loss of vision, early manifestation of arcuate field defect and typical atrophy of the optic disc known as 'cupping'. Chronic glaucoma is classified into high-tension glaucoma (HTG) and normal-tension glaucoma (NTG). Although both types manifest with the same typical visual field defect and cupping of the optic disc, high-tension glaucoma has elevated intraocular pressure whereas in normal-tension glaucoma the intraocular pressure (IOP) is within the normal range (10-21 mmHg). There are several theories about the pathogenesis of chronic glaucoma ranging from high intraocular pressure directly damaging the optic disc to programmed death(apoptosis) of the ganglion cells of the retina. But none of them satisfactorily explain the manifestation of the early arcuate field defect which is a pathognomonic feature of both types of chronic glaucoma. This article focuses on two main issues. First, how and why the arcuate field defects are produced in the early stages of glaucoma and secondly to find out the common ground in the pathogenesis of both high and normal tension glaucoma. The early arcuate field defects are an important lead in discovering the pathogenesis of glaucoma, therefore if any factor or site which could not possibly produce initial sharply defined arcuate field defects was ruled out. This article presents an unconventional approach to the pathogenesis of glaucoma. Instead of looking for various factors causing glaucoma, emphasis was placed on determining the primary site of injury which could produce the initial arcuate field defects. Keeping the arcuate visual field defects in mind, the primary site of injury appears to be at the scleral edge and not the optic disc or the retina in chronic glaucoma. The border tissue which separates the sclera and choroid from the nerve fibers would atrophy due to chronic ischemia as a result of high intraocular pressure in HTG, whereas due to poor systemic circulation in NTG. In both types of chronic glaucoma, the ciliary circulation supplying the prelaminar and border tissue is compromised. As a result of atrophy of the border tissue, the optic disc sinks as a whole beginning temporally due to its tilted position and causing nerve fibers to stretch, kink, and cut at the scleral edge. This process of optic disc sinking would accelerate due to loss of nerve fibers which also provides anchorage to the optic disc. This cycle would continue until all the nerve fibers are cut at the scleral edge and the optic disc is destroyed. PMID:16824694

Hasnain, Syed Sikandar

2006-07-07

92

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

PubMed Central

AIMS—To evaluate the effect of acute elevation of intraocular pressure (IOP) on optic disc cupping.?METHODS—10 emmetropic and 10 myopic volunteers were included in this study. The cup area (CA) and cup volume (CV) of the optic disc were determined with the Heidelberg retina tomograph (HRT). After baseline determinations, a suction cup was used to increase the intraocular pressure (IOP) to 20-25 mm Hg above the baseline and HRT images were obtained.?RESULTS—Baseline IOP was 13.5 (SD 1.3) mm Hg and 12.6 (2.6) mm Hg in the emmetropic and myopic groups, respectively. The IOP was elevated to 35.4 (3.3) mm Hg and 34.4 (2.5) mm Hg in the emmetropic and myopic groups, respectively. When compared with their baseline values, the cupping variables (CA and CV) were significantly increased (p<0.05) during the suction treatment in both emmetropic and myopic subjects.?CONCLUSION—There was a significant enlargement in the optic disc cupping during the artificial increment of intraocular pressure in both emmetropic and myopic eyes. In non-glaucomatous eyes the optic nerve head has a partially dynamic topography dependent upon the level of IOP.?? Keywords: optic disc; intraocular pressure; compliance; glaucoma

Azuara-Blanco, A.; Harris, A.; Cantor, L.; Abreu, M.; Weinland, M.

1998-01-01

93

Choosing an Optical Disc System: A Guide for Users and Resellers.  

ERIC Educational Resources Information Center

|Presents a guide for selecting an optional disc system. Highlights include storage hierarchy; standards; data life cycles; security; implementing an optical jukebox system; optimizing the system; performance; quality and reliability; software; cost of online versus near-line; and growing opportunities. Sidebars provide additional information on…

Vane-Tempest, Stewart

1995-01-01

94

Optic Disc, Foveal, and Extrafoveal Damage Due to Surgical Separation of the Vitreous  

Microsoft Academic Search

cal separation of the vitreous from the internal limiting lamina (ILL) of the posterior retina and surface of the optic disc were performed on 25 young adult cynomol- gus monkey eyes in vivo. Lectin histochemical studies were used to evaluate the vitreoretinal interface. Mor- phologic outcomes were tabulated. Results: In 11 of 25 eye regions, residual vitreous re- mained attached

Stephen R. Russell; Gregory S. Hageman

95

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

96

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

97

MEMS focus control and spherical aberration correction for multilayer optical discs  

NASA Astrophysics Data System (ADS)

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

Lukes, Sarah J.; Dickensheets, David L.

2012-02-01

98

Dilemma of the swollen optic disc: a fluorescein retinal angiography study.  

PubMed Central

In all of 100 consecutive patients referred for retinal angiography with a clinical diagnosis of probable or possible papilloedema a definite diagnosis was made from neurological assessment, neuroradiological investigations, and follow-up. The cases have been divided into 2 groups--those with proved papilloedema and those which have been called either normal or pseudopapilloedema. In all cases the retinal angiograms showed normal or increased optic disc vascularity and normal or increased early and late disc fluorescence. On the basis of these alone clear differences could be shown between the groups. All cases with papilloedema showed a combination of either excess late fluorescence with excess early fluorescence or excess late fluorescence with excess disc vascularity. Only 2 cases of pseudopapilloedema (both with optic disc drusen) showed this combination, and in both the pattern of disc fluorescence was different from that seen in papilloedema. Retinal angiography therefore seems to be of considerable value in differentiating true from pseudopapilloedema, though this is possible only when each stage of the angiogram is carefully studied. Images

Cartlidge, N E; Ng, R C; Tilley, P J

1977-01-01

99

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

Microsoft Academic Search

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

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

100

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

Microsoft Academic Search

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

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

1998-01-01

101

Surgical Excision of the Lumbar Disc Herniation in Elementary School Age  

PubMed Central

Study Design A retrospective study. Purpose To assess the radiological, clinical features and surgical outcomes of six patients of elementary school age with lumbar disc herniation (LDH). Overview of Literature LDH is common in people in their fourth and fifth decades. However, the condition is extremely rare in children of elementary school age. Moreover, the clinical symptoms and treatments are different from those of adults. Methods We reviewed a series of 6 patients under the age of 12 years, who underwent surgery for LDH at our institution between 1992-2002. Initially, all patients were treated conservatively. The indications for surgery were failure of conservative treatment for 3 months, intractable pain and/or progressive neurological impairment. Results The surgical findings revealed a protruding disc in five cases and a ruptured disc in one. In addition, separation of the vertebral ring apophysis was observed in 3 cases. The symptoms had disappeared completely at the last follow-up. At the last follow-up, the Japanese Orthopaedic Association score was 10 points in 5 cases and 9 points in 1, and the Kirkaldy-Willis criteria was excellent in all patients. No intervertebral disc space narrowing was observed in any patient at last follow up. In addition, there were no degenerative changes in the vertebral endplate and facet joint. Conclusions Patients with symptoms that persist for more than 3 months or those with a progressive neurological deficit must be considered for surgical discectomy.

Kim, Youn-Soo; Park, Il-Jung; Rhyu, Kee-Won; Lee, Sang-Uk

2009-01-01

102

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

103

Optic disc assessment in the emergency department: a comparative study between the PanOptic and direct ophthalmoscopes.  

PubMed

Optic disc assessment is an essential part of the neurological examination of acutely unwell patients. This study compares the PanOptic ophthalmoscope with the direct ophthalmoscope for accuracy of diagnosis and ease of use. Patient satisfaction was also compared for the two instruments. A single-masked prospective observational study was carried out. The authors showed that the PanOptic ophthalmoscope was more sensitive (p=0.03) and specific (p=0.03) than the direct ophthalmoscope. The PanOptic ophthalmoscope was preferred by both doctors (p=0.001) and patients (p=0.04) in terms of comfort and ease of use. PMID:21998469

Petrushkin, Harry; Barsam, Allon; Mavrakakis, Milt; Parfitt, Andy; Jaye, Peter

2011-10-13

104

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

105

Optic disc pit with peripapillary retinoschisis presenting as a localized retinal nerve fiber layer defect.  

PubMed

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. PMID:22131786

Song, In Seok; Shin, Joong Won; Shin, Yong Woon; Uhm, Ki Bang

2011-11-22

106

Optic disc topography and short-term increase in intraocular pressure.  

PubMed

Intraocular pressure is intra- and interindividually inconstant. It is influenced by numerous ocular and general factors. We evaluated the question as to whether a short-term increase in intraocular pressure might change the two-dimensional topography of the optic nerve head. Optic disc photographs of 63 glaucomatous eyes in 33 Caucasian patients and 39 normal eyes in 22 subjects were taken at a baseline intraocular pressure of less than 20 mm Hg and at 1 and 8 s after pressure elevations of 10 and 20 mm Hg. No significant differences in the size and form of the optic disc, optic cup, neuroretinal rim, peripapillary scleral ring or parapapillary chorioretinal atrophy were found. The retinal vessels mostly reacted to the intraocular pressure elevation by an initial decrease and subsequent re-increase in their diameter; this change was significant (P less than 0.05) for the pressure elevation of 20 mm Hg. We conclude that the two-dimensional optic disc topography is not significantly changed by a short-term increase in intraocular pressure. PMID:2265766

Jonas, J B; Gareis, O; Naumann, G O

1990-01-01

107

The age distribution of the stellar disc of NGC 5907  

NASA Astrophysics Data System (ADS)

Disks of galaxies are dynamically heated by some gravitational scattering process. The velocity dispersion and the scale height increase with the age of the stellar populations as can be observed directly in the solar neighbourhood. This evolutionary effect can be used to derive the heating rate and the star formation history from the vertical structure of spiral galaxies seen edge-on. For an analysis of vertical luminosity and colour profiles a detailed model of the stellar composition and a reasonable dust distribution is needed. We use a physical model of a self--gravitating disk composed of isothermal subpopulations with increasing age and velocity dispersion and an exponential dust distribution (Just et al. 1996, A&A 309, 715). The stellar emissivities in the different bands are calculated from the luminosities of single age populations which are computed with the method of photometric evolutionary synthesis (Einsel et al. 1995, A&A 296, 347). The disk model of NGC 5907 is based on deep images in U,B,V,R, and I, which we have observed with CAFOS at the 2.2m telescope on Calar Alto. For a separation of the effects of dust extinction, the age distribution, and the heating rate, we made a multi-colour analysis of the vertical profiles. The basic disk parameters (scale length, scale height, inclination) are consistent with earlier determinations. We find good fits of the profiles in all bands which give constraints on the star formation rate (it is moderately decreasing with time) and the dynamical heating function. From the dust model we get an estimate of the total amount of dust and combined with H II--data the global dust-to-gas ratio can be computed. A comparison with estimates for the dust component based on simple models shows that the amount of dust is usually strongly underestimated.

Just, A.; Moellenhoff, C.

108

Quantitative differences in intervertebral disc-matrix composition with age-related degeneration.  

PubMed

This study was carried out to determine the effect of age on the intervertebral disc, using a rabbit model. Anulus fibrosus and nucleus pulposus tissue from New Zealand white rabbits aged 3 years old (old rabbits) and 6 months old (young rabbits) were used. The water content, the proteoglycan, the DNA content, and the mRNA levels of aggrecan, type I collagen, and type II collagen were all measured for each sample. Water, proteoglycan, DNA, and the mRNA levels of aggrecan and type II collagen were all greater in the nucleus pulposus of the young rabbits as compared to the old. For the anulus fibrosus, the difference between young and old is less marked with only proteoglycan and DNA being greater in the young disc as compared to the old. Clearly, according to our results, it is the nucleus pulposus that suffers the brunt of the changes with age. PMID:20151333

Murakami, Hideki; Yoon, Tim S; Attallah-Wasif, Emad S; Kraiwattanapong, Chaiwat; Kikkawa, Ichiro; Hutton, William C

2010-02-12

109

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

110

Evaluation of I-line and DUV photoresists for high-density optical disc mastering  

NASA Astrophysics Data System (ADS)

The next generation in the optical media family which follows Compact Disc and DVD formats, will be a high density format that contains up to 25 GB of information on a surface area similar to that of a Compact Disc. The information is recorded as a spiral track of pits on a master disc by applying a lithographic process where a focused and modulated laser spot exposes a positive photoresist (`mastering' process). Compact Disc and DVD formats can typically be mastered with 413nm Kr-laser and conventional broadband novolak/DNQ-photoresists. When striving for higher densities, a reduction in exposure wavelength is needed to obtain a smaller laser spot and thus to create smaller pits. A frequency-doubled Ar laser is therefore chosen as recording laser, (lambda) = 257nm. The design of a DUV exposure tool will be outlined. The wavelength reduction is insufficient to obtain the required reduction in feature size. Consequently, a higher contrast photoresist process is necessary. Different types of broadband, I-line and chemically amplified photoresists were evaluated for this specific application. The main target was to obtain maximum resist contrast ((gamma) ) and minimal feature size. The maximum resist contrast obtained was 3 with I-line resist and 8 using a chemically amplified type. Features of 120 nm wide and 85 nm high were mastered. The photoresist layer thickness varies between 40nm and 85nm. The I-line photoresist with the highest contrast is Shipley Ultra-i-123. With this type of photoresist an optical disc with a capacity of 20.7GB of information has been produced. The quality of such a disc is indicated by the time resolution in the read-out signal, expressed as the so-called jitter (=time error/clock time). For the optical disc with 20.7GB of information the measured jitter equals 7.5% which is regarded as acceptable in optical read-out signals. For these results the process has been optimized by varying developer concentration, developer type and the exposure dose. Decreasing the concentration of hydroxide in metal ion containing developer (sodium and potassium based) increases the contrast and decreases the surface roughness. Due to the limits of I-line photoresist at 257nm wavelength further experiments with chemically amplified (3.2) and 257nm photoresists (3.3) have been carried out. Airborne molecular contamination causes some problems with the use of chemically amplified photoresist.

Tacken, Roland; Rodenburg, Elise C.; van der Veer, Mark; van Vegchel, Jos H.; Eijmberts, Richard

2001-08-01

111

The collagen structure of bovine intervertebral disc studied using polarization-sensitive optical coherence tomography  

NASA Astrophysics Data System (ADS)

Polarization-sensitive optical coherence tomography (PS-OCT) is used to measure the birefringence properties of bovine intervertebral disc and equine flexor tendon. For equine tendon the birefringence Dgrn is (6.0 ± 0.2) × 10-3 at a wavelength of 1.3 µm. This is somewhat larger than the values reported for bovine tendon. The surface region of the annulus fibrosus of a freshly excised intact bovine intervertebral disc displays an identical value of birefringence, Dgrn = (6.0 ± 0.6) × 10-3 at 1.3 µm. The nucleus pulposus does not display birefringence, the measured apparent value of Dgrn = (0.39 ± 0.01) × 10-3 being indistinguishable from the effects of depolarization due to multiple scattering. A clear difference is found between the depth-resolved retardance of equine tendon and that of bovine intervertebral disc. This apparently relates to the lamellar structure of the latter tissue, in which the collagen fibre orientation alternates between successive lamellae. A semi-empirical model based on Jones calculus shows that the measurements are in reasonable agreement with previous optical and x-ray data. These results imply that PS-OCT could be a useful tool to study collagen organization within the intervertebral disc in vitro and possibly in vivo and its variation with applied load and disease.

Matcher, Stephen J.; Winlove, C. Peter; Gangnus, Sergei V.

2004-04-01

112

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

113

A comparative study of two methods of optic disc evaluation in patients of glaucoma  

PubMed Central

Introduction: Glaucoma is a progressive disorder and requires serial evaluation in order to monitor disease progression and optimize therapy. Objective: The objective of this study was to determine the correlation between each of cup/disc (C/D) ratio and the disc damage likelihood scale (DDLS) with retinal nerve fiber layer (RNFL) and global indices in Humphrey field analyzer II (HFA II). Design: Cross-sectional study. Materials and Methods: A total of 50 patients diagnosed with primary open angle glaucoma were examined to grade DDLS score and C/D ratio. The average (avg) RNFL was obtained using the Fast RNFL protocol on optical coherence tomography (OCT) (4.0.2 Carl Zeiss). HFA II Swedish Interactive Threshold Algorithm Standard 24-2 visual fields were obtained within 1 month of clinical examination. The correlation of C/D ratio with avg RNFL thickness, Mean deviation and Pattern standard deviation was calculated by Pearson correlation coefficient (r). Similar coefficients were obtained for DDLS. Results: The P value for the difference in the r between C/D ratio with RNFL (?0.628) and DDLS with RNFL (?0.8369) was significant (P < 0.01) when correlation of C/D, DDLS with RNFL was considered. Conclusion: The DDLS shows stronger correlation with structural changes in OCT than C/D ratio. The disc diameter and rim width increases the value of clinical optic disc examination.

Chandra, Anuradha; Bandyopadhyay, Arun Kumar; Bhaduri, Gautam

2013-01-01

114

Optic cup and disk extraction from retinal fundus images for determination of cup-to-disc ratio  

Microsoft Academic Search

The ratio of the optic cup to disc (CDR) in retinal fundus images is one of the principal physiological characteristics in the diagnosis of glaucoma. Currently the CDR is manually determined which can be subjective and limits its use in mass screening. To automatically extract the disc, a variational level set method is proposed in this paper. For the cup,

J. Liu; D. W. K. Wong; J. H. Lim; X. Jia; F. Yin; H. Li; W. Xiong; T. Y. Wong

2008-01-01

115

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

SciTech Connect

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

116

Phase-change optical disc of 20-GB capacity using NRZI+, Turbo coding with blue laser  

NASA Astrophysics Data System (ADS)

Recently, there has been much research on high-density recording of phase change optical disc using blue laser. In most research, RLL (Run Length Limited) modulation such as (1,7) RLL and EFM (Eight to Fourteen Modulation) modulation is used for high-density recording and channel clock regenerating. NRZI (Non Return to Zero Inverse) modulation has a wider window width than other modulation methods. This is a superior characteristic for achieving a high-density recording system of optical disc. We introduced NRZI+ modulation to suppress the low frequency components. And we obtained a result of a bER (bit Error Rate) of less than 1×10-4 at a bit length of 0.13?m using Turbo coding with an objective lens of NA 0.7 and a blue laser of 405 nm wavelength. This result shows that a recording capacity of 20 GB is feasible using NRZI modulation.

Kishida, Takanori; Kuma, Toshitaka; Asano, Kenji; Sumi, Satoshi; Ichiura, Shuichi

2003-09-01

117

Estimating the clinical usefulness of optic disc biometry for detecting glaucomatous change over time  

Microsoft Academic Search

PurposeFirst, to determine the absolute measurement precision of scanning laser ophthalmoscopy (SLO) parameters, by expressing them as 95% limits of agreement (LA95%). Second, to propose a method for mathematically estimating the clinical ability of a parameter to monitor disease progression, expressed as the Discriminating Capacity Index (DCI).MethodsWe measured the optic disc of 14 healthy volunteers and 14 glaucoma patients. LA95%-values

G J M Tangelder; N J Reus; H G Lemij

2006-01-01

118

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

119

A comparison of monocular and 'stereoscopic' photographs of the optic disc in the identification of glaucomatous visual field defects.  

PubMed Central

From a comparison of the results obtained by examining 'monocular' and 'stereoscopic' photographs of the optic disc it was concluded that each afforded similar levels of accuracy in identifying glaucomatous visual field defects. Images

Sharma, N K; Hitchings, R A

1983-01-01

120

A comparison of monocular and 'stereoscopic' photographs of the optic disc in the identification of glaucomatous visual field defects  

Microsoft Academic Search

From a comparison of the results obtained by examining 'monocular' and 'stereoscopic' photographs of the optic disc it was concluded that each afforded similar levels of accuracy in identifying glaucomatous visual field defects.

N K Sharma; R A Hitchings

1983-01-01

121

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

122

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

2013-01-09

123

An approach to identify optic disc in human retinal images using ant colony optimization method.  

PubMed

In this work, an attempt has been made to identify optic disc in retinal images using digital image processing and optimization based edge detection algorithm. The edge detection was carried out using Ant Colony Optimization (ACO) technique with and without pre-processing and was correlated with morphological operations based method. The performance of the pre-processed ACO algorithm was analysed based on visual quality, computation time and its ability to preserve useful edges. The results demonstrate that the ACO method with pre-processing provides high visual quality output with better optic disc identification. Computation time taken for the process was also found to be less. This method preserves nearly 50% more edge pixel distribution when compared to morphological operations based method. In addition to improve optic disc identification, the proposed algorithm also distinctly differentiates between blood vessels and macula in the image. These studies appear to be clinically relevant because automated analyses of retinal images are important for ophthalmological interventions. PMID:20703628

Kavitha, Ganesan; Ramakrishnan, Swaminathan

2009-04-28

124

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

125

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

PubMed Central

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

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

2010-01-01

126

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

PubMed

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. PMID:23961031

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

2012-10-01

127

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

128

Design and fabrication of substrates with microstructures for bio-applications through the modified optical disc process  

NASA Astrophysics Data System (ADS)

The modified optical disc process has been investigated and demonstrated to enable fast prototyping in fabricating molds and replicating substrates with various microstructures including micro-chambers and micro-channels. A disc-like microfluidic device was created and the testing results showed good performance in bonding and packaging. The switching of the nozzle-like micro-valve was also validated to work well. Furthermore, the relevant procedures of liquid samples loading, separating and mixing were also accomplished through food experiments.

Chiu, Kuo-Chi; Chang, Sheng-Li; Huang, Chu-Yu; Guan, Hann-Wen

2011-05-01

129

Trend of the incidence of lumbar disc herniation: decreasing with aging in the elderly  

PubMed Central

Background Compelling evidence has shown that the incidence of lumbar disc herniation (LDH) increases with age. In this study, retrospective clinical analysis of 601 cases of LDH has been conducted to investigate the role of age in the incidence of LDH in the elderly. The aim of the study is to investigate the relationship between the process of aging and the occurrence of LDH in old adults. Methods Clinical cases (n = 601) of LDH were retrospectively analyzed. Results The imaging examination with computed tomography and/or magnetic resonance imaging showed the occurrence of degeneration in LDH patients over 65 years of age. The most common site of LDH is toward the bottom of the spine at L4–L5 and/or L5–S1. The incidence of LDH drops with age in the elderly, especially after the age of 80 years. There is an obvious decrease in LDH in the elderly female. Conclusion A decreasing incidence of LDH with aging occurs in the elderly. This investigation indicates that aging is not a contributor to the performance of LDH in the elderly although the incidence of LDH is proportional to age.

Ma, Daoyou; Liang, Yunbiao; Wang, Daoming; Liu, Zejiang; Zhang, Wei; Ma, Tantan; Zhang, Liang; Lu, Xingjun; Cai, Zhiyou

2013-01-01

130

Variation with Age in the Pattern of Type X Collagen Expression in Normal and Scoliotic Human Intervertebral Discs  

Microsoft Academic Search

.   The distribution and expression of type X collagen, a calcium-binding collagen, which is a marker of hypertrophic chondrocytes\\u000a and thought to be involved in cartilage calcification, was examined in situ in nondegenerate (grade I or II) human discs taken at autopsy over a wide age range (fetal–>80 years) and also in scoliotic\\u000a discs removed at surgery. In the fetal

T. Aigner; K.-R. Greskötter; J. C. T. Fairbank; K. von der Mark; J. P. G. Urban

1998-01-01

131

Surgical approach and optic coherence tomographic evaluation of optic disc anomaly in association with serous macular detachment.  

PubMed

Serous macular detachment (SMD) may accompany optic disc pit (ODP) and cause visual loss if untreated. We want to present different therapeutic approaches and interesting optical coherence tomography (OCT) findings in three consecutive cases. In this case series, two patients with SMD and one patient with partial macular detachment and inferior retinal detachment accompanying ODP were evaluated before and after surgical intervention clinically and by spectral-domain OCT. The patients were 44 (case 1), 22 (case 2) and 24 (case 3) years old. Pars plana vitrectomy (PPV) + silicone oil + laser, PPV + sulfur hexafluoride gas (SF6) + laser and pneumatic retinopexy were applied, respectively. The patients were followed for 18, 15 and 14 months. Preoperative best-corrected visual acuities (BCVAs) were 5/100, 7/10 and counting fingers at 1 m. Vision improved in all cases with resolution of subretinal fluid. Final BCVAs were 3/10, 10/10 and 1/10, respectively. OCT images revealed optic disc anomaly details and changes after surgical intervention, photoreceptor outer segment alterations at the detached area and macular surface changes. Surgical intervention should be tailored individually in cases with SMD. OCT is efficient for in vivo evaluation of this pathological condition and anatomical outcomes of surgery. PMID:23392899

Güven, Dilek; Balc?o?lu, Nihal; Türker, Ca?r?; Baydar, Yasemin; Sendül, Yekta

2013-02-01

132

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

133

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

Microsoft Academic Search

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

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

1999-01-01

134

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

135

3D optic disc reconstruction via a global fundus stereo algorithm.  

PubMed

This paper presents a novel method to recover 3D structure of the optic disc in the retina from two uncalibrated fundus images. Retinal images are commonly uncalibrated when acquired clinically, creating rectification challenges as well as significant radiometric and blur differences within the stereo pair. By exploiting structural peculiarities of the retina, we modified the Graph Cuts computational stereo method (one of current state-of-the-art methods) to yield a highquality algorithm for fundus stereo reconstruction. Extensive qualitative and quantitative experimental evaluation (where OCT scans are used as 3D ground truth) on our and publicly available datasets shows the superiority of the proposed method in comparison to other alternatives. PMID:24111076

Bansal, M; Sizintsev, M; Eledath, J; Sawhney, H; Pearson, D J; Stone, R A

2013-07-01

136

Nanopattern Profile Control Technology Using Reactive Ion Etching for 100 GB Optical Disc Mastering  

NASA Astrophysics Data System (ADS)

We had developed an electron beam recorder (EBR) and studied a process technology for high-density optical disc mastering. In this study, we aimed at controlling a nanopattern profile by adopting inductively coupled plasma reactive ion etching (ICP-RIE) under simple conditions. To control a pattern inclination angle, we introduced an etching power ratio of antenna to bias and investigated the relationship. From the results of our investigation, we confirmed that inclination angle depended on etching power ratio linearly. Furthermore, in the case of a 100 GB read-only memory (ROM) equivalent pattern, we formed two kinds of inclined pattern by adopting ICP-RIE. We evaluated line edge roughness (LER) to determine the difference in pit profile accurately. As the result, we confirmed that LER was improved at a steep inclination angle. In addition, we applied ICP-RIE to a 300 GB ROM pattern.

Fujimura, Megumi; Hosoda, Yasuo; Katsumura, Masahiro; Kobayashi, Masaki; Kitahara, Hiroaki; Hashimoto, Kazunobu; Kasono, Osamu; Iida, Tetsuya; Kuriyama, Kazumi; Yokogawa, Fumihiko

2006-02-01

137

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

Microsoft Academic Search

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

Corina Marcauteanu; Enikö Demjan; Cosmin Sinescu; Meda Negrutiu; Adrian Motoc; Rodica Lighezan; Liliana Vasile; Mike Hughes; Adrian Bradu; George Dobre; Adrian G. Podoleanu

2010-01-01

138

Diagnostic accuracy of nerve fibre layer, macular thickness and optic disc measurements made with the RTVue-100 optical coherence tomograph to detect glaucoma  

PubMed Central

Purpose To evaluate the diagnostic accuracy of retinal nerve fibre layer thickness (RNFLT), ganglion cell complex (GCC), and optic disc measurements made with the RTVue-100 Fourier-domain optical coherence tomography (OCT) to detect glaucoma in a Caucasian referral population. Methods One randomly selected eye of 286 Caucasian patients (93 healthy, 36 ocular hypertensive, 46 preperimetric glaucoma, and 111 perimetric glaucoma eyes) was evaluated. Results Using the software-provided classification, for the total population sensitivity did not exceed 73.6% for the optic nerve head parameters, and 62.7% for the other parameters. Specificity was high (94.6–100%) for most RNFLT and GCC parameters, but low (72.0–76.3%) for the optic disc parameters. Positive predictive value varied between 98.1 and 100% for the main RNFLT parameters, 92.6 and 100% for the 16 RNFLT sectors, 92.4 and 99.0% for the GCC parameters, but did not exceed 86.3% for any of the optic disc parameters. Positive likelihood ratio (PLR) was higher than 10 for average, inferior and superior RNFLT (25.5 to infinite), 12 of the 16 RNFLT sectors (12.6 to infinite), and three of the four GCC parameters (40.0 to 48.6). No optic disc parameter had a PLR higher than 3.0. Conclusions RNFLT and GCC parameters of the RTVue-100 Fourier-domain OCT showed moderate sensitive but high specificity, positive predictive value and PLR for detection of glaucoma. The optic disc parameters had lower diagnostic accuracy than the RNFLT and GCC parameters.

Garas, A; Vargha, P; Hollo, G

2011-01-01

139

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

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

140

Optical-to-virial velocity ratios of local disc galaxies from combined kinematics and galaxy-galaxy lensing  

NASA Astrophysics Data System (ADS)

In this paper, we measure the optical-to-virial velocity ratios Vopt/V200c of disc galaxies in the Sloan Digital Sky Survey (SDSS) at a mean redshift of = 0.07 and with stellar masses 109 < M* < 1011 M?. Vopt/V200c, the ratio of the circular velocity measured at the optical radius of the disc (˜10 kpc) to that at the virial radius of the dark matter halo (˜150 kpc), is a powerful observational constraint on disc galaxy formation. It links galaxies to their dark matter haloes dynamically and constrains the total mass profile of disc galaxies over an order of magnitude in length scale. For this measurement, we combine Vopt derived from the Tully-Fisher relation (TFR) from Reyes et al. with V200c derived from halo masses measured with galaxy-galaxy lensing. In anticipation of this combination, we use similarly selected galaxy samples for both the TFR and lensing analysis. For three M* bins with lensing-weighted mean stellar masses of 0.6, 2.7 and 6.5 × 1010 M?, we find halo-to-stellar mass ratios M200c/M* = 41, 23 and 26, with 1? statistical uncertainties of around 0.1 dex, and Vopt/V200c = 1.27 ± 0.08, 1.39 ± 0.06 and 1.27 ± 0.08 (1?), respectively. Our results suggest that the dark matter and baryonic contributions to the mass within the optical radius are comparable, if the dark matter halo profile has not been significantly modified by baryons. The results obtained in this work will serve as inputs to and constraints on disc galaxy formation models, which will be explored in future work. Finally, we note that this paper presents a new and improved galaxy shape catalogue for weak lensing that covers the full SDSS Data Release 7 footprint.

Reyes, R.; Mandelbaum, R.; Gunn, J. E.; Nakajima, R.; Seljak, U.; Hirata, C. M.

2012-10-01

141

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

142

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

143

Resonance measurements techniques of optical whispering gallery mode mini-disc resonators for microwave photonics applications  

NASA Astrophysics Data System (ADS)

The aim of this work is to compare advantages and disadvantages of different techniques for coupling a mini-discoptical- resonator to determine quality factor of its resonance. Optical fiber coupled to a resonator consists in a mini disc with whispering gallery modes at its circumference. We choose to work with three materials and design compact miniresonators. Fused silica is found to be suitable for these applications thanks to its hardness in the range 6-7 and the behavior to mechanical shocks, despite its sensitivity to water pollution. With its tetragonal crystal and a good behavior with risk of water pollution, Calcium fluoride is a good candidate despite sensitivity to mechanical shocks. Magnesium fluoride is the third material used. As a critical step, taper coupling is set with a 20nm resolution positioning system. Miniresonator is excited from a system equipped with a tunable laser diode with a tunability from 1490 to 1640 nm and a linewidth narrower than 300kHz. Light is coupled into the microsphere either from glass or fiber prism or with fiber taper via evanescent field. We have also used a single frequency 660nm laser diode with a linewidth narrower than 100kHz which can be tuned about 10pm to test a single resonant peak. Both sources are used with either a tapered fiber or a filed fiber. Resonance is observed and quality factor of the resonators is found to be in the range of 108.

Salzenstein, Patrice; Jelínek, Michal; Chembo, Yanne K.; Pogurmiskiy, Maxim; Tavernier, Hervé; Volyanskiy, Kirill; Phan Huy, Kien; Chauvet, Mathieu; Larger, Laurent; Kubecek, Václav

2011-05-01

144

Optic disc changes in normotensive persons with unilateral exfoliation syndrome: a 3-year follow-up study  

Microsoft Academic Search

· Background: If, at the time of glaucoma diagnosis, the intraocular pressure (IOP) is higher and the initial field loss more\\u000a advanced in glaucomatous eyes with than without exfoliation, the cause of the optic disc damage has been suggested to be the\\u000a high IOP associated with the exfoliation syndrome (EXS). We decided to investigate whether EXS alone, without the contributory

P. Puska; Eija Vesti; Goji Tomita; Kyoko Ishida; Christina Raitta

1999-01-01

145

Morphology of Optic Disc Through Heidelberg Retina Tomograph in Retinal Vein Occlusions Alone or in Combination with Primary Open Angle Glaucoma§  

PubMed Central

Purpose: To evaluate the morphology of optic discs in eyes suffering from retinal vein occlusion (RVO) alone or in combination with primary open-angle glaucoma (POAG). Methods: Prospective, observational study. 48 consecutive patients were enrolled, 30 with unilateral RVO diagnosis, 18 with unilateral retinal vein occlusion (RVO) associated with POAG. We divided RVOs on the basis of occlusion site: arterio-venous crossing (AV-RVO), optic cup (OC-RVO), optic nerve (ON-RVO) with head nerve swelling (ONHS-RVO) or without it (NONHS-RVO). A control group of 25 patients who were sex and age matched was selected. Results: Comparing the fellow eyes of the patients with RVO and control healthy eyes, no differences emerged in cup/disc ratio but they came out for the HRT values in Rim Area, cup shape measure and height variation contour (p<0.05). The most frequent occlusion site was at the level of an arteriovenous crossing in patients not suffering from POAG (36.7%) and at the level of the optic cup in patients with RVO and POAG (50%). In the RVO group without POAG, the OC-RVO subgroup has shown an higher cup area (0.366±0.094) and cup/disc area ratio (0.184±0.063), a lower rim volume (0.374±0.021) and a different cup shape measure (-0.221±0.066) (p<0.05) compared with the AV and NONHS sites. Compared with NONHS group differences emerged also for the fibres parameters and in the height variation contour (0.346±0.081). Also in the RVO group with POAG significant differences (p<0.05) have been surveyed between OC-RVO and other occlusion sites in cup area (0.119±0.029), cup/disc area ratio (0.532±0.09), rim volume (0.374±0.07), cup/shape measure (-0.079±0.013). Conclusions: Classification of the analyzed parameters on the basis of the occlusion site provides a basis for which clinical decisions and research on causal factors in future studies can be based on.

Actis, Alessandro Guido; Belli, Luca; Dall'orto, Laura; Penna, Rachele; Brogliatti, Beatrice; Rolle, Teresa

2013-01-01

146

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

147

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

PubMed

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. PMID:24143070

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

2013-10-11

148

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

149

Optic disc detection from normalized digital fundus images by means of a vessels' direction matched filter.  

PubMed

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 algorithm is based on matching the expected directional pattern of the retinal blood vessels. Hence, a simple matched filter is proposed to roughly match the direction of the vessels at the OD vicinity. The retinal vessels are segmented using a simple and standard 2-D Gaussian matched filter. Consequently, a vessels direction map of the segmented retinal vessels is obtained using the same segmentation algorithm. The segmented vessels are then thinned, and filtered using local intensity, to represent finally the OD-center candidates. The difference between the proposed matched filter resized into four different sizes, and the vessels' directions at the surrounding area of each of the OD-center candidates is measured. The minimum difference provides an estimate of the OD-center coordinates. The proposed method was evaluated using a subset of the STARE project's dataset, containing 81 fundus images of both normal and diseased retinas, and initially used by literature OD detection methods. The OD-center was detected correctly in 80 out of the 81 images (98.77%). In addition, the OD-center was detected correctly in all of the 40 images (100%) using the publicly available DRIVE dataset. PMID:18270057

Youssif, A R; Ghalwash, A Z; Ghoneim, A R

2008-01-01

150

Twin study on cup/disc ratio of the optic nerve head.  

PubMed Central

Seventeen healthy twin pairs (10 monozygotic and seven dizygotic) from the Finnish Twin Cohort Study were examined to study the impact of heredity v environment in the determination of cup-to-disc area ratio. These twins were free from any known eye disease. The cup/disc ratio was determined using stereo photography and a computer assisted analysis technique. The zygosity of all twin pairs was confirmed with the DNA 'fingerprint' technique. The intrapair correlations were high among monozygotic pairs compared with those among dizygotic twin pairs. The difference of cup/disc area ratios between the right eyes of members of monozygotic twin pairs was statistically significantly smaller than that of dizygotic twin pairs (p < 0.001). The same was true for left eyes (p < 0.01). This result confirms a genetic determination in cup/disc area ratio in normal eyes. Images

Teikari, J. M.; Airaksinen, J. P.

1992-01-01

151

Uveal melanomas near the optic disc or fovea. Visual results after proton beam irradiation  

SciTech Connect

Proximity to the disc and fovea is a risk factor for visual loss after proton beam irradiation of uveal melanomas. Of 562 eyes treated over a 10-year period with pretreatment visual acuity of 20/200 or better, 363 (64.6%) contained tumors within 2 disc diameters (DD) of the disc or fovea. Rates of visual loss after treatment to worse than 20/200 and causes of visual decline were evaluated using Kaplan-Meier analysis. Cumulative rates of visual loss among subjects with tumors near the disc or fovea were 33 and 47% 1 and 2 years after treatment compared to 17 and 28%, respectively, for subjects with tumors located farther from both structures. The leading cause of visual loss in the first year among eyes with tumors near the disc or fovea was retinal detachment. Controlling for other predictors of visual loss to worse than 20/200, location near the disc or fovea was independently related to visual loss primarily due to retinal detachment, cataract, and radiation retinopathy. Despite the unfavorable location of these tumors, over half of patients with 20/200 or better pretreatment visual acuity had useful vision 2 years after treatment.

Seddon, J.M.; Gragoudas, E.S.; Egan, K.M.; Glynn, R.J.; Munzenrider, J.E.; Austin-Seymour, M.; Goitein, M.; Verhey, L.; Urie, M.; Koehler, A.

1987-04-01

152

CT-guided percutaneous laser disc decompression with Ceralas D, a diode laser with 980-nm wavelength and 200-?m fiber optics  

Microsoft Academic Search

.   The aim of this study was to evaluate the compact, portable Ceralas-D diode laser (CeramOptec; 980 + 30 nm wavelength, 200-?m\\u000a optical fiber) concerning clinical usefulness, handling, and clinical results in the CT-guided treatment of herniated lumbar\\u000a discs. The positioning of the canula in intradiscal space, the placement of the laser fiber into the disc through the lying\\u000a canula,

A. Gevargez; D. W. H. Groenemeyer; F. Czerwinski

2000-01-01

153

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

154

On how optical depth tunes the effects of the interstellar medium on debris discs  

Microsoft Academic Search

The flux of neutral atoms of the interstellar medium (ISM) surrounding stars and their environment affects the motion of dust particles in debris discs, causing a significant dynamical evolution. Large values of eccentricity and inclination can be excited, and strong correlations settle in among the orbital angles. This dynamical behaviour, in particular for bound dust grains, can potentially cause significant

F. Marzari; P. Thébault

2011-01-01

155

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

156

Is the transport of a gadolinium-based contrast agent decreased in a degenerated or aged disc? A post contrast MRI study.  

PubMed

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. PMID:24146913

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

2013-10-11

157

Radiation from dwarf nova discs.  

NASA Astrophysics Data System (ADS)

The authors use the Shaviv and Wehrse (1991) code to model the vertical structure and the emission properties of quiescent dwarf nova disc. They find that in the case of HT Cas the quiescent disc must be optically thin, in contradiction with the requirements of the standard disc instability model. They find a viscosity parameter ? ? 1. Although this is much less than values (?102) obtained in isothermal slab models it is not consistent with the accretion disc model assumptions.

Idan, I.; Lasota, J. P.; Hameury, J.-M.; Shaviv, G.

1999-04-01

158

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

159

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

ERIC Educational Resources Information Center

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

Wilson, Kathleen S.

160

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

ERIC Educational Resources Information Center

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

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

1992-01-01

161

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

ERIC Educational Resources Information Center

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

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

1992-01-01

162

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

Microsoft Academic Search

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

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

2000-01-01

163

Morphometric evaluation of changes with time in optic disc structure and thickness of retinal nerve fibre layer in chronic ocular hypertensive monkeys  

Microsoft Academic Search

We examined the time course of changes in optic disc structure by means of a scanning laser ophthalmoscope (Heidelberg Retina Tomograph, HRT) in ocular hypertensive (experimental glaucoma) monkeys, and clarified the relationships between the histological RNFL thickness and HRT parameters. Further, the time course of changes in retinal nerve fiber layer (RNFL) thickness in individual eyes was measured using a

Masamitsu Shimazawa; Goji Tomita; Takazumi Taniguchi; Masaaki Sasaoka; Hideaki Hara; Yoshiaki Kitazawa; Makoto Araie

2006-01-01

164

Age-related accumulation of pentosidine in aggrecan and collagen from normal and degenerate human intervertebral discs  

PubMed Central

During aging and degeneration, many changes occur in the structure and composition of human cartilaginous tissues, which include the accumulation of the AGE (advanced glycation end-product), pentosidine, in long-lived proteins. In the present study, we investigated the accumulation of pentosidine in constituents of the human IVD (intervertebral disc), i.e. collagen, aggrecan-derived PG (proteoglycan) (A1) and its fractions (A1D1–A1D6) in health and pathology. We found that, after maturity, pentosidine accumulates with age. Over the age range studied, a linear 6-fold increase was observed in pentosidine accumulation for A1 and collagen with respective rates of 0.12 and 0.66 nmol·(g of protein)?1·year?1. Using previously reported protein turnover rate constants (kT) obtained from measurements of the D-isomer of aspartic residue in collagen and aggrecan of human IVD, we could calculate the pentosidine formation rate constants (kF) for these constituents [Sivan, Tsitron, Wachtel, Roughley, Sakkee, van der Ham, DeGroot, Roberts and Maroudas (2006) J. Biol. Chem. 281, 13009–13014; Tsitron (2006) MSc Thesis, Technion-Israel Institute of Technology, Haifa, Israel]. In spite of the comparable formation rate constants obtained for A1D1 and collagen [1.81±0.25 compared with 3.71±0.26 ?mol of pentosidine·(mol of lysine)?1·year?1 respectively], the higher pentosidine accumulation in collagen is consistent with its slower turnover (0.005 year?1 compared with 0.134 year?1 for A1D1). Pentosidine accumulation increased with decreasing buoyant density and decreasing turnover of the proteins from the most glycosaminoglycan-rich PG components (A1D1) to the least (A1D6), with respective kF values of 1.81±0.25 and 3.18±0.37 ?mol of pentosidine·(mol of lysine)?1·year?1. We concluded that protein turnover is an important determinant of pentosidine accumulation in aggrecan and collagen of human IVD, as was found for articular cartilage. Correlation of pentosidine accumulation with protein half-life in both normal and degenerate discs further supports this finding.

Sivan, Sarit Sara; Tsitron, Eve; Wachtel, Ellen; Roughley, Peter; Sakkee, Nico; van der Ham, Frits; Degroot, Jeroen; Maroudas, Alice

2006-01-01

165

Comparison of optical and electrical investigations of meat ageing  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

166

Optical features for chronological aging and photoaging skin by optical coherence tomography.  

PubMed

The characteristics of skins in different aging processes were obtained by optical coherence tomography (OCT) single scattering model, and their optical parameters were analyzed quantitatively. Significant differences were found in epidermis thickness and attenuation coefficients in chronological aging skins and photonaging skins. These parameters can be served as indicators of skin type as well as the progress of aging. These results are valuable to the study of aging skin, and they could further help to understand the mechanism of aging. PMID:22415573

Wu, Shulian; Li, Hui; Zhang, Xiaoman; Li, Zhifang

2012-03-14

167

Automated volumetric evaluation of stereoscopic disc photography  

PubMed Central

PURPOSE: To develop a fully automated algorithm (AP) to perform a volumetric measure of the optic disc using conventional stereoscopic optic nerve head (ONH) photographs, and to compare algorithm-produced parameters with manual photogrammetry (MP), scanning laser ophthalmoscope (SLO) and optical coherence tomography (OCT) measurements. METHODS: One hundred twenty-two stereoscopic optic disc photographs (61 subjects) were analyzed. Disc area, rim area, cup area, cup/disc area ratio, vertical cup/disc ratio, rim volume and cup volume were automatically computed by the algorithm. Latent variable measurement error models were used to assess measurement reproducibility for the four techniques. RESULTS: AP had better reproducibility for disc area and cup volume and worse reproducibility for cup/disc area ratio and vertical cup/disc ratio, when the measurements were compared to the MP, SLO and OCT methods. CONCLUSION: AP provides a useful technique for an objective quantitative assessment of 3D ONH structures.

Xu, Juan; Ishikawa, Hiroshi; Wollstein, Gadi; Bilonick, Richard A; Kagemann, Larry; Craig, Jamie E; Mackey, David A; Hewitt, Alex W; Schuman, Joel S

2010-01-01

168

Optic Disc Swelling and Vision Loss in a Patient with Cystic Fibrosis and Diabetes  

PubMed Central

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.

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

2013-01-01

169

Thermal and optical properties of high purity CVD-diamond discs doped with boron and nitrogen  

Microsoft Academic Search

The effect of nitrogen and boron doping on the thermal and optical properties of high purity CVD-diamond grown by microwave plasma (MW-CVD) and DC arc-jet chemical vapor deposition (DCAJ-CVD) is investigated. Boron and nitrogen doping was carried out by adding to the process gas trimethylborate and nitrogen, respectively. Secondary ion mass spectrometry (SIMS) was used to quantify the incorporated boron

E. Wörner; E. Pleuler; C. Wild; P. Koidl

2003-01-01

170

78 FR 64009 - Certain Optical Disc Drives, Components Thereof, and Products Containing the Same; Institution of...  

Federal Register 2010, 2011, 2012, 2013

Notice is hereby given that a complaint was filed with the U.S. International Trade Commission on September 3, 2013, under section 337 of the Tariff Act of 1930, as amended, 19 U.S.C. 1337, on behalf of Optical Devices, LLC of Peterborough, New Hampshire. A letter supplementing the complaint was filed on September 20, 2013. The complaint alleges violations of section 337 based upon the......

2013-10-25

171

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

NASA Astrophysics Data System (ADS)

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

Burkhardt, Anke; Geissler, Stefan; Koch, Edmund

2010-04-01

172

A survey of 286 Virgo cluster galaxies at optical griz and near-IR H band: surface brightness profiles and bulge-disc decompositions  

NASA Astrophysics Data System (ADS)

We present and g-, r-, i-, z- and H-band surface brightness profiles and bulge-disc decompositions for a morphologically broad sample of 286 Virgo Cluster Catalogue (VCC) galaxies. The H-band data come from a variety of sources including our survey of 171 VCC galaxies at the University of Hawaii (UH) 2.2-m telescope, Canada-France-Hawaii Telescope (CFHT) and United Kingdom Infrared Telescope (UKIRT), and another 115 galaxies from the Two Micron All Sky Survey (2MASS) and GOLDMine archives. The optical data for all 286 VCC galaxies were extracted from the Sloan Digital Sky Survey (SDSS) images. The H-band and the SDSS griz data were analysed in a homogeneous manner using our own software, yielding a consistent set of deep, multiband surface brightness profiles for each galaxy. Average surface brightness profiles per morphological bin were created in order to characterize the variety of galaxy light profiles across the Hubble sequence. The 1D bulge-disc decomposition parameters, as well as non-parametric galaxy measures, such as effective radius, effective surface brightness and light concentration, are presented for all 286 VCC galaxies in each of the five optical/near-infrared wavebands. The profile decompositions account for bulge and disc components, spiral arms, nucleus and atmospheric blurring. The Virgo spiral galaxy bulges typically have a Sérsic index n˜ 1, while elliptical galaxies prefer n˜ 2. No galaxy spheroid requires n > 3. The light profiles for 70 per cent of the Virgo elliptical galaxies reveal the presence of both a spheroid and disc component. A more in-depth discussion of the structural parameter trends can be found in McDonald, Courteau & Tully. The data provided here should serve as a base for studies of galaxy structure and stellar populations in the cluster environment. The galaxy light profiles and bulge-disc decomposition results are available at the Centre de Données astronomiques de Strasbourg (CDS; ) and the author's own website ().

McDonald, Michael; Courteau, Stéphane; Tully, R. Brent; Roediger, Joel

2011-07-01

173

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

PubMed Central

AIM—To determine if global and segmental changes in optic disc parameters of sequential Heidelberg retina tomograph (HRT) images develop in individual ocular hypertensive (OHT) patients without white on white visual field defects.?METHODS—Patients and normal controls were recruited from a prospective ocular hypertension treatment trial. The subject groups consisted of 21 OHT patients who had converted to early glaucoma on the basis of visual field criteria (24-2 program on the Humphrey perimeter), 164 OHT subjects with normal visual fields, and 21 normal controls. Sequential HRT images 16-21 months apart were obtained for each subject and segmental optic disc parameters were measured to determine if any change had occurred. From the analysis of sequential HRT images of the 21 normal eyes we established normal limits of interimage variation. Individual discs in each group showing changes above the 95% limit of normal variability were then sought.?RESULTS—Several segmental and global optic disc parameters were found to show significant change in the converter group before confirmed visual field change, confirming our previously published results. Individual optic disc analysis using the 95% limit of normal variability data demonstrated glaucomatous change in 13 out of 21 converter eyes. 47 of the 164 OHT eyes with normal visual fields showed change in global and segmental parameters in a "glaucomatous" direction above the level expected for normal variability. The parameters which changed most frequently in the OHT eyes were: global cup volume (6.7% of discs), inferonasal cup volume (11%), inferotemporal cup volume (8.5%), and superotemporal cup area (7.3%).? CONCLUSIONS—We have identified change in a subset of ocular hypertensive patients which could predate the development of glaucomatous visual field loss. The HRT could be of value in the sequential follow up of those suspected of having glaucoma by identifying eyes at risk of developing glaucoma. However, further refinement of the technique is required to eliminate some of the inherent variability of the analysis method described, and to increase the ability to detect at risk individuals.??

Kamal, D; Garway-Heath, D; Hitchings, R; Fitzke, F

2000-01-01

174

A comparative study of argon laser and krypton laser in the treatment of diabetic optic disc neovascularisation  

Microsoft Academic Search

A comparative study of the relative efficacy of the krypton and argon lasers in the treatment of disc new vessels in diabetic retinopathy was made. Resolution of the disc new vessels was achieved in both instances. There were clinical differences in the use and effects of the 2 lasers.

W E Schulenburg; A M Hamilton; R K Blach

1979-01-01

175

Influence of optic disc size on the diagnostic performance of macular ganglion cell complex and peripapillary retinal nerve fiber layer analyses in glaucoma  

PubMed Central

Aim To evaluate the influence of optic disc size on the diagnostic accuracy of macular ganglion cell complex (GCC) and conventional peripapillary retinal nerve fiber layer (pRNFL) analyses provided by spectral domain optical coherence tomography (SD-OCT) in glaucoma. Methods Eighty-two glaucoma patients and 30 healthy subjects were included. All patients underwent GCC (7 × 7 mm macular grid, consisting of RNFL, ganglion cell and inner plexiform layers) and pRNFL thickness measurement (3.45 mm circular scan) by SD-OCT. One eye was randomly selected for analysis. Initially, receiver operating characteristic (ROC) curves were generated for different GCC and pRNFL parameters. The effect of disc area on the diagnostic accuracy of these parameters was evaluated using a logistic ROC regression model. Subsequently, 1.5, 2.0, and 2.5 mm2 disc sizes were arbitrarily chosen (based on data distribution) and the predicted areas under the ROC curves (AUCs) and sensitivities were compared at fixed specificities for each. Results Average mean deviation index for glaucomatous eyes was ?5.3 ± 5.2 dB. Similar AUCs were found for the best pRNFL (average thickness = 0.872) and GCC parameters (average thickness = 0.824; P = 0.19). The coefficient representing disc area in the ROC regression model was not statistically significant for average pRNFL thickness (?0.176) or average GCC thickness (0.088; P ? 0.56). AUCs for fixed disc areas (1.5, 2.0, and 2.5 mm2) were 0.904, 0.891, and 0.875 for average pRNFL thickness and 0.834, 0.842, and 0.851 for average GCC thickness, respectively. The highest sensitivities – at 80% specificity for average pRNFL (84.5%) and GCC thicknesses (74.5%) – were found with disc sizes fixed at 1.5 mm2 and 2.5 mm2. Conclusion Diagnostic accuracy was similar between pRNFL and GCC thickness parameters. Although not statistically significant, there was a trend for a better diagnostic accuracy of pRNFL thickness measurement in cases of smaller discs. For GCC analysis, an inverse effect was observed.

Cordeiro, Daniela Valenca; Lima, Veronica Castro; Castro, Dinorah P; Castro, Leonardo C; Pacheco, Maria Angelica; Lee, Jae Min; Dimantas, Marcelo I; Prata, Tiago Santos

2011-01-01

176

Optical RF communications adjunct: Coming of age  

Microsoft Academic Search

The concept of Free Space Optical (FSO) communications has been around since the late 1960's.This paper will describe some recent experimental results that demonstrate and validate hybrid FSO\\/RF communication links as viable components in a tactical high data rate network. In particular, we will describe air-mountain link closure up to ranges of 200 km under heavy atmospheric turbulence. These links

L. B. Stotts; B. Stadler; P. Kolodzy; A. Pike; T. G. Moore; D. W. Young; R. Smith; Z. Bagley; N. Plasson; B. Graves; D. Daugherty; J. Douglas; T. Martin

2009-01-01

177

Rate of visual field progression in eyes with optic disc hemorrhages in the ocular hypertension treatment study.  

PubMed

OBJECTIVE To compare rates of visual field (VF) change in ocular hypertensive eyes with and without optic disc hemorrhage (DH). METHODS Ocular Hypertension Treatment Study subjects (minimum 10 reliable VF tests, followed up ?5 years) were included. Trend analyses of VF sequences over time of DH and non-DH eyes were assessed by regression of mean deviation (MDR) and pointwise linear regression (PLR). The main outcome measures were rates of VF change in DH and non-DH eyes. RESULTS Two thousand six hundred seven eyes (1378 participants) were included. The mean (SD) number of VF tests per eye was 23.7 (4.9) spanning a mean (SD) of 12.2 (2.0) years. At least 1 DH was detected in 187 eyes (7.2%), of which 52 eyes had recurrent DH. Mean deviation rate of change was significantly worse in DH compared with non-DH eyes (mean [SD], -0.17 [0.27] vs -0.07 [0.19] dB/y; P < .01). Significant PLR progression occurred more frequently in eyes with DH (odds ratio, 3.6; P < .01), which increased when 2 or more DHs were present (odds ratio, 4.2; P = .01). Eyes initially randomized to treatment were less likely to have a DH during follow-up. CONCLUSIONS Eyes with DH had more rapid VF deterioration when assessed by global (MDR) or local (PLR) trend analysis than eyes without DH. Eyes with recurrent DH had similar rates of global VF change (MDR) when compared with eyes with a single DH but reached criteria for rapid PLR change more often. Intraocular pressure reduction in ocular hypertension reduces the risk of developing a DH. Ocular hypertensive eyes with DH should be monitored closely and may need more aggressive therapy. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00000125. PMID:22892940

De Moraes, Carlos Gustavo; Demirel, Shaban; Gardiner, Stuart K; Liebmann, Jeffrey M; Cioffi, George A; Ritch, Robert; Gordon, Mae O; Kass, Michael A

2012-12-01

178

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

179

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

180

Clinical Characteristics of Optic Neuritis in Koreans Greater than 50 Years of Age  

PubMed Central

Purpose To report clinical characteristics of optic neuritis (ON) in Koreans >50 years of age. Methods A retrospective chart review was performed on patients with ON between January 2000 and December 2009. We obtained the best-corrected visual acuity (BCVA), Goldmann perimetry, relative afferent pupillary defect (RAPD), and color function tests as well as brain magnetic resonance imaging (MRI) findings in patients who were in the acute stage of the disorder. Results Nine eyes in eight patients were included. The mean age of patients at presentation was 60.5 years (range, 53 to 71 years). Six patients were female, and two were male. There was one patient with bilateral ON. The mean BCVA at presentation was 20 / 400 (no light perception-20 / 70). Eight eyes (89%) complained of pain with eye movement. Six eyes (66%) had disc edema. Central scotoma was the most common field defect. All eyes had color abnormalities. Five eyes in four patients showed abnormalities of the involved optic nerves on MRI. The patients were followed for a mean of 11.3 months (range, 2 to 34 months). All of the patients recovered to a BCVA of 20 / 40 or better within 2 months. On the last follow-up, the mean BCVA was 20 / 20 (20 / 40 to 20 / 16). Four eyes showed remnant central scotoma. One eye had remnant RAPD, and two eyes had mild color abnormalities. Conclusions Although ON is uncommon in elderly patients, it can develop in patients >50 years of age, and clinical features of optic neuritis in elderly patients are similar to those of younger patients.

Choi, Jin; Chang, Ji Woong; Kim, Jeong Hun; Yu, Young Suk

2012-01-01

181

Herniated lumbar disc  

PubMed Central

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

2009-01-01

182

Accelerated optical polymer aging studies for LED luminaire applications  

NASA Astrophysics Data System (ADS)

There is a need in the lighting industry to design and implement accelerated aging methods that accurately simulate the aging process of LED luminaire components. In response to this need, we have built a flexible and reliable system to study the aging characteristics of optical polymer materials, and we have employed it to study a commercially available LED luminaire diffuser made of PMMA. The experimental system consists of a "Blue LED Emitter" and a working surface. Both the temperatures of the samples and the optical powers of the LEDs are appropriately characterized in the system. Several accelerated aging experiments are carried out at different temperatures and optical powers over a 90 hour period and the measured transmission values are used as inputs to a degradation model derived using plausibility arguments. This model seems capable of predicting the behavior of the material as a function of time, temperature and optical power. The model satisfactorily predicts the measured transmission values of diffusers aged in luminaires at two different times and thus can be used to make application recommendations for this material. Specifically, at 35000 hours (the manufacturer's stated life of the luminaire) and at the typical operational temperature of the diffuser, the model predicts a transmission loss of only a few percent over the original transmission of the material at 450 nm, which renders this material suitable for this application.

Estupiñán, Edgar; Wendling, Peter; Kostrun, Marijan; Garner, Richard

2013-09-01

183

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

184

Architecture and applications of generic disc  

NASA Astrophysics Data System (ADS)

The generic disc defines a data structure in which the data content stored on the disc is not limited to a particular data type or encoding scheme or the physical format of the optical media. This is achieved by making the logical layer of the disc independent from the physical layer of the disc. In this way, different types of content and different applications related to this content can co-exist on the same optical disc and interact with each other, independent of the physical format of the disc. This paper gives a brief introduction of the generic disc concept in the introduction section. Then a detailed description of the system architecture, software architecture, player flowchart and application software flowchart are provided in the rest of this paper.

Wang, Michelle; Kim, Sheng; Wei, Gongming

2004-09-01

185

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

Microsoft Academic Search

Layered hexagonal discs of CuO were synthesized on a large scale via low-temperature hydrothermal growth process at 130 °C using copper nitrate, hexamethylenediamine and NH4OH. The detailed morphological investigations by field emission scanning electron microscopy and transmission electron microscopy (TEM) clearly revealed that the synthesized CuO structures are made by the well layer-by-layer accumulation of several sheets which arranged themselves

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

2011-01-01

186

Optic disc and retinal nerve fiber layer parameters as indicators of neurodegenerative brain changes in patients with obstructive sleep apnea syndrome.  

PubMed

PURPOSE: Retina is a unique part of the central nervous system (CNS) for visualizing the processes of axonal and neuronal degeneration. Optical coherence tomography (OCT) allows direct visualization and measurement of retinal nerve fiber layer (RNFL) thickness, macular volume, and optic disc (OD) parameters. One of the disorders associated with atrophy in different brain regions is obstructive sleep apnea syndrome (OSAS). In the present study, we aimed to determine OD and RNFL changes measured by OCT for investigating the progress of neurodegeneration development in OSAS, excluding all the other conditions that can directly affect RNFL thickness and optic nerve parameters. METHODS: Both eyes of 101 patients with OSAS and 20 controls were investigated by OCT. Full-night polysomnography (PSG) and ophthalmologic examination including automated visual field (VF) examination and OCT were performed in all of the patients. RESULTS: According to the OSAS grading, patients were grouped as mild (n?=?15), moderate (n?=?27), and severe (n?=?59). We found significant decrease in RNFL thickness only in the patients with severe OSAS compared with the other groups and decreased macular ganglion cell thickness in the severe OSAS group compared with the control group. VF parameters were significantly worsened in all the OSAS subgroups compared to the control group. We found different data such as normal or increased optic nerve parameters as result of subtle OD edema, which may mask possible peripapillar axonal loss. CONCLUSIONS: We think that evaluation of neurodegeneration in OSAS is not always possible by examining OD and RNFL because there are difficulties due to the confounding issues of cerebral atrophy and OD edema. PMID:23636560

Huseyinoglu, Nergiz; Ekinci, Metin; Ozben, Serkan; Buyukuysal, Cagatay; Kale, Murat Yildirim; Sanivar, Hilal Safak

2013-05-01

187

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

188

An Analysis of Burst Disc Pressure Instability  

SciTech Connect

During the development stage of the 1X Acorn burst disc, burst pressure test results exhibited an unexpected increase of 8 to 14% over times of 90--100 days from initial fabrication. This increase is a concern where design constraints require stability. The disc material, 316L stainless steel sheet, is formed to a dome-like geometry and scored to produce a thin-walled, high-strength ligament. The fracture events controlling burst occur in that ligament. Thus it has been characterized both for tensile properties and microstructure through nanoindentation, magnetic measurements, optical and transmission electron microscopy. These results compare favorably with finite element simulation of the properties of the ligament. The ligament exhibits a highly heterogeneous microstructure; its small volume and microstructural heterogeneity make it difficult to identify which microstructural feature controls fracture and hence burst pressure. Bulk mechanical test specimens were fabricated to emulate mid-ligament properties, and aged at both room and elevated temperatures to characterize and accelerate the temporal behavior of the burst disc. Property changes included yield and ultimate tensile strength increases, and fracture strain decreases with aging. Specimens were subjected to a reversion anneal identical to that given the burst disc to eliminate the martensite phase formed during rolling. Reversion-annealed samples exhibited no change in properties in room temperature or accelerated aging, showing that the reversion-anneal eliminated the aging phenomenon. Aging was analyzed in terms of diffusion controlled precipitate growth kinetics, showing that carbon migration to dislocations is consistent with the strength increases. A vacancy-assisted diffusion mechanism for carbon transport is proposed, giving rise to rapid aging, which replaces interstitial carbon diffusion until excess vacancies from deformation are consumed. Mechanical activation parameters in stress relaxation were measured, indicating that the deformation structures formed at high strains typical of the score ligament are resistant to annealing, and mimic the behavior of a thermal obstacles. This model also qualitatively explains the different rates of aging resulting from a range of levels of cold work.

S. L. Robinson; B. C. Odegard, Jr.; N. r. Moody; S. H. Goods

2000-06-01

189

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

190

Testing protoplanetary disc dispersal with radio emission  

NASA Astrophysics Data System (ADS)

We consider continuum free-free radio emission from the upper atmosphere of protoplanetary discs as a probe of the ionized luminosity impinging upon the disc. Making use of previously computed hydrodynamic models of disc photoevaporation within the framework of extreme-ultraviolet (EUV) and X-ray irradiation, we use radiative transfer post-processing techniques to predict the expected free-free emission from protoplanetary discs. In general, the free-free luminosity scales roughly linearly with ionizing luminosity in both EUV- and X-ray-driven scenarios, where the emission dominates over the dust tail of the disc and is partial optically thin at cm wavelengths. We perform a test observation of GM Aur at 14-18 GHz and detect an excess of radio emission above the dust tail to a very high level of confidence. The observed flux density and spectral index are consistent with free-free emission from the ionized disc in either the EUV- or the X-ray-driven scenario. Finally, we suggest a possible route to testing the EUV- and X-ray-driven dispersal model of protoplanetary discs, by combining observed free-free flux densities with measurements of mass-accretion rates. On the point of disc dispersal one would expect to find an dot{M}_*^2 scaling with free-free flux in the case of EUV-driven disc dispersal or an dot{M}* scaling in the case of X-ray-driven disc dispersal.

Owen, James E.; Scaife, Anna M. M.; Ercolano, Barbara

2013-10-01

191

Global optical\\/infrared-X-ray correlations in X-ray binaries: quantifying disc and jet contributions  

Microsoft Academic Search

The optical\\/near-infrared (OIR) region of the spectra of low-mass X-ray binaries (XBs) appears to lie at the intersection of a variety of different emission processes. In this paper we present quasi-simultaneous OIR-X-ray observations of 33 XBs in an attempt to estimate the contributions of various emission processes in these sources, as a function of X-ray state and luminosity. A global

D. M. Russell; R. P. Fender; R. I. Hynes; C. Brocksopp; J. Homan; P. G. Jonker; M. M. Buxton

2006-01-01

192

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.

2013-10-01

193

Multilayer Optical Read-Only-Memory Disk Applicable to Blu-ray Disc Standard Using a Photopolymer Sheet with a Recording Capacity of 100 GB  

NASA Astrophysics Data System (ADS)

We have been investigating a multilayer optical disk applicable to Blu-ray Disc (BD) standard using a photopolymer (2P) sheet in order to realize a recording capacity of 100 GB on a 12-cm-diameter disk. We had already developed a 2P sheet utilizing the multilayer disk. In this study, we developed a BD-type quad-layer disk using the 2P sheet, and investigated readout signals from each layer. The jitter values of layer 0 (L0), layer 1 (L1), layer 2 (L2) and layer 3 (L3) in the quad-layer disk were 6.5%, 7.1%, 7.3% and 6.6%, respectively. According to the analysis of the components of jitter values, the main factor behind the deterioration of jitter values is the crosstalk from adjacent layers. However, the jitter value of each layer was sufficient to reproduce the recorded data. From these results, we proved the feasibility of realizing the BD-type multilayer read-only-memory (ROM) disk with the recording capacity of 100 GB.

Shida, Noriyoshi; Higuchi, Takanobu; Hosoda, Yasuo; Miyoshi, Hiroko; Nakano, Akio; Tsuchiya, Katsunori

2004-07-01

194

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

Microsoft Academic Search

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

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

2005-01-01

195

Effect of aging on optical characteristics of full-spectrum fiber  

NASA Astrophysics Data System (ADS)

The availability of the E-band with full spectrum fiber is possible by a new fiber manufacturing process. This increased bandwidth let the full spectrum fiber superior choice for metropolitan and access optical networks. In optical fiber application, the hydrogen aging effect is important factor in the long-term reliability of an optical fiber. In this work, we report a test results for hydrogen aging effect of full spectrum fiber. The attenuations of the fibers are varying even in a hydrogen-free environment after aging test. It is also found that so small bending of full spectrum fiber in hydrogen aging test chamber cause significant variations in optical characteristics.

Fang, Yih; Wu, Chia-Hsien; Hsieh, Lai-Ming; Lin, Sheng-Fwu; Tsai, Fwu-Yuan

2005-01-01

196

Intervertebral disc degeneration: evidence for two distinct phenotypes.  

PubMed

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

Adams, Michael A; Dolan, Patricia

2012-08-12

197

DSC Study of Collagen in Disc Disease  

PubMed Central

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

Skrzynski, S.; Sionkowska, A.; Marciniak, A.

2009-01-01

198

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

199

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

200

Artificial Disc Replacement  

MedlinePLUS

... and a replacement device is implanted into the space between the vertebra. With a disc nucleus replacement, only the center of the disc (the nucleus) is removed and replaced with an implant. The outer part of the disc (the annulus) is not ...

201

Automotive disc brake squeal  

Microsoft Academic Search

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

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

2003-01-01

202

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

Microsoft Academic Search

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

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

2007-01-01

203

On the accretion disc and evolutionary stage of ? Lyrae  

NASA Astrophysics Data System (ADS)

We modelled the V-band light curve of ? Lyrae (Lyr) with two stellar components plus an optically thick accretion disc around the gainer assuming a semidetached configuration. We present the results of this calculation, giving physical parameters for the stars and the disc, along with general system dimensions. We discuss the evolutionary stage of the system finding the best match with one of the evolutionary models of Van Rensbergen et al. According to this model, the system is found at age 2.30 × 107 yr, in the phase of rapid mass transfer, the second one in the life of this binary, in a Case-B mass-exchange stage with dot{M} = 1.58× 10^{-5} M? yr-1. This result, along with the reported rate of orbital period change and observational evidence of mass-loss, suggests that the mass transfer in ? Lyr is quasi-conservative. The best model indicates that ? Lyr finished a relatively large mass-loss episode 31 400 yr ago. The light-curve model that best fit the observations has inclination angle i = 81°, M1 = 13.2 M?, M2 = 3.0 M?, R1 = 6.0 R? and R2 = 15.2 R?. The disc contributes 22 per cent to the total V-band light curve at quadrature, has a radius of 28.3 R? and the outer edge thickness is 11.2 R?. The light-curve model is significantly better with two bright regions in the disc rim with temperatures 10 and 20 per cent higher than the disc outer edge temperature. We compare our results with earlier studies of this interacting binary.

Mennickent, R. E.; Djuraševi?, G.

2013-06-01

204

The patchy accretion disc in HT Cassiopeiae  

NASA Astrophysics Data System (ADS)

We reconstruct the temperatures and surface densities in the quiescent accretion disc in HT Cas by performing a Physical Parameter Eclipse Mapping analysis of archival UBVR observations. Using a simple hydrogen slab model and demanding a smooth, maximally artefact-free reconstruction, we derive a formal distance to HT Cas of 207+/-10pc, significantly larger than the 133+/-14pc we derive from a re-analysis of the data in the literature. The accretion disc is small (0.3-0.4R L1 ) and moderately optically thin, but becomes nearly optically thick near the white dwarf. The temperatures and surface densities in the disc range from 9500K and 0.013gcm-2 in the centre to about 4000K and 0.04gcm-2 at the disc edge. The mass-accretion rate in the disc is roughly constant but - at the derived distance - uncomfortably close to the rate that would prohibit the dwarf nova eruptions. We argue that the larger derived distance is probably incorrect but is not produced by inaccuracies in our spectral model or optimization method. The discrepancy can be resolved if the emission regions on the disc are patchy with a filling factor of about 40 per cent of the disc's surface. This solves the problem with the high effective temperatures in the disc - reducing them to around 6500K within a radius of 0.2R L1 - and reduces the derived temperature of the white dwarf and/or boundary layer from 22600 to 15500K. The viscosity parameters ? derived from all reconstructed temperatures and surface densities are of order 10-100 and cannot be lowered significantly by invoking a lower distance or the filling factor. This situation is easily explained using the same patchy nature of the emitting material, since the quiescent disc cannot consist of optically thin regions alone, but also of a dark and hence cold and dense disc which could easily contain most of the matter. If we require global values of ? of order 0.1, the implied total surface densities are 1-100gcm-2 - just like those expected for quiescent discs awaiting the next eruption. We discuss several possible sources of the chromospheric emission and its patchiness, including irradiation of the disc, thermal instabilities, spiral-wave-like global structures, and magnetically active regions associated with dynamo action and/or Balbus-Hawley instabilities.

Vrielmann, Sonja; Hessman, Frederic V.; Horne, Keith

2002-05-01

205

Premise and Prediction - How Optic Nerve Head Biomechanics Underlies the Susceptibility and Clinical Behavior of the Aged Optic Nerve Head  

PubMed Central

We propose that age-related alterations in optic nerve head (ONH) biomechanics underlie the clinical behavior and increased susceptibility of the aged ONH to glaucomatous damage. The literature which suggests that the aged ONH is more susceptible to glaucomatous damage at all levels of intraocular pressure is reviewed. The relevant biomechanics of the aged ONH are discussed and a biomechanical explanation for why, on average, the stiffened peripapillary scleral and lamina cribrosa connective tissues of the aged eye should lead to a shallow (senile sclerotic) form of cupping is proposed. A logic for why age-related axon loss and the optic neuropathy of glaucoma in the aged eye may overlap is discussed. Finally, we argue for a need to characterize all forms of clinical cupping into prelaminar and laminar components so as to add precision to the discussion of clinical cupping which does not currently exist. Such characterization may lead to the early detection of ONH axonal and connective tissue pathology in ocular hypertension and eventually aid in the assessment of etiology in all forms of optic neuropathy including those that may be purely age-related.

Burgoyne, Claude F.; Downs, J. Crawford

2009-01-01

206

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

207

Percutaneous lumbar disc decompression.  

PubMed

Chronic low back pain is a major social, economic, and healthcare issue in the United States. Various techniques are utilized in managing discogenic pain, with or without disc herniation. Percutaneous techniques are rapidly replacing traditional open surgery in operations requiring discectomy, decompression, and fusion. The percutaneous access to the disc was first used in the 1950s to biopsy the disc with needles. Percutaneous access to the disc using endoscopic techniques was developed in the 1970s. Technical advances in the use of intradiscal therapies led to the development of intradiscal electrothermal annuloplasty (IDET), DISC Nucleoplasty, and DeKompressor, along with laser-assisted, endoscopic, and Nucleotome disc decompressions. The indications for percutaneous lumbar disc decompression include low back and lower extremity pain caused by a symptomatic disc. Internal disc disruptions and disc herniations are common causes of low back and/or lower extremity pain which may become chronic, if not diagnosed and treated. Annular tears lead to migration of the nuclear material and deranged internal architecture. In the chronically damaged intervertebral disc, leakage of nuclear material from annular tears can initiate, promote, and continue the inflammatory process and delay or stop recovery of vital remaining intradiscal tissue. The most often stated goal of central nuclear decompression is to lower the pressure in the nucleus and to allow room for the herniated fragment to implode inward. Provocative discography prior to percutaneous lumbar disc decompression is recommended. Percutaneous disc decompression may result in a small number of complications but occasionally, these could be serious. PMID:16703975

Singh, Vijay; Derby, Richard

2006-04-01

208

Impact of high-oxygen thermal annealing on the structural, optical and electrical properties of ZnO discs made from 20-nm ZnO nanoparticles  

NASA Astrophysics Data System (ADS)

20-nm nanoparticles of zinc oxide (ZnO) were used to make high-density ZnO discs by uniaxial pressing at 4 ton/cm2 pressure and sintering at 1200 °C for 1 hour. High-oxygen thermal annealing performed on the ZnO discs was found to have a profound impact especially enhanced grain growth even at a low annealing temperature of only 400 °C. Moreover, we observed a unique secondary growth of ZnO nanoparticles and growth of multilayer grains that have not been reported elsewhere. The strong solid state reaction during annealing was probably attributed to the high surface area of the 20-nm ZnO nanoparticles that promoted strong surface reaction even at low annealing temperatures. The ZnO discs have been found to contain a very high concentration of structural defects (oxygen vacancies and zinc/oxygen interstitials) that was indicated by the dominant and broad visible photoluminescence (PL) emission in the green band with peaks at (519 - 533) nm, and it was found that this visible emission was greatly increased after annealing treatment especially at 800 °C. Annealing treatment also was found to improved the grain crystallinity as illustrated by the lowering of intrinsic compressive stress based on the XRD lattice constant and full-wave half-maximum (FWHM) data. The electrical properties of the ZnO discs were also greatly influenced by the annealing treatment especially a big drop in the breakdown voltage from 362 V (as-grown sample) to 170 V (800 °C sample). The resistivity also experienced a dramatic drop from 267 k?.cm (as-grown sample) to 74.6 k?.cm (800 °C sample). High-oxygen thermal annealing can be employed as a new technique in controlling the breakdown voltage of ZnO discs made from ZnO nanoparticles with improved structural properties.

Sendi, Rabab Khalid; Mahmud, Shahrom

2012-09-01

209

Accelerated aging studies for polycarbonate optical disk substrates  

Microsoft Academic Search

Accelerated aging studies demonstrated that polycarbonate substrates degrade by a hydrolytic cleavage of the polymer chain. Data collected at different temperatures obeyed an Arrhenius relation. The activation energy for polycarbonate degradation was 68.0 kJ\\/mol.

David E. Nikles; Charles E. Forbes

1991-01-01

210

Accelerated aging studies for polycarbonate optical disk substrates  

NASA Astrophysics Data System (ADS)

Accelerated aging studies demonstrated that polycarbonate substrates degrade by a hydrolytic cleavage of the polymer chain. Data collected at different temperatures obeyed an Arrhenius relation. The activation energy for polycarbonate degradation was 68.0 kJ/mol.

Nikles, David E.; Forbes, Charles E.

1991-07-01

211

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

212

A survey of 286 Virgo cluster galaxies at optical griz and near-IR H band: surface brightness profiles and bulge-disc decompositions  

Microsoft Academic Search

We present and g-, r-, i-, z- and H-band surface brightness profiles and bulge-disc decompositions for a morphologically broad sample of 286 Virgo Cluster Catalogue (VCC) galaxies. The H-band data come from a variety of sources including our survey of 171 VCC galaxies at the University of Hawaii (UH) 2.2-m telescope, Canada-France-Hawaii Telescope (CFHT) and United Kingdom Infrared Telescope (UKIRT),

Michael McDonald; Stéphane Courteau; R. Brent Tully; Joel Roediger

2011-01-01

213

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

214

Investigation of optical loss changes in siloxane polymer waveguides during thermal curing and aging  

NASA Astrophysics Data System (ADS)

In high performance electronic systems, with increasing chip speed and larger number of processors, the system performance is being limited by off-chip metal interconnects. In such systems, optical interconnects are being considered to replace electrical interconnects because of their high capacity for bandwidth and due to having less constraints on link length. Polymer waveguides are attractive as an optical interconnect medium because they can enable low-cost and high-density interconnects, and can be relatively easily integrated into organic board-level processes. The optical loss in the polymer optical waveguides is the key criterion used to evaluate their performance. Although thermal curing and aging factors can change the optical loss of polymer waveguides significantly, there is limited study on the effect of those factors. Also the field-use conditions of an embedded optoelectronic package with these polymer waveguides have not been reported in existing literature. In this research, the relationship between optical loss variations in polymer waveguides with polymer properties during thermal curing is investigated. The evolution of degree-of-cure is determined from differential scanning calorimetry and compared to optical absorption from spectroscopy. Optical loss due to scattering mechanisms is related to local density fluctuations, which is studied using dielectric analysis. Optical loss measurements are conducted on both uncladded and cladded waveguides during isothermal cure, which result in certain optical loss trends. Based on the trends, the underlying mechanisms for the optical loss variations are proposed and a cure process schedule to realize the lowest optical loss is recommended. Process-induced thermal stresses can also affect the polymer waveguide by introducing stress birefringence. In this work, the stress-optical coefficients of the siloxane polymer are extracted and employed in a numerical modeling method to determine the stress-induced birefringence in an optical waveguide system. The outlined methodology is generic in nature and can be applied to different waveguide geometries, planarization materials, and substrate/board materials to assess how stress-induced birefringence can be minimized for a given polymer core material. This research also seeks to understand the effect of thermal aging in polymer waveguides, and develop an optical loss model to ensure that the optical performance over extended field-use conditions is within the optical loss budget. The thermal-aging dependent optical loss is determined for waveguide samples at several different accelerated temperature conditions. To determine the field-use conditions, the temperature distribution in the vicinity of the embedded laser and the polymer waveguide is determined. Using such thermal experimental data, the analytical reliability models were employed to determine the optical loss with time, and provide a practical way of determining whether the optical waveguides would perform within the optical loss budget during field-use conditions.

Hegde, Shashikant G.

215

Quantitative analysis of intervertebral disc structure.  

PubMed

A reduction in signal intensity from the nucleus can be a feature of intervertebral disc disease. It has been established that T1 and T2 relaxation times of the nucleus decrease with age and that evidence of disc degeneration can be determined before classical clinical features are apparent. A robust multiple point algorithm has been developed which now enables proton density and T1 and T2 values to be computed for each pixel, providing images which are effectively spatial maps of these parameters. Such high resolution maps have provided quantitative data from volunteers, patients and cadavers. These studies have been carried out with specially constructed coils and the cadaveric information compared with cut sections. The spatial maps revealed detailed anatomic structures including the laminae of the annulus and relative levels of hydration. These levels, which are known to be related to the ability of the disc to withstand compressive loads, can now be measured in vivo. Analysis of the proton density and relaxation times in vivo has demonstrated that both water content and the chemical environment in the nucleus change during aging. The results are consistent with changes in the glycosaminoglycan content and fixed charged density measured by other chemical and physical techniques. Such detailed methods can be used to investigate the effects of aging and disease on disc structure and have enabled observations to be made of the effects of stress on the normal disc. PMID:2980538

Isherwood, I; Prendergast, D J; Hickey, D S; Jenkins, J P

1986-01-01

216

On total disc replacement.  

PubMed

Low back pain consumes a large part of the community's resources dedicated to health care and sick leave. Back disorders also negatively affect the individual leading to pain suffering, decreased quality-of-life and disability. Chronic low back pain (CLBP) due to degenerative disc disease (DDD) is today often treated with fusion when conservative treatment has failed and symptoms are severe. This treatment is as successful as arthroplasty is for hip arthritis in restoring the patient's quality of life and reducing disability. Even so, there are some problems with this treatment, one of these being recurrent CLBP from an adjacent segment (ASD) after primarily successful surgery. This has led to the development of alternative surgical treatments and devices that maintain or restore mobility, in order to reduce the risk for ASD. Of these new devices, the most frequently used are the disc prostheses used in Total Disc Replacement (TDR). This thesis is based on four studies comparing total disc replacement with posterior fusion. The studies are all based on a material of 152 patients with DDD in one or two segments, aged 20-55 years that were randomly treated with either posterior fusion or TDR. The first study concerned clinical outcome and complications. Follow-up was 100% at both one and two years. It revealed that both treatment groups had a clear benefit from treatment and that patients with TDR were better in almost all outcome scores at one-year follow-up. Fusion patients continued to improve during the second year. At two-year follow-up there was a remaining difference in favour of TDR for back pain. 73% in the TDR group and 63% in the fusion group were much better or totally pain-free (n.s.), while twice as many patients in the TDR group were totally pain free (30%) compared to the fusion group (15%). Time of surgery and total time in hospital were shorter in the TDR group. There was no difference in complications and reoperations, except that seventeen of the patients in the fusion group were re-operated for removal of their implants. The second study concerned sex life and sexual function. TDR is performed via an anterior approach, an approach that has been used for a long time for various procedures on the lumbar spine. A frequent complication reported in males when this approach is used is persistent retrograde ejaculation. The TDR group in this material was operated via an extra-peritoneal approach to the retroperitoneal space, and there were no cases of persistent retrograde ejaculation. There was a surprisingly high frequency of men in the fusion group reporting deterioration in ability to have an orgasm postoperatively. Preoperative sex life was severely hampered in the majority of patients in the entire material, but sex life underwent a marked improvement in both treatment groups by the two-year follow-up that correlated with reduction in back pain. The third study was on mobility in the lumbar spinal segments, where X-rays were taken in full extension and flexion prior to surgery and at two-year follow-up. Analysis of the films showed that 78% of the patients in the fusion group reached the surgical goal (non-mobility) and that 89% of the TDR patients maintained mobility. Preoperative disc height was lower than in a normative database in both groups, and remained lower in the fusion group, while it became higher in the TDR group. Mobility in the operated segment increased in the TDR group postoperatively. Mobility at the rest of the lumbar spine increased in both treatment groups. Mobility in adjacent segments was within the norm postoperatively, but slightly larger in the fusion group. In the fourth study the health economics of TDR vs Fusion was analysed. The hospital costs for the procedure were higher for patients in the fusion group compared to the TDR group, and the TDR patients were on sick-leave two months less. In all, these studies showed that the results in the TDR group were as good as in the fusion group. Patients are more likely to be totally pain-free when treated with TDR compared to fusion

Berg, Svante

2011-02-01

217

Herniated Cervical Disc  

MedlinePLUS

... outer layer can also tear. This can allow displacement of the disc's center (called a herniated or ... diagnosed? A thorough clinical evaluation to determine the character and location of the pain plus an examination ...

218

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

Microsoft Academic Search

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

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

2003-01-01

219

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

220

Of life cycles real and imaginary: The unexpectedly long old age of optical lithography  

Microsoft Academic Search

The history of many industries can be characterized as a series of technological ‘life cycles’. This has led some to argue that the limits to a technology are a predictable function of its underlying physics and the structure of the dominant design. This paper uses the unexpectedly long old age of optical photolithographic alignment technology to suggest that this belief

Rebecca Henderson

1995-01-01

221

Baguera cervical disc prosthesis  

Microsoft Academic Search

A new high performance tool, the disc prosthesis, endows the degenerative cervical rachidian pathology. It allows us to fill\\u000a the fusions’ lacunas by protecting the adjacent levels from an accelerated degeneration while preserving the anatomical and\\u000a physiological characteristics of the cervical spine, especially its mobility. At the present time, there exist several models\\u000a of cervical disc prosthesis on the market.

M. Benmekhbi; J. Mortada; G. Lungu; D. Eichler; R. Srour; J. M. Vital

2008-01-01

222

The disc as the basis of treatment for glaucoma.  

PubMed

The goal of the treatment of patients with glaucoma is to prevent disability or, if disability already exists, to repair the disability or at the least to prevent further disability from developing. To achieve these goals requires knowing what will happen if there is no treatment and what will happen if there is treatment. That is, one must know the possible benefits from the therapy in comparison to the damage caused by the therapy. As we will demonstrate, the classic risk factors do not provide accurate estimates of the development of disability and do not answer these two questions. The most helpful clues are provided by what the patient says, by whether the disc is damaged and by whether the disc is deteriorating. The severity of disease is best estimated by the nature of the optic disc and how it changes. This report is primarily focused on increasing the skill of the physician in being able to estimate the nature of the optic disc and how that changes. This does not, however, lessen the tremendous importance of careful history-taking and of gonioscopy. In this report, however, we focus on the evaluation of the disc. Currently disc evaluation is often not adequate because of poor examination techniques, reliance on cup/disc ratios, and reliance on the results of image analyzers. We will present here the Disc Damage Likelihood Scale, which is a user-friendly method which correlates accurately with visual field changes. PMID:23960952

Zangalli, Camila; Gupta, Shelly R; Spaeth, George L

2011-07-30

223

The disc as the basis of treatment for glaucoma  

PubMed Central

The goal of the treatment of patients with glaucoma is to prevent disability or, if disability already exists, to repair the disability or at the least to prevent further disability from developing. To achieve these goals requires knowing what will happen if there is no treatment and what will happen if there is treatment. That is, one must know the possible benefits from the therapy in comparison to the damage caused by the therapy. As we will demonstrate, the classic risk factors do not provide accurate estimates of the development of disability and do not answer these two questions. The most helpful clues are provided by what the patient says, by whether the disc is damaged and by whether the disc is deteriorating. The severity of disease is best estimated by the nature of the optic disc and how it changes. This report is primarily focused on increasing the skill of the physician in being able to estimate the nature of the optic disc and how that changes. This does not, however, lessen the tremendous importance of careful history-taking and of gonioscopy. In this report, however, we focus on the evaluation of the disc. Currently disc evaluation is often not adequate because of poor examination techniques, reliance on cup/disc ratios, and reliance on the results of image analyzers. We will present here the Disc Damage Likelihood Scale, which is a user-friendly method which correlates accurately with visual field changes.

Zangalli, Camila; Gupta, Shelly R.; Spaeth, George L.

2011-01-01

224

Circumplanetary Discs: Truncation and Outbursts  

NASA Astrophysics Data System (ADS)

After a planet with a mass greater than that of Nepture forms it opens a gap in the circumstellar disc. Material continues to flow on to the planet and a circumplanetary disc forms. We model circumplanetary discs as accretion discs subject to the tidal forces of the central star. The tidal torques remove the disc angular momentum near the disc outer edge and permit the accreting disc gas to lose angular momentum at the rate appropriate for steady accretion. Circumplanetary discs are truncated near the radius where periodic ballistic orbits cross, where tidal forces on the disc are strong. This radius occurs at approximately 0.4 times the planet Hill radius. During the T Tauri stage of disc accretion, the disc is fairly thick with aspect ratio H/r>0.2. We model the disc structure using one-dimensional time-dependent and steady-state models and also two-dimensional SPH simulations. The circumplanetary disc structure depends on the variation of the disc turbulent viscosity with radius and is insensitive to the angular distribution of the accreting gas. If the disc is turbulent throughout, the predicted disc structure near the location of the regular Jovian and Saturnian satellites is smooth with no obvious feature that would favor formation at their current locations. Dead zones form in accretion discs where the temperature is too low for the disc to be fully thermally ionised. They are even more favorable in circumplanetary discs than in circumstellar discs because the surface densities are high while the temperature remains low enough to avoid thermal ionisation. We consider the conditions under which dead zones form and the resulting unsteady accretion on to the planet. Outbursts in the accretion rate on to the planet have observational implications for planet detection.

Martin, Rebecca G.; Lubow, S. H.

2011-09-01

225

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

226

Irradiated Accretion Disc Models  

NASA Astrophysics Data System (ADS)

Most of the known accretion discs in binary systems are composed of hydrogen rich material. A few years ago, a new type of binary system was discovered, in which the disc is obviously free of hydrogen and helium. Nowadays six systems are known, with an accretion disc mainly composed of C, O, Ne and Mg (Juett, Psaltis & Chakrabarty 2001; Schulz et al. 2001). The most prominent representative of these ultra compact binary systems is the LMXB 4U 1626-67. The system is consisting of a 7.66 s X-ray pulsar as primary component and a 0.02 solar mass white dwarf as secondary (Chakrabarty 1998). Having a binary separation of only 300 0000 km (Schulz et al. 2001) one can not neglect the external irradiation of the accretion disc by the neutron star. The external irradiation dominates the disc spectrum over a wide range. In the UV one sees emission lines of highly ionised elements, like OV or CIV. One of the biggest numerical problems, occurring during the calculation of an irradiated accretion disc model, is the extreme temperature stratification and structure. This causes severe problems with the occupation numbers of some atomic levels. These problems should be solved by implementing the depth dependent model atom, during my thesis work. During his PhD thesis, Nagel (2003) has developed the numeric code package AcDc. Therewith one can calculate the vertical structure and the emergent synthetic spectrum of an accretion disc. During the work presented here the depth dependent model atom (DEPTOM) was developed and implemented in AcDc as a code module. DEPTOM identifies the trouble making ionisation stages and deactivates them. Thus the calculation is numerically more stable and, hence, makes AcDc more powerful.

Hammer, N. J.

2004-08-01

227

Intervertebral disc infection (Discitis) in childhood  

Microsoft Academic Search

Discitis is an inflammatory process of the intervertebral disc space occurring in the pediatric age range. Its etiology is usually unknown; staphylococcus aureus is the most common microorganism present in the few cases with positive bacteriological cultures. The clinical presentation can mimic medical or surgical emergencies and thus unnecessary investigations or surgical procedures are frequently performed. Irritability, refusal to sit

A. Galil; R. Gorodischer; J. Bar-Ziv; T. Hallel; Ch. Malkin; R. Garty

1982-01-01

228

Resolved DEBRIS Discs  

NASA Astrophysics Data System (ADS)

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

Booth, Mark; DEBRIS Team

2011-09-01

229

Microlensing evidence for super-Eddington disc accretion in quasars  

NASA Astrophysics Data System (ADS)

Microlensing by the stellar population of lensing galaxies provides an important opportunity to resolve the accretion disc structure spatially in strongly lensed quasars. Disc sizes estimated in this way are on average larger than the predictions of the standard Shakura-Sunyaev accretion disc model. An analysis of the observational data on microlensing variability suggests that some fraction of lensed quasars (primarily smaller-mass objects) are accreting in the super-Eddington regime. Super-Eddington accretion leads to the formation of an optically thick envelope scattering the radiation formed in the disc. This makes the apparent disc size larger and practically independent of wavelength. In the framework of our model, it is possible to make self-consistent estimates of mass accretion rates and black hole masses for the cases when both amplification-corrected fluxes and radii are available.

Abolmasov, P.; Shakura, N. I.

2012-12-01

230

Quantification of overload injuries to thoracolumbar vertebrae and discs in persons exposed to heavy physical exertions or vibration at the work-place The shape of vertebrae and intervertebral discs - study of a young, healthy population and a middle-aged control group.  

PubMed

The ongoing search for causes (and strategies for prevention) of low back trouble in sub-groups of the population exposed to heavy physical exertions or whole body vibration requires reliable data on the prevalence of lower-spine overload damage. Because published reports on this topic are rare and mostly qualitative, the present study was initiated to assess, objectively and quantitatively, overload damage to vertebrae and intervertebral discs. Part I of the work has involved the establishment of a normative database of shape parameters from measurements of 683 (539 male, 144 female) lateral radiographic views of the thoracolumbar spine of young (17-30 years), healthy subjects. In addition, age-related shape alterations were explored from measurements of 364 male middle-aged (31-57 years), non-exposed controls. Advanced methods for shape analysis and shape parameter construction were required, and duly developed, in order to minimise the influence of confounding factors such as radiographic magnification, image distortion, axial rotation or lateral tilt. The results revealed that the variation in shape parameters varies between 2% and 10% within the group of normals (this being largely biological variability as opposed to measurement error). Within this normal group subtle but statistically significant differences due to gender and geographic origin were observed. Comparison of the normals with the controls revealed only slight, but clearly demonstrable differences. The narrow range of 'normal shape' together with the high accuracy of shape analysis are the foundation for Part II of this study which will involve a comparison of exposed cohorts with the normal standard (adjusted for ageing effects). This will, for the first time, enable objective quantification of the prevalence of overload damage to the spines of persons exposed to heavy physical stresses and whole body vibration, and thus form the basis of a scientific rationale for recommendation of safety guidelines. PMID:23906922

Brinckmann, P; Frobin, W; Biggemann, M; Hilweg, D; Seidel, S; Burton, K; Tillotson, M; Sandover, J; Atha, J; Quinnell, R

1994-01-01

231

Modeling the Compact Disc Read System in Lab  

ERIC Educational Resources Information Center

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

Hinaus, Brad; Veum, Mick

2009-01-01

232

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

233

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

234

[Contributory factors for glaucomatous disc cupping. 4. Generalized expansion type and localized type].  

PubMed

It is widely recognized that there are two types progressive disc cupping in glaucoma. One of them is the localized type (L type) in which the cupping extends to a certain direction and the other is the generalized expansion type (G type) in which the cupping expands generally. We evaluated the optic disc in 86 eyes with primary open angle glaucoma (G type 44 eyes L type 42 eyes) to evaluate correlations of age and visual field defects between the 2 groups. Our study revealed that G type patients were significantly younger than those with L type when matched according to visual field defects. We also found that G type was revealed as the nasal step alone but not in L type. These results suggest that in G type, the optic nerve head is diffusely damaged by elevated intraocular pressure and the total nerve fibers are destroyed uniformly. On the other hand, in L type, the vulnerable portion of the optic nerve head is selectively damaged and nerve fibers constituting the optic rim area are destroyed. As a result, L type is likely to form cupping notch and reveal Bjerrum scotoma. These facts correspond to the anatomical structures of nerve fiber layers. PMID:2773699

Tetsumoto, K; Nakahashi, K; Iga, T; Mizokami, K

1989-02-01

235

Angiogenesis in the degeneration of the lumbar intervertebral disc  

PubMed Central

The goal of the study is to show the histological and biochemical changes that indicate the angiogenesis of the intervertebral disc in lumbar intervertebral disc hernia and the existence of epidemiological correlations between these changes and the risk factors of lumbar intervertebral disc hernia, as well as the patient's quality of life (QOL). We have studied 50 patients aged between 18 and 73 years old, who have undergone lumbar intervertebral disc hernia surgery, making fibroblast growth factor and vascular endothelial growth factor level measurements, as elements in the process of appreciating the disc angiogenesis. Also, pre–surgery and post–surgery QOL has been measured, as well as the intensity of the pain syndrome. We have identified factors capable of stimulating vascular endothelial growth (VEGF, FGF–2) for the examined disc material, but histological examination did not show angiogenesis. The process of angiogenesis at the degenerated intervertebral disc level affects the patient's quality of life both pre and postoperatively, and may be a predictive factor for the post–operative results. Patients can prevent the appearance of angiogenesis type degenerative processes of the intervertebral disc by avoiding angiogenesis correlated factors (weight control, physical effort, and smoking).

David, Gh; Iencean, SM; Mohan, A

2010-01-01

236

Analysis of the effects of outdoor and accelerated ageing on the optical properties of reflector materials for solar energy applications  

Microsoft Academic Search

Lifetime tests of solar reflector materials are eligible prior to application, to prove the stability of the optical properties. In this work, six reflector materials were aged outdoors and in a climatic test chamber. The surfaces of the samples were inspected using profilometry and optical microscopy. The total and specular reflectance spectra were measured using spectrophotometry and the weighted solar

Maria Brogren; Björn Karlsson; Arne Roos; Anna Werner

2004-01-01

237

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

PubMed Central

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

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

2013-01-01

238

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

239

Molecular gas and star formation in the red-sequence counter-rotating disc galaxy NGC 4550  

NASA Astrophysics Data System (ADS)

We present observations of the CO(1-0) emission in the central 750 pc (10 arcsec) of the counter-rotating disc galaxy NGC 4550, obtained at the Institut de Radioastronomie Millimétrique (IRAM) Plateau de Bure Interferometer. Very little molecular gas is detected, only 1×107Msolar, and its distribution is lopsided, with twice as much molecular gas observed at positive relative velocities than at negative relative velocities. The velocity gradient in the CO(1-0) emission shows that the molecular gas rotates like the thicker of the two stellar discs, which is an unexpected alignment of rotations if the thinner disc was formed by a major gas accretion event. However, a simulation shows that the gas rotating like the thicker disc naturally results from the coplanar merger of two counter-rotating disc galaxies, demonstrating the feasibility of this scenario for the formation of NGC 4550. We investigate various star formation tracers to determine whether the molecular gas in NGC 4550 is currently forming stars. Ultraviolet (UV) imaging data and optical absorption line strengths both suggest a recent star formation episode; the best-fitting two-population model to the UV-optical colours yields a mass of young stars of 5.9×107Msolar with an age of 280 Myr. The best information on the current star formation rate is a far-infrared-based upper limit of only 0.02Msolaryr-1. We are thus witnessing NGC 4550 either in a dip within a bursty star formation period or during a more continuous low-level star formation episode.

Crocker, Alison F.; Jeong, Hyunjin; Komugi, Shinya; Combes, Francoise; Bureau, Martin; Young, Lisa M.; Yi, Sukyoung

2009-03-01

240

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

241

Disc heating: comparing the Milky Way with cosmological simulations  

NASA Astrophysics Data System (ADS)

We present an analysis of a suite of simulations run with different particle- and grid-based cosmological hydrodynamical codes and compare them with observational data of the Milky Way. This is the first study to make comparisons of properties of galaxies simulated with particle- and grid-based codes. Our analysis indicates that there is broad agreement between these different modelling techniques. We study the velocity dispersion-age relation for disc stars at z= 0 and find that four of the simulations are more consistent with observations by Holmberg, Nordstroem & Andersen in which the stellar disc appears to undergo continual/secular heating. Two other simulations are in better agreement with the Quillen & Garnett observations that suggest 'saturation' in the heating profile for young stars in the disc. None of the simulations has thin discs as old as that of the Milky Way. We also analyse the kinematics of disc stars at the time of their birth for different epochs in the galaxies' evolution and find that in some simulations old stars are born cold within the disc and are subsequently heated, while other simulations possess old stellar populations which are born relatively hot. The models which are in better agreement with observations of the Milky Way's stellar disc undergo significantly lower minor-merger/assembly activity after the last major merger, that is, once the disc has formed. All of the simulations are significantly 'hotter' than the Milky Way disc; on top of the effects of mergers, we find a 'floor' in the dispersion that is related to the underlying treatment of the heating and cooling of the interstellar medium, and the low density threshold which such codes use for star formation. This finding has important implications for all studies of disc heating that use hydrodynamical codes.

House, E. L.; Brook, C. B.; Gibson, B. K.; Sánchez-Blázquez, P.; Courty, S.; Few, C. G.; Governato, F.; Kawata, D.; Roškar, R.; Steinmetz, M.; Stinson, G. S.; Teyssier, R.

2011-08-01

242

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

243

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

244

Revival of the jumping disc  

NASA Astrophysics Data System (ADS)

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 (~3.5 m s-1), the acceleration (~30 000 m s-2) and the lower and upper snap temperature (~31; ~99 °C). High speed videos give even deeper insight into the jump.

Ucke, C.; Schlichting, H.-J.

2009-11-01

245

37 CFR 1.52 - Language, paper, writing, margins, compact disc specifications.  

Code of Federal Regulations, 2010 CFR

... false Language, paper, writing, margins, compact disc specifications...1.52 Language, paper, writing, margins, compact disc specifications...contrast between the paper and the writing thereon to permit the direct...electronic capture by use of digital imaging and optical...

2009-07-01

246

37 CFR 1.52 - Language, paper, writing, margins, compact disc specifications.  

Code of Federal Regulations, 2010 CFR

... false Language, paper, writing, margins, compact disc specifications...1.52 Language, paper, writing, margins, compact disc specifications...contrast between the paper and the writing thereon to permit the direct...electronic capture by use of digital imaging and optical...

2010-07-01

247

Bitemporal visual field defects mimicking chiasmal compression in eyes with tilted disc syndrome  

Microsoft Academic Search

BackgroundTilted disc syndrome (TDS) is a congenital optic nerve coloboma occurring from embryonic dysgenesis. Several features characterize TDS, including an inferiorly located conus, situs inversus of the major retinal vessels, and an anomalous disc shape. Commensurate with axonal dysgenesis, visual field defects may often occur from TDS, the most common of which involve the temporal and superior temporal visual field.

Joseph W. Sowka; Vincent V. Luong

2009-01-01

248

Treatment of lumbar disc herniation in the second decade of life  

Microsoft Academic Search

Lumbar disc herniation is rare in patients under the age of 20 years. In the department of orthopaedic surgery of the University Hospital of Frankfurt, 33 patients below the age of 20 with lumbar disc herniation were treated over a period of 10 years. Eighteen were managed conservatively and 15 surgically. The purpose of this study is to report on

A. A. Kurth; S. Rau; C. Wang; E. Schmitt

1996-01-01

249

Preparation of ormetoprim sulfadimethoxine medicated discs for disc diffusion assay  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

250

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

251

Origin and structure of the Galactic disc(s)  

NASA Astrophysics Data System (ADS)

We examine the chemical and dynamical structure in the solar neighbourhood of a model Galaxy that is the endpoint of a simulation of the chemical evolution of the Milky Way in the presence of radial mixing of stars and gas. Although the simulation's star formation rate declines monotonically from its unique peak and no merger or tidal event ever takes place, the model replicates all known properties of a thick disc, as well as matching special features of the local stellar population such as a metal-poor extension of the thin disc that has high rotational velocity. We divide the disc by chemistry and relate this dissection to observationally more convenient kinematic selection criteria. We conclude that the observed chemistry of the Galactic disc does not provide convincing evidence for a violent origin of the thick disc, as has been widely claimed.

Schönrich, Ralph; Binney, James

2009-11-01

252

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

253

Three-dimensional ultrahigh resolution optical coherence tomography imaging of age-related macular degeneration?  

PubMed Central

Ultrahigh resolution optical coherence tomography (OCT) enhances the ability to visualize different intra retinal layers. In age-related macular degeneration (AMD), pathological changes in individual retinal layers, including photoreceptor inner and outer segments and retinal pigment epithelium, can be detected. OCT using spectral / Fourier domain detection enables high speed, volumetric imaging of the macula, which provides comprehensive three-dimensional tomographic and morphologic information. We present a case series of AMD patients, from mild drusen to more advanced geographic atrophy and exudative AMD. Patients were imaged with a research prototype, ultrahigh resolution spectral / Fourier domain OCT instrument with 3.5 ?m axial image resolution operating at 25,000 axial scans per second. These cases provide representative volumetric datasets of well-documented AMD pathologies which could be used for the development of visualization and imaging processing methods and algorithms.

Chen, Yueli; Vuong, Laurel N.; Liu, Jonathan; Ho, Joseph; Srinivasan, Vivek J.; Gorczynska, Iwona; Witkin, Andre J.; Duker, Jay S.; Schuman, Joel; Fujimoto, James G.

2009-01-01

254

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

255

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

256

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

257

Mechanical profiling of intervertebral discs  

PubMed Central

Despite recent advances in imaging diagnostic technology and additional treatment options our ability to prevent or inhibit discogenic back pain has not drastically improved. The challenge of linking early degenerative patterns to dysfunction and pain remains. Using a novel material testing device designated the Tissue Diagnostic Instrument (TDI) we measured the local stiffness and strain energy absorption in the radial direction of 13 intact intervertebral discs; effectively generating a mechanical profile of each disc. Prior to measuring mechanical properties, an MR image was taken of each spine segment and the discs were radiologically scored according to the Pfirrmann scale. After testing, a sagittal portion of each L1-L2 disc was excised from each of four spines for histology. No significant correlations were found between Pfirrmann grade and mechanical data. However, polarized light microscopy images of disc sections indicated correlations between local tissue modulus measured with the TDI and the clarity and density of lamellar striations.

Schultz, David S.; Rodriguez, Azucena G.; Hansma, Paul K.; Lotz, Jeffrey C.

2009-01-01

258

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

259

Effect of aging on morphology, hygroscopicity, and optical properties of soot aerosol  

NASA Astrophysics Data System (ADS)

Soot from incomplete combustion represents one of the major forms of particulate matter pollution, profoundly impacting human health, air quality, and climate. The direct and indirect radiative effects of soot aerosol depend on particle composition and morphology, which may vary significantly when aerosol is subjected to atmospheric aging. We will present an overview of a comprehensive set of experimental measurements performed in our laboratory at Texas A&M to study the effect of internal mixing with atmospheric species on morphology, hygroscopicity, and optical properties of combustion soot. In our experiments, size-classified soot aerosol was exposed to 0.1 - 1000 ppb (part per billion) mixing ratios of sulfuric acid and dicarboxylic organic acids and resulting changes particle morphology and mixing state under dry and humid conditions were characterized through mass-mobility measurements by aerosol particle mass analyzer (APM) and tandem differential mobility analyzer (TDMA). Light absorption and scattering cross-sections for well-characterized fresh and coated soot aerosol were derived using a cavity ring-down spectrometer and an integrating nephelometer in order to assess the effect of atmospheric processing on the radiative properties of atmospheric soot. Internally mixed soot shows significant changes in particle morphology, increasing with the mass fraction of the coating material and relative humidity. Restructuring was the strongest for aggregates coated by sulfuric and glutaric acids whereas succinic acid coating did not result in observable morphology change. Sulfuric acid - coated particles experienced large hygroscopic growth at sub-saturated conditions and activated to cloud droplets at atmospherically relevant supersaturations. Furthermore, coating and subsequent hygroscopic growth considerably altered the optical properties of soot aerosol, increasing light scattering and absorption cross-sections. We found that irreversible restructuring of soot aggregates is a major contributor to the enhancement in optical properties for internally mixed soot. Extrapolation of our results to atmospheric conditions shows that condensation of sulfuric acid and organics is likely a major mechanism of soot aging with profound implications atmospheric soot lifetime and direct and indirect climate forcing.

Khalizov, A. F.; Xue, H.; Pagels, J.; McMurry, P. H.; Zhang, R.

2009-12-01

260

Double-disc gate valve  

DOEpatents

This invention relates to an improvement in a conventional double-disc gate valve having a vertically movable gate assembly including a wedge, spreaders slidably engaged therewtih, a valve disc carried by the spreaders. When the gate assembly is lowered to a selected point in the valve casing, the valve discs are moved transversely outward to close inlet and outlet ports in the casing. The valve includes hold-down means for guiding the disc-and-spreader assemblies as they are moved transversely outward and inward. If such valves are operated at relatively high differential pressures, they sometimes jam during opening. Such jamming has been a problem for many years in gate valves used in gaseous diffusion plants for the separtion of uranium isotopes. The invention is based on the finding that the above-mentioned jamming results when the outlet disc tilts about its horizontal axis in a certain way during opening of the valve. In accordance with the invention, tilting of the outlet disc is maintained at a tolerable value by providing the disc with a rigid downwardly extending member and by providing the casing with a stop for limiting inward arcuate movement of the member to a preselected value during opening of the valve.

Wheatley, Seth J. (Oak Ridge, TN)

1979-01-01

261

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

2013-09-01

262

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

263

Diagnosis and prognosis in lumbar disc herniation.  

PubMed

In a prospective 2-year followup study of 160 consecutive patients undergoing primary surgery for suspected lumbar disc herniation, the authors studied the diagnostic and prognostic factors by using stepwise logistic regression analysis. When the different factors were entered in the same order as presented clinically, history and pain analysis contained most of the predictive information available. When all factors were entered simultaneously in the computations, the following factors (in order of relative importance) predicted relief of sciatica after 2 years: rupture of the anulus (as opposed to bulging disc or negative exploration), no preoperative comorbidity, and male gender. The following factors predicted return to work at 2 years: no preoperative comorbidity, duration of sciatica less than 7 months, education or vocational training in addition to compulsory school, age younger than 41 years, male gender, and no previous nonspinal surgery. Return to work does not seem to be a valid result parameter in lumbar disc surgery. The most important physical signs were root tension tests and lumbar range of motion, whereas neurologic signs were of secondary importance. Many people have asymptomatic herniations, and today supersensitive diagnostic imaging is widely available. Thus, the importance of clinical evaluation has increased, and most of the relevant information can be obtained by listening to the patient. A simple anamnesis apparently is a good alternative to psychologic tests in surgical triage. PMID:10212604

Vucetic, N; Astrand, P; Güntner, P; Svensson, O

1999-04-01

264

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

265

The mechanical effects of intervertebral disc lesions  

Microsoft Academic Search

Objective. To determine the mechanical effect of individual concentric tears, radial tears and rim lesions of the intervertebral disc anulus.Design. In vitro dynamic mechanical testing of sheep discs comparing the mechanical behaviour before and after lesion creation.Background. Structural changes to the disc in the form of anular lesions are a feature of disc degeneration and degeneration has been related to

Rosemary E. Thompson; Mark J. Pearcy; Timothy M. Barker

2004-01-01

266

Vertical structure of debris discs  

NASA Astrophysics Data System (ADS)

Context: The vertical thickness of debris discs is often used as a measure of these systems' dynamical excitation, and as clues to the presence of hidden massive perturbers such as planetary embryos. However, this argument might be flawed because the observed dust should be naturally placed on inclined orbits by the combined effect of radiation pressure and mutual collisions. Aims: We critically reinvestigate this issue and numerically estimate the “natural” vertical thickness of a collisionally evolving disc, in the absence of any additional perturbing body. Methods: We use a deterministic collisional code, to follow the dynamical evolution of a population of indestructible test grains suffering mutual inelastic impacts. Grain differential sizes as well as the effect of radiation pressure are taken into account. Results: We find that, under the coupled effect of radiation pressure and collisions, grains naturally acquire inclinations of a few degrees. The disc is stratified with respect to grain sizes, the smallest grains having the largest vertical dispersion and the largest being clustered closer to the midplane. Conclusions: Debris discs should have a minimum “natural” observed aspect ratio hmin ~ 0.04±0.02 from visible to mid-IR wavelengths, where the flux is dominated by the smallest bound grains. These values are comparable to the estimated thicknesses of several vertically resolved debris discs, as illustrated by the specific example of AU Mic. For all systems with h ~ hmin, the presence (or absence) of embedded perturbing bodies cannot be inferred from the vertical dispersion of the disc.

Thébault, P.

2009-10-01

267

Characterizing thermal sweeping: a rapid disc dispersal mechanism  

NASA Astrophysics Data System (ADS)

We consider the properties of protoplanetary discs that are undergoing inside-out clearing by photoevaporation. In particular, we aim to characterize the conditions under which a protoplanetary disc may undergo `thermal sweeping', a rapid (?104 years) disc destruction mechanism proposed to occur when a clearing disc reaches sufficiently low surface density at its inner edge and where the disc is unstable to runaway penetration by the X-rays. We use a large suite of 1D radiation-hydrodynamic simulations to probe the observable parameter space, which is unfeasible in higher dimensions. These models allow us to determine the surface density at which thermal sweeping will take over the disc's evolution and to evaluate this critical surface density as a function of X-ray luminosity, stellar mass and inner hole radius. We find that this critical surface density scales linearly with X-ray luminosity, increases with inner hole radius and decreases with stellar mass, and we develop an analytic model that reproduces these results. This surface density criterion is then used to determine the evolutionary state of protoplanetary discs at the point that they become unstable to destruction by thermal sweeping. We find that transition discs created by photoevaporation will undergo thermal sweeping when their inner holes reach 20-40 au, implying that transition discs with large holes and no accretion (which were previously a predicted outcome of the later stages of all flavours of the photoevaporation model) will not form. Thermal sweeping thus avoids the production of large numbers of large, non-accreting holes (which are not observed) and implies that the majority of holes created by photoevaporation should still be accreting. We emphasize that the surface density criteria that we have developed apply to all situations where the disc develops an inner hole that is optically thin to X-rays. It thus applies not only to the case of holes originally created by photoevaporation but also to holes formed, for example, by the tidal influence of planets.

Owen, James E.; Hudoba de Badyn, Mathias; Clarke, Cathie J.; Robins, Luke

2013-09-01

268

Planet signatures in collisionally active debris discs: scattered light images  

NASA Astrophysics Data System (ADS)

Context. Planet perturbations have been often invoked as a potential explanation for many spatial structures that have been imaged in debris discs. So far this issue has been mostly investigated with pure N-body numerical models, which neglect the crucial effect collisions within the disc can have on the disc's response to dynamical perturbations. Aims: We numerically investigate how the coupled effect of collisions and radiation pressure can affect the formation and survival of radial and azimutal structures in a disc perturbed by a planet. We consider two different set-ups: a planet embedded within an extended disc and a planet exterior to an inner debris ring. One important issue we want to address is under which conditions a planet's signature can be observable in a collisionally active disc. Methods: We use our DyCoSS code, which is designed to investigate the structure of perturbed debris discs at dynamical and collisional steady-state, and derive synthetic images of the system in scattered light. The planet's mass and orbit, as well as the disc's collisional activity (parameterized by its average vertical optical depth ?0) are explored as free parameters. Results: We find that collisions always significantly damp planet-induced spatial structures. For the case of an embedded planet, the planet's signature, mostly a density gap around its radial position, should remain detectable in head-on images if Mplanet ? MSaturn. If the system is seen edge-on, however, inferring the presence of the planet is much more difficult, as only weak asymmetries remain in a collisionally active disc, although some planet-induced signatures might be observable under very favourable conditions. For the case of an inner ring and an external planet, planetary perturbations cannot prevent collision-produced small fragments from populating the regions beyond the ring. The radial luminosity profile exterior to the ring is in most cases close to the one it should have in the absence of the external planet. The most significant signature left by a Jovian planet on a circular orbit are precessing azimutal structures that can be used to indirectly infer its presence. For a planet on an eccentric orbit, we show that the ring becomes elliptic and that the well known pericentre glow effect is visible despite of collisions and radiation pressure, but that detecting such features in observed discs is not an unambiguous indicator of the presence of an outer planet. Movies are available in electronic form at http://www.aanda.org

Thebault, P.; Kral, Q.; Ertel, S.

2012-11-01

269

A SCUBA-2 850-?m survey of protoplanetary discs in the ? Orionis cluster  

NASA Astrophysics Data System (ADS)

We present the results from a large 850-?m survey of the ? Orionis cluster using the SCUBA-2 camera on the James Clerk Maxwell Telescope. The 0.5° diameter circular region we surveyed contains 297 young stellar objects with an age estimated at about 3 Myr. We detect nine of these objects, eight of which have infrared excesses from an inner disc. We also serendipitously detect three non-stellar sources at >5? that are likely background submillimetre galaxies. The nine detected stars have inferred disc masses ranging from 5 to about 17 MJup, assuming similar dust properties as Taurus discs and an interstellar medium gas-to-dust ratio of 100. There is a net positive signal towards the positions of the individually undetected infrared excess sources indicating a mean disc mass of 0.5 MJup. Stacking the emission towards those stars without infrared excesses constrains their mean disc mass to less than 0.3 MJup, or an equivalent Earth mass in dust. The submillimetre luminosity distribution is significantly different from that in the younger Taurus region, indicating disc mass evolution as star-forming regions age and the infrared excess fraction decreases. Submillimetre Array observations reveal CO emission towards four sources demonstrating that some, but probably not much, molecular gas remains in these relatively evolved discs. These observations provide new constraints on the dust and gas mass of protoplanetary discs during the giant planet building phase and provide a reference level for future studies of disc evolution.

Williams, Jonathan P.; Cieza, Lucas A.; Andrews, Sean M.; Coulson, Iain M.; Barger, Amy J.; Casey, Caitlin M.; Chen, Chian-Chou; Cowie, Lennox L.; Koss, Michael; Lee, Nicholas; Sanders, David B.

2013-10-01

270

Comparison between Clinical Evaluations, Ster Comparison between Clinical Evaluations, Stereoscopic Photographic eoscopic Photographic analysis and Confocal Scanning Laser Ophthalmoscope in estimating analysis and Confocal Scanning Laser Ophthalmoscope in estimating Cup\\/Disc Ratio Cup\\/Disc Ratio  

Microsoft Academic Search

Objective: To find out the agreement in cup\\/disc ratio measurements obtained by clinical evaluation, analysis of stereoscopic photographs of optic disc, and Confocal Scanning Laser Ophthalmoscope (Heidelberg Retina Tomograph II Software Version 1.5) in healthy persons and patients with early glaucoma. Patients and Methods: Thirty healthy persons and thirty patients with early and moderate primary open angle glaucoma were selected

M. S. Shehzad; K. M. Ashraf; M. Siddique; Z. A. Qazi; M. T. Khan

271

Stellar encounters: a stimulus for disc fragmentation?  

NASA Astrophysics Data System (ADS)

An interaction between a star-disc system and another star will perturb the disc, possibly resulting in a significant modification of the disc structure and its properties. It is still unclear if such an encounter can trigger fragmentation of the disc to form brown dwarfs or gas giant planets. This paper details high-resolution smoothed particle hydrodynamics (SPH) simulations investigating the influence of stellar encounters on disc dynamics. Star-star encounters (where the primary has a self-gravitating, marginally stable protostellar disc, and the secondary has no disc) were simulated with various orbital parameters to investigate the resulting disc structure and dynamics. This work is the first of its kind to incorporate realistic radiative transfer techniques to realistically model the resulting thermodynamics. The results suggest that the effect of stellar encounters is to prohibit fragmentation - compressive and shock heating stabilizes the disc, and the radiative cooling is insufficient to trigger gravitational instability. The encounter strips the outer regions of the disc (either through tidal tails or by capture of matter to form a disc around the secondary), which triggers a readjustment of the primary disc to a steeper surface density profile (and a flatter Toomre Q profile). The disc around the secondary plays a role in the potential capture of the secondary to form a binary. However, this applies only to orbits that are parabolic - hyperbolic encounters do not form a secondary disc, and are not captured.

Forgan, Duncan; Rice, Ken

2009-12-01

272

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

273

Hot Water Aging Performance Improvement through Controlling Curing Characteristics of Polymer Coated Silica Optical Fiber  

Microsoft Academic Search

For mechanical reliability of optical fiber in rigorous environment, robust coating system and optimization of critical coating related parameters are required. Stability of optical fiber coating in hot (85ºC) water in terms of strength degradation and adhesion to glass can be used to evaluate robustness of the coating system for mechanical reliability requirement. Published literature described relation between hot water

Sudipta Bhaumik

274

THE COMING OF AGE OF ADVANCED DIGITAL OPTICAL SCANNING TECHNOLOGY FOR PIPELINE ASSESSMENT  

Microsoft Academic Search

This paper presents the development and advancement of digital optical scanning technology brought by the SSET (Sewer Scanner and Evaluation Technology). Chronological development history and evolution of the optical scanner technology is outlined. The inner works of the scanner and example outputs are given. Advantages of the digital technology over the conventional analog CCTV are discussed.

Kenzi Karasaki; Hiromasa Shima; Tom Iseley

275

Morphologic and molecular evidence for gap junctions and connexin 43 and 45 expression in annulus fibrosus cells from the human intervertebral disc  

Microsoft Academic Search

Data are presented which provide evidence for gap junction formation and connexin (Cx) 43 and 45 gene expression in human intervertebral disc cells in vivo and in vitro. These findings in cells from the annulus are important in conjunction with the well-recognized loss of disc cells during aging and disc degeneration. As a result of this loss of cells, cell–cell

Helen E. Gruber; Defang Ma; Edward N. Hanley; Jane Ingram; Dean T. Yamaguchi

2001-01-01

276

Early Clinical Experience with the Mobi-C Disc Prosthesis  

PubMed Central

Purpose We have experienced 23 patients who had underwent cervical disc replacement with Mobi-C disc prosthesis and analyzed their radiological results to evaluate its efficacy. Patients and Methods This study was performed on 23 patients with degenerative cervical disc disease who underwent CDR with Mobi-C disc prosthesis from March 2006 to June 2006. Results The age of the study population ranged from 31 to 62 years with mean of 43 years, and 16 male and 7 female cases. Regarding axial pain, the average preoperative VAS score was 6.47 ± 1.4, while at final follow-up it was 1.4 ± 0.7 (p < 0.001). The preoperatively VAS score for radiculopathy was 6.7 ± 0.7 compared with an average score of 0 ± 0 at the final follow-up (p < 0.001). At postoperative 6th month, Odom's criteria were excellent, good, or fair for all 23 patients (100%). 7 patients (30.4%) were classified as excellent, 15 patients (65.2%) as good, and 1 patients (4.4%) as fair. Prolo economic and functional rating scale was average 8.9 ± 0.7 at postoperative 6th month. ROM in C2-7, ROM of FSU, and ROM in upper adjacent level were well preserved after CDR. Conclusion This report would be the first document about the CDR with Mobi-C disc prosthesis in the treatment of degenerative cervical disc disease. CDR with Mobi-C disc prosthesis provided a favorable clinical and radiological outcome in this study. However, Long-term follow-up studies are required to prove its efficacy and ability to prevent adjacent segment disease.

Kim, Sang Hyun; Shin, Hyun Chul; Shin, Dong Ah; Kim, Keung Nyun

2007-01-01

277

Evaluation of optical coherence tomography findings in age-related macular degeneration: a reproducibility study of two independent reading centres  

Microsoft Academic Search

Background\\/aimsTo determine the reproducibility among readers of two independent certified centres, the Vienna Reading Center (VRC) and the University of Wisconsin-Madison Reading Center (UW-FPRC) for optical coherence tomography (OCT) images in age-related macular degeneration (AMD).MethodsFast macular thickness scans and 6 mm cross hair scans were obtained from 100 eyes with all subtypes of AMD using Stratus OCT. Consensus readings were

Markus Ritter; Julee Elledge; Christian Simader; Gabor G Deak; Thomas Benesch; Barbara A Blodi; Ursula M Schmidt-Erfurth

2010-01-01

278

Spectral-Domain versus Time Domain Optical Coherence Tomography before and after Ranibizumab for Age-Related Macular Degeneration  

Microsoft Academic Search

Purpose: To study the ability to appreciate qualitative features that indicate disease activity in patients with neovascular age-related macular degeneration (AMD) and to analyze the differences in automated retinal thickness measurement, using 1 time domain optical coherence tomography (TD-OCT) and 2 different spectral-domain OCT (SD-OCT) machines. Methods: Thirty-three consecutive naïve patients with neovascular AMD underwent Stratus TD-OCT, Cirrus SD-OCT and

Giuseppe Querques; Raimondo Forte; Elya Berboucha; Domenico Martinelli; Gabriel Coscas; Gisele Soubrane; Eric H. Souied

2011-01-01

279

The dispersal of protoplanetary discs  

NASA Astrophysics Data System (ADS)

Protoplanetary discs are a natural consequence of the star formation process and as such are ubiquitous around low-mass stars. They are fundamental to planet formation as they hold the reservoir of material from which planets form. Their evolution and final dispersal and the timescales that regulate these process are therefore of particular interest. In this contribution I will review the observational evidence for the dispersal of discs being dominated by two timescales and for the final dispersal to occur quickly and from the inside out. I will discuss the current theoretical models, including X-ray photoevaporation, showing that the latter provides a natural explanation to the observed behaviour and review supporting and contrasting evidence. I will finally introduce a new mechanism based on the interaction between planet formation and photoevaporation that may explain a particular class of transition discs with large inner holes and high accretion rates that are problematic for photoevaporation models and planet formation models alone.

Ercolano, Barbara

2013-04-01

280

The jets and disc of SS 433 at super-Eddington luminosities  

NASA Astrophysics Data System (ADS)

We examine the jets and the disc of SS 433 at super-Eddington luminosities with by time-dependent two-dimensional radiation hydrodynamical calculations, assuming an ?-model for the viscosity. One-dimensional supercritical accretion disc models with mass loss or advection are used as the initial configurations of the disc. As a result, from the initial advective disc models with ? = 0.001 and 0.1, we obtain total luminosities ~2.5 × 1040 and 2.0 × 1040ergs-1. The total mass-outflow rates are ~4 × 10-5 and 10-4Msolaryr-1, and the rates of the relativistic axial outflows in a small half opening angle of ~1° are about 10-6Msolaryr-1: the values are generally consistent with the corresponding observed rates of the wind and the jets, respectively. From the initial models with mass loss but without advection, we obtain total mass-outflow and axial outflow rates smaller than or comparable to the observed rates of the wind and the jets, respectively, depending on ?. In the advective disc model with ? = 0.1, the initially radiation-pressure-dominant, optically thick disc evolves to a gas-pressure-dominated, optically thin state in the inner region of the disc, and the inner disc is unstable. Consequently, we find remarkable modulations of the disc luminosity and the accretion rate through the inner edge. These modulations manifest themselves as recurrent hot blobs with high temperatures and low densities at the disc plane, which develop outwards and upwards and produce quasi-periodic oscillations (QPOs) of the total luminosity with an amplitude of a factor of ~2 and quasi-periods of ~10-25 s. This may explain the massive jet ejection and the QPO phenomena observed in SS 433.

Okuda, T.; Lipunova, G. V.; Molteni, D.

2009-10-01

281

PG 1700+518 Revisited: Adaptive-Optics Imaging and a Revised Starburst Age for the Companion  

NASA Astrophysics Data System (ADS)

We present the results of adaptive-optics imaging of the z=0.2923 QSO PG 1700+518 in the J and H bands. The extension to the north of the QSO is clearly seen to be a discrete companion with a well-defined tidal tail, rather than a feature associated with the host galaxy of PG 1700+518 itself. On the other hand, an extension to the southwest of the QSO (seen best in deeper, but lower resolution, optical images) does likely comprise tidal material from the host galaxy. The spectral energy distribution (SED) derived from images in J, H, and two nonstandard optical bands indicates the presence of dust intermixed with the stellar component. We use our previously reported Keck spectrum of the companion, the SED found from the imaging data, and updated spectral synthesis models to constrain the stellar populations in the companion and to redetermine the age of the starburst. While our best-fit age of 0.085 Gyr is nearly the same as our earlier determination, the fit of the new models is considerably better. This age is found to be remarkably robust with respect to different assumptions about the nature of the older stellar component and the effects of dust.

Stockton, Alan; Canalizo, Gabriela; Close, Laird M.

1998-06-01

282

Rewritable dual-layer blu-ray disc media  

NASA Astrophysics Data System (ADS)

The Blu-ray Disc (BD) optical recording system utilizes a blue laser (405 nm wavelength) in combination with a high-numerical-aperture (NA = 0.85) objective lens. This BD-format allows storing 23 - 27 GB on a single-layer and 46 - 54 GB on a dual-layer 12 cm disc at 36 Mbps user data rate. This paper reports on the design, manufacturing, and the recording performance of our dual-layer rewritable optical media. These media are based on the eutectic, fast-growth phase-change materials, which are promising candidates for high-speed applications. The performance of these materials in the case of dual-layer recording is discussed, with special attention for transmission balance for the semitransparent recording stack.

Mijiritskii, Andrei V.; Hellmig, Jochen; Borg, Herman J.; Vromans, Piet H.; Musialkova, Katerina; Van Haaren, Jos A.

2003-04-01

283

Polarimetry of Galactic Discs: A Brief Review  

NASA Astrophysics Data System (ADS)

This paper reviews galactic discs observed in polarimetry at optical to mid-IR (MIR) wavelengths. Polarization maps of galaxies can be used as probes of galactic dust chemistry, dust distribution, and of the large-scale magnetic fields that thread through galaxies. Whilst polarimeters have been available to galaxy researchers for numerous years, it became clear during the literature survey for this review that there has been relatively little research performed in this field, either observationally or theoretically. This paper therefore concentrates on a limited number of papers in greater detail, and discusses the closely related field of activity in galactic nuclei (AGN). After providing this disclaimer, we apologize to those authors whose work is not included in this review.

Packham, C.; Young, S.; Axon, D. J.

2011-11-01

284

Combining Information From 3 Anatomic Regions in the Diagnosis of Glaucoma With Time-Domain Optical Coherence Tomography.  

PubMed

PURPOSE:: To improve the diagnosis of glaucoma by combining time-domain optical coherence tomography (TD-OCT) measurements of the optic disc, circumpapillary retinal nerve fiber layer (RNFL), and macular retinal thickness. PATIENTS AND METHODS:: Ninety-six age-matched normal and 96 perimetric glaucoma participants were included in this observational, cross-sectional study. Or-logic, support vector machine, relevance vector machine, and linear discrimination function were used to analyze the performances of combined TD-OCT diagnostic variables. RESULTS:: The area under the receiver-operating curve (AROC) was used to evaluate the diagnostic accuracy and to compare the diagnostic performance of single and combined anatomic variables. The best RNFL thickness variables were the inferior (AROC=0.900), overall (AROC=0.892), and superior quadrants (AROC=0.850). The best optic disc variables were horizontal integrated rim width (AROC=0.909), vertical integrated rim area (AROC=0.908), and cup/disc vertical ratio (AROC=0.890). All macular retinal thickness variables had AROCs of 0.829 or less. Combining the top 3 RNFL and optic disc variables in optimizing glaucoma diagnosis, support vector machine had the highest AROC, 0.954, followed by or-logic (AROC=0.946), linear discrimination function (AROC=0.946), and relevance vector machine (AROC=0.943). All combination diagnostic variables had significantly larger AROCs than any single diagnostic variable. There are no significant differences among the combination diagnostic indices. CONCLUSIONS:: With TD-OCT, RNFL and optic disc variables had better diagnostic accuracy than macular retinal variables. Combining top RNFL and optic disc variables significantly improved diagnostic performance. Clinically, or-logic classification was the most practical analytical tool with sufficient accuracy to diagnose early glaucoma. PMID:22828002

Wang, Mingwu; Lu, Ake Tzu-Hui; Varma, Rohit; Schuman, Joel S; Greenfield, David S; Huang, David

2012-07-23

285

Effect of Aging on the Mechanical Properties of UV Curable Optical Fiber Coatings  

Microsoft Academic Search

A dual-layer urethane acrylate UV-cured coating is widely used to protect optical fibers because of its well-balanced mechanical properties, weathering resistance and rapid curing. The long-term mechanical behavior of fiber coatings is important for the reliability of optical fibers. Long-term exposure of UV-cured polyether urethane acrylate films was carried out in dry air and in water at elevated temperatures. Tensile

P.-A. Högström; S. Karlsson; U. W. Gedde

2000-01-01

286

46 CFR 64.61 - Rupture disc.  

Code of Federal Regulations, 2011 CFR

...SECURITY (CONTINUED) MARINE ENGINEERING MARINE PORTABLE TANKS AND CARGO HANDLING SYSTEMS Pressure Relief Devices and Vacuum Relief Devices for MPTs § 64.61 Rupture disc. If a rupture disc is the only pressure relief device on the tank,...

2011-10-01

287

Optically stimulated luminescence age controls on late Pleistocene and Holocene coastal lithosomes, North Carolina, USA  

Microsoft Academic Search

Luminescence ages from a variety of coastal features on the North Carolina Coastal Plain provide age control for shoreline formation and relative sea-level position during the late Pleistocene. A series of paleoshoreline ridges, dating to Marine Isotope Stage (MIS) 5a and MIS 3 have been defined. The Kitty Hawk beach ridges, on the modern Outer Banks, yield ages of 3

David Mallinson; Kevin Burdette; Shannon Mahan; George Brook

2008-01-01

288

Two-level total lumbar disc replacement  

Microsoft Academic Search

Total lumbar disc replacement (TDR) has been widely used as a treatment option for 2-level symptomatic degenerative disc disease.\\u000a However, recent studies have presented conflicting results and some authors concluded that outcome deteriorated when disc\\u000a replacement was performed bisegmentally, with an increase of complications for bisegmental replacements in comparison with\\u000a monosegmental disc arthroplasty. The goal of the present retrospective study

Mario Di Silvestre; Georgios Bakaloudis; Francesco Lolli; Francesco Vommaro; Patrizio Parisini

2009-01-01

289

Disc haemorrhages, precursors of open angle glaucoma  

Microsoft Academic Search

In a long-term study of 1270 patients with at least one of the findings, open-angle glaucoma, disc haemorrhages or retinal vein occlusions, disc haemorrhages were witnessed in approximately 20% of the cases with open-angle glaucoma, and were a precursor of glaucomatous disc changes and associated visual field defects. Disc haemorrhages also preceded a rising intraocular pressure (IOP) in the destructive

Bo Sonnsjö; Yvonne Dokmo; Torsten Krakau

2002-01-01

290

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

291

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

292

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

293

Disc frequencies for brown dwarfs in the Upper Scorpius OB association: implications for brown dwarf formation theories  

NASA Astrophysics Data System (ADS)

We have investigated the brown dwarf (BD) and stellar disc fractions in the Upper Scorpius (USco) OB association and compared them with several other young regions. We have compiled the most complete sample of all spectroscopically confirmed BDs in USco and have made use of the Wide-field Infrared Survey Explorer (WISE) catalogue to identify the disc candidates. We report on the discovery of 12 new BD discs in USco, with spectral types between M6 and M8.5. The WISE colours for the new discs are similar to the primordial (transition) discs earlier detected in USco. Combining with previous surveys, we find the lowest inner disc fractions (˜20-25 per cent) for a wide range in stellar masses (˜0.01-4.0 M?) in the USco association. The low disc fractions for high-mass stars in USco (and the other clusters) are consistent with an evolutionary decline in inner disc frequency with age. However, BD disc fractions are higher than those for the stars in 1-3 Myr clusters, but very low in the ˜5 Myr old USco. Also, primordial BD discs are still visible in the ˜10 Myr old TW Hydrae association, whereas the higher mass stars have all transitioned to the debris stage by this age. The disc frequencies for BDs and low-mass stars do not show any dependence on the stellar density or the BD/star number ratio in a cluster. We also find no convincing evidence that any of the well-known disc dispersal mechanisms for stars are active in BD discs. We suggest that the large differences in the observed BD disc fractions between regions may well be due to different BD formation mechanisms and therefore different initial disc fractions/properties. We also present a WISE spectral energy distribution classification scheme, based on the Ks and WISE bands of 3.4-12 ?m. We have determined certain thresholds in the WISE spectral slope versus spectral type diagrams to distinguish between the red population of Class I/II systems and the Class III sequence. We have found the WISE [3.4] - [12] colour to provide the best distinction between the photospheric and the disc population. Our work includes a comparison of the sensitivities of WISE and Spitzer disc surveys. We estimate that WISE can be incomplete for discs at spectral type later than M8 in distant clusters such as SOri. WISE should be able to recover the M8-M9 discs in the nearby young clusters.

Riaz, B.; Lodieu, N.; Goodwin, S.; Stamatellos, D.; Thompson, M.

2012-03-01

294

Stable counteralignment of a circumbinary disc  

NASA Astrophysics Data System (ADS)

In general, when gas accretes on to a supermassive black hole (SMBH) binary, it is likely to have no prior knowledge of the binary angular momentum. Therefore, a circumbinary disc forms with a random inclination angle ? to the binary. It is known that for ? < 90° the disc will coalign with respect to the binary. If ? > 90°, the disc wholly counteraligns if it satisfies cos ? < -Jd/2Jb, where Jd and Jb are the magnitudes of the disc and binary angular momentum vectors, respectively. If, however, ? > 90° and this criterion is not satisfied, the same disc may counteralign its inner regions and, on longer time-scales, coalign its outer regions. I show that for typical disc parameters, describing an accretion event on to an SMBH binary, a misaligned circumbinary disc is likely to wholly coalign or counteralign with the binary plane. This is because the binary angular momentum dominates the disc angular momentum. However, with extreme parameters (binary mass ratio M2/M1? 1 or binary eccentricity e˜ 1), the same disc may simultaneously coalign and counteralign. It is known that coplanar prograde circumbinary discs are stable. I show that coplanar retrograde circumbinary discs are also stable. A chaotic accretion event on to an SMBH binary will therefore result in a coplanar circumbinary disc that is either prograde or retrograde with respect to the binary plane.

Nixon, Christopher J.

2012-07-01

295

Modelling the Milky Way disc  

NASA Astrophysics Data System (ADS)

RAVE, SEGUE and Hipparcos data are used to study the dynamics of stars in the extended solar neighbourhood. The asymmetric drift of thin disc dwarfs is studied as a function of colour and metallicity. Linear extrapolation of the data falls within the error bars from Aumer & Binney (2009) for local standard of rest. The observed metallicity dependence of the asymmetric drift is consistent with the known radial metallicity distribution in the disc. Implying the asymmetric drift correction to the SEGUE data allows us to reconstruct the behaviour of the rotation curve of the Milky Way in the extended solar neighbourhood. The rotation curve appears to be essentially flat, giving no hint for a dip just outside the solar radius followed by an increase observed in some other data sets. The data are supplemented by tangent point measurements for the inner rotation curve. Thus a synthetic rotation curve of the Milky Way is obtained. It is fitted by a density model consisting of a D! ehnen bulge, an exponential disc with a hole, and a flattened dark matter halo with either cored isothermal or NFW density profile. In this fitting the parameters are constrained to reproduce the local surface density of the disc and the local volume density of the halo, which are known from local stellar dynamics in the solar neighbourhood. Thus the density model of the Milky Way is reconstructed. The vertical structure of the disc of theMilkyWay is consistent with the model by Just & Jahreiß (2010). Some basic features of distribution functions of the Milky Way and of the dynamical heating are also discussed.

Golubov, Oleksiy

2012-10-01

296

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

297

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

298

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

299

Peripheral Disc Margin Shape and Internal Disc Derangement: Imaging Correlation in Significantly Painful Discs Identified at Provocation Lumbar Discography  

PubMed Central

Summary Annular margin shape is used to characterize lumbar disc abnormality on CT/MR imaging studies. Abnormal discs also have internal derangement including annular degeneration and radial defects. The purpose of this study was to evaluate potential correlation between disc-margin shape and annular internal derangement on post-discogram CT in significantly painful discs encountered at provocation lumbar discography (PLD). Significantly painful discs were encountered at 126 levels in 86 patients (47 male, 39 female) studied by PLD where no prior surgery had been performed and response to intradiscal lidocaine after provocation resulted in either substantial/total relief or no improvement after lidocaine administration. Post-discogram CT and discogram imaging was evaluated for disc-margin characteristics (bulge/protrusion), features of disc internal derangement (radial annular defect [RD: radial tear/fissure/annular gap], annular degeneration) and presence/absence of discographic contrast leakage. In discs with focal protrusion, 50 of 63 (79%) demonstrated Grade 3 RD with 13 (21%) demonstrating severe degenerative change only. In discs with generalized-bulge-only, 48 of 63 (76%) demonstrated degenerative change only (primarily Dallas Grade 3) with 15 of 63 (24%) demonstrating a RD (Dallas Grade 3). Differences were highly statistically significant (p<0.001). Pain elimination with intra-discal lidocaine correlated with discographic contrast leakage (p<0.001). Disc-margin shape correlates with features of internal derangement in significantly painful discs encountered at PLD. Discs with focal protrusion typically demonstrate RD while generalized bulging discs typically demonstrated degenerative changes only (p<0.001). Disc-margin shape may provide an important imaging clue to the cause of chronic discogenic low back pain.

Bartynski, W.S.; Rothfus, W.E.

2012-01-01

300

Peripheral disc margin shape and internal disc derangement: imaging correlation in significantly painful discs identified at provocation lumbar discography.  

PubMed

Annular margin shape is used to characterize lumbar disc abnormality on CT/MR imaging studies. Abnormal discs also have internal derangement including annular degeneration and radial defects. The purpose of this study was to evaluate potential correlation between disc-margin shape and annular internal derangement on post-discogram CT in significantly painful discs encountered at provocation lumbar discography (PLD). Significantly painful discs were encountered at 126 levels in 86 patients (47 male, 39 female) studied by PLD where no prior surgery had been performed and response to intradiscal lidocaine after provocation resulted in either substantial/total relief or no improvement after lidocaine administration. Post-discogram CT and discogram imaging was evaluated for disc-margin characteristics (bulge/protrusion), features of disc internal derangement (radial annular defect [RD: radial tear/fissure/annular gap], annular degeneration) and presence/absence of discographic contrast leakage. In discs with focal protrusion, 50 of 63 (79%) demonstrated Grade 3 RD with 13 (21%) demonstrating severe degenerative change only. In discs with generalized-bulge-only, 48 of 63 (76%) demonstrated degenerative change only (primarily Dallas Grade 3) with 15 of 63 (24%) demonstrating a RD (Dallas Grade 3). Differences were highly statistically significant (p<0.001). Pain elimination with intra-discal lidocaine correlated with discographic contrast leakage (p<0.001). Disc-margin shape correlates with features of internal derangement in significantly painful discs encountered at PLD. Discs with focal protrusion typically demonstrate RD while generalized bulging discs typically demonstrated degenerative changes only (p<0.001). Disc-margin shape may provide an important imaging clue to the cause of chronic discogenic low back pain. PMID:22681741

Bartynski, W S; Rothfus, W E

2012-06-04

301

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

302

Stem cell therapy for degenerative disc disease.  

PubMed

Low back pain is widely recognized as one of the most prevalent pathologies in the developed world. In the United States, low back pain is the most common health problem for adults under the age of 50, resulting in significant societal and personal costs. While the causes of low back pain are myriad, it has been significantly associated with intervertebral disc (IVD) degeneration. Current first-line therapies for IVD degeneration such as physical therapy and spinal fusion address symptoms, but do not treat the underlying degeneration. The use of tissue engineering to treat IVD degeneration provides an opportunity to correct the pathological process. Novel techniques are currently being investigated and have shown mixed results. One major avenue of investigation has been stem cell injections. Mesenchymal stem cells (MSCs) have shown promise in small animal models, but results in larger vertebrates have been mixed. PMID:22593830

Drazin, Doniel; Rosner, Jack; Avalos, Pablo; Acosta, Frank

2012-04-24

303

Stem Cell Therapy for Degenerative Disc Disease  

PubMed Central

Low back pain is widely recognized as one of the most prevalent pathologies in the developed world. In the United States, low back pain is the most common health problem for adults under the age of 50, resulting in significant societal and personal costs. While the causes of low back pain are myriad, it has been significantly associated with intervertebral disc (IVD) degeneration. Current first-line therapies for IVD degeneration such as physical therapy and spinal fusion address symptoms, but do not treat the underlying degeneration. The use of tissue engineering to treat IVD degeneration provides an opportunity to correct the pathological process. Novel techniques are currently being investigated and have shown mixed results. One major avenue of investigation has been stem cell injections. Mesenchymal stem cells (MSCs) have shown promise in small animal models, but results in larger vertebrates have been mixed.

Drazin, Doniel; Rosner, Jack; Avalos, Pablo; Acosta, Frank

2012-01-01

304

Sixteen-Layer Write Once Disc with a Separated Guide Layer  

NASA Astrophysics Data System (ADS)

We proposed a new recordable multilayer optical disc and its recording system. The new optical disc has multiple-plane-recordable layers and a separated guide layer, and we fabricated 16 recording layers made of high-transmittance inorganic recording materials stacked on the separated guide layer. The recorded signals were evaluated on all recording layers by using jitter and i-MLSE as the evaluation indicators. As a result, the technical feasibility of our proposal was confirmed to achieve the total capacities of 400 and 512 Gbytes, respectively, by the continuous recording of all 16 recording layers with a track pitch of 0.32 ?m and two bit lengths. We believe that our multilayer optical disc and recording system are the most practical solutions for realizing huge-capacity data storage.

Ogasawara, Masakazu; Takahashi, Kazuo; Nakano, Masaharu; Inoue, Motohiro; Kosuda, Atsuko; Kikukawa, Takashi

2011-09-01

305

Ochronosis and lumbar disc herniation  

Microsoft Academic Search

Summary  Alkaptonuria is a rare, autosomal recessive metabolic disorder in which the homogentisic acid oxidase activity is absent.\\u000a Its incidence is as low as 0.001%. Ochronosis is the pigmentation of connective tissues and this pigmentation leads to degenerative\\u000a changes in alkaptonuric patients.\\u000a \\u000a Alkaptonuria most prominently involves the lumbar region, but lumbar disc herniation as the presenting feature of alkaptonuria\\u000a is not

D. Gürkanlar; M. Daneyemez; I. Solmaz; C. Temiz

2006-01-01

306

Anterior Ischemic Optic Neuropathy Associated with Udenafil  

PubMed Central

We report a case of anterior ischemic optic neuropathy associated with udenafil. A 54-year-old male presented with an acute onset visual field defect of the right eye after udenafil use. Examination revealed a relative afferent pupillary defect and a swollen disc. Automated visual fields revealed an enlarged blind spot and a narrowed visual field. Fluorescein angiography revealed both an inferior choroidal filling delay and an inferior sector filling delay of the optic disc in the arteriovenous phase as well as diffuse leakage of the optic disc in the late phase. Optical coherent tomography revealed increased thickness of the retinal nerve fiber layer, especially in the area of the inferior disc. The patient was counseled to discontinue the use of udenafil and to monitor his blood pressure regularly. The disc swelling was resolved with residual optic atrophy one month after discontinuing the use of udenafil.

Kim, In-Gun

2012-01-01

307

Accretion discs trapped near corotation  

NASA Astrophysics Data System (ADS)

We show that discs accreting on to the magnetosphere of a rotating star can end up in a trapped state, in which the inner edge of the disc stays near the corotation radius, even at low and varying accretion rates. The accretion in these trapped states can be steady or cyclic; we explore these states over a wide range of parameter space. We find two distinct regions of instability: one related to the buildup and release of mass in the disc outside corotation, and the other to mass storage within the transition region near corotation. With a set of calculations over long time-scales, we show how trapped states evolve from both non-accreting and fully accreting initial conditions, and also calculate the effects of cyclic accretion on the spin evolution of the star. Observations of cycles such as found here would provide important clues on the physics of magnetospheric accretion. Recent observations of cyclic and other unusual variability in T Tauri stars (EXors) and X-ray binaries are discussed in this context.

D'Angelo, Caroline R.; Spruit, Hendrik C.

2012-02-01

308

Percutaneous cervical nucleoplasty in the treatment of cervical disc herniation.  

PubMed

Percutaneous disc decompression procedures have been performed in the past. Various percutaneous techniques such as percutaneous discectomy, laser discectomy, and nucleoplasty have been successful. Our prospective study was directly to evaluate the results of percutaneous cervical nucleoplasty (PCN) surgery for cervical disc herniation, and illustrate the effectiveness of PCN in symptomatic patients who had cervical herniated discs. From July of 2002 to June of 2005, 126 consecutive patients with contained cervical disc herniations have presented at the authors' clinic and treated by PCN. The patients' gender distribution for PCN was 65 male, 61 female. The age of patients ranged from 34 to 66 years (mean 51.9 +/- 10.2 years). The levels of involvement were 21 cases at C3-4, 30 cases at C4-5, 40 cases at C5-6, and 35 cases at C6-7. The clinical outcomes, pain reduction and the segment stability were all recorded during this study. A clinical outcome was quantified by the Macnab standard and using VAS. The angular displacement (AD) > or =11 degrees or horizontal displacement (HD) > or =3 mm was considered to be radiographically unstable. In the results of this study, puncture of the needle into the disc space was accurately performed under X-ray guidance in all cases. There was one case where the Perc-D Spine Wand had broken in the disc space during the procedure. The partial Perc-D Spine Wand, which had broken in the disc space could not be removed by the percutaneous cervical discectomy and thus remained there. There were no recurrent cases or complications in our series. Macnab standard results were excellent in 62 cases, good in 41 cases and fair in 23 cases. The rate of excellent and good was 83.73%. The VAS scores demonstrated statistically significant improvement in PCN at the 2-week, 1, 3, 6, and 12-month follow-up visits when compared to preoperational values (P < 0.01). There were no cases of instability following the PCN procedure. There was no significant difference in stability either preoperatively or postoperatively (P > 0.05). Our findings confirm that PCN for the treatment of cervical disc herniation results in a good outcome without any tampering of the stability of the cervical spine. Hence, PCN as a procedure is safe, minimally invasive, less traumatic, requiring less time with an excellent clinical outcome. PCN should be performed for those patients who fail conservative medical management including medication, physical therapy, behavioral management, psychotherapy, and who are unwilling to undergo a more invasive technique such as spinal surgery. PMID:18830638

Li, Jian; Yan, Deng-lu; Zhang, Zai-Heng

2008-10-01

309

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

310

Optical properties of aged Asian aerosols observed over the U.S. Pacific Northwest  

NASA Astrophysics Data System (ADS)

A suite of gas-phase and aerosol measurements were made during spring 2008 and spring 2009 at the Mount Bachelor Observatory (2763 masl), located in Oregon. Here we focus on multiwavelength observations of low RH submicron (?m) aerosol scattering (?sp) and absorption (?ap), made with an integrating nephelometer and a particle soot absorption photometer. Using a combination of in situ observations, trajectory calculations and satellite observations, we identified seven plumes of Asian origin. These plumes included many of the highest ?sp (34.8 Mm-1) and ?ap (5.7 Mm-1) hourly average values observed at MBO over the 2008 and 2009 campaigns. Of interest in this analysis is (1) whether the intensive optical properties differ between these seven plumes, (2) whether these differences can be linked to differences in composition, and (3) whether the intensive optical properties change during transpacific transport. Results show that the plumes clustered in terms of their optical properties; plumes hypothesized to contain a large fraction of mineral dust were the most distinct. We observed variability between plumes in the scattering Ångström (Ås) exponent. The average submicrometer Ås for all seven plumes was significantly larger than the same parameter observed closer to Asia. Therefore, we hypothesize that the aerosol size distribution shifts toward smaller particles during transpacific transport. The average submicrometer low-RH aerosol single scatter albedo (?) observed at MBO (0.88) was slightly larger than previous observations closer to the Asian coast, and the average backscatter fraction (b) was smaller, on the order of 20%.

Fischer, E. V.; Jaffe, D. A.; Marley, N. A.; Gaffney, J. S.; Marchany-Rivera, A.

2010-10-01

311

Optically stimulated luminescence age controls on late Pleistocene and Holocene coastal lithosomes, North Carolina, USA  

USGS Publications Warehouse

Luminescence ages from a variety of coastal features on the North Carolina Coastal Plain provide age control for shoreline formation and relative sea-level position during the late Pleistocene. A series of paleoshoreline ridges, dating to Marine Isotope Stage (MIS) 5a and MIS 3 have been defined. The Kitty Hawk beach ridges, on the modern Outer Banks, yield ages of 3 to 2??ka. Oxygen-isotope data are used to place these deposits in the context of global climate and sea-level change. The occurrence of MIS 5a and MIS 3 shorelines suggests that glacio-isostatic adjustment (GIA) of the study area is large (ca. 22 to 26??m), as suggested and modeled by other workers, and/or MIS 3 sea level was briefly higher than suggested by some coral reef studies. Correcting the shoreline elevations for GIA brings their elevation in line with other sea-level indicators. The age of the Kitty Hawk beach ridges places the Holocene shoreline well west of its present location at ca. 3 to 2??ka. The age of shoreline progradation is consistent with the ages of other beach ridge complexes in the southeast USA, suggesting some regionally contemporaneous forcing mechanism. ?? 2007 University of Washington.

Mallinson, D.; Burdette, K.; Mahan, S.; Brook, G.

2008-01-01

312

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

313

OPTICAL-ULTRAVIOLET SPECTRUM AND PROPER MOTION OF THE MIDDLE-AGED PULSAR B1055-52  

SciTech Connect

PSR B1055-52 is a middle-aged ({tau} = 535 kyr) radio, X-ray, and {gamma}-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 (PL{sub O}) component (F{sub {nu}}{proportional_to}{nu}{sup -}{alpha}{sub O}), presumably emitted from the pulsar magnetosphere, and a Rayleigh-Jeans (RJ) component emitted from the NS surface. The spectral index of the PL{sub O} component, {alpha}{sub O} = 1.05 {+-} 0.34, is larger than for other pulsars with optical counterparts. The RJ component, with a brightness temperature T {sub O} = (0.66 {+-} 0.10) d {sup 2} {sub 350} R {sup -2} {sub O,13} MK (where d {sub 350} and R {sub 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 0.''15. From comparison with previous observations, we measured the pulsar proper motion, {mu} = 42 {+-} 5 mas yr{sup -1}, which corresponds to a transverse velocity V{sub t} = (70 {+-} 8) d {sub 350} km s{sup -1}.

Mignani, R. P. [Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey, RH5 6NT (United Kingdom); Pavlov, G. G. [Department of Astronomy and Astrophysics, Pennsylvania State University, PA 16802 (United States); Kargaltsev, O., E-mail: rm2@mssl.ucl.ac.u, E-mail: pavlov@astro.psu.ed, E-mail: oyk100@astro.ufl.ed [Department of Astronomy, University of Florida, FL 32611 (United States)

2010-09-10

314

Accretion discs with strong toroidal magnetic fields  

NASA Astrophysics Data System (ADS)

Simulations and analytic arguments suggest that the turbulence driven by magnetorotational instability (MRI) in accretion discs can amplify the toroidal (azimuthal) component of the magnetic field to a point at which magnetic pressure exceeds the combined gas + radiation pressure in the disc. Arguing from the recent analysis by Pessah & Psaltis, and other MRI results in the literature, we conjecture that the limiting field strength for a thin disc is such that the Alfvén speed roughly equals the geometric mean of the Keplerian speed and the speed of sound in gas. We examine the properties of such magnetically dominated discs, and show that they resolve a number of outstanding problems in accretion disc theory. The discs would be thicker than standard (Shakura-Sunyaev) discs at the same radius and accretion rate, and would tend to have higher colour temperatures. If they transport angular momentum according to an ? prescription, they would be stable against the thermal and viscous instabilities that are found in standard disc models. In discs fuelling active galactic nuclei, magnetic pressure support could also alleviate the restriction on accretion rate imposed by disc self-gravity.

Begelman, M. C.; Pringle, J. E.

2007-03-01

315

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

316

Effect of Slow Aging Reactions on Optical Properties of Secondary Organic Aerosol Prepared by Oxidation of Selected Monoterpenes  

NASA Astrophysics Data System (ADS)

Organic particulate matter (PM) has a major impact on atmospheric chemistry, climate, and human health. Secondary organic aerosol (SOA) accounts for a rather significant fraction of organic PM; this includes SOA produced by oxidation of biogenically emitted monoterpenes. Once such SOA is formed, it is believed to undergo slow aging processes, which may have large effects on the physical and chemical properties of the particles. This presentation focuses on the effect of slow chemical aging on optical properties of SOA formed from the ozone-induced oxidation of limonene, myrcene, and other selected monoterpenes. Several complementary techniques including high resolution electrospray ionization mass spectrometry, FTIR spectroscopy, UV/vis spectroscopy, NMR spectroscopy, 3D-fluorescence spectroscopy, and photodissociation spectroscopy are used to probe the aging-induced changes in physical properties and chemical composition of laboratory generated SOA. Limonene SOA appears to undergo a dramatic change in its absorption spectrum on a time scale of hours; it develops strong visible bands in the 400-500 nm region, and becomes fluorescent. This transformation is catalyzed by ammonium sulfate and certain amino acids. This rather unusual aging process can potentially contribute to the formation of brown carbon in biogenic SOA.

Nizkorodov, S. A.; Bones, D. L.; Henricksen, D. K.; Mang, S. A.; Bateman, A. P.; Pan, X.; Nguyen, T. B.; Gonsior, M.; Cooper, W.; Laskin, J.; Laskin, A.

2009-05-01

317

The bar PANDA Focussing-Lightguide Disc DIRC  

NASA Astrophysics Data System (ADS)

bar PANDA will be a fixed target experiment internal to the HESR antiproton storage ring at the future FAIR complex. The bar PANDA detector requires excellent particle-identification capabilities in order to achieve its scientific potential. Cherenkov counters employing the DIRC principle were chosen as PID detectors for the Target Spectrometer. The proposed Focussing-Lightguide Disc DIRC will cover the forward part of the Target Spectrometer acceptance in the angular range between 5° and 22°. Its design includes a novel approach to mitigate dispersion effects in the solid radiator of a DIRC counter using optical elements. The dispersion correction will enable the Focussing-Lightguide Disc DIRC to provide pion-kaon identification for momenta well above 3.5 GeV/c.

Cowie, E.; Föhl, K.; Glazier, D.; Hill, G.; Hoek, M.; Kaiser, R.; Keri, T.; Murray, M.; Rosner, G.; Seitz, B.

2009-09-01

318

Thermal emission of a disc body of semitransparent material  

NASA Astrophysics Data System (ADS)

By introducing the concept of radiosity intensity to diffuse surfaces, the ray tracing method is improved to analyze the thermal emission of a disc body of gray semitransparent material. The two plane surfaces of the disc body are both specularly reflecting, and the flank surface is either diffusely reflecting or specularly reflecting. The apparent thermal emission from one plane surface is investigated with considering the influences of the characteristic optical thickness, the dimensionless radius, the refractive index of the material and the reflecting characteristics of the flank surface. The directional and hemispherical emissions show considerable differences under different reflecting characteristics of the flank surface. Moreover, in some cases, the emission not only varies with the viewing direction but also with the apparent emitting position on the plane surface. Some interesting results are presented and discussed.

Xia, Xinlin; Tan, Heping; Yu, Qizheng; Sun, Fengxian

1998-09-01

319

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

320

Heidelberg Retina Tomography Analysis in Optic Disks with Anatomic Particularities  

PubMed Central

Due to its objectivity, reproducibility and predictive value confirmed by many large scale statistical clinical studies, Heidelberg Retina Tomography has become one of the most used computerized image analysis of the optic disc in glaucoma. It has been signaled, though, that the diagnostic value of Moorfieds Regression Analyses and Glaucoma Probability Score decreases when analyzing optic discs with extreme sizes. The number of false positive results increases in cases of megalopapilllae and the number of false negative results increases in cases of small size optic discs. The present paper is a review of the aspects one should take into account when analyzing a HRT result of an optic disc with anatomic particularities.

Alexandrescu, C; Pascu, R; Ilinca, R; Popescu, V; Ciuluvica, R; Voinea, L; Celea, C

2010-01-01

321

On the properties of discs around accreting brown dwarfs  

NASA Astrophysics Data System (ADS)

We present a grid of models of accreting brown dwarf systems with circumstellar discs. The calculations involve a self-consistent solution of both vertical hydrostatic and radiative equilibrium along with a sophisticated treatment of dust sublimation. We have simulated observations of the spectral energy distributions and several broad-band photometric systems. Analysis of the disc structures and simulated observations reveals a natural dichotomy in accretion rates, with ? and ?-9 classed as extreme and typical accretors, respectively. Derivation of ages and masses from our simulated photometry using isochrones is demonstrated to be unreliable even for typical accretors. Although current brown dwarf disc candidate selection criteria have been shown to be largely reliable when applied to our model grid we suggest improved selection criteria in several colour indices. We show that as accretion rates increase brown dwarf disc systems are less likely to be correctly identified. This suggests that, within our grid, systems with higher accretion rates would be preferentially lost during brown dwarf target selection. We suggest that observations used to assert a ? relationship may contain an intrinsic selection bias.

Mayne, Nathan J.; Harries, Tim J.

2010-12-01

322

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

323

Formation of galaxies in ?cold dark matter cosmologies - I. The fine structure of disc galaxies  

NASA Astrophysics Data System (ADS)

In this work we present a detailed analysis of the global and fine structure of four middle-mass disc galaxies obtained from hydrodynamic simulations in a ?cold dark matter (?CDM) scenario. These objects have photometric disc-to-total ratios in good agreement with those observed for late-type spirals, as well as kinematic properties in agreement with the observational I-band Tully-Fisher relation. We identify the different dynamical components at redshift zero on the basis of both orbital parameters and the binding energy of stars in the galaxy. In this way, we recognize a slowly rotating centrally concentrated spheroid, and two disc components supported by rotation: a thin disc with stars in nearly circular orbits, and a thick disc with orbital parameters transitional between the thin disc and the spheroid. The spheroidal component is composed mainly by old, metal-poor and ?-enhanced stars. The distribution of metals in this component shows, however, a clear bimodality with a low-metallicity peak, which could be related to a classical bulge formed from rapid collapse at early times, and a high-metallicity peak, which could be related to a pseudo-bulge formed from instabilities of the inner disc. The thin disc appears in our simulations as the youngest and most metal-rich component, with median stellar ages ranging from 3.8 to 6.7 Gyr. The radial distribution of ages and colours in this component is U-shaped: the new stars are forming in the inner regions, where the galaxy is bluer, and then migrate through secular processes reaching the outer parts. Finally, we also find in all simulated galaxies a thick disc containing about 16 per cent of the total stellar mass and with properties that are intermediate between those of the thin disc and the spheroid. Its low-metallicity stars are ?-enhanced when compared to thin disc stars of the same metallicity. The structural parameters (e.g. the scale height) of the simulated thick discs suggest that such a component could result from the combination of different thickening mechanisms that include merger-driven processes, but also long-lived internal perturbations of the thin disc.

Doménech-Moral, M.; Martínez-Serrano, F. J.; Domínguez-Tenreiro, R.; Serna, A.

2012-04-01

324

Application of Optical Diagnosis to Aged Low-Voltage Cable Insulation in Nuclear Plants  

NASA Astrophysics Data System (ADS)

We have developed a novel non-destructive optical diagnosis technique for low-voltage cable insulations used in nuclear power plants. The key features of this diagnosis are the use of two wavelengths to measure the change in reflective absorbance (?AR), the use of polarized light to measure crystallinity and the use of element volatilizing to measure fluorescence. Chemical kinetics is used to predict the lifetimes of the cable insulations. When cable insulations darken and harden by time degradation, the ?AR and depolarization parameters increase. This means that the cross-linking density in the cable insulations increases due to deterioration reactions. When the cross-linking density of insulation increases, its elasticity, corresponding to the material's life, increases. Similarly, as the crystallinity increases due to the change in the high-order structure of the insulating resin caused by irradiation, its elongation property decreases. The elongation property of insulation is one of the most important parameters that can be used to evaluate material lifetimes, because it relates to elasticity. The ?AR correlated with the elongation property, and the correlation coefficient of an accelerated experiment using model pieces was over 0.9. Thus, we concluded that this optical diagnosis should be applied to evaluate the degradation of cable insulations used in nuclear power plants.

Katagiri, Junichi; Takezawa, Yoshitaka; Shouji, Hiroshi

325

Effect of age-stiffening tissues and intraocular pressure on optic nerve damages.  

PubMed

Age-stiffening of ocular tissues is statistically linked to glaucoma in the elderly. In this study, the effects of age-stiffening on the lamina cribrosa, the primary site of glaucomatous nerve damages, were modeled using computational finite element analysis. We showed that glaucomatous nerve damages and peripheral vision loss behavior can be phenomenologically modeled by shear-based damage criterion. Using this damage criterion, the potential vision loss for 30 years old with mild hypertension of 25 mmHg intraocular pressure (IOP) was estimated to be 4%. When the IOP was elevated to 35 mmHg, the potential vision loss rose to 45%; and age-stiffening from 35 to 60 years old increased the potential vision loss to 52%. These results showed that while IOP plays a central role in glaucomatous damages, age-stiffening facilitates glaucomatous damages and may be the principal factor that resulted in a higher rate of glaucoma in the elderly than the general population. PMID:23113376

Leung, Leo K K; Ko, Match W L; Lam, David C C

2012-06-01

326

Magnetic field dragging in accretion discs  

NASA Astrophysics Data System (ADS)

Accretion discs are composed of ionized gas in motion around a central object. Sometimes, the disc is the source of powerful bipolar jets along its rotation axis. Theoretical models invoke the existence of a bipolar magnetic field crossing the disc and require two conditions to produce powerful jets: field lines need to be bent enough at the disc surface and the magnetic field needs to be close to equipartition. The work of Petrucci et al (2008) on the variability of X-ray binaries supposes that transitions between pure accretion phases and accretion-ejection phases are due to some variations of the disc magnetization. This rises the problem of the magnetic field dragging in accretion discs. We revisit the method developed by Lubow et al (1994) by including momentum and mass conservation equations in a time-dependent 1D MHD code.

de Guiran, R.; Ferreira, J.

2010-12-01

327

MSC response to pH levels found in degenerating intervertebral discs  

Microsoft Academic Search

Painful degenerative disc disease is a major health problem and for successful tissue regeneration, MSCs must endure and thrive in a harsh disc microenvironment that includes matrix acidity as a critical factor. MSCs were isolated from bone marrow of Sprague–Dawley rats from two different age groups (<1 month, n=6 and 4–5 months, n=6) and cultured under four different pH conditions

Karin Wuertz; Karolyn Godburn; James C. Iatridis

2009-01-01

328

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.

2013-09-01

329

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

330

Resolved debris discs around A stars in the Herschel DEBRIS survey  

NASA Astrophysics Data System (ADS)

The majority of debris discs discovered so far have only been detected through infrared excess emission above stellar photospheres. While disc properties can be inferred from unresolved photometry alone under various assumptions for the physical properties of dust grains, there is a degeneracy between disc radius and dust temperature that depends on the grain size distribution and optical properties. By resolving the disc we can measure the actual location of the dust. The launch of Herschel, with an angular resolution superior to previous far-infrared telescopes, allows us to spatially resolve more discs and locate the dust directly. Here we present the nine resolved discs around A stars between 20 and 40 pc observed by the Disc Emission via a Bias-free Reconnaissance in the Infrared/Submillimetre (DEBRIS) survey. We use these data to investigate the disc radii by fitting narrow ring models to images at 70, 100 and 160 ?m and by fitting blackbodies to full spectral energy distributions. We do this with the aim of finding an improved way of estimating disc radii for unresolved systems. The ratio between the resolved and blackbody radii varies between 1 and 2.5. This ratio is inversely correlated with luminosity and any remaining discrepancies are most likely explained by differences to the minimum size of grain in the size distribution or differences in composition. We find that three of the systems are well fit by a narrow ring, two systems are borderline cases and the other four likely require wider or multiple rings to fully explain the observations, reflecting the diversity of planetary systems.

Booth, Mark; Kennedy, Grant; Sibthorpe, Bruce; Matthews, Brenda C.; Wyatt, Mark C.; Duchêne, Gaspard; Kavelaars, J. J.; Rodriguez, David; Greaves, Jane S.; Koning, Alice; Vican, Laura; Rieke, George H.; Su, Kate Y. L.; Moro-Martín, Amaya; Kalas, Paul

2013-01-01

331

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

332

Endoscopic Discectomy for Extraforaminal Lumbar Disc Herniation  

Microsoft Academic Search

The microendoscopic discectomy (MED) technique has been one of the promising surgeries for lumbar disc herniation in the last few years. The purpose of this study is to report the feasibility of a minimally invasive technique for extraforaminal lumbar disc herniation. Ten patients with extraforaminal lumbar disc herniation (one at L3-4, four at L4-5, and five at L5-S1) underwent MED

Yuichi Takano; Nobuhiro Yuasa

333

Spectra of accretion discs around white dwarfs  

NASA Astrophysics Data System (ADS)

We present the spectra of accretion discs around white dwarfs calculated with an improved and updated version of Shaviv and Wehrse [Shaviv, G., Wehrse, R., 1991. A&A 251, 117] model. The new version includes line opacities and convective energy transport and can be used to calculate the spectra of hot discs in bright systems (nova-like variables or dwarf novae in outburst) as well as the spectra of cold accretion discs in quiescent dwarf novae.

Idan, Irit; Lasota, Jean-Pierre; Hameury, Jean-Marie; Shaviv, Giora

2008-05-01

334

Thoracic extruded disc mimicking spinal cord tumor  

Microsoft Academic Search

Background context: Thoracic disc herniation is a rare condition. Distinguishing between a herniated disc and tumor for a lesion found at the thoracic level can be a diagnostic challenge.Purpose: To describe a case of thoracic disc herniation that mimicked a spinal cord tumor.Study design\\/setting: Case report and review of the literature.Patient sample: Case report.Outcome measures: Report of postoperative symptoms.Methods\\/description: A

Bikash Bose

2003-01-01

335

Grain charging in protoplanetary discs  

NASA Astrophysics Data System (ADS)

Context. Recent work identified a growth barrier for dust coagulation that originates in the electric repulsion between colliding particles. Depending on its charge state, dust material may have the potential to control key processes towards planet formation such as magnetohydrodynamic (MHD) turbulence and grain growth, which are coupled in a two-way process. Aims: We quantify the grain charging at different stages of disc evolution and differentiate between two very extreme cases: compact spherical grains and aggregates with fractal dimension Df = 2. Methods: Applying a simple chemical network that accounts for collisional charging of grains, we provide a semi-analytical solution. This allowed us to calculate the equilibrium population of grain charges and the ionisation fraction efficiently. The grain charging was evaluated for different dynamical environments ranging from static to non-stationary disc configurations. Results: The results show that the adsorption/desorption of neutral gas-phase heavy metals, such as magnesium, effects the charging state of grains. The greater the difference between the thermal velocities of the metal and the dominant molecular ion, the greater the change in the mean grain charge. Agglomerates have more negative excess charge on average than compact spherical particles of the same mass. The rise in the mean grain charge is proportional to N1/6 in the ion-dust limit. We find that grain charging in a non-stationary disc environment is expected to lead to similar results. Conclusions: The results indicate that the dust growth and settling in regions where the dust growth is limited by the so-called "electro-static barrier" do not prevent the dust material from remaining the dominant charge carrier.

Ilgner, M.

2012-02-01

336

Percutaneous disc decompression using nucleoplasty.  

PubMed

The objective of this study was to evaluate the effectiveness of Nucleoplasty for decompression of contained herniated discs, in a prospective, single site study that evaluated 49 consecutive patients with complaints of back with or without leg pain secondary to a contained focal protrusion. Access to the disc was obtained via the posterolateral discography approach, with a 17-gauge introducer needle inserted through the annulus and into the nucleus. The introducer remained in place within the outer annulus during the entire procedure, providing access for the SpineWand into the nucleus. The procedure was performed on an outpatient basis. One month, three month, six-month and twelve month outcomes were assessed by the treating physician and support staff. Success was defined as a minimum 2-point reduction on a Visual Analog Scale (VAS), patient satisfaction, absence of narcotic use, and return to work if not working secondary to back pain. The pre-procedure and post-procedure VAS differences were 4.28 (p<0.001), 4.66 (p<0.001), 4.75 (p<0.001), and 3.3 (p=0.002) at the one month, 3 month, 6 month, and 12 month intervals respectively. Overall, there was a 79% success rate, with 67% success in the group of patients that had previous surgery and 82% success in the group that had no prior surgical intervention. Results indicate that Nucleoplasty may be a promising and efficacious minimally invasive procedure for the treatment of symptoms associated with contained herniated discs. Randomized, controlled studies with subgroup analysis are required to further delineate the role for this procedure. PMID:16902662

Sharps, Lewis S; Isaac, Zacharia

2002-04-01

337

Crown Gall Tumor Disc Bioassay  

PubMed Central

Seventeen samples consisting of purified compounds and various ethanol extracts from plant sources were tested for activity on the initiation of crown gall tumors on potato discs. The results demonstrated definite correlation between the ability of these samples to inhibit the formation of crown gall tumors and their activity on the P388 leukemia system in mice. Samples showing only cytotoxic effects in KB cell cultures did not affect tumor initiation in our system. The active materials had no effects on bacterial viability or on the ability of the bacteria to attach to a tumorbinding site.

Galsky, Alan G.; Wilsey, James P.; Powell, Richard G.

1980-01-01

338

Laser microbeams for DNA damage induction, optical tweezers for the search on blood pressure relaxing drugs: contributions to ageing research  

NASA Astrophysics Data System (ADS)

One essential cause of human ageing is the accumulation of DNA damages during lifetime. Experimental studies require quantitative induction of damages and techniques to visualize the subsequent DNA repair. A new technique, the "immuno fluorescent comet assay", is used to directly visualize DNA damages in the microscope. Using DNA repair proteins fluorescently labeled with green fluorescent protein, it could be shown that the repair of the most dangerous DNA double strand breaks starts with the inaccurate "non homologous end joining" pathway and only after 1 - 1 ½ minutes may switch to the more accurate "homologous recombination repair". One might suggest investigating whether centenarians use "homologous recombination repair" differently from those ageing at earlier years and speculate whether it is possible, for example by nutrition, to shift DNA repair to a better use of the error free pathway and thus promote healthy ageing. As a complementary technique optical tweezers, and particularly its variant "erythrocyte mediated force application", is used to simulate the effects of blood pressure on HUVEC cells representing the inner lining of human blood vessels. Stimulating one cell induces in the whole neighbourhood waves of calcium and nitric oxide, known to relax blood vessels. NIFEDIPINE and AMLODIPINE, both used as drugs in the therapy of high blood pressure, primarily a disease of the elderly, prolong the availability of nitric oxide. This partially explains their mode of action. In contrast, VERAPAMILE, also a blood pressure reducing drug, does not show this effect, indicating that obviously an alternative mechanism must be responsible for vessel relaxation.

Grigaravicius, P.; Monajembashi, S.; Hoffmann, M.; Altenberg, B.; Greulich, K. O.

2009-08-01

339

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

340

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 chondrogenic medium for a maximum of six weeks. Relative expression of the genes, aggrecan, type I collagen and type II collagen present in the TMJ disc extracellular matrix increased in the ASC-seeded PLA discs in the chondrogenic medium. The hypertrophic marker, type X collagen, was moderately induced. Alcian blue staining showed accumulation of sulphated glycosaminoglycans. ASC differentiation in the PLA discs was close to that observed in pellet cultures. Comparison of the mRNA levels revealed that the degree of ASC differentiation was lower than that in TMJ disc-derived cells and tissue. The pellet format supported the phenotype of the TMJ disc-derived cells under chondrogenic conditions and also enhanced their hyalinization potential, which is considered part of the TMJ disc degeneration process. Accordingly, the combination of ASCs and PLA discs has potential for the development of a tissue-engineered TMJ disc replacement.

Maenpaa, Katja; Ella, Ville; Mauno, Jari; Kellomaki, Minna; Suuronen, Riitta; Ylikomi, Timo; Miettinen, Susanna

2010-01-01

341

Intervertebral Disc Cell Therapy for Regeneration: Mesenchymal Stem Cell Implantation in Rat Intervertebral Discs  

Microsoft Academic Search

This study explores the use of mesenchymal stem cells (MSCs) for intervertebral disc regeneration. We used an in vivo model to investigate the feasibility of exogenous cell delivery, retention, and survival in the pressurized disc space. MSC injection into rat coccygeal discs was performed using 15% hyaluronan gel as a carrier. Injections of gel with or without MSCs were performed.

Gwen Crevensten; Andrew J. L. Walsh; Dheera Ananthakrishnan; Paul Page; George M. Wahba; Jeffrey C. Lotz; Sigurd Berven

2004-01-01

342

DISC1 in Schizophrenia: Genetic Mouse Models and Human Genomic Imaging  

PubMed Central

Schizophrenia and related disorders have a major genetic component. Several large-scale studies have uncovered a number of possible candidate genes, but these have yet to be consistently replicated and their underlying biological function remains elusive. One exception is ‘Disrupted in schizophrenia 1’ (DISC1), a gene locus originally identified in a large Scottish family, showing a heavy burden of major mental illnesses associated with a balanced t(1;11)(q42.1;q14.3) chromosome translocation. Substantial genetic and biological research on DISC1 has been reported in the intervening 10 years: DISC1 is now recognized as a genetic risk factor for a spectrum of psychiatric disorders and DISC1 impacts on many aspects of central nervous system (CNS) function, including neurodevelopment, neurosignaling, and synaptic functioning. Evidence has emerged from genetic studies showing a relationship between DISC1 and quantitative traits, including working memory, cognitive aging, gray matter volume in the prefrontal cortex, and abnormalities in hippocampal structures and function. DISC1 interacts with numerous proteins also involved in neuronal migration, neurite outgrowth, cytoskeletal modulation, and signal transduction, some of which have been reported as independent genetic susceptibility factors for psychiatric morbidity. Here, we focus on the growing literature relating genetic variation in the DISC1 pathway to functional and structural studies of the brain in humans and in the mouse.

Johnstone, Mandy; Thomson, Pippa A.; Hall, Jeremy; McIntosh, Andrew M.; Lawrie, Stephen M.; Porteous, David J.

2011-01-01

343

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

344

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

345

Maternal immune activation during gestation interacts with Disc1 point mutation to exacerbate schizophrenia-related behaviors in mice.  

PubMed

Schizophrenia is thought to result from interactions between susceptible genotypes and environmental risk factors. DISC1 is an important gene for schizophrenia and mood disorders based on both human and animal studies. In the present study we sought to investigate interactions between two distinct point mutations in the mouse Disc1 gene (L100P and Q31L) and maternal immune activation (MIA) during pregnancy with polyinosinic:polycytidylic acid (polyI:C). PolyI:C given at 5 mg/kg impaired cognitive and social behavior in both wild-type (WT) and Disc1-Q31L(+/-) offspring, and reduced prepulse inhibition at 16 but not 8 weeks of age. Disc1-L100P(+/-) mutants were more sensitive to MIA than WT or Disc1-Q31L(+/-) mice. Interleukin-6 (IL-6) is a critical cytokine for mediating the behavioral and transcriptional effects of polyI:C. We found a more pronounced increase of IL-6 in response to polyI:C in fetal brain in Disc1-L100P(+/-) mice compared with WT or Disc1-Q31L(+/-) mice. Coadministration of an anti-IL-6 antibody with polyI:C reversed schizophrenia-related behavioral phenotypes in Disc1-L100P(+/-) mice. In summary, we found specific interactions between discrete genetic (Disc1-L100P(+/-)) and environmental factors (MIA) that exacerbate schizophrenia-related phenotypes. IL-6 may be important in the pathophysiology of this interaction. PMID:23637159

Lipina, Tatiana V; Zai, Clement; Hlousek, Daniela; Roder, John C; Wong, Albert H C

2013-05-01

346

From Disc Wind Models to Observations of TTauri Microjets  

NASA Astrophysics Data System (ADS)

Two decades after their discovery jets from accreting young stars still represent a major challenge for theorists. Several theoretical scenarii have been proposed but only models involving large scale magnetic fields have proved capable of producing self-collimated jets. However the launching region remains unknown: is it the star the surrounding accretion disc or their interaction zone? Progresses in high angular resolution offer now the opportunity to test the various proposed models. I will first review the results on magnetized disc winds based on the only MHD model describing self-consistently these accretion-ejection structures. Then I will show how the thermal and ionization states of the outflowing matter can be consistently computed once the dominant heating source has been chosen (ambipolar diffusion alfven wave damping or some local mechanical heating). A set of observational predictions (emission maps line fluxes/ratios and line profiles) for selected optical forbidden lines can then be calculated. As an illustration I will compare these predictions with new sub-arcsecond spectroimaging observations of the DG Tau and RW Aur jets and discuss the constraints they set on disc winds in TTauri stars.

Ferreira, Jonathan; Casse, Fabien; Garcia, Paulo; Darren, O'brien; Sylvie, Cabrit; Catherine, Dougados; Pesenti, Nicolas; Luc, Binette

347

Spectral Domain Optical Coherence Tomography in Glaucoma: Qualitative and Quantitative Analysis of the Optic Nerve Head and Retinal Nerve Fiber Layer (An AOS Thesis)  

PubMed Central

Purpose: To demonstrate that video-rate spectral domain optical coherence tomography (SDOCT) can qualitatively and quantitatively evaluate optic nerve head (ONH) and retinal nerve fiber layer (RNFL) glaucomatous structural changes. To correlate quantitative SDOCT parameters with disc photography and visual fields. Methods: SDOCT images from 4 glaucoma eyes (4 patients) with varying stages of open-angle glaucoma (ie, early, moderate, late) were qualitatively contrasted with 2 age-matched normal eyes (2 patients). Of 61 other consecutive patients recruited in an institutional setting, 53 eyes (33 patients) met inclusion/exclusion criteria for quantitative studies. Images were obtained using two experimental SDOCT systems, one utilizing a superluminescent diode and the other a titanium:sapphire laser source, with axial resolutions of about 6 ?m and 3 ?m, respectively. Results: Classic glaucomatous ONH and RNFL structural changes were seen in SDOCT images. An SDOCT reference plane 139 ?m above the retinal pigment epithelium yielded cup-disc ratios that best correlated with masked physician disc photography cup-disc ratio assessments. The minimum distance band, a novel SDOCT neuroretinal rim parameter, showed good correlation with physician cup-disc ratio assessments, visual field mean deviation, and pattern standard deviation (P values range, .0003–.024). RNFL and retinal thickness maps correlated well with disc photography and visual field testing. Conclusions: To our knowledge, this thesis presents the first comprehensive qualitative and quantitative evaluation of SDOCT images of the ONH and RNFL in glaucoma. This pilot study provides basis for developing more automated quantitative SDOCT-specific glaucoma algorithms needed for future prospective multicenter national trials.

Chen, Teresa C.

2009-01-01

348

Reoperations after first lumbar disc herniation surgery; a special interest on residives during a 5-year follow-up  

PubMed Central

Background The overall rate of operations after recurrent lumbar disc herniation has been shown to be 3–11%. However, little is known about the rate of residives. Thus the aim of this study was to explore the cumulative rates of re-operations and especially residive disc herniations at the same side and level as the primary disc herniation after first lumbar disc herniation surgery and the factors that influence the risk of re-operations over a five year follow-up study. Methods 166 virgin lumbar disc herniation patients (mean age 42 years, 57% males) were studied. Data on patients' initial disc operations and type and timing of re-operations during the follow-up were collected from patient files. Back and leg pain on visual analog scale and employment status were collected by questionnaires. Results The cumulative rate of re-operations for lumbar disc herniation was 10.2% (95% Cl 6.0 to 15.1). The rate of residives at initial site was 7.4% (95% Cl 3.7 to 11.3) and rate of lumbar disc herniations at other sites was 3.1% (95% Cl 0.6 to 6.2). The occurrence of residive lumbar disc herniations was evenly distributed across the 5 years. Neither age, gender, preoperative symptoms, physical activity nor employment had effect on the probability of re-operation. Conclusion Seven percent of the lumbar disc patients had a residive lumbar disc operation within five years of their first operation. No specific factors influencing the risk for re-operation were found.

Hakkinen, Arja; Kiviranta, Ilkka; Neva, Marko H; Kautiainen, Hannu; Ylinen, Jari

2007-01-01

349

21 CFR 866.1620 - Antimicrobial susceptibility test disc.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Antimicrobial susceptibility test disc. 866...Diagnostic Devices § 866.1620 Antimicrobial susceptibility test disc. (a) Identification. An antimicrobial susceptibility test disc...

2010-04-01

350

21 CFR 866.1620 - Antimicrobial susceptibility test disc.  

Code of Federal Regulations, 2010 CFR

...2009-04-01 2009-04-01 false Antimicrobial susceptibility test disc. 866...Diagnostic Devices § 866.1620 Antimicrobial susceptibility test disc. (a) Identification. An antimicrobial susceptibility test disc...

2009-04-01

351

Conjugate heat transfer on a non-isothermal rotating disc  

NASA Astrophysics Data System (ADS)

A derivation of the conjugation criterion for a rotating disc is reported. Characteristics of conjugate heat transfer on a single disc and in a cavity formed by two discs, one rotating and the other stationary, are analysed.

Mironova, M. V.; Kortikov, N. N.

2011-12-01

352

Environmentally benign manufacturing of compact disc stampers [Final Phase II report  

SciTech Connect

Optical data storage is currently a $10B/yr. business. With the introduction of the high capacity Digital Versatile Disc (D/D) as well as the continued growth of CD-Audio and CD-ROM worldwide sales of optical data products as a whole are growing at rate of more than 10% per year. In North America, more than 2.5 billion optical discs will be sold in 1998. By 1999, the numbers of optical discs produced for the North American market will grow to almost three billion. The optical disc manufacturing industry is dominated by Asian and European companies (e.g. Sony of Japan and Philips of Netherlands). Prism Corporation has created a process that could significantly improve US competitiveness in the business of optical disc production. The objectives of the Phase II STTR project were to build and test an ion machining system (IMS) for stamper fabrication, prove overall manufacturing system feasibility by fabrication stampers and replicas, and evaluate alternative materials and alternative process parameters to optimize the process. During tie period of the Phase II project Prism Corporation was able to meet these objectives. In the course of doing so, adjustments had been made to better the project and in turn the final product. An ion machining system was designed and built that produced stampers ready for the molding process. Also, many control steps in the manufacturing process were studied to improve the current process and make it even more compatible with the industry standards, fitting seamlessly into current manufacturing lines.

None

1999-07-08

353

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

NASA Astrophysics Data System (ADS)

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.

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

2011-07-01

354

Gene therapy for degenerative disc disease  

Microsoft Academic Search

Degenerative disc disease (DDD) is a chronic process that can become clinically manifest in multiple disorders such as idiopathic low back pain, disc herniation, radiculopathy, myelopathy, and spinal stenosis. The limited available technology for the treatment of these and other pathologic and disabling conditions arising from DDD is highly invasive (eg, surgical discectomy and fusion), manifesting a certain degree of

S Sobajima; JS Kim; LG Gilbertson; JD Kang

2004-01-01

355

Thick gas discs in faint dwarf galaxies  

NASA Astrophysics Data System (ADS)

We determine the intrinsic axial ratio distribution of the gas discs of extremely faint MB < -14.5 dwarf irregular galaxies. We start with the measured (beam corrected) distribution of apparent axial ratios in the HI 21-cm images of dwarf irregular galaxies observed as part of the Faint Irregular Galaxy GMRT Survey (FIGGS). Assuming that the discs can be approximated as oblate spheroids, the intrinsic axial ratio distribution can be obtained from the observed apparent axial ratio distribution. We use a variety of methods to do this, and our final results are based on using Lucy's deconvolution algorithm. This method is constrained to produce physically plausible distributions, and also has the added advantage of allowing for observational errors to be accounted for. While one might a priori expect that gas discs would be thin (because collisions between gas clouds would cause them to quickly settle down to a thin disc), we find that the HI discs of faint dwarf irregulars are quite thick, with mean axial ratio ~ 0.6. While this is substantially larger than the typical value of ~0.2 for the stellar discs of large spiral galaxies, it is consistent with the much larger ratio of velocity dispersion to rotational velocity (?/vc) in dwarf galaxy HI discs as compared to that in spiral galaxies. Our findings have implications for studies of the mass distribution and the Tully-Fisher relation for faint dwarf irregular galaxies, where it is often assumed that the gas is in a thin disc.

Roychowdhury, Sambit; Chengalur, Jayaram N.; Begum, Ayesha; Karachentsev, Igor D.

2010-05-01

356

Fulda Gap Video Disc - A Tactical Decision.  

National Technical Information Service (NTIS)

My presentation describes a video disc based system which was developed to demonstrate potential applications as a tactical decision aid. It covers the creation of the video disc containing data for the Fluda Gap area of Germany, the system for exploitati...

K. M. Mattson R. B. Lambert

1986-01-01

357

D-Zero Cryostat Supplemental Rupture Disc  

SciTech Connect

The common relief and rupture disc vent line requires a double disc assembly with vented interspace for accurate disc burst pressures. The first disc must take pump and purge vacuum loading, but be set to operate at 110% of the MAWP, 18.3 psig (ASME code). The available solution is 18.3 psig with a burst tolerance of +/- psig. The interspace should be locally vented by a flow limiting vent valve to decouple the vent line backpressure from the vessel rupture disc. The second disc must take the worst case vent line backpressure, the steady state value found in D-Zero engineering note 3740.000-EN-63 with all three cryostats simultaneously venting at the fire condition into the 4-inch x 6-inch and 6-inch x 8-inch sections. This value is less than 2 psid. The maximum rupture value for the second disc must be less than the minimum rupture value for the first disc less 2 psid i.e. < 16.3.

Mulholland, G.T.; /Fermilab

1987-08-03

358

Accretion discs models with the ?-viscosity prescription derived from laboratory experiments  

NASA Astrophysics Data System (ADS)

We examine under which conditions one may apply, to steady state Keplerian accretion discs, the beta -viscosity prescription which has been derived from rotating shear flow experiments (nu = beta Omega R2, where Omega is the angular velocity at radius R and beta is a constant of order 10-5; Richard & Zahn \\cite{richard99}). Using a vertically averaged model, we show that this law may be suitable for all three families of known systems: in young stellar objects, evolved binary stars and Active Galactic Nuclei discs (except in their outer gas pressure dominated regions where turbulence becomes hypersonic). According to the standard criterion for viscous stability, beta -discs are always stable throughout. Using realistic opacities and equation of state, we demonstrate that these discs are thermally unstable in the temperature domain where hydrogen recombines, when they are optically thick, and this could lead to limit cycle behavior. Radiation pressure dominated regions are thermally stable, in contrast with alpha -discs. This results in a fully stable solution for the innermost parts of AGN discs.

Huré, J.-M.; Richard, D.; Zahn, J.-P.

2001-03-01

359

Optic neuritis: differential diagnosis.  

PubMed

Optic neuritis can be mimicked by other optic neuropathies and by anterior segment, choroidal or retinal diseases. Retinal diseases may cause central visual loss when they involve the macular or peripapillary area. Central serous retinopathy, hereditary retinal diseases, white dots syndromes and autoimmune retinopathies may present a clinical picture similar to that of optic neuritis. Complete neuro-ophthalmological examination must be performed to differentiate optic nerve damage from other ocular structures involvement. As in optic neuritis, optic disc and macula appearance may be completely normal in several retinal diseases. Fluorescein angiography and electrophysiological testing are relevant for the differential diagnosis in many challenging cases. PMID:11794478

Bianchi Marzoli, S; Martinelli, V

2001-11-01

360

Interactive Visualization of a Thin Disc around a Schwarzschild Black Hole  

ERIC Educational Resources Information Center

|In a first course in general relativity, the Schwarzschild spacetime is the most discussed analytic solution to Einstein's field equations. Unfortunately, there is rarely enough time to study the optical consequences of the bending of light for some advanced examples. In this paper, we present how the visual appearance of a thin disc around a…

Muller, Thomas; Frauendiener, Jorg

2012-01-01

361

Disc haemorrhages, precursors of open angle glaucoma.  

PubMed

In a long-term study of 1270 patients with at least one of the findings, open-angle glaucoma, disc haemorrhages or retinal vein occlusions, disc haemorrhages were witnessed in approximately 20% of the cases with open-angle glaucoma, and were a precursor of glaucomatous disc changes and associated visual field defects. Disc haemorrhages also preceded a rising intraocular pressure (IOP) in the destructive process among open-angle glaucoma cases. Similar glaucomatous development appears among cases independent of IOP or detection of exfoliation syndrome. Retinal vein occlusions and disc haemorrhages behave similarly with respect to glaucoma. The large number of transgressions is an argument against dividing glaucoma into different types. These findings support a vascular genesis to open-angle glaucoma, presented in earlier epidemiological studies. PMID:11906810

Sonnsjö, Bo; Dokmo, Yvonne; Krakau, Torsten

2002-01-01

362

Intervertebral disc cell therapy for regeneration: mesenchymal stem cell implantation in rat intervertebral discs.  

PubMed

This study explores the use of mesenchymal stem cells (MSCs) for intervertebral disc regeneration. We used an in vivo model to investigate the feasibility of exogenous cell delivery, retention, and survival in the pressurized disc space. MSC injection into rat coccygeal discs was performed using 15% hyaluronan gel as a carrier. Injections of gel with or without MSCs were performed. Immediately after injection, fluorescently labeled stem cells were visible on sections of cell-injected discs. Seven and 14 days after injection, stem cells were still present within the disc, but their numbers were significantly decreased. At 28 days, a return to the initial number of injected cells was observed, and viability was 100%. A trend of increased disc height compared to blank gel suggests an increase in matrix synthesis. The results indicate that MSCs can maintain viability and proliferate within the rat intervertebral disc. PMID:15095817

Crevensten, Gwen; Walsh, Andrew J L; Ananthakrishnan, Dheera; Page, Paul; Wahba, George M; Lotz, Jeffrey C; Berven, Sigurd

2004-03-01

363

Accretion Flow in the inner Accretion Discs of Cataclysmic Variables  

NASA Astrophysics Data System (ADS)

We study nature of time variability of brightness of non-magnetic cataclysmic variables. We show that lightcurtves of all analyzed DN systems in UV and X-ray energy bands demonstrate band limited noise, which can be adequately described in the framework of the model of propagating fluctuations. The frequency of the break indicates the inner disc truncation with a range of radii (10-3)e+9 cm. We analyse the RXTE and optical (RTT150) data of SS Cyg in outburst and quiescence which show that during the outburst the inner disk radius moves towards the white dwarf and receeds as the outburst declines to quiescence. Cross-correlations between the simultaneous UV and X-ray light curves find time lags in the X-rays of 90-180 sec consistent with travel time of matter from a truncated inner disc to the white dwarf surface. This suggests that DN and other plausible nonmagnetic systems have truncated accretion discs indicating that the accretion may occur through coronal flows in the disc. We compare and contrast magnetic and nonmagnetic systems in terms of their aperiodic noise characteristics and the model of propagating fluctuations. The comparison of the X-ray/UV time lag observed by us in the case of non-magnetic CVs with those, detected for magnetic CVs allows us to make an rough estimate of the viscosity parameter. Multi band simultaneous observations of coming observattories like ASTROSAT will give us the opportunity to study time variability of brightness variations of accretion disks in cataclysmic variables in quiescence and outburst using LAXPC and UVIT/OPT instruments. We will elaborate on the nature and possible outcomes of such research.

Balman, Solen; Revnivtsev, Mikhail

2012-07-01

364

Structure and evolutionary history of DISC1.  

PubMed

Evolutionary and protein structural analyses can provide functional insights into genes implicated in human psychiatric diseases. Even eukaryotic organisms lacking nervous systems contain homologues of many key signalling molecules of animal neurons implying that human cognition derives, in part, from modifications of ancestral molecules and complexes. One protein whose evolutionary origin is obscure is DISC1 (disrupted in schizophrenia 1) whose gene locus has been associated with many psychiatric conditions including schizophrenia, clinical depression and bipolar disorder. This protein's rapid evolution and its unusual amino acid and ?-helix composition have hindered searches for DISC1 homologues in species other than vertebrates. Here, we review the evolution and structure of the DISC1 protein in the light of in-depth sequence analyses. These predict DISC1 orthologues in diverse eukaryotic organisms, including early-branching animals such as amphioxus, sea anemone, amoebas and Trichoplax, and in plants and algae. DISC1 thus is widespread among eukaryotes, although it remains absent from fungi, nematodes and Diptera, including fruit flies. These observations now permit studies of DISC1 function in simple non-vertebrate model organisms. Surprisingly, these analyses also identify between two and four sequence repeats in DISC1 orthologues. The first two of these repeats show significant sequence similarity to the UVR family of globular domains. These UVR-like repeats are predicted to contain, not coiled coil structures, but rather two closely associated antiparallel ?-helices. One common missense variant in DISC1 (L607F) lies within the second DISC1 UVR-like domain. These observations should assist in delineating the functional regions of the DISC1 protein. PMID:21852244

Sanchez-Pulido, Luis; Ponting, Chris P

2011-08-18

365

Simple discs with flat roatation curves  

NASA Astrophysics Data System (ADS)

The aim of this paper is to understand why the squared axial ratio of the velocity ellipse, ?phi_^2^/?_R_^2^, of old disc stars in the Galaxy is less than 1/2. To this end, two infinitesimally thin steady-state axisymmetric discs with asymptotically flat circular velocity curves are presented. The first model - which we designate the Rybicki disc has surface density decaying inversely with radius. The second model is Freeman's exponential disc, which is immersed in the gravity field of the halo simulated by Mestel's potential. For both discs, we provide an infinite family of simple distribution functions, which form a sequence of increasing pressure support. In the Rybicki disc, the stellar streaming velocity increases outwards with radius, which typically causes ?phi_^2^/?_R_^2^ to be greater than 1/2. For our exponential disc distribution functions, the stellar streaming velocity declines outwards with radius, which typically causes ?phi^2^/?_R_^2^ to be less than 1/2. Our exponential disc distribution functions have the property that ?_R_^2^ decays only inversely with galactocentric radius R. If the diminution is faster, the ratio ?phi_^2^/?_R_^2^ rises above 1/2 at the Sun as the mean streaming velocity declines only in the inner disk. To investigate this, exponential discs with exponentially falling radial velocity dispersion are built. These are in conflict with the observations on the axial ratio, even allowing for a mismatch in the photometric and kinematic scalelengths. There are a number of possible resolutions of the contradiction: (1) the galactic disc is not in a steady state or is non-axisymmetric; (2) the circular velocity curve is locally declining; (3) the description of all stellar populations by a single distribution function is invalid; (4) the radial velocity dispersion does not drop off exponentially fast, but much more slowly; (5) the sampling of moving clusters and transient associations of stars creates a biased data set.

Evans, N. W.; Collett, J. L.

1993-09-01

366

Rotation rates, sizes and star formation efficiencies of a representative population of simulated disc galaxies  

NASA Astrophysics Data System (ADS)

We examine the rotation rates, sizes and star formation (SF) efficiencies of a representative population of simulated disc galaxies extracted from the Galaxies-Intergalactic Medium Interaction Calculation (GIMIC) suite of cosmological hydrodynamic simulations. These simulations include efficient, but energetically feasible supernova feedback, but have not been tuned in any way to produce 'realistic' disc galaxies. Yet, they generate a large number of discs, without requiring extremely high resolution. Over the wide galaxy stellar mass range, 9.0 ? log 10 [M*(M?)] < 10.5, the simulations reproduce the observed Tully-Fisher relation, the rotation curves of disc galaxies in bins of stellar mass, the mass-size relation of disc galaxies, the optical rotation to virial circular velocity ratio ('Vopt/Vvir') and the SF efficiencies of disc galaxies as inferred from stacked weak lensing and stacked satellite kinematics observations. They also reproduce the specific star formation rates of ˜L* galaxies but predict too low levels of SF for low-mass galaxies, which is plausibly due to the finite resolution of the simulations. At higher stellar masses, log10[M*(M?)] > 10.6, the simulated galaxies are too concentrated and have too high SF efficiencies. We conjecture that this shortcoming reflects the neglect of feedback from accreting supermassive black holes in these simulations. We conclude that it is possible to generate a representative population of disc galaxies that reproduces many of the observed trends of local disc galaxies using standard numerical hydrodynamic techniques and a plausible implementation of the 'subgrid' astrophysical processes thought to be relevant to galaxy formation.

McCarthy, I. G.; Schaye, J.; Font, A. S.; Theuns, T.; Frenk, C. S.; Crain, R. A.; Dalla Vecchia, C.

2012-11-01

367

[Dorsal disc herniation. 13 cases].  

PubMed

Thirteen patients with thoracic disc herniation have been operated on between 1960 and 1984. Nine presented with a progressive cord compression syndrome affecting sensory function more than motor. Four patients presented with acute cord compression. During this period, the authors have abandoned medullary angiography and myelography. The diagnosis is now based on computerised myelotomography. Three cases were treated by laminectomy with two postoperative deteriorations. Two cases were treated by a transthoracic approach which seemed to be too risky. Eight cases were treated through a postero-lateral approach, six being through a transverse arthropediculectomy using a microscope for better dissection of the vessels and Harrington rods to avoid secondary kyphosis. Seven of 9 cord syndromes were improved. Four cases with predominantly radicular syndromes were all improved. PMID:3797727

Lesoin, F; Rousseaux, M; Autricque, A; Villette, L; Clarisse, J; Jomin, M

1986-01-01

368

Prevalence of Disc Degeneration in Asymptomatic Korean Subjects. Part 1 : Lumbar Spine  

PubMed Central

Objective Asymptomatic patients show high degeneration prevalence at lumbar disc in previous literatures. Unfortunately, there are few Korean data, so the authors attempted to analyze the prevalence of disc degeneration in highly selective asymptomatic Korean subjects using MRI. Methods We performed 3 T MRI sagittal scans from T12 to S1 on 102 asymptomatic subjects (50 men and 52 women) who visited our hospital between the ages of 14 and 82 years (mean age 46.3 years). All images were read independently by three observers (two neurosurgeons and one neuroradiologist) who were not given any information about the subjects. We classified grading for lumbar disc herniation (HN), annular fissure (AF), and nucleus degeneration (ND), using disc degeneration classification. Results The prevalence of HN, AF, and ND were 81.4%, 76.1%, and 75.8% respectively. Almost all levels showed an age-related proportional tendency with some exceptions. Conclusion In asymptomatic Korean subjects, the abnormal findings showed high prevalence of AF, ND, and extrusion. Especially in young ages, the authors found that bulging, protrusion, and AF showed high prevalence at L4/5 and L5/S1. And ND showed high prevalence at L5/S1. So, all lumbar disc degenerations are not pathologic, especially in children and adolescents.

Lee, Tae Hoon; Lim, Soo Mee

2013-01-01

369

Demonstration of remote fiber optic spectroscopy using mid-IR sensors for in-situ monitoring of solid rocket propellent cure and aging  

Microsoft Academic Search

A study of real-time in situ monitoring of the chemical states of urethane cross-linked solid rocket propellant during cure and aging using an embedded fiber optic sensor and a Fourier transform IR spectrometer is presented. The aging study focused on the monitoring and identification of chemical species that migrate across the propellant-insulation bondline. In this work, a short length of

Paul J. Glatkowski; Mark A. Druy; William A. Stevenson

1994-01-01

370

Intrinsic disc emission and the soft X-ray excess in active galactic nuclei  

NASA Astrophysics Data System (ADS)

Narrow-line Seyfert 1 (NLS1) galaxies have low-mass black holes and mass accretion rates close to (or exceeding) Eddington, so a standard blackbody accretion disc should peak in the extreme ultraviolet. However, the lack of true absorption opacity in the disc means that the emission is better approximated by a colour temperature corrected blackbody, and this colour temperature correction is large enough (˜2.4) that the bare disc emission from a zero spin black hole can extend into the soft X-ray bandpass. Part of the soft X-ray excess seen in these objects must be intrinsic emission from the disc unless the vertical structure is very different to that predicted. None the less, this is not the whole story even for the extreme NLS1 as the shape of the soft excess is much broader than predicted by a bare disc spectrum, indicating some Compton upscattering by warm, optically thick material. We associate this with the disc itself, so it must ultimately be powered by mass accretion. We build an energetically self-consistent model assuming that the emission thermalizes to a (colour temperature corrected) blackbody only at large radii. At smaller radii the gravitational energy is split between powering optically thick Comptonized disc emission (forming the soft X-ray excess) and an optically thin corona above the disc (forming the tail to higher energies). We show examples of this model fit to the extreme NLS1 RE J1034+396, and to the much lower Eddington fraction broad-line Seyfert 1 PG 1048+231. We use these to guide our fits and interpretations of three template spectra made from co-adding multiple sources to track out a sequence of active galactic nucleus (AGN) spectra as a function of L/LEdd. Both the individual objects and template spectra show the surprising result that the Compton upscattered soft X-ray excess decreases in importance with increasing L/LEdd. The strongest soft excesses are associated with low mass accretion rate AGN rather than being tied to some change in disc structure around Eddington. We argue that this suggests a true break in accretion flow properties between stellar and supermassive black holes. The new model is publicly available within the XSPEC spectral fitting package.

Done, Chris; Davis, S. W.; Jin, C.; Blaes, O.; Ward, M.

2012-03-01

371

Quantitative evaluation of the optic nerve head in early glaucoma  

Microsoft Academic Search

AIMSProgressive loss of neuroretinal rim tissue is known to occur early in glaucoma and measurement of the neuroretinal rim area is possible by magnification corrected analysis of optic disc photographs (planimetry). This study was performed to determine whether the facility to distinguish between glaucomatous and normal optic discs could be improved upon by: (a) taking into account the known relation

D F Garway-Heath; R A Hitchings

1998-01-01

372

Nutrient supply and intervertebral disc metabolism.  

PubMed

The metabolic environment of disc cells is governed by the avascular nature of the tissue. Because cellular energy metabolism occurs mainly through glycolysis, the disc cells require glucose for survival and produce lactic acid at high rates. Oxygen is also necessary for cellular activity, although not for survival; its pathway of utilization is unclear. Because the tissues are avascular, disc cells depend on the blood supply at the margins of the discs for their nutrients. The nucleus and inner anulus of the disc are supplied by capillaries that arise in the vertebral bodies, penetrate the subchondral bone, and terminate at the bone-disc junction. Small molecules such as glucose and oxygen then reach the cells by diffusion under gradients established by the balance between the rate of transport through the tissue to the cells and the rate of cellular demand. Metabolites such as lactic acid are removed by the reverse pathway. The concentrations of nutrients farthest from the source of supply can thus be low; oxygen concentrations as low as 1% have been measured in the discs of healthy animals. Although gradients cannot be measured easily in humans, they can be calculated. Measured concentrations in surgical patients are in agreement with calculated values. PMID:16595440

Grunhagen, Thijs; Wilde, Geoffrey; Soukane, Dahbia Mokhbi; Shirazi-Adl, Saeed A; Urban, Jill P G

2006-04-01

373

Dynamical instabilities in disc-planet interactions  

NASA Astrophysics Data System (ADS)

Protoplanetary discs may become dynamically unstable due to structure induced by an embedded giant planet. In this thesis, I discuss the stability of such systems and explore the consequence of instability on planetary migration. I begin with non-self-gravitating, low viscosity discs and show that giant planets induce shocks inside its co-orbital region, leading to a profile unstable to vortex formation around a potential vorticity minimum. This instability is commonly known as the vortex or Rossby wave instability. Vortex-planet interaction lead to episodic phases of migration, which can be understood in the framework of type III migration. I then examine the effect of disc self-gravity on gap stability. The linear theory of the Rossby wave instability is extended to include disc gravity, which shows that self-gravity is effective at stabilising the vortex instability at small azimuthal wavenumber. This is consistent with the observation that more vortices develop with increasing disc mass in hydrodynamic simulations. Vortices in self-gravitating discs also resist merging, and is most simply understood as pair-vortices undergoing mutual horsehoe turns upon encounter. I show that in sufficiently massive discs vortex modes are suppressed. Instead, global spiral instabilities develop which are associated with a potential vorticity maximum at the gap edge. These edge modes can be physically understood as a result of unstable interaction between the gap edge and the exterior disc through gravity. I show the spiral arms can provide a positive torque on the planet, leading to fast migration outwards. I confirm the above results, obtained from razor-thin disc models, persist in three-dimensions.

Lin, Min-Kai

2012-03-01

374

Composition and exposure age of the Apollo 16 Cayley and Descartes regions from Clementine data: Normalizing the optical effects of space weathering  

Microsoft Academic Search

In order to quantitatively assess the composition of the lunar surface from reflectance spectroscopy, it is necessary to be able to differentiate between the optical effects due to composition and those due to exposure to space weathering processes. Laboratory analyses of returned lunar soils are used to show that limited quantitative compositional information and the exposure age of the lunar

Erich M. Fischerand Carl; M. Pieters

375

Composition and exposure age of the Apollo 16 Cayley and Descartes regions from Clementine data: Normalizing the optical effects of space weathering  

Microsoft Academic Search

In order to quantitatively assess the composition of the lunar surface from reflectance spectroscopy, it is necessary to be able to differentiate between the optical effects due to composition and those due to exposure to space weathering processes. Laboratory analyses of returned lunar soils are used to show that limited quantitative compositional information and the exposure age of the lunar

M. Pieters

1996-01-01

376

DISC1 genetics, biology and psychiatric illness  

PubMed Central

Psychiatric disorders are highly heritable, and in many individuals likely arise from the combined effects of genes and the environment. A substantial body of evidence points towards DISC1 being one of the genes that influence risk of schizophrenia, bipolar disorder and depression, and functional studies of DISC1 consequently have the potential to reveal much about the pathways that lead to major mental illness. Here, we review the evidence that DISC1 influences disease risk through effects upon multiple critical pathways in the developing and adult brain.

THOMSON, Pippa A.; MALAVASI, Elise L.V.; GRUNEWALD, Ellen; SOARES, Dinesh C.; BORKOWSKA, Malgorzata; MILLAR, J. Kirsty

2012-01-01

377

Laser-induced activation of regeneration processes in spine disc cartilage  

NASA Astrophysics Data System (ADS)

The effect of laser radiation on the regeneration processes in spine disk cartilage has been studied in-vivo. We used rabbits as a model and a Holmium (2.09 micrometer) and an Erbium fiber (1.56 micrometer) lasers for irradiation the discs which were preliminary opened to remove annulus fibrosus and the nucleus pulposus of the intervertebral disc. The irradiated zone has been examined using an optical coherent tomography in one month after the operation and conventional histological technique in two months after the laser operation. It has been shown that laser radiation promotes the growth of the new cartilaginous tissue of fibrous and hyaline types.

Sobol, Emil N.; Vorobjeva, Natalia N.; Sviridov, Alexander P.; Omel'chenko, Alexander I.; Baskov, Andrey V.; Shekhter, Anatoliy B.; Baskov, Vladimir A.; Feldchtein, Felix I.; Kamensky, Vladislav A.; Kuranov, Roman V.

2000-05-01

378

How Does Lumbar Degenerative Disc Disease Affect the Disc Deformation at the Cephalic Levels In Vivo?  

PubMed Central

Study Design Case-control study. Objective . To evaluate the effect of lumbar degenerative disc disease (DDD) on the disc deformation at the adjacent level and at the level one above the adjacent level during end ranges of lumbar motion. Summary of Background Data It has been reported that in patients with DDD, the intervertebral discs adjacent to the diseased levels have a greater tendency to degenerate. Although altered biomechanics have been suggested to be the causative factors, few data have been reported on the deformation characteristics of the adjacent discs in patients with DDD. Methods Ten symptomatic patients with discogenic low back pain between L4 and S1 and with healthy discs at the cephalic segments were involved. Eight healthy subjects recruited in our previous studies were used as a reference comparison. The in vivo kinematics of L3–L4 (the cephalic adjacent level to the degenerated discs) and L2–L3 (the level one above the adjacent level) lumbar discs of both groups were obtained using a combined magnetic resonance imaging and dual fluoroscopic imaging technique at functional postures. Deformation characteristics, in terms of areas of minimal deformation (defined as less than 5%), deformations at the center of the discs, and maximum tensile and shear deformations, were compared between the two groups at the two disc levels. Results In the patients with DDD, there were significantly smaller areas of minimal disc deformation at L3–L4 and L2–L3 than the healthy subjects (18% compared with 45% of the total disc area, on average). Both L2–L3 and L3–L4 discs underwent larger tensile and shear deformations in all postures than the healthy subjects. The maximum tensile deformations were higher by up to 23% (of the local disc height in standing) and the maximum shear deformations were higher by approximately 25% to 40% (of the local disc height in standing) compared with those of the healthy subjects. Conclusion Both the discs of the adjacent level and the level one above experienced higher tensile and shear deformations during end ranges of lumbar motion in the patients with DDD before surgical treatments when compared with the healthy subjects. The larger disc deformations at the cephalic segments were otherwise not detectable using conventional magnetic resonance imaging techniques. Future studies should investigate the effect of surgical treatments, such as fusion or disc replacement, on the biomechanics of the adjacent segments during end ranges of lumbar motion.

Wang, Shaobai; Xia, Qun; Passias, Peter; Li, Weishi; Wood, Kirkham; Li, Guoan

2013-01-01

379

The lower limits of disc fragmentation and the prospects for observing fragmenting discs  

NASA Astrophysics Data System (ADS)

A large fraction of brown dwarfs and low-mass hydrogen-burning stars may form by gravitational fragmentation of protostellar discs. We explore the conditions for disc fragmentation and find that they are satisfied when a disc is large enough (?100 au) so that its outer regions can cool efficiently, and it has enough mass to be gravitationally unstable, at such radii. We perform radiative hydrodynamic simulations and show that even a disc with mass 0.25 M? and size 100 au fragments. The disc mass, radius and the ratio of disc to star mass (MD/M?? 0.36) are smaller than in previous studies. We find that fragmenting discs drastically decrease in mass and size within a few 104 yr of their formation, since a fraction of their mass, especially outside ˜100 au is consumed by the new stars and brown dwarfs that form. Fragmenting discs end up with masses ˜0.001-0.1 M? and sizes ˜20-100 au. On the other hand, discs that are marginally stable evolve on a viscous time-scale, thus living longer (˜1-10 Myr). We produce simulated images of fragmenting discs and find that observing discs that are undergoing fragmentation is possible using current (e.g. IRAM Plateau de Bure interferometer) and future (e.g. ALMA) interferometers, but highly improbable due to the short duration of this process. Comparison with observations shows that many observed discs may be remnants of discs that have fragmented at an earlier stage. However, there are only a few candidates that are possibly massive and large enough to currently be gravitationally unstable. The rarity of massive (?0.2 M?), extended (?100 au) discs indicates that either such discs are highly transient (i.e. form, increase in mass becoming gravitationally unstable due to infall of material from the surrounding envelope and quickly fragment) or their formation is suppressed (e.g. by magnetic fields). We conclude that current observations of early-stage discs cannot exclude the mechanism of disc fragmentation.

Stamatellos, Dimitris; Maury, Anaëlle; Whitworth, Anthony; André, Philippe

2011-05-01

380

Biomechanical properties of human thoracic spine disc segments  

PubMed Central

Background: The objective was to determine the age-dependent compressive and tensile properties of female and male thoracic spine segments using postmortem human subjects (PMHS). Materials and Methods: Forty-eight thoracic disc segments at T4-5, T6-7, T8-9, and T10-11 levels from 12 PMHS T3-T11 spinal columns were divided into groups A and B based on specimen age and loaded in compression and tension. Stiffness and elastic modulus were computed. Stiffness was defined as the slope in the linear region of the force—displacement response. Elastic modulus was defined as the slope of the stress strain curve. Analysis of Variance (ANOVA) was used to determine significant differences (P<0.05) in the disc cross-sectional area, stiffness, and elastic modulus based on gender, spinal level, and group. Results: Specimen ages in group A (28 ± 8 years) were significantly lower than in group B (70 ± 7 years). Male discs had significantly greater area (7.2 ± 2.0 sq cm) than female discs (5.9 ± 1.8 sq cm). Tensile and compressive stiffness values were significantly different between the two age groups, but not between gender and level. Specimens in group A had greater tensile (486 ± 108 N/mm) and compressive (3300 ± 642 N/mm) stiffness values compared to group B specimens (tension: 397 ± 124 N/mm, compression: 2527 ± 734 N/mm). Tensile and compressive elastic modulus values depended upon age group and gender, but not on level. Group A specimens had significantly greater tensile and compressive moduli (2.9 ± 0.8 MPa, 19.5 ± 4.1 MPa) than group B specimens (1.7 ± 0.6 MPa, 10.6 ± 3.4 MPa). Female specimens showed significantly greater tensile and compressive moduli (2.6 ± 1.0 MPa, 16.6 ± 6.4 MPa) than male specimens (2.0 ± 0.7 MPa, 13.7 ± 5.0 MPa). Discussion: Using the two groups to represent "young" and "old" specimens, this study showed that the mechanical response decreases in older specimens, and the decrease is greater in compressive than distractive properties. While the decrease is expected, the relative change between the two modes of loading has not been reported. Another conclusion from the study is that the mechanical properties depend on gender, although not as decisive due to sample size.

Stemper, Brian D.; Board, Derek; Yoganandan, Narayan; Wolfla, Christopher E.

2010-01-01

381

The internal mechanical properties of cervical intervertebral discs as revealed by stress profilometry  

PubMed Central

Extensive anatomical differences suggest that cervical and lumbar discs may have functional differences also. We investigated human cervical discs using “stress profilometry”. Forty-six cadaveric cervical motion segments aged 48-90 years were subjected to a compressive load of 200 N for 20 s, while compressive ‘stress’ was recorded along the posterior-anterior midline of the disc using a pressure transducer, side-mounted in a 0.9 mm diameter needle. Stress profiles were repeated with the transducer orientated horizontally and vertically, and with the specimen in neutral, flexed and extended postures. Profiles were repeated again following creep loading (150 N, 2 h) which simulated diurnal water loss in vivo. Stress profiles were reproducible, and measured “stress” at each location was proportional to applied load. Stress profiles usually showed a hydrostatic nucleus with regions of higher compressive stress concentrated anteriorly in flexion, and posteriorly in extension. Stress concentrations increased in degenerated discs and following creep. Some features were unique to cervical discs: many showed a stress gradient across their central regions, even though vertical and horizontal stresses were equal to each other, and stress concentrations in the posterior annulus were generally small. Central regions of many cervical discs show the characteristics of a “tethered fluid” which can equalise stress over small distances, but not large. This may be attributable to their fibrous texture. The small radial diameter of the cervical posterior annulus may facilitate buckling and thereby prevent it from sustaining high compressive stresses.

Skrzypiec, Daniel M.; Pollintine, Phillip; Przybyla, Andrzej; Dolan, Patricia

2007-01-01

382

Grading of Age-Related Macular Degeneration: Comparison between Color Fundus Photography, Fluorescein Angiography, and Spectral Domain Optical Coherence Tomography  

PubMed Central

Purpose. To compare color fundus photography (FP), fluorescein angiography (FA), and spectral domain optical coherence tomography (SDOCT) for the detection of age-related macular degeneration (AMD), choroidal neovascularisation (CNV), and CNV activity. Methods. FPs, FAs, and SDOCT volume scans from 120 eyes of 66 AMD and control patients were randomly collected. Control eyes were required to show no AMD, but other retinal pathology was allowed. The presence of drusen, pigmentary changes, CNV, and signs for CNV activity was independently analyzed for all imaging modalities. Results. AMD was diagnosed based on FP in 75 eyes. SDOCT and FA showed sensitivity (specificity) of 89% (76%) and 92% (82%), respectively. CNV was present on FA in 68 eyes. Sensitivity (specificity) was 78% (100%) for FP and 94% (98%) for SDOCT. CNV activity was detected by SDOCT or FA in 60 eyes with an agreement in 46 eyes. Sensitivity was 88% for SDOCT and 88% for FA. FP showed sensitivity of 38% and specificity of 98%. Conclusions. CNV lesions and activity may be missed by FP alone, but FP may help identifying drusen and pigmentary changes. SDOCT is highly sensitive for the detection of AMD, CNV, and CNV activity; however, it cannot fully replace FA.

Mokwa, Nils F.; Keane, Pearse A.; Kirchhof, Bernd; Sadda, Srinivas R.

2013-01-01

383

Total disc replacement surgery for symptomatic degenerative lumbar disc disease: a systematic review of the literature  

Microsoft Academic Search

The objective of this study is to evaluate the effectiveness and safety of total disc replacement surgery compared with spinal\\u000a fusion in patients with symptomatic lumbar disc degeneration. Low back pain (LBP), a major health problem in Western countries,\\u000a can be caused by a variety of pathologies, one of which is degenerative disc disease (DDD). When conservative treatment fails,\\u000a surgery

Karin D. van den Eerenbeemt; Raymond W. Ostelo; Barend J. van Royen; Wilco C. Peul; Maurits W. van Tulder

2010-01-01

384

New strategies for disc repair: novel preclinical trials  

Microsoft Academic Search

Degeneration of lumbar intervertebral discs is a major cause of low back complaints, an irreversible occurrence with no currently available treatment. Furthermore, various surgical procedures can accelerate disc degeneration. On the other hand, recent experimental studies on disc cells have demonstrated an important role for the nucleus pulposus in preserving overall disc structure. The author’s group has already found that

Joji Mochida

2005-01-01

385

21 CFR 866.1620 - Antimicrobial susceptibility test disc.  

Code of Federal Regulations, 2013 CFR

...antimicrobic-impregnated paper discs used to measure by a disc-agar diffusion technique or a disc-broth elution technique the in vitro...bacterial pathogens to antimicrobial agents. In the disc-agar diffusion technique, bacterial susceptibility is...

2013-04-01

386

46 CFR 64.61 - Rupture disc.  

Code of Federal Regulations, 2012 CFR

...disc. 64.61 Section 64.61 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING MARINE PORTABLE TANKS AND CARGO HANDLING SYSTEMS Pressure Relief Devices and Vacuum Relief Devices for MPTs...

2012-10-01

387

Mach disc formation in cylindrical recovery systems  

SciTech Connect

Cylindrical recovery systems have been used to shock-load polymers to pressures exceeding 50 GPa. In order to determine the pressures generated in these recovery systems the formation of the Mach disc on axis and its approach to steady state was monitored. The relation of the Mach disc diameter to the lateral dimension of the high explosive used to compress the polymer samples was also investigated.

Morris, C.E.; McQueen, R.G.; Marsh, S.P.

1983-01-01

388

Two-Level Thoracic Disc Herniation  

Microsoft Academic Search

We report a rare case of two-level thoracic disc herniation that occurred in a 48-year-old woman. She was referred with a 10-month history of pain on the right side of the thorax. On examination, she had hypoesthesia and hypalgesia in the right T6-T8 dermatomes. An MRI scan revealed a large herniated disc at the T7\\/8 level and a smaller herniated

NIELS LEVI; KJELD DONS

389

Simulation of a spinstabilised sports disc  

Microsoft Academic Search

The spin-stabilised sports disc, more commonly known as the Frisbee, is used for a variety of recreation and sporting activities.\\u000a Frisbees have unique flying characteristics compared to other sports projectiles because they depend on spin for stability\\u000a during flight and, at typical launch speeds, aerodynamic lift is greater than or equal to the weight of the disc. In this\\u000a paper,

W. J. Crowther; J. R. Potts

2007-01-01

390

Revision surgery for lumbar disc herniation  

Microsoft Academic Search

We reviewed 45 patients who had undergone repeated open operations for lumbar disc herniation. There were 26 men and 19 women with a mean follow up of 4.3 years. Twenty-four patients had had one previous discectomy, 12 had 2, and 9 had 3 or more; 11 needed a fusion without instrumentation. Residual or re-extruded disc hernias, either sub- or transligamentous,

H. Baba; Q. Chen; K. Kamitani; S. Imura; K. Tomita

1995-01-01

391

Spinal fusion in degenerative disc disease.  

PubMed

Low back pain caused by degenerative disc disease is of such intensity in a low percentage of cases that surgery is indicated. Surgery must not only stabilize, but it must above all correct the deformity, recovering the disc space. Among all of the methods available circumferential fusion with a double combined approach, that is, anterior and posterior, is held to be the most effective. PMID:8076465

Gallinaro, P; Indemini, E; Tabasso, G; Abbate, M

392

Human intervertebral disc: structure and function.  

PubMed

This review begins with a brief introduction in which the d