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1

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

2

Medical Information on Optical Disc*  

PubMed Central

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

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

1987-01-01

3

The Optical Disc Roundup.  

ERIC Educational Resources Information Center

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

Galbreath, Jeremy

1993-01-01

4

Computer animation via optical video disc  

E-print Network

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

Bender, Walter

1981-01-01

5

Clinical characteristics of nonglaucomatous optic disc cupping  

PubMed Central

Pathological optic disc cupping (ODC) is predominantly referred to as glaucoma; however, it is not only glaucoma that leads to pathological optic disc excavation. A number of other nonglaucomatous diseases also result in optic atrophy and excavation of the optic disc. Therefore, in the present study, the etiology of nonglaucomatous optic disc cupping (NGODC) was analyzed and differentiated from glaucomatous optic disc cupping (GODC). The morphology and clinical data of 19 eyes, from 12 patients exhibiting NGODC, were analyzed. Of the 12 cases, none were diagnosed with glaucoma, four presented with optic neuritis, one with Devic’s disease, one with Leber’s hereditary optic neuropathy, two with pituitary adenoma, one with basal ganglia cerebral hemorrhage, one with cilioretinal artery occlusion associated with central retinal vein occlusion, one with central retinal artery occlusion and the remaining patient exhibited optic nerve injuries. The key features that differentiated NGODC from GODC were the color of the optic disc rim and the correlation between visual field defects and the disc appearance. The focally notched disc also aided in distinguishing between the two disorders. The results of the present study indicated that it is critical to acknowledge that nonglaucomatous diseases also lead to ODC and that distinguishing between them is necessary. PMID:24669265

ZHANG, YI-XIN; HUANG, HOU-BIN; WEI, SHI-HUI

2014-01-01

6

Clinical characteristics of nonglaucomatous optic disc cupping.  

PubMed

Pathological optic disc cupping (ODC) is predominantly referred to as glaucoma; however, it is not only glaucoma that leads to pathological optic disc excavation. A number of other nonglaucomatous diseases also result in optic atrophy and excavation of the optic disc. Therefore, in the present study, the etiology of nonglaucomatous optic disc cupping (NGODC) was analyzed and differentiated from glaucomatous optic disc cupping (GODC). The morphology and clinical data of 19 eyes, from 12 patients exhibiting NGODC, were analyzed. Of the 12 cases, none were diagnosed with glaucoma, four presented with optic neuritis, one with Devic's disease, one with Leber's hereditary optic neuropathy, two with pituitary adenoma, one with basal ganglia cerebral hemorrhage, one with cilioretinal artery occlusion associated with central retinal vein occlusion, one with central retinal artery occlusion and the remaining patient exhibited optic nerve injuries. The key features that differentiated NGODC from GODC were the color of the optic disc rim and the correlation between visual field defects and the disc appearance. The focally notched disc also aided in distinguishing between the two disorders. The results of the present study indicated that it is critical to acknowledge that nonglaucomatous diseases also lead to ODC and that distinguishing between them is necessary. PMID:24669265

Zhang, Yi-Xin; Huang, Hou-Bin; Wei, Shi-Hui

2014-04-01

7

Acute visual loss in a patient with optic disc drusen.  

PubMed

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

Tan, Deborah Kl; Tow, Sharon Lc

2013-01-01

8

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. PMID:23658477

Tan, Deborah KL; Tow, Sharon LC

2013-01-01

9

Optical disc system for baseband HDTV signal  

NASA Astrophysics Data System (ADS)

We developed a new type of optical disc system for baseband high definition television (signal. In conventional technology we cannot record HDTV signal for sufficiently long time because it has very wide bandwidth. In this system we can solve this problem based on the following technology HDTV signal is divided into two channels recorded on the both sides of a 30 cm diameter disc and reproduced with two optical pickups at the same time. As a result this system can continuously play HDTV signal for more than 30 minutes with constant-linear-velocity (CLV) disc. 1 .

Matsushita, Katsuhiko; Ohnaka, Takashi; Hosohara, Nabuhiro; Idegata, Osamu; Tanaka, Tatsuo

1992-08-01

10

[Recognizing the pitfalls. Non-glaucomatous optic disc cupping].  

PubMed

Pathological optic disc cupping is most often caused by open angle glaucoma. More rarely, other optic neuropathies may be associated with acquired pathological optic disc cupping, sometimes mimicking glaucoma. A careful interpretation of the history, optic disc characteristics and visual fields are the main tools in the decision process of glaucomatous versus non-glaucomatous optic disc cupping, avoiding inappropriate, expensive neuroimaging examinations. PMID:17646798

Milea, D

2007-05-01

11

Detection and prognostic significance of optic disc hemorrhages during the Ocular Hypertension Treatment Study  

PubMed Central

Purpose: To compare the rates of detection of optic disc hemorrhages by clinical examination and by review of optic disc photographs at the Optic Disc Reading Center (ODRC), to assess the incidence of and the predictive factors for disc hemorrhages in the annual disc photographs of the Ocular Hypertension Treatment Study (OHTS), and to determine whether optic disc hemorrhages predict the development of primary open-angle glaucoma (POAG) in the OHTS. Design: Cohort study. Participants: 3,236 eyes of 1,618 participants. Methods: Both eyes of participants were examined for optic disc hemorrhages every 6 months by clinical examination, with dilated fundus examinations every 12 months, and by annual review of stereoscopic disc photographs at the ODRC. Main Outcome Measures: Incidence of optic disc hemorrhages and POAG endpoints. Results: Median follow-up was 96.3 months. Stereophotograph-confirmed glaucomatous optic disc hemorrhages were detected in 128 eyes of 123 participants prior to POAG. Twenty one (16%) were detected by both clinical examination and review of photographs and 107 (84%) only by review of photographs (P <0.0001). Baseline factors associated with disc hemorrhages were older age, thinner corneas, larger vertical cup/disc ratio, larger PSD index on perimetry, family history of glaucoma, and smoking. The occurrence of a disc hemorrhage increased the risk of developing POAG 6-fold in a univariate analysis, (p<0.001; 95% confidence interval 3.6 – 10.1), and 3.7-fold in a multivariate analysis that included baseline factors predictive of POAG (p<0.001; 95% confidence interval 2.1 – 6.6). The 96-month cumulative incidence of POAG in the eyes without optic disc hemorrhage was 5.2% compared to 13.6% in the eyes with optic disc hemorrhage. In eyes with a disc hemorrhage that developed a POAG endpoint, the median time between the two events was 13 months. Conclusion: Review of stereo photographs was more sensitive at detecting optic disc hemorrhage than clinical examination. The occurrence of an optic disc hemorrhage was associated with an increased risk of developing a POAG endpoint in participants in the OHTS. However, the majority of eyes (86.7%) that developed a disc hemorrhage have not developed a POAG endpoint to date. PMID:16996592

Budenz, Donald L.; Anderson, Douglas R.; Feuer, William J.; Beiser, Julia A.; Schiffman, Joyce; Parrish, Richard K.; Piltz-Seymour, Jody R.; Gordon, Mae O.; Kass, Michael A.

2007-01-01

12

Superresolution technology applied to optical discs  

NASA Astrophysics Data System (ADS)

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

Zhou, Changhe; Luo, Hongxin

2005-09-01

13

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

NASA Astrophysics Data System (ADS)

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

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

2007-05-01

14

Compatible optical pickup actuator for next generation versatile disc system  

Microsoft Academic Search

Nowadays, high-density disc and high-speed optical disk drive have become popular as optical disc has many merits such as cost effectiveness, high data transfer rate, large storage capacity, removability and compatibility. In this paper, we presented a compatible optical pickup actuator for next generation versatile disc (NVD) system. This actuator has high AC sensitivities and good 2nd resonance frequency through

Lei Zhong; Jianshe Ma; Xuemin Cheng; Buqing Zhang

2008-01-01

15

Optic disc measurement: a comparison of indirect ophthalmoscopic methods  

Microsoft Academic Search

AIMS--Two methods of indirect ophthalmoscopic estimation of optic disc size, the 78 dioptre lens and optic disc biometer were evaluated. METHODS--Twenty nine eyes of 29 patients were measured by both methods and compared with optic disc size calculated using the three planimetric corrections described by Bengtsson and Krakau. RESULTS--The closest agreement with the clinical measurements was found using correction 3.

A F Spencer; S A Vernon

1995-01-01

16

Automatic Handling Mechanisms For An Optical Disc Mass Memory System  

NASA Astrophysics Data System (ADS)

An optical disc mass memory system is being developed which will provide automatic access to any data in a store of 1013 bits within five seconds. This system contains a library of 128 optical discs with mechanisms for retrieving any disc, loading it onto a turntable, and recording or playing digital data at a rate of 50 Mb/s. The optical discs are housed in protective cartridges to facilitate handling by the operating personnel and automatic disc handling mechanisms. Cartridges are moved from the store to a load station by a belt-driven X-Y transport mechanism. The load station then mounts the discs onto a precision turntable, and they are spun up to speed while housed within their protective cartridges. A window in the cartridge wall provides access for the record and play laser beams to operate on the disc media. The disc handling mechanisms were designed to minimize mechanical shock and vibration while providing a rapid, smooth operation. A special centering hub design, for the turntable minimizes disc eccentricities during multiple load/unload cycles and allows easy inter-changeability among machines. This paper will describe the cartridge, turntable, and disc handling mechanisms designs. Test results from an engineering model implementing these designs will also be presented.

Ammon, G. J.; Siryj, B. W.

1983-09-01

17

Optic disc detection using ant colony optimization  

NASA Astrophysics Data System (ADS)

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

Dias, Marcy A.; Monteiro, Fernando C.

2012-09-01

18

Multilayer optical disc system using homodyne detection  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

19

Systemic Abnormalities in Children with Congenital Optic Disc Excavations.  

PubMed

Abstract Purpose: Together with optic disc hypoplasia, excavated optic disc anomalies represent the most frequent congenital abnormality involving the optic nerve head. The purpose of the present study was to retrospectively review the results of a screening for extraocular abnormalities in children presenting with congenital optic disc excavations. Materials and methods: The medical records of 37 patients diagnosed with a unilateral or bilateral non glaucomatous optic disc excavation were retrospectively reviewed to analyze the result of the extra ocular evaluation and to report the associated ocular abnormalities. Results: An ocular abnormality was observed in conjunction with the excavated optic disc in 31% of the eyes. The systematic investigations revealed the presence of at least one extra-ocular disorder in 48% of the cases, and the optic disc excavation could be considered as syndromic in 30% of patients. The prevalence of extraocular malformations was significantly higher in infants presenting with associated ocular malformations or abnormal vision/development. Conclusions: The present study suggests that a systematic approach to search for any associated systemic abnormalities could be envisioned in patients presenting with congenital excavated optic discs, and particularly those presenting with abnormal vision, associated ocular defects or abnormal development. PMID:24911672

Beby, Francis

2014-06-01

20

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

NASA Astrophysics Data System (ADS)

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

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

2010-02-01

21

Thermal and Optical Properties of Metal Azo Dyes for Digital Video Disc-Recordable Discs  

Microsoft Academic Search

The effects of the optical and thermal properties of metal azo dyes on the recording characteristics of digital video disc-recordable (DVD-R) discs have been studied. A sharp threshold for thermal decomposition of the dye assures a clear mark edge and low jitter for the minimum mark length of 0.4 0.44 µm. A steep absorption edge at the 635 nm side

Yuki Suzuki; Michikazu Horie; Yuuko Okamoto; Yutaka Kurose; Shuichi Maeda

1998-01-01

22

The galactic disc age-metallicity relation  

E-print Network

New ages are computed for stars in the Solar Neighbourhood from the Edvardsson et al. (1993) data set. Distances derived from the Hipparcos parallaxes were adopted to obtain reliable ages (uncertainty less than 12%) for a subset of stars. There is no apparent age-metallicity relation for stars with an age less than 10 Gyr. Only if we consider older stars a slope of ~0.07 dex/Gyr appears. This relation is compared with those obtained from other methods, i.e. galactic open clusters, stellar population synthesis (star counts), and chemical evolution models.

Y. K. Ng; G. Bertelli; G. Carraro; L. Portinari

1997-09-18

23

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

PubMed Central

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

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

2014-01-01

24

Qualitative changes with age of proteoglycans of human lumbar discs.  

PubMed Central

A detailed study of the biochemistry of each of the lower lumbar intervertebral discs from 3 spines aged 8, 16, and 44 years has shown progressive changes down the spine in a number of biochemical parameters. These were most apparent in the 44-year-old spine. The chemical composition of proteoglycans of the nucleus pulposus and of its constituent proteoglycans differed from those of the corresponding annulus fibrosus of all three spines. The interaction of proteoglycans with collagen, as assessed by extractability, changed markedly with advancing age, while the molecular size of the proteoglycans from both regions decreased and their keratan sulphate content increased. These changes would be expected to affect the mechanical properties of the disc. PMID:135533

Adams, P; Muir, H

1976-01-01

25

Bilateral peripapillary serous retinal detachment in association with congenital optic disc pits  

PubMed Central

A middle-aged asymptomatic patient was referred to the eye clinic by her optician because of unusual optic nerve heads. She was found to have optic disc pits with bilateral serous retinal detachments which were non-progressive. She did not need any treatment and was safely followed up in the community. This uncommon condition is discussed along with possible pathophysiology and treatment. PMID:23417933

Shafi, Aabgina; Twaij, Suhair; Ibraheim, A

2013-01-01

26

Inflammatory optic disc edema due to Sarcoidosis mimicking malignant hypertension.  

PubMed

A common ocular manifestation of sarcoidosis is anterior uveitis. Posterior uveitis is uncommon and optic disc edema is rare. We report one such case in which the initial presentation was mimicking malignant hypertension as the patient had a recent record of high blood pressure. However, the painful progressive vision loss due to optic disc edema, along with anterior uveitis, and histological proof of non-caseating granulomas on transbronchial lung biopsy clinched the diagnosis of ocular sarcoidosis. There was complete resolution of signs and symptoms with institution of steroids. There was also probable cardiac involvement. This case highlights the fact that all disc edemas in a diabetic and hypertensive patients is not just due to malignant hypertension, even if there is a recent history of elevated blood pressure. PMID:25351429

Sharma, Aman; Sagar, Vinay; Singla, Veenu; Sharma, Kusum; Singh, Ramandeep; Singh, Surjit; Gupta, Amod

2014-10-28

27

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

PubMed

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

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

2013-06-01

28

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

PubMed Central

Degenerative disc disease (DDD) is still a poorly understood phenomenon because of the lack of availability of precise definition of healthy, ageing and degenerated discs. Decreased nutrition is the final common pathway for DDD and the status of the endplate (EP) plays a crucial role in controlling the extent of diffusion, which is the only source of nutrition. The vascular channels in the subchondral plate have muscarinic receptors but the possibility of enhancing diffusion pharmacologically by dilation of these vessels has not been probed. Although it is well accepted that EP damage will affect diffusion and thereby nutrition, there is no described method to quantify the extent of EP damage. Precise definitions with an objective method of differentiating healthy, ageing and degenerated discs on the basis of anatomical integrity of the disc and physiological basis of altered nutrition will be useful. This information is an urgent necessity for better understanding of DDD and also strategizing prevention and treatment. Seven hundred and thirty endplates of 365 lumbar discs from 73 individuals (26 healthy volunteers and 47 patients) with age ranging from 10–64 years were evaluated by pre-contrast and 10 min, 2, 4, 6 and 12 h post contrast MRI after IV injection of 0.3 mmol/kg of Gadodiamide. End plates were classified according to the extent of damage into six grades and an incremental score was given for each category. A total endplate score (TEPS) was derived by adding the EP score of the two endplates for each concerned disc. The base line value (SIbase) and the signal intensity at particular time periods were used to derive the enhancement percentage for each time period (Enhancement (%) = SItp – SIbase/SIbase × 100). The enhancement percentage for each time period, the time for peak enhancement (T-max) and the time intensity curve (TIC) over 12 h were used to study and compare the diffusion characteristics. The differences in pattern of diffusion were obvious visually at 4 h which was categorized into five patterns—Pattern A representing normal diffusion to Pattern E representing a total abnormality in diffusion. Degeneration was classified according to Pfirrmann’s grading and this was correlated to the TEPS and the alterations in diffusion patterns. The relationship of TEPS on the increase in DDD was evaluated by a logistic curve and the cut point for severe DDD was found by ROC curve. The influence of the variables of age, level, Modic changes, instability, annulus fibrosis defect (DEBIT), TEPS and diffusion patterns on DDD was analyzed by multiple and stepwise regression analysis. Oral nimodipine study: Additional forty lumbar end-plates from four young healthy volunteers were studied to document the effect of oral nimodipine. Pre-drug diffusion levels were studied by pre and post contrast MRI (0.3 mmol/kg of gadodiamide) at 10 min, 2, 4, 6, 12 and 24 h. Oral nimodipine was administered (30 mg QID) for 5 days and post-contrast MRI studies were performed similarly. Enhancement was calculated at vertebral body-VB; subchondral bone-SCB; Endplate Zone-EPZ and at superior and inferior peripheral nucleus pulposus-PNP and central nucleus pulposus-CNP, using appropriate cursors by a blinded investigator. Paired sample t test and area under curve (AUC) measurements were done. The incidence of disc degeneration had a significant correlation with increasing TEPS (Trend Chi-square, P < 0.01). Only one out of 83 (1.2%) disc had either Pfirrmann Grade IV or V when the score was 4 or below when compared to 34/190 (17.9%) for scores 5–7; 41 of 72 (56.9%) for scores 8–10 and 18 of 20 (90%) for scores 11 and 12 (P < 0.001 for all groups). Pearson’s correlation between TEPS and DDD was statistically significant, irrespective of the level of disc or different age groups (r value was above 0.6 and P < 0.01 for all age groups). Logistic curve fit analysis and R

Venkatadass, K.; Naresh Babu, J.; Ganesh, K.; Shetty, Ajoy P.

2008-01-01

29

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

PubMed Central

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

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

2014-01-01

30

High-Density Near-Field Optical Disc Recording  

NASA Astrophysics Data System (ADS)

We developed a high-density near-field optical recording disc system using a solid immersion lens. The near-field optical pick-up consists of a solid immersion lens with a numerical aperture of 1.84. The laser wavelength for recording is 405 nm. In order to realize the near-field optical recording disc, we used a phase-change recording media and a molded polycarbonate substrate. A clear eye pattern of 112 GB capacity with 160 nm track pitch and 50 nm bit length was observed. The equivalent areal density is 80.6 Gbit/in2. The bottom bit error rate of 3 tracks-write was 4.5× 10-5. The readout power margin and the recording power margin were ± 30.4% and ± 11.2%, respectively.

Shinoda, Masataka; Saito, Kimihiro; Ishimoto, Tsutomu; Kondo, Takao; Nakaoki, Ariyoshi; Ide, Naoki; Furuki, Motohiro; Takeda, Minoru; Akiyama, Yuji; Shimouma, Takashi; Yamamoto, Masanobu

2005-05-01

31

On the galactic disc age-metallicity relation  

E-print Network

A comparison is made between the age-metallicity relation obtained from four different types of studies: F and G stars in the Solar Neighbourhood, analysis of open clusters, galactic structure studies with the stellar population synthesis technique, and chemical evolution models. Metallicities of open clusters are corrected for the effects of the radial gradient, which we find to be -0.09 dex/kpc and to be most likely constant in time. We do not correct for the vertical gradient, since its existence and value are not firmly established. Stars and clusters trace a similar age-metallicity relation, showing an excess of rather metal-rich objects in the age range 5-9 Gyr. Galactic structure studies tend to give a more metal-poor relation than chemical evolution models. Both relations do not explain the presence of old, relatively metal-rich stars and clusters. This might be due to uncertainties in the ages of the local stars, or to pre-enrichment of the disc with material from the bulge, possibly as a result of a merger event in the early phases of the formation of our Galaxy.

G. Carraro; Y. K. Ng; L. Portinari

1998-01-21

32

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. PMID:23961015

Eken, Volkan; Nilüfer Yalç?nda?, F.; Bat?o?lu, Figen; I??kay, Canan Togay

2012-01-01

33

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

34

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 PMID:6203209

Wirtschafter, J D

1983-01-01

35

Sapphire optical discs for long term data storage  

NASA Astrophysics Data System (ADS)

Results of implementation of technical solution for long term data storage technology on the basis of single crystal sapphire are presented. The effect of birefringence on the distribution of the focused laser beam through a uniaxial birefringent medium having a vertical orientation of the optical axis is analyzed. An expression for the calculation of the geometric aberrations of the focused laser beam in single-crystal substrate of the optical disc has been presented. It is shown that the problem of data reading through a substrate of negative single crystal sapphire can be solved by using for reading a special optical system with a plate of positive single crystal materials. The experimental results confirm the efficiency of the proposed technical solution.

Kryuchyn, Andriy A.; Petrov, Viacheslav V.; Shanoilo, Semen M.; Lapchuk, Anatoliy S.; Morozov, Yevhenii M.

2014-09-01

36

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. PMID:21227470

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

37

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

38

Spectral domain optical coherence tomography morphology in optic disc pit associated maculopathy  

PubMed Central

Purpose: Our purpose was to study the clinical manifestation and course of optic pit maculopathy using Spectral Domain Optical Coherence Tomography (SD- OCT) images. Materials and Methods: We used SD-OCT to examine 20 eyes of 19 patients with a macular detachment in combination with an optic. Results: We observed five different fovea appearances in regard to fluid localization. In five eyes, we recorded changes in the fluid distribution with SD-OCT. In 17/20 eyes, we noted a communication between the perineural and subretinal and/or intraretinal space at the margin of the optic disc. Conclusion: 3-dimensional SD-OCT (3D-SDOCT) scans revealed a three-fold connection, between subretinal and intraretinal space, perineural space, and the vitreous cavity. Therefore, we suppose that intraretinal or subretinal fluid in optic pit maculopathy may have both a vitreous and cerebrospinal origin. A membrane, covering the optic nerve was noted in 14 cases. Even if it seems intact in some B-scans, it is not complete in others several micrometers apart. Additionally, we observed fluid accumulation below the margin of the optic disc and hyperreflective porous tissue in the optic disc excavation. Those findings do not influence the course of maculopathy. PMID:25116769

Michalewski, Janusz; Michalewska, Zofia; Nawrocki, Jerzy

2014-01-01

39

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

40

Laser-Induced Forward Transfer-printing of pre-machined crystalline magneto-optic garnet discs  

E-print Network

Laser-Induced Forward Transfer-printing of pre-machined crystalline magneto-optic garnet discs-optic Yttrium Iron Garnet films. Debris-free circular micro-discs with smooth edges and surface uniformity have

Sóbester, András

41

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

PubMed

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

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

2014-06-15

42

Aquaporin-1 and Aquaporin-3 Expressions in the Intervertebral Disc of Rats with Aging  

PubMed Central

Objective: The intervertebral disc (IVD) undergoes biochemical and morphologic degenerative changes during the process of aging. Aquaporins (AQPs) are a family of water channel proteins that facilitate water and small solute movement in tissues and may have a potential role in the aging degeneration of IVDs. One of the important problems in understanding disc degeneration is to find cellular molecules which contribute to the pathogenesis of IVDs. XThe aim of this study was to demonstrate the expression of aquaporin 1 and 3 in nucleus pulposus (NP), annulus fibrosus (AF) cells of rat lumbar intervertebral discs from both young and aged animals using immunohistochemistry. Material and Methods: Twenty Wistar-albino rats were included in the study. The rats were separated into two groups: 2-month-old rats (n=10) as the young group, 18-month-old rats (n=10) as the old group. The intervertebral disc tissues obtained from the lumbar spine (L1–L4, 4 discs) were used for immunohistochemical staining of AQP-1 and 3. Results: This study demonstrated that AQP-1 and AQP-3 immunoreactivity significantly decreased in NP and AF of aged rats compared to the young rats. Conclusion: We suggest that AQP-1 and 3 may contribute to the age related degeneration of the intervertebral disc. PMID:25207032

Ta?, Ufuk; Çayl?, Sevil; ?nan?r, Ahmet; Özyurt, Birsen; Ocakl?, Seda; Karaca, Zafer ?smail; Sars?lmaz, Mustafa

2012-01-01

43

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

PubMed Central

Purpose To investigate the etiology of bilateral disc swelling in Japanese. Methods Using Kitasato University’s Department of Neuro-Ophthalmology medical records and fundus photographs of the period December 1977 through November 2010, we retrospectively identified 121 outpatients who had been initially confirmed with bilateral disc swelling. Results The most common cause of the bilateral disc swelling was increased intracranial pressure (ICP) (59%); followed by pseudopapillitis (16%); uveitis (8%); hypertensive retinopathy (5%); bilateral optic neuritis, acute disseminated encephalomyelitis (ADEM) and optic disc drusen (all at 2% each); and leukemia (1%). Unknown etiology accounted for 6% of the cases. Conclusion Although increased ICP is the most common etiology for bilateral disc swelling, it can also be triggered by a variety of other causes. Pseudopapillitis is the most important progenitor of bilateral disc swelling in Japanese. PMID:25031527

Iijima, Kei; Shimizu, Kimiya; Ichibe, Yoshiaki

2014-01-01

44

Liquid immersion deep-UV optical disc mastering for high data capacity ROM discs  

NASA Astrophysics Data System (ADS)

In this paper we describe the liquid immersion mastering technique and its application to the mastering of ROM discs for the Blu-ray Disc system and for ROM discs with considerably higher data densities. Replicated 25GB BD-ROM discs were evaluated using a standard blue test player (?=405nm, NA=0.85). A bottom jitter value with limit equalizer of less than 5% was measured. Also the values of asymmetry, normalized push pull and symbol error rate were well within the Blu-ray Disc format specification, offering a large process window. Full-format BD-ROM test discs with high definition video content were mastered and their successful read-back was demonstrated. In addition we show that liquid immersion mastering can successfully be applied for mastering of considerably higher densities. Measurements on replicated discs up to data densities above 40GB per layer are discussed. The present results demonstrate that liquid immersion mastering is a proven technology for the mass-production of high data capacity ROM discs.

Neijzen, Jaap H. M.; Meinders, Erwin R.; Boamfa, Marius I.; Chen, Dianyong

2005-09-01

45

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

PubMed Central

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

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

2007-01-01

46

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

PubMed Central

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

2013-01-01

47

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

PubMed

Oxidative damage is a well-established driver of aging. Evidence of oxidative stress exists in aged and degenerated discs, but it is unclear how it affects disc metabolism. In this study, we first determined whether oxidative stress negatively impacts disc matrix metabolism using disc organotypic and cell cultures. Mouse disc organotypic culture grown at atmospheric oxygen (20% O(2)) exhibited perturbed disc matrix homeostasis, including reduced proteoglycan synthesis and enhanced expression of matrix metalloproteinases, compared to discs grown at low oxygen levels (5% O(2)). Human disc cells grown at 20% O(2) showed increased levels of mitochondrial-derived superoxide anions and perturbed matrix homeostasis. Treatment of disc cells with the mitochondria-targeted reactive oxygen species (ROS) scavenger XJB-5-131 blunted the adverse effects caused by 20% O(2). Importantly, we demonstrated that treatment of accelerated aging Ercc1(-/?) mice, previously established to be a useful in vivo model to study age-related intervertebral disc degeneration (IDD), also resulted in improved disc total glycosaminoglycan content and proteoglycan synthesis. This demonstrates that mitochondrial-derived ROS contributes to age-associated IDD in Ercc1(-/?) mice. Collectively, these data provide strong experimental evidence that mitochondrial-derived ROS play a causal role in driving changes linked to aging-related IDD and a potentially important role for radical scavengers in preventing IDD. PMID:23389888

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

2013-07-01

48

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

NASA Astrophysics Data System (ADS)

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

Schwartz, Bernard; Takamoto, Takenori

1980-07-01

49

Estimated Rates of Retinal Ganglion Cell Loss in Glaucomatous Eyes with and without Optic Disc Hemorrhages  

PubMed Central

Purpose To evaluate whether optic disc hemorrhages are associated with faster rates of estimated retinal ganglion cell (RGC) loss in glaucoma. Methods A longitudinal observational cohort study of 222 eyes of 122 patients with glaucoma recruited from the Diagnostic Innovations Glaucoma Study (DIGS) followed for an average of 3.74±0.85 years. All subjects had optical coherence tomography and standard automated perimetry during follow up. Optic disc hemorrhages were detected by masked evaluation of stereophotographs. Rates of change in estimated numbers of RGCs were determined using a previously described method. A random coefficients model was used to investigate the relationship between disc hemorrhages and rates of change in estimated RGC counts over time. Results 19 eyes of 18 subjects had at least one disc hemorrhage during follow up. At baseline, average estimated RGC counts in eyes with and without disc hemorrhages were 677,994 cells and 682,021 cells, respectively (P?=?0.929). Eyes with optic disc hemorrhages during follow-up had significantly faster rates of estimated RGC loss than eyes without disc hemorrhages (22,233 cells/year versus 10,704 cells/year, P?=?0.020). The effect of disc hemorrhages on the rates of estimated RGC loss remained significant after adjusting for confounding variables. Conclusion Eyes with disc hemorrhages showed faster rates of RGC loss compared to eyes without disc hemorrhages. These results provide further evidence that disc hemorrhages should be considered as an indicator of increased risk for faster neural loss in glaucoma. PMID:25157619

Gracitelli, Carolina P. B.; Tatham, Andrew J.; Zangwill, Linda M.; Weinreb, Robert N.; Liu, Ting; Medeiros, Felipe A.

2014-01-01

50

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

NASA Astrophysics Data System (ADS)

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

Martig, Marie; Minchev, Ivan; Flynn, Chris

2014-08-01

51

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

PubMed

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

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

2011-07-01

52

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

PubMed Central

Background: To examine the effect of optic disc area on peripapillary RNFLT (retinal nerve fiber layer thickness) measurement at circle diameter of 3.4 mm around optic nerve head using spectral OCT/SLO (Optical coherence tomography/scanning laser ophthalmoscope). Materials and Methods: In this prospective, cross sectional study, one hundred and two eyes of 102 normal subjects underwent RNFLT and disc area measurement using spectral OCT/SLO. Based on disc area, subjects were divided into three groups i.e., <3 mm2 (32 eyes), 3-4 mm2 (36 eyes) and >4 mm2 (34 eyes). The effect of disc area on RNFLT parameters was analyzed using linear regression analysis. Results: The mean and quadrant RNFLT did not show significant correlation with disc area in subjects with disc area of <4 mm2, however in eyes with disc area >4 mm2, average RNFLT, superior and temporal quadrant RNFLT showed negative correlation with disc area, which was statistically significant (P = 0.004, P = 0.005 and P = 0.002, respectively) Conclusion: In healthy eyes of disc area <4 mm2, disc size does not appear to affect peripapillary RNFLT measurement by spectral OCT/SLO. Average, superior and temporal quadrant RNFLT measurements were inversely proportional to disc area in eyes with disc area >4 mm2. Hence, RNFLT measurement by OCT in eyes with optic disc area of >4 mm2 should be interpreted carefully. PMID:24881611

Mansoori, Tarannum; Balakrishna, Nagalla; Viswanath, Kalluri

2014-01-01

53

Genotoxic stress accelerates age-associated degenerative changes in intervertebral discs.  

PubMed

Intervertebral disc degeneration (IDD) is the leading cause of debilitating spinal disorders such as chronic lower back pain. Aging is the greatest risk factor for IDD. Previously, we demonstrated IDD in a murine model of a progeroid syndrome caused by reduced expression of a key DNA repair enzyme. This led us to hypothesize that DNA damage promotes IDD. To test our hypothesis, we chronically exposed adult wild-type (Wt) and DNA repair-deficient Ercc1(-/?) mice to the cancer therapeutic agent mechlorethamine (MEC) or ionization radiation (IR) to induce DNA damage and measured the impact on disc structure. Proteoglycan, a major structural matrix constituent of the disc, was reduced 3-5× in the discs of MEC- and IR-exposed animals compared to untreated controls. Expression of the protease ADAMTS4 and aggrecan proteolytic fragments was significantly increased. Additionally, new PG synthesis was reduced 2-3× in MEC- and IR-treated discs compared to untreated controls. Both cellular senescence and apoptosis were increased in discs of treated animals. The effects were more severe in the DNA repair-deficient Ercc1(-/?) mice than in Wt littermates. Local irradiation of the vertebra in Wt mice elicited a similar reduction in PG. These data demonstrate that genotoxic stress drives degenerative changes associated with IDD. PMID:23262094

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

2013-01-01

54

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

PubMed Central

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

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

2013-01-01

55

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

Microsoft Academic Search

This study was carried out to determine the effect of age on the intervertebral disc, using a rabbit model. Anulus fibrosus\\u000a and nucleus pulposus tissue from New Zealand white rabbits aged 3 years old (old rabbits) and 6 months old (young rabbits)\\u000a were used. The water content, the proteoglycan, the DNA content, and the mRNA levels of aggrecan, type I collagen, and

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

2010-01-01

56

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

57

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. PMID:24167327

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

2013-01-01

58

Case Report of Optic Disc Drusen with Simultaneous Peripapillary Subretinal Hemorrhage and Central Retinal Vein Occlusion  

PubMed Central

A 52-year-old Chinese gentleman presented with right eye floaters and photopsia over one week. His visual acuities were 20/20 bilaterally. Posterior segment examination showed a right eye swollen optic disc and central retinal vein occlusion (CRVO) associated with an area of subretinal hemorrhage adjacent to the optic disc. Fundus fluorescein (FA) and indocyanine green angiographies (ICGA) of the right eye did not demonstrate choroidal neovascularization (CNV), polypoidal choroidal vasculopathy (PCV), or retinal ischemia. Ultrasound B-scan revealed optic disc drusen (ODD). In view of good vision and absence of CNV, he was managed conservatively with spontaneous resolution after two months. Commonly, ODD may directly compress and mechanically rupture subretinal vessels at the optic disc, resulting in peripapillary subretinal hemorrhage, as was likely the case in our patient. Mechanical impairment of peripapillary circulation also results in retinal ischemia and may trigger the development of choroidal neovascularization (CNV) and/or polypoidal choroidal vasculopathy (PCV), leading to subretinal haemorrhage. Compromise in central venous outflow with increased retinal central venous pressure from the direct mechanical effects of enlarging ODD results in central retinal vein occlusion (CRVO). Patients with subretinal hemorrhage and CRVO from ODD should be monitored closely for the development of potentially sight-threatening complications. PMID:25544921

Law, David Zhiwei; Yang, Francine Pei Lin; Teoh, Stephen Charn Beng

2014-01-01

59

Etiology and Pathogenetic Mechanisms of Optic Disc Swelling with Visual Loss  

Microsoft Academic Search

A nonrandomized, prospective, interdisciplinary pilot study of 102 patients with noncompressive optic disc swelling with visual loss (ODSWVL) was performed in order to investigate etiologic and pathogenetic mechanisms. Forty-six patients suffered from underlying inflammatory disease. Seventeen patients suffered from highly probable cardiogenic embolization, 16 patients from multiple vascular risk factors. The remaining patients of the noninflammatory disease group suffered from

Johannes Stammen; Renate Unsöld; Gabriele Arendt; Ernst G. Vester; Peter Heering; Hans-Joachim Freund; Bodo-Eckehard Strauer; Bernd Grabensee

1999-01-01

60

Channel model for InSb-based superresolution optical disc system.  

PubMed

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

Hepper, Dietmar; Knappmann, Stephan

2010-04-01

61

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

Microsoft Academic Search

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

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

2008-01-01

62

Vectorial high NA computation of the light electric field near the focus and inside the thin film stack of optical discs  

Microsoft Academic Search

The trends in optical recording on discs are to use higher numerical apertures and lower wavelengths. The next generation of discs will certainly use NA=0.85 focusing optics and ?=400 nm laser sources (DVR). In order to simulate thermal processes while recording and reading an optical disc, it is essential to determine the exact beat source. With such high apertures, and

A. Lagrange; L. Poupinet

2002-01-01

63

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.

2012-03-01

64

PhaseChange Optical Disc with the Data Recording Rate of 100 Mbps  

Microsoft Academic Search

We have developed a new phase-change optical disc having a transparent cover layer on the basis of the new optical recording system (DVR) with a blue laser (405 nm) and a dual objective lens with a numerical aperture (NA) of 0.85. We have developed the new technologies as follows. We used a transparent cover layer made of spin-coated UV resin,

Hiroyasu Inoue; Hideki Hirata; Tsuyoshi Komaki; Tatsuya Kato; Hiroshi Shingai; Naoki Hayashida; Hajime Utsunomiya

2002-01-01

65

Glaucoma-Induced Optic Disc Morphometric Changes and Glaucoma Diagnostic Ability of Heidelberg Retina Tomograph II in Highly Myopic Eyes  

PubMed Central

Purpose This study was performed to first investigate the morphological differences in the optic nerve head between highly myopic non-glaucomatous controls and highly myopic glaucomatous eyes in comparison with the differences between emmetropic non-glaucomatous controls and emmetropic glaucomatous eyes using confocal scanning laser ophthalmoscopy. Further, the ability of the apparatus in glaucoma diagnosis in highly myopic eyes was compared with that in emmetropic eyes. Methods Healthy subjects and age-matched patients with early-stage open-angle glaucoma were divided into two groups: emmetropic eyes (?1.0 to +1.0 diopters) and highly myopic eyes (?12.0 to ?5.0 diopters).The participants were comprised of 65 emmetropic normal eyes, 59 emmetropic glaucomatous eyes, 62 highly myopic normal eyes, and 68 highly myopic glaucomatous eyes and eyes with pathologic myopia were carefully excluded. Confocal scanning laser tomographic parameters were compared among all subjects after adjustment for age and disc area. The ROC curves and sensitivity and specificity for glaucoma detection using several clinical methods were then compared between the emmetropic and highly myopic eyes. Results Rim area, cup/disc area ratio, mean cup depth, and cup shape measure of glaucoma eyes are significantly different from those of normal eyes in both highly myopic eyes and emmetropic eyes. Methodological overestimation of retinal nerve fiber layer cross sectional area due to optic disc tilting was suggested in the highly myopic eyes. The diagnostic performance of glaucoma using several discriminant methods significantly deteriorated in the highly myopic eyes. Conclusions In the highly myopic glaucomatous eyes, confocal scanning laser tomographic parameters were significantly different from that of non-glaucomatous highly myopic eyes but diagnostic performance of glaucoma was deteriorated than that in emmetropic eyes. These findings demonstrate the utility and limitations of the apparatus in diagnosing glaucoma in highly myopic patients. PMID:24475117

Mayama, Chihiro; Tsutsumi, Tae; Saito, Hitomi; Asaoka, Ryo; Tomidokoro, Atsuo; Iwase, Aiko; Otani, Shinichiro; Miyata, Kazunori; Araie, Makoto

2014-01-01

66

Peculiar arcuate scotoma in pathologic myopia—optical coherence tomography to detect peripapillary neural tissue loss over the disc crescent  

Microsoft Academic Search

Background: Optical co- herence tomography (OCT) was used to detect peripapillary neural tissue loss (PPNTL) over the disc crescent in pathologic myopia. The retinal neural tissue loss located inside the disc crescent in pathologic myopia is a newly recognized fundus lesion. Methods: Review of ten eyes of ten patients with peripapillary yellowish- white retinal lesions who underwent OCT for evaluation

Tzyy-Chang Ho; Yung-Feng Shih; Szu-Yung Lin; Luke L.-K. Lin; Muh-Shy Chen

2005-01-01

67

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

PubMed Central

BACKGROUND CONTEXT Destruction of extracellular matrix (ECM) leads to intervertebral disc degeneration (IDD), which underlies many spine-related disorders. Matrix metalloproteinases (MMPs), and disintegrins and metalloproteinases with thrombospondin motifs (ADAMTSs) are believed to be the major proteolytic enzymes responsible for ECM degradation in the intervertebral disc (IVD). PURPOSE To summarize the current literature on gene expression and regulation of MMPs, ADAMTSs, and tissue inhibitors of metalloproteinases (TIMPs) in IVD aging and IDD. METHODS A comprehensive literature review of gene expression of MMP, ADAMTS, and TIMP in human IDD and reported studies on regulatory factors controlling their expressions and activities in both human and animal model systems. RESULTS Upregulation of specific MMPs (MMP-1, -2, -3, -7, -8, -10, and -13) and ADAMTS (ADAMTS-1, -4, and -15) were reported in human degenerated IVDs. However, it is still unclear from conflicting published studies whether the expression of ADAMTS-5, the predominant aggrecanase, is increased with IDD. Tissue inhibitors of metalloproteinase-3 is downregulated, whereas TIMP-1 is upregulated in human degenerated IVDs relative to nondegenerated IVDs. Numerous studies indicate that the expression levels of MMP and ADAMTS are modulated by a combination of many factors, including mechanical, inflammatory, and oxidative stress, some of which are mediated in part through the p38 mitogen-activated protein kinase pathway. Genetic predisposition also plays an important role in determining gene expression of MMP-1, -2, -3, and -9. CONCLUSIONS Upregulation of MMP and ADAMTS expression and enzymatic activity is implicated in disc ECM destruction, leading to the development of IDD. Future IDD therapeutics depends on identifying specific MMPs and ADAMTSs whose dysregulation result in pathological proteolysis of disc ECM. PMID:23369495

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

2013-01-01

68

From Clinical Examination of the Optic Disc to Clinical Assessment of the Optic Nerve Head: A Paradigm Change  

PubMed Central

Purpose To review and interpret optic nerve head (ONH) anatomy detected with spectral domain optical coherence tomography (SD-OCT) pertaining to the clinical examination of the optic disc and propose that a paradigm change for clinical assessment of the ONH is necessary. Design Perspective. Methods Presently, the clinician evaluates neuroretinal rim health according to the appearance of the optic disc, the clinically visible surface of the ONH. Recent anatomic findings with SD-OCT have challenged the basis and accuracy of current rim evaluation. We demonstrate why incorporation of SD-OCT imaging of the ONH into the clinical examination of the disc is required. Results Disc margin based rim evaluation lacks a solid anatomic basis and results in variably inaccurate measurements for two reasons. First, the clinically visible disc margin is an unreliable outer border of rim tissue due to clinically and photographically invisible extensions of Bruch’s membrane. Second, rim tissue orientation is not considered in width measurements. We propose alternative anatomically and geometrically accurate SD-OCT based approaches for rim assessment that have enhanced detection of glaucoma. We also argue for new data acquisition and analysis strategies with SD-OCT that account for the large inter-individual variability in the angle between the fovea and ONH. Conclusions We propose a 4-point paradigm change for clinical assessment of the ONH that is anchored to the eye-specific anatomy and geometry of the ONH and fovea. Our approach is designed to enhance the accuracy and consistency of rim width, as well as peripapillary and macular intraretinal thickness measurements. PMID:23768651

Chauhan, Balwantray C.; Burgoyne, Claude F.

2013-01-01

69

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. PMID:24082669

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

2013-01-01

70

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

PubMed

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

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

2014-04-01

71

Near IR photometry of the old open clusters Berkeley 17 and Berkeley 18. Probing the age of the galactic disc  

E-print Network

We report on near IR ($J$ and $K$ bands) observations of two $8 \\times 8 \\~(arcmin)^{2}$ regions centered on the old open clusters Berkeley~17 and Berkeley~18, for which only optical photometry (in $B$,$V$ and $I$ bands) exists. $J$ and $K$ photometry allows us to obtain an independent estimate of cluster metallicity by means of the relationship between the spectroscopic metallicity and the Red Giant Branch (RGB) slope calibrated by Tiede et al (1997). From the analysis of the colour magnitude diagram (CMD) and luminosity function (LF), Berkeley~17 turns out to have a metal content $[Fe/H]~\\sim~-0.35$. It is $9~Gyr$ old, suffers from a reddening $E(B-V) = 0.58 mag$ and has an heliocentric distance of $2.5 kpc$. Berkeley~17 comes out to be substantially younger than in previous work (age $\\approx 13~Gyr$). On the other hand Berkeley~18 is found to have solar metal abundance, and to be younger than Berkeley~17, with an age of about $4~Gyr$. While we confirm Kaluzny (1997) reddening estimate, we significantly revise the distance of the cluster, which lies $4.5 kpc$ from the Sun. These results on two open clusters believed to be between the oldest put constraints on the age and the evolution of the Galactic Disc. The absence of clusters older than $8-9~Gyr$ suggests the possibility that the Galaxy underwent a star formation minimum between 13 and $10~Gyr$ ago.

Giovanni Carraro; Antonella Vallenari; Leo Girardi; Andrea Richichi

1998-12-15

72

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

PubMed Central

Background This case is unique because it is the first reported case of Down syndrome with morning glory optic disc anomaly in literature. Case presentation A 15-year-old girl with features of Down syndrome presented to the Clinic of Ophthalmology for a regular ophthalmologic examination. Her best corrected visual acuity was 20/50 in the right eye and 20/20 in the left eye. The fundus examination revealed findings compatible with unilateral morning glory optic disc anomaly in the right eye. The patient underwent a complete ophthalmologic and systemic evaluation to explore possible associated findings. Conclusion This case report emphasizes the importance of ophthalmic screening-examinations in Down children to rule out any vision relevant pathology. PMID:24725623

2014-01-01

73

Optical Disc Technology and the Cooperative Television Library.  

ERIC Educational Resources Information Center

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

Kranch, Douglas

1989-01-01

74

The Phase Change Optical Disc with the Data Recording Rate of 140 Mbps  

Microsoft Academic Search

We have been developing a new phase change optical disc on the base of the recording system (DVR) with a blue laser (405 nm) and dual objective lens with a numerical aperture (\\\\mathit{NA}) of 0.85. We have achieved the data recording rate of 140 Mbps. The significant techniques to achieve the recording rate as follows: rearrangement of the AgInSbTeGe composition

Tatsuya Kato; Hideki Hirata; Tsuyoshi Komaki; Hiroyasu Inoue; Hiroshi Shingai; Naoki Hayashida; Hajime Utsunomiya

2002-01-01

75

Quantitative chemical tagging, stellar ages and the chemo-dynamical evolution of the Galactic disc  

NASA Astrophysics Data System (ADS)

The early science results from the new generation of high-resolution stellar spectroscopic surveys, such as Galactic Archaeology with HERMES (GALAH) and the Gaia European Southern Observatory survey (Gaia-ESO), will represent major milestones in the quest to chemically tag the Galaxy. Yet this technique to reconstruct dispersed coeval stellar groups has remained largely untested until recently. We build on previous work that developed an empirical chemical tagging probability function, which describes the likelihood that two field stars are conatal, that is, they were formed in the same cluster environment. In this work, we perform the first ever blind chemical tagging experiment, i.e. tagging stars with no known or otherwise discernible associations, on a sample of 714 disc field stars with a number of high-quality high-resolution homogeneous metal abundance measurements. We present evidence that chemical tagging of field stars does identify coeval groups of stars, yet these groups may not represent distinct formation sites, e.g. as in dissolved open clusters, as previously thought. Our results point to several important conclusions, among them that group finding will be limited strictly to chemical abundance space, e.g. stellar ages, kinematics, colours, temperature and surface gravity do not enhance the detectability of groups. We also demonstrate that in addition to its role in probing the chemical enrichment and kinematic history of the Galactic disc, chemical tagging represents a powerful new stellar age determination technique.

Mitschang, A. W.; De Silva, G.; Zucker, D. B.; Anguiano, B.; Bensby, T.; Feltzing, S.

2014-03-01

76

Electro-Optic Resonant FSR Modulators Based on a Dual-Disc Resonator for Increasing the Sensitivity-Bandwidth Product  

Microsoft Academic Search

Resonant free-spectral-range (FSR) RF-optic modulators using dual-disc resonators with a 2:1 ratio of the radii of the discs have been proposed and theoretically analyzed to increase the sensitivity-bandwidth product compared with that of a single resonator modulator. The transmission of the coupled resonator structure is analyzed for various coupling parameters. The phase of the larger resonator is electro-optically modulated, and

Yoo Seung Lee; Sang-Shin Lee; William H. Steier

2010-01-01

77

Optical measurement of pulp quantity in a rotating disc refiner  

NASA Astrophysics Data System (ADS)

An optical method based on light extinction was used in measuring pulp quantity in the plate gap of a 10 MW thermomechanical pulping refiner for the first time. The relationship between pulp quantity and light extinction was determined by empirical laboratory experiments. The empirical relationship was then applied to interpret the image data obtained from field measurements. The results show the local distribution of pulp in the refiner plate gap for different rotor plate positions and refiner operation points. The maximum relative uncertainty in the measured pulp quantity was 50%. Relative pulp distributions were measured at higher accuracy. The measurements have influenced the development of a laser-based optical diagnostic method that can be applied to the quantitative visualization of technically demanding industrial processes.

Alahautala, Taito; Lassila, Erkki; Hernberg, Rolf; Härkönen, Esko; Vuorio, Petteri

2004-11-01

78

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

PubMed

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

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

2013-04-01

79

Displacement of foveal area toward optic disc after macular hole surgery with internal limiting membrane peeling  

PubMed Central

Purpose To determine whether there is a displacement of the fovea toward the optic disc after successful macular hole (MH) surgery with internal limiting membrane (ILM) peeling. Methods The medical records of 54 eyes of 53 patients that had undergone pars plana vitrectomy with ILM peeling and gas or air tamponade for an idiopathic MH were evaluated. Spectral-domain optical coherence tomography (OCT) had been performed before and >6 months after the surgery. The preoperative distances between the center of the MH and the optic disc (MH-OD), center of the MH and the bifurcation or crossing of retinal vessels (MH-RV) were measured in the OCT images. In addition, the postoperative distance between the center of the fovea and optic disc (F-OD) and the center of the fovea and the same bifurcation or crossing of retinal vessels (F-RV) were measured in the OCT images. Results The F-OD was 2.67±0.33 disc diameters (DD), which was significantly shorter than that of the MH-OD of 2.77±0.33 DD (P<0.001). The F-RV was also significantly shorter than the MH-RV on the inner nasal area (from 0.85±0.16DD to 0.79±0.15DD; P<0.001), the inner temporal area (from 0.82±0.15DD to 0.77±0.14DD; P<0.001), and outer nasal area (from 1.70±0.31DD to 1.65±0.32DD; P<0.001), but it was significantly longer than the MH-RV in the outer temporal area (from 1.65±0.29DD to 1.68±0.29DD; P<0.001). Conclusion Our results showed that successful closure of a MH by vitrectomy with ILM peeling and gas tamponade leads to a displacement of the center of the macula toward the optic disc. PMID:23703632

Kawano, K; Ito, Y; Kondo, M; Ishikawa, K; Kachi, S; Ueno, S; Iguchi, Y; Terasaki, H

2013-01-01

80

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

Microsoft Academic Search

Background  The present study was conducted to address whether the intervertebral disc of rabbit could be considered (i) as a valuable\\u000a model to provide new insights into the tissue and cellular changes of Nucleus pulposus aging and (ii) as an appropriate tool\\u000a to investigate the efficacy of Nucleus pulposus cell-based biotherapies.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  Lumbar intervertebral disc from rabbits with increasing ages (1, 6

Johann Clouet; Marianne Pot-Vaucel; Gaël Grimandi; Martial Masson; Julie Lesoeur; Borhane H Fellah; Olivier Gauthier; Marion Fusellier; Yan Cherel; Yves Maugars; Jérôme Guicheux; Claire Vinatier

2011-01-01

81

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

PubMed

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

Hepper, Dietmar

2011-06-10

82

Reduction of Interlayer Crosstalk of Multilayer Optical Disc by Using Phase-Diversity Homodyne Detection  

NASA Astrophysics Data System (ADS)

We theoretically and experimentally studied the effects of phase-diversity homodyne detection on the interlayer crosstalk of a multilayer optical disc by comparison with those of conventional intensity detection. From analytical studies, we clarified the differences in interlayer crosstalk of both detections. Interlayer crosstalk consists of two noises, the intensity of the stray light N1 and the interference between the signal and stray light N2. The noise N1, which is dominant between these two, drastically decreases with layer spacing in phase-diversity homodyne detection owing to mismatch in the phase distribution between reference and stray light compared with that in intensity detection. Simulations and experiments on a dual-layer Blu-ray DiscTM having a layer spacing less than 10 µm demonstrated that phase-diversity homodyne detection provided higher tolerance to interlayer crosstalk than the conventional intensity detection.

Ide, Tatsuro; Osawa, Kentaro; Mikami, Hideharu; Watanabe, Koichi

2012-08-01

83

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

NASA Astrophysics Data System (ADS)

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

Zhang, Xue-Guang

2015-02-01

84

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

PubMed Central

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

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

2014-01-01

85

Optic disc topography in Malay patients with normal-tension glaucoma and primary open-angle glaucoma  

PubMed Central

Background There are limited data concerning the optic disc topography in normal-tension glaucoma (NTG) and primary open-angle glaucoma (POAG) patients living in Southeast Asian countries. This study aims to compare optic disc parameters in patients with NTG and POAG in Malaysia and to discuss the results in comparison with studies of NTG and POAG in other Asian countries. Methods This prospective cross-sectional study was performed in two hospitals with glaucoma service in Malaysia from 2010 to 2012. Seventy-seven patients of Malay ethnicity were enrolled in this study, including 32 NTG patients and 45 POAG patients. Using the Heidelberg Retinal Tomograph III, we measured optic disc area, cup area, rim area, cup volume, rim volume, cup-to-disc area ratio, mean cup depth, maximum cup depth, cup shape measure, height variation contour, mean retinal nerve fiber layer thickness, and retinal nerve fiber layer cross-sectional area. Results The eyes for NTG patients had significantly larger optic disc areas (2.65 [standard deviation, 0.41] vs 2.40 [standard deviation, 0.36] mm2, respectively; P=0.006) and cup areas (1.54 [standard deviation, 0.43] vs 1.32 [standard deviation, 0.40] mm2, respectively; P=0.027) compared with the eyes of POAG patients. Comparison of the other parameters between the two groups revealed no significant difference (P>0.050). The moderate and severe NTG patients showed significantly deeper cups and larger disc and cup areas when compared with the moderate and severe POAG patients (P<0.050). Conclusion The NTG patients in this study have notably larger optic disc and cup areas than the POAG patients. Our observations are consistent with those reported in studies of NTG and POAG patients in Korea. The deeper cups and larger disc and cup areas may serve as indicators of severity when comparing NTG with POAG. However, these findings require verification with IOP and visual field results. PMID:25540578

Adlina, Abdul Rahim; Alisa-Victoria, Koh; Shatriah, Ismail; Liza-Sharmini, Ahmad Tajudin; Ahmad, Mt Saad

2014-01-01

86

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

PubMed

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

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

2012-07-01

87

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

2011-03-01

88

How age influences unravelling morphology of annular lamellae - a study of interfibre cohesivity in the lumbar disc.  

PubMed

Although age- and degeneration-related changes in the morphology and biochemistry of the annulus fibrosus have been extensively reported, studies of tensile strength changes show only a weak correlation with maturity. Given that the disc is a tissue system in which significant levels of deformation occur with normal physiological loading, there may be structure-related properties that provide a better indicator of the influence of ageing on its function. This study is a morphological investigation of lamellar interfibre cohesivity with respect to maturity. Anterior segments of ovine lumbar discs in two age groups were cut at one of two section angles to generate intralamellar and interlamellar slices. These slices of hydrated annular tissue were subjected separately to microtensile and swelling forces, and examined using differential interference contrast microscopy. There were distinct differences in microstructural responses to transverse extension between the immature and mature intralamellar slices. The immature tissue exhibited a diffuse expansion of the array to form a fine fibrous net. In contrast, the mature tissue displayed a discontinuous expansion with the development of clefts and localized fibre buckling. A difference was also observed in the free-swelling response; the immature slices remained planar, whereas the cropped lamellar fibres in the mature slices exhibited a folded, buckled morphology. Morphological evidence from these experiments infers differences in fibre cohesivity between the immature and mature tissues, consistent with biochemical and histological studies. More extreme levels of deformation in the mature tissue could result in discontinuous opening of the fibrous arrays, which might have the potential to lead to cleft formation. These clefts may, in turn, provide micropaths through which nuclear material could extrude. Importantly, with many animal studies carried out on immature discs, the results here suggest that some caution is required with respect to extrapolating annular behaviour beyond this age group. PMID:20447247

Schollum, Meredith L; Robertson, Peter A; Broom, Neil D

2010-03-01

89

How age influences unravelling morphology of annular lamellae – a study of interfibre cohesivity in the lumbar disc  

PubMed Central

Although age- and degeneration-related changes in the morphology and biochemistry of the annulus fibrosus have been extensively reported, studies of tensile strength changes show only a weak correlation with maturity. Given that the disc is a tissue system in which significant levels of deformation occur with normal physiological loading, there may be structure-related properties that provide a better indicator of the influence of ageing on its function. This study is a morphological investigation of lamellar interfibre cohesivity with respect to maturity. Anterior segments of ovine lumbar discs in two age groups were cut at one of two section angles to generate intralamellar and interlamellar slices. These slices of hydrated annular tissue were subjected separately to microtensile and swelling forces, and examined using differential interference contrast microscopy. There were distinct differences in microstructural responses to transverse extension between the immature and mature intralamellar slices. The immature tissue exhibited a diffuse expansion of the array to form a fine fibrous net. In contrast, the mature tissue displayed a discontinuous expansion with the development of clefts and localized fibre buckling. A difference was also observed in the free-swelling response; the immature slices remained planar, whereas the cropped lamellar fibres in the mature slices exhibited a folded, buckled morphology. Morphological evidence from these experiments infers differences in fibre cohesivity between the immature and mature tissues, consistent with biochemical and histological studies. More extreme levels of deformation in the mature tissue could result in discontinuous opening of the fibrous arrays, which might have the potential to lead to cleft formation. These clefts may, in turn, provide micropaths through which nuclear material could extrude. Importantly, with many animal studies carried out on immature discs, the results here suggest that some caution is required with respect to extrapolating annular behaviour beyond this age group. PMID:20447247

Schollum, Meredith L; Robertson, Peter A; Broom, Neil D

2010-01-01

90

A 3D optical profilometer using a compact disc reading head  

NASA Astrophysics Data System (ADS)

The design, construction and performance of a novel optical profilometer based on the laser reading head of a compact disc player is described. The instrument is capable of self-guided scanning along arbitrary contours by utilizing the focus and radial tracking signals from the sensor head. The sensor is mounted on an x, y, 0957-0233/9/8/019/img6 motorized stage. The radial tracking signal provides the feedback for the angular position of the sensor, ensuring that the optical axis of the sensor is always perpendicular to the profile preventing the signal loss that occurs in conventional profilometers due to deflection of the light beam. The focus signal has a sensitivity in the nanometre range which makes the precision of the stages used to perform the scanning movements the dominant limiting factor for the measuring accuracy. The sensor head intermittently follows the contour, collecting datapoints at a predetermined lateral resolution. The profile is digitized in the form of x, y, and 0957-0233/9/8/019/img6 coordinates for each scanpoint. The accuracy of the instrument was verified by scanning standard measures with flat and circular cross sections. The mechanical structure of the prototype instrument was purpose built for the measurement of rigid corneal contact lenses. Various lenses have been measured and profile graphs are illustrated.

Ehrmann, Klaus; Ho, Arthur; Schindhelm, Klaus

1998-08-01

91

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

92

Super-Resolution Optical Disc with Radial Density Increased by Narrowed Track Pitch Corresponding to Diffraction Limit  

NASA Astrophysics Data System (ADS)

In-Sb-based super-resolution near-field structure read-only-memory discs with radial density increased by introducing a narrow track pitch corresponding to the diffraction limit of an optical system were developed. Using an optical system with a laser diode with a wavelength of 405 nm and an objective lens with a numerical aperture of 0.85, we confirmed that differential phase detection (DPD) could detect track errors from disc samples recorded random data including a minimum pit length of 75 nm in a 240 nm track period. It has higher capability of track error detection than push-pull detection at a narrowed track pitch. Moreover, bit error rates satisfying the criterion of 3.0×10-4 were experimentally obtained for 66.7-GB-capacity disc samples with a 240 nm track pitch through signal processing with the partial response maximum likelihood of the (1,2,2,1)-type, by applying DPD to tracking servo control. The feasibility of increasing the track density of the Blu-ray DiscTM physical format by 1.33 times was indicated.

Nakai, Kenya; Ohmaki, Masayuki; Takeshita, Nobuo; Hyot, Bérangère; André, Bernard; Poupinet, Ludovic; Shima, Takayuki

2013-09-01

93

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

Microsoft Academic Search

Lower back pain due to intervertebral disc (IVD) degeneration is a prevalent problem which drastically affects the quality of life of millions of sufferers. Healthy IVDs begin with high populations of notochordal cells in the nucleus pulposus, while by the second stage of degeneration, these cells will be replaced by chondrocyte-like cells. Because the IVD is avascular, these cells rely

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

2011-01-01

94

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

PubMed Central

Purpose To report a case of spontaneous resolution of a long-standing serous macular detachment associated with an optic disc pit, leading to significant visual improvement. Case Presentation A 63-year-old female presented with a 6-month history of blurred vision and micropsia in her left eye. Her best-corrected visual acuity was 6/24 in the left eye, and fundoscopy revealed serous macular detachment associated with optic disc pit, which was confirmed by optical coherence tomography (OCT). The patient was offered vitrectomy as a treatment alternative, but she preferred to be reviewed conservatively. Three years after initial presentation, neither macular detachment nor subretinal fluid was evident in OCT, while the inner segment/outer segment (IS/OS) junction line was intact. Her visual acuity was improved from 6/24 to 6/12 in her left eye, remaining stable at the 6-month follow-up after resolution. Conclusion We present a case of spontaneous resolution of a long-standing macular detachment associated with an optic disc pit with significant visual improvement, postulating that the integrity of the IS/OS junction line may be a prognostic factor for final visual acuity and suggesting OCT as an indicator of visual prognosis and the probable necessity of a surgical management. PMID:24761149

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

2014-01-01

95

BLU-RAY DISC  

Microsoft Academic Search

In the two decades that followed the initial CD-press conference in 1979, the optical storage industry had grown up. A complete\\u000a family of CD formats has been defined and developed. There were read-only, write once and rewritable discs on the market.\\u000a The price of these discs had gradually come down to very affordable levels. Many suppliers offered popular optical disc

J. A. M. M. Haaren; M. Kuijper; Yourii V. Martynov; Benno H. W. Hendriks; Ferry Zijp; Jan Aarts; Jan-Peter Baartman; Gerard Rosmalen; Jean J. H. B. Schleipen; Henk Houten; Tatsuya Narahara; Shoei Kobayashi; Masayuki Hattori; Yoshihide Shimpuku; Gijs J. Enden; Joost A. H. M. Kahlman; Marten Dijk; Roel Woudenberg; I. Ubbens; L. Spruijt; J. M. ter Meulen; K. Schep; Shigeru Furumiya; Bert Stek; Hiromichi Ishibashi; Tamotsu Yamagami; Jaap H. M. Neijzen; Erwin R. Meinders; Helmar Santen

96

Optic Disc Detection by Earth Mover’s Distance Template Matching  

E-print Network

Abstract—This paper presents a method for the detection of OD in the retina which takes advantage of the powerful preprocessing techniques such as the contrast enhancement, Gabor wavelet transform for vessel segmentation, mathematical morphology and Earth Mover’s distance (EMD) as the matching process. The OD detection algorithm is based on matching the expected directional pattern of the retinal blood vessels. Vessel segmentation method produces segmentations by classifying each image pixel as vessel or nonvessel, based on the pixel’s feature vector. Feature vectors are composed of the pixel’s intensity and 2D Gabor wavelet transform responses taken at multiple scales. A simple matched filter is proposed to roughly match the direction of the vessels at the OD vicinity using the EMD. The minimum distance provides an estimate of the OD center coordinates. The method’s performance is evaluated on publicly available DRIVE and STARE databases. On the DRIVE database the OD center was detected correctly in all of the 40 images (100%) and on the STARE database the OD was detected correctly in 76 out of the 81 images, even in rather difficult pathological situations. Keywords—Diabetic retinopathy, Earth Mover’s distance, Gabor wavelets, optic disc detection, retinal images T I.

O C. Monteiro; Vasco Cadavez

97

Reversal of optic disc cupping with improvement of visual field and stereometric parameters after trabeculectomy in young adult patients (two case reports).  

PubMed

The authors report two cases of mid- to long-term reversal of optic disc cupping after trabeculectomy with mitomycine-C in young adult patients suffering from secondary glaucoma. The cup to disc ratio reversed from 0.80 and 0.60 to 0.65 and 0.40 respectively and remained unchanged until the last follow-up visit at 6 and 36 months respectively. Concomitantly, there was an improvement of the visual field and of the optic disc stereometric parameters on the Heidelberg Retina Tomograph. PMID:21305812

Swinnen, S; Stalmans, I; Stalmans, A; Zeyen, T

2010-01-01

98

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

99

Comparing ophthalmoscopy, slide viewing, and semiautomated systems in optic disc morphometry  

Microsoft Academic Search

PurposeTo compare disc measurements obtained by indirect ophthalmoscopy, the Heidelberg Retina Tomograph (HRT), stereoscopic slide viewing (SSV) of color transparencies, and the Topcon ImageNet System (ImageNet).

M. Kamran Ikram; Petra H Borger; Jacqueline J. M Assink; Jost B Jonas; Albert Hofman; Paulus T. V. M de Jong

2002-01-01

100

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

PubMed

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

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

2015-02-01

101

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

102

Harmonic fields on the extended projective disc and a problem in optics  

Microsoft Academic Search

The Hodge equations for 1-forms are studied on Beltrami's projective disc\\u000amodel for hyperbolic space. Ideal points lying beyond projective infinity arise\\u000anaturally in both the geometric and analytic arguments. An existence theorem\\u000afor weakly harmonic 1-fields, changing type on the unit circle, is derived\\u000aunder Dirichlet conditions imposed on the non-characteristic portion of the\\u000aboundary. A similar system arises

Thomas H. Otway

2004-01-01

103

Agreement in Assessing Cup-to-Disc Ratio Measurement Among Stereoscopic Optic Nerve Head Photographs, HRT II, and Stratus OCT  

PubMed Central

Purpose To compare the level of agreement between subjective and objective methods in estimating horizontal and vertical cupto-disc ratios (HCDR and VCDR, respectively) to determine if objective techniques may be used as surrogates for subjective cup-to-disc (CDR) estimation. Methods Fifty-one glaucoma patients and 49 control subjects underwent full ophthalmic examination, stereoscopic optic nerve head photographs (ONHPs), confocal scanning laser ophthalmoscopy (Heidelberg Retina Tomography II [HRT II]), and optical coherence tomography (Stratus OCT). The intra-class correlation coefficient (ICC) and Bland Altman plots were used to assess the agreement across the three methods. Repeated measures analysis of variance (ANOVA), Tukey adjustment, and pairwise P values were used to compare the HCDR and VCDR estimates between three clinicians who reviewed photos, Stratus OCT, and HRT II. Results For the clinicians, the agreement in subjectively assessed HCDR and VCDR was substantial (ICC = 0.84 and 0.85, respectively), and for all three methods, overall agreement was good (ICC = 0.75 and 0.77 for the HCDR and VCDR, respectively). Stratus OCT provided the largest overall mean ± SD HCDR (0.68 ± 0.14) and VCDR (0.62 ± 0.13). The smallest overall mean ± SD HCDR was provided by ONHP (0.32 ± 0.16), and the smallest overall mean ± SD VCDR was provided by HRT II (0.26 ± 0.20). Repeated measures ANOVA test demonstrated significant differences across the three methods for glaucomatous (P = 0.0017 and 0.0016, HCDR and VCDR, respectively) and normal (P = 0.0001 for both HCDR and VCDR) eyes. Tukey adjustment demonstrated specific statistical differences between pairs of methods. Conclusions Although the overall agreement between various methods was good, the mean estimates were statistically different. Additional studies are needed to evaluate the sources of variability, their level of significance, and longitudinal agreement between various methods of the CDR estimation. PMID:16778638

Arthur, Stella N.; Aldridge, Aric J.; De León-Ortega, Julio; McGwin, Gerald; Xie, Aiyuan; Girkin, Christopher A.

2015-01-01

104

Environmental effects on optical component aging  

NASA Astrophysics Data System (ADS)

The optical performances of components exposed to high power laser beams during long periods are generally decreasing with time. We analyze surface modifications that occur after some hundreds of hours at a fluence of 0.5 kW/cm2 to 10 kW/cm2. The results obtained with two dedicated test benches over thousands of hours are discussed. Exposition of tens of components has been achieved in the multi-component bench to simulate real optical systems and to acquire statistical confidence in the results. The single component bench allows continuous measurements of the surface temperature and of the scattered light. These measurements show how these beamprints can lead to the surface destruction. We investigate the effects of the beam fluence, the laser wavelength and the chamber pressure. Experiments at two wavelengths have shown that the deposition rate and the surface absorption increase with decreasing wavelength. The efficiency of oxygen in reducing the contamination speed has been investigated using absorption mappings. Laser cleaned surface absorptions are comparable to initial measurements, showing that damage did not occur. ESCA analysis of the beamprints showed that a few nanometers carbon layer has been implanted.

Bruel, Laurent

2003-05-01

105

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

2008-04-01

106

Harmonic fields on the extended projective disc and a problem in optics  

E-print Network

The Hodge equations for 1-forms are studied on Beltrami's projective disc model for hyperbolic space. Ideal points lying beyond projective infinity arise naturally in both the geometric and analytic arguments. An existence theorem for weakly harmonic 1-fields, changing type on the unit circle, is derived under Dirichlet conditions imposed on the non-characteristic portion of the boundary. A similar system arises in the analysis of wave motion near a caustic. A class of elliptic-hyperbolic boundary-value problems is formulated for those equations as well. For both classes of boundary-value problems, an arbitrarily small lower-order perturbation of the equations is shown to yield solutions which are strong in the sense of Friedrichs.

Thomas H. Otway

2007-04-02

107

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

Microsoft Academic Search

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

Marc Lalonde; Mario Beaulieu; Langis Gagnon

2001-01-01

108

Accretion discs  

NASA Astrophysics Data System (ADS)

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

Abramowicz, Marek A.; Straub, Odele

2014-08-01

109

Fast and robust optic disc detection using pyramidal decomposition and Hausdorff-based template matching.  

PubMed

We report about the design and test of an image processing algorithm for the localization of the optic disk (OD) in low-resolution (about 20 micro/pixel) color fundus images. The design relies on the combination of two procedures: 1) a Hausdorff-based template matching technique on edge map, guided by 2) a pyramidal decomposition for large scale object tracking. The two approaches are tested against a database of 40 images of various visual quality and retinal pigmentation, as well as of normal and small pupils. An average error of 7% on OD center positioning is reached with no false detection. In addition, a confidence level is associated to the final detection that indicates the "level of difficulty" the detector has to identify the OD position and shape. PMID:11700746

Lalonde, M; Beaulieu, M; Gagnon, L

2001-11-01

110

Coplanar circumbinary debris discs  

NASA Astrophysics Data System (ADS)

We present resolved Herschel images of circumbinary debris discs in the ? CrB (HD 139006) and ? Tri (HD13161) systems. By modelling their structure, we find that both discs are consistent with being aligned with the binary orbital planes. Though secular perturbations from the binary can bring the disc into alignment, in both cases the alignment time at the distances at which the disc is resolved is greater than the stellar age, so we conclude that the coplanarity was primordial. Neither disc can be modelled as a narrow ring, requiring extended radial distributions. To satisfy both the Herschel and mid-infrared images of the ? CrB disc, we construct a model that extends from 1 to 300 au, whose radial profile is broadly consistent with a picture where planetesimal collisions are excited by secular perturbations from the binary. However, this model is also consistent with stirring by other mechanisms, such as the formation of Pluto-sized objects. The ? Tri disc is modelled as a disc that extends from 50 to 400 au. A model with depleted (rather than empty) inner regions also reproduces the observations and is consistent with binary and other stirring mechanisms. As part of the modelling process, we find that the Herschel PACS (Photodetector and Array Camera & Spectrometer) beam varies by as much as 10 per cent at 70 ?m and a few per cent at 100 ?m. The 70 ?m variation can therefore hinder image interpretation, particularly for poorly resolved objects. The number of systems in which circumbinary debris disc orientations have been compared with the binary plane is now 4. More systems are needed, but a picture in which discs around very close binaries (? CrB, ? Tri and HD 98800, with periods of a few weeks to a year) are aligned, and discs around wider binaries (99 Her, with a period of 50 yr) are misaligned, may be emerging. This picture is qualitatively consistent with the expectation that the protoplanetary discs from which the debris emerged are more likely to be aligned if their binaries have shorter periods.

Kennedy, G. M.; Wyatt, M. C.; Sibthorpe, B.; Phillips, N. M.; Matthews, B. C.; Greaves, J. S.

2012-11-01

111

Long-wavelength observations of debris discs around sun-like stars  

NASA Astrophysics Data System (ADS)

Context: Tracing the evolution of debris discs is essential for our understanding of the architecture of planetary system. Even though the evolution of their inner discs has been recently studied with the Spitzer Space Telescope at mid- to far-infrared wavelengths, the outer discs are best characterised by sensitive millimetre observations. Aims: The goal of our study is to understand the evolution timescale of circumstellar debris discs, and the physical mechanisms responsible for such evolution around solar-type stars. In addition, we make a detailed characterisation of the detected debris discs. Methods: Two deep surveys of circumstellar discs around solar-type stars at different ages were carried out at 350 ?m with the CSO and at 1.2 mm with the IRAM 30-m telescope. The dust disc masses were computed from the millimetre emission, where the discs are optically thin. Theoretically, the mass of the disc is expected to decrease with time. To test this hypothesis, we performed the generalised Kendall's tau correlation and three different two-sample tests. A characterisation of the detected debris discs has been obtained by computing the collision and Poynting-Robertson timescales and by modelling the spectral energy distribution. Results: The Kendall's tau correlation yields a probability of 76% that the mass of debris discs and their age are correlated. Similarly, the three two-sample tests give a probability between 70 and 83% that younger and older debris systems belong to different parent populations in terms of dust mass. We detected submillimetre/millimetre emission from six debris discs, enabling a detailed SED modelling. Conclusions: Our results on the correlation and evolution of dust mass as a function of age are conditioned by the sensitivity limit of our survey. Deeper millimetre observations are needed to confirm the evolution of debris material around solar-like stars. In the case of the detected discs, the comparison between collision and Poynting-Robertson timescales supports the hypothesis that these discs are dominated by collisions. All detected debris disc systems show the inner part evacuated from small micron-sized grains. This work is based on observations made with the IRAM (Institut de Radioastonomie Millimétrique) 30-m telescope and the CSO (Caltech Submillimetre Observatory) 10-m telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).

Roccatagliata, V.; Henning, Th.; Wolf, S.; Rodmann, J.; Corder, S.; Carpenter, J. M.; Meyer, M. R.; Dowell, D.

2009-04-01

112

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

2012-03-01

113

Optical sensing system based on wireless paired emitter detector diode device and ionogels for lab-on-a-disc water quality analysis.  

PubMed

This work describes the first use of a wireless paired emitter detector diode device (PEDD) as an optical sensor for water quality monitoring in a lab-on-a-disc device. The microfluidic platform, based on an ionogel sensing area combined with a low-cost optical sensor, is applied for quantitative pH and qualitative turbidity monitoring of water samples at point-of-need. The autonomous capabilities of the PEDD system, combined with the portability and wireless communication of the full device, provide the flexibility needed for on-site water testing. Water samples from local fresh and brackish sources were successfully analysed using the device, showing very good correlation with standard bench-top systems. PMID:23070147

Czugala, Monika; Gorkin, Robert; Phelan, Thomas; Gaughran, Jennifer; Curto, Vincenzo Fabio; Ducrée, Jens; Diamond, Dermot; Benito-Lopez, Fernando

2012-12-01

114

Alteration of lunar optical properties: age and composition effects.  

PubMed

A model for lunar surface processes is presented which explains the main albedo and color contrasts and the temporal changes in these optical properties. Evidence from Apollo 11 and Apollo 12 samples and telescopic spectral reflectivity measurements indicates that the maria are similar in mineralogy on a regional scale and that the highlands are consistent with an anorthositic-gabbro composition. Bright craters and rays in both regions expose materials that are relatively crystalline compared with their backgrounds, which are richer in dark glass. With age, bright craters and rays in the maria darken in place by meteorite impact-induced vitrification and mixing with the surrounding material. Highland bright craters and rays may, however, darken primarily through regional contamination by iron- and titanium-rich mare material. PMID:17734782

Adams, J B; McCord, T B

1971-02-12

115

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

116

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

E-print Network

Kinetics of degradation during fatigue and aging of fused silica optical fiber M. John Matthewson Fiber Optic Materials Research Program Department of Ceramics Rutgers University, Piscataway, NJ 08855-0909 Hakan H. Yuce Belicore Morristown, NJ 07960-643 8 ABSTRACT Fused silica optical fiber tested

Matthewson, M. John

117

Intervertebral disc: anatomy-physiology-pathophysiology-treatment.  

PubMed

This review article describes anatomy, physiology, pathophysiology and treatment of intervertebral disc. The intervertebral discs lie between the vertebral bodies, linking them together. The components of the disc are nucleus pulposus, annulus fibrosus and cartilagenous end-plates. The blood supply to the disc is only to the cartilagenous end-plates. The nerve supply is basically through the sinovertebral nerve. Biochemically, the important constituents of the disc are collagen fibers, elastin fibers and aggrecan. As the disc ages, degeneration occurs, osmotic pressure is lost in the nucleus, dehydration occurs, and the disc loses its height. During these changes, nociceptive nuclear material tracks and leaks through the outer rim of the annulus. This is the main source of discogenic pain. While this is occurring, the degenerative disc, having lost its height, effects the structures close by, such as ligamentum flavum, facet joints, and the shape of the neural foramina. This is the main cause of spinal stenosis and radicular pain due to the disc degeneration in the aged populations. Diagnosis is done by a strict protocol and treatment options are described in this review. The rationale for new therapies are to substitute the biochemical constituents, or augment nucleus pulposus or regenerate cartilaginous end-plate or finally artificial disc implantation.. PMID:18211591

Raj, P Prithvi

2008-01-01

118

Impact of optical and structural aging in As?S? microstructured optical fibers on mid-infrared supercontinuum generation.  

PubMed

We analyze optical and structural aging in As?S? microstructured optical fibers (MOFs) that may have an impact on mid-infrared supercontinuum generation. A strong alteration of optical transparency at the fundamental OH absorption peak is measured for high-purity As?S? MOF stored in atmospheric conditions. The surface evolution and inherent deviation of corresponding chemical composition confirm that the optical and chemical properties of MOFs degrade upon exposure to ambient conditions because of counteractive surface process. This phenomenon substantially reduces the optical quality of the MOFs and therefore restrains the spectral expansion of generated supercontinuum. This aging process is well confirmed by the good matching between previous experimental results and the reported numerical simulations based on the generalized nonlinear Schrödinger equation. PMID:25321968

Mouawad, O; Amrani, F; Kibler, B; Picot-Clémente, J; Strutynski, C; Fatome, J; Désévédavy, F; Gadret, G; Jules, J-C; Heintz, O; Lesniewska, E; Smektala, F

2014-10-01

119

Percutaneous diode laser disc nucleoplasty  

NASA Astrophysics Data System (ADS)

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

Menchetti, P. P.; Longo, Leonardo

2004-09-01

120

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

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

121

Quantitative evaluation of the optic nerve head in early glaucoma  

PubMed Central

AIMS—Progressive loss of neuroretinal rim tissue is known to occur early in glaucoma and measurement of the neuroretinal rim area is possible by magnification corrected analysis of optic disc photographs (planimetry). This study was performed to determine whether the facility to distinguish between glaucomatous and normal optic discs could be improved upon by: (a) taking into account the known relation between optic disc size and neuroretinal rim area, and (b) measuring rim area in a number of segments, in order to detect focal changes.?METHODS—Planimetric examination of the optic disc photographs of 88 control subjects and 51 patients with early visual field defects was performed. In the control group, multiple linear regression analysis was performed between neuroretinal rim area and optic disc area, age, sex, eye side, refraction, and keratometry. This was repeated for the whole disc and for each of twelve 30 degree segments. Normal ranges were defined by the 98% prediction intervals of the regression analysis and the sensitivity and specificity for correct identification of optic discs in the two groups determined.?RESULTS—Multiple linear regression demonstrated significant associations between the neuroretinal rim area and optic disc area and age in normal subjects. Sensitivity and specificity for glaucoma diagnosis, using the cut off derived from the 98% prediction intervals, was 37.7% and 98.9% respectively when total neuroretinal rim area alone was considered, and 88.7% and 94.3% respectively when the 30 degree segments were included. The most frequent pattern of neuroretinal rim loss was diffuse, followed by thinning in more than one sector and then by thinning in the inferotemporal sector alone.?CONCLUSIONS—This method of optic disc analysis enables the examiner to identify glaucomatous optic discs at the stage of early perimetric loss with a high degree of precision. Optic disc photography is simple, and fundus cameras are widely available. This method for glaucoma case identification may therefore be suitable for the primary care setting as well as hospital practice.?? Keywords: optic disc; glaucoma; case finding; imaging PMID:9640180

Garway-Heath, D; Hitchings, R

1998-01-01

122

Optical characterization and age estimates of river plumes on the US West Coast  

E-print Network

Optical characterization and age estimates of river plumes on the US West Coast Raphael M. Kudelaa aging and dilution by surrounding waters. The objectives of this study were to (1) identify initial for juvenile salmon. Some constituents act as tracers of the plume as it flows from the river mouth. Plume

Hickey, Barbara

123

ON THE AGE AND METALLICITY ESTIMATION OF SPIRAL GALAXIES USING OPTICAL AND NEAR-INFRARED PHOTOMETRY  

E-print Network

ON THE AGE AND METALLICITY ESTIMATION OF SPIRAL GALAXIES USING OPTICAL AND NEAR-INFRARED PHOTOMETRY-infrared photometry show surprisingly orthogonal grids as age and metallicity are varied, and they are coming headinggs: galaxies: abundances -- galaxies: evolution -- galaxies: photometry -- galaxies: spiral

Lee, Hyun-chul

124

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

SciTech Connect

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

Sano, Haruyuki, E-mail: h-sano@ishikawa-nct.ac.jp [Ishikawa National College of Technology, Kitacyujo, Tsubata, Ishikawa 929-0392 (Japan); Shima, Takayuki; Kuwahara, Masashi [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba 305-8565 (Japan); Fujita, Yoshiya; Uchiyama, Munehisa; Aono, Yoshiyuki [Pulstec Industrial Co., Ltd., 7000-35, Nakagawa, Hosoe-cho, Kita-ku, Hamamatsu 431-1304 (Japan)

2014-04-21

125

Stability of a hot two-temperature accretion disc with advection  

E-print Network

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

Xue-Bing Wu

1997-08-01

126

Counterrotating stars in simulated galaxy discs  

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

127

Turbine disc sealing assembly  

DOEpatents

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

Diakunchak, Ihor S.

2013-03-05

128

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

NASA Astrophysics Data System (ADS)

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

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

2002-01-01

129

Age related optic nerve axonal loss in adult Brown Norway rats.  

PubMed

The effect of age on the number and morphology of optic nerve axons in adult Brown Norway rats (5-31 months old) (n=29) was examined using transmission electron microscopy (TEM). By manually counting every axon in areas representing 60% of the optic nerve cross-section, we found a significant negative correlation between age and axon count (R(2)=0.18, P<0.05). However, when the oldest animals were omitted, the relationship was no longer statistically significant. Simultaneously, the proportion of spontaneously degenerating axons increased at an exponential rate (R(2)=0.79, P<0.05), with significantly more degeneration in the 31-month group than in 5-month-old animals (ANOVA, P<0.05). This study demonstrates, using quantitative TEM methods, that optic nerve axonal numbers are relatively constant throughout the majority of the adult life of the Brown Norway rat, an increasingly popular strain for glaucoma research. Total axonal loss with aging is substantially less than that reported for other strains. The reduction in axonal numbers and the rate of axonal degeneration do not appear significantly altered until the last few months of life, failing to support some studies that have concluded that optic nerve axon loss in adult rats is linear. However, they do agree with other studies in the rat, and a similar study performed in non-human primate eyes, that concluded that aging changes in the optic nerve and retina follow a complex pattern. Therefore, the impact of animal age must be considered when modeling the course and pathophysiology of experimental glaucomatous optic nerve damage in rats. PMID:15939045

Cepurna, William O; Kayton, Robert J; Johnson, Elaine C; Morrison, John C

2005-06-01

130

Aging-related changes of optic nerve of Wistar albino rats.  

PubMed

Aging is a biological phenomenon that involves an increase of oxidative stress associated with gradual degradation of the structure and function of the optic nerve. Gender differences and subsequent deterioration of optic nerve are an interesting topic, especially because there is little published work concerning it. One hundred male and female Wistar albino rats' with ages 1, 6, 18, 24, and 30 months (n?=?20 equal for male and female) were used. At the time interval, optic nerve was investigated by light and transmission electron microscopy (TEM), assessments of antioxidant enzymes (catalase, superoxide dismustase, and glutathione-S-transferase), caspase 3 and 7, malondialdhyde, flow cytometry of DNA, annexin v, and CD8, immunochemistry of vascular endothelial growth factor (VEGF), CD31, and CD45, and single-strand DNA fragmentation. Light and TEM observations of the older specimens (24 and 30 months) revealed apparent deterioration of optic nerve axons, abundant oligodendrocytes with pyknotic nuclei, swollen astrocytes, angiogenesis, vacuolar degeneration, and mitochondrial damage. Females were highly susceptible to aging processes. Concomitantly, there was a marked reduction of antioxidant's enzymes and an increase of lipid peroxidation and apoptotic markers. Old age exhibited a marked increase of G1 apoptosis, UR and LR of annexin V and CD8 as well as increased immuno-positive reaction with VEGR, CD31 and CD45. We conclude that aging contributed to an increase of oxidative stress resulting from damage of mitochondria in axons, oligodendrocytes, and astrocytes. Age-related loss of optic nerve axons is associated with multifactorial agents including reduction in antioxidant enzymes, disruption of vasculature, astrocyte, and oligodendrocyte, demyelination, and damage of mitochondria, which enhance the liberation of reactive oxygen species as assessed by an increase of apoptotic markers malondialdhyde and caspase 3 and 7. PMID:23996059

El-Sayyad, Hassan I H; Khalifa, Soad A; El-Sayyad, Fawkia I; Al-Gebaly, Asma S; El-Mansy, Ahmed A; Mohammed, Ezaldin A M

2014-04-01

131

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.

132

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

PubMed Central

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

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

2014-01-01

133

Aging Related Changes of Retina and Optic Nerve of Uromastyx aegyptia and Falco tinnunculus  

PubMed Central

Aging is a biological phenomenon that involves gradual degradation of the structure and function of the retina and optic nerve. To our knowledge, little is known about the aging-related ocular cell loss in avian (Falco tinnunculus) and reptilian species (Uromastyx aegyptia). A selected 90 animals of pup, middle, and old age U. aegyptia (reptilian) and F. tinnunculus (avian) were used. The retinae and optic nerves were investigated by light and transmission electron microscopy (TEM) and assessments of neurotransmitters, antioxidant enzymes (catalase, superoxide dismustase and glutathione s transferase), caspase-3 and -7, malonadialdhyde, and DNA fragmentation. Light and TEM observations of the senile specimens revealed apparent deterioration of retinal cell layers, especially the pigmented epithelium and photoreceptor outer segments. Their inclusions of melanin were replaced by lipofuscins. Also, vacuolar degeneration and demyelination of the optic nerve axons were detected. Concomitantly, there was a marked increase of oxidative stress involved reduction of neurotransmitters and antioxidant enzymes and an increase of lipid peroxidation, caspase-3 and -7, subG0/G1 apoptosis, and P53. We conclude that aging showed an inverse relationship with the neurotransmitters and antioxidant enzymes and a linear relationship of caspases, malondialdhyde, DNA apoptosis, and P53 markers of cell death. These markers reflected the retinal cytological alterations and lipofuscin accumulation within inner segments. PMID:24215233

2013-01-01

134

Aging related changes of retina and optic nerve of Uromastyx aegyptia and Falco tinnunculus.  

PubMed

Aging is a biological phenomenon that involves gradual degradation of the structure and function of the retina and optic nerve. To our knowledge, little is known about the aging-related ocular cell loss in avian (Falco tinnunculus) and reptilian species (Uromastyx aegyptia). A selected 90 animals of pup, middle, and old age U. aegyptia (reptilian) and F. tinnunculus (avian) were used. The retinae and optic nerves were investigated by light and transmission electron microscopy (TEM) and assessments of neurotransmitters, antioxidant enzymes (catalase, superoxide dismustase and glutathione s transferase), caspase-3 and -7, malonadialdhyde, and DNA fragmentation. Light and TEM observations of the senile specimens revealed apparent deterioration of retinal cell layers, especially the pigmented epithelium and photoreceptor outer segments. Their inclusions of melanin were replaced by lipofuscins. Also, vacuolar degeneration and demyelination of the optic nerve axons were detected. Concomitantly, there was a marked increase of oxidative stress involved reduction of neurotransmitters and antioxidant enzymes and an increase of lipid peroxidation, caspase-3 and -7, subG0/G1 apoptosis, and P53. We conclude that aging showed an inverse relationship with the neurotransmitters and antioxidant enzymes and a linear relationship of caspases, malondialdhyde, DNA apoptosis, and P53 markers of cell death. These markers reflected the retinal cytological alterations and lipofuscin accumulation within inner segments. PMID:24215233

El-Sayyad, Hassan I H; Khalifa, Soad A; Al-Gebaly, Asma S; El-Mansy, Ahmed A

2014-01-15

135

Aging affects the ability to use optic flow in the control of heading during locomotion.  

PubMed

Perceived self-motion from optic flow is implicated in the control of locomotion. Aging, which affects visual perception and sensorimotor integration, may result in an inability to use optic flow to guide heading while walking. The purpose of this study was to examine whether advanced age could impact on the steering of locomotion, when changing optic flow directions were presented in an immersive virtual environment (VE). Nine young adults (21.56 +/- 3.20 years) and nine older adults (66.11 +/- 3.95 years) participated in the study. Subjects were asked to walk while viewing a VE through a head-mounted display unit (Kaiser). The VE viewed by the subjects was a large room displayed as an expanding translational optic flow, with the focus of expansion (FOE) located at neutral, 20 degrees or 40 degrees to the right or left. Their task was to walk straight with respect to the VE. Kinematic data in 3D were collected, from which the body's centre of mass (CoM) position and heading direction were calculated. Young subjects were able to make proper heading adjustments in the VE, with respect to FOE shifts, but not older individuals. Young subjects altered their CoM trajectory so that it was oriented in the direction opposite to the FOE in the physical environment and resulted in small deviation in the VE. The older adults did not adjust their locomotor patterns in response to the different flows presented and maintained similar walking trajectories across all trials. Advanced age results in an altered control of steering of locomotion in response to changing directions of optic flow. This may be related to an impaired perception and/or use of the optic flow, or due to inherent problems in sensorimotor integration. PMID:19139863

Berard, Jessica R; Fung, Joyce; McFadyen, Bradford J; Lamontagne, Anouk

2009-04-01

136

Phase Change Disc for High Data Rate Recording  

Microsoft Academic Search

We have developed a phase change disc having a thin transparent cover layer corresponding to the new optical recording system (DVR) using a blue laser (405 nm) and a numerical aperture (NA) of 0.85. We have achieved a user capacity of 22 GB per side of the 120 mm diameter disc, and a user data recording rate of 70 Mbps

Hiroyasu Inoue; Hideki Hirata; Tatsuya Kato; Hiroshi Shingai; Hajime Utsunomiya

2001-01-01

137

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

SciTech Connect

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

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

2001-09-01

138

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

E-print Network

Enhanced fatigue and aging resistance using reactive powders in the optical fiber buffer coating V causes a dramatic improvement in the fatigue and aging resistance both in aqueous and in constant for the surface roughening that causes the fatigue knee and strength degradation during zero-stress aging

Matthewson, M. John

139

New Laser Labeling Technology for Recordable Digital Versatile Disc  

NASA Astrophysics Data System (ADS)

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

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

2007-06-01

140

Advances in Susceptibility Genetics of Intervertebral Degenerative Disc Disease  

PubMed Central

The traditional view that the etiology of lumbar disc herniation is primarily due to age, gender, occupation, smoking and exposure to vehicular vibration dominated much of the last century. Recent research indicates that heredity may be largely responsible for the degeneration as well as herniation of intervertebral discs. Since 1998, genetic influences have been confirmed by the identification of several genes forms associated with disc degeneration. These researches are paving the way for a better understanding of the biologic mechanisms. Now, many researchers unanimously agree that lumbar disc herniation appears to be similar to other complex diseases, whose etiology has both environmental and hereditary influence, each with a part of contribution and relative risk. Then addressing the etiological of lumbar disc herniation, it is important to integrate heredity with the environment factors. For the purpose of this review, we have limited our discussion to several susceptibility genes associated with disc degeneration. PMID:18781226

Zhang, Yin'gang; Sun, Zhengming; Liu, Jiangtao; Guo, Xiong

2008-01-01

141

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. PMID:23589675

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

2013-01-01

142

Characterization of 980-nm aged pump laser by using electrical and optical noise  

NASA Astrophysics Data System (ADS)

The knowledge of the noise levels is important for pump laser diodes as it allows to study and to locate the noise sources and their origin. 980 nm fresh and aged pump laser have been characterized by using electrical and optical noise measurements. In this work, we present the electrical and optical noises at low - medium frequency for fresh pump laser diodes emitting at 980 nm (reference laser), and we study the parametric evolution and the defects generated in aged 980nm single-mode ridge lasers, stressed during 400hrs at 50°C and high current injection (500 mA) (aged laser). The dynamic resistance, above threshold current, is not constant. It shows a proportionality of about Rd?I-1/2. The injection of the carriers is associated to space charge limited current effect (SCLC). The study of the electrical and optical noise which represents the fluctuations of intensity at low and medium frequency is very significant of degradation of the active layer. The spectra are dominated by 1/f (fliker) noise at very weak current. And at weak current, the Current Noise Spectrale Density (CNSD) at 10 Hz is dominated by I3/2. The deffect is associated with carrier transport controlled by the interfaces n+n- and p+p- and the trapping defect density near the n+n- and p+p- interfaces, also it due to pinching of the space charge limited current SCLC effect An excess noise due to longitudinal mode hopping is related with output power fluctuations.

Asaad, Imad; Orsal, Bernard P.; Perez, Jean Philippe; Signoret, Philippe; Alabedra, Robert M.; Pommies, Matthieu; Bettiati, Mauro A.

2003-05-01

143

Changes in angle of optic nerve and angle of ocular orbit with increasing age in Japanese children  

PubMed Central

Purpose To study changes in the opening angle of the optic nerve and the angle of the ocular orbit with increasing age in normal Japanese children. Methods We studied 147 normal children (aged 6?months to 18?years) who had undergone CT as a diagnostic procedure. Measurements were performed on axial CT images that included the entire optic nerve of both eyes. The opening angle of the optic nerve was defined as the angle formed by the intersection of a line running through the left optic nerve and a vertical line passing through the centre of the nose. The opening angle of the orbit was defined as the angle formed by the intersection of a line running tangentially along the deep lateral wall of the left orbit and a vertical line passing through the centre of the nose. The relationship between age and these opening angles was analysed by regression analysis. Results The correlation between age and opening angle of the optic nerve was not significant. In contrast, the opening angle of the orbit decreased relatively rapidly until about 2–3?years of age, and then it stabilised. The decrease in the opening angle of the orbit with increasing age was significant (p<0.001). The relationship between these two parameters was best fitted by a logarithmic regression curve. Conclusions Because the opening angle of the orbit decreased significantly with increasing age, this factor must be considered when diagnosing and treating strabismus in children. PMID:25147368

Tsukitome, Hideyuki; Hatsukawa, Yoshikazu; Morimitsu, Tomoko; Yagasaki, Teiji; Kondo, Mineo

2015-01-01

144

Radiation magnetohydrodynamics in global simulations of protoplanetary discs  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

145

Herniated Lumbar Disc  

MedlinePLUS

... 50. A herniated lumbar disc may also cause back pain, although back pain alone (without leg pain) can have many causes ... 90% success); surgery is less effective in relieving back pain. Nonsurgical treatment Your doctor may prescribe nonsurgical treatments ...

146

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

147

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

PubMed

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

Yassa, Hanan Dawood

2014-07-01

148

Macular pigment optical density in wet age-related macular degeneration among Indians  

PubMed Central

Purpose To estimate the value of macular pigment optical density (MPOD) in adult south Indian population with wet age-related macular degeneration (AMD). Methods A total of 33 patients with wet AMD and 29 age-matched controls >50 years of age underwent MPOD measurement with the macular densitometer. The patients were also tested for their dietary intake of carotenoids, smoking history, and lifetime UV exposure. Results The mean MPOD values in the Indian population with wet AMD was 0.23 (95% CI: 0.18–0.29) vs control was 0.43 (95% CI: 0.37–0.49), P<0.0001, at 0.5° eccentricity. Ex-smokers had a lower MPOD than non-smokers (0.16 (0.09–0.23) vs 0.28 (0.22–0.34), P=0.026) and the lowest level of carotenoids intake had 48% lower MPOD than the highest level (0.14 (0.08–0.21) vs 0.33 (0.24–0.43), P=0.012). There was no significant age-related decline or gender variation in MPOD. Conclusion This study establishes the MPOD in adult Indian population with wet AMD, with a lack of macular pigment in association with wet AMD. PMID:22627475

Raman, R; Biswas, S; Vaitheeswaran, K; Sharma, T

2012-01-01

149

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

NASA Astrophysics Data System (ADS)

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

Du, Jin-Hua; Wang, Xu-Long

2014-09-01

150

Macular Thickness by Age and Gender in Healthy Eyes Using Spectral Domain Optical Coherence Tomography  

PubMed Central

Purpose To determine normal macular thickness and its variation by age and gender in healthy eyes using spectral-domain optical coherence tomography (SD-OCT). Methods In this cross-sectional analysis, two hundred and twenty eyes of 220 healthy subjects underwent raster scanning using Topcon SD-OCT system, at the Department of Ophthalmology, Dow University of Health Sciences and Civil Hospital Karachi, Pakistan. Macular thickness from all 9 regions of the ETDRS map was documented for each subject. Variations in macular thickness measurements by age and gender were determined. Results The 220 subjects had a mean age of 45.3 years (16–80 years). Using the ETDRS map, foveal thickness for all subjects was measured to be 229±20.46 µm. Mean macular thickness for all subjects was 262.8±13.34 µm. Male gender was associated with greater foveal (p<0.0001) and mean macular (p<0.0001) thickness compared to females. There was no association of mean macular thickness (r2?=?0.01; p>0.05) and foveal thickness (r2?=?0.00004; p>0.05) with age. Conclusion We have provided normative data for macular thickness using Topcon SD-OCT system. Our results are comparable to some and vary from other reports using the similar OCT system. Our results suggest that male gender is associated with greater macular thickness, while macular thickness has no association with age in healthy eyes. This is the first normative data for macular thickness from Pakistan; benchmark for diagnosing and monitoring macular pathologies. The values obtained in this study may be useful for comparison with other populations, other SD-OCT systems and future imaging technologies. PMID:22629435

Adhi, Mehreen; Aziz, Sumbul; Muhammad, Kashif; Adhi, Mohammad I.

2012-01-01

151

On the accretion disc and evolutionary stage of beta Lyrae  

E-print Network

We modeled the V-band light curve of beta Lyrae 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 2.30E7 years, in the phase of rapid mass transfer, the second one in the life of this binary, in a Case-B mass-exchange stage with dM/dt = 1.58E-5 Msun/year. This result, along with the reported rate of orbital period change and observational evidence of mass loss, suggests that the mass transfer in beta Lyrae, is quasi-conservative. The best model indicates that beta Lyrae finished a relatively large mass loss episode 31400 years ago. The light curve model that best fit the observations has inclination angle i = 81 degree, M...

Mennickent, R E

2013-01-01

152

Role of load history in intervertebral disc mechanics and intradiscal pressure generation.  

PubMed

Solid-fluid interactions play an important role in mediating viscoelastic behaviour of biological tissues. In the intervertebral disc, water content is governed by a number of factors, including age, disease and mechanical loads, leading to changes in stiffness characteristics. We hypothesized that zonal stress distributions depend on load history, or the prior stresses experienced by the disc. To investigate these effects, rat caudal motion segments were subjected to compressive creep biomechanical testing in vitro using a protocol that consisted of two phases: a Prestress Phase (varied to represent different histories of load) followed immediately by an Exertion Phase, identical across all Prestress groups. Three analytical models were used to fit the experimental data in order to evaluate load history effects on gross and zonal disc mechanics. Model results indicated that while gross transient response was insensitive to load history, there may be changes in the internal mechanics of the disc. In particular, a fluid transport model suggested that the role of the nucleus pulposus in resisting creep during Exertion depended on Prestress conditions. Separate experiments using similarly defined load history regimens were performed to verify these predictions by measuring intradiscal pressure with a fibre optic sensor. We found that the ability for intradiscal pressure generation was load history-dependent and exhibited even greater sensitivity than predicted by analytical models. A 0.5 MPa Exertion load resulted in 537.2 kPa IDP for low magnitude Prestress compared with 373.7 kPa for high magnitude Prestress. Based on these measurements, we developed a simple model that may describe the pressure-shear environment in the nucleus pulposus. These findings may have important implications on our understanding of how mechanical stress contributes to disc health and disease etiology. PMID:21380846

Hwang, David; Gabai, Adam S; Yu, Miao; Yew, Alvin G; Hsieh, Adam H

2012-01-01

153

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. PMID:19259245

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

154

The Galaxy Optical Luminosity Function from the AGN and Galaxy Evolution Survey (AGES)  

E-print Network

We present the galaxy optical luminosity function for the redshift range 0.05AGES), a spectroscopic survey of 7.6 sq. deg. in the Bootes field of the NOAO Deep Wide-Field Survey. Our statistical sample is comprised of 12,473 galaxies with known redshifts down to I=20.4 (AB). Our results at low redshift are consistent with those from SDSS; at higher redshift, we find strong evidence for evolution in the luminosity function, including differential evolution between blue and red galaxies. We find that the luminosity density evolves as (1+z)^(0.54+/-0.64) for red galaxies and (1+z)^(1.64+/-0.39) for blue galaxies.

Cool, Richard J; Kochanek, Christopher S; Brown, Michael J I; Caldwell, Nelson; Dey, Arjun; Forman, William R; Hickox, Ryan C; Jannuzi, Buell T; Jones, Christine; Moustakas, John; Murray, Stephen S

2012-01-01

155

Laser microbeams and optical tweezers to study DNA repair and ageing  

NASA Astrophysics Data System (ADS)

Incorrect DNA repair is probably one cause of healthy ageing. Laser microbeams or optical tweezers are emerging as convenient tools in the study of repair mechanisms. Using such tools, DNA damage can be induced in a preselected volume element of a cell nucleus and at a preselected time point - an effect which is hardly to achieve with any other tool. On the other hand damage induction highly depends on a subtle combination of laser mircobeam parameters such as dose, pulse peak power and wavelength. In consequence DNA repair at the sites of damage may work differently. Furthermore, such sites are occasionally stationary, occasionally they migrate towards each other, indicating a considerable dynamics of DNA repair inside a cell nucleus. As an example for the application of optical tweezers, Erythrocyte Mediated Force Application (EMFA) is used to induce nitric oxide production in cells of the endothelium, i. e. the inner layer of (human) blood vessels. It is shown that upon stimulation by EMFA, endothelial cells initially activate the calcium homeostasis and develop calcium humps, concentration plateaus and oscillations.

Grigaravicius, Paulius; Monajembashi, Shamci; Pilarczyk, Götz; Rapp, Alexander; Greulich, Karl Otto

2007-09-01

156

Senescence in human intervertebral discs  

Microsoft Academic Search

Intervertebral discs demonstrate degenerative changes relatively early in life. Disc degeneration, in turn, is associated\\u000a with back pain and disc herniation, both of which cause considerable clinical problems in the western world. Cell senescence\\u000a has been linked to degenerative diseases of other connective tissues such as osteoarthritis. Thus we investigated the degree\\u000a of cell senescence in different regions of discs

S. Roberts; E. H. Evans; D. Kletsas; D. C. Jaffray; S. M. Eisenstein

2006-01-01

157

Herniated Cervical Disc  

MedlinePLUS

... may be recommended if you have severe arm pain. These are injections of corticosteroid into the epidural space (the area ... muscles along the spine. While occasionally useful for pain control, trigger point injections do not help heal a herniated cervical disc. ...

158

Collapse of a molecular cloud core to stellar densities: the radiative impact of stellar core formation on the circumstellar disc  

NASA Astrophysics Data System (ADS)

We present results from the first three-dimensional radiation hydrodynamical calculations to follow the collapse of a molecular cloud core beyond the formation of the stellar core. We find that the energy released by the formation of the stellar core, within the optically thick first hydrostatic core, is comparable to the binding energy of the disc-like first core. This heats the inner regions of the disc, drives a shock wave through the disc, dramatically decreases the accretion rate on to the stellar core and launches a temporary bipolar outflow perpendicular to the rotation axis that travels in excess of 50 au into the infalling envelope. This outburst may assist the young protostar in launching a conventional magnetic jet. Furthermore, if these events are cyclic, they may provide a mechanism for intense bursts of accretion separated by long periods of relatively quiescent accretion which can potentially solve both the protostellar luminosity problem and the apparent age spread of stars in young clusters. Such outbursts may also provide a formation mechanism for the chondrules found in meteorites, with the outflow transporting them to large distances in the circumstellar disc.

Bate, Matthew R.

2010-05-01

159

Gas modelling in the disc of HD 163296  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

160

Mechanotransduction in intervertebral discs  

PubMed Central

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

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

2014-01-01

161

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

162

Counter-rotating accretion discs  

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

163

TMT-AGE: wide field of regard multi-object adaptive optics for TMT  

NASA Astrophysics Data System (ADS)

We introduce current status of the feasibility study on a wide field of regard (FoR) Multi-Object Adaptive Optics (MOAO) system for TMT (TMT-AGE: TMT-Analyzer for Galaxies in the Early universe). MOAO is a system which realize high spatial-resolution observations of multiple objects scattered in a wide FoR. In this study, we put emphasise on the FoR as wide as 10' diameter. The wide FoR is crucial to effectively observe very high-redshift galaxies, which have low surface number density. Simulations of an MOAO system with 8 LGSs show close-to-diffraction-limited correction can be achieved within 5' diameter FoR and moderate AO correction can be achieved within 10' diameter FoR. We discuss overall system design of the wide FoR MOAO system considering the constraint from the stroke of small-size deformable mirror (DM). We also introduce current status of developments of key components of an MOAO system; high-dynamic range wavefront sensor (WFS) and large-stroke small-size DM, and real time computer (RTC) with fast tomographic reconstruction.

Akiyama, Masayuki; Oya, Shin; Ono, Yoshito H.; Takami, Hideki; Ozaki, Shinobu; Hayano, Yutaka; Iwata, Ikuru; Hane, Kazuhiro; Wu, Tong; Yamamuro, Tomoyasu; Ikeda, Yuji

2014-07-01

164

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

2011-09-01

165

Enclosed rotary disc air pulser  

DOEpatents

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

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

1989-01-01

166

Numbered nasal discs for waterfowl  

USGS Publications Warehouse

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

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

1964-01-01

167

Dead discs, unstable discs and the stars they surround  

NASA Astrophysics Data System (ADS)

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

D'Angelo, Caroline

2014-01-01

168

The vertical structure of T Tauri accretion discs. III. Consistent interpretation of spectra and visibilities with a two-layer model  

Microsoft Academic Search

We present a two-layer accretion disc model developed to simultaneously fit optical long baseline visibilities and spectral energy distributions of T Tauri accretion discs. This model allows us to access easily the physical conditions in the disc as the mid-plane or the surface temperature. Our model includes viscous heating, absorption of stellar irradiation, and thermalisation with the surrounding medium. The

Regis Lachaume; Fabien Malbet; J.-L. Monin

2003-01-01

169

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

PubMed

The archaeological deposits at Mumba rockshelter, northern Tanzania, have been excavated for more than 70 years, starting with Margit and Ludwig Köhl-Larsen in the 1930s. The assemblages of Middle Stone Age (MSA) and Later Stone Age (LSA) artefacts collected from this site constitute the type sequences for these cultural phases in East Africa. Despite its archaeological importance, however, the chronology of the site is poorly constrained, despite the application since the 1980s of several dating methods (radiocarbon, uranium-series and amino acid racemisation) to a variety of materials recovered from the deposits. Here, we review these previous chronologies for Mumba and report new ages obtained from optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL) measurements on single grains of quartz and multi-grain aliquots of potassium (K) feldspar from the MSA and LSA deposits. Measurements of single grains of quartz allowed the rejection of unrepresentative grains and the application of appropriate statistical models to obtain the most reliable age estimates, while measurements of K-feldspars allowed the chronology to be extended to older deposits. The seven quartz ages and four K-feldspar ages provide improved temporal constraints on the archaeological sequence at Mumba. The deposits associated with the latest Kisele Industry (Bed VI-A) and the earliest Mumba Industry (Bed V) are dated to 63.4 ± 5.7 and 56.9 ± 4.8 ka (thousands of years ago), respectively, thus constraining the time of transition between these two archaeological phases to ~60 ka. An age of 49.1 ± 4.3 ka has been obtained for the latest deposits associated with the Mumba Industry, which show no evidence for post-depositional mixing and contain ostrich eggshell (OES) beads and abundant microlithics. The Nasera Industry deposits (Bed III) contain large quantities of OES beads and date to 36.8 ± 3.4 ka. We compare the luminescence ages with the previous chronologies for Mumba, and briefly discuss how the revised chronology fits in the context of existing archaeological records and palaeoclimatic reconstructions for East Africa. PMID:22425240

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

2012-04-01

170

Adolescent female craniofacial morphology associated with advanced bilateral TMJ disc displacement  

Microsoft Academic Search

SUMMARY The aim of this study was to determine if cephalometric measurement differ- ences occurred between two groups of similarly aged female adolescents which differed with respect to their diagnoses of temporomandibular joint disc position on magnetic reson- ance images (MRI). One group consisted of 17 female adolescents exhibiting complete bilateral disc displacement affecting the temporomandibular joints (TMJ), while the

B. Nebbe; P. W. Major; N. G. N. Prasad

1998-01-01

171

Magnetic fields near the peripheries of galactic discs  

NASA Astrophysics Data System (ADS)

Context. Magnetic fields are observed beyond the peripheries of optically detected galactic discs, while numerical models of their origin and the typical magnitudes are still absent. Previously, studies of galactic dynamo have avoided considering the peripheries of galactic discs because of the very limited (though gradually growing) knowledge about the local properties of the interstellar medium. Aims: Here we investigate the possibility that magnetic fields can be generated in the outskirts of discs, taking the Milky Way as an example. Methods: We consider a simple evolving galactic dynamo model in the "no-z" formulation, applicable to peripheral regions of galaxies, for various assumptions about the radial and vertical profiles of the ionized gas disc. Results: The magnetic field may grow as galaxies evolve, even in the more remote parts of the galactic disc, out to radii of 15 to 30 kpc, becoming substantial after times of about 10 Gyr. This result depends weakly on the adopted distributions of the half thickness and surface density of the ionized gas component. The model is robust to changes in the amplitude of the initial field and the position of its maximum strength. The magnetic field in the remote parts of the galactic disc could be generated in situ from a seed field by local dynamo action. Another possibility is field production in the central regions of a galaxy, followed by transport to the disc's periphery by the joint action of the dynamo and turbulent diffusivity. Conclusions: Our results demonstrate the possibilities for the appearance and strengthening of magnetic fields at the peripheries of disc galaxies and emphasize the need for observational tests with new and anticipated radio telescopes (LOFAR, MWA, and SKA).

Mikhailov, E.; Kasparova, A.; Moss, D.; Beck, R.; Sokoloff, D.; Zasov, A.

2014-08-01

172

Close stellar encounters with planetesimal discs: the dynamics of asymmetry in the b Pictoris system  

E-print Network

Pictoris system J. D. Larwood1w and P. G. Kalas2w 1 Astronomy Unit, Queen Mary & Westfield College, Mile attributed to the edge-on dusty disc of b Pictoris. In addition we present new optical coronagraphic

Kalas, Paul G.

173

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

174

Congenital fibrosis of the extraocular muscles type 1, distinctive conjunctival changes and intrapapillary disc colobomata.  

PubMed

A 6-month-old boy presented with a congenital eye movement disorder consistent with congenital fibrosis of the extraocular muscles type 1 (CFEOM1). Mutational analysis confirmed the most common mutation in the CFEOM1 gene KIF21A. In addition to the typical findings in CFEOM1, distinctive conjunctival changes and small bilateral optic disc colobomata were also noted. It is suggested that optic disc colobomata represent a new association of CFEOM1. PMID:19373680

Flaherty, Maree P; Balachandran, Chandra; Jamieson, Robyn; Engle, Elizabeth C

2009-06-01

175

Thresholds and the Chemical Evolution of Galactic Discs  

NASA Astrophysics Data System (ADS)

Observations by Kennicutt suggest that significant star formation in galactic discs only occurs when a criterion for disc instability is satisfied and that, when star formation is occurring, departure from the marginal state is not great. We have studied galactic disc models in which there is no star formation until the disc has a threshold surface density at which an instability criterion is satisfied. We assume that the rate of the subsequent star formation is just such as to keep the criterion marginally satisfied. Our models contain many approximations and free parameters, but they do have properties which resemble those of real galactic discs. These include a slow variation of the star formation rate with time and a slow change in both space and time of the gas random velocity. There is good general agreement with the observed stellar age/metallicity relation. After a time, at any radial position, the rate of star formation is close to a power law in the gas surface density. Because of the threshold, no stars are produced until some time after the disc starts forming and, if the model were valid, there would therefore be no luminous discs at very high red shift. Moreover, there should not be a large density of hidden matter in the form of elementary particles in the solar neighbourhood. The threshold model cannot readily explain the G-dwarf distribution in the solar neighbourhood, and it is necessary to suppose that the disc starts with a non-zero initial metallicity. The model in which gas infall proceeds on the same time-scale at all radii does not produce abundance gradients as large as those observed. There is some improvement if the infall is biased, occurring more slowly at larger radii.

Chamcham, K.; Pitts, E.; Tayler, R. J.

1993-08-01

176

Factors associated with lumbar intervertebral disc degeneration in the elderly  

Microsoft Academic Search

Background contextLumbar intervertebral disc degeneration (DD) precedes degenerative diseases of the lumbar spine. Various factors in addition to normal aging are reported to be associated with DD, and recently atherosclerosis and risk factors for cardiovascular diseases (cardiovascular risk factors) have received much attention; however, the links between these risk factors and DD are unclear.

Mika Hangai; Koji Kaneoka; Shinya Kuno; Shiro Hinotsu; Masataka Sakane; Naotaka Mamizuka; Shinsuke Sakai; Naoyuki Ochiai

2008-01-01

177

Intervertebral disc (IVD): Structure, degeneration, repair and regeneration  

Microsoft Academic Search

Low back pain affects a large portion of the population, resulting in high care costs for therapy and treatment. One primary cause of low back pain is the degeneration of the intervertebral disc (IVD) resulting in the compression of the spinal nerves and adjacent vertebrae. Exact causes of degeneration are unknown, but it is thought that natural aging, and both

Benjamin R. Whatley; Xuejun Wen

178

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

179

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

PubMed Central

Purpose. To report choroidal thickness and volume in healthy eyes using swept source optical coherence tomography (SS-OCT). Methods. A prospective observational study of 122 patients examined with swept source OCT (DRI-OCT, Topcon, Japan). In each eye, we performed 256 horizontal scans, 12?mm in length and centered on the fovea. We calculated choroidal thickness manually with a built-in caliper and automatically using DRI-OCT mapping software. Choroidal volume was also automatically calculated. We measured axial length with optical low-coherence reflectometry (Lenstar LS 900, Haag-Streit, Switzerland). Results. The choroid has focally increased thickness under the fovea. Choroid was thinnest in the outer nasal quadrant. In stepwise regression analysis, age was estimated as the most significant factor correlating with decreased choroidal thickness (F = 23.146, P < 0.001) followed by axial length (F = 4.902, P = 0.03). Refractive error was not statistically significant (F = 1.16, P = 0.28). Conclusions. SS-OCT is the first commercially available system that can automatically create choroidal thickness and volume maps. Choroidal thickness is increased at the fovea and is thinnest nasally. Age and axial length are critical for the estimation of choroidal thickness and volume. Choroidal measurements derived from SS-OCT images have potential value for objectively documenting disease-related choroidal thickness abnormalities and monitoring progressive changes over time. PMID:25013793

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

2014-01-01

180

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

PubMed

This review suggests why some discs degenerate rather than age normally. Intervertebral discs are avascular pads of fibrocartilage that allow movement between vertebral bodies. Human discs have a low cell density and a limited ability to adapt to mechanical demands. With increasing age, the matrix becomes yellowed, fibrous, and brittle, but if disc structure remains intact, there is little impairment in function, and minimal ingrowth of blood vessels or nerves. Approximately half of old lumbar discs degenerate in the sense of becoming physically disrupted. The posterior annulus and lower lumbar discs are most affected, presumably because they are most heavily loaded. Age and genetic inheritance can weaken discs to such an extent that they are physically disrupted during everyday activities. Damage to the endplate or annulus typically decompresses the nucleus, concentrates stress within the annulus, and allows ingrowth of nerves and blood vessels. Matrix disruption progresses by mechanical and biological means. The site of initial damage leads to two disc degeneration "phenotypes": endplate-driven degeneration is common in the upper lumbar and thoracic spine, and annulus-driven degeneration is common at L4-S1. Discogenic back pain can be initiated by tissue disruption, and amplified by inflammation and infection. Healing is possible in the outer annulus only, where cell density is highest. We conclude that some discs degenerate because they are disrupted by excessive mechanical loading. This can occur without trauma if tissues are weakened by age and genetic inheritance. Moderate mechanical loading, in contrast, strengthens all spinal tissues, including discs. Clin. Anat. 28:195-204, 2015. © 2014 Wiley Periodicals, Inc. PMID:24753325

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

2015-03-01

181

Measurement of cranial optical path length as a function of age using phase resolved near infrared spectroscopy.  

PubMed

Near infrared spectroscopy (NIRS) has been used to measure concentration changes of cerebral hemoglobin and cytochrome in neonates, children, and adults, to study cerebral oxygenation and hemodynamics. To derive quantitative concentration changes from measurements of light attenuation, the optical path length must be known. This is obtained by multiplying the source/ detector separation by a laboratory measured differential path length factor (DPF) which accounts for the increased distance traveled by light due to scattering. DPF has been measured by time of flight techniques on small populations of adults and postmortem infants. The values for adults are greater than those for newborns, and it is not clear how to interpolate the present data for studies on children. Recent developments in instrumentation using phase resolved spectroscopy techniques have produced a bedside unit which can measure optical path length on any subject. We have developed an intensity modulated optical spectrometer which measures path length at four wavelengths. Two hundred and eighty three subjects from 1 d of age to 50 y were studied. Measurements were made at a fixed frequency of 200 MHz and a source detector separation of 4.5 cm. Results suggest a slowly varying age dependence of DPF, following the relation DPF690 = 5.38 + 0.049A0.877, DPF744 = 5.11 + 0.106A0.723, DPF807 = 4.99 + 0.067A0.814, and DPF832 = 4.67 + 0.062A0.819, where DPF690 is the DPF measured at 690 nm and A is age is expressed in years from full term. There was a wide scatter of values, however, implying that ideally DPF should be measured at the time of each study. PMID:8726247

Duncan, A; Meek, J H; Clemence, M; Elwell, C E; Fallon, P; Tyszczuk, L; Cope, M; Delpy, D T

1996-05-01

182

Tissue engineering: A live disc  

NASA Astrophysics Data System (ADS)

A material-cell hybrid device that mimics the anatomic shape of the intervertebral disc has been made and successfully implanted into mice to show that tissue engineering may, in the future, benefit sufferers from back pain.

Hukins, David W. L.

2005-12-01

183

Testing thermal reprocessing in active galactic nuclei accretion discs  

NASA Astrophysics Data System (ADS)

The thermal reprocessing hypothesis in active galactic nuclei (AGN), where extreme ultraviolet/X-ray photons are reprocessed by the accretion disc into optical/UV photons, predicts wavelength-dependent time-delays between the optical continuum at different wavelengths. Recent photometric monitoring by Sergeev et al. has shown that the time-delay is observed in 14 AGN, and generally seen to increase with increasing wavelength, as predicted in the reprocessing scenario. We fit the observed time-delays and optical spectral energy distribution using a disc reprocessing model. The model delivers estimates for the nuclear reddening, the product of black hole mass and accretion rate, and the distance to each object. However, the distances at face value give H0 = 44 +/- 5 km s-1 Mpc-1 - a factor of 1.6 smaller than generally accepted. We discuss the implications of this on the reprocessing model.

Cackett, Edward M.; Horne, Keith; Winkler, Hartmut

2007-09-01

184

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

PubMed Central

Optical manipulation of neuronal activity has rapidly developed into the most powerful and widely used approach to study mechanisms related to neuronal connectivity over a range of scales. Since the early use of single site uncaging to map network connectivity, rapid technological development of light modulation techniques has added important new options, such as fast scanning photostimulation, massively parallel control of light stimuli, holographic uncaging, and two-photon stimulation techniques. Exciting new developments in optogenetics complement neurotransmitter uncaging techniques by providing cell-type specificity and in vivo usability, providing optical access to the neural substrates of behavior. Here we review the rapid evolution of methods for the optical manipulation of neuronal activity, emphasizing crucial recent developments. PMID:22275886

Jerome, Jason; Heck, Detlef H.

2011-01-01

185

Imaging diagnostics for transitional discs  

NASA Astrophysics Data System (ADS)

Transitional discs are a special type of protoplanetary disc, where planet formation is thought to be taking place. These objects feature characteristic inner cavities and/or gaps of a few tens of AUs in sub-millimetre images of the disc. This signature suggests a localised depletion of matter in the disc that could be caused by planet formation processes. However, recent observations have revealed differences in the structures imaged at different wavelengths in some of these discs. In this paper, we aim to explain these observational differences using self-consistent physical 2D hydrodynamical and dust evolution models of these objects, assuming their morphology is indeed generated by the presence of a planet. We use these models to derive the distribution of gas and dust in a theoretical planet-hosting disc for various planet masses and orbital separations. We then simulate observations of the emitted and scattered light from these models with Very Large Telescope (VLT)/SPHERE-ZIMPOL, Subaru/HiCIAO, VLT/VISIR, and ALMA. We do this by first computing the full resolution images of the models at different wavelengths and then simulating the observations while accounting for the characteristics of each particular instrument. The presence of the planet generates pressure bumps in the gas distribution of the disc, whose characteristics strongly depend on the planet mass and position. These bumps cause large grains to accumulate, while small grains are allowed into inner regions. This spatial differentiation of the grain sizes explains the differences in the observations, since different wavelengths and observing techniques trace different parts of the dust size distribution. Based on this effect, we conclude that the combination of visible/near-infrared polarimetric and sub-mm images is the best strategy to constrain the properties of the unseen planet responsible for the disc structure.

de Juan Ovelar, M.; Min, M.; Dominik, C.; Thalmann, C.; Pinilla, P.; Benisty, M.; Birnstiel, T.

2013-12-01

186

Planet signatures and Size Segregation in Debris Discs  

NASA Astrophysics Data System (ADS)

The response of a debris disc to a planetary perturber is the result of the complex interplay between gravitational effects, grain collisions and stellar radiation pressure (Stark & Kuchner (2009). We investigate to what extent this response can depart from the pure gravitational case when including grain collisional production and radiation pressure. We use the DyCoSS code (Thébault (2012), designed to study the coupled effect of collisions and dynamics for systems at steady state with one perturbing body. We focus on two outcomes: the 2D surface density profile of the disc+planet system, and the way the Particle Size Distribution (PSD) is spatially segregated within the disc. We consider two set-ups: 1) a narrow ring with an exterior ``shepherding'' planet, and 2) an extended disc in which a planet is embedded. For each case, the planet mass and orbit are explored as free parameters, and an unperturbed ``no-planet'' case is also considered. Another parameter is the disc's collisional activity, as parameterized by its optical depth ?.

Thébault, Philippe

2014-01-01

187

A geometrically thin accretion disc around a Maclaurin spheroid  

NASA Astrophysics Data System (ADS)

We investigated a semi-analytic and numerical model to study a geometrically thin and optically thick accretion disc around a Maclaurin spheroid (MS). The main interest is in the inner region of the so-called ?-disc, ? being the viscosity parameter. Analytical calculations are done assuming radiation pressure and gas pressure dominated for close to the Eddington mass accretion rate and dot{M} ? 0.1dot{M}_Edd, respectively. We found that the change in the eccentricity of the MS causes a change at the high-frequency region in the emitted spectra. We found that disc parameters are dependent on the eccentricity of the MS. Our semi-analytic results show that qualitatively an increase in the eccentricity of the MS has the same behaviour as a decrease in the mass accretion rate. Numerical work has been carried out to see the viscous time evolution of the accretion disc around an MS. In a numerical model, we showed that if the eccentricity of an object is high, the matter will diffuse slowly during its viscous evolution. This gives a clue how spin-up or spin-down can change the time evolution of the accretion disc using a simple Newtonian approach. The change in spectra can be used to determine the eccentricity and thus the period of the MS.

Mishra, B.; Vaidya, B.

2015-02-01

188

Aging of savanna biomass burning aerosols: Consequences on their optical properties  

Microsoft Academic Search

During the FOS-DECAFE experiment at Lamto, Ivory Coast, in January 1991, various ground studies were undertaken simultaneously in order to investigate the physical and chemical characteristics of smoke emitted by savanna biomass burning. Here we present sunphotometer ground-based results which allow the measurements of the spectral optical depth between 450 and 850 nm, the atmospheric water vapour content and the

C. Liousse; C. Devaux; F. Dulac; H. Cachier

1995-01-01

189

Changes in mechanical behaviour of optical fibers aged in surfactant solutions  

NASA Astrophysics Data System (ADS)

A solution containing surfactants presents appreciable changes in physical and chemical properties at the critical micelle concentration (CMC). Besides signal transmission for telecommunications, optical fibers are used in an increasing number of devices. Among different CMC determination techniques, optical fiber sensors have been increasingly used. However, reliability issues must be addressed for optical fiber sensors operating under particular conditions such as immersion in surfactants at CMC. The purpose of this work was to study the mechanical behavior of both silica coated and naked fibers in contact with two surfactants (sodium dodecyl sulphate (SDS) and Triton X-100) at the critical micelle concentration. Fatigue tests were implemented using a tensile test set-up. Optical fibers were wound onto pulleys and submitted to a tensile test using different velocities. Result analysis proves that immersion in SDS and Triton X-100 decreased the fiber strength especially near the CMC point. Beyond the CMC point, a fine surfactant molecule layer covered all the fiber surfaces and led to a small increase of fiber strength.

El Abdi, R.; Poulain, M.

2012-09-01

190

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

PubMed

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

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

2014-07-01

191

Simulation of the Continuous Spectrum of Substars with Protoplanetary Discs  

NASA Astrophysics Data System (ADS)

The continuous spectra of the substars with surrounding protoplanetary disks were calculated. The results reveal that protoplanetary disc average temperature decreases to 3 K during the period of 5 Myr for substars with masses 0.01M_{_{bigodot}} and during the period of 160 Myr for substars with masses 0.08M_{_{bigodot}}. Estimations of protoplanetary discs flux maximum depending on the substar mass at the age of 1 Myr are: 4.6 kJy (for 0.01M_{_{bigodot}}) and 3.4 MJy (for 0.08M_{_{bigodot}}). Maximum of protoplanetary disc radiation before it reaches the temperature of the cosmic microwave background changes within the ranges: from 0.07 mm to 0.58 mm (for substar mass 0.01M_{_{bigodot}}) and from 0.02 mm to 0.29 mm (for substar mass 0.08M_{_{bigodot}}).

Zakhozhay, O. V.; Vid'Machenko, A. P.; Zakhozhay, V. A.

2007-12-01

192

Signs of a faint disc population at polluted white dwarfs  

NASA Astrophysics Data System (ADS)

Observations of atmospheric metals and dust discs around white dwarfs provide important clues to the fate of terrestrial planetary systems around intermediate-mass stars. We present Spitzer Infrared Array Camera observations of 15 metal polluted white dwarfs to investigate the occurrence and physical properties of circumstellar dust created by the disruption of planetary bodies. We find subtle infrared excess emission consistent with warm dust around KUV 15519+1730 and HS 2132+0941, and weaker excess around the DZ white dwarf G245-58, which, if real, makes it the coolest white dwarf known to exhibit a 3.6 ?m excess and the first DZ star with a bright disc. All together our data corroborate a picture where (1) discs at metal-enriched white dwarfs are commonplace and most escape detection in the infrared (possibly as narrow rings), (2) the discs are long lived, having lifetimes on the order of 106 yr or longer and (3) the frequency of bright, infrared detectable discs decreases with age, on a time-scale of roughly 500 Myr, suggesting large planetesimal disruptions decline on this same time-scale.

Bergfors, C.; Farihi, J.; Dufour, P.; Rocchetto, M.

2014-11-01

193

Disc Heating: Comparing the Milky Way with Cosmological Simulations  

E-print Network

We present the 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 et al. (2008) in which the stellar disc appears to undergo continual/secular heating. Two other simulations are in better agreement with the Quillen & Garnett (2001) observations that suggest a "saturation" in the heating profile for young stars in the disc. None of the simulations have 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 ...

House, Elisa; Gibson, Brad K; Sanchez-Blazquez, Patricia; Courty, Stephanie; Few, Christopher G; Governato, Fabio; Kawata, Daisuke; Roskar, Rok; Steinmetz, Matthias; Stinson, Gregory S; Teyssier, Romain

2011-01-01

194

21 CFR 872.3970 - Interarticular disc prosthesis (interpositional implant).  

Code of Federal Regulations, 2011 CFR

...2011-04-01 false Interarticular disc prosthesis (interpositional implant). 872... § 872.3970 Interarticular disc prosthesis (interpositional implant). (a) Identification. An interarticular disc prosthesis (interpositional implant) is...

2011-04-01

195

Survival of icy grains in debris discs. The role of photosputtering  

E-print Network

We put theoretical constraints on the presence and survival of icy grains in debris discs. Particular attention is paid to UV sputtering of water ice, which has so far not been studied in detail in this context. We present a photosputtering model based on available experimental and theoretical studies. We quantitatively estimate the erosion rate of icy and ice-silicate grains, under the influence of both sublimation and photosputtering, as a function of grain size, composition and distance from the star. The effect of erosion on the grain's location is investigated through numerical simulations coupling the grain size to its dynamical evolution. Our model predicts that photodesorption efficiently destroy ice in optically thin discs, even far beyond the sublimation snow line. For the reference case of beta Pictoris, we find that only > 5mm grains can keep their icy component for the age of the system in the 50-150AU region. When taking into account the collisional reprocessing of grains, we show that the water ice survival on grains improves (grains down to ~ 20 um might be partially icy). However, estimates of the amount of gas photosputtering would produce on such a hypothetical population of big icy grains lead to values for the OI column density that strongly exceed observational constraints for beta Pic, thus ruling out the presence of a significant amount of icy grains in this system. Erosion rates and icy grains survival timescales are also given for a set of 11 other debris disc systems. We show that, with the possible exception of M stars, photosputtering cannot be neglected in calculations of icy grain lifetimes.

Anna Grigorieva; Ph. Thebault; P. Artymowicz; A. Brandeker

2007-09-06

196

Collinear technology for holographic versatile disc (HVD) system  

NASA Astrophysics Data System (ADS)

Holographic Versatile Disc (HVD TM) using Collinear TM Technologies is proposed by OPTWARE Corporation, in which the information and reference beams are displayed co-axially by the same SLM. With this unique configuration the optical pickup can be designed as small as the DVD's, and can be placed on one side of the recording disc. In HVD TM structure, the pre-formatted meta-data reflective layer is used for the focus/tracking servo and reading address information, and the dichroic mirror layer is used for detecting holographic recording information without interfering with the preformatted information. A 2-dimensional digital page data format is used and the shift-multiplexing method is employed to increased recording density of HVD TM. Experimental and theoretical studies suggest that the holographic material is very effective to increased recording density of the system. As the servo technology is being introduced to control the objective lens to be maintained precisely to the disc in the recording and the reconstructing process, a vibration isolator is no longer necessary. HVD TM will be compatible with existing disc storage systems, like CD and DVD, and enable us to expand its applications into other optical information storage systems.

Tan, Xiaodi; Horimai, Hideyoshi; Shimura, Tsutomu; Ichimura, Shotaro; Fujimura, Ryushi; Kuroda, Kazuo

2006-09-01

197

The nature of the red disc-like galaxies at high redshift: dust attenuation and intrinsically red stellar populations  

NASA Astrophysics Data System (ADS)

We investigate which conditions of dust attenuation and stellar populations allow models of dusty, continuously star-forming, bulge-less disc galaxies at 0.8 <~z<~ 3.2 to meet the different colour selection criteria of high-z`red' galaxies (e.g. RC-K > 5.3, IC-K > 4, J-K > 2.3). As a main novelty, we use stellar population models that include the thermally pulsating asymptotic giant branch (TP-AGB) phase of stellar evolution. The star formation rate of the models declines exponentially as a function of time, the e-folding time being longer than 3 Gyr. In addition, we use calculations of radiative transfer of the stellar and scattered radiation through different dusty interstellar media in order to explore the wide parameter space of dust attenuation. We find that synthetic discs can exhibit red optical/near-infrared colours because of reddening by dust, but only if they have been forming stars for at least ~1 Gyr. Extremely few models barely exhibit RC-K > 5.3, if the inclination i= 90° and if the opacity 2 ×?V>~ 6. Hence, RC-K-selected galaxies at 1 <~z<~ 2 most probably are either systems with an old, passively evolving bulge or starbursts. Synthetic discs at 1 <~z<~ 2 exhibit 4 < IC-K < 4.8, if they are seen edge on (i.e. at i~ 90°) and if 2 ×?V>~ 0.5. This explains the large fraction of observed, edge-on disc-like galaxies with Ks < 19.5 and F814W-Ks>~ 4. Finally, models with 2 <~z<~ 3.2 exhibit 2.3 < J-K < 3, with no bias towards i~ 90° and for a large range in opacity (e.g. 2 ×?V > 1 for i~ 70°). In conclusion, red disc-like galaxies at 0.8 <~z<~ 3.2 may not necessarily be dustier than nearby disc galaxies (with 0.5 <~ 2 ×?V<~ 2) and/or much older than ~1 Gyr. This result is due both to a realistic description of dust attenuation and to the emission contribution by TP-AGB stars, with ages of 0.2 to 1-2 Gyr and intrinsically red colours.

Pierini, D.; Maraston, C.; Gordon, K. D.; Witt, A. N.

2005-10-01

198

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

199

Incidence of optic neuritis in Stockholm, Sweden 1990-1995: I. Age, sex, birth and ethnic-group related patterns.  

PubMed

We studied the incidence of monosymptomatic optic neuritis (MON) in Stockholm county, Sweden and its variation with person-related factors. Patients with suspected or diagnosed MON between January 1, 1990 and December 31, 1995 were referred from ophthalmologists and neurologists to a research registry. The diagnosis was based on accepted clinical criteria only, and verified by an ophthalmologist who examined all the patients. Data were collected by interview using a structured questionnaire. The crude mean annual incidence, based on 147 patients, 118 females and 29 males, diagnosed with MON, was 1.46 per 100,000 person-years, 2.28 for females and 0.59 for males. The corresponding age-adjusted incidences were 1.40, 2.28 and 0.53. The age-specific incidence curve for both sexes suggested a bimodal distribution with peaks at 30-34 years and 45-49 years. The smoothed cumulative incidences in 1 year birth cohorts showed a notchy profile, related to bimodality. The incidence among residents born out of the Nordic countries was low, 0.28 per 100,000. Patients with onset of MON before 40 years of age had a significantly higher frequency of mononuclear pleocytosis in cerebrospinal fluid and shorter duration to conversion to multiple sclerosis. In summary, MON occurred in Stockholm at a relatively low frequency, particularly among males. The presence of particular birth date and birth place related patterns might be etiologically relevant. PMID:9700712

Jin, Y P; de Pedro-Cuesta, J; Söderström, M; Stawiarz, L; Link, H

1998-07-15

200

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

PubMed Central

Purpose To evaluate the effect of age on optic nerve axon counts, spectral-domain optical coherence tomography (SDOCT) scan quality, and peripapillary retinal nerve fiber layer thickness (RNFLT) measurements in healthy monkey eyes. Methods In total, 83 healthy rhesus monkeys were included in this study (age range: 1.2–26.7 years). Peripapillary RNFLT was measured by SDOCT. An automated algorithm was used to count 100% of the axons and measure their cross-sectional area in postmortem optic nerve tissue samples (N = 46). Simulation experiments were done to determine the effects of optical changes on measurements of RNFLT. An objective, fully-automated method was used to measure the diameter of the major blood vessel profiles within each SDOCT B-scan. Results Peripapillary RNFLT was negatively correlated with age in cross-sectional analysis (P < 0.01). The best-fitting linear model was RNFLT(?m) = ?0.40 × age(years) + 104.5 ?m (R2 = 0.1, P < 0.01). Age had very little influence on optic nerve axon count; the result of the best-fit linear model was axon count = ?1364 × Age(years) + 1,210,284 (R2 < 0.01, P = 0.74). Older eyes lost the smallest diameter axons and/or axons had an increased diameter in the optic nerve of older animals. There was an inverse correlation between age and SDOCT scan quality (R = ?0.65, P < 0.0001). Simulation experiments revealed that approximately 17% of the apparent cross-sectional rate of RNFLT loss is due to reduced scan quality associated with optical changes of the aging eye. Another 12% was due to thinning of the major blood vessels. Conclusions RNFLT declines by 4 ?m per decade in healthy rhesus monkey eyes. This rate is approximately three times faster than loss of optic nerve axons. Approximately one-half of this difference is explained by optical degradation of the aging eye reducing SDOCT scan quality and thinning of the major blood vessels. Translational Relevance Current models used to predict retinal ganglion cell losses should be reconsidered. PMID:24932430

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

2014-01-01

201

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. PMID:22662096

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

2012-01-01

202

Short dissipation times of proto-planetary discs - an artifact of selection effects?  

E-print Network

The frequency of discs around young stars, a key parameter for understanding planet formation, is most readily determined in young stellar clusters where many relatively coeval stars are located in close proximity. Observational studies seem to show that the disc frequency decreases rapidly with cluster age with 3Myr only stars that originally populated the densest areas of very populous clusters, which are prone to disc erosion, are actually considered. This tiny sample may not be representative of the majority of stars. In fact, the higher disc fractions in co-moving groups indicate that it is likely that over 30% of all field stars retain their discs well beyond 10 Myr, leaving ample time for planet growth. Equally our solar system, with a likely formation time > 10 Myr, need no longer be an exception but in fact typical of planetary systems.

Pfalzner, Susanne; Menten, Karl

2014-01-01

203

Potential regenerative treatment strategies for intervertebral disc degeneration in dogs  

PubMed Central

Pain due to spontaneous intervertebral disc (IVD) disease is common in dogs. In chondrodystrophic (CD) dogs, IVD disease typically develops in the cervical or thoracolumbar spine at about 3–7 years of age, whereas in non-chondrodystrophic (NCD) dogs, it usually develops in the caudal cervical or lumbosacral spine at about 6–8 years of age. IVD degeneration is characterized by changes in the biochemical composition and mechanical integrity of the IVD. In the degenerated IVD, the content of glycosaminoglycan (GAG, a proteoglycan side chain) decreases and that of denatured collagen increases. Dehydration leads to tearing of the annulus fibrosus (AF) and/or disc herniation, which is clinically characterized by pain and/or neurological signs. Current treatments (physiotherapy, anti-inflammatory/analgesic medication, surgery) for IVD disease may resolve neurological deficits and reduce pain (although in many cases insufficient), but do not lead to repair of the degenerated disc. For this reason, there is interest in new regenerative therapies that can repair the degenerated disc matrix, resulting in restoration of the biomechanical function of the IVD. CD dogs are considered a suitable animal model for human IVD degeneration because of their spontaneous IVD degeneration, and therefore studies investigating cell-, growth factor-, and/or gene therapy-based regenerative therapies with this model provide information relevant to both human and canine patients. The aim of this article is to review potential regenerative treatment strategies for canine IVD degeneration, with specific emphasis on cell-based strategies. PMID:24387033

2014-01-01

204

Fully automated detection of diabetic macular edema and dry age-related macular degeneration from optical coherence tomography images  

PubMed Central

We present a novel fully automated algorithm for the detection of retinal diseases via optical coherence tomography (OCT) imaging. Our algorithm utilizes multiscale histograms of oriented gradient descriptors as feature vectors of a support vector machine based classifier. The spectral domain OCT data sets used for cross-validation consisted of volumetric scans acquired from 45 subjects: 15 normal subjects, 15 patients with dry age-related macular degeneration (AMD), and 15 patients with diabetic macular edema (DME). Our classifier correctly identified 100% of cases with AMD, 100% cases with DME, and 86.67% cases of normal subjects. This algorithm is a potentially impactful tool for the remote diagnosis of ophthalmic diseases. PMID:25360373

Srinivasan, Pratul P.; Kim, Leo A.; Mettu, Priyatham S.; Cousins, Scott W.; Comer, Grant M.; Izatt, Joseph A.; Farsiu, Sina

2014-01-01

205

Hydrodynamic instability in eccentric astrophysical discs  

E-print Network

Eccentric Keplerian discs are believed to be unstable to three-dimensional hydrodynamical instabilities driven by the time-dependence of fluid properties around an orbit. These instabilities could lead to small-scale turbulence, and ultimately modify the global disc properties. We use a local model of an eccentric disc, derived in a companion paper, to compute the nonlinear vertical ("breathing mode") oscillations of the disc. We then analyse their linear stability to locally axisymmetric disturbances for any disc eccentricity and eccentricity gradient using a numerical Floquet method. In the limit of small departures from a circular reference orbit, the instability of an isothermal disc is explained analytically. We also study analytically the small-scale instability of an eccentric neutrally stratified polytropic disc with any polytropic index using a WKB approximation. We find that eccentric discs are generically unstable to the parametric excitation of small-scale inertial waves. The nonlinear evolution o...

Barker, Adrian J

2014-01-01

206

Disc Replacement for Low Back Pain  

MedlinePLUS

... for Low Back Pain Disc Replacement for Low Back Pain Page Content The evolution of disc replacement surgery may help select patients who have chronic low back pain. However, choosing which type of patient this procedure ...

207

The use of encoded discs in the angle measurement systems of modern theodolites  

Microsoft Academic Search

The angle reading mechanism of the modern electronic theodolite is totally different from the classically accepted optical system due to the implementation of an electro-optical read encoded glass disc. This paper discusses some of the different systems utilised by different manufacturers. These are grouped as the incremental, absolute and dynamic methods, and reference is given to specific instruments.

Graeme M. Brooke

1988-01-01

208

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

209

Metric evaluation of partially displaced temporomandibular joint disc.  

PubMed

The objective was to determine the quantitative relationship between the condyle and disc position in the glenoid fossa between two different slices of the same temporomandibular joints (TMJs) with partial anterior disc displacement (DD). The study was conducted on 40 patients with DD of TMJs (mean age, 35.5 years). The clinical diagnosis of DD was confirmed by magnetic resonance imaging. Joints from the patient groups were analyzed according to the laterality and depending on disc displacement (a total of 80 joints). Comparison was made between two different slices of 9 joints with partial DD with reduction: partial DD was analyzed in the representative centrolateral or centromedial parasagittal slice of the TMJ (TMJ partial DD--slice DD). The contralateral slice of the same joint was without DD (TMJ partial DD--slice NDD). The analysis also included 34 healthy joints without DD (TMJ NDD) of the same patients. The position of the condyle and disc was calculated using the Kurita et al. method on the parasagittal view of the TMJ. A statistically significant difference was recorded for different slices of the same TMJs with partial DD (TMJ partial DD--slice DD and TMJ partial DD--slice NDD) (p < 0.01), but no difference was found in condyle positions depending on the existence of partial DD (p > 0.05). The compared values between slice TMJ partial DD--slice NDD with the group of TMJ NDD showed no significant difference in either disc position or condyle position (p > 0.05). There were differences of disc position in various slices of the same joint with visually confirmed partial DD. The dorsocranial condyle position could not indicate partial anterior DD. PMID:25509241

Laškarin, Mirko; Badel, Tomislav; Kern, Josipa; Pavi?in, Ivana Savi?; Zadravec, Dijana

2014-09-01

210

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

211

Study on the movement measurement for an objective lens actuator in optical pickup  

Microsoft Academic Search

This paper deals with the actuator movement measurement for objective lens actuator in optical pickup. An optical pickup is an optical apparatus to record and\\/or reproduce information from an optical disc, and move in a radial direction on the optical disc. The objective lens actuator helps move an objective lens in a tracking direction, a focusing direction, and\\/or a tilting

Xuemin Cheng; Jianshe Ma; Longfa Pan; Buqing Zhang

2007-01-01

212

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

213

Intramural Sports Ultimate Disc "Hat"  

E-print Network

not provide health or accident insurance that covers intramural sports participants. The Intramural SportsIntramural Sports Ultimate Disc "Hat" Tournament Summer 2014 Intramural Sports Calendar of Events on the day of the tournament, teams will be drawn out of a hat and mixed for play. Sports and Special

Escher, Christine

214

Glycosaminoglycans of cat invertebral disc  

PubMed Central

The glycosaminoglycan contents of samples from cat intervertebral discs were examined by using cetylpyridinium chloride salt elution techniques. The values obtained related to the region of the vertebral column from which they were derived, to the area of the disc, and to water content. In wet tissue there was a significant difference between regions of the vertebral column and between areas of the disc and findings agreed with previous histological reports. The greater part of the glycosaminoglycans present consisted of chondroitin sulphate and dermatan sulphate with smaller amounts of hyaluronic acid; little keratan sulphate was found. The maximum amounts of chondroitin sulphate and dermatan sulphate occurred in the 0.5m-magnesium chloride fractions usually, but moved towards higher molar concentrations in samples derived from some sites, particularly in the lumbar region. Mean values for the water content of the areas of the disc were: nucleus pulposus, 82.4%; inner anulus, 65.6%; outer anulus, 50.5%. The water content was directly related to the amounts of chondroitin sulphate and dermatan sulphate. ImagesPLATE 1 PMID:4256903

Butler, W. F.; Wels, C. M.

1971-01-01

215

Wnt signaling activates Shh signaling in early postnatal intervertebral discs, and re-activates Shh signaling in old discs in the mouse.  

PubMed

Intervertebral discs (IVDs) are strong fibrocartilaginous joints that connect adjacent vertebrae of the spine. As discs age they become prone to failure, with neurological consequences that are often severe. Surgical repair of discs treats the result of the disease, which affects as many as one in seven people, rather than its cause. An ideal solution would be to repair degenerating discs using the mechanisms of their normal differentiation. However, these mechanisms are poorly understood. Using the mouse as a model, we previously showed that Shh signaling produced by nucleus pulposus cells activates the expression of differentiation markers, and cell proliferation, in the postnatal IVD. In the present study, we show that canonical Wnt signaling is required for the expression of Shh signaling targets in the IVD. We also show that Shh and canonical Wnt signaling pathways are down-regulated in adult IVDs. Furthermore, this down-regulation is reversible, since re-activation of the Wnt or Shh pathways in older discs can re-activate molecular markers of the IVD that are lost with age. These data suggest that biological treatments targeting Wnt and Shh signaling pathways may be feasible as a therapeutic for degenerative disc disease. PMID:24892825

Winkler, Tamara; Mahoney, Eric J; Sinner, Debora; Wylie, Christopher C; Dahia, Chitra Lekha

2014-01-01

216

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

PubMed Central

Intervertebral discs (IVDs) are strong fibrocartilaginous joints that connect adjacent vertebrae of the spine. As discs age they become prone to failure, with neurological consequences that are often severe. Surgical repair of discs treats the result of the disease, which affects as many as one in seven people, rather than its cause. An ideal solution would be to repair degenerating discs using the mechanisms of their normal differentiation. However, these mechanisms are poorly understood. Using the mouse as a model, we previously showed that Shh signaling produced by nucleus pulposus cells activates the expression of differentiation markers, and cell proliferation, in the postnatal IVD. In the present study, we show that canonical Wnt signaling is required for the expression of Shh signaling targets in the IVD. We also show that Shh and canonical Wnt signaling pathways are down-regulated in adult IVDs. Furthermore, this down-regulation is reversible, since re-activation of the Wnt or Shh pathways in older discs can re-activate molecular markers of the IVD that are lost with age. These data suggest that biological treatments targeting Wnt and Shh signaling pathways may be feasible as a therapeutic for degenerative disc disease. PMID:24892825

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

2014-01-01

217

Long-term evolution, X-ray outburst and optical/infrared emission of SGR 0501+4516  

NASA Astrophysics Data System (ADS)

We have analysed the long-term evolution and the X-ray outburst light curve of SGR 0501+4516 in the fallback disc model. We have shown that the X-ray luminosity, period and period derivative of this typical soft gamma repeater can be achieved by a neutron star with a large range of initial disc masses provided that the source has a magnetic dipole field of ˜1.4 × 1012 G on the pole of the star. At present, the star is accreting matter from the disc, which has an age ˜3 × 104 yr, and will remain in the accretion phase until t ˜2-5 × 105 yr depending on the initial disc mass. With its current rotational rate, this source is not expected to give pulsed radio emission even if the accretion on to the star is hindered by some mechanism. The X-ray enhancement light curve of SGR 0501+4516 can be accounted for by the same model applied earlier to the X-ray enhancement light curves of other anomalous X-ray pulsars/soft gamma repeaters with the same basic disc parameters. We have further shown that the optical/infrared data of SGR 0501+4516 are in good agreement with the emission from an irradiated fallback disc with the properties consistent with our long-term evolution model.

Benli, O.; ?Çal??kan, ?.; Ertan, Ü.

2015-03-01

218

Biomechanics of a Fixed–Center of Rotation Cervical Intervertebral Disc Prosthesis  

PubMed Central

Background Past in vitro experiments studying artificial discs have focused on range of motion. It is also important to understand how artificial discs affect other biomechanical parameters, especially alterations to kinematics. The purpose of this in vitro investigation was to quantify how disc replacement with a ball-and-socket disc arthroplasty device (ProDisc-C; Synthes, West Chester, Pennsylvania) alters biomechanics of the spine relative to the normal condition (positive control) and simulated fusion (negative control). Methods Specimens were tested in multiple planes by use of pure moments under load control and again in displacement control during flexion-extension with a constant 70-N compressive follower load. Optical markers measured 3-dimensional vertebral motion, and a strain gauge array measured C4-5 facet loads. Results Range of motion and lax zone after disc replacement were not significantly different from normal values except during lateral bending, whereas plating significantly reduced motion in all loading modes (P < .002). Plating but not disc replacement shifted the location of the axis of rotation anteriorly relative to the intact condition (P < 0.01). Coupled axial rotation per degree of lateral bending was 25% ± 48% greater than normal after artificial disc replacement (P = .05) but 37% ± 38% less than normal after plating (P = .002). Coupled lateral bending per degree of axial rotation was 37% ± 21% less than normal after disc replacement (P < .001) and 41% ± 36% less than normal after plating (P = .001). Facet loads did not change significantly relative to normal after anterior plating or arthroplasty, except that facet loads were decreased during flexion in both conditions (P < .03). Conclusions In all parameters studied, deviations from normal biomechanics were less substantial after artificial disc placement than after anterior plating.

Crawford, Neil R.; Baek, Seungwon; Sawa, Anna G.U.; Safavi-Abbasi, Sam; Sonntag, Volker K.H.; Duggal, Neil

2012-01-01

219

A phenotypic comparison of intervertebral disc and articular cartilage cells in the rat  

Microsoft Academic Search

The basic molecular characteristics of intervertebral disc cells are still poorly defined. This study compared the phenotypes\\u000a of nucleus pulposus (NP), annulus fibrosus (AF) and articular cartilage (AC) cells using rat coccygeal discs and AC from both\\u000a young and aged animals and a combination of microarray, real-time RT-PCR and immunohistochemistry. Microarray analysis identified\\u000a 63 genes with at least a fivefold

Cynthia R. Lee; Daisuke Sakai; Tomoko Nakai; Kanae Toyama; Joji Mochida; Mauro Alini; Sibylle Grad

2007-01-01

220

Evolution of linear warps in accretion discs and applications to protoplanetary discs in binaries  

NASA Astrophysics Data System (ADS)

Warped accretion discs are expected in many protostellar binary systems. In this paper, we study the long-term evolution of disc warp and precession for discs with dimensionless thickness H/r larger than their viscosity parameter ?, such that bending waves can propagate and dominate the warp evolution. For small warps, these discs undergo approximately rigid-body precession. We derive analytical expressions for the warp/twist profiles of the disc and the alignment time-scale for a variety of models. Applying our results to circumbinary discs, we find that these discs align with the orbital plane of the binary on a time-scale comparable to the global precession time of the disc, and typically much smaller than its viscous time-scale. We discuss the implications of our finding for the observations of misaligned circumbinary discs (such as KH 15D) and circumbinary planetary systems (such as Kepler-413); these observed misalignments provide useful constraints on the uncertain aspects of the disc warp theory. On the other hand, we find that circumstellar discs can maintain large misalignments with respect to the plane of the binary companion over their entire lifetime. We estimate that inclination angles larger than ˜20° can be maintained for typical disc parameters. Overall, our results suggest that while highly misaligned circumstellar discs in binaries are expected to be common, such misalignments should be rare for circumbinary discs. These expectations are consistent with current observations of protoplanetary discs and exoplanets in binaries, and can be tested with future observations.

Foucart, Francois; Lai, Dong

2014-12-01

221

On the age vs depth and optical clarity of deep ice at South Pole  

E-print Network

The first four strings of phototubes for the AMANDA high-energy neutrino observatory are now frozen in place at a depth of 800 to 1000 m in ice at the South Pole. During the 1995-96 season an additional six strings will be deployed at greater depths. Provided absorption, scattering, and refraction of visible light are sufficiently small, the trajectory of a muon into which a neutrino converts can be determined by using the array of phototubes to measure the arrival times of \\v{C}erenkov light emitted by the muon. To help in deciding on the depth for implantation of the six new strings, we discuss models of age vs depth for South Pole ice, we estimate mean free paths for scattering from bubbles and dust as a function of depth, and we assess distortion of light paths due to refraction at crystal boundaries and interfaces between air-hydrate inclusions and normal ice. We conclude that the depth interval 1600 to 1800 m will be suitably transparent for the next six AMANDA strings and, moreover, that the interval 1600 to 2100 m will be suitably transparent for a future 1-km$^3$ observatory except possibly in a region a few tens of meters thick at a depth corresponding to a peak in the dust concentration at 60 kyr BP.

The AMANDA collaboration

1995-01-23

222

Vertebral height growth predominates over intervertebral disc height growth in adolescents with scoliosis.  

PubMed Central

Study Design A cross sectional study of spinal stereo radiographs of adolescents with scoliosis to measure growth. Objective To determine the relative contributions of the vertebral bodies and the intervertebral discs to the increase in spinal length between T5 to L5 over the age range 7.5 to 20 years. Summary of Background Data The progression of spinal deformity (scoliosis) is associated with skeletal growth, but the relative roles of asymmetrical growth and remodelling of the vertebrae and discs during adolescent growth is unclear. Methods An existing database of 406 spinal stereo radiographic studies of 188 adolescents with idiopathic scoliosis, aged between 7.5 and 20 years was used to measure the heights of vertebral bodies and of intervertebral discs and the summation of both (spinal length). Results Spinal length was observed to increase from about 250 mm to 350 mm over this range of ages. Spinal growth was associated with increase in vertebral height after age 10 years, with minimal if any increase in disc height. The contribution of vertebral and discal height was estimated to be about 17 and 8 mm per year respectively at age 7.5 years, but discal height growth was estimated to be effectively zero after age 12. Conclusion Spinal growth of patients with scoliosis aged between 10 and 20 years occurs almost exclusively by height increases in the vertebrae, not the discs. Mini-Abstract Spinal length over the range T5 to L5, and its components due to vertebral height and discal height were measured from 406 spinal stereo radiographic studies of 188 adolescents with idiopathic scoliosis, aged between 7.5 and 20 years. This cross-sectional analysis indicated that after age 10 years spinal growth was associated with increase in vertebral height, with minimal if any increase in disc height. PMID:16778695

Stokes, Ian A.F.; Windisch, Luke

2006-01-01

223

The clinical study of percutaneous disc decompression of treating herniation of cervical disc with Nd:YAG laser  

NASA Astrophysics Data System (ADS)

Objective: The possibility of PLDD (percutaneous laser disc decompression) and an ideal non-operative method which is long everlasting effect for PLDD was investigated. Methods: 159 patients of Cervical Disc Herniation with PLDD were studied. All the herniated discs were irradiated with 10­15J/S Nd:YAG laser quantum through optical-fiber under the supervision of C-arm X-ray. Results: All the patients were followed and reexamined CT or MRI after one to six months of PLDD. The result of cured (67.92%), excellent (24.53%), moderation (5.66%), non-effect (1.88%) was got. The excellent rate was 88.24%. The effective rate was 97.65%. Non-effective rate was 2.35%. Conclusion: When irradiated with Nd:YAG laser, the nucleus pulposus was vapouring, charring and coagulating. The volume and inner-pressure of the disc decreased. So the symptoms and signs improved. The main value of this methods were micro-damage, non-operation, no bleeding, no bone injury, good therapy effect, quick recovery, lesser pain, safety and excellent long everlasting effect. It is an ideal non-operative method of treating PLDD.

Zhang, Dianxue; Cheng, Hefu; Wang, Jindong

2005-07-01

224

A young hierarchical triple system harbouring a candidate debris disc  

NASA Astrophysics Data System (ADS)

We report the detection of a wide young hierarchical triple system where the primary has a candidate debris disc. The primary, TYC 5241-986-1 A, is a known Tycho star which we classify as a late-K star with emission in the X-ray, near- and far-ultraviolet (UV) and H? suggestive of youth. Its proper motion, photometric distance (65-105 pc) and radial velocity lead us to associate the system with the broadly defined Local Association of young stars but not specifically with any young moving group. The presence of weak lithium absorption and X-ray and calcium H and K emission support an age in the 20 to ˜125 Myr range. The secondary is a pair of M4.5 ± 0.5 dwarfs with near- and far-UV and H? emission separated by approximately 1 arcsec (˜65-105 au projected separation) which lie of 145 arcsec (9200-15200 au) from the primary. The primary has a Wide-field Infrared Survey Explorer (WISE) 22 ?m excess and follow-up Herschel observations also detect an excess at 70 ?m. The excess emissions are indicative of a 100-175 K debris disc. We also explore the possibility that this excess could be due to a coincident background galaxy and conclude that this is unlikely. Debris discs are extremely rare around stars older than 15 Myr, hence if the excess is caused by a disc this is an extremely novel system.

Deacon, N. R.; Schlieder, J. E.; Olofsson, J.; Johnston, K. G.; Henning, Th.

2013-09-01

225

Migration of protoplanets with surfaces through discs with steep temperature gradients  

NASA Astrophysics Data System (ADS)

We perform three-dimensional self-gravitating radiative transfer simulations of protoplanet migration in circumstellar discs to explore the impact upon migration of the radial temperature profiles in these discs. We model protoplanets with masses ranging between 10-100 M?, in discs with surface density profiles of ??r-1/2, and temperature profiles of the form T?r-?, where ? ranges 0-2. We find that steep (? > 1) temperature profiles lead to outward migration of low-mass protoplanets in interstellar grain opacity discs, but in more optically thin discs the migration is always inwards. The trend in migration rates with changing ? obtained from our models shows good agreement with those obtained using recent analytic descriptions which include consideration of the coorbital torques and their saturation. We find that switching between two models of the protoplanet, one in which accretion acts by evacuating gas and one in which gas piles up on a surface to form an atmosphere, leads to a small shift in the migration rates. If comparing these models in discs with conditions which lead to a marginally inward migration, the small shift can lead to outward migration. However, the direction and speed of migration is dominated by disc conditions rather than by the specific prescription used to model the flow near the protoplanet.

Ayliffe, Ben A.; Bate, Matthew R.

2011-07-01

226

Automated optic disk localization and detection in colored retinal images  

Microsoft Academic Search

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

M. Usman Akram; Anam Tariq

2009-01-01

227

Numerical simulations of protostellar encounters II. Coplanar disc-disc encounters  

E-print Network

It is expected that an average protostar will undergo at least one impulsive interaction with a neighbouring protostar whilst a large fraction of its mass is still in a massive, extended disc. Such interactions must have a significant impact upon the evolution of the protostars and their discs. We have carried out a series of simulations of coplanar encounters between two stars, each possessing a massive circumstellar disc, using an SPH code that models gravitational, hydrodynamic and viscous forces. We find that during a coplanar encounter, disc material is swept up into a shock layer between the two interacting stars, and the layer then fragments to produce new protostellar condensations. The truncated remains of the discs may subsequently fragment; and the outer regions of the discs may be thrown off to form circumbinary disc-like structures around the stars. Thus coplanar disc-disc encounters lead efficiently to the formation of multiple star systems and small-N clusters.

S. J. Watkins; A. S. Bhattal; H. M. J. Boffin; N. Francis; A. P. Whitworth

1998-05-28

228

Analysis of Choroidal Thickness in Age-Related Macular Degeneration Using Spectral-Domain Optical Coherence Tomography  

PubMed Central

Purpose To understand the relationship between choroidal thickness and various disease factors in patients with age-related macular degeneration (AMD) using spectral-domain optical coherence tomography. Design Cross-sectional, retrospective analysis. Methods Fifty-seven eyes of 47 patients with wet and dry AMD seen between November 2009 and January 2010 at the New England Eye Center, Boston, Massachusetts, were analyzed. Choroidal thickness was measured by 2 independent observers at 11 sites with high-definition horizontal 1-line raster scans through the foveal center. A retrospective chart review was performed to obtain data concerning duration of disease, number of intravitreal anti–vascular endothelial growth factor injections, visual acuity, lens status, and concomitant retinal pathologic features. The Pearson correlation and Student t test were used for statistical analysis for assessment of choroidal thickness changes in wet and dry AMD. Results The choroid in eyes with wet and dry AMD demonstrated a wide range of thicknesses above and below the normal mean (range, 77.5 to 399.5 ?m; standard deviation [SD], 90.2). Nearly one third (33.3%) of the eyes with AMD measured less than 1 SD below the mean. Eyes with wet AMD demonstrated a mean subfoveal choroidal thickness of 194.6 ?m (SD, 88.4; n = 40) compared with 213.4 ?m (SD, 92.2; n = 17) in the dry AMD group. The choroidal thickness in eyes with dry AMD was correlated inversely with age (r = ?0.703; P = .002); however, analysis of the number of intravitreal anti–vascular endothelial growth factor injections, number of years of disease, and visual acuity failed to demonstrate any significant correlations with choroidal thickness. Conclusions This study demonstrated that choroidal thickness can be measured by spectral-domain optical coherence tomography and that variable choroidal thickness exists among patients with the clinical diagnosis of wet and dry AMD. However, it is unclear at this time why in some eyes, choroidal thickness either increases or decreases with the disease. Further studies need to be carried out to understand the significance of choroidal thickness with respect to visual function and disease progression over time. PMID:21708378

Manjunath, Varsha; Goren, Jordana; Fujimoto, James G.; Duker, Jay S.

2012-01-01

229

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

230

Irradiated, colour-temperature-corrected accretion discs in ultraluminous X-ray sources  

NASA Astrophysics Data System (ADS)

Although attempts have been made to constrain the stellar types of optical counterparts to ultraluminous X-ray sources (ULXs), the detection of optical variability instead suggests that they may be dominated by reprocessed emission from X-rays which irradiate the outer accretion disc. Here, we report results from a combined X-ray and optical spectral study of a sample of ULXs, which were selected for having broadened disc-like X-ray spectra and known optical counterparts. We simultaneously fit optical and X-ray data from ULXs with a new spectral model of emission from an irradiated, colour-temperature-corrected accretion disc around a black hole, with a central Comptonizing corona. We find that the ULXs require reprocessing fractions of ˜10-3, which is similar to sub-Eddington thermal dominant state black hole binaries (BHBs), but less than has been reported for ULXs with soft ultraluminous X-ray spectra. We suggest that the reprocessing fraction may be due to the opposing effects of self-shielding in a geometrically thick supercritical accretion disc and reflection from far above the central black hole by optically thin material ejected in a natal super-Eddington wind. Then, the higher reprocessing fractions reported for ULXs with wind-dominated X-ray spectra may be due to enhanced scattering on to the outer disc via the stronger wind in these objects. Alternatively, the accretion discs in these ULXs may not be particularly geometrically thick, rather they may be similar in this regard to the thermal dominant state BHBs.

Sutton, Andrew D.; Done, Chris; Roberts, Timothy P.

2014-11-01

231

Spontaneous cervical intradural disc herniation.  

PubMed

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

Warade, Abhijit G; Misra, Basant K

2014-05-01

232

Laminated composite disc flywheel development  

NASA Astrophysics Data System (ADS)

A flywheel concept for an electric powered vehicle uses a laminated disc and a filament wound outer ring assembled with an interference fit between these two components. The laminated, central disc is made of S2-glass-epoxy and the outer ring is filament-wound graphite-epoxy. Projections for this particular flywheel design indicate that it will be both practical and relatively inexpensive to produce, and that it will have a high energy density capacity. Two hybrid composite flywheels of 37 cm O.D. were successfully assembled. The spin test data are summarized, the nondestructive test dat are discussed and the fabrication techniques developed for the hybrid flywheel assembly are described.

Nimmer, R. P.; Torossian, K.; Hickey, J.

1980-02-01

233

Ptolemy relations for punctured discs  

E-print Network

We construct frieze patterns of type D_N with entries which are numbers of matchings between vertices and triangles of corresponding triangulations of a punctured disc. For triangulations corresponding to orientations of the Dynkin diagram of type D_N, we show that the numbers in the pattern can be interpreted as specialisations of cluster variables in the corresponding Fomin-Zelevinsky cluster algebra.

Baur, Karin

2007-01-01

234

Thermal cracking in disc brakes  

Microsoft Academic Search

Disc brakes are exposed to large thermal stresses during routine braking and extraordinary thermal stresses during hard braking. High-g decelerations typical of passenger vehicles are known to generate temperatures as high as 900°C in a fraction of a second. These large temperature excursions have two possible outcomes: thermal shock that generates surface cracks; and\\/or large amounts of plastic deformation in

Thomas J. Mackin; Steven C. Noe; K. J. Ball; B. C. Bedell; D. P. Bim-Merle; M. C. Bingaman; D. M. Bomleny; G. J. Chemlir; D. B. Clayton; H. A. Evans; R. Gau; J. L. Hart; J. S. Karney; B. P. Kiple; R. C. Kaluga; P. Kung; A. K. Law; D. Lim; R. C. Merema; B. M. Miller; T. R. Miller; T. J. Nielson; T. M. O'Shea; M. T. Olson; H. A. Padilla; B. W. Penner; C. Penny; R. P. Peterson; V. C. Polidoro; A. Raghu; B. R. Resor; B. J. Robinson; D. Schambach; B. D. Snyder; E. Tom; R. R. Tschantz; B. M. Walker; K. E. Wasielewski; T. R. Webb; S. A. Wise; R. S. Yang; R. S. Zimmerman

2002-01-01

235

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

236

Thin, thick and dark discs in LCDM  

E-print Network

In a LCDM cosmology, the Milky Way accretes satellites into the stellar disc. We use cosmological simulations to assess the frequency of near disc plane and higher inclination accretion events, and collisionless simulations of satellite mergers to quantify the final state of the accreted material and the effect on the thin disc. On average, a Milky Way-sized galaxy has 3 subhalos with vmax>80km/s; 7 with vmax>60km/s; and 15 with vmax>40km/s merge at redshift z>1. Assuming isotropic accretion, a third of these merge at an impact angle 20 degrees) are twice as likely as low inclination ones. These lead to structures that closely resemble the recently discovered inner/outer stellar halos. They also do more damage to the Milky Way stellar disc creating a more pronounced flare, and warp; both long-lived and consistent with current observations. The most massive mergers (vmax>80km/s) heat the thin disc enough to produce a thick disc. These heated thin disc stars are essential for obtaining a thick disc as massive as that seen in the Milky Way; they likely comprise some ~50-90% of the thick disc stars. The Milky Way thin disc must reform from fresh gas after z=1 [abridged].

J. I. Read; G. Lake; O. Agertz; Victor P. Debattista

2008-03-19

237

Spectral-domain optical coherence tomography in subjects over 60 years of age, and its implications for designing clinical trials  

PubMed Central

Aims To study the variability of central retinal thickness (CRT), its concordance to the fellow eye, and the implications for designing future clinical trials using spectral-domain optical coherence tomography (SD-OCT). Methods Cross-sectional retrospective analysis of European Genetic Database. 632 eyes of 316 subjects over 60?years of age without macular pathology were examined using SD-OCT. Results Mean CRT was 280.22?µm and 281.02?µm for the right and left eyes, respectively. There was a strong concordance for all measured values between right and left eyes. Men had significantly thicker CRT than women. Variation up to 23?µm difference between both eyes was seen. To detect a change of at least 30?µm in CRT, a sample size of 90 or 176 per group is needed for a single-arm or double-arm study, respectively (?=0.05, power=0.80, no loss to follow up, assuming SD in future studies=100?µm). Conclusions Clinical trials using CRT as an endpoint are feasible in terms of sample size needed. PMID:22863948

Caramoy, Albert; Foerster, Jonathan; Allakhiarova, Elvira; Hoyng, Carel B; Dröge, Katharina; Kirchhof, Bernd; Fauser, Sascha

2012-01-01

238

Compact Optical Module of Homodyne Detection  

NASA Astrophysics Data System (ADS)

Homodyne detection is a detection technique that significantly amplifies optical signals. It is useful for the readout of multilayer optical discs, where the signal level is quite low. The improvement of optical disc readout signal quality by homodyne detection has been demonstrated experimentally. However, homodyne detection requires a complicated optical system, which causes large-scale implementation and high cost, which prevents practical use of the technique in optical disc systems. In this report, we demonstrated compact implementation of homodyne detection. We proposed and assembled two types of optical module for homodyne detection. The sizes of the modules were 10×30 and 10×40 mm2, which were comparable to that of the current optical pickup. Jitter of the attenuated Blu-ray DiscTM recordable (BD-R) readout signals was improved from 15 to 7.8% by applying one of the modules.

Mikami, Hideharu; Kurokawa, Takahiro; Watanabe, Koichi

2012-08-01

239

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

240

Spontaneous disc degeneration in the baboon model: magnetic resonance imaging and histopathologic correlation.  

PubMed

Degenerative disc disease is a major source of disability in humans. The baboon model is an excellent natural disease model to study comparable human disease, because baboons are relatively large (adult males 20-26 kg, adult females 12-17 kg), long-lived (30-45 years), well defined, easy to use, and closely related to humans. Published investigations with plain radiographs of disc degeneration in baboons indicated vertebral anatomy and changes that were remarkably similar to those seen in humans, and it would be valuable to determine if magnetic resonance imaging (MRI) and histopathologic evaluation would be useful methods for studying the model, as MRI allows multi-planar visualization of tissues without the use of intravenous contrast and it is superior for evaluating disc hydration, annulus tears, and herniations. The thoracolumbar junctions from 47 randomly selected baboons, ranging in age from 2 weeks to 34 years, were evaluated with MRI and histopathology. Excellent correlation with MRI was observed for changes in disc desiccation, height, and age (P < 0.001). The pathologic analysis demonstrated P values of < 0.001 when comparing histopathology with age and MRI results. All severely degenerated discs seen by MRI were in baboons 14 years of age or older. PMID:11990242

Platenberg, R C; Hubbard, G B; Ehler, W J; Hixson, C J

2001-10-01

241

Rossby wave instability in astrophysical discs  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

242

Update on the pathophysiology of degenerative disc disease and new developments in treatment strategies  

PubMed Central

Degenerative disc disease (DDD) continues to be a prevalent condition that afflicts populations on a global scale. The economic impact and decreased quality of life primarily stem from back pain and neurological deficits associated with intervertebral disc degeneration. Although much effort has been invested into understanding the etiology of DDD and its relationship to the onset of back pain, this endeavor is a work in progress. The purpose of this review is to provide focused discussion on several areas in which recent advances have been made. Specifically, we have categorized these advances into early, middle, and late phases of age-related or degenerative changes in the disc and into promising minimally invasive treatments, which aim to restore mechanical and biological functions to the disc. PMID:24198557

Hsieh, Adam H; Yoon, S Tim

2010-01-01

243

Automated detection of kinks from blood vessels for optic cup segmentation in retinal images  

Microsoft Academic Search

The accurate localization of the optic cup in retinal images is important to assess the cup to disc ratio (CDR) for glaucoma screening and management. Glaucoma is physiologically assessed by the increased excavation of the optic cup within the optic nerve head, also known as the optic disc. The CDR is thus an important indicator of risk and severity of

D. W. K. Wong; J. Liu; J. H. Lim; H. Li; T. Y. Wong

2009-01-01

244

Inner dusty regions of protoplanetary discs - I. High-resolution temperature structure  

NASA Astrophysics Data System (ADS)

Our current understanding of the physical conditions in the inner regions of protoplanetary discs is being increasingly challenged by more detailed observational and theoretical explorations. The calculation of the dust temperature is one of the key features that we strive to understand and this is a necessary step in image and flux reconstruction. Here, we explore the coexistence of small (0.1-?m radius) and large (2-?m radius) dust grains, which can coexist at distances from the star where small grains would not survive without large grains shielding them from the direct starlight. Our study required a high-resolution radiative transfer calculation, which is capable of resolving the large temperature gradients and disc-surface curvatures caused by dust sublimation. This method of calculation was also capable of resolving the temperature inversion effect in large grains, where the maximum dust temperature is at a visual optical depth of ?V˜ 1.5. We also show disc images and spectra, with disentangled contributions from small and large grains. Large grains dominate the near-infrared flux, mainly because of the bright hot inner disc rim. Small grains populate almost the entire interior of the inner disc, but they appear at the disc's surface at distances 2.2 times larger than the closest distance of the large grains from the star. Nevertheless, small grains can contribute to the image surface brightness at smaller radii because they are visible below the optically thin surface defined by stellar heating. Our calculations demonstrate that the sublimation temperature does not provide a unique boundary condition for radiative transfer models of optically thick discs. The source of this problem is the temperature inversion effect, which allows the survival of optically thin configurations of large grains closer to the star than the inner radius of the optically thick disc. Future attempts to derive more realistic multigrain inner disc models will need the numerical resolution shown in our study, especially if the dust dynamics is considered where grains can travel through zones of local temperature maxima.

Vinkovi?, Dejan

2012-02-01

245

Stirring in massive, young debris discs from spatially resolved Herschel images  

NASA Astrophysics Data System (ADS)

A significant fraction of main-sequence stars are encircled by dusty debris discs, where the short-lived dust particles are replenished through collisions between planetesimals. Most destructive collisions occur when the orbits of smaller bodies are dynamically stirred up, either by the gravitational effect of locally formed Pluto-sized planetesimals (self-stirring scenario), or via secular perturbation caused by an inner giant planet (planetary stirring). The relative importance of these scenarios in debris systems is unknown. Here, we present new Herschel Space Observatory imagery of 11 discs selected from the most massive and extended known debris systems. All discs were found to be extended at far-infrared wavelengths, five of them being resolved for the first time. We evaluated the feasibility of the self-stirring scenario by comparing the measured disc sizes with the predictions of the model calculated for the ages of our targets. We concluded that the self-stirring explanation works for seven discs. However, in four cases, the predicted pace of outward propagation of the stirring front, assuming reasonable initial disc masses, was far too low to explain the radial extent of the cold dust. Therefore, for HD 9672, HD 16743, HD 21997, and HD 95086, another explanation is needed. We performed a similar analysis for ? Pic and HR 8799, reaching the same conclusion. We argue that planetary stirring is a promising possibility to explain the disc properties in these systems. In HR 8799 and HD 95086, we may already know the potential perturber, since their known outer giant planets could be responsible for the stirring process. Interestingly, the discs around HD 9672, HD 21997, and ? Pic are also unique in harbouring detectable amount of molecular CO gas. Our study demonstrates that among the largest and most massive debris discs self-stirring may not be the only active scenario, and potentially planetary stirring is responsible for destructive collisions and debris dust production in a number of systems.

Moór, A.; Kóspál, Á.; Ábrahám, P.; Apai, D.; Balog, Z.; Grady, C.; Henning, Th.; Juhász, A.; Kiss, Cs.; Krivov, A. V.; Pawellek, N.; Szabó, Gy. M.

2015-02-01

246

Stellar capture by an accretion disc  

E-print Network

Long-term evolution of a stellar orbit captured by a massive galactic center via successive interactions with an accretion disc has been examined. An analytical solution describing evolution of the stellar orbital parameters during the initial stage of the capture was found. Our results are applicable to thin Keplerian discs with an arbitrary radial distribution of density and rather general prescription for the star-disc interaction. Temporal evolution is given in the form of quadrature which can be carried out numerically.

D. Vokrouhlicky; V. Karas

1997-10-15

247

Close-packing of growing discs  

SciTech Connect

Spiral lattices are derived by allowing growing discs to aggregate under a close-packing rule. Both Fibonacci and Lucas numbers of visible spirals arise naturally, dependent only on the choice of growth centre. Both the rate of convergence towards an ideal spiral, and chirality, are determined by the initial placement of the first few discs (initial conditions). Thus the appearance of spiral packings is no more or less mysterious than the appearance of hexagonal packed arrays of equal discs.

Bursill, L.A.; Xudong, F. (Melbourne Univ., Parkville (Australia). School of Physics)

1988-12-01

248

Close-Packing of Growing Discs  

NASA Astrophysics Data System (ADS)

Spiral lattices are derived by allowing growing discs to aggregate under a close-packing rule. Both Fibonacci and Lucas numbers of visible spirals arise naturally, dependent only on the choice of growth centre. Both the rate of convergence towards an ideal spiral, and chirality, are determined by the initial placement of the first few discs (initial conditions). Thus the appearance of spiral packings is no more or less mysterious than the appearance of hexagonal packed arrays of equal discs.

Bursill, L. A.; Xudong, Fan

249

Turbulent drag reduction through oscillating discs  

NASA Astrophysics Data System (ADS)

The changes of a turbulent channel flow subjected to oscillations of wall flush-mounted rigid discs are studied by means of direct numerical simulations. The Reynolds number is $R_\\tau$=$180$, based on the friction velocity of the stationary-wall case and the half channel height. The primary effect of the wall forcing is the sustained reduction of wall-shear stress, which reaches a maximum of 20%. A parametric study on the disc diameter, maximum tip velocity, and oscillation period is presented, with the aim to identify the optimal parameters which guarantee maximum drag reduction and maximum net energy saving, computed by taking into account the power spent to actuate the discs. This may be positive and reaches 6%. The Rosenblat viscous pump flow is used to predict the power spent for disc motion in the turbulent channel flow and to estimate localized and transient regions over the disc surface subjected to the turbulent regenerative braking effect, for which the wall turbulence exerts work on the discs. The FIK identity is employed to show that the wall-friction reduction is due to two distinguished effects. One effect is linked to the direct shearing action of the near-wall oscillating disc boundary layer on the wall turbulence, which causes the attenuation of the turbulent Reynolds stresses. The other effect is due the additional disc-flow Reynolds stresses produced by the inter-disc structures. The contribution to drag reduction due to turbulent Reynolds stress attenuation depends on the penetration thickness of the disc-flow boundary layer, while the contribution due to the elongated structures scales linearly with a simple function of the maximum tip velocity and oscillation period for the largest disc diameter tested, a result suggested by the Rosenblat flow solution. A brief discussion on the future applicability of the oscillating-disc technique is also presented.

Wise, Daniel J.; Ricco, Pierre

2014-05-01

250

Disc repositioning: does it really work?  

PubMed

Although limited, there is evidence to support the assumption that temporomandibular joint (TMJ) articular disc repositioning indeed works; to date, there is no evidence that TMJ articular disc repositioning does not work. Despite the controversy among professionals in private practice and academia, TMJ articular disc repositioning is a procedure based on (still limited) evidence; the opposition is based solely on clinical preference and influenced by the ability to perform it or not. PMID:25483446

Gonçalves, João Roberto; Cassano, Daniel Serra; Rezende, Luciano; Wolford, Larry M

2015-02-01

251

Cobb Angle Progression in Adolescent Scoliosis Begins at the Intervertebral Disc  

PubMed Central

Study Design Longitudinal radiographic study of patients with progressive idiopathic scoliosis. Objective To determine the relative contributions of vertebral and disc wedging to the increase in Cobb angle during 3 phases of adolescent skeletal growth and maturation. Summary of Background Data Both disc wedging and vertebral body wedging are found in progressive scoliosis, but their relative contribution to curve progression over time is unknown. Which occurs first is important for understanding how scoliosis progresses and for developing methods to halt progression. Previous studies have not properly identified maturity and provide conflicting results. Methods Eighteen girls were followed through their adolescent growth spurt with serial spine and hand skeletal age radiographs. Each Cobb angle was divided into disc wedge angles and vertebral wedge angles. The corresponding hand radiographs provided a measure of maturity level, the Digital Skeletal Age (DSA). The disc versus bone contributions to the Cobb angle were then compared during 3 growth phases: prior to the growth spurt, during the growth spurt and after the growth spurt. Significance of relative changes was assessed with the Wilcoxon two-sided mean rank test. Results Prior to the growth spurt, there was no difference in relative contributions of the disc and the bone (3° vs 0°, p=0.38) to curve progression. During the growth spurt, the mean disc component progressed significantly more than that of the vertebrae (15° vs 0°, p=0.0002). This reversed following the growth spurt with the vertebral component progressing more than the disc (10° vs 0°, p=0.01). Conclusion Adolescent idiopathic scoliosis initially increases through disc wedging during the rapid growth spurt with progressive vertebral wedging occurring later. PMID:19940737

Will, Ryan E; Stokes, Ian A; Qiu, Xing; Walker, Matthew R.; Sanders, James O

2009-01-01

252

HD 98800: A most unusual debris disc  

E-print Network

The dynamics of planetesimals in the circumbinary debris disc of the quadruple star system HD 98800 are investigated. Evolving a spherical shell of test particles from a million years ago to the present day indicates that both coplanar and retrograde warped discs could exist, as well as a high inclination halo of material. Significant gaps are seen in the discs, as well as unexpected regions of stability due to the retrograde nature of the stellar orbits. Despite a viewing angle almost perpendicular to the direction of the warp of the planetesimal disc it is still intersected by the line of sight for eccentricities of the outer orbit of 0.5 or less.

P. E. Verrier; N. W. Evans

2008-07-31

253

On the evolution of the protolunar disc.  

PubMed

The structure and viscous evolution of a post-impact, protolunar disc is examined. The equations for a silicate disc in two-phase (vapour-liquid) equilibrium are employed to derive an analytical solution to vertical structure. Both a vertically mixed phase disc and a stratified disc, where a magma layer exists in the mid-plane surrounded by a vapour reservoir, are considered. The former largely reproduces the low gas mass fraction, x?1, profiles of the disc described in earlier literature that proposed that the disc would hover on the brink of gravitational instability. In the latter, the vapour layer has x?1 and is generally gravitationally stable, while the magma layer is vigorously unstable. The viscous evolution of the stratified model is then explored. Initially, the disc quickly settles to a quasi-steady state with a vapour reservoir containing the majority of the disc mass. The magma layer viscously spreads on a time scale of approximately 3-4 years, during which vapour continuously condenses into droplets that settle to the mid-plane, maintaining the magma surface density in spite of disc spreading. Material flowing inwards is accreted by the Earth; material flowing outwards past the Roche boundary can become incorporated into accreting moonlets. This evolution persists until the vapour reservoir is depleted in approximately 50-100 years, depending on its initial mass. PMID:25114314

Ward, William R

2014-09-13

254

Association of macular pigment optical density with risk factors for wet age-related macular degeneration in the Indian population  

PubMed Central

Purpose To investigate macular pigment optical density (MPOD) in patients with and without wet age-related macular degeneration (AMD) and to elucidate the association between MPOD and the risk factors for AMD in an Indian population. Methods Thirty-three subjects with wet AMD and 29 controls above 50 years old underwent MPOD measurement with the ‘Macular Densitometer'. The subjects were also tested for their smoking history, lifetime ultraviolet (UV) exposure, dietary intake of carotenoids, and body mass index (BMI). Results Smokers had a higher risk for AMD than the non-smokers (P=0.032) and a lower MPOD level than non-smokers (mean (95% CI)) (0.16 (0.09–0.23) vs 0.28 (0.22–0.34), adjusted P=0.026). Subjects with lowest UV exposure had higher MPOD than those with the highest (0.46 (0.38–0.54) vs 0.17 (0.01–0.33), P=0.01). MPOD was significantly lower among those with the lowest quartile of dietary intake of carotenoids (0.14 (0.08–0.21) vs 0.25 (0.13–0.36), P=0.012). Smoking, obesity, and UV index showed an inverse association with the MPOD. Low MPOD, smoking, and UV exposure had 5.11 (1.73–15.08), 3.54 (1.08–11.57), and 5.24 (1.06–25.96) odds for AMD, respectively, whereas higher dietary intake of carotenoids showed a protective effect for AMD. Conclusion We found an inverse association between wet AMD and MPOD. Among the established risk factors of wet AMD, we found an inverse association of smoking, UV index, and obesity with MPOD, whereas a positive association was found between dietary intake of carotenoids and MPOD. PMID:22562185

Raman, R; Biswas, S; Gupta, A; Kulothungan, V; Sharma, T

2012-01-01

255

Optical Coherence Tomography in Glaucoma  

NASA Astrophysics Data System (ADS)

Retinal nerve fiber layer (RNFL) thinning and optic nerve head cupping are key diagnostic features of glaucomatous optic neuropathy. The higher resolution of the recently introduced SD-OCT offers enhanced visualization and improved segmentation of the retinal layers, providing a higher accuracy in identification of subtle changes of the optic disc and RNFL thinning associated with glaucoma.

Berisha, Fatmire; Hoffmann, Esther M.; Pfeiffer, Norbert

256

21 cm absorption by compact hydrogen discs around black holes in radio-loud nuclei of galaxies  

SciTech Connect

The clumpy maser discs observed in some galactic nuclei mark the outskirts of the accretion disc that fuels the central black hole and provide a potential site of nuclear star formation. Unfortunately, most of the gas in maser discs is currently not being probed; large maser gains favor paths that are characterized by a small velocity gradient and require rare edge-on orientations of the disc. Here we propose a method for mapping the atomic hydrogen distribution in nuclear discs through its 21 cm absorption against the radio continuum glow around the central black hole. In NGC 4258, the 21 cm optical depth may approach unity for high angular resolution (VLBI) imaging of coherent clumps which are dominated by thermal broadening and have the column density inferred from x-ray absorption data, {approx}10{sup 23} cm{sup -2}. Spreading the 21 cm absorption over the full rotation velocity width of the material in front of the narrow radio jets gives a mean optical depth of {approx}0.1. Spectroscopic searches for the 21 cm absorption feature in other galaxies can be used to identify the large population of inclined gaseous discs which are not masing in our direction. Follow-up imaging of 21 cm silhouettes of accelerating clumps within these discs can in turn be used to measure cosmological distances.

Loeb, Abraham, E-mail: aloeb@cfa.harvard.edu [Astronomy Department, Harvard University, 60 Garden Street, Cambridge, MA 02138 (United States)] [Astronomy Department, Harvard University, 60 Garden Street, Cambridge, MA 02138 (United States)

2008-05-15

257

21 cm absorption by compact hydrogen discs around black holes in radio-loud nuclei of galaxies  

NASA Astrophysics Data System (ADS)

The clumpy maser discs observed in some galactic nuclei mark the outskirts of the accretion disc that fuels the central black hole and provide a potential site of nuclear star formation. Unfortunately, most of the gas in maser discs is currently not being probed; large maser gains favor paths that are characterized by a small velocity gradient and require rare edge-on orientations of the disc. Here we propose a method for mapping the atomic hydrogen distribution in nuclear discs through its 21 cm absorption against the radio continuum glow around the central black hole. In NGC 4258, the 21 cm optical depth may approach unity for high angular resolution (VLBI) imaging of coherent clumps which are dominated by thermal broadening and have the column density inferred from x-ray absorption data, ~1023 cm-2. Spreading the 21 cm absorption over the full rotation velocity width of the material in front of the narrow radio jets gives a mean optical depth of ~0.1. Spectroscopic searches for the 21 cm absorption feature in other galaxies can be used to identify the large population of inclined gaseous discs which are not masing in our direction. Follow-up imaging of 21 cm silhouettes of accelerating clumps within these discs can in turn be used to measure cosmological distances.

Loeb, Abraham

2008-05-01

258

The influence of fallback discs on the spectral and timing properties of neutron stars  

NASA Astrophysics Data System (ADS)

Fallback discs around neutron stars (NSs) are believed to be an expected outcome of supernova explosions. Here we investigate the consequences of such a common outcome for the timing and spectral properties of the associated NS population, using Monte Carlo population synthesis models. We find that the long-term torque exerted by the fallback disc can substantially influence the late-time period distribution, but with quantitative differences which depend on whether the initial spin distribution is dominated by slow or fast pulsars. For the latter, a single-peaked initial spin distribution becomes bimodal at later times. Timing ages tend to underestimate the real age of older pulsars, and overestimate the age of younger ones. Braking indices cluster in the range 1.5 ?n? 3 for slow-born pulsars, and -0.5 ?n? 5 for fast-born pulsars, with the younger objects found predominantly below n? 3. Large values of n, while not common, are possible, and associated with torque transitions in the NS+disc system. The 0.1-10 keV thermal luminosity of the NS+disc system is found to be generally dominated by the disc emission at early times, ? yr, but this declines faster than the thermal surface emission of the NS. Depending on the initial parameters, there can be occasional periods in which some NSs switch from the propeller to the accretion phase, increasing their luminosity up to the Eddington limit for ˜103-104 years.

Yan, T.; Perna, R.; Soria, R.

2012-07-01

259

Be star disc characteristics near the central object  

NASA Astrophysics Data System (ADS)

Context: A recent analysis of visual Fe ii emission lines of 17 classic Be stars using the self-absorption curve (SAC) method revealed that these lines are optically thick and that they form in circumstellar disc (CD) regions within two stellar radii from the central star on average. Aims: The aim of this paper is to study the physical characteristics of CD regions situated close to the central star. Methods: We used the Fe ii emission line optical depths derived for a sample of the above mentioned classic Be stars that are seen either nearly pole-on or equator-on. The disc properties sought are then inferred by reproducing the average pole-on and equator-on Fe ii line optical depths using simple CD models with different density and temperature distributions. Results: We found that the CD regions near the star, which account for the average Fe ii line opacities obtained with the SAC method, have semi-height scales perpendicular to the equatorial plane h?0.5Ro and particle density distribution laws N(R)=N_o(R_o/R)n with n?1 at R?3Ro (Ro is the stellar radius; No is the particle density at R=R_o). Multi-scattering Monte Carlo simulations show that CD with particle density distributions N˜ R-n, where n depends on the distance R and n˜0.5 near the star, might account for the near-UV spectroplorarimetry of Be stars. CD with enhanced scale heights could explain the [ H?, E(J-L)] correlation as they may produce about the same H? line emission, but larger IR flux excesses than thin discs. The enlarged CD scale heights do not contradict the existing interferometric measurements and should enable us to treat more consistently Balmer line emission formation in Be stars.

Zorec, J.; Arias, M. L.; Cidale, L.; Ringuelet, A. E.

2007-07-01

260

Herschel observations of the debris disc around HIP 92043  

NASA Astrophysics Data System (ADS)

Context. Typical debris discs are composed of particles ranging from several micron sized dust grains to km sized asteroidal bodies, and their infrared emission peaks at wavelengths 60-100 ?m. Recent Herschel DUNES observations have identified several debris discs around nearby Sun-like stars (F, G and K spectral type) with significant excess emission only at 160 ?m. Aims: We observed HIP 92043 (110 Her, HD 173667) at far-infrared and sub-millimetre wavelengths with Herschel PACS and SPIRE. Identification of the presence of excess emission from HIP 92043 and the origin and physical properties of any excess was undertaken through analysis of its spectral energy distribution (SED) and the PACS images. Methods: The PACS and SPIRE images were produced using the HIPE photProject map maker routine. Fluxes were measured using aperture photometry. A stellar photosphere model was scaled to optical and near infrared photometry and subtracted from the far-infared and sub-mm fluxes to determine the presence of excess emission. Source radial profiles were fitted using a 2D Gaussian and compared to a PSF model based on Herschel observations of ? Boo to check for extended emission. Results: Clear excess emission from HIP 92043 was observed at 70 and 100 ?m. Marginal excess was observed at 160 and 250 ?m. Analysis of the images reveals that the source is extended at 160 ?m. A fit to the source SED is inconsistent with a photosphere and single temperature black body. Conclusions: The excess emission from HIP 92043 is consistent with the presence of an unresolved circumstellar debris disc at 70 and 100 ?m, with low probability of background contamination. The extended 160 ?m emission may be interpreted as an additional cold component to the debris disc or as the result of background contamination along the line of sight. The nature of the 160 ?m excess cannot be determined absolutely from the available data, but we favour a debris disc interpretation, drawing parallels with previously identified cold disc sources in the DUNES sample. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

Marshall, J. P.; Krivov, A. V.; del Burgo, C.; Eiroa, C.; Mora, A.; Montesinos, B.; Ertel, S.; Bryden, G.; Liseau, R.; Augereau, J.-C.; Bayo, A.; Danchi, W.; Löhne, T.; Maldonado, J.; Pilbratt, G. L.; Stapelfeldt, K.; Thebault, P.; White, G. J.; Wolf, S.

2013-09-01

261

Lifestyle factors and lumbar disc disease: results of a German multi-center case-control study (EPILIFT)  

PubMed Central

Introduction In the large-scale case-control study EPILIFT, we investigated the dose-response relationship between lifestyle factors (weight, smoking amount, cumulative duration of different sports activities) and lumbar disc disease. Methods In four German study regions (Frankfurt am Main, Freiburg, Halle/Saale, Regensburg), 564 male and female patients with lumbar disc herniation and 351 patients with lumbar disc narrowing (chondrosis) aged 25 to 70 years were prospectively recruited. From the regional population registers, 901 population control subjects were randomly selected. In a structured personal interview, we enquired as to body weight at different ages, body height, cumulative smoking amount and cumulative duration of different sports activities. Confounders were selected according to biological plausibility and to the change-in-estimate criterion. Adjusted, gender-stratified odds ratios with 95% confidence intervals were calculated using unconditional logistic regression analysis. Results The results of this case-control study reveal a positive association between weight and lumbar disc herniation as well as lumbar disc narrowing among men and women. A medium amount of pack-years was associated with lumbar disc herniation and narrowing in men and women. A non-significantly lowered risk of lumbar disc disease was found in men with high levels of cumulative body building and strength training. Conclusions According to our multi-center case-control study, body weight might be related to lumbar disc herniation as well as to lumbar disc narrowing. Further research should clarify the potential protective role of body building or strength training on lumbar disc disease. PMID:20955546

2010-01-01

262

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

263

Retinal Images: Optic Disk Localization and Detection  

Microsoft Academic Search

\\u000a Automated localization and detection of the optic disc (OD) is an essential step in the analysis of digital diabetic retinopathy\\u000a systems. Accurate localization and detection of optic disc boundary is very useful in proliferative diabetic retinopathy where\\u000a fragile vessels develop in the retina. In this paper, we propose an automated system for optic disk localization and detection.\\u000a Our method localizes

M. Usman Akram; Aftab Khan; Khalid Iqbal; Wasi Haider Butt

2010-01-01

264

New disc-based technologies for diagnostic and research applications.  

PubMed

The role of genotypic analysis in disease diagnostics and drug response assessment is continually expanding. New genomic discoveries combined with new, novel technologies may provide a greater range of testing capabilities in the near future. We describe the application of nanotechnology, in which DNA microarrays have been placed in a microchannel environment that can be read and analyzed in an optical (CD/DVD) disc drive system. The potential exists to combine molecular and immunological applications together into a rapid, low-cost, high-capacity screening platform. The relevance of this technology is discussed in respect to infectious agent detection, pharmacogenomics, neurogenomics and genetic variations associated with neurologic diseases. PMID:12454524

Barathur, Raj; Bookout, Jack; Sreevatsan, Srinand; Gordon, John; Werner, Martina; Thor, Gautam; Worthington, Mark

2002-12-01

265

Shearing waves and the MRI dynamo in stratified accretion discs  

E-print Network

distances the gas is optically thin, allowing observations to give estimates of the total disc mass (Beckwith et al.[13] using telescopes MPIfR and IRAM, or more recently Andrews and Williams[2] using the SMA: they extrapolate to an average temperature... in the final stages of accretion; the Herschel Space observatory covered a similar range of wavelengths until it was shut down in April of this year. We refer to the five part analysis of the SST Infrared Survey by Kessler-Silacci et al.[62], which detected...

Donnelly, Cara

2014-01-07

266

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

267

Measuring the wear of diamond discs  

Microsoft Academic Search

Before grinding, the face of the pneumatic instrument's measuring nozzle 1 is set opposite the working surface 2 of the diamond disc 3 and the face of the nozzle 6 opposite the surface 5, which forms part of the disc's body and is located near its working surface and, therefore, is displaced owing to thermal expansion together with the latter

E. S. Zemlyanskii

1974-01-01

268

[Spontaneous regression of symptomatic lumbar disc herniation].  

PubMed

Lumbar disc herniation is very common, sometimes leading to disability of the patient, and in a significant number of cases can only be solved with surgery. This paper reports a case with a large symptomatic disc herniation, which suffered spontaneous regression, and no surgery was necessary. The case is documented on serial MRI, consistent with the clinical improvement of the patient. PMID:22472931

Ribeiro, R Pimenta; Matos, R Milheiro; Vieira, A; Costa, J M; Proença, R; Pinto, R

2011-01-01

269

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

270

Copyright 1996, American Institute of Aeronautics and Astronautics, Inc. AIAA Meeting Papers on Disc, June 1996  

E-print Network

Copyright ©1996, American Institute of Aeronautics and Astronautics, Inc. AIAA Meeting Papers on Disc, June 1996 A9636675, AIAA Paper 96-2221 Status of the development and implementation of optical, Goettingen, Germany J. Jourdan DLR, Inst. fuer Stroemungsmechanik, Goettingen, Germany AIAA, Advanced

Peinke, Joachim

271

Exploring the parameter space of disc shaped silver nanoparticles for thin film silicon photovoltaics  

E-print Network

We numerically simulate, using finite-difference time-domain, the optical properties of silver nano discs deposited on the front surface of silicon solar cells. We explore the effect of each of the parameters of such a system, in order to draw some general design rules for the subsequent fabrication of such structures.

Figeys, Bruno

2011-01-01

272

Hydrodynamic instability in warped astrophysical discs  

E-print Network

Warped astrophysical discs are usually treated as laminar viscous flows, which have anomalous properties when the disc is nearly Keplerian and the viscosity is small: fast horizontal shearing motions and large torques are generated, which cause the warp to evolve rapidly, in some cases at a rate that is inversely proportional to the viscosity. However, these flows are often subject to a linear hydrodynamic instability, which may produce small-scale turbulence and modify the large-scale dynamics of the disc. We use a warped shearing sheet to compute the oscillatory laminar flows in a warped disc and to analyse their linear stability by the Floquet method. We find widespread hydrodynamic instability deriving from the parametric resonance of inertial waves. Even very small, unobservable warps in nearly Keplerian discs of low viscosity can be expected to generate hydrodynamic turbulence, or at least wave activity, by this mechanism.

Ogilvie, Gordon I

2013-01-01

273

Complications of Bryan cervical disc replacement.  

PubMed

The primary goals of cervical disc replacement are to avoid fusion in the affected segment, maintain the mobility and function of the involved cervical segments, allow patients to quickly return to routine activities and reduce or eliminate adjacent-segment disease. A large number of patients have already undergone, and more and more patients will in the future undergo, cervical disc replacement. The cervical device which best preserves movement, and has therefore been the device of choice, has been the Bryan cervical disc. Although a safe surgical technique has been demonstrated and favorable results of using the Bryan disc reported, some complications have also accompanied this arthroplasty. Complications of Bryan cervical disc replacement include those related to the operative approach and decompression process, loosening and failure of the device, postoperative kyphosis, heterotopic ossification, and loss of movement due to spontaneous fusion. In order to avoid these complications, strict patient selection criteria and a meticulous knowledge of anatomy are necessary. PMID:22009921

Cao, Jun-ming; Zhang, Ying-ze; Shen, Yong; Ding, Wen-yuan

2010-05-01

274

Stochastic Wobble of Accretion Discs and Jets from Turbulent Rocket Torques  

E-print Network

Models of accretion discs and their associated outflows often incorporate assumptions of axisymmetry and symmetry across the disc plane. However, for turbulent discs these symmetries only apply to averaged quantities and do not apply locally. The local asymmetries can induce local imbalances in outflow power across the disc mid-plane, which can in turn induce local tilting torques. Here we calculate the effect of the resulting stochastic torques on disc annuli that are a consequence of standard mean field accretion disc models. The torques induce a random walk of the vector perpendicular to the plane of each averaged annulus. This random walk is characterized by a radially dependent diffusion coefficient which we calculate for small angle tilt. We use the coefficient to calculate a radially dependent time scale for annular tilt and associated jet wobble. The wobble time depends on the square of the wander angle so the age of a given system determines the maximum wobble angle. We apply this to examples of blazars, young stellar objects and binary engines of pre-planetary nebulae and microquasars. It is noteworthy that for an averaging time $t_w\\sim 3$ days, we estimate a wobble angle for jets in SS433 of $\\theta\\sim 0.8$ degrees, not inconsistent with observational data. In general the non-periodic nature of the stochastic wobble could distinguish it from faster periodic jet precession.

Ryan Pettibone; Eric G. Blackman

2009-04-03

275

Outcome of symptomatic upper lumbar disc herniation.  

PubMed

"Upper" lumbar disc herniations (LDH) are different from the "lower" and possess increased chance of neural compromise and cauda equina syndrome that necessitates operative management despite of contradictory surgical outcome. We underwent the study to assess the clinical and functional outcome of symptomatic upper LDH surgery from July 2003 to June 2012 in BSMMU, Dhaka, Bangladesh. The records of 123 patients (age range, 30-69 years), 56 men and 67 women (mean 52 years) having upper lumbar discectomy were reviewed. The surgical time, intra-operative blood loss, self evaluated back pain and thigh and/or groin pain status [using Visual Analogue Score (VAS)] and the disability status [using Oswestry disability (ODI) questionnaire] was analyzed. Radiological stability (using Posner's criteria), functional outcome [using Japanese Orthopaedic Association (JOA) Score] and overall outcome (using MacNab`s criteria), was calculated. Chi-squared test and z-test using SPSS revealed mean operative time and mean blood loss had no significant (p>0.05) difference. Pain, sensory, motor and reflex status as well as VAS, ODI and all the components of JOA questionnaire had significant (p<0.05) improvement. In spite of intra-operative complications in 20.32% cases, overall satisfactory outcome was achieved in 83.74% cases. The postoperative complications (08.13%) could be managed conservatively. However, carefully decided surgical alternatives resulted in satisfactory clinical and functional outcome in upper LDH surgery. PMID:25481595

Awwal, M A; Ahsan, M K; Sakeb, N

2014-10-01

276

Stochastic angular momentum slews and flips and their effect on discs in galaxy formation models  

NASA Astrophysics Data System (ADS)

The angular momentum of galactic discs in semi-analytic models of galaxy formation is usually updated in time as material is accreted to the disc by adopting a constant dimensionless spin parameter and little attention is paid to the effects of accretion with misaligned angular momenta. These effects are the subject of this paper, where we adopt a Monte Carlo simulation for the changes in the direction of the angular momentum of a galaxy disc as it accretes matter based on accurate measurements from dark-matter haloes in the Millennium II simulation. In our semi-analytic model implementation, the flips seen in the dark-matter haloes are assumed to be the same for the cold baryons; however, we also assume that in the latter the flip also entails a difficulty for the disc to increase its angular momentum which causes the disc to become smaller relative to a no-flip case. This makes star formation to occur faster, especially in low-mass galaxies at all redshifts allowing galaxies to reach higher stellar masses faster. We adopt a new condition for the triggering of starbursts during mergers. As these produce the largest flips it is natural to adopt the disc instability criterion to evaluate the triggering of bursts in mergers instead of one based on mass ratios as in the original model. The new implementation reduces the average lifetimes of discs by a factor of ˜2, while still allowing old ages for the present-day discs of large spiral galaxies. It also provides a faster decline of star formation in massive galaxies and a better fit to the bright end of the luminosity function at z = 0.

Padilla, Nelson D.; Salazar-Albornoz, Salvador; Contreras, Sergio; Cora, Sofía A.; Ruiz, Andrés N.

2014-09-01

277

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

278

X-ray variability of SS 433: effects of the supercritical accretion disc  

NASA Astrophysics Data System (ADS)

We study a stochastic variability of SS 433 in the 10-4-5 × 10-2 Hz frequency range based on RXTE data, and on simultaneous observations with RXTE and optical telescopes. We find that the cross-correlation functions and power spectra depend drastically on the precession phase of the supercritical accretion disc. When the wind funnel of the disc is maximally open to the observer, a flat part emerges in the power spectrum; a break is observed at the frequency 1.7 × 10-3 Hz, with a power-law index ? ? 1.67 at higher frequencies. The soft emission forming mostly in the jets lags behind the hard and optical emission. When the observer does not see the funnel and jets (the `edge-on' disc), the power spectrum is described by a single power-law with ? ? 1.34 and no correlations between X-ray ranges are detected. We investigated two mechanisms to explain the observed variability at the open disc phase: (1) reflection of radiation at the funnel wall (X-rays and optical) and (2) the gas cooling in the jets (X-rays only). The X-ray variability is determined by the contribution of both mechanisms; however, the contribution of the jets is much higher. We found that the funnel size is (2-2.5) × 1012 cm, and the opening angle is ?f ˜ 50°. X-ray jets may consist of three fractions with different densities: 8 × 1013, 3 × 1013 and 5 × 1011 cm-3, with most of the jet's mass falling within the latter fraction. We suppose that revealed flat part in the power spectrum may be related to an abrupt change in the disc structure and viscous time-scale at the spherization radius, because the accretion disc becomes thick at this radius, h/r ˜ 1. The extent of the flat spectrum depends on the variation of viscosity at the spherization radius.

Atapin, Kirill; Fabrika, Sergei; Medvedev, Aleksei; Vinokurov, Alexander

2015-01-01

279

Autologous adipose stem cells and polylactide discs in the replacement of the rabbit temporomandibular joint disc.  

PubMed

The temporomandibular joint (TMJ) disc lacks functional replacement after discectomy. We investigated tissue-engineered bilayer polylactide (PLA) discs and autologous adipose stem cells (ASCs) as a potential replacement for the TMJ disc. These ASC discs were pre-cultured either in control or in differentiation medium, including transforming growth factor (TGF)-?1 for one week. Prior to implantation, expression of fibrocartilaginous genes was measured by qRT-PCR. The control and differentiated ASC discs were implanted, respectively, in the right and left TMJs of rabbits for six (n = 5) and 12 months (n = 5). Thereafter, the excised TMJ areas were examined with cone beam computed tomography (CBCT) and histology. No signs of infection, inflammation or foreign body reactions were detected at histology, whereas chronic arthrosis and considerable condylar hypertrophy were observed in all operated joints at CBCT. The left condyle treated with the differentiated ASC discs appeared consistently smoother and more sclerotic than the right condyle. The ASC disc replacement resulted in dislocation and morphological changes in the rabbit TMJ. The ASC discs pre-treated with TGF-?1 enhanced the condylar integrity. While adverse tissue reactions were not shown, the authors suggest that with improved attachment and design, the PLA disc and biomaterial itself would hold potential for TMJ disc replacement. PMID:23720535

Ahtiainen, Katja; Mauno, Jari; Ellä, Ville; Hagström, Jaana; Lindqvist, Christian; Miettinen, Susanna; Ylikomi, Timo; Kellomäki, Minna; Seppänen, Riitta

2013-08-01

280

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

281

Outer edges of debris discs: how sharp is sharp?  

E-print Network

Ring-like features have been observed in several debris discs. Outside the main ring, while some systems exhibit smooth surface brightness profiles (SB) that fall off roughly as r**-3.5, others display large luminosity drops at the ring's outer edge and steeper radial SB profiles. We seek to understand this diversity of outer edge profiles under the ``natural'' collisional evolution of the system, without invoking external agents such as planets or gas. We use a statistical code to follow the evolution of a collisional population, ranging from dust grains (submitted to radiation pressure) to planetesimals and initially confined within a belt (the 'birth ring'). The system typically evolves toward a "standard" steady state, with no sharp edge and SB \\propto r**-3.5 outside the birth ring. Deviations from this standard profile, in the form of a sharp outer edge and a steeper fall-off, occur only when two parameters take their extreme values: 1) When the birth ring is so massive that it becomes radially optically thick for the smallest grains. However, the required disc mass is here probably too high to be realistic. 2) When the dynamical excitation of the dust-producing planetesimals is so low ( <0.01) that the smallest grains, which otherwise dominate the total optical depth, are preferentially depleted. This low-excitation case, although possibly not generic, cannot be ruled out by observations. Our "standard" profile provides a satisfactory explanation for a large group of debris discs with outer edges and SB falling as r**-3.5. Systems with sharper outer edges, barring other confining agents, could still be explained by ``natural'' collisional evolution if their dynamical excitation is very low. We show that such a dynamically-cold case provides a satisfactory fit for HR4796A

Philippe Thebault; Yanqin Wu

2008-02-04

282

Effect of repetitive laser pulses on the electrical conductivity of intervertebral disc tissue  

SciTech Connect

The thermomechanical effect of 1.56-{mu}m fibre laser pulses on intervertebral disc cartilage has been studied using ac conductivity measurements with coaxial electrodes integrated with an optical fibre for laser radiation delivery to the tissue. The observed time dependences of tissue conductivity can be interpreted in terms of hydraulic effects and thermomechanical changes in tissue structure. The laserinduced changes in the electrical parameters of the tissue are shown to correlate with the structural changes, which were visualised using shadowgraph imaging. Local ac conductivity measurements in the bulk of tissue can be used to develop a diagnostic/monitoring system for laser regeneration of intervertebral discs. (laser biology and medicine)

Omel'chenko, A I; Sobol', E N [Institute of Laser and Information Technologies, Russian Academy of Sciences, Troitsk, Moscow Region (Russian Federation)

2009-03-31

283

Optic disk excavation in nonarteritic anterior ischemic optic neuropathy.  

PubMed

Most ischemic optic neuropathies are attributed to interference of blood flow originating within the posterior ciliary circulation. In patients with the most common type of ischemic optic neuropathy, nonarteritic anterior ischemic optic neuropathy (NAION), the microvascular ischemia predominantly affects the intraocular portion of the optic nerve. NAION most commonly occurs in eyes with small, "crowded" optic disks and usually does not result in optic disk excavation. We report a patient who presented with NAION and subsequently developed optic disc excavation typical of glaucomatous optic neuropathy. PMID:20436358

Punjabi, Omar S; Tanna, Angelo P; Rosenberg, Michael A

2011-02-01

284

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. PMID:23550053

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

2012-01-01

285

Nanostructures produced by co-sputtering to study the optical properties of artistic middle-age nano-cermets: The lustres  

NASA Astrophysics Data System (ADS)

Nano-structures are not an invention of the 20th century. In Middle Age already, craftsmen were able to produce multi-layer structures of nano-particles at the surface of potteries creating lustres, this means potteries with shining effects. In order to study the optical properties of these objects and because, as a part of our patrimony, they cannot be destroyed, we decided to reproduce the structures observed by co-sputtering. Developing a model, we were able to predict the reflection spectrum of the created samples with a good accuracy, validating it. However, this work is a first experimental step and improvements are needed from both theoretical and experimental sides in order to understand fully the optical properties of the lustres.

Reillon, Vincent; Berthier, Serge; Chénot, Stéphane

2007-05-01

286

Magnetic Turbulence and Thermodynamics in the Inner Region of Protoplanetary Discs  

E-print Network

Using radiation magnetohydrodynamics simulations with realistic opacities and equation of state, and zero net magnetic flux, we have explored thermodynamics in the inner part of protoplanetary discs where magnetic turbulence is expected. The thermal equilibrium curve consists of the upper, lower, and middle branches. The upper (lower) branch corresponds to hot (cool) and optically very (moderately) thick discs, respectively, while the middle branch is characterized by convective energy transport near the midplane. Convection is also the major energy transport process near the low surface density end of the upper branch. There, convective motion is fast with Mach numbers reaching $\\gtrsim 0.01$, and enhances both magnetic turbulence and cooling, raising the ratio of vertically-integrated shear stress to vertically-integrated pressure by a factor of several. This convectively enhanced ratio seems a robust feature in accretion discs having an ionization transition. We have also examined causes of the S-shaped th...

Hirose, Shigenobu

2015-01-01

287

Appearance of an accretion disc perturbed by fractional Brownian Motion density  

NASA Astrophysics Data System (ADS)

This paper aims to investigate/map the effects that perturbations applied to an accretion disc might produce on the registered light curves (LCs). The case of accretion discs around supermassive active black holes (AGNs) is studied with the goal to explain some of the statistical properties of the observed intraday variability (IDV). The region producing optical IDV is perturbed by allowing it to develop a mass density of a fractional Brownian Motion-like type. The LCs and spectral slopes are calculated and compared to observational data for different Hurst parameters. The spectral slopes of the simulated LCs vary in the range (0.4, 2.5). The agreement with observational data shows that a magnetized disc subjected to stochastic perturbations can produce some of the features observed in the LCs.

Mocanu, G.; Magyar, N.; Pardi, A.; Marcu, A.

2014-04-01

288

The effects of tidally induced disc structure on white dwarf accretion in intermediate polars  

E-print Network

We investigate the effects of tidally induced asymmetric disc structure on accretion onto the white dwarf in intermediate polars. Using numerical simulation, we show that it is possible for tidally induced spiral waves to propagate sufficiently far into the disc of an intermediate polar that accretion onto the central white dwarf could be modulated as a result. We suggest that accretion from the resulting asymmetric inner disc may contribute to the observed X-ray and optical periodicities in the light curves of these systems. In contrast to the stream-fed accretion model for these periodicities, the tidal picture predicts that modulation can exist even for systems with weaker magnetic fields where the magnetospheric radius is smaller than the radius of periastron of the mass transfer stream. We also predict that additional periodic components should exist in the emission from low mass ratio intermediate polars displaying superhumps.

J. R. Murray; P. J. Armitage; L. Ferrario; D. T Wickramasinghe

1998-09-10

289

Treatment of lumbar disc herniation by percutaneous laser disc decompression (PLDD) and modified PLDD  

NASA Astrophysics Data System (ADS)

Objective: To study the micro-invasive operative method and to compare the effect of treatment of PLDD and modified PLDD for Lumbar Disc Herniation. Method: Vaporized part of the nucleus pulposus in single or multiple point after acupuncture into lumbar disc, to reach the purpose of the decompression of the lumbar disc. Result: Among the 19 cases of the regular PLDD group, the excellent and good rate was 63.2%, and among the 40 cases of the modified PLDD group, the excellent and good rate was 82.5%. Conclusion: The modified PLDD has good effect on the treatment for lumbar disc herniation.

Chi, Xiao fei; Li, Hong zhi; Wu, Ru zhou; Sui, Yun xian

2005-07-01

290

Spinal Neurofibroma Masquerading as a Herniated Disc  

PubMed Central

We present the only case in English medical literature of a spinal neurofibroma misdiagnosed as a herniated disc using magnetic resonance imaging (MRI). This case presented with typical symptoms and radiological findings of a herniated disc. Intraoperatively, an abnormality was noted at the S1 nerve root sleeve. Further exploration revealed a spinal neurofibroma which was completely resected, resulting in an improvement in the patient’s symptoms. Currently, there is heavy reliance on MRI as a highly sensitive and specific tool used in the diagnosis of herniated lumbar discs. Although there have been occasional reports of misdiagnoses using MRI, there are no reported cases of a spinal neurofibroma being misdiagnosed as a herniated lumbar disc. Despite great advances in radiological diagnostic imaging, surgical surprises do still occur. Ultimately, instinct is still essential in intraoperative surgical decisions. PMID:23275853

Lamki, Tariq; Ammirati, Mario

2012-01-01

291

Only marginal alignment of disc galaxies  

E-print Network

Testing theories of angular-momentum acquisition of rotationally supported disc galaxies is the key to understand the formation of this type of galaxies. The tidal-torque theory tries to explain this acquisition process in a cosmological framework and predicts positive autocorrelations of angular-momentum orientation and spiral-arm handedness on distances of 1Mpc/h. This disc alignment can also cause systematic effects in weak-lensing measurements. Previous observations claimed discovering such correlations but did not account for errors in redshift, ellipticity and morphological classifications. We explain how to rigorously propagate all important errors. Analysing disc galaxies in the SDSS database, we find that positive autocorrelations of spiral-arm handedness and angular-momentum orientations on distances of 1Mpc/h are plausible but not statistically significant. This result agrees with a simple hypothesis test in the Local Group, where we find no evidence for disc alignment. Moreover, we demonstrate tha...

Andrae, Rene

2011-01-01

292

Stellar Wind Erosion of Protoplanetary Discs  

E-print Network

An analytic model is developed for the erosion of protoplanetary gas discs by high velocity magnetized stellar winds. The winds are centrifugally driven from the surface of rapidly rotating, strongly magnetized young stars. The presence of the magnetic field in the wind leads to Reynolds numbers sufficiently large to cause a strongly turbulent wind/disk boundary layer which entrains and carries away the disc gas. The model uses the conservation of mass and momentum in the turbulent boundary layer. The time-scale for significant erosion depends on the disc accretion speed, accretion rate and on the wind mass loss rate. The time-scale is estimated to be ~2E6 yr. The stellar wind erosion may act in conjunction with photo-evaporation of the discs.

Schnepf, Neesha R; Romanova, Marina

2014-01-01

293

The Value of Measurement of Macular Carotenoid Pigment Optical Densities and Distributions in Age-Related Macular Degeneration and Other Retinal Disorders  

PubMed Central

There is increasing recognition that the optical and antioxidant properties of the xanthophyll carotenoids lutein and zeaxanthin play an important role in maintaining the health and function of the human macula. In this review article, we assess the value of non-invasive quantification of macular pigment levels and distributions to identify individuals potentially at risk for visual disability or catastrophic vision loss from age-related macular degeneration, and we consider the strengths and weaknesses of the diverse measurement methods currently available. PMID:19854211

Bernstein, Paul S.; Delori, François C.; Richer, Stuart; van Kuijk, Frederik J. M.; Wenzel, Adam J.

2009-01-01

294

Kinematic structures in galactic disc simulations  

NASA Astrophysics Data System (ADS)

N-body and test particle simulations have been used to characterize the stellar streams in the galactic discs of Milky Way type galaxies. Tools such as the second and third order moments of the velocity ellipsoid and clustering methods -EM-WEKA and FoF- allow characterizing these kinematic structures and linking them to the stellar overdensities and to the resonant regions all through the disc.

Roca-Fàbrega, S.; Romero-Gómez, M.; Figueras, F.; Antoja, T.; Valenzuela, O.

2011-10-01

295

Investigation of cryogenic rupture disc design  

NASA Technical Reports Server (NTRS)

Rupture disc designs of both the active (command actuated) and passive (pressure ruptured) types were evaluated for performance characteristics at cryogenic temperatures and for capability to operate in a variety of cryogens, including gaseous and liquid fluorine. The test results, coupled with information from literature and industry searches, were used to establish a statement of design criteria and recommended practices for application of rupture discs to cryogenic rocket propellant feed and vent systems.

Keough, J. B.; Oldland, A. H.

1973-01-01

296

Particle Acceleration in (by) Accretion Discs  

E-print Network

I present a model for acceleration of protons by the second-order Fermi process acting on randomly scrambled magnetic flux arches above an accretion disc. The accelerated protons collide with thermal protons in the disc, producing degraded energetic protons, charged and neutral pions, and neutrons. The pions produce gamma-rays by spontaneous decay of $\\pi^0$ and by bremsstrahlung and Compton processes following the decay of $\\pi^\\pm$ to $e^\\pm$.

J. I. Katz

1992-05-04

297

Intradural disc mimicking: a spinal tumor lesion  

Microsoft Academic Search

Study design: A case report of intradural disc hernia mimicking an intradural extramedullary spinal tumor lesion in radiological evaluation.Objective: To describe a lumbar intradural disc herniation with atypical radiological appearance and point out the role of contrast magnetic resonance imaging (MRI) of the lumbar spine.Setting: Turkey.Case report: A 58-year-old man with suspected lumbar intradural mass and neurological involvement received L5

M V Aydin; S Ozel; O Sen; B Erdogan; T Yildirim

2004-01-01

298

Disc valve for sampling erosive process streams  

DOEpatents

A four-port disc valve for sampling erosive, high temperature process streams. A rotatable disc defining opposed first and second sampling cavities rotates between fired faceplates defining flow passageways positioned to be alternatively in axial alignment with the first and second cavities. Silicon carbide inserts and liners composed of .alpha. silicon carbide are provided in the faceplates and in the sampling cavities to limit erosion while providing lubricity for a smooth and precise operation when used under harsh process conditions.

Mrochek, John E. (Oak Ridge, TN); Dinsmore, Stanley R. (Norris, TN); Chandler, Edward W. (Knoxville, TN)

1986-01-01

299

The JCMT Gould Belt Survey: low-mass protoplanetary discs from a SCUBA-2 census of NGC 1333  

NASA Astrophysics Data System (ADS)

NGC 1333 is a 1-2 Myr old cluster of stars in the Perseus molecular cloud. We used 850 ?m data from the Gould Belt Survey with SCUBA-2 on the James Clerk Maxwell Telescope to measure or place limits on disc masses for 82 Class II sources in this cluster. Eight disc candidates were detected; one is estimated to have mass of about 9 MJup in dust plus gas, while the others host only 2-4 MJup of circumstellar material. None of these discs exceeds the threshold for the `minimum mass solar nebula' (MMSN). This reinforces previous claims that only a small fraction of Class II sources at an age of 1-2 Myr have discs exceeding the MMSN threshold and thus can form a planetary system like our own. However, other regions with similarly low fractions of MMSN discs (IC 348, UpSco, ? Ori) are thought to be older than NGC 1333. Compared with coeval regions, the exceptionally low fraction of massive discs in NGC 1333 cannot easily be explained by the effects of UV radiation or stellar encounters. Our results indicate that additional environmental factors significantly affect disc evolution and the outcome of planet formation by core accretion.

Dodds, P.; Greaves, J. S.; Scholz, A.; Hatchell, J.; Holland, W. S.; JCMT Gould Belt Survey Team

2015-02-01

300

Fibrin in intervertebral disc tissue engineering.  

PubMed

Fibrin is clinically employed as a versatile, safe, and clinically applicable sealant and cell carrier. It has been able to support disc cell survival, favor extracellular matrix production, and enhance the efficiency of cell transfer in the intervertebral disc (IVD). The aim of this review was to evaluate how fibrin has been used in vitro, in vivo, and in clinical trials for IVD tissue engineering. Within the in vitro studies, disc cells were cultured in fibrin alone or combined with other materials and a difference in the behavior of nucleus pulposus (NP) and annulus fibrosus (AF) cells was sometimes reported, but in general, the formation of fibrocartilaginous matrix was observed. Moreover, data concerning the fibrin long-term stability and its anti-inflammatory properties were found. Disc cells of human origin were never employed in combination with fibrin in vivo or in clinical trials. In vivo, disc degeneration models used to test the fibrin properties essentially involved NP injuries. The addition of cells, in particular if terminally differentiated, to the injected fibrin seemed to promote a more physiological matrix in comparison with fibrin alone. Important aspects should be further investigated in future studies such as the use of fibrin to treat AF lesions as well as the mechanical properties of the fibrin-based biomaterials and of the neoformed tissue. Finally, in vivo studies and clinical trials with in situ injection of fibrin and human disc cells should be performed. PMID:24961887

Colombini, Alessandra; Ceriani, Cristina; Banfi, Giuseppe; Brayda-Bruno, Marco; Moretti, Matteo

2014-12-01

301

The Disc-Jet Connection  

E-print Network

A large body of theoretical and computational work shows that jets - modelled as magnetized disk winds - exert an external torque on their underlying disks that can efficiently remove angular momentum and act as major drivers of disk accretion. These predictions have recently been confirmed in direct HST measurements of the jet rotation and angular momentum transport in low mass protostellar systems. We review the theory of disc winds and show that their physics is universal and scales to jets from both low and high mass star forming regions. This explains the observed properties of outflows in massive star forming regions, before the central massive star generates an ultracompact HII region. We also discuss the recent numerical studies on the formation of massive accretion disks and outflows through gravitational collapse, including our own work on 3D Adaptive Mesh simulations (using the FLASH code) of the hydromagnetic collapse of an initial rotating, and cooling Bonner-Ebert sphere. Magnetized collapse gives rise to outflows. Our own simulations show that both a jet-like disk wind on sub AU scales, and a larger scale molecular outflow occur (Banerjee and Pudritz 2005).

Ralph E. Pudritz; Robi Banerjee

2005-07-11

302

Lumbar Disc Herniation in a Patient With Congenital Vertebral Body Anomaly: A Case Report  

PubMed Central

Lumbar disc herniation is characterized with low back and leg pain resulting from the degenerated lumbar disc compressing the spinal nerve root. The etiology of degenerative spine is related to age, smoking, microtrauma, obesity, disorders of familial collagen structure, occupational and sports-related physical activity. However, disc herniations induced by congenital lumbar vertebral anomalies are rarely seen. Vertebral fusion defect is one of the causes of congenital anomalies. The pathogenesis of embryological corpus vertebral fusion anomaly is not fully known. In this paper, a 30-year-old patient who had the complaints of low back and right leg pain after falling from a height is presented. She had right L5-S1 disc herniation that had developed on the basis of S1 vertebra corpus fusion anomaly in Lumbar computed tomography. This case has been discussed in the light of literature based on evaluations of Lumbar Computed Tomography (CT) and Magnetic Resonance Imaging (MRI). This case is unique in that it is the first case with development of lumbar disc herniation associated with S1 vertebral corpus fusion anomaly. Congenital malformations with unusual clinical presentation after trauma should be evaluated through advanced radiological imaging techniques. PMID:25620987

Atabey, Cem; Topuz, Ali Kivanc; Velio?lu, Murat; Demircan, Mehmet Nusret

2014-01-01

303

Lumbar disc herniation in a patient with congenital vertebral body anomaly: a case report.  

PubMed

Lumbar disc herniation is characterized with low back and leg pain resulting from the degenerated lumbar disc compressing the spinal nerve root. The etiology of degenerative spine is related to age, smoking, microtrauma, obesity, disorders of familial collagen structure, occupational and sports-related physical activity. However, disc herniations induced by congenital lumbar vertebral anomalies are rarely seen. Vertebral fusion defect is one of the causes of congenital anomalies. The pathogenesis of embryological corpus vertebral fusion anomaly is not fully known. In this paper, a 30-year-old patient who had the complaints of low back and right leg pain after falling from a height is presented. She had right L5-S1 disc herniation that had developed on the basis of S1 vertebra corpus fusion anomaly in Lumbar computed tomography. This case has been discussed in the light of literature based on evaluations of Lumbar Computed Tomography (CT) and Magnetic Resonance Imaging (MRI). This case is unique in that it is the first case with development of lumbar disc herniation associated with S1 vertebral corpus fusion anomaly. Congenital malformations with unusual clinical presentation after trauma should be evaluated through advanced radiological imaging techniques. PMID:25620987

Atabey, Cem; Ero?lu, Ahmet; Topuz, Ali Kivanc; Velio?lu, Murat; Demircan, Mehmet Nusret

2014-12-01

304

Mechanical Vibrations Reduce the Intervertebral Disc Swelling and Muscle Atrophy from Bed Rest  

NASA Technical Reports Server (NTRS)

Loss of functional weight bearing, such as experienced during space flight or bed rest (BR), distorts intervertebral disc (IVD) and muscle morphology. IVDs are avascular structures consisting of cells that may derive their nutrition and waste removal from the load induced fluid flow into and out of the disc. A diurnal cycle is produced by forces related to weight bearing and muscular activity, and comprised of a supine and erect posture over a 24 hr period. A diurnal cycle will include a disc volume change of approx. 10-13%. However, in space there are little or no diurnal changes because of the microgravity, which removes the gravitational load and compressive forces to the back muscles. The BR model and the etiology of the disc swelling and muscle atrophy could provide insight into those subjects confined to bed for chronic disease/injury and aging. We hypothesize that extremely low-magnitude, high frequency mechanical vibrations will abate the disc degeneration and muscle loss associated with long-term BR.

Holguin, Nilsson; Muir, Jesse; Evans, Harlan J.; Qin, Yi-Xian; Rubin, Clinton; Wagshul, Mark; Judex, Stefan

2007-01-01

305

Treatment of the degenerated intervertebral disc; closure, repair and regeneration of the annulus fibrosus.  

PubMed

Degeneration of the intervertebral disc (IVD) and disc herniation are two causes of low back pain. The aetiology of these disorders is unknown, but tissue weakening, which primarily occurs due to inherited genetic factors, ageing, nutritional compromise and loading history, is the basic factor causing disc degeneration. Symptomatic disc herniation mainly causes radicular pain. Current treatments of intervertebral disc degeneration and low back pain are based on alleviating the symptoms and comprise administration of painkillers or surgical methods such as spinal fusion. None of these methods is completely successful. Current research focuses on regeneration of the IVD and particularly on regeneration of the nucleus pulposus. Less attention has been directed to the repair or regeneration of the annulus fibrosus, although this is the key to successful nucleus pulposus, and therewith IVD, repair. This review focuses on the importance of restoring the function of the annulus fibrosus, as well as on the repair, replacement or regeneration of the annulus fibrosus in combination with restoration of the function of the nucleus pulposus, to treat low back pain. Copyright © 2014 John Wiley & Sons, Ltd. PMID:24616324

Sharifi, Shahriar; Bulstra, Sjoerd K; Grijpma, Dirk W; Kuijer, Roel

2014-02-25

306

Numerical simulations of protostellar encounters III. Non-coplanar disc-disc encounters  

E-print Network

It is expected that an average protostar will undergo at least one impulsive interaction with a neighbouring protostar whilst a large fraction of its mass is still in a massive, extended disc. If protostars are formed individually within a cluster before falling together and interacting, there should be no preferred orientation for such interactions. As star formation within clusters is believed to be coeval, it is probable that during interactions, both protostars possess massive, extended discs. We have used an SPH code to carry out a series of simulations of non-colpanar disc-disc interactions. We find that non-coplanar interactions trigger gravitational instabilities in the discs, which may then fragment to form new companions to the existing stars. (This is different from coplanar interactions, in which most of the new companion stars form after material in the discs has been swept up into a shock layer, and this then fragments.) The original stars may also capture each other, leading to the formation of a small-N cluster. If every star undergoes a randomly oriented disc-disc interaction, then the outcome will be the birth of many new stars. Approximately two-thirds of the stars will end up in multiple systems.

S. J. Watkins; A. S. Bhattal; H. M. J. Boffin; N. Francis; A. P. Whitworth

1998-05-28

307

Isolation and Characterization of Adult Spinal Disc Stem Cells from Healthy Human Spinal Disc Tissues  

PubMed Central

This report details the isolation, culture, and characterization of spinal disc stem cells derived from human adult spinal disc tissue specimens. Using stem cell suspension culture methods and biology, human adult spinal disc stem cells were isolated and monoclonally cultured into multicellular sphere-like clusters (discospheres). Discospheres from the first culture series were collected, processed, and replated as single stem cells for serial expansion studies using suspension culture, demonstrating linear expansion was possible. Discospheres and adult spinal disc stem cells were plated on matrix coated culture surfaces in stem cell media for several hours to allow fixation, and assayed for the stem cell biomarkers. Discospheres and adult spinal disc stem cells were plated on laminin-coated culture surfaces in chondrogenic media and culture conditions for 14 days to differentiate them into NP cells. NP cells cultured from these experiments demonstrated NP morphology and phenotype; NP biomarker expression, secretion of extracellular matrix, and the ability to be serially passaged with large volume expansion possible. Tissue engineering studies using the “burst kinetic assay”, demonstrated that discospheres have remarkable intrinsic developmental and tissue engineering biology that is robust and organized. In summary, adult disc stem cells and NP cells have been isolated, cultured, and characterized, from healthy spinal disc tissues. These findings demonstrate the important potential to be explored for using stem cell based tissue engineering for the treatment of degenerative disc disease (DDD).

Duntsch, Christopher; Dillard, Erika; Akbar, Umar

2015-01-01

308

Modeling and optimization of an elastic arthroplastic disc for a degenerated disc  

NASA Astrophysics Data System (ADS)

A three-dimensional finite element model (FEM) of the L3-L4 motion segment using ABAQUS v 6.9 has been developed. The model took into account the material nonlinearities and is imposed different loading conditions. In this study, we validated the model by comparison of its predictions with several sets of experimental data. Disc deformation under compression and segmental rotational motions under moment loads for the normal disc model agreed well with the corresponding in vivo studies. By linking ABAQUS with MATLAB 2010.a, we determined the optimal Young s modulus as well as the Poisson's ratio for the artificial disc under different physiologic loading conditions. The results of the present study confirmed that a well-designed elastic arthroplastic disc preferably has an annulus modulus of 19.1 MPa and 1.24 MPa for nucleus section and Poisson ratio of 0.41 and 0.47 respectively. Elastic artificial disc with such properties can then achieve the goal of restoring the disc height and mechanical function of intact disc under different loading conditions and so can reduce low back pain which is mostly caused due to disc degeneration.

Ghouchani, Azadeh; Ravari, Mohammad; Mahmoudi, Farid

2011-10-01

309

Luminosity-colour relations for thin-disc main-sequence stars  

NASA Astrophysics Data System (ADS)

In this study we present the absolute magnitude calibrations of thin-disc main-sequence stars in the optical , and in the near-infrared . Thin-disc stars are identified by means of Padova isochrones, and absolute magnitudes for the sample are evaluated via the newly reduced Hipparcos data. The obtained calibrations cover a large range of spectral types: from A0 to M4 in the optical and from A0 to M0 in the near-infrared. Also, we discuss the effects of binary stars and evolved stars on the absolute magnitude calibrations. The usage of these calibrations can be extended to the estimation of galactic model parameters for the thin disc individually, in order to compare these parameters with the corresponding ones estimated by statistics (which provides galactic model parameters for thin and thick discs and halo simultaneously) to test any degeneracy between them. The calibrations can also be used in other astrophysical researches where distance plays an important role in that study.

Bilir, S.; Karaali, S.; Ak, S.; Yaz, E.; Cabrera-Lavers, A.; Co?kuno?lu, K. B.

2008-11-01

310

Percutaneous Thoracic Intervertebral Disc Nucleoplasty: Technical Notes from 3 Patients with Painful Thoracic Disc Herniations  

PubMed Central

Symptomatic thoracic disc herniation is an uncommon condition and early surgical approaches were associated with significant morbidity and even mortality. We are the first to describe the technique of percutaneous thoracic nucleoplasty in three patients with severe radicular pain due to thoracic disc herniation. Two of the patients experienced more than 75% pain relief and one patient experienced more than 50% pain relief. Post-procedural pain relief was maintained up to an average of 10 months after nucleoplasty. One patient with preoperative neurological signs improved postoperatively. There were no reported complications in all three patients. In view of the reduced morbidity and shorter operating time, thoracic intervertebral disc nucleoplasty can be considered in patients with pain due to thoracic disc herniation, with no calcification of the herniated disc, and in patients who may be otherwise be unfit for conventional surgery. PMID:21386942

Gültuna, Ismail; Riezebos, Patricia; Beems, Tjemme; Vissers, Kris C.

2011-01-01

311

Angular Momentum Transfer in Star-Discs Encounters: The Case of Low-Mass Discs  

E-print Network

A prerequisite for the formation of stars and planetary systems is that angular momentum is transported in some way from the inner regions of the accretion disc. Tidal effects may play an important part in this angular momentum transport. Here the angular momentum transfer in an star-disc encounter is investigated numerically for a variety of encounter parameters in the case of low mass discs. Although good agreement is found with analytical results for the entire disc, the loss {\\it inside} the disc can be up to an order of magnitude higher than previously assumed. The differences in angular momentum transport by secondaries on a hyperbolic, parabolic and elliptical path are shown, and it is found that a succession of distant encounters might be equally, if not more, successful in removing angular momentum than single close encounter.

S. Pfalzner

2003-10-27

312

Incidental extraspinal findings on magnetic resonance imaging of intervertebral discs  

PubMed Central

Introduction We aimed to evaluate pathological extraspinal findings and congenital anomalies/anatomical variations that were incidentally detected on the magnetic resonance imaging (MRI) scans of intervertebral discs, to find the frequencies of these incidental findings, and to emphasise the clinical importance of them. Material and methods A retrospective study including 1031 consecutive patients (730 females and 301 males, with a median age of 46 years) was conducted by evaluating a total of 1106 MRI examinations of intervertebral discs. Examinations were performed with a 1.5 T MRI unit. Incidental findings were classified as pathological findings and congenital anomalies/anatomical variations. Results The percentages of incidental extraspinal pathological findings and congenital anomalies/anatomical variations were 16.6% (95% confidence interval (CI): 14.4–18.8) and 3.7% (95% CI: 2.6–4.3), respectively. The percentage of incidental extraspinal pathological findings on cervical spinal MRI was 25.7% (95% CI: 20.1–31.7), thyroid nodules being the most common incidental findings. On thoracic spinal MRI (n = 19), inferior pole thyroid nodules were demonstrated as incidental extraspinal pathological findings, with a percentage of 10.5% (95% CI: 9.6–11.5). On lumbar spinal MRI, incidental pathological findings were detected with a percentage of 14.2% (95% CI: 11.9–16.6), while the percentage of congenital anomalies/anatomical variations was 4.8% (95% CI: 3.4–6.3). Eventually, 6.5% (95% CI: 2.6–9.4) of all cases with incidental extraspinal pathological findings underwent surgery. Conclusions On MRI examination of intervertebral discs, paying attention to incidentally detected pathological extraspinal findings and congenital anomalies/anatomical variations is very important due to the fact that they can alter the treatment of the patient or affect the patient's life. PMID:25276162

Ayaz, Umit Yasar; Turanl?, Sevim; Saltas, Hakan; Karabacak, Osman Raif; Damar, Cagr?; Hekimoglu, Baki

2014-01-01

313

Stochastic oscillations of general relativistic discs  

NASA Astrophysics Data System (ADS)

We analyse the general relativistic oscillations of thin accretion discs around compact astrophysical objects interacting with the surrounding medium through non-gravitational forces. The interaction with the external medium (a thermal bath) is modelled via a friction force and a random force, respectively. The general equations describing the stochastically perturbed discs are derived by considering the perturbations of trajectories of the test particles in equatorial orbits, assumed to move along the geodesic lines. By taking into account the presence of a viscous dissipation and of a stochastic force, we show that the dynamics of the stochastically perturbed discs can be formulated in terms of a general relativistic Langevin equation. The stochastic energy transport equation is also obtained. The vertical oscillations of the discs in the Schwarzschild and Kerr geometries are considered in detail, and they are analysed by numerically integrating the corresponding Langevin equations. The vertical displacements, velocities and luminosities of the stochastically perturbed discs are explicitly obtained for both the Schwarzschild and the Kerr cases.

Harko, Tiberiu; Mocanu, Gabriela Raluca

2012-04-01

314

Design concepts in lumbar total disc arthroplasty  

PubMed Central

The implantation of lumbar disc prostheses based on different design concepts is widely accepted. This paper reviews currently available literature studies on the biomechanics of TDA in the lumbar spine, and is targeted at the evaluation of possible relationships between the aims of TDA and the geometrical, mechanical and material properties of the various available disc prostheses. Both theoretical and experimental studies were analyzed, by a PUBMED search (performed in February 2007, revised in January 2008), focusing on single level TDA. Both semi-constrained and unconstrained lumbar discs seem to be able to restore nearly physiological IAR locations and ROM values. However, both increased and decreased ROM was stated in some papers, unrelated to the clinical outcome. Segmental lordosis alterations after TDA were reported in most cases, for both constrained and unconstrained disc prostheses. An increase in the load through the facet joints was documented, for both semi-constrained and unconstrained artificial discs, but with some contrasting results. Semi-constrained devices may be able to share a greater part of the load, thus protecting the surrounding biological structure from overloading and possible early degeneration, but may be more susceptible to wear. The next level of development will be the biomechanical integration of compression across the motion segment. All these findings need to be supported by long-term clinical outcome studies. PMID:18946684

Bellini, Chiara M.; Zweig, Thomas; Ferguson, Stephen; Raimondi, Manuela T.; Lamartina, Claudio; Brayda-Bruno, Marco; Fornari, Maurizio

2008-01-01

315

A photometric and spectroscopic study of WW And - an Algol-type, long period binary system with an accretion disc  

NASA Astrophysics Data System (ADS)

We have analysed the available spectra of WW And and for the first time obtained a reasonably well defined radial velocity curve of the primary star. Combined with the available radial velocity curve of the secondary component, these data led to the first determination of the spectroscopic mass ratio of the system at qspec = 0.16 ± 0.03. We also determined the radius of the accretion disc from analysis of the double-peaked H? emission lines. Our new, high-precision, Johnson VRI and the previously-available Strömgren vby light curves were modelled with stellar and accretion disc models. A consistent model for WW And - a semidetached system harbouring an accretion disc which is optically thick in its inner region, but optically thin in the outer parts - agrees well with both spectroscopic and photometric data.

Siwak, Michal; Zola, Stanislaw; Szymanski, Tomasz; Kurpinska-Winiarska, Maria; Winiarski, Maciej; Koziel-Wierzbowska, Dorota; Waniak, Waclaw; Drahus, Michal

2012-11-01

316

Thermal stresses and end-bulging in the laser disc from a tetragonal [1?0?0]-cut crystal  

NASA Astrophysics Data System (ADS)

The problem of thermal stresses and strains is considered in relation to the laser disc from a tetragonal crystal cut along [1?0?0] axis under plane stress approximation (for diode-pumped lasers). The formula describing the contribution of end-bulging of the disc to the optical power of the thermal lens is obtained. It is shown that end-bulging for anisotropic crystal is partially responsible for the astigmatism of the thermal lens. The relationship between the anisotropy of thermal expansion and the position of the principal meridional planes of the thermal lens is shown. Thermal stresses, strains and displacements, as well as the end-bulging term of the ‘generalized’ thermo-optic coefficient are calculated for a disc from an a-cut yttrium vanadate, Nd:YVO4. The stress fracture issues for this crystal are also analyzed.

Yumashev, K. V.; Loiko, P. A.

2015-01-01

317

Evidence from stellar rotation of enhanced disc dispersal: (I) The case of the triple visual system BD-21 1074 in the $\\beta$ Pictoris association  

E-print Network

The early stage of stellar evolution is characterized by a star-disc locking mechanism. The disc-locking prevents the star to spin its rotation up, and its timescale depends on the disc lifetime. Some mechanisms can significantly shorten this lifetime, allowing a few stars to start spinning up much earlier than other stars. In the present study, we aim to investigate how the properties of the circumstellar environment can shorten the disc lifetime. We have identified a few multiple stellar systems, composed of stars with similar masses, which belong to associations with a known age. Since all parameters that are responsible for the rotational evolution, with the exception of environment properties and initial stellar rotation, are similar for all components, we expect that significant differences among the rotation periods can only arise from differences in the disc lifetimes. A photometric timeseries allowed us to measure the rotation periods of each component, while high-resolution spectra provided us with ...

Messina, S; Biazzo, K; Melo, C H F; Frasca, A

2014-01-01

318

Current concepts in the diagnosis, pathogenesis and management of nonarteritic anterior ischaemic optic neuropathy.  

PubMed

Nonarteritic anterior ischaemic optic neuropathy (NAION) is the most common acute optic neuropathy in patients over the age of 50 and is the second most common cause of permanent optic nerve-related visual loss in adults after glaucoma. Patients typically present with acute, painless, unilateral loss of vision associated with a variable visual field defect, a relative afferent pupillary defect, a swollen, hyperaemic optic disc, and one or more flame-shaped peripapillary retinal haemorrhages. The pathogenesis of this condition is unknown, but it occurs primarily in patients with structurally small optic discs that have little or no cup and a variety of underlying vascular disorders that may or may not be known at the time of visual loss. There is no consistently beneficial medical or surgical treatment for the condition, but there are now animal models that allow testing of various potential therapies. About 40% of patients experience spontaneous improvement in visual acuity. Patients in whom NAION occurs in one eye have a 15-19% risk of developing a similar event in the opposite eye over the subsequent 5 years. PMID:24993324

Miller, N R; Arnold, A C

2015-01-01

319

Age and metallicity distribution of the Galactic bulge from extensive optical and near-IR stellar photometry  

Microsoft Academic Search

We present a new determination of the metallicity distribution, age, and luminosity function of the Galactic bulge stellar population. By combining near-IR data from the 2MASS survey, from the SOFI imager at ESO NTT and the NICMOS camera on board HST we were able to construct color-magnitude diagrams (CMD) and luminosity functions (LF) with large statistics and small photometric errors

M. Zoccali; A. Renzini; S. Ortolani; L. Greggio; I. Saviane; S. Cassisi; M. Rejkuba; B. Barbuy; R. M. Rich; E. Bica

2003-01-01

320

MSC response to pH levels found in degenerating intervertebral discs  

SciTech Connect

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 representative of the healthy, mildly or severely degenerated intervertebral disc (pH 7.4, 7.1, 6.8, and 6.5) for 5 days. Acidity caused an inhibition of aggrecan, collagen-1, and TIMP-3 expression, as well as a decrease in proliferation and viability and was associated with a change in cell morphology. Ageing had generally minor effects but young MSCs maintained greater mRNA expression levels. As acidic pH levels are typical of increasingly degenerated discs, our findings demonstrate the importance of early interventions and predifferentiation when planning to use MSCs for reparative treatments.

Wuertz, Karin [School of Engineering, University of Vermont, Burlington, Vermont (United States); Spine Research Group, Competence Center for Applied Biotechnology and Molecular Medicine, University of Zurich, Zurich (Switzerland)], E-mail: wuertz@cabmm.uzh.ch; Godburn, Karolyn; Iatridis, James C. [School of Engineering, University of Vermont, Burlington, Vermont (United States)

2009-02-20

321

Indications for Lumbar Total Disc Replacement: Selecting the Right Patient with the Right Indication for the Right Total Disc  

PubMed Central

Summary of Background Data As with any surgery, care should be taken to determine patient selection criteria for lumbar TDR based on safety and optimizing outcome. These goals may initially be addressed by analyzing biomechanical implant function and early clinical experience, ongoing evaluation is needed to refine indications. Objective The purpose of this work was to synthesize information published on general indications for lumbar TDR. A secondary objective was to determine if indications vary for different TDR designs. Methods A comprehensive literature search was conducted to identify lumbar TDR articles. Articles were reviewed and patient selection criteria and indications were synthesized. Results With respect to safety, there was good agreement in the literature to exclude patients with osteopenia/osteoporosis or fracture. Risk of injury to vascular structures due to the anterior approach was often addressed by excluding patients with previous abdominal surgery in the area of disc pathology or increased age. The literature was very consistent on the primary indication for TDR being painful disc degeneration unresponsive to at least 6 months of nonoperative care. Literature investigating the impact of previous spine surgery was mixed; however, prior surgery was not necessarily a contra-indication, provided the patient otherwise met selection criteria. The literature was mixed on setting a minimum preoperative disc height as a selection criterion. There were no publications investigating whether some patients are better/worse candidates for specific TDR designs. Based on the literature a proposal for patient selection criteria is offered. Conclusions Several TDR indications and contra-indications are widely accepted. No literature addresses particular TDR design being preferable for some patients. As with any spine surgery, ongoing evaluation of TDR outcomes will likely lead to more detailed general and device design specific indications.

Guyer, Richard D.; Ohnmeiss, Donna D.

2014-01-01

322

Spinning out of control: Wall turbulence over rotating discs  

NASA Astrophysics Data System (ADS)

The friction drag reduction in a turbulent channel flow generated by surface-mounted rotating disc actuators is investigated numerically. The wall arrangement of the discs has a complex and unexpected effect on the flow. For low disc-tip velocities, the drag reduction scales linearly with the percentage of the actuated area, whereas for higher disc-tip velocity, the drag reduction can be larger than the prediction found through the linear scaling with the actuated area. For medium disc-tip velocities, all the cases which display this additional drag reduction exhibit stationary-wall regions between discs along the streamwise direction. This effect is caused by the viscous boundary layer which develops over the portions of stationary wall due to the radial flow produced by the discs. For the highest disc-tip velocity, the drag reduction even increases by halving the number of discs. The power spent to activate the discs is instead independent of the disc arrangement and scales linearly with the actuated area for all disc-tip velocities. The Fukagata-Iwamoto-Kasagi identity and flow visualizations are employed to provide further insight into the dynamics of the streamwise-elongated structures appearing between discs. Sufficient interaction between adjacent discs along the spanwise direction must occur for the structures to be created at the disc side where the wall velocity is directed in the opposite direction to the streamwise mean flow. Novel half-disc and annular actuators are investigated to improve the disc-flow performance, resulting in a maximum of 26% drag reduction.

Wise, Daniel J.; Alvarenga, Claudia; Ricco, Pierre

2014-12-01

323

Accretion disc mapping of the shortest period eclipsing binary SDSS J0926+36  

NASA Astrophysics Data System (ADS)

AM CVn stars are ultracompact binaries (P_{orb}< 65 min) where a hydrogen-deficient low-mass, degenerate donor star overfills its Roche lobe and transfers matter to a companion white dwarf via an accretion disc. SDSS J0926+36 is currently the only eclipsing AM CVn star and also the shortest period eclipsing binary known. Its light curve displays deep (˜ 2 mag) eclipses every 28.3 min, which last for ˜ 2 min, as well as ˜ 2 mag amplitude outbursts every ˜ 100-200 d. Superhumps were seen in its quiescent light curve in some occasions, probably as a reminiscence of a (in some cases undetected) previous outburst. Its eclipsing nature allows a unique opportunity to disentangle the emission from several different light sources, and to map the surface brightness distribution of its hydrogen-deficient accretion disc with the aid of maximum entropy eclipse mapping techniques. Here we report the eclipse mapping analysis of optical light curves of SDSS J0926+36, collected with the 2.4 m Liverpool Robotic Telescope, covering 20 orbits of the binary over 5 nights of observations between 2012 February and March. The object was in quiescence at all runs. Our data show no evidence of superhumps nor of orbital modulation due to anisotropic emission from a bright spot at disc rim. Accordingly, the average out-of-eclipse flux level is consistent with that of the superhump-subtracted previous light curves. We combined all runs to obtain an orbital light curve of improved S/N. The corresponding eclipse map shows a compact source at disc centre (T_{b}simeq 17000 K), a faint, cool accretion disc (˜ 4000 K) plus enhanced emission along the gas stream (˜ 6000 K) beyond the impact point at the outer disc rim, suggesting the occurrence of gas stream overflow at that epoch.

Schlindwein, W.; Baptista, R.

2014-10-01

324

Effect of intervertebral disc degeneration on disc cell viability: a numerical investigation.  

PubMed

Degeneration of the intervertebral disc may be initiated and supported by impairment of the nutrition processes of the disc cells. The effects of degenerative changes on cell nutrition are, however, only partially understood. In this work, a finite volume model was used to investigate the effect of endplate calcification, water loss, reduction of disc height and cyclic mechanical loading on the sustainability of the disc cell population. Oxygen, lactate and glucose diffusion, production and consumption were modelled with non-linear coupled partial differential equations. Oxygen and glucose consumption and lactate production were expressed as a function of local oxygen concentration, pH and cell density. The cell viability criteria were based on local glucose concentration and pH. Considering a disc with normal water content, cell death was initiated in the centre of the nucleus for oxygen, glucose, and lactate diffusivities in the cartilaginous endplate below 20% of the physiological values. The initial cell population could not be sustained even in the non-calcified endplates when a reduction of diffusion inside the disc due to water loss was modelled. Alterations in the disc shape such as height loss, which shortens the transport route between the nutrient sources and the cells, and cyclic mechanical loads, could enhance cell nutrition processes. PMID:21970697

Galbusera, Fabio; Mietsch, Antje; Schmidt, Hendrik; Wilke, Hans-Joachim; Neidlinger-Wilke, Cornelia

2013-01-01

325

Joint Nonparametric Alignment for Analyzing Spatial Gene Expression Patterns in Drosophila Imaginal Discs  

E-print Network

or computer. Many dipteran organisms, including the fruit fly Drosophila melanogaster, have a three-stage life. First row: wing discs, second row: haltere discs, third row: leg discs, fourth row: eye discs

Sastry, S. Shankar

326

Disc valve for sampling erosive process streams  

DOEpatents

A four-port disc valve is described for sampling erosive, high temperature process streams. A rotatable disc defining opposed first and second sampling cavities rotates between fired faceplates defining flow passageways positioned to be alternatively in axial alignment with the first and second cavities. Silicon carbide inserts and liners composed of [alpha] silicon carbide are provided in the faceplates and in the sampling cavities to limit erosion while providing lubricity for a smooth and precise operation when used under harsh process conditions. 1 fig.

Mrochek, J.E.; Dinsmore, S.R.; Chandler, E.W.

1986-01-07

327

Hard Discs on the Hyperbolic Plane  

E-print Network

We examine a simple hard disc fluid with no long range interactions on the two dimensional space of constant negative Gaussian curvature, the hyperbolic plane. This geometry provides a natural mechanism by which global crystalline order is frustrated, allowing us to construct a tractable model of disordered monodisperse hard discs. We extend free area theory and the virial expansion to this regime, deriving the equation of state for the system, and compare its predictions with simulation near an isostatic packing in the curved space.

Carl D. Modes; Randall D. Kamien

2007-11-30

328

Fractured occluder disc: a previously unrecognized complication of the Starr-Edwards disc prosthesis.  

PubMed

Fracture of the occluder disc of a low-profile Starr-Edwards prosthesis is a hitherto unrecognized complication. We describe a patient who presented with right heart failure and severe pulmonary hypertension 27 years after mitral valve replacement with a model 6520 caged-disc prosthesis. At surgery, there was a longitudinal split in the occluder disc, and organized thrombus was lodged between the split segments. This case offers a unique opportunity to study the long-term effects of wear on the polyethylene poppet and Stellite cage. PMID:11206761

Malouf, J F; Hannoush, H M; Odell, J A

2001-01-01

329

Global simulations of axisymmetric radiative black hole accretion discs in general relativity with a mean-field magnetic dynamo  

NASA Astrophysics Data System (ADS)

We present a mean-field model that emulates the magnetic dynamo operating in magnetized accretion discs. We have implemented this model in the general relativisic radiation magnetohydrodynamic (GRRMHD) code KORAL, using results from local shearing sheet simulations of the magnetorotational instability to fix the parameters of the dynamo. With the inclusion of this dynamo, we are able to run 2D axisymmetric GRRMHD simulations of accretion discs for arbitrarily long times. The simulated discs exhibit sustained turbulence, with the poloidal and toroidal magnetic field components driven towards a state similar to that seen in 3D studies. Using this dynamo code, we present a set of long-duration global simulations of super-Eddington, optically thick discs around non-spinning and spinning black holes. Super-Eddington discs around non-rotating black holes exhibit a surprisingly large efficiency, ? ? 0.04, independent of the accretion rate, where we measure efficiency in terms of the total energy output, both radiation and mechanical, flowing out to infinity. This value significantly exceeds the efficiency predicted by slim disc models for these accretion rates. Super-Eddington discs around spinning black holes are even more efficient, and appear to extract black hole rotational energy through a process similar to the Blandford-Znajek mechanism. All the simulated models are characterized by highly super-Eddington radiative fluxes collimated along the rotation axis. We also present a set of simulations that were designed to have Eddington or slightly sub-Eddington accretion rates (dot{M} ? 2dot{M}_Edd). None of these models reached a steady state. Instead, the discs collapsed as a result of runaway cooling, presumably because of a thermal instability.

S?dowski, Aleksander; Narayan, Ramesh; Tchekhovskoy, Alexander; Abarca, David; Zhu, Yucong; McKinney, Jonathan C.

2015-02-01

330

SDSSJ084539.17+225728.0: the first DBZ white dwarf with a metal-rich gaseous debris disc  

E-print Network

We report the discovery of a third white dwarf hosting a gaseous debris disc, SDSSJ084539.17+225728.0. The typical double-peaked CaII 8498,8542,8662A emission lines can be modelled in terms of a Keplerian gas disc with a radial extent from ~0.5Rsun to ~1.0. The effective temperature of SDSS0845+2257, Teff=18600+-500K, is comparable to the two other white dwarfs with gaseous discs, SDSS1043+0855 and SDSS1228+1040, and hence substantially hotter than the bulk of white dwarfs where dusty debris discs were identified through the presence of infrared excess flux. This may suggest that the conditions to produce emission lines from debris discs in the optical wavelength range are only met for a relatively narrow range in Teff. The observed asymmetry in the line profiles indicates a substantial eccentricity in the disc. Two spectra obtained four years apart reveal a significant change in the shapes and equivalent widths of the line profiles, implying that the circumstellar disc evolves on relatively short time scales. In contrast to SDSS1043+0855 and SDSS1228+1040, SDSS0845+2257 has a helium-dominated atmosphere. We detect photospheric absorption lines of He, Ca, Mg, and Si in the Sloan Digital Sky Survey spectrum, and hence classify SDSS0845+2257 as DBZ white dwarf. The abundances for the three metals determined from model atmosphere fits are Ca/He~1.3x10^-7, Mg/He~6.0x10^-6, and Si/He~8.0x10^-6. From the non-detection of Halpha we derive H/He~1000 times lower than in the Sun. This lends strong support to the hypothesis that the gaseous and dusty debris discs found around roughly a dozen white dwarfs originate from the disruption of rocky planetary material.

B. T. Gaensicke; D. Koester; T. R. Marsh; A. Rebassa-Mansergas; J. Southworth

2008-09-15

331

Instabilities in Circumstellar Discs Charles F. Gammie 1  

E-print Network

Instabilities in Circumstellar Discs Charles F. Gammie 1 Isaac Newton Institute, 20 Clarkson Rd is governed by angular momentum transport; without torques the disc gas would remain in orbit and not accrete

Gammie, Charles F.

332

College of Engineering 3/9/2014 M. Frank, RevComp Cross-Disc. Intro for Beyond Moore  

E-print Network

in question Novel device physics cannot help (CNTs, optics, quantum) Fancy error correction codes cannot help Total energy/reliability of encoded bit still subject to argument! 3/9/2014 M. Frank, RevComp Cross-Disc. Intro for Beyond Moore group 4 #12;FAMU-FSU College of Engineering An Absolute Requirement

Frank, Michael P.

333

Chapter 39 Measuring Cone Density in a Japanese Macaque (Macaca fuscata) Model of Age-Related Macular Degeneration with Commercially Available Adaptive Optics  

PubMed Central

The aim of this study was to assess the feasibility of using a commercially available high-resolution adaptive optics (AO) camera to image the cone mosaic in Japanese macaques (Macaca fuscata) with dominantly inherited drusen. The macaques examined develop drusen closely resembling those seen in humans with age-related macular degeneration (AMD). For each animal, we acquired and processed images from the AO camera, montaged the results into a composite image, applied custom cone-counting software to detect individual cone photoreceptors, and created a cone density map of the macular region. We conclude that flood-illuminated AO provides a promising method of visualizing the cone mosaic in nonhuman primates. Future studies will quantify the longitudinal change in the cone mosaic and its relationship to the severity of drusen in these animals. PMID:24664712

Pennesi, Mark E.; Garg, Anupam K.; Feng, Shu; Michaels, Keith V.; Smith, Travis B.; Fay, Jonathan D.; Weiss, Alison R.; Renner, Laurie M.; Hurst, Sawan; McGill, Trevor J.; Cornea, Anda; Rittenhouse, Kay D.; Sperling, Marvin; Fruebis, Joachim; Neuringer, Martha

2015-01-01

334

Prevalence and Severity of Preoperative Disabilities in Iranian Patients with Lumbar Disc Herniation  

PubMed Central

Background: Literature recommends that refractory cases with lumbar disc herniation and appropriate indications are better to be treated surgically, but do all the patients throughout the world consent to the surgery with a same disability and pain threshold? We aim to elucidate the prevalence and severity of disabilities and pain in Iranian patients with lumbar disc herniation who have consented to the surgery. Methods: In this case series study, we clinically evaluated 194 (81 female and 113 male) admitted patients with primary, simple, and stable L4-L5 or L5-S1 lumbar disc herniation who were undergoing surgical discectomy. The mean age of the patients was 38.3±11.2 (range: 18-76 years old). Disabilities were evaluated by the items of the Oswestry Disability Index (ODI) questionnaire and severity of pain by the Visual Analogue Scale (VAS). Chi-square test was used to compare the qualitative variables. Results: Severe disability (39.2%) and crippled (29.9%) were the two most common types of disabilities. Mean ODI score was 56.7±21.1 (range: 16-92). Total mean VAS in all patients was 6.1±1.9 (range: 0-10). Sex and level of disc herniation had no statistical effect on preoperative ODI and VAS. The scale of six was the most frequent scale of preoperative VAS in our patients. Conclusion: Iranian patients with lumbar disc herniation who consented to surgery have relatively severe pain or disability. These severities in pain or disabilities have no correlation with sex or level of disc herniation and are not equal with developed countries. PMID:25207293

Omidi-Kashani, Farzad; Hasankhani, Ebrahim Ghayem; Moghadam, Mohammad Hallaj; Esfandiari, Mohammad Sadegh

2013-01-01

335

DISC1 as a therapeutic target for mental illnesses  

PubMed Central

Introduction Many genetic studies have indicated that DISC1 is not merely “disrupted-in-schizophrenia,” but is more generally implicated in various brain dysfunctions associated with aberrant neurodevelopment and intracellular signaling pathways. Thus, the DISC1 gene is mildly associated with a variety of brain disorders, including schizophrenia, mood disorders, and autism. This novel concept fits with the results from biological studies of DISC1, which include cell and animal models. Areas covered We review the molecular structure and functions of DISC1, particularly those in conjunction with its important interactors. Functions of these interacting proteins are also introduced under the concept of the “DISC1 interactome.” Finally, we discuss how the DISC1 interactome can provide potential therapeutic targets for mental illnesses. Expert opinion Modulation of DISC1 stability and post-transcriptional modifications may be key targets to address DISC1-related pathology. In addition, modulation of DISC1 interactors and the mechanisms of their interactions with DISC1 may also provide drug targets. Disc1 rodent models can subsequently be used as templates for in vivo validations of compounds designed for DISC1 and its interacting proteins. Furthermore, these rodents will serve as genetic models for schizophrenia and related conditions, especially in conjunction with their pathologies during the neurodevelopmental trajectory. PMID:23130881

Hikida, Takatoshi; Gamo, Nao J.; Sawa, Akira

2014-01-01

336

Influences of osteoporosis and disc degeneration on lumbar spinal stability  

Microsoft Academic Search

Disc degeneration and osteoporosis are two main factors affecting the elderly and impacting the quality of life. The aims of this study were to provide the information on mechanical changes resulting from disc degeneration and osteoporosis and further to understand their roles in segmental instability. The influences of disc degeneration and osteoporosis were investigated using a 3?dimensional finite element model

2003-01-01

337

ORNL concept would greatly increase optical data storage  

SciTech Connect

ORNL researchers have developed a technique, surface-enhanced Raman optical data storage (SERODS), which uses the light-emitting properties of molecules to pack considerably more information into compact discs. This new technology has the potential to store 10 days of music-instead of just 90 minutes-on a single disc.

Not Available

1990-01-01

338

Describing a new syndrome in L5-S1 disc herniation: Sexual and sphincter dysfunction without pain and muscle weakness  

PubMed Central

Context: Little seems to be known about the sexual dysfunction (SD) in lumbar intervertebral disc herniation. Aims: Investigation of sexual and sphincter dysfunction in patient with lumbar disc hernitions. Settings and Design: A retrospective analysis. Materials and Methods: Sexual and sphincter dysfunction in patients admitted with lumbar disc herniations between September 2012-March 2014. Statistical Analysis Used: Statistical analysis was performed using the Predictive Analytics SoftWare (PASW) Statistics 18.0 for Windows (Statistical Package for the Social Sciences, SPSS Inc., Chicago, Illinois). The statistical significance was set at P < 0.05. The Wilcoxon signed ranks test was used to evaluate the difference between patients. Results: Four patients with sexual and sphincter dysfunction were found, including two women and two men, aged between 20 and 52 years. All of them admitted without low back pain. In addition, on neurological examination, reflex and motor deficit were not found. However, almost all patients had perianal sensory deficit and sexual and sphincter dysfunction. Magnetic resonance imaging (MRI) of three patients displayed a large extruded disc fragment at L5-S1 level on the left side. In fourth patient, there were not prominent disc herniations. There was not statistically significant difference between pre-operative and post-operative sexual function, anal-urethral sphincter function, and perianal sensation score. A syndrome in L5-S1 disc herniation with sexual and sphincter dysfunction without pain and muscle weakness was noted. We think that it is crucial for neurosurgeons to early realise that paralysis of the sphincter and sexual dysfunction are possible in patients with lumbar L5-S1 disc disease. Conclusion: A syndrome with perianal sensory deficit, paralysis of the sphincter, and sexual dysfunction may occur in patients with lumbar L5-S1 disc disease. The improvement of perianal sensory deficit after surgery was counteracted by a trend toward disturbed sexual function. Further researches are needed to explore the extent of this problem.

Akca, Nezih; Ozdemir, Bulent; Kanat, Ayhan; Batcik, Osman Ersagun; Yazar, Ugur; Zorba, Orhan Unal

2014-01-01

339

Artificial Cervical Disc Replacement Improves Mobility  

MedlinePLUS Videos and Cool Tools

... see it gets inserted, it’s very rough. It’s titanium plasma sprayed, and this allows for the body ... the ProDisc C implant have a plasma-sprayed titanium coding to provide bony coating to promote bony ...

340

The Astral Curved Disc of Chevroches (France)  

NASA Astrophysics Data System (ADS)

The excavation of the unexplored secondary agglomeration in Chevroches (Nièvre), from 2001 to 2002, directed by F. Devevey (INRAP), has led to the discovery of an astrological bronze curved disc of a type unknown in the ancient world; it is inscribed with three lines in Greek transcribing Egyptian an Roman months, and the twelve signs of the zodiac. This article presents the first observations.

Devevey, F. Rousseau, A.

2009-08-01

341

The Substitution-Elimination Mechanistic Disc Method  

ERIC Educational Resources Information Center

A method designed to facilitate prediction of mechanism and products by developing critical thinking skills and reducing memorization is presented. The mechanistic disc method requiring students to utilize their understanding of charge stabilization, structural organic chemistry, and the fundamental mechanisms of aliphatic substitution and…

Buonora, Paul T.; Yu Jin Lim

2004-01-01

342

Metamorphosis of imaginal discs of Drosophila melanogaster  

Microsoft Academic Search

Imaginal discs ofDrosophila melanogaster larvae, 24–53 hrs after oviposition, were transplanted into mature immobile larval hosts. The transplants did not respond to the hormonal stimuli of metamorphosis, but instead completed their larval development. When reinjected into mature larval hosts, they now differentiated the full set of their presumptive imaginal structures. The process of acquiring competence for metamorphosis appears to be

Géza Mindek

1972-01-01

343

Disc Turbulence and Viscosity By AXEL BRANDENBURG  

E-print Network

. Introduction Accretion discs are a bit like waterfalls. Potential energy gets converted into kinetic stream splashes to the bottom. Equating the change of internal energy, c v ffiT , with the potential energy difference suggests a temperature increase ffiT of only 0.1 Kelvin. This is of course consistent

Brandenburg, Axel

344

Paraplegia due to thoracic disc herniation.  

PubMed

Disc herniation at the thoracic the spine level is more common than generally thought. Localisation of pain may be vague and may erroneously point to cardiopulmonary, gastrointestinal, genito-urinary or even psychiatric disease. Magnetic resonance imaging is the investigation of choice, especially if spinal cord compression is suspected. PMID:9338030

Pal, B; Johnson, A

1997-07-01

345

Global Structure of Magnetorotationally Turbulent Protoplanetary Discs  

E-print Network

The aim of the present paper is to investigate the spatial structure of a protoplanetary disc whose dynamics is governed by magnetorotational turbulence. We perform a series of local 3D chemo-radiative MHD simulations located at different radii of a disc which is twice as massive as the standard minimum mass solar nebula of Hayashi (1981). The ionisation state of the disc is calculated by including collisional ionisation, stellar X-rays, cosmic rays and the decay of radionuclides as ionisation sources, and by solving a simplified chemical network which includes the effect of the absorption of free charges by {\\mu}m-sized dust grains. In the region where the ionisation is too low to assure good coupling between matter and magnetic fields, a non-turbulent central "dead zone" forms, which ranges approximately from a distance of 2 AU to 4 AU from the central star. The approach taken in the present work allows for the first time to derive the global spatial structure of a protoplanetary disc from a set of physical...

Flaig, M; Kley, W; Kissmann, R

2011-01-01

346

Rossby-wave instability in viscous discs  

NASA Astrophysics Data System (ADS)

Rossby-wave instability (RWI), which depends on density bumps and extrema in the vortensities of differentially rotating discs, plays an important role in the evolution of protoplanetary discs. In this article, we investigate the effect of viscosity on non-axisymmetric RWI in self-graviting accretion discs. For this purpose, we add viscosity to the work of Lovelace & Hohlfeld. Consideration of viscosity complicates the problem, so we use a numerical method to investigate stable and unstable modes. We consider three ranges of viscosity: high viscosity in the range 0.1 ? ? ? 0.4, moderate viscosity in the range 0.01 ? ? < 0.1 and low viscosity in the range ? < 0.01. The results show that the occurrence of RWI is related to the value of viscosity, so that the effect of high viscosity is important, while low viscosity is negligible. These results may be applied to the study of the role of RWI in planet formation and angular momentum transport for different kinds of protoplanetary discs with different viscosities.

Gholipour, Mahmoud; Nejad-Asghar, Mohsen

2014-07-01

347

Stellar metallicity evolution in a simulated disc galaxy  

NASA Astrophysics Data System (ADS)

We explore the chemical evolution of two galaxies simulated using the same initial conditions but different feedback schemes (MUGS and MaGICC). We examine the age-metallicity relation (AMR), time—[O/Fe] and metallicity-[O/Fe] distributions of the stars in different galactic components, e.g. the bulge, disc and halo. The MUGS galaxy is replete with substructure, which is lacking in MaGICC, because MUGS feedback allows for more satellites. The AMR saturates at a certain point for each galaxy, while the metallicity of some objects can even decrease with time. This implies that the common assumption that metallicity is an increasing function of time, used in reconstructions of star formation histories of galaxies, is far from justified.

Snaith, Owain; Bailin, Jeremy; Gibson, Brad K.; Bell, Eric F.

2015-01-01

348

Grain size segregation in debris discs  

NASA Astrophysics Data System (ADS)

Context. In most debris discs, dust grain dynamics is strongly affected by stellar radiation pressure. Because this mechanism is size-dependent, we expect dust grains to be spatially segregated according to their sizes. However, because of the complex interplay between radiation pressure, grain processing by collisions, and dynamical perturbations, this spatial segregation of the particle size distribution (PSD) has proven difficult to investigate and quantify with numerical models. Aims: We propose to thoroughly investigate this problem by using a new-generation code that can handle some of the complex coupling between dynamical and collisional effects. We intend to explore how PSDs behave in both unperturbed discs at rest and in discs pertubed by planetary objects. Methods: We used the DyCoSS code to investigate the coupled effect of collisions, radiation pressure, and dynamical perturbations in systems that have reached a steady-state. We considered two setups: a narrow ring perturbed by an exterior planet, and an extended disc into which a planet is embedded. For both setups we considered an additional unperturbed case without a planet. We also investigated the effect of possible spatial size segregation on disc images at different wavelengths. Results: We find that PSDs are always spatially segregated. The only case for which the PSD follows a standard dn ? s-3.5ds law is for an unperturbed narrow ring, but only within the parent-body ring itself. For all other configurations, the size distributions can strongly depart from such power laws and have steep spatial gradients. As an example, the geometrical cross-section of the disc is very rarely dominated by the smallest grains on bound orbits, as it is expected to be in standard PSDs in sq with q ? -3. Although the exact profiles and spatial variations of PSDs are a complex function of the set-up that is considered, we are still able to derive some reliable results that will be useful for image or SED-fitting models of observed discs.

Thebault, P.; Kral, Q.; Augereau, J.-C.

2014-01-01

349

Deuk Laser Disc Repair® is a safe and effective treatment for symptomatic cervical disc disease  

PubMed Central

Background: Deuk Laser Disc Repair® is a new full-endoscopic surgical procedure to repair symptomatic cervical disc disease. Methods: A prospective cohort of 66 consecutive patients underwent cervical Deuk Laser Disc Repair® for one (n = 21) or two adjacent (n = 45) symptomatic levels of cervical disc disease and were evaluated postoperatively for resolution of headache, neck pain, arm pain, and radicular symptoms. All patients were candidates for anterior cervical discectomy and fusion (ACDF) or arthroplasty. The Mann–Whitney Wilcoxon test was used to calculate P values. Results: All patients (n = 66) had significant improvement in preoperative symptoms with an average symptom resolution of 94.6%. Fifty percent (n = 33) had 100% resolution of all preoperative cervicogenic symptoms. Only 4.5% (n = 3) had less than 80% resolution of preoperative symptoms. Visual analog scale (VAS) significantly improved from 8.7 preoperatively to 0.5 postoperatively (P < 0.001) for the cohort. Average operative and recovery times were 57 and 52 minutes, respectively. There were no perioperative complications. Recurrent disc herniation occurred in one patient (1.5%). Average postoperative follow-up was 94 days and no significant intergroup difference in outcomes was observed (P = 0.111) in patients with <90 days (n = 52) or >90 days (n = 14, mean 319 days) follow-up. No significant difference in outcomes was observed (P = 0.774) for patients undergoing one or two level Deuk Laser Disc Repair®. Patients diagnosed with postoperative cervical facet syndrome did significantly worse (P < 0.001). Conclusion: Deuk Laser Disc Repair® is a safe and effective alternative to ACDF or arthroplasty for the treatment of one or two adjacent symptomatic cervical disc herniations with an overall success rate of 94.6%. PMID:23776754

Deukmedjian, Ara J.; Jason Cutright, S. T.; Augusto Cianciabella, PA-C; Deukmedjian, Arias

2013-01-01

350

A new way to measure supermassive black hole spin in accretion disc-dominated active galaxies  

NASA Astrophysics Data System (ADS)

We show that disc continuum fitting can be used to constrain black hole spin in a subclass of narrow-line Seyfert 1 (NLS1) active galactic nuclei as their low mass and high mass accretion rate means that the disc peaks at energies just below the soft X-ray bandpass. We apply the technique to the NLS1 PG1244+026, where the optical/UV/X-ray spectrum is consistent with being dominated by a standard disc component. This gives a best estimate for black hole spin which is low, with a firm upper limit of a* <0.86. This contrasts with the recent X-ray determinations of (close to) maximal black hole spin in other NLS1 based on relativistic smearing of the iron profile. While our data on PG1244+026 do not have sufficient statistics at high energy to give a good measure of black hole spin from the iron line profile, cosmological simulations predict that black holes with similar masses have similar growth histories and so should have similar spins. This suggests that there is a problem either in our understanding of disc spectra, or/and X-ray reflection or/and the evolution of black hole spin.

Done, Chris; Jin, C.; Middleton, M.; Ward, Martin

2013-09-01

351

Outflows from accretion discs formed in neutron star mergers: effect of black hole spin  

NASA Astrophysics Data System (ADS)

The accretion disc that forms after a neutron star merger is a source of neutron-rich ejecta. The ejected material contributes to a radioactively powered electromagnetic transient, with properties that depend sensitively on the composition of the outflow. Here, we investigate how the spin of the black hole (BH) remnant influences mass ejection on the thermal and viscous time-scales. We carry out two-dimensional, time-dependent hydrodynamic simulations of merger remnant accretion discs including viscous angular momentum transport and approximate neutrino self-irradiation. The gravity of the spinning BH is included via a pseudo-Newtonian potential. We find that a disc around a spinning BH ejects more mass, up to a factor of several, relative to the non-spinning case. The enhanced mass-loss is due to energy release by accretion occurring deeper in the gravitational potential, raising the disc temperature and hence the rate of viscous heating in regions where neutrino cooling is ineffective. The mean electron fraction of the outflow increases moderately with BH spin due to a highly irradiated (though not neutrino-driven) wind component. While the bulk of the ejecta is still very neutron-rich, thus generating heavy r-process elements, the leading edge of the wind contains a small amount of Lanthanide-free material. This component can give rise to an ?1 d blue optical `bump' in a kilonova light curve, even in the case of prompt BH formation, which may facilitate its detection.

Fernández, Rodrigo; Kasen, Daniel; Metzger, Brian D.; Quataert, Eliot

2015-01-01

352

Enhancement of Overgrowth by Gene Interactions in Lethal(2)giant Discs Imaginal Discs from Drosophila Melanogaster  

PubMed Central

Recessive lethal mutations of the lethal(2)giant discs (l(2)gd) and lethal(2)fat (l(2)ft) loci of Drosophila melanogaster cause imaginal disc hyperplasia during a prolonged larval stage. Imaginal discs from l(2)ft l(2)gd or Gl(2)gd double homozygotes show more extensive overgrowth than in either single homozygote, and double homozygous l(2)ft l(2)gd mitotic clones in adult flies show much more overgrowth than is seen in clones homozygous for either l(2)gd or l(2)ft alone. dachsous (ds) also acts as an enhancer of l(2)gd, producing dramatically overgrown discs and causing failure to pupariate in double homozygotes. The comb gap (cg) mutation, which also interacts with ds, greatly enhances the tendency of imaginal discs from l(2)gd larvae to duplicate as they overgrow. If l(2)gd homozygotes are made heterozygous for l(2)ft, then several discs duplicate, indicating that l(2)ft acts as a dominant enhancer of l(2)gd. l(2)ft also acts as a dominant enhancer of l(2)gd, and conversely l(2)gd acts as a dominant modifier of l(2)ft. The enhancement of overgrowth caused by various mutant combinations is accompanied by changes in expression of Decapentaplegic and Wingless. These results show that tumor suppressor genes act in combination to control cell proliferation, and that tissue hyperplasia can be associated with ectopic expression of genes involved in pattern formation. PMID:9335602

Buratovich, M. A.; Bryant, P. J.

1997-01-01

353

Coupling effects of disc flexibility on the dynamic behaviour of multi disc-shaft systems  

NASA Astrophysics Data System (ADS)

The dynamic behaviour of a rotor consisting of multidiscs on a solid or hollow shaft, as used in gas or steam turbines, is considered. The effect of shaft flexibility on the dynamic characteristics of the discs and the coupling effects between the shaft and disc modes are investigated. The influence of the disc flexibility on the shaft system is also investigated. A new, thick, three-dimensional, cylindrical element is developed for the dynamic analysis and applied to various geometry of the discs-shaft system. Advantage is fully taken in the analysis of the rotational periodicity of the wave propagation. Results presented for various cases with differing flexibility and geometry show clearly the coupling effects in a multi disc-shaft system. Inference diagrams are developed, from which the dynamic behaviour of a system can be predicted for differing flexibility relationships between the solid or hollow shafts and the discs. The effect of various fixing conditions and boundary conditions on the coupling characteristics are also presented. The theoretical results show very close agreement with the experimental results.

Shahab, A. A. S.; Thomas, J.

1987-05-01

354

Collisional dust avalanches in debris discs  

E-print Network

We quantitatively investigate how collisional avalanches may developin debris discs as the result of the initial break-up of a planetesimal or comet-like object, triggering a collisional chain reaction due to outward escaping small dust grains. We use a specifically developed numerical code that follows both the spatial distribution of the dust grains and the evolution of their size-frequency distribution due to collisions. We investigate how strongly avalanche propagation depends on different parameters (e.g., amount of dust released in the initial break-up, collisional properties of dust grains and their distribution in the disc). Our simulations show that avalanches evolve on timescales of ~1000 years, propagating outwards following a spiral-like pattern, and that their amplitude exponentially depends on the number density of dust grains in the system. We estimate a probability for witnessing an avalanche event as a function of disc densities, for a gas-free case around an A-type star, and find that features created by avalanche propagation can lead to observable asymmetries for dusty systems with a beta Pictoris-like dust content or higher. Characteristic observable features include: (i) a brightness asymmetry of the two sides for a disc viewed edge-on, and (ii) a one-armed open spiral or a lumpy structure in the case of face-on orientation. A possible system in which avalanche-induced structures might have been observed is the edge-on seen debris disc around HD32297, which displays a strong luminosity difference between its two sides.

Anna Grigorieva; Pawel Artymowicz; Philippe Thébault

2006-09-01

355

Stellar orbit evolution in close circumstellar disc encounters  

NASA Astrophysics Data System (ADS)

The formation and early evolution of circumstellar discs often occurs within dense, newborn stellar clusters. For the first time, we apply the moving-mesh code AREPO, to circumstellar discs in 3D, focusing on disc-disc interactions that result from stellar flybys. Although a small fraction of stars are expected to undergo close approaches, the outcomes of the most violent encounters might leave an imprint on the discs and host stars that will influence both their orbits and their ability to form planets. We first construct well-behaved 3D models of self-gravitating discs, and then create a suite of numerical experiments of parabolic encounters, exploring the effects of pericentre separation rp, disc orientation and disc-star mass ratio (Md/M*) on the orbital evolution of the host stars. Close encounters (2rp ? disc radius) can truncate discs on very short time-scales. If discs are massive, close encounters facilitate enough orbital angular momentum extraction to induce stellar capture. We find that for realistic primordial disc masses Md ? 0.1M*, non-colliding encounters induce minor orbital changes, which is consistent with analytic calculations of encounters in the linear regime. The same disc masses produce entirely different results for grazing/colliding encounters. In the latter case, rapidly cooling discs lose orbital energy by radiating away the energy excess of the shock-heated gas, thus causing capture of the host stars into a bound orbit. In rare cases, a tight binary with a circumbinary disc forms as a result of this encounter.

Muñoz, D. J.; Kratter, K.; Vogelsberger, M.; Hernquist, L.; Springel, V.

2015-01-01

356

Cumulative occupational lumbar load and lumbar disc disease – results of a German multi-center case-control study (EPILIFT)  

PubMed Central

Background The to date evidence for a dose-response relationship between physical workload and the development of lumbar disc diseases is limited. We therefore investigated the possible etiologic relevance of cumulative occupational lumbar load to lumbar disc diseases in a multi-center case-control study. Methods In four study regions in Germany (Frankfurt/Main, Freiburg, Halle/Saale, Regensburg), patients seeking medical care for pain associated with clinically and radiologically verified lumbar disc herniation (286 males, 278 females) or symptomatic lumbar disc narrowing (145 males, 206 females) were prospectively recruited. Population control subjects (453 males and 448 females) were drawn from the regional population registers. Cases and control subjects were between 25 and 70 years of age. In a structured personal interview, a complete occupational history was elicited to identify subjects with certain minimum workloads. On the basis of job task-specific supplementary surveys performed by technical experts, the situational lumbar load represented by the compressive force at the lumbosacral disc was determined via biomechanical model calculations for any working situation with object handling and load-intensive postures during the total working life. For this analysis, all manual handling of objects of about 5 kilograms or more and postures with trunk inclination of 20 degrees or more are included in the calculation of cumulative lumbar load. Confounder selection was based on biologic plausibility and on the change-in-estimate criterion. Odds ratios (OR) and 95% confidence intervals (CI) were calculated separately for men and women using unconditional logistic regression analysis, adjusted for age, region, and unemployment as major life event (in males) or psychosocial strain at work (in females), respectively. To further elucidate the contribution of past physical workload to the development of lumbar disc diseases, we performed lag-time analyses. Results We found a positive dose-response relationship between cumulative occupational lumbar load and lumbar disc herniation as well as lumbar disc narrowing among men and women. Even past lumbar load seems to contribute to the risk of lumbar disc disease. Conclusion According to our study, cumulative physical workload is related to lumbar disc diseases among men and women. PMID:19422710

Seidler, Andreas; Bergmann, Annekatrin; Jäger, Matthias; Ellegast, Rolf; Ditchen, Dirk; Elsner, Gine; Grifka, Joachim; Haerting, Johannes; Hofmann, Friedrich; Linhardt, Oliver; Luttmann, Alwin; Michaelis, Martina; Petereit-Haack, Gabriela; Schumann, Barbara; Bolm-Audorff, Ulrich

2009-01-01

357

Pain and disability correlated with disc degeneration via magnetic resonance imaging in scoliosis patients  

PubMed Central

Prior imaging studies of scoliosis patients attempted to demonstrate a relationship between plain radiographic curve patterns and curve progression and pain, or used magnetic resonance imaging (MRI) to focus on spinal cord abnormalities. Pain in scoliosis patients may differ from nondeformity patients, yet may still be discogenic. The purpose of this study was to assess the possible relationship of degenerative disc findings on MRI to scoliosis patients’ pain. This prospective study enrolled scoliosis and control patients, all of whom had assessment for back pain (visual analog scale) and disability (Oswestry Index) and spinal MRI to identify prevalence and distribution of degenerative disc findings. Specifically, we assessed 60 consecutive pediatric and adult idiopathic scoliosis patients who had progressed to surgical treatment, 60 age- and gender-matched asymptomatic controls, and 172 nondeformity symptomatic degenerative disc disease patients who had progressed to surgical treatment. All subjects had independent analysis of their preoperative MRI for disc degeneration, disc herniation, Schmorl’s nodes, and inflammatory end plate changes. Imaging findings of the scoliosis patients were compared to those from asymptomatic and symptomatic control groups. Our results found that both pediatric and adult scoliosis patients had significantly more pain and disability than did asymptomatic controls (P < 0.001). The adult idiopathic scoliosis patients had pain and disability similar to those of surgical degenerative disc disease control groups. Disc degeneration and herniation (contained) were not related to pain. However, in the pediatric scoliosis patients, those with Schmorl’s nodes often had greater pain than those without (P = 0.01). Adults with painful scoliosis, typically occurring at the apex of the scoliosis or at the lumbosacral junction, had a significantly higher frequency of inflammatory end plate changes on MRI than did controls (P < 0.001). Prior studies have demonstrated a correlation of inflammatory end plate changes to lumbar discogenic pain. In conclusions, scoliosis patients who have progressed to surgical intervention, pediatric patients have varying degrees of pain, and those with Schmorl’s nodes may be at greater risk for pain. Adult scoliosis patients have multifactorial pain of which one component may be related to degeneration of the lower lumbar discs similar to that in nondeformity patients. Additionally, adult scoliosis patients may have MRI findings consistent with discogenic pain at the apex of their curvature, most commonly at the proximal lumbar levels. PMID:17973128

Mullin, William J.

2007-01-01

358

First experiences with a distractible titanium implant in ventral cervical disc surgery: report on 30 consecutive cases  

Microsoft Academic Search

A new titanium implant for ventral cervical fusion after microsurgical discectomy via a conventional antero-lateral approach is presented. The implant consists of a ventral fixation plate and a distractible disc space graft whose extension can be changed by adjusting a set screw. Additional fixation is achieved by four monocortical spongiosa screws. Thirty patients (14 men, mean age 46.5 years; 16

L. Russegger; H. Monstadt; F. Wenz

1997-01-01

359

Examination of turbine discs from nuclear power plants  

SciTech Connect

Investigations were performed on a cracked turbine disc from the Cooper Nuclear Power Station, and on two failed turbine discs (governor and generator ends) from the Yankee-Rowe Nuclear Power Station. Cooper is a boiling water reactor (BWR) which went into commercial operation in July 1974, and Yankee-Rowe is a pressurized water reactor (PWR) which went into commercial operation in June 1961. Cracks were identified in the bore of the Cooper disc after 41,913 hours of operation, and the disc removed for repair. At Yankee-Rowe two discs failed after 100,000 hours of operation. Samples of the Cooper disc and both Yankee-Rowe disc (one from the governor and one from the generator end of the LP turbine) were sent to Brookhaven National Laboratory (BNL) for failure analysis.

Czajkowski, C.J.; Weeks, J.R.

1982-01-01

360

Computer assisted characterization of cervical intervertebral disc degeneration in MRI  

NASA Astrophysics Data System (ADS)

A texture-based pattern recognition system is proposed for the automatic characterization of cervical intervertebral disc degeneration from saggital magnetic resonance images of the spine. A case sample of 50 manually segmented ROIs, corresponding to 25 normal and 25 degenerated discs, was analyzed and textural features were generated from each disc-ROI. Student's t-test verified the existence of statistically significant differences between textural feature values generated from normal and degenerated discs. This finding is indicative of disc image texture differentiation due to the degeneration of the disc. The generated features were employed in the design of a pattern recognition system based on the Least Squares Minimum Distance classifier. The system achieved a classification accuracy of 94{%} and it may be of value to physicians for the assessment of cervical intervertebral disc degeneration in MRI.

Michopoulou, S.; Boniatis, I.; Costaridou, L.; Cavouras, D.; Panagiotopoulos, E.; Panayiotakis, G.

2009-05-01

361

A novel classification system of lumbar disc degeneration.  

PubMed

The Pfirrmann and modified Pfirrmann grading systems are currently used to classify lumbar disc degeneration. These systems, however, do not incorporate variables that have been associated with lumbar disc degeneration, including Modic changes, a high intensity zone, and a significant reduction in disc height. A system that incorporates these variables that is easy to apply may be useful for research and clinical purposes. A grading system was developed that incorporates disc structure and brightness, presence or absence of Modic changes, presence or absence of a high intensity zone, and reduction in disc height (disc height less than 5mm). MRI of 300 lumbar discs in 60 patients were analyzed twice by two neurosurgeons. Intra and inter-observer reliabilities were assessed by calculating Cohen's ? values. There were 156 grade zero ("normal"), 50 grade one, 57 grade two, 26 grade three, 10 grade four, and one grade five ("worst") discs. Inter-observer reliability was substantial (?=0.66 to 0.77) for disc brightness/structure, Modic changes, and disc height. Inter-observer reliability was moderate (?=0.41) for high intensity zone. Intra-observer reliability was moderate to excellent (?=0.53 to 0.94) in all categories. Agreement on the total grade between reviewers occurred 71% of the time and a difference of one grade occurred in an additional 25% of cases. Lumbar disc degeneration can be graded reliably by this novel system. The advantage of this system is that it incorporates disc brightness/structure, Modic changes, high intensity zone, and a rigid definition of loss of disc height. This system might be useful in research studies evaluating disc degeneration. Further studies are required to demonstrate possible clinical utility in predicting outcomes after spinal treatments such as fusion. PMID:25443079

Riesenburger, Ron I; Safain, Mina G; Ogbuji, Richard; Hayes, Jackson; Hwang, Steven W

2015-02-01

362

Chemical depletion in the Large Magellanic Cloud: RV Tauri stars and the photospheric feedback from their dusty discs  

NASA Astrophysics Data System (ADS)

Aims. By studying the photospheric abundances of 4 RV Tauri stars in the LMC, we test whether the depletion pattern of refractory elements, seen in similar Galactic sources, is also common for extragalactic sources. Since this depletion process probably only occurs through interaction with a stable disc, we investigate the circumstellar environment of these sources. Methods: A detailed photospheric abundance study was performed using high-resolution UVES optical spectra. To study the circumstellar environment we use photometric data to construct the spectral energy distributions of the stars, and determine the geometry of the circumstellar environment, whereas low-resolution Spitzer-IRS infrared spectra are used to trace its mineralogy. Results: Our results show that, also in the LMC, the photospheres of RV Tauri stars are commonly affected by the depletion process, although it can differ significantly in strength from source to source. From our detailed disc modelling and mineralogy study, we find that this process, as in the Galaxy, appears closely related to the presence of a stable Keplerian disc. The newly studied extragalactic objects have similar observational characteristics as Galactic post-AGB binaries surrounded by a dusty disc, and are therefore also believed to be part of a binary system. One source shows a very small infrared excess, atypical for a disc source, but still has evidence for depletion. We speculate this could point to the presence of a very evolved disc, similar to debris discs seen around young stellar objects. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France.

Gielen, C.; van Winckel, H.; Reyniers, M.; Zijlstra, A.; Lloyd Evans, T.; Gordon, K. D.; Kemper, F.; Indebetouw, R.; Marengo, M.; Matsuura, M.; Meixner, M.; Sloan, G. C.; Tielens, A. G. G. M.; Woods, P. M.

2009-12-01

363

[Diagnostics and therapy of spinal disc herniation].  

PubMed

Degenerative processes in a movement segment of the vertebral column, which can potentially give rise to herniation of elements of the nucleus pulposus, are complex and of variable clinical and radiological dimensions; however the mere assumption that degenerative changes precede disc herniation remains a matter of debate. By definition, spinal disc herniation (SDH) refers to components of the gelatinous nucleus pulposus protruding beyond the dorsal level of the vertebral body margin through tears in the annulus fibrosus. Clinical presentation may include pain, paresis and sensory disturbances. Magnetic resonance imaging (MRI) is considered the gold standard in the diagnosis of SDH. In the majority of patients a conservative approach with physical therapy exercises and adequate analgesic and antiphlogistic medical treatment results in a substantial improvement of symptoms. PMID:25398570

Zimmer, A; Reith, W

2014-11-01

364

Oxygen abundance distribution in the Galactic disc  

NASA Astrophysics Data System (ADS)

We performed a non-local thermodynamic equilibrium (NLTE) analysis of the infrared oxygen triplet for a large number of Cepheid spectra obtained with the Hobby-Eberly Telescope. These data were combined with our previous NLTE results for stars observed with the Max Planck Gesellschaft Telescope with the aim of investigating the oxygen abundance distribution in the Galactic thin disc. We found the slope of the radial (O/H) distribution to be equal -0.058 dex kpc-1. However, we found some evidence that the distribution might become flatter in the outer parts of the disc. This is supported by the results of other authors who have studied open clusters, planetary nebulae and H II regions. Some mechanisms of flattening are discussed.

Korotin, S. A.; Andrievsky, S. M.; Luck, R. E.; Lépine, J. R. D.; Maciel, W. J.; Kovtyukh, V. V.

2014-11-01

365

New Experiments with Spinning Metallic Discs  

NASA Technical Reports Server (NTRS)

A number of recent advanced theories related to torsion properties of the space-time matrix predict the existence of an interaction between classically spinning objects. Indeed, some experimental data suggest that spinning magnetic bodies discernibly interact with Earth's natural fields. If there are interactions between rotating bodies then nuclear spins could be used for detection. Thus, assuming a spinning body induces a hypothetical torsion field, a sensor based on the giant magnetoresistance effect would detect local changes. Experimentally, spinning a brass wheel shielded from Earth's magnetic field showed no measurable change in signals; with no shielding a Faraday disc phenomenon was observed. Unexpected experimental measurements from the non-axial Faraday disc configuration were recorded and a theoretical model was derived to explain them.

Mazuruk, Konstantin; Grugel, Richard N.

2003-01-01

366

Doppler disc tomography applied to low-mass AGN spin  

NASA Astrophysics Data System (ADS)

Doppler tomography can provide a powerful means of determining black hole spin when our view to the central regions are revealed and obscured by optically thick orbiting material, and can provide an independent estimate that does not suffer as many degeneracies as traditional methods. For low-mass active galactic nuclei (AGN), time-dependent obscuration is expected to leave a signature in the changing spectrum of the disc emission which extends into the soft X-ray bandpass. We create a spectral model incorporating Doppler tomography and apply it to the case of the low-mass (8 × 105 M?) AGN, RX J1301.9+2747 which shows unusual timing properties in the form of short-lived flares that we argue are best explained by the orbit of a window through an optically thick wind. Modelling the phase-resolved spectrum over the course of the highest data quality flare indicates a very low spin even when we relax our constraints. This is the lowest mass AGN for which a spin has been measured and the first via this technique. We note that, as the mass and spin are very low, this appears to favour supermassive black hole (SMBH) growth by chaotic rather than constant accretion.

Middleton, Matthew J.; Ingram, Adam R.

2015-01-01

367

Inner disc obscuration in GRS 1915+105 based on relativistic slim disc model  

NASA Astrophysics Data System (ADS)

We study the observational signatures of the relativistic slim disc of 10 M? black hole, in a wide range of mass accretion rate, dot{m}, dimensionless spin parameter, a*, and viewing angle, i. In general, the innermost temperature, Tin, increases with the increase of i for a fixed value of dot{m} and a*, due to the Doppler effect. However, for i > 50° and dot{m}>dot{m}_turn, Tin starts to decrease with the increase of dot{m}. This is a result of self-obscuration - the radiation from the innermost hot part of the disc is blocked by the surrounding cooler part. The value of dot{m}_turn and the corresponding luminosities depend on a* and i. Such obscuration effects cause an interesting behaviour on the disc luminosity (Ldisc)-Tin plane for high inclinations. In addition to the standard disc branch which appears below dot{m}_turn and which obeys L_disc ? T_in4 relation, another branch above dot{m}_turn, which is nearly horizontal, may be observed at luminosities close to the Eddington luminosity. We show that these features are likely observed in a Galactic X-ray source, GRS 1915+105. We support a high spin parameter (a* > 0.9) for GRS 1915+105 since otherwise the high value of Tin and small size of the emitting region (rin < 1rS) cannot be explained.

Vierdayanti, K.; Sadowski, A.; Mineshige, S.; Bursa, M.

2013-11-01

368

Quantified H I morphology - V. H I discs in the Virgo cluster  

NASA Astrophysics Data System (ADS)

We explore the quantified morphology of atomic hydrogen (H I) discs in the Virgo cluster. These galaxies display a wealth of phenomena in their H I morphology, e.g., tails, truncation and warps. These morphological disturbances are related to the ram pressure stripping and tidal interaction that galaxies undergo in this dense cluster environment. To quantify the morphological transformation of the H I discs, we compute the morphological parameters of Concentration, Asymmetry, Smoothness, Gini and M20 and our own GM for 51 galaxies in 48 H I column density maps from the VLA Imaging of Virgo spirals in Atomic gas (VIVA) project. Some morphological phenomena can be identified in this space of relatively low-resolution H I data. Truncation of the H I disc can be cleanly identified via the Concentration parameter (C < 1), and Concentration can also be used to identify H I deficient discs (1 < C < 5). Tidal interaction is typically identified using combinations of these morphological parameters, applied to (optical) images of galaxies. We find that some selection criteria (Gini-M20, Asymmetry and a modified Concentration-M20) are still applicable for the coarse (˜15 arcsec full width at half - maximum) VIVA H I data. We note that Asymmetry is strongly affected by the choice for the centre of these galaxies. The phenomena of tidal tails can be reasonably well identified using the Gini-M20 criterion (60 per cent of galaxies with tails identified but with as many contaminants). Ram pressure does move H I discs into and out of most of our interaction criteria: the ram pressure sequence identified by previous authors tracks into and out of some of these criteria (Asymmetry-based and the Gini-M20 selections, but not the Concentration-M20 or the GM-based ones). Therefore, future searches for interaction using H I morphologies should take ram pressure into account as a mechanism to disturb H I discs enough to make them appear as gravitationally interacting. One mechanism would be to remove all the H I deficient (C < 5) discs from the sample, as these have undergone more than one H I removal mechanism.

Holwerda, B. W.; Pirzkal, N.; de Blok, W. J. G.; van Driel, W.

2011-10-01

369

Percutaneous treatment of intervertebral disc herniation.  

PubMed

Interventional radiology plays a major role in the management of symptomatic intervertebral disc herniations. In the absence of significant pain relief with conservative treatment including oral pain killers and anti-inflammatory drugs, selective image-guided periradicular infiltrations are generally indicated. The precise control of needle positioning allows optimal distribution of steroids along the painful nerve root. After 6 weeks of failure of conservative treatment including periradicular infiltration, treatment aiming to decompress or remove the herniation is considered. Conventional open surgery offers suboptimal results and is associated with significant morbidity. To achieve minimally invasive discal decompression, different percutaneous techniques have been developed. Their principle is to remove a small volume of nucleus, which results in an important reduction of intradiscal pressure and subsequently reduction of pressure inside the disc herniation. However, only contained disc herniations determined by computed tomography or magnetic resonance are indicated for these techniques. Thermal techniques such as radiofrequency or laser nucleotomy seem to be more effective than purely mechanical nucleotomy; indeed, they achieve discal decompression but also thermal destruction of intradiscal nociceptors, which may play a major role in the physiopathology of discal pain. The techniques of image-guided spinal periradicular infiltration and percutaneous nucleotomy with laser and radiofrequency are presented with emphasis on their best indications. PMID:21629404

Buy, Xavier; Gangi, Afshin

2010-06-01

370

Evidences for an Accretion Disc in the Spectrum of the Symbiotic Binary Z And during its Outburst at the end of 2002  

NASA Astrophysics Data System (ADS)

High resolution observations in the region of the lines H? and H? of the spectrum of the symbiotic binary Z And were performed during its small amplitude brightening at the end of 2002. The profiles of the two lines were double-peaked and the velocity of the dip between the two peaks was the same. This behavior was interpreted with emission mainly of an optically thin accretion disc. The H? line had broad wings which were supposed to be due to high velocity stellar wind. The line H? had a broad emission component which was thought to be emitted by an optically thin accretion disc or a high velocity stellar wind.

Tomov, N. A.; Tomova, M. T.; Bisikalo, D. V.

2009-04-01

371

Development of the full-disc telescope for EST. (Czech Title: Vývoj celodiskového dalekohledu pro EST)  

NASA Astrophysics Data System (ADS)

At present, a development study takes place of the 4-meter European Solar Telescope (EST), the status of which is summarized in the introduction of this contribution. A part of the study is the design of the Auxiliary Full-Disc Telescope (AFDT), developed in the AI and IPP of the AS CR. The telescope, 150 mm in diameter, will serve for positioning the observer on the solar disc and in its surroundings, steering the main EST telescope towards the selected object, accurate coordinate measurements and EST coordinate system corrections. AFDT will also be used as an autonomous robotic telescope for synoptic observations of solar activity. In this paper we describe the current status of the AFDT special mechanical design, optical system design, and the principles of the telescope control system.

Sobotka, M.; Klva?a, M.; Melich, Z.; Rail, Z.

2010-12-01

372

Write Strategy Optimization Method with Two-Step Search for Blu-ray Disc Recording  

NASA Astrophysics Data System (ADS)

A new write strategy (WS) optimization method with a two-step search process for Blu-ray Disc (BD) recording is developed to shorten the optimization time. This method is realized by the WS optimization system, which is constructed with an optical pickup, a disc tester, and the WS optimization algorithm. The optimization is executed according to the two-step search process along the mathematical axis, which is experimentally derived from the sample WS parameters. As the experimental result, the optimization time is reduced by nearly two-thirds from that achieved using the conventional method performed by the experts. All the jitter values of the playback signal derived from the recorded marks are smaller than the 7% target value and the effectiveness of this new method is experimentally confirmed.

Takeshita, Nobuo; Kanatake, Yusuke; Kishigami, Tomo; Ikuta, Koichi

2010-08-01

373

Laser-Disc Storage For All Digital X-Ray Images In A Large Hospital  

NASA Astrophysics Data System (ADS)

In this paper we will discuss a plan for an experimental application in clinical context of optical disc storage in diagnostic radiology. First computerized tomography (CT) and ultra-sound (US), later digital vascular imaging (DVI , intravenous angiography) and new digital device images such as digital radiography and nuclear magnetic resonance (NPR) will be stored permanently in a digital way. This image data base must be considered as an extension of the already operational hospital information system (ZIS). Replacing the costly, unique, bulky and operation-intensive film in a versatile, fast access- fast relocatable digital manner has obvious advantages and intrinsic,but limited, disadvantages. The aim of this experiment will be to evaluate easeof use, reliability and economic aspects of laser-disc based picture archiving and communication in a clinical experiment.

Cuigniez, Francis J. G.; Kouwenberg, Jef M. L.

1982-01-01

374

The origin and formation of the circumstellar disc  

NASA Astrophysics Data System (ADS)

The formation and evolution of the circumstellar disc in the collapsing molecular cloud with and without magnetic field is investigated from the pre-stellar stage resolving both the molecular cloud core and the protostar itself. In the collapsing cloud core, the first (adiabatic) core appears prior to the protostar formation. Reflecting the thermodynamics of the collapsing gas, the first core is much more massive than the protostar. When the molecular cloud has no angular momentum, the first core falls on to the protostar and disappears a few years after the protostar formation. On the other hand, when the molecular cloud has an angular momentum, the first core does not disappear even after the protostar formation, and directly evolves into the circumstellar disc with a Keplerian rotation. There are two paths for the formation of the circumstellar disc. When the initial cloud has a considerably small rotational energy, two nested discs appear just after the protostar formation. During the early main accretion phase, the inner disc increases its size and merges with the outer disc (i.e. first core) to form a single circumstellar disc with a Keplerian rotation. On the other hand, when the molecular cloud has a rotational energy comparable to observations, a single centrifugally supported disc that corresponds to the first core already exists prior to the protostar formation. In such a cloud, the first core density gradually increases, maintaining the Keplerian rotation and forms the protostar inside it. The magnetic field rarely affects the early formation of the circumstellar disc because the magnetic field dissipates in the high-density gas region where the circumstellar disc forms. As a result, in any case, the protostar at its formation is already surrounded by a massive circumstellar disc. The circumstellar disc is about 10-100 times more massive than the protostar in the main accretion phase. Such discs are favourable sites for the formation of binary companions and gas-giant planets.

Machida, Masahiro N.; Matsumoto, Tomoaki

2011-06-01

375

Notochordal cell disappearance and modes of apoptotic cell death in a rat tail static compression-induced disc degeneration model  

PubMed Central

Introduction The intervertebral disc has a complex structure originating developmentally from both the mesenchyme and notochord. Notochordal cells disappear during adolescence, which is also when human discs begin to show degenerative signs. During degeneration later in life, disc cells decline because of apoptosis. Although many animal models have been developed to simulate human disc degeneration, few studies have explored the long-term changes in cell population and phenotype. Our objective was to elucidate the time-dependent notochordal cell disappearance and apoptotic cell death in a rat tail static compression-induced disc degeneration model. Methods Twenty-four 12-week-old male Sprague–Dawley rat tails were instrumented with an Ilizarov-type device and loaded statically at 1.3 MPa for up to 56 days. Loaded and distal-unloaded discs were harvested. Changes in cell number and phenotype were assessed with histomorphology and immunofluorescence. Apoptosis involvement was determined with terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining and immunohistochemistry. Results The number of disc nucleus pulposus and annulus fibrosus cells decreased with the loading period; particularly, the decrease was notable at day 7 in larger, vacuolated, cytokeratin-8- and galectin-3-co-positive cells, indicating notochordal origin. Subsequently, the proportion of cells positive for TUNEL and cleaved caspase-3, markers of apoptosis induction, increased from day 7 through day 56. Although the percentage of cells immunopositive for cleaved caspase-8, a marker of apoptosis initiation through the death-receptor pathway, increased only at day 7, the percentage of cells immunopositive for cleaved caspase-9 and p53-regulated apoptosis-inducing protein 1 (p53AIP1), markers of apoptosis initiation through the p53-mediated mitochondrial pathway, increased from day 7 through day 56. The percentage of cells immunopositive for B-cell lymphoma 2 (Bcl-2) and silent mating type information regulation 2 homolog 1 (SIRT1), antiapoptotic proteins, decreased consistently with compression. Conclusions This rat tail model mimics notochordal cell disappearance and apoptotic cell death in human disc aging and degeneration. Sustained static compression induces transient activation of apoptosis through the death-receptor pathway and persistent activation of apoptosis through the p53-mediated mitochondrial pathway in disc cells. The increased proapoptotic and decreased antiapoptotic proteins observed at all time points signify static compression-induced disc cell death and degeneration. PMID:24472667

2014-01-01

376

Atomic Absorption Spectrometry Analysis of Trace Elements in Degenerated Intervertebral Disc Tissue  

PubMed Central

Background Few studies have investigated trace elements (TE) in human intervertebral disc (IVD) tissue. Trace element presence can have diverse meanings: essential TE show the metabolic modalities of the tissue, while environmentally-related TE indicate pollution and tissue-specific absorption and accumulation. IVD is a highly specific compartment with impaired communication with adjacent bone. Analysis of TE in IVD provides new insights regarding tissue metabolism and IVD communication with other tissues. Material/Methods Thirty intervertebral discs were acquired from 22 patients during surgical treatment for degenerative disease. Atomic absorption spectrometry was used to evaluate the concentrations of Al, Cd, Pb, Cu, Ni, Mo, Mg, and Zn. Results Al, Pb, Cu, Mg, and Zn were detected in all samples. Pb was significantly positively correlated with age, and Ni concentration was weakly correlated with population count in the patient’s place of residence. Only Cu was observed in higher concentrations in IVD compared to in other tissues. Significant positive correlations were observed between the following pairs: Mg/Zn, Mg/Al, Mg/Pb, Zn/Al, Zn/Pb, and Al/Pb. Negative correlations were observed between Mg/Cd, Zn/Cd, Mg/Mo, and Mo/Pb. Conclusions This study is one of few to profile the elements in intervertebral discs in patients with degenerative changes. We report significant differences between trace element concentrations in intervertebral discs compared to in other tissues. Knowledge of the TE accumulation pattern is vital for better understanding intervertebral disc nutrition and metabolism. PMID:25366266

Kubaszewski, ?ukasz; Zio?a-Frankowska, Anetta; Frankowski, Marcin; Nowakowski, Andrzej; Czabak-Garbacz, Ró?a; Kaczmarczyk, Jacek; Gasik, Robert

2014-01-01

377

Outcome of physiotherapy after surgery for cervical disc disease: a prospective randomised multi-centre trial  

PubMed Central

Background Many patients with cervical disc disease require leave from work, due to long-lasting, complex symptoms, including chronic pain and reduced levels of physical and psychological function. Surgery on a few segmental levels might be expected to resolve disc-specific pain and reduce neurological deficits, but not the non-specific neck pain and the frequent illness. No study has investigated whether post-surgery physiotherapy might improve the outcome of surgery. The main purpose of this study was to evaluate whether a well-structured rehabilitation programme might add benefit to the customary post-surgical treatment for cervical disc disease, with respect to function, disability, work capability, and cost effectiveness. Methods/Design This study was designed as a prospective, randomised, controlled, multi-centre study. An independent, blinded investigator will compare two alternatives of rehabilitation. We will include 200 patients of working age, with cervical disc disease confirmed by clinical findings and symptoms of cervical nerve root compression. After providing informed consent, study participants will be randomised to one of two alternative physiotherapy regimes; (A) customary treatment (information and advice on a specialist clinic); or (B) customary treatment plus active physiotherapy. Physiotherapy will follow a standardised, structured programme of neck-specific exercises combined with a behavioural approach. All patients will be evaluated both clinically and subjectively (with questionnaires) before surgery and at 6 weeks, 3 months, 6 months, 12 months, and 24 months after surgery. The main outcome variable will be neck-specific disability. Cost-effectiveness will also be calculated. Discussion We anticipate that the results of this study will provide evidence to support physiotherapeutic rehabilitation applied after surgery for cervical radiculopathy due to cervical disc disease. Trial registration ClinicalTrials.gov identifier: NCT01547611 PMID:24502414

2014-01-01

378

Hotspots and a clumpy disc: variability of brown dwarfs and stars in the young ?Ori cluster  

NASA Astrophysics Data System (ADS)

The properties of accretion discs around stars and brown dwarfs in the ?Ori cluster (age 3Myr) are studied based on near-infrared (IR) time series photometry supported by mid-IR spectral energy distributions (SEDs). We monitor ~30 young low-mass sources over eight nights in the J and K band using the duPont telescope at Las Campanas. We find three objects showing variability with J-band amplitudes >=0.5mag five additional objects exhibit low-level variations. All three highly variable sources have been previously identified as highly variable; thus, we establish the long-term nature of their flux changes. The light curves contain periodic components with time-scales of ~0.5-8d, but have additional irregular variations superimposed - the characteristic behaviour for classical T Tauri stars. Based on the colour variability, we conclude that hotspots are the dominant cause of variations in two objects (#19 and #33), including one likely brown dwarf, with spot temperatures in the range of 6000-7000K. For the third one (#2), a brown dwarf or very low-mass star, inhomogeneities at the inner edge of the disc are the likely origin of variability. Based on mid-IR data from Spitzer, we confirm that the three highly variable sources are surrounded by circum-(sub)-stellar discs. They show typical SEDs for T Tauri-like objects. Using SED models, we infer an enhanced scaleheight in the disc for the object #2, which favours the detection of disc inhomogeneities in light curves and is thus consistent with the information from variability. In the ?Ori cluster, about every fifth accreting low-mass object shows persistent high-level photometric variability. We demonstrate that estimates for fundamental parameters in such objects can be significantly improved by determining the extent and origin of the variations.

Scholz, A.; Xu, X.; Jayawardhana, R.; Wood, K.; Eislöffel, J.; Quinn, C.

2009-09-01

379

NAVY PRECISION OPTICAL INTERFEROMETER OBSERVATIONS OF THE EXOPLANET HOST {kappa} CORONAE BOREALIS AND THEIR IMPLICATIONS FOR THE STAR'S AND PLANET'S MASSES AND AGES  

SciTech Connect

We used the Navy Precision Optical Interferometer to measure the limb-darkened angular diameter of the exoplanet host star {kappa} CrB and obtained a value of 1.543 {+-} 0.009 mas. We calculated its physical radius (5.06 {+-} 0.04 R{sub Sun }) and used photometric measurements from the literature with our diameter to determine {kappa} CrB's effective temperature (4788 {+-} 17 K) and luminosity (12.13 {+-} 0.09 L{sub Sun }). We then placed the star on an Hertzsprung-Russell diagram to ascertain the star's age (3.42{sup +0.32}{sub -0.25} Gyr) and mass (1.47 {+-} 0.04 M{sub Sun }) using a metallicity of [Fe/H] = +0.15. With this mass, we calculated the system's mass function with the orbital elements from a variety of sources, which produced a range of planetary masses: m{sub p}sin i = 1.61-1.88 M{sub Jup}. We also updated the extent of the habitable zone for the system using our new temperature.

Baines, Ellyn K.; Armstrong, J. Thomas [Remote Sensing Division, Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375 (United States); Van Belle, Gerard T., E-mail: ellyn.baines@nrl.navy.mil [Lowell Observatory, Flagstaff, AZ 86001 (United States)

2013-07-01

380

Navy Precision Optical Interferometer Observations of the Exoplanet Host ? Coronae Borealis and Their Implications for the Star's and Planet's Masses and Ages  

NASA Astrophysics Data System (ADS)

We used the Navy Precision Optical Interferometer to measure the limb-darkened angular diameter of the exoplanet host star ? CrB and obtained a value of 1.543 ± 0.009 mas. We calculated its physical radius (5.06 ± 0.04 R ?) and used photometric measurements from the literature with our diameter to determine ? CrB's effective temperature (4788 ± 17 K) and luminosity (12.13 ± 0.09 L ?). We then placed the star on an Hertzsprung-Russell diagram to ascertain the star's age (3.42^+0.32_-0.25 Gyr) and mass (1.47 ± 0.04 M ?) using a metallicity of [Fe/H] = +0.15. With this mass, we calculated the system's mass function with the orbital elements from a variety of sources, which produced a range of planetary masses: m psin i = 1.61-1.88 M Jup. We also updated the extent of the habitable zone for the system using our new temperature.

Baines, Ellyn K.; Armstrong, J. Thomas; van Belle, Gerard T.

2013-07-01

381

Clinical Features and Surgical Results of Cervical Myelopathy Caused by Soft Disc Herniation  

PubMed Central

Objective There are many causes of cervical myelopathy including trauma, degenerative conditions, tumors and demyelinating disorders. However, myelopathy caused by soft disc herniation might be seen rarely than the spondylosis caused by hard disc. Here, authors retrospectively analyzed the clinical features and results of cervical myelopathy caused by soft disc herniation. Methods From March 2010 to December 2010, 134 patients with degenerative cervical spinal disease were treated with anterior cervical discectomy and interbody fusion. Among them, 21 patients with cervical myelopathy secondary to cervical soft disc herniation were analyzed. Their clinical features, preoperative and, postoperative clinical results were evaluated by Nurick Grade and Japanese Orthopaedic Association scale (JOA) retrospectively. Preoperative clinical features including duration of myelopathy, pain intensity and postoperative clinical results including improvement rate of myelopathy and radiculopathy were retrospectively analyzed by Nurick Grade and JOA scale. We also evaluated correlation between the duration of symptom, type of the disc herniation, pain intensity and clinical outcome. Results Mean age was 49.7 and male was predominant. Gait disturbance with mild to moderate pain was most common symptom in clinical features. Severe pain was shown in only 9 cases, and the other 12 cases experienced mild to moderate pain. Mean duration of myelopathy was 1.18 month. The mean JOA scores were 11.22 before surgery and 14.2 after surgery. The mean Nurick grades were 2.78 before treatment and 1.67 after treatment. Neurologic status of mild or moderate pain group on preoperative state is worse than that of severe pain group. The patients with duration of myelopathy symptom (<1 month) showed lower clinical improvement rate than the patients with myelopathy over 1 month. Patients with median type of disc herniation showed poorer neurological status than those with paramedian type of herniation in preoperative state. Conclusion Authors reviewed the clinical features and surgical outcome of the cervical myelopathy secondary to cervical soft disc herniation. We presumed that patients of more than one month of symptom duration, mild to moderate initial symptom would be related with better postoperative improvement rate. PMID:24757475

Park, Sung Joo; Kim, Min Ki; Lee, Sung Ho; Oh, In Ho

2013-01-01

382

Nucleus disc arthroplasty with the NUBAC™ device: 2-year clinical experience.  

PubMed

Low back pain (LBP) due to degenerative disc disease (DDD) is a common condition that can be treated along a continuum of care: from conservative therapies to several surgical choices. Nucleus arthroplasty is an emerging technology that could potentially fill part of the gap in the spine continuum of care. The introduction of recent technologies that allow the replacement of the degenerated disc nucleus using prosthetic devices may be considered an additional therapeutic tool that can be used by the surgeon in selected cases of LBP due to DDD. Nucleus arthroplasties are designed to treat early stages of DDD, which are one of the most common spinal disorders in the population under 65 years of age. NUBAC™ is the first articulating nucleus disc prosthesis, designed to optimally respect the lumbar anatomy, kinematics, and biomechanics, constructed in unique two-piece manufactured from polyetheretherketone (PEEK) with an inner ball/socket articulation. The optimal indications for NUBAC™ implantation are: disc height >5 mm, degenerative disc changes at an early stage (Pfirmann 2, 3), single level affection, integrity of posterior facet joints, lack of local anatomical contraindication, failure of conservative treatment for at least 6 months. From December 2006 to January 2009, a total of 39 patients underwent nucleus disc arthroplasty with NUBAC™ device. 22 cases have 2-year follow up. There have been no major intra-operative or post-operative vascular or neurological complications in this series. The data showed that there were significant decreases in both Visual Analogue Scale (VAS) and Oswestry Disability Index (ODI) after the procedure, with a meaningful improvement of symptoms in all patients. Although preliminary, the initial results are encouraging. The absence of any major intra-operative and post-operative complications supports the design rationale of the NUBAC™, being less invasive comparing to total disc replacement (TDA) and with a low rate of surgical risk. The effectiveness of data as seen in 2-year follow-up on both VAS and ODI have also suggested that the NUBAC™ could be considered a viable treatment option for patients with LBP caused by DDD. PMID:21416380

Balsano, M; Zachos, A; Ruggiu, A; Barca, F; Tranquilli-Leali, P; Doria, C

2011-05-01

383

Genetic and Functional Studies of the Intervertebral Disc: A Novel Murine Intervertebral Disc Model  

PubMed Central

Intervertebral disc (IVD) homeostasis is mediated through a combination of micro-environmental and biomechanical factors, all of which are subject to genetic influences. The aim of this study is to develop and characterize a genetically tractable, ex vivo organ culture model that can be used to further elucidate mechanisms of intervertebral disc disease. Specifically, we demonstrate that IVD disc explants (1) maintain their native phenotype in prolonged culture, (2) are responsive to exogenous stimuli, and (3) that relevant homeostatic regulatory mechanisms can be modulated through ex-vivo genetic recombination. We present a novel technique for isolation of murine IVD explants with demonstration of explant viability (CMFDA/propidium iodide staining), disc anatomy (H&E), maintenance of extracellular matrix (ECM) (Alcian Blue staining), and native expression profile (qRT-PCR) as well as ex vivo genetic recombination (mT/mG reporter mice; AdCre) following 14 days of culture in DMEM media containing 10% fetal bovine serum, 1% L-glutamine, and 1% penicillin/streptomycin. IVD explants maintained their micro-anatomic integrity, ECM proteoglycan content, viability, and gene expression profile consistent with a homeostatic drive in culture. Treatment of genetically engineered explants with cre-expressing adenovirus efficaciously induced ex vivo genetic recombination in a variety of genetically engineered mouse models. Exogenous administration of IL-1ß and TGF-ß3 resulted in predicted catabolic and anabolic responses, respectively. Genetic recombination of TGFBR1fl/fl explants resulted in constitutively active TGF-ß signaling that matched that of exogenously administered TGF-ß3. Our results illustrate the utility of the murine intervertebral disc explant to investigate mechanisms of intervertebral disc degeneration. PMID:25474689

Pelle, Dominic W.; Peacock, Jacqueline D.; Schmidt, Courtney L.; Kampfschulte, Kevin; Scholten, Donald J.; Russo, Scott S.; Easton, Kenneth J.; Steensma, Matthew R.

2014-01-01

384

Enhanced prolylhydroxylase activity in the posterior annulus fibrosus of canine intervertebral discs following long-term running exercise.  

PubMed

The effect of long-term excercise on the intervertebral disc collagen concentration (hydroxyproline), collagen-synthesizing enzymes (prolyl-4-hydroxylase, PH, and galactosyl-hydroxylysyl glucosyltransferase, GGT) and hydroxypyridinium crosslinks was studied in ten female beagle dogs. The dogs were run on a treadmill for 1 year starting at the age of 15 weeks. The daily running distance was gradually increased to 40km, which distance the dogs ran for the final 15 weeks. Ten untrained dogs from the same breeding colony served as controls. The nucleus pulposus and anterior and posterior halves of the annulus fibrosus of C2-3, T10-12, L4-5 disc segments were analysed. Crosslinks were measured from the anterior annulus fibrosus of the T10-11 disc. Hydroxyproline and hydroxypyridinium concentrations remained similar in both groups. PH and GGT were significantly elevated by running in the posterior annulus fibrosus of the thoracic and lumbar discs and in the lumbar nucleus pulposus. In the thoracic nucleus pulposus GGT was reduced significantly. The results suggest activated collagen metabolism in the posterior annulus fibrosus of the thoracic and lumbar discs as a result of locally increased strains on the spine. PMID:20058463

Puustjärvi, K; Takala, T; Wang, W; Tammi, M; Helminen, H J; Kovanen, V

1993-10-01

385

Disc1 Variation Leads to Specific Alterations in Adult Neurogenesis  

PubMed Central

Disrupted in schizophrenia 1 (DISC1) is a risk factor for a spectrum of neuropsychiatric illnesses including schizophrenia, bipolar disorder, and major depressive disorder. Here we use two missense Disc1 mouse mutants, described previously with distinct behavioural phenotypes, to demonstrate that Disc1 variation exerts differing effects on the formation of newly generated neurons in the adult hippocampus. Disc1 mice carrying a homozygous Q31L mutation, and displaying depressive-like phenotypes, have fewer proliferating cells while Disc1 mice with a homozygous L100P mutation that induces schizophrenia-like phenotypes, show changes in the generation, placement and maturation of newly generated neurons in the hippocampal dentate gyrus. Our results demonstrate Disc1 allele specific effects in the adult hippocampus, and suggest that the divergence in behavioural phenotypes may in part stem from changes in specific cell populations in the brain. PMID:25272038

Chandran, Jayanth S.; Kazanis, Ilias; Clapcote, Steven J.; Ogawa, Fumiaki; Millar, J. Kirsty; Porteous, David J.; ffrench-Constant, Charles

2014-01-01

386

The Application of Fiber-Reinforced Materials in Disc Repair  

PubMed Central

The intervertebral disc degeneration and injury are the most common spinal diseases with tremendous financial and social implications. Regenerative therapies for disc repair are promising treatments. Fiber-reinforced materials (FRMs) are a kind of composites by embedding the fibers into the matrix materials. FRMs can maintain the original properties of the matrix and enhance the mechanical properties. By now, there are still some problems for disc repair such as the unsatisfied static strength and dynamic properties for disc implants. The application of FRMs may resolve these problems to some extent. In this review, six parts such as background of FRMs in tissue repair, the comparison of mechanical properties between natural disc and some typical FRMs, the repair standard and FRMs applications in disc repair, and the possible research directions for FRMs' in the future are stated. PMID:24383057

Pei, Bao-Qing; Li, Hui; Zhu, Gang; Li, De-Yu; Fan, Yu-Bo; Wu, Shu-Qin

2013-01-01

387

Local and global dynamics of warped astrophysical discs  

E-print Network

Astrophysical discs are warped whenever a misalignment is present in the system, or when a flat disc is made unstable by external forces. The evolution of the shape and mass distribution of a warped disc is driven not only by external influences but also by an internal torque, which transports angular momentum through the disc. This torque depends on internal flows driven by the oscillating pressure gradient associated with the warp, and on physical processes operating on smaller scales, which may include instability and turbulence. We introduce a local model for the detailed study of warped discs. Starting from the shearing sheet of Goldreich & Lynden-Bell, we impose the oscillating geometry of the orbital plane by means of a coordinate transformation. This warped shearing sheet (or box) is suitable for analytical and computational treatments of fluid dynamics, magnetohydrodynamics, etc., and it can be used to compute the internal torque that drives the large-scale evolution of the disc. The simplest hyd...

Ogilvie, Gordon I

2013-01-01

388

Unilateral tilted disc and ipsilateral keratoconus in the same eye  

PubMed Central

The objective of this case was to report unilateral tilted disc in a boy with ipsilateral keratoconus. The tilted disc syndrome is a non-hereditary bilateral condition. This configuration is accompanied by situs inversus of the retinal vessels, congenital inferonasal conus, thinning of the inferonasal retinal pigment epithelium and choroid, and myopic astigmatism. Unilateral tilted disc syndrome is a rare condition. Keratoconus is a disorder characterised by progressive corneal steepening. The author present a case of unilateral tilted disc in a boy with ipsilateral keratoconus. Pterygium is a common disorder and tilted disc syndrome is a bilateral condition. But unilateral tilted disc in a boy with ipsilateral keratoconus is the first report in literature. Due to these clinical presentation, this report is an exception in literature and reported an unknown clinical coincident. PMID:22692492

Ciftci, Suleyman

2011-01-01

389

Towards a fully consistent Milky Way disc model - I. The local model based on kinematic and photometric data  

NASA Astrophysics Data System (ADS)

We present a fully consistent evolutionary disc model of the solar cylinder. The model is based on a sequence of stellar subpopulations described by the star formation history (SFR) and the dynamical heating law [given by the age-velocity dispersion relation (AVR)]. The stellar subpopulations are in dynamical equilibrium and the gravitational potential is calculated self-consistently including the influence of the dark matter halo and the gas component. The combination of kinematic data from Hipparcos and the finite lifetimes of main-sequence (MS) stars enables us to determine the detailed vertical disc structure independent of individual stellar ages and only weakly dependent on the initial mass function (IMF). The disc parameters are determined by applying a sophisticated best-fitting algorithm to the MS star velocity distribution functions in magnitude bins. We find that the AVR is well constrained by the local kinematics, whereas for the SFR the allowed range is larger. The model is consistent with the local kinematics of MS stars and fulfils the known constraints on scaleheights, surface densities and mass ratios. A simple chemical enrichment model is included in order to fit the local metallicity distribution of G dwarfs. In our favoured Model A, the power-law index of the AVR is 0.375 with a minimum and maximum velocity dispersion of 5.1 and 25.0km s-1, respectively. The SFR shows a maximum 10 Gyr ago and declines by a factor of four to the present-day value of 1.5Msolarpc-2Gyr-1. A best fit of the IMF leads to power-law indices of -1.46 below and -4.16 above 1.72Msolar avoiding a kink at 1Msolar. An isothermal thick-disc component with local density of ~6 per cent of the stellar density is included. A thick disc containing more than 10 per cent of local stellar mass is inconsistent with the local kinematics of K and M dwarfs. Neglecting the thick-disc component results in slight variations of the thin-disc properties, but has a negligible influence on the AVR and the normalized SFR. The model allows detailed predictions of the density, age, metallicity and velocity distribution functions of MS stars as a function of height above the mid-plane. The complexity of the model does not allow to rule out other star formation scenarios using the local data alone. The incorporation of multiband star count and kinematic data of larger samples in the near future will improve the determination of the disc structure and evolution significantly.

Just, A.; Jahreiß, H.

2010-02-01

390

Overview of disc arthroplasty—past, present and future  

Microsoft Academic Search

Degenerative disc disease is one of the most frequent spinal disorders. The anatomy and the biomechanics of the intervertebral\\u000a disc are very complex, and the pathomechanics of its degeneration are poorly understood. Despite this complexity and uncertainty,\\u000a great advances have been made in the field of disc replacement technology, with promising results. Difficulties are continuously\\u000a being encountered, but careful analysis

Tamás Fülöp Fekete; François Porchet

2010-01-01

391

Herschel DEBRIS survey of debris discs around A stars  

NASA Astrophysics Data System (ADS)

The Herschel DEBRIS survey (Disc Emission via a Bias-free Reconnaissance in the Infrared/Submillimetre) brings a unique perspective to the study of debris discs around main-sequence A-type stars. We have observed a sample of 89 A-stars with the Photodetector Array Camera and Spectrometer (PACS) on the Herschel space telescope at 100 and 160 ?m. A statistical analysis of the data shows a lower debris disc rate than has previously been found. The drop is due in part to the fact that some excess sources were resolved as background objects by the superior angular resolution (a factor of 2.5) of PACS-100 relative to that of Spitzer (MIPS-70). We found a 3-? detection rate of 23 myblue which is similar to the the detection rate around main-sequence F, G and K stars. Most of the debris discs were detected around the youngest and hottest stars in our sample. The incidence of discs in single and multiple systems was similar. The debris discs in multiple systems ware found either in tight binary systems (<1 AU) or wide ones (>100 AU). Debris discs in both tight and wide binary systems have physical properties that are statistically similar to those of discs around single stars. We did not detect any debris discs in binary systems with intermediate separation, in which the orbit and the debris disc would be on the same scale. One possible explanation is that discs in intermediate systems have evolved much faster owing to the disc-companion interactions and they are now undetectable.

Thureau, N.

2014-11-01

392

Gravitational instability in protostellar discs at low metallicities  

NASA Astrophysics Data System (ADS)

Fragmentation of protostellar discs controls the growth of protostars and plays a key role in determining the final mass of newborn stars. In this paper, we investigate the structure and gravitational stability of the protostellar discs in the full metallicity range between zero and the solar value. Using the mass-accretion rates evaluated from the thermal evolution in the preceding collapse phase of the pre-stellar cores, we calculate disc structures and their evolution in the framework of the standard steady discs. Overall, with higher metallicity, more efficient cooling results in the lower accretion rate and lower temperature inside the disc: at zero metallicity, the accretion rate is ˜10-3 M? yr-1 and the disc temperature is ˜1000 K, while at solar metallicity, ˜10-6 M? yr-1 and ˜10 K. Despite the large difference in these values, the zero- and solar-metallicity discs have similar stability properties: the Toomre parameter for the gravitational stability, which can be written using the ratio of temperatures in the disc and in the envelope as QT ˜ (Tdisc/Tenv)3/2, is ? 1, i.e. marginally stable. At intermediate metallicities of 10-5 to 10-3 Z?, however, the discs are found to be strongly unstable with QT ˜ 0.1-1 since dust cooling, which is effective only in the discs due to their high density ( ? 1010 cm- 3), makes the temperature in the discs lower than that in the envelopes. This indicates that masses of the individual stars formed as a result of the protostellar disc fragmentation can be significantly smaller than their parent core in this metallicity range. The typical stellar mass in this case would be a few M?, which is consistent with the observationally suggested mass-scale of extremely metal-poor stars.

Tanaka, Kei E. I.; Omukai, Kazuyuki

2014-04-01

393

New Brown Dwarf Discs in Upper Scorpius Observed with WISE  

NASA Technical Reports Server (NTRS)

We present a census of the disc population for UKIDSS selected brown dwarfs in the 5-10 Myr old Upper Scorpius OB association. For 116 objects originally identified in UKIDSS, the majority of them not studied in previous publications, we obtain photometry from the Wide-Field Infrared Survey Explorer data base. The resulting colour magnitude and colour colour plots clearly show two separate populations of objects, interpreted as brown dwarfs with discs (class II) and without discs (class III). We identify 27 class II brown dwarfs, 14 of them not previously known. This disc fraction (27 out of 116, or 23%) among brown dwarfs was found to be similar to results for K/M stars in Upper Scorpius, suggesting that the lifetimes of discs are independent of the mass of the central object for low-mass stars and brown dwarfs. 5 out of 27 discs (19 per cent) lack excess at 3.4 and 4.6 microns and are potential transition discs (i.e. are in transition from class II to class III). The transition disc fraction is comparable to low-mass stars.We estimate that the time-scale for a typical transition from class II to class III is less than 0.4 Myr for brown dwarfs. These results suggest that the evolution of brown dwarf discs mirrors the behaviour of discs around low-mass stars, with disc lifetimes of the order of 5 10 Myr and a disc clearing time-scale significantly shorter than 1 Myr.

Dawson, P.; Scholz, A.; Ray, T. P.; Natta, A.; Marsh, K. A.; Padgett, D.; Ressler, M. E.

2013-01-01

394

Numerical simulations of protostellar encounters I. Star-disc encounters  

E-print Network

It appears that most stars are born in clusters, and that at birth most stars have circumstellar discs which are comparable in size to the separations between the stars. Interactions between neighbouring stars and discs are therefore likely to play a key role in determining disc lifetimes, stellar masses, and the separations and eccentricities of binary orbits. Such interactions may also cause fragmentation of the discs, thereby triggering the formation of additional stars. We have carried out a series of simulations of disc-star interactions using an SPH code which treats self-gravity, hydrodynamic and viscous forces. We find that interactions between discs and stars provide a mechanism for removing energy from, or adding energy to, the orbits of the stars, and for truncating the discs. However, capture during such encounters is unlikely to be an important binary formation mechanism. A more significant consequence of such encounters is that they can trigger fragmentation of the disc, via tidally and compressionally induced gravitational instabilities, leading to the formation of additional stars. When the disc-spins and stellar orbits are randomly oriented, encounters lead to the formation of new companions to the original star in 20% of encounters. If most encounters are prograde and coplanar, as suggested by simulations of dynamically-triggered star formation, then new companions are formed in approximately 50% of encounters.

H. M. J. Boffin; S. J. Watkins; A. S. Bhattal; N. Francis; A. P. Whitworth

1998-05-28

395

On the fragmentation criteria of self-gravitating protoplanetary discs  

NASA Astrophysics Data System (ADS)

We investigate the fragmentation criterion in massive self-gravitating discs. We present new analysis of the fragmentation conditions which we test by carrying out global three-dimensional numerical simulations. Whilst previous work has placed emphasis on the cooling time-scale in units of the orbital time-scale, ?, we find that at a given radius the surface mass density (i.e. disc mass and profile) and star mass also play a crucial role in determining whether a disc fragments or not as well as where in the disc fragments form. We find that for shallow surface mass density profiles (p < 2, where ??R-p), fragments form in the outer regions of the disc. However for steep surface mass density profiles (p > rsim 2), fragments form in the inner regions of a disc. In addition, we also find that the critical value of the cooling time-scale in units of the orbital time-scale, ?crit, found in previous simulations is only applicable to certain disc surface mass density profiles and for particular disc radii and is not a general rule for all discs. We find an empirical fragmentation criterion between the cooling time-scale in units of the orbital time-scale, ?, the surface mass density, the star mass and the radius.

Meru, Farzana; Bate, Matthew R.

2011-01-01

396

Stacked-disc structure for fluid filter or valve silencer  

NASA Technical Reports Server (NTRS)

A stacked-disc structure is comprised of a stack of annular discs (13) scalloped along the outer edge to provide lobes (13a) and etched on one side to provide lands (13a). A web (13d) is retained in the lobes to strengthen the discs so that they will not collapse due to high fluid pressure. The stack of discs is retained by a housing (10) having a fluted interior wall to retain the ends of the lobes. End plates (11 and 12) secure the stack of discs with a spacer (14) at one end having lands (14a) on lobes which match the lobes of the stacked discs to allow fluid to flow into, or out of, the spaces between the lobes of the stacked discs. The spaces between the lands on the etched discs provide passages for fluid flow into or out of the hollow core of the stack. The height of the lands (i.e., depth of the etch) determines the size of the smallest particle that will be permitted to flow through. The stacked-disc structure may be connected to the inlet of a valve, or be incorporated into the valve housing on the inlet side of the valve seat to assure substantially constant fluid velocity, and thereby reduce valve noise when the valve is operated.

Hagler, Jr., Ray (Inventor)

1983-01-01

397

MECHANICAL DESIGN CRITERIA FOR INTERVERTEBRAL DISC TISSUE ENGINEERING  

PubMed Central

Due to the inability of current clinical practices to restore function to degenerated intervertebral discs, the arena of disc tissue engineering has received substantial attention in recent years. Despite tremendous growth and progress in this field, translation to clinical implementation has been hindered by a lack of well-defined functional benchmarks. Because successful replacement of the disc is contingent upon replication of some or all of its complex mechanical behaviour, it is critically important that disc mechanics be well characterized in order to establish discrete functional goals for tissue engineering. In this review, the key functional signatures of the intervertebral disc are discussed and used to propose a series of native tissue benchmarks to guide the development of engineered replacement tissues. These benchmarks include measures of mechanical function under tensile, compressive and shear deformations for the disc and its substructures. In some cases, important functional measures are identified that have yet to be measured in the native tissue. Ultimately, native tissue benchmark values are compared to measurements that have been made on engineered disc tissues, identifying measures where functional equivalence was achieved, and others where there remain opportunities for advancement. Several excellent reviews exist regarding disc composition and structure, as well as recent tissue engineering strategies; therefore this review will remain focused on the functional aspects of disc tissue engineering. PMID:20080239

Nerurkar, Nandan L.; Elliott, Dawn M.; Mauck, Robert L.

2009-01-01

398

Analysis of rabbit intervertebral disc physiology based on water metabolism. II. Changes in normal intervertebral discs under axial vibratory load  

SciTech Connect

Metabolic changes induced by axial vibratory load to the spine were investigated based on water metabolism in normal intervertebral discs of rabbits with or without pentobarbital anesthesia. Tritiated water concentration in the intervertebral discs of unanesthetized rabbits was reduced remarkably by axial vibration for 30 minutes using the vibration machine developed for this study. Repeated vibratory load for 18 and 42 hours duration showed the recovery of /sup 3/H/sub 2/O concentration of the intervertebral disc without anesthesia. Computer simulation suggested a reduction of blood flow surrounding the intervertebral disc following the vibration stress. However, no reduction of the /sup 3/H/sub 2/O concentration in the intervertebral disc was noted under anesthesia. Emotional stress cannot be excluded as a factor in water metabolism in the intervertebral disc.

Hirano, N.; Tsuji, H.; Ohshima, H.; Kitano, S.; Itoh, T.; Sano, A.

1988-11-01

399

The star formation history and dust content in the far outer disc of M31  

NASA Astrophysics Data System (ADS)

We present a detailed analysis of two fields located 26 kpc (˜5 radial scalelengths) from the centre of M31 along the south-west semimajor axis of the disc. One field samples the major axis populations - the Outer Disc field - while the other is offset by ˜18 arcmin and samples the warp in the stellar disc - the warp field. The colour-magnitude diagrams (CMDs) based on Hubble Space Telescope Advanced Camera for Surveys imaging reach old main-sequence turn-offs (˜12.5 Gyr). We apply the CMD-fitting technique to the warp field to reconstruct the star formation history (SFH). We find that after undergoing roughly constant star formation until about 4.5 Gyr ago, there was a rapid decline in activity and then a ˜1.5 Gyr lull, followed by a strong burst lasting 1.5 Gyr and responsible for 25 per cent of the total stellar mass in this field. This burst appears to be accompanied by a decline in global metallicity which could be a signature of the inflow of metal-poor gas. The onset of the burst (˜3 Gyr ago) corresponds to the last close passage of M31 and M33 as predicted by detailed N-body modelling, and may have been triggered by this event. We reprocess the deep M33 outer disc field data of Barker et al. in order to compare consistently derived SFHs. This reveals a similar duration burst that is exactly coeval with that seen in the M31 warp field, lending further support to the interaction hypothesis. We reliably trace star formation as far back as 12-13 Gyr ago in the outer disc of M31, while the onset of star formation occurred about 2 Gyr later in M33, with median stellar ages of 7.5 and 4.5 Gyr, respectively. The complex SFHs derived, as well as the smoothly varying age-metallicity relations, suggest that the stellar populations observed in the far outer discs of both galaxies have largely formed in situ rather than migrated from smaller galactocentric radii. The strong differential reddening affecting the CMD of the Outer Disc field prevents derivation of the SFH using the same method. Instead, we quantify this reddening and find that the fine-scale distribution of dust precisely follows that of the H I gas. This indicates that the outer H I disc of M31 contains a substantial amount of dust and therefore suggests significant metal enrichment in these parts, consistent with inferences from our CMD analysis. a Projected radial distance. b Deprojected radial distances are calculated assuming (m-M)0= 24.47 (Holland 1998) and an inclined disc with PA = 38°1 (Ferguson et al. 2002) and i= 77°5 (Ma, Peng & Gu 1997). c Values from Schlegel, Finkbeiner & Davis (1998). d Individual and total exposure times in the F606W band. e Individual and total exposure times in the F814W band.

Bernard, Edouard J.; Ferguson, Annette M. N.; Barker, Michael K.; Hidalgo, Sebastian L.; Ibata, Rodrigo A.; Irwin, Michael J.; Lewis, Geraint F.; McConnachie, Alan W.; Monelli, Matteo; Chapman, Scott C.

2012-03-01