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1

Libraries in the Information Age: Where Are the Microcomputer and Laser Optical Disc Technologies Taking Us?  

ERIC Educational Resources Information Center

This discussion of information technology and its impact on library operations and services emphasizes the development of microcomputer and laser optical disc technologies. Libraries' earlier responses to bibliographic utilities, online databases, and online public access catalogs are described, and future directions for library services are…

Chen, Ching-chih

1986-01-01

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

Precision manufacture of optical disc master stampers  

E-print Network

details a new manufacturing process R)r compact disc master stamper production. Stamper is an optical disc industry term for the mold used to replicate polymer compact discs (CDs) in an injection molding device are growing at more than 30% per year. In North America, more than one billion compact discs (CDs) were sold

4

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

5

Optical Discs: New Storage Media for Education.  

ERIC Educational Resources Information Center

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

Helgerson, Linda W.

1987-01-01

6

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

7

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

8

Diffractive read-out of optical discs Joseph Braat  

E-print Network

the CD (Compact Disc) , the DVD (Digital Versatile Disc) and the blue light DVR system. After a short1 Diffractive read-out of optical discs Joseph Braat Optics Research Group Faculty of Applied especially pay attention to the modelling of the signal read-out in an optical disc player and we

9

Optical Disc Systems in Libraries: Problems and Issues.  

ERIC Educational Resources Information Center

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

Harter, Stephen P.; Jackson, Susan M.

1988-01-01

10

Optic disc vasculitis in epidemic dropsy.  

PubMed

During an outbreak of epidemic dropsy in Delhi, 233 patients were studied. Retinal changes including venous dilatation and tortuosity, haemorrhages and disc oedema were observed. A clinical picture compatible with type I optic disc vasculitis was seen in 13 eyes and that of type II in 3 eyes. Fluorescein angiography was carried out in 23 randomly selected cases. Relevant angiographic findings included dilated and tortuous retinal veins, prominent vascular staining, blocked fluorescence, microaneurysms, disc oedema and peripapillary dye spillage. Presence of positive angiographic findings correlated well with the severity of the systemic disease, glaucoma, however, revealed no correlation. Papillophlebitis, a new ocular manifestation of Argemone mexicana oil toxicity, as also the fluorescein angiographic picture in epidemic dropsy is being reported for the first time in the literature. PMID:3430862

Sachdev, M S; Sood, N N; Mohan, M; Sachdev, H P; Gupta, S K

1987-01-01

11

Digital Versatile Disc Read-Only Disc, Rewritable Disc and Compact Disc Compatible Optical Pickup with a Two-Wavelength Laser Diode Unit  

Microsoft Academic Search

We have developed an optical pickup with a two-wavelength laser diode unit which can read all the compact disc (CD) and digital versatile disc (DVD) family, including DVD rewritable discs (DVD-RAMs). To enable DVD-RAMs to be read, it is necessary to increase the light power efficiency of the optical system and to reduce the so-called track-crossing noise. This paper discusses

Eishin Mori; Yoshiaki Komma; Katsuhiko Yasuda; Naoya Hotta; Osamu Imafuji; Atsuo Kikuchi; Tatsuo Itoh

2002-01-01

12

Comparison of Optic Disc Morphology of Optic Nerve Atrophy between Compressive Optic Neuropathy and Glaucomatous Optic Neuropathy  

PubMed Central

Objectives To compare the optic nerve head (ONH) structure between compressive optic neuropathy (CON) and glaucomatous optic neuropathy (GON), and to determine whether selected ONH quantitative parameters effectively discriminate between GON and CON, especially CON cases presenting with a glaucoma-like disc. Methods We prospectively assessed 34 patients with CON, 34 age-matched patients with moderate or severe GON, and 34 age-matched healthy control subjects. The quantitative parameters of ONH structure were compared using the Heidelberg Retina Tomograph 2 (HRT2) and Spectralis optical coherence tomography with an enhanced depth imaging method. Results The mean and maximum cup depths of CON were significantly smaller than those with GON (P<0.001 and P<0.001, respectively). The distance between Bruch's membrane opening and anterior surface of the lamina cribrosa (BMO-anterior LC) of CON was also significantly smaller than that of glaucoma but was similar to that of the healthy group (P<0.001 and P?=?0.47, respectively). Based on Moorfields regression analysis of the glaucoma classification of HRT2, 15 eyes with CON were classified with a glaucoma-like disc. The cup/disc area ratio did not differ between cases of CON with a glaucoma-like disc and cases of GON (P?=?0.16), but the BMO-anterior LC and mean and maximum cup depths of CON cases with a glaucoma-like disc were smaller than those in GON (P?=?0.005, P?=?0.003, and P?=?0.001, respectively). Conclusions Measurements of the cup depths and the LC depth had good ability to differentiate between CON with a glaucoma-like disc and glaucoma. There was no laminar remodeling detected by laminar surface position in the patients with CON compared to those with GON. PMID:25375855

Hata, Masayuki; Miyamoto, Kazuaki; Oishi, Akio; Makiyama, Yukiko; Gotoh, Norimoto; Kimura, Yugo; Akagi, Tadamichi; Yoshimura, Nagahisa

2014-01-01

13

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

14

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

15

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

PubMed Central

Purpose: To study the optical coherence tomography (OCT) patterns in optic disc pit maculopathy and retinal changes after vitreous surgery. Materials and Methods: Retrospective review of consecutive cases with optic disc pit maculopathy seen at two tertiary eye institutes from January 2005 to June 2009. Results: Twenty-four eyes of 23 patients are included. The presenting visual acuity ranged from 20/400 to 20/20 (median:20/80). The median age at presentation was 24 years (range, 6-57 years). Optical coherence tomography demonstrated a combination of retinoschisis and outer layer detachment (OLD) in 19 (79.17%) eyes, OLD only in 3 (12.5%) eyes and retinoschisis only in 2 (8.33%) eyes. An obvious communication (outer layer hole) between the schisis and OLD was seen in 14 (73.68%) of the 19 eyes with both features. Of the 21 eyes with retinoschisis, schisis was present in multiple layers in 15 (71.43%) and single layer in 6 (28.57%) eyes. Eleven eyes underwent pars plana vitrectomy including creation of posterior vitreous detachment (PVD), fluid-air exchange, low intensity laser photocoagulation at the temporal edge of the optic disc pit and non-expansile perfluoropropane gas (14%) injection. Five (45.45%) of 11 eyes undergoing vitrectomy had complete resolution and 4 (36.36%) eyes had partial resolution of maculopathy. Visual acuity improved in 8 (72.72%) of 11 eyes. Conclusion: Optical coherence tomography demonstrates multiple layer schisis and outer layer detachment as main features of optic disc pit maculopathy. Vitrectomy with PVD induction, laser photocoagulation and gas tamponade results in anatomical and visual improvement in most cases with optic disc pit maculopathy. PMID:23619493

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

2014-01-01

16

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

PubMed Central

Purpose To assess the difference in retinal nerve fiber layer (RNFL) and optic disc algorithms between glaucomatous and normal Arab subjects using optical coherence tomography (OCT). Methods RNFL thickness and optic disc parameters were obtained in 65 patients aged 50.1 ± 7.7 years. Percentage differences in all parameters were calculated and analyzed between groups. Results The mean RNFL thickness around the disc and at all quadrants was significantly thinner in glaucomatous eyes than in normal eyes (P < 0.01). The greatest decrease in RNFL thickness was observed at the inferior (39.5%) and superior (39.3%) quadrants and at 1 o’clock (43%) and 5 o’clock (40%) hour sectors. Significant differences were observed between glaucomatous and control eyes in all disc parameters (P < 0.005) assessed. The disc area, cup area, mean cup/disc ratio, and vertical and horizontal cup/disc ratios were significantly larger (P < 0.01), whereas the vertical integrated rim area, horizontal integrated rim width, and rim area were significantly smaller (P < 0.001) in glaucomatous eyes than in normal eyes. Conclusion Stratus OCT is still a valuable tool in the diagnosis of early glaucoma changes and, as such, its use should be encouraged in glaucoma clinics in Saudi Arabia. The best OCT parameters for detecting early glaucoma change were RNFL thickness in the inferior, superior, and 1 o’clock hour sector; the cup area; and the vertical integrated rim area of the optic disc. PMID:24109175

Zeried, Ferial M; Osuagwu, Uchechukwu L

2013-01-01

17

Compact disc players in the laboratory: experiments in optical storage, error correction, and optical fiber communication  

Microsoft Academic Search

The compact disc player is a synergy of optics, communication theory, digital signal processing, and control engineering. This familiar consumer product may be employed as a cost-effective laboratory instrument to teach the fundamentals of optical storage, error detection and correction, and optical communication. The compact disc audio system, from analog input, through optical storage and distribution, to audio reproduction, provides

Ronnie Van Dommelen; Michael Cada

2001-01-01

18

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

19

Quantitative evaluation of optic disc pallor in pseudotumor cerebri patients  

Microsoft Academic Search

We quantified optic disc pallor in patients with pseudotumor cerebri with the Rodenstock Optic Nerve Head Analyzer before and after optic nerve sheath decompression. Mean frequency distribution of pallor peaked between the pallor values of 0.10 and 0.20 in four pseudotumor cerebri patients and between 0.50 and 0.60 in five normal subjects. The red dominant pallor reflectance in pseudotumor cerebri

Sang Y. Lee; Dong H. Shin; Thomas C. Spoor; Clark S. Tsai; Chaesik Kim; Sang H. Lee

1992-01-01

20

Integrated Optical Unit Employing Two-Wavelength Laser Diode for Digital Versatile Disc/Compact Disc Optical Pickup  

NASA Astrophysics Data System (ADS)

We have developed an integrated optical unit employing a two-wavelength laser diode for a digital versatile disc (DVD)/compact disc (CD) optical pickup. In this paper, we propose a new design method to share a holographic optical element for 780 and 650 nm light beams in an integrated optical unit. To share the holographic optical element, we have introduced an additional aberration to reduce the focusing error signal offset of the 780 nm light beam. Moreover, we have introduced the phase-shift differential push-pull (PS-DPP) method for both the 650 and 780 nm light beams. We have evaluated the performance of this integrated optical unit and confirmed that the performance of this unit is sufficient for both DVD and CD systems.

Miyazaki, Osamu; Ueyama, Tetsuo; Watanabe, Yukio; Iwasaki, Hiroaki; Nakata, Yasuo; Kurata, Yukio

2006-08-01

21

Compatible optical system for three optical disc systems (HD-DVD/DVD/CD)  

NASA Astrophysics Data System (ADS)

A compatible optical system with high light efficiency for three optical disc systems (HD-DVD/DVD/CD) has been developed. This system is based on refraction principle and has unique shaped objective lens named 'Multi aspherical shaped compatible lens'.

Kanai, Tomonori; Miyauchi, Mitsuhiro; Sugi, Yasuyuki; Makino, Yutaka; Maruyama, Takesuke

2007-06-01

22

Unilateral optic disc swelling in a fighter pilot.  

PubMed

Optic disc swelling occurs when there is an obstruction to axonal transport at the level of the lamina cribrosa. This may result from compression, ischemia, inflammation, or metabolic and toxic etiologies. Some of these etiologies may be life threatening and others may be self-limited. Thus, differentiating the different etiologies is important, albeit often difficult. We present a case of a 25-yr-old high-performance fighter aviator who presented with unilateral optic disc swelling 2 d after an F-16 flight, in which decompression was suspected. Visual acuity of the affected eye was decreased to 20/25, with enlarged blind spot and shallow arcuate scotomata on visual field testing. Pupil function, brightness intensity, and color vision were normal. Marked swelling of the entire optic disc, retinal flame-shaped hemorrhages, and engorgement of the retinal veins were seen. Since decompression sickness with nitrogen bubbles obstructing the optic nerve head vasculature was suspected, he was treated with hyperbaric oxygen. He rapidly improved, recovering full vision function within 6 d. No concurrent disease was found on extensive investigation. He returned to high-performance aviation 3 mo after onset of symptoms. No recurrence was seen during 3 yr of follow-up. PMID:19817243

Pokroy, Russell; Barenboim, Erez; Carter, Dan; Assa, Amit; Alhalel, Amir

2009-10-01

23

Performance Comparison of Detection Methods in Magneto-optical Disc System with (1, 7)RLL Code  

E-print Network

has been used for compact disc, possesses long wavelength for MOD application. Therefore, secondPerformance Comparison of Detection Methods in Magneto-optical Disc System with (1, 7)RLL Code Min@dosa.snu.ac.kr Abstract-The performance of detection methods is analyzed in the magneto-optical disc (MOD) system with (1

Lee, Jae Hong

24

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

25

Risk factors associated with optic disc haemorrhage in patients with normal tension glaucoma  

Microsoft Academic Search

PurposeTo evaluate the risk factors associated with optic disc haemorrhage in patients with normal tension glaucoma (NTG).Patients and methodsTwo hundred and eighty-one eyes of 281 patients with NTG (113 eyes with optic disc haemorrhage and 168 eyes without haemorrhage) were included in this study. Associations between optic disc haemorrhage and various patient-related variables (diabetes; hypertension; hypotension; cardiac disease; stroke; cold

Y-d Kim; S B Han; K H Park; S H Kim; S J Kim; M Seong; T W Kim; D M Kim

2010-01-01

26

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

27

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

1997-07-16

28

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

PubMed

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

Pereira, Carla; Gonçalves, Luís; Ferreira, Manuel

2013-03-01

29

Automatic optic disc segmentation based on image brightness and contrast  

NASA Astrophysics Data System (ADS)

Untreated glaucoma leads to permanent damage of the optic nerve and resultant visual field loss, which can progress to blindness. As glaucoma often produces additional pathological cupping of the optic disc (OD), cupdisc- ratio is one measure that is widely used for glaucoma diagnosis. This paper presents an OD localization method that automatically segments the OD and so can be applied for the cup-disc-ratio based glaucoma diagnosis. The proposed OD segmentation method is based on the observations that the OD is normally much brighter and at the same time have a smoother texture characteristics compared with other regions within retinal images. Given a retinal image we first capture the ODs smooth texture characteristic by a contrast image that is constructed based on the local maximum and minimum pixel lightness within a small neighborhood window. The centre of the OD can then be determined according to the density of the candidate OD pixels that are detected by retinal image pixels of the lowest contrast. After that, an OD region is approximately determined by a pair of morphological operations and the OD boundary is finally determined by an ellipse that is fitted by the convex hull of the detected OD region. Experiments over 71 retinal images of different qualities show that the OD region overlapping reaches up to 90.37% according to the OD boundary ellipses determined by our proposed method and the one manually plotted by an ophthalmologist.

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

2010-03-01

30

The Applications of a Liquid Crystal Aberration Compensator for the Optical Disc Systems - Invited Paper  

NASA Astrophysics Data System (ADS)

An optical disc such as Compact Disc (CD) or Digital Versatile Disc (DVD) is one of the most familiar and indispensable storage media in our daily life, because of its better portability and lower production cost than other storage media. Recently there have been many approaches and studies to increase an optical disc capacity by employing a higher Numerical Aperture (NA) objective lens and a shorter wavelength laser. The problems of aberrations caused by a deviation from the disc standard and a dispersion of the quality of an optical pick-up head become more serious when these high-density techniques are applied to an optical disc system. Applying an adaptive optics to these optical disc systems is believed to be the best solution to compensate for these aberrations. On the other hand, the consumer optical disc system requires the adaptive optics device to be low cost and simple, and to achieve high stability, easy controllability and so on. We believe the most suitable adaptive optics device having potential to meet these requirements is a Liquid Crystal Aberration Compensator (LCAC) [1]. In this report we describe our fundamental researches on the LCAC and introduce our application studies of the LCAC in our latest DVD drive.

Ogasawara, Masakazu; Sato, Makoto

2008-01-01

31

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

PubMed

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. PMID:23224009

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

2012-10-01

32

Trend of High-Power Laser Diodes for Recordable Optical Disc Drive  

NASA Astrophysics Data System (ADS)

Historical development trend of high-power laser diodes for recordable optical disc as CD-R and DVD-R is explained in a view point of not only how to realize highly reliable high-power operation but also how to adopt laser diodes into optical disc drives.

Yagi, Tetsuya

33

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

Microsoft Academic Search

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

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

2000-01-01

34

Compact design for a unitary photo detector and single-path combo optical pickup head for Blu-ray disc, digital versatile disc and compact disc systems  

NASA Astrophysics Data System (ADS)

We present a compact design for a unitary photo detector and single-path combination optical pickup head (OPH) which can be used for Blu-ray Disc, digital versatile disc and compact disc systems. The number of components in the OPH design can be reduced by focusing three discrete wavelength laser beams on the photo detector. The three laser diode chips and a photo detector can be encapsulated within an integrated optical unit (IOU), which is then combined with a compensator and rhomboid beam-splitter prism. The blazed holographic optical elements (HOEs) are designed for concentrating the diffracted light power to the 0th-order and the 1st-order to improve the round-trip efficiency. The simulation results, including the S-curve and optical efficiency, are compared for this combo-OPH with three IOUs. The optical efficiency of the proposed OPH for BD/DVD/CD systems as detected by the photo detector are 5.545%, 3.889%, and 3.517%, respectively. Our design results show that the combo-OPH with one IOU is better than the combo-OPH with three IOUs.

Sun, Wen-Shing; Lin, Yan-Nan; Tien, Chuen-Lin; Tsuei, Chih-Hsuan; Kuo, Chien-Cheng; Chang, Jenq-Yang

2012-09-01

35

Influence of automated disc margin determination on Stratus OCT optic nerve head measurements  

PubMed Central

Purpose To analyze the influence of manual correction of the automatically determined edge of the optic nerve head (ONH) in optic disc measurements in cases in which the optical coherence tomography did not identify the disc limits correctly. Methods The study included 127 eyes from 127 consecutive patients with glaucoma, suspects, and healthy individuals. In a retrospective analysis, eyes that underwent testing with the Stratus OCT (software version 4.0, Carl Zeiss Meditec, Dublin, CA, USA) Fast Optic Disc protocol were evaluated. Forty-seven eyes in which either the manual assignment was not necessary or the signal strength was below six were excluded. After image acquisition and processing, one expert examiner manually corrected the determination of the edge of the ONH, identified as the end of the retinal pigment epithelium/choriocapillaris complex. Disc area, cup area, rim area, and cup/disc area ratio results were compared before and after the optic disc margin manually corrected determination. Paired t-test was performed to evaluate the differences, and Bland–Altman plots were used to display the relationships between measurements. Results Eighty eyes from 80 individuals were included in the analyses. No statistically signifiant difference (P=.538) was found when analyzing results obtained with automated and manual determination of rim area (mean ± standard deviation; 1.30±0.45 mm2 and 1.29±0.39 mm2, respectively). Cup area (1.39±0.58 mm2 and 1.31±0.55 mm2, respectively), cup/disc area ratio (0.50±0.16 mm2 and 0.49±0.15 mm2, respectively), and disc area results (2.69±0.55 mm2 and 2.60±0.51 mm2, respectively) were significantly different. Conclusion The Stratus OCT ONH Report results were little influenced when optic disc limits were manually determined. Therefore the standard automated Stratus OCT disc margin assignment is adequate, and manual correction is not necessary. PMID:24623973

Soares de Camargo, Andre; Melo, Luiz Alberto Soares; Hirai, Flavio Eduardo; Tavares, Ivan Maynart

2014-01-01

36

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

37

Optical effects related to Keplerian discs orbiting Kehagias-Sfetsos naked singularities  

E-print Network

We demonstrate possible optical signatures of the Kehagias-Sfetsos naked singularity spacetimes representing spherically symmetric vacuum solution of the modified Ho\\v{r}ava gravity. In such spacetimes, accretion structures significantly different from those present in the standard black hole spacetimes occur due to the "antigravity" effect causing existence of an internal static sphere surrounded by Keplerian discs. We focus our attention on the optical effects related to the Keplerian accretion discs, constructing the optical appearance of the Keplerian discs, the spectral continuum due to their thermal radiation, and spectral profiled lines generated in the innermost parts of such discs. The KS naked singularity signature is strongly encoded in the characteristics of predicted optical effects, especially in the case of the spectral continuum and spectral lines profiled by the strong gravity of the spacetimes, due to the region of the vanishing of the angular velocity gradient influencing the effectivity of...

Stuchlik, Zdenek

2014-01-01

38

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

PubMed Central

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

Iverson, S M; Sehi, M

2013-01-01

39

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

PubMed Central

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

Mohammed, Osman Abdelzaher; Pai, Anant

2013-01-01

40

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

41

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

NASA Astrophysics Data System (ADS)

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

Marzari, F.; Thébault, P.

2011-09-01

42

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

PubMed

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

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

2013-04-01

43

Optic Disc and Cup Segmentation from Color Fundus Photograph Using Graph Cut with Priors  

PubMed Central

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

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

2014-01-01

44

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

Microsoft Academic Search

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

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

2012-01-01

45

Early detection of glaucoma by longitudinal monitoring of the optic disc structure  

Microsoft Academic Search

Computerized disc analysis (optic nerve-head analyzer, Rodenstock) and automated perimetry (Octopus 2000R, program G1) were used for the longitudinal monitoring of 25 subjects with elevated intraocular pressure (47 eyes). The mean follow-up time was 17.9 months (range, 12–30 months). The average number of disc examinations per eye during the follow-up period was 4.4 (range, 3–7). A progressive decrease in neuroretinal

Jens Funk

1991-01-01

46

Re-visiting the relations: Galactic thin disc age-velocity dispersion relation  

E-print Network

The velocity dispersion of stars in the solar neighbourhood thin disc increases with time after star formation. Nordstrom et al. (2004) is the most recent observational attempt to constrain the age-velocity dispersion relation. They fitted the age-velocity dispersion relations of each Galactic cardinal direction space velocity component, U (towards the Galactic centre), V (in the direction of Galactic rotation) and W (towards the North Galactic Pole), with power laws and interpreted these as evidence for continuous heating of the disc in all directions throughout its lifetime. We re-visit these relations with their data and use Famaey et al. (2005) to show that structure in the local velocity distribution function distorts the in-plane (U and V) velocity distributions away from Gaussian so that a dispersion is not an adequate parametrization of their functions. The age-sigma(W) relation can however be constrained because the sample is well phase-mixed vertically. We do not find any local signature of the stellar warp in the Galactic disc. Vertical disc heating does not saturate at an early stage. Our new result is that a power law is not required by the data: disc heating models that saturate after ~ 4.5 Gyr are equally consistent with observations.

G. M. Seabroke; G. Gilmore

2007-07-06

47

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

48

Changes in the Molecular Phenotype of Nucleus Pulposus Cells with Intervertebral Disc Aging  

PubMed Central

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

Tang, Xinyan; Jing, Liufang; Chen, Jun

2012-01-01

49

The optical characteristics in the layers of Compact Disc-Recordable  

Microsoft Academic Search

The optical characteristics of the laser beam in the layers of Compact Disc Recordable (CD-R) has been studied. The optical\\u000a disk which is compatible with currently used CD-drive consists of transparent polycarbonate (PC) substrate, organic dye recording\\u000a layer, reflective gold layer, and ultra-violet (UV) cured protecting layer. For proper design of the layer structure, modeling\\u000a of the optical characteristics in

Jong Sung Kim; Tae Young Nam; Young Jae Huh

1997-01-01

50

Automated localisation of the optic disc, fovea, and retinal blood vessels from digital colour fundus images  

PubMed Central

AIM—To recognise automatically the main components of the fundus on digital colour images.?METHODS—The main features of a fundus retinal image were defined as the optic disc, fovea, and blood vessels. Methods are described for their automatic recognition and location. 112 retinal images were preprocessed via adaptive, local, contrast enhancement. The optic discs were located by identifying the area with the highest variation in intensity of adjacent pixels. Blood vessels were identified by means of a multilayer perceptron neural net, for which the inputs were derived from a principal component analysis (PCA) of the image and edge detection of the first component of PCA. The foveas were identified using matching correlation together with characteristics typical of a fovea—for example, darkest area in the neighbourhood of the optic disc. The main components of the image were identified by an experienced ophthalmologist for comparison with computerised methods.?RESULTS—The sensitivity and specificity of the recognition of each retinal main component was as follows: 99.1% and 99.1% for the optic disc; 83.3% and 91.0% for blood vessels; 80.4% and 99.1% for the fovea.?CONCLUSIONS—In this study the optic disc, blood vessels, and fovea were accurately detected. The identification of the normal components of the retinal image will aid the future detection of diseases in these regions. In diabetic retinopathy, for example, an image could be analysed for retinopathy with reference to sight threatening complications such as disc neovascularisation, vascular changes, or foveal exudation.?? PMID:10413690

Sinthanayothin, C.; Boyce, J.; Cook, H.; Williamson, T.

1999-01-01

51

Expression of Matrix Metalloproteinases is Positively Related to the Severity of Disc Degeneration and Growing Age in the East Asian Lumbar Disc Herniation Patients.  

PubMed

Matrix metalloproteinases (MMPs) have been known to play a pivotal role in the age- and/or disease-related degradation of intervertebral discs. We aimed to explore as to whether the expression of these enzymes is correlated to disc degeneration caused by increasing age and severity of herniation in the East Asian population. Thus, we studied the expressions of MMP-1 (collagenase), MMP-2 (gelatinase) and MMP-14 (membrane-type protease) in 65 patients diagnosed with lumbar disc herniation. The patients were divided into 3 groups according to their age, and the severity of herniation was graded on the basis of magnetic resonance imaging (MRI). Immunohistochemistry analysis was conducted to determine the expression of different MMPs in the post-surgery disc specimens. The results showed that expressions of these three enzymes were directly and positively related to the degree of disc degradation. Whereas, the MMP-1 expression was found to be elevated with the increasing age, the MMP-2 and MMP-14 remained unchanged in groups of different ages. A direct correlation between the expressions of MMP-2 and MMP-14 suggested a role of MMP-14 in the modulation of MMP-2 expression. PMID:24874308

Xu, Haidong; Mei, Qiang; Xu, Bin; Liu, Gang; Zhao, Jianning

2014-11-01

52

Optical effects related to Keplerian discs orbiting Kehagias–Sfetsos naked singularities  

NASA Astrophysics Data System (ADS)

We demonstrate possible optical signatures of the Kehagias–Sfetsos (KS) naked singularity spacetimes representing a spherically symmetric vacuum solution of the modified Ho?ava gravity. In such spacetimes, accretion structures significantly different from those present in standard black hole spacetimes occur due to the ‘antigravity’ effect, which causes an internal static sphere surrounded by Keplerian discs. We focus our attention on the optical effects related to the Keplerian accretion discs, constructing the optical appearance of the Keplerian discs, the spectral continuum due to their thermal radiation, and the spectral profiled lines generated in the innermost parts of such discs. The KS naked singularity signature is strongly encoded in the characteristics of predicted optical effects, especially in cases where the spectral continuum and spectral lines are profiled by the strong gravity of the spacetimes due to the vanishing region of the angular velocity gradient influencing the effectiveness of the viscosity mechanism. We can conclude that optical signatures of KS naked singularities can be well distinguished from the signatures of standard black holes.

Stuchlík, Zden?k; Schee, Jan

2014-10-01

53

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

54

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

55

AUTOMATIC EXTRACTION OF THE OPTIC DISC BOUNDARY FOR DETECTING RETINAL DISEASES  

E-print Network

Boundary extraction, fundus image, Automatic Feature Detection, Glaucoma, Active Shape Model 1 Introduction Haleem, Liangxiu Han, Baihua Li and Andy Nisbet School of Mathemetics, Computing and Digital Technology diagnoses. The overall accuracy of the al- gorithm was 92% on a set of 110 images. KEY WORDS Optic Disc

Li, Baihua

56

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

PubMed Central

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

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

2012-01-01

57

New method of two-photon multi-layer optical disc storage  

NASA Astrophysics Data System (ADS)

Multi-layer data storage based on nonlinear effect caused by two-photon absorption is an attractive approach in the field of mass data storage. A two-photon multi-layer optical disc storage system with disc rotation structure has been proposed. The multi-layer fluorescent disc used in this system consists of three layers. A transparent substrate (under layer) and a thin reflective layer (middle layer) are bonded together forming a kind of structure similar to DVD disc, which is necessary to servo the vertical and radial deviation. Two-photon bits are recorded in top layer. The storage system has two modules: servo module and confocal module. The former keeps following the vertical and radial deviations by means of focusing and tracking servo technologies used in current two-dimensional optical storage devices, so the system can be compatible with CD/DVD. According to the driving signal of actuators in servo pick-up, the confocal module can also follow the disc deviation in both recording and reading processes. The servo module has been finished and the result of preliminary experiment is presented. Using the actuator and the objective lens (NA 0.6) in SANYO pick-up, we successfully recorded and read three data layers in photobleaching material with a homemade femtosecond laser. The layer separation was 15?m and the transverse bit separation was 4 ?m.

Jiang, Bing; Shen, Zhaolong; Cai, Jianwen; Tang, Huohong; Xing, Hui; Huang, Wenhao

2006-02-01

58

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

59

Unifying disc-jet behaviour in X-ray binaries: an optical/IR approach  

E-print Network

Synchrotron emission from jets produced by X-ray binaries can be detected at optical and infrared (IR) frequencies. I show that optical/IR colour-magnitude diagrams of the outbursts of nine X-ray binaries successfully separate thermal disc emission from non-thermal jet emission, in both black hole and neutron star sources. A heated single-temperature blackbody is able to reproduce the observed relations between colour and magnitude, except when excursions are made to a redder colour than expected, which is due to jet emission. The general picture that is developed is then incorporated into the unified picture of disc-jet behaviour in black hole X-ray binaries. At a given position of a source in the X-ray hardness-intensity diagram, the radio, IR and optical properties can be inferred. Similarly, it is possible to predict the X-ray and radio luminosities and spectral states from optical/IR monitoring.

David M. Russell; Dipankar Maitra; Rob P. Fender; Fraser Lewis

2008-11-18

60

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

61

Replication of continuous-relief diffractive optical elements by conventional compact disc injection-molding techniques  

Microsoft Academic Search

Continuous-relief diffractive optical elements have been replicated by use of conventional compact disc injection-molding techniques. Two continuous-relief microstructures, a blazed grating and a fan-out element, were chosen to evaluate the replication process. Original elements were fabricated by direct-write electron-beam lithography. Optical measurements and atomic force microscopy were used for investigating the replication fidelity.

Fredrik Nikolajeff; Stellan Jacobsson; Sverker Hård; Åke Billman; Lars Lundbladh; Curt Lindell

1997-01-01

62

Compatible Objective Lens for Blu-ray Disc and Degital Versatile Disc Using Diffractive Optical Element and Phase-Step Element which Corrects both Chromatic and Spherical Aberrations  

NASA Astrophysics Data System (ADS)

A compatible lens with a diffractive optical element that overcomes differences in disk thickness and longitudinal chromatic aberration and phase steps that eliminate chromatic spherical aberrations are proposed. Both blue and red parallel incident rays can be converged on both disks; therefore, the servo and readout signals can be detected by a single common photodetector. A compatible optical head, which can write Blu-ray Discs (BDs) and degital versatile discs (DVDs) with only one objective lens assembly and one photodetector, can be achieved. We show the convergence of the blue and red parallel incident rays and signal readout using the compatible objective lens.

Komma, Yoshiaki; Tanaka, Yasuhiro; Mizuno, Sadao

2004-07-01

63

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

64

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

65

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

PubMed Central

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

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

2000-01-01

66

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

PubMed

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

Goh, S; Tan, C; Price, R I; Edmondston, S J; Song, S; Davis, S; Singer, K P

2000-11-01

67

Two-stage feedforward tracking control system with error-based disturbance observer for optical discs  

NASA Astrophysics Data System (ADS)

Recently, the scaling up of the storage capacity and data transfer rate of digital storage media has been required. However, increasing in the storage capacity and transfer rate makes optical head control more difficult. Thus, a tracking control system for optical discs must exhibit a high degree of precision control. Consequently, a new two-stage feedforward control (TSFFC) system for high-precision control is proposed in this paper. The proposed system is constructed using two zero phase error tracking (ZPET) control systems based on error prediction and an error-based disturbance observer (EDOB) that uses a notch filter to suppress non periodic disturbances. The proposed control system is designed for DDU-1000 for digital versatile discs (DVDs). The experimental results demonstrate that the proposed system effectively suppresses tracking errors.

Sakimura, Naohide; Ohashi, Takahiro; Ohishi, Kiyoshi; Miyazaki, Toshimasa

2014-09-01

68

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

DOEpatents

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

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

2012-07-10

69

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

Microsoft Academic Search

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

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

1993-01-01

70

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

Microsoft Academic Search

Polarization-sensitive optical coherence tomography (PS-OCT) is used to measure the birefringence properties of bovine intervertebral disc and equine flexor tendon. For equine tendon the birefringence ?n is (6.0 0.2) 10?3 at a wavelength of 1.3 m. This is somewhat larger than the values reported for bovine tendon. The surface region of the annulus fibrosus of a freshly excised intact bovine

Stephen J Matcher; C Peter Winlove; Sergei V Gangnus

2004-01-01

71

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

NASA Astrophysics Data System (ADS)

The optic disc margin is of interest due to its use for detecting and managing glaucoma. We developed a method for segmenting the optic disc margin of the optic nerve head (ONH) in spectral-domain optical coherence tomography (OCT) images using a graph-theoretic approach. A small number of slices surrounding the Bruch's membrane opening (BMO) plane was taken and used for creating planar 2-D projection images. An edge-based cost function - more specifically, a signed edge-based term favoring a dark-to-bright transition in the vertical direction of polar projection images (corresponding to the radial direction in Cartesian coordinates) - was obtained. Information from the segmented vessels was used to suppress the vasculature influence by modifying the polar cost function and remedy the segmentation difficulty due to the presence of large vessels. The graph search was performed in the modified edge-based cost images. The algorithm was tested on 22 volumetric OCT scans. The segmentation results were compared with expert segmentations on corresponding stereo fundus disc photographs. We found a signed mean difference of 0.0058 +/- 0.0706 mm and an unsigned mean difference of 0.1083 +/- 0.0350 mm between the automatic and expert segmentations.

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

2009-02-01

72

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

73

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

PubMed

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

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

1979-01-01

74

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

75

Triplet collimator lens design of blu-ray disc optical pick-up  

NASA Astrophysics Data System (ADS)

During the design process of Blu-ray Disc Optical Pick-Up (BD OPU), the optical system design plays a significant role, and the collimator lens design is especially important. According to the PW optical design formulas, this paper calculates the initial parameters of collimator lens. It chooses the triplet type collimator lens instead of aspheric lens to design in order to reduce the manufacture difficulty according to the real situation in China. And then based on the initial parameters of collimator lens, the paper optimizes the triplet collimator lens to reach a good quality effect of parallel beam. At last it puts these design data into manufacture and adjusts the distance between the LD and the collimator lens by using the sleeve mechanism structure to see the real effect of collimating. Finally the assembly experiment of whole BD OPU validates these design that it can be used in BD OPU very well.

Li, Lihua; Lu, Junhui; Pan, Longfa; Ma, Jianshe

2008-12-01

76

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

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

77

Video Discs in Education.  

ERIC Educational Resources Information Center

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

Barker, Philip

1986-01-01

78

In vivo age- and sex-related creep of human lumbar motion segments and discs in pure centric tension.  

PubMed

In vivo creep of human lumbar motion segments and discs subject to pure centric tension is presented, in terms of aging, sex and disc level. Time-related elongations of segments L3-4, L4-5 and L5-S1 were measured during the usual 20 min long traction hydrotherapy of patients, by using a computerized subaqual ultrasound measuring method [Kurutz et al., 2002a. Orvosi Hetilap 143 (13), 673-684; Kurutz et al., 2003. Journal of Bioengineering and Biomechanics 5 (1), 67-92]. Elongation of segments was considered as a change of the distance between two adjacent spinous processes. Based on these experiments, in vivo creep of human lumbar FSUs was investigated in centric tension, in terms of sex, age and disc level. Three-parameter rheological models were used to determine viscoelastic tensile moduli of human lumbar FSUs and discs. From three time-related measured elongation values, in vivo damping constants with creep functions were calculated for each segment, in terms of sex, aging and disc level. It has been demonstrated that initial elastic elongations decrease, concerning stiffness increase with aging. Similarly, tensile creep elongations decrease, damping properties increase with aging. Former observations concerning the difference in deformation propagation of men and women in time, have been verified by means of creep analysis: although males have higher initial elastic deformability, due to a smaller damping of females, the deformation propagation of women overtakes men in creep process. This tendency is more significant with aging. Increasing damping was observed in distal direction, both for males and females. PMID:15925372

Kurutz, Marta

2006-01-01

79

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

PubMed

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

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

2012-01-01

80

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

PubMed Central

Purpose. To compare stereometric parameters obtained by three-dimensional (3D) optic disc photography and optical coherence tomography (OCT) and assess interobserver agreement on the disc damage likelihood scale (DDLS). Methods. This retrospective study included 190 eyes from 190 patients classified as normal, glaucoma suspect, or glaucomatous. Residents at different levels of training completed the DDLS for each patient before and after attending a training module. 3D optic disc photography and OCT were performed on each eye, and correlations between the DDLS and various parameters obtained by each device were calculated. Results. We found moderate agreement (weighted kappa value, 0.59?±?0.03) between DDLS scores obtained by 3D optic disc photography and the glaucoma specialist. The weighted kappa values for agreement and interobserver concordance increased among residents after the training module. Interobserver concordance was the poorest at DDLS stages 5 and 6. The DDLS scored by the glaucoma specialist had the highest predictability value (0.941). Conclusions. The DDLS obtained by 3D optic disc photography is a useful diagnostic tool for glaucoma. A supervised teaching program increased trainee interobserver agreement on the DDLS. DDLS stages 5 and 6 showed the poorest interobserver agreement, suggesting that caution is required when recording these stages. PMID:24804081

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

2014-01-01

81

Comparing acromegalic patients to healthy controls with respect to intraocular pressure, central corneal thickness, and optic disc topography findings  

PubMed Central

Aims: The aim was to compare the intraocular pressure (IOP), central corneal thickness (CCT), and optic disc topography findings of biochemically controlled acromegalic patients and the control group and to evaluate the effect of the duration of acromegaly and serum growth hormone and insulin-like growth factor-1 (IGF-1) levels on these ocular parameters. Materials and Methods: IOP measurement with Goldmann applanation tonometry, CCT measurement with ultrasonic pachymetry, and topographic analysis with Heidelberg retinal tomograph III were performed on 35 biochemically controlled acromegalic patients and 36 age- and gender-matched controls. Results: Mean IOP and CCT were 14.7 ± 2.9 mmHg and 559.5 ± 44.9 ?m in the acromegaly patients and 13.0 ± 1.6 mmHg and 547.1 ± 26.7 ?m in controls (P = 0.006 and P = 0.15, respectively). A significant moderate correlation was found between the duration of acromegaly and CCT (r = 0.391) and IOP (r = 0.367). Mean retinal nerve fiber layer (RNFL) thickness was significantly lower in the acromegalic patients (0.25 ± 0.05 mm) as compared to controls (0.31 ± 0.09 mm) (P = 0.01). A significant moderate correlation was detected between IGF-1 level and disc area (r = 0.362), cup area (r = 0.389) and cup volume (r = 0.491). Conclusion: Biochemically controlled acromegalic patients showed significantly higher CCT and IOP levels and lower RNFL thickness compared to healthy controls and the duration of disease was correlated with CCT and IOP levels. PMID:25230958

Sen, Emine; Tutuncu, Yasemin; Elgin, Ufuk; Balikoglu-Yilmaz, Melike; Berker, Dilek; Aksakal, F. Nur; Ozturk, Faruk; Guler, Serdar

2014-01-01

82

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

Microsoft Academic Search

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

Viranee Thongnuch; Bunyarit Uyyanonvara

83

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

PubMed Central

AIM To evaluate concordance between the clinical assessment of glaucomatous progression of the optic disc photography and progression identified by Heidelberg Retina Tomograph (HRT) in patients with suspected primary juvenile open angle glaucoma (JOAG). METHODS Optic disc photographs and corresponding HRT II series were reviewed. Optic disc changes between first and final photographs were noted as well as progression identified by HRT topographic change analysis (TCA) and rim area regression line (RARL) Agreement between progression indentified by photography and HRT methods was assessed. Progression, determined from optic disc photographs by consensus assessment was used as the reference standard. RESULTS A total of 31 patients (59 eyes) with suspected JOAG were studied. Agreement for progression/no progression between TCA and photography was obtained in 4 progressing eyes and 38 stable eyes (71.19%, k=0.11). Agreement for progression/no progression between RARL and photography was detected in 5 progressing eyes and in 34 stable eyes (66.10%, k=0.15). The number of HRT per patient was statistically higher in the progressing group (P=0.034). CONCLUSION Agreement for detection of longitudinal changes between photography and HRT analysis was poor. One way to improve the chance of discovery of the progression could be increasing the number of HRT examinations. PMID:24967194

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

2014-01-01

84

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

Microsoft Academic Search

Optic disc (OD) detection is an important step in developing systems for automated diagnosis of various serious ophthalmic pathologies. This paper presents a new template-based methodology for segmenting the OD from digital retinal images. This methodology uses morphological and edge detection techniques followed by the Circular Hough Transform to obtain a circular OD boundary approximation. It requires a pixel located

Arturo Aquino; Manuel Emilio Gegúndez-Arias; Diego Marin

2010-01-01

85

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

86

Completely Erasable Phase Change Optical Disc II: Application of Ag-In-Sb-Te Mixed-Phase System for Rewritable Compact Disc Compatible with CD-Velocity and Double CD-Velocity  

Microsoft Academic Search

Aiming to obtain a rewritable compact disc (CD-rewritable) with high performance at both CD-velocity (CD1X) and double CD-velocity (CD2X), the phase change optical disc with the Ag-In-Sb-Te system has been developed. In the one-pass overwriting mode with eight-to-fourteen modulation, high carrier-to-noise ratio, wide power margin and high erase ratio have been obtained at both velocities. As for stability, we acquired

Hiroko Iwasaki; Makoto Harigaya; Osamu Nonoyama; Yoshiyuki Kageyama; Masaetsu Takahashi; Katsuyuki Yamada; Hiroshi Deguchi; Yukio Ide

1993-01-01

87

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

88

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

PubMed Central

Purpose: To evaluate the morphology of optic discs in eyes suffering from retinal vein occlusion (RVO) alone or in combination with primary open-angle glaucoma (POAG). Methods: Prospective, observational study. 48 consecutive patients were enrolled, 30 with unilateral RVO diagnosis, 18 with unilateral retinal vein occlusion (RVO) associated with POAG. We divided RVOs on the basis of occlusion site: arterio-venous crossing (AV-RVO), optic cup (OC-RVO), optic nerve (ON-RVO) with head nerve swelling (ONHS-RVO) or without it (NONHS-RVO). A control group of 25 patients who were sex and age matched was selected. Results: Comparing the fellow eyes of the patients with RVO and control healthy eyes, no differences emerged in cup/disc ratio but they came out for the HRT values in Rim Area, cup shape measure and height variation contour (p<0.05). The most frequent occlusion site was at the level of an arteriovenous crossing in patients not suffering from POAG (36.7%) and at the level of the optic cup in patients with RVO and POAG (50%). In the RVO group without POAG, the OC-RVO subgroup has shown an higher cup area (0.366±0.094) and cup/disc area ratio (0.184±0.063), a lower rim volume (0.374±0.021) and a different cup shape measure (-0.221±0.066) (p<0.05) compared with the AV and NONHS sites. Compared with NONHS group differences emerged also for the fibres parameters and in the height variation contour (0.346±0.081). Also in the RVO group with POAG significant differences (p<0.05) have been surveyed between OC-RVO and other occlusion sites in cup area (0.119±0.029), cup/disc area ratio (0.532±0.09), rim volume (0.374±0.07), cup/shape measure (-0.079±0.013). Conclusions: Classification of the analyzed parameters on the basis of the occlusion site provides a basis for which clinical decisions and research on causal factors in future studies can be based on. PMID:23961303

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

2013-01-01

89

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

Microsoft Academic Search

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

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

1999-01-01

90

Macular and optic disc edema and retinal vascular leakage in familial amyloid polyneuropathy with a transthyretin Val30Met mutation: a case report  

PubMed Central

Introduction Familial amyloid polyneuropathy is a group of autosomal dominant disorders characterized by extracellular amyloid deposition in several target organs. This paper aims to report an unusual manifestation of retinal vascular leakage including optic disc and macular edema in a patient with familial amyloid polyneuropathy. Case presentation A 37-year-old Portuguese Caucasian man with Val30Met transthyretin-related familial amyloid polyneuropathy presented with rapidly progressing visual loss in his left eye. He had undergone liver transplantation at the age of 30 with neurologic stabilization. Fundoscopy and fluorescein angiogram revealed optic disc and macular edema as well as vessel wall staining with leakage in the posterior pole and mid-periphery, without vitreous opacities. A diagnostic work-up for infectious, autoimmune and neoplasic conditions was negative. Systemic immunosuppression was increased but without improvement. Sustained resolution of macular edema was observed after intravitreal injection of dexamethasone implant and laser panretinal photocoagulation. Conclusions To the best of our knowledge, this is the first report of a rare ocular manifestation of familial amyloid polyneuropathy which represents a new therapeutic challenge. Intravitreal injection of sustained release dexamethasone implant and panretinal photocoagulation may be an effective eye-saving therapeutic approach. PMID:25282612

2014-01-01

91

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

92

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

PubMed Central

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

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

2014-01-01

93

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

94

Impact of sintering temperature on the structural, electrical, and optical properties of doped ZnO nanoparticle-based discs  

NASA Astrophysics Data System (ADS)

In the current study, 20 nm zinc oxide (ZnO) nanoparticles were used to make high-density ZnO discs doped with Bi2O3 and Mn2O3 via the conventional ceramic processing method. Different sintering temperatures were found to have significant impacts on the ZnO discs, especially on enhancing grain growth even at a low sintering temperature of only 980 °C. The strong solid-state reaction during sintering may be attributed to the high surface area of the 20 nm ZnO nanoparticles that promoted a strong surface reaction even at low sintering temperatures. Moreover, the sintering process also improved the grain crystallinity, as shown in the lowering of the intrinsic compressive stress based on the X-ray diffraction lattice constant and full-wave half-maximum data. The sintering temperatures also significantly influenced the electrical properties of the doped ZnO discs with a marked drop in the breakdown voltage from 330 V (sample at 980 °C) to 80 V (sample at 1380 °C). The resistivity also experienced a dramatic drop from 304.4 k? cm (sample at 980 °C) to 98.86 k? cm (sample at 1380 °C). The observed shift in the energy band-gap from a higher to a lower value may be attributed to the conversion of compressive stress to tensile stress with increasing sintering temperature. The Raman spectra indicate that the sintering temperatures and dopants in the discs had significant effects on the E2(high) phonon mode and ZnO crystal structures. Therefore, the sintering process can be used as a new technique for controlling the breakdown voltage of doped ZnO discs made from ZnO nanoparticles with improved structural and optical properties.

Sendi, Rabab Khalid; Mahmud, Shahrom

2012-11-01

95

Ultrahigh-Sensitivity Biomarker Sensing System Based on the Combination of Optical Disc Technologies and Nanobead Technologies  

NASA Astrophysics Data System (ADS)

The detection of biomarkers in body fluids is useful for the early detection of diseases or preventive medical care. Various types of equipment that detect biomarkers have been developed and used for various occasions. It is expected that further improvement of the detection sensitivity of biomarkers will enable the extension for their applications to various diseases. In this paper, we propose a new biomarker sensing system with higher sensitivity. In the system, by combining optical disc technologies and nanobead technologies, we developed a new sensing method. Target biomarkers are specifically immobilized onto the optical disc surface through an antigen-antibody reaction, then the nanobeads are immobilized on top of the biomarkers. Since the biomarkers and beads bind to each other one-on-one, the number of target biomarkers can be measured by counting the number of nanobeads using an optical pickup. The most significant advantage of this method is that measurement can be carried out in a fully digital scheme, in contrast to current sensing systems which measure light intensity in an analog scheme.

Tsujita, Koji; Hasegawa, Yuichi; Ono, Masayuki; Itonaga, Makoto; Sakamoto, Satoshi; Hatakeyama, Mamoru; Handa, Hiroshi

2013-09-01

96

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

Microsoft Academic Search

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

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

2000-01-01

97

Malignant transformation of optic disc melanocytoma? A clinical dilemma at presentation with a review of the literature.  

PubMed

Malignant transformation of optic disc melanocytoma is an uncommon feature, although in the past a few cases have been reported. Though our case, a healthy 30-year-old female, presented with all clinical features of melanocytoma, the triad of moderate visual loss, elevation of the lesion of 5.2 mm and an atypical ultrasonic picture could be an indication of malignant change at presentation. In the event of a moderate visual loss, long-term follow-up with serial fundus photographs and ultrasonic measurements is necessary for further management. PMID:12207136

Sharma, Parul M; Sangal, Kartikeya; Malik, Praveen; Mathur, M B

2002-01-01

98

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

NASA Astrophysics Data System (ADS)

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

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

2006-03-01

99

TNF-alpha-induced NF-kappaB signaling reverses age-related declines in VEGF induction and angiogenic activity in intervertebral disc tissues.  

PubMed

We previously demonstrated that VEGF and its receptors were expressed in human herniated discs (HD). TNF-alpha induced VEGF, resulting in neovascularization of disc tissues in a model of HD. The goal of the current research was to investigate the precise role of TNF-alpha-induced VEGF and the mechanism of angiogenesis in disc tissues. We performed ELISAs, Western blots, and immunohistological examinations to assess the role of TNF-alpha-induced VEGF using organ disc cultures with wild type, TNF receptor 1-null (TNF-RI(null)), or TNF receptor 2-null (TNF-RII(null)) mice. VEGF induction was inhibited when we used TNF-RI(null)-derived disc tissues. NF-kappaB pathway inhibitors also strongly suppressed VEGF induction. Thus, TNF-alpha induced VEGF expression in disc cells primarily through the NF-kappaB pathway. In addition, VEGF immunoreactivity was detected predominantly in annulus fibrosus cells and increased after TNF-alpha stimulation. TNF-alpha treatment also resulted in CD31 expression on endothelial cells and formation of an anastomosing network. In contrast, angiogenic activity was strongly inhibited in the presence of NF-kappaB inhibitors or anti-VEGF antibody. Our data show angiogenesis activity in disc tissues is regulated by VEGF and the NF-kappaB pathway, both of which are induced by TNF-alpha. The level of angiogenic activity in disc tissues was closely related to aging. Because neovascularization of HD is indispensable for HD resorption, the prognosis of HD and the rate of the resorption process in patients may vary as a function of the patient's age. PMID:18683887

Ohba, Tetsuro; Haro, Hirotaka; Ando, Takashi; Wako, Masanori; Suenaga, Fumiko; Aso, Yoshinori; Koyama, Kensuke; Hamada, Yoshiki; Nakao, Atsuhito

2009-02-01

100

Finite conjugate spherical aberration compensation in high numerical-aperture optical disc readout  

E-print Network

.) With a spacing of the two layers of a BD double-layer disc of 25 m the amount of spher- ical aberration is 126 m of a double-layer BD, and into a second state when data are read from or writ- ten to the lower layer of a double-layer BD. The most straightforward way of compensating for spherical aberration is to use finite

Stallinga, Sjoerd

101

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

NASA Astrophysics Data System (ADS)

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

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

2009-02-01

102

Lumbar Disc Herniation in Adolescence  

Microsoft Academic Search

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

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

2007-01-01

103

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

ERIC Educational Resources Information Center

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

Wilson, Kathleen S.

104

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

ERIC Educational Resources Information Center

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

Fulton, Alan R.

1990-01-01

105

Holographic versatile disc system  

NASA Astrophysics Data System (ADS)

A Holographic Versatile Disc (HVD) system, using Collinear Technologies for a high capacity and high data transfer rates storage system, is proposed. With its unique configuration the optical pickup can be designed as small as a DVD's, and can be placed on one side of the disc. With the HVD's special structure, the system can servo the focus/track and locate reading/writing address. A unique selectable capacity recording format of HVD and its standardization activity are also introduced. Experimental and theoretical studies suggest that the tilt, wavelength, defocus and de-track margins are wide enough to miniaturize the HVD system at a low cost. HVD systems using Collinear Technologies will be compatible with existing disc storage systems, like CD and DVD, and will enable us to expand its applications into other optical information storage systems.

Horimai, Hideyoshi; Tan, Xiaodi

2005-09-01

106

Estrogen deficiency accelerates aging of the optic nerve  

PubMed Central

Objective To provide a comprehensive review on hormone-based pathophysiology of aging of the optic nerve and glaucoma. Methods A literature review and expert opinions. Results Glaucoma, a group of intraocular pressure-related optic neuropathies, is characterized by the slow progressive neurodegeneration of retinal ganglion cells and their axons resulting in irreversible visual sensitivity loss and blindness. Increasing evidence suggests that glaucoma represents the accelerated aging of the optic nerve and is a neurodegenerative disease of the central nervous system. This review highlights the high burden of glaucoma in elderly women and the importance of understanding the hormone-related pathophysiology of optic nerve aging and glaucoma in women. Conclusions Strong epidemiological, clinical, and experimental evidence supports the proposed hypothesis that the early loss of estrogen leads to premature aging and increased susceptibility of the optic nerve to glaucomatous damage. Future investigations into the hormone-related mechanisms of aging and glaucoma will support the development of novel sex-specific preventive and therapeutic strategies in glaucoma. PMID:22415565

Vajaranant, Thasarat S.; Pasquale, Louis R.

2012-01-01

107

Ageing of the nonlinear optical susceptibility in soft matter  

NASA Astrophysics Data System (ADS)

We investigate the nonlinear optics response of a colloidal dispersion undergoing dynamics slowing down with age, by using Z-scan and dynamic light scattering measurements. We study the high optical nonlinearity of an organic dye (rhodamine B) dispersed in a water-clay (laponite) suspension. We consider different clay concentrations (2.0-2.6 wt%) experiencing dynamics arrest. We find that (i) the concentration dependent exponential growth of both mean relaxation time and nonlinear absorption coefficient can be individually scaled to a master curve and (ii) the scaling times are the same for the two physical quantities. These findings indicate that the optical nonlinear susceptibility exhibits the same ageing universal scaling behaviour, typical of disordered out of equilibrium systems.

Ghofraniha, N.; Conti, C.; Di Leonardo, R.; Ruzicka, B.; Ruocco, G.

2007-05-01

108

Learning Language on Disc.  

ERIC Educational Resources Information Center

Presents a comparison of two types of compact disc (CD-ROM) foreign language tutorials: (1) those made by publishers who favor an immersion approach; and (2) those made by publishers who use grammar-based approaches. Both types of CD-ROMs address various age groups, skill levels, and learning styles. (JMV)

Desmarais, Norman

1995-01-01

109

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

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

110

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

111

Aging of the Nonlinear Optical Susceptibility of colloidal solutions  

E-print Network

Using Z-scan and dynamic light scattering measurements we investigate the nonlinear optics response of a colloidal solution undergoing dynamics slowing down with age. We study the high optical nonlinearity of an organic dye (Rhodamine B) dispersed in a water-clay (Laponite) solution, at different clay concentrations (2.0 wt% - 2.6 wt%), experiencing the gelation process. We determine the clay platelets self diffusion coefficient and, by its comparison with the structural relaxation time, we conclude that the gelation process proceeds through the structuring of interconnecting clay platelets network rather than through clusters growth and aggregation.

Neda Ghofraniha; Claudio Conti; Giancarlo Ruocco

2006-09-26

112

Aging of the nonlinear optical susceptibility in doped colloidal suspensions  

NASA Astrophysics Data System (ADS)

Using Z -scan and dynamic light-scattering measurements, we investigate the nonlinear optical response of a colloidal solution undergoing dynamics slowing down with age. We study the high optical nonlinearity of an organic dye (Rhodamine B) dispersed in a water-clay (Laponite) solution, at different clay concentrations (2.0-2.6wt%) , experiencing the gelation process. We determine the clay platelet self-diffusion coefficient and, by its comparison with the structural relaxation time, we conclude that the gelation process proceeds through the structuring of interconnecting clay platelet network rather than through cluster growth and aggregation.

Ghofraniha, Neda; Conti, Claudio; Ruocco, Giancarlo

2007-06-01

113

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

114

Chemical and optical changes to black carbon during aging  

NASA Astrophysics Data System (ADS)

Black carbon (BC) is the second most important contributor to global warming. Due to its short atmospheric lifetime (~days), reductions in BC may be one of the fastest mechanisms to reduce warming. Recent field measurements indicate that BC is a chemically and physically dynamic atmospheric constituent, suggesting that radiative forcing effects of BC may evolve quickly (on the timescale of hours) in the atmosphere. The specifics of how (and even if) the radiative forcing potential of BC changes as it ages, however, is currently under debate, thus leading to significant uncertainties on the magnitude of BC contribution to radiative forcing. We attempt to help constrain this uncertainty using a series of laboratory measurements that systematically study the aging process of BC. These laboratory measurements are carried out using a photo-oxidation chamber and an extensive suite of measurements including an Aerodyne Soot-Particle Aerosol Mass Spectrometer (SP-AMS) and measurements of aerosol optical properties. Using this instrument suite, we characterize how the chemical and optical properties of BC change as it is aged heterogeneously (by OH and ozone) and as it is coated by organic material.

Browne, E. C.; Franklin, J. P.; Kroll, J. H.

2013-12-01

115

Janus discs.  

PubMed

We describe the synthesis and the solution properties of sheet- and disclike Janus particles, containing an inner crosslinked polybutadiene (PB) layer and two different outer sides of polystyrene (PS) and poly(tert-butyl methacrylate) (PtBMA). The structures formed upon adsorption of the flat Janus particles onto solid substrates as well as in THF solution are investigated. The Janus discs are obtained in a template-assisted synthetic pathway followed by sonication. Selectively crosslinking the lamellar PB domains in a well-ordered lamellar microphase-separated bulk morphology of PS-block-PB-block-PtBMA (SBT) block terpolymers leads to the conservation of the compartmentalization of the two outer blocks. Sonication of the crosslinked block terpolymer templates renders soluble sheet- and disclike Janus particles, the size of which can be tuned from the micrometer range down to the nanometer scale. Small-angle X-ray scattering, transmission electron microscopy, dynamic light scattering, scanning force microscopy, and scanning electron microscopy are used to characterize the template-assisted synthetic process and the solution properties. Cryogenic transmission electron microscopy in THF and TEM of particles, embedded into a photo-crosslinkable silicon oil, indicate a supramolecular aggregation behavior of the Janus discs in concentrated solutions. Pendant drop tensiometry demonstrates that Janus sheets and discs can be used to stabilize liquid-liquid interfaces, rendering these materials interesting for future applications. PMID:17441717

Walther, Andreas; André, Xavier; Drechsler, Markus; Abetz, Volker; Müller, Axel H E

2007-05-16

116

Color naming, lens aging, and grue: What the optics of the aging eye can teach us about color language  

E-print Network

) propose that this correlation is caused by premature lens aging. When younger observers view simulated, 1988). Individuals experiencing premature lens aging would receive less short-wavelength light1 Color naming, lens aging, and grue: What the optics of the aging eye can teach us about color

Kay, Paul

117

Recording of MultiLevel Run-Length-Limited Modulation Signals on Compact Disc\\/Digital Versatile Disc Rewritable Discs  

Microsoft Academic Search

Multi-level (ML) recording technology increases the capacity of standard compact disc (CD) and digital versatile disc (DVD) rewritable systems with no change to the optical\\/mechanical unit. The feasibility of applying ternary run-length-limited (3L-RLL) modulation to recording\\/playback on standard CD\\/DVD phase change discs is discussed. The use of 3L-RLL modulation increases the recording density 50% relative to conventional binary RLL (2L-RLL)

Feng-Hsiang Lo; Ji-Wen Kuo; Nai-Heng Tseng; Jau-Jiu Ju; Dennis Howe

2004-01-01

118

Lens Thickness with Age and Accommodation by Optical Coherence Tomography  

PubMed Central

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

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

2010-01-01

119

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

120

Chemical and optical aging of forest fire plumes  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

121

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

PubMed

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

Shahbeig, Saleh; Pourghassem, Hossein

2013-01-01

122

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

NASA Astrophysics Data System (ADS)

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

Popescu, Cristina C.; Tuffs, Richard J.

2013-12-01

123

Congenital disorders of the optic nerve: excavations and hypoplasia  

Microsoft Academic Search

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

G N Dutton

2004-01-01

124

Broken discs: warp propagation in accretion discs  

NASA Astrophysics Data System (ADS)

We simulate the viscous evolution of an accretion disc around a spinning black hole. In general, any such disc is misaligned, and warped by the Lense-Thirring effect. Unlike previous studies, we use effective viscosities constrained to be consistent with the internal fluid dynamics of the disc. We find that non-linear fluid effects, which reduce the effective viscosities in warped regions, can promote breaking of the disc into two distinct planes. This occurs when the Shakura & Sunyaev dimensionless viscosity parameter ? is ?0.3 and the initial angle of misalignment between the disc and hole is ?45°. The break can be a long-lived feature, propagating outwards in the disc on the usual alignment time-scale, after which the disc is fully co-aligned or counter-aligned with the hole. Such a break in the disc may be significant in systems where we know the inclination of the outer accretion disc to the line of sight, such as some X-ray binaries: the inner disc, and so any jets, may be noticeably misaligned with respect to the orbital plane.

Nixon, Christopher J.; King, Andrew R.

2012-04-01

125

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

126

Intervertebral disc degeneration: evidence for two distinct phenotypes  

PubMed Central

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

Adams, Michael A; Dolan, Patricia

2012-01-01

127

Three dimensional SPH simulations of radiation-driven warped accretion discs  

Microsoft Academic Search

We present three dimensional smoothed particle hydrodynamics (SPH) calculations of warped accretion discs in X-ray binary systems. Geometrically thin, optically thick accretion discs are illuminated by a central radiation source. This illumination exerts a non-axisymmetric radiation pressure on the surface of the disc resulting in a torque that acts on the disc to induce a twist or warp. Initially planar

Stephen B. Foulkes; Carole A. Haswell; James D. Murray

2006-01-01

128

Laser diode array pumped Yb:YAG/BIBO 515 nm thin disc laser with four-pass optical coupling system  

NASA Astrophysics Data System (ADS)

We presented a new simple flat-concave cavity system to produce compact and low-cost 515 nm laser, and the validity has been demonstrated. The Yb:YAG crystal with 10% concentration was 300 ?m thickness and 10 mm in diameter. The four-pass optical coupling system was well designed with two spherical imaging mirrors (? = 30 mm, R = 50 mm). Taking into account mode matching, the pump-spot radius in the laser crystal was calculated by LightTools software. The 2 × 2 × 1.5 mm3 BIBO crystal cutting at a type-I phase-matching direction of (?, ?) = (166.8°, 90°) was employed. With 4.4 W incident power, the maximum output power of 14.3 mW at 515 nm was obtained without optimization of soldering technique, and the single-frequency phenomenon was first observed when the output power was 3 mW.

Tian, Y. B.; Tian, Z. H.; Tan, H. M.; Liu, X. Y.

2010-04-01

129

Are the determinants of vertebral endplate changes and severe disc degeneration in the lumbar spine the same? A magnetic resonance imaging study in middle-aged male workers  

Microsoft Academic Search

BACKGROUND: Modic changes are bone marrow lesions visible in magnetic resonance imaging (MRI), and they are assumed to be associated with symptomatic intervertebral disc disease, especially changes located at L5-S1. Only limited information exists about the determinants of Modic changes. The objective of this study was to evaluate the determinants of vertebral endplate (Modic) changes, and whether they are similar

Mari Kuisma; Jaro Karppinen; Marianne Haapea; Jaakko Niinimäki; Risto Ojala; Markku Heliövaara; Raija Korpelainen; Kaisu Kaikkonen; Simo Taimela; Antero Natri; Osmo Tervonen

2008-01-01

130

Prevalence of radiographic detectable intervertebral disc calcifications in Dachshunds surgically treated for disc extrusion  

PubMed Central

Background An association between the occurrence of calcified discs, visible on radiographic examination (CDVR), and disc extrusions has been suggested in published literature over the past 10-20 years, mainly from Nordic countries. It has also been postulated that dogs without CDVR would not develop disc extrusions. Furthermore, inheritance of CDVR has been calculated and it has been postulated that, by selecting dogs for breeding with few, or no CDVR, the prevalence of disc extrusions in the Dachshund population may be reduced. Methods The prevalence of radiographic detectable intervertebral disc calcifications was calculated from one hundred surgeries for disc extrusion, performed in 95 Dachshunds, in order to determine if the disc causing clinically significant IVDD, had radiographic signs of calcification at the time of confirmed disc extrusion. Inclusion criteria, for each dog, included a complete physical, orthopedic and neurologic examination, radiographs of the entire vertebral column, a myelogram or magnetic resonance imaging examination indicating extradural spinal cord compression, and finally a surgical procedure confirming the diagnosis of a disc extrusion. In addition to descriptive statistics, age correlation with number of calcifications visible at radiographic examination and with CDVR at the surgery site was examined. Results We found that disc extrusions occur as frequently in discs that are found to have radiographic evidence of calcification as those discs that do not have signs of radiographic calcification, and that IVDD (intervertebral disc disease) requiring surgery does occur in the absence of any calcified discs on radiographic examination. We found that calcified discs were more frequent in our Dachshund population compared to previous studies suggesting that disc calcification might be a serious risk factor for developing disc extrusion. Further studies are needed to show, conclusively, if selection of breeding dogs based on CDVR in the Dachshund will reduce the incidence of IVDD. The presence of the calcifications of intervertebral disc should be evaluated with caution, as only part of the calcifications will be detected and the real extent of the disc degeneration may be underestimated. PMID:20398282

2010-01-01

131

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

132

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

133

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

134

Artificial Discs for Lumbar and Cervical Degenerative Disc Disease -Update  

PubMed Central

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

2006-01-01

135

Spectroscopic Parameters of Lumbar Intervertebral Disc Material  

NASA Astrophysics Data System (ADS)

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

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

2009-06-01

136

Childhood intervertebral disc calcification  

Microsoft Academic Search

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

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

1993-01-01

137

Juvenile intervertebral disc calcification  

Microsoft Academic Search

Juvenile intervertebral disc calcification is a rare but well described disorder of childhood. The syndrome consists of specific roentgenologic changes: calcification of nucleus pulposus in the intervertebral discs and occasional flattening and anterior wedging of the adjacent vertebral bodies. These changes can be accompanied by clinical symptoms such as neck pain, torticollis, general malaise and slight fever. The etiology and

Lisbet Rosenkrantz Grage; Mogens Egeblad

1992-01-01

138

Dark Matter in Disc Galaxies  

E-print Network

Recent work on the mass distribution in spiral galaxies, using mainly HI observations, is reviewed. The principal problem is still to determine to what extent the dark matter is important in the inner parts of a galaxy, or in other words, how dominant is the self-gravitation of the disc. Studies of the shapes of rotation curves show that in detail there is sufficient individuality in spiral galaxies to prohibit the construction of ``Universal Rotation Curves''. A detailed account is given of the method of Athanassoula et al. (1987), where swing amplifier criteria are applied to set a range in the mass-to-light ratio of the disc. To restrict this range further, other methods might be useful. For a number of bright spirals the rotation curve drops just outside the optical image, but this feature by itself cannot constrain unambiguously the mass models. The use of velocity dispersions seems a promising way, though the observational problems are hard. Within the uncertainties, discs can be close to ``maximum'', even though a range of values cannot be excluded.

A. Bosma

1998-12-01

139

A simple model for the evolution of disc galaxies: The Milky Way  

E-print Network

A simple model for the evolution of disc galaxies is presented. We adopt three numbers from observations of the Milky Way disc, the local surface mass density, the stellar scale length (of the assumedly exponential disc) and the amplitude of the (assumedly flat) rotation curve, and physically, the (local) dynamical Kennicutt star formation prescription, standard chemical evolution equations assuming and a model for spectral evolution of stellar populations. We can determine the detailed evolution of the model with only the addition of standard cosmological scalings with time of the dimensional parameters. A surprising wealth of detailed specifications follows from this prescription including the gaseous infall rate as a function of radius and time, the distribution of stellar ages and metallicities with time and radius, surface brightness profiles at different wavelengths, colours etc. At the solar neighbourhood stars start to form $\\approx 10 Gyrs$ ago at an increasing rate peaking 4 billion years ago and then slowly declining in good agreement with observations. The mean age of long lived stars at the solar neighbourhood is about $4 Gyrs$. The local surface density of the stars and gas are 35 and $15 M_{\\odot}pc^{-2}$, respectively. The metallicity distribution of the stars at the solar radius is narrow with a peak at $[Z/Z_{\\odot}] = -0.1$.Both a Salpeter IMF and a Chabrier IMF are consistent with observations. Comparisons with the current and local fossil evidence provides support for the model which can then be used to assess other local disc galaxies, the evolution of disc galaxies in deep optical surveys and also for theoretical investigations such as simulations of merging disc galaxies (abbreviated).

Thorsten Naab; Jeremiah P. Ostriker

2005-05-30

140

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

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

141

Accelerated-aging tests of fiber Bragg gratings written in hydrogen loaded tapered optical fibers  

NASA Astrophysics Data System (ADS)

In this paper we show preliminary experimental studies on accelerated aging-tests of tapered fiber Bragg gratings (TFBG). Examined gratings were fabricated on tapered and then hydrogenated optical fibers using uniform phase mask and scanning technique. In particular, the impact of isothermal annealing of TFBGs on their spectral and dispersion characteristics was analyzed. Experimental results show that although reflectance levels of TFBGs significantly reduce due to the aging process, slopes of the group delay characteristics remain practically unchanged. New knowledge on spectral and dispersion characteristics of TFBGs written in hydrogen loaded optical fibers is important in possible applications, where long-term stability and reliability is required.

Osuch, Tomasz; Herman, Dorota; Markowski, Konrad; Jedrzejewski, Kazimierz

2014-05-01

142

Cell transplantation in lumbar spine disc degeneration disease  

Microsoft Academic Search

Low back pain is an extremely common symptom, affecting nearly three-quarters of the population sometime in their life. Given\\u000a that disc herniation is thought to be an extension of progressive disc degeneration that attends the normal aging process,\\u000a seeking an effective therapy that staves off disc degeneration has been considered a logical attempt to reduce back pain.\\u000a The most apparent

C. Hohaus; T. M. Ganey; Y. Minkus; H. J. Meisel

2008-01-01

143

Discovery of the Fomalhaut C debris disc  

NASA Astrophysics Data System (ADS)

Fomalhaut is one of the most interesting and well-studied nearby stars, hosting at least one planet, a spectacular debris ring and two distant low-mass stellar companions (TW PsA and LP 876-10, a.k.a. Fomalhaut B and C). We observed both companions with Herschel, and while no disc was detected around the secondary, TW PsA, we have discovered the second debris disc in the Fomalhaut system, around LP 876-10. This detection is only the second case of two debris discs seen in a multiple system, both of which are relatively wide (?3000 au for HD 223352/40 and 158 kau [0.77 pc] for Fomalhaut/LP 876-10). The disc is cool (24 K) and relatively bright, with a fractional luminosity Ldisc/L? = 1.2 × 10-4, and represents the rare observation of a debris disc around an M dwarf. Further work should attempt to find if the presence of two discs in the Fomalhaut system is coincidental, perhaps simply due to the relatively young system age of 440 Myr, or if the stellar components have dynamically interacted and the system is even more complex than it currently appears.

Kennedy, G. M.; Wyatt, M. C.; Kalas, P.; Duchêne, G.; Sibthorpe, B.; Lestrade, J.-F.; Matthews, B. C.; Greaves, J.

2014-02-01

144

Dispersion in the lifetime and accretion rate of T Tauri discs  

E-print Network

We compare evolutionary models for protoplanetary discs that include disc winds with observational determinations of the disc lifetime and accretion rate in Taurus. Using updated estimates for stellar ages in Taurus, together with published classifications, we show that the evolution of the disc fraction with stellar age is similar to that derived for ensembles of stars within young clusters. Around 30 percent of stars lose their discs within 1 Myr, while the remainder have disc lifetimes that are typically in the 1-10 Myr range. We show that the latter range of ages is consistent with theoretical models for disc evolution, provided that there is a dispersion of around 0.5 in the log of the initial disc mass. The same range of initial conditions brackets the observed variation in the accretion rate of Classical T Tauri stars at a given age. We discuss the expected lifetime of discs in close binary systems, and show that our models predict that the disc lifetime is almost constant for separations exceeding 10 au. This implies a low predicted fraction of binaries that pair a Classical T Tauri star with a Weak-lined T Tauri star, and is in better agreement with observations of the disc lifetime in binaries than disc models that do not include disc mass loss in a wind.

Philip J. Armitage; Cathie J. Clarke; Francesco Palla

2003-03-14

145

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

Microsoft Academic Search

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

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

2000-01-01

146

Herniated Lumbar Disc  

MedlinePLUS

... be treated with nonprescription medications such as aspirin, ibuprofen, naproxen or acetaminophen. If you have severe persistent ... a result of disc herniation. These include asprin, ibuprofen, naproxen and a variety of prescription drugs. If ...

147

Prevalence of lumbar disc degeneration observed by magnetic resonance in symptomless women.  

PubMed

302 women aged 16-80 without symptoms of spinal disease had their lumbar intervertebral discs examined by magnetic resonance. The prevalence of one or more degenerate discs increased linearly with age but disc degeneration was already present in over one-third of women aged 21-40; these young women may prove to be at special risk of disc prolapse later in life. The high prevalence of symptomless disc degeneration must be taken into account when magnetic resonance is used for assessment of spinal symptoms. PMID:2878228

Powell, M C; Wilson, M; Szypryt, P; Symonds, E M; Worthington, B S

1986-12-13

148

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

149

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

PubMed Central

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

Wenger, Markus; Markwalder, Thomas-Marc

2010-01-01

150

Strength degradation and recovery during zero-stress aging of fused silica optical fibers G. M. Camilot  

E-print Network

Strength degradation and recovery during zero-stress aging of fused silica optical fibers G. M Fiber Optics Materials Research Program, Department of Ceramics Rutgers University, Piscataway, New polymer coated and bare fibers in liquid nitrogen after the fibers were first aged in an aggressive

Matthewson, M. John

151

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

E-print Network

of small quantities of colloidal silica to the UV- curable polymer coating of fused silica optical fiberEnhanced fatigue and aging resistance using reactive powders in the optical fiber buffer coating V. V. Rondinella M. J. Matthewson P. R. Foy Fiber Optic Materials Research Program, Department

Matthewson, M. John

152

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

153

Diagnostics of Accretion Disc in AGN  

NASA Astrophysics Data System (ADS)

The active galactic nuclei(AGN)are the most luminous objects in the universe. Total power radiated by an AGN is greater than the total power emitted by all the stars in the host galaxy.The direct diagnostics of the conditions within AGNs come from radiations produced by a wide variety of mechanisms including high energy gamma ray processes atmospheric reprocessing dust emissions and synchrotron radiation. In addition to optical and X-ray photonsthe emssion includes MeV GeV and also TeV gamma rays. We have considered that AGNs are powered by an accretion disc around a supermassive blackhole of 10E+08 solar mass. The structure and heights from the central plane of an accretion disc around such a blackhole depends on the composition of disc materialaccretion rate self gravityand magnetic field in the accreting material. We have considered three types of composition of the disc material: 1.X=0.600;Y=0.380;Z=0.020 2.X=0.700;Y=0.280;Z=0.020 3.X=0..800;Y=0.199;Z=0.001 XYand Z represent hydrogenhelium and metal abundances respectively and the three accretion rates are 0.010.001 0.005 solar mass per year respectively. The result shows that the disc height decreases as the accretion rate decreases

Borah, Surendra Nath; Duorah, Hira Lal

154

Diagnostics of accretion disc in AGN  

NASA Astrophysics Data System (ADS)

The active galactic nuclei(AGN)are the most luminous objects in the universe. Total power radiated by an AGN is greater than the total power emitted by all the stars in the host galaxy.The direct diagnostics of the conditions within AGNs come from radiations produced by a wide variety of mechanisms including high energy gamma ray processes atmospheric reprocessing dust emissions and synchrotron radiation. In addition to optical and X-ray photonsthe emssion includes MeV GeV and also TeV gamma rays. We have considered that AGNs are powered by an accretion disc around a supermassive blackhole of 10E+08 solar mass. The structure and heights from the central plane of an accretion disc around such a blackhole depends on the composition of disc materialaccretion rate self gravityand magnetic field in the accreting material. We have considered three types of composition of the disc material: 1.X=0.600;Y=0.380;Z=0.020 2.X=0.700;Y=0.280;Z=0.020 3.X=0..800;Y=0.199;Z=0.001 XYand Z represent hydrogenhelium and metal abundances respectively and the three accretion rates are 0.010.001 0.005 solar mass per year respectively. The result shows that the disc height decreases as the accretion rate decreases.

Borah, Surendra Nath; Duorah, Hira Lal

2005-01-01

155

Menopause is associated with lumbar disc degeneration: a review of 4230 intervertebral discs.  

PubMed

Abstract Objective The main objective of this study was to investigate, in a population of normal postmenopausal women, the association between menopause and severity of lumbar disc degeneration from the first lumbar to the first sacral vertebra on magnetic resonance imaging. Methods Between January 2010 and May 2013, 846 normal women and 4230 intervertebral discs were retrospectively analyzed. Age, height, weight and years since menopause (YSM) were recorded. Disc degeneration was evaluated using the modified Pfirrmann grading system. Results Compared to premenopausal and perimenopausal women, postmenopausal women had more severe disc degeneration after removal of age, height and weight effects (p < 0.0001). Postmenopausal women were divided into six subgroups for every 5 YSM. When YSM was below 15 years, there was a significant difference between every two groups, i.e. groups 1-5 YSM, 6-10 YSM and 11-15 YSM (p < 0.01). A positive trend was observed between YSM and severity of disc degeneration, respectively, i.e. L1/L2 (r = 0.235), L2/L3 (r = 0.161), L3/L4 (r = 0.173), L4/L5 (r = 0.146), L5/S1 (r = 0.137) and all lumbar discs (r = 0.259) (p < 0.05 or 0.01). However, when YSM was above 15, there was no difference, i.e. groups 16-20 YSM, 21-25 YSM and 26-30 YSM (p > 0.05), and the significance correlation also disappeared (p > 0.05). Conclusion Menopause is associated with disc degeneration in the lumbar spine. The association almost entirely occurred in the first 15 years since menopause, suggesting estrogen decrease may be a risk factor for lumbar disc degeneration. PMID:25017806

Lou, C; Chen, H-L; Feng, X-Z; Xiang, G-H; Zhu, S-P; Tian, N-F; Jin, Y-L; Fang, M-Q; Wang, C; Xu, H-Z

2014-12-01

156

The Evolution of Stellar Exponential Discs  

E-print Network

Models of disc galaxies which invoke viscosity-driven radial flows have long been known to provide a natural explanation for the origin of stellar exponential discs, under the assumption that the star formation and viscous timescales are comparable. We present models which invoke simultaneous star formation, viscous redistribution of gas and cosmologically-motivated gaseous infall and explore the predictions such models make for the scale length evolution and radial star formation history of galactic stellar discs. While the inclusion of viscous flows is essential for ensuring that the stellar disc is always exponential over a significant range in radius, we find that such flows play essentially no role in determining the evolution of the disc scale length. In models in which the main infall phase precedes the onset of star formation and viscous evolution, we find the exponential scale length to be rather invariant with time. On the other hand, models in which star formation/viscous evolution and infall occur concurrently result in a smoothly increasing scale length with time, reflecting the mean angular momentum of material which has fallen in at any given epoch. The disc stellar populations in these models are predominantly young (ie. ages < 5 Gyr) beyond a few scale lengths. In both cases, viscous flows are entirely responsible for transporting material to very large radii. We discuss existing observational constraints on these models from studies of both local and moderate redshift disc galaxies. In particular, a good agreement is found between the solar neighbourhood star formation history predicted by our infall model and the recent observational determination of this quantity by Rocha-Pinto et al (2000).

Annette Ferguson; Cathie Clarke

2001-03-14

157

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

Microsoft Academic Search

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

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

1993-01-01

158

Magnetic fields near the peripheries of galactic discs  

E-print Network

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. Here we investigate the possibility that magnetic fields can be generated in the outskirts of discs, taking the Milky Way as an example. 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. 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 t...

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

2014-01-01

159

Microlensing evidence for super-Eddington disc accretion in quasars  

NASA Astrophysics Data System (ADS)

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

Abolmasov, P.; Shakura, N. I.

2012-12-01

160

Optical and fast nondestructive identification of the ages of leaded ancient pottery  

NASA Astrophysics Data System (ADS)

In this paper, based on the one-dimensional (1D) optical superlattice model, we calculate the average reflectivities (ARs) of leaded ancient pottery (AP) made within the last 2000 years, and find that for incident light with a suitable wavelength, the AR of the leaded AP increases monotonously with the increase in the layer number of the silvery glaze (SG) media. Based on this property, we propose an optical nondestructive method for identifying the age of leaded AP by detecting the AR. By using the exhaust algorithm and the discriminant function of variance, we obtain the optimal wavelength range of the incident light to identify the ages of the leaded AP. It is found that in the visible light band, if we choose green light with a wavelength range of 540-540.1 nm as the incident light, leaded AP made within the last 2000 years can be identified swiftly and precisely by detecting the ARs. This will be useful for designing optical instruments for the fast nondestructive identification of the ages of leaded AP.

Wu, Fang-Yuan; Yang, Xiang-Bo

2012-05-01

161

Herschel PACS and SPIRE Observations of TWA brown dwarf discs  

E-print Network

We present Herschel SPIRE observations for the TW Hydrae association (TWA) brown dwarf discs SSSPM J1102-3431 (SS1102) and 2MASSW J1207334-393254 (2M1207). Both discs are undetected in the SPIRE 200-500mu bands. We have also analyzed the archival PACS data and find no detection for either source in the 160mu band. Based on radiative transfer modeling, we estimate an upper limit to the disc mass for both sources of 0.1 M_Jup. The lack of detection in the SPIRE bands could be due to a paucity of millimeter sized dust grains in the 2M1207 and SS1102 discs. We also report a non-detection for the brown dwarf 2MASS J1139511-315921 (2M1139) in the PACS 70 and 160mu bands. We have argued for the presence of a warm debris disc around 2M1139, based on an excess emission observed at 24mu. The mid-infrared colors for 2M1139 are similar to the transition discs in the Taurus and Ophuichus regions. A comparison of the brown dwarf disc masses over a ~1-10 Myr age interval suggests a decline in the disc mass with the age of t...

Riaz, B

2012-01-01

162

Taking the pulse of aging: Mapping pulse pressure and elasticity in cerebral arteries with optical methods.  

PubMed

Cerebrovascular support is crucial for healthy cognitive and brain aging. Arterial stiffening is a cause of reduced brain blood flow, a predictor of cognitive decline, and a risk factor for cerebrovascular accidents and Alzheimer's disease. Arterial health is influenced by lifestyle factors, such as cardiorespiratory fitness (CRF). We investigated new noninvasive optical measures of cerebrovascular health, which provide estimates of arterial pulse parameters (pulse pressure, transit time, and compliance/elasticity) within specific cerebral arteries and cortical regions, and low-resolution maps of large superficial cerebral arteries. We studied naturally occurring variability in these parameters in adults (aged 55-87), and found that these indices of cerebrovascular health are negatively correlated with age and positively with CRF and gray and white matter volumes. Further, regional pulse transit time predicts specific neuropsychological performance. PMID:25100639

Fabiani, Monica; Low, Kathy A; Tan, Chin-Hong; Zimmerman, Benjamin; Fletcher, Mark A; Schneider-Garces, Nils; Maclin, Edward L; Chiarelli, Antonio M; Sutton, Bradley P; Gratton, Gabriele

2014-11-01

163

Contribution of particulate water to the measured aerosol optical properties of aged aerosol  

NASA Astrophysics Data System (ADS)

Measurements of aged aerosol scattering in the Eastern Mediterranean at ambient and low relative humidity (RH) are combined with measurements of its size composition distribution and its aerosol water content to gain insights about its hygroscopic and optical properties. The particle water uptake above 60% RH can be explained by the water absorption by the inorganic particulate matter in this sulphate rich environment. However, the particles were supersaturated aqueous solutions at low RH and this water cannot be explained just by the water associated with their inorganic components in a metastable state. We estimate that approximately 20% of this water may be contributed by the aged organic particulate matter. A semi-empirical equation is derived allowing the estimation of the aged aerosol Volume Growth Factor (VGF) from the ratios of scattering at ambient and low RH. The predictions of the equation are in good agreement with the measurement dataset obtained during the study.

Pilinis, Christodoulos; Charalampidis, Panagiotis E.; Mihalopoulos, Nikolaos; Pandis, Spyros N.

2014-01-01

164

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

USGS Publications Warehouse

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

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

2007-01-01

165

The DISC Quotient  

NASA Astrophysics Data System (ADS)

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

Elliott, John R.; Baxter, Stephen

2012-09-01

166

The Teddy Bears' Disc.  

ERIC Educational Resources Information Center

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

Laurillard, Diana

1985-01-01

167

Compact WLAN disc antennas  

Microsoft Academic Search

A novel conical beam patch antenna design, suitable for local area network applications, uses a central cylindrical connection from the disc to ground to achieve a large reduction in resonant size. Results on efficiency, bandwidth, and pattern are reported for several prototypes.

Neil J. McEwan; Raed A. Abd-Alhameed; Embarak M. Ibrahim; Peter S. Excell; Nazar T. Ali

2002-01-01

168

Use of polystyrene spin-coated compact discs for microimmunoassaying  

Microsoft Academic Search

The analytical potential of polystyrene (PS) spin-coated modified compact discs (CDs) surface as platforms for the development of microarray immunoassays is presented. The surface maintained the optical characteristics of compact discs, obtaining a transparent and smooth film polymer of 70nm thickness, the track being read (? 780nm) without errors in a commercial CD reader\\/writer. The analytical capability of the methodology

Jesús Tamarit-López; Sergi Morais; Rosa Puchades; Ángel Maquieira

2008-01-01

169

On the possibility of a warped disc origin of the inclined stellar discs at the Galactic Centre  

NASA Astrophysics Data System (ADS)

The central parsec of our Galaxy hosts a population of young stars. At distances of r ˜ 0.03-0.5 pc, most of these stars seem to form a system of mutually inclined discs of clockwise and counterclockwise rotating stars. We present a possible warped disc origin scenario for these stars assuming that an initially flat accretion disc becomes warped due to a central radiation source via the Pringle instability or due to a spinning black hole via the Bardeen-Petterson effect before it cools, fragments and forms stars. From simple arguments, we show that this is plausible if the star formation efficiency is high, ?SF ? 1, and the viscosity parameter ? ˜ 0.1. After fragmentation, we model the disc as a collection of concentric, circular rings tilted with respect to each other, and construct time evolution models of warped discs for mass ratios and other parameters relevant to the Galactic Centre environment, but also for more massive discs. We take into account the disc's self-gravity in the non-linear regime and the torques exerted by a slightly flattened surrounding star cluster. Our simulations show that a self-gravitating low-mass disc (Md/Mbh ˜ 0.001) precesses with its integrity maintained in the lifetime of the stars, but precesses essentially freely when the torques from a non-spherical cluster are included. An intermediate-mass disc (Md/Mbh ˜ 0.01) breaks into pieces, which precess as independent discs in the self-gravity-only case, and become disrupted in the presence of the star cluster torques. Finally, for a high-mass disc (Md/Mbh ˜ 0.1), the evolution is dominated by self-gravity and the disc is broken but not dissolved. The time-scale after which the disc breaks into pieces scales almost linearly with Md/Mbh for self-gravitating models. Typical values are longer than the age of the stars for Md/Mbh ˜ 0.001, and are in the range ˜8 × 104-105 yr for Md/Mbh ˜ 0.1-0.01, respectively. None of these discs explains the two Galactic Centre discs with their rotation properties. A comparison of the models with the better defined clockwise rotating disc shows that the lowest mass model in a spherical star cluster matches the data best.

Ulubay-Siddiki, A.; Bartko, H.; Gerhard, O.

2013-01-01

170

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

171

Impact of optical and structural aging in As2S3 microstructured optical fibers on mid-infrared supercontinuum generation.  

PubMed

We analyze optical and structural aging in As2S3 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 As2S3 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

172

Disc degeneration in Scheuermann disease.  

PubMed

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

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

1989-01-01

173

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

NASA Astrophysics Data System (ADS)

We are conducting a feasibility study on a wide field of regard Multi-Object Adaptive Optics system for TMT (TMT-AGE:TMT-Analyzer for Galaxies in the Early universe). The wide FoR is crucial to effectively observe very high-redshift UV-bright galaxies at z>5, which have low surface number density. Simulations of an MOAO system show moderate AO correction can be achieved within 10 arcmin diameter FoR. We discuss overall system design of the wide FoR MOAO system considering the system constraint from the stroke of small-size deformable mirror.

Akiyama, Masayuki; Oya, S.; Ono, Y. H.; TMT-AGE Team

2014-07-01

174

Liquid-core optical waveguide dosimetry ageing of a dosimeter with sub-linear response  

NASA Astrophysics Data System (ADS)

The simple dosimeter system: LED-liquid optical waveguide dosimeter-neutral OWG-photodiode shows a sublinear response of absorbance vs absorbed dose due to the polychromaticity of the light source. It is shown that if the sensitivity of measurement is high and the "dosimetric" reaction in unirradiated compound takes place spontaneously with time (ageing), the use of a system with sublinear response can hardly be advised. This has been demonstrated with a solution of hexahydroxyethyl pararosaniline cyanide for which, based on the separately determined G-value and molar absorption coefficient, the theoretical behavior of the system in the gamma radiation field has been derived.

Še?erov, B. Lj.; Radak, B. B.

175

Biomechanics of disc degeneration.  

PubMed

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

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

2012-01-01

176

Mechanotransduction in intervertebral discs.  

PubMed

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

2014-12-01

177

Biomechanics of Disc Degeneration  

PubMed Central

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

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

2012-01-01

178

Digital Versatile Disc\\/Compact Disc-Compatible Pickup Head with Dual-Lens Lever Actuator for Next-Generation Applications  

Microsoft Academic Search

As the track density and disc rotational speed of digital versatile disc (DVD) increase rapidly, an optical pickup head with better performance is required. In this paper, the design requirements of pickup heads aiming at high speed and high recording density are discussed. A new pickup head with a dual-lens lever actuator is proposed. The prototype of the lever actuator

Changsoo Han; Junghyun Lee; Soohyun Kim

2000-01-01

179

Canine intervertebral disc degeneration  

Microsoft Academic Search

Introduction: Due to advancements in veterinary care and veterinary\\u000adiets in the last four decades, dogs that are kept as companion animals\\u000ahave reached a life expectancy of 10 to 15 years. Together with\\u000aintensive breeding of chondrodystrophic and non-chondrodystrophic\\u000adogs canine intervertebral disc degeneration (IVDD) has become an\\u000aincreasingly important veterinary disorder.\\u000aMethods: IVDD occurs as a clinical entity

B. P. Meij; L. A. Smolders; N. Bergknut

2010-01-01

180

Total disc replacement.  

PubMed

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

Vital, J-M; Boissière, L

2014-02-01

181

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

182

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

E-print Network

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

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

2008-09-23

183

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

Microsoft Academic Search

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

Ay?egül Güven

2012-01-01

184

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

Microsoft Academic Search

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

R F Walters; D J Spalton

1990-01-01

185

How Do the Stellar Disc and Thick Disc Stop ?  

E-print Network

As part of a stellar population sampling program, a series of photometric probes at various field sizes and depths have been obtained in a low extinction window in the galactic anticentre direction. Very deep CCD frames probe the most external parts of the disc, providing strong evidence that the galactic density scale length for the old disc population is rather short (2.5 kpc) and drops abruptly beyond 5.5-6 kpc. Deeper frames in the I band allow to estimate photometric distances and confirm the position of the disc edge. A few stars are found at larger distances. Their number is exactly what we expect if the thick disc does not have any cutoff. We discuss the implications for the formation and evolution of the disc, for the star formation threshold, and for the origin of the thick disc population.

Annie C. Robin; Michel Creze; Vijay Mohan

1994-11-22

186

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

187

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

E-print Network

We develop a chemical evolution model in order to study the star formation history of the Milky Way. Our model assumes that the Milky Way is formed from a closed box-like system in the inner regions, while the outer parts of the disc experience some accretion. Unlike the usual procedure, we do not fix the star formation prescription (e.g. Kennicutt law) in order to reproduce the chemical abundance trends. Instead, we fit the abundance trends with age in order to recover the star formation history of the Galaxy. Our method enables one to recover with unprecedented accuracy the star formation history of the Milky Way in the first Gyrs, in both the inner (R9-10kpc) discs as sampled in the solar vicinity. We show that, in the inner disc, half of the stellar mass formed during the thick disc phase, in the first 4-5 Gyr. This phase was followed by a significant dip in the star formation activity (at 8-9 Gyr) and a period of roughly constant lower level star formation for the remaining 8 Gyr. The thick disc phase ha...

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

2014-01-01

188

Disc resonator gyroscope fabrication process requiring no bonding alignment  

NASA Technical Reports Server (NTRS)

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

Shcheglov, Kirill V. (Inventor)

2010-01-01

189

Evolution of disc degeneration in lumbar spine: a comparative histological study between herniated and postmortem retrieved disc specimens.  

PubMed

This is a prospective comparative histological study on blood supply between lumbar herniated discs and postmortem retrieved ones. The aim of this study is to observe the evolution of disc degeneration in relation to its blood supply changes. Disc vascularization is present early in life, but the nucleus pulposus becomes avascular after adolescence. Vascularization of the annulus fibrosus (AF) probably also occurs late in life in association with degenerative changes and in response to trauma. Capillary neoformation and hypervascularity in degenerated discs have also been mentioned, based on animal cases. In the present study, intervertebral lumbar disc specimens were surgically removed from 84 patients with an average age of 41 years (range 24-60 years) operated on for disc herniation. In addition, control autopsy specimens were selected from 24 cadavera with an age of 39 years (range 24th gestation week to 80 years). The material was fixed in neutral buffered formalin, and 4-microm-thick sections were stained with hematoxylin-eosin and reticulin. In addition, with use of an immunohistochemical avidin-biotin complex technique, paraffin sections were stained for Ulex europaeus agglutinin receptors (UEA-1) after binding UEA-1 to the tissue. In surgical specimens, small blood vessels were identified in 45% of the disc cases. They were of the capillary-type vessels and were intermingled with proliferating endothelial cells, fibroblasts, and few mononuclear cells. All of them were located along the edges of the surgically retrieved fibrocartilage fragments. Sometimes thin bands of fibrin were attached to them and extravasated erythrocytes were occasionally seen. In autopsy specimens, blood vessels were identified in 78% of the retrieved discs. In contrast to the edge neovascularity observed in surgical specimens, capillaries were observed at the outer layer of AF surrounded by dense hyalinized and inactive-appearing collagen. From these results it is concluded that the blood vessels in extruded tissue from every type of herniation are newly formed, possibly through metaplasia of undifferentiated mesenchymal cells. It is also possible that they are derived from blood vessels that have invaded the AF as a result of disc degeneration. The finding of detection of progressive disc degeneration in both groups after 20-25 years seems to be of special interest because disc degeneration is a process that may not be directly correlated to disc herniation in these age groups. PMID:9493769

Repanti, M; Korovessis, P G; Stamatakis, M V; Spastris, P; Kosti, P

1998-02-01

190

Disc Manufacturing, Inc. A QUIXOTE COMPANY  

E-print Network

rights reserved. #12;WHO IS DMI? Disc Manufacturing, Inc. (DMI) manufactures all compact disc formats (i discs of various types since 1981. In 1983, DMI manufactured the first compact disc in the United States-ROM Production Compact Disc Terminology - 2nd Edition A Glossary of CD and CD-ROM Terms These are available upon

Gupta, Varun

191

Photo-crosslinkable hybrid material with improved aging stability for integrated optics  

NASA Astrophysics Data System (ADS)

In the last decade, the processing of the waveguide structures on various substrates under mild conditions has been an appealing aim. The lithographic patterning of organic-inorganic hybrid materials processed by means of sol-gel technology allows the production of waveguides and other optical components. We describe the synthesis of a new, photo-patternable, organically modified material with an improved ageing stability. Synthesis step does not involve widely used zirconia precursors, but it retains the same possibility of altering the refractive index by tailoring of the material composition. Refractive index values varied from 1.4700 to 1.5100. Measured birefringence values meet the requirements of most integrated planar optic applications. The synthesized material is compatible with silicon, glass and plastic substrates. Material was analyzed using 29Si NMR techniques. The processed slab waveguides were characterized by using the prism coupling technique at various wavelengths. The attenuation in the waveguide was determined by the cut-back method, and it was found to be less than 0.5dB/cm at the wavelength of 830 nm. The morphology of the microstructures was measured by using the interferometer equipment. Slab waveguides rms values were in order of only 2 nm.

Kusevic, Maja; Maaninen, Arto; Hiltunen, Jussi; Hiltunen, Marianne; Tuominen, Jarkko; Karioja, Pentti

2004-08-01

192

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

193

Measuring system of transient temperature distribution on the brake disc rotor  

Microsoft Academic Search

A system to measure transient temperature distribution on the brake disc rotor at high speed braking has been developed and its measuring principle and configuration are discussed in this paper. This system consists of two revolution sensors and two sets of optical fiber array, photoelectric elements, and microprocessor, which fiber array is so arranged that it faces the brake disc

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

1987-01-01

194

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

NASA Astrophysics Data System (ADS)

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

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

2010-03-01

195

Hydrogen-losing planets in transition discs around young protostars  

NASA Astrophysics Data System (ADS)

We point out that protoplanets created in the framework of the tidal downsizing (TD) theory for planet formation play a very important role for the evolution of accretion discs hosting them. Since all TD protoplanets are initially as massive as ˜10MJ, they are able to open very deep gaps in their discs, and even completely isolate the inner disc flows from the outer ones. Furthermore, in contrast to other planet formation theories, TD protoplanets are mass donors for their protostars. One potentially observable signature of planets being devoured by their protostars are FU Ori like outbursts, and episodic protostar accretion more generally, as discussed by a number of authors recently. Here, we explore another observational implication of the TD hypothesis: dust poor inner accretion flows, which we believe may be relevant to some of the observed millimetre-bright transitional discs around protostars. In our model, a massive protoplanet interrupts the flow of the outer dust-rich disc on its protostar, and at the same time loses a part of its dust-poor envelope into the inner disc. This then powers the observed gas-but-no-dust accretion on to the star. Upon a more detailed investigation, we find that this scenario is quite natural for young massive discs but is less so for older discs, e.g., those whose self-gravitating phase has terminated a fraction of a Myr or more ago. This stems from the fact that TD protoplanets of such an age should have contracted significantly, and so are unlikely to lose much mass. Therefore, we conclude that either (i) the population of `transition discs' with large holes and dust-poor accretion is much younger than generally believed, or (ii) there is a poorly understood stage for late removal of dust-poor envelopes from TD planets; (iii) another explanation for the observations is correct.

Nayakshin, Sergei

2013-05-01

196

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

NASA Astrophysics Data System (ADS)

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

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

2012-01-01

197

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

PubMed

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

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

2011-01-01

198

The magnetization of protoplanetary discs  

Microsoft Academic Search

The remanent magnetization of meteorite material in the Solar system indicates that magnetic fields of several gauss are present in the protoplanetary disc. It is shown that such relatively strong magnetic fields can be generated in dusty protoplanetary discs by relative shear motions of the charged dust and the neutral gas components. Self-consistent multi-fluid simulations show that, for typical plasma

G. T. Birk; H. Wiechen; A. Kopp; H. Lesch

2003-01-01

199

Spiral waves in accretion discs  

Microsoft Academic Search

This thesis discusses observations of the interacting binary IP Pegasi and shows that its accretion disc carries strong, tidally driven spiral arms during outburst. The distribution of line emission across the accretion disc is resolved using Doppler tomography and reveals a two armed spiral pattern in a variety of emission lines. The spirals persist as a strong co-rotating pattern throughout

D. Steeghs

1999-01-01

200

Galaxy Zoo: CANDELS barred discs and bar fractions  

NASA Astrophysics Data System (ADS)

The formation of bars in disc galaxies is a tracer of the dynamical maturity of the population. Previous studies have found that the incidence of bars in discs decreases from the local Universe to z ˜ 1, and by z > 1 simulations predict that bar features in dynamically mature discs should be extremely rare. Here, we report the discovery of strong barred structures in massive disc galaxies at z ˜ 1.5 in deep rest-frame optical images from the Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey. From within a sample of 876 disc galaxies identified by visual classification in Galaxy Zoo, we identify 123 barred galaxies. Selecting a subsample within the same region of the evolving galaxy luminosity function (brighter than L*), we find that the bar fraction across the redshift range 0.5 ? z ? 2 ( f_{bar} = 10.7^{+6.3}_{-3.5} per cent after correcting for incompleteness) does not significantly evolve. We discuss the implications of this discovery in the context of existing simulations and our current understanding of the way disc galaxies have evolved over the last 11 billion years.

Simmons, B. D.; Melvin, Thomas; Lintott, Chris; Masters, Karen L.; Willett, Kyle W.; Keel, William C.; Smethurst, R. J.; Cheung, Edmond; Nichol, Robert C.; Schawinski, Kevin; Rutkowski, Michael; Kartaltepe, Jeyhan S.; Bell, Eric F.; Casteels, Kevin R. V.; Conselice, Christopher J.; Almaini, Omar; Ferguson, Henry C.; Fortson, Lucy; Hartley, William; Kocevski, Dale; Koekemoer, Anton M.; McIntosh, Daniel H.; Mortlock, Alice; Newman, Jeffrey A.; Ownsworth, Jamie; Bamford, Steven; Dahlen, Tomas; Faber, Sandra M.; Finkelstein, Steven L.; Fontana, Adriano; Galametz, Audrey; Grogin, N. A.; Grützbauch, Ruth; Guo, Yicheng; Häußler, Boris; Jek, Kian J.; Kaviraj, Sugata; Lucas, Ray A.; Peth, Michael; Salvato, Mara; Wiklind, Tommy; Wuyts, Stijn

2014-12-01

201

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

E-print Network

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

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

2006-09-29

202

Track Seeking Hybrid Fuzzy Controller for the Compact Disc Player  

Microsoft Academic Search

A hybrid track seeking fuzzy controller for an optical compact disc player is proposed. It is shown that the proposed hybrid fuzzy controller smoothes the applied voltage to the sled motor and improves the track seeking efficiency. The proposed hybrid fuzzy controller consists of three subsystems including parking time controller, driving force controller and parameter tuner. All three of subsystems

Yao Leehter; An-min Wang; Yung-fu Cheng

2001-01-01

203

Inhomogeneous accretion discs and the soft states of black hole X-ray binaries  

NASA Astrophysics Data System (ADS)

Observations of black hole binaries (BHBs) have established a rich phenomenology of X-ray states. The soft states range from the low variability, accretion disc dominated thermal (TD) state to the higher variability, non-thermal steep power law (SPL) state. The disc component in all states is typically modelled with standard thin disc accretion theory. However, this theory is inconsistent with optical/UV spectral, variability and gravitational microlensing observations of active galactic nuclei (AGNs), the supermassive analogues of BHBs. An inhomogeneous disc (ID) model with large (?0.4 dex) temperature fluctuations in each radial annulus can qualitatively explain all of these AGN observations. The inhomogeneity may be a consequence of instabilities in radiation-dominated discs, and therefore may be present in BHBs as well. We show that ID models can explain many features of the TD and SPL states of BHBs. The observed relationships between spectral hardness, disc fraction and rms variability amplitude in BHBs are reproduced with temperature fluctuations similar to those inferred in AGNs, suggesting a unified picture of luminous accretion discs across orders of magnitude in black hole mass. This picture can be tested with spectral fitting of ID models, X-ray polarization observations and radiation magnetohydrodynamic simulations. If BHB accretion discs are indeed inhomogeneous, only the most disc-dominated states (disc fraction ?0.95) can be used to robustly infer black hole spin using current continuum fitting methods.

Dexter, Jason; Quataert, Eliot

2012-10-01

204

Optical Disks.  

ERIC Educational Resources Information Center

This four-article section focuses on information storage capacity of the optical disk covering the information workstation (uses microcomputer, optical disk, compact disc to provide reference information, information content, work product support); use of laser videodisc technology for dissemination of agricultural information; encoding databases…

Gale, John C.; And Others

1985-01-01

205

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

Microsoft Academic Search

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

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

2008-01-01

206

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

Microsoft Academic Search

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

Adrian Glasser; Melanie C. W. Campbell

1999-01-01

207

New Recordable Compact Disc with Inorganic Material, AgOx  

Microsoft Academic Search

A new recordable compact disc (CD-R) was formed with sputtered silver oxide, instead of organic dye. The optical and electrical properties were mostly equal to those of a CD-R with organic dye. The optical absorption of sputtered AgOx is uniform over a wide range of light wavelength, and more than 70% of the reflectance can be obtained at any laser

Junji Tominaga; Susumu Haratani; Kenji Uchiyama; Suguru Takayama

1992-01-01

208

A 1kW CW thin disc laser  

Microsoft Academic Search

The thin disc laser is presented as an optimal laser design for the operation of a quasi-three-level laser active medium in the high power regime with high optical efficiency. Numerical calculations of the laser output power show that operation with an output power up to 1 kW with an optical efficiency of 50% and more is possible at room temperature

Christian Stewen; Karsten Contag; Mikhail Larionov; Adolf Giesen; Helmut Hügel

2000-01-01

209

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

PubMed Central

Purpose Describe qualitative spectral-domain optical coherence tomography (SD-OCT) characteristics of eyes classified as intermediate age-related macular degeneration (nonadvanced AMD) from Age-Related Eye Disease Study 2 (AREDS2) color fundus photography (CFP) grading. Design Prospective cross-sectional study. Participants We included 345 AREDS2 participants from 4 study centers and 122 control participants who lack CFP features of intermediate AMD. Methods Both eyes were imaged with SD-OCT and CFP. The SD-OCT macular volume scans were graded for the presence of 5 retinal, 5 subretinal, and 4 drusen characteristics. In all, 314 AREDS2 participants with ?1 category-3 AMD eye and all controls each had 1 eye entered into SD-OCT analysis, with 63 eyes regraded to test reproducibility. Main Outcome Measures We assessed SD-OCT characteristics at baseline. Results In 98% of AMD eyes, SD-OCT grading of all characteristics was successful, detecting drusen in 99.7%, retinal pigment epithelium (RPE) atrophy/absence in 22.9%, subfoveal geographic atrophy in 2.5%, and fluid in or under the retina in 25.5%. Twenty-eight percent of AMD eyes had characteristics of possible advanced AMD on SD-OCT. Two percent of control eyes had drusen on SD-OCT. Vision loss was not correlated with foveal drusen alone, but with foveal drusen that were associated with other foveal pathology and with overlying focal hyperreflectivity. Focal hyperreflectivity over drusen, drusen cores, and hyper- or hyporeflectivity of drusen were also associated with RPE atrophy. Conclusions Macular pathologies in AMD can be qualitatively and reproducibly evaluated with SD-OCT, identifying pathologic features that are associated with vision loss, RPE atrophy, and even possibly the presence of advanced AMD not apparent on CFP. Qualitative and detailed SD-OCT analysis can contribute to the anatomic characterization of AMD in clinical studies of vision loss and disease progression. PMID:22968145

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

2012-01-01

210

The prevalence of disc degeneration associated with neural arch defects of the lumbar spine assessed by magnetic resonance imaging.  

PubMed

The morphology of the intervertebral discs in 40 patients with spondylolytic and mild spondylolisthetic defects of the lumbar spine were assessed using magnetic resonance imaging. The results were compared with an age- and sex-matched asymptomatic population, and the difference in prevalence of disc degeneration between the two groups was noted. Under the age of 25 years, degeneration was uncommon in both the disc associated with the neural arch defect and the comparable disc in the control population. However, after this age, the prevalence of the disc degeneration rose in both groups, but was more marked in the spondylytic group, and this difference was statistically significant (P = 0.025). The results suggest that a neural arch defect is associated with an increased prevalence of disc degeneration, which is greater than is seen in a normal aging population. PMID:2789436

Szypryt, E P; Twining, P; Mulholland, R C; Worthington, B S

1989-09-01

211

Model-based optic nerve head segmentation on retinal fundus images  

Microsoft Academic Search

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

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

2011-01-01

212

In Vivo Measurement of Age-Related Stiffening in the Crystalline Lens by Brillouin Optical Microscopy  

PubMed Central

Abtract The biophysical and biomechanical properties of the crystalline lens (e.g., viscoelasticity) have long been implicated in accommodation and vision problems, such as presbyopia and cataracts. However, it has been difficult to measure such parameters noninvasively. Here, we used in vivo Brillouin optical microscopy to characterize material acoustic properties at GHz frequency and measure the longitudinal elastic moduli of lenses. We obtained three-dimensional elasticity maps of the lenses in live mice, which showed biomechanical heterogeneity in the cortex and nucleus of the lens with high spatial resolution. An in vivo longitudinal study of mice over a period of 2 months revealed a marked age-related stiffening of the lens nucleus. We found remarkably good correlation (log-log linear) between the Brillouin elastic modulus and the Young's modulus measured by conventional mechanical techniques at low frequencies (?1 Hz). Our results suggest that Brillouin microscopy is potentially useful for basic and animal research and clinical ophthalmology. PMID:21943436

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

2011-01-01

213

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

214

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

SciTech Connect

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

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

1993-12-01

215

Compact Disc Interactive.  

ERIC Educational Resources Information Center

This overview of a digital optical storage medium with a multimedia capability includes a global description of specifications, current status, and elements required to make a CD-I (compact disk interactive) launch possible. (Author/CLB)

Valk, Anton

1987-01-01

216

Multimedia Compact Disc: Play Therapy Counseling Skills  

Microsoft Academic Search

Multimedia compact discs have become an important part of counseling education. Many educators recognize the value of compact discs in training and methods of instruction. The purpose of this study was to develop an instructional compact disc and to survey counseling students' perceptions of the compact disc. Participants included 71 counseling graduate students from two universities in the southern part

Roxane L. Dufrene; Zoë Tanner

2009-01-01

217

Radiative Transfer Through Discs of Cataclysmic Variables  

E-print Network

], [3] and [4]. The velocity shear in the disc, caused by the Keplerian motion, changes line profilesRadiative Transfer Through Discs of Cataclysmic Variables D. Korcáková , T. Nagel , K. Werner , V transfer through the discs of cataclysmic variables. All the disc structure, the radial and latitude

Barnstedt, Jürgen

218

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

219

Disc piezoelectric ceramic transformers.  

PubMed

In this contribution, we present our study on disc-shaped and homogeneously poled piezoelectric ceramic transformers working in planar-extensional vibration modes. Transformers are designed with electrodes divided into wedge, axisymmetrical ring-dot, moonie, smile, or yin-yang segments. Transformation ratio, efficiency, and input and output impedances were measured for low-power signals. Transformer efficiency and transformation ratio were measured as a function of frequency and impedance load in the secondary circuit. Optimum impedance for the maximum efficiency has been found. Maximum efficiency and no-load transformation ratio can reach almost 100% and 52 for the fundamental resonance of ring-dot transformers and 98% and 67 for the second resonance of 2-segment wedge transformers. Maximum efficiency was reached at optimum impedance, which is in the range from 500 ? to 10 k?, depending on the electrode pattern and size. Fundamental vibration mode and its overtones were further studied using frequency-modulated digital holographic interferometry and by the finite element method. Complementary information has been obtained by the infrared camera visualization of surface temperature profiles at higher driving power. PMID:25004532

Erhart, Jirií; P?lpán, Petr; Dole?ek, Roman; Psota, Pavel; Lédl, Vít

2013-08-01

220

The mass budget of planet-forming discs: isolating the epoch of planetesimal formation  

NASA Astrophysics Data System (ADS)

The high rate of planet detection among solar-type stars argues that planet formation is common. It is also generally assumed that planets form in protoplanetary discs like those observed in nearby star-forming regions. On what time-scale does the transformation from discs to planets occur? Here, we show that current inventories of planets and protoplanetary discs are sensitive enough to place basic constraints on the time-scale and efficiency of the planet formation process. A comparison of planet detection statistics and the measured solid reservoirs in T Tauri discs suggests that planet formation is likely already underway at the few Myr age of the discs in Taurus-Auriga, with a large fraction of solids having been converted into large objects with low millimetre opacity and/or sequestered at small disc radii where they are difficult to detect at millimetre wavelengths.

Najita, J. R.; Kenyon, S. J.

2014-12-01

221

Clinical Evaluation of Disc Battery Ingestion in Children  

PubMed Central

BACKGROUND The purpose of this study was to evaluate the characteristics, management, and outcomes of disc battery ingestion in children. METHODS We reviewed the medical records of children admitted to Mofid Children’s Hospital due to disc battery ingestion from January 2006 to January 2010. Clear history, clinical symptoms and results of imaging studies revealed diagnosis of disc battery ingestion in suspected patients. The clinical data reviewed included age, gender, clinical manifestation, radiologic findings, location of disc battery, duration of ingestion, endoscopic results and surgical treatment. RESULTS We found 22 cases (11 males and 11 females) of disc battery ingestion with a mean age of 4.3 years (range: 9 months to 12 years). Common symptoms were vomiting, cough, dysphagia, and dyspnea. The mean duration of ingestion was 2.7 days (4 hours to 1.5 months). A total of 19 patients had histories of disc battery ingestion, but three cases referred with the above symptoms, and the batteries were accidentally found by x-ray. Only three cases had batteries impacted in the esophagus. Twelve batteries were removed endoscopically, 6 batteries spontaneously passed through the gastrointestinal (GI) tract within 5 to 7 days, and 4 patients underwent surgery due to complications: 3 due to tracheo-esophageal fistula (TEF) and 1 due to intestinal perforation. There was no mortality in our study. CONCLUSION Most cases of disc battery ingestion run uneventful courses, but some may be complicated. If the battery lodges in the esophagus, emergency endoscopic management is necessary. However, once in the stomach, it will usually pass through the GI tract. PMID:24829643

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

2012-01-01

222

Counter-Rotating Accretion Discs  

E-print Network

Counter-rotating discs can arise from the accretion of a counter-rotating gas cloud onto the surface of an existing co-rotating disc or from the counter-rotating gas moving radially inward 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 center. We discuss high-resolution axisymmetric hydrodynamic simulations of a viscous counter-rotating disc for cases where the two components are vertically separated and radially separated. The viscosity is described by an isotropic $\\alpha-$viscosity including all terms in the viscous stress tensor. For the vertically separated components a shear layer forms between them. The middle of this layer free-falls to the disk center. The accretion rates are increased by factors $\\sim 10^2-10^4$ over that of a conventional disc rotating in one direction with the same viscosity. The vertical width of the shear layer and the accretion rate are strongly dep...

Dyda, Sergei; Ustyugova, Galina V; Romanova, Marina M; Koldoba, Alexander V

2014-01-01

223

Accretion disc onto a static non-baryonic compact object  

E-print Network

We study the emissivity properties of a geometrically thin, optically thick, steady accretion disc about a static boson star. Starting from a numerical computation of the metric potentials and the rotational velocities of the particles in the vicinity of the compact object, we obtain the power per unit area, the temperature of the disc, and the spectrum of the emitted radiation. In order to see if different central objects could be actually distinguished, all these results are compared with the case of a central Schwarzschild black hole of equal mass. We considered different situations both for the boson star, assumed with and without self-interactions, and the disc, whose internal commencement can be closer to the center than in the black hole case. We finally make some considerations about the Eddington luminosity, which becomes radially dependent for a transparent object. We found that, particularly at high energies, differences in the emitted spectrum are notorious. Reasons for that are discussed.

Diego F. Torres

2002-01-17

224

Planet signatures in collisionally active debris discs: scattered light images  

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

225

Human Disc Nucleus Properties and Vertebral Endplate Permeability  

PubMed Central

Study of human cadaveric discs quantifying endplate permeability and porosity and correlating these with measures of disc quality: cell density, proteoglycan content, and overall degeneration. Permeability and porosity increased with age and were not correlated with cell density or overall degeneration, suggesting that endplate calcification may not accelerate disc degeneration. Study Design Experimental quantification of relationships between vertebral endplate morphology, permeability, disc cell density, glycosaminoglycan content and degeneration in samples harvested from human cadaveric spines. Objective To test the hypothesis that variation in endplate permeability and porosity contribute to changes in intervertebral disc cell density and overall degeneration. Summary of Background Data Cells within the intervertebral disc are dependent on diffusive exchange with capillaries in the adjacent vertebral bone. Previous findings suggest that blocked routes of transport negatively affect disc quality, yet there are no quantitative relationships between human vertebral endplate permeability, porosity, cell density and disc degeneration. Such relationships would be valuable for clarifying degeneration risk factors, and patient features that may impede efforts at disc tissue engineering. Methods Fifty-one motion segments were harvested from 13 frozen cadaveric human lumbar spines (32 to 85 years) and classified for degeneration using the MRI-based Pfirrmann scale. A cylindrical core was harvested from the center of each motion segment that included vertebral bony and cartilage endplates along with adjacent nucleus tissue. The endplate mobility, a type of permeability, was measured directly using a custom-made permeameter before and after the cartilage endplate was removed. Cell density within the nucleus tissue was estimated using the picogreen method while the nuclear GAG content was quantified using the DMMB technique. Specimens were imaged at 8 ?m resolution using microCT, bony porosity was calculated. Analysis of variance, linear regression, and multiple comparison tests were used to analyze the data. Results Nucleus cell density increased as the disc height decreased (R2=0.13; p=0.01) but was not related to subchondral bone porosity (p>0.5), total mobility (p>0.4) or age (p>0.2). When controlling for disc height however, a significant, negative effect of age on cell density was observed (p=0.03). In addition to this, GAG content decreased with age non-linearly (R2=0.83, p<0.0001) and a cell function measurement, GAGs/cell decreased with degeneration (R2=0.24; p<0.0001). Total mobility (R2=0.14; p<0.01) and porosity (R2=0.1, p<0.01) had a positive correlation with age. Conclusion Although cell density increased with degeneration, cell function indicated that GAGs/cell decreased. Since permeability and porosity increase with age and degeneration, this implies that cell dysfunction, rather than physical barriers to transport, accelerate disc disease. PMID:21240044

Rodriguez, Azucena G.; Slichter, Chloe K.; Acosta, Frank L.; Rodriguez-Soto, Ana E.; Burghardt, Andrew J.; Majumdar, Sharmila; Lotz, Jeffrey C.

2010-01-01

226

Subaru optical observations of the two middle-aged pulsars PSR B0656+14 and Geminga  

Microsoft Academic Search

Aims.We carried out a deep subarcsecond BRI imaging of the two middle-aged pulsars to establish their properties in the optical range. Methods.Astrometry and photometry methods are applied to identify the pulsars and to measure their fluxes. We also reanalyze archival ESO\\/NTT and HST broadband data and find that some published fluxes for Geminga were estimated inaccurately. The resulting dereddened broadband

Y. A. Shibanov; Sergei V. Zharikov; V. N. Komarova; Nobuyuki Kawai; Yuji Urata; A. B. Koptsevich; Vladimir V. Sokolov; Shinpei Shibata; Noriaki Shibazaki

2006-01-01

227

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

Microsoft Academic Search

We present polarization-sensitive optical coherence tomography (PS-OCT) for quantitative assessment of retinal pathologies in age-related macular degeneration (AMD). On the basis of the polarization scrambling characteristics of the retinal pigment epithelium, novel segmentation algorithms were developed that allow one to segment pathologic features such as drusen and atrophic zones in dry AMD as well as to determine their dimensions. Results

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

2010-01-01

228

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

229

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

Code of Federal Regulations, 2010 CFR

...2010-04-01 false Interarticular disc prosthesis (interpositional implant). 872... § 872.3970 Interarticular disc prosthesis (interpositional implant). (a) Identification. An interarticular disc prosthesis (interpositional implant) is...

2010-04-01

230

Damage accumulation location under cyclic loading in the lumbar disc shifts from inner annulus lamellae to peripheral annulus with increasing disc degeneration.  

PubMed

It is difficult to study the breakdown of lumbar disc tissue over several years of exposure to bending and lifting by experimental methods. In our earlier published study we have shown how a finite element model of a healthy lumbar motion segment was used to predict the damage accumulation location and number of cyclic to failure under different loading conditions. The aim of the current study was to extend the continuum damage mechanics formulation to the degenerated discs and investigate the initiation and progression of mechanical damage. Healthy disc model was modified to represent degenerative discs (Thompson grade III and IV) by incorporating both geometrical and biochemical changes due to degeneration. Analyses predicted decrease in the number of cycles to failure with increasing severity of disc degeneration. The study showed that the damage initiated at the posterior inner annulus adjacent to the endplates and propagated outwards towards its periphery in healthy and grade III degenerated discs. The damage accumulated preferentially in the posterior region of the annulus. However in grade IV degenerated disc damage initiated at the posterior outer periphery of the annulus and propagated circumferentially. The finite element model predictions were consistent with the infrequent occurrence of rim lesions at early age but a much higher incidence in severely degenerated discs. PMID:24231247

Qasim, Muhammad; Natarajan, Raghu N; An, Howard S; Andersson, Gunnar B J

2014-01-01

231

Phase object imaging inside the airy disc  

NASA Astrophysics Data System (ADS)

The possibility of phase objects superresoluton imaging is theoretically justifieth The measurements with CPM " AIRYSCAN" showed the reality of O structures observations when the Airy disc di ameter i s 0 86 j. . m SUMMARY It has been known that the amount of information contained in the image of any object is mostly determined by the number of points measured i ndependentl y or by spati al resol uti on of the system. From the classic theory of the optical systems it follows that for noncoherent sources the -spatial resolution is limited by the aperture dd 6LX/N. A. ( Rayleigh criterion where X is wave length NA numerical aperture. ) The use of this criterion is equivalent tO the statement that any object inside the Airy disc of radius d that is the difraction image of a point is practical ly unresolved. However at the coherent illumination the intensity distribution in the image plane depends also upon the phase iq (r) of the wave scattered by the object and this is the basis of the Zernike method of phasecontrast microscopy differential interference contrast (DIC) and computer phase microscopy ( CPM ). In theoretical foundation of these methods there was no doubt in the correctness of Rayleigh criterion since the phase information is derived out of intensity distribution and as we know there were no experiments that disproved this

Tychinsky, Vladimir P.

1991-03-01

232

Galaxy Zoo: The Environmental Dependence of Bars and Bulges in Disc Galaxies  

E-print Network

We present an analysis of the environmental dependence of bars and bulges in disc galaxies, using a volume-limited catalogue of 15810 galaxies at zZoo 2 project. We find that the likelihood of having a bar, or bulge, in disc galaxies increases when the galaxies have redder (optical) colours and larger stellar masses, and observe a transition in the bar and bulge likelihoods, such that massive disc galaxies are more likely to host bars and bulges. We use galaxy clustering methods to demonstrate statistically significant environmental correlations of barred, and bulge-dominated, galaxies, from projected separations of 150 kpc/h to 3 Mpc/h. These environmental correlations appear to be independent of each other: i.e., bulge-dominated disc galaxies exhibit a significant bar-environment correlation, and barred disc galaxies show a bulge-environment correlation. We demonstrate that approximately half (50 +/- 20%) of the bar-environm...

Skibba, Ramin A; Nichol, Robert C; Zehavi, Idit; Hoyle, Ben; Edmondson, Edward M; Bamford, Steven P; Cardamone, Carolin N; Keel, William C; Lintott, Chris; Schawinski, Kevin; Williams, Michael J

2011-01-01

233

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

234

Complications of artificial disc replacement: a report of 27 patients with the SB Charité disc.  

PubMed

Disc prosthesis surgery is rapidly becoming an option in treating patients with symptomatic degenerative disc disease. Only short-term and midterm results are described in the literature. Most operated patients belong to the age group of 30-50 years. In these active patients, complications can be expected to increase with longer follow-up, similar to total joint replacements in the extremities. Reported here is a series of 27 patients from another institution, who presented with unsatisfactory results or complications after SB Charité disc replacement. The objective of this work was to describe the possible short- and long-term unsatisfactory results of disc prosthesis surgery. Twenty-seven patients were seen in a tertiary university referral center with persisting back and leg complaints after having received a Charité disc prosthesis. All patients were operated on in a neighboring hospital. Most patients were operated on at the L4-L5 and /or the L5-S1 vertebral levels. The patients were evaluated with plain radiography, some with flexion-extension x-rays, and most of them with computed tomography scans. The group consisted of 15 women and 12 men. Their mean age was 40 years (range 30-67 years) at the time of operation. The patients presented to us a mean of 53 months (range 11-127 months) following disc replacement surgery. In two patients, an early removal of a prosthesis was required and in two patients a late removal. In 11 patients, a second spinal reconstructive salvage procedure was performed. Mean follow-up for 26 patients with mid- and long-term evaluation was 91 months (range 15-157 months). Early complications were the following: In one patient, an anterior luxation of the prosthesis after 1 week necessitated removal and cage insertion, which failed to unite. In another patient with prostheses at L4-L5 and L5-S1, the prosthesis at L5-S1 dislocated anteriorly after 3 months and was removed after 12 months. Abdominal wall hematoma occurred in four cases. Retrograde ejaculation with loss of libido was seen in one case and erection weakness in another case. A temporary benefit was experienced by 12 patients, while 14 patients reported no benefit at all. Main causes of persistent complaints were degeneration at another level in 14, subsidence of the prosthesis in 16, and facet joint arthrosis in 11. A combination of pathologies was often present. Slow anterior migration was present in two cases, with compression on the iliac vessels in one case. Polyethylene wear was obvious in one patient 12 years after operation. In eight cases, posterior fusion with pedicle screws was required. In two cases, the prosthesis was removed and the segment was circumferentially fused. These procedures resulted in suboptimal long-term results. In this relatively small group of patients operated on with a Charité disc prosthesis, most problems arose from degeneration of other lumbar discs, facet joint arthrosis at the same or other levels, and subsidence of the prosthesis. It is to be expected that many more patients will be seen with late problems some years after this operation as the survivorship will decrease with time. PMID:12902953

van Ooij, André; Oner, F Cumhur; Verbout, Ab J

2003-08-01

235

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

236

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 ...

237

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

238

Kelvin-Helmholtz Instability of Counter-Rotating Discs  

E-print Network

Observations of galaxies and models of accreting systems point to the occurrence of counter-rotating discs where the inner part of the disc ($rfree-fall towards the disc's center over the surface of the inner disc.

Quach, Dan; Lovelace, Richard V E

2014-01-01

239

Migrated herniated disc mimicking a neoplasm  

Microsoft Academic Search

Disc sequestration is defined as migration of a herniated disc fragment into the epidural space such that it is completely\\u000a separated from the parent disc. We report a case of a migrated herniated disc that was initially pathologically diagnosed\\u000a as a cartilage neoplasm. In addition to confounding morphological features, this interpretation may have been influenced by\\u000a an initial radiological interpretation

Benjamin Hoch; George Hermann

2010-01-01

240

Disc Space Infections in Children  

Microsoft Academic Search

Intractable low back pain in children is often due to disc space infections. The clinical presentation, diagnostic workup, and treatment of four cases are presented. Symptoms often occur well before radiographic findings are evident. The diagnosis can only be made by a high degree of suspicion and repeated X-rays. Antecedent causes, such as urinary infection or intravenous administration of narcotics

Robert C. Rubin; George B. Jacobs; Paul R. Cooper; Rosanne L. Wille

1977-01-01

241

A simulation model of focus and radial servos in Compact Disc players with Disc surface defects  

E-print Network

A simulation model of focus and radial servos in Compact Disc players with Disc surface defects P {odgaard, jakob, pa}@control.auc.dk victor@math.wustl.edu hfm@bang-olufsen.dk Abstract Compact Disc players have been solved. A large remain- ing problem to solve is the handling of Compact Discs with severe

Wickerhauser, M. Victor

242

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

243

Artificial Cervical Disc Replacement Improves Mobility  

MedlinePLUS

... The implant components work together with the surrounding spinal structures to provide stability and function. The ProDisc C implant is secured to the vertebral bodies above and below the disc space and held in place with two central keels. All bone contacting surfaces of the ProDisc ...

244

Intervertebral disc extrusion in six cats  

Microsoft Academic Search

Existing reports concerning intervertebral disc disease (IVDD) have focused almost exclusively on dogs, although a small number of individual case reports of IVDD of cats has been published. The medical records of six cats with IVDD were reviewed. Radiographic studies confirmed narrowed intervertebral disc spaces, mineralised intervertebral discs, and one or more extradural compressive lesions of the spinal cord in

MF Knipe; KM Vernau; WJ Hornof; RA LeCouteur

2001-01-01

245

Relevance of jet emitting disc physics to microquasars: application to Cygnus X-1  

NASA Astrophysics Data System (ADS)

Context. Interpretation of the X-ray spectra of X-ray binaries during their hard states requires a hot, optically thin medium. There are several accretion disc models that account for this aspect. However, none is designed to simultaneously explain powerful jets detected during these states. Aims: A new quasi-Keplerian hot accretion disc solution, a jet emitting disc (JED hereafter), which is part of a global disc-jet MHD structure producing stationary super-alfvénic ejection, is investigated here. Its radiative and energetic properties are then compared to the observational constraints found in Cygnus X-1. Methods: We solve the disc energy equation by balancing the local heating term with advection and cooling by synchrotron, bremsstrahlung, and Comptonization processes. The heating term, disc density, accretion velocity, and magnetic field amplitude were taken from published self-similar models of accretion-ejection structures. Both optically thin and thick regimes are considered in a one-temperature, gas-supported disc. Results: Three branches of solutions are found to be possible at a given radius, but we only investigate the hot, optically thin and geometrically slim solutions. These solutions give simultaneously and consistently the radiative and energetics properties of the disc-jet system. They are able to reproduce the global accretion-ejection properties of Cygnus X-1 very well, namely its X-ray spectral emission, jet power, and jet velocity. About half of the released accretion power is used to produce two mildly relativistic (v/c? 0.5) jets, and for a luminosity of about 1% of the Eddington luminosity, the JED temperature and optical depth are close to what is observed in the hard state of Cygnus X-1. Conclusions: The accretion and ejection properties of JEDs agree with the observations of the prototypical black hole binary Cygnus X-1. The JED solutions are likely to be relevant to the whole class of microquasars.

Petrucci, P. O.; Ferreira, J.; Henri, G.; Malzac, J.; Foellmi, C.

2010-11-01

246

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

247

Effect of Intravitreous Anti–Vascular Endothelial Growth Factor Therapy on Choroidal Thickness in Neovascular Age-Related Macular Degeneration Using Spectral-Domain Optical Coherence Tomography  

E-print Network

A critical method of monitoring patients with neovascular age-related macular degeneration (AMD) being treated with anti–vascular endothelial growth factor (anti-VEGF) is optical coherence tomography (OCT), which uses ...

Branchini, Lauren

248

The Effect of Diffusion Rates in Optical Fiber Polymer Coatings on Aging Janet L. Armstrong,a M. John Matthewson, Mayra G. Juarez, Catherine Y. Chou  

E-print Network

The Effect of Diffusion Rates in Optical Fiber Polymer Coatings on Aging Janet L. Armstrong,a M. John Matthewson, Mayra G. Juarez, Catherine Y. Chou Ceramic and Materials Engineering, Rutgers University, Piscataway, NJ 08854-8065 ABSTRACT Optical fibers have been found to exhibit an accelerated rate

Matthewson, M. John

249

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

E-print Network

, fresh water, and dissolved and particulate organic matter to the Oregon/Washington shelf. The optical, nitrate, trace metals, pollution, fresh water; and dissolved and particulate organic matter ABSTRACT The Columbia River Plume is a highly dynamic water mass that supplies silicate and trace metals

Hickey, Barbara

250

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

251

Anisotropic X-ray emission in AGN accretion discs  

E-print Network

Straight-forward models of X-ray reflection in the inner region of accretion discs predict that primary X-ray flux and the flux reflected off the surface of the disc should vary together, albeit a short light travel time delay. Most of the observations, however, show that the X-ray flux can vary while the reflected features remain constant. Here we propose a simple explanation to this. In all likelihood, the emission of a moderately optically thick magnetic flare atop an accretion disc is anisotropic. A constant energy release rate in a flare will appear to produce a variable X-ray flux as the flare rotates with the accretion disc anchoring the magnetic tube. The reflector, on the other hand, receives a constant X-ray flux from the flare. Since the reflected emission is azimuthally symmetric, the observer will see a roughly constant reflected flux (neglecting relativistic effects). The model does not produce quasi-periodic oscillations (QPO) if magnetic flux tubes are sheared out faster than they complete one orbit.

Sergei Nayakshin

2006-11-10

252

Anisotropic X-ray emission in AGN accretion discs  

E-print Network

Straight-forward models of X-ray reflection in the inner region of accretion discs predict that primary X-ray flux and the flux reflected off the surface of the disc should vary together, albeit a short light travel time delay. Most of the observations, however, show that the X-ray flux can vary while the reflected features remain constant. Here we propose a simple explanation to this. In all likelihood, the emission of a moderately optically thick magnetic flare atop an accretion disc is anisotropic. A constant energy release rate in a flare will appear to produce a variable X-ray flux as the flare rotates with the accretion disc anchoring the magnetic tube. The reflector, on the other hand, receives a constant X-ray flux from the flare. Since the reflected emission is azimuthally symmetric, the observer will see a roughly constant reflected flux (neglecting relativistic effects). The model does not produce quasi-periodic oscillations (QPO) if magnetic flux tubes are sheared out faster than they complete one...

Nayakshin, S

2006-01-01

253

Development of hapten-linked microimmunoassays on polycarbonate discs.  

PubMed

An amino-modified polycarbonate surface of compact discs is used to link haptens covalently and directly as an alternative to the classic protein-hapten conjugate adsorption coating strategy employed in immunoassays. The modified surface maintains its physical and optical properties, and a standard disk drive can then read the assay results. Advantages are evaluated, such as the use of a broader spectrum of coupling media including organic solvents that are inappropriate for proteins but necessary for some water-insoluble haptens and the bypassing of the synthesis and purification for protein conjugates. As proof of concept, competitive microimmunoassays were developed for chlorpyrifos, atrazine, and 2-(2,4,5-trichlorophenoxy)propionic acid (2,4,5-TP), in microarray format, obtaining detection limits of 37.2, 8.1, and 76 ng/L, respectively. The sensitivity was 1 order of magnitude better than that obtained for all the studied systems using hapten-protein conjugates adsorbed on polystyrene enzyme-linked immunosorbent assay (ELISA) plates and polycarbonate surfaces. Further, the influence of hapten structure and presentation on molecular recognition pattern is discussed. To our knowledge, this is the first time that microarray and compact disc technologies converge with this particular hapten immobilization mode. The great potential of the approach is demonstrated through the high-throughput capability of the disc in a range of analytical applications, as well as the inherent advantages of compact disc reading technology. PMID:20131798

Tamarit-López, Jesús; Morais, Sergi; Bañuls, María-José; Puchades, Rosa; Maquieira, Angel

2010-03-01

254

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

USGS Publications Warehouse

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

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

2008-01-01

255

Shortest Paths for Disc Obstacles  

Microsoft Academic Search

\\u000a Given a number of obstacles in a plane, the problem of computing a geodesic (or the shortest path) between two points has\\u000a been studied extensively. However, the case where the obstacles are circular discs has not been explored as much as it deserves.\\u000a In this paper, we present an algorithm to compute a geodesic among a set of mutually disjoint

Deok-soo Kim; Kwangseok Yu; Youngsong Cho; Donguk Kim; Chee-keng Yap

2004-01-01

256

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

NASA Astrophysics Data System (ADS)

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

Lai, Dong

2014-06-01

257

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

NASA Astrophysics Data System (ADS)

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

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

2010-09-01

258

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

259

The Effect of Age, Retinal Eccentricity, and Speed on the Detection of Optic Flow Components  

Microsoft Academic Search

Forty observers participated in a study examining the effect of age on the detection of motion in central and peripheral vision. Detection of lamellar (Experiment 1) and radial flow (Experiment 2) was measured for 20 younger observers and 20 older observers (10 men and 10 women in each group). Motion thresholds were measured for angles of 0°, 10°, 20°, and

Paul Atchley; George J. Andersen

1998-01-01

260

High Response Twin-Objective Actuator with Radial Tilt Function for Blu-ray Disc Recorder  

NASA Astrophysics Data System (ADS)

We have developed Blu-ray Disc (BD) optical pick-up with a twin-objective lens actuator which is compatible with compact disc (CD) and digital versatile disc (DVD) in the high-speed BD-read only memory (ROM) and BD Recorder. In order to readout CD and DVD in BD Recorder, we adopted twin-objective lens actuator in consideration of optical utilization efficiency, optical performance and insurance of sufficient working distance (WD). This twin-objective lens actuator has two objectives in radial direction, one is for CD/DVD and the other is for BD. Through our careful investigation in design process, this actuator has extremely high AC sensitivities and good 2nd resonance characteristics in consideration of twin-objective actuator. Also, this actuator has linearity in wide focus range, that is to say, more than ± 1.0 mm and has radial tilt function which is tilt range more than 7 deg.

Kim, Seok Jung; Heor, Tae Youn; Kim, Tae Kyung; Ahn, Young Man; Chung, Chong Sam; Park, Soo Han

2005-05-01

261

The Aerodynamics of a Flying Sports Disc  

NASA Astrophysics Data System (ADS)

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

Potts, Jonathan R.; Crowther, William J.

2001-11-01

262

Hydrodynamic instability in eccentric astrophysical discs  

NASA Astrophysics Data System (ADS)

Eccentric Keplerian discs are believed to be unstable to three-dimensional hydrodynamical instabilities driven by the time-dependence of fluid properties around an orbit. These instabilities could lead to small-scale turbulence, and ultimately modify the global disc properties. We use a local model of an eccentric disc, derived in a companion paper, to compute the non-linear vertical (`breathing mode') oscillations of the disc. We then analyse their linear stability to locally axisymmetric disturbances for any disc eccentricity and eccentricity gradient using a numerical Floquet method. In the limit of small departures from a circular reference orbit, the instability of an isothermal disc is explained analytically. We also study analytically the small-scale instability of an eccentric neutrally stratified polytropic disc with any polytropic index using a Wentzel-Kramers-Brillouin (WKB) approximation. We find that eccentric discs are generically unstable to the parametric excitation of small-scale inertial waves. The non-linear evolution of these instabilities should be studied in numerical simulations, where we expect them to lead to a decay of the disc eccentricity and eccentricity gradient as well as to induce additional transport and mixing. Our results highlight that it is essential to consider the three-dimensional structure of eccentric discs, and their resulting vertical oscillatory flows, in order to correctly capture their evolution.

Barker, A. J.; Ogilvie, G. I.

2014-12-01

263

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

NASA Astrophysics Data System (ADS)

If intermediate-mass black holes (IMBHs) grow efficiently in gas discs around supermassive black holes, their host active galactic nucleus (AGN) discs should exhibit myriad observational signatures. Gap-opening IMBHs in AGN discs can exhibit spectral features and variability analogous to gapped protoplanetary discs. A gap-opening IMBH in the innermost disc imprints ripples and oscillations on the broad Fe K? line which may be detectable with future X-ray missions. A non-gap-opening IMBH will accrete and produce a soft X-ray excess relative to continuum emission. An IMBH on a retrograde orbit in an AGN disc will not open a gap and will generate soft X-rays from a bow-shock `headwind'. Accreting IMBH in a large cavity can generate ULX-like X-ray luminosities and LINER-like optical line ratios from local ionized gas. We propose that many LINERs house a weakly accreting MBH binary in a large central disc cavity and will be luminous sources of gravitational waves (GW). IMBHs in galactic nuclei may also be detected via intermittent observational signatures including: UV/X-ray flares due to tidal disruption events, asymmetric X-ray intensity distributions as revealed by AGN transits, quasi-periodic oscillations and underluminous Type Ia supernovae. GW emitted during IMBH inspiral and collisions may be detected with eLISA and LIGO, particularly from LINERs. We summarize observational signatures and compare to current data where possible or suggest future observations.

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

2014-06-01

264

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

265

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

Microsoft Academic Search

Solid–fluid interactions play an important role in mediating viscoelastic behaviour of biological tissues. In the intervertebral\\u000a disc, water content is governed by a number of factors, including age, disease and mechanical loads, leading to changes in\\u000a stiffness characteristics. We hypothesized that zonal stress distributions depend on load history, or the prior stresses experienced\\u000a by the disc. To investigate these effects,

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

266

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

267

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

268

Stellar population and kinematic profiles in spiral bulges and discs: population synthesis of integrated spectra  

NASA Astrophysics Data System (ADS)

We present a detailed study of the stellar populations (SPs) and kinematics of the bulge and inner disc regions of eight nearby spiral galaxies (Sa-Sd) based on deep Gemini/GMOS data. The long-slit spectra extend to 1-2 disc scalelengths with S/N/Å >= 50. Several different model fitting techniques involving absorption-line indices and full spectrum fitting are explored, and found to weigh age, metallicity and abundance ratios differently. We find that the SPs of spiral galaxies are not well matched by single episodes of star formation; more representative SPs must involve average SP values integrated over the star formation history (SFH) of the galaxy. Our `full population synthesis' method is an optimized linear combination of model templates to the full spectrum with masking of regions poorly represented by the models. Realistic determinations of the SP parameters and kinematics (rotation and velocity dispersion) also rely on careful attention to data/model matching (resolution and flux calibration). The population fits reveal a wide range of age and metallicity gradients (from negative to positive) in the bulge, allowing for diverse formation mechanisms. The observed positive age gradients within the effective radius of some late-type bulges helps reconcile the long-standing conundrum of the coexistence of secular-like kinematics, light profile shape and stellar bar with the `classical'-like old and ?-enhanced SPs in the Milky Way bulge. The discs, on the other hand, almost always show mildly decreasing to flat profiles in both age and metallicity, consistent with inside-out formation. Our spiral bulges follow the same correlations of increasing light-weighted age and metallicity with central velocity dispersion as those of elliptical galaxies and early-type bulges found in other studies, but when SFHs more complex and realistic than a single burst are invoked, the trend with age is shallower and the scatter much reduced. In a mass-weighted context, however, all bulges are predominantly composed of old and metal-rich SPs. While secular contributions to the evolution of many of our bulges are clearly evident, with young (0.001-1Gyr) SPs contributing as much as 90 per cent of the optical (V-band) light, the bulge mass fraction from young stars is small (<~25 per cent). The implies a bulge formation dominated by early processes that are common to all spheroids, whether they currently reside in discs or not. While monolithic collapse cannot be ruled out in some cases, merging must be invoked to explain the SP gradients in most bulges. Further bulge growth via secular processes or `rejuvenated' star formation generally contributes minimally to the stellar mass budget, with the relative secular weight increasing with decreasing central velocity dispersion.

MacArthur, Lauren A.; González, J. Jesús; Courteau, Stéphane

2009-05-01

269

Dynamics of stress wave propagation in a chain of photoelastic discs impacted by a planar shock wave; Part I, experimental investigation  

Microsoft Academic Search

The propagation of stress waves through a chain of discs has been studied experimentally. Optically transparent 20-mm diameter\\u000a discs, made of epoxy, were loaded dynamically by head-on collision with an incident planar shock wave. The loading was done\\u000a in a vertical shock tube. The head-on collision between the punch-plate, placed on top of the chain of discs, and the incident

B. Glam; O. Igra; A. Britan; G. Ben-Dor

2007-01-01

270

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

271

Magnetic resonance imaging of adolescent disc herniation.  

PubMed

Magnetic resonance imaging (MRI) was used to compare the appearance of the spine in 20 adolescents with proven symptomatic intervertebral disc herniations with that in 20 asymptomatic patients who acted as controls. Abnormality in the signal from the nucleus pulposus of one or more discs was present in all patients, while only four of the 20 controls had any abnormal signals. In all the patients the symptomatic disc produced an abnormal signal and in most a herniated fragment of the nucleus pulposus was identified. Fifteen of the 20 patients had multiple-disc abnormality: six had three abnormal discs and nine had two. This suggests there was an underlying diathesis in patients who later developed disc herniation. PMID:3680327

Gibson, M J; Szypryt, E P; Buckley, J H; Worthington, B S; Mulholland, R C

1987-11-01

272

Intervertebral disc extrusion in six cats.  

PubMed

Existing reports concerning intervertebral disc disease (IVDD) have focused almost exclusively on dogs, although a small number of individual case reports of IVDD of cats has been published. The medical records of six cats with IVDD were reviewed. Radiographic studies confirmed narrowed intervertebral disc spaces, mineralised intervertebral discs, and one or more extradural compressive lesions of the spinal cord in each cat. All disc extrusions were located in the thoracolumbar region. Surgical decompression of the spinal cord was achieved in all cats by means of hemilaminectomy and removal of compressive extradural material confirmed to be degenerative disc material. Good to excellent neurological recovery was noted in five of the six cats included in this report. Based on this review, it appears that IVDD of cats has many similarities to IVDD of dogs, and that healthy cats with acute intervertebral disc extrusion(s) respond favourably to surgical decompression of the spinal cord. PMID:11876633

Knipe, M F; Vernau, K M; Hornof, W J; LeCouteur, R A

2001-09-01

273

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

PubMed

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

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

2006-08-01

274

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

275

Thoracic extruded disc mimicking spinal cord tumor  

Microsoft Academic Search

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

Bikash Bose

2003-01-01

276

Anisotropic inverse Compton scattering of photons from the circumstellar disc in PSR B1259-63  

NASA Astrophysics Data System (ADS)

The gamma-ray binary system PSR B1259-63/LS 2883 consists of a 48 ms pulsar orbiting a Be star. The system is particularly interesting because it is the only gamma-ray binary system where the nature of the compact object is known. The non-thermal radiation from the system is powered by the spin-down luminosity of the pulsar and the unpulsed radiation originates from the stand-off shock front which forms between the pulsar and stellar wind. The Be star/optical companion in the system produces an excess infrared (IR) flux from the associated circumstellar disc. This IR excess provides an additional photon source for inverse Compton scattering. We discuss the effects of the IR excess near periastron, for anisotropic inverse Compton scattering and associated gamma-ray production. We determine the IR excess from the circumstellar disc using a modified version of a curve of growth method, which takes into account the changing optical depth through the circumstellar disc during the orbit. The model is constrained using archive data and additional mid-IR observations obtained with the Very Large Telescope (VLT) during 2011 January. The inverse Compton scattering rate was calculated for three orientations of the circumstellar disc. The predicted gamma-ray light curves show that the disc contribution is a maximum around periastron and not around the disc crossing epoch. This is a result of the disc being brightest near the stellar surface. Additional spectroscopic and near-IR observations were obtained of the system and these are discussed in relation to the possibility of shock heating during the disc crossing epoch. Based, in part, on observations made with ESO Telescopes at the Paranal Observatory under programme ID 086.D-0136(B), and on observations made with the Southern African Large Telescope (SALT) under programme 2012-1-RSA-003.

van Soelen, B.; Meintjes, P. J.; Odendaal, A.; Townsend, L. J.

2012-11-01

277

Grain charging in protoplanetary discs  

NASA Astrophysics Data System (ADS)

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

Ilgner, M.

2012-02-01

278

Global Gravitational Instabilities in Discs with Infall  

E-print Network

Gravitational instability plays an important role in driving gas accretion in massive protostellar discs. Particularly strong is the global gravitational instability, which arises when the disc mass is of order 0.1 of the mass of the central star and has a characteristic spatial scale much greater than the disc's vertical scale-height. In this paper we use three-dimensional numerical hydrodynamics to study the development of gravitational instabilities in a disc which is embedded in a dense, gaseous envelope. We find that global gravitational instabilities are the dominant mode of angular momentum transport in the disc with infall, in contrast to otherwise identical isolated discs. The accretion torques created by low-order, global modes of the gravitational instability in a disc subject to infall are larger by a factor of several than an isolated disc of the same mass. We show that this global gravitational instability is driven by the strong vertical shear at the interface between the disc and the envelope,...

Harsono, D; Levin, Yuri

2010-01-01

279

Accretion Discs Show Their True Colours  

NASA Astrophysics Data System (ADS)

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

2008-07-01

280

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

281

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

282

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

PubMed

We present polarization-sensitive optical coherence tomography (PS-OCT) for quantitative assessment of retinal pathologies in age-related macular degeneration (AMD). On the basis of the polarization scrambling characteristics of the retinal pigment epithelium, novel segmentation algorithms were developed that allow one to segment pathologic features such as drusen and atrophic zones in dry AMD as well as to determine their dimensions. Results from measurements in the eyes of AMD patients prove the ability of PS-OCT for quantitative imaging based on the retinal features polarizing properties. Repeatability measurements were performed in retinas diagnosed with drusen and geographic atrophy in order to evaluate the performance of the described methods. PS-OCT appears as a promising imaging modality for three-dimensional retinal imaging and ranging with additional contrast based on the structures' tissue-inherent polarization properties. PMID:21198152

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

2010-01-01

283

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

PubMed Central

We present polarization-sensitive optical coherence tomography (PS-OCT) for quantitative assessment of retinal pathologies in age-related macular degeneration (AMD). On the basis of the polarization scrambling characteristics of the retinal pigment epithelium, novel segmentation algorithms were developed that allow one to segment pathologic features such as drusen and atrophic zones in dry AMD as well as to determine their dimensions. Results from measurements in the eyes of AMD patients prove the ability of PS-OCT for quantitative imaging based on the retinal features polarizing properties. Repeatability measurements were performed in retinas diagnosed with drusen and geographic atrophy in order to evaluate the performance of the described methods. PS-OCT appears as a promising imaging modality for three-dimensional retinal imaging and ranging with additional contrast based on the structures’ tissue-inherent polarization properties. PMID:21198152

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

2011-01-01

284

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

PubMed

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

2014-10-01

285

Disc degeneration in young patients with isthmic spondylolisthesis treated operatively or conservatively: a long-term follow-up.  

PubMed

The purpose of this long-term follow-up was (1) to investigate disc changes in the olisthetic segment in patients treated conservatively, (2) to compare disc changes above the slipped vertebra in conservatively treated patients with those in operatively treated patients, and (3) to establish possible relations of disc changes to the degree of the slip and to subjective back pain symptoms of the patients. The subjects were 227 patients with isthmic L5 olisthesis diagnosed under 20 years of age (mean 13.8 years) with a mean follow-up of 15.4 (range 5-30) years. Of these, 145 patients had been treated with segmental fusion and 82 had been treated conservatively. At follow-up, standing anteroposterior and lateral radiographs as well as flexion/extension views of the lumbar spine were taken. Disc degeneration was graded semiquantitatively: 0 = normal disc height, 1 = decrease of disc height < 50%, 2 = decrease > or = 50%, and 3 = obliteration of the disc. In the conservatively treated patients degeneration of the olisthetic disc was distributed by grade as follows: O: n = 38, 1: n = 24, 2: n = 14, 3: n = 6. No motion at all was observed in the olisthetic segment in 40 patients (48%) with a mean slip of 30%, segmental motion of 4 degrees-18 degrees was found in 42 patients with a mean slip of 14%. There was a statistically significant association of the degree of slip to the severity of disc degeneration and non-mobility of the segment. Grade 1 degeneration of the L4/5 disc occurred in 25.6% of the conservatively treated patients and in 32% of 48 patients treated with L5-S1 fusion. This correlated with the severity of the slip, but not with pain symptoms or pathologic segmental mobility at the time of follow-up. Out of 84 patients with L4-S1 fusion, in 17% grade 1 degeneration of the L3/4 disc was observed, and 3 out of 13 patients (23%) with L3-S1 fusion had grade 1 degeneration of the disc above the fusion. The disc changes had no correlation with subjective pain symptoms. It is concluded that the natural course of isthmic spondylolisthesis is associated with disc degeneration and spontaneous stabilization of the olisthetic segment. Fusion operations do not significantly increase the rate of disc degeneration in the adjacent disc above the fusion after a mean postoperative follow-up of 13.8 years. No correlation between the number of degenerated discs or the degree of degeneration and subjective low back pain symptoms was found. PMID:9455667

Seitsalo, S; Schlenzka, D; Poussa, M; Osterman, K

1997-01-01

286

Prevalence of radiographic detectable intervertebral disc calcifications in Dachshunds surgically treated for disc extrusion  

Microsoft Academic Search

BACKGROUND: An association between the occurrence of calcified discs, visible on radiographic examination (CDVR), and disc extrusions has been suggested in published literature over the past 10-20 years, mainly from Nordic countries. It has also been postulated that dogs without CDVR would not develop disc extrusions. Furthermore, inheritance of CDVR has been calculated and it has been postulated that, by

Cecilia Rohdin; Janis Jeserevic; Ranno Viitmaa; Sigitas Cizinauskas

2010-01-01

287

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

Microsoft Academic Search

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

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

2004-01-01

288

Intervertebral disc viscoelastic parameters and residual mechanics spatially quantified using a hybrid confined/in situ indentation method.  

PubMed

With advancing age, injury, musculoskeletal pathology or a combination of these, a degenerative cascade of biomechanical, biochemical, and nutritional alterations diminish the intervertebral discs' ability to maintain its structure and function. While the biomechanics of isolated disc tissues has been investigated across this degenerative spectrum, none have attempted to retain the in situ disc-endplate morphology during compressive tissue characterization. The objective of this study was to spatially quantify the viscoelastic parameters of the intervertebral disc throughout degeneration, including the as yet unreported residual stress/strain. This required the development of a hybrid confined/in situ indentation methodology, which preserves the disc structural morphology. At four locations of the disc (anterior-AF, right and left lateral AF, and NP) stress-relaxation tests were performed using the hybrid confined/in situ indentation method, which utilizes the vertebral endplate as the porous indenter tip. This method allows the endplate to remain interwoven with the disc tissue, retaining its native orientation. Healthy disc tissue exhibited significantly higher residual stress values compared to both moderate and severe degeneration in all locations (p<0.0156). Furthermore, the equilibrium stress at 15% strain (stress relaxation) was significantly diminished with advancing disc degeneration (p<0.0241). The equilibrium viscoelastic parameters show healthy discs encounter higher forces at the same strain level, and are able to maintain this force, where degenerated discs are unable to maintain this force throughout time. This morphology-conserved method provides insight into the spatial compressive mechanical properties of the intervertebral disc across the degeneration spectrum and will aid in modeling these tissue changes. PMID:22197186

Ellingson, Arin M; Nuckley, David J

2012-02-01

289

Theory of Black Hole Accretion Discs  

NASA Astrophysics Data System (ADS)

Part I. Observations of Black Holes: 1. Black holes in our Galaxy: observations P. Charles; 2. Black holes in Active Galactic Nuclei: observations G. M. Madejski; Part II. Physics Close to a Black Hole: 3. Physics of black holes I. D. Novikov; 4. Physics of black hole accretion M. A. Abramowicz; Part III. Turbulence, Viscosity: 5. Disc turbulence and viscosity A. Brandenburg; Part IV. Radiative Processes: 6. The role of electron-positron pairs in accretion flows G. Björnsson; 7. Accretion disc-corona models and X/Y-ray spectra of accreting black holes J. Poutanen; 8. Emission lines: signatures of relativistic rotation A. C. Fabian; Part V. Accretion Discs: 9. Spectral tests of models for accretion disks around black holes J. H. Krolik; 10. Advection-dominated accretion around black holes R. Narayan, R. Mahadevan and E. Quataert; 11. Accretion disc instabilities and advection dominated accretion flows J.-P. Lasota; 12. Magnetic field and multi-phase gas in AGN A. Celotti and M. J. Rees; Part V. Discs in Binary Black Holes: 13. Supermassive binary black holes in galaxies P. Artymowicz; Part VI. Stability of Accretion Discs: 14. Large scale perturbation of an accretion disc by a black hole binary companion J. C. B. Papaloizou, C. Terquem and D. N. C. Lin; 15. Stable oscillations of black hole accretion discs M. Nowak and D. Lehr; Part VI. Coherant Structures: 16. Spotted discs A. Bracco, A. Provenzale, E. A. Spiegel and P. Yecko; Self-organized critically in accretion discs P. Wiita and Y. Xiong; Summary: old and new advances in black hole accretion disc theory R. Svensson.

Abramowicz, Marek A.; Björnsson, Gunnlaugur; Pringle, James E.

2010-08-01

290

Theory of Black Hole Accretion Discs  

NASA Astrophysics Data System (ADS)

Part I. Observations of Black Holes: 1. Black holes in our Galaxy: observations P. Charles; 2. Black holes in Active Galactic Nuclei: observations G. M. Madejski; Part II. Physics Close to a Black Hole: 3. Physics of black holes I. D. Novikov; 4. Physics of black hole accretion M. A. Abramowicz; Part III. Turbulence, Viscosity: 5. Disc turbulence and viscosity A. Brandenburg; Part IV. Radiative Processes: 6. The role of electron-positron pairs in accretion flows G. Björnsson; 7. Accretion disc-corona models and X/Y-ray spectra of accreting black holes J. Poutanen; 8. Emission lines: signatures of relativistic rotation A. C. Fabian; Part V. Accretion Discs: 9. Spectral tests of models for accretion disks around black holes J. H. Krolik; 10. Advection-dominated accretion around black holes R. Narayan, R. Mahadevan and E. Quataert; 11. Accretion disc instabilities and advection dominated accretion flows J.-P. Lasota; 12. Magnetic field and multi-phase gas in AGN A. Celotti and M. J. Rees; Part V. Discs in Binary Black Holes: 13. Supermassive binary black holes in galaxies P. Artymowicz; Part VI. Stability of Accretion Discs: 14. Large scale perturbation of an accretion disc by a black hole binary companion J. C. B. Papaloizou, C. Terquem and D. N. C. Lin; 15. Stable oscillations of black hole accretion discs M. Nowak and D. Lehr; Part VI. Coherant Structures: 16. Spotted discs A. Bracco, A. Provenzale, E. A. Spiegel and P. Yecko; Self-organized critically in accretion discs P. Wiita and Y. Xiong; Summary: old and new advances in black hole accretion disc theory R. Svensson.

Abramowicz, Marek A.; Björnsson, Gunnlaugur; Pringle, James E.

1999-03-01

291

Kinematics and excitation of the molecular hydrogen accretion disc in NGC 1275  

NASA Astrophysics Data System (ADS)

We report the results of high spatial and spectral resolution integral-field spectroscopy of the central ˜3 × 3 arcsec2 of the active galaxy NGC 1275 (Perseus A), based on observations with the Near-infrared Integral Field Spectrograph (NIFS) and the ALTitude conjugate Adaptive optics for the InfraRed (ALTAIR) adaptive-optics system on the Gemini North telescope. The circum-nuclear disc in the inner R ˜ 50 pc of NGC 1275 is seen in both the H2 and [Fe II] lines. The disc is interpreted as the outer part of a collisionally excited turbulent accretion disc. The kinematic major axis of the disc at a position angle of 68° is oriented perpendicular to the radio jet. A streamer-like feature to the south-west of the disc, detected in H2 but not in [Fe II], is discussed as one of possibly several molecular streamers, presumably falling into the nuclear region. Indications of an ionization structure within the disc are deduced from the He I and Br? emission lines, which may partially originate from the inner portions of the accretion disc. The kinematics of these two lines agrees with the signature of the circum-nuclear disc, but both lines display a larger central velocity dispersion than the H2 line. The ro-vibrational H2 transitions from the core of NGC 1275 are indicative of thermal excitation caused by shocks and agree with excitation temperatures of ˜1360 and ˜4290 K for the lower and higher energy H2 transitions, respectively. The data suggest X-ray heating as the dominant excitation mechanism of [Fe II] emission in the core, while fast shocks are a possible alternative. The [Fe II] lines indicate an electron density of ˜4000 cm-3. The H2 disc is modelled using simulated NIFS data cubes of H2 emission from inclined discs in Keplerian rotation around a central mass. Assuming a disc inclination of 45° ± 10°, the best-fitting models imply a central mass of (8 + 7 - 2) × 108 M?. Taken as a black hole mass estimate, this value is larger than previous estimates for the black hole mass in NGC 1275, but is in agreement with the M-? relation within the rms scatter. However, the molecular gas mass in the core region is tentatively estimated to be non-negligible, which suggests that the central mass may rather represent an upper limit for the black hole mass. In comparison to other H2-luminous radio galaxies, we discuss the relative role of jet feedback and accretion in driving shocks and turbulence in the molecular gas component.

Scharwächter, J.; McGregor, P. J.; Dopita, M. A.; Beck, T. L.

2013-03-01

292

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

293

Changes in disc herniation after CT-guided Percutaneous Laser Disc Decompression (PLDD): MR findings  

NASA Astrophysics Data System (ADS)

The aim of Percutaneous Laser Disc Decompression (PLDD) is to vaporize a small portion of the nucleus pulposus. Clinical efficacy of this technique is largely proven. However, time-evolution of intervertebral disc and its hernia after PLDD is not known. This study analyses changes in disc herniation and its native intervertebral disc at a mean follow-up of 7.5 months after PLDD in asymptomatic patients. Main observations at MRI are appearance of a high signal on T2WI in the hernia in 59%, shrinking of the hernia in 66% and overall stability of disc height.

Brat, Hugues G.; Bouziane, Tarik; Lambert, Jean; Divano, Luisa

2004-09-01

294

The tidal disruption of protoplanetary accretion discs  

Microsoft Academic Search

In this paper we revisit the problem of the tidal interaction occurring between a protostellar accretion disc and a secondary point mass following a parabolic trajectory. We model the disc response analytically and we compare our results with three-dimensional SPH simulations. Inviscid as well as viscous hydrodynamics is considered. We show that in a viscous system the response derived from

John D. Larwood

1997-01-01

295

Anisothermal modelling applied to brake discs  

Microsoft Academic Search

An anisothermal elastoviscoplastic three-dimensional model is used in order to predict the response of brake discs mounted on the French TGV (high speed train). The brake disc is subjected simultaneously to mechanical and thermal cyclic loadings by the application of brake pads to the friction surface. This anisothermal law is based on the internal thermodynamic variables and takes into account

R. El Abdi; H. Samrout

1999-01-01

296

Arrays on disc for screening and quantification of pollutants.  

PubMed

A rapid compact disc based methodology for screening and quantification of organic pollutants in mandarin juices is presented. The assay is established on the coating conjugate indirect competitive principle and developed under disc-array configuration. The detection is based on the acquisition of attenuated reflective signals that were proportional to optical density of the immunoreaction product. The competitive assay is applied to quantify simultaneously, in a selective manner, non-systemic insecticides in mandarin juices. The detection limits were 0.2 and 0.1 ?g L(-1) and the sensitivity 2.1 and 1.5 ?g L(-1), for chlorpyrifos and fenthion, respectively. Pollutants were directly quantified after sample dilution in a total time of 40 min. Also, the implementation of positive and negative controls into the array configuration served as an automatic quality control test. The effect of thermal treatment on pesticide dissipation was studied and found that it was insignificant under the studied conditions. Recovery intervals ranged from 96-105% to 94-103%, for chlorpyrifos and fenthion, respectively and were similar to those obtained with gas chromatography coupled to mass spectrometry. In the current configuration, 64 samples can be simultaneously analyzed on a disc at a very competitive value, demonstrating its potential for high-throughput multiplexed screening applications for controlled monitoring programs in low-level labs or outside the lab setting. PMID:23746409

Navarro, Patricia; Morais, Sergi; Gabaldón, Jose A; Pérez, Antonio J; Puchades, Rosa; Maquieira, Angel

2013-06-19

297

Constant rate shearing on two-dimensional cohesive discs  

Microsoft Academic Search

We performed two-dimensional molecular dynamics simulations of cohesive discs under shear. The cohesion between the discs is added by the action of springs between very next neighbouring discs, modelling capillary forces. The geometry of the cell allows disc-disc shearing and not disc-cell wall shearing as is commonly found in the literature. Does a stick-slip phenomenon happen though the upper cover

N. Olivi-Tran; O. Pozo; N. Fraysse

2005-01-01

298

Simulations of the Galactic Centre Stellar Discs In a Warped Disc Origin Scenario  

NASA Astrophysics Data System (ADS)

The Galactic Center (GC) hosts a population of young stars some of which seem to form a system of mutually inclined warped discs. While the presence of young stars in the close vicinity of the massive black hole is already problematic, their orbital configuration makes the situation even more puzzling. We present a possible warped disc origin scenario for these stars, which assumes an initially flat accretion disc which develops a warp through Pringle instability, or Bardeen-Petterson Effect. By working out the critical radii and the time scales involved, we argue that disc warping is plausible for GC parameters. We construct time evolution models for such discs considering the discs' self-gravity, and the torques exerted by the surrounding old star cluster. Our simulations suggest that the best agreement for a purely self-gravitating model is obtained for a disc-to-black hole mass ratio of Md/Mbh ~ 0.001.

Ulubay-Siddiki, A.; Bartko, H.

2012-07-01

299

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

300

Structure and evolutionary history of DISC1.  

PubMed

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

Sanchez-Pulido, Luis; Ponting, Chris P

2011-10-15

301

Compositional Dependence of Optical Constants and Microstructures of GeSbTe Thin Films for Compact-Disc-Rewritable (CD-RW) Readable with Conventional CD-ROM Drives  

Microsoft Academic Search

We studied the dependence of optical constants and microstructures of (GeTe)x(Sb2Te3)1-x films on composition to determine the optimal composition of phase change recording materials. The maximal differences in optical constants between crystalline and amorphous phases and the minimal crystalline grain sizes of the films were obtained at Ge39Sb10Te51. Using Ge39Sb10Te51 as a recording layer and TiO2 and SiO2 as interference

Naohiko Kato; Yasuhiko Takeda; Tatsuo Fukano; Tomoyoshi Motohiro; Shouichi Kawai; Hironari Kuno

1999-01-01

302

Detection of surface defects and servo signal restoration for a compact disc player  

Microsoft Academic Search

Compact disc (CD) players have been on the market for more than two decades, and the involved technologies, including control are very mature. Some problems, however, still remain with respect to playing CDs having to surface defects like scratches and fingerprints. Two servo control loops are used to keep the optical pick-up unit (OPU) focused and radially locked to the

Peter Fogh Odgaard; Jakob Stoustrup; Palle Andersen; Henrik Fløe Mikkelsen

2006-01-01

303

Optical ages on loess derived from outwash surfaces constrain the advance of the Laurentide Ice Sheet out of the Lake Superior Basin, USA  

E-print Network

such an application: the timing of the advance of the Laurentide Ice Sheet in Wisconsin. Considerable de- bate existsOptical ages on loess derived from outwash surfaces constrain the advance of the Laurentide Ice Sheet out of the Lake Superior Basin, USA Randall J. Schaetzl a, , Steven L. Forman b , John W. Attig c

Schaetzl, Randall

304

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

305

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

306

Intervertebral disc properties: challenges for biodevices.  

PubMed

Intervertebral disc biodevices that employ motion-preservation strategies (e.g., nucleus replacement, total disc replacement and posterior stabilization devices) are currently in use or in development. However, their long-term performance is unknown and only a small number of randomized controlled trials have been conducted. In this article, we discuss the following biodevices: interbody cages, nuclear pulposus replacements, total disc replacements and posterior dynamic stabilization devices, as well as future biological treatments. These biodevices restore some function to the motion segment; however, contrary to expectations, the risk of adjacent-level degeneration does not appear to have been reduced. The short-term challenge is to replicate the complex biomechanical function of the motion segment (e.g., biphasic, viscoelastic behavior and nonlinearity) to improve the quality of motion and minimize adjacent level problems, while ensuring biodevice longevity for the younger, more active patient. Biological strategies for regeneration and repair of disc tissue are being developed and these offer exciting opportunities (and challenges) for the longer term. Responsible introduction and rigorous assessment of these new technologies are required. In this article, we will describe the properties of the disc, explore biodevices currently in use for the surgical treatment of low back pain (with an emphasis on lumbar total disc replacement) and discuss future directions for biological treatments. Finally, we will assess the challenges ahead for the next generation of biodevices designed to replace the disc. PMID:21542708

Costi, John J; Freeman, Brian J C; Elliott, Dawn M

2011-05-01

307

Optics  

NSDL National Science Digital Library

This page allows users to simulate standard optic elements (lens, mirror, dielectrics, sources, apertures) and observe how light rays propagate through these elements. Element properties, such as position and focal length, can be adjusted using and a click and drag metaphor.

Christian, Wolfgang; Belloni, Mario

2008-02-09

308

Dynamical instabilities in disc-planet interactions  

NASA Astrophysics Data System (ADS)

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

Lin, Min-Kai

2012-03-01

309

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

310

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.; GRUNEWALD, Ellen; SOARES, Dinesh C.; BORKOWSKA, Malgorzata; MILLAR, J. Kirsty

2012-01-01

311

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

2008-06-27

312

The Mitek mini anchor for TMJ disc repositioning: surgical technique and results.  

PubMed

This study evaluated our treatment outcomes in 105 patients (188 discs) using the Mitek mini anchor for temporomandibular joint (TMJ) articular disc repositioning surgery, with 88 patients having simultaneous orthognathic surgery. Criteria for inclusion into the study were: (1) Presurgical TMJ disc displacement with salvageable disc; (2) No prior TMJ surgery; (3) TMJ disc repositioning with the Mitek mini anchor; (4) Absence of connective tissue/autoimmune disease; (5) Absence of postsurgical trauma; and (6) Minimum of 12 months postsurgery follow up. Presurgery (T1), immediately postsurgery (T2), and longest follow up (LFU) clinical and radiographic evaluations were performed. The mean age of the patients was 32.6 years (range 14-57 years), and mean follow-up time was 46.2 months (range 14-84 months). Radiographic evaluation at LFU demonstrated no significant condylar resorption or positional changes of the anchors. At LFU, there was a statistically significant reduction in: TMJ pain, facial pain, headaches, TMJ noises and disability, and improvement in jaw function and diet. Maximum incisal opening improved slightly and lateral excursive movements decreased slightly. The Mitek mini anchor provides a predictable method for stabilizing the TMJ articular disc to the condyle and a high success rate in decreasing TMJ dysfunction and pain in patients with no previous TMJ surgery. PMID:11829231

Mehra, P; Wolford, L M

2001-12-01

313

Optical ages indicate the southwestern margin of the Green Bay Lobe in Wisconsin, USA, was at its maximum extent until about 18,500 years ago  

USGS Publications Warehouse

Samples for optical dating were collected to estimate the time of sediment deposition in small ice-marginal lakes in the Baraboo Hills of Wisconsin. These lakes formed high in the Baraboo Hills when drainage was blocked by the Green Bay Lobe when it was at or very near its maximum extent. Therefore, these optical ages provide control for the timing of the thinning and recession of the Green Bay Lobe from its maximum position. Sediment that accumulated in four small ice-marginal lakes was sampled and dated. Difficulties with field sampling and estimating dose rates made the interpretation of optical ages derived from samples from two of the lake basins problematic. Samples from the other two lake basins-South Bluff and Feltz basins-responded well during laboratory analysis and showed reasonably good agreement between the multiple ages produced at each site. These ages averaged 18.2. ka (n= 6) and 18.6. ka (n= 6), respectively. The optical ages from these two lake basins where we could carefully select sediment samples provide firm evidence that the Green Bay Lobe stood at or very near its maximum extent until about 18.5. ka.The persistence of ice-marginal lakes in these basins high in the Baraboo Hills indicates that the ice of the Green Bay Lobe had not experienced significant thinning near its margin prior to about 18.5. ka. These ages are the first to directly constrain the timing of the maximum extent of the Green Bay Lobe and the onset of deglaciation in the area for which the Wisconsin Glaciation was named. ?? 2011 Elsevier B.V.

Attig, J.W.; Hanson, P.R.; Rawling, J.E.; Young, A.R.; Carson, E.C.

2011-01-01

314

ENGINEERED DISC-LIKE ANGLE-PLY STRUCTURES FOR INTERVERTEBRAL DISC REPLACEMENT  

PubMed Central

Study Design Develop construction algorithm in which electrospun nanofibrous scaffolds are coupled with a biocompatible hydrogel to engineer a mesenchymal stem cell (MSC)-based disc replacement. Objective Engineer a disc-like angle-ply structure (DAPS) that replicates the multi-scale architecture of the intervertebral disc. Summary of Background Data Successful engineering of a replacement for the intervertebral disc requires replication of its mechanical function and anatomic form. Despite many attempts to engineer a replacement for ailing and degenerated discs, no prior study has replicated the multi-scale hierarchical architecture of the native disc, and very few have assessed the mechanical function of formed neo-tissues. Methods A new algorithm for the construction of a disc analogue was developed, using agarose to form a central nucleus pulposus and electrospun nanofibrous scaffolds to form the annulus fibrosus region (AF, based on oriented nanofibrous scaffolds). Bovine MSCs were seeded into both regions and biochemical, histological, and mechanical maturation were observed with in vitro culture. Results We show that mechanical testing in compression and torsion, two loading modalities commonly used to assess disc mechanics, reveal equilibrium and time-dependent behaviors that are qualitatively similar to native tissue, although lesser in magnitude. Further, we demonstrate that cells seeded into the two regions adopt distinct morphologies that mirror those seen in native tissue, and that, in the AF region, this ordered community of cells deposited matrix that is organized in an angle-ply configuration. Finally, constructs demonstrated functional development with long-term in vitro culture. Conclusion These findings provide a new approach for disc tissue engineering that replicates multi-scale form and function of the intervertebral disc, providing a foundation from which to build a multi-scale, biologic, anatomically and hierarchically relevant composite disc analogue for eventual disc replacement. PMID:20354467

Nerurkar, Nandan L.; Sen, Sounok; Huang, Alice H.; Elliott, Dawn M.; Mauck, Robert L.

2012-01-01

315

Cervical intervertebral disc injury during simulated frontal impact  

Microsoft Academic Search

Cervical disc injury due to frontal impact has been observed in both clinical and biomechanical investigations; however, there is a lack of data that elucidate the mechanisms of disc injury during these collisions. The goals of the current study were to determine the peak dynamic disc annular tissue strain and disc shear strain during simulated frontal impact of the whole

S. Ito; P. C. Ivancic; A. M. Pearson; Y. Tominaga; S. E. Gimenez; W. Rubin; Manohar M. Panjabi

2005-01-01

316

A simple approach to the evolution of twisted accretion discs  

Microsoft Academic Search

A simple set of equations is introduced which governs the time evolution of a twisted accretion disc. The time evolution is governed by two 'viscosities', one governing shear within the plane of the disc and the other governing shear perpendicular to the disc (brought about by non-planarity of the disc). It is shown that these equations can be put in

J. E. Pringle

1992-01-01

317

Inside-out evacuation of transitional protoplanetary discs by the  

E-print Network

, a linear instability that amplifies magnetic fields in shearing discs and drives turbulence2 . The innerLETTERS Inside-out evacuation of transitional protoplanetary discs by the magneto.1038/nphys661 A newborn star is encircled by a remnant disc of gas and dust. A fraction of the disc coalesces

Loss, Daniel

318

Magnetic and vertical shear instabilities in accretion discs  

Microsoft Academic Search

ABSTRA C T The stability properties of magnetized discs rotating with angular velocity Q º Q?s; zfi, dependent on both the radial and the vertical coordinates s and z, are considered. Such a rotation law is adequate for many astrophysical discs (e.g., galactic and protoplanetary discs, as well as accretion discs in binaries). In general, the angular velocity depends on

V. Urpin; A. Brandenburg

1997-01-01

319

Clinical experience in cell-based therapeutics: Disc chondrocyte transplantation  

Microsoft Academic Search

Disc herniation treated by discectomy results in a significant loss of nucleus material and disc height. Biological restoration through the use of autologous disc chondrocyte transplantation offers a potential to achieve functional integration of disc metabolism and mechanics.Chondrocytes that have been removed from damaged cartilaginous tissues maintain a capacity to proliferate, produce and secrete matrix components and respond to physical

Hans Jörg Meisel; Vilma Siodla; Timothy Ganey; Yvonne Minkus; William C. Hutton; Olivera J. Alasevic

2007-01-01

320

HYPERBOLIC RELATIVELY HYPERBOLIC GRAPHS AND DISC URSULA HAMENSTADT  

E-print Network

to investigate the geometry of graphs of discs in a handlebody. A handlebody of genus g 1 is a compact threeHYPERBOLIC RELATIVELY HYPERBOLIC GRAPHS AND DISC GRAPHS URSULA HAMENST¨ADT Abstract. We show, we show that the disc graph and the electrified disc graph of a handlebody H of genus g 2

Hamenstädt, Ursula

321

21 CFR 866.1620 - Antimicrobial susceptibility test disc.  

Code of Federal Regulations, 2013 CFR

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

2013-04-01

322

21 CFR 866.1620 - Antimicrobial susceptibility test disc.  

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

2014-04-01

323

21 CFR 866.1620 - Antimicrobial susceptibility test disc.  

Code of Federal Regulations, 2010 CFR

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

2010-04-01

324

21 CFR 866.1620 - Antimicrobial susceptibility test disc.  

Code of Federal Regulations, 2011 CFR

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

2011-04-01

325

21 CFR 866.1620 - Antimicrobial susceptibility test disc.  

Code of Federal Regulations, 2012 CFR

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

2012-04-01

326

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

327

L5-S1 disc replacement after two previous fusion surgeries for scoliosis.  

PubMed

Following scoliosis surgery, lumbar motion segment degeneration below the level of fusion is not uncommon. Especially long fusions extending to the mid and lower lumbar spine increase the likelihood of degeneration of the remaining motion segments. The management for these patients is controversial and depends on the clinical presentation and level of degeneration. The increasing confidence in motion-preserving technology leads to a dilemma on whether to fuse the remaining lumbar levels or risk utilising disc arthroplasty to preserve the remaining motion segments and facilitate coronal balance in patients with previous long fusion for scoliosis. We present an interesting case of a 44-year-old lady, who underwent two-stage corrective surgery for progressive idiopathic scoliosis at the age of 22 years. In the first stage, she had T11-L3 anterior fusion, whilst in the second stage posterior fusion was done from T5 to L3. At 22 years after the initial surgery, she presented with worsening low back pain and bilateral L4 radicular symptoms. MRI scan confirmed severe disc degeneration at L3-4 and L5-S1 levels with preserved L4-5 disc. She initially underwent L3-L4 decompression and posterolateral fusion at that level, which relieved her radicular symptoms. However, she had persistent pain at the lumbosacral junction with Modic I changes. The options of an anterior L5-S1 fusion or disc replacement were considered and discussed with the patient. The disc replacement option was decided upon with the patient, as anterior fusion was judged to increase the risk of coronal imbalance. At the 1-year follow-up, she reported significant improvement in the back pain. The radiographs at 1 year showed satisfactory position and function of the artificial disc replacement. The disc was flexed laterally, accommodating the coronal balance of the spine. We conclude that L5-S1 motion segment can be preserved with artificial disc replacement in patients with previous long fusion for scoliosis surgery. The real difficulty arises when choosing between disc replacement and extension of fusion. In our patient, the disc replacement has worked well so far. However, the disc is clearly at a mechanical disadvantage, and loss of function in the mid- or long term would not be surprising. PMID:20803157

Jehan, Shah; Elsayed, Sherief; Webb, John; Boszczyk, Bronek

2011-05-01

328

Protoplanetary disc evolution affected by star-disc interactions in young stellar clusters  

E-print Network

Most stars form in a clustered environment. Therefore, it is important to assess how this environment influences the evolution of protoplanetary discs around young stars. In turn, this affects their ability to produce planets and ultimately life. We present here for the first time 3D SPH/N-body simulations that include both the hydrodynamical evolution of the discs around their natal stars, as well as the dynamics of the stars themselves. The discs are viscously evolving, accreting mass onto the central star and spreading. We find penetrating encounters to be very destructive for the discs as in previous studies, although the frequency of such encounters is low. We also find, however, that encounter influence the disc radii more strongly than other disc properties such as the disc mass. The disc sizes are set by the competition between viscous spreading and the disruptive effect of encounters. As discs spread, encounters become more and more important. In the regime of rapid spreading encounters simply trunca...

Rosotti, Giovanni P; Ovelar, Maria de Juan; Hubber, David A; Kruijssen, J M Diederik; Ercolano, Barbara; Walch, Stefanie

2014-01-01

329

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

330

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

331

The tidal disruption of protoplanetary accretion discs  

Microsoft Academic Search

In this paper we revisit the problem of the tidal interaction occuring\\u000abetween a protostellar accretion disc and a secondary point mass following a\\u000aparabolic trajectory. We model the disc response analytically and we compare\\u000aour results with three-dimensional SPH simulations. Inviscid as well as viscous\\u000ahydrodynamics is considered. We show that in a viscous system the response\\u000aderived from

John D. Larwood

1997-01-01

332

Numerical analysis of railway brake disc  

Microsoft Academic Search

A certain number of railway brake discs made of gray cast iron, showed the presence of small cracks only after a few thousand\\u000a kilometers. To investigate main causes of a brake disc failure, numerical analysis was done by using ABAQUS software. Numerical\\u000a analysis resulted from a physical model of heat flux in dependence of braking time. Physical model was applied

Blaž Šamec; Grega Oder; Tone Lerher; Iztok Potr?

2011-01-01

333

Simulation of a spinstabilised sports disc  

Microsoft Academic Search

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

W. J. Crowther; J. R. Potts

2007-01-01

334

Markers of lutein and zeaxanthin status in two age groups of men and women: dietary intake, serum concentrations, lipid profile and macular pigment optical density  

PubMed Central

Background & aims Lutein and zeaxanthin accumulate in retina (macular pigment). Their nutritional status can be assessed using dietary or biochemical markers and both have been associated with macular pigment optical density. We proposed to assess dietary and status markers of lutein and zeaxanthin in a group of healthy Spanish volunteers, considering the potential influence of age, gender and serum lipids to investigate the predictors of the macular pigment optical density. Methods Serum lutein and zeaxanthin concentrations, dietary intake and macular pigment optical density were determined in 108 healthy men and women (20–35 and 45–65 years), using high-performance liquid chromatography, 3-day food records and heterochromic flicker photometry, respectively. Mann–Whitney U-test, Spearman correlation coefficient and multivariate regression analysis were used for the statistical study. Results Serum concentrations and dietary intake of lutein plus zeaxanthin (p?optical density was lower (p?=?0.038). The highest correlation coefficients between intake and serum were for fruit and serum lutein (??=?0.452, p?optical density correlated with serum xanthophylls (??=?0.223, p?=?0.02) and fruit and vegetable intake (??=?0.350, p?=?0.0002), showing highest correlations when lutein and zeaxanthin were expressed in relation to serum lipids in older subjects (??=?0.262, p?=?0.006). Multivariate regression analysis identified age and serum lutein as major predictors of macular pigment optical density (total sample), and a coefficient of determination of 29.7% for the model including lutein?+?zeaxathin/cholesterol?+?triglycerides, sex and fruit?+?vegetables in the older group. Conclusions The establishment of normal/reference ranges for serum lutein and zeaxanthin should consider age ranges and be expressed in relation to lipid concentrations, at least in subjects over 45 years, as this could influence macular pigment optical density. The macular pigment optical density showed age-specific correlations with lutein plus zeaxanthin expressed in relation to serum lipid concentrations as well as with the fruit and vegetable intake. PMID:24889185

2014-01-01

335

Optical spectra of the carbon-oxygen accretion discs in the ultra-compact X-ray binaries 4U 0614+09, 4U 1543-624 and 2S 0918-549  

E-print Network

We present optical spectra in the range 4600 -- 8600 A for three low-mass X-ray binaries which have been suggested to belong to the class of ultra-compact X-ray binaries based on their X-ray spectra. Our spectra show no evidence for hydrogen or helium emission lines, as are seen in classical X-ray binaries. The spectrum of 4U~0614+09 does show emission lines which we identify with carbon and oxygen lines of CII, CIII, OII and OIII. While the spectra of 4U 1543-624 and 2S 0918-549 have a lower signal-to-noise ratio, and thus are more difficult to interpret, some of the characteristic features of 4U 0614+09 are present in these spectra too, although sometimes they are clearly weaker. We conclude that the optical spectra give further evidence for the ultra-compact nature of these X-ray binaries and for their donor stars being carbon-oxygen white dwarfs.

G. Nelemans; P. G. Jonker; T. R. Marsh; M. van der Klis

2003-12-01

336

Turbulent drag reduction through oscillating discs  

E-print Network

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...

Wise, Daniel J

2014-01-01

337

Photoevaporation of protoplanetary discs I: hydrodynamic models  

E-print Network

In this paper we consider the effect of the direct ionizing stellar radiation field on the evolution of protoplanetary discs subject to photoevaporative winds. We suggest that models which combine viscous evolution with photoevaporation of the disc (e.g. Clarke, Gendrin & Sotomayor 2001) incorrectly neglect the direct field after the inner disc has drained, at late times in the evolution. We construct models of the photoevaporative wind produced by the direct field, first using simple analytic arguments and later using detailed numerical hydrodynamics. We find that the wind produced by the direct field at late times is much larger than has previously been assumed, and we show that the mass-loss rate scales as $R_{in}^{1/2}$ (where $R_{in}$ is the radius of the instantaneous inner disc edge). We suggest that this result has important consequences for theories of disc evolution, and go on to consider the effects of this result on disc evolution in detail in a companion paper (Alexander, Clarke & Pringle 2006b).

R. D. Alexander; C. J. Clarke; J. E. Pringle

2006-03-09

338

Quantitative Subanalysis of Optical Coherence Tomography after treatment with Ranibizumab for Neovascular Age-Related Macular Degeneration  

PubMed Central

Purpose To investigate the effects of ranibizumab on retinal morphology in patients with neovascular age-related macular degeneration (AMD) using optical coherence tomography (OCT) quantitative subanalysis. Methods Data from 95 patients receiving intravitreal ranibizumab for neovascular AMD were collected. StratusOCT images were analyzed using custom software entitled “OCTOR” which allows precise positioning of pre-specified boundaries on every B-scan. Changes in thickness/volume of the retina, subretinal fluid (SRF), subretinal tissue (SRT), and pigment epithelial detachments (PEDs) at week 1, and at months 1, 3, 6 and 9 post-treatment were calculated. Results Total retinal volume reached its nadir at month 1, with an average reduction of 0.43 mm3 (P<0.001). By month 9, this initial change had been reduced to a mean reduction of 0.32 mm3 (P=0.0011). Total SRF volume reached its lowest level by month 1, with an average reduction of 0.24 mm3 (P<0.001). This reduction lessened subsequently, to 0.18 mm3 by month 9. There was an average 0.3 mm3 decrease in total PED volume by month 1 (P<0.001), and this later declined further, to 0.45 mm3 by month 9 (P=0.0014). Total SRT volume was reduced by an average of 0.07 mm3 at month 1 (P=0.0159) and subsequently remained constant. Conclusions Although neurosensory retinal edema and SRF, showed an early reduction to nadir following initiation of ranibizumab therapy, the effect on the retina was attenuated over time, suggesting a possible tachyphylaxis. PED volume showed a slower but progressive reduction. Manual quantitative OCT subanalysis may allow a more precise understanding of anatomic outcomes and their correlation with visual acuity. PMID:18408176

Keane, Pearse A.; Liakopoulos, Sandra; Ongchin, Sharel C.; Heussen, Florian M.; Msutta, Sandeep; Chang, Karen T.; Walsh, Alexander C.

2008-01-01

339

Imaging of the retinal pigment epithelium in age-related macular degeneration using polarization-sensitive optical coherence tomography.  

PubMed

Purpose. Spectral-domain optical coherence tomography (SD-OCT) provides new insights into the understanding of age-related macular degeneration (AMD) but limited information on the nature of hyperreflective tissue at the level of the retinal pigment epithelium. Therefore, polarization-sensitive (PS) SD-OCT was used to identify and characterize typical RPE findings in AMD. Methods. Forty-four eyes of 44 patients with AMD were included in this prospective case series representing the entire AMD spectrum from drusen (n = 11), geographic atrophy (GA; n = 11), neovascular AMD (nAMD; n = 11) to fibrotic scars (n = 11). Imaging systems were used for comparative imaging. A PS-SD-OCT instrument was developed that was capable of recording intensity and polarization parameters simultaneously during a single scan. Results. In drusen, PS-SD-OCT identified a continuous RPE layer with focal elevations. Discrete RPE atrophy (RA) could be observed in two patients. In GA, the extension of the RA was significantly larger. Residual RPE islands could be detected within the atrophic zone. PS-SD-OCT identified multiple foci of RPE loss in patients with nAMD and allowed recognition of advanced RPE disease associated with choroidal neovascularization. Wide areas of RA containing residual spots of intact retinal pigment epithelium could be identified in fibrotic scars. Conclusions. PS-SD-OCT provided precise identification of retinal pigment epithelium in AMD. Recognition of these disease-specific RA patterns in dry and wet forms of AMD is of particular relevance to identify the status and progression of RPE disease and may help to better estimate the functional prognosis of AMD. PMID:19797228

Ahlers, Christian; Götzinger, Erich; Pircher, Michael; Golbaz, Isabelle; Prager, Franz; Schütze, Christopher; Baumann, Bernhard; Hitzenberger, Christoph K; Schmidt-Erfurth, Ursula

2010-04-01

340

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

341

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

342

X-ray polarization properties of a centrally illuminated accretion disc  

NASA Astrophysics Data System (ADS)

The polarization of the X-rays reflected by a centrally illuminated, optically thick and geometrically thin accretion disc is calculated as a function of the source and disc parameters. The degree of polarization of the reflected radiation depends strongly on the disc inclination, and could be greater than 20 percent; the polarization angle is 90 deg, i.e. the polarization vector lies in the meridian plane. Due to the dilution of the primary source, assumed unpolarized, the net polarization depends strongly on photon energy, and could reach values as high as about 6 percent at energies greater than a few tens of keV. When relativistic effects in the Schwarzschild metric are taken into account, the degree of polarization generally increases, and the polarization angle becomes greater than 90 deg. The model could be tested by the SXRP experiment for several galactic X-ray binaries, and at least for one active galaxy, i.e. Centaurus A.

Matt, Giorgio

1993-02-01

343

Posterior Transpedicular Dynamic Stabilization versus Total Disc Replacement in the Treatment of Lumbar Painful Degenerative Disc Disease: A Comparison of Clinical Results  

PubMed Central

Study Design. Prospective clinical study. Objective. This study compares the clinical results of anterior lumbar total disc replacement and posterior transpedicular dynamic stabilization in the treatment of degenerative disc disease. Summary and Background Data. Over the last two decades, both techniques have emerged as alternative treatment options to fusion surgery. Methods. This study was conducted between 2004 and 2010 with a total of 50 patients (25 in each group). The mean age of the patients in total disc prosthesis group was 37,32 years. The mean age of the patients in posterior dynamic transpedicular stabilization was 43,08. Clinical (VAS and Oswestry) and radiological evaluations (lumbar lordosis and segmental lordosis angles) of the patients were carried out prior to the operation and 3, 12, and 24 months after the operation. We compared the average duration of surgery, blood loss during the surgery and the length of hospital stay of both groups. Results. Both techniques offered significant improvements in clinical parameters. There was no significant change in radiologic evaluations after the surgery for both techniques. Conclusion. Both dynamic systems provided spine stability. However, the posterior dynamic system had a slight advantage over anterior disc prosthesis because of its convenient application and fewer possible complications. PMID:23401784

Oktenoglu, Tunc; Ozer, Ali Fahir; Sasani, Mehdi; Ataker, Yaprak; Gomleksiz, Cengiz; Celebi, Irfan

2013-01-01

344

Accretion discs as regulators of stellar angular momentum evolution in the ONC and Taurus-Auriga  

NASA Astrophysics Data System (ADS)

In light of recent substantial updates to spectral type estimations and newly established intrinsic colours, effective temperatures, and bolometric corrections for pre-main sequence (PMS) stars, we re-address the theory of accretion disc-regulated stellar angular momentum (AM) evolution. We report on the compilation of a consistent sample of fully convective stars within two of the most well-studied and youngest, nearby regions of star formation: the Orion nebula Cluster and Taurus-Auriga. We calculate the average specific stellar AM (j?) assuming solid body rotation, using surface rotation periods gathered from the literature and new estimates of stellar radii and ages. We use published Spitzer IRAC fluxes to classify our stars as Class II or Class III and compare their j? evolution. Our results suggest that disc dispersal is a rapid process that occurs at a variety of ages. We find a consistent j? reduction rate between the Class II and Class III PMS stars which we interpret as indicating a period of accretion disc-regulated AM evolution followed by near-constant AM evolution once the disc has dissipated. Furthermore, assuming our observed spread in stellar ages is real, we find that the removal rate of j? during the Class II phase is more rapid than expected by contraction at constant stellar rotation rate. A much more efficient process of AM removal must exist, most likely in the form of an accretion-driven stellar wind or other outflow from the star-disc interaction region or extended disc surface.

Davies, Claire L.; Gregory, Scott G.; Greaves, Jane S.

2014-10-01

345

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

346

Only marginal alignment of disc galaxies  

NASA Astrophysics Data System (ADS)

Testing theories of angular-momentum acquisition of rotationally supported disc galaxies is the key to understanding the formation of this type of galaxies. The tidal-torque theory aims to explain this acquisition process in a cosmological framework and predicts positive autocorrelations of angular-momentum orientation and spiral-arm handedness, i.e. alignment of disc galaxies, on short distance scales of 1 Mpc h-1. This disc alignment can also cause systematic effects in weak-lensing measurements. Previous observations claimed discovering these correlations but are overly optimistic in the reported level of statistical significance of the detections. Errors in redshift, ellipticity and morphological classifications were not taken into account, although they have a significant impact. We explain how to rigorously propagate all the important errors through the estimation process. Analysing disc galaxies in the Sloan Digital Sky Survey (SDSS) data base, we find that positive autocorrelations of spiral-arm handedness and angular-momentum orientations on distance scales of 1 Mpc h-1 are plausible but not statistically significant. Current data appear not good enough to constrain parameters of theory. This result agrees with a simple hypothesis test in the Local Group, where we also find no evidence for disc alignment. Moreover, we demonstrate that ellipticity estimates based on second moments are strongly biased by galactic bulges even for Scd galaxies, thereby corrupting correlation estimates and overestimating the impact of disc alignment on weak-lensing studies. Finally, we discuss the potential of future sky surveys. We argue that photometric redshifts have too large errors, i.e. PanSTARRS and LSST cannot be used. Conversely, the EUCLID project will not cover the relevant redshift regime. We also discuss the potentials and problems of front-edge classifications of galaxy discs in order to improve the autocorrelation estimates of angular-momentum orientation.

Andrae, René; Jahnke, Knud

2011-12-01

347

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

348

Synthesis of Organic Matter of Prebiotic Chemistry at the Protoplanetary Disc  

NASA Astrophysics Data System (ADS)

We have carried out scanning electron microscopic examination of CM carbonaceous chondrites meteorites Migey, Murchison, Staroe Boriskino aged more than 4.56 billion years (about 50 million years from the beginning of the formation of the Solar system). Our study confirmed the conclusion of Rozanov, Hoover and other researchers about the presence of microfossils of bacterial origin in the matrix of all these meteorites. Since the time of the Solar system formation is 60 - 100 million years, the primary biocenosis emerged in the protoplanetary disc of the Solar system before meteorites or simultaneously with them. It means that prebiological processes and RNA world appeared even earlier in the circumsolar protoplanetary disc. Most likely, this appearance of prebiotic chemistry takes place nowday in massive and medium-massive discs of the observed young stellar objects (YSO) class 0 and I. The timescale of the transition from chemical to biological evolution took less than 50 million years for the Solar system. Further evolution of individual biocenosis in a protoplanetary disc associated with varying physico-chemical conditions during the formation of the Solar system bodies. Biocenosis on these bodies could remove or develop under the influence of many cosmic factors and geological processes in the case of Earth. To complete the primary biosphere formation in short evolution time - millions of years - requires highly efficient chemical syntheses. In industrial chemistry for the efficient synthesis of ammonia, hydrogen cyanide, methanol and other organic species, that are the precursors to obtain prebiotic compounds, catalytic reactors of high pressure are used. Thus (1) necessary amount of the proper catalyst in (2) high pressure areas of the disc can trigger these intense syntheses. The disc contains the solids with the size from nanoparticle to pebble. Iron and magnesium is catalytically active ingredient for such solids. The puzzle is a way to provide hydrogen pressure inside the disc from tens to hundred atmospheres. We simulated unsteady processes in massive circumstellar discs around YSO class O and I. In the computational experiments, we have shown that at a certain stage of its evolution the circumstellar discs of gas and solids produces local areas of high pressure. According to the classical heterogeneous catalysis, a wide range of organic and prebiotic compounds could have been synthesized in these areas. Can we capture these areas of high pressure synthesis in observation of circumstellar discs? Due to the small sizes of such areas they can be hardly ever resolved even with the modern telescopes such as ALMA. However, we can try to detect their signatures in the disc, since the gas of the disc keep the set of organic synthesis products. The idea is to define the signature of the process using laboratory experiments. Varying gas temperature and pressure in laboratory setup we can carry out the catalytic high pressure syntheses and specify the set of gaseous products. These sets of organic compounds observed in the discs may serve as indicators of the emergence of high-pressure areas of prebiotic chemistry. Thus, there is a special interest to the study of YSO class 0 and I by means of observational astronomy. For these objects, first data on the presence of individual organic compounds in massive hydrogen-helium component of the discs appear. The origin of the organic compounds that are associated with chemical reactions in the discs should be separated from the set of organic compounds of the initial molecular cloud.

Snytnikov, Valeriy; Stoynovskaya, Olga; Rudina, Nina

349

Growth Factors and Anticatabolic Substances for Prevention and Management of Intervertebral Disc Degeneration  

PubMed Central

Intervertebral disc (IVD) degeneration is frequent, appearing from the second decade of life and progressing with age. Conservative management often fails, and patients with IVD degeneration may need surgical intervention. Several treatment strategies have been proposed, although only surgical discectomy and arthrodesis have been proved to be predictably effective. Biological strategies aim to prevent and manage IVD degeneration, improving the function and anabolic and reparative capabilities of the nucleus pulposus and annulus fibrosus cells and inhibiting matrix degradation. At present, clinical applications are still in their infancy. Further studies are required to clarify the role of growth factors and anticatabolic substances for prevention and management of intervertebral disc degeneration. PMID:25098367

Longo, Umile Giuseppe; Petrillo, Stefano; Franceschetti, Edoardo; Maffulli, Nicola; Denaro, Vincenzo

2012-01-01

350

Adjacent segment disc pressures following two-level cervical disc replacement versus simulated anterior cervical fusion.  

PubMed

Anterior cervical fusion (ACF) has been shown to alter the biomechanics of adjacent segments of the cervical spine. The goal of total disc replacement is to address pathology at a given disc with minimal disruption of the operated or adjacent segments. This study compares the pressure within discs adjacent to either a two-level simulated ACDF or a two-level total disc replacement with the ProDisc-C. A special automated motion testing apparatus was constructed. Four fresh cadaveric cervical spine specimens were affixed to the test stand and tested in flexion and extension under specific loads. Intradiscal, miniature strain-gauge-based transducers were placed in the discs above and below the "treated" levels. The specimens were then tested in flexion and extension. Pressure and overall angular displacement were measured. In the most extreme and highest quality specimen the difference at C3/C4 registered 800 kPa and the difference at C6/C7 registered 50 kPa. This same quality specimen treated with the ProDisc reached a flexion angle at much lower moments, 24.3 degrees at 5 N-m, when compared to the the SACF 12.2 degrees at 8.6 N-m. Therefore, the moment needed to achieve 15 degrees of flexion with the SACF treatment was 5.5 N-m and the ProDisc treatment was only 2.9 N-m. This initial data would indicate that adjacent level discs experience substantially lower pressure after two-level disc replacement when compared to two-level SACF. Additional testing to further support these observations is ongoing. PMID:17108473

Laxer, Eric B; Darden, Bruce V; Murrey, Daniel B; Milam, R Alden; Rhyne, Alfred L; Claytor, Brian; Nussman, Donna S; Powers, Timothy W; Davies, Matthew A; Bryant, S Chad; Larsen, Scott P; Bhatt, Meghal; Brodziak, John; Polic, Jelena

2006-01-01

351

Stellar population gradients in galaxy discs from the CALIFA survey. The influence of bars  

NASA Astrophysics Data System (ADS)

While studies of gas-phase metallicity gradients in disc galaxies are common, very little has been done towards the acquisition of stellar abundance gradients in the same regions. We present here a comparative study of the stellar metallicity and age distributions in a sample of 62 nearly face-on, spiral galaxies with and without bars, using data from the CALIFA survey. We measure the slopes of the gradients and study their relation with other properties of the galaxies. We find that the mean stellar age and metallicity gradients in the disc are shallow and negative. Furthermore, when normalized to the effective radius of the disc, the slope of the stellar population gradients does not correlate with the mass or with the morphological type of the galaxies. In contrast to this, the values of both age and metallicity at ~2.5 scale lengths correlate with the central velocity dispersion in a similar manner to the central values of the bulges, although bulges show, on average, older ages and higher metallicities than the discs. One of the goals of the present paper is to test the theoretical prediction that non-linear coupling between the bar and the spiral arms is an efficient mechanism for producing radial migrations across significant distances within discs. The process of radial migration should flatten the stellar metallicity gradient with time and, therefore, we would expect flatter stellar metallicity gradients in barred galaxies. However, we do not find any difference in the metallicity or age gradients between galaxies with and without bars. We discuss possible scenarios that can lead to this lack of difference. Tables 1-3 and Appendices are available in electronic form at http://www.aanda.org

Sánchez-Blázquez, P.; Rosales-Ortega, F. F.; Méndez-Abreu, J.; Pérez, I.; Sánchez, S. F.; Zibetti, S.; Aguerri, J. A. L.; Bland-Hawthorn, J.; Catalán-Torrecilla, C.; Cid Fernandes, R.; de Amorim, A.; de Lorenzo-Caceres, A.; Falcón-Barroso, J.; Galazzi, A.; García Benito, R.; Gil de Paz, A.; González Delgado, R.; Husemann, B.; Iglesias-Páramo, Jorge; Jungwiert, B.; Marino, R. A.; Márquez, I.; Mast, D.; Mendoza, M. A.; Mollá, M.; Papaderos, P.; Ruiz-Lara, T.; van de Ven, G.; Walcher, C. J.; Wisotzki, L.

2014-10-01

352

On the history of the Secchi disc  

NASA Astrophysics Data System (ADS)

The first records on regular, tabulated, measurements of transparency of natural waters are those by the German naturalist Adelbert von Chamisso during the Russian "Rurik" Expedition 1815-1818 under the command of Otto von Kotzebue. A standardized method to determine the water clarity (transparency) was adopted at the end of the nineteenth century. This method (lowering a white painted disc into the water until it disappeared out of sight) was described by Pietro Angelo Secchi in Il Nuovo Cimento and was published in 1865. The Austrian scientist Josef Roman Lorenz von Liburnau, experimenting with submersible objects, like white discs, in the Gulf of Quarnero (Croatia) in the eighteen-fifties, well before Secchi started his investigations, questioned the naming of the white disc. However, the experiments performed by Secchi and Cialdi in 1864, on such an intensive scale, where never performed before. At the beginning of the twentieths century this method, water transparency observations by means of a 30 centimetres -- white disc, was named the Secchi-disc method.

Wernand, M. R.

2010-04-01

353

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

354

Predictive Findings of Visual Outcome in Spectral Domain Optical Coherence Tomography after Ranibizumab Treatment in Age-related Macular Degeneration  

PubMed Central

Purpose To investigate which spectral domain optical coherence tomography (SD-OCT) findings predict visual outcome after anti-vascular endothelial growth factor (VEGF) treatment in neovascular age-related macular degeneration (NV-AMD). Methods We reviewed the medical records of patients with treatment-naïve NV-AMD who underwent three or more consecutive anti-VEGF injections. The patients were divided into three groups according to their changes of visual acuity (VA); improved (group I), static (group S), or worsened (group W). We assessed the incidences and values of all available SD-OCT findings of these groups, compared these findings between the three groups and compared the initial values with the post-treatment values. Results Better initial VA and longer external limiting membrane (ELM) length were associated with less change in VA after anti-VEGF treatment. The initial VA was mildly correlated with initial photoreceptor inner and outer segment junction (IS/OS) length and initial ELM length. The final VA was also mildly correlated with the final IS/OS length and the final ELM length. VA was significantly changed after anti-VEGF treatment in groups W and I. With regard to incidence, disruption of the IS/OS (IS/OS-D), disruption of the ELM (ELM-D) and ELM length differed significantly between the three groups, particularly ELM-D. The incidences of IS/OS-D and ELM-D in group I were significantly lower than those in groups S and W, and those in group S were also lower than those in group W. The ELM length in group I was significantly longer than it was in groups S and W, and the ELM length in group S was longer than that for group W. However, these three findings did not change after the anti-VEGF treatment. Conclusions Initial IS/OS-D, ELM length and particularly ELM-D can be useful predictors of the visual outcome after anti-VEGF treatment in NV-AMD patients. PMID:25276080

Kwon, Yoon Hyung; Lee, Dong Kyu; Kim, Hyung Eun

2014-01-01

355

Thermal disc emission from a rotating black hole: X-ray polarization signatures  

NASA Astrophysics Data System (ADS)

Thermal emission from the accretion disc around a black hole can be polarized, due to Thomson scattering in a disc atmosphere. In Newtonian space, the polarization angle must be either parallel or perpendicular to the projection of the disc axis on the sky. As first pointed out by Stark and Connors in 1977, General Relativity effects strongly modify the polarization properties of the thermal radiation as observed at infinity. Among these effects, the rotation of the polarization angle with energy is particularly useful as a diagnostic tool. In this paper, we extend the Stark and Connors calculations by including the spectral hardening factor, several values of the optical depth of the scattering atmosphere and rendering the results to the expected performances of planned X-ray polarimeters. In particular, to assess the perspectives for the next generation of X-ray polarimeters, we consider the expected sensitivity of the detectors on board the planned POLARIX and International X-ray Observatory missions. We assume the two cases of a Schwarzschild and an extreme Kerr black hole with a standard thin disc and a scattering atmosphere. We compute the expected polarization degree and the angle as functions of the energy as they could be measured for different inclinations of the observer, optical thickness of the atmosphere and different values of the black hole spin. We assume the thermal emission dominates the X-ray band. Using the flux level of the microquasar GRS 1915+105 in the thermal state, we calculate the observed polarization.

Dov?iak, M.; Muleri, F.; Goosmann, R. W.; Karas, V.; Matt, G.

2008-11-01

356

Gold, carbon, and aluminum low-reflectivity compact discs as microassaying platforms.  

PubMed

Compact disc (CD) surface modification with different reflective materials offers new working perspectives as bioanalytical platforms. The potential of gold, carbon, and aluminum low-reflectivity compact discs as a substrate for microassaying is presented. CD polycarbonate bases were coated with these reflecting materials, maintaining optical properties. Probes immobilization onto reflective layers was studied by both passive adsorption and covalent linking. Different chemical modifications were made on substrates to provide functional groups capable of anchoring probes with primary amines covalently. Thus, self-assembled monolayers were performed by chemisorption of 11-mercaptoundecanoic acid on gold surfaces, and silanization with N-(trimethoxysilylpropyl)ethylenediamine triacetic acid on aluminum to provide a carboxylic acid functional group. Carbon oxidation with oxygen plasma afforded similar functionalization on the discs coated with this material. Performance of the studied materials as reflective layers was evaluated, and as proof of concept, a microimmunoassay for a neurotoxic compound was studied on the three surfaces. The results show the possibility of doing assays on this new supports with good analytical performances while maintaining discs' optical and mechanical properties to be read by a CD player. PMID:23489115

Brun, Eva M; Puchades, Rosa; Maquieira, Ángel

2013-04-16

357

REVIEW Open Access Dominant optic atrophy  

E-print Network

normal to legal blindness. The ophthalmic examination discloses on fundoscopy isolated optic disc pallor and the control of apoptosis. Diagnosis: Patients are usually diagnosed during their early childhood, because

Paris-Sud XI, Université de

358

Evaluation of the accuracy of brain optical properties estimation at different ages using the frequency-domain multi-distance method  

NASA Astrophysics Data System (ADS)

NIRS is safe, non-invasive and offers the possibility to record local hemodynamic parameters at the bedside, avoiding the transportation of neonates and critically ill patients. In this work, we evaluate the accuracy of the frequency-domain multi-distance (FD-MD) method to retrieve brain optical properties from neonate to adult. Realistic measurements are simulated using a 3D Monte Carlo modeling of light propagation. Height different ages were investigated: a term newborn of 38 weeks gestational age, two infants of 6 and 12 months of age, a toddler of 2 year (yr.) old, two children of 5 and 10 years of age, a teenager of 14 yr. old, and an adult. Measurements are generated at multiple distances on the right parietal area of head models and fitted to a homogeneous FD-MD model to estimate the brain optical properties. In the newborn, infants, toddler and 5 yr. old child models, the error was dominated by the head curvature, while the superficial layer in the 10 yr. old child, teenager and adult heads. The influence of the CSF is also evaluated. In this case, absorption coefficients suffer from an additional error. In all cases, measurements at 5 mm provided worse estimation because of the diffusion approximation.

Dehaes, Mathieu; Grant, P. Ellen; Sliva, Danielle D.; Roche-Labarbe, Nadège; Pienaar, Rudolph; Boas, David A.; Franceschini, Maria Angela; Selb, Juliette

2011-03-01

359

The Accretion Disc Dynamo in the Solar Nebula  

E-print Network

The nearest accretion disc to us in space if not time was the protosolar nebula. Remnants of this nebula thus potentially offer unique insight into how discs work. In particular the existence of chondrules, which must have formed in the disc as small molten droplets, requires strong and intermittent heating of disc material. We argue that this places important constraints on the way gravitational energy is released in accretion discs, which are not met by current shearing--box simulations of MRI--driven dynamos. A deeper understanding of accretion energy release in discs may require a better model for these dynamos.

King, A R

2010-01-01

360

Satellites in Discs: Regulating the Accretion Luminosity  

E-print Network

We demonstrate, using a simple analytic model, that the presence of a massive satellite can globally modify the structure and emission properties of an accretion disc to which it is tidally coupled. We show, using two levels of numerical approximation, that the analytic model gives reasonable results. The results are applicable to two astrophysical situations. In the case of an active galactic nucleus, we consider the case of a $\\sim 10^3\\Msun$ compact companion to the central black-hole and show that it could modulate the emitted spectrum on a timescale of $\\sim10^5$ years. In the case of a T Tauri accretion disc, a satellite such as a sub-dwarf or giant planet could modify the disc spectral energy distribution over a substantial fraction of the T Tauri star lifetime.

Dave Syer; Cathie Clarke

1995-05-04

361

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

362

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

363

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

364

Magnetohydrodynamic turbulence in warped accretion discs  

E-print Network

Warped, precessing accretion discs appear in a range of astrophysical systems, for instance the X-ray binary Her X-1 and in the active nucleus of NGC4258. In a warped accretion disc there are horizontal pressure gradients that drive an epicyclic motion. We have studied the interaction of this epicyclic motion with the magnetohydrodynamic turbulence in numerical simulations. We find that the turbulent stress acting on the epicyclic motion is comparable in size to the stress that drives the accretion, however an important ingredient in the damping of the epicyclic motion is its parametric decay into inertial waves.

U. Torkelsson; G. I. Ogilvie; A. Brandenburg; J. E. Pringle; AA. Nordlund; R. F. Stein

2001-03-03

365

An extension of the disc Algebra  

E-print Network

We identify all uniform limits of polynomials on the closed unit disc with respect to the chordal metric \\c{hi} . One such limit is f=oo. The other limits are holomorphic functions f:-->C so that for every {\\zeta} in the boundary of unit disc D the limf(z) while z-->{\\zeta} exists in C U {oo}. The class of the above functions is denoted by A(D)~. We study properties of the members of A(D)~, as well as, some topological properties of A(D)~ endowed with its natural metric topology. There are several open questions and new directions of investigation.

Nestoridis, Vassilis

2010-01-01

366

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

367

Write Strategy for Dual-Layer Digital Versatile Discs  

NASA Astrophysics Data System (ADS)

A novel write strategy for rewritable dual-layer digital versatile discs (DVDs) was studied. This new strategy involves the erase top pulse which is included in the conventional write strategy for single-layer DVDs in present market. By thermal calculations, it was confirmed that this erase top pulse has an affect on the rapid heating of recording films. We observed that this new strategy enabled the improvement in data qualities on the layer near the laser incident (L0) effectively in 2 × and 4 ×-speed recordings even if L0 had a high optical transparency. Furthermore we also demonstrated a combination of what with the 2T-period strategy on the layer far from the laser incident (L1) realized a well-balanced signal performance for dual-layer DVD media.

Tabata, Hiroshi; Tokui, Kenji; Higuchi, Shinji; Moriizumi, Hirokazu; Matsumoto, Ikuo

2006-02-01

368

An analysis of HCN observations of the Circumnuclear Disc at the Galactic Centre  

NASA Astrophysics Data System (ADS)

The Circumnuclear Disc (CND) is a torus of dust and molecular gas rotating about the Galactic Centre and extending from approximately 1.6 pc to 7 pc from the central massive black hole, SgrA*. Large Velocity Gradient modelling of the intensities of the HCN 1-0, 3-2 and 4-3 transitions is used to infer hydrogen density and HCN optical depth. From HCN observations we find the molecular hydrogen density ranges from 0.1 to 2 × 106 cm-3, about an order of magnitude less than inferred previously. The 1-0 line is weakly inverted with line-centre optical depth approx -0.1, in stark contrast to earlier estimates of 4. The estimated mass of the ring is approximately 3-4 × 105 M?, consistent with estimates based on thermal dust emission. The tidal shear in the disc implies that star formation is not expected to occur without some significant triggering event.

Smith, I. L.; Wardle, M.

2014-02-01

369

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

370

Stellar orbit evolution in close circumstellar disc encounters  

E-print Network

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 3-D, focusing on disc-disc interactions that result from stellar fly-bys. 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 3-D models of self-gravitating discs, and then create a suite of numerical experiments of parabolic encounters, exploring the effects of pericenter separation r_p, disc orientation and disc-star mass ratio (M_d/M_*) on the orbital evolution of the host stars. Close encounters (2r_porbital angular momentum extraction to induce stellar capture. We find that ...

Muñoz, Diego J; Vogelsberger, Mark; Hernquist, Lars; Springel, Volker

2014-01-01

371

Optical and thermoluminescence dating of Middle Stone Age and Kintampo bearing sediments at Birimi, a multi-component archaeological site in Ghana  

NASA Astrophysics Data System (ADS)

We report the first luminescence ages for the archeological and geological sediments forming the substrate of the Birimi archaeological site in the Northern Region of Ghana. The site's significance rests on the fact that it contains a rich collection of artifact assemblages representative of three distinct cultures, and that, on the basis of artifact typology, the earliest assemblage is diagnostic of the Middle Stone Age (MSA) . In situ occurrences of MSA artifacts are found at over 1 m below today's surface. They are overlain by a ceramic-rich complex of a sedentary or semi-sendentary Later Stone Age culture known as the Kintampo. The western half of the site is dominated by the industrial remains of Iron Age smelting activity. Elemental, mineralogical, and sedimentological analysis of the cultural and sub-cultural sedimentary horizons at the site revealed at least three distinct lithostratigraphic units. The quartz sediments are derived from the sandstone of the Gambaga escarpment, mass wasted and accreted fluvially at a rate of 3.2 cm/ka, forming a wide terrace at Birimi. Silts and finer fractions derive from windblown dust, likely from White Volta River and granitic sources to the north. Soil forming processes and wide fluctuations in moisture have progressively reduced the sediments at depth to the resistant quartz and kaolinite, with rich iron oxide coatings, and created two ironstone horizons composed of goethite-cemented quartz nodules. Multiple aliquot green-light stimulated optical ages for 125-150 ?m quartz grains yielded ages of 23.6±2.9 and 40.8±11.8 ka for the MSA-bearing sediments, and 58.4±15.3 ka for the base of the terrace. Radiocarbon ages on charcoal from Kintampo-bearing units are 3.36-3.83 ka cal BP, and are supported by thermoluminescence (TL) ages on pottery sherds and burnt house daub fragments of this cultural complex. A 0.4 ka age on sediment from the site's surface confirms that the quartz zeroes well when exposed to natural light. Sediments bearing the Kintampo artifacts, however, yielded ages of 7.8-16.9 ka. These ages were obtained on sediments from large pits, some over 50 cm deep, and they deviate only slightly from the ages expected for naturally aggraded sediments at these depths. We conclude, therefore, that extensive digging of pits by the Kintampo dwellers was followed by rapid refilling, and that the bulk mobilization of the matrix did not permit the sedimentary quartz grains to experience any appreciable zeroing at that time.

Quickert, Nicole A.; Godfrey-Smith, Dorothy I.; Casey, Joanna L.

2003-05-01

372

Efficacy of percutaneous laser disc decompression on lumbar spinal stenosis.  

PubMed

The objective of this study is to observe the effect of percutaneous laser disc decompression (PLDD) on lumbar spinal stenosis (LSS). Thirty-two LSS patients were treated using pulsed Nd: YAG laser, of which 21 cases (11 males and 10 females with an average age of 64 years old) were followed up for 2 years. All of the 21 patients had intermittent claudication with negative straight leg raising test results. Fifteen patients suffered from anterior central disc herniation which often compressed the cauda equina but seldom compressed the posterior part; six patients suffered from posterior ligamentum flavum hypertrophy which often compressed the cauda equina but seldom compressed the anterior part. The efficacy was evaluated 1, 3, 6, 12 and 24 months after surgery on 21 patients using the performance evaluation criteria of the lumbago treatment by the Japanese Orthopaedic Association (JOA 29 scores). The fineness (i.e. excellent and good treatment outcome) rate 1, 3, 6, 12 and 24 months after the operation were 46.7%, 66.7%, 66.7%, 66.7% and 66.7%, respectively, in patients with severe anterior compression and 16.7%, 33.3%, 33.3%, 33.3% and 33.3%, respectively, in patients with severe posterior compression. PLDD had certain positive efficacy on the treatment of lumbar spinal stenosis, which was more significant on LSS dominated by the anterior compression than that by the posterior compression. PMID:23996073

Ren, Longxi; Han, Zhengfeng; Zhang, Jianhua; Zhang, Tongtong; Yin, Jian; Liang, Xibin; Guo, Han; Zeng, Yanjun

2014-05-01

373

Low Jitter and Wide Range VCO for CD\\/DVD\\/Blu-ray Disc  

Microsoft Academic Search

A voltage-controlled oscillator (VCO) for optical-disc-drive (ODD) applications was developed. This VCO selects the most appropriate current-controlled oscillator (CCO) from three CCOs in order to satisfy various ODD read\\/write speeds. It produces the frequency characteristics of a maximum frequency limiter in order to prevent unlocking of a PLL. Moreover, the VCO applies a trimming method to correct degradation of frequency

T. Kawamoto; M. Kokuno; S. Kusakabe; T. Yokohama

2006-01-01

374

Images of shear-induced phase separation in a dispersion of hard nanoscale discs  

Microsoft Academic Search

Optical microscopy has been used to study the flow behaviour of a dispersion of plate-like particles. The sample of hexagonal discs of nickel hydroxide stabilised with a short-chain, charged polymer was investigated over a range of shear rates up to 100s?1 with a polarising, transmitted light microscope. Direct evidence for a shear-induced phase transition with a change in alignment of

A. B. D Brown; A. R Rennie

2001-01-01

375

AIRS Data Products at GES DISC DAAC  

NASA Technical Reports Server (NTRS)

This list contains the names and some characteristics of Atmospheric InfraRed Sounder (AIRS) data products at the Goddard Earth Sciences (GES) Data and Information Services Center (DISC) Distributed Active Archive Center (DAAC). The list includes variables, units, dimensions, and descriptions for each of the data products, which include infrared radiances and brightness temperatures.

2003-01-01

376

Planetesimal Formation In Self-Gravitating Discs  

E-print Network

We study particle dynamics in local two-dimensional simulations of self-gravitating accretion discs with a simple cooling law. It is well known that the structure which arises in the gaseous component of the disc due to a gravitational instability can have a significant effect on the evolution of dust particles. Previous results using global simulations indicate that spiral density waves are highly efficient at collecting dust particles, creating significant local over-densities which may be able to undergo gravitational collapse. We expand on these findings, using a range of cooling times to mimic the conditions at a large range of radii within the disc. Here we use the Pencil Code to solve the 2D local shearing sheet equations for gas on a fixed grid together with the equations of motion for solids coupled to the gas solely through aerodynamic drag force. We find that spiral density waves can create significant enhancements in the surface density of solids, equivalent to 1-10cm sized particles in a disc fol...

Gibbons, P G; Mamatsashvili, G R

2012-01-01

377

Vortices in self-gravitating gaseous discs  

E-print Network

(abridged) Vortices are believed to play a role in the formation of km-sized planetesimals. However, vortex dynamics is commonly studied in non-self-gravitating discs. The main goal here is to examine the effects of disc self-gravity on vortex dynamics. For this purpose, we employ the 2D self-gravitating shearing sheet approximation. A simple cooling law with a constant cooling time is adopted, such that the disc settles down into a quasi-steady gravitoturbulent state. In this state, vortices appear as transient structures undergoing recurring phases of formation, growth to sizes comparable to a local Jeans scale and eventual shearing and destruction due to the combined effects of self-gravity and background Keplerian shear. Each phase typically lasts about 2 orbital periods or less. As a result, in self-gravitating discs the overall dynamical picture of vortex evolution is irregular consisting of many transient vortices at different evolutionary stages and, therefore, with various sizes up to the local Jeans...

Mamatsashvili, G R

2009-01-01

378

GEODESIC DISCS AND Sp(2n, Z)  

Microsoft Academic Search

These are (enhanced) notes of an expository lecture given at the conference 'Outerspace and Teichuller Space' held at CIRM in Luminy in February 2007. The purpose is to describe the relationship between, on the one hand, a pseudo-Anosov diffeomor- phism and its associated Teichmuller disc and, on the other hand, the induced symplectic automorphism of first homology and an in-

CHRISTOPHER M. JUDGE

379

The Edge of the Galactic Disc  

E-print Network

As part of a stellar population sampling program, a series of photometric probes at various field sizes and depths have been obtained in a low extinction window in the galactic anticentre direction. Such data set strong constraints on the radial structure of the disc. At the forefront of this "drilling" program, very deep CCD frames probe the most external parts of the disc. Over the whole effective magnitude range (18 to 25), all contributions in the statistics which should be expected from old disc stars beyond 6 kpc vanish, although such stars dominate by far at distances less than 5 kpc. This is the signature of a sharp cut-off in the star density: the edge of the galactic disc between 5.5 and 6 kpc. As a consequence, the galactic radius does not exceed 14 kpc (assuming $R/-/(//sun/)$=8.5). Colours of elliptical galaxies measured in the field rule out the risk of being misled by undetected extinction.

Annie C. Robin; Michel Creze; Vijay Mohan

1992-10-02

380

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

381

Indoor radon detected by compact discs  

Microsoft Academic Search

An approach for a precise retrospective assessment of the indoor radon exposure using commercial compact discs (CDs) is proposed. It is based on the remarkable radon absorption and ? track-etch properties of polycarbonate — the basic material of the CDs. The experimental results indicate that the useful range of this approach is able to cover practically the entire range of

D. Pressyanov; J. Buysse; A. Van Deynse; A. Poffijn; G. Meesen

2001-01-01

382

Robust control of a compact disc player  

Microsoft Academic Search

The design of robust controllers for a compact disc mechanism is considered. Using ? synthesis, a controller has been designed for good track-following. The design problem involves time-domain constraints on signals and robustness requirements for norm-bounded structured plant uncertainty. It is shown that by using weighting functions in the ? framework this problem can be solved, but at the cost

Maarten Steinbuch; Gerrit Schootstra; Okko H. Bosgra

1992-01-01

383

Compact Disc Cataloging Product User Survey.  

ERIC Educational Resources Information Center

In late 1988, a compact disc cataloging product was introduced to the library market. In order to learn more about the needs of current users, a survey was developed to include questions concerning software features and operations, software enhancements, bibliographic and authority subsets, and hardware issues. This study was conducted among all…

Whitehair, David E.

384

Molecular screening on a compact disc  

Microsoft Academic Search

A method is described to screen the recognition between small molecule ligands and biomolecules using a conventional compact disc (CD) player. A procedure was developed to attach ligands to the reading face of a CD by activating the terminus of polycarbonate, a common polymer composite within the reading face of a CD. Terminal residues of the polycarbonate surface 1 were

James J. La Clair; Michael D. Burkart

2003-01-01

385

Analog disc recorder system: operator's reference manual  

SciTech Connect

The FM Analog Disc Recorder System is a cost-efficient means of capturing analog transient data from many channels; it has high-frequency response and long record time. It can digitize recorded signals, correct internal distortion, and present the data as plots either on a CRT, hardcopy plot, or both. The system is easy to use, self-contained, and compact.

O'Brien, J.D.; Smith, E.L.

1984-07-01

386

Exome sequencing and functional analyses suggest that SIX6 is a gene involved in an altered proliferation-differentiation balance early in life and optic nerve degeneration at old age.  

PubMed

Primary open-angle glaucoma (POAG) is a hereditary neurodegenerative disease, characterized by optic nerve changes including increased excavation, notching and optic disc hemorrhages. The excavation can be described by the vertical cup-disc ratio (VCDR). Previously, genome-wide significant evidence for the association of rs10483727 in SIX1-SIX6 locus with VCDR and subsequent POAG was found. Using 1000 genomes-based imputation of four independent population-based cohorts in the Netherlands, we identified a missense variant rs33912345 (His141Asn) in SIX6 associated with VCDR (Pmeta = 7.74 × 10(-7), n = 11 473) and POAG (Pmeta = 6.09 × 10(-3), n = 292). Exome sequencing analysis revealed another missense variant rs146737847 (Glu129Lys) also in SIX6 associated with VCDR (P = 5.09 × 10(-3), n = 1208). These two findings point to SIX6 as the responsible gene for the previously reported association signal. Functional characterization of SIX6 in zebrafish revealed that knockdown of six6b led to a small eye phenotype. Histological analysis showed retinal lamination, implying an apparent normal development of the eye, but an underdeveloped lens, and reduced optic nerve diameter. Expression analysis of morphants at 3 dpf showed a 5.5-fold up-regulation of cdkn2b, a cyclin-dependent kinase inhibitor, involved in cell cycle regulation and previously associated with VCDR and POAG in genome-wide association studies (GWASs). Since both six6b and cdkn2b play a key role in cell proliferation, we assessed the proliferative activity in the eye of morphants and found an alteration in the proliferative pattern of retinal cells. Our findings in humans and zebrafish suggest a functional involvement of six6b in early eye development, and open new insights into the genetic architecture of POAG. PMID:24150847

Iglesias, Adriana I; Springelkamp, Henriët; van der Linde, Herma; Severijnen, Lies-Anne; Amin, Najaf; Oostra, Ben; Kockx, Christel E M; van den Hout, Mirjam C G N; van Ijcken, Wilfred F J; Hofman, Albert; Uitterlinden, André G; Verdijk, Rob M; Klaver, Caroline C W; Willemsen, Rob; van Duijn, Cornelia M

2014-03-01

387

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

388

Self-gravitating warped discs around supermassive black holes  

Microsoft Academic Search

We consider warped equilibrium configurations for stellar and gaseous discs in the Keplerian force field of a supermassive black hole, assuming that the self-gravity of the disc provides the only acting torques. Modelling the disc as a collection of concentric circular rings and computing the torques in the non-linear regime, we show that stable, strongly warped precessing equilibria are possible.

A. Ulubay-Siddiki; O. Gerhard; M. Arnaboldi

2009-01-01

389

The evolution of misaligned accretion discs and spinning black holes  

Microsoft Academic Search

In this paper, we consider the process of alignment of a spinning black hole and a surrounding misaligned accretion disc. We use a simplified set of equations, that describe the evolution of the system in the case where the propagation of warping disturbances in the accretion disc occurs diffusively, a situation likely to be common in the thin discs in

G. Lodato; J. E. Pringle

2006-01-01

390

3-DIMENSIONAL COMPACT DISC (CD) MICROFLUIDIC PLATFORM Presented to the  

E-print Network

3-DIMENSIONAL COMPACT DISC (CD) MICROFLUIDIC PLATFORM _______________ A Thesis Presented OF THE THESIS 3-Dimensional Compact Disc (CD) Microfluidic Platform by Nitin Edmund Harwood Master of Science in a compact disc (CD) microfluidics platform involving two or more layers. The traditional 2-Dimensional

Kassegne, Samuel Kinde

391

Dynamic Shear Properties of the Temporomandibular Joint Disc  

Microsoft Academic Search

Shear stress might be an important factor associated with fatigue failure and damage of the temporomandibular joint disc. Little information, however, is available on the dynamic behavior of the disc in shear. Since the disc is an anisotropic and viscoelastic structure, in the present study the dependency of the dynamic shear behavior on the direction and frequency of loading was

E. Tanaka; K. Hanaoka; T. van Eijden; M. Tanaka; M. Watanabe; M. Nishi; N. Kawai; H. Murata; T. Hamada; K. Tanne

2003-01-01

392

Observational implications of precessing protostellar discs and jets  

Microsoft Academic Search

We consider the dynamics of a protostellar disc in a binary system where the disc is misaligned with the orbital plane of the binary, with the aim of determining the observational consequences for such systems. The disc wobbles with a period approximately equal to half the orbital period of the binary and precesses on a longer time-scale. We determine the

M. R. Bate; I. A. Bonnell; C. J. Clarke; S. H. Lubow; G. I. Ogilvie; J. E. Pringle; C. A. Tout

2000-01-01

393

Hydrodynamic simulations of cataclysmic variable accretion discs in outburst  

Microsoft Academic Search

We study the outburst phase of cataclysmic variable (CV) accretion discs in the (r, pi) plane with full hydrodynamics. Vertically the disc is treated using the one-zone model of Stehle & Spruit, which allows us to follow the fundamental mode of vertical disc oscillations correctly. alpha-type shear viscosity (Shakura & Sunyaev) and energy loss at the surface of the accretion

R. Stehle

1999-01-01

394

An experimental investigation of hot spots in railway disc brakes  

Microsoft Academic Search

An experimental study of hot spots occurrence in railway disc brakes is reported on. The aim of this study was to better classify and to explain the thermal gradients appearance on the surface of the disc. Thermographic measurements with an infrared camera have been carried out on the rubbing surface of brake discs on a full-scale test bench. Based on

S. Panier; P. Dufrénoy; D. Weichert

2004-01-01

395

FEATURE BASED HANDLING OF SURFACE FAULTS IN COMPACT DISC PLAYERS  

E-print Network

FEATURE BASED HANDLING OF SURFACE FAULTS IN COMPACT DISC PLAYERS Peter Fogh Odgaard ,1 Jakob & Olufsen A/S, Peter Bangs Vej 15, DK-7600 Struer, Denmark Abstract: Compact Disc players have been. However, there are still problems with playing Compact Discs related to surface faults like scratches

Wickerhauser, M. Victor

396

ICCM 2007 Vol. II 14 Loop space and holomorphic disc  

E-print Network

and holomorphic disc 3 Theorem 1.4 Let L M be a compact Lagrangian submanifold of a compact (or convexICCM 2007 · Vol. II · 1­4 Loop space and holomorphic disc -summary- Kenji Fukaya Abstract We-holomorphic disc, to symplectic topology of Lagrangian submanifold. Our result was anounced in [5] before. We

Fukaya, Kenji

397

Using the Shannon Sampling Theorem to Design Compact Discs  

E-print Network

Using the Shannon Sampling Theorem to Design Compact Discs Susan E. Kelly Abstract The Shannon this theory, music can be stored on a compact disc by recording the function's amplitude at points sampled with students at both of these levels. Have you ever wondered how music is stored on a compact disc

Kelly, Susan

398

Convex-compact sets and Banach discs I. Monterde  

E-print Network

Convex-compact sets and Banach discs I. Monterde and V. Montesinos Abstract Every relatively convex-compact) and the Universidad Polit´ecnica de Valencia. Keywords: weakly compact sets, convex-compact sets, Banach discs. 1 #12 convex subset of a locally convex space is contained in a Banach disc. Moreover, an upper bound

Montesinos Santalucía, Vicente

399

Compact Discs--A Revolution in the Making.  

ERIC Educational Resources Information Center

Discusses the theory behind the system of the compact disc (encoding process, decoding system), its potential for growth, and its possible impact on the way libraries handle sound recordings. Guidelines for purchase of compact disc equipment are given. A comparison of compact discs and long-playing records is appended. (37 references) (EJS)

Ridgway, Jim

1986-01-01

400

Biological response of the intervertebral disc to dynamic loading  

Microsoft Academic Search

Disc degeneration is a chronic remodeling process that results in alterations of matrix composition and decreased cellularity. This study tested the hypothesis that dynamic mechanical forces are important regulators in vivo of disc cellularity and matrix synthesis. A murine model of dynamic loading was developed that used an external loading device to cyclically compress a single disc in the tail.

Andrew J. L. Walsh; Jeffrey C. Lotz

2004-01-01

401

Hydrodynamic simulations of cataclysmic variable accretion discs in outburst  

NASA Astrophysics Data System (ADS)

We study the outburst phase of cataclysmic variable (CV) accretion discs in the (r, pi) plane with full hydrodynamics. Vertically the disc is treated using the one-zone model of Stehle & Spruit, which allows us to follow the fundamental mode of vertical disc oscillations correctly. alpha-type shear viscosity (Shakura & Sunyaev) and energy loss at the surface of the accretion disc by radiation are included. We run accretion disc models with different masses M_1 and M_2 for the primary and the secondary stars and different values of alpha. In all calculations we observe strong spiral shock arms, which dominate the disc evolution on a hydrodynamical time-scale. In cases where the surface mass density Sigma (r) decreases with radius r the disc pattern is stable. In cases where Sigma (r) increases with r we observe a quasi-periodic cycle of disc size. During the phase where the disc is large, the spiral arm close to the L_1 point connects to the secondary, and about 1 per cent of the total disc mass is lost to the secondary per cycle. However, in none of our calculations are we able to find an eccentric and precessing accretion disc, even though the disc edge is outside the 3:1 tidal resonance radius R_31. Our calculations therefore cannot confirm the tidal instability model, presently the only model for superhumps in SU UMa CVs during superoutbursts.

Stehle, R.

1999-04-01

402

DISC1–ATF4 transcriptional repression complex: dual regulation of the cAMP-PDE4 cascade by DISC1  

E-print Network

Disrupted-In-Schizophrenia 1 (DISC1), a risk factor for major mental illnesses, has been studied extensively in the context of neurodevelopment. However, the role of DISC1 in neuronal signaling, particularly in conjunction ...

Ishizuka, K

403

Debris discs around M stars: non-existence versus non-detection  

NASA Astrophysics Data System (ADS)

Motivated by the reported dearth of debris discs around M stars, we use survival models to study the occurrence of planetesimal discs around them. These survival models describe a planetesimal disc with a small number of parameters, determine if it may survive a series of dynamical processes and compute the associated infrared excess. For the Wide-field Infrared Survey Explorer (WISE) satellite, we demonstrate that the dearth of debris discs around M stars may be attributed to the small semimajor axes generally probed if either: (1) the dust grains behave like blackbodies emitting at a peak wavelength coincident with the observed one; (2) or the grains are hotter than predicted by their blackbody temperatures and emit at peak wavelengths that are shorter than the observed one. At these small distances from the M star, planetesimals are unlikely to survive or persist for time-scales of 300 Myr or longer if the disc is too massive. Conversely, our survival models allow for the existence of a large population of low-mass debris discs that are too faint to be detected with current instruments. We gain further confidence in our interpretation by demonstrating the ability to compute infrared excesses for Sun-like stars that are broadly consistent with reported values in the literature. However, our interpretation becomes less clear and large infrared excesses are allowed if only one of these scenarios holds: (3) the dust grains are hotter than blackbody and predominantly emit at the observed wavelength; (4) or are blackbody in nature and emit at peak wavelengths longer than the observed one. Both scenarios imply that the parent planetesimals reside at larger distances from the star than inferred if the dust grains behaved like blackbodies. In all scenarios, we show that the infrared excesses detected at 22 ?m (via WISE) and 70 ?m (via Spitzer) from AU Mic are easily reconciled with its young age (12 Myr). Conversely, the existence of the old debris disc (2-8 Gyr) from GJ 581 is due to the large semimajor axes probed by the Herschel PACS instrument. We elucidate the conditions under which stellar wind drag may be neglected when considering dust populations around M stars. The WISE satellite should be capable of detecting debris discs around young M stars with ages ˜10 Myr.

Heng, Kevin; Malik, Matej

2013-07-01

404

Scaling from discs to pleated devices.  

PubMed

Membrane discs offer a convenient format for evaluating membrane performance in normal flow filtration. However, while pleated devices of different sizes tend to scale in close proportion to their contained areas, they do not necessarily scale in direct proportion from flat discs. The objectives of this study are to quantify differences in performance among sterilizing-grade membrane devices as a function of device type and size, to develop an understanding of the factors that affect device scalability, and to develop a mathematical model to predict a cartridge-to-disc scalability factor based on membrane properties and porous support properties and dimensions. Measured and predicted normalized water permeability scalability factors for seven types of pleated cartridges, including 0.1-micro and 0.2-micro rated PES, and 0.2-micro rated polyvinylidene fluoride (PVDF) sterilizing-grade filters in nominal 1-inch to 5-inch lengths, were determined. The results of this study indicate that pleated cartridge performance can be closely predicted based on 47-mm disc performance provided that a number of measured device parameters are properly accounted for, most importantly parasitic pressure losses in the filter device and plumbing connections, intrinsic membrane variability, true effective device filtration area, and the hydraulic properties of all porous support materials. Throughput scalability factors (discs to devices) tend to converge towards unity, especially for highly plugging streams. As the membrane fouls, the resistance through the membrane dominates other resistances, so the flux scales more linearly with membrane area and the overall scaling factor becomes close to one. The results of throughput tests on seven different cartridge types and five different challenge streams (with widely varying fouling characteristics) show that most of the throughput scaling factors were within +/-10% of 1.0. As part of this study, the effects of pressure and temperature were also evaluated. Neither of these factors was found to have a significant effect on scalability. PMID:17933212

Giglia, Sal; Yavorsky, David

2007-01-01

405

Both endoplasmic reticulum and mitochondria are involved in disc cell apoptosis and intervertebral disc degeneration in rats  

Microsoft Academic Search

Intervertebral disc cell apoptosis occurs through either death receptor or mitochondrial pathway, but whether disc cell apoptosis\\u000a is also mediated by the endoplasmic reticulum (ER) pathway remains unclear. The objective of this study was to investigate\\u000a whether ER and mitochondria are co-involved in disc cell apoptosis and intervertebral disc degeneration (IVDD) in rats. Forty-eight\\u000a rats were used for in vivo

Chang-Qing Zhao; Yue-Hui Zhang; Sheng-Dan Jiang; Lei-Sheng Jiang; Li-Yang Dai

2010-01-01

406

Follow-up study on the motion range after treatment of degenerative disc disease with the Bryan cervical disc prosthesis.  

PubMed

This study examined effect of a new intervertebral cervical disc prosthesis in relieving the neurological symptoms and signs, improving the patients' ability to perform daily activities, reducing pain, and maintaining the stability and segmental motion. From December 2003 to October 2004, 12 patients, who had received 14 replacements of cervical artificial discs, were followed-up for 2 to 8 months (with a mean of 5.2 months). Of them 5 had cervical spondylotic myelopathy and 7 had cervical disc herniation. The patients included 7 males and 5 females, with their age ranging from 35 to 62 y and a mean of 50.3 y. Single-level replacements were performed in 10 cases and 2 cases received two-level replacement. Operation time of the single-level surgery averaged 130+/-50 min and the time of two-level surgery was 165+/-53 min on average (from skin incision to skin suturing). Neurological or vascular complications during or after surgery was not observed. Japanese Orthopedic Association scores (JOA scores) increased from 8.6 to 15.8 on average. There was no prothesis subsidence or excursion. Replaced segments were stable and the range of motion was partially restored, being 4.68 degrees (3.6 degrees -6.1 degrees ) in flexion and extension position and 3.51 degrees (2.5 degrees -4.6 degrees ), 3.42 degrees (2.6 degrees -4.3 degrees ) in left and right bending position. No obvious loss of physiological curvature was noted. CT or MRI follow-up showed that excursion was less than 1.5 mm) in 2 of 14 levels and between 1.5 mm and 3 mm) in 1 of 14 levels. No ossification in the replaced levels was observed. It is concluded that satisfactory short-term results were achieved in the 12 cases of artificial disc replacements. Different from anterior cervical discectomy and fusion, the replacement could achieve quick functional recovery and did not lead to the movement limitation of cervical vertebrae. At least a 5-years follow-up was needed to assess the long-term effect of the prosthesis on its neighboring segments. PMID:17497290

Yang, Shuhua; Hu, Yong; Zhao, Jijun; He, Xianfeng; Liu, Yong; Xu, Weihua; Du, Jingyuan; Fu, Dehao

2007-04-01

407

Optical Structure and Proper-Motion Age of the Oxygen-rich Supernova Remnant 1E 0102-7219 in the Small Magellanic Cloud  

E-print Network

We present new optical emission-line images of the young SNR 1E 0102-7219 (E0102) in the SMC obtained with the HST Advanced Camera for Surveys (ACS). E0102 is a member of the oxygen-rich class of SNRs showing strong oxygen, neon , and other metal-line emissions in its optical and X-ray spectra, and an absence of H and He. The progenitor of E0102 may have been a Wolf-Rayet star that underwent considerable mass loss prior to exploding as a Type Ib/c or IIL/b SN. The ejecta in this SNR are fast-moving (V > 1000 km/s) and emit as they are compressed and heated in the reverse shock. In 2003, we obtained optical [O III], H-alpha, and continuum images with the ACS Wide Field Camera. The [O III] image captures the full velocity range of the ejecta, and shows considerable high-velocity emission projected in the middle of the SNR that was Doppler-shifted out of the narrow F502N bandpass of a previous Wide Field and Planetary Camera 2 image from 1995. Using these two epochs separated by ~8.5 years, we measure the transverse expansion of the ejecta around the outer rim in this SNR for the first time at visible wavelengths. From proper-motion measurements of 12 ejecta filaments, we estimate a mean expansion velocity for the bright ejecta of ~2000 km/s and an inferred kinematic age for the SNR of \\~2050 +/- 600 years. The age we derive from HST data is about twice that inferred by Hughes et al.(2000) from X-ray data, though our 1-sigma error bars overlap. Our proper-motion age is consistent with an independent optical kinematic age derived by Eriksen et al.(2003) using spatially resolved [O III] radial-velocity data. We derive an expansion center that lies very close to X-ray and radio hotspots, which could indicate the presence of a compact remnant (neutron star or black hole).

Steven L. Finkelstein; Jon A. Morse; James C. Green; Jeffrey L. Linsky; J. Michael Shull; Theodore P. Snow; John T. Stocke; Kenneth R. Brownsberger; Dennis C. Ebbets; Erik Wilkinson; Sara R. Heap; Claus Leitherer; Blair D. Savage; Oswald H. Siegmund; Alan Stern

2006-01-24

408

Cervical Deuk Laser Disc Repair®: A novel, full-endoscopic surgical technique for the treatment of symptomatic cervical disc disease  

PubMed Central

Background: Cervical Deuk Laser Disc Repair® is a novel full-endoscopic, anterior cervical, trans-discal, motion preserving, laser assisted, nonfusion, outpatient surgical procedure to safely treat symptomatic cervical disc diseases including herniation, spondylosis, stenosis, and annular tears. Here we describe a new endoscopic approach to cervical disc disease that allows direct visualization of the posterior longitudinal ligament, posterior vertebral endplates, annulus, neuroforamina, and herniated disc fragments. All patients treated with Deuk Laser Disc Repair were also candidates for anterior cervical discectomy and fusion (ACDF). Methods: A total of 142 consecutive adult patients with symptomatic cervical disc disease underwent Deuk Laser Disc Repair during a 4-year period. This novel procedure incorporates a full-endoscopic selective partial decompressive discectomy, foraminoplasty, and posterior annular debridement. Postoperative complications and average volume of herniated disc fragments removed are reported. Results: All patients were successfully treated with cervical Deuk Laser Disc Repair. There were no postoperative complications. Average volume of herniated disc material removed was 0.09 ml. Conclusions: Potential benefits of Deuk Laser Disc Repair for symptomatic cervical disc disease include lower cost, smaller incision, nonfusion, preservation of segmental motion, outpatient, faster recovery, less postoperative analgesic use, fewer complications, no hardware failure, no pseudoarthrosis, no postoperative dysphagia, and no increased risk of adjacent segment disease as seen with fusion. PMID:23230523

Deukmedjian, Ara J.; Cianciabella, Augusto; Cutright, Jason; Deukmedjian, Arias

2012-01-01

409

Translational research of herniated discs: current status of diagnosis and treatment.  

PubMed

Lumbar herniated discs commonly occur in patients 20-40 years of age, and result in acute symptoms of shooting and intractable pain in the low back and/or lower extremities. However, the prognosis of these patients is considered to be very good. Moreover, 70% of these patients have been reported to be free from sciatica at approximately 6 months after the first onset. Magnetic resonance imaging (MRI) studies have described the spontaneous resorption process of herniated discs, which is a major cause of the reduction of symptoms in patients. New advancements in MRI have recently been developed that have facilitated the examination of nerve tract fibers and identification of symptomatic nerve tissue. Furthermore, the mechanism underlying the resorption process of a herniated disc has been determined. Inflammatory cytokines such as TNF (tumor necrosis factor)-?, angiogenic factors such as vascular endothelial growth factor, and enzymes such as matrix metalloproteinases are intricately related to each other. In our previous studies, matrix metalloproteinase-7 (MMP-7) has been shown to play a crucial role in the initiation of herniated disc resorption. Therefore, we developed recombinant human MMP-7 for intradiscal therapy through an industry-university joint research program. We have already performed in vitro and in vivo experiments to confirm its efficacy; this therapy avoids the side effects associated with surgery, such as nerve tissue damage. Moreover, the phase 1/2 studies of recombinant human (rh) MMP-7 are currently ongoing in the United States, and careful monitoring is required for these clinical trials. In conclusion, patients with lumbar herniated discs may benefit from the development of a less invasive treatment for disc herniation, which can be applied even immediately after the onset of disease symptoms. PMID:24777237

Haro, Hirotaka

2014-07-01

410

Iron K-Alpha Lines from Ionized Discs in Z-Type X-Ray  

NASA Astrophysics Data System (ADS)

The properties of the iron K? line emitted by a photoionized accretion