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1

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 ...

2

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

3

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

4

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

5

[Diagnostics and therapy of spinal disc herniation].  

PubMed

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

Zimmer, A; Reith, W

2014-11-01

6

Intradural disc herniations pathogenesis, clinical picture, diagnosis and treatment  

Microsoft Academic Search

Summary The relatively rare occurrence and uncertainty about pathogenesis of intradurally displaced disc herniations stimulated an anatomico-pathological study into intradural disc herniations. The relation between the ventral dura and posterior longitudinal ligament in the cervical, thoracic, lumbar and sacral regions were examined macroscopically and microscopically, and ventral and dorsal durai thickness was compared in 20 adult autopsies on patients who

A. Yildizhan; A. Pa?ao?lu; T. Okten; N. Ekinci; K. Aycan; Ö. Aral

1991-01-01

7

Sacral Perineural Cyst Accompanying Disc Herniation  

PubMed Central

Although most of sacral perineural cysts are asymptomatic, some may produce symptoms. Specific radicular pain may be due to distortion, compression, or stretching of nerve root by a space occupying cyst. We report a rare case of S1 radiculopathy caused by sacral perineural cyst accompanying disc herniation. The patient underwent a microscopic discectomy at L5-S1 level. However, the patient's symptoms did not improved. The hypesthesia persisted, as did the right leg pain. Cyst-subarachnoid shunt was set to decompress nerve root and to equalize the cerebrospinal fluid pressure between the cephalad thecal sac and cyst. Immediately after surgery, the patient had no leg pain. After 6 months, the patient still remained free of leg pain. PMID:19352483

Ju, Chang Il; Shin, Ho; Kim, Hyeun Sung

2009-01-01

8

Sacral perineural cyst accompanying disc herniation.  

PubMed

Although most of sacral perineural cysts are asymptomatic, some may produce symptoms. Specific radicular pain may be due to distortion, compression, or stretching of nerve root by a space occupying cyst. We report a rare case of S1 radiculopathy caused by sacral perineural cyst accompanying disc herniation. The patient underwent a microscopic discectomy at L5-S1 level. However, the patient's symptoms did not improved. The hypesthesia persisted, as did the right leg pain. Cyst-subarachnoid shunt was set to decompress nerve root and to equalize the cerebrospinal fluid pressure between the cephalad thecal sac and cyst. Immediately after surgery, the patient had no leg pain. After 6 months, the patient still remained free of leg pain. PMID:19352483

Ju, Chang Il; Shin, Ho; Kim, Seok Won; Kim, Hyeun Sung

2009-03-01

9

Lumbar Spine Disc Herniation Diagnosis with a Joint Shape Model  

E-print Network

Lumbar Spine Disc Herniation Diagnosis with a Joint Shape Model Raja S Alomari1 , Jason J Corso1 clinically known as Herniation) using shape potentials. We extract these shape potentials by jointly applying cold. In fact, it is the most common reason patients visited the emergency room in the U.S. in 2008

Corso, Jason J.

10

Intradural disc herniation at L5 level mimicking an intradural spinal tumor  

Microsoft Academic Search

Intradural lumbar disc herniation is a rare complication of disc disease. The reason for the tearing of the dura matter by\\u000a a herniated disc is not clearly known. Intradural disc herniations usually occur at the disc levels and are often seen at\\u000a L4–L5 level but have also been reported at other intervertebral disc levels. However, intradural disc herniation at mid-vertebral

Chang-Chih Liu; Chih-Ta Huang; Chih-Ming Lin; Kan-Nan Liu

2011-01-01

11

Thoracic Disc Herniation Presenting with Transient Anterior Spinal Artery Syndrome  

PubMed Central

Summary This report is a clinical and radiologic correlation of anterior spinal arterial distribution ischemia with a thoracic disc herniation affecting the artery of Adamkiewicz. We could only find one other similar reported case. A 38-year-old woman developed sudden onset of severe back pain and radiculopathy, followed by rapidly evolving paraparesis. The neurological examination was consistent with a deficit caused by anterior spinal artery ischemia. MRI revealed T2 signal change in the thoracolumbar spinal cord and a laterally placed, non-calcified disc herniation. Selective spinal angiography performed 30 hours after onset revealed displacement of the left T9 radicular feeding artery by the disc herniation; at this time the artery was patent. The patient experienced some resolution of symptoms within the first 24 hours and was managed conservatively and made a significant recovery within two weeks. Appropriately located thoracic disc herniations can disturb the blood supply to the thoracolumbar spinal cord. PMID:20667212

Guest, J.D.; Griesdale, D.E.; Marotta, T.

2000-01-01

12

Posterior thecal lumbar disc herniation mimicking synovial cyst  

Microsoft Academic Search

We describe a 70 year-old-patient with a rare, misleading presentation of lumbar disc prolapse, which on CT mimicked a synovial cyst. The whole nucleus pulposus had herniated, become sequestrated, and migrated behind the theca adjacent to the L4–5 facet joint. There was no continuity of the disc material with the intervertebral space. A fenestration was performed and the sequestrated disc

D. E. Sakas; M. A. Farrell; S. Young; J. Toland

1995-01-01

13

Posterior thecal lumbar disc herniation mimicking synovial cyst  

Microsoft Academic Search

We describe a 70 year-old-patient with a rare, misleading presentation of lumbar disc prolapse, which on CT mimicked a synovial cyst. The whole nucleus pulposus had herniated, become sequestrated, and migrated behind the theca adjacent to the L4-5 facet joint. There was no continuity of the disc material with the intervertebral space. A fenestration was performed and the sequestrated disc

D. E. Sakas; M. A. Farrell; S. Young; J. Toland

1995-01-01

14

Spontaneous Intracranial Hypotension Secondary to Lumbar Disc Herniation  

PubMed Central

Spontaneous intracranial hypotension is often idiopathic. We report on a patient presenting with symptomatic intracranial hypotension and pain radiating to the right leg caused by a transdural lumbar disc herniation. Magnetic resonance (MR) imaging of the brain revealed classic signs of intracranial hypotension, and an additional spinal MR confirmed a lumbar transdural herniated disc as the cause. The patient was treated with a partial hemilaminectomy and discectomy. We were able to find the source of cerebrospinal fluid leak, and packed it with epidural glue and gelfoam. Postoperatively, the patient's headache and log radiating pain resolved and there was no neurological deficit. Thus, in this case, lumbar disc herniation may have been a cause of spontaneous intracranial hypotension. PMID:20157378

Kim, Kyoung-Tae

2010-01-01

15

The cost-utility of lumbar disc herniation surgery.  

PubMed

The cost and utility of surgery for a herniated lumbar disc has not been determined simultaneously in a single cohort. The aim of this study is to perform a cost-utility analysis of surgical and nonsurgical treatment of patients with lumbar disc herniation. Ninety-two individuals in a cohort of 1,146 Swedish subjects underwent lumbar disc herniation surgery during a 2-year study. Each person operated on was individually matched with one treated conservatively. The effects and costs of the treatments were determined individually. By estimating quality of life before and after the treatment, the number of quality adjusted life years (QALY) gained with and without surgery was calculated. The medical costs were much higher for surgical treatment; however, the total costs, including disability costs, were lower among those treated surgically. Surgery meant fewer recurrences and less permanent disability benefits. The gain in QALY was ten times higher among those operated. Lower total costs and better utility resulted in a better cost utility for surgical treatment. Surgery for lumbar disc herniation was cost-effective. The total costs for surgery were lower due to lower recurrence rates and fewer disability benefits, and surgery improved quality of life much more than nonsurgical treatments. PMID:16683121

Hansson, Elisabeth; Hansson, Tommy

2007-03-01

16

Automatic diagnosis of lumbar disc herniation with shape and appearance features from MRI  

NASA Astrophysics Data System (ADS)

Intervertebral disc herniation is a major reason for lower back pain (LBP), which is the second most common neurological ailment in the United States. Automation of herniated disc diagnosis reduces the large burden on radiologists who have to diagnose hundreds of cases each day using clinical MRI. We present a method for automatic diagnosis of lumbar disc herniation using appearance and shape features. We jointly use the intensity signal for modeling the appearance of herniated disc and the active shape model for modeling the shape of herniated disc. We utilize a Gibbs distribution for classification of discs using appearance and shape features. We use 33 clinical MRI cases of the lumbar area for training and testing both appearance and shape models. We achieve over 91% accuracy in detection of herniation in a cross-validation experiment with specificity of 91% and sensitivity of 94%.

Alomari, Raja'S.; Corso, Jason J.; Chaudhary, Vipin; Dhillon, Gurmeet

2010-03-01

17

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

18

Psychopathological Influence of Lumbar Disc Herniation in Male Adolescent  

PubMed Central

Purpose There is no report about psychopathological effect causing by disc herniation. The disease could impose psychopathological influence on the social life, the treatment period, and response to the treatment. This study was to evaluate retrospectively the psychopathological influence of lumbar disc herniation (LDH) among Korean 19-year-old males. Materials and Methods We compared the Korean military multiphasic personality inventory (KMPI) profiles of 74 LDH cases with the KMPI profiles of 150 controls. The LDH groups were categorized to 2 groups according to the presence of thecal sac compression by disc materials, and evaluated the relation between the KMPI and LDH. Results The decrease of the faking-good response scale and increase of the faking-bad response scale were observed more in the LDH group than in the normal volunteer group (p<0.05). The neurosis set such as anxiety, depression and somatization was markedly increased in the LDH group compared to the normal volunteers group (p<0.05). The scale of personality disorder was also increased more in the LDH group (p=0.002). The differences of KMPI scales were not correlated with the severe pathology of LDH. Conclusion Young male with LDH may tend to have more abnormal results of multiphasic personality inventory test compared to the normal volunteers, suggesting that LDH may be related to the psychopathology in young males in Korea. Therefore, clinicians are recommended to evaluate and treat the psychopathological aspects in patients with LDH. PMID:23709412

Kim, Tae Woo; Oh, Chang Hyun; Shim, Yu Sik; Park, Hyeong-chun; Park, Chong Oon

2013-01-01

19

Posteriorly migrated thoracic disc herniation: a case report  

PubMed Central

Introduction Posterior epidural migration of thoracic disc herniation is extremely rare but may occur in the same manner as in the lumbar spine. Case presentation A 53-year-old Japanese man experienced sudden onset of incomplete paraplegia after lifting a heavy object. Magnetic resonance imaging revealed a posterior epidural mass compressing the spinal cord at the T9-T10 level. The patient underwent emergency surgery consisting of laminectomy at T9-T10 with right medial facetectomy, removal of the mass lesion, and posterior instrumented fusion. Histological examination of the mass lesion yielded findings consistent with sequestered disc material. His symptoms resolved, and he was able to resume walking without a cane 4 weeks after surgery. Conclusions Pre-operative diagnosis of posterior epidural migration of herniated thoracic disc based on magnetic resonance imaging alone may be overlooked, given the rarity of this pathology. However, this entity should be considered among the differential diagnoses for an enhancing posterior thoracic extradural mass. PMID:23402642

2013-01-01

20

Sagittal spinal alignment in patients with lumbar disc herniation.  

PubMed

A retrospective cross-sectional study was designed to evaluate total sagittal spinal alignment in patients with lumbar disc herniation (LDH) and healthy subjects. Abnormal sagittal spinal alignment could cause persistent low back pain in lumbar disease. Previous studies analyzed sciatic scoliotic list in patients with lumbar disc herniation; but there is little or no information on the relationship between sagittal alignment and subjective findings. The study subjects were 61 LDH patients and 60 age-matched healthy subjects. Preoperative and 6-month postoperatively lateral whole-spine standing radiographs were assessed for the distance between C7 plumb line and posterior superior corner on the top margin of S1 sagittal vertical axis (SVA), lumbar lordotic angle between the top margin of the first lumbar vertebra and first sacral vertebra (L1S1), pelvic tilting angle (PA), and pelvic morphologic angle (PRS1). Subjective symptoms were evaluated by the Japanese Orthopedic Association (JOA) score for lower back pain (nine points). The mean SVA value of the LDH group (32.7 +/- 46.5 mm, +/- SD) was significantly larger than that of the control (2.5 +/- 17.1 mm), while L1S1 was smaller (36.7 +/- 14.5 degrees ) and PA was larger (25.1 +/- 9.0 degrees ) in LDH than control group (49.0 +/- 10.0 degrees and 18.2 +/- 6.0 degrees , respectively). At 6 months after surgery, the malalignment recovered to almost the same level as the control group. SVA correlated with the subjective symptoms measured by the JOA score. Sagittal spinal alignment in LDH exhibits more anterior translation of the C7 plumb line, less lumbar lordosis, and a more vertical sacrum. Measurements of these spinal parameters allowed assessment of the pathophysiology of LDH. PMID:20091188

Endo, Kenji; Suzuki, Hidekazu; Tanaka, Hidetoshi; Kang, Yupeng; Yamamoto, Kengo

2010-03-01

21

Adolescent lumbar disc herniation in a Tae Kwon Do martial artist: a case report  

PubMed Central

Lumbar disc herniations are rare in children. The etiology and clinical picture may be different in children than in adults. Conservative management is the treatment of choice. Tae Kwon Do is a Korean martial art which is notorious for its high fast kicks. Tae Kwon Do will be an official Olympic sport in the year 2000. Low back pain is occasionally reported by Tae Kwon Do athletes but there are no reported cases in the literature on disc herniation in a Tae Kwon Do athlete. A case report is presented to illustrate clinical presentation, diagnosis, radiological assessment and conservative management of lumbar disc herniation in children. ImagesFigure 1Figure 2

Kazemi, Mohsen

1999-01-01

22

Ultrasound-Guided Posterolateral Approach for Midline Calcified Thoracic Disc Herniation  

PubMed Central

Objective Symptomatic thoracic disc herniation often requires prompt surgical treatment to prevent neurological deterioration and permanent deficits. Anterior approaches offer direct visualization and access to the herniated disc and anterior dura but require access surgeons and are often associated with considerable postoperative pain and pulmonary complications. A disadvantage with using posterior approaches in the setting of central calcified thoracic disc herniation however, has been the limited visualization of anterior dura and difficulty to accurately assess the extent of decompression. Methods We report our experience with intraoperative ultrasound (US) guidance during a modified posterior transpedicular approach for removal of a central calcified thoracic disc herniation with a review of pertinent literature. Results The herniated thoracic disc was successfully removed with posterior approach with the aid of intraoperative US. The patient had significant neurological improvement at three months follow-up. Conclusion Intraoperative ultrasound is a simple yet valuable tool for real-time imaging during transpedicular thoracic discectomy. Visualization provided by intraoperative US increases the safety profile of posterior approaches and may make thoracotomy unnecessary in a selected group of patients, especially when a patient has existing pulmonary disease or is otherwise not medically fit for the transthoracic approach.

Lopes, Demetrius K.; Fontes, Ricardo B. V.

2014-01-01

23

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

24

Relationship between low-back pain, muscle spasm and pressure pain thresholds in patients with lumbar disc herniation  

Microsoft Academic Search

It is not known whether or not muscle spasm of the back muscles presented in patients with sciatic scoliosis caused by lumbar disc herniation produces muscle pain and\\/or tenderness. Pressure pain thresholds (PPTs) of the lower back and low-back pain were examined in 52 patients (13 of 52 presenting sciatic scoliosis) with lumbar disc herniation who complained of radicular pain

Jiro Hirayama; Masatsune Yamagata; Satoshi Ogata; Koh Shimizu; Yoshikazu Ikeda; Kazuhisa Takahashi

2006-01-01

25

Effect of ligamenta flava hypertrophy on lumbar disc herniation with contralateral symptoms and signs: a clinical and morphometric study  

PubMed Central

Introduction The purpose of this study was to determine whether ligamentum flavum hypertrophy among disc herniated patients causes contralateral pain symptoms. For this reason we measured the thickness of the ligament in disc herniated patients with ipsilateral or contralateral symptoms. Material and methods Two hundred disc herniated patients with ipsilateral symptoms as group I were compared with five disc herniated patients with only contralateral symptoms as group II. Ligamenta flava thicknesses and spinal canal diameters of both groups were measured on magnetic resonance imaging (MRI) with a micro-caliper. Results Both groups underwent surgery only on the disc herniated side. The total thicknesses of the ligamenta flava in group II was thicker than in group I. There was no spinal stenosis in either group and no significance difference between the groups. Statistically significant differences were found for both ipsilateral and contralateral thickness of the ligament flava in both groups. We also compared thickness of the ligamenta flava for each level of disc herniation in group I; ligamenta flava hypertrophy was more common at L3-L4 and L4-L5 levels of vertebrae in females. Conclusions Aetiology of contralateral sciatica among disc herniated patients may be related to hypertrophy of the ligamenta flava, especially on the opposite side. Surgical approaches of the disc herniated side alone may be sufficient for a good outcome. PMID:22371809

Yildizhan, Ahmet; Atar, Elmas K.; Yaycioglu, Soner; Gocmen-Mas, Nuket; Yazici, Canan

2010-01-01

26

Spontaneous intradural disc herniation with focal distension of the subarachnoid space in a dog  

PubMed Central

Myelo-computed tomography of a paraparetic 14-year-old dog revealed subarachnoid distension with an intradural filling defect above the T13–L1 disc space. T12–L1 hemilaminectomy followed by durotomy allowed removal of a large piece of degenerated disc material that compressed the spinal parenchyma. Full return to function was achieved 10 days post-surgery. The distension was likely secondary to the intradural herniation, and is a rare and distinct finding. PMID:23633713

Barnoon, Itai; Chai, Orit; Srugo, Itai; Peeri, Dana; Konstantin, Lilach; Brenner, Ori; Shamir, Merav H.

2012-01-01

27

Endoscopic Transforaminal Thoracic Foraminotomy and Discectomy for the Treatment of Thoracic Disc Herniation  

PubMed Central

Thoracic disc herniation is a relatively rare yet challenging-to-diagnose condition. Currently there is no universally accepted optimal surgical treatment for symptomatic thoracic disc herniation. Previously reported surgical approaches are often associated with high complication rates. Here we describe our minimally invasive technique of removing thoracic disc herniation, and report the primary results of a series of cases. Between January 2009 and March 2012, 13 patients with symptomatic thoracic disc herniation were treated with endoscopic thoracic foraminotomy and discectomy under local anesthesia. A bone shaver was used to undercut the facet and rib head for foraminotomy. Discectomy was achieved by using grasper, radiofrequency, and the Holmium-YAG laser. We analyzed the clinical outcomes of the patients using the visual analogue scale (VAS), MacNab classification, and Oswestry disability index (ODI). At the final follow up (mean: 17 months; range: 6–41 months), patient self-reported satisfactory rate was 76.9%. The mean VAS for mid back pain was improved from 9.1 to 4.2, and the mean ODI was improved from 61.0 to 43.8. One complication of postoperative spinal headache occurred during the surgery and the patient was successfully treated with epidural blood patch. No other complications were observed or reported during and after the surgery. PMID:24455232

Nie, Hong-Fei; Liu, Kai-Xuan

2013-01-01

28

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

29

Lumbar disc herniation in a child with cystic fibrosis: case report.  

PubMed

We report a case of child with cystic fibrosis and lumbar disc herniation. An 8-year-old boy presented with low back pain that exacerbated on coughing, sitting, walking, or bending and diminished when lying down. The straight leg raising test was positive when the right leg was lifted at 60 degrees. Crossed leg raising test was negative. Lumbar MRI revealed a L5-S1central disc protrusion. Conservative treatment was not effective and the patient underwent surgery. Postoperatively the patient experienced regression of the pain. To the best of our knowledge this is the first reported case of lumbar disc herniation in a child with cystic fibrosis. Although this case might be coincidental, thorough investigation of back pain, which is frequent in patients with cystic fibrosis, should be performed. PMID:24584798

Alexiou, George A; Stefanaki, Kalliopi; Sfakianos, George; Prodromou, Neofytos

2014-04-01

30

Spontaneous Cervical Intradural Disc Herniation Associated with Ossification of Posterior Longitudinal Ligament  

PubMed Central

Intradural herniation of a cervical disc is rare; less than 35 cases have been reported to date. A 52-year-old man with preexisting ossification of posterior longitudinal ligament developed severe neck pain with Lt hemiparesis while asleep. Neurological exam was consistent with Brown-Séquard syndrome. Magnetic resonance images showed a C5-6 herniated disc that was adjacent to the ossified ligament and indenting the cord. The mass was surrounded by cerebrospinal fluid signal intensity margin, and caudally the ventral dura line appears divided into two, consistent with the “Y-sign” described by Sasaji et al. Cord edema were noted. Because of preexisting canal stenosis and spinal cord at risk, a laminoplasty was performed, followed by an anterior C6 corpectomy. Spot-weld type adhesions of the posterior longitudinal ligament to the dura was noted, along with a longitudinal tear in the dura. An intradural extra-arachnoid fragment of herniated disc was removed. Clinical exam at 6 months after surgery revealed normal muscle strength but persistent mild paresthesias. It is difficult to make a definite diagnosis of intradural herniation preoperatively; however, the clinical findings and radiographic signs mentioned above are suggestive and should alert the surgeon to look for an intradural fragment. PMID:25295205

Wang, Dachuan; Wang, Haifeng; Shen, Wun-Jer

2014-01-01

31

Revisional Percutaneous Full Endoscopic Disc Surgery for Recurrent Herniation of Previous Open Lumbar Discectomy  

PubMed Central

Study Design A retrospective study. Purpose To determine the feasibility and effectiveness of revisional percutaneous full endoscopic discectomy for recurrent herniation after conventional open disc surgery. Overview of the Literature Repeated open discectomy with or without fusion has been the most common procedure for recurrent lumbar disc herniation. Percutaneous endoscopic lumbar discectomy for recurrent herniation has been thought of as an impossible procedure. Despite good results with open revisional surgery, major problems may be caused by injuries to the posterior stabilized structures. Our team did revisional full endoscopic lumbar disc surgery on the basis of our experience doing primary full endoscopic disc surgery. Methods Between February 2004 and August 2009 a total of 41 patients in our hospital underwent revisional percutaneous endoscopic lumbar discectomy using a YESS endoscopic system and a micro-osteotome (designed by the authors). Indications for surgery were recurrent disc herniation following conventional open discectomy; with compression of the nerve root revealed by Gadolinium-enhanced magnetic resonance imaging; corresponding radiating pain which was not alleviated after conservative management over 6 weeks. Patients with severe neurologic deficits and isolated back pain were excluded. Results The mean follow-up period was 16 months (range, 13 to 42 months). The visual analog scale for pain in the leg and back showed significant post-treatment improvement (p < 0.001). Based on a modified version of MacNab's criteria, 90.2% showed excellent or good outcomes. There was no measurable blood loss. There were two cases of recurrence of and four cases with complications. Conclusions Percutaneous full-endoscopic revisional disc surgery without additional structural damage is feasible and effective in terms of there being less chance of fusion and bleeding. This technique can be an alternative to conventional repeated discectomy. PMID:21386940

Chang, Ho-Guen; Rhee, Nam Kyou; Lim, Kwahn Sue

2011-01-01

32

Adjacent Lumbar Disc Herniation after Lumbar Short Spinal Fusion  

PubMed Central

A 70-year-old outpatient presented with a chief complaint of sudden left leg motor weakness and sensory disturbance. He had undergone L4/5 posterior interbody fusion with L3–5 posterior fusions for spondylolisthesis 3 years prior, and the screws were removed 1 year later. He has been followed up for 3 years, and there had been no adjacent segment problems before this presentation. Lumbar magnetic resonance imaging (MRI) showed a large L2/3 disc hernia descending to the L3/4 level. Compared to the initial MRI, this hernia occurred in an “intact” disc among multilevel severely degenerated discs. Right leg paresis and bladder dysfunction appeared a few days after admission. Microscopic lumbar disc herniotomy was performed. The right leg motor weakness improved just after the operation, but the moderate left leg motor weakness and difficulty in urination persisted. PMID:25276453

Iwatsuki, Koichi; Ohnishi, Yu-ichiro; Yoshimine, Toshiki

2014-01-01

33

Matrix metalloproteinase expression levels suggest distinct enzyme roles during lumbar disc herniation and degeneration  

PubMed Central

The disruption of the extracellular disc matrix is a major hallmark of disc degeneration. This has previously been shown to be associated with an up-regulation of major matrix metalloproteinase (MMP) expression and activity. However, until now hardly any data are available for MMP/TIMP regulation and thereby no concept exists as to which MMP/TIMP plays a major role in disc degeneration. The objective of this study was, therefore, to identify and quantify the putative up-regulation of MMPs/TIMPs on the mRNA and protein level and their activity in disc material in relation to clinical data and histological evidence for disc degeneration. A quantitative molecular analysis of the mRNA expression levels for the MMPs (MMPs-1, -2, -3, -7, -8, -9, -13) and the MMP inhibitors (TIMPs-1 and -2) was performed on 37 disc specimens obtained from symptomatic disc herniation or degeneration. In addition, disc specimens from patients without disc degeneration/herniation (=controls) were analyzed. Expression of MMPs-1, -2, -3, -7, -8, -9, -13 and TIMPs-1, -2 was analyzed using quantitative RT-PCR, normalized to the expression level of a house keeping gene (GAPDH). Gene expression patterns were correlated with MMP activity (in situ zymography), protein expression patterns (immunohistochemistry), degeneration score (routine histology) and clinical data. MMP-3 mRNA levels were consistently and substantially up-regulated in samples with histological evidence for disc degeneration. A similar but less pronounced up-regulation was observed for MMP-8. This up-regulation was paralleled by the expression of TIMP-1 and to a lesser extent TIMP-2. In general, these findings could be confirmed with regard to protein expression and enzyme activity. This study provides data on the gene and protein level, which highlights the key role of MMP-3 in the degenerative cascade leading to symptomatic disc degeneration and herniation. Control of the proteolytic activity of MMP-3 may, therefore, come into the focus when aiming to develop new treatment options for early disc degeneration. PMID:19466462

Bachmeier, Beatrice E.; Nerlich, Andreas; Mittermaier, Norbert; Weiler, Christoph; Lumenta, Christianto; Wuertz, Karin

2009-01-01

34

The Impact of Epidural Steroid Injections on the Outcomes of Patients Treated for Lumbar Disc Herniation  

PubMed Central

Background: The Spine Patient Outcomes Research Trial (SPORT) is a prospective, multicenter study of operative versus nonoperative treatment of lumbar intervertebral disc herniation. It has been suggested that epidural steroid injections may help improve patient outcomes and lower the rate of crossover to surgical treatment. Methods: One hundred and fifty-four patients included in the intervertebral disc herniation arm of the SPORT who had received an epidural steroid injection during the first three months of the study and no injection prior to the study (the ESI group) were compared with 453 patients who had not received an injection during the first three months of the study or prior to the study (the No-ESI group). Results: There was a significant difference in the preference for surgery between groups (19% in the ESI group compared with 56% in the No-ESI group, p < 0.001). There was no difference in primary or secondary outcome measures at four years between the groups. A higher percentage of patients changed from surgical to nonsurgical treatment in the ESI group (41% versus 12% in the No-ESI, p < 0.001). Conclusions: Patients with lumbar disc herniation treated with epidural steroid injection had no improvement in short or long-term outcomes compared with patients who were not treated with epidural steroid injection. There was a higher prevalence of crossover to nonsurgical treatment among surgically assigned ESI-group patients, although this was confounded by the increased baseline desire to avoid surgery among patients in the ESI group. Given these data, we concluded that more studies are necessary to establish the value of epidural steroid injection for symptomatic lumbar intervertebral disc herniation. Level of Evidence: Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence. PMID:22739998

Radcliff, Kristen; Hilibrand, Alan; Lurie, Jon D.; Tosteson, Tor D.; Delasotta, Lawrence; Rihn, Jeffrey; Zhao, Wenyan; Vaccaro, Alexander; Albert, Todd J.; Weinstein, James N.

2012-01-01

35

Disc herniation in the thoracolumbar junction treated by minimally invasive transforaminal interbody fusion surgery.  

PubMed

Minimally invasive surgery-transforaminal lumbar interbody fusion (MIS-TLIF) has demonstrated efficacy in the treatment of lumbar degenerative diseases. Use of this procedure for thoracolumbar junction disc herniation remains challenging. Reports concerning MIS-TLIF at the thoracolumbar junction are rare. Thus, we performed a retrospective analysis of the clinical outcomes of 10 patients with thoracolumbar junction disc herniation treated by MIS-TLIF between December 2007 and October 2010. The purpose of this study was to investigate the efficacy and safety of MIS-TLIF for disc herniation in the thoracolumbar junction. Clinical and radiological data were collected and analyzed. Fusion levels included T12-L1 (two patients), L1-L2 (four patients) and L2-L3 (four patients). Clinical outcome was assessed using the Visual Analogue Scale (VAS) and Oswestry Disability Index (ODI). The average follow-up period was 39.2 months, with a minimum of 24 months. The mean ± standard error of the mean of the operative time, intraoperative blood loss, and x-ray exposure were 128 ± 36 minutes, 204 ± 35 mL, and 43 ± 12 seconds, respectively. The VAS for back and leg pain decreased significantly postoperatively from 6.4 ± 2.7 to 1.5 ± 0.6 (p<0.01), and from 7.1 ± 2.4 to 1.3 ± 0.4 (p<0.01) respectively, as did the ODI from 39.3 ± 11.2 to 16.5 ± 4.7 (p<0.01). Bone fusion was observed in eight patients. There were no other major complications at last follow-up. MIS-TIF is a safe and effective procedure for disc herniation in the thoracolumbar junction. Occurrence of non-union is relatively high compared to previous findings. PMID:24225365

Wang, Jian; Zhou, Yue; Zhang, Zheng Feng; Li, Chang Qing; Zheng, Wen Jie; Huang, Bo

2014-03-01

36

Comparison of Two Methods of Epidural Steroid Injection in the Treatment of Recurrent Lumbar Disc Herniation  

PubMed Central

Study Design Prospective study. Purpose We compared the effects of two methods of epidural steroid injection in patients with recurrent disc herniation. Overview of Literature To our knowledge, there is no previous report of such a comparison in these patients. Methods The study was performed with 30 patients with relapsed lumbar disc herniation whose pain was not relieved by conservative remedies. The patients were divided into two groups, each of 15 patients, and entered the study for caudal or transforaminal injections. The degree of pain, ability to stand and walk, and the Prolo function score were evaluated in both groups before the injection and 2 months and 6 months after the injection. Results The degrees of pain reduction in the caudal injection group in the second and sixth months were 0.6 and 1.63, respectively, and in the transforaminal injection group were 1.33 and 1.56, respectively. The difference between the two methods was not statistically significant. Similarly, no other evaluated criterion showed a significant difference between the methods. Conclusions In the current study, the caudal and transforaminal steroid injection methods showed similar outcomes in the treatment of relapsed lumbar disc herniation. However, more detailed patient categorizing may help in finding possible subgroups with differences.

Ebrahimi-Nejad, Ali; Shahsavarani, Shahram; Keikhosravi, Ehsan; Shahba, Mohsen; Ebrahimi, Farzaneh

2014-01-01

37

Dorsal Extradural Lumbar Disc Herniation Causing Cauda Equina Syndrome : A Case Report and Review of Literature  

PubMed Central

A 73-year-old male presented with a rare dorsally sequestrated lumbar disc herniation manifesting as severe radiating pain in both leg, progressively worsening weakness in both lower extremities, and urinary incontinence, suggesting cauda equina syndrome. Magnetic resonance imaging suggested the sequestrated disc fragment located in the extradural space at the L4-L5 level had surrounded and compressed the dural sac from the lateral to dorsal sides. A bilateral decompressive laminectomy was performed under an operating microscope. A large extruded disc was found to have migrated from the ventral aspect, around the thecal sac, and into the dorsal aspect, which compressed the sac to the right. After removal of the disc fragment, his sciatica was relieved and the patient felt strength of lower extremity improved. PMID:20379476

Lee, Sang-Ho; Arbatti, Nikhil J.

2010-01-01

38

Spinal Epidural Arteriovenous Hemangioma Mimicking Lumbar Disc Herniation  

PubMed Central

A spinal epidural hemangioma is rare. In this case, a 51 year-old female patient had low back pain and right thigh numbness. She was initially misdiagnosed as having a ruptured disc with possible sequestration of granulation tissue formation due to the limited number of spinal epidural hemangiomas and little-known radiological findings. Because there are no effective diagnostic tools to verify the hemangioma, more effort should be put into preoperative imaging tests to avoid misdiagnosis and poor decisions). PMID:23133733

Kim, Kyung Hyun; Song, Sang Woo; Lee, Soo Eon

2012-01-01

39

Management of Chronic Pain of Cervical Disc Herniation and Radiculitis with Fluoroscopic Cervical Interlaminar Epidural Injections  

PubMed Central

Study Design: A randomized, double-blind, active controlled trial. Objective: To evaluate the effectiveness of cervical interlaminar epidural injections of local anesthetic with or without steroids in the management of chronic neck pain and upper extremity pain in patients with disc herniation and radiculitis. Summary of Background Data: Epidural injections in managing chronic neck and upper extremity pain are commonly employed interventions. However, their long-term effectiveness, indications, and medical necessity, of their use and their role in various pathologies responsible for persistent neck and upper extremity pain continue to be debated, even though, neck and upper extremity pain secondary to disc herniation and radiculitis, is described as the common indication. There is also paucity of high quality literature. Methods: One-hundred twenty patients were randomly assigned to one of 2 groups: Group I patients received cervical interlaminar epidural injections of local anesthetic (lidocaine 0.5%, 5 mL); Group II patients received 0.5% lidocaine, 4 mL, mixed with 1 mL of nonparticulate betamethasone. Primary outcome measure was ? 50 improvement in pain and function. Outcome assessments included Numeric Rating Scale (NRS), Oswestry Disability Index (ODI), opioid intake, employment, and changes in weight. Results: Significant pain relief and functional status improvement (? 50%) was demonstrated in 72% of patients who received local anesthetic only and 68% who received local anesthetic and steroids. In the successful group of participants, significant improvement was illustrated in 77% in local anesthetic group and 82% in local anesthetic with steroid group. Conclusions: Cervical interlaminar epidural injections with or without steroids may provide significant improvement in pain and function for patients with cervical disc herniation and radiculitis. PMID:22859902

Manchikanti, Laxmaiah; Cash, Kimberly A.; Pampati, Vidyasagar; Wargo, Bradley W.; Malla, Yogesh

2012-01-01

40

A Novel Approach to the Surgical Treatment of Lumbar Disc Herniations: Indications of Simple Discectomy and Posterior Transpedicular Dynamic Stabilization Based on Carragee Classification  

PubMed Central

Surgery of lumbar disc herniation is still a problem since Mixter and Barr. Main trouble is dissatisfaction after the operation. Today there is a debate on surgical or conservative treatment despite spending great effort to provide patients with satisfaction. The main problem is segmental instability, and the minimally invasive approach via microscope or endoscope is not necessarily appropriate solution for all cases. Microsurgery or endoscopy would be appropriate for the treatment of Carragee type I and type III herniations. On the other hand in Carragee type II and type IV herniations that are prone to develop recurrent disc herniation and segmental instability, the minimal invasive techniques might be insufficient to achieve satisfactory results. The posterior transpedicular dynamic stabilization method might be a good solution to prevent or diminish the recurrent disc herniation and development of segmental instability. In this study we present our experience in the surgical treatment of disc herniations. PMID:23653862

Ozer, A. F.; Keskin, F.; Oktenoglu, T.; Suzer, T.; Ataker, Y.; Gomleksiz, C.; Sasani, M.

2013-01-01

41

Composite features for automatic diagnosis of intervertebral disc herniation from lumbar MRI.  

PubMed

Lower back pain is widely prevalent in the world today, and the situation is aggravated due to a shortage of radiologists. Intervertebral disc disorders like desiccation, degeneration and herniation are some of the major causes of lower back pain. In this paper, we propose a robust computer-aided herniation diagnosis system for lumbar MRI by first extracting an approximate Region Of Interest (ROI) for each disc and then using a combination of viable features to produce a highly accurate classifier. We describe the extraction of raw, LBP (Local Binary Patterns), Gabor, GLCM (Gray-Level Co-occurrence Matrix), shape, and intensity features from lumbar SPIR T2-weighted MRI and also present a thorough performance comparison of individual and combined features. We perform 5-fold cross validation experiments on 35 cases and report a very high accuracy of 98.29% using a combination of features. Also, combining the desired features and reducing the dimensionality using LDA, we achieve a high sensitivity (true positive rate) of 98.11%. PMID:22255478

Ghosh, Subarna; Alomari, Raja' S; Chaudhary, Vipin; Dhillon, Gurmeet

2011-01-01

42

Lumbar disc herniation and cauda equina syndrome following spinal manipulative therapy: a review of six court decisions in Canada.  

PubMed

The purpose of this review is to expand practitioners' knowledge on areas of liability when treating low back pain patients. Six cases where chiropractors in Canada were sued for allegedly causing or aggravating lumbar disc herniation after spinal manipulative therapy were retrieved using the CANLII search database. The case series involves 4 men and 2 women with an average age of 37.3 years (range, 31-48 years). Trial courts' decisions were rendered between 2000 and 2011. This study highlights the following conclusions from Canadian courts: 1) informed consent is an ongoing process that cannot be entirely delegated to office personnel; 2) when the patient's history reveals risk factors for lumbar disc herniation the chiropractor has the duty to rule out disc pathology as an etiology for the symptoms presented by the patients before beginning anything but conservative palliative treatment; 3) lumbar disc herniation may be triggered by spinal manipulative therapy on vertebral segments distant from the involved herniated disc such as the thoracic spine. PMID:24485443

Boucher, Pierre; Robidoux, Sébastien

2014-02-01

43

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

44

Risk factors for back pain-related loss of working time after surgery for lumbar disc herniation: a 5-year follow-up study  

Microsoft Academic Search

The aim of this study is to explore the occurrence and the risk factors of back-related loss of working time in patients undergoing\\u000a surgery for lumbar disc herniation. One hundred and fifty-two gainfully employed patients underwent surgery for lumbar disc\\u000a herniation. Two months postoperatively, those patients completed a self-report questionnaire including queries on back and\\u000a leg pain (VAS), functional capacity

K. Puolakka; J. Ylinen; M. H. Neva; H. Kautiainen; A. Häkkinen

2008-01-01

45

Do preoperative fear avoidance model factors predict outcomes after lumbar disc herniation surgery? A systematic review  

PubMed Central

Background Lumbar disc herniation (LDH) surgery is usually recommended when conservative treatments fail to manage patients’ symptoms. However, many patients undergoing LDH surgery continue to report pain and disability. Preoperative psychological factors have shown to be predictive for postoperative outcomes. Our aim was to systematically review studies that prospectively examined the prognostic value of factors in the Fear Avoidance Model (FAM), including back pain, leg pain, catastrophizing, anxiety, fear-avoidance, depression, physical activity and disability, to predict postoperative outcomes in patients undergoing LDH surgery. Methods We performed a systematic literature review of prospective studies that measured any FAM factors preoperatively to predict postoperative outcomes for patients undergoing LDH surgery. Our search databases included PubMed, CINAHL, and PsycINFO. We assessed the quality of each included study using a certain quality assessment list. Degree of agreement between reviewers on quality assessment was examined. Results related to FAM factors in the included studies were summarized. Results Thirteen prospective studies met our inclusion criteria. Most studies were considered high quality. Heterogeneity was present between the included studies in many aspects. The most common FAM factors examinered were baseline pain, disability and depression. In, general, depression, fear-avoidance behaviors, passive pain coping, and anxiety FAM factors appeared to have negative influence on LDH surgical outcome. Baseline back pain and leg pain appeared to have differing prognostic value on LDH surgical outcomes. Conclusions FAM factors seem to influence LDH surgical outcomes. Patients with high levels of depression, anxiety and fear-avoidance behaviors are more likely to have poor outcomes following LDH surgery. Conversely, high levels of leg pain, but not back pain seem to be predictor for favorable LDH surgery outcome. More research is needed to determine the exact role of FAM factors on LDH surgical outcome and the value for screening for these factors. PMID:24237581

2013-01-01

46

Fluoroscopic caudal epidural injections in managing chronic axial low back pain without disc herniation, radiculitis, or facet joint pain  

PubMed Central

Background Chronic low back pain without disc herniation is common. Various modalities of treatments are utilized in managing this condition, including epidural injections. However, there is continued debate on the effectiveness, indications, and medical necessity of any treatment modality utilized for managing axial or discogenic pain, including epidural injections. Methods A randomized, double-blind, actively controlled trial was conducted. The objective was to evaluate the ability to assess the effectiveness of caudal epidural injections of local anesthetic with or without steroids for managing chronic low back pain not caused by disc herniation, radiculitis, facet joints, or sacroiliac joints. A total of 120 patients were randomized to two groups; one group did not receive steroids (group 1) and the other group did (group 2). There were 60 patients in each group. The primary outcome measure was at least 50% improvement in Numeric Rating Scale and Oswestry Disability Index. Secondary outcome measures were employment status and opioid intake. These measures were assessed at 3, 6, 12, 18, and 24 months after treatment. Results Significant pain relief and functional status improvement (primary outcome) defined as a 50% or more reduction in scores from baseline, were observed in 54% of patients in group 1 and 60% of patients in group 2 at 24 months. In contrast, 84% of patients in group 1 and 73% in group 2 saw significant pain relief and functional status improvement in the successful groups at 24 months. Conclusion Caudal epidural injections of local anesthetic with or without steroids are effective in patients with chronic axial low back pain of discogenic origin without facet joint pain, disc herniation, and/or radiculitis. PMID:23091395

Manchikanti, Laxmaiah; Cash, Kimberly A; McManus, Carla D; Pampati, Vidyasagar

2012-01-01

47

Translaminar Microendoscopic Herniotomy for Cranially Migrated Lumbar Disc Herniations Encroaching on the Exiting Nerve Root in the Preforaminal and Foraminal Zones  

PubMed Central

Study Design Case series. Purpose The aim of this study was to describe translaminar microendoscopic herniotomy (TL-MEH) for cranially migrated lumbar disc herniations encroaching on the exiting nerve root in the preforaminal and foraminal zones and to report preliminary results of the procedure. Overview of Literature Conventional interlaminar approaches for preforaminal and foraminal lumbar disc herniations result in extensive removal of the lamina and facet joint to remove disc fragments safely. More destructive approaches increase the risk of postoperative segmental instability. Methods TL-MEH is a minimally invasive procedure for herniotomy via the translaminar approach using a microendoscopic technique. TL-MEH was performed in seven patients with a cranially migrated lumbar disc herniation encroaching on the exiting nerve root. The disc fragments were located in the preforaminal zone in four patients, and in the preforaminal and foraminal zones in three. Results All patients experienced immediate relief from symptoms after surgery and satisfactory results at the final follow-up. Surgical complications, such as a dural tear, nerve injury, and surgical site infection, were not investigated. Conclusions TL-MEH seemed to be an effective and safe alternative minimally invasive surgical option for patients with a cranially migrated lumbar disc herniation encroaching the exiting nerve root in the preforaminal and foraminal zones. PMID:24066214

Tono, Osamu; Senba, Hideyuki; Kitamura, Takahiro; Komiya, Norihiro; Oga, Masayoshi; Shidahara, Satoshi

2013-01-01

48

Hemifacial hyperhidrosis associated with ipsilateral/contralateral cervical disc herniation myelopathy. Functional considerations on how compression pattern determines the laterality  

PubMed Central

Summary Sweating is an important mechanism for ensuring constant thermoregulation, but hyperhidrosis may be disturbing. We present five cases of hemifacial hyperhidrosis as a compensatory response to an/hypohidrosis caused by cervical disc herniation. All the patients complained of hemifacial hyperhidrosis, without anisocoria or blepharoptosis. Sweat function testing and thermography confirmed hyperhidrosis of hemifacial and adjacent areas. Neck MRI showed cervical disc herniation. Three of the patients had lateral compression with well-demarcated hypohidrosis below the hyperhidrosis on the same side as the cervical lesion. The rest had paramedian compression with poorly demarcated hyperhidrosis and hypohidrosis on the contralateral side. Although MRI showed no intraspinal pathological signal intensity, lateral dural compression might influence the circulation to the sudomotor pathway, and paramedian compression might influence the ipsilateral sulcal artery, which perfuses the sympathetic descending pathway and the intermediolateral nucleus. Sweat function testing and thermography should be performed to determine the focus of the hemifacial hyperhidrosis, and the myelopathy should be investigated on both sides. PMID:25014051

Iwase, Satoshi; Inukai, Yoko; Nishimura, Naoki; Sato, Maki; Sugenoya, Junichi

2014-01-01

49

Acute spontaneous cervical disc herniation causing rapidly progressive myelopathy in a patient with comorbid ossified posterior longitudinal ligament: Case report and literature review  

PubMed Central

Background: Ossification of the posterior longitudinal ligament (OPLL) and cervical disc herniation are commonly encountered neurosurgical conditions. Here we present an unusual case of nontraumatic rapidly progressive myelopathy due to cervical disc herniation with comorbid OPLL and conduct a literature review focusing on the frequency and management of disc herniations with OPLL. Case Description: A 52-year-old healthy female presented with a 72-h history of rapid progression of dense quadriparesis with sensory deficits, with a precedent 4-week history of nontraumatic midline neck pain. Clinical examination revealed profound motor deficits below the C5 myotome. Spinal neuroimaging revealed OPLL (computed tomography [CT]) and a cervical disc herniation spanning from C4/5 to C5/6 with significant retrovertebral disease (magnetic resonance imaging [MRI]). Operative management involved an anterior cervical corpectomy and instrumented fusion, with removal of both the sequestered disc material and the locally compressive OPLL. The patient recovered full motor function and independent ambulation with no residual signs or symptoms of myelopathy at the time of discharge. Conclusion: This unique case of a spontaneous cervical disc herniation in the context of OPLL causing rapidly progressive myelopathy illustrates the complementarity of CT and MRI in diagnosing the underlying cause of a rapidly progressive neurologic deficit in the absence of antecedent trauma. Though the optimal surgical management of such pathology remains uncertain; in this case, the anterior approach was motivated by the significant retrovertebral ventrally compressive sequestrum, and provided for excellent neurologic outcome. This article also reviews the occurrence/management of such acute cervical discs with OPLL.

Westwick, Harrison J.; Goldstein, Christina L.; Shamji, Mohammed F.

2014-01-01

50

Fluoroscopic cervical epidural injections in chronic axial or disc-related neck pain without disc herniation, facet joint pain, or radiculitis  

PubMed Central

Background While chronic neck pain is a common problem in the adult population, with a typical 12-month prevalence of 30%–50%, there is a lack of consensus regarding its causes and treatment. Despite limited evidence, cervical epidural injections are one of the commonly performed nonsurgical interventions in the management of chronic neck pain. Methods A randomized, double-blind, active, controlled trial was conducted to evaluate the effectiveness of cervical interlaminar epidural injections of local anesthetic with or without steroids for the management of chronic neck pain with or without upper extremity pain in patients without disc herniation, radiculitis, or facet joint pain. Results One hundred and twenty patients without disc herniation or radiculitis and negative for facet joint pain by means of controlled diagnostic medial branch blocks were randomly assigned to one of two treatment groups, ie, injection of local anesthetic only (group 1) or local anesthetic mixed with nonparticulate betamethasone (group 2). The primary outcome of significant pain relief and improvement in functional status (?50%) was demonstrated in 72% of group 1 and 68% of group 2. The overall average number of procedures per year was 3.6 in both groups with an average total relief per year of 37–39 weeks in the successful group over a period of 52 weeks. Conclusion Cervical interlaminar epidural injections of local anesthetic with or without steroids may be effective in patients with chronic function-limiting discogenic or axial pain. PMID:22826642

Manchikanti, Laxmaiah; Cash, Kimberly A; Pampati, Vidyasagar; Malla, Yogesh

2012-01-01

51

Guideline update for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 8: lumbar fusion for disc herniation and radiculopathy.  

PubMed

Patients suffering from a lumbar herniated disc will typically present with signs and symptoms consistent with radiculopathy. They may also have low-back pain, however, and the source of this pain is less certain, as it may be from the degenerative process that led to the herniation. The surgical alternative of choice remains a lumbar discectomy, but fusions have been performed for both primary and recurrent disc herniations. In the original guidelines, the inclusion of a fusion for routine discectomies was not recommended. This recommendation continues to be supported by more recent evidence. Based on low-level evidence, the incorporation of a lumbar fusion may be considered an option when a herniation is associated with evidence of spinal instability, chronic low-back pain, and/or severe degenerative changes, or if the patient participates in heavy manual labor. For recurrent disc herniations, there is low-level evidence to support the inclusion of lumbar fusion for patients with evidence of instability or chronic low-back pain. PMID:24980585

Wang, Jeffrey C; Dailey, Andrew T; Mummaneni, Praveen V; Ghogawala, Zoher; Resnick, Daniel K; Watters, William C; Groff, Michael W; Choudhri, Tanvir F; Eck, Jason C; Sharan, Alok; Dhall, Sanjay S; Kaiser, Michael G

2014-07-01

52

Minimum Two-Year Follow-Up of Cases with Recurrent Disc Herniation Treated with Microdiscectomy and Posterior Dynamic Transpedicular Stabilisation  

PubMed Central

The objective of this article is to evaluate two-year clinical and radiological follow-up results for patients who were treated with microdiscectomy and posterior dynamic transpedicular stabilisation (PDTS) due to recurrent disc herniation. This article is a prospective clinical study. We conducted microdiscectomy and PDTS (using a cosmic dynamic screw-rod system) in 40 cases (23 males, 17 females) with a diagnosis of recurrent disc herniation. Mean age of included patients was 48.92 ± 12.18 years (range: 21-73 years). Patients were clinically and radiologically evaluated for follow-up for at least two years. Patients’ postoperative clinical results and radiological outcomes were evaluated during the 3rd, 12th, and 24th months after surgery. Forty patients who underwent microdiscectomy and PDTS were followed for a mean of 41 months (range: 24-63 months). Both the Oswestry and VAS scores showed significant improvements two years postoperatively in comparison to preoperative scores (p<0.01). There were no significant differences between any of the three measured radiological parameters (?, LL, IVS) after two years of follow-up (p > 0.05). New recurrent disc herniations were not observed during follow-up in any of the patients. We observed complications in two patients. Performing microdiscectomy and PDTS after recurrent disc herniation can decrease the risk of postoperative segmental instability. This approach reduces the frequency of failed back syndrome with low back pain and sciatica. PMID:20448822

Kaner, Tuncay; Sasani, Mehdi; Oktenoglu, Tunc; Aydin, Ahmet Levent; Ozer, Ali Fahir

2010-01-01

53

Cytokine expression in the epidural space: a model of non-compressive disc herniation-induced inflammation  

PubMed Central

Study Design Animal study Objective Development of an animal model for the study of biochemical changes that occur in the epidural space after intervertebral disc herniation. Summary of Background Data Although strong evidence for an inflammatory component exists, the biochemical processes underlying pain following disc herniation remain unknown. Methods Epidural lavage was performed in 48 rats after L5 dorsal root ganglion (DRG) exposure at baseline and 3, 6, or 24 hours after placement of autologous nucleus pulposus (NP) (N = 15), saline (N = 15), or NP + an interferon-gamma antibody (anti-IFN?; N = 18) directly onto the DRG. Multiplex assays quantifying interleukin (IL-)-1-?, IL-1?, IL-2, IL-4, IL-6, IL-10, TNF?, IFN? and GM-CSF were performed. NP (N = 7) was also analyzed for these cytokines by placing NP into saline and measuring the relative concentration. Results Cytokines measured low at baseline (0–100pg/ml) in all groups. Compared to saline, NP application caused IL-6 elevation, peaking at T=3hr, that was prevented by anti-IFN?. NP induced elevation of TNF?, peaking at T=24hr and was prevented by anti-IFN?. IFN? was elevated after NP at T=3hr and T=24hr. IL-1? was similar after saline versus NP. The concentrations of IL-1? and IL-10 were elevated at T=3hr, 6hr and 24hr in all groups without between-groups difference. The level of IL-4 peaked at T=3hr in the NP group and was different than saline and NP +anti-IFN? groups but the time effect was insignificant. There was no change for GM-CSF. The concentration of cytokines measured in normal NP was < 2pg/ml for all cytokines except TNF?. Conclusion In this model of acute non-compressive disc herniation, NP caused the elevation of epidural IL-6, TNF? and IFN?; all attenuated by IFN? blockade. IL-1? and IL-10 were both significantly elevated by saline alone and their response was not prevented by IFN? blockade. This model may prove useful for the study of the biochemical processes by which NP induces inflammation-induced nerve root irritation and radiculopathic pain. PMID:22648034

Cuellar, Jason M.; Borges, Paula M.; Cuellar, Vanessa Gabrovsky; Yoo, Andrew; Scuderi, Gaetano J.; Yeomans, David C.

2012-01-01

54

Percutaneous kyphoplasty for the treatment of osteoporotic thoracolumbar fractures with neurological deficit: radicular pain can mimic disc herniation  

PubMed Central

Osteoporotic vertebral fractures (OVFs) are the common disease found in elderly population. Neurological deficit in OVFs is rare despite the involved posterior cortex of the fractured vertebral body, severe kyphotic deformity, or the instability at the fracture site. OVF with resulting neurological deficit was considered as a contraindication for vertebral augmentation techniques. We reported a rare case of a 75-year-old woman with L1, L2 osteoporotic vertebral fractures and L5/S1 disc herniation who presented with back pain and radicular pain extending along the posterior aspect of the left leg. Physical examination showed slight weakness of her flexor hallucis longus and absence of ankle jerk on her left leg. The result of a straight leg-raising test was limited to an angle of 50 degrees. The radiographs showed that the nerve root was compressed by the retropulsed bone fragment of the L2 vertebral body and a herniated disc at the level of L5/S1 on the left side. After L1 and L2 kyphoplasty the radicular pain as well as the back pain was completely disappeared. At her two-year follow-up examination, the patient was completely symptom free and reported no radicular pain. This case suggested that minimally invasive techniques such as kyphoplasty or vertebroplasty are effective in certain OVF patients with neurological deficit. Radicular pain could be caused by osteoporotic fracture that involves the posterior cortex of the vertebral body. Understanding the anatomy of nerve roots and pathogenetic mechanism of radicular pain is particularly important for treatment option.

Niu, Jun-Jie; Shen, Min-Jie; Meng, Bin; Yang, Yan; Yang, Hui-Lin

2014-01-01

55

Percutaneous kyphoplasty for the treatment of osteoporotic thoracolumbar fractures with neurological deficit: radicular pain can mimic disc herniation.  

PubMed

Osteoporotic vertebral fractures (OVFs) are the common disease found in elderly population. Neurological deficit in OVFs is rare despite the involved posterior cortex of the fractured vertebral body, severe kyphotic deformity, or the instability at the fracture site. OVF with resulting neurological deficit was considered as a contraindication for vertebral augmentation techniques. We reported a rare case of a 75-year-old woman with L1, L2 osteoporotic vertebral fractures and L5/S1 disc herniation who presented with back pain and radicular pain extending along the posterior aspect of the left leg. Physical examination showed slight weakness of her flexor hallucis longus and absence of ankle jerk on her left leg. The result of a straight leg-raising test was limited to an angle of 50 degrees. The radiographs showed that the nerve root was compressed by the retropulsed bone fragment of the L2 vertebral body and a herniated disc at the level of L5/S1 on the left side. After L1 and L2 kyphoplasty the radicular pain as well as the back pain was completely disappeared. At her two-year follow-up examination, the patient was completely symptom free and reported no radicular pain. This case suggested that minimally invasive techniques such as kyphoplasty or vertebroplasty are effective in certain OVF patients with neurological deficit. Radicular pain could be caused by osteoporotic fracture that involves the posterior cortex of the vertebral body. Understanding the anatomy of nerve roots and pathogenetic mechanism of radicular pain is particularly important for treatment option. PMID:25232437

Niu, Jun-Jie; Shen, Min-Jie; Meng, Bin; Yang, Yan; Yang, Hui-Lin

2014-01-01

56

Oxygen-ozone therapy for herniated lumbar disc in patients with subacute partial motor weakness due to nerve root compression.  

PubMed

Intradiscal oxygen-ozone (O2-O3) chemonucleolysis is a well-known effective treatment for pain caused by protruding disc disease and nerve root compression due to bulging or herniated disc. The most widely used therapeutic combination is intradiscal injection of an O2-O3 mixture (chemonucleolysis), followed by periradicular injection of O2-O3, steroid and local anaesthetic to enhance the anti-inflammatory and analgesic effect. The treatment is designed to resolve pain and is administered to patients without motor weakness, whereas patients with acute paralysis caused by nerve root compression undergo surgery 24-48h after the onset of neurological deficit. This paper reports on the efficacy of O2-O3 chemonucleolysis associated with anti-inflammatory foraminal injection in 13 patients with low back pain and cruralgia, low back pain and sciatica and subacute partial motor weakness caused by nerve root compression unresponsive to medical treatment. All patients were managed in conjunction with our colleagues in the Neurosurgery Unit of Bellaria Hospital and the IRCCS Institute of Neurological Sciences, Bologna. The outcomes obtained are promising: 100% patients had a resolution of motor weakness, while 84.6% had complete pain relief. Our results demonstrate that O2-O3 therapy can be considered a valid treatment option for this category of patients. PMID:25363257

Dall'Olio, Massimo; Princiotta, Ciro; Cirillo, Luigi; Budai, Caterina; de Santis, Fabio; Bartolini, Stefano; Serchi, Elena; Leonardi, Marco

2014-10-31

57

Microdiscectomy for the treatment of lumbar disc herniation: an evaluation of reoperations and long-term outcomes.  

PubMed

Design?Retrospective case series. Objective?The objective of this study was to assess the reoperation rate after microdiscectomy for the treatment of lumbar disc herniation (LDH) in patients with???5-year follow-up and identify demographic, perioperative, and outcome-related differences between patients with and without a reoperation. Methods?The medical records, operative reports, and office notes of patients who had undergone microdiscectomy at a single institution between March 1994 and December 2007 were reviewed and long-term follow-up was assessed via a telephone questionnaire. Results?Forty patients (M:24, F:16) with an average age at surgery of 39.9?±?12.5 years (range: 18-80) underwent microdiscectomy at the levels L5-S1 (n?=?28, 70%), L4-L5 (n?=?9, 22.5%), L3-L4 (n?=?2, 5.0%), and L1-L2 (n?=?1, 2.5%). After an average of 40.4?±?40.1 months (range: 1-128), 25% of patients (10/40) required further spine surgery related to the initial microdiscectomy. At an average postoperative follow-up of 11.1?±?4.0 years (range: 5-19), additional symptoms apart from back and leg pain were reported more frequently by patients who underwent a reoperation (p?=?0.005). Patient satisfaction was significantly higher in patients who did not undergo a reoperation (p?=?0.041). For the Oswestry disability index, pain intensity (p?=?0.036), and pain-related sleep disturbances (p?=?0.006) were reported to be more severe in the reoperation group. Conclusions?Microdiscectomy for the treatment of LDH results in a favorable long-term outcome in the majority of cases. The reoperation rate was higher in our series than reported in previous investigations with shorter follow-up. Although there were no statistically significant pre-/perioperative differences between patients with and without reoperation, our findings suggest a difference in self-reported long-term outcome measures. PMID:25278881

Aichmair, Alexander; Du, Jerry Y; Shue, Jennifer; Evangelisti, Gisberto; Sama, Andrew A; Hughes, Alexander P; Lebl, Darren R; Burket, Jayme C; Cammisa, Frank P; Girardi, Federico P

2014-10-01

58

Subgaleal hemorrhage with dural tear and parietal-lobe herniation in association with a vacuum extraction  

Microsoft Academic Search

Use of the vacuum for operative vaginal deliveries has become more favorable with fewer obstetricians and family practitioners trained in the use of forceps. When compared with forcep-assisted deliveries, the vacuum has been associated with a higher incidence of subgaleal hemorrhage (SGH), cephalhematomas, skull and clavicular fractures, Erb's Palsy, intracranial hemorrhage and need for ICN admission. We report the case

S D Kicklighter; D Wolfe; J V Perciaccante

2007-01-01

59

Reabilitação precoce de atletas utilizando hidroterapia após o tratamento cirúrgico de hérnia discal lombar: relato preliminar de 3 casos Early rehabilitation of athletes using hydrotherapy after surgical treatment of lumbar disc herniation: preliminary report of three cases  

Microsoft Academic Search

SUMMARY Three male athletes submitted to surgical treatment of lumbar disc herniation were assessed aiming to evaluate the results of a rehabilitation protocol based on aquatic therapy. This method allowed early rehabilitation of the athletes, within a week after surgery. The athletes were evaluated in 5 occasions: pre-operatively and in the 4 following months. Complete improvement of pain was observed

MARCELO W AJCHEMBERG; LEONARDO P IRES; REYNALDO C. RODRIGUES; KARINA S. MANO; MORGANA DE SÁ SOTTOMAIOR; MOISÉS COHEN; RENE J. ABDALLA; EDUARDO B. PUERTAS

2002-01-01

60

The Effects of Stretching with Lumbar Traction on VAS and Oswestry Scales of Patients with Lumbar 4-5 Herniated Intervertebral Disc  

PubMed Central

[Purpose] This study investigated the effect of stretching with lumbar traction on VAS and Oswestry scale scores of lumbar 4–5 herniated intervertebral disc (HIVD) patients. [Subjects] We recruited 20 lumbar 4–5 HIVD patients. [Methods] We performed stretching with lumbar traction for lumbar 4–5 HIVD patients during 4 weeks. The VAS and Oswestry scales were measured before and 4 weeks after the intervention. [Results] The results showed a significant decrease in VAS scale scores for stretching with lumbar traction in lumbar 4–5 HIVD patients, from 18±1.29 to 2.1±1.35. The Oswestry scale scores also decreased significantly, from 20.35±2.01 to 3.5±2.84, after stretching with lumbar traction. [Conclusion] Thus, we suggest stretching with lumbar traction for lumbar 4–5 HIVD patients. PMID:25140094

Yang, Hae-sun; Yoo, Won-gyu

2014-01-01

61

Plasma metabonomic profiling of lumbar disc herniation and its traditional Chinese medicine subtypes in patients by using gas chromatography coupled with mass spectrometry.  

PubMed

Lumbar disc herniation (LDH) is a commonly occurring disease, threatening human health and life quality. Lack of a gold standard of diagnosis has hindered the efficiency and efficacy of clinical therapy against LDH. Traditional Chinese medicine (TCM) has provided an experience-based but subjective diagnosis system for LDH, demanding objective evidence and explanation. In this study, we adopted a metabonomics approach using gas chromatography-mass spectrometry (GC-MS) to profile metabolic characteristics of LDH and its TCM subtypes. Plasma samples of 41 LDH patients and 25 healthy controls were collected. LDH patients were classified into two main subtypes, the reality syndrome and deficiency syndrome, according to TCM theory. By using multivariate statistical analysis and metabolism network analysis, we found diverse perturbations of metabolites in amino acid metabolism and carbohydrate metabolism, in which the amino acids (glutamic acid, aspartic acid, glycine, etc.) were up-regulated and a key carbohydrate metabolite (glucose 1-phosphate) was down-regulated. Few differences were found between the two TCM subtypes. Our findings reveal the metabolic disorders of LDH for the first time and demonstrate the feasibility of the metabonomics approach for LDH research but not for its TCM subtypes. PMID:25144444

Shan, Letian; Liao, Fei; Jin, Hongting; Ye, Fusheng; Tong, Peijian; Xiao, Luwei; Zhou, Jia; Wu, Chengliang

2014-09-30

62

Foraminoplastic transfacet epidural endoscopic approach for removal of intraforaminal disc herniation at the L5-S1 level  

PubMed Central

Transforaminal endoscopic disc removal in the L5-S1 motion segment of the lumbar spine creates a technical challenge due to anatomical reasons and individual variability. The majority of surgeons prefer a posterior classical or minimally invasive approach. There is only one foraminoplastic modification of the technique in the literature so far. In this paper we present a new technique with a foraminoplastic transfacet approach that may be suitable in older patients with advanced degenerative disease of the spine. PMID:24729817

Kaczmarczyk, Jacek; Nowakowski, Andrzej; Sulewski, Adam

2014-01-01

63

Herniated disk  

MedlinePLUS

... weakness. The lower back (lumbar area) of the spine is the most common area for a slipped disk. The neck (cervical) disks are sometimes affected. The upper-to-mid-back (thoracic) disks are rarely involved. A herniated disk is ...

64

Psychometric properties of the Polish language version of the Chronic Pain Coping Inventory-42 for patients treated surgically due to herniated lumbar discs and spondylotic changes  

PubMed Central

Background The development of a pain-management program tailored to the specific needs of patients with chronic low back pain (CLBP) requires the proper assessment of psychosocial factors affecting each individual. The Chronic Pain Coping Inventory-42 (CPCI-42) refers to coping strategies, which are commonly defined as the cognitive and behavioral techniques an individual may resort to in stressful or demanding situations. Evidence from a number of sources suggests that differences in pain coping strategies may significantly affect how an individual deals with chronic pain. We aimed to adapt the CPCI-42 to Polish cultural conditions (PL-CPCI-42) and then verify its psychometric properties based on a group of patients treated surgically due to herniated lumbar discs and coexisting spondylotic changes. Material/Methods The average age of the study participants (n=90) was 43.47 years (SD 10.21). The average duration of chronic low back pain (CLBP) was 49.37 months (SD 64.71). Lumbosacral spine X-rays and magnetic resonance imaging scans were performed and all patients completed the PL-CPCI-42 and the Polish versions of the Numeric Pain Rating Scale (NPRS-PL) twice. Internal consistency of the PL-CPCI-42, floor and ceiling effects, test-retest reliability, and criterion validity were analyzed. Results Resting, guarding, and coping self-statements were frequently used as coping strategies both in the test and in the retest, in contrast to relaxation and exercise/stretch. The NPRS-PL result was 5.70 cm in the test and 5.66 in the retest. Cronbach’s alpha values were recorded for the asking for assistance, coping self-statements, and seeking social support domains (0.83, 0.80, 0.83, respectively). Test-retest reliability of the PL-CPCI-42 varied from 0.53 (relaxation domain) to 0.84 (asking for assistance and coping self-statements domains). Conclusions The present study provides evidence of the validity of the PL-CPCI-42 and supports its usefulness in assessing chronic pain coping strategies, which are especially important to pain adjustment and in the creation of multidisciplinary pain management programs for patients with severe CLBP. PMID:24824781

Misterska, Ewa; Jankowski, Roman; Glowacki, Maciej

2014-01-01

65

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

66

A combinatorial relative mass value evaluation of endogenous bioactive proteins in three-dimensional cultured nucleus pulposus cells of herniated intervertebral discs: identification of potential target proteins for gene therapeutic approaches.  

PubMed

Painful degenerative disc diseases have been targeted by different biological treatment approaches. Nucleus pulposus (NP) cells play a central role in intervertebral disc (IVD) maintenance by orchestrating catabolic, anabolic and inflammatory factors that affect the extracellular matrix. IVD degeneration is associated with imbalances of these factors, resulting in a catabolic inflammatory metabolism. Therefore, accurate knowledge about their quantity and quality with regard to matrix synthesis is vital for a rational gene therapeutic approach. NP cells were isolated from 63 patients operated due to lumbar disc herniation (mean age 56 / range 29 - 84 years). Then, three-dimensional culture with low-glucose was completed in a collagen type I scaffold for four weeks. Subsequently cell proliferation evaluation was performed using 3-(4, 5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide and intracellular concentration of 28 endogenously expressed anabolic, catabolic, inflammatory factors and relevant matrix proteins was determined by enzyme-linked immunosorbent assay. Specimen-related grades of degeneration were confirmed by preoperative magnetic resonance imaging. Independent from gender, age and grade of degeneration proliferation rates remained similar in all groups of NP cells. Progressive grades of degeneration, however, showed a significant influence on accumulation of selective groups of factors such as disintegrin and metalloproteinase with thrombospondin motifs 4 and 5, matrix metalloproteinase 3, metalloproteinase inhibitor 1 and 2, interleukin-1? and interleukin-1 receptor. Along with these changes, the key NP matrix proteins aggrecan and collagen II decreased significantly. The concentration of anabolic factors bone morphogenetic proteins 2, 4, 6 and 7, insulin-like growth factor 1, transforming growth factor beta 1 and 3, however, remained below the minimal detectable quantities. These findings indicate that progressive degenerative changes in NP may be problematic with regard to biologic treatment strategies. Hence, gene therapeutic interventions regulating relevant bioactive factors identified in this work might contribute to the development of regenerative treatment approaches for degenerative disc diseases. PMID:24278441

Mern, Demissew S; Fontana, Johann; Beierfuß, Anja; Thomé, Claudius; Hegewald, Aldemar A

2013-01-01

67

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

68

Spontaneous resorption of a large cervical herniated nucleus pulposus.  

PubMed

The majority of patients with symptomatic herniated discs can be successfully and conservatively managed and can achieve clinical improvement without surgical intervention. Resorption of the herniated nucleus pulposus (HNP) is 1 conservative mechanism for clinical improvement. We present the case of a 76-year-old healthy man with acute cervical radicular right arm pain and positive Spurling test. Magnetic resonance imaging (MRI) showed a large disc extrusion behind the C6 vertebral body, causing severe central canal stenosis and right-greater-than-left foraminal stenosis. The patient did not want surgical intervention, and his symptoms resolved with conservative treatment. A follow-up MRI 7 months after his initial presentation showed almost complete resorption of the herniated disc. The patient returned to his normal activities and has not had recurrence of symptoms for 2 years. This report provides an interesting example of complete resorption of a large, extruded cervical herniated disc in a symptomatic patient and a review of the literature on resorption of herniated discs. The review suggests that larger herniations with an epidural location (penetration of the posterior longitudinal ligament) have a greater chance of resorption. PMID:25046190

Cvetanovich, Gregory L; Hsu, Andrew R; Frank, Rachel M; An, Howard S; Andersson, Gunnar B

2014-07-01

69

Quantitative Discomanometry: Correlation of Intradiscal Pressure Values to Pain Reduction in Patients With Intervertebral Disc Herniation Treated With Percutaneous, Minimally Invasive, Image-Guided Techniques  

SciTech Connect

Purpose: To illustrate quantitative discomanometry's (QD) diagnostic efficacy and predictive value in discogenic-pain evaluation in a prospective study correlating intradiscal pressure values with pain reduction after percutaneous image-guided technique (i.e., percutaneous decompression, PD). Materials and Methods: During the last 3 years, 36 patients [21 male and 15 female (mean age 36 {+-} 5.8 years)] with intervertebral disc hernia underwent QD before PD. Under absolute sterilization and fluoroscopy, a mixture of contrast medium and normal saline (3:1 ratio) was injected. A discmonitor performed a constant rate injection and recorded pressure and volume values, thus producing the relative pressure-volume curve. PD was then performed. Pain reduction and improved mobility were recorded at 3, 12, and 24 months after PD using clinical evaluation and a numeric visual scale (NVS; 0 to 10 units). Results: Mean pain values of 7.5 {+-} 1.9 (range 4 to 8) NVS units were recorded before PD; these decreased to 2.9 {+-} 2.44 at 3 months, 1.0 {+-} 1.9 at 12 months, and 1.0 {+-} 1.9 NVS units at 24 months after PD. Recorded correlations (pressure, volume, significant pain-reduction values) with bilateral statistical significance included a maximum injected volume of 2.4 ml (p = 0.045), P{sub o} < 14 psi [initial pressure required to inject 0.1 ml of the mixture inside the disc (p = 0.05)], P{sub max} {<=} 65 psi [greatest pressure value on the curve (p = 0.018)], and P{sub max} - P{sub o} {<=} 47 psi (p = 0.038). Patients meeting these pressure or volume cut-off points, either independently or as a total, had significant pain reduction (>4 NVS units) after PD. No complications were noted. Conclusions: QD is an efficient technique that may have predictive value for discogenic pain evaluation. It might serve as a useful tool for patient selection for intervertebral disc therapies.

Filippiadis, Dimitrios K., E-mail: dfilippiadis@yahoo.gr; Mazioti, A., E-mail: argyromazioti@yahoo.gr; Papakonstantinou, O., E-mail: sogofianol@gmail.com; Brountzos, E., E-mail: ebrountz@med.uoa.gr [University General Hospital 'Attikon', Second Radiology Department (Greece); Gouliamos, A., E-mail: agouliam@med.uoa.gr [University General Hospital 'Areteion', First Radiology Department (Greece); Kelekis, N., E-mail: kelnik@med.uoa.gr; Kelekis, A., E-mail: akelekis@med.uoa.gr [University General Hospital 'Attikon', Second Radiology Department (Greece)

2012-10-15

70

Chronic pain coping styles in patients with herniated lumbar discs and coexisting spondylotic changes treated surgically: Considering clinical pain characteristics, degenerative changes, disability, mood disturbances, and beliefs about pain control  

PubMed Central

Background Pain catastrophizing, appraisals of pain control, styles of coping, and social support have been suggested to affect functioning in patients with low back pain. We investigated the relation of chronic pain coping strategies to psychological variables and clinical data, in patients treated surgically due to lumbar disc herniation and coexisting spondylotic changes. Material/Methods The average age of study participants (n=90) was 43.47 years (SD 10.21). Patients completed the Polish versions of the Chronic Pain Coping Inventory-42 (PL-CPCI-42), Beck Depression Inventory (BDI-PL), Coping Strategies Questionnaire (CSQ-PL), Beliefs about Pain Control Questionnaire (BPCQ-PL), and Roland-Morris Disability Questionnaire (RMQ-PL). Results In the PL-CPCI-42 results, resting, guarding and coping self-statements were frequently used as coping strategies (3.96 SD 1.97; 3.72 SD 1.72; 3.47 SD 2.02, respectively). In the CSQ-PL domains, catastrophizing and praying/hoping were frequently used as coping strategies (3.62 SD 1.19). The mean score obtained from the BDI-PL was 11.86 SD 7.23, and 12.70 SD 5.49 from the RMDQ-PL. BPCQ-PL results indicate that the highest score was in the subscale measuring beliefs that powerful others can control pain (4.36 SD 0.97). Exercise correlated significantly with beliefs about internal control of pain (rs=0.22). We identified associations between radiating pain and guarding (p=0.038) and between sports recreation and guarding (p=0.013) and task persistence (p=0.041). Conclusions Back pain characteristics, depressive mood, disability, and beliefs about personal control of pain are related to chronic LBP coping styles. Most of the variables related to advancement of degenerative changes were not associated with coping efforts. PMID:24370564

Misterska, Ewa; Jankowski, Roman; Glowacki, Maciej

2013-01-01

71

Apparent diffusion coefficient in normal and abnormal pattern of intervertebral lumbar discs: initial experience?  

PubMed Central

The aim of the present study was to compare the relationship of morphologically defined non-bulging/herniated, bulging and herniated intervertebral lumbar discs with quantitative apparent diffusion coefficient (ADC). Thirty-two healthy volunteers and 28 patients with back pain or sciatica were examined by MRI. All intervertebral lumbar discs from L1 to S1 were classified according to morphological abnormality and degenerated grades. The ADC values of nucleus pulposus (NP) were measured and recorded. The significant differences about mean ADC values of NP were found between non-bulging/herniated discs and bulging discs as well as herniated discs (P < 0.05), whereas there were no significant differences in ADC values between bulging and herniated discs (P > 0.05). Moreover, statistically significant relationship was found in the mean ADC values of NP between “non-bulging/herniated and non-degenerated discs” and “non-bulging/herniated degenerated discs” as well as herniated discs (P < 0.05). Linear regression analysis between ADC value and disc level revealed an inverse correlation (r = -0.18). The ADC map of the NP is a potentially useful tool for the quantitative assessment of componential and molecular alterations accompanied with lumbar disc abnormalities. PMID:23554690

Niu, Gang; Yu, Xuewen; Yang, Jian; Wang, Rong; Zhang, Shaojuan; Guo, Youmin

2011-01-01

72

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

73

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

74

CT recognition of lateral lumbar disk herniation  

SciTech Connect

Although computed tomography (CT) has been shown to be useful in diagnosing posterolateral and central lumbar disk herniations, its effectiveness in demonstrating lateral herniated disks has not been emphasized. The myelographic recognition of those herniations may be difficult because root sheaths or dural sacs may not be deformed. A total of 274 CT scans interpreted as showing lumbar disk herniation was reviewed. Fourteen (5%) showed a lateral disk herniation. The CT features of a lateral herniated disk included: (1) focal protrusion of the disk margin within or lateral to the intervertebral foramen: (2) displacement of epidural fat within the intervertebral foramen; (3) absence of dural sac deformity; and (4) soft-tissue mass within or lateral to the intervertebral foramen. Because it can image the disk margin and free disk fragments irrespective of dural sac or root sheath deformity, CT may be more effective than myelography for demonstrating the presence and extent of lateral disk herniation.

Williams, A.L.; Haughton, V.M.; Daniels, D.L.; Thornton, R.S.

1982-08-01

75

A collagen-GAG matrix for the growth of intervertebral disc tissue  

E-print Network

Intervertebral disc (IVD) degeneration and herniation is a significant problem, more so in the aviation field. The IVD also changes during spaceflight. Current treatments for IVD problems can have unfavorable long-term ...

Hastreiter, Dawn (Dawn Marie), 1973-

2002-01-01

76

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

77

MR guidance of laser disc decompression: preliminary in vivo experience  

Microsoft Academic Search

.   The purpose of this study was to perform percutaneous laser disc decompression (PLDD) under MR guidance in an open configuration\\u000a 0.5-T MR system. Following failed conservative treatment for 6 months, eight patients with contained disc herniations were\\u000a enrolled in the study. Following MR guided introduction of the laser fiber into the targeted disc space, the laser-induced\\u000a temperature distribution was

P. Steiner; K. Zweifel; R. Botnar; A. W. Schoenenberger; J. F. Debatin; G. K. von Schulthess; J. Hodler

1998-01-01

78

Symptomatic intravertebral disc herniation (Schmorl's node) in the cervical spine.  

PubMed Central

A case of a Schmorl's node in the cervical vertebra causing neck pain is reported. An inflammatory focus was found on histological examination of Schmorl's node indicating a possible mechanism of pain production. Images PMID:4083942

Lipson, S J; Fox, D A; Sosman, J L

1985-01-01

79

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

80

Incidence of trocar site herniation following robotic gynecologic surgery  

PubMed Central

Objective Trocar site herniation is a recognized complication of minimally invasive surgery, but published data on trocar site herniation after robotic surgery are scarce. We sought to determine the incidence of trocar site herniation in women undergoing robotic surgery for gynecologic disease. Methods A retrospective review of robotic surgeries performed from January 1, 2006, through December 31, 2012, was conducted. Postoperative trocar site herniations were identified, along with time to presentation, location of herniation, and management. Patients were excluded if surgery was converted to laparotomy or traditional laparoscopy. The Wilcoxon rank-sum test was used to compare patients with and without herniation with respect to continuous variables, and Fisher's exact test was used to compare these 2 groups with respect to categorical variables. Results The study included 500 patients, 3 of whom experienced herniation at a single trocar site. The patients with and without herniation did not differ with respect to age, body mass index, smoking status, medical comorbidities, operating time, or estimated blood loss. All 3 herniations occurred at 12-mm trocar sites. Two herniations occurred at assistant port sites, and 1 occurred at the umbilical camera port site. The median time to herniation was 21 days (range, 8-38 days). One patient required immediate surgical intervention; the other 2 patients had conservative management. Conclusions Trocar site herniation is a rare complication following robotic surgery. The most important risk factor for trocar site herniation appears to be larger trocar size, as all herniations occurred at 12-mm port sites. PMID:23988416

Clark, Leslie H.; Soliman, Pamela T.; Odetto, Diego; Munsell, Mark F.; Schmeler, Kathleen M.; Fleming, Nicole; Westin, Shannon N.; Nick, Alpa M.; Ramirez, Pedro T.

2014-01-01

81

Intercostal lung herniation - The role of imaging  

PubMed Central

Extrathoracic lung hernias can be congenital or acquired. Acquired hernias may be classified by etiology into traumatic, spontaneous, and pathologic. We present a case of a 40-year-old male with a history of bronchial asthma and a blunt chest trauma who presented complaining of sharp chest pain of acute onset that began after five consecutive days of vigorous coughing. Upon physical examination a well-demarcated deformity overlying the third intercostal space of the left upper anterior hemithorax was revealed. Thoracic CT scan showed that a portion of the anterior bronchopulmonary segment of the left upper lobe had herniated through a chest wall defect. The role of imaging, especially chest computed tomography with multiplanar image reconstructions and maximum (MIP) and minimum intensity projection (MinIP) reformats can clearly confirm the presence of the herniated lung, the hernial sac, the hernial orifice in the chest wall, and exclude possible complications such as lung tissue strangulation. PMID:24967031

Detorakis, Efstathios E.; Androulidakis, Emmanuel

2014-01-01

82

Lumbar disk herniation surgery: outcome and predictors.  

PubMed

Study Design?A retrospective cohort study. Objectives?To determine the outcome and any differences in the clinical results of three different surgical methods for lumbar disk herniation and to assess the effect of factors that could predict the outcome of surgery. Methods?We evaluated 148 patients who had operations for lumbar disk herniation from March 2006 to March 2011 using three different surgical techniques (laminectomy, microscopically assisted percutaneous nucleotomy, and spinous process osteotomy) by using Japanese Orthopaedic Association (JOA) Back Pain Evaluation Questionnaire, Resumption of Activities of Daily Living scale and changes of visual analog scale (VAS) for low back pain and radicular pain. Our study questionnaire addressed patient subjective satisfaction with the operation, residual complaints, and job resumption. Data were analyzed with SPSS version 16.0 (SPSS, Inc., Chicago, Illinois, United States). Statistical significance was set at 0.05. For statistical analysis, chi-square test, Mann-Whitney U test, Kruskal-Wallis test, and repeated measure analysis were performed. For determining the confounding factors, univariate analysis by chi-square test was used and followed by logistic regression analysis. Results?Ninety-four percent of our patients were satisfied with the results of their surgeries. VAS documented an overall 93.3% success rate for reduction of radicular pain. Laminectomy resulted in better outcome in terms of JOA Back Pain Evaluation Questionnaire. The outcome of surgery did not significantly differ by age, sex, level of education, preoperative VAS for back, preoperative VAS for radicular pain, return to previous job, or level of herniation. Conclusion?Surgery for lumbar disk herniation is effective in reducing radicular pain (93.4%). All three surgical approaches resulted in significant decrease in preoperative radicular pain and low back pain, but intergroup variation in the outcome was not achieved. As indicated by JOA Back Pain Evaluation Questionnaire-Low Back Pain (JOABPQ-LBP) and lumbar function functional scores, laminectomy achieved significantly better outcome compared with other methods. It is worth mentioning that relief of radicular pain was associated with subjective satisfaction with the surgery among our study population. Predictive factors for ineffective surgical treatment for lumbar disk herniation were female sex and negative preoperative straight leg raising. Age, level of education, and preoperative VAS for low back pain were other factors that showed prediction power. PMID:25396104

Sedighi, Mahsa; Haghnegahdar, Ali

2014-12-01

83

Lung herniation: a rare complication in minimally invasive cardiothoracic surgery  

Microsoft Academic Search

Objective: Lung herniation, defined as a protrusion of the lung parenchyma with pleural membranes through a defect of the thoracic wall, is a rare entity. As minimally invasive cardiac procedures evolve, different complications may be evident such as lung herniation. A retrospective review of all patients submitted to minimally invasive cardiac or transplant surgery through anterior mini-thoracotomy at our department

Kalliopi Athanassiadi; Erik Bagaev; Andre Simon; Axel Haverich

2010-01-01

84

Lung herniation: a rare complication in minimally invasive cardiothoracic surgery  

Microsoft Academic Search

Objective: Lung herniation, defined as a protrusion of the lung parenchyma with pleural membranes through a defect of the thoracic wall, is a rare entity. As minimally invasive cardiac procedures evolve, different complications may be evident such as lung herniation. A retrospective review of all patients submitted to minimally invasive cardiac or transplant surgery through anterior mini-thoracotomy at our department

Kalliopi Athanassiadi; Erik Bagaev; Andre Simon; Axel Haverich

2008-01-01

85

DETAIL OF DENVER DISC FILTER IN CO91107, SUCTION END. NOTE ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

DETAIL OF DENVER DISC FILTER IN CO-91-107, SUCTION END. NOTE BEARING HOUSING WITH CAST LOGO, SUCTION PIPE GOING OFF TO THE RIGHT, AND FILTER DISC IN BACKGROUND. VACUUM INSIDE DISCS FURTHER DEWATERED CONCENTRATE. AS DISC SLOWLY ROTATED A BAR SCRAPED DRIED CONCENTRATE FROM OUTSIDE OF FILTER CLOTH. - Shenandoah-Dives Mill, 135 County Road 2, Silverton, San Juan County, CO

86

Higher risk of dural tears and recurrent herniation with lumbar micro-endoscopic discectomy  

PubMed Central

Existing studies on micro-endoscopic lumbar discectomy report similar outcomes to those of open and microdiscectomy and conflicting results on complications. We designed a randomised controlled trial to investigate the hypothesis of different outcomes and complications obtainable with the three techniques. 240 patients aged 18–65 years affected by posterior lumbar disc herniation and symptoms lasting over 6 weeks of conservative management were randomised to micro-endoscopic (group 1), micro (group 2) or open (group 3) discectomy. Exclusion criteria were less than 6 weeks of pain duration, cauda equina compromise, foraminal or extra-foraminal herniations, spinal stenosis, malignancy, previous spinal surgery, spinal deformity, concurrent infection and rheumatic disease. Surgery and follow-up were made at a single Institution. A biomedical researcher independently collected and reviewed the data. ODI, back and leg VAS and SF-36 were the outcome measures used preoperatively, postoperatively and at 6-, 12- and 24-month follow-up. 212/240 (91%) patients completed the 24-month follow-up period. VAS back and leg, ODI and SF36 scores showed clinically and statistically significant improvements within groups without significant difference among groups throughout follow-up. Dural tears, root injuries and recurrent herniations were significantly more common in group 1. Wound infections were similar in group 2 and 3, but did not affect patients in group 1. Overall costs were significantly higher in group 1 and lower in group 3. In conclusion, outcome measures are equivalent 2 years following lumbar discectomy with micro-endoscopy, microscopy or open technique, but severe complications are more likely and costs higher with micro-endoscopy. PMID:20127495

Lovi, Alessio; Brayda-Bruno, Marco; Zagra, Antonino; Corriero, Andrea; Giudici, Fabrizio; Minoia, Leone

2010-01-01

87

Standards of Practice: Quality Assurance Guidelines for Percutaneous Treatments of Intervertebral Discs  

SciTech Connect

Percutaneous treatments are used in the therapy of small- to medium-sized hernias of intervertebral discs to reduce the intradiscal pressure in the nucleus and theoretically create space for the herniated fragment to implode inward, thus reducing pain and improving mobility and quality of life. These techniques involve the percutaneous removal of the nucleus pulposus by using a variety of chemical, thermal, or mechanical techniques and consist of removal of all or part of nucleus pulposus to induce more rapid healing of the abnormal lumbar disc. These guidelines are written to be used in quality improvement programs for assessing fluoroscopy- and/or computed tomography-guided percutaneous intervertebral disc ablative techniques.

Kelekis, Alexis D., E-mail: akelekis@med.uoa.gr; Filippiadis, Dimitris K., E-mail: dfilippiadis@yahoo.g [Attikon University Hospital, 2nd Radiology Department (Greece); Martin, Jean-Baptiste, E-mail: jbmartin@cird.c [Geneva University Hospital, Service d'Imagerie Medicale (Switzerland); Brountzos, Elias, E-mail: ebrountz@med.uoa.g [Attikon University Hospital, 2nd Radiology Department (Greece)

2010-10-15

88

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

89

Idiopathic brain herniation. A report of two paediatric cases.  

PubMed

SUMMARY - 'Idiopathic' herniation of the brain is a rare entity previously reported in 13 cases. It may be incidentally encountered in neuroimaging studies acquired for various clinical indications. We herein describe two cases of idiopathic brain herniation that were incidentally diagnosed. A 12-year-old boy presented with a six-month history of daytime sleepiness and sudden spells of sleep. Herniation of the left inferior temporal gyrus was revealed in MRI acquired with the suspicion of epilepsy. His overnight polysomnogram and multiple sleep latency tests were compatible with the diagnosis of narcolepsy. The other case, a two-year-old girl, was transferred from an outside hospital due to partial seizures with the fever. Herniation of the precuneal gyrus was encountered in MRI acquired after controlling her seizures with the initiation of phenytoin. The brain herniations of both patients were considered to be inconsistent with their medical conditions, so that they were symptom-free with only medical treatment for following three and six months, respectively. This is a rare presentation of idiopathic brain herniation as an incidental finding that accompanied narcolepsy and epilepsy. Awareness of this entity would avoid excessive surgical and medical treatments. PMID:25260205

Koc, Gonca; Doganay, Selim; Bayram, Ayse Kacar; Gorkem, Sureyya Burcu; Dogan, Mehmet Sait; Per, Huseyin; Coskun, Abdulhakim

2014-10-01

90

Immune cascades in human intervertebral disc: the pros and cons  

PubMed Central

The unique structural hallmark of the intervertebral disc has made its central composition, the nucleus pulposus (NP), excluded from the immunologic tolerance. Consequently, the intervertebral disc is identified as an immune-privileged organ. Traditionally, local detrimental immune activities caused by NP at the lesion sites of the disc are noted as a significant factor contributing to disc degeneration. However, given the beneficial activities of immune cells in other immune-privileged sites on basis of current evidence, the degenerate disc might need the assistance of a subpopulation of immune cells to restore its structure and lessen inflammation. In addition, the beneficial impact of immune cells can be seen in the absorption of the herniated NP, which is an important factor causes the mechanical compression of nerve roots. Consequently, a modulated immune network in degenerate disc is essential for the restoration of this immune-privileged organ. Until now, the understandings of immune response in disc degeneration still rest on the harmful aspect. Further studies are needed to explore its beneficial influence. Accordingly, there are no absolutely the pros and cons in terms of immune reactions caused by NP. PMID:23696917

Sun, Zhen; Zhang, Ming; Zhao, Xu-Hong; Liu, Zhi-Heng; Gao, Yang; Samartzis, Dino; Wang, Hai-Qiang; Luo, Zhuo-Jing

2013-01-01

91

Outcomes of cervical and lumbar disk herniations in Major League Baseball pitchers.  

PubMed

The effects of disk herniations on the career and performance outcomes of Major League Baseball (MLB) pitchers are unknown. The purpose of this study is to determine the outcomes after a cervical or lumbar disk herniation for MLB pitchers. Forty MLB pitchers from 1984 to 2009 with a cervical disk herniation or lumbar disk herniation were identified using a previously established protocol. Cervical disk herniation was identified in 11 pitchers, 8 of which were treated operatively. The majority of pitchers with cervical disk herniation (8/11) returned to play at an average of 11.6 months. Lumbar disk herniation was identified in 29 pitchers, 20 of which were treated operatively. All pitchers with lumbar disk herniation (29/29) returned to play at an average of 7.3 months after diagnosis. PMID:21800814

Roberts, David W; Roc, Gilbert J; Hsu, Wellington K

2011-08-01

92

Intraspinal Extradural Cysts Communicating with Adjacent Herniated Disks: Imaging Characteristics and Possible Pathogenesis  

Microsoft Academic Search

Summary: We report two cases of intraspinal extradural cysts communicating with an adjacent herniated disk that we term ''disk cysts.'' These cysts were well defined and homogeneous, and were present in the ventrolateral ex- tradural space adjacent to a lumbar herniated disk. They had rim enhancement on contrast-enhanced MR images, and communication with a herniated disk was revealed by diskography.

Kinuko Kono; Hiroaki Nakamura; Yuichi Inoue; Terue Okamura; Miyuki Shakudo; Ryusaku Yamada

93

Repair of tibialis anterior muscle herniation using periosteum.  

PubMed

Muscular herniation consists of focal muscular protrusions through an acquired or congenital fascial defect. The anterior tibialis muscle is most frequently affected. Asymptomatic muscle hernias are usually treated conservatively. For severe symptoms or cosmetic complaints, several surgical techniques are available to treat muscle herniation, including fasciotomy, fascial patch grafting using autologous fascia lata, or synthetic mesh. However, the optimal surgical approach remains debatable. The authors propose a novel and reproducible surgical method using a periosteal turn-down technique. This surgical technique has the advantages of fewer complications, greater cost-effectiveness, and high reproducibility. The authors find this to be a useful technique. [Orthopedics. 2014; 37(11):748-750.]. PMID:25361358

Harwin, Steven F; Choi, Young-Rak; Hong, Chul-Gie

2014-11-01

94

Disc replacement using Pro-Disc C versus fusion: a prospective randomised and controlled radiographic and clinical study  

PubMed Central

Anterior cervical discectomy and fusion (ACDF) may be considered to be the gold standard for treatment of symptomatic degenerative disc disease within the cervical spine. However, fusion of the segment may result in progressive degeneration of the adjacent segments. Therefore, dynamic stabilization procedures have been introduced. Among these, artificial disc replacement by disc prosthesis seems to be promising. However, to be so, segmental motion must be preserved. This, again, is very difficult to judge and has not yet been proven. The aim of the current study was to first analyse the segmental motion following artificial disc replacement using a disc prosthesis. A second aim was to compare both segmental motion as well as clinical result to the current gold standard (ACDF). This is a prospective controlled study. Twenty-five patients with cervical disc herniation were enrolled and assigned to either study group (receiving a disc prosthesis) or control group (receiving ACDF, using a cage with bone graft and an anterior plate.) Radiostereometric analysis was used to quantify intervertebral motion immediately as well as 3, 6, 12 and 24 weeks postoperatively. Further, clinical results were judged using visual analogue scale and neuro-examination. Cervical spine segmental motion decreased over time in the presence of disc prosthesis or ACDF. However, the loss of segmental motion is significantly higher in the ACDF group, when looked at 3, 6, 12 and 24 weeks after surgery. We observed significant pain reduction in neck and arm postoperatively, without significant difference between both groups (P > 0.05). Cervical spine disc prosthesis preserves cervical spine segmental motion within the first 6 months after surgery. The clinical results are the same when compared to the early results following ACDF. PMID:17106665

Ahlhelm, F.; Pitzen, T.; Steudel, W. I.; Jung, J.; Shariat, K.; Steimer, O.; Bachelier, F.; Pape, D.

2006-01-01

95

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

96

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

97

Non-reclosing pressure relief device for vacuum systems  

DOEpatents

A non-reclosing overpressure protection device such as a rupture disc provides a non-reclosing opening upon forcible contact with a knife blade. A bellows, having an inlet capable of being sealably connected to a source of pressure (the vacuum system) and an outlet containing the rupture disc, transmits the pressure in the system to the disc. The bellows maintains the disc away from the knife when the pressure is below an overpressure amount, and carries the disc to a position when the pressure is above an overpressure amount where the disc is ruptured by the knife. 6 figures.

Swansiger, W.A.

1994-02-08

98

Flaccid quadriplegia from tonsillar herniation in pneumococcal meningitis  

Microsoft Academic Search

A young woman with fulminant pyogenic meningitis became quadriplegic, areflexic and flaccid due to herniation of the cerebellar tonsils and compression of the upper cervical cord. This state of spinal shock was associated with absent F-waves. Intracranial pressure was greatly elevated and there was an uncertain relationship of tonsillar descent to a preceding lumbar puncture. Partial recovery occurred over 2

A. H. Ropper; K. B. Kanis

2000-01-01

99

Skull malformation and cerebellar herniation in captive African lions  

Microsoft Academic Search

Thickening of the cranial vault with a resulting cerebellar herniation is described in a series of litters of lion cubs, all with the same parents, one of whom was also very mildly affected. This animal, when mated to his daughter, also produced affected cubs. The aetiology of the condition is discussed and it is considered that vitamin A deficiency may

JR Baker; DG Lyon

1977-01-01

100

Spontaneous intracranial hypotension due to intradural thoracic osteophyte with superimposed disc herniation: report of two cases  

Microsoft Academic Search

Spontaneous intracranial hypotension (SIH) is a clinical syndrome in which absolute or relative hypovolemia of the cerebrospinal\\u000a fluid (CSF) results in various neurological symptoms. The etiology of spontaneous CSF leaks often remains unknown. However,\\u000a it is believed that the most common cause is the fragility of spinal meninges at the level of radicular nerve root sleeve.\\u000a These tears can be

Zehra Isik Hasiloglu; Bashar Abuzayed; Ahmet Esat Imal; Emin Cagil; Sait Albayram

101

Surgical treatment of thoracic disc disease via minimally invasive lateral transthoracic trans/retropleural approach: analysis of 33 patients.  

PubMed

Thoracic disc herniations are associated with serious neurological consequences if not treated appropriately. Although a number of techniques have been described, there is no consensus about the best surgical approach. In this study, the authors report their experience in the operative management of patients with thoracic disc herniations using minimally invasive lateral transthoracic trans/retropleural approach. A series of 33 consecutive patients with thoracic disc herniations who underwent anterior spinal cord decompression followed by instrumented fusion through lateral approach is being reported. Demographic and radiographic data, perioperative complications, and clinical outcomes were reviewed. Forty disc levels in 33 patients (18F/15M; mean age, 52.9) were treated. Twenty-three patients presented with myelopathy (69 %), 31 had radiculopathy (94 %), and 31 had axial pain (94 %). Among patients with myelopathy, 14 (42.4 %) had bladder and/or bowel dysfunction. In the last eight cases (24 %), the approach was retropleural instead of transpleural. Patients were followed up for 18.2 months on average. The mean length of hospital stay was 5 days. None of the patients developed neurological deterioration postoperatively. Among 23 patients who had myelopathy signs, 21 (91 %) had improved postoperatively. The mean preoperative visual analog scale pain score, Oswestry Disability Index score, SF-36 PCS, and mental component summary scores were 7.5, 42.4, 29.6, and 37.5 which improved to 3.5, 33.2, 35.5, and 52.6, respectively. Perioperative complications occurred in six patients (18.1 %), all of which resolved uneventfully. Minimally invasive lateral transthoracic trans/retropleural approach is a safe and efficacious technique for achieving adequate decompression in thoracic disc herniations in a less invasive manner than conventional approaches. PMID:23572229

Nacar, Osman Arikan; Ulu, Mustafa Onur; Pekmezci, Murat; Deviren, Vedat

2013-07-01

102

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

103

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

104

Asymptomatic tonsillar herniation in a neonate with cleidocranial dysplasia.  

PubMed

A male neonate was antenatally diagnosed with cleidocranial dysplasia on the basis of prenatal ultrasound findings and molecular testing of the RUNX2 gene. The patient presented with urosepsis at 24 days of life and subsequently developed apneas after endoscopic examination of the vocal cords. Computed tomography and MRI studies of the head revealed crowding of the posterior fossa with tonsillar and uncal herniation. Apneas were initially thought to be related to brainstem compression; however, the patient responded immediately to caffeine and subsequently stabilized with antibiotic therapy. To our knowledge, this is the first published MRI study of the brain of a neonate with cleidocranial dysplasia to demonstrate the striking posterior fossa findings seen secondary to the reduced bony skull structures. However, despite the dramatic herniation, brainstem function was not compromised. PMID:24446448

Myers, Kenneth A; Thomas, Mary Ann; Wei, Xing-Chang; Scantlebury, Morris H

2014-02-01

105

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

106

Exploring the utility of axial lumbar MRI for automatic diagnosis of intervertebral disc abnormalities  

NASA Astrophysics Data System (ADS)

In this paper, we explore the importance of axial lumbar MRI slices for automatic detection of abnormalities. In the past, only the sagittal views were taken into account for lumbar CAD systems, ignoring the fact that a radiologist scans through the axial slices as well, to confirm the diagnosis and quantify various abnormalities like herniation and stenosis. Hence, we present an automatic diagnosis system from axial slices using CNN(Convolutional Neural Network) for dynamic feature extraction and classification of normal and abnormal lumbar discs. We show 80:81% accuracy (with a specificity of 85:29% and sensitivity of 75:56%) on 86 cases (391 discs) using only an axial slice for each disc, which implies the usefulness of axial views for automatic lumbar abnormality diagnosis in conjunction with sagittal views.

Ghosh, Subarna; Chaudhary, Vipin; Dhillon, Gurmeet

2013-03-01

107

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

108

Herniation of the temporomandibular joint into the external auditory meatus secondary to benign necrotising otitis externa  

Microsoft Academic Search

The temporomandibular joint (TMJ) is intimately related to the external auditory meatus (EAM). Herniation of the joint into the EAM occurs secondary to neoplasia, trauma, inflammation and developmental problems [Conover GL, Crammond RJ. Tympanic plate fracture from mandibular trauma. J Oral Maxillofac Surg 1985;43:292–4; Ali TS, Rubinstein JT. Rheumatoid arthritis of the temporomandibular joint with herniation into the external auditory

Neil C.-W. Tan; Alan Wilson; Jonathan Buckland

2009-01-01

109

Recurrent wound dehiscence and small bowel herniation following Caesarean section in a woman with hidradenitis suppurativa.  

PubMed

Caesarean wound dehiscence that is severe enough to result in bowel herniation is exceptionally rare. This case describes a woman who experienced wound dehiscence following each of her two Caesarean sections, with bowel herniation present in the second case. The contribution of her comorbid hidradenitis suppurativa will be discussed. PMID:24876503

Fernando, Magage; Schultz, Meleesa J

2014-01-01

110

Recurrent wound dehiscence and small bowel herniation following Caesarean section in a woman with hidradenitis suppurativa  

PubMed Central

Caesarean wound dehiscence that is severe enough to result in bowel herniation is exceptionally rare. This case describes a woman who experienced wound dehiscence following each of her two Caesarean sections, with bowel herniation present in the second case. The contribution of her comorbid hidradenitis suppurativa will be discussed. PMID:24876503

Fernando, Magage; Schultz, Meleesa J.

2014-01-01

111

Hindbrain herniation develops in surgically created myelomeningocele but is absent after repair in fetal lambs  

Microsoft Academic Search

Objective: The purpose of our study was to determine whether prenatal repair of myelomeningocele prevents or reverses hindbrain herniation in the sheep model. Study Design: A myelomeningocele was surgically created in fetal sheep. One group was repaired later in utero; the others were delivered without repair. After delivery, lambs were assessed for the presence of hindbrain herniation. Results: In all

Bettina W. Paek; Diana L. Farmer; C. Corbett Wilkinson; Craig T. Albanese; Warrick Peacock; Michael R. Harrison; Russell W. Jennings

2000-01-01

112

Role of death receptor, mitochondrial and endoplasmic reticulum pathways in different stages of degenerative human lumbar disc.  

PubMed

Intervertebral disc (IVD) cell apoptosis has been suggested to play an important role in promoting the degeneration process. It has been demonstrated that IVD cell apoptosis occurs through either death receptor, mitochondrial or endoplasmic reticulum (ER) pathway. Our study aimed to explore the relationship among these three pathways and grade of IVD degeneration (IVDD). IVDs were collected from patients with lumbar fracture, vertebral tumor, disc herniation or spondylolisthesis. IVDs were distinguished by MRI and histomorphological examination, cell apoptosis was detected by TUNEL staining. Biomarkers of these three apoptosis pathways were detected by RT-PCR and Western blot. Furthermore, the correlation between apoptosis pathways biomarkers and disc pathology were analyzed. Nucleus pulposus cell density decreased with degeneration process, and increased apoptotic ratio. ER pathway was predominant in mild stage of IVDD (GRP78, GADD153 upregulation and caspase-4 activation), death receptor pathway was predominant in mild and moderate stages (Fas, FasL up-regulation and caspase-8 activation) and mitochondrial pathway was predominant in moderate and severe stages (Bcl-2 down-regulation, Bax up-regulation, cytochrome-c accumulation in cytoplasm and caspase-9 activation). There were significant differences in the expressions of Fas, FasL, Bax, GADD153, cytochrome-c and cleaved caspase-8/9/3 between contained and non-contained discs. In conclusion, apoptosis occurs via these three apoptosis pathways together in IVDD. ER pathway plays a more critical role in the mild compared to moderate and severe stages, death receptor pathway in mild and moderate, and mitochondrial pathway in moderate and severe stages of IVDD. Disc cells apoptosis may progress rapidly after herniation, and may depend on the type of herniation. PMID:21879322

Wang, Hua; Liu, Hui; Zheng, Zhao-Min; Zhang, Kui-Bo; Wang, Tai-Ping; Sribastav, Shilabant-Sen; Liu, Wen-Sheng; Liu, Ting

2011-10-01

113

Tissue-engineered intervertebral discs produce new matrix, maintain disc height, and restore biomechanical function to the rodent spine  

PubMed Central

Lower back and neck pain are leading physical conditions for which patients see their doctors in the United States. The organ commonly implicated in this condition is the intervertebral disc (IVD), which frequently herniates, ruptures, or tears, often causing pain and limiting spinal mobility. To date, approaches for replacement of diseased IVD have been confined to purely mechanical devices designed to either eliminate or enable flexibility of the diseased motion segment. Here we present the evaluation of a living, tissue-engineered IVD composed of a gelatinous nucleus pulposus surrounded by an aligned collagenous annulus fibrosus in the caudal spine of athymic rats for up to 6 mo. When implanted into the rat caudal spine, tissue-engineered IVD maintained disc space height, produced de novo extracellular matrix, and integrated into the spine, yielding an intact motion segment with dynamic mechanical properties similar to that of native IVD. These studies demonstrate the feasibility of engineering a functional spinal motion segment and represent a critical step in developing biological therapies for degenerative disc disease. PMID:21808048

Bowles, Robby D.; Gebhard, Harry H.; Hartl, Roger; Bonassar, Lawrence J.

2011-01-01

114

Vacuum Technology  

SciTech Connect

The environmental condition called vacuum is created any time the pressure of a gas is reduced compared to atmospheric pressure. On earth we typically create a vacuum by connecting a pump capable of moving gas to a relatively leak free vessel. Through operation of the gas pump the number of gas molecules per unit volume is decreased within the vessel. As soon as one creates a vacuum natural forces (in this case entropy) work to restore equilibrium pressure; the practical effect of this is that gas molecules attempt to enter the evacuated space by any means possible. It is useful to think of vacuum in terms of a gas at a pressure below atmospheric pressure. In even the best vacuum vessels ever created there are approximately 3,500,000 molecules of gas per cubic meter of volume remaining inside the vessel. The lowest pressure environment known is in interstellar space where there are approximately four molecules of gas per cubic meter. Researchers are currently developing vacuum technology components (pumps, gauges, valves, etc.) using micro electro mechanical systems (MEMS) technology. Miniature vacuum components and systems will open the possibility for significant savings in energy cost and will open the doors to advances in electronics, manufacturing and semiconductor fabrication. In conclusion, an understanding of the basic principles of vacuum technology as presented in this summary is essential for the successful execution of all projects that involve vacuum technology. Using the principles described above, a practitioner of vacuum technology can design a vacuum system that will achieve the project requirements.

Biltoft, P J

2004-10-15

115

Vacuum mechatronics  

NASA Technical Reports Server (NTRS)

The discipline of vacuum mechatronics is defined as the design and development of vacuum-compatible computer-controlled mechanisms for manipulating, sensing and testing in a vacuum environment. The importance of vacuum mechatronics is growing with an increased application of vacuum in space studies and in manufacturing for material processing, medicine, microelectronics, emission studies, lyophylisation, freeze drying and packaging. The quickly developing field of vacuum mechatronics will also be the driving force for the realization of an advanced era of totally enclosed clean manufacturing cells. High technology manufacturing has increasingly demanding requirements for precision manipulation, in situ process monitoring and contamination-free environments. To remove the contamination problems associated with human workers, the tendency in many manufacturing processes is to move towards total automation. This will become a requirement in the near future for e.g., microelectronics manufacturing. Automation in ultra-clean manufacturing environments is evolving into the concept of self-contained and fully enclosed manufacturing. A Self Contained Automated Robotic Factory (SCARF) is being developed as a flexible research facility for totally enclosed manufacturing. The construction and successful operation of a SCARF will provide a novel, flexible, self-contained, clean, vacuum manufacturing environment. SCARF also requires very high reliability and intelligent control. The trends in vacuum mechatronics and some of the key research issues are reviewed.

Hackwood, Susan; Belinski, Steven E.; Beni, Gerardo

1989-01-01

116

Vacuum Virtues  

ERIC Educational Resources Information Center

Upright vacuums, like cars, vary in quality, features and performance. Like automobiles, some uprights are reliable, others may be problematic, and some become a problem as a result of neglect or improper use. So, how do education institutions make an informed choice and, having done so, ensure that an upright vacuum goes the distance? In this…

Rathey, Allen

2007-01-01

117

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

118

Thermalized Vacuum and Vacuum Effects  

E-print Network

Some of the well-known effects regarding the vacuum are revisited under the formalism of the imaginary-time field theory. From these effects, they could imply the existence of one thermal vacuum in different circumstances. The imaginary-time hamiltonian of the vacuum is found to provide not only exact distribution functions in the calculations of the Casimir effect and the Van der Waals force but also cutoff functions. The thermal bath for the Unruh effect is constructed from the imaginary-time Green function. From the field theory in the curved space-time, field quantizations are defined according to different vacuum states and lead to the Hawking radiation; the introduced conformal invariance agree with the formalism of the imaginary-time field theory. The induced Green functions in the curved space-time are in accordance with those from the picture given from the thermal vacuum.

Yi-Cheng Huang

2013-11-14

119

Diaphragmatic Herniation through Prosthetic Material after Extrapleural Pneumonectomy: Be Aware of Tumor Recurrence  

PubMed Central

Extrapleural pneumonectomy (EPP) is indicated in selected group of patients with pleural mesothelioma. Diaphragmatic reconstruction represents a part of this complex operation. We present the case of a late diaphragmatic gastric herniation through prosthetic material after EPP. PMID:25360411

Pop, Daniel; Cohen, Charlotte; Schneck, Anne-Sophie; Nadeemy, Ahmad S.; Venissac, Nicolas; Mouroux, Jerome

2013-01-01

120

Tegmen Tympani Defect and Brain Herniation Secondary to Mastoid Surgery: Case Presentation  

PubMed Central

Brain herniation into the middle ear is very rarely seen. In addition to reasons like congenital factors, trauma, and infection, tegmen defect may develop as a result of iatrogenic events secondary to chronic otitis media surgery with or without cholesteatoma. Since it may cause life-threatening complications, patients must be evaluated and monitored for tegmen defect. In this paper, diagnosis and treatment of a brain herniation case due to iatrogenic tegmen defect were described along with relevant literature. PMID:25140266

Egilmez, Oguz Kadir; Hanege, Fatih Mehmet; Kalcioglu, M. Tayyar; Kaner, Tuncay; Kokten, Numan

2014-01-01

121

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

122

A pilot study of the prevalence of lumbar disc degeneration in elite athletes with lower back pain at the Sydney 2000 Olympic Games  

PubMed Central

Objectives: To observe the prevalence of lumbar intervertebral disc degeneration in elite athletes as compared with published literature of changes seen in non-athletes—that is, normal population. Methods: The lumbar spines of 31 Olympic athletes who presented to the Olympic Polyclinic with low back pain and/or sciatica were examined using magnetic resonance imaging. Three criteria were looked at: (a) the loss of disc signal intensity; (b) the loss of disc height; (c) the presence of disc displacement. The results were then recorded and correlated with the lumbar levels. Results: The disc signal intensity was progressively reduced the more caudal the disc space. It was most common at the L5/S1 level, and, of the abnormal group, 36% (n = 11) showed the most degenerative change. Disc height reduction was also found to be most common at the L5/S1 level. However, the most common height reduction was only mild. A similar trend of increased prevalence of disc herniation was noted with more caudal levels. At the L5/S1 level, 58% were found to have an element of disc displacement, most of which were disc bulges. Compared with changes seen in the normal population (non-athletes) as described in the literature, disc degeneration defined by the above criteria was found to be significantly more severe in these Olympic athletes. Conclusions: Although the study was limited, the results suggest that elite athletes have a greater prevalence and greater degree of lumbar disc degeneration than the normal population. A more detailed follow up study should be considered to investigate which particular training activities have the most impact on the lumbar spine, and how to modify training methods so as to avoid the long term sequelae of degenerative disc disease of the lumbar spine. PMID:12782554

Ong, A; Anderson, J; Roche, J

2003-01-01

123

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

124

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

125

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

126

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

127

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

128

[Abdominal wall closure by incisional hernia and herniation after laparostoma].  

PubMed

As hernias and abdominal wall defects have a variety of etiologies each with its own complications and comorbidities in various constellations, efficient treatment requires patient-oriented management. There is no recommended standard treatment and the very different clinical pictures demand an individualized interdisciplinary approach. Particularly in the case of complicated hernias, the planning of the operation should focus on the problems posed by the individual patient. Treatment mainly depends on the etiology of the hernia, immediate or long-term complications and the efficiency of individual repair techniques. Abdominal wall repair for recurrent herniation requires direct closure of the fascia generally using the sublay technique with a lightweight mesh. It is still unclear whether persistent inflammation, mesh dislocation, fistula formation or other long-term complications are due to certain materials or to the surgical technique. With mesh infections it has been shown to be advantageous to remove a polytetrafluoroethylene (PTFE) mesh, while the combination of systemic and local treatment appears to suffice for a polypropylene or polyester mesh. Heavier meshes in the sublay position or plastic reconstruction with autologous tissue are indicated as substitutes for the abdominal wall for giant hernias, repeated recurrences and large abdominal wall defects. A laparostoma is increasingly more often created to treat septic intra-abdominal processes but is very often responsible for a complicated hernia. If primary repair of the abdominal wall is not an option, resorbable material or split skin is used for coverage under the auspices of a planned hernia repair. PMID:20145901

Mischinger, H-J; Kornprat, P; Werkgartner, G; El Shabrawi, A; Spendel, S

2010-03-01

129

Vacuum Gauges  

NSDL National Science Digital Library

This is a description for a learning module from Maricopa Advanced Technology Education Center. This PDF describes the module; access may be purchased by visiting the MATEC website. Semiconductor manufacturing equipment requires the use of many different types of vacuum gauges. Selection is based on range of process operations and production requirements. This MATEC module explores the theory and functionality of vacuum gauges and provides many examples of different types of gauges. The focus is on understanding the operating ranges and application constraints of each type of gauge. Mathematical equations are used to explain calibration, sensitivity, and overall operations of each type of gauge.

2012-11-28

130

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

131

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

132

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

133

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

134

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

135

Enucleation/partial nephrectomy for large mixed epithelial stromal tumor and herniating into the pelvicalyceal system  

PubMed Central

Objectives: Mixed Epithelial and Stromal Tumor of the kidney is an adult renal neoplasm. It is mostly benign in nature. Typically it is composed of a mixture of epithelial and mesenchymal components. We hereby report on the feasibility of performing partial nephrectomy/enucleation for Huge Mixed Epithelial Stromal Tumor of the kidney without sacrificing the involved renal unit even in the tumors herniating into the collecting system. Methods: Two female patients on long term hormonal therapy developed large enhancing multiloculated and septated renal masses. Kidney mass size was 18.5 cms in one patient and 11.5 in the second. In one patient, the mass was herniating into the collecting system. Both patients had enucleation/partial nephrectomy. Results: Enucleation and partial nephrectomy were successfully performed in both patients. In the patient with the mass herniating into the collecting system, the horns of the mass herniating into the collecting system were easily enucleated with repair of the collecting system and salvage of the involved renal unit. Post op pathology revealed MEST in both patients. There were no intraoperative or postoperative complications. Conclusions: Enucleation and partial nephrectomy for huge MEST is feasible. Mixed Epithelial Stromal Tumor herniating into the pelvicalyceal system may not warrant nephroureterectomy as previously reported. PMID:25371624

Kamel, Mohamed H.; Davis, Rodney; Cox, Roni M.; Cole, Adam; Eltahawy, Ehab

2014-01-01

136

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

137

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

138

Vacuum Technology: Vacuum Technology III  

NSDL National Science Digital Library

This is a link to a PDF version of lecture slides that discuss gas sources in a vacuum. The presentation explains concepts such as vapor pressure curves, thermal desorption and first and second order desorption. Keywords: Vaporization, desorption, diffusion, permeation, backstreaming

Rack, Philip D.

2012-12-12

139

Herniation of the temporomandibular joint into the external auditory meatus secondary to benign necrotising otitis externa.  

PubMed

The temporomandibular joint (TMJ) is intimately related to the external auditory meatus (EAM). Herniation of the joint into the EAM occurs secondary to neoplasia, trauma, inflammation and developmental problems [Conover GL, Crammond RJ. Tympanic plate fracture from mandibular trauma. J Oral Maxillofac Surg 1985;43:292-4; Ali TS, Rubinstein JT. Rheumatoid arthritis of the temporomandibular joint with herniation into the external auditory canal. Ann Otol Rhinol Laryngol 2000;109:177-9]. Benign necrotising otitis externa (BNOE) is an uncommon condition characterized by avascular necrosis of the tympanic plate that has been described as a sequela of simple otitis externa. [Wormald PJ. Surgical management of benign necrotizing otitis externa. J Laryngol Otol 1994;108:101-5.] We present a case of BNOE that resulted in a posterior herniation of the TMJ capsule into the EAM. PMID:18848375

Tan, Neil C-W; Wilson, Alan; Buckland, Jonathan

2009-03-01

140

Vacuum waves  

NASA Astrophysics Data System (ADS)

An exact solution of the five-dimensional field equations is studied which describes waves in the classical Einstein vacuum. While the solution is essentially 5D in nature, the waves exist in ordinary 3D space. They should not be confused with standard gravitational waves, since their phase velocity can exceed that of light. They resemble de Broglie waves, and may give insight to wave-particle duality.

Wesson, Paul S.

2013-05-01

141

The Inguinal Herniation of the Ovary in the Newborn: Ultrasound and Color Doppler Ultrasound Findings  

PubMed Central

Inguinal hernias in the newborn age group are seldom encountered. In the affected female patient, the ovaries, fallopian tubes, and the intestines may settle in the hernia sac. The early diagnosis of torsion in cases in which the ovary is herniated into the inguinal canal is of utmost importance in order to give surgery the chance of reduction and correction. In this paper, a case of an ovarian herniation into the inguinal canal without the presence of torsion is being presented, and the place of US and CDUS in the differential diagnosis of the situation is being discussed. PMID:24795829

Kaya, Omer; Esen, Kaan; Gulek, Bozkurt; Yilmaz, Cengiz; Soker, Gokhan; Onem, Onder

2014-01-01

142

Port Site Herniation of the Small Bowel following Laparoscopic-Myomectomy  

PubMed Central

Bowel herniation, through fascial defects secondary to laparoscopic surgery at the site of trocar entry, is a rare, but potentially serious, complication. Closure of the fascia at port sites measuring 10mm or more has been highly recommended to avoid such complications. We report a case of a small bowel which herniated and strangulated through the port site immediately after laparoscopic myomectomy. Resection of the strangulated bowel with primary anastomosis was required to manage this complication. We present this case report with literature review to discuss the risk factors and the methods to prevent such a complication post laparoscopic surgery. PMID:21509090

Elshafie, Ghazi A; Al-Wahaibi, Khalifa; Al-Azri, Ahmed; Al-Qadhi, Hani; Al-Harthi, Abdullah

2010-01-01

143

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

144

Transcript Levels of Major Interleukins in Relation to the Clinicopathological Profile of Patients with Tuberculous Intervertebral Discs and Healthy Controls  

PubMed Central

Objectives The purpose of the present study was to simultaneously examine the transcript levels of a large number of interleukins (ILs; IL-9, IL-10, IL-12, IL-13, IL-16, IL-17, IL-18, IL-26, and IL-27) and investigate their correlation with the clinicopathological profiles of patients with tuberculous intervertebral discs. Methods Clinical data were collected from 150 patients participating in the study from January 2013 to December 2013. mRNA expression levels in 70 tuberculous, 70 herniated, and 10 control intervertebral disc specimens were determined by real-time polymerase chain reaction. Results IL-10, IL-16, IL-17, IL-18, and IL-27 displayed stronger expression in tuberculous spinal disc tissue than in normal intervertebral disc tissue (P<0.05). Our results illustrated multiple correlations among IL-10, IL-16, IL-17, IL-18, and IL-27 mRNA expression in tuberculous samples. Smoking habits were found to have a positive correlation with IL-17 transcript levels and a negative correlation with IL-10 transcript levels (P<0.05). Pain intensity, symptom duration, C-reactive protein levels, and the erythrocyte sedimentation rate exhibited multiple correlations with the transcript levels of several ILs (P<0.05). Conclusions The experimental data imply a double-sided effect on the activity of ILs in tuberculous spinal intervertebral discs, suggesting that they may be involved in intervertebral discs destruction. Our findings also suggest that smoking may affect the intervertebral discs destruction process of spinal tuberculosis. However, further studies are necessary to elucidate the exact role of ILs in the intervertebral discs destruction process of spinal tuberculosis. PMID:24971599

Liu, Chong; Zhan, Xinli; Xiao, Zengming; Fan, Qie; Deng, Li; Cui, Mingxing; Xiong, Chunxiang; Xue, Jingbo; Xie, Xiangtao

2014-01-01

145

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

146

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

147

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

148

Single Lung Retransplantation for Graft Infarction due to Herniation of Heart  

PubMed Central

A young woman with terminal respiratory failure due to idiopathic pulmonary hypertension underwent bilateral lung transplantation. The postoperative course was complicated by herniation of the heart through over the cut pericardial edge on left side leading to left-sided graft infarction requiring pneumonectomy. Unable to wean off mechanical ventilation, patient required lobar transplantation on the left side. PMID:25360412

Mohite, Prashant N.; Sabashnikov, Anton; Rao, Praveen; Zych, Bartlomiej; Simon, Andre

2013-01-01

149

Idiopathic Ventral Spinal Cord Herniation: An Increasingly Recognized Cause of Thoracic Myelopathy  

PubMed Central

Idiopathic spinal cord herniation (ISCH), where a segment of the spinal cord has herniated through a ventral defect in the dura, is a rarely encountered cause of thoracic myelopathy. The purpose of our study was to increase the clinical awareness of this condition by presenting our experience with seven consecutive cases treated in our department since 2005. All the patients developed pronounced spastic paraparesis or Brown-Séquard syndrome for several years (mean, 4.7 years) prior to diagnosis. MRI was consistent with a transdural spinal cord herniation in the mid-thoracic region in all the cases. The patients underwent surgical reduction of the herniated spinal cord and closure of the dural defect using an artificial dural patch. At follow-up, three patients experienced considerable clinical improvement, one had slight improvement, one had transient improvement, and two were unchanged. Two of the four patients with sphincter dysfunction regained sphincter control. MRI showed realignment of the spinal cord in all the patients. ISCH is probably a more common cause of thoracic myelopathy than previously recognized. The patients usually develop progressive myelopathy for several years before the correct diagnosis is made. Early diagnosis is important in order to treat the patients before the myelopathy has become advanced. PMID:25336997

Berg-Johnsen, Jon; Ilstad, Eivind; Kolstad, Frode; Zuchner, Mark; Sundseth, Jarle

2014-01-01

150

Herniation and strangulation of the gallbladder through the foramen of Winslow  

SciTech Connect

Herniation of the gallbladder through the foramen of Winslow into the lesser sac is rare. In this case, the diagnosis was suggested by sonography, investigated further by radionuclide and computed tomographic (CT) studies, and confirmed by percutaneous needle puncture and opacification.

Bach, D.B.; Satin, R.; Palayew, M.; Lisbona, R.; Tessler, F.

1984-03-01

151

Discriminating extrusive and bulging disk herniations by using serum hs CRP.  

PubMed

It has been proposed that because there is inflammation around the nerve roots in disk herniation, there might be an association between serum C Reactive Protein (CRP) with this disease. This study aimed to distinguish between two forms of disk herniation (extrusion, bulging) by comparing the level of serum high-sensitivity CRP (hs CRP). In this perspective study, a total of 62 candidates for lumbar disk herniation surgery were recruited in Tabriz Imam Reza Hospital from 2012 to 2013. The patients categorized in two groups; with extrusion (n = 34) and with bulging (n = 28). Pre-operative serum hs CRP was measured by turbidimetric immunoassay. Both extrusion and bulging groups were matched for their patients' sex (males: 61.8% vs. 57.1%, respectively; p = 0.71) and age (mean: 52.22 +/- 7.32 years vs. 49.69 +/- 9.40 years, respectively; p = 0.48). The mean serum hs CRP was significantly higher in the extrusion group (3.56 +/- 2.90 with a range of 0.1 to 19 mg dL(-1) vs. 0.74 +/- 0.91 with a range of 0 to 5 mg dL(-1); p < 0.001). Based on the results of the receiver operator characteristics (ROC) cure, a cut-off point of hs CRP was =2.6 was highly indicative of extrusion, with a sensitivity and specificity of 66 and 63%, respectively. Based on the findings of the present study, the mean serum hs CRP is significantly higher in the patients with extrusive disk herniation vs. those with bulging. The proposed cut-off point may be useful as a preliminary indicator of the type of herniation, before more detailed imaging becomes available. PMID:24511758

Talghini, S; Vahedi, Amir; Lotfinia, I

2013-11-01

152

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

153

End Plate Disproportion and Degenerative Disc Disease: A Case-Control Study  

PubMed Central

Study Design Case-control. Purpose To determine whether a disproportion between two neighboring vertebral end plates is associated with degenerative disc disease. Overview of Literature Recently, it has been suggested that disproportion of the end plates of two adjacent vertebrae may increase the risk of disc herniation. Methods Magnetic resonance (MR) images (n=160) with evidence of grades I-II lumbar degenerative disc disease (modified Pfirrmann's classification) and normal MR images of the lumbar region (n=160) were reviewed. On midsagittal sections, the difference of anteroposterior diameter of upper and lower end plates neighboring a degenerated (in the case group) or normal (in the control group) intervertebral disc was calculated (difference of end plates [DEP]). Results Mean DEP was significantly higher in the case group at the L5-S1 level (2.73±0.23 mm vs. 2.21±0.12 mm, p=0.03). Differences were not statistically significant at L1-L2 (1.31±0.13 mm in the cases vs. 1.28±0.08 mm in the controls, p=0.78), L2-L3 (1.45±0.12 mm in the cases vs. 1.37±0.08 mm in the controls, p=0.58), L3-L4 (1.52±0.13 mm in the cases vs. 1.49±0.10 mm in the controls, p=0.88), and L4-L5 (2.15±0.21 mm in the cases vs. 2.04±0.20 mm in the controls, p=0.31) levels. The difference at the L5-S1 level did not remain significant after adjusting for body mass index (BMI), which was significantly higher in the patients. Conclusions End plate disproportion may be a significant, BMI-dependent risk factor for lumbar degenerative disc disease.

Poureisa, Masoud; Daghighi, Mohammad Hossein; Mesbahi, Sepideh; Hagigi, Amir

2014-01-01

154

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

155

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

156

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

157

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

158

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

159

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

160

Region Specific Response of Intervertebral Disc Cells to Complex Dynamic Loading: An Organ Culture Study Using a Dynamic Torsion-Compression Bioreactor  

PubMed Central

The spine is routinely subjected to repetitive complex loading consisting of axial compression, torsion, flexion and extension. Mechanical loading is one of the important causes of spinal diseases, including disc herniation and disc degeneration. It is known that static and dynamic compression can lead to progressive disc degeneration, but little is known about the mechanobiology of the disc subjected to combined dynamic compression and torsion. Therefore, the purpose of this study was to compare the mechanobiology of the intervertebral disc when subjected to combined dynamic compression and axial torsion or pure dynamic compression or axial torsion using organ culture. We applied four different loading modalities [1. control: no loading (NL), 2. cyclic compression (CC), 3. cyclic torsion (CT), and 4. combined cyclic compression and torsion (CCT)] on bovine caudal disc explants using our custom made dynamic loading bioreactor for disc organ culture. Loads were applied for 8 h/day and continued for 14 days, all at a physiological magnitude and frequency. Our results provided strong evidence that complex loading induced a stronger degree of disc degeneration compared to one degree of freedom loading. In the CCT group, less than 10% nucleus pulposus (NP) cells survived the 14 days of loading, while cell viabilities were maintained above 70% in the NP of all the other three groups and in the annulus fibrosus (AF) of all the groups. Gene expression analysis revealed a strong up-regulation in matrix genes and matrix remodeling genes in the AF of the CCT group. Cell apoptotic activity and glycosaminoglycan content were also quantified but there were no statistically significant differences found. Cell morphology in the NP of the CCT was changed, as shown by histological evaluation. Our results stress the importance of complex loading on the initiation and progression of disc degeneration. PMID:24013824

Chan, Samantha C. W.; Walser, Jochen; Kappeli, Patrick; Shamsollahi, Mohammad Javad; Ferguson, Stephen J.; Gantenbein-Ritter, Benjamin

2013-01-01

161

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

162

Naturally Occurring Disk Herniation in Dogs: An Opportunity for Pre-Clinical Spinal Cord Injury Research  

PubMed Central

Abstract Traumatic spinal cord injuries represent a significant source of morbidity in humans. Despite decades of research using experimental models of spinal cord injury to identify candidate therapeutics, there has been only limited progress toward translating beneficial findings to human spinal cord injury. Thoracolumbar intervertebral disk herniation is a naturally occurring disease that affects dogs and results in compressive/contusive spinal cord injury. Here we discuss aspects of this disease that are analogous to human spinal cord injury, including injury mechanisms, pathology, and metrics for determining outcomes. We address both the strengths and weaknesses of conducting pre-clinical research in these dogs, and include a review of studies that have utilized these animals to assess efficacy of candidate therapeutics. Finally, we consider a two-species approach to pre-clinical data acquisition, beginning with a reproducible model of spinal cord injury in the rodent as a tool for discovery with validation in pet dogs with intervertebral disk herniation. PMID:21438715

Levine, Gwendolyn J.; Porter, Brian F.; Topp, Kimberly; Noble-Haeusslein, Linda J.

2011-01-01

163

Incarcerated Thoracic Gastric Herniation after Nephrectomy: A Report of Two Cases  

PubMed Central

Iatrogenic diaphragmatic hernias can occur after abdominal or thoracic surgery. Acute presentation of a diaphragmatic hernia varies depending on the extent and nature of the organ which has herniated. The initial diagnosis can be challenging due to the nonspecific nature of the presenting symptoms. Delay in diagnosis poses a significant risk to the patient, and a rapid deterioration can occur in the context of strangulation. We outline two cases of acute gastric herniation through a defect in the diaphragm after an open and a laparoscopic nephrectomy. Both had characteristic findings on imaging, required emergency, surgery and had a successful outcome. Both cases highlight the potential for late presentation with non-specific symptoms and the necessity for urgent surgical management where gastric perfusion is compromised. PMID:23762738

Fitzgerald, Conall; Mc Cormack, Orla; Awan, Faisal; Elliott, Jessie; Ravi, Narayanasamy; Reynolds, John V.

2013-01-01

164

Patho-anatomy of Herniation of the Reticulum Through the Diaphragm in the Bovine  

PubMed Central

Dissection of embalmed and untreated water buffalo carcasses (n=10) revealed that hernias had occurred at the musculotendinous junction of the diaphragm, ventral to the foramen venae cavae and slightly lateral to the median plane. The diameter of the hernial ring varied from 7 cm to 20 cm. Herniation was more common in the right thoracic cavity with the reticulum firmly adherent to the hernia ring. Adhesions between the herniated portion of the reticulum and pleura, lung, pericardium or thoracic wall were present, while in a few cases thick fibrous tracts concealing metallic bodies were found. In two cases, involvement of esophageal groove with malalignment of cardia and reticulo-omasal opening was observed. Displacement and compression of the heart was observed in four animals. ImagesFigure 1.Figure 2.Figure 3. PMID:7340924

Deshpande, K. S.; Krishnamurthy, D.; Nigam, J. M.; Sharma, D. N.

1981-01-01

165

Effects of lumbar disk herniation on the careers of professional baseball players.  

PubMed

Outcomes after lumbar disk herniation in baseball athletes are currently unknown. It has been postulated that the repetitive torque-producing motions of a baseball player may have negative implications after a disk injury. Sixty-nine lumbar disk herniations (40 treated operatively, 29 nonoperatively) in 64 professional baseball players were identified, and important outcome measures including successful return to play, time to recovery, career longevity, and performance based on vital statistics to each position were documented. Ninety-seven percent of baseball athletes successfully returned to play at an average of 6.6 months after diagnosis. Athletes treated operatively required significantly more time to return to play than those managed nonoperatively (8.7 vs 3.6 months, respectively; P<.0001). PMID:22229920

Earhart, Jeffrey S; Roberts, David; Roc, Gilbert; Gryzlo, Stephen; Hsu, Wellington

2012-01-01

166

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

167

Swyer–James–MacLeod syndrome with ipsilateral herniation of hyperinflated hyperlucent lung  

Microsoft Academic Search

Swyer–James–MacLeod syndrome is characterised by unilateral hyperlucency on chest radiograph with small or normal-sized lung on the affected side and compensatory hyperinflation of opposite lung. Hyperinflation of the affected lung is a very rarely reported entity. An adult female patient, who presented with exertional breathlessness and diagnosed to have hypoplastic left pulmonary artery with hyperlucent, hyperinflated and herniated left lung

Rajiv Garg; Pallavi Aga; S Saheer; Jabeed P; Abhijeet Singh; Ghulam Hassan; Rajendra Prasad

2011-01-01

168

Sinking Skin Flaps, Paradoxical Herniation, and External Brain Tamponade: A Review of Decompressive Craniectomy Management  

Microsoft Academic Search

Decompressive craniectomy is reclaiming a role in neurocritical care. The altered pathophysiology found in a cranium converted\\u000a from a ‘closed’ box to an ‘open’ box’ carries benefits and risks. In some craniectomy patients, the forces of atmospheric\\u000a pressure and gravity overwhelm intracranial pressures, and the brain appears sunken. This can lead to paradoxical herniation\\u000a and the sinking skin flap syndrome,

Paul T. Akins; Kern H. Guppy

2008-01-01

169

Matrix mechanical properties of transversalis fascia in inguinal herniation as a model for tissue expansion.  

PubMed

Inguinal herniation represents a common condition requiring surgical intervention. Despite being regarded as a connective tissue disorder of uncertain cause, research has focused predominantly on biochemical changes in the key tissue layer, the transversalis fascia (TF) with little direct analysis of functional tissue mechanics. Connective tissue tensile properties are dominated by collagen fibril density and architecture. This study has correlated mechanical properties of herniated TF (HTF) and non-herniated TF (NHTF) with fibrillar properties at the ultrastructural level by quasi-static tensile mechanical analysis and image analysis of collagen electron micrographs. No significant difference was found between any of the key mechanical properties (break stress, strain or modulus) for HTF and NHTF. In addition, no significant differences were found in average collagen fibril diameter, density or fibre bundle spacing. However, both groups displayed anisotropy with greater break stress (p=0.001) on average in the transverse anatomical plane compared to the longitudinal plane in a mean ratio of 2:1 (anisotropy ratio), though there was no evidence of a difference in this ratio for HTF and NHTF for both break stress and modulus. It was noted that this anisotropy ratio corresponds closely with the expected force distribution on a model cylindrical structure loaded axially. The absence of other functional differences does not support the idea of a failing (injured) tissue but is consistent with it being a tissue undergoing chronic growth/expansion under multi-vectored mechanical loading. These findings provide new clues to collagen tissue herniation for mathematical modelling and model tissue engineering. PMID:19012890

Kureshi, Alvena; Vaiude, Partha; Nazhat, Showan N; Petrie, Aviva; Brown, Robert A

2008-12-01

170

Vacuum self-magnetization?  

Microsoft Academic Search

We study vacuum properties in a strong magnetic field as the zero temperature and zero density limit of quantum statistics. For charged vector bosons (W bosons) the vacuum energy density diverges for B > Bc = mw2\\/e, leading to vacuum instability. A logarithmic divergence of vacuum magnetization is found for B = Bc, which suggests that if the magnetic field

H. Pe´rez Rojas; E. Rodri´guez Querts

2006-01-01

171

Survival with good outcome after cerebral herniation and Duret hemorrhage caused by traumatic brain injury.  

PubMed

Brainstem hemorrhage can occur as a primary or secondary event in traumatic brain injury (TBI). Secondary brainstem hemorrhage that evolves from raised intracranial pressure and transtentorial herniation is referred to as Duret hemorrhage. Duret hemorrhage following TBI has been considered an irreversible and terminal event. The authors report on the case of a young adult patient with TBI who presented with a low Glasgow Coma Scale score and advanced signs of cerebral herniation. She underwent an urgent decompressive hemicraniectomy for evacuation of an acute epidural hematoma and developed a Duret hemorrhage postoperatively. In accordance with the family's wishes, aggressive TBI monitoring and treatment in the intensive care unit was continued even though the anticipated outcome was poor. After a lengthy hospital course, the patient improved dramatically and was discharged ambulatory, with good cognitive functioning and a Glasgow Outcome Scale score of 4. Duret hemorrhage secondary to raised intracranial pressure is not always a terminal event, and by itself should not trigger a decision to withdraw care. Aggressive intracranial monitoring and treatment of a Duret hemorrhage arising secondary to cerebral herniation may enable a good recovery in selected patients after severe TBI. PMID:19012479

Stiver, Shirley I; Gean, Alisa D; Manley, Geoffrey T

2009-06-01

172

Natural vacuum electronics  

NASA Technical Reports Server (NTRS)

The ambient natural vacuum of space is proposed as a basis for electron valves. Each valve is an electron controlling structure similiar to a vacuum tube that is operated without a vacuum sustaining envelope. The natural vacuum electron valves discussed offer a viable substitute for solid state devices. The natural vacuum valve is highly resistant to ionizing radiation, system generated electromagnetic pulse, current transients, and direct exposure to space conditions.

Leggett, Nickolaus

1990-01-01

173

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

174

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

175

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

176

Indian Vacuum Society: The Indian Vacuum Society  

NASA Astrophysics Data System (ADS)

The Indian Vacuum Society (IVS) was established in 1970. It has over 800 members including many from Industry and R & D Institutions spread throughout India. The society has an active chapter at Kolkata. The society was formed with the main aim to promote, encourage and develop the growth of Vacuum Science, Techniques and Applications in India. In order to achieve this aim it has conducted a number of short term courses at graduate and technician levels on vacuum science and technology on topics ranging from low vacuum to ultrahigh vacuum So far it has conducted 39 such courses at different parts of the country and imparted training to more than 1200 persons in the field. Some of these courses were in-plant training courses conducted on the premises of the establishment and designed to take care of the special needs of the establishment. IVS also regularly conducts national and international seminars and symposia on vacuum science and technology with special emphasis on some theme related to applications of vacuum. A large number of delegates from all over India take part in the deliberations of such seminars and symposia and present their work. IVS also arranges technical visits to different industries and research institutes. The society also helped in the UNESCO sponsored post-graduate level courses in vacuum science, technology and applications conducted by Mumbai University. The society has also designed a certificate and diploma course for graduate level students studying vacuum science and technology and has submitted a syllabus to the academic council of the University of Mumbai for their approval, we hope that some colleges affiliated to the university will start this course from the coming academic year. IVS extended its support in standardizing many of the vacuum instruments and played a vital role in helping to set up a Regional Testing Centre along with BARC. As part of the development of vacuum education, the society arranges the participation of expert members on the subject to deliver lectures and take part in devising courses in the universities. IVS publishes a quarterly called the `Bulletin of Indian Vacuum Society' since its inception, in which articles on vacuum and related topics are published. NIRVAT, news, announcements, and reports are the other features of the Bulletin. The articles in the Bulletin are internationally abstracted. The Bulletin is distributed free to all the members of the society. The society also publishes proceedings of national/international symposia and seminars, manuals, lecture notes etc. It has published a `Vacuum Directory' containing very useful information on vacuum technology. IVS has also set up its own website http://www.ivsnet.org in January 2002. The website contains information about IVS, list of members, list of EC members, events and news, abstracts of articles published in the `Bulletin of Indian Vacuum Society', utilities, announcements, reports, membership and other forms which can be completed online and also gives links to other vacuum societies. Our Society has been a member of the executive council of the International Union of Vacuum Science, Techniques and Applications (IUVSTA) and its various committees since 1970. In 1983 IVS conducted an International Symposium on Vacuum Technology and Nuclear Applications in BARC, Mumbai, under the sponsorship of IUVSTA. In 1987 IVS arranged the Triennial International Conference on Thin Films in New Delhi, where more than 200 foreign delegates participated. IVS also hosted the IUVSTA Executive Council Meeting along with the conference. The society organized yet again an International Conference on Vacuum Science and Technology and SRS Vacuum Systems at CAT, Indore in1995. IVS arranges the prestigious Professor Balakrishnan Memorial Lecture in memory of its founder vice-president. Leading scientists from India and abroad in the field are invited to deliver the talks. So far 23 lectures have been held in this series. IVS has instituted the `IVS- Professor D Y Phadke Memorial Prize' in memory of our founder presid

Saha, T. K.

2008-03-01

177

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 ...

178

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

179

Radiographic Markers of Femoroacetabular Impingement: Correlation of Herniation Pit and Femoral Bump with a Positive Cross-Over Ratio  

PubMed Central

Introduction. The goal of this study was to research the association of femoral bumps and herniation pits with the overlap-ratio of the cross-over sign. Methods. Pelvic X-rays and CT-scans of 2925 patients with good assessment of the anterior and the posterior acetabular wall and absence of neutral pelvic tilt were enrolled in the investigation. Finally pelvic X-rays were assessed for the presence of a positive cross-over sign, and CT-scans for a femoral bump or a herniation pit. Additionally, if a positive cross-over sign was discovered, the overlap-ratio was calculated. Results. A femoral bump was found in 53.3% (n = 1559), and a herniation pit in 27.2% (n = 796) of all hips. The overlap-ratio correlated positively with the presence of a femoral bump, while a negative correlation between the overlap-ratio and the presence of a herniation pit was found. The latter was significantly more often combined with a femoral bump than without. Conclusions. We detected an increased prevalence of femoral bump with increasing overlap-ratios of the cross-over sign indicating a relation to biomechanical stress. The observed decreased prevalence of herniation pits with increasing overlap-ratios could be explained by reduced mechanical stress due to nontightened iliofemoral ligament in the presence of retroversion of the acetabulum. PMID:24876972

Scheyerer, Max J.; Copeland, Carol E.; Stromberg, Jeffrey; Ruckstuhl, Thomas; Werner, Clement M. L.

2014-01-01

180

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

181

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

182

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

183

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 ...

184

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

185

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

186

Educational Vacuum Trainers  

NSDL National Science Digital Library

Have you inherited a bell jar vacuum system and are scratching your head over how to set it up or are unsure of its operations or capabilities? Or do you want to do more with your bell jar vacuum? The forum on Bell Jar Vacuums - with the topic Vacuum Trainers can help you. The intent of this forum is for this to be a place where technical issues, classroom exercises, activities, etc. can be discussed. There's no endorsement by manufacturers and commercial issues are off limits. Steve Hansen (bell jar expert) gives some brief descriptions of the vacuum trainers that are or have been available over the past decade or so - Varian, MKS, Science Source, American Vacuum Society. Links are provided to various data sheets, articles and online exercises. Steve, the forum moderator has experience in all of these.Keywords: vacuum, "vacuum trainer","bell jar" and/or belljar, MKSVarian, VPAL, VTS, sputtering, plasma

Hansen, Steve

2012-07-31

187

Transforaminal percutaneous endoscopic surgery for far lateral lumbar intervertebral disk herniation.  

PubMed

Far lateral lumbar intervertebral disk herniation (FLLIDH) most commonly occurs far lateral to the intervertebral facet at L3-L4 and L4-L5 and accounts for 3.8% of all lumbar disk herniations. Traditional surgery for FLLIDH involves massive surgical trauma, damage to the spinal structure, and instability of the lumbar spine. The goals of this study were to perform a systematic review of the literature and investigate the clinical outcomes of transforaminal percutaneous endoscopic surgery in the treatment of FLLIDH. Between October 2010 and May 2012, fifteen patients diagnosed with FLLIDH underwent transforaminal percutaneous endoscopic surgery at the authors' institution to remove the herniated disk and release the nerve root. Pain was measured pre- and postoperatively with a visual analog pain scale (VAS), and postoperative outcomes were evaluated using MacNab's criteria. A PubMed database search was conducted for the systematic review. Median operative time was 100 minutes (range, 80-140 minutes). Median volume of intraoperative blood loss was 20 mL (range, 10-50 mL). Patients were followed postoperatively for a median of 6 months (range, 1-12 months). MacNab's criteria rated 12 (80.0%) surgical outcomes as excellent, 2 (13.3%) as good, and 1 (6.7%) as fair. The systematic review included 14 studies. Transforaminal percutaneous endoscopic surgery appears to be a safe and effective minimally invasive procedure for treating FLLIDH. However, as demand for this type of surgery increases, the possibility of intraoperative aggravated leg pain and compression injury of the ganglion must be considered. PMID:25102508

Liao, Zhong; Chen, Wei; Wang, Chao-Hui

2014-08-01

188

Stainless Steel Vacuum Chambers  

Microsoft Academic Search

The vacuum properties of stainless steel are excellent. The fabrication and welding process can be handled easily by a large number of vacuum manufacturers. In particular, the use for intermediate energy light sources gives a lot of advantages, which leads to a cost effective and industrial vacuum system design. Several design solutions are compared in this paper. The common fabrication

Lothar Schulz

189

The pathogenesis of degeneration of the intervertebral disc and emerging therapies in the management of back pain.  

PubMed

This article reviews the current knowledge of the intervertebral disc (IVD) and its association with low back pain (LBP). The normal IVD is a largely avascular and aneural structure with a high water content, its nutrients mainly diffusing through the end plates. IVD degeneration occurs when its cells die or become dysfunctional, notably in an acidic environment. In the process of degeneration, the IVD becomes dehydrated and vascularised, and there is an ingrowth of nerves. Although not universally the case, the altered physiology of the IVD is believed to precede or be associated with many clinical symptoms or conditions including low back and/or lower limb pain, paraesthesia, spinal stenosis and disc herniation. New treatment options have been developed in recent years. These include biological therapies and novel surgical techniques (such as total disc replacement), although many of these are still in their experimental phase. Central to developing further methods of treatment is the need for effective ways in which to assess patients and measure their outcomes. However, significant difficulties remain and it is therefore an appropriate time to be further investigating the scientific basis of and treatment of LBP. PMID:23015552

Hughes, S P F; Freemont, A J; Hukins, D W L; McGregor, A H; Roberts, S

2012-10-01

190

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

191

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

192

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

193

Differentiation of idiopathic spinal cord herniation from CSF-isointense intraspinal extramedullary lesions displacing the cord.  

PubMed

Focal spinal cord displacement can be caused by idiopathic spinal cord herniation (ISCH), in which the cord protrudes through a dural defect into the epidural space, causing cord displacement and tethering. ISCH is uncommon and often is misdiagnosed initially, which results in delayed management. ISCH can be mimicked by space-occupying cerebrospinal fluid (CSF)-isointense intraspinal extramedullary lesions, such as epidermoid cysts or teratomas, intradural arachnoid cysts, epidural hematomas or abscesses, cystic nerve sheath tumors, synovial or Tarlov cysts, meningoceles, and pseudomeningoceles. Initial computed tomography (CT) and unenhanced magnetic resonance (MR) imaging studies may depict focal cord displacement and a widened CSF space but often are not sufficient to identify the underlying cause. High-resolution thin-section MR imaging can delineate the exact location of the dural defect and the protrusion of the herniated cord through this defect into the epidural space. At imaging, unimpeded CSF pulsation artifacts seen within a widened CSF space exclude a space-occupying lesion. A filling defect seen at conventional or CT myelography can help confirm a CSF-isointense space-occupying lesion; intravenous contrast agent administration can help exclude a rim-enhancing cystic extramedullary lesion. The clinical presentation usually is nonspecific, but symptom acuity, fever, and trauma can guide the imaging evaluation and help narrow the differential diagnosis. A multimodality imaging approach is essential to differentiate ISCH from space-occupying CSF-isointense intraspinal extramedullary lesions. PMID:24617681

Haber, Marc D; Nguyen, Dustin D; Li, Shan

2014-01-01

194

Treatment of localized neuropathic pain after disk herniation with 5% lidocaine medicated plaster  

PubMed Central

Objective To assess treatment with the 5% lidocaine medicated plaster for peripheral neuropathic pain after disk herniation. Study design Case series, single center, retrospective data. Patients and methods Data of 23 patients treated for neuropathic pain with the lidocaine plaster for up to 24 months after a protrusion or prolapse of the cervical, thoracic, or lumbar vertebral disks were retrospectively analyzed. Changes in overall pain intensity, in intensity of different pain qualities and of allodynia and hyperalgesia were evaluated. Results Patients (14 female/nine male, mean age 53.5 ± 10.4 years) presented with radiating pain into the abdomen, back, neck, shoulder, or legs and feet with a mean pain intensity of 8.3 ± 1.5 on the 11-point Likert scale. Mean treatment duration was 7.6 months; 52% of the patients received lidocaine plaster as monotherapy. At the end of the observation, mean overall pain intensity had been reduced to 3.1 ± 1.8. All other parameters also improved. The treatment was well tolerated. Conclusion These results point to a safe and effective treatment approach with 5% lidocaine medicated plaster for localized neuropathic pain related to disk herniation. However, owing to the small sample size, further investigation in a larger-scale controlled trial is warranted. PMID:22973116

Likar, Rudolf; Kager, Ingo; Obmann, Michael; Pipam, Wolfgang; Sittl, Reinhard

2012-01-01

195

Herniated near-term pregnancy through an incisional hernia treated with polypropylene mesh: A case report.  

PubMed

The management of a large incisional hernia amidst gravid uterus in its sac is a very challenging obstetric entity. Because of the uncommonness of this entity, there has not been any evidence-based guideline regarding the optimal mode of treatment and so treatment is largely individualised. We present the case of a 32-year-old booked G7P6+0 Nigerian woman with two living children who was already booked for elective repeat lower segment Caesarean section (CS) and 'Caesarean' herniorrhaphy at 38 weeks of gestation but only to present at 36-weeks gestation with a 4-hour history of labour pains. She had an emergency lower segment CS 2 years earlier due to obstructed labour but the CS was complicated by wound infection. Examination revealed gravid uterus that herniated through the incisional hernia. She subsequently had emergency lower segment CS with the repair of the hernia with polypropylene mesh. She had uneventful post-operative recovery. Herniated uterus of near-term pregnancy through an incisional hernia has not been reported in our hospital. As in our case, triumphant management required brave but multidisciplinary approach and currently there are emerging management options such as the use of mesh and laparoscopic technique. PMID:25013263

Uchenna, Eleje George; Chukwuneme, Okpala Boniface; Ejike, Enendu Stephen; Mbanefo, Okeke Paul; Benjamin, Ejikeme Toochukwu

2014-05-01

196

Herniated near-term pregnancy through an incisional hernia treated with polypropylene mesh: A case report  

PubMed Central

The management of a large incisional hernia amidst gravid uterus in its sac is a very challenging obstetric entity. Because of the uncommonness of this entity, there has not been any evidence-based guideline regarding the optimal mode of treatment and so treatment is largely individualised. We present the case of a 32-year-old booked G7P6+0 Nigerian woman with two living children who was already booked for elective repeat lower segment Caesarean section (CS) and ‘Caesarean’ herniorrhaphy at 38 weeks of gestation but only to present at 36-weeks gestation with a 4-hour history of labour pains. She had an emergency lower segment CS 2 years earlier due to obstructed labour but the CS was complicated by wound infection. Examination revealed gravid uterus that herniated through the incisional hernia. She subsequently had emergency lower segment CS with the repair of the hernia with polypropylene mesh. She had uneventful post-operative recovery. Herniated uterus of near-term pregnancy through an incisional hernia has not been reported in our hospital. As in our case, triumphant management required brave but multidisciplinary approach and currently there are emerging management options such as the use of mesh and laparoscopic technique. PMID:25013263

Uchenna, Eleje George; Chukwuneme, Okpala Boniface; Ejike, Enendu Stephen; Mbanefo, Okeke Paul; Benjamin, Ejikeme Toochukwu

2014-01-01

197

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

198

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

199

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

200

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

201

Brain death due to fat embolism -- could moderate hypercapnia and prone position be blamed for the tonsillar herniation?  

PubMed Central

Fat embolism to the systemic circulation in polytrauma patients is very common. The fat embolism syndrome (FES), however, is a rare condition. We describe a case of traumatic femur fracture with FES that was presented as acute tonsillar herniation (coning) and brain death postoperatively. We believe that in this case the prone position and moderate hypercapnia contributed to the acute coning. PMID:23977867

Larsson, Anders

2013-01-01

202

Space vacuum processing  

NASA Technical Reports Server (NTRS)

The unique ultra-vacuum environment of low-earth orbit space is to be utilized for vacuum processing of advanced semiconductor and superconductor materials through epitaxial thin-film growth. The quality of semiconductor single crystal (epitaxial) thin-films can be significantly enhanced in the space ultra-vacuum through the reduction of impurities. This will be accomplished by the development of the free-flying Wake Shield Facility presently being built by the Space Vacuum Epitaxy Center in conjunction with industry and NASA under a low-cost, short time commercial approach to space hardware development.

Ignatiev, A.; Shih, H. D.; Daniels, M.; Sega, R.; Bonner, T.

1991-01-01

203

NSLS II Vacuum System  

SciTech Connect

National Synchrotron Light Source II, being constructed at Brookhaven, is a 3-GeV, 500 mA, 3rd generation synchrotron radiation facility with ultra low emittance electron beams. The storage ring vacuum system has a circumference of 792 m and consists of over 250 vacuum chambers with a simulated average operating pressure of less than 1 x 10{sup -9} mbar. A summary of the update design of the vacuum system including girder supports of the chambers, gauges, vacuum pumps, bellows, beam position monitors and simulation of the average pressure will be shown. A brief description of the techniques and procedures for cleaning and mounting the chambers are given.

Ferreira, M.; Doom, L.; Hseuh, H.; Longo, C.; Settepani, P.; Wilson, K.; Hu, J.

2009-09-13

204

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

205

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

206

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

207

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

208

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

209

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

210

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

211

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

212

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

213

Vacuum control valve  

Microsoft Academic Search

A vacuum modulating chamber of a vacuum control valve is communicated with a diaphragm chamber of a EGR valve for controlling an amount of exhaust gas to be recirculated into combustion chambers of an engine, so that a modulated negative pressure is applied thereto. The chamber is provided with a diaphragm deflected responding to the negative pressure in the chamber.

M. Naito; K. Itou; K. Tsuzuki; K. Yano

1984-01-01

214

Working in a Vacuum  

ERIC Educational Resources Information Center

In this article, the author discusses several myths about vacuum cleaners and offers tips on evaluating and purchasing this essential maintenance tool. These myths are: (1) Amps mean performance; (2) Everyone needs high-efficiency particulate air (HEPA): (3) Picking up a "bowling ball" shows cleaning power; (4) All vacuum bags are the same; (5)…

Rathey, Allen

2005-01-01

215

Vacuum pump aids ejectors  

Microsoft Academic Search

The steam ejector\\/vacuum pump hybrid system has been operating satisfactorily since the summer of 1981. This system has essentially been as troublefree as the all-ejector system and, of course, has provided a substantial cost savings. Construction is currently under way to convert the vacuum system of another crude still which is equipped with steam ejectors and barometric condensers to the

1982-01-01

216

Vacuum Energy Decay  

E-print Network

The problem of the vacuum energy decay is studied through the analysis of the vacuum survival amplitude ${\\mathcal A}(z, z')$. Transition amplitudes are computed for finite time-span, $Z\\equiv z^\\prime-z$, and their {\\em late time} behavior is discussed up to first order in the coupling constant, $\\l$.

Enrique Álvarez; Roberto Vidal

2011-11-09

217

Stellarator helical vacuum vessel  

Microsoft Academic Search

A design study of a stainless steel, heavy wall, helically shaped vacuum torus has been made for use in a proposed Stellarator configuration. The study concerns itself with the shape of the vacuum vessel and the division of the vessel into components that can be machined and welded together into a helical configuration. A complication in the design requires that

Yavornik

1983-01-01

218

Assessing the Effect of Spaceflight on the Propensity for Astronauts to Develop Disk Herniation  

NASA Technical Reports Server (NTRS)

A previous study [1] reported the instantaneous risk of developing a Herniated Nucleus Pulosus (HNP) was higher in astronauts who had flown at least one mission, as compared with those in the corps who had not yet flown. However, the study only analyzed time to HNP after the first mission (if any) and did not account for the possible effects of multiple missions. While many HNP's occurred well into astronauts' careers or in some cases years after retirement, the higher incidence of HNPs relatively soon after completion of space missions appears to indicate that spaceflight may lead to an increased risk of HNP. The purpose of this study was to support the Human System Risk Boards assessment of back pain, assess the risk of injury due to dynamic loads, and update the dataset analyzed which contained data through December 31, 2006.

Feiveson, Alan H.; Mendez, C. M.; Somers, J. T.

2015-01-01

219

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

220

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

221

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

222

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

223

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

224

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

225

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

226

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

227

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

228

Vacuum-driven Metamorphosis  

E-print Network

We show that nonperturbative vacuum effects can produce a vacuum-driven transition from a matter-dominated universe to one in which the effective equation of state is that of radiation plus cosmological constant. The actual material content of the universe after the transition remains that of non-relativistic matter. This metamorphosis of the equation of state can be traced to nonperturbative vacuum effects that cause the scalar curvature to remain nearly constant at a well-defined value after the transition, and is responsible for the observed acceleration of the recent expansion of the universe.

Parker, L; Parker, Leonard; Raval, Alpan

1999-01-01

229

Vacuum-driven Metamorphosis  

E-print Network

We show that nonperturbative vacuum effects can produce a vacuum-driven transition from a matter-dominated universe to one in which the effective equation of state is that of radiation plus cosmological constant. The actual material content of the universe after the transition remains that of non-relativistic matter. This metamorphosis of the equation of state can be traced to nonperturbative vacuum effects that cause the scalar curvature to remain nearly constant at a well-defined value after the transition, and is responsible for the observed acceleration of the recent expansion of the universe.

Leonard Parker; Alpan Raval

1999-08-26

230

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

231

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

232

Collapse of Vacuum Bubbles in a Vacuum  

E-print Network

Motivated by the discovery of a plenitude of metastable vacua in a string landscape and the possibility of rapid tunneling between these vacua, we revisit the dynamics of a false vacuum bubble in a background de Sitter spacetime. We find that there exists a large parameter space that allows the bubble to collapse into a black hole or to form a wormhole. This may have interesting implications to inflationary physics.

Kin-Wang Ng; Shang-Yung Wang

2010-06-17

233

Cervical spinal canal stenosis and central disc herniation c3/4 in a man with primary complaint of thigh pain.  

PubMed

Purpose?The purpose of this report is to describe the clinical course of a patient who had a primary complaint of isolated right lateral thigh pain 3 years prior that was nonresponsive to conservative measures. Hypoesthesia in the lateral side of the right forearm, deltoid and biceps, as well as triceps paresis, was also diagnosed. Results?Immediately after surgery, the patient reported substantial improvement in his right thigh symptoms. The signs and symptoms associated with the right C6 and C7 radiculopathy did improve. Conclusion?Although the presentation described in this case is somewhat unique, the eventual myelopathic signs and symptoms were not. It was these myelopathic signs and symptoms that led to cervical magnetic resonance imaging, the diagnosis of cervical cord compressive myelopathy, and surgical management. PMID:24303344

Akhavan-Sigari, R; Rohde, V; Alaid, A

2013-12-01

234

A 3-Arm, Randomized, Controlled Trial of Heat-Sensitive Moxibustion Therapy to Determine Superior Effect among Patients with Lumbar Disc Herniation  

PubMed Central

Systematic reviews of moxibustion for LDH have identified ponderable evidence, especially for heat-sensitive moxibustion (HSM). Therefore, we designed and carried out the large sample trial to evaluate it. 456 patients were recruited from 4 centers in China and were randomly divided into three groups by the ratio of 1?:?1?:?1 to HSM (152) group, conventional moxibustion (152) group, and conventional drug plus acupuncture (152) group. Compared with usual care, there was a statistically significant reduction in mean M-JOA score at 2 weeks and 6 months for HSM (3.8 ± 2.6 versus 8.5 ± 2.9; 3.7 ± 2.2 versus 10.1 ± 2.9) and conventional moxibustion (7.9 ± 3.0 versus 8.5 ± 2.9; 8.9 ± 3.1 versus 10.1 ± 2.9). Compared with conventional moxibustion group, HSM group showed greater improvement in all the outcomes. The mean dose of moxibustion was 41.13 ± 5.26 (range 21–60) minutes in the HSM group. We found that HSM was more effective in treating patients with LDH, compared with conventional moxibustion and conventional drug plus acupuncture. This finding indicated that the application of moxibustion on the heat-sensitive points is a good moxibustion technique in treating disease. PMID:25152757

Chen, Rixin; Chen, Mingren; Su, Tongsheng; Zhou, Meiqi; Sun, Jianhua; Xiong, Jun; Chi, Zhenhai; Xie, Dingyi; Zhang, Bo

2014-01-01

235

Welding space vacuum technology  

NASA Technical Reports Server (NTRS)

The objective was to assist the EH 42 Division in putting together a vacuum system that could attain the desired pressure and be large enough to accommodate the gas-metal arc (GMA) welding fixture apparatus. A major accomplishment was the design and fabrication of the controller/annunciator for the 4' by 8' system. It contains many safety features such as thermocouple set point relays that will only allow inlet and exit gas and vacuum valves to be operated at pre-selected system pressures, and a fail safe mode for power interruptions and operator mistakes. It is felt that significant progress was made in this research effort to weld in a vacuum environment. With continued efforts to increase the pump speeds for vacuum chambers and further studies on weld fixtures and gas inlet pressures, the NASA program will be successful.

Johnson, R. Barry

1991-01-01

236

Welding space vacuum technology  

NASA Astrophysics Data System (ADS)

The objective was to assist the EH 42 Division in putting together a vacuum system that could attain the desired pressure and be large enough to accommodate the gas-metal arc (GMA) welding fixture apparatus. A major accomplishment was the design and fabrication of the controller/annunciator for the 4' by 8' system. It contains many safety features such as thermocouple set point relays that will only allow inlet and exit gas and vacuum valves to be operated at pre-selected system pressures, and a fail safe mode for power interruptions and operator mistakes. It is felt that significant progress was made in this research effort to weld in a vacuum environment. With continued efforts to increase the pump speeds for vacuum chambers and further studies on weld fixtures and gas inlet pressures, the NASA program will be successful.

Johnson, R. Barry

1991-12-01

237

Vacuum Camera Cooler  

NASA Technical Reports Server (NTRS)

Acquiring cheap, moving video was impossible in a vacuum environment, due to camera overheating. This overheating is brought on by the lack of cooling media in vacuum. A water-jacketed camera cooler enclosure machined and assembled from copper plate and tube has been developed. The camera cooler (see figure) is cup-shaped and cooled by circulating water or nitrogen gas through copper tubing. The camera, a store-bought "spy type," is not designed to work in a vacuum. With some modifications the unit can be thermally connected when mounted in the cup portion of the camera cooler. The thermal conductivity is provided by copper tape between parts of the camera and the cooled enclosure. During initial testing of the demonstration unit, the camera cooler kept the CPU (central processing unit) of this video camera at operating temperature. This development allowed video recording of an in-progress test, within a vacuum environment.

Laugen, Geoffrey A.

2011-01-01

238

Vacuum control valve  

SciTech Connect

A vacuum modulating chamber of a vacuum control valve is communicated with a diaphragm chamber of a EGR valve for controlling an amount of exhaust gas to be recirculated into combustion chambers of an engine, so that a modulated negative pressure is applied thereto. The chamber is provided with a diaphragm deflected responding to the negative pressure in the chamber. The vacuum control valve is further provided with a cam member and a spring which urges the diaphragm in one direction so as to change a value at which the pressure in the vacuum modulating chamber is controlled. A push rod is movably held by a cam follower and another spring is provided for urging the push rod in the above direction. The spring force of the other spring is applied to the diaphragm, when a rotational angle of the cam member exceeds a predetermined angle, so that the negative pressure is changed rapidly.

Naito, M.; Itou, K.; Tsuzuki, K.; Yano, K.

1984-04-03

239

Vacuum Boundary Effects  

E-print Network

The effect of boundary conditions on the vacuum structure of quantum field theories is analysed from a quantum information viewpoint. In particular, we analyse the role of boundary conditions on boundary entropy and entanglement entropy. The analysis of boundary effects on massless free field theories points out the relevance of boundary conditions as a new rich source of information about the vacuum structure. In all cases the entropy does not increase along the flow from the ultraviolet to the infrared.

M. Asorey; J. M. Munoz-Castaneda

2008-03-18

240

Unilateral pupillary mydriasis from nebulized ipratropium bromide: A false sign of brain herniation in the intensive care unit.  

PubMed

Although there are many causes of anisocoria in the intensive care setting, the development of unilateral mydriasis in patients with intracranial hemorrhage or tumor is a neurological emergency, as it may herald the onset of uncal herniation. We describe two patients with a hemiparesis from neurosurgical disorder who subsequently developed a fixed and dilated pupil. The pupillary abnormality was caused by nebulized ipratropium bromide in both cases, and resolved when the medication was discontinued. Nebulized ipratropium may leak from the mask into ipsilateral eye and cause mydriasis in patients with facial weakness. This benign cause of anisocoria in the intensive care setting is distinguished from uncal herniation by the laterality of neurologic findings, and lack of mental status change, ptosis, and extraocular movement impairment. PMID:24701070

Chaudhry, Priyanka; Friedman, Deborah I; Yu, Wengui

2014-03-01

241

Unilateral pupillary mydriasis from nebulized ipratropium bromide: A false sign of brain herniation in the intensive care unit  

PubMed Central

Although there are many causes of anisocoria in the intensive care setting, the development of unilateral mydriasis in patients with intracranial hemorrhage or tumor is a neurological emergency, as it may herald the onset of uncal herniation. We describe two patients with a hemiparesis from neurosurgical disorder who subsequently developed a fixed and dilated pupil. The pupillary abnormality was caused by nebulized ipratropium bromide in both cases, and resolved when the medication was discontinued. Nebulized ipratropium may leak from the mask into ipsilateral eye and cause mydriasis in patients with facial weakness. This benign cause of anisocoria in the intensive care setting is distinguished from uncal herniation by the laterality of neurologic findings, and lack of mental status change, ptosis, and extraocular movement impairment. PMID:24701070

Chaudhry, Priyanka; Friedman, Deborah I.; Yu, Wengui

2014-01-01

242

Vacuum self-magnetization?  

SciTech Connect

We study vacuum properties in a strong magnetic field as the zero temperature and zero density limit of quantum statistics. For charged vector bosons (W bosons) the vacuum energy density diverges for B > B{sub c} = m{sub w}{sup 2}/e, leading to vacuum instability. A logarithmic divergence of vacuum magnetization is found for B = Bc, which suggests that if the magnetic field is large enough, it is self-consistently maintained, and this mechanism actually prevents B from reaching the critical value Bc. For virtual neutral vector bosons bearing an anomalous magnetic moment, the instability of the ground state for B > B{sub c}{sup '} = m{sub n}{sup 2}/q also leads to the vacuum energy density divergence for fields B > B{sub c}{sup '} and to the magnetization divergence for B B{sub c}{sup '}. The possibility of virtual electron-positron pairs bosonization in strong magnetic field and the applicability of the neutral bosons model to describe the virtual positronium behavior in a magnetic field are discussed. We conjecture that this could lead to vacuum self-magnetization in QED.

Perez Rojas, H.; Rodriguez Querts, E. [Instituto de Cibernetica, Matematica y Fisica, Calle E No. 309, esq. a 15 Vedado, C. Havana (Cuba)

2006-06-19

243

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

244

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

245

Learning curve of full-endoscopic technique through interlaminar approach for l5/s1 disk herniations.  

PubMed

Although minimally invasive full-endoscopic (FE) spine surgery through the interlaminar approach has proved safe and effective for surgical treatment of lumbar disk herniation, the learning curve of the procedure has not been sufficiently established. The purpose of this study is to determine the learning curve for the FE surgery through interlaminar approach for treating the L5/S1 disk herniation. Thirty-six patients with lumbar disk herniation (L5/S1 segment) who underwent FE lumbar discectomy through the interlaminar approach between March 2011 and March 2012 were equally divided into Group A, B, and C by the study time of the surgeons. Clinical evaluation data included perioperative parameters (operative duration, intraoperative blood loss, and the amount of intraoperative bone and ligament excision), clinical curative effect index [visual analog scale (VAS) score for leg and back pain], complications, and the rate of conversion to open surgery. The operation duration, intraoperative bleeding, and the amount of bone and ligament excision were gradually and significantly reduced in the Groups A, B, and C (P < 0.01) and reflected in steep curves of proficiency suggesting that the rate of learning was fast. The VAS scores of leg and back pain were significantly improved (P < 0.01) and no symptomatic recurrence was noticed during the follow-up period (1-1.5 years). The outcomes the three groups were not significantly different. The clinical outcomes of the minimally invasive surgery for the treatment of L5/S1 segment disk herniation through the interlaminar approach were excellent suggesting of a satisfactory curative effect. The steep learning curves of perioperative parameters plotted against the number of surgeries conducted suggest that proficiency can be reached reasonably fast. PMID:24839114

Xu, Haidong; Liu, Xiaozhou; Liu, Gang; Zhao, Jiangning; Fu, Qiang; Xu, Bin

2014-11-01

246

Spontaneous migration of a redundant nerve root accompanied by absorption of lumbar disk herniation. A case report.  

PubMed

A redundant nerve root is defined as a large, elongated and tortuous nerve root commonly associated with severe lumbar spinal canal stenosis. Elongation of nerve roots as a result of mechanical trapping at stenotic level is assumed to be a possible mechanism. Here we present a case in a patient who showed a redundant nerve root above the level of a lumbar canal stenosis caused by disk herniation and redundancy spontaneously migrating to a lower lumbar stenosis level accompanied by absorption of the herniated disk as shown by magnetic resonance imaging (MRI). A 67-year-old Japanese woman presented with bilateral thigh/leg pain and intermittent claudication. A midsagittal T2-weighted MR image of the lumbar spine revealed severe spinal canal stenosis at the L3-4 and L4-5 levels. At the L3-4 level, central disk herniation compressed the dural tube. An MR image revealed redundant nerve roots just cranial to the severely compressed L3-4 level. A follow-up MRI study revealed regression of disk herniation at the L3-4 level. In contrast, there was no significant change of the stenosis at the L4-5 level. Sagittal T2-weighted MR imaging at follow-up revealed redundant nerve roots just cranial to the L4-5 level, whereas the redundant nerve roots cranial to the L3-4 level had disappeared. The MRI findings of the present case support the "squeeze" hypothesis as causative of redundant nerve roots. PMID:24029099

Koda, M; Rokkaku, T; Mannoji, C; Okamoto, Y; Kon, T; Murakami, M; Furuya, T; Yamazaki, M

2012-11-01

247

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

248

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

249

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

250

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

251

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

252

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

253

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

254

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

255

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

256

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

257

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

258

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

259

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

260

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

261

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

262

Stellarator helical vacuum vessel  

SciTech Connect

A design study of a stainless steel, heavy wall, helically shaped vacuum torus has been made for use in a proposed Stellarator configuration. The study concerns itself with the shape of the vacuum vessel and the division of the vessel into components that can be machined and welded together into a helical configuration. A complication in the design requires that a circular magnet coil be located at the minor toroidal axis and that this coil be embedded within the periphery of the vacuum vessel. The vacuum vessel has a minor toroidal axis diameter of 4 meters, a 68.6-cm shell diameter, and a 1.9-cm wall thickness. It twists about the minor toroidal axis twice in 360/sup 0/C. (An n value of 2). It is proposed that the unit be made of cylindrical segments with the ends of the cylinders cut at appropriate lengths and angles to form the helix. A mathematical derivation of the dimensions necessary to produce the required shapes of the segments has been made. Also, drawings of the vacuum vessel components have been produced on LANL's CTR CAD/CAM system. The procedure developed can be used for any value of n as dictated by physics requirements.

Yavornik, E.J.

1983-01-01

263

(Reverse) Engineering Vacuum Alignment  

E-print Network

In the presence of spontaneous symmetry breaking, the alignment of the vacuum with respect to the gauge group is often controlled by quadratically divergent operators in the low energy non-linear sigma model. In principle the magnitudes and signs of these operators can be changed by making different assumptions about the ultraviolet physics, but in practice all known ways of regulating these theories preserve the naive vacuum alignment. We show that by "integrating in" different sets of heavy spin-one fields, it is possible to UV extend certain non-linear sigma models into two distinct UV insensitive theories. These UV extensions have identical low energy degrees of freedom but different radiative potentials, making it possible to engineer two different vacuum alignments for the original non-linear sigma model. Our construction employs "non-square" theory spaces which generically violate the common lore that the preferred vacuum alignment preserves the maximal gauge symmetry. By UV extending the SO(9)/(SO(4) X SO(5)) little Higgs model, we find a radiative potential that deviates from the naive expectation but does not stabilize the correct vacuum for proper electroweak symmetry breaking.

Clifford Cheung; Jesse Thaler

2006-04-28

264

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

265

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

266

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

267

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

268

Vacuum tight window through which a high power laser beam and a high energy particle beam can be transmitted within close proximity to each other  

SciTech Connect

An apparatus and method by which a high-power laser beam and a high-energy particle beam may enter or exit a region, typically filled with gas, to or from another region, typically under vacuum. The two beams are spaced about 3-4 mm apart center-to-center at the entry/exit point and no gas is permitted to leak into the vacuum region. A disc of material capable of resisting high radiation fluxes without forming color centers is sealed into a metallic holding block. Prior to sealing of the disc, a hole approximately 0.16 cm is drilled into the disc while the disc is tilted at or above Brewster's angle forming an eliptical hole. A thin film, approximately 6000 A, indium metallization is sputtered in a circular pattern about the hole and around the edges of a beryllium disc. An indium disc is then sandwiched between the disc with the hole and the beryllium disc touching the indium metallization on each piece.

Kimura, W.D.

1984-05-22

269

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

270

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

271

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

272

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

273

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

274

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

275

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

276

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

277

Acceleration and vacuum temperature  

NASA Astrophysics Data System (ADS)

The quantum fluctuations of an “accelerated” vacuum state, that is, vacuum fluctuations in the presence of a constant electromagnetic field, can be described by the temperature TM. Considering TM for the gyromagnetic factor g=1 we show that TM(g=1)=TU, where TU is the Unruh temperature experienced by an accelerated observer. We conjecture that both particle production and nonlinear field effects inherent in the Unruh accelerated observer case are described by the case g=1 QED of strong fields. We present rates of particle production for g=0, 1, 2 and show that the case g=1 is experimentally distinguishable from g=0, 2. Therefore, either accelerated observers are distinguishable from accelerated vacuum or there is unexpected modification of the theoretical framework.

Labun, Lance; Rafelski, Johann

2012-08-01

278

Vacuum Arc Ion Sources  

E-print Network

The vacuum arc ion source has evolved into a more or less standard laboratory tool for the production of high-current beams of metal ions, and is now used in a number of different embodiments at many laboratories around the world. Applications include primarily ion implantation for material surface modification research, and good performance has been obtained for the injection of high-current beams of heavy-metal ions, in particular uranium, into particle accelerators. As the use of the source has grown, so also have the operational characteristics been improved in a variety of different ways. Here we review the principles, design, and performance of vacuum arc ion sources.

Brown, I

2014-01-01

279

Vacuum arc deposition devices  

SciTech Connect

The vacuum arc is a high-current, low-voltage electrical discharge which produces a plasma consisting of vaporized and ionized electrode material. In the most common cathodic arc deposition systems, the arc concentrates at minute cathode spots on the cathode surface and the plasma is emitted as a hypersonic jet, with some degree of contamination by molten droplets [known as macroparticles (MPs)] of the cathode material. In vacuum arc deposition systems, the location and motion of the cathode spots are confined to desired surfaces by an applied magnetic field and shields around undesired surfaces. Substrates are mounted on a holder so that they intercept some portion of the plasma jet. The substrate often provides for negative bias to control the energy of depositing ions and heating or cooling to control the substrate temperature. In some systems, a magnetic field is used to guide the plasma around an obstacle which blocks the MPs. These elements are integrated with a deposition chamber, cooling, vacuum gauges and pumps, and power supplies to produce a vacuum arc deposition system.

Boxman, R.L.; Zhitomirsky, V.N. [Electrical Discharge and Plasma Laboratory, Faculty of Engineering, Tel Aviv University, P.O. Box 39040, Tel Aviv 69978 (Israel)

2006-02-15

280

Experiments with Vacuum Tubes  

Microsoft Academic Search

IN my letter published in the last number of NATURE I omitted to say that we have compared vacuum tubes without electrodes with a tube containing water. A tube was filled about nine-tenths full of water and then sealed hermetically. It was then applied to the prime conductor of the electric machine and electrified in the same way as the

J. T. Bottomley

1881-01-01

281

Cryogenic vacuum techniques  

Microsoft Academic Search

A survey is made of the state-of-the-art in cryopumping technologies. Among the aspects of the technology reviewed are: molecular flow in nonisothermal vacuum chambers, diverse methods of cryopumping such as condensation, cryosorption at solid gas condensates, and at porous solids such as molecular sieves and activated charcoal, cryotrapping and cryogettering at metal films. Also covered are calculation of cryopump systems

R. A. Haefer

1981-01-01

282

Vacuum ultraviolet holography  

NASA Technical Reports Server (NTRS)

The authors report the first demonstration of holographic techniques in the vacuum ultraviolet spectral region. Holograms were produced with coherent 1182 A radiation. The holograms were recorded in polymethyl methacrylate and read out with an electron microscope. A holographic grating with a fringe spacing of 836 A was produced and far-field Fraunhofer holograms of sub-micron particles were recorded.

Bjorklund, G. C.; Harris, S. E.; Young, J. F.

1974-01-01

283

Sorption vacuum trap  

NASA Technical Reports Server (NTRS)

Modified sorption trap for use in high vacuum systems contains provisions for online regeneration of sorbent material. Trap is so constructed that it has a number of encapsulated resistance heaters and a valving and pumping device for removing gases from heated sorbing material. Excessive downtime is eliminated with this trap.

Barrington, A. E.; Caruso, A. J.

1970-01-01

284

Vacuum thermal insulation panel  

Microsoft Academic Search

A vacuum thermal insulation panel comprises a pair of laminated plastic and aluminum sheets together with a plastic edge strip sealed to the edges of the sheets so as to define an evacuable volume in which a glass fiber mat is disposed. The insulation panel of the present invention takes advantage of the light-weight, low cost and low thermal conductivity

J. R. Young; R. M. Schreck

1984-01-01

285

Topics in vacuum decay  

NASA Astrophysics Data System (ADS)

If a theory has more than one classically stable vacuum, quantum tunneling and thermal jumps make the transition between the vacua possible. The transition happens through a first order phase transition started by nucleation of a bubble of the new vacuum. The outward pressure of the truer vacuum makes the bubble expand and consequently eat away more of the old phase. In the presence of gravity this phenomenon gets more complicated and meanwhile more interesting. It can potentially have important cosmological consequences. Some aspects of this decay are studied in this thesis. Solutions with different symmetry than the generically used O(4) symmetry are studied and their actions calculated. Vacuum decay in a spatial vector field is studied and novel features like kinky domain walls are presented. The question of stability of vacua in a landscape of potentials is studied and the possible instability in large dimension of fields is shown. Finally a compactification of the Einstein-Maxwell theory is studied which can be a good lab to understand the decay rates in compactification models of arbitrary dimensions.

Masoumi, Ali

286

Langmuir vacuum and superconductivity  

SciTech Connect

It is shown that, in the 'jelly' model of cold electron-ion plasma, the interaction between electrons and the quantum electromagnetic vacuum of Langmuir waves involves plasma superconductivity with an energy gap proportional to the energy of the Langmuir quantum.

Veklenko, B. A. [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation)

2012-06-15

287

Welding space vacuum technology  

Microsoft Academic Search

The objective was to assist the EH 42 Division in putting together a vacuum system that could attain the desired pressure and be large enough to accommodate the gas-metal arc (GMA) welding fixture apparatus. A major accomplishment was the design and fabrication of the controller\\/annunciator for the 4' by 8' system. It contains many safety features such as thermocouple set

R. Barry Johnson

1991-01-01

288

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

289

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

290

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

291

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

292

Demonstrations with a Vacuum: Old Demonstrations for New Vacuum Pumps.  

ERIC Educational Resources Information Center

Explains mechanisms of 19th-century vacuum pumps. Describes demonstrations using the pump including guinea and feather tube, aurora tube, electric egg, Gassiots cascade, air mill, bell in vacuum, density and buoyancy of air, fountain in vacuum, mercury shower, palm and bladder glasses, Bacchus demonstration, pneumatic man-lifter, and Magdeburg…

Greenslade, Thomas B., Jr.

1989-01-01

293

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

294

Mechanisms of cerebellar tonsil herniation in patients with Chiari malformations as guide to clinical management  

PubMed Central

Background The pathogenesis of Chiari malformations is incompletely understood. We tested the hypothesis that different etiologies have different mechanisms of cerebellar tonsil herniation (CTH), as revealed by posterior cranial fossa (PCF) morphology. Methods In 741 patients with Chiari malformation type I (CM-I) and 11 patients with Chiari malformation type II (CM-II), the size of the occipital enchondrium and volume of the PCF (PCFV) were measured on reconstructed 2D-CT and MR images of the skull. Measurements were compared with those in 80 age- and sex-matched healthy control individuals, and the results were correlated with clinical findings. Results Significant reductions of PCF size and volume were present in 388 patients with classical CM-I, 11 patients with CM-II, and five patients with CM-I and craniosynostosis. Occipital bone size and PCFV were normal in 225 patients with CM-I and occipitoatlantoaxial joint instability, 55 patients with CM-I and tethered cord syndrome (TCS), 30 patients with CM-I and intracranial mass lesions, and 28 patients with CM-I and lumboperitoneal shunts. Ten patients had miscellaneous etiologies. The size and area of the foramen magnum were significantly smaller in patients with classical CM-I and CM-I occurring with craniosynostosis and significantly larger in patients with CM-II and CM-I occurring with TCS. Conclusions Important clues concerning the pathogenesis of CTH were provided by morphometric measurements of the PCF. When these assessments were correlated with etiological factors, the following causal mechanisms were suggested: (1) cranial constriction; (2) cranial settling; (3) spinal cord tethering; (4) intracranial hypertension; and (5) intraspinal hypotension. PMID:20440631

Nishikawa, Misao; Kula, Roger W.; Dlugacz, Yosef D.

2010-01-01

295

Tritium handling in vacuum systems  

SciTech Connect

This report provides a course in Tritium handling in vacuum systems. Topics presented are: Properties of Tritium; Tritium compatibility of materials; Tritium-compatible vacuum equipment; and Tritium waste treatment.

Gill, J.T. [Monsanto Research Corp., Miamisburg, OH (United States). Mound Facility; Coffin, D.O. [Los Alamos National Lab., NM (United States)

1986-10-01

296

Vacuum Energy in Quantum Graphs  

E-print Network

We calculate the vacuum energy in quantum graphs. Vacuum energy arose in quantum physics but has an independent mathematical interest as a functional carrying information about the eigenvalue spectrum of a system. A quantum graph is a metric graph...

Wilson, Justin

2007-07-14

297

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

298

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

299

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

300

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

301

Vacuum Frying of Carrot Chips  

Microsoft Academic Search

Vacuum frying is an alternative method to produce high quality vegetable or fruit chips. The effect of frying temperature and vacuum degree on moisture content, oil content, color, and texture of fried carrot chips were investigated. During the early stage of vacuum frying, the rate of moisture removal and oil absorption increased with increasing frying oil temperature and degree of

Liu-ping Fan; Min Zhang; Arun S. Mujumdar

2005-01-01

302

Portable vacuum object handling device  

DOEpatents

The disclosure relates to a portable device adapted to handle objects which are not to be touched by hand. A piston and bore wall form a vacuum chamber communicating with an adaptor sealably engageable with an object to be lifted. The piston is manually moved and set to establish vacuum. A valve is manually actuatable to apply the vacuum to lift the object.

Anderson, Gordon H. (Los Alamos, NM)

1983-08-09

303

Vacuum Energy: Myths and Reality  

E-print Network

We discuss the main myths related to the vacuum energy and cosmological constant, such as: ``unbearable lightness of space-time''; the dominating contribution of zero point energy of quantum fields to the vacuum energy; non-zero vacuum energy of the false vacuum; dependence of the vacuum energy on the overall shift of energy; the absolute value of energy only has significance for gravity; the vacuum energy depends on the vacuum content; cosmological constant changes after the phase transition; zero-point energy of the vacuum between the plates in Casimir effect must gravitate, that is why the zero-point energy in the vacuum outside the plates must also gravitate; etc. All these and some other conjectures appear to be wrong when one considers the thermodynamics of the ground state of the quantum many-body system, which mimics macroscopic thermodynamics of quantum vacuum. In particular, in spite of the ultraviolet divergence of the zero-point energy, the natural value of the vacuum energy is comparable with the observed dark energy. That is why the vacuum energy is the plausible candidate for the dark energy.

G. E. Volovik

2006-04-14

304

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

305

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

306

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

307

Compact vacuum insulation  

DOEpatents

An ultra-thin compact vacuum insulation panel is comprised of two hard, but bendable metal wall sheets closely spaced apart from each other and welded around the edges to enclose a vacuum chamber. Glass or ceramic spacers hold the wall sheets apart. The spacers can be discrete spherical beads or monolithic sheets of glass or ceramic webs with nodules protruding therefrom to form essentially "point" or "line" contacts with the metal wall sheets. In the case of monolithic spacers that form "line" contacts, two such spacers with the line contacts running perpendicular to each other form effectively "point" contacts at the intersections. Corrugations accommodate bending and expansion, tubular insulated pipes and conduits, and preferred applications are also included.

Benson, David K. (Golden, CO); Potter, Thomas F. (Denver, CO)

1993-01-01

308

Compact vacuum insulation embodiments  

DOEpatents

An ultra-thin compact vacuum insulation panel is comprised of two hard, but bendable metal wall sheets closely spaced apart from each other and welded around the edges to enclose a vacuum chamber. Glass or ceramic spacers hold the wall sheets apart. The spacers can be discrete spherical beads or monolithic sheets of glass or ceramic webs with nodules protruding therefrom to form essentially "point" or "line" contacts with the metal wall sheets. In the case of monolithic spacers that form "line" contacts, two such spacers with the line contacts running perpendicular to each other form effectively "point" contacts at the intersections. Corrugations accommodate bending and expansion, tubular insulated pipes and conduits, and preferred applications are also included.

Benson, David K. (Golden, CO); Potter, Thomas F. (Denver, CO)

1992-01-01

309

Vacuum Structure and Potential  

E-print Network

Based on overall experimental observations, especially the pair processes, I developed a model structure of the vacuum along with a basic-particle formation scheme begun in 2000 (with collaborator P-I Johansson). The model consists in that the vacuum is, briefly, filled of neutral but polarizable vacuuons, consisting each of a p-vaculeon and n- vaculeon of charges $+e$ and $-e$ of zero rest masses but with spin motions, assumed interacting each other with a Coulomb force. The model has been introduced in full in a book (Nova Sci, 2005) and referred to in a number of journal/E-print papers. I outline in this easier accessible paper the detailed derivation of the model and a corresponding quantitative determination of the vacuuon size.

J. X. Zheng-Johansson

2007-04-02

310

An automated vacuum system  

SciTech Connect

Software tools available with the Ground Test Accelerator (GTA) control system provide the capability to express a control problem as a finite state machine. System states and transitions are expressed in terms of accelerator parameters and actions are taken based on state transitions. This is particularly useful for sequencing operations which are modal in nature or are unwieldy when implemented with conventional programming. State diagrams are automatically translated into code which is executed by the control system. These tools have been applied to the vacuum system for the GTA accelerator to implement automatic sequencing of operations. With a single request, the operator may initiate a complete pump-down sequence. He can monitor the progress and is notified if an anomaly occurs requiring intervention. The operator is not required to have detailed knowledge of the vacuum system and is protected from taking inappropriate actions. 1 ref., 6 figs.

Atkins, W.H. (Oak Ridge National Lab., TN (USA)); Vaughn, G.D. (Los Alamos National Lab., NM (USA)); Bridgman, C. (Grumman Corp., Bethpage, NY (USA))

1991-01-01

311

Vacuum tool manipulator  

DOEpatents

Apparatus for manipulating a vacuum hose in a reactor vessel comprises a housing with two opposing openings, an arm carried by the housing and deployable from a stowed position essentially completely within the housing to an extended position where the arm extends through the two openings in a generally horizontal position. The arm preferably has a two-fingered gripping device for gripping the vacuum hose but may carry a different end effector such as a grinding wheel. The fingers are opened and closed by one air cylinder. A second air cylinder extends the device. A third air cylinder within the housing pivotally pulls the opposing end of the arm into the housing via a pivoting member pivotally connected between the third air cylinder shaft and the arm.

Zollinger, William T. (3927 Almon Dr., Martinez, GA 30907)

1993-01-01

312

Integrated structure vacuum tube  

NASA Technical Reports Server (NTRS)

High efficiency, multi-dimensional thin film vacuum tubes suitable for use in high temperature, high radiation environments are described. The tubes are fabricated by placing thin film electrode members in selected arrays on facing interior wall surfaces of an alumina substrate envelope. Cathode members are formed using thin films of triple carbonate. The photoresist used in photolithography aids in activation of the cathodes by carbonizing and reacting with the reduced carbonates when heated in vacuum during forming. The finely powdered triple carbonate is mixed with the photoresist used to delineate the cathode locations in the conventional solid state photolithographic manner. Anode and grid members are formed using thin films of refractory metal. Electron flow in the tubes is between grid elements from cathode to anode as in a conventional three-dimensional tube.

Dimeff, J.; Kerwin, W. J. (inventors)

1976-01-01

313

Is vacuum dispersive?  

E-print Network

The question we ask is: does the speed of light {\\it{in vacuo}} depend on its frequency? While the answer is NO in the frame of classical physics, we point out that the opposite could be true if one takes into account the polarization of Dirac sea. We estimate the dependence of the index of refraction of vacuum + Dirac sea versus the wavelength of an incoming beam, and suggest a way to test this effect.

Yves Pomeau

2014-09-02

314

The vacuum energy crisis  

E-print Network

The smallness of the vacuum energy density and its near coincidence with the average matter density of the universe are naturally explained by anthropic selection. An alternative explanation, based on the cyclic model of Steinhardt and Turok, does not address the coincidence problem and is therefore less convincing. This article appeared in ``Science'' (4 May 2006) as a ``perspective'' for Steinhardt and Turok's paper in the same issue (astro-ph/0605173).

Alexander Vilenkin

2006-05-09

315

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

316

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

317

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

318

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

319

Vacuum Energy: Myths and Reality  

E-print Network

We discuss the main myths related to the vacuum energy and cosmological constant, such as: ``unbearable lightness of space-time''; the dominating contribution of zero point energy of quantum fields to the vacuum energy; non-zero vacuum energy of the false vacuum; dependence of the vacuum energy on the overall shift of energy; the absolute value of energy only has significance for gravity; the vacuum energy depends on the vacuum content; cosmological constant changes after the phase transition; zero-point energy of the vacuum between the plates in Casimir effect must gravitate, that is why the zero-point energy in the vacuum outside the plates must also gravitate; etc. All these and some other conjectures appear to be wrong when one considers the thermodynamics of the ground state of the quantum many-body system, which mimics macroscopic thermodynamics of quantum vacuum. In particular, in spite of the ultraviolet divergence of the zero-point energy, the natural value of the vacuum energy is comparable with the...

Volovik, G E

2006-01-01

320

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

321

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

322

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

323

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

324

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

325

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

326

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

327

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

328

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

329

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

330

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.

331

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

332

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

333

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

334

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

335

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

336

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

337

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

338

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

339

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

340

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

341

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

342

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

343

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

344

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

345

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

346

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

347

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

348

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

349

Prevalence of Disc Degeneration in Asymptomatic Korean Subjects. Part 3 : Cervical and Lumbar Relationship  

PubMed Central

Objective There are many cases in which degenerative changes are prevalent in both the cervical and lumbar spine, and the relation between both spinal degenerative findings of MRI is controversial. The authors analyzed the prevalence of abnormal findings on MRI, and suggested a model to explain the relationship between cervical and lumbar disc in asymptomatic Korean subjects. Methods We performed 3 T MRI sagittal scans on 102 asymptomatic subjects (50 men and 52 women) who visited our hospital between the ages of 14 and 82 years (mean age 46.3 years). Scores pertaining to herniation (HN), annular fissure (AF), and nucleus degeneration (ND) were analyzed. The total scores for the cervical and lumbar spine were analyzed using correlation coefficients and multiple linear regression with various predictive parameters, including weight, height, sex, age, smoking, occupation, and sedentary fashion. Results The correlation coefficients of HN, AF, and ND were 0.44, 0.50, and 0.59, respectively. We made the best model for relationship by using multiple linear regression. Conclusion The results of the current study showed that there was a close relationship between the cervical score (CS) and lumbar score (LS). In addition, the correlation between CS and LS, as well as the LS value itself, can be altered by other explanatory variables. Although not absolute, there was also a linear relationship between degenerative changes of the cervical and lumbar spine. Based on these results, it can be inferred that degenerative changes of the lumbar spine will be useful in predicting the degree of cervical spine degeneration in an actual clinical setting. PMID:23634267

Lee, Tae Hoon; Yi, Seong

2013-01-01

350

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

351

Charged vacuum bubble stability  

NASA Astrophysics Data System (ADS)

A type of scenario is considered where electrically charged vacuum bubbles, formed from degenerate or nearly degenerate vacua separated by a thin domain wall, are cosmologically produced due to the breaking of a discrete symmetry, with the bubble charge arising from fermions residing within the domain wall. Stability issues associated with wall tension, fermion gas, and Coulombic effects for such configurations are examined. The stability of a bubble depends upon parameters such as the symmetry breaking scale and the fermion coupling. A dominance of either the Fermi gas or the Coulomb contribution may be realized under certain conditions, depending upon parameter values.

Morris, J. R.

1999-01-01

352

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

353

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

354

R&D ERL: Vacuum  

SciTech Connect

The ERL Vacuum systems are depicted in a figure. ERL has eight vacuum volumes with various sets of requirements. A summary of vacuum related requirements is provided in a table. Five of the eight volumes comprise the electron beamline. They are the 5-cell Superconducting RF Cavity, Superconducting e-gun, injection, loop and beam dump. Two vacuum regions are the individual cryostats insulating the 5-cell Superconducting RF Cavity and the Superconducting e-gun structures. The last ERL vacuum volume not shown in the schematic is the laser transport line. The beamline vacuum regions are separated by electropneumatic gate valves. The beam dump is common with loop beamline but is considered a separate volume due to geometry and requirements. Vacuum in the 5-cell SRF cavity is maintained in the {approx}10{sup -9} torr range at room temperature by two 20 l/s ion pumps and in the e-gun SRF cavity by one 60 l/s ion pump. Vacuum in the SRF cavities operated at 2{sup o}K is reduced to low 10{sup -11} torr via cryopumping of the cavity walls. The cathode of the e-gun must be protected from poisoning, which can occur if vacuum adjacent to the e-gun in the injection line exceeds 10-11 torr range in the injection warm beamline near the e-gun exit. The vacuum requirements for beam operation in the loop and beam dump are 10-9 torr range. The beamlines are evacuated from atmospheric pressure to high vacuum level with a particulate free, oil free turbomolecular pumping cart. 25 l/s shielded ion pumps distributed throughout the beamlines maintain the vacuum requirement. Due to the more demanding vacuum requirement of the injection beamline proximate to the e-gun, a vacuum bakeout of the injection beamline is required. In addition, two 200 l/s diode ion pumps and supplemental pumping provided by titanium sublimation pumps are installed in the injection line just beyond the exit of the e-gun. Due to expected gas load a similar pumping arrangement is planned for the beam dump. The cryostat vacuum thermally insulating the SRF cavities need only reduce the convective heat load such that heat loss is primarily radiation through several layers of multi-layer insulation and conductive end-losses which are contained by 5{sup o}K thermal transitions. Prior to cool down rough vacuum {approx}10{sup -5} torr range is established and maintained by a dedicated turbomolecular pump station. Cryopumping by the cold mass and heat shields reduces the insulating vacuum to 10{sup -7} torr range after cool down.

Mapes, M.; Smart, L.; Weiss, D.; Steszyn, A.; Todd, R.

2010-01-01

355

Vacuum vapor deposition  

NASA Technical Reports Server (NTRS)

A method and apparatus is described for vapor deposition of a thin metallic film utilizing an ionized gas arc directed onto a source material spaced from a substrate to be coated in a substantial vacuum while providing a pressure differential between the source and the substrate so that, as a portion of the source is vaporized, the vapors are carried to the substrate. The apparatus includes a modified tungsten arc welding torch having a hollow electrode through which a gas, preferably inert, flows and an arc is struck between the electrode and the source. The torch, source, and substrate are confined within a chamber within which a vacuum is drawn. When the arc is struck, a portion of the source is vaporized and the vapors flow rapidly toward the substrate. A reflecting shield is positioned about the torch above the electrode and the source to ensure that the arc is struck between the electrode and the source at startup. The electrode and the source may be confined within a vapor guide housing having a duct opening toward the substrate for directing the vapors onto the substrate.

Poorman, Richard M. (inventor); Weeks, Jack L. (inventor)

1995-01-01

356

Accelerator Vacuum Protection System  

NASA Astrophysics Data System (ADS)

A new and elaborate automatic vacuum protection system using fast acting valve has been installed to avoid accidental venting of accelerator from experimental chamber side. To cover all the beam lines and to reduce the system cost, it has been installed at a common point from where all the seven beam lines originate. The signals are obtained by placing fast response pressure sensing gauges (HV SENSOR) near all the experimental stations. The closing time of the fast valve is 10 milli-second. The fast closing system protects only one vacuum line at a time. At IUAC, we have seven beam lines so one sensor was placed in each of the beam lines near experimental chamber and a multiplexer was incorporated into the fast closing system. At the time of experiment, the sensor of the active beam line is selected through the multiplexer and the Fast closing valve is interlocked with the selected sensor. As soon as the pressure sensor senses the pressure rise beyond a selected pressure, the signal is transferred and the fast valve closes within 10 to 12 millisecond.

Barua, Pradip; Kothari, Ashok; Archunan, M.; Joshi, Rajan

2012-11-01

357

Portable vacuum object handling device  

DOEpatents

The disclosure relates to a portable device adapted to handle objects which are not to be touched by hand. A piston and bore wall form a vacuum chamber communicating with an adaptor sealably engageable with an object to be lifted. The piston is manually moved and set to establish vacuum. A valve is manually actuatable to apply the vacuum to lift the object. 1 fig.

Anderson, G.H.

1983-08-09

358

Evolution of galactic discs: multiple patterns, radial migration, and disc outskirts  

NASA Astrophysics Data System (ADS)

We investigate the evolution of galactic discs in N-body tree-SPH simulations. We find that discs, initially truncated at three scale-lengths, can triple their radial extent, solely driven by secular evolution. At the same time, the initial radial metallicity gradients are flattened and even reversed in the outer discs. Both Type I (single exponential) and Type II (down-turning) observed disc surface-brightness profiles can be explained by our findings. We show that profiles with breaks beyond the bar's outer Lindblad resonance, at present only explained as the effect of star-formation threshold, can occur even if no star formation is considered. We explain these results with the strong angular momentum outward transfer, resulting from torques and radial migration associated with multiple patterns, such as central bars and spiral waves of different multiplicity. We find that even for stars ending up on cold orbits, the changes in angular momentum exhibit complex structure as a function of radius, unlike the expected effect of transient spirals alone. We show that the bars in all of our simulations are the most effective drivers of radial migration through their corotation resonance, throughout the 3 Gyr of evolution studied. Focussing on one of our models, we find evidence for non-linear coupling among m = 1,2,3 and 4 density waves, where m is the pattern multiplicity. In this way the waves involved conspire to carry the energy and angular momentum extracted by the first mode from the inner parts of the disc much farther out than a single mode could. We suggest that the naturally occurring larger resonance widths at galactic radii beyond four scale-lengths may have profound consequences on the formation and location of breaks in disc density profiles, provided spirals are present at such large distances. We also consider the effect of gas inflow and show that when in-plane smooth gas accretion of ~5 M?/yr is included, the outer discs become more unstable, leading to a strong increase in the stellar velocity dispersion. This, in turn, causes the formation of a Type III (up-turning) profile in the old stellar population. We propose that observations of Type III surface brightness profiles, combined with an up-turn in the stellar velocity dispersions beyond the disc break, could be a signature of ongoing gas-accretion. The results of this study suggest that disc outskirts comprised of stars migrated from the inner disc would have relatively large radial velocity dispersions (>30 km s-1 at 6 scale-lengths for Milky Way-size systems), and significant thickness when seen edge-on.

Minchev, I.; Famaey, B.; Quillen, A. C.; Di Matteo, P.; Combes, F.; Vlaji?, M.; Erwin, P.; Bland-Hawthorn, J.

2012-12-01

359

Vacuum leak detector and method  

DOEpatents

Apparatus and method for detecting leakage in a vacuum system involves a moisture trap chamber connected to the vacuum system and to a pressure gauge. Moisture in the trap chamber is captured by freezing or by a moisture adsorbent to reduce the residual water vapor pressure therein to a negligible amount. The pressure gauge is then read to determine whether the vacuum system is leaky. By directing a stream of carbon dioxide or helium at potentially leaky parts of the vacuum system, the apparatus can be used with supplemental means to locate leaks.

Edwards, Jr., David (7 Brown's La., Bellport, NY 11713)

1983-01-01

360

Manipulator For A Vacuum Chamber  

NASA Technical Reports Server (NTRS)

Rotary seal provides for external actuators. Positioner in vacuum employs four actuators; up/down, horizontal rotary, horizontal, and vertical rotary. External up/down and azimuthal actuators drives shaft entering vacuum chamber through sliding and rotating seal. Placement of actuator motors outside vacuum chamber reduces heat-removal load on system. Atop 2.5-cm-diameter shaft is stage supporting masses as great as 15 kg. Small motors on stage provide horizontal translation and rotation in vertical plane. Manipulator developed for calibrating plasma detectors by subjecting them to particle beams in vacuum. Standard, commercially available parts used.

Hunsaker, F.; Ogilvie, K.

1988-01-01

361

Turbulence-induced disc formation in strongly magnetized cloud cores  

NASA Astrophysics Data System (ADS)

We present collapse simulations of strongly magnetized, turbulent molecular cloud cores with masses ranging from 2.6 to 1000 M? in order to study the influence of the initial conditions on the turbulence-induced disc formation mechanism proposed recently by Seifried et al. We find that Keplerian discs are formed in all cases independently of the core mass, the strength of turbulence or the presence of global rotation. The discs appear within a few kyr after the formation of the protostar, are 50-150 au in size, and have masses between 0.05 and a few 0.1 M?. During the formation of the discs the mass-to-flux ratio stays well below the critical value of 10 for Keplerian disc formation. Hence, flux-loss alone cannot explain the formation of Keplerian discs. The formation of rotationally supported discs at such early phases is rather due to the disordered magnetic field structure and due to turbulent motions in the surroundings of the discs, two effects lowering the classical magnetic braking efficiency. Binary systems occurring in the discs are mainly formed via the disc capturing mechanism rather than via disc fragmentation, which is largely suppressed by the presence of magnetic fields.

Seifried, D.; Banerjee, R.; Pudritz, R. E.; Klessen, R. S.

2013-07-01

362

Accreting planets as dust dams in `transition' discs  

E-print Network

We investigate under what circumstances an embedded planet in a protoplanetary disc may sculpt the dust distribution such that it observationally presents as a `transition' disc. We concern ourselves with `transition' discs that have large holes ($\\gtrsim 10$ AU) and high accretion rates ($\\sim 10^{-9}-10^{-8}$ M$_\\odot$ yr$^{-1}$). Particularly, those discs which photoevaporative models struggle to explain. Assuming the standard picture for how massive planets sculpt their parent discs, along with the observed accretion rates in `transition' discs, we find that the accretion luminosity from the forming planet is significant, and can dominate over the stellar luminosity at the gap edge. This planetary accretion luminosity can apply a significant radiation pressure to small ($s\\lesssim 1\\mu$m) dust particles provided they are suitably decoupled from the gas. Secular evolution calculations that account for the evolution of the gas and dust components in a disc with an embedded, accreting planet, show that only ...

Owen, James E

2014-01-01

363

Examination of turbine discs from nuclear power plants  

SciTech Connect

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

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

1982-01-01

364

Vertical shear instability in accretion disc models with radiation transport  

E-print Network

The origin of turbulence in accretion discs is still not fully understood. While the magneto-rotational instability is considered to operate in sufficiently ionized discs, its role in the poorly ionized protoplanetary disc is questionable. Recently, the vertical shear instability (VSI) has been suggested as a possible alternative. Our goal is to study the characteristics of this instability and the efficiency of angular momentum transport, in extended discs, under the influence of radiative transport and irradiation from the central star. We use multi-dimensional hydrodynamic simulations to model a larger section of an accretion disc. First we study inviscid and weakly viscous discs using a fixed radial temperature profile in two and three spatial dimensions. The simulations are then extended to include radiative transport and irradiation from the central star. In agreement with previous studies we find for the isothermal disc a sustained unstable state with a weak positive angular momentum transport of the o...

Stoll, Moritz H R

2014-01-01

365

Accretion Disc Evolution in Single and Binary T Tauri Stars  

E-print Network

We present theoretical models for the evolution of T Tauri stars surrounded by circumstellar discs. The models include the effects of pre-main-sequence stellar and time dependent disc evolution, and incorporate the effects of stellar magnetic fields acting on the inner disc. For single stars, consistency with observations in Taurus-Auriga demands that disc dispersal occurs rapidly, on much less than the viscous timescale of the disc, at roughly the epoch when heating by stellar radiation first dominates over internal viscous dissipation. Applying the models to close binaries, we find that because the initial conditions for discs in binaries are uncertain, studies of extreme mass ratio systems are required to provide a stringent test of theoretical disc evolution models. We also note that no correlation of the infra-red colours of T Tauri stars with their rotation rate is observed, in apparent contradiction to the predictions of simple magnetospheric accretion models.

Philip J. Armitage; C. J. Clarke; C. A. Tout

1998-10-30

366

Interface Modes and Their Instabilities in Accretion Disc Boundary Layers  

E-print Network

We study global non-axisymmetric oscillation modes trapped near the inner boundary of an accretion disc. Observations indicate that some of the quasi-periodic oscillations (QPOs) observed in the luminosities of accreting compact objects (neutron stars, black holes and white dwarfs) are produced in the inner-most regions of accretion discs or boundary layers. Two simple models are considered in this paper: The magnetosphere-disc model consists of a thin Keplerian disc in contact with a uniformly rotating magnetosphere with and low plasma density, while the star-disc model involves a Keplerian disc terminated at the stellar atomosphere with high density and small density scale height. We find that the interface modes at the magnetosphere-disc boundary are generally unstable due to Rayleigh-Taylor and/or Kelvin-Helmholtz instabilities. However, differential rotation of the disc tends to suppress Rayleigh-Taylor instability and a sufficiently high disc sound speed (or temperature) is needed to overcome this suppression and to attain net mode growth. On the other hand, Kelvin-Helmholtz instability may be active at low disc sound speeds. We also find that the interface modes trapped at the boundary between a thin disc and an unmagnetized star do not suffer Rayleigh-Taylor or Kelvin-Helmholtz instability, but can become unstable due to wave leakage to large disc radii and, for sufficiently steep disc density distributions, due to wave absorption at the corotation resonance in the disc. The non-axisymmetric interface modes studied in this paper may be relevant to the high-frequency QPOs observed in some X-ray binaries and in cataclysmic variables.

David Tsang; Dong Lai

2008-12-20

367

Cosmic Vacuum Prevents Radiopanspermia  

NASA Astrophysics Data System (ADS)

The paper describes the new physical mechanism for the explanation of the irreversible damage of vegetative cells and spores of microorganisms (m/o) under space thermovacuum conditions (tvc) (vacuum+high temperatures), developed by the authors based on the published experimental data of various authors. The suggestion was made that this mechanism could inactivate most vegetative cells and spores of the m/o at the initial stage of their spontaneous migration into the cosmos from the platforms where life has originated and evolved. The authors believe the Earth and Earth-like planets to be such platforms. Such a mechanism could restrict the application of the radiopanspermia hypothesis to the explanation of the origin of life on the Earth.

Nussinov, M. D.; Lysenko, S. V.

1983-12-01

368

Vacuum thermal insulation panel  

SciTech Connect

A vacuum thermal insulation panel comprises a pair of laminated plastic and aluminum sheets together with a plastic edge strip sealed to the edges of the sheets so as to define an evacuable volume in which a glass fiber mat is disposed. The insulation panel of the present invention takes advantage of the light-weight, low cost and low thermal conductivity of plastic materials to form an evacuable volume into which a glass fiber insulating mat is disposed for support of the panel which is evacuated to provide improved thermal insulation. Additionally, a gas permeation barrier is employed on the edge strip of the panel to minimize gas permeation at its edges. A metal foil layer provides gas permeation protection through the large surface areas of the sheets themselves.

Young, J.R.; Schreck, R.M.

1984-04-24

369

Future complete vacuum spacetimes  

E-print Network

In this paper we prove a global existence theorem, in the direction of cosmological expansion, for sufficiently small perturbations of a family of spatially compact variants of the $k=-1$ Friedmann--Robertson--Walker vacuum spacetime. We use a special gauge defined by constant mean curvature slicing and a spatial harmonic coordinate condition, and develop energy estimates through the use of the Bel-Robinson energy and its higher order generalizations. In addition to the smallness condition on the data, we need a topological constraint on the spatial manifold to exclude the possibility of a non--trivial moduli space of flat spacetime perturbations, since the latter could not be controlled by curvature--based energies such as those of Bel--Robinson type. Our results also demonstrate causal geodesic completeness of the perturbed spacetimes (in the expanding direction) and establish precise rates of decay towards the background solution which serves as an attractor asymptotically.

Lars Andersson; Vincent Moncrief

2003-03-11

370

New Experiments with Spinning Metallic Discs  

NASA Technical Reports Server (NTRS)

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

Mazuruk, Konstantin; Grugel, Richard N.

2003-01-01

371

Oxygen abundance distribution in the Galactic disc  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

372

Disc heating agents across the Hubble sequence  

NASA Astrophysics Data System (ADS)

We measure the shape of the velocity ellipsoid in two late-type spiral galaxies (Hubble types Sc and Scd) and combine these results with our previous analyses of six early-type spirals (Sa to Sbc) to probe the relation between galaxy morphology and the ratio of the vertical and radial dispersions. We confirm at much higher significance (99.9 per cent) our prior detection of a tight correlation between these quantities. We explore the trends of the magnitude and shape of the velocity ellipsoid axes with galaxy properties (colour, gas surface mass density and spiral arm structure). The observed relationships allow for an observational identification of the radial and vertical disc heating agents in external disc galaxies. Based on observations made with ESO Telescopes at the La Silla Observatory under programmes 074.B-0550(A) and 078.B-0152(A).

Gerssen, J.; Shapiro Griffin, K.

2012-07-01

373

Cervical disc arthroplasty: Pros and cons  

PubMed Central

Background: Cervical disc arthroplasty has emerged as a promising potential alternative to anterior cervical discectomy and fusion (ACDF) in appropriately selected patients. Despite a history of excellent outcomes after ACDF, the question as to whether a fusion leads to adjacent segment degeneration remains unanswered. Numerous US investigational device exemption trials comparing cervical arthroplasty to fusion have been conducted to answer this question. Methods: This study reviews the current research regarding cervical athroplasty, and emphasizes both the pros and cons of arthroplasty as compared with ACDF. Results: Early clinical outcomes show that cervical arthroplasty is as effective as the standard ACDF. However, this new technology is also associated with an expanding list of novel complications. Conclusion: Although there is no definitive evidence that cervical disc replacement reduces the incidence of adjacent segment degeneration, it does show other advantages; for example, faster return to work, and reduced need for postoperative bracing. PMID:22905327

Moatz, Bradley; Tortolani, P. Justin

2012-01-01

374

Abdominal intrauterine vacuum aspiration.  

PubMed

Evaluating and "cleaning" of the uterine cavity is probably the most performed operation in women. It is done for several reasons: abortion, evaluation of irregular bleeding in premenopausal period, and postmenopausal bleeding. Abortion is undoubtedly the number one procedure with more than 44 million pregnancies terminated every year. This procedure should not be underestimated and a careful preoperative evaluation is needed. Ideally a sensitive pregnancy test should be done together with an ultrasound in order to confirm a uterine pregnancy, excluding extra-uterine pregnancy, and to detect genital and/or uterine malformations. Three out of four abortions are performed by surgical methods. Surgical methods include a sharp, blunt, and suction curettage. Suction curettage or vacuum aspiration is the preferred method. Despite the fact that it is a relative safe procedure with major complications in less than one percent of cases, it is still responsible for 13% of all maternal deaths. All the figures have not declined in the last decade. Trauma, perforation, and bleeding are a danger triage. When there is a perforation, a laparoscopy should be performed immediately, in order to detect intra-abdominal lacerations and bleeding. The bleeding should be stopped as soon as possible in order to not destabilize the patient. When there is a perforation in the uterus, this "entrance" can be used to perform the curettage. This is particularly useful if there is trauma of the isthmus and uterine wall, and it is difficult to identify the uterine canal. A curettage is a frequent performed procedure, which should not be underestimated. If there is a perforation in the uterus, then this opening can safely be used for vacuum aspiration. PMID:25134300

Tjalma, W A A

2014-01-01

375

Galaxy Zoo: bars in disc galaxies  

NASA Astrophysics Data System (ADS)

We present first results from Galaxy Zoo 2, the second phase of the highly successful Galaxy Zoo project (). Using a volume-limited sample of 13 665 disc galaxies (0.01 < z < 0.06 and Mr < -19.38), we study the fraction of galaxies with bars as a function of global galaxy properties like colour, luminosity and bulge prominence. Overall, 29.4 ± 0.5 per cent of galaxies in our sample have a bar, in excellent agreement with previous visually classified samples of galaxies (although this overall fraction is lower than that measured by automated bar-finding methods). We see a clear increase in the bar fraction with redder (g-r) colours, decreased luminosity and in galaxies with more prominent bulges, to the extent that over half of the red, bulge-dominated disc galaxies in our sample possess a bar. We see evidence for a colour bimodality for our sample of disc galaxies, with a 'red sequence' that is both bulge and bar dominated, and a 'blue cloud' which has little, or no, evidence for a (classical) bulge or bar. These results are consistent with similar trends for barred galaxies seen recently both locally and at higher redshift, and with early studies using the RC3. We discuss these results in the context of internal (secular) galaxy evolution scenarios and the possible links to the formation of bars and bulges in disc galaxies. This publication has been made possible by the participation of more than 200 000 volunteers in the Galaxy Zoo project. Their contributions are individually acknowledged at http://www.galaxyzoo.org/Volunteers.aspx

Masters, Karen L.; Nichol, Robert C.; Hoyle, Ben; Lintott, Chris; Bamford, Steven P.; Edmondson, Edward M.; Fortson, Lucy; Keel, William C.; Schawinski, Kevin; Smith, Arfon M.; Thomas, Daniel

2011-03-01

376

Programmed cell death in intervertebral disc degeneration  

Microsoft Academic Search

Intervertebral disc (IVD) degeneration is largely a process of destruction and failure of the extracellular matrix (ECM),\\u000a and symptomatic IVD degeneration is thought to be one of the leading causes of morbidity or life quality deterioration in\\u000a the elderly. To date, however, the mechanism of IVD degeneration is still not fully understood. Cellular loss from cell death\\u000a in the process

Chang-Qing Zhao; Lei-Sheng Jiang; Li-Yang Dai

2006-01-01

377

Intervertebral disc space inflammation in children  

Microsoft Academic Search

Discitis in children commonly presents with fever, back pain, irritability, and an inability to walk. An elevated ESR and\\u000a characteristic changes on plain X-rays or bone scan are sufficient for diagnosis, but MRI is more sensitive and more specific,\\u000a and it shows pathologic changes earlier. Intravenous antibiotics are administered when cultures of the disc space are positive,\\u000a but in more

Lloyd I. Maliner; Dennis L. Johnson

1997-01-01

378

synthesis for a compact disc player  

Microsoft Academic Search

SUMMARY This paper considers the design and implementation of robust multivariable controllers for a compact disc mechanism.The design objective is to achieve good track-following and focusing performance in the presence of track disturbances, external mechanical shocks and structured norm-bounded plant uncertainty. This robust performance problem has been solved in the k-framework using the DK-iteration scheme. Limits of implementation necessitate the

Maarten Steinbuch; Pieter J. M. Van Groos; Gerrit Schootstra; Pepijn M. R. Wortelboer; Okko H. Bosgra

1998-01-01

379

Compact Disc Standards: An Introductory Overview  

Microsoft Academic Search

The success of the compact disc (CD) as a storage medium for digital audio has, over the last ten years, resulted in a number of initiatives to use the CD for other applications as well, e.g., as read-only memory for computers, as a storage medium for audio-visual material for multimedia applications, and as a storage medium for photographs. Each of

Jan H. M. Korst; Verus Pronk

1994-01-01

380

Gradient composite materials for artificial intervertebral discs.  

PubMed

Composites with the gradient of Young's modulus constitute a new group of biomimetic materials which affect the proper distribution of stresses between the implant and the bone. The aim of this article was to examine the mechanical properties of gradient materials based on carbon fibre-polysulfone composite, and to compare them to the properties of a natural intervertebral disc. Gradient properties were provided by different orientation or volume fraction of carbon fibres in particular layers of composites. The results obtained during in vitro tests displayed a good durability of the gradient materials put under long-term static load. However, the configuration based on a change in the volume fraction of the fibres seems more advantageous than the one based on a change of the fibres' orientation. The materials under study were designed to replace the intervertebral disc. The effect of Young's modulus of the material layers on the stress distribution between the tissue and the implant was analyzed and the biomimetic character of the gradient composites was stated. Unlike gradient materials, the pure polysulfone and the non-gradient composite resulted in the stress concentration in the region of nucleus pulposus, which is highly disadvantageous and does not occur in the stress distribution of natural intervertebral discs. PMID:25306938

Migacz, Katarzyna; Ch?opek, Jan; Morawska-Chochó?, Anna; Ambroziak, Maciej

2014-01-01

381

Foramen of Huschke (tympanicum) in a Nigerian male with articular soft-tissue herniation into the external auditory meatus.  

PubMed

The protrusion of articular soft-tissue from the temporomandibular joint (TMJ) into the external ear in the absence of trauma, neoplasm or inflammation is rare. We present below a Nigerian adult male with retrodiscal herniation of soft-tissues of the TMJ into the external auditory meatus through a persistent foramen of Huschke. We are not aware of any reports of this developmental defect or its prevalence in the Nigerian medical literature. Therefore, this case is presented to heighten the index of suspicion of physicians when managing patients with otorrhea and otalgia; which is often primarily diagnosed or misdiagnosed as otitis externa. This will help avoid complications associated with the anomaly, some of which could be very serious. PMID:25287039

Olarinoye-Akorede, S A; Olanrewaju, I S; Suleiman, A O

2014-01-01

382

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

383

Vacuum enhanced cutaneous biopsy instrument  

DOEpatents

A syringe-like disposable cutaneous biopsy instrument equipped with a tubular blade at its lower end, and designed so that a vacuum is created during use, said vacuum serving to retain undeformed a plug of tissue cut from a patient's skin.

Collins, Joseph (St. Petersburg, FL)

2000-01-01

384

Vacuum pyrolysis of sugarcane bagasse  

Microsoft Academic Search

The objective of this study was to provide background data on sugarcane bagasse vacuum pyrolysis. Product yields and properties were investigated. Vacuum pyrolysis tests were performed at bench and pilot plant scales. The bagasse finest particles with a diameter smaller than 450 ?m were removed in order to overcome difficulties caused by their low density and high ash content. In

Abdelkader Chaala; Christian Roy

2002-01-01

385

Vacuum flash evaporated polymer composites  

DOEpatents

A method for fabrication of polymer composite layers in a vacuum is disclosed. More specifically, the method of dissolving salts in a monomer solution, vacuum flash evaporating the solution, condensing the flash evaporated solution as a liquid film, and forming the condensed liquid film into a polymer composite layer on a substrate is disclosed.

Affinito, J.D.; Gross, M.E.

1997-10-28

386

Statistical mechanics of the vacuum  

E-print Network

The vacuum is full of virtual particles which exist for short moments of time. In this paper we construct a chaotic model of vacuum fluctuations associated with a fundamental entropic field that generates an arrow of time. The dynamics can be physically interpreted in terms of fluctuating virtual momenta. This model leads to a generalized statistical mechanics that distinguishes fundamental constants of nature.

Christian Beck

2011-12-07

387

Vacuum flash evaporated polymer composites  

DOEpatents

A method for fabrication of polymer composite layers in a vacuum is disclosed. More specifically, the method of dissolving salts in a monomer solution, vacuum flash evaporating the solution, condensing the flash evaporated solution as a liquid film, and forming the condensed liquid film into a polymer composite layer on a substrate is disclosed.

Affinito, John D. (Kennewick, WA); Gross, Mark E. (Pasco, WA)

1997-01-01

388

Vacuum Technology for Ion Sources  

E-print Network

The basic notions of vacuum technology for ion sources are presented, with emphasis on pressure profile calculation and choice of pumping technique. A Monte Carlo code (Molflow+) for the evaluation of conductances and the vacuum-electrical analogy for the calculation of time-dependent pressure variations are introduced. The specific case of the Linac4 H- source is reviewed.

Chiggiato, P

2013-01-01

389

Vacuum Gas Tungsten Arc Welding  

NASA Technical Reports Server (NTRS)

A two-year program investigated vacuum gas tungsten arc welding (VGTAW) as a method to modify or improve the weldability of normally difficult-to-weld materials. After a vacuum chamber and GTAW power supply were modified, several difficult-to-weld materials were studied and key parameters developed. Finally, Incoloy 903 weld overlays were produced without microfissures.

Weeks, J. L.; Todd, D. T.; Wooten, J. R.

1997-01-01

390

Cosmology with decaying vacuum energy  

SciTech Connect

Motivated by recent attempts to solve the cosmological constant problem, we examine the observational consequences of a vacuum energy density which decays in time. For all times later than t approx. 1 sec, the ratio of the vacuum to the total energy density of the universe must be small. Although the vacuum cannot provide the ''missing mass'' required to close the universe today, its presence earlier in the history of the universe could have important consequences. We discuss restrictions on the vacuum energy arising from primordial nucleosynthesis, the microwave and gamma ray background spectra, and galaxy formation. A small vacuum component at the era of nucleosynthesis, 0.01 < rho/sub vac//rho/sup rad/ < 0.1, increase the number of allowed neutino species to N/sup nu/ > 5, but in some cases would severely distort the microwave spectrum. 9 refs., 3 figs.

Freese, K.; Adams, F.; Frieman, J.; Mottola, E.

1987-09-01

391

Bubbling the False Vacuum Away  

E-print Network

We investigate the role of nonperturbative, bubble-like inhomogeneities on the decay rate of false-vacuum states in two and three-dimensional scalar field theories. The inhomogeneities are induced by setting up large-amplitude oscillations of the field about the false vacuum as, for example, after a rapid quench or in certain models of cosmological inflation. We show that, for a wide range of parameters, the presence of large-amplitude bubble-like inhomogeneities greatly accelerates the decay rate, changing it from the well-known exponential suppression of homogeneous nucleation to a power-law suppression. It is argued that this fast, power-law vacuum decay -- known as resonant nucleation -- is promoted by the presence of long-lived oscillons among the nonperturbative fluctuations about the false vacuum. A phase diagram is obtained distinguishing three possible mechanisms for vacuum decay: homogeneous nucleation, resonant nucleation, and cross-over. Possible applications are briefly discussed.

Marcelo Gleiser; Barrett Rogers; Joel Thorarinson

2007-08-28

392

Deterioration of Mechanical Properties of Discs in Chronically Inflamed TMJ.  

PubMed

Temporomandibular joint (TMJ) discs frequently undergo degenerative changes in arthritis. However, the biomechanical properties of pathogenic discs remain to be explored. In this study, we evaluated the effects of chronic inflammation on the biomechanical properties of TMJ discs in rats. Chronic inflammation of TMJs was induced by double intra-articular injections of complete Freund's adjuvant for 5 weeks, and biomechanical properties and ultrastructure of the discs were examined by mechanical testing, scanning electron microscopy, and transmission electron microscopy. The instantaneous compressive moduli of the anterior and posterior bands of discs in inflamed TMJs were decreased significantly compared with those in the control group. The instantaneous tensile moduli of the discs of inflamed TMJs also showed significant decreases in both the anterior-posterior and mesial-lateral directions. The relaxation moduli of the discs of inflamed TMJs showed nearly the same tendency as the instantaneous moduli. The surfaces of the discs of inflamed TMJs became rough and porous due to the loss of the superficial gel-like stratum, with many collagen fibers exposed and degradation of the sub-superficial collagen fibrils. Our results suggested that chronic inflammation of TMJ could lead to deterioration of mechanical properties and alteration of disc ultrastructure, which might contribute to TMJ disc displacement. PMID:25266714

Wang, X D; Cui, S J; Liu, Y; Luo, Q; Du, R J; Kou, X X; Zhang, J N; Zhou, Y H; Gan, Y H

2014-11-01

393

Density waves in debris discs and galactic nuclei  

NASA Astrophysics Data System (ADS)

We study the linear perturbations of collisionless near-Keplerian discs. Such systems are models for debris discs around stars and the stellar discs surrounding supermassive black holes at the centres of galaxies. Using a finite-element method, we solve the linearized collisionless Boltzmann equation and Poisson's equation for a wide range of disc masses and rms orbital eccentricities to obtain the eigenfrequencies and shapes of normal modes. We find that these discs can support large-scale 'slow' modes, in which the frequency is proportional to the disc mass. Slow modes are present for arbitrarily small disc mass so long as the self-gravity of the disc is the dominant source of apsidal precession. We find that slow modes are of two general types: parent modes and hybrid child modes, the latter arising from resonant interactions between parent modes and singular van Kampen modes. The most prominent slow modes have azimuthal wavenumbers m= 1 and m= 2. We illustrate how slow modes in debris discs are excited during a fly-by of a neighbouring star. Many of the non-axisymmetric features seen in debris discs (clumps, eccentricity, spiral waves) that are commonly attributed to planets could instead arise from slow modes; the two hypotheses can be distinguished by long-term measurements of the pattern speed of the features.

Jalali, Mir Abbas; Tremaine, Scott

2012-04-01

394

Vertical shear instability in accretion disc models with radiation transport  

NASA Astrophysics Data System (ADS)

Context. The origin of turbulence in accretion discs is still not fully understood. While the magneto-rotational instability is thought to operate in sufficiently ionised discs, its role in the poorly ionised protoplanetary disc is questionable. Recently, the vertical shear instability (VSI) has been suggested as a possible alternative. Aims: Our goal is to study the characteristics of this instability and the efficiency of angular momentum transport, in extended discs, under the influence of radiative transport and irradiation from the central star. Methods: We use multi-dimensional hydrodynamic simulations to model a larger section of an accretion disc. First we study inviscid and weakly viscous discs using a fixed radial temperature profile in two and three spatial dimensions. The simulations are then extended to include radiative transport and irradiation from the central star. Results: In agreement with previous studies, for the isothermal disc we find a sustained unstable state with a weak positive angular momentum transport of the order of ? ? 10-4. Under the inclusion of radiative transport the disc cools off and the turbulence terminates. For discs irradiated from the central star we again find a persistent instability with a similar ? value as for the isothermal case. Conclusions: We find that the VSI can indeed generate sustained turbulence in discs, albeit at a relatively low level with ? about few times 10-4.

Stoll, Moritz H. R.; Kley, Wilhelm

2014-12-01

395

Cartilage intermediate layer protein promotes lumbar disc degeneration.  

PubMed

Lumbar disc disease (LDD) is one of the most common musculoskeletal disorders, and accompanies intervertebral disc degeneration. CILP encodes cartilage intermediate layer protein, which is highly associated with LDD. Moreover, CILP inhibits transcriptional activation of cartilage matrix genes in nucleus pulposus (NP) cells in vitro by binding to TGF-?1 and inhibiting the phosphorylation of Smads. However, the aetiology and mechanism of pathogenesis of LDD in vivo are unknown. To demonstrate the role of CILP in LDD in vivo, we generated transgenic mice that express CILP specifically in the intervertebral disc tissues and assessed whether CILP exacerbates disc degeneration. Degeneration of the intervertebral discs was assessed using magnetic resonance imaging (MRI) and histology. The level of phosphorylation of Smad2/3 in intervertebral discs was measured to determine whether overexpressed CILP suppressed TGF-beta signalling. Although the macroscopic skeletal phenotype of transgenic mice appeared normal, histological findings revealed significant degeneration of lumbar discs. MRI analysis of the lumbar intervertebral discs indicated a significantly lower signal intensity of the nucleus pulposus where CILP was overexpressed. Intervertebral disc degeneration was also observed. The number of phosphorylation of Smad2/3 immuno-positive cells in the NP significantly was decreased in CILP transgenic mice compared with normal mice. In summary, overexpression of CILP in the NP promotes disc degeneration, indicating that CILP plays a direct role in the pathogenesis of LDD. PMID:24631904

Seki, Shoji; Tsumaki, Noriyuki; Motomura, Hiraku; Nogami, Makiko; Kawaguchi, Yoshiharu; Hori, Takeshi; Suzuki, Kayo; Yahara, Yasuhito; Higashimoto, Mami; Oya, Takeshi; Ikegawa, Shiro; Kimura, Tomoatsu

2014-04-18

396

The hunt for the Milky Way's accreted disc  

NASA Astrophysics Data System (ADS)

The Milky Way is expected to host an accreted disc of stars and dark matter. This forms as massive ?1 : 10 mergers are preferentially dragged towards the disc plane by dynamical friction and then tidally shredded. The accreted disc likely contributes only a tiny fraction of the Milky Way's thin and thick stellar disc. However, it is interesting because (i) its associated `dark disc' has important implications for experiments hoping to detect a dark matter particle in the laboratory; and (ii) the presence or absence of such a disc constrains the merger history of our Galaxy. In this work, we develop a chemodynamical template to hunt for the accreted disc. We apply our template to the high-resolution spectroscopic sample from Ruchti et al., finding at present no evidence for accreted disc stars. Our results are consistent with a quiescent Milky Way with no ?1 : 10 mergers since the disc formed and a correspondingly light `dark disc'. However, we caution that while our method can robustly identify accreted stars, our incomplete stellar sample makes it more challenging to definitively rule them out. Larger unbiased stellar samples will be required for this.

Ruchti, Gregory R.; Read, Justin I.; Feltzing, Sofia; Pipino, Antonio; Bensby, Thomas

2014-10-01

397

Astrometric signatures of self-gravitating protoplanetary discs  

E-print Network

We use high resolution numerical simulations to study whether gravitational instabilities within circumstellar discs can produce astrometrically detectable motion of the central star. For discs with masses of M_disc = 0.1 M_star, which are permanantly stable against fragmentation, we find that the magnitude of the astrometric signal depends upon the efficiency of disc cooling. Short cooling times produce prominent filamentary spiral structures in the disc, and lead to stellar motions that are potentially observable with future high precision astrometric experiments. For a disc that is marginally unstable within radii of \\~10 au, we estimate astrometric displacements of 10-100 microarcsec on decade timescales for a star at a distance of 100 pc. The predicted displacement is suppressed by a factor of several in more stable discs in which the cooling time exceeds the local dynamical time by an order of magnitude. We find that the largest contribution comes from material in the outer regions of the disc and hence, in the most pessimistic scenario, the stellar motions caused by the disc could confuse astrometric searches for low mass planets orbiting at large radii. They are, however, unlikely to present any complications in searches for embedded planets orbiting at small radii, relative to the disc size, or Jupiter mass planets or greater orbiting at large radii.

W. K. M. Rice; P. J. Armitage; M. R. Bate; I. A. Bonnell

2002-09-09

398

The Photoevaporation of Discs Around Young Stars in Massive Clusters  

E-print Network

We present models in which the photoevaporation of discs around young stars by an external ultraviolet source (as computed by Adams et al 2004) is coupled with the internal viscous evolution of the discs. These models are applied to the case of the Orion Nebula Cluster, where the presence of a strong ultraviolet field from the central OB stars, together with a detailed census of circumstellar discs and photoevaporative flows, is well established. In particular we investigate the constraints that are placed on the initial disc properties in the ONC by the twin requirement that most stars possess a disc on a scale of a few A.U., but that only a minority ($ 0.1 M_\\odot$). The ubiquity of discs on a small scale, on the other hand, mainly constrains the timespan over which the discs have been exposed to the ultraviolet field ($< 2 $Myr). We argue that the discs that are resolved by HST represent a population of discs in which self-gravity was important at the time that the dominant central OB star switched on, but that, according to our models, self-gravity is unlikely to be important in these discs at the present time. We discuss the implications of our results for the so-called proplyd lifetime problem.

C. J. Clarke

2007-02-05

399

Vacuum energy, antigravity, and modern cosmology  

E-print Network

Vacuum energy, antigravity, and modern cosmology John Peacock, University of Edinburgh Loretto and zero- point energy (inevitable from uncertainty principle) ­ not the only contribution to vacuum energy;Vacuum energy: Einstein's missed chance Now: `Dark Energy' can cause the

Peacock, John

400

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

401

NCSX Vacuum Vessel Fabrication  

SciTech Connect

The National Compact Stellarator Experiment (NCSX) is being constructed at the Princeton Plasma Physics Laboratory (PPPL) in conjunction with the Oak Ridge National Laboratory (ORNL). The goal of this experiment is to develop a device which has the steady state properties of a traditional stellarator along with the high performance characteristics of a tokamak. A key element of this device is its highly shaped Inconel 625 vacuum vessel. This paper describes the manufacturing of the vessel. The vessel is being fabricated by Major Tool and Machine, Inc. (MTM) in three identical 120º vessel segments, corresponding to the three NCSX field periods, in order to accommodate assembly of the device. The port extensions are welded on, leak checked, cut off within 1" of the vessel surface at MTM and then reattached at PPPL, to accommodate assembly of the close-fitting modular coils that surround the vessel. The 120º vessel segments are formed by welding two 60º segments together. Each 60º segment is fabricated by welding ten press-formed panels together over a collapsible welding fixture which is needed to precisely position the panels. The vessel is joined at assembly by welding via custom machined 8" (20.3 cm) wide spacer "spool pieces." The vessel must have a total leak rate less than 5 X 10-6 t-l/s, magnetic permeability less than 1.02?, and its contours must be within 0.188" (4.76 mm). It is scheduled for completion in January 2006.

Viola, M. E.; Brown, T.; Heitzenroeder, P.; Malinowski, F.; Reiersen, W.; Sutton, L.; Goranson, P.; Nelson, B.; Cole, M.; Manuel, M.; McCorkle, D.

2005-10-07

402

Vacuum plasma spray coating  

NASA Technical Reports Server (NTRS)

Currently, protective plasma spray coatings are applied to space shuttle main engine turbine blades of high-performance nickel alloys by an air plasma spray process. Originally, a ceramic coating of yttria-stabilized zirconia (ZrO2.12Y2O3) was applied for thermal protection, but was removed because of severe spalling. In vacuum plasma spray coating, plasma coatings of nickel-chromium-aluminum-yttrium (NiCrAlY) are applied in a reduced atmosphere of argon/helium. These enhanced coatings showed no spalling after 40 MSFC burner rig thermal shock cycles between 927 C (1700 F) and -253 C (-423 F), while current coatings spalled during 5 to 25 test cycles. Subsequently, a process was developed for applying a durable thermal barrier coating of ZrO2.8Y2O3 to the turbine blades of first-stage high-pressure fuel turbopumps utilizing the enhanced NiCrAlY bond-coating process. NiCrAlY bond coating is applied first, with ZrO2.8Y2O3 added sequentially in increasing amounts until a thermal barrier coating is obtained. The enchanced thermal barrier coating has successfully passed 40 burner rig thermal shock cycles.

Holmes, Richard R.; Mckechnie, Timothy N.

1989-01-01

403

Vacuum energy and cosmological evolution  

E-print Network

An expanding universe is not expected to have a static vacuum energy density. The so-called cosmological constant $\\Lambda$ should be an approximation, certainly a good one for a fraction of a Hubble time, but it is most likely a temporary description of a true dynamical vacuum energy variable that is evolving from the inflationary epoch to the present day. We can compare the evolving vacuum energy with a Casimir device where the parallel plates slowly move apart ("expand"). The total vacuum energy density cannot be measured, only the effect associated to the presence of the plates, and then also their increasing separation with time. In the universe there is a nonvanishing spacetime curvature $R$ as compared to Minkowskian spacetime that is changing with the expansion. The vacuum energy density must change accordingly, and we naturally expect $\\delta\\Lambda\\sim R\\sim H^2$. A class of dynamical vacuum models that trace such rate of change can be constructed. They are compatible with the current cosmological data, and conveniently extended can account for the complete cosmic evolution from the inflationary epoch till the present days. These models are very close to the $\\Lambda$CDM model for the late universe, but very different from it at the early times. Traces of the inherent vacuum dynamics could be detectable in our recent past.

Joan Sola

2014-02-27

404

Vacuum Brazing of Accelerator Components  

NASA Astrophysics Data System (ADS)

Commonly used materials for accelerator components are those which are vacuum compatible and thermally conductive. Stainless steel, aluminum and copper are common among them. Stainless steel is a poor heat conductor and not very common in use where good thermal conductivity is required. Aluminum and copper and their alloys meet the above requirements and are frequently used for the above purpose. The accelerator components made of aluminum and its alloys using welding process have become a common practice now a days. It is mandatory to use copper and its other grades in RF devices required for accelerators. Beam line and Front End components of the accelerators are fabricated from stainless steel and OFHC copper. Fabrication of components made of copper using welding process is very difficult and in most of the cases it is impossible. Fabrication and joining in such cases is possible using brazing process especially under vacuum and inert gas atmosphere. Several accelerator components have been vacuum brazed for Indus projects at Raja Ramanna Centre for Advanced Technology (RRCAT), Indore using vacuum brazing facility available at RRCAT, Indore. This paper presents details regarding development of the above mentioned high value and strategic components/assemblies. It will include basics required for vacuum brazing, details of vacuum brazing facility, joint design, fixturing of the jobs, selection of filler alloys, optimization of brazing parameters so as to obtain high quality brazed joints, brief description of vacuum brazed accelerator components etc.

Singh, Rajvir; Pant, K. K.; Lal, Shankar; Yadav, D. P.; Garg, S. R.; Raghuvanshi, V. K.; Mundra, G.

2012-11-01

405

Vacuum energy and cosmological evolution  

NASA Astrophysics Data System (ADS)

An expanding universe is not expected to have a static vacuum energy density. The so-called cosmological constant ? should be an approximation, certainly a good one for a fraction of a Hubble time, but it is most likely a temporary description of a true dynamical vacuum energy variable that is evolving from the inflationary epoch to the present day. We can compare the evolving vacuum energy with a Casimir device where the parallel plates slowly move apart ("expand"). The total vacuum energy density cannot be measured, only the effect associated to the presence of the plates, and then also their increasing separation with time. In the universe there is a nonvanishing spacetime curvature R as compared to Minkowskian spacetime that is changing with the expansion. The vacuum energy density must change accordingly, and we naturally expect ??˜R˜H2. A class of dynamical vacuum models that trace such rate of change can be constructed. They are compatible with the current cosmological data, and conveniently extended can account for the complete cosmic evolution from the inflationary epoch till the present days. These models are very close to the ?CDM model for the late universe, but very different from it at the early times. Traces of the inherent vacuum dynamics could be detectable in our recent past.

Solà, Joan

2014-07-01

406

Disc1 Variation Leads to Specific Alterations in Adult Neurogenesis  

PubMed Central

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

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

2014-01-01

407

Intervertebral disc regeneration: do nutrients lead the way?  

PubMed

Strategies for the biological repair of intervertebral discs derive from the premise that disc degeneration results from impaired cellular activity and, therefore, that these structures can be induced to regenerate by implanting active cells or providing factors that restore normal cellular activity. In vitro and animal studies using this approach have had some success, but whether this success can be reproduced in degenerate human lumbar discs is unknown. Successful repair requires that the disc cells remain viable and active; they therefore need an adequate supply of nutrients. However, as the disc degenerates, the nutrient supply decreases, thereby limiting cell activity and viability. Current biologic approaches might place additional demands on an already precarious nutrient supply. Here, we discuss whether the loss of nutrients associated with disc degeneration limits the effectiveness of biologic approaches, and indicate that this neglected problem requires investigation if clinical application of such therapies is to succeed. PMID:24914695

Huang, Yong-Can; Urban, Jill P G; Luk, Keith D K

2014-09-01

408

Discs around A-type and related stars  

NASA Astrophysics Data System (ADS)

Circumstellar discs are formed together with stars during the process of gravitational collapse of protostellar clouds, and they play an important role during the pre-main sequence phase of stellar evolution. Discs are responsible for the formation of jets and bi-conical outflows, and they are the reservoir of material from which planetary systems are formed. The main source of information about circumstellar discs is the infrared and sub-mm regions of the spectrum. In the case of the Herbig Ae stars the observations in the visual region are also a very useful source of information about the dynamical processes in the inner regions of the discs. In this review I discuss the properties and evolution of discs around these stars and related objects in the context of possible grain growth and disc dissipation via planet formation.

Grinin, V. P.

2014-11-01

409

The localized quantum vacuum field  

NASA Astrophysics Data System (ADS)

A model for the localized quantum vacuum is proposed in which the zero-point energy (ZPE) of the quantum electromagnetic field originates in energy- and momentum-conserving transitions of material systems from their ground state to an unstable state with negative energy. These transitions are accompanied by emissions and re-absorptions of real photons, which generate a localized quantum vacuum in the neighborhood of material systems. The model could help resolve the cosmological paradox associated with the ZPE of electromagnetic fields, while reclaiming quantum effects associated with quantum vacuum such as the Casimir effect and the Lamb shift. It also offers a new insight into the Zitterbewegung of material particles.

Dragoman, D.

2008-03-01

410

Vacuum Function Operation and Systems  

NSDL National Science Digital Library

The understanding of vacuum function and systems is essential for students and employees working within the micro- and nanofabrication industry. This presentation/webinar highlights the use, construction, and examples of current vacuum technology systems today. Prepared by WHO, of the Nanotechnology Applications and Career Knowledge (NACK), a National ATE Center, this presentation provides material presented from the instructor/engineer viewpoint. Discussions include vacuum pump function, gauge use and ranges, applicable design considerations, as well as insight on cost and equipment training methodologies that have been utilized by the NACK Center. This site requires a free log-in to access.

2009-10-06

411

The evolution of misaligned accretion discs and spinning black holes  

E-print Network

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 Active Galactic Nuclei (AGN). We also allow the direction of the hole spin to move under the action of the disc torques. In such a way, the evolution of the hole-disc system is computed self-consistently. We consider a number of different situations and we explore the relevant parameter range, by varying the location of the warp radius Rw and the propagation speed of the warp. We find that the dissipation associated with the twisting of the disc results in a large increase in the accretion rate through the disc, so that AGN accreting from a misaligned disc are likely to be significantly more luminous than those accreting from a flat disc. We compute explicitly the time-scales for the warping of the disc and for the alignment process and compare our results with earlier estimates based on simplified steady-state solutions. We also confirm earlier predictions that, under appropriate circumstances, accretion can proceed in a counter-aligned fashion, so that the accreted material will spin-down the hole, rather than spinning it up. Our results have implication in a number of different observational features of AGN such as the orientation and shape of jets, the shape of X-ray iron lines, and the possibility of obscuration and absorption of X-ray by the outer disc as well as the general issue of the spin history of black holes during their growth. Key words: accretion, accretion discs – black hole physics – galaxies: active – galaxies: nuclei 1

G. Lodato; J. E. Pringle

2008-01-01

412

New Brown Dwarf Discs in Upper Scorpius Observed with WISE  

NASA Technical Reports Server (NTRS)

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

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

2013-01-01

413

Macroscopic and histological observations on the human sternoclavicular joint disc  

Microsoft Academic Search

To know the detailed morphology of the human sternoclavicular joint and its articular disc is essential to understanding the\\u000a movement of this joint and the functional role of the disc. In the present study, 51 articular discs of the sternoclavicular\\u000a joint of 29 Japanese cadavers were macroscopically examined and then embedded in paraffin to make a complete series of coronal

Kenji Emura; Takamitsu Arakawa; Toshio Terashima; Akinori Miki

2009-01-01

414

Herschel DEBRIS survey of debris discs around A stars  

NASA Astrophysics Data System (ADS)

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

Thureau, N.

2014-11-01

415

Welding of combustion turbine rotors and discs  

SciTech Connect

Weld repair of steam turbine rotors and discs by Westinghouse has been performed successfully and has proven itself in operation for the last 15 years. Since 1978, over 200 low pressure (LP) rotors and discs have been weld repaired using the Gas Tungsten Arc Welding (GTAW) process. This process yields properties equal to or better than the original rotor/disc forging for LP alloys. In 1987, the GTAW process was extended to include repair on high pressure (HP) rotor alloys. Since that time, over 45 high pressure and intermediate pressure (IP) rotors have been successfully weld repaired and returned to service. Recently, to meet the demand for repair of combustion turbine alloys, a development program was initiated to make a step increase in the current LP welding process and filler materials from 100--110 ksi weld metal yield strength (on LP alloys) to 140 ksi needed on many areas of a combustion turbine. The challenge to increase the strength by 30% could not be achieved at the expense of the other critical properties particularly toughness. This paper first reviews the successful LP and HP welding programs which were fundamental building blocks for welding combustion turbines. Secondly, the development and testing of a new filler material for welding combustion turbines is reviewed which demonstrated the ability to achieve approximately 135 ksi yield strength. This new program was implemented on lower stress areas of several production parts which are described in part three. The paper concludes with a summary of possible future work to achieve nominal yield strengths near 145 ksi.

Driver, T.L.; Amos, D.R. [Westinghouse Turbine Generator Plant, Charlotte, NC (United States); Clark, R.E. [Westinghouse Electric Corp., Orlando, FL (United States)

1995-12-31

416

An accretion disc instability induced by a temperature sensitive ? parameter  

NASA Astrophysics Data System (ADS)

In the standard thin-disc formalism, the dimensionless ? parameter is usually assumed to be constant. However, there are good theoretical reasons for believing, as well as evidence from simulations, that ? is dependent on intrinsic disc properties. In this paper, we analyse the conditions for the stability of a thin accretion disc in which ? is a function of the magnetic Prandtl number, the ratio of collisional viscosity to resistivity. In the inner disc, where the free electron opacity and radiation viscosity dominate, the disc is unstable if ? is proportional to the magnetic Prandtl number with an exponent >0.5. This is within the range of values for the power-law index found in magnetohydrodynamic simulations with simple energetics. We calculate the evolution of the unstable disc within the ?-formalism and show that the physically accessible solutions form a limit cycle, analogous to the behaviour seen in recurrent dwarf novae. It is noteworthy that the time-dependent global behaviour of the instability results in cyclic heating of the inner section of the disc, when parameters appropriate for an X-ray binary system are used. We calculate a model spectrum of the disc in the flaring and quiescent states and show that the behaviour is compatible with X-ray observations of the thermal accretion disc in flaring X-ray binary systems.

Potter, William J.; Balbus, Steven A.

2014-06-01

417

Stacked-disc structure for fluid filter or valve silencer  

NASA Technical Reports Server (NTRS)

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

Hagler, Jr., Ray (Inventor)

1983-01-01

418

MECHANICAL DESIGN CRITERIA FOR INTERVERTEBRAL DISC TISSUE ENGINEERING  

PubMed Central

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

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

2009-01-01

419

A disc-type magneto-rheologic fluid damper.  

PubMed

A disc-type magneto-rheological fluid damper operating in shear mode is proposed in this paper, which is based on the special characteristics of the magneto-rheological (MR) fluid with rapid, reversible and dramatic change in its rheological properties by the application of an external magnetic field. The magnetic field of the disc-type MR fluid damper is analysed by the finite element method; the controllability of the disc-type MR fluid damper on the dynamic behaviour of a rotor system; and the effectiveness of the disc-type MR fluid damper in controlling the vibration of a rotor system, are studied in a flexible rotor system with an over-hung disc. It is shown that the magnetic flux density of the disc-type MR fluid damper in the working areas can significantly change with the applied current in the coil; and that the dynamic behavior of the disc-type MR fluid damper can be varied by the application of an external magnetic field produced by a low voltage electromagnetic coil. The disc-type MR fluid damper can significantly change the dynamic characteristics of a rotor system, provided that the location of the disk-type MR fluid damper is carefully chosen. The disc-type MR fluid damper is a new actuator with good dynamic characteristics for rotating machinery. PMID:12958708

Zhu, Chang-sheng

2003-01-01

420

Numerical modeling of gravitational instability outcomes in multiphase circumstellar discs  

NASA Astrophysics Data System (ADS)

To suggest consistent route toward planetesimal and planetary core formation in circumstellar discs we study gravitational instability outcomes in massive multiphase (gas-collisionless bodies) disc. Such unstable massive disc can be formed together with protostar in molecular cloud collapse with increased ratio of solids to gas density. In our calculations we found regimes when low-massive solid bodies subdisc drastically affect global structure formation in the disc, whose mass is constituted mainly by the gas. We demonstrated also that solitary areas of high gas density can concentrate solids, producing multiphase clumps, which can be considered as a cradle of large bodies formation.

Stoyanovskaya, Olga P.; Snytnikov, Valeriy N.

2013-04-01

421

Stability of accretion discs threaded by a strong magnetic field  

NASA Astrophysics Data System (ADS)

We study the stability of poloidal magnetic fields anchored in a thin accretion disc. The two-dimensional hydrodynamics in the disc plane is followed by a grid-based numerical simulation including the vertically integrated magnetic forces. The three-dimensional magnetic field outside the disc is calculated in a potential field approximation from the magnetic flux density distribution in the disc. For uniformly rotating discs we confirm numerically the existence of the interchange instability as predicted by Spruit, Stehle & Papaloizou. In agreement with predictions from the shearing sheet model, discs with Keplerian rotation are found to be stabilized by the shear, as long as the contribution of magnetic forces to support against gravity is small. When this support becomes significant, we find a global instability which transports angular momentum outwardly and allows mass to accrete inwardly. The instability takes the form of a m=1 rotating `crescent', reminiscent of the purely hydrodynamic non-linear instability previously found in pressure-supported discs. A model where the initial surface mass density ?(r) and Bz(r) decrease with radius as power laws shows transient mass accretion during about six orbital periods, and settles into a state with surface density and field strength decreasing approximately exponentially with radius. We argue that this instability is likely to be the main angular momentum transport mechanism in discs with a poloidal magnetic field sufficiently strong to suppress magnetic turbulence. It may be especially relevant in jet-producing discs.

Stehle, R.; Spruit, H. C.

2001-05-01

422

Correlation between Voronoi volumes in disc packings  

E-print Network

We measure the two-point correlation of free Voronoi volumes in binary disc packings, where the packing fraction $\\phi_{\\rm avg}$ ranges from 0.8175 to 0.8380. We observe short-ranged correlations over the whole range of $\\phi_{\\rm avg}$ and anti-correlations for $\\phi_{\\rm avg}>0.8277$. The spatial extent of the anti-correlation increases with $\\phi_{\\rm avg}$ while the position of the maximum of the anti-correlation and the extent of the positive correlation shrink with $\\phi_{\\rm avg}$. We conjecture that the onset of anti-correlation corresponds to dilatancy onset in this system.

Song-Chuan Zhao; Stacy Sidle; Harry L. Swinney; Matthias Schröter

2011-09-05

423

The Radial Structure of the Galactic Disc  

E-print Network

Three colour photometry on CCD frames in the Special Area SpA23 provides a deep probe of the galactic disc in a low absorption window towards the anticenter. Magnitudes to better than 10% at V = 25 and B-V colour down to V = 23 have been obtained. These new data, used in combination with lower magnitude photographic data in a wider field, give a strong evidence that the galactic density scale length is rather short (2.5 kpc) and drops abruptly beyond 6 kpc.

Annie C. Robin; Michel Creze; Vijay Mohan

1992-09-04

424

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

425

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

SciTech Connect

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

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

1988-11-01

426

Eccentric disc instability in stellar discs formed from inspiralling gas clouds in the Galactic Centre  

NASA Astrophysics Data System (ADS)

The inspiral of a turbulent molecular cloud in the Galactic Centre may result in the formation of a small, dense and moderately eccentric gas disc around the supermassive black hole (SMBH). Such a disc is unstable to fragmentation and may lead to the formation of young massive stars in the central parsec of the Galaxy. Here we perform high-accuracy direct summation N-body simulations of a ring of massive stars (with initial semimajor axes 0.1 ? a (pc) ? 0.4 and eccentricities 0.2 ? e ? 0.4), subject to the potential of the SMBH, a stellar cusp and the parent gas disc, to study how the orbital elements of the ring evolve in time. The initial conditions for the stellar ring are drawn from the results of previous simulations of molecular cloud infall and disruption in the SMBH potential. While semimajor axes do not evolve significantly, the distribution of eccentricities spreads out very fast (?1 Myr) as a consequence of cusp precession. In particular, stellar orbits with initial eccentricity e > 0.3 (e < 0.3) tend to become even more (less) eccentric, resulting in a bimodal eccentricity distribution. The distribution is qualitatively consistent with that of the massive stars observed in the Galactic Centre's clockwise disc.

Gualandris, Alessia; Mapelli, Michela; Perets, Hagai B.

2012-12-01

427

Vacuum energy and cosmological evolution  

E-print Network

An expanding universe is not expected to have a static vacuum energy density. The so-called cosmological constant $\\Lambda$ should be an approximation, certainly a good one for a fraction of a Hubble time, but it is most likely a temporary description of a true dynamical vacuum energy variable that is evolving from the inflationary epoch to the present day. We can compare the evolving vacuum energy with a Casimir device where the parallel plates slowly move apart ("expand"). The total vacuum energy density cannot be measured, only the effect associated to the presence of the plates, and then also their increasing separation with time. In the universe there is a nonvanishing spacetime curvature $R$ as compared to Minkowskian spacetime that is changing with the expansion. The vacuum energy density must change accordingly, and we naturally expect $\\delta\\Lambda\\sim R\\sim H^2$. A class of dynamical vacuum models that trace such rate of change can be constructed. They are compatible with the current cosmological d...

Sola, Joan

2014-01-01

428

Cold cathode vacuum gauging system  

DOEpatents

A vacuum gauging system of the cold cathode type is provided for measuring the pressure of a plurality of separate vacuum systems, such as in a gas centrifuge cascade. Each casing is fitted with a gauge tube assembly which communicates with the vacuum system in the centrifuge casing. Each gauge tube contains an anode which may be in the form of a slender rod or wire hoop and a cathode which may be formed by the wall of the gauge tube. The tube is provided with an insulated high voltage connector to the anode which has a terminal for external connection outside the vacuum casing. The tube extends from the casing so that a portable magnet assembly may be inserted about the tube to provide a magnetic field in the area between the anode and cathode necessary for pressure measurements in a cold cathode-type vacuum gauge arrangement. The portable magnetic assembly is provided with a connector which engages the external high voltage terminal for providing power to the anode within in the gauge tube. Measurement is made in the same manner as the prior cold cathode gauges in that the current through the anode to the cathode is measured as an indication of the pressure. By providing the portable magnetic assembly, a considerable savings in cost, installation, and maintenance of vacuum gauges for pressure measurement in a gas centrifuge cascade is realizable.

Denny, Edward C. (Knoxville, TN)

2004-03-09

429

Technical specification for vacuum systems  

SciTech Connect

The vacuum systems at the Stanford Linear Accelerator Center (SLAC) are primarily of all-metal construction and operate at pressures from 10/sup -5/ to 10/sup -11/ Torr. The primary gas loads during operation result from thermal desorption and beam-induced desorption from the vacuum chamber walls. These desorption rates can be extremely high in the case of hydrocarbons and other contaminants. These specifications place a major emphasis on eliminating contamination sources. The specifications and procedures have been written to insure the cleanliness and vacuum integrity of all SLAC vacuum systems, and to assist personnel involved with SLAC vacuum systems in choosing and designing components that are compatible with existing systems and meet the quality and reliability of SLAC vacuum standards. The specification includes requirements on design, procurement, fabrication, chemical cleaning, clean room practices, welding and brazing, helium leak testing, residual gas analyzer testing, bakeout, venting, and pumpdown. Also appended are specifications regarding acceptable vendors, isopropyl alcohol, bakeable valve cleaning procedure, mechanical engineering safety inspection, notes on synchrotron radiation, and specifications of numerous individual components. (LEW)

Khaw, J. (ed.)

1987-01-01

430

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

431

Fragmenting protostellar discs: properties and observational signatures  

NASA Astrophysics Data System (ADS)

Using numerical hydrodynamic simulations, we study the gravitational fragmentation of an unstable protostellar disc formed during the collapse of a pre-stellar core with a mass of 1.2 M?. The forming fragments span a mass range from about a Jupiter mass to very low mass protostars and are located at distances from a few tens to a thousand au, with a dearth of objects at ? 100 au. We explore the possibility of observational detection of the fragments in discs viewed through the outflow cavity at a distance of 250 pc. We demonstrate that one hour of integration time with the Atacama Large Millimeter/sub-millimeter Array (ALMA) is sufficient to detect the fragments with masses as low as 1.5MJup at orbital distances up to 800 au from the protostar. The ALMA resolution sets the limit on the minimum orbital distance of detectable fragments. For the adopted resolution of our simulated ALMA images of 0.1 arcsec, the fragments can be detected at distances down to 50 au. At smaller distances, the fragments usually merge with the central density peak. The likelihood for detecting the fragments reduces significantly for a lower resolution of 0.5 arcsec. Some of the most massive fragments, regardless of their orbital distance, can produce characteristic peaks at ? 5 ?m and hence their presence can be indirectly inferred from the observed spectral energy distributions of protostars.

Vorobyov, Eduard I.; Zakhozhay, Olga V.; Dunham, Michael M.

2013-08-01

432

Turbulence and its parameterization in accretion discs  

E-print Network

Accretion disc turbulence is investigated in the framework of the shearing box approximation. The turbulence is either driven by the magneto-rotational instability or, in the non-magnetic case, by an explicit and artificial forcing term in the momentum equation. Unlike the magnetic case, where most of the dissipation occurs in the disc corona, in the f