Vacuum Disc Research Articles

Spinning superconducting electrovacuum soliton

In nonlinear electrodynamics coupled to general relativity and satisfying the weak energy condition, a spherically symmetric electrically charged electrovacuum soliton has obligatory de Sitter center in which the electric field vanishes while the energy density of electromagnetic vacuum achieves its maximal value. De Sitter vacuum supplies a particle with the finite positive electromagnetic mass related to breaking of space-time symmetry from the de Sitter group in the origin. By the G\"urses-G\"ursey algorithm based on the Newman-Trautman technique it is transformed into a spinning electrovacuum soliton asymptotically Kerr-Newman for a distant observer. De Sitter center becomes de Sitter equatorial disk which has both perfect conductor and ideal diamagnetic properties. The interior de Sitter vacuum disk displays superconducting behavior within a single spinning soliton. This behavior found for an arbitrary nonlinear lagrangian ${\cal L}(F)$, is generic for the class of regular spinning electrovacuum solutions describing both black holes and particle-like structures.

Symptomatic Spinal Epidural Gas-Containing Cystic Lesions: Reports of 2 Cases

Symptomatic spinal epidural gas-containing cystic lesion is a rare clinical disease entity. We recently experienced two cases of symptomatic epidural gas-containing cysts that were the main cause of the patients’ radiculopathy and the cysts were removed surgically. These lesions were actually gas containing ruptured disc herniations from the vacuum discs at the same level. We report herein on the radiological findings along with conducting a review of the related literature.

The Changes of Adjacent Segments after Long Segment Posterolateral Fusion: Comparative Study of 3 year versus over the 7 year Follow-up Patients

Purpose: To compare the 3 year and over the 7 year results after long-segment posterolateral fusion and to analyze the changes of adjacent segments and the changes according to the segmental lordosis angle of the fusion segments. Materials and Methods: A retrospective review was carried out 62 patients of long segment fusion for 7 years follow up and compared that of the 3 year and over the 7 year results. The changes of adjacent segments were evaluated by simple radiography for disc space narrowing, traction spur, endplate sclerosis and vacuum phenomenon. In last follow-up, segmental lordosis angle of fusion level was evaluated by Gelb,s criteria and clinical results were analyzed by Katz,s classification. Results: In the changes of adjacent segments, disc space narrowing was increased 27.4% to 38.7%, traction spur was 22.6% to 35.5%, endplate sclerosis was 19.4% to 32.2% and vacuum phenomenon was 8.1% to 12.9%. The changes of adjacent segments were observed that from 3.4% to 20.7% in physiologic group and from 33.3% to 90.9% in un-physiologic group. The clinical results showed 83.9% satisfaction and 16.1% un-satisfaction.Conclusion: In long-term follow up of long-segment posterolateral fusion, physiologic segmental lordosis angle should be preserved for decrease of changes of adjacent segments in long-segment posterolateral fusion.

Plans for a new ECRH system at ASDEX upgrade

A new ECRH system is being constructed for ASDEX Upgrade with a total power of 4 MW, generated by four gyrotrons, and a pulse duration of 10 s. Particular features are the use of gyrotrons which can work at various frequencies in the range 104–140 GHz and correspondingly broad band transmission components. The transmission will be at normal air pressure, and at the torus we will have a tunable double disk vacuum window. A further aim is the installation of fast moveable mirrors for a feedback controlled localized power deposition.

Gas-filled intradural cyst of the lumbar spine

The authors describe the case of a gas-filled intradural cyst of the lumbar spine that caused radicular pain. The cyst was similar to an intervertebral vacuum disc phenomenon and the cystic gas collection resembled the features of gas-containing pseudocyst, herniated intradiscal gas, or free gas, all of which have been found in the epidural space.

Vacuum disk and facet phenomenon in a dog with cauda equina syndrome

A 7-year-old castrated male Rottweiler was evaluated for an 18-month history of bilateral hind limb lameness, signs of pain on rising, and mild ataxia. A gas-filled lumbosacral disk space (vacuum disk phenomenon) was revealed by use of computed tomography. Additional smaller gas bubbles were in the periphery of the disk and between the degenerated L5-L6 dorsal articular facets (vacuum facet phenomenon). Vacuum disk and facet phenomena have been described in humans with degenerative disk and vertebral articular facet joint disease; gas attracted from surrounding tissues accumulates within clefts of the degenerated disk or in unstable facet joints. Vacuum disk phenomenon has been reported in dogs and indicates degenerative disk disease. The phenomenon is more commonly observed by use of computed tomography, compared with conventional radiography, and can be elicited by hyperextension of the vertebral column.

Can imaging findings help differentiate spinal neuropathic arthropathy from disk space infection? Initial experience.

To determine if radiographic, computed tomographic (CT), and magnetic resonance (MR) imaging findings can help differentiate spinal neuropathic arthropathy from disk space infection. Imaging studies in 33 patients were evaluated, including 14 patients with spinal neuropathic arthropathy (12 radiographic, seven CT, and six MR studies) and 19 with disk space infection (13 radiographic, nine CT, and 12 MR studies). Potential imaging discriminators, including endplate sclerosis or erosions, osteophytes, spondylolisthesis, facet involvement (narrowing or erosions), vacuum disk, paraspinal soft-tissue mass, joint disorganization, and osseous joint debris, were recorded, as were MR imaging signal intensity and gadolinium-enhancement characteristics. The most helpful findings for diagnosis of spinal neuropathic arthropathy were vacuum disk on radiographs and CT images, debris on radiographs and CT and MR images, disorganization on radiographs and CT and MR images, facet involvement on radiographs and CT and MR images, spondylolisthesis on CT and MR images, diffuse signal intensity patterns in vertebral bodies on MR images, and rim enhancement of disks on gadolinium-enhanced MR images. Findings that were not helpful included endplate sclerosis and erosions, osteophytes, paraspinal soft-tissue mass, and decreased disk height. Vacuum disk, facet involvement, vertebral body spondylolisthesis, joint disorganization and debris, and gadolinium-enhancement patterns of vertebral bodies and disks may help differentiate spinal neuropathic arthropathy from infection.

High Signal Intensity on T1-Weighted MR Image Related to Vacuum Cleft in the Intervertebral Disk: Clinical and Phantom Study

Purpose: To determine the possible mechanism by which an area of high signal intensity appears on T1-weighted MR images adjacent to a vacuum cleft in intervertebral disks. Materials and Methods: We analyzed a total of 14 disks in nine patients in whom a vacuum cleft with T1-signal hyperintensity was observed. Lesions were present from T11-12 to L5-S1 using a 1.5-T whole-body imager, sagittal spine-echo T1-weighted and gradient-echo images (flip angle, 20 and 60) were obtained. In order to identify the vacuum cleft, using plain radiographs in all patients and CT scans in two were also ob-tained. A 3% agar-gel block containing empty slits to form a magnetic susceptibility difference, a phantom was designed. The air spaces were 1.6 mm in thickness, 25 mm in width, and 20 to 25 mm in depth with 1.6-mm spacing. Results: In all patients, vacuum clefts were confirmed by plain radiographs and CT scans. At the level containing air, T1-weighted images (both spin-echo and gradient-echo) showed a signal void resulting from the intervertebral disk vacuum cleft. A hyperintense band adjacent to the vacuum cleft was, however, observed. A gradient-echo image with a 60 flip angle showed a brighter signal intensity than one with a 20 angle. Our phantom study gave the same results. Conclusion: The magnetic susceptibility artifact may be responsible for the T1-signal hyperintensity observed adjacent to the vacuum cleft in intervertebral disks. In addition, in order to generate signal hyperintensity, the desiccating disk material must contain a certain amount of water molecules.

Application of magnetic forces to disk vacuum filtration in the laboratory and plant

The use of magnetic forces to enhance solid/liquid separation of magnetic pulps in a laboratory drum vacuum filter has previously been demonstrated to have potential, especially for steel industry waste materials and iron ore industry pulps. However, the novel process has been used to date in only limited applications, and has only been demonstrated on a bench top scale. This paper details the extension of magnetic vacuum filtration to a laboratory disk filter, and subsequently to an industrial vacuum disk filter. The design of the laboratory disk filter and the evaluation of magnetic field strengths and gradients is described, and results presented for the treatment of steelmaking and magnetite pulps. The modification of an industrial disk filter is then detailed and results presented for tests on the dewatering of pulps containing finely ground magnetite. The research results indicate that magnetic forces can be successfully applied to a disk filter with capacity enhancements of 30–50% being found for the treatment of steelmaking sludges containing approximately 20% magnetics, and for 50/50 magnetite/quartz mixtures. The filter cake was found to discharge easily from the disk despite the magnetic field, but cake moistures did increase due to the formation of magnetic flocs entrapping water. The magnetically modified industrial disk filter gave increased cake rates of over 100%, and the air pressure discharge had no difficulties removing the filter cake in the presence of the magnetic field. Cake moisture contents were slightly higher in the presence of a magnetic field.

Vacuum disc: frequency of high signal intensity on T2-weighted MR images.

To determine the frequency of lumbar intervertebral disc vacuum clefts demonstrating high signal intensity on T2-weighted magnetic resonance (MR) images. MR images of the lumbosacral spine of 100 patients with radiographic evidence of the lumbar intervertebral disc vacuum phenomenon were retrospectively studied for the signal pattern of the intervertebral disc vacuum clefts. Twelve of the reviewed MR studies demonstrated high signal intensity of the vacuum clefts on long TR and TE sequences while the remaining 88 cases demonstrated the vacuum as signal void on both T1- and T2-weighted images. It is concluded that vacuum clefts not infrequently show high T2 signal intensity.

The Intravertebral Vacuum Phenomenon ("Vertebral Osteonecrosis")

Retrospective cohort. To compare the prevalence of the association between contiguous intervertebral disc and vertebral collapses with or without an intravertebral vacuum phenomenon. The mechanism of occasional gas accumulation within some vertebral collapses is poorly known. The current hypothesis is that this phenomenon is indicative of bone ischemia. In fact, avascular necrosis as the main pathologic event remains speculative, and should not explain per se the presence of gas within a vertebral body. Comparison of the prevalence of intervertebral disc vacuum phenomenon adjacent to the affected vertebral body in 23 cases of intravertebral vacuum phenomenon in 19 patients (intravertebral vacuum phenomenon group) and in 708 osteoporotic collapses without intravertebral vacuum phenomenon in 199 patients (control group). There were no differences in sex and age between the two groups, and all the patients in the intravertebral vacuum phenomenon group had signs of underlying osteoporosis. A vacuum phenomenon in at least one intervertebral disc adjacent to the collapses on radiographs, conventional tomography, computed tomography, or magnetic resonance imaging was found in 19 cases (83%) in the intravertebral vacuum phenomenon group, compared with 13% in the control group (P < 0.0001). Considering plain radiographs only, this association was found in 50% of the intravertebral vacuum phenomenon group and in 9.7% of the control group (P < 0.0001). The intervertebral and intravertebral gaseous collections were connected through a fractured endplate in six cases. The high prevalence of the association of contiguous intervertebral and intravertebral vacuum phenomenon could have implications in the pathogenesis of the intravertebral vacuum phenomenon. We hypothesize that the intravertebral vacuum phenomenon could simply be the result of migration of an intradiscal-gaseous collection through the fractured endplate of some osteoporotic collapses.

Application of a high critical temperature superconductor bearing for high vacuum measurement

A novel and ultrahigh vacuum compatible, high critical temperature superconductor suspension is described in its application to a rotating disc vacuum gauge. The noncontacting and robust suspension comprises a permanent magnet (and attached disc) suspended freely in a vacuum and below a liquid nitrogen cooled YBa2Cu3O7 pellet which is held outside the vacuum chamber. This configuration supersedes a fiber suspension. Molecular torque developed from a high speed disc accelerates the suspended disc and facilitates a measurement of total pressure. The offset of the superconductor suspension (analogous to that of the spinning rotor gauge) is about 5×10−6 mbar, nitrogen equivalent. After 50 h the offset reduced by up to 21% of its initial value. In the range 1.6×10−3–3.6×10−6 mbar, the pressure measured using this device was within ±20% of that measured by a spinning rotor gauge; at lower pressures the agreement with an ionization gauge degraded to ±80%. Improvements in pellet structure reduce internal losses in the bearing and in the offset term, by a factor of 10, and should enable measurements in ultrahigh vacuum.

Performance of a rotating disc vacuum gauge in transitional and viscous flow regimes

The performance of a rotating disc vacuum gauge has been investigated in the transitional flow regime between molecular and viscous flow. This regime is usually described as extending from Knudsen numbers unity to approximately 0.01. A complete knowledge of the behaviour of the gauge under molecular flow conditions assists the interpretation of its behaviour and characteristic edge effects in the transitional flow regime as a combination of viscous and molecular contributions. The results suggest that the transitional regime extends from Knudsen numbers of approximately 1.0 to 0.02. The molecular-viscous intersection point is indicated to be at a Knudsen number of 0.30. The measured value of the viscosity of air at room temperature was 1.74 × 10 −5 Pa s, within 4% of the accepted value. Pressures measured utilising a semiempirical formula show limited agreement with a spinning rotor gauge in the transitional regime.

The dependence of the characteristics of a rotating disk vacuum gauge on disk sizes and rotor speed

The characteristic edge effect loss factor of a rotating disk vacuum gauge has been measured experimentally in hydrogen, helium, nitrogen, and krypton. The results are in good agreement with analytical calculations at low speeds and Monte Carlo calculations at high speeds. The characteristics of the gauge in various unequal size disk configurations measured in nitrogen are also presented.

Lumbar radiculopathy and intraspinal gas

Gas within the spinal canal is uncommon and has been associated with trauma, infection and disc degeneration and vacuum phenomenon. We report a 73-year-old man with a history of intermittent low back pain who developed sharp low back pain with radiation to the left calf and ankle when ambulating or standing. Relief was obtained with sitting or lying down, which led to the clinical impression of spinal stenosis. The neuromuscular exam was unremarkable and no sciatic nerve tension sign was present. Electrodiagnostic studies were consistent with an acute S1 radiculopathy, while a dermatomal somatosensory evoked potential was interpreted as essentially normal. A CT scan showed gas in the left lateral spinal canal at L4-S1. After 2 weeks, spontaneous improvement occurred and the patient resumed normal activities. A repeat CT scan after 0.5 years showed the intraspinal gas was diminished while the L5-S1 disc vacuum phenomenon had worsened and a right disc extrusion occurred. The natural history of intraspinal gas, disc vacuum phenomenon and related complications are discussed.

Intervertebral disk vacuum phenomenon secondary to vertebral collapse: prevalence and significance.

To evaluate the prevalence of the intervertebral vacuum phenomenon in disks adjacent to vertebral collapses of various causes. The authors retrospectively studied 310 consecutive patients who had at least one vertebral collapse. The vacuum phenomena were divided into collapse-related (ie, adjacent to a collapse) and degenerative (ie, not associated with a vertebral fracture) ones. Plain radiography was performed in all patients, and, in addition, conventional tomography, computed tomography, and/or magnetic resonance imaging was performed in 175 patients. Collapse-related vacuum phenomena were seen in 15% of patients with plain radiography and in 21% when all of the imaging modalities were considered. They occurred in association with all of the causes of collapse (ie, osteoporosis, multiple myeloma, metastasis, acute trauma, and vertebral osteomyelitis), although the prevalence was lower in association with metastasis or trauma (P = .008). The occurrence of collapse-related vacuum phenomenon was correlated with age (P = .001) and with the coexistence of degenerative disk-related vacuum phenomenon in the same patient (P = .0002). Occurrence of a vacuum cleft in disks adjacent to a vertebral collapse is common and appears as the second cause of vacuum phenomenon after degenerative disk disease.

The theory of the rotating disc vacuum gauge

The rarefield gas dynamic of momentum transfer from a spinning disc to a stationary coaxial parallel disc is considered in the absence of molecular collisions with a surface tangential momentum accommodation coefficient of unity. The analysis is performed for the case of low and high rotation speeds, with an approximation derived for the intermediate case. Analytical studies are complemented by simulation using a Monte Carlo technique to give accurate results throughout the domain. The results are in excellent agreement with detailed experiments. It is concluded that the resulting rotating disc vacuum gauge can be used as an absolute instrument for measuring pressure in high vacua.

Methods of Filter Cake Removal in Continuous Vacuum Filters

The paper describes the presently used methods of cake removal in disk vacuum filters, and points out some of their drawbacks. A new, unique method elaborated by the author is introduced, and its effectiveness is compared with that of other methods.

Automatic Control of Coal Flotation and Dewatering Processes

Coal preparation plant operators often do not optimize the flotation and dewatering processes. In order for these processes to operate efficiently, the equipment should be adjusted after every change in feed rate or quality. Unfortunately, neglect of the final coal processes causes processing additives and coal to be wasted and in some cases, unnecessary outages of the entire cleaning plant. Consequently, revenues decrease. A control system for the froth flotation and dewatering processes was developed and is now operational in four bituminous coal preparation plants owned by Consolidation Coal Company (CONSOL Inc.). The system controls 1) the flotation tailings ash content via flotation reagent adjustment. 2) the froth cell level by adjusting the tailings dart valve positioning, and 3) the vacuum disc filter level via filter rotational speed and flocculant feed rate adjustments. Central to the system operation is a newly developed sensor. This innovative optoelectronic sensor is used to estimate the amou...

Equipment

Valmet Paper Machinery of Turku, Finland has developed a new filtering method for mechanical dewatering of sludge and suspensions without using expensive heat energy. The product based on this method, called Ecosuc, is similar to a vacuum disk filter and has applications in the chemical and mining industries as well as in metallurgy.