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PubMed2004

Active control of radiation from a piston set in a rigid sphere.

Active control of the sound radiated from a piston set in a rigid sphere with a set of control point sources around is considered in this paper, where the scattering sound field of the control sound from the rigid sphere has been taken into account to minimize the total radiated sound power. Analytic results of the sound power are obtained and numerical simulations show that it is possible to reduce the radiation from a small piston set in a rigid sphere similar to the size of a human head up to a certain frequency. It is found that the introduction of the scattering object makes significant differences from the active control without scattering objects. This being the case, the scattering object makes the active noise control easier. To increase the global reduction of sound-power output, the optimal number and locations of the control sources and the optimal number and locations of error sensors are discussed. Finally, experiments with one control source and one error sensor around a head simulator have been carried out to verify the simulation results.

Acoustics↗
PubMed2006

Effects of the inclination of a rigid wall on the free vibration characteristics of acoustic modes in a trapezoidal cavity.

The coupling between rigid-walled modes of a rectangular cavity (RC modes) is used to obtain the shapes and resonance frequencies of rigid-walled modes of a trapezoidal cavity (TC modes) with an inclined rigid wall. A method is established to identify the TC modes, where the modes can be defined to evolve from individual RC modes. The wall inclination generates two coupling mechanisms, namely, the local coupling where the RC modes couple at the inclined wall, and the global coupling where the RC modes couple throughout the trapezoidal volume. The latter arises from the nonorthogonality of the RC modes in the trapezoidal volume. Both couplings are selective that only RC modes with the same number of nodes in the direction perpendicular to the inclination are coupled to each other. For small inclinations, each TC mode possesses the distorted shape of the RC mode that evolves it. When the inclination is increased, the TC-mode shape becomes complicated and unrecognizable, and extrema can also exist in the resonance frequency of the TC mode. These behaviors are determined by the behaviors of the local and global couplings of the RC mode. This paper provides an understanding of how the free vibration characteristics of TC modes change with the inclination and what determines these changes.

Journal Article↗
PubMed1999

Comparison of electrohydraulic lithotripters with rigid and pressure-release ellipsoidal reflectors. II. Cavitation fields.

Dramatically different cavitation was produced by two separate acoustic pulses that had different shapes but similar duration, frequency content, and peak positive and negative pressure. Both pulses were produced by a Dornier HM-3 style lithotripter: one pulse when the ellipsoidal reflector was rigid, the other when the reflector was pressure release. The cavitation, or bubble action, generated by the conventional rigid-reflector pulse was nearly 50 times longer lived and 3-13 times stronger than that produced by the pressure-release-reflector pulse. Cavitation durations measured by passive acoustic detection and high-speed video agreed with calculations based on the Gilmore equation. Cavitation intensity, or destructive potential, was judged (1) experimentally by the size of pits in aluminum foil detectors and (2) numerically by the calculated amplitude of the shock wave emitted by a collapsing bubble. The results indicate that the trailing positive spike in the pressure-release-reflector waveform stifles bubble growth and mitigates the collapse, whereas the trough after the positive spike in the rigid-reflector waveform triggers inertially driven growth and collapse. The two reflectors therefore provide a tool to compare effects in weakly and strongly cavitating fields and thereby help assess cavitation's role in lithotripsy.

Acoustics↗
PubMed1985

The rigid spine syndrome--a myopathy of uncertain nosological position.

Four patients meeting the clinical criteria of the rigid spine syndrome are presented; they are one girl with a positive family history and three boys. Clinical and histological findings are discussed in relation to the 14 cases of rigid spine syndrome reported in the literature. The delineations of the syndrome from other benign myopathies with early contractures are discussed suggesting that the rigid spine syndrome probably does not represent a single nosological entity.

Adolescent↗
PubMed1992

The role of rigid oesophagoscopy in oesophageal carcinoma.

The efficacy and safety of rigid oesophagoscopy in diagnostic and therapeutic settings in a consecutive series of 404 patients with oesophageal carcinoma were studied and compared to that for flexible oesophagoscopy in the same group. In addition, we examined the same parameters in a smaller group who had undergone radiotherapy with subsequent malignant stricturing. We performed 328 rigid procedures and 118 flexible procedures in a single regional surgical referral unit over a 7 year period. The combined perforation rate was 1.3%, with an overall mortality of 1% from 446 procedures. We conclude that rigid oesophagoscopy in the presence of carcinoma retains an important diagnostic and therapeutic role which can be achieved with low incidence of perforation in high-risk patients.

Dilatation↗
PubMed2007

Evaluation of a laryngoscope and a rigid endoscope for the examination of the oral cavity of small mammals.

The oral cavities of 65 rabbits, 35 chinchillas, 38 guinea pigs, 19 degus and 13 prairie dogs suffering from a lack of appetite, hypersalivation, moist dermatitis, swelling of the lower jaw or mild exophthalmos were examined with a paediatric laryngoscope and rigid endoscope. The laryngoscope was safe and satisfactory for a preliminary examination, but changes in the less accessible caudal parts of the cavity could not be identified precisely. A rigid endoscope with 30 degrees optics made it possible to examine all parts of the oral cavity and oropharynx, and make detailed observations of surface lesions on the premolar and molar teeth and the mucosal surface of the gingiva, tongue and hard palate; endoscopy with 70 degrees optics provided an excellent view of the occlusal tooth surfaces, tooth crowns, and buccal mucosa. The collection of biopsy samples, the removal of foreign objects and the correction of malocclusions were greatly simplified by the use of the endoscope owing to the clear visualisation of the procedures, and the risk of injury was minimised. The examinations with a laryngoscope were made effectively on animals that were manually restrained, but a thorough examination with a rigid endoscope required the animals to be anaesthetised.

Anesthesia↗
PubMed1992

Mechanism preventing backflow from the canine corpora cavernosa to arteries in the rigid phase of penile erection.

The present study was performed in dogs to determine the site preventing the backflow from the corpus cavernosum to the arterial vessels when the corporeal pressure rises more than the systemic pressure (rigid phase). We confirmed a great gradient (325 +/- 81 mm Hg, mean +/- SD) between the corporeal pressure and the deep arterial pressure; the latter was measured at the distal point over the tunica albuginea, namely within the corpus cavernosum. This finding indicated that the mechanism preventing the arterial backflow existed within the corpus cavernosum. This assumption was supported by our light-microscopic findings that the helicine arteries were closed in the rigid phase, whereas they were dilated when the corporeal pressure was lower than the systemic pressure (tumescence/full erection phase). The results suggest that the helicine arteries play an essential role in the prevention of the arterial backflow in the rigid phase.

Animals↗
PubMed1993

The interaction of luminance, velocity, and shape information in the perception of motion transparency, coherence, and non-rigid motion.

The perception of luminance transparency for superimposed patterns depends on how luminance, figural, and topological conditions are simultaneously satisfied. Motion transparency or coherence for two superimposed patterns, which correspond to the perception of both patterns moving across one another or to the perception of compound motion of the regions of pattern intersection, depends on the relation between the local velocity, luminance, and shape information. This study analyzes how luminance, shape, and local velocity interact in the perception of motion transparency and coherence. Psychophysical experiments done with sinusoidally modulated bar patterns are presented which show that the perception of motion transparency or coherence can be described as the result of the interaction of two integration modules: the velocity-luminance and the velocity-shape processes. The velocity-luminance process describes the integration of the local velocity with luminance information. When the luminance transparency rules are satisfied this process always generates the perception of motion transparency independently of the shape or contour information. On the other hand, when the luminance transparency rules are violated one can either perceive motion coherence or non-rigid motion; one perceives motion coherence when the patterns have small or zero amplitude, and non-rigid motion when the patterns have large amplitude. The velocity-shape process describes the integration of local velocity with shape information, and this depends on the relation between the error in the extraction of the local velocity and the magnitude of the contour amplitude. As a result of these experiments it is conjectured that the velocity-luminance and the velocity-shape processes do interact constructively or destructively. The constructive interaction occurs when the luminance transparency rules are satisfied. The destructive interaction occurs when the luminance transparency rules are violated, and such that, although the patterns contain sufficient shape information to solve the aperture problem and therefore generate the perception of motion transparency, one perceives non-rigid motion. This shows that global information describing the stratification of superimposed patterns can affect the integration of local velocity information with, for example, shape information, and this is not described by current motion theories.

Form Perception↗
PubMed2003

Topographical thickness of the epithelium and total cornea after overnight wear of reverse-geometry rigid contact lenses for myopia reduction.

PURPOSE: To investigate topographical thickness changes of the epithelium and total cornea measured with optical coherence tomography (OCT) after overnight wear of rigid gas-permeable lenses. METHODS: Reverse geometry design CRT (Dk=100) rigid (test) lenses (Paragon Vision Sciences, Mesa, AZ) were randomly fitted on one eye of each of 20 neophyte subjects (mean age, 24.6 +/- 2.7 years) and the other eye was fitted with an alignment tricurve rigid lens of the same material (control). Epithelial and total corneal thickness was measured at intervals of 10 degrees across a 10-mm zone of the horizontal meridian of the cornea, before and after overnight wear. Refractive error was measured with an autorefractor. These measurements were repeated 20 and 60 minutes and 3, 6, and 12 hours after lens removal. RESULTS: After one night of lens wear, myopia decreased in the test eye by 1.18 +/- 0.81 D, which was significantly different from baseline (P<0.001). No significant change was found in the control eye. Twelve hours after removal, two thirds of the myopic reduction was still present. Different topographical swelling patterns were induced by the two lens designs, with greatest swelling occurring in the center with the control lens and in the midperiphery with the test lenses (polynomial regression: P<0.005). Significantly greater central corneal swelling was found with the control lens than the test lens (6.9% +/- 3.1% vs. 4.9% +/- 2.0%, respectively, P=0.006). The effect on epithelial thickness differed between lenses and depended on both position and time (F(48,912)=2.3; P=0.000). Immediately after removal of the test lens, the central epithelium was 5.1% +/- 4.5% thinner than baseline, and all other locations (P<0.005 post hoc tests) and the epithelium in the midperiphery showed significant thickening (1.9% on the temporal side and 2.4% on the nasal side, both P<0.006 compared with the baseline). There were no significant changes in epithelial thickness with the control lens during the study period (post hoc tests: P>0.05). CONCLUSIONS: The optical coherence tomograph is a sensitive instrument that can detect small changes in epithelial and corneal thickness across the entire cornea. Topographical thickness changes of the epithelium and total cornea induced by one night of reverse-geometry lens wear appear to be associated with the decrease of myopia.

Adult↗
PubMedDate not supplied

Neodymium:YAG laser fiber steering device for carbon dioxide laser rigid bronchoscope set.

A steering device for the Nd:YAG laser fiber to be used in conjunction with the rigid carbon dioxide laser bronchoscope set has been designed. This device inserts into the proximal end of the rigid bronchoscope and has the ability to accept a rigid optical telescope and the Nd:YAG laser fiber, and to evacuate smoke from the operative field.

Bronchoscopes↗
PubMed1993

Rigid bronchoscopy balloon catheter dilation for bronchial stenosis in infants.

Stenosis of the tracheobronchial tree can be a life-threatening problem. Management options for symptomatic stenosis include serial dilation, cryotherapy, laser resection, and open surgical correction. Recently, balloon angioplasty catheters have been used to dilate stenotic airway segments. The experience in infants is limited and has for the most part utilized guide wires and fluoroscopy for balloon placement. We present two infants with symptomatic bronchial stenosis who underwent endoscopic angioplasty balloon catheter dilation. Operative technique involved catheter placement under direct vision with a rigid bronchoscope. Catheters (6F) with 8-mm-diameter balloons were used. Balloon expansion was controlled with a hand-held manometer. Both infants demonstrated significant lumen size improvement intraoperatively and marked clinical improvement postoperatively, substantiated by endoscopy and radiographs. One infant has required one repeat dilation and has subsequently been asymptomatic. The other infant has had no further respiratory problems. Our technique, using a rigid bronchoscope with direct visualization of catheter placement, obviates the need for guide wires and C-arm fluoroscopy as previously described. Endoscopic placement enables direct visualization of balloon position, and fine adjustments are possible if further dilation is necessary. Rigid bronchoscopic balloon catheter dilation can be a successful technique for bronchial stenosis and should be considered prior to attempting more invasive surgical correction.

Bronchial Diseases↗
PubMed2004

Initial fixation strength of flexible all-inside meniscus suture anchors in comparison to conventional suture technique and rigid anchors: biomechanical evaluation of new meniscus refixation systems.

BACKGROUND: The newest generation of meniscus repair devices is designed to combine the benefits of the all-inside technique with the biomechanical properties of sutures. HYPOTHESIS: New flexible all-inside suture anchors have better fixation strength than rigid anchors, but there is no difference when compared to conventional horizontal and vertical mattress sutures. STUDY DESIGN: Controlled laboratory study. METHODS: In fresh-frozen bovine menisci, initial fixation strength, stiffness, and failure mode of different meniscus fixation techniques (FastT-Fix, RapidLoc, Meniscus Arrow, horizontal and vertical 2.0 Ethibond sutures) were evaluated in a computer-based materials testing machine at a rate of 12.5 mm/sec. RESULTS: The vertical and horizontal FastT-Fix suture anchors were the strongest devices with regard to pullout strength, with no significant difference compared to the vertical 2-0 Ethibond sutures. Horizontal sutures, Meniscus Arrow, and RapidLoc had significantly lower pullout strength. Vertical and horizontal FastT-Fix suture anchors showed significantly higher stiffness than the other devices. CONCLUSIONS: Biomechanical properties of flexible all-inside meniscus anchors (FastT-Fix) are comparable to conventional vertical suture techniques. Characteristics of the flexible RapidLoc are comparable to rigid anchors (Meniscus Arrow). CLINICAL RELEVANCE: From the biomechanical point of view, flexible all-inside meniscus refixation devices are an alternative to conventional suture techniques and rigid meniscus anchors.

Animals↗
PubMed2003

Rigid bronchoscopy induces bacterial translocation: an experimental study in rats.

Bronchoscopy has the potential to propagate infections. Bacterial translocation was hypothesised to be the cause of infections observed following bronchoscopy and this study was designed to assess the risk of bacterial translocation following rigid bronchoscopy in rats. A total of 30 rats were evaluated. The study group (n=15) underwent rigid bronchoscopy. Arterial blood gas analysis was performed in all rats. Blood and tissue cultures from the ileum, caecum, mesenteric lymph nodes, liver, spleen, mediastinal lymph nodes and lung were obtained 24 h following bronchoscopy. Bacterial translocation to the mesenteric lymph nodes was found in seven of 15 rats (46.7%) that underwent bronchoscopy, compared with none of the controls. Of the seven positives, three rats (42.8%) also demonstrated other organ involvement, such as the liver and spleen. Escherichia coli, Salmonella typhymirium, S. enteritidis and Pseudomonas spp. were found as translocating bacteria. In the study group, pH and arterial oxygen tension were significantly lower and arterial carbon dioxide tension was higher, compared with controls. This study shows that rigid bronchoscopy may induce bacterial translocation in rats. Further investigations aimed at understanding the clinical consequences of this phenomenon are warranted.

Animals↗
PubMed1997

Use of the paediatric bronchoscope, flexible and rigid, in 51 European centres.

We have undertaken a survey to establish current practices and differences in the use of bronchoscopes in children in European centres. A questionnaire was sent to all 220 members of the Paediatric Assembly of the European Respiratory Society (ERS). The questions concerned the following points: indications for bronchoscopy; site of bronchoscopy; type of sedation; any oxygen supplementation during the procedure; number of procedures performed in the previous 12 months; number of procedures performed in the neonatal intensive care unit; number of bronchoalveolar lavages (BALs); side-effects during and after the procedures; and diagnostic yield. Fifty one European centres (40.8% of the European centres contacted) took part in the study. A total of 7,446 bronchoscopies had been performed in the last 12 months: 4,587 using the flexible bronchoscope and 2,859 using the rigid bronchoscope. At centres using only the fibreoptic bronchoscope, the most frequent indication was "recurrent/persistent pneumonia" (17%); at centres using only the rigid bronchoscope, it was "foreign body inhalation" (36.7%); at centres using both methods, the most frequent indication was "other indications" (23.9%). In 12 months, 2,231 BALs were performed: 1,419 in immunocompetent children and 812 in immunocompromised patients. In centres using only the fibreoptic bronchoscope, the highest yield was for "stridor" (81%); in centres using only the rigid bronchoscope, the highest yield was for "persistent atelectasis" (68%); and in centres using both instruments, it was for "foreign body inhalation" (93%). The results of the study suggest that bronchoscopy in children is now a well-established procedure at several European centres, while others are just beginning to use this technique.

Bronchoalveolar Lavage Fluid↗
PubMed1993

Controlled trial of a semi-rigid bandage ('Scotchrap') in patients with ankle ligament lesions.

A randomized, controlled, parallel-group study was performed to compare the clinical efficacy of a semi-rigid bandage ('Scotchrap') with the standard adhesive tape treatment for ankle ligament injuries. The semi-rigid bandage support wrap consists of a knitted fibreglass fabric impregnated with a polyurethane resin. The cotton stockinet and the synthetic cast padding are used for protection of pressure points and any bony prominences. Prior to application, the 'Scotchrap' must be soaked in water after which it is applied in a way similar to that used for a plaster of paris bandage. The finished bandage remains elastic, allowing normal dorsal and plantar flexion of the foot, but preventing inversion and eversion, and pronation and supination. At rest, the bandage always redresses the immobilized ankle into the neutral position. One hundred and thirty-six patients were included in the study. The semi-rigid bandage group comprised 59 patients and the tape group had 57 patients. These two groups were statistically comparable. The intake questionnaire included a general and a specific anamnesis form as well as a physical examination form. Follow-up data were recorded every 2 weeks. After termination of the treatment, the patients evaluated treatment efficacy. Statistical analysis of 126 items per patient with chi 2-tests (p < or = 0.05) and Fisher's exact tests (p < or = 0.05) revealed no statistical significant differences in treatment result. The patient assessments of treatment efficacy of both types of bandage were also comparable. Both types of bandage gave sufficient stability (98%; p < 0.005) and were equally effective.(ABSTRACT TRUNCATED AT 250 WORDS)

Adhesives↗
PubMed1980

Fluid and rigid boundaries of paranoid and nonparanoid schizophrenics on a role-playing task.

The concepts of fluid and rigid boundaries were assessed in an improvisational role-playing task in an attempt to differentiate paranoid from nonparanoid schizophrenics. Thirty-one schizophrenic patients divided into paranoid, intermediate, and nonparanoid groups were given an improvisational role-playing task. The resulting scenes were analyzed by Fluid Boundary and Rigid Boundary scales, which were developed on the basis of specific aspects of the physical and verbal representations of characters, objects, and settings. The hypothesis that variations in the disruption or emphasis of representational boundaries differentiate paranoid and nonparanoid symptomatology received support. Paranoid schizophrenics scored higher on the Rigid Boundary scale, i.e erecting and/or exaggerating physical and interpersonal boundaries; and nonparanoid schizophrenics scored higher on Fluid Boundary scale, i.e. showing fused and fluid representations of characters, objects, and settings. Improvisational role-playing seems to hold promise as a medium with diagnostic value.

Adolescent↗
PubMed2006

Simultaneous image-guided and endoscopic navigation without rigid cranial fixation: application in infants: technical case report.

OBJECTIVE AND IMPORTANCE: Infants and young children demonstrate a variety of intraventricular and periventricular lesions. Endoscopy has proven useful in the treatment of many of these lesions, but its benefit is limited if it is applied to complex loculated cysts or if the disease is concealed by normal ependymal boundaries. In adults and older children, endoscopy can be augmented by the simultaneous use of frameless stereotaxy, but this combined modality has not been possible in infants and young children without rigid cranial fixation. We describe a method of achieving simultaneous stereotactic and endoscopic navigation in infants and young children by using a pinless, frameless stereotactic assembly. CLINICAL PRESENTATION: The first patient was a 6-week-old boy with macrocephaly and a bulging fontanelle. Computed tomographic and magnetic resonance imaging revealed a complex arachnoid cyst and obstructive hydrocephalus. The second patient was a 7-month-old, ex-premature (27-wk gestational age) boy who developed posthemorrhagic hydrocephalus. He underwent multiple shunt revisions, one of which was complicated by enterococcal ventriculitis. Despite bilateral ventriculoperitoneal shunts, he developed increasing head circumference, listlessness, and irritability. Imaging revealed an enlarged, multiloculated, and asymmetric ventricular system. INTERVENTION: Simultaneous image-guided and endoscopic neuronavigation was implemented in both patients. Before the procedure, a cranial reference arc was secured to the outer table of the cranium through a small incision adjacent to the operative field. After the stereotactic apparatus was registered, the software was used to plan a trajectory for the approach. A burr hole was then made, and a rigid 6-mm endoscope was inserted for direct visualization. Once advanced past the endoscopic port tip, the electromagnetic coil stylet was used to stereotactically track position and identify areas for fenestration, biopsy, and catheter insertion. CONCLUSION: Endoscopic views of complex hydrocephalus and arachnoid cysts alone are often difficult to interpret. Simultaneous image-guided and endoscopic neuronavigation may be advantageous in the management of complex cases that are anatomically related to the ventricular system in infants for whom rigid cranial fixation could lead to increased procedure-related morbidity.

Brain Diseases↗
PubMed2003

Aquatic turning performance by the whirligig beetle: constraints on maneuverability by a rigid biological system.

Turning performance is constrained by morphology, where the flexibility of the body and the mobility and position of the control surfaces determine the level of performance. The use of paddling appendages in conjunction with the rigid bodies of aquatic arthropods could potentially limit their turning performance. Whirligig beetles (Coleoptera: Gyrinidae) are rigid-bodied, but these aquatic insects can swim rapidly in circular patterns. Turning performance of swimming whirligig beetles (Dineutes horni) was assessed by videotaping beetles in a small (115 mm diameter) arena at 500 frames s(-1) and 1000 frames s(-1). Curved trajectories were executed as continuous powered turns. Asymmetrical paddling of the outboard legs was used to power the turn. Turns were produced also by abduction of the inboard elytra and vectored thrust generated from sculling of the wing at 47.14 Hz. The abducted elytra increased drag and acted as a pivot. Swimming speeds varied from 0.06 m s(-1) to 0.55 m s(-1) (4.7-44.5 L s(-1)). Relative minimum radius was 24% of body length. Maximum rate of turn was 4428 degrees s(-1) with maximum centripetal acceleration of 2.86 g. Turning radius was weakly associated with swimming velocity, although minimum values of the radius showed no correlation with velocity. Turning rate was also related indirectly to radius and directly to centripetal acceleration. Compared to vertebrates with flexible bodies, the relative turning radius of whirligig beetles is constrained by a rigid body and use of drag-based propulsive mechanisms. However, these mechanisms permit continuous turning, and the size of the beetle permits higher turn rates with lower centripetal accelerations.

Animals↗