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At least 415 records · Page 23Linked to original sources
PubMed2006

Consequences of increased rigidity in palatal implants for snoring: a randomized controlled study.

OBJECTIVE: Palatal implants have seen an increased role in the treatment of snoring. In this study, we evaluate the safety and possible treatment effect of adding further stiffness to the palate through the use of a more rigid implant. STUDY DESIGN: Randomized double-blind study of 20 patients with primary snoring. Three polyethylene teralphate implants were placed in the soft palate with the patient under local anesthesia. Ten patients received regular implants (rigidity 1.0) and 10 patients received stiffer implants (rigidity 1.8). The patients and their bed partners were followed for 6 months with questionnaires and office visits. A sleep study was performed preoperatively and at the last follow-up. RESULTS: Four of the 10 patients with stiffer implants had 5 partial extrusions in the observation period. There was a nonsignificant reduction in snoring intensity from 8.1 to 6.1 evaluated by the bed partner on a visual analogue scale in this group. No extrusions were seen in the group with regular implants. This group showed a significant reduction in snoring intensity from 7.7 to 4.7. No other major adverse events were observed. CONCLUSIONS AND SIGNIFICANCE: Rigid implants cause short time extrusions with loss of treatment effect. Regular implants reduce palatal snoring intensity with high patient and bed partner satisfaction. EBM RATING: A-1b.

Adult↗
PubMed2000

Effects of semi-rigid arch-support orthotics: an investigation with potential ergonomic implications.

For many years, arch-support orthotics have been prescribed for individuals with discomfort and/or abnormal skeletal alignments in the structures of the lower extremity. Recently there has been an increased interest in promoting semi-rigid orthotics as an ergonomic aid for asymptomatic workers who must stand all day at their workplace. A laboratory study was performed to assess the biomechanical impact of prefabricated semi-rigid orthotics on asymptomatic individuals. Ten subjects wore semi-rigid arch-support orthotics (experimental condition) for two months and flexible polyurethane/Sorbothane shoe inserts (control condition) for two months. Throughout this 18-week testing period, the subjects returned to the lab to perform a battery of assessment tests at regularly scheduled intervals. These tests examined subject strength, standing posture, stability, fatigue effects, and body part discomfort. The results of this study showed no significant changes in the strength, posture, or stability as a function of insert type. The subjects reported a reduction in low-back discomfort along with an increase in foot discomfort during a fatiguing exertion task while wearing the semi-rigid orthotics as compared to the control condition.

Adult↗
PubMed1999

Interactions of elastic and rigid vesicles with human skin in vitro: electron microscopy and two-photon excitation microscopy.

Interactions between vesicle formulations and human skin were studied, in vitro, in relation to their composition and elasticity. The skin ultrastructure was investigated using transmission electron microscopy (TEM), freeze-fracture electron microscopy (FFEM) and two-photon fluorescence microscopy (TPE). The main difference between the vesicle formulations was their elasticity. Elastic vesicle formulations contained bilayer forming surfactants/lipids and single-chain surfactant octaoxyethylenelaurate-ester (PEG-8-L), whereas rigid vesicles contained bilayer surfactants in combination with cholesterol. TEM results showed three types of interactions after non-occlusive application of elastic PEG-8-L containing vesicle formulations on human skin: (1) the presence of spherical lipid structures containing or surrounded by electron dense spots; (2) oligolamellar vesicles were observed between the corneocytes in the upper part of the stratum corneum; and (3) large areas containing lipids, surfactants and electron dense spots were observed deeper down into the stratum corneum. Furthermore, after treatment with vesicles containing PEG-8-L and a saturated C12-chain surfactant, small stacks of bilayers were found in intercellular spaces of the stratum corneum. Rigid vesicles affected only the most apical corneocytes to some extent. FFEM observations supported the TEM findings. Major morphological changes in the intercellular lipid bilayer structure were only observed after treatment with PEG-8-L containing elastic vesicles. TPE showed a distinct difference in penetration pathways after non-occlusive application of elastic or rigid vesicles. After treatment with elastic vesicles, thread-like channels were formed within the entire stratum corneum and the polygonal cell shape of corneocytes could not be distinguished. Fluorescent label incorporated in rigid vesicles was confined to the intercellular spaces of the upper 2-5 micrometer of the stratum corneum and the cell contours could still be distinguished.

Freeze Fracturing↗
PubMed1998

Characterization of the growth of 2D protein crystals on a lipid monolayer by ellipsometry and rigidity measurements coupled to electron microscopy.

We present here some sensitive optical and mechanical experiments for monitoring the process of formation and growth of two-dimensional (2D) crystals of proteins on a lipid monolayer at an air-water interface. The adsorption of proteins on the lipid monolayer was monitored by ellipsometry measurements. An instrument was developed to measure the shear elastic constant (in plane rigidity) of the monolayer. These experiments have been done using cholera toxin B subunit (CTB) and annexin V as model proteins interacting with a monosialoganglioside (GM1) and dioleoylphosphatidylserine (DOPS), respectively. Electron microscopy observations of the protein-lipid layer transferred to grids were systematically used as a control. We found a good correlation between the measured in-plane rigidity of the monolayer and the presence of large crystalline domains observed by electron microscopy grids. Our interpretation of these data is that the crystallization process of proteins on a lipid monolayer passes through at least three successive stages: 1) molecular recognition between protein and lipid-ligand, i.e., adsorption of the protein on the lipid layer; 2) nucleation and growth of crystalline patches whose percolation is detected by the appearance of a non-zero in-plane rigidity; and 3) annealing of the layer producing a slower increase of the lateral or in-plane rigidity.

Annexin A5↗
PubMed2004

Foldable acrylic versus rigid polymethylmethacrylate intraocular lens in combined phacoemulsification and trabeculectomy.

BACKGROUND: Combined trabeculectomy and phacoemulsification is a widely accepted option in treating patients with glaucoma who also have cataracts. Implantation of a foldable intraocular lens (IOL) in cataract surgery has several theoretical advantages. We performed a study to determine the results of combined phacoemulsification and trabeculectomy with mitomycin C and implantation of either a foldable acrylic or rigid polymethylmethacrylate (PMMA) IOL. METHODS: Review of the charts of 58 consecutive patients (60 eyes) who underwent combined phacotrabeculectomy for concomitant cataract and glaucoma at a university-affiliated hospital in Montreal between September 2001 and December 2002. Forty-one eyes received a foldable acrylic lens (3.2-mm-wide incision), and 19 eyes received a rigid PMMA lens (5.2-mm-wide incision). Outcome measures included visual acuity, intraocular pressure (IOP) and postoperative complications. The results in the two groups were compared. RESULTS: There were no differences in baseline characteristics between the two groups. Earlier recovery of visual acuity was noted in the foldable IOL group than in the rigid IOL group (p = 0.013 for the difference at day 7). IOP control was similar in the two groups, as was the incidence of IOP spikes in the early postoperative period. INTERPRETATION: The results suggest that combined phacotrabeculectomy with mitomycin C using a foldable acrylic IOL allows for good postoperative IOP control and earlier visual recovery than the same procedure with insertion of a rigid PMMA lens.

Aged↗
PubMed2002

Objects are individuals but stuff doesn't count: perceived rigidity and cohesiveness influence infants' representations of small groups of discrete entities.

Young infants construct models of the world composed of objects tracked through time and occlusion. To date little is known about the degree to which these models are sensitive to the material make-up of the represented individuals. Two experiments probed 8-month-olds' ability to represent different kinds of entities: rigid, cohesive objects, flexible, cohesive objects, and non-rigid, non-cohesive portions of sand. In Experiment 1, infants represented an array of two rigid, cohesive objects hidden behind a single screen, but failed to represent hidden arrays of two flexible objects or two portions of sand. In Experiment 2, entities were hidden behind two screens instead of one, thereby reducing the information processing demands of the task. In that case, infants succeeded in representing arrays of both types of object stimuli, but again failed to represent the portions of sand. It is argued that (1) the processes by which infants individuate and track entities are sensitive to material kind, (2) rigid cohesive objects occupy a privileged status in this system, and (3) early knowledge about objects and substances has a quantificational aspect.

Cognition↗
PubMed2002

The rigidity of repaired flexor tendons increases following ex vivo cyclic loading.

Transected flexor tendons are typically treated by suture repair followed by rehabilitation that generates repetitive tendon loading. Recent results in an in vivo canine model indicate that during the first 10 days after injury and repair, there is an increase in the rigidity of the tendon repair site. Our objective was to determine whether or not ex vivo cyclic loading of repaired flexor tendons causes a similar increase in repair-site rigidity. We simulated 10 days of rehabilitation by applying 6000 loading cycles to repaired canine flexor tendons ex vivo at force levels generated during passive motion rehabilitation; we then evaluated their tensile mechanical properties. High-force (peak force, 17 N) cyclic loading increased repair-site rigidity by 100% and decreased repair-site strain by 50%, whereas low-force (5 N) loading did not change the properties of the repair site. This mechanical conditioning effect may explain, in part, the changes in tensile properties observed after only 10 days of healing in vivo. Mechanical conditioning of repaired flexor tendons by repetitive forces applied during rehabilitation may lead to increases in repair-site rigidity and decreases in strain, thereby altering the mechanical loading environment of tissues and cells at the repair site.

Animals↗
PubMed1988

Relationship between perineal muscle contractions, penile tumescence, and penile rigidity during nocturnal erections.

The mechanism of penile erection and erectile dysfunction is still unclear and widely debated. The role of the perineal muscles in the erectile process, especially in changes in intracavernous pressure, is increasingly being studied on the hypothesis that perineal muscular contractions are essential to full penile rigidity. In a previous investigation we studied the correlation between voluntary perineal muscle contractions and intracavernous pressure during artificially induced erections. The purpose of the current study was to examine whether under normal conditions of nocturnal erection a similar relationship exists between the electromyographic activities of perineal muscles and changes in penile rigidity. Nocturnal penile recordings were made of seven volunteers with psychogenic erectile dysfunctions. During nocturnal erections simultaneous computerized recordings were made of penile tumescence, penile rigidity, and electromyographic activities of perineal muscles. The peaks for the three variables were reached simultaneously. The results of this study suggest the existence of two different physiologic phases: a vascular phase and a muscular phase. Furthermore, in cases of dysfunctions, specific diagnostic assessment and therapeutic management will be required for both penile tumescence and penile rigidity.

Adult↗
PubMed1997

Extracellular matrix rigidity causes strengthening of integrin-cytoskeleton linkages.

To move forward, migrating cells must generate traction forces through surface receptors bound to extracellular matrix molecules coupled to a rigid structure. We investigated whether cells sample and respond to the rigidity of the anchoring matrix. Movement of beads coated with fibronectin or an anti-integrin antibody was restrained with an optical trap on fibroblasts to mimic extracellular attachment sites of different resistance. Cells precisely sense the restraining force on fibronectin beads and respond by a localized, proportional strengthening of the cytoskeleton linkages, allowing stronger force to be exerted on the integrins. This strengthening was absent or transient with antibody beads, but restored with soluble fibronectin. Hence, ligand binding site occupancy was required. Finally, phenylarsine oxide inhibited strengthening of cytoskeletal linkages, indicating a role for dephosphorylation. Thus, the strength of integrin-cytoskeleton linkages is dependent on matrix rigidity and on its biochemical composition. Matrix rigidity may, therefore, serve as a guidance cue in a process of mechanotaxis.

3T3 Cells↗
PubMed1997

A comparison of skeletal stability after mandibular advancement and use of two rigid internal fixation techniques.

PURPOSE: Two different methods of rigid fixation were compared for postoperative stability 6 months after mandibular advancement for treatment of Class II malocclusion. MATERIAL AND METHODS: Sixty (30 + 30) patients from two different oral and maxillofacial units treated for a Class II malocclusion by bilateral saggital split osteotomy (BSSO), and two different methods of internal rigid fixation were prospectively investigated. Two groups (S1, n = 15; S2, n = 15) had bicortical noncompressive screws inserted in the gonial area through a transcutaneous approach, and the other two groups (P1, n = 15; P2, n = 15) had the bone segments fixed with unicortical screws and miniplates on the lateral surface of the mandibular body. Cephalograms were taken preoperatively, 2 days postoperatively and 6 months after the operation. A computer program was used to superimpose the three cephalograms and to register the mandibular advancement and postoperative change both sagittally and vertically. RESULTS: These were minor differences in the advancement and postoperative changes between the four groups, but statistically no significant difference was shown in either sagittal or vertical directions. However, statistically verified differences proved that increasing age was associated with a smaller amount of postsurgical relapse. Low-angle cases (ML/NSL < 25 degrees) had a bigger amount of surgical (P = .0008) and postsurgical (P = .0195) movement compared with the patients in the high-angle group (ML/NSL < 38 degrees). Using a multiple regression test, a positive correlation was also shown between the amount of surgical advancement and the amount of postsurgical instability (P = .018). CONCLUSIONS: This prospective dual-center study indicates that the two different methods of internal rigid fixation after surgical advancement of the mandible by BSSO did not significantly differ from each other, and it is up to the individual operator to choose the method for internal rigid fixation.

Adolescent↗
PubMed1998

Rigid-body oscillations of alpha-helices: implications for protein thermal stability.

A quasi-continuity model protein consisting of two alpha-helices undergoing rigid-body torsional oscillations demonstrates that factors stabilizing the model protein, such as increased helix rigidity and hydrophobicity, are the same factors that stabilize thermophilic proteins relative to their mesophilic analogs. The model predicts oscillatory motions with frequencies in the microwave (10(10) Hz) range. These oscillations decrease in frequency with increasing helix rigidity because of compensating increases in the force constant and moment of inertia, thus explaining the retention of activity in the more rigid thermophilic enzymes. Implications for protein design, based on the predictions of the model, are discussed.

Journal Article↗
PubMed1996

Comparison of a vacuum splint device to a rigid backboard for spinal immobilization.

In this study, comparison of a vacuum splint device to a rigid backboard was made with respect to comfort, speed of application, and degree of immobilization. The study was a prospective, nonblinded comparative study conducted at a statewide emergency medical services (EMS) training facility and included a convenience sample of emergency medical technician (EMT) and paramedic students. The vacuum splint was judged to be significantly more comfortable on a 10-point scale than the rigid backboard after subjects had been lying on each device for 30 minutes (P < .001). It was also faster to apply: 131.6 +/- 24.3 seconds versus 154.6 +/- 22.2 seconds (P < .001). Various measures of immobilization were similar for the two devices. The vacuum splint provided better Immobilization of the torso and less slippage on a gradual lateral tilt. The rigid backboard with head blocks was slightly better at immobilizing the head. Vacuum splints offer a significant improvement in comfort over a traditional backboard for the patient with possible spinal injury. They can be applied in reasonable time frames and provide a similar degree of immobilization when compared to a standard rigid backboard.

Emergency Medical Services↗
PubMedDate not supplied

A comparative study of warping and rigid body registration for the prostate and pelvic MR volumes.

A three-dimensional warping registration algorithm was created and compared to rigid body registration of magnetic resonance (MR) pelvic volumes including the prostate. The rigid body registration method combines the advantages of mutual information (MI) and correlation coefficient at different resolutions. Warping registration is based upon independent optimization of many interactively placed control points (CP's) using MI and a thin plate spline transformation. More than 100 registration experiments with 17 MR volume pairs determined the quality of registration under conditions simulating potential interventional MRI-guided treatments of prostate cancer. For image pairs that stress rigid body registration (e.g. supine, the diagnostic position, and legs raised, the treatment position), both visual and numerical evaluation methods showed that warping consistently worked better than rigid body. Experiments showed that approximately 180 strategically placed CP's were sufficiently expressive to capture important features of the deformation.

Algorithms↗
PubMed2002

Clinical and imaging findings in six cases of congenital muscular dystrophy with rigid spine syndrome linked to chromosome 1p (RSMD1).

We report clinical and imaging findings in six cases from five families affected by the form of congenital muscular dystrophy with rigid spine linked to the locus rigid spine muscular dystrophy 1 on chromosome 1p35-36. All cases showed rigidity of the spine, predominant neck and trunk weakness and frequent and severe thoracic scoliosis. Respiratory impairment was always observed in the first decade. Muscle imaging showed a marked involvement of adductors, sartorius and biceps femoris while rectus femoris and gracilis were relatively spared. This pattern of selective muscle involvement was consistent in all six cases and could be easily observed on either computerised tomography or magnetic resonance imaging. The results of this study suggest that muscle imaging, in combination with clinical assessment can help to identify the rigid spine muscular dystrophy 1 form of congenital muscular dystrophy and can help to target the appropriate genetic investigations.

Adolescent↗
PubMed1998

Medical complications associated with the use of rigid handcuffs: a pilot study.

The provision of Police Officers with an updated form of rigid handcuffs in 1992 resulted in adverse publicity with regard to the purported 'serious injuries' that these new handcuffs produced and there was a suggestion that they 'may have to be withdrawn'. However, the police appeared to appreciate the ease of application and control of the detained person that these rigid handcuffs afforded. This pilot study documents injuries to the wrist and other sites on 41 detained persons who had been placed in rigid handcuffs in one Metropolitan Police station during a 7-month period. Nearly all of the wrist injuries that were detected were minor and required no specific treatment. Nonetheless, there is a need for further research comparing the medical complications of rigid handcuffs and other handcuffs currently in use.

Journal Article↗
PubMed2003

A unified non-rigid feature registration method for brain mapping.

This paper describes the design, implementation and results of a unified non-rigid feature registration method for the purposes of anatomical MRI brain registration. An important characteristic of the method is its ability to fuse different types of anatomical features into a single point-set representation. We demonstrate the application of the method using two different types of features: the outer cortical surface and major sulcal ribbons. Non-rigid registration of the combined feature point-sets is then performed using a new robust non-rigid point matching algorithm. The point matching algorithm implements an iterative joint clustering and matching (JCM) strategy which effectively reduces the computational complexity without sacrificing accuracy. We have conducted carefully designed synthetic experiments to gauge the effect of using different types of features either separately or together. A validation study examining the accuracy of non-rigid alignment of many brain structures is also presented. Finally, we present anecdotal results on the alignment of two subject MRI brain data.

Algorithms↗
PubMed1998

The effect of rigid lens design on fluorescein fit.

This paper describes an evaluation of rigid lens design undertaken using a computer spreadsheet-based model of fluorescein fit. The study systematically varied rigid lens parameters and corneal topography while monitoring the following key aspects of lens fit. percentage area of apparent corneal alignment, average tear layer thickness and edge clearance. The effect of changes in corneal curvature, corneal asphericity, astigmatism, back optic zone radius, back optic zone diameter and peripheral radii were evaluated. The findings enable a clearer understanding of the relationship between corneal topography, rigid lens parameters and rigid lens fit.

Journal Article↗
PubMed2004

Thermodynamic and kinetic stability of synthetic multifunctional rigid-rod beta-barrel pores: evidence for supramolecular catalysis.

The lessons learned from p-octiphenyl beta-barrel pores are applied to the rational design of synthetic multifunctional pore 1 that is unstable but inert, two characteristics proposed to be ideal for practical applications. Nonlinear dependence on monomer concentration provided direct evidence that pore 1 is tetrameric (n = 4.0), unstable, and "invisible," i.e., incompatible with structural studies by conventional methods. The long lifetime of high-conductance single pores in planar bilayers demonstrated that rigid-rod beta-barrel 1 is inert and large (d approximately 12 A). Multifunctionality of rigid-rod beta-barrel 1 was confirmed by adaptable blockage of pore host 1 with representative guests in planar (8-hydroxy-1,3,6-pyrenetrisulfonate, KD = 190 microM, n = 4.9) and spherical bilayers (poly-L-glutamate, KD < or = 105 nM, n = 1.0; adenosine triphosphate, KD = 240 microM, n = 2.0) and saturation kinetics for the esterolysis of a representative substrate (8-acetoxy-1,3,6-pyrenetrisulfonate, KM = 0.6 microM). The thermodynamic instability of rigid-rod beta-barrel 1 provided unprecedented access to experimental evidence for supramolecular catalysis (n = 3.7). Comparison of the obtained kcat = 0.03 min(-1) with the kcat approximately 0.18 min(-1) for stable analogues gave a global KD approximately 39 microM3 for supramolecular catalyst 1 with a monomer/barrel ratio approximately 20 under experimental conditions. The demonstrated "invisibility" of supramolecular multifunctionality identified molecular modeling as an attractive method to secure otherwise elusive insights into structure. The first molecular mechanics modeling (MacroModel, MMFF94) of multifunctional rigid-rod beta-barrel pore hosts 1 with internal 1,3,6-pyrenetrisulfonate guests is reported.

Arginine↗