Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “RIGIDITY”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 595 records · Page 33Linked to original sources
PubMed2000

Correction of severe caudal deflections with a cartilage "plating" rigid fixation graft.

OBJECTIVE: To evaluate a technique for correction of severe caudal septal defects. DESIGN: For all patients, preoperative photographs were analyzed and subjective nasal airway patency surveys were conducted. The caudal septal defects were then repaired with the cartilage "plating" rigid fixation technique. The intraoperative findings were documented in pictorial diagrams. Postoperative photographs and repeated airway surveys were obtained during the subsequent follow-up visits. Preoperative data and long-term postoperative data were compared and analyzed. SETTING: Private practice, ambulatory surgical center. PATIENTS: Thirty-six patients had significant caudal septal deviations and functional airway obstruction. MAIN OUTCOME MEASURES: Accuracy and stability of the correction, airway improvement, patient satisfaction, and morbidity. RESULTS: Since 1988, 36 patients were treated for severe caudal septal defects using cartilage plating rigid fixation. Follow-up visits have ranged from 3 to more than 9 years. All patients have maintained an accurate correction of their caudal septal deflections. All patients have also noted subjective improvement of their nasal airway. No complication has been encountered. CONCLUSION: Cartilage plating rigid fixation seems to be an effective method of correcting the functional problems associated with severe caudal septal deformities.

Cartilage↗
PubMed1993

Comparative postoperative infection rates in midfacial trauma using intermaxillary fixation, wire fixation, and rigid internal fixation implants.

The use of rigid internal fixation implants in the repair of midfacial fractures requires more extensive bone exposure, soft-tissue manipulation, and operative time. We wished to determine the relative contribution of this method of repair to postoperative infection rates. Midfacial trauma cases occurring between the years 1984 and 1991 at the University of Iowa Hospitals and Clinics, Iowa City, were reviewed. Patients were grouped according to method of repair (intermaxillary fixation, open reduction with wire fixation, or open reduction with rigid internal fixation plates). Postoperative infection data (wound infections, sinusitis, etc) were obtained by chart review and telephone interview. Minimum follow-up for inclusion in the study was 3 months, with an average follow-up for all groups of 28.8 months. We found no significant difference in the rate, or the type, of postoperative infections in all three groups. We conclude that rigid internal fixation implants do not contribute increased postoperative infection rates in midfacial trauma.

Adult↗
PubMed1995

Rigid fixation of vascularized bone grafts in mandibular reconstruction.

OBJECTIVE: To evaluate the nature of complications and complication rates with the use of three different reconstruction plates for the rigid fixation of vascularized bone grafts in oromandibular reconstruction. DESIGN: We conducted a case series of 95 patients over a 6-year period, with a minimum follow-up of 6 months and a maximum follow-up of 66 months. SETTING: Academic tertiary referral medical center. PATIENTS: Forty-eight patients had vascularized bone grafts fixated to native mandible with AO stainless steel reconstruction plates; 25 patients, with AO titanium plates; and 22 patients, with titanium hollow screw reconstruction plates (THORPs). Types of vascularized flaps, mandibular defects to be reconstructed, and use of radiation therapy were similar among the three groups. INTERVENTION: The surgical approach involved oromandibular reconstruction with a vascularized bone graft rigidly fixated with a reconstruction plate. OUTCOME MEASURES: Clinically and radiographically noted complications and resultant treatment. RESULTS: In the grafts fixated with AO stainless steel reconstruction plates, three plate fractures, seven instances of loose screws, eight plate exposures, and two cases of nonunion occurred. No cases of plate fracture or nonunion occurred in the titanium or THORP groups. One titanium plate and two THORPs were exposed during the study period. One instance of loose screws occurred in the titanium group; none in the THORP group. Seventy-four percent of those complications occurred within 12.4 months (the mean follow-up time of the THORP group). The incidence of complications in the stainless steel group was significantly greater than that in the titanium or THORP groups. No statistically significant increase in the rate of complications was noted when radiation therapy was used as a component of treatment. CONCLUSIONS: To our knowledge, this is the first study to compare three different reconstruction plates for fixation in vascularized bone reconstruction of the mandible. AO THORPs are now used almost exclusively to rigidly fixate vascularized bone grafts because of their advanced design and their potential for osseointegration and because fewer screws are necessary to attain adequate fixation than with conventional AO reconstruction plates.

Adult↗
PubMed1998

Bent stents: a method to facilitate delivery of the Palmaz-Schatz stent in tortuous and rigid coronary arteries.

The Palmaz-Schatz stent delivery system (PS 153) and "bare" PS 204 stents are relatively high-profile, rigid devices that can be difficult to deliver to lesions beyond tortuous, irregular, or rigid proximal segments. Described herein is a method of mounting and shaping a Palmaz-Schatz stent on a low-profile balloon that provides a steerable, low-profile, and secure stent delivery system. Also described is the successful use of this method in four consecutive cases where Palmaz-Schatz stents could not be delivered to the lesion site due to severely angulated, irregular, or rigid proximal vessel segments.

Aged↗
PubMed1997

Familial mixed congenital myopathy with rigid spine phenotype.

We describe a father and daughter with a rigid spine syndrome and proximal myopathy. The index patient was a 42-year-old man, who died from respiratory failure after a lifelong, slowly progressive proximal myopathy and a rigid spine phenotype. This was morphologically characterized by cytoplasmic bodies, increased desmin, features of reducing-body myopathy, and sarcoplasmic and intranuclear tubulofilamentous inclusions. These cases are characterized by an early onset and possibly autosomal-dominant inheritance, with associated complex structural hallmarks of both desmin-related and inclusion body myopathies. Together they may be defined as a complex mixed congenital myopathy with a rigid spine phenotype.

Adult↗
PubMed1999

Validation of the flexible and rigid control dimensions of dietary restraint.

OBJECTIVE: Two subscales for the Eating Inventory (Three-Factor Eating Questionnaire) are developed and validated: Rigid and Flexible control of eating behavior. METHOD: Study I is an analysis of questionnaire data and a 7-day food diary of 54,517 participants in a computer-assisted weight reduction program. Study II is a study of 85 subjects used to develop a final item pool. Study III is a questionnaire survey of a random sample (N = 1,838) from the West German population aged 14 years and above used to validate the developed subscales. RESULTS: Rigid control is associated with higher scores of Disinhibition, with higher body mass index (BMI), and more frequent and more severe binge eating episodes. Flexible control is associated with lower Disinhibition, lower BMI, less frequent and less severe binge eating episodes, lower self-reported energy intake, and a higher probability of successful weight reduction during the 1-year weight reduction program. DISCUSSION: Rigid and flexible control represent distinct aspects of restraint having different relations to disturbed eating patterns and successful weight control.

Adolescent↗
PubMed2000

Rigid-rod beta-barrels as lipocalin models: probing confined space by carotenoid encapsulation.

Herein, we describe the design, synthesis, structure, and function of synthetic, supramolecular beta-barrel models. Assembly of octi(p-phenylene)s with complementary -Lys-Leu-Lys-NH2 and Glu-Leu-Glu-NH2 side chains yielded water-soluble rigid-rod beta-barrels of precise length and with flexible diameter. A hydrophobic interior was evidenced by guest encapsulation. Host-guest complexes with planarized, monomeric beta-carotene within tetrameric rigid-rod beta-barrels, and disc micellar astaxanthin J-aggregates surrounded by about dodecameric rigid-rod "bicycle tires" were prepared from mixed micelles by dialytic detergent removal. The significance of these findings for future bioorganic chemistry in confined, intratoroidal space is discussed in comparison with pertinent biological examples.

Carotenoids↗
PubMed2000

Soft versus rigid vacuum extractor cups for assisted vaginal delivery.

BACKGROUND: The original cups used for vacuum extraction delivery of the fetus were rigid metal cups. Subsequently, soft cups of flexible materials such as silicone rubber or plastic were introduced. Soft cups are thought to have a poorer success rate than metal cups. However they are also thought to be less likely to be associated with scalp trauma and less likely to injure the mother. OBJECTIVES: The objective of this review was to assess the effects of soft versus rigid vacuum extractor cups on perineal injury, fetal scalp injury and success rate. SEARCH STRATEGY: We searched the Cochrane Pregnancy and Childbirth Group trials register and the Cochrane Controlled Trials Register. Date of last search: February 2000. SELECTION CRITERIA: Acceptably controlled comparisons of soft versus rigid vacuum extractor cups. DATA COLLECTION AND ANALYSIS: Two reviewers assessed trial quality and extracted data. Study authors were contacted for additional information. MAIN RESULTS: Nine trials involving 1375 women were included. The trials were of average quality. Soft cups are significantly more likely to fail to achieve vaginal delivery (odds ratio 1.65, 95% confidence interval 1.19 to 2.29). However, they were associated with less scalp injury (odds ratio 0.45, 95% confidence interval 0.15 to 0.60). There was no difference between the two groups in terms of maternal injury. REVIEWER'S CONCLUSIONS: Metal cups appear to be more suitable for 'occipito-posterior', transverse and difficult 'occipito-anterior' position deliveries. The soft cups seem to be appropriate for straightforward deliveries.

Female↗
PubMed2004

Linkage and association analysis at the serotonin transporter (SLC6A4) locus in a rigid-compulsive subset of autism.

Autism is a complex genetic neurodevelopmental disorder in which affected individuals display deficits in language, social relationships, and patterns of compulsive and stereotyped behaviors and rigidity. Linkage analysis in our dataset of 57 New England and 80 AGRE multiplex autism families reveals a multipoint heterogeneity LOD (HLOD) score of 2.74 at D17S1871 in 17q11.2. Analysis of phenotypic subsets shows an increased HLOD of 3.62 in families with compulsive behaviors and rigidity. The serotonin transporter locus (SLC6A4) maps nearby and is considered a functional candidate gene in autism and obsessive-compulsive disorder. We genotyped an insertion/deletion polymorphism in the promoter (5-HTTLPR), and seven single nucleotide polymorphisms (SNPs) across the 38-kb transcriptional unit. Transmission disequilibrium (TD) analysis reveals nominal association at a SNP in intron 5 (P = 0.02) as well as 5-HTTLPR (P = 0.01), corresponding to over-transmission of the short allele. TD analysis in the rigid-compulsive subset shows no evidence for association. Intermarker linkage disequilibrium was determined. All SNPs define a single haplotype block, while 5-HTTLPR lies 5' to this block. Three SNPs are sufficient to detect all common alleles (> or =5%) in this > 26-kb block. Analysis of haplotypes for these markers demonstrates no evidence for association to autism. These data indicate that a common allele within the coding region of SLC6A4 is not responsible for the observed linkage. However, the presence of heterogeneous disease variants within the block or the existence of a common disease-associated allele either upstream or downstream of this block is possible. In fact, such variants may well account for linkage to 17q11.2 in our families.

Autistic Disorder↗
PubMed1990

Dynamic bending rigidity of DNA.

Rapidly relaxing components in the decay of the transient electric dichroism of DNA restriction fragments were reported by Diekmann et al. [(1982) Biophys. Chem. 15, 263-270] and Pörschke et al. [(1987) Biopolymers 26, 1971-1974]. These are analyzed using a new normal mode theory for weakly bending rods and assigned to bending. The longest bending relaxation times for fragments with 95-250 base pairs coincide with the theoretical curve calculated for a dynamic bending rigidity corresponding to a dynamic persistence length Pd = 2100 A. Analysis of the relative amplitudes of fast and slow components following weak orienting pulses is also consistent with a rather large dynamic persistence length. The enhancement of the relative amplitude of the fast component in large electric fields is attributed to steady-state bending of initially perpendicular DNAs by the field. Several reasons are proposed why the dynamic bending rigidity is 4 times larger than the apparent static bending rigidity inferred from equilibrium persistence length measurements on the same fragments.

Chemical Phenomena↗
PubMed1991

Virtual rigid body dynamics.

An important direction in biological simulations is the development of methods that permit the study of larger systems and/or longer simulation time scales than is currently feasible by molecular dynamics. One such method designed with this objective in mind is stochastic boundary molecular dynamics (SBMD). SBMD was developed for the characterization of spatially localized processes in proteins, and has been shown to successfully reproduce structural and dynamical properties of these macromolecules, as compared to a molecular dynamics control simulation, when concerted or global motions are not present. The virtual rigid body dynamics method presented in this work extends the range of applicability of the SBMD method, by providing a framework to include these important long time scale conformational transitions. In this paper we describe the two-step implementation of the virtual rigid body model: first, the reduction of the full atomic representation to a reduced particle (virtual bond) model, and second, the propagation of the dynamics of flexibly connected rigid bodies containing virtual atom sites.

Biopolymers↗
PubMed2005

Protein flexibility and ligand rigidity: a thermodynamic and kinetic study of ITAM-based ligand binding to Syk tandem SH2.

The Syk tandem Src homology 2 domain (Syk tSH2) constitutes a flexible protein module involved in the regulation of Syk kinase activity. The Syk tSH2 domain is assumed to function by adapting the distance between its two SH2 domains upon bivalent binding to diphosphotyrosine ligands. A thermodynamic and kinetic analysis of ligand binding was performed by using surface plasmon resonance (SPR). Furthermore, the effect of binding on the Syk tSH2 structural dynamics was probed by hydrogen/deuterium exchange and electrospray mass spectrometry (ESI-MS). Two ligands were studied: 1, a flexible peptide derived from the tSH2 recognition ITAM sequence at the gamma chain of the FcepsilonRI-receptor, and 2, a ligand in which the amino acids between the two SH2 binding motifs in ligand 1 have been replaced by a rigid linker of comparable length. Both ligands display comparable affinity for Syk tSH2 at 25 degrees C, yet a major difference in thermodynamics is observed. Upon binding of the rigid ligand, 2, the expected entropy advantage is not realized. On the contrary, 2 binds with a considerably higher entropy price of approximately 9 kcal mol-1, which is attributed to a further decrease in protein flexibility upon binding to this rigid ligand. The significant reduction in deuterium incorporation in the Syk tSH2 protein upon binding of either 1 or 2, as monitored by ESI-MS, indicates a major reduction in protein dynamics upon binding. The results are consistent with a two-step binding model: after an initial binding step, a rapid structural change of the protein occurs, followed by a second binding step. Such a bivalent binding model allows high affinity and fast dissociation kinetics, which are very important in transient signal-transduction processes.

Intracellular Signaling Peptides and Proteins↗
PubMed2002

Toward catalytic rigid-rod beta-barrels: a hexamer with multiple histidines.

Rigid-rod beta-barrels are composed of interdigitating, short, amphiphilic peptide strands that are flanked by stabilizing rigid-rod "staves." As a first step toward the construction of catalytic rigid-rod beta-barrels, we here report synthesis and study of a new barrel designed to comprise alternating leucine and histidine residues at the inner and lysine and glutamate residues at the outer barrel surface. Synthesis of p-octiphenyls with lateral tripeptide strands followed procedures described previously. Barrel formation by programmed assembly of complementary tripeptide-p-octiphenyl rods was monitored by circular dichroism (CD). CD-mixing curves (Job-plots) were consistent with 1:1-stoichiometry. Guanidinium chloride denaturation experiments gave a DeltaG(H20) = -1.8 kcal mol(-1) with a C(50) = 1.9 M. Size exclusion chromatography suggested quantitative formation of a hexamer. Facile barrel deconstruction by acid and divalent cations demonstrated the presence of internal, nonproximal histidines. Inclusion complex formation with fluorescent guests corroborated internal hydrophobicity of beta-barrel hosts and potential for intratoroidal catalysis.

Journal Article↗
PubMed2004

Design of braided composite cardiovascular catheters based on required axial, flexural, and torsional rigidities.

Cardiovascular catheterization is a common medical procedure. A single braided catheter with different rigidities at the proximal and distal ends can, if properly designed, provide the necessary control and flexibility and thus replace the current two-piece (external catheter/internal guidewire) system. An analytical model based on classical laminate plate theory was developed in order to predict the elastic properties of angle-plied, single-overlap two-dimensional fiber composite tubular braids, which are required for the determination of the axial, flexural, and torsional rigidities. In this work the analytical model has been used to design one-piece cardiovascular catheters with axial, flexural, and torsional rigidities similar to those values for existing two-piece catheters, thus validating the model as a tool for designing braided cardiovascular catheters.

Biocompatible Materials↗
PubMed2006

Buckling test as a new approach to testing flexural rigidities of angiographic catheters.

The general design of catheters is bound by many needs. Angiographic catheters must be rigid enough to be torquable and to maintain lumen structural integrity, but also flexible enough to bend with the curves of a blood vessel. They should cause minimal tissue damage; avoid biocompatibility-related complications, and be reliable over time. This study proposes a new testing approach to clearly identify the flexural rigidity of catheters by using a buckling test to evaluate the peak compressive load. This study also tests several angiographic catheters for axial and torsional rigidity. Seven different catheters used for short-term procedures, with and without reinforcement and of various sizes, were evaluated as a preliminary evaluation of test methods for future in vitro testing of catheters; it was found that the buckling test works very well and provides repeatable results.

Angiography↗
PubMed1988

Influence of gamma radiation on the gel rigidity index and binding capability of gelatin.

Changes in the rigidity indices of gelatin gel before and after gamma irradiation were characterized by dynamic mechanical testing, and the significance of these changes on the strength of granules was evaluated. Results illustrate the difficulty of obtaining reproducible values for gels containing less than 20% gelatin. However, rigidity indices for gels with a gelatin content of 20% and higher are consistent and may provide a useful controlling factor for preparation of gelatins of more precise specifications. The data indicate that rigidity degradation kinetics of several concentrations of gelatin gel at different radiation doses are complex, showing both increasing and decreasing rates. These findings strongly suggest that doses of less than 2.0 Mrad of gamma radiation should be used in order to obtain gelatins of acceptable quality for pharmaceutical applications. The crushing strength of granules of lactose powder granulated with irradiated gelatin reveals that the binding capability of such gelatin is significantly reduced. The results obtained for various size fractions and granule hardnesses containing different binder concentrations also suggest that particle size influences the granule strength to a lesser extent than does binder concentration and its consistency.

Cobalt Radioisotopes↗
PubMed2004

Experimental application of pulsed Ho:YAG laser-induced liquid jet as a novel rigid neuroendoscopic dissection device.

BACKGROUND AND OBJECTIVES: Although water jet technology has been considered as a feasible neuroendoscopic dissection methodology because of its ability to perform selective tissue dissection without thermal damage, problems associated with continuous use of water and the ensuing fountain-effect-with catapulting of the tissue-could make water jets unsuitable for endoscopic use, in terms of safety and ease of handling. Therefore, the authors experimented with minimization of water usage during the application of a pulsed holmium:yttrium-aluminum-garnet (Ho:YAG) laser-induced liquid jet (LILJ), while assuring the dissection quality and the controllability of a conventional water jet dissection device. We have developed the LILJ generator for use as a rigid neuroendoscope, discerned its mechanical behavior, and evaluated its dissection ability using the cadaveric rabbit ventricular wall. STUDY DESIGN/MATERIALS AND METHODS: The LILJ generator is incorporated into the tip of a stainless steel tube (length: 22 cm; internal diameter: 1.0 mm; external diameter: 1.4 mm), so that the device can be inserted into a commercial, rigid neuroendoscope. Briefly, the LILJ is generated by irradiating an internally supplied water column within the stainless steel tube using the pulsed Ho:YAG laser (wave length: 2.1 microm, pulse duration time: 350 microseconds) and is then ejected through the metal nozzle (internal diameter: 100 microm). The Ho:YAG laser pulse energy is conveyed through optical quartz fiber (core diameter: 400 microm), while cold water (5 degrees C) is internally supplied at a rate of 40 ml/hour. The relationship between laser energy (range: 40-433 mJ/pulse), standoff distance (defined as the distance between the tip of the optical fiber and the nozzle end; range: 10-30 mm), and the velocity, shape, pressure, and average volume of the ejected jet were analyzed by means of high-speed camera, PVDF needle hydrophone, and digital scale. The quality of the dissection plane, the preservation of blood vessels, and the penetration depth were evaluated using five fresh cadaveric rabbit ventricular walls, under neuroendoscopic vision. RESULTS: Jet velocity (7.0-19.6 m/second) and pressure (0.07-0.28 MPa) could be controlled by varying the laser energy, which determined the penetration depth in the cadaveric rabbit ventricular wall (0.07-1.30 mm/shot). The latter could be cut into desirable shapes-without thermal effects-under clear neuroendoscopic vision. The average volume of a single ejected jet could be confined to 0.42-1.52 microl/shot, and there was no accompanying generation of shock waves. Histological specimens revealed a sharp dissection plane and demonstrated that blood vessels of diameter over 100 microm could be preserved, without thermal damage. CONCLUSIONS: The present pulsed LILJ system holds promise as a safe and reliable dissection device for deployment in a rigid neuroendoscope.

Animals↗
PubMed2006

Development of a functional magnetic resonance imaging simulator for modeling realistic rigid-body motion artifacts.

Functional magnetic resonance imaging (FMRI) is a noninvasive method of imaging brain function in vivo. However, images produced in FMRI experiments are imperfect and contain several artifacts that contaminate the data. These artifacts include rigid-body motion effects, B0-field inhomogeneities, chemical shift, and eddy currents. To investigate these artifacts, with the eventual aim of minimizing or removing them completely, a computational model of the FMR image acquisition process was built that can simulate all of the above-mentioned artifacts. This paper gives an overview of the development of the FMRI simulator. The simulator uses the Bloch equations together with a geometric definition of the object (brain) and a varying T2* model for the BOLD activations. Furthermore, it simulates rigid-body motion of the object by solving Bloch equations for given motion parameters that are defined for an object moving continuously in time, including during the read-out period, which is a novel approach in the area of MRI computer simulations. With this approach it is possible, in a controlled and precise way, to simulate the full effects of various rigid-body motion artifacts in FMRI data (e.g. spin-history effects, B0-motion interaction, and within-scan motion blurring) and therefore formulate and test algorithms for their reduction.

Algorithms↗