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Query: UMLS:C0344329 (collapse)
 28,634 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This paper is concerned with the airway closure problem and investigates the quasi-steady deformation characteristics of strongly collapsed (buckled) airways occluded by liquid bridges of high surface tension. The airway wall is modeled as a thin-walled elastic shell, which deforms in response to an external pressure and to the compression due to the surface tension of the liquid bridge. The governing equations are solved numerically using physiological parameter values. It is shown that axisymmetric configurations are statically unstable, as are buckled tubes whose opposite walls are not in contact. The quasi-steady deformation characteristics of strongly collapsed airways whose walls are in opposite wall contact show a pronounced hysteresis during the collapse/reopening cycle. Buckling is shown to occur over a short axial length with moderate circumferential wavenumbers. Finally, further implications of the results for the airway collapse/reopening problem are discussed.
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PMID:Airway closure: occluding liquid bridges in strongly buckled elastic tubes. 1052 15

Periodic soft nanostructures are building blocks for small devices. However, mechanical failure in the form of structure buckling or distortion from their original shape is often reported when the dimension of these soft structures were reduced to below submicron scale. Such a phenomenon seriously limits a reliable impact of these nanostructures to greater applications. Current understandings of buckling of soft 2-D nanostructures are limited. The substrate for these soft nanostructures is usually very compliant. Neighboring nanostructures could interact through the deformation of the substrate. We analyze the collective buckling of a two-dimensional array of nanoscale columns with their lower ends built into an elastic substrate. Buckling of these nanostructures is mathematically described by an eigenvalue problem. Numerical analyses show patterned collapse for these 2-D nanostructures, qualitatively matching reported experimental findings. Our efforts are useful toward the understanding and manufacturing of many two-dimensional nanoscale features.
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PMID:Collective buckling of a two-dimensional array of nanoscale columns. 1897 55

Spinal tuberculosis is the most common cause of severe kyphosis in many parts of the world. Three percent of patients treated conservatively end up with a deformity greater than 60 degrees which can cause serious cosmetic, psychological, cardio-respiratory and neurological problems. Severe kyphotic deformities are usually the result of childhood spinal deformities and 'Spine at risk' radiological signs are helpful to identify children at risk of deformity. In children, a severe type of collapse, termed as 'Buckling Collapse' is also noted where the kyphosis is more than 120 degrees. Risk factors for buckling collapse include an age of less than seven years at the time of infection, thoracolumbar involvement, loss of more than two vertebral bodies and the presence of radiographic 'Spine-at-risk' signs. In correction of established deformity, posterior only surgery with a variety of osteotomies is now preferred. In patients with deformity of more than 90 degrees, an opening-closing wedge osteotomy must be done to prevent neurological deficit.
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PMID:Kyphotic deformity in spinal tuberculosis and its management. 2223 5

We report the results of a numerical and theoretical study of buckling in elastic columns containing a line of holes. Buckling is a common failure mode of elastic columns under compression, found over scales ranging from metres in buildings and aircraft to tens of nanometers in DNA. This failure usually occurs through lateral buckling, described for slender columns by Euler's theory. When the column is perforated with a regular line of holes, a new buckling mode arises, in which adjacent holes collapse in orthogonal directions. In this paper, we firstly elucidate how this alternate hole buckling mode coexists and interacts with classical Euler buckling modes, using finite-element numerical calculations with bifurcation tracking. We show how the preferred buckling mode is selected by the geometry, and discuss the roles of localized (hole-scale) and global (column-scale) buckling. Secondly, we develop a novel predictive model for the buckling of columns perforated with large holes. This model is derived without arbitrary fitting parameters, and quantitatively predicts the critical strain for buckling. We extend the model to sheets perforated with a regular array of circular holes and use it to provide quantitative predictions of their buckling.
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PMID:On the buckling of an elastic holey column. 2922 98

Buckling collapse is the term typically used to describe severe kyphosis >100 degrees, characteristically seen in thoracolumbar tuberculosis. Neurofibromatosis is rarely associated with severe cervical kyphosis. Dystrophic changes in vertebra make surgical correction and fusion challenging. Single-stage cervical osteotomies (e.g., pedicle subtraction osteotomy, vertebral column resection) are commonly done in cervicothoracic junction. However, it is technically challenging and associated with high risk of vertebral artery injury, neural injury, etc. when performed in higher cervical spine. Hence in our case we did a staged procedure performing circumferential osteotomy for buckling kyphosis in the midcervical spine. Because it involved midcervical spine and there was no chin-to-chest deformity, we preferred the anterior-posterior-anterior sequence.
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PMID:Buckling Collapse of Midcervical Spine Secondary to Neurofibromatosis. 2955 May 97