Effects of surface tension and intraluminal fluid on mechanics of small airways

1997 ◽  
Vol 82 (1) ◽  
pp. 233-239 ◽  
Author(s):  
Mark J. Hill ◽  
Theodore A. Wilson ◽  
Rodney K. Lambert
Keyword(s):  
Surface Tension ◽  
Bending Stiffness ◽  
Liquid Interface ◽  
Cross Sectional Area ◽  
Pressure Curve ◽  
Small Airways ◽  
Sectional Area ◽  
Cross Sectional ◽  
Inner Surface ◽  
Air Liquid Interface

Hill, Mark J., Theodore A. Wilson, and Rodney K. Lambert.Effects of surface tension and intraluminal fluid on the mechanics of small airways. J. Appl. Physiol.82(1): 233–239, 1997.—Airway constriction is accompanied by folding of the mucosa to form ridges that run axially along the inner surface of the airways. The muscosa has been modeled (R. K. Lambert. J. Appl. Physiol. 71: 666–673, 1991) as a thin elastic layer with a finite bending stiffness, and the contribution of its bending stiffness to airway elastance has been computed. In this study, we extend that work by including surface tension and intraluminal fluid in the model. With surface tension, the pressure on the inner surface of the elastic mucosa is modified by the pressure difference across the air-liquid interface. As folds form in the mucosa, intraluminal fluid collects in pools in the depressions formed by the folds, and the curvature of the air-liquid interface becomes nonuniform. If the amount of intraluminal fluid is small, <2% of luminal volume, the pools of intraluminal fluid are small, the air-liquid interface nearly coincides with the surface of the mucosa, and the area of the air-liquid interface remains constant as airway cross-sectional area decreases. In that case, surface energy is independent of airway area, and surface tension has no effect on airway mechanics. If the amount of intraluminal fluid is >2%, the area of the air-liquid interface decreases as airway cross-sectional area decreases, and surface tension contributes to airway compression. The model predicts that surface tension plus intraluminal fluid can cause an instability in the area-pressure curve of small airways. This instability provides a mechanism for abrupt airway closure and abrupt reopening at a higher opening pressure.

A Multipurpose Apparatus To Measure Viscosity and Surface Tension of Solutions. The Measurement of the Molecular Cross-Sectional Area of n-Propanol.

2004 ◽  
Vol 81 (6) ◽  
pp. 850 ◽  
Author(s):  
Xin Zhang ◽  
Shouxin Liu ◽  
Baoxin Li ◽  
Fan Zhang ◽  
Na An
Keyword(s):  
Surface Tension ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional

Solder Joint Formation in Surface Mount Technology—Part II: Design

1990 ◽  
Vol 112 (3) ◽  
pp. 219-222 ◽  
Author(s):  
S. M. Heinrich ◽  
N. J. Nigro ◽  
A. F. Elkouh ◽  
P. S. Lee
Keyword(s):  
Surface Tension ◽  
Solder Joint ◽  
Solder Joints ◽  
Cross Sectional Area ◽  
Surface Mount Technology ◽  
Sectional Area ◽  
Cross Sectional ◽  
Joint Formation ◽  
Surface Mount ◽  
Surface Tension Model

In this paper dimensionless design curves relating fillet height and length to joint cross-sectional area are presented for surface-mount solder joints. Based on an analytical surface tension model, the advantage of these dimensionless curves is that they may be used for arbitrary values of solder density and surface tension. The range of applicability of previously developed approximate formulae for predicting joint dimensions is also investigated. A simple example problem is included to illustrate the use of both the design curves and the approximate formulae.

scholarly journals Pharyngeal mucosal wall folds in subjects with obstructive sleep apnea

2015 ◽  
Vol 118 (6) ◽  
pp. 707-715 ◽  
Author(s):  
Kristina Kairaitis ◽  
Sheryl Foster ◽  
Jason Amatoury ◽  
Manisha Verma ◽  
John R. Wheatley ◽  
...  
Keyword(s):  
Surface Tension ◽  
Obstructive Sleep Apnea ◽  
Healthy Subjects ◽  
Liquid Surface ◽  
Upper Airway ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Liquid Surface Tension ◽  
Obstructive Sleep

Mechanical processes underlying pharyngeal closure have not been examined. We hypothesized that the pharyngeal mucosal surface would fold during closure, and lowering the upper airway lining liquid surface tension would unfold areas of mucosal apposition, i.e., folds. We compared baseline pharyngeal fold numbers and response to reduction in upper airway liquid surface tension in healthy and obstructive sleep apnea (OSA) subjects. Awake, gated magnetic resonance pharyngeal airway images of 10 healthy and 11 OSA subjects were acquired before and after exogenous surfactant administration (beractant). Upper airway liquid surface tension was measured at the beginning and end of image acquisition and averaged. Velopharyngeal and oropharyngeal images were segmented and analyzed separately for average cross-sectional area, circumference, and fold number. Compared with healthy subjects, at baseline, velopharynx for OSA subjects had a smaller cross-sectional area (98.3 ± 32.5 mm2 healthy, 52.3 ± 23.6 mm2 OSA) and circumference (46.5 ± 8.1 mm healthy, 30.8 ± 6.1 mm OSA; both P < 0.05, unpaired t-test), and fewer folds (4.9 ± 1.6 healthy, 3.1 ± 1.8 OSA, P < 0.03). There were no differences in oropharynx for cross-sectional area, circumference, or folds. Reduction in upper airway liquid surface tension from 61.3 ± 1.2 to 55.3 ± 1.5 mN/m ( P < 0.0001) did not change cross-sectional area or circumference for velopharynx or oropharynx in either group; however, in OSA subjects, oropharyngeal folds fell from 6.8 ± 3.1 to 4.7 ± 1.2 ( n = 8, P < 0.05), and velopharyngeal folds from 3.3 ± 1.9 to 2.3 ± 1.2 ( P = 0.08), and were unchanged in healthy subjects. Subjects with OSA have fewer velopharyngeal wall folds, which decrease further when surface tension falls. We speculate that reduced pharyngeal wall folds contribute to an increase in pharyngeal collapsibility.

Pelvic Canal Narrowing Caused by Triple Pelvic Osteotomy in the Dog

1994 ◽  
Vol 07 (03) ◽  
pp. 110-113 ◽  
Author(s):  
D. L. Holmberg ◽  
M. B. Hurtig ◽  
H. R. Sukhiani
Keyword(s):  
Postoperative Complications ◽  
Pelvic Osteotomy ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Canal Width ◽  
Operative Complications ◽  
Post Operative Complications

SummaryDuring a triple pelvic osteotomy, rotation of the free acetabular segment causes the pubic remnant on the acetabulum to rotate into the pelvic canal. The resulting narrowing may cause complications by impingement on the organs within the pelvic canal. Triple pelvic osteotomies were performed on ten cadaver pelves with pubic remnants equal to 0, 25, and 50% of the hemi-pubic length and angles of acetabular rotation of 20, 30, and 40 degrees. All combinations of pubic remnant lengths and angles of acetabular rotation caused a significant reduction in pelvic canal-width and cross-sectional area, when compared to the inact pelvis. Zero, 25, and 50% pubic remnants result in 15, 35, and 50% reductions in pelvic canal width respectively. Overrotation of the acetabulum should be avoided and the pubic remnant on the acetabular segment should be minimized to reduce postoperative complications due to pelvic canal narrowing.When performing triple pelvic osteotomies, the length of the pubic remnant on the acetabular segment and the angle of acetabular rotation both significantly narrow the pelvic canal. To reduce post-operative complications, due to narrowing of the pelvic canal, overrotation of the acetabulum should be avoided and the length of the pubic remnant should be minimized.

Jump performance and thigh muscle cross-sectional area in young female rhythmic gymnasts

2019 ◽  
Vol 178 (3) ◽  
Author(s):  
Antonio Cicchella ◽  
Monica Mannai ◽  
Jaan Ereline ◽  
Mati Paasuke ◽  
Helena Gapeyeva
Keyword(s):  
Young Female ◽  
Cross Sectional Area ◽  
Thigh Muscle ◽  
Sectional Area ◽  
Cross Sectional ◽  
Jump Performance ◽  
Muscle Cross Sectional Area ◽  
Rhythmic Gymnasts

DETERMINATION OF THE FUNCTION OF THE ROD’S CROSS-SECTIONAL AREA USING VIBRATION EIGENFREQUENCIES

2020 ◽  
Vol 0 (4) ◽  
pp. 19-24
Author(s):  
I.M. UTYASHEV ◽  
◽  
A.A. AITBAEVA ◽  
A.A. YULMUKHAMETOV ◽  
◽  
...  
Keyword(s):  
Cross Sectional Area ◽  
Variable Cross ◽  
Sectional Area ◽  
Longitudinal Vibrations ◽  
Cross Sectional ◽  
Method Error ◽  
Various Boundary Conditions ◽  
Elastic Fixation ◽  
Crosssectional Area

The paper presents solutions to the direct and inverse problems on longitudinal vibrations of a rod with a variable cross-sectional area. The law of variation of the cross-sectional area is modeled as an exponential function of a polynomial of degree n . The method for reconstructing this function is based on representing the fundamental system of solutions of the direct problem in the form of a Maclaurin series in the variables x and λ. Examples of solutions for various section functions and various boundary conditions are given. It is shown that to recover n unknown coefficients of a polynomial, n eigenvalues are required, and the solution is dual. An unambiguous solution was obtained only for the case of elastic fixation at one of the rod’s ends. The numerical estimation of the method error was made using input data noise. It is shown that the error in finding the variable crosssectional area is less than 1% with the error in the eigenvalues of longitudinal vibrations not exceeding 0.0001.

Changes in the parameters of nasal breathing and parameters of the upper respiratory tract during orthognathic operations in patients with II and III skeletal class of jaw anomalies

2020 ◽  
pp. 22-27
Author(s):  
S.Sh. Gammadaeva ◽  
M.I. Misirkhanova ◽  
A.Yu. Drobyshev
Keyword(s):  
Respiratory Tract ◽  
Nasal Cavity ◽  
Nasal Septum ◽  
Cross Sectional Area ◽  
Upper Respiratory Tract ◽  
Sectional Area ◽  
Nasal Breathing ◽  
Cross Sectional ◽  
Skeletal Class ◽  
Upper Respiratory

The study analyzed the functional parameters of nasal breathing, linear parameters of the nasal aperture, nasal cavity and nasopharynx, volumetric parameters of the upper airways in patients with II and III skeletal class of jaw anomalies before and after orthognathic surgery. The respiratory function of the nose was assessed using a rhinomanometric complex. According to rhinoresistometry data, nasal resistance and hydraulic diameter were assessed. According to the data of acoustic rhinometry, the minimum cross-sectional area along the internal valve, the minimum cross-sectional area on the head of the inferior turbinate and nasal septum and related parameters were estimated. According to the CBCT data, the state of the nasal septum, the inferior turbinates, the nasal aperture, the state of the nasal cavity, and the linear values of the upper respiratory tract (nasopharynx) were analyzed. The patients were divided into 4 groups according to the classification of the patency of the nasal passages by

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