A Cellular Model of Lung Elasticity

1987 ◽  
Vol 109 (2) ◽  
pp. 126-131 ◽  
Author(s):  
E. Kimmel ◽  
R. D. Kamm ◽  
A. H. Shapiro
Keyword(s):  
Elastic Moduli ◽  
Individual Cell ◽  
Transpulmonary Pressure ◽  
Lung Parenchyma ◽  
Force Balance ◽  
Cellular Structures ◽  
Distorted Structure ◽  
Deformation Law ◽  
Experimental Values ◽  
Good Agreement

The mechanics of the lung parenchyma is studied using models comprised of line members interconnected to form 3-D cellular structures. The mechanical properties are represented as elastic constants of a continuum. These are determined by perturbing each individual cell from a reference state by an increment in stress which is superimposed upon the uniform stretching forces initially present in the members due to the transpulmonary pressure. A force balance on the distorted structure, together with a force-deformation law for the members, leads to a calculation of the strain increments of the members. Predictions based on the analysis of the 3-D isotropic dodecahedron are in good agreement with experimental values for the Young’s, shear, and bulk moduli reported in the literature. The model provides an explanation for the dependence of the elastic moduli on transpulmonary pressure, the geometrical details of the structure, and the stress-strain law of the tissue.

Parenchymal stability

1992 ◽  
Vol 73 (2) ◽  
pp. 596-602 ◽  
Author(s):  
D. Stamenovic ◽  
T. A. Wilson
Keyword(s):  
Surface Tension ◽  
Surface Density ◽  
Continuum Model ◽  
Elastic Moduli ◽  
Micromechanical Model ◽  
Volume Ratio ◽  
Transpulmonary Pressure ◽  
Lung Parenchyma ◽  
Micromechanical Modeling ◽  
The Continuum

Both continuum and micromechanical models have been used to describe the mechanics of lung parenchyma. Different authors, using different models, have come to different conclusions about parenchymal stability. We show that the continuum model, augmented by bounds on the elastic moduli obtained from recent micromechanical modeling, yields the same conclusions about stability that have been obtained from purely micromechanical modeling: if the lung were homogeneous, it would be stable; local atelectasis would not occur at positive transpulmonary pressure. However, the same analysis yields the prediction that if the surface-to-volume ratio is not uniform throughout the lung, regions of higher surface density collapse if surface tension is large and insensitive to surface area. A micromechanical model that illustrates regional collapse is described.

Surface Tension and the Dodecahedron Model for Lung Elasticity

1990 ◽  
Vol 112 (2) ◽  
pp. 160-167 ◽  
Author(s):  
E. Kimmel ◽  
B. Budiansky
Keyword(s):  
Surface Tension ◽  
Elastic Moduli ◽  
Transpulmonary Pressure ◽  
Lung Parenchyma ◽  
Elastic Stiffness ◽  
Experimental Information ◽  
Hydrostatic Tension ◽  
Regular Dodecahedron ◽  
Tension Members ◽  
Variational Statement

Macroscopic elastic moduli governing the incremental deformations of lung parenchyma are calculated on the basis of a model for an individual lung element in the shape of a regular dodecahedron. Elastic stiffness within the element is provided by pin-jointed tension members along the edges of the dodecahedron, surface tension is incorporated into its pentagonal faces, and the influence of transpulmonary pressure is simulated by an externally applied hydrostatic tension. The analysis is based on a variational statement of nonlinear structural mechanics, and the results show how the moduli depend on the effective inflation pressure, the constitutive behavior of the idealized truss members, and the surface-area dependent surface tension. The theory is discussed in the light of available experimental information. A more general analysis is needed to account for the effects of structural as well as surface-tension hysteresis.

Mechanical dissociation of bronchi from parenchyma in the immature piglet lung

2000 ◽  
Vol 89 (1) ◽  
pp. 228-234 ◽  
Author(s):  
Anthony L. Mansell ◽  
Allison L. McAteer ◽  
Eben H. Oldmixon
Keyword(s):  
Elastic Moduli ◽  
Age Groups ◽  
Transpulmonary Pressure ◽  
Lung Parenchyma ◽  
Postnatal Growth ◽  
Percent Change ◽  
Mechanical Dissociation ◽  
Mature Group ◽  
Two Age Groups

Previous studies of isolated piglet lungs suggested that local distending forces around bronchi might be relatively weak before postnatal growth and maturation. The present study used tantalum bronchograms to compare pressure-diameter relationships of bronchi in situ and after excision from the parenchyma in immature (3- to 7-day-old) and mature (3-mo-old) piglets. The mature group reproduced behavior that is well established in mature lungs from other species; i.e., bronchial diameters maintained a constant relationship to the parenchyma as the lungs were deflated from maximum to minimum volume. In sharp contrast, diameters failed to change until the immature lungs were deflated to <5 cmH2O transpulmonary pressure. Total percent change in bronchial diameter was then only 24% in the immature lungs compared with 47% in the mature lungs ( P < 0.002). Total elastances of mature generation 3–8 bronchi did not change when they were excised from the parenchyma. However, in the same generations of immature bronchi, total elastances were lower after than before (1.06 vs. 1.60 cmH2O/%, P < 0.05) excision from the parenchyma. Elastances of the excised immature and mature bronchi were then the same (1.06 vs. 1.03 cmH2O/%, not significant). Because elastic moduli of the lung parenchyma are also similar in the two age groups, it was concluded that local features of airway-parenchyma coupling limited the generation of local parenchymal recoil around bronchi in the immature lungs.

Systematic calculations of energy levels and transitions rates in Mo XXVIII

2020 ◽  
Vol 75 (8) ◽  
pp. 739-747
Author(s):  
Feng Hu ◽  
Yan Sun ◽  
Maofei Mei
Keyword(s):  
Energy Levels ◽  
Oscillator Strengths ◽  
Atomic Data ◽  
Data Sets ◽  
Electron Systems ◽  
Excitation Energies ◽  
Experimental Values ◽  
Qed Effects ◽  
Hyperfine Structures ◽  
Good Agreement

AbstractComplete and consistent atomic data, including excitation energies, lifetimes, wavelengths, hyperfine structures, Landé gJ-factors and E1, E2, M1, and M2 line strengths, oscillator strengths, transitions rates are reported for the low-lying 41 levels of Mo XXVIII, belonging to the n = 3 states (1s22s22p6)3s23p3, 3s3p4, and 3s23p23d. High-accuracy calculations have been performed as benchmarks in the request for accurate treatments of relativity, electron correlation, and quantum electrodynamic (QED) effects in multi-valence-electron systems. Comparisons are made between the present two data sets, as well as with the experimental results and the experimentally compiled energy values of the National Institute for Standards and Technology wherever available. The calculated values including core-valence correction are found to be in a good agreement with other theoretical and experimental values. The present results are accurate enough for identification and deblending of emission lines involving the n = 3 levels, and are also useful for modeling and diagnosing plasmas.

scholarly journals DFT calculation and assignment of vibrational spectra of aryl and alkyl chlorophosphates

2014 ◽  
Vol 12 (2) ◽  
pp. 153-163
Author(s):  
Viktor Anishchenko ◽  
Vladimir Rybachenko ◽  
Konstantin Chotiy ◽  
Andrey Redko
Keyword(s):  
Vibrational Spectra ◽  
Basis Sets ◽  
Heavy Atoms ◽  
Wide Range ◽  
Complete Assignment ◽  
Key Factor ◽  
Polarization Functions ◽  
Experimental Values ◽  
Semi Empirical ◽  
Good Agreement

AbstractDFT calculations of vibrational spectra of chlorophosphates using wide range of basis sets and hybrid functionals were performed. Good agreement between calculated and experimental vibrational spectra was reached by the combination of non-empirical functional PBE0 with both middle and large basis sets. The frequencies of the stretching vibrations of the phosphate group calculated using semi-empirical functional B3LYP for all basis sets deviate significantly from the experimental values. The number of polarization functions on heavy atoms was shown to be a key factor for the calculation of vibrational frequencies of organophosphates. The importance of consideration of all the stable rotamers for a complete assignment of fundamental modes was shown.

scholarly journals Structural elastic and thermal properties of SrxCd1−x O mixed compounds — a theoretical approach

2014 ◽  
Vol 32 (3) ◽  
pp. 350-357
Author(s):  
Purvee Bhardwaj
Keyword(s):  
Phase Transition ◽  
Vibrational Energy ◽  
Zero Point ◽  
Study Phase ◽  
Energy Effect ◽  
Phase Transition Pressure ◽  
Vegard’S Law ◽  
Extended Interaction ◽  
Experimental Values ◽  
Good Agreement

AbstractIn the present paper, the structural and mechanical properties of alkaline earth oxides mixed compound SrxCd1−x O (0 ≤ x ≤ 1) under high pressure have been reported. An extended interaction potential (EIP) model, including the zero point vibrational energy effect, has been developed for this study. Phase transition pressures are associated with a sudden collapse in volume. Phase transition pressure and associated volume collapses [ΔV (Pt)/V(0)] calculated from this approach are in good agreement with the experimental values for the parent compounds (x = 0 and x = 1). The results for the mixed crystal counterparts are also in fair agreement with experimental data generated from the application of Vegard’s law to the data for the parent compounds.

Effect of transpulmonary pressure on airway closure in immature and mature rabbits

1995 ◽  
Vol 78 (2) ◽  
pp. 505-512 ◽  
Author(s):  
R. S. Tepper ◽  
S. J. Gunst ◽  
C. M. Doerschuk ◽  
X. Shen ◽  
W. Bray
Keyword(s):  
Smooth Muscle ◽  
Small Volume ◽  
Transpulmonary Pressure ◽  
Lung Parenchyma ◽  
Tracheal Smooth Muscle ◽  
Airway Closure ◽  
Maximal Stimulation ◽  
In Vitro Sensitivity ◽  
Airway Opening

The transpulmonary pressures (Ptp values) at which airway closure occurred during maximal stimulation with methacholine were compared in 10 mature and 9 immature rabbit lungs by using an alveolar capsule technique to assess airway closure. After maximal constriction, airway opening and alveolar capsule pressures were recorded during small volume oscillations as Ptp was lowered from 12 to 4 cmH2O. At each Ptp, the proportion of alveolar capsules indicating airway closure was greater for the immature than for the mature lungs (P < 0.025). At Ptp of 4 cmH2O, only 20% of alveolar capsules indicated airway closure in the mature lungs in contrast to 85% indicating closure in the immature lungs (P < 0.001). The in vitro sensitivity of tracheal smooth muscle to acetylcholine and histamine was greater in tissues from immature than from mature rabbits. We conclude that the more frequent airway closure observed in immature rabbits could reflect maturational differences in the structure of the bronchi or lung parenchyma or differences in the coupling between the parenchyma and the airways.

Microscopic vs. macroscopic deformation of the pulmonary alveolar duct

1992 ◽  
Vol 72 (4) ◽  
pp. 1348-1354 ◽  
Author(s):  
D. Yager ◽  
H. Feldman ◽  
Y. C. Fung
Keyword(s):  
Human Lung ◽  
Lung Parenchyma ◽  
Stretch Ratio ◽  
Area Ratio ◽  
Force Balance ◽  
Load Carrying ◽  
Macroscopic Deformation ◽  
Alveolar Duct ◽  
Deformed State ◽  
Length And Area

The stretch of the perimeters of alveolar ducts was measured at the surface of saline-filled specimens of human and dog lung parenchyma that were stretched biaxially. The microscopic stretch of these ducts was measured at several levels of isotropic biaxial macroscopic stretch of the parenchyma with stretch ratio (lambda x = lambda y) in the range of 1.20–1.40, which roughly corresponds to tidal breathing in humans and dogs. Alveolar walls were found to be load-carrying elements in the saline-filled lung, as seen by their straightness at all levels of stretch. Quantitatively, let l, A, L, and S denote, respectively, the duct perimeter length and area and the parenchymal target perimeter and area in the deformed state and lo, Ao, Lo, and So the corresponding variables in the undeformed state. The microscopic stretch ratio of the ducts (l/lo) was found to be approximately 4% larger than the macroscopic stretch ratio (L/Lo) in human lung and approximately 10% larger in dog lung. The microscopic area ratio of the ducts (A/Ao) was found to be approximately 10% larger than the macroscopic area ratio (S/So) in human lung and approximately 22% larger in dog lung. Ducts within human parenchyma were seen to be about twice as stiff as ducts within dog parenchyma over the range of macroscopic stretch studied. This correlates with the volume fractions of collagen and elastin being higher in the human lung than in dog lung. The observed nonuniformity in strain field at the microstructural level suggests the need to include a force balance between alveolar ducts and septal walls when modeling the mechanics of saline-filled parenchyma.

Speed of stress wave propagation in lung

1986 ◽  
Vol 61 (2) ◽  
pp. 701-705 ◽  
Author(s):  
R. T. Yen ◽  
Y. C. Fung ◽  
H. H. Ho ◽  
G. Butterman
Keyword(s):  
Wave Propagation ◽  
Stress Wave ◽  
Impact Loading ◽  
Wave Speed ◽  
Dynamic Pressure ◽  
Transpulmonary Pressure ◽  
Lung Parenchyma ◽  
Surface Velocity ◽  
Stress Wave Propagation ◽  
Rabbit Lung

The speed of stress waves in the lung parenchyma was investigated to understand why, among all internal organs, the lung is the most easily injured when an animal is subjected to an impact loading. The speed of the sound is much less in the lung than that in other organs. To analyze the dynamic response of the lung to impact loading, it is necessary to know the speed of internal wave propagation. Excised lungs of the rabbit and the goat were impacted with water jet at dynamic pressure in the range of 7–35 kPa (1–5 psi) and surface velocity of 1–15 m/s. The stress wave was measured by pressure transducer. The distance between the point of impact and the sensor at another point on the far side of the lung and the transit time of the stress wave were measured. The wave speed in the goat lung was found to vary from 31.4 to 64.7 m/s when the transpulmonary pressure Pa-Ppl was varied from 0 to 20 cmH2O where Pa represents airway pressure and Ppl represents pleural pressure. In rabbit lung the wave speed varied from 16.5 to 36.9 m/s when Pa-Ppl was varied from 0 to 16 cmH2O. Using measured values of the bulk modulus, shear modulus, and density of the parenchyma, reasonable agreement between theoretical and experimental wave speeds were obtained.

Cavitation Inception Behind a Jet-Propelled Body

2007 ◽  
Author(s):  
William Hambleton ◽  
Eduard Amromin ◽  
Roger E. A. Arndt ◽  
Svetlana Kovinskaya
Keyword(s):  
Velocity Ratio ◽  
The Body ◽  
Force Balance ◽  
Water Tunnel ◽  
Minimum Diameter ◽  
Cavitation Inception ◽  
Initial Comparison ◽  
Jet Velocity ◽  
Good Agreement

Cavitation inception behind an axissymmetric body driven by a waterjet has been studied experimentally and numerically. Water tunnel tests have been performed with the body mounted on a force balance. The transom of the body contained a nozzle located along the centerline. Tests were carried out for various water tunnel speeds such that jet velocity ratio, VJ/U, could be varied in the range 0 to 2. Distinctly different cavitation patterns were observed at zero jet velocity (when cavitation appeared in spiral vortices in such flows) and at a various jet velocity ratios (when cavitation appeared between counter-rotating vortices around the jet in such flows). Cavitation inception/disappearance has been determined visually. The body drag was also measured. An analytical method for determination of cavitation inception index has been developed on the basis of a viscous-inviscid interaction concept, with employment of special semiempirical approximations for vortices and consideration of surface tension. These approximations have been preliminarily validated for nozzle jet cavitation (for nozzle discharge in co-flow). It was assumed that visualization allows detection of cavities (bubbles) of 0.4mm-0.5mm diameter or larger. The cavitation inception index is defined as the cavitation index for cavities of such minimum diameter when these cavities are located between counter-rotating vortices. The initial comparison of predicted and measured values of the cavitation inception index shows good agreement.

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