Sensitivity of CO2 washout to changes in acinar structure in a single-path model of lung airways

1991 ◽  
Vol 19 (6) ◽  
pp. 679-697 ◽  
Author(s):  
Jeffrey D. Schwardt ◽  
Sherif R. Gobran ◽  
Gordon R. Neufeld ◽  
Stanley J. Aukburg ◽  
Peter W. Scherer
Keyword(s):  
Path Model ◽  
Acinar Structure ◽  
Co2 Washout ◽  
Lung Airways ◽  
Single Path

An Axisymmetric Single-Path Model for Gas Transport in the Conducting Airways

2005 ◽  
Vol 128 (1) ◽  
pp. 69-75 ◽  
Author(s):  
Srinath Madasu ◽  
Ali Borhan ◽  
James S. Ultman
Keyword(s):  
Finite Element ◽  
Numerical Solutions ◽  
Diffusion Processes ◽  
Path Model ◽  
Navier Stokes ◽  
Straight Tube ◽  
Element Analysis ◽  
Continuity Equations ◽  
Longitudinal Position ◽  
Single Path

In conventional one-dimensional single-path models, radially averaged concentration is calculated as a function of time and longitudinal position in the lungs, and coupled convection and diffusion are accounted for with a dispersion coefficient. The axisymmetric single-path model developed in this paper is a two-dimensional model that incorporates convective-diffusion processes in a more fundamental manner by simultaneously solving the Navier-Stokes and continuity equations with the convection-diffusion equation. A single airway path was represented by a series of straight tube segments interconnected by leaky transition regions that provide for flow loss at the airway bifurcations. As a sample application, the model equations were solved by a finite element method to predict the unsteady state dispersion of an inhaled pulse of inert gas along an airway path having dimensions consistent with Weibel’s symmetric airway geometry. Assuming steady, incompressible, and laminar flow, a finite element analysis was used to solve for the axisymmetric pressure, velocity and concentration fields. The dispersion calculated from these numerical solutions exhibited good qualitative agreement with the experimental values, but quantitatively was in error by 20%–30% due to the assumption of axial symmetry and the inability of the model to capture the complex recirculatory flows near bifurcations.

scholarly journals The effect of alveolar mixing on particle retention and deposition investigated by a dynamic single-path model

2020 ◽  
Vol 54 (9) ◽  
pp. 1102-1115
Author(s):  
Filippos Filippitzis ◽  
Konstantinos Gourgoulianis ◽  
Zoi Daniil ◽  
Vasileios Bontozoglou
Keyword(s):  
Path Model ◽  
Particle Retention ◽  
Single Path

Longitudinal Distribution of Ozone Absorption in the Lung: Simulation with a Single-Path Model

1996 ◽  
Vol 140 (2) ◽  
pp. 219-226 ◽  
Author(s):  
Michele L. Bush ◽  
Troy Raybold ◽  
Shimon Abeles ◽  
Shu-Chieh Hu ◽  
Abdellaziz Ben-Jebria ◽  
...  
Keyword(s):  
Path Model ◽  
Longitudinal Distribution ◽  
Ozone Absorption ◽  
Lung Simulation ◽  
Single Path

Bidirectional Associations Between Self-Perceptions of Aging and Processing Speed Across 3 Years

GeroPsych ◽  
2017 ◽  
Vol 30 (2) ◽  
pp. 49-59 ◽  
Author(s):  
Anna L. Seidler ◽  
Julia K. Wolff
Keyword(s):  
Processing Speed ◽  
Personal Growth ◽  
Significant Loss ◽  
Path Model ◽  
Outcome Variable ◽  
Beneficial Effects ◽  
Self Perceptions ◽  
Chi Squared ◽  
Perceptions Of Aging ◽  
Bidirectional Associations

Abstract. Background: Previous studies point to a potential relationship between self-perceptions of aging (SPA) and cognitive performance. However, most of these studies are limited by their experimental design. Previous longitudinal studies looked solely at memory as an outcome variable without examining the directionality of effects. The present study examines the direction of effects between two domains of SPA (personal growth and physical losses) and processing speed (PS). Methods: The sample consists of 8,198 participants of the German Ageing Survey (DEAS), aged between 40 and 93 years. A cross-lagged path model was estimated to examine directions of relationships across 3 years via chi-squared difference tests for each domain of SPA. Results: In the unconstrained models, the effect of SPA domain personal growth in 2008 on PS in 2011 and vice versa were marginally significant. For SPA domain physical losses, the effect of SPA on PS was significant, whereas the other direction of the effect did not reach significance. However, the cross-lagged paths of both domains of SPA on PS and vice versa could be set equal without a significant loss of model fit. The resulting associations indicate a significant bidirectional relationship between both domains of SPA and PS. Discussion and conclusion: This study provides initial evidence that SPA can influence trajectories of cognitive decline and vice versa. The results emphasize the detrimental and beneficial effects that stereotypes can have on individuals and add further evidence to the theory of stereotype embodiment.

Passive Facebook Use and Depression

2020 ◽  
Vol 32 (4) ◽  
pp. 165-175 ◽  
Author(s):  
Leman Pınar Tosun ◽  
Ezgi Kaşdarma
Keyword(s):  
Social Comparisons ◽  
Path Model ◽  
The Other ◽  
Facebook Use ◽  
Psychological Mechanism ◽  
Model Fits

Abstract. In the current study we examined a psychological mechanism linking Facebook use to depression. A survey was conducted with 319 undergraduates about their passive Facebook use, their frequency of making upward social comparisons on Facebook, the emotions evoked through these comparisons, and their levels of depression. Half of the participants were given questions about the Facebook comparisons they made with their close friends, while the other half were given questions about the Facebook comparisons they made with acquaintances. Analysis of the whole sample revealed that upward Facebook comparison elicited assimilative emotions (inspiration, optimism, and admiration) more than contrastive emotions did (envy and resentment). A path model was developed in which passive use of Facebook predicted the frequency of making upward social comparisons, and, in turn, the frequency of making upward Facebook comparisons predicted depression through two routes: one through contrastive emotions and other through assimilative emotions. The results suggested that the model fits the data. As expected, the frequency of upward Facebook comparisons was associated with the increases in frequency of both contrastive and assimilative emotions, and the associations of these two types of emotions with depression were in opposite directions: Depression increased as the frequency of contrastive emotions increased, and it decreased as the frequency of assimilative emotions increased. The strength of the latter aforementioned association was stronger when the comparison targets were acquaintances rather than close friends.

The effects of cross training teams: A meta-analytic path model

2009 ◽  
Author(s):  
Kevin C. Stagl ◽  
Cameron Klein ◽  
Patrick J. Rosopa ◽  
Deborah DiazGranados ◽  
Eduardo Salas ◽  
...  
Keyword(s):  
Path Model ◽  
Cross Training

Interconnect Limits on Gigascale Integration (GSI)

1997 ◽  
Vol 473 ◽  
Author(s):  
J. A. Davis ◽  
J. D. Meindl
Keyword(s):  
Response Time ◽  
Length Distribution ◽  
Path Model ◽  
System Level ◽  
Wire Length ◽  
Clock Frequency ◽  
Gigascale Integration ◽  
Logic Network ◽  
Binary Switching ◽  
Quantitative Definition

ABSTRACTOpportunities for Gigascale Integration (GSI) are governed by a hierarchy of physical limits. The levels of this hierarchy have been codified as: 1) fundamental, 2) material, 3) device, 4) circuit and 5) system. Many key limits at all levels of the hierarchy can be displayed in the power, P, versus delay, td, plane and the reciprocal length squared, L-2, versus response time, τ, plane. Power, P, is the average power transfer during a binary switching transition and delay, td, is the time required for the transition. Length, L, is the distance traversed by an interconnect that joins two nodes on a chip and response time, τ, characterizes the corresponding interconnect circuit. At the system level of the hierarchy, quantitative definition of both the P versus td and the L-2 versus τ displays requires an estimate of the complete stochastic wiring distribution of a chip.Based on Rent's Rule, a well known empirical relationship between the number of signal input/output terminals on a block of logic and the number of gate circuits with the block, a rigorous derivation of a new complete stochastic wire length distribution for an on-chip random logic network is described. This distribution is compared to actual data for modern microprocessors and to previously described distributions. A methodology for estimating the complete wire length distribution for future GSI products is proposed. The new distribution is then used to enhance the critical path model that determines the maximum clock frequency of a chip; to derive a preliminary power dissipation model for a random logic network; and, to define an optimal architecture of a multilevel interconnect network that minimizes overall chip size. In essence, a new complete stochastic wiring distribution provides a generic basis for maximizing the value obtained from a multilevel interconnect technology.

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