Conventional tissue engineering scaffolds have limited ability to undergo programmed changes in physical properties. Here we present a thermo-responsive and biocompatible tissue engineering scaffold prepared by electrospinning a shape memory polymer (SMP). SMPs have characteristics which allow them to be manipulated and fixed in a temporary shape and later recover back to their permanent shape on command. We hypothesized that a programmed change in scaffold architecture could control cell body orientation. To test this hypothesis, we uniaxially stretched an initially random mesh (the permanent state) and fixed it to a temporarily aligned mesh. After first seeding cells on the temporarily aligned mesh, we triggered a change in shape by increasing the temperature from 30°C to 37°C which resulted in the scaffold structure recovering back to its initial random structure. Alignment of cell bodies was quantified by two-dimensional fast Fourier transform (2D FFT) analysis of filamentous actin fibers. We found that before triggering a change in shape, cells aligned preferentially along the direction of fiber orientation. After the shape-memory-activated structure change, cells lost their preferential alignment. Shape-changing scaffolds based on this concept are anticipated to provide a powerful tool to study cell mechanobiology and increase tissue engineering scaffold functionality.
Report describes the development of the Langley annular transonic tunnel, a facility in which test Mach numbers from 0.6 to slightly over 1.0 are achieved by rotating the test model in an annular passage between two concentric cylinders. Data obtained for two-dimensional airfoil models in the Langley annular transonic tunnel at subsonic and sonic speeds are shown to be in reasonable agreement with experimental data from other sources and with theory when comparisons are made for nonlifting conditions or for equal normal-force coefficients rather than for equal angles of attack. The trends of pressure distributions obtained from measurements in the Langley annular transonic tunnel are consistent with distributions calculated for Prandtl-Meyer flow.
Focal adhesion complexes function as the mediators of cell-extracellular matrix interactions to sense and transmit the extracellular signals. Previous studies have demonstrated that cardiomyocyte focal adhesions can be modulated by surface topographic features. However, the response of focal adhesions to dynamic surface topographic changes remains underexplored. To study this dynamic responsiveness of focal adhesions, we utilized a shape memory polymer-based substrate that can produce a flat-to-wrinkle surface transition triggered by an increase of temperature. Using this dynamic culture system, we analyzed three proteins (paxillin, vinculin and zyxin) from different layers of the focal adhesion complex in response to dynamic extracellular topographic change. Hence, we quantified the dynamic profile of cardiomyocyte focal adhesion in a time-dependent manner, which provides new understanding of dynamic cardiac mechanobiology.
Abstract : This report summarizes the studies made to date by the Army Missile Command on the effects of the rocket jet plume on the Stability characteristics of a body of revolution with various fin configurations and at various fin positions on the body. The Mach numbers ranged from 0.2 to 2.3. A normal jet plume simulator was used to obtain the desired plume effects. This report concerns itself with those tests conducted on a 5-in. diameter, 52-in. long model, with a 3 caliber tangent ogive nose.
Extrusion-based (fused filament fabrication) three-dimensional (3D) printing of shape-memory polymers (SMPs) has the potential to rapidly produce highly customized smart-material parts. Yet, the effects of printing parameters on the shape-memory properties of printed SMPs remain poorly understood. To study the extent to which the 3D printing process affects the shape-memory properties of a printed SMP part, here temperature, extrusion rate multiplier, and fiber orientation were systematically varied, and their effect on shape-memory fixing and recovery ratios was evaluated. Fiber orientation, as determined by print path relative to the direction(s) of loading during shape-memory programming, was found to significantly impact the fixing ratio and the recovery ratio. Temperature and multiplier had little effect on either fixing ratio or recovery ratio. To facilitate the use of printed SMP parts in biomedical applications, a cell viability assay was performed on 3D-printed samples prepared using varied temperature and multiplier. Reduction in multiplier was found to increase cell viability. The results indicate that fiber orientation can critically impact the shape-memory functionality of 3D-printed SMP parts, and that multiplier can affect cytocompatibility of those parts. Thus, researchers and manufacturers employing SMPs in 3D-printed parts and devices could achieve improved part functionality if print paths are designed to align fiber direction with the axis(es) in which strain will be programmed and recovered and if the multiplier is optimized in biomedical applications in which a part will contact cells.
Cellular tracking has been employed to investigate complex cell-cell and cell-material interactions that play critical roles in tissue development and disease progression. Tracking is often performed manually, however limitations associated with manual tracking make it impractical for tracking dense populations of cells. To address these limitations, several automated tracking algorithms have been developed, buy most of these algorithms are incapable of tracking cells after occlusion events or cell divisions. Here we have developed a custom algorithm in MATLAB that employs a contour-based segmentation approach to identify and track cell divisions and occlusion events. The algorithm further analyzes cell tracks during occlusion events using a cost analysis to detect and relabel mislabeled cells.
Abstract The results of a series of laboratory flood tests using liquid iso-butane to displace refined oils from test cores are presented and interpreted on an empirical basis. The study revealed the similarity of the miscible liquid displacement to that of the immiscible-fluid displacement mechanism. The efficiency of the iso-butane flood decreased markedly as the oil viscosity increased, but the effect of injection rate on the effectiveness of the primary production stage was negligible over the range investigated. The presence of free-gas saturation prior to iso-butane breakthrough increased the volume of isobutane required to recover a given percentage of the oil present. Injection of liquid iso-butane prior to water flood resulted in a marked improvement in oil recovery by the water flood. Introduction The production of petroleum is often enhanced by the injection of extraneous fluids into the reservoir. It has been suggested that the injection or cycling of a wet gas or a liquefied petroleum gas would be instrumental in increasing the efficiency of oil recovery to a greater degree than the commonly injected fluids, dry gas and water. Although instances of injection of light liquid hydrocarbons are not unknown, a systematic recording of the results is unavailable; and superficially, the practice gives the impression of being economically unsound. For specific types of displacement, analytic solutions have been advanced which aid in understanding the physical mechanisms involved. However, there is no generalized theoretical concept which permits adequate prediction of displacement efficiency from a knowledge of readily measured reservoir rock and fluid properties. The Buckley-Leverett approach to oil displacement by an immiscible phase is an admirable analysis of that type of mechanism. Dykstra and Parsons have introduced a useful concept in their evaluation of the role of the mobility ratio and its merit in rationalizing displacement phenomena. Everett, Gooch and Calhoun in their report on the effect of viscosity ratio and miscibility have pointed out the lack of a comprehensive theoretical approach and the desirability of investigating the mechanism of miscible-miscible displacement. In lieu of a well-developed theory concerning miscible-miscible displacement and in view of the scarcity of engineering information on actual LPG injection trials, the limited program of laboratory experimentation described below was undertaken.
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