Mechanical Properties of the Canine Aorta Following Hypercholesterolemia

1980 ◽  
Vol 102 (2) ◽  
pp. 98-102 ◽  
Author(s):  
R. C. Haut ◽  
B. D. Garg ◽  
M. Metke ◽  
M. Josa ◽  
M. P. Kaye
Keyword(s):  
Mechanical Properties ◽  
Saturated Fat ◽  
Elastic Fibers ◽  
Atherosclerotic Plaques ◽  
Histological Changes ◽  
Experimental Pathology ◽  
Tensile Response ◽  
Strain Axis ◽  
And Control ◽  
Canine Aorta

The effect of hypercholesterolemia on the transverse wall properties of the upper descending thoracic aorta was studied in canines. Hypothyroid animals were fed a free diet supplemented with cholesterol, propylthiouracil, and saturated fat (lard) for 11 mo. The mechanical properties of the wall showed marked changes following experimental pathology. The failure stress, failure elongation, and energy to failure decreased following hypercholesterolemia. The tensile response was bilinear in both the pathological and control tissues. In the initial region, which is controlled by elastic fibers, the response was left unchanged by the experimental pathology. In the secondary region, which is controlled by stretching of the collagen fibers, the intercept with the strain axis and the slope were decreased by the pathology. This indicates that there are changes in the strength-bearing collagen and its interaction with the amorphous matrix. However, no significant parallel histological changes were observed in the structure of collagen and elastic fibers. Although this phenomenon precedes the development of atherosclerotic plaques which are charateristic of a diagnosed human disease, the aortic wall is already “hardened” because of its reduced compliance resulting from the shift in the onset of secondary (collagenous) response.

Mechanical properties of the tracheal mucosal membrane in the rabbit. II. Morphometric analysis

2000 ◽  
Vol 88 (3) ◽  
pp. 1022-1028 ◽  
Author(s):  
Lu Wang ◽  
Kenneth L. Pinder ◽  
Joel L. Bert ◽  
Mitsushi Okazawa ◽  
Peter D. Paré
Keyword(s):  
Mechanical Properties ◽  
Volume Fraction ◽  
Mechanical Load ◽  
Morphological Structure ◽  
Longitudinal Direction ◽  
Smooth Muscle Contraction ◽  
Elastic Fibers ◽  
Tissue Samples ◽  
Mucosal Membrane ◽  
Simple Geometry

Folding of the airway mucosal membrane provides a mechanical load that impedes airway smooth muscle contraction. Mechanical testing of rabbit tracheal mucosal membrane showed that the membrane is stiffer in the longitudinal than in the circumferential direction of the airway. To explain this difference in the mechanical properties, we studied the morphological structure of the rabbit tracheal mucosal membrane in both longitudinal and circumferential directions. The collagen fibers were found to form a random meshwork, which would not account for differences in stiffness in the longitudinal and circumferential directions. The volume fraction of the elastic fibers was measured using a point-counting technique. The orientation of the elastic fibers in the tissue samples was measured using a new method based on simple geometry and probability. The results showed that the volume fraction of the elastic fibers in the rabbit tracheal mucosal membrane was ∼5% and that the elastic fibers were mainly oriented in the longitudinal direction. Age had no statistically significant effect on either the volume fraction or the orientation of the elastic fibers. Linear correlations were found between the steady-state stiffness and the quantity of the elastic fibers oriented in the direction of testing.

scholarly journals Effect of Different Hydrothermal Treatments (Steam and Hot Compressed Water) on Physical Properties and Drying Behavior of Yellow-Poplar (Liriodendron tulipifera)

2019 ◽  
Vol 69 (1) ◽  
pp. 42-52
Author(s):  
Sohrab Rahimi ◽  
Kaushlendra Singh ◽  
David DeVallance
Keyword(s):  
Mechanical Properties ◽  
High Pressure ◽  
Moisture Content ◽  
Yellow Poplar ◽  
Pressure Steam ◽  
Percent Moisture ◽  
Drying Behavior ◽  
Hot Compressed Water ◽  
And Control ◽  
Control Samples

Abstract Nonchemical high-pressure steam treatments have been intensively researched and commercialized to produce chemical-free wood products with enhanced properties. However, the utilization of high-pressure steam involves vapor-phase reactions using high-temperature steam generated at the expense of high energy input. In this research, influences of reaction media (steam and hot-compressed water) and temperature (100°C and 140°C) during thermal treatment on physical properties and drying behavior of yellow-poplar (Liriodendron tulipifera) heartwood were compared. The length, width, and thickness of the samples were 22.53 mm, 17.18 mm, and 16.72 mm, respectively. After the treatment, the samples were dried under an isothermal temperature condition of 105°C. Data on moisture content and time of drying from drying experiments were fitted with unsteady-state molecular transport equations to calculate overall liquid diffusion coefficients. Dimensions, weight, and true volume of samples were measured for green, thermally treated, and dried samples and the values were used to calculate selected physical characteristics. Additionally, selected mechanical properties were evaluated for samples conditioned to 13 percent moisture content. Results showed that intensified hot-compressed water-treated and control samples had the highest and lowest saturated moisture contents (101% and 44%), respectively, immediately after treatments. Intensified steam-treated and control samples had the highest and lowest total porosity (95% and 82%), respectively. Furthermore, mild hot-compressed water-treated samples showed the greatest compression strength (47.8 MPa) at 13 percent moisture content. Except for steam treatment at 140°C, other treatments significantly decreased the diffusion coefficient. Collectively, samples treated with hot-compressed water at 100°C showed the most improved mechanical properties.

scholarly journals NI-11 PATHOLOGICAL ASSESSMENT IN THE IMPACT OF ONE-SHOT BEVACIZUMAB ON UPTAKE OF 11C-METHIONINE

2019 ◽  
Vol 1 (Supplement_2) ◽  
pp. ii27-ii28
Author(s):  
Takaaki Beppu ◽  
Yuichi Sato ◽  
Kuniaki Ogasawara
Keyword(s):  
Amino Acid ◽  
Microvascular Density ◽  
Control Group ◽  
Tumor Removal ◽  
Histological Changes ◽  
Positron Emission ◽  
Newly Diagnosed Glioblastoma ◽  
And Control ◽  
The Impact ◽  
Single Intravenous Administration

Abstract BACKGROUND This study aimed to clarify how one-time administration of bevacizumab (BEV) changes histological features in glioblastoma, and how histological changes affect the uptake of 11C-methyl-L-methionine (11C-met) as an amino-acid tracer. MATERIALS AND METHODS Subjects were 18 patients with newly diagnosed glioblastoma who were assigned to 2 groups: BEV group, single intravenous administration of BEV before surgical tumor removal; and control group, surgical tumor removal alone. After surgery, we compared the densities of tumor cells and microvessels, and microvascular structures including vascular pericytes and L-type amino acid transporter-1 (LAT1), between the BEV and control groups. Correlations between 11C-met uptake on positron emission tomography before surgery, microvascular density, and LAT1 expression were assessed in each group. RESULTS BEV induced significant reductions in microvascular density, while tumor cell density and proliferation were retained in the BEV group. Percentages of vessels with pericytes and vascular endothelium with LAT1 expression were lower in the BEV group than in controls. Uptake of 11C-met correlated significantly with microvascular density in the BEV group, but not with LAT1expression. CONCLUSIONS The present study showed that even one course of BEV administration induced reductions in microvessels, vascular pericytes, and LAT1 expression in glioblastomas. One course of BEV therapy also reduced 11C-met uptake, which might have been largely attributed to reductions in microvessels rather than reductions in LAT1 expression, in addition to reduction of vascular permeability.

scholarly journals Performance of lightweight mortar reinforced with doum palm fiber

2020 ◽  
pp. 002199832097519
Author(s):  
Fatma Naiiri ◽  
Allègue Lamis ◽  
Salem Mehdi ◽  
Zitoune Redouane ◽  
Zidi Mondher
Keyword(s):  
Mechanical Properties ◽  
Thermal Properties ◽  
Natural Fiber ◽  
Cement Mortar ◽  
Low Cost ◽  
Natural Fibers ◽  
Construction Materials ◽  
Mechanical And Thermal Properties ◽  
Palm Fiber ◽  
And Control

Natural fibers are increasingly used in composites because of their low cost and good mechanical properties. Cement reinforced with natural fibersis contemplates as a new generation of construction materials with superior mechanical and thermal performance. This study of three sizes’effect of Doum palm fiber explores the mortar’s behavior reinforced with different fiber ratio. The aim is to determine the optimal addition to improve mechanical and thermal properties of natural fiber reinforced cements. Physical, mechanical and thermal properties of composite are examined. Tensile properties of Doum fibers are verified to determine their potential as reinforced material. Findings prove that the use of alkali-treated Doum fiber as reinforcement in cement mortar composite leads to the upgrading of the mechanical properties including thermo-physical properties against composites reinforced with raw fibers and control cement mortars. While, the compression and flexural strength of the cement mortar reinforced with alkali-treated Doum fiber with diameter 0.3 mm (CT3) are metered to be 11.11 MPa, 5.22 MPa, respectively for fiber content 0.5%. Additionally, based on thermo-physical tests, it is assessed that the thermal conductivity and diffusivity decrease for cement mortar reinforced with Doum fiber with diameter 0.2 mm (CT2).

Complex Sparse-Filled Mechanical Property Prediction Methods for Direct Digital Manufacturing

2013 ◽  
Author(s):  
David N. Kordonowy ◽  
Sydney A. Giblin
Keyword(s):  
Mechanical Properties ◽  
Additive Manufacturing ◽  
Flexible Manufacturing ◽  
Test Methods ◽  
Low Noise ◽  
Digital Manufacturing ◽  
Cycle Times ◽  
Mechanical Property Prediction ◽  
Direct Digital Manufacturing ◽  
And Control

This paper describes how direct digital manufacturing mechanical properties can be analytically estimated for structural use and the associated analytical and test methods used in the design and fabrication of airframes manufactured using additive manufacturing. Complex shape structures, which are now possible using additive manufacturing, and their associated mechanical properties can be predicted in order to allow operationally safe and highly predictive structures to be fabricated. Direct digital manufacturing allows for much greater flexibility and control over the design of airframes, leading to more structurally efficient and capable airframes. These advantages are revealed by application of direct digital manufacturing methods on a series of fixed wing subsonic transport concept wind tunnel scale models that are carried out as a part of the NASA N+3 program, which is paving the way for next generation aircraft that are highly fuel efficient, low-noise, and low-emission. Verification of these methods through test shows excellent correlation that provides reliability in complex sparse filled additive manufacturing design. The outcome of this is a knowledge base, which can then be applied to a system in operation. The combined potential of a flexible manufacturing system and proven predictive analysis tools shorten development time and expand the opportunities for mass customization. These combined benefits enable industry to fabricate affordable highly optimized custom products while concurrently reducing the cycle times required to field new products.

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