Experimental evaluation of geomembrane/geotextile interface as base isolating system

The objective of this study is to evaluate the effect of the geomembrane/geotextile interface on the seismic response of small-to-moderate height structures. Three building models with first-mode natural frequencies changing between 2-4 Hz (representing two, three and four storey structures) were tested with and without the addition of geomembrane/geotextile interface using the shaking table test setup by employing harmonic and modified/ scaled ground motions. Experimental results showed that the geomembrane/geotextile interface significantly reduced the floor accelerations, especially at moderate-to-high ground shaking levels. The interaction between the first-mode natural frequency of the model and the predominant frequency of the input motion is significant, and the interface is most effective when these two frequencies are close to each other. This effect is more clearly seen when the harmonic motions are employed during the tests compared to the modified/scaled ground motions. The results of the tests with modified/ scaled ground motions were used to evaluate the efficiency of the composite liner system in reducing the spectral accelerations in the frequency domain. The results presented here document that the geomembrane/geotextile interface reduces the floor accelerations in a certain frequency range and underline the potential of this interface to be used as a base isolation material

3D settlement analysis of underpinning piles under raft foundation subjected to nonuniform vertical loading

Existing rafts under the design loads sometimes experience excessive settlements or confront such a possibility in the future if the modified functionality of building is induced to increase the foundation loading. Differential settlement and deflection may also be observed in case of eccentric loading especially when these structures are built on soft soils. One of such precedents was observed in a silo structure used as a cement plant located in Douala, Cameroon. The structure that is founded on deep, soft clay with high ground water table rests on a raft supporting the storage tanks located at one side of the building conveying non-uniform loading to the existing raft. In one and a half year after completion of the construction, the silo structure had significantly settled and deflected. The underpinning pile remediation system allowing the continuity of cement production is applied from the outside of building using the rigidly connected protruding reinforced concrete section as a capping beam. In this study, the entire foundation system is numerically analyzed using the presented 3D finite element (FE) models. The back-analyses are used for the calibration concurring with the actual measurements of settlement and deflection at the site. The foundation systems with and without the underpinning piles are compared with each other to reveal how the remedial improvement is achieved by the presented underpinning pile system

Cartilage tissue engineering using dermis isolated adult stem cells: the use of hypoxia during expansion versus chondrogenic differentiation.

Dermis isolated adult stem (DIAS) cells, a subpopulation of dermis cells capable of chondrogenic differentiation in the presence of cartilage extracellular matrix, are a promising source of autologous cells for tissue engineering. Hypoxia, through known mechanisms, has profound effects on in vitro chondrogenesis of mesenchymal stem cells and could be used to improve the expansion and differentiation processes for DIAS cells. The objective of this study was to build upon the mechanistic knowledge of hypoxia and translate it to tissue engineering applications to enhance chondrogenic differentiation of DIAS cells through exposure to hypoxic conditions (5% O2) during expansion and/or differentiation. DIAS cells were isolated and expanded in hypoxic (5% O2) or normoxic (20% O2) conditions, then differentiated for 2 weeks in micromass culture on chondroitin sulfate-coated surfaces in both environments. Monolayer cells were examined for proliferation rate and colony forming efficiency. Micromasses were assessed for cellular, biochemical, and histological properties. Differentiation in hypoxic conditions following normoxic expansion increased per cell production of collagen type II 2.3 fold and glycosaminoglycans 1.2 fold relative to continuous normoxic culture (p<0.0001). Groups expanded in hypoxia produced 51% more collagen and 23% more GAGs than those expanded in normoxia (p<0.0001). Hypoxia also limited cell proliferation in monolayer and in 3D culture. Collectively, these data show hypoxic differentiation following normoxic expansion significantly enhances chondrogenic differentiation of DIAS cells, improving the potential utility of these cells for cartilage engineering

Evaluating smartphone-based user interface designs for a 2D psychological questionnaire

This study explored various user interface designs to transition a two dimensional (2D) questionnaire from its paper-and-pencil testing format to the mobile platform. The current administration of the test limits its usage beyond the lab environment. Creating a mobile version would facilitate ubiquitous administration of the test. Yet, the mobile design must be at least as good as its paper-based counterpart in terms of input accuracy and user interaction efforts. We developed four user interface designs, each of which featured a specific interaction approach. These approaches included displaying the 2D space of the questionnaire in its original form (M1), inputting one variable at a time on the 2D space (M2), dissolving the 2D space into two one-dimensional ordinal scales (M3), and orienting the input selections to the diagonal axes (M4). The designs were tested by a total of 34 participants, aged 18 to 52 years. The study results find the first three interaction approaches (M1-M3) effective but the fourth approach inefficient. Furthermore, the results indicate that the two-tap designs (M2 and M3) are equally as good as the one-tap design (M1)

Effects of shear stresses and rotary inertia on the stability and vibration of sandwich cylindrical shells with FGM core surrounded by elastic medium

The vibration and stability of axially loaded sandwich cylindrical shells with the functionally graded (FG) core with and without shear stresses and rotary inertia resting Pasternak foundation are investigated. The dynamic stability is derived based on the first order shear deformation theory (FSDT) including shear stresses. The axial load and dimensionless fundamental frequency for FG sandwich shell with shear stresses and rotary inertia and resting on the Pasternak foundation. Finally, the influences of variations of FG core, elastic foundations, shear stresses and rotary inertia on the fundamental frequencies and critical axial loads are investigated

Stability of EG cylindrical shells with shear stresses on a Pasternak foundation

This article is the result of an investigation on the influence of a Pasternak elastic foundation on the stability of exponentially graded (EG) cylindrical shells under hydrostatic pressure, based on the first-order shear deformation theory (FOSDT) considering the shear stresses. The shear stresses shape function is distributed parabolic manner through the shell thickness. The governing equations of EG orthotropic cylindrical shells resting on the Pasternak elastic foundation on the basis of FOSDT are derived in the framework of Donnell-type shell theory. The novelty of present work is to achieve closed-form solutions for critical hydrostatic pressures of EG orthotropic cylindrical shells resting on Pasternak elastic foundation based on FOSDT. The expressions for critical hydrostatic pressures of EG orthotropic cylindrical shells with and without an elastic foundation based on CST are obtained, in special cases. Finally, the effects of Pasternak foundation, shear stresses, orthotropy and heterogeneity on critical hydrostatic pressures, based on FOSDT are investigated

Collagen accumulation during micromass culture.

<p>Hypoxic expansion led to increased total collagen accumulation (A) and collagen accumulation per cell (C) during differentiation. Overall collagen type II production was greatest in the NH group (B) as was collagen type II production per cell (D) and relative to total collagen production (E). Data are mean ± S.D. Groups not connected by letters are significantly different. Significance defined as <i>p</i><0.05.</p

Histological sections of micromasses after 2 weeks.

<p>Collagen type I staining was strongest for HH (first row), while collagen type II staining was strongest for NH (second row). All groups stained positive for collagen (third row).</p

Hypoxia limits proliferation during 3D culture.

<p>Cells were seeded at 2×10⁵ per micromass (dashed line). Data are mean ± S.D. Groups not connected by letters are significantly different with <i>p</i><0.05.</p