Cavity expansion is a fundamental theoretical problem in geomechanics. For the cylindrical cavity expansion problem, derivations of solutions are usually based on the assumption that the soil is ...subject to the plane strain condition. However, this is untrue for cavity expansion in pressuremeter tests. This study first derived the equilibrium equation for cylindrical cavity expansion under the constant vertical stress condition. Then, the equilibrium equation was solved for modified Cam clay soils with different overconsolidation ratios (OCRs). The solutions were compared with the responses in the same soils under the plane strain condition. It was found that the ratio of the limiting cavity pressure in the latter to that in the former ranged from 1.31 to 2.76 and increased with an increase in the OCR. Under the constant vertical stress condition, significant heaving occurred in the vicinity of the cavity, and volumetric strain evolved from contraction to dilation as the OCR increased. Significant differences were noted in the stress paths of the two different loading conditions. These results indicate that the assumption of the plane strain condition will lead to overestimation of the limiting cavity pressure and inaccurate prediction of the stress path in the pressuremeter test, especially for heavily overconsolidated soils.
With the aim of gathering temporal trends on bacterial epidemiology and resistance from multiple laboratories in China, the CHINET surveillance system was organized in 2005. Antimicrobial ...susceptibility testing was carried out according to a unified protocol using the Kirby-Bauer method or automated systems. Results were analyzed according to Clinical and Laboratory Standards Institute (CLSI) 2014 definitions. Between 2005 and 2014, the number of bacterial isolates ranged between 22 774 and 84 572 annually. Rates of extended-spectrum β-lactamase production among Escherichia coli isolates were stable, between 51.7 and 55.8%. Resistance of E. coli and Klebsiella pneumoniae to amikacin, ciprofloxacin, piperacillin/tazobactam and cefoperazone/sulbactam decreased with time. Carbapenem resistance among K. pneumoniae isolates increased from 2.4 to 13.4%. Resistance of Pseudomonas aeruginosa strains against all of antimicrobial agents tested including imipenem and meropenem decreased with time. On the contrary, resistance of Acinetobacter baumannii strains to carbapenems increased from 31 to 66.7%. A marked decrease of methicillin resistance from 69% in 2005 to 44.6% in 2014 was observed for Staphylococcus aureus. Carbapenem resistance rates in K. pneumoniae and A. baumannii in China are high. Our results indicate the importance of bacterial surveillance studies.
The morphological features of sand particles play a key role in the mechanical response of the particle assemblage. Advancement of microfocus X-ray computed tomography (μXCT) technology has enabled ...3D visualization of particles at the grain-scale with reasonably high resolution to reveal the particle morphology. This paper utilizes the real part of spherical harmonic (SH) functions to describe the morphology of general-shape sand particles acquired from μXCT images. The influence of the maximum degree of SH functions and mesh fineness on the determination of size and shape descriptors of the particles are systematically investigated. Correlations between different shape descriptors of the studied sands are examined. Utilizing principal component analysis (PCA) and the empirical cumulative distribution function (ECDF), a probabilistic approach considering both intrinsic and phenomenological correlations between SH coefficients is proposed to three-dimensionally regenerate the sand particles. Based on comprehensive and quantitative comparisons between the morphological characteristics of scanned and generated particles, we conclude that the proposed approach performs satisfactorily.
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•Real forms of spherical harmonic functions are employed to reconstruct general-shape particles.•Influence of the maximum degree of SH functions and mesh fineness are systematically investigated.•A probabilistic approach based on PCA and ECDF is proposed to regenerate particles.•Both intrinsic and phenomenological correlations between SH coefficients are considered.•Virtual and real particles bear similar correlations between different shape descriptors.
Summary
The immune system undergoes age‐associated changes known as immunosenescence, resulting in increased susceptibility to infections, cancers and autoimmunity in the aged. The basis of our ...understanding of immunosenescence has been derived primarily from studies examining intrinsic defects within many of the cells of the immune system. While these studies have provided insight into the mechanisms of immunosenescence, a picture is now emerging that the stromal microenvironment within lymphoid organs also contributes significantly to the age‐associated decline of immune function. These extrinsic defects appear to impact the functional activity of immune cells and may offer a potential target to recover immune activity. Indeed, rejuvenation studies which have targeted the stromal niche have restored immune function in aged successfully, highlighting the impact of the microenvironment towards the aetiology of immunosenescence.
Whilst the exact mechanisms underlying immunosenescence are still unclear, several studies have identified intrinsic defects within many of the cells of the immune system. Despite the stromal niche playing a critical role in the development, maintenance and activation of immune cells the role of the microenvironment in immunosenescence remains an overlook area, but is increasingly becoming recognised as playing an important role in the decline of immune function in the aged.
Nowadays, it is still questionable whether denatured collagen (DCol) can replace the native collagen (Col) as a bioactive protein in cartilage engineering. We sought to study the advantages of Col ...with a triple-helical structure in the collagen-based composite materials for cartilage engineering.
We presented new three-dimensional (3D) Col and DCol scaffolds with shape memory properties. The effects of Col and DCol scaffolds on rabbit chondrocytes' proliferation, adhesion, differentiation and interaction with matrix were investigated. Tissue compatibility was performed in a subcutaneous Sprague Dawley (SD) rat model. The repair ability of different scaffolds with chondrocytes for full-thickness articular cartilage defects in knee joints of New Zealand white rabbits were investigated.
The results indicated that the Col scaffolds (with concentration 1.6wt% and 0.8wt%, respectively) promoted the proliferation, adhesion and redifferentiation of chondrocytes, as well as chondrocyte–matrix interaction, to a greater degree than the DCol scaffolds. In the animal experiment, the Col scaffolds filled in the defect hole significantly maintained chondrocytes function, promoted cartilage and subchondral bone regeneration, compared with the DCol scaffolds, and the scaffolds loaded with chondrocytes were better than the cell-free scaffolds, especially in the case of the Col scaffolds (1.6 wt%).
Taken together, these insights suggest that the better proliferation, adhesion and redifferentiation of chondrocytes in Col scaffolds with the triple-helical structure may contribute to the greater cartilage repair ability. Col scaffolds may be more appropriate for repairing cartilage defects than DCol scaffolds, and DCol cannot as an alternative when using collagen-based materials for cartilage engineering applications.
Macroscopic mechanical properties of granular materials are closely related to particle morphology. For practical reasons, the morphological features are commonly examined from projected ...two-dimensional (2D) images of the three-dimensional (3D) particles. This brings forward the need for quantifying the correlations between the 2D and 3D particle descriptors. This paper addresses these correlations for irregular granular particles. Three-dimensional images of sand particles were acquired through microfocus X-ray computed tomography, based on which 3D surfaces of the particles were reconstructed using spherical harmonic analyses. The 3D particle size and shape descriptors were subsequently evaluated. All-around projection and random projection of the particles onto 2D planes were undertaken numerically to obtain the projected 2D images and thus the corresponding 2D size and shape descriptors. The results indicate that there are close correlations between 3D and 2D size descriptors averaged from the all-around projections. 2D and 3D shape descriptors can be approximately fitted with a linear relationship. The mean value of 2D descriptors of the tested sands obtained from a series of independent random-projection tests is essentially identical to that from the all-around projections; except that the data from the random-projection tests show a larger scatter. In light of the relationships among the descriptors, a novel and promising approach to predict the cumulative distribution of 3D descriptors from that of 2D descriptors evaluated from a random-projection test is proposed.
•An indirect bridge frequency estimation strategy utilizing two vehicles is proposed.•The estimation strategy improves the detectability of the bridge frequency.•Sensitivity of the strategy with ...respect to vehicle’s mass and stiffness variation is investigated.•The estimation strategy is proved to be feasible through a field experiment.
Bridge natural frequencies are among fundamental properties of bridges. However, natural frequencies of most bridges remain unknown. Natural frequency identification through acceleration measurement with sensors installed on bridges is not practical if a large number of bridges are investigated. Indirect methods to detect the frequencies from the acceleration responses of a vehicle driving over bridges, on the other hand, still have difficulties. Vehicle responses contains various components, making it difficult to distinguish the bridge frequency from other frequency components. This study proposes new frequency estimation strategy utilizing two vehicles. The key idea is that bridge vibration, a common vibration component among responses of multiple vehicles, is extracted through signal processing involving cross-spectral density function estimation. Numerical analyses employing a vehicle-bridge interaction (VBI) model are conducted to examine the algorithm performance under various conditions. The numerical simulations have confirmed the feasibility of such indirect frequency detection. An experimental study featuring synchronized-sensing of two vehicles is then performed. The first natural frequency of the bridge has been identified under various driving speed combinations, demonstrating the performance of the proposed approach.
microRNA-200a (miR-200a) targets multiple signaling pathways that are involved in osteogenic differentiation and bone development. However, its therapeutic function in osteogenesis and bone ...regeneration remains unknown. In this study, we use in vitro and in vivo models to investigate the molecular function of miR-200a overexpression and miR-200a inhibition using a plasmid-based miR inhibitor system (PMIS) on osteogenic differentiation and bone regeneration. Inhibition of miR-200a using PMIS-miR-200a significantly increased osteogenic biomarkers of human embryonic palatal mesenchyme cells and promoted bone regeneration in rat tooth socket defects. In rat maxillary M1 molar extractions, the supporting tooth structures were removed with an implant drill to yield a 3-mm defect in the alveolar bone. A collagen sponge was inserted into the open alveolar defect and PMIS-miR-200a plasmid DNA was added to the sponge and the wound sutured to protect the sponge and close the defect. It was important to remove the existing tooth supporting structure, which can influence alveolar bone regeneration. The alveolar bone was regenerated in 4 wk. The collagen sponge acts to stabilize and deliver the PMIS-miR-200a DNA to cells entering the sponge in the bone defect. We show that mesenchymal stem cells expressing CD90 and Stro-1 enter the sponges, take up the DNA, and express PMIS-miR-200a. PMIS-miR-200a initiates a bone regeneration program in transformed cells in vivo. In vitro inhibition of miR-200a was found to upregulate Wnt and BMP signaling activity as well as Runx2, OCN, Lef-1, Msx2, and Dlx5 associated with osteogenesis. Liver and blood toxicity testing of PMIS-miR-200a–treated rats showed no increase in several biomarkers of liver disease. These results demonstrate the therapeutic function of PMIS-miR-200a for rapid bone regeneration. Furthermore, the studies were designed to demonstrate the ease of use of PMIS-miR-200a in solution and applied using a syringe in the clinic through a simple one-time application.
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