Magnetorheological landing gear: 2. Validation using experimental data

Aircraft landing gears are subjected to a wide range of excitation conditions with conflicting damping requirements. A novel solution to this problem is to implement semi-active damping using magnetorheological (MR) fluids. In part 1 of this contribution, a methodology was developed that enables the geometry of a flow mode MR valve to be optimized within the constraints of an existing passive landing gear. The device was designed to be optimal in terms of its impact performance, which was demonstrated using numerical simulations of the complete landing gear system. To perform the simulations, assumptions were made regarding some of the parameters used in the MR shock strut model. In particular, the MR fluid's yield stress, viscosity, and bulk modulus properties were not known accurately. Therefore, the present contribution aims to validate these parameters experimentally, via the manufacture and testing of an MR shock strut. The gas exponent, which is used to model the shock strut's nonlinear stiffness, is also investigated. In general, it is shown that MR fluid property data at high shear rates are required in order to accurately predict performance prior to device manufacture. Furthermore, the study illustrates how fluid compressibility can have a significant influence on the device time constant, and hence on potential control strategies

Calcite distribution and orientation in the tergite exocuticle of the isopods porcellio scaber and armadillidium vulgare (Oniscidea, Crustacea) - A combined FE-SEM, polarized SCm-RSI and EBSD study

The crustacean cuticle is a bio-composite consisting of hierarchically organized chitin-protein fibres, reinforced with calcite, amorphous calcium carbonate and phosphates. Comparative studies revealed that the structure and composition of tergite cuticle of terrestrial isopods is adapted to the habitat of the animals, and to their behavioural patterns to avoid predation. In this contribution we use FE-SEM, polarized SCm-RSI and EBSD to investigate micro- and nano-patterns of mineral phase distribution and crystal orientation within the tergite cuticle of the two terrestrial isopod species Armadillidium vulgare and Porcellio scaber. The results show that the proximal regions of the exocuticle contain both calcite and ACC, with ACC located within the pore canals. Calcite forms hierarchically organised mesocrystalline aggregates of similar crystallographic orientation. Surprisingly, c-axis orientation preference is horizontal in regard to the local cuticle surface for both species, in contrast to mollusc and brachiopod shell structures in which the c-axis is always perpendicular to the shell surface. The overall sharpness of calcite crystal orientation is weak compared to that of mollusc shells. However, there are considerable differences in texture sharpness between the two isopod species. In the thick cuticle of the slow-walking A. vulgare calcite is more randomly oriented resulting in more isotropic mechanical properties of the cuticle. In contrast, the rather thin and more flexible cuticle of the fast- running P. scaber texture sharpness is stronger with a preference of c-axis orientation being parallel to the bilateral symmetry-plane of the animal, leading to more anisotropic mechanical properties of the cuticle. These differences may represent adaptations to different external and/or internal mechanical loads the cuticle has to resist during predatory attempts

Psychometric properties of the Centers for Disease Control and Prevention Health-Related Quality of Life (CDC HRQOL) items in adults with arthritis

BACKGROUND: Measuring health-related quality of life (HRQOL) is important in arthritis and the SF-36v2 is the current state-of-the-art. It is only emerging how well the Centers for Disease Control and Prevention (CDC) HRQOL measures HRQOL for people with arthritis. This study's purpose is to assess the psychometric properties of the 9-item CDC HRQOL (4-item Healthy Days Core Module and 5-item Healthy Days Symptoms Module) in an arthritis sample using the SF-36v2 as a comparison. METHODS: In Fall 2002, a cross-sectional study acquired survey data including the CDC HRQOL and SF-36v2 from 2 North Carolina populations of adult patients reporting osteoarthritis, rheumatoid arthritis, and fibromyalgia; 2182 (52%) responded. The first item of both the CDC HRQOL and the SF-36v2 was general health (GEN). All 8 other CDC HRQOL items ask for the number of days in the past 30 days that respondents experienced various aspects of HRQOL. Exploratory principal components analyses (PCA) were conducted on each sample and the combined samples of the CDC HRQOL. The multitrait-multimethod matrix (MTMM) was used to compute correlations between each trait (physical health and mental health) and between each method of measurement (CDC HRQOL and SF36v2). The relative contribution of the CDC HRQOL in predicting the physical component summary (PCS) and the mental component summary (MCS) was determined by regressing the CDC HRQOL items on the PCS and MCS scales. RESULTS: All 9 CDC HRQOL items loaded primarily onto 1 factor (explaining 57% of the item variance) representing a reasonable solution for capturing overall HRQOL. After rotation a 2 factor interpretation for the 9 items was clear, with 4 items capturing physical health (physical, activity, pain, and energy days) and 3 items capturing mental health (mental, depression, and anxiety days). All of the loadings for these two factors were greater than 0.70. The CDC HRQOL physical health factor correlated with PCS (r = -.78, p < 0.0001) and the mental health factor correlated with MCS (r = -.71, p < 0.0001). The relative contribution of the CDC HRQOL in predicting PCS was 73% (R(2 )= .73) when GEN was included in the CDC HRQOL score and 65% (R(2 )= .65) when GEN was removed. The relative contribution of the CDC HRQOL in predicting MCS was 56% (R(2 )= .56) when GEN was included and removed. CONCLUSION: The CDC HRQOL appears to have strong psychometric properties in individuals with arthritis in both community-based and subspecialty clinical settings. The 9 item CDC HRQOL is a reasonable measure for overall HRQOL and the two subscales, representing physical and mental health, are reasonable when the goal is to examine those aspects

Use of Complementary and Alternative Medicine Among Patients With Arthritis

Introduction: Previous studies suggest that people with arthritis have high rates of using complementary and alternative medicine (CAM) approaches for managing their arthritis, in addition to conventional treatments such as prescription medications. However, little is known about the use of CAM by diagnosis, or which forms of CAM are most frequently used by people with arthritis. This study was designed to provide detailed information about use of CAM for symptoms associated with arthritis in patients followed in primary care and specialty clinics in North Carolina. Methods: Using a cross-sectional design, we drew our sample from primary care (n = 1,077) and specialist (n = 1,063) physician offices. Summary statistics were used to calculate differences within and between diagnostic groups, practice settings, and other characteristics. Logistic regression models clustered at the site level were used to determine the effect of patient characteristics on ever and current use of 9 CAM categories and an overall category of "any use." Results: Most of the participants followed by specialists (90.5%) and a slightly smaller percentage of those in the primary care sample (82.8%) had tried at least 1 complementary therapy for arthritis symptoms. Participants with fibromyalgia used complementary therapies more often than those with rheumatoid arthritis, osteoarthritis, or chronic joint symptoms. More than 50% of patients in both samples used over-the-counter topical pain relievers, more than 25% used meditation or drew on religious or spiritual beliefs, and more than 19% used a chiropractor. Women and participants with higher levels of education were more likely to report current use of alternative therapies. Conclusion: Most arthritis patients in both primary care and specialty settings have used CAM for their arthritis symptoms. Health care providers (especially musculoskeletal specialists) should discuss these therapies with all arthritis patients

Imperfections in a two-dimensional hierarchical structure

Hierarchical and fractal designs have been shown to yield high mechanical efficiency under a variety of loading conditions. Here a fractal frame is optimized for compressive loading in a two-dimensional space. We obtain the dependence of volume required for stability against loading for which the structure is optimized and a set of scaling relationships is found. We evaluate the dependence of the Hausdorff dimension of the optimal structure on the applied loading and establish the limit to which it tends under gentle loading. We then investigate the effect of a single imperfection in the structure through both analytical and simulational techniques. We find that a single asymmetric perturbation of beam thickness, increasing or decreasing the failure load of the individual beam, causes the same decrease in overall stability of the structure. A scaling relationship between imperfection magnitude and decrease in failure loading is obtained. We calculate theoretically the limit to which the single perturbation can effect the overall stability of higher generation frames

Mouse Model of Mutated in Colorectal Cancer Gene Deletion Reveals Novel Pathways in Inflammation and Cancer

© 2019 The Authors Background & Aims: The early events by which inflammation promotes cancer are still not fully defined. The MCC gene is silenced by promoter methylation in colitis-associated and sporadic colon tumors, but its functional significance in precancerous lesions or polyps is not known. Here, we aimed to determine the impact of Mcc deletion on the cellular pathways and carcinogenesis associated with inflammation in the mouse proximal colon. Methods: We generated knockout mice with deletion of Mcc in the colonic/intestinal epithelial cells (MccΔIEC) or in the whole body (MccΔ/Δ). Drug-induced lesions were analyzed by transcriptome profiling (at 10 weeks) and histopathology (at 20 weeks). Cell-cycle phases and DNA damage proteins were analyzed by flow cytometry and Western blot of hydrogen peroxide–treated mouse embryo fibroblasts. Results: Transcriptome profiling of the lesions showed a strong response to colon barrier destruction, such as up-regulation of key inflammation and cancer-associated genes as well as 28 interferon γ–induced guanosine triphosphatase genes, including the homologs of Crohn's disease susceptibility gene IRGM. These features were shared by both Mcc-expressing and Mcc-deficient mice and many of the altered gene expression pathways were similar to the mesenchymal colorectal cancer subtype known as consensus molecular subtype 4 (CMS4). However, Mcc deletion was required for increased carcinogenesis in the lesions, with adenocarcinoma in 59% of MccΔIEC compared with 19% of Mcc-expressing mice (P =.002). This was not accompanied by hyperactivation of β-catenin, but Mcc deletion caused down-regulation of DNA repair genes and a disruption of DNA damage signaling. Conclusions: Loss of Mcc may promote cancer through a failure to repair inflammation-induced DNA damage. We provide a comprehensive transcriptome data set of early colorectal lesions and evidence for the in vivo significance of MCC silencing in colorectal cancer

The phosphatase calcineurin regulates pathological TDP-43 phosphorylation

Detergent insoluble inclusions of TDP-43 protein are hallmarks of the neuropathology in over 90% of amyotrophic lateral sclerosis (ALS) cases and approximately half of frontotemporal dementia (FTLD-TDP) cases. In TDP-43 proteinopathy disorders, lesions containing aggregated TDP-43 protein are extensively post-translationally modified, with phosphorylated TDP-43 (pTDP) being the most consistent and robust marker of pathological TDP-43 deposition. Abnormally phosphorylated TDP-43 has been hypothesized to mediate TDP-43 toxicity in many neurodegenerative disease models. To date several different kinases have been implicated in the genesis of pTDP, but no phosphatases have been shown to reverse pathological TDP-43 phosphorylation. We have identified the phosphatase calcineurin as an enzyme binding to and catalyzing the removal of pathological C-terminal phosphorylation of TDP-43 in vitro. In C. elegans models of TDP-43 proteinopathy, genetic elimination of calcineurin results in accumulation of excess pTDP, exacerbated motor dysfunction, and accelerated neurodegenerative changes. In cultured human cells, treatment with FK506 (tacrolimus), a calcineurin inhibitor, results in accumulation of pTDP species. Lastly, calcineurin co-localizes with pTDP in degenerating areas of the central nervous system in subjects with FTLD-TDP and ALS. Taken together these findings suggest calcineurin acts on pTDP as a phosphatase in neurons. Furthermore, patient treatment with calcineurin inhibitors may have unappreciated adverse neuropathological consequences

Explicit expressions for the estimation of the elastic constants of lamellar bone as a function of the volumetric mineral content using a multi-scale approach

[EN] In this work, explicit expressions to estimate all the transversely isotropic elastic constants of lamellar bone as a function of the volumetric bone mineral density (BMD) are provided. The methodology presented is based on the direct homogenization procedure using the finite element method, the continuum approach based on the Hill bounds, the least-square method and the mean field technique. Firstly, a detailed description of the volumetric content of the different components of bone is provided. The parameters defined in this step are related to the volumetric BMD considering that bone mineralization process occurs at the smallest scale length of the bone tissue. Then, a thorough description provides the details of the numerical models and the assumptions adopted to estimate the elastic behaviour of the forward scale lengths. The results highlight the noticeable influence of the BMD on the elastic modulus of lamellar bone. Power law regressions fit the Young's moduli, shear stiffness moduli and Poisson ratios. In addition, the explicit expressions obtained are applied to the estimation of the elastic constants of cortical bone. At this scale length, a representative unit cell of cortical bone is analysed including the fibril orientation pattern given by Wagermaier et al. (Biointerphases 1:1-5, 2006) and the BMD distributions observed by Granke et al. (PLoS One 8:e58043, 2012) for the osteon. Results confirm that fibril orientation arrangement governs the anisotropic behaviour of cortical bone instead of the BMD distribution. The novel explicit expressions obtained in this work can be used for improving the accuracy of bone fracture risk assessment.The authors acknowledge the Ministerio de Economia y Competitividad for the financial support received through the project DPI2013-46641-R and to the Generalitat Valenciana for Programme PROMETEO 2016/007. 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