Background Bone mineral deficits are one of the most common complications in cancer survivors. However, there are no studies evaluating bone mineral density (BMD) and the prevalence of osteopenia and osteoporosis among patients with different types of cancers. Aim The objective was to assess BMD and evaluate the prevalence of osteopenia and osteoporosis among US adults with cancer. Design A cross-section propensity score matching study. Methods We extracted data from National Health and Nutrition Examination Survey database from 2005 to 2018. We compared BMD in participants with and without cancer which was further analyzed according to cancer type. We conducted logistic regression to evaluate adjusted odds ratios of osteopenia and osteoporosis and determine risk factors for their development. Results We found that BMD was significantly higher in participants without cancer than cancer patients. Furthermore, the median BMD of patients with breast cancer or skin cancer (including melanoma) was significantly lower than participants without cancer. People with breast, lung, genitourinary and skin cancers were more likely to incur osteopenia/osteoporosis than those without cancer. Conclusions BMD differs depending upon type in survivors. Individuals with a history of cancer have a poor understanding of osteoporosis and its risk factors. Understanding risk factors in patients with cancers identified in our study may be helpful for preventing osteoporosis and fractures and the development of screening guidelines.
The aim of the present paper is to study experimentally and numerically the frictional behaviour of engineering surfaces within all lubrication regions of point contacts. For this reason, a numerical solution proposed elsewhere by the current authors, which can predict friction under the different lubrication modes of elastohydrodynamic, mixed, and boundary lubrications, is introduced. Based on a deterministic model of mixed lubrication, the solution was combined with the variation of the lubricating films' physical state during the transition of lubrication modes. Results show that roughness amplitude has a great effect on the transition of friction regimes. In addition, it is also observed that variation of the friction coefficient has nearly the same trend as the true contact area ratio in the mixed lubrication state. Meanwhile, it is concluded that transverse roughness has better film-forming capacity than longitudinal roughness and thus leads to a lower magnitude of friction coefficient if the operating conditions are the same. Analysis of the mechanism of friction behaviour suggests that the true contact area ratio determines the friction behaviour of engineering surfaces in mixed lubrication. In smooth contacts, the comparison of experiment tests and simulation results suggests that friction variation results from gradual change of the liquid lubricant to solid-like matter with diminishing film thickness.
The present work investigates the effects of a circumferential feeding groove in a short squeezefilm damper (SFD) on fluid force and dynamic responses of a rotor in SFDs. The groove is taken as a special damper to analyse the effects. The dynamic performance of the SFD with the groove is attributed to two film lands, the special damper and their interactions. From this viewpoint, the fluid force in the groove is analysed on the basis of the linearized Navier-Stokes equations. Analysis of the fluid force in film lands is carried out using a simplified Navier-Stokes equation to include fluid inertia. Then, from the continuity condition and the Navier-Stokes equation, fluid interactions between the groove and the film lands are investigated. The two analyses are combined together by investigation of the interactions, resulting in new models for fluid force predictions. The new models are compared with published work. The comparisons show that the new models give better predictions and correction with experimental data than traditional theory. The new models provide a significant improvement on the results obtained by traditional theory, especially for tangential force. Based on the new models, the present work also analyses effects of the groove on the unbalance response and stability of a rigid rotor in SFDs. Comparisons with published work show that the groove affects the unbalance response of a rotor system. The effects of the groove on dynamic coefficients of SFD cause the response of the rotor system to be stable for some range of system parameters, being different from the results of traditional theory. This is important for designing a rotor system.
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