Evaluation of temperature distribution for bone drilling considering aging factor

Bone drilling is a routine operation in surgeries,such as neurosurgery and orthopedics.However,the excessive drilling temperature may cause severe thermal damage to the bone tissue.Therefore,the drilling temperature determination of bone tissue can reduce the harm caused by thermal damage.A time-varying temperature field simulation model of bone drilling was set up by ABAQUS software in this paper,based on the Johnson-Cook model.Then it was validated with experiments by drilling cortical bone of fresh bovine shaft of the femur.The relative error between the experimental values and the theoretical values within 7.67%showed a good consistency.Furthermore,the aging factor is also considered to evaluate the temperature field of bone drilling.The results showed that the drilling temperature near the bone-drill area increased significantly.The drilling temperature of cortical bone decreases sharply with the radial distance and exhibits a hysteresis lag in the axial distribution.The aging factor mainly affects the peak of drilling temperature.The peak of drilling temperature tends to increase with age.The peak drilling temperature in the elderly(70y)was up to 6.8%higher than that in the young(20y),indicating that the elderly is more prone to excessive drilling temperature.Therefore,special attention should be paid to the temperature control of elderly bone tissue.

Age-related pro-inflammatory and pro-angiogenic changes in human aqueous humor

AIM： To reveal age-related aqueous cytokine changes in human aqueous humor.METHODS： Aqueous humor was collected from 12 young children（3-6.5 years old） and 71 healthy adults（22-106 years old） with cataract but without other systemic or ocular disorders. Levels of 22 cytokines, chemokines and vascular endothelial growth factor（VEGF） were measured and analyzed.RESULTS： The following proteins showed significant increase from childhood to adult： interferon-gamma（IFN-γ）, interleukin（IL）-13, IL-6, IL-12（p70）, IL-10, CCL2, CCL3, CCL4, CXCL8, CXCL9, CXCL10, IFN-α2 and VEGF（all P〈0.05）. IFN-γ, IL-13, IL-12（p70）, IL-10, CCL3, CXCL9 and VEGF also showed moderate strength age-related increase in the adult group（r〉0.5）. The strength of correlation between aging and CCL4 were fair（r=0.398）. The concentrations of IL-2, IL-4, IL-5, IL-1β and TNF-α were low in both groups.CONCLUSION： From childhood to adult, the immunological milieu of the anterior chamber become more pro-inflammatory and pro-angiogenic. Such changes may represent the parainflammation state of the human eye.

Ethanol based foamed asphalt as potential alternative for low emission asphalt technology

Foamed asphalt typically relies on water as a foaming agent because water becomes gaseous at elevated temperatures, generating numerous tiny bubbles in the asphalt and causing spontaneous foaming. In this study, ethanol was used as a potential alternative to water as a foaming agent. Ethanol is expected to be a physical blowing agent in the same manner as water, except it requires less energy to foam due to its 78 ℃ boiling point. This study compares the performance of water and ethanol as foaming agents through the measurements of rotational viscosity, the reduction in temperature during foaming, and volatile loss. The ethanol-foamed asphalt binders were prepared at 80 ~C and 100 ~C, while the water-foamed asphalt binders were prepared at 100 ~C and 120 ~＇C. Additionally, the rolling thin film oven （RTFO） was used to generate short-term aging of the foamed asphalt binders. A rotational viscometer was used to determine the viscosity of the asphalt binders at 80 ~C, 100 ~C, 120 ~C, 140 ~C, and 160 ~C. Overall, ethanol can function in the same manner as water but requires less energy to foam. It is proven based on the smaller drop in temperature of the asphalt binder foamed using ethanol compared with that prepared with water. This is due to the lower latent heat capacity of ethanol, which requires less energy to vaporize compared with water. Through the rotational viscometer test, ethanol performs better in lowering the viscosity of asphalt binders, which is essential in allowing produc- tion processes at low temperatures, as well as a better workability and aggregate coating. Ethanol can be expelled from the foamed asphalt binders at a higher rate due to its lower boiling point and latent heat.