Natural convection of SiO_2-water nanofluid in square cavity with thermal square column

A square with a thermal square column is a simple but nontrivial research prototype for nanofluid research. However, until now, the effects of the temperature of the square column on the heat and mass transfer of nanofluids have not been revealed comprehensively, especially on entropy generation. To deepen insight into this important field, the natural convection of the SiO2-water nanofluid in a square cavity with a square thermal column is studied numerically in this study. The effects of the thermal column temperature （T = 0.0, 0.5, 1.0, 1.5）, the Rayleigh number （ranging from 103 to 106）, and the volume fraction of the nanoparticle （varying from 0.01 to 0.04） on the fluid flow, heat transfer, and entropy generation are investigated, respectively. It is found that, no matter at a low or high Rayleigh number, the volume fraction of the nanoparticle shows no considerable effects on the flow field and temperature field for all the temperatures of the thermal column. With an increase in the volume fraction, the mean Nusselt number increases slightly. At the same time, it is found that, with an increase in the temperature of the thermal column, the average Nusselt number gradually decreases at all values of the Rayleigh number. Meanwhile, it is found that, at a high Rayleigh number, the heat transfer mechanism is the main parameter affecting the increase in the total entropy generation rather than the volume fraction. In addition, no matter at a high or low Rayleigh number, when T = 0.5, the total entropy generation is the minimum.

Reinforcement of Self-Healing Polyacrylic Acid Hydrogel with Acrylamide Modified Microcrystalline Cellulose

Self-healing hydrogel such as polyacrylic acid(PAA)hydrogel has attracted increasing attention based on its promising potential applications.However,it usually suffers from low strength especially as mechanical device.Herein,a commercial microcrystalline cellulose(MCC)was modified with acrylamide to graft polyacrylamide(PAM)chains on the particle surface.The acrylamide-modified MCC(AM-MCC)was then dispersed in monomer solution of acrylic acid to prepare composite hydrogel.The mechanical properties of the obtained composite hydrogels and the self-healed hydrogels were carefully measured by compressive and tensile tests,and by dynamic mechanical analysis.Our results demonstrate that introduction of a small amount of AM-MCC such as 3 wt%can not only reinforce the original hydrogel and the healed hydrogel markedly,but also improve self-healing efficiency obviously.The analyses indicate that in addition to the reversible multi-interactions such as hydrogen bonding and ionic interactions,the entanglements between the PAA chains of the hydrogel matrix and the PAM chains grafted on the MCC particles have also played an important role on the improvement in mechanical performances and the healing ability of the hydrogel.Moreover,the responsiveness to exterior ion has been tested to indicate potential application of the composite hydrogel as self-healable sensor.

Intensity modulated radiation therapy in elderly patients with nasopharyngeal carcinoma

Purpose To evaluate the outcomes in elderly patients with nasopharyngeal carcinoma(NPC)treated by intensity modulated radiation therapy(IMRT).Methods Patients with NPC aged≥70 years old who received intensity-modulated radiation therapy≥60 Gy were recruited into this study.The overall survival(OS),progression-free survival(PFS),cancer-specific survival(CSS),locoregional recurrence-free rate(LRFR)and distant metastasis-free rate(DMFR)were calculated using the Kaplan–Meier method.The Cox proportional hazards model was applied to perform multivariate analysis for independent prognosticators using meaningful variables from the univariate analysis.Results One hundred ninety seven patients with NPC≥70 years were recruited from the 4351 newly diagnosed NPC patients from January 2011 to December 2020.The 5-year OS,CSS,PFS,LRFR and DMFR were 59.6%,78.9%,51.3%,91.6%and 78.9%,respectively.the plasma EBV DNA was the only prognostic factor for OS,the overall staging was the only prognostic factor for CSS,and plasma EBV DNA and N category were borderline significant factor for DMFR.We did not find any prognosticator for PFS and LRFR.Conclusions The survival after IMRT for elderly patients with NPC is suboptimal.Further study stratified by comorbidity and geriatric assessment is needed.