Effects of zinc-substituted nano-hydroxyapatite coatings on bone integration with implant surfaces

Objective:The purpose of this study was to investigate the effects of a zinc-substituted nano-hydroxyapatite(Zn-HA) coating,applied by an electrochemical process,on implant osseointegraton in a rabbit model.Methods:A Zn-HA coating or an HA coating was deposited using an electrochemical process.Surface morphology was examined using field-emission scanning electron microscopy.The crystal structure and chemical composition of the coatings were examined using an X-ray diffractometer(XRD) and Fourier transform infrared spectroscopy(FTIR).A total of 78 implants were inserted into femurs and tibias of rabbits.After two,four,and eight weeks,femurs and tibias were retrieved and prepared for histomorphometric evaluation and removal torque(RTQ) tests.Results:Rod-like HA crystals appeared on both implant surfaces.The dimensions of the Zn-HA crystals seemed to be smaller than those of HA.XRD patterns showed that the peaks of both coatings matched well with standard HA patterns.FTIR spectra showed that both coatings consisted of HA crystals.The Zn-HA coating significantly improved the bone area within all threads after four and eight weeks(P<0.05),the bone to implant contact(BIC) at four weeks(P<0.05),and RTQ values after four and eight weeks(P<0.05).Conclusions:The study showed that an electrochemically deposited Zn-HA coating has potential for improving bone integration with an implant surface.

大鼠骨髓间充质干细胞和成骨细胞在钛表面掺锶羟基磷灰石涂层上的成骨研究

目的：本研究旨在比较体外三种类型钛表面对促进成骨的作用：掺锶羟基磷灰石（Sr-HA）涂层表面．纳米HA涂层表面以及无涂层的粗糙表面。材料和方法：通过电化学沉积方法将Sr-HA和HA沉积于粗糙的钛表面上。在Sr-HA涂层、HA涂层和无涂层的粗糙钛表面上进行MC3T3-E1前成骨细胞和小鼠骨髓间充质干细胞培养，在不同时间点测定细胞的黏附、增殖、存活、分化和矿化结节形成。结果：对比于无涂层的粗糙钛表面和纳米HA涂层表面，通过简单的电化学沉积处理，Sr-HA涂层明显提高了小鼠骨髓间充质干细胞和MC3T3-E1细胞黏附、铺展，碱性磷酸酶活性和细胞外基质钙矿化。结论：这项研究表明．通过电化学沉积产生的掺锶纳米羟基磷灰石涂层Sr-HA提高了微粗糙钛表面的骨传导性。

Resource allocation algorithm with limited feedback for multicast single frequency networks

The single frequency network (SFN) can provide a multimedia broadcast multicast service over a large coverage area. However, the application of SFN is still restricted by a large amount of feedback. Therefore, we propose a multicast resource allocation scheme based on limited feedback to maximize the total rate while guaranteeing the quality of service (QoS) requirement of real-time services. In this scheme, we design a user feedback control algorithm to effectively reduce feedback load. The algorithm determines to which base stations the users should report channel state information. We then formulate a joint subcarrier and power allocation issue and find that it has high complexity. Hence, we first distribute subcarriers under the assumption of equal power and develop a proportional allocation strategy to achieve a tradeoff between fairness and QoS. Next, an iterative water-filling power allocation is proposed to fully utilize the limited power. To further decrease complexity, a power iterative scheme is introduced. Simulation results show that the proposed scheme significantly improves system performance while reducing 68% of the feedback overhead. In addition, the power iterative strategy is suitable in practice due to low complexity.

Review of elemental mercury(Hg^(0))removal by CuO-based materials

Mercury emission has become a great environmental concern because of its high toxicity,bioaccumulation,and persistence.Adsorption is an effective method to remove Hg^(0)from coal-fired flue gas,with adsorbents playing a dominant role.Extensive investigations have been conducted on the use of CuO-based materials for Hg^(0)removal,and some fruitful results have been obtained.In this review,we summarize advances in the application of CuO-based materials for Hg^(0)capture.Firstly,the fundamentals of CuO,including its crystal information and synthesis methods,are introduced.Then,the Hg^(0)removal capability of some typical CuO-based adsorbents is discussed.Considering that coal-fired flue gas also contains a certain amount of NO,SO_(2),H_(2)O,NH_(3),and HCl,the impacts of these species on adsorbent Hg^(0)removal efficiency are summarized next.By generalizing the mechanisms dominating the Hg^(0)removal process,the rate-determining step and the key intermediates can be discovered.Apart from Hg^(0),some other air pollutants,such as CO,NOx,and volatile organic compounds(VOCs),account for a certain portion of flue gas.In view of their similar abatement mechanisms,simultaneous removal of Hg^(0)and other air pollutants has become a hot topic in the environmental field.Considering the Hg^(0)re-emission phenomena in wet flue gas desulfurization(WFGD),mercury capture performance under different conditions in this device is discussed.Finally,we conclude that new adsorbents suitable for long-term operation in coal-fired flue gas should be developed to realize the effective reduction of mercury emissions.

CH_(4) and C0_(2) observations from a melting high mountain glacier,Laohugou Glacier No.12

With global warming,glaciers in the high mountains of China are retreating rapidly.However,few data have been reported on whether greenhouse gases from these glaciers are released into the atmosphere or absorbed by glacial meltwater.In this study,we collected meltwater and ice samples from Laohugou Glacier No.12 in western China and measured CH_(4)and CO_(2)concentrations.Meltwater from the glacier terminus was continually sampled between 3 and 5 August 2020 to measure CH_(4)and CO_(2)concentrations.The results demonstrated that meltwater is a source of CH_(4)because the average saturations are over 100%.It could be con eluded that CH_(4)in the atmosphere can be released by glacial meltwater.However,the CO_(2)saturations are various,and CO_(2)fluxes exhibit positive(released CO_(2))or negative(absorbed CO_(2))values because the water and atmospheric conditions are variable.More importantly,the CH_(4)and CO_(2)concentrations were higher in meltwater samples from the glacier terminus than in samples from the surface ice(including an ice core)and a surface stream.Although the meltwater effect from the upper part of the glacier cannot be excluded,we speculated that subglacial drainage systems with an anaerobic environment may represent the CH_(4)source,but it needs to be further investigated in the future.However,high mountain glaciers are currently ignored in global carbon budgets,and the increased melting of glaciers with global warming may accelerate the absorption of much more CO_(2)and lead to the release of CH_(4).