铋牺牲法制备石墨烯负载Fe-N单原子位点增效氧还原催化和锌-空气电池性能

催化氧反应(ORR)是锌空电池和氢燃料电池能量转化的关键过程,然而其反应速率往往较低,因此开发高活性且耐久的催化材料至关重要.当前,研发低成本、高效率且稳定的氧还原催化剂已成为国内外的研究热点.其中,富含金属-氮-碳活性位点的低成本ORR催化材料,因其具有替代贵金属的潜力,成为重要的候选材料.然而,在制备这类催化剂时,所用分子前驱体在热解过程中易团聚形成金属基硬颗粒,如何减少热解过程中金属成分的自发聚集和不良副产物的生成,提高活性单原子的利用率,特别是在使用廉价分子前驱体(如三聚氰胺和铁盐)时,仍面临挑战.本研究旨在探索有效的制备策略,以优化催化剂性能,推动其在能源转换领域的应用.本文报道了一种以硝酸铋为牺牲剂,石墨烯为导电载体,通过热解廉价的三聚氰胺和铁盐,合成石墨烯负载丰富Fe-N-C活性位点催化剂的新方法.该方法中硝酸铋前驱体高温热解生成的铋铁合金或氧化铋因表面没有碳层,而容易被热酸除去,形成更多的可接近的FeNx活性位点,从而有效地抑制铁基颗粒和管状碳结构的形成,实现了催化剂的高效合成.双球差矫正电镜、X-射线光电子能谱和X-射线吸收结构光谱等表征证明,铋化合物去除后留下空位被铁原子取代,增加了Fe-N-C位点密度,并且铁以单原子活性位形式存在.实验结果表明,所制备的催化剂表现出高氧还原性能,在碱性和酸性条件下的半波电位分别为0.916和0.784 V.石墨烯基催化剂的动力学电流密度(0.9 V vs.RHE)达到10.41 mA cm^(-2),是不加铋化合物样品的6倍,贵金属Pt/C催化剂的4倍.此外,催化剂的塔菲尔斜率为59 mV dec^(-1),低于不加铋化合物样品(80 mV dec^(-1))、不加石墨烯样品(93 mV dec^(-1))、无金属样品(88 mV dec^(-1))和Pt/C(80 mV dec^(-1)).在0.1 mol L^(-1) KOH条件下,催化剂循环10000圈后,半波电位仅衰减15 mV,低于Pt/C(36 mV)和无铋对照样(20 mV),表明催化剂具有较好的稳定性.由于电化学法制备的石墨烯比热解法制备的非晶碳具有更好的耐腐蚀性,从而可以提高阴极氧还原的稳定性.另外,所制备的催化剂应用在锌-空气电池中时,最大功率密度可达201.4 mW cm-2,且循环1000次后电池电压几乎没有衰减.综上,本研究通过引入铋化合物,显著提升了廉价前驱物铁-三聚氰胺的金属单原子化效率.利用电化学法合成了石墨烯负载的Fe-N-C催化活性位,制备出高活性、高稳定的催化剂.将该低成本催化剂应用于锌-空气电池的阴极,其表现出良好的长循环性能.本研究为制备低成本、高性能的金属-氮-碳基电催化剂提供了新思路.

Correlation between the cumulative analgesic effect of electroacupuncture intervention and synaptic plasticity of hypothalamic paraventricular nucleus neurons in rats with sciatica

In the present study, a rat model of chronic neuropathic pain was established by ligation of the sciatic nerve and a model of learning and memory impairment was established by ovariectomy to investigate the analgesic effect of repeated electroacupuncture stimulation at bilateral Zusanfi （ST36） and Yanglingquan （GB34）. In addition, associated synaptic changes in neurons in the paraventricular nucleus of the hypothalamus were examined. Results indicate that the thermal pain threshold （paw withdrawal latency） was significantly increased in rats subjected to 2-week electroacupuncture intervention compared with 2-day electroacupuncture, but the analgesic effect was weakened remarkably in ovariectomized rats with chronic constrictive injury. 2-week electroacupuncture intervention substantially reversed the chronic constrictive injury-induced increase in the synaptic cleft width and thinning of the postsynaptic density. These findings indicate that repeated electroacupuncture at bilateral Zusanfi and Yanglingquan has a cumulative analgesic effect and can effectively relieve chronic neuropathic pain by remodeling the synaptic structure of the hypothalamic paraventricular nucleus.

The cumulative analgesic effect of repeated electroacupuncture involves synaptic remodeling in the hippocampal CA3 region

In the present study, we examined the analgesic effect of repeated electroacupuncture at bilateral Zusanfi （ST36） and Yanglingquan （GB34） once a day for 14 consecutive days in a rat model of chronic sciatic nerve constriction injury-induced neuropathic pain. In addition, concomitant changes in calcium/calmodulin-dependent protein kinase II expression and synaptic ultrastructure of neurons in the hippocampal CA3 region were examined. The thermal pain threshold （paw withdrawal latency） was increased significantly in both groups at 2 weeks after electroacupuncture intervention compared with 2 days of electroacupuncture. In ovariectomized rats with chronic constriction injury, the analgesic effect was significantly reduced. Electroacupuncture for 2 weeks significantly diminished the injury-induced increase in synaptJc cleft width and thinning of the postsynaptJc density, and it significantly suppressed the down-regulation of intracellular calcium/ calmodulin-dependent protein kinase II expression in the hippocampal CA3 region. Repeated electroacupuncture intervention had a cumulative analgesic effect on injury-induced neuropathic pain reactions, and it led to synaptic remodeling of hippocampal neurons and upregulated calcium/calmodulin-dependent protein kJnase II expression in the hippocampal CA3 region.

Folate-chitosan-gemcitabine core-shell nanoparticles targeted to pancreatic cancer

Objective：Human pancreatic cancer is one of the most common clinical malignancies.The effect of comprehensive treatment based on surgery is general.The effects of chemotherapy were not obvious mainly because of lack of targeting and chemoresistance in pancreatic cancer.This study aimed to investigate the effects of folate receptor （FR）-mediated gemcitabine FA-Chi-Gem nanoparticles with a core-shell structure by electrostatic spray on pancreatic cancer.Methods：In this study,the levels of expression of FR in six human pancreatic cancer cell lines were studied by immunohistochemical analysis.The uptake rate of isothiocyanate-labeled FA-Chi nanoparticles in FR high expression cell line COLO357 was assessed by fluorescence microscope and the inhibition rate of FA-Chi-Gem nanoparticles on COLO357 cells was evaluated by MTT assay.Moreover,the biodistribution of PEG-FA-ICGDER02-Chi in the orthotopic pancreatic tumor model was observed using near-infrared imaging and the human pancreatic cancer orthotopic xenografts were treated with different nanoparticles and normal saline control.Results：The expression of FR in COLO357 was the highest among the six pancreatic cancer cell lines.The FR mainly distributed on cell membrane and fewer in the cytoplasm in pancreatic cancer.Moreover,the absorption rate of the FA-Chi-Gem nanoparticles was more than the Chi nanoparticles without FA modified.The proliferation of COLO357 was significantly inhibited by FA-Chi-Gem nanoparticles.The PEG-FA-ICGDER02-Chi nanoparticles were enriched in tumor tissue in human pancreatic cancer xenografts,while non-targeted nanoparticles were mainly in normal liver tissue.PEG-FA-Gem-Chi significantly inhibited the growth of human pancreatic cancer xenografts （PEG-FA-Gem-Chi vs.Gem,t=22.950,P=0.000）.Conclusions：PEG-FA-FITC-Chi nanoparticles might be an effective targeted drug for treating human FR-positive pancreatic cancer.

Identification of the structure of Ni active sites for ethylene oligomerization on an amorphous silica-alumina supported nickel catalyst

The structure of Ni active sites supported on amorphous silica-alumina supports with different contents of Al_(2)O_(3)loadings in relation to their activities in ethylene oligomerization were investigated.Two kinds of Ni sites were detected by in situ FTIR-CO and H_(2)-TPR experiments,that are Ni^(2+)cations as grafted on weak acidic silanols and Ni^(2+)cations at ion-exchange positions.The ethylene oligomerization activities of these Ni/ASA catalysts were found an ascending tendency as the Al_(2)O_(3)loading decreased,which could be attributed to the enriched concentration of Ni^(2+)species on acidic silanols with a weaker interaction with the amorphous silica-alumina support.These Ni^(2+)species were more easily to be evolved into Ni^(+)species,which has been identified to be the active sites of ethylene oligomerization.Thus,it seems reasonable to conclude that Ni^(2+)species grafted on acidic silanols were the precursors of active sites.

Auricular vagus nerve acupressure for patients with emotional distress under the COVID-19 pandemic:A smartphone-based,randomized controlled trial

Objective: To confirm whether self-administered AVNA treatment is effective in improving emotional distressunder the COVID-19 pandemic.Methods: A smartphone-based online, randomized, controlled trial was designed from 26 February 2020 to 28April 2020 in four study sites, including Wuhan, Beijing, Shenyang, and Guangzhou of China. Local residentswho had considerable emotional distress with a score of the Hospital Anxiety and Depression Scale (HADS) ≥9 were recruited. Participants were randomly assigned to three times of AVNA (n = 191) per day, in morning,around noon, and in evening or usual care (UC, n = 215) once daily for 14 days. The primary outcome was theresponse rate, which was the proportion of participants whose Hospital Anxiety and Depression Scale (HADS)score reduced from baseline by ≥ 50%. The assessment was conducted at baseline, 3 days, and 14 days.Results: The AVNA group had a markedly higher response rate than the UC group at 3 days (35.6% vs. 24.9%,P = 0.02) and at 14 days (70.7% vs. 60.6%, P = 0.02). The AVNA group showed significantly greater reductionin scores of HADS at the two measurement points and BAI at 3 days (P ≤ 0.03), with average respective effectsize of 0.217 and 0.195. Participants with AVNA spent less time falling asleep and rated their sleep qualitybeing remarkably higher than those with UC at endpoint.Conclusion: During COVID-19 pandemic period, treatment with self-administrated AVNA was more effectivethan UC in reducing emotional distress of isolated populations. These findings support self-administered AVNAas a treatment option for patients with emotional distress under the COVID-19 pandemic or other emergentevents.

Ultrabright bimetallic AuAg complex:From luminescence mechanism to biological application

Metal clusters have attracted wide interests due to their unique electronic and optical properties,but the low luminescence quantum yield(QY)prevents them from potential biomedical applications.In this work,silver-doped Au nanoclusters(NCs)are shown to be able to improve the QY of metal clusters.We succeeded in synthesizing ultrabright glutathione(GSH)protected AuAg clusters with 10.8%QY by a one-pot route.Their florescence is about 7.5 times brighter than pure Au NCs,with super photostability and good biocompatibility in physiological environment.Based on density functional theory(DFT)calculations,we investigated the electronic structures and optical properties of the AuAg NCs.The results show that the increase of the density of states of the lowest unoccupied molecular orbital(LUMO)leads to the fluorescence enhancement.In addition,two-photon excitation fluorescence imaging has been performed to show their great potential for biomedicine.

Intricacies of TGF-βsignaling in Treg and Th17 cell biology

Balanced immunity is pivotal for health and homeostasis.CD4+helper T(Th)cells are central to the balance between immune tolerance and immune rejection.Th cells adopt distinct functions to maintain tolerance and clear pathogens.Dysregulation of Th cell function often leads to maladies,including autoimmunity,inflammatory disease,cancer,and infection.Regulatory T(Treg)and Th17 cells are critical Th cell types involved in immune tolerance,homeostasis,pathogenicity,and pathogen clearance.It is therefore critical to understand how Treg and Th17 cells are regulated in health and disease.Cytokines are instrumental in directing Treg and Th17 cell function.The evolutionarily conserved TGF-β(transforming growth factor-β)cytokine superfamily is of particular interest because it is central to the biology of both Treg cells that are predominantly immunosuppressive and Th17 cells that can be proinflammatory,pathogenic,and immune regulatory.How TGF-βsuperfamily members and their intricate signaling pathways regulate Treg and Th17 cell function is a question that has been intensely investigated for two decades.Here,we introduce the fundamental biology of TGF-βsuperfamily signaling,Treg cells,and Th17 cells and discuss in detail how the TGF-βsuperfamily contributes to Treg and Th17 cell biology through complex yet ordered and cooperative signaling networks.

Compressor geometric uncertainty quantification under conditions from near choke to near stall

Geometric and working condition uncertainties are inevitable in a compressor,deviating the compressor performance from the design value.It’s necessary to explore the influence of geometric uncertainty on performance deviation under different working conditions.In this paper,the geometric uncertainty influences at near stall,peak efficiency,and near choke conditions under design speed and low speed are investigated.Firstly,manufacturing geometric uncertainties are analyzed.Next,correlation models between geometry and performance under different working conditions are constructed based on a neural network.Then the Shapley additive explanations(SHAP)method is introduced to explain the output of the neural network.Results show that under real manufacturing uncertainty,the efficiency deviation range is small under the near stall and peak efficiency conditions.However,under the near choke conditions,efficiency is highly sensitive to flow capacity changes caused by geometric uncertainty,leading to a significant increase in the efficiency deviation amplitude,up to a magnitude of-3.6%.Moreover,the tip leading-edge radius and tip thickness are two main factors affecting efficiency deviation.Therefore,to reduce efficiency uncertainty,a compressor should be avoided working near the choke condition,and the tolerances of the tip leading-edge radius and tip thickness should be strictly controlled.

基于优慕课平台的混合式教学模式在口腔数字化技术课程中的实践研究

目的:探讨基于优慕课平台的混合式教学模式在高职口腔医学技术专业口腔数字化课程教学中的应用价值。方法:选取北京卫生职业学院五年制口腔医学技术专业2020级35名学生为观察组,2019级35名学生为对照组。分别采用传统教学模式和基于优慕课平台的混合式教学模式开展教学活动。比较两组学生的课程总成绩、参与度和评教结果等。结果:观察组学生平时成绩、期末技能实操考核、素质评价成绩高于对照组,组间差异有统计学意义(t=3.168,t=3.876,t=3.932;P<0.05);观察组学生教学活动的完成率、参与频次优于对照组,组间差异有统计学意义(t=4.906,t=4.306;P<0.05);观察组学生自我价值评价个人技能、方法能力、内驱力、职业素养评分好于对照组,组间差异有统计学意义(t=3.171,t=4.843,t=4.512,t=5.769;P<0.05)。结论:基于优慕课平台的混合式教学设计能有效地解决教学中存在的问题,提高学生学习的积极性和学习效果,在口腔医学技术专业口腔数字化技术课程教学中具有较高的应用价值。

Highly efficient catalytic scavenging of oxygen free radicals with graphene-encapsulated metal nanoshields

Normal levels of oxygen free radicals play an important role in cellular signal transduction, redox homeostasis, regulatory pathways, and metabolic processes. However, radiolysis of water induced by high-energy radiation can produce excessive amounts of exogenous oxygen free radicals, which cause severe oxidative damages to all cellular components, disrupt cellular structures and signaling pathways, and eventually lead to death. Herein, we show that hybrid nanoshields based on single-layer graphene encapsulating metal nanoparticles exhibit high catalytic activity in scavenging oxygen superoxide （·O2^-）, hydroxyl （·OH）, and hydroperoxyl （HO2·） free radicals via electron transfer between the single-layer graphene and the metal core, thus achieving biocatalytic scavenging both in vitro and in vivo. The levels of the superoxide enzyme, DNA, and reactive oxygen species measured in vivo dearly show that the nanoshields can efficiently eliminate harmful oxygen free radicals at the cellular level, both in organs and circulating blood. Moreover, the nanoshields lead to an increase in the overall survival rate of gamma ray-irradiated mice to up to 90%, showing the great potential of these systems as protective agents against ionizing radiation.

Enhanced catalysis of ultrasmall Au-MoS_2 clusters against reactive oxygen species for radiation protection

Ionizing radiation produces excessive reactive oxygen species （ROS） which impose detrimental effects on biological systems. Thus, it is important to explore clinically safe and efficacious radioprotection agents to scavenge ROS and reduce the risks of radiotherapy. Recently, emerging catalytic nanomaterials such as sulfide nanomaterials have shown capability of clearing ROS in vivo by unique electron transfers between atoms, but their catalytic activities are yet suboptimal. As such, there is an unmet need to improve cat- alytic properties for stronger antioxidant activities and radiation protection. Herein, we prepared ultra- small Au-MoS2 clusters （~2.Snm） and they showed enhanced catalytic properties via gold intercalation facilitating increased active sites and synergistic effects. Electrocatalysis results revealed that the catalytic activity of Au-MoS2 towards 1-1202 was superior to ultrasmall MoS2 without Au. As a result, we found that improving the electrocatalytic property of Au-MoS2 can effectively enhance corre- sponding antioxidant activities and radioprotection effects in vivo. In addition, Au-MoS2 also showed sig- nificant radioprotection in vitro and dramatically reduced the excess of radiation-induced adverse ROS. It also rescued radiation-induced DNA damages and protected the bone marrow hematopoietic system from ionizing radiation.

Catalytic PtPd bimetal nanocrystals with high-index facets for radiation injury repair

Radiotherapy is one of the most important clinical cancer treatments,which works mainly by delive ring a prescribed radiation dose to the tumor tissues.However,high doses of radiation may also lead many irreversible damages to the surrounding normal tissues.Thereby,how to effectively reduce these sideeffects has been a significant factor in influencing cancer therapeutic effect.In this work,we synthesized the hollow PtPd nanocubes with high-index facets,and investigated the radiation protection capability in vitro and in vivo.Our results showed the PtPd nanocrystals can decrease the ROS level and improve the survival rate of radiated cells.Meanwhile,survival rate of radiated mice can significantly increase from 0 to 30%after PtPd treatment.Consequently,the enzyme and ROS level in radiated mice can be recovered.