Sulfur doped iron-nitrogen-hard carbon nanosheets as efficient and robust noble metal-free catalysts for oxygen reduction reaction in PEMFC

Transition metal-nitrogen-carbon(M-N-C)as a promising substitute for the conventional noble metalbased catalyst still suffers from low activity and durability for oxygen reduction reaction(ORR)in proton exchange membrane fuel cells(PEMFCs).To tackle the issue,herein,a new type of sulfur-doped ironnitrogen-hard carbon(S-Fe-N-HC)nanosheets with high activity and durability in acid media were developed by using a newly synthesized precursor of amide-based polymer with Fe ions based on copolymerizing two monomers of 2,5-thiophene dicarboxylic acid(TDA)as S source and 1,8-diaminonaphthalene(DAN)as N source via an amination reaction.The as-synthesized S-Fe-N-HC features highly dispersed atomic Fe Nxmoieties embedded into rich thiophene-S doped hard carbon nanosheets filled with highly twisted graphite-like microcrystals,which is distinguished from the majority of M-N-C with soft or graphitic carbon structures.These unique characteristics endow S-Fe-N-HC with high ORR activity and outstanding durability in 0.5 M H_(2)SO_(4).Its initial half-wave potential is 0.80 V and the corresponding loss is only 21 m V after 30,000 cycles.Meanwhile,its practical PEMFC performance is a maximum power output of 628.0 mW cm^(-2)and a slight power density loss is 83.0 m W cm^(-2)after 200-cycle practical operation.Additionally,theoretical calculation shows that the activity of Fe Nxmoieties on ORR can be further enhanced by sulfur doping at meta-site near FeN_(4)C.These results evidently demonstrate that the dual effect of hard carbon substrate and S doping derived from the precursor platform of amid-polymers can effectively enhance the activity and durability of Fe-N-C catalysts,providing a new guidance for developing advanced M-N-C catalysts for ORR.

Role of extracellular polymeric substances in resistance to allelochemical stress on Microcystis aeruginsosa and its mechanism

Using allelochemicals to suppress cyanobacteria growth is a prospective method for its high efficiency and ecological safety.However,the suppression efficiency is affected inevitably by the extracellular polymeric substances(EPS)produced by cyanobacteria,and the knowledge about the roles of EPS in resistance to allelochemical stress is scarce.For the study,two typical anti-cyanobacterial allelochemicals were adopted to investigate the role of EPS in resistance to allelochemical stress on Microcystis aeruginosa.Results show that EPS was crucial in alleviating the toxicity of allelochemicals to algae,especially in stabilizing the metabolism and photosynthetic activity of algal cells.The aggregation rate of algal cells increased with the increase of EPS secretion,which alleviated the stress of allelopathy.Tryptophan proteins and humic acids in EPS provided a binding site for allelochemicals,and the EPS-allelochemicals complex were formed by chemical bonding.This study improved our comprehension of the role of EPS in algal inhibition by allelochemicals.

Low profile cavity-embedded ultra-wideband UHF array antenna with end-fire beams

A low-profile,vertically polarized,ultra-wideband array antenna with end-fire beams operating in an ultra-high frequency(UHF)band is developed in this paper.The array antenna consists of 1×16 log-periodic top-hat loaded monopole antenna arrays and is feasible to embed into a shallow cavity to further reduce the array height.Capacitance is introduced in the proposed antenna element to reduce profile height and the rectangular top hats are carefully designed to minimize the transverse dimension.Simulated results show that when the antenna array operates in a frequency range of 300 MHz-900 MHz,the end-fire radiation pattern achieves±45°scanning range in the horizontal plane.Then prototypes of the proposed end-fire antenna element and a uniformly spaced linear array(1×2)are fabricated and validated.The end-fire antenna array should be suitable for airborne applications where low-profile and conformal scanning phased antenna arrays with end-fire radiations are required.This design is attractive for airborne platform applications that are used to search,discover,identify,and scout the aerial target with vertically polarized beams.

Influence of anisotropic stress path and stress history on stiffness of calcareous sands from Western Australia and the Philippines

Investigation of dynamic properties of carbonate/calcareous soils is important in earthquake and offshore engineering as these soils are commonly encountered in large-scale projects related with energy geomechanics and land reclamation.In this study,the stiffness and stiffness anisotropy of two types of calcareous sands(CS)from the Western Australia and the Philippines were examined using bender elements configured in different directions in stress path setups.Stiffness measurements were taken on specimens subjected to constant p’compression/extension and biaxial stress paths and additional tests were performed on three types of silica sands with different geological origins and particle shapes,which were used as benchmark materials in the study.Compared with the three brands of silica sands,the stiffness of the CS was found to be more significantly influenced by anisotropic loading;an important observation of the experimental results was that stress anisotropy had different weighted influences on the stiffness in different directions,thus influencing stiffness anisotropy.Comparisons were made between the specimens subjected to complex loading paths,and respected model parameters as suggested from published expressions in the literature.These comparisons further highlighted that calcareous soils have different responses in terms of stiffness,stiffness anisotropy and loading history,compared with that of silica-based sands.

Electronic, optical property and carrier mobility of graphene, black phosphorus, and molybdenum disulfide based on the first principles

The band structure, density of states, optical properties, carrier mobility, and loss function of graphene, black phosphorus（BP）, and molybdenum disulfide（MoS_2） were investigated by the first-principles method with the generalized-gradient approximation. The graphene was a zero-band-gap semiconductor. The band gaps of BP and MoS_2 were strongly dependent on the number of layers. The relationships between layers and band gap were built to predict the band gap of few-layer BP and MoS_2. The absorption showed an explicit anisotropy for light polarized in（1 0 0） and（0 0 1） directions of graphene, BP,and MoS_2. This behavior may be readily detected in spectroscopic measurements and exploited for optoelectronic applications. Moreover, graphene（5.27 × 10~4 cm^2·V^（-1）·s^（-1））, BP（1.5 × 10~4 cm^2·V^（-1）·s^（-1））, and MoS_2（2.57×102 cm2·V-1·s-1）have high carrier mobility. These results show that graphene, BP, and MoS_2 are promising candidates for future electronic applications.

A note on influence of stress anisotropy on the Poisson's ratio of dry sand

In this study, extender and bender element tests were conducted investigating the small-strain Poisson’s ratio of variable sands, with a focus on the effect of stress anisotropy in order to quantify the sensitivity of Poisson’s ratio to the applied deviatoric stress. Four different uniform sands were tested, including a biogenic sand, a crushed rock and two natural sands, covering a wide range of particle shapes. From these sands, eleven samples were prepared in the laboratory and were tested under variable stress paths,maintaining a constant mean effective pressure while increasing the deviatoric compressive load. Under the application of these given stress paths, the data analysis indicated that the sensitivity of Poisson’s ratio to the stress ratio was more pronounced for sands with irregularly shaped particles in comparison to sands with fairly rounded and spherical grains. For sands with very irregularly shaped particles, the increase of Poisson’s ratio from the isotropic to the anisotropic stress state reached 50%, while this increase for natural sands with fairly rounded particles was in the order of 20%.

日本防晒产品的管理制度及对我国的启示

我国的化妆品类产品在日本按照化妆品和医药部外品进行分类管理。其中防晒产品是非常具有代表性的一类,既包括化妆品又包括医药部外品。通过对日本化妆品和医药部外品的法律法规及文献进行分析,研究和总结了产品分类、测试方法、原料管理、产品备案审批制度和标签管理等技术要求及监管要求;结合我国化妆品的监管实际情况,对两国的法规要求和管理现状进行了对比分析,为我国化妆品监管提供了参考,在我国化妆品行业蓬勃发展、监管法规逐步完善的现状下,进一步促进行业的高质量发展。

Early enteral nutrition supplemented with probiotics improved the clinical outcomesin patients with severe head injury： protocol for a meta-analysis of randomizedcontrolled trials

Objective： The aim of this systematic review of randomized controlled trials （RCTs） is to determine the effects of earlyenteral nutrition supplemented with probiotics on clinical outcomes in patients with SHI.Methods and analysis： A systematic search will be carried out in PubMed, Cochrane Central Register of ControlledTrials （CENTRAL）, China National Knowledge Infrastructure （CNKI）, WanFang database, and Chinese BiomedicalLiterature （CBM） in order to identify the randomized controlled trials （RCTs） investigated the potential of early enteralnutrition supplemented with probiotics on patients with severe head injury, as well as we will also manually check thebibliographies of eligible studies and topic-related reviews. We will assign two investigators to independently search allpotential citations, extracted data, and appraised risk of bias accordingly, and then STATA software version 12.0 will beused to statistically analyze all data.Ethics and dissemination： The ethics approval and patient written informed consent will not be required because allanalyses in the present study will be performed based on data from published studies. We will submit our systematicreview to a peer-reviewed scientific journal for publication.

A novel multi-cavity Helmholtz muffler

A novel multi-cavity Helmholtz muffler is proposed. The multi-cavity Helmholtz muffler is composed of steel structures and silicone membranes. With suitable construction, the Helmholtz muffler can be designed to exhibit negative mass density in low frequency, and the muffling frequency can be adjusted when we change the internal structure of the cavity,which will be very attractive for noise control. In this paper, we investigate the influence of the membranes and the cavities on noise reduction characteristics with theoretical calculations and simulations. The results show that the numbers of membranes and the volumes of the cavities can have a great effect on the position of the muffling frequency. The number of cavities can have a great effect on the width of the muffling frequency(reduce the noise by 10 dB). With different combinations of the membranes and cavities, we can get different muffling frequencies, which can meet different muffling demands in practical applications and is more flexible than the traditional Helmholtz cavity.

TRAF7 enhances degradation of ubiquitinated KLF4 to promote hepatocellular carcinoma progression

Objective:The tumor necrosis factor receptor-associated factor 7(TRAF7)is one of the components of the tumor necrosis factor alpha(TNF-α)/nuclear factor kappa B(NF-κB)pathway and a putative E3-ubiquitin ligase.This study aims to explore the biologic effects and the molecular mechanisms of deregulated TRAF7 signaling in hepatocellular carcinoma(HCC)progression.

Isolation and structural elucidation of the compounds from the fruits of Camptotheca acuminate

The fruit of Camptotheca acuminate is used as a traditional Chinese medicine.Eight compounds were isolated from the fruit of Camptotheca acuminate for the first time,including(+)-(S)-abscisic acid(1),blumenol A(2),(E)-3-hydroxymegastigm-7-en-9-one(3),(-)-(3R)-3,5-dimethyl-8-methoxy-3,4-dihydroisocoumarin(4),(-)-(3R)-8-methoxy-3-methyl-3,4-dihydro-1H-isochromen-1-one(5),neocnidilide(6),(3S)-butylphthalide(7)and senkyunolide I(8).Their structures were determined by comprehensive spectroscopic methods,including HRESIMS and 1D NMR.

Effect of extracellular polymeric substances on Dolichospermum aggregation during temperature rise

Dolichospermum,a typical model filamentous of cyanobacteria,has the potential to cause severely bloom.Extracellular polymeric substances(EPSs)are considered to influence the aggregation of the algae,and temperature is a significant factor affecting EPSs secretion.However,the mechanism of how EPSs affects the aggregation of Dolichospermum is still unclear because the structure and composition of EPSs are complex.In this study,the effects of EPSs on the aggregation of Dolichospermum during the rise of temperature(7-37℃)were determined.The results showed that the concentration of extracellular polysaccharides and proteins changed significantly with increasing temperature(P<0.01).Firstly,during the increasing temperature,the polysaccharide content of EPSs increased from 20.34 to 54.64 mg/L,and the polysaccharides in the soluble EPS(S-EPS)layer changed significantly.The protein content reached maximum value at 21℃(14.52 mg/L)and varied significantly in S-EPS and loosely bound EPS(LB-EPS).In the EPSs matrix,humus substances and protein were main components of S-EPS and LB-EPS,and protein was the main component of tightly bound EPS(TB-EPS).Secondly,the cell density of Dolichospermum increased during the temperature rise while the aggregation ratio decreased.Moreover,zeta potential and surface thermodynamic analysis of Dolichospermum revealed that the interfacial free energy and electrostatic repulsion increased gradually with increasing temperature,which further reduced the aggregation of Dolichospermum.Finally,principal component analysis(PCA)analysis showed the aggregation of Dolichospermum was directly related to the changes of protein in EPSs(especially S-EPS and LB-EPS)and zeta potential,and polysaccharides in EPSs inhibited the aggregation of Dolichospermum.Based on these results,it was illustrated that the composition and concentration of EPSs affected the cell surface properties of Dolichospermum with the change of temperature and thus affected the aggregation of Dolichospermum.

Double-confined nanoheterostructure Sb/Sb_(2)S_(3)@Ti_(3)C_(2)T_(x)@C toward ultra-stable Li-/Na-ion batteries

Antimony-based materials with high capacities and moderate potentials are promising anodes for lithium-/-sodium-ion batteries.However,their tremendous volume expansion and inferior conductivity lead to poor structural stability and sluggish reaction kinetics.Herein,a doubleconfined nanoheterostructure Sb/Sb_(2)S_(3)@Ti_(3)C_(2)T_(x)@C has been fabricated through a solvothermal method followed by low-temperature heat treatment.The dual protection of“MXene”and“carbon”can better accommodate the volume expansion of Sb/Sb_(2)S_(3).The strong covalent bond(Ti-S,Ti-O-Sb,C-O-Sb)can firmly integrate Sb-based material with Ti_(3)C_(2)T_(x)and carbon,which significantly improves the structure stability.In addition,the carbon layer can restrain the oxidation of MXenes,and the nano-Sb/Sb_(2)S_(3)can facilitate electron/ion transport and suppress the restacking of MXenes.The heterogeneous interface between Sb and Sb_(2)S_(3)can further promote interfacial charge transfer.The MXene-Sb/Sb_(2)S_(3)@C-1 with the optimal Sb content shows high specific capacities,comparable rate properties and ultra-stable cycling performances(250 m Ah·g^(-1)after 2500 cycles at 1 A·g^(-1)for sodium-ion batteries).Ex situ X-ray diffractometer(XRD)test reveals the storage mechanism including the conversion and alloying process of MXene-Sb/Sb_(2)S_(3)@C-1.Cyclic voltammetry(CV)test results demonstrate that the pseudocapacitance behavior is dominant in MXene-Sb/Sb_(2)S_(3)@C-1,especially at large current.This design paves the way for exploring high-performance alloy-based/conversion-type anode for energy storage devices.

Dissolved organic matter accelerates microbial degradation of 17 alpha-ethinylestradiol in the presence of iron mineral

Dissolved organic matter(DOM)and iron minerals widely existing in the natural aquatic environment can mediate the migration and transformation of organic pollutants.However,the mechanism of interaction between DOM and iron minerals in the microbial degradation of pollutants deserves further investigation.In this study,the mechanism of 17 alphaethinylestradiol(EE2)biodegradation mediated by humic acid(HA)and three kinds of iron minerals(goethite,magnetite,and pyrite)was investigated.The results found that HA and iron minerals significantly accelerated the biodegradation process of EE2,and the highest degradation efficiency of EE2(48%)was observed in the HA-mediated microbial system with pyrite under aerobic conditions.Furthermore,it had been demonstrated that hydroxyl radicals(HO·)was the main active substance responsible for the microbial degradation of EE2.HO·is primarily generated through the reaction between hydrogen peroxide secreted by microorganisms and Fe(II),with aerobic conditions being more conducive.The presence of iron minerals and HA could change the microbial communities in the EE2 biodegradation system.These findings provide new information for exploring the migration and transformation of pollutants by microorganisms in iron-rich environments.

基于在线大气化学模式太阳能预报的改进

基于在线大气化学模式WRF/chem,考虑气溶胶直接辐射效应,模拟2015年1月1日—12月31日天津地区地面太阳辐射通量,并与未考虑气溶胶辐射效应的同参数中尺度气象模式WRF进行对比,分析在雾霾频发的天津地区,增加气溶胶直接辐射效应后对太阳能预报的改进效果。结果表明,在雾霾频发的天津地区,气溶胶对地面太阳辐射预测的影响不可忽略,以2015年计算,全年影响均值27.42 W·m^(-2),即全年太阳辐射辐照量下降864 MJ·m^(-2);在太阳能预报重点关注的9:00—16:00,影响值约为73.3 W·m^(-2)。由于气溶胶的作用,全年有6.3%的时日太阳辐射被削减50%,19%的时日太阳辐射被削减超过30%,尤其是在雾霾频发的11月—次年2月,约有18%~25%的太阳辐射+6被大气中气溶胶吸收和散射而未能到达地面。大气化学模式WRF/chem由于考虑了气溶胶直接辐射效应,可以显著地改善地面太阳辐射的预报性能,降低模式预报的正偏差,其均值偏差由44.74 W·m^(-2)降低到16.09 W·m^(-2),相关系数由0.88提高到0.92,相对均方根误差由36.6%降低到23.2%,相对误差由27.8%下降到15%。在雾霾影响较为严重的区域,基于在线大气化学模式开展的太阳能预报效果优于中尺度天气模式预报。

不同麻醉方式下儿童睑板腺囊肿切除术的综合疗效分析

目的:对比全身麻醉与局部麻醉下进行儿童霰粒肿切除术的综合疗效。方法:回顾性病例对照研究。将2015-01/2016-12在我院接受霰粒肿切除手术的双眼霰粒肿患儿(4～10周岁),根据采用的麻醉方法分为两组:全身麻醉组(全麻组,67例134眼)和局部麻醉组(局麻组,72例144眼)。分析两组患者的疼痛及术后心理创伤,以及术后1mo眼表健康状况、术后1a内复发率和并发症等四个方面的差异。结果:全麻组和局麻组患儿均未出现麻醉相关并发症和意外。全麻组患儿术中不存在疼痛,术后3h的面部表情疼痛量表(FPS-R)值为4.94"1.23分,低于局麻组(7.00"1.14分),差异有统计学意义(P<0.001)。全麻组患儿有12例出现再次就医回避,局麻组为35例,差异有统计学意义(P<0.01)。全麻组的泪膜破裂时间、泪膜脂质层厚度和泪河高度均高于局麻组,差异有统计学意义(P<0.001);其睑脂性状评分也低于局麻组,差异有统计学意义(P<0.01)。全麻组患儿囊肿复发率为6.0%,低于局麻组的20.8%,差异有统计学意义(P<0.05)。全麻组患儿出现并发症发生率为4.5%,局麻组为15.3%,差异有统计学意义(P<0.05)。结论:全身麻醉下进行儿童霰粒肿手术具有术后疼痛轻、患儿依从性好的基本优点。与局部麻醉下手术相比,全身麻醉术中能够进行精细操作,术后眼表健康情况更好,并发症更少。

Occurrence, partition behavior, source and ecological risk assessment of nitro-PAHs in the sediment and water of Taige Canal, China

Nitrated polycyclic aromatic hydrocarbons(NPAHs)are widespread organic pollutants that possess carcinogenic and mutagenic properties,so they may pose a risk to the environment and human health.In this study,the concentrations of 15 NPAHs and 16 polycyclic aromatic hydrocarbons(PAHs)in 30 surface water samples and 26 sediment samples were measured in 2018 from the Taige Canal,one of the main rivers flowing into Taihu Lake,China.The total NPAH concentrations in water and sediment ranged from 14.7 to 235 ng/L and 22.9 to 96.5 ng/g dw,respectively.9-nitrophenanthrene(nd–76.3 ng/L)was the dominant compound in surface water,while 2+3-nitrofluoranthene(1.73–18.1 ng/g dw)dominated in sediment.Among PAHs,concentration ranging from 1,097 to 2,981 ng/L and 1,089 to 4,489 ng/g dw in surface water and sediment,respectively.There was a strong positive correlation between the log octanol-water partition coefficient(Kow)and log sediment-water partition coefficient due to hydrophobic interaction.The fugacity fraction value increased with the decrease of log Kow,and chrysene was transferred from water into sediment.The residual NPAHs in surface water and sediment of the Taige Canal have partial correlation.Diesel engine and coal combustion emissions were probably the principal sources of NPAHs in surface water and sediment.The results of ecological risk assessment showed that some NPAHs inwater(e.g,1-nitropyrene and 6-nitrochrysene)and sediment(e.g.,2-nitrobiphenyl,5-nitroacenaphthene,9-nitrophenanthrene and 2+3-nitrofluoranthene)had moderate ecological risks,which should be of concern.

热休克转录因子1在硼替佐米诱导的多发性骨髓瘤细胞凋亡中的作用

目的:探究热休克转录因子1(heat shock factor1, HSF1)在硼替佐米(bortezomib, BTZ)诱导的多发性骨髓瘤细胞凋亡中的作用及机制。方法:利用BTZ刺激骨髓瘤细胞RPMI 8226及U266,核浆分离检测HSF1分别在骨髓瘤细胞胞核、胞质的表达;利用发卡RNA抑制HSF1表达,并结合BTZ刺激骨髓瘤细胞,检测其表达对骨髓瘤细胞增殖、细胞凋亡的影响;最后构建骨髓瘤细胞体外黏附培养模型,进一步验证HSF1表达对骨髓瘤细胞凋亡的影响。结果 :BTZ作用骨髓瘤细胞过程中,HSF1向胞核分布显著增加;HSF1低表达可以促进BTZ诱导的骨髓瘤细胞凋亡;利用HSF1抑制剂处理骨髓瘤细胞验证了上述结果;利用骨髓基质细胞HS-5与骨髓瘤细胞共培养,抑制HSF1表达可以显著增加BTZ诱导的骨髓瘤细胞死亡数量。结论:BTZ刺激骨髓瘤细胞可以诱导HSF1胞核表达,HSF1表达上调可以促进BTZ诱导的骨髓瘤细胞凋亡。

Simulation and experimental investigation of low-frequency vibration reduction of honeycomb phononic crystals

The honeycomb phononic crystal displays good performance in reducing vibration, especially at low frequency, but there are few corresponding experiments involving this kind of phononic crystal and the influence of geometric parameters on the bandgap is unclear. We design a honeycomb phononic crystal, which is assembled by using a chemigum plate and a steel column, calculate the bandgaps of the phononic crystal, and analyze the vibration modes. In the experiment, we attach a same-sized rubber plate and a phononic crystal to a steel plate separately in order to compare their vibration reduction performances. We use 8×8 unit cells as a complete phononic crystal plate to imitate an infinite period structure and choose a string suspension arrangement to support the experiment. The results show that the honeycomb phononic crystal can reduce the vibrating plate magnitude by up to 60 dB in a frequency range of 600 Hz–900 Hz, while the rubber plate can reduce only about 20 dB. In addition, we study the effect of the thickness of plate and the height and the radius of the column in order to choose the most superior parameters to achieve low frequency and wide bandgap.

Workability Tests on Fresh Concrete Formulated with Eco-friendly Admixture

Extra-cellular compounds, secreted by microorganisms into their surroundings, can be integrated in concrete composition as admixtures. These substances are important in biofilm formation and some of them can be used as corrosion inhibitor of concrete reinforcement. This paper deals with products made with biological surface active compounds/agents allowing the development of more eco-friendly concrete. The influence of this environmentally friendly bio admixture on setting time, workability, bending and compressive strengths of various mortar based materials made of CEM I, CEM III and CEM V was studied. Mechanical tests were carried out to highlight the influence of admixture in workability and hardening of samples containing the biological product with ratio in the range of 0-2.5%. It was demonstrated that the presence of the new bio-compound admixture in mortar decreases their compressive strength after 28 days of standard curing, in spite of remaining higher than standard minimal strength. Furthermore, Vicat needle experiments have shown a tendency of this admixture to decrease the setting time. A discussion was finally proposed in order to correlate the setting times and the decrease of the mortar compressive strength, corresponding in fact to a hardening delay. This setting time delay could be linked to a delay of the admixtured mortar to increase its resistance. The slump results highlight the action of bio-admixture as a plasticizer on mortars because it increases their workability for a same water-cement ratio. This effect seems variable according to the added amount.